Pressure-induced amorphization and reactivity of solid dimethyl acetylene probed by in situ FTIR and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Guan, Jiwen; Daljeet, Roshan; Kieran, Arielle; Song, Yang

2018-06-01

Conjugated polymers are prominent semiconductors that have unique electric conductivity and photoluminescence. Synthesis of conjugated polymers under high pressure is extremely appealing because it does not require a catalyst or solvent used in conventional chemical methods. Transformation of acetylene and many of its derivatives to conjugated polymers using high pressure has been successfully achieved, but not with dimethyl acetylene (DMA). In this work, we present a high-pressure study on solid DMA using a diamond anvil cell up to 24.4 GPa at room temperature characterized by in situ Fourier transform infrared and Raman spectroscopy. Our results show that solid DMA exists in a phase II crystal structure and is stable up to 12 GPa. Above this pressure, amorphization was initiated and the process was completed at 24.4 GPa. The expected polymeric transformation was not evident upon compression, but only observed upon decompression from a threshold compression pressure (e.g. 14.4 GPa). In situ florescence measurements suggest excimer formation via crystal defects, which induces the chemical reactions. The vibrational spectral analysis suggests the products contain the amorphous poly(DMA) and possibly additional amorphous hydrogenated carbon material.

Pressure-induced amorphization and reactivity of solid dimethyl acetylene probed by in situ FTIR and Raman spectroscopy.

PubMed

Guan, Jiwen; Daljeet, Roshan; Kieran, Arielle; Song, Yang

2018-06-06

Conjugated polymers are prominent semiconductors that have unique electric conductivity and photoluminescence. Synthesis of conjugated polymers under high pressure is extremely appealing because it does not require a catalyst or solvent used in conventional chemical methods. Transformation of acetylene and many of its derivatives to conjugated polymers using high pressure has been successfully achieved, but not with dimethyl acetylene (DMA). In this work, we present a high-pressure study on solid DMA using a diamond anvil cell up to 24.4 GPa at room temperature characterized by in situ Fourier transform infrared and Raman spectroscopy. Our results show that solid DMA exists in a phase II crystal structure and is stable up to 12 GPa. Above this pressure, amorphization was initiated and the process was completed at 24.4 GPa. The expected polymeric transformation was not evident upon compression, but only observed upon decompression from a threshold compression pressure (e.g. 14.4 GPa). In situ florescence measurements suggest excimer formation via crystal defects, which induces the chemical reactions. The vibrational spectral analysis suggests the products contain the amorphous poly(DMA) and possibly additional amorphous hydrogenated carbon material.

Raman studies on molecular and ionic forms in solid layers of nitrogen dioxide - Temperature and light induced effects

NASA Astrophysics Data System (ADS)

Givan, A.; Loewenschuss, A.

1990-12-01

Raman spectra of zero-pressure-formed N2O4 solid layers are reported. Sample composition is extremely dependent upon deposition conditions. For ordered and pure solid N2O4(D2h), produced by slow NO2 deposition, temperature cycling over the range in which the solid is stable shows no significant spectral changes and does not result in autoionization, as argued in a previous Raman study. Fast and low temperature deposited layers are amorphous and multicomponent, showing bands of disordered and isomeric molecular N2O4 and of ionic NO + NO3, nitrosonium nitrate. For nitrosonium nitrate, three solid modifications can be characterized spectroscopically. In the amorphous phase, a light induced, temperature dependent, reversible transition between molecular and ionic nitrogen tetroxide is observed below 150 K. The paths leading to nitrosonium nitrate formation are examined.

Role of fluttering dislocations in the thermal interface resistance between a silicon crystal and plastic solid 4He

NASA Astrophysics Data System (ADS)

Amrit, Jay; Ramiere, Aymeric; Volz, Sebastian

2018-01-01

A quantum solid (solid 4He) in contact with a classical solid defines a new class of interfaces. In addition to its quantum nature, solid 4He is indeed a very plastic medium. We examine the thermal interface resistance upon solidification of superfluid 4He in contact with a silicon crystal surface (111) and show that dislocations play a crucial role in the thermal interface transport. The growth of solid 4He and the measurements are conducted at the minimum of the melting curve of helium (0.778 K and ˜25 bar ). The results display a first-order transition in the Kapitza resistance from a value of RK ,L=(80 ±8 ) c m2K /W at a pressure of 24.5 bar to a value of RK ,S=(41.7 ±8 ) c m2K /W after the formation of solid helium at ˜25.2 bar . The drop in RK ,S is only of a factor of ˜2 , although transverse phonon modes in solid 4He now participate in heat transmission at the interface. We provide an explanation for the measured RK ,S by considering the interaction of thermal phonons with vibrating dislocations in solid 4He. We demonstrate that this mechanism, also called fluttering, induces a thermal resistance RF l∝NdT-6 , where T is the temperature and Nd is the density of dislocations. We estimate that for dislocation densities on the order of ˜107c m-2 , RF l predominates over the boundary resistance RK ,S. These fundamental findings shed light on the role of dislocations and provide a quantitative explanation for previous experiments which showed no measurable change in the Kapitza resistance between Cu and superfluid 4He upon solidification of the latter. This demonstrates the possibility of using dislocations as an additional means to tailor thermal resistances at interfaces, formed especially with a plastic material.

Directional amorphization of boron carbide subjected to laser shock compression

PubMed Central

Zhao, Shiteng; Kad, Bimal; Remington, Bruce A.; LaSalvia, Jerry C.; Wehrenberg, Christopher E.; Behler, Kristopher D.; Meyers, Marc A.

2016-01-01

Solid-state shock-wave propagation is strongly nonequilibrium in nature and hence rate dependent. Using high-power pulsed-laser-driven shock compression, unprecedented high strain rates can be achieved; here we report the directional amorphization in boron carbide polycrystals. At a shock pressure of 45∼50 GPa, multiple planar faults, slightly deviated from maximum shear direction, occur a few hundred nanometers below the shock surface. High-resolution transmission electron microscopy reveals that these planar faults are precursors of directional amorphization. It is proposed that the shear stresses cause the amorphization and that pressure assists the process by ensuring the integrity of the specimen. Thermal energy conversion calculations including heat transfer suggest that amorphization is a solid-state process. Such a phenomenon has significant effect on the ballistic performance of B4C. PMID:27733513

Directional amorphization of boron carbide subjected to laser shock compression

DOE PAGES

Zhao, Shiteng; Kad, Bimal; Remington, Bruce A.; ...

2016-10-12

Solid-state shock-wave propagation is strongly nonequilibrium in nature and hence rate dependent. When using high-power pulsed-laser-driven shock compression, an unprecedented high strain rates can be achieved; we report the directional amorphization in boron carbide polycrystals. At a shock pressure of 45~50 GPa, multiple planar faults, slightly deviated from maximum shear direction, occur a few hundred nanometers below the shock surface. High-resolution transmission electron microscopy reveals that these planar faults are precursors of directional amorphization. We also propose that the shear stresses cause the amorphization and that pressure assists the process by ensuring the integrity of the specimen. Thermal energy conversionmore » calculations including heat transfer suggest that amorphization is a solid-state process. Such a phenomenon has significant effect on the ballistic performance of B 4C.« less

Effect of rotation on the elastic moduli of solid 4He

NASA Astrophysics Data System (ADS)

Tsuiki, T.; Takahashi, D.; Murakawa, S.; Okuda, Y.; Kono, K.; Shirahama, K.

2018-02-01

We report measurements of elastic moduli of hcp solid 4He down to 15 mK when the samples are rotated unidirectionally. Recent investigations have revealed that the elastic behavior of solid 4He is dominated by gliding of dislocations and pinning of them by 3He impurities, which move in the solidlike Bloch waves (impuritons). Motivated by the recent controversy of torsional oscillator studies, we have performed direct measurements of shear and Young's moduli of annular solid 4He using pairs of quarter-circle-shape piezoelectric transducers (PZTs) while the whole apparatus is rotated with angular velocity Ω up to 4 rad/s. We have found that shear modulus μ is suppressed by rotation below 80 mK, when shear strain applied by PZT exceeds a critical value, above which μ decreases because the shear strain unbinds dislocations from 3He impurities. The rotation-induced decrement of μ at Ω =4 rad/s is about 14.7(12.3)% of the total change of temperature dependent μ for solid samples of pressure 3.6(5.4) MPa. The decrements indicate that the probability of pinning of 3He on dislocation segment G decreases by several orders of magnitude. We propose that the motion of 3He impuritons under rotation becomes strongly anisotropic by the Coriolis force, resulting a decrease in G for dislocation lines aligning parallel to the rotation axis.

Amorphous stabilization and dissolution enhancement of amorphous ternary solid dispersions: combination of polymers showing drug-polymer interaction for synergistic effects.

PubMed

Prasad, Dev; Chauhan, Harsh; Atef, Eman

2014-11-01

The purpose of this study was to understand the combined effect of two polymers showing drug-polymer interactions on amorphous stabilization and dissolution enhancement of indomethacin (IND) in amorphous ternary solid dispersions. The mechanism responsible for the enhanced stability and dissolution of IND in amorphous ternary systems was studied by exploring the miscibility and intermolecular interactions between IND and polymers through thermal and spectroscopic analysis. Eudragit E100 and PVP K90 at low concentrations (2.5%-40%, w/w) were used to prepare amorphous binary and ternary solid dispersions by solvent evaporation. Stability results showed that amorphous ternary solid dispersions have better stability compared with amorphous binary solid dispersions. The dissolution of IND from the ternary dispersion was substantially higher than the binary dispersions as well as amorphous drug. Melting point depression of physical mixtures reveals that the drug was miscible in both the polymers; however, greater miscibility was observed in ternary physical mixtures. The IR analysis confirmed intermolecular interactions between IND and individual polymers. These interactions were found to be intact in ternary systems. These results suggest that the combination of two polymers showing drug-polymer interaction offers synergistic enhancement in amorphous stability and dissolution in ternary solid dispersions. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

Boron carbide coatings for neutron detection probed by x-rays, ions, and neutrons to determine thin film quality

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nowak, G., E-mail: Gregor.Nowak@hzg.de; Störmer, M.; Horstmann, C.

2015-01-21

Due to the present shortage of {sup 3}He and the associated tremendous increase of its price, the supply of large neutron detection systems with {sup 3}He becomes unaffordable. Alternative neutron detection concepts, therefore, have been invented based on solid {sup 10}B converters. These concepts require development in thin film deposition technique regarding high adhesion, thickness uniformity and chemical purity of the converter coating on large area substrates. We report on the sputter deposition of highly uniform large-area {sup 10}B{sub 4}C coatings of up to 2 μm thickness with a thickness deviation below 4% using the Helmholtz-Zentrum Geesthacht large area sputtering system.more » The {sup 10}B{sub 4}C coatings are x-ray amorphous and highly adhesive to the substrate. Material analysis by means of X-ray-Photoelectron Spectroscopy, Secondary-Ion-Mass-Spectrometry, and Rutherford-Back-Scattering (RBS) revealed low impurities concentration in the coatings. The isotope composition determined by Secondary-Ion-Mass-Spectrometry, RBS, and inelastic nuclear reaction analysis of the converter coatings evidences almost identical {sup 10}B isotope contents in the sputter target and in the deposited coating. Neutron conversion and detection test measurements with variable irradiation geometry of the converter coating demonstrate an average relative quantum efficiency ranging from 65% to 90% for cold neutrons as compared to a black {sup 3}He-monitor. Thus, these converter coatings contribute to the development of {sup 3}He-free prototype detectors based on neutron grazing incidence. Transferring the developed coating process to an industrial scale sputtering system can make alternative {sup 3}He-free converter elements available for large area neutron detection systems.« less

Boron carbide coatings for neutron detection probed by x-rays, ions, and neutrons to determine thin film quality

NASA Astrophysics Data System (ADS)

Nowak, G.; Störmer, M.; Becker, H.-W.; Horstmann, C.; Kampmann, R.; Höche, D.; Haese-Seiller, M.; Moulin, J.-F.; Pomm, M.; Randau, C.; Lorenz, U.; Hall-Wilton, R.; Müller, M.; Schreyer, A.

2015-01-01

Due to the present shortage of 3He and the associated tremendous increase of its price, the supply of large neutron detection systems with 3He becomes unaffordable. Alternative neutron detection concepts, therefore, have been invented based on solid 10B converters. These concepts require development in thin film deposition technique regarding high adhesion, thickness uniformity and chemical purity of the converter coating on large area substrates. We report on the sputter deposition of highly uniform large-area 10B4C coatings of up to 2 μm thickness with a thickness deviation below 4% using the Helmholtz-Zentrum Geesthacht large area sputtering system. The 10B4C coatings are x-ray amorphous and highly adhesive to the substrate. Material analysis by means of X-ray-Photoelectron Spectroscopy, Secondary-Ion-Mass-Spectrometry, and Rutherford-Back-Scattering (RBS) revealed low impurities concentration in the coatings. The isotope composition determined by Secondary-Ion-Mass-Spectrometry, RBS, and inelastic nuclear reaction analysis of the converter coatings evidences almost identical 10B isotope contents in the sputter target and in the deposited coating. Neutron conversion and detection test measurements with variable irradiation geometry of the converter coating demonstrate an average relative quantum efficiency ranging from 65% to 90% for cold neutrons as compared to a black 3He-monitor. Thus, these converter coatings contribute to the development of 3He-free prototype detectors based on neutron grazing incidence. Transferring the developed coating process to an industrial scale sputtering system can make alternative 3He-free converter elements available for large area neutron detection systems.

Polymeric Amorphous Solid Dispersions: A Review of Amorphization, Crystallization, Stabilization, Solid-State Characterization, and Aqueous Solubilization of Biopharmaceutical Classification System Class II Drugs.

PubMed

Baghel, Shrawan; Cathcart, Helen; O'Reilly, Niall J

2016-09-01

Poor water solubility of many drugs has emerged as one of the major challenges in the pharmaceutical world. Polymer-based amorphous solid dispersions have been considered as the major advancement in overcoming limited aqueous solubility and oral absorption issues. The principle drawback of this approach is that they can lack necessary stability and revert to the crystalline form on storage. Significant upfront development is, therefore, required to generate stable amorphous formulations. A thorough understanding of the processes occurring at a molecular level is imperative for the rational design of amorphous solid dispersion products. This review attempts to address the critical molecular and thermodynamic aspects governing the physicochemical properties of such systems. A brief introduction to Biopharmaceutical Classification System, solid dispersions, glass transition, and solubility advantage of amorphous drugs is provided. The objective of this review is to weigh the current understanding of solid dispersion chemistry and to critically review the theoretical, technical, and molecular aspects of solid dispersions (amorphization and crystallization) and potential advantage of polymers (stabilization and solubilization) as inert, hydrophilic, pharmaceutical carrier matrices. In addition, different preformulation tools for the rational selection of polymers, state-of-the-art techniques for preparation and characterization of polymeric amorphous solid dispersions, and drug supersaturation in gastric media are also discussed. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Infrared Spectra and Optical Constants of Elusive Amorphous Methane

NASA Technical Reports Server (NTRS)

Gerakines, Perry A.; Hudson, Reggie L.

2015-01-01

New and accurate laboratory results are reported for amorphous methane (CH4) ice near 10 K for the study of the interstellar medium (ISM) and the outer Solar System. Near- and mid-infrared (IR) data, including spectra, band strengths, absorption coefficients, and optical constants, are presented for the first time for this seldom-studied amorphous solid. The apparent IR band strength near 1300 cm(exp -1) (7.69 micrometer) for amorphous CH4 is found to be about 33% higher than the value long used by IR astronomers to convert spectral observations of interstellar CH4 into CH4 abundances. Although CH4 is most likely to be found in an amorphous phase in the ISM, a comparison of results from various laboratory groups shows that the earlier CH4 band strength at 1300 cm(exp -1) (7.69 micrometer) was derived from IR spectra of ices that were either partially or entirely crystalline CH4 Applications of the new amorphous-CH4 results are discussed, and all optical constants are made available in electronic form.

The effect of temperature and moisture on the amorphous-to-crystalline transformation of stavudine.

PubMed

Strydom, Schalk; Liebenberg, Wilna; Yu, Lian; de Villiers, Melgardt

2009-09-08

Stavudine is a nucleoside reverse transcriptase inhibitor active against HIV, and is known to exist in two polymorphic forms designated as forms I and II, and a hydrate form III. An amorphous solid of stavudine was successfully prepared and characterized during this investigation. A comprehensive evaluation of the stability of this amorphous solid showed that the amorphous solid transforms to either form II (anhydrous) or form III (hydrate) when exposed to temperature, in the absence or presence of moisture, respectively. The amorphous-to-hydrate transformation occurred at relatively low RH (>32%) and led to the formation of crystal aggregates of the hydrated form. Steady state growth rate analyses also showed that the amorphous-to-crystalline transformation occurs at a greater rate in the presence of moisture, compared to the transformation at the same temperature in a dry environment. Crystal growth studies showed that it is possible to stabilize the amorphous solid of stavudine against crystal transformations in the absence of moisture by coating it with poly(methyl methacrylate). However, this polymer coating could not prevent crystal growth from the amorphous solid during exposure to moisture.

Mermin-Wagner fluctuations in 2D amorphous solids.

PubMed

Illing, Bernd; Fritschi, Sebastian; Kaiser, Herbert; Klix, Christian L; Maret, Georg; Keim, Peter

2017-02-21

In a recent commentary, J. M. Kosterlitz described how D. Thouless and he got motivated to investigate melting and suprafluidity in two dimensions [Kosterlitz JM (2016) J Phys Condens Matter 28:481001]. It was due to the lack of broken translational symmetry in two dimensions-doubting the existence of 2D crystals-and the first computer simulations foretelling 2D crystals (at least in tiny systems). The lack of broken symmetries proposed by D. Mermin and H. Wagner is caused by long wavelength density fluctuations. Those fluctuations do not only have structural impact, but additionally a dynamical one: They cause the Lindemann criterion to fail in 2D in the sense that the mean squared displacement of atoms is not limited. Comparing experimental data from 3D and 2D amorphous solids with 2D crystals, we disentangle Mermin-Wagner fluctuations from glassy structural relaxations. Furthermore, we demonstrate with computer simulations the logarithmic increase of displacements with system size: Periodicity is not a requirement for Mermin-Wagner fluctuations, which conserve the homogeneity of space on long scales.

Mermin-Wagner fluctuations in 2D amorphous solids

NASA Astrophysics Data System (ADS)

Illing, Bernd; Fritschi, Sebastian; Kaiser, Herbert; Klix, Christian L.; Maret, Georg; Keim, Peter

2017-02-01

In a recent commentary, J. M. Kosterlitz described how D. Thouless and he got motivated to investigate melting and suprafluidity in two dimensions [Kosterlitz JM (2016) J Phys Condens Matter 28:481001]. It was due to the lack of broken translational symmetry in two dimensions—doubting the existence of 2D crystals—and the first computer simulations foretelling 2D crystals (at least in tiny systems). The lack of broken symmetries proposed by D. Mermin and H. Wagner is caused by long wavelength density fluctuations. Those fluctuations do not only have structural impact, but additionally a dynamical one: They cause the Lindemann criterion to fail in 2D in the sense that the mean squared displacement of atoms is not limited. Comparing experimental data from 3D and 2D amorphous solids with 2D crystals, we disentangle Mermin-Wagner fluctuations from glassy structural relaxations. Furthermore, we demonstrate with computer simulations the logarithmic increase of displacements with system size: Periodicity is not a requirement for Mermin-Wagner fluctuations, which conserve the homogeneity of space on long scales.

Mermin–Wagner fluctuations in 2D amorphous solids

PubMed Central

Illing, Bernd; Fritschi, Sebastian; Kaiser, Herbert; Klix, Christian L.; Maret, Georg; Keim, Peter

2017-01-01

In a recent commentary, J. M. Kosterlitz described how D. Thouless and he got motivated to investigate melting and suprafluidity in two dimensions [Kosterlitz JM (2016) J Phys Condens Matter 28:481001]. It was due to the lack of broken translational symmetry in two dimensions—doubting the existence of 2D crystals—and the first computer simulations foretelling 2D crystals (at least in tiny systems). The lack of broken symmetries proposed by D. Mermin and H. Wagner is caused by long wavelength density fluctuations. Those fluctuations do not only have structural impact, but additionally a dynamical one: They cause the Lindemann criterion to fail in 2D in the sense that the mean squared displacement of atoms is not limited. Comparing experimental data from 3D and 2D amorphous solids with 2D crystals, we disentangle Mermin–Wagner fluctuations from glassy structural relaxations. Furthermore, we demonstrate with computer simulations the logarithmic increase of displacements with system size: Periodicity is not a requirement for Mermin–Wagner fluctuations, which conserve the homogeneity of space on long scales. PMID:28137872

Solid-state diffusion in amorphous zirconolite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, C.; Dove, M. T.; Trachenko, K.

2014-11-14

We discuss how structural disorder and amorphization affect solid-state diffusion, and consider zirconolite as a currently important case study. By performing extensive molecular dynamics simulations, we disentangle the effects of amorphization and density, and show that a profound increase of solid-state diffusion takes place as a result of amorphization. Importantly, this can take place at the same density as in the crystal, representing an interesting general insight regarding solid-state diffusion. We find that decreasing the density in the amorphous system increases pre-factors of diffusion constants, but does not change the activation energy in the density range considered. We also findmore » that atomic species in zirconolite are affected differently by amorphization and density change. Our microscopic insights are relevant for understanding how solid-state diffusion changes due to disorder and for building predictive models of operation of materials to be used to encapsulate nuclear waste.« less

Amorphous salts formed from rapid dehydration of multicomponent chloride and ferric sulfate brines: Implications for Mars.

PubMed

Sklute, Elizabeth C; Rogers, A Deanne; Gregerson, Jason C; Jensen, Heidi B; Reeder, Richard J; Dyar, M Darby

2018-03-01

Salts with high hydration states have the potential to maintain high levels of relative humidity (RH) in the near subsurface of Mars, even at moderate temperatures. These conditions could promote deliquescence of lower hydrates of ferric sulfate, chlorides, and other salts. Previous work on deliquesced ferric sulfates has shown that when these materials undergo rapid dehydration, such as that which would occur upon exposure to present day Martian surface conditions, an amorphous phase forms. However, the fate of deliquesced halides or mixed ferric sulfate-bearing brines are presently unknown. Here we present results of rapid dehydration experiments on Ca-, Na-, Mg- and Fe-chloride brines and multi-component (Fe 2 (SO 4 ) 3 ± Ca, Na, Mg, Fe, Cl, HCO 3 ) brines at ∼21°C, and characterize the dehydration products using visible/near-infrared (VNIR) reflectance spectroscopy, mid-infrared attenuated total reflectance spectroscopy, and X-ray diffraction (XRD) analysis. We find that rapid dehydration of many multicomponent brines can form amorphous solids or solids with an amorphous component, and that the presence of other elements affects the persistence of the amorphous phase under RH fluctuations. Of the pure chloride brines, only Fe-chloride formed an amorphous solid. XRD patterns of the multicomponent amorphous salts show changes in position, shape, and magnitude of the characteristic diffuse scattering observed in all amorphous materials that could be used to help constrain the composition of the amorphous salt. Amorphous salts deliquesce at lower RH values compared to their crystalline counterparts, opening up the possibility of their role in potential deliquescence-related geologic phenomena such as recurring slope lineae (RSLs) or soil induration. This work suggests that a wide range of aqueous mixed salt solutions can lead to the formation of amorphous salts and are possible for Mars; detailed studies of the formation mechanisms, stability and transformation behaviors of amorphous salts are necessary to further constrain their contribution to Martian surface materials.

Amorphous salts formed from rapid dehydration of multicomponent chloride and ferric sulfate brines: Implications for Mars

NASA Astrophysics Data System (ADS)

Sklute, Elizabeth C.; Rogers, A. Deanne; Gregerson, Jason C.; Jensen, Heidi B.; Reeder, Richard J.; Dyar, M. Darby

2018-03-01

Salts with high hydration states have the potential to maintain high levels of relative humidity (RH) in the near subsurface of Mars, even at moderate temperatures. These conditions could promote deliquescence of lower hydrates of ferric sulfate, chlorides, and other salts. Previous work on deliquesced ferric sulfates has shown that when these materials undergo rapid dehydration, such as that which would occur upon exposure to present day Martian surface conditions, an amorphous phase forms. However, the fate of deliquesced halides or mixed ferric sulfate-bearing brines are presently unknown. Here we present results of rapid dehydration experiments on Ca-, Na-, Mg- and Fe-chloride brines and multicomponent (Fe2(SO4)3 ± Ca, Na, Mg, Fe, Cl, HCO3) brines at ∼21 °C, and characterize the dehydration products using visible/near-infrared (VNIR) reflectance spectroscopy, mid-infrared attenuated total reflectance spectroscopy, and X-ray diffraction (XRD) analysis. We find that rapid dehydration of many multicomponent brines can form amorphous solids or solids with an amorphous component, and that the presence of other elements affects the persistence of the amorphous phase under RH fluctuations. Of the pure chloride brines, only Fe-chloride formed an amorphous solid. XRD patterns of the multicomponent amorphous salts show changes in position, shape, and magnitude of the characteristic diffuse scattering observed in all amorphous materials that could be used to help constrain the composition of the amorphous salt. Amorphous salts deliquesce at lower RH values compared to their crystalline counterparts, opening up the possibility of their role in potential deliquescence-related geologic phenomena such as recurring slope lineae (RSLs) or soil induration. This work suggests that a wide range of aqueous mixed salt solutions can lead to the formation of amorphous salts and are possible for Mars; detailed studies of the formation mechanisms, stability and transformation behaviors of amorphous salts are necessary to further constrain their contribution to Martian surface materials.

Amorphous salts formed from rapid dehydration of multicomponent chloride and ferric sulfate brines: Implications for Mars

PubMed Central

Sklute, Elizabeth C.; Rogers, A. Deanne; Gregerson, Jason C.; Jensen, Heidi B.; Reeder, Richard J.; Dyar, M. Darby

2018-01-01

Salts with high hydration states have the potential to maintain high levels of relative humidity (RH) in the near subsurface of Mars, even at moderate temperatures. These conditions could promote deliquescence of lower hydrates of ferric sulfate, chlorides, and other salts. Previous work on deliquesced ferric sulfates has shown that when these materials undergo rapid dehydration, such as that which would occur upon exposure to present day Martian surface conditions, an amorphous phase forms. However, the fate of deliquesced halides or mixed ferric sulfate-bearing brines are presently unknown. Here we present results of rapid dehydration experiments on Ca–, Na–, Mg– and Fe–chloride brines and multi-component (Fe2 (SO4)3 ± Ca, Na, Mg, Fe, Cl, HCO3) brines at ∼21°C, and characterize the dehydration products using visible/near-infrared (VNIR) reflectance spectroscopy, mid-infrared attenuated total reflectance spectroscopy, and X-ray diffraction (XRD) analysis. We find that rapid dehydration of many multicomponent brines can form amorphous solids or solids with an amorphous component, and that the presence of other elements affects the persistence of the amorphous phase under RH fluctuations. Of the pure chloride brines, only Fe–chloride formed an amorphous solid. XRD patterns of the multicomponent amorphous salts show changes in position, shape, and magnitude of the characteristic diffuse scattering observed in all amorphous materials that could be used to help constrain the composition of the amorphous salt. Amorphous salts deliquesce at lower RH values compared to their crystalline counterparts, opening up the possibility of their role in potential deliquescence-related geologic phenomena such as recurring slope lineae (RSLs) or soil induration. This work suggests that a wide range of aqueous mixed salt solutions can lead to the formation of amorphous salts and are possible for Mars; detailed studies of the formation mechanisms, stability and transformation behaviors of amorphous salts are necessary to further constrain their contribution to Martian surface materials. PMID:29670302

Formation of amorphous materials

DOEpatents

Johnson, William L.; Schwarz, Ricardo B.

1986-01-01

Metastable amorphous or fine crystalline materials are formed by solid state reactions by diffusion of a metallic component into a solid compound or by diffusion of a gas into an intermetallic compound. The invention can be practiced on layers of metals deposited on an amorphous substrate or by intermixing powders with nucleating seed granules. All that is required is that the diffusion of the first component into the second component be much faster than the self-diffusion of the first component. The method is practiced at a temperature below the temperature at which the amorphous phase transforms into one or more crystalline phases and near or below the temperature at which the ratio of the rate of diffusion of the first component to the rate of self-diffusion is at least 10.sup.4. This anomalous diffusion criteria is found in many binary, tertiary and higher ordered systems of alloys and appears to be found in all alloy systems that form amorphous materials by rapid quenching. The method of the invention can totally convert much larger dimensional materials to amorphous materials in practical periods of several hours or less.

First-principles modeling of quantum nuclear effects and atomic interactions in solid 4He at high pressure

NASA Astrophysics Data System (ADS)

Cazorla, Claudio; Boronat, Jordi

2015-01-01

We present a first-principles computational study of solid 4He at T =0 K and pressures up to ˜160 GPa. Our computational strategy consists in using van der Waals density functional theory (DFT-vdW) to describe the electronic degrees of freedom in this material, and the diffusion Monte Carlo (DMC) method to solve the Schrödinger equation describing the behavior of the quantum nuclei. For this, we construct an analytical interaction function based on the pairwise Aziz potential that closely matches the volume variation of the cohesive energy calculated with DFT-vdW in dense helium. Interestingly, we find that the kinetic energy of solid 4He does not increase appreciably with compression for P ≥85 GPa. Also, we show that the Lindemann ratio in dense solid 4He amounts to 0.10 almost independently of pressure. The reliability of customary quasiharmonic DFT (QH DFT) approaches in describing quantum nuclear effects in solids is also studied. We find that QH DFT simulations, although provide a reasonable equation of state in agreement with experiments, are not able to reproduce correctly these critical effects in compressed 4He. In particular, we disclose huge discrepancies of at least ˜50 % in the calculated 4He kinetic energies using both the QH DFT and present DFT-DMC methods.

Solid state properties and drug release behavior of co-amorphous indomethacin-arginine tablets coated with Kollicoat® Protect.

PubMed

Petry, Ina; Löbmann, Korbinian; Grohganz, Holger; Rades, Thomas; Leopold, Claudia S

2017-10-01

A promising approach to improve the solubility of poorly water-soluble drugs and to overcome the stability issues related to the plain amorphous form of the drugs, is the formulation of drugs as co-amorphous systems. Although polymer coatings have been proven very useful with regard to tablet stability and modifying drug release, there is little known on coating co-amorphous formulations. Hence, the aim of the present study was to investigate whether polymer coating of co-amorphous formulations is possible without inducing recrystallization. Tablets containing either a physical mixture of crystalline indomethacin and arginine or co-amorphous indomethacin-arginine were coated with a water soluble polyvinyl alcohol-polyethylene glycol graft copolymer (Kollicoat® Protect) and stored at 23°C/0% RH and 23°C/75% RH. The solid state properties of the coated tablets were analyzed by XRPD and FTIR and the drug release behavior was tested for up to 4h in phosphate buffer pH 4.5. The results showed that the co-amorphous formulation did not recrystallize during the coating process or during storage at both storage conditions for up to three months, which confirmed the high physical stability of this co-amorphous system. Furthermore, the applied coating could partially inhibit recrystallization of indomethacin during drug release testing, as coated tablets reached a higher level of supersaturation compared to the respective uncoated formulations and showed a lower decrease of the dissolved indomethacin concentration upon precipitation. Thus, the applied coating enhanced the AUC of the dissolution curve of the co-amorphous tablets by about 30%. In conclusion, coatings might improve the bioavailability of co-amorphous formulations. Copyright © 2017 Elsevier B.V. All rights reserved.

Response of Solid He-4 to External Stress: Interdigital Capacitor Solid Level Detector and Optical Interferometer

NASA Technical Reports Server (NTRS)

Fay, J.; Wada, Y.; Masutomi, R.; Elkholy, T.; Kojima, H.

2003-01-01

Two experiments are being conducted to observe the liquid/solid interface of He-4 near 1 K. Interesting instabilities are expected to occur when the solid is non-hydrostatically stressed. (1)A compact interdigital capacitor is used as a level detector to observe solid He-4 to which stresses are applied externally. The capacitor consists of 38 interlaced 50 m wide and 3.8 mm long gold films separated by 50 m and deposited onto a 5 mm by 5 mm sapphire substrate. The capacitor is placed on one flat end wall of a cylindrical chamber (xx mm diameter and xx mm long). The solid is grown to a known height and a stress is applied by a tubular PZT along the cylindrical axis. The observed small change in height of the solid at the wall is linearly proportional to the applied stress. The solid height decreases under compressive stress but does not change under tensile stress. The response of the solid on compressive stress is consistent with the expected quadratic dependence on strain. (2)Interferometric techniques are being developed for observing the solid He-4 surface profile. A laser light source is brought into the low temperature region via single mode optical fiber. The interference pattern is transmitted back out of the low temperature apparatus via optical fiber bundle. The solid He-4 growth chamber will be equipped with two PZT's such that stress can be applied from orthogonal directions. Orthogonally applied stress is expected to induce surface instability with island-like deformation on a grid pattern. Apparatus design and progress of its construction are described.

Positive Ion Induced Solidification of He4

NASA Astrophysics Data System (ADS)

Moroshkin, P.; Lebedev, V.; Weis, A.

2009-03-01

We have observed bulk solidification of He4 induced by nucleation on positive alkali ions in pressurized superfluid helium. The ions are extracted into the liquid from alkali-doped solid He by a static electric field. The experiments prove the existence of charged particles in a solid structure composed of doped He that was recently shown to coexist with superfluid helium below the He solidification pressure. This supports our earlier suggestion that the Coulomb interaction of positive ions surrounded by a solid He shell (snowballs) and electrons trapped in spherical cavities (electron bubbles), together with surface tension, is responsible for the stability of that structure against melting. We have determined the density of charges in the sample by two independent methods.

Investigation for the amorphous state of ER-34122, a dual 5-lipoxygenase/cyclooxygenase inhibitor with poor aqueous solubility, in HPMC solid dispersion prepared by the solvent evaporation method.

PubMed

Kushida, Ikuo; Gotoda, Masaharu

2013-10-01

ER-34122, a poorly water-soluble dual 5-lipoxygenase/cyclooxygenase inhibitor, exists as a crystalline form. According to an Oak Ridge thermal ellipsoid plot drawing, carbonyl oxygen O (5) makes an intermolecular hydrogen bond with the hydrogen bonded to N (3) in the crystal structure. The FTIR and the solid-state ¹³C NMR spectra suggest that the network is spread out in the amorphous state and the hydrogen bonding gets weaker than that in the crystalline phase, because the carbonyl signals significantly shift in both spectra. When amorphous ER-34122 was heated, crystallization occurred at around 140°C. Similar crystallization happened in the solid dispersion; however, the degree of crystallization was much lower than that observed in the pure amorphous material. Also, the DSC thermogram of the solid dispersion did not show any exothermic peaks implying crystallization. The heat of fusion (ΔHf) determined in the pure amorphous material was nearly equal to that for the crystalline form, whereas the ΔHf value obtained in the solid dispersion was less than a third of them. These data prove that crystallization of the amorphous form is dramatically restrained in the solid dispersion system. The carbonyl wavenumber shifts in the FTIR spectra indicate that the average hydrogen bond in the solid dispersion is lower than that in the pure amorphous material. Therefore, HPMC will suppress formation of the intermolecular network observed in ER-34122 crystal and preserve the amorphous state, which is thermodynamically less stable, in the solid dispersed system.

Amorphous and nanocrystalline luminescent Si and Ge obtained via a solid-state chemical metathesis synthesis route

NASA Astrophysics Data System (ADS)

McMillan, Paul F.; Gryko, Jan; Bull, Craig; Arledge, Richard; Kenyon, Anthony J.; Cressey, Barbara A.

2005-03-01

A new solid-state metathesis synthesis route was applied to obtain bulk samples of amorphous or microcrystalline Si and Ge. The method involves reaction of Zintl phases such as NaSi or NaGe, with ammonium or metal (e.g., CuCl, CoBr 2) halides. The driving force for the solid-state reaction is provided by the formation of alkali halides and the transition metals or metal silicides, or gaseous ammonia and hydrogen. The semiconductors were purified by washing to remove other solid products. The amorphous semiconductors were obtained in bulk form from reactions carried out at 200-300 °C. Syntheses at higher temperatures gave rise to microcrystalline semiconductors, or to micro-/nanocrystalline particles contained within the amorphous material. Similar crystalline/amorphous composites were obtained after heat treatment of bulk amorphous materials.

Orally Disintegrating Tablets Containing Melt Extruded Amorphous Solid Dispersion of Tacrolimus for Dissolution Enhancement.

PubMed

Ponnammal, Poovizhi; Kanaujia, Parijat; Yani, Yin; Ng, Wai Kiong; Tan, Reginald B H

2018-03-16

In order to improve the aqueous solubility and dissolution of Tacrolimus (TAC), amorphous solid dispersions of TAC were prepared by hot melt extrusion with three hydrophilic polymers, Polyvinylpyrrolidone vinyl acetate (PVP VA64), Soluplus ® and Hydroxypropyl Cellulose (HPC), at a drug loading of 10% w / w . Molecular modeling was used to determine the miscibility of the drug with the carrier polymers by calculating the Hansen Solubility Parameters. Powder X-ray diffraction and differential scanning calorimetry (DSC) studies of powdered solid dispersions revealed the conversion of crystalline TAC to amorphous form. Fourier transform Infrared (FTIR) spectroscopy results indicated formation of hydrogen bond between TAC and polymers leading to stabilization of TAC in amorphous form. The extrudates were found to be stable under accelerated storage conditions for 3 months with no re-crystallization, indicating that hot melt extrusion is suitable for producing stable amorphous solid dispersions of TAC in PVP VA64, Soluplus ® and HPC. Stable solid dispersions of amorphous TAC exhibited higher dissolution rate, with the solid dispersions releasing more than 80% drug in 15 min compared to the crystalline drug giving 5% drug release in two hours. These stable solid dispersions were incorporated into orally-disintegrating tablets in which the solid dispersion retained its solubility, dissolution and stability advantage.

Orally Disintegrating Tablets Containing Melt Extruded Amorphous Solid Dispersion of Tacrolimus for Dissolution Enhancement

PubMed Central

Ponnammal, Poovizhi; Kanaujia, Parijat; Ng, Wai Kiong; Tan, Reginald B. H.

2018-01-01

In order to improve the aqueous solubility and dissolution of Tacrolimus (TAC), amorphous solid dispersions of TAC were prepared by hot melt extrusion with three hydrophilic polymers, Polyvinylpyrrolidone vinyl acetate (PVP VA64), Soluplus® and Hydroxypropyl Cellulose (HPC), at a drug loading of 10% w/w. Molecular modeling was used to determine the miscibility of the drug with the carrier polymers by calculating the Hansen Solubility Parameters. Powder X-ray diffraction and differential scanning calorimetry (DSC) studies of powdered solid dispersions revealed the conversion of crystalline TAC to amorphous form. Fourier transform Infrared (FTIR) spectroscopy results indicated formation of hydrogen bond between TAC and polymers leading to stabilization of TAC in amorphous form. The extrudates were found to be stable under accelerated storage conditions for 3 months with no re-crystallization, indicating that hot melt extrusion is suitable for producing stable amorphous solid dispersions of TAC in PVP VA64, Soluplus® and HPC. Stable solid dispersions of amorphous TAC exhibited higher dissolution rate, with the solid dispersions releasing more than 80% drug in 15 min compared to the crystalline drug giving 5% drug release in two hours. These stable solid dispersions were incorporated into orally-disintegrating tablets in which the solid dispersion retained its solubility, dissolution and stability advantage. PMID:29547585

Methods of amorphization and investigation of the amorphous state.

PubMed

Einfal, Tomaž; Planinšek, Odon; Hrovat, Klemen

2013-09-01

The amorphous form of pharmaceutical materials represents the most energetic solid state of a material. It provides advantages in terms of dissolution rate and bioavailability. This review presents the methods of solid- -state amorphization described in literature (supercooling of liquids, milling, lyophilization, spray drying, dehydration of crystalline hydrates), with the emphasis on milling. Furthermore, we describe how amorphous state of pharmaceuticals differ depending on the method of preparation and how these differences can be screened by a variety of spectroscopic (X-ray powder diffraction, solid state nuclear magnetic resonance, atomic pairwise distribution, infrared spectroscopy, terahertz spectroscopy) and calorimetry methods.

New transformations between crystalline and amorphous ice

NASA Technical Reports Server (NTRS)

Hemley, R. J.; Chen, L. C.; Mao, H. K.

1989-01-01

High-pressure optical and spectroscopic techniques were used to obtain directly the ice I(h) - hda-ice transformation in a diamond-anvil cell, and the stability of the amorphous form is examined as functions of pressure and temperature. It is demonstrated that hda-ice transforms abruptly at 4 GPa and 77 K to a crystalline phase close in structure to orientationally disordered ice-VII and to a more highly ordered, ice-VIII-like structure at higher temperatures. This is the first time that an amorphous solid is observed to convert to a crystalline solid at low temperatures by compression alone. Phase transitions of this type may be relevant on icy planetary satellites, and there may also be implications for the high-pressure behavior of silica.

Deformation-induced localized solid-state amorphization in nanocrystalline nickel.

PubMed

Han, Shuang; Zhao, Lei; Jiang, Qing; Lian, Jianshe

2012-01-01

Although amorphous structures have been widely obtained in various multi-component metallic alloys, amorphization in pure metals has seldom been observed and remains a long-standing scientific curiosity and technological interest. Here we present experimental evidence of localized solid-state amorphization in bulk nanocrystalline nickel introduced by quasi-static compression at room temperature. High-resolution electron microscope observations illustrate that nano-scale amorphous structures present at the regions where severe deformation occurred, e.g. along crack paths or surrounding nano-voids. These findings have indicated that nanocrystalline structures are highly desirable for promoting solid-state amorphization, which may provide new insights for understanding the nature of the crystalline-to-amorphous transformation and suggested a potential method to produce elemental metallic glasses that have hardly been available hitherto through rapid solidification.

Deformation-induced localized solid-state amorphization in nanocrystalline nickel

PubMed Central

Han, Shuang; Zhao, Lei; Jiang, Qing; Lian, Jianshe

2012-01-01

Although amorphous structures have been widely obtained in various multi-component metallic alloys, amorphization in pure metals has seldom been observed and remains a long-standing scientific curiosity and technological interest. Here we present experimental evidence of localized solid-state amorphization in bulk nanocrystalline nickel introduced by quasi-static compression at room temperature. High-resolution electron microscope observations illustrate that nano-scale amorphous structures present at the regions where severe deformation occurred, e.g. along crack paths or surrounding nano-voids. These findings have indicated that nanocrystalline structures are highly desirable for promoting solid-state amorphization, which may provide new insights for understanding the nature of the crystalline-to-amorphous transformation and suggested a potential method to produce elemental metallic glasses that have hardly been available hitherto through rapid solidification. PMID:22768383

Amorphous and nanocrystalline luminescent Si and Ge obtained via a solid-state chemical metathesis synthesis route

DOE Office of Scientific and Technical Information (OSTI.GOV)

McMillan, Paul F.; Gryko, Jan; Bull, Craig

A new solid-state metathesis synthesis route was applied to obtain bulk samples of amorphous or microcrystalline Si and Ge. The method involves reaction of Zintl phases such as NaSi or NaGe, with ammonium or metal (e.g., CuCl, CoBr{sub 2}) halides. The driving force for the solid-state reaction is provided by the formation of alkali halides and the transition metals or metal silicides, or gaseous ammonia and hydrogen. The semiconductors were purified by washing to remove other solid products. The amorphous semiconductors were obtained in bulk form from reactions carried out at 200-300{sup o}C. Syntheses at higher temperatures gave rise tomore » microcrystalline semiconductors, or to micro-/nanocrystalline particles contained within the amorphous material. Similar crystalline/amorphous composites were obtained after heat treatment of bulk amorphous materials.« less

Search for supersolidity in solid 4He using multiple-mode torsional oscillators

PubMed Central

Eyal, Anna; Mi, Xiao; Talanov, Artem V.; Reppy, John D.

2016-01-01

In 2004, Kim and Chan (KC) reported a decrease in the period of torsional oscillators (TO) containing samples of solid 4He, as the temperature was lowered below 0.2 K [Kim E, Chan MHW (2004) Science 305(5692):1941–1944]. These unexpected results constituted the first experimental evidence that the long-predicted supersolid state of solid 4He may exist in nature. The KC results were quickly confirmed in a number of other laboratories and created great excitement in the low-temperature condensed-matter community. Since that time, however, it has become clear that the period shifts seen in the early experiments can in large part be explained by an increase in the shear modulus of the 4He solid identified by Day and Beamish [Day J, Beamish J (2007) Nature 450(7171):853–856]. Using multiple-frequency torsional oscillators, we can separate frequency-dependent period shifts arising from changes in the elastic properties of the solid 4He from possible supersolid signals, which are expected to be independent of frequency. We find in our measurements that as the temperature is lowered below 0.2 K, a clear frequency-dependent contribution to the period shift arising from changes in the 4He elastic properties is always present. For all of the cells reported in this paper, however, there is always an additional small frequency-independent contribution to the total period shift, such as would be expected in the case of a transition to a supersolid state. PMID:27222579

An improved kinetics approach to describe the physical stability of amorphous solid dispersions.

PubMed

Yang, Jiao; Grey, Kristin; Doney, John

2010-01-15

The recrystallization of amorphous solid dispersions may lead to a loss in the dissolution rate, and consequently reduce bioavailability. The purpose of this work is to understand factors governing the recrystallization of amorphous drug-polymer solid dispersions, and develop a kinetics model capable of accurately predicting their physical stability. Recrystallization kinetics was measured using differential scanning calorimetry for initially amorphous efavirenz-polyvinylpyrrolidone solid dispersions stored at controlled temperature and relative humidity. The experimental measurements were fitted by a new kinetic model to estimate the recrystallization rate constant and microscopic geometry of crystal growth. The new kinetics model was used to illustrate the governing factors of amorphous solid dispersions stability. Temperature was found to affect efavirenz recrystallization in an Arrhenius manner, while recrystallization rate constant was shown to increase linearly with relative humidity. Polymer content tremendously inhibited the recrystallization process by increasing the crystallization activation energy and decreasing the equilibrium crystallinity. The new kinetic model was validated by the good agreement between model fits and experiment measurements. A small increase in polyvinylpyrrolidone resulted in substantial stability enhancements of efavirenz amorphous solid dispersion. The new established kinetics model provided more accurate predictions than the Avrami equation.

Dislocation Mobility and Anomalous Shear Modulus Effect in ^4He Crystals

NASA Astrophysics Data System (ADS)

Malmi-Kakkada, Abdul N.; Valls, Oriol T.; Dasgupta, Chandan

2017-02-01

We calculate the dislocation glide mobility in solid ^4He within a model that assumes the existence of a superfluid field associated with dislocation lines. Prompted by the results of this mobility calculation, we study within this model the role that such a superfluid field may play in the motion of the dislocation line when a stress is applied to the crystal. To do this, we relate the damping of dislocation motion, calculated in the presence of the assumed superfluid field, to the shear modulus of the crystal. As the temperature increases, we find that a sharp drop in the shear modulus will occur at the temperature where the superfluid field disappears. We compare the drop in shear modulus of the crystal arising from the temperature dependence of the damping contribution due to the superfluid field, to the experimental observation of the same phenomena in solid ^4He and find quantitative agreement. Our results indicate that such a superfluid field plays an important role in dislocation pinning in a clean solid ^4He at low temperatures and in this regime may provide an alternative source for the unusual elastic phenomena observed in solid ^4He.

Electrical Characterization of Irradiated Semiconducting Amorphous Hydrogenated Boron Carbide

NASA Astrophysics Data System (ADS)

Peterson, George Glenn

Semiconducting amorphous partially dehydrogenated boron carbide has been explored as a neutron voltaic for operation in radiation harsh environments, such as on deep space satellites/probes. A neutron voltaic device could also be used as a solid state neutron radiation detector to provide immediate alerts for radiation workers/students, as opposed to the passive dosimetry badges utilized today. Understanding how the irradiation environment effects the electrical properties of semiconducting amorphous partially dehydrogenated boron carbide is important to predicting the stability of these devices in operation. p-n heterojunction diodes were formed from the synthesis of semiconducting amorphous partially dehydrogenated boron carbide on silicon substrates through the use of plasma enhanced chemical vapor deposition (PECVD). Many forms of structural and electrical measurements and analysis have been performed on the p-n heterojunction devices as a function of both He+ ion and neutron irradiation including: transmission electron microscopy (TEM), selected area electron diffraction (SAED), current versus voltage I(V), capacitance versus voltage C(V), conductance versus frequency G(f), and charge carrier lifetime (tau). In stark contrast to nearly all other electronic devices, the electrical performance of these p-n heterojunction diodes improved with irradiation. This is most likely the result of bond defect passivation and resolution of degraded icosahedral based carborane structures (icosahedral molecules missing a B, C, or H atom(s)).

A Molecular-Level View of the Physical Stability of Amorphous Solid Dispersions

NASA Astrophysics Data System (ADS)

Yuan, Xiaoda

Many pharmaceutical compounds being developed in recent years are poorly soluble in water. This has led to insufficient oral bioavailability of many compounds in vitro. The amorphous formulation is one of the promising techniques to increase the oral bioavailability of these poorly water-soluble compounds. However, an amorphous drug substance is inherently unstable because it is a high energy form. In order to increase the physical stability, the amorphous drug is often formulated with a suitable polymer to form an amorphous solid dispersion. Previous research has suggested that the formation of an intimately mixed drug-polymer mixture contributes to the stabilization of the amorphous drug compound. The goal of this research is to better understand the role of miscibility, molecular interactions and mobility on the physical stability of amorphous solid dispersions. Methods were developed to detect different degrees of miscibility on nanometer scale and to quantify the extent of hydrogen-bonding interactions between the drug and the polymer. Miscibility, hydrogen-bonding interactions and molecular mobility were correlated with physical stability during a six-month period using three model systems. Overall, this research provides molecular-level insights into many factors that govern the physical stability of amorphous solid dispersions which can lead to a more effective design of stable amorphous formulations.

Shape of Strained Solid He-4 at Low Temperatures

NASA Technical Reports Server (NTRS)

Kojima, Harry

2004-01-01

(1) Interferometer apparatus for measuring surface profile (2) For small strains, the expected linear decrease in height is not seen. (3) For large strains, undulation and irreversible deformations begin to set in, but we cannot yet make clear connection with stress-driven instability theory. Torii and Balibar have observed appearances of deformations beyond threshold stress on He-4 solid surface. The difference of our results from theory real? We are not ready to claim in affirmative. To be able to answer: 1) improve crystal growth techniques; (orientation, annealing, better pressure control) 2) improve homogeneity of stress; (better alignment with vertical, better understanding of interaction between solid He-4 and walls) 4) improve optics.

Compressibility determination by electrical resistance measurement: a universal method for both crystalline and amorphous solids

NASA Astrophysics Data System (ADS)

Yan, Xiaozhi; He, Duanwei; Xu, Chao; Ren, Xiangting; Zhou, Xiaoling; Liu, Shenzuo

2012-12-01

A new method is introduced for investigating the compressibility of solids under high pressure by in situ electrical resistance measurement of a manganin wire, which is wrapped around the sample. This method does not rely on the lattice parameters measurement, and the continuous volume change of the sample versus pressure can be obtained. Therefore, it is convenient to look at the compressibility of solids, especially for the X-ray diffraction amorphous materials. The I-II and II-III phase transition of Bi accompanying with volume change of 4.5% and 3.5% has been detected using the method, respectively, while the volume change for the phase transition of Tl occurring at 3.67 GPa is determined as 0.5%. The fit of the third-order Birch-Murnaghan equation of state to our data yields a zero-pressure bulk modulus K 0=28.98±0.03 GPa for NaCl and 6.97±0.02 GPa for amorphous red phosphorus.

Activation of weak IR fundamentals of two species of astrochemical interest in the T(d) point group--the importance of amorphous ices.

PubMed

Hudson, R L; Gerakines, P A; Loeffler, M J

2015-05-21

New measurements are reported on the weak ν1 and ν2 fundamentals of frozen CH4, a solid of considerable astrochemical interest. Infrared spectra in the ν1 and ν2 regions are presented for three CH4-ice phases at 10-30 K with new absorption coefficients and band strengths to quantify the results. In contrast to the situation with the two crystalline phases of CH4, both ν1 and ν2 were seen clearly in methane's amorphous phase. To support our CH4 work, we also present new results for NH4SH, a component of Jupiter's atmosphere, showing that the ν2 vibration of NH4(+) undergoes a dramatic loss of intensity during an amorphous-to-crystalline phase transition, but is regenerated in equally-dramatic fashion by radiation-induced amorphization of the sample. Results are compared to work recently published in this journal and elsewhere.

Effect of milling conditions on solid-state amorphization of glipizide, and characterization and stability of solid forms.

PubMed

Xu, Kailin; Xiong, Xinnuo; Zhai, Yuanming; Wang, Lili; Li, Shanshan; Yan, Jin; Wu, Di; Ma, Xiaoli; Li, Hui

2016-09-10

In this study, the amorphization of glipizide was systematically investigated through high-energy ball milling at different temperatures. The results of solid-state amorphization through milling indicated that glipizide underwent direct crystal-to-glass transformation at 15 and 25°C and crystal-to-glass-to-crystal conversion at 35°C; hence, milling time and temperature had significant effects on the amorphization of glipizide, which should be effectively controlled to obtain totally amorphous glipizide. Solid forms of glipizide were detailedly characterized through analyses of X-ray powder diffraction, morphology, thermal curves, vibrational spectra, and solid-state nuclear magnetic resonance. The physical stability of solid forms was investigated under different levels of relative humidity (RH) at 25°C. Forms I and III are kinetically stable and do not form any new solid-state forms at various RH levels. By contrast, Form II is kinetically unstable, undergoing direct glass-to-crystal transformation when RH levels higher than 32.8%. Therefore, stability investigation indicated that Form II should be stored under relatively dry conditions to prevent rapid crystallization. High temperatures can also induce the solid-state transformation of Form II; the conversion rate increased with increasing temperature. Copyright © 2016 Elsevier B.V. All rights reserved.

Neutron Time-of-Flight Diffractometer HIPPO at LANSCE

NASA Astrophysics Data System (ADS)

Vogel, Sven; Williams, Darrick; Zhao, Yusheng; Bennett, Kristin; von Dreele, Bob; Wenk, Hans-Rudolf

2004-03-01

The High-Pressure Preferred Orientation (HIPPO) neutron diffractometer is the first third-generation neutron time-of-flight powder diffractometer to be constructed in the United States. It produces extremely high intensity by virtue of a short (9 m) initial flight path on a high intensity water moderator and 1380 3He detector tubes covering 4.5 m2 of detector area from 10' to 150' in scattering angles. HIPPO was designed and manufactured as a joint effort between LANSCE and University of California with the goals of attaining world-class science and making neutron powder diffractometry an accessible and available tool to the national user community. Over two decades of momentum transfer are available (0.1-30 A-1) to support studies of amorphous solids; magnetic diffraction; small crystalline samples; and samples subjected to extreme environments such as temperature, pressure, or magnetic fields. The exceptionally high data rates of HIPPO also make it useful for time-resolved studies. In addition to the standard ancillary equipment (100-position sample/texture changer, closed-cycle He refrigerator, furnace), HIPPO has unique high-pressure cells capable of achieving pressures of 30 GPA at ambient and high (2000 K) temperature with samples up to 100 mm3 in volume.

Search for anisotropy in the Debye-Waller factor of HCP solid 4He

NASA Astrophysics Data System (ADS)

Barnes, Ashleigh L.; Hinde, Robert J.

2016-02-01

The properties of hexagonal close packed (hcp) solid 4He are dominated by large atomic zero point motions. An accurate description of these motions is therefore necessary in order to accurately calculate the properties of the system, such as the Debye-Waller (DW) factors. A recent neutron scattering experiment reported significant anisotropy in the in-plane and out-of-plane DW factors for hcp solid 4He at low temperatures, where thermal effects are negligible and only zero-point motions are expected to contribute. By contrast, no such anisotropy was observed either in earlier experiments or in path integral Monte Carlo (PIMC) simulations of solid hcp 4He. However, the earlier experiments and the PIMC simulations were both carried out at higher temperatures where thermal effects could be substantial. We seek to understand the cause of this discrepancy through variational quantum Monte Carlo simulations utilizing an accurate pair potential and a modified trial wavefunction which allows for anisotropy. Near the melting density, we find no anisotropy in an ideal hcp 4He crystal. A theoretical equation of state is derived from the calculated energies of the ideal crystal over a range of molar volumes from 7.88 to 21.3 cm3, and is found to be in good qualitative agreement with experimental data.

On the Nature of Disorder in Solid 4He

NASA Astrophysics Data System (ADS)

Krainyukova, N. V.

2010-02-01

We apply a modified Debye approach to calculate the Gibbs free energy for different structural phases and crystallite sizes in 4He. Atoms are assumed to interact via the Aziz potential. We have found that some intermediate (between hcp and bcc) phase predicted previously is more favorable than hcp at low temperatures and for small sizes. We show that it can exist in a wide pressure range up to 60 bar in 4He for crystallite sizes about 3,000 atoms. For larger sizes (10,000 atoms or more) this phase becomes unfavorable. In multidomain structures the intermediate phase competes with hcp and metastable fcc that can be a reason for disorder in solid 4He.

Highly solid-state emissive pyridinium-substituted tetraphenylethylene salts: emission color-tuning with counter anions and application for optical waveguides.

PubMed

Hu, Fang; Zhang, Guanxin; Zhan, Chi; Zhang, Wei; Yan, Yongli; Zhao, Yongsheng; Fu, Hongbing; Zhang, Deqing

2015-03-18

In this paper seven salts of pyridinium-substituted tetraphenylethylene with different anions are reported. They show typical aggregation-induced emission. Crystal structures of three of the salts with (CF(3)SO(2))(2) N(-), CF(3) SO(3)(-), and SbF(6)(-) as the respective counter anions, are determined. The emission behavior of their amorphous and crystalline solids is investigated. Both amorphous and crystalline solids, except for the one with I(-), are highly emissive. Certain amorphous solids are red-emissive with almost the same quantum yields and fluorescence life-times. However, some crystalline solids are found to show different emission colors varying from green to yellow. Thus, their emission colors can be tuned by the counter anions. Furthermore, certain crystalline solids are highly emissive compared to the respective amorphous solids. Such solid-state emission behavior of these pyridinium-substituted tetraphenylethylene salts is interpreted on the basis of their crystal structures. In addition, optical waveguiding behavior of fabricated microrods is presented. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Charging and Discharging of Amorphous Solid Water Ice: Effects of Porosity

NASA Astrophysics Data System (ADS)

Bu, Caixia; Baragiola, Raul A.

2015-11-01

Introduction: Amorphous solid water (ASW) is abundant on Saturn’s icy satellites and rings [1,2], where it is subject to bombardment of energetic ions, electrons, and photons; together with secondary electron and ion emission, this may leave the surfaces charged. Surface potential can affect the flux of incoming charged particles, altering surface evolution. We examined the role of porosity [3] on electrostatic charging and discharging of ASW films at 30-140 K.Experiment: Experiments were performed in ultra-high vacuum [4]. ASW films were deposited at 30 K onto a liquid-He-cooled quartz crystal microbalance (QCM). Film porosity was calculated from the areal mass via the QCM and thickness via a UV-visible interferometry. ASW films were charged at 30 K using 500 eV He+. Surface potentials (Vs) of the films were measured with a Kelvin probe, and infrared spectra were collected using a Fourier transform infrared spectrometer.Results: We measured Vs of the ASW film at 30 K as a function of ion fluence (F). The Vs(F) deviates from a straight line at low fluence, attributed to emitted secondary electrons due to the negative polarization voltage [5,6], and increases linearly when the Vs is positive. We also measured Vs as a function of annealing temperature. We prepared ASW films with various porosities by annealing the films to different temperatures (Ta) prior to irradiation or varying the vapor-beam incidence angle (θ). Upon heating, we observed sharp decreases of the Vs at temperatures that strongly depend on Ta and θ. Decreases of the infrared absorbance of the dangling OH bands of the charged film share similar trends as that of the Vs. We propose a model that includes porosity for electrostatic charging/discharging of ASW films at temperatures below 100 K. Results are applicable to the study of plasma-surface interactions of icy satellites and rings.References: [1] Jurac et al., J. Geophys. Res. 100, 14821 (1995); [2] A. L. Graps et al., Space Sci. Rev. 137, 435 (2008); [3] U. Raut et al., J. Chem. Phys. 127, 204713 (2007); [4] C. Bu and R. B. Baragiola, J. Chem. Phys. 143, 074702 (2015); [5] C. Bu et al., J. Chem. Phys. 142, 134702 (2015); [6] M. J. Iedema et al., J. Phys. Chem. B 102, 9203 (1998).

Solid state amorphization kinetic of alpha lactose upon mechanical milling.

PubMed

Caron, Vincent; Willart, Jean-François; Lefort, Ronan; Derollez, Patrick; Danède, Florence; Descamps, Marc

2011-11-29

It has been previously reported that α-lactose could be totally amorphized by ball milling. In this paper we report a detailed investigation of the structural and microstructural changes by which this solid state amorphization takes place. The investigations have been performed by Powder X-ray Diffraction, Solid State Nuclear Magnetic Resonance ((13)C CP-MAS) and Differential Scanning Calorimetry. The results reveal the structural complexity of the material in the course of its amorphization so that it cannot be considered as a simple mixture made of a decreasing crystalline fraction and an increasing amorphous fraction. Heating this complexity can give rise to a fully nano-crystalline material. The results also show that chemical degradations upon heating are strongly connected to the melting process. Copyright © 2011 Elsevier Ltd. All rights reserved.

Magnetomechanical coupling in thermal amorphous solids

NASA Astrophysics Data System (ADS)

Hentschel, H. George E.; Ilyin, Valery; Mondal, Chandana; Procaccia, Itamar

2018-05-01

Standard approaches to magnetomechanical interactions in thermal magnetic crystalline solids involve Landau functionals in which the lattice anisotropy and the resulting magnetization easy axes are taken explicitly into account. In glassy systems one needs to develop a theory in which the amorphous structure precludes the existence of an easy axis, and in which the constituent particles are free to respond to their local amorphous surroundings and the resulting forces. We present a theory of all the mixed responses of an amorphous solid to mechanical strains and magnetic fields. Atomistic models are proposed in which we test the predictions of magnetostriction for both bulk and nanofilm amorphous samples in the paramagnetic phase. The application to nanofilms with emergent self-affine free interfaces requires a careful definition of the film "width" and its change due to the magnetostriction effect.

Low frequency sonochemical synthesis of nanoporous amorphous manganese dioxide (MnO2) and adsorption of remazol reactive dye

NASA Astrophysics Data System (ADS)

Hasan, Siti Zubaidah; Yusop, Muhammad Rahimi; Othman, Mohamed Rozali

2015-09-01

Nanoporous amorphous-MnO2 was synthesized by sonochemical process (sonication) on the solid manganese (II) acetate tetrahydrate (Mn(CH3COO)2.4H2O) in 0.1 M KMnO4. The product was characterized by X-ray diffraction (XRD), morphology of the material was scanned by Field Emission Scanning Electron Microscopy (FE-SEM) and absorptions of MnO2 bonding was characterized by Fourier Transform Infra-Red Spectrometer (FT-IR). Remazol reactive dye or Red 3BS, was used in the adsorption study using nanoporous amorphous-MnO2. In batch experiment, 10 ppm of Remazol reactive dye was used and experiment was carried out at room temperature. Adsorption of Remazol dye on 0.2g synthesized nanoporous amorphous-MnO2 showed 99 - 100% decolorization.

Enhanced Physical Stability of Amorphous Drug Formulations via Dry Polymer Coating.

PubMed

Capece, Maxx; Davé, Rajesh

2015-06-01

Although amorphous solid drug formulations may be advantageous for enhancing the bioavailability of poorly soluble active pharmaceutical ingredients, they exhibit poor physical stability and undergo recrystallization. To address this limitation, this study investigates stability issues associated with amorphous solids through analysis of the crystallization behavior for acetaminophen (APAP), known as a fast crystallizer, using a modified form of the Avrami equation that kinetically models both surface and bulk crystallization. It is found that surface-enhanced crystallization, occurring faster at the free surface than in the bulk, is the major impediment to the stability of amorphous APAP. It is hypothesized that a novel use of a dry-polymer-coating process referred to as mechanical-dry-polymer-coating may be used to inhibit surface crystallization and enhance stability. The proposed process, which is examined, simultaneously mills and coats amorphous solids with polymer, while avoiding solvents or solutions, which may otherwise cause stability or crystallization issues during coating. It is shown that solid dispersions of APAP (64% loading) with a small particle size (28 μm) could be prepared and coated with the polymer, carnauba wax, in a vibratory ball mill. The resulting amorphous solid was found to have excellent stability as a result of inhibition of surface crystallization. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

Nanoscale amorphization of GeTe nanowire with conductive atomic force microscope.

PubMed

Kim, JunHo

2014-10-01

We fabricated GeTe nanowires by using Au catalysis mediated vapor-liquid-solid method. The fabricated nanowires were confirmed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. For a nanowire with - 150 nm diameter, we performed amorphization experiment with conductive atomic force microscope. We examined the structural change of the nanowire with several bias voltages from 0 V to 10 V. Above bias voltage of 6-7 V, some points of the nanowire showed transition to amorphous phase. The consumed energy for the amorphization was estimated to be 4-5 nJ, which was close to the other result of nanowire tested with a four probe device.

On Structure and Properties of Amorphous Materials

PubMed Central

Stachurski, Zbigniew H.

2011-01-01

Mechanical, optical, magnetic and electronic properties of amorphous materials hold great promise towards current and emergent technologies. We distinguish at least four categories of amorphous (glassy) materials: (i) metallic; (ii) thin films; (iii) organic and inorganic thermoplastics; and (iv) amorphous permanent networks. Some fundamental questions about the atomic arrangements remain unresolved. This paper focuses on the models of atomic arrangements in amorphous materials. The earliest ideas of Bernal on the structure of liquids were followed by experiments and computer models for the packing of spheres. Modern approach is to carry out computer simulations with prediction that can be tested by experiments. A geometrical concept of an ideal amorphous solid is presented as a novel contribution to the understanding of atomic arrangements in amorphous solids. PMID:28824158

Recent Progress in Studies of Nanostructured Impurity Helium Solids

NASA Astrophysics Data System (ADS)

Khmelenko, V. V.; Kunttu, H.; Lee, D. M.

2007-07-01

Impurity helium (Im He) solids are porous materials formed inside superfluid 4He by nanoclusters of impurities injected from the gas phase. The results of studies of these materials have relevance to soft condensed matter physics, matrix isolation of free radicals and low temperature chemistry. Recent studies by a variety of experimental techniques, including CW and pulse ESR, X-ray diffraction, ultrasound and Raman spectroscopy allow a better characterization of the properties of Im He solids. The structure of Im He solids, the trapping sites of stabilized atoms and the possible energy content of the samples are analyzed on the basis of experimental data. The kinetics of exchange tunneling reactions of hydrogen isotopes in nanoclusters and the changes of environment of the atoms during the course of these reactions are reviewed. Analysis of the ESR data shows that very large fraction of the stabilized atoms in Im He solids reside on the surfaces of impurity nanoclusters. The future directions for studying Im He solids are described. Among the most attractive are the studies of Im He solids with high concentrations of stabilized atoms at ultralow (10 20 mK) temperature for the observation of new collective quantum phenomena, the studies of practical application of Im He solids as a medium in neutron moderator for efficient production of ultracold (˜1 mK) neutrons, and the possibilities of obtaining high concentration of atomic nitrogen embedded in N2 clusters for energy storage.

The photoexcitation of crystalline ice and amorphous solid water: A molecular dynamics study of outcomes at 11 K and 125 K.

PubMed

Crouse, J; Loock, H-P; Cann, N M

2015-07-21

Photoexcitation of crystalline ice Ih and amorphous solid water at 7-9 eV is examined using molecular dynamics simulations and a fully flexible water model. The probabilities of photofragment desorption, trapping, and recombination are examined for crystalline ice at 11 K and at 125 K and for amorphous solid water at 11 K. For 11 K crystalline ice, a fully rigid water model is also employed for comparison. The kinetic energy of desorbed H atoms and the distance travelled by trapped fragments are correlated to the location and the local environment of the photoexcited water molecule. In all cases, H atom desorption is found to be the most likely outcome in the top bilayer while trapping of all photofragments is most probable deeper in the solid where the likelihood for recombination of the fragments into H2O molecules also rises. Trajectory analysis indicates that the local hydrogen bonding network in amorphous solid water is more easily distorted by a photodissociation event compared to crystalline ice. Also, simulations indicate that desorption of OH radicals and H2O molecules are more probable in amorphous solid water. The kinetic energy distributions for desorbed H atoms show a peak at high energy in crystalline ice, arising from photoexcited water molecules in the top monolayer. This peak is less pronounced in amorphous solid water. H atoms that are trapped may be displaced by up to ∼10 water cages, but migrate on average 3 water cages. Trapped OH fragments tend to stay near the original solvent cage.

In vitro characterization of a novel polymeric system for preparation of amorphous solid drug dispersions.

PubMed

Mahmoudi, Zahra N; Upadhye, Sampada B; Ferrizzi, David; Rajabi-Siahboomi, Ali R

2014-07-01

Preparation of amorphous solid dispersions using polymers is a commonly used formulation strategy for enhancing the solubility of poorly water-soluble drugs. However, often a single polymer may not bring about a significant enhancement in solubility or amorphous stability of a poorly water-soluble drug. This study describes application of a unique and novel binary polymeric blend in preparation of solid dispersions. The objective of this study was to investigate amorphous solid dispersions of glipizide, a BCS class II model drug, in a binary polymeric system of polyvinyl acetate phthalate (PVAP) and hypromellose (hydroxypropyl methylcellulose, HPMC). The solid dispersions were prepared using two different solvent methods: rotary evaporation (rotavap) and fluid bed drug layering on sugar spheres. The performance and physical stability of the dispersions were evaluated with non-sink dissolution testing, powder X-ray diffraction (PXRD), and modulated differential scanning calorimetry (mDSC). PXRD analysis demonstrated an amorphous state for glipizide, and mDSC showed no evidence of phase separation. Non-sink dissolution testing in pH 7.5 phosphate buffer indicated more than twofold increase in apparent solubility of the drug with PVAP-HPMC system. The glipizide solid dispersions demonstrated a high glass transition temperature (Tg) and acceptable chemical and physical stability during the stability period irrespective of the manufacturing process. In conclusion, the polymeric blend of PVAP-HPMC offers a unique formulation approach for developing amorphous solid dispersions with the flexibility towards the use of these polymers in different ratios and combined quantities depending on drug properties.

The utilization of drug-polymer interactions for improving the chemical stability of hot-melt extruded solid dispersions.

PubMed

Guo, Zhefei; Lu, Ming; Li, Yongcheng; Pang, Huishi; Lin, Ling; Liu, Xu; Wu, Chuanbin

2014-02-01

Interactions between drugs and polymers were utilized to lower the processing temperature of hot-melt extrusion (HME), and thus minimize the thermal degradation of heat-sensitive drugs during preparation of amorphous solid dispersions. Diflunisal (DIF), which would degrade upon melting, was selected as a model drug. Hydrogen bonds between DIF and polymeric carriers (PVP K30, PVP VA64, hydroxypropyl methylcellulose and Soluplus) were revealed by differential scanning calorimetry and Fourier transform infrared spectroscopy. The hot-melt extruded solid dispersion was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-performance liquid chromatography (HPLC). The results of hot-stage polar microscopy indicated that DIF was dissolved in molten polymers at 160°C, much lower than the melting point of DIF (215°C). At this temperature, amorphous solid dispersions were successfully produced by HME, as confirmed by XRD and SEM. The related impurities in amorphous solid dispersions detected by HPLC were lower than 0.3%, indicating that thermal degradation was effectively minimized. The dissolution of DIF from amorphous solid dispersions was significantly enhanced as compared with the pure crystalline drug. This technique based on drug-polymer interactions to prepare chemically stable amorphous solid dispersions by HME provides an attractive opportunity for development of heat-sensitive drugs. © 2013 Royal Pharmaceutical Society.

Relating hydrogen-bonding interactions with the phase behavior of naproxen/PVP K 25 solid dispersions: evaluation of solution-cast and quench-cooled films.

PubMed

Paudel, Amrit; Nies, Erik; Van den Mooter, Guy

2012-11-05

In this work, we investigated the relationship between various intermolecular hydrogen-bonding (H-bonding) interactions and the miscibility of the model hydrophobic drug naproxen with the hydrophilic polymer polyvinylpyrrolidone (PVP) across an entire composition range of solid dispersions prepared by quasi-equilibrium film casting and nonequilibrium melt quench cooling. The binary phase behavior in solid dispersions exhibited substantial processing method dependence. The solid state solubility of crystalline naproxen in PVP to form amorphous solid dispersions was 35% and 70% w/w naproxen in solution-cast films and quench-cooled films, respectively. However, the presence of a single mixed phase glass transition indicated the amorphous miscibility to be 20% w/w naproxen for the films, beyond which amorphous-amorphous and/or crystalline phase separations were apparent. This was further supported by the solution state interactions data such as PVP globular size distribution and solution infrared spectral profiles. The borderline melt composition showed cooling rate dependence of amorphization. The glass transition and melting point depression profiles of the system were treated with the analytical expressions based on Flory-Huggins mixing theory to interpolate the equilibrium solid solubility. FTIR analysis and subsequent spectral deconvolution revealed composition and miscibility dependent variations in the strength of drug-polymer intermolecular H-bonding. Two types of H-bonded populations were evidenced from 25% w/w and 35% w/w naproxen in solution-cast films and quench-cooled films, respectively, with the higher fraction of strongly H-bonded population in the drug rich domains of phase separated amorphous film compositions and highly drug loaded amorphous quench-cooled dispersions.

Physical stabilization of low-molecular-weight amorphous drugs in the solid state: a material science approach.

PubMed

Qi, Sheng; McAuley, William J; Yang, Ziyi; Tipduangta, Pratchaya

2014-07-01

Use of the amorphous state is considered to be one of the most effective approaches for improving the dissolution and subsequent oral bioavailability of poorly water-soluble drugs. However as the amorphous state has much higher physical instability in comparison with its crystalline counterpart, stabilization of amorphous drugs in a solid-dosage form presents a major challenge to formulators. The currently used approaches for stabilizing amorphous drug are discussed in this article with respect to their preparation, mechanism of stabilization and limitations. In order to realize the potential of amorphous formulations, significant efforts are required to enable the prediction of formulation performance. This will facilitate the development of computational tools that can inform a rapid and rational formulation development process for amorphous drugs.

Development of spray-dried co-precipitate of amorphous celecoxib containing storage and compression stabilizers.

PubMed

Dhumal, Ravindra S; Shimpi, Shamkant L; Paradkar, Anant R

2007-09-01

The purpose of this study was to obtain an amorphous system with minimum unit operations that will prevent recrystallization of amorphous drugs since preparation, during processing (compression) and further storage. Amorphous celecoxib, solid dispersion (SD) of celecoxib with polyvinyl pyrrollidone (PVP) and co-precipitate with PVP and carrageenan (CAR) in different ratios were prepared by the spray drying technique and compressed into tablets. Saturation solubility and dissolution studies were performed to differentiate performance after processing. Differential scanning calorimetry and X-ray powder difraction revealed the amorphous form of celecoxib, whereas infrared spectroscopy revealed hydrogen bonding between celecoxib and PVP. The dissolution profile of the solid dispersion and co-precipitate improved compared to celecoxib and amorphous celecoxib. Amorphous celecoxib was not stable on storage whereas the solid dispersion and co-precipitate powders were stable for 3 months. Tablets of the solid dispersion of celecoxib with PVP and physical mixture with PVP and carrageenan showed better resistance to recrystallization than amorphous celecoxib during compression but recrystallized on storage. However, tablets of co-precipitate with PVP and carageenan showed no evidence of crystallinity during stability studies with comparable dissolution profiles. This extraordinary stability of spray-dried co-precipitate tablets may be attributed to the cushioning action provided by the viscoelastic polymer CAR and hydrogen bonding interaction between celecoxib and PVP. The present study demonstrates the synergistic effect of combining two types of stabilizers, PVP and CAR, on the stability of amorphous drug during compression and storage as compared to their effect when used alone.

Characterization of Two Distinct Amorphous Forms of Valsartan by Solid-State NMR.

PubMed

Skotnicki, Marcin; Apperley, David C; Aguilar, Juan A; Milanowski, Bartłomiej; Pyda, Marek; Hodgkinson, Paul

2016-01-04

Valsartan (VAL) is an antihypertensive drug marketed in an amorphous form. Amorphous materials can have different physicochemical properties depending on preparation method, thermal history, etc., but the nature of such materials is difficult to study by diffraction techniques. This study characterizes two different amorphous forms of valsartan (AR and AM) using solid-state NMR (SSNMR) as a primary investigation tool, supported by solution-state NMR, FT-IR, TMDSC, and dissolution tests. The two forms are found to be clearly distinct, with a significantly higher level of structural arrangement in the AR form, as observed in (13)C, (15)N, and (1)H SSNMR. (13)C and (15)N NMR indicates that the fully amorphous material (AM) contains an approximately equal ratio of cis-trans conformers about the amide bond, whereas the AR form exists mainly as one conformer, with minor conformational "defects". (1)H ultrafast MAS NMR shows significant differences in the hydrogen bonding involving the tetrazole and acid hydrogens between the two materials, while (15)N NMR shows that both forms exist as a 1,2,3,4-tetrazole tautomer. NMR relaxation times show subtle differences in local and bulk molecular mobility, which can be connected with the glass transition, the stability of the glassy material, and its response to aging. Counterintuitively the fully amorphous material is found to have a significantly lower dissolution rate than the apparently more ordered AR material.

Low frequency sonochemical synthesis of nanoporous amorphous manganese dioxide (MnO{sub 2}) and adsorption of remazol reactive dye

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hasan, Siti Zubaidah; Yusop, Muhammad Rahimi; Othman, Mohamed Rozali, E-mail: rozali@ukm.edu.my

2015-09-25

Nanoporous amorphous-MnO{sub 2} was synthesized by sonochemical process (sonication) on the solid manganese (II) acetate tetrahydrate (Mn(CH{sub 3}COO){sub 2}.4H{sub 2}O) in 0.1 M KMnO{sub 4}. The product was characterized by X-ray diffraction (XRD), morphology of the material was scanned by Field Emission Scanning Electron Microscopy (FE-SEM) and absorptions of MnO{sub 2} bonding was characterized by Fourier Transform Infra-Red Spectrometer (FT-IR). Remazol reactive dye or Red 3BS, was used in the adsorption study using nanoporous amorphous-MnO{sub 2}. In batch experiment, 10 ppm of Remazol reactive dye was used and experiment was carried out at room temperature. Adsorption of Remazol dye onmore » 0.2g synthesized nanoporous amorphous-MnO{sub 2} showed 99 – 100% decolorization.« less

Connecting defects and amorphization in UiO-66 and MIL-140 metal–organic frameworks: a combined experimental and computational study.

PubMed

Bennett, Thomas D; Todorova, Tanya K; Baxter, Emma F; Reid, David G; Gervais, Christel; Bueken, Bart; Van de Voorde, B; De Vos, Dirk; Keen, David A; Mellot-Draznieks, Caroline

2016-01-21

The mechanism and products of the structural collapse of the metal–organic frameworks (MOFs) UiO-66, MIL-140B and MIL-140C upon ball-milling are investigated through solid state 13C NMR and pair distribution function (PDF) studies, finding amorphization to proceed by the breaking of a fraction of metal–ligand bonding in each case. The amorphous products contain inorganic–organic bonding motifs reminiscent of the crystalline phases. Whilst the inorganic Zr6O4(OH)4 clusters of UiO-66 remain intact upon structural collapse, the ZrO backbone of the MIL-140 frameworks undergoes substantial distortion. Density functional theory calculations have been performed to investigate defective models of MIL-140B and show, through comparison of calculated and experimental 13C NMR spectra, that amorphization and defects in the materials are linked.

Experimental study of the polyamorphism of water. I. The isobaric transitions from amorphous ices to LDA at 4 MPa.

PubMed

Handle, Philip H; Loerting, Thomas

2018-03-28

The existence of more than one solid amorphous state of water is an extraordinary feature. Since polyamorphism might be connected to the liquid-liquid critical point hypothesis, it is particularly important to study the relations amongst the different amorphous ices. Here we study the polyamorphic transformations of several high pressure amorphous ices to low-density amorphous ice (LDA) at 4 MPa by isobaric heating utilising in situ volumetry and ex situ X-ray diffraction. We find that very-high density amorphous ice (VHDA) and unannealed high density amorphous ice (HDA) show significant relaxation before transforming to LDA, whereby VHDA is seen to relax toward HDA. By contrast, expanded HDA shows almost no relaxation prior to the transformation. The transition to LDA itself obeys criteria for a first-order-like transition in all cases. In the case of VHDA, even macroscopic phase separation is observed. These findings suggest that HDA and LDA are two clearly distinct polyamorphs. We further present evidence that HDA reaches the metastable equilibrium at 140 K and 0.1 GPa but only comes close to that at 140 K and 0.2 GPa. The most important is the path independence of the amorphous phase reached at 140 K and 0.1 GPa.

Experimental study of the polyamorphism of water. I. The isobaric transitions from amorphous ices to LDA at 4 MPa

NASA Astrophysics Data System (ADS)

Handle, Philip H.; Loerting, Thomas

2018-03-01

The existence of more than one solid amorphous state of water is an extraordinary feature. Since polyamorphism might be connected to the liquid-liquid critical point hypothesis, it is particularly important to study the relations amongst the different amorphous ices. Here we study the polyamorphic transformations of several high pressure amorphous ices to low-density amorphous ice (LDA) at 4 MPa by isobaric heating utilising in situ volumetry and ex situ X-ray diffraction. We find that very-high density amorphous ice (VHDA) and unannealed high density amorphous ice (HDA) show significant relaxation before transforming to LDA, whereby VHDA is seen to relax toward HDA. By contrast, expanded HDA shows almost no relaxation prior to the transformation. The transition to LDA itself obeys criteria for a first-order-like transition in all cases. In the case of VHDA, even macroscopic phase separation is observed. These findings suggest that HDA and LDA are two clearly distinct polyamorphs. We further present evidence that HDA reaches the metastable equilibrium at 140 K and 0.1 GPa but only comes close to that at 140 K and 0.2 GPa. The most important is the path independence of the amorphous phase reached at 140 K and 0.1 GPa.

Formation and structure of Al-Zr metallic glasses studied by Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Li, J. H.; Zhao, S. Z.; Dai, Y.; Cui, Y. Y.; Liu, B. X.

2011-06-01

Based on the recently constructed n-body potential, both molecular dynamics and Monte Carlo simulations revealed that the Al-Zr amorphous alloy or metallic glass can be obtained within the composition range of 24-66 at. % Zr. The revealed composition range could be considered the intrinsic glass-forming range and it quantitatively indicates the glass-forming ability of the Al-Zr system. The underlying physics of the finding is that, within the composition range, the amorphous alloys are energetically favored to form. In addition, it is proposed that the energy difference between a solid solution and the amorphous phase could serve as the driving force of the crystalline to amorphous transition and the driving force should be sufficiently large for amorphization to take place. The minimum driving forces for fcc Al-based and hcp Zr-based Al-Zr solid solutions to amorphize are calculated to be about -0.05 and -0.03 eV/atom, respectively, whereas the maximum driving force is found to be -0.23 eV/atom at the alloy stoichiometry of Al60Zr40. A thermodynamics parameter γ¯, defined as the ratio of the driving force to the formation energy of the solid solution, is further proposed to indicate the glass-forming ability of an Al-Zr alloy. Thermodynamics calculations show that the glass-forming ability of the Al56Zr44 alloy is the largest, implying that the Al56Zr44 amorphous alloy is more ready to form than other alloys in the Al-Zr system. Besides, Voronoi analysis found that there exists a strong correlation between the coordinate number and structure. Amorphization could result in increase of coordinate numbers and about 1.5% volume-expansion. The volume-expansion induced by amorphization can be attributed to two factors, i.e., the total bond number of the Al-Zr amorphous phase is greater than that of the corresponding solid solution, and the averaged bond length of the Al-Zr amorphous phase is longer than that of the corresponding solid solution. For the Al-Zr alloys, especially for the Al-Zr amorphous phase, there exists a negative chemical micro-inhomogeneity in the alloys, suggesting that metallic bonds prefer to be formed between the atoms of dissimilar species. Finally, it is found that there is a weak correspondence between the bond-angle distributions of Al-Zr amorphous alloys and the solid solutions. It is further suggested that the configuration of Al-Zr amorphous alloys embodies some hybrid imprint of bcc, fcc, and hcp structures. More interestingly, the short-range order is also observed in the bond-angle distributions.

Continuum limit of the vibrational properties of amorphous solids.

PubMed

Mizuno, Hideyuki; Shiba, Hayato; Ikeda, Atsushi

2017-11-14

The low-frequency vibrational and low-temperature thermal properties of amorphous solids are markedly different from those of crystalline solids. This situation is counterintuitive because all solid materials are expected to behave as a homogeneous elastic body in the continuum limit, in which vibrational modes are phonons that follow the Debye law. A number of phenomenological explanations for this situation have been proposed, which assume elastic heterogeneities, soft localized vibrations, and so on. Microscopic mean-field theories have recently been developed to predict the universal non-Debye scaling law. Considering these theoretical arguments, it is absolutely necessary to directly observe the nature of the low-frequency vibrations of amorphous solids and determine the laws that such vibrations obey. Herein, we perform an extremely large-scale vibrational mode analysis of a model amorphous solid. We find that the scaling law predicted by the mean-field theory is violated at low frequency, and in the continuum limit, the vibrational modes converge to a mixture of phonon modes that follow the Debye law and soft localized modes that follow another universal non-Debye scaling law.

Continuum limit of the vibrational properties of amorphous solids

PubMed Central

Mizuno, Hideyuki; Ikeda, Atsushi

2017-01-01

The low-frequency vibrational and low-temperature thermal properties of amorphous solids are markedly different from those of crystalline solids. This situation is counterintuitive because all solid materials are expected to behave as a homogeneous elastic body in the continuum limit, in which vibrational modes are phonons that follow the Debye law. A number of phenomenological explanations for this situation have been proposed, which assume elastic heterogeneities, soft localized vibrations, and so on. Microscopic mean-field theories have recently been developed to predict the universal non-Debye scaling law. Considering these theoretical arguments, it is absolutely necessary to directly observe the nature of the low-frequency vibrations of amorphous solids and determine the laws that such vibrations obey. Herein, we perform an extremely large-scale vibrational mode analysis of a model amorphous solid. We find that the scaling law predicted by the mean-field theory is violated at low frequency, and in the continuum limit, the vibrational modes converge to a mixture of phonon modes that follow the Debye law and soft localized modes that follow another universal non-Debye scaling law. PMID:29087941

High-temperature supersolid of He 4 in a one-dimensional periodic potential

DOE PAGES

Olsen, Raina J.

2015-03-02

The search for robust experimental proof of supersolidity has encountered many complicating factors, such as temperature dependent changes in the mechanical properties of solid 4He which mimic the signature of superfluid flow. As a result, the physical existence and true nature of this unique state of matter are still under debate. Here we consider 4He stabilized by a one-dimensional periodic potential whose lattice spacing is similar to the length scale of the 4He- 4He interaction. We use the Bogoliubov transformation to calculate the excitation spectrum, finding that when interactions between nearest or next-nearest neighbors are attractive, there is a finitemore » positive gap in energy between the delocalized ground state and the lowest energy excitations which, under certain conditions, is significantly larger than both the melting temperature and the lambda temperature. This means that it should be possible to observe a supersolid at a high enough temperature that superfluidity in bulk liquid 4He or changes in the mechanical properties of bulk solid 4He do not obscure it. Lastly, we also discuss the properties of experimentally achievable materials which could support this type of supersolid.« less

Ion irradiation damage in ilmenite at 100 K

USGS Publications Warehouse

Mitchell, J.N.; Yu, N.; Devanathan, R.; Sickafus, K.E.; Nastasi, M.A.; Nord, G.L.

1997-01-01

A natural single crystal of ilmenite (FeTiO3) was irradiated at 100 K with 200 keV Ar2+. Rutherford backscattering spectroscopy and ion channeling with 2 MeV He+ ions were used to monitor damage accumulation in the surface region of the implanted crystal. At an irradiation fluence of 1 ?? 1015 Ar2+/cm2, considerable near-surface He+ ion dechanneling was observed, to the extent that ion yield from a portion of the aligned crystal spectrum reached the yield level of a random spectrum. This observation suggests that the near-surface region of the crystal was amorphized by the implantation. Cross-sectional transmission electron microscopy and electron diffraction on this sample confirmed the presence of a 150 nm thick amorphous layer. These results are compared to similar investigations on geikielite (MgTiO3) and spinel (MgAl2O4) to explore factors that may influence radiation damage response in oxides.

Black GE based on crystalline/amorphous core/shell nanoneedle arrays

DOEpatents

Javey, Ali; Chueh, Yu-Lun; Fan, Zhiyong

2014-03-04

Direct growth of black Ge on low-temperature substrates, including plastics and rubber is reported. The material is based on highly dense, crystalline/amorphous core/shell Ge nanoneedle arrays with ultrasharp tips (.about.4 nm) enabled by the Ni catalyzed vapor-solid-solid growth process. Ge nanoneedle arrays exhibit remarkable optical properties. Specifically, minimal optical reflectance (<1%) is observed, even for high angles of incidence (.about.75.degree.) and for relatively short nanoneedle lengths (.about.1 .mu.m). Furthermore, the material exhibits high optical absorption efficiency with an effective band gap of .about.1 eV. The reported black Ge can have important practical implications for efficient photovoltaic and photodetector applications on nonconventional substrates.

The photoexcitation of crystalline ice and amorphous solid water: A molecular dynamics study of outcomes at 11 K and 125 K

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crouse, J.; Loock, H.-P., E-mail: hploock@chem.queensu.ca; Cann, N. M., E-mail: ncann@chem.queensu.ca

2015-07-21

Photoexcitation of crystalline ice Ih and amorphous solid water at 7-9 eV is examined using molecular dynamics simulations and a fully flexible water model. The probabilities of photofragment desorption, trapping, and recombination are examined for crystalline ice at 11 K and at 125 K and for amorphous solid water at 11 K. For 11 K crystalline ice, a fully rigid water model is also employed for comparison. The kinetic energy of desorbed H atoms and the distance travelled by trapped fragments are correlated to the location and the local environment of the photoexcited water molecule. In all cases, H atommore » desorption is found to be the most likely outcome in the top bilayer while trapping of all photofragments is most probable deeper in the solid where the likelihood for recombination of the fragments into H{sub 2}O molecules also rises. Trajectory analysis indicates that the local hydrogen bonding network in amorphous solid water is more easily distorted by a photodissociation event compared to crystalline ice. Also, simulations indicate that desorption of OH radicals and H{sub 2}O molecules are more probable in amorphous solid water. The kinetic energy distributions for desorbed H atoms show a peak at high energy in crystalline ice, arising from photoexcited water molecules in the top monolayer. This peak is less pronounced in amorphous solid water. H atoms that are trapped may be displaced by up to ∼10 water cages, but migrate on average 3 water cages. Trapped OH fragments tend to stay near the original solvent cage.« less

Improved Vemurafenib Dissolution and Pharmacokinetics as an Amorphous Solid Dispersion Produced by KinetiSol® Processing.

PubMed

Ellenberger, Daniel J; Miller, Dave A; Kucera, Sandra U; Williams, Robert O

2018-03-14

Vemurafenib is a poorly soluble, low permeability drug that has a demonstrated need for a solubility-enhanced formulation. However, conventional approaches for amorphous solid dispersion production are challenging due to the physiochemical properties of the compound. A suitable and novel method for creating an amorphous solid dispersion, known as solvent-controlled coprecipitation, was developed to make a material known as microprecipitated bulk powder (MBP). However, this approach has limitations in its processing and formulation space. In this study, it was hypothesized that vemurafenib can be processed by KinetiSol into the same amorphous formulation as MBP. The KinetiSol process utilizes high shear to rapidly process amorphous solid dispersions containing vemurafenib. Analysis of the material demonstrated that KinetiSol produced amorphous, single-phase material with acceptable chemical purity and stability. Values obtained were congruent to analysis conducted on the comparator material. However, the materials differed in particle morphology as the KinetiSol material was dense, smooth, and uniform while the MBP comparator was porous in structure and exhibited high surface area. The particles produced by KinetiSol had improved in-vitro dissolution and pharmacokinetic performance for vemurafenib compared to MBP due to slower drug nucleation and recrystallization which resulted in superior supersaturation maintenance during drug release. In the in-vivo rat pharmacokinetic study, both amorphous solid dispersions produced by KinetiSol exhibited mean AUC values at least two-fold that of MBP when dosed as a suspension. It was concluded that the KinetiSol process produced superior dosage forms containing vemurafenib with the potential for substantial reduction in patient pill burden.

Variable-amplitude oscillatory shear response of amorphous materials.

PubMed

Perchikov, Nathan; Bouchbinder, Eran

2014-06-01

Variable-amplitude oscillatory shear tests are emerging as powerful tools to investigate and quantify the nonlinear rheology of amorphous solids, complex fluids, and biological materials. Quite a few recent experimental and atomistic simulation studies demonstrated that at low shear amplitudes, an amorphous solid settles into an amplitude- and initial-conditions-dependent dissipative limit cycle, in which back-and-forth localized particle rearrangements periodically bring the system to the same state. At sufficiently large shear amplitudes, the amorphous system loses memory of the initial conditions, exhibits chaotic particle motions accompanied by diffusive behavior, and settles into a stochastic steady state. The two regimes are separated by a transition amplitude, possibly characterized by some critical-like features. Here we argue that these observations support some of the physical assumptions embodied in the nonequilibrium thermodynamic, internal-variables based, shear-transformation-zone model of amorphous viscoplasticity; most notably that "flow defects" in amorphous solids are characterized by internal states between which they can make transitions, and that structural evolution is driven by dissipation associated with plastic deformation. We present a rather extensive theoretical analysis of the thermodynamic shear-transformation-zone model for a variable-amplitude oscillatory shear protocol, highlighting its success in accounting for various experimental and simulational observations, as well as its limitations. Our results offer a continuum-level theoretical framework for interpreting the variable-amplitude oscillatory shear response of amorphous solids and may promote additional developments.

Enabling thermal processing of ritonavir-polyvinyl alcohol amorphous solid dispersions by KinetiSol® Dispersing.

PubMed

LaFountaine, Justin S; Jermain, Scott V; Prasad, Leena Kumari; Brough, Chris; Miller, Dave A; Lubda, Dieter; McGinity, James W; Williams, Robert O

2016-04-01

Polyvinyl alcohol has received little attention as a matrix polymer in amorphous solid dispersions (ASDs) due to its thermal and rheological limitations in extrusion processing and limited organic solubility in spray drying applications. Additionally, in extrusion processing, the high temperatures required to process often exclude thermally labile APIs. The purpose of this study was to evaluate the feasibility of processing polyvinyl alcohol amorphous solid dispersions utilizing the model compound ritonavir with KinetiSol® Dispersing (KSD) technology. The effects of KSD rotor speed and ejection temperature on the physicochemical properties of the processed material were evaluated. Powder X-ray diffraction and modulated differential scanning calorimetry were used to confirm amorphous conversion. Liquid chromatography-mass spectroscopy was used to characterize and identify degradation pathways of ritonavir during KSD processing and (13)C nuclear magnetic resonance spectroscopy was used to investigate polymer stability. An optimal range of processing conditions was found that resulted in amorphous product and minimal to no drug and polymer degradation. Drug release of the ASD produced from the optimal processing conditions was evaluated using a non-sink, pH-shift dissolution test. The ability to process amorphous solid dispersions with polyvinyl alcohol as a matrix polymer will enable further investigations of the polymer's performance in amorphous systems for poorly water-soluble compounds. Copyright © 2016 Elsevier B.V. All rights reserved.

Melt Extrusion of High-Dose Co-Amorphous Drug-Drug Combinations : Theme: Formulation and Manufacturing of Solid Dosage Forms Guest Editors: Tony Zhou and Tonglei Li.

PubMed

Arnfast, Lærke; Kamruzzaman, Md; Löbmann, Korbinian; Aho, Johanna; Baldursdottir, Stefania; Rades, Thomas; Rantanen, Jukka

2017-12-01

Many future drug products will be based on innovative manufacturing solutions, which will increase the need for a thorough understanding of the interplay between drug material properties and processability. In this study, hot melt extrusion of a drug-drug mixture with minimal amount of polymeric excipient was investigated. Using indomethacin-cimetidine as a model drug-drug system, processability of physical mixtures with and without 5% (w/w) of polyethylene oxide (PEO) were studied using Differential Scanning Calorimetry (DSC) and Small Amplitude Oscillatory Shear (SAOS) rheometry. Extrudates containing a co-amorphous glass solution were produced and the solid-state composition of these was studied with DSC. Rheological analysis indicated that the studied systems display viscosities higher than expected for small molecule melts and addition of PEO decreased the viscosity of the melt. Extrudates of indomethacin-cimetidine alone displayed amorphous-amorphous phase separation after 4 weeks of storage, whereas no phase separation was observed during the 16 week storage of the indomethacin-cimetidine extrudates containing 5% (w/w) PEO. Melt extrusion of co-amorphous extrudates with low amounts of polymer was found to be a feasible manufacturing technique. Addition of 5% (w/w) polymer reduced melt viscosity and prevented phase separation.

Study of the solid-state amorphization of (GaSb){sub 1-x}Ge{sub x} semiconductors by real-time neutron diffraction and electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fedotov, V. K., E-mail: fedotov@issp.ac.ru; Ponyatovsky, E. G.

2011-12-15

The spontaneous amorphization of high-pressure quenched phases of the GaSb-Ge system has been studied by neutron diffraction while slowly heating the phases at atmospheric pressure. The sequence of changes in the structural parameters of the initial crystalline phase and the final amorphous phase is established. The behavior of the phases and the correlation in the structural features of the phase transitions and anomalous thermal effects exhibit signs of the inhomogeneous model of solid-state amorphization.

Photoluminescence spectral reliance on aggregation order of 1,1-Bis(2'-thienyl)-2,3,4,5-tetraphenylsilole.

PubMed

Chen, Junwu; Xu, Bin; Yang, Kaixia; Cao, Yong; Sung, Herman H Y; Williams, Ian D; Tang, Ben Zhong

2005-09-15

1,1-Bis(2'-thienyl)-2,3,4,5-tetraphenylsilole (1) was prepared and characterized crystallographically. Silole 1 exhibited aggregation-induced emission (AIE) behavior like other 2,3,4,5-tetraphenylsiloles. Unexpectedly, aggregates formed in water/acetone (6:4 by volume) mixture emitted a blue light that peaked at 474 nm, while aggregates formed in the mixtures with higher water fractions emitted green light that peaked at 500 nm. Transmission electron microscopy demonstrated that the aggregates formed in the mixture with water fraction of 60% were single crystals, while aggregates that formed in the mixture with water fraction of 90% were irregular and poorly ordered particles. The unusual PL spectral reliance on aggregation order was further confirmed by PL emissions of macroscopic crystal powders and amorphous powders of the silole in the dry state. PL spectral blue shifting was observed upon aging of the poorly ordered aggregates formed in mixtures with water fractions of 70-90%, and they finally exhibited the same blue emission as the crystalline aggregates. The as-deposited thin solid film was amorphous and it could be transformed to a transparent crystalline film upon treatment in the vapor of an ethanol/water (1:1 by volume) mixture, along with PL spectral blue shifting due to changing of aggregation order. It was also found that the crystalline film showed a blue-shifted absorption spectrum relative to the amorphous film and the shift of the absorption edge of the spectra could match that of corresponding PL spectra. The FT-IR spectrum of crystal powders of 1 displayed more vibration modes compared with that of amorphous powders, suggesting the existence of different pi-overlaps or different molecular conformations. The crystals of 1-methyl-1,2,3,4,5-pentaphenylsilole and hexaphenylsilole also showed blue-shifted PL emissions of their amorphous solids, with a comparable PL spectral shift of 1. Developing of a silole solution on a TLC plate readily brought about an amorphous thin layer. Our results suggest that crystalline films of AIE-active siloles are potential emissive layers for efficient blue OLEDs with stable color and long lifetime.

Multivariate Quantification of the Solid State Phase Composition of Co-Amorphous Naproxen-Indomethacin.

PubMed

Beyer, Andreas; Grohganz, Holger; Löbmann, Korbinian; Rades, Thomas; Leopold, Claudia S

2015-10-27

To benefit from the optimized dissolution properties of active pharmaceutical ingredients in their amorphous forms, co-amorphisation as a viable tool to stabilize these amorphous phases is of both academic and industrial interest. Reports dealing with the physical stability and recrystallization behavior of co-amorphous systems are however limited to qualitative evaluations based on the corresponding X-ray powder diffractograms. Therefore, the objective of the study was to develop a quantification model based on X-ray powder diffractometry (XRPD), followed by a multivariate partial least squares regression approach that enables the simultaneous determination of up to four solid state fractions: crystalline naproxen, γ-indomethacin, α-indomethacin as well as co-amorphous naproxen-indomethacin. For this purpose, a calibration set that covers the whole range of possible combinations of the four components was prepared and analyzed by XRPD. In order to test the model performances, leave-one-out cross validation was performed and revealed root mean square errors of validation between 3.11% and 3.45% for the crystalline molar fractions and 5.57% for the co-amorphous molar fraction. In summary, even four solid state phases, involving one co-amorphous phase, can be quantified with this XRPD data-based approach.

Coplanar amorphous-indium-gallium-zinc-oxide thin film transistor with He plasma treated heavily doped layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeong, Ho-young; LG Display R and D Center, 245 Lg-ro, Wollong-myeon, Paju-si, Gyeonggi-do 413-811; Lee, Bok-young

We report thermally stable coplanar amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) with heavily doped n{sup +} a-IGZO source/drain regions. Doping is through He plasma treatment in which the resistivity of the a-IGZO decreases from 2.98 Ω cm to 2.79 × 10{sup −3} Ω cm after treatment, and then it increases to 7.92 × 10{sup −2} Ω cm after annealing at 300 °C. From the analysis of X-ray photoelectron spectroscopy, the concentration of oxygen vacancies in He plasma treated n{sup +}a-IGZO does not change much after thermal annealing at 300 °C, indicating thermally stable n{sup +} a-IGZO, even for TFTs with channel length L = 4 μm. Field-effect mobility of the coplanar a-IGZO TFTsmore » with He plasma treatment changes from 10.7 to 9.2 cm{sup 2}/V s after annealing at 300 °C, but the performance of the a-IGZO TFT with Ar or H{sub 2} plasma treatment degrades significantly after 300 °C annealing.« less

In Situ and Ex Situ TEM Study of Lithiation Behaviours of Porous Silicon Nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Chenfei; Ge, Mingyuan; Luo, Langli

Here in this work, we study the lithiation behaviours of both porous silicon (Si) nanoparticles and porous Si nanowires by in situ and ex situ transmission electron microscopy (TEM) and compare them with solid Si nanoparticles and nanowires. The in situ TEM observation reveals that the critical fracture diameter of porous Si particles reaches up to 1.52 μm, which is much larger than the previously reported 150 nm for crystalline Si nanoparticles and 870 nm for amorphous Si nanoparticles. After full lithiation, solid Si nanoparticles and nanowires transform to crystalline Li 15Si 4 phase while porous Si nanoparticles and nanowiresmore » transform to amorphous Li xSi phase, which is due to the effect of domain size on the stability of Li 15Si 4 as revealed by the first-principle molecular dynamic simulation. Ex situ TEM characterization is conducted to further investigate the structural evolution of porous and solid Si nanoparticles during the cycling process, which confirms that the porous Si nanoparticles exhibit better capability to suppress pore evolution than solid Si nanoparticles. The investigation of structural evolution and phase transition of porous Si nanoparticles and nanowires during the lithiation process reveal that they are more desirable as lithium-ion battery anode materials than solid Si nanoparticles and nanowires.« less

In Situ and Ex Situ TEM Study of Lithiation Behaviours of Porous Silicon Nanostructures

NASA Astrophysics Data System (ADS)

Shen, Chenfei; Ge, Mingyuan; Luo, Langli; Fang, Xin; Liu, Yihang; Zhang, Anyi; Rong, Jiepeng; Wang, Chongmin; Zhou, Chongwu

2016-08-01

In this work, we study the lithiation behaviours of both porous silicon (Si) nanoparticles and porous Si nanowires by in situ and ex situ transmission electron microscopy (TEM) and compare them with solid Si nanoparticles and nanowires. The in situ TEM observation reveals that the critical fracture diameter of porous Si particles reaches up to 1.52 μm, which is much larger than the previously reported 150 nm for crystalline Si nanoparticles and 870 nm for amorphous Si nanoparticles. After full lithiation, solid Si nanoparticles and nanowires transform to crystalline Li15Si4 phase while porous Si nanoparticles and nanowires transform to amorphous LixSi phase, which is due to the effect of domain size on the stability of Li15Si4 as revealed by the first-principle molecular dynamic simulation. Ex situ TEM characterization is conducted to further investigate the structural evolution of porous and solid Si nanoparticles during the cycling process, which confirms that the porous Si nanoparticles exhibit better capability to suppress pore evolution than solid Si nanoparticles. The investigation of structural evolution and phase transition of porous Si nanoparticles and nanowires during the lithiation process reveal that they are more desirable as lithium-ion battery anode materials than solid Si nanoparticles and nanowires.

In Situ and Ex Situ TEM Study of Lithiation Behaviours of Porous Silicon Nanostructures

PubMed Central

Shen, Chenfei; Ge, Mingyuan; Luo, Langli; Fang, Xin; Liu, Yihang; Zhang, Anyi; Rong, Jiepeng; Wang, Chongmin; Zhou, Chongwu

2016-01-01

In this work, we study the lithiation behaviours of both porous silicon (Si) nanoparticles and porous Si nanowires by in situ and ex situ transmission electron microscopy (TEM) and compare them with solid Si nanoparticles and nanowires. The in situ TEM observation reveals that the critical fracture diameter of porous Si particles reaches up to 1.52 μm, which is much larger than the previously reported 150 nm for crystalline Si nanoparticles and 870 nm for amorphous Si nanoparticles. After full lithiation, solid Si nanoparticles and nanowires transform to crystalline Li15Si4 phase while porous Si nanoparticles and nanowires transform to amorphous LixSi phase, which is due to the effect of domain size on the stability of Li15Si4 as revealed by the first-principle molecular dynamic simulation. Ex situ TEM characterization is conducted to further investigate the structural evolution of porous and solid Si nanoparticles during the cycling process, which confirms that the porous Si nanoparticles exhibit better capability to suppress pore evolution than solid Si nanoparticles. The investigation of structural evolution and phase transition of porous Si nanoparticles and nanowires during the lithiation process reveal that they are more desirable as lithium-ion battery anode materials than solid Si nanoparticles and nanowires. PMID:27571919

In Situ and Ex Situ TEM Study of Lithiation Behaviours of Porous Silicon Nanostructures

DOE PAGES

Shen, Chenfei; Ge, Mingyuan; Luo, Langli; ...

2016-08-30

Here in this work, we study the lithiation behaviours of both porous silicon (Si) nanoparticles and porous Si nanowires by in situ and ex situ transmission electron microscopy (TEM) and compare them with solid Si nanoparticles and nanowires. The in situ TEM observation reveals that the critical fracture diameter of porous Si particles reaches up to 1.52 μm, which is much larger than the previously reported 150 nm for crystalline Si nanoparticles and 870 nm for amorphous Si nanoparticles. After full lithiation, solid Si nanoparticles and nanowires transform to crystalline Li 15Si 4 phase while porous Si nanoparticles and nanowiresmore » transform to amorphous Li xSi phase, which is due to the effect of domain size on the stability of Li 15Si 4 as revealed by the first-principle molecular dynamic simulation. Ex situ TEM characterization is conducted to further investigate the structural evolution of porous and solid Si nanoparticles during the cycling process, which confirms that the porous Si nanoparticles exhibit better capability to suppress pore evolution than solid Si nanoparticles. The investigation of structural evolution and phase transition of porous Si nanoparticles and nanowires during the lithiation process reveal that they are more desirable as lithium-ion battery anode materials than solid Si nanoparticles and nanowires.« less

Solid state amorphization of nanocrystalline nickel by cryogenic laser shock peening

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Chang, E-mail: cye@uakron.edu; Ren, Zhencheng; Zhao, Jingyi

2015-10-07

In this study, complete solid state amorphization in nanocrystalline nickel has been achieved through cryogenic laser shock peening (CLSP). High resolution transmission electron microscopy has revealed the complete amorphous structure of the sample after CLSP processing. A molecular dynamic model has been used to investigate material behavior during the shock loading and the effects of nanoscale grain boundaries on the amorphization process. It has been found that the initial nanoscale grain boundaries increase the initial Gibbs free energy before plastic deformation and also serve as dislocation emission sources during plastic deformation to contribute to defect density increase, leading to themore » amorphization of pure nanocrystalline nickel.« less

In situ observation of shear-driven amorphization in silicon crystals.

PubMed

He, Yang; Zhong, Li; Fan, Feifei; Wang, Chongmin; Zhu, Ting; Mao, Scott X

2016-10-01

Amorphous materials are used for both structural and functional applications. An amorphous solid usually forms under driven conditions such as melt quenching, irradiation, shock loading or severe mechanical deformation. Such extreme conditions impose significant challenges on the direct observation of the amorphization process. Various experimental techniques have been used to detect how the amorphous phases form, including synchrotron X-ray diffraction, transmission electron microscopy (TEM) and Raman spectroscopy, but a dynamic, atomistic characterization has remained elusive. Here, by using in situ high-resolution TEM (HRTEM), we show the dynamic amorphization process in silicon nanocrystals during mechanical straining on the atomic scale. We find that shear-driven amorphization occurs in a dominant shear band starting with the diamond-cubic (dc) to diamond-hexagonal (dh) phase transition and then proceeds by dislocation nucleation and accumulation in the newly formed dh-Si phase. This process leads to the formation of an amorphous Si (a-Si) band, embedded with dh-Si nanodomains. The amorphization of dc-Si via an intermediate dh-Si phase is a previously unknown pathway of solid-state amorphization.

Amorphous solid dispersion of cyclosporine A prepared with fine droplet drying process: Physicochemical and pharmacokinetic characterization.

PubMed

Suzuki, Hiroki; Moritani, Tatsuru; Morinaga, Tadahiko; Seto, Yoshiki; Sato, Hideyuki; Onoue, Satomi

2017-03-15

The present study aimed to develop an amorphous solid dispersion (ASD) of cyclosporine A (CsA) by a fine droplet drying (FDD) process for improvement in oral absorption of CsA. CsA and hydroxypropyl cellulose-SSL were dissolved in 1,4-dioxane, and the solution was powdered by the FDD process to obtain the ASD formulation of CsA (ASD/CsA). The ASD/CsA was characterized in terms of morphology, particle size distribution, crystallinity, dissolution behavior, physicochemical stability, and pharmacokinetic behavior in rats. The ASD/CsA was obtained in the form of uniform spherical particles, and the span factor was calculated to be ca. 0.4. CsA in the formulation existed in an amorphous state. The ASD/CsA exhibited a higher dissolution behavior of CsA than amorphous CsA, whereas storage of the ASD/CsA under accelerated conditions led to impairment in the dissolution behavior. The constant release of CsA from non-aged ASD/CsA was observed during dissolution testing. After oral administration of CsA samples (10mg-CsA/kg) in rats, the ASD/CsA showed a high and sustained plasma concentration of CsA as evidenced by a 18-fold increase in the oral bioavailability of CsA compared with amorphous CsA. From these findings, the FDD process might be an efficacious option for the ASD formulation of CsA with enhanced biopharmaceutics properties. Copyright © 2017 Elsevier B.V. All rights reserved.

Phase change in CoTi2 induced by MeV electron irradiation

NASA Astrophysics Data System (ADS)

Zensho, Akihiro; Sato, Kazuhisa; Yasuda, Hidehiro; Mori, Hirotaro

2018-07-01

The phase change induced by MeV electron irradiation in the intermetallic compound E93-CoTi2 was investigated using high-voltage electron microscopy. Under MeV electron irradiation, CoTi2 was first transformed into an amorphous phase and, with continued irradiation, crystallite formation in the amorphous phase (i.e. formation of crystallites of a solid-solution phase within the amorphous phase) was induced. The critical temperature for amorphisation was around 250 K. The total dose (dpa) required for crystallite formation (i.e. that required for partial crystallisation) was high (i.e. 27-80 dpa) and, even after prolonged irradiation, the amorphous phase was retained in the irradiated sample. Such partial crystallisation behaviour of amorphous Co33Ti67 was clearly different from the crystallisation behaviour (i.e. amorphous-to-solid solution, polymorphous transformation) of amorphous Cr67Ti33 reported in the literature. A possible cause of the difference is discussed.

Impact of polymers on the crystallization and phase transition kinetics of amorphous nifedipine during dissolution in aqueous media.

PubMed

Raina, Shweta A; Alonzo, David E; Zhang, Geoff G Z; Gao, Yi; Taylor, Lynne S

2014-10-06

The commercial and clinical success of amorphous solid dispersions (ASD) in overcoming the low bioavailability of poorly soluble molecules has generated momentum among pharmaceutical scientists to advance the fundamental understanding of these complex systems. A major limitation of these formulations stems from the propensity of amorphous solids to crystallize upon exposure to aqueous media. This study was specifically focused on developing analytical techniques to evaluate the impact of polymers on the crystallization behavior during dissolution, which is critical in designing effective amorphous formulations. In the study, the crystallization and polymorphic conversions of a model compound, nifedipine, were explored in the absence and presence of polyvinylpyrrolidone (PVP), hydroxypropylmethyl cellulose (HPMC), and HPMC-acetate succinate (HPMC-AS). A combination of analytical approaches including Raman spectroscopy, polarized light microscopy, and chemometric techniques such as multivariate curve resolution (MCR) were used to evaluate the kinetics of crystallization and polymorphic transitions as well as to identify the primary route of crystallization, i.e., whether crystallization took place in the dissolving solid matrix or from the supersaturated solutions generated during dissolution. Pure amorphous nifedipine, when exposed to aqueous media, was found to crystallize rapidly from the amorphous matrix, even when polymers were present in the dissolution medium. Matrix crystallization was avoided when amorphous solid dispersions were prepared, however, crystallization from the solution phase was rapid. MCR was found to be an excellent data processing technique to deconvolute the complex phase transition behavior of nifedipine.

Application of melt extrusion in the development of a physically and chemically stable high-energy amorphous solid dispersion of a poorly water-soluble drug.

PubMed

Lakshman, Jay P; Cao, Yu; Kowalski, James; Serajuddin, Abu T M

2008-01-01

Formulation of active pharmaceutical ingredients (API) in high-energy amorphous forms is a common strategy to enhance solubility, dissolution rate and, consequently, oral bioavailability of poorly water-soluble drugs. Amorphous APIs are, however, susceptible to recrystallization and, therefore, there is a need to physically stabilize them as solid dispersions in polymeric carriers. Hot melt extrusion has in recent years gained wide acceptance as a method of choice for the preparation of solid dispersions. There is a potential that the API, the polymer or both may degrade if excessively high temperature is needed in the melt extrusion process, especially when the melting point of the API is high. This report details a novel method where the API was first converted to an amorphous form by solvent evaporation and then melt-extruded with a suitable polymer at a drug load of at least 20% w/w. By this means, melt extrusion could be performed much below the melting temperature of the drug substance. Since the glass transition temperature of the amorphous drug was lower than that of the polymer used, the drug substance itself served as the plasticizer for the polymer. The addition of surfactants in the matrix enhanced dispersion and subsequent dissolution of the drug in aqueous media. The amorphous melt extrusion formulations showed higher bioavailability than formulations containing the crystalline API. There was no conversion of amorphous solid to its crystalline form during accelerated stability testing of dosage forms.

Characterization of the temperature and humidity-dependent phase diagram of amorphous nanoscale organic aerosols.

PubMed

Rothfuss, Nicholas E; Petters, Markus D

2017-03-01

Atmospheric aerosols can exist in amorphous semi-solid or glassy phase states. These states are determined by the temperature (T) and relative humidity (RH). New measurements of viscosity for amorphous semi-solid nanometer size sucrose particles as a function of T and RH are reported. Viscosity is measured by inducing coagulation between two particles and probing the thermodynamic states that induce the particle to relax into a sphere. It is shown that the glass transition temperature can be obtained by extrapolation to 10 12 Pa s from the measured temperature-dependent viscosity in the 10 6 to 10 7 Pa s range. The experimental methodology was refined to allow isothermal probing of RH dependence and to increase the range of temperatures over which the dry temperature dependence can be studied. Several experiments where one monomer was sodium dodecyl sulfate (SDS), which remains solid at high RH, are also reported. These sucrose-SDS dimers were observed to relax into a sphere at T and RH similar to those observed in sucrose-sucrose dimers, suggesting that amorphous sucrose will flow over an insoluble particle at a viscosity similar to that characteristic of coalescence between two sucrose particles. Possible physical and analytical implications of this observation are considered. The data reported here suggest that semi-solid viscosity between 10 4 and 10 12 Pa s can be modelled over a wide range of T and RH using an adapted Vogel-Fulcher-Tammann equation and the Gordon-Taylor mixing rule. Sensitivity of modelled viscosity to variations in dry glass transition temperature, Gordon-Taylor constant, and aerosol hygroscopicity are explored, along with implications for atmospheric processes such as ice nucleation of glassy organic aerosols in the upper free troposphere. The reported measurement and modelling framework provides a template for characterizing the phase diagram of other amorphous aerosol systems, including secondary organic aerosols.

Three-body interactions and the elastic constants of hcp solid 4He

NASA Astrophysics Data System (ADS)

Barnes, Ashleigh L.; Hinde, Robert J.

2017-09-01

The effect of three-body interactions on the elastic properties of hexagonal close packed solid 4He is investigated using variational path integral (VPI) Monte Carlo simulations. The solid's nonzero elastic constants are calculated, at T = 0 K and for a range of molar volumes from 7.88 cm3/mol to 20.78 cm3/mol, from the bulk modulus and the three pure shear constants C0, C66, and C44. Three-body interactions are accounted for using our recently reported perturbative treatment based on the nonadditive three-body potential of Cencek et al. Previous studies have attempted to account for the effect of three-body interactions on the elastic properties of solid 4He; however, these calculations have treated zero point motions using either the Einstein or Debye approximations, which are insufficient in the molar volume range where solid 4He is characterized as a quantum solid. Our VPI calculations allow for a more accurate treatment of the zero point motions which include atomic correlation. From these calculations, we find that agreement with the experimental bulk modulus is significantly improved when three-body interactions are considered. In addition, three-body interactions result in non-negligible differences in the calculated pure shear constants and nonzero elastic constants, particularly at higher densities, where differences of up to 26.5% are observed when three-body interactions are included. We compare to the available experimental data and find that our results are generally in as good or better agreement with experiment as previous theoretical investigations.

An example of how to handle amorphous fractions in API during early pharmaceutical development: SAR114137--a successful approach.

PubMed

Petzoldt, Christine; Bley, Oliver; Byard, Stephen J; Andert, Doris; Baumgartner, Bruno; Nagel, Norbert; Tappertzhofen, Christoph; Feth, Martin Philipp

2014-04-01

The so-called pharmaceutical solid chain, which encompasses drug substance micronisation to the final tablet production, at pilot plant scale is presented as a case study for a novel, highly potent, pharmaceutical compound: SAR114137. Various solid-state analytical methods, such as solid-state Nuclear Magnetic Resonance (ssNMR), Differential Scanning Calorimetry (DSC), Dynamic Water Vapour Sorption Gravimetry (DWVSG), hot-stage Raman spectroscopy and X-ray Powder Diffraction (XRPD) were applied and evaluated to characterise and quantify amorphous content during the course of the physical treatment of crystalline active pharmaceutical ingredient (API). DSC was successfully used to monitor the changes in amorphous content during micronisation of the API, as well as during stability studies. (19)F solid-state NMR was found to be the method of choice for the detection and quantification of low levels of amorphous API, even in the final drug product (DP), since compaction during tablet manufacture was identified as a further source for the formation of amorphous API. The application of different jet milling techniques was a critical factor with respect to amorphous content formation. In the present case, the change from spiral jet milling to loop jet milling led to a decrease in amorphous API content from 20-30 w/w% to nearly 0 w/w% respectively. The use of loop jet milling also improved the processability of the API. Stability investigations on both the milled API and the DP showed a marked tendency for recrystallisation of the amorphous API content on exposure to elevated levels of relative humidity. No significant impact of amorphous API on either the chemical stability or the dissolution rate of the API in drug formulation was observed. Therefore, the presence of amorphous content in the oral formulation was of no consequence for the clinical trial phases I and II. Copyright © 2013 Elsevier B.V. All rights reserved.

Effect of Molecular Weight on Mechanical and Electrochemical Performance of All Solid-State Polymer Electrolyte Membranes

NASA Astrophysics Data System (ADS)

He, Ruixuan; Ward, Daniel; Echeverri, Mauricio; Kyu, Thein

2015-03-01

Guided by ternary phase diagrams of polyethylene glycol diacrylate (PEGDA), succinonitrile plasticizer, and LiTFSI salt, completely amorphous solid-state transparent polymer electrolyte membranes (ss-PEM) were fabricated by UV irradiation in the isotropic melt state. Effects of PEGDA molecular weight (700 vs 6000 g/mol) on ss-PEM performance were investigated. These amorphous PEMs have superionic room temperature ionic conductivity of ~10-3 S/cm, whereby PEGDA6000-PEM outperforms its PEGDA700 counterpart, which may be ascribed to lower crosslinking density and greater segmental mobility. The longer chain between crosslinked points of PEGDA6000-PEM is responsible for greater extensibility of ~80% versus ~7% of PEGDA700-PEM. Besides, both PEMs exhibited thermal stability up to 120 °C and electrochemical stability versus Li+/Li up to 4.7V. LiFePO4/PEM/Li and Li4Ti5O12 /PEM/Li half-cells exhibited stable cyclic behavior up to 50 cycles tested with a capacity of ~140mAh/g, suggesting that LiFePO4/PEM/Li4Ti5O12 may be a promising full-cell for all solid-state lithium battery. We thank NSF-DMR 1161070 for providing funding of this project.

Solid state microwave synthesis of highly crystalline ordered mesoporous hausmannite Mn 3 O 4 films

DOE PAGES

Xia, Yanfeng; Qiang, Zhe; Lee, Byeongdu; ...

2017-06-23

Microwave calcination of ordered micelle templated manganese carbonate films leads to highly crystalline, ordered mesoporous manganese oxide, while similar temperatures in a furnace lead to disordered, amorphous manganese oxide.

Mesoscale modeling of strain induced solid state amorphization in crystalline materials

NASA Astrophysics Data System (ADS)

Lei, Lei

Solid state amorphization, and in particular crystalline to amorphous transformation, can be observed in metallic alloys, semiconductors, intermetallics, minerals, and also molecular crystals when they undergo irradiation, hydrogen gas dissolution, thermal interdiffusion, mechanical alloying, or mechanical milling. Although the amorphization mechanisms may be different, the transformation occurs due to the high level of disorder introduced into the material. Milling induced solid state amorphization is proposed to be the result of accumulation of crystal defects, specifically dislocations, as the material is subjected to large deformations during the high energy process. Thus, understanding the deformation mechanisms of crystalline materials will be the first step in studying solid state amorphization in crystalline materials, which not only has scientific contributions, but also technical consequences. A phase field dislocation dynamics (PFDD) approach is employed in this work to simulate plastic deformation of molecular crystals. This PFDD model has the advantage of tracking all of the dislocations in a material simultaneously. The model takes into account the elastic interaction between dislocations, the lattice resistance to dislocation motion, and the elastic interaction of dislocations with an external stress field. The PFDD model is employed to describe the deformation of molecular crystals with pharmaceutical applications, namely, single crystal sucrose, acetaminophen, gamma-indomethacin, and aspirin. Stress-strain curves are produced that result in expected anisotropic material response due to the activation of different slip systems and yield stresses that agree well with those from experiments. The PFDD model is coupled to a phase transformation model to study the relation between plastic deformation and the solid state amorphization of crystals that undergo milling. This model predicts the amorphous volume fraction in excellent agreement with experimental observation. Finally, we incorporate the effect of stress free surfaces to model the behavior of dislocations close to these surfaces and in the presence of voids.

Mechanism-based selection of stabilization strategy for amorphous formulations: Insights into crystallization pathways.

PubMed

Edueng, Khadijah; Mahlin, Denny; Larsson, Per; Bergström, Christel A S

2017-06-28

We developed a step-by-step experimental protocol using differential scanning calorimetry (DSC), dynamic vapour sorption (DVS), polarized light microscopy (PLM) and a small-scale dissolution apparatus (μDISS Profiler) to investigate the mechanism (solid-to-solid or solution-mediated) by which crystallization of amorphous drugs occurs upon dissolution. This protocol then guided how to stabilize the amorphous formulation. Indapamide, metolazone, glibenclamide and glipizide were selected as model drugs and HPMC (Pharmacoat 606) and PVP (K30) as stabilizing polymers. Spray-dried amorphous indapamide, metolazone and glibenclamide crystallized via solution-mediated nucleation while glipizide suffered from solid-to-solid crystallization. The addition of 0.001%-0.01% (w/v) HPMC into the dissolution medium successfully prevented the crystallization of supersaturated solutions of indapamide and metolazone whereas it only reduced the crystallization rate for glibenclamide. Amorphous solid dispersion (ASD) formulation of glipizide and PVP K30, at a ratio of 50:50% (w/w) reduced but did not completely eliminate the solid-to-solid crystallization of glipizide even though the overall dissolution rate was enhanced both in the absence and presence of HPMC. Raman spectroscopy indicated the formation of a glipizide polymorph in the dissolution medium with higher solubility than the stable polymorph. As a complementary technique, molecular dynamics (MD) simulations of indapamide and glibenclamide with HPMC was performed. It was revealed that hydrogen bonding patterns of the two drugs with HPMC differed significantly, suggesting that hydrogen bonding may play a role in the greater stabilizing effect on supersaturation of indapamide, compared to glibenclamide. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Interfacial interaction track of amorphous solid dispersions established by water-soluble polymer and indometacin.

PubMed

Li, Jing; Fan, Na; Wang, Xin; Li, Chang; Sun, Mengchi; Wang, Jian; Fu, Qiang; He, Zhonggui

2017-08-30

The present work studied interfacial interactions of amorphous solid dispersions matrix of indometacin (IMC) that established using PVP K30 (PVP) and PEG 6000 (PEG) by focusing on their interaction forces and wetting process. Infrared spectroscopy (IR), raman spectroscopy, X-ray photoelectron spectra and contact angle instrument were used throughout the study. Hydrogen bond energy formed between PEG and IMC were stronger than that of PVP and IMC evidenced by molecular modeling measurement. The blue shift of raman spectroscopy confirmed that hydrogen bonding forces were formed between IMC and two polymers. The contact angle study can be used as an easy method to determine the dissolution mechanism of amorphous solid dispersions through fitting the profile of contact angle of water on a series of tablets. It is believed that the track of interfacial interactions will certainly become powerful tools to for designing and evaluating amorphous solid dispersions. Copyright © 2017 Elsevier B.V. All rights reserved.

Development and in-vivo assessment of the bioavailability of oridonin solid dispersions by the gas anti-solvent technique.

PubMed

Li, Songming; Liu, Ying; Liu, Tao; Zhao, Ling; Zhao, Jihui; Feng, Nianping

2011-06-15

We developed solid dispersions, using the gas anti-solvent technique (GAS), to improve the oral bioavailability of the poorly water-soluble active component oridonin. The solubility of oridonin in supercritical carbon dioxide was measured under various pressures and temperatures. To prepare oridonin solid dispersions using the GAS technique, ethanol was used as the solvent, CO(2) was used as the anti-solvent and the hydrophilic polymer polyvinylpyrrolidone K17 (PVP K17) was used as the drug carrier matrix. Characterization of the obtained preparations was undertaken using scanning electron microscopy (SEM), X-ray diffraction (XRD) analyses and a drug release study. Oridonin solid dispersions were formed and oridonin was present in an amorphous form in these dispersions. Oridonin solid dispersions significantly increased the drug dissolution rate compared with that of oridonin powder, primarily through drug amorphization. Compared with the physical mixture of oridonin and PVP K17, oridonin solid dispersions gave higher values of AUC and C(max), and the absorption of oridonin from solid dispersions resulted in 26.4-fold improvement in bioavailability. The present study illustrated the feasibility of applying the GAS technique to prepare oridonin solid dispersions, and of using them for the delivery of oridonin via the oral route. Copyright © 2011 Elsevier B.V. All rights reserved.

Modeling Physical Stability of Amorphous Solids Based on Temperature and Moisture Stresses.

PubMed

Zhu, Donghua Alan; Zografi, George; Gao, Ping; Gong, Yuchuan; Zhang, Geoff G Z

2016-09-01

Isothermal microcalorimetry was utilized to monitor the crystallization process of amorphous ritonavir (RTV) and its hydroxypropylmethylcellulose acetate succinate-based amorphous solid dispersion under various stressed conditions. An empirical model was developed: ln(τ)=ln(A)+EaRT-b⋅wc, where τ is the crystallization induction period, A is a pre-exponential factor, Ea is the apparent activation energy, b is the moisture sensitivity parameter, and wc is water content. To minimize the propagation of errors associated with the estimates, a nonlinear approach was used to calculate mean estimates and confidence intervals. The physical stability of neat amorphous RTV and RTV in hydroxypropylmethylcellulose acetate succinate solid dispersions was found to be mainly governed by the nucleation kinetic process. The impact of polymers and moisture on the crystallization process can be quantitatively described by Ea and b in this Arrhenius-type model. The good agreement between the measured values under some less stressful test conditions and those predicted, reflected by the slope and R(2) of the correlation plot of these 2 sets of data on a natural logarithm scale, indicates its predictability of long-term physical stability of amorphous RTV in solid dispersions. To further improve the model, more understanding of the impact of temperature and moisture on the amorphous physical stability and fundamentals regarding nucleation and crystallization is needed. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Melt extrusion vs. spray drying: The effect of processing methods on crystalline content of naproxen-povidone formulations.

PubMed

Haser, Abbe; Cao, Tu; Lubach, Joe; Listro, Tony; Acquarulo, Larry; Zhang, Feng

2017-05-01

Our hypothesis is that melt extrusion is a more suitable processing method than spray drying to prepare amorphous solid dispersions of drugs with a high crystallization tendency. Naproxen-povidone K25 was used as the model system in this study. Naproxen-povidone K25 solid dispersions at 30% and 60% drug loadings were characterized by modulated DSC, powder X-ray diffraction, FT-IR, and solid-state 13 C NMR to identify phase separation and drug recrystallization during processing and storage. At 30% drug loading, hydrogen bond (H-bond) sites of povidone K25 were not saturated and the glass transition (T g ) temperature of the formulation was higher. As a result, both melt-extruded and spray-dried materials were amorphous initially and remained so after storage at 40°C. At 60% drug loading, H-bond sites were saturated, and T g was low. We were not able to prepare amorphous materials. The initial crystallinity of the formulations was 0.4%±0.2% and 5.6%±0.6%, and increased to 2.7%±0.3% and 21.6%±1.0% for melt-extruded and spray-dried materials, respectively. Spray-dried material was more susceptible to re-crystallization during processing, due to the high diffusivity of naproxen molecules in the formulation matrix and lack of kinetic stabilization from polymer solution. A larger number of crystalline nucleation sites and high surface area made the spray-dried material more susceptible to recrystallization during storage. This study demonstrated the unique advantages of melt extrusion over spray drying for the preparation of amorphous solid dispersions of naproxen at high drug level. Copyright © 2017 Elsevier B.V. All rights reserved.

Design of Amorphous Manganese Oxide@Multiwalled Carbon Nanotube Fiber for Robust Solid-State Supercapacitor.

PubMed

Shi, Peipei; Li, Li; Hua, Li; Qian, Qianqian; Wang, Pengfei; Zhou, Jinyuan; Sun, Gengzhi; Huang, Wei

2017-01-24

Solid-state fiber-based supercapacitors have been considered promising energy storage devices for wearable electronics due to their lightweight and amenability to be woven into textiles. Efforts have been made to fabricate a high performance fiber electrode by depositing pseudocapacitive materials on the outer surface of carbonaceous fiber, for example, crystalline manganese oxide/multiwalled carbon nanotubes (MnO 2 /MWCNTs). However, a key challenge remaining is to achieve high specific capacitance and energy density without compromising the high rate capability and cycling stability. In addition, amorphous MnO 2 is actually preferred due to its disordered structure and has been proven to exhibit superior electrochemical performance over the crystalline one. Herein, by incorporating amorphous MnO 2 onto a well-aligned MWCNT sheet followed by twisting, we design an amorphous MnO 2 @MWCNT fiber, in which amorphous MnO 2 nanoparticles are distributed in MWCNT fiber uniformly. The proposed structure gives the amorphous MnO 2 @MWCNT fiber good mechanical reliability, high electrical conductivity, and fast ion-diffusion. Solid-state supercapacitor based on amorphous MnO 2 @MWCNT fibers exhibits improved energy density, superior rate capability, exceptional cycling stability, and excellent flexibility. This study provides a strategy to design a high performance fiber electrode with microstructure control for wearable energy storage devices.

Amorphization of itraconazole by inorganic pharmaceutical excipients: comparison of excipients and processing methods.

PubMed

Grobelny, Pawel; Kazakevich, Irina; Zhang, Dan; Bogner, Robin

2015-01-01

The aim of this study was to investigate the effects of solid carriers and processing routes on the properties of amorphous solid dispersions of itraconazole. Three solid carriers with a range of surface properties were studied, (1) a mesoporous silicate, magnesium aluminum silicate (Neusilin US2), (2) a nonporous silicate of corresponding composition (Veegum) and (3) a non-silicate, inorganic excipient, calcium phosphate dibasic anhydrous (A-TAB). The drug was incorporated via either solvent-deposition or ball milling. Both the maximum drug deposited by solvent-based method that produced an amorphous composite and the time for complete amorphization by co-milling was determined by X-ray powder diffraction (XRPD). Changes in the drug and excipients were monitored by nitrogen adsorption and wettability of the powder. The ability of the excipients to amorphize the drug and enhance its dissolution was related to the powder characteristics. Neusilin provided the fastest amorphization time in the mill and highest drug loading by solvent-deposition, compared with the other two excipients. Solvent-deposition provided greater dissolution enhancement than milling, due to the reduction in Neusilin porosity during high energy milling.This study confirms that substrates as well as the processing routes have notable influence on the drug deposition, amorphization, physical stability and drug in vitro release.

Fast surface crystallization of amorphous griseofulvin below T g.

PubMed

Zhu, Lei; Jona, Janan; Nagapudi, Karthik; Wu, Tian

2010-08-01

To study crystal growth rates of amorphous griseofulvin (GSF) below its glass transition temperature (T (g)) and the effect of surface crystallization on the overall crystallization kinetics of amorphous GSF. Amorphous GSF was generated by melt quenching. Surface and bulk crystal growth rates were determined using polarized light microscope. X-ray powder diffraction (XRPD) and Raman microscopy were used to identify the polymorph of the crystals. Crystallization kinetics of amorphous GSF powder stored at 40 degrees C (T (g)-48 degrees C) and room temperature (T (g)-66 degrees C) was monitored using XRPD. Crystal growth at the surface of amorphous GSF is 10- to 100-fold faster than that in the bulk. The surface crystal growth can be suppressed by an ultrathin gold coating. Below T (g), the crystallization of amorphous GSF powder was biphasic with a rapid initial crystallization stage dominated by the surface crystallization and a slow or suspended late stage controlled by the bulk crystallization. GSF exhibits the fastest surface crystallization kinetics among the known amorphous pharmaceutical solids. Well below T (g), surface crystallization dominated the overall crystallization kinetics of amorphous GSF powder. Thus, surface crystallization should be distinguished from bulk crystallization in studying, modeling and controlling the crystallization of amorphous solids.

Impact of surfactants on the crystallization of aqueous suspensions of celecoxib amorphous solid dispersion spray dried particles.

PubMed

Chen, Jie; Ormes, James D; Higgins, John D; Taylor, Lynne S

2015-02-02

Amorphous solid dispersions are frequently prepared by spray drying. It is important that the resultant spray dried particles do not crystallize during formulation, storage, and upon administration. The goal of the current study was to evaluate the impact of surfactants on the crystallization of celecoxib amorphous solid dispersions (ASD), suspended in aqueous media. Solid dispersions of celecoxib with hydroxypropylmethylcellulose acetate succinate were manufactured by spray drying, and aqueous suspensions were prepared by adding the particles to acidified media containing various surfactants. Nucleation induction times were evaluated for celecoxib in the presence and absence of surfactants. The impact of the surfactants on drug and polymer leaching from the solid dispersion particles was also evaluated. Sodium dodecyl sulfate and Polysorbate 80 were found to promote crystallization from the ASD suspensions, while other surfactants including sodium taurocholate and Triton X100 were found to inhibit crystallization. The promotion or inhibition of crystallization was found to be related to the impact of the surfactant on the nucleation behavior of celecoxib, as well as the tendency to promote leaching of the drug from the ASD particle into the suspending medium. It was concluded that surfactant choice is critical to avoid failure of amorphous solid dispersions through crystallization of the drug.

Entropic Comparison of Atomic-Resolution Electron Tomography of Crystals and Amorphous Materials.

PubMed

Collins, S M; Leary, R K; Midgley, P A; Tovey, R; Benning, M; Schönlieb, C-B; Rez, P; Treacy, M M J

2017-10-20

Electron tomography bears promise for widespread determination of the three-dimensional arrangement of atoms in solids. However, it remains unclear whether methods successful for crystals are optimal for amorphous solids. Here, we explore the relative difficulty encountered in atomic-resolution tomography of crystalline and amorphous nanoparticles. We define an informational entropy to reveal the inherent importance of low-entropy zone-axis projections in the reconstruction of crystals. In turn, we propose considerations for optimal sampling for tomography of ordered and disordered materials.

Containerless synthesis of amorphous and nanophase organic materials

DOEpatents

Benmore, Chris J.; Weber, Johann R.

2016-05-03

The invention provides a method for producing a mixture of amorphous compounds, the method comprising supplying a solution containing the compounds; and allowing at least a portion of the solvent of the solution to evaporate while preventing the solute of the solution from contacting a nucleation point. Also provided is a method for transforming solids to amorphous material, the method comprising heating the solids in an environment to form a melt, wherein the environment contains no nucleation points; and cooling the melt in the environment.

Itraconazole solid dispersion prepared by a supercritical fluid technique: preparation, in vitro characterization, and bioavailability in beagle dogs.

PubMed

Yin, Xuezhi; Daintree, Linda Sharon; Ding, Sheng; Ledger, Daniel Mark; Wang, Bing; Zhao, Wenwen; Qi, Jianping; Wu, Wei; Han, Jiansheng

2015-01-01

This research aimed to develop a supercritical fluid (SCF) technique for preparing a particulate form of itraconazole (ITZ) with good dissolution and bioavailability characteristics. The ITZ particulate solid dispersion was formulated with hydroxypropyl methylcellulose, Pluronic F-127, and L-ascorbic acid. Aggregated particles showed porous structure when examined by scanning electron microscopy. Powder X-ray diffraction and Fourier transform infrared spectra indicated an interaction between ITZ and excipients and showed that ITZ existed in an amorphous state in the composite solid dispersion particles. The solid dispersion obtained by the SCF process improved the dissolution of ITZ in media of pH 1.0, pH 4.5, and pH 6.8, compared with a commercial product (Sporanox(®)), which could be ascribed to the porous aggregated particle shape and amorphous solid state of ITZ. While the solid dispersion did not show a statistical improvement (P=0.50) in terms of oral bioavailability of ITZ compared with Sporanox(®), the C max (the maximum plasma concentration of ITZ in a pharmacokinetic curve) of ITZ was raised significantly (P=0.03) after oral administration. Thus, the SCF process has been shown to be an efficient, single step process to form ITZ-containing solid dispersion particles with good dissolution and oral bioavailability characteristics.

Yield stress in amorphous solids: A mode-coupling-theory analysis

NASA Astrophysics Data System (ADS)

Ikeda, Atsushi; Berthier, Ludovic

2013-11-01

The yield stress is a defining feature of amorphous materials which is difficult to analyze theoretically, because it stems from the strongly nonlinear response of an arrested solid to an applied deformation. Mode-coupling theory predicts the flow curves of materials undergoing a glass transition and thus offers predictions for the yield stress of amorphous solids. We use this approach to analyze several classes of disordered solids, using simple models of hard-sphere glasses, soft glasses, and metallic glasses for which the mode-coupling predictions can be directly compared to the outcome of numerical measurements. The theory correctly describes the emergence of a yield stress of entropic nature in hard-sphere glasses, and its rapid growth as density approaches random close packing at qualitative level. By contrast, the emergence of solid behavior in soft and metallic glasses, which originates from direct particle interactions is not well described by the theory. We show that similar shortcomings arise in the description of the caging dynamics of the glass phase at rest. We discuss the range of applicability of mode-coupling theory to understand the yield stress and nonlinear rheology of amorphous materials.

Formation, Physicochemical Characterization, and Thermodynamic Stability of the Amorphous State of Drugs and Excipients.

PubMed

Martino, Piera Di; Magnoni, Federico; Peregrina, Dolores Vargas; Gigliobianco, Maria Rosa; Censi, Roberta; Malaj, Ledjan

2016-01-01

Drugs and excipients used for pharmaceutical applications generally exist in the solid (crystalline or amorphous) state, more rarely as liquid materials. In some cases, according to the physicochemical nature of the molecule, or as a consequence of specific technological processes, a compound may exist exclusively in the amorphous state. In other cases, as a consequence of specific treatments (freezing and spray drying, melting and co-melting, grinding and compression), the crystalline form may convert into a completely or partially amorphous form. An amorphous material shows physical and thermodynamic properties different from the corresponding crystalline form, with profound repercussions on its technological performance and biopharmaceutical properties. Several physicochemical techniques such as X-ray powder diffraction, thermal methods of analysis, spectroscopic techniques, gravimetric techniques, and inverse gas chromatography can be applied to characterize the amorphous form of a compound (drug or excipient), and to evaluate its thermodynamic stability. This review offers a survey of the technologies used to convert a crystalline solid into an amorphous form, and describes the most important techniques for characterizing the amorphous state of compounds of pharmaceutical interest.

Barrier coated drug layered particles for enhanced performance of amorphous solid dispersion dosage form.

PubMed

Puri, Vibha; Dantuluri, Ajay K; Bansal, Arvind K

2012-01-01

Amorphous solid dispersions (ASDs) may entail tailor-made dosage form design to exploit their solubility advantage. Surface phenomena dominated the performance of amorphous celecoxib solid dispersion (ACSD) comprising of amorphous celecoxib (A-CLB), polyvinylpyrrolidone, and meglumine (7:2:1, w/w). ACSD cohesive interfacial interactions hindered its capsule dosage form dissolution (Puri V, Dhantuluri AK, Bansal AK 2011. J Pharm Sci 100:2460-2468). Furthermore, ACSD underwent significant devitrification under environmental stress. In the present study, enthalpy relaxation studies revealed its free surface to contribute to molecular mobility. Based on all these observations, barrier coated amorphous CLB solid dispersion layered particles (ADLP) were developed by Wurster process, using microcrystalline cellulose as substrate and polyvinyl alcohol (PVA), inulin, and polyvinyl acetate phthalate (PVAP) as coating excipients. Capsule formulations of barrier coated-ADLP could achieve rapid dispersibility and high drug release. Evaluation under varying temperature and RH conditions suggested the crystallization inhibitory efficiency in order of inulin < PVA ≈ PVAP; however, under only temperature treatment, crystallization inhibition increased with increase in T(g) of the coating material. Simulated studies using DSC evidenced drug-polymer mixing at the interface as a potential mechanism for surface stabilization. In conclusion, surface modification yielded a fast dispersing robust high drug load ASD based dosage form. Copyright © 2011 Wiley-Liss, Inc.

Evolution of supersaturation of amorphous pharmaceuticals: the effect of rate of supersaturation generation.

PubMed

Sun, Dajun D; Lee, Ping I

2013-11-04

The combination of a rapidly dissolving and supersaturating "spring" with a precipitation retarding "parachute" has often been pursued as an effective formulation strategy for amorphous solid dispersions (ASDs) to enhance the rate and extent of oral absorption. However, the interplay between these two rate processes in achieving and maintaining supersaturation remains inadequately understood, and the effect of rate of supersaturation buildup on the overall time evolution of supersaturation during the dissolution of amorphous solids has not been explored. The objective of this study is to investigate the effect of supersaturation generation rate on the resulting kinetic solubility profiles of amorphous pharmaceuticals and to delineate the evolution of supersaturation from a mechanistic viewpoint. Experimental concentration-time curves under varying rates of supersaturation generation and recrystallization for model drugs, indomethacin (IND), naproxen (NAP) and piroxicam (PIR), were generated from infusing dissolved drug (e.g., in ethanol) into the dissolution medium and compared with that predicted from a comprehensive mechanistic model based on the classical nucleation theory taking into account both the particle growth and ripening processes. In the absence of any dissolved polymer to inhibit drug precipitation, both our experimental and predicted results show that the maximum achievable supersaturation (i.e., kinetic solubility) of the amorphous solids increases, the time to reach maximum decreases, and the rate of concentration decline in the de-supersaturation phase increases, with increasing rate of supersaturation generation (i.e., dissolution rate). Our mechanistic model also predicts the existence of an optimal supersaturation rate which maximizes the area under the curve (AUC) of the kinetic solubility concentration-time profile, which agrees well with experimental data. In the presence of a dissolved polymer from ASD dissolution, these observed trends also hold true except the de-supersaturation phase is more extended due to the crystallization inhibition effect. Since the observed kinetic solubility of nonequilibrium amorphous solids depends on the rate of supersaturation generation, our results also highlight the underlying difficulty in determining a reproducible solubility advantage for amorphous solids.

Evaluation of the recrystallization kinetics of hot-melt extruded polymeric solid dispersions using an improved Avrami equation

PubMed Central

Feng, Xin; Ye, Xingyou; Park, Jun-Bom; Lu, Wenli; Morott, Joe; Beissner, Brad; Lian, Zhuoyang John; Pinto, Elanor; Bi, Vivian; Porter, Stu; Durig, Tom; Majumdar, Soumyajit; Repka, Michael A.

2017-01-01

The recrystallization of an amorphous drug in a solid dispersion system could lead to a loss in the drug solubility and bioavailability. The primary objective of the current research was to use an improved kinetic model to evaluate the recrystallization kinetics of amorphous structures and to further understand the factors influencing the physical stability of amorphous solid dispersions. Amorphous solid dispersions of fenofibrate with different molecular weights of hydroxypropylcellulose, HPC (Klucel™ LF, EF, ELF) were prepared utilizing hot-melt extrusion technology. Differential scanning calorimetry was utilized to quantitatively analyze the extent of recrystallization in the samples stored at different temperatures and relative humidity (RH) conditions. The experimental data were fitted into the improved kinetics model of a modified Avrami equation to calculate the recrystallization rate constants. Klucel LF, the largest molecular weight among the HPCs used, demonstrated the greatest inhibition of fenofibrate recrystallization. Additionally, the recrystallization rate (k) decreased with increasing polymer content, however exponentially increased with higher temperature. Also k increased linearly rather than exponentially over the range of RH studied. PMID:25224341

Evaluation of the recrystallization kinetics of hot-melt extruded polymeric solid dispersions using an improved Avrami equation.

PubMed

Feng, Xin; Ye, Xingyou; Park, Jun-Bom; Lu, Wenli; Morott, Joe; Beissner, Brad; Lian, Zhuoyang John; Pinto, Elanor; Bi, Vivian; Porter, Stu; Durig, Tom; Majumdar, Soumyajit; Repka, Michael A

2015-01-01

The recrystallization of an amorphous drug in a solid dispersion system could lead to a loss in the drug solubility and bioavailability. The primary objective of the current research was to use an improved kinetic model to evaluate the recrystallization kinetics of amorphous structures and to further understand the factors influencing the physical stability of amorphous solid dispersions. Amorphous solid dispersions of fenofibrate with different molecular weights of hydroxypropylcellulose, HPC (Klucel™ LF, EF, ELF) were prepared utilizing hot-melt extrusion technology. Differential scanning calorimetry was utilized to quantitatively analyze the extent of recrystallization in the samples stored at different temperatures and relative humidity (RH) conditions. The experimental data were fitted into the improved kinetics model of a modified Avrami equation to calculate the recrystallization rate constants. Klucel LF, the largest molecular weight among the HPCs used, demonstrated the greatest inhibition of fenofibrate recrystallization. Additionally, the recrystallization rate (k) decreased with increasing polymer content, however exponentially increased with higher temperature. Also k increased linearly rather than exponentially over the range of RH studied.

Using Flory-Huggins phase diagrams as a pre-formulation tool for the production of amorphous solid dispersions: a comparison between hot-melt extrusion and spray drying.

PubMed

Tian, Yiwei; Caron, Vincent; Jones, David S; Healy, Anne-Marie; Andrews, Gavin P

2014-02-01

Amorphous drug forms provide a useful method of enhancing the dissolution performance of poorly water-soluble drugs; however, they are inherently unstable. In this article, we have used Flory-Huggins theory to predict drug solubility and miscibility in polymer candidates, and used this information to compare spray drying and melt extrusion as processes to manufacture solid dispersions. Solid dispersions were prepared using two different techniques (hot-melt extrusion and spray drying), and characterised using a combination of thermal (thermogravimetric analysis and differential scanning calorimetry), spectroscopic (Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction methods. Spray drying permitted generation of amorphous solid dispersions across a wider drug concentration than melt extrusion. Melt extrusion provided sufficient energy for more intimate mixing to be achieved between drug and polymer, which may improve physical stability. It was also confirmed that stronger drug-polymer interactions might be generated through melt extrusion. Remixing and dissolution of recrystallised felodipine into the polymeric matrices did occur during the modulated differential scanning calorimetry analysis, but the complementary information provided from FTIR confirms that all freshly prepared spray-dried samples were amorphous with the existence of amorphous drug domains within high drug-loaded samples. Using temperature-composition phase diagrams to probe the relevance of temperature and drug composition in specific polymer candidates facilitates polymer screening for the purpose of formulating solid dispersions. © 2013 Royal Pharmaceutical Society.

Heterogeneous water oxidation: surface activity versus amorphization activation in cobalt phosphate catalysts.

PubMed

González-Flores, Diego; Sánchez, Irene; Zaharieva, Ivelina; Klingan, Katharina; Heidkamp, Jonathan; Chernev, Petko; Menezes, Prashanth W; Driess, Matthias; Dau, Holger; Montero, Mavis L

2015-02-16

Is water oxidation catalyzed at the surface or within the bulk volume of solid oxide materials? This question is addressed for cobalt phosphate catalysts deposited on inert electrodes, namely crystallites of pakhomovskyite (Co3(PO4)2⋅8 H2O, Pak) and phosphate-containing Co oxide (CoCat). X-ray spectroscopy reveals that oxidizing potentials transform the crystalline Pak slowly (5-8 h) but completely into the amorphous CoCat. Electrochemical analysis supports high-TOF surface activity in Pak, whereas its amorphization results in dominating volume activity of the thereby formed CoCat material. In the directly electrodeposited CoCat, volume catalysis prevails, but not at very low levels of the amorphous material, implying high-TOF catalysis at surface sites. A complete picture of heterogeneous water oxidation requires insight in catalysis at the electrolyte-exposed "outer surface", within a hydrated, amorphous volume phase, and modes and kinetics of restructuring upon operation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnetotransport properties of microstructured AlCu2Mn Heusler alloy thin films in the amorphous and crystalline phase

NASA Astrophysics Data System (ADS)

Barzola-Quiquia, José; Stiller, Markus; Esquinazi, Pablo D.; Quispe-Marcatoma, Justiniano; Häussler, Peter

2018-06-01

We have studied the resistance, magnetoresistance and Hall effect of AlCu2Mn Heusler alloy thin films prepared by flash evaporation on substrates cooled at 4He liquid temperature. The as-prepared samples were amorphous and were annealed stepwise to induce the transformation to the crystalline phase. The amorphous phase is metastable up to above room temperature and the transition to the crystalline phase was observed by means of resistance measurements. Using transmission electron microscopy, we have determined the structure factor S (K) and the pair correlation function g (r) , both results indicate that amorphous AlCu2Mn is an electronic stabilized phase. The X-ray diffraction of the crystallized film shows peaks corresponding to the well ordered L21 phase. The resistance shows a negative temperature coefficient in both phases. The magnetoresistance (MR) is negative in both phases, yet larger in the crystalline state compared to the amorphous one. The magnetic properties were studied further by anomalous Hall effect measurements, which were present in both phases. In the amorphous state, the anomalous Hall effect disappears at temperatures below 175 K and is present up to above room temperature in the case of crystalline AlCu2Mn.

Liquid-vapor equilibrium and interfacial properties of square wells in two dimensions

NASA Astrophysics Data System (ADS)

Armas-Pérez, Julio C.; Quintana-H, Jacqueline; Chapela, Gustavo A.

2013-01-01

Liquid-vapor coexistence and interfacial properties of square wells in two dimensions are calculated. Orthobaric densities, vapor pressures, surface tensions, and interfacial thicknesses are reported. Results are presented for a series of potential widths λ* = 1.4, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 5, where λ* is given in units of the hard core diameter σ. Critical and triple points are explored. No critical point was found for λ* < 1.4. Corresponding states principle analysis is performed for the whole series. For λ* = 1.4 and 1.5 evidence is presented that at an intermediate temperature between the critical and the triple point temperatures the liquid branch becomes an amorphous solid. This point is recognized in Armas-Pérez et al. [unpublished] as a hexatic phase transition. It is located at reduced temperatures T* = 0.47 and 0.35 for λ* = 1.4 and 1.5, respectively. Properties such as the surface tension, vapor pressure, and interfacial thickness do not present any discontinuity at these points. This amorphous solid branch does not follow the corresponding state principle, which is only applied to liquids and gases.

Effect of solid-phase amorphization on the spectral characteristics of europium-doped gadolinium molybdate

NASA Astrophysics Data System (ADS)

Shmurak, S. Z.; Kiselev, A. P.; Kurmasheva, D. M.; Red'Kin, B. S.; Sinitsyn, V. V.

2010-05-01

A method is proposed for detecting spectral characteristics of optically inactive molybdates of rare-earth elements by their doping with rare-earth ions whose luminescence lies in the transparency region of all structural modifications of the sample. Gadolinium molybdate is chosen as the object of investigations, while europium ions are used as an optically active and structurally sensitive admixture. It is shown that after the action of a high pressure under which gadolinium molybdate passes to the amorphous state, the spectral characteristics of Gd1.99Eu0.01(MoO4)3 (GMO:Eu) change radically; namely, considerable line broadening is observed in the luminescence spectra and the luminescence excitation spectra, while the long-wave threshold of optical absorption is shifted considerably (by approximately 1.1 eV) towards lower energies. It is found that by changing the structural state of GMO:Eu by solid-state amorphization followed by annealing, the spectral characteristics of the sample can be purposefully changed. This is extremely important for solving the urgent problem of designing high-efficiency light-emitting diodes producing “white” light.

Improving the chemical stability of amorphous solid dispersion with cocrystal technique by hot melt extrusion.

PubMed

Liu, Xu; Lu, Ming; Guo, Zhefei; Huang, Lin; Feng, Xin; Wu, Chuanbin

2012-03-01

To explore in-situ forming cocrystal as a single-step, efficient method to significantly depress the processing temperature and thus minimize the thermal degradation of heat-sensitive drug in preparation of solid dispersions by melting method (MM) and hot melt extrusion (HME). Carbamazepine (CBZ)-nicotinamide (NIC) cocrystal solid dispersions were prepared with polymer carriers PVP/VA, SOLUPLUS and HPMC by MM and/or HME. The formation of cocrystal was investigated by differential scanning calorimetry and hot stage polarized optical microscopy. State of CBZ in solid dispersion was characterized by X-ray powder diffraction and optical microscopy. Interactions between CBZ, NIC and polymers were investigated by FTIR. Dissolution behaviors of solid dispersions were compared with that of pure CBZ. CBZ-NIC cocrystal with melting point of 160°C was formed in polymer carriers during heating process, and the preparation temperature of amorphous CBZ solid dispersion was therefore depressed to 160°C. The dissolution rate of CBZ-NIC cocrystal solid dispersion was significantly increased. By in-situ forming cocrystal, chemically stable amorphous solid dispersions were prepared by MM and HME at a depressed processing temperature. This method provides an attractive opportunity for HME of heat-sensitive drugs.

Newly recognized hosts for uranium in the Hanford Site vadose zone

USGS Publications Warehouse

Stubbs, J.E.; Veblen, L.A.; Elbert, D.C.; Zachara, J.M.; Davis, J.A.; Veblen, D.R.

2009-01-01

Uranium contaminated sediments from the U.S. Department of Energy's Hanford Site have been investigated using electron microscopy. Six classes of solid hosts for uranium were identified. Preliminary sediment characterization was carried out using optical petrography, and electron microprobe analysis (EMPA) was used to locate materials that host uranium. All of the hosts are fine-grained and intergrown with other materials at spatial scales smaller than the analytical volume of the electron microprobe. A focused ion beam (FIB) was used to prepare electron-transparent specimens of each host for the transmission electron microscope (TEM). The hosts were identified as: (1) metatorbernite [Cu(UO2)2(PO4)2??8H2O]; (2) coatings on sediment clasts comprised mainly of phyllosilicates; (3) an amorphous zirconium (oxyhydr)oxide found in clast coatings; (4) amorphous and poorly crystalline materials that line voids within basalt lithic fragments; (5) amorphous palagonite surrounding fragments of basaltic glass; and (6) Fe- and Mn-oxides. These findings demonstrate the effectiveness of combining EMPA, FIB, and TEM to identify solid-phase contaminant hosts. Furthermore, they highlight the complexity of U geochemistry in the Hanford vadose zone, and illustrate the importance of microscopic transport in controlling the fate of contaminant metals in the environment. ?? 2008 Elsevier Ltd.

High-density amorphous ice: A path-integral simulation

NASA Astrophysics Data System (ADS)

Herrero, Carlos P.; Ramírez, Rafael

2012-09-01

Structural and thermodynamic properties of high-density amorphous (HDA) ice have been studied by path-integral molecular dynamics simulations in the isothermal-isobaric ensemble. Interatomic interactions were modeled by using the effective q-TIP4P/F potential for flexible water. Quantum nuclear motion is found to affect several observable properties of the amorphous solid. At low temperature (T = 50 K) the molar volume of HDA ice is found to increase by 6%, and the intramolecular O-H distance rises by 1.4% due to quantum motion. Peaks in the radial distribution function of HDA ice are broadened with respect to their classical expectancy. The bulk modulus, B, is found to rise linearly with the pressure, with a slope ∂B/∂P = 7.1. Our results are compared with those derived earlier from classical and path-integral simulations of HDA ice. We discuss similarities and discrepancies with those earlier simulations.

Influence of isotopic disorder on solid state amorphization and polyamorphism in solid H2O -D2O solutions

NASA Astrophysics Data System (ADS)

Gromnitskaya, E. L.; Danilov, I. V.; Lyapin, A. G.; Brazhkin, V. V.

2015-10-01

We present a low-temperature and high-pressure ultrasonic study of elastic properties of isotopic H2O-D2O solid solutions, comparing their properties with those of the isotopically pure H2O and D2O ices. Measurements were carried out for solid state amorphization (SSA) from 1h to high-density amorphous (HDA) ice upon compression up to 1.8 GPa at 77 K and for the temperature-induced (77 -190 K ) u-HDA (unrelaxed HDA) → e-HDA (expanded HDA) → low-density amorphous (LDA )→1 c cascade of ice transformations near room pressure. There are many similarities in the elasticity behaviour of H2O ,D2O , and H2O-D2O solid solutions, including the softening of the shear elastic modulus as a precursor of SSA and the HDA →LDA transition. We have found significant isotopic effects during H/D substitution, including elastic softening of H2O -D2O solid solutions with respect to the isotopically pure ices in the case of the bulk moduli of ices 1c and 1h and for both bulk and shear elastic moduli of HDA ice at high pressures (>1 GPa ) . This softening is related to the configurational isotopic disorder in the solid solutions. At low pressures, the isotope concentration dependence of the elastic moduli of u-HDA ice changes remarkably and becomes monotonic with pronounced change of the bulk modulus (≈20 %) .

Communication: Unraveling the 4He droplet-mediated soft-landing from ab initio-assisted and time-resolved density functional simulations: Au@4He300/TiO2(110)

NASA Astrophysics Data System (ADS)

de Lara-Castells, María Pilar; Aguirre, Néstor F.; Stoll, Hermann; Mitrushchenkov, Alexander O.; Mateo, David; Pi, Martí

2015-04-01

An ab-initio-based methodological scheme for He-surface interactions and zero-temperature time-dependent density functional theory for superfluid 4He droplets motion are combined to follow the short-time collision dynamics of the Au@4He300 system with the TiO2(110) surface. This composite approach demonstrates the 4He droplet-assisted sticking of the metal species to the surface at low landing energy (below 0.15 eV/atom), thus providing the first theoretical evidence of the experimentally observed 4He droplet-mediated soft-landing deposition of metal nanoparticles on solid surfaces [Mozhayskiy et al., J. Chem. Phys. 127, 094701 (2007) and Loginov et al., J. Phys. Chem. A 115, 7199 (2011)].

Inert gas annealing effect in solution-processed amorphous indium-gallium-zinc-oxide thin-film transistors

NASA Astrophysics Data System (ADS)

Lee, Seungwoon; Jeong, Jaewook

2017-08-01

In this paper, the annealing effect of solution-processed amorphous indium-gallium-zinc-oxide thin-film transistors (a-IGZO TFTs), under ambient He (He-device), is systematically analyzed by comparison with those under ambient O2 (O2-device) and N2 (N2-device), respectively. The He-device shows high field-effect mobility and low subthreshold slope owing to the minimization of the ambient effect. The degradation of the O2- and N2-device performances originate from their respective deep acceptor-like and shallow donor-like characteristics, which can be verified by comparison with the He-device. However, the three devices show similar threshold voltage instability under prolonged positive bias stress due to the effect of excess oxygen. Therefore, annealing in ambient He is the most suitable method for the fabrication of reference TFTs to study the various effects of the ambient during the annealing process in solution-processed a-IGZO TFTs.

New measurements of the sticking coefficient and binding energy of molecules on non-porous amorphous solid water in the submonolayer regime

NASA Astrophysics Data System (ADS)

He, Jiao; Acharyya, Kinsuk; Emtiaz, S. M.; Vidali, Gianfranco

2016-06-01

Sticking and adsorption of molecules on dust grains are two important processes in gas-grain interactions. We accurately measured both the sticking coefficient and the binding energy of several key molecules on the surface of amorphous solid water as a function of coverage.A time-resolved scattering technique was used to measure sticking coefficient of H2, D2, N2, O2, CO, CH4, and CO2 on non-porous amorphous solid water (np-ASW) in the low coverage limit over a wide range of surface temperatures. We found that the time-resolved scattering technique is advantageous over the conventional King-Wells method that underestimates the sticking coefficient. Based on the measured values we suggest a useful general formula of the sticking coefficient as a function of grain temperature and molecule-surface binding energy.We measured the binding energy of N2, CO, O2, CH4, and CO2 on np-ASW, and of N2 and CO on porous amorphous solid water (p-ASW). We were able to measure binding energies down to a fraction of 1% of a layer, thus making these measurements more appropriate for astrochemistry than the existing values. We found that CO2 forms clusters on np-ASW surface even at very low coverage; this may help in explaining the segregation of CO2 in ices. The binding energies of N2, CO, O2, and CH4 on np-ASW decrease with coverage in the submonolayer regime. Their values in the low coverage limit are much higher than what is commonly used in gas-grain models. An empirical formula was used to describe the coverage dependence of the binding energies. We used the newly determined binding energy distributions in a simulation of gas-grain chemistry for cold dense clouds and hot core models. We found that owing to the higher value of desorption energy in the sub-monlayer regime a fraction of all these ices stays much longer and to higher temperature on the grain surface compared to the case using single value energies as currently done in astrochemical models.This work was supported in part by a grant to GV from NSF --- Astronomy & Astrophysics Division (#1311958)

Moisture-Induced Amorphous Phase Separation of Amorphous Solid Dispersions: Molecular Mechanism, Microstructure, and Its Impact on Dissolution Performance.

PubMed

Chen, Huijun; Pui, Yipshu; Liu, Chengyu; Chen, Zhen; Su, Ching-Chiang; Hageman, Michael; Hussain, Munir; Haskell, Roy; Stefanski, Kevin; Foster, Kimberly; Gudmundsson, Olafur; Qian, Feng

2018-01-01

Amorphous phase separation (APS) is commonly observed in amorphous solid dispersions (ASD) when exposed to moisture. The objective of this study was to investigate: (1) the phase behavior of amorphous solid dispersions composed of a poorly water-soluble drug with extremely low crystallization propensity, BMS-817399, and PVP, following exposure to different relative humidity (RH), and (2) the impact of phase separation on the intrinsic dissolution rate of amorphous solid dispersion. Drug-polymer interaction was confirmed in ASDs at different drug loading using infrared (IR) spectroscopy and water vapor sorption analysis. It was found that the drug-polymer interaction could persist at low RH (≤75% RH) but was disrupted after exposure to high RH, with the advent of phase separation. Surface morphology and composition of 40/60 ASD at micro-/nano-scale before and after exposure to 95% RH were also compared. It was found that hydrophobic drug enriched on the surface of ASD after APS. However, for the 40/60 ASD system, the intrinsic dissolution rate of amorphous drug was hardly affected by the phase behavior of ASD, which may be partially attributed to the low crystallization tendency of amorphous BMS-817399 and enriched drug amount on the surface of ASD. Intrinsic dissolution rate of PVP decreased resulting from APS, leading to a lower concentration in the dissolution medium, but supersaturation maintenance was not anticipated to be altered after phase separation due to the limited ability of PVP to inhibit drug precipitation and prolong the supersaturation of drug in solution. This study indicated that for compounds with low crystallization propensity and high hydrophobicity, the risk of moisture-induced APS is high but such phase separation may not have profound impact on the drug dissolution performance of ASDs. Therefore, application of ASD technology on slow crystallizers could incur low risks not only in physical stability but also in dissolution performance. Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Topical delivery of roxithromycin solid-state forms entrapped in vesicles.

PubMed

Csongradi, Candice; du Plessis, Jeanetta; Aucamp, Marique Elizabeth; Gerber, Minja

2017-05-01

Recently, considerable interest developed in using newer/improved antibiotics for the treatment of Acne vulgaris. During this study, different roxithromycin solid-state forms (i.e. crystalline and amorphous) were encapsulated into vesicle systems (niosomes, proniosomes, ufosomes and pro-ufosomes) for dermis targeted delivery. Characterization of the vesicles was done with transmission electron microscopy, light microscopy, droplet size, droplet size distribution, pH, zeta-potential and entrapment efficiency percentage. Finally, comparative release and topical diffusion studies were performed, to evaluate if targeted topical delivery was obtained and if the roxithromycin solid-state amorphous forms resulted in improved topical delivery. Vesicle systems containing different roxithromycin (2%) solid-state forms were successfully prepared and characterized. The vesicles showed optimal properties for topical delivery. All carrier systems had topical delivery to the epidermis-dermis, whilst no roxithromycin was found in the receptor compartment or stratum corneum-epidermis. The niosomes were the leading formulation and the two amorphous forms had better topical delivery than the crystalline form. Successful targeted delivery of roxithromycin was obtained in the dermis, where the activity against Propionibacterium acnes is needed. The amorphous forms seemed to have held their solid-state form during formulation and in the vesicles, showing improved topical delivery in comparison to the crystalline form. Copyright © 2017 Elsevier B.V. All rights reserved.

The study of the thermal behavior of a new semicrystalline polyimide

NASA Technical Reports Server (NTRS)

Cheng, Stephen Z. D.; Chalmers, Tammy M.

1992-01-01

Thermal properties of a new semicrystalline polyimide synthesized from 3,3',4,4' benzophenone tetracarboxylic dianhydride (BTDA) and 2,2 dimethyl 1,2-(4 aminophenoxy) propane (DMDA) were studied. Heat capacities in the solid and liquid states of BTDA-DMDA were measured. The heat capacity increase at the glass transition temperature (T sub g = 230 C) is 145 J/(C mol) for amorphous BTDA-DMDA. The equilibrium heat of fusion of the BTDA-DMDA crystals was obtained using wide angle X ray diffraction and differential scanning calorimetry measurements, and it is 75.8 kJ/mol. Based on the information of crystallinity and the heat capacity increase at T sub g, a rigid amorphous fraction is identified in semicrystalline BTDA-DMDA samples. The rigid amorphous fraction represents an interfacial region between the crystalline and amorphous states. In particular, this fraction increases with the crystallinity of the sample which should be associated with crystal sizes, and therefore, with crystal morphology. It was also found that this polymer has a high temperature crystal phase upon annealing above its original melting temperature. The thermal degradation activation energies are determined to be 154 and 150 kJ/mol in nitrogen and air, respectively.

Characterization of Physical and Mechanical Properties of Miscible Lactose-Sugars Systems.

PubMed

Li, Runjing; Roos, Yrjö H; Miao, Song

2017-09-01

Lactose-sugars systems were produced by spray drying. They were lactose, lactose-glucose (4:1) mixtures, lactose-maltose (4:1) mixtures, lactose-sucrose (4:1) mixtures, lactose-trehalose (4:1) mixtures, and lactose-corn syrup solids (CSS) (4:1) mixtures. The physical characteristics, water sorption behavior, glass transition, and mechanical properties of miscible lactose-sugars systems were investigated. Lactose-glucose mixtures had larger particle size than other lactose-sugars systems after spray drying. The presence of glucose or sucrose in lactose-sugars mixtures decreased the glass transition temperatures of amorphous systems, while the presence of maltose and trehalose had only minor impact on the glass transition temperatures. Moreover, glucose accelerated the crystallization of amorphous system at 0.44 a w , but its presence delayed the loss of sorbed water at higher water activities (≥0.54 a w ). Mechanical property study indicated that glucose and sucrose in amorphous system could result in an increase of molecular mobility, while the presence of CSS could decrease the free volume and maintain the stiffness of the miscible systems. © 2017 Institute of Food Technologists®.

Different amorphous solid-state forms of roxithromycin: A thermodynamic and morphological study.

PubMed

Milne, Marnus; Liebenberg, Wilna; Aucamp, Marique Elizabeth

2016-02-10

The striking impact that different preparation methods have on the characteristics of amorphous solid-state forms has attracted considerable attention during the last two decades. The pursuit of more extensive knowledge regarding polyamorphism therefore continues. The aim of this study was firstly, to investigate the influence of different preparation techniques to obtain amorphous solid-state forms for the same active pharmaceutical ingredient, namely roxithromycin. The preparation techniques also report on a method utilizing hot air, which although it is based on a melt intermediary step, is considered a novel preparation method. Secondly, to conduct an in-depth investigation into any physico-chemical differences between the resulting amorphous forms and thirdly, to bring our findings into context with that of previous work done, whilst simultaneously discussing a well-defined interpretation for the term polyamorphism and propose a discernment between true polyamorphism and pseudo-polyamorphism/atypical-polyamorphism. The preparation techniques included melt, solution, and a combination of solution-mechanical disruption as intermediary steps. The resulting amorphous forms were investigated using differential scanning calorimetry, X-ray powder diffraction, hot-stage microscopy, scanning electron microscopy, and vapor sorption. Clear and significant thermodynamic differences were determined between the four amorphous forms. It was also deduced from this study that different preparation techniques have a mentionable impact on the morphological properties of the resulting amorphous roxithromycin powders. Thermodynamic properties as well as the physical characteristics of the amorphous forms greatly governed other physico-chemical properties i.e. solubility and dissolution. Copyright © 2015 Elsevier B.V. All rights reserved.

Investigation of solid phase composition on tablet surfaces by grazing incidence X-ray diffraction.

PubMed

Koradia, Vishal; Tenho, Mikko; Lopez de Diego, Heidi; Ringkjøbing-Elema, Michiel; Møller-Sonnergaard, Jørn; Salonen, Jarno; Lehto, Vesa-Pekka; Rantanen, Jukka

2012-01-01

To investigate solid state transformations of drug substances during compaction using grazing incidence X-ray diffraction (GIXD). The solid forms of three model drugs-theophylline (TP), nitrofurantoin (NF) and amlodipine besylate (AMB)-were compacted at different pressures (from 100 to 1000 MPa); prepared tablets were measured using GIXD. After the initial measurements of freshly compacted tablets, tablets were subjected to suitable recrystallization treatment, and analogous measurements were performed. Solid forms of TP, NF and AMB showed partial amorphization as well as crystal disordering during compaction; the extent of these effects generally increased as a function of pressure. The changes were most pronounced at the outer surface region. The different solid forms showed difference in the formation of amorphicity/crystal disordering. Dehydration due to compaction was observed for the TP monohydrate, whereas hydrates of NF and AMB were stable towards dehydration. With GIXD measurements, it was possible to probe the solid form composition at the different depths of the tablet surfaces and to obtain depth-dependent information on the compaction-induced amorphization, crystal disordering and dehydration.

Amorphous solid dispersions of piroxicam and Soluplus(®): Qualitative and quantitative analysis of piroxicam recrystallization during storage.

PubMed

Lust, Andres; Strachan, Clare J; Veski, Peep; Aaltonen, Jaakko; Heinämäki, Jyrki; Yliruusi, Jouko; Kogermann, Karin

2015-01-01

The conversion of active pharmaceutical ingredient (API) from amorphous to crystalline form is the primary stability issue in formulating amorphous solid dispersions (SDs). The aim of the present study was to carry out qualitative and quantitative analysis of the physical solid-state stability of the SDs of poorly water-soluble piroxicam (PRX) and polyvinyl caprolactam-polyvinyl acetate-polyethylene-glycol graft copolymer (Soluplus(®)). The SDs were prepared by a solvent evaporation method and stored for six months at 0% RH/6 °C, 0% RH/25 °C, 40% RH/25 °C and 75% RH/25 °C. Fourier transform infrared spectroscopy equipped with attenuated total reflection accessory (ATR-FTIR) and Raman spectroscopy were used for characterizing the physical solid-state changes and drug-polymer interactions. The principal component analysis (PCA) and multivariate curve resolution alternating least squares (MCR-ALS) were used for the qualitative and quantitative analysis of Raman spectra collected during storage. When stored at 0% RH/6 °C and at 0% RH/25 °C, PRX in SDs remained in an amorphous form since no recrystallization was observed by ATR-FTIR and Raman spectroscopy. Raman spectroscopy coupled with PCA and MCR-ALS and ATR-FTIR spectroscopy enabled to detect the recrystallization of amorphous PRX in the samples stored at higher humidity. Copyright © 2015 Elsevier B.V. All rights reserved.

Development of an analytical method for crystalline content determination in amorphous solid dispersions produced by hot-melt extrusion using transmission Raman spectroscopy: A feasibility study.

PubMed

Netchacovitch, L; Dumont, E; Cailletaud, J; Thiry, J; De Bleye, C; Sacré, P-Y; Boiret, M; Evrard, B; Hubert, Ph; Ziemons, E

2017-09-15

The development of a quantitative method determining the crystalline percentage in an amorphous solid dispersion is of great interest in the pharmaceutical field. Indeed, the crystalline Active Pharmaceutical Ingredient transformation into its amorphous state is increasingly used as it enhances the solubility and bioavailability of Biopharmaceutical Classification System class II drugs. One way to produce amorphous solid dispersions is the Hot-Melt Extrusion (HME) process. This study reported the development and the comparison of the analytical performances of two techniques, based on backscattering and transmission Raman spectroscopy, determining the crystalline remaining content in amorphous solid dispersions produced by HME. Principal Component Analysis (PCA) and Partial Least Squares (PLS) regression were performed on preprocessed data and tended towards the same conclusions: for the backscattering Raman results, the use of the DuoScan™ mode improved the PCA and PLS results, due to a larger analyzed sampling volume. For the transmission Raman results, the determination of low crystalline percentages was possible and the best regression model was obtained using this technique. Indeed, the latter acquired spectra through the whole sample volume, in contrast with the previous surface analyses performed using the backscattering mode. This study consequently highlighted the importance of the analyzed sampling volume. Copyright © 2017 Elsevier B.V. All rights reserved.

Preparation and characterization of azithromycin--Aerosil 200 solid dispersions with enhanced physical stability.

PubMed

Li, Xuechao; Peng, Huanhuan; Tian, Bin; Gou, Jingxin; Yao, Qing; Tao, Xiaoguang; He, Haibing; Zhang, Yu; Tang, Xing; Cai, Cuifang

2015-01-01

The main purpose of this study was to investigate the feasibility of azithromycin (AZI)--Aerosil 200 solid dispersions specifically with high stability under accelerated condition (40 °C/75% RH). Ball milling (BM) and hot-melt extrusion (HME) were used to prepare AZI solid dispersions. The physical properties of solid dispersions were evaluated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). For solid dispersions prepared with both methods, no crystalline of AZI was detected (except for AZI: Aerosil 200=75:25) by DSC or PXRD, indicating the amorphous state of AZI in solid dispersions. The FT-IR results demonstrated the loss of crystallization water and the formation of hydrogen bonds between Aerosil 200 and AZI during the preparation of solid dispersions. After 4 weeks storage under accelerated condition, the degree of crystallinity of AZI increased in solid dispersions prepared by BM, whereas for solid dispersions containing AZI, Aerosil 200 and glyceryl behenate (GB) prepared by HME, no crystalline of AZI was identified. This high stability can be attributed to the hydrophobic properties of GB and the presence of hydrogen bonds. Based on the above results, it is inferred the protection of hydrogen bonds between AZI and Aerosil 200 formed during preparation process effectively inhibited the recrystallization of AZI and improved the physical stability of amorphous AZI in the presence of Aerosil 200. Copyright © 2015 Elsevier B.V. All rights reserved.

Formation of soft magnetic high entropy amorphous alloys composites containing in situ solid solution phase

NASA Astrophysics Data System (ADS)

Wei, Ran; Sun, Huan; Chen, Chen; Tao, Juan; Li, Fushan

2018-03-01

Fe-Co-Ni-Si-B high entropy amorphous alloys composites (HEAACs), which containing high entropy solid solution phase in amorphous matrix, show good soft magnetic properties and bending ductility even in optimal annealed state, were successfully developed by melt spinning method. The crystallization phase of the HEAACs is solid solution phase with body centered cubic (BCC) structure instead of brittle intermetallic phase. In addition, the BCC phase can transformed into face centered cubic (FCC) phase with temperature rise. Accordingly, Fe-Co-Ni-Si-B high entropy alloys (HEAs) with FCC structure and a small amount of BCC phase was prepared by copper mold casting method. The HEAs exhibit high yield strength (about 1200 MPa) and good plastic strain (about 18%). Meanwhile, soft magnetic characteristics of the HEAs are largely reserved from HEAACs. This work provides a new strategy to overcome the annealing induced brittleness of amorphous alloys and design new advanced materials with excellent comprehensive properties.

Electron-rich driven electrochemical solid-state amorphization in Li-Si alloys.

PubMed

Wang, Zhiguo; Gu, Meng; Zhou, Yungang; Zu, Xiaotao; Connell, Justin G; Xiao, Jie; Perea, Daniel; Lauhon, Lincoln J; Bang, Junhyeok; Zhang, Shengbai; Wang, Chongmin; Gao, Fei

2013-09-11

The physical and chemical behaviors of materials used in energy storage devices, such as lithium-ion batteries (LIBs), are mainly controlled by an electrochemical process, which normally involves insertion/extraction of ions into/from a host lattice with a concurrent flow of electrons to compensate charge balance. The fundamental physics and chemistry governing the behavior of materials in response to the ions insertion/extraction is not known. Herein, a combination of in situ lithiation experiments and large-scale ab initio molecular dynamics simulations are performed to explore the mechanisms of the electrochemically driven solid-state amorphization in Li-Si systems. We find that local electron-rich condition governs the electrochemically driven solid-state amorphization of Li-Si alloys. This discovery provides the fundamental explanation of why lithium insertion in semiconductor and insulators leads to amorphization, whereas in metals, it leads to a crystalline alloy. The present work correlates electrochemically driven reactions with ion insertion, electron transfer, lattice stability, and phase equilibrium.

Electron-Rich Driven Electrochemical Solid-State Amorphization in Li-Si Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zhiguo; Gu, Meng; Zhou, Yungang

2013-08-14

The physical and chemical behaviors of materials used in energy storage devices, such as lithium-ion batteries (LIBs), are mainly controlled by an electrochemical process, which normally involves insertion/extraction of ions into/from a host lattice with a concurrent flow of electrons to compensate charge balance. The fundamental physics and chemistry governing the behavior of materials in response to the ions insertion/extraction is not known. Herein, a combination of in situ lithiation experiments and large-scale ab initio molecular dynamics simulations are performed to explore the mechanisms of the electrochemically driven solid-state amorphization in Li-Si systems. We find that local electron-rich condition governsmore » the electrochemically driven solid-state amorphization of Li-Si alloys. This discovery provides the fundamental explanation of why lithium insertion in semiconductor and insulators leads to amorphization, whereas in metals, it leads to a crystalline alloy. The present work correlates electrochemically driven reactions with ion insertion, electron transfer, lattice stability and phase equilibrium.« less

Amorphization within the tablet: Using microwave irradiation to form a glass solution in situ.

PubMed

Doreth, Maria; Hussein, Murtadha Abdul; Priemel, Petra A; Grohganz, Holger; Holm, René; Lopez de Diego, Heidi; Rades, Thomas; Löbmann, Korbinian

2017-03-15

In situ amorphization is a concept that allows to amorphize a given drug in its final dosage form right before administration. Hence, this approach can potentially be used to circumvent recrystallization issues that other amorphous formulation approaches are facing during storage. In this study, the feasibility of microwave irradiation to prepare amorphous solid dispersions (glass solutions) in situ was investigated. Indomethacin (IND) and polyvinylpyrrolidone K12 (PVP) were tableted at a 1:2 (w/w) ratio. In order to study the influence of moisture content and energy input on the degree of amorphization, tablet formulations were stored at different relative humidity (32, 43 and 54% RH) and subsequently microwaved using nine different power-time combinations up to a maximum energy input of 90kJ. XRPD results showed that up to 80% (w/w) of IND could be amorphized within the tablet. mDSC measurements revealed that with increasing microwaving power and time, the fractions of crystalline IND and amorphous PVP reduced, whereas the amount of in situ formed IND-PVP glass solution increased. Intrinsic dissolution showed that the dissolution rate of the microwaved solid dispersion was similar to that of a quench cooled, fully amorphous glass solution even though the microwaved samples contained residual crystalline IND. Copyright © 2017 Elsevier B.V. All rights reserved.

Decoupling of Solid 4He Layers under the Superfluid Overlayer

NASA Astrophysics Data System (ADS)

Ishibashi, Kenji; Hiraide, Jo; Taniguchi, Junko; Suzuki, Masaru

2018-03-01

It has been reported that in a large oscillation amplitude, the mass decoupling of multilayer 4He films adsorbed on graphite results from the depinning of the second solid atomic layer. This decoupling suddenly vanishes below a certain low temperature TD due to the cancellation of mass decoupling by the superfluid counterflow of the the overylayer. We studied the relaxation of the depinned state at various temperatures, after reduction of oscillation amplitude below TD . It was found that above the superfluid transition temperature the mass decoupling revives with a relaxation time of several 100 s. It strongly supports that the depinned state of the second solid atomic layer remains underneath the superfluid overlayer.

Atomistic modeling of crystal-to-amorphous transition and associated kinetics in the Ni-Nb system by molecular dynamics simulations.

PubMed

Dai, X D; Li, J H; Liu, B X

2005-03-17

With the aid of ab initio calculations, an n-body potential of the Ni-Nb system is constructed under the Finnis-Sinclair formalism and the constructed potential is capable of not only reproducing some static physical properties but also revealing the atomistic mechanism of crystal-to-amorphous transition and associated kinetics. With application of the constructed potential, molecular dynamics simulations using the solid solution models reveal that the physical origin of crystal-to-amorphous transition is the crystalline lattice collapsing while the solute atoms are exceeding the critical solid solubilities, which are determined to be 19 atom % Ni and 13 atom % Nb for the Nb- and Ni-based solid solutions, respectively. It follows that an intrinsic glass-forming ability of the Ni-Nb system is within 19-87 atom % Ni, which matches well with that observed in ion beam mixing/solid-state reaction experiments. Simulations using the Nb/Ni/Nb (Ni/Nb/Ni) sandwich models indicate that the amorphous layer at the interfaces grows in a layer-by-layer mode and that, upon dissolving solute atoms, the Ni lattice approaches and exceeds its critical solid solubility faster than the Nb lattice, revealing an asymmetric behavior in growth kinetics. Moreover, an energy diagram is obtained by computing the energetic sequence of the Ni(x)Nb(100)(-)(x) alloy in fcc, bcc, and amorphous structures, respectively, over the entire composition range, and the diagram could serve as a guide for predicting the metastable alloy formation in the Ni-Nb system.

Formulation and process design for a solid dosage form containing a spray-dried amorphous dispersion of ibipinabant.

PubMed

Leane, Michael M; Sinclair, Wayne; Qian, Feng; Haddadin, Raja; Brown, Alan; Tobyn, Mike; Dennis, Andrew B

2013-01-01

Amorphous forms of poorly soluble drugs are more frequently being incorporated into solid dispersions for administration and extensive research has led to a reasonable understanding of how these dispersions, although still kinetically unstable, improve stability relative to the pure amorphous form. There remains however a paucity of literature describing the effects on such solid dispersions of subsequent processing into solid dosage forms such as tablets. This paper addresses this area by looking at the effects of the addition of common excipients and different manufacturing routes on the stability of a spray-dried dispersion (SDD) of the cannabinoid CB-1 antagonist, ibipinabant. A marked difference in physical stability of tablets was seen with the different fillers with microcrystalline cellulose (MCC) giving the best stability profile. It was found that minimising the number of compression steps led to improved formulation stability with a direct compression process giving the best results. Increased levels of crystallinity were seen in coated tablets most likely due to the exposure of the amorphous matrix to moisture and heat during the coating process. DSIMS analysis of the SDD particles indicated increased levels of polymer on the surface.

Communication: Unraveling the {sup 4}He droplet-mediated soft-landing from ab initio-assisted and time-resolved density functional simulations: Au@{sup 4}He{sub 300}/TiO{sub 2}(110)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lara-Castells, María Pilar de, E-mail: Pilar.deLara.Castells@csic.es; Aguirre, Néstor F.; Stoll, Hermann

2015-04-07

An ab-initio-based methodological scheme for He-surface interactions and zero-temperature time-dependent density functional theory for superfluid {sup 4}He droplets motion are combined to follow the short-time collision dynamics of the Au@{sup 4}He{sub 300} system with the TiO{sub 2}(110) surface. This composite approach demonstrates the {sup 4}He droplet-assisted sticking of the metal species to the surface at low landing energy (below 0.15 eV/atom), thus providing the first theoretical evidence of the experimentally observed {sup 4}He droplet-mediated soft-landing deposition of metal nanoparticles on solid surfaces [Mozhayskiy et al., J. Chem. Phys. 127, 094701 (2007) and Loginov et al., J. Phys. Chem. A 115,more » 7199 (2011)].« less

Mathematical model to analyze the dissolution behavior of metastable crystals or amorphous drug accompanied with a solid-liquid interface reaction.

PubMed

Hirai, Daiki; Iwao, Yasunori; Kimura, Shin-Ichiro; Noguchi, Shuji; Itai, Shigeru

2017-04-30

Metastable crystals and the amorphous state of poorly water-soluble drugs in solid dispersions (SDs), are subject to a solid-liquid interface reaction upon exposure to a solvent. The dissolution behavior during the solid-liquid interface reaction often shows that the concentration of drugs is supersaturated, with a high initial drug concentration compared with the solubility of stable crystals but finally approaching the latter solubility with time. However, a method for measuring the precipitation rate of stable crystals and/or the potential solubility of metastable crystals or amorphous drugs has not been established. In this study, a novel mathematical model that can represent the dissolution behavior of the solid-liquid interface reaction for metastable crystals or amorphous drug was developed and its validity was evaluated. The theory for this model was based on the Noyes-Whitney equation and assumes that the precipitation of stable crystals at the solid-liquid interface occurs through a first-order reaction. Moreover, two models were developed, one assuming that the surface area of the drug remains constant because of the presence of excess drug in the bulk and the other that the surface area changes in time-dependency because of agglomeration of the drug. SDs of Ibuprofen (IB)/polyvinylpyrrolidone (PVP) were prepared and their dissolution behaviors under non-sink conditions were fitted by the models to evaluate improvements in solubility. The model assuming time-dependent surface area showed good agreement with experimental values. Furthermore, by applying the model to the dissolution profile, parameters such as the precipitation rate and the potential solubility of the amorphous drug were successfully calculated. In addition, it was shown that the improvement in solubility with supersaturation was able to be evaluated quantitatively using this model. Therefore, this mathematical model would be a useful tool to quantitatively determine the supersaturation concentration of a metastable drug from solid dispersions. Copyright © 2017 Elsevier B.V. All rights reserved.

Why natural monazite never becomes amorphous: Experimental evidence for alpha self-healing

DOE PAGES

Seydoux-Guillaume, Anne -Magali; Deschanels, Xavier; Baumier, Cedric; ...

2018-05-01

Monazite, a common accessory rare-earth orthophosphate mineral in the continental crust widely used in U-Pb geochronology, holds promise for (U-Th)/He thermochronology and for the immobilization of Pu and minor actinides (MA) coming from spent nuclear fuel reprocessing. Previous results obtained on natural and plutonium-doped monazite have demonstrated the ability of this structure to maintain a crystalline state despite high radiation damage levels. However, the low critical temperature (180 °C), above which amorphization cannot be achieved in natural monazite under ion irradiation, does not explain this old and unsolved paradox: why do natural monazites, independent of their geological history, remain crystallinemore » even when they did not experience any thermal event that could heal the defects? This is what the present study aims to address. Synthetic polycrystals of LaPO 4-monazite were irradiated sequentially and simultaneously with α particles (He) and gold (Au) ions. Here, our results demonstrate experimentally for the first time in monazite, the existence of the defect recovery mechanism, called α-healing, acting in this structure due to electronic energy loss of α particles, which explains the absence of amorphization in natural monazite samples. This mechanism is critically important for monazite geo- and thermochronology and to design and predictively model the long-term behavior of ceramic matrices for nuclear waste conditioning.« less

Why natural monazite never becomes amorphous: Experimental evidence for alpha self-healing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seydoux-Guillaume, Anne -Magali; Deschanels, Xavier; Baumier, Cedric

Monazite, a common accessory rare-earth orthophosphate mineral in the continental crust widely used in U-Pb geochronology, holds promise for (U-Th)/He thermochronology and for the immobilization of Pu and minor actinides (MA) coming from spent nuclear fuel reprocessing. Previous results obtained on natural and plutonium-doped monazite have demonstrated the ability of this structure to maintain a crystalline state despite high radiation damage levels. However, the low critical temperature (180 °C), above which amorphization cannot be achieved in natural monazite under ion irradiation, does not explain this old and unsolved paradox: why do natural monazites, independent of their geological history, remain crystallinemore » even when they did not experience any thermal event that could heal the defects? This is what the present study aims to address. Synthetic polycrystals of LaPO 4-monazite were irradiated sequentially and simultaneously with α particles (He) and gold (Au) ions. Here, our results demonstrate experimentally for the first time in monazite, the existence of the defect recovery mechanism, called α-healing, acting in this structure due to electronic energy loss of α particles, which explains the absence of amorphization in natural monazite samples. This mechanism is critically important for monazite geo- and thermochronology and to design and predictively model the long-term behavior of ceramic matrices for nuclear waste conditioning.« less

Experimental evidence for a crossover between two distinct mechanisms of amorphization in ice Ih under pressure.

PubMed

Strässle, Thierry; Klotz, Stefan; Hamel, Gérard; Koza, Michael M; Schober, Helmut

2007-10-26

We report neutron scattering data which reveal the central role of phonon softening leading to a negative melting line, solid-state amorphization, and negative thermal expansion of ice. We find that pressure-induced amorphization is due to mechanical melting at low temperatures, while at higher temperatures amorphization is governed by thermal melting (violations of Born's and Lindemann's criteria, respectively). This confirms earlier conjectures of a crossover between two distinct amorphization mechanisms and provides a natural explanation for the strong annealing observed in high-density amorphous ice.

Extensively Reversible Thermal Transformations of a Bistable, Fluorescence-Switchable Molecular Solid: Entry into Functional Molecular Phase-Change Materials.

PubMed

Srujana, P; Radhakrishnan, T P

2015-06-15

Functional phase-change materials (PCMs) are conspicuously absent among molecular materials in which the various attributes of inorganic solids have been realized. While organic PCMs are primarily limited to thermal storage systems, the amorphous-crystalline transformation of materials like Ge-Sb-Te find use in advanced applications such as information storage. Reversible amorphous-crystalline transformations in molecular solids require a subtle balance between robust supramolecular assembly and flexible structural elements. We report novel diaminodicyanoquinodimethanes that achieve this transformation by interlinked helical assemblies coupled with conformationally flexible alkoxyalkyl chains. They exhibit highly reversible thermal transformations between bistable (crystalline/amorphous) forms, along with a prominent switching of the fluorescence emission energy and intensity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cefuroxime axetil solid dispersion with polyglycolized glycerides for improved stability and bioavailability.

PubMed

Dhumal, Ravindra S; Biradar, Shailesh V; Aher, Suyog; Paradkar, Anant R

2009-06-01

Cefuroxime axetil (CA), a poorly soluble, broad spectrum cephalosporin ester prodrug, is hydrolysed by intestinal esterase prior to absorption, leading to poor and variable bioavailability. The objective was therefore to formulate a stable amorphous solid dispersion of the drug with enhanced solubility and stability against enzymatic degradation. Spray drying was used to obtain a solid dispersion of CA with Gelucire 50/13 and Aerosil 200 (SDCAGA), and a solid dispersion of CA with polyvinyl pyrrolidone (SDCAP); amorphous CA (ACA) was obtained by spray drying CA alone. The formulations were characterized by differential scanning calorimetry, X-ray powder diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy studies, and compared for solubility, dissolution and bioavailability in rats. SDCAP and SDCAGA showed improved solubility and dissolution profiles owing to amorphization and formation of solid dispersions with hydrophilic carriers. The improved stability of amorphous CA in solid dispersions compared to ACA alone was attributed to hydrogen bonding interactions involving the amide of CA with the carbonyl of polyvinyl pyrrolidone in SDCAP, whereas in SDCAGA the interactions were at multiple sites involving the amide and carbonyl of CA with the carbonyl and hydroxyl of Gelucire 50/13. However, SDCAGA showed superior bioavailability compared to SDCAP, ACA and CA. Improvement in physical stability of solid dispersions was attributed to hydrogen bonding, while improvement in bioavailability of SDCAGA compared to SDCAP, in spite of comparable solubility and dissolution profile, may be attributed to Gelucire, which utilizes intestinal esterase for lipolysis, protecting the prodrug from enzymatic degradation to its non-absorbable base form.

Pressure-induced silica quartz amorphization studied by iterative stochastic surface walking reaction sampling.

PubMed

Zhang, Xiao-Jie; Shang, Cheng; Liu, Zhi-Pan

2017-02-08

The crystal to amorphous transformation is a common phenomenon in Nature and has important impacts on material properties. Our current knowledge on such complex solid transformation processes is, however, limited because of their slow kinetics and the lack of long-range ordering in amorphous structures. To reveal the kinetics in the amorphization of solids, this work, by developing iterative reaction sampling based on the stochastic surface walking global optimization method, investigates the well-known crystal to amorphous transformation of silica (SiO 2 ) under external pressures, the mechanism of which has long been debated for its non-equilibrium, pressure-sensitive kinetics and complex product components. Here we report for the first time the global potential energy surface (PES) and the lowest energy pathways for α-quartz amorphization from first principles. We show that the pressurization at 15 GPa, the reaction condition, can lift the quartz phase energetically close to the amorphous zone, which thermodynamically initializes the amorphization. More importantly, the large flexibility of Si cation coordination (including four, five and six coordination) results in many kinetically competing routes to more stable dense forms, including the known MI, stishovite, newly-identified MII and TI phases. All these pathways have high barriers due to the local Si-O bond breaking and are mediated by amorphous structures with five-fold Si. This causes simultaneous crystal-to-crystal and crystal-to-amorphous transitions. The high barrier and the reconstructive nature of the phase transition are the key kinetics origin for silica amorphization under pressures.

Application of Solid-State NMR Relaxometry for Characterization and Formulation Optimization of Grinding-Induced Drug Nanoparticle.

PubMed

Ueda, Keisuke; Higashi, Kenjirou; Moribe, Kunikazu

2016-03-07

The formation mechanism of drug nanoparticles was investigated using solid-state nuclear magnetic resonance (NMR) techniques for the efficient discovery of an optimized nanoparticle formulation. The cogrinding of nifedipine (NIF) with polymers, including hydroxypropyl methylcellulose (HPMC) and polyvinylpyrrolidone (PVP), and sodium dodecyl sulfate (SDS) was performed to prepare the NIF nanoparticle formulations. Then, solid-state NMR relaxometry was used for the nanometer-order characterization of NIF in the polymer matrix. Solid-state NMR measurements revealed that the crystal size of NIF was reduced to several tens of nanometers with amorphization of NIF by cogrinding with HPMC and SDS for 100 min. Similarly, the size of the NIF crystal was reduced to less than 90 nm in the 40 min ground mixture of NIF/PVP/SDS. Furthermore, 100 min grinding of NIF/PVP/SDS induced amorphization of almost all the NIF crystals followed by nanosizing. The hydrogen bond between NIF and PVP led to the efficient amorphization of NIF in the NIF/PVP/SDS system compared with NIF/HPMC/SDS system. The efficient nanosizing of the NIF crystal in the solid state, revealed by the solid-state NMR relaxation time measurements, enabled the formation of large amounts of NIF nanoparticles in water followed by the polymer dissolution. In contrast, excess amorphization of the NIF crystals failed to efficiently prepare the NIF nanoparticles. The solid-state characterization of the crystalline NIF revealed good correlation with the NIF nanoparticles formation during aqueous dispersion. Furthermore, the solid-state NMR measurements including relaxometry successfully elucidated the nanometer-order dispersion state of NIF in polymer matrix, leading to the discovery of optimized conditions for the preparation of suitable drug nanoparticles.

Low Energy Nuclear Reactions: Status at the Beginning of the New Millenium

NASA Astrophysics Data System (ADS)

Mallove, Eugene F.

2001-03-01

This talk will summarize some of the more convincing recent experiments that show that ^4He,^3He (including impossible to explain changes in the ^4He/^3He isotopic ratio), nuclear scale excess energy, tritium, low-level neutron production, and the transmutation of heavy elements can occur near room temperature in relatively simple systems. Despite inappropriate theory-based arguments against it and unethical attacks by people unfamiliar with the supporting experiments, the new field of solid state nuclear reactions is progressing. The physical theory behind the associated phenomena continues to be debated among theorists. But progress is being made. The facts of the history of this scientific controversy suggest that it is inadvisable to rush to judgment against allegedly ``impossible" new phenomena when increasingly careful experiments have revealed new vistas in physics. Detailed discussion of evidence for solid state nuclear reactions is available

The Influence of Drug Physical State on the Dissolution Enhancement of Solid Dispersions Prepared Via Hot-Melt Extrusion: A Case Study Using Olanzapine

PubMed Central

Pina, Maria Fátima; Zhao, Min; Pinto, João F; Sousa, João J; Craig, Duncan Q M

2014-01-01

In this study, we examine the relationship between the physical structure and dissolution behavior of olanzapine (OLZ) prepared via hot-melt extrusion in three polymers [polyvinylpyrrolidone (PVP) K30, polyvinylpyrrolidone-co-vinyl acetate (PVPVA) 6:4, and Soluplus® (SLP)]. In particular, we examine whether full amorphicity is necessary to achieve a favorable dissolution profile. Drug–polymer miscibility was estimated using melting point depression and Hansen solubility parameters. Solid dispersions were characterized using differential scanning calorimetry, X-ray powder diffraction, and scanning electron microscopy. All the polymers were found to be miscible with OLZ in a decreasing order of PVP>PVPVA>SLP. At a lower extrusion temperature (160°C), PVP generated fully amorphous dispersions with OLZ, whereas the formulations with PVPVA and SLP contained 14%–16% crystalline OLZ. Increasing the extrusion temperature to 180°C allowed the preparation of fully amorphous systems with PVPVA and SLP. Despite these differences, the dissolution rates of these preparations were comparable, with PVP showing a lower release rate despite being fully amorphous. These findings suggested that, at least in the particular case of OLZ, the absence of crystalline material may not be critical to the dissolution performance. We suggest alternative key factors determining dissolution, particularly the dissolution behavior of the polymers themselves. PMID:24765654

Hydration products in sulfoaluminate cements: Evaluation of amorphous phases by XRD/solid-state NMR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gastaldi, D., E-mail: dgastaldi@buzziunicem.it; Paul, G., E-mail: geo.paul@uniupo.it; Marchese, L.

The hydration of four sulfoaluminate cements have been studied: three sulfoaluminate systems, having different content of sulfate and silicate, and one blend Portland-CSA-calcium sulfate binder. Hydration was followed up to 90 days by means of a combination of X-ray diffraction and solid state MAS-NMR; Differential scanning calorimetry and Scanning electron microscopy were also performed in order to help the interpretation of experimental data. High amount of amorphous phases were found in all the four systems: in low-sulfate cements, amorphous part is mainly ascribed to monosulfate and aluminium hydroxide, while strätlingite is observed if belite is present in the cement; inmore » the blend system, C-S-H contributes to the amorphous phase beyond monosulfate.« less

Uptake properties of Ni2+ by nCaO.Al2O3.2SiO2 (n=1-4) prepared from solid-state reaction of kaolinite and calcite.

PubMed

Jha, Vinay Kumar; Kameshima, Yoshikazu; Nakajima, Akira; Okada, Kiyoshi; MacKenzie, Kenneth J D

2005-08-31

A series of nCaO.Al2O3.2SiO2 samples (n=1-4) were prepared by solid-state reaction of mechanochemically treated mixtures of kaolinite and calcite fired at 600-1000 degrees C for 24 h. All the samples were X-ray amorphous after firing at 600-800 degrees C but had crystallized by 900 degrees C. The main crystalline phases were anorthite (n=1), gehlenite (n=2 and 3) and larnite (n=4). The uptake of Ni2+ by nCaO.Al2O3.2SiO2 samples fired at 800 and 900 degrees C was investigated at room temperature using solutions with initial Ni2+ concentrations of 0.1-50 mmol/l. Amorphous samples (fired at 800 degrees C) showed a higher Ni2+ uptake capacity than crystalline samples (fired at 900 degrees C). Ni2+ uptake was found to increase with increasing of CaO content. Amorphous 4CaO.Al2O3.2SiO2 showed the highest Ni2+ uptake capacity (about 9 mmol/g). The Ni2+ uptake abilities of the present samples are higher than those of other materials reported in the literature. Since the sorbed Ni2+/released Ca2+ ratios of these samples are close to unity, ion replacement of Ni2+ for Ca2+ is thought to be the principal mechanism of Ni2+ uptake by the present samples.

Solid-state amorphization of rebamipide and investigation on solubility and stability of the amorphous form.

PubMed

Xiong, Xinnuo; Xu, Kailin; Li, Shanshan; Tang, Peixiao; Xiao, Ying; Li, Hui

2017-02-01

Solid-state amorphization of crystalline rebamipide (RBM) was realized by ball milling and spray drying. The amorphous content of samples milled for various time was quantified using X-ray powder diffraction. Crystalline RBM and three amorphous RBM obtained by milling and spray drying were characterized by morphological analysis, X-ray diffraction, thermal analysis and vibrational spectroscopy. The crystal structure of RBM was first determined by single-crystal X-ray diffraction. In addition, the solubility and dissolution rate of the RBM samples were investigated in different media. Results indicated that the solubility and the dissolution rates of spray-dried RBM-PVP in different media were highly improved compared with crystalline RBM. The physical stabilities of the three amorphous RBM were systematically investigated, and the stability orders under different storage temperatures and levels of relative humidity (RH) were both as follows: spray dried RBM < milled RBM < spray dried RBM-PVP. A direct glass-to-crystal transformation was induced under high RH, and the transformation rate rose with increasing RH. However, amorphous RBM could stay stable at RH levels lower than 57.6% (25 °C).

Si amorphization by focused ion beam milling: Point defect model with dynamic BCA simulation and experimental validation.

PubMed

Huang, J; Loeffler, M; Muehle, U; Moeller, W; Mulders, J J L; Kwakman, L F Tz; Van Dorp, W F; Zschech, E

2018-01-01

A Ga focused ion beam (FIB) is often used in transmission electron microscopy (TEM) analysis sample preparation. In case of a crystalline Si sample, an amorphous near-surface layer is formed by the FIB process. In order to optimize the FIB recipe by minimizing the amorphization, it is important to predict the amorphous layer thickness from simulation. Molecular Dynamics (MD) simulation has been used to describe the amorphization, however, it is limited by computational power for a realistic FIB process simulation. On the other hand, Binary Collision Approximation (BCA) simulation is able and has been used to simulate ion-solid interaction process at a realistic scale. In this study, a Point Defect Density approach is introduced to a dynamic BCA simulation, considering dynamic ion-solid interactions. We used this method to predict the c-Si amorphization caused by FIB milling on Si. To validate the method, dedicated TEM studies are performed. It shows that the amorphous layer thickness predicted by the numerical simulation is consistent with the experimental data. In summary, the thickness of the near-surface Si amorphization layer caused by FIB milling can be well predicted using the Point Defect Density approach within the dynamic BCA model. Copyright © 2017 Elsevier B.V. All rights reserved.

Phase Behavior of Ritonavir Amorphous Solid Dispersions during Hydration and Dissolution.

PubMed

Purohit, Hitesh S; Taylor, Lynne S

2017-12-01

The aim of this research was to study the interplay of solid and solution state phase transformations during the dissolution of ritonavir (RTV) amorphous solid dispersions (ASDs). RTV ASDs with polyvinylpyrrolidone (PVP), polyvinylpyrrolidone vinyl acetate (PVPVA) and hydroxypropyl methylcellulose acetate succinate (HPMCAS) were prepared at 10-50% drug loading by solvent evaporation. The miscibility of RTV ASDs was studied before and after exposure to 97% relative humidity (RH). Non-sink dissolution studies were performed on fresh and moisture-exposed ASDs. RTV and polymer release were monitored using ultraviolet-visible spectroscopy. Techniques including fluorescence spectroscopy, confocal imaging, scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC) and nanoparticle tracking analysis (NTA) were utilized to monitor solid and the solution state phase transformations. All RTV-PVP and RTV-PVPVA ASDs underwent moisture-induced amorphous-amorphous phase separation (AAPS) on high RH storage whereas RTV-HPMCAS ASDs remained miscible. Non-sink dissolution of PVP- and PVPVA-based ASDs at low drug loadings led to rapid RTV and polymer release resulting in concentrations in excess of amorphous solubility, liquid-liquid phase separation (LLPS) and amorphous nanodroplet formation. High drug loading PVP- and PVPVA-based ASDs did not exhibit LLPS upon dissolution as a consequence of extensive AAPS in the hydrated ASD matrix. All RTV-HPMCAS ASDs led to LLPS upon dissolution. RTV ASD dissolution is governed by a competition between the dissolution rate and the rate of phase separation in the hydrated ASD matrix. LLPS was observed for ASDs where the drug release was polymer controlled and only ASDs that remained miscible during the initial phase of dissolution led to LLPS. Techniques such as fluorescence spectroscopy, confocal imaging and SEM were useful in understanding the phase behavior of ASDs upon hydration and dissolution and were helpful in elucidating the mechanism of generation of amorphous nanodroplets.

Helium Irradiation and Implantation Effects on the Structure of Amorphous Silicon Oxycarbide

DOE PAGES

Su, Qing; Inoue, Shinsuke; Ishimaru, Manabu; ...

2017-06-20

Despite recent interest in amorphous ceramics for a variety of nuclear applications, many details of their structure before and after irradiation/implantation remain unknown. Here we investigated the short-range order of amorphous silicon oxycarbide (SiOC) alloys by using the atomic pair-distribution function (PDF) obtained from electron diffraction. The PDF results show that the structure of SiOC alloys are nearly unchanged after both irradiation up to 30 dpa and He implantation up to 113 at%. TEM characterization shows no sign of crystallization, He bubble or void formation, or segregation in all irradiated samples. Irradiation results in a decreased number of Si-O bondsmore » and an increased number of Si-C and C-O bonds. This study sheds light on the design of radiation-tolerant materials that do not experience helium swelling for advanced nuclear reactor applications.« less

Helium Irradiation and Implantation Effects on the Structure of Amorphous Silicon Oxycarbide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, Qing; Inoue, Shinsuke; Ishimaru, Manabu

Despite recent interest in amorphous ceramics for a variety of nuclear applications, many details of their structure before and after irradiation/implantation remain unknown. Here we investigated the short-range order of amorphous silicon oxycarbide (SiOC) alloys by using the atomic pair-distribution function (PDF) obtained from electron diffraction. The PDF results show that the structure of SiOC alloys are nearly unchanged after both irradiation up to 30 dpa and He implantation up to 113 at%. TEM characterization shows no sign of crystallization, He bubble or void formation, or segregation in all irradiated samples. Irradiation results in a decreased number of Si-O bondsmore » and an increased number of Si-C and C-O bonds. This study sheds light on the design of radiation-tolerant materials that do not experience helium swelling for advanced nuclear reactor applications.« less

Preparation of amorphous solid dispersions by rotary evaporation and KinetiSol Dispersing: approaches to enhance solubility of a poorly water-soluble gum extract.

PubMed

Bennett, Ryan C; Brough, Chris; Miller, Dave A; O'Donnell, Kevin P; Keen, Justin M; Hughey, Justin R; Williams, Robert O; McGinity, James W

2015-03-01

Acetyl-11-keto-β-boswellic acid (AKBA), a gum resin extract, possesses poor water-solubility that limits bioavailability and a high melting point making it difficult to successfully process into solid dispersions by fusion methods. The purpose of this study was to investigate solvent and thermal processing techniques for the preparation of amorphous solid dispersions (ASDs) exhibiting enhanced solubility, dissolution rates and bioavailability. Solid dispersions were successfully produced by rotary evaporation (RE) and KinetiSol® Dispersing (KSD). Solid state and chemical characterization revealed that ASD with good potency and purity were produced by both RE and KSD. Results of the RE studies demonstrated that AQOAT®-LF, AQOAT®-MF, Eudragit® L100-55 and Soluplus with the incorporation of dioctyl sulfosuccinate sodium provided substantial solubility enhancement. Non-sink dissolution analysis showed enhanced dissolution properties for KSD-processed solid dispersions in comparison to RE-processed solid dispersions. Variances in release performance were identified when different particle size fractions of KSD samples were analyzed. Selected RE samples varying in particle surface morphologies were placed under storage and exhibited crystalline growth following solid-state stability analysis at 12 months in comparison to stored KSD samples confirming amorphous instability for RE products. In vivo analysis of KSD-processed solid dispersions revealed significantly enhanced AKBA absorption in comparison to the neat, active substance.

Rapid detection of HSO4- in water: Novel immobilized azo-azomethine colorimetric anion receptors on solid supports

NASA Astrophysics Data System (ADS)

Hezaveh, Saba Mahdavi; Khanmohammadi, Hamid; Zendehdel, Mojgan

2018-06-01

The immobilized azo-azomethine receptors on amorphous SiO2, S-B, SiO2 nanoparticles, S-NPs, and NaY zeolite, S-ZY, have been prepared and applied as solid phase sensors for detection of HSO4-, over other interfering anions, in 100% aqueous media. Remarkably, S-B and S-ZY show unique and rapid sensitivity towards HSO4-, which could it easily visualized through naked eye detection even at 5 × 10-4 mol L-1 and 4 × 10-4 mol L-1, respectively. The fabricated solid phase sensors were characterized using powder XRD diffraction, TGA-DTA, FE-SEM and also FT-IR techniques. Moreover, the related molecular anion receptor, HL, has been prepared and used for naked eye detection of F- and AcO-, in dry DMSO. The anions recognition ability of HL was also evaluated using UV-Vis and 1H NMR spectroscopic methods.

The Structure of Liquid and Amorphous Hafnia.

PubMed

Gallington, Leighanne C; Ghadar, Yasaman; Skinner, Lawrie B; Weber, J K Richard; Ushakov, Sergey V; Navrotsky, Alexandra; Vazquez-Mayagoitia, Alvaro; Neuefeind, Joerg C; Stan, Marius; Low, John J; Benmore, Chris J

2017-11-10

Understanding the atomic structure of amorphous solids is important in predicting and tuning their macroscopic behavior. Here, we use a combination of high-energy X-ray diffraction, neutron diffraction, and molecular dynamics simulations to benchmark the atomic interactions in the high temperature stable liquid and low-density amorphous solid states of hafnia. The diffraction results reveal an average Hf-O coordination number of ~7 exists in both the liquid and amorphous nanoparticle forms studied. The measured pair distribution functions are compared to those generated from several simulation models in the literature. We have also performed ab initio and classical molecular dynamics simulations that show density has a strong effect on the polyhedral connectivity. The liquid shows a broad distribution of Hf-Hf interactions, while the formation of low-density amorphous nanoclusters can reproduce the sharp split peak in the Hf-Hf partial pair distribution function observed in experiment. The agglomeration of amorphous nanoparticles condensed from the gas phase is associated with the formation of both edge-sharing and corner-sharing HfO 6,7 polyhedra resembling that observed in the monoclinic phase.

The Structure of Liquid and Amorphous Hafnia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gallington, Leighanne; Ghadar, Yasaman; Skinner, Lawrie

Understanding the atomic structure of amorphous solids is important in predicting and tuning their macroscopic behavior. Here, we use a combination of high-energy X-ray diffraction, neutron diffraction, and molecular dynamics simulations to benchmark the atomic interactions in the high temperature stable liquid and low-density amorphous solid states of hafnia. The diffraction results reveal an average Hf–O coordination number of ~7 exists in both the liquid and amorphous nanoparticle forms studied. The measured pair distribution functions are compared to those generated from several simulation models in the literature. We have also performed ab initio and classical molecular dynamics simulations that showmore » density has a strong effect on the polyhedral connectivity. The liquid shows a broad distribution of Hf–Hf interactions, while the formation of low-density amorphous nanoclusters can reproduce the sharp split peak in the Hf–Hf partial pair distribution function observed in experiment. The agglomeration of amorphous nanoparticles condensed from the gas phase is associated with the formation of both edge-sharing and corner-sharing HfO 6,7 polyhedra resembling that observed in the monoclinic phase.« less

The Structure of Liquid and Amorphous Hafnia

DOE PAGES

Gallington, Leighanne; Ghadar, Yasaman; Skinner, Lawrie; ...

2017-11-10

Understanding the atomic structure of amorphous solids is important in predicting and tuning their macroscopic behavior. Here, we use a combination of high-energy X-ray diffraction, neutron diffraction, and molecular dynamics simulations to benchmark the atomic interactions in the high temperature stable liquid and low-density amorphous solid states of hafnia. The diffraction results reveal an average Hf–O coordination number of ~7 exists in both the liquid and amorphous nanoparticle forms studied. The measured pair distribution functions are compared to those generated from several simulation models in the literature. We have also performed ab initio and classical molecular dynamics simulations that showmore » density has a strong effect on the polyhedral connectivity. The liquid shows a broad distribution of Hf–Hf interactions, while the formation of low-density amorphous nanoclusters can reproduce the sharp split peak in the Hf–Hf partial pair distribution function observed in experiment. The agglomeration of amorphous nanoparticles condensed from the gas phase is associated with the formation of both edge-sharing and corner-sharing HfO 6,7 polyhedra resembling that observed in the monoclinic phase.« less

He+ ion irradiation response of Fe–TiO2 multilayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderoglu, O.; Zhou, M. J.; Zhang, J.

2013-04-01

The accumulation of radiation-induced defect clusters and He bubble formation in He+ ion irradiated nanocrystalline TiO2 and Fe–TiO2 multilayer thin films were investigated using transmission electron microscopy (TEM). Prior to ion irradiation it was found that the crystallinity of TiO2 layers depends on the individual layer thickness: While all TiO2 layers are amorphous at 5 nm individual layer thickness, at 100 nm they are crystalline with a rutile polymorph. After He+ irradiation up to ~6 dpa at room temperature, amorphization of TiO2 layers was not observed in both nanocrystalline TiO2 single layers and Fe–TiO2 multilayers. The suppression of radiation-induced amorphizationmore » in TiO2 is interpreted in terms of a high density of defect sinks in these nano-composites in the form of Fe–TiO2 interphase boundaries and columnar grains within each layer with nano-scale intercolumnar porosity. In addition, a high concentration of He is believed to be trapped at these interfaces in the form of sub-nanometer-scale clusters retarding the formation of relatively larger He bubbles that can be resolved in TEM.« less

Blends of POSS-PEO(n=4)(8) and high molecular weight poly(ethylene oxide) as solid polymer electrolytes for lithium batteries.

PubMed

Zhang, Hanjun; Kulkarni, Sunil; Wunder, Stephanie L

2007-04-12

Solid polymer electrolyte blends were prepared with POSS-PEO(n=4)8 (3K), poly(ethylene oxide) (PEO(600K)), and LiClO4 at different salt concentrations (O/Li = 8/1, 12/1, and 16/1). POSS-PEO(n=4)8/LiClO4 is amorphous at all O/Li investigated, whereas PEO(600K) is amorphous only for O/Li = 8/1 and semicrystalline for O/Li = 12/1 and 16/1. The tendency of PEO(600K) to crystallize limited the amount of POSS-PEO(n=4)(8) that could be incorporated into the blends, so that the greatest incorporation of POSS-PEO(n=4)(8) occurred for O/Li = 8/1. Blends of POSS-PEO(n=4)(8)/PEO(600K)/LiClO4 (O/Li = 8/1 and 12/1) microphase separated into two amorphous phases, a low T(g) phase of composition 85% POSS-PEO(n=4)(8)/15% PEO(600K) and a high T(g) phase of composition 29% POSS-PEO(n=4)(8)/71% PEO(600K). For O/Li = 16/1, the blends contained crystalline (pure PEO(600K)), and two amorphous phases, one rich in POSS-PEO(n=4)(8) and one rich in PEO(600K). Microphase, rather than macrophase separation was believed to occur as a result of Li(+)/ether oxygen cross-link sites. The conductivity of the blends depended on their composition. As expected, crystallinity decreased the conductivity of the blends. For the amorphous blends, when the low T(g) (80/20) phase was the continuous phase, the conductivity was intermediate between that of pure PEO(600K) and POSS-PEO(n=4)(8). When the high T(g) (70/30, 50/50, 30/70, and 20/80) phase was the continuous phase, the conductivity of the blend and PEO(600K) were identical, and lower than that for the POSS-PEO(n=4)(8) over the whole temperature range (10-90 degrees C). This suggests that the motions of the POSS-PEO(n=4)(8) were slowed down by the dynamics of the long chain PEO(600K) and that the minor, low Tg phase was not interconnected and thus did not contribute to enhanced conductivity. At temperatures above T(m) of PEO(600K), addition of the POSS-PEO(n=4)(8) did not result in conductivity improvement. The highest RT conductivity, 8 x 10(-6) S/cm, was obtained for a 60% POSS-PEO(n=4)(8)/40% PEO(600K)/LiClO4 (O/Li = 12/1) blend.

Neutron Scattering Analysis of Water's Glass Transition and Micropore Collapse in Amorphous Solid Water.

PubMed

Hill, Catherine R; Mitterdorfer, Christian; Youngs, Tristan G A; Bowron, Daniel T; Fraser, Helen J; Loerting, Thomas

2016-05-27

The question of the nature of water's glass transition has continued to be disputed over many years. Here we use slow heating scans (0.4  K min^{-1}) of compact amorphous solid water deposited at 77 K and an analysis of the accompanying changes in the small-angle neutron scattering signal, to study mesoscale changes in the ice network topology. From the data we infer the onset of rotational diffusion at 115 K, a sudden switchover from nondiffusive motion and enthalpy relaxation of the network at <121  K to diffusive motion across sample grains and sudden pore collapse at >121  K, in excellent agreement with the glass transition onset deduced from heat capacity and dielectric measurements. This indicates that water's glass transition is linked with long-range transport of water molecules on the time scale of minutes and, thus, clarifies its nature. Furthermore, the slow heating rates combined with the high crystallization resistance of the amorphous sample allow us to identify the glass transition end point at 136 K, which is well separated from the crystallization onset at 144 K-in contrast to all earlier experiments in the field.

The Effects of Polymer Carrier, Hot Melt Extrusion Process and Downstream Processing Parameters on the Moisture Sorption Properties of Amorphous Solid Dispersions

PubMed Central

Feng, Xin; Vo, Anh; Patil, Hemlata; Tiwari, Roshan V.; Alshetaili, Abdullah S.; Pimparade, Manjeet B.; Repka, Michael A.

2017-01-01

Objective The aim of this study was to evaluate the effect of polymer carrier, hot melt extrusion (HME) and downstream processing parameters on the water uptake properties of amorphous solid dispersions. Methods Three polymers and a model drug were used to prepare amorphous solid dispersions utilizing HME technology. The sorption-desorption isotherms of solid dispersions and their physical mixtures were measured by the Dynamic Vapor Sorption system, and the effect of polymer hydrophobicity, hygroscopicity, molecular weight and the HME process were investigated. FTIR imaging was performed to understand the phase separation driven by the moisture. Key findings Solid dispersions with polymeric carriers with lower hydrophilicity, hygroscopicity, and higher molecular weight could sorb less moisture under the high RH conditions. The water uptake ability of polymer-drug solid dispersion systems were decreased compared to the physical mixture after HME, which might be due to the decreased surface area and porosity. The FTIR imaging indicated the homogeneity of the drug molecularly dispersed within the polymer matrix was changed after exposure to high RH. Conclusion Understanding the effect of formulation and processing on the moisture sorption properties of solid dispersions is essential for the development of drug products with desired physical and chemical stability. PMID:26589107

Investigation of process temperature and screw speed on properties of a pharmaceutical solid dispersion using corotating and counter-rotating twin-screw extruders.

PubMed

Keen, Justin M; Martin, Charlie; Machado, Augie; Sandhu, Harpreet; McGinity, James W; DiNunzio, James C

2014-02-01

The use of corotating twin screw hot-melt extruders to prepare amorphous drug/polymer systems has become commonplace. As small molecule drug candidates exiting discovery pipelines trend towards higher MW and become more structurally complicated, the acceptable operating space shifts below the drug melting point. The objective of this research is to investigate the extrusion process space, which should be selected to ensure that the drug is solubilized in the polymer with minimal thermal exposure, is critical in ensuring the performance, stability and purity of the solid dispersion. The properties of a model solid dispersion were investigated using both corotating and counter-rotating hot-melt twin-screw extruders operated at various temperatures and screw speeds. The solid state and dissolution performance of the resulting solid dispersions was investigated and evaluated in context of thermodynamic predictions from Flory-Huggins Theory. In addition, the residence time distributions were measured using a tracer, modelled and characterized. The amorphous content in the resulting solid dispersions was dependent on the combination of screw speed, temperature and operating mode. The counter-rotating extruder was observed to form amorphous solid dispersions at a slightly lower temperature and with a narrower residence time distribution, which also exhibited a more desirable shape. © 2013 Royal Pharmaceutical Society.

Physicochemical characterization of atorvastatin calcium/ezetimibe amorphous nano-solid dispersions prepared by electrospraying method.

PubMed

Jahangiri, Azin; Barzegar-Jalali, Mohammad; Javadzadeh, Yousef; Hamishehkar, Hamed; Adibkia, Khosro

2017-09-01

In the present study, electrospraying was applied as a novel method for the fabrication of amorphous nano-solid dispersions (N-SDs) of atorvastatin calcium (ATV), ezetimibe (EZT), and ATV/EZT combination as poorly water-soluble drugs. N-SDs were prepared using polyvinylpyrrolidone K30 as an amorphous carrier in 1:1 and 1:5 drug to polymer ratios and the total solid (including drug and polymer) concentrations of 10 and 20% (w/v). The prepared formulations were further investigated for their morphological, physicochemical, and dissolution properties. Scanning electron microscopy studies indicated that the morphology and diameter of the electrosprayed samples (ESs) were influenced by the solution concentration and drug:polymer ratio, so that an increase in the solution concentration resulted in fiber formation while an increase in the polymer ratio led to enhancement of the particle diameter. Differential scanning calorimetry and X-ray powder diffraction studies together with in vitro dissolution test revealed that the ESs were present in an amorphous form with improved dissolution properties. Infrared spectroscopic studies showed hydrogen-bonding interaction between the drug and polymer in ESs. Since the electrospraying method benefits from the both amorphization and nanosizing effect, this novel approach seems to be an efficient method for the fabrication of N-SDs of poorly water-soluble drugs.

Recrystallization of nifedipine and felodipine from amorphous molecular level solid dispersions containing poly(vinylpyrrolidone) and sorbed water.

PubMed

Marsac, Patrick J; Konno, Hajime; Rumondor, Alfred C F; Taylor, Lynne S

2008-03-01

To compare the physical stability of amorphous molecular level solid dispersions of nifedipine and felodipine, in the presence of poly(vinylpyrrolidone) (PVP) and small amounts of moisture. Thin amorphous films of nifedipine and felodipine and amorphous molecular level solid dispersions with PVP were stored at various relative humidities (RH) and the nucleation rate was measured. The amount of water sorbed at each RH was measured using isothermal vapor sorption and glass transition temperatures (Tg) were determined using differential scanning calorimetry. The solubility of each compound in methyl pyrrolidone was measured as a function of water content. Nifedipine crystallizes more easily than felodipine at any given polymer concentration and in the presence of moisture. The glass transition temperatures of each compound, alone and in the presence of PVP, are statistically equivalent at any given water content. The nifedipine systems are significantly more hygroscopic than the corresponding felodipine systems. Variations in the physical stability of the two compounds could not be explained by differences in Tg. However, the relative physical stability is consistent with differences in the degree of supersaturation of each drug in the solid dispersion, treating the polymer and water as a co-solvent system for each drug compound.

Effect of three-body interactions on the zero-temperature equation of state of HCP solid 4He

NASA Astrophysics Data System (ADS)

Barnes, Ashleigh L.; Hinde, Robert J.

2017-03-01

Previous studies have pointed to the importance of three-body interactions in high density 4He solids. However the computational cost often makes it unfeasible to incorporate these interactions into the simulation of large systems. We report the implementation and evaluation of a computationally efficient perturbative treatment of three-body interactions in hexagonal close packed solid 4He utilizing the recently developed nonadditive three-body potential of Cencek et al. This study represents the first application of the Cencek three-body potential to condensed phase 4He systems. Ground state energies from quantum Monte Carlo simulations, with either fully incorporated or perturbatively treated three-body interactions, are calculated in systems with molar volumes ranging from 21.3 cm3/mol down to 2.5 cm3/mol. These energies are used to derive the zero-temperature equation of state for comparison against existing experimental and theoretical data. The equations of state derived from both perturbative and fully incorporated three-body interactions are found to be in very good agreement with one another, and reproduce the experimental pressure-volume data with significantly better accuracy than is obtained when only two-body interactions are considered. At molar volumes below approximately 4.0 cm3/mol, neither two-body nor three-body equations of state are able to accurately reproduce the experimental pressure-volume data, suggesting that below this molar volume four-body and higher many-body interactions are becoming important.

Dielectric Constant Measurements of Solid 4He

NASA Astrophysics Data System (ADS)

Yin, L.; Xia, J. S.; Huan, C.; Sullivan, N. S.; Chan, M. H. W.

2011-03-01

Careful measurements of the dielectric properties of solid 4He have been carried out down to 35 mK, considerably lower than the temperature range of previous studies. The sample was prepared from high purity gas with 3He concentrations of the order of 200 ppb and were formed by the blocked capillary method. The molar volume of the sample was 20.30 cm3. The dielectric constant of the samples was found to be independent of temperature down to 120 mK before showing a continuous increase with decreasing temperature and saturating below 50 mK. The total increase in ɛ is 2 parts in 10-5. The temperature dependence of ɛ mimics the increase in the resonant frequency found in the torsional oscillator studies and also the increase found in the shear modulus measurements.

Effects of polymer type and storage relative humidity on the kinetics of felodipine crystallization from amorphous solid dispersions.

PubMed

Rumondor, Alfred C F; Stanford, Lindsay A; Taylor, Lynne S

2009-12-01

The objective of this study was to investigate the effects of polymer type and storage relative humidity (RH) on the crystallization kinetics of felodipine from amorphous solid dispersions. Crystallization of the model drug felodipine from amorphous solid dispersion samples containing poly(vinyl pyrrolidone) (PVP) and hypromellose acetate succinate (HPMCAS) were evaluated. Samples at three different drug-polymer weight ratios (10, 25, and 50 wt. % polymer) were prepared and stored at six different RHs (0%, 32%, 52% or 66%, 75%, 86%, and 93%). Periodically, the fraction of the drug that had crystallized from the samples was quantified using powder X-ray diffractometry (PXRD). Felodipine crystallization rates from PVP-containing dispersions were found to be very sensitive to changes in storage RH, while crystallization rates from HPMCAS-containing dispersions were not. PVP and HPMCAS were similar in terms of their ability to inhibit crystallization at low RH, but when the storage RH was increased to 75% or above, felodipine crystallization from PVP-containing solid dispersions proceeded much faster. It is hypothesized that this trend was caused by moisture-induced drug-polymer immiscibility in PVP-felodipine system. For PVP-containing solid dispersion samples stored at 75% RH and above, crystallization of the model drug felodipine seemed to approach a kinetic plateau, whereby a fraction of the drug still remained amorphous even after storage for 500 days or more. The physical stability of solid dispersions as a function of RH is highly dependent on the polymer used to form the solid dispersion, with PVP-containing dispersions being much less physically stable at high RH than HPMCAS-containing dispersions.

High-pressure phase transitions, amorphization, and crystallization behaviors in Bi2Se3.

PubMed

Zhao, Jinggeng; Liu, Haozhe; Ehm, Lars; Dong, Dawei; Chen, Zhiqiang; Gu, Genda

2013-03-27

The phase transition, amorphization, and crystallization behaviors of the topological insulator bismuth selenide (Bi2Se3) were discovered by performing in situ high-pressure angle-dispersive x-ray diffraction experiments during an increasing, decreasing, and recycling pressure process. In the compression process, Bi2Se3 transforms from the original rhombohedral structure (phase I(A)) to a monoclinic structure (phase II) at about 10.4 GPa, and further to a body-centered tetragonal structure (phase III) at about 24.5 GPa. When releasing pressure to ambient conditions after the complete transformation from phase II to III, Bi2Se3 becomes an amorphous solid (AM). In the relaxation process from this amorphous state, Bi2Se3 starts crystallizing into an orthorhombic structure (phase I(B)) about five hours after releasing the pressure to ambient. A review of the pressure-induced phase transition behaviors of A2B3-type materials composed from the V and VI group elements is presented.

Atomic transport during solid-phase epitaxial recrystallization of amorphous germanium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Radek, M.; Bracht, H., E-mail: bracht@uni-muenster.de; Johnson, B. C.

2015-08-24

The atomic mixing of matrix atoms during solid-phase epitaxy (SPE) is studied by means of isotopically enriched germanium (Ge) multilayer structures that were amorphized by Ge ion implantation up to a depth of 1.5 μm. Recrystallization of the amorphous structure is performed at temperatures between 350 °C and 450 °C. Secondary-ion-mass-spectrometry is used to determine the concentration-depth profiles of the Ge isotope before and after SPE. An upper limit of 0.5 nm is deduced for the displacement length of the Ge matrix atoms by the SPE process. This small displacement length is consistent with theoretical models and atomistic simulations of SPE, indicating that themore » SPE mechanism consists of bond-switching with nearest-neighbours across the amorphous-crystalline (a/c) interface.« less

Enhancement of dissolution rate through eutectic mixture and solid solution of posaconazole and benznidazole.

PubMed

Figueirêdo, Camila Bezerra Melo; Nadvorny, Daniela; de Medeiros Vieira, Amanda Carla Quintas; Soares Sobrinho, José Lamartine; Rolim Neto, Pedro José; Lee, Ping I; de La Roca Soares, Monica Felts

2017-06-15

Benznidazole (BNZ), the only commercialized antichagasic drug, and the antifungal compound posaconazole (PCZ) have shown synergistic action in the therapy of Chagas disease, however both active pharmaceutical ingredients (APIs) exhibit low aqueous solubility potentially limiting their bioavailability and therapeutic efficacy. In this paper, we report for the first time the formation of a eutectic mixture as well as an amorphous solid solution of PCZ and BNZ (at the same characteristic ratio of 80:20wt%), which provided enhanced solubility and dissolution rate for both APIs. This eutectic system was characterized by DSC and the melting points obtained were used for the construction of a phase diagram. The preservation of the characteristic PXRD patterns and the IR spectra of the parent APIs, and the visualization of a characteristic eutectic lamellar crystalline microstructure using Confocal Raman Microscopy confirm this system as a true eutectic mixture. The PXRD result also confirms the amorphous nature of the prepared solid solution. Theoretical chemical analyses indicate the predominance of π-stacking interactions in the amorphous solid solution, whereas an electrostatic interaction between the APIs is responsible for maintaining the alternating lamellar crystalline microstructure in the eutectic mixture. Both the eutectic mixture and the amorphous solid solution happen to have a characteristic PCZ to BNZ ratio similar to that of their pharmacological doses for treating Chagas disease, thus providing a unique therapeutic combination dose with enhanced apparent solubility and dissolution rate. Copyright © 2017 Elsevier B.V. All rights reserved.

Investigating the Interaction Pattern and Structural Elements of a Drug-Polymer Complex at the Molecular Level.

PubMed

Nie, Haichen; Mo, Huaping; Zhang, Mingtao; Song, Yang; Fang, Ke; Taylor, Lynne S; Li, Tonglei; Byrn, Stephen R

2015-07-06

Strong associations between drug and polymeric carriers are expected to contribute to higher drug loading capacities and better physical stability of amorphous solid dispersions. However, molecular details of the interaction patterns and underlying mechanisms are still unclear. In the present study, a series of amorphous solid dispersions of clofazimine (CLF), an antileprosy drug, were prepared with different polymers by applying the solvent evaporation method. When using hypromellose phthalate (HPMCP) as the carrier, the amorphous solid dispersion system exhibits not only superior drug loading capacity (63% w/w) but also color change due to strong drug-polymer association. In order to further explain these experimental observations, the interaction between CLF and HPMCP was investigated in a nonpolar volatile solvent system (chloroform) prior to forming the solid dispersion. We observed significant UV/vis and (1)H NMR spectral changes suggesting the protonation of CLF and formation of ion pairs between CLF and HPMCP in chloroform. Furthermore, nuclear Overhauser effect spectroscopy (NOESY) and diffusion order spectroscopy (DOSY) were employed to evaluate the strength of associations between drug and polymers, as well as the molecular mobility of CLF. Finally, by correlating the experimental values with quantum chemistry calculations, we demonstrate that the protonated CLF is binding to the carboxylate group of HPMCP as an ion pair and propose a possible structural model of the drug-polymer complex. Understanding the drug and carrier interaction patterns from a molecular perspective is critical for the rational design of new amorphous solid dispersions.

One-step continuous extrusion process for the manufacturing of solid dispersions.

PubMed

Maniruzzaman, M; Nair, A; Scoutaris, N; Bradley, Michael S A; Snowden, M J; Douroumis, D

2015-12-30

The purpose of this study was to evaluate the performance of synthetic magnesium aluminometasilicate (MAS) as a novel inorganic carrier in hot melt extrusion (HME) processing of indomethacin (IND) for the development of solid dispersions. A continuous extrusion process at various IND/excipient blend ratios (20%, 30% and 40%) was performed using a twin-screw extruder. Physicochemical characterization carried out by SEM, DSC, and XRPD demonstrated the presence of IND in amorphous nature within the porous network of the inorganic material for all extruded formulations. Further, AFM and FTIR studies revealed a single-phase amorphous system and intermolecular H-bonding formation. The IND/MAS extrudates showed enhanced INM dissolution rates within 100% been released within 1h. Stability studies under accelerated conditions (40°C, RH 75%) showed that MAS retained the physical stability of the amorphous solid dispersions even at high drug loadings for 12 months. Copyright © 2015 Elsevier B.V. All rights reserved.

Exploring the complex free-energy landscape of the simplest glass by rheology.

PubMed

Jin, Yuliang; Yoshino, Hajime

2017-04-11

For amorphous solids, it has been intensely debated whether the traditional view on solids, in terms of the ground state and harmonic low energy excitations on top of it, such as phonons, is still valid. Recent theoretical developments of amorphous solids revealed the possibility of unexpectedly complex free-energy landscapes where the simple harmonic picture breaks down. Here we demonstrate that standard rheological techniques can be used as powerful tools to examine nontrivial consequences of such complex free-energy landscapes. By extensive numerical simulations on a hard sphere glass under quasistatic shear at finite temperatures, we show that above the so-called Gardner transition density, the elasticity breaks down, the stress relaxation exhibits slow, and ageing dynamics and the apparent shear modulus becomes protocol-dependent. Being designed to be reproducible in laboratories, our approach may trigger explorations of the complex free-energy landscapes of a large variety of amorphous materials.

Exploring the complex free-energy landscape of the simplest glass by rheology

NASA Astrophysics Data System (ADS)

Jin, Yuliang; Yoshino, Hajime

2017-04-01

For amorphous solids, it has been intensely debated whether the traditional view on solids, in terms of the ground state and harmonic low energy excitations on top of it, such as phonons, is still valid. Recent theoretical developments of amorphous solids revealed the possibility of unexpectedly complex free-energy landscapes where the simple harmonic picture breaks down. Here we demonstrate that standard rheological techniques can be used as powerful tools to examine nontrivial consequences of such complex free-energy landscapes. By extensive numerical simulations on a hard sphere glass under quasistatic shear at finite temperatures, we show that above the so-called Gardner transition density, the elasticity breaks down, the stress relaxation exhibits slow, and ageing dynamics and the apparent shear modulus becomes protocol-dependent. Being designed to be reproducible in laboratories, our approach may trigger explorations of the complex free-energy landscapes of a large variety of amorphous materials.

Molecular Factors Governing the Liquid and Glassy States Recrystallization of Celecoxib in Binary Mixtures with Excipients of Different Molecular Weights.

PubMed

Grzybowska, K; Chmiel, K; Knapik-Kowalczuk, J; Grzybowski, A; Jurkiewicz, K; Paluch, M

2017-04-03

Transformation of poorly water-soluble crystalline pharmaceuticals to the amorphous form is one of the most promising strategies to improve their oral bioavailability. Unfortunately, the amorphous drugs are usually thermodynamically unstable and may quickly return to their crystalline form. A very promising way to enhance the physical stability of amorphous drugs is to prepare amorphous compositions of APIs with certain excipients which can be characterized by significantly different molecular weights, such as polymers, acetate saccharides, and other APIs. By using different experimental techniques (broadband dielectric spectroscopy, differential scanning calorimetry, X-ray diffraction) we compare the effect of adding the large molecular weight polymer-polyvinylpyrrolidone (PVP K30)-and the small molecular weight excipient-octaacetylmaltose (acMAL)-on molecular dynamics as well as the tendency to recrystallization of the amorphous celecoxib (CEL) in the amorphous solid dispersions: CEL-PVP and CEL-acMAL. The physical stability investigations of the binary systems were performed in both the supercooled liquid and glassy states. We found that acMAL is a better inhibitor of recrystallization of amorphous CEL than PVP K30 deep in the glassy state (T < T g ). In contrast, PVP K30 is a better crystallization inhibitor of CEL than acMAL in the supercooled liquid state (at T > T g ). We discuss molecular factors governing the recrystallization of amorphous CEL in examined solid dispersions.

Solid He: Progress, Status, and Outlook for Mass Flux Measurements

NASA Astrophysics Data System (ADS)

Hallock, R. B.

2015-07-01

After a brief introduction, what is provided there is brief summary of work with solid He done at the University of Massachusetts Amherst and an outlook for future work. What is presented here is based on a presentation made at the Quantum Gases Fluids and Solids Workshop in Sao Paulo, Brazil in August of 2014. Our work with solid He is aimed at the question: Can a sample cell filled with solid He support a mass flux through the cell? The answer, as will be shown here, is yes. Evidence for this from several types of experiments will be reviewed. There will be an emphasis on more recent work, work that explores how the flux observed depends on temperature and on the He impurity level. The behavior observed suggests that solid He may be an example of a material that demonstrates Bosonic Luttinger liquid behavior. The normalized He flux has a universal temperature dependence. The presence of He at different impurity levels shows that the He blocks the flux at a characteristic temperature. The behavior appears to be consistent with the cores of dislocations as the entity that carries the flux, but it is clear that more work needs to be done to fully understand solid He.

Variability of the Degassing Flux of 4He as an impact of 4He -Dating of Groundwaters

NASA Astrophysics Data System (ADS)

Torgersen, T.

2009-12-01

4He dating of groundwater is often confounded by an external flux of 4He as the result of a crustal degassing. Estimates of this external flux have been made but what is the impact on estimates of the 4He groundwater age? The existing measures of the 4He flux across the Earth’s solid surface have been evaluated collectively. The time-and-area weighted arithmetic mean (standard deviation) of n=33 4He degassing fluxes is 3.32(±0.45) x 1010 4He atoms m-2s-1. The log normal mean of 271 measures of the flux into Precambrian shield lakes of Canada is 4.57 x 1010atoms 4He m-2s-1 with a variance of */3.9x. The log normal mean of measurements (n=33) of the crustal flux is 3.63 x 1010 4He m-2s-1 with a best estimate one sigma log normal error of */36x based on an assumption of symmetric error bars. (For comparison, the log normal mean heat flow is 62.2 mW m-2 with a log normal variance of */1.8x; the best estimate mean is 65±1.6 Wm-2, Polach et al., 1993). The variance of the continental flux is shown to increase with decreasing time scales (*/ ~106x at 0.5yr) and decreasing space scales (*/ ~106x at 1km) suggesting that the mechanisms of crustal helium transport and degassing contain a high degree of spatial and temporal variability. This best estimate of the mean and variance in the flux of 4He from continents remains approximately equivalent to the radiogenic production rate of 4He in the whole crust. The small degree of variance in the Canadian lake data (n=271), Precambrian terrain, suggests that it may represent a best approximation of “steady state” crustal degassing. Large scale vertical mass transport in continental crust is estimated as scaled values to be of the order 10-5 cm2s-1 for helium (over 2Byr and 40km vertically) vs. 10-2 cm2s-1 for heat. The mass transport rate requires not only release of 4He from the solid phase via fracturing or comminution but also an enhanced rate of mass transport facilitated by some degree of fluid advection (as has been suggested by metamorphic geology) and further imply a separation of heat and mass during transport.

Effect of ball milling on the physicochemical properties of atorvastatin calcium sesquihydrate: the dissolution kinetic behaviours of milled amorphous solids.

PubMed

Kobayashi, Makiko; Hattori, Yusuke; Sasaki, Tetsuo; Otsuka, Makoto

2017-01-01

The purposes of this study were to clarify the amorphization by ball milling of atorvastatin calcium sesquihydrate (AT) and to analyse the change in dissolution kinetics. The amorphous AT was prepared from crystal AT by ball milling and analysed in terms of the changes of its physicochemical properties by powder X-ray diffraction analysis (XRD), thermal analysis and infrared spectroscopy (IR). Moreover, to evaluate the usefulness of the amorphous form for pharmaceutical development, intrinsic solubility of the ground product was evaluated using a dissolution kinetic method. The XRD results indicated that crystalline AT was transformed into amorphous solids by more than 30-min milling. The thermal analysis result suggested that chemical potential of the ground AT are changed significantly by milling. The IR spectra of the AT showed the band shift from the amide group at 3406 cm -1 with an intermolecular hydrogen bond to a free amide group at 3365 cm -1 by milling. The dissolution of amorphous AT follows a dissolution kinetic model involving phase transformation. The initial dissolution rate of the ground product increased with the increase in milling time to reflect the increase in the intrinsic solubility based on the amorphous state. © 2016 Royal Pharmaceutical Society.

Defect-induced solid state amorphization of molecular crystals

NASA Astrophysics Data System (ADS)

Lei, Lei; Carvajal, Teresa; Koslowski, Marisol

2012-04-01

We investigate the process of mechanically induced amorphization in small molecule organic crystals under extensive deformation. In this work, we develop a model that describes the amorphization of molecular crystals, in which the plastic response is calculated with a phase field dislocation dynamics theory in four materials: acetaminophen, sucrose, γ-indomethacin, and aspirin. The model is able to predict the fraction of amorphous material generated in single crystals for a given applied stress. Our results show that γ-indomethacin and sucrose demonstrate large volume fractions of amorphous material after sufficient plastic deformation, while smaller amorphous volume fractions are predicted in acetaminophen and aspirin, in agreement with experimental observation.

Influence of helium atoms on the shear behavior of the fiber/matrix interphase of SiC/SiC composite

NASA Astrophysics Data System (ADS)

Jin, Enze; Du, Shiyu; Li, Mian; Liu, Chen; He, Shihong; He, Jian; He, Heming

2016-10-01

Silicon carbide has many attractive properties and the SiC/SiC composite has been considered as a promising candidate for nuclear structural materials. Up to now, a computational investigation on the properties of SiC/SiC composite varying in the presence of nuclear fission products is still missing. In this work, the influence of He atoms on the shear behavior of the SiC/SiC interphase is investigated via Molecular Dynamics simulation following our recent paper. Calculations are carried out on three dimensional models of graphite-like PyC/SiC interphase and amorphous PyC/SiC interphase with He atoms in different regions (the SiC region, the interface region and the PyC region). In the graphite-like PyC/SiC interphase, He atoms in the SiC region have little influence on the shear strength of the material, while both the shear strength and friction strength may be enhanced when they are in the PyC region. Low concentration of He atoms in the interface region of the graphite-like PyC/SiC interphase increases the shear strength, while there is a reduction of shear strength when the He concentration is high due to the switch of sliding plane. In the amorphous PyC/SiC interphase, He atoms can cause the reduction of the shear strength regardless of the regions that He atoms are located. The presence of He atoms may significantly alter the structure of SiC/SiC in the interface region. The influence of He atoms in the interface region is the most significant, leading to evident shear strength reduction of the amorphous PyC/SiC interphase with increasing He concentration. The behaviors of the interphases at different temperatures are studied as well. The dependence of the shear strengths of the two types of interphases on temperatures is studied as well. For the graphite-like PyC/SiC interphase, it is found strongly related to the regions He atoms are located. Combining these results with our previous study on pure SiC/SiC system, we expect this work may provide new insight into the mechanism of interphase evolution when SiC/SiC is applied as nuclear materials.

Thermal Regeneration of Sulfuric Acid Hydrates after Irradiation

NASA Technical Reports Server (NTRS)

Loeffler, Mark J.; Hudson, Reggie L.

2012-01-01

In an attempt to more completely understand the surface chemistry of the jovian icy satellites, we have investigated the effect of heating on two irradiated crystalline sulfuric acid hydrates, H2SO4 4H2O and H2SO4 H2O. At temperatures relevant to Europa and the warmer jovian satellites, post-irradiation heating recrystallized the amorphized samples and increased the intensities of the remaining hydrate's infrared absorptions. This thermal regeneration of the original hydrates was nearly 100% efficient, indicating that over geological times, thermally-induced phase transitions enhanced by temperature fluctuations will reform a large fraction of crystalline hydrated sulfuric acid that is destroyed by radiation processing. The work described is the first demonstration of the competition between radiation-induced amorphization and thermally-induced recrystallization in icy ionic solids relevant to the outer Solar System.

Very low temperature materials and self-alignment technology for amorphous hydrated silicon thin film transistors fabricated on transparent large area plastic substrates

NASA Astrophysics Data System (ADS)

Yang, Chien-Sheng

The purpose of this research has been to (1) explore materials prepared using plasma enhanced chemical vapor deposition (PECVD) at 110sp°C for amorphous silicon thin film transistors (TFT's) fabricated on low temperature compatible, large area flexible polyethylene terephthalate (PET) substrates, and (2) develop full self-alignment technology using selective area n+ PECVD for source/drain contacts of amorphous silicon TFT's. For item (1), silicon nitride films, as gate dielectrics of TFT's, were deposited using SiHsb4+NHsb3, SiHsb4+NHsb3+Nsb2, SiHsb4+NHsb3+He, or SiHsb4+NHsb3+Hsb2 gases. Good quality silicon nitride films can be deposited using a SiHsb4+NHsb3 gas with high NHsb3/SiHsb4 ratios, or using a SiHsb4+NHsb3+Nsb2 gas with moderate NHsb3/SiHsb4 ratios. A chemical model was proposed to explain the Nsb2 dilution effect. This model includes calculations of (a) the electron energy distribution function in a plasma, (b) rate constants of electron impact dissociation, and (3) the (NHsbx) / (SiHsby) ratio in a plasma. The Nsb2 dilution was shown to have a effect of shifting the electron energy distribution into high energy, thus enhancing the (NHsbx) / (SiHsbyrbrack ratio in a plasma and promoting the deposition of N-rich silicon nitride films, which leads to decreased trap state density and a shift in trap state density to deeper in the gap. Amorphous silicon were formed successfully at 110sp°C on large area glass and plastic(PET) substrates. Linear mobilities are 0.33 and 0.12 cmsp2/Vs for TFT's on glass and plastic substrates, respectively. ON/OFF current ratios exceed 10sp7 for TFT's on glass and 10sp6 for TFT's on PET. For item (2), a novel full self-alignment process was developed for amorphous silicon TFT's. This process includes (1) back-exposure using the bottom gate metal as the mask, and (2) selective area n+ micro-crystalline silicon PECVD for source/drain contacts of amorphous silicon TFT's. TFT's fabricated using the full self-alignment process showed linear mobilities ranging from 0.5 to 1.0 cmsp2/Vs.

Thermodynamics of water-solid interactions in crystalline and amorphous pharmaceutical materials.

PubMed

Sacchetti, Mark

2014-09-01

Pharmaceutical materials, crystalline and amorphous, sorb water from the atmosphere, which affects critical factors in the development of drugs, such as the selection of drug substance crystal form, compatibility with excipients, dosage form selection, packaging, and product shelf-life. It is common practice to quantify the amount of water that a material sorbs at a given relative humidity (RH), but the results alone provide minimal to no physicochemical insight into water-solid interactions, without which pharmaceutical scientists cannot develop an understanding of their materials, so as to anticipate and circumvent potential problems. This research was conducted to advance the science of pharmaceutical materials by examining the thermodynamics of solids with sorbed water. The compounds studied include nonhygroscopic drugs, a channel hydrate drug, a stoichiometric hydrate excipient, and an amorphous excipient. The water sorption isotherms were measured over a range of temperature to extract the partial molar enthalpy and entropy of sorbed water as well as the same quantities for some of the solids. It was found that water-solid interactions spanned a range of energy and entropy as a function of RH, which was unique to the solid, and which could be valuable in identifying batch-to-batch differences and effects of processing in material performance. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.

Amorphous ices explained in terms of nonequilibrium phase transitions in supercooled water

NASA Astrophysics Data System (ADS)

Limmer, David; Chandler, David

2013-03-01

We analyze the phase diagram of supercooled water out-of-equilibrium using concepts from space-time thermodynamics and the dynamic facilitation theory of the glass transition, together with molecular dynamics simulations. We find that when water is driven out-of-equilibrium, it can exist in multiple amorphous states. In contrast, we find that when water is at equilibrium, it can exist in only one liquid state. The amorphous non-equilibrium states are solids, distinguished from the liquid by their lack of mobility, and distinguished from each other by their different densities and local structure. This finding explains the experimentally observed polyamorphism of water as a class of nonequilibrium phenomena involving glasses of different densities. While the amorphous solids can be long lived, they are thermodynamically unstable. When allowed to relax to equilibrium, they crystallize with pathways that pass first through liquid state configurations and then to ordered ice.

The effects of polymer carrier, hot melt extrusion process and downstream processing parameters on the moisture sorption properties of amorphous solid dispersions.

PubMed

Feng, Xin; Vo, Anh; Patil, Hemlata; Tiwari, Roshan V; Alshetaili, Abdullah S; Pimparade, Manjeet B; Repka, Michael A

2016-05-01

The aim of this study was to evaluate the effect of polymer carrier, hot melt extrusion and downstream processing parameters on the water uptake properties of amorphous solid dispersions. Three polymers and a model drug were used to prepare amorphous solid dispersions utilizing the hot melt extrusion technology. The sorption-desorption isotherms of solid dispersions and their physical mixtures were measured by the dynamic vapour sorption system, and the effects of polymer hydrophobicity, hygroscopicity, molecular weight and the hot melt extrusion process were investigated. Fourier transform infrared (FTIR) imaging was performed to understand the phase separation driven by the moisture. Solid dispersions with polymeric carriers with lower hydrophilicity, hygroscopicity and higher molecular weight could sorb less moisture under the high relative humidity (RH) conditions. The water uptake ability of polymer-drug solid dispersion systems were decreased compared with the physical mixture after hot melt extrusion, which might be due to the decreased surface area and porosity. The FTIR imaging indicated that the homogeneity of the drug molecularly dispersed within the polymer matrix was changed after exposure to high RH. Understanding the effect of formulation and processing on the moisture sorption properties of solid dispersions is essential for the development of drug products with desired physical and chemical stability. © 2015 Royal Pharmaceutical Society.

Investigating the effect of moisture protection on solid-state stability and dissolution of fenofibrate and ketoconazole solid dispersions using PXRD, HSDSC and Raman microscopy.

PubMed

Kanaujia, Parijat; Lau, Grace; Ng, Wai Kiong; Widjaja, Effendi; Schreyer, Martin; Hanefeld, Andrea; Fischbach, Matthias; Saal, Christoph; Maio, Mario; Tan, Reginald B H

2011-09-01

Enhanced dissolution of poorly soluble active pharmaceutical ingredients (APIs) in amorphous solid dispersions often diminishes during storage due to moisture-induced re-crystallization. This study aims to investigate the influence of moisture protection on solid-state stability and dissolution profiles of melt-extruded fenofibrate (FF) and ketoconazole (KC) solid dispersions. Samples were kept in open, closed and Activ-vials(®) to control the moisture uptake under accelerated conditions. During 13-week storage, changes in API crystallinity were quantified using powder X-ray diffraction (PXRD) (Rietveld analysis) and high sensitivity differential scanning calorimetry (HSDSC) and compared with any change in dissolution profiles. Trace crystallinity was observed by Raman microscopy, which otherwise was undetected by PXRD and HSDSC. Results showed that while moisture protection was ineffective in preventing the re-crystallization of amorphous FF, KC remained X-ray amorphous despite 5% moisture uptake. Regardless of the degree of crystallinity increase in FF, the enhanced dissolution properties were similarly diminished. Moisture uptake above 10% in KC samples also led to re-crystallization and significant decrease in dissolution rates. In conclusion, eliminating moisture sorption may not be sufficient in ensuring the stability of solid dispersions. Analytical quantification of API crystallinity is crucial in detecting subtle increase in crystallinity that can diminish the enhanced dissolution properties of solid dispersions.

Thermodynamics of dilute 3He-4He solid solutions with hcp structure

NASA Astrophysics Data System (ADS)

Chishko, K. A.

2018-02-01

To interpret the anomalies in heat capacity CV(T) and temperature-dependent pressure P(T) of solid hexagonal close-packed (hcp) 4He we exploit the model of hcp crystalline polytype with specific lattice degrees of freedom and describe the thermodynamics of impurity-free 4He solid as superposition of phononic and polytypic contributions. The hcp-based polytype is a stack of 2D basal atomic monolayers on triangular lattice packed with arbitrary long (up to infinity) spatial period along the hexagonal c axis perpendicular to the basal planes. It is a crystal with perfect ordering along the layers, but without microscopic translational symmetry in perpendicular direction (which remains, nevertheless, the rotational crystallographic axis of third order, so that the polytype can be considered as semidisordered system). Each atom of the hcp polytype has twelve crystallographic neighbors in both first and second coordination spheres at any arbitrary packing order. It is shown that the crystal of such structure behaves as anisotropic elastic medium with specific dispersion law of phonon excitations along c axis. The free energy and the heat capacity consist of two terms: one of them is a normal contribution [with CV(T) ˜ T3] from phonon excitations in an anisotropic lattice of hexagonal symmetry, and another term (an "excessive" heat) is a contribution resulted by packing entropy from quasi-one-dimensional system of 2D basal planes on triangular lattice stacked randomly along c axis without braking the closest pack between neighboring atomic layers. The excessive part of the free energy has been treated within 1D quasi-Ising (lattice gas) model using the transfer matrix approach. This model makes us possible to interpret successfully the thermodynamic anomaly (heat capacity peak in hcp 4He) observed experimentally.

Impact of polymer type on bioperformance and physical stability of hot melt extruded formulations of a poorly water soluble drug.

PubMed

Mitra, Amitava; Li, Li; Marsac, Patrick; Marks, Brian; Liu, Zhen; Brown, Chad

2016-05-30

Amorphous solid dispersion formulations have been widely used to enhance bioavailability of poorly soluble drugs. In these formulations, polymer is included to physically stabilize the amorphous drug by dispersing it in the polymeric carrier and thus forming a solid solution. The polymer can also maintain supersaturation and promote speciation during dissolution, thus enabling better absorption as compared to crystalline drug substance. In this paper, we report the use of hot melt extrusion (HME) to develop amorphous formulations of a poorly soluble compound (FaSSIF solubility=1μg/mL). The poor solubility of the compound and high dose (300mg) necessitated the use of amorphous formulation to achieve adequate bioperformance. The effect of using three different polymers (HPMCAS-HF, HPMCAS-LF and copovidone), on the dissolution, physical stability, and bioperformance of the formulations was demonstrated. In this particular case, HPMCAS-HF containing HME provided the highest bioavailability and also had better physical stability as compared to extrudates using HPMCAS-LF and copovidone. The data demonstrated that the polymer type can have significant impact on the formulation bioperformance and physical stability. Thus a thorough understanding of the polymer choice is imperative when designing an amorphous solid dispersion formulation, such that the formulation provides robust bioperformance and has adequate shelf life. Copyright © 2016 Elsevier B.V. All rights reserved.

Glass-liquid phase separation in highly supersaturated aqueous solutions of telaprevir.

PubMed

Mosquera-Giraldo, Laura I; Taylor, Lynne S

2015-02-02

Amorphous solid dispersions are of great current interest because they can improve the delivery of poorly water-soluble compounds. It has been recently noted that the highly supersaturated solutions generated by dissolution of some ASDs can undergo a phase transition to a colloidal, disordered, drug-rich phase when the concentration exceeds the "amorphous solubility" of the drug. The purpose of this study was to investigate the phase behavior of supersaturated solutions of telaprevir, which is formulated as an amorphous solid dispersion in the commercial product. Different analytical techniques including proton nuclear magnetic resonance spectroscopy (NMR), ultraviolet spectroscopy (UV), fluorescence spectroscopy and flux measurements were used to evaluate the properties of aqueous supersaturated solutions of telaprevir. It was found that highly supersaturated solutions of telaprevir underwent glass-liquid phase separation (GLPS) when the concentration exceeded 90 μg/mL, forming a water-saturated colloidal, amorphous drug-rich phase with a glass transition temperature of 52 °C. From flux measurements, it was observed that the "free" drug concentration reached a maximum at the concentration where GLPS occurred, and did not increase further as the concentration was increased. This phase behavior, which results in a precipitate and a metastable equilibrium between a supersaturated solution and a drug-rich phase, is obviously important in the context of evaluating amorphous solid dispersion formulations and their crystallization routes.

Stochastic approach to plasticity and yield in amorphous solids.

PubMed

Hentschel, H G E; Jaiswal, Prabhat K; Procaccia, Itamar; Sastry, Srikanth

2015-12-01

We focus on the probability distribution function (PDF) P(Δγ;γ) where Δγ are the measured strain intervals between plastic events in a athermal strained amorphous solids, and γ measures the accumulated strain. The tail of this distribution as Δγ→0 (in the thermodynamic limit) scales like Δγ(η). The exponent η is related via scaling relations to the tail of the PDF of the eigenvalues of the plastic modes of the Hessian matrix P(λ) which scales like λ(θ), η=(θ-1)/2. The numerical values of η or θ can be determined easily in the unstrained material and in the yielded state of plastic flow. Special care is called for in the determination of these exponents between these states as γ increases. Determining the γ dependence of the PDF P(Δγ;γ) can shed important light on plasticity and yield. We conclude that the PDF's of both Δγ and λ are not continuous functions of γ. In slowly quenched amorphous solids they undergo two discontinuous transitions, first at γ=0(+) and then at the yield point γ=γ(Y) to plastic flow. In quickly quenched amorphous solids the second transition is smeared out due to the nonexisting stress peak before yield. The nature of these transitions and scaling relations with the system size dependence of 〈Δγ〉 are discussed.

Investigation of Deteriorated Dissolution of Amorphous Itraconazole: Description of Incompatibility with Magnesium Stearate and Possible Solutions.

PubMed

Démuth, B; Galata, D L; Szabó, E; Nagy, B; Farkas, A; Balogh, A; Hirsch, E; Pataki, H; Rapi, Z; Bezúr, L; Vigh, T; Verreck, G; Szalay, Z; Demeter, Á; Marosi, G; Nagy, Z K

2017-11-06

Disadvantageous crystallization phenomenon of amorphous itraconazole (ITR) occurring in the course of dissolution process was investigated in this work. A perfectly amorphous form (solid dispersion) of the drug was generated by the electroblowing method (with vinylpyrrolidone-vinyl acetate copolymer), and the obtained fibers were formulated into tablets. Incomplete dissolution of the tablets was noticed under the circumstances of the standard dissolution test, after which a precipitated material could be filtered. The filtrate consisted of ITR and stearic acid since no magnesium content was detectable in it. In parallel with dissolution, ITR forms an insoluble associate, stabilized by hydrogen bonding, with stearic acid deriving from magnesium stearate. This is why dissolution curves do not have the plateaus at 100%. Two ways are viable to tackle this issue: change the lubricant (with sodium stearyl fumarate >95% dissolution can be accomplished) or alter the polymer in the solid dispersion to a type being able to form hydrogen bonds with ITR (e.g., hydroxypropyl methylcellulose). This work draws attention to one possible phenomenon that can lead to a deterioration of originally good dissolution of an amorphous solid dispersion.

Amorphous surface layer versus transient amorphous precursor phase in bone - A case study investigated by solid-state NMR spectroscopy.

PubMed

Von Euw, Stanislas; Ajili, Widad; Chan-Chang, Tsou-Hsi-Camille; Delices, Annette; Laurent, Guillaume; Babonneau, Florence; Nassif, Nadine; Azaïs, Thierry

2017-09-01

The presence of an amorphous surface layer that coats a crystalline core has been proposed for many biominerals, including bone mineral. In parallel, transient amorphous precursor phases have been proposed in various biomineralization processes, including bone biomineralization. Here we propose a methodology to investigate the origin of these amorphous environments taking the bone tissue as a key example. This study relies on the investigation of a bone tissue sample and its comparison with synthetic calcium phosphate samples, including a stoichiometric apatite, an amorphous calcium phosphate sample, and two different biomimetic apatites. To reveal if the amorphous environments in bone originate from an amorphous surface layer or a transient amorphous precursor phase, a combined solid-state nuclear magnetic resonance (NMR) experiment has been used. The latter consists of a double cross polarization 1 H→ 31 P→ 1 H pulse sequence followed by a 1 H magnetization exchange pulse sequence. The presence of an amorphous surface layer has been investigated through the study of the biomimetic apatites; while the presence of a transient amorphous precursor phase in the form of amorphous calcium phosphate particles has been mimicked with the help of a physical mixture of stoichiometric apatite and amorphous calcium phosphate. The NMR results show that the amorphous and the crystalline environments detected in our bone tissue sample belong to the same particle. The presence of an amorphous surface layer that coats the apatitic core of bone apatite particles has been unambiguously confirmed, and it is certain that this amorphous surface layer has strong implication on bone tissue biogenesis and regeneration. Questions still persist on the structural organization of bone and biomimetic apatites. The existing model proposes a core/shell structure, with an amorphous surface layer coating a crystalline bulk. The accuracy of this model is still debated because amorphous calcium phosphate (ACP) environments could also arise from a transient amorphous precursor phase of apatite. Here, we provide an NMR spectroscopy methodology to reveal the origin of these ACP environments in bone mineral or in biomimetic apatite. The 1 H magnetization exchange between protons arising from amorphous and crystalline domains shows unambiguously that an ACP layer coats the apatitic crystalline core of bone et biomimetic apatite platelets. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Enhancing the bioavailability of magnolol in rabbits using melting solid dispersion with polyvinylpyrrolidone.

PubMed

Lin, Shiuan-Pey; Hou, Yu-Chi; Liao, Tzu-Yun; Tsai, Shang-Yuan

2014-03-01

Preparation of magnolol-loaded amorphous solid dispersion was investigated for improving the bioavailability. A solid dispersion of magnolol was prepared with polyvinylpyrrolidone K-30 (PVP) by melting method, and the physical properties were characterized by using differential scanning calorimetry, powder X-ray diffractometry, Fourier transformation-infrared spectroscopy and scanning electron microscope. In addition, dissolution test was also performed. Subsequently, the bioavailability of magnolol pure compound, its physical mixture and solid dispersion were compared in rabbits. The blood samples withdrawn via marginal ear vein at specific time points were assayed by HPLC method. Oral administration of the solid dispersion of magnolol with PVP significantly increased the systemic exposures of magnolol and magnolol sulfates/glucuronides by 80.1% and 142.8%, respectively, compared to those given with magnolol pure compound. Magnolol-loaded amorphous solid dispersion with PVP has demonstrated enhanced bioavailability of magnolol in rabbits.

Swift heavy ion-beam induced amorphization and recrystallization of yttrium iron garnet.

PubMed

Costantini, Jean-Marc; Miro, Sandrine; Beuneu, François; Toulemonde, Marcel

2015-12-16

Pure and (Ca and Si)-substituted yttrium iron garnet (Y3Fe5O12 or YIG) epitaxial layers and amorphous films on gadolinium gallium garnet (Gd3Ga5O12, or GGG) single crystal substrates were irradiated by 50 MeV (32)Si and 50 MeV (or 60 MeV) (63)Cu ions for electronic stopping powers larger than the threshold value (~4 MeV μm(-1)) for amorphous track formation in YIG crystals. Conductivity data of crystalline samples in a broad ion fluence range (10(11)-10(16) cm(-2)) are modeled with a set of rate equations corresponding to the amorphization and recrystallization induced in ion tracks by electronic excitations. The data for amorphous layers confirm that a recrystallization process takes place above ~10(14) cm(-2). Cross sections for both processes deduced from this analysis are discussed in comparison to previous determinations with reference to the inelastic thermal-spike model of track formation. Micro-Raman spectroscopy was also used to follow the related structural modifications. Raman spectra show the progressive vanishing and randomization of crystal phonon modes in relation to the ion-induced damage. For crystalline samples irradiated at high fluences (⩾10(14) cm(-2)), only two prominent broad bands remain like for amorphous films, thereby reflecting the phonon density of states of the disordered solid, regardless of samples and irradiation conditions. The main band peaked at ~660 cm(-1) is assigned to vibration modes of randomized bonds in tetrahedral (FeO4) units.

High Mobility Flexible Amorphous IGZO Thin-Film Transistors with a Low Thermal Budget Ultra-Violet Pulsed Light Process.

PubMed

Benwadih, M; Coppard, R; Bonrad, K; Klyszcz, A; Vuillaume, D

2016-12-21

Amorphous, sol-gel processed, indium gallium zinc oxide (IGZO) transistors on plastic substrate with a printable gate dielectric and an electron mobility of 4.5 cm 2 /(V s), as well as a mobility of 7 cm 2 /(V s) on solid substrate (Si/SiO 2 ) are reported. These performances are obtained using a low temperature pulsed light annealing technique. Ultraviolet (UV) pulsed light system is an innovative technique compared to conventional (furnace or hot-plate) annealing process that we successfully implemented on sol-gel IGZO thin film transistors (TFTs) made on plastic substrate. The photonic annealing treatment has been optimized to obtain IGZO TFTs with significant electrical properties. Organic gate dielectric layers deposited on this pulsed UV light annealed films have also been optimized. This technique is very promising for the development of amorphous IGZO TFTs on plastic substrates.

Probing the mechanisms of drug release from amorphous solid dispersions in medium-soluble and medium-insoluble carriers.

PubMed

Sun, Dajun D; Lee, Ping I

2015-08-10

The objective of the current study is to mechanistically differentiate the dissolution and supersaturation behaviors of amorphous drugs from amorphous solid dispersions (ASDs) based on medium-soluble versus medium-insoluble carriers under nonsink dissolution conditions through a direct head-to-head comparison. ASDs of indomethacin (IND) were prepared in several polymers which exhibit different solubility behaviors in acidic (pH1.2) and basic (pH7.4) dissolution media. The selected polymers range from water-soluble (e.g., PVP and Soluplus) and water-insoluble (e.g., ethylcellulose and Eudragit RL PO) to those only soluble in an acidic or basic dissolution medium (e.g., Eudragit E100, Eudragit L100, and HPMCAS). At 20wt.% drug loading, DSC and powder XRD analysis confirmed that the majority of incorporated IND was present in an amorphous state. Our nonsink dissolution results confirm that whether the carrier matrix is medium soluble determines the release mechanism of amorphous drugs from ASD systems which has a direct impact on the rate of supersaturation generation, thus in turn affecting the evolution of supersaturation in amorphous systems. For example, under nonsink dissolution conditions, the release of amorphous IND from medium-soluble carriers is governed by a dissolution-controlled mechanism leading to an initial surge of supersaturation followed by a sharp decline in drug concentration due to rapid nucleation and crystallization. In contrast, the dissolution of IND ASD from medium-insoluble carriers is more gradual as drug release is regulated by a diffusion-controlled mechanism by which drug supersaturation is built up gradually and sustained over an extended period of time without any apparent decline. Since several tested carrier polymers can be switched from soluble to insoluble by simply changing the pH of the dissolution medium, the results obtained here provide unequivocal evidence of the proposed transition of kinetic solubility profiles from the same ASD system induced by changes in the drug release mechanism in dissolution medium of a different pH. Copyright © 2015 Elsevier B.V. All rights reserved.

Physical stability and recrystallization kinetics of amorphous ibipinabant drug product by fourier transform raman spectroscopy.

PubMed

Sinclair, Wayne; Leane, Michael; Clarke, Graham; Dennis, Andrew; Tobyn, Mike; Timmins, Peter

2011-11-01

The solid-state physical stability and recrystallization kinetics during storage stability are described for an amorphous solid dispersed drug substance, ibipinabant, at a low concentration (1.0%, w/w) in a solid oral dosage form (tablet). The recrystallization behavior of the amorphous ibipinabant-polyvinylpyrrolidone solid dispersion in the tablet product was characterized by Fourier transform (FT) Raman spectroscopy. A partial least-square analysis used for multivariate calibration based on Raman spectra was developed and validated to detect less than 5% (w/w) of the crystalline form (equivalent to less than 0.05% of the total mass of the tablet). The method provided reliable and highly accurate predictive crystallinity assessments after exposure to a variety of stability storage conditions. It was determined that exposure to moisture had a significant impact on the crystallinity of amorphous ibipinabant. The information provided by the method has potential utility for predictive physical stability assessments. Dissolution testing demonstrated that the predicted crystallinity had a direct correlation with this physical property of the drug product. Recrystallization kinetics was measured using FT Raman spectroscopy for the solid dispersion from the tablet product stored at controlled temperature and relative humidity. The measurements were evaluated by application of the Johnson-Mehl-Avrami (JMA) kinetic model to determine recrystallization rate constants and Avrami exponent (n = 2). The analysis showed that the JMA equation could describe the process very well, and indicated that the recrystallization kinetics observed was a two-step process with an induction period (nucleation) followed by rod-like crystal growth. Copyright © 2011 Wiley-Liss, Inc.

Study of the high-pressure helium phase diagram using molecular dynamics

NASA Astrophysics Data System (ADS)

Koci, L.; Ahuja, R.; Belonoshko, A. B.; Johansson, B.

2007-01-01

The rich occurrence of helium and hydrogen in space makes their properties highly interesting. By means of molecular dynamics (MD), we have examined two interatomic potentials for 4He. Both potentials are demonstrated to reproduce high-pressure solid and liquid equation of state (EOS) data. The EOS, solid-solid transitions and melting at high pressures (P) were studied using a two-phase method. The Buckingham potential shows a good agreement with theoretical and experimental EOS, but does not reproduce experimental melting data. The Aziz potential shows a perfect match with theoretical melting data. We conclude that there is a stable body-centred-cubic (bcc) phase for 4He at temperatures (T) above 340 K and pressures above 22 GPa for the Buckingham potential, whereas no bcc phase is found for the Aziz potential in the applied PT range.

Investigating the Crystallization Propensity of Structurally Similar Organic Molecules From Amorphous State

NASA Astrophysics Data System (ADS)

Kalra, Arjun

Combinatorial chemistry and high-throughput screening approaches utilized during drug discovery have resulted in many potent pharmacologically active molecules with low aqueous solubility and consequently poor bioavailability. Enabling technologies, such as amorphous solid dispersions (ASD's), can obviate these challenges and provide an efficient route to formulate the drug as an oral solid dosage form. However, high-energy amorphous materials have an inherent tendency to crystallize and in doing so can negate the apparent solubility advantage achieved by using such formulations. Crystallization can occur during (1) cooling the drug molecule from the melt state (such as during hot melt extrusion); (2) during storage of an amorphous formulation; (3) during pharmaceutical processing unit operations such as compression, granulation etc. Current knowledge with regards to the relationship between crystallization propensity of an active pharmaceutical ingredient (API) from the amorphous state (supercooled liquid and glass) and its thermodynamic, kinetic and molecular properties is limited. Furthermore, examining the mechanistic steps involved in crystallization of organic molecules under conditions of supercooling provides an opportunity to examine supramolecular aggregation events occurring during early stages of crystallization. Studying crystallization mechanism from amorphous state is important for pharmaceutical formulation development because a molecular-level understanding of the crystallization process would provide clues regarding the intermolecular interactions at the early stages of nucleation and help in rational selection of polymeric excipients to hinder such events. The primary goal of this research is to develop an understanding of phase transition from amorphous pharmaceuticals, specifically focusing on the role of thermodynamic, kinetic and molecular properties of a series of structurally similar compounds. It is hypothesized that the there exists a link between thermodynamics quantities, kinetic properties, molecular interactions and glass forming ability. Furthermore, it is hypothesized that the molecular heterogeneity in supercooled liquids and glassy state, manifested through intermolecular interactions and conformational flexibility impacts the observed crystallization behavior. Understanding the phase transition kinetics and mechanism of crystallization from amorphous pharmaceuticals is critical for development of stable formulations for drug delivery. The specific goals of this research include: (1) Investigating the link between thermodynamic and kinetic factors affecting the crystallization propensity of organic compounds from supercooled liquid state. (2) Evaluating the role of intermolecular interactions and conformational distribution on glass forming ability and stability. (3) Examining the relationship between supramolecular aggregates present in glassy state and polymorphic outcome. It is believed that successful completion of this research will provide a fundamental understanding of amorphous solid-state chemistry as well as provide useful tools for the implementation of ASD's as solid oral dosage forms.

Molecular implications of drug-polymer solubility in understanding the destabilization of solid dispersions by milling.

PubMed

Yang, Ziyi; Nollenberger, Kathrin; Albers, Jessica; Qi, Sheng

2014-07-07

The solubility of drugs in polymer matrixes has been recognized as one of the key factors governing the physical stability of solid dispersions. This study has explored the implications of drug solubility on the destabilization that occurs on milling, which is often used as an additional process for hot melt extruded (HME) solid dispersions. The theoretical drug solubility in the polymer was first predicted using various theoretical and experimental approaches. The destabilization effects of high-energy mechanical milling on the solid dispersions with drug loadings below and above the predicted solubility were then investigated using a range of thermal, microscopic, and spectroscopic techniques. Four model drug-polymer combinations were studied. The HME formulations with drug loading below the predicted solid solubility (undersaturated and true molecular dispersion) showed good stability against milling. In contrast, milling destabilized supersaturated HME dispersions via increasing molecular mobility and creating phase-separated, amorphous, drug-rich domains. However, these additional amorphous drug-rich domains created by milling show good stability under ambient conditions, though crystallization can be accelerated by additional heating. These results highlighted that the processing method used to prepare the solid dispersions may play a role in facilitating the stabilization of amorphous drug in supersaturated solid dispersions. The degree of supersaturation of the drug in the polymer showed significant impact on the destabilization behavior of milling on solid dispersions. An improved understanding of the destabilization behavior of solid dispersions upon milling can provide new insights into the processing related apparent solubility of drugs in polymers.

Synthesis and acid catalysis of cellulose-derived carbon-based solid acid

NASA Astrophysics Data System (ADS)

Suganuma, Satoshi; Nakajima, Kiyotaka; Kitano, Masaaki; Yamaguchi, Daizo; Kato, Hideki; Hayashi, Shigenobu; Hara, Michikazu

2010-06-01

SO 3H-bearing amorphous carbon, prepared by partial carbonization of cellulose followed by sulfonation in fuming H 2SO 4, was applied as a solid catalyst for the acid-catalyzed hydrolysis of β-1,4 glucan, including cellobiose and crystalline cellulose. Structural analyses revealed that the resulting carbon material consists of graphene sheets with 1.5 mmol g -1 of SO 3H groups, 0.4 mmol g -1 of COOH, and 5.6 mmol g -1 of phenolic OH groups. The carbon catalyst showed high catalytic activity for the hydrolysis of β-1,4 glycosidic bonds in both cellobiose and crystalline cellulose. Pure crystalline cellulose was not hydrolyzed by conventional strong solid Brønsted acid catalysts such as niobic acid, Nafion ® NR-50, and Amberlyst-15, whereas the carbon catalyst efficiently hydrolyzes cellulose into water-soluble saccharides. The catalytic performance of the carbon catalyst is due to the large adsorption capacity for hydrophilic reactants and the adsorption ability of β-1,4 glucan, which is not adsorbed to other solid acids.

Amorphization of thiamine chloride hydrochloride: A study of the crystallization inhibitor properties of different polymers in thiamine chloride hydrochloride amorphous solid dispersions.

PubMed

Arioglu-Tuncil, Seda; Bhardwaj, Vivekanand; Taylor, Lynne S; Mauer, Lisa J

2017-09-01

Amorphous solid dispersions of thiamine chloride hydrochloride (THCl) were created using a variety of polymers with different physicochemical properties in order to investigate how effective the various polymers were as THCl crystallization inhibitors. THCl:polymer dispersions were prepared by lyophilizing solutions of THCl and amorphous polymers (guar gum, pectin, κ-carrageenan, gelatin, and polyvinylpyrrolidone (PVP)). These dispersions were stored at select temperature (25 and 40°C) and relative humidity (0, 23, 32, 54, 75, and 85% RH) conditions and monitored at different time points using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Moisture sorption isotherms of all samples were also obtained. Initially amorphous THCl was produced in the presence of ≥40% w/w pectin, κ-carrageenan, gelatin, and guar gum or ≥60% w/w PVP. Trends in polymer THCl crystallization inhibition (pectin≥κ-carrageenan>gelatin>guar gum≫PVP) were primarily based on the ability of the polymer to interact with THCl via hydrogen bonding and/or ionic interactions. The onset of THCl crystallization from the amorphous dispersions was also related to storage conditions. THCl remained amorphous at low RH conditions (0 and 23% RH) in all 1:1 dispersions except THCl:PVP. THCl crystallized in some dispersions below the glass transition temperature (T g ) but remained amorphous in others at T~T g . At high RHs (75 and 85% RH), THCl crystallized within one day in all samples. Given the ease of THCl amorphization in the presence of a variety of polymers, even at higher vitamin concentrations than would be found in foods, it is likely that THCl is amorphous in many low moisture foods. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fabrication of metallic glass structures

DOEpatents

Cline, Carl F.

1986-01-01

Amorphous metal powders or ribbons are fabricated into solid shapes of appreciable thickness by the application of compaction energy. The temperature regime wherein the amorphous metal deforms by viscous flow is measured. The metal powders or ribbons are compacted within the temperature range.

Fabrication of metallic glass structures

DOEpatents

Cline, C.F.

1983-10-20

Amorphous metal powders or ribbons are fabricated into solid shapes of appreciable thickness by the application of compaction energy. The temperature regime wherein the amorphous metal deforms by viscous flow is measured. The metal powders or ribbons are compacted within the temperature regime.

NMR Relaxometry to Characterize the Drug Structural Phase in a Porous Construct.

PubMed

Thrane, Linn W; Berglund, Emily A; Wilking, James N; Vodak, David; Seymour, Joseph D

2018-06-14

Nuclear magnetic resonance (NMR) frequency spectra and T 2 relaxation time measurements, using a high-power radio frequency probe, are shown to characterize the presence of an amorphous drug in a porous silica construct. The results indicate the ability of non-solid-state NMR methods to characterize crystalline and amorphous solid structural phases in drugs. Two-dimensional T 1 - T 2 magnetic relaxation time correlation experiments are shown to monitor the impact of relative humidity on the drug in a porous silica tablet.

Preparation, characterization and in vitro/vivo evaluation of tectorigenin solid dispersion with improved dissolution and bioavailability.

PubMed

Shuai, Shuping; Yue, Shanlan; Huang, Qingting; Wang, Wei; Yang, Junyi; Lan, Ke; Ye, Liming

2016-08-01

The purpose of this study was to develop and evaluate a novel amorphous solid dispersion system for tectorigenin (TG). TG is one of isoflavone aglycones extracted from Iris tectorum and flowers of Pueraria thunbergiana, but its poor water solubility and low membrane permeability have severely restricted the clinical application. To increase the aqueous solubility and oral bioavailability of TG, we prepared the solid dispersions of tectorigenin (TG-SD) using a simple solvent evaporation process with TG, polyvinylpyrrolidone (PVP) and PEG4000 at weight ratio of 7:54:9 after tested in several ratios. The prepared solid dispersions of tectorigenin are duly characterized for drug morphological conversion, in vitro dissolution and in vivo bioavailability. The X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) studies have indicated the morphological conversion of tectorigenin to amorphous form. In vitro release profiles revealed that the % release of TG-SD was achieved 4.35-fold higher than that of the pure drug after 150 min. The oral bioavailability of the solid dispersion in rats was also increased based on AUC0-t and C max of TG-SD, which were 4.8- and 13.1-fold higher than that of TG crystal, respectively. It is worth noting that physical mixture containing TG, PEG4000 and PVP produced a similar level of oral exposure as TG-SD, suggesting that PEG4000 and PVP were able to enhance bioavailability of TG in rats. However, with the reduction of particle size, TG-SD provided the fastest oral absorption compared to physical mixture and pure drug. These results demonstrated that the efficacy of solid dispersions for the enhancement of TG oral bioavailability was by increasing its aqueous solubility and the solid dispersion formulation could be a viable option for enhancing the oral bioavailability of TG.

Characterization of the molecular distribution of drugs in glassy solid dispersions at the nano-meter scale, using differential scanning calorimetry and gravimetric water vapour sorption techniques.

PubMed

van Drooge, D J; Hinrichs, W L J; Visser, M R; Frijlink, H W

2006-03-09

The molecular distribution in fully amorphous solid dispersions consisting of poly(vinylpyrrolidone) (PVP)-diazepam and inulin-diazepam was studied. One glass transition temperature (T(g)), as determined by temperature modulated differential scanning calorimetry (TMDSC), was observed in PVP-diazepam solid dispersions prepared by fusion for all drug loads tested (10-80 wt.%). The T(g) of these solid dispersions gradually changed with composition and decreased from 177 degrees C for pure PVP to 46 degrees C for diazepam. These observations indicate that diazepam was dispersed in PVP on a molecular level. However, in PVP-diazepam solid dispersions prepared by freeze drying, two T(g)'s were observed for drug loads above 35 wt.% indicating phase separation. One T(g) indicated the presence of amorphous diazepam clusters, the other T(g) was attributed to a PVP-rich phase in which diazepam was dispersed on a molecular level. With both the value of the latter T(g) and the DeltaC(p) of the diazepam glass transition the concentrations of molecular dispersed diazepam could be calculated (27-35 wt.%). Both methods gave similar results. Water vapour sorption (DVS) experiments revealed that the PVP-matrix was hydrophobised by the incorporated diazepam. TMDSC and DVS results were used to estimate the size of diazepam clusters in freeze dried PVP-diazepam solid dispersions, which appeared to be in the nano-meter range. The inulin-diazepam solid dispersions prepared by spray freeze drying showed one T(g) for drug loads up to 35 wt.% indicating homogeneous distribution on a molecular level. However, this T(g) was independent of the drug load, which is unexpected because diazepam has a lower T(g) than inulin (46 and 155 degrees C, respectively). For higher drug loads, a T(g) of diazepam as well as a T(g) of the inulin-rich phase was observed, indicating the formation of amorphous diazepam clusters. From the DeltaC(p) of the diazepam glass transition the amount of molecularly dispersed diazepam was calculated (12-27 wt.%). In contrast to the PVP-diazepam solid dispersions, DVS-experiments revealed that inulin was not hydrophobised by diazepam. Consequently, the size of diazepam clusters could not be estimated. It was concluded that TMDSC enables characterization and quantification of the molecular distribution in amorphous solid dispersions. When the hygroscopicity of the carrier is reduced by the drug, DVS in combination with TMDSC can be used to estimate the size of amorphous drug clusters.

In situ photodeposition of amorphous CoSx on the TiO2 towards hydrogen evolution

NASA Astrophysics Data System (ADS)

Chen, Feng; Luo, Wei; Mo, Yanping; Yu, Huogen; Cheng, Bei

2018-02-01

Cocatalyst modification of photocatalysts is an important strategy to enhance the photocatalytic performance by promoting effective separation of photoinduced electron-hole pairs and providing abundant active sites. In this study, a facile in situ photodeposition method was developed to prepare amorphous CoSx-modified TiO2 photocatalysts. It was found that amorphous CoSx nanoparticles were solidly loaded on the TiO2 surface, resulting in a greatly improved photocatalytic H2-evolution performance. When the amount of amorphous CoSx was 10 wt%, the hydrogen evolution rate of the CoSx/TiO2 reached 119.7 μmol h-1, which was almost 16.7 times that of the pure TiO2. According to the above experimental results, a reasonable mechanism of improved photocatalytic performance is proposed for the CoSx/TiO2 photocatalysts, namely, the photogenerated electrons of TiO2 can rapidly transfer to amorphous CoSx nanoparticles due to the solid contact between them, and then amorphous CoSx can provide plenty of sulfur active sites to rapidly adsorb protons from solution to produce hydrogen by the photogenerated electrons. Considering the facile synthesis method, the present cheap and highly efficient amorphous CoSx-modified TiO2 photocatalysts would have great potential for practical use in photocatalytic H2 production.

Mechanism of generation of drug nanocrystals in celecoxib: mannitol nanocrystalline solid dispersion.

PubMed

Bhatt, Varun; Shete, Ganesh; Bansal, Arvind Kumar

2015-11-10

Objective of this work was to understand the mechanism of formation of celecoxib nanocrystals in celecoxib: mannitol nanocrystalline solid dispersion (NSD). Solution of celecoxib and mannitol was spray dried in 1:1 (g:g) proportion to obtain NSD, with average crystallite size of 214.07 ± 45.27 nm. Solubility parameters of celecoxib and mannitol were 23.1 MPa(1/2) and 38.5 MPa(1/2), respectively, hinting their immiscibility. Formation of nanocrystals during NanoCrySP proceeds via intermediate amorphous form of the drug. Earlier work from our lab on hesperetin-mannitol system, had underlined the role of plasticization of amorphous drug by excipient in the formation of nanocrystals. However, in present case, mannitol failed to plasticize amorphous celecoxib and Tg of amorphous celecoxib (56.8°C) showed a negligible change (54.8°C) in presence of mannitol. However, DSC data also suggested crystallization inducing potential of mannitol on amorphous celecoxib. Polarized light microscopy provided evidence that, mannitol facilitated heterogeneous nucleation of amorphous celecoxib at their interface. Transmission electron microscopy analysis suggested that, mannitol acted as a physical barrier to crystal growth of celecoxib crystallites. Thus, though mannitol did not plasticize amorphous celecoxib, it aided in nanocrystal generation by heterogeneous nucleation and providing physical barrier to crystal growth. Copyright © 2015 Elsevier B.V. All rights reserved.

Near-infrared analysis of hydrogen-bonding in glass- and rubber-state amorphous saccharide solids.

PubMed

Izutsu, Ken-ichi; Hiyama, Yukio; Yomota, Chikako; Kawanishi, Toru

2009-01-01

Near-infrared (NIR) spectroscopic analysis of noncrystalline polyols and saccharides (e.g., glycerol, sorbitol, maltitol, glucose, sucrose, maltose) was performed at different temperatures (30-80 degrees C) to elucidate the effect of glass transition on molecular interaction. Transmission NIR spectra (4,000-12,000 cm(-1)) of the liquids and cooled-melt amorphous solids showed broad absorption bands that indicate random configuration of molecules. Heating of the samples decreased an intermolecular hydrogen-bonding OH vibration band intensity (6,200-6,500 cm(-1)) with a concomitant increase in a free and intramolecular hydrogen-bonding OH group band (6,600-7,100 cm(-1)). Large reduction of the intermolecular hydrogen-bonding band intensity at temperatures above the glass transition (T(g)) of the individual solids should explain the higher molecular mobility and lower viscosity in the rubber state. Mixing of the polyols with a high T(g) saccharide (maltose) or an inorganic salt (sodium tetraborate) shifted both the glass transition and the inflection point of the hydrogen-bonding band intensity to higher temperatures. The implications of these results for pharmaceutical formulation design and process monitoring (PAT) are discussed.

Oxidative Dissolution of Arsenopyrite by Mesophilic and Moderately Thermophilic Acidophiles †

PubMed Central

Tuovinen, Olli H.; Bhatti, Tariq M.; Bigham, Jerry M.; Hallberg, Kevin B.; Garcia, Oswaldo; Lindström, E. Börje

1994-01-01

The purpose of this work was to determine solution- and solid-phase changes associated with the oxidative leaching of arsenopyrite (FeAsS) by Thiobacillus ferrooxidans and a moderately thermoacidophilic mixed culture. Jarosite [KFe3(SO4)2(OH)6], elemental sulfur (S0), and amorphous ferric arsenate were detected by X-ray diffraction as solid-phase products. The oxidation was not a strongly acid-producing reaction and was accompanied by a relatively low redox level. The X-ray diffraction lines of jarosite increased considerably when ferrous sulfate was used as an additional substrate for T. ferroxidans. A moderately thermoacidophilic mixed culture oxidized arsenopyrite faster at 45°C than did T. ferroxidans at 22°C, and the oxidation was accompanied by a nearly stoichiometric release of Fe and As. The redox potential was initially low but subsequently increased during arsenopyrite oxidation by the thermoacidophiles. Jarosite, S0, and amorphous ferric arsenate were also formed under these conditions. PMID:16349379

Low-temperature internal friction in quenched amorphous selenium films

NASA Astrophysics Data System (ADS)

Metcalf, Thomas; Liu, Xiao; Abernathy, Matthew; Stephens, Richard

Using ultra-high-quality-factor silicon mechanical resonators, we have measured the internal friction and shear modulus of amorphous selenium (a-Se) films at liquid helium temperatures. The glass transition temperature of selenium lies at a conveniently accessible 40 -50° C, facilitating a series of in- and ex-situ annealing and quench cycles. The a-Se films exhibit the low-temperature internal friction plateau (10-4 <=Q-1 <=10-3) found in almost all amorphous solids, which is a result of (and direct measure of) a broad distribution of two-level tunneling systems (TLS), whose origin is still unknown. We find a clear correlation between the post-anneal quench rate and the value of this plateau. The implications of these observations for understanding the microscopic origin of TLS will be discussed. Principally, the observed changes in the internal friction plateau could show the way in which the density of TLS could be manipulated or suppressed in other amorphous systems. Work supported by the Office of Naval Research and the University of Pennsylvania Materials Research Science and Engineering Center.

(234)U/(238)U signatures associated with uranium ore bodies: part 1 Ranger 3.

PubMed

Lowson, Richard T; McIntyre, Mark G

2013-04-01

The Ranger 3 ore body is an early Proterozoic U ore body in the Alligator Rivers U province, Northern Territory, Australia. It has surface expression with a redox front located between 30 and 50 m below the surface. The ground water U concentration and (234)U/(238)U AR signature in the top 10 m of the weathered zone are reported for 357 samples collected over 4 wet seasons, at 5 depths, along a transect in-line with the hydraulic gradient and along the centre line of the ore body and its associated dispersion halo. The results show that the weathered zone displays a general U isotope feature for this type of ore body with the (234)U/(238)U AR for the ground water and amorphous phase of the solid matrix being less than 1. The ground water (234)U/(238)U AR is independent of the annual monsoonal climate and depth within the range surface to 10 m. In the vicinity of the U ore body the ground water (234)U/(238)U AR is 0.75 and is very similar to the (234)U/(238)U AR of the amorphous phase of the solid (0.76). The (234)U/(238)U ARs of the amorphous phase and ground water rise and separate to values of 0.88 and 1.02 at the end of the transect. The rise and separation in (234)U/(238)U AR are interpreted as evidence that the source of the U in the ground water is from the water-soluble sub-phase of the amorphous phase and that the ground water flow is too fast to allow the processes occurring across the solid-water interface to reach chemical equilibrium. The data set is a robust characterisation of the coarse and fine detail of the (234)U/(238)U AR signature in the weathered zone of U ore bodies. Copyright © 2012 Elsevier Ltd. All rights reserved.

Enhanced stability and local structure in biologically relevant amorphous materials containing pyrophosphate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slater, Colin; Laurencin, Danielle; Burnell, Victoria

2012-10-25

There is increasing evidence that amorphous inorganic materials play a key role in biomineralisation in many organisms, however the inherent instability of synthetic analogues in the absence of the complex in vivo matrix limits their study and clinical exploitation. To address this, we report here an approach that enhances long-term stability to >1 year of biologically relevant amorphous metal phosphates, in the absence of any complex stabilizers, by utilizing pyrophosphates (P{sub 2}O{sub 7}{sup 4-}); species themselves ubiquitous in vivo. Ambient temperature precipitation reactions were employed to synthesise amorphous Ca{sub 2}P{sub 2}O{sub 7}.nH{sub 2}O and Sr{sub 2}P{sub 2}O{sub 7}.nH{sub 2}O (3.8more » < n < 4.2) and their stability and structure were investigated. Pair distribution functions (PDF) derived from synchrotron X-ray data indicated a lack of structural order beyond 8 {angstrom} in both phases, with this local order found to resemble crystalline analogues. Further studies, including {sup 1}H and {sup 31}P solid state NMR, suggest the unusually high stability of these purely inorganic amorphous phases is partly due to disorder in the P-O-P bond angles within the P{sub 2}O{sub 7} units, which impede crystallization, and to water molecules, which are involved in H-bonds of various strengths within the structures and hamper the formation of an ordered network. In situ high temperature powder X-ray diffraction data indicated that the amorphous nature of both phases surprisingly persisted to 450 C. Further NMR and TGA studies found that above ambient temperature some water molecules reacted with P{sub 2}O{sub 7} anions, leading to the hydrolysis of some P-O-P linkages and the formation of HPO{sub 4}{sup 2-} anions within the amorphous matrix. The latter anions then recombined into P{sub 2}O{sub 7} ions at higher temperatures prior to crystallization. Together, these findings provide important new materials with unexplored potential for enzyme-assisted resorption and establish factors crucial to isolate further stable amorphous inorganic materials.« less

Development of stability-enhanced ternary solid dispersions via combinations of HPMCP and Soluplus® processed by hot melt extrusion.

PubMed

Albadarin, Ahmad B; Potter, Catherine B; Davis, Mark T; Iqbal, Javed; Korde, Sachin; Pagire, Sudhir; Paradkar, Anant; Walker, Gavin

2017-10-30

The aim of this study was to evaluate a novel combination of hydroxypropyl methylcellulose phthalate (HPMCP-HP-50) and Soluplus ® polymers for enhanced physicochemical stability and solubility of the produced amorphous solid dispersions (ASDs). This was achieved using hot melt extrusion (HME) to convert the crystalline active pharmaceutical ingredient (API) into a more soluble amorphous form within the ternary systems. Itraconazole (ITZ), a Biopharmaceutics Classification System class II (BCS II) API, was selected as the model drug. The ASDs were characterized by Powder X-Ray diffraction (PXRD), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Fourier Transform Infrared (FTIR) spectroscopy, Solid State Nuclear Magnetic Resonance (ssNMR) and dissolution studies. The data showed that the ASDs were physically and chemically stable at 20°C and 50% RH over 12 months. PXRD results indicated that the ITZ in the ASDs was in the amorphous state and no recrystallization occurred. DSC scans confirmed that each formulation exhibited a single intermediate glass transition (T g ), around 96.4°C, indicating that ITZ was completely miscible in the polymeric blends of HPMCP and Soluplus ® at up to 30% (w/w) drug loading and that the two polymers were miscible with each other in the presence of ITZ. The FTIR analysis indicated the formation of strong hydrogen bonding between ITZ, HPMCP and Soluplus ® . The dissolution end-point of the ASDs was determined to be approximately 10 times greater than that of the crystalline ITZ. Copyright © 2017 Elsevier B.V. All rights reserved.

Adsorption onto Mesoporous Silica Using Supercritical Fluid Technology Improves Dissolution Rate of Carbamazepine-a Poorly Soluble Compound.

PubMed

Gandhi, Aditya V; Thipsay, Priyanka; Kirthivasan, Bharat; Squillante, Emilio

2017-11-01

The purpose of this research was to design and characterize an immediate-release formulation of carbamazepine (CBZ), a poorly soluble anti-epileptic drug, using a porous silica carrier. Carbon dioxide in its supercritical state (2000 psi, 30-35°C) was used as an anti-solvent to precipitate CBZ onto two particle size variants of silica. Adsorption isotherms were used as a pre-formulation strategy to select optimum ratios of silica and CBZ. The obtained drug-silica formulations were characterized by dissolution studies, differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). This formulation strategy resulted in a 2.4-fold improvement in dissolution rate when compared to pure drug after 30 min of dissolution testing. PXRD and DSC confirmed the amorphous nature of CBZ in the formulations as well as the differences in polymorphic forms of commercial and supercritical fluid-processed CBZ. Additionally, solid-state NMR spectroscopy showed that the spin-lattice relaxation time for bulk drug (without silica) was ∼7.5 times greater than that for silica-confined CBZ, implying that when CBZ was adsorbed onto mesoporous silica, it is structurally disordered and had higher structural mobility, a characteristic of amorphous solids. The mesoporous silica matrix prevented CBZ crystal growth by imposing spatial constraint on CBZ nuclei and hence resulted in faster dissolution compared to bulk solid drug. Adsorption onto mesoporous silica using supercritical fluid technology may be used as a novel formulation strategy for amorphization of poorly soluble compounds, in turn improving their dissolution rate.

Characterization of carbon ion implantation induced graded microstructure and phase transformation in stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Kai; Wang, Yibo; Li, Zhuguo, E-mail: lizg@sjtu.edu.cn

Austenitic stainless steel 316L is ion implanted by carbon with implantation fluences of 1.2 × 10{sup 17} ions-cm{sup −} {sup 2}, 2.4 × 10{sup 17} ions-cm{sup −} {sup 2}, and 4.8 × 10{sup 17} ions-cm{sup −} {sup 2}. The ion implantation induced graded microstructure and phase transformation in stainless steel is investigated by X-ray diffraction, X-ray photoelectron spectroscopy and high resolution transmission electron microscopy. The corrosion resistance is evaluated by potentiodynamic test. It is found that the initial phase is austenite with a small amount of ferrite. After low fluence carbon ion implantation, an amorphous layer and ferrite phase enrichedmore » region underneath are formed. Nanophase particles precipitate from the amorphous layer due to energy minimization and irradiation at larger ion implantation fluence. The morphology of the precipitated nanophase particles changes from circular to dumbbell-like with increasing implantation fluence. The corrosion resistance of stainless steel is enhanced by the formation of amorphous layer and graphitic solid state carbon after carbon ion implantation. - Highlights: • Carbon implantation leads to phase transformation from austenite to ferrite. • The passive film on SS316L becomes thinner after carbon ion implantation. • An amorphous layer is formed by carbon ion implantation. • Nanophase precipitate from amorphous layer at higher ion implantation fluence. • Corrosion resistance of SS316L is improved by carbon implantation.« less

Effects of crystallization on structural and dielectric properties of thin amorphous films of (1 - x)BaTiO3-xSrTiO3 (x=0-0.5, 1.0)

NASA Astrophysics Data System (ADS)

Kawano, H.; Morii, K.; Nakayama, Y.

1993-05-01

The possibilities for fabricating solid solutions of (Ba1-x,Srx)TiO3 (x≤0.5,1.0) by crystallization of amorphous films and for improving their dielectric properties by adjusting the Sr content were investigated. Thin amorphous films were prepared from powder targets consisting of mixtures of BaTiO3 and SrTiO3 by sputtering with a neutralized Ar-ion beam. The amorphous films crystallized into (Ba1-x, Srx)TiO3 solid solutions with a cubic perovskite-type structure after annealing in air at 923 K for more than 1 h. The Debye-type dielectric relaxation was observed for the amorphous films, whereas the crystallized films showed paraelectric behavior. The relative dielectric constants were of the order of 20 for the amorphous samples, but increased greatly after crystallization to about 60-200, depending on the composition; a larger increase in the dielectric constant was observed in the higher Sr content films, in the range x≤0.5, which could be correlated with an increase in the grain size of the crystallites. The crystallization processes responsible for the difference in the grain size are discussed based on the microstructural observations.

Underlying role of mechanical rigidity and topological constraints in physical sputtering and reactive ion etching of amorphous materials

NASA Astrophysics Data System (ADS)

Bhattarai, Gyanendra; Dhungana, Shailesh; Nordell, Bradley J.; Caruso, Anthony N.; Paquette, Michelle M.; Lanford, William A.; King, Sean W.

2018-05-01

Analytical expressions describing ion-induced sputter or etch processes generally relate the sputter yield to the surface atomic binding energy (Usb) for the target material. While straightforward to measure for the crystalline elemental solids, Usb is more complicated to establish for amorphous and multielement materials due to composition-driven variations and incongruent sublimation. In this regard, we show that for amorphous multielement materials, the ion-driven yield can instead be better understood via a consideration of mechanical rigidity and network topology. We first demonstrate a direct relationship between Usb, bulk modulus, and ion sputter yield for the elements, and then subsequently prove our hypothesis for amorphous multielement compounds by demonstrating that the same relationships exist between the reactive ion etch (RIE) rate and nanoindentation Young's modulus for a series of a -Si Nx :H and a -Si OxCy :H thin films. The impact of network topology is further revealed via application of the Phillips-Thorpe theory of topological constraints, which directly relates the Young's modulus to the mean atomic coordination () for an amorphous solid. The combined analysis allows the trends and plateaus in the RIE rate to be ultimately reinterpreted in terms of the atomic structure of the target material through a consideration of . These findings establish the important underlying role of mechanical rigidity and network topology in ion-solid interactions and provide additional considerations for the design and optimization of radiation-hard materials in nuclear and outer space environments.

Crystallization Kinetics of Indomethacin/Polyethylene Glycol Dispersions Containing High Drug Loadings.

PubMed

Duong, Tu Van; Van Humbeeck, Jan; Van den Mooter, Guy

2015-07-06

The reproducibility and consistency of physicochemical properties and pharmaceutical performance are major concerns during preparation of solid dispersions. The crystallization kinetics of drug/polyethylene glycol solid dispersions, an important factor that is governed by the properties of both drug and polymer has not been adequately explored, especially in systems containing high drug loadings. In this paper, by using standard and modulated differential scanning calorimetry and X-ray powder diffraction, we describe the influence of drug loading on crystallization behavior of dispersions made up of indomethacin and polyethylene glycol 6000. Higher drug loading increases the amorphicity of the polymer and inhibits the crystallization of PEG. At 52% drug loading, polyethylene glycol was completely transformed to the amorphous state. To the best of our knowledge, this is the first detailed investigation of the solubilization effect of a low molecular weight drug on a semicrystalline polymer in their dispersions. In mixtures containing up to 55% indomethacin, the dispersions exhibited distinct glass transition events resulting from amorphous-amorphous phase separation which generates polymer-rich and drug-rich domains upon the solidification of supercooled polyethylene glycol, whereas samples containing at least 60% drug showed a single amorphous phase during the period in which crystallization normally occurs. The current study demonstrates a wide range in physicochemical properties of drug/polyethylene glycol solid dispersions as a result of the complex nature in crystallization of this system, which should be taken into account during preparation and storage.

Ability of different polymers to inhibit the crystallization of amorphous felodipine in the presence of moisture.

PubMed

Konno, Hajime; Taylor, Lynne S

2008-04-01

To investigate the ability of various polymers to inhibit the crystallization of amorphous felodipine from amorphous molecular dispersions in the presence of absorbed moisture. Spin coated films of felodipine with poly(vinylpyrrolidone) (PVP), hydroxypropylmethylcellulose acetate succinate (HPMCAS) and hydroxypropylmethylcellulose (HPMC) were exposed to different storage relative humidities and nucleation rates were measured using polarized light microscopy. Solid dispersions were further characterized using differential scanning calorimetry, infrared spectroscopy and gravimetric measurement of water vapor sorption. It was found that the polymer additive reduced nucleation rates whereas absorbed water enhanced the nucleation rate as anticipated. When both polymer and water were present, nucleation rates were reduced relative to those of the pure amorphous drug stored at the same relative humidity, despite the fact that the polymer containing systems absorbed more water. Differences between the stabilizing abilities of the various polymers were observed and these were explained by the variations in the moisture contents of the solid dispersions caused by the different hygroscopicities of the component polymers. No correlations could be drawn between nucleation rates and the glass transition temperature (Tg) of the system. PVP containing solid dispersions appeared to undergo molecular level changes on exposure to moisture which may be indicative of phase separation. In conclusion, it was found that for a given storage relative humidity, although the addition of a polymer increases the moisture content of the system relative to that of the pure amorphous drug, the crystallization tendency was still reduced.

Solid state amorphization of metastable Al 0.5TiZrPdCuNi high entropy alloy investigated by high voltage electron microscopy

DOE PAGES

Nagase, Takeshi; Takeuchi, Akira; Amiya, Kenji; ...

2017-07-18

Here, the phase stability of high entropy alloy (HEA), Al 0.5TiZrPdCuNi, under fast electron irradiation was studied by in-situ high voltage electron microscopy (HVEM). The initial phase of this alloy quenched from the melt was dependent on cooling rate. At high cooling rates an amorphous phase was obtained, whereas a body-centered cubic ( b.c.c.) phase were obtained at low cooling rates. By thermal crystallization of the amorphous phase b.c.c. phase nano-crystals were formed. Upon fast electron irradiation solid state amorphization (SSA) was observed in b.c.c. phase regardless of the initial microstructure (i.e., “coarse crystalline structure” or “nano-crystalline structure with grainmore » boundaries as a sink for point defects”). SSA behavior in the Al 0.5TiZrPdCuNi HEAs was investigated by in-situ transmission electron microscopy observations. Because the amorphization is very rarely achieved in a solid solution phase under fast electron irradiation in common metallic materials, this result suggests that the Al 0.5TiZrPdCuNi HEA from other common alloys and the other HEAs. The differences in phase stability against the irradiation between the Al 0.5TiZrPdCuNi HEA and the other HEAs were discussed. This is the first experimental evidence of SSA in HEAs stimulated by fast electron irradiation.« less

Dissolution enhancement of a drug exhibiting thermal and acidic decomposition characteristics by fusion processing: a comparative study of hot melt extrusion and KinetiSol dispersing.

PubMed

Hughey, Justin R; DiNunzio, James C; Bennett, Ryan C; Brough, Chris; Miller, Dave A; Ma, Hua; Williams, Robert O; McGinity, James W

2010-06-01

In this study, hot melt extrusion (HME) and KinetiSol Dispersing (KSD) were utilized to prepare dissolution-enhanced solid dispersions of Roche Research Compound A (ROA), a BCS class II drug. Preformulation characterization studies showed that ROA was chemically unstable at elevated temperatures and acidic pH values. Eudragit L100-55 and AQOAT LF (HPMCAS) were evaluated as carrier polymers. Dispersions were characterized for ROA recovery, crystallinity, homogeneity, and non-sink dissolution. Eudragit L100-55 dispersions prepared by HME required the use of micronized ROA and reduced residence times in order to become substantially amorphous. Compositions containing HPMCAS were also prepared by HME, but an amorphous dispersion could not be obtained. All HME compositions contained ROA-related impurities. KSD was investigated as a method to reduce the decomposition of ROA while rendering compositions amorphous. Substantially amorphous, plasticizer free compositions were processed successfully by KSD with significantly higher ROA recovery values and amorphous character than those achieved by HME. A near-infrared chemical imaging analysis was conducted on the solid dispersions as a measure of homogeneity. A statistical analysis showed similar levels of homogeneity in compositions containing Eudragit L100-55, while differences were observed in those containing HMPCAS. Non-sink dissolution analysis of all compositions showed rapid supersaturation after pH adjustment to approximately two to three times the equilibrium solubility of ROA, which was maintained for at least 24 h. The results of the study demonstrated that KSD is an effective method of forming dissolution-enhanced amorphous solid solutions in cases where HME is not a feasible technique.

Effects of magnetic impurity scattering on superfluid 3He in aerogel

NASA Astrophysics Data System (ADS)

Aoyama, Kazushi; Ikeda, Ryusuke

2009-02-01

We investigate impurity effects on superfluid 3He in aerogel whose surface is not coated with 4He, different from most experimental situations. In systems with no 4He coating, spins of solid 3He absorbed on the aerogel surface are active and interact with spins of quasiparticles relevant to superfluidity and, for this reason, such an aerogel is treated as magnetic scatterers. It is found that, in the ABM pairing state affected by magnetic scatterings, not only the l-vector but also the d-vector has no long-ranged orientational order, and that the strong-coupling correction due to impurity scatterings is less suppressed than that in the nonmagnetic case, implying an expansion of the A-like phase region.

GEANT4 simulations of a novel 3He-free thermalization neutron detector

NASA Astrophysics Data System (ADS)

Mazzone, A.; Finocchiaro, P.; Lo Meo, S.; Colonna, N.

2018-05-01

A novel concept for 3He-free thermalization detector is here investigated by means of GEANT4 simulations. The detector is based on strips of solid-state detectors with 6Li deposit for neutron conversion. Various geometrical configurations have been investigated in order to find the optimal solution, in terms of value and energy dependence of the efficiency for neutron energies up to 10 MeV. The expected performance of the new detector are compared with those of an optimized thermalization detector based on standard 3He tubes. Although an 3He-based detector is superior in terms of performance and simplicity, the proposed solution may become more appealing in terms of costs in case of shortage of 3He supply.

Mechanism of solid state amorphization of glucose upon milling.

PubMed

Dujardin, N; Willart, J F; Dudognon, E; Danède, F; Descamps, M

2013-02-07

Crystalline α-glucose is known to amorphize upon milling at -15 °C while it remains structurally invariant upon milling at room temperature. We have taken advantage of this behavior to compare the microstructural evolutions of the material in both conditions in order to identify the essential microstructural features which drive the amorphization process upon milling. The investigations have been performed by differential scanning calorimetry and by powder X-ray diffraction. The results indicate that two different amorphization mechanisms occur upon milling: an amorphization at the surface of crystallites due to the mechanical shocks and a spontaneous amorphization of the crystallites as they reach a critical size, which is close to 200 Å in the particular case of α-glucose.

Modification of the solid-state nature of sulfathiazole and sulfathiazole sodium by spray drying.

PubMed

Bianco, Stefano; Caron, Vincent; Tajber, Lidia; Corrigan, Owen I; Nolan, Lorraine; Hu, Yun; Healy, Anne Marie

2012-06-01

Solid-state characterisation of a drug following pharmaceutical processing and upon storage is fundamental to successful dosage form development. The aim of the study was to investigate the effects of using different solvents, feed concentrations and spray drier configuration on the solid-state nature of the highly polymorphic model drug, sulfathiazole (ST) and its sodium salt (STNa). The drugs were spray-dried from ethanol, acetone and mixtures of these organic solvents with water. Additionally, STNa was spray-dried from pure water. The physicochemical properties including the physical stability of the spray-dried powders were compared to the unprocessed materials. Spray drying of ST from either acetonic or ethanolic solutions with the spray drier operating in a closed cycle mode yielded crystalline powders. In contrast, the powders obtained from ethanolic solutions with the spray drier operating in an open cycle mode were amorphous. Amorphous ST crystallised to pure form I at ≤35 % relative humidity (RH) or to polymorphic mixtures at higher RH values. The usual crystal habit of form I is needle-like, but spherical particles of this polymorph were generated by spray drying. STNa solutions resulted in an amorphous material upon processing, regardless of the solvent and the spray drier configuration employed. Moisture induced crystallisation of amorphous STNa to a sesquihydrate, whilst crystallisation upon heating gave rise to a new anhydrous polymorph. This study indicated that control of processing and storage parameters can be exploited to produce drugs with a specific/desired solid-state nature.

Spectral Photosensitization of Optical Anisotropy in Solid Poly(Vinyl Cinnamate) Films

NASA Astrophysics Data System (ADS)

Kozenkov, V. M.; Spakhov, A. A.; Belyaev, V. V.; Chausov, D. N.; Chigrinov, V. G.

2018-04-01

The possibility and features of formation of sensitized photoinduced optical anisotropy in amorphous films of poly(vinyl cinnamate) and its derivative poly(vinyl-4-metoxicinnamate) under the action of polarized light (including light that is not absorbed by polymer macromolecules themselves) have been investigated. It is found that the effect of induced optical anisotropy is based on the transfer of electron excitation energy from donor (sensitizer) molecules to acceptor molecules and is observed in the course of phototopochemical biomolecular cyclization reaction of cinnamate fragments in polymer macromolecules. The detected photoinduced anisotropy in solid films of poly(vinyl cinnamate) and its derivative poly(vinyl-4-metoxicinnamate) ensures sensitized photo-orientation of low-molecular thermotropic liquid crystals.

Synthesis of POSS-based ionic conductors with low glass transition temperatures for efficient solid-state dye-sensitized solar cells.

PubMed

Zhang, Wei; Wang, Zhong-Sheng

2014-07-09

Replacing liquid-state electrolytes with solid-state electrolytes has been proven to be an effective way to improve the durability of dye-sensitized solar cells (DSSCs). We report herein the synthesis of amorphous ionic conductors based on polyhedral oligomeric silsesquioxane (POSS) with low glass transition temperatures for solid-state DSSCs. As the ionic conductor is amorphous and in the elastomeric state at the operating temperature of DSSCs, good pore filling in the TiO2 film and good interfacial contact between the solid-state electrolyte and the TiO2 film can be guaranteed. When the POSS-based ionic conductor containing an allyl group is doped with only iodine as the solid-state electrolyte without any other additives, power conversion efficiency of 6.29% has been achieved with good long-term stability under one-sun soaking for 1000 h.

Spectroscopy of Rb{sub 2} dimers in solid {sup 4}He

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moroshkin, P.; Hofer, A.; Ulzega, S.

We present experimental and theoretical studies of the absorption, emission, and photodissociation spectra of Rb{sub 2} molecules in solid helium. We have identified 11 absorption bands of Rb{sub 2}. All laser-excited molecular states are quenched by the interaction with the He matrix. The quenching results in efficient population of a metastable (1) {sup 3}{pi}{sub u} state, which emits fluorescence at 1042 nm. In order to explain the fluorescence at the forbidden transition and its time dependence we propose a new molecular exciplex Rb{sub 2}({sup 3}{pi}{sub u})He{sub 2}. We have also found evidence for the formation of diatomic bubble states followingmore » photodissociation of Rb{sub 2}.« less

Conventional physics can explain cold fusion excess heat

NASA Astrophysics Data System (ADS)

Chubb, S. R.

In 1989, when Fleischmann, Pons and Hawkins (FP), claimed they had created room temperature, nuclear fusion in a solid, a firestorm of controversy erupted. Beginning in 1991, the Office of Naval Research began a decade-long study of the FP excess heat effect. This effort documented the fact that the excess heat that FP observed is the result of a form of nuclear fusion that can occur in solids at reduced temperature, dynamically, through a deuteron (d)+d□4He reaction, without high-energy particles or □ rays. A key reason this fact has not been accepted is the lack of a cogent argument, based on fundamental physical ideas, justifying it. In the paper, this question is re-examined, based on a generalization of conventional energy band theory that applies to finite, periodic solids, in which d's are allowed to occupy wave-like, ion band states, similar to the kinds of states that electrons occupy in ordinary metals. Prior to being experimentally observed, the Ion Band State Theory (IBST) of cold fusion predicted a potential d+d□4He reaction, without high energy particles, would explain the excess heat, the 4He would be found in an unexpected place (outside heat-producing electrodes), and high-loading, x□1, in PdDx, would be required.

Application of a Salt Coformer in a Co-Amorphous Drug System Dramatically Enhances the Glass Transition Temperature: A Case Study of the Ternary System Carbamazepine, Citric Acid, and l-Arginine.

PubMed

Ueda, Hiroshi; Wu, Wenqi; Löbmann, Korbinian; Grohganz, Holger; Müllertz, Anette; Rades, Thomas

2018-05-07

The use of co-amorphous systems containing a combination of low molecular weight drugs and excipients is a relatively new technology in the pharmaceutical field to improve the solubility of poorly water-soluble drugs. However, some co-amorphous systems show a lower glass transition temperature ( T g ) than many of their polymeric solid dispersion counterparts. In this study, we aimed at designing a stable co-amorphous system with an elevated T g . Carbamazepine (CBM) and citric acid (CA) were employed as the model drug and the coformer, respectively. co-amorphous CBM-CA at a 1:1 molar ratio was formed by ball milling, but a transition from the glassy to the supercooled melt state was observed under ambient conditions, due to the relatively low T g of 38.8 °C of the co-amorphous system and moisture absorption. To improve the T g of the coformer, salt formation of a combination of l-arginine (ARG) with CA was studied. First, ball milling of CA-ARG at molar ratios of 1:1, 1:2, and 1:3 forming co-amorphous systems was performed and led to a dramatic enhancement of the T g , depending on the CA-ARG ratio. Salt formation between CA and ARG was observed by infrared spectroscopy. Next, ball milling of CBM-CA-ARG at molar ratios of 1:1:1, 1:1:2, and 1:1:3 resulted in co-amorphous blends, which had a single T g at 77.8, 105.3, and 127.8 °C, respectively. These ternary co-amorphous samples remained in a solid amorphous form for 2 months at 40 °C. From these results, it can be concluded that blending of the salt coformer with a drug is a promising strategy to design stable co-amorphous formulations.

He + and Ar + bombardment induced chemical changes in CrOSi layers

NASA Astrophysics Data System (ADS)

Bertóti, I.; Tóth, A.; Mohai, M.; Kelly, R.; Marletta, G.

1996-08-01

The effects of 2 keV He + and Ar + bombardment on the surface composition and on the short range chemical structure of sputter deposited amorphous CrOSi layers (with approx. 1 : 1 : 1 atomic ratio) have been studied by XPS. It was found that Ar + bombardment causes an essentially complete reduction of chromium to metallic state (Cr 0) whereas it was partly oxidized in the as-received sample. At the same time about 30% of the oxidized silicon is converted to Si 0 which is stabilized by forming SiCr bonds. He + bombardment, on the contrary, leads to the disruption of SiCr bonds formed by the preceding Ar + bombardment, converting Cr 0 and Si 0 essentially to Cr 3+O, Cr 4+O and Si 4+O, and, at the same time raises the surface oxygen concentration up to three times of the nominal bulk value. The observed transformations are discussed, in connection with the great differences in energy deposition, in terms of direct energy transfer and of ion induced diffusion, together with a significant contribution from thermodynamic driving forces.

Mechanical properties and microstructural change of W–Y2O3 alloy under helium irradiation

PubMed Central

Tan, Xiaoyue; Luo, Laima; Chen, Hongyu; Zhu, Xiaoyong; Zan, Xiang; Luo, Guangnan; Chen, Junling; Li, Ping; Cheng, Jigui; Liu, Dongping; Wu, Yucheng

2015-01-01

A wet-chemical method combined with spark plasma sintering was used to prepare a W–Y2O3 alloy. High-temperature tensile tests and nano-indentation microhardness tests were used to characterize the mechanical properties of the alloy. After He-ion irradiation, fuzz and He bubbles were observed on the irradiated surface. The irradiation embrittlement was reflected by the crack indentations formed during the microhardness tests. A phase transformation from α-W to γ-W was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Polycrystallization and amorphization were also observed in the irradiation damage layer. The W materials tended to exhibit lattice distortion, amorphization, polycrystallization and phase transformation under He-ion irradiation. The transformation mechanism predicted by the atomic lattice model was consistent with the available experimental observations. These findings clarify the mechanism of the structural transition of W under ion irradiation and provide a clue for identifying materials with greater irradiation resistance. PMID:26227480

Effect of characteristics of compounds on maintenance of an amorphous state in solid dispersion with crospovidone.

PubMed

Shibata, Yusuke; Fujii, Makiko; Kokudai, Makiko; Noda, Shinobu; Okada, Hideko; Kondoh, Masuo; Watanabe, Yoshiteru

2007-06-01

Solid dispersion (SD) of indomethacin with crospovidone (CrosPVP) shows useful characteristics for preparation of dosage forms. This study aimed to determine the types of drugs that could adopt a stable amorphous form in SD. Twenty compounds with various melting points (70-218 degrees C), molecular weights (135-504) and functional groups (amide, amino, carbonyl, hydroxyl, ketone etc.) were prepared in SD with CrosPVP. The CrosPVP SDs were prepared using a mechanical mixing and heating method. Melting point and molecular weight were found to have no influence on the ability of a compound to maintain an amorphous state in SD. All compounds containing hydrogen-bond-donor functional groups existed in an amorphous state in SD for at least 6 months. Infrared spectra suggested an interaction between the functional groups of these compounds and amide carbonyl group of CrosPVP. Compounds without hydrogen-bond-donor groups could not maintain an amorphous state and underwent recrystallization within 1 month. It was suggested that the presence of a hydrogen-bond-donor functional group in a compound is an important factor affecting the stable formation of SD with CrosPVP, which contains a hydrogen-bond acceptor.

Pressure-induced amorphization in plagioclase feldspars: A time-resolved powder diffraction study during rapid compression

NASA Astrophysics Data System (ADS)

Sims, M.; Jaret, S.; Carl, E. R.; Schrodt, N.; Rhymer, B.; Mohrholz, V.; Konopkova, Z.; Smith, J.; Liermann, H. P.; Glotch, T. D.; Ehm, L.

2017-12-01

Impact cratering is important in planetary body formation and evolution [1]. The pressure and temperature conditions during impacts are classified using systems [2] that stem from 1) petrographic features and 2) the presence of high pressure mineral phases observed in impactites. Maskelynite, amorphous plagioclase ((Na1-x Cax)Al1+x Si2-x O8), is a key indicator of petrographic type S5 (strongly shocked) and forms between 25 and 45 GPa. However, the formation pressure of maskelynite differs substantially depending on the experimental technique producing it. Shock experiments produce amorphization at > 10 GPa higher than static diamond anvil cell (DAC) experiments. We utilize a new technique, fast compression in combination with time-resolved powder diffraction, to study the effect of strain rate on plagioclase amorphization pressure. Anorthite and albite were compressed to 80 GPa at multiple rates from 0.05 GPa/s to 80 GPa/s, and we observed a decrease in amorphization pressure with increasing compression rate for strain rates of about 10-3 s-1. This decrease demonstrates negative strain rate sensitivity, which is likely caused by structural defects. Negative strain rate sensitivity implies that faster rates are more ductile and heterogeneous and slower rates are more brittle and homogeneous. Our results fit into the deformation framework proposed by Huffman and Reimold [3] and are consistent with the formation mechanism for maskelynite by "shear melting" proposed by Grady [4]. [1] Chao, E.C.T., Shock Metamorphism of Natural Materials., Baltimore, Md: Mono Book Corp, 1968; [2] Stöffler, D., J. Geophys. Res, 76(23), 5541, 1971; [3] Huffman, A.R. and W.U. Reimold, Tectonophysics, 256(1-4), 165-217, 1996; [4] Grady, D., J. Geophys. Res. Solid Earth, 85(B2), 913-924, 1980.

Molecular dynamics simulations of Li transport between cathode crystals

NASA Astrophysics Data System (ADS)

Garofalini, S. H.

The molecular dynamics (MD) computer simulation technique has been used to study the effect of an amorphous intergranular film (IGF) present in a polycrystalline cathode on Li transport. The solid electrolyte is a model lithium silicate glass while the cathode is a nanocrystalline vanadia with an amorphous V 2O 5 IGF separating the crystals. Thin (˜1 to a few nanometer thick) IGFs are known to be present in most polycrystalline oxide materials. However, the role of such a film on Li transport in oxide cathodes has not been addressed. Current scanning probe microscopy (SPM) studies have shown that the orientation of the layered nanocrystalline vanadia crystals near the cathode/solid electrolyte interface is not optimized for Li ion transport. While the precise structure of the material between the crystals has not been identified, initially it can be initially considered as likely to be a thin non-crystalline (amorphous) film. This is based on the ubiquitous presence of such a structure in other polycrystalline oxides. Also, and with more relevance to the materials used in thin film batteries, an amorphous film can be expected to form between nanocrystals that crystallized from an amorphous matrix, as would be the case in a deposited thin film cathode. Consistent with simulations of Li transport in amorphous vanadia, the current simulations show that Li ions diffuse more rapidly into the amorphous intergranular thin film than into the layered vanadia with the (0 0 1) planes parallel to the cathode/electrolyte interface.

Amorphous Sulfadoxine: A Physical Stability and Crystallization Kinetics Study.

PubMed

Aucamp, Marique; Milne, Marnus; Liebenberg, Wilna

2016-10-01

Poor aqueous solubility of drugs and the improvement thereof has always been a challenge for the pharmaceutical industry. With this, one of the focuses of the pharmaceutical research scientist involves investigating possible metastable forms of a given drug to be incorporated into solid dosage forms. The rationale being, the improved solubility offered by the metastable solid-state forms of drugs. Solubility remains a major challenge for formulation scientists, especially with antimicrobial agents where the emergence of resistance is directly dependent on the concentration and duration of the parasite exposed to the drug. Sulfadoxine-pyrimethamine combination therapies are still the recommended treatments for uncomplicated Plasmodium falciparum malaria. The aim of this study was to prepare an amorphous form of sulfadoxine and to investigate the stability and recrystallization behavior thereof. The amorphous form was prepared by the well-known quench cooling of the melt. The physico-chemical properties and stability of amorphous sulfadoxine were studied using hot-stage microscopy (HSM), scanning electron microscopy (SEM), x-ray powder diffractometry (XRPD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), as well as microcalorimetry. The recrystallization kinetics were studied isothermally by applying the Johnson-Mehl-Avrami model and non-isothermally by applying the Kissinger model. The physical stabilization of the amorphous form was investigated using physical mixtures of amorphous sulfadoxine with polyvinylpyrrolidone-25 (PVP-25). It was proved that sulfadoxine is a good glass former with relative high physical stability; however, water acts as a strong plasticizer for amorphous sulfadoxine, detrimentally affecting the stability during exposure to high moisture conditions.

UNIDENTIFIED INFRARED EMISSION BANDS: PAHs or MAONs?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun Kwok; Yong Zhang, E-mail: sunkwok@hku.hk

2013-07-01

We suggest that the carrier of the unidentified infrared emission (UIE) bands is an amorphous carbonaceous solid with mixed aromatic/aliphatic structures, rather than free-flying polycyclic aromatic hydrocarbon molecules. Through spectral fittings of the astronomical spectra of the UIE bands, we show that a significant amount of the energy is emitted by the aliphatic component, implying that aliphatic groups are an essential part of the chemical structure. Arguments in favor of an amorphous, solid-state structure rather than a gas-phase molecule as a carrier of the UIE are also presented.

Fracture-induced amorphization of polycrystalline SiO2 stishovite: a potential platform for toughening in ceramics

PubMed Central

Nishiyama, Norimasa; Wakai, Fumihiro; Ohfuji, Hiroaki; Tamenori, Yusuke; Murata, Hidenobu; Taniguchi, Takashi; Matsushita, Masafumi; Takahashi, Manabu; Kulik, Eleonora; Yoshida, Kimiko; Wada, Kouhei; Bednarcik, Jozef; Irifune, Tetsuo

2014-01-01

Silicon dioxide has eight stable crystalline phases at conditions of the Earth's rocky parts. Many metastable phases including amorphous phases have been known, which indicates the presence of large kinetic barriers. As a consequence, some crystalline silica phases transform to amorphous phases by bypassing the liquid via two different pathways. Here we show a new pathway, a fracture-induced amorphization of stishovite that is a high-pressure polymorph. The amorphization accompanies a huge volume expansion of ~100% and occurs in a thin layer whose thickness from the fracture surface is several tens of nanometers. Amorphous silica materials that look like strings or worms were observed on the fracture surfaces. The amount of amorphous silica near the fracture surfaces is positively correlated with indentation fracture toughness. This result indicates that the fracture-induced amorphization causes toughening of stishovite polycrystals. The fracture-induced solid-state amorphization may provide a potential platform for toughening in ceramics. PMID:25297473

Fracture-induced amorphization of polycrystalline SiO2 stishovite: a potential platform for toughening in ceramics.

PubMed

Nishiyama, Norimasa; Wakai, Fumihiro; Ohfuji, Hiroaki; Tamenori, Yusuke; Murata, Hidenobu; Taniguchi, Takashi; Matsushita, Masafumi; Takahashi, Manabu; Kulik, Eleonora; Yoshida, Kimiko; Wada, Kouhei; Bednarcik, Jozef; Irifune, Tetsuo

2014-10-09

Silicon dioxide has eight stable crystalline phases at conditions of the Earth's rocky parts. Many metastable phases including amorphous phases have been known, which indicates the presence of large kinetic barriers. As a consequence, some crystalline silica phases transform to amorphous phases by bypassing the liquid via two different pathways. Here we show a new pathway, a fracture-induced amorphization of stishovite that is a high-pressure polymorph. The amorphization accompanies a huge volume expansion of ~100% and occurs in a thin layer whose thickness from the fracture surface is several tens of nanometers. Amorphous silica materials that look like strings or worms were observed on the fracture surfaces. The amount of amorphous silica near the fracture surfaces is positively correlated with indentation fracture toughness. This result indicates that the fracture-induced amorphization causes toughening of stishovite polycrystals. The fracture-induced solid-state amorphization may provide a potential platform for toughening in ceramics.

Infrared Spectra and Band Strengths of Amorphous and Crystalline N2O

NASA Technical Reports Server (NTRS)

Hudson, R. L.; Loeffler, M. J.; Gerakines, P. A.

2017-01-01

Infrared transmission spectra from 4000 to 400 cm (exp -1), and associated band strengths and absorption coefficients, are presented for the first time for both amorphous and crystalline N2O. Changes in the spectra as a function of ice thickness and ice temperature are shown. New measurements of density, refractive index, and specific refraction are reported for amorphous and crystalline N2O. Comparisons are made to published results, and the most-likely reason for some recent disagreements in the literature is discussed. As with CO2, its isoelectronic congener, the formation of amorphous N2O is found to require greater care than the formation of amorphous solids from more-polar molecules.

Possible quantum liquid crystal phases of helium monolayers

NASA Astrophysics Data System (ADS)

Nakamura, S.; Matsui, K.; Matsui, T.; Fukuyama, Hiroshi

2016-11-01

The second-layer phase diagrams of 4He and 3He adsorbed on graphite are investigated. Intrinsically rounded specific-heat anomalies are observed at 1.4 and 0.9 K, respectively, over extended density regions in between the liquid and incommensurate solid phases. They are identified to anomalies associated with the Kosterlitz-Thouless-Halperin-Nelson-Young type two-dimensional melting. The prospected low temperature phase (C2 phase) is a commensurate phase or a quantum hexatic phase with quasi-bond-orientational order, both containing zero-point defectons. In either case, this would be the first atomic realization of the quantum liquid crystal, a new state of matter. From the large enhancement of the melting temperature over 3He, we propose to assign the observed anomaly of 4He-C 2 phase at 1.4 K to the hypothetical supersolid or superhexatic transition.

Biomimetic Dissolution: A Tool to Predict Amorphous Solid Dispersion Performance.

PubMed

Puppolo, Michael M; Hughey, Justin R; Dillon, Traciann; Storey, David; Jansen-Varnum, Susan

2017-11-01

The presented study describes the development of a membrane permeation non-sink dissolution method that can provide analysis of complete drug speciation and emulate the in vivo performance of poorly water-soluble Biopharmaceutical Classification System class II compounds. The designed membrane permeation methodology permits evaluation of free/dissolved/unbound drug from amorphous solid dispersion formulations with the use of a two-cell apparatus, biorelevant dissolution media, and a biomimetic polymer membrane. It offers insight into oral drug dissolution, permeation, and absorption. Amorphous solid dispersions of felodipine were prepared by hot melt extrusion and spray drying techniques and evaluated for in vitro performance. Prior to ranking performance of extruded and spray-dried felodipine solid dispersions, optimization of the dissolution methodology was performed for parameters such as agitation rate, membrane type, and membrane pore size. The particle size and zeta potential were analyzed during dissolution experiments to understand drug/polymer speciation and supersaturation sustainment of felodipine solid dispersions. Bland-Altman analysis was performed to measure the agreement or equivalence between dissolution profiles acquired using polymer membranes and porcine intestines and to establish the biomimetic nature of the treated polymer membranes. The utility of the membrane permeation dissolution methodology is seen during the evaluation of felodipine solid dispersions produced by spray drying and hot melt extrusion. The membrane permeation dissolution methodology can suggest formulation performance and be employed as a screening tool for selection of candidates to move forward to pharmacokinetic studies. Furthermore, the presented model is a cost-effective technique.

Growth process of hydrogenated amorphous carbon films synthesized by atmospheric pressure plasma enhanced CVD using nitrogen and helium as a dilution gas

NASA Astrophysics Data System (ADS)

Mori, Takanori; Sakurai, Takachika; Sato, Taiki; Shirakura, Akira; Suzuki, Tetsuya

2016-04-01

Hydrogenated amorphous carbon films with various thicknesses were synthesized by dielectric barrier discharge-based plasma deposition under atmospheric pressure diluted with nitrogen (N2) and helium (He) at various pulse frequencies. The C2H2/N2 film showed cauliflower-like-particles that grew bigger with the increase in film’s thickness. At 5 kHz, the film with a thickness of 2.7 µm and smooth surface was synthesized. On the other hand, the films synthesized from C2H2/He had a smooth surface and was densely packed with domed particles. The domed particles extended with the increase in the film thickness, enabling it to grow successfully to 37 µm with a smooth surface.

Delocalization via Sliding in Solid 4He: Is It Plausible?

NASA Astrophysics Data System (ADS)

Krainyukova, N. V.

2010-02-01

The modified Debye approach was used to calculate the Gibbs free energy for solid 4He and energetic profiles for different atomic displacements with respect to an equilibrium lattice. Atoms interact via the applied Aziz potential. We have found that individual atomic displacements may hardly give rise to any delocalization because of huge barriers but cooperative plane sliding is highly plausible especially in the intermediate phase, which was found to be more favorable than hcp for small cluster sizes. In the latter case the roughness of the potential profile is less than one kelvin. In some particular sliding cases the energy levels in the nearest wells nearly coincide that is a well-known precursor for the delocalization effect.

Laboratory Experiments to Study Spherical, Iron Oxide Concretion Growth Without Solid Nuclei: Implications for Understanding Meridiani "Blueberries"

NASA Astrophysics Data System (ADS)

Ormö, J.; Souza-Egipsy, V.; Chan, M. A.; Park, A. J.; Stich, M.; Komatsu, G.

2006-03-01

Spherical hematite concretions can form without a nucleus. Self-organized zones of super-saturated solution cause spherical precipitates of amorphous iron-hydroxide. Diffusion of Fe ions towards the outer perimeter of the amorphous sphere forms a rind, which then grows inwards.

Fe and O EELS Studies of Ion Irradiated Murchison CM2 Carbonaceous Chondrite Matrix

NASA Technical Reports Server (NTRS)

Keller, L. P.; Christofferson, R.; Dukes, C. A.; Baragiola, R. A.; Rahman, Z.

2015-01-01

Introduction: The physical and chemical response of hydrated carbonaceous chondrite materials to space weathering processes is poorly understood. Improving this understanding is a key part of establishing how regoliths on primitive carbonaceous asteroids respond to space weathering processes, knowledge that supports future sample return missions (Hayabusa 2 and OSIRISREx) that are targeting objects of this type. We previously reported on He+ irradiation of Murchison matrix and showed that the irradiation resulted in amorphization of the matrix phyllosilicates, loss of OH, and surface vesiculation. Here, we report electron energy-loss spectroscopy (EELS) measurements of the irradiated material with emphasis on the Fe and O speciation. Sample and Methods: A polished thin section of the Murchison CM2 carbonaceous chondrite was irradiated with 4 kilovolts He(+) (normal incidence) to a total dose of 1 x 10(exp 18) He(+) per square centimeter. We extracted thin sections from both irradiated and unirradiated regions in matrix using focused ion beam (FIB) techniques with electron beam deposition for the protective carbon strap to minimize surface damage artifacts from the FIB milling. The FIB sections were analyzed using a JEOL 2500SE scanning and transmission electron microscope (STEM) equipped with a Gatan Tridiem imaging filter. EELS spectra were collected from 50 nanometer diameter regions with an energy resolution of 0.7 electronvolts FWHM at the zero loss. EELS spectra were collected at low electron doses to minimize possible artifacts from electron-beam irradiation damage. Results and Discussion: Fe L (sub 2,3) EELS spectra from matrix phyllosilicates in CM chondrites show mixed Fe(2+)/Fe(3+) oxidation states with Fe(3+)/Sigma Fe approximately 0.5. Fe L(sub 2,3) spectra from the irradiated/ amorphized matrix phyllosilicates show higher Fe(2+)/Fe(3+) ratios compared to spectra obtained from pristine material at depths beyond the implantation/amorphization layer. We also obtained O Ka spectra from phyllosilicates in both regions of the sample. The O Ka spectra show a pre-edge feature at approximately 530.5 electronvolts that is related to O 2p states hybridized with Fe 3d states. The intensity ratio of the O Ka pre-edge peak relative to the main part of the O Ka edge (that results from transitions of O 1s to 2p states) is lower in the irradiated layer compared to the pristine material and may reflect the loss of O (as OH) as was observed by IR spectroscopy. Conclusions: In addition to amorphization and OH loss, EELS spectra of He(+) irradiated matrix phyllosilicates in Murchison show that some of the Fe(3+) is reduced to Fe(2+). Spectral deconvolution is underway to extract quantitative ratios from the EELS spectra.

Photoacoustic Spectroscopy of Chemically Modified Surfaces.

DTIC Science & Technology

1981-08-01

Science.4 In that I 2 paper he told of the accidental discovery of the optoacoustic effect in solids. He observed that a rapidly modulated beam of...0L - -LJ Lii Lnf cobr 0D CDV 214 Figure 17. Photoacoustic spectrum of (I) Co 304 ground with y-alumina and (II) CoO-enhanced cobalt oxide ground with y

Amorphous Mixed-Metal Oxide Thin Films from Aqueous Solution Precursors with Near-Atomic Smoothness.

PubMed

Kast, Matthew G; Cochran, Elizabeth A; Enman, Lisa J; Mitchson, Gavin; Ditto, Jeffrey; Siefe, Chris; Plassmeyer, Paul N; Greenaway, Ann L; Johnson, David C; Page, Catherine J; Boettcher, Shannon W

2016-12-28

Thin films with tunable and homogeneous composition are required for many applications. We report the synthesis and characterization of a new class of compositionally homogeneous thin films that are amorphous solid solutions of Al 2 O 3 and transition metal oxides (TMO x ) including VO x , CrO x , MnO x , Fe 2 O 3 , CoO x , NiO, CuO x , and ZnO. The synthesis is enabled by the rapid decomposition of molecular transition-metal nitrates TM(NO 3 ) x at low temperature along with precondensed oligomeric Al(OH) x (NO 3 ) 3-x cluster species, both of which can be processed from aq solution. The films are dense, ultrasmooth (R rms < 1 nm, near 0.1 nm in many cases), and atomically mixed amorphous metal-oxide alloys over a large composition range. We assess the chemical principles that favor the formation of amorphous homogeneous films over rougher phase-segregated nanocrystalline films. The synthesis is easily extended to other compositions of transition and main-group metal oxides. To demonstrate versatility, we synthesized amorphous V 0.1 Cr 0.1 Mn 0.1 Fe 0.1 Zn 0.1 Al 0.5 O x and V 0.2 Cr 0.2 Fe 0.2 Al 0.4 O x with R rms ≈ 0.1 nm and uniform composition. The combination of ideal physical properties (dense, smooth, uniform) and broad composition tunability provides a platform for film synthesis that can be used to study fundamental phenomena when the effects of transition metal cation identity, solid-state concentration of d-electrons or d-states, and/or crystallinity need to be controlled. The new platform has broad potential use in controlling interfacial phenomena such as electron transfer in solar-cell contacts or surface reactivity in heterogeneous catalysis.

Elucidation and visualization of solid-state transformation and mixing in a pharmaceutical mini hot melt extrusion process using in-line Raman spectroscopy.

PubMed

Van Renterghem, Jeroen; Kumar, Ashish; Vervaet, Chris; Remon, Jean Paul; Nopens, Ingmar; Vander Heyden, Yvan; De Beer, Thomas

2017-01-30

Mixing of raw materials (drug+polymer) in the investigated mini pharma melt extruder is achieved by using co-rotating conical twin screws and an internal recirculation channel. In-line Raman spectroscopy was implemented in the barrels, allowing monitoring of the melt during processing. The aim of this study was twofold: to investigate (I) the influence of key process parameters (screw speed - barrel temperature) upon the product solid-state transformation during processing of a sustained release formulation in recirculation mode; (II) the influence of process parameters (screw speed - barrel temperature - recirculation time) upon mixing of a crystalline drug (tracer) in an amorphous polymer carrier by means of residence time distribution (RTD) measurements. The results indicated a faster mixing endpoint with increasing screw speed. Processing a high drug load formulation above the drug melting temperature resulted in the production of amorphous drug whereas processing below the drug melting point produced solid dispersions with partially amorphous/crystalline drug. Furthermore, increasing the screw speed resulted in lower drug crystallinity of the solid dispersion. RTD measurements elucidated the improved mixing capacity when using the recirculation channel. In-line Raman spectroscopy has shown to be an adequate PAT-tool for product solid-state monitoring and elucidation of the mixing behavior during processing in a mini extruder. Copyright © 2016 Elsevier B.V. All rights reserved.

Extensive Diminution of Particle Size and Amorphization of a Crystalline Drug Attained by Eminent Technology of Solid Dispersion: A Comparative Study.

PubMed

Singh, Gurjeet; Sharma, Shailesh; Gupta, Ghanshyam Das

2017-07-01

The present study emphasized on the use of solid dispersion technology to triumph over the drawbacks associated with the highly effective antihypertensive drug telmisartan using different polymers (poloxamer 188 and locust bean gum) and methods (modified solvent evaporation and lyophilization). It is based on the comparison between selected polymers and methods for enhancing solubility through particle size reduction. The results showed different profiles for particle size, solubility, and dissolution of formulated amorphous systems depicting the great influence of polymer/method used. The resulting amorphous solid dispersions were characterized using x-ray diffraction (XRD), differential scanning calorimetry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and particle size analysis. The optimized solid dispersion (TEL 19) prepared with modified locust bean gum using lyophilization technique showed reduced particle size of 184.5 ± 3.7 nm and utmost solubility of 702 ± 5.47 μg/mL in water, which is quite high as compared to the pure drug (≤1 μg/mL). This study showed that the appropriate selection of carrier may lead to the development of solid dispersion formulation with desired solubility and dissolution profiles. The optimized dispersion was later formulated into fast-dissolving tablets, and further optimization was done to obtain the tablets with desired properties.

Thermal Processing of PVP- and HPMC-Based Amorphous Solid Dispersions.

PubMed

LaFountaine, Justin S; Prasad, Leena Kumari; Brough, Chris; Miller, Dave A; McGinity, James W; Williams, Robert O

2016-02-01

Thermal processing technologies continue to gain interest in pharmaceutical manufacturing. However, the types and grades of polymers that can be utilized in common thermal processing technologies, such as hot-melt extrusion (HME), are often limited by thermal or rheological factors. The objectives of the present study were to compare and contrast two thermal processing methods, HME and KinetiSol® Dispersing (KSD), and investigate the influence of polymer type, polymer molecular weight, and drug loading on the ability to produce amorphous solid dispersions (ASDs) containing the model compound griseofulvin (GRIS). Dispersions were analyzed by a variety of imaging, solid-state, thermal, and solution-state techniques. Dispersions were prepared by both HME and KSD using polyvinylpyrrolidone (PVP) K17 or hydroxypropyl methylcellulose (HPMC) E5. Dispersions were only prepared by KSD using higher molecular weight grades of HPMC and PVP, as these could not be extruded under the conditions selected. Powder X-ray diffraction (PXRD) analysis showed that dispersions prepared by HME were amorphous at 10% and 20% drug load; however, it showed significant crystallinity at 40% drug load. PXRD analysis of KSD samples showed all formulations and drug loads to be amorphous with the exception of trace crystallinity seen in PVP K17 and PVP K30 samples at 40% drug load. These results were further supported by other analytical techniques. KSD produced amorphous dispersions at higher drug loads than could be prepared by HME, as well as with higher molecular weight polymers that were not processable by HME, due to its higher rate of shear and torque output.

Lowering the operational temperature of all-solid-state lithium polymer cell with highly conductive and interfacially robust solid polymer electrolytes

NASA Astrophysics Data System (ADS)

Aldalur, Itziar; Martinez-Ibañez, Maria; Piszcz, Michal; Rodriguez-Martinez, Lide M.; Zhang, Heng; Armand, Michel

2018-04-01

Novel solid polymer electrolytes (SPEs), comprising of comb polymer matrix grafted with soft and disordered polyether moieties (Jeffamine®) and lithium bis(fluorosulfonyl)imide (LiFSI) are investigated in all-solid-state lithium metal (Li°) polymer cells. The LiFSI/Jeffamine-based SPEs are fully amorphous at room temperature with glass transitions as low as ca. -55 °C. They show higher ionic conductivities than conventional poly(ethylene oxide) (PEO)-based SPEs at ambient temperature region, and good electrochemical compatibility with Li° electrode. These exceptional properties enable the operational temperature of Li° | LiFePO4 cells to be decreased from an elevated temperature (70 °C) to room temperature. Those results suggest that LiFSI/Jeffamine-based SPEs can be promising electrolyte candidates for developing safe and high performance all-solid-state Li° batteries.

Synthesis, conductivity and high-pressure phase transition of amorphous boron carbon nitride

NASA Astrophysics Data System (ADS)

Bai, Suo Zhu; Yao, Bin; Xing, Guo Zhong; Zhang, Ke; Su, Wen-Hui

2007-06-01

Amorphous BCN was prepared by chemical solid-state reaction between boracic acid (H 3BO 3) and melamine (C 3N 6H 6) in mass ratios of H 3BO 3 to C 3N 6H 6 of 1:2-1:4 and heat treatment at 1273 K under 10 -3 Pa. The amorphous B sbnd C sbnd N behave insulating property below 890 K, but semiconductor conductivity above 890 K and show different conductivity-temperature relationships in temperature ranges of 913-963 and 963-1083 K. The conductive activation energy was calculated to be 0.26-0.34 eV at 913-963 K and 1.02-1.10 eV at 963-1083 K, implying that the conduction mechanisms are different in the different temperature ranges. Annealed for 40 min at 1473 K under 4.0 GPa, the amorphous BCN with the chemical composition B 0.48C 0.29N 0.23 was prepared in the mass ratio of 1:3 crystallizes into single-phase hexagonal (h-BCN) compound with lattice constants of a=0.2506 nm and c=0.6652 nm. Raman scattering peaks were observed at 1330, 1364,1584 and 1617 cm -1 in the Raman spectrum (RS) of h-BCN, of which the peaks located at 1330 and 1617 cm -1 are assigned to characteristic peaks of the h-BCN.

Geometric charges in theories of elasticity and plasticity

NASA Astrophysics Data System (ADS)

Moshe, Michael

The mechanics of many natural systems is governed by localized sources of stresses. Examples include ''plastic events'' that occur in amorphous solids under external stress, defects formation in crystalline material, and force-dipoles applied by cells adhered to an elastic substrate. Recent developments in a geometric formulation of elasticity theory paved the way for a unifying mathematical description of such singular sources of stress, as ''elastic charges''. In this talk I will review basic results in this emerging field, focusing on the geometry and mechanics of elastic charges in two-dimensional solid bodies. I will demonstrate the applicability of this new approach in three different problems: failure of an amorphous solid under load, mechanics of Kirigami, and wrinkle patterns in geometrically-incompatible elastic sheets.

Synthesis and characterization of P-doped amorphous and nanocrystalline Si

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jialing; Ganguly, Shreyashi; Sen, Sabyasachi

Intentional impurity doping lies at the heart of the silicon technology. The dopants provide electrons or holes as necessary carriers of the electron current and can significantly modify the electric, optical and magnetic properties of the semiconductors. P-doped amorphous Si (a-Si) was prepared by a solid state and solution metathesis reaction of a P-doped Zintl phase precursor, NaSi 0.99P 0.01, with an excess of NH 4X (X = Br, I). After the salt byproduct was removed from the solid state reaction, the a-Si material was annealed at 600 °C under vacuum for 2 h, resulting in P-doped nanocrystalline Si (nc-Si)more » material embedded in a-Si matrix. The product from the solution reaction also shows a combination of nc-Si embedded in a-Si; however, it was fully converted to nc-Si after annealing under argon at 650 °C for 30 min. Powder X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) show the amorphous nature of the P-doped Si material before the annealing and the nanocrystallinity after the annealing. Fourier Transform Infrared (FTIR) spectroscopy shows that the P-doped Si material surface is partially capped by H and O or with solvent. Finally, electron microprobe wavelength dispersive spectroscopy (WDS) as well as energy dispersive spectroscopy (EDS) confirm the presence of P in the Si material. 29Si and 31P solid state magic-angle-spinning nuclear magnetic resonance (MAS NMR) spectroscopy data provide the evidence of P doping into the Si structure with the P concentration of approximately 0.07 at.%.« less

Hot melt extrusion versus spray drying: hot melt extrusion degrades albendazole.

PubMed

Hengsawas Surasarang, Soraya; Keen, Justin M; Huang, Siyuan; Zhang, Feng; McGinity, James W; Williams, Robert O

2017-05-01

The purpose of this study was to enhance the dissolution properties of albendazole (ABZ) by the use of amorphous solid dispersions. Phase diagrams of ABZ-polymer binary mixtures generated from Flory-Huggins theory were used to assess miscibility and processability. Forced degradation studies showed that ABZ degraded upon exposure to hydrogen peroxide and 1 N NaOH at 80 °C for 5 min, and the degradants were albendazole sulfoxide (ABZSX), and ABZ impurity A, respectively. ABZ was chemically stable following exposure to 1 N HCl at 80 °C for one hour. Thermal degradation profiles show that ABZ, with and without Kollidon ® VA 64, degraded at 180 °C and 140 °C, respectively, which indicated that ABZ could likely be processed by thermal processing. Following hot melt extrusion, ABZ degraded up to 97.4%, while the amorphous ABZ solid dispersion was successfully prepared by spray drying. Spray-dried ABZ formulations using various types of acids (methanesulfonic acid, sulfuric acid and hydrochloric acid) and polymers (Kollidon ® VA 64, Soluplus ® and Eudragit ® E PO) were studied. The spray-dried ABZ with methanesulfonic acid and Kollidon ® VA 64 substantially improved non-sink dissolution in acidic media as compared to bulk ABZ (8-fold), physical mixture of ABZ:Kollidon ® VA 64 (5.6-fold) and ABZ mesylate salt (1.6-fold). No degradation was observed in the spray-dried product for up to six months and less than 5% after one-year storage. In conclusion, amorphous ABZ solid dispersions in combination with an acid and polymer can be prepared by spray drying to enhance dissolution and shelf-stability, whereas those made by melt extrusion are degraded.

Experiment and Theory for Nuclear Reactions in Nano-Materials Show e14 - e16 Solid-State Fusion Reactions

NASA Astrophysics Data System (ADS)

George, Russ

2005-03-01

Nano-lattices of deuterium loving metals exhibit coherent behavior by populations of deuterons (d's) occupying a Bloch state. Therein, coherent d-overlap occurs wherein the Bloch condition reduces the Coulomb barrier.Overlap of dd pairs provides a high probability fusion will/must occur. SEM photo evidence showing fusion events is now revealed by laboratories that load or flux d into metal nano-domains. Solid-state dd fusion creates an excited ^4He nucleus entangled in the large coherent population of d's.This contrasts with plasma dd fusion in collision space where an isolated excited ^4He nucleus seeks the ground state via fast particle emission. In momentum limited solid state fusion,fast particle emission is effectively forbidden.Photographed nano-explosive events are beyond the scope of chemistry. Corroboration of the nuclear nature derives from photographic observation of similar events on spontaneous fission, e.g. Cf. We present predictive theory, heat production, and helium isotope data showing reproducible e14 to e16 solid-state fusion reactions.

Spatial Distribution of Amorphization Intensity in B4C during Rate-Dependent Indentation and Ballistic Impact Processes [1.2 Solid Mechanics

DTIC Science & Technology

2017-11-17

SECURITY CLASSIFICATION OF: At high pressures, such as those encountered in ballistic impact, boron carbide (B4C) suffers from loss of crystallinity...ELEMENT NUMBER 5b. GRANT NUMBER 5a. CONTRACT NUMBER Form Approved OMB NO . 0704-0188 3. DATES COVERED (From - To) - Approved for public release...Highway, Suite 1204, Arlington VA, 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject

A solid-state amorphous selenium avalanche technology for low photon flux imaging applications

PubMed Central

Wronski, M. M.; Zhao, W.; Reznik, A.; Tanioka, K.; DeCrescenzo, G.; Rowlands, J. A.

2010-01-01

Purpose: The feasibility of a practical solid-state technology for low photon flux imaging applications was investigated. The technology is based on an amorphous selenium photoreceptor with a voltage-controlled avalanche multiplication gain. If this photoreceptor can provide sufficient internal gain, it will be useful for an extensive range of diagnostic imaging systems. Methods: The avalanche photoreceptor under investigation is referred to as HARP-DRL. This is a novel concept in which a high-gain avalanche rushing photoconductor (HARP) is integrated with a distributed resistance layer (DRL) and sandwiched between two electrodes. The avalanche gain and leakage current characteristics of this photoreceptor were measured. Results: HARP-DRL has been found to sustain very high electric field strengths without electrical breakdown. It has shown avalanche multiplication gains as high as 104 and a very low leakage current (≤20 pA∕mm2). Conclusions: This is the first experimental demonstration of a solid-state amorphous photoreceptor which provides sufficient internal avalanche gain for photon counting and photon starved imaging applications. PMID:20964217

Bonding structure in amorphous carbon nitride: A spectroscopic and nuclear magnetic resonance study

NASA Astrophysics Data System (ADS)

Sánchez-López, J. C.; Donnet, C.; Lefèbvre, F.; Fernández-Ramos, C.; Fernández, A.

2001-07-01

Since the prediction of Liu and Cohen [Science 245, 841 (1989)] of the potential extraordinary mechanical properties of crystalline β-C3N4, many authors have attempted its synthesis. However, in most cases, the obtained materials are amorphous phases with a complex bonding structure. Their characterization is complicated due to the absence of a reference compound, the lack of long-range order, and the poor knowledge about their bonding structure. In this article, we present 1H, 13C, and 15N solid-state nuclear magnetic resonance (NMR) measurements for the determination of the bonding types in amorphous CNx films. NMR measurements do not require long-range order and are able to clearly identify the signals from the sp2- and sp3-bonded phases. The analysis of the data obtained by other characterization techniques, such as infrared spectroscopy, x-ray photoelectron spectroscopy, electron energy-loss spectroscopy, and x-ray absorption near-edge spectroscopy on the same sample, based on the information acquired by NMR, enables the description of a structure model for the studied amorphous-CNx phase prepared by dc-magnetron sputtering and to revise the interpretation found in the literature.

Measurement of helium isotopes in soil gas as an indicator of tritium groundwater contamination.

PubMed

Olsen, Khris B; Dresel, P Evan; Evans, John C; McMahon, William J; Poreda, Robert

2006-05-01

The focus of this study was to define the shape and extent of tritium groundwater contamination emanating from a legacy burial ground and to identify vadose zone sources of tritium using helium isotopes (3He and 4He) in soil gas. Helium isotopes were measured in soil-gas samples collected from 70 sampling points around the perimeter and downgradient of a burial ground that contains buried radioactive solid waste. The soil-gas samples were analyzed for helium isotopes using rare gas mass spectrometry. 3He/4He ratios, reported as normalized to the air ratio (RA), were used to locate the tritium groundwater plume emanating from the burial ground. The 3He (excess) suggested that the general location of the tritium source is within the burial ground. This study clearly demonstrated the efficacy of the 3He method for application to similar sites elsewhere within the DOE weapons complex.

Laboratory Investigation of the Growth and Crystal Structure of Nitric Acid Hydrates by Transmission Electron Microscopy (TEM)

NASA Technical Reports Server (NTRS)

Blake, David F.; Chang, Sherwood (Technical Monitor)

1994-01-01

A great deal of recent laboratory work has focussed on the characterization of the nitric acid hydrates, thought to be present in type I Polar Stratospheric Clouds (PSCs). Phase relationships and vapor pressure measurements (1-3) and infrared characterizations (4-5) have been made. However, the observed properties of crystalline solids (composition, melting point, vapor pressure, surface reactivity, thermodynamic stability, extent of solid solution with other components, etc.) are controlled by their crystal structure. The only means of unequivocal structural identification for crystalline solids is diffraction (using electrons, X-rays, neutrons, etc.). Other observed properties of crystalline solids, such as their infrared spectra, their vapor pressure as a function of temperature, etc. yield only indirect information about what phases are present, their relative proportions, or whether they are crystalline or amorphous.

First principles prediction of amorphous phases using evolutionary algorithms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nahas, Suhas, E-mail: shsnhs@iitk.ac.in; Gaur, Anshu, E-mail: agaur@iitk.ac.in; Bhowmick, Somnath, E-mail: bsomnath@iitk.ac.in

2016-07-07

We discuss the efficacy of evolutionary method for the purpose of structural analysis of amorphous solids. At present, ab initio molecular dynamics (MD) based melt-quench technique is used and this deterministic approach has proven to be successful to study amorphous materials. We show that a stochastic approach motivated by Darwinian evolution can also be used to simulate amorphous structures. Applying this method, in conjunction with density functional theory based electronic, ionic and cell relaxation, we re-investigate two well known amorphous semiconductors, namely silicon and indium gallium zinc oxide. We find that characteristic structural parameters like average bond length and bondmore » angle are within ∼2% of those reported by ab initio MD calculations and experimental studies.« less

Structural Elucidation of Poloxamer 237 and Poloxamer 237/Praziquantel Solid Dispersions: Impact of Poly(Vinylpyrrolidone) over Drug Recrystallization and Dissolution.

PubMed

Orlandi, Silvina; Priotti, Josefina; Diogo, Hermínio P; Leonardi, Dario; Salomon, Claudio J; Nunes, Teresa G

2018-04-01

Praziquantel (PZQ) is the recommended, effective, and safe treatment against all forms of schistosomiasis. Solid dispersions (SDs) in water-soluble polymers have been reported to increase solubility and bioavailability of poorly water-soluble drugs like PZQ, generally due to the amorphous form stabilization. In this work, poloxamer (PLX) 237 and poly(vinylpyrrolidone) (PVP) K30 were evaluated as potential carriers to revert PZQ crystallization. Binary and ternary SDs were prepared by the solvent evaporation method. PZQ solubility increased similarly with PLX either as binary physical mixtures or SDs. Such unpredicted data correlated well with crystalline PZQ and PLX as detected by solid-state NMR (ssNMR) and differential scanning calorimetry in those samples. Ternary PVP/PLX/PZQ SDs showed both ssNMR broad and narrow superimposed signals, thus revealing the presence of amorphous and crystalline PZQ, respectively, and exhibited the highest PZQ dissolution efficiency (up to 82% at 180 min). SDs with PVP provided a promising way to enhance solubility and dissolution rate of PZQ since PLX alone did not prevent recrystallization of amorphous PZQ. Based on ssNMR data, novel evidences on PLX structure and molecular dynamics were also obtained. As shown for the first time using ssNMR, propylene glycol and ethylene glycol constitute the PLX amorphous and crystalline components, respectively.

Picosecond amorphization of SiO2 stishovite under tension.

PubMed

Misawa, Masaaki; Ryuo, Emina; Yoshida, Kimiko; Kalia, Rajiv K; Nakano, Aiichiro; Nishiyama, Norimasa; Shimojo, Fuyuki; Vashishta, Priya; Wakai, Fumihiro

2017-05-01

It is extremely difficult to realize two conflicting properties-high hardness and toughness-in one material. Nano-polycrystalline stishovite, recently synthesized from Earth-abundant silica glass, proved to be a super-hard, ultra-tough material, which could provide sustainable supply of high-performance ceramics. Our quantum molecular dynamics simulations show that stishovite amorphizes rapidly on the order of picosecond under tension in front of a crack tip. We find a displacive amorphization mechanism that only involves short-distance collective motions of atoms, thereby facilitating the rapid transformation. The two-step amorphization pathway involves an intermediate state akin to experimentally suggested "high-density glass polymorphs" before eventually transforming to normal glass. The rapid amorphization can catch up with, screen, and self-heal a fast-moving crack. This new concept of fast amorphization toughening likely operates in other pressure-synthesized hard solids.

Low temperature production of large-grain polycrystalline semiconductors

DOEpatents

Naseem, Hameed A [Fayetteville, AR; Albarghouti, Marwan [Loudonville, NY

2007-04-10

An oxide or nitride layer is provided on an amorphous semiconductor layer prior to performing metal-induced crystallization of the semiconductor layer. The oxide or nitride layer facilitates conversion of the amorphous material into large grain polycrystalline material. Hence, a native silicon dioxide layer provided on hydrogenated amorphous silicon (a-Si:H), followed by deposited Al permits induced crystallization at temperatures far below the solid phase crystallization temperature of a-Si. Solar cells and thin film transistors can be prepared using this method.

Improving the dissolution rate of poorly water soluble drug by solid dispersion and solid solution: pros and cons.

PubMed

Chokshi, Rina J; Zia, Hossein; Sandhu, Harpreet K; Shah, Navnit H; Malick, Waseem A

2007-01-01

The solid dispersions with poloxamer 188 (P188) and solid solutions with polyvinylpyrrolidone K30 (PVPK30) were evaluated and compared in an effort to improve aqueous solubility and bioavailability of a model hydrophobic drug. All preparations were characterized by differential scanning calorimetry, powder X-ray diffraction, intrinsic dissolution rates, and contact angle measurements. Accelerated stability studies also were conducted to determine the effects of aging on the stability of various formulations. The selected solid dispersion and solid solution formulations were further evaluated in beagle dogs for in vivo testing. Solid dispersions were characterized to show that the drug retains its crystallinity and forms a two-phase system. Solid solutions were characterized to be an amorphous monophasic system with transition of crystalline drug to amorphous state. The evaluation of the intrinsic dissolution rates of various preparations indicated that the solid solutions have higher initial dissolution rates compared with solid dispersions. However, after storage at accelerated conditions, the dissolution rates of solid solutions were lower due to partial reversion to crystalline form. The drug in solid dispersion showed better bioavailability in comparison to solid solution. Therefore, considering physical stability and in vivo study results, the solid dispersion was the most suitable choice to improve dissolution rates and hence the bioavailability of the poorly water soluble drug.

Structure of Oxide Glass and Melts at High-Pressure: A View from Inelastic X-ray Scattering and 2D Solid-State NMR

NASA Astrophysics Data System (ADS)

Lee, S.; Mysen, B. O.; Fei, Y.; Cody, G. D.; Mao, H.; Eng, P.

2006-12-01

Full understanding of the atomic arrangement of oxides glasses and melts both at ambient and high-pressure has long been one of the fundamental and yet difficult problems in earth sciences, condensed matter physics as well as glass sciences. The structures of archetypal oxide glasses (e.g. SiO2 and B2O3) as well as complex silicate glasses (ternary and quaternary aluminosilicate glasses) at high pressure are essential to elucidate origins of anomalous macroscopic properties of melts and global geophysical processes in the Earth's interior. Recent progress in inelastic x-ray scattering (IXS) with high brilliance 3rd generation synchrotron x-rays combined with DAC techniques allows us to explore pressure-induced changes in the bonding nature of archetypal amorphous oxide, illustrating a new opportunity to study amorphous oxides with IXS (Lee SK et al. Nature Materials 2005, 4, p851). 2 dimensional solid-state NMR have offered much improved resolution over conventional 1D NMR, unveiling previously unknown structural details of amorphous silicates at high pressure (Lee SK. Geochim. Cosmochim. Acta 2005, 69, p3695; J. Phys. Chem. B. 2006, 110, p16408) Here, we report the synchrotron inelastic x-ray scattering results (oxygen and boron K-edge) for divers oxide glasses at pressure up to 40 GPa, revealing the nature of pressure-induced bonding changes and the structure. Direct in-situ measurements provide evidence for a continuous transformation with multiple densification mechanisms. 2D solid-state NMR spectra for silicate and germinate glasses shows detailed information about extent of disorder among framework units at high pressure. The chemical ordering among framework units leads to the formation of ^{[5,6]}Si-O-^{[4]}Si in silicates and ^{[5,6]}Al-O-^{[4]}Si in aluminosilicates. Whereas the densification mechanism can be dependent on the chemical composition and the fraction of non-bridging oxygen, the pressure dependence of both simple and complex multi-component silicate glasses showed similar characteristics: low pressure regime was marked with topological variation without coordination transformation and inter-mediate pressure region (about 5-10 GPa) was characterized by the largest (d(^{[4]}B or ^{[5,6]}Si)/dP) value. Finally high-pressure regime (above 10 GPa) was characterized by a larger energy penalty for coordination transformation than in intermediate pressure regime. These results provide improved prospect for the bonding nature of amorphous materials at high pressure using synchrotron inelastic x-ray scattering and 2D NMR and aid in understanding the microscopic origins of the properties of melts and geological processes in the Earth's interior.

Selective metallization of amorphous-indium-gallium-zinc-oxide thin-film transistor by using helium plasma treatment

NASA Astrophysics Data System (ADS)

Jang, Hun; Lee, Su Jeong; Porte, Yoann; Myoung, Jae-Min

2018-03-01

In this study, the effects of helium (He) plasma treatment on amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) have been investigated. The He plasma treatment induced a dramatic decrease of the resistivity in a-IGZO thin films from 1.25 × 106 to 5.93 mΩ cm. After 5 min He plasma treatment, the a-IGZO films showed an increase in carrier concentration to 6.70 × 1019 cm-3 combined with a high hall mobility of 15.7 cm2 V-1 s-1. The conductivity improvement was linked to the formation of oxygen vacancies during the He plasma treatment, which was observed by x-ray photoelectron spectroscopy analysis. The a-IGZO films did not appear to be damaged on the surface following the plasma treatment and showed a high transmittance of about 88.3% at a wavelength of 550 nm. The He plasma-treated a-IGZO films were used as source/drain (S/D) electrodes in a-IGZO TFTs. The devices demonstrated promising characteristics, on pair with TFTs using Al electrodes, with a threshold voltage (V T) of -1.97 V, sub-threshold slope (SS) of 0.52 V/decade, saturation mobility (μ sat) of 8.75 cm2 V-1 s-1, and on/off current ratio (I on/I off) of 2.66 × 108.

High-harmonic generation in amorphous solids

DOE Office of Scientific and Technical Information (OSTI.GOV)

You, Yong Sing; Yin, Yanchun; Wu, Yi

High-harmonic generation in isolated atoms and molecules has been widely utilized in extreme ultraviolet photonics and attosecond pulse metrology. Recently, high-harmonic generation has been observed in solids, which could lead to important applications such as all-optical methods to image valance charge density and reconstruct electronic band structures, as well as compact extreme ultraviolet light sources. So far these studies are confined to crystalline solids; therefore, decoupling the respective roles of long-range periodicity and high density has been challenging. Here we report the observation of high-harmonic generation from amorphous fused silica. We also decouple the role of long-range periodicity by comparingmore » harmonics generated from fused silica and crystalline quartz, which contain the same atomic constituents but differ in long-range periodicity. These results advance current understanding of the strong-field processes leading to high-harmonic generation in solids with implications for the development of robust and compact extreme ultraviolet light sources.« less

Graphene nanocomposites for electrochemical cell electrodes

DOEpatents

Zhamu, Aruna; Jang, Bor Z.; Shi, Jinjun

2015-11-19

A composite composition for electrochemical cell electrode applications, the composition comprising multiple solid particles, wherein (a) a solid particle is composed of graphene platelets dispersed in or bonded by a first matrix or binder material, wherein the graphene platelets are not obtained from graphitization of the first binder or matrix material; (b) the graphene platelets have a length or width in the range of 10 nm to 10 .mu.m; (c) the multiple solid particles are bonded by a second binder material; and (d) the first or second binder material is selected from a polymer, polymeric carbon, amorphous carbon, metal, glass, ceramic, oxide, organic material, or a combination thereof. For a lithium ion battery anode application, the first binder or matrix material is preferably amorphous carbon or polymeric carbon. Such a composite composition provides a high anode capacity and good cycling response. For a supercapacitor electrode application, the solid particles preferably have meso-scale pores therein to accommodate electrolyte.

High-harmonic generation in amorphous solids

DOE PAGES

You, Yong Sing; Yin, Yanchun; Wu, Yi; ...

2017-09-28

High-harmonic generation in isolated atoms and molecules has been widely utilized in extreme ultraviolet photonics and attosecond pulse metrology. Recently, high-harmonic generation has been observed in solids, which could lead to important applications such as all-optical methods to image valance charge density and reconstruct electronic band structures, as well as compact extreme ultraviolet light sources. So far these studies are confined to crystalline solids; therefore, decoupling the respective roles of long-range periodicity and high density has been challenging. Here we report the observation of high-harmonic generation from amorphous fused silica. We also decouple the role of long-range periodicity by comparingmore » harmonics generated from fused silica and crystalline quartz, which contain the same atomic constituents but differ in long-range periodicity. These results advance current understanding of the strong-field processes leading to high-harmonic generation in solids with implications for the development of robust and compact extreme ultraviolet light sources.« less

Avalanches in Strained Amorphous Solids: Does Inertia Destroy Critical Behavior?

NASA Astrophysics Data System (ADS)

Salerno, K. Michael; Maloney, Craig E.; Robbins, Mark O.

2012-09-01

Simulations are used to determine the effect of inertia on athermal shear of amorphous two-dimensional solids. In the quasistatic limit, shear occurs through a series of rapid avalanches. The distribution of avalanches is analyzed using finite-size scaling with thousands to millions of disks. Inertia takes the system to a new underdamped universality class rather than driving the system away from criticality as previously thought. Scaling exponents are determined for the underdamped and overdamped limits and a critical damping that separates the two regimes. Systems are in the overdamped universality class even when most vibrational modes are underdamped.

On the structure of amorphous calcium carbonate--a detailed study by solid-state NMR spectroscopy.

PubMed

Nebel, Holger; Neumann, Markus; Mayer, Christian; Epple, Matthias

2008-09-01

The calcium carbonate phases calcite, aragonite, vaterite, monohydrocalcite (calcium carbonate monohydrate), and ikaite (calcium carbonate hexahydrate) were studied by solid-state NMR spectroscopy ( (1)H and (13)C). Further model compounds were sodium hydrogencarbonate, potassium hydrogencarbonate, and calcium hydroxide. With the help of these data, the structure of synthetically prepared additive-free amorphous calcium carbonate (ACC) was analyzed. ACC contains molecular water (as H 2O), a small amount of mobile hydroxide, and no hydrogencarbonate. This supports the concept of ACC as a transient precursor in the formation of calcium carbonate biominerals.

Preferred orientations of laterally grown silicon films over amorphous substrates using the vapor-liquid-solid technique

NASA Astrophysics Data System (ADS)

LeBoeuf, J. L.; Brodusch, N.; Gauvin, R.; Quitoriano, N. J.

2014-12-01

A novel method has been optimized so that adhesion layers are no longer needed to reliably deposit patterned gold structures on amorphous substrates. Using this technique allows for the fabrication of amorphous oxide templates known as micro-crucibles, which confine a vapor-liquid-solid (VLS) catalyst of nominally pure gold to a specific geometry. Within these confined templates of amorphous materials, faceted silicon crystals have been grown laterally. The novel deposition technique, which enables the nominally pure gold catalyst, involves the undercutting of an initial chromium adhesion layer. Using electron backscatter diffraction it was found that silicon nucleated in these micro-crucibles were 30% single crystals, 45% potentially twinned crystals and 25% polycrystals for the experimental conditions used. Single, potentially twinned, and polycrystals all had an aversion to growth with the {1 0 0} surface parallel to the amorphous substrate. Closer analysis of grain boundaries of potentially twinned and polycrystalline samples revealed that the overwhelming majority of them were of the 60° Σ3 coherent twin boundary type. The large amount of coherent twin boundaries present in the grown, two-dimensional silicon crystals suggest that lateral VLS growth occurs very close to thermodynamic equilibrium. It is suggested that free energy fluctuations during growth or cooling, and impurities were the causes for this twinning.

Crystallization Kinetics of an Amorphous Pharmaceutical Compound Using Fluorescence-Lifetime-Imaging Microscopy.

PubMed

Rautaniemi, Kaisa; Vuorimaa-Laukkanen, Elina; Strachan, Clare J; Laaksonen, Timo

2018-05-07

Pharmaceutical scientists are increasingly interested in amorphous drug formulations especially because of their higher dissolution rates. Consequently, the thorough characterization and analysis of these formulations are becoming more and more important for the pharmaceutical industry. Here, fluorescence-lifetime-imaging microscopy (FLIM) was used to monitor the crystallization of an amorphous pharmaceutical compound, indomethacin. Initially, we identified different solid indomethacin forms, amorphous and γ- and α-crystalline, on the basis of their time-resolved fluorescence. All of the studied indomethacin forms showed biexponential decays with characteristic fluorescence lifetimes and amplitudes. Using this information, the crystallization of amorphous indomethacin upon storage in 60 °C was monitored for 10 days with FLIM. The progress of crystallization was detected as lifetime changes both in the FLIM images and in the fluorescence-decay curves extracted from the images. The fluorescence-lifetime amplitudes were used for quantitative analysis of the crystallization process. We also demonstrated that the fluorescence-lifetime distribution of the sample changed during crystallization, and when the sample was not moved between measuring times, the lifetime distribution could also be used for the analysis of the reaction kinetics. Our results clearly show that FLIM is a sensitive and nondestructive method for monitoring solid-state transformations on the surfaces of fluorescent samples.

Anomalous Elasticity of 4He Films at the Quantum Phase Transition

NASA Astrophysics Data System (ADS)

Shirahama, Keiya; Takahashi, Daisuke; Kogure, Takayuki; Yoshimura, Hitomi; Higashino, Rama

4 He films on solid substrates exhibit a quantum phase transition between localized (nonsuperfluid) and superfluid states by changing coverage n. We have made torsional oscillator (TO) studies for 4He films adsorbed on nanoporous glasses. A TO with localized films showed an apparent ''supersolid'' behavior, an increase in TO frequency f with broad peak in Q-1. Combining with FEM analyses for TO's with different designs, we conclude that the behavior results from the softening of adsorbed 4He films at high temperatures. The features in f and Q-1 are fitted well to a Debye-like activation with a distributed energy gap Δ, so the elasticity is accounted by thermal excitation of localized atoms to an ''extended'' state. As the critical coverage nc approaches the gap decreases to zero with a powerlaw Δ ~(n -nc) 1 . 2 . Assuming that the 4He chemical potential μ (n) is located in the middle of the gap, we can estimate the elastic constant κ-1 =n2 ∂μ / ∂n . The elasticity agrees with shear moduli of 4He films obtained from the FEM analysis within factor of three. The energetics proposed from the elastic behavior naturally explains other properties of He films adsorbed on disordered substrates.

An IR investigation of solid amorphous ethanol - Spectra, properties, and phase changes

NASA Astrophysics Data System (ADS)

Hudson, Reggie L.

2017-12-01

Mid- and far-infrared spectra of condensed ethanol (CH3CH2OH) at 10-160 K are presented, with a special focus on amorphous ethanol, the form of greatest astrochemical interest, and with special attention given to changes at 155-160 K. Infrared spectra of amorphous and crystalline forms are shown. The refractive index at 670 nm of amorphous ethanol at 16 K is reported, along with three IR band strengths and a density. A comparison is made to recent work on the isoelectronic compound ethanethiol (CH3CH2SH), and several astrochemical applications are suggested for future study.

An IR Investigation of Solid Amorphous Ethanol-Spectra, Properties, and Phase Changes

NASA Technical Reports Server (NTRS)

Hudson, Reggie L.

2017-01-01

Mid- and far-infrared spectra of condensed ethanol (CH3CH2OH) at 10-160 K are presented, with a special focus on amorphous ethanol, the form of greatest astrochemical interest, and with special attention given to changes at 155-160 K. Infrared spectra of amorphous and crystalline forms are shown. The refractive index at 670 nm of amorphous ethanol at 16 K is reported, along with three IR band strengths and a density. A comparison is made to recent work on the isoelectronic compound ethanethiol (CH3CH2SH), and several astrochemical applications are suggested for future study.

An approach to tune the amplitude of surface ripple patterns

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Tanuj; Kanjilal, D.; Kumar, Ashish

An approach is presented to tune the amplitude of ripple patterns using ion beam. By varying the depth location of amorphous/crystalline interface, ripple patterns of different amplitude with similar wavelength were grown on the surface of Si (100) using 50 keV Ar{sup +} beam irradiation. Atomic force microscopy study demonstrates the tuning of amplitude of ripples patterns for wide range. Rutherford backscattering channeling measurement was performed to measure the depth location of amorphous/crystalline interface. It is postulated that the ion beam stimulated solid flow inside the amorphous layer controls the wavelength, whereas mass rearrangement at amorphous/crystalline interface controls the amplitude.

Crystallization of amorphous solid dispersions of resveratrol during preparation and storage-Impact of different polymers.

PubMed

Wegiel, Lindsay A; Mauer, Lisa J; Edgar, Kevin J; Taylor, Lynne S

2013-01-01

The objective of this study was to investigate intermolecular interactions between resveratrol and polymers in amorphous blends and to study the potential correlations between compound-polymer interactions, manufacturability, and stability of the amorphous system to crystallization during storage. Polymers included two grades of poly (vinylpyrrolidone) (PVP), Eudragit E100 (E100), hydroxypropyl methylcellulose (HPMC), hydroxypropyl methylcellulose acetate succinate (HPMCAS), carboxymethyl cellulose acetate butyrate, and poly (acrylic acid) (PAA). Amorphous blends ("solid dispersions") were prepared by dissolving both resveratrol and polymer in a solvent followed by rotary evaporation. Crystallinity was evaluated using X-ray powder diffraction and was studied as a function of time. Mid-infrared (IR) spectroscopy was used to investigate resveratrol-polymer interactions. Polymer influence on the crystallization behavior of resveratrol varied and could be correlated to the polymer structure, whereby polymers with good hydrogen bond acceptor groups performed better as crystallization inhibitors. Resveratrol-polymer hydrogen bonding interactions could be inferred from the IR spectra. Somewhat surprisingly, E100 and resveratrol showed evidence of an acid-base reaction, in addition to intermolecular hydrogen bonding interactions. PVP K29/32 appeared to form stronger hydrogen bond interactions with resveratrol relative to HPMC, HPMCAS, and PAA, consistent with acceptor group chemistry. Long-term stability of the systems against crystallization suggested that stability is linked to the type and strength of intermolecular interactions present. whereby resveratrol blended with E100 and PVP K29/32 showed the greatest stability to crystallization. In conclusion, amorphous resveratrol is unstable and difficult to form, requiring the assistance of a polymeric crystallization inhibitor to facilitate the formation of an amorphous solid dispersion. Polymers effective at inhibiting crystallization were identified, and it is rationalized that their effectiveness is based on the type and strength of their intermolecular interactions with resveratrol. Copyright © 2012 Wiley Periodicals, Inc.

11% efficiency solid-state dye-sensitized solar cells with copper(II/I) hole transport materials

PubMed Central

Cao, Yiming; Saygili, Yasemin; Ummadisingu, Amita; Teuscher, Joël; Luo, Jingshan; Pellet, Norman; Giordano, Fabrizio; Zakeeruddin, Shaik Mohammed; Moser, Jacques -E.; Freitag, Marina; Hagfeldt, Anders; Grätzel, Michael

2017-01-01

Solid-state dye-sensitized solar cells currently suffer from issues such as inadequate nanopore filling, low conductivity and crystallization of hole-transport materials infiltrated in the mesoscopic TiO2 scaffolds, leading to low performances. Here we report a record 11% stable solid-state dye-sensitized solar cell under standard air mass 1.5 global using a hole-transport material composed of a blend of [Cu (4,4′,6,6′-tetramethyl-2,2′-bipyridine)2](bis(trifluoromethylsulfonyl)imide)2 and [Cu (4,4′,6,6′-tetramethyl-2,2′-bipyridine)2](bis(trifluoromethylsulfonyl)imide). The amorphous Cu(II/I) conductors that conduct holes by rapid hopping infiltrated in a 6.5 μm-thick mesoscopic TiO2 scaffold are crucial for achieving such high efficiency. Using time-resolved laser photolysis, we determine the time constants for electron injection from the photoexcited sensitizers Y123 into the TiO2 and regeneration of the Y123 by Cu(I) to be 25 ps and 3.2 μs, respectively. Our work will foster the development of low-cost solid-state photovoltaic based on transition metal complexes as hole conductors. PMID:28598436

The significance of the amorphous potential energy landscape for dictating glassy dynamics and driving solid-state crystallisation.

PubMed

Ruggiero, Michael T; Krynski, Marcin; Kissi, Eric Ofosu; Sibik, Juraj; Markl, Daniel; Tan, Nicholas Y; Arslanov, Denis; van der Zande, Wim; Redlich, Britta; Korter, Timothy M; Grohganz, Holger; Löbmann, Korbinian; Rades, Thomas; Elliott, Stephen R; Zeitler, J Axel

2017-11-15

The fundamental origins surrounding the dynamics of disordered solids near their characteristic glass transitions continue to be fiercely debated, even though a vast number of materials can form amorphous solids, including small-molecule organic, inorganic, covalent, metallic, and even large biological systems. The glass-transition temperature, T g , can be readily detected by a diverse set of techniques, but given that these measurement modalities probe vastly different processes, there has been significant debate regarding the question of why T g can be detected across all of them. Here we show clear experimental and computational evidence in support of a theory that proposes that the shape and structure of the potential-energy surface (PES) is the fundamental factor underlying the glass-transition processes, regardless of the frequency that experimental methods probe. Whilst this has been proposed previously, we demonstrate, using ab initio molecular-dynamics (AIMD) simulations, that it is of critical importance to carefully consider the complete PES - both the intra-molecular and inter-molecular features - in order to fully understand the entire range of atomic-dynamical processes in disordered solids. Finally, we show that it is possible to utilise this dependence to directly manipulate and harness amorphous dynamics in order to control the behaviour of such solids by using high-powered terahertz pulses to induce crystallisation and preferential crystal-polymorph growth in glasses. Combined, these findings provide compelling evidence that the PES landscape, and the corresponding energy barriers, are the ultimate controlling feature behind the atomic and molecular dynamics of disordered solids, regardless of the frequency at which they occur.

Evaluate the ability of PVP to inhibit crystallization of amorphous solid dispersions by density functional theory and experimental verify.

PubMed

Wang, Bing; Wang, Dandan; Zhao, Shan; Huang, Xiaobin; Zhang, Jianbin; Lv, Yan; Liu, Xiaocen; Lv, Guojun; Ma, Xiaojun

2017-01-01

In this study, we used density functional theory (DFT) to predict polymer-drug interactions, and then evaluated the ability of poly (vinyl pyrrolidone) (PVP) to inhibit crystallization of amorphous solid dispersions by experimental-verification. Solid dispersions of PVP/resveratrol (Res) and PVP/griseofulvin (Gri) were adopted for evaluating the ability of PVP to inhibit crystallization. The density functional theory (DFT) with the B3LYP was used to calculate polymer-drug and drug-drug interactions. Fourier transform infrared spectroscopy (FTIR) was used to confirm hydrogen bonding interactions. Polymer-drug miscibility and drug crystallinity were characterized by the modulated differential scanning calorimetry (MDSC) and X-ray powder diffraction (XRD). The release profiles were studied to investigate the dissolution advantage. DFT results indicated that E PVP-Res >E Res-Res (E: represents hydrogen bonding energy). A strong interaction was formed between PVP and Res. In addition, Fourier transform infrared spectroscopy (FTIR) analysis showed hydrogen bonding formed between PVP and Res, but not between PVP and Gri. MDSC and XRD results suggested that 70-90wt% PVP/Res and PVP/Gri solid dispersions formed amorphous solid dispersions (ASDs). Under the accelerated testing condition, PVP/Res dispersions with higher miscibility quantified as 90/10wt% were more stable than PVP/Gri dispersions. The cumulative dissolution rate of 90wt% PVP/Res dispersions still kept high after 90days storage due to the strong interaction. However, the cumulative dissolution rate of PVP/Gri solid dispersions significantly dropped because of the recrystallization of Gri. Copyright © 2016 Elsevier B.V. All rights reserved.

Local structure of ion pair interaction in lapatinib amorphous dispersions characterized by synchrotron x-ray diffraction and pair distribution function analysis

DOE PAGES

de Araujo, Gabriel L. B.; Benmore, Chris J.; Byrn, Stephen R.

2017-04-11

For many years, the idea of analyzing atom-atom contacts in amorphous drug-polymer systems has been of major interest, because this method has always had the potential to differentiate between amorphous systems with domains and amorphous systems which are molecular mixtures. In this study, local structure of ionic and noninonic interactions were studied by High-Energy X-ray Diffraction and Pair Distribution Function (PDF) analysis in amorphous solid dispersions of lapatinib in hypromellose phthalate (HPMCP) and hypromellose (HPMC-E3). The strategy of extracting lapatinib intermolecular drug interactions from the total PDF x-ray pattern was successfully applied allowing the detection of distinct nearest neighbor contactsmore » for the HPMC-E3 rich preparations showing that lapatinib molecules do not cluster in the same way as observed in HPMC-P, where ionic interactions are present. Orientational correlations up to nearest neighbor molecules at about 4.3 Å were observed for polymer rich samples; both observations showed strong correlation to the stability of the systems. Lasty, the superior physical stability of 1:3 LP:HPMCP was consistent with the absence of significant intermolecular interactions in (ΔD inter LP(r)) in the range of 3.0 to 6.0 Å, which are attributed to C-C, C-N and C-O nearest neighbor contacts present in drug-drug interactions.« less

Local structure of ion pair interaction in lapatinib amorphous dispersions characterized by synchrotron x-ray diffraction and pair distribution function analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

de Araujo, Gabriel L. B.; Benmore, Chris J.; Byrn, Stephen R.

For many years, the idea of analyzing atom-atom contacts in amorphous drug-polymer systems has been of major interest, because this method has always had the potential to differentiate between amorphous systems with domains and amorphous systems which are molecular mixtures. In this study, local structure of ionic and noninonic interactions were studied by High-Energy X-ray Diffraction and Pair Distribution Function (PDF) analysis in amorphous solid dispersions of lapatinib in hypromellose phthalate (HPMCP) and hypromellose (HPMC-E3). The strategy of extracting lapatinib intermolecular drug interactions from the total PDF x-ray pattern was successfully applied allowing the detection of distinct nearest neighbor contactsmore » for the HPMC-E3 rich preparations showing that lapatinib molecules do not cluster in the same way as observed in HPMC-P, where ionic interactions are present. Orientational correlations up to nearest neighbor molecules at about 4.3 Å were observed for polymer rich samples; both observations showed strong correlation to the stability of the systems. Lasty, the superior physical stability of 1:3 LP:HPMCP was consistent with the absence of significant intermolecular interactions in (ΔD inter LP(r)) in the range of 3.0 to 6.0 Å, which are attributed to C-C, C-N and C-O nearest neighbor contacts present in drug-drug interactions.« less

Local Structure of Ion Pair Interaction in Lapatinib Amorphous Dispersions characterized by Synchrotron X-Ray diffraction and Pair Distribution Function Analysis

NASA Astrophysics Data System (ADS)

de Araujo, Gabriel L. B.; Benmore, Chris J.; Byrn, Stephen R.

2017-04-01

For many years, the idea of analyzing atom-atom contacts in amorphous drug-polymer systems has been of major interest, because this method has always had the potential to differentiate between amorphous systems with domains and amorphous systems which are molecular mixtures. In this study, local structure of ionic and noninonic interactions were studied by High-Energy X-ray Diffraction and Pair Distribution Function (PDF) analysis in amorphous solid dispersions of lapatinib in hypromellose phthalate (HPMCP) and hypromellose (HPMC-E3). The strategy of extracting lapatinib intermolecular drug interactions from the total PDF x-ray pattern was successfully applied allowing the detection of distinct nearest neighbor contacts for the HPMC-E3 rich preparations showing that lapatinib molecules do not cluster in the same way as observed in HPMC-P, where ionic interactions are present. Orientational correlations up to nearest neighbor molecules at about 4.3 Å were observed for polymer rich samples; both observations showed strong correlation to the stability of the systems. Finally, the superior physical stability of 1:3 LP:HPMCP was consistent with the absence of significant intermolecular interactions in (Δ) in the range of 3.0 to 6.0 Å, which are attributed to C-C, C-N and C-O nearest neighbor contacts present in drug-drug interactions.

Mineralogical and geochemical characterization of arsenic in an abandoned mine tailings of Korea.

PubMed

Ahn, Joo Sung; Park, Young Seog; Kim, Ju-Yong; Kim, Kyoung-Woong

2005-04-01

The mineralogical and chemical characteristics of As solid phases in arsenic-rich mine tailings from the Nakdong As-Bi mine in Korea was investigated. The tailings generated from the ore roasting process contained 4.36% of As whereas the concentration was up to 20.2% in some tailings from the cyanidation process for the Au extraction. Thin indurated layers and other secondary precipitates had formed at the surfaces of the tailings piles and the As contents of the hardened layers varied from 2.87 to 16.0%. Scorodite and iron arsenate (Fe3AsO7) were the primary As-bearing crystalline minerals. Others such as arsenolamprite, bernardite and titanium oxide arsenate were also found. The amorphous As-Fe phases often showed framboidal aggregates and gel type textures with desiccation cracks. Sequential extraction results also showed that 55.7-91.1% of the As in tailings were NH(4)-oxalate extractable As, further confirmed the predominance of amorphous As-Fe solid phases. When the tailings were equilibrated with de-ionized water, the solution exhibited extremely acidic conditions (pH 2.01-3.10) and high concentrations of dissolved As (up to 29.5 mg L(-1)), indicating high potentials for As to be released during rainfall events. The downstream water was affected by drainage from tailings and contained 12.7-522 microg L(-1) of As. The amorphous As-Fe phases in tailings have not entirely been stabilized through the long term natural weathering processes. To remediate the environmental harms they had caused, anthropogenic interventions to stabilize or immobilize As in the tailings pile should be explored.

Formation of ultrathin Ni germanides: solid-phase reaction, morphology and texture

NASA Astrophysics Data System (ADS)

van Stiphout, K.; Geenen, F. A.; De Schutter, B.; Santos, N. M.; Miranda, S. M. C.; Joly, V.; Detavernier, C.; Pereira, L. M. C.; Temst, K.; Vantomme, A.

2017-11-01

The solid-phase reaction of ultrathin (⩽10 nm) Ni films with different Ge substrates (single-crystalline (1 0 0), polycrystalline, and amorphous) was studied. As thickness goes down, thin film texture becomes a dominant factor in both the film’s phase formation and morphological evolution. As a consequence, certain metastable microstructures are epitaxially stabilized on crystalline substrates, such as the ɛ-Ni5Ge3 phase or a strained NiGe crystal structure on the single-crystalline substrates. Similarly, the destabilizing effect of axiotaxial texture on the film’s morphology becomes more pronounced as film thicknesses become smaller. These effects are contrasted by the evolution of germanide films on amorphous substrates, on which neither epitaxy nor axiotaxy can form, i.e. none of the (de)stabilizing effects of texture are observed. The crystallization of such amorphous substrates however, drives the film breakup.

Effect of particle size of drug on conversion of crystals to an amorphous state in a solid dispersion with crospovidone.

PubMed

Sugamura, Yuka; Fujii, Makiko; Nakanishi, Sayaka; Suzuki, Ayako; Shibata, Yusuke; Koizumi, Naoya; Watanabe, Yoshiteru

2011-01-01

The effect of particle size on amorphization of drugs in a solid dispersion (SD) was investigated for two drugs, indomethacin (IM) and nifedipine (NP). The SD of drugs were prepared in a mixture with crospovidone by a variety of mechanical methods, and their properties investigated by particle sizing, thermal analysis, and powder X-ray diffraction. IM, which had an initial particle size of 1 µm and tends to aggregate, was forced through a sieve to break up the particles. NP, which had a large initial particle size, was jet-milled. In both cases, reduction of the particle size of the drugs enabled transition to an amorphous state below the melting point of the drug. The reduction in particle size is considered to enable increased contact between the crospovidone and drug particles, increasing interactions between the two compounds. © 2011 Pharmaceutical Society of Japan

Reversibility and criticality in amorphous solids

DOE PAGES

Regev, Ido; Weber, John; Reichhardt, Charles; ...

2015-11-13

The physical processes governing the onset of yield, where a material changes its shape permanently under external deformation, are not yet understood for amorphous solids that are intrinsically disordered. Here, using molecular dynamics simulations and mean-field theory, we show that at a critical strain amplitude the sizes of clusters of atoms undergoing cooperative rearrangements of displacements (avalanches) diverges. We compare this non-equilibrium critical behaviour to the prevailing concept of a ‘front depinning’ transition that has been used to describe steady-state avalanche behaviour in different materials. We explain why a depinning-like process can result in a transition from periodic to chaoticmore » behaviour and why chaotic motion is not possible in pinned systems. As a result, these findings suggest that, at least for highly jammed amorphous systems, the irreversibility transition may be a side effect of depinning that occurs in systems where the disorder is not quenched.« less

WKB calculation of multiple spin exchange in monolayer solid 3He

NASA Astrophysics Data System (ADS)

Ashizawa, Hisayuki; Hirashima, D. S.

2000-10-01

An insight is given into the multiple spin exchange in the registered 3×3 phase of solid 3He adsorbed on graphite with a WKB calculation taking account of the corrugation of the substrate potential. The corrugation is essential for this phase to be realized, and is found to suppress the exchange processes of many (>=4) particles to make only the two- and the three-spin exchanges relevant. When the magnitude of the corrugation is modest, the exchange can be ferromagnetic, in agreement with the experiment by Ikegami et al. [Phys. Rev. Lett. 81, 2478 (1998)]. Validity and limitation of the WKB approximation are also discussed.

The effect of processing on the surface physical stability of amorphous solid dispersions.

PubMed

Yang, Ziyi; Nollenberger, Kathrin; Albers, Jessica; Moffat, Jonathan; Craig, Duncan; Qi, Sheng

2014-11-01

The focus of this study was to investigate the effect of processing on the surface crystallization of amorphous molecular dispersions and gain insight into the mechanisms underpinning this effect. The model systems, amorphous molecular dispersions of felodipine-EUDRAGIT® E PO, were processed both using spin coating (an ultra-fast solvent evaporation based method) and hot melt extrusion (HME) (a melting based method). Amorphous solid dispersions with drug loadings of 10-90% (w/w) were obtained by both processing methods. Samples were stored under 75% RH/room temperatures for up to 10months. Surface crystallization was observed shortly after preparation for the HME samples with high drug loadings (50-90%). Surface crystallization was characterized by powder X-ray diffraction (PXRD), ATR-FTIR spectroscopy and imaging techniques (SEM, AFM and localized thermal analysis). Spin coated molecular dispersions showed significantly higher surface physical stability than hot melt extruded samples. For both systems, the progress of the surface crystal growth followed zero order kinetics on aging. Drug enrichment at the surfaces of HME samples on aging was observed, which may contribute to surface crystallization of amorphous molecular dispersions. In conclusion it was found the amorphous molecular dispersions prepared by spin coating had a significantly higher surface physical stability than the corresponding HME samples, which may be attributed to the increased process-related apparent drug-polymer solubility and reduced molecular mobility due to the quenching effect caused by the rapid solvent evaporation in spin coating. Copyright © 2014 Elsevier B.V. All rights reserved.

On the determination of the glass forming ability of AlxZr1-x alloys using molecular dynamics, Monte Carlo simulations, and classical thermodynamics

NASA Astrophysics Data System (ADS)

Harvey, Jean-Philippe; Gheribi, Aïmen E.; Chartrand, Patrice

2012-10-01

In this work, the glass forming ability of Al-Zr alloys is quantified using Monte Carlo (MC) and molecular dynamic (MD) simulations as well as classical thermodynamic calculations. The total energy of each studied structure of the Al-Zr system is described using the modified embedded atom model in the second-nearest-neighbour formalism. The parameterized Al-Zr cross potential which has been extensively validated using available experimental and ab initio data for several solid structures and for the liquid phase is used to evaluate thermodynamic, structural, and physical properties of the glass state and of the fully disordered (FD) face-centered cubic (FCC) solid solution with no short range order (SRO). The local environment of the Al-Zr amorphous phase is identified to be similar to that of a FCC solid structure with short range chemical order. A new approach to model the Gibbs energy of the amorphous phase based on the cluster variation method in the tetrahedron approximation is presented. The Gibbs energy of the fully disordered FCC solid solution with no short range order is determined and compared to the Gibbs energy of the amorphous phase. According to our volumetric and energetic criteria defined in our work to evaluate the possible formation of a glass structure at room temperature and zero pressure, a glass forming range of (0.25≤XZr≤0.75) and of (0.21≤XZr≤0.75) are identified, respectively. All the available quantitative experimental data regarding the amorphization of Al-Zr alloys are compared to the prediction of our MD/MC simulations throughout this study.

Molecular Dynamical Simulation of Thermal Conductivity in Amorphous Structures

NASA Astrophysics Data System (ADS)

Deangelis, Freddy; Henry, Asegun

While current descriptions of thermal transport exists for well-ordered materials such as crystal latices, new methods are needed to describe thermal transport in disordered materials, including amorphous solids. Because such structures lack periodic, long-range order, a group velocity cannot be defined for thermal modes of vibration; thus, the phonon gas model cannot be applied to these structures. Instead, a new framework must be applied to analyze such materials. Using a combination of density functional theory and molecular dynamics, we have analyzed thermal transport in amorphous structures, chiefly amorphous germanium. The analysis allows us to categorize vibrational modes as propagons, diffusons, or locons, and to determine how they contribute to thermal conductivity within amorphous structures. This method is also being extended to other disordered structures such as amorphous polymers. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1148903.

Picosecond amorphization of SiO2 stishovite under tension

PubMed Central

Misawa, Masaaki; Ryuo, Emina; Yoshida, Kimiko; Kalia, Rajiv K.; Nakano, Aiichiro; Nishiyama, Norimasa; Shimojo, Fuyuki; Vashishta, Priya; Wakai, Fumihiro

2017-01-01

It is extremely difficult to realize two conflicting properties—high hardness and toughness—in one material. Nano-polycrystalline stishovite, recently synthesized from Earth-abundant silica glass, proved to be a super-hard, ultra-tough material, which could provide sustainable supply of high-performance ceramics. Our quantum molecular dynamics simulations show that stishovite amorphizes rapidly on the order of picosecond under tension in front of a crack tip. We find a displacive amorphization mechanism that only involves short-distance collective motions of atoms, thereby facilitating the rapid transformation. The two-step amorphization pathway involves an intermediate state akin to experimentally suggested “high-density glass polymorphs” before eventually transforming to normal glass. The rapid amorphization can catch up with, screen, and self-heal a fast-moving crack. This new concept of fast amorphization toughening likely operates in other pressure-synthesized hard solids. PMID:28508056

In Vivo Monitoring of pH, Redox Status, and Glutathione Using L-Band EPR for Assessment of Therapeutic Effectiveness in Solid Tumors

PubMed Central

Bobko, Andrey A.; Eubank, Timothy D.; Voorhees, Jeffrey L.; Efimova, Olga V.; Kirilyuk, Igor A.; Petryakov, Sergey; Trofimiov, Dmitrii G.; Marsh, Clay B.; Zweier, Jay L.; Grigor’ev, Igor A.; Samouilov, Alexandre; Khramtsov, Valery V.

2011-01-01

Approach for in vivo real-time assessment of tumor tissue extracellular pH (pHe), redox, and intracellular glutathione based on L-band EPR spectroscopy using dual function pH and redox nitroxide probe and disulfide nitroxide biradical, is described. These parameters were monitored in PyMT mice bearing breast cancer tumors during treatment with granulocyte macrophage colony-stimulating factor. It was observed that tumor pHe is about 0.4 pH units lower than that in normal mammary gland tissue. Treatment with granulocyte macrophage colony-stimulating factor decreased the value of pHe by 0.3 units compared with PBS control treatment. Tumor tissue reducing capacity and intracellular glutathione were elevated compared with normal mammary gland tissue. Granulocyte macrophage colony-stimulating factor treatment resulted in a decrease of the tumor tissue reducing capacity and intracellular glutathione content. In addition to spectroscopic studies, pHe mapping was performed using recently proposed variable frequency proton–electron double-resonance imaging. The pH mapping superimposed with MRI image supports probe localization in mammary gland/tumor tissue, shows high heterogeneity of tumor tissue pHe and a difference of about 0.4 pH units between average pHe values in tumor and normal mammary gland. In summary, the developed multifunctional approach allows for in vivo, noninvasive pHe, extracellular redox, and intracellular glutathione content monitoring during investigation of various therapeutic strategies for solid tumors. Magn Reson Med 000:000–000, 2011. PMID:22113626

Thermochemistry of amorphous and crystalline zirconium and hafnium silicates.

NASA Astrophysics Data System (ADS)

Ushakov, S.; Brown, C. E.; Navrotsky, Alexandra; Boatner, L. A.; Demkov, A. A.; Wang, C.; Nguyen, B.-Y.

2003-03-01

Calorimetric investigation of amorphous and crystalline zirconium and hafnium silicates was performed as part of a research program on thermochemistry of alternative gate dielectrics. Amorphous hafnium and zirconium silicates with varying SiO2 content were synthesized by a sol-gel process. Crystalline zirconium and hafnium silicates (zircon and hafnon) were synthesized by solid state reaction at 1450 °C from amorphous gels and grown as single crystals from flux. High temperature oxide melt solution calorimetry in lead borate (2PbO.B2O3) solvent at 800 oC was used to measure drop solution enthalpies for amorphous and crystalline zirconium and hafnium silicates and corresponding oxides. Applying appropriate thermochemical cycles, formation enthalpy of crystalline ZrSiO4 (zircon) from binary oxides (baddeleite and quartz) at 298 K was calculated as -23 +/-2 kJ/mol and enthalpy difference between amorphous and crystalline zirconium silicate (vitrification enthalpy) was found to be 61 +/-3 kJ/mol. Crystallization onset temperatures of amorphous zirconium and hafnium silicates, as measured by differential scanning calorimetry (DSC), increased with silica content. The resulting crystalline phases, as characterized by X-ray diffraction (XRD), were tetragonal HfO2 and ZrO2. Critical crystallite size for tetragonal to monoclinic transformation of HfO2 in the gel was estimated as 6 +/-2 nm from XRD data Crystallization enthalpies per mole of hafnia and zirconia in gels decrease slightly together with crystallite size with increasing silica content, for example from -22 to -15 +/-1 kJ per mol of HfO2 crystallized at 740 and 1006 °C from silicates with 10 and 70 mol Applications of thermal analyses and solution calorimetry techniques together with first-principles density functional calculations to estimate interface and surface energies are discussed.

Thon rings from amorphous ice and implications of beam-induced Brownian motion in single particle electron cryo-microscopy.

PubMed

McMullan, G; Vinothkumar, K R; Henderson, R

2015-11-01

We have recorded dose-fractionated electron cryo-microscope images of thin films of pure flash-frozen amorphous ice and pre-irradiated amorphous carbon on a Falcon II direct electron detector using 300 keV electrons. We observe Thon rings [1] in both the power spectrum of the summed frames and the sum of power spectra from the individual frames. The Thon rings from amorphous carbon images are always more visible in the power spectrum of the summed frames whereas those of amorphous ice are more visible in the sum of power spectra from the individual frames. This difference indicates that while pre-irradiated carbon behaves like a solid during the exposure, amorphous ice behaves like a fluid with the individual water molecules undergoing beam-induced motion. Using the measured variation in the power spectra amplitude with number of electrons per image we deduce that water molecules are randomly displaced by a mean squared distance of ∼1.1 Å(2) for every incident 300 keV e(-)/Å(2). The induced motion leads to an optimal exposure with 300 keV electrons of 4.0 e(-)/Å(2) per image with which to observe Thon rings centred around the strong 3.7 Å scattering peak from amorphous ice. The beam-induced movement of the water molecules generates pseudo-Brownian motion of embedded macromolecules. The resulting blurring of single particle images contributes an additional term, on top of that from radiation damage, to the minimum achievable B-factor for macromolecular structure determination. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

In situ observation of shear-driven amorphization in silicon crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Yang; Zhong, Li; Fan, Feifei

Amorphous materials have attracted great interest in the scientific and technological fields. An amorphous solid usually forms under the externally driven conditions of melt-quenching, irradiation and severe mechanical deformation. However, its dynamic formation process remains elusive. Here we report the in situ atomic-scale observation of dynamic amorphization processes during mechanical straining of nanoscale silicon crystals by high resolution transmission electron microscopy (HRTEM). We observe the shear-driven amorphization (SDA) occurring in a dominant shear band. The SDA involves a sequence of processes starting with the shear-induced diamond-cubic to diamond-hexagonal phase transition that is followed by dislocation nucleation and accumulation in themore » newly formed phase, leading to the formation of amorphous silicon. The SDA formation through diamond-hexagonal phase is rationalized by its structural conformity with the order in the paracrystalline amorphous silicon, which maybe widely applied to diamond-cubic materials. Besides, the activation of SDA is orientation-dependent through the competition between full dislocation nucleation and partial gliding.« less

Probing hydrogen bonding in cocrystals and amorphous dispersions using (14)N-(1)H HMQC solid-state NMR.

PubMed

Tatton, Andrew S; Pham, Tran N; Vogt, Frederick G; Iuga, Dinu; Edwards, Andrew J; Brown, Steven P

2013-03-04

Cocrystals and amorphous solid dispersions have generated interest in the pharmaceutical industry as an alternative to more established solid delivery forms. The identification of intermolecular hydrogen bonding interactions in a nicotinamide palmitic acid cocrystal and a 50% w/w acetaminophen-polyvinylpyrrolidone solid dispersion are reported using advanced solid-state magic-angle spinning (MAS) NMR methods. The application of a novel (14)N-(1)H HMQC experiment, where coherence transfer is achieved via through-space couplings, is shown to identify specific hydrogen bonding motifs. Additionally, (1)H isotropic chemical shifts and (14)N electric field gradient (EFG) parameters, both accessible from (14)N-(1)H HMQC experiments, are shown to be sensitive to changes in hydrogen bonding geometry. Numerous indicators of molecular association are accessible from this experiment, including NH cross-peaks occurring from intermolecular hydrogen bonds and changes in proton chemical shifts or electric field gradient parameters. First-principles calculations using the GIPAW approach that yield accurate estimates of isotropic chemical shifts, and EFG parameters were used to assist in assignment. It is envisaged that (14)N-(1)H HMQC solid state NMR experiments could become a valuable screening technique of solid delivery forms in the pharmaceutical industry.

Development of solid dispersion systems of dapivirine to enhance its solubility.

PubMed

Gorajana, Adinarayana; Ying, Chan Chiew; Shuang, Yeen; Fong, Pooi; Tan, Zhi; Gupta, Jyoti; Talekar, Meghna; Sharma, Manisha; Garg, Sanjay

2013-06-01

Dapivirine, formerly known as TMC 120, is a poorly-water soluble anti-HIV drug, currently being developed as a vaginal microbicide. The clinical use of this drug has been limited due to its poor solubility. The aim of this study was to design solid dispersion systems of Dapivirine to improve its solubility. Solid dispersions were prepared by solvent and fusion methods. Dapivirine release from the solid dispersion system was determined by conducting in-vitro dissolution studies. The physicochemical characteristics of the drug and its formulation were studied using Differential Scanning Calorimetry (DSC), powder X-ray Diffraction (XRD), Fourier-transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). A significant improvement in drug dissolution rate was observed with the solid dispersion systems. XRD, SEM and DSC results indicated the transformation of pure Dapivirine which exists in crystalline form into an amorphous form in selected solid dispersion formulations. FTIR and HPLC analysis confirmed the absence of drug-excipient interactions. Solid dispersion systems can be used to improve the dissolution rate of Dapivirine. This improvement could be attributed to the reduction or absence of drug crystallinity, existence of drug particles in an amorphous form and improved wettability of the drug.

Novel Molecular Architectures Developed for Improved Solid Polymer Electrolytes for Lithium Polymer Batteries

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B.; Kinder, James D.; Bennett, William R.

2002-01-01

Lithium-based polymer batteries for aerospace applications need the ability to operate in temperatures ranging from -70 to 70 C. Current state-of-the-art solid polymer electrolytes (based on amorphous polyethylene oxide, PEO) have acceptable ionic conductivities (10-4 to 10-3 S/cm) only above 60 C. Higher conductivity can be achieved in the current systems by adding solvent or plasticizers to the solid polymer to improve ion transport. However, this can compromise the dimensional and thermal stability of the electrolyte, as well as compatibility with electrode materials. One of NASA Glenn Research Center's objectives in the PERS program is to develop new electrolytes having unique molecular architectures and/or novel ion transport mechanisms, leading to good ionic conductivity at room temperature and below without solvents or plasticizers.

Fenton-treated functionalized diamond nanoparticles as gene delivery system.

PubMed

Martín, Roberto; Alvaro, Mercedes; Herance, José Raúl; García, Hermenegildo

2010-01-26

When raw diamond nanoparticles (Dnp, 7 nm average particle size) obtained from detonation are submitted to harsh Fenton-treatment, the resulting material becomes free of amorphous soot matter and the process maintains the crystallinity, reduces the particle size (4 nm average particle size), increases the surface OH population, and increases water solubility. All these changes are beneficial for subsequent Dnp covalent functionalization and for the ability of Dnp to cross cell membranes. Fenton-treated Dnps have been functionalized with thionine and the resulting sample has been observed in HeLa cell nuclei. A triethylammonium-functionalized Dnp pairs electrostatically with a plasmid having the green fluorescent protein gene and acts as gene delivery system permitting the plasmid to cross HeLa cell membrane, something that does not occur for the plasmid alone without assistance of polycationic Dnp.

Solid-phase extraction-fluorimetric high performance liquid chromatographic determination of domoic acid in natural seawater mediated by an amorphous titania sorbent.

PubMed

Chan, Ivy O M; Tsang, Vic W H; Chu, K K; Leung, S K; Lam, Michael H W; Lau, T C; Lam, Paul K S; Wu, Rudolf S S

2007-01-30

The feasibility of using sol-gel amorphous titania (TiO2) as a solid-phase sorbent for the pre-concentration of domoic acid (DA), a potent amnesic shellfish poisoning (ASP) toxin, directly from seawater was explored. The sol-gel titania material is able to adsorb DA from seawater, via the formation of ester-linkage between the carboxylic moieties of DA and the Ti-OH groups on the sorbent surface, at low pH and desorb it at high pH. The chemisorption process is not significantly interfered by the seawater matrix. The optimum pH values for the adsorption and desorption of DA were found to be pH 4 and 11, respectively. The optimal sorbent loading for the batch-type solid-phase extraction of DA was 0.67 mg-TiO2 ng-DA(-1) and adsorption equilibrium was achieved in 2 h at room temperature. The desorbed DA in 500 microL of 0.1 M alkaline borate buffer can be directly derviatized by 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) in aqueous media for fluorimetric HPLC quantification. Analyte recovery, repeatability and detection limit of this titania SPE-fluorimetric HPLC determination are 89%, 6.2% and 120 pg-DA mL(-1) (n=7, P<0.05), respectively, for a sample volume of 30 mL. This titania SPE technique should also be applicable to the pre-concentration of other polar carboxylate- and phosphonate-containing biomolecules and pharmaceuticals in complex and interfering environmental sample matrices.

Clathrate hydrate formation in amorphous cometary ice analogs in vacuo

NASA Technical Reports Server (NTRS)

Blake, David; Allamandola, Louis; Sandford, Scott; Hudgins, Doug; Freund, Friedemann

1991-01-01

Experiments conducted in clathrate hydrates with a modified electron microscope have demonstrated the possibility of such compounds' formation during the warming of vapor-deposited amorphous ices in vacuo, through rearrangements in the solid state. Subsolidus crystallization of compositionally complex amorphous ices may therefore be a general and ubiquitous process. Phase separations and microporous textures thus formed may be able to account for such anomalous cometary phenomena as the release of gas at large radial distances from the sun and the retention of volatiles to elevated temperatures.

Solid state amorphization in the Al-Fe binary system during high energy milling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urban, P., E-mail: purban@us.es; Montes, J. M.; Cintas, J.

2013-12-16

In the present study, mechanical alloying (MA) of Al75Fe25 elemental powders mixture was carried out in argon atmosphere, using a high energy attritor ball mill. The microstructure of the milled products at different stages of milling was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The results showed that the amorphous phase content increased by increasing the milling time, and after 50 hours the amorphization process became complete. Heating the samples resulted in the crystallization of the synthesized amorphous alloys and the appearance of the equilibrium intermetallic compounds Al{sub 5}Fe{submore » 2}.« less

In-line monitoring of compaction properties on a rotary tablet press during tablet manufacturing of hot-melt extruded amorphous solid dispersions.

PubMed

Grymonpré, W; Verstraete, G; Van Bockstal, P J; Van Renterghem, J; Rombouts, P; De Beer, T; Remon, J P; Vervaet, C

2017-01-30

As the number of applications for polymers in pharmaceutical development is increasing, there is need for fundamental understanding on how such compounds behave during tableting. This research is focussed on the tableting behaviour of amorphous polymers, their solid dispersions and the impact of hot-melt extrusion on the compaction properties of these materials. Soluplus, Kollidon VA 64 and Eudragit EPO were selected as amorphous polymers since these are widely studied carriers for solid dispersions, while Celecoxib was chosen as BCS class II model drug. Neat polymers and physical mixtures (up to 35% drug load) were processed by hot-melt extrusion (HME), milled and sieved to obtain powders with comparable particle sizes as the neat polymer. A novel approach was used for in-line analysis of the compaction properties on a rotary tablet press (Modul P, GEA) using complementary sensors and software (CDAAS, GEA). By combining 'in-die' and 'out-of-die' techniques, it was possible to investigate in a comprehensive way the impact of HME on the tableting behaviour of amorphous polymers and their formulations. The formation of stable glassy solutions altered the formulations towards more fragmentary behaviour under compression which was beneficial for the tabletability. Principal component analysis (PCA) was applied to summarize the behaviour during compaction of the formulations, enabling the selection of Soluplus and Kollidon VA 64 as the most favourable polymers for compaction of glassy solutions. Copyright © 2016 Elsevier B.V. All rights reserved.

Solubility and dissolution performances of spray-dried solid dispersion of Efavirenz in Soluplus.

PubMed

Lavra, Zênia Maria Maciel; Pereira de Santana, Davi; Ré, Maria Inês

2017-01-01

Efavirenz (EFV), a first-line anti-HIV drug largely used as part of antiretroviral therapies, is practically insoluble in water and belongs to BCS class II (low solubility/high permeability). The aim of this study was to improve the solubility and dissolution performances of EFV by formulating an amorphous solid dispersion of the drug in polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (Soluplus ® ) using spray-drying technique. To this purpose, spray-dried dispersions of EFV in Soluplus ® at different mass ratios (1:1.25, 1:7, 1:10) were prepared and characterized using particle size measurements, SEM, XRD, DSC, FTIR and Raman microscopy mapping. Solubility and dissolution were determined in different media. Stability was studied at accelerated conditions (40 °C/75% RH) and ambient conditions for 12 months. DSC and XRD analyses confirmed the EFV amorphous state. FTIR spectroscopy analyses revealed possible drug-polymer molecular interaction. Solubility and dissolution rate of EFV was enhanced remarkably in the developed spray-dried solid dispersions, as a function of the polymer concentration. Spray-drying was concluded to be a proper technique to formulate a physically stable dispersion of amorphous EFV in Soluplus ® , when protected from moisture.

Facile synthesis of amorphous FeOOH/MnO2 composites as screen-printed electrode materials for all-printed solid-state flexible supercapacitors

NASA Astrophysics Data System (ADS)

Lu, Qiang; Liu, Li; Yang, Shuanglei; Liu, Jun; Tian, Qingyong; Yao, Weijing; Xue, Qingwen; Li, Mengxiao; Wu, Wei

2017-09-01

More convenience and intelligence life lead by flexible/wearable electronics requires innovation and hommization of power sources. Here, amorphous FeOOH/MnO2 composite as screen-printed electrode materials for supercapacitors (SCs) is synthesized by a facile method, and solid-state flexible SCs with aesthetic design are fabricated by fully screen-printed process on different substrates, including PET, paper and textile. The amorphous FeOOH/MnO2 composite shows a high specific capacitance and a good rate capability (350.2 F g-1 at a current density of 0.5 A g-1 and 159.5 F g-1 at 20 A g-1). It also possesses 95.6% capacitance retention even after 10 000 cycles. Moreover, the all-printed solid-state flexible SC device exhibits a high area specific capacitance of 5.7 mF cm-2 and 80% capacitance retention even after 2000 cycles. It also shows high mechanical flexibility. Simultaneously, these printed SCs on different substrates in series are capable to light up a 1.9 V yellow light emitting diode (LED), even after bending and stretching.

Effect of elastic collisions and electronic excitation on lattice structure of NiTi bulk intermetallic compound irradiated with energetic ions

NASA Astrophysics Data System (ADS)

Ochi, M.; Kojima, H.; Hori, F.; Kaneno, Y.; Semboshi, S.; Saitoh, Y.; Okamoto, Y.; Ishikawa, N.; Iwase, A.

2018-07-01

NiTi bulk intermetallic compound with the B19‧ structure was irradiated with 1 MeV He, 5 MeV Al, 16 MeV Au and 200 MeV Xe ions, and the change in lattice structure near the surface by the ion bombardment was investigated by using the grazing incidence X-ray diffraction (GIXD) and the extended X-ray absorption fine structure (EXAFS). The lattice structure transformation by the irradiation strongly depends on ion species and/or energies. For the 1 MeV He irradiation, the lattice structure changed from B19‧ to the A2 structure, but did not show an amorphization even after the high fluence irradiation. For the 5 MeV Al irradiation, the samples are partially amorphized. For the 16 MeV Au irradiation, the lattice structure of the NiTi samples changed nearly completely from the B19‧ structure to the amorphous state via the A2 structure. The value of dpa (displacement per atom) which is needed for the amorphization is, however, much smaller than the case of the Al ion irradiation. For the 200 MeV Xe ion irradiation, the lattice structure completely changed to the A2 structure even by a small ion fluence. The dependence of the lattice structure transformation on elastic collisions (dpa), the spectrum of the primary knock-on (PKA) atoms and the density of energy deposited through electronic excitation was discussed.

Ginzburg-Landau theory for the solid-liquid interface of bcc elements. II - Application to the classical one-component plasma, the Wigner crystal, and He-4

NASA Technical Reports Server (NTRS)

Zeng, X. C.; Stroud, D.

1989-01-01

The previously developed Ginzburg-Landau theory for calculating the crystal-melt interfacial tension of bcc elements to treat the classical one-component plasma (OCP), the charged fermion system, and the Bose crystal. For the OCP, a direct application of the theory of Shih et al. (1987) yields for the surface tension 0.0012(Z-squared e-squared/a-cubed), where Ze is the ionic charge and a is the radius of the ionic sphere. Bose crystal-melt interface is treated by a quantum extension of the classical density-functional theory, using the Feynman formalism to estimate the relevant correlation functions. The theory is applied to the metastable He-4 solid-superfluid interface at T = 0, with a resulting surface tension of 0.085 erg/sq cm, in reasonable agreement with the value extrapolated from the measured surface tension of the bcc solid in the range 1.46-1.76 K. These results suggest that the density-functional approach is a satisfactory mean-field theory for estimating the equilibrium properties of liquid-solid interfaces, given knowledge of the uniform phases.

Prediction of Phase Behavior of Spray-Dried Amorphous Solid Dispersions: Assessment of Thermodynamic Models, Standard Screening Methods and a Novel Atomization Screening Device with Regard to Prediction Accuracy

PubMed Central

Chavez, Pierre-François; Meeus, Joke; Robin, Florent; Schubert, Martin Alexander; Somville, Pascal

2018-01-01

The evaluation of drug–polymer miscibility in the early phase of drug development is essential to ensure successful amorphous solid dispersion (ASD) manufacturing. This work investigates the comparison of thermodynamic models, conventional experimental screening methods (solvent casting, quench cooling), and a novel atomization screening device based on their ability to predict drug–polymer miscibility, solid state properties (Tg value and width), and adequate polymer selection during the development of spray-dried amorphous solid dispersions (SDASDs). Binary ASDs of four drugs and seven polymers were produced at 20:80, 40:60, 60:40, and 80:20 (w/w). Samples were systematically analyzed using modulated differential scanning calorimetry (mDSC) and X-ray powder diffraction (XRPD). Principal component analysis (PCA) was used to qualitatively assess the predictability of screening methods with regards to SDASD development. Poor correlation was found between theoretical models and experimentally-obtained results. Additionally, the limited ability of usual screening methods to predict the miscibility of SDASDs did not guarantee the appropriate selection of lead excipient for the manufacturing of robust SDASDs. Contrary to standard approaches, our novel screening device allowed the selection of optimal polymer and drug loading and established insight into the final properties and performance of SDASDs at an early stage, therefore enabling the optimization of the scaled-up late-stage development. PMID:29518936

Mechanical stresses and amorphization of ion-implanted diamond

NASA Astrophysics Data System (ADS)

Khmelnitsky, R. A.; Dravin, V. A.; Tal, A. A.; Latushko, M. I.; Khomich, A. A.; Khomich, A. V.; Trushin, A. S.; Alekseev, A. A.; Terentiev, S. A.

2013-06-01

Scanning white light interferometry and Raman spectroscopy were used to investigate the mechanical stresses and structural changes in ion-implanted natural diamonds with different impurity content. The uniform distribution of radiation defects in implanted area was obtained by the regime of multiple-energy implantation of keV He+ ions. A modification of Bosia's et al. (Nucl. Instrum. Meth. B 268 (2010) 2991) method for determining the internal stresses and the density variation in an ion-implanted diamond layer was proposed that suggests measuring, in addition to the surface swelling of a diamond plate, the radius of curvature of the plate. It is shown that, under multiple-energy implantation of He+, mechanical stresses in the implanted layer may be as high as 12 GPa. It is shown that radiation damage reaches saturation for the implantation fluence characteristic of amorphization of diamond but is appreciably lower than the graphitization threshold.

Evaluation of crystallization behavior on the surface of nifedipine solid dispersion powder using inverse gas chromatography.

PubMed

Miyanishi, Hideo; Nemoto, Takayuki; Mizuno, Masayasu; Mimura, Hisashi; Kitamura, Satoshi; Iwao, Yasunori; Noguchi, Shuji; Itai, Shigeru

2013-02-01

To investigate crystallization behavior on the surface of amorphous solid dispersion powder using inverse gas chromatography (IGC) and to predict the physical stability at temperatures below the glass transition temperature (T (g)). Amorphous solid dispersion powder was prepared by melt-quenching of a mixture of crystalline nifedipine and polyvinylpyrrolidon (PVP) K-30. IGC was conducted by injecting undecane (probe gas) and methane (reference gas) repeatedly to the solid dispersion at temperatures below T (g). Surface crystallization was evaluated by the retention volume change of undecane based on the observation that the surface of the solid dispersion with crystallized nifedipine gives an increased retention volume. On applying the retention volume change to the Hancock-Sharp equation, surface crystallization was found to follow a two-dimensional growth of nuclei mechanism. Estimation of the crystallization rates at temperatures far below T (g) using the Avrami-Erofeev equation and Arrhenius equation showed that, to maintain its quality for at least three years, the solid dispersion should be stored at -20°C (T (g) - 65°C). IGC can be used to evaluate crystallization behavior on the surface of a solid dispersion powder, and, unlike traditional techniques, can also predict the stability of the solid dispersion based on the surface crystallization behavior.

Preferred orientations of laterally grown silicon films over amorphous substrates using the vapor–liquid–solid technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

LeBoeuf, J. L., E-mail: jerome.leboeuf@mail.mcgill.ca; Brodusch, N.; Gauvin, R.

2014-12-28

A novel method has been optimized so that adhesion layers are no longer needed to reliably deposit patterned gold structures on amorphous substrates. Using this technique allows for the fabrication of amorphous oxide templates known as micro-crucibles, which confine a vapor–liquid–solid (VLS) catalyst of nominally pure gold to a specific geometry. Within these confined templates of amorphous materials, faceted silicon crystals have been grown laterally. The novel deposition technique, which enables the nominally pure gold catalyst, involves the undercutting of an initial chromium adhesion layer. Using electron backscatter diffraction it was found that silicon nucleated in these micro-crucibles were 30%more » single crystals, 45% potentially twinned crystals and 25% polycrystals for the experimental conditions used. Single, potentially twinned, and polycrystals all had an aversion to growth with the (1 0 0) surface parallel to the amorphous substrate. Closer analysis of grain boundaries of potentially twinned and polycrystalline samples revealed that the overwhelming majority of them were of the 60° Σ3 coherent twin boundary type. The large amount of coherent twin boundaries present in the grown, two-dimensional silicon crystals suggest that lateral VLS growth occurs very close to thermodynamic equilibrium. It is suggested that free energy fluctuations during growth or cooling, and impurities were the causes for this twinning.« less

Water–solid interactions in amorphous maltodextrin-crystalline sucrose binary mixtures

PubMed Central

Ghorab, Mohamed K.; Toth, Scott J.; Simpson, Garth J.; Mauer, Lisa J.; Taylor, Lynne S.

2016-01-01

Amorphous and crystalline solids are commonly found together in a variety of pharmaceutical and food products. In this study, the influence of co-formulation of amorphous maltodextrins (MDs) and crystalline sucrose (S) on moisture sorption, deliquescence, and glass transition (Tg) properties of powder blends was investigated. Individual components and binary mixtures of four different molecular weight MDs with sucrose in 1:1 w/w ratios were exposed to various relative humidity (RH) environments and their equilibrium and dynamic moisture contents were monitored. The deliquescence point (RH0) and dissolution behavior of sucrose alone and in blends was also monitored by polarized light microscopy and second harmonic generation imaging. In S:MD blends, the deliquescence RH of sucrose was lower than the RH0 of sucrose alone, and synergistic moisture sorption also occurred at RHs lower than the RH0. Intimate contact of sucrose crystals with the amorphous MDs resulted in complete dissolution of sucrose at RH < RH0. When blends were stored at conditions exceeding the Tg of the individual MDs (25 °C and 60%, 49% and 34%RH for MD21, MD29 and MD40, respectively), the Tg of the blends was lower than that of individual MDs. Thus, co-formulation of amorphous MDs with crystalline sucrose sensitizes the blend to moisture, potentially leading to deleterious changes in the formulation if storage conditions are not adequately controlled. PMID:23477494

Short-range correlations control the G/K and Poisson ratios of amorphous solids and metallic glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zaccone, Alessio; Terentjev, Eugene M.

2014-01-21

The bulk modulus of many amorphous materials, such as metallic glasses, behaves nearly in agreement with the assumption of affine deformation, namely that the atoms are displaced just by the amount prescribed by the applied strain. In contrast, the shear modulus behaves as for nonaffine deformations, with additional displacements due to the structural disorder which induce a marked material softening to shear. The consequence is an anomalously large ratio of the bulk modulus to the shear modulus for disordered materials characterized by dense atomic packing, but not for random networks with point atoms. We explain this phenomenon with a microscopicmore » derivation of the elastic moduli of amorphous solids accounting for the interplay of nonaffinity and short-range particle correlations due to excluded volume. Short-range order is responsible for a reduction of the nonaffinity which is much stronger under compression, where the geometric coupling between nonaffinity and the deformation field is strong, whilst under shear this coupling is weak. Predictions of the Poisson ratio based on this model allow us to rationalize the trends as a function of coordination and atomic packing observed with many amorphous materials.« less

Pharmaceutical solvates, hydrates and amorphous forms: A special emphasis on cocrystals.

PubMed

Healy, Anne Marie; Worku, Zelalem Ayenew; Kumar, Dinesh; Madi, Atif M

2017-08-01

Active pharmaceutical ingredients (APIs) may exist in various solid forms, which can lead to differences in the intermolecular interactions, affecting the internal energy and enthalpy, and the degree of disorder, affecting the entropy. Differences in solid forms often lead to differences in thermodynamic parameters and physicochemical properties for example solubility, dissolution rate, stability and mechanical properties of APIs and excipients. Hence, solid forms of APIs play a vital role in drug discovery and development in the context of optimization of bioavailability, filing intellectual property rights and developing suitable manufacturing methods. In this review, the fundamental characteristics and trends observed for pharmaceutical hydrates, solvates and amorphous forms are presented, with special emphasis, due to their relative abundance, on pharmaceutical hydrates with single and two-component (i.e. cocrystal) host molecules. Copyright © 2017 Elsevier B.V. All rights reserved.

Criticality in the Approach to Failure in Amorphous Solids

NASA Astrophysics Data System (ADS)

Lin, Jie; Gueudré, Thomas; Rosso, Alberto; Wyart, Matthieu

2015-10-01

Failure of amorphous solids is fundamental to various phenomena, including landslides and earthquakes. Recent experiments indicate that highly plastic regions form elongated structures that are especially apparent near the maximal shear stress Σmax where failure occurs. This observation suggested that Σmax acts as a critical point where the length scale of those structures diverges, possibly causing macroscopic transient shear bands. Here, we argue instead that the entire solid phase (Σ <Σmax) is critical, that plasticity always involves system-spanning events, and that their magnitude diverges at Σmax independently of the presence of shear bands. We relate the statistics and fractal properties of these rearrangements to an exponent θ that captures the stability of the material, which is observed to vary continuously with stress, and we confirm our predictions in elastoplastic models.

Mechanism of Formation of Li 7 P 3 S 11 Solid Electrolytes through Liquid Phase Synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yuxing; Lu, Dongping; Bowden, Mark

Crystalline Li7P3S11 is a promising solid electrolyte for all solid state lithium/lithium ion batteries. A controllable liquid phase synthesis of Li7P3S11 is more desirable compared to conventional mechanochemical synthesis, but recent attempts suffer from reduced ionic conductivities. Here we elucidate the formation mechanism of crystalline Li7P3S11 synthesized in the liquid phase (acetonitrile, or ACN). We conclude that the crystalline Li7P3S11 forms through a two-step reaction: 1) formation of solid Li3PS4∙ACN and amorphous Li2S∙P2S5 phases in the liquid phase; 2) solid-state conversion of the two phases. The implication of this two-step reaction mechanism to the morphology control and the transport propertiesmore » of liquid phase synthesized Li7P3S11 is identified and discussed.« less

On the Plasticity of Amorphous Solids

NASA Astrophysics Data System (ADS)

Lin, Jie

Mechanical behaviors of amorphous materials under external stress are central to various phenomena including earthquakes and landslides. Most amorphous materials possess a well defined yield stress when thermal fluctuations are negligible. Only when the shear stress is above the yield stress, the material can flow as a fluid, otherwise it deforms as a solid. There are accumulating evidences that the yielding transition between the flowing and solid phase is a critical phenomenon, and one evidence is the long ranged correlations of plastic strain during adiabatic shear. In spite of this, we still have not fully understood the associated critical exponents and their scaling relations. In the last decade, it has been widely accepted that the elementary rearrangements in amorphous solids are not well-defined topological defects as crystals, instead they are local irreversible rearrangements of a few particles, denoted as shear transformations. Because a single shear transformation changes the local arrangement of particles, it therefore generates an elastic stress field propagating over the whole system. The resulting changes in the local stresses in other regions of the system may in turn trigger more shear transformations. A central feature that complicates the yielding transition is the long range and anisotropic stress field generated by shear transformations. This peculiar interaction between shear transformations leads to two important characteristics: 1.the mechanical noises generated by plastic deformation are broadly distributed 2.those regions that are undergoing plastic deformation has equal probability to make other parts of the material to be more stable or more unstable, depending on the direction between them. In this thesis, we show that these two important factors leads to a singular density of shear transformations, P( x) xtheta at small x, where x is a local measure of stability, namely, the extra stress one needs to add locally to reach the elastic instabilities. We denote such a singular distribution as a pseudo gap, and the theta exponent as the pseudo gap exponent. The fact that the plastic avalanche rates, i.e., number of avalanches per unit strain, during quasi-static shear is not proportional to system size implies the existence of a finite pseudo gap exponent. Arguments based on stability against local perturbations lead to a lower bound of the pseudo gap exponents. In the flowing phase, we construct the scaling description of the yielding transition of soft amorphous solids at zero temperature. The yielding transition shares similarities with another well studied dynamic phase transition, the depinning transition where an elastic interface is driven in a disordered medium, however, there are also striking differences between them. Avalanches are fractal in the yielding transition, characterized by a fractal dimension smaller than the spatial dimension, while avalanches are compact with a fractal dimension, not smaller than the spatial dimension in the depinning transition. We make connections between the Herschel-Bulkley exponent characterizing the singularity of the flow curve near the yield stress, the extension and duration of the avalanches of plasticity, and the pseudo gap exponent. On the other hand, in the solid phase, the pseudo gap also plays a significant role as one increases the shear stress adiabatically. We point out the connection between the local slope of stress-strain curve in the transient state and mean avalanche sizes as the system approaches failure. We argue that the entire solid phase below the yield stress is critical as long as there is finite amount of plastic strain, and plasticity always involves system-spanning events because of the finite pseudo gap exponent. We use the elasto-plastic model, a mesoscopic approach, to verify our theoretical predictions and obtain satisfying results. Finally, a mean field description of plastic flow in amorphous solids are proposed and solved analytically. The mean field models captures the broad distribution of mechanical noise generated by plasticity, leading to a biased Levy flight behavior of local stresses, with the elastic instabilities as the absorbing boundary. The mean field model implies an upper critical dimension as dc = 4.

In situ studies of ion irradiated inverse spinel compound magnesium stannate (Mg 2SnO 4)

NASA Astrophysics Data System (ADS)

Xu, P.; Tang, M.; Nino, J. C.

2009-06-01

Magnesium stannate spinel (Mg 2SnO 4) was synthesized through conventional solid state processing and then irradiated with 1.0 MeV Kr 2+ ions at low temperatures 50 and 150 K. Structural evolutions during irradiation were monitored and recorded through bright field images and selected-area electron diffraction patterns using in situ transmission electron microscopy. The amorphization of Mg 2SnO 4 was achieved at an ion dose of 5 × 10 19 Kr ions/m 2 at 50 K and 10 20 Kr ions/m 2 at 150 K, which is equivalent to an atomic displacement damage of 5.5 and 11.0 dpa, respectively. The spinel crystal structure was thermally recovered at room temperature from the amorphous phase caused by irradiation at 50 K. The calculated electronic and nuclear stopping powers suggest that the radiation damage caused by 1 MeV Kr 2+ ions in Mg 2SnO 4 is mainly due to atomic displacement induced defect accumulation. The radiation tolerance of Mg 2SnO 4 was finally compared with normal spinel MgAl 2O 4.

Room-Temperature Performance of Poly(Ethylene Ether Carbonate)-Based Solid Polymer Electrolytes for All-Solid-State Lithium Batteries.

PubMed

Jung, Yun-Chae; Park, Myung-Soo; Kim, Duck-Hyun; Ue, Makoto; Eftekhari, Ali; Kim, Dong-Won

2017-12-13

Amorphous poly(ethylene ether carbonate) (PEEC), which is a copolymer of ethylene oxide and ethylene carbonate, was synthesized by ring-opening polymerization of ethylene carbonate. This route overcame the common issue of low conductivity of poly(ethylene oxide)(PEO)-based solid polymer electrolytes at low temperatures, and thus the solid polymer electrolyte could be successfully employed at the room temperature. Introducing the ethylene carbonate units into PEEC improved the ionic conductivity, electrochemical stability and lithium transference number compared with PEO. A cross-linked solid polymer electrolyte was synthesized by photo cross-linking reaction using PEEC and tetraethyleneglycol diacrylate as a cross-linking agent, in the form of a flexible thin film. The solid-state Li/LiNi 0.6 Co 0.2 Mn 0.2 O 2 cell assembled with solid polymer electrolyte based on cross-linked PEEC delivered a high initial discharge capacity of 141.4 mAh g -1 and exhibited good capacity retention at room temperature. These results demonstrate the feasibility of using this solid polymer electrolyte in all-solid-state lithium batteries that can operate at ambient temperatures.

Solid-state synthesis of uniform Li2MnSiO4/C/graphene composites and their performance in lithium-ion batteries

NASA Astrophysics Data System (ADS)

Gong, Huaxu; Zhu, Yongchun; Wang, Linlin; Wei, Denghu; Liang, Jianwen; Qian, Yitai

2014-01-01

Uniform nanospherical Li2MnSiO4/C/graphene composites have been obtained by polyethylene glycol-600 (PEG-600) assisted solid-state reaction using spherical SiO2 as precursor, and heat treatment with the mixed carbon sources (glucose, cellulose acetate and graphene oxide). The transmission electron microscope (TEM) images show that Li2MnSiO4 nanospheres with size of 50 nm are embedded in the three-dimensional (3D) nest-like carbon network. Electrochemical measurements reveal that the composites exhibit first discharge capacity of 215.3 mAh g-1 under 0.05 C, together with a stable discharge capacity of 175 mAh g-1 after 40 cycles. The 3D carbon network and the carbon layer (amorphous carbon and graphene) are favorable for improving the electrochemical performance.

Rapid thermal annealing of WSi x. In-situ resistance measurements

NASA Astrophysics Data System (ADS)

Nobili, C.; Bosi, M.; Ottaviani, G.; Queirolo, G.; Bacci, L.

1991-11-01

In-situ sheet resistance measurements have been performed on amorphous WSi 2.5 alloy films deposited by low pressure chemical vapour deposition either on thermal oxide or on polysilicon. The heat treatments were performed in vacuum up to 1000°C at a heating rate ranging from 5 to 6000°C/min. The temperature was measured with a thermocouple placed underneath and in contact with the sample; the film sheet resistance was measured with a four-point probe in van der Pauw configuration. The in-depth elemental composition was determined by 2 MeV 4He + backscattering technique. Nuclear reaction was used to monitor the quantity of flourine present in the sample. The phases formed were identified by X-ray diffraction. The sheet resistance versus temperature curves are all similar and present, after a small initial decrease, first a sharp increase followed, after about 200°C, by a decrease. X-ray diffraction measurements indicate that the increase is due to the amorphous-hexagonal phase transformation; the decrease is due to the formation of the tetragonal WSi 2 phase. The temperature at which the two variations occur increases with the heating rate indicating thermally activated processes. The activation energies are 1.4 ±0.1 and 2.4 ±0.1 eV for the amorphous-hexagonal and hexagonal-tetragonal transformation, respectively. Silicon segregation at the inner interface occurs only on the samples where the silicide alloy was deposited on polysilicon and for heating rates lower than 200°C/min. The total flourine content is not affected by the kind of heat treatment performed.

A Solid-State NMR Experiment: Analysis of Local Structural Environments in Phosphate Glasses

ERIC Educational Resources Information Center

Anderson, Stanley E.; Saiki, David; Eckert, Hellmut; Meise-Gresch, Karin

2004-01-01

An experiment that can be used to directly study the local chemical environments of phosphorus in solid amorphous materials is demonstrated. The experiment aims at familiarizing the students of chemistry with the principles of solid-state NMR, by having them synthesize a simple phosphate glass, and making them observe the (super 31)P NMR spectrum,…

Evaluation of the Crystallization Tendency of Commercially Available Amorphous Tacrolimus Formulations Exposed to Different Stress Conditions.

PubMed

Trasi, Niraj S; Purohit, Hitesh S; Taylor, Lynne S

2017-10-01

Tacrolimus, an immunosuppressant, is a poorly water soluble compound whereby the commercially available capsule formulations contain the drug in amorphous form. The goal of this study was to evaluate the robustness of the innovator product and five generic formulations to crystallization following storage at stress conditions. Products were purchased from a pharmacy and stored at 40°C/75% relative humidity (RH), open dish conditions. Crystallinity was determined using X-ray diffraction. The quantity of the ingredients in the formulations were determined using different approaches and the various factors that might cause instability in the formulations were studied. After 4 weeks of open dish storage at 40°C/75% RH, one of the generic formulations showed evidence of tacrolimus crystallization. Further investigations revealed batch-to-batch variations in crystallization tendency with the extent of crystallinity varying between 50 and 100% for different batches. Crystallization was also observed at lower storage temperatures (30°C) when the RH was maintained at 75%. It was found that crystallization could be induced in a model formulation by wet granulating an ethanolic solution of the drug with lactose and drying at 60-70°C followed by exposure to stress conditions. It seems probable that the generic that was susceptible to crystallization contains amorphous drug physically mixed with polymeric excipients, rather than as an amorphous solid dispersion. This study highlights the importance of considering the manufacturing process on the stability of the resultant amorphous product.

Exclusive measurements of mean pion multiplicities in 4He-nucleus reactions from 200 to 800 MeV/nucleon

NASA Technical Reports Server (NTRS)

L'Hote, D.; Alard, J. P.; Augerat, J.; Babinet, R.; Brochard, F.; Fodor, Z.; Fraysse, L.; Girard, J.; Gorodetzky, P.; Gosset, J.;

An electron tunneling study of superconductivity in amorphous Sn(sub 1-x)Cu(sub x) thin films

NASA Technical Reports Server (NTRS)

Naugle, D. G.; Watson, P. W., III; Rathnayaka, K. D. D.

1995-01-01

The amorphous phase of Sn would have a superconducting transition temperature near 8 K, much higher than that of crystalline Sn with T(sub c) = 3.5 K. To obtain the amorphous phase, however, it is necessary to use a Sn alloy, usually Cu, and quench condense the alloy films onto a liquid He temperature substrate. Alloying with Cu reduces the superconducting transition temperature almost linearly with Cu concentration with an extrapolation of T(sub c) to zero for x = 0.85. Analysis of the tunneling characteristics between a normal metal electrode with an insulating barrier and superconducting amorphous Sn-Cu films provides detailed information on the changes in the electron-phonon coupling which determines T(sub c) in these alloys. The change from very strong electron-phonon coupling to weak-coupling with the increase in Cu content of amorphous Sn-Cu alloys for the range 0.08 is less than or equal to x is less than or equal to 0.41 is presented and discussed in terms of theories of electron-phonon coupling in disordered metals.

Solid dispersion of efavirenz in PVP K-30 by conventional solvent and kneading methods.

PubMed

Alves, Lariza Darlene Santos; de La Roca Soares, Mônica Felts; de Albuquerque, Camila Tavares; da Silva, Elica Rodrigues; Vieira, Alexandre Couto Carneiro; Fontes, Danilo Augusto Ferreira; Figueirêdo, Camila Bezerra Melo; Soares Sobrinho, José Lamartine; Rolim Neto, Pedro José

2014-04-15

Efavirenz (EFV) used as a part of the treatment of first choice in antiretroviral therapy for AIDS has low aqueous solubility and presents problems of absorption. We thus initially present a phase solubility diagram with carriers of different classes. With a view to obtaining a solid dispersion (SD) with suitable consistency to that of a solid formulation, we chose to use PVP K-30, since polymers present some of the best results. The kneading (KN) and solvent evaporation (EV) methods were thus used at different rates. These were characterized by the way of DSC, FT-IR, SEM, DR-X and dissolution. SD EV proved unsatisfactory, resulting in a decreased dissolution rate, despite the amorphous state of the samples, while the SD KN 4:1 (EFV:polymer) and physical mixtures (PM) had a higher rate of dissolution. SD KN and PM 4:1 were also evaluated for stability after storage, with benefits being observed in relation to EFV. Copyright © 2014. Published by Elsevier Ltd.

Alloy with metallic glass and quasi-crystalline properties

DOEpatents

Xing, Li-Qian; Hufnagel, Todd C.; Ramesh, Kaliat T.

2004-02-17

An alloy is described that is capable of forming a metallic glass at moderate cooling rates and exhibits large plastic flow at ambient temperature. Preferably, the alloy has a composition of (Zr, Hf).sub.a Ta.sub.b Ti.sub.c Cu.sub.d Ni.sub.e Al.sub.f, where the composition ranges (in atomic percent) are 45.ltoreq.a.ltoreq.70, 3.ltoreq.b.ltoreq.7.5, 0.ltoreq.c.ltoreq.4, 3.ltoreq.b+c.ltoreq.10, 10.ltoreq.d.ltoreq.30, 0.ltoreq.e.ltoreq.20, 10.ltoreq.d+e.ltoreq.35, and 5.ltoreq.f.ltoreq.15. The alloy may be cast into a bulk solid with disordered atomic-scale structure, i.e., a metallic glass, by a variety of techniques including copper mold die casting and planar flow casting. The as-cast amorphous solid has good ductility while retaining all of the characteristic features of known metallic glasses, including a distinct glass transition, a supercooled liquid region, and an absence of long-range atomic order. The alloy may be used to form a composite structure including quasi-crystals embedded in an amorphous matrix. Such a composite quasi-crystalline structure has much higher mechanical strength than a crystalline structure.

Glassy materials for lithium batteries: electrochemical properties and devices performances

NASA Astrophysics Data System (ADS)

Duclot, Michel; Souquet, Jean-Louis

Amorphous or glassy materials may be used as electrolyte or electrode materials for lithium primary or secondary batteries. A first generation proceeded from classical coin cells in which the organic electrolyte was replaced by a high lithium conductive glassy electrolyte. The solid components were assembled under isostatic pressure. The main advantages of such cells are a good storage stability and ability to operate until 200°C. Nevertheless, the high resistivity of the glassy electrolyte below room temperature and a limited depth for charge and discharge cycles makes these cells not competitive compared to conventional lithium-ion batteries. More promising, are the thin films solid state microbatteries realised by successive depositions of electrodes and electrolyte. The low resistance of the electrolyte amorphous layer allows cycling at temperatures as low as -10°C. The total thickness of thin film batteries, including packaging is less than 100 μm. A capacity of about 100 μAh cm -2 with over 10 4 charge-discharge cycles at 90% in depth of discharge is well suited for energy independent smart cards or intelligent labels, which represent for these devices a large and unrivalled market.

Silicon Nitride Equation of State

NASA Astrophysics Data System (ADS)

Swaminathan, Pazhayannur; Brown, Robert

2015-06-01

This report presents the development a global, multi-phase equation of state (EOS) for the ceramic silicon nitride (Si3N4) . Structural forms include amorphous silicon nitride normally used as a thin film and three crystalline polymorphs. Crystalline phases include hexagonal α-Si3N4, hexagonalβ-Si3N4, and the cubic spinel c-Si3N4. Decomposition at about 1900 °C results in a liquid silicon phase and gas phase products such as molecular nitrogen, atomic nitrogen, and atomic silicon. The silicon nitride EOS was developed using EOSPro which is a new and extended version of the PANDA II code. Both codes are valuable tools and have been used successfully for a variety of material classes. Both PANDA II and EOSPro can generate a tabular EOS that can be used in conjunction with hydrocodes. The paper describes the development efforts for the component solid phases and presents results obtained using the EOSPro phase transition model to investigate the solid-solid phase transitions in relation to the available shock data. Furthermore, the EOSPro mixture model is used to develop a model for the decomposition products and then combined with the single component solid models to study the global phase diagram. Sponsored by the NASA Goddard Space Flight Center Living With a Star program office.

Spontaneous crystalline-to-amorphous phase transformation of organic or medicinal compounds in the presence of porous media, part 2: amorphization capacity and mechanisms of interaction.

PubMed

Qian, Ken K; Suib, Steven L; Bogner, Robin H

2011-11-01

Amorphization of crystalline compounds using mesoporous media is a promising technique to improve the solubility and dissolution rate of poorly soluble compounds. The objective of this paper is to determine the capacity of amorphization and understand the mechanisms of phase transformation. Commercial grades of mesoporous silicon dioxide (SiO(2)) samples (5- to 30-nm mean pore diameters) with either constant surface area or constant pore volume were used. The amorphization capacity of naphthalene was not proportional to either the surface area or the pore volume measured using adsorption chambers. Instead, the amorphization capacity correlated with surface curvature, that is, the smaller the pore diameter and the higher the surface curvature, the greater the amorphization capacity. The change in surface chemistry due to a highly curved surface may be responsible for the enhanced amorphization capacity as well. The amorphization of crystalline compounds was facilitated through capillary condensation, with the decrease in pore volume as the direct experimental evidence. The amorphization capacity was also enhanced by the dipole-dipole or dipole-induced dipole interaction, promoted by the hydroxyl groups on the surface of SiO(2). The enthalpy of vapor-solid condensation of crystalline compounds was a useful indicator to predict the rank order of amorphization capacity. Copyright © 2011 Wiley-Liss, Inc.

Pick-off annihilation of positronium in matter using full correlation single particle potentials: solid He.

PubMed

Zubiaga, A; Tuomisto, F; Puska, M J

2015-01-29

We investigate the modeling of positronium (Ps) states and their pick-off annihilation trapped at open volumes pockets in condensed molecular matter. Our starting point is the interacting many-body system of Ps and a He atom because it is the smallest entity that can mimic the energy gap between the highest occupied and lowest unoccupied molecular orbitals of molecules, and yet the many-body structure of the HePs system can be calculated accurately enough. The exact-diagonalization solution of the HePs system enables us to construct a pairwise full-correlation single-particle potential for the Ps-He interaction, and the total potential in solids is obtained as a superposition of the pairwise potentials. We study in detail Ps states and their pick-off annihilation rates in voids inside solid He and analyze experimental results for Ps-induced voids in liquid He obtaining the radii of the voids. More importantly, we generalize our conclusions by testing the validity of the Tao-Eldrup model, widely used to analyze ortho-Ps annihilation measurements for voids in molecular matter, against our theoretical results for the solid He. Moreover, we discuss the influence of the partial charges of polar molecules and the strength of the van der Waals interaction on the pick-off annihilation rate.

Confocal Raman studies in determining crystalline nature of PECVD grown Si nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmed, Nafis; Bhargav, P. Balaji; Ramasamy, P.

2015-06-24

Silicon nanowires of diameter ∼200 nm and length of 2-4 µm are grown in the plasma enhanced chemical vapour deposition technique using nanoclustered Au catalyst assisted vapour-liquid-solid process. The crystallinity in the as-grown and annealed samples is studied using confocal Raman spectroscopic studies. Amorphous phase is formed in the as-grown samples. Structural studies using high resolution transmission electron microscopy confirm the polycrystalline nature in the annealed sample.

OPTICAL AND SPECTROSCOPIC STUDIES OF Fe2O3-Bi2O3-B2O3:V2O5 GLASSES

NASA Astrophysics Data System (ADS)

Sanjay; Kishore, N.; Agarwal, A.; Dahiya, S.; Pal, Inder; Kumar, Navin

2013-11-01

The glasses of compositions xFe2O3ṡ (40 - x)Bi2O3ṡ60B2O3ṡ2V2O5 have been prepared by the standard melt-quenching technique. Amorphous nature of these samples is ascertained by XRD patterns. The presence of BO3 and BO4 units is identified by IR spectra of glass samples. The absorption edge (λcut-off) shifts toward longer wavelengths with an increase in Fe2O3 content in the glass matrix. The values of optical band gap energy for indirect allowed and forbidden transitions have been determined and it is found to decrease with increase in transition metal ions. The Urbach's energy is used to characterize the degree of disorder in amorphous solids.

Rational Design of a Water-Storable Hierarchical Architecture Decorated with Amorphous Barium Oxide and Nickel Nanoparticles as a Solid Oxide Fuel Cell Anode with Excellent Sulfur Tolerance.

PubMed

Song, Yufei; Wang, Wei; Ge, Lei; Xu, Xiaomin; Zhang, Zhenbao; Julião, Paulo Sérgio Barros; Zhou, Wei; Shao, Zongping

2017-11-01

Solid oxide fuel cells (SOFCs), which can directly convert chemical energy stored in fuels into electric power, represent a useful technology for a more sustainable future. They are particularly attractive given that they can be easily integrated into the currently available fossil fuel infrastructure to realize an ideal clean energy system. However, the widespread use of the SOFC technology is hindered by sulfur poisoning at the anode caused by the sulfur impurities in fossil fuels. Therefore, improving the sulfur tolerance of the anode is critical for developing SOFCs for use with fossil fuels. Herein, a novel, highly active, sulfur-tolerant anode for intermediate-temperature SOFCs is prepared via a facile impregnation and limited reaction protocol. During synthesis, Ni nanoparticles, water-storable BaZr 0.4 Ce 0.4 Y 0.2 O 3- δ (BZCY) perovskite, and amorphous BaO are formed in situ and deposited on the surface of a Sm 0.2 Ce 0.8 O 1.9 (SDC) scaffold. More specifically, a porous SDC scaffold is impregnated with a well-designed proton-conducting perovskite oxide liquid precursor with the nominal composition of Ba(Zr 0.4 Ce 0.4 Y 0.2 ) 0.8 Ni 0.2 O 3- δ (BZCYN), calcined and reduced in hydrogen. The as-synthesized hierarchical architecture exhibits high H 2 electro-oxidation activity, excellent operational stability, superior sulfur tolerance, and good thermal cyclability. This work demonstrates the potential of combining nanocatalysts and water-storable materials in advanced electrocatalysts for SOFCs.

Inhibiting surface crystallization of amorphous indomethacin by nanocoating.

PubMed

Wu, Tian; Sun, Ye; Li, Ning; de Villiers, Melgardt M; Yu, Lian

2007-04-24

An amorphous solid (glass) may crystallize faster at the surface than through the bulk, making surface crystallization a mechanism of failure for amorphous pharmaceuticals and other materials. An ultrathin coating of gold or polyelectrolytes inhibited the surface crystallization of amorphous indomethacin (IMC), an anti-inflammatory drug and model organic glass. The gold coating (10 nm) was deposited by sputtering, and the polyelectrolyte coating (3-20 nm) was deposited by an electrostatic layer-by-layer assembly of cationic poly(dimethyldiallyl ammonium chloride) (PDDA) and anionic sodium poly(styrenesulfonate) (PSS) in aqueous solution. The coating also inhibited the growth of existing crystals. The inhibition was strong even with one layer of PDDA. The polyelectrolyte coating still permitted fast dissolution of amorphous IMC and improved its wetting and flow. The finding supports the view that the surface crystallization of amorphous IMC is enabled by the mobility of a thin layer of surface molecules, and this mobility can be suppressed by a coating of only a few nanometers. This technique may be used to stabilize amorphous drugs prone to surface crystallization, with the aqueous coating process especially suitable for drugs of low aqueous solubility.

Early Days of Superfluid ^3He: An Experimenter's View

NASA Astrophysics Data System (ADS)

Lee, David

2010-03-01

The formulation of the BCS theory led theorists to investigate possible non-S-wave pairing in liquid ^3He. Unfortunately as time went on, estimates for the pairing temperature became unattainably low. Nevertheless, the push to lower temperatures by experimentalists continued and was facilitated by the invention of the dilution refrigerator. Nuclear adiabatic demagnetization could then be used to cool liquid ^3He to ˜1 mK as demonstrated by Goodkind. An alternate approach, suggested by Pomeranchuk, involved adiabatic compression of liquid ^3He into the solid phase. Efforts to develop this technique at the Kapitza Institute, La Jolla and Cornell achieved success in demonstrating cooling of mixtures of liquid and solid ^3He to ˜ 1 mK following dilution refrigerator pre-cooling. Although there was great pessimism regarding the possible observation of pairing in liquid ^3He, the unsettled problem of magnetic ordering in solid ^3He beckoned. Ultimately two phase transition along the melting curve were observed by Osheroff et al at Cornell. Although first associated with solid ^3He, extensive NMR studies showed them to be two new phases of liquid ^3He. A brief history of experiments at various laboratories following the discovery is given, along with early interpretations given by Anderson and Morel and Balian and Werthamer. The key role of Leggett's spin dynamics is also discussed.

Development of the new generation of glass-based neutron detection materials

NASA Astrophysics Data System (ADS)

Dosovitskiy, Alexey E.; Dosovitskiy, Georgy A.; Korjik, Mikhail V.

2012-10-01

Approach to obtaining of neutron detector material alternative to 3He containing ionization gas detectors is proposed. Recently, a severe deficit of the 3He has pushed its price up strongly, so alternative cheaper detecting materials are demanded. Possible alternatives to 3He are materials containing 10B and 6Li isotopes. These two elements form many inorganic materials, either crystalline or amorphous. Glass scintillators look very advantageous as detector materials, especially for large area detectors, as their manufacturing could be cheaper and easier-to-scale, compared to single crystals and ceramics. A poor exciton transport, which is a fundamental feature of glass scintillators, limits their light yield and, therefore, practical use. Here we discuss a possibility to improve energy transfer to luminescent centers by creation of high concentration of crystalline luminophore particles in the glass matrix. This could be achieved through the controlled crystallization of the glass. We demonstrate how this approach works in well known Li-Al-Si (LAS) glass system. Partially crystallized Ce3+-doped glass with nanocrystalline inclusions is obtained, which shows the superior scintillation properties compared to amorphous glass. The material is characterized by an emission spectrum shift towards shorter wavelengths, which provides low light self-absorption.

Shear Induced Structural Relaxation in a Supercooled Colloidal Liquid

NASA Astrophysics Data System (ADS)

Chen, Dandan; Semwogerere, Denis; Weeks, Eric R.

2009-11-01

Amorphous materials include many common products we use everyday, such as window glass, moisturizer, shaving cream and peanut butter. These materials have liquid-like disordered structure, but keep their shapes like a solid. The rheology of dense amorphous materials under large shear strain is not fully understood, partly due to the difficulty of directly viewing the microscopic details of such materials. We use a colloidal suspension to simulate amorphous materials, and study the shear- induced structural relaxation with fast confocal microscopy. We quantify the plastic rearrangements of the particles using standard analysis techniques based on the motion of the particles.

Exploring Molecular Speciation and Crystallization Mechanism of Amorphous 2-Phenylamino Nicotinic Acid.

PubMed

Kalra, Arjun; Lubach, Joseph W; Munson, Eric J; Li, Tonglei

2018-02-07

Molecular understanding of phase stability and transition of the amorphous state helps in formulation and manufacturing of poorly-soluble drugs. Crystallization of a model compound, 2-phenylamino nicotinic acid (2PNA), from the amorphous state was studied using solid-state analytical methods. Our previous report suggests that 2PNA molecules mainly develop intermolecular -COOH∙∙∙pyridine N (acid-pyridine) interactions in the amorphous state. In the current study, the molecular speciation is explored with regard to the phase transition from the amorphous to the crystalline state. Using spectroscopic techniques, the molecular interactions and structural evolvement during the recrystallization from the glassy state were investigated. The results unveiled that the structurally heterogeneous amorphous state contains acid-pyridine aggregates - either as hydrogen-bonded neutral molecules or as zwitterions - as well as a population of carboxylic acid dimers. Phase transition from the amorphous state results in crystal structures composed of carboxylic acid dimer (acid-acid) synthon or acid-pyridine chains depending on the crystallization conditions employed. The study underlines the structural evolvement, as well as its impact on the metastability, of amorphous samples from local, supramolecular assemblies to long-range intermolecular ordering through crystallization.

A case study of real-time monitoring of solid-state phase transformations in acoustically levitated particles using near infrared and Raman spectroscopy.

PubMed

Rehder, Sönke; Wu, Jian X; Laackmann, Julian; Moritz, Hans-Ulrich; Rantanen, Jukka; Rades, Thomas; Leopold, Claudia S

2013-01-23

The objective of this study was to monitor the amorphous-to-crystalline solid-state phase transformation kinetics of the model drug ibuprofen with spectroscopic methods during acoustic levitation. Chemical and physical information was obtained by real-time near infrared (NIRS) and Raman spectroscopy measurements. The recrystallisation kinetic parameters (overall recrystallisation rate constant β and the time needed to reach 50% of the equilibrated level t(50)), were determined using a multivariate curve resolution approach. The acoustic levitation device coupled with non-invasive spectroscopy enabled monitoring of the recrystallisation process of the difficult-to-handle (adhesive) amorphous sample. The application of multivariate curve resolution enabled isolation of the underlying pure spectra, which corresponded well with the reference spectra of amorphous and crystalline ibuprofen. The recrystallisation kinetic parameters were estimated from the recrystallisation profiles. While the empirical recrystallisation rate constant determined by NIR and Raman spectroscopy were comparable, the lag time for recrystallisation was significantly lower with Raman spectroscopy as compared to NIRS. This observation was explained by the high energy density of the Raman laser beam, which might have led to local heating effects of the sample and thus reduced the recrystallisation onset time. It was concluded that acoustic levitation with NIR and Raman spectroscopy combined with multivariate curve resolution allowed direct determination of the recrystallisation kinetics of amorphous drugs and thus is a promising technique for monitoring solid-state phase transformations of adhesive small-sized samples during the early phase of drug development. Copyright © 2012 Elsevier B.V. All rights reserved.

He, U, and Th Depth Profiling of Apatite and Zircon Using Laser Ablation Noble Gas Mass Spectrometry and SIMS

NASA Astrophysics Data System (ADS)

Monteleone, B. D.; van Soest, M. C.; Hodges, K. V.; Hervig, R.; Boyce, J. W.

2008-12-01

Conventional (U-Th)/He thermochronology utilizes single or multiple grain analyses of U- and Th-bearing minerals such as apatite and zircon and does not allow for assessment of spatial variation in concentration of He, U, or Th within individual crystals. As such, age calculation and interpretation require assumptions regarding 4He loss through alpha ejection, diffusive redistribution of 4He, and U and Th distribution as an initial condition for these processes. Although models have been developed to predict 4He diffusion parameters, correct for the effect of alpha ejection on calculated cooling ages, and account for the effect of U and Th zonation within apatite and zircon, measurements of 4He, U, and Th distribution have not been combined within a single crystal. We apply ArF excimer laser ablation, combined with noble gas mass spectrometry, to obtain depth profiles within apatite and zircon crystals in order to assess variations in 4He concentration with depth. Our initial results from pre-cut, pre-heated slabs of Durango apatite, each subjected to different T-t schedules, suggest a general agreement of 4He profiles with those predicted by theoretical diffusion models (Farley, 2000). Depth profiles through unpolished grains give reproducible alpha ejection profiles in Durango apatite that deviate from alpha ejection profiles predicted for ideal, homogenous crystals. SIMS depth profiling utilizes an O2 primary beam capable of sputtering tens of microns and measuring sub-micron resolution variation in [U], [Th], and [Sm]. Preliminary results suggest that sufficient [U] and [Th] zonation is present in Durango apatite to influence the form of the 4He alpha ejection profile. Future work will assess the influence of measured [U] and [Th] zonation on previously measured 4He depth profiles. Farley, K.A., 2000. Helium diffusion from apatite; general behavior as illustrated by Durango fluorapatite. J. Geophys. Res., B Solid Earth Planets 105 (2), 2903-2914.

Both solubility and chemical stability of curcumin are enhanced by solid dispersion in cellulose derivative matrices.

PubMed

Li, Bin; Konecke, Stephanie; Wegiel, Lindsay A; Taylor, Lynne S; Edgar, Kevin J

2013-10-15

Amorphous solid dispersions (ASD) of curcumin (Cur) in cellulose derivative matrices, hydroxypropylmethylcellulose acetate succinate (HPMCAS), carboxymethylcellulose acetate butyrate (CMCAB), and cellulose acetate adipate propionate (CAAdP) were prepared in order to investigate the structure-property relationship and identify polymer properties necessary to effectively increase Cur aqueous solution concentration. XRD results indicated that all investigated solid dispersions were amorphous, even at a 9:1 Cur:polymer ratio. Both stability against crystallization and Cur solution concentration from these ASDs were significantly higher than those from physical mixtures and crystalline Cur. Remarkably, curcumin was also stabilized against chemical degradation in solution. Chemical stabilization was polymer-dependent, with stabilization in CAAdP>CMCAB>HPMCAS>PVP, while matrices enhanced solution concentration as PVP>HPMCAS>CMCAB≈CAAdP. HPMCAS/Cur dispersions have useful combinations of pH-triggered release profile, chemical stabilization, and strong enhancement of Cur solution concentration. Copyright © 2013 Elsevier Ltd. All rights reserved.

Investigation of Phase Mixing in Amorphous Solid Dispersions of AMG 517 in HPMC-AS Using DSC, Solid-State NMR, and Solution Calorimetry.

PubMed

Calahan, Julie L; Azali, Stephanie C; Munson, Eric J; Nagapudi, Karthik

2015-11-02

Intimate phase mixing between the drug and the polymer is considered a prerequisite to achieve good physical stability for amorphous solid dispersions. In this article, spray dried amorphous dispersions (ASDs) of AMG 517 and HPMC-as were studied by differential scanning calorimetry (DSC), solid-state NMR (SSNMR), and solution calorimetry. DSC analysis showed a weakly asymmetric (ΔTg ≈ 13.5) system with a single glass transition for blends of different compositions indicating phase mixing. The Tg-composition data was modeled using the BKCV equation to accommodate the observed negative deviation from ideality. Proton spin-lattice relaxation times in the laboratory and rotating frames ((1)H T1 and T1ρ), as measured by SSNMR, were consistent with the observation that the components of the dispersion were in intimate contact over a 10-20 nm length scale. Based on the heat of mixing calculated from solution calorimetry and the entropy of mixing calculated from the Flory-Huggins theory, the free energy of mixing was calculated. The free energy of mixing was found to be positive for all ASDs, indicating that the drug and polymer are thermodynamically predisposed to phase separation at 25 °C. This suggests that miscibility measured by DSC and SSNMR is achieved kinetically as the result of intimate mixing between drug and polymer during the spray drying process. This kinetic phase mixing is responsible for the physical stability of the ASD.

Building solids inside nano-space: from confined amorphous through confined solvate to confined 'metastable' polymorph.

PubMed

Nartowski, K P; Tedder, J; Braun, D E; Fábián, L; Khimyak, Y Z

2015-10-14

The nanocrystallisation of complex molecules inside mesoporous hosts and control over the resulting structure is a significant challenge. To date the largest organic molecule crystallised inside the nano-pores is a known pharmaceutical intermediate - ROY (259.3 g mol(-1)). In this work we demonstrate smart manipulation of the phase of a larger confined pharmaceutical - indomethacin (IMC, 357.8 g mol(-1)), a substance with known conformational flexibility and complex polymorphic behaviour. We show the detailed structural analysis and the control of solid state transformations of encapsulated molecules inside the pores of mesoscopic cellular foam (MCF, pore size ca. 29 nm) and controlled pore glass (CPG, pore size ca. 55 nm). Starting from confined amorphous IMC we drive crystallisation into a confined methanol solvate, which upon vacuum drying leads to the stabilised rare form V of IMC inside the MCF host. In contrast to the pure form, encapsulated form V does not transform into a more stable polymorph upon heating. The size of the constraining pores and the drug concentration within the pores determine whether the amorphous state of the drug is stabilised or it recrystallises into confined nanocrystals. The work presents, in a critical manner, an application of complementary techniques (DSC, PXRD, solid-state NMR, N2 adsorption) to confirm unambiguously the phase transitions under confinement and offers a comprehensive strategy towards the formation and control of nano-crystalline encapsulated organic solids.

Solid-state flat panel imager with avalanche amorphous selenium

NASA Astrophysics Data System (ADS)

Scheuermann, James R.; Howansky, Adrian; Goldan, Amir H.; Tousignant, Olivier; Levéille, Sébastien; Tanioka, K.; Zhao, Wei

2016-03-01

Active matrix flat panel imagers (AMFPI) have become the dominant detector technology for digital radiography and fluoroscopy. For low dose imaging, electronic noise from the amorphous silicon thin film transistor (TFT) array degrades imaging performance. We have fabricated the first prototype solid-state AMFPI using a uniform layer of avalanche amorphous selenium (a-Se) photoconductor to amplify the signal to eliminate the effect of electronic noise. We have previously developed a large area solid-state avalanche a-Se sensor structure referred to as High Gain Avalanche Rushing Photoconductor (HARP) capable of achieving gains of 75. In this work we successfully deposited this HARP structure onto a 24 x 30 cm2 TFT array with a pixel pitch of 85 μm. An electric field (ESe) up to 105 Vμm-1 was applied across the a-Se layer without breakdown. Using the HARP layer as a direct detector, an X-ray avalanche gain of 15 +/- 3 was achieved at ESe = 105 Vμm-1. In indirect mode with a 150 μm thick structured CsI scintillator, an optical gain of 76 +/- 5 was measured at ESe = 105 Vμm-1. Image quality at low dose increases with the avalanche gain until the electronic noise is overcome at a constant exposure level of 0.76 mR. We demonstrate the success of a solid-state HARP X-ray imager as well as the largest active area HARP sensor to date.

Recovery of Stishovite-Structure at Ambient Conditions out of Shock-Generated Amorphous Silica

NASA Astrophysics Data System (ADS)

Luo, S. N.; Tschauner, O.; Asimow, P. D.; Ahrens, T. J.

2006-12-01

We show that bulk amorphous silica recovered from shock wave experiments on quartz to 56 GPa is not a true glass but rather keeps a large degree of long range structural information that can be recovered by static cold recompression to 13 GPa. At this pressure shock-retrieved silica assumes the structure of crystalline stishovite. This amorphous-crystal transition is characterized by long coherence length, resulting in formation of large crystallites. Therefore, the shock-recovered amorphous material studied here is a slightly disordered six-fold coordinated silica phase but not a glass, which possesses only medium range order [1]. It is therefore most likely that stishovite or a structurally closely related solid phase represent the state this material had assumed during shock, while post-shock heating to 500 -1000 K [2-4] induces the observed slight disorder. This probable memory-effect allows for physically more precise characterization of diaplectic silica `glass' and may be extended to other diaplectic `glasses' [1] O.Tschauner, S.N. Luo, P.D.Asimow, T.J. Ahrens, Am. Min. in print (2006) [2] J. Wackerle, Journal of Applied Physics, 33, 922 - 937 (1962) [3] M.B. Boslough, Journal of Geophysical Research, 93, 6477 - 9484 (1988) [4] S.N. Luo, T.J. Ahrens, P.D. Asimow, Journal of Geophysical Research, 108, 2421- 2434 (2003) Supported under the NNSA Cooperative Agreement DE-FC88-01NV14049 and under NASA PGG Grant NNG04G107G and Contribution # 9144, Division of Geological and Planetary Sciences, California Institute of Technology.

In Situ Hydrothermally Grown TiO2@C Core-Shell Nanowire Coating for Highly Sensitive Solid Phase Microextraction of Polycyclic Aromatic Hydrocarbons.

PubMed

Wang, Fuxin; Zheng, Juan; Qiu, Junlang; Liu, Shuqin; Chen, Guosheng; Tong, Yexiang; Zhu, Fang; Ouyang, Gangfeng

2017-01-18

Nanostructured materials have great potential for solid phase microextraction (SPME) on account of their tiny size, distinct architectures and superior physical and chemical properties. Herein, a core-shell TiO 2 @C fiber for SPME was successfully fabricated by the simple hydrothermal reaction of a titanium wire and subsequent amorphous carbon coating. The readily hydrothermal procedure afforded in situ synthesis of TiO 2 nanowires on a titanium wire and provided a desirable substrate for further coating of amorphous carbon. Benefiting from the much larger surface area of subsequent TiO 2 and good adsorption property of the amorphous carbon coating, the core-shell TiO 2 @C fiber was utilized for the SPME device for the first time and proved to have better performance in extraction of polycyclic aromatic hydrocarbons. In comparison to the polydimethylsiloxane (PDMS) and PDMS/divinylbenzene (DVB) fiber for commercial use, the TiO 2 @C fiber obtained gas chromatography responses 3-8 times higher than those obtained by the commercial 100 μm PDMS and 1-9 times higher than those obtained by the 65 μm PDMS/DVB fiber. Under the optimized extraction conditions, the low detection limits were obtained in the range of 0.4-7.1 ng L -1 with wider linearity in the range of 10-2000 ng L -1 . Moreover, the fiber was successfully used for the determination of polycyclic aromatic hydrocarbons in Pearl River water, which demonstrated the applicability of the core-shell TiO 2 @C fiber.

Opacification of piggyback IOLs associated with an amorphous material attached to interlenticular surfaces.

PubMed

Werner, L; Shugar, J K; Apple, D J; Pandey, S K; Escobar-Gomez, M; Visessook, N; Evans, B B

2000-11-01

To report the pathological and ultrastructural features and interval surgical management of an atypical case of opacification between piggyback intraocular lenses (IOLs). Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, and Nature Coast EyeCare Institute and Surgery Center, Perry, Florida, USA. Opacification between 2 acrylic piggyback lenses was observed 16 months after implantation, with decreased best corrected visual acuity and a hyperopic shift. Elschnig pearls were observed in the peripheral interface between the lenses, and the central interface was occupied by an amorphous material. The pearls were surgically aspirated, but attempts to remove the central material were unsuccessful. The lenses were explanted and sent to the laboratory. Staining with hematoxylin and eosin (H&E), examination under a light microscope, and scanning electron microscopic analysis were performed. The surfaces of the anterior IOL were relatively clear. The amorphous material, mostly attached to the center of the anterior surface of the posterior IOL, was homogeneously stained with H&E. No cell nucleus was observed in this region. Scanning electron microscopy showed that the IOL edge presented a smooth, regular surface relatively free of deposits. The most central region was covered by an irregular layer of an amorphous compact material with some cracks, fissures, or both on its surface. Although the exact composition of the material between the lenses could not be established, hypotheses were advanced to understand the pathological mechanism associated with this condition. This case is different from those in previous reports of opacification composed of cortex and cells between piggyback IOLs.

Towards improved solubility of poorly water-soluble drugs: cryogenic co-grinding of piroxicam with carrier polymers.

PubMed

Penkina, Anna; Semjonov, Kristian; Hakola, Maija; Vuorinen, Sirpa; Repo, Timo; Yliruusi, Jouko; Aruväli, Jaan; Kogermann, Karin; Veski, Peep; Heinämäki, Jyrki

2016-01-01

Amorphous solid dispersions (SDs) open up exciting opportunities in formulating poorly water-soluble active pharmaceutical ingredients (APIs). In the present study, novel catalytic pretreated softwood cellulose (CPSC) and polyvinylpyrrolidone (PVP) were investigated as carrier polymers for preparing and stabilizing cryogenic co-ground SDs of poorly water-soluble piroxicam (PRX). CPSC was isolated from pine wood (Pinus sylvestris). Raman and Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) were used for characterizing the solid-state changes and drug-polymer interactions. High-resolution scanning electron microscope (SEM) was used to analyze the particle size and surface morphology of starting materials and final cryogenic co-ground SDs. In addition, the molecular aspects of drug-polymer interactions and stabilization mechanisms are presented. The results showed that the carrier polymer influenced both the degree of amorphization of PRX and stabilization against crystallization. The cryogenic co-ground SDs prepared from PVP showed an enhanced dissolution rate of PRX, while the corresponding SDs prepared from CPSC exhibited a clear sustained release behavior. In conclusion, cryogenic co-grinding provides a versatile method for preparing amorphous SDs of poorly water-soluble APIs. The solid-state stability and dissolution behavior of such co-ground SDs are to a great extent dependent on the carrier polymer used.

Hierarchical structures of amorphous solids characterized by persistent homology

PubMed Central

Hiraoka, Yasuaki; Nakamura, Takenobu; Hirata, Akihiko; Escolar, Emerson G.; Matsue, Kaname; Nishiura, Yasumasa

2016-01-01

This article proposes a topological method that extracts hierarchical structures of various amorphous solids. The method is based on the persistence diagram (PD), a mathematical tool for capturing shapes of multiscale data. The input to the PDs is given by an atomic configuration and the output is expressed as 2D histograms. Then, specific distributions such as curves and islands in the PDs identify meaningful shape characteristics of the atomic configuration. Although the method can be applied to a wide variety of disordered systems, it is applied here to silica glass, the Lennard-Jones system, and Cu-Zr metallic glass as standard examples of continuous random network and random packing structures. In silica glass, the method classified the atomic rings as short-range and medium-range orders and unveiled hierarchical ring structures among them. These detailed geometric characterizations clarified a real space origin of the first sharp diffraction peak and also indicated that PDs contain information on elastic response. Even in the Lennard-Jones system and Cu-Zr metallic glass, the hierarchical structures in the atomic configurations were derived in a similar way using PDs, although the glass structures and properties substantially differ from silica glass. These results suggest that the PDs provide a unified method that extracts greater depth of geometric information in amorphous solids than conventional methods. PMID:27298351

Atypical effects of incorporated surfactants on stability and dissolution properties of amorphous polymeric dispersions.

PubMed

Al-Obaidi, Hisham; Lawrence, M Jayne; Buckton, Graham

2016-11-01

To understand the impact of ionic and non-ionic surfactants on the dissolution and stability properties of amorphous polymeric dispersions using griseofulvin (GF) as a model for poorly soluble drugs. Solid dispersions of the poorly water-soluble drug, griseofulvin (GF) and the polymers, poly(vinylpyrrolidone) (PVP) and poly(2-hydroxypropyl methacrylate) (PHPMA), have been prepared by spray drying and bead milling and the effect of the ionic and non-ionic surfactants, namely sodium dodecyl sulphate (SDS) and Tween-80, on the physico-chemical properties of the solid dispersions studied. The X-ray powder diffraction data and hot-stage microscopy showed a fast re-crystallisation of GF. While dynamic vapour sorption (DVS) measurements indicated an increased water uptake, slow dissolution rates were observed for the solid dispersions incorporating surfactants. The order by which surfactants free dispersions were prepared seemed critical as indicated by DVS and thermal analysis. Dispersions prepared by milling with SDS showed significantly better stability than spray-dried dispersions (drug remained amorphous for more than 6 months) as well as improved dissolution profile. We suggest that surfactants can hinder the dissolution by promoting aggregation of polymeric chains, however that effect depends mainly on how the particles were prepared. © 2016 Royal Pharmaceutical Society.

Template-assisted mineral formation via an amorphous liquid phase precursor route

NASA Astrophysics Data System (ADS)

Amos, Fairland F.

The search for alternative routes to synthesize inorganic materials has led to the biomimetic route of producing ceramics. In this method, materials are manufactured at ambient temperatures and in aqueous solutions with soluble additives and insoluble matrix, similar to the biological strategy for the formation of minerals by living organisms. Using this approach, an anionic polypeptide additive was used to induce an amorphous liquid-phase precursor to either calcium carbonate or calcium phosphate. This precursor was then templated on either organic or inorganic substrates. Non-equilibrium morphologies, such as two-dimensional calcium carbonate films, one-dimensional calcium carbonate mesostructures and "molten" calcium phosphate spherulites were produced, which are not typical of the traditional (additive-free) solution grown crystals in the laboratory. In the study of calcium carbonate, the amorphous calcium carbonate mineral formed via the liquid-phase precursor, either underwent a dissolution-recrystallization event or a pseudo-solid-state transformation to produce different morphologies and polymorphs of the mineral. Discrete or aggregate calcite crystals were formed via the dissolution of the amorphous phase to allow the reprecipitation of the stable crystal. Non-equilibrium morphologies, e.g., films, mesotubules and mesowires were templated using organic and inorganic substrates and compartments. These structures were generated via an amorphous solid to crystalline solid transformation. Single crystalline tablets and mesowires of aragonite, which are reported to be found only in nature as skeletal structures of marine organisms, such as mollusk nacre and echinoderm teeth, were successfully synthesized. These biomimetic structures were grown via the polymer-induced liquid-phase precursor route in the presence of magnesium. Only low magnesium-bearing calcite was formed in the absence of the polymer. A similar approach of using a polymeric additive was implemented in calcium phosphate. Spherulitic crystals and films, seemingly formed from a molten state, were produced. These structures served as nucleating surfaces for the radial formation of calcium oxalate minerals. The composite calcium phosphate-calcium oxalate assemblies are similar to the core-shell structures found in certain kidney stones.

Importance of the Direct Contact of Amorphous Solid Particles with the Surface of Monolayers for the Transepithelial Permeation of Curcumin.

PubMed

Kimura, Shunsuke; Kasatani, Sachiha; Tanaka, Megumi; Araki, Kaeko; Enomura, Masakazu; Moriyama, Kei; Inoue, Daisuke; Furubayashi, Tomoyuki; Tanaka, Akiko; Kusamori, Kosuke; Katsumi, Hidemasa; Sakane, Toshiyasu; Yamamoto, Akira

2016-02-01

The amorphization has been generally known to improve the absorption and permeation of poorly water-soluble drugs through the enhancement of the solubility. The present study focused on the direct contact of amorphous solid particles with the surface of the membrane using curcumin as a model for water-insoluble drugs. Amorphous nanoparticles of curcumin (ANC) were prepared with antisolvent crystallization method using a microreactor. The solubility of curcumin from ANC was two orders of magnitude higher than that of crystalline curcumin (CC). However, the permeation of curcumin from the saturated solution of ANC was negligible. The transepithelial permeation of curcumin from ANC suspension was significantly increased as compared to CC suspension, while the permeation was unlikely correlated with the solubility, and the increase in the permeation was dependent on the total concentration of curcumin in ANC suspension. The absorptive transport of curcumin (from apical to basal, A to B) from ANC suspension was much higher than the secretory transport (from basal to apical, B to A). In vitro transport of curcumin through air-interface monolayers is large from ANC but negligible from CC particles. These findings suggest that the direct contact of ANC with the absorptive membrane can play an important role in the transport of curcumin from ANC suspension. The results of the study suggest that amorphous particles may be directly involved in the transepithlial permeation of curcumin.

Polymer Encapsulation of an Amorphous Pharmaceutical by initiated Chemical Vapor Deposition for Enhanced Stability

PubMed Central

2016-01-01

The usage of amorphous solids in practical applications, such as in medication, is commonly limited by the poor long-term stability of this state, because unwanted crystalline transitions occur. In this study, three different polymeric coatings are investigated for their ability to stabilize amorphous films of the model drug clotrimazole and to protect against thermally induced transitions. For this, drop cast films of clotrimazole are encapsulated by initiated chemical vapor deposition (iCVD), using perfluorodecyl acrylate (PFDA), hydroxyethyl methacrylate (HEMA), and methacrylic acid (MAA). The iCVD technique operates under solvent-free conditions at low temperatures, thus leaving the solid state of the encapsulated layer unaffected. Optical microscopy and X-ray diffraction data reveal that at ambient conditions of about 22 °C, any of these iCVD layers extends the lifetime of the amorphous state significantly. At higher temperatures (50 or 70 °C), the p-PFDA coating is unable to provide protection, while the p-HEMA and p-MAA strongly reduce the crystallization rate. Furthermore, p-HEMA and p-MAA selectively facilitate a preferential alignment of clotrimazole and, interestingly, even suppress crystallization upon a temporary, rapid temperature increase (3 °C/min, up to 150 °C). The results of this study demonstrate how a polymeric coating, synthesized directly on top of an amorphous phase, can act as a stabilizing agent against crystalline transitions, which makes this approach interesting for a variety of applications. PMID:27467099

Polymer Encapsulation of an Amorphous Pharmaceutical by initiated Chemical Vapor Deposition for Enhanced Stability.

PubMed

Christian, Paul; Ehmann, Heike M A; Coclite, Anna Maria; Werzer, Oliver

2016-08-24

The usage of amorphous solids in practical applications, such as in medication, is commonly limited by the poor long-term stability of this state, because unwanted crystalline transitions occur. In this study, three different polymeric coatings are investigated for their ability to stabilize amorphous films of the model drug clotrimazole and to protect against thermally induced transitions. For this, drop cast films of clotrimazole are encapsulated by initiated chemical vapor deposition (iCVD), using perfluorodecyl acrylate (PFDA), hydroxyethyl methacrylate (HEMA), and methacrylic acid (MAA). The iCVD technique operates under solvent-free conditions at low temperatures, thus leaving the solid state of the encapsulated layer unaffected. Optical microscopy and X-ray diffraction data reveal that at ambient conditions of about 22 °C, any of these iCVD layers extends the lifetime of the amorphous state significantly. At higher temperatures (50 or 70 °C), the p-PFDA coating is unable to provide protection, while the p-HEMA and p-MAA strongly reduce the crystallization rate. Furthermore, p-HEMA and p-MAA selectively facilitate a preferential alignment of clotrimazole and, interestingly, even suppress crystallization upon a temporary, rapid temperature increase (3 °C/min, up to 150 °C). The results of this study demonstrate how a polymeric coating, synthesized directly on top of an amorphous phase, can act as a stabilizing agent against crystalline transitions, which makes this approach interesting for a variety of applications.

High performance of SDC and GDC core shell type composite electrolytes using methane as a fuel for low temperature SOFC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Irshad, Muneeb; Siraj, Khurram, E-mail: razahussaini786@gmail.com, E-mail: khurram.uet@gmail.com; Javed, Fayyaz

Nanocomposites Samarium doped Ceria (SDC), Gadolinium doped Ceria (GDC), core shell SDC amorphous Na{sub 2}CO{sub 3} (SDCC) and GDC amorphous Na{sub 2}CO{sub 3} (GDCC) were synthesized using co-precipitation method and then compared to obtain better solid oxide electrolytes materials for low temperature Solid Oxide Fuel Cell (SOFCs). The comparison is done in terms of structure, crystallanity, thermal stability, conductivity and cell performance. In present work, XRD analysis confirmed proper doping of Sm and Gd in both single phase (SDC, GDC) and dual phase core shell (SDCC, GDCC) electrolyte materials. EDX analysis validated the presence of Sm and Gd in bothmore » single and dual phase electrolyte materials; also confirming the presence of amorphous Na{sub 2}CO{sub 3} in SDCC and GDCC. From TGA analysis a steep weight loss is observed in case of SDCC and GDCC when temperature rises above 725 °C while SDC and GDC do not show any loss. The ionic conductivity and cell performance of single phase SDC and GDC nanocomposite were compared with core shell GDC/amorphous Na{sub 2}CO{sub 3} and SDC/ amorphous Na{sub 2}CO{sub 3} nanocomposites using methane fuel. It is observed that dual phase core shell electrolytes materials (SDCC, GDCC) show better performance in low temperature range than their corresponding single phase electrolyte materials (SDC, GDC) with methane fuel.« less

Lag and light-transfer characteristics of amorphous selenium photoconductive film with tellurium-doped layer

NASA Astrophysics Data System (ADS)

Park, Wug-Dong; Tanioka, Kenkichi

2016-07-01

Amorphous selenium (a-Se) high-gain avalanche rushing amorphous photoconductor (HARP) films have been used for highly sensitive imaging devices. To study a-Se HARP films for a solid-state image sensor, current-voltage, lag, spectral response, and light-transfer characteristics of 0.4-µm-thick a-Se HARP films are investigated. Also, to clarify a suitable Te-doped a-Se layer thickness in the a-Se photoconductor, we considered the effects of Te-doped layer thickness on the lag, spectral response, and light-transfer characteristics of 0.4-µm-thick a-Se HARP films. The threshold field, at which avalanche multiplication occurs in the a-Se HARP targets, decreases when the Te-doped layer thickness increases. The lag of 0.4-µm-thick a-Se HARP targets with Te-doped layers is higher than that of the target without Te doping. The lag of the targets with Te-doped layers is caused by the electrons trapped in the Te-doped layers within the 0.4-µm-thick a-Se HARP films. From the results of the spectral response measurement of about 15 min, the 0.4-µm-thick a-Se HARP targets with Te-doped layers of 90 and 120 nm are observed to be unstable owing to the electrons trapped in the Te-doped a-Se layer. From the light-transfer characteristics of 0.4-µm-thick a-Se HARP targets, as the slope at the operating point of signal current-voltage characteristics in the avalanche mode increases, the γ of the a-Se HARP targets decreases. Considering the effects of dark current on the lag and spectral response characteristics, a Te-doped layer of 60 nm is suitable for 0.4-µm-thick a-Se HARP films.

Silicon nitride equation of state

NASA Astrophysics Data System (ADS)

Brown, Robert C.; Swaminathan, Pazhayannur K.

2017-01-01

This report presents the development of a global, multi-phase equation of state (EOS) for the ceramic silicon nitride (Si3N4).1 Structural forms include amorphous silicon nitride normally used as a thin film and three crystalline polymorphs. Crystalline phases include hexagonal α-Si3N4, hexagonal β-Si3N4, and the cubic spinel c-Si3N4. Decomposition at about 1900 °C results in a liquid silicon phase and gas phase products such as molecular nitrogen, atomic nitrogen, and atomic silicon. The silicon nitride EOS was developed using EOSPro which is a new and extended version of the PANDA II code. Both codes are valuable tools and have been used successfully for a variety of material classes. Both PANDA II and EOSPro can generate a tabular EOS that can be used in conjunction with hydrocodes. The paper describes the development efforts for the component solid phases and presents results obtained using the EOSPro phase transition model to investigate the solid-solid phase transitions in relation to the available shock data that have indicated a complex and slow time dependent phase change to the c-Si3N4 phase. Furthermore, the EOSPro mixture model is used to develop a model for the decomposition products; however, the need for a kinetic approach is suggested to combine with the single component solid models to simulate and further investigate the global phase coexistences.

Solubilization of the poorly water soluble drug, telmisartan, using supercritical anti-solvent (SAS) process.

PubMed

Park, Junsung; Cho, Wonkyung; Cha, Kwang-Ho; Ahn, Junhyun; Han, Kang; Hwang, Sung-Joo

2013-01-30

Telmisartan is a biopharmaceutical classification system (BCS) class II drug that has extremely low water solubility but is freely soluble in highly alkalized solutions. Few organic solvents can dissolve telmisartan. This solubility problem is the main obstacle achieving the desired bioavailability. Because of its unique characteristics, the supercritical anti-solvent (SAS) process was used to BCS class II drug in a variety of ways including micronization, amorphization and solid dispersion. Solid dispersions were prepared using hydroxypropylmethylcellulose/polyvinylpyrrolidone (HPMC/PVP) at 1:0.5, 1:1, and 1:2 weight ratios of drug to polymer, and pure telmisartan was also treated using the SAS process. Processed samples were characterized for morphology, particle size, crystallinity, solubility, dissolution rate and polymorphic stability. After the SAS process, all samples were converted to the amorphous form and were confirmed to be hundreds nm in size. Solubility and dissolution rate were increased compared to the raw material. Solubility tended to increase with increases in the amount of polymer used. However, unlike the solubility results, the dissolution rate decreased with increases in polymer concentration due to gel layer formation of the polymer. Processed pure telmisartan showed the best drug release even though it had lower solubility compared to other solid dispersions; however, because there were no stabilizers in processed pure telmisartan, it recrystallized after 1 month under severe conditions, while the other solid dispersion samples remained amorphous form. We conclude that after controlling the formulation of solid dispersion, the SAS process could be a promising approach for improving the solubility and dissolution rate of telmisartan. Copyright © 2012 Elsevier B.V. All rights reserved.

Size effects on the thermal conductivity of amorphous silicon thin films

DOE PAGES

Thomas Edwin Beechem; Braun, Jeffrey L.; Baker, Christopher H.; ...

2016-04-01

In this study, we investigate thickness-limited size effects on the thermal conductivity of amorphous silicon thin films ranging from 3 to 1636 nm grown via sputter deposition. While exhibiting a constant value up to ~100 nm, the thermal conductivity increases with film thickness thereafter. The thickness dependence we demonstrate is ascribed to boundary scattering of long wavelength vibrations and an interplay between the energy transfer associated with propagating modes (propagons) and nonpropagating modes (diffusons). A crossover from propagon to diffuson modes is deduced to occur at a frequency of ~1.8 THz via simple analytical arguments. These results provide empirical evidencemore » of size effects on the thermal conductivity of amorphous silicon and systematic experimental insight into the nature of vibrational thermal transport in amorphous solids.« less

He-irradiation effects on glass-ceramics for joining of SiC-based materials

NASA Astrophysics Data System (ADS)

Gozzelino, L.; Casalegno, V.; Ghigo, G.; Moskalewicz, T.; Czyrska-Filemonowicz, A.; Ferraris, M.

2016-04-01

CaO-Al2O3 (CA) and SiO2-Al2O3-Y2O3 (SAY) glass-ceramics are promising candidates for SiC/SiC indirect joints. In view of their use in locations where high radiation level is expected (i.e. fusion plants) it is important to investigate how radiation-induced damage can modify the material microstructure. To this aim, pellets of both types were irradiated with 5.5 MeV 4He+ ions at an average temperature of 75 °C up to a fluence of almost 2.3·1018 cm-2. This produces a displacement defect density that increases with depth and reaches a value of about 40 displacements per atom in the ion implantation region, where the He-gas reaches a concentration of several thousands of atomic parts per million. X-ray diffractometry and scanning electron microscopy showed no change in the microstructure and in the morphology of the pellet surface. Moreover, a transmission electron microscopy investigation on cross-section lamellas revealed the occurrence of structural defects and agglomerates of He-bubbles in the implantation region for the CA sample and a more homogeneous He-bubble distribution in the SAY pellet, even outside the implantation layer. In addition, no amorphization was found in both samples, even in correspondence to the He implantation zone. The radiation damage induced only occasional micro-cracks, mainly located at grain boundaries (CA) or within the grains (SAY).

Precipitation of Co(2+) carbonates from aqueous solution: insights on the amorphous to crystalline transformation.

NASA Astrophysics Data System (ADS)

González-López, Jorge; Fernández-González, Ángeles; Jiménez, Amalia

2016-04-01

Cobalt is toxic metal that is present only as a trace in the Earth crust. However, Co might concentrate on specific areas due to both natural and anthropogenic factors and thus, soils and groundwater can be contaminated. It is from this perspective that we are interested in the precipitation of cobalt carbonates, since co-precipitation with minerals phases is a well-known method for metal immobilization in the environment. In particular, the carbonates are widely used due to its reactivity and natural abundance. In order to evaluate the cobalt carbonate precipitation at room temperature, a simple experimental work was carried out in this work. The precipitation occurred via reaction of two common salts: 0.05M of CoCl2 and 0.05M of Na2CO3 in aqueous solution. After reaction, the precipitated solid was kept in the remaining water at 25 oC and under constant stirring for different aging times of 5 min, 1 and 5 hours, 1, 2, 4, 7, 30 and 60 days. In addition to the aging and precipitation experiments, we carried out experiments to determine the solubility of the solids. In these experiments each precipitate was dissolved in Milli-Q water until equilibrium was reached and then the aqueous solution was analyzed regarding Co2+ and total alkalinity. Furthermore, acid solution calorimetry of the products were attained. Finally, we modeled the results using the PHREEQC code. Solid and aqueous phase identification and characterization have been extensively reported in a previous work (González-López et al., 2015). The main results of our investigation were the initial precipitation of an amorphous cobalt carbonate that evolve towards a poorly crystalline cobalt hydroxide carbonate with aging treatment. Solubility of both phases have been calculated under two different approaches: precipitation and dissolution. Values of solubility from each approach were obtained with a general error due to differences in experiment conditions, for instance, ionic strength, temperature and water content. It was surprising the low solubility product (Ksp) of the new phase Co2CO3(OH)2 in the order of 10-30 and this could explain its appearance only after 7 days of aging. On the other hand, the high solubility product of amorphous is consistent with its instantaneous precipitation at the beginning of the reaction. Solution calorimetry shows a higher value of exothermic solution enthalpy for crystalline cobalt hydroxide carbonate and hence, the solubility result are confirmed. Although geochemical models indicated that aqueous solution was supersaturated with respect both phases, the sequence of obtained phases (first amorphous and next crystalline) indicate that the evolution of the saturation index has to be dropped with respect to amorphous phase with time. These results points towards a simultaneous dissolution of the amorphous and the precipitation of crystalline phase Co2CO3(OH)2 at the first stages of the reaction. González-López, J. ; Fernández-González, Á. ; Jiménez, A. (2015) Prepublication: Crystallization of nanostructured cobalt hydroxide carbonate at ambient conditions: a key precursor of Co3O4. DOI: http://dx.doi.org/10.1180/minmag.2015.079.7.02

Devitrification of amorphous celecoxib.

PubMed

Gupta, Piyush; Bansal, Arvind K

2005-09-30

The purpose of this research was to analyze the devitrification of amorphous celecoxib (CEL) in the presence of different stressors (temperature, pressure, and/or humidity) encountered during processing of solid dosage forms. Amorphous CEL was prepared in situ in the analytical instruments, as well as in laboratory, by quench-cooling of melt process, and analyzed by dynamic mechanical thermal analysis, differential scanning calorimetry, microscopy, and Fourier-transform infrared spectroscopy. Amorphous CEL prepared in situ in the analytical instruments was resistant to crystallization under the influence of temperature and/or pressure, because of its protection from the external environment during preparation. These samples exhibited structural relaxation during annealing at 25 degrees C/0% relative humidity (RH) for 16 hours. Generation of amorphous CEL in the laboratory resulted in partially crystalline samples, because of exposure to environmental temperature and humidity, resulting in incomplete vitrification. Subjection to thermal stress favored crystallization of amorphous CEL into metastable polymorphic forms, which were not obtained by solvent recrystallization approach. Temperature and humidity were identified as the major factors promoting devitrification of amorphous CEL, leading to loss of solubility advantage. Exposure to International Conference on Harmonization-specified accelerated stability storage conditions (40 degrees C/75% RH) resulted in complete devitrification of amorphous CEL within 15 days. The phase-transformation process of amorphous CEL along the temperature scale was examined visually, as well as spectrally. This propensity for devitrification of amorphous CEL seemed to depend on the strength of differential molecular interactions between the amorphous and crystalline form.

Spectral Properties of Gas-phase Condensed Fullerene-like Carbon Nanoparticles from Far-ultraviolet to Infrared Wavelengths

NASA Astrophysics Data System (ADS)

Jäger, C.; Mutschke, H.; Henning, Th.; Huisken, F.

2008-12-01

Carbon solids are ubiquitous material in interstellar space. However, the formation pathway of carbonaceous matter in astrophysical environments, as well as in terrestrial gas-phase condensation reactions, is not yet understood. Laser ablation of graphite in different quenching gas atmospheres, such as pure He, He/H2, and He/H2O at varying pressures, is used to synthesize very small, fullerene-like carbon nanoparticles. The particles are characterized by very small diameters between 1 and 4 nm and a disturbed onion-like structure. The soot particles extracted from the condensation zone obviously represent a very early stage of particle condensation. The spectral properties have been measured from the far-ultraviolet (FUV; λ = 120 nm) to the mid-infrared (MIR; λ = 15 μm). The seedlike soot particles show strong absorption bands in the 3.4 μm range. The profile and the intensity pattern of the 3.4 μm band of the diffuse interstellar medium can be well reproduced by the measured 3.4 μm profile of the condensed particles; however, all the carbon which is left to form solids is needed to fit the intensity of the interstellar bands. In contrast to the assumption that onion-like soot particles could be the carriers of the interstellar ultraviolet (UV) bump, our very small onion-like carbon nanoparticles do not show distinct UV bands due to (π-π*) transitions.

Composition and structure of acid leached LiMn 2-yTi yO 4 (0.2≤ y≤1.5) spinels

NASA Astrophysics Data System (ADS)

Avdeev, Georgi; Amarilla, José Manuel; Rojo, José María; Petrov, Kostadin; Rojas, Rosa María

2009-12-01

Lithium manganese titanium spinels, LiMn 2-yTi yO 4, (0.2≤ y≤1.5) have been synthesized by solid-state reaction between TiO 2 (anatase), Li 2CO 3 and MnCO 3. Li + was leached from the powdered reaction products by treatment in excess of 0.2 N HCl at 85 °C for 6 h, under reflux. The elemental composition of the acidic solution and solid residues of leaching has been determined by complexometric titration, atomic absorption spectroscopy and X-ray fluorescence analysis. Powder X-ray diffraction was used for structural characterization of the crystalline fraction of the solid residues. It has been found that the amount of Li + leached from LiMn 2-yTi yO 4 decreases monotonically with increasing y in the interval 0.2≤ y≤1.0 and abruptly drops to negligibly small values for y>1.0. The content of Mn and Li in the liquid phase and of Mn and Ti in the solid (amorphous plus crystalline) residue, were related to the composition and cation distribution in the pristine compounds. A new formal chemical equation describing the process of leaching and a mechanism of the structural transformation undergone by the initial solids as a result of Li + removal has been proposed.

Thin film silicon by a microwave plasma deposition technique: Growth and devices, and, interface effects in amorphous silicon/crystalline silicon solar cells

NASA Astrophysics Data System (ADS)

Jagannathan, Basanth

Thin film silicon (Si) was deposited by a microwave plasma CVD technique, employing double dilution of silane, for the growth of low hydrogen content Si films with a controllable microstructure on amorphous substrates at low temperatures (<400sp°C). The double dilution was achieved by using a Ar (He) carrier for silane and its subsequent dilution by Hsb2. Structural and electrical properties of the films have been investigated over a wide growth space (temperature, power, pressure and dilution). Amorphous Si films deposited by silane diluted in He showed a compact nature and a hydrogen content of ˜8 at.% with a photo/dark conductivity ratio of 10sp4. Thin film transistors (W/L = 500/25) fabricated on these films, showed an on/off ratio of ˜10sp6 and a low threshold voltage of 2.92 volts. Microcrystalline Si films with a high crystalline content (˜80%) were also prepared by this technique. Such films showed a dark conductivity ˜10sp{-6} S/cm, with a conduction activation energy of 0.49 eV. Film growth and properties have been compared for deposition in Ar and He carrier systems and growth models have been proposed. Low temperature junction formation by undoped thin film silicon was examined through a thin film silicon/p-type crystalline silicon heterojunctions. The thin film silicon layers were deposited by rf glow discharge, dc magnetron sputtering and microwave plasma CVD. The hetero-interface was identified by current transport analysis and high frequency capacitance methods as the key parameter controlling the photovoltaic (PV) response. The effect of the interface on the device properties (PV, junction, and carrier transport) was examined with respect to modifications created by chemical treatment, type of plasma species, their energy and film microstructure interacting with the substrate. Thermally stimulated capacitance was used to determine the interfacial trap parameters. Plasma deposition of thin film silicon on chemically clean c-Si created electron trapping sites while hole traps were seen when a thin oxide was present at the interface. Under optimized conditions, a 10.6% efficient cell (11.5% with SiOsb2 A/R) with an open circuit voltage of 0.55 volts and a short circuit current density of 30 mA/cmsp2 was fabricated.

Physicochemical and Pharmacokinetic Characterization of Amorphous Solid Dispersion of Meloxicam with Enhanced Dissolution Property and Storage Stability.

PubMed

Ochi, Masanori; Kimura, Keisuke; Kanda, Atsushi; Kawachi, Takaki; Matsuda, Akitoshi; Yuminoki, Kayo; Hashimoto, Naofumi

2016-08-01

The aim of the present study was to develop amorphous solid dispersion (ASD) of meloxicam (MEL) for providing rapid onset of action. ASDs of MEL with polyvinylpyrrolidone (PVP) K-30 (MEL/PVP), HPC-SSL (MEL/HPC), and Eudragit EPO (MEL/EPO) were prepared. The physicochemical properties were characterized by focusing on morphology, crystallinity, dissolution properties, stability, and the interaction of MEL with coexisting polymers. MEL/EPO was physicochemically stable after storage at 40°C/75% RH for 30 days. In contrast, recrystallization of MEL was observed in MEL/PVP and MEL/HPC at 40°C/50% RH for 30 days. Infrared spectroscopic studies and (1)H NMR analyses of MEL/EPO revealed that Eudragit EPO interacted with MEL and reduced intermolecular binding between MEL molecules. Intermolecular interaction of drug molecules is necessary for the formation of crystalline. Thus, the interaction of MEL with Eudragit EPO and interruption of the formation of supramolecular interaction between MEL molecules might lead to the inhibition of crystal growth of MEL. Of all the MEL solid dispersions prepared, MEL/EPO showed the largest improvement in dissolution behavior. Oral administration of MEL/EPO to rats showed rapid and enhanced MEL exposure with a 2.4-fold increase in bioavailability compared with crystalline MEL. Based on these findings, MEL/EPO was physicochemically stable and provided a rapid onset of action and enhanced bioavailability after oral administration.

Magnetic coupling between liquid 3He and a solid state substrate: a new approach

NASA Astrophysics Data System (ADS)

Klochkov, Alexander V.; Naletov, Vladimir V.; Tayurskii, Dmitrii A.; Tagirov, Murat S.; Suzuki, Haruhiko

2000-07-01

We suggest a new approach for solving the long-standing problem of a magnetic coupling between liquid 3He and a solid state substrate at temperatures above the Fermi temperature. The approach is based on our previous careful investigations of the physical state of a solid substrate by means of several experimental methods (EPR, NMR, conductometry, and magnetization measurements). The developed approach allows, first, to get more detailed information about the magnetic coupling phenomenon by varying the repetition time in pulse NMR investigations of liquid 3He in contact with the solid state substrate and, second, to compare the obtained dependences and the data of NMR-cryoporometry and AFM-microscopy.

A quantitative link between microplastic instability and macroscopic deformation behaviors in metallic glasses

NASA Astrophysics Data System (ADS)

Wu, Y.; Chen, G. L.; Hui, X. D.; Liu, C. T.; Lin, Y.; Shang, X. C.; Lu, Z. P.

2009-10-01

Based on mechanical instability of individual shear transformation zones (STZs), a quantitative link between the microplastic instability and macroscopic deformation behavior of metallic glasses was proposed. Our analysis confirms that macroscopic metallic glasses comprise a statistical distribution of STZ embryos with distributed values of activation energy, and the microplastic instability of all the individual STZs dictates the macroscopic deformation behavior of amorphous solids. The statistical model presented in this paper can successfully reproduce the macroscopic stress-strain curves determined experimentally and readily be used to predict strain-rate effects on the macroscopic responses with the availability of the material parameters at a certain strain rate, which offer new insights into understanding the actual deformation mechanism in amorphous solids.

Elastic moduli in nano-size samples of amorphous solids: System size dependence

NASA Astrophysics Data System (ADS)

Cohen, Yossi; Procaccia, Itamar

2012-08-01

This letter is motivated by some recent experiments on pan-cake-shaped nano-samples of metallic glass that indicate a decline in the measured shear modulus upon decreasing the sample radius. Similar measurements on crystalline samples of the same dimensions showed a much more modest change. In this letter we offer a theory of this phenomenon; we argue that such results are generically expected for any amorphous solid, with the main effect being related to the increased contribution of surfaces with respect to the bulk when the samples get smaller. We employ exact relations between the shear modulus and the eigenvalues of the system's Hessian matrix to explore the role of surface modes in affecting the elastic moduli.

New Optical Constants for Amorphous and Crystalline H2O-ice and H2O-mixtures.

NASA Technical Reports Server (NTRS)

Mastrapa, Rachel; Bernstein, Max; Sandford, Scott

2006-01-01

We will present the products of new laboratory measurements of ices relevant to Trans-Neptunian Objects. We have calculated the real and imaginary indices of refraction for amorphous and crystalline H2O-ice and also H2O-rich ices containing other molecular species. We create ice samples by condensing gases onto a cold substrate. We measure the thickness of the sample by reflecting a He-Ne laser off of the sample and counting interference fringes as it grows. We then collect transmission spectra of the samples in the wavelength range from 0.7-22 micrometers. Using the thickness and the transmission spectra of the ice we calculate the imaginary part of the index of refraction. We then use a Kramers-Kronig calculation to calculate the real part of the index of refraction (Berland et al. 1994; Hudgins et al. 1993). These optical constants can then be used to create model spectra for comparison to spectra from Solar System objects, including TNOs. We will summarize the difference between the amorphous and crystalline H2O-ice spectra. These changes include weakening of features and shifting of features to shorter wavelength. One important result is that the 2 pm feature is stronger in amorphous H2O ice than it is in crystalline H2O-ice. We will also discuss the changes seen when H2O is mixed with other components, including CO2, CH4, HCN, and NH3 (Bernstein et al. 2005; Bernstein et al. 2006).

A green emissive amorphous fac-Alq3 solid generated by grinding crystalline blue fac-Alq3 powder.

PubMed

Bi, Hai; Chen, Dong; Li, Di; Yuan, Yang; Xia, Dandan; Zhang, Zuolun; Zhang, Hongyu; Wang, Yue

2011-04-14

A novel green emissive Alq(3) solid with a facial isomeric form has been obtained by grinding the typical blue luminescent fac-Alq(3) crystalline powder. This is the first report, to the best of our knowledge, that a fac-Alq(3) isomer emits green light.

Core-shell silicon nanowire solar cells

PubMed Central

Adachi, M. M.; Anantram, M. P.; Karim, K. S.

2013-01-01

Silicon nanowires can enhance broadband optical absorption and reduce radial carrier collection distances in solar cell devices. Arrays of disordered nanowires grown by vapor-liquid-solid method are attractive because they can be grown on low-cost substrates such as glass, and are large area compatible. Here, we experimentally demonstrate that an array of disordered silicon nanowires surrounded by a thin transparent conductive oxide has both low diffuse and specular reflection with total values as low as < 4% over a broad wavelength range of 400 nm < λ < 650 nm. These anti-reflective properties together with enhanced infrared absorption in the core-shell nanowire facilitates enhancement in external quantum efficiency using two different active shell materials: amorphous silicon and nanocrystalline silicon. As a result, the core-shell nanowire device exhibits a short-circuit current enhancement of 15% with an amorphous Si shell and 26% with a nanocrystalline Si shell compared to their corresponding planar devices. PMID:23529071

Measurement of the adsorption energy difference between ortho- and para-D2 on an amorphous ice surface.

PubMed

Amiaud, L; Momeni, A; Dulieu, F; Fillion, J H; Matar, E; Lemaire, J-L

2008-02-08

Molecular hydrogen interaction on water ice surfaces is a major process taking place in interstellar dense clouds. By coupling laser detection and classical thermal desorption spectroscopy, it is possible to study the effect of rotation of D(2) on adsorption on amorphous solid water ice surfaces. The desorption profiles of ortho- and para-D(2) are different. This difference is due to a shift in the adsorption energy distribution of the two lowest rotational states. Molecules in J''=1 rotational state are on average more strongly bound to the ice surface than those in J''=0 rotational state. This energy difference is estimated to be 1.4+/-0.3 meV. This value is in agreement with previous calculation and interpretation. The nonspherical wave function J'' =1 has an interaction with the asymmetric part of the adsorption potential and contributes positively in the binding energy.

Supercritical antisolvent versus coevaporation: preparation and characterization of solid dispersions.

PubMed

Majerik, Viktor; Horváth, Géza; Szokonya, László; Charbit, Gérard; Badens, Elisabeth; Bosc, Nathalie; Teillaud, Eric

2007-09-01

The objective of this work was to improve the dissolution rate and aqueous solubility of oxeglitazar. Solid dispersions of oxeglitazar in PVP K17 (polyvinilpyrrolidone) and poloxamer 407 (polyoxyethylene-polyoxypropylene block copolymer) were prepared by supercritical antisolvent (SAS) and coevaporation (CoE) methods. Drug-carrier formulations were characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, gas chromatography, UV/VIS spectroscopy and in vitro dissolution tests. The highest dissolution rate (nearly 3-fold higher than raw drug) was achieved by preparation of drug/PVP K17 coevaporate. Oxeglitazar/PVP K17 solid dispersions were stabilized by hydrogen bonding but contained higher amount of residual dichloromethane (DCM) than poloxamer 407 formulations regardless of the method of preparation. SAS prepared oxeglitazar/poloxamer 407 dissolved more than two times faster than raw drug. However, unlike PVP K17, poloxamer 407 did not form a single phase amorphous solid solution with oxeglitazar which has been manifested in higher degrees of crystallinity, too. Among the two techniques, evaluated in this work, conventional coevaporation resulted in higher amorphous content but SAS reduced residual solvent content more efficiently.

Observation of the spiral flow and vortex induced by a suction pump in superfluid 4He

NASA Astrophysics Data System (ADS)

Yano, H.; Ohyama, K.; Obara, K.; Ishikawa, O.

2018-03-01

A suction flow generates a whirlpool, namely a bathtub vortex, in a classical fluid; in contrast, rotating containers, which are usually used for studies of superfluid helium, can produce only simple solid rotation. In the present work, the superfluid flow and concentrated quantized vortices induced by a cryogenic motor immersed in superfluid 4He were investigated. Using a motor with six blades in a cylinder caused the free surface of the superfluid 4He to take on a parabolic shape, indicating that the motor produces a rotating superfluid flow. To drive a suction flow in superfluid helium, the motor was mounted in a cylindrical container with a small hole at the center of the top and a slit at the side, acting as a superfluid pump. This pump was successfully used to generate a spiral flow and a vortex with a funnel-shaped core in superfluid 4He, suggesting that the resulting suction flow transports and centralizes quantized vortices to the suction hole, increasing the vortex circulation and sucking the free surface of the superfluid down.

In Situ and Ex Situ TEM Study of Lithiation Behaviours of Porous Silicon Nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Chenfei; Ge, Mingyuan; Luo, Langli

In this work, we study the lithiation behaviours of both porous silicon (Si) nanoparticles and porous Si nanowires by in situ and ex situ transmission electron microscopy (TEM) and compare them with solid Si nanoparticles and nanowires. The in situ TEM observation reveals that the critical fracture diameter of porous Si particles reaches up to 1.52 μm, which is much larger than the previously reported 150 nm for crystalline Si nanoparticles and 870 nm for amorphous Si nanoparticles. After full lithiation, solid Si nanoparticles and nanowires transform to crystalline Li15Si4 phase while porous Si nanoparticles and nanowires transform to amorphousmore » LixSi phase, which is due to the effect of domain size on the stability of Li15Si4 as revealed by the first-principle molecular dynamic simulation. Ex situ TEM characterization is conducted to further investigate the structural evolution of porous and solid Si nanoparticles during the cycling process, which confirms that the porous Si nanoparticles exhibit better capability to suppress pore evolution than solid Si nanoparticles. The investigation of structural evolution and phase transition of porous Si nanoparticles and nanowires during the lithiation process reveal that they are more desirable as lithium-ion battery anode materials than solid Si nanoparticles and nanowires.« less

Proceedings of the Symposium on Fluid-Solid Surface Intractions (2nd) Held at the Naval Ship Research and Development Center, Bethesda, Maryland, June 5-7, 1974,

DTIC Science & Technology

1974-11-29

6 . It is reasonable to define 0.01 < C/ 6 ( 4 ) as a boundary to the slip flow regime...stress layer. The result is 7 Z (2- aE RE 100 (42)7 2-a £1 + 7 • 1 6 aE The parameter 6 /Z is the same as that given in section 4 . Again, values below...Selective adsorption data for "He on clean NaF. After Meyers et alE., reference 30. A B 4 4 He (80K) Ho o NoFL 2wr - 6.07 -’ N = 6 . 7 K- F 1.9 2 A Kx (-) 4

Surfactant-Free Solid Dispersions of Hydrophobic Drugs in an Amorphous Sugar Matrix Dried from an Organic Solvent.

PubMed

Takeda, Koji; Gotoda, Yuto; Hirota, Daichi; Hidaka, Fumihiro; Sato, Tomo; Matsuura, Tsutashi; Imanaka, Hiroyuki; Ishida, Naoyuki; Imamura, Koreyoshi

2017-03-06

The technique for homogeneously dispersing hydrophobic drugs in a water-soluble solid matrix (solid dispersion) is a subject that has been extensively investigated in the pharmaceutical industry. Herein, a novel technique for dispersing a solid, without the need to use a surfactant, is reported. A freeze-dried amorphous sugar sample was dissolved in an organic solvent, which contained a soluble model hydrophobic component. The suspension of the sugar and the model hydrophobic component was vacuum foam dried to give a solid powder. Four types of sugars and methanol were used as representative sugars and the organic medium. Four model drugs (indomethacin, ibuprofen, gliclazide, and nifedipine) were employed. Differential scanning calorimetry analyses indicated that the sugar and model drug (100:1) did not undergo segregation during the drying process. The dissolution of the hydrophobic drugs in water from the solid dispersion was then evaluated, and the results indicated that the C max and AUC 0-60 min of the hydrophobic drug in water were increased when the surfactant-free solid dispersion was used. Palatinose and/or α-maltose were superior to the other tested carbohydrates in increasing C max and AUC 0-60 min for all tested model drugs, and the model drug with a lower water solubility tended to exhibit a greater extent of over-dissolution.

Investigating Sodium Storage Mechanisms in Tin Anodes: A Combined Pair Distribution Function Analysis, Density Functional Theory, and Solid-State NMR Approach.

PubMed

Stratford, Joshua M; Mayo, Martin; Allan, Phoebe K; Pecher, Oliver; Borkiewicz, Olaf J; Wiaderek, Kamila M; Chapman, Karena W; Pickard, Chris J; Morris, Andrew J; Grey, Clare P

2017-05-31

The alloying mechanism of high-capacity tin anodes for sodium-ion batteries is investigated using a combined theoretical and experimental approach. Ab initio random structure searching (AIRSS) and high-throughput screening using a species-swap method provide insights into a range of possible sodium-tin structures. These structures are linked to experiments using both average and local structure probes in the form of operando pair distribution function analysis, X-ray diffraction, and 23 Na solid-state nuclear magnetic resonance (ssNMR), along with ex situ 119 Sn ssNMR. Through this approach, we propose structures for the previously unidentified crystalline and amorphous intermediates. The first electrochemical process of sodium insertion into tin results in the conversion of crystalline tin into a layered structure consisting of mixed Na/Sn occupancy sites intercalated between planar hexagonal layers of Sn atoms (approximate stoichiometry NaSn 3 ). Following this, NaSn 2 , which is predicted to be thermodynamically stable by AIRSS, forms; this contains hexagonal layers closely related to NaSn 3 , but has no tin atoms between the layers. NaSn 2 is broken down into an amorphous phase of approximate composition Na 1.2 Sn. Reverse Monte Carlo refinements of an ab initio molecular dynamics model of this phase show that the predominant tin connectivity is chains. Further reaction with sodium results in the formation of structures containing Sn-Sn dumbbells, which interconvert through a solid-solution mechanism. These structures are based upon Na 5-x Sn 2 , with increasing occupancy of one of its sodium sites commensurate with the amount of sodium added. ssNMR results indicate that the final product, Na 15 Sn 4 , can store additional sodium atoms as an off-stoichiometry compound (Na 15+x Sn 4 ) in a manner similar to Li 15 Si 4 .

Investigating Sodium Storage Mechanisms in Tin Anodes: A Combined Pair Distribution Function Analysis, Density Functional Theory, and Solid-State NMR Approach

DOE PAGES

Stratford, Joshua M.; Mayo, Martin; Allan, Phoebe K.; ...

2017-05-04

Here, the alloying mechanism of high-capacity tin anodes for sodium-ion batteries is investigated using a combined theoretical and experimental approach. Ab initio random structure searching (AIRSS) and high-throughput screening using a species-swap method provide insights into a range of possible sodium–tin structures. These structures are linked to experiments using both average and local structure probes in the form of operando pair distribution function analysis, X-ray diffraction, and 23Na solid-state nuclear magnetic resonance (ssNMR), along with ex situ 119Sn ssNMR. Through this approach, we propose structures for the previously unidentified crystalline and amorphous intermediates. The first electrochemical process of sodium insertionmore » into tin results in the conversion of crystalline tin into a layered structure consisting of mixed Na/Sn occupancy sites intercalated between planar hexagonal layers of Sn atoms (approximate stoichiometry NaSn 3). Following this, NaSn 2, which is predicted to be thermodynamically stable by AIRSS, forms; this contains hexagonal layers closely related to NaSn 3, but has no tin atoms between the layers. NaSn 2 is broken down into an amorphous phase of approximate composition Na 1.2Sn. Reverse Monte Carlo refinements of an ab initio molecular dynamics model of this phase show that the predominant tin connectivity is chains. Further reaction with sodium results in the formation of structures containing Sn–Sn dumbbells, which interconvert through a solid-solution mechanism. These structures are based upon Na 5–xSn 2, with increasing occupancy of one of its sodium sites commensurate with the amount of sodium added. ssNMR results indicate that the final product, Na 15Sn 4, can store additional sodium atoms as an off-stoichiometry compound (Na 15+xSn 4) in a manner similar to Li 15Si 4.« less

Investigating Sodium Storage Mechanisms in Tin Anodes: A Combined Pair Distribution Function Analysis, Density Functional Theory, and Solid-State NMR Approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stratford, Joshua M.; Mayo, Martin; Allan, Phoebe K.

Here, the alloying mechanism of high-capacity tin anodes for sodium-ion batteries is investigated using a combined theoretical and experimental approach. Ab initio random structure searching (AIRSS) and high-throughput screening using a species-swap method provide insights into a range of possible sodium–tin structures. These structures are linked to experiments using both average and local structure probes in the form of operando pair distribution function analysis, X-ray diffraction, and 23Na solid-state nuclear magnetic resonance (ssNMR), along with ex situ 119Sn ssNMR. Through this approach, we propose structures for the previously unidentified crystalline and amorphous intermediates. The first electrochemical process of sodium insertionmore » into tin results in the conversion of crystalline tin into a layered structure consisting of mixed Na/Sn occupancy sites intercalated between planar hexagonal layers of Sn atoms (approximate stoichiometry NaSn 3). Following this, NaSn 2, which is predicted to be thermodynamically stable by AIRSS, forms; this contains hexagonal layers closely related to NaSn 3, but has no tin atoms between the layers. NaSn 2 is broken down into an amorphous phase of approximate composition Na 1.2Sn. Reverse Monte Carlo refinements of an ab initio molecular dynamics model of this phase show that the predominant tin connectivity is chains. Further reaction with sodium results in the formation of structures containing Sn–Sn dumbbells, which interconvert through a solid-solution mechanism. These structures are based upon Na 5–xSn 2, with increasing occupancy of one of its sodium sites commensurate with the amount of sodium added. ssNMR results indicate that the final product, Na 15Sn 4, can store additional sodium atoms as an off-stoichiometry compound (Na 15+xSn 4) in a manner similar to Li 15Si 4.« less

FIRST INFRARED BAND STRENGTHS FOR AMORPHOUS CO{sub 2}, AN OVERLOOKED COMPONENT OF INTERSTELLAR ICES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gerakines, Perry A.; Hudson, Reggie L., E-mail: Reggie.Hudson@NASA.gov

2015-08-01

Solid carbon dioxide (CO{sub 2}) has long been recognized as a component of both interstellar and solar system ices, but a recent literature search has revealed significant qualitative and quantitative discrepancies in the laboratory spectra on which the abundances of extraterrestrial CO{sub 2} are based. Here we report new infrared (IR) spectra of amorphous CO{sub 2}-ice along with band intensities (band strengths) of four mid-IR absorptions, the first such results in the literature. A possible thickness dependence for amorphous-CO{sub 2} IR band shapes and positions also is investigated, and the three discordant reports of amorphous CO{sub 2} spectra in themore » literature are addressed. Applications of our results are discussed with an emphasis on laboratory investigations and results from astronomical observations. A careful comparison with earlier work shows that the IR spectra calculated from several databases for CO{sub 2} ices, all ices being made near 10 K, are not for amorphous CO{sub 2}, but rather for crystalline CO{sub 2} or crystalline-amorphous mixtures.« less

An investigation of voids formation mechanisms and their effects on freeze and thaw processes of lithium and lithium fluoride

NASA Technical Reports Server (NTRS)

El-Genk, Mohamed S.; Yang, Jae-Young

1991-01-01

The mechanisms of void formation during the cooldown and freezing of lithium coolant within the primary loop of SP-100 type systems are investigated. These mechanisms are: (1) homogeneous nucleation; (2) heterogeneous nucleation; (3) normal segregation of helium gas dissolved in liquid lithium; and (4) shrinkage of lithium during freezing. To evaluate the void formation potential due to segregation, a numerical scheme that couples the freezing and mass diffusion processes in both the solid and liquid regions is developed. The results indicated that the formation of He bubbles is unlikely by either homogeneous or heterogeneous nucleation during the cooldown process. However, homogeneous nucleation of He bubbles following the segregation of dissolved He in liquid lithium ahead of the solid-liquid interface is likely to occur. Results also show that total volume of He void is insignificant when compared to that of shrinkage voids. In viewing this, the subsequent research focuses on the effects of shrinkage void forming during freezing of lithium on subsequent thaw processes are investigated using a numerical scheme that is based on a single (solid/liquid) cell approach. The cases of lithium-fluoride are also investigated to show the effect of larger volume shrinkage upon freezing on the freeze and thaw processes. Results show that a void forming at the wall appreciably reduces the solid-liquid interface velocity, during both freeze and thaw, and causes a substantial rise in the wall temperature during thaw. However, in the case of Li, the maximum wall temperature was much lower than the melting temperature of PWC-11, which is used as the structure material in the SP-100 system. Hence, it is included that a formation of hot spots is unlikely during the startup or restart of the SP-100 system.

Atomic Layer Deposition of the Solid Electrolyte LiPON

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kozen, Alexander C.; Pearse, Alexander J.; Lin, Chuan -Fu

We demonstrate an atomic layer deposition (ALD) process for the solid electrolyte lithium phosphorousoxynitride (LiPON) using lithium tert-butoxide (LiO tBu), H 2O, trimethylphosphate (TMP), and plasma N 2 ( PN 2) as precursors. We use in-situ spectroscopic ellipsometry to determine growth rates for process optimization to design a rational, quaternary precursor ALD process where only certain substrate–precursor chemical reactions are favorable. We demonstrate via in-situ XPS tunable nitrogen incorporation into the films by variation of the PN 2 dose and find that ALD films over approximately 4.5% nitrogen are amorphous, whereas LiPON ALD films with less than 4.5% nitrogen aremore » polycrystalline. Lastly, we characterize the ionic conductivity of the ALD films as a function of nitrogen content and demonstrate their functionality on a model battery electrode—a Si anode on a Cu current collector.« less

Atomic Layer Deposition of the Solid Electrolyte LiPON

DOE PAGES

Kozen, Alexander C.; Pearse, Alexander J.; Lin, Chuan -Fu; ...

2015-07-09

We demonstrate an atomic layer deposition (ALD) process for the solid electrolyte lithium phosphorousoxynitride (LiPON) using lithium tert-butoxide (LiO tBu), H 2O, trimethylphosphate (TMP), and plasma N 2 ( PN 2) as precursors. We use in-situ spectroscopic ellipsometry to determine growth rates for process optimization to design a rational, quaternary precursor ALD process where only certain substrate–precursor chemical reactions are favorable. We demonstrate via in-situ XPS tunable nitrogen incorporation into the films by variation of the PN 2 dose and find that ALD films over approximately 4.5% nitrogen are amorphous, whereas LiPON ALD films with less than 4.5% nitrogen aremore » polycrystalline. Lastly, we characterize the ionic conductivity of the ALD films as a function of nitrogen content and demonstrate their functionality on a model battery electrode—a Si anode on a Cu current collector.« less

Quantitative crystallinity determination for E1010, a novel carbapenem antibiotic, using differential scanning calorimetry.

PubMed

Kushida, Ikuo

2012-03-01

The objective of this study was to develop a quantitative crystallinity analysis method for the bulk drug of E1010 ((+)-(4R,5S,6S)-6-[(R)-1-hydroxyethyl]-3-[(2S,4S)-2-[(R)-1-hydroxy-1-[(R)-pyrrolidin-3 -yl]methyl]pyrrolidin-4-yl]thio-4-methyl-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid monohydrochloride), a novel carbapenem antibiotic. X-ray analyses, thermal analyses and hygroscopicity measurements were used to elucidate the crystal structure and the solid state properties. To develop a quantitative method for the crystallinity of E1010 bulk drug, the relationship between enthalpy change obtained by differential scanning calorimetry (DSC) and crystalline form ratio was investigated. E1010 bulk drug was found to exist in a crystalline trihydrate formed in two layers, i.e. a layer of E1010 free form, and a layer consisting of chloride ions and water molecules. The thermal analysis showed an endothermic peak derived from dehydration with the loss of crystal lattices at around 100°C as an onset. The enthalpy change value for the endothermic peak correlated well with crystalline content in binary physical mixtures of the crystalline trihydrate and the amorphous form. In addition, for nine lots of the bulk drug, a positive correlation between the enthalpy change and chemical stability in the solid state was observed. This quantitative analysis of crystallinity using DSC could be applicable for the quality control of the bulk drug to detect variability among manufacturing batches and to estimate the chemical stability of partially amorphous samples. © 2011 The Author. JPP © 2011 Royal Pharmaceutical Society.

Structural transformations of 3-fluoro and 3-fluoro-4-methoxy benzaldehydes under cryogenic conditions: A computational and low temperature infrared spectroscopy investigation

NASA Astrophysics Data System (ADS)

Ogruc Ildiz, G.; Konarska, J.; Fausto, R.

2018-05-01

Structural transformations of 3-fluorobenzaldehyde (C7H5FO; 3FBA) and 3-fluoro-4-methoxybenzaldehyde (C8H7FO2; 3F4MBA), taking place in different solid phase environments and at low temperature, were investigated by infrared spectroscopy, complemented by quantum chemistry calculations undertaken at the DFT(B3LYP)/6-311++G(d,p) level of approximation. The studied compounds were isolated from gas phase into cryogenic inert matrices (Ar, Xe), allowing to characterize their equilibrium conformational composition in gas-phase at room temperature. In both cases, two conformers differing by the orientation of the aldehyde moiety (with the carbonyl aldehyde bond cis or trans in relation to the aromatic ring fluorine substituent) were found to coexist, with the cis conformer being slightly more populated than the trans form. In situ narrowband UV irradiation of the as-deposited matrices led either to preferential isomerization of the cis conformer into the trans form or decarbonylation of both conformers, depending on the used excitation wavelength. Deposition of the vapours of 3F4MBA only, onto the cold (15 K) substrate, produced an amorphous solid containing also both the cis and trans conformers of the compound. Subsequent heating of the amorphous phase up to 268 K led to crystallization of the compound, which is accompanied by conformational selection, the cis form being the single species present in the crystal. The experimentally observed transformations of the studied compounds, together with the structural and vibrational results obtained from the performed quantum chemical calculations, allowed a detailed structural and vibrational characterization of the individual conformers.

Acid-Base Interactions of Polystyrene Sulfonic Acid in Amorphous Solid Dispersions Using a Combined UV/FTIR/XPS/ssNMR Study.

PubMed

Song, Yang; Zemlyanov, Dmitry; Chen, Xin; Nie, Haichen; Su, Ziyang; Fang, Ke; Yang, Xinghao; Smith, Daniel; Byrn, Stephen; Lubach, Joseph W

2016-02-01

This study investigates the potential drug-excipient interactions of polystyrene sulfonic acid (PSSA) and two weakly basic anticancer drugs, lapatinib (LB) and gefitinib (GB), in amorphous solid dispersions. Based on the strong acidity of the sulfonic acid functional group, PSSA was hypothesized to exhibit specific intermolecular acid-base interactions with both model basic drugs. Ultraviolet (UV) spectroscopy identified red shifts, which correlated well with the color change observed in lapatinib-PSSA solutions. Fourier transform infrared (FTIR) spectra suggest the protonation of the quinazoline nitrogen atom in both model compounds, which agrees well with data from the crystalline ditosylate salt of lapatinib. X-ray photoelectron spectroscopy (XPS) detected increases in binding energy of the basic nitrogen atoms in both lapatinib and gefitinib, strongly indicating protonation of these nitrogen atoms. (15)N solid-state NMR spectroscopy provided direct spectroscopic evidence for protonation of the quinazoline nitrogen atoms in both LB and GB, as well as the secondary amine nitrogen atom in LB and the tertiary amine nitrogen atom in GB. The observed chemical shifts in the LB-PSSA (15)N spectrum also agree very well with the lapatinib ditosylate salt where proton transfer is known. Additionally, the dissolution and physical stability behaviors of both amorphous solid dispersions were examined. PSSA was found to significantly improve the dissolution of LB and GB and effectively inhibit the crystallization of LB and GB under accelerated storage conditions due to the beneficial strong intermolecular acid-base interaction between the sulfonic acid groups and basic nitrogen centers.

Amorphous Solid Dispersion of Epigallocatechin Gallate for Enhanced Physical Stability and Controlled Release.

PubMed

Cao, Yizheng; Teng, Jing; Selbo, Jon

2017-11-09

Epigallocatechin gallate (EGCG) has been recognized as the most prominent green tea extract due to its healthy influences. The high instability and low bioavailability, however, strongly limit its utilization in food and drug industries. This work, for the first time, develops amorphous solid dispersion of EGCG to enhance its bioavailability and physical stability. Four commonly used polymeric excipients are found to be compatible with EGCG in water-dioxane mixtures via a stepwise mixing method aided by vigorous mechanical interference. The dispersions are successfully generated by lyophilization. The physical stability of the dispersions is significantly improved compared to pure amorphous EGCG in stress condition (elevated temperature and relative humidity) and simulated gastrointestinal tract environment. From the drug release tests, one of the dispersions, EGCG-Soluplus ® 50:50 ( w / w ) shows a dissolution profile that only 50% EGCG is released in the first 20 min, and the remains are slowly released in 24 h. This sustained release profile may open up new possibilities to increase EGCG bioavailability via extending its elimination time in plasma.

Phase field crystal simulation of stress induced localized solid-state amorphization in nanocrystalline materials

NASA Astrophysics Data System (ADS)

Xi, Wen; Song, Xiaoqing; Hu, Shi; Chen, Zheng

2017-11-01

In this work, the phase field crystal (PFC) method is used to study the localized solid-state amorphization (SSA) and its dynamic transformation process in polycrystalline materials under the uniaxial tensile deformation with different factors. The impacts of these factors, including strain rates, temperatures and grain sizes, are analyzed. Kinetically, the ultra-high strain rate causes the lattice to be seriously distorted and the grain to gradually collapse, so the dislocation density rises remarkably. Therefore, localized SSA occurs. Thermodynamically, as high temperature increases the activation energy, the atoms are active and prefer to leave the original position, which induce atom rearrangement. Furthermore, small grain size increases the percentage of grain boundary and the interface free energy of the system. As a result, Helmholtz free energy increases. The dislocations and Helmholtz free energy act as the seed and driving force for the process of the localized SSA. Also, the critical diffusion-time step and the percentage of amorphous region areas are calculated. Through this work, the PFC method is proved to be an effective means to study localized SSA under uniaxial tensile deformation.

Phase field crystal simulation of stress induced localized solid-state amorphization in nanocrystalline materials.

PubMed

Xi, Wen; Song, Xiaoqing; Hu, Shi; Chen, Zheng

2017-11-29

In this work, the phase field crystal (PFC) method is used to study the localized solid-state amorphization (SSA) and its dynamic transformation process in polycrystalline materials under the uniaxial tensile deformation with different factors. The impacts of these factors, including strain rates, temperatures and grain sizes, are analyzed. Kinetically, the ultra-high strain rate causes the lattice to be seriously distorted and the grain to gradually collapse, so the dislocation density rises remarkably. Therefore, localized SSA occurs. Thermodynamically, as high temperature increases the activation energy, the atoms are active and prefer to leave the original position, which induce atom rearrangement. Furthermore, small grain size increases the percentage of grain boundary and the interface free energy of the system. As a result, Helmholtz free energy increases. The dislocations and Helmholtz free energy act as the seed and driving force for the process of the localized SSA. Also, the critical diffusion-time step and the percentage of amorphous region areas are calculated. Through this work, the PFC method is proved to be an effective means to study localized SSA under uniaxial tensile deformation.

Relating dynamics of model unentangled, crystallizable polymeric liquids to their local structure

NASA Astrophysics Data System (ADS)

Nguyen, Hong T.; Hoy, Robert S.

We study the liquid-state dynamics of a recently developed, crystallizable bead-spring polymer model. The model possesses a single ground state (NCP, wherein monomers close-pack and chains are nematically aligned) for all finite bending stiffnesses kb, but the solid morphologies formed under cooling vary strongly with kb, varying from NCP to amorphous. We find that systems with kb producing amorphous order are good glass-formers exhibiting the classic Vogel-Fulcher slowdown with decreasing temperature T. In contrast, systems with kb producing crystalline solids exhibit a simpler dynamics when kb is small. Larger kb produce more complex dynamics, but these are associated with the existence of an intermediate nematic liquid rather than glassy slowdown. We relate these differences to local, cluster-level structure measured via TCC analyses. Formation propensities and lifetimes of various clusters (associated with amorphous or crystalline order) vary strongly with kb and T. We relate these differences to those measured by the self-intermediate scattering function and other macroscopic measures of dynamics. Our results should aid in understanding the competition between crystallization and glass-formation in synthetic polymers.

Molecular motions in sucrose-PVP and sucrose-sorbitol dispersions-II. Implications of annealing on secondary relaxations.

PubMed

Bhattacharya, Sisir; Bhardwaj, Sunny P; Suryanarayanan, Raj

2014-10-01

To determine the effect of annealing on the two secondary relaxations in amorphous sucrose and in sucrose solid dispersions. Sucrose was co-lyophilized with either PVP or sorbitol, annealed for different time periods and analyzed by dielectric spectroscopy. In an earlier investigation, we had documented the effect of PVP and sorbitol on the primary and the two secondary relaxations in amorphous sucrose solid dispersions (1). Here we investigated the effect of annealing on local motions, both in amorphous sucrose and in the dispersions. The average relaxation time of the local motion (irrespective of origin) in sucrose, decreased upon annealing. However, the heterogeneity in relaxation time distribution as well as the dielectric strength decreased only for β1- (the slower relaxation) but not for β2-relaxations. The effect of annealing on β2-relaxation times was neutralized by sorbitol while PVP negated the effect of annealing on both β1- and β2-relaxations. An increase in local mobility of sucrose brought about by annealing could be negated with an additive.

Interdiffusion in nanometer-scale multilayers investigated by in situ low-angle x-ray diffraction

NASA Astrophysics Data System (ADS)

Wang, Wei-Hua; Bai, Hai Yang; Zhang, Ming; Zhao, J. H.; Zhang, X. Y.; Wang, W. K.

1999-04-01

An in situ low-angle x-ray diffraction technique is used to investigate interdiffusion phenomena in various metal-metal and metal-amorphous Si nanometer-scale compositionally modulated multilayers (ML's). The temperature-dependent interdiffusivities are obtained by accurately monitoring the decay of the first-order modulation peak as a function of annealing time. Activation enthalpies and preexponential factors for the interdiffusion in the Fe-Ti, Ag-Bi, Fe-Mo, Mo-Si, Ni-Si, Nb-Si, and Ag-Si ML's are determined. Activation enthalpies and preexponential factors for the interdiffusion in the ML's are very small compared with that in amorphous alloys and crystalline solids. The relation between the atomic-size difference and interdiffusion in the ML's are investigated. The observed interdiffusion characteristics are compared with that in amorphous alloys and crystalline α-Zr, α-Ti, and Si. The experimental results suggest that a collective atomic-jumping mechanism govern the interdiffusion in the ML's, the collective proposal involving 8-15 atoms moving between extended nonequilibrium defects by thermal activation. The role of the interdiffusion in the solid-state reaction in the ML's is also discussed.

Amorphous Solid Dispersion of Epigallocatechin Gallate for Enhanced Physical Stability and Controlled Release

PubMed Central

Cao, Yizheng; Teng, Jing; Selbo, Jon

2017-01-01

Epigallocatechin gallate (EGCG) has been recognized as the most prominent green tea extract due to its healthy influences. The high instability and low bioavailability, however, strongly limit its utilization in food and drug industries. This work, for the first time, develops amorphous solid dispersion of EGCG to enhance its bioavailability and physical stability. Four commonly used polymeric excipients are found to be compatible with EGCG in water-dioxane mixtures via a stepwise mixing method aided by vigorous mechanical interference. The dispersions are successfully generated by lyophilization. The physical stability of the dispersions is significantly improved compared to pure amorphous EGCG in stress condition (elevated temperature and relative humidity) and simulated gastrointestinal tract environment. From the drug release tests, one of the dispersions, EGCG-Soluplus® 50:50 (w/w) shows a dissolution profile that only 50% EGCG is released in the first 20 min, and the remains are slowly released in 24 h. This sustained release profile may open up new possibilities to increase EGCG bioavailability via extending its elimination time in plasma. PMID:29120370

The 1.083 micron tunable CW semiconductor laser

NASA Technical Reports Server (NTRS)

Wang, C. S.; Chen, Jan-Shin; Lu, Ken-Gen; Ouyang, Keng

1991-01-01

A tunable CW laser is desired to produce light equivalent to the helium spectral line at 1.08 microns. This laser will serve as an optical pumping source for He-3 and He-4 atoms used in space magnetometers. This light source can be fabricated either as a semiconductor laser diode or a pumped solid state laser. Continuous output power of greater than 10 mW is desired. Semiconductor lasers can be thermally tuned, but must be capable of locking onto the helium resonance lines. Solid state lasers must have efficient pumping sources suitable for space configuration. Additional requirements are as follows: space magnetometer applications will include low mass (less than 0.5 kg), low power consumption (less than 0.75 W), and high stability/reliability for long missions (5-10 years).

Thermodynamically controlled crystallization of glucose pentaacetates from amorphous phase

NASA Astrophysics Data System (ADS)

Wlodarczyk, P.; Hawelek, L.; Hudecki, A.; Wlodarczyk, A.; Kolano-Burian, A.

2016-08-01

The α and β glucose pentaacetates are known sugar derivatives, which can be potentially used as stabilizers of amorphous phase of active ingredients of drugs (API). In the present work, crystallization behavior of equimolar mixture of α and β form in comparison to both pure anomers is revealed. It was shown that despite the same molecular interactions and similar molecular dynamics, crystallization from amorphous phase is significantly suppressed in equimolar mixture. Time dependent X-ray diffraction studies confirmed higher stability of the quenched amorphous equimolar mixture. Its tendency to crystallization is about 10 times lower than for pure anomers. Calorimetric studies revealed that the α and β anomers don't form solid solutions and have eutectic point for xα = 0.625. Suppressed crystallization tendency in the mixture is probably caused by the altered thermodynamics of the system. The factors such as difference of free energy between crystalline and amorphous state or altered configurational entropy are probably responsible for the inhibitory effect.

Disorder-induced amorphization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lam, N.Q.; Okamoto, P.R.; Li, Mo

1997-03-01

Many crystalline materials undergo a crystalline-to-amorphous (c-a) phase transition when subjected to energetic particle irradiation at low temperatures. By focusing on the mean-square static atomic displacement as a generic measure of chemical and topological disorder, we are led quite naturally to a generalized version of the Lindemann melting criterion as a conceptual framework for a unified thermodynamic approach to solid-state amorphizing transformations. In its simplest form, the generalized Lindemann criterion assumes that the sum of the static and dynamic mean-square atomic displacements is constant along the polymorphous melting curve so that c-a transformations can be understood simply as melting ofmore » a critically-disordered crystal at temperatures below the glass transition temperature where the supercooled liquid can persist indefinitely in a configurationally-frozen state. Evidence in support of the generalized Lindemann melting criterion for amorphization is provided by a large variety of experimental observations and by molecular dynamics simulations of heat-induced melting and of defect-induced amorphization of intermetallic compounds.« less

Thermodynamically controlled crystallization of glucose pentaacetates from amorphous phase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wlodarczyk, P., E-mail: patrykw@imn.gliwice.pl; Hawelek, L.; Hudecki, A.

The α and β glucose pentaacetates are known sugar derivatives, which can be potentially used as stabilizers of amorphous phase of active ingredients of drugs (API). In the present work, crystallization behavior of equimolar mixture of α and β form in comparison to both pure anomers is revealed. It was shown that despite the same molecular interactions and similar molecular dynamics, crystallization from amorphous phase is significantly suppressed in equimolar mixture. Time dependent X-ray diffraction studies confirmed higher stability of the quenched amorphous equimolar mixture. Its tendency to crystallization is about 10 times lower than for pure anomers. Calorimetric studiesmore » revealed that the α and β anomers don’t form solid solutions and have eutectic point for x{sub α} = 0.625. Suppressed crystallization tendency in the mixture is probably caused by the altered thermodynamics of the system. The factors such as difference of free energy between crystalline and amorphous state or altered configurational entropy are probably responsible for the inhibitory effect.« less

De-vitrification of nanoscale phase-separated amorphous thin films in the immiscible copper-niobium system

NASA Astrophysics Data System (ADS)

Puthucode, A.; Devaraj, A.; Nag, S.; Bose, S.; Ayyub, P.; Kaufman, M. J.; Banerjee, R.

2014-05-01

Copper and niobium are mutually immiscible in the solid state and exhibit a large positive enthalpy of mixing in the liquid state. Using vapour quenching via magnetron co-sputter deposition, far-from equilibrium amorphous Cu-Nb films have been deposited which exhibit a nanoscale phase separation. Annealing these amorphous films at low temperatures (~200 °C) initiates crystallization via the nucleation and growth of primary nanocrystals of a face-centred cubic Cu-rich phase separated by the amorphous matrix. Interestingly, subsequent annealing at a higher temperature (>300 °C) leads to the polymorphic nucleation and growth of large spherulitic grains of a body-centred cubic Nb-rich phase within the retained amorphous matrix of the partially crystallized film. This sequential two-stage crystallization process has been investigated in detail by combining transmission electron microscopy [TEM] (including high-resolution TEM) and atom probe tomography studies. These results provide new insights into the crystallization behaviour of such unusual far-from equilibrium phase-separated metallic glasses in immiscible systems.

Solid phase studies and geochemical modelling of low-cost permeable reactive barriers.

PubMed

Bartzas, Georgios; Komnitsas, Kostas

2010-11-15

A continuous column experiment was carried out under dynamic flow conditions in order to study the efficiency of low-cost permeable reactive barriers (PRBs) to remove several inorganic contaminants from acidic solutions. A 50:50 w/w waste iron/sand mixture was used as candidate reactive media in order to activate precipitation and promote sorption and reduction-oxidation mechanisms. Solid phase studies of the exhausted reactive products after column shutdown, using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), confirmed that the principal Fe corrosion products identified in the reactive zone are amorphous iron (hydr)oxides (maghemite/magnetite and goethite), intermediate products (sulfate green rust), and amorphous metal sulfides such as amFeS and/or mackinawite. Geochemical modelling of the metal removal processes, including interactions between reactive media, heavy metal ions and sulfates, and interpretation of the ionic profiles was also carried out by using the speciation/mass transfer computer code PHREEQC-2 and the WATEQ4F database. Mineralogical characterization studies as well as geochemical modelling calculations also indicate that the effect of sulfate and silica sand on the efficiency of the reactive zone should be considered carefully during design and operation of low-cost field PRBs. Copyright © 2010 Elsevier B.V. All rights reserved.

Allowing for crystalline structure effects in Geant4

DOE PAGES

Bagli, Enrico; Asai, Makoto; Dotti, Andrea; ...

2017-03-24

In recent years, the Geant4 toolkit for the Monte Carlo simulation of radiation with matter has seen large growth in its divers user community. A fundamental aspect of a successful physics experiment is the availability of a reliable and precise simulation code. Geant4 currently does not allow for the simulation of particle interactions with anything other than amorphous matter. To overcome this limitation, the GECO (GEant4 Crystal Objects) project developed a general framework for managing solid-state structures in the Geant4 kernel and validate it against experimental data. As a result, accounting for detailed geometrical structures allows, for example, simulation ofmore » diffraction from crystal planes or the channeling of charged particle.« less

Zirconia ceramics for excess weapons plutonium waste

NASA Astrophysics Data System (ADS)

Gong, W. L.; Lutze, W.; Ewing, R. C.

2000-01-01

We synthesized a zirconia (ZrO 2)-based single-phase ceramic containing simulated excess weapons plutonium waste. ZrO 2 has large solubility for other metallic oxides. More than 20 binary systems A xO y-ZrO 2 have been reported in the literature, including PuO 2, rare-earth oxides, and oxides of metals contained in weapons plutonium wastes. We show that significant amounts of gadolinium (neutron absorber) and yttrium (additional stabilizer of the cubic modification) can be dissolved in ZrO 2, together with plutonium (simulated by Ce 4+, U 4+ or Th 4+) and impurities (e.g., Ca, Mg, Fe, Si). Sol-gel and powder methods were applied to make homogeneous, single-phase zirconia solid solutions. Pu waste impurities were completely dissolved in the solid solutions. In contrast to other phases, e.g., zirconolite and pyrochlore, zirconia is extremely radiation resistant and does not undergo amorphization. Baddeleyite (ZrO 2) is suggested as the natural analogue to study long-term radiation resistance and chemical durability of zirconia-based waste forms.

In-Situ Welding Carbon Nanotubes into a Porous Solid with Super-High Compressive Strength and Fatigue Resistance

PubMed Central

Lin, Zhiqiang; Gui, Xuchun; Gan, Qiming; Chen, Wenjun; Cheng, Xiaoping; Liu, Ming; Zhu, Yuan; Yang, Yanbing; Cao, Anyuan; Tang, Zikang

2015-01-01

Carbon nanotube (CNT) and graphene-based sponges and aerogels have an isotropic porous structure and their mechanical strength and stability are relatively lower. Here, we present a junction-welding approach to fabricate porous CNT solids in which all CNTs are coated and welded in situ by an amorphous carbon layer, forming an integral three-dimensional scaffold with fixed joints. The resulting CNT solids are robust, yet still highly porous and compressible, with compressive strengths up to 72 MPa, flexural strengths up to 33 MPa, and fatigue resistance (recovery after 100,000 large-strain compression cycles at high frequency). Significant enhancement of mechanical properties is attributed to the welding-induced interconnection and reinforcement of structural units, and synergistic effects stemming from the core-shell microstructures consisting of a flexible CNT framework and a rigid amorphous carbon shell. Our results provide a simple and effective method to manufacture high-strength porous materials by nanoscale welding. PMID:26067176

In-Situ Welding Carbon Nanotubes into a Porous Solid with Super-High Compressive Strength and Fatigue Resistance.

PubMed

Lin, Zhiqiang; Gui, Xuchun; Gan, Qiming; Chen, Wenjun; Cheng, Xiaoping; Liu, Ming; Zhu, Yuan; Yang, Yanbing; Cao, Anyuan; Tang, Zikang

2015-06-11

Carbon nanotube (CNT) and graphene-based sponges and aerogels have an isotropic porous structure and their mechanical strength and stability are relatively lower. Here, we present a junction-welding approach to fabricate porous CNT solids in which all CNTs are coated and welded in situ by an amorphous carbon layer, forming an integral three-dimensional scaffold with fixed joints. The resulting CNT solids are robust, yet still highly porous and compressible, with compressive strengths up to 72 MPa, flexural strengths up to 33 MPa, and fatigue resistance (recovery after 100,000 large-strain compression cycles at high frequency). Significant enhancement of mechanical properties is attributed to the welding-induced interconnection and reinforcement of structural units, and synergistic effects stemming from the core-shell microstructures consisting of a flexible CNT framework and a rigid amorphous carbon shell. Our results provide a simple and effective method to manufacture high-strength porous materials by nanoscale welding.

In-Situ Welding Carbon Nanotubes into a Porous Solid with Super-High Compressive Strength and Fatigue Resistance

NASA Astrophysics Data System (ADS)

Lin, Zhiqiang; Gui, Xuchun; Gan, Qiming; Chen, Wenjun; Cheng, Xiaoping; Liu, Ming; Zhu, Yuan; Yang, Yanbing; Cao, Anyuan; Tang, Zikang

2015-06-01

Carbon nanotube (CNT) and graphene-based sponges and aerogels have an isotropic porous structure and their mechanical strength and stability are relatively lower. Here, we present a junction-welding approach to fabricate porous CNT solids in which all CNTs are coated and welded in situ by an amorphous carbon layer, forming an integral three-dimensional scaffold with fixed joints. The resulting CNT solids are robust, yet still highly porous and compressible, with compressive strengths up to 72 MPa, flexural strengths up to 33 MPa, and fatigue resistance (recovery after 100,000 large-strain compression cycles at high frequency). Significant enhancement of mechanical properties is attributed to the welding-induced interconnection and reinforcement of structural units, and synergistic effects stemming from the core-shell microstructures consisting of a flexible CNT framework and a rigid amorphous carbon shell. Our results provide a simple and effective method to manufacture high-strength porous materials by nanoscale welding.

Evaluating the Mobility of Arsenic in Synthetic Iron-containing Solids Using a Modified Sequential Extraction Method.

PubMed

Shan, Jilei; Sáez, A Eduardo; Ela, Wendell P

2010-02-01

Many water treatment technologies for arsenic removal that are used today produce arsenic-bearing residuals which are disposed in non-hazardous landfills. Previous works have established that many of these residuals will release arsenic to a much greater extent than predicted by standard regulatory leaching tests (e.g. the toxicity characteristic leaching procedure, TCLP) and, consequently, require stabilization to ensure benign behavior after disposal. In this work, a four-step sequential extraction method was developed in an effort to determine the proportion of arsenic in various phases in untreated as well as stabilized iron-based solid matrices. The solids synthesized using various potential stabilization techniques included: amorphous arsenic-iron sludge (ASL), reduced ASL via reaction with zero valent iron (RASL), amorphous ferrous arsenate (PFA), a mixture of PFA and SL (M1), crystalline ferrous arsenate (HPFA), and a mixture of HPFA and SL (M2). The overall arsenic mobility of the tested samples increased in the following order: ASL > RASL > PFA > M1 > HPFA > M2.

Investigating the Dissolution Performance of Amorphous Solid Dispersions Using Magnetic Resonance Imaging and Proton NMR.

PubMed

Tres, Francesco; Coombes, Steven R; Phillips, Andrew R; Hughes, Leslie P; Wren, Stephen A C; Aylott, Jonathan W; Burley, Jonathan C

2015-09-10

We have investigated the dissolution performance of amorphous solid dispersions of poorly water-soluble bicalutamide in a Kollidon VA64 polymeric matrix as a function of the drug loading (5% vs. 30% bicalutamide). A combined suite of state-of-the-art analytical techniques were employed to obtain a clear picture of the drug release, including an integrated magnetic resonance imaging UV-Vis flow cell system and 1H-NMR. Off-line 1H-NMR was used for the first time to simultaneously measure the dissolution profiles and rates of both the drug and the polymer from a solid dispersion. MRI and 1H-NMR data showed that the 5% drug loading compact erodes linearly, and that bicalutamide and Kollidon VA64 are released at approximately the same rate from the molecular dispersion. For the 30% extrudate, data indicated a slower water ingress into the compact which corresponds to a slower dissolution rate of both bicalutamide and Kollidon VA64.

Improvement of the dissolution rate of poorly soluble drugs by solid crystal suspensions.

PubMed

Thommes, Markus; Ely, David R; Carvajal, M Teresa; Pinal, Rodolfo

2011-06-06

We present a novel extrusion based approach where the dissolution rate of poorly soluble drugs (griseofulvin, phenytoin and spironolactone) is significantly accelerated. The drug and highly soluble mannitol are coprocessed in a hot melt extrusion operation. The obtained product is an intimate mixture of the crystalline drug and crystalline excipient, with up to 50% (w/w) drug load. The in vitro drug release from the obtained solid crystalline suspensions is over 2 orders of magnitude faster than that of the pure drug. Since the resulting product is crystalline, the accelerated dissolution rate does not bear the physical stability concerns inherent to amorphous formulations. This approach is useful in situations where the drug is not a good glass former or in cases where it is difficult to stabilize the amorphous drug. Being thermodynamically stable, the dissolution profile and the solid state properties of the product are maintained after storage at 40 °C, 75% RH for at least 90 days.

Catalyseur d'hydrocraquage à base de sulfure de NiMo déposé sur une zéolithe HEMT modifiée

NASA Astrophysics Data System (ADS)

Baalala, M.; Becue, T.; Leglise, J.; Manoli, J. M.; van Gestel, J. N. M.; Lamotte, J.; Bensitel, M.; Goupil, J. M.; Cornet, D.

1999-02-01

Treating a NH4EMT zeolite with a solution of (NH4)2SiF6 at 80 °C affords a solid containing amorphous SiO2 intimately mixed with the zeolite. This acidic support EMT-Si was loaded with NiMo sulfide in order to prepare a bifunctional catalyst, which was tested for the hydrogenation of benzene and the hydrocracking of n-heptane. This NiMo/EMT-Si catalyst was found more active for hydrogenation than the analogous NiMo/HY. This is ascribed to a higher dispersion of the NiMo sulfide, which is almost equally shared between the internal mesopores in the modified EMT solid, and the fissures, which were created throughout the zeolite grains upon inserting the NiMo sulfide. The catalyst with the EMT-Si support was also found more active than the NiMo/HY for the hydrocracking of heptane, with a slightly higher selectivity into heptane isomers. Le traitement d'une zéolithe NH4EMT par une solution de (NH4)2SiF6 fournit un solide comportant une phase SiO2 amorphe intimement mélangée aux parties intactes de la zéolithe. Sur ce support acide EMT-Si, on a greffé un sulfure de NiMo afin de préparer un catalyseur bifonctionnel qui a été testé dans les réactions d'hydrogénation du benzène et d'hydrocraquage du n-heptane. Ce catalyseur NiMo/EMT-Si s'avère plus actif en hydrogénation que son analogue NiMo/HY, en raison d'une meilleure dispersion du sulfure de NiMo. Sur le solide EMT modifié, le sulfure se répartit à peu près également entre les mésopores internes et les fissures crées dans les grains de zéolithe lors de l'insertion du sulfure de NiMo. Au contraire sur le support Y, une partie du sulfure est externe aux grains de zéolithe et inactive en catalyse. Le catalyseur NiMo/EMT-Si est aussi trouvé plus actif que le NiMo/HY en hydrocraquage du n-heptane, et un peu plus sélectif en isomères.

Factors Affecting the Dissolution of Indomethacin Solid Dispersions.

PubMed

Zhang, Wei; Zhang, Chen-Ning; He, Yue; Duan, Ban-Yan; Yang, Guang-Yi; Ma, Wei-Dong; Zhang, Yong-Hong

2017-11-01

The aim of this study was to investigate the influence of factors such as carrier type, drug/carrier ratio, binary carriers, and preparation method on the dissolution of an insoluble drug, indomethacin (IM), under supersaturation conditions. Using a solvent evaporation (SE) method, poloxamer 188 and PVP K30 showed better dissolution among the selected carriers. Furthermore, as the ratio of carriers increased (drug/carrier ratio from 1:0.5 to 1:2), the dissolution rate increased especially in almost two times poloxamer 188 solid dispersions (SDs), while the reverse results were observed for PVP K30 SDs. For the binary carrier SD, a lower dissolution was found. Under hot melt extrusion (HME), the dissolution of poloxamer 188 SD and PVP K30 SD was 0.83- and 0.94-folds lower than that using SE, respectively, while the binary carrier SD showed the best dissolution. For poloxamer 188 SDs, the drug's crystal form changed when using SE, while no crystal form change was observed using HME. IM was amorphous in PVP K30 SDs prepared by both methods. For binary carrier systems, amorphous and crystalline drugs coexisted in SD using SE, and negligible amorphous IM was in SD using HME. This study indicated that a higher amorphous proportion in SD did not correlate with higher dissolution rate, and other factors, such as carrier type, particle size, and density, were also critical.

Haste Makes Waste: The Interplay Between Dissolution and Precipitation of Supersaturating Formulations.

PubMed

Sun, Dajun D; Lee, Ping I

2015-11-01

Contrary to the early philosophy of supersaturating formulation design for oral solid dosage forms, current evidence shows that an exceedingly high rate of supersaturation generation could result in a suboptimal in vitro dissolution profile and subsequently could reduce the in vivo oral bioavailability of amorphous solid dispersions. In this commentary, we outline recent research efforts on the specific effects of the rate and extent of supersaturation generation on the overall kinetic solubility profiles of supersaturating formulations. Additional insights into an appropriate definition of sink versus nonsink dissolution conditions and the solubility advantage of amorphous pharmaceuticals are also highlighted. The interplay between dissolution and precipitation kinetics should be carefully considered in designing a suitable supersaturating formulation to best improve the dissolution behavior and oral bioavailability of poorly water-soluble drugs.

Humidity induced phase transformation of poloxamer 188 and its effect on physical stability of amorphous solid dispersion of AMG 579, a PDE10A inhibitor.

PubMed

Wu, Qiong; Kennedy, Michael T; Nagapudi, Karthik; Kiang, Y-H

2017-04-15

Poloxamer 188, a commonly used emulsifying and solubilizing agent, was found to be the cause of crystallization of an investigational drug, AMG 579, from its amorphous solid dispersion at accelerated storage conditions. Investigation of this physical stability issue included thorough characterization of poloxamer 188 at non-ambient conditions. At 40°C, poloxamer 188 becomes deliquescent above relative humidity of 75%. Upon returning to ambient conditions, the deliquescent poloxamer 188 loses water and re-solidifies. The reversible phase transformation of poloxamer 188 may cause physical and chemical stability issues and this risk should be assessed when selecting it as an excipient for formulation development. Copyright © 2017 Elsevier B.V. All rights reserved.

Challenges and Strategies in Thermal Processing of Amorphous Solid Dispersions: A Review.

PubMed

LaFountaine, Justin S; McGinity, James W; Williams, Robert O

2016-02-01

Thermal processing of amorphous solid dispersions continues to gain interest in the pharmaceutical industry, as evident by several recently approved commercial products. Still, a number of pharmaceutical polymer carriers exhibit thermal or viscoelastic limitations in thermal processing, especially at smaller scales. Additionally, active pharmaceutical ingredients with high melting points and/or that are thermally labile present their own specific challenges. This review will outline a number of formulation and process-driven strategies to enable thermal processing of challenging compositions. These include the use of traditional plasticizers and surfactants, temporary plasticizers utilizing sub- or supercritical carbon dioxide, designer polymers tailored for hot-melt extrusion processing, and KinetiSol® Dispersing technology. Recent case studies of each strategy will be described along with potential benefits and limitations.

Localization and stability in damageable amorphous solids

NASA Astrophysics Data System (ADS)

de Tommasi, D.; Marzano, S.; Puglisi, G.; Saccomandi, G.

2010-01-01

In the present article, based on a recently proposed model (De Tommasi et al. in J Rheol 50:495-512, 2006; Phys Rev Lett 100:085502, 2008), we analyze the influence of the microstructure properties on the damage behavior of amorphous materials. In accordance with the experimental observations, different scenarios of damage nucleation and evolution are associated to different material distributions at the microscale. In particular, we observe the possibilities of uniform or localized damage and strain geometries with a macroscopic behavior that may range from brittle to ductile or rubber-like. To describe the possibility of extending our stability analysis to three-dimensional damageable amorphous bodies we consider a simple boundary value problem of engineering interest.

High temperature coercive field behavior of Fe-Zr powder

NASA Astrophysics Data System (ADS)

Mishra, Debabrata; Perumal, A.; Srinivasan, A.

2009-04-01

We report the investigation of high temperature coercive field behavior of Fe80Zr20 nanocrystalline alloy powder having two-phase microstructure prepared by mechanical alloying process. Thermomagnetization measurement shows the presence of two different magnetic phase transitions corresponding to the amorphous matrix and nonequilibrium Fe(Zr) solid solution. Temperature dependent coercivity exhibits a sharp increase in its value close to the Curie temperature of the amorphous matrix. This feature is attributed to the loss of intergranular ferromagnetic exchange coupling between the nanocrystallites due to the paramagnetic nature of the amorphous matrix. The temperature dependent coercive field behavior is ascribed to the variations in both the effective anisotropy and the exchange stiffness constant with temperature.

Reaction dynamics studies for the system 7Be+58Ni

NASA Astrophysics Data System (ADS)

Torresi, D.; Mazzocco, M.; Acosta, L.; Boiano, A.; Boiano, C.; Diaz-Torres, A.; Fierro, N.; Glodariu, T.; Grilj, L.; Guglielmetti, A.; Keeley, N.; La Commara, M.; Martel, I.; Mazzocchi, C.; Molini, P.; Pakou, A.; Parascandolo, C.; Parkar, V. V.; Patronis, N.; Pierroutsakou, D.; Romoli, M.; Rusek, K.; Sanchez-Benitez, A. M.; Sandoli, M.; Signorini, C.; Silvestri, R.; Soramel, F.; Stiliaris, E.; Strano, E.; Stroe, L.; Zerva, K.

2015-04-01

The study of reactions induced by exotic weakly bound nuclei at energies around the Coulomb barrier had attracted a large interest in the last decade, since the features of these nuclei can deeply affect the reaction dynamics. The discrimination between different reaction mechanisms is, in general, a rather difficult task. It can be achieved by using detector arrays covering high solid angle and with high granularity that allow to measure the reaction products and, possibly, coincidences between them, as, for example, recently done for stable weakly bound nuclei [1, 2]. We investigated the collision of the weakly bound nucleus 7Be on a 58Ni target at the beam energy of 1.1 times the Coulomb barrier, measuring the elastic scattering angular distribution and the energy and angular distributions of 3He and 4He. The 7Be radioactive ion beam was produced by the facility EXOTIC at INFN-LNL with an energy of 22 MeV and an intensity of ~3×105 pps. Results showed that the 4He yeld is about 4 times larger than 3He yield, suggesting that reaction mechanisms other than the break-up mostly produce the He isotopes. Theoretical calculations for transfer channels and compound nucleus reactions suggest that complete fusion accounts for (41±5%) of the total reaction cross section extracted from optical model analysis of the elastic scattering data, and that 3He and 4He stripping are the most populated reaction channels among direct processes. Eventually estimation of incomplete fusion contributions to the 3,4He production cross sections was performed through semi-classical calculations with the code PLATYPUS [3].

Superconductor-Insulator transition in sputtered amorphous MoRu and MoRuN thin films

NASA Astrophysics Data System (ADS)

Makise, K.; Shinozaki, B.; Ichikawa, F.

2018-03-01

This work shows the experimental results of the superconductor-insulator (S-I) transition for amorphous molybdenum ruthenium (MoRu) and molybdenum ruthenium nitride (MoRuN) films. These amorphous films onto c-plane sapphire substrates have been interpreted to be homogeneous by XRD and AFM measurements. Electrical and superconducting properties measurements were carried out on MoRu and MoRuN thin films deposited by reactive sputtering technique. We have analysed the data on R sq (T) based on excess conductivity of superconducting films by the AL and MT term and weak localization and electron-electron interaction for the conductance. MoRu films which offer the most homogeneous film morphology, showed a critical sheet resistance of transition, Rc, of ∼ 2 kΩ. This values is smaller than those previously our reported for quench-condensed MoRu films on SiO underlayer held at liquid He temperature.

Water-mediated solid-state transformation of a polymorphic drug during aqueous-based drug-layer coating of pellets.

PubMed

Lust, Andres; Lakio, Satu; Vintsevits, Julia; Kozlova, Jekaterina; Veski, Peep; Heinämäki, Jyrki; Kogermann, Karin

2013-11-01

During aqueous drug-layer coating, drug substance(s) are exposed to water and elevated temperatures which can lead to water-mediated process induced transformations (PITs). The effects of aqueous drug-layer coating of pellets (Cellets(®)) on the anhydrous piroxicam, PRX, were investigated in the miniaturized coating equipment and with free films. Hydroxypropyl methylcellulose (HPMC) was used as a carrier coating polymer. Free films were prepared by using an in-house small-scale rotating plate system equipped with an atomization air nozzle. Raman spectroscopy, X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were used to characterize the solid-state properties and surface morphology of the pellets and free films. The results showed that anhydrous PRX form I (AH) and monohydrate (MH) were stable during drug-layer coating, but amorphous PRX in solid dispersion (SD) crystallized as MH already after 10 min of coating. Furthermore, the increase in a dissolution rate was achieved from the drug-layer coated inert pellets compared to powder forms. In conclusion, water-mediated solid-state PITs of amorphous PRX is evident during aqueous-based drug-layer coating of pellets, and solid-state change can be verified using Raman spectroscopy. Copyright © 2013 Elsevier B.V. All rights reserved.

Liquid?solid helium interface: some conceptual questions

NASA Astrophysics Data System (ADS)

Leggett, A. J.

2003-12-01

I raise, and discuss qualitatively, some conceptual issues concerning the interface between the crystalline solid and superfluid liquid phases of 4He emphasizing, in particular, the fact that the ground-state wave functions of the two phases are prima facie qualitatively quite different, in that the superfluid liquid phase possesses off-diagonal long-range order (ODLRO), while the crystalline solid does not. The fact that the statics and dynamics of the interface do not appear to be particularly sensitive to the presence of ODLRO in the liquid is tentatively explained by the fact that because of a subtlety associated with the Bose statistics obeyed by the atoms, the solid and liquid wave functions are not locally very different.

The liquid⟷amorphous transition and the high pressure phase diagram of carbon

NASA Astrophysics Data System (ADS)

Robinson, David R.; Wilson, Mark

2013-04-01

The phase diagram of carbon is mapped to high pressure using a computationally-tractable potential model. The use of a relatively simple (Tersoff-II) potential model allows a large range of phase space to be explored. The coexistence (melting) curve for the diamond crystal/liquid dyad is mapped directly by modelling the solid/liquid interfaces. The melting curve is found to be re-entrant and belongs to a conformal class of diamond/liquid coexistence curves. On supercooling the liquid a phase transition to a tetrahedral amorphous form (ta-C) is observed. The liquid ⟷ amorphous coexistence curve is mapped onto the pT plane and is found to also be re-entrant. The entropy changes for both melting and the amorphous ⟶ liquid transitions are obtained from the respective coexistence curves and the associated changes in molar volume. The structural change on amorphization is analysed at different points on the coexistence curve including for transitions that are both isochoric and isocoordinate (no change in nearest-neighbour coordination number). The conformal nature of the melting curve is highlighted with respect to the known behaviour of Si. The relationship of the observed liquid/amorphous coexistence curve to the Si low- and high-density amorphous (LDA/HDA) transition is discussed.

Chemically sensitive free-volume study of amorphization of Cu60Zr40 induced by cold rolling and folding

NASA Astrophysics Data System (ADS)

Puff, Werner; Rabitsch, Herbert; Wilde, Gerhard; Dinda, Guru P.; Würschum, Roland

2007-06-01

With the aim to contribute to a microscopical understanding of the processes of solid-state amorphization, the chemically sensitive technique of background—reduced Doppler broadening of positron-electron annihilation radiation in combination with positron lifetime spectroscopy and microstructural characterization is applied to a free volume study of the amorphization of Cu60Zr40 induced by consecutive folding and rolling. Starting from the constituent pure metal foils, a nanosale multilayer structure of elemental layers and amorphous interlayers develops in an intermediate state of folding and rolling, where free volumes with a Zr-rich environment occur presumably located in the hetero-interfaces between the various layers or in grain boundaries of the Cu layers. After complete intermixing and amorphization, the local chemical environment of the free volumes reflects the average chemical alloy composition. In contrast to other processes of amorphization, free volumes of the size of few missing atoms occur in the rolling-induced amorphous state. Self-consistent results from three different methods for analyzing the Doppler broadening spectra, i.e., S-W-parameter correlation, multicomponent fit, and the shape of ratio curves, demonstrate the potential of the background-reduced Doppler technique for chemically sensitive characterization of structurally complex materials on an atomic scale.

Effect of raw material ratios on the compressive strength of magnesium potassium phosphate chemically bonded ceramics.

PubMed

Wang, Ai-juan; Yuan, Zhi-long; Zhang, Jiao; Liu, Lin-tao; Li, Jun-ming; Liu, Zheng

2013-12-01

The compressive strength of magnesium potassium phosphate chemically bonded ceramics is important in biomedical field. In this work, the compressive strength of magnesium potassium phosphate chemically bonded ceramics was investigated with different liquid-to-solid and MgO-to-KH2PO4 ratios. X-ray diffractometer was applied to characterize its phase composition. The microstructure was imaged using a scanning electron microscope. The results showed that the compressive strength of the chemically bonded ceramics increased with the decrease of liquid-to-solid ratio due to the change of the packing density and the crystallinity of hydrated product. However, with the increase of MgO-to-KH2PO4 weight ratio, its compressive strength increased firstly and then decreased. The low compressive strength in lower MgO-to-KH2PO4 ratio might be explained by the existence of the weak phase KH2PO4. However, the low value of compressive strength with the higher MgO-to-KH2PO4 ratio might be caused by lack of the joined phase in the hydrated product. Besides, it has been found that the microstructures were different in these two cases by the scanning electron microscope. Colloidal structure appeared for the samples with lower liquid-to-solid and higher MgO-to-KH2PO4 ratios possibly because of the existence of amorphous hydrated products. The optimization of both liquid-to-solid and MgO-to-KH2PO4 ratios was important to improve the compressive strength of magnesium potassium phosphate chemically bonded ceramics. © 2013.

A shear localization mechanism for lubricity of amorphous carbon materials

PubMed Central

Ma, Tian-Bao; Wang, Lin-Feng; Hu, Yuan-Zhong; Li, Xin; Wang, Hui

2014-01-01

Amorphous carbon is one of the most lubricious materials known, but the mechanism is not well understood. It is counterintuitive that such a strong covalent solid could exhibit exceptional lubricity. A prevailing view is that lubricity of amorphous carbon results from chemical passivation of dangling bonds on surfaces. Here we show instead that lubricity arises from shear induced strain localization, which, instead of homogeneous deformation, dominates the shearing process. Shear localization is characterized by covalent bond reorientation, phase transformation and structural ordering preferentially in a localized region, namely tribolayer, resulting in shear weakening. We further demonstrate an anomalous pressure induced transition from stick-slip friction to continuous sliding with ultralow friction, due to gradual clustering and layering of graphitic sheets in the tribolayer. The proposed shear localization mechanism sheds light on the mechanism of superlubricity, and would enrich our understanding of lubrication mechanism of a wide variety of amorphous materials. PMID:24412998

Synthesis and characterization of palm oil fuel ash (POFA) and metakaolin based geopolymer for possible application in nanocoating

NASA Astrophysics Data System (ADS)

Khan, Ihsan Ullah; Bhat, A. H.; Masset, Patrick J.; Khan, Farman Ullah; Rehman, Wajid Ur

2016-11-01

The main aim of this study was to synthesize and characterize highly amorphous geopolymer from palm oil fuel ash (POFA) and metakaolin, to be used as nanocoating. Geopolymers are man-made aluminosilicate materials that are amorphous analogues of zeolites. The geopolymers were made by condensing a mixture of raw materials metakaolin and palm oil fuel ash (POFA) with alkaline activator at a fixed ratio at room temperature. The kaolin type clay was calcined at 700 °C for 4hrs to transform it into amorphous metakaolin which is more reactive precursor for geopolymer formation. The characteristics of metakaolin and geopolymers (metakaolin and palm oil fuel ash based geopolymers) were analyzed by using x-ray fluorescence (XRF), Fourier transform infra-red spectrometry (FTIR), Thermogravimetric analysis (TG/DTA) and scanning electron microscopy with energy dispersive x-ray analysis (SEM-EDX). FTIR revealed the presence of Al-O and Si-O stretching vibrations of amorphous alumino-silicate structure for metakaolin, palm oil fuel ash and geopolymers. SEM-EDX images showed the presence of reaction product complementary to NASH (N = Na2O, A = Al2O3, S = SiO2, H = H2O) solid. The resulting geopolymers that were synthesized with NaOH/Na2SiO3 solution cured at 60 °C for 3 days. The results demonstrated the suitability of metakaolin and palm oil fuel ash (POFA) for synthesis of geopolymer at room temperatures.

Room-Temperature Activation of InGaZnO Thin-Film Transistors via He+ Irradiation.

PubMed

Stanford, Michael G; Noh, Joo Hyon; Mahady, Kyle; Ievlev, Anton V; Maksymovych, Peter; Ovchinnikova, Olga S; Rack, Philip D

2017-10-11

Amorphous indium gallium zinc oxide (a-IGZO) is a transparent semiconductor which has demonstrated excellent electrical performance as thin-film transistors (TFTs). However, a high-temperature activation process is generally required which is incompatible for next-generation flexible electronic applications. In this work, He + irradiation is demonstrated as an athermal activation process for a-IGZO TFTs. Controlling the He + dose enables the tuning of charge density, and a dose of 1 × 10 14 He + /cm 2 induces a change in charge density of 2.3 × 10 12 cm -2 . Time-dependent transport measurements and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) indicate that the He + -induced trapped charge is introduced because of preferential oxygen-vacancy generation. Scanning microwave impedance microscopy confirms that He + irradiation improves the conductivity of the a-IGZO. For realization of a permanent activation, IGZO was exposed with a He + dose of 5 × 10 14 He + /cm 2 and then aged 24 h to allow decay of the trapped oxide charge originating for electron-hole pair generation. The resultant shift in the charge density is primarily attributed to oxygen vacancies generated by He + sputtering in the near-surface region.

Possible Existence of Two Amorphous Phases of D-Mannitol Related by a First-Order Transition

NASA Astrophysics Data System (ADS)

Zhu, Men; Wang, Jun-Qiang; Perepezko, John; Yu, Lian

We report that the common polyalcohol D-mannitol may have two amorphous phases related by a first-order transition. Slightly above Tg (284 K), the supercooled liquid (SCL) of D-mannitol transforms to a low-energy, apparently amorphous phase (Phase X). The enthalpy of Phase X is roughly halfway between those of the known amorphous and crystalline phases. The amorphous nature of Phase X is suggested by its absence of birefringence, transparency, broad X-ray diffraction, and broad Raman and NIR spectra. Phase X has greater molecular spacing, higher molecular order, fewer intra- and more inter-molecular hydrogen bonds than the normal liquid. On fast heating, Phase X transforms back to SCL near 330 K. Upon temperature cycling, it shows a glass-transition-like change of heat capacity. The presence of D-sorbitol enables a first-order liquid-liquid transition (LLT) from SCL to Phase X. This is the first report of polyamorphism at 1 atm for a pharmaceutical relevant substance. As amorphous solids are explored for many applications, polyamorphism could offer a tool to engineer the properties of materials. (Ref: M. Zhu et al., J. Chem. Phys. 2015, 142, 244504)

Gas/solid carbon branching ratios in surface-mediated reactions and the incorporation of carbonaceous material into planetesimals

PubMed Central

Nuth, Joseph A.; Johnson, Natasha M.; Ferguson, Frank T.; Carayon, Alicia

2018-01-01

We report the ratio of the initial carbon available as CO that forms gas-phase compounds compared to the fraction that deposits as a carbonaceous solid (the gas/solid branching ratio) as a function of time and temperature for iron, magnetite, and amorphous iron silicate smoke catalysts during surface-mediated reactions in an excess of hydrogen and in the presence of N2. This fraction varies from more than 99% for an amorphous iron silicate smoke at 673 K to less than 40% for a magnetite catalyst at 873 K. The CO not converted into solids primarily forms methane, ethane, water, and CO2, as well as a very wide range of organic molecules at very low concentration. Carbon deposits do not form continuous coatings on the catalytic surfaces, but instead form extremely high surface area per unit volume “filamentous” structures. While these structures will likely form more slowly but over much longer times in protostellar nebulae than in our experiments due to the much lower partial pressure of CO, such fluffy coatings on the surfaces of chondrules or calcium aluminum inclusions could promote grain–grain sticking during low-velocity collisions. PMID:29563766

Gas/Solid Carbon Branching Ratios in Surface Mediated Reactions and the Incorporation of Carbonaceous Material into Planetesimals

NASA Technical Reports Server (NTRS)

Nuth, Joseph A.; Johnson, Natasha M.; Ferguson, Frank T.; Carayon, Alicia

2016-01-01

We report the ratio of the initial carbon available as CO that forms gas-phase compounds compared to the fraction that deposits as a carbonaceous solid (the gas solid branching ratio) as a function of time and temperature for iron, magnetite, and amorphous iron silicate smoke catalysts during surface-mediated reactions in an excess of hydrogen and in the presence of N2. This fraction varies from more than 99 for an amorphous iron silicate smoke at 673 K to less than 40% for a magnetite catalyst at 873 K. The CO not converted into solids primarily forms methane, ethane, water, and CO2, as well as a very wide range of organic molecules at very low concentration. Carbon deposits do not form continuous coatings on the catalytic surfaces, but instead form extremely high surface area per unit volume filamentous structures. While these structures will likely form more slowly but over much longer times in protostellar nebulae than in our experiments due to the much lower partial pressure of CO, such fluffy coatings on the surfaces of chondrules or calcium aluminum inclusions could promote grain-grain sticking during low-velocity collisions.

Methods of making metallic glass foil laminate composites

DOEpatents

Vianco, P.T.; Fisher, R.W.; Hosking, F.M.; Zanner, F.J.

1996-08-20

A process for the fabrication of a rapidly solidified foil laminate composite. An amorphous metallic glass foil is flux treated and coated with solder. Before solidification of the solder the foil is collected on a take-up spool which forms the composite into a solid annular configuration. The resulting composite exhibits high strength, resiliency and favorable magnetic and electrical properties associated with amorphous materials. The composite also exhibits bonding strength between the foil layers which significantly exceeds the bulk strength of the solder alone. 6 figs.

Methods of making metallic glass foil laminate composites

DOEpatents

Vianco, Paul T.; Fisher, Robert W.; Hosking, Floyd M.; Zanner, Frank J.

1996-01-01

A process for the fabrication of a rapidly solidified foil laminate composite. An amorphous metallic glass foil is flux treated and coated with solder. Before solidification of the solder the foil is collected on a take-up spool which forms the composite into a solid annular configuration. The resulting composite exhibits high strength, resiliency and favorable magnetic and electrical properties associated with amorphous materials. The composite also exhibits bonding strength between the foil layers which significantly exceeds the bulk strength of the solder alone.

Amorphous tantala and its relationship with the molten state

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alderman, Oliver L.G.; Benmore, C. J.; Neuefeind, Joerg C.

The structure factors of molten Ta 2O 5 and Nb 2O 5 have been measured by high-energy x-ray and pulsed neutron diffraction. These are compared to transmission-mode x-ray diffraction through a self-supported 15-μm ion-beam sputtered amorphous tantala film. Atomistic models derived from the diffraction data by means of empirical potential structure refinement reveal that tantala and niobia liquids are very close to isomorphous, as confirmed by measurement of a molten mixture, Ta 0.8Nb 1.2O 5. Nonetheless, peak Nb-O bond lengths are about 1% shorter than those for Ta-O, at temperatures, T*=T/T melt, scaled to the melting points. Mean coordination numbersmore » are n MO≃5.6(1),n OM≃2.23(4) in the liquid state, and n TaO≃6.6(2),n OTa≃2.63(8) in the solid. The liquids are built from five- and six-fold M-O polyhedra which connect principally by corner sharing, with a minority of edge sharing; a-Ta 2O 5 on the other hand has a local structure more akin to the crystalline polymorphs, built primarily from six- and seven-fold polyhedra, with a larger degree of edge sharing. The structural differences between liquid and amorphous Ta 2O 5, coupled with observations of increasing peak bond lengths upon cooling, are consistent with the interpretation that the amorphous film reaches a supercooled liquidlike metastable equilibrium during deposition. In other words, the amorphous film shares a common progenitor state with a hypothetical glass quenched from a fragile melt. In addition, we show that recent classical interatomic potentials do not fully reproduce the diffraction data, and infer that inclusion of attractive (non-Coulombic) Ta-Ta interactions is important, particularly for obtaining the correct degree of edge sharing, coordination numbers, and densities. In conclusion, nanoscale inhomogeneity of the amorphous film is confirmed by the observation of small-angle x-ray scattering.« less

Amorphous tantala and its relationship with the molten state

NASA Astrophysics Data System (ADS)

Alderman, O. L. G.; Benmore, C. J.; Neuefeind, J.; Coillet, E.; Mermet, A.; Martinez, V.; Tamalonis, A.; Weber, R.

2018-04-01

The structure factors of molten T a2O5 and N b2O5 have been measured by high-energy x-ray and pulsed neutron diffraction. These are compared to transmission-mode x-ray diffraction through a self-supported 15-μm ion-beam sputtered amorphous tantala film. Atomistic models derived from the diffraction data by means of empirical potential structure refinement reveal that tantala and niobia liquids are very close to isomorphous, as confirmed by measurement of a molten mixture, T a0.8N b1.2O5 . Nonetheless, peak Nb-O bond lengths are about 1 % shorter than those for Ta-O, at temperatures, T*=T /Tmelt , scaled to the melting points. Mean coordination numbers are nM O≃5.6 (1 ) ,nO M≃2.23 (4 ) in the liquid state, and nTaO≃6.6 (2 ) ,nOTa≃2.63 (8 ) in the solid. The liquids are built from five- and six-fold M -O polyhedra which connect principally by corner sharing, with a minority of edge sharing; a-T a2O5 on the other hand has a local structure more akin to the crystalline polymorphs, built primarily from six- and seven-fold polyhedra, with a larger degree of edge sharing. The structural differences between liquid and amorphous T a2O5 , coupled with observations of increasing peak bond lengths upon cooling, are consistent with the interpretation that the amorphous film reaches a supercooled liquidlike metastable equilibrium during deposition. In other words, the amorphous film shares a common progenitor state with a hypothetical glass quenched from a fragile melt. In addition, we show that recent classical interatomic potentials do not fully reproduce the diffraction data, and infer that inclusion of attractive (non-Coulombic) Ta-Ta interactions is important, particularly for obtaining the correct degree of edge sharing, coordination numbers, and densities. Nanoscale inhomogeneity of the amorphous film is confirmed by the observation of small-angle x-ray scattering.

Amorphous tantala and its relationship with the molten state

DOE PAGES

Alderman, Oliver L.G.; Benmore, C. J.; Neuefeind, Joerg C.; ...

2018-04-01

The structure factors of molten Ta 2O 5 and Nb 2O 5 have been measured by high-energy x-ray and pulsed neutron diffraction. These are compared to transmission-mode x-ray diffraction through a self-supported 15-μm ion-beam sputtered amorphous tantala film. Atomistic models derived from the diffraction data by means of empirical potential structure refinement reveal that tantala and niobia liquids are very close to isomorphous, as confirmed by measurement of a molten mixture, Ta 0.8Nb 1.2O 5. Nonetheless, peak Nb-O bond lengths are about 1% shorter than those for Ta-O, at temperatures, T*=T/T melt, scaled to the melting points. Mean coordination numbersmore » are n MO≃5.6(1),n OM≃2.23(4) in the liquid state, and n TaO≃6.6(2),n OTa≃2.63(8) in the solid. The liquids are built from five- and six-fold M-O polyhedra which connect principally by corner sharing, with a minority of edge sharing; a-Ta 2O 5 on the other hand has a local structure more akin to the crystalline polymorphs, built primarily from six- and seven-fold polyhedra, with a larger degree of edge sharing. The structural differences between liquid and amorphous Ta 2O 5, coupled with observations of increasing peak bond lengths upon cooling, are consistent with the interpretation that the amorphous film reaches a supercooled liquidlike metastable equilibrium during deposition. In other words, the amorphous film shares a common progenitor state with a hypothetical glass quenched from a fragile melt. In addition, we show that recent classical interatomic potentials do not fully reproduce the diffraction data, and infer that inclusion of attractive (non-Coulombic) Ta-Ta interactions is important, particularly for obtaining the correct degree of edge sharing, coordination numbers, and densities. In conclusion, nanoscale inhomogeneity of the amorphous film is confirmed by the observation of small-angle x-ray scattering.« less

Combined effects of radiation damage and He accumulation on bubble nucleation in Gd2Ti2O7

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taylor, Caitlin A.; Patel, Maulik K.; Aguiar, Jeffery A.

2016-10-01

Pyrochlores have long been considered as host phases for long-term immobilization of radioactive waste nuclides that would undergo ..alpha..-decay for hundreds of thousands of years. This work utilizes ion-beam irradiations to examine the combined effects of radiation damage and He accumulation on bubble formation in Gd2Ti2O7 over relevant waste-form timescales. Helium bubbles are not observed in pre-damaged Gd2Ti2O7 implanted with 2 x 1016 He/cm2, even after post-implantation irradiations with 7 MeV Au3+ at 300, 500, and 700 K. However, He bubbles with average diameters of 1.5 nm and 2.1 nm are observed in pre-damaged (amorphous) Gd2Ti2O7 and pristine Gd2Ti2O7, respectively,more » after implantation of 2 x 1017 He/cm2. The critical He concentration for bubble nucleation in Gd2Ti2O7 is estimated to be 6 at.% He.« less

Diffusion and the Thermal Stability of Amorphous Copper-Zirconium

NASA Astrophysics Data System (ADS)

Stelter, Eric Carl

Measurements have been made of diffusion and thermal relaxation in amorphous Cu(,50)Zr(,50). Samples were prepared by melt-spinning under vacuum. Diffusion measurements were made over the temperature range from 317 to 385 C, using Ag and Au as substitutional impurities, by means of Auger electron spectrometry (AES) and Rutherford backscattering spectrometry (RBS). Thermal measurements were made by differential scanning calorimetry (DSC) up to 550 C. The diffusion coefficients of Ag and Au in amorphous Cu(,50)Zr(,50) are found to be somewhat higher than, but very close in magnitude to the coefficient of self-diffusion in crystalline Cu at the same temperatures. The activation energies for diffusion in the amorphous alloy are 0.72 to 1.55 eV/atom, much closer to the activation energy for self-diffusion in liquid Cu, 0.42 eV/atom, than that for the crystalline solid, 2.19 eV/atom. The mechanism for diffusion in the amorphous metal is presumably quite different from the monovacancy mechanism dominant in the crystalline solid. The pre-exponential terms are found to be extremely small, on the order of 10('-10) to 10('-11) cm('2)/sec for Ag diffusion. This indicates that diffusion in amorphous Cu(,50)Zr(,50) may involve an extended defect of 10 or more atoms. Analysis of the data in terms of the free -volume model also lends strength to this conclusion and indicates that the glass is composed of liquid-like clusters of 15 to 20 atoms. The initial stage of relaxation in amorphous CuZr occurs with a spectrum of activation energies. The lowest activation energy involved, 0.78 eV/atom, is almost identical to the average activation energy of Ag diffusion in the glass, 0.77 eV/atom, indicating that relaxation occurs primarily through diffusion. The activation energy of crystallization, determined by Kissinger's method, is 3.10 eV/atom. The large difference, on the order of 2.3 eV/atom, between the activation energies of crystallization and diffusion is attributed to the energy required to nucleate the crystalline phase.

Degradation of L-Ascorbic Acid in the Amorphous Solid State.

PubMed

Sanchez, Juan O; Ismail, Yahya; Christina, Belinda; Mauer, Lisa J

2018-03-01

Ascorbic acid degradation in amorphous solid dispersions was compared to its degradation in the crystalline state. Physical blends and lyophiles of ascorbic acid and polymers (pectins and polyvinylpyrrolidone [PVP]) were prepared initially at 50:50 (w/w), with further studies using the polymer that best inhibited ascorbic acid crystallization in the lyophiles in 14 vitamin : PVP ratios. Samples were stored in controlled environments (25 to 60 °C, 0% to 23% RH) for 1 mo and analyzed periodically to track the physical appearance, change in moisture content, physical state (powder x-ray diffraction and polarized light microscopy), and vitamin loss (high performance liquid chromatography) over time. The glass transition temperatures of select samples were determined using differential scanning calorimetry, and moisture sorption profiles were generated. Ascorbic acid in the amorphous form, even in the glassy amorphous state, was more labile than in the crystalline form in some formulations at the highest storage temperature. Lyophiles stored at 25 and 40 °C and those in which ascorbic acid had crystallized at 60 °C (≥70% ascorbic acid : PVP) had no significant difference in vitamin loss (P > 0.05) relative to physical blend controls, and the length of storage had little effect. At 60 °C, amorphous ascorbic acid lyophiles (≤60% ascorbic acid : PVP) lost significantly more vitamin (P < 0.05) relative to physical blend controls after 1 wk, and vitamin loss significantly increased over time. In these lyophiles, vitamin degradation also significantly increased (P < 0.05) at lower proportions of ascorbic acid, a scenario likely encountered in foods wherein vitamins are naturally present or added at low concentrations and production practices may promote amorphization of the vitamin. Vitamin C is one of the most unstable vitamins in foods. This study documents that amorphous ascorbic acid is less stable than crystalline ascorbic acid in some environments (for example, higher temperatures within 1 wk), especially when the vitamin is present at low concentrations in a product. These findings increase the understanding of how material science properties influence the stability of vitamin C. © 2018 Institute of Food Technologists®.

Symposium Report. Battery materials : amorphous carbons and polymer electrolytes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gerald, R. E., II; Chemical Engineering

2000-01-01

The motivation for research in battery materials lies in the expanding consumer demand for compact, high-energy density power sources for portable electronic devices, and environmental issues such as global warming and air pollution that have provided the impetus for mass transportation by electric vehicles. The Battery Materials Symposium, chaired by Jacqueline Johnson (ANL), focused on three topics: the structure and electrochemical properties of new and existing electrolytes, devices for fabricating and investigating thin films, and large-scale computer simulations. The symposium opened with a presentation by the author on a recently invented device for in situ investigations of batteries using nuclearmore » magnetic resonance. Joop Schoonman (Delft University) described several methods for preparing and analyzing thin films made of solid electrolytes. These methods included chemical vapor deposition, electrostatic spray deposition and the Solufill process. Aiichiro Nakano discussed large-scale (10 million to 2 billion atoms) computer simulations of polymer and ceramic systems. An overview was given of a DOE Cooperative Research 2000 program, in the initial stages, that was set up to pursue these atomistic simulations. Doug MacFarlane (Monash University) described conductive plastic crystals based on pyrrolidinium imides. Joseph Pluth (U of Chicago) presented his recent crystallographic studies of Pb compounds found in the ubiquitous lead-acid battery. He showed the structures of tribasic lead sulfate and tetrabasic lead sulfate. Austen Angell (Arizona State Univ.) discussed the general problem of electrolyte polarization in Li-ion battery systems with cation transference numbers less than unity. Steven Greenbaum (Hunter College) provided an introduction of NMR interactions that are useful for investigations of lithium-ion battery materials. Analysis by NMR is nuclear specific, probes local environments and dynamics, and is non-destructive. He discussed {sup 7}Li NMR results of a solid electrolyte system composed of LiI dissolved in PEO. Work on oriented polymer electrolyte samples is ongoing. Yuri Andreev (U. of St. Andrews) gave a historical overview of a number of crystal structures of polymer electrolytes solved using XRD in the group of Peter Bruce. The last speaker of the symposium was Peter Papanek (U. of Pennsylvania). He spoke about various disordered carbon materials used as anodes in Li-ion batteries. He also described his inelastic neutron scattering studies of carbon materials derived from pyrolyzed epoxy novolak resins. His data supports the graphene sheet model and is also consistent with calculations of interior and edge carbon atoms in pyrene that chemically reacted with lithium.« less

An attempt to stabilize tanshinone IIA solid dispersion by the use of ternary systems with nano-CaCO3 and poloxamer 188.

PubMed

Yan, Hong-Mei; Zhang, Zhen-Hai; Jiang, Yan-Rong; Ding, Dong-Mei; Sun, E; Jia, Xiao-Bin

2014-04-01

Tanshinone IIA (TSIIA) on solid dispersions (SDs) has thermodynamical instability of amorphous drug. Ternary solid dispersions (tSDs) can extend the stability of the amorphous form of drug. Poloxamer 188 was used as a SD carrier. Nano-CaCO3 played an important role in adsorption of biomolecules and is being developed for a host of biotechnological applications. The aim of the present study was to investigate the dissolution behavior and accelerated stability of TSIIA on solid dispersions (SDs) by the use of ternary systems with nano-CaCO3 and poloxamer 188. The TSIIA tSDs were prepared by a spray-drying method. First, the effect of combination of poloxamer 188 and nano-CaCO3 on TSIIA dissolution was studied. Subsequently, a set of complementary techniques (DSC, XRPD, SEM and FTIR) was used to monitor the physical changes of TSIIA in the SDs. Finally, stability test was carried out under the conditions 40°C/75% RH for 6 months. The characterization of tSDs by differential scanning calorimetry analysis (DSC) and X-ray powder diffraction (XRPD) showed that TSIIA was present in its amorphous form. Fourier transforms infrared spectroscopy (FTIR) suggested the presence of interactions between TSIIA and carriers in tSDs. Improvement in the dissolution rate was observed for all SDs. The stability study conducted on SDs with nano-CaCO3 showed stable drug content and dissolution behavior, over the period of 6 months as compared with freshly prepared SDs. SDs preparation with nano-CaCO3 and poloxamer 188 may be a promising approach to enhance the dissolution and stability of TSIIA.

Processing thermally labile drugs by hot-melt extrusion: The lesson with gliclazide.

PubMed

Huang, Siyuan; O'Donnell, Kevin P; Delpon de Vaux, Sophie M; O'Brien, John; Stutzman, John; Williams, Robert O

2017-10-01

The formation of molecularly dispersed amorphous solid dispersions by the hot-melt extrusion technique relies on the thermal and mechanical energy inputs, which can cause chemical degradation of drugs and polymeric carriers. Additionally, drug degradation may be exacerbated as drugs convert from a more stable crystalline form to a higher energy amorphous form. Therefore, it is imperative to study how drug degrades and evaluate methods to minimize drug degradation during the extrusion process. In this work, gliclazide was used as a model thermally labile drug for the degradation kinetics and process optimization studies. Preformulation studies were conducted using thermal analyses, and liquid chromatography-mass spectroscopy to identify drug degradation pathways and to determine initial extrusion conditions. Formulations containing 10% drug and 90% AFFINISOL™ HPMC HME 100LV were then extruded using a twin screw extruder, and the extrudates were characterized using X-ray powder diffraction, modulated dynamic scanning calorimetry, and potency testing to evaluate physicochemical properties. The energies of activation for both amorphous gliclazide, crystalline gliclazide, and gliclazide solution were calculated using the Arrhenius equation to further guide the extrusion optimization process. Preformulation studies identify two hydrolysis degradation pathways of gliclazide at elevated temperatures. The activation energy study indicates a significantly higher degradation rate for the amorphous gliclazide compared to the crystalline form. After optimization of the hot-melt extrusion process, including improved screw designs, machine setup, and processing conditions, gliclazide amorphous solid dispersion with ∼95% drug recovery was achieved. The ability to process thermally labile drugs and polymers using hot-melt extrusion will significantly expand the possible applications of this manufacturing process. Copyright © 2017 Elsevier B.V. All rights reserved.

From crystalline to amorphous calcium pyrophosphates: A solid state Nuclear Magnetic Resonance perspective.

PubMed

Gras, Pierre; Baker, Annabelle; Combes, Christèle; Rey, Christian; Sarda, Stéphanie; Wright, Adrian J; Smith, Mark E; Hanna, John V; Gervais, Christel; Laurencin, Danielle; Bonhomme, Christian

2016-02-01

Hydrated calcium pyrophosphates (CPP, Ca2P2O7·nH2O) are a fundamental family of materials among osteoarticular pathologic calcifications. In this contribution, a comprehensive multinuclear NMR (Nuclear Magnetic Resonance) study of four crystalline and two amorphous phases of this family is presented. (1)H, (31)P and (43)Ca MAS (Magic Angle Spinning) NMR spectra were recorded, leading to informative fingerprints characterizing each compound. In particular, different (1)H and (43)Ca solid state NMR signatures were observed for the amorphous phases, depending on the synthetic procedure used. The NMR parameters of the crystalline phases were determined using the GIPAW (Gauge Including Projected Augmented Wave) DFT approach, based on first-principles calculations. In some cases, relaxed structures were found to improve the agreement between experimental and calculated values, demonstrating the importance of proton positions and pyrophosphate local geometry in this particular NMR crystallography approach. Such calculations serve as a basis for the future ab initio modeling of the amorphous CPP phases. The general concept of NMR crystallography is applied to the detailed study of calcium pyrophosphates (CPP), whether hydrated or not, and whether crystalline or amorphous. CPP are a fundamental family of materials among osteoarticular pathologic calcifications. Their prevalence increases with age, impacting on 17.5% of the population after the age of 80. They are frequently involved or associated with acute articular arthritis such as pseudogout. Current treatments are mainly directed at relieving the symptoms of joint inflammation but not at inhibiting CPP formation nor at dissolving these crystals. The combination of advanced NMR techniques, modeling and DFT based calculation of NMR parameters allows new original insights in the detailed structural description of this important class of biomaterials. Copyright © 2016. Published by Elsevier Ltd.

Mechanism for enhanced absorption of a solid dispersion formulation of LY2300559 using the artificial stomach duodenum model.

PubMed

Polster, Christopher S; Wu, Sy-Juen; Gueorguieva, Ivelina; Sperry, David C

2015-04-06

An artificial stomach duodenum (ASD) model has been used to demonstrate the performance difference between two formulations of LY2300559, a low-solubility acidic developmental drug. The two formulations investigated were a conventional high-shear wet granulation (HSWG) formulation and a solid dispersion formulation. A pharmacokinetic study in humans demonstrated the enhanced performance of the solid dispersion formulation relative to the HSWG formulation. The Cmax and AUC of the solid dispersion was 2.6 and 1.9 times greater, respectively, compared to the HSWG formulation. In the ASD, the solid dispersion formulation performance was characterized by three main phases: (1) rapid release in the stomach, creating a supersaturated concentration of drug, (2) precipitation in the stomach, and (3) rapid redissolution of the precipitate in the duodenum to concentration levels that are supersaturated relative to crystalline drug. A series of complementary experiments were employed to describe this performance behavior mechanistically. Imaging experiments with a pH indicating dye showed that local pH gradients from meglumine in the solid dispersion formulation were responsible for creating a high initial supersaturation concentration in the stomach. Upon dissipation of meglumine, the drug precipitated in the stomach as an amorphous solid. Because the precipitated drug is in an amorphous form, it can then rapidly redissolve as it transits to the more neutral environment of the duodenum. This unexpected sequence of physical state changes gives a mechanistic explanation for the enhanced in vivo performance of the solid dispersion formulation relative to the HSWG formulation.

Electrical, thermal and structural properties of plasticized waste cooking oil-based polyurethane solid polymer electrolyte

NASA Astrophysics Data System (ADS)

Huzaizi, Rahmatina Mohd; Tahir, Syuhada Mohd; Mahbor, Kamisah Mohamad

2017-12-01

Waste cooking oil-based polyol was synthesized using epoxidation and hydroxylation methods. The polyol was combined with 4,4-diphenylmethane diisocyanate to produce polyurethane (PU) to be used as polymer host in solid polymer electrolyte. 30 wt% LiClO4 was added as doping salt and two types of plasticizers were used; ethylene carbonate (PU-EC) and polyethylene glycol (PU-PEG). The SPE films were characterized using Fourier transform infrared spectroscopy, electrochemical impedance spectroscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The highest conductivity achieved was 8.4 x 10-8 S cm-1 upon addition of 10 wt% EC. The XRD results showed a decrease of crystalline peaks in PU-EC and the increase in PU-PEG. DSC results revealed that the films; PU, PU-EC and PU-PEG had glass transition temperatures of 159.7, 106.0 and 179.7 °C, respectively. The results showed that the addition of EC increased the amorphous region and the free volume in the SPE structure, thus resulted in higher ionic conductivity.

An experimental study on PEO polymer electrolyte based all-solid-state supercapacitor

NASA Astrophysics Data System (ADS)

Yijing, Yin

Supercapacitors are one of the most important electrochemical energy storage and conversion devices, however low ionic conductivity of solid state polymer electrolytes and the poor accessibility of the ions to the active sites in the porous electrode will cause low performance for all-solid-state supercapacitors and will limit their application. The objective of the dissertation is to improve the performance of all-solid-state supercapactor by improving electrolyte conductivity and solving accessibility problem of the ions to the active sites. The low ionic conductivity (10-8 S/cm) of poly(ethylene oxide) (PEO) limits its application as an electrolyte. Since PEO is a semicrystal polymer and the ion conduction take place mainly in the amorphous regions of the PEO/Lithium salt complex, improvements in the percentage of amorphous phase in PEO or increasing the charge carrier concentration and mobility could increase the ionic conductivity of PEO electrolyte. Hot pressing along with the additions of different lithium salts, inorganic fillers and plasticizers were applied to improve the ionic conductivity of PEO polymer electrolytes. Four electrode methods were used to evaluate the conductivity of PEO based polymer electrolytes. Results show that adding certain lithium salts, inorganic fillers, and plasticizers could improve the ionic conductivity of PEO electrolytes up 10-4 S/cm. Further hot pressing treatment could improve the ionic conductivity of PEO electrolytes up to 10-3 S/cm. The conductivity improvement after hot pressing treatment is elucidated as that the spherulite crystal phase is convert into the fringed micelle crystal phase or the amorphous phase of PEO electrolytes. PEO electrolytes were added into active carbon as a binder and an ion conductor, so as to provide electrodes with not only ion conduction, but also the accessibility of ion to the active sites of electrodes. The NaI/I 2 mediator was added to improve the conductivity of PEO electrolyte and provide pseudocapacitance for all-solid-state supercapacitors. Impedance, cyclic voltammetry, and gavalnostatic charge/discharge measurements were conducted to evaluate the electrochemical performance of PEO polymer electrolytes based all-solid-state supercapacitors. Results demonstrate that the conductivity of PEO electrolyte could be improved to 0.1 S/cm with a mediator concentration of 50wt%. A high conductivity in the PEO electrolyte with mediator is an indication of a high electron exchange rate between the mediator and mediator. The high electron exchange rates at mediator carbon interface and between mediator and mediator are essential in order to obtain a high response rate and high power. This automatically solves the accessibility problem. With the addition of NaI/I2 mediator, the specific capacitance increased more than 30 folds, specific power increased almost 20 folds, and specific energy increased around 10 folds. Further addition of filler to the electrodes along with the mediator could double the specific capacitor and specific power of the all-solid-state supercapacitor. The stability of the corresponded supercapacitor is good within 2000 cycles.

Irradiation effects and hydrogen behavior in H2+ and He+ implanted γ-LiAlO2 single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Weilin; Zhang, Jiandong; Kovarik, Libor

2017-02-01

Gamma-phase lithium aluminate (gamma-LiAlO2) is a breeder material for tritium, a necessary substance for strategic stockpile and fusion power systems. A fundamental study of structural evolution and tritium diffusion in gamma-LiAlO2 under displacive irradiation is needed to fully assess the material performance. This study utilizes ion implantation of protium (surrogate for tritium) and helium in gamma-LiAlO2 single crystals at elevated temperatures to emulate the irradiation effects. The results show that at 573 K there are two distinct disorder saturation stages to 1 dpa without full amorphization; overlapping implantation of H2+ and He+ ions suggests possible formation of gas bubbles. Formore » irradiation to 1E21 H+/m2 (0.36 dpa at peak) at 773 K, amorphization occurs at surface with H diffusion and dramatic Li loss; the microstructure contains bubbles and cubic LiAl5O8 precipitates with sizes up to 200 nm or larger. In addition, significant H diffusion and release are observed during thermal annealing.« less

Use of surfactants as plasticizers in preparing solid dispersions of poorly soluble API: stability testing of selected solid dispersions.

PubMed

Ghebremeskel, Alazar N; Vemavarapu, Chandra; Lodaya, Mayur

2006-08-01

The purpose of the study is to evaluate the effect of surfactant-plasticizers on the physical stability of amorphous drug in polymer matrices formed by hot melt extrusion. Solid dispersions of a poorly soluble drug were prepared using PVP-K30, Plasdone-S630, and HPMC-E5 as the polymeric carriers and surfactants as plasticizers. The solid dispersions were produced by hot melt extrusion at temperatures 10 degrees C above and below the glass transition temperature (Tg) of the carrier polymers using a 16 mm-Haake Extruder. The surfactants tested in this study included Tween-80 and Docusate Sodium. The particle size of the extrudate was reduced to have mean of 100-200 micron. The physical stability of the solid dispersions produced was monitored at 30 degrees C/60% for six-months and at 60 degrees C/85% for two-months in open HDPE bottles. Modulated differential scanning calorimetry, polarized light microscopy, powder X-ray diffraction and dissolution testing was performed to assess the physical stability of solid dispersions upon stress testing. The dispersions containing HPMC-E5 were observed especially to be susceptible to physical instability under an accelerated stress conditions (60 degrees C/85%RH) of the solid dispersion. About 6% conversion of amorphous drug to crystalline form was observed. Consequently, the system exhibits similar degree of re-crystallization upon addition of the surfactant. However, under 30 degrees C/60%RH condition, the otherwise amorphous Drug-HPMC-E5 system has been destabilized by the addition of the surfactant. This effect is much more reduced in the extruded solid dispersions where polymeric carriers such as Plasdone S-603 and PVP-K30 (in addition to surfactants) are present. Furthermore, the drug release from the solid dispersions was unaffected at the stress conditions reported above. Possible reasons for the enhanced stability of the dispersions are due to the surfactants ability to lower the viscosity of the melt, increase the API solubility and homogeneity in the carrier polymer. In contrast, while it is possible for the surfactants to destabilize the system by lowering the Tg and increasing the water uptake, the study confirms that this effect is minimal. By and large, the surfactants appear to be promising plasticizers to produce solid dispersions by hot melt extrusion, in so doing improving dissolution rate without compromising the physical stability of the systems.

Transmission Line for 258 GHz Gyrotron DNP Spectrometry

NASA Astrophysics Data System (ADS)

Bogdashov, Alexandr A.; Belousov, Vladimir I.; Chirkov, Alexey V.; Denisov, Gregory G.; Korchagin, Vyacheslav V.; Kornishin, Sergey Yu.; Tai, Evgeny M.

2011-06-01

We describe the design and test results of the transmission line for liquid-state (LS) and solid-state (SS) DNP spectrometers with the second-harmonic 258.6 GHz gyrotron at the Institute of the Biophysical Chemistry Center of Goethe University (Frankfurt). The 13-meter line includes a mode converter, HE11 waveguides, 4 mitre bends, a variable polarizer-attenuator, directional couplers, a water-flow calorimeter and a mechanical switch. A microwave power of about 15 W was obtained in the pure HE11 mode at the spectrometer inputs.

Metastable Eutectic Equilibrium in Natural Environments: Recent Developments and Research Opportunities

NASA Technical Reports Server (NTRS)

Rietmeijer, Fans J. M.; Nuth, Joseph A., II; Jablonska, Mariola; Karner, James M.

2000-01-01

Chemical ordering at metastable eutectics was recognized in non-equilibrium gas-to- solid condensation experiments to constrain 'silicate' dust formation in O-rich circumstellar environments. The predictable metastable eutectic behavior successfully predicted the observed ferromagnesiosilica, compositions of circumstellar dust, presolar and solar nebula grains in the matrix of the collected aggregate IDPs. Many of the experimentally determined metastable eutectic solids match the fundamental building blocks of common rock-forming layer silicates: this could have implications for the origin of Life. The physical conditions conducive to metastable eutectic behavior, i.e. high temperature and (ultra)fast quenching, lead to unique amorphous, typically nano- to micrometer-sized, materials. The new paradigm of metastable eutectic behavior opens the door to new and exciting research opportunities in uncovering the many implications of these unique amorphous and typically nano- to micrometer-sized, metastable eutectic materials.

Uranyl peroxide nanoclusters at high-pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turner, Katlyn M.; Szymanowski, Jennifer E. S.; Zhang, Fuxiang

Here, U 60 ([UO 2(O 2)(OH)] 60 60– in water) is a uranyl peroxide nanocluster with a fullerene topology and O h symmetry. U 60 clusters can exist in crystalline solids or in liquids; however, little is known of their behavior at high pressures. We compressed the U 60-bearing material: Li 68K 12(OH) 20[UO 2(O 2)(OH)] 60(H 2O) 310 ( Fm3¯; a = 37.884 Å) in a diamond anvil cell to determine its response to increasing pressure. Three length scales and corresponding structural features contribute to the compression response: uranyl peroxide bonds (<0.5 nm), isolated single nanoclusters (2.5 nm), andmore » the long-range periodicity of nanoclusters within the solid (>3.7 nm). Li 68K 12(OH) 20[UO 2(O 2)(OH)] 60(H 2O) 310 transformed to a tetragonal structure below 2 GPa and irreversibly amorphized between 9.6 and 13 GPa. The bulk modulus of the tetragonal U 60-bearing material was 25 ± 2 GPa. The pressure-induced amorphous phase contained intact U 60 clusters, which were preserved beyond the loss of long-range periodicity. The persistence of U 60 clusters at high pressure may have been enhanced by the interaction between U 60 nanoclusters and the alcohol pressure medium. Once formed, U 60 nanoclusters persist regardless of their associated long-range ordering—in crystals, amorphous solids, or solutions.« less

Uranyl peroxide nanoclusters at high-pressure

DOE PAGES

Turner, Katlyn M.; Szymanowski, Jennifer E. S.; Zhang, Fuxiang; ...

2017-08-14

Here, U 60 ([UO 2(O 2)(OH)] 60 60– in water) is a uranyl peroxide nanocluster with a fullerene topology and O h symmetry. U 60 clusters can exist in crystalline solids or in liquids; however, little is known of their behavior at high pressures. We compressed the U 60-bearing material: Li 68K 12(OH) 20[UO 2(O 2)(OH)] 60(H 2O) 310 ( Fm3¯; a = 37.884 Å) in a diamond anvil cell to determine its response to increasing pressure. Three length scales and corresponding structural features contribute to the compression response: uranyl peroxide bonds (<0.5 nm), isolated single nanoclusters (2.5 nm), andmore » the long-range periodicity of nanoclusters within the solid (>3.7 nm). Li 68K 12(OH) 20[UO 2(O 2)(OH)] 60(H 2O) 310 transformed to a tetragonal structure below 2 GPa and irreversibly amorphized between 9.6 and 13 GPa. The bulk modulus of the tetragonal U 60-bearing material was 25 ± 2 GPa. The pressure-induced amorphous phase contained intact U 60 clusters, which were preserved beyond the loss of long-range periodicity. The persistence of U 60 clusters at high pressure may have been enhanced by the interaction between U 60 nanoclusters and the alcohol pressure medium. Once formed, U 60 nanoclusters persist regardless of their associated long-range ordering—in crystals, amorphous solids, or solutions.« less

Synthesis and electrochemical property of amorphous carbon nanotubes wrapped sulfur particles as cathode material for lithium-sulfur batteries

NASA Astrophysics Data System (ADS)

Hu, Jingtian; Zhao, Tingkai; Ji, Xianglin; Peng, Xiarong; Jin, Wenbo; Yang, Wenbo; Zhang, Lei; Gao, Junjie; Dang, Alei; Li, Hao; Li, Tiehu

2017-11-01

Amorphous carbon nanotube (ACNT)/sulfur composites were prepared by solution reaction method. The electrochemical results showed that both ACNT/S composite and ACNT/S mixture had a first reversible capacity of 1020 mA h·g-1, and the capacity retention of ACNT/S composite was 77% after 100 cycles while that of ACNT/S mixture was only 35% with the initial capacity being 850 mA h·g-1. The experimental results showed that the reversible lithium insertion capacity of the composite was obviously high and the cycling stability was good, which was mainly due to the solid and uniform dispersion of the sulfur and amorphous carbon nanotube matrix in the composite.

Apparatus for production of ultrapure amorphous metals utilizing acoustic cooling

NASA Technical Reports Server (NTRS)

Lee, M. C. (Inventor)

1985-01-01

Amorphous metals are produced by forming a molten unit of metal and deploying the unit into a bidirectional acoustical levitating field or by dropping the unit through a spheroidizing zone, a slow quenching zone, and a fast quenching zone in which the sphere is rapidly cooled by a bidirectional jet stream created in the standing acoustic wave field produced between a half cylindrical acoustic driver and a focal reflector or a curved driver and a reflector. The cooling rate can be further augmented first by a cryogenic liquid collar and secondly by a cryogenic liquid jacket surrounding a drop tower. The molten unit is quenched to an amorphous solid which can survive impact in a unit collector or is retrieved by a vacuum chuck.

Communication: A combined periodic density functional and incremental wave-function-based approach for the dispersion-accounting time-resolved dynamics of ⁴He nanodroplets on surfaces: ⁴He/graphene.

PubMed

de Lara-Castells, María Pilar; Stoll, Hermann; Civalleri, Bartolomeo; Causà, Mauro; Voloshina, Elena; Mitrushchenkov, Alexander O; Pi, Martí

2014-10-21

In this work we propose a general strategy to calculate accurate He-surface interaction potentials. It extends the dispersionless density functional approach recently developed by Pernal et al. [Phys. Rev. Lett. 103, 263201 (2009)] to adsorbate-surface interactions by including periodic boundary conditions. We also introduce a scheme to parametrize the dispersion interaction by calculating two- and three-body dispersion terms at coupled cluster singles and doubles and perturbative triples (CCSD(T)) level via the method of increments [H. Stoll, J. Chem. Phys. 97, 8449 (1992)]. The performance of the composite approach is tested on (4)He/graphene by determining the energies of the low-lying selective adsorption states, finding an excellent agreement with the best available theoretical data. Second, the capability of the approach to describe dispersionless correlation effects realistically is used to extract dispersion effects in time-dependent density functional simulations on the collision of (4)He droplets with a single graphene sheet. It is found that dispersion effects play a key role in the fast spreading of the (4)He nanodroplet, the evaporation-like process of helium atoms, and the formation of solid-like helium structures. These characteristics are expected to be quite general and highly relevant to explain experimental measurements with the newly developed helium droplet mediated deposition technique.

Kinetic Modeling of Accelerated Stability Testing Enabled by Second Harmonic Generation Microscopy.

PubMed

Song, Zhengtian; Sarkar, Sreya; Vogt, Andrew D; Danzer, Gerald D; Smith, Casey J; Gualtieri, Ellen J; Simpson, Garth J

2018-04-03

The low limits of detection afforded by second harmonic generation (SHG) microscopy coupled with image analysis algorithms enabled quantitative modeling of the temperature-dependent crystallization of active pharmaceutical ingredients (APIs) within amorphous solid dispersions (ASDs). ASDs, in which an API is maintained in an amorphous state within a polymer matrix, are finding increasing use to address solubility limitations of small-molecule APIs. Extensive stability testing is typically performed for ASD characterization, the time frame for which is often dictated by the earliest detectable onset of crystal formation. Here a study of accelerated stability testing on ritonavir, a human immunodeficiency virus (HIV) protease inhibitor, has been conducted. Under the condition for accelerated stability testing at 50 °C/75%RH and 40 °C/75%RH, ritonavir crystallization kinetics from amorphous solid dispersions were monitored by SHG microscopy. SHG microscopy coupled by image analysis yielded limits of detection for ritonavir crystals as low as 10 ppm, which is about 2 orders of magnitude lower than other methods currently available for crystallinity detection in ASDs. The four decade dynamic range of SHG microscopy enabled quantitative modeling with an established (JMAK) kinetic model. From the SHG images, nucleation and crystal growth rates were independently determined.

Understanding API-polymer proximities in amorphous stabilized composite drug products using fluorine-carbon 2D HETCOR solid-state NMR.

PubMed

Abraham, Anuji; Crull, George

2014-10-06

A simple and robust method for obtaining fluorine-carbon proximities was established using a (19)F-(13)C heteronuclear correlation (HETCOR) two-dimensional (2D) solid-state nuclear magnetic resonance (ssNMR) experiment under magic-angle spinning (MAS). The method was applied to study a crystalline active pharmaceutical ingredient (API), avagacestat, containing two types of fluorine atoms and its API-polymer composite drug product. These results provide insight into the molecular structure, aid with assigning the carbon resonances, and probe API-polymer proximities in amorphous spray dried dispersions (SDD). This method has an advantage over the commonly used (1)H-(13)C HETCOR because of the large chemical shift dispersion in the fluorine dimension. In the present study, fluorine-carbon distances up to 8 Å were probed, giving insight into the API structure, crystal packing, and assignments. Most importantly, the study demonstrates a method for probing an intimate molecular level contact between an amorphous API and a polymer in an SDD, giving insights into molecular association and understanding of the role of the polymer in API stability (such as recrystallization, degradation, etc.) in such novel composite drug products.

Effect of storage conditions on the recrystallization of drugs in solid dispersions with crospovidone.

PubMed

Shibata, Yusuke; Fujii, Makiko; Suzuki, Ayako; Koizumi, Naoya; Kanada, Ken; Yamada, Masaki; Watanabe, Yoshiteru

2014-06-01

The physical stability of amorphous solid dispersions (SDs) is influenced by their storage conditions. The goal of this work was to investigate the factors affecting the recrystallization of drugs in SDs after storage under conditions of high temperature and high humidity. SDs of three drugs (dipyridamole, nifedipine and indomethacin) with different functional groups (amino, carbonyl and hydroxyl) and onset times for crystallization of the amorphous state were prepared using crospovidone (CrosPVP). All of the drugs in the SDs remained in an amorphous state at 25 °C/50% relative humidity (RH) in closed glass bottles for at least six months. Under conditions of high temperature (40 °C/75%RH/closed and 60 °C/open), differences in interactions between the hydrogen bond donors of the drugs and the amide carbonyl group of CrosPVP are essential factors for recrystallization of the drugs in the SDs. On the other hand, under condition of high humidity (40 °C/75%RH/open), in addition to the difference in the interaction between the drug and CrosPVP, the rate of increase in moisture content affects their recrystallization in SDs.

Synthesis and characterization of ester and amide derivatives of titanium(IV) carboxymethylphosphonate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melánová, Klára, E-mail: klara.melanova@upce.cz; Beneš, Ludvík; Trchová, Miroslava

2013-06-15

A set of layered ester and amide derivatives of titanium(IV) carboxymethylphosphonate was prepared by solvothermal treatment of amorphous titanium(IV) carboxymethylphosphonate with corresponding 1-alkanols, 1,ω-alkanediols, 1-aminoalkanes, 1,ω-diaminoalkanes and 1,ω-amino alcohols and characterized by powder X-ray diffraction, IR spectroscopy and thermogravimetric analysis. Whereas alkyl chains with one functional group form bilayers tilted to the layers, 1,ω-diaminoalkanes and most of 1,ω-alkanediols form bridges connecting the adjacent layers. In the case of amino alcohols, the alkyl chains form bilayer and either hydroxyl or amino group is used for bonding. This simple method for the synthesis of ester and amide derivatives does not require preparationmore » of acid chloride derivative as a precursor or pre-intercalation with alkylamines and can be used also for the preparation of ester and amide derivatives of titanium carboxyethylphosphonate and zirconium carboxymethylphosphonate. - Graphical abstract: Ester and amide derivatives of layered titanium carboxymethylphosphonate were prepared by solvothermal treatment of amorphous solid with alkanol or alkylamine. - Highlights: • Ester and amide derivatives of titanium carboxymethylphosphonate. • Solvothermal treatment of amorphous solid with alkanol or alkylamine. • Ester and amide formation confirmed by IR spectroscopy.« less

Microcrystals and Amorphous Material in Comets and Primitive Meteorites: Keys to Understanding Processes in the Early Solar System

NASA Technical Reports Server (NTRS)

Nuth, J. A.; Brearley, A. J.; Scott, E. R. D.

2004-01-01

Comets, fine-grained matrices of chondrites, and chondritic interplanetary dust particles (IDPs) are each composed of both crystalline and amorphous silicates. The primitive solar nebula, in which comets and asteroids accreted, was formed from the collapsed core of a Giant Molecular Cloud, that, in turn, condensed from materials present in the interstellar medium (ISM). Despite observations that reveal the presence of crystalline magnesium silicate minerals in the shells of very high mass-loss-rate stars [1,2], typical silicate grains in the ISM are most likely to be amorphous, given their relatively long residence time in such a high radiation environment. An upper limit of 3% crystalline grains can be derived from their non-detection in spectra of ISM solids [3]. If the vast majority of grains that enter the primitive solar nebula are amorphous, then the observation of crystalline dust in comets and primitive chondrite matrices indicates the action of specific processes required to transform the amorphous starting materials into the crystals that are observed.

In situ TEM observation of alpha-particle induced annealing of radiation damage in Durango apatite.

PubMed

Li, Weixing; Shen, Yahui; Zhou, Yueqing; Nan, Shuai; Chen, Chien-Hung; Ewing, Rodney C

2017-10-26

A major issue in thermochronology and U-Th-Pb dating is the effect of radiation damage, created by α-recoils from α-decay events, on the diffusion of radiogenic elements (e.g., He and Pb) in host mineral. Up until now, thermal events have been considered as the only source of energy for the recovery of radiation-damage. However, irradiation, such as from the α-particle of the α-decay event, can itself induce damage recovery. Quantification of radiation-induced recovery caused by α-particles during α-decay events has not been possible, as the recovery process at the atomic-scale has been difficult to observe. Here we present details of the dynamics of the amorphous-to-crystalline transition process during α-particle irradiations using in situ transmission electron microscopy (TEM) and consecutive ion-irradiations: 1 MeV Kr 2+ (simulating α-recoil damage), followed by 400 keV He + (simulating α-particle annealing). Upon the He + irradiation, partial recrystallization of the original, fully-amorphous Durango apatite was clearly evident and quantified based on the gradual appearance of new crystalline domains in TEM images and new diffraction maxima in selected area electron diffraction patterns. Thus, α-particle induced annealing occurs and must be considered in models of α-decay event damage and its effect on the diffusion of radiogenic elements in geochronology and thermochronology.

Nuclear magnetic resonance studies of DNP-ready trehalose obtained by solid state mechanochemical amorphization

NASA Astrophysics Data System (ADS)

Filibian, M.; Elisei, E.; Colombo Serra, S.; Rosso, A.; Tedoldi, F.; Cesàro, A.; Carretta, P.

$^1$H nuclear spin-lattice relaxation and Dynamic Nuclear Polarization (DNP) have been studied in amorphous samples of trehalose sugar doped with TEMPO radicals by means of mechanical milling, in the 1.6 K $\\div$ 4.2 K temperature range. The radical concentration was varied between 0.34 and 0.81 $\\%$. The highest polarization of 15 \\% at 1.6 K, observed in the sample with concentration $0.50 \\%$, is of the same order of magnitude of that reported in standard frozen solutions with TEMPO. The temperature and concentration dependence of the spin-lattice relaxation rate $1/T_{\\text{1}}$, dominated by the coupling with the electron spins, were found to follow power laws with an exponent close to $3$ in all samples. The observed proportionality between $1/T_{\\text{1}}$ and the polarization rate $1/T_{\\text{pol}}$, with a coefficient related to the electron polarization, is consistent with the presence of Thermal Mixing (TM) and a good contact between the nuclear and the electron spins. At high electron concentration additional relaxation channels causing a decrease in the nuclear polarization must be considered. These results provide further support for a more extensive use of amorphous DNP-ready samples, obtained by means of comilling, in dissolution DNP experiments and possibly for $\\textit{in vivo}$ metabolic imaging.

Nuclear magnetic resonance studies of DNP-ready trehalose obtained by solid state mechanochemical amorphization.

PubMed

Filibian, M; Elisei, E; Colombo Serra, S; Rosso, A; Tedoldi, F; Cesàro, A; Carretta, P

2016-06-22

(1)H nuclear spin-lattice relaxation and Dynamic Nuclear Polarization (DNP) have been studied in amorphous samples of trehalose sugar doped with TEMPO radicals by means of mechanical milling, in the 1.6-4.2 K temperature range. The radical concentration was varied between 0.34 and 0.81%. The highest polarization of 15% at 1.6 K, observed in the sample with concentration 0.50%, is of the same order of magnitude of that reported in standard frozen solutions with TEMPO. The temperature and concentration dependence of the spin-lattice relaxation rate 1/T1, dominated by the coupling with the electron spins, were found to follow power laws with an exponent close to 3 in all samples. The observed proportionality between 1/T1 and the polarization rate 1/Tpol, with a coefficient related to the electron polarization, is consistent with the presence of Thermal Mixing (TM) and a good contact between the nuclear and the electron spins. At high electron concentration additional relaxation channels causing a decrease in the nuclear polarization must be considered. These results provide further support for a more extensive use of amorphous DNP-ready samples, obtained by means of comilling, in dissolution DNP experiments and possibly for in vivo metabolic imaging.

Two-level tunneling systems in amorphous alumina

NASA Astrophysics Data System (ADS)

Lebedeva, Irina V.; Paz, Alejandro P.; Tokatly, Ilya V.; Rubio, Angel

2014-03-01

The decades of research on thermal properties of amorphous solids at temperatures below 1 K suggest that their anomalous behaviour can be related to quantum mechanical tunneling of atoms between two nearly equivalent states that can be described as a two-level system (TLS). This theory is also supported by recent studies on microwave spectroscopy of superconducting qubits. However, the microscopic nature of the TLS remains unknown. To identify structural motifs for TLSs in amorphous alumina we have performed extensive classical molecular dynamics simulations. Several bistable motifs with only one or two atoms jumping by considerable distance ~ 0.5 Å were found at T=25 K. Accounting for the surrounding environment relaxation was shown to be important up to distances ~ 7 Å. The energy asymmetry and barrier for the detected motifs lied in the ranges 0.5 - 2 meV and 4 - 15 meV, respectively, while their density was about 1 motif per 10 000 atoms. Tuning of motif asymmetry by strain was demonstrated with the coupling coefficient below 1 eV. The tunnel splitting for the symmetrized motifs was estimated on the order of 0.1 meV. The discovered motifs are in good agreement with the available experimental data. The financial support from the Marie Curie Fellowship PIIF-GA-2012-326435 (RespSpatDisp) is gratefully acknowledged.

FOREWORD: Some thoughts about Jürgen Hafner's work in computational materials science Some thoughts about Jürgen Hafner's work in computational materials science

NASA Astrophysics Data System (ADS)

Heine, Volker

2011-10-01

Jürgen Hafner started in the early 1970s with pseudopotential calculations on the structures and properties of sp-bonded metals, improving on work done elsewhere [1]. This expanded in four directions: transition metals, molten metals, magnetism and alloys, and combinations of these. As well as electronic structure calculations, he helped to advance the statistical mechanical classical theory of liquids for the molten metals [2]. In magnetism he was one of the pioneers of calculations with non-collinear spins [3, 4]. As well as simple (solid and molten) alloys, he also treated materials with strong chemical interaction such as sulphides and liquids such as arsenic and tellurium [5, 6]. All this fed into two directions which dominated much of his work for many years, namely the theory of glassy metals [7] and that of quasicrystals [8]. One notable result in the latter was to show that it was possible to construct hypothetical materials for which the quasicrystalline state is indeed the lowest energy structure. This displaced the established wisdom of the time that quasicrystals were necessarily metastable forms. In more recent years he has turned to calculations in surface science [9, 10], including catalysis of chemical reactions on surfaces [11, 12]. What really brought Jürgen first to my attention was that he had managed to do a better job than we had of calculations with the new approach of pseudopotentials, particularly regarding the screening part of the calculation. This is very important in alloys where there is a large difference in the electron density in the two types of atom due to their different volumes or valences such as in the phase diagram and structure of LiK or KPb [5, 13]. We have been in contact over many years including one close collaboration and I always learned something new in talking with Jürgen. In the late 1970s in Cambridge we performed phonon calculations on models of amorphous silicon [14], to see if these could distinguish between different models such as those with or without odd-membered rings of Si atoms. We used the so-called recursion method with force constants to near neighbours [15], and sampled the phonon density of modes projected onto individual atoms. This meant quite a large number of calculations were required to sample enough atoms out of the amorphous cluster. However Jürgen showed that it could be done much more simply when he became interested in the analogous problem of the phonon spectrum of his glassy metals. He calculated the phonon density of modes projected onto a vector spanning all the atoms but with random phases [16]. This summed coherently the local density of modes on all the atoms, which is what one wanted, plus off-diagonal parts with random phases which therefore cancelled to a good approximation and which could be further reduced by summing over a few such calculations varying the random phase factors. This greatly reduced the computational effort, and in practice meant that one could deal with larger and more realistic computer samples. A continuing common interest has been phase diagrams, particularly how structures vary with pressure (change of atomic volume) and with element in a column of the periodic table or in alloying [17]. In particular, the behaviour of the group IV elements under pressure can be plotted qualitatively on a universal phase diagram. Together we made calculations [18] characterizing sp-bonded elements (or 'virtual' elements in the virtual crystal approximation for alloys) by just three parameters, namely the valence Z, ion core radius Rc in the Ashcroft 'empty core' model of the pseudopotential, and volume (per atom) which can be varied with pressure. Of course such a model is grossly simplified, but for valence 3 the results showed well the transition for Z = 3 from the close-packed fcc structure in aluminum, through more open and distorted structures in gallium and indium, to a close-packed structure again in thallium. Hafner and his groups extended these studies to molten [19] and quasicrystalline metals. The stunning result was that among the distorted structures there was a region where quasicrystals were stable with the lowest energy among all the structures they tried and which had shown up elsewhere [20]. In addition to Jürgen Hafner's actual research work published in over 600 research papers, including numerous review articles, several contributions to books and one monograph, he has done a great deal to establish our field of electronic structure calculation as the basis for understanding materials in Austria and across Europe. The founding and expansion of the Computational Materials Science Centre (CMS) in Vienna owes much to him, as well as the development of the European Psi-k network where he served as acting chairman in 1997-1999. He has been one of the leaders of the 'Surfaces and Catalysis Working Group' of Psi-k, and the instigator of several 'Theory Meets Industry' workshops [21] to stimulate the transfer of our methodology to industrial problems. Jürgen Hafner has always aimed for the highest intellectual standards. His nose for finding the most advanced work going on elsewhere has resulted in many international cooperations, including some in the USA and Japan. His list of international joint research projects runs to many pages. This in turn has been a major contributor to European cooperation, and in making it now the leading area in the world for our field. Hafner's research has always been linked closely to understanding puzzling experimental results, and in this way he has helped to establish a good reputation for computational physics within the mainstream of condensed matter physics of materials. It has taken quite a long time to establish computer simulations as a respectable component of research in condensed matter physics. "It is not real theory" people sneered from one side, and "computer simulations are not like real experiments" from the other. In the late 1990s a young German said to me that one could never get a professorship of theoretical physics in Germany doing the kind of things that I have done during my life: maybe in 'materials physics' or 'applied physics' but not a chair in theoretical physics. I think the situation has changed now, with computer simulations making an essential contribution to research across diverse fields. Hafner's high intellectual standards have contributed a lot to help bring about this change in attitudes in Europe. Another aspect of Hafner's high standards has been that he was never a friend of big computing for the sake of computing. All the research has been guided by trying to achieve scientific understanding of puzzling results, and being closely allied to experimental findings. Thus he has been a favourite invited speaker at many conferences around the world. At this point I would like to add something more on this comment on high standards, which is also relevant to European cooperation. I often quote a remark by the late Sir Nevill Mott who was head of the Cavendish Lab when I was young: "In basic research, second class work is almost not worth doing." If the work is already behind the front line of research when it is being done, it is not likely to contribute much to moving that frontier forward which is what basic research is about. Jürgen Hafner has always sought out the most advanced work anywhere in the world that is relevant to his projects, which has brought him into many international collaborations. He has recognized clearly that any one European country is not a large enough unit to have all the latest expertise in our subject, and this has led him to help build up strong European cooperation through the Psi-k European network already mentioned. Other people will know better than I do the large number of graduate students who have passed through Jürgen Hafner's hands, many continuing in on-going research collaborations. In this regard the special connection of Hafner's group, and the Computational Materials Science Centre generally, with the surrounding countries of Central Europe has been of great importance to science in those countries, particularly during the communist era. As well as his major fields of research interest that I have mentioned, one sees on his publication list several forays into applying our methodology in other areas of science. In particular there are papers on silicate minerals and zeolites, on fullerenes and some biological applications to rhodopsin, which is the light-sensitive material in the eye. In conclusion, there is an enormous amount to celebrate in the scientific contributions of Professor Jürgen Hafner and his personal group and the Vienna Computational Materials Science Centre which he has fostered. References [1] Hafner J and Nowotny H 1971 A first principles calculation of binding energies, structures, and lattice constants of simple metals Phys. Lett. A 37 335-6 [2] Hafner J 1977 Structure and thermodynamics of liquid metals and alloys Phys. Rev. A 16 351-64 [3] Lorenz R and Hafner J 1995 Noncollinear magnetic structures in amorphous iron and iron-based alloys J. Magn. Magn. Mater. 139 209-27 [4] Hobbs D, Kresse G and Hafner J 2000 Fully unconstrained noncollinear magnetism within the projector augmented-wave method Phys. Rev. B 62 11556-73 [5] Hafner J 1989 The structure of liquid arsenic: Peierls distortion versus Friedel modulation Phys. Rev. Lett. 62 784-7 [6] Hafner J 1990 Structure of liquid tellurium: entangled, broken chains J. Phys.: Condens. Matter 2 1271-80 [7] Hafner J 1986 Electronic aspects of the structure and of the glass-forming ability of metallic alloys Amorphous Metals and Semiconductors ed P Haasen and R I Jaffee (Oxford: Pergamon) pp 151-67 [8] Hafner J and Krajčí M 1999 Quasicrystals: elementary excitations and physical properties Physical Properties of Quasicrystals (Solid State Science Series vol 126) ed Z M Stadnik (Berlin: Springer) pp 209-56 [9] Furthmüller J, Hafner J and Kresse G 1994 Structral and electronic properties of clean and hydrogenated diamond (100) surfaces Europhys. Lett. 28 659-64 [10] Krajčí and Hafner J 2008 Ab-initio studies of quasicrystalline surfaces Quasicrystals (Handbook of Metal Physics vol 2) ed T Fujiwara and Y Ishii (Amsterdam: Elsevier) chapter 9, pp 313-55 [11] Raybaud P, Hafner J, Kresse G, Kasztelan S and Toulhoat H 2000 Structure, energetics and electronic properties of the surface of a promoted MoS2 catalyst: an ab-initio local-density-functional study J. Catalysis 190 128-43 [12] Hafner J, Benco L and Bucko T 2006 Acid-based catalysis in zeolites investigated by density-functional methods Top. Catalysis 37 41-54 [13] Hafner J 1989 Formation of polyanionic clusters in liquid potassium-lead alloys: a molecular-dynamics study J. Phys.: Condens. Matter 1 1133-40 [14] Meeks P E 1976 Vibrational spectra and topological structure of tetrahedrally bonded amorphous semiconductors Phil. Mag. 33 897-908 [15] See articles by Heine V, Bullet D, Haydock R and Kelly M J 1980 Solid State Physics—Advances in Research and Applications vol 35, ed H Ehrenreich, D Turnbull and F Seitz (New York: Academic) [16] Hafner J 1980 The dynamical properties of metallic glasses Liquids and Amorphous Metals (NATO-ASI Ser. E vol 36) ed E Lüscher and H Coufal (Sijthoff and Nordhoff: Alpen van Rijn) pp 199-209 [17] Hafner J 1987 From Hamiltonians to Phase Diagrams—The Electronic and Statistical-Mechanical Theory of sp-Bonded Metals and Alloys (Solid State Sciences Series vol 70) (Berlin: Springer) p 415 [18] Hafner J and Heine V 1983 The crystal structure of the elements: pseudopotential theory revisited J. Phys. F: Met. Phys. 13 2479-501 [19] Hafner J and Kahl G 1984 The structure of the elements in the liquid state J. Phys. F: Met. Phys. 14 2259-78 [20] Denton A R and Hafner J 1997 Thermodynamically stable one-component quasicrystals: a density-functional survey of relative stabilities Phys. Rev. B 56 2469-82 [21] Hafner J (ed) 2008 J. Phys.: Condens. Matter 20 (special issue) Tanaka I, Hafner J, Wimmer E and Asahi R (eds) 2010 J. Phys.: Condens. Matter 22 (special issue)