Instrument and method for focusing X-rays, gamma rays and neutrons

DOEpatents

Smither, Robert K.

1984-01-01

A crystal diffraction instrument or diffraction grating instrument with an improved crystalline structure or grating spacing structure having a face for receiving a beam of photons or neutrons and diffraction planar spacing or grating spacing along that face with the spacing increasing progressively along the face to provide a decreasing Bragg diffraction angle for a monochromatic radiation and thereby increasing the usable area and acceptance angle. The increased planar spacing for the diffraction crystal is provided by the use of a temperature differential across the crystalline structure, by assembling a plurality of crystalline structures with different compositions, by an individual crystalline structure with a varying composition and thereby a changing planar spacing along its face, and by combinations of these techniques. The increased diffraction grating element spacing is generated during the fabrication of the diffraction grating by controlling the cutting tool that is cutting the grooves or controlling the laser beam, electron beam or ion beam that is exposing the resist layer, etc. It is also possible to vary this variation in grating spacing by applying a thermal gradient to the diffraction grating in much the same manner as is done in the crystal diffraction case.

Hf--Co--B alloys as permanent magnet materials

DOEpatents

McGuire, Michael Alan; Rios, Orlando; Ghimire, Nirmal Jeevi

2017-01-24

An alloy composition is composed essentially of Hf.sub.2-XZr.sub.XCo.sub.11B.sub.Y, wherein 0

Stimulation of processes of self-propagating high temperature synthesis in system Ti + Al at low temperatures by influence of γ-quanta

NASA Astrophysics Data System (ADS)

Sobachkin, A. V.; Loginova, M. V.; Sitnikov, A. A.; Yakovlev, V. I.; Filimonov, V. Yu; Gradoboev, A. V.

2018-03-01

In the present work, the influence of the irradiation with gamma-quanta 60Co upon the structural and phase state of the components of the mechanically activated powder composition of Ti+Al is investigated. The phase composition, structural parameters, and crystallinity are examined by means of X-ray diffractometry. It is found out that the irradiation with gamma-quanta changes the structure of the mechanically activated powder composition. The higher irradiation dose, the higher the structure crystallinity of both components with no change in phase state. At the same time, the parameters of Ti and Al crystal lattices approach to the initial parameters observed before the mechanical activation. The irradiation with gammaquanta leads to decrease of internal stresses in the mechanically activated powder composition while nanocrystallinity of the structure remains unchanged. Using of powder compositions exposed to the irradiation with gamma-quanta for the SH-synthesis helps to increase speed of the reaction, decrease the peak firing temperature and improve homogeneity, as well as the main phase of the produced material is TiAl.

Tools to Study Interfaces for Superconducting, Thermoelectric, and Magnetic Materials at the University of Houston

DTIC Science & Technology

2016-09-01

The MBE system, which grows crystalline thin films in ultrahigh vacuum (UHV) with precise control of thickness, composition, and morphology, will...used on our sputtering system to fabricate thin films with interfaces. - The electronic structures of these materials will be investigated using the...magnetization/transport measurements. The MBE system, which grows crystalline thin films in ultrahigh vacuum (UHV) with precise control of thickness, composition

Composition-dependent stability of the medium-range order responsible for metallic glass formation

DOE PAGES

Zhang, Feng; Ji, Min; Fang, Xiao-Wei; ...

2014-09-18

The competition between the characteristic medium-range order corresponding to amorphous alloys and that in ordered crystalline phases is central to phase selection and morphology evolution under various processing conditions. We examine the stability of a model glass system, Cu–Zr, by comparing the energetics of various medium-range structural motifs over a wide range of compositions using first-principles calculations. Furthermore, we focus specifically on motifs that represent possible building blocks for competing glassy and crystalline phases, and we employ a genetic algorithm to efficiently identify the energetically favored decorations of each motif for specific compositions. These results show that a Bergman-type motifmore » with crystallization-resisting icosahedral symmetry is energetically most favorable in the composition range 0.63 < xCu < 0.68, and is the underlying motif for one of the three optimal glass-forming ranges observed experimentally for this binary system (Li et al., 2008). This work establishes an energy-based methodology to evaluate specific medium-range structural motifs which compete with stable crystalline nuclei in deeply undercooled liquids.« less

Substrate Structures For Growth Of Highly Oriented And/Or Epitaxial Layers Thereon

DOEpatents

Arendt, Paul N.; Foltyn, Stephen R.; Groves, James R.; Jia, Quanxi

2005-07-26

A composite substrate structure including a substrate, a layer of a crystalline metal oxide or crystalline metal oxynitride material upon the substrate, a layer of an oriented cubic oxide material having a rock-salt-like structure upon the crystalline metal oxide or crystalline metal oxynitride material layer is provided together with additional layers such as one or more layers of a buffer material upon the oriented cubic oxide material layer. Jc's of 2.3×106 A/cm2 have been demonstrated with projected Ic's of 320 Amperes across a sample 1 cm wide for a superconducting article including a flexible polycrystalline metallic substrate, an inert oxide material layer upon the surface of the flexible polycrystalline metallic substrate, a layer of a crystalline metal oxide or crystalline metal oxynitride material upon the layer of the inert oxide material, a layer of an oriented cubic oxide material having a rock-salt-like structure upon the crystalline metal oxide or crystalline metal oxynitride material layer, a layer of a buffer material upon the oriented cubic oxide material layer, and, a top-layer of a high temperature superconducting material upon the layer of a buffer material.

Process of making carbon-carbon composites

NASA Technical Reports Server (NTRS)

Kowbel, Witold (Inventor); Withers, James C. (Inventor); Bruce, Calvin (Inventor); Vaidyanathan, Ranji (Inventor); Loutfy, Raouf O. (Inventor)

2000-01-01

A carbon composite structure, for example, an automotive engine piston, is made by preparing a matrix including of a mixture of non crystalline carbon particulate soluble in an organic solvent and a binder that has a liquid phase. The non crystalline particulate also contains residual carbon hydrogen bonding. An uncured structure is formed by combining the matrix mixture, for example, carbon fibers such as graphite dispersed in the mixture and/or graphite cloth imbedded in the mixture. The uncured structure is cured by pyrolyzing it in an inert atmosphere such as argon. Advantageously, the graphite reinforcement material is whiskered prior to combining it with the matrix mixture by a novel method involving passing a gaseous metal suboxide over the graphite surface.

Liquid crystalline composites containing phyllosilicates

DOEpatents

Chaiko, David J.

2004-07-13

The present invention provides phyllosilicate-polymer compositions which are useful as liquid crystalline composites. Phyllosilicate-polymer liquid crystalline compositions of the present invention can contain a high percentage of phyllosilicate while at the same time be transparent. Because of the ordering of the particles liquid crystalline composite, liquid crystalline composites are particularly useful as barriers to gas transport.

The Effect of 4-Octyldecyloxybenzoic Acid on Liquid-Crystalline Polyurethane Composites with Triple-Shape Memory and Self-Healing Properties

PubMed Central

Ban, Jianfeng; Zhu, Linjiang; Chen, Shaojun; Wang, Yiping

2016-01-01

To better understand shape memory materials and self-healing materials, a new series of liquid-crystalline shape memory polyurethane (LC-SMPU) composites, named SMPU-OOBAm, were successfully prepared by incorporating 4-octyldecyloxybenzoic acid (OOBA) into the PEG-based SMPU. The effect of OOBA on the structure, morphology, and properties of the material has been carefully investigated. The results demonstrate that SMPU-OOBAm has liquid crystalline properties, triple-shape memory properties, and self-healing properties. The incorporated OOBA promotes the crystallizability of both soft and hard segments of SMPU, and the crystallization rate of the hard segment of SMPU decreases when the OOBA-content increases. Additionally, the SMPU-OOBAm forms a two-phase separated structure (SMPU phase and OOBA phase), and it shows two-step modulus changes upon heating. Therefore, the SMPU-OOBAm exhibits triple-shape memory behavior, and the shape recovery ratio decreases with an increase in the OOBA content. Finally, SMPU-OOBAm exhibits self-healing properties. The new mechanism can be ascribed to the heating-induced “bleeding” of OOBA in the liquid crystalline state and the subsequent re-crystallization upon cooling. This successful combination of liquid crystalline properties, triple-shape memory properties, and self-healing properties make the SMPU-OOBAm composites ideal for many promising applications in smart optical devices, smart electronic devices, and smart sensors. PMID:28773914

Native Cellulose: Structure, Characterization and Thermal Properties

PubMed Central

Poletto, Matheus; Ornaghi Júnior, Heitor L.; Zattera, Ademir J.

2014-01-01

In this work, the relationship between cellulose crystallinity, the influence of extractive content on lignocellulosic fiber degradation, the correlation between chemical composition and the physical properties of ten types of natural fibers were investigated by FTIR spectroscopy, X-ray diffraction and thermogravimetry techniques. The results showed that higher extractive contents associated with lower crystallinity and lower cellulose crystallite size can accelerate the degradation process and reduce the thermal stability of the lignocellulosic fibers studied. On the other hand, the thermal decomposition of natural fibers is shifted to higher temperatures with increasing the cellulose crystallinity and crystallite size. These results indicated that the cellulose crystallite size affects the thermal degradation temperature of natural fibers. This study showed that through the methods used, previous information about the structure and properties of lignocellulosic fibers can be obtained before use in composite formulations. PMID:28788179

Crystallization of lithium borate glasses

NASA Technical Reports Server (NTRS)

Goktas, A. A.; Neilson, G. F.; Weinberg, M. C.

1992-01-01

The glass-forming ability and crystallization behavior of lithium borate compositions, in the diborate-to-metaborate-range, were studied. In particular, the nature and sequence of formation of crystalline phases and the tendency toward devitrification were investigated as functions of temperature, thermal history and batch composition. It was found that the sequence of crystalline phase formation was sensitive to all of the three latter factors, and it was observed that under certain conditions metastable defect structures of the metaborate can appear.

Single-crystalline dendritic bimetallic and multimetallic nanocubes.

PubMed

Kuang, Yun; Zhang, Ying; Cai, Zhao; Feng, Guang; Jiang, Yingying; Jin, Chuanhong; Luo, Jun; Sun, Xiaoming

2015-12-01

Developing facial synthetic routes for fabrication of multimetallic nanocatalysts with open porous morphology, tunable composition and tailored crystalline structure is a big challenge for fabrication of low-cost electrocatalysts. Here we report on the synthesis of single-crystalline dendritic bimetallic and multimetallic nanocubes via a solvothermal co-reduction method. These cubes show highly porous, complex 3D inner connections but single-crystalline structure. Tuning the reduction kinetics of metal precursors and introducing galvanic reaction at the active sites during growth were believed to be the keys for the formation of such unique nanostructure. Electro-catalytic oxygen reduction (ORR) and methanol oxidation (MOR) on these catalysts showed dramatic enhancements for both cathodic and anodic electrocatalysis in fuel cells, which were attributed to their unique morphology and crystalline structure, as well as synergetic effect of the multi-metallic components. This work uncovers the formation mechanism of such complex single-crystalline dendritic multimetallic nanocrystals and offers a promising synthetic strategy for geometric and crystalline control of multimetallic nanocrystals with tailored physical and chemical properties, which will benefit the development of clean energy.

Synthesis, structural and optical properties of ZnO spindle/reduced graphene oxide composites with enhanced photocatalytic activity under visible light irradiation

NASA Astrophysics Data System (ADS)

Prabhu, S.; Pudukudy, M.; Sohila, S.; Harish, S.; Navaneethan, M.; Navaneethan, D.; Ramesh, R.; Hayakawa, Y.

2018-05-01

In the present work, spindle-shaped ZnO and reduced graphene oxide sheets were successfully synthesized by a hydrothermal method and then ZnO/r-GO composite was prepared by a direct solution mixing method. Various characterization results confirmed the interior and surface decoration of spindle-shaped ZnO on the reduced graphene oxide sheets. The phase formation, crystalline structure, morphology, surface states and optical properties were characterized using Powder X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR) and UV-Vis spectroscopy. The X-ray diffraction analysis showed the formation of the hexagonal wurtzite crystalline structure of ZnO with high crystalline quality. The band gap of the ZnO/r-GO composite was found to be low (3.03eV) compared to the band gap of spindle shaped ZnO (3.13 eV), as calculated from optical studies. The spindle-like morphology of the single crystalline ZnO was clearly shown in the electron microscopic images. The chemical bonding and surface states of the samples were studied using XPS measurement. Moreover, a possible growth mechanism for the ZnO spindle was proposed. The catalytic activity of the as-synthesized samples was evaluated for the photodegradation of methylene blue under visible light irradiation. Among the synthesized samples, the ZnO/r-GO composite showed higher degradation efficiency of 93% and successfully reused for four consecutive run without any activity loss.

Effect Of Chromium Underlayer On The Properties Of Nano-Crystalline Diamond Films

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

Garratt, Elias; AlFaify, Salem; Yoshitake, T.

2013-01-11

This paper investigated the effect of chromium underlayer on the structure, microstructure and composition of the nano-crystalline diamond films. Nano-crystalline diamond thin films were deposited at high temperature in microwave-induced plasma diluted with nitrogen, on silicon substrate with a thin film of chromium as an underlayer. The composition, structure and microstructure of the deposited layers were analyzed using non-Rutherford Backscattering Spectrometry, Raman Spectroscopy, Near-Edge X-Ray Absorption Fine Structure, X-ray Diffraction and Atomic Force Microscopy. Nanoindentation studies showed that the films deposited on chromium underlayer have higher hardness values compared to those deposited on silicon without an underlayer. Diamond and graphiticmore » phases of the films evaluated by x-ray and optical spectroscopic analysis determined consistency between sp2 and sp3 phases of carbon in chromium sample to that of diamond grown on silicon. Diffusion of chromium was observed using ion beam analysis which was correlated with the formation of chromium complexes by x-ray diffraction.« less

γS-Crystallin Proteins from the Antarctic Nototheniid Toothfish: A Model System for Investigating Differential Resistance to Chemical and Thermal Denaturation

PubMed Central

2015-01-01

The γS1- and γS2-crystallins, structural eye lens proteins from the Antarctic toothfish (Dissostichus mawsoni), are homologues of the human lens protein γS-crystallin. Although γS1 has the higher thermal stability of the two, it is more susceptible to chemical denaturation by urea. The lower thermodynamic stability of both toothfish crystallins relative to human γS-crystallin is consistent with the current picture of how proteins from organisms endemic to perennially cold environments have achieved low-temperature functionality via greater structural flexibility. In some respects, the sequences of γS1- and γS2-crystallin are typical of psychrophilic proteins; however, their amino acid compositions also reflect their selection for a high refractive index increment. Like their counterparts in the human lens and those of mesophilic fish, both toothfish crystallins are relatively enriched in aromatic residues and methionine and exiguous in aliphatic residues. The sometimes contradictory requirements of selection for cold tolerance and high refractive index make the toothfish crystallins an excellent model system for further investigation of the biophysical properties of structural proteins. PMID:25372016

Oxygen ion-conducting dense ceramic

DOEpatents

Balachandran, Uthamalingam; Kleefisch, Mark S.; Kobylinski, Thaddeus P.; Morissette, Sherry L.; Pei, Shiyou

1998-01-01

Preparation, structure, and properties of mixed metal oxide compositions and their uses are described. Mixed metal oxide compositions of the invention have stratified crystalline structure identifiable by means of powder X-ray diffraction patterns. In the form of dense ceramic membranes, the present compositions demonstrate an ability to separate oxygen selectively from a gaseous mixture containing oxygen and one or more other volatile components by means of ionic conductivities.

Mechanical, Dielectric, and Spectroscopic Characteristics of "Micro/Nanocellulose + Oxide" Composites.

PubMed

Nedielko, Maksym; Hamamda, Smail; Alekseev, Olexander; Chornii, Vitalii; Dashevskii, Mykola; Lazarenko, Maksym; Kovalov, Kostiantyn; Nedilko, Sergii G; Tkachov, Sergii; Revo, Sergiy; Scherbatskyi, Vasyl

2017-12-01

The set of composite materials that consist of micro/nanocellulose and complex K 2 Eu(MoO 4 )(PO 4 ) luminescent oxide particles was prepared. The composites were studied by means of scanning electron microscopy, XRD analysis, dilatometry, differential scanning calorimetry and thermogravimetric analysis, and dielectric and luminescence spectroscopy.Dependencies of density, crystallinity, relative extension, thermal extension coefficient, dielectric relaxation parameters, intensity and shape of photoluminescence bands on temperature, and content of oxide component were studied. The structure of the composite without oxide is formed by grains of nearly 5-50 μm in size (crystallinity is about ~56%). Structure of the micro/nanocellulose samples which contain oxide particles is similar, but the cellulose grains are deformed by oxide particles. Dependencies of the abovementioned properties on temperature and oxide content were analyzed together with data on the size distribution of oxide particles for the samples for various oxide and molecules of water concentrations.

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.

Structural Evolution of Iron Antimonides from Amorphous Precursors to Crystalline Products Studied by Total Scattering Techniques.

PubMed

Bauers, Sage R; Wood, Suzannah R; Jensen, Kirsten M Ø; Blichfeld, Anders B; Iversen, Bo B; Billinge, Simon J L; Johnson, David C

2015-08-05

Homogeneous reaction precursors may be used to form several solid-state compounds inaccessible by traditional synthetic routes, but there has been little development of techniques that allow for a priori prediction of what may crystallize in a given material system. Here, the local structures of FeSbx designed precursors are determined and compared with the structural motifs of their crystalline products. X-ray total scattering and atomic pair distribution function (PDF) analysis are used to show that precursors that first nucleate a metastable FeSb3 compound share similar local structure to the product. Interestingly, precursors that directly crystallize to thermodynamically stable FeSb2 products also contain local structural motifs of the metastable phase, despite their compositional disagreement. While both crystalline phases consist of distorted FeSb6 octahedra with Sb shared between either two or three octahedra as required for stoichiometry, a corner-sharing arrangement indicative of AX3-type structures is the only motif apparent in the PDF of either precursor. Prior speculation was that local composition controlled which compounds nucleate from amorphous intermediates, with different compositions favoring different local arrangements and hence different products. This data suggests that local environments in these amorphous intermediates may not be very sensitive to overall composition. This can provide insight into potential metastable phases which may form in a material system, even with a precursor that does not crystallize to the kinetically stabilized product. Determination of local structure in homogeneous amorphous reaction intermediates from techniques such as PDF can be a valuable asset in the development of systematic methods to prepare targeted solid-state compounds from designed precursors.

Crystal Structure and Chemical Composition of a Presolar Silicate from the Queen Elizabeth Range 99177 Meteorite

NASA Technical Reports Server (NTRS)

Nguyen, A. N.; Keller, L. P.; Rahman, Z.; Messenger, S.

2013-01-01

Mineral characterization of presolar silicate grains, the most abundant stardust phase, has provided valuable information about the formation conditions in circumstellar environments and in super-nova (SN) outflows. Spectroscopic observations of dust around evolved stars suggest a majority of amor-phous, Mg-rich olivine grains, but crystalline silicates, most of which are pyroxene, have also been observed [1]. The chemical compositions of hundreds of presolar silicates have been determined by Auger spectroscopy and reveal high Fe contents and nonstoichiometric compositions intermediate to olivine and pyroxene [2-6]. The unexpectedly high Fe contents can partly be attributed to secondary alteration on the meteorite parent bodies, as some grains have Fe isotopic anomalies from their parent stellar source [7]. Only about 35 presolar silicates have been studied for their mineral structures and chemical compositions by transmission electron microscopy (TEM). These grains display a wide range of compositions and structures, including crystalline forsterite, crystalline pyroxene, nanocrystalline grains, and a majority of amorphous nonstoichiometric grains. Most of these grains were identified in the primitive Acfer 094 meteorite. Presolar silicates from this meteorite show a wide range of Fe-contents, suggestive of secondary processing on the meteorite parent body. The CR chondrite QUE 99177 has not suffered as much alteration [8] and displays the highest presolar silicate abundance to date among carbonaceous chondrites [3, 6]. However, no mineralogical studies of presolar silicates from this meteorite have been performed. Here we examine the mineralogy of a presolar silicate from QUE 99177.

Liquid crystalline composites containing phyllosilicates

DOEpatents

Chaiko,; David, J [Naperville, IL

2007-05-08

The present invention provides barrier films having reduced gas permeability for use in packaging and coating applications. The barrier films comprise an anisotropic liquid crystalline composite layer formed from phyllosilicate-polymer compositions. Phyllosilicate-polymer liquid crystalline compositions of the present invention can contain a high percentage of phyllosilicate while remaining transparent. Because of the ordering of the particles in the liquid crystalline composite, barrier films comprising liquid crystalline composites are particularly useful as barriers to gas transport.

Thermally Stable and Electrically Conductive, Vertically Aligned Carbon Nanotube/Silicon Infiltrated Composite Structures for High-Temperature Electrodes.

PubMed

Zou, Qi Ming; Deng, Lei Min; Li, Da Wei; Zhou, Yun Shen; Golgir, Hossein Rabiee; Keramatnejad, Kamran; Fan, Li Sha; Jiang, Lan; Silvain, Jean-Francois; Lu, Yong Feng

2017-10-25

Traditional ceramic-based, high-temperature electrode materials (e.g., lanthanum chromate) are severely limited due to their conditional electrical conductivity and poor stability under harsh circumstances. Advanced composite structures based on vertically aligned carbon nanotubes (VACNTs) and high-temperature ceramics are expected to address this grand challenge, in which ceramic serves as a shielding layer protecting the VACNTs from the oxidation and erosive environment, while the VACNTs work as a conductor. However, it is still a great challenge to fabricate VACNT/ceramic composite structures due to the limited diffusion of ceramics inside the VACNT arrays. In this work, we report on the controllable fabrication of infiltrated (and noninfiltrated) VACNT/silicon composite structures via thermal chemical vapor deposition (CVD) [and laser-assisted CVD]. In laser-assisted CVD, low-crystalline silicon (Si) was quickly deposited at the VACNT subsurfaces/surfaces followed by the formation of high-crystalline Si layers, thus resulting in noninfiltrated composite structures. Unlike laser-assisted CVD, thermal CVD activated the precursors inside and outside the VACNTs simultaneously, which realized uniform infiltrated VACNT/Si composite structures. The growth mechanisms for infiltrated and noninfiltrated VACNT/ceramic composites, which we attributed to the different temperature distributions and gas diffusion mechanism in VACNTs, were investigated. More importantly, the as-farbicated composite structures exhibited excellent multifunctional properties, such as excellent antioxidative ability (up to 1100 °C), high thermal stability (up to 1400 °C), good high velocity hot gas erosion resistance, and good electrical conductivity (∼8.95 Sm -1 at 823 K). The work presented here brings a simple, new approach to the fabrication of advanced composite structures for hot electrode applications.

Synthesis and characterization of bulk metallic glasses prepared by laser direct deposition

NASA Astrophysics Data System (ADS)

Ye, Xiaoyang

Fe-based and Zr-based metallic glasses have attracted extensive interest for structural applications due to their excellent glass forming ability, superior mechanical properties, unique thermal and corrosion properties. In this study, the feasibility of synthesizing metallic glasses with good ductility by laser direct deposition is explored. Both in-situ synthesis with elemental powder mixture and ex-situ synthesis with prealloyed powder are discussed. Microstructure and properties of laser direct deposited metallic glass composites are analyzed. Synthesis of Fe-Cr-Mo-W-Mn-C-Si-B metallic glass composite with a large fraction of amorphous phase was accomplished using laser direct deposition. X-ray diffraction (XRD) and transmission electron microscopy investigations revealed the existence of amorphous structure. Microstructure analyses by optical microscopy and scanning electron microscopy (SEM) indicated the periodically repeated microstructures of amorphous and crystalline phases. Partially crystallized structure brought by laser reheating and remelting during subsequent laser scans aggregated in the overlapping area between each scan. XRD analysis showed that the crystalline particle embedded in the amorphous matrix was Cr 1.07Fe18.93 phase. No significant microstructural differences were found from the first to the last layer. Microhardness of the amorphous phase (HV0.2 1591) showed a much higher value than that of the crystalline phase (HV0.2 947). Macrohardness of the top layer had a value close to the microhardness of the amorphous region. Wear resistance property of deposited layers showed a significant improvement with the increased fraction of amorphous phase. Zr65Al10Ni10Cu15 amorphous composites with a large fraction of amorphous phase were in-situ synthesized by laser direct deposition. X-ray diffraction confirmed the existence of both amorphous and crystalline phases. Laser parameters were optimized in order to increase the fraction of amorphous phase. The microstructure analysis by scanning electron microscopy revealed the deposited structure was composed of periodically repeated amorphous and crystalline phases. Overlapping regions with nanoparticles aggregated were crystallized by laser reheating and remelting processes during subsequent laser scans. Vickers microhardness of the amorphous region showed around 35% higher than that of crystalline region. Average hardness obtained by a Rockwell macrohardness tester was very close to the microhardness of the amorphous region. The compression test showed that the fracture strain of Zr65Al10Ni10Cu15 amorphous composites was enhanced from less than 2% to as high as 5.7%, compared with fully amorphous metallic glass. Differential scanning calorimetry test results further revealed the amorphous structure and glass transition temperature Tg was observed to be around 655K. In 3 mol/L NaCl solution, laser direct deposited amorphous composites exhibited distinctly improved corrosion resistance, compared with fully-crystallized samples.

Optimal Composite Material for Low Cost Fabrication of Large Composite Aerospace Structures using NASA Resins or POSS Nanoparticle Modifications

NASA Technical Reports Server (NTRS)

Lamontia, Mark A.; Gruber, Mark B.; Jensen, Brian J.

2006-01-01

Thermoplastic laminates in situ consolidated via tape or tow placement require full mechanical properties. Realizing full properties requires resin crystallinity to be controlled - partial crystallinity leads to unacceptably low laminate compression properties. There are two approaches: utilize an amorphous matrix resin; or place material made from a semi-crystalline resin featuring kinetics faster than the process. In this paper, a matrix resin evaluation and trade study was completed with commercial and NASA amorphous polyimides on the one hand, and with PEKK mixed with POSS nanoparticles for accelerated crystallinity growth on the other. A new thermoplastic impregnated material, 6 mm wide (0.25-in) AS-4 carbon/LaRC(TradeMark)8515 dry polyimide tow, was fabricated. Since LaRC(TradeMark)8515 is fully amorphous, it attains full properties following in situ consolidation, with no post processing required to build crystallinity. The tow in situ processing was demonstrated via in situ thermoplastic filament winding it into rings.

Nano-Sized Structurally Disordered Metal Oxide Composite Aerogels as High-Power Anodes in Hybrid Supercapacitors.

PubMed

Huang, Haijian; Wang, Xing; Tervoort, Elena; Zeng, Guobo; Liu, Tian; Chen, Xi; Sologubenko, Alla; Niederberger, Markus

2018-03-27

A general method for preparing nano-sized metal oxide nanoparticles with highly disordered crystal structure and their processing into stable aqueous dispersions is presented. With these nanoparticles as building blocks, a series of nanoparticles@reduced graphene oxide (rGO) composite aerogels are fabricated and directly used as high-power anodes for lithium-ion hybrid supercapacitors (Li-HSCs). To clarify the effect of the degree of disorder, control samples of crystalline nanoparticles with similar particle size are prepared. The results indicate that the structurally disordered samples show a significantly enhanced electrochemical performance compared to the crystalline counterparts. In particular, structurally disordered Ni x Fe y O z @rGO delivers a capacity of 388 mAh g -1 at 5 A g -1 , which is 6 times that of the crystalline sample. Disordered Ni x Fe y O z @rGO is taken as an example to study the reasons for the enhanced performance. Compared with the crystalline sample, density functional theory calculations reveal a smaller volume expansion during Li + insertion for the structurally disordered Ni x Fe y O z nanoparticles, and they are found to exhibit larger pseudocapacitive effects. Combined with an activated carbon (AC) cathode, full-cell tests of the lithium-ion hybrid supercapacitors are performed, demonstrating that the structurally disordered metal oxide nanoparticles@rGO||AC hybrid systems deliver high energy and power densities within the voltage range of 1.0-4.0 V. These results indicate that structurally disordered nanomaterials might be interesting candidates for exploring high-power anodes for Li-HSCs.

Liquid Crystalline Systems Based on Glyceryl Monooleate and Penetration Enhancers for Skin Delivery of Celecoxib: Characterization, In Vitro Drug Release, and In Vivo Studies.

PubMed

Dante, Mariane de Cássia Lima; Borgheti-Cardoso, Livia Neves; Fantini, Marcia Carvalho de Abreu; Praça, Fabíola Silva Garcia; Medina, Wanessa Silva Garcia; Pierre, Maria Bernadete Riemma; Lara, Marilisa Guimarães

2018-03-01

Celecoxib (CXB) is a widely used anti-inflammatory drug that also acts as a chemopreventive agent against several types of cancer, including skin cancer. As the long-term oral administration of CXB has been associated with severe side effects, the skin delivery of this drug represents a promising alternative for the treatment of skin inflammatory conditions and chemoprevention of skin cancer. We prepared and characterized liquid crystalline systems based on glyceryl monooleate and water containing penetration enhancers which were primarily designed to promote skin delivery of CXB. Analysis of their phase behavior revealed the formation of cubic and hexagonal phases depending on the systems' composition. The systems' structure and composition markedly affected the in vitro CXB release profile. Oleic acid reduced CXB release rate, but association oleic acid/propylene glycol increased the drug release rate. The developed systems significantly reduced inflammation in an aerosil-induced rat paw edema model. The systems' composition and liquid crystalline structure influenced their anti-inflammatory potency. Cubic phase systems containing oleic acid/propylene glycol association reduced edema in a sustained manner, indicating that they modulate CXB release and permeation. Our findings demonstrate that the developed liquid crystalline systems are potential carriers for the skin delivery of CXB. Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Thermoset molecular composites

DOEpatents

Benicewicz, Brian C.; Douglas, Elliot P.; Hjelm, Jr., Rex P.

1996-01-01

A polymeric composition including a liquid crystalline polymer and a thermosettable liquid crystalline monomer matrix, said polymeric composition characterized by a phase separation on the scale of less than about 500 Angstroms and a polymeric composition including a liquid crystalline polymer and a liquid crystalline thermoset matrix, said polymeric composition characterized by a phase separation on the scale of less than about 500 Angstroms are disclosed.

Drawing dependent structures, mechanical properties and cyclization behaviors of polyacrylonitrile and polyacrylonitrile/carbon nanotube composite fibers prepared by plasticized spinning.

PubMed

Li, Xiang; Qin, Aiwen; Zhao, Xinzhen; Liu, Dapeng; Wang, Haiye; He, Chunju

2015-09-14

Drawing to change the structural properties and cyclization behaviors of the polyacrylonitrile (PAN) chains in crystalline and amorphous regions is carried out on PAN and PAN/carbon nanotube (CNT) composite fibers. Various characterization methods including Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction and thermal gravimetric analysis are used to monitor the structural evolution and cyclization behaviors of the fibers. With an increase of the draw ratio during the plasticized spinning process, the structural parameters of the fibers, i.e. crystallinity and planar zigzag conformation, are decreased at first, and then increased, which are associated with the heat exchange rate and the oriented-crystallization rate. A possible mechanism for plasticized spinning is proposed to explain the changing trends of crystallinity and planar zigzag conformation. PAN and PAN/CNT fibers exhibit various cyclization behaviors induced by drawing, e.g., the initiation temperature for the cyclization (Ti) of PAN fibers is increased with increasing draw ratio, while Ti of PAN/CNT fibers is decreased. Drawing also facilitates cyclization and lowers the percentage of β-amino nitrile for PAN/CNT fibers during the stabilization.

Rapid Obtaining of Nano-Hydroxyapatite Bioactive Films on NiTi Shape Memory Alloy by Electrodeposition Process

NASA Astrophysics Data System (ADS)

Lobo, A. O.; Otubo, J.; Matsushima, J. T.; Corat, E. J.

2011-07-01

Nano-hydroxyapatite (n-HA) crystalline films have been developed in this study by electrodeposition method on NiTi shape memory alloy (SMA). The electrodeposition of the n-HA films was carried out using 0.042 mol/L Ca(NO3)2 · 4H2O + 0.025 mol/L (NH4) · 2HPO4 electrolytes by applying a constant potential of -2.0 V for 120 min and keeping the solution temperature at 70 °C. The characterization of n-HA films is of special importance since bioactive properties related to n-HA have been directly identified with its specific composition and crystalline structure. AFM, XRD, EDX, FEG-SEM and Raman spectroscopy shows a homogeneous film, with high crystallinity, special composition, and bioactivity properties (Ca/P = 1.93) of n-HA on NiTi SMA surfaces. The n-HA coating with special structure would benefit the use of NiTi alloy in orthopedic applications.

Electrochemical synthesis of self-organized TiO2 crystalline nanotubes without annealing

NASA Astrophysics Data System (ADS)

Giorgi, Leonardo; Dikonimos, Theodoros; Giorgi, Rossella; Buonocore, Francesco; Faggio, Giuliana; Messina, Giacomo; Lisi, Nicola

2018-03-01

This work demonstrates that upon anodic polarization in an aqueous fluoride-containing electrolyte, TiO2 nanotube array films can be formed with a well-defined crystalline phase, rather than an amorphous one. The crystalline phase was obtained avoiding any high temperature annealing. We studied the formation of nanotubes in an HF/H2O medium and the development of crystalline grains on the nanotube wall, and we found a facile way to achieve crystalline TiO2 nanotube arrays through a one-step anodization. The crystallinity of the film was influenced by the synthesis parameters, and the optimization of the electrolyte composition and anodization conditions (applied voltage and time) were carried out. For comparison purposes, crystalline anatase TiO2 nanotubes were also prepared by thermal treatment of amorphous nanotubes grown in an organic bath (ethylene glycol/NH4F/H2O). The morphology and the crystallinity of the nanotubes were studied by field emission gun-scanning electron microscopy (FEG-SEM) and Raman spectroscopy, whereas the electrochemical and semiconducting properties were analyzed by means of linear sweep voltammetry, impedance spectroscopy, and Mott-Schottky plots. X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) allowed us to determine the surface composition and the electronic structure of the samples and to correlate them with the electrochemical data. The optimal conditions to achieve a crystalline phase with high donor concentration are defined.

EELS from organic crystalline materials

NASA Astrophysics Data System (ADS)

Brydson, R.; Eddleston, M. D.; Jones, W.; Seabourne, C. R.; Hondow, N.

2014-06-01

We report the use of the electron energy loss spectroscopy (EELS) for providing light element chemical composition information from organic, crystalline pharmaceutical materials including theophylline and paracetamol and discuss how this type of data can complement transmission electron microscopy (TEM) imaging and electron diffraction when investigating polymorphism. We also discuss the potential for the extraction of bonding information using electron loss near-edge structure (ELNES).

Electronic Theory of 2-6 and Related Semiconducting Materials and Structures

DTIC Science & Technology

1985-10-01

standard crystalline band-structure techniques to ordered alloy configurations. This approach is especially interesting in view of recent experimental5(’fid...WEAKLY NONLINEAR... 10973 Eq. (10). The resulting expression for Z, exhibits interest- -. ing behavior, especially near the percolation threshold, (b...of A. Metal-insulator composite composites, especially near the percolation threshold. In It is well known that normal-metal-insulator compos

Development and characterisation of semi-crystalline composite granules: The effect of particle chemistry and the electrostatic charging

NASA Astrophysics Data System (ADS)

Haque, Syed N.; Hussain, Tariq; Chowdhry, Babur Z.; Douroumis, Dennis; Scoutaris, Nikolaos; Nokhodchi, Ali; Maniruzzaman, Mohammed

2017-12-01

This study investigated the surface of semi-crystalline composite granules produced via a novel mechano-chemical process and assessed the effect of electrostatic charging. Ibuprofen (IBU), a model drug with low solubility and known associated processing challenges was loaded in composite granules to improve its processibility and dissolution rates. Synthetic amorphous mesoporous magnesium alumina metasilicate (MAS) was co-processed with hydrophilic HPMC polymer in the presence of polyethylene glycol 2000 (PEG) and deionised water. The solid state analyses conducted by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) revealed the existence of semi-crystalline IBU in the complex composite structures. Dynamic vapour sorption (DVS) study showed the water sorption and desorption profiles of the manufactured composite granules as well as the effect of water on the solid-state stability of IBU in various formulations. Advanced surface analysis conducted via energy dispersive X-ray (EDS) revealed homogenous distribution of the drug/excipients on the surface of the granules while atomic force microscopy (AFM) complemented the findings. The electrostatic charge analysis showed variable charge property which is affected by the size of the particles/granules. As expected, the in vitro dissolution study showed about 5 fold increase in the release rates of IBU compared to that of the bulk drug. The mechanochemical processing has been demonstrated as an efficient technique to develop semi-crystalline composite granules with enhanced dissolution rates of water insoluble drugs.

γ-Irradiation assisted synthesis of graphene oxide sheets supported Ag nanoparticles with single crystalline structure and parabolic distribution from interlamellar limitation

NASA Astrophysics Data System (ADS)

Yue, Yunhao; Zhou, Baoming; Shi, Jie; Chen, Cheng; Li, Nan; Xu, Zhiwei; Liu, Liangsen; Kuang, Liyun; Ma, Meijun; Fu, Hongjun

2017-05-01

This paper reported a method to fabricate graphene oxide sheets supported Ag nanoparticles (AgNPs/GOS) with single crystalline structure and parabolic distribution without surfactant or functional agent. We used imidazole silver nitrate as intercalation precursor into the layers of graphite oxide, and subsequently reduction and growth of interlamellar AgNPs were induced via γ-irradiation. The results illustrated that the synergism of interlamellar limitation of graphite oxide and fragmentation ability of γ-irradiation could prevent coalescent reaction of AgNPs with other oligomeric clusters, and the single crystalline and small-sized (below 13.9 nm) AgNPs were prepared. Moreover, the content and size of AgNPs exhibited parabolic distribution on GOS surface because the graphite oxide exfoliated to GOS from the edge to the central area of layers. In addition, complete exfoliation degree of GOS and large-sized AgNPs were obtained simultaneously under suitable silver ions concentration. Optimized composites exhibited outstanding surface-enhanced Raman scattering properties for crystal violet with enhancement factor of 1.3 × 106 and detection limit of 1.0 × 10-7 M, indicating that the AgNPs/GOS composites could be applied to trace detection of organic dyes molecules. Therefore, this study presented a strategy for developing GOS supported nanometal with single crystalline structure and parabolic distribution based on γ-irradiation.

Production and characterization of bacterial cellulose membranes with hyaluronic acid from chicken comb.

PubMed

de Oliveira, Sabrina Alves; da Silva, Bruno Campos; Riegel-Vidotti, Izabel Cristina; Urbano, Alexandre; de Sousa Faria-Tischer, Paula Cristina; Tischer, Cesar Augusto

2017-04-01

The bacterial cellulose (BC), from Gluconacetobacter hansenii, is a biofilm with a high degree of crystallinity that can be used for therapeutic purposes and as a candidate for healing wounds. Hyaluronic acid (HA) is a constitutive polysaccharide found in the extracellular matrix and is a material used in tissue engineering and scaffolding for tissue regeneration. In this study, polymeric composites were produced in presence of hyaluronic acid isolated from chicken comb on different days of fermentation, specifically on the first (BCHA-SABT0) and third day (BCHA-SABT3) of fermentation. The structural characteristics, thermal stability and molar mass of hyaluronic acid from chicken comb were evaluated. Native membrane and polymeric composites were characterized with respect to their morphology and crystallinity. The optimized process of extraction and purification of hyaluronic acid resulted in low molar mass hyaluronic acid with structural characteristics similar to the standard commercial hyaluronic acid. The results demonstrate that the polymeric composites (BC/HA-SAB) can be produced in situ. The membranes produced on the third day presented better incorporation of HA-SAB between cellulose microfiber, resulting in membranes with higher thermal stability, higher roughness and lower crystallinity. The biocompatiblily of bacterial cellulose and the importance of hyaluronic acid as a component of extracellular matrix qualify the polymeric composites as promising biomaterials for tissue engineering. Copyright © 2017 Elsevier B.V. All rights reserved.

A Conceptual Model for Shear-Induced Phase Behavior in Crystallizing Cocoa Butter

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

Mazzanti,G.; Guthrie, S.; Marangoni, A.

2007-01-01

We propose a conceptual model to explain the quantitative data from synchrotron X-ray diffraction experiments on the shear-induced phase behavior of cocoa butter, the main structural component of chocolate. We captured two-dimensional diffraction patterns from cocoa butter at crystallization temperatures of 17.5, 20.0, and 22.5 {sup o}C under shear rates from 45 to 1440 s{sup -1} and under static conditions. From the simultaneous analysis of the integrated intensity, correlation length, lamellar thickness, and crystalline orientation, we postulate a conceptual model to provide an explanation for the distribution of phases II, IV, V, and X and the kinetics of the process.more » As previously proposed in the literature, we assume that the crystallites grow layer upon layer of slightly different composition. The shear rate and temperature applied define these compositions. Simultaneously, the shear and temperature define the crystalline interface area available for secondary nucleation by promoting segregation and affecting the size distribution of the crystallites. The combination of these factors (composition, area, and size distribution) favors dramatically the early onset of phase V under shear and determines the proportions of phases II, IV, V, and X after the transition. The experimental observations, the methodology used, and the proposed explanation are of fundamental and industrial interest, since the structural properties of crystalline networks are determined by their microstructure and polymorphic crystalline state. Different proportions of the phases will thus result in different characteristics of the final material.« less

Improved luminescence intensity and stability of thermal annealed ZnO incorporated Alq3 composite films.

PubMed

Cuba, M; Muralidharan, G

2015-11-01

The 30 wt% of ZnO (weight percentage of ZnO has been optimised) incorporated tris- (8-hydroxyquinoline)aluminum (Alq3) has been synthesised and coated on to glass substrates using dip coating method. The structural and optical properties of the Alq3/ZnO composite film after thermal annealing from 50 to 300 °C insteps 50° has been studied and reported. XRD pattern reveals the presence of crystalline ZnO in all the annealed films. The films annealed above 150 °C reveal the presence of crystalline Alq3 along with crystalline ZnO. The FTIR spectra confirm the presence of hydroxyquinoline and ZnO vibration in all the annealed composite films. The composite films annealed above 150 °C show a partial sublimation and degradation of hydroxyquinoline compounds. The ZnO incorporated composite films (Alq3/ZnO) exhibit two emission peaks, one corresponding to ZnO at 487 nm and another at 513 nm due to Alq3. The films annealed at 200 °C exhibit maximum photoluminescence (PL) intensity than pristine film at 513 nm when excited at 390 nm.

Thermoelastic martensitic transformations in ternary Ni50Mn50- z Ga z alloys

NASA Astrophysics Data System (ADS)

Belosludtseva, E. S.; Kuranova, N. N.; Marchenkova, E. B.; Popov, A. G.; Pushin, V. G.

2016-01-01

We have studied the effect of gallium alloying on the structure, phase composition, and physical properties of ternary alloys of the Ni50Mn50- z Ga z (0 ≤ z ≤ 25 at %) quasi-binary section in a broad temperature range. Dependences of the type of crystalline structure of the high-temperature austenite phase and martensite, as well as the critical temperatures of martensitic transformations on the alloy composition, are determined. A phase diagram of the structural and magnetic transformations is constructed. Concentration boundaries of the existence of tetragonal L10 (2 M) martensite and martensitic phases (10 M and 14 M) with complex multilayer crystalline lattices are found. It is established that the predominant martensite morphology is determined by the hierarchy of packets of thin coherent nano- and submicrocrystalline plates with habit planes close to {011} B2, pairwise twinned along one of 24 equivalent {011}<011> B2 twinning shear systems.

Stomatal cell wall composition: distinctive structural patterns associated with different phylogenetic groups

PubMed Central

Shtein, Ilana; Shelef, Yaniv; Marom, Ziv; Zelinger, Einat; Schwartz, Amnon; Popper, Zoë A.; Bar-On, Benny

2017-01-01

Background and Aims Stomatal morphology and function have remained largely conserved throughout ∼400 million years of plant evolution. However, plant cell wall composition has evolved and changed. Here stomatal cell wall composition was investigated in different vascular plant groups in attempt to understand their possible effect on stomatal function. Methods A renewed look at stomatal cell walls was attempted utilizing digitalized polar microscopy, confocal microscopy, histology and a numerical finite-elements simulation. The six species of vascular plants chosen for this study cover a broad structural, ecophysiological and evolutionary spectrum: ferns (Asplenium nidus and Platycerium bifurcatum) and angiosperms (Arabidopsis thaliana and Commelina erecta) with kidney-shaped stomata, and grasses (angiosperms, family Poaceae) with dumbbell-shaped stomata (Sorghum bicolor and Triticum aestivum). Key Results Three distinct patterns of cellulose crystallinity in stomatal cell walls were observed: Type I (kidney-shaped stomata, ferns), Type II (kidney-shaped stomata, angiosperms) and Type III (dumbbell-shaped stomata, grasses). The different stomatal cell wall attributes investigated (cellulose crystallinity, pectins, lignin, phenolics) exhibited taxon-specific patterns, with reciprocal substitution of structural elements in the end-walls of kidney-shaped stomata. According to a numerical bio-mechanical model, the end walls of kidney-shaped stomata develop the highest stresses during opening. Conclusions The data presented demonstrate for the first time the existence of distinct spatial patterns of varying cellulose crystallinity in guard cell walls. It is also highly intriguing that in angiosperms crystalline cellulose appears to have replaced lignin that occurs in the stomatal end-walls of ferns serving a similar wall strengthening function. Such taxon-specific spatial patterns of cell wall components could imply different biomechanical functions, which in turn could be a consequence of differences in environmental selection along the course of plant evolution. PMID:28158449

Viscoelastic damping in crystalline composites and alloys

NASA Astrophysics Data System (ADS)

Ranganathan, Raghavan; Ozisik, Rahmi; Keblinski, Pawel

We use molecular dynamics simulations to study viscoelastic behavior of model Lennard-Jones (LJ) crystalline composites subject to an oscillatory shear deformation. The two crystals, namely a soft and a stiff phase, individually show highly elastic behavior and a very small loss modulus. On the other hand, when the stiff phase is included within the soft matrix as a sphere, the composite exhibits significant viscoelastic damping and a large phase shift between stress and strain. In fact, the maximum loss modulus in these model composites was found to be about 20 times greater than that given by the theoretical Hashin-Shtrikman upper bound. We attribute this behavior to the fact that in composites shear strain is highly inhomogeneous and mostly accommodated by the soft phase, corroborated by frequency-dependent Grüneisen parameter analysis. Interestingly, the frequency at which the damping is greatest scales with the microstructural length scale of the composite. Finally, a critical comparison between damping properties of these composites with ordered and disordered alloys and superlattice structures is made.

Electroplating and magnetostructural characterization of multisegmented Co54Ni46/Co85Ni15 nanowires from single electrochemical bath in anodic alumina templates

PubMed Central

2013-01-01

Highly hexagonally ordered hard anodic aluminum oxide membranes, which have been modified by a thin cover layer of SiO2 deposited by atomic layer deposition method, were used as templates for the synthesis of electrodeposited magnetic Co-Ni nanowire arrays having diameters of around 180 to 200 nm and made of tens of segments with alternating compositions of Co54Ni46 and Co85Ni15. Each Co-Ni single segment has a mean length of around 290 nm for the Co54Ni46 alloy, whereas the length of the Co85Ni15 segments was around 430 nm. The composition and crystalline structure of each Co-Ni nanowire segment were determined by transmission electron microscopy and selected area electron diffraction techniques. The employed single-bath electrochemical nanowire growth method allows for tuning both the composition and crystalline structure of each individual Co-Ni segment. The room temperature magnetic behavior of the multisegmented Co-Ni nanowire arrays is also studied and correlated with their structural and morphological properties. PMID:23735184

Properties of Graphene/Shape Memory Thermoplastic Polyurethane Composites Actuating by Various Methods

PubMed Central

Park, Jin Ho; Dao, Trung Dung; Lee, Hyung-il; Jeong, Han Mo; Kim, Byung Kyu

2014-01-01

Shape memory behavior of crystalline shape memory polyurethane (SPU) reinforced with graphene, which utilizes melting temperature as a shape recovery temperature, was examined with various external actuating stimuli such as direct heating, resistive heating, and infrared (IR) heating. Compatibility of graphene with crystalline SPU was adjusted by altering the structure of the hard segment of the SPU, by changing the structure of the graphene, and by changing the preparation method of the graphene/SPU composite. The SPU made of aromatic 4,4′-diphenylmethane diisocyanate (MSPU) exhibited better compatibility with graphene, having an aromatic structure, compared to that made of the aliphatic hexamethylene diisocyanate. The finely dispersed graphene effectively reinforced MSPU, improved shape recovery of MSPU, and served effectively as a filler, triggering shape recovery by resistive or IR heating. Compatibility was enhanced when the graphene was modified with methanol. This improved shape recovery by direct heating, but worsened the conductivity of the composite, and consequently the efficiency of resistive heating for shape recovery also declined. Graphene modified with methanol was more effective than pristine graphene in terms of shape recovery by IR heating. PMID:28788529

Temperature-Induced Transitions in the Structure and Interfacial Rheology of Human Meibum

PubMed Central

Leiske, Danielle L.; Leiske, Christopher I.; Leiske, Daniel R.; Toney, Michael F.; Senchyna, Michelle; Ketelson, Howard A.; Meadows, David L.; Fuller, Gerald G.

2012-01-01

Meibomian lipids are the primary component of the lipid layer of the tear film. Composed primarily of a mixture of lipids, meibum exhibits a range of melt temperatures. Compositional changes that occur with disease may alter the temperature at which meibum melts. Here we explore how the mechanical properties and structure of meibum from healthy subjects depend on temperature. Interfacial films of meibum were highly viscoelastic at 17°C, but as the films were heated to 30°C the surface moduli decreased by more than two orders of magnitude. Brewster angle microscopy revealed the presence of micron-scale inhomogeneities in meibum films at higher temperatures. Crystalline structure was probed by small angle x-ray scattering of bulk meibum, which showed evidence of a majority crystalline structure in all samples with lamellar spacing of 49 Å that melted at 34°C. A minority structure was observed in some samples with d-spacing at 110 Å that persisted up to 40°C. The melting of crystalline phases accompanied by a reduction in interfacial viscosity and elasticity has implications in meibum behavior in the tear film. If the melt temperature of meibum was altered significantly from disease-induced compositional changes, the resultant change in viscosity could alter secretion of lipids from meibomian glands, or tear-film stabilization properties of the lipid layer. PMID:22339874

Liquid crystalline tactoids: ordered structure, defective coalescence and evolution in confined geometries

NASA Astrophysics Data System (ADS)

Wang, Pei-Xi; MacLachlan, Mark J.

2017-12-01

Tactoids are liquid crystalline microdroplets that spontaneously nucleate from isotropic dispersions, and transform into macroscopic anisotropic phases. These intermediate structures have been found in a range of molecular, polymeric and colloidal liquid crystals. Typically only studied by polarized optical microscopy, these ordered but easily deformable microdroplets are now emerging as interesting components for structural investigations and developing new materials. In this review, we highlight the structure, property and transformation of tactoids in different compositions, but especially cellulose nanocrystals. We have selected references that illustrate the diversity and most exciting developments in tactoid research, while capturing the historical development of this field. This article is part of a discussion meeting issue `New horizons for cellulose nanotechnology'.

Computer simulation of low-temperature composites sintering processes for additive technologies

NASA Astrophysics Data System (ADS)

Tovpinets, A. O.; Leytsin, V. N.; Dmitrieva, M. A.

2017-12-01

This is impact research of mixture raw components characteristics on the low-temperature composites structure formation during the sintering process. The obtained results showed that the structure determination of initial compacts obtained after thermal destruction of the polymer binder lets quantify the concentrations of main components and the refractory crystalline product of thermal destruction. Accounting for the distribution of thermal destruction refractory product allows us to refine the forecast of thermal stresses in the matrix of sintered composite. The presented results can be considered as a basis for optimization of initial compositions of multilayer low-temperature composites obtained by additive technologies.

Native fat globules of different sizes selected from raw milk: thermal and structural behavior.

PubMed

Michalski, Marie-Caroline; Ollivon, Michel; Briard, Valérie; Leconte, Nadine; Lopez, Christelle

2004-12-01

The aim of this study was to characterize differences in the thermal and structural behavior between different sized native milk fat globules. A novel microfiltration process permits the selection of native small fat globules (SFG, 1-3 microm) and large fat globules (LFG, >5 microm) in raw milk, that were analyzed by X-ray diffraction (XRD) coupled to differential scanning calorimetry (DSC). There were no major differences in triglyceride crystalline structures between SFG and LFG, after eliminating thermal history and the influence of cooling rates. The three main 3L and 2L crystalline structures appearing under slow cooling existed regardless of globule size. The supercooling increased for the SFG, mainly due to heterogeneous nucleation in winter milk, and also to compositional variations in spring milk. Differences appeared regarding stabilized crystalline forms at 20 degrees C and subsequent cooling: the SFG contained less 2L triglyceride structures than the LFG. These results can be important in dairy manufactures using tempering periods.

Investigation of the Influence of Heat Balance Shifts on the Freeze Microstructure and Composition in Aluminum Smelting Bath System: Cryolite-CaF2-AlF3-Al2O3

NASA Astrophysics Data System (ADS)

Liu, Jingjing; Fallah-Mehrjardi, Ata; Shishin, Denis; Jak, Evgueni; Dorreen, Mark; Taylor, Mark

2017-12-01

In an aluminum electrolysis cell, the side ledge forms on side walls to protect it from the corrosive cryolitic bath. In this study, a series of laboratory analogue experiments have been carried out to investigate the microstructure and composition of side ledge (freeze linings) at different heat balance steady states. Three distinct layers are found in the freeze linings formed in the designed Cryolite-CaF2-AlF3-Al2O3 electrolyte system: a closed (columnar) crystalline layer, an open crystalline layer, and a sealing layer. This layered structure changes when the heat balance is shifted between different steady states, by melting or freezing the open crystalline layer. Phase chemistry of the freeze lining is studied in this paper to understand the side ledge formation process upon heat balance shifts. Electron probe X-ray microanalysis (EPMA) is used to characterize the microstructure and compositions of distinct phases existing in the freeze linings, which are identified as cryolite, chiolite, Ca-cryolite, and alumina. A freeze formation mechanism is further developed based on these microstructural/compositional investigations and also thermodynamic calculations through the software—FactSage. It is found that entrapped liquid channels exist in the open crystalline layer, assisting with the mass transfer between solidified crystals and bulk molten bath.

Mo(3)Sb(7-x)Te(x) for Thermoelectric Power Generation

NASA Technical Reports Server (NTRS)

Snyder, G. Jeffrey; Gascoin, Frank S.; Rasmussen, Julia

2009-01-01

Compounds having compositions of Mo(3)Sb(7-x)Te(x) (where x = 1.5 or 1.6) have been investigated as candidate thermoelectric materials. These compounds are members of a class of semiconductors that includes previously known thermoelectric materials. All of these compounds have complex crystalline and electronic structures. Through selection of chemical compositions and processing conditions, it may be possible to alter the structures to enhance or optimize thermoelectric properties.

Thermal Diffusivity of High-Density Polyethylene Samples of Different Crystallinity Evaluated by Indirect Transmission Photoacoustics

NASA Astrophysics Data System (ADS)

Nesic, M.; Popovic, M.; Rabasovic, M.; Milicevic, D.; Suljovrujic, E.; Markushev, D.; Stojanovic, Z.

2018-02-01

In this work, thermal diffusivity of crystalline high-density polyethylene samples of various thickness, and prepared using different procedures, was evaluated by transmission gas-microphone frequency photoacoustics. The samples' composition analysis and their degree of crystallinity were determined from the wide-angle X-ray diffraction, which confirmed that high-density polyethylene samples, obtained by slow and fast cooling, were equivalent in composition but with different degrees of crystallinity. Structural analysis, performed by differential scanning calorimetry, demonstrated that all of the used samples had different levels of crystallinity, depending not only on the preparing procedure, but also on sample thickness. Therefore, in order to evaluate the samples' thermal diffusivity, it was necessary to modify standard photoacoustic fitting procedures (based on the normalization of photoacoustic amplitude and phase characteristics on two thickness levels) for the interpretation of photoacoustic measurements. The calculated values of thermal diffusivity were in the range of the expected literature values. Besides that, the obtained results indicate the unexpected correlation between the values of thermal diffusivity and thermal conductivity with the degree of crystallinity of the investigated geometrically thin samples. The results indicate the necessity of additional investigation of energy transport in macromolecular systems, as well as the possible employment of the photoacoustic techniques in order to clarify its mechanism.

Colour stability of aesthetic brackets: ceramic and plastic.

PubMed

Filho, Hibernon Lopes; Maia, Lúcio Henrique; Araújo, Marcus V; Eliast, Carlos Nelson; Ruellas, Antônio Carlos O

2013-05-01

The colour stability of aesthetic brackets may differ according to their composition, morphology and surface property, which may consequently influence their aesthetic performance. To assess the colour stability of aesthetic brackets (ceramic and plastic) after simulating aging and staining. Twelve commercially manufactured ceramic brackets and four different plastic brackets were assessed. To determine possible colour change (change of E*(ab)) and the value of the NBS (National Bureau of Standards) unit system, spectrophotometric colour measurements for CIE L*, a* and b* were taken before and after the brackets were aged and stained. Statistical analysis was undertaken using a one-way ANOVA analysis of variance and a Tukey multiple comparison test (alpha = 0.05). The colour change between the various (ceramic and plastic) materials was not significant (p > 0.05), but still varied significantly (p < 0.001) between the brackets of the same composition or crystalline structure and among commercial brands. Colour stability cannot be confirmed simply by knowing the type of material and crystalline composition or structure.

High Resolution Quantification of Crystalline Cellulose Accumulation in Arabidopsis Roots to Monitor Tissue-specific Cell Wall Modifications.

PubMed

Fridman, Yulia; Holland, Neta; Elbaum, Rivka; Savaldi-Goldstein, Sigal

2016-05-10

Plant cells are surrounded by a cell wall, the composition of which determines their final size and shape. The cell wall is composed of a complex matrix containing polysaccharides that include cellulose microfibrils that form both crystalline structures and cellulose chains of amorphous organization. The orientation of the cellulose fibers and their concentrations dictate the mechanical properties of the cell. Several methods are used to determine the levels of crystalline cellulose, each bringing both advantages and limitations. Some can distinguish the proportion of crystalline regions within the total cellulose. However, they are limited to whole-organ analyses that are deficient in spatiotemporal information. Others relying on live imaging, are limited by the use of imprecise dyes. Here, we report a sensitive polarized light-based system for specific quantification of relative light retardance, representing crystalline cellulose accumulation in cross sections of Arabidopsis thaliana roots. In this method, the cellular resolution and anatomical data are maintained, enabling direct comparisons between the different tissues composing the growing root. This approach opens a new analytical dimension, shedding light on the link between cell wall composition, cellular behavior and whole-organ growth.

High Resolution Quantification of Crystalline Cellulose Accumulation in Arabidopsis Roots to Monitor Tissue-specific Cell Wall Modifications

PubMed Central

Fridman, Yulia; Holland, Neta; Elbaum, Rivka; Savaldi-Goldstein, Sigal

2016-01-01

Plant cells are surrounded by a cell wall, the composition of which determines their final size and shape. The cell wall is composed of a complex matrix containing polysaccharides that include cellulose microfibrils that form both crystalline structures and cellulose chains of amorphous organization. The orientation of the cellulose fibers and their concentrations dictate the mechanical properties of the cell. Several methods are used to determine the levels of crystalline cellulose, each bringing both advantages and limitations. Some can distinguish the proportion of crystalline regions within the total cellulose. However, they are limited to whole-organ analyses that are deficient in spatiotemporal information. Others relying on live imaging, are limited by the use of imprecise dyes. Here, we report a sensitive polarized light-based system for specific quantification of relative light retardance, representing crystalline cellulose accumulation in cross sections of Arabidopsis thaliana roots. In this method, the cellular resolution and anatomical data are maintained, enabling direct comparisons between the different tissues composing the growing root. This approach opens a new analytical dimension, shedding light on the link between cell wall composition, cellular behavior and whole-organ growth. PMID:27214583

Low temperature synthesis of polyaniline-crystalline TiO2-halloysite composite nanotubes with enhanced visible light photocatalytic activity.

PubMed

Li, Cuiping; Wang, Jie; Guo, Hong; Ding, Shujiang

2015-11-15

A series of one-dimensional polyaniline-crystalline TiO2-halloysite composite nanotubes with different mass ratio of polyaniline to TiO2 are facilely prepared by employing the low-temperature synthesis of crystalline TiO2 on halloysite nanotubes. The halloysite nanotubes can adsorb TiO2/polyaniline precursors and induce TiO2 nanocrystals/polyaniline to grow on the support in situ simultaneously. By simply adjusting the acidity of reaction system, PANI-crystalline TiO2-HA composite nanotubes composed of anatase, a mixed phase TiO2 and different PANI redox state are obtained. The XRD and UV-vis results show that the surface polyaniline sensitization has no effect on the crystalline structure of halloysite and TiO2 and the light response of TiO2 is extended to visible-light regions. Photocatalysis test results reveal the photocatalytic activity will be affected by the pH value and the volume ratio of ANI to TTIP. The highest photocatalytic activity is achieved with the composite photocatalysts prepared at pH 0.5 and 1% volume ratio of ANI and TTIP owing to the sensitizing effect of polyaniline and the charge transfer from the photoexcited PANI sensitizer to TiO2. Moreover, the PANI-TiO2-HA composite nanotubes synthesized by one-step at pH 0.5 with 1% volume ratio of ANI to TTIP exhibit higher visible light photocatalytic activity than those synthesized by the two-step. Heterogeneous PANI-TiO2-HA composite nanotubes prepared at pH 0.5 exhibit a higher degradation activity than that prepared at pH 1.5. The redoped experiment proves that the PANI redox state plays the main contribution to the enhanced visible light catalytic degradation efficiency of PANI-TiO2-HA prepared at pH 0.5. Furthermore, the heterogeneous PANI-crystalline TiO2-HA nanotubes have good photocatalytic stability and can be reused four times with only gradual loss of activity under visible light irradiation. Copyright © 2015 Elsevier Inc. All rights reserved.

Silicon nitride/silicon carbide composite densified materials prepared using composite powders

DOEpatents

Dunmead, S.D.; Weimer, A.W.; Carroll, D.F.; Eisman, G.A.; Cochran, G.A.; Susnitzky, D.W.; Beaman, D.R.; Nilsen, K.J.

1997-07-01

Prepare silicon nitride-silicon carbide composite powders by carbothermal reduction of crystalline silica powder, carbon powder and, optionally, crystalline silicon nitride powder. The crystalline silicon carbide portion of the composite powders has a mean number diameter less than about 700 nanometers and contains nitrogen. The composite powders may be used to prepare sintered ceramic bodies and self-reinforced silicon nitride ceramic bodies.

Preservation of rodent bones from El Harhoura 2 cave (Morocco, Neolithic - Middle Palaeolithic): Microstructure, mineralogy, crystallinity and composition

NASA Astrophysics Data System (ADS)

Farre, Bastien; Massard, Pierre; Nouet, Julius; Dauphin, Yannicke

2014-04-01

Thin sections, scanning electron microscopy (SEM), diffraction X (DRX) and infrared spectrometry (FTIR) have been used to study the structure, mineralogy, crystallinity and bulk composition of fossil rodent long bones extracted from a succession of sedimentary layers in a cave from Morocco (Neolithic - Middle Palaeolithic, El Harhoura 2). The microstructure of fossil bones is well-preserved at this scale of observation, and encrusted deposits are rare. All bones are preserved in apatite, but the crystallinity is modified, as well as the crystallite shape, the organic content and the organic-mineral ratio. No fluor enrichment has been observed. Alone or together, the studied parameters do not show a regular trend from the upper to the lower layers of the cave. The preservation of the fossil bones does not confirm the sequence of arid and humid periods inferred from taphonomic analyses.

Synthesis of graphene supported Li2SiO3 as a high performance anode material for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Yang, Shuai; Wang, Qiufen; Miao, Juan; Zhang, Jingyang; Zhang, Dafeng; Chen, Yumei; Yang, Hong

2018-06-01

The Li2SiO3-graphene composite is successfully synthesized through an easy hydrothermal method. The structures and morphologies of the produced samples are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectrum, Brunauer-Emmett-Teller formalism, scanning electron microscope, transmission electron microscope, and electrochemistry methods. The result shows a well crystalline of the Li2SiO3-GE composite. The existence of graphene doesn't change the crystalline of Li2SiO3. In addition, the Li2SiO3 compound with an average diameter of 20 nm can be seen on the surface of graphene with uniform distribution. After the composite with graphene, the composite displays large surface area which ensures the well electrochemistry of the composite. Finally, the Li2SiO3-graphene composite delivers a high initial capacity of 878.3 mAh g-1 at 1C as well as a high recovery capacity of 400 mAh g-1 after 200 cycles. When charged and discharged at high rate, the Li2SiO3-doping graphene composite still exhibits a high specific capacity of 748.3 mAh g-1 (at 2C, and 576 mAh g-1 at 5C) and well cycling performance. The well synthesized composite possesses well structure and well electrochemistry performance.

Fabrication of Ti substrate grain dependent C/TiO2 composites through carbothermal treatment of anodic TiO2.

PubMed

Rüdiger, Celine; Favaro, Marco; Valero-Vidal, Carlos; Calvillo, Laura; Bozzolo, Nathalie; Jacomet, Suzanne; Hejny, Clivia; Gregoratti, Luca; Amati, Matteo; Agnoli, Stefano; Granozzi, Gaetano; Kunze-Liebhäuser, Julia

2016-04-07

Composite materials of titania and graphitic carbon, and their optimized synthesis are highly interesting for application in sustainable energy conversion and storage. We report on planar C/TiO2 composite films that are prepared on a polycrystalline titanium substrate by carbothermal treatment of compact anodic TiO2 with acetylene. This thin film material allows for the study of functional properties of C/TiO2 as a function of chemical composition and structure. The chemical and structural properties of the composite on top of individual Ti substrate grains are examined by scanning photoelectron microscopy and micro-Raman spectroscopy. Through comparison of these data with electron backscatter diffraction, it is found that the amount of generated carbon and the grade of anodic film crystallinity correlate with the crystallographic orientation of the Ti substrate grains. On top of Ti grains with ∼(0001) orientations the anodic TiO2 exhibits the highest grade of crystallinity, and the composite contains the highest fraction of graphitic carbon compared to Ti grains with other orientations. This indirect effect of the Ti substrate grain orientation yields new insights into the activity of TiO2 towards the decomposition of carbon precursors.

Multifunctional cerium-based nanomaterials and methods for producing the same

DOEpatents

O'Keefe, Matthew J.; Castano Londono, Carlos E.; Fahrenholtz, William G.

2018-01-09

Embodiments relate to a cerium-containing nano-coating composition, the composition including an amorphous matrix including one or more of cerium oxide, cerium hydroxide, and cerium phosphate; and crystalline regions including one or more of crystalline cerium oxide, crystalline cerium hydroxide, and crystalline cerium phosphate. The diameter of each crystalline region is less than about 50 nanometers.

Chiral SiO2 and Ag@SiO2 Materials Templated by Complexes Consisting of Comblike Polyethyleneimine and Tartaric Acid.

PubMed

Yao, Dong-Dong; Murata, Hiroki; Tsunega, Seiji; Jin, Ren-Hua

2015-10-26

A facile avenue to fabricate micrometer-sized chiral (L-, D-) and meso-like (dl-) SiO2 materials with unique structures by using crystalline complexes (cPEI/tart), composed of comblike polyethyleneimine (cPEI) and L-, D-, or dl-tartaric acid, respectively, as catalytic templates is reported. Interestingly, both chiral crystalline complexes appeared as regularly left- and right-twisted bundle structures about 10 μm in length and about 5 μm in diameter, whereas the dl-form occurred as circular structures with about 10 μm diameter. Subsequently, SiO2 @cPEI/tart hybrids with high silica content (>55.0 wt %) were prepared by stirring a mixture containing tetramethoxysilane (TMOS) and the aggregates of the crystalline complexes in water. The chiral SiO2 hybrids and calcined chiral SiO2 showed very strong CD signals and a nanofiber-based morphology on their surface, whereas dl-SiO2 showed no CD activity and a nanosheet-packed disklike shape. Furthermore, metallic silver nanoparticles (Ag NPs) were encapsulated in each silica hybrid to obtain chiral (D and L forms) and meso-like (dl form) Ag@SiO2 composites. Also, the reaction between L-cysteine (Lcys) and these Ag@SiO2 composites was preliminarily investigated. Only chiral L- and D-Ag@SiO2 composites promoted the reaction between Lcys and Ag NPs to produce a molecular [Ag-Lcys]n complex with remarkable exciton chirality, whereas the reaction hardly occurred in the case of meso-like (dl-) Ag@SiO2 composite. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dicyanamide Salts that Adopt Smectic, Columnar, or Bicontinuous Cubic Liquid-Crystalline Mesophases.

PubMed

Park, Geonhui; Goossens, Karel; Shin, Tae Joo; Bielawski, Christopher W

2018-04-25

Although dicyanamide (i.e., [N(CN) 2 ] - ) has been commonly used to obtain low-viscosity, halogen-free, room-temperature ionic liquids, liquid-crystalline salts containing such anions have remained virtually unexplored. Here we report a series of amphiphilic dicyanamide salts that, depending on their structures and compositions, adopt smectic, columnar, or bicontinuous cubic thermotropic liquid-crystalline mesophases, even at room temperature in some cases. Their thermal properties were explored by polarized light optical microscopy, differential scanning calorimetry, thermogravimetric analysis (including evolved gas analysis), and variable-temperature synchrotron X-ray diffraction. Comparison of the thermal phase characteristics of these new liquid-crystalline salts featuring "V-shaped" [N(CN) 2 ] - anions with those of structural analogues containing [SCN] - , [BF 4 ] - , [PF 6 ] - , or [CF 3 SO 3 ] - anions indicated that not only the size of the counterion but also its shape should be considered in the development of mesomorphic salts. Collectively, these discoveries may be expected to facilitate the design of thermotropic ionic liquid crystals that form inverted-type bicontinuous cubic and other sophisticated liquid-crystalline phases. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Indium Gallium Zinc Oxide: Phase Formation and Crystallization Kinetics during Millisecond Laser Spike Annealing

NASA Astrophysics Data System (ADS)

Lynch, David Michael

Flat panel displays have become ubiquitous, enabling products from highresolution cell phones to ultra-large television panels. Amorphous silicon (a- Si) has been the industry workhorse as the active semiconductor in pixeladdressing transistors due to its uniformity and low production costs. However, a-Si can no longer support larger and higher-resolution displays, and new materials with higher electron mobilities are required. Amorphous indium gallium zinc oxide (a-IGZO), which retains the uniformity and low cost of amorphous films, has emerged as a viable candidate due to its enhanced transport properties. However, a-IGZO devices suffer from long-term instabilities--the origins of which are not yet fully understood--causing a drift in switching characteristics over time and affecting product lifetime. More recently, devices fabricated from textured nanocrystalline IGZO, termed c-axis aligned crystalline (CAAC), have demonstrated superior stability. Unfortunately, little is known regarding the phase formation and crystallization kinetics of either the CAAC structure or in the broader ternary IGZO system. Crystallinity and texture of CAAC IGZO films deposited by RF reactive sputtering were studied and characterized over a wide range of deposition conditions. The characteristic CAAC (0 0 9) peak at 2theta = 30° was observed by X-ray diffraction, and nanocrystalline domain texture was determined using a general area detector diffraction system (GADDS). Highly ordered CAAC films were obtained near the InGaZnO4 composition at a substrate temperature of 310 °C and in a 10%O2/90% Ar sputtering ambient. High-resolution transmission electron microscopy (HRTEM) confirmed the formation of CAAC and identified 2-3 nm domains coherently aligned over large ranges extending beyond the field of view (15 nm x 15 nm). Cross-section HRTEM of the CAAC/substrate interface shows formation of an initially disordered IGZO layer prior to CAAC formation, suggesting a nucleation mechanism similar to ZnO thin films. A classical nucleation and growth model is proposed and compared to alternative models proposed in literature. Extending this study of CAAC IGZO, the formation and growth of crystalline IGZO over a wide composition range and processing conditions were explored. IGZO itself is one composition of a class of homologous structures in the pseudo-binary InGaO3(ZnO)m system. For integer m, the equilibrium structure is known and well-characterized; however, for non-integer m, disorder must exist and the kinetics of the structural development remain almost completely unknown. A high-throughput (combinatorial) approach utilizing co-sputter deposition, millisecond timescale thermal gradient laser annealing, and spatially-resolved characterization using microbeam wide-angle X-ray scattering was used to probe the structural evolution as a function of temperature, time, and composition. As-deposited films were amorphous in the InGaO3- rich composition range, becoming crystalline (wurtzite) with increasing ZnO content. Under millisecond heating, films evolved toward the equilibrium layered structure consisting of nearly pure In2O3 layers with (Ga, Zn)Ox interlayers. Composition deviations (non-integer m) are discussed within a model of cationic disorder in both the In2O3 layers and the (Ga, Zn)O x layers. Crystal-tocrystal transformations in the high-ZnO region are discussed within the context of a new growth model for these homologous structures. This deeper understanding of the nature of crystalline IGZO will help to enable the successful implementation of CAAC IGZO for high-performance display applications.

Silicon nitride/silicon carbide composite powders

DOEpatents

Dunmead, Stephen D.; Weimer, Alan W.; Carroll, Daniel F.; Eisman, Glenn A.; Cochran, Gene A.; Susnitzky, David W.; Beaman, Donald R.; Nilsen, Kevin J.

1996-06-11

Prepare silicon nitride-silicon carbide composite powders by carbothermal reduction of crystalline silica powder, carbon powder and, optionally, crystalline silicon nitride powder. The crystalline silicon carbide portion of the composite powders has a mean number diameter less than about 700 nanometers and contains nitrogen. The composite powders may be used to prepare sintered ceramic bodies and self-reinforced silicon nitride ceramic bodies.

Crystalline solution series and order-disorder within the natrolite mineral group

USGS Publications Warehouse

Ross, M.; Flohr, M.J.K.; Ross, D.R.

1992-01-01

Electron microprobe and X-ray analyses were made of natrolite, tetranatrolite, gonnardite, and thomsonite from the Magnet Cove alkaline igneous complex, Arkansas, and of selected specimens from the U.S. National Museum. This information and data from the literature indicate that natrolite, mesolite, scolecite, edingtonite, and tetraedingtonite show only small deviations from the ideal stoichiometry. In contrast, gonnardite, tetranatrolite, and thomsonite show large deviations from the ideal end-member compositions and compose three crystalline series. The structures of the natrolite minerals are defined by combining each of the three types of framework structures with various combinations of channel-occupying polyhedra. Various polysomatic series can be constructed by combining slices of two basic structures to form new hybrid structures. -from Authors

Long-range ordering of composites for organic electronics: TIPS-pentacene single crystals with incorporated nano-fibers

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

Li, Huanbin; Xue, Guobiao; Wu, Jiake

Multi-component active materials are widely used for organic electronic devices, with every component contributing complementary and synergistic optoelectronic functions. Mixing these components generally leads to lowered crystallinity and weakened charge transport. Therefore, preparing the active materials without substantially disrupting the crystalline lattice is highly desired. In this paper, we show that crystallization of TIPS-pentacene from solutions in the presence of fluorescent nanofibers of a perylene bisimide derivative (PBI) leads to formation of composites with nanofiber guest incorporated in the crystal host. In spite of the binary composite structure, the TIPS-pentacene maintains the single-crystalline nature. As a result, the incorporation ofmore » the PBI guest introduces additional fluorescence function but does not significantly reduce the charge transport property of the TIPS-pentacene host, exhibiting field-effect mobility as high as 3.34 cm 2 V -1 s -1 even though 26.4% of the channel area is taken over by the guest. Finally, as such, this work provides a facile approach toward high-performance multifunctional organic electronic materials.« less

Long-range ordering of composites for organic electronics: TIPS-pentacene single crystals with incorporated nano-fibers

DOE PAGES

Li, Huanbin; Xue, Guobiao; Wu, Jiake; ...

2017-08-18

Multi-component active materials are widely used for organic electronic devices, with every component contributing complementary and synergistic optoelectronic functions. Mixing these components generally leads to lowered crystallinity and weakened charge transport. Therefore, preparing the active materials without substantially disrupting the crystalline lattice is highly desired. In this paper, we show that crystallization of TIPS-pentacene from solutions in the presence of fluorescent nanofibers of a perylene bisimide derivative (PBI) leads to formation of composites with nanofiber guest incorporated in the crystal host. In spite of the binary composite structure, the TIPS-pentacene maintains the single-crystalline nature. As a result, the incorporation ofmore » the PBI guest introduces additional fluorescence function but does not significantly reduce the charge transport property of the TIPS-pentacene host, exhibiting field-effect mobility as high as 3.34 cm 2 V -1 s -1 even though 26.4% of the channel area is taken over by the guest. Finally, as such, this work provides a facile approach toward high-performance multifunctional organic electronic materials.« less

Synthesis and Screening of Phase Change Chalcogenide Thin Film Materials for Data Storage.

PubMed

Guerin, Samuel; Hayden, Brian; Hewak, Daniel W; Vian, Chris

2017-07-10

A combinatorial synthetic methodology based on evaporation sources under an ultrahigh vacuum has been used to directly synthesize compositional gradient thin film libraries of the amorphous phases of GeSbTe alloys at room temperature over a wide compositional range. An optical screen is described that allows rapid parallel mapping of the amorphous-to-crystalline phase transition temperature and optical contrast associated with the phase change on such libraries. The results are shown to be consistent with the literature for compositions where published data are available along the Sb 2 Te 3 -GeTe tie line. The results reveal a minimum in the crystallization temperature along the Sb 2 Te 3 -Ge 2 Te 3 tie line, and the method is able to resolve subsequent cubic-to-hexagonal phase transitions in the GST crystalline phase. HT-XRD has been used to map the phases at sequentially higher temperatures, and the results are reconciled with the literature and trends in crystallization temperatures. The results clearly delineate compositions that crystallize to pure GST phases and those that cocrystallize Te. High-throughput measurement of the resistivity of the amorphous and crystalline phases has allowed the compositional and structural correlation of the resistivity contrast associated with the amorphous-to-crystalline transition, which range from 5-to-8 orders of magnitude for the compositions investigated. The results are discussed in terms of the compromises in the selection of these materials for phase change memory applications and the potential for further exploration through more detailed secondary screening of doped GST or similar classes of phase change materials designed for the demands of future memory devices.

Conductive ceramic composition and method of preparation

DOEpatents

Smith, J.L.; Kucera, E.H.

1991-04-16

A ceramic anode composition is formed of a multivalent metal oxide or oxygenate such as an alkali metal, transition metal oxygenate. The anode is prepared as a non-stoichiometric crystalline structure by reaction and conditioning in a hydrogen gas cover containing minor proportions of carbon dioxide and water vapor. The structure exhibits a single phase and substantially enhanced electrical conductivity over that of the corresponding stoichiometric structure. Unexpectedly, such oxides and oxygenates are found to be stable in the reducing anode fuel gas of a molten carbonate fuel cell. 4 figures.

Conductive ceramic composition and method of preparation

DOEpatents

Smith, James L.; Kucera, Eugenia H.

1991-01-01

A ceramic anode composition is formed of a multivalent metal oxide or oxygenate such as an alkali metal, transition metal oxygenate. The anode is prepared as a non-stoichiometric crystalline structure by reaction and conditioning in a hydrogen gas cover containing minor proportions of carbon dioxide and water vapor. The structure exhibits a single phase and substantially enhanced electrical conductivity over that of the corresponding stoichiometric structure. Unexpectedly, such oxides and oxygenates are found to be stable in the reducing anode fuel gas of a molten carbonate fuel cell.

Conduit for high temperature transfer of molten semiconductor crystalline material

NASA Technical Reports Server (NTRS)

Fiegl, George (Inventor); Torbet, Walter (Inventor)

1983-01-01

A conduit for high temperature transfer of molten semiconductor crystalline material consists of a composite structure incorporating a quartz transfer tube as the innermost member, with an outer thermally insulating layer designed to serve the dual purposes of minimizing heat losses from the quartz tube and maintaining mechanical strength and rigidity of the conduit at the elevated temperatures encountered. The composite structure ensures that the molten semiconductor material only comes in contact with a material (quartz) with which it is compatible, while the outer layer structure reinforces the quartz tube, which becomes somewhat soft at molten semiconductor temperatures. To further aid in preventing cooling of the molten semiconductor, a distributed, electric resistance heater is in contact with the surface of the quartz tube over most of its length. The quartz tube has short end portions which extend through the surface of the semiconductor melt and which are lef bare of the thermal insulation. The heater is designed to provide an increased heat input per unit area in the region adjacent these end portions.

Nanocrystalline ordered vanadium carbide: Superlattice and nanostructure

NASA Astrophysics Data System (ADS)

Kurlov, A. S.; Gusev, A. I.; Gerasimov, E. Yu.; Bobrikov, I. A.; Balagurov, A. M.; Rempel, A. A.

2016-02-01

The crystal structure, micro- and nanostructure of coarse- and nanocrystalline powders of ordered vanadium carbide V8C7 have been examined by X-ray and neutron diffraction and electron microscopy methods. The synthesized coarse-crystalline powder of ordered vanadium carbide has flower-like morphology. It was established that the real ordered phase has the composition V8C7-δ (δ ≅ 0.03) deviating from perfect stoichiometric composition V8C7. The vanadium atoms forming the octahedral environment □V6 of vacant sites in V8C7-δ are displaced towards the vacancy □. The presence of carbon onion-like structures was found in the vanadium carbide powders with a small content of free (uncombined) carbon. The nanopowders of V8C7-δ carbide with average particle size of 20-30 nm produced by high-energy milling of coarse-crystalline powder retain the crystal structure of the initial powder, but differ in the lattice deformation distortion anisotropy.

The thermodynamic scale of inorganic crystalline metastability

PubMed Central

Sun, Wenhao; Dacek, Stephen T.; Ong, Shyue Ping; Hautier, Geoffroy; Jain, Anubhav; Richards, William D.; Gamst, Anthony C.; Persson, Kristin A.; Ceder, Gerbrand

2016-01-01

The space of metastable materials offers promising new design opportunities for next-generation technological materials, such as complex oxides, semiconductors, pharmaceuticals, steels, and beyond. Although metastable phases are ubiquitous in both nature and technology, only a heuristic understanding of their underlying thermodynamics exists. We report a large-scale data-mining study of the Materials Project, a high-throughput database of density functional theory–calculated energetics of Inorganic Crystal Structure Database structures, to explicitly quantify the thermodynamic scale of metastability for 29,902 observed inorganic crystalline phases. We reveal the influence of chemistry and composition on the accessible thermodynamic range of crystalline metastability for polymorphic and phase-separating compounds, yielding new physical insights that can guide the design of novel metastable materials. We further assert that not all low-energy metastable compounds can necessarily be synthesized, and propose a principle of ‘remnant metastability’—that observable metastable crystalline phases are generally remnants of thermodynamic conditions where they were once the lowest free-energy phase. PMID:28138514

Radio- and photoluminescence properties of Ce/Tb co-doped glasses with huntite-like composition

NASA Astrophysics Data System (ADS)

Lorenzi, Roberto; Golubev, Nikita V.; Ziaytdinova, Mariyam Z.; Jarý, Vítězslav; Babin, Vladimir; Malashkevich, Georgii E.; Paleari, Alberto; Sigaev, Vladimir N.; Fasoli, Mauro; Nikl, Martin

2018-04-01

Optical properties of yttria-aluminoborate (YAB) glasses with general composition 10(CexTbyY(1-x-y))-30Al2O3-60B2O3 are investigated and compared with data available on YAB crystals with huntite-like structure. Ce doped samples show optical features ascribable to preferential location of rare earth ions in sites with specific geometry similar to that observed in crystalline structures. Samples prepared with Tb ions as emission activator and Ce ions as sensitizer have been studied within the framework of non-radiative energy transfer. The resulting Förster radius is of 4.6 ± 0.5 Å comparable with that observed in Ce/Tb co-doped YAl3(BO3)4 crystals. The investigated materials possess radio- and photoluminescence emission efficiencies and performances comparable to that of crystalline counterparts with the advantage of having easiness of preparation and workability typical of glassy systems.

Non-spectroscopic composition measurements of SrTiO 3-La 0.7Sr 0.3MnO 3 multilayers using scanning convergent beam electron diffraction

DOE PAGES

Ophus, Colin; Ercius, Peter; Huijben, Mark; ...

2017-02-08

The local atomic structure of a crystalline sample aligned along a zone axis can be probed with a focused electron probe, which produces a convergent beam electron diffraction pattern. The introduction of high speed direct electron detectors has allowed for experiments that can record a full diffraction pattern image at thousands of probe positions on a sample. By incoherently summing these patterns over crystalline unit cells, we demonstrate in this paper that in addition to crystal structure and thickness, we can also estimate the local composition of a perovskite superlattice sample. This is achieved by matching the summed patterns tomore » a library of simulated diffraction patterns. Finally, this technique allows for atomic-scale chemical measurements without requiring a spectrometer or hardware aberration correction.« less

Band gap tuning in transition metal oxides by site-specific substitution

DOEpatents

Lee, Ho Nyung; Chisholm, Jr., Matthew F; Jellison, Jr., Gerald Earle; Singh, David J; Choi, Woo Seok

2013-12-24

A transition metal oxide insulator composition having a tuned band gap includes a transition metal oxide having a perovskite or a perovskite-like crystalline structure. The transition metal oxide includes at least one first element selected form the group of Bi, Ca, Ba, Sr, Li, Na, Mg, K, Pb, and Pr; and at least one second element selected from the group of Ti, Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Hf, Ta, W, Re, Os, Ir, and Pt. At least one correlated insulator is integrated into the crystalline structure, including REMO.sub.3, wherein RE is at least one Rare Earth element, and wherein M is at least one element selected from the group of Co, V, Cr, Ni, Mn, and Fe. The composition is characterized by a band gap of less of 4.5 eV.

Impact of polymer structure and composition on fully resorbable endovascular scaffold performance

PubMed Central

Ferdous, Jahid; Kolachalama, Vijaya B.; Shazly, Tarek

2014-01-01

Fully erodible endovascular scaffolds are being increasingly considered for the treatment of obstructive arterial disease owing to their potential to mitigate long-term risks associated with permanent alternatives. While complete scaffold erosion facilitates vessel healing, generation and release of material degradation by-products from candidate materials such as poly-l-lactide (PLLA) may elicit local inflammatory responses that limit implant efficacy. We developed a computational framework to quantify how the compositional and structural parameters of PLLA-based fully erodible endovascular scaffolds affect degradation kinetics, erosion kinetics and the transient accumulation of material by-products within the arterial wall. Parametric studies reveal that, while some material properties have similar effects on these critical processes, others induce qualitatively opposing responses. For example, scaffold degradation is only mildly responsive to changes in either PLLA polydispersity or the initial degree of crystallinity, while the erosion kinetics is comparatively sensitive to crystallinity. Moreover, lactide doping can effectively tune both scaffold degradation and erosion, but a concomitant increase in local byproduct accumulation raises concerns about implant safety. Optimized erodible endovascular scaffolds must precisely balance therapeutic function and biological response over the implant lifetime, where compositional and structural parameters will have differential effects on implant performance. PMID:23261926

Electrochemically synthesized amorphous and crystalline nanowires: dissimilar nanomechanical behavior in comparison with homologous flat films

NASA Astrophysics Data System (ADS)

Zeeshan, M. A.; Esqué-de Los Ojos, D.; Castro-Hartmann, P.; Guerrero, M.; Nogués, J.; Suriñach, S.; Baró, M. D.; Nelson, B. J.; Pané, S.; Pellicer, E.; Sort, J.

2016-01-01

The effects of constrained sample dimensions on the mechanical behavior of crystalline materials have been extensively investigated. However, there is no clear understanding of these effects in nano-sized amorphous samples. Herein, nanoindentation together with finite element simulations are used to compare the properties of crystalline and glassy CoNi(Re)P electrodeposited nanowires (φ ~ 100 nm) with films (3 μm thick) of analogous composition and structure. The results reveal that amorphous nanowires exhibit a larger hardness, lower Young's modulus and higher plasticity index than glassy films. Conversely, the very large hardness and higher Young's modulus of crystalline nanowires are accompanied by a decrease in plasticity with respect to the homologous crystalline films. Remarkably, proper interpretation of the mechanical properties of the nanowires requires taking the curved geometry of the indented surface and sink-in effects into account. These findings are of high relevance for optimizing the performance of new, mechanically-robust, nanoscale materials for increasingly complex miniaturized devices.The effects of constrained sample dimensions on the mechanical behavior of crystalline materials have been extensively investigated. However, there is no clear understanding of these effects in nano-sized amorphous samples. Herein, nanoindentation together with finite element simulations are used to compare the properties of crystalline and glassy CoNi(Re)P electrodeposited nanowires (φ ~ 100 nm) with films (3 μm thick) of analogous composition and structure. The results reveal that amorphous nanowires exhibit a larger hardness, lower Young's modulus and higher plasticity index than glassy films. Conversely, the very large hardness and higher Young's modulus of crystalline nanowires are accompanied by a decrease in plasticity with respect to the homologous crystalline films. Remarkably, proper interpretation of the mechanical properties of the nanowires requires taking the curved geometry of the indented surface and sink-in effects into account. These findings are of high relevance for optimizing the performance of new, mechanically-robust, nanoscale materials for increasingly complex miniaturized devices. Electronic supplementary information (ESI) available: Additional details on experimental and analysis methods, additional results on crystalline CoNi(Re)P alloys and two movies to illustrate the stress distribution during deformation of the amorphous and crystalline nanowires. See DOI: 10.1039/c5nr04398k

Processing and characterization of Zr-based metallic glass by laser direct deposition

NASA Astrophysics Data System (ADS)

Bae, Heehun

Bulk Metallic Glass has become famous for its exceptional mechanical and corrosion properties. Especially, Zirconium has been the prominent constituent in Bulk Metallic Glass due to its superior glass forming ability, the ability to form amorphous phase with low cooling rate, thereby giving advantages in structural applications. In this study, Zirconium powder was alloyed with Aluminum, Nickel and Copper powder at an atomic ratio of 65:10:10:15, respectively. Using the ball milling process to mix the powders, Zr65Al10Ni 10Cu15 amorphous structure was manufactured by laser direct deposition. Laser power and laser scanning speed were optimized to increase the fraction of amorphous phase. X-ray Diffraction confirmed the existence of both amorphous and crystalline phase by having a wide halo peak and sharp intense peak in the spectrum. Differential Scanning Calorimetry proved the presence of amorphous phase and glass transition was observed to be around 655 K. Scanning electron microscopy showed the microstructure of the deposited sample to have repetitive amorphous and crystalline phase as XRD examined. Crystalline phase resulted from the laser reheating and remelting process due to subsequent laser scan. Laser direct deposited amorphous/crystalline composite showed Vickers Hardness of 670 Hv and exhibited improved corrosion resistance in comparison to fully-crystallized sample. The compression test showed that, due to the existence of crystalline phase, fracture strain of Zr65Al10Ni10Cu 15 amorphous composites was enhanced from less than 2% to as high as 5.7%, compared with fully amorphous metallic glass.

Confocal Raman mapping of collagen cross-link and crystallinity of human dentin-enamel junction

NASA Astrophysics Data System (ADS)

Slimani, Amel; Nouioua, Fares; Desoutter, Alban; Levallois, Bernard; Cuisinier, Frédéric J. G.; Tassery, Hervé; Terrer, Elodie; Salehi, Hamideh

2017-08-01

The separation zone between enamel and dentin [dentin-enamel junction (DEJ)] with different properties in biomechanical composition has an important role in preventing crack propagation from enamel to dentin. The understanding of the chemical structure (inorganic and organic components), physical properties, and chemical composition of the human DEJ could benefit biomimetic materials in dentistry. Spatial distribution of calcium phosphate crystallinity and the collagen crosslinks near DEJ were studied using confocal Raman microscopy and calculated by different methods. To obtain collagen crosslinking, the ratio of two peaks 1660 cm-1 over 1690 cm-1 (amide I bands) is calculated. For crystallinity, the inverse full-width at half maximum of phosphate peak at 960 cm-1, and the ratio of two Raman peaks of phosphate at 960/950 cm-1 is provided. In conclusion, the study of chemical and physical properties of DEJ provides many benefits in the biomaterial field to improve the synthesis of dental materials in respect to the natural properties of human teeth. Confocal Raman microscopy as a powerful tool provides the molecular structure to identify the changes along DEJ and can be expanded for other mineralized tissues.

Structural and chemical alteration of crystalline olivine under low energy He+ irradiation

NASA Astrophysics Data System (ADS)

Demyk, K.; Carrez, Ph.; Leroux, H.; Cordier, P.; Jones, A. P.; Borg, J.; Quirico, E.; Raynal, P. I.; d'Hendecourt, L.

2001-03-01

We present the results of irradiation experiments on crystalline olivine with He+ ions at energies of 4 and 10 keV and fluences varying from 5 1016 to 1018 ions/cm2. The aim of these experiments is to simulate ion implantation into interstellar grains in shocks in the ISM. Irradiated samples were analysed by transmission electron microscopy (TEM). The irradiation causes the amorphization of the olivine, at all He+ fluences considered. The thickness of the amorphized region is 40 +/- 15 nm and 90 +/- 10 nm for the 4 keV and 10 keV experiments, respectively. The amorphization of the olivine occurs in conjunction with an increase in the porosity of the material due to the formation of bubbles. In addition, the amorphized layer is deficient in oxygen and magnesium. We find that the O/Si and Mg/Si ratios decrease as the He+ fluence increases. These experiments show that the irradiation of dust in supernova shocks can efficiently alter the dust structure and composition. Our result are consistent with the lack of crystalline silicates in the interstellar medium and also with the compositional evolution observed from olivine-type silicates around evolved stars to pyroxene-type silicates around protostars.

Self-assembled hierarchically structured organic-inorganic composite systems.

PubMed

Tritschler, Ulrich; Cölfen, Helmut

2016-05-13

Designing bio-inspired, multifunctional organic-inorganic composite materials is one of the most popular current research objectives. Due to the high complexity of biocomposite structures found in nacre and bone, for example, a one-pot scalable and versatile synthesis approach addressing structural key features of biominerals and affording bio-inspired, multifunctional organic-inorganic composites with advanced physical properties is highly challenging. This article reviews recent progress in synthesizing organic-inorganic composite materials via various self-assembly techniques and in this context highlights a recently developed bio-inspired synthesis concept for the fabrication of hierarchically structured, organic-inorganic composite materials. This one-step self-organization concept based on simultaneous liquid crystal formation of anisotropic inorganic nanoparticles and a functional liquid crystalline polymer turned out to be simple, fast, scalable and versatile, leading to various (multi-)functional composite materials, which exhibit hierarchical structuring over several length scales. Consequently, this synthesis approach is relevant for further progress and scientific breakthrough in the research field of bio-inspired and biomimetic materials.

Stomatal cell wall composition: distinctive structural patterns associated with different phylogenetic groups.

PubMed

Shtein, Ilana; Shelef, Yaniv; Marom, Ziv; Zelinger, Einat; Schwartz, Amnon; Popper, Zoë A; Bar-On, Benny; Harpaz-Saad, Smadar

2017-04-01

Stomatal morphology and function have remained largely conserved throughout ∼400 million years of plant evolution. However, plant cell wall composition has evolved and changed. Here stomatal cell wall composition was investigated in different vascular plant groups in attempt to understand their possible effect on stomatal function. A renewed look at stomatal cell walls was attempted utilizing digitalized polar microscopy, confocal microscopy, histology and a numerical finite-elements simulation. The six species of vascular plants chosen for this study cover a broad structural, ecophysiological and evolutionary spectrum: ferns ( Asplenium nidus and Platycerium bifurcatum ) and angiosperms ( Arabidopsis thaliana and Commelina erecta ) with kidney-shaped stomata, and grasses (angiosperms, family Poaceae) with dumbbell-shaped stomata ( Sorghum bicolor and Triticum aestivum ). Three distinct patterns of cellulose crystallinity in stomatal cell walls were observed: Type I (kidney-shaped stomata, ferns), Type II (kidney-shaped stomata, angiosperms) and Type III (dumbbell-shaped stomata, grasses). The different stomatal cell wall attributes investigated (cellulose crystallinity, pectins, lignin, phenolics) exhibited taxon-specific patterns, with reciprocal substitution of structural elements in the end-walls of kidney-shaped stomata. According to a numerical bio-mechanical model, the end walls of kidney-shaped stomata develop the highest stresses during opening. The data presented demonstrate for the first time the existence of distinct spatial patterns of varying cellulose crystallinity in guard cell walls. It is also highly intriguing that in angiosperms crystalline cellulose appears to have replaced lignin that occurs in the stomatal end-walls of ferns serving a similar wall strengthening function. Such taxon-specific spatial patterns of cell wall components could imply different biomechanical functions, which in turn could be a consequence of differences in environmental selection along the course of plant evolution. © The Author 2017. Published by Oxford University Press on behalf of the Annals of Botany Company.

Studies on the effect of storage time and plasticizers on the structural variations in thermoplastic starch.

PubMed

Schmitt, H; Guidez, A; Prashantha, K; Soulestin, J; Lacrampe, M F; Krawczak, P

2015-01-22

Starch was combined with plasticizers such as glycerol, sorbitol, glycerol/sorbitol and urea/ethanolamine blends by means of high shear extrusion process to prepare thermoplastic starch (TPS). Effect of storage time and plasticizers on the structural stability of melt processed TPS was investigated. Morphological observation, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy reveal that melt extrusion process is efficient in transforming granular starch into a plasticized starch for all plasticizer compositions. XRD analysis highlights major changes in the microstructure of plasticized starch, and dependence of crystalline type and degree of crystallinity mainly on the plasticizer composition and storage time. Dynamical mechanical analysis (DMA) yields a decrease of the peak intensity of loss factor with aging time. The effect of ageing on tensile strength also appears to be highly dependent on the plasticizer composition. Thus, through different plasticizer combinations and ageing, starch-based materials with significant differences in tensile properties can be obtained, which may be tuned to meet the requirements of a wide range of applications. Copyright © 2014 Elsevier Ltd. All rights reserved.

Construction of a hydrazone-linked chiral covalent organic framework-silica composite as the stationary phase for high performance liquid chromatography.

PubMed

Zhang, Kai; Cai, Song-Liang; Yan, Yi-Lun; He, Zi-Hao; Lin, Hui-Mei; Huang, Xiao-Ling; Zheng, Sheng-Run; Fan, Jun; Zhang, Wei-Guang

2017-10-13

Covalent organic frameworks (COFs), as an emerging class of crystalline porous organic polymers, have great potential for applications in chromatographic separation owning to their fascinating crystalline structures and outstanding properties. However, development of COF materials as novel stationary phases in high performance liquid chromatography (HPLC) is just in its infancy. Herein, we report the design and construction of a new hydrazone-linked chiral COF, termed BtaMth COF, from a chiral hydrazide building block (Mth) and present a one-pot synthetic method for the fabrication of BtaMth@SiO 2 composite for HPLC separation of isomers. The as-synthesized BtaMth chiral COF displays good crystallinity, high porosity, as well as excellent chemical stability. Meanwhile, the fabricated HPLC column by using BtaMth@SiO 2 composite as the new stationary phase exhibits high resolution performances for the separation of positional isomers including nitrotoluene and nitrochlorobenzene, as well as cis-trans isomers including beta-cypermethrin and metconazole. Additionally, some effects such as the composition of the mobile phase and column temperature for HPLC separations on the BtaMth@SiO 2 packed column also have been studied in detail. The successful applications indicate the great potentials of hydrazone-linked chiral COF-silica composite as novel stationary phase for the efficient HPLC separation. Copyright © 2017 Elsevier B.V. All rights reserved.

Enhancing the enzymatic hydrolysis of corn stover by an integrated wet-milling and alkali pretreatment.

PubMed

He, Xun; Miao, Yelian; Jiang, Xuejian; Xu, Zidong; Ouyang, Pingkai

2010-04-01

An integrated wet-milling and alkali pretreatment was applied to corn stover prior to enzymatic hydrolysis. The effects of NaOH concentration in the pretreatment on crystalline structure, chemical composition, and reducing-sugar yield of corn stover were investigated, and the mechanism of increasing reducing-sugar yield by the pretreatment was discussed. The experimental results showed that the crystalline structure of corn stover was disrupted, and lignin was removed, while cellulose and hemicellulose were retained in corn stover by the pretreatment with 1% NaOH in 1 h. The reducing-sugar yield from the pretreated corn stovers increased from 20.2% to 46.7% when the NaOH concentration increased from 0% to 1%. The 1% NaOH pretreated corn stover had a holocellulose conversion of 55.1%. The increase in reducing-sugar yield was related to the crystalline structure disruption and delignification of corn stover. It was clarified that the pretreatment significantly enhanced the conversion of cellulose and hemicellulose in the corn stover to sugars.

Aerogel materials with periodic structures imprinted with cellulose nanocrystals.

PubMed

Xu, Yi-Tao; Dai, Yiling; Nguyen, Thanh-Dinh; Hamad, Wadood Y; MacLachlan, Mark J

2018-02-22

Novel aerogel materials with periodic structures derived from chiral nematic liquid crystalline cellulose nanocrystals (CNCs) are reported. The liquid crystalline structure of phase-separated CNCs is locked by a simple solvent exchange method or silica condensation. Both cellulose and silica/cellulose aerogel materials were obtained after critical point drying, and subsequent calcination of the silica/cellulose composite afforded a silica aerogel with periodic order. Gas adsorption and electron microscopy studies revealed that these materials have high surface areas and a unique chiral nematic structure imparted from the helicoidal CNC template. This is a new, scalable approach to aerogel materials with highly anisotropic structures. The high porosity and periodic, chiral features of these new materials may make them suitable for applications that require anisotropic properties or as hard templates for the construction of other ordered aerogels.

New thermoresistant polymorph from CO2 recrystallization of minocycline hydrochloride.

PubMed

Rodrigues, Miguel A; Tiago, João M; Padrela, Luis; Matos, Henrique A; Nunes, Teresa G; Pinheiro, Lídia; Almeida, António J; de Azevedo, Edmundo Gomes

2014-11-01

To prepare and thoroughly characterize a new polymorph of the broad-spectrum antibiotic minocycline from its hydrochloride dehydrate salts. The new minocycline hydrochloride polymorph was prepared by means of the antisolvent effect caused by carbon dioxide. Minocycline recrystallized as a red crystalline hydrochloride salt, starting from solutions or suspensions containing CO2 and ethanol under defined conditions of temperature, pressure and composition. This novel polymorph (β-minocycline) revealed characteristic PXRD and FTIR patterns and a high melting point (of 247 ºC) compared to the initial minocycline hydrochloride hydrates (α-minocycline). Upon dissolution the new polymorph showed full anti-microbial activity. Solid-state NMR and DSC studies evidenced the higher chemical stability and crystalline homogeneity of β-minocycline compared to the commercial chlorohydrate powders. Molecular structures of both minocyclines present relevant differences as shown by multinuclear solid-state NMR. This work describes a new crystalline structure of minocycline and evidences the ability of ethanol-CO2 system in removing water molecules from the crystalline structure of this API, at modest pressure, temperature and relatively short time (2 h), while controlling the crystal habit. This process has therefore the potential to become a consistent alternative towards the control of the solid form of APIs.

Comparative electrochemical analysis of crystalline and amorphous anodized iron oxide nanotube layers as negative electrode for LIB.

PubMed

Pervez, Syed Atif; Kim, Doohun; Farooq, Umer; Yaqub, Adnan; Choi, Jung-Hee; Lee, You-Jin; Doh, Chil-Hoon

2014-07-23

This work is a comparative study of the electrochemical performance of crystalline and amorphous anodic iron oxide nanotube layers. These nanotube layers were grown directly on top of an iron current collector with a vertical orientation via a simple one-step synthesis. The crystalline structures were obtained by heat treating the as-prepared (amorphous) iron oxide nanotube layers in ambient air environment. A detailed morphological and compositional characterization of the resultant materials was performed via transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and Raman spectroscopy. The XRD patterns were further analyzed using Rietveld refinements to gain in-depth information on their quantitative phase and crystal structures after heat treatment. The results demonstrated that the crystalline iron oxide nanotube layers exhibit better electrochemical properties than the amorphous iron oxide nanotube layers when evaluated in terms of the areal capacity, rate capability, and cycling performance. Such an improved electrochemical response was attributed to the morphology and three-dimensional framework of the crystalline nanotube layers offering short, multidirectional transport lengths, which favor rapid Li(+) ions diffusivity and electron transport.

Effects of laser polishing on surface microstructure and corrosion resistance of additive manufactured CoCr alloys

NASA Astrophysics Data System (ADS)

Wang, W. J.; Yung, K. C.; Choy, H. S.; Xiao, T. Y.; Cai, Z. X.

2018-06-01

Laser polishing of 3D printed metal components has drawn great interest in view of its potential applications in the dental implant industries. In this study, corrosion resistance, surface composition and crystalline structure of CoCr alloys were investigated. The corrosion resistance, micromorphology, composition, phase transformations and crystalline structures of samples were characterized using an electrochemical analyzer, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and transmission electron microscope (TEM), respectively. The results indicate that high laser powers and low object distances within a certain range can facilitate the formation of complex oxide films, which exhibits high corrosion resistance. Further, object distances have a significant influence on cooling rates during the solidification of the melt pool in laser polishing, and fast cooling generates vast amounts of vacancies and defects, which result in the crystalline phase transformation from γ to ε. Consequently, the formed oxides play an important role in corrosion resistance on the outer layer, and inner layer with γ phase also helps keep the CoCr alloys in a stable structure with high resistant to corrosion. The two process parameters in laser polishing, laser power and object distances, are demonstrated as being important for controlling the surface microstructures and corrosion resistance of the additive manufactured CoCr alloy components.

Vertically Integrated MEMS SOI Composite Porous Silicon-Crystalline Silicon Cantilever-Array Sensors: Concept for Continuous Sensing of Explosives and Warfare Agents

NASA Astrophysics Data System (ADS)

Stolyarova, Sara; Shemesh, Ariel; Aharon, Oren; Cohen, Omer; Gal, Lior; Eichen, Yoav; Nemirovsky, Yael

This study focuses on arrays of cantilevers made of crystalline silicon (c-Si), using SOI wafers as the starting material and using bulk micromachining. The arrays are subsequently transformed into composite porous silicon-crystalline silicon cantilevers, using a unique vapor phase process tailored for providing a thin surface layer of porous silicon on one side only. This results in asymmetric cantilever arrays, with one side providing nano-structured porous large surface, which can be further coated with polymers, thus providing additional sensing capabilities and enhanced sensing. The c-Si cantilevers are vertically integrated with a bottom silicon die with electrodes allowing electrostatic actuation. Flip Chip bonding is used for the vertical integration. The readout is provided by a sensitive Capacitance to Digital Converter. The fabrication, processing and characterization results are reported. The reported study is aimed towards achieving miniature cantilever chips with integrated readout for sensing explosives and chemical warfare agents in the field.

One - step nanosecond laser microstructuring, sulfur hyperdoping, and annealing of silicon surfaces in liquid carbondisulfide

NASA Astrophysics Data System (ADS)

Van Luong, Nguyen; Danilov, P. A.; Ionin, A. A.; Khmel'nitskii, P. A.; Kudryashov, S. I.; Mel'nik, N. N.; Saraeva, I. N.; Смirnov, H. A.; Rudenko, A. A.; Zayarny, D. A.

2017-09-01

We perform a single-shot IR nanosecond laser processing of commercial silicon wafers in ambient air and under a 2 mm thick carbon disulfide liquid layer. We characterize the surface spots modified in the liquid ambient and the spots ablated under the same conditions in air in terms of its surface topography, chemical composition, band-structure modification, and crystalline structure by means of SEM and EDX microscopy, as well as of FT-IR and Raman spectroscopy. These studies indicate that single-step microstructuring and deep (up to 2-3% on the surface) hyperdoping of the crystalline silicon in its submicron surface layer, preserving via pulsed laser annealing its crystallinity and providing high (103 - 104 cm-1) spectrally at near- and mid-IR absorption coefficients, can be obtained in this novel approach, which is very promising for thin - film silicon photovoltaic devices

Low resistance Ohmic contact to p-type crystalline silicon via nitrogen-doped copper oxide films

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

Zhang, Xinyu, E-mail: xinyu.zhang@anu.edu.au; Wan, Yimao; Bullock, James

2016-08-01

This work explores the application of transparent nitrogen doped copper oxide (CuO{sub x}:N) films deposited by reactive sputtering to create hole-selective contacts for p-type crystalline silicon (c-Si) solar cells. It is found that CuO{sub x}:N sputtered directly onto crystalline silicon is able to form an Ohmic contact. X-ray photoelectron spectroscopy and Raman spectroscopy measurements are used to characterise the structural and physical properties of the CuO{sub x}:N films. Both the oxygen flow rate and the substrate temperature during deposition have a significant impact on the film composition, as well as on the resulting contact resistivity. After optimization, a low contactmore » resistivity of ∼10 mΩ cm{sup 2} has been established. This result offers significant advantages over conventional contact structures in terms of carrier transport and device fabrication.« less

Single-crystalline BaTiO3 films grown by gas-source molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Matsubara, Yuya; Takahashi, Kei S.; Tokura, Yoshinori; Kawasaki, Masashi

2014-12-01

Thin BaTiO3 films were grown on GdScO3 (110) substrates by metalorganic gas-source molecular beam epitaxy. Titanium tetra-isopropoxide (TTIP) was used as a volatile precursor that provides a wide growth window of the supplied TTIP/Ba ratio for automatic adjustment of the film composition. Within the growth window, compressively strained films can be grown with excellent crystalline quality, whereas films grown outside of the growth window are relaxed with inferior crystallinity. This growth method will provide a way to study the intrinsic properties of ferroelectric BaTiO3 films and their heterostructures by precise control of the stoichiometry, structure, and purity.

Current-voltage characteristics and electroresistance in LaMnO3-δ/La0.7Ca0.3MnO3/LaAlO3 thin film composites.

PubMed

Gadani, Keval; Keshvani, M J; Rajyaguru, Bhargav; Dhruv, Davit; Kataria, B R; Joshi, A D; Asokan, K; Shah, N A; Solanki, P S

2017-11-08

In this communication, we report results of the electrical transport properties across the interface of composites consisting of n-type LaMnO 3-δ (LMO) and p-type La 0.7 Ca 0.3 MnO 3 (LCMO) manganites grown on LaAlO 3 (LAO) single crystalline substrates using low cost wet chemical solution deposition (CSD) and sophisticated, well-controlled dry chemical vapor deposition (CVD) chemical techniques. The XRD ϕ-scan studies reveal the single crystalline nature of both bilayered composites, with parallel epitaxial growth of LMO and LCMO layers onto the LAO substrate. The valence states of Mn ions in both layers of both composites were identified by performing X-ray photoelectron spectroscopy (XPS). The I-V characteristics of the LMO/LCMO interfaces show strong backward diode-like behavior at higher applied voltages well above the crossover voltage (V NB ). Below V NB , the interfaces demonstrate normal diode-like characteristics throughout the studied temperature range. The electric field-induced modulation of the LMO/LCMO junction resistance of the interfaces has been observed. Electric field-dependent electroresistance (ER) modifications at different temperatures have also been studied. The electrical transport properties have been discussed in the context of various mechanisms, such as charge injection, tunneling, depletion region modification and thermal processes across the interface. The effects of structurally and chemically developed sharp interfaces between the LMO and LCMO layers on the transport properties of the presently studied bilayered thin film composites have been discussed on the basis of correlation between the physicochemical characterization and charge transport behavior. A comparison of different aspects of the transport properties has been presented in the context of the structural strain and crystallinity of the composites grown using both wet and dry chemical techniques.

Heavy ion irradiation effects of brannerite-type ceramics

NASA Astrophysics Data System (ADS)

Lian, J.; Wang, L. M.; Lumpkin, G. R.; Ewing, R. C.

2002-05-01

Brannerite, UTi 2O 6, occurs in polyphase Ti-based, crystalline ceramics that are under development for plutonium immobilization. In order to investigate radiation effects caused by α-decay events of Pu, a 1 MeV Kr + irradiation on UTi 2O 6, ThTi 2O 6, CeTi 2O 6 and a more complex material, composed of Ca-containing brannerite and pyrochlore, was performed over a temperature range of 25-1020 K. The ion irradiation-induced crystalline-to-amorphous transformation was observed in all brannerite samples. The critical amorphization temperatures of the different brannerite compositions are: 970 K, UTi 2O 6; 990 K, ThTi 2O 6; 1020 K, CeTi 2O 6. The systematic increase in radiation resistance from Ce-, Th- to U-brannerite is related to the difference of mean atomic mass of A-site cation in the structure. As compared with the pyrochlore structure-type, brannerite phases are more susceptible to ion irradiation-induced amorphization. The effects of structure and chemical compositions on radiation resistance of brannerite-type and pyrochlore-type ceramics are discussed.

Multi-Functional BN-BN Composite

NASA Technical Reports Server (NTRS)

Kang, Jin Ho (Inventor); Bryant, Robert G. (Inventor); Park, Cheol (Inventor); Sauti, Godfrey (Inventor); Gibbons, Luke (Inventor); Lowther, Sharon (Inventor); Thibeault, Sheila A. (Inventor); Fay, Catharine C. (Inventor)

2017-01-01

Multifunctional Boron Nitride nanotube-Boron Nitride (BN-BN) nanocomposites for energy transducers, thermal conductors, anti-penetrator/wear resistance coatings, and radiation hardened materials for harsh environments. An all boron-nitride structured BN-BN composite is synthesized. A boron nitride containing precursor is synthesized, then mixed with boron nitride nanotubes (BNNTs) to produce a composite solution which is used to make green bodies of different forms including, for example, fibers, mats, films, and plates. The green bodies are pyrolized to facilitate transformation into BN-BN composite ceramics. The pyrolysis temperature, pressure, atmosphere and time are controlled to produce a desired BN crystalline structure. The wholly BN structured materials exhibit excellent thermal stability, high thermal conductivity, piezoelectricity as well as enhanced toughness, hardness, and radiation shielding properties. By substituting with other elements into the original structure of the nanotubes and/or matrix, new nanocomposites (i.e., BCN, BCSiN ceramics) which possess excellent hardness, tailored photonic bandgap and photoluminescence, result.

Mimicking the Humidity Response of the Plant Cell Wall by Using Two-Dimensional Systems: The Critical Role of Amorphous and Crystalline Polysaccharides.

PubMed

Niinivaara, Elina; Faustini, Marco; Tammelin, Tekla; Kontturi, Eero

2016-03-01

Of the composite materials occurring in nature, the plant cell wall is among the most intricate, consisting of a complex arrangement of semicrystalline cellulose microfibrils in a dissipative matrix of lignin and hemicelluloses. Here, a biomimetic, two-dimensional cellulose system of the cell wall structure is introduced where cellulose nanocrystals compose the crystalline portion and regenerated amorphous cellulose composes the dissipative matrix. Spectroscopic ellipsometry and QCM-D are used to study the water vapor uptake of several two-layer systems. Quantitative analysis shows that the vapor-induced swelling of these ultrathin films can be controlled by varying ratios of the chemically identical ordered and unordered cellulose components. Intriguingly, increasing the share of crystalline cellulose appeared to increase the vapor uptake but only in cases for which the interfacial area between the crystalline and amorphous area was relatively large and the thickness of an amorphous overlayer was relatively small. The results show that a biomimetic approach may occasionally provide answers as to why certain native structures exist.

Radio-frequency oxygen-plasma-enhanced pulsed laser deposition of IGZO films

NASA Astrophysics Data System (ADS)

Chou, Chia-Man; Lai, Chih-Chang; Chang, Chih-Wei; Wen, Kai-Shin; Hsiao, Vincent K. S.

2017-07-01

We demonstrate the crystalline structures, optical transmittance, surface and cross-sectional morphologies, chemical compositions, and electrical properties of indium gallium zinc oxide (IGZO)-based thin films deposited on glass and silicon substrates through pulsed laser deposition (PLD) incorporated with radio-frequency (r.f.)-generated oxygen plasma. The plasma-enhanced pulsed laser deposition (PEPLD)-based IGZO thin films exhibited a c-axis-aligned crystalline (CAAC) structure, which was attributed to the increase in Zn-O under high oxygen vapor pressure (150 mTorr). High oxygen vapor pressure (150 mTorr) and low r.f. power (10 W) are the optimal deposition conditions for fabricating IGZO thin films with improved electrical properties.

Photomobile polymer materials with crosslinked liquid-crystalline structures: molecular design, fabrication, and functions.

PubMed

Ube, Toru; Ikeda, Tomiki

2014-09-22

Crosslinked liquid-crystalline polymer materials that macroscopically deform when irradiated with light have been extensively studied in the past decade because of their potential in various applications, such as microactuators and microfluidic devices. The basic motions of these materials are contraction-expansion and bending-unbending, which are observed mainly in polysiloxanes and polyacrylates that contain photochromic moieties. Other sophisticated motions such as twisting, oscillation, rotation, and translational motion have also been achieved. In recent years, efforts have been made to improve the photoresponsive and mechanical properties of this novel class of materials through the modification of molecular structures, development of new fabrication methods, and construction of composite structures. Herein, we review structures, functions, and working mechanisms of photomobile materials and recent advances in this field. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Porous Ceramic Composite ZrO2(MgO)-MgO for Osteoimplantology

NASA Astrophysics Data System (ADS)

Buyakov, A. S.; Kulkov, S. N.

2017-02-01

Pore and crystalline structure, biocompatibility of ceramic composite ZrO2(MgO)-MgO were studied. The main mechanical characteristics were determined and it has been shown that compression strength directly depends on microstresses obtained from X-ray data. In-vitro studies of mesenchymal stromal stem cells (MMSC), cultivated on material surface are shown that cell proliferation and differentiation of MMSC goes throw osteogenic type.

Structure and blood compatibility of highly oriented PLA/MWNTs composites produced by solid hot drawing.

PubMed

Li, Zhengqiu; Zhao, Xiaowen; Ye, Lin; Coates, Phil; Caton-Rose, Fin; Martyn, Michasel

2014-03-01

Highly oriented poly(lactic acid) (PLA)/multi-walled carbon nanotubes (MWNTs) composites were fabricated through solid hot drawing technology in an effort to improve the mechanical properties and blood biocompatibility of PLA as blood-contacting medical devices. It was found that proper MWNTs content and drawing orientation can improve the tensile strength and modulus of PLA dramatically. With the increase in draw ratio, the cold crystallization peak became smaller, and the glass transition and the melting peak of PLA moved to high temperature, while the crystallinity increased, and the grain size decreased, indicating the stress-induced crystallization of PLA during drawing. MWNTs showed a nucleation effect on PLA, leading to the rise in the melting temperature, increase in crystallinity and reduction of spherulite size for the composites. Moreover, the intensity of (002) diffraction of MWNTs increased with draw ratio, indicating that MWNTs were preferentially aligned and oriented during drawing. Microstructure observation demonstrated that PLA matrix had an ordered fibrillar bundle structure, and MWNTs in the composite tended to align parallel to the drawing direction. In addition, the dispersion of MWNTs in PLA was also improved by orientation. Introduction of MWNTs and drawing orientation could significantly enhance the blood compatibility of PLA by prolonging kinetic clotting time, reducing hemolysis ratio and platelet activation.

Confocal Raman mapping of collagen cross-link and crystallinity of human dentin-enamel junction.

PubMed

Slimani, Amel; Nouioua, Fares; Desoutter, Alban; Levallois, Bernard; Cuisinier, Frédéric J G; Tassery, Hervé; Terrer, Elodie; Salehi, Hamideh

2017-08-01

The separation zone between enamel and dentin [dentin-enamel junction (DEJ)] with different properties in biomechanical composition has an important role in preventing crack propagation from enamel to dentin. The understanding of the chemical structure (inorganic and organic components), physical properties, and chemical composition of the human DEJ could benefit biomimetic materials in dentistry. Spatial distribution of calcium phosphate crystallinity and the collagen crosslinks near DEJ were studied using confocal Raman microscopy and calculated by different methods. To obtain collagen crosslinking, the ratio of two peaks 1660  cm-1 over 1690  cm-1 (amide I bands) is calculated. For crystallinity, the inverse full-width at half maximum of phosphate peak at 960  cm-1, and the ratio of two Raman peaks of phosphate at 960/950  cm-1 is provided. In conclusion, the study of chemical and physical properties of DEJ provides many benefits in the biomaterial field to improve the synthesis of dental materials in respect to the natural properties of human teeth. Confocal Raman microscopy as a powerful tool provides the molecular structure to identify the changes along DEJ and can be expanded for other mineralized tissues. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Formation of Helically Structured Chitin/CaCO3 Hybrids through an Approach Inspired by the Biomineralization Processes of Crustacean Cuticles.

PubMed

Matsumura, Shunichi; Kajiyama, Satoshi; Nishimura, Tatsuya; Kato, Takashi

2015-10-01

Chitin/CaCO3 hybrids with helical structures are formed through a biomineralization-inspired crystallization process under ambient conditions. Liquid-crystalline chitin whiskers are used as helically ordered templates. The liquid-crystalline structures are stabilized by acidic polymer networks which interact with the chitin templates. The crystallization of CaCO3 is conducted by soaking the templates in the colloidal suspension of amorphous CaCO3 (ACC) at room temperature. At the initial stage of crystallization, ACC particles are introduced inside the templates, and they crystallize to CaCO3 nanocrystals. The acidic polymer networks induce CaCO3 crystallization. The characterization of the resultant hybrids reveals that they possess helical order and homogeneous hybrid structures of chitin and CaCO3 , which resemble the structure and composition of the exoskeleton of crustaceans. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Instrument and method for focusing x rays, gamma rays, and neutrons

DOEpatents

Smither, R.K.

1982-03-25

A crystal-diffraction instrument or diffraction-grating instrument is described with an improved crystalline structure or grating spacing structure having a face for receiving a beam of photons or neutrons and diffraction planar spacing or grating spacing along that face with the spacing increasing progressively along the face to provide a decreasing Bragg diffraction angle for a monochromatic radiation and thereby increasing the usable area and acceptance angle. The increased planar spacing for the diffraction crystal is provided by the use of a temperature differential across the line structures with different compositions, by an individual crystalline structure with a varying composition and thereby a changing planar spacing along its face, and by combinations of these techniques. The increased diffraction grating element spacing is generated during the fabrication of the diffraction grating by controlling the cutting tool that is cutting the grooves or controlling the laser beam, electron beam, or ion beam that is exposing the resist layer, etc. It is also possible to vary this variation in grating spacing by applying a thermal gradient to the diffraction grating in much the same manner as is done in the crystal-diffraction case.

High-rate nano-crystalline Li 4Ti 5O 12 attached on carbon nano-fibers for hybrid supercapacitors

NASA Astrophysics Data System (ADS)

Naoi, Katsuhiko; Ishimoto, Shuichi; Isobe, Yusaku; Aoyagi, Shintaro

A lithium titanate (Li 4Ti 5O 12)-based electrode which can operate at unusually high current density (300 C) was developed as negative electrode for hybrid capacitors. The high-rate Li 4Ti 5O 12 electrode has a unique nano-structure consisting of unusually small nano-crystalline Li 4Ti 5O 12 (ca. 5-20 nm) grafted onto carbon nano-fiber anchors (nc-Li 4Ti 5O 12/CNF). This nano-structured nc-Li 4Ti 5O 12/CNF composite are prepared by simple sol-gel method under ultra-centrifugal force (65,000 N) followed by instantaneous annealing at 900 °C for 3 min. A model hybrid capacitor cell consisting of a negative nc-Li 4Ti 5O 12/CNF composite electrode and a positive activated carbon electrode showed high energy density of 40 Wh L -1 and high power density of 7.5 kW L -1 comparable to conventional EDLCs.

Separations method for polar molecules

DOEpatents

Thoma, Steven G.; Bonhomme, Francois R.

2004-07-27

A method for separating at least one compound from a liquid mixture containing different compounds where anew crystalline manganese phosphate composition with the formula Mn.sub.3 (PO.sub.4).sub.4.2(H.sub.3 NCH.sub.2 CH.sub.2).sub.3 N.6(H.sub.2 O) is dispersed in the liquid mixture, selectively intercalating one or more compounds into the crystalline structure of the Mn.sub.3 (PO.sub.4).sub.4.2(H.sub.3 NCH.sub.2 CH.sub.2).sub.3 N.6(H.sub.2 O).

3D Reconstruction of SPM Probes by Electron Tomography

NASA Astrophysics Data System (ADS)

Xu, X.; Peng, Y.; Saghi, Z.; Gay, R.; Inkson, B. J.; Möbus, G.

2007-04-01

Three-dimensional morphological and compositional structures of tungsten tips consisting of layered amorphous oxide shell and crystalline W core are reconstructed by electron tomography using both coherent and incoherent imaging modes. The fidelity of the reconstruction is dependent on three criteria, suppression of unwanted crystal orientation contrast in the crystalline core, nonlinear intensity-thickness relations above a certain thickness limit, and artefacts due to missing angular ranges when acquiring a tilt series of images. Annular dark field (ADF), and EDX chemical mapping are discussed as alternatives to standard bright field (BF) TEM imaging.

Chemical composition, crystal size and lattice structural changes after incorporation of strontium into biomimetic apatite.

PubMed

Li, Z Y; Lam, W M; Yang, C; Xu, B; Ni, G X; Abbah, S A; Cheung, K M C; Luk, K D K; Lu, W W

2007-03-01

Recently, strontium (Sr) as ranelate compound has become increasingly popular in the treatment of osteoporosis. However, the lattice structure of bone crystal after Sr incorporation is yet to be extensively reported. In this study, we synthesized strontium-substituted hydroxyapatite (Sr-HA) with different Sr content (0.3%, 1.5% and 15% Sr-HA in mole ratio) to simulate bone crystals incorporated with Sr. The changes in chemical composition and lattice structure of apetite after synthetic incorporation of Sr were evaluated to gain insight into bone crystal changes after incorporation of Sr. X-ray diffraction (XRD) patterns revealed that 0.3% and 1.5% Sr-HA exhibited single phase spectrum, which was similar to that of HA. However, 15% Sr-HA induced the incorporation of HPO4(2-) and more CO3(2-), the crystallinity reduced dramatically. Transmission electron microscopy (TEM) images showed that the crystal length and width of 0.3% and 1.5% Sr-HA increased slightly. Meanwhile, the length and width distribution were broadened and the aspect ratio decreased from 10.68+/-4.00 to 7.28+/-2.80. The crystal size and crystallinity of 15% Sr-HA dropped rapidly, which may suggest that the fundamental crystal structure is changed. The findings from this work indicate that current clinical dosage which usually results in Sr incorporation of below 1.5% may not change chemical composition and lattice structure of bone, while it will broaden the bone crystal size distribution and strengthen the bone.

Composition and structure of calcium aluminosilicate microspheres

NASA Astrophysics Data System (ADS)

Sharonova, O. M.; Oreshkina, N. A.; Zhizhaev, A. M.

2017-06-01

The composition was studied of calcium aluminosilicate microspheres of three morphological types in high-calcium fly ash from combustion of brown coal from the Kansk-Achinsk basin in slag-tap boilers at temperatures from 1400 to 1500°C and sampled in the first field of electrostatic precipitators at the Krasnoyarsk Cogeneration Power Station no. 2 (TETs-2). Gross compositions and the composition of local areas were determined using a scanning electron microscopy technique and an energy-dispersive analysis with full mapping of globules. With a high content of basic oxides O ox (68 to 79 wt %) and a low content of acid oxides K ox (21 to 31 wt %), type 1 microspheres are formed. They consist of heterogeneous areas having a porous structure and crystalline components in which the content of CaO, SiO2, or Al2O3 differs by two to three times and the content of MgO differs by seven times. With a lower content of O ox (55 to 63 wt %) and an elevated content of K ox (37 to 45 wt %), type 2 microspheres are formed. They are more homogeneous in the composition and structure and consist of similar crystalline components. Having a close content of O ox (46 to 53 wt %) and K ox (47 to 54 wt %), type 3 microspheres, which are a dense matter consisting of amorphous substance with submicron- and nanostructure of crystalline components, are formed. The basic precursor in formation of high-calcium aluminosilicate microspheres is calcium from the organomineral matter of coals with various contribution of Mg, Fe, S, or Na from the coal organic matter and Al, Fe, S, or Si in the form of single mineral inclusions in a coal particle. On the basis of the available data, the effect was analyzed of the composition of a CaO-MgO-Al2O3-SiO2-FeO system on the melting and viscous properties of the matter in microspheres and formation of globules of different morphology. The results of this analysis will help to find a correlation with properties of microspheres in their use as functional microaggregates in cement or polymeric composite materials, or in the production of ceramic membranes or zeolite sorbents.

Dose dependence of radiation damage in nano-structured amorphous SiOC/crystalline Fe composite

DOE PAGES

Su, Qing; Price, Lloyd; Shao, Lin; ...

2015-10-29

Here, through examination of radiation tolerance properties of amorphous silicon oxycarbide (SiOC) and crystalline Fe composite to averaged damage levels, from approximately 8 to 30 displacements per atom (dpa), we demonstrated that the Fe/SiOC interface and the Fe/amorphous Fe xSi yO z interface act as efficient defect sinks and promote the recombination of vacancies and interstitials. For thick Fe/SiOC multilayers, a clear Fe/SiOC interface remained and no irradiation-induced mixing was observed even after 32 dpa. For thin Fe/SiOC multilayers, an amorphous Fe xSi yO z intermixed layer was observed to form at 8 dpa, but no further layer growth wasmore » observed for higher dpa levels.« less

Reinforcement effect of poly(butylene succinate) (PBS)-grafted cellulose nanocrystal on toughened PBS/polylactic acid blends.

PubMed

Zhang, Xuzhen; Zhang, Yong

2016-04-20

Poly(butylene succinate) (PBS)/polylactic acid (PLA) blends modified with dicumyl peroxide (DCP) were reinforced by PBS-g-cellulose nanocrystal (CNC) through melt mixing. PBS-g-CNC was prepared through in situ polymerization and its structure was confirmed by FTIR, (13)C NMR, XPS and GPC analysis after saponification. The morphological analysis of PBS/PLA/PBS-g-CNC composites before and after etched by CH2Cl2 shows that the addition of DCP and PBS-g-CNC could decrease the size of PBS as a dispersed phase in PLA matrix and improve the dispersion of PBS-g-CNC in both PBS and PLA phases, which could affect the crystallization and mechanical properties of composites. The crystallinity of PLA α'-phase crystal in PBS/PLA/PBS-g-CNC composites is increased obviously by the addition of PBS-g-CNC, leading to an increase of the crystallinity of the composites. PBS/PLA blends modified by DCP have high Notched Izod impact strength and moduli, and the values are increased by the addition of PBS-g-CNC. Both storage modulus and glass translation temperature of PBS/PLA blend are increased by DCP and PBS-g-CNC, which is proved by DMA results, showing a weak molecular segment mobility of PBS/PLA matrix. The addition of DCP decreases the crystallization temperature and crystallinity of PBS/PLA composite, but increases the thermal stability of composites, mostly because of the crosslink effect of DCP on PBS/PLA matrix. Copyright © 2015 Elsevier Ltd. All rights reserved.

Biological Activity of Mesoporous Dendrimer-Coated Titanium Dioxide: Insight on the Role of the Surface-Interface Composition and the Framework Crystallinity.

PubMed

Milowska, Katarzyna; Rybczyńska, Aneta; Mosiolek, Joanna; Durdyn, Joanna; Szewczyk, Eligia M; Katir, Nadia; Brahmi, Younes; Majoral, Jean-Pierre; Bousmina, Mosto; Bryszewska, Maria; El Kadib, Abdelkrim

2015-09-16

Hitherto, the field of nanomedicine has been overwhelmingly dominated by the use of mesoporous organosilicas compared to their metal oxide congeners. Despite their remarkable reactivity, titanium oxide-based materials have been seldom evaluated and little knowledge has been gained with respect to their "structure-biological activity" relationship. Herein, a fruitful association of phosphorus dendrimers (both "ammonium-terminated" and "phosphonate-terminated") and titanium dioxide has been performed by means of the sol-gel process, resulting in mesoporous dendrimer-coated nanosized crystalline titanium dioxide. A similar organo-coating has been reproduced using single branch-mimicking dendrimers that allow isolation of an amorphous titanium dioxide. The impact of these materials on red blood cells was evaluated by studying cell hemolysis. Next, their cytotoxicity toward B14 Chinese fibroblasts and their antimicrobial activity were also investigated. Based on their variants (cationic versus anionic terminal groups and amorphous versus crystalline titanium dioxide phase), better understanding of the role of the surface-interface composition and the nature of the framework has been gained. No noticeable discrimination was observed for amorphous and crystalline material. In contrast, hemolysis and cytotoxicity were found to be sensitive to the nature of the interface composition, with the ammonium-terminated dendrimer-coated titanium dioxide being the most hemolytic and cytotoxic material. This surface-functionalization opens the door for creating a new synergistic machineries mechanism at the cellular level and seems promising for tailoring the biological activity of nanosized organic-inorganic hybrid materials.

Processing and properties of ceramic matrix-polymer composites for dental applications

NASA Astrophysics Data System (ADS)

Huang, Hsuan Yao

The basic composite structure of natural hard tissue was used to guide the design and processing of dental restorative materials. The design incorporates the methodology of using inorganic minerals as the main structural phase reinforced with a more ductile but tougher organic phase. Ceramic-polymer composites were prepared by slip casting a porous ceramic structure, heating and chemical treating the porous preform, infiltrating with monomer and then curing. The three factors that determined the mechanical properties of alumina-polymer composites were the type of polymer used, the method of silane treatments, and the type of bond between particles in the porous preforms. Without the use of silane coupling agents, the composites were measured to have a lower strength. The composite with a more "flexible" porous alumina network had a greater ability to plastically dissipate the energy of propagating cracks. However, the aggressive nature of the alumina particles on opposing enamel requires that these alumina-polymer composites have a wear compatible coating for practical application. A route to dense bioactive apatite wollastonite glass ceramics (AWGC)-polymer composites was developed. The problems associated with glass dissolution into the aqueous medium for slip casting were overcome with the use of silane. The role of heating rate and development of ceramic compact microstructure on composite properties was explored. In general, if isothermal heating was not applied, decreasing heating rate increased glass crystallinity and particle-particle fusion, but decreased pore volume. Also composite strength and fracture toughness decreased while modulus and hardness increased with decreasing heating rate. If isothermal heating was applied, glass crystallinity, pore content, and composite mechanical properties showed relatively little change regardless of the initial heating rate. The potential of AWGC-polymer composites for dental and implant applications was explored. Strengths and toughnesses were not severely degraded by immersion in simulated body fluids up to 30 days. The composite elastic modulus approached that of hard tissues and its wear behavior with opposing tooth was excellent. Growth of apatite over the entire composite surface was achieved in SBF. Growth of apatite in human whole saliva was achieved on the bioactive glass surface, but not on the composite surface.

Impact of change of matrix crystallinity and polymorphism on ovalbumin release from lipid-based implants.

PubMed

Duque, Luisa; Körber, Martin; Bodmeier, Roland

2018-05-30

The objectives of this study were to prepare lipid-based implants by hot melt extrusion (HME) for the prolonged release of ovalbumin (OVA), and to relate protein release to crystallinity and polymorphic changes of the lipid matrix. Two lipids, glycerol tristearate and hydrogenated palm oil, with different composition and degree of crystallinity were studied. Solid OVA was dispersed within the lipid matrixes, which preserved its stability during extrusion. This was partially attributed to a protective effect of the lipidic matrix. The incorporation of OVA decreased the mechanical strength of the implants prepared with the more crystalline matrix, glycerol tristearate, whereas it remained comparable for the hydrogenated palm oil because of stronger physical and non-covalent interactions between the protein and this lipid. This was also the reason for the faster release of OVA from the glycerol tristearate matrix when compared to the hydrogenated palm oil (8 vs. 28 weeks). Curing induced and increased crystallinity, and changes in the release rate, especially for the more crystalline matrix. In this case, both an increase and a decrease in release, were observed depending on the tempering condition. Curing at higher temperatures induced a melt-mediated crystallization and solid state transformation of the glycerol tristearate matrix and led to rearrangements of the inner structure with the formation of larger pores, which accelerated the release. In contrast, changes in the hydrogenated palm oil under the same curing conditions were less noticeable leading to a more robust formulation, because of less polymorphic changes over time. This study helps to understand the effect of lipid matrix composition and crystallinity degree on the performance of protein-loaded implants, and to establish criteria for the selection of a lipid carrier depending on the release profile desired. Copyright © 2018. Published by Elsevier B.V.

Evaluation of environmental scanning electron microscopy for analysis of Proteus mirabilis crystalline biofilms in situ on urinary catheters

PubMed Central

Holling, Nina; Dedi, Cinzia; Jones, Caroline E; Hawthorne, Joseph A; Hanlon, Geoffrey W; Salvage, Jonathan P; Patel, Bhavik A; Barnes, Lara M; Jones, Brian V

2014-01-01

Proteus mirabilis is a common cause of catheter-associated urinary tract infections and frequently leads to blockage of catheters due to crystalline biofilm formation. Scanning electron microscopy (SEM) has proven to be a valuable tool in the study of these unusual biofilms, but entails laborious sample preparation that can introduce artefacts, undermining the investigation of biofilm development. In contrast, environmental scanning electron microscopy (ESEM) permits imaging of unprocessed, fully hydrated samples, which may provide much insight into the development of P. mirabilis biofilms. Here, we evaluate the utility of ESEM for the study of P. mirabilis crystalline biofilms in situ, on urinary catheters. In doing so, we compare this to commonly used conventional SEM approaches for sample preparation and imaging. Overall, ESEM provided excellent resolution of biofilms formed on urinary catheters and revealed structures not observed in standard SEM imaging or previously described in other studies of these biofilms. In addition, we show that energy-dispersive X-ray spectroscopy (EDS) may be employed in conjunction with ESEM to provide information regarding the elemental composition of crystalline structures and demonstrate the potential for ESEM in combination with EDS to constitute a useful tool in exploring the mechanisms underpinning crystalline biofilm formation. PMID:24786314

Block coordination copolymers

DOEpatents

Koh, Kyoung Moo; Wong-Foy, Antek G; Matzger, Adam J; Benin, Annabelle I; Willis, Richard R

2014-11-11

The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

Block coordination copolymers

DOEpatents

Koh, Kyoung Moo; Wong-Foy, Antek G.; Matzger, Adam J.; Benin, Annabelle I.; Willis, Richard R.

2012-12-04

The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

Block coordination copolymers

DOEpatents

Koh, Kyoung Moo; Wong-Foy, Antek G; Matzger, Adam J; Benin, Annabelle I; Willis, Richard R

2012-11-13

The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

Preparation and characterization of collagen-hydroxyapatite/pectin composite.

PubMed

Wenpo, Feng; Gaofeng, Liang; Shuying, Feng; Yuanming, Qi; Keyong, Tang

2015-03-01

Pectin, a kind of plant polysaccharide, was introduced into collagen-hydroxyapatite composite system, and prepared collagen-hydroxyapatite/pectin (Col-HA/pectin) composite in situ. The structure of the composite was investigated by XRD, SEM, and FT-IR. The mechanical properties, water absorption, enzyme degradation, and cytotoxicity of the composite were investigated as well. The results show that the inorganic substance in the composite materials is hydroxyapatite in relatively low crystallinity. A new interface appeared by the interaction among hydroxyapatite and collagen-pectin, and formed smooth fine particles. The mechanical properties, water absorption, enzyme degradation, and cytotoxicity indicate a potential use in bone replacement for the new composite. Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis of novel sulfosalt materials with curved crystalline habits

NASA Astrophysics Data System (ADS)

Crawford, Guy Moore

Minerals and man-made materials with circular crystalline habit are very rare. A group of the complex iron-containing sulfosalt minerals exhibit a non-commensurate layered crystalline structure and are found with curved crystals. Cylindrite, named because of its cylindrical crystal habit, is the most easily recognized member of the group. The other members of the family, franckeite, incaite and potosiite, have similar compositions and are all lamellar. The two incommensurate interpenetrating sublattices have different but definite structures. One sublattice is PbS-type pseudotetragonal and the other SnS 2-type pseudohexagonal. Iron is found in both sublattices. The detailed crystal structures of these minerals remains unsolved. With the exception of a few phase studies, little is known about the chemistry of the minerals or the mechanism that prompts the formation of these misfit-layered materials. As sulfides, these minerals are of interest for their potential electronic and magnetic applications. A series of synthesis reactions were carried out to examine the effects on the properties and structures of the sulfosalts that are induced by the substitutions into the crystal lattice. Other transition metals were substituted in the place of iron in the incommensurate minerals, and selenium and tellurium replaced sulfur in cylindrite. The structure and properties were evaluated by environmental scanning electron microscopy, X-ray diffraction and differential thermal analysis. Curved and lamellar features were observed in several phases of the synthetic substitutional products. No correlations were immediately evident relating the composition to the propensity to form curved features.* *This dissertation is multimedia (contains text and other applications not available in printed format). The CD requires the following system application: Microsoft Office.

Update on the Chemical Composition Of Crystalline, Smectite, and Amorphous Components for Rocknest Soil and John Klein and Cumberland Mudstone Drill Fines at Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Morris, R. V.; Ming, D. W.; Gellert, R.; Vaniman, D. T.; Bish, D. L.; Blake, D. F.; Chipera, S. J.; Morrison, S. M.; Downs, R. T.; Rampe, E. B.;

Inorganic Biominerals in Crustaceans are Structurally Independent of Organic Framework

NASA Astrophysics Data System (ADS)

Mergelsberg, S. T.; Michel, F. M.; Mukhopadhyay, B.; Dove, P. M.

2015-12-01

Biomineralization of calcium carbonate (CaCO3) as crystalline calcite or amorphous CaCO3 (ACC) occurs in the exoskeletons of all crustaceans. These cuticles are complex composites of inorganic mineral and organic macromolecules with highly divergent morphologies that are adapted to the extreme variations in environmental pressures within their diverse ecological niches. The remarkable variations and adaptations that form, infer a highly efficient and regulated mechanism for biomineralization that is most likely orchestrated by a myriad of biomacromolecules (Ziegler A 2012). The roles of these peptides and organic metabolites during CaCO3 biomineralization are not well understood. In part, this is due to a lack of knowledge of crustacean homeostasis. In a step toward understanding cuticle mineralization in crustaceans, this study asks: Which molecules affect biomineralization? Do the biomineral-active molecules vary greatly between species and body parts? Recent studies of polysaccharide controls on mineralization also raise the question of whether small heterogeneities in chitin, the most abundant biopolymer of the composite, could be primarily responsible for differences in CaCO3 crystallinity. This study used a novel spectroscopic approach to characterize the mineral and organic components of exoskeletons from three Malacostraca organisms — American Lobster (Homarus americanus), Dungeness Crab (Metacarcinus magister), and Red Rock Crab (Cancer productus). Using high-energy x-ray diffraction and Raman spectroscopy, the cuticles of three major body parts from these organisms were analyzed for the structure and bulk chemistry of its chitin and CaCO3 components. The findings indicate that Raman spectroscopy provides adequate resolution to show that crystallinity of chitin and the CaCO3 mineral component are chemically independent of each other, although their crystallinities co-vary for Brachyura species (Dungeness and Red Rock Crabs). Insights from this study suggest chitin provides the structural framework of the cuticle, without direct chemical control on the biomineralization of CaCO3. Peptides and small metabolites are likely to be more directly involved in the mechanisms controlling polymerization, crystallization, and composition of both chitin and CaCO3.

Method for producing silicon nitride/silicon carbide composite

DOEpatents

Dunmead, Stephen D.; Weimer, Alan W.; Carroll, Daniel F.; Eisman, Glenn A.; Cochran, Gene A.; Susnitzky, David W.; Beaman, Donald R.; Nilsen, Kevin J.

1996-07-23

Silicon carbide/silicon nitride composites are prepared by carbothermal reduction of crystalline silica powder, carbon powder and optionally crsytalline silicon nitride powder. The crystalline silicon carbide portion of the composite has a mean number diameter less than about 700 nanometers and contains nitrogen.

Ti-Si-C thin films produced by magnetron sputtering: correlation between physical properties, mechanical properties and tribological behavior.

PubMed

Cunha, L; Vaz, F; Moura, C; Munteanu, D; Ionescu, C; Rivière, J P; Le Bourhis, E

2010-04-01

Ti-Si-C thin films were deposited onto silicon, stainless steel and high-speed steel substrates by magnetron sputtering, using different chamber configurations. The composition of the produced films was obtained by Electron Probe Micro-Analysis (EPMA) and the structure by X-ray diffraction (XRD). The hardness and residual stresses were obtained by depth-sensing indentation and substrate deflection measurements (using Stoney's equation), respectively. The tribological behavior of the produced films was studied by pin-on-disc. The increase of the concentration of non-metallic elements (carbon and silicon) caused significant changes in their properties. Structural analysis revealed the possibility of the coexistence of different phases in the prepared films, namely Ti metallic phase (alpha-Ti or beta-Ti) in the films with higher Ti content. The coatings with highest carbon contents, exhibited mainly a sub-stoichiometric fcc NaCI TiC-type structure. These structural changes were also confirmed by resistivity measurements, whose values ranged from 10(3) omega/sq for low non-metal concentration, up to 10(6) omega/sq for the highest metalloid concentration. A strong increase of hardness and residual stresses was observed with the increase of the non-metal concentration in the films. The hardness (H) values ranged between 11 and 27 GPa, with a clear dependence on both crystalline structure and composition features. Following the mechanical behavior, the tribological results showed similar trends, with both friction coefficients and wear revealing also a straight correlation with the composition and crystalline structure of the coatings.

Amorphous Calcium Carbonate Based-Microparticles for Peptide Pulmonary Delivery.

PubMed

Tewes, Frederic; Gobbo, Oliviero L; Ehrhardt, Carsten; Healy, Anne Marie

2016-01-20

Amorphous calcium carbonate (ACC) is known to interact with proteins, for example, in biogenic ACC, to form stable amorphous phases. The control of amorphous/crystalline and inorganic/organic ratios in inhalable calcium carbonate microparticles may enable particle properties to be adapted to suit the requirements of dry powders for pulmonary delivery by oral inhalation. For example, an amorphous phase can immobilize and stabilize polypeptides in their native structure and amorphous and crystalline phases have different mechanical properties. Therefore, inhalable composite microparticles made of inorganic (i.e., calcium carbonate and calcium formate) and organic (i.e., hyaluronan (HA)) amorphous and crystalline phases were investigated for peptide and protein pulmonary aerosol delivery. The crystalline/amorphous ratio and polymorphic form of the inorganic component was altered by changing the microparticle drying rate and by changing the ammonium carbonate and HA initial concentration. The bioactivity of the model peptide, salmon calcitonin (sCT), coprocessed with alpha-1-antitrypsin (AAT), a model protein with peptidase inhibitor activity, was maintained during processing and the microparticles had excellent aerodynamic properties, making them suitable for pulmonary aerosol delivery. The bioavailability of sCT after aerosol delivery as sCT and AAT-loaded composite microparticles to rats was 4-times higher than that of sCT solution.

A general representation scheme for crystalline solids based on Voronoi-tessellation real feature values and atomic property data

PubMed Central

Jalem, Randy; Nakayama, Masanobu; Noda, Yusuke; Le, Tam; Takeuchi, Ichiro; Tateyama, Yoshitaka; Yamazaki, Hisatsugu

2018-01-01

Abstract Increasing attention has been paid to materials informatics approaches that promise efficient and fast discovery and optimization of functional inorganic materials. Technical breakthrough is urgently requested to advance this field and efforts have been made in the development of materials descriptors to encode or represent characteristics of crystalline solids, such as chemical composition, crystal structure, electronic structure, etc. We propose a general representation scheme for crystalline solids that lifts restrictions on atom ordering, cell periodicity, and system cell size based on structural descriptors of directly binned Voronoi-tessellation real feature values and atomic/chemical descriptors based on the electronegativity of elements in the crystal. Comparison was made vs. radial distribution function (RDF) feature vector, in terms of predictive accuracy on density functional theory (DFT) material properties: cohesive energy (CE), density (d), electronic band gap (BG), and decomposition energy (Ed). It was confirmed that the proposed feature vector from Voronoi real value binning generally outperforms the RDF-based one for the prediction of aforementioned properties. Together with electronegativity-based features, Voronoi-tessellation features from a given crystal structure that are derived from second-nearest neighbor information contribute significantly towards prediction. PMID:29707064

A general representation scheme for crystalline solids based on Voronoi-tessellation real feature values and atomic property data.

PubMed

Jalem, Randy; Nakayama, Masanobu; Noda, Yusuke; Le, Tam; Takeuchi, Ichiro; Tateyama, Yoshitaka; Yamazaki, Hisatsugu

2018-01-01

Increasing attention has been paid to materials informatics approaches that promise efficient and fast discovery and optimization of functional inorganic materials. Technical breakthrough is urgently requested to advance this field and efforts have been made in the development of materials descriptors to encode or represent characteristics of crystalline solids, such as chemical composition, crystal structure, electronic structure, etc. We propose a general representation scheme for crystalline solids that lifts restrictions on atom ordering, cell periodicity, and system cell size based on structural descriptors of directly binned Voronoi-tessellation real feature values and atomic/chemical descriptors based on the electronegativity of elements in the crystal. Comparison was made vs. radial distribution function (RDF) feature vector, in terms of predictive accuracy on density functional theory (DFT) material properties: cohesive energy (CE), density ( d ), electronic band gap (BG), and decomposition energy (Ed). It was confirmed that the proposed feature vector from Voronoi real value binning generally outperforms the RDF-based one for the prediction of aforementioned properties. Together with electronegativity-based features, Voronoi-tessellation features from a given crystal structure that are derived from second-nearest neighbor information contribute significantly towards prediction.

Modeling hygroelastic properties of genetically modified aspen

Treesearch

Laszlo Horvath; Perry Peralta; Ilona Peszlen; Levente Csoka; Balazs Horvath; Joseph Jakes

2012-01-01

Numerical and three-dimensional finite element models were developed to improve understanding of major factors affecting hygroelastic wood properties. Effects of chemical composition, microfibril angle, crystallinity, structure of microfibrils, moisture content, and hydrophilicity of the cell wall were included in the model. Wood from wild-type and decreased-lignin...

Biofibres from biofuel industrial byproduct-Pongamia pinnata seed hull.

PubMed

Manjula, Puttaswamy; Srinikethan, Govindan; Shetty, K Vidya

2017-01-01

Biodiesel production using Pongamia pinnata (P. pinnata) seeds results in large amount of unused seed hull. These seed hulls serve as a potential source for cellulose fibres which can be exploited as reinforcement in composites. These seed hulls were processed using chlorination and alkaline extraction process in order to isolate cellulose fibres. Scanning electron microscopy (SEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR) analysis demonstrated the morphological changes in the fibre structure. Cellulose microfibres of diameter 6-8 µm, hydrodynamic diameter of 58.4 nm and length of 535 nm were isolated. Thermal stability was enhanced by 70 °C and crystallinity index (CI) by 19.8% ensuring isolation of crystalline cellulose fibres. The sequential chlorination and alkaline treatment stemmed to the isolation of cellulose fibres from P. pinnata seed hull. The isolated cellulose fibres possessed enhanced morphological, thermal, and crystalline properties in comparison with P. pinnata seed hull. These cellulose microfibres may potentially find application as biofillers in biodegradable composites by augmenting their properties.

Facile green synthesis of silver doped fluor-hydroxyapatite/β-cyclodextrin nanocomposite in the dual acting fluorine-containing ionic liquid medium for bone substitute applications

NASA Astrophysics Data System (ADS)

Jegatheeswaran, S.; Selvam, S.; Sri Ramkumar, V.; Sundrarajan, M.

2016-05-01

A novel green route has approached for the synthesis of silver doped fluor-hydroxyapatite/β-cyclodextrin composite by the assistance of fluorine-based ionic liquid. The selected [BMIM]BF4 ionic liquid for this work plays a dual role as fluoride source and templating agent. It helps to improve the crystalline structures and the shape of the composites. The crystallinity, surface morphology, topographical studies of the synthesized composite were validated. The XRD results of the composite show typical Ag reflection peaks at 38.1°, 44.2° and 63.4°. The ionic liquid assisted composite displayed the hexagonal shaped HA particles, which are surrounded by spherical nano-Ag particles and these particles are uniformly dispersed in the β-cyclodextrin matrix in both horizontal and cross sections from surface morphology observations. The Ionic liquid assisted silver doped fluor-hydroxyapatite/β-cyclodextrin composite exhibited very good antibacterial activities against Escherichia coli, Salmonella typhi, Klebsiella pneumonia and Serratia liquefaciens pathogens. The antibacterial proficiencies were established using Confocal Laser Scanning Microscopic developed biofilms images and bacterial growth curve analysis. The cytotoxicity results of the ionic liquid assisted composite analyzed by cell proliferation in vitro studies using human osteosarcoma cell line (MG-63) and this study has shown excellent biocompatibility.

Amylopectin molecular structure in relation to physicochemical properties of quinoa starch.

PubMed

Li, Guantian; Zhu, Fan

2017-05-15

Structure-function relationships of starch components remain a subject of research interest. Quinoa starch has very small granules (∼2μm) with unique properties. In this study, nine quinoa starches varied greatly in composition, structure, and physicochemical properties were selected for the analysis of structure-function relationships. Pearson correlation analysis revealed that the properties related to gelatinization such as swelling power, water solubility index, crystallinity, pasting, and thermal properties are much affected by the amylopectin chain profile and amylose content. The parameters of gel texture and amylose leaching are much related to amylopectin internal structure. Other properties such as enzyme susceptibility and particle size distribution are also strongly correlated with starch composition and amylopectin structure. Interesting findings indicate the importance of amylopectin internal structure and individual unit chain profile in determining the physicochemical properties of starch. This work highlights some relationships among composition, amylopectin structure and physicochemical properties of quinoa starch. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

Garn, Troy G; Law, Jack D; Greenhalgh, Mitchell R

A composite media including at least one crystalline aluminosilicate material in polyacrylonitrile. A method of forming a composite media is also disclosed. The method comprises dissolving polyacrylonitrile in an organic solvent to form a matrix solution. At least one crystalline aluminosilicate material is combined with the matrix solution to form a composite media solution. The organic solvent present in the composite media solution is diluted. The composite media solution is solidified. In addition, a method of processing a fluid stream is disclosed. The method comprises providing a beads of a composite media comprising at least one crystalline aluminosilicate material dispersedmore » in a polyacrylonitrile matrix. The beads of the composite media are contacted with a fluid stream comprising at least one constituent. The at least one constituent is substantially removed from the fluid stream.« less

Effect of chromium underlayer on the properties of nano-crystalline diamond films

NASA Astrophysics Data System (ADS)

Garratt, E.; AlFaify, S.; Yoshitake, T.; Katamune, Y.; Bowden, M.; Nandasiri, M.; Ghantasala, M.; Mancini, D. C.; Thevuthasan, S.; Kayani, A.

2013-01-01

This paper investigated the effect of chromium underlayer on the structure, microstructure, and composition of the nano-crystalline diamond films. Nano-crystalline diamond thin films were deposited at high temperature in microwave-induced plasma diluted with nitrogen, on single crystal silicon substrate with a thin film of chromium as an underlayer. Characterization of the film was implemented using non-Rutherford backscattering spectrometry, Raman spectroscopy, near-edge x-ray absorption fine structure, x-ray diffraction, and atomic force microscopy. Nanoindentation studies showed that the films deposited on chromium underlayer have higher hardness values compared to those deposited on silicon without an underlayer. Diamond and graphitic phases of the films evaluated by x-ray and optical spectroscopic analyses determined consistency between the sp2 and sp3 phases of carbon in chromium sample to that of diamond grown on silicon. Diffusion of chromium was observed using ion beam analysis which was correlated with the formation of chromium complexes by x-ray diffraction.

The Structure and Composition Statistics of 6A Binary and Ternary Crystalline Materials.

PubMed

Hever, Alon; Oses, Corey; Curtarolo, Stefano; Levy, Ohad; Natan, Amir

2018-01-16

The fundamental principles underlying the arrangement of elements into solid compounds with an enormous variety of crystal structures are still largely unknown. This study presents a general overview of the structure types appearing in an important subset of the solid compounds, i.e., binary and ternary compounds of the 6A column oxides, sulfides and selenides. It contains an analysis of these compounds, including the prevalence of various structure types, their symmetry properties, compositions, stoichiometries and unit cell sizes. It is found that these compound families include preferred stoichiometries and structure types that may reflect both their specific chemistry and research bias in the available empirical data. Identification of nonoverlapping gaps and missing stoichiometries in these structure populations may be used as guidance in the search for new materials.

Synthesis and characterization of Chitosan-CuO-MgO polymer nanocomposites

NASA Astrophysics Data System (ADS)

Praffulla, S. R.; Bubbly, S. G.

2018-05-01

In the present work, we have synthesized Chitosan-CuO-MgO nanocomposites by incorporating CuO and MgO nanoparticles in chitosan matrix. Copper oxide and magnesium oxide nanoparticles synthesized by precipitation method were characterized by X-ray diffraction and the diffraction patterns confirmed the monoclinic and cubic crystalline structures of CuO and MgO nanoparticles respectively. Chitosan-CuO-MgO composite films were prepared using solution- cast method with different concentrations of CuO and MgO nanoparticles (15 - 50 wt % with respect to chitosan) and characterized by XRD, FTIR and UV-Vis spectroscopy. The X-ray diffraction pattern shows that the crystallinity of the chitosan composite increases with increase in nanoparticle concentration. FTIR spectra confirm the chemical interaction between chitosan and metal oxide nanoparticles (CuO and MgO). UV absorbance of chitosan nanocomposites were up to 17% better than pure chitosan, thus confirming its UV shielding properties. The mechanical and electrical properties of the prepared composites are in progress.

Phosphorus K-edge XANES spectroscopy of mineral standards

PubMed Central

Ingall, Ellery D.; Brandes, Jay A.; Diaz, Julia M.; de Jonge, Martin D.; Paterson, David; McNulty, Ian; Elliott, W. Crawford; Northrup, Paul

2011-01-01

Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy was performed on phosphate mineral specimens including (a) twelve specimens from the apatite group covering a range of compositional variation and crystallinity; (b) six non-apatite calcium-rich phosphate minerals; (c) 15 aluminium-rich phosphate minerals; (d) ten phosphate minerals rich in either reduced iron or manganese; (e) four phosphate minerals rich in either oxidized iron or manganese; (f) eight phosphate minerals rich in either magnesium, copper, lead, zinc or rare-earth elements; and (g) four uranium phosphate minerals. The identity of all minerals examined in this study was independently confirmed using X-ray powder diffraction. Minerals were distinguished using XANES spectra with a combination of pre-edge features, edge position, peak shapes and post-edge features. Shared spectral features were observed in minerals with compositions dominated by the same specific cation. Analyses of apatite-group minerals indicate that XANES spectral patterns are not strongly affected by variations in composition and crystallinity typical of natural mineral specimens. PMID:21335905

Synthesis and characterization of polymeric V2O5/AlO(OH) with nanopores on alumina support.

PubMed

Ahmad, A L; Abd Shukor, S R; Leo, C P

2006-12-01

Polymeric vanadium pentoxide gel was formed via the reaction of V2O5 powder with hydrogen peroxide. The polymeric vanadium pentoxide gel was then dispersed in alumina gel. Different vanadium loading composites were coated on alumina support and calcined at 500 degrees C for 1 hr. These composite layers were characterized using TGA, FT-IR, XRD, SEM, and Autosorb. It was found that the lamellar structure of polymerized vanadium pentoxide was retained in the inorganic matrix. Crystalline alumina in gamma phase was formed after calcinations. However, the vanadium-alumina mixed oxides are lack of the well defined PXRD peaks for polycrystalline V2O5. This is possibly because the vanadia species are highly dispersed in the alumina matrix or the vanadia species are dispersed as crystalline which is smaller than 4 nm. In addition, the imbedded polymeric vanadium oxide improved the specific area and average pore diameter of the composite layer.

Thin film composition with biological substance and method of making

DOEpatents

Campbell, Allison A.; Song, Lin

1999-01-01

The invention provides a thin-film composition comprising an underlying substrate of a first material including a plurality of attachment sites; a plurality of functional groups chemically attached to the attachment sites of the underlying substrate; and a thin film of a second material deposited onto the attachment sites of the underlying substrate, and a biologically active substance deposited with the thin-film. Preferably the functional groups are attached to a self assembling monolayer attached to the underlying substrate. Preferred functional groups attached to the underlying substrate are chosen from the group consisting of carboxylates, sulfonates, phosphates, optionally substituted, linear or cyclo, alkyl, alkene, alkyne, aryl, alkylaryl, amine, hydroxyl, thiol, silyl, phosphoryl, cyano, metallocenyl, carbonyl, and polyphosphate. Preferred materials for the underlying substrate are selected from the group consisting of a metal, a metal alloy, a plastic, a polymer, a proteic film, a membrane, a glass or a ceramic. The second material is selected from the group consisting of inorganic crystalline structures, inorganic amorphus structures, organic crystalline structures, and organic amorphus structures. Preferred second materials are phosphates, especially calcium phosphates and most particularly calcium apatite. The biologically active molecule is a protein, peptide, DNA segment, RNA segment, nucleotide, polynucleotide, nucleoside, antibiotic, antimicrobal, radioisotope, chelated radioisotope, chelated metal, metal salt, anti-inflamatory, steriod, nonsteriod anti-inflammatory, analgesic, antihistamine, receptor binding agent, or chemotherapeutic agent, or other biologically active material. Preferably the biologically active molecule is an osteogenic factor the compositions listed above.

Glass transition and composite formation in InF{sub 3}-containing oxyfluoroniobate system

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

Savchenko, N. N.; Ignatieva, L. N.; Marchenko, Yu. V.

2016-05-18

The glasses in the system MnNbOF{sub 5}-BaF{sub 2}-InF{sub 3} have been firstly synthesized and studied. The thermal parameters of these glasses are analyzed. It was stated that glass of the composition 40MnNbOF{sub 5}-40BaF{sub 2}-20InF{sub 3} is the most thermal stable in the system under study. By X-ray analysis the compositions of the crystalline phases obtained at the glass thermal treatment were determined: the main phases are Ba{sub 3}In{sub 2}F{sub 12} and BaNbOF{sub 5}. By Raman and IR spectra analysis it was stated that the networks of glasses in the system are built by the structural type of the glasses inmore » NbO{sub 2}F-BaF{sub 2} system: (NbO{sub n}F{sub m}) polyhedra joined oxygen bridges. Indium trifluoride forms InF{sub 6} polyhedra, which are embeded between oxyfluoroniobate ions, forming a common networks or forms its own layers from InF{sub 6} polyhedra. IR-spectroscopy method showed that at devitrification of the sample 30MnNbOF{sub 5}-50BaF{sub 2}-20InF{sub 3} the band position and shape change in going from glass state to crystalline. The bands in the range 900–700 cm{sup −1} shift into the low-frequency range and transformed into narrow peaks characteristic for the crystalline state. It was determined that for this sample the IR-spectroscopy method fixes the presence of the crystalline phases at 340°C without time of exposure, despite the fact that X-ray analysis shows an amorphous state for this sample at the same temperature. It was suggested, that controlling the composition and conditions of annealing of the glasses it can be obtain the transparent glass-ceramics of definite composition.« less

High-Yield Synthesis of Stoichiometric Boron Nitride Nanostructures

DOE PAGES

Nocua, José E.; Piazza, Fabrice; Weiner, Brad R.; ...

2009-01-01

Boron nimore » tride (BN) nanostructures are structural analogues of carbon nanostructures but have completely different bonding character and structural defects. They are chemically inert, electrically insulating, and potentially important in mechanical applications that include the strengthening of light structural materials. These applications require the reliable production of bulk amounts of pure BN nanostructures in order to be able to reinforce large quantities of structural materials, hence the need for the development of high-yield synthesis methods of pure BN nanostructures. Using borazine ( B 3 N 3 H 6 ) as chemical precursor and the hot-filament chemical vapor deposition (HFCVD) technique, pure BN nanostructures with cross-sectional sizes ranging between 20 and 50 nm were obtained, including nanoparticles and nanofibers. Their crystalline structure was characterized by (XRD), their morphology and nanostructure was examined by (SEM) and (TEM), while their chemical composition was studied by (EDS), (FTIR), (EELS), and (XPS). Taken altogether, the results indicate that all the material obtained is stoichiometric nanostructured BN with hexagonal and rhombohedral crystalline structure.« less

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.

Investigation on Explosive Welding of Zr53Cu35Al12 Bulk Metallic Glass with Crystalline Copper

NASA Astrophysics Data System (ADS)

Feng, Jianrui; Chen, Pengwan; Zhou, Qiang

2018-05-01

A Zr53Cu35Al12 bulk metallic glass (BMG) was welded to a crystalline Cu using explosive welding technique. The morphology and the composition of the composite were characterized using optical microscopy, scanning electron microscopy, energy-dispersive x-ray spectroscopy and transmission electron microscopy. The investigation indicated that the BMG and Cu were tightly joined together without visible defects, and a thin diffusion layer appeared at the interface. The captured jet at the end of the welding region mostly comes from the Cu side. Amorphous and partially crystallized structures have been observed within the diffusion layer, but the BMG in close proximity to the interface still retains its amorphous state. Nanoindentation tests reveal that the interface exhibits an increment in hardness compared with the matrix on both sides.

A-site compositional effects in Ga-doped hollandite materials of the form BaxCsyGa2x+yTi8−2x−yO16: implications for Cs immobilization in crystalline ceramic waste forms

PubMed Central

Xu, Yun; Wen, Yi; Grote, Rob; Amoroso, Jake; Shuller Nickles, Lindsay; Brinkman, Kyle S.

2016-01-01

The hollandite structure is a promising crystalline host for Cs immobilization. A series of Ga-doped hollandite BaxCsyGa2x+yTi8−2x−yO16 (x = 0, 0.667, 1.04, 1.33; y = 1.33, 0.667, 0.24, 0) was synthesized through a solid oxide reaction method resulting in a tetragonal hollandite structure (space group I4/m). The lattice parameter associated with the tunnel dimension was found to increases as Cs substitution in the tunnel increased. A direct investigation of cation mobility in tunnels using electrochemical impedance spectroscopy was conducted to evaluate the ability of the hollandite structure to immobilize cations over a wide compositional range. Hollandite with the largest tunnel size and highest aspect ratio grain morphology resulting in rod-like microstructural features exhibited the highest ionic conductivity. The results indicate that grain size and optimized Cs stoichiometry control cation motion and by extension, the propensity for Cs release from hollandite. PMID:27273791

Structure and tribological properties of composite materials based on Al-Cu-Fe formed at high pressure

NASA Astrophysics Data System (ADS)

Golovkova, E. A.; Ekimov, E. A.; Ivanov, A. S.; Kruglov, V. S.; Pal', A. F.; Ryabinkin, A. N.; Serov, A. O.; Starostin, A. N.; Tsetlin, M. B.

2017-11-01

The use of high pressure ( 8 GPa) in the formation of composite quasi-crystalline materials from powders made it possible to create practically poreless samples with a density close to the maximum known for this type of quasi-crystals. For samples with a nickel binder, sintered at a temperature of 550°C, a very low coefficient of friction was obtained, which retain its value during the testing.

Engineering of III-Nitride Semiconductors on Low Temperature Co-fired Ceramics.

PubMed

Mánuel, J M; Jiménez, J J; Morales, F M; Lacroix, B; Santos, A J; García, R; Blanco, E; Domínguez, M; Ramírez, M; Beltrán, A M; Alexandrov, D; Tot, J; Dubreuil, R; Videkov, V; Andreev, S; Tzaneva, B; Bartsch, H; Breiling, J; Pezoldt, J; Fischer, M; Müller, J

2018-05-02

This work presents results in the field of advanced substrate solutions in order to achieve high crystalline quality group-III nitrides based heterostructures for high frequency and power devices or for sensor applications. With that objective, Low Temperature Co-fired Ceramics has been used, as a non-crystalline substrate. Structures like these have never been developed before, and for economic reasons will represent a groundbreaking material in these fields of Electronic. In this sense, the report presents the characterization through various techniques of three series of specimens where GaN was deposited on this ceramic composite, using different buffer layers, and a singular metal-organic chemical vapor deposition related technique for low temperature deposition. Other single crystalline ceramic-based templates were also utilized as substrate materials, for comparison purposes.

Simultaneous influence of pectin and xyloglucan on structure and mechanical properties of bacterial cellulose composites.

PubMed

Szymańska-Chargot, Monika; Chylińska, Monika; Cybulska, Justyna; Kozioł, Arkadiusz; Pieczywek, Piotr M; Zdunek, Artur

2017-10-15

The impact of the matrix polysaccharides on the cellulose microfibrils structure as well as on the mechanical properties of cell walls still remains an open question. Therefore, the aim of investigations was to determine the simultaneous influence of (i) different concentrations of pectins with constant concentration of xyloglucan, and (ii) different concentrations of xyloglucan with constant concentration of pectins on cellulose structure. Composites of bacterial cellulose (BC) produced by Komagataeibacter xylinus are considered to mimic natural plant cell walls. This investigation showed that the lower the ratio of xyloglucan to pectin was, the higher Young's modulus of BC composite was and also obtained cellulose microfibrils were thinner. The increasing concentration of xyloglucan to pectin also caused the drop down in microfibrils crystallinity degree with predominant structure of cellulose I β . In that case, also the length of cellulose chains was growing and reaching the highest value among all BC composites. Copyright © 2017 Elsevier Ltd. All rights reserved.

Voltage-induced switching dynamics based on an AZO/VO2/AZO sandwiched structure

NASA Astrophysics Data System (ADS)

Xiao, Han; Li, Yi; Fang, Baoying; Wang, Xiaohua; Liu, Zhimin; Zhang, Jiao; Li, Zhengpeng; Huang, Yaqin; Pei, Jiangheng

2017-11-01

A vanadium dioxide (VO2) thin film was prepared on an Al-doped ZnO (AZO) conductive glass substrate by DC magnetron sputtering and a post-annealing process. The AZO/VO2/AZO sandwiched structure was fabricated on the VO2/AZO composite film using photolithography and a chemical etching process. The composition, microstructure and optical properties of the VO2/AZO composite film were tested. The results showed that the VO2/AZO composite film was poly-crystalline and the AZO layer did not change the preferred growth orientation of VO2. When the voltage was applied on both of the transparent conductive layers of the AZO/VO2/AZO sandwiched structure, an abrupt change in the current was observed at different temperatures. The temperature dependence of I-V characteristic curves for the AZO/VO2/AZO sandwiched structure was analyzed. The phase transition voltage value is 7.5 V at 20 °C and decreases with increasing temperature.

Preparation and study on the structure of keratin/PVA membrane containing wool fibers

NASA Astrophysics Data System (ADS)

Wu, Min; Shen, Shuming; Yang, Xuhong; Tang, Rencheng

2017-10-01

The urea / sodium sulfide / sodium dodecyl sulfate (SDS) method was used to dissolve the wool in this study. Then the Wool fiber/keratin/PVA composites with different proportions were prepared, and the surface morphology, molecular structure, mechanical property of the composite films and the influence of the proportions on their structure and properties were studied. The results showed that, there are α-helix structure, β-sheet and random coil conformations in the pure keratin film, as well as in the wool fiber. Compared with wool fiber, the crystallinity of keratin decreased. PVA can obviously improve the mechanical property of the blended film. When the blended ratio of keratin/PVA is 20/80, the mechanical property of the blended film is greatly improved. The composite films with 8%-16% of wool fibers have better flexibility than those without wool fibers.

Multiscale mechanisms of nutritionally induced property variation in spider silks.

PubMed

Blamires, Sean J; Nobbs, Madeleine; Martens, Penny J; Tso, I-Min; Chuang, Wei-Tsung; Chang, Chung-Kai; Sheu, Hwo-Shuenn

2018-01-01

Variability in spider major ampullate (MA) silk properties at different scales has proven difficult to determine and remains an obstacle to the development of synthetic fibers mimicking MA silk performance. A multitude of techniques may be used to measure multiscale aspects of silk properties. Here we fed five species of Araneoid spider solutions that either contained protein or were protein deprived and performed silk tensile tests, small and wide-angle X-ray scattering (SAXS/WAXS), amino acid composition analyses, and silk gene expression analyses, to resolve persistent questions about how nutrient deprivation induces variations in MA silk mechanical properties across scales. Our analyses found that the properties of each spider's silk varied differently in response to variations in their protein intake. We found changes in the crystalline and non-crystalline nanostructures to play specific roles in inducing the property variations we found. Across treatment MaSp expression patterns differed in each of the five species. We found that in most species MaSp expression and amino acid composition variations did not conform with our predictions based on a traditional MaSp expression model. In general, changes to the silk's alanine and proline compositions influenced the alignment of the proteins within the silk's amorphous region, which influenced silk extensibility and toughness. Variations in structural alignment in the crystalline and non-crystalline regions influenced ultimate strength independent of genetic expression. Our study provides the deepest insights thus far into the mechanisms of how MA silk properties vary from gene expression to nanostructure formations to fiber mechanics. Such knowledge is imperative for promoting the production of synthetic silk fibers.

Similar local order in disordered fluorite and aperiodic pyrochlore structures

DOE PAGES

Shamblin, Jacob; Tracy, Cameron; Palomares, Raul; ...

2017-10-01

A major challenge to understanding the response of materials to extreme environments (e.g., nuclear fuels/waste forms and fusion materials) is to unravel the processes by which a material can incorporate atomic-scale disorder, and at the same time, remain crystalline. While it has long been known that all condensed matter, even liquids and glasses, possess short-range order, the relation between fully-ordered, disordered, and aperiodic structures over multiple length scales is not well understood. For example, when defects are introduced (via pressure or irradiation) into materials adopting the pyrochlore structure, these complex oxides either disorder over specific crystallographic sites, remaining crystalline, ormore » become aperiodic. Here we present neutron total scattering results characterizing the irradiation response of two pyrochlores, one that is known to disorder (Er2Sn2O7) and the other to amorphize (Dy2Sn2O7) under ion irradiation. The results demonstrate that in both cases, the local pyrochlore structure is transformed into similar short range configurations that are best fit by the orthorhombic weberite structure, even though the two compositions have distinctly different structures, aperiodic vs. disordered-crystalline, at longer length scales. Thus, a material's resistance to amorphization may not depend primarily on local defect formation energies, but rather on the structure's compatibility with meso-scale modulations of the local order in a way that maintains long-range periodicity.« less

Magnetic properties of CoNiFe alloys electrodeposited under potential and current control conditions

NASA Astrophysics Data System (ADS)

Perez, L.; Attenborough, K.; De Boeck, J.; Celis, J. P.; Aroca, C.; Sánchez, P.; López, E.; Sánchez, M. C.

2002-04-01

Electrodeposited CoNiFe alloys have been produced under potential and current control conditions. It was found that composition, crystalline structure and magnetic properties are the same irrespective of which plating control is used. Magnetic anisotropy is present in the softest samples. A study of the dependence of magnetic properties and domain structure on the thickness of the films is also reported.

Effect of laser irradiation on crystalline structure of enamel surface during whitening treatment with hydrogen peroxide.

PubMed

Son, Jung-Hyun; An, Ji-Hae; Kim, Byung-Kuk; Hwang, In-Nam; Park, Yeong-Joon; Song, Ho-Jun

2012-11-01

This study is to evaluate the effect of laser activation on the whitening and crystalline structure of enamel surface during whitening treatment with hydrogen peroxide. Bovine teeth were treated with whitening gel containing 35% hydrogen peroxide. A whitening gel was applied on the enamel surface for a period of 5 min, and then irradiated using a diode laser (740 nm) during whitening treatment for 0, 30, 60, 120 and 180s for the GL0-W, GL30-W, GL60-W, GL120-W and GL180-W groups, respectively. The total whitening application time was 30 min for all groups. Laser-irradiated enamel groups showed a similar lightness compared to the GL0-W group. The thickness of porous layer observed on the enamel surface of GL0-W group was decreased by increasing the laser irradiation time. While the Ca and P contents of the GL0-W group were lower than those of the non-whitening treated group (GL0-C), the Ca and P contents of the GL180-W group were similar to those of the GL180-C group. The enamel crystallinity was dramatically decreased by whitening treatment without laser irradiation. However, the decrease of crystallinity was protected by laser irradiation during whitening treatment. Raman measurement verified that laser irradiation could prevent the loss of mineral compositions on enamel and maintain its crystalline structure. The professional whitening treatment with hydrogen peroxide and diode laser activation improves not only the whitening effect but also protects the change of enamel structure compared to the treatment with only gel. Copyright © 2012 Elsevier Ltd. All rights reserved.

Oxygen ion-conducting dense ceramic

DOEpatents

Balachandran, Uthamalingam; Kleefisch, Mark S.; Kobylinski, Thaddeus P.; Morissette, Sherry L.; Pei, Shiyou

1996-01-01

Preparation, structure, and properties of mixed metal oxide compositions containing at least strontium, cobalt, iron and oxygen are described. The crystalline mixed metal oxide compositions of this invention have, for example, structure represented by Sr.sub..alpha. (Fe.sub.1-x Co.sub.x).sub..alpha.+.beta. O.sub..delta. where x is a number in a range from 0.01 to about 1, .alpha. is a number in a range from about 1 to about 4, .beta. is a number in a range upward from 0 to about 20, and .delta. is a number which renders the compound charge neutral, and wherein the composition has a non-perovskite structure. Use of the mixed metal oxides in dense ceramic membranes which exhibit oxygen ionic conductivity and selective oxygen separation, are described as well as their use in separation of oxygen from an oxygen-containing gaseous mixture.

Oxygen ion-conducting dense ceramic

DOEpatents

Balachandran, Uthamalingam; Kleefisch, Mark S.; Kobylinski, Thaddeus P.; Morissette, Sherry L.; Pei, Shiyou

1997-01-01

Preparation, structure, and properties of mixed metal oxide compositions containing at least strontium, cobalt, iron and oxygen are described. The crystalline mixed metal oxide compositions of this invention have, for example, structure represented by Sr.sub..alpha. (Fe.sub.1-x Co.sub.x).sub..alpha.+.beta. O.sub..delta. where x is a number in a range from 0.01 to about 1, .alpha. is a number in a range from about 1 to about 4, .beta. is a number in a range upward from 0 to about 20, and .delta. is a number which renders the compound charge neutral, and wherein the composition has a non-perovskite structure. Use of the mixed metal oxides in dense ceramic membranes which exhibit oxygen ionic conductivity and selective oxygen separation, are described as well as their use in separation of oxygen from an oxygen-containing gaseous mixture.

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

Zhang, Fei; Wu, Yuan; Lou, Hongbo

Polymorphism, which describes the occurrence of different lattice structures in a crystalline material, is a critical phenomenon in materials science and condensed matter physics. Recently, configuration disorder was compositionally engineered into single lattices, leading to the discovery of high-entropy alloys and high-entropy oxides. For these novel entropy-stabilized forms of crystalline matter with extremely high structural stability, is polymorphism still possible? Here by employing in situ high-pressure synchrotron radiation X-ray diffraction, we reveal a polymorphic transition from face-centred-cubic (fcc) structure to hexagonal-close-packing (hcp) structure in the prototype CoCrFeMnNi high-entropy alloy. The transition is irreversible, and our in situ high-temperature synchrotron radiationmore » X-ray diffraction experiments at different pressures of the retained hcp high-entropy alloy reveal that the fcc phase is a stable polymorph at high temperatures, while the hcp structure is more thermodynamically favourable at lower temperatures. Lastly, as pressure is increased, the critical temperature for the hcp-to-fcc transformation also rises.« less

Polymorphism in a high-entropy alloy

DOE PAGES

Zhang, Fei; Wu, Yuan; Lou, Hongbo; ...

2017-06-01

Polymorphism, which describes the occurrence of different lattice structures in a crystalline material, is a critical phenomenon in materials science and condensed matter physics. Recently, configuration disorder was compositionally engineered into single lattices, leading to the discovery of high-entropy alloys and high-entropy oxides. For these novel entropy-stabilized forms of crystalline matter with extremely high structural stability, is polymorphism still possible? Here by employing in situ high-pressure synchrotron radiation X-ray diffraction, we reveal a polymorphic transition from face-centred-cubic (fcc) structure to hexagonal-close-packing (hcp) structure in the prototype CoCrFeMnNi high-entropy alloy. The transition is irreversible, and our in situ high-temperature synchrotron radiationmore » X-ray diffraction experiments at different pressures of the retained hcp high-entropy alloy reveal that the fcc phase is a stable polymorph at high temperatures, while the hcp structure is more thermodynamically favourable at lower temperatures. Lastly, as pressure is increased, the critical temperature for the hcp-to-fcc transformation also rises.« less

The effect of radiation on the thermal properties of chitosan/mimosa tenuiflora and chitosan/mimosa tenuiflora/multiwalled carbon nanotubes (MWCNT) composites for bone tissue engineering

NASA Astrophysics Data System (ADS)

Martel-Estrada, S. A.; Santos-Rodríguez, E.; Olivas-Armendáriz, I.; Cruz-Zaragoza, E.; Martínez-Pérez, C. A.

2014-07-01

The purpose of this study is to examine the effect of gamma radiation and UV radiation on the microstructure, chemical structure and thermal stability of Chitosan/Mimosa Tenuiflora and Chitosan/Mimosa Tenuiflora/MWCNT composites scaffolds produced by thermally induced phase separation. The composites were irradiated and observed to undergo radiation-induced degradation through chain scission. Morphology, thermal properties and effects on chemical and semi-crystalline structures were obtained by scanning electronic microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), FT-IR analysis and X-ray Diffraction. A relationship between radiation type and the thermal stability of the composites, were also established. This relationship allows a more accurate and precise control of the life span of Chitosan/Mimosa Tenuiflora and Chitosan/Mimosa Tenuiflora/MWCNT composites through the use of radiation in materials for use in tissue engineering.

Structural and growth aspects of electron beam physical vapor deposited NiO-CeO{sub 2} nanocomposite films

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

Kuanr, Sushil Kumar; K, Suresh Babu, E-mail: sureshbabu.nst@pondiuni.edu.in

2016-03-15

Deposition of composite materials as thin film by electron beam physical vapor deposition technique (EB-PVD) still remains as a challenge. Here, the authors report the deposition of NiO-CeO{sub 2} (30/70 wt. %) composites on quartz substrate by EB-PVD. Two NiO-CeO{sub 2} nanocomposite targets—one as green compact and the other after sintering at 1250 °C—were used for the deposition. Though the targets varied with respect to physical properties such as crystallite size (11–45 nm) and relative density (44% and 96%), the resultant thin films exhibited a mean crystallite size in the range of 20–25 nm underlining the role of physical nature of deposition. In spitemore » of the crystalline nature of the targets and similar elemental concentration, a transformation from amorphous to crystalline structure was observed in thin films on using sintered target. Postannealing of the as deposited film at 800 °C resulted in a polycrystalline structure consisting of CeO{sub 2} and NiO. Deposition using pure CeO{sub 2} or NiO as target resulted in the preferential orientation toward (111) and (200) planes, respectively, showing the influence of adatoms on the evaporation and growth process of NiO-CeO{sub 2} composite. The results demonstrate the influence of electron beam gun power on the adatom energy for the growth process of composite oxide thin films.« less

Evaluation of environmental scanning electron microscopy for analysis of Proteus mirabilis crystalline biofilms in situ on urinary catheters.

PubMed

Holling, Nina; Dedi, Cinzia; Jones, Caroline E; Hawthorne, Joseph A; Hanlon, Geoffrey W; Salvage, Jonathan P; Patel, Bhavik A; Barnes, Lara M; Jones, Brian V

2014-06-01

Proteus mirabilis is a common cause of catheter-associated urinary tract infections and frequently leads to blockage of catheters due to crystalline biofilm formation. Scanning electron microscopy (SEM) has proven to be a valuable tool in the study of these unusual biofilms, but entails laborious sample preparation that can introduce artefacts, undermining the investigation of biofilm development. In contrast, environmental scanning electron microscopy (ESEM) permits imaging of unprocessed, fully hydrated samples, which may provide much insight into the development of P. mirabilis biofilms. Here, we evaluate the utility of ESEM for the study of P. mirabilis crystalline biofilms in situ, on urinary catheters. In doing so, we compare this to commonly used conventional SEM approaches for sample preparation and imaging. Overall, ESEM provided excellent resolution of biofilms formed on urinary catheters and revealed structures not observed in standard SEM imaging or previously described in other studies of these biofilms. In addition, we show that energy-dispersive X-ray spectroscopy (EDS) may be employed in conjunction with ESEM to provide information regarding the elemental composition of crystalline structures and demonstrate the potential for ESEM in combination with EDS to constitute a useful tool in exploring the mechanisms underpinning crystalline biofilm formation. © 2014 The Authors. FEMS Microbiology Letters published by John Wiley & Sons Ltd on behalf of Federation of European Microbiological Societies.

Inflammatory cell response to ultra-thin amorphous and crystalline hydroxyapatite surfaces.

PubMed

Rydén, Louise; Omar, Omar; Johansson, Anna; Jimbo, Ryo; Palmquist, Anders; Thomsen, Peter

2017-01-01

It has been suggested that surface modification with a thin hydroxyapatite (HA) coating enhances the osseointegration of titanium implants. However, there is insufficient information about the biological processes involved in the HA-induced response. This study aimed to investigate the inflammatory cell response to titanium implants with either amorphous or crystalline thin HA. Human mononuclear cells were cultured on titanium discs with a machined surface or with a thin, 0.1 μm, amorphous or crystalline HA coating. Cells were cultured for 24 and 96 h, with and without lipopolysaccharide (LPS) stimulation. The surfaces were characterized with respect to chemistry, phase composition, wettability and topography. Biological analyses included the percentage of implant-adherent cells and the secretion of pro-inflammatory cytokine (TNF-α) and growth factors (BMP-2 and TGF-β1). Crystalline HA revealed a smooth surface, whereas the amorphous HA displayed a porous structure, at nano-scale, and a hydrophobic surface. Higher TNF-α secretion and a higher ratio of adherent cells were demonstrated for the amorphous HA compared with the crystalline HA. TGF-β1 secretion was detected in all groups, but without any difference. No BMP-2 secretion was detected in any of the groups. The addition of LPS resulted in a significant increase in TNF-α in all groups, whereas TGF-β1 was not affected. Taken together, the results show that thin HA coatings with similar micro-roughness but a different phase composition, nano-scale roughness and wettability are associated with different monocyte responses. In the absence of strong inflammatory stimuli, crystalline hydroxyapatite elicits a lower inflammatory response compared with amorphous hydroxyapatite.

Cellulose Nanocrystals vs. Cellulose Nanofibrils: A Comparative study on Their Microstructures and Effects as Polymer Reinforcing Agents

Treesearch

Xuezhu Xu; Fei Liu; Long Jiang; J.Y. Zhu; Darrin Haagenson; Dennis P. Wiesenborn

2013-01-01

Both cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) are nanoscale cellulose fibers that have shown reinforcing effects in polymer nanocomposites. CNCs and CNFs are different in shape, size and composition. This study systematically compared their morphologies, crystalline structure, dispersion properties in polyethylene oxide (PEO) matrix, interactions...

SAPO-34/AlMCM-41, as a novel hierarchical nanocomposite: preparation, characterization and investigation of synthesis factors using response surface methodology

NASA Astrophysics Data System (ADS)

Roohollahi, Hossein; Halladj, Rouein; Askari, Sima; Yaripour, Fereydoon

2018-06-01

SAPO-34/AlMCM-41, as a new hierarchical nanocomposite was successfully synthesized via hydrothermal and dry-gel conversion. In an experimental and statistical study, effect of five input parameters including synthesis period, drying temperature, NaOH/Si, water/dried-gel and SAPO% were investigated on range-order degree of mesochannels and the relative crystallinity. X-ray diffraction (XRD) patterns were recorded to characterize the ordered AlMCM-41 and crystalline SAPO-34 structures. Nitrogen adsorption-desorption technique, scanning electron microscopy (SEM), field-emission SEM (FESEM) equipped with an energy-dispersive X-ray spectroscopy (EDS-Map) and transmission electron microscopy (TEM) were used to study the textural properties, morphology and surface elemental composition. Two reduced polynomials were fitted to the responses with good precision. Further, based on analysis of variances, SAPO% and time duration of dry-gel conversion were observed as the most effective parameters on the composite structure. The hierarchical porosity, narrow pore size distribution, high external surface area and large specific pore volume were of interesting characteristics for this novel nanocomposite.

Laser ablation and deposition of wide bandgap semiconductors: plasma and nanostructure of deposits diagnosis

NASA Astrophysics Data System (ADS)

Sanz, M.; López-Arias, M.; Rebollar, E.; de Nalda, R.; Castillejo, M.

2011-12-01

Nanostructured CdS and ZnS films on Si (100) substrates were obtained by nanosecond pulsed laser deposition at the wavelengths of 266 and 532 nm. The effect of laser irradiation wavelength on the surface structure and crystallinity of deposits was characterized, together with the composition, expansion dynamics and thermodynamic parameters of the ablation plume. Deposits were analyzed by environmental scanning electron microscopy, atomic force microscopy and X-ray diffraction, while in situ monitoring of the plume was carried out with spectral, temporal and spatial resolution by optical emission spectroscopy. The deposits consist of 25-50 nm nanoparticle assembled films but ablation in the visible results in larger aggregates (150 nm) over imposed on the film surface. The aggregate free films grown at 266 nm on heated substrates are thicker than those grown at room temperature and in the former case they reveal a crystalline structure congruent with that of the initial target material. The observed trends are discussed in reference to the light absorption step, the plasma composition and the nucleation processes occurring on the substrate.

Sustainable thermoelectric materials fabricated by using Cu2Sn1-xZnxS3 nanoparticles as building blocks

NASA Astrophysics Data System (ADS)

Zhou, Wei; Shijimaya, Chiko; Takahashi, Mari; Miyata, Masanobu; Mott, Derrick; Koyano, Mikio; Ohta, Michihiro; Akatsuka, Takeo; Ono, Hironobu; Maenosono, Shinya

2017-12-01

Uniform Cu2Sn1-xZnxS3 (x = 0-0.2) nanoparticles (NPs) with a characteristic size of about 40 nm were chemically synthesized. The primary crystal phase of the NPs was wurtzite (WZ) with a mean crystalline size of about 20 nm. The NPs were sintered to form nanostructured pellets with different compositions preserving the composition and grain size of the original NPs by the pulse electric current sintering technique. The pellets had a zinc blende (ZB) structure with a residual WZ phase, and the mean crystalline size was found to remain virtually unchanged for all pellets. Among all samples, the pellets of Cu2Sn0.95Zn0.05S3 and Cu2Sn0.85Zn0.15S3 exhibited the highest ZT value (0.37 at 670 K) which is 10 times higher than that of a non-nanostructured Cu2SnS3 bulk crystal thanks to effective phonon scattering by nanograins, the phase-pure ZB crystal structure, and the increase in hole carrier density by Zn doping.

Titania bound sodium titanate ion exchanger

DOEpatents

DeFilippi, Irene C. G.; Yates, Stephen Frederic; Shen, Jian-Kun; Gaita, Romulus; Sedath, Robert Henry; Seminara, Gary Joseph; Straszewski, Michael Peter; Anderson, David Joseph

1999-03-23

This invention is method for preparing a titania bound ion exchange composition comprising admixing crystalline sodium titanate and a hydrolyzable titanium compound and, thereafter drying the titania bound crystalline sodium titanate and subjecting the dried titania bound ion exchange composition to optional compaction and calcination steps to improve the physical strength of the titania bound composition.

A method for distinguishing between propagons, diffusions, and locons

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

Seyf, Hamid Reza; Henry, Asegun; School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332

2016-07-14

The majority of intuition on phonon transport has been derived from studies of homogenous crystalline solids, where the atomic composition and structure are periodic. For this specific class of materials, the solutions to the equations of motions for the atoms (in the harmonic limit) result in plane wave modulated velocity fields for the normal modes of vibration. However, it has been known for several decades that whenever a system lacks periodicity, either compositional or structural, the normal modes of vibration can still be determined (in the harmonic limit), but the solutions take on different characteristics and many modes may notmore » be plane wave modulated. Previous work has classified the types of vibrations into three primary categories, namely, propagons, diffusions, and locons. One can use the participation ratio to distinguish locons, from propagons and diffusons, which measures the extent to which a mode is localized. However, distinguishing between propagons and diffusons has remained a challenge, since both are spatially delocalized. Here, we present a new method that quantifies the extent to which a mode's character corresponds to a propagating mode, e.g., exhibits plane wave modulation. This then allows for clear and quantitative distinctions between propagons and diffusons. By resolving this issue quantitatively, one can now automate the classification of modes for any arbitrary material or structure, subject to a single constraint that the atoms must vibrate stably around their respective equilibrium sites. Several example test cases are studied including crystalline silicon and germanium, crystalline silicon with different defect concentrations, as well as amorphous silicon, germanium, and silica.« less

Crustal Structure of the Andean Foreland in Northern Argentina: Results From Data-Integrative Three-Dimensional Density Modeling

NASA Astrophysics Data System (ADS)

Meeßen, C.; Sippel, J.; Scheck-Wenderoth, M.; Heine, C.; Strecker, M. R.

2018-02-01

Previous thermomechanical modeling studies indicated that variations in the temperature and strength of the crystalline crust might be responsible for the juxtaposition of domains with thin-skinned and thick-skinned crustal deformation along strike the foreland of the central Andes. However, there is no evidence supporting this hypothesis from data-integrative models. We aim to derive the density structure of the lithosphere by means of integrated 3-D density modeling, in order to provide a new basis for discussions of compositional variations within the crust and for future thermal and rheological modeling studies. Therefore, we utilize available geological and geophysical data to obtain a structural and density model of the uppermost 200 km of the Earth. The derived model is consistent with the observed Bouguer gravity field. Our results indicate that the crystalline crust in northern Argentina can be represented by a lighter upper crust (2,800 kg/m3) and a denser lower crust (3,100 kg/m3). We find new evidence for high bulk crustal densities >3,000 kg/m3 in the northern Pampia terrane. These could originate from subducted Puncoviscana wackes or pelites that ponded to the base of the crystalline crust in the late Proterozoic or indicate increasing bulk content of mafic material. The precise composition of the northern foreland crust, whether mafic or felsic, has significant implications for further thermomechanical models and the rheological behavior of the lithosphere. A detailed sensitivity analysis of the input parameters indicates that the model results are robust with respect to the given uncertainties of the input data.

The growing outer epidermal wall: design and physiological role of a composite structure.

PubMed

Kutschera, U

2008-04-01

The cells of growing plant organs secrete an extracellular fibrous composite (the primary wall) that allows the turgid protoplasts to expand irreversibly via wall-yielding events, which are regulated by processes within the cytoplasm. The role of the epidermis in the control of stem elongation is described with special reference to the outer epidermal wall (OEW), which forms a 'tensile skin'. The OEW is much thicker and less extensible than the walls of the inner tissues. Moreover, in the OEW the amount of cellulose per unit wall mass is considerably greater than in the inner tissues. Ultrastructural studies have shown that the expanding OEW is composed of a highly ordered internal and a diffuse outer half, with helicoidally organized cellulose microfibrils in the inner (load-bearing) region of this tension-stressed organ wall. The structural and mechanical backbone of the wall consists of helicoids, i.e. layers of parallel, inextensible cellulose microfibrils. These 'plywood laminates' contain crystalline 'cables' orientated in all directions with respect to the axis of elongation (isotropic material). Cessation of cell elongation is accompanied by a loss of order, i.e. the OEW is a dynamic structure. Helicoidally arranged extracellular polymers have also been found in certain bacteria, algae, fungi and animals. In the insect cuticle crystalline cutin nanofibrils form characteristic 'OEW-like' herringbone patterns. Theoretical considerations, in vitro studies and computer simulations suggest that extracellular biological helicoids form by directed self-assembly of the crystalline biopolymers. This spontaneous generation of complex design 'without an intelligent designer' evolved independently in the protective 'skin' of plants, animals and many other organisms.

Effect of Fe(II)/Ce(III) dosage ratio on the structure and anion adsorptive removal of hydrothermally precipitated composites: Insights from EXAFS/XANES, XRD and FTIR.

PubMed

Chubar, Natalia; Gerda, Vasyl; Banerjee, Dipanjan; Yablokova, Ganna

2017-02-01

In this work, we present material chemistry in the hydrothermal synthesis of new complex structure materials based on various dosage ratios of Fe and Ce (1:0, 2:1, 1:1, 1:2, 0:1), characterize them by the relevant methods that allow characterization of both crystalline and amorphous phases and correlate their structure/surface properties with the adsorptive performance of the five toxic anions. The applied synthesis conditions resulted in the formation of different compounds of Fe and Ce components. The Fe-component was dominated by various phases of Fe hydrous oxides, whereas the Ce-component was composed of various phases of Ce carbonates. The presence of two metal salts in raw materials resulted in the formation of a mesoporous structure and averaged the surface area compared to one metal-based material. The surface of all Fe-Ce composites was abundant in Fe component phases. Two-metal systems showed stronger anion removal performance than one-metal materials. The best adsorption was demonstrated by Fe-Ce based materials that had low crystallinity, that were rich in phases and that exhibited surfaces were abundant in greater number of surface functional groups. Notably, Fe extended fine structures simulated by EXAFS in these better adsorbents were rich from oscillations from both heavy and light atoms. This work provides new insights on the structure of composite inorganic materials useful to develop their applications in adsorption and catalysis. It also presents new inorganic anion exchangers with very high removal potential to fluoride and arsenate. Copyright © 2016 Elsevier Inc. All rights reserved.

Raman structural study of melt-mixed blends of isotactic polypropylene with polyethylene of various densities

NASA Astrophysics Data System (ADS)

Prokhorov, K. A.; Nikolaeva, G. Yu; Sagitova, E. A.; Pashinin, P. P.; Guseva, M. A.; Shklyaruk, B. F.; Gerasin, V. A.

2018-04-01

We report a Raman structural study of melt-mixed blends of isotactic polypropylene with two grades of polyethylene: linear high-density and branched low-density polyethylenes. Raman methods, which had been suggested for the analysis of neat polyethylene and isotactic polypropylene, were modified in this study for quantitative analysis of polyethylene/polypropylene blends. We revealed the dependence of the degree of crystallinity and conformational composition of macromolecules in the blends on relative content of the blend components and preparation conditions (quenching or annealing). We suggested a simple Raman method for evaluation of the relative content of the components in polyethylene/polypropylene blends. The degree of crystallinity of our samples, evaluated by Raman spectroscopy, is in good agreement with the results of analysis by differential scanning calorimetry.

Crystalline Structure, Defect Chemistry and Room Temperature Colossal Permittivity of Nd-doped Barium Titanate

NASA Astrophysics Data System (ADS)

Sun, Qiaomei; Gu, Qilin; Zhu, Kongjun; Jin, Rongying; Liu, Jinsong; Wang, Jing; Qiu, Jinhao

2017-02-01

Dielectric materials with high permittivity are strongly demanded for various technological applications. While polarization inherently exists in ferroelectric barium titanate (BaTiO3), its high permittivity can only be achieved by chemical and/or structural modification. Here, we report the room-temperature colossal permittivity (~760,000) obtained in xNd: BaTiO3 (x = 0.5 mol%) ceramics derived from the counterpart nanoparticles followed by conventional pressureless sintering process. Through the systematic analysis of chemical composition, crystalline structure and defect chemistry, the substitution mechanism involving the occupation of Nd3+ in Ba2+ -site associated with the generation of Ba vacancies and oxygen vacancies for charge compensation has been firstly demonstrated. The present study serves as a precedent and fundamental step toward further improvement of the permittivity of BaTiO3-based ceramics.

Crystalline Structure, Defect Chemistry and Room Temperature Colossal Permittivity of Nd-doped Barium Titanate.

PubMed

Sun, Qiaomei; Gu, Qilin; Zhu, Kongjun; Jin, Rongying; Liu, Jinsong; Wang, Jing; Qiu, Jinhao

2017-02-13

Dielectric materials with high permittivity are strongly demanded for various technological applications. While polarization inherently exists in ferroelectric barium titanate (BaTiO 3 ), its high permittivity can only be achieved by chemical and/or structural modification. Here, we report the room-temperature colossal permittivity (~760,000) obtained in xNd: BaTiO 3 (x = 0.5 mol%) ceramics derived from the counterpart nanoparticles followed by conventional pressureless sintering process. Through the systematic analysis of chemical composition, crystalline structure and defect chemistry, the substitution mechanism involving the occupation of Nd 3+ in Ba 2+ -site associated with the generation of Ba vacancies and oxygen vacancies for charge compensation has been firstly demonstrated. The present study serves as a precedent and fundamental step toward further improvement of the permittivity of BaTiO 3 -based ceramics.

Crystalline Structure, Defect Chemistry and Room Temperature Colossal Permittivity of Nd-doped Barium Titanate

PubMed Central

Sun, Qiaomei; Gu, Qilin; Zhu, Kongjun; Jin, Rongying; Liu, Jinsong; Wang, Jing; Qiu, Jinhao

2017-01-01

Dielectric materials with high permittivity are strongly demanded for various technological applications. While polarization inherently exists in ferroelectric barium titanate (BaTiO3), its high permittivity can only be achieved by chemical and/or structural modification. Here, we report the room-temperature colossal permittivity (~760,000) obtained in xNd: BaTiO3 (x = 0.5 mol%) ceramics derived from the counterpart nanoparticles followed by conventional pressureless sintering process. Through the systematic analysis of chemical composition, crystalline structure and defect chemistry, the substitution mechanism involving the occupation of Nd3+ in Ba2+ -site associated with the generation of Ba vacancies and oxygen vacancies for charge compensation has been firstly demonstrated. The present study serves as a precedent and fundamental step toward further improvement of the permittivity of BaTiO3-based ceramics. PMID:28205559

Breaking the icosahedra in boron carbide

PubMed Central

Xie, Kelvin Y.; An, Qi; Sato, Takanori; Breen, Andrew J.; Ringer, Simon P.; Goddard, William A.; Cairney, Julie M.; Hemker, Kevin J.

2016-01-01

Findings of laser-assisted atom probe tomography experiments on boron carbide elucidate an approach for characterizing the atomic structure and interatomic bonding of molecules associated with extraordinary structural stability. The discovery of crystallographic planes in these boron carbide datasets substantiates that crystallinity is maintained to the point of field evaporation, and characterization of individual ionization events gives unexpected evidence of the destruction of individual icosahedra. Statistical analyses of the ions created during the field evaporation process have been used to deduce relative atomic bond strengths and show that the icosahedra in boron carbide are not as stable as anticipated. Combined with quantum mechanics simulations, this result provides insight into the structural instability and amorphization of boron carbide. The temporal, spatial, and compositional information provided by atom probe tomography makes it a unique platform for elucidating the relative stability and interactions of primary building blocks in hierarchically crystalline materials. PMID:27790982

Experimental input for the design of metallic glass/crystalline composites

NASA Astrophysics Data System (ADS)

Hutchinson, Nicholas Willis

Bulk metallic glasses often exhibit exceptional strength and large elastic strains, but the structural applications of bulk metallic glasses are limited by their extremely low tensile ductility. Below the glass transition temperature of the alloy, plastic deformation occurs primarily in narrow shear bands, which propagate unimpeded through the monolithic glass structure, resulting in catastrophic failure under tensile loading. A number of studies have added crystalline reinforcements to the glassy matrix in an effort to block shear band propagation and increase ductility. The reinforcements in these bulk metallic glass matrix composites (BMGMC's) can be added as ex situ particles or fibers infiltrated by the glass-forming liquid [1], or can be formed in situ, either via devitrification of the glass during post-processing [2] or as a second phase that precipitates from the melt during solidification [3]. The size, distribution, and mechanical properties of the reinforcement phase have significant impact on the ductility of the composite. However, surprisingly little quantitative microstructural information is available for BMGMC's, particularly those formed by precipitation from the melt. In this work, we examine two in situ BMGMC's in which a ductile crystalline phase precipitates during solidification of the melt, resulting in a complex dendritic structure embedded in a continuous glass matrix. A 3D serial sectioning process was used to image the microstructure at regular intervals by removing slices of material using a dual beam focused ion-scanning electron microscope (FIB). Due to the complex nature of the microstructure, measurements of key features were conducted using a 3D measurement method that was developed for this purpose. Experiments were also conducted to provide experimental input for the development and tuning of finite element models. Changes in the elastic modulus of the composite were evaluated over a range of stresses that encompassed the yield point of the composite. An interesting increase in the modulus was observed prior to yielding. The work is concluded with a study of the accumulation of strain within the composite microstructure during tensile loading. The strain was determined and evaluated by a digital image correlation method. [1] R. B. Dandliker, R. D. Conner, and W. L. Johnson, "Melt infiltration casting of bulk metallic-glass matrix composites," J. Mater. Res., vol. 13, no. 10, pp. 2896--2901, 1998. [2] J. Eckert, J. Das, S. Pauly, and C. Duhamel, "Mechanical Properties of Bulk Metallic Glasses and Composites," J. Mater. Res., vol. 22, no. 2, pp. 285--301, 2007. [3] D. C. Hofmann, J.-Y. Suh, A. Wiest, G. Duan, M.-L. Lind, M. D. Demetriou, and W. L. Johnson, "Designing metallic glass matrix composites with high toughness and tensile ductility.," Nature, vol. 451, no. 7182, pp. 1085--9, Feb. 2008.

Polyaniline/Carbon nanotube Electrochromic Films: Electrochemical Polymerization and characterization

NASA Astrophysics Data System (ADS)

Li, Xiao-Xia; Zhao, Liang; Ma, De-Yue; Zeng, Yu-Run

2018-02-01

Polyaniline/Carbon nanotube (PANI/CNT) composite films doped with dodecyl-benzene sulfonic acid were synthesized by cyclic voltammetry on an ITO-coated glass substrate. FTIR, XRD and electrochemical analyzer were used to characterize the micro-morphology, chemical structure, crystallinity and electrochromic behavior of the films, respectively. The effect of CNT content on the properties of the films was investigated. Results show that the introducing CNTs make aniline polymerize easier than before. Within a range, the conductivity and crystallinity of PANI/CNT composites improves with CNT content increasing. The electrochromic device made from the PAN/CNT film with a CNT content of 2.5wt% presents a reflectance contrast of 38.8%, a mean response time of 2.3s and a coloration efficiency of 386.4cm2/C at 540nm. The PAN/CNT film shows better electrochromic behaviors due to some interaction between CNTs and the PANI backbones than PANI film.

The structural and electronic properties of amorphous HgCdTe from first-principles calculations

NASA Astrophysics Data System (ADS)

Zhao, Huxian; Chen, Xiaoshuang; Lu, Jianping; Shu, Haibo; Lu, Wei

2014-01-01

Amorphous mercury cadmium telluride (a-MCT) model structures, with x being 0.125 and 0.25, are obtained from first-principles calculations. We generate initial structures by computation alchemy method. It is found that most atoms in the network of amorphous structures tend to be fourfold and form tetrahedral structures, implying that the chemical ordered continuous random network with some coordination defects is the ideal structure for a-MCT. The electronic structure is also concerned. The gap is found to be 0.30 and 0.26 eV for a-Hg0.875Cd0.125Te and a-Hg0.75Cd0.25Te model structures, independent of the composition. By comparing with the properties of crystalline MCT with the same composition, we observe a blue-shift of energy band gap. The localization of tail states and its atomic origin are also discussed.

Electrical switching in Sb doped Al23Te77 glasses

NASA Astrophysics Data System (ADS)

Pumlianmunga; Ramesh, K.

2017-08-01

Bulk glasses (Al23Te77)Sbx (0≤ x≤10) prepared by melt quenching method show a change in switching type from threshold to memory for x≥5. An increase in threshold current (Ith) and a concomitant decrease in threshold voltage (Vth) and resisitivity(ρ) have been observed with the increase of Sb content. Raman spectra of the switched region in memory switching compositions show a red shift with respect to the as prepared glasses whereas in threshold switching compositions no such shift is observed. The magic angle spinning nuclear magnetic resonance (MAS NMR) of 27Al atom shows three different environments for Al ([4]Al, [5]Al and [6]Al). The samples annealed at their respective crystallization temperatures show rapid increase in [4]Al sites by annihilating [5]Al sites. The melts of threshold switching glasses (x≤2.5) quenched in water at room temperature (27 °C) show amorphous structure whereas, the melt of memory switching glasses (x>2.5) solidify into crystalline structure. The higher coordination of Al increases the cross-linking and rigidity. The addition of Sb increases the glass transition(Tg) and decreases the crystallization temperature(Tc). The decrease in the interval between the Tg and Tc eases the transition between the amorphous and crystalline states and improves the memory properties. The temperature rise at the time of switching can be as high as its melting temperature and the material in between the electrodes may melt to form a filament. The filament may consists of temporary (high resistive amorphous) and permanent (high conducting crystalline) units. The ratio between the temporary and the permanent units may decide the switching type. The filament is dominated by the permanent units in memory switching compositions and by the temporary units in threshold switching compositions. The present study suggests that both the threshold and memory switching can be understood by the thermal model and filament formation.

Structural responses of metallic glasses under neutron irradiation.

PubMed

Yang, L; Li, H Y; Wang, P W; Wu, S Y; Guo, G Q; Liao, B; Guo, Q L; Fan, X Q; Huang, P; Lou, H B; Guo, F M; Zeng, Q S; Sun, T; Ren, Y; Chen, L Y

2017-12-01

Seeking nuclear materials that possess a high resistance to particle irradiation damage is a long-standing issue. Permanent defects, induced by irradiation, are primary structural changes, the accumulation of which will lead to structural damage and performance degradation in crystalline materials served in nuclear plants. In this work, structural responses of neutron irradiation in metallic glasses (MGs) have been investigated by making a series of experimental measurements, coupled with simulations in ZrCu amorphous alloys. It is found that, compared with crystalline alloys, MGs have some specific structural responses to neutron irradiation. Although neutron irradiation can induce transient vacancy-like defects in MGs, they are fully annihilated after structural relaxation by rearrangement of free volumes. In addition, the rearrangement of free volumes depends strongly on constituent elements. In particular, the change in free volumes occurs around the Zr atoms, rather than the Cu centers. This implies that there is a feasible strategy for identifying glassy materials with high structural stability against neutron irradiation by tailoring the microstructures, the systems, or the compositions in alloys. This work will shed light on the development of materials with high irradiation resistance.

Ultra-Small-Angle X-ray Scattering – X-ray Photon Correlation Spectroscopy Studies of Incipient Structural Changes in Amorphous Calcium Phosphate Based Dental Composites

PubMed Central

Zhang, F.; Allen, A.J.; Levine, L.E.; Espinal, L.; Antonucci, J.M.; Skrtic, D.; O’Donnell, J.N.R.; Ilavsky, J.

2012-01-01

The local structural changes in amorphous calcium phosphate (ACP) based dental composites were studied under isothermal conditions using both static, bulk measurement techniques and a recently developed methodology based on combined ultra-small angle X-ray scattering – X-ray photon correlation spectroscopy (USAXS-XPCS), which permits a dynamic approach. While results from conventional bulk measurements do not show clear signs of structural change, USAXS-XPCS results reveal unambiguous evidence for local structural variations on a similar time scale to that of water loss in the ACP fillers. A thermal-expansion based simulation indicates that thermal behavior alone does not account for the observed dynamics. Together, these results suggest that changes in the water content of ACP affect the composite morphology due to changes in ACP structure that occur without an amorphous-to-crystalline conversion. It is also noted that biomedical materials research could benefit greatly from USAXS-XPCS, a dynamic approach. PMID:22374649

Silicon Whisker and Carbon Nanofiber Composite Anode

NASA Technical Reports Server (NTRS)

Ma, Junqing (Inventor); Newman, Aron (Inventor); Lennhoff, John (Inventor)

2015-01-01

A carbon nanofiber can have a surface and include at least one crystalline whisker extending from the surface of the carbon nanofiber. A battery anode composition can be formed from a plurality of carbon nanofibers each including a plurality of crystalline whiskers.

Quercetagetin-Loaded Zein-Propylene Glycol Alginate Ternary Composite Particles Induced by Calcium Ions: Structure Characterization and Formation Mechanism.

PubMed

Sun, Cuixia; Wei, Yang; Li, Ruirui; Dai, Lei; Gao, Yanxiang

2017-05-17

The complexation of zein and propylene glycol alginate (PGA) was confirmed to improve the entrapment efficiency and loading capacity of quercetagetin (Q) in our previous study. The present work focused on the influence and induction mechanism of calcium ions on structures of Q-loaded zein-PGA ternary composite particles. The incorporation of Ca 2+ resulted in the formation of aggregates with a large dimension between zein particles, led to obvious conformational, secondary, and tertiary structural changes of zein, and caused the disappearance of crystalline structure of zein. PGA exhibited a fine filamentous network structure and became much thicker and stronger in the presence of Ca 2+ . The presence of Q promoted the affinity and binding capacity of Ca 2+ to zein and PGA. An interwoven network structure with enhanced firmness and density was observed in Q-loaded zein-PGA composite particles, leading to improved thermal stability. Three potential mechanisms were proposed to explain the structural characteristics induced by Ca 2+ , including particle-particle collision for zein particles, chain-chain association for PGA molecules, and simultaneous cross-linking coupled with aggregating for Q-loaded zein-PGA composite particles.

Molecular tandem repeat strategy for elucidating mechanical properties of high-strength proteins

PubMed Central

Jung, Huihun; Pena-Francesch, Abdon; Saadat, Alham; Sebastian, Aswathy; Kim, Dong Hwan; Hamilton, Reginald F.; Albert, Istvan; Allen, Benjamin D.; Demirel, Melik C.

2016-01-01

Many globular and structural proteins have repetitions in their sequences or structures. However, a clear relationship between these repeats and their contribution to the mechanical properties remains elusive. We propose a new approach for the design and production of synthetic polypeptides that comprise one or more tandem copies of a single unit with distinct amorphous and ordered regions. Our designed sequences are based on a structural protein produced in squid suction cups that has a segmented copolymer structure with amorphous and crystalline domains. We produced segmented polypeptides with varying repeat number, while keeping the lengths and compositions of the amorphous and crystalline regions fixed. We showed that mechanical properties of these synthetic proteins could be tuned by modulating their molecular weights. Specifically, the toughness and extensibility of synthetic polypeptides increase as a function of the number of tandem repeats. This result suggests that the repetitions in native squid proteins could have a genetic advantage for increased toughness and flexibility. PMID:27222581

Influence of the Size and Structural Factors on the Magnetism of Multilayer Films Based on 3 d and 4 f Metals

NASA Astrophysics Data System (ADS)

Svalov, A. V.; Vas'kovskiy, V. O.; Kurlyandskaya, G. V.

2017-12-01

This work has presented some data on the layer structuring of films of 3 d and 4 f metals and their alloys, which have potential for practical use in magnetic sensors. The decrease in the thickness of magnetic layers with this structuring entails natural worsening of the crystallinity and leads to a degradation of magnetic ordering. However, the manifestation of these tendencies depends to a great extent on the conditions of preparation, the composition, and the sequence of the deposition of the contacting layers in the multilayer structures. The combination of these factors makes it possible to realize an optimum composition and optimum structural states of the films, which in a number of cases lead to the appearance of new combinations of functional properties.

Estimation of crystallinity in a model thermoplastic composite

NASA Technical Reports Server (NTRS)

Wakelyn, N. T.

1986-01-01

Crystallinities as low as 16 percent have been estimated by determination of the interplanar spacing on PET/carbonaceous filament composites with resin content of aobut 25 percent w/w using wide-angle X-ray scattering (WAXS) in the angular range 2 theta = 16-18 deg. The diffraction pattern of the carbonaceous reinforcements masks the major reflections of the resin, and the resin content and the crystallinity are kept low to make the simulation reasonable.

USSR Report, Chemistry

DTIC Science & Technology

1987-03-17

conductivity with respect to silver, copper, fluorine and hydrogen ions, selection of the chemical composition and type of crystalline structure...distillates. It was found that residual petroleum asphalt, NKG demulsifier and "neftegaz-4" varnish oil improved the rheological properties and decreased...mass loss, and accumulation of macromolecular fragments bearing substituted phenols, in order to determine criteria on which shelflife of varnish

Electronically conductive ceramics for high temperature oxidizing environments

DOEpatents

Kucera, Gene H.; Smith, James L.; Sim, James W.

1986-01-01

A high temperature, ceramic composition having electronic conductivity as measured by resistivity below about 500 ohm-cm, chemical stability particularly with respect to cathode conditions in a molten carbonate fuel cell, and composed of an alkali metal, transition metal oxide containing a dopant metal in the crystalline structure to replace a portion of the alkali metal or transition metal.

Tribological Performance of Green Lubricant Enhanced by Sulfidation IF-MoS2

PubMed Central

Shi, Shih-Chen

2016-01-01

Biopolymers reinforced with nanoparticle (NP) additives are widely used in tribological applications. In this study, the effect of NP additives on the tribological properties of a green lubricant hydroxypropyl methylcellulose (HPMC) composite was investigated. The IF-MoS2 NPs were prepared using the newly developed gas phase sulfidation method to form a multilayered, polyhedral structure. The number of layers and crystallinity of IF-MoS2 increased with sulfidation time and temperature. The dispersity of NPs in the HPMC was investigated using Raman and EDS mapping and showed great uniformity. The use of NPs with HPMC enhanced the tribological performance of the composites as expected. The analysis of the worn surface shows that the friction behavior of the HPMC composite with added NPs is very sensitive to the NP structure. The wear mechanisms vary with NP structure and depend on their lubricating behaviors. PMID:28773976

Multiscale mechanisms of nutritionally induced property variation in spider silks

PubMed Central

Nobbs, Madeleine; Martens, Penny J.; Tso, I-Min; Chuang, Wei-Tsung; Chang, Chung-Kai; Sheu, Hwo-Shuenn

2018-01-01

Variability in spider major ampullate (MA) silk properties at different scales has proven difficult to determine and remains an obstacle to the development of synthetic fibers mimicking MA silk performance. A multitude of techniques may be used to measure multiscale aspects of silk properties. Here we fed five species of Araneoid spider solutions that either contained protein or were protein deprived and performed silk tensile tests, small and wide-angle X-ray scattering (SAXS/WAXS), amino acid composition analyses, and silk gene expression analyses, to resolve persistent questions about how nutrient deprivation induces variations in MA silk mechanical properties across scales. Our analyses found that the properties of each spider’s silk varied differently in response to variations in their protein intake. We found changes in the crystalline and non-crystalline nanostructures to play specific roles in inducing the property variations we found. Across treatment MaSp expression patterns differed in each of the five species. We found that in most species MaSp expression and amino acid composition variations did not conform with our predictions based on a traditional MaSp expression model. In general, changes to the silk’s alanine and proline compositions influenced the alignment of the proteins within the silk’s amorphous region, which influenced silk extensibility and toughness. Variations in structural alignment in the crystalline and non-crystalline regions influenced ultimate strength independent of genetic expression. Our study provides the deepest insights thus far into the mechanisms of how MA silk properties vary from gene expression to nanostructure formations to fiber mechanics. Such knowledge is imperative for promoting the production of synthetic silk fibers. PMID:29390013

Influence of diurnal photosynthetic activity on the morphology, structure, and thermal properties of normal and waxy barley starch.

PubMed

Goldstein, Avi; Annor, George; Vamadevan, Varatharajan; Tetlow, Ian; Kirkensgaard, Jacob J K; Mortensen, Kell; Blennow, Andreas; Hebelstrup, Kim H; Bertoft, Eric

2017-05-01

This study investigated the influence of diurnal photosynthetic activity on the morphology, molecular composition, crystallinity, and gelatinization properties of normal barley starch (NBS) and waxy barley starch (WBS) granules from plants cultivated in a greenhouse under normal diurnal (16h light) or constant light photosynthetic conditions. Growth rings were observed in all starch samples regardless of lighting conditions. The size distribution of whole and debranched WBS analyzed by gel-permeation chromatography did not appear to be influenced by the different lighting regimes, however, a greater relative crystallinity measured by wide-angle X-ray scattering and greater crystalline quality as judged by differential scanning calorimetry was observed under the diurnal lighting regime. NBS cultivated under the diurnal photosynthetic lighting regime displayed lower amylose content (18.7%), and shorter amylose chains than its counterpart grown under constant light. Although the relative crystallinity of NBS was not influenced by lighting conditions, lower onset, peak, and completion gelatinization temperatures were observed in diurnally grown NBS compared to constant light conditions. It is concluded that normal barley starch is less influenced by the diurnal photosynthetic lighting regime than amylose-free barley starch suggesting a role of amylose to prevent structural disorder and increase starch granule robustness against environmental cues. Copyright © 2017 Elsevier B.V. All rights reserved.

Investigation on the Activity Activation and Cementitious Property of Coal Gangue with High Iron and Silica Contents

NASA Astrophysics Data System (ADS)

Wu, Hong; Li, Yu; Teng, Min; Yang, Yu

2017-11-01

The activity of coal gangue by thermal activation and composite activation technologies was investigated. The crystal composition, framework structure and morphology change were analyzed by XRD, FT-IR and SEM, respectively. The cementitious property of coal gangue was measured by strength test. The results showed that thermal activation decomposed kaolinite in coal gangue, and formed the metastable structure with a porous state, multiple internal broken bonds and large specific surface areas. Based on thermal activation, the added lime provided the alkaline environment, then this reduced the bond energy of reactant particles and the degree of crystallinity of quartz in coal gangue. The two activation methods could effectively improve the cementitious property of coal gangue based unburned bricks, and that the composite activation technology was superior performance.

Environmental biodegradation of haloarchaea-produced poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in activated sludge.

PubMed

Liu, Xiao-Bin; Wu, Lin-Ping; Hou, Jing; Chen, Jun-Yu; Han, Jing; Xiang, Hua

2016-08-01

Novel poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) copolymers produced by haloarchaea are excellent candidate biomaterials. However, there is no report hitherto focusing on the biodegradation of PHBHV synthesized by haloarchaea. In this study, an environmental biodegradation of haloarchaea-produced PHBHV films, with 10~60 mol% 3-hydroxyvalerate (3HV) composition and different microchemical structures, was studied in nutrition-depleted activated sludge. The changes in mass, molar mass, chemical composition, thermal properties, and surface morphology were monitored. The mass and molar mass of each film decreased significantly, while the PHA monomer composition remained unchanged with time. Interestingly, the sample of random copolymer PHBHV-2 (R-PHBHV-2) (3HV, 30 mol%) had the lowest crystallinity and was degraded faster than R-PHBHV-3 containing the highest 3HV content or the higher-order copolymer PHBHV-1 (O-PHBHV-1) possessing the highest surface roughness. The order of biodegradation rate was in the opposite trend to the degree of crystallizability of the films. Meanwhile, thermal degradation temperature of most films decreased after biodegradation. Additionally, the surface erosion of films was confirmed by scanning electron microscopy. The dominant bacteria probably responsible for the degradation process were identified in the activated sludge. It was inferred that the degradation rate of haloarchaea-produced PHBHV films mainly depended on sample crystallinity, which was determined by monomer composition and microchemical structure and in turn strongly influenced surface morphology.

Design of unique composites based on aromatic thermosetting copolyesters

NASA Astrophysics Data System (ADS)

Parkar, Zeba

Aromatic thermosetting copolyester (ATSP) has promise in high-temperature applications. It can be employed as a bulk polymer, as a coating and as a matrix for carbon fiber composites (ATSP/C composites). This work focuses on the applications of high performance ATSP/C composites. The morphology of the ATSP matrix in the presence of carbon fiber was studied. The effect of liquid crystalline character of starting oligomers used to prepare ATSP on the final crystal structure of the ATSP/C composite was evaluated. Matrices obtained by crosslinking of both liquid crystalline oligomers (ATSP2) and non-liquid crystalline oligomers (ATSP1) tend to crystallize in presence of carbon fibers. The crystallite size of ATSP2 is 4 times that of ATSP1. Composites made from ATSP2 yield tougher matrices compared to those made from ATSP1. Thus toughened matrices could be achieved without incorporating any additives by just changing the morphology of the final polymer. The flammability characteristics of ATSP were also studied. The limiting oxygen index (LOI) of bulk ATSP was found to be 40% whereas that of ATSP/C composites is estimated to be 85%. Thus, ATSP shows potential to be used as a flame resistant material, and also as an aerospace reentry shield. Mechanical properties of the ATSP/C composite were characterized. ATSP was observed to bond strongly with reinforcing carbon fibers. The tensile strength, modulus and shear modulus were comparable to those of conventionally used high temperature epoxy resins. ATSP shows a unique capability for healing of interlaminar cracks on application of heat and pressure, via the Interchain Transesterification Reaction (ITR). ITR can also be used for reduction in void volume and healing of microcracks. Thus, ATSP resin systems provide a unique intrinsic repair mechanism compared to any other thermosetting systems in use today. Preliminary studies on measurement of residual stresses for ATSP/C composites indicate that the stresses induced are much lower than that in epoxy/C composites. Thermal fatigue testing suggests that ATSP shows better resistance to microcracking compared to epoxy resins.

Homocomposites of Polylactide (PLA) with Induced Interfacial Stereocomplex Crystallites

PubMed Central

2015-01-01

The demand for “green” degradable composite materials increases with growing environmental awareness. The key challenge is achieving the preferred physical properties and maintaining their eco-attributes in terms of the degradability of the matrix and the filler. Herein, we have designed a series of “green” homocomposites materials based purely on polylactide (PLA) polymers with different structures. Film-extruded homocomposites were prepared by melt-blending PLA matrixes (which had different degrees of crystallinity) with PLLA and PLA stereocomplex (SC) particles. The PLLA and SC particles were spherical and with 300–500 nm size. Interfacial crystalline structures in the form of stereocomplexes were obtained for certain particulate-homocomposite formulations. These SC crystallites were found at the particle/matrix interface when adding PLLA particles to a PLA matrix with d-lactide units, as confirmed by XRD and DSC data analyses. For all homocomposites, the PLLA and SC particles acted as nucleating agents and enhanced the crystallization of the PLA matrixes. The SC particles were more rigid and had a higher Young’s modulus compared with the PLLA particles. The mechanical properties of the homocomposites varied with particle size, rigidity, and the interfacial adhesion between the particles and the matrix. An improved tensile strength in the homocomposites was achieved from the interfacial stereocomplex formation. Hereafter, homocomposites with tunable crystalline arrangements and subsequently physical properties, are promising alternatives in strive for eco-composites and by this, creating materials that are completely degradable and sustainable. PMID:26523245

Integrating Reflection Seismic, Gravity and Magnetic Data to Reveal the Structure of Crystalline Basement: Implications for Understanding Rift Development

NASA Astrophysics Data System (ADS)

Lenhart, Antje; Jackson, Christopher A.-L.; Bell, Rebecca E.; Duffy, Oliver B.; Fossen, Haakon; Gawthorpe, Robert L.

2016-04-01

Numerous rifts form above crystalline basement containing pervasive faults and shear zones. However, the compositional and mechanical heterogeneity within crystalline basement and the geometry and kinematics of discrete and pervasive basement fabrics are poorly understood. Furthermore, the interpretation of intra-crustal structures beneath sedimentary basins is often complicated by limitations in the depth of conventional seismic imaging, the commonly acoustically transparent nature of basement, limited well penetrations, and complex overprinting of multiple tectonic events. Yet, a detailed knowledge of the structural and lithological complexity of crystalline basement rocks is crucial to improve our understanding of how rifts evolve. Potential field methods are a powerful but perhaps underutilised regional tool that can decrease interpretational uncertainty based solely on seismic reflection data. We use petrophysical data, high-resolution 3D reflection seismic volumes, gridded gravity and magnetic data, and 2D gravity and magnetic modelling to constrain the structure of crystalline basement offshore western Norway. Intra-basement structures are well-imaged on seismic data due to relatively shallow burial of the basement beneath a thin (<3.5 km) sedimentary cover. Variations in basement composition were interpreted from detailed seismic facies analysis and mapping of discrete intra-basement reflections. A variety of data filtering and isolation techniques were applied to the original gravity and magnetic data in order to enhance small-scale field variations, to accentuate formation boundaries and discrete linear trends, and to isolate shallow and deep crustal anomalies. In addition, 2D gravity and magnetic data modelling was used to verify the seismic interpretation and to further constrain the configuration of the upper and lower crust. Our analysis shows that the basement offshore western Norway is predominantly composed of Caledonian allochthonous nappes overlying large-scale anticlines of Proterozoic rocks of the Western Gneiss Region. Major Devonian extensional brittle faults, detachments and shear zones transect those tectono-stratigraphic units. Results from structural analysis of enhanced gravity and magnetic data indicate the presence of distinct intra-basement bodies and structural lineaments at different scales and depth levels which correlate with our seismic data interpretation and can be linked to their onshore counterparts exposed on mainland Norway. 2D forward models of gravity and magnetic data further support our interpretation and quantitatively constrain variations in magnetic and density properties of principal basement units. We conclude that: i) enhanced gravity and magnetic data are a powerful tool to constrain the geometry of individual intra-basement bodies and to detect structural lineaments not imaged in seismic data; ii) insights from this study can be used to evaluate the role of pre-existing basement structures on the evolution of rift basins; and iii) the integration of a range of geophysical datasets is crucial to improve our understanding of the deep subsurface.

Crystal-Chemical Analysis Martian Minerals in Gale Crater

NASA Technical Reports Server (NTRS)

Morrison, S. M.; Downs, R. T.; Blake, D. F.; Bish, D. L.; Ming, D. W.; Morris, R. V.; Yen, A. S.; Chipera, S. J.; Treiman, A. H.; Vaniman, D. T.;

Preparation of nanocellulose from micro-crystalline cellulose: The effect on the performance and properties of agar-based composite films.

PubMed

Shankar, Shiv; Rhim, Jong-Whan

2016-01-01

A facile approach has been performed to prepare nanocellulose (NC) from micro-crystalline cellulose (MCC) and test their effect on the performance properties of agar-based composite films. The NC was characterized by STEM, XRD, FTIR, and TGA. The NC was well dispersed in distilled water after sonication and their size was in the range of 100-500nm. The XRD results revealed the crystallinity of NC. The crystallinity index of NC (0.71) was decreased compared to the MCC (0.81). The effect of NC or MCC content (1, 3, 5 and 10wt% based on agar) on the mechanical, water vapor permeability (WVP), and thermal properties of the composites were studied. The NC obtained from MCC can be used as a reinforcing agent for the preparation of biodegradable composites films for their potential use in the development of biodegradable food packaging materials. Copyright © 2015 Elsevier Ltd. All rights reserved.

Stamp forming optimization for formability and crystallinity

NASA Astrophysics Data System (ADS)

Donderwinkel, T. G.; Rietman, B.; Haanappel, S. P.; Akkerman, R.

2016-10-01

The stamp forming process is well suited for high volume production of thermoplastic composite parts. The process can be characterized as highly non-isothermal as it involves local quench-cooling of a molten thermoplastic composite blank where it makes contact with colder tooling. The formability of the thermoplastic composite depends on the viscoelastic material behavior of the matrix material, which is sensitive to temperature and degree of crystallinity. An experimental study was performed to determine the effect of temperature and crystallinity on the storage modulus during cooling for a woven glass fiber polyamide-6 composite material. An increase of two decades in modulus was observed during crystallization. As this will significantly impede the blank formability, the onset of crystallization effectively governs the time available for forming. Besides the experimental work, a numerical model is developed to study the temperature and crystallinity throughout the stamp forming process. A process window can be determined by feeding the model with the experimentally obtained data on crystallization.

The influence of chemical structure on thermal properties and surface morphology of polyurethane materials.

PubMed

Brzeska, Joanna; Morawska, Magda; Heimowska, Aleksandra; Sikorska, Wanda; Wałach, Wojciech; Hercog, Anna; Kowalczuk, Marek; Rutkowska, Maria

2018-01-01

The surface morphology and thermal properties of polyurethanes can be correlated to their chemical composition. The hydrophilicity, surface morphology, and thermal properties of polyurethanes (differed in soft segments and in linear/cross-linked structure) were investigated. The influence of poly([ R , S ]-3-hydroxybutyrate) presence in soft segments and blending of polyurethane with polylactide on surface topography were also estimated. The linear polyurethanes (partially crystalline) had the granular surface, whereas the surface of cross-linked polyurethanes (almost amorphous) was smooth. Round aggregates of polylactide un-uniformly distributed in matrix of polyurethane were clearly visible. It was concluded that some modification of soft segment (by mixing of poly([ R , S ]-3-hydroxybutyrate) with different polydiols and polytriol) and blending of polyurethanes with small amount of polylactide influence on crystallinity and surface topography of obtained polyurethanes.

Topological phase diagram and saddle point singularity in a tunable topological crystalline insulator

DOE PAGES

Neupane, Madhab; Xu, Su-Yang; Sankar, R.; ...

2015-08-20

Here we report the evolution of the surface electronic structure and surface material properties of a topological crystalline insulator (TCI), Pb 1more » $${-}$$xSnxSe, as a function of various material parameters including composition x, temperature T , and crystal structure. Our spectroscopic data demonstrate the electronic ground-state condition for the saddle point singularity, the tunability of surface chemical potential, and the surface states’ response to circularly polarized light. Our results show that each material parameter can tune the system between the trivial and topological phase in a distinct way, unlike that seen in Bi 2Se 3 and related compounds, leading to a rich topological phase diagram. Our systematic studies of the TCI Pb 1$${-}$$xSnxSe are a valuable materials guide to realize new topological phenomena.« less

Detecting a Difference in Clay Minerals at Two Gale Crater Sites

NASA Image and Video Library

2016-12-13

Data graphed here from the Chemistry and Camera (CheMin) instrument on NASA's Mars Curiosity rover show a difference between clay minerals in powder drilled from mudstone outcrops at two locations in Mars' Gale Crater: "Yellowknife Bay" and "Murray Buttes." CheMin's X-ray diffraction analysis reveals information about the crystalline structure of minerals in the rock. The intensity peaks marked with dotted vertical lines in this chart indicate that the crystalline structure of the two sites' clay minerals differs. The difference can be tied to a compositional difference in the clay minerals, as depicted in a diagram at PIA21148. The Yellowknife Bay site is on the floor of Gale Crater. The Murray Buttes site is on lower Mount Sharp, the layered mound in the center of the crater. http://photojournal.jpl.nasa.gov/catalog/PIA21147

Nuclear waste disposal—pyrochlore (A2B2O7): Nuclear waste form for the immobilization of plutonium and "minor" actinides

NASA Astrophysics Data System (ADS)

Ewing, Rodney C.; Weber, William J.; Lian, Jie

2004-06-01

During the past half-century, the nuclear fuel cycle has generated approximately 1400 metric tons of plutonium and substantial quantities of the "minor" actinides, such as Np, Am, and Cm. The successful disposition of these actinides has an important impact on the strategy for developing advanced nuclear fuel cycles, weapons proliferation, and the geologic disposal of high-level radioactive waste. During the last decade, there has been substantial interest in the use of the isometric pyrochlore structure-type, A2B2O7, for the immobilization of actinides. Most of the interest has focused on titanate-pyrochlore because of its chemical durability; however, these compositions experience a radiation-induced transition from the crystalline-to-aperiodic state due to radiation damage from the alpha-decay of actinides. Depending on the actinide concentration, the titanate pyrochlore will become amorphous in less than 1000 years of storage. Recently, systematic ion beam irradiations of a variety of pyrochlore compositions has revealed that many zirconate pyrochlores do not become amorphous, but remain crystalline as a defect fluorite structure-type due to disordering of the A- and B-site cations. The zirconate pyrochlores will remain crystalline even to very high doses, greater than 100 displacements per atom. Systematic experimental studies of actinide-doped and ion beam-irradiated pyrochlore, analyses of natural U- and Th-bearing pyrochlore, and simulations of the energetics of the disordering process now provide a rather detailed understanding of the structural and chemical controls on the response of pyrochlore to radiation. These results provide a solid basis for predicting the behavior and durability of pyrochlore used to immobilize plutonium.

Low-temperature formation of crystalline Si:H/Ge:H heterostructures by plasma-enhanced CVD in combination with Ni-nanodots seeding nucleation

NASA Astrophysics Data System (ADS)

Lu, Yimin; Makihara, Katsunori; Takeuchi, Daichi; Ikeda, Mitsuhisa; Ohta, Akio; Miyazaki, Seiichi

2017-06-01

Hydrogenated microcrystalline (µc) Si/Ge heterostructures were prepared on quartz substrates by plasma-enhanced chemical vapor deposition (CVD) from VHF inductively coupled plasma of SiH4 just after GeH4 employing Ni nanodots (NDs) as seeds for crystalline nucleation. The crystallinity of the films and the progress of grain growth were characterized by Raman scattering spectroscopy and atomic force microscopy (AFM), respectively. When the Ge films were grown on Ni-NDs at 250 °C, the growth of µc-Ge films with crystallinity as high as 80% was realized without an amorphous phase near the Ge film/quartz substrate interface. After the subsequent Si film deposition at 250 °C, fine grains were formed in the early stages of film growth on µc-Ge films with compositional mixing (µc-Si0.85Ge0.15:H) caused by the release of large lattice mismatch between c-Si and c-Ge. With further increase in Si:H film thickness, the formation of large grain structures accompanied by fine grains was promoted. These results suggest that crystalline Si/Ge heterojunctions can be used for efficient carrier collection in solar cell application.

Sponge-like nanoporous single crystals of gold

PubMed Central

Khristosov, Maria Koifman; Bloch, Leonid; Burghammer, Manfred; Kauffmann, Yaron; Katsman, Alex; Pokroy, Boaz

2015-01-01

Single crystals in nature often demonstrate fascinating intricate porous morphologies rather than classical faceted surfaces. We attempt to grow such crystals, drawing inspiration from biogenic porous single crystals. Here we show that nanoporous single crystals of gold can be grown with no need for any elaborate fabrication steps. These crystals are found to grow following solidification of a eutectic composition melt that forms as a result of the dewetting of nanometric thin films. We also present a kinetic model that shows how this nano-porous single-crystalline structure can be obtained, and which allows the potential size of the porous single crystal to be predicted. Retaining their single-crystalline nature is due to the fact that the full crystallization process is faster than the average period between two subsequent nucleation events. Our findings clearly demonstrate that it is possible to form single-crystalline nano porous metal crystals in a controlled manner. PMID:26554856

Nanowires, nanostructures and devices fabricated therefrom

DOEpatents

Majumdar, Arun; Shakouri, Ali; Sands, Timothy D.; Yang, Peidong; Mao, Samuel S.; Russo, Richard E.; Feick, Henning; Weber, Eicke R.; Kind, Hannes; Huang, Michael; Yan, Haoquan; Wu, Yiying; Fan, Rong

2005-04-19

One-dimensional nanostructures having uniform diameters of less than approximately 200 nm. These inventive nanostructures, which we refer to as "nanowires", include single-crystalline homostructures as well as heterostructures of at least two single-crystalline materials having different chemical compositions. Because single-crystalline materials are used to form the heterostructure, the resultant heterostructure will be single-crystalline as well. The nanowire heterostructures are generally based on a semiconducting wire wherein the doping and composition are controlled in either the longitudinal or radial directions, or in both directions, to yield a wire that comprises different materials. Examples of resulting nanowire heterostructures include a longitudinal heterostructure nanowire (LOHN) and a coaxial heterostructure nanowire (COHN).

Properties of CuInS₂ Nano-Particles on TiO₂ by Spray Pyrolysis for CuInS₂/TiO₂ Composite Solar Cell.

PubMed

Park, Gye-Choon; Li, Zhen-Yu; Yang, O-Bong

2017-04-01

In this letter, for the absorption layer of a CuInS₂/TiO₂ composite solar cell, I–III–VI2 chalcopyrite semiconductor CuInS₂ nano-particles were deposited by using spray pyrolysis method on TiO2 porous film. Their material characteristics including structural and optical properties of CuInS₂ nano-particles on TiO₂ nanorods were analyzed as a function of its composition ratios of Cu:In:S. Crystalline structure, surface morphology and crystalline size were also investigated by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), and High-Resolution TEM (HRTEM), respectively. On the other hand, optical property was characterized by an UV-Visible Spectrophotometer. As a result, it was found that the size of CuInS₂ nano-particles, which was formed at 300±5 °C, was smaller than 16 nm from HRTEM analyses, and it was identified that the CuInS₂ particle size was increased as increasing the heat-treatment temperature and time. However, as the size of CuInS₂ nano-particle becomes smaller, optical absorption edge of ternary compound film tends to move to the blue wavelength band. It turns out that the optical energy-band gap of the compound films was ranging from 1.48 eV to 1.53 eV.

Formation of Ti-Al-Cr-B-N coatings by ion-magnetron sputtering of composite targets

NASA Astrophysics Data System (ADS)

Sergeev, Oleg V.; Kalashnikov, Mark P.; Voronov, Andrey V.; Sergeev, Victor P.; Panin, Victor E.

2017-12-01

The research addresses the influence of bombardment by high-energy ions (Cr + B)+ with a low fluence 4 × 1017 cm-2 on the tribological and mechanical properties of Ti-Al-N coatings. The wear resistance decreases 2.6 times whereas the microhardness decreases 1.2 times. The structural-phase state and the chemical composition of the surface layer of the modified coating are determined. The research is carried out by transmission and scanning of the electron microscopy and the secondary ion mass spectrometry. In the ion-modified coating layer the average concentration of titanium, aluminum and nitrogen decreases and those of chromium and boron increase when at a fluence of 4 × 1017 cm-2 the maximum values of Cr and B reach 16 and 23 at %, respectively, and the minimum values of Ti, Al and N amount to 15, 7 and 39 at %. In this layer the columnar structure is broken; its volume is divided into the alternative local nanosize zone-crystalline and amorphous. The phase composition of the crystalline regions is represented by TiN and AlN phases and a new CrB4 phase. The observed decrease of the tribomechanical properties can be due to both the amorphization of the surface layer and the transformation of a high-strength phase in a brittle one.

A composite hydrogels-based photonic crystal multi-sensor

NASA Astrophysics Data System (ADS)

Chen, Cheng; Zhu, Zhigang; Zhu, Xiangrong; Yu, Wei; Liu, Mingju; Ge, Qiaoqiao; Shih, Wei-Heng

2015-04-01

A facile route to prepare stimuli-sensitive poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) gelated crystalline colloidal array photonic crystal material was developed. PVA was physically gelated by utilizing an ethanol-assisted method, the resulting hydrogel/crystal composite film was then functionalized with PAA to form an interpenetrating hydrogel film. This sensor film is able to efficiently diffract the visible light and rapidly respond to various environmental stimuli such as solvent, pH and strain, and the accompanying structural color shift can be repeatedly changed and easily distinguished by naked eye.

Phase-Change Memory Properties of Electrodeposited Ge-Sb-Te Thin Film.

PubMed

Huang, Ruomeng; Kissling, Gabriela P; Jolleys, Andrew; Bartlett, Philip N; Hector, Andrew L; Levason, William; Reid, Gillian; De Groot, C H 'Kees'

2015-12-01

We report the properties of a series of electrodeposited Ge-Sb-Te alloys with various compositions. It is shown that the Sb/Ge ratio can be varied in a controlled way by changing the electrodeposition potential. This method opens up the prospect of depositing Ge-Sb-Te super-lattice structures by electrodeposition. Material and electrical characteristics of various compositions have been investigated in detail, showing up to three orders of magnitude resistance ratio between the amorphous and crystalline states and endurance up to 1000 cycles.

Phase-Change Memory Properties of Electrodeposited Ge-Sb-Te Thin Film

NASA Astrophysics Data System (ADS)

Huang, Ruomeng; Kissling, Gabriela P.; Jolleys, Andrew; Bartlett, Philip N.; Hector, Andrew L.; Levason, William; Reid, Gillian; De Groot, C. H. `Kees'

2015-11-01

We report the properties of a series of electrodeposited Ge-Sb-Te alloys with various compositions. It is shown that the Sb/Ge ratio can be varied in a controlled way by changing the electrodeposition potential. This method opens up the prospect of depositing Ge-Sb-Te super-lattice structures by electrodeposition. Material and electrical characteristics of various compositions have been investigated in detail, showing up to three orders of magnitude resistance ratio between the amorphous and crystalline states and endurance up to 1000 cycles.

Electronically conductive ceramics for high temperature oxidizing environments

DOEpatents

Kucera, G.H.; Smith, J.L.; Sim, J.W.

1983-11-10

This invention pertains to a high temperature, ceramic composition having electronic conductivity as measured by resistivity below about 500 ohm-cm, chemical stability particularly with respect to cathode conditions in a molten carbonate fuel cell, and composed of an alkali metal, transition metal oxide containing a dopant metal in the crystalline structure to replace a portion of the alkali metal or transition metal.

Comparison between Cellulose Nanocrystal and Cellulose Nanofibril Reinforced Poly(ethylene oxide) Nanofibers and Their Novel Shish-Kebab-Like Crystalline Structures

Treesearch

Xuezhu Xu; Haoran Wang; Long Jiang; Xinnan Wang; Scott A. Payne; J.Y. Zhu; Ruipeng Li

2014-01-01

Poly(ethylene oxide) (PEO) nanofiber mats were produced by electrospinning. Biobased cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) as reinforcement nanofillers were also added to the polymer to produce composite nanofiber mats. The effects of the two cellulose nanofillers on the rheological properties of the PEO solutions and the microstructure,...

Synthesis of biocompatible poly(ɛ-caprolactone)- block-poly(propylene adipate) copolymers appropriate for drug nanoencapsulation in the form of core-shell nanoparticles

PubMed Central

Nanaki, Stavroula G; Pantopoulos, Kostas; Bikiaris, Dimitrios N

2011-01-01

Poly(propylene adipate)-block-poly(ɛ-caprolactone) copolymers were synthesized using a combination of polycondensation and ring-opening polymerization of ɛ-caprolactone in the presence of poly(propylene adipate). Gel permeation chromatography was used for molecular weight determination, whereas hydrogen-1 nuclear magnetic resonance and carbon-13 nuclear magnetic resonance spectroscopy were employed for copolymer characterization and composition evaluation. The copolymers were found to be block while their composition was similar to the feeding ratio. They formed semicrystalline structures, while only poly(ɛ-caprolactone) formed crystals, as shown by wide angle X-ray diffraction. Differential scanning calorimetry data suggest that the melting point and heat of fusion of copolymers decreased by increasing the poly(propylene adipate) amount. The synthesized polymers exhibited low cytotoxicity and were used to encapsulate desferrioxamine, an iron-chelating drug. The desferrioxamine nanoparticles were self-assembled into core shell structures, had mean particle size <250 nm, and the drug remained in crystalline form. Further studies revealed that the dissolution rate was mainly related to the melting temperature, as well as to the degree of crystallinity of copolymers. PMID:22162656

Synthesis and structural analysis of Fe doped TiO2 nanoparticles using Williamson Hall and Scherer Model

NASA Astrophysics Data System (ADS)

Patle, L. B.; Labhane, P. K.; Huse, V. R.; Gaikwad, K. D.; Chaudhari, A. L.

2018-05-01

The nanoparticles of Pure and doped Ti1-xFexO were synthesized by modified co-precipitation method successfully with nominal composite of x=0.0, 0.01, 0.03 and 0.05 at room temperature. The precursors were further calcined at 500°C for 6hrs in muffle furnace which results in the formation of different TiO2 phase compositions. The structural analysis carried out by XRD (Bruker D8 Cu-Kα1). X-ray peak broadening analysis was used to evaluate the crystalline sizes, the lattice parameters, atomic packing fraction, c/a ratio, X-ray density and Volume of unit cell. The Williamson Hall analysis is used to find grain size and Strain of prepared TiO2 nano particles. Crystalline TiO2 with a Tetragonal Anatase phase is confirmed by XRD results. The grain size of pure and Fe doped samples were found in the range of 10nm to 18nm. All the physical parameters of anatase tetragonal TiO2 nanoparticles were calculated more precisely using modified W-H plot a uniform deformation model (UDM). The results calculated from both the techniques were approximately similar.

Calcium titanium silicate based glass-ceramic for nuclear waste immobilisation

NASA Astrophysics Data System (ADS)

Sharma, K.; Srivastav, A. P.; Goswami, M.; Krishnan, Madangopal

2018-04-01

Titanate based ceramics (synroc) have been studied for immobilisation of nuclear wastes due to their high radiation and thermal stability. The aim of this study is to synthesis glass-ceramic with stable phases from alumino silicate glass composition and study the loading behavior of actinides in glass-ceramics. The effects of CaO and TiO2 addition on phase evolution and structural properties of alumino silicate based glasses with nominal composition x(10CaO-9TiO2)-y(10Na2O-5 Al2O3-56SiO2-10B2O3); where z = x/y = 1.4-1.8 are reported. The glasses are prepared by melt-quench technique and characterized for thermal and structural properties using DTA and Raman Spectroscopy. Glass transition and peak crystallization temperatures decrease with increase of CaO and TiO2 content, which implies the weakening of glass network and increased tendency of glasses towards crystallization. Sphene (CaTiSiO5) and perovskite (CaTiO3) crystalline phases are confirmed from XRD which are well known stable phase for conditioning of actinides. The microsturcture and elemental analysis indicate the presence of actinide in stable crystalline phases.

Synthesis of biocompatible poly(ɛ-caprolactone)- block-poly(propylene adipate) copolymers appropriate for drug nanoencapsulation in the form of core-shell nanoparticles.

PubMed

Nanaki, Stavroula G; Pantopoulos, Kostas; Bikiaris, Dimitrios N

2011-01-01

Poly(propylene adipate)-block-poly(ɛ-caprolactone) copolymers were synthesized using a combination of polycondensation and ring-opening polymerization of ɛ-caprolactone in the presence of poly(propylene adipate). Gel permeation chromatography was used for molecular weight determination, whereas hydrogen-1 nuclear magnetic resonance and carbon-13 nuclear magnetic resonance spectroscopy were employed for copolymer characterization and composition evaluation. The copolymers were found to be block while their composition was similar to the feeding ratio. They formed semicrystalline structures, while only poly(ɛ-caprolactone) formed crystals, as shown by wide angle X-ray diffraction. Differential scanning calorimetry data suggest that the melting point and heat of fusion of copolymers decreased by increasing the poly(propylene adipate) amount. The synthesized polymers exhibited low cytotoxicity and were used to encapsulate desferrioxamine, an iron-chelating drug. The desferrioxamine nanoparticles were self-assembled into core shell structures, had mean particle size <250 nm, and the drug remained in crystalline form. Further studies revealed that the dissolution rate was mainly related to the melting temperature, as well as to the degree of crystallinity of copolymers.

Deposition of magnesium nitride thin films on stainless steel-304 substrates by using a plasma focus device

NASA Astrophysics Data System (ADS)

Ramezani, Amir Hoshang; Habibi, Maryam; Ghoranneviss, Mahmood

2014-08-01

In this research, for the first time, we synthesize magnesium nitride thin films on 304-type stainless steel substrates using a Mather-type (2 kJ) plasma focus (PF) device. The films of magnesium nitride are coated with different number of focus shots (like 15, 25 and 35) at a distance of 8 cm from the anode tip and at 0° angular position with respect to the anode axis. For investigation of the structural properties and surface morphology of magnesium nitride films, we utilized the X-ray diffractometer (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis, respectively. Also, the elemental composition is characterized by energy-dispersive X-ray (EDX) analysis. Furthermore, Vicker's microhardness is used to study the mechanical properties of the deposited films. The results show that the degree of crystallinity of deposited thin films (from XRD), the average size of particles and surface roughness (from AFM), crystalline growth of structures (from SEM) and the hardness values of the films depend on the number of focus shots. The EDX analysis demonstrates the existence of the elemental composition of magnesium in the deposited samples.

Modification of the structure and composition of Ca10(PO4)6(OH)2 ceramic coatings by changing the deposition conditions in O2 and Ar

NASA Astrophysics Data System (ADS)

Donkov, N.; Zykova, A.; Safonov, V.; Kolesnikov, D.; Goncharov, I.; Yakovin, S.; Georgieva, V.

2014-05-01

Hydroxyapatite Ca10(PO4)6(OH)2 (HAp) is a material considered to be used to form structural matrices in the mineral phase of bone, dentin and enamel. HAp ceramic materials and coatings are widely applied in medicine and dentistry because of their ability to increase the tissue response to the implant surface and promote bone ingrowth and osseoconduction processes. The deposition conditions affect considerably the structure and bio-functionality of the HAp coatings. We focused our research on developing deposition methods allowing a precise control of the structure and stoichiometric composition of HAp thin films. We found that the use of O2 as a reactive gas improves the quality of the sputtered hydroxyapatite coatings by resulting in the formation of films of better stoichiometry with a fine crystalline structure.

[Study on spectroscopic characterization and property of PES/ micro-nano cellulose composite membrane material].

PubMed

Tang, Huan-Wei; Zhang, Li-Ping; Li, Shuai; Zhao, Guang-Jie; Qin, Zhu; Sun, Su-Qin

2010-03-01

In the present paper, the functional groups of PES/micro-nano cellulose composite membrane materials were characterized by Fourier transform infrared spectroscopy (FTIR). Also, changes in crystallinity in composite membrane materials were analyzed using X-ray diffraction (XRD). The effects of micro-nano cellulose content on hydrophilic property of composite membrane material were studied by measuring hydrophilic angle. The images of support layer structure of pure PES membrane material and composite membrane material were showed with scanning electron microscope (SEM). These results indicated that in the infrared spectrogram, the composite membrane material had characteristic peaks of both PES and micro-nano cellulose without appearance of other new characteristics peaks. It revealed that there were no new functional groups in the composite membrane material, and the level of molecular compatibility was achieved, which was based on the existence of inter-molecular hydrogen bond association between PES and micro-nano cellulose. Due to the existence of micro-nano cellulose, the crystallinity of composite membrane material was increased from 37.7% to 47.9%. The more the increase in micro-nano cellulose mass fraction, the better the van de Waal force and hydrogen bond force between composite membrane material and water were enhanced. The hydrophilic angle of composite membrane material was decreased from 55.8 degrees to 45.8 degrees and the surface energy was raised from 113.7 to 123.5 mN x m(-2). Consequently, the hydrophilic property of composite membrane material was improved. The number of pores in the support layer of composite membrane material was lager than that of pure PES membrane. Apparently, pores were more uniformly distributed.

Co-precipitation synthesis of nano-composites consists of zinc and tin oxides coatings on glass with enhanced photocatalytic activity on degradation of Reactive Blue 160 KE2B.

PubMed

Habibi, Mohammad Hossein; Mardani, Maryam

2015-02-25

Nano-composite containing zinc oxide-tin oxide was obtained by a facile co-precipitation route using tin chloride tetrahydrate and zinc chloride as precursors and coated on glass by Doctor Blade deposition. The crystalline structure and morphology of composites were evaluated by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The XRD results showed peaks relative to zinc oxide with hexagonal wurtzite structure and tin oxide with tetragonal structure. FESEM observations showed that the nano-composite consisted of aggregates of particles with an average particle size of 18 nm. The photocatalytic activity of the pure SnO2, pure ZnO, ZnSnO3-Zn2SnO4 and ZnO-SnO2 nano-structure thin films was examined using the degradation of a textile dye Reactive Blue 160 (KE2B). ZnO-SnO2 nano-composite showed enhanced photo-catalytic activity than the pure zinc oxide and tin oxide. The enhanced photo-catalytic activity of the nano-composite was ascribed to an improved charge separation of the photo-generated electron-hole pairs. Copyright © 2014 Elsevier B.V. All rights reserved.

Chemical Dynamics of nano-Aluminum and Iodine Based Oxidizers

NASA Astrophysics Data System (ADS)

Little, Brian; Ridge, Claron; Overdeep, Kyle; Slizewski, Dylan; Lindsay, Michael

2017-06-01

As observed in previous studies of nanoenergetic powder composites, micro/nano-structural features such as particle morphology and/or reactant spatial distance are expected to strongly influence properties that govern the combustion behavior of energetic materials (EM). In this study, highly reactive composites containing crystalline iodine (V) oxide or iodate salts with nano-sized aluminum (nAl) were blended by two different processing techniques and then collected as a powder for characterization. Physiochemical techniques such as thermal gravimetric analysis, calorimetry, X-ray diffraction, electron microscopy, high speed photography, pressure profile analysis, temperature programmed reactions, and spectroscopy were employed to characterize these EM with emphasis on correlating the chemical reactivity with inherent structural features and variations in stoichiometry. This work is a continuation of efforts to probe the chemical dynamics of nAl-iodine based composites.

Crystallized alkali-silica gel in concrete from the late 1890s

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

Peterson, Karl; Gress, David; Van Dam, Tom

The Elon Farnsworth Battery, a concrete structure completed in 1898, is in an advanced state of disrepair. To investigate the potential for rehabilitation, cores were extracted from the battery. Petrographic examination revealed abundant deposits of alkali silica reaction products in cracks associated with the quartz rich metasedimentary coarse aggregate. The products of the alkali silica reaction are variable in composition and morphology, including both amorphous and crystalline phases. The crystalline alkali silica reaction products are characterized by quantitative X-ray energy dispersive spectrometry (EDX) and X-ray diffraction (XRD). The broad extent of the reactivity is likely due to elevated alkali levelsmore » in the cements used.« less

Ab initio study of the composite phase diagram of Ni-Mn-Ga shape memory alloys

NASA Astrophysics Data System (ADS)

Sokolovskaya, Yu. A.; Sokolovskiy, V. V.; Zagrebin, M. A.; Buchelnikov, V. D.; Zayak, A. T.

2017-07-01

The magnetic and structural properties of a series of nonstoichiometric Ni-Mn-Ga Heusler alloys are theoretically investigated in terms of the density functional theory. Nonstoichiometry is formed in the coherent potential approximation. Concentration dependences of the equilibrium lattice parameter, the bulk modulus, and the total magnetic moment are obtained and projected onto the ternary phase diagram of the alloys. The stable crystalline structures and the magnetic configurations of the austenitic phase are determined.

Structural studies of gels and gel-glasses in the SiO2-GeO2 system using vibrational spectroscopy

NASA Technical Reports Server (NTRS)

Mukherjee, Shyama P.; Sharma, Shiv K.

1986-01-01

GeO2 gel and gels in the SiO2-GeO2 system synthesized by the hydrolytic polycondensation of metal alkoxides have been studied by infrared and Raman spectroscopic techniques. The molecular structures, hydroxyl contents, and crystallinity of gels and gel-glasses in relation to the thermal history and GeO2 concentration were investigated. The binary compositions having up to 70 mol percent GeO2 were examined.

Multi-Scale Simulation of Interfacial Phenomena and Nano-Particle Placement in Polymer Matrix Composites

DTIC Science & Technology

2012-08-01

Molecular Dynamics Simulations Coarse-Grain Particle Dynamics Simulations Local structure; Force field parameterization Extended structure...K) C8H18 C12H26 C16H34 Adhesive forces can cause local density gradients and defects " Pronounced layering of polymer near interfaces...reactive end groups (CnH2n+1S) on Cu Gap SubPc on C60 Pentacene on a-SiO2 Cyclopentene on Au Crystalline CuPc on Al Polyimide on Si

Strong temperature-dependent crystallization, phase transition, optical and electrical characteristics of p-type CuAlO2 thin films.

PubMed

Liu, Suilin; Wu, Zhiheng; Zhang, Yake; Yao, Zhiqiang; Fan, Jiajie; Zhang, Yiqiang; Hu, Junhua; Zhang, Peng; Shao, Guosheng

2015-01-07

We report here a reliable and reproducible single-step (without post-annealing) fabrication of phase-pure p-type rhombohedral CuAlO2 (r-CuAlO2) thin films by reactive magnetron sputtering. The dependence of crystallinity and phase compositions of the films on the growth temperature was investigated, revealing that highly-crystallized r-CuAlO2 thin films could be in situ grown in a narrow temperature window of ∼940 °C. Optical and electrical property studies demonstrate that (i) the films are transparent in the visible light region, and the bandgaps of the films increased to ∼3.86 eV with the improvement of crystallinity; (ii) the conductance increased by four orders of magnitude as the film was evolved from the amorphous-like to crystalline structure. The predominant role of crystallinity in determining CuAlO2 film properties was demonstrated to be due to the heavy anisotropic characteristics of the O 2p-Cu 3d hybridized valence orbitals.

Surface characterization and corrosion behavior of calcium phosphate-base composite layer on titanium and its alloys via plasma electrolytic oxidation: A review paper.

PubMed

Rafieerad, A R; Ashra, M R; Mahmoodian, R; Bushroa, A R

2015-12-01

In recent years, calcium phosphate-base composites, such as hydroxyapatite (HA) and carbonate apatite (CA) have been considered desirable and biocompatible coating layers in clinical and biomedical applications such as implants because of the high resistance of the composites. This review focuses on the effects of voltage, time and electrolytes on a calcium phosphate-base composite layer in case of pure titanium and other biomedical grade titanium alloys via the plasma electrolytic oxidation (PEO) method. Remarkably, these parameters changed the structure, morphology, pH, thickness and crystallinity of the obtained coating for various engineering and biomedical applications. Hence, the structured layer caused improvement of the biocompatibility, corrosion resistance and assignment of extra benefits for Osseo integration. The fabricated layer with a thickness range of 10 to 20 μm was evaluated for physical, chemical, mechanical and tribological characteristics via XRD, FESEM, EDS, EIS and corrosion analysis respectively, to determine the effects of the applied parameters and various electrolytes on morphology and phase transition. Moreover, it was observed that during PEO, the concentration of calcium, phosphor and titanium shifts upward, which leads to an enhanced bioactivity by altering the thickness. The results confirm that the crystallinity, thickness and contents of composite layer can be changed by applying thermal treatments. The corrosion behavior was investigated via the potentiodynamic polarization test in a body-simulated environment. Here, the optimum corrosion resistance was obtained for the coating process condition at 500 V for 15 min in Ringer solution. This review has been summarized, aiming at the further development of PEO by producing more adequate titanium-base implants along with desired mechanical and biomedical features. Copyright © 2015 Elsevier B.V. All rights reserved.

Recreating the synthesis of starch granules in yeast

PubMed Central

Pfister, Barbara; Sánchez-Ferrer, Antoni; Diaz, Ana; Lu, Kuanjen; Otto, Caroline; Holler, Mirko; Shaik, Farooque Razvi; Meier, Florence; Mezzenga, Raffaele; Zeeman, Samuel C

2016-01-01

Starch, as the major nutritional component of our staple crops and a feedstock for industry, is a vital plant product. It is composed of glucose polymers that form massive semi-crystalline granules. Its precise structure and composition determine its functionality and thus applications; however, there is no versatile model system allowing the relationships between the biosynthetic apparatus, glucan structure and properties to be explored. Here, we expressed the core Arabidopsis starch-biosynthesis pathway in Saccharomyces cerevisiae purged of its endogenous glycogen-metabolic enzymes. Systematic variation of the set of biosynthetic enzymes illustrated how each affects glucan structure and solubility. Expression of the complete set resulted in dense, insoluble granules with a starch-like semi-crystalline organization, demonstrating that this system indeed simulates starch biosynthesis. Thus, the yeast system has the potential to accelerate starch research and help create a holistic understanding of starch granule biosynthesis, providing a basis for the targeted biotechnological improvement of crops. DOI: http://dx.doi.org/10.7554/eLife.15552.001 PMID:27871361

Investigation of composition and structure of spongy and hard bone tissue using FTIR spectroscopy, XRD and SEM

NASA Astrophysics Data System (ADS)

Al-Akhras, M.-Ali H.; Hasan Qaseer, M. K.; Albiss, B. A.; Alebrhim, M. Anwar; Gezawa, Umar S.

2018-02-01

Valuable structural and chemical features can be obtained for spongy and hard bone by infrared spectroscopy and X-ray diffraction. A better understanding of chemical and structural differences between spongy and hard bone is a very important contributor to bone quality. Our data according to IR data showed that the collagen cross-links occurred to be higher in spongy bone, and crystallinity was lower in spongy bone. Deconvolution of the infrared band near 870 cm-1 reveals evidence for A2-type carbonate substitution on hydroxyapatite of spongy bone in addition to the A and B type carbonate substitution that are also found in hard bone. IR and XRD data confirmed the results of each other since full width at half maximum of 002-apatite pattern of XRD showed that the crystallinity was lower in spongy bone. The microstructure was examined by using scanning electron microscope and the result showed that the lattice of thin threads in spongy bone and is less dense than hard bone.

CIT-7, a crystalline, molecular sieve with pores bounded by 8 and 10-membered rings

DOE PAGES

Schmidt, Joel E.; Xie, Dan; Rea, Thomas; ...

2015-01-23

A new crystalline molecular sieve, denoted CIT-7, is synthesized using an imidazolium-based diquaternary organic structure directing agent (OSDA). The framework structure is determined from a combination of rotation electron diffraction and synchrotron X-ray powder diffraction data. The structure has 10 crystallographically unique tetrahedral atoms (T-atoms) in the unit cell, and can be described as an ordered arrangement of the [4 25 46 2] mtw building unit and a previously unreported [4 45 2] building unit. The framework contains a 2-dimensional pore system that is bounded by 10 T-atom rings (10-ring, 5.1 Å × 6.2 Å opening) that are connected withmore » oval 8-rings (2.9 Å × 5.5 Å opening) through medium-sized cavities (~7.9 Å) at the channel intersections. CIT-7 can be synthesized over a broad range of compositions including pure-silica and heteroatom, e.g., aluminosilicate and titanosilicate, containing variants.« less

Structural properties of GaAsN grown on (001) GaAs by metalorganic molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Ok, Young-Woo; Choi, Chel-Jong; Seong, Tae-Yeon; Uesugi, K.; Suemune, I.

2001-07-01

Detailed transmission electron microscopy (TEM) and transmission electron diffraction (TED) examination has been made of metalorganic molecular beam epitaxial GaAsN layers grown on (001) GaAs substrates. TEM results show that lateral composition modulation occurs in the GaAs1-xNx layer (x 6.75%). It is shown that increasing N composition and Se (dopant) concentration leads to poor crystallinity. It is also shown that the addition of Se increases N composition. Atomic force microscopy (AFM) results show that the surfaces of the samples experience a morphological change from faceting to islanding, as the N composition and Se concentration increase. Based on the TEM and AFM results, a simple model is given to explain the formation of the lateral composition modulation.

Liquid crystalline cellulose-based nematogels

DOE PAGES

Liu, Qingkun; Smalyukh, Ivan I.

2017-08-18

Physical properties of composite materials can be pre-engineered by controlling their structure and composition at the mesoscale. However, approaches to achieving this are limited and rarely scalable. We introduce a new breed of self-assembled nematogels formed by an orientationally ordered network of thin cellulose nanofibers infiltrated with a thermotropic nematic fluid. The interplay between orientational ordering within the nematic network and that of the small-molecule liquid crystal around it yields a composite with highly tunable optical properties. By means of combining experimental characterization and modeling, we demonstrate submillisecond electric switching of transparency and facile responses of the composite to temperaturemore » changes. Finally, we discuss a host of potential technological uses of these self-assembled nematogel composites, ranging from smart and privacy windows to novel flexible displays.« less

Formation of crystalline phase in the glass matrix of Zr-Co-Al glass-matrix composites and its effect on their mechanical properties

NASA Astrophysics Data System (ADS)

Kim, Woo Chul; Kim, Kang Chul; Na, Min Young; Jeong, Seok Hoan; Kim, Won Tae; Kim, Do Hyang

2017-11-01

The microstructural evolution and mechanical properties of Zr-Co-Al alloys, with compositions of (Zr50Co50)x (Zr56Co26Al18)1-x (x = 1/6, 2/6, 3/6, 4/6, 5/6, 1) and Zr54Co35Al11, (referred to as Z1, Z2, Z3, Z4, Z5, Z6, and Z4.5), were investigated. Alloys Z1-Z3 consisted of crystalline phases, while alloys Z4 and Z4.5 consisted of crystalline phase particles ( 3 vol% and 35 vol%, respectively) embedded within the glassy matrix. Alloys Z5 and Z6 consisted of a monolithic glass phase. The crystalline phase of alloys Z1-Z4.5 consisted of primary B2-ZrCo dendrite and an interdendritic B2-ZrCo/Zr6CoAl2 eutectic phase. The B2-ZrCo dendritic phase exhibited a high work-hardening rate, which originated from the deformation-induced B2-to-B33 martensitic transformation. However, when the brittle interdendritic B2-ZrCo/Zr6CoAl2 eutectic phase fraction increased, the work-hardening rate significantly decreased. The ductility of the glass-matrix composites was significantly impaired by the presence of the interdendritic eutectic phase in the crystalline phase. The results indicate that the design of the crystalline particle microstructure is important with regard to enhancing the plasticity of glass-matrix composites.

Methods of fabricating nanostructures and nanowires and devices fabricated therefrom

DOEpatents

Majumdar, Arun [Orinda, CA; Shakouri, Ali [Santa Cruz, CA; Sands, Timothy D [Moraga, CA; Yang, Peidong [Berkeley, CA; Mao, Samuel S [Berkeley, CA; Russo, Richard E [Walnut Creek, CA; Feick, Henning [Kensington, CA; Weber, Eicke R [Oakland, CA; Kind, Hannes [Schaffhausen, CH; Huang, Michael [Los Angeles, CA; Yan, Haoquan [Albany, CA; Wu, Yiying [Albany, CA; Fan, Rong [El Cerrito, CA

2009-08-04

One-dimensional nanostructures having uniform diameters of less than approximately 200 nm. These inventive nanostructures, which we refer to as "nanowires", include single-crystalline homostructures as well as heterostructures of at least two single-crystalline materials having different chemical compositions. Because single-crystalline materials are used to form the heterostructure, the resultant heterostructure will be single-crystalline as well. The nanowire heterostructures are generally based on a semiconducting wire wherein the doping and composition are controlled in either the longitudinal or radial directions, or in both directions, to yield a wire that comprises different materials. Examples of resulting nanowire heterostructures include a longitudinal heterostructure nanowire (LOHN) and a coaxial heterostructure nanowire (COHN).

Methods Of Fabricating Nanosturctures And Nanowires And Devices Fabricated Therefrom

DOEpatents

Majumdar, Arun; Shakouri, Ali; Sands, Timothy D.; Yang, Peidong; Mao, Samuel S.; Russo, Richard E.; Feick, Henning; Weber, Eicke R.; Kind, Hannes; Huang, Michael; Yan, Haoquan; Wu, Yiying; Fan, Rong

2006-02-07

One-dimensional nanostructures having uniform diameters of less than approximately 200 nm. These inventive nanostructures, which we refer to as "nanowires", include single-crystalline homostructures as well as heterostructures of at least two single-crystalline materials having different chemical compositions. Because single-crystalline materials are used to form the heterostructure, the resultant heterostructure will be single-crystalline as well. The nanowire heterostructures are generally based on a semiconducting wire wherein the doping and composition are controlled in either the longitudinal or radial directions, or in both directions, to yield a wire that comprises different materials. Examples of resulting nanowire heterostructures include a longitudinal heterostructure nanowire (LOHN) and a coaxial heterostructure nanowire (COHN).

Methods of fabricating nanostructures and nanowires and devices fabricated therefrom

DOEpatents

Majumdar, Arun; Shakouri, Ali; Sands, Timothy D.; Yang, Peidong; Mao, Samuel S.; Russo, Richard E.; Feick, Henning; Weber, Eicke R.; Kind, Hannes; Huang, Michael; Yan, Haoquan; Wu, Yiying; Fan, Rong

2010-11-16

One-dimensional nanostructures having uniform diameters of less than approximately 200 nm. These inventive nanostructures, which we refer to as "nanowires", include single-crystalline homostructures as well as heterostructures of at least two single-crystalline materials having different chemical compositions. Because single-crystalline materials are used to form the heterostructure, the resultant heterostructure will be single-crystalline as well. The nanowire heterostructures are generally based on a semiconducting wire wherein the doping and composition are controlled in either the longitudinal or radial directions, or in both directions, to yield a wire that comprises different materials. Examples of resulting nanowire heterostructures include a longitudinal heterostructure nanowire (LOHN) and a coaxial heterostructure nanowire (COHN).

Methods of fabricating nanostructures and nanowires and devices fabricated therefrom

DOEpatents

Majumdar, Arun; Shakouri, Ali; Sands, Timothy D.; Yang, Peidong; Mao, Samuel S.; Russo, Richard E.; Feick, Henning; Weber, Eicke R.; Kind, Hannes; Huang, Michael; Yan, Haoquan; Wu, Yiying; Fan, Rong

2018-01-30

One-dimensional nanostructures having uniform diameters of less than approximately 200 nm. These inventive nanostructures, which we refer to as "nanowires", include single-crystalline homostructures as well as heterostructures of at least two single-crystalline materials having different chemical compositions. Because single-crystalline materials are used to form the heterostructure, the resultant heterostructure will be single-crystalline as well. The nanowire heterostructures are generally based on a semiconducting wire wherein the doping and composition are controlled in either the longitudinal or radial directions, or in both directions, to yield a wire that comprises different materials. Examples of resulting nanowire heterostructures include a longitudinal heterostructure nanowire (LOHN) and a coaxial heterostructure nanowire (COHN).

Using high pressure processing (HPP) to pretreat sugarcane bagasse.

PubMed

Castañón-Rodríguez, J F; Torrestiana-Sánchez, B; Montero-Lagunes, M; Portilla-Arias, J; Ramírez de León, J A; Aguilar-Uscanga, M G

2013-10-15

High pressure processing (HPP) technology was used to modify the structural composition of sugarcane bagasse. The effect of pressure (0, 150 and 250 MPa), time (5 and 10 min) and temperature (25 and 50 °C) as well as the addition of phosphoric acid, sulfuric acid and NaOH during the HPP treatment were assessed in terms of compositional analysis of the lignocellulosic fraction, structural changes and crystallinity of the bagasse. The effect of HPP pretreatment on the bagasse structure was also evaluated on the efficiency of the enzymatic hydrolysis of bagasse. Results showed that 68.62 and 45.84% of the hemicellulose fraction was degraded by pretreating at 250 MPa with sulfuric and phosphoric acids, respectively. The removal of lignin (54.10%) was higher with the HPP-NaOH treatment. The compacted lignocellulosic structure of the raw bagasse was modified by the HPP treatments and showed few cracks, tiny holes and some fragments flaked off from the surface. Structural changes were higher at 250 MPa and 50 °C. The X ray diffraction (XRD) patterns of the raw bagasse showed a major diffraction peak of the cellulose crystallographic 2θ planes ranging between 22 and 23°. The distribution of the crystalline structure of cellulose was affected by increasing the pressure level. The HPP treatment combined with NaOH 2% led to the higher glucose yield (25 g/L) compared to the combination of HPP with water and acids (>5 g/L). Results from this work suggest that HPP technology may be used to pretreat sugarcane bagasse. Copyright © 2013 Elsevier Ltd. All rights reserved.

Fabrication and Characterizations of Ethanol Sensor Based on CuO Nanoparticles.

PubMed

Al-Hadeethi, Yas; Umar, Ahmad; Kumar, Rajesh; Al-Heniti, Saleh H; Raffah, Bahaaudin M

2018-04-01

In this paper, we report the synthesis, characterization and ethanol sensing applications of CuO nanoparticles. The CuO nanoparticles were prepared by a facile, low-temperature hydrothermal method and characterized in detail in terms of their structural, morphological, compositional and crystalline properties, through different characterization techniques including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) attached with energy dispersive spectroscopy (EDS), and Fourier transform infrared (FTIR) spectroscopy. The detailed studies revealed that the synthesized CuO nanoparticles were well-crystalline and possessed monoclinic crystal structure. The synthesized CuO nanoparticles were utilized for the fabrication of highly sensitive ethanol gas sensor. At an optimized temperature of 320 °C, high sensitivity (Ra/Rg) of 39.29 was observed for 200 ppm of ethanol gas. Additionally, very low response (τres = 14 s) and recovery (τrec = 30 s) times were observed for 100 ppm of ethanol.

Solute segregation and deviation from bulk thermodynamics at nanoscale crystalline defects.

PubMed

Titus, Michael S; Rhein, Robert K; Wells, Peter B; Dodge, Philip C; Viswanathan, Gopal Babu; Mills, Michael J; Van der Ven, Anton; Pollock, Tresa M

2016-12-01

It has long been known that solute segregation at crystalline defects can have profound effects on material properties. Nevertheless, quantifying the extent of solute segregation at nanoscale defects has proven challenging due to experimental limitations. A combined experimental and first-principles approach has been used to study solute segregation at extended intermetallic phases ranging from 4 to 35 atomic layers in thickness. Chemical mapping by both atom probe tomography and high-resolution scanning transmission electron microscopy demonstrates a markedly different composition for the 4-atomic-layer-thick phase, where segregation has occurred, compared to the approximately 35-atomic-layer-thick bulk phase of the same crystal structure. First-principles predictions of bulk free energies in conjunction with direct atomistic simulations of the intermetallic structure and chemistry demonstrate the breakdown of bulk thermodynamics at nanometer dimensions and highlight the importance of symmetry breaking due to the proximity of interfaces in determining equilibrium properties.

Solute segregation and deviation from bulk thermodynamics at nanoscale crystalline defects

PubMed Central

Titus, Michael S.; Rhein, Robert K.; Wells, Peter B.; Dodge, Philip C.; Viswanathan, Gopal Babu; Mills, Michael J.; Van der Ven, Anton; Pollock, Tresa M.

2016-01-01

It has long been known that solute segregation at crystalline defects can have profound effects on material properties. Nevertheless, quantifying the extent of solute segregation at nanoscale defects has proven challenging due to experimental limitations. A combined experimental and first-principles approach has been used to study solute segregation at extended intermetallic phases ranging from 4 to 35 atomic layers in thickness. Chemical mapping by both atom probe tomography and high-resolution scanning transmission electron microscopy demonstrates a markedly different composition for the 4–atomic-layer–thick phase, where segregation has occurred, compared to the approximately 35–atomic-layer–thick bulk phase of the same crystal structure. First-principles predictions of bulk free energies in conjunction with direct atomistic simulations of the intermetallic structure and chemistry demonstrate the breakdown of bulk thermodynamics at nanometer dimensions and highlight the importance of symmetry breaking due to the proximity of interfaces in determining equilibrium properties. PMID:28028543

Crystal Graph Convolutional Neural Networks for an Accurate and Interpretable Prediction of Material Properties

NASA Astrophysics Data System (ADS)

Xie, Tian; Grossman, Jeffrey C.

2018-04-01

The use of machine learning methods for accelerating the design of crystalline materials usually requires manually constructed feature vectors or complex transformation of atom coordinates to input the crystal structure, which either constrains the model to certain crystal types or makes it difficult to provide chemical insights. Here, we develop a crystal graph convolutional neural networks framework to directly learn material properties from the connection of atoms in the crystal, providing a universal and interpretable representation of crystalline materials. Our method provides a highly accurate prediction of density functional theory calculated properties for eight different properties of crystals with various structure types and compositions after being trained with 1 04 data points. Further, our framework is interpretable because one can extract the contributions from local chemical environments to global properties. Using an example of perovskites, we show how this information can be utilized to discover empirical rules for materials design.

Flexible regenerated cellulose/polypyrrole composite films with enhanced dielectric properties.

PubMed

Raghunathan, Sreejesh Poikavila; Narayanan, Sona; Poulose, Aby Cheruvathur; Joseph, Rani

2017-02-10

Flexible regenerated cellulose/polypyrrole (RC-PPy) conductive composite films were prepared by insitu polymerization of pyrrole on regenerated cellulose (RC) matrix using ammonium persulphate as oxidant. FTIR, XPS and XRD analysis of RC-PPy composite films revealed strong interaction between polypyrrole (PPy) and RC matrix. XRD results indicated that crystalline structure of RC matrix remains intact even after composite formation. SEM micrographs revealed the formation of a continuous conductive network of PPy particles in the RC matrix, leading to significant improvement in electrical and dielectric properties. The electrical conductivity of RC-PPy composites with 12wt% of PPy was 3.2×10 -5 S/cm, which is approximately seven fold higher than that of RC. Composites showed high dielectric constant and low dielectric loss values, which is essential in capacitor application. Copyright © 2016 Elsevier Ltd. All rights reserved.

Comparative static curing versus dynamic curing on tablet coating structures.

PubMed

Gendre, Claire; Genty, Muriel; Fayard, Barbara; Tfayli, Ali; Boiret, Mathieu; Lecoq, Olivier; Baron, Michel; Chaminade, Pierre; Péan, Jean Manuel

2013-09-10

Curing is generally required to stabilize film coating from aqueous polymer dispersion. This post-coating drying step is traditionally carried out in static conditions, requiring the transfer of solid dosage forms to an oven. But, curing operation performed directly inside the coating equipment stands for an attractive industrial application. Recently, the use of various advanced physico-chemical characterization techniques i.e., X-ray micro-computed tomography, vibrational spectroscopies (near infrared and Raman) and X-ray microdiffraction, allowed new insights into the film-coating structures of dynamically cured tablets. Dynamic curing end-point was efficiently determined after 4h. The aim of the present work was to elucidate the influence of curing conditions on film-coating structures. Results demonstrated that 24h of static curing and 4h of dynamic curing, both performed at 60°C and ambient relative humidity, led to similar coating layers in terms of drug release properties, porosity, water content, structural rearrangement of polymer chains and crystalline distribution. Furthermore, X-ray microdiffraction measurements pointed out different crystalline coating compositions depending on sample storage time. An aging mechanism might have occur during storage, resulting in the crystallization and the upward migration of cetyl alcohol, coupled to the downward migration of crystalline sodium lauryl sulfate within the coating layer. Interestingly, this new study clearly provided further knowledge into film-coating structures after a curing step and confirmed that curing operation could be performed in dynamic conditions. Copyright © 2013 Elsevier B.V. All rights reserved.

Crystallinity and compositional changes in carbonated apatites: Evidence from 31P solid-state NMR, Raman, and AFM analysis

NASA Astrophysics Data System (ADS)

McElderry, John-David P.; Zhu, Peizhi; Mroue, Kamal H.; Xu, Jiadi; Pavan, Barbara; Fang, Ming; Zhao, Guisheng; McNerny, Erin; Kohn, David H.; Franceschi, Renny T.; Holl, Mark M. Banaszak; Tecklenburg, Mary M. J.; Ramamoorthy, Ayyalusamy; Morris, Michael D.

2013-10-01

Solid-state (magic-angle spinning) NMR spectroscopy is a useful tool for obtaining structural information on bone organic and mineral components and synthetic model minerals at the atomic-level. Raman and 31P NMR spectral parameters were investigated in a series of synthetic B-type carbonated apatites (CAps). Inverse 31P NMR linewidth and inverse Raman PO43-ν1 bandwidth were both correlated with powder XRD c-axis crystallinity over the 0.3-10.3 wt% CO32- range investigated. Comparison with bone powder crystallinities showed agreement with values predicted by NMR and Raman calibration curves. Carbonate content was divided into two domains by the 31P NMR chemical shift frequency and the Raman phosphate ν1 band position. These parameters remain stable except for an abrupt transition at 6.5 wt% carbonate, a composition which corresponds to an average of one carbonate per unit cell. This near-binary distribution of spectroscopic properties was also found in AFM-measured particle sizes and Ca/P molar ratios by elemental analysis. We propose that this transition differentiates between two charge-balancing ion-loss mechanisms as measured by Ca/P ratios. These results define a criterion for spectroscopic characterization of B-type carbonate substitution in apatitic minerals.

X-Ray Absorption Spectroscopy of Fe-Substituted Allophane and Imogolite

NASA Astrophysics Data System (ADS)

Baker, L. L.; Strawn, D. G.; Nickerson, R. D.; McDaniel, P.

2011-12-01

Martian rocks and sediments contain weathering products including clay minerals formed as a result of interaction between rocks and water, and these materials can act as important indicators of past surface conditions on Mars. Weathering of terrestrial volcanic rocks similar to those on Mars produces nano-sized, variably hydrated aluminosilicate and iron oxide minerals, including allophane, imogolite, halloysite, hisingerite, and ferrihydrite. The nanoaluminosilicates can contain isomorphically substituted Fe, which may affect their spectral and physical properties as well as their eventual recrystallization products. Detection and quantification of such minerals in natural environments on Earth is difficult due to their variable chemical composition and lack of long-range crystalline order. Their accurate detection and quantification on Mars requires a better understanding of how composition affects their spectral properties and evolution to more crystalline phases. Aluminosilicate nanoparticles of varying composition were synthesized with isomorphically substituted Fe at Fe:Al ratios of 1:100. Allophanes were synthesized with Al:Si ratios of 2:1, 1:1, and 1:3. The substituted Fe was probed using Fe K-edge X-ray absorption fine structure spectroscopy (XAFS). The XAFS spectrum contains information about the molecular environment surrounding the target atom, and is an ideal technique for studying poorly crystalline materials that are difficult to characterize using bulk methods such as XRD. The near-edge (XANES) and extended (EXAFS) portions of the XAFS spectrum were examined, and allophane backscattering paths were fit using coordinates for a modified nanoball model (1). XANES spectra rule out ferrihydrite in the synthetic samples, suggesting all Fe was incorporated into the aluminosilicate structure. The XAFS results suggest that Fe substituted into the allophane structure is present as Fe(III) in octahedral coordination in a well-ordered sheet. Some Fe substitution in tetrahedral sites occurs in allophane with Al:Si = 2:1, but not in higher-Si compositions. These results support the nanoball model for allophane (1) based on a rolled octahedral sheet and indicate that sheet is well ordered. They do not support proposed models of an incomplete octahedral sheet in high-Si allophanes. Analysis of Fe distribution suggests considerable Fe clustering in the octahedral sheet which increases with sample aging. This clustering could lead to eventual nucleation of a separate Fe (oxyhydr)oxide phase. (1) Creton et al. (2008) J Phys Chem C 112, 358.

In vitro investigation of oxide nanoparticle and carbon nanotube toxicity and intracellular accumulation in A549 human pneumocytes.

PubMed

Simon-Deckers, A; Gouget, B; Mayne-L'hermite, M; Herlin-Boime, N; Reynaud, C; Carrière, M

2008-11-20

If released in the environment, nanomaterials might be inhaled by populations and cause damage to the deepest regions of the respiratory tract, i.e., the alveolar compartment. To model this situation, we studied the response of A549 human pneumocytes after exposure to aluminium oxide or titanium oxide nanoparticles, and to multi-walled carbon nanotubes. The influence of size, crystalline structure and chemical composition was investigated. After a detailed identification of nanomaterial physico-chemical characteristics, cells were exposed in vitro and viability and intracellular accumulation were assessed. In our conditions, carbon nanotubes were more toxic than metal oxide nanoparticles. Our results confirmed that both nanotubes and nanoparticles are able to rapidly enter into cells, and distribute in the cytoplasm and intracellular vesicles. Among nanoparticles, we demonstrate significant difference in biological response as a function of size, crystalline phase and chemical composition. Their toxicity was globally lower than nanotubes toxicity. Among nanotubes, the length did not influence cytotoxicity, neither the presence of metal catalyst impurities.

Electrical and Magnetic Properties of Binary Amorphous Transition Metal Alloys.

NASA Astrophysics Data System (ADS)

Liou, Sy-Hwang

The electrical, superconductive and magnetic properties of several binary transition metal amorphous and metastable crystalline alloys, Fe(,x)Ti(,100-x) (30 (LESSTHEQ) x (LESSTHEQ) 100), Fe(,x)Zr(,100-x) (20 (LESSTHEQ) x (LESSTHEQ) 93), Fe(,x)Hf(,100-x) (20 (LESSTHEQ) x (LESSTHEQ) 100), Fe(,x)Nb(,100 -x) (22 (LESSTHEQ) x (LESSTHEQ) 85), Ni(,x)Nb(,100-x) (20 (LESSTHEQ) x (LESSTHEQ) 80), Cu(,x)Nb(,100-x) (10 (LESSTHEQ) x (LESSTHEQ) 90) were studied over a wide composition range. Films were made using a magnetron sputtering system, and the structure of the films was investigated by energy dispersive x-ray diffraction. The composition region of each amorphous alloys system was determined and found in good agreement with a model proposed by Egami and Waseda. The magnetic properties and hyperfine interactions in the films were investigated using a conventional Mossbauer spectrometer and a ('57)Co in Rh matrix source. In all Fe-early transition metal binary alloys systems, Fe does not retain its moment in the low iron concentration region and the result is that the critical concentration for magnetic order (x(,c)) is much larger than anticipated from percolation considerations. A direct comparison between crystalline alloys and their amorphous counterparts of the same composition illustrate no clear correlation between crystalline and amorphous states. Pronounced discontinuities in the magnetic properties with variation in Fe content of all Fe-early transition metal alloys at phase boundaries separating amorphous and crystalline states have been observed. This is caused by the differences in the atomic arrangement and the electronic structure between crystalline and amorphous solids. The temperature dependence of resistivity, (rho)(T), of several binary amorphous alloys of Fe-TM (where TM = Ti, Zr, Hf, Nb etc.) has been studied from 2K to 300K. The Fe-poor (x < x(,c)) samples and the Fe-rich (x > x(,c)) samples have distinctive differences in (rho)(T) at low temperature (below 30K). All the magnetic samples show a logarithmic dependence at low temperature that can be described by Kondo scattering. In addition, there is a change in slope of (rho)(T) at a temperature close to the magnetic ordering temperature, indicating a contribution attributed to magnetic ordering. Several Nb-based amorphous alloys (Fe-Nb, Ni-Nb, Cu-Nb) have also been systematically studied. The effect of the magnetic species on superconductivity is investigated. The value of superconducting transition temperature (T(,s)) increases linearly with increasing Nb concentration. (Abstract shortened with permission of author.).

Growth and characterization of n-AlGaN 1-D structures with varying Al composition using u-GaN seeds

NASA Astrophysics Data System (ADS)

Kang, San; Chatterjee, Uddipta; Um, Dae-Young; Seo, In Seok; Lee, Cheul-Ro

2017-12-01

Like all the ternary alloys in III-nitride materials family, aluminum gallium nitride (AlGaN) has unique band gap tuning property which enables the alloy to be suitable for many opto-electronic applications. The direct band gap of AlGaN can be tuned from 3.4 to 6.2 eV by changing the composition. In this article, the growth of ternary n-AlGaN micro and nano structures on Si (1 1 1) substrate is demonstrated via 2-step growth method employing metal organic chemical vapor deposition. During the growth flow of Trimethygallium is varied to modulate the final Al/Ga ratio. After the growth, various morphological, crystalline and optical characterizations are carried out to probe in the properties of the grown structures. Recorded X-ray diffraction patterns reveal that the realized structures are wurtzite single crystalline n-AlGaN having a near homogeneous Al distribution and validated by energy dispersive X-ray spectroscopy. Low temperature cathodoluminescence spectra show band edge emission in deep UV region which enables the grown n-AlGaN structures to efficiently find opto-electronic applications in the aforementioned region. Finally, planar photoconductive devices are fabricated using the grown 1-D structures and photocurrent evolution is measured. Structure bearing highest Al content shows a manifold enhancement in photo activity compared to other grown samples. Absolute photoresponsivities of the grown samples are calculated to be 301.47, 116 and 38.13 mA/W which is in accord with the findings of low temperature cathodoluminescence investigation. Therefore, it can be concluded that the successful realization of n-AlGaN 1-D structures varying Al content facilitates the further developments of the field concerning nano- and opto-electronic devices.

Synthesis, structural, characterization and dielectric spectroscopy of PVDF - BaTiO3 polymer composite

NASA Astrophysics Data System (ADS)

Kulkarni, S. S.; Belavi, P. B.; Khadke, U. V.

2018-05-01

In this paper we report the method of synthesis of ferroelectric polymer Polyvinyldene fluoride (PVDF) and Barium Titanate (BaTiO3) composite self supporting thin films and its dielectric response. BaTiO3 was synthesized by solid state reaction method. The PVDF - BaTiO3 polymer composites with various concentrations were synthesized by solution mixing method using Dimethylformadide (DMF) as a solvent. The phase transformation and surface methodology of the prepared composites were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) respectively. The XRD pattern confirms the formation of tetragonal pervoskite structure of ferroelectric phase. The XRD pattern shows the proper mixing of BaTiO3 particles intestinally and found to be improving its crystallinity with increase of BaTiO3 composition in the PVDF matrix. The dielectric properties of the composites as a function of frequency were computed using impedance analyzer. The dielectric constant decreases with increase of frequency shows the Maxwell - Wagner type of interfacial polarization in accordance with Koop's phenomenological theory.

Effect of modification of isotactic polypropylene by additives of polyamide 6/66 on structural characteristics of composites

NASA Astrophysics Data System (ADS)

Vorontsov, N. V.; Popov, A. A.; Margolin, A. L.

2017-12-01

Changes in the supramolecular structure of polymer composites based on isotactic polypropylene (PP) and polyamide 6/66 (PA) are studied depending on the PP : PA ratio. Temperatures and enthalpies of melting and crystallization of both PP and PA and their composites are determined depending on the composition of the mixtures. It was shown that the initial melting point of a composite does not change with increasing PA content in the blends. The crystallization temperature of the mixtures is shown to increase with the addition of PA and becomes much higher than the crystallization temperatures of both PP and PA. The observed effect can be due to a strong interaction between the PP and PA molecules, thus decreasing the molecular mobility and increasing the crystallization temperature. The crystallization and melting of PP-PA mixtures are found to proceed at the close temperatures, although the crystallization and melting temperatures of pure PP and pure PA differ widely. The melting and crystallization enthalpies decrease with increasing PA concentration in the mixtures, which indicates a decrease in the degree of crystallinity of the composite.

Investigation of crystalline structure of plasticized poly (lactic acid)/Banana nanofibers composites

NASA Astrophysics Data System (ADS)

Farid, T.; Herrera, V. N.; Kristiina, O.

2018-05-01

Polylactic acid (PLA) is a promising biodegradable candidate to replace synthetic commodity plastics in many applications. However, this polymer shows high brittleness, slow rate and lower degree of crystallization. The addition of plasticizing agents can enhance the toughness, but its effects on the crystallization behavior remain inconclusive. Therefore, this research is aiming to cast light on this area. Using differential scanning calorimetry (DSC) at a 2°C/min cooling rate, extruded neat PLA samples showed lower degree of crystallinity and thermal stability. This material shows cold crystallization upon heating and does recrystallize prior melting. These results indicate a clear instability in the crystalline state are confirmed by the crystallographic results by the X-ray diffractions (XRD) pattern and atomic force microscopic imagery. The addition of around 20 wt% of glycerol triacetate (GTA) with 1wt% of banana nanofibers (BNF) almost doubled the crystallinity. This modification is believed to occur through a dilution mechanism in order to increase crystallization rate yielding a more stable crystalline structure as shown by the XRD. However, the dynamic mechanical thermal analysis (DMTA) showed a 30 to 50% reduction in the room temperature storage modulus (stiffness) is in plasticized samples when compared to neat 100% PLA. Although these results shows the possibility to enhance the crystallization through a combination of plasticizing and nanoreinforcing effects, further studies is still needed to optimize the material formulation in order to find the best ratios to secure both a good crystallization and mechanical properties. This will definitively result in a new material that can be used for current and futuristic applications.

Tracking Sodium-Antimonide Phase Transformations in Sodium-Ion Anodes: Insights from Operando Pair Distribution Function Analysis and Solid-State NMR Spectroscopy

DOE PAGES

Allan, Phoebe K.; Griffin, John M.; Darwiche, Ali; ...

2016-01-29

We use operando pair distribution function (PDF) analysis and ex situ 23Na magic-angle spinning solid-state nuclear magnetic resonance (MAS ssNMR) spectroscopy to gain insight into the alloying mechanism of high-capacity antimony anodes for sodium-ion batteries. Subtraction of the PDF of crystalline Na xSb phases from the total PDF, an approach constrained by chemical phase information gained from 23Na ssNMR in reference to relevant model compounds, identifies two previously uncharacterized intermediate species formed electrochemically; a-Na 3–xSb (x ≈ 0.4–0.5), a structure locally similar to crystalline Na 3Sb (c-Na 3Sb) but with significant numbers of sodium vacancies and a limited correlation length,more » and a-Na1.7Sb, a highly amorphous structure featuring some Sb–Sb bonding. The first sodiation breaks down the crystalline antimony to form first a-Na 3–xSb and, finally, crystalline Na 3Sb. Desodiation results in the formation of an electrode formed of a composite of crystalline and amorphous antimony networks. We link the different reactivity of these networks to a series of sequential sodiation reactions manifesting as a cascade of processes observed in the electrochemical profile of subsequent cycles. The amorphous network reacts at higher voltages reforming a-Na 1.7Sb, then a-Na 3–xSb, whereas lower potentials are required for the sodiation of crystalline antimony, which reacts to form a-Na 3–xSb without the formation of a-Na 1.7Sb. a-Na 3–xSb is converted to crystalline Na 3Sb at the end of the second discharge. In the end, we find no evidence of formation of NaSb. Variable temperature 23Na NMR experiments reveal significant sodium mobility within c-Na 3Sb; this is a possible contributing factor to the excellent rate performance of Sb anodes.« less

Tracking Sodium-Antimonide Phase Transformations in Sodium-Ion Anodes: Insights from Operando Pair Distribution Function Analysis and Solid-State NMR Spectroscopy

PubMed Central

2016-01-01

Operando pair distribution function (PDF) analysis and ex situ 23Na magic-angle spinning solid-state nuclear magnetic resonance (MAS ssNMR) spectroscopy are used to gain insight into the alloying mechanism of high-capacity antimony anodes for sodium-ion batteries. Subtraction of the PDF of crystalline NaxSb phases from the total PDF, an approach constrained by chemical phase information gained from 23Na ssNMR in reference to relevant model compounds, identifies two previously uncharacterized intermediate species formed electrochemically; a-Na3–xSb (x ≈ 0.4–0.5), a structure locally similar to crystalline Na3Sb (c-Na3Sb) but with significant numbers of sodium vacancies and a limited correlation length, and a-Na1.7Sb, a highly amorphous structure featuring some Sb–Sb bonding. The first sodiation breaks down the crystalline antimony to form first a-Na3–xSb and, finally, crystalline Na3Sb. Desodiation results in the formation of an electrode formed of a composite of crystalline and amorphous antimony networks. We link the different reactivity of these networks to a series of sequential sodiation reactions manifesting as a cascade of processes observed in the electrochemical profile of subsequent cycles. The amorphous network reacts at higher voltages reforming a-Na1.7Sb, then a-Na3–xSb, whereas lower potentials are required for the sodiation of crystalline antimony, which reacts to form a-Na3–xSb without the formation of a-Na1.7Sb. a-Na3–xSb is converted to crystalline Na3Sb at the end of the second discharge. We find no evidence of formation of NaSb. Variable temperature 23Na NMR experiments reveal significant sodium mobility within c-Na3Sb; this is a possible contributing factor to the excellent rate performance of Sb anodes. PMID:26824406

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

Allan, Phoebe K.; Griffin, John M.; Darwiche, Ali

We use operando pair distribution function (PDF) analysis and ex situ 23Na magic-angle spinning solid-state nuclear magnetic resonance (MAS ssNMR) spectroscopy to gain insight into the alloying mechanism of high-capacity antimony anodes for sodium-ion batteries. Subtraction of the PDF of crystalline Na xSb phases from the total PDF, an approach constrained by chemical phase information gained from 23Na ssNMR in reference to relevant model compounds, identifies two previously uncharacterized intermediate species formed electrochemically; a-Na 3–xSb (x ≈ 0.4–0.5), a structure locally similar to crystalline Na 3Sb (c-Na 3Sb) but with significant numbers of sodium vacancies and a limited correlation length,more » and a-Na1.7Sb, a highly amorphous structure featuring some Sb–Sb bonding. The first sodiation breaks down the crystalline antimony to form first a-Na 3–xSb and, finally, crystalline Na 3Sb. Desodiation results in the formation of an electrode formed of a composite of crystalline and amorphous antimony networks. We link the different reactivity of these networks to a series of sequential sodiation reactions manifesting as a cascade of processes observed in the electrochemical profile of subsequent cycles. The amorphous network reacts at higher voltages reforming a-Na 1.7Sb, then a-Na 3–xSb, whereas lower potentials are required for the sodiation of crystalline antimony, which reacts to form a-Na 3–xSb without the formation of a-Na 1.7Sb. a-Na 3–xSb is converted to crystalline Na 3Sb at the end of the second discharge. In the end, we find no evidence of formation of NaSb. Variable temperature 23Na NMR experiments reveal significant sodium mobility within c-Na 3Sb; this is a possible contributing factor to the excellent rate performance of Sb anodes.« less

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

Allan, Phoebe K.; Griffin, John M.; Darwiche, Ali

Operando pair distribution function (PDF) analysis and ex situ Na-23 magic-angle spinning solid-state nuclear magnetic resonance (MAS ssNMR) spectroscopy are used to gain insight into the alloying mechanism of high-capacity antimony anodes for sodium-ion batteries. Subtraction of the PDF of crystalline NaxSb phases from the total PDF, an approach constrained by chemical phase information gained from Na-23 ssNMR in reference to relevant model compounds, identifies two previously uncharacterized intermediate species formed electro-chemically; a-Na3-xSb (x approximate to 0.4-0.5), a structure locally similar to crystalline Na3Sb (c-Na3Sb) but with significant numbers of sodium vacancies and a limited correlation length, and a-Na1.7Sb, amore » highly amorphous structure featuring some Sb-Sb bonding. The first sodiation breaks down the crystalline antimony to form first a-Na3-xSb and, finally, crystalline Na3Sb. Desodiation results in the formation of an electrode formed of a composite of crystalline and amorphous antimony networks. We link the different reactivity of these networks to a series of sequential sodiation reactions manifesting as a cascade of processes observed in the electrochemical profile of subsequent cycles. The amorphofis network reacts at higher voltages reforming a-Na1.7Sb, then a-Na3-xSb, whereas lower potentials are required for the sodiation of crystalline antimony, which reacts to form a-Na3-xSb without the formation of a-Na3-xSb. a-Na3-xSb is converted to crystalline Na3Sb at the end of the second discharge. We find no evidence of formation of NaSb. Variable temperature Na-23 NMR experiments reveal significant sodium mobility within c-Na3Sb; this is a possible contributing factor to the excellent rate performance of Sb anodes.« less

Dynamic and Structure of Polymer-Cellulose Composite Electrolyte for Li-ion Battery

NASA Astrophysics Data System (ADS)

Zhan, Pengfei; Maranas, Janna

Crystalline PEO6LiX complex is a tunnel-like polymer/salt structure that promotes fast Li motion. The application is limited because high ion conductivity is only observed with short molecular weight PEO, as the molecular weight increase, tunnels are misaligned and the conductivity is decreased. High aspect ratio nanofillers based on cellulose nanowhiskers are hypothesized to promote the formation of tunnel structures. Compared with unfilled electrolyte, the room temperature ion conductivity increased as much as 1100% in filled electrolyte. With wide angle x-ray scattering (WAXS), we observe that the structure transitions from amorphous phase to crystalline phase as we add cellulose nanowhiskers and this is because the interaction between cellulose surface and polymer chain enhances the crystallization. From the temperature dependence of conductivity, the calculated Li+ hopping activation energy is shown to be lower in acidic cellulose nanowhisker filled samples. Our quasi-elastic neutron scattering (QENS) indicates with acidic surface, the rotation of PEO6 channels are more stabilized and this could be the origin of the low activation energy and high conductivity

Positron annihilation lifetime spectroscopy (PALS) as a characterization technique for nanostructured self-assembled amphiphile systems.

PubMed

Dong, Aurelia W; Pascual-Izarra, Carlos; Pas, Steven J; Hill, Anita J; Boyd, Ben J; Drummond, Calum J

2009-01-08

Positron annihilation lifetime spectroscopy (PALS) has potential as a novel rapid characterization method for self-assembly amphiphile systems; however, a lack of systematic correlation of PALS parameters with structural attributes has limited its more widespread application. In this study, using the well-characterized phytantriol/water and the phytantriol/vitamin E acetate/water self-assembly amphiphile systems, the impact of systematic structural changes controlled by changes in composition and temperature on PALS parameters has been studied. The PALS parameters (orthopositronium (oPs) lifetime and intensity signatures) were shown to be sensitive to the molecular packing and mobility of the self-assembled lipid molecules in various lyotropic liquid crystalline phases, enabling differentiation between liquid crystalline structures. The oPs lifetime, related to the molecular packing and mobility, is correlated with rheological properties of the individual mesophases. The oPs lifetime links the lipid chain packing and mobility in the various mesophases to resultant macroscopic properties, such as permeability, which is critical for the use of these mesophase structures as diffusion-controlled release matrices for active liposoluble compounds.

Structure of New Zealand sweetpotato starch.

PubMed

Zhu, Fan; Xie, Qian

2018-05-15

New Zealand sweetpotatoes (kumara) (Ipomoea batatas) represent unique genetic resources for sweetpotato diversity, though they are much under-studied. In this study, 7 New Zealand sweetpotato varieties with commercial significance were collected for the characterization of the molecular and granular structure of the starches. In particular, the internal molecular structure of the amylopectins was detailed by chromatographic and enzymatic techniques. Maize and potato starches with normal amylose contents, which are among the most important commercial starch sources, were employed for comparison. The results revealed a degree of diversity in amylose composition, unit and internal chain composition, granule size distribution, and degree of crystallinity among the 7 sweetpotato starches. All the sweetpotato starches showed C A -type polymorph. The sweetpotato amylopectins have intermediate amounts of both short and long internal unit chains among amylopectins of different botanical sources. The differences in the structure of sweetpotato starches suggest differences in physicochemical properties. Copyright © 2018 Elsevier Ltd. All rights reserved.

Demixing by a Nematic Mean Field: Coarse-Grained Simulations of Liquid Crystalline Polymers

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

Ramírez-Hernández, Abelardo; Hur, Su-Mi; Armas-Pérez, Julio

2017-03-01

Liquid crystalline polymers exhibit a particular richness of behaviors that stems from their rigidity and their macromolecular nature. On the one hand, the orientational interaction between liquid-crystalline motifs promotes their alignment, thereby leading to the emergence of nematic phases. On the other hand, the large number of configurations associated with polymer chains favors formation of isotropic phases, with chain stiffness becoming the factor that tips the balance. In this work, a soft coarse-grained model is introduced to explore the interplay of chain stiffness, molecular weight and orientational coupling, and their role on the isotropic-nematic transition in homopolymer melts. We alsomore » study the structure of polymer mixtures composed of stiff and flexible polymeric molecules. We consider the effects of blend composition, persistence length, molecular weight and orientational coupling strength on the melt structure at the nano-and mesoscopic levels. Conditions are found where the systems separate into two phases, one isotropic and the other nematic. We confirm the existence of non-equilibrium states that exhibit sought-after percolating nematic domains, which are of interest for applications in organic photovoltaic and electronic devices.« less

Relationship Between Crystalline Structure and Hardness of Ti-Si-N-O Coatings Fabricated by dc Sputtering

NASA Astrophysics Data System (ADS)

García-González, Leandro; Hernández-Torres, Julián; Mendoza-Barrera, Claudia; Meléndez-Lira, Miguel; García-Ramírez, Pedro J.; Martínez-Castillo, Jaime; Sauceda, Ángel; Herrera-May, Agustin L.; Muñoz Saldaña, Juan; Espinoza-Beltrán, Francisco J.

2008-08-01

Ti-Si-N-O coatings were deposited on AISI D2 tool steel and silicon substrates by dc reactive magnetron co-sputtering using a target of Ti-Si with a constant area ratio of 0.2. The substrate temperature was 400 °C and reactive atmosphere of nitrogen and argon. For all samples, argon flow was maintained constant at 25 sccm, while the flow of the nitrogen was varied to analyze the structural changes related to chemical composition and resistivity. According to results obtained by x-ray diffraction and stoichiometry calculations by x-ray energy dispersive spectroscopy the Ti-Si-N-O coatings contain two solid solutions. The higher crystalline part corresponds to titanium oxynitrure. Hardness tests on the coatings were carried out using the indentation work model and the hardness value was determined. Finally, the values of hardness were corroborated by nanoindentation test, and values of Young’s modulus and elastic recovery were discussed. We concluded that F2TSN sample ( F Ar = 25 sccm, F N = 5 sccm, P = 200 W, and P W = 8.9 × 10-3 mbar) presented the greatest hardness and the lowest resistivity values, due to its preferential crystalline orientation.

Single crystalline wurtzite ZnO/zinc blende ZnS coaxial heterojunctions and hollow zinc blende ZnS nanotubes: synthesis, structural characterization and optical properties.

PubMed

Huang, Xing; Willinger, Marc-Georg; Fan, Hua; Xie, Zai-lai; Wang, Lei; Klein-Hoffmann, Achim; Girgsdies, Frank; Lee, Chun-Sing; Meng, Xiang-Min

2014-08-07

Synthesis of ZnO/ZnS heterostructures under thermodynamic conditions generally results in the wurtzite (WZ) structure of the ZnS component because its WZ phase is thermodynamically more stable than its zinc blende (ZB) phase. In this report, we demonstrate for the first time the preparation of ZnO/ZnS coaxial nanocables composed of single crystalline ZB structured ZnS epitaxially grown on WZ ZnO via a two-step thermal evaporation method. The deposition temperature is believed to play a crucial role in determining the crystalline phase of ZnS. Through a systematic structural analysis, the ZnO core and the ZnS shell are found to have an orientation relationship of (0002)ZnO(WZ)//(002)ZnS(ZB) and [01-10]ZnO(WZ)//[2-20]ZnS(ZB). Observation of the coaxial nanocables in cross-section reveals the formation of voids between the ZnO core and the ZnS shell during the coating process, which is probably associated with the nanoscale Kirkendall effect known to result in porosity. Furthermore, by immersing the ZnO/ZnS nanocable heterojunctions in an acetic acid solution to etch away the inner ZnO cores, single crystalline ZnS nanotubes orientated along the [001] direction of the ZB structure were also achieved for the first time. Finally, optical properties of the hollow ZnS tubes were investigated and discussed in detail. We believe that our study could provide some insights into the controlled fabrication of one dimensional (1D) semiconductors with desired morphology, structure and composition at the nanoscale, and the synthesized WZ ZnO/ZB ZnS nanocables as well as ZB ZnS nanotubes could be ideal candidates for the study of optoelectronics based on II-VI semiconductors.

Orientation dependences of atomic structures in chemically heterogeneous Cu{sub 50}Ta{sub 50}/Ta glass-crystal interfaces

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

Yang, Guiqin; Gao, Xiaoze; Li, Jinfu

2015-01-07

Molecular dynamics simulations based on an angular-dependent potential were performed to examine the structural properties of chemically heterogeneous interfaces between amorphous Cu{sub 50}Ta{sub 50} and crystalline Ta. Several phenomena, namely, layering, crystallization, intermixing, and composition segregation, were observed in the Cu{sub 50}Ta{sub 50} region adjacent to the Ta layers. These interfacial behaviors are found to depend on the orientation of the underlying Ta substrate: Layering induced by Ta(110) extends the farthest into Cu{sub 50}Ta{sub 50}, crystallization in the Cu{sub 50}Ta{sub 50} region is most significant for interface against Ta(100), while inter-diffusion is most pronounced for Ta(111). It turns out thatmore » the induced layering behavior is dominated by the interlayer distances of the underlying Ta layers, while the degree of inter-diffusion is governed by the openness of the Ta crystalline layers. In addition, composition segregations are observed in all interface models, corresponding to the immiscible nature of the Cu-Ta system. Furthermore, Voronoi polyhedra 〈0,5,2,6〉 and 〈0,4,4,6〉 are found to be abundant in the vicinity of the interfaces for all models, whose presence is believed to facilitate the structural transition between amorphous and body centered cubic.« less

Reduced graphene oxide-germanium quantum dot nanocomposite: electronic, optical and magnetic properties

NASA Astrophysics Data System (ADS)

Amollo, Tabitha A.; Mola, Genene T.; Nyamori, Vincent O.

2017-12-01

Graphene provides numerous possibilities for structural modification and functionalization of its carbon backbone. Localized magnetic moments can, as well, be induced in graphene by the formation of structural defects which include vacancies, edges, and adatoms. In this work, graphene was functionalized using germanium atoms, we report the effect of the Ge ad atoms on the structural, electrical, optical and magnetic properties of graphene. Reduced graphene oxide (rGO)-germanium quantum dot nanocomposites of high crystalline quality were synthesized by the microwave-assisted solvothermal reaction. Highly crystalline spherical shaped germanium quantum dots, of diameter ranging between 1.6-9.0 nm, are anchored on the basal planes of rGO. The nanocomposites exhibit high electrical conductivity with a sheet resistance of up to 16 Ω sq-1. The electrical conductivity is observed to increase with the increase in Ge content in the nanocomposites. High defect-induced magnetization is attained in the composites via germanium adatoms. The evolution of the magnetic moments in the nanocomposites and the coercivity showed marked dependence on the Ge quantum dots size and concentration. Quantum confinement effects is evidenced in the UV-vis absorbance spectra and photoluminescence emission spectra of the nanocomposites which show marked size-dependence. The composites manifest strong absorption in the UV region, strong luminescence in the near UV region, and a moderate luminescence in the visible region.

Nano-crystalline phase evolution and structural modification in Co/V substituted Li2O-Bi2O3-B2O3 glasses

NASA Astrophysics Data System (ADS)

Yadav, Arti; Dahiya, M. S.; Hooda, A.; Agarwal, A.; Khasa, S.

2018-05-01

Co/V substituted Li2O-Bi2O3-B2O3 glasses having composition 7CoO•23Li2O•20Bi2O3•50B2O3(CLBB) and xCoO•(30-x)Li2O•20Bi2O3•50B2O3(x = 0.0, 2.0, 5.0, 7.0 and 10.0 mol%, CVLBB1-5 respectively) developed via melt- quench route. The effect of annealing on structural properties of prepared samples was investigated by using XRD patterns and FTIR spectroscopy. Glasses annealed at 400˚C remained amorphous whereas glasses annealed at 500˚C changes from glasses to glass ceramics. The different crystalline phases i.e. Bi2(V0.9Co0.1)O5.25, LiCoVO4, V2O5 & Bi2(VO5) evolve on annealing at 500°C for 6 hours confirmed from the corresponding XRD patterns. The crystallite size of prepared samples were found to vary as 38-60nm This indicated that CoO and V2O5 introduced in matrix act as crystallizing agents and cause structural modification as studied by the FTIR spectra for all heat treated compositions.

Liquid crystalline composites toward organic photovoltaic application (Conference Presentation)

NASA Astrophysics Data System (ADS)

Shimizu, Yo; Sosa-Vargas, Lydia; Shin, Woong; Higuchi, Yumi; Itani, Hiromichi; Kawano, Koki; Dao, Quang Duy; Fujii, Akihiko; Ozaki, Masanori

2017-02-01

Liquid crystalline semiconductor is an interesting category of organic electronic materials and also has been extensively studied in terms of "Printed Electronics". For the wider diversity in research toward new applications, one can consider how to use a combination of miscibility and phase separation in liquid crystals. Here we report discotic liquid crystals in making a composite of which structural order is controlled in nano-scale toward photovoltaic applications. Discotic columnar LCs were studied on their resultant molecular order and carrier transport properties. Liquid crystals of phthalocyanine and its analogues which exhibit columnar mesomorphism with high carrier mobility (10-1 cm2/Vs) were examined with making binary phase diagrams and the correlation to carrier transport properties by TOF measurements was discussed. The shape-analogues in chemical structure shows a good miscibility even for the different lattice-type of columnar arrangement and the carrier mobility is mostly decrease except for a case of combination with a metal-free and the metal complex. For the mixtures with non-mesogenic C60 derivatives, one sees a phase-separated structure due to its immiscibility, though the columnar order is remained in a range of component ratio.Especially, in a range of the ratio, it was observed the phase separated C60 derivatives are fused into the matrix of columnar bundles, indicating C60 derivatives could be diffused in columnar arrays in molecular level.

Nonlinear optical properties of metal alkanoate composites with hybrid core/shell nanoparticles

NASA Astrophysics Data System (ADS)

Rudenko, V.; Tolochko, A.; Zhulai, D.; Klimusheva, G.; Mirnaya, T.; Yaremchuk, G.; Asaula, V.

2018-02-01

New composites with hybrid CdSe/ZnS and Au/CdSe nanoparticles (NPs) were chemically synthesized in the thermotropic liquid crystalline phase (smectic A) of cadmium octanoate. Features of structure and nonlinear optical properties of glassy cadmium octanoate composites with hybrid core/shell NPs were studied using small-angle X-ray scattering method and Z-scan technique. Experimental optical setup (Z-scan) is based on a Nd: YAG laser, generating 9 ns pulses with a repetition rate of 0,5 Hz on a wavelength of 532 nm. The effects of the influence of hybrid NPs on the nonlinear optical properties of nanocomposites are considered in this study.

Synthesis and characterization of poly(lactic acid)/ montmorillonite nanocomposites by in situ polycondensation catalyzed by non-metal-based compound.

PubMed

Kaewprapan, Kulwadee; Phattanarudee, Siriwan

2012-01-01

Poly(lactic acid)/montmorillonite nanocomposites were prepared by using non-toxic catalysts, i.e., phthalic acid and succinimide, via in situ polycondensation in presence of silicate. Concentrations of catalysts and clay were varied in a range of 0-3% wt and 0-0.5% wt, respectively. The reaction condition was controlled at 180 degrees C for 24 hr under a reduced pressure. Viscosity average molecular weight of the synthesized polymers and nanocomposites were characterized and compared using an Ubbelohde viscometer. Pattern of silicate distribution in the composites was investigated by X-ray diffraction to correlate with thermal properties evaluated by differential scanning calorimetry and thermogravimetric analysis. The results showed that the addition of catalysts at 2% wt gave the highest product yield (55-60%). The presence of silicate affected on molecular weight reduction, and the diffracted patterns suggested an intercalated structure. With a small amount of added filler, a significant improvement in thermal property and crystallinity of the resultant composites was obtained compared to those of the catalyzed polymers, in which the composites with succinimide exhibited overall better thermal stability and higher crystallinity than the ones prepared with phthalic acid.

Effect of TiO, nanoparticles on the interface in the PET-rubber composites.

PubMed

Vladuta, Cristina; Andronic, Luminita; Duta, Anca

2010-04-01

Usually, ceramic powders (SiO2, ZnO) are used as fillers for enhancing rubber mechanical strength. Poly-ethylene terephthalate (PET)-rubber nanocomposites were prepared by compression molding using titanium oxide (TiO2) nanoparticles as low content fillers (<2% wt). The interface properties of PET-rubber nanocomposites were studied before and after keeping the samples under UV-radiation for a week. UV-radiation has interesting potential for the photochemical modification of polymers and TiO2. The influence of UV radiation on the properties of the interface polymer-TiO2 nanoparticles was evaluated. The impact of nanoparticle aggregates on the nanometer to micrometer organization of PET-rubber composites was studied with Atomic Force Microscopy (AFM). The interface properties were explained by measuring the contact angles and surface tensions. The interactions between components of nanocomposites were investigated with Fourier Transform-Infrared (FTIR) and the effects of TiO2 nanoparticle on the interfaces and composites crystalline structure were evaluated by X-ray diffraction (XRD). The results proved that the TiO2 nanoparticles, in different weight percentages, did not alter the nanocomposites crystallinity or the average crystallites size, but improve the interface properties.

Structure and microhardness of the plasma sprayed composite coatings after combined treatment

NASA Astrophysics Data System (ADS)

Ivannikov, A. Yu; Kalita, V. I.; Komlev, D. I.; Radyuk, A. A.; Bagmutov, V. P.; Zakharov, I. N.; Parshev, S. N.; Denisevich, D. S.

2018-04-01

The principal aim of this study was to evaluate the effect of combination of electromechanical treatment (EMT) and ultrasonic treatment on structure and microhardness of air plasma sprayed composite coatings from Ni–20Cr alloy and R6M5 high speed steel (HSS). The results of the microstructural studies showed fundamental changes of the treated by the EMT plasma sprayed coating with the formation of nanostructured crystalline phases. As a consequence of the coating thus formed, the number of pores in the coating structure reduced from 10.0±1.5% to 2.0±0.5%, the surface microhardness increased from 3100±500 MPa to 7900±400 MPa. Additional ultrasonic treatment on the selected mode decreased surface waviness, which was formed on the surface of the plasma sprayed composite coatings after the EMT. The obtained results revealed the high potential of the combined treatment for post-treatment of the plasma sprayed coatings.

Transformation of graphite by tectonic and hydrothermal processes in an active plate boundary fault zone, Alpine Fault, New Zealand

NASA Astrophysics Data System (ADS)

Kirilova, Matina; Toy, Virginia; Timms, Nicholas; Halfpenny, Angela; Menzies, Catriona; Craw, Dave; Rooney, Jeremy; Giorgetti, Carolina

2017-04-01

Graphite is a material with one of the lowest frictional strengths, with coefficient of friction of 0.1 and thus in natural fault zones it may act as a natural solid lubricant. Graphitization, or the transformation of organic matter (carbonaceous material, or CM) into crystalline graphite, is induced by compositional and structural changes during diagenesis and metamorphism. The supposed irreversible nature of this process has allowed the degree of graphite crystallinity to be calibrated as an indicator of the peak temperatures reached during progressive metamorphism. We examine processes of graphite emplacement and deformation in the Alpine Fault Zone, New Zealand's active continental tectonic plate boundary. Raman spectrometry indicates that graphite in the distal, amphibolite-facies Alpine Schist, which experienced peak metamorphic temperatures up to 640 ◦C, is highly crystalline and occurs mainly along grain boundaries within quartzo-feldspathic domains. The subsequent mylonitisation in the Alpine Fault Zone resulted in progressive reworking of CM under lower temperature conditions (500◦C-600◦C) in a structurally controlled environment, resulting in spatial clustering in lower-strain protomylonites, and further foliation-alignment in higher-strain mylonites. Subsequent brittle deformation of the mylonitised schists resulted in cataclasites that contain over three-fold increase in the abundance of graphite than mylonites. Furthermore, cataclasites contain graphite with two different habits: highly-crystalline, foliated forms that are inherited mylonitic graphite; and lower-crystallinity, less mature patches of finer-grained graphite. The observed graphite enrichment and the occurrence of poorly-organised graphite in the Alpine Fault cataclasites could result from: i) hydrothermal precipitation from carbon-supersaturated fluids; and/or ii) mechanical degradation by structural disordering of mylonitic graphite combined with strain-induced graphite localisation. The lack of published systematic studies of mechanical modification of the structure of graphite inhibits further conclusion to be drawn. Thus, we performed laboratory deformation experiments during which we sheared highly crystalline graphite powder at room temperature, normal stresses of 5 MPa and 25 MPa and sliding velocities of 1 µm/s, 10 µm/s and 100 µm/s. The degree of graphite crystallinity, both in the starting and resulting materials, was analysed by Raman microspectroscopy. Our results demonstrate consistent decrease of graphite crystallinity with increasing shear strain. We conclude that: i) graphite 'thermometers' are unreliable in brittely deformed rocks; ii) a shear strain calibration of graphite 'thermometers' is needed; iii) fault creep is very likely responsible for the observed structural and textural characteristics of graphite in the Alpine Fault cataclasites. Finally, to investigate the possibility of hydrothermal origin for at least some of the graphite in the Alpine Fault cataclasites we will also present synchrotron FTIR and carbon isotope analysis of the Alpine fault rocks.

Isolation of aramid nanofibers for high strength multiscale fiber reinforced composites

NASA Astrophysics Data System (ADS)

Lin, Jiajun; Patterson, Brendan A.; Malakooti, Mohammad H.; Sodano, Henry A.

2018-03-01

Aramid fibers are famous for their high specific strength and energy absorption properties and have been intensively used for soft body armor and ballistic protection. However, the use of aramid fiber reinforced composites is barely observed in structural applications. Aramid fibers have smooth and inert surfaces that are unable to form robust adhesion to polymeric matrices due to their high crystallinity. Here, a novel method to effectively integrate aramid fibers into composites is developed through utilization of aramid nanofibers. Aramid nanofibers are prepared from macroscale aramid fibers (such as Kevlar®) and isolated through a simple and scalable dissolution method. Prepared aramid nanofibers are dispersible in many polymers due to their improved surface reactivity, meanwhile preserve the conjugated structure and likely the strength of their macroscale counterparts. Simultaneously improved elastic modulus, strength and fracture toughness are observed in aramid nanofiber reinforced epoxy nanocomposites. When integrated in continuous fiber reinforced composites, aramid nanofibers can also enhance interfacial properties by forming hydrogen bonds and π-π coordination to bridge matrix and macroscale fibers. Such multiscale reinforcement by aramid nanofibers and continuous fibers results in strong polymeric composites with robust mechanical properties that are necessary and long desired for structural applications.

Crystal phase identification

DOEpatents

Michael, Joseph R.; Goehner, Raymond P.; Schlienger, Max E.

2001-01-01

A method and apparatus for determining the crystalline phase and crystalline characteristics of a sample. This invention provides a method and apparatus for unambiguously identifying and determining the crystalline phase and crystalline characteristics of a sample by using an electron beam generator, such as a scanning electron microscope, to obtain a backscattered electron Kikuchi pattern of a sample, and extracting crystallographic and composition data that is matched to database information to provide a quick and automatic method to identify crystalline phases.

Synthesis and microwave absorption property of graphene oxide/carbon nanotubes modified with cauliflower-like Fe3O4 nanospheres

NASA Astrophysics Data System (ADS)

Yan, Shaojiu; Wang, Lina; Wang, Tihong; Zhang, Liqiang; Li, Yongfeng; Dai, Shenglong

2016-03-01

We report a simple procedure to fabricate graphene oxide/carbon nanotube hybrids coated with cauliflower-like Fe3O4 sphere. Characterizations have been carried out to investigate the morphology, crystalline structure of the composites by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Fe3O4 particles have the morphologies of multi-lacuna; moreover, some spheres are hollow. As a kind of potential microwave absorption material, the composites are lightweight and exhibit excellent microwave absorbing ability in the range of 2-16 GHz.

Engineering and characterizing nanoscale multilayered structures for magnetic tunnel junctions

NASA Astrophysics Data System (ADS)

Yang, J. Joshua

Magnetic tunnel junction (MTJ) has generated considerable attention due to its potential applications in improved magnetic sensors, read heads in HDDs and nonvolatile RAM. The materials issues play a crucial role in the performance of MTJs. In the work described in this thesis, we have engineered some interesting nanoscale multilayered structures mainly via thermodynamics considerations for MTJs. The insulator is usually an ultra-thin (<2nm) oxide, formed by oxidizing a pre-deposited metal, such as Al etc. We have developed novel fabrication approaches for obtaining clean and smooth interfaces between the insulator and the ferromagnets. These approaches include selectively oxidizing the pre-deposited tunnel barrier precursor metal, amorphizing the tunnel barrier precursor metal by alloying it with other elements, and in-situ annealing the bottom ferromagnetic layer. About 72% tunneling magnetoresistance (TMR) has been achieved at room temperature with AlOx and CoFe based MTJs. We have made a systemic study of the TMR vs. the Co1-xFe x electrode composition for AlOx based MTJs. A significant variation of TMR with Fe concentration has been observed. It is well known that the crystal structure of Co1-xFex changes from fcc to bcc with increasing Fe concentration. The concomitant composition change cast doubts on the role played by the crystal structure of the Co1-x Fex electrode on the TMR. By introducing different strains to an epitaxial Co1-xFex layer, we were able to fix its composition but alter its crystalline structure from fcc to bcc and found that the bcc structure resulted in much higher TMR values than found for the fcc structure. This is one of the few direct experimental confirmatory results showing the role of the FM electronic structure on the MTJ properties. Using Ag as a template, different 3d ferromagnets have been epitaxially grown on the Si substrate with hcp, fcc and bcc crystalline structures, respectively. By combining the selective oxidation method with the epitaxial growth technique, we have successfully created a single-crystal-like layer on top of an amorphous layer, which may have broad applications in thin film devices including MTJs.

Structure-property relationships in semicrystalline copolymers and ionomers

NASA Astrophysics Data System (ADS)

Wakabayashi, Katsuyuki

Many outstanding physical properties of ethylene/(meth)acrylic acid (E/(M)AA) copolymers and ionomers are associated with their nanometer-scale morphology, which consists of ethylene crystallites, amorphous segments, and acid/ionic functional groups. The goal of this dissertation is a fundamental understanding of the interplay between these structural motifs and the consequent effects on the material properties. We identify small-strain modulus as a key mechanical property and investigate its dependence upon material structure through X-ray scattering, calorimetry, and mechanical property measurements. We first treat E/(M)AA copolymers as composites of polyethylene crystallites and amorphous regions, and establish a quantitative combining rule to describe the copolymer modulus. At temperatures above the Tg of the copolymers, a monotonic increase in modulus with crystallinity is quantitatively described by the Davies equation for two-phase composites, which serves as the basis for separating the effects of amorphous and crystalline phases throughout this dissertation. The room-temperature modulus of E/(M)AA copolymers is concurrently affected by ethylene crystallinity and proximity to the amorphous phase Tg, which rises through room temperature with increasing comonomer content. In E/(M)AA ionomers, phase separation and aggregation of ionic groups provide additional stiffness and toughness. Ionomers are modeled as composites of crystallites and ionically crosslinked rubber, whose amorphous phase modulus far above the ionomer Tg is satisfactorily described by simple rubber elasticity theory. Thermomechanical analyses probe the multi-step relaxation behavior of E/(M)AA ionomers and lead to the development of a new semicrystalline ionomer morphological model, wherein secondary crystallites and ionic aggregates together form rigid percolated pathways throughout the amorphous phase. Metal soaps are oligomeric analogs of E/(M)AA ionomers, which can be blended into ionomers to achieve high ion content and in turn desirable physical properties. We assess the compatibility of various types of metal soaps with E/(M)AA ionomers, and investigate how the soap modifies the ionomers' structure and properties. The mechanical properties and phase behavior of these hybrids, which are found to differ significantly depending on the neutralizing cation type and crystallinizability of the metal soap, are traced back to various levels of molecular coassembly involving the hydrocarbon chains and/or the ionic groups of both entities.

Age-related changes in the water-soluble lens protein composition of Wistar and accelerated-senescence OXYS rats

PubMed Central

Kopylova, Lyudmila V.; Cherepanov, Ivan V.; Snytnikova, Olga A.; Rumyantseva, Yuliya V.; Kolosova, Nataliya G.; Sagdeev, Renad Z.

2011-01-01

Purpose To determine the age-related and the cataract-specific changes in the crystallin composition in lenses of accelerated-senescence OXYS (cataract model) and Wistar (control) rats. Methods The water soluble (WS) and insoluble (WIS) fractions of the lens proteins were separated; the identity and relative abundance of each crystallin in WS fraction were determined with the use of two-dimensional electrophoresis (2-DE) and Matrix-Assisted Laser Desorption Ionization – Time Of Flight (MALDI-TOF) mass spectrometry. All statistical calculations were performed using the software package Statistica 6.0 by factor dispersion analysis (ANOVA/MANOVA) and Newman-Keuls post-hoc test for comparison of group mean values. Results The WIS protein content increased significantly in the aged animal lenses; the WIS/WS ratio increases in approximately 8 times to the age of 62 weeks. The interstrain difference was insignificant in this experiment. 2-DE maps of the young rat lenses (3 weeks) showed single spots for each lens protein while in older lenses (12 and 62 weeks) each crystallin was presented by several spots. The abundance of γA-γF-crystallins in WS fraction significantly decreases with age. A significant increase in the percentage abundance was also found for α-crystallins and βB2-crystallin from 3 to 12 weeks. The major differences between Wistar and OXYS lenses are the faster decay of the content of γA-γF-crystallins in OXYS lenses, and the significant decrease of unmodified αA-crystallin abundance in old OXYS lenses. Conclusions The presented results demonstrate that the increase of the water-insoluble (WIS) protein fraction is rather age-specific than cataract-specific phenomenon. The major age-related changes in WS protein composition are the fast insolubilization of γ-crystallins, and the increase of αB- and βB2-crystallin abundance. The main interstrain differences, which could be attributed to the cataract-specific processes, are the faster decay of the content of γ-crystallins and the significant decrease of unmodified αA-crystallin abundance in the OXYS lenses. PMID:21677790

Bi12TiO20 crystallization in a Bi2O3-TiO2-SiO2-Nd2O3 system

NASA Astrophysics Data System (ADS)

Slavov, S.; Jiao, Z.

2018-03-01

Polycrystalline mono-phase bismuth titanate was produced by free cooling from melts heated to 1170 °C. The control over the initial amounts in the starting compositions in the system Bi2O3/TiO2/SiO2/Nd2O3 and over the thermal gradient of the heat process resulted in the formation of specific structures and microstructures of monophase sillenite ceramics. The main phase Bi12TiO20 belongs to the amorphous network groups based on oxides of silicon, bismuth and titanium. In this work, we demonstrated a way to control the crystalline and amorphous phase formation in bulk poly-crystalline materials in the selected system.

Stabilisation of Ce-Cu-Fe amorphous alloys by addition of Al

NASA Astrophysics Data System (ADS)

Kelhar, Luka; Ferčič, Jana; Boulet, Pascal; Maček-Kržmanc, Marjeta; Šturm, Sašo; Lamut, Martin; Markoli, Boštjan; Kobe, Spomenka; Dubois, Jean-Marie

2016-10-01

The present work describes the formation of amorphous alloys in the (Al1-xCex)62Cu25Fe13 quaternary system (0 ≤ x ≤ 1). When the amount of Ce falls in the range 0.67 ≤ x ≤ 0.83, the alloys obtained exhibit a completely amorphous structure confirmed by powder X-ray diffraction. Otherwise, at compositions x = 0.5, 0.58, 0.92 and 1, a primary crystalline phase forms together with an amorphous matrix. The crystallisation temperature (Tx) decreases with increasing Ce content, varying from 593 K for x = 0.5-383 K for x = 1. Composition x = 0.75 is considered as the best glass former, exhibiting a large supercooled liquid region of 40 K width that precedes crystallisation. In order to form bulk amorphous alloys, ribbons with this later composition were consolidated into few millimetre thick discs using pulsed electric current sintering at different temperatures, yet preserving the amorphous structure. Meanwhile, increasing temperature above 483 K triggers crystallisation of a primary phase isostructural to AlCe3. Further increase in the temperature up to 573 K yields a higher fraction of the crystalline phase. Testing mechanical properties, using nanoindentation, revealed that both elastic modulus (E) and hardness (H) depend on the Al content, ranging from E = 85.6 ± 3.7 GPa and H = 6.2 ± 0.7 GPa for x = 0.5 down to E = 39.8 ± 1.0 GPa and H = 3.1 ± 0.2 GPa for x = 0.92.

Using galvanostatic electroforming of Bi 1–xSb x nanowires to control composition, crystallinity, and orientation

DOE PAGES

Limmer, Steven J.; Medlin, Douglas L.; Siegal, Michael P.; ...

2014-12-03

When using galvanostatic pulse deposition, we studied the factors influencing the quality of electroformed Bi 1–xSb x nanowires with respect to composition, crystallinity, and preferred orientation for high thermoelectric performance. Two nonaqueous baths with different Sb salts were investigated. The Sb salts used played a major role in both crystalline quality and preferred orientations. Nanowire arrays electroformed using an SbI 3 -based chemistry were polycrystalline with no preferred orientation, whereas arrays electroformed from an SbCl 3-based chemistry were strongly crystallographically textured with the desired trigonal orientation for optimal thermoelectric performance. From the SbCl 3 bath, the electroformed nanowire arraysmore » were optimized to have nanocompositional uniformity, with a nearly constant composition along the nanowire length. Moreover, nanowires harvested from the center of the array had an average composition of Bi 0.75 Sb 0.25. However, the nanowire compositions were slightly enriched in Sb in a small region near the edges of the array, with the composition approaching Bi 0.70Sb 0.30.« less

The crystal structure and morphology of NiO-YSZ composite that prepared from local zircon concentrate of Bangka Island

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

Rahmawati, F., E-mail: fitria@mipa.uns.ac.id; Apriyani, K.; Heraldy, E.

2016-03-29

In order to increase the economic value of local zircon concentrate from Bangka Island, NiO-YSZ was synthesized from Zirconia, ZrO{sub 2} that was prepared from local zircon concentrate. The NiO-YSZ composite was synthesized by solid state reaction method. XRD analysis equipped with Le Bail refinement was carried out to analyze the crystal structure and cell parameters of the prepared materials. The result showed that zirconia was crystallized in tetragonal structure with a space group of P42/NMC. Yttria-Stabilized-Zirconia (YSZ) was prepared by doping 8% mol yttrium oxide into zirconia and then sintered at 1250°C for 3 hours. Doping of 8% molmore » Yttria allowed phase transformation of zirconia from tetragonal into the cubic structure. Meanwhile, the composite of NiO-YSZ consists of two crystalline phases, i.e. the NiO with cubic structure and the YSZ with cubic structure. SEM analysis of the prepared materials shows that the addition of NiO into YSZ allows the morphology to become more roughness with larger grain size.« less

Nanocrystalline nickel ferrite particles synthesized by non-hydrolytic sol-gel method and their composite with biodegradable polymer.

PubMed

Yin, H; Casey, P S; Chow, G M

2012-11-01

Targeted drug delivery has been one of the most important biomedical applications for magnetic particles. Such applications require magnetic particles to have functionalized surfaces/surface coatings that facilitate their incorporation into a polymer matrix to produce a polymer composite. In this paper, nanocrystalline nickel ferrite particles with an oleic acid surface coating were synthesized using a non-hydrolytic sol-gel method and incorporated into a biodegradable polymer matrix, poly(D,L-lactide) PLA prepared using a double emulsion method. As-synthesized nickel ferrite particles had a multi-crystalline structure with chemically adsorbed oleic acid on their surface. After forming the PLA composite, nickel ferrite particles were encapsulated in PLA microspheres. At low nickel ferrite concentrations, composites showed very similar surface charges to that of PLA. The composites were magnetically responsive and increasing the nickel ferrite concentration was found to increase magnetization of the composite.

Thermal and damping behaviour of magnetic shape memory alloy composites

NASA Astrophysics Data System (ADS)

Glock, Susanne; Michaud, Véronique

2015-06-01

Single crystals of ferromagnetic shape memory alloys (MSMA) exhibit magnetic field and stress induced strains via energy dissipating twinning. Embedding single crystalline MSMA particles into a polymer matrix could thus produce composites with enhanced energy dissipation, suitable for damping applications. Composites of ferromagnetic, martensitic or austenitic Ni-Mn-Ga powders embedded in a standard epoxy matrix were produced by casting. The martensitic powder composites showed a crystal structure dependent damping behaviour that was more dissipative than that of austenitic powder or Cu-Ni reference powder composites and than that of the pure matrix. The loss ratio also increased with increasing strain amplitude and decreasing frequency, respectively. Furthermore, Ni-Mn-Ga powder composites exhibited an increased damping behaviour at the martensite/austenite transformation temperature of the Ni-Mn-Ga particles in addition to that at the glass transition temperature of the epoxy matrix, creating possible synergetic effects.

Construction of physical crosslink-based chitosan/liquid crystal composite hydrogel and evaluation on their cytocompatibility

PubMed Central

Du, Lin; Yang, Xiaohui; Li, Wenqiang; Luo, Xuhui; Wu, Hao; Zhang, Jiaqing; Tu, Mei

2017-01-01

In order to provide a novel biomimetic composite substrate for tissue engineering and explore the interaction between cells and this type of material, we developed chitosan/liquid crystal (CS/LC) composite hydrogel with embedded LC phases by composing of cholesterol hydroxypropyl cellulose ester liquid crystalline material and CS. The micromorphology of CS/LC composite hydrogels exhibited ‘islands-sea’ phase separation structures similar to the ‘fluid mosaic model’ of biomembrane. In vitro cell compatibility study suggested that 3T3 is fibroblasts exhibited better initial cell adhesions and higher proliferation rates on the composite hydrogel than on the polystyrene control plate and the pure LC membrane. This novel CS/LC composite hydrogel provides more favorable interface for cell growth and proliferation and may serve as potentially active substrate for engineering interfaces to live cells. PMID:28149528

Differences in Cellulosic Supramolecular Structure of Compositionally Similar Rice Straw Affect Biomass Metabolism by Paddy Soil Microbiota

PubMed Central

Ogura, Tatsuki; Date, Yasuhiro; Kikuchi, Jun

2013-01-01

Because they are strong and stable, lignocellulosic supramolecular structures in plant cell walls are resistant to decomposition. However, they can be degraded and recycled by soil microbiota. Little is known about the biomass degradation profiles of complex microbiota based on differences in cellulosic supramolecular structures without compositional variations. Here, we characterized and evaluated the cellulosic supramolecular structures and composition of rice straw biomass processed under different milling conditions. We used a range of techniques including solid- and solution-state nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy followed by thermodynamic and microbial degradability characterization using thermogravimetric analysis, solution-state NMR, and denaturing gradient gel electrophoresis. These measured data were further analyzed using an “ECOMICS” web-based toolkit. From the results, we found that physical pretreatment of rice straw alters the lignocellulosic supramolecular structure by cleaving significant molecular lignocellulose bonds. The transformation from crystalline to amorphous cellulose shifted the thermal degradation profiles to lower temperatures. In addition, pretreated rice straw samples developed different microbiota profiles with different metabolic dynamics during the biomass degradation process. This is the first report to comprehensively characterize the structure, composition, and thermal degradation and microbiota profiles using the ECOMICS toolkit. By revealing differences between lignocellulosic supramolecular structures of biomass processed under different milling conditions, our analysis revealed how the characteristic compositions of microbiota profiles develop in addition to their metabolic profiles and dynamics during biomass degradation. PMID:23840554

Bacterial cellulose composites: Synthetic strategies and multiple applications in bio-medical and electro-conductive fields.

PubMed

Ul-Islam, Mazhar; Khan, Shaukat; Ullah, Muhammad Wajid; Park, Joong Kon

2015-12-01

Bacterial cellulose (BC), owing to its pure nature and impressive physicochemical properties, including high mechanical strength, crystallinity, porous fibrous structure, and liquid absorbing capabilities, has emerged as an advanced biomaterial. To match the market demand and economic values, BC has been produced through a number of synthetic routes, leading to slightly different structural features and physical appearance. Chemical nature, porous geometry, and 3D fibrous structure of BC make it an ideal material for composites synthesis that successfully overcome certain deficiencies of pure BC. In this review, we have focused various strategies developed for synthesizing BC and BC composites. Reinforcement materials including nanoparticles and polymers have enhanced the antimicrobial, conducting, magnetic, biocompatible, and mechanical properties of BC. Both pure BC and its composites have shown impressive applications in medical fields and in the development of optoelectronic devices. Herein, we have given a special attention to discuss its applications in the medical and electronic fields. In conclusion, BC and BC composites have realistic potential to be used in future development of medical devices, artificial organs and electronic and conducting materials. The contents discussed herein will provide an eye-catching theme to the researchers concerned with practical applications of BC and BC composites. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

UiO-66-NH₂/GO Composite: Synthesis, Characterization and CO₂ Adsorption Performance.

PubMed

Cao, Yan; Zhang, Hongmei; Song, Fujiao; Huang, Tao; Ji, Jiayu; Zhong, Qin; Chu, Wei; Xu, Qi

2018-04-11

In this work, a new composite materials of graphene oxide (GO)-incorporated metal-organic framework (MOF)(UiO-66-NH₂/GO) were in-situ synthesized, and were found to exhibit enhanced high performances for CO₂ capture. X-ray diffraction (XRD), scanning electron microscope (SEM), N₂ physical adsorption, and thermogravimetric analysis (TGA) were applied to investigate the crystalline structure, pore structure, thermal stability, and the exterior morphology of the composite. We aimed to investigate the influence of the introduction of GO on the stability of the crystal skeleton and pore structure. Water, acid, and alkali resistances were tested for physical and chemical properties of the new composites. CO₂ adsorption isotherms of UiO-66, UiO-66-NH₂, UiO-66/GO, and UiO-66-NH₂/GO were measured at 273 K, 298 K, and 318 K. The composite UiO-66-NH₂/GO exhibited better optimized CO₂ uptake of 6.41 mmol/g at 273 K, which was 5.1% higher than that of UiO-66/GO (6.10 mmol/g). CO₂ adsorption heat and CO₂/N₂ selectivity were then calculated to further evaluate the CO₂ adsorption performance. The results indicated that UiO-66-NH₂/GO composites have a potential application in CO₂ capture technologies to alleviate the increase in temperature of the earth's atmosphere.

Method to reduce dislocation density in silicon using stress

DOEpatents

Buonassisi, Anthony; Bertoni, Mariana; Argon, Ali; Castellanos, Sergio; Fecych, Alexandria; Powell, Douglas; Vogl, Michelle

2013-03-05

A crystalline material structure with reduced dislocation density and method of producing same is provided. The crystalline material structure is annealed at temperatures above the brittle-to-ductile transition temperature of the crystalline material structure. One or more stress elements are formed on the crystalline material structure so as to annihilate dislocations or to move them into less harmful locations.

Structural studies of polytene chromosomes and bone implant coatings: Raman microspectroscopy and atomic force microscopy

NASA Astrophysics Data System (ADS)

de Grauw, Kees

Raman microscopy and atomic force microscopy (AFM) are used for the investigation of the composition and structure of the banding patterns of polytene chromosomes and of hydroxyapatite bone-implant coatings. For Raman microspectroscopy two new measuring methods are introduced: line-scan Raman and Low-wavenumber Raman microspectroscopy. A transparent and easy to use model to predict the depth resolution of a confocal microscope is described. A Chevron-type of filter set was developed for simultaneous measurements of Stokes and anti-Stokes Raman scattering close to the exciting laser frequency. Bands of polytene chromosomes appeared to contain a higher concentration of DNA and proteins compared to interbands. AFM measurements revealed that bands consist of a densely packed chromatin structure and are hardly affected by stretching of the chromosome. Interbands have a more open chromatin structure and are more accessible to solvent molecules. For the study of bone implant coatings Raman micro spectroscopy appeared to provide an easy, non- destructive, way to obtain information about the apatite structure and the degree of crystallinity. It was shown that the degree of crystallinity was constant over coatings produced by plasma spraying while the material density did vary.

XRD and FTIR structural investigation of gadolinium-zinc-borate glass ceramics

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

Borodi, G.; Pascuta, P.; Dan, V.

2013-11-13

X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy measurements have been employed to investigate the (Gd{sub 2}O{sub 3}){sub x}⋅(B{sub 2}O{sub 3}){sub (60−x)}⋅(ZnO){sub 40} glass ceramics system, with 0 ≤ x ≤ 15 mol%. After heat treatment applied at 860 °C for 2 h, some structural changes were observed and new crystalline phases appeared in the structure of the samples. In these glass ceramics four crystalline phases were identified using powder diffraction files (PDF 2), namely ZnB{sub 4}O{sub 7}, Zn{sub 4}O(B{sub 6}O{sub 12}), Zn{sub 3}(BO{sub 3}){sub 2} and GdBO{sub 3}. From the XRD data, the average unit-cell parameter and themore » quantitative ratio of the crystallographic phases in the studied samples were evaluated. FTIR data revealed that the BO{sub 3}, BO{sub 4} and ZnO{sub 4} are the main structural units of these glass ceramics network. The compositional dependence of the different structural units which appear in the studied samples was followed.« less

Microstructure and dielectric properties of cellulose acetate-ZnO/ITO composite films based on water hyacinth

NASA Astrophysics Data System (ADS)

Diantoro, M.; Mustikasari, A. A.; Wijayanti, N.; Yogihati, C.; Taufiq, A.

2017-05-01

The electrical properties of Cellulose Acetate (CA), especially extracted from water hyacinth, is rarely informed. CA is generally more stable compared to its cellulose. It has a good potential for electronic application with specific modifications such as inducing metal oxide. A combination of intrinsic properties of Zinc Oxide (ZnO) and CA is expected as a great potential for electrical and optical applications. CA-ZnO/ITO composite film was investigated in relation with its structure, dielectric constant, and the effect of light intensity on their dielectric constant. CA-ZnO composite films were prepared with different mass of ZnO i.e. 0; 0,02; 0,04; 0,06 and 0,08 grams. CA-ZnO solution was synthesized via the mixing method with PEG:DMF solvents by using a magnetic hotplate stirrer with the rotation rate of 1500 rpm at 80°C. The CA-ZnO solution was then deposited onto ITO/glass substrate by using spin coating technique. The CA-ZnO/ITO films were annealed at 160°C to remove the remaining solvents. The effects of ZnO composition on the structure (crystallinity and morphology) and dielectric constant properties were investigated by using X-Ray Diffractometer, Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, and LCR meter. It was shown that cellulose can be isolated from water hyacinth with the yield of 67,72 % by Chesson method and can further be transformed into CA. The X-ray diffraction pattern showed that there are 2 phases formed i.e. CA and ZnO. Furthermore, greater ZnO amount increased the crystallinity of composite films. The CA-ZnO films exhibit porous films with ZnO distributed on the CA surface films. Therefore, ZnO increases the dielectric constant of CA-ZnO composite films.

The role of macromolecular crowding in the evolution of lens crystallins with high molecular refractive index.

PubMed

Zhao, Huaying; Magone, M Teresa; Schuck, Peter

2011-08-01

Crystallins are present in the lens at extremely high concentrations in order to provide transparency and generate a high refractive power of the lens. The crystallin families prevalent in the highest density lens tissues are γ-crystallins in vertebrates and S-crystallins in cephalopods. As shown elsewhere, in parallel evolution, both have evolved molecular refractive index increments 5-10% above those of most proteins. Although this is a small increase, it is statistically very significant and can be achieved only by very unusual amino acid compositions. In contrast, such a molecular adaptation to aid in the refractive function of the lens did not occur in crystallins that are preferentially located in lower density lens tissues, such as vertebrate α-crystallin and taxon-specific crystallins. In the current work, we apply a model of non-interacting hard spheres to examine the thermodynamic contributions of volume exclusion at lenticular protein concentrations. We show that the small concentration decrease afforded by the higher molecular refractive index increment of crystallins can amplify nonlinearly to produce order of magnitude differences in chemical activities, and lead to reduced osmotic pressure and the reduced propensity for protein aggregation. Quantitatively, this amplification sets in only at protein concentrations as high as those found in hard lenses or the nucleus of soft lenses, in good correspondence to the observed crystallin properties in different tissues and different species. This suggests that volume exclusion effects provide the evolutionary driving force for the unusual refractive properties and the unusual amino acid compositions of γ-crystallins and S-crystallins.

The role of macromolecular crowding in the evolution of lens crystallins with high molecular refractive index

PubMed Central

Zhao, Huaying; Magone, M. Teresa; Schuck, Peter

2011-01-01

Crystallins are present in the lens at extremely high concentrations in order to provide transparency and generate a high refractive power of the lens. The crystallin families prevalent in the highest density lens tissues are γ crystallins in vertebrates and S crystallins in cephalopods. In parallel evolution, both have evolved molecular refractive index increments 5 – 10 % above those of most proteins. Although this is a small increase, it is statistically very significant and can be achieved only by very unusual amino acid compositions. In contrast, such a molecular adaptation to aid in the refractive function of the lens did not occur in crystallins that are preferentially located in lower density lens tissues, such as vertebrate α crystallin and taxon specific crystallins. In the current work, we apply a model of non-interacting hard spheres to examine the thermodynamic contributions of volume exclusion at lenticular protein concentrations. We show that the small concentration decrease afforded by the higher molecular refractive index increment of crystallins can amplify nonlinearly to produce order of magnitude differences in chemical activities, and lead to reduced osmotic pressure and the reduced propensity for protein aggregation. Quantitatively, this amplification sets in only at protein concentrations as high as those found in hard lenses or the nucleus of soft lenses, in good correspondence to the observed crystalline properties in different tissues and different species. This suggests that volume exclusion effects provide the evolutionary driving force for the unusual refractive properties and the unusual amino acid compositions of γ crystallins and S crystallins. PMID:21566271

Chemical compositions, infrared spectroscopy, and X-ray diffractometry study on brown-rotted woods

Treesearch

Gai-Yun Li; Luo-Hua Huang; Chung Hse; Te-Fu Qin

2011-01-01

The effect of brown-rot decay on the chemical composition and crystallinity of Masson pine was studied by exposing it to Wolfiporia cocos (Schwein.) Ryvarden and Gilbn. for durations of up to 15 weeks in the field. The holocellulose content, α-cellulose content, and wood crystallinity decreased slowly in the initial stage, followed by a significant reduction...

The annealing temperature dependences of microstructures and magnetic properties in electro-chemical deposited CoNiFe thin films

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

Suharyadi, Edi, E-mail: esuharyadi@ugm.ac.id; Riyanto, Agus; Abraha, Kamsul

2016-04-19

CoNiFe thin films with various compositions had been successfully fabricated using electro-chemical deposition method. The crystal structure of Co{sub 65}Ni{sub 15}Fe{sub 20}, Co{sub 62}Ni{sub 15}Fe{sub 23}, and Co{sub 55}Ni{sub 15}Fe{sub 30} thin films was fcc, bcc-fcc mix, and bcc, respectively. The difference crystal structure results the difference in magnetic properties. The saturation magnetic flux density (Bs) of Co{sub 65}Ni{sub 15}Fe{sub 20}, Co{sub 62}Ni{sub 15}Fe{sub 23}, and Co{sub 55}Ni{sub 15}Fe{sub 30} thin films was 1.89 T, 1.93 T, and 2.05 T, respectively. An optimal annealing temperature was determined for controlling the microstructure and magnetic properties of CoNiFe thin films. Depending onmore » annealing temperature, the ratio of bcc and fcc structure varied without changing the film composition. By annealing at temperature of T ≥ 350°C, the intensity ratio of X-ray diffraction peaks for bcc(110) to fcc(111) increased. The increase of phase ratio of bcc(110) to fcc(111) caused the increase of Bs, from 1.89 T to 1.95 T. Coercivity (Hc) also increased after annealing, from 2.6 Oe to 18.6 Oe for fcc phase thin films, from 2.0 Oe to 12.0 Oe for fcc-bcc mix phase thin films, and 7.8 Oe to 8 Oe for bcc phase thin films. The changing crystal structures during annealing process indicated that the thermal treatment at high temperature cause the changing crystallinity and atomic displacement. The TEM bright-field images with corresponding selected-area electron diffraction (SAED) patterns showed that there are strongly effects of thermal annealing on the size of fcc and bcc phase crystalline grain as described by size of individual spot and discontinuous rings. The size of crystalline grains increased by thermal annealing. The evolution of bcc and fcc structures of CoNiFe during annealing is though to be responsible for the change of magnetic properties.« less

Preparation of YBa2Cu3O7 High Tc Superconducting Coatings by Plasma Spraying

NASA Astrophysics Data System (ADS)

Danroc, J.; Lacombe, J.

The following sections are included: * INTRODUCTION * THE COMPOUND YBa2Cu3O7-δ * Structure * Critical temperature * Critical current density * Phase equilibria in the YBaCuO system * PREPARATION OF YBa2Cu3O7 COATINGS * General organisation of the preparation process * The powder * Hot plasma spraying of YBa2Cu3O7 * The post-spraying thermal treatment * CHARACTERISTICS OF THE YBa2Cu3O7-δ COATINGS * Chemical composition * Crystalline structure * Morphology of the coatings * Electrical and magnetic characteristics * Conclusion * REFERENCES

Ion Implantation Metallurgy: A Study of the Composition, Structure and Corrosion Behavior of Surface Alloys Formed by Ion Implantation.

DTIC Science & Technology

1980-04-01

spots are due to the " phase ). Dark field imaging of the a" phase shows a large density of small precipitates uniformly distributed in the ferrite . In...density of defect structures and small precipitates of Fe 16N2 (a"). Although there exists some evidence of martensitic transformation in aged speci...implantation into 304 stainless steel ha-s been shown to produce a micro- crystalline surface alloy saturated with P. Combined electrochemical and XPS studies

Structural, optical and AFM characterization of PVA:La3+ polymer films

NASA Astrophysics Data System (ADS)

Ali, F. M.; Maiz, F.

2018-02-01

In this paper the structural and optical properties of pure Polyvinyl alcohol (PVA) and La3+-doped PVA films in the concentration range of 4%, 12% and 20% weight percent of Lanthanum were prepared by the conventional casting technique. X-ray diffraction pattern and atomic force microscopy studies of the investigated samples reveal their semi-crystalline nature. It is found that, absorption coefficient and cluster size of lanthanum:PVA composite increase with increasing salt concentration. However, the optical energy gap shows a slight decreasing trend.

Effects of Ni content on nanocrystalline Fe-Co-Ni ternary alloys synthesized by a chemical reduction method

NASA Astrophysics Data System (ADS)

Chokprasombat, Komkrich; Pinitsoontorn, Supree; Maensiri, Santi

2016-05-01

Magnetic properties of Fe-Co-Ni ternary alloys could be altered by changing of the particle size, elemental compositions, and crystalline structures. In this work, Fe50Co50-xNix nanoparticles (x=10, 20, 40, and 50) were prepared by the novel chemical reduction process. Hydrazine monohydrate was used as a reducing agent under the concentrated basic condition with the presence of poly(vinylpyrrolidone). We found that the nanoparticles were composed of Fe, Co and Ni with compositions according to the molar ratio of the metal sources. Interestingly, the particles were well-crystalline at the as-prepared state without post-annealing at high temperature. Increasing Ni content resulted in phase transformation from body centered cubic (bcc) to face centered cubic (fcc). For the fcc phase, the average particle size decreased when increased the Ni content; the Fe50Ni50 nanoparticles had the smallest average size with the narrowest size distribution. In additions, the particles exhibited ferromagnetic properties at room temperature with the coercivities higher than 300 Oe, and the saturation magnetiation decreased with increasing Ni content. These results suggest that the structural and magnetic properties of Fe-Co-Ni alloys could be adjusted by varying the Ni content.

Influence of microstructure and chemical composition of sputter deposited TiO2 thin films on in vitro bioactivity.

PubMed

Lilja, Mirjam; Genvad, Axel; Astrand, Maria; Strømme, Maria; Enqvist, Håkan

2011-12-01

Functionalisation of biomedical implants via surface modifications for tailored tissue response is a growing field of research. Crystalline TiO(2) has been proven to be a bone bioactive, non-resorbable material. In contact with body fluids a hydroxyapaptite (HA) layer forms on its surface facilitating the bone contact. Thus, the path of improving biomedical implants via deposition of crystalline TiO(2) on the surface is interesting to follow. In this study we have evaluated the influence of microstructure and chemical composition of sputter deposited titanium oxide thin films on the in vitro bioactivity. We find that both substrate bias, topography and the flow ratio of the gases used during sputtering affect the HA layer formed on the films after immersion in simulated body fluid at 37°C. A random distribution of anatase and rutile crystals, formed at negative substrate bias and low Ar to O(2) gas flow ratios, are shown to favor the growth of flat HA crystal structures whereas higher flow ratios and positive substrate bias induced growth of more spherical HA structures. These findings should provide valuable information when optimizing the bioactivity of titanium oxide coatings as well as for tailoring process parameters for sputtered-based production of bioactive titanium oxide implant surfaces.

Non-Destructive Study of Bulk Crystallinity and Elemental Composition of Natural Gold Single Crystal Samples by Energy-Resolved Neutron Imaging

PubMed Central

Tremsin, Anton S.; Rakovan, John; Shinohara, Takenao; Kockelmann, Winfried; Losko, Adrian S.; Vogel, Sven C.

2017-01-01

Energy-resolved neutron imaging enables non-destructive analyses of bulk structure and elemental composition, which can be resolved with high spatial resolution at bright pulsed spallation neutron sources due to recent developments and improvements of neutron counting detectors. This technique, suitable for many applications, is demonstrated here with a specific study of ~5–10 mm thick natural gold samples. Through the analysis of neutron absorption resonances the spatial distribution of palladium (with average elemental concentration of ~0.4 atom% and ~5 atom%) is mapped within the gold samples. At the same time, the analysis of coherent neutron scattering in the thermal and cold energy regimes reveals which samples have a single-crystalline bulk structure through the entire sample volume. A spatially resolved analysis is possible because neutron transmission spectra are measured simultaneously on each detector pixel in the epithermal, thermal and cold energy ranges. With a pixel size of 55 μm and a detector-area of 512 by 512 pixels, a total of 262,144 neutron transmission spectra are measured concurrently. The results of our experiments indicate that high resolution energy-resolved neutron imaging is a very attractive analytical technique in cases where other conventional non-destructive methods are ineffective due to sample opacity. PMID:28102285

Structural and optical properties of tin disulphide thin films grown by flash evaporation

NASA Astrophysics Data System (ADS)

Banotra, Arun; Padha, Naresh

2018-04-01

Tin Disulphide thin films were deposited by Flash Evaporation method on corning Glass Substrate at different substrate temperatures. The deposited films were undertaken for Structural, Optical and compositional characterizations. Compositional analysis of the films exhibited decrease in the sulphur content enabling S/Sn ratio to vary from 2.05 to 1.32 with increasing substrate temperature. X-ray diffraction reveals amorphous nature of the as-deposited films with varying substrate temperatures. Optical measurements estimated from absorbance spectra suggest higher absorbance at λ≤500nm and higher transmission at λ≥500nm with bandgap changes from 2.45eV to 2.09eV. The 323K as-deposited films were undertaken for annealing which transforms the films into crystalline form corresponding to hexagonal SnS2 phase at 423K and above. However, the optical response for the annealed samples shows a higher transmission of 70% in the visible region which increases further in the Infrared region of the spectrum achieving maximum transmission upto 98%. This higher transmission in the Visible to Infrared region of the solar spectrum in amorphous as well as crystalline form makes the film suitable for their use as a window layer in the Solar Cell Design.

Pore structure characterization of Chang-7 tight sandstone using MICP combined with N2GA techniques and its geological control factors

NASA Astrophysics Data System (ADS)

Cao, Zhe; Liu, Guangdi; Zhan, Hongbin; Li, Chaozheng; You, Yuan; Yang, Chengyu; Jiang, Hang

2016-11-01

Understanding the pore networks of unconventional tight reservoirs such as tight sandstones and shales is crucial for extracting oil/gas from such reservoirs. Mercury injection capillary pressure (MICP) and N2 gas adsorption (N2GA) are performed to evaluate pore structure of Chang-7 tight sandstone. Thin section observation, scanning electron microscope, grain size analysis, mineral composition analysis, and porosity measurement are applied to investigate geological control factors of pore structure. Grain size is positively correlated with detrital mineral content and grain size standard deviation while negatively related to clay content. Detrital mineral content and grain size are positively correlated with porosity, pore throat radius and withdrawal efficiency and negatively related to capillary pressure and pore-to-throat size ratio; while interstitial material is negatively correlated with above mentioned factors. Well sorted sediments with high debris usually possess strong compaction resistance to preserve original pores. Although many inter-crystalline pores are produced in clay minerals, this type of pores is not the most important contributor to porosity. Besides this, pore shape determined by N2GA hysteresis loop is consistent with SEM observation on clay inter-crystalline pores while BJH pore volume is positively related with clay content, suggesting N2GA is suitable for describing clay inter-crystalline pores in tight sandstones.

Pore structure characterization of Chang-7 tight sandstone using MICP combined with N2GA techniques and its geological control factors

PubMed Central

Cao, Zhe; Liu, Guangdi; Zhan, Hongbin; Li, Chaozheng; You, Yuan; Yang, Chengyu; Jiang, Hang

2016-01-01

Understanding the pore networks of unconventional tight reservoirs such as tight sandstones and shales is crucial for extracting oil/gas from such reservoirs. Mercury injection capillary pressure (MICP) and N2 gas adsorption (N2GA) are performed to evaluate pore structure of Chang-7 tight sandstone. Thin section observation, scanning electron microscope, grain size analysis, mineral composition analysis, and porosity measurement are applied to investigate geological control factors of pore structure. Grain size is positively correlated with detrital mineral content and grain size standard deviation while negatively related to clay content. Detrital mineral content and grain size are positively correlated with porosity, pore throat radius and withdrawal efficiency and negatively related to capillary pressure and pore-to-throat size ratio; while interstitial material is negatively correlated with above mentioned factors. Well sorted sediments with high debris usually possess strong compaction resistance to preserve original pores. Although many inter-crystalline pores are produced in clay minerals, this type of pores is not the most important contributor to porosity. Besides this, pore shape determined by N2GA hysteresis loop is consistent with SEM observation on clay inter-crystalline pores while BJH pore volume is positively related with clay content, suggesting N2GA is suitable for describing clay inter-crystalline pores in tight sandstones. PMID:27830731

Bio-composites of cassava starch-green coconut fiber: part II-Structure and properties.

PubMed

Lomelí-Ramírez, María Guadalupe; Kestur, Satyanarayana G; Manríquez-González, Ricardo; Iwakiri, Setsuo; de Muniz, Graciela Bolzon; Flores-Sahagun, Thais Sydenstricker

2014-02-15

Development of any new material requires its complete characterization to find potential applications. In that direction, preparation of bio-composites of cassava starch containing up to 30 wt.% green coconut fibers from Brazil by thermal molding process was reported earlier. Their characterization regarding physical and tensile properties of both untreated and treated matrices and their composites were also reported. Structural studies through FTIR and XRD and thermal stability of the above mentioned composites are presented in this paper. FT-IR studies revealed decomposition of components in the matrix; the starch was neither chemically affected nor modified by either glycerol or the amount of fiber. XRD studies indicated increasing crystallinity of the composites with increasing amount of fiber content. Thermal studies through TGA/DTA showed improvement of thermal stability with increasing amount of fiber incorporation, while DMTA showed increasing storage modulus, higher glass transition temperature and lower damping with increasing fiber content. Improved interfacial bonding between the matrix and fibers could be the cause for the above results. Copyright © 2013 Elsevier Ltd. All rights reserved.

High crystalline Cu2ZnSnS4 semiconductor prepared from low toxicity ethanol-based precursors

NASA Astrophysics Data System (ADS)

Munir, Badrul; Prastyo, Bayu Eko; Nurjaya, Dwi Marta; Muslih, Ersan Yudhapratama; Alfauzan, Sahri Karim

2017-01-01

At this moment, we present a new, cost-effective, and environmentally friendly method of preparing a high crystalline Cu2ZnSnS4 (CZTS) absorber layer for thin film solar cells using ethanol-based solutions. Ethanolamine (ETA) and 2-mercaptopropionic acid (MPA) were studied as a stabilizer and to improve wetting ability of the precursors during the deposition process. Cu2ZnSnS4 precursors are deposited onto soda lime glass using spin coater in different molar of cations in the precursor. The effects of a precursor system, ethanol-ETA-MPA, and ethanol-MPA, on the structure, morphology, composition and optical properties of CZTS thin films have been investigated in details. X-ray diffraction and energy-dispersive X-ray spectroscopy analyses confirmed the successful fabrication of high crystalline Cu2ZnSnS4 kesterite phase. The crystallinity of CZTS is continue increasing before reaching 2.2 molar cations of the ethanol-MPA precursors. The crystallinity of ethanol-ETA-MPA precursors remains similar in the experiment using 1.2 molar and 1.6 molars. The highest crystallinity was achieved using 2 molar cations of the ethanol-MPA precursor. Its band gap energy is found to be around 1.4 eV. The SEM micrographs of CZTS film shows the average grain size around 1.5 µm and some porosity which indicated the room of improvement. The high-crystallinity CZTS achieved in the present study brings a low-cost absorber semiconductor one step closer to practical use.

Poling of PVDF matrix composites for integrated structural load sensing

NASA Astrophysics Data System (ADS)

Haghiashtiani, Ghazaleh; Greminger, Michael A.; Zhao, Ping

2014-03-01

The purpose of this study is to create and evaluate a smart composite structure that can be used for integrated load sensing and structural health monitoring. In this structure, PVDF films are used as the matrix material instead of epoxy resin or other thermoplastics. The reinforcements are two layers of carbon fiber with one layer of Kevlar separating them. Due to the electrical conductivity properties of carbon fiber and the dielectric effect of Kevlar, the structure acts as a capacitor. Furthermore, the piezoelectric properties of the PVDF matrix can be used to monitor the response of the structure under applied loads. In order to exploit the piezoelectric properties of PVDF, the PVDF material must be polarized to align the dipole moments of its crystalline structure. The optimal condition for poling the structure was found by performing a 23 factorial design of experiment (DoE). The factors that were studied in DoE were temperature, voltage, and duration of poling. Finally, the response of the poled structure was monitored by exposing the samples to an applied load.

Cubic liquid crystalline nanoparticles: optimization and evaluation for ocular delivery of tropicamide.

PubMed

Verma, Purnima; Ahuja, Munish

2016-10-01

The purpose of this study was to investigate the potential of cubic liquid crystalline nanoparticles for ocular delivery of tropicamide. Ultrasound-assisted fragmentation of cubic liquid crystalline bulk phases resulted in cubic liquid crystalline nanoparticles employing Pluronic F127 as dispersant. The effects of process variables such as sonication time, sonication amplitude, sonication depth, and pre-mixing time on particle size and polydispersity index was investigated using central composite design. The morphology of tropicamide-loaded nanoparticles was found to be nearly cubical in shape by transmission electron microscopy observation. Further, small angle X-ray scattering experiment confirmed the presence of D and P phase cubic structures in coexistence. The optimized tropicamide-loaded cubic nanoparticles showed in vitro corneal permeation of tropicamide across isolated porcine cornea comparable to its commercial preparation, Tropicacyl®. Ocular tolerance was evaluated by Hen's egg-chorioallantoic membrane test and histological studies. The results of in vivo mydriatic response study demonstrated a remarkably higher area under mydriatic response curve (AUC 0→1440 min ) values of cubic nanoparticles over Tropicacyl® indicating better therapeutic value of cubic nanoparticles. Furthermore, tropicamide-loaded cubic nanoparticles exhibited prolonged mydriatic effect on rabbits as compared to commercial conventional aqueous ophthalmic solution.

Porous and single-crystalline ZnO nanobelts: fabrication with annealing precursor nanobelts, and gas-sensing and optoelectronic performance

NASA Astrophysics Data System (ADS)

Jin, Xiao-Bo; Li, Yi-Xiang; Su, Yao; Guo, Zheng; Gu, Cui-Ping; Huang, Jia-Rui; Meng, Fan-Li; Huang, Xing-Jiu; Li, Min-Qiang; Liu, Jin-Huai

2016-09-01

Porous and single-crystalline ZnO nanobelts have been prepared through annealing precursors of ZnSe · 0.5N2H4 well-defined and smooth nanobelts, which have been synthesized via a simple hydrothermal method. The composition and morphology evolutions with the calcination temperatures have been investigated in detail for as-prepared precursor nanobelts, suggesting that they can be easily transformed into ZnO nanobelts by preserving their initial morphology via calcination in air. In contrast, the obtained ZnO nanobelts are densely porous, owing to the thermal decomposition and oxidization of the precursor nanobelts. More importantly, the achieved porous ZnO nanobelts are single-crystalline, different from previously reported ones. Motivated by the intrinsic properties of the porous structure and good electronic transporting ability of single crystals, their gas-sensing performance has been further explored. It is demonstrated that porous ZnO single-crystalline nanobelts exhibit high response and repeatability toward volatile organic compounds, such as ethanol and acetone, with a short response/recovery time. Furthermore, their optoelectronic behaviors indicate that they can be promisingly employed to fabricate photoelectrochemical sensors.

Induced amphotropic and thermotropic ionic liquid crystallinity in phosphonium halides: "lubrication" by hydroxyl groups.

PubMed

Ma, Kefeng; Somashekhar, B S; Gowda, G A Nagana; Khetrapal, C L; Weiss, Richard G

2008-03-18

The influence of covalently attaching hydroxymethylene to the methyl groups of methyl-tri-n-alkylphosphonium halides (where the alkyl chains are decyl, tetradecyl, or octadecyl and the halide is chloride or bromide) or adding methanol as a solute to the salts on their solid, liquid-crystalline (smectic A2), and isotropic phases has been investigated using a variety of experimental techniques. These structural and compositional changes are found to induce liquid crystallinity in some cases and to enhance the temperature range and lower the onset temperature of the liquid-crystalline phases in some others. The results are interpreted in terms of the lengths of the three n-alkyl chains attached to the phosphorus cation, the nature of the halide anion, the influence of H-bonding interactions at the head group regions of the layered phases, and other solvent-solute interactions. The fact that at least 1 molar equiv of methanol must be added to effect complete (isothermal) conversion of a solid methyl-tri-n-alkylphosphonium salt to a liquid crystal demonstrates a direct and strong association between individual methanol molecules and the phosphonium salts. Possible applications of such systems are suggested.

Local Structural Investigations, Defect Formation, and Ionic Conductivity of the Lithium Ionic Conductor Li 4 P 2 S 6

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

Dietrich, Christian; Sadowski, Marcel; Sicolo, Sabrina

Glassy, glass–ceramic, and crystalline lithium thiophosphates have attracted interest in their use as solid electrolytes in all-solid-state batteries. Despite similar structural motifs, including PS 4 3–, P 2S 6 4–, and P 2S 7 4– polyhedra, these materials exhibit a wide range of possible compositions, crystal structures, and ionic conductivities. Here, we present a combined approach of Bragg diffraction, pair distribution function analysis, Raman spectroscopy, and 31P magic angle spinning nuclear magnetic resonance spectroscopy to study the underlying crystal structure of Li 4P 2S 6. In this work, we show that the material crystallizes in a planar structural arrangement asmore » a glass ceramic composite, explaining the observed relatively low ionic conductivity, depending on the fraction of glass content. Calculations based on density functional theory provide an understanding of occurring diffusion pathways and ionic conductivity of this Li + ionic conductor.« less

Fine Structure Study of the Plasma Coatings B4C-Ni-P

NASA Astrophysics Data System (ADS)

Kornienko, E. E.; Bezrukova, V. A.; Kuz'min, V. I.; Lozhkin, V. S.; Tutunkova, M. K.

2017-12-01

The article considers structure of coatings formed of the B4C-Ni-P powder. The coatings were deposited using air-plasma spraying with the unit for annular injection of powder. The pipes from steel 20 (0.2 % C) were used as a substrate. The structure and phase composition of the coatings were studied by optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffractometry. It is shown that high-density composite coatings consisting of boron carbide particles distributed in the nickel boride metal matrix are formed using air-plasma spraying. The areas with round inclusions characterized by the increased amount of nickel, phosphorus and boron are located around the boron carbide particles. Boron oxides and nickel oxides are also present in the coatings. Thin interlayers with amorphous-crystalline structure are formed around the boron carbide particles. The thickness of these interlayers does not exceed 1 μm. The metal matrix material represents areas with nanocrystalline structure and columnar crystals.

Crystallization kinetics of Mg–Cu–Yb–Ca–Ag metallic glasses

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

Tsarkov, Andrey A., E-mail: tsarkov@misis.ru; WPI Advanced Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 980-8577; Zanaeva, Erzhena N.

The paper presents research into a Mg–Cu–Yb system based metallic glassy alloys. Metallic glasses were prepared using induction melting and further injection on a spinning copper wheel. The effect of alloying by Ag and Ca on the glass forming ability and the kinetics of crystallization of Mg–Cu–Yb system based alloys were studied. The differential scanning calorimeter and X-ray diffractometer were used to investigate the kinetics of crystallization and the phase composition of the samples. An indicator of glass forming ability, effective activation energy of crystallization, and enthalpy of mixing were calculated. An increase of the Ca and Ag content hasmore » a positive effect on the glass forming ability, the effective activation energy of crystallization, and the enthalpy of mixing. The highest indicators of the glass forming ability and the thermal stability were found for alloys that contain both alloying elements. The Ag addition suppresses precipitation of the Mg{sub 2}Cu phase during crystallization. A dual-phase glassy-nanocrystalline Mg structure was obtained in Mg{sub 65}Cu{sub 25}Yb{sub 10} and Mg{sub 59.5}Cu{sub 22.9}Yb{sub 11}Ag{sub 6.6} alloys after annealing. Bulk samples with a composite glassy-crystalline structure were obtained in Mg{sub 59.5}Cu{sub 22.9}Yb{sub 11}Ag{sub 6.6} and Mg{sub 64}Cu{sub 21}Yb{sub 9.5}Ag{sub 5.5} alloys. A thermodynamic database for the Mg–Cu–Yb–Ca–Ag system was created to compare the process of crystallization of alloys with polythermal sections of the Mg–Cu–Yb–Ca–Ag phase diagram. - Highlights: • New alloy compositions based on Mg–Cu–Yb system were developed and investigated. • Increasing content of Ag and Ca leads to improving GFA. • Bulk samples with a composite glassy-crystalline structure were obtained. • Thermodynamic database for Mg–Cu–Yb–Ca–Ag system was created.« less

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

Solla, E.L., E-mail: esolla@uvigo.es

Herein, we report on the micro- and nanostructure of the calcium phosphate coating produced by pulsed laser deposition (PLD), using focused ion beam (FIB) lamella sample preparation and transmission electron microscopy (TEM) as the characterization technique. The initial selected area electron diffraction (SAED) data demonstrated the presence of hydroxyapatite (HA) over any other possible calcium phosphate crystalline structure and the polycrystalline nature of the coating. Moreover, the SAED analyses showed clear textured ring patterns coherent with the presence of a preferred orientation in the HA nano-crystal growth. The SAED data also indicated that the coating appears to be textured inmore » the 〈002〉 crystalline direction. Dark-field images obtained using 002 as the working reflection showed a clear oriented crystal growth in columns, from bottom to top. These columns have a peculiar arrangement of nano-crystals since, in some cases, the preferred orientation appears to start at a certain distance from the substrate. Direct d-spacing measurements on high-resolution TEM images provided further proof of the presence of an HA nano-crystal structure. The reported data may be of interest in the future to adjust the microstructure of the HA coatings. - Highlights: •The FIB lift-out technique allows a very site-specific sample preparation method for HRTEM analysis. •It also permits a fast assessment of the HA coating thickness and elemental composition (EDS). •The coatings exhibit a nano-crystalline nature, with a texturing effect along the 002 planes. •PLD is suitable for the production of crystalline c-axis oriented hydroxyapatite coatings. •The crystalline HA phase in the PLD coating is very similar to the present in bone.« less

Optimization of chemical vapor deposition diamond films growth on steel: correlation between mechanical properties, structure, and composition.

PubMed

Laikhtman, A; Rapoport, L; Perfilyev, V; Moshkovich, A; Akhvlediani, R; Hoffman, A

2011-09-01

In the present work we perform optimization of mechanical and crystalline properties of CVD microcrystalline diamond films grown on steel substrates. A chromium-nitride (Cr-N) interlayer had been previously proposed to serve as a buffer for carbon and iron inter-diffusion and as a matching layer for the widely differing expansion coefficients of diamond and steel. However, adhesion and wear as well as crystalline perfection of diamond films are strongly affected by conditions of both Cr-N interlayer preparation and CVD diamond deposition. In this work we assess the effects of two parameters. The first one is the temperature of the Cr-N interlayer preparation: temperatures in the range of 500 degrees C-800 degrees C were used. The second one is diamond film thickness in the 0.5 microm-2 microm range monitored through variation of the deposition time from approximately 30 min to 2 hours. The mechanical properties of so deposited diamond films were investigated. For this purpose, scratch tests were performed at different indentation loads. The friction coefficient and wear loss were assessed. The mechanical and tribological properties were related to structure, composition, and crystalline perfection of diamond films which were extensively analyzed using different microscopic and spectroscopic techniques. It was found that relatively thick diamond film deposited on the Cr-N interlayer prepared at the temperature similar to that of the CVD process has the best mechanical and adhesion strength. This film was stable without visible cracks around the wear track during all scratch tests with different indentation loads. In other cases, cracking and delamination of the films took place at low to moderate indentation loads.

Ring distributions in alkali- and alkaline-earth aluminosilicate framework glasses- a raman spectroscopic study

USGS Publications Warehouse

Sharma, S.K.; Philpotts, J.A.; Matson, D.W.

1985-01-01

Raman spectra of crystalline polymorphs of a number of tectosilicate minerals having various sizes of smallest rings of TO4 tetrahedra (T = Si, Al) have been investigated to identify the bands that are sensitive indicators of the smallest rings in the network. The information obtained from the Raman spectra of tectosilicate minerals (e.g., SiO2 polymorphs, NaAlSi3O8 (Ab), NaAlSiO4 (Ne), KAlSi3O8 (Or), and KAlSi2O6 (Lc)) is used to interpret the Raman spectra of the isochemical glasses. It is shown that the frequency of the dominant ??s (TOT) band in the spectra of both crystals and glasses is related to the dominant size of TO4 rings in the structure. In agreement with previous X-ray RDF work, it is found that in the glasses of Ab and Jd (NaAlSi2O6) compositions, six-membered rings of TO4 tetrahedra predominate. The Raman spectrum of Or glass, however, indicates that clusters of intermixed four- and six-membered rings of TO4 tetrahedra, similar to those existing in crystalline leucite, are also present in the glass. Raman evidence indicates that four-membered rings of TO4 tetrahedra predominate in the glass of An composition. Similarly, the higher frequency of the ??s (TOT) band in the spectrum of Ne glass as compared with the frequency the ??s (TOT) band in the spectra of crystalline cargenieite and nephelite indicates either an admixture of the four- and six-membered rings or the puckering of six-membered rings in the glass structure. ?? 1985.

Magnetization enhancement due to incorporation of non-magnetic nitrogen content in (Co{sub 84}Zr{sub 16})N{sub x} nano-composite films

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

Singh, Jitendra, E-mail: jitendra@ceeri.ernet.in; Akhtar, Jamil; Academy of Scientific and Innovative Research, New Delhi 110001

We report the magnetic, electronic, and structural properties of nano-composite (Co{sub 84}Zr{sub 16})N{sub x} or CZN films prepared by reactive co-sputter deposition method. As-deposited CZN films have shown enhancement in magnetization (M{sub s}) with incorporation of nitrogen content, which is related to the evolution of nano-composite phase. X-ray diffraction study has confirmed poly-crystalline growth of CZN films with fcc(331) and fcc(422) phases. High-resolution transmission electron microscope study reveals that CZN films are composed of ordered and crystalline ferromagnetic Co nano-clusters, which are embedded in the nano-composite matrix. Photoemission measurements show the change in the intensity near the Fermi level mostmore » likely due to defects and shift in the core-levels binding energy with nitrogen concentration. Raman spectroscopy data show an increase in the intensity of the Raman lines with nitrogen concentration upto 20%. However, the intensity is significantly lower for 30% sample. This indicates that less nitrogen or defect states are being substituted into the lattice above 20% and is consistent with the observed magnetic behavior. Our studies indicate that defects induced due to the incorporation of non-magnetic nitrogen content play a key role to enhance the magnetization.« less

Effect of preparation conditions on the characteristics and photocatalytic activity of TiO2/purified diatomite composite photocatalysts

NASA Astrophysics Data System (ADS)

Sun, Zhiming; Hu, Zhibo; Yan, Yang; Zheng, Shuilin

2014-09-01

TiO2/purified diatomite composite materials were prepared through a modified hydrolysis-deposition method under low temperature using titanium tetrachloride as precursor combined with a calcination crystallization process. The microstructure and crystalline phases of the obtained composites prepared under different preparation conditions were characterized by high resolution scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively. The photocatalytic performance of TiO2/purified diatomite composites was evaluated by Rhodamine B as the target pollutant under UV irradiation, and the optimum preparation conditions of composites were obtained. The TiO2 crystal form in composites prepared under optimum conditions was anatase, the grain size of which was 34.12 nm. The relationships between structure and property of composite materials were analyzed and discussed. It is indicated that the TiO2 nanoparticles uniformly dispersed on the surface of diatoms, and the photocatalytic performance of the composite materials was mainly determined by the dispersity and grain size of loaded TiO2 nanoparticles.

Depth-Profiling Electronic and Structural Properties of Cu(In,Ga)(S,Se)2 Thin-Film Solar Cell.

PubMed

Chiang, Ching-Yu; Hsiao, Sheng-Wei; Wu, Pin-Jiun; Yang, Chu-Shou; Chen, Chia-Hao; Chou, Wu-Ching

2016-09-14

Utilizing a scanning photoelectron microscope (SPEM) and grazing-incidence X-ray powder diffraction (GIXRD), we studied the electronic band structure and the crystalline properties of the pentanary Cu(In,Ga)(S,Se)2 (CIGSSe) thin-film solar cell as a function of sample depth on measuring the thickness-gradient sample. A novel approach is proposed for studying the depth-dependent information on thin films, which can provide a gradient thickness and a wide cross-section of the sample by polishing process. The results exhibit that the CIGSSe absorber layer possesses four distinct stoichiometries. The growth mechanism of this distinctive compositional distribution formed by a two-stage process is described according to the thermodynamic reaction and the manufacturing process. On the basis of the depth-profiling results, the gradient profiles of the conduction and valence bands were constructed to elucidate the performance of the electrical properties (in this case, Voc = 620 mV, Jsc = 34.6 mA/cm(2), and η = 14.04%); the valence-band maxima (VBM) measured with a SPEM in the spectroscopic mode coincide with this band-structure model, except for a lowering of the VBM observed in the surface region of the absorber layer due to the ordered defect compound (ODC). In addition, the depth-dependent texturing X-ray diffraction pattern presents the crystalline quality and the residual stress for each depth of a thin-film device. We find that the randomly oriented grains in the bottom region of the absorber layer and the different residual stress between the underlying Mo and the absorber interface, which can deteriorate the electrical performance due to peeling-off effect. An anion interstitial defect can be observed on comparing the anion concentration of the elemental distribution with crystalline composition; a few excess sulfur atoms insert in interstitial sites at the front side of the absorber layer, whereas the interstitial selenium atoms insert at the back side.

Nanostructured Tungsten Oxide Composite for High-Performance Gas Sensors

PubMed Central

Feng-Chen, Siyuan; Aldalbahi, Ali; Feng, Peter Xianping

2015-01-01

We report the results of composite tungsten oxide nanowires-based gas sensors. The morphologic surface, crystallographic structures, and chemical compositions of the obtained nanowires have been investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman scattering, respectively. The experimental measurements reveal that each wire consists of crystalline nanoparticles with an average diameter of less than 250 nm. By using the synthesized nanowires, highly sensitive prototypic gas sensors have been designed and fabricated. The dependence of the sensitivity of tungsten oxide nanowires to the methane and hydrogen gases as a function of time has been obtained. Various sensing parameters such as sensitivity, response time, stability, and repeatability were investigated in order to reveal the sensing ability. PMID:26512670

Growth Structure and Properties of Gradient Nanocrystalline Coatings of the Ti-Al-Si-Cu-N System

NASA Astrophysics Data System (ADS)

Ovchinnikov, S. V.; Pinzhin, Yu. P.

2016-10-01

Methods of electron microprobe analysis, X-ray structure analysis and electron microscopy were used to study the element composition and features of the structure-phase, elastic stress state of nanocrystalline coatings of the Ti- Al- Si- Cu- N system with gradient of copper concentration across their thickness. The authors established the effects of element composition modification, non-monotonous behavior of the lattice constant of alloyed nitride and rise in the bending-torsion value of the crystalline lattice in individual nanocrystals to values of around 400 degrees/μm with increase in copper concentration, whereas the sizes of alloyed nitride crystals remained practically unchanged. Mechanical (hardness), adhesion and tribological properties of coatings were examined. Comparative analysis demonstrates higher values of adhesion characteristics in the case of gradient coatings of the Ti- Al- Si- Cu- N system than in the case of single-layer (with constant element concentration) analogues.

Calcium phosphate coatings modified with zinc- or copper- incorporation on Ti-40Nb alloy

NASA Astrophysics Data System (ADS)

Komarova, E. G.; Sedelnikova, M. B.; Sharkeev, Yu P.; Kazakbaeva, A. A.; Glukhov, I. A.; Khimich, M. A.

2017-05-01

The influence of the microarc oxidation parameters and electrolyte composition on the structure, properties and composition of CaP coatings modified with Zn- or Cu- incorporation on the Ti-40mas.%Nb (Ti-40Nb) alloy was investigated. The linear growth of thickness, roughness, and size of structural elements with process voltage increasing has been revealed. It was shown that the CaP coatings have the low contact angles with liquids and, consequently, high free surface energy. This indicates a high hydrophilicity of the coatings. X-ray diffraction analysis showed that the coatings have X-ray amorphous structure. The increase of the process voltage leads to the formation of such crystalline phases as CaHPO4 and β-Ca2P2O7 in the coatings. The maximum Ca/P atomic ratio was equal to 0.4, and Zn or Cu contents was equal to 0.3 or 0.2 at.%, respectively.

Multi-scale model for the hierarchical architecture of native cellulose hydrogels.

PubMed

Martínez-Sanz, Marta; Mikkelsen, Deirdre; Flanagan, Bernadine; Gidley, Michael J; Gilbert, Elliot P

2016-08-20

The structure of protiated and deuterated cellulose hydrogels has been investigated using a multi-technique approach combining small-angle scattering with diffraction, spectroscopy and microscopy. A model for the multi-scale structure of native cellulose hydrogels is proposed which highlights the essential role of water at different structural levels characterised by: (i) the existence of cellulose microfibrils containing an impermeable crystalline core surrounded by a partially hydrated paracrystalline shell, (ii) the creation of a strong network of cellulose microfibrils held together by hydrogen bonding to form cellulose ribbons and (iii) the differential behaviour of tightly bound water held within the ribbons compared to bulk solvent. Deuterium labelling provides an effective platform on which to further investigate the role of different plant cell wall polysaccharides in cellulose composite formation through the production of selectively deuterated cellulose composite hydrogels. Copyright © 2016 Elsevier Ltd. All rights reserved.

Microstructure and Mechanical Behaviors of Titanium Matrix Composites Containing In Situ Whiskers Synthesized via Plasma Activated Sintering.

PubMed

Sun, Yi; Zhang, Jian; Luo, Guoqiang; Shen, Qiang; Zhang, Lianmeng

2018-04-02

In this paper, titanium matrix composites with in situ TiB whiskers were synthesized by the plasma activated sintering technique; crystalline boron and amorphous boron were used as reactants for in situ reactions, respectively. The influence of the sintering process and the crystallography type of boron on the microstructure and mechanical properties of composites were studied and compared. The densities were evaluated using Archimedes' principle. The microstructure and mechanical properties were characterized by SEM, XRD, EBSD, TEM, a universal testing machine, and a Vickers hardness tester. The prepared composite material showed a high density and excellent comprehensive performance under the PAS condition of 20 MPa at 1000 °C for 3 min. Amorphous boron had a higher reaction efficiency than crystalline boron, and it completely reacted with the titanium matrix to generate TiB whiskers, while there was still a certain amount of residual crystalline boron combining well with the titanium matrix at 1100 °C. The composite samples with a relative density of 98.33%, Vickers hardness of 389.75 HV, compression yield strength of up to 1190 MPa, and an ultimate compressive strength of up to 1710 MPa were obtained. Compared with the matrix material, the compressive strength of TC4 titanium alloy containing crystalline boron and amorphous boron was increased by 7.64% and 15.50%, respectively.

Microstructure and Mechanical Behaviors of Titanium Matrix Composites Containing In Situ Whiskers Synthesized via Plasma Activated Sintering

PubMed Central

Luo, Guoqiang; Shen, Qiang; Zhang, Lianmeng

2018-01-01

In this paper, titanium matrix composites with in situ TiB whiskers were synthesized by the plasma activated sintering technique; crystalline boron and amorphous boron were used as reactants for in situ reactions, respectively. The influence of the sintering process and the crystallography type of boron on the microstructure and mechanical properties of composites were studied and compared. The densities were evaluated using Archimedes’ principle. The microstructure and mechanical properties were characterized by SEM, XRD, EBSD, TEM, a universal testing machine, and a Vickers hardness tester. The prepared composite material showed a high density and excellent comprehensive performance under the PAS condition of 20 MPa at 1000 °C for 3 min. Amorphous boron had a higher reaction efficiency than crystalline boron, and it completely reacted with the titanium matrix to generate TiB whiskers, while there was still a certain amount of residual crystalline boron combining well with the titanium matrix at 1100 °C. The composite samples with a relative density of 98.33%, Vickers hardness of 389.75 HV, compression yield strength of up to 1190 MPa, and an ultimate compressive strength of up to 1710 MPa were obtained. Compared with the matrix material, the compressive strength of TC4 titanium alloy containing crystalline boron and amorphous boron was increased by 7.64% and 15.50%, respectively. PMID:29614842

Telomere maintenance in liquid crystalline chromosomes of dinoflagellates.

PubMed

Fojtová, Miloslava; Wong, Joseph T Y; Dvorácková, Martina; Yan, Kosmo T H; Sýkorová, Eva; Fajkus, Jirí

2010-10-01

The organisation of dinoflagellate chromosomes is exceptional among eukaryotes. Their genomes are the largest in the Eukarya domain, chromosomes lack histones and may exist in liquid crystalline state. Therefore, the study of the structural and functional properties of dinoflagellate chromosomes is of high interest. In this work, we have analysed the telomeres and telomerase in two Dinoflagellata species, Karenia papilionacea and Crypthecodinium cohnii. Active telomerase, synthesising exclusively Arabidopsis-type telomere sequences, was detected in cell extracts. The terminal position of TTTAGGG repeats was determined by in situ hybridisation and BAL31 digestion methods and provides evidence for the linear characteristic of dinoflagellate chromosomes. The length of telomeric tracts, 25-80 kb, is the largest among unicellular eukaryotic organisms to date. Both the presence of long arrays of perfect telomeric repeats at the ends of dinoflagellate chromosomes and the existence of active telomerase as the primary tool for their high-fidelity maintenance demonstrate the general importance of these structures throughout eukaryotes. We conclude that whilst chromosomes of dinoflagellates are unique in many aspects of their structure and composition, their telomere maintenance follows the most common scenario.

Dehydration-induced amorphous phases of calcium carbonate.

PubMed

Saharay, Moumita; Yazaydin, A Ozgur; Kirkpatrick, R James

2013-03-28

Amorphous calcium carbonate (ACC) is a critical transient phase in the inorganic precipitation of CaCO3 and in biomineralization. The calcium carbonate crystallization pathway is thought to involve dehydration of more hydrated ACC to less hydrated ACC followed by the formation of anhydrous ACC. We present here computational studies of the transition of a hydrated ACC with a H2O/CaCO3 ratio of 1.0 to anhydrous ACC. During dehydration, ACC undergoes reorganization to a more ordered structure with a significant increase in density. The computed density of anhydrous ACC is similar to that of calcite, the stable crystalline phase. Compared to the crystalline CaCO3 phases, calcite, vaterite, and aragonite, the computed local structure of anhydrous ACC is most-similar to those of calcite and vaterite, but the overall structure is not well described by either. The strong hydrogen bond interaction between the carbonate ions and water molecules plays a crucial role in stabilizing the less hydrated ACC compositions compared to the more hydrated ones, leading to a progressively increasing hydration energy with decreasing water content.

In-situ Polymerization of Polyaniline/Polypyrrole Copolymer using Different Techniques

NASA Astrophysics Data System (ADS)

Hammad, A. S.; Noby, H.; Elkady, M. F.; El-Shazly, A. H.

2018-01-01

The morphology and surface area of the poly(aniline-co-pyrrole) copolymer (PANPY) are important properties which improve the efficiency of the copolymer in various applications. In this investigation, different techniques were employed to produce PANPY in different morphologies. Aniline and pyrrole were used as monomers, and ammonium peroxydisulfate (APS) was used as an oxidizer with uniform molar ratio. Rapid mixing, drop-wise mixing, and supercritical carbon dioxide (ScCO2) polymerization techniques were appointed. The chemical structure, crystallinity, porosity, and morphology of the composite were distinguished by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Brunauer, Emmett and Teller (BET) analysis, and transmission electron microscopy (TEM) respectively. The characterization tests indicated that the polyaniline/polypyrrole copolymer was successfully prepared with different morphologies. Based on the obtained TEM, hollow nanospheres were formed using rapid mixing technique with acetic acid that have a diameter of 75 nm and thickness 26 nm approximately. Also, according to the XRD, the produced structures have a semi- crystalline structure. The synthesized copolymer with ScCO2-assisted polymerization technique showed improved surface area (38.1 m2/g) with HCl as dopant.

Phase behavior of 1-dodecyl-3-methylimidazolium fluorohydrogenate salts (C12MIm(FH)(n)F, n = 1.0-2.3) and their anisotropic ionic conductivity as ionic liquid crystal electrolytes.

PubMed

Xu, Fei; Matsumoto, Kazuhiko; Hagiwara, Rika

2012-08-23

The effects of the HF composition, n, in 1-dodecyl-3-methylimidazolium fluorohydrogenate salts (C(12)MIm(FH)(n)F, n = 1.0-2.3) on their physicochemical and structural properties have been investigated using infrared spectroscopy, thermal analysis, polarized optical microscopy, X-ray diffraction, and anisotropic ionic conductivity measurements. The phase diagram of C(12)MIm(FH)(n)F (n vs transition temperature) suggests that C(12)MIm(FH)(n)F is a mixed crystal system that has a boundary around n = 1.9. For all compositions, a liquid crystalline mesophase with a smectic A interdigitated bilayer structure is observed. The temperature range of the mesophase decreases with increasing n value (from 61.8 °C for C(12)MIm(FH)(1.0)F to 37.0 °C for C(12)MIm(FH)(2.3)F). The layer spacing of the smectic structure decreases with increasing n value or increasing temperature. Two structural types with different layer spacings are observed in the crystalline phase (type I, 1.0 ≤ n ≤ 1.9, and type II, 1.9 ≤ n ≤ 2.3). Ionic conductivities parallel and perpendicular to the smectic layers (σ(||) and σ([perpendicular])) increase with increasing n value, whereas the anisotropy of the ionic conductivities (σ(||)/σ([perpendicular])) is independent of the n value, since the thickness of the insulating sheet formed by the dodecyl group remains nearly unchanged.

Dielectric relaxation of near-percolated carbon nanofiber polypropylene composites

NASA Astrophysics Data System (ADS)

Paleo, A. J.; Zille, A.; Van Hattum, F. W.; Ares-Pernas, A.; Agostinho Moreira, J.

2017-07-01

In this work, the morphological, structural and dielectric analysis of near-percolated polypropylene (PP) composites containing carbon nanofibers (CNF) processing by melt-mixing are investigated. Whereas the morphological analysis shows that CNF exhibit some tendency to agglomerate within the PP matrix, the structural analysis showed first a general decrease in the intensity of the IR bands as a consequence of the interaction between carbon nanofibers and PP matrix and second an increase of the crystallinity degree of the PP/CNF composites when compared to the pure PP. The dielectric analysis demonstrates enhanced dielectric constants (from 2.97 for neat polymer to 9.7 for 1.9 vol% loaded composites at 200 Hz) and low dielectric losses. Furthermore, the dielectric relaxation for composites with concentrations in the vicinity of percolation is evidenced and well described by the generalized polydispersive Cole-Cole model from which the values of static dielectric constant (εs) , high frequency dielectric constant (ε∞) , distribution of relaxation time (α) and mean relaxation time (τo), are determined, suggesting that this latter analysis constitutes a strong tool for understanding the relationships between microstructure and dielectric properties in this type of polymer composites.

Alloy and method of producing the same

DOEpatents

Hufnagel, Todd C.; Ott, Ryan T.; Fan, Cang; Kecskes, Laszlo

2005-07-19

In accordance with a preferred embodiment of the invention, an alloy or other composite material is provided formed of a bulk metallic glass matrix with a microstructure of crystalline metal particles. The alloy preferably has a composition of (X.sub.a Ni.sub.b Cu.sub.c).sub.100-d-c Y.sub.d Al.sub.c, wherein the sum of a, b and c equals 100, wherein 40.ltoreq.a.ltoreq.80, 0.ltoreq.b.ltoreq.35, 0.ltoreq.c.ltoreq.40, 4.ltoreq.d.ltoreq.30, and 0.ltoreq.e.ltoreq.20, and wherein preferably X is composed of an early transition metal and preferably Y is composed of a refractory body-centered cubic early transition metal. A preferred embodiment of the invention also provides a method of producing an alloy composed of two or more phases at ambient temperature. The method includes the steps of providing a metastable crystalline phase composed of at least two elements, heating the metastable crystalline phase together with at least one additional element to form a liquid, casting the liquid, and cooling the liquid to form the alloy. In accordance with a preferred embodiment of the invention, the composition and cooling rate of the liquid can be controlled to determine the volume fraction of the crystalline phase and determine the size of the crystalline particles, respectively.

Modeling deformation behavior of Cu-Zr-Al bulk metallic glass matrix composites

NASA Astrophysics Data System (ADS)

Pauly, S.; Liu, G.; Wang, G.; Das, J.; Kim, K. B.; Kühn, U.; Kim, D. H.; Eckert, J.

2009-09-01

In the present work we prepared an in situ Cu47.5Zr47.5Al5 bulk metallic glass matrix composite derived from the shape memory alloy CuZr. We use a strength model, which considers percolation and a three-microstructural-element body approach, to understand the effect of the crystalline phase on the yield stress and the fracture strain under compressive loading, respectively. The intrinsic work-hardenability due to the martensitic transformation of the crystalline phase causes significant work hardening also of the composite material.

The effect of PS porosity on the structure, optical and electrical properties of ZnS/PS

NASA Astrophysics Data System (ADS)

Wang, Cai-Feng; Hu, Bo; Yi, Hou-Hui; Li, Wei-Bing

2014-03-01

ZnS films were deposited on porous silicon (PS) substrates with different porosities by pulsed laser deposition (PLD). The crystalline structure, surface morphology of ZnS films on PS substrates and optical, electrical properties of ZnS/PS composites were studied. The results show that, ZnS films deposited on PS substrates were grown in preferred orientation along β-ZnS (111) direction corresponding to crystalline structure of cubic phase. With the increase of PS porosity, the XRD diffraction peak intensity of ZnS films decreases. Some voids and cracks appear in the films. Compared with as-prepared PS, the PL peak of PS for ZnS/PS has a blueshift. The larger the porosity of PS, the greater the blueshift is. A new green light emission located around 550 nm is observed with increasing PS porosity, which is ascribed to defect-center luminescence of ZnS. The blue, green emission of ZnS combined with the red emission of PS, a broad photoluminescence band (450-750 nm) is formed. ZnS/PS composites exhibited intense white light emission. The I-V characteristics of ZnS/PS heterojunctions showed rectifying behavior. Under forward bias conditions, the current density is large. Under reverse bias conditions, the current density nearly to be zero. The forward current increases with increasing PS porosity. This work lay a foundation for the realization of electroluminescence of ZnS/PS and solid white light emission devices.

Study of marbles from Middle Atlas (Morocco): elemental, mineralogical and structural analysis

NASA Astrophysics Data System (ADS)

Khrissi, S.; Bejjit, L.; Haddad, M.; Falguères, C.; Ait Lyazidi, S.; El Amraoui, M.

2018-05-01

A series of marbles sampled from the region of Middle Atlas (Morocco), are characterized by different complementary spectroscopic techniques. X-Ray fluorescence is used to determine elemental composition of rock while X-Ray diffraction and the Raman spectroscopy are used to determine major crystalline phases (calcite and dolomite) and minor ones (quartz).The samples display typical EPR spectra of Mn2+ in calcite and reveal the presence of Fe3+ ions.

Shock induced crystallization of amorphous Nickel powders

NASA Astrophysics Data System (ADS)

Cherukara, Mathew; Strachan, Alejandro

2015-06-01

Recent experimental work has shown the efficacy of amorphous Ni/crystalline Al composites as energetic materials, with flame velocities twice that of a comparable crystalline Ni/crystalline Al system. Of further interest is the recrystallization mechanisms in the pure amorphous Ni powders, both thermally induced and mechanically induced. We present large-scale molecular dynamics simulations of shock-induced recrystallization in loosely packed amorphous Nickel powders. We study the time dependent nucleation and growth processes by holding the shocked samples at the induced pressures and temperatures for extended periods following the passage of the shock (up to 6 ns). We find that the nanostructure of the recrystallized Ni and time scales of recrystallization are dependent on the piston velocity. At low piston velocities, nucleation events are rare, leading to long incubation times and a relatively coarse nanostructure. At higher piston velocities, local variations in temperature due to jetting phenomena and void collapse, give rise to multiple nucleation events on time scales comparable to the passage of the shock wave, leading to the formation of a fine-grained nanostructure. Interestingly, we observe that the nucleation and growth process occurs in two steps, with the first nuclei crystallizing into the BCC structure, before evolving over time into the expected FCC structure. U.S. Defense Threat Reduction Agency, HDTRA1-10-1-0119 (Program Manager Suhithi Peiris).

Single-crystalline MFe(2)O(4) nanotubes/nanorings synthesized by thermal transformation process for biological applications.

PubMed

Fan, Hai-Ming; Yi, Jia-Bao; Yang, Yi; Kho, Kiang-Wei; Tan, Hui-Ru; Shen, Ze-Xiang; Ding, Jun; Sun, Xiao-Wei; Olivo, Malini Carolene; Feng, Yuan-Ping

2009-09-22

We report a general thermal transformation approach to synthesize single-crystalline magnetic transition metal oxides nanotubes/nanorings including magnetite Fe(3)O(4), maghematite gamma-Fe(2)O(3), and ferrites MFe(2)O(4) (M = Co, Mn, Ni, Cu) using hematite alpha-Fe(2)O(3) nanotubes/nanorings template. While the straightforward reduction or reduction-oxides process was employed to produce Fe(3)O(4) and gamma-Fe(2)O(3), the alpha-Fe(2)O(3)/M(OH)(2) core/shell nanostructure was used as precursor to prepare MFe(2)O(4) nanotubes via MFe(2)O(4-x) (0 < x < 1) intermediate. The transformed ferrites nanocrystals retain the hollow structure and single-crystalline nature of the original templates. However, the crystallographic orientation-relationships of cubic spinel ferrites and trigonal hematite show strong correlation with their morpologies. The hollow-structured MFe(2)O(4) nanocrystals with tunable size, shape, and composition have exhibited unique magnetic properties. Moreover, they have been demonstrated as a highly effective peroxidase mimic catalysts for laboratory immunoassays or as a universal nanocapsules hybridized with luminescent QDs for magnetic separation and optical probe of lung cancer cells, suggesting that these biocompatible magnetic nanotubes/nanorings have great potential in biomedicine and biomagnetic applications.

Structure-property-composition relationships in doped zinc oxides: enhanced photocatalytic activity with rare earth dopants.

PubMed

Goodall, Josephine B M; Illsley, Derek; Lines, Robert; Makwana, Neel M; Darr, Jawwad A

2015-02-09

In this paper, we demonstrate the use of continuous hydrothermal flow synthesis (CHFS) technology to rapidly produce a library of 56 crystalline (doped) zinc oxide nanopowders and two undoped samples, each with different particle properties. Each sample was produced in series from the mixing of an aqueous stream of basic zinc nitrate (and dopant ion or modifier) solution with a flow of superheated water (at 450 °C and 24.1 MPa), whereupon a crystalline nanoparticle slurry was rapidly formed. Each composition was collected in series, cleaned, freeze-dried, and then characterized using analytical methods, including powder X-ray diffraction, transmission electron microscopy, Brunauer-Emmett-Teller surface area measurement, X-ray photoelectron spectroscopy, and UV-vis spectrophotometry. Photocatalytic activity of the samples toward the decolorization of methylene blue dye was assessed, and the results revealed that transition metal dopants tended to reduce the photoactivity while rare earth ions, in general, increased the photocatalytic activity. In general, low dopant concentrations were more beneficial to having greater photodecolorization in all cases.

Temperature-Dependent Helium Ion-Beam Mixing in an Amorphous SiOC/Crystalline Fe Composite

DOE PAGES

Su, Qing; Price, Lloyd; Shao, Lin; ...

2016-10-31

Temperature dependent He-irradiation-induced ion-beam mixing between amorphous silicon oxycarbide (SiOC) and crystalline Fe was examined with a transmission electron microscope (TEM) and via Rutherford backscattering spectrometry (RBS). The Fe marker layer (7.2 ± 0.8 nm) was placed in between two amorphous SiOC layers (200 nm). The amount of ion-beam mixing after 298, 473, 673, 873, and 1073 K irradiation was investigated. Both TEM and RBS results showed no ion-beam mixing between Fe and SiOC after 473 and 673 K irradiation and a very trivial amount of ion-beam mixing (~2 nm) after 298 K irradiation. At irradiation temperatures higher than 873more » K, the Fe marker layer broke down and RBS could no longer be used to quantitatively examine the amount of ion mixing. The results indicate that the Fe/SiOC nanocomposite is thermally stable and tends to demix in the temperature range from 473 to 673 K. For application of this composite structure at temperatures of 873 K or higher, layer stability is a key consideration.« less

Effect of Bi(Mg1/2Ti1/2)O3 addition on the electrical properties of Si-Mn modified on SrTiO3

NASA Astrophysics Data System (ADS)

Roh, Yoon-ah; Masaki, Takaki; Yoon, Dae-Ho

2015-05-01

Single-Crystalline Strontium titanate (SrTiO3) has been widely used in many fields such as catalyst, semiconductors and dielectrics. SrTiO3 is a typical perovskite-type oxide, the physical properties of which strongly depend on its chemical composition, structure, shape, size, and crystallinity. In this work, the effects of Bi(Mg1/2Ti1/2)O3 addition on the nanostructure and the dielectric properties of Si-Mn modified SrTiO3 were investigated to develop nano-sized particles and low-temperature-fired SrTiO3-based ceramics with stable temperature characteristics. The dielectric constant of SrTiO3-Bi(Mg1/2Ti1/2)O3 was found to range from 900 to 1200 at 1 kHz for samples sintered at 1200°C. This new composition, SrTiO3-Bi(Mg1/2Ti1/2)O3, can be applied as a nano-sized dielectric materials in various fields.

Investigation of transient photoresponse of WSSe ternary alloy crystals

NASA Astrophysics Data System (ADS)

Chauhan, Payal; Solanki, G. K.; Tannarana, Mohit; Pataniya, Pratik; Patel, K. D.; Pathak, V. M.

2018-05-01

Transition metal chalcogenides have been studied intensively in recent time due to their tunability of electronic properties by compositional change, alloying and by transforming bulk material into crystalline 2D structure. These changes lead to the development of verities of next generation opto-electronic device applications such as solar cells, FETs and flexible detectors etc. In present work, we report growth and characterization of crystalline ternary alloy WSSe by direct vapour transport technique. A photodetector is constructed using grown crystals to study its transient photoresponse under polychromatic radiation. The WSSe crystals are mechanically exfoliated to thickness of 3 µm and the lateral dimension of prepared sample is 2.25 mm2. The time-resolved photoresponse is studied under polychromatic illumination of power density ranging from 10 to 40 mW/cm2. The photo response is also studied under different bias voltages ranging from 0.1 V to 0.5 V. The typical photodetector parameters i.e. photocurrent, rise and fall time, responsivity and sensitivity are evaluated and discussed in light of the ternary alloy composition.

Characterization of the crosslinking reaction in high performance phenolic resins

NASA Astrophysics Data System (ADS)

Patel, Jigneshkumar; Zou, Guo Xiang; Hsu, Shaw Ling; university of massachusetts/Polymer science; Engineering Team

In this study, a combination of thermal analysis, infrared spectroscopy (near and mid) in conjunction with low field NMR, was used to characterize the crosslinking reaction involving phenol formaldehyde resin and a crosslinking agent, Hexamethylenetetramine (HMTA). The strong hydrogen bonds in the resin and the completely crystalline HMTA (Tm = 280 °C) severely hamper the crosslinking process. Yet the addition of a small amount of plasticizer can induce a highly efficient crosslinking reaction to achieve the desired mechanical properties needed in a number of high performance organic-inorganic composites. The infrared spectroscopy clarifies the dissolution process of the crystalline crosslinker and the specific interactions needed to achieve miscibility of the reactants. The thermal analysis enabled us to follow the changing mobility of the system as a function of temperature. The low field NMR with the T1 inverse recovery technique allowed us to monitor the crosslinking process directly. For the first time, it is now possible to identify the functionality of the plasticizer and correlate the crosslinked structure achieved to the macroscopic performance needed for high performance organic-inorganic composites.

Non-oxidic nanoscale composites: single-crystalline titanium carbide nanocubes in hierarchical porous carbon monoliths.

PubMed

Sonnenburg, Kirstin; Smarsly, Bernd M; Brezesinski, Torsten

2009-05-07

We report the preparation of nanoscale carbon-titanium carbide composites with carbide contents of up to 80 wt%. The synthesis yields single-crystalline TiC nanocubes 20-30 nm in diameter embedded in a hierarchical porous carbon matrix. These composites were generated in the form of cylindrical monoliths but can be produced in various shapes using modern sol-gel and nanocasting methods in conjunction with carbothermal reduction. The monolithic material is characterized by a combination of microscopy, diffraction and physisorption. Overall, the results presented in this work represent a concrete design template for the synthesis of non-oxidic nanoscale composites with high surface areas.

Site-selective laser spectroscopy of Nd3+ ions in 0.8CaSiO3-0.2Ca3(PO4)2 biocompatible eutectic glass-ceramics.

PubMed

Sola, D; Balda, R; Peña, J I; Fernández, J

2012-05-07

In this work we report the influence of the crystallization stage of the host matrix on the spectroscopic properties of Nd3+ ions in biocompatible glass-ceramic eutectic rods of composition 0.8CaSiO3-0.2Ca3(PO4)2 doped with 1 and 2 wt% of Nd2O3. The samples were obtained by the laser floating zone technique at different growth rates between 50 and 500 mm/h. The microstructural analysis shows that a growth rate increase or a rod diameter decrease leads the system to a structural arrangement from three (two crystalline and one amorphous) to two phases (one crystalline and one amorphous). Electron backscattering diffraction analysis shows the presence of Ca2SiO4 and apatite-like crystalline phases. Site-selective laser spectroscopy in the (4)I(9/2)→(4)F(3/2)/(4)F(5/2) transitions confirms that Nd(3+) ions are incorporated in crystalline and amorphous phases in these glass-ceramic samples. In particular, the presence of Ca(2)SiO(4) crystalline phase in the samples grown at low rates, which has an excellent in vitro bioactivity, can be unambiguously identified from the excitation spectra and lifetime measurements of the (4)F(3/2) state of Nd(3+) ions.

Bond-length relaxation in crystalline Si1-xGex alloys: An extended x-ray-absorption fine-structure study

NASA Astrophysics Data System (ADS)

Kajiyama, Hiroshi; Muramatsu, Shin-Ichi; Shimada, Toshikazu; Nishino, Yoichi

1992-06-01

Extended x-ray-absorption fine-structure spectra for crystalline Si1-xGex alloys, measured at the K edge of Ge at room temperature, are analyzed with a curve-fitting method based on the spherical-wave approximation. The Ge-Ge and Ge-Si bond lengths, coordination numbers of Ge and Si atoms around a Ge atom, and Debye-Waller factors of Ge and Si atoms are obtained. It is shown that Ge-Ge and Ge-Si bonds relax completely, for all Ge concentrations of their study, while the lattice constant varies monotonically, following Vegard's law. As noted by Bragg and later by Pauling and Huggins, the Ge-Ge and Ge-Si bond lengths are close to the sum of their constituent-element atomic radii: nearly 2.45 Å for Ge-Ge bonds and 2.40 Å for Ge-Si bonds. A study on the coordination around a Ge atom in the alloys revealed that Ge and Si atoms mix randomly throughout the compositional range studied.

Cellulose fibers extracted from rice and oat husks and their application in hydrogel.

PubMed

Oliveira, Jean Paulo de; Bruni, Graziella Pinheiro; Lima, Karina Oliveira; Halal, Shanise Lisie Mello El; Rosa, Gabriela Silveira da; Dias, Alvaro Renato Guerra; Zavareze, Elessandra da Rosa

2017-04-15

The commercial cellulose fibers and cellulose fibers extracted from rice and oat husks were analyzed by chemical composition, morphology, functional groups, crystallinity and thermal properties. The cellulose fibers from rice and oat husks were used to produce hydrogels with poly (vinyl alcohol). The fibers presented different structural, crystallinity, and thermal properties, depending on the cellulose source. The hydrogel from rice cellulose fibers had a network structure with a similar agglomeration sponge, with more homogeneous pores compared to the hydrogel from oat cellulose fibers. The hydrogels prepared from the cellulose extracted from rice and oat husks showed water absorption capacity of 141.6-392.1% and high opacity. The highest water absorption capacity and maximum stress the compression were presented by rice cellulose hydrogel at 25°C. These results show that the use of agro-industrial residues is promising for the biomaterial field, especially in the preparation of hydrogels. Copyright © 2016 Elsevier Ltd. All rights reserved.

Amorphous nickel boride membrane on a platinum-nickel alloy surface for enhanced oxygen reduction reaction.

PubMed

He, Daping; Zhang, Libo; He, Dongsheng; Zhou, Gang; Lin, Yue; Deng, Zhaoxiang; Hong, Xun; Wu, Yuen; Chen, Chen; Li, Yadong

2016-08-09

The low activity of the oxygen reduction reaction in polymer electrolyte membrane fuel cells is a major barrier for electrocatalysis, and hence needs to be optimized. Tuning the surface electronic structure of platinum-based bimetallic alloys, a promising oxygen reduction reaction catalyst, plays a key role in controlling its interaction with reactants, and thus affects the efficiency. Here we report that a dealloying process can be utilized to experimentally fabricate the interface between dealloyed platinum-nickel alloy and amorphous nickel boride membrane. The coating membrane works as an electron acceptor to tune the surface electronic structure of the platinum-nickel catalyst, and this composite catalyst composed of crystalline platinum-nickel covered by amorphous nickel boride achieves a 27-times enhancement in mass activity relative to commercial platinum/carbon at 0.9 V for the oxygen reduction reaction performance. Moreover, this interactional effect between a crystalline surface and amorphous membrane can be readily generalized to facilitate the 3-times higher catalytic activity of commercial platinum/carbon.

Enhanced Hydrate Nucleation Near the Limit of Stability.

PubMed

Jimenez-Angeles, Felipe; Firoozabadi, Abbas

2015-03-30

Clathrate hydrates are crystalline structures composed of small guest molecules trapped into cages formed by hydrogen-bonded water molecules. In hydrate nucleation, water and the guest molecules may stay in a metastable fluid mixture for a long period. Metastability is broken if the concentration of the guest is above certain limit. We perform molecular dynamics (MD) simulations of supersaturated water-propane solutions close to the limit of stability. We show that hydrate nucleation can be very fast in a very narrow range of composition at moderate temperatures. Propane density fluctuations near the fluid-fluid demixing are coupled with crystallization producing en- hanced nucleation rates. This is the first report of propane-hydrate nucleation by MD simulations. We observe motifs of the crystalline structure II in line with experiments and new hydrate cages not reported in the literature. Our study relates nucleation to the fluid-fluid spinodal decomposition and demonstration that the enhanced nucleation phenomenon is more general than short range attractive interactions as suggested in nucleation of proteins.

Crystallization Behavior of Poly(ethylene oxide) in Vertically Aligned Carbon Nanotube Array.

PubMed

Sheng, Jiadong; Zhou, Shenglin; Yang, Zhaohui; Zhang, Xiaohua

2018-03-27

We investigate the effect of the presence of vertically aligned multiwalled carbon nanotubes (CNTs) on the orientation of poly(ethylene oxide) (PEO) lamellae and PEO crystallinity. The high alignment of carbon nanotubes acting as templates probably governs the orientation of PEO lamellae. This templating effect might result in the lamella planes of PEO crystals oriented along a direction parallel to the long axis of the nanotubes. The presence of aligned carbon nanotubes also gives rise to the decreases in PEO crystallinity, crystallization temperature, and melting temperature due to the perturbation of carbon nanotubes to the crystallization of PEO. These effects have significant implications for controlling the orientation of PEO lamellae and decreasing the crystallinity of PEO and thickness of PEO lamellae, which have significant impacts on ion transport in PEO/CNT composite and the capacitive performance of PEO/CNT composite. Both the decreased PEO crystallinity and the orientation of PEO lamellae along the long axes of vertically aligned CNTs give rise to the decrease in the charge transfer resistance, which is associated with the improvements in the ion transport and capacitive performance of PEO/CNT composite.

Evidence for phase change memory behavior in In2(SexTe1-x)3 thin films

NASA Astrophysics Data System (ADS)

Matheswaran, P.; Sathyamoorthy, R.; Asokan, K.

2012-08-01

Crystalline In2(Se0.5Te0.5)3 thin films are prepared by thermal evaporation and subsequently annealed at 300°C in Ar atmosphere. SEM image of the crystalline sample shows spherical nature of constituents, distributed uniformly throughout the surface. Island structure of the surface is clearly visible after switching. Elemental composition of the sample remains unchanged even after switching. Temperature dependent I-V analysis shows stoichiometric phase change at 80°C [from In2(Se0.5Te0.5)3 to In2Te3 and In2Se3 phase], where current switches three orders of magnitude higher than that in lower temperature. Further rise in temperature results increase in current only after switching, where threshold voltage remains constant.

The effect of adding CTAB template in ZSM-5 synthesis

NASA Astrophysics Data System (ADS)

Widayat, Widayat; Annisa, Arianti Nuur

2017-11-01

In general, ZSM-5 synthesis is performed using a hydrothermal process that takes place at high temperature and high pressure (> 373 K,> 1 bar). The synthesis of ZSM-5 is influenced by the organic template used. The organic template serves as a determinant of the zeolite crystal structure formation. CTAB is an easily found organic template and the price is cheap so the production cost of ZSM-5 synthesis would be more efficient. In this research, ZSM-5 is synthesized by varying temperature and crystallization time. The result showed the optimal condition of ZSM-5 synthesis was at 363 K for the crystallization temperature with 8 hours of crystallization time. The crystalline product had 60.07% of crystallinity with an aluminosilicate composition of 72% w/w.

In-situ magnetization/heating electron holography to study the magnetic ordering in arrays of nickel metallic nanowires.

PubMed

Ortega, Eduardo; Santiago, Ulises; Giuliani, Jason G; Monton, Carlos; Ponce, Arturo

2018-05-01

Magnetic nanostructures of different size, shape, and composition possess a great potential to improve current technologies like data storage and electromagnetic sensing. In thin ferromagnetic nanowires, their magnetization behavior is dominated by the competition between magnetocrystalline anisotropy (related to the crystalline structure) and shape anisotropy. In this way electron diffraction methods like precession electron diffraction (PED) can be used to link the magnetic behavior observed by Electron Holography (EH) with its crystallinity. Using off-axis electron holography under Lorentz conditions, we can experimentally determine the magnetization distribution over neighboring nanostructures and their diamagnetic matrix. In the case of a single row of nickel nanowires within the alumina template, the thin TEM samples showed a dominant antiferromagnetic arrangement demonstrating long-range magnetostatic interactions playing a major role.

Iron-Terephthalate Coordination Network Thin Films Through In-Situ Atomic/Molecular Layer Deposition.

PubMed

Tanskanen, A; Karppinen, M

2018-06-12

Iron terephthalate coordination network thin films can be fabricated using the state-of-the-art gas-phase atomic/molecular layer deposition (ALD/MLD) technique in a highly controlled manner. Iron is an Earth-abundant and nonhazardous transition metal, and with its rich variety of potential applications an interesting metal constituent for the inorganic-organic coordination network films. Our work underlines the role of the metal precursor used when aiming at in-situ ALD/MLD growth of crystalline inorganic-organic thin films. We obtain crystalline iron terephthalate films when FeCl 3 is employed as the iron source whereas depositions based on the bulkier Fe(acac) 3 precursor yield amorphous films. The chemical composition and structure of the films are investigated with GIXRD, XRR, FTIR and XPS.

In-situ magnetization/heating electron holography to study the magnetic ordering in arrays of nickel metallic nanowires

NASA Astrophysics Data System (ADS)

Ortega, Eduardo; Santiago, Ulises; Giuliani, Jason G.; Monton, Carlos; Ponce, Arturo

2018-05-01

Magnetic nanostructures of different size, shape, and composition possess a great potential to improve current technologies like data storage and electromagnetic sensing. In thin ferromagnetic nanowires, their magnetization behavior is dominated by the competition between magnetocrystalline anisotropy (related to the crystalline structure) and shape anisotropy. In this way electron diffraction methods like precession electron diffraction (PED) can be used to link the magnetic behavior observed by Electron Holography (EH) with its crystallinity. Using off-axis electron holography under Lorentz conditions, we can experimentally determine the magnetization distribution over neighboring nanostructures and their diamagnetic matrix. In the case of a single row of nickel nanowires within the alumina template, the thin TEM samples showed a dominant antiferromagnetic arrangement demonstrating long-range magnetostatic interactions playing a major role.

CIT-7, a crystalline, molecular sieve with pores bounded by 8 and 10-membered rings† †Electronic supplementary information (ESI) available: Details of the synthesis and characterization of all materials as well as details on the synchrotron and RED data collection and structure determination, including the cif file. See DOI: 10.1039/c4sc03935a Click here for additional data file.

PubMed Central

Schmidt, Joel E.; Xie, Dan; Rea, Thomas

2015-01-01

A new crystalline molecular sieve, denoted CIT-7, is synthesized using an imidazolium-based diquaternary organic structure directing agent (OSDA). The framework structure is determined from a combination of rotation electron diffraction and synchrotron X-ray powder diffraction data. The structure has 10 crystallographically unique tetrahedral atoms (T-atoms) in the unit cell, and can be described as an ordered arrangement of the [425462] mtw building unit and a previously unreported [4452] building unit. The framework contains a 2-dimensional pore system that is bounded by 10 T-atom rings (10-ring, 5.1 Å × 6.2 Å opening) that are connected with oval 8-rings (2.9 Å × 5.5 Å opening) through medium-sized cavities (∼7.9 Å) at the channel intersections. CIT-7 can be synthesized over a broad range of compositions including pure-silica and heteroatom, e.g., aluminosilicate and titanosilicate, containing variants. PMID:29163872

Doping effects on structural and magnetic properties of Heusler alloys Fe2Cr1-xCoxSi

NASA Astrophysics Data System (ADS)

Liu, Yifan; Ren, Lizhu; Zheng, Yuhong; He, Shikun; Liu, Yang; Yang, Ping; Yang, Hyunsoo; Teo, Kie Leong

2018-05-01

In this work, 30nm Fe2Cr1-xCoxSi (FCCS) magnetic films were deposited on Cr buffered MgO (100) substrates by sputtering. Fe2Cr0.5Co0.5Si exhibits the largest magnetization and optimal ordered L21 cubic structure at in-situ annealing temperature (Tia) of 450°C. The Co composition dependence of crystalline structures, surface morphology, defects, lattice distortions and their correlation with the magnetic properties are analyzed in detail. The Co-doped samples show in-plane M-H loops with magnetic squareness ratio of 1 and increasing anisotropy energy density with Co composition. Appropriate Co doping composition promotes L21 phase but higher Co composition converts L21 to B2 phase. Doping effect and lattice mismatch both are proved to increase the defect density. In addition, distortions of the FCCS lattice are found to be approximately linear with Co composition. The largest lattice distortion (c/a) is 0.969 for Fe2Cr0.25Co0.75Si and the smallest is 0.983 for Fe2CrSi. Our analyses suggest that these tetragonal distortions mainly induced by an elastic stress from Cr buffer account for the large in-plane anisotropy energy. This work paves the way for further tailoring the magnetic and structural properties of quaternary Heusler alloys.

The mechanical properties and morphology of a graphite oxide nanoplatelet/polyurethane composite.

PubMed

Cai, Dongyu; Yusoh, Kamal; Song, Mo

2009-02-25

Significant reinforcement of polyurethane (PU) using graphite oxide nanoplatelets (GONPs) is reported. Morphologic study shows that, due to the formation of chemical bonding, there is a strong interaction between the GONPs and the hard segment of the PU, which allows effective load transfer. The GONPs can prevent the formation of crystalline hard segments due to their two-dimensional structure. With the incorporation of 4.4 wt% of GONPs, the Young's modulus and hardness of the PU are significantly increased by approximately 900% and approximately 327%, respectively. The resultant high resistance to scratching indicates promise for application of these composite materials in surface coating.

Mechanical, morphological and structural properties of cellulose nanofibers reinforced epoxy composites.

PubMed

Saba, N; Mohammad, F; Pervaiz, M; Jawaid, M; Alothman, O Y; Sain, M

2017-04-01

Present study, deals about isolation and characterization of cellulose nanofibers (CNFs) from the Northern Bleached Softwood Kraft (NBSK) pulp, fabrication by hand lay-up technique and characterization of fabricated epoxy nanocomposites at different filler loadings (0.5%, 0.75%, 1% by wt.). The effect of CNFs loading on mechanical (tensile, impact and flexural), morphological (scanning electron microscope and transmission electron microscope) and structural (XRD and FTIR) properties of epoxy composites were investigated. FTIR analysis confirms the introduction of CNFs into the epoxy matrix while no considerable change in the crystallinity and diffraction peaks of epoxy composites were observed by the XRD patterns. Additions of CNFs considerably enhance the mechanical properties of epoxy composites but a remarkable improvement is observed for 0.75% CNFs as compared to the rest epoxy nanocomposites. In addition, the electron micrographs revealed the perfect distribution and dispersion of CNFs in the epoxy matrix for the 0.75% CNFs/epoxy nanocomposites, while the existence of voids and agglomerations were observed beyond 0.75% CNFs filler loadings. Overall results analysis clearly revealed that the 0.75% CNFs filler loading is best and effective with respect to rest to enhance the mechanical and structural properties of the epoxy composites. Copyright © 2017 Elsevier B.V. All rights reserved.

How Stress Treatments Influence the Performance of Biodegradable Poly(Butylene Succinate)-Based Copolymers with Thioether Linkages for Food Packaging Applications

PubMed Central

Genovese, Laura

2017-01-01

Biodegradable poly(butylene succinate) (PBS)-based random copolymers containing thioether linkages (P(BSxTDGSy)) of various compositions have been investigated and characterized from the gas barrier, thermal, and mechanical point of view, after food contact simulants or thermal and photoaging processes. Each stress treatment was performed on thin films and the results obtained have been compared to the same untreated film, used as a standard. Barrier properties with different gases (O2 and CO2) were evaluated, showing that the polymer chemical composition strongly influenced the permeability behavior. The relationships between the diffusion coefficients (D) and solubility (S) with polymer composition were also investigated. The results highlighted a correlation between polymer chemical structure and treatment. Gas transmission rate (GTR) mainly depending on the performed treatment, as GTR increased with the increase of TDGS co-unit amount. Thermal and mechanical tests allowed for the recording of variations in the degree of crystallinity and in the tensile properties. An increase in the crystallinity degree was recorded after contact with simulant liquids and aging treatments, together with a molecular weight decrease, a slight enhancement of the elastic modulus and a decrement of the elongation at break, proportional to the TDGS co-unit content. PMID:28867806

How Stress Treatments Influence the Performance of Biodegradable Poly(Butylene Succinate)-Based Copolymers with Thioether Linkages for Food Packaging Applications.

PubMed

Siracusa, Valentina; Genovese, Laura; Munari, Andrea; Lotti, Nadia

2017-08-30

Biodegradable poly(butylene succinate) (PBS)-based random copolymers containing thioether linkages (P(BSxTDGSy)) of various compositions have been investigated and characterized from the gas barrier, thermal, and mechanical point of view, after food contact simulants or thermal and photoaging processes. Each stress treatment was performed on thin films and the results obtained have been compared to the same untreated film, used as a standard. Barrier properties with different gases (O₂ and CO₂) were evaluated, showing that the polymer chemical composition strongly influenced the permeability behavior. The relationships between the diffusion coefficients ( D ) and solubility ( S ) with polymer composition were also investigated. The results highlighted a correlation between polymer chemical structure and treatment. Gas transmission rate ( GTR ) mainly depending on the performed treatment, as GTR increased with the increase of TDGS co-unit amount. Thermal and mechanical tests allowed for the recording of variations in the degree of crystallinity and in the tensile properties. An increase in the crystallinity degree was recorded after contact with simulant liquids and aging treatments, together with a molecular weight decrease, a slight enhancement of the elastic modulus and a decrement of the elongation at break, proportional to the TDGS co-unit content.

High energy X-ray diffraction study of a dental ceramics–titanium functional gradient material prepared by field assisted sintering technique

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

Witte, K., E-mail: kerstin.witte@uni-rostock.de; Bodnar, W.; Schell, N.

A functional gradient material with eleven layers composed of a dental ceramics and titanium was successfully consolidated using field assisted sintering technique in a two-step sintering process. High energy X-ray diffraction studies on the gradient were performed at High Energy Material Science beamline at Desy in Hamburg. Phase composition, crystal unit edges and lattice mismatch along the gradient were determined applying Rietveld refinement procedure. Phase analysis revealed that the main crystalline phase present in the gradient is α-Ti. Crystallinity increases stepwisely along the gradient with a decreasing increment between every next layer, following rather the weight fraction of titanium. Themore » crystal unit edge a of titanium remains approximately constant with a value of 2.9686(1) Å, while c is reduced with increasing amount of titanium. In the layer with pure titanium the crystal unit edge c is constant with a value of 4.7174(2) Å. The lattice mismatch leading to an internal stress was calculated over the whole gradient. It was found that the maximal internal stress in titanium embedded in the studied gradient is significantly smaller than its yield strength, which implies that the structure of titanium along the whole gradient is mechanically stable. - Highlights: • High energy XRD studies of dental ceramics–Ti gradient material consolidated by FAST. • Phase composition, crystallinity and lattice parameters are determined. • Crystallinity increases stepwisely along the gradient following weight fraction of Ti. • Lattice mismatch leading to internal stress is calculated over the whole gradient. • Internal stress in α-Ti embedded in the gradient is smaller than its yield strength.« less

The effect of structurally related impurities on crystallinity reduction of sulfamethazine by grinding.

PubMed

Hamada, Yoshito; Ono, Makoto; Ohara, Motomu; Yonemochi, Etsuo

2016-12-30

In this study, the effect of structurally related impurities on crystallinity reduction of sulfamethazine by grinding was evaluated. The crystallinity of sulfamethazine was not decreased when it was ground alone. However, when structurally related impurities with sulfonamide derivatives were blended, the crystallinity of sulfamethazine was decreased by grinding. Other materials without a sulfonamide moiety showed no such effect. The Raman spectra of sulfamethazine demonstrated that there was a difference between its crystalline and amorphous states within its sulfonamide structure. It was suggested that the sulfonamide structure of the impurities was important in causing the inhibition of recrystallization of sulfamethazine during grinding. Copyright © 2016 Elsevier B.V. All rights reserved.

From Graphene Oxide to Reduced Graphene Oxide: Impact on the Physiochemical and Mechanical Properties of Graphene-Cement Composites.

PubMed

Gholampour, Aliakbar; Valizadeh Kiamahalleh, Meisam; Tran, Diana N H; Ozbakkaloglu, Togay; Losic, Dusan

2017-12-13

Graphene materials have been extensively explored and successfully used to improve performances of cement composites. These formulations were mainly optimized based on different dosages of graphene additives, but with lack of understanding of how other parameters such as surface chemistry, size, charge, and defects of graphene structures could impact the physiochemical and mechanical properties of the final material. This paper presents the first experimental study to evaluate the influence of oxygen functional groups of graphene and defectiveness of graphene structures on the axial tension and compression properties of graphene-cement mortar composites. A series of reduced graphene oxide (rGO) samples with different levels of oxygen groups (high, mild, and low) were prepared by the reduction of graphene oxide (GO) using different concentrations of hydrazine (wt %, 0.1, 0.15, 0.2, 0.3, and 0.4%) and different reduction times (5, 10, 15, 30, and 60 min) and were added to cement mortar composites at an optimal dosage of 0.1%. A series of characterization methods including scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, thermogravimetric analysis, and Fourier transform infrared spectroscopy were performed to determine the distribution and mixing of the prepared rGO in the cement matrix and were correlated with the observed mechanical properties of rGO-cement mortar composites. The measurement of the axial tension and compression properties revealed that the oxygen level of rGO additives has a significant influence on the mechanical properties of cement composites. An addition of 0.1% rGO prepared by 15 min reduction and 0.2% (wt %) hydrazine with mild level of oxygen groups resulted in a maximum enhancement of 45.0 and 83.7%, respectively, in the 28-day tensile and compressive strengths in comparison with the plain cement mortar and were higher compared to the composite prepared with GO (37.5 and 77.7%, respectively). These results indicate that there is a strong influence of the level of oxygen groups and crystallinity of graphene structures on the physiochemical and mechanical properties. The influence of these two parameters are interconnected and their careful balancing is required to provide an optimum level of oxygen groups on rGO sheets to ensure that there is sufficient bonding between the calcium silicate hydrate (C-S-H) components in the cement matrix and minimum level of defects and higher crystallinity of graphene structures, which will improve the mechanical properties of the composite. Finding the optimized balance between these two parameters is required to formulate graphene cement composites with the highest performance.

Structural analysis of bioceramic materials for denture application

NASA Astrophysics Data System (ADS)

Rauf, Nurlaela; Tahir, Dahlang; Arbiansyah, Muhammad

2016-03-01

Structural analysis has been performed on bioceramic materials for denture application by using X-ray diffraction (XRD), X-ray fluorescence (XRF), and Scanning Electron Microscopy (SEM). XRF is using for analysis chemical composition of raw materials. XRF shows the ratio 1 : 1 : 1 : 1 between feldspar, quartz, kaolin and eggshell, respectively, resulting composition CaO content of 56.78 %, which is similar with natural tooth. Sample preparation was carried out on temperature of 800 °C, 900 °C and 1000 °C. X-ray diffraction result showed that the structure is crystalline with trigonal crystal system for SiO2 (a=b=4.9134 Å and c=5.4051 Å) and CaH2O2 (a=b=3.5925 Å and c=4.9082 Å). Based on the Scherrer's equation showed the crystallite size of the highest peak (SiO2) increase with increasing the temperature preparation. The highest hardness value (87 kg/mm2) and match with the standards of dentin hardness. The surface structure was observed by using SEM also discussed.

Making mushy magma chambers in the lower continental crust: Cold storage and compositional bimodality

NASA Astrophysics Data System (ADS)

Jackson, Matthew; Blundy, Jon; Sparks, Steve

2017-04-01

Increasing geological and geophysical evidence suggests that crustal magma reservoirs are normally low melt fraction 'mushes' rather than high melt fraction 'magma chambers'. Yet high melt fractions must form within these mush reservoirs to explain the observed flow and eruption of low crystallinity magmas. In many models, crystallinity is linked directly to temperature, with higher temperature corresponding to lower crystallinity (higher melt fraction). However, increasing temperature yields less evolved (silicic) melt composition for a given starting material. If mobile, low crystallinity magmas require high temperature, it is difficult to explain how they can have evolved composition. Here we use numerical modelling to show that reactive melt flow in a porous and permeable mush reservoir formed by the intrusion of numerous basaltic sills into the lower continental crust produces magma in high melt fraction (> 0.5) layers akin to conventional magma chambers. These magma-chamber-like layers contain evolved (silicic) melt compositions and form at low (close to solidus) temperatures near the top of the mush reservoir. Evolved magma is therefore kept in 'cold storage' at low temperature, but also at low crystallinity so the magma is mobile and can leave the mush reservoir. Buoyancy-driven reactive flow and accumulation of melt in the mush reservoir controls the temperature and composition of magma that can leave the reservoir. The modelling also shows that processes in lower crustal mush reservoirs produce mobile magmas that contain melt of either silicic or mafic composition. Intermediate melt compositions are present but are not within mobile magmas. Silicic melt compositions are found at high melt fraction within the magma-chamber like layers near the top of the mush reservoir. Mafic melt compositions are found at high melt fraction within the cooling sills. Melt elsewhere in the reservoir has intermediate composition, but remains trapped in the reservoir because the local melt fraction is too low to form a mobile magma. The model results are consistent with geochemical data suggesting that lower crustal magma reservoirs supply silicic and mafic melts to arc volcanoes, but intermediate magmas are formed by mixing in shallower reservoirs. We suggest here that lower crustal magma chambers primarily form in response to changes in bulk composition caused by melt migration and chemical reaction in a mush reservoir. This process is different to the conventional and widely applied models of magma chamber formation. Similar processes are likely to operate in shallow mush reservoirs, but will likely be further complicated by the presence of volatile phases, and mixing of different melt compositions sourced from deeper mush reservoirs.

Crystalline polyoxometalate (POM)–polyethylene glycol (PEG) composites aimed as non-humidified intermediate-temperature proton conductors

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

Tsuboi, Masaki; Hibino, Mitsuhiro; Mizuno, Noritaka

2016-02-15

Crystalline polyoxometalate (POM)–polyethylene glycol (PEG) composites aimed as non-humidified intermediate-temperature proton conductors were synthesized and characterized by single crystal and powder XRD, solid state MASNMR, and TG-DTA measurements. Among the POM–PEG composites, Cs{sub 2.7}H{sub 0.3}[PW{sub 12}O{sub 40}]·1.2PEG1000 (CsHPW-PEG1000) possessed one-dimensional channels with diameters of ca. 6 and 8 Å, where PEG probably resided, and showed the best performance as a proton conductor (1.2×10{sup −5} S cm{sup −1} at 443 K). Proton conductivities of POM–PEG composites decreased by the increase in molecular weights of PEG (CsHPW-PEG12,000) or anion charges (CsHSiW-PEG1000). Variable contact time {sup 13}C-CP (cross polarization) MASNMR revealed that localmore » mobility (i.e., segmental motion) of PEG is related to the trends in proton conductivities. These results show that amount of acidic protons (H{sup +}) is not the primary factor in proton conduction and that segmental motion of PEG assists the proton hopping among POMs in the crystal lattice of POM–PEG composites. - Graphical abstract: Non-humidified intermediate-temperature proton conduction in crystalline polyoxometalate (POM)–polyethylene (PEG) composites are assisted by the segmental motion of PEG. - Highlights: • Crystalline polyoxometalate–polyethlene glycol (PEG) composites were synthesized. • CsHPW-PEG1000 possessed one-dimensional channels and showed the highest proton conductivity. • {sup 13}C CPMASNMR revealed that segmental motion of PEG is related to the proton conduction.« less

Shocked Quartz Aggregates of the Cretaceous-Tertiary Boundary at Colorado, USA

NASA Astrophysics Data System (ADS)

Miura, Y.; Okamoto, M.; Iancu, O. G.

1993-07-01

Shock-metamorphosed quartz (i.e., shocked quartz) at the Cretaceous-Tertiary boundary (K/T) at Colorado [1,2] reveals the following mineralogical data by X-ray diffractometry and high-resolution electron micrograph with energy- dispersive spectrometry. 1. Shocked quartz is not normal (perfect crystalline) quartz mineral but various quartz aggregates that show relatively low X-ray intensity (i.e., imperfect crystalline) and shock lamellae with crystalline quartz and amorphous glass [3]. 2. Analytical electron micrographs indicate that crystalline quartz silica with spotty dislocation features is included in dendritic amorphous glasses of potassium (K) feldspar composition. Various compositions of glassy materials are found in shocked quartz aggregates as matrix or alternate shock lamellae, which is important to estimate the target rock of impact. The composition of glassy matrix is dendritic K-feldspar in the K/T boundary at Clear Creak North (CCN), Colorado, whereas that in the Barringer Crater is quartz-rich composition from the target rock of sandstone (or some mixture with iron meteorite), and that in artificial impact rock [3] is dendritic silica composition. It is found in this study that shocked quartz aggregates from the CCN K/T boundary samples are supplied from quartz and K-feldspar-bearing target rock at impact event (Table 1). Table 1, which appears here in the hard copy, shows the compositions, texture, and origin of shocked quartz aggregates. References: [1] Alvarez L. W. et al. (1980) Science, 208, 1095-1107. [2] Izett G. (1989) GSA Spec. Pap. 249, 1-194. [3] Miura Y. (1991) Shock Waves, 1, 35-41, Springer-Verlag.

Thermal properties of silica-filled high density polyethylene composites compatibilized with glut palmitate

NASA Astrophysics Data System (ADS)

Samsudin, Dalina; Ismail, Hanafi; Othman, Nadras; Hamid, Zuratul Ain Abdul

2017-07-01

A study of thermal properties resulting from the utilization of Glut Palmitate (GP) on the silica filled high density polyethylene (HDPE) composites was carried out. The composites with the incorporation of GP at 0.5, 1.0, 2.0 and 3.0 phr were prepared by using an internal mixer at the temperature 180 °C and the rotor speed of 50 rpm. The thermal behaviours of the composites were then investigated using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). It was found that the crystallinity and the thermal stability of the composites increased with the incorporation of GP. The highest crystallinity contents and decomposition temperatures were observed at the 1 phr GP loading.

Phase change compositions

DOEpatents

Salyer, Ival O.; Griffen, Charles W.

1986-01-01

Compositions containing crystalline, long chain, alkyl hydrocarbons as phase change materials including cementitious compositions containing the alkyl hydrocarbons neat or in pellets or granules formed by incorporating the alkyl hydrocarbons in polymers or rubbers; and polymeric or elastomeric compositions containing alkyl hydrocarbons.

Phase change compositions

DOEpatents

Salyer, Ival O.

1989-01-01

Compositions containing crystalline, straight chain, alkyl hydrocarbons as phase change materials including cementitious compositions containing the alkyl hydrocarbons neat or in pellets or granules formed by incorporating the alkyl hydrocarbons in polymers or rubbers; and polymeric or elastomeric compositions containing alkyl hydrocarbons.

The structure of volcanic cristobalite in relation to its toxicity; relevance for the variable crystalline silica hazard

PubMed Central

2012-01-01

Background Respirable crystalline silica (RCS) continues to pose a risk to human health worldwide. Its variable toxicity depends on inherent characteristics and external factors which influence surface chemistry. Significant population exposure to RCS occurs during volcanic eruptions, where ashfall may cover hundreds of square km and exposure may last years. Occupational exposure also occurs through mining of volcanic deposits. The primary source of RCS from volcanoes is through collapse and fragmentation of lava domes within which cristobalite is mass produced. After 30 years of research, it is still not clear if volcanic ash is a chronic respiratory health hazard. Toxicological assays have shown that cristobalite-rich ash is less toxic than expected. We investigate the reasons for this by determining the physicochemical/structural characteristics which may modify the pathogenicity of volcanic RCS. Four theories are considered: 1) the reactivity of particle surfaces is reduced due to co-substitutions of Al and Na for Si in the cristobalite structure; 2) particles consist of aggregates of cristobalite and other phases, restricting the surface area of cristobalite available for reactions in the lung; 3) the cristobalite surface is occluded by an annealed rim; 4) dissolution of other volcanic particles affects the surfaces of RCS in the lung. Methods The composition of volcanic cristobalite crystals was quantified by electron microprobe and differences in composition assessed by Welch’s two sample t-test. Sections of dome-rock and ash particles were imaged by scanning and transmission electron microscopy, and elemental compositions of rims determined by energy dispersive X-ray spectroscopy. Results Volcanic cristobalite contains up to 4 wt. % combined Al2O3 and Na2O. Most cristobalite-bearing ash particles contain adhered materials such as feldspar and glass. No annealed rims were observed. Conclusions The composition of volcanic cristobalite particles gives insight into previously-unconsidered inherent characteristics of silica mineralogy which may affect toxicity. The structural features identified may also influence the hazard of other environmentally and occupationally produced silica dusts. Current exposure regulations do not take into account the characteristics that might render the silica surface less harmful. Further research would facilitate refinement of the existing simple, mass-based silica standard by taking into account composition, allowing higher standards to be set in industries where the silica surface is modified. PMID:23164071

The structure of volcanic cristobalite in relation to its toxicity; relevance for the variable crystalline silica hazard.

PubMed

Horwell, Claire J; Williamson, Benedict J; Donaldson, Ken; Le Blond, Jennifer S; Damby, David E; Bowen, Leon

2012-11-19

Respirable crystalline silica (RCS) continues to pose a risk to human health worldwide. Its variable toxicity depends on inherent characteristics and external factors which influence surface chemistry. Significant population exposure to RCS occurs during volcanic eruptions, where ashfall may cover hundreds of square km and exposure may last years. Occupational exposure also occurs through mining of volcanic deposits. The primary source of RCS from volcanoes is through collapse and fragmentation of lava domes within which cristobalite is mass produced. After 30 years of research, it is still not clear if volcanic ash is a chronic respiratory health hazard. Toxicological assays have shown that cristobalite-rich ash is less toxic than expected. We investigate the reasons for this by determining the physicochemical/structural characteristics which may modify the pathogenicity of volcanic RCS. Four theories are considered: 1) the reactivity of particle surfaces is reduced due to co-substitutions of Al and Na for Si in the cristobalite structure; 2) particles consist of aggregates of cristobalite and other phases, restricting the surface area of cristobalite available for reactions in the lung; 3) the cristobalite surface is occluded by an annealed rim; 4) dissolution of other volcanic particles affects the surfaces of RCS in the lung. The composition of volcanic cristobalite crystals was quantified by electron microprobe and differences in composition assessed by Welch's two sample t-test. Sections of dome-rock and ash particles were imaged by scanning and transmission electron microscopy, and elemental compositions of rims determined by energy dispersive X-ray spectroscopy. Volcanic cristobalite contains up to 4 wt. % combined Al(2)O(3) and Na(2)O. Most cristobalite-bearing ash particles contain adhered materials such as feldspar and glass. No annealed rims were observed. The composition of volcanic cristobalite particles gives insight into previously-unconsidered inherent characteristics of silica mineralogy which may affect toxicity. The structural features identified may also influence the hazard of other environmentally and occupationally produced silica dusts. Current exposure regulations do not take into account the characteristics that might render the silica surface less harmful. Further research would facilitate refinement of the existing simple, mass-based silica standard by taking into account composition, allowing higher standards to be set in industries where the silica surface is modified.

Macroporous Calcium Phosphate/Chitosan Composites Prepared via Unidirectional Ice Segregation and Subsequent Freeze-Drying

PubMed Central

Aranaz, Inmaculada; Martínez-Campos, Enrique; Moreno-Vicente, Carolina; Civantos, Ana; García-Arguelles, Sara; del Monte, Francisco

2017-01-01

Calcium phosphate chitosan-based composites have gained much interest in recent years for biomedical purposes. In this paper, three-dimensional calcium phosphate chitosan-based composites with different mineral contents were produced using a green method called ice segregation induced self-assembly (ISISA). In this methodology, ice crystals were used as a template to produce porous structures from an aqueous solution of chitosan (CS) and hydroxyapatite (Hap) also containing acetic acid (pH = 4.5). For better characterization of the nature of the inorganic matter entrapped within the resulting composite, we performed either oxygen plasma or calcination processes to remove the organic matter. The nature of the phosphate salts was studied by XRD and NMR studies. Amorphous calcium phosphate (ACP) was identified as the mineral phase in the composites submitted to oxygen plasma, whereas crystalline Hap was obtained after calcination. SEM microscopy revealed the formation of porous structures (porosity around 80–85%) in the original composites, as well as in the inorganic matrices obtained after calcination, with porous channels of up to 50 µm in diameter in the former case and of up to 20 µm in the latter. The biocompatibility of the composites was assessed using two different cell lines: C2C12GFP premyoblastic cells and MC3T3 preosteoblastic cells. PMID:28772874

Structure of high alumina content Al2O3-SiO2 composition glasses.

PubMed

Weber, Richard; Sen, Sabyasachi; Youngman, Randall E; Hart, Robert T; Benmore, Chris J

2008-12-25

The structure of binary aluminosilicate glasses containing 60-67 mol % Al2O3 were investigated using high-resolution 27Al NMR and X-ray and neutron diffraction. The glasses were made by aerodynamic levitation of molten oxides. The 67% alumina composition required a cooling rate of approximately 1600 degrees C s(1-) to form glass from submillimeter sized samples. NMR results show that the glasses contain aluminum in 4-, 5-, and 6-fold coordination in the approximate ratio 4:5:1. The average Al coordination increases from 4.57 to 4.73 as the fraction of octahedral Al increases with alumina content. The diffraction results on the 67% composition are consistent with a disordered Al framework with Al ions in a range of coordination environments that are substantially different from those found in the equilibrium crystalline phases. Analysis of the neutron and X-ray structure factors yields an average bond angle of 125 +/- 4 degrees between an Al ion and the adjoining cation via a bridging oxygen. We propose that the structure of the glass is a "transition state" between the alumina-rich liquid and the equilibrium mullite phase that are dominated by 4- and 6-coordinated aluminum ions, respectively.

Crystallization kinetics and thermal resistance of bamboo fiber reinforced biodegradable polymer composites

NASA Astrophysics Data System (ADS)

Thumsorn, S.; Srisawat, N.; On, J. Wong; Pivsa-Art, S.; Hamada, H.

2014-05-01

Bamboo fiber reinforced biodegradable polymer composites were prepared in this study. Biodegradable poly(butylene succinate) (PBS) was blended with bamboo fiber in a twin screw extruder with varied bamboo content from 20-0wt%. PBS/bamboo fiber composites were fabricated by compression molding process. The effect of bamboo fiber contents on properties of the composites was investigated. Non-isothermal crystallization kinetic study of the composites was investigated based on Avrami equation. The kinetic parameters indicated that bamboo fiber acted as heterogeneous nucleation and enhanced crystallinity of the composites. Bamboo fiber was well dispersed on PBS matrix and good adhered with the matrix. Tensile strength of the composites slightly deceased with adding bamboo fiber. However, tensile modulus and impact strength of the composites increased when increasing bamboo fiber contents. It can be noted that bamboo fiber promoted crystallization and crystallinity of PBS in the composites. Therefore, the composites were better in impact load transferring than neat PBS, which exhibited improving on impact performance of the composites.

Amino acid mediated synthesis of silver nanoparticles and preparation of antimicrobial agar/silver nanoparticles composite films.

PubMed

Shankar, Shiv; Rhim, Jong-Whan

2015-10-05

Silver nanoparticles (AgNPs) were synthesized using amino acids (tyrosine and tryptophan) as reducing and capping agents, and they were incorporated into the agar to prepare antimicrobial composite films. The AgNPs solutions exhibited characteristic absorption peak at 420 nm that showed a red shift to ∼434 nm after forming composite with agar. XRD data demonstrated the crystalline structure of AgNPs with dominant (111) facet. Apparent surface color and transmittance of agar films were greatly influenced by the AgNPs. The incorporation of AgNPs into agar did not exhibit any change in chemical structure, thermal stability, moisture content, and water vapor permeability. The water contact angle, tensile strength, and modulus decreased slightly, but elongation at break increased after AgNPs incorporation. The agar/AgNPs nanocomposite films possessed strong antibacterial activity against Listeria monocytogenes and Escherichia coli. The agar/AgNPs film could be applied to the active food packaging by controlling the food-borne pathogens. Copyright © 2015 Elsevier Ltd. All rights reserved.

Condensation polyimides

NASA Technical Reports Server (NTRS)

Hergenrother, P. M.

1989-01-01

Polyimides belong to a class of polymers known as polyheterocyclics. Unlike most other high temperature polymers, polyimides can be prepared from a variety of inexpensive monomers by several synthetic routes. The glass transition and crystalline melt temperature, thermooxidative stability, toughness, dielectric constant, coefficient of thermal expansion, chemical stability, mechanical performance, etc. of polyimides can be controlled within certain boundaries. This versatility has permitted the development of various forms of polyimides. These include adhesives, composite matrices, coatings, films, moldings, fibers, foams and membranes. Polyimides are synthesized through both condensation (step-polymerization) and addition (chain growth polymerization) routes. The precursor materials used in addition polyimides or imide oligomers are prepared by condensation method. High molecular weight polyimide made via polycondensation or step-growth polymerization is studied. The various synthetic routes to condensation polyimides, structure/property relationships of condensation polyimides and composite properties of condensation polyimides are all studied. The focus is on the synthesis and chemical structure/property relationships of polyimides with particular emphasis on materials for composite application.

X-ray diffraction analysis of hydroxyapatite-coated in different plasma gas atmosphere on Ti and Ti-6Al-4V

PubMed Central

Kotian, Ravindra; Rao, P. Prasad; Madhyastha, Prashanthi

2017-01-01

Objective: The aim is to study the effect of plasma working gas on composition, crystallinity, and microstructure of hydroxyapatite (HA) coated on Ti and Ti-6Al-4V metal substrates. Materials and Methods: Ti and Ti-6Al-4V metal substrates were coated with HA by plasma spray using four plasma gas atmospheres of argon, argon/hydrogen, nitrogen, and nitrogen/hydrogen. The degree of crystallinity, the phases present, and microstructure of HA coating were characterized using X-ray diffraction and scanning electron microscopy. Results: Variation in crystallinity and the microstructure of HA coating on plasma gas atmosphere was observed. Micro-cracks due to thermal stresses and shift in the 2θ angle of HA compared to feedstock was seen. Conclusion: Plasma gas atmosphere has a significant influence on composition, crystallinity, and micro-cracks of HA-coated dental implants. PMID:29279668

Characterization nano crystalline cellulose from sugarcane baggase for reinforcement in polymer composites: Effect of formic acid concentrations

NASA Astrophysics Data System (ADS)

Aprilia, N. A. S.; Mulyati, S.; Alam, P. N.; Karmila; Ambarita, A. C.

2018-04-01

Nanocellulose from sugarcane bagasse for reinforcement in polymer composites has isolated from formic acid (FA) with different concentration. This research was conducted with three level concentration of FA ei. 15, 30 and 50%. The nanocellulose were successfully prepared with variations of total yields of 66.66, 67.33 and 69.33% respectively with increase of FA concentrations at 6 hours of hidrolysis time. The obtained nanocellulose were characterized by fourier transform infrared (FT-IR) spectroscopy confirmed the introduction of carboxyl goups on the surface of cellulose. The X-ray diffraction (XRD) spectra proved the existence of cellulose, with a highly crystalline of 62.466, 71.033, and 76.296% with increase of FA concentrations. The size of crystallinity of nanocellulose were decreased with increased of FA concentration. The result investigated that size of crystallinity of nano cellulose reduced from 4.37, 4.15 and 3.94 nm.

Enhanced rates of enzymatic saccharification and catalytic synthesis of biofuel substrates in gelatinized cellulose generated by trifluoroacetic acid

DOE PAGES

Shiga, Tânia M.; Xiao, Weihua; Yang, Haibing; ...

2017-12-27

The crystallinity of cellulose is a principal factor limiting the efficient hydrolysis of biomass to fermentable sugars or direct catalytic conversion to biofuel components. We evaluated the impact of TFA-induced gelatinization of crystalline cellulose on enhancement of enzymatic digestion and catalytic conversion to biofuel substrates. Low-temperature swelling of cotton linter cellulose in TFA at subzero temperatures followed by gentle heating to 55 degrees C dissolves the microfibril structure and forms composites of crystalline and amorphous gels upon addition of ethanol. The extent of gelatinization of crystalline cellulose was determined by reduction of birefringence in darkfield microscopy, loss of X-ray diffractability,more » and loss of resistance to acid hydrolysis. Upon freeze-drying, an additional degree of crystallinity returned as mostly cellulose II. Both enzymatic digestion with a commercial cellulase cocktail and maleic acid/AlCl3-catalyzed conversion to 5-hydroxymethylfurfural and levulinic acid were markedly enhanced with the low-temperature swollen cellulose. Only small improvements in rates and extent of hydrolysis and catalytic conversion were achieved upon heating to fully dissolve cellulose. Low-temperature swelling of cellulose in TFA substantially reduces recalcitrance of crystalline cellulose to both enzymatic digestion and catalytic conversion. In a closed system to prevent loss of fluorohydrocarbons, the relative ease of recovery and regeneration of TFA by distillation makes it a potentially useful agent in large-scale deconstruction of biomass, not only for enzymatic depolymerization but also for enhancing rates of catalytic conversion to biofuel components and useful bio-products.« less

Enhanced rates of enzymatic saccharification and catalytic synthesis of biofuel substrates in gelatinized cellulose generated by trifluoroacetic acid

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

Shiga, Tânia M.; Xiao, Weihua; Yang, Haibing

The crystallinity of cellulose is a principal factor limiting the efficient hydrolysis of biomass to fermentable sugars or direct catalytic conversion to biofuel components. We evaluated the impact of TFA-induced gelatinization of crystalline cellulose on enhancement of enzymatic digestion and catalytic conversion to biofuel substrates. Low-temperature swelling of cotton linter cellulose in TFA at subzero temperatures followed by gentle heating to 55 degrees C dissolves the microfibril structure and forms composites of crystalline and amorphous gels upon addition of ethanol. The extent of gelatinization of crystalline cellulose was determined by reduction of birefringence in darkfield microscopy, loss of X-ray diffractability,more » and loss of resistance to acid hydrolysis. Upon freeze-drying, an additional degree of crystallinity returned as mostly cellulose II. Both enzymatic digestion with a commercial cellulase cocktail and maleic acid/AlCl3-catalyzed conversion to 5-hydroxymethylfurfural and levulinic acid were markedly enhanced with the low-temperature swollen cellulose. Only small improvements in rates and extent of hydrolysis and catalytic conversion were achieved upon heating to fully dissolve cellulose. Low-temperature swelling of cellulose in TFA substantially reduces recalcitrance of crystalline cellulose to both enzymatic digestion and catalytic conversion. In a closed system to prevent loss of fluorohydrocarbons, the relative ease of recovery and regeneration of TFA by distillation makes it a potentially useful agent in large-scale deconstruction of biomass, not only for enzymatic depolymerization but also for enhancing rates of catalytic conversion to biofuel components and useful bio-products.« less

Pyrolytic Synthesis of Carbon Nanotubes from Sucrose on a Mesoporous Silicate

NASA Technical Reports Server (NTRS)

Abdel-Fattah, Tarek; Siochi, Mia; Crooks, Roy

2005-01-01

Multiwall carbon nanotubes were synthesized from sucrose by a pyrolytic technique using mesoporous MCM-41 silicate templates without transition metal catalysts. The Nanotubes were examined in the carbon/silicate composite and after dissolution of the silicate. High resolution transmission electron microscopy study of the multiwall nanotubes showed them to be 15 nm in diameter, 200 nm in length and close-ended. There was variation in crystallinity with some nanotubes showing disordered wall structures.

Resistance of alpha-crystallin quaternary structure to UV irradiation.

PubMed

Krivandin, A V; Muranov, K O; Yakovlev, F Yu; Poliansky, N B; Wasserman, L A; Ostrovsky, M A

2009-06-01

The damaging effect of UV radiation (lambda > 260 nm) on bovine alpha-crystallin in solution was studied by small-angle X-ray scattering, gel permeation chromatography, electrophoresis, absorption and fluorescence spectroscopy, and differential scanning calorimetry. The results obtained show that damage to even a large number of subunits within an alpha-crystallin oligomer does not cause significant rearrangement of its quaternary structure, aggregation of oligomers, or the loss of their solubility. Due to the high resistance of its quaternary structure, alpha-crystallin is able to prevent aggregation of destabilized proteins (especially of gamma- and beta-crystallins) and so to maintain lens transparency throughout the life of an animal (the chaperone-like function of alpha-crystallin).

Preparation of MWCNT-Fe3O4 Nanocomposites from Iron Sand Using Sonochemical Route

NASA Astrophysics Data System (ADS)

Rahmawati, R.; Melati, A.; Taufiq, A.; Sunaryono; Diantoro, M.; Yuliarto, B.; Suyatman, S.; Nugraha, N.; Kurniadi, D.

2017-05-01

The composites of multi-walled carbon nanotube (MWCNT) and magnetite (Fe3O4) nanoparticles from iron sand were successfully prepared via the sonochemical route. In this experiment, the MWCNT-Fe3O4 nanocomposites were prepared with different compositions of MWCNT (0.01%, 0.02%, and 0.04%) with the constant composition of Fe3O4 particles. The characterizations were performed by means of X-Ray Diffractometry (XRD), Fourier Transform Infra-Red (FTIR) Spectrometer and Scanning Electron Microscopy (SEM) integrated with Energy Dispersive X-Ray (EDX). The XRD data analysis showed that the Fe3O4 crystallize in spinel structure in nanometric size. Furthermore, the crystallinity of the samples tended to reduce by increasing the MWCNT compositions. The SEM images showed that Fe3O4 tend to agglomerate in nanometric size. The FTIR spectra detected the functional groups of Fe-O bonding that showed the existence of Fe2+ and Fe3+. In the composites, the Fe3O4 nanoparticles were physically mixed with the MWCNTs constructing a unique structure. The as prepared MWCNT-Fe3O4 nanocomposites have the potential for bio-applications.

Petrophysics Features of the Hydrocarbon Reservoirs in the Precambrian Crystalline Basement

NASA Astrophysics Data System (ADS)

Plotnikova, Irina

2014-05-01

A prerequisite for determining the distribution patterns of reservoir zones on the section of crystalline basement (CB) is the solution of a number of problems connected with the study of the nature and structure of empty spaces of reservoirs with crystalline basement (CB) and the impact of petrological, and tectonic factors and the intensity of the secondary transformation of rocks. We decided to choose the Novoelhovskaya well # 20009 as an object of our research because of the following factors. Firstly, the depth of the drilling of the Precambrian crystalline rocks was 4077 m ( advance heading - 5881 m) and it is a maximum for the Volga-Urals region. Secondly, petrographic cut of the well is made on core and waste water, and the latter was sampled regularly and studied macroscopically. Thirdly, a wide range of geophysical studies were performed for this well, which allowed to identify promising areas of collector with high probability. Fourth, along with geological and technical studies that were carried out continuously (including washing and bore hole redressing periods), the studies of the gaseous component of deep samples of clay wash were also carried out, which indirectly helped us estimate reservoir properties and fluid saturation permeable zones. As a result of comprehensive analysis of the stone material and the results of the geophysical studies we could confidently distinguish 5 with strata different composition and structure in the cut of the well. The dominating role in each of them is performed by rocks belonging to one of the structural-material complexes of Archean, and local variations in composition and properties are caused by later processes of granitization on different stages and high temperature diaphthoresis imposed on them. Total capacity of reservoir zones identified according to geophysical studies reached 1034.2 m, which corresponds to 25.8% of the total capacity of 5 rock masses. However, the distribution of reservoirs within the cut is uneven. The manifestation of reservoir properties of crystalline rocks and their gas content is to a high degree connected with those parts of the cut of the well that are represented by Bolshecheremshanskaya series of rocks. The analysis of the distribution of reservoir intervals that were identified in the well section # 20009 according to the geophysical studies showed that they tend to coincide with the intervals of intensive secondary changes and rock breaking, or with contacts of series of rocks or thick layers of rocks that differ greatly in physical and mechanical properties. About half of the potential reservoir zones are characterized by explicit, well-defined fractures, which was determined according to core and wastewater samples, as well as with the help of caliper gauge. The rocks of a Bolshecheremshanskaya series were more exposed to the repeated impact of the parallel processes (mylonitization, diaphtoresis, migmatization, etc.), or they were simply more affected by these processes, and that led to the characteristic distribution of collector areas, temperature and gas anomalies along the borehole cut. The presence of Bolshecheremshanskaya quartz series in the material composition of the rocks caused, firstly, increased amount of fractures, and secondly, the preservation of the porous-cavernous space frame within the superimposed secondary processes.

Thermal properties of poly(3-hydroxybutyrate)/vegetable fiber composites

NASA Astrophysics Data System (ADS)

Vitorino, Maria B. C.; Reul, Lízzia T. A.; Carvalho, Laura H.; Canedo, Eduardo L.

2015-05-01

The present work studies the thermal properties of composites of poly(3-hydroxybutyrate) (PHB) - a fully biodegradable semi-crystalline thermo-plastic obtained from renewable resources through low-impact biotechno-logical process, biocompatible and non-toxic - and vegetable fiber from the fruit (coconut) of babassu palm tree. PHB is a highly crystalline resin and this characteristic leads to suboptimal properties in some cases. Consequently, thermal properties, in particular those associated with the crystallization of the matrix, are important to judge the suitability of the compounds for specific applications. PHB/babassu composites with 0-50% load were prepared in an internal mixer. Two different types of babassu fibers with two different particle size ranges were compounded with PHB and test specimens molded by compression. Melting and crystallization behavior were studied by differential scanning calorimetry (DSC) at heating/cooling rates between 2 and 30°C/min. Several parameters, including melting point, crystallization temperature, crystallinity, and rate of crystallization, were estimated as functions of load and heating/cooling rates. Results indicate that fibers do not affect the melting process, but facilitate crystallization from the melt. Crystallization temperatures are 30 to 40°C higher for the compounds compared with the neat resin. However, the amount of fiber added has little effect on crystallinity and the degree of crystallinity is hardly affected by the load. Fiber type and initial particle size do not have a significant effect on thermal properties.

Impact of pretreated Switchgrass and biomass carbohydrates on Clostridium thermocellum ATCC 27405 cellulosome composition: a quantitative proteomic analysis.

PubMed

Raman, Babu; Pan, Chongle; Hurst, Gregory B; Rodriguez, Miguel; McKeown, Catherine K; Lankford, Patricia K; Samatova, Nagiza F; Mielenz, Jonathan R

2009-01-01

Economic feasibility and sustainability of lignocellulosic ethanol production requires the development of robust microorganisms that can efficiently degrade and convert plant biomass to ethanol. The anaerobic thermophilic bacterium Clostridium thermocellum is a candidate microorganism as it is capable of hydrolyzing cellulose and fermenting the hydrolysis products to ethanol and other metabolites. C. thermocellum achieves efficient cellulose hydrolysis using multiprotein extracellular enzymatic complexes, termed cellulosomes. In this study, we used quantitative proteomics (multidimensional LC-MS/MS and (15)N-metabolic labeling) to measure relative changes in levels of cellulosomal subunit proteins (per CipA scaffoldin basis) when C. thermocellum ATCC 27405 was grown on a variety of carbon sources [dilute-acid pretreated switchgrass, cellobiose, amorphous cellulose, crystalline cellulose (Avicel) and combinations of crystalline cellulose with pectin or xylan or both]. Cellulosome samples isolated from cultures grown on these carbon sources were compared to (15)N labeled cellulosome samples isolated from crystalline cellulose-grown cultures. In total from all samples, proteomic analysis identified 59 dockerin- and 8 cohesin-module containing components, including 16 previously undetected cellulosomal subunits. Many cellulosomal components showed differential protein abundance in the presence of non-cellulose substrates in the growth medium. Cellulosome samples from amorphous cellulose, cellobiose and pretreated switchgrass-grown cultures displayed the most distinct differences in composition as compared to cellulosome samples from crystalline cellulose-grown cultures. While Glycoside Hydrolase Family 9 enzymes showed increased levels in the presence of crystalline cellulose, and pretreated switchgrass, in particular, GH5 enzymes showed increased levels in response to the presence of cellulose in general, amorphous or crystalline. Overall, the quantitative results suggest a coordinated substrate-specific regulation of cellulosomal subunit composition in C. thermocellum to better suit the organism's needs for growth under different conditions. To date, this study provides the most comprehensive comparison of cellulosomal compositional changes in C. thermocellum in response to different carbon sources. Such studies are vital to engineering a strain that is best suited to grow on specific substrates of interest and provide the building blocks for constructing designer cellulosomes with tailored enzyme composition for industrial ethanol production.

Grafting of bacterial polyhydroxybutyrate (PHB) onto cellulose via in situ reactive extrusion with dicumyl peroxide.

PubMed

Wei, Liqing; McDonald, Armando G; Stark, Nicole M

2015-03-09

Polyhydroxybutyrate (PHB) was grafted onto cellulose fiber by dicumyl peroxide (DCP) radical initiation via in situ reactive extrusion. The yield of the grafted (cellulose-g-PHB) copolymer was recorded and grafting efficiency was found to be dependent on the reaction time and DCP concentration. The grafting mechanism was investigated by electron spin resonance (ESR) analysis and showed the presence of radicals produced by DCP radical initiation. The grafted copolymer structure was determined by nuclear magnetic resonance (NMR) spectroscopy. Scanning electronic microscopy (SEM) showed that the cellulose-g-PHB copolymer formed a continuous phase between the surfaces of cellulose and PHB as compared to cellulose-PHB blends. The relative crystallinity of cellulose and PHB were quantified from Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD) results, while the absolute degree of crystallinity was evaluated by differential scanning calorimetry (DSC). The reduction of crystallinity indicated the grafting reaction occurred not just in the amorphous region but also slightly in crystalline regions of both cellulose and PHB. The smaller crystal sizes suggested the brittleness of PHB was decreased. Thermogravimetric analysis (TGA) showed that the grafted copolymer was stabilized relative to PHB. By varying the reaction parameters the compositions (%PHB and %cellulose) of resultant cellulose-g-PHB copolymer are expected to be manipulated to obtain tunable properties.

Effects of Helium Ion Irradiation on Properties of Crystalline and Amorphous Multiphase Ceramic Coatings

NASA Astrophysics Data System (ADS)

Chen, Yong; Hu, Liangbin; Qiu, Changjun; He, Bin; Wang, Zhongchang

2017-08-01

The Al2O3-TiO2 crystalline and amorphous multiphase ceramic coatings were prepared on a martensitic steel by laser in situ reaction technique and impose irradiation with 200 keV He ions at different doses. The helium ion irradiation goes 1.55 μm deep from the surface of coating, and the displacement per atom (dpa) for the Al2O3-TiO2 coating is 20.0. When the irradiation fluency is 5 × 1017 ions/cm2, defects are identified in crystalline areas and there form interfacial areas in the coating. These crystal defects tend to migrate and converge at the interfaces. Moreover, helium ion irradiation is found to exert no effect on surface chemical composition and phase constitution of the coatings, while surface mechanical properties for the coatings after irradiation differ from those before irradiation. Further nano-indentation experiments reveal that surface nano-hardness of the Al2O3-TiO2 multiphase coatings decreases as the helium ions irradiation flux increases. Such Al2O3-TiO2 crystalline and amorphous multiphase ceramic coatings exhibit the strongest resistance against helium ion irradiation which shall be applied as candidate structural materials for accelerator-driven sub-critical system to handle the nuclear waste under extreme conditions.

Laser-induced nonlinear crystalline waveguide on glass fiber format and diode-pumped second harmonic generation

NASA Astrophysics Data System (ADS)

Shi, Jindan; Feng, Xian

2018-03-01

We report a diode pumped self-frequency-doubled nonlinear crystalline waveguide on glass fiber. A ribbon fiber has been drawn on the glass composition of 50GeO2-25B2O3-25(La,Yb)2O3. Surface channel waveguides have been written on the surface of the ribbon fiber, using space-selective laser heating method with the assistance of a 244 nm CW UV laser. The Raman spectrum of the written area indicates that the waveguide is composed of structure-deformed nonlinear (La,Yb)BGeO5 crystal. The laser-induced surface wavy cracks have also been observed and the forming mechanism of the wavy cracks has been discussed. Efficient second harmonic generation has been observed from the laser-induced crystalline waveguide, using a 976 nm diode pump. 13 μW of 488 nm output has been observed from a 17 mm long waveguide with 26.0 mW of launched diode pump power, corresponding to a normalized conversion efficiency of 4.4%W-1.

Effect of gradual ordering of Ge/Sb atoms on chemical bonding: A proposed mechanism for the formation of crystalline Ge2Sb2Te5

NASA Astrophysics Data System (ADS)

Singh, Janpreet; Singh, Gurinder; Kaura, Aman; Tripathi, S. K.

2018-04-01

Using first principle calculations, we study the atomic arrangement and bonding mechanism in the crystalline phase of Ge2Sb2Te5 (GST). It is found that the stability of GST depends on the gradual ordering of Ge/Sb atoms. The configurations with different concentration of Ge/Sb in layers have been analyzed by the partial density of state, electron localization function and Bader charge distribution. The s and p-states of Ge atom alter with different stacking configurations but there is no change in Sb and Te atom states. Our findings show that the bonding between Ge-Te is not only responsible for the stability of GST alloy but can also predict which composition can show generic features of phase change material. As the number of Ge atoms near to vacancy layer decreases, Ge donates more charge. A growth model has been proposed for the formation of crystalline phase which justifies the structure models proposed in the literature.

Zinc-doped cerium oxide nanoparticles: Sol-gel synthesis, characterization, and investigation of their in vitro cytotoxicity effects

NASA Astrophysics Data System (ADS)

Akbari, Alireza; Khammar, Mansoureh; Taherzadeh, Danial; Rajabian, Arezoo; Khorsand Zak, Ali; Darroudi, Majid

2017-12-01

Zinc-doped cerium oxide nanoparticles (Zn-doped CeO2-NPs) with Ce1-xZnxO2 composition, where x equals to 0.0, 0.01, 0.03, and 0.05 are synthesized through a green based sol-gel method from nitrate precursors and gelatin at the fixed calcination temperature of 600 °C maintained for 2 h. The powder X-ray diffraction (PXRD) patterns displayed the single-crystalline structure of these particular samples, which seemed to be completely indexed with the cubic fluorite phase. The evolution of crystalline phases in Ce1-xZnxO2 are assured by the observed broadening in PXRD peaks, while the field emission scanning electron microscopy (FE-SEM) images revealed that the spherical-shaped single-crystalline NPs do exist and confirmed the size estimations that were obtained from the Scherrer's equation. A dose dependent toxicity with non-toxic effects of concentrations up to 31.25 μg/ml is illustrated through the In vitro cytotoxicity studies regarding Neuro2A cells.

Vesicular delivery of crystalline calcium minerals to ECM in biomineralized nanoclay composites

NASA Astrophysics Data System (ADS)

Katti, Kalpana S.; Ambre, Avinash H.; Payne, Scott; Katti, Dinesh R.

2015-04-01

The mechanisms of mineralization and new bone formation were explored in newly formed extracellular matrix in a nanoclay based composite. Nanoclay films were prepared by intercalating the clays with amino acids and using the amino acids for mineralization of hydroxyapatite. The biomineralized hydroxyapatite (HAP) inside nanoclay galleries or in situ HAP/clay was further used to make films (substrates) using polycaprolactone (PCL) that were seeded with mesenchymal stem cells in a two-stage seeding process. SEM imaging experiments performed on PCL/in situ HAPclay composite films seeded with human MSCs indicated formation of matrix vesicles. The vesicles appear to emerge from the cells that are adhered to the nanoclay HAP films and also deposited in the extracellular space. Vesicles are also observed to be embedded in the cells or under the surface of cells. Crystalline structures with Ca and P were found inside vesicles. The Ca/P ratios obtained using energy dispersive spectroscopy indicate values ranging from below 0.7 to the stoichiometric HAP value of 1.67. The Ca/P ratios were obtained to be closer to the stoichiometric value for single seeding experiments as compared to the double seeding experiments indicating more new bone formation in double seeding experiments. New bone formation with bone mimetic mineralization is thus observed on the in situ HAP nanoclay PCL samples. Hence the PCL/in situ HAPclay composites besides being osteoinductive are also capable of providing a favorable micro-environment for cell dependent processes involved in bone mineral formation.

Variation on Molecular Structure, Crystallinity, and Optical Properties of Dentin Due to Nd:YAG Laser and Fluoride Aimed at Tooth Erosion Prevention

PubMed Central

Freitas, Anderson Z.; Bachmann, Luciano; Benetti, Carolina; Ana, Patricia A.

2018-01-01

This in vitro study evaluated the compositional, crystalline, and morphological effects promoted by Nd:YAG laser on root dentin, and verified the effects of laser and topical acidulated phosphate fluoride application (APF-gel) on dentin erosion. 180 bovine dentin slabs were randomized into 4 groups (n = 45): G1–untreated, G2–APF-gel (1.23% F−, 4 min), G3–Nd:YAG (1064 nm, 84.9 J/cm2, 10 Hz), and G4–APF-gel application followed by Nd:YAG laser irradiation. The compositional, crystalline, and morphological effects promoted by treatments were investigated on five samples of each experimental group. The other samples were submitted to a 5-day, 10-day, or 15-day erosive and abrasive demineralization and remineralization cycling in order to create erosion lesions. The area and depth of lesions, as well as the optical attenuation coefficient, were assessed, and all data were statistically analysed (p < 0.05). Nd:YAG laser promoted the reduction of carbonate, the formation of tetracalcium phosphate, as well as the melting and recrystallization of the dentin surface. Laser significantly decreased the area and depth of erosion lesions and altered the optical attenuation coefficient when compared to untreated and APF-gel groups, but the association of APF-gel and laser did not promote an additional effect. Nd:YAG laser irradiation can be a promissory treatment to prevent dentin erosion and the abrasion process. PMID:29389868

Small Angle Neutron Scattering Studies on Blends of Poly (Styrene-ran-Vinyl Phenol) with Liquid Crystalline Polyurethane

NASA Astrophysics Data System (ADS)

Mehta, Rujul

2005-03-01

Molecular composites, composed of uniformly dispersed rigid-rod liquid crystalline polymer (LCP) molecules in a flexible amorphous polymer matrix, have remained hitherto elusive due to a scarcity of miscible systems containing a LCP and an amorphous polymer. The production of such a blend, with an experimentally accessible miscibility window, has become possible by modifying the architecture of the flexible polymer, so as to induce favorable intermolecular hydrogen bonding. Specifically, liquid crystalline polyurethanes (LCPU) are found to be miscible with a copolymer of styrene and vinyl phenol; with optimum hydrogen bonding between the carbonyl groups of the urethane linkages and the hydroxyl groups present in the styrenic matrix. Availability of a truly miscible molecular composite presents a unique opportunity of studying the confirmation of polymer chains containing rigid-rods that are uniformly dispersed in a flexible coil matrix. A system consisting of the LCPU and the deuterated styrenic copolymer containing 20% vinyl phenol is examined by Small Angle Neutron Scattering at the National Center for Neutron Research at Gaithersburg and Technology, and the Institute of Solid State Research (IFF) at Jülich. Scattering curves for neat dPS-VPh did not fit the Debye-Bueche model; indicating complex structure. A two correlation length Debye-Bueche model was considered to accommodate for this nonlinear behavior. This model utilizes four fitting parameters, including two correlation lengths a1 and a2, corresponding to a Debye-Bueche model and Guinier model.

Anchoring ZnO Nanoparticles in Nitrogen-Doped Graphene Sheets as a High-Performance Anode Material for Lithium-Ion Batteries.

PubMed

Yuan, Guanghui; Xiang, Jiming; Jin, Huafeng; Wu, Lizhou; Jin, Yanzi; Zhao, Yan

2018-01-10

A novel binary nanocomposite, ZnO/nitrogen-doped graphene (ZnO/NG), is synthesized via a facile solution method. In this prepared ZnO/NG composite, highly-crystalline ZnO nanoparticles with a size of about 10 nm are anchored uniformly on the N-doped graphene nanosheets. Electrochemical properties of the ZnO/NG composite as anode materials are systematically investigated in lithium-ion batteries. Specifically, the ZnO/NG composite can maintain the reversible specific discharge capacity at 870 mAh g -1 after 200 cycles at 100 mA g -1 . Besides the enhanced electronic conductivity provided by interlaced N-doped graphene nanosheets, the excellent lithium storage properties of the ZnO/NG composite can be due to nanosized structure of ZnO particles, shortening the Li⁺ diffusion distance, increasing reaction sites, and buffering the ZnO volume change during the charge/discharge process.

Low energy milling method, low crystallinity alloy, and negative electrode composition

DOEpatents

Le, Dihn B; Obrovac, Mark N; Kube, Robert Y; Landucci, James R

2012-10-16

A method of making nanostructured alloy particles includes milling a millbase in a pebble mill containing milling media. The millbase comprises: (i) silicon, and (ii) at least one of carbon or a transition metal, and wherein the nanostructured alloy particles are substantially free of crystalline domains greater than 50 nanometers in size. A method of making a negative electrode composition for a lithium ion battery including the nanostructured alloy particles is also disclosed.

Biomimetic composite microspheres of collagen/chitosan/nano-hydroxyapatite: In-situ synthesis and characterization.

PubMed

Teng, Shu-Hua; Liang, Mian-Hui; Wang, Peng; Luo, Yong

2016-01-01

The collagen/chitosan/hydroxyapatite (COL/CS/HA) composite microspheres with a good spherical form and a high dispersity were successfully obtained using an in-situ synthesis method. The FT-IR and XRD results revealed that the inorganic phase in the microspheres was crystalline HA containing carbonate ions. The morphology of the composite microspheres was dependent on the HA content, and a more desirable morphology was achieved when 20 wt.% HA was contained. The composite microspheres exhibited a narrow particle distribution, most of which ranged from 5 to 10 μm. In addition, the needle-like HA nano-particles were uniformly distributed in the composite microspheres, and their crystallinity and crystal size decreased with the HA content. Copyright © 2015 Elsevier B.V. All rights reserved.

Controlling compositional homogeneity and crystalline orientation in Bi 0.8 Sb 0.2 thermoelectric thin films [Control of composition and crystallinity in Bi 0.8Sb 0.2 thermoelectric thin films].

DOE PAGES

Rochford, C.; Medlin, D. L.; Erickson, K. J.; ...

2015-12-01

Controlling alloy composition, crystalline quality, and crystal orientation is necessary to achieve high thermoelectric performance in Bi 1-xSb x thin films. These microstructural attributes are demonstrated in this letter via co-sputter deposition of Bi and Sb metals on Si/SiO 2 substrates followed by ex-situ post anneals ranging from 200 – 300 °C in forming gas with rapid cooling to achieve orientation along the trigonal axis. We show with cross-sectional transmission electron microscopy and energy-dispersive X-ray spectrometry that 50 – 95% of the Sb segregates at the surface upon exposure to air during transfer. This then forms a nanocrystalline Sb 2Omore » 3 layer upon annealing, leaving the bulk of the film primarily Bi metal which is a poor thermoelectric material. We demonstrate a SiN capping technique to eliminate Sb segregation and preserve a uniform composition throughout the thickness of the film. Given that the Bi 1-xSb x solid solution melting point depends on the Sb content, the SiN cap allows one to carefully approach but not exceed the melting point during annealing. This leads to the strong orientation along the trigonal axis and high crystalline quality desired for thermoelectric applications.« less

The organic matrix of gallstones

PubMed Central

Sutor, D. June; Wooley, Susan E.

1974-01-01

Dissolution of gallstones consisting of cholesterol, calcium carbonate, or calcium phosphate in different solvents left an amorphous organic gel-like substance (the matrix). Matrix from cholesterol stones could be colourless but was usually orange, yellow, or brown while that from calcium carbonate and calcium phosphate stones was almost invariably coloured black or dark brown. These pigments were also shown to be organic and amorphous. The amount of matrix present and its structure varied with the texture of the crystalline material. Irrespective of their composition, laminated pieces of material yielded compact laminated matrix of the same shape as the original piece and areas of loose crystalline material gave small pieces of non-cohesive matrix. Only large cholesterol crystals which usually radiate from the stone nucleus had no associated matrix. ImagesFig 1Fig 2Fig 3Fig 4Fig 5 PMID:4854981

High-mobility field-effect transistor based on crystalline ZnSnO3 thin films

NASA Astrophysics Data System (ADS)

Minato, Hiroya; Fujiwara, Kohei; Tsukazaki, Atsushi

2018-05-01

We propose crystalline ZnSnO3 as a new channel material for field-effect transistors. By molecular-beam epitaxy on LiNbO3(0001) substrates, we synthesized films of ZnSnO3, which crystallizes in the LiNbO3-type polar structure. Field-effect transistors on ZnSnO3 exhibit n-type operation with field-effect mobility of as high as 45 cm2V-1s-1 at room temperature. Systematic examination of the transistor operation for channels with different Zn/Sn compositional ratios revealed that the observed high-mobility reflects the nature of stoichiometric ZnSnO3 phase. Moreover, we found an indication of coupling of transistor characteristics with intrinsic spontaneous polarization in ZnSnO3, potentially leading to a distinct type of polarization-induced conduction.

Tailoring ZSM-5 Zeolites for the Fast Pyrolysis of Biomass to Aromatic Hydrocarbons.

PubMed

Hoff, Thomas C; Gardner, David W; Thilakaratne, Rajeeva; Wang, Kaige; Hansen, Thomas W; Brown, Robert C; Tessonnier, Jean-Philippe

2016-06-22

The production of aromatic hydrocarbons from cellulose by zeolite-catalyzed fast pyrolysis involves a complex reaction network sensitive to the zeolite structure, crystallinity, elemental composition, porosity, and acidity. The interplay of these parameters under the reaction conditions represents a major roadblock that has hampered significant improvement in catalyst design for over a decade. Here, we studied commercial and laboratory-synthesized ZSM-5 zeolites and combined data from 10 complementary characterization techniques in an attempt to identify parameters common to high-performance catalysts. Crystallinity and framework aluminum site accessibility were found to be critical to achieve high aromatic yields. These findings enabled us to synthesize a ZSM-5 catalyst with enhanced activity, which offers the highest aromatic hydrocarbon yield reported to date. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A composite CdS thin film/TiO2 nanotube structure by ultrafast successive electrochemical deposition toward photovoltaic application

NASA Astrophysics Data System (ADS)

Fu, Han; Liu, Hong; Shen, Wenzhong

2014-11-01

Fabricating functional compounds on substrates with complicated morphology has been an important topic in material science and technology, which remains a challenging issue to simultaneously achieve a high growth rate for a complex nanostructure with simple controlling factors. Here, we present a novel simple and successive method based on chemical reactions in an open reaction system manipulated by an electric field. A uniform CdS/TiO2 composite tubular structure has been fabricated in highly ordered TiO2 nanotube arrays in a very short time period (~90 s) under room temperature (RT). The content of CdS in the resultant and its crystalline structure was tuned by the form and magnitude of external voltage. The as-formed structure has shown a quite broad and bulk-like light absorption spectrum with the absorption of photon energy even below that of the bulk CdS. The as-fabricated-sensitized solar cell based on this composite structure has achieved an efficiency of 1.43% without any chemical doping or co-sensitizing, 210% higher than quantum dot-sensitized solar cell (QDSSC) under a similar condition. Hopefully, this method can also easily grow nanostructures based on a wide range of compound materials for energy science and electronic technologies, especially for fast-deploying devices.

Nanowire structures and electrical devices

DOEpatents

Bezryadin, Alexey; Remeika, Mikas

2010-07-06

The present invention provides structures and devices comprising conductive segments and conductance constricting segments of a nanowire, such as metallic, superconducting or semiconducting nanowire. The present invention provides structures and devices comprising conductive nanowire segments and conductance constricting nanowire segments having accurately selected phases including crystalline and amorphous states, compositions, morphologies and physical dimensions, including selected cross sectional dimensions, shapes and lengths along the length of a nanowire. Further, the present invention provides methods of processing nanowires capable of patterning a nanowire to form a plurality of conductance constricting segments having selected positions along the length of a nanowire, including conductance constricting segments having reduced cross sectional dimensions and conductance constricting segments comprising one or more insulating materials such as metal oxides.

Chemical and physical controls on the transformation of amorphous calcium carbonate into crystalline CaCO3 polymorphs

NASA Astrophysics Data System (ADS)

Blue, C. R.; Giuffre, A.; Mergelsberg, S.; Han, N.; De Yoreo, J. J.; Dove, P. M.

2017-01-01

Calcite and other crystalline polymorphs of CaCO3 can form by pathways involving amorphous calcium carbonate (ACC). Apparent inconsistencies in the literature indicate the relationships between ACC composition, local conditions, and the subsequent crystalline polymorphs are not yet established. This experimental study quantifies the control of solution composition on the transformation of ACC into crystalline polymorphs in the presence of magnesium. Using a mixed flow reactor to control solution chemistry, ACC was synthesized with variable Mg contents by tuning input pH, Mg/Ca, and total carbonate concentration. ACC products were allowed to transform within the output suspension under stirred or quiescent conditions while characterizing the evolving solutions and solids. As the ACC transforms into a crystalline phase, the solutions record a polymorph-specific evolution of pH and Mg/Ca. The data provide a quantitative framework for predicting the initial polymorph that forms from ACC based upon the solution aMg2+/aCa2+ and aCO32-/aCa2+ and stirring versus quiescent conditions. This model reconciles discrepancies among previous studies that report on the nature of the polymorphs produced from ACC and supports the previous claim that monohydrocalcite may be an important, but overlooked, transient phase on the way to forming some aragonite and calcite deposits. By this construct, organic additives and extreme pH are not required to tune the composition and nature of the polymorph that forms. Our measurements show that the Mg content of ACC is recorded in the resulting calcite with a ≈1:1 dependence. By correlating composition of these calcite products with the Mgtot/Catot of the initial solutions, we find a ≈3:1 dependence that is approximately linear and general to whether calcite is formed via an ACC pathway or by the classical step-propagation process. Comparisons to calcite grown in synthetic seawater show a ≈1:1 dependence. The relationships suggest that the local Mg2+/Ca2+ at the time of precipitation determines the calcite composition, independent of whether growth occurs via an amorphous intermediate or classical pathway for a range of supersaturations and pH conditions. The findings reiterate the need to revisit the traditional picture of chemical and physical controls on CaCO3 polymorph selection. Mineralization by pathways involving ACC can lead to the formation of crystalline phases whose polymorphs and compositions are out of equilibrium with local growth media. As such, classical thermodynamic equilibria may not provide a reliable predictor of observed compositions.

Structure and Properties of Amorphous Transparent Conducting Oxides

NASA Astrophysics Data System (ADS)

Medvedeva, Julia

Driven by technological appeal, the research area of amorphous oxide semiconductors has grown tremendously since the first demonstration of the unique properties of amorphous indium oxide more than a decade ago. Today, amorphous oxides, such as a-ITO, a-IZO, a-IGZO, or a-ZITO, exhibit the optical, electrical, thermal, and mechanical properties that are comparable or even superior to those possessed by their crystalline counterparts, pushing the latter out of the market. Large-area uniformity, low-cost low-temperature deposition, high carrier mobility, optical transparency, and mechanical flexibility make these materials appealing for next-generation thin-film electronics. Yet, the structural variations associated with crystalline-to-amorphous transition as well as their role in carrier generation and transport properties of these oxides are far from being understood. Although amorphous oxides lack grain boundaries, factors like (i) size and distribution of nanocrystalline inclusions; (ii) spatial distribution and clustering of incorporated cations in multicomponent oxides; (iii) formation of trap defects; and (iv) piezoelectric effects associated with internal strains, will contribute to electron scattering. In this work, ab-initio molecular dynamics (MD) and accurate density-functional approaches are employed to understand how the properties of amorphous ternary and quaternary oxides depend on quench rates, cation compositions, and oxygen stoichiometries. The MD results, combined with thorough experimental characterization, reveal that interplay between the local and long-range structural preferences of the constituent oxides gives rise to a complex composition-dependent structural behavior in the amorphous oxides. The proposed network models of metal-oxygen polyhedra help explain the observed intriguing electrical and optical properties in In-based oxides and suggest ways to broaden the phase space of amorphous oxide semiconductors with tunable properties. The work is supported by NSF-MRSEC program.

Chemical composition of crystalline rock fragments from Luna 16 and Luna 20 fines

NASA Technical Reports Server (NTRS)

Cimbalnikova, A.; Palivcova, M.; Frana, J.; Mastalka, A.

1977-01-01

The chemical composition (bulk, rare earth, and trace elements) of the Luna 16 mare regolith and luna 20 highland regolith is discussed. The rock samples considered are 14 basaltic rock fragments (Luna 16) and 13 rock fragments of the ANT suite (Luna 20). On the basis of bulk composition, two types of basaltic rocks have been differentiated and defined in the Luna 16 regolith: mare basalts (fundamental crystalline rocks of Mare Fecunditatis) and high-alumina basalts. The bulk analyses of rock fragments of the ANT suite also enabled distinction of two rock types: anorthositic norites and troctolites and/or spinal-troctolites (the most abundant crystalline rocks of the highland region, the landing site of luna 20), and anorthosites. The chemical compositions of Luna 16 and Luna 20 regolith samples are compared. Differences in the chemistry of the Luna 16 mare regolith and that of mare basalts are discussed. The chemical affinity between the Luna 20 highland regolith and (a) anorthositic norites and (b) troctolites and/or spinel-troctolites has been ascertained.

Structural basis for the slow digestion property of native cereal starches.

PubMed

Zhang, Genyi; Venkatachalam, Mahesh; Hamaker, Bruce R

2006-11-01

Native cereal starches are ideal slowly digestible starches (SDS), and the structural basis for their slow digestion property was investigated. The shape, size, surface pores and channels, and degree of crystallinity of starch granules were not related to the proportion of SDS, while semicrystalline structure was critical to the slow digestion property as evidenced by loss of SDS after cooking. The high proportion of SDS in cereal starches, as compared to potato starch, was related to their A-type crystalline structure with a lower degree of perfection as indicated by a higher amount of shortest A chains with a degree of polymerization (DP) of 5-10. The A-type amorphous lamellae, an important component of crystalline regions of native cereal starches, also affect the amount of SDS as shown by a reduction of SDS in lintnerized maize starches. These observations demonstrate that the supramolecular A-type crystalline structure, including the distribution and perfection of crystalline regions (both crystalline and amorphous lamellae), determines the slow digestion property of native cereal starches.

Achieving phase transformation and structure control of crystalline anatase TiO2@C hybrids from titanium glycolate precursor and glucose molecules.

PubMed

Cheng, Gang; Stadler, Florian J

2015-01-15

Considerable efforts have focused on functional TiO2@carbonaceous hybrid nanostructured materials (TiO2@C) to satisfy the future requirements of environmental photocatalysis and energy storage using these advanced materials. In this study, we developed a two-step solution-phase reaction to prepare hybrid TiO2@C with tuneable structure and composition from the hydrothermal carbonization (HTC) of glucose. X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) were used to determine the crystallite size, composition, and phase purity. The results of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high resolution TEM (HRTEM) showed that the morphology of the as-synthesized TiO2@C hybrids could be controlled by varying the amount of glucose, also acting as the carbon source. Based on the observations made with different glucose concentrations, a formation mechanism of nanoparticulate and nanoporous TiO2@C hybrids was proposed. In addition, the as-synthesized TiO2@C hybrids with different compositions and structures showed enhanced adsorption of visible light and improved dye-adsorption capacity, which supported their potential use as photocatalysts with good activity. This new synthetic approach, using a nanoprecursor, provides a simple and versatile way to prepare TiO2@C hybrids with tuneable composition, structures, and properties, and is expected to lead to a family of composites with designed properties. Copyright © 2014 Elsevier Inc. All rights reserved.

Solid solutions of gadolinium doped zinc oxide nanorods by combined microwave-ultrasonic irradiation assisted crystallization

NASA Astrophysics Data System (ADS)

Kiani, Armin; Dastafkan, Kamran; Obeydavi, Ali; Rahimi, Mohammad

2017-12-01

Nanocrystalline solid solutions consisting of un-doped and gadolinium doped zinc oxide nanorods were fabricated by a modified sol-gel process utilizing combined ultrasonic-microwave irradiations. Polyvinylpyrrolidone, diethylene glycol, and triethylenetetramine respectively as capping, structure directing, and complexing agents were used under ultrasound dynamic aging and microwave heating to obtain crystalline nanorods. Crystalline phase monitoring, lattice parameters and variation, morphology and shape, elemental analysis, functional groups, reducibility, and the oxidation state of emerged species were examined by PXRD, FESEM, TEM, EDX, FTIR, micro Raman, H2-TPR, and EPR techniques. Results have verified that irradiation mechanism of gelation and crystallization reduces the reaction time, augments the crystal quality, and formation of hexagonal close pack structure of Wurtzite morphology. Besides, dissolution of gadolinium within host lattice involves lattice deformation, unit cell distortion, and angular position variation. Structure related shape and growth along with compositional purity were observed through microscopic and spectroscopic surveys. Furthermore, TPR and EPR studies elucidated more detailed behavior upon exposure to the exerted irradiations and subsequent air-annealing including the formed oxidation states and electron trapping centers, presence of gadolinium, zinc, and oxygen disarrays and defects, as well as alteration in the host unit cell via gadolinium addition.

Preparation and photocatalytic performance of fibrous Tb3+-doped TiO2 using collagen fiber as template

NASA Astrophysics Data System (ADS)

Luo, Ting; Wan, Xiang-Jun; Jiang, Shang-Xuan; Zhang, Li-Yuan; Hong, Zheng-Qu; Liu, Jiao

2018-04-01

Fibrous Tb3+-doped TiO2 were prepared using collagen fiber as template. Morphology, crystalline structure, surface area, element content, chemical composition and elemental chemical status, microstructure and element distribution of the prepared samples were characterized by using scanning electron microscopy, X-ray diffraction, specific surface area analysis, inductively coupled plasma atomic emission spectrometer, X-ray photoelectron spectroscopy, transmission electron microscope and element mapping, respectively. The photocatalytic activities were evaluated by following degradation of methyl orange. The results showed that the fiber structure of collagen template was fully preserved when the calcination temperature was 500-800 °C. However, with the increase of calcination temperature, crystallinity and average particle size were increased, and the photocatalytic performance was decreased. For 2% Tb3+-TiO2 calcined at 500 °C, the degradation rate of methyl orange reached 93.87% after 6 h when a high-pressure mercury lamp (150 W) was used as the light source for photocatalytic degradation. Titanium tanning agent performance was excellent, the yield of TiO2 was high, and the fiber structure was presented when 0.2 mol/L citric acid/sodium citrate buffer solution was used.

Evolution of LiFePO4 thin films interphase with electrolyte

NASA Astrophysics Data System (ADS)

Dupré, N.; Cuisinier, M.; Zheng, Y.; Fernandez, V.; Hamon, J.; Hirayama, M.; Kanno, R.; Guyomard, D.

2018-04-01

Many parameters may control the growth and the characteristics of the interphase, such as surface structure and morphology, structural defects, grain boundaries, surface reactions, etc. However, polycrystalline surfaces contain these parameters simultaneously, resulting in a quite complicated system to study. Working with model electrode surfaces using crystallographically oriented crystalline thin films appears as a novel and unique approach to understand contributions of preferential orientation and rugosity of the surface. In order to rebuild the interphase architecture along electrochemical cycling, LiFePO4 epitaxial films offering ideal 2D (100) interfaces are here investigated through the use of non-destructive depth profiling by Angular Resolved X-ray Photoelectron Spectroscopy (ARXPS). The composition and structure of the interphase is then monitored upon cycling for samples stopped at the end of charge and discharge for various numbers of cycles, and discussed in the light of combined XPS and X-ray reflectivity (XRR) measurements. Such an approach allows describing the interphase evolution on a specific model LiFePO4 crystallographic orientation and helps understanding the nature and evolution of the LiFePO4/electrolyte interphase forming on the surface of LiFePO4 poly-crystalline powder.

Characterizing Crystalline-Vitreous Structures: From Atomically Resolved Silica to Macroscopic Bubble Rafts

ERIC Educational Resources Information Center

Burson, Kristen M.; Schlexer, Philomena; Bu¨chner, Christin; Lichtenstein, Leonid; Heyde, Markus; Freund, Hans-Joachim

2015-01-01

A two-part experiment using bubble rafts to analyze amorphous structures is presented. In the first part, the distinctions between crystalline and vitreous structures are examined. In the second part, the interface between crystalline and amorphous regions is considered. Bubble rafts are easy to produce and provide excellent analogy to recent…

Structure of a Highly Active Cephalopod S-crystallin Mutant: New Molecular Evidence for Evolution from an Active Enzyme into Lens-Refractive Protein

PubMed Central

Tan, Wei-Hung; Cheng, Shu-Chun; Liu, Yu-Tung; Wu, Cheng-Guo; Lin, Min-Han; Chen, Chiao-Che; Lin, Chao-Hsiung; Chou, Chi-Yuan

2016-01-01

Crystallins are found widely in animal lenses and have important functions due to their refractive properties. In the coleoid cephalopods, a lens with a graded refractive index provides good vision and is required for survival. Cephalopod S-crystallin is thought to have evolved from glutathione S-transferase (GST) with various homologs differentially expressed in the lens. However, there is no direct structural information that helps to delineate the mechanisms by which S-crystallin could have evolved. Here we report the structural and biochemical characterization of novel S-crystallin-glutathione complex. The 2.35-Å crystal structure of a S-crystallin mutant from Octopus vulgaris reveals an active-site architecture that is different from that of GST. S-crystallin has a preference for glutathione binding, although almost lost its GST enzymatic activity. We’ve also identified four historical mutations that are able to produce a “GST-like” S-crystallin that has regained activity. This protein recapitulates the evolution of S-crystallin from GST. Protein stability studies suggest that S-crystallin is stabilized by glutathione binding to prevent its aggregation; this contrasts with GST-σ, which do not possess this protection. We suggest that a tradeoff between enzyme activity and the stability of the lens protein might have been one of the major driving force behind lens evolution. PMID:27499004

ZnxCd1-xSe alloy nanowires covering the entire compositional range grown by metalorganic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Shan, C. X.; Liu, Z.; Ng, C. M.; Hark, S. K.

2005-07-01

We show that preferentially oriented, single-crystalline ZnxCd1-xSe alloy nanowires can be grown on GaAs (100) surface using Au as a catalyst over the entire compositional range in a metalorganic chemical vapor deposition system. The composition of the alloy nanowires can be simply adjusted through the ratio of the flow rates of group-II precursors. Electron microscopy shows that the nanowires are smooth and uniform in shape; their diameters range from 20 to 80 nm and lengths exceed a few micrometers. Nanowires containing more than 13% Zn are zinc blende structured and grow along the ⟨110⟩ direction. Those containing less Zn are wurtzite structured and grow along the ⟨210⟩ direction. Compared with the bulk alloy, the change from zinc blende to wurtzite structure in nanowires occurs at far smaller x. The preferred orientation and the persistence of the zinc blende structure both reflect the influence of the substrate on the growth of the nanowires. Photoluminescence measurements identify a strong near-band-edge emission for all samples and show that its peak energy tracks the band gap of ZnxCd1-xSe epilayer for x>0.13. The growth of alloy nanowires at many compositions opens up the possibility of realizing quasi-one-dimensional heterojunctions.

Lattice instability and elastic response of metastable Mo1-xSix thin films

NASA Astrophysics Data System (ADS)

Fillon, A.; Jaouen, C.; Michel, A.; Abadias, G.; Tromas, C.; Belliard, L.; Perrin, B.; Djemia, Ph.

2013-11-01

We present a detailed experimental study on Mo1-xSix thin films, an archetypal alloy system combining metallic and semiconductor materials. The correlations between structure and elastic response are comprehensively investigated. We focus on assessing trends for understanding the evolution of elastic properties upon Si alloying in relation to the structural state (crystalline vs amorphous), bonding character (metallic vs covalent), and local atomic environment. By combining picosecond ultrasonics and Brillouin light scattering techniques, a complete set of effective elastic constants and mechanical moduli (B, G, E) is provided in the whole compositional range, covering bcc solid solutions (x < 0.20) and the amorphous phase (0.20 < x < 1.0). A softening of the shear and Young moduli and a concomitant decrease of the Debye temperature is revealed for crystalline alloys, with a significant drop being observed at x ˜ 0.2 corresponding to the limit of crystal lattice stability. Amorphous alloys exhibit a more complex elastic response, related to variations in coordination number, atomic volume, and bonding state, depending on Si content. Finally, distinct evolutions of the G/B ratio as a function of Cauchy pressure are reported for crystalline and amorphous alloys, enabling us to identify signatures of ductility vs brittleness in the features of the local atomic environment. This work paves the way to design materials with improved mechanical properties by appropriate chemical substitution or impurity incorporation during thin-film growth.

Controlled synthesis of germanium nanoparticles by nonthermal plasmas

NASA Astrophysics Data System (ADS)

Ahadi, Amir Mohammad; Hunter, Katharine I.; Kramer, Nicolaas J.; Strunskus, Thomas; Kersten, Holger; Faupel, Franz; Kortshagen, Uwe R.

2016-02-01

The size, composition, and crystallinity of plasma produced nanoparticles are crucial factors for their physical and chemical properties. Here, we investigate the role of the process gas composition, particularly the hydrogen (H2) flow rate, on germanium (Ge) nanoparticles synthesized from a chlorinated precursor by nonthermal plasma. We demonstrate that the gas composition can significantly change the nanoparticle size and also adjust the surface chemistry by altering the dominant reaction mechanisms. A red shift of the Ge-Clx infrared absorptions with increasing H2 flow indicates a weakening of the Ge-Clx bonds at high H2 content. Furthermore, by changing the gas composition, the nanoparticles microstructure can be controlled from mostly amorphous at high hydrogen flow to diamond cubic crystalline at low hydrogen flow.

Comparative advantages and limitations of the basic metrology methods applied to the characterization of nanomaterials.

PubMed

Linkov, Pavel; Artemyev, Mikhail; Efimov, Anton E; Nabiev, Igor

2013-10-07

Fabrication of modern nanomaterials and nanostructures with specific functional properties is both scientifically promising and commercially profitable. The preparation and use of nanomaterials require adequate methods for the control and characterization of their size, shape, chemical composition, crystalline structure, energy levels, pathways and dynamics of physical and chemical processes during their fabrication and further use. In this review, we discuss different instrumental methods for the analysis and metrology of materials and evaluate their advantages and limitations at the nanolevel.

Understanding the Effect of Preparative Approaches in the Formation of “Flower-like” Li 4Ti 5O 12 —Multiwalled Carbon Nanotube Composite Motifs with Performance as High-Rate Anode Materials for Li-Ion Battery Applications

DOE PAGES

Wang, Lei; Zhang, Yiman; McBean, Coray L.; ...

2017-01-18

Herein we highlight the significance of nanoscale attachment modality as an important determinant of observed electrochemical performance. Specifically, controlled loading ratios of multi-walled carbon nanotubes (MWNTs) have been successfully anchored onto the surfaces of a unique “flower-like” Li 4Ti 5O 12 (LTO) micro-scale sphere motif, for the first time, using a number of different and distinctive preparative approaches, including (i) a sonication method, (ii) an in situ direct-deposition approach, (iii) a covalent attachment protocol, as well as (iv) a π-π interaction strategy. In terms of structural characterization, the composites generated by physical sonication as well as non-covalent π-π interactions retainedmore » the intrinsic hierarchical “flower-like” morphology and exhibited a similar crystallinity profile as compared with that of pure LTO. By comparison, the composite prepared by an in situ direct deposition approach yielded not only a fragmented LTO structure, likely due to the possible interfering presence of the MWNTs themselves during the relevant hydrothermal reaction, but also a larger crystallite size, owing to the higher annealing temperature associated with its preparation. Finally, the composite created via covalent attachment was covered with an amorphous insulating linker, which probably led to a decreased contact area between the LTO and the MWNTs and hence, a lower crystallinity in the resulting composite. In addition electrode tests suggested that the composite generated by π-π interactions out-performed the other three analogous heterostructures, due to a smaller charge transfer resistance as well as a faster Li-ion diffusion. In particular, the LTO-MWNT composite, produced by π-π interactions, exhibited a reproducibly high rate capability as well as a reliably solid cycling stability, delivering 132 mA h g -1 at 50 C, after 100 discharge/charge cycles, including 40 cycles at a high (>20 C) rate. To conclude, such data denote the highest electrochemical performance measured to date as compared with any LTO-carbon nanotube-based composite materials previously reported, under high discharge rate conditions, and tangibly underscore the correlation between preparative methodology and the resulting performance metrics.« less

Understanding the Effect of Preparative Approaches in the Formation of “Flower-like” Li 4Ti 5O 12 —Multiwalled Carbon Nanotube Composite Motifs with Performance as High-Rate Anode Materials for Li-Ion Battery Applications

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

Wang, Lei; Zhang, Yiman; McBean, Coray L.

Herein we highlight the significance of nanoscale attachment modality as an important determinant of observed electrochemical performance. Specifically, controlled loading ratios of multi-walled carbon nanotubes (MWNTs) have been successfully anchored onto the surfaces of a unique “flower-like” Li 4Ti 5O 12 (LTO) micro-scale sphere motif, for the first time, using a number of different and distinctive preparative approaches, including (i) a sonication method, (ii) an in situ direct-deposition approach, (iii) a covalent attachment protocol, as well as (iv) a π-π interaction strategy. In terms of structural characterization, the composites generated by physical sonication as well as non-covalent π-π interactions retainedmore » the intrinsic hierarchical “flower-like” morphology and exhibited a similar crystallinity profile as compared with that of pure LTO. By comparison, the composite prepared by an in situ direct deposition approach yielded not only a fragmented LTO structure, likely due to the possible interfering presence of the MWNTs themselves during the relevant hydrothermal reaction, but also a larger crystallite size, owing to the higher annealing temperature associated with its preparation. Finally, the composite created via covalent attachment was covered with an amorphous insulating linker, which probably led to a decreased contact area between the LTO and the MWNTs and hence, a lower crystallinity in the resulting composite. In addition electrode tests suggested that the composite generated by π-π interactions out-performed the other three analogous heterostructures, due to a smaller charge transfer resistance as well as a faster Li-ion diffusion. In particular, the LTO-MWNT composite, produced by π-π interactions, exhibited a reproducibly high rate capability as well as a reliably solid cycling stability, delivering 132 mA h g -1 at 50 C, after 100 discharge/charge cycles, including 40 cycles at a high (>20 C) rate. To conclude, such data denote the highest electrochemical performance measured to date as compared with any LTO-carbon nanotube-based composite materials previously reported, under high discharge rate conditions, and tangibly underscore the correlation between preparative methodology and the resulting performance metrics.« less

[Infrared spectrophotometry for crystalline composition of staghorn calculi].

PubMed

Ma, Kai; Huang, Xiao-bo; Xu, Qing-quan; Li, Jian-xing; Xiong, Liu-lin; Yang, Bo; Ye, Xiong-jun; Chen, Liang; Wang, Xiao-feng; Na, Yan-qun

2010-11-30

To provide theoretic rationales for treatment and prevention of staghorn calculi by analyzing stone composition and studying the relationship between stone and urinary tract infections. The clinical data of 51 staghorn calculi patients were analyzed retrospectively. The stone compositions were studied by infrared spectrophotometry. Six types of stone compositions were obtained. There were calcium oxalate monohydrate, calcium oxalate dehydrate, carbonate apatite, magnesium ammonium phosphate hexahydrate, uric acid and L-cystine. The majority of stones were of mixed compositions, pure stones were found in 15 cases (29.4%). Among all stones, calcium oxalate stones were found in 41 cases (80.4%) and uric stones in 10 cases (19.6%). Infectious stones were found in 26 cases (51.0%). Urinary tract infections were found in 40 (78.4%) patients and positive urine/stone culture was detected in 33 (64.7%) patients. With multiple crystalline compositions and etiological factors, the staghorn calculi are closely correlated with urinary tract infections.

Chemical order in the glassy As/sub x/S/sub 1-//sub x/ system: An x-ray-absorption spectroscopy study

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

Yang, C.Y.; Paesler, M.A.; Sayers, D.E.

1989-05-15

We have examined chemical ordering in the glassy As/sub x/S/sub 1-//sub x/ system by determining the effect of composition on the local structure of these chalcogenide glasses using x-ray-absorption spectroscopy. Structural changes associated with composition indicate that with increasing S content, the S-rich glasses on the As site have a similar local structure to crystalline As/sub 2/S/sub 3/ (orpiment), but the As-S-As linkages are replaced by As-S-S linkages at higher S concentration. In As-rich glasses a breakdown of the local AsS/sub 3/ configuration is evident and the formation of As-As bonds is observed. Further comparison between As-rich alloys and crystallinemore » As/sub 4/S/sub 4/ (realgar) suggests that a significant fraction of disordered As/sub 4/S/sub 4/ molecular fragments is contained in the As-rich region.« less

A structural investigation into the compaction behavior of pharmaceutical composites using powder X-ray diffraction and total scattering analysis.

PubMed

Moore, Michael D; Steinbach, Alison M; Buckner, Ira S; Wildfong, Peter L D

2009-11-01

To use advanced powder X-ray diffraction (PXRD) to characterize the structure of anhydrous theophylline following compaction, alone, and as part of a binary mixture with either alpha-lactose monohydrate or microcrystalline cellulose. Compacts formed from (1) pure theophylline and (2) each type of binary mixture were analyzed intact using PXRD. A novel mathematical technique was used to accurately separate multi-component diffraction patterns. The pair distribution function (PDF) of isolated theophylline diffraction data was employed to assess structural differences induced by consolidation and evaluated by principal components analysis (PCA). Changes induced in PXRD patterns by increasing compaction pressure were amplified by the PDF. Simulated data suggest PDF dampening is attributable to molecular deviations from average crystalline position. Samples compacted at different pressures were identified and differentiated using PCA. Samples compacted at common pressures exhibited similar inter-atomic correlations, where excipient concentration factored in the analyses involving lactose. Practical real-space structural analysis of PXRD data by PDF was accomplished for intact, compacted crystalline drug with and without excipient. PCA was used to compare multiple PDFs and successfully differentiated pattern changes consistent with compaction-induced disordering of theophylline as a single component and in the presence of another material.

Phase composition and in vitro bioactivity of porous implants made of bioactive glass S53P4.

PubMed

Fagerlund, S; Massera, J; Moritz, N; Hupa, L; Hupa, M

2012-07-01

This work studied the influence of sintering temperature on the phase composition, compression strength and in vitro properties of implants made of bioactive glass S53P4. The implants were sintered within the temperature range 600-1000°C. Over the whole temperature range studied, consolidation took place mainly via viscous flow sintering, even though there was partial surface crystallization. The mechanical strength of the implants was low but increased with the sintering temperature, from 0.7 MPa at 635°C to 10 MPa at 1000°C. Changes in the composition of simulated body fluid (SBF), the immersion solution, were evaluated by pH measurements and ion analysis using inductively coupled plasma optical emission spectrometry. The development of a calcium phosphate layer on the implant surfaces was verified using scanning electron microscopy-electron-dispersive X-ray analysis. When immersed in SBF, a calcium phosphate layer formed on all the samples, but the structure of this layer was affected by the surface crystalline phases. Hydroxyapatite formed more readily on amorphous and partially crystalline implants containing both primary Na(2)O·CaO·2SiO(2) and secondary Na(2)Ca(4)(PO(4))(2)SiO(4) crystals than on implants containing only primary crystals. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The Metastable Persistence of Vapor-Deposited Amorphous Ice at Anomalously High Temperatures

NASA Technical Reports Server (NTRS)

Blake, David F.; Jenniskens, Peter; DeVincenzi, Donald L. (Technical Monitor)

1995-01-01

Studies of the gas release, vaporization behavior and infrared (IR) spectral properties of amorphous and crystalline water ice have direct application to cometary and planetary outgassing phenomena and contribute to an understanding of the physical properties of astrophysical ices. Several investigators report anomalous phenomena related to the warming of vapor-deposited astrophysical ice analogs. However gas release, ice volatilization and IR spectral features are secondary or tertiary manifestations of ice structure or morphology. These observations are useful in mimicking the bulk physical and chemical phenomena taking place in cometary and other extraterrestrial ices but do not directly reveal the structural changes which are their root cause. The phenomenological interpretation of spectral and gas release data is probably the cause of somewhat contradictory explanations invoked to account for differences in water ice behavior in similar temperature regimes. It is the microstructure, micromorphology and microchemical heterogeneity of astrophysical ices which must be characterized if the mechanisms underlying the observed phenomena are to be understood. We have been using a modified Transmission Electron Microscope to characterize the structure of vapor-deposited astrophysical ice analogs as a function of their deposition, temperature history and composition. For the present experiments, pure water vapor is deposited at high vacuum onto a 15 K amorphous carbon film inside an Hitachi H-500H TEM. The resulting ice film (approx. 0.05 micrometers thick) is warmed at the rate of 1 K per minute and diffraction patterns are collected at 1 K intervals. These patterns are converted into radial intensity distributions which are calibrated using patterns of crystalline gold deposited on a small part of the carbon substrate. The small intensity contributed by the amorphous substrate is removed by background subtraction. The proportions of amorphous and crystalline material in each pattern are determined by subtracting a percentage of crystalline component relative to amorphous and pure crystalline endmembers. Vapor-deposited water ice undergoes two amorphous to amorphous structural transformations in the temperature range 15-130 K with important astrophysical implications. The onset of cubic crystallization occurs at 142-160 K (at 1K per minute heating rates) during which the 220 and 311 diffraction maxima appear and 0.1 micrometer crystallites can be seen in bright field images. This transition is time dependent.

Physical and structural properties of polyaniline/microcrystalline cellulose nanocomposite

NASA Astrophysics Data System (ADS)

Abdi, Mahnaz M.; Liyana, Rawaida; Tahir, Paridah Md; Heng, Lee Yook; Sulaiman, Yusran; Waheeda, Nur Farhana; Hassan, Nabihah Abu

2017-12-01

A composite of Polyaniline/Microcrystalline Cellulose (PAni/MCC) was prepared via a chemical polymerization method in the presence of ammonium persulfate (NH4)2S2O8 as oxidant and cetyltrimethylammonium bromide (CTAB) as a cationic surfactant. The results of FESEM showed that the morphology of nanocomposite depends on the monomer concentration. Wire-like and porous nanostructure was observed for PAni/MCC/CTAB composite that could be suitable for enzyme immobilization and sensor applications. The electrochemical properties of the composites were studied using Cyclic Voltammetry (CV) and it was shown that PAni/MCC/CTAB composite generated a higher current response compared to the pure PAni. The synergy effect of MCC and CTAB on the physical and electrochemical properties of composite resulted in higher electron transferring in PAni/MCC/CTAB. The presence of significant peaks of PAni and MCC in FT-IR spectrum of nanocomposite indicating polymerization of aniline on the surface of MCC. Characteristic peaks of crystalline cellulose were observed at 22.8 and 14.7 2theta in XRD pattern.

A study on EMI shielding enhancement behaviors of Ni-plated CFs-reinforced polymer matrix composites by post heat treatment

NASA Astrophysics Data System (ADS)

Kim, Kwan-Woo; Han, Woong; Kim, Byoung-Suhk; Kim, Byung-Joo; An, Kay-Hyeok

2017-09-01

In order to develop the high quality electromagnetic interference shielding efficiency (EMI-SE) materials, Ni-plated carbon fiber fabrics (Ni-CFFs) were prepared by an electroless method. Effects of post heat-treatment conditions on EMI-SE and electrical conductivity of Ni-CFFs/epoxy composites were also investigated. The morphologies and structural properties of Ni-CFFs were measured by a SEM and a XRD. It was found that all the Ni peaks increased with increasing post-heat treatment temperature, indicating that some impurities were removed and nickel particle sharp crystalline peaks. Also, It was found that the EMI-SE of composites enhanced was increased after post heat-treatment. In the frequency range of electromagnetic wave occurred from appliances (3.0 × 107-6.0 × 108), EMI-SE of post-heat treatment Ni-CFs was increased. This result concludes that the EMI-SE of the composites can be enhanced according to the microstructure of Ni in the Ni-CFFs/epoxy composites.

Effect of TiO2 nanoparticles doping on structural and electrical properties of PVA: NaBr polymer electrolyte

NASA Astrophysics Data System (ADS)

Sagar, Rohan N.; Ravindrachary, V.; Guruswamy, B.; Hegde, Shreedatta; Mahanthesh, B. K.; Kumari, R. Padma

2018-05-01

The effect of TiO2 nanoparticles on morphology and electrical properties of PVA: NaBr composite films were carried out using various techniques. The pure and TiO2 nanoparticle doped PVA: NaBr composite films were prepared using solvent casting method. The FTIR spectral studies shows that the Ti+ ions of TiO2 interacts with hydroxyl group (OH) of PVA via hydrogen bonding and forms the charge transfer complexes (CTC). These interactions are of inter/intra molecular type and affects the surface morphology as well as the electrical properties of composite films. XRD study shows that the crystallinity of the composite increases with doping level. SEM studies shows that the increase in roughness of the surface of the composite films and uniform dispersion of nanofillers in polymer matrix. Electrical properties are analyzed using impedance analyzer and higher conductivity (10-4Scm-1) is achieved for 5 wt % TiO2 doping concentration.

Effective role of deposition duration on the growth of V2O5 nanostructured thin films

NASA Astrophysics Data System (ADS)

Sharma, Rabindar Kumar; Saini, Sujit Kumar; Singh, Megha; Reddy, G. B.

2016-05-01

In this report, vanadium pentoxide nanostructured thin films (NSTs) with nanoplates (NPs) have synthesized on Ni coated glass substrate employing plasma assisted sublimation process (PASP), as a function of deposition/growth durations. The effect of deposition durations on the morphological, structural, vibrational, and compositional properties have been investigated one by one. The structural and vibrational studies endorsed that the grown NPs have only orthorhombic phase, no other sub oxide phases are recorded in the limit of resolution. The morphological results of all samples using SEM, revealed that the features, coverage density, and alignments of NPs are greatly controlled by deposition duration and the best sample is obtained for 25 min (S2). Further, the more insight information is accomplished by HRTEM/SAED on the best featured sample, which confirmed the single crystalline nature of NPs. The XPS result again confirmed the compositional purity and the nearly stoichiometric nature of NPs.

The crystallization water of gypsum rocks is a relevant water source for plants.

PubMed

Palacio, Sara; Azorín, José; Montserrat-Martí, Gabriel; Ferrio, Juan Pedro

2014-08-18

Some minerals, like gypsum, hold water in their crystalline structure. Although still unexplored, the use of such crystallization water by organisms would point to a completely new water source for life, critical under dry conditions. Here we use the fact that the isotopic composition of free water differs from gypsum crystallization water to show that plants can use crystallization water from the gypsum structure. The composition of the xylem sap of gypsum plants during summer shows closer values to gypsum crystallization water than to free soil water. Crystallization water represents a significant water source for organisms growing on gypsum, especially during summer, when it accounts for 70-90% of the water used by shallow-rooted plants. Given the widespread occurrence of gypsum in dry lands throughout the Earth and in Mars, these results may have important implications for arid land reclamation and exobiology.

Neutron irradiation and high temperature effects on amorphous Fe-based nano-coatings on steel - A macroscopic assessment

NASA Astrophysics Data System (ADS)

Simos, N.; Zhong, Z.; Dooryhee, E.; Ghose, S.; Gill, S.; Camino, F.; Şavklıyıldız, İ.; Akdoğan, E. K.

2017-06-01

The study revealed that loss of ductility in an amorphous Fe-alloy coating on a steel substrate composite structure was essentially prevented from occurring, following radiation with modest neutron doses of ∼2 × 1018 n/cm2. At the higher neutron dose of ∼2 × 1019, macroscopic stress-strain analysis showed that the amorphous Fe-alloy nanostructured coating, while still amorphous, experienced radiation-induced embrittlement, no longer offering protection against ductility loss in the coating-substrate composite structure. Neutron irradiation in a corrosive environment revealed exemplary oxidation/corrosion resistance of the amorphous Fe-alloy coating, which is attributed to the formation of the Fe2B phase in the coating. To establish the impact of elevated temperatures on the amorphous-to-crystalline transition in the amorphous Fe-alloy, electron microscopy was carried out which confirmed the radiation-induced suppression of crystallization in the amorphous Fe-alloy nanostructured coating.

Laser deposition and direct-writing of thermoelectric misfit cobaltite thin films

NASA Astrophysics Data System (ADS)

Chen, Jikun; Palla-Papavlu, Alexandra; Li, Yulong; Chen, Lidong; Shi, Xun; Döbeli, Max; Stender, Dieter; Populoh, Sascha; Xie, Wenjie; Weidenkaff, Anke; Schneider, Christof W.; Wokaun, Alexander; Lippert, Thomas

2014-06-01

A two-step process combining pulsed laser deposition of calcium cobaltite thin films and a subsequent laser induced forward transfer as micro-pixel is demonstrated as a direct writing approach of micro-scale thin film structures for potential applications in thermoelectric micro-devices. To achieve the desired thermo-electric properties of the cobaltite thin film, the laser induced plasma properties have been characterized utilizing plasma mass spectrometry establishing a direct correlation to the corresponding film composition and structure. The introduction of a platinum sacrificial layer when growing the oxide thin film enables a damage-free laser transfer of calcium cobaltite thereby preserving the film composition and crystallinity as well as the shape integrity of the as-transferred pixels. The demonstrated direct writing approach simplifies the fabrication of micro-devices and provides a large degree of flexibility in designing and fabricating fully functional thermoelectric micro-devices.

Optical, structural and morphological properties of zirconia nanoparticles prepared by laser ablation in liquids

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

Borodina, T I; Val'yano, G E; Gololobova, O A

2014-09-30

Absorption, fluorescence and Raman spectra, the structural composition and morphology of zirconia nanoparticles synthesised via the laser ablation of a metal in water and aqueous solutions of the sodium dodecyl sulphate (SDS) surfactant have been studied using absorption spectroscopy, Raman spectroscopy, X-ray diffraction and scanning electron microscopy. The results demonstrate that, exposing zirconium to intense nanosecond laser pulses at a high repetition rate in these liquids, one can obtain stable cubic, tetragonal and monoclinic crystalline phases of nanozirconia with a particle size in the range 40 – 100 nm and a Zr – SDS organic – inorganic composite. The absorptionmore » and fluorescence of the synthesised zirconia strongly depend on the SDS concentration in the starting solution. The gas – vapour bubbles forming during ablation are shown to serve as templates for the formation of hollow nanoand microstructures. (nanostructures)« less

As-synthesis of nanostructure AgCl/Ag/MCM-41 composite

NASA Astrophysics Data System (ADS)

Sohrabnezhad, Sh.; Pourahmad, A.

2012-02-01

In this work, we present the simple synthetic route for silver chloride/silver nanoparticles (AgCl/Ag-NPs) using as-synthesis method. The structure, composition and optical properties of such material were investigated by transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (UV-vis DRS), X-ray diffraction (XRD) and FTIR. Powder X-ray diffraction showed that when AgNO 3 content is below 0.1 wt.% in synthetic gel, the guest AgCl/Ag-NPs is formed on the silica channel wall, and lower exists in the crystalline state. When AgNO 3 content exceeds this value, AgCl/Ag nanoparticles can be observed in high crystalline state. The absorption at 327 nm ascribed to the characteristic absorption of the AgCl semiconductor. Ag nanoparticles have been shown to exist in the nanocomposite at 375 nm. When AgNO 3 content is above 0.1 wt.% in synthetic gel, spectra exhibited stronger absorption at 450-700 nm that was attributed to the surface plasmonic resonance of silver nanoparticles. The obtained AgCl/Ag/MCM-41 sample exhibit enhanced photocatalytic activity for the degradation of methylene blue under visible-light irradiation.

Structural, optical and electrical properties of WO3-Ag nanocomposites for the electro-optical devices

NASA Astrophysics Data System (ADS)

Najafi-Ashtiani, Hamed; Bahari, Ali; Gholipour, Samira; Hoseinzadeh, Siamak

2018-01-01

The composites of tungsten trioxide and silver are synthesized by sodium tungstate and silver nitrate precursors. The structural properties of composite coatings are studied by FTIR, XRD, and XPS. The FTIR analysis of synthesized composite powder corroborated the bonds between tungsten and oxygen elements in WO3 molecules. Furthermore, the XRD spectra show crystalline nature while particle size analysis that is investigated by X-powder software shows average particle size of 24 and 25 nm for samples. The structural analyses show that the addition of silver dopant does not change the stoichiometry of tungsten trioxide and only increase the size of the aggregation in the films. Furthermore, these films have an average approximate roughness of about 10.7, 13.1 and 14.2 nm for sample 1, 2 and 3, respectively. The real and imaginative parts of permittivity are investigated using LCR meter in the frequency range 1 Hz-10 GHz. The optical spectra of composite coatings are characterized in the 300-900 nm wavelength range and the calculation of optical band gaps of them exhibited the directly allowed transition with the values of 3.8 and 3.85 eV. From UV-visible spectroscopy studies, the absorption coefficient of the composite thin films is determined to be of the order of 105 cm- 1 and the obtained refraction and extinction indexes indicated normal dispersive coatings. Due to their optical and electrical properties, the synthesized composite material is a promising candidate for use in electro-optical applicants.

UiO-66-NH2/GO Composite: Synthesis, Characterization and CO2 Adsorption Performance

PubMed Central

Cao, Yan; Zhang, Hongmei; Song, Fujiao; Huang, Tao; Ji, Jiayu; Zhong, Qin; Chu, Wei; Xu, Qi

2018-01-01

In this work, a new composite materials of graphene oxide (GO)-incorporated metal-organic framework (MOF)(UiO-66-NH2/GO) were in-situ synthesized, and were found to exhibit enhanced high performances for CO2 capture. X-ray diffraction (XRD), scanning electron microscope (SEM), N2 physical adsorption, and thermogravimetric analysis (TGA) were applied to investigate the crystalline structure, pore structure, thermal stability, and the exterior morphology of the composite. We aimed to investigate the influence of the introduction of GO on the stability of the crystal skeleton and pore structure. Water, acid, and alkali resistances were tested for physical and chemical properties of the new composites. CO2 adsorption isotherms of UiO-66, UiO-66-NH2, UiO-66/GO, and UiO-66-NH2/GO were measured at 273 K, 298 K, and 318 K. The composite UiO-66-NH2/GO exhibited better optimized CO2 uptake of 6.41 mmol/g at 273 K, which was 5.1% higher than that of UiO-66/GO (6.10 mmol/g). CO2 adsorption heat and CO2/N2 selectivity were then calculated to further evaluate the CO2 adsorption performance. The results indicated that UiO-66-NH2/GO composites have a potential application in CO2 capture technologies to alleviate the increase in temperature of the earth’s atmosphere. PMID:29641476

Establishing the solubility and local structure(s) of Amorphous Calcium Carbonate (ACC): Toward an understanding of invertebrate biomineralization

NASA Astrophysics Data System (ADS)

Mergelsberg, S. T.; Ulrich, R. N.; Michel, F. M.; Dove, P. M.

2017-12-01

Recent advances in high-resolution imaging show the widespreadd occurrence of multistep pathways to mineralization in biological and geological settings (De Yoreo et al., 2015, Science). For example, carbonate biomineralization often involves precipitation of amorphous calcium carbonate (ACC) as a reactive intermediate that subsequently transforms to crystalline products with diverse structures. Although current carbonate mineral proxies are based upon the composition of final crystalline products, the final signatures may be recording the properties of the initial amorphous phase. Thus, it is critical to establish the physical properties of ACC and understand the factors that influence its evolution to final products at conditions that approximate biological environments. This disconnect limits our ability to build a process-based understanding of when/how minor and trace elements are recorded in mineral composition proxies. In this experimental study, we quantified the chemical and physical properties of ACC and its evolution to final products. We first determined ACC solubility under controlled chemical conditions using a new type of flow-through reactor developed by our research group (Blue and Dove, 2015, GCA; Blue et al., 2017, GCA). The experimental design varied Mg concentration and total alkalinity while maintaining a mild pH that approximates biological environments. ACC solubility was measured at specific time points during the precipitation (from super- and undersaturated conditions) and during its subsequent evolution. Parallel experiments characterized the structure of the corresponding amorphous products using in situ pair distribution function (PDF) and small-angle x-ray scattering (SAXS) analyses. The measurements demonstrate at least two types of ACC can be produced by tuning Mg concentration and alkalinity. Each "phase" exhibits distinct short-range ordering that demonstrates structure-specific solubility. We also find temporal changes in the short-range order of each type of ACC that are dependent upon Mg content. Insights from this study hold promise for quantifying the chemical and structural properties of ACC and reconcile discrepancies in the literature.

Structure and function of small heat shock/alpha-crystallin proteins: established concepts and emerging ideas.

PubMed

MacRae, T H

2000-06-01

Small heat shock/alpha-crystallin proteins are defined by conserved sequence of approximately 90 amino acid residues, termed the alpha-crystallin domain, which is bounded by variable amino- and carboxy-terminal extensions. These proteins form oligomers, most of uncertain quaternary structure, and oligomerization is prerequisite to their function as molecular chaperones. Sequence modelling and physical analyses show that the secondary structure of small heat shock/alpha-crystallin proteins is predominately beta-pleated sheet. Crystallography, site-directed spin-labelling and yeast two-hybrid selection demonstrate regions of secondary structure within the alpha-crystallin domain that interact during oligomer assembly, a process also dependent on the amino terminus. Oligomers are dynamic, exhibiting subunit exchange and organizational plasticity, perhaps leading to functional diversity. Exposure of hydrophobic residues by structural modification facilitates chaperoning where denaturing proteins in the molten globule state associate with oligomers. The flexible carboxy-terminal extension contributes to chaperone activity by enhancing the solubility of small heat shock/alpha-crystallin proteins. Site-directed mutagenesis has yielded proteins where the effect of the change on structure and function depends upon the residue modified, the organism under study and the analytical techniques used. Most revealing, substitution of a conserved arginine residue within the alpha-crystallin domain has a major impact on quaternary structure and chaperone action probably through realignment of beta-sheets. These mutations are linked to inherited diseases. Oligomer size is regulated by a stress-responsive cascade including MAPKAP kinase 2/3 and p38. Phosphorylation of small heat shock/alpha-crystallin proteins has important consequences within stressed cells, especially for microfilaments.

Influence of Ag substitution on structural and dielectric properties of TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Ali, T.; Ahmed, Ateeq; Siddique, M. Naseem; Aftab, Tabish; Tripathi, P.

2018-04-01

In this paper, we report the structural, electrical and dielectric properties of Ag-substituted TiO2 nanoparticles synthesized by sol-gel method. The X-ray diffraction (XRD) spectra revealed that the synthesized nanoparticles are pure and crystalline in nature and showing tetragonal anatase phase of TiO2. TEM micrograph shows that shapes of the nanoparticles are non-spherical. We have also studied the dielectric properties and in relation to it the dielectric constants, dielectric loss and A.C. conductivity have been studied as the function of frequency and composition of iron. The above theory may be explained by `Maxwell Wagner Model'.

Fabrication of low-crystalline carbonate apatite foam bone replacement based on phase transformation of calcite foam.

PubMed

Maruta, Michito; Matsuya, Shigeki; Nakamura, Seiji; Ishikawa, Kunio

2011-01-01

Carbonate apatite (CO(3)Ap) foam may be an ideal bone substitute as it is sidelined to cancellous bone with respect to its chemical composition and structure. However, CO(3)Ap foam fabricated using α-tricalcium phosphate foam showed limited mechanical strength. In the present study, feasibility of the fabrication of calcite which could be a precursor of CO(3)Ap was studied. Calcite foam was successfully fabricated by the so-called "ceramic foam" method using calcium hydroxide coated polyurethane foam under CO(2)+O(2) atmosphere. Then the calcite foam was immersed in Na(2)HPO(4) aqueous solution for phase transformation based on dissolution-precipitation reaction. When CaO-free calcite foam was immersed in Na(2)HPO(4) solution, low-crystalline CO(3)Ap foam with 93-96% porosity and fully interconnected porous structure was fabricated. The compressive strength of the foam was 25.6 ± 6 kPa. In light of these results, we concluded that the properties of the precursor foam were key factors for the fabrication of CO(3)Ap foams.

MgCoAl and NiCoAl LDHs synthesized by the hydrothermal urea hydrolysis method: Structural characterization and thermal decomposition

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

Chagas, L.H., E-mail: lhchagas-prometro@inmetro.gov.br; Instituto Nacional de Metrologia Qualidade e Tecnologia, Divisão de Metrologia de Materiais, 25250-020 Duque de Caxias, RJ; De Carvalho, G.S.G.

Highlights: • We synthesized MgCoAl and NiCoAl LDHs by the urea hydrolysis method. • Aluminum rich and crystalline materials have been formed. • The calcination of the LDHs generated mixed oxides with high surface areas. - Abstract: Layered double hydroxides (LDHs) with Mg/Co/Al and Ni/Co/Al were synthesized for the first time by the urea hydrolysis method. The experimental conditions promoted aluminum rich and crystalline materials. The formation of LDHs was investigated by powder X-ray diffraction (XRD), chemical analysis, solid state nuclear magnetic resonance with magic angle spinning ({sup 27}Al-MAS-NMR), simultaneous thermogravimetric/differential thermal analysis (TGA/DTA), FTIR spectroscopy, scanning electron microscopy (SEM),more » and N{sub 2} adsorption–desorption experiments. A single phase corresponding to LDH could be obtained in all the investigated compositions. Thermal calcination of these LDHs at 500 °C resulted in the formation of solid solutions in which Al{sup 3+} was dissolved. All the calcined materials have rock-salt like structures and high surface areas.« less

Synthesis of ligand-stabilized metal oxide nanocrystals and epitaxial core/shell nanocrystals via a lower-temperature esterification process.

PubMed

Ito, Daisuke; Yokoyama, Shun; Zaikova, Tatiana; Masuko, Keiichiro; Hutchison, James E

2014-01-28

The properties of metal oxide nanocrystals can be tuned by incorporating mixtures of matrix metal elements, adding metal ion dopants, or constructing core/shell structures. However, high-temperature conditions required to synthesize these nanocrystals make it difficult to achieve the desired compositions, doping levels, and structural control. We present a lower temperature synthesis of ligand-stabilized metal oxide nanocrystals that produces crystalline, monodisperse nanocrystals at temperatures well below the thermal decomposition point of the precursors. Slow injection (0.2 mL/min) of an oleic acid solution of the metal oleate complex into an oleyl alcohol solvent at 230 °C results in a rapid esterification reaction and the production of metal oxide nanocrystals. The approach produces high yields of crystalline, monodisperse metal oxide nanoparticles containing manganese, iron, cobalt, zinc, and indium within 20 min. Synthesis of tin-doped indium oxide (ITO) can be accomplished with good control of the tin doping levels. Finally, the method makes it possible to perform epitaxial growth of shells onto nanocrystal cores to produce core/shell nanocrystals.

Ferromagnetic viscoelastic liquid crystalline materials

NASA Astrophysics Data System (ADS)

Schlesier, Cristina; Shibaev, Petr; McDonald, Scott

2012-02-01

Novel ferromagnetic liquid crystalline materials were designed by mixing ferromagnetic nanoparticles with glass forming oligomers and low molar mass liquid crystals. The matrix in which nanoparticles are embedded is highly viscous that reduces aggregation of nanoparticles and stabilizes the whole composition. Mechanical and optical properties of the composite material are studied in the broad range of nanoparticle concentrations. The mechanical properties of the viscoelastic composite material resemble those of chemically crosslinked elastomers (elasticity and reversibility of deformations). The optical properties of ferromagnetic cholesteric materials are discussed in detail. It is shown that application of magnetic field leads to the shift of the selective reflection band of the cholesteric material and dramatically change its color. Theoretical model is suggested to account for the observed effects; physical properties of the novel materials and liquid crystalline elastomers are compared and discussed. [1] P.V. Shibaev, C. Schlesier, R. Uhrlass, S. Woodward, E. Hanelt, Liquid Crystals, 37, 1601 (2010) [2] P.V. Shibaev, R. Uhrlass, S. Woodward, C. Schlesier, Md R. Ali, E. Hanelt, Liquid Crystals, 37, 587 (2010)

Enhanced fatigue endurance of metallic glasses through a staircase-like fracture mechanism.

PubMed

Gludovatz, Bernd; Demetriou, Marios D; Floyd, Michael; Hohenwarter, Anton; Johnson, William L; Ritchie, Robert O

2013-11-12

Bulk-metallic glasses (BMGs) are now candidate materials for structural applications due to their exceptional strength and toughness. However, their fatigue resistance can be poor and inconsistent, severely limiting their potential as reliable structural materials. As fatigue limits are invariably governed by the local arrest of microscopically small cracks at microstructural features, the lack of microstructure in monolithic glasses, often coupled with other factors, such as the ease of crack formation in shear bands or a high susceptibility to corrosion, can lead to low fatigue limits (some ~1/20 of their tensile strengths) and highly variable fatigue lives. BMG-matrix composites can provide a solution here as their duplex microstructures can arrest shear bands at a second phase to prevent cracks from exceeding critical size; under these conditions, fatigue limits become comparable with those of crystalline alloys. Here, we report on a Pd-based glass that similarly has high fatigue resistance but without a second phase. This monolithic glass displays high intrinsic toughness from extensive shear-band proliferation with cavitation and cracking effectively obstructed. We find that this property can further promote fatigue resistance through extrinsic crack-tip shielding, a mechanism well known in crystalline metals but not previously reported in BMGs, whereby cyclically loaded cracks propagate in a highly "zig-zag" manner, creating a rough "staircase-like" profile. The resulting crack-surface contact (roughness-induced crack closure) elevates fatigue properties to those comparable to crystalline alloys, and the accompanying plasticity helps to reduce flaw sensitivity in the glass, thereby promoting structural reliability.

Enhanced fatigue endurance of metallic glasses through a staircase-like fracture mechanism

PubMed Central

Gludovatz, Bernd; Demetriou, Marios D.; Floyd, Michael; Hohenwarter, Anton; Johnson, William L.; Ritchie, Robert O.

2013-01-01

Bulk-metallic glasses (BMGs) are now candidate materials for structural applications due to their exceptional strength and toughness. However, their fatigue resistance can be poor and inconsistent, severely limiting their potential as reliable structural materials. As fatigue limits are invariably governed by the local arrest of microscopically small cracks at microstructural features, the lack of microstructure in monolithic glasses, often coupled with other factors, such as the ease of crack formation in shear bands or a high susceptibility to corrosion, can lead to low fatigue limits (some ∼1/20 of their tensile strengths) and highly variable fatigue lives. BMG-matrix composites can provide a solution here as their duplex microstructures can arrest shear bands at a second phase to prevent cracks from exceeding critical size; under these conditions, fatigue limits become comparable with those of crystalline alloys. Here, we report on a Pd-based glass that similarly has high fatigue resistance but without a second phase. This monolithic glass displays high intrinsic toughness from extensive shear-band proliferation with cavitation and cracking effectively obstructed. We find that this property can further promote fatigue resistance through extrinsic crack-tip shielding, a mechanism well known in crystalline metals but not previously reported in BMGs, whereby cyclically loaded cracks propagate in a highly “zig-zag” manner, creating a rough “staircase-like” profile. The resulting crack-surface contact (roughness-induced crack closure) elevates fatigue properties to those comparable to crystalline alloys, and the accompanying plasticity helps to reduce flaw sensitivity in the glass, thereby promoting structural reliability. PMID:24167284

Structural and fractal characterization of tungstophosphoric acid modified titanium dioxide photocatalyst

NASA Astrophysics Data System (ADS)

Petrović, S.; Rožić, Lj; Vuković, Z.; Grbić, B.; Radić, N.; Stojadinović, S.; Vasilić, R.

2017-04-01

This article presents the comparison of structural and fractal properties of nanocrystalline titanium dioxide (TiO2) and TiO2 modified with tungstophosphoric acid (TiO2/HPW) and their impact on the photocatalytic degradation of hazardous water pollutants. TiO2 and TiO2/HPW samples were synthesized by a combined sol-gel and hydrothermal processing. The XRD analysis of pure TiO2 samples revealed that phase composition was mainly dependent on the calcination temperature, changing from amorphous TiO2 to crystalline anatase and rutile by increasing the temperature. On the other hand, the XRD of TiO2/HPW samples calcined at temperatures above 600 °C showed crystalline peaks associated to formation of WO3 and WO2.92 crystalline domains. The N2 adsorption-desorption isotherm and pore size distribution of TiO2/HPW samples detected the existence of mesoporous characteristic with very narrow bimodal pores in the mesoporous region. The structural heterogeneity of samples was analyzed by means of pore size distribution functions, while the variation in fractal dimension were determined from the nitrogen adsorption isotherms, using the modified Frenkel-Halsey-Hill method. The results demonstrate that the approach is capable of characterizing complex textures such as those present in the TiO2 and TiO2/HPW photocatalysts. Besides, the effect of calcinations condition on photocatalytic properties of the samples was also investigated. The highest efficiency with respect to methyl orange photodecomposition was observed for TiO2/HPW photocatalysts calcined at 700 °C.

Preparation of 1D Hierarchical Material Mesosilica/Pal Composite and Its Performance in the Adsorption of Methyl Orange

PubMed Central

Wu, Mei; Han, Haifeng; Ni, Lingli; Song, Daiyun; Li, Shuang; Hu, Tao; Jiang, Jinlong; Chen, Jing

2018-01-01

This paper highlights the synthesis of a one-dimensional (1D) hierarchical material mesosilica/palygorskite (Pal) composite and evaluates its adsorption performance for anionic dye methyl orange (MO) in comparison with Pal and Mobile crystalline material-41 (MCM-41). The Mesosilica/Pal composite is consisted of mesosilica coated Pal nanorods and prepared through a dual template approach using cetyltrimethyl ammonium bromide (CTAB) and Pal as soft and hard templates, respectively. The composition and structure of the resultant material was characterized by a scanning electron microscope (SEM), transmissionelectron microscopy (TEM), N2 adsorption-desorption analysis, small-angle X-Ray powder diffraction (XRD), and zeta potential measurement. Adsorption experiments were carried out with different absorbents at different contact times and pH levels. Compared with Pal and MCM-41, the mesosilica/Pal composite exhibited the best efficiency for MO adsorption. Its adsorption ratio is as high as 70.4%. Its adsorption equilibrium time is as short as 30 min. Results testify that the MO retention is promoted for the micro-mesoporous hierarchical structure and positive surface charge electrostatic interactions of the mesosilica/Pal composite. The regenerability of the mesosilica/Pal composite absorbent was also assessed. 1D morphology makes it facile to separate from aqueous solutions. It can be effortlessly recovered and reused for up to nine cycles. PMID:29361713

Preparation of 1D Hierarchical Material Mesosilica/Pal Composite and Its Performance in the Adsorption of Methyl Orange.

PubMed

Wu, Mei; Han, Haifeng; Ni, Lingli; Song, Daiyun; Li, Shuang; Hu, Tao; Jiang, Jinlong; Chen, Jing

2018-01-20

This paper highlights the synthesis of a one-dimensional (1D) hierarchical material mesosilica/palygorskite (Pal) composite and evaluates its adsorption performance for anionic dye methyl orange (MO) in comparison with Pal and Mobile crystalline material-41 (MCM-41). The Mesosilica/Pal composite is consisted of mesosilica coated Pal nanorods and prepared through a dual template approach using cetyltrimethyl ammonium bromide (CTAB) and Pal as soft and hard templates, respectively. The composition and structure of the resultant material was characterized by a scanning electron microscope (SEM), transmissionelectron microscopy (TEM), N₂ adsorption-desorption analysis, small-angle X-Ray powder diffraction (XRD), and zeta potential measurement. Adsorption experiments were carried out with different absorbents at different contact times and pH levels. Compared with Pal and MCM-41, the mesosilica/Pal composite exhibited the best efficiency for MO adsorption. Its adsorption ratio is as high as 70.4%. Its adsorption equilibrium time is as short as 30 min. Results testify that the MO retention is promoted for the micro-mesoporous hierarchical structure and positive surface charge electrostatic interactions of the mesosilica/Pal composite. The regenerability of the mesosilica/Pal composite absorbent was also assessed. 1D morphology makes it facile to separate from aqueous solutions. It can be effortlessly recovered and reused for up to nine cycles.

Microwave-assisted synthesis of porous carbon-titania and highly crystalline titania nanostructures.

PubMed

Parker, Alison; Marszewski, Michal; Jaroniec, Mietek

2013-03-01

Porous carbon-titania and highly crystalline titania nanostructured materials were obtained through a microwave-assisted one-pot synthesis. Resorcinol and formaldehyde were used as carbon precursors, triblock copolymer Pluronic F127 as a stabilizing agent, and titanium isopropoxide as a titania precursor. This microwave-assisted one-pot synthesis involved formation of carbon spheres according to the recently modified Stöber method followed by hydrolysis and condensation of titania precursor. This method afforded carbon-titania composite materials containing anatase phase with specific surface areas as high as 390 m(2) g(-1). The pure nanostructured titania, obtained after removal of carbon through calcination of the composite material in air, was shown to be the anatase phase with considerably higher degree of crystallinity and the specific surface area as high as 130 m(2) g(-1). The resulting titania, because of its high surface area, well-developed porosity, and high crystallinity, is of great interest for catalysis, water treatment, lithium batteries, and other energy-related applications.

Insights from the Lattice-Strain Evolution on Deformation Mechanisms in Metallic-Glass-Matrix Composites

DOE PAGES

Jia, Haoling; Zheng, Lili; Li, Weidong; ...

2015-02-18

In this paper, in situ high-energy synchrotron X-ray diffraction experiments and micromechanics-based finite element simulations have been conducted to examine the lattice-strain evolution in metallic-glass-matrix composites (MGMCs) with dendritic crystalline phases dispersed in the metallic-glass matrix. Significant plastic deformation can be observed prior to failure from the macroscopic stress–strain curves in these MGMCs. The entire lattice-strain evolution curves can be divided into elastic–elastic (denoting deformation behavior of matrix and inclusion, respectively), elastic–plastic, and plastic–plastic stages. Characteristics of these three stages are governed by the constitutive laws of the two phases (modeled by free-volume theory and crystal plasticity) and geometric informationmore » (crystalline phase morphology and distribution). The load-partitioning mechanisms have been revealed among various crystalline orientations and between the two phases, as determined by slip strain fields in crystalline phase and by strain localizations in matrix. Finally, implications on ductility enhancement of MGMCs are also discussed.« less

Method for preparing polyolefin composites containing a phase change material

DOEpatents

Salyer, Ival O.

1990-01-01

A composite useful in thermal energy storage, said composite being formed of a polyolefin matrix having a phase change material such as a crystalline alkyl hydrocarbon incorporated therein. The composite is useful in forming pellets, sheets or fibers having thermal energy storage characteristics; methods for forming the composite are also disclosed.

Structural and optical characterization of pure Si-rich nitride thin films

PubMed Central

2013-01-01

The specific dependence of the Si content on the structural and optical properties of O- and H-free Si-rich nitride (SiNx>1.33) thin films deposited by magnetron sputtering is investigated. A semiempirical relation between the composition and the refractive index was found. In the absence of Si-H, N-H, and Si-O vibration modes in the FTIR spectra, the transverse and longitudinal optical (TO-LO) Si-N stretching pair modes could be unambiguously identified using the Berreman effect. With increasing Si content, the LO and the TO bands shifted to lower wavenumbers, and the LO band intensity dropped suggesting that the films became more disordered. Besides, the LO and the TO bands shifted to higher wavenumbers with increasing annealing temperature which may result from the phase separation between Si nanoparticles (Si-np) and the host medium. Indeed, XRD and Raman measurements showed that crystalline Si-np formed upon 1100°C annealing but only for SiNx<0.8. Besides, quantum confinement effects on the Raman peaks of crystalline Si-np, which were observed by HRTEM, were evidenced for Si-np average sizes between 3 and 6 nm. A contrario, visible photoluminescence (PL) was only observed for SiNx>0.9, demonstrating that this PL is not originating from confined states in crystalline Si-np. As an additional proof, the PL was quenched while crystalline Si-np could be formed by laser annealing. Besides, the PL cannot be explained neither by defect states in the bandgap nor by tail to tail recombination. The PL properties of SiNx>0.9 could be then due to a size effect of Si-np but having an amorphous phase. PMID:23324447

Structural and optical characterization of pure Si-rich nitride thin films

NASA Astrophysics Data System (ADS)

Debieu, Olivier; Nalini, Ramesh Pratibha; Cardin, Julien; Portier, Xavier; Perrière, Jacques; Gourbilleau, Fabrice

2013-01-01

The specific dependence of the Si content on the structural and optical properties of O- and H-free Si-rich nitride (SiN x>1.33) thin films deposited by magnetron sputtering is investigated. A semiempirical relation between the composition and the refractive index was found. In the absence of Si-H, N-H, and Si-O vibration modes in the FTIR spectra, the transverse and longitudinal optical (TO-LO) Si-N stretching pair modes could be unambiguously identified using the Berreman effect. With increasing Si content, the LO and the TO bands shifted to lower wavenumbers, and the LO band intensity dropped suggesting that the films became more disordered. Besides, the LO and the TO bands shifted to higher wavenumbers with increasing annealing temperature which may result from the phase separation between Si nanoparticles (Si-np) and the host medium. Indeed, XRD and Raman measurements showed that crystalline Si-np formed upon 1100°C annealing but only for SiN x<0.8. Besides, quantum confinement effects on the Raman peaks of crystalline Si-np, which were observed by HRTEM, were evidenced for Si-np average sizes between 3 and 6 nm. A contrario, visible photoluminescence (PL) was only observed for SiN x>0.9, demonstrating that this PL is not originating from confined states in crystalline Si-np. As an additional proof, the PL was quenched while crystalline Si-np could be formed by laser annealing. Besides, the PL cannot be explained neither by defect states in the bandgap nor by tail to tail recombination. The PL properties of SiN x>0.9 could be then due to a size effect of Si-np but having an amorphous phase.

Residual glass and crystalline phases in a barium disilicate glass–ceramic

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

Araujo, Marcel C.C.; Botta, Walter J.; Kaufmann, Michael J.

2015-12-15

Investigations about the presence of residual glass are scarce, despite its fundamental role in the crystallization kinetics and luminescent properties of barium disilicate glass–ceramics (BaO·2SiO{sub 2}–BS{sub 2}) with a quasi-stoichiometric composition. Non-isothermal (DTA/DSC) experiments have demonstrated that BS{sub 2} presents a polymorphic transformation, where the h-BS{sub 2} (monoclinic structure) phase is completely transformed in l-BS{sub 2} (orthorhombic structure) at temperatures higher than 1020 °C (10 °C/min). In this study, BS{sub 2} monolithic samples were heat-treated at 1000 °C (BS2-10) and 1100 °C (BS2-11) in a DSC furnace at a heating rate of 10 °C/min. In addition, the crystalline and amorphousmore » phases were characterized and quantified by Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) experiments, respectively. Although the complete polymorphic transformation from h-BS2 to l-BS2 was achieved at 1100 °C, our results demonstrated that BS2-11 contains a minor, albeit not negligible, amount of residual glass. - Highlights: • The crystalline and amorphous phases in a barium disilicate glass were characterized and quantified by XRD and TEM. • The BS2-10 sample was constituted by two main crystalline phases, which consists of 2 polymorphic forms: h-BS2 and l-BS2. • The orthorhombic BS2 phase (l-BS2) was predominant at 1100 °C. • The complete polymorphic transformation from h-BS2 to l-BS2 was achieved at 1100 °C. • Nevertheless, our XRD and TEM results demonstrated that BS2-11 contains a minor amount of residual glass.« less

Characterization of clay scales forming in Philippine geothermal wells

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

Reyes, A.G.; Cardile, C.M.

1989-01-01

Smectite scales occur in 24 out of the 36 blocked wells located in Tongonan, Palinpinon and Bacon-Manito. These comprise 2-85% of the well scales and form at depths of 33-2620 m, where measured and fluid inclusion temperatures are 40-320{sup 0}C. Most, however, occur below the production casing show where temperatures are {ge}230{sup 0}C, often at depths coinciding with aquifers. The clay scales are compositionally and structurally different from the bentonite used in drilling, which is essentially sodium-rich montmorillonite. The clay deposits are expanding, generally disordered, and combine the characteristics of a montmorillonite, saponite and vermiculite in terms of reaction tomore » cationic exchange treatments, structure and composition. Six types of clay scales are identified, but the predominant one, comprising 60-100% of the clay deposits in a well, is Mg- and Fe-rich and referred to as a vermiculitic species. The crystallinity, degree of disorder, textures, optical characteristics, structure and relative amounts of structural Al, Mg and Fe vary with time, temperature and fluid composition, but not with depth and measured pressure. Despite its variance from bentonite characteristics, one of the dominant suggested mechanisms of clay scale formation uses the drilling mud in the well as a substrate, from which the Mg- and Fe-rich clay evolves.« less

Lens protein composition, glycation and high molecular weight aggregation in aging rats.

PubMed

Swamy, M S; Abraham, E C

1987-10-01

Because of minimal or no turnover, lens proteins are subjected to substantial post-translational modifications which in turn disrupt lens architecture and change the optical properties leading to senile cataract formation. Progressive glycation is believed to have the potential to initiate the changes that are conducive to lens opacification. Fisher 344 rats were systematically followed from juvenile to older and aged phases of their life to study the relationship between lens glycation and high molecular weight (HMW) aggregate formation as well as quantitative and qualitative changes in lens crystallins. Levels of glycated proteins were quantified by affinity chromatography. Changes in lens crystallin composition and HMW aggregate formation were monitored by molecular sieve HPLC, further confirmed by SDS-PAGE and IEF techniques. As the age advances HMW and insoluble proteins increase with a concomitant disappearance of gamma-crystallins from soluble fraction. This disappearance of gamma-crystallins coincided with increased glycation (approximately 2-fold higher in insoluble fraction) and decreased sulfhydryl groups from soluble fraction. It appears that lens protein glycation, disappearance of gamma-crystallins and sulfhydryls from soluble fraction and increase of insoluble fraction and HMW aggregate are interrelated.

Catalysis, nanostructure and macroscopic property triangle in bioactive calcium-containing ceramic systems.

PubMed

Meiszterics, Anikó; Havancsák, Károly; Sinkó, Katalin

2013-04-01

Calcium silicate ceramics are intended for application as long-term implant materials. In the present work, attention was paid to understand the correlations between the nanostructure (aggregate size, crystallinity, porosity) and the macroscopic properties (solubility in water and simulated body fluids, SBF; hardness) varying the chemical composition. Varying the catalyst (from a base to various acids) during the chemical synthesis was shown to significantly impact on the pore size, crystallinity and mechanical properties. The basic catalyst yields the ceramics with the highest mechanical strength. Ammonia used in 1.0 or 10.0 molar ratio results in bulk ceramics with parameters required for a biomedical application, good hardness (180-200 HV) and low solubility (1-3%) in water and in SBF. The fine porosity (~50 nm) and homogeneous amorphous structure induce good mechanical character. Copyright © 2012 Elsevier B.V. All rights reserved.

Comparison of aqueous ammonia and dilute acid pretreatment of bamboo fractions: Structure properties and enzymatic hydrolysis.

PubMed

Xin, Donglin; Yang, Zhong; Liu, Feng; Xu, Xueru; Zhang, Junhua

2015-01-01

The effect of two pretreatments methods, aqueous ammonia (SAA) and dilute acid (DA), on the chemical compositions, cellulose crystallinity, morphologic change, and enzymatic hydrolysis of bamboo fractions (bamboo yellow, timber, green, and knot) was compared. Bamboo fractions with SAA pretreatment had better hydrolysability than those with DA pretreatment. High crystallinity index resulted in low hydrolysis yield in the conversion of SAA pretreated bamboo fractions, not DA pretreated fractions. The increase of cellulase loading had modestly positive effect in the hydrolysis of both SAA and DA pretreated bamboo fractions, while supplement of xylanase significantly increased the hydrolysis of the pretreated bamboo fractions, especially after SAA pretreatment. The results indicated that SAA pretreatment was more effective than DA pretreatment in conversion of bamboo fractions, and supplementation of xylanase was necessary in effective conversion of the SAA pretreated fractions into fermentable sugars. Copyright © 2014 Elsevier Ltd. All rights reserved.

Liquid crystalline spinning of spider silk

NASA Astrophysics Data System (ADS)

Vollrath, Fritz; Knight, David P.

2001-03-01

Spider silk has outstanding mechanical properties despite being spun at close to ambient temperatures and pressures using water as the solvent. The spider achieves this feat of benign fibre processing by judiciously controlling the folding and crystallization of the main protein constituents, and by adding auxiliary compounds, to create a composite material of defined hierarchical structure. Because the `spinning dope' (the material from which silk is spun) is liquid crystalline, spiders can draw it during extrusion into a hardened fibre using minimal forces. This process involves an unusual internal drawdown within the spider's spinneret that is not seen in industrial fibre processing, followed by a conventional external drawdown after the dope has left the spinneret. Successful copying of the spider's internal processing and precise control over protein folding, combined with knowledge of the gene sequences of its spinning dopes, could permit industrial production of silk-based fibres with unique properties under benign conditions.

Ultraviolet photosensitivity of sulfur-doped micro- and nano-crystalline diamond

DOE PAGES

Mendoza, Frank; Makarov, Vladimir; Hidalgo, Arturo; ...

2011-06-06

The room-temperature photosensitivity of sulfur-doped micro- (MCD), submicro- (SMCD) and nano- (NCD) crystalline diamond films synthesized by hot-filament chemical vapor deposition was studied. The structure and composition of these diamond materials were characterized by Raman spectroscopy, scanning electron microscopy and X-ray diffraction. The UV sensitivity and response time were studied for the three types of diamond materials using a steady state broad UV excitation source and two pulsed UV laser radiations. It was found that they have high sensitivity in the UV region, as high as 10 9 sec -1mV -1 range, linear response in a broad spectral range belowmore » 320 nm, photocurrents around ~10 -5 A, and short response time better than 100 ns, which is independent of fluency intensity. A phenomenological model was applied to help understand the role of defects and dopant concentration on the materials’ photosensitivity.« less

Structural response of Nd-stabilized zirconia and its composite under extreme conditions of swift heavy ion irradiation

NASA Astrophysics Data System (ADS)

Nandi, Chiranjit; Grover, V.; Kulriya, P. K.; Poswal, A. K.; Prakash, Amrit; Khan, K. B.; Avasthi, D. K.; Tyagi, A. K.

2018-02-01

Inert matrix fuel concept for minor actinide transmutation proposes stabilized zirconia as the major component for inert matrix. The present study explores Nd-stabilized zirconia (Zr0.8Nd0.2O1.9; Nd as surrogate for Am) and its composites for radiation tolerance against fission fragments. The introduction of MgO in the composite with stabilised zirconia is performed from the point of view to enhance the thermal conductivity. The radiation damage is also compared with Nd-stabilized zirconia co-doped with Y3+ (Zr0.8Nd0.1Y0.1O1.9) in order to mimic doping of minor actinides in Y3+ containing stabilized zirconia (Nd as surrogate for Am). The compositions were synthesized by gel combustion followed by high temperature sintering and characterised by XRD, SEM and EDS. Irradiation was carried out by 120 MeV Au ions at various fluences and irradiation induced structural changes were probed by in-situ X-ray diffraction (XRD). XRD demonstrated the retention of crystallinity for all the three samples but the extent of the damage was found to be highly dependent on the nominal composition. It was observed that introduction of Y3+ along with Nd3+ to stabilize cubic zirconia imparted poorer radiation stability. On the other hand, formation of a CERCER composite of MgO with Nd-stabilised zirconia enhanced its behaviour against swift heavy ion irradiation. Investigating these compositions by XANES spectroscopy post irradiation did not show any change in local electronic structure of constituent ions.

Single Molecule Study of Cellulase Hydrolysis of Crystalline Cellulose

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

Liu, Y.-S.; Luo, Y.; Baker, J. O.

This report seeks to elucidate the role of cellobiohydrolase-I (CBH I) in the hydrolysis of crystalline cellulose. A single-molecule approach uses various imaging techniques to investigate the surface structure of crystalline cellulose and changes made in the structure by CBH I.

A method for the quantitative determination of crystalline phases by X-ray

NASA Technical Reports Server (NTRS)

Petzenhauser, I.; Jaeger, P.

1988-01-01

A mineral analysis method is described for rapid quantitative determination of crystalline substances in those cases in which the sample is present in pure form or in a mixture of known composition. With this method there is no need for prior chemical analysis.

Mechanochemical spinodal decomposition: a phenomenological theory of phase transformations in multi-component, crystalline solids

DOE PAGES

Rudraraju, Shiva; Van der Ven, Anton; Garikipati, Krishna

2016-06-10

Here, we present a phenomenological treatment of diffusion-driven martensitic phase transformations in multi-component crystalline solids that arise from non-convex free energies in mechanical and chemical variables. The treatment describes diffusional phase transformations that are accompanied by symmetry-breaking structural changes of the crystal unit cell and reveals the importance of a mechanochemical spinodal, defined as the region in strain-composition space, where the free-energy density function is non-convex. The approach is relevant to phase transformations wherein the structural order parameters can be expressed as linear combinations of strains relative to a high-symmetry reference crystal. The governing equations describing mechanochemical spinodal decomposition aremore » variationally derived from a free-energy density function that accounts for interfacial energy via gradients of the rapidly varying strain and composition fields. A robust computational framework for treating the coupled, higher-order diffusion and nonlinear strain gradient elasticity problems is presented. Because the local strains in an inhomogeneous, transforming microstructure can be finite, the elasticity problem must account for geometric nonlinearity. An evaluation of available experimental phase diagrams and first-principles free energies suggests that mechanochemical spinodal decomposition should occur in metal hydrides such as ZrH 2-2c. The rich physics that ensues is explored in several numerical examples in two and three dimensions, and the relevance of the mechanism is discussed in the context of important electrode materials for Li-ion batteries and high-temperature ceramics.« less

Electronic structure and glass forming ability in early and late transition metal alloys

NASA Astrophysics Data System (ADS)

Babić, E.; Ristić, R.; Figueroa, I. A.; Pajić, D.; Skoko, Ž.; Zadro, K.

2018-03-01

A correlation between the change in magnetic susceptibility (Δχexp) upon crystallisation of Cu-Zr and Hf metallic glasses (MG) with their glass forming ability (GFA) observed recently, is found to apply to Cu-Ti and Zr-Ni alloys, too. In particular, small Δχexp, which reflects similar electronic structures, ES, of glassy and corresponding crystalline alloys, corresponds to high GFA. Here, we studied Δχexp for five Cu-Ti and four Cu-Zr and Ni-Zr MGs. The fully crystalline final state of all alloys was verified from X-ray diffraction patterns. The variation of GFA with composition in Cu-Ti, Cu-Zr and Cu-Hf MGs was established from the variation of the corresponding critical casting thickness, dc. Due to the absence of data for dc in Ni-Zr MGs their GFA was described using empirical criteria, such as the reduced glass transition temperature. A very good correlation between Δχexp and dc (and/or other criteria for GFA) was observed for all alloys studied. The correlation between the ES and GFA showed up best for Cu-Zr and NiZr2 alloys where direct data for the change in ES (ΔES) upon crystallisation are available. The applicability of the Δχexp (ΔES) criterion for high GFA (which provides a simple way to select the compositions with high GFA) to other metal-metal MGs (including ternary and multicomponent bulk MGs) is briefly discussed.

Organic-Inorganic Composites Toward Biomaterial Application.

PubMed

Miyazaki, Toshiki; Sugawara-Narutaki, Ayae; Ohtsuki, Chikara

2015-01-01

Bioactive ceramics are known to exhibit specific biological affinities and are able to show direct integration with surrounding bone when implanted in bony defects. However, their inadequate mechanical properties, such as low fracture toughness and high Young's modulus in comparison to natural bone, limit their clinical application. Bone is a kind of organic-inorganic composite where apatite nanocrystals are precipitated onto collagen fibre networks. Thus, one way to address these problems is to mimic the natural composition of bone by using bioactive ceramics via material designs based on organic-inorganic composites. In this chapter, the current research on the development of the various organic-inorganic composites designed for biomaterial applications has been reviewed. Various compounds such as calcium phosphate, calcium sulphate and calcium carbonate can be used for the inorganic phases to design composites with the desired mechanical and biological properties of bone. Not only classical mechanical mixing but also coating of the inorganic phase in aqueous conditions is available for the fabrication of such composites. Organic modifications using various polymers enable the control of the crystalline structure of the calcium carbonate in the composites. These approaches on the fabrication of organic-inorganic composites provide important options for biomedical materials with novel functions. © 2015 S. Karger AG, Basel.

A comprehensive study of woven carbon fiber-reinforced nylon 6 composites

NASA Astrophysics Data System (ADS)

Pillay, Selvum

Liquid molding of thermoset composites has become very popular in all industry sectors, including aerospace, automotive, mass transit, and sporting goods, but the cost of materials and processing has limited the use to high-end applications. Thermoplastic composites are relatively cheap; however, the use has been limited to components with short fiber reinforcing. The high melt viscosity and short processing window precludes their use in the liquid molding of large structures and applications with continuous fiber reinforcement. The current research addresses the processing parameters, methodology, and limitations of vacuum assisted resin transfer molding (VARTM) of carbon fabric-reinforced, thermoplastic polyamide 6 (PA6). The material used is casting grade PA6. The process developed for using VARTM to produce carbon fabric-reinforced PA6 composites is explained in detail. The effects of infusion temperature and flow distance on the fiber weight fraction and crystallinity of the PA6 resin are presented. The degree of conversion from monomer to polymer was determined. Microscopic studies to show the wet-out of the fibers at the filament level are also presented. Tensile, flexural, short beam shear strength (SBSS), and low-velocity impact test results are presented and compared to a equivalent thermoset matrix composite. The rubber toughened epoxy system (SC-15) was chosen for the comparative study because the system has been especially developed to overcome the brittle nature of epoxy composites. The environmental effects of moisture and ultraviolet (UV) radiation on the carbon/nylon 6 composite were investigated. The samples were immersed in boiling water for 100 hr, and mechanical tests were conducted. Results showed that moisture causes plasticization of the matrix and attacks the fiber matrix interface. This leads to deterioration of the mechanical properties. The samples were also exposed to UV for up to 600 hr, and post exposure tests were conducted. The exposure to UV caused an increase in the degree of crystallinity of the PA6. The mechanical properties were not affected by the exposure to UV for 600 hr.

Synthesis of PANi-SiO2 Nanocomposite with In-Situ Polymerization Method: Nanoparticle Silica (NPS) Amorphous and Crystalline Phase

NASA Astrophysics Data System (ADS)

Munasir; Luvita, N. R. D.; Kusumawati, D. H.; Putri, N. P.; Triwikantoro; Supardi, Z. A. I.

2018-03-01

Silica which is synthesized from natural materials such as Bancar Tuban’s sand composited with Polyaniline (PANi), where the silica used are silica has an amorphous phase and cristobalite phase. In this research, the composite method used is in- situ polymerization, which is silica entered during the fabrication of PANi, then automatically silica will be substitute into the chain bonding of PANi. The aim of this research is to find out the results of a composite process using in-situ methods as well as differences in the morphology of PANi/a- SiO2 and PANi/c-SiO2. For the characterization of samples tested in the form of FTIR to determine the functional groups of the composite and SEM to determine the morphology of the sample. From the test results of FTIR are known composite possibility has occurred because there are several functional groups belonging to silica also functional groups belonging polyaniline, functional group that’s happened in wave numbers were almost identical between PANi/a-SiO2 and PANi/c-SiO2, but there are little differences were seen in the form of a graph generated from the peak and intensity that occurred charts for PANi/c-SiO2 has peak more pointed or sharp compared to PANi/a-SiO2 because that bond of crystal is strong, stiff and has a larger particle size than the amorphous composite. Then from the data of SEM seen clearly their morphological differences between PANi/a-SiO2 and PANi/c-SiO2 where polyaniline is composited with amorphous silica will have a fault that is not uniform or irregular different from PANi/c -SiO2 has a regular fault and this is corresponding with the nature of the typical structure of amorphous and crystalline.

Basaltic Soil of Gale Crater: Crystalline Component Compared to Martian Basalts and Meteorites

NASA Technical Reports Server (NTRS)

Treiman, A. H.; Bish, D. L.; Ming, D. W.; Morris, R. V.; Schmidt, M.; Downs, R. T.; Stolper, E. M.; Blake, D. F.; Vaniman, D. T.; Achilles, C. N.;

Interfacial crystalline structures in injection over-molded polypropylene and bond strength.

PubMed

Yan, Bowen; Wu, Hong; Jiang, Genjie; Guo, Shaoyun; Huang, Jian

2010-11-01

This paper describes interfacial crystalline structures found in injection overmolded polypropylene components and the relationship of these structures to bond strength between the components. The combined effects of the development of hierarchical gradient structures and the particular thermomechanical environment near the interface on the interfacial crystalline structures were investigated in detail by PLM, SEM, DSC, WAXD, and infrared dichroism spectroscopy. The experimental results showed that during molding there was competitive formation of interfacial crystalline structures consisted of "shish-kebab" layer (SKL) and a transcrystalline layers (TCL). Variation in shear stress (controlled by injection pressure and injection speed) plays an important role in the formation of the SKL. The formation of TCL is influenced by the thermal environment, namely melt temperature and mold temperature. Increasing within certain limits, interfacial temperature and the thermal gradient near the interface promotes β-iPP growth. The relationship between interfacial crystalline structures and interfacial bond strength was established by lap shear measurement. The interfacial bond strength is improved by enhancing the formation of TCL, but reduced if SKL predominates.

Synthesis and characterization of potential iron–platinum drugs and supplements by laser liquid photolysis

PubMed Central

Nkosi, Steven S; Mwakikunga, Bonex W; Sideras-Haddad, Elias; Forbes, Andrew

2012-01-01

Highly crystalline nanospherical iron–platinum systems were produced by 248 nm laser irradiation of a liquid precursor at different laser fluences, ranging from 100–375 mJ/cm2. The influence of laser intensity on particle size, iron composition, and structure was systematically investigated. Different nanostructures of iron–platinum alloy and chemically disordered iron–platinum L10 phase were obtained without annealing. The prepared precursor solution underwent deep photolysis to polycrystalline iron–platinum nanoalloys through Fe(III) acetylacetonate and Pt(II) acetylacetonate. Fe(II) and Pt(I) acetylacetone decomposed into Fe0 and Pt0 nanoparticles. We found that the (001) diffraction peak shifted linearly to a lower angle, with the last peak shifting in opposition to the others. This caused the face-centered cubic L10 structure to change its composition according to laser fluence. The nanostructures were shown to contain iron and platinum only by energy-dispersive spectroscopy at several spots. The response of these iron–platinum nanoparticles to infrared depends on their stoichiometric composition, which is controlled by laser fluence. PMID:24198494

Dielectric Properties of Ca0.7Bi0.3Ti0.7Cr0.3O3 (CBTC)-CaCu3Ti4O12 (CCTO) Composite

NASA Astrophysics Data System (ADS)

Mallmann, E. J. J.; Silva, M. A. S.; Sombra, A. S. B.; Botelho, M. A.; Mazzetto, S. E.; de Menezes, A. S.; Almeida, A. F. L.; Fechine, P. B. A.

2015-01-01

The main object of this work is to study two materials with giant dielectric constants: CaCu3Ti4O12 (CCTO) and Ca0.7Bi0.3Ti0.7Cr0.3O3 (CBTC). CBTC1- x -CCTO x composites were also obtained to create a new dielectric material with dielectric properties between these two phases. Structural properties were studied by x-ray powder diffraction (XRPD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and dielectric measurements. CCTO showed a cubic phase and CBTC an orthorhombic phase. An interesting result was that the dielectric constant ( K) did not follow the rule of the mixture of Lichtnecker, and this happened due to the presence of other phases of its crystalline structure, which decreases the value of K when compared to the predicted values of Lichtnecker. It was also found that the dielectric properties of the composite are very promising for use in microelectronics, according to the miniaturization factor, which is crucial for those applications.

Chemical synthesis and structural characterization of small AuZn nanoparticles

NASA Astrophysics Data System (ADS)

Juárez-Ruiz, E.; Pal, U.; Lombardero-Chartuni, J. A.; Medina, A.; Ascencio, J. A.

2007-03-01

In this paper, we report the aqueous synthesis of bimetallic Au-Zn nanoparticles of different compositions by the simultaneous reduction technique. The stability and atomic configuration of the particles are studied through high-resolution transmission electron microscopy (HRTEM) and UV-Vis optical absorption techniques. Depending on the composition, small bimetallic nanoparticles of 1 15 nm in size were obtained. The average size and size distribution of the bimetallic nanoparticles are seen to be critically dependent on the atomic ratio of the constituting elements Au and Zn. While a 1:1 atomic proportion of Au and Zn produced most stable nanoparticles of smallest average size, nanoparticles produced with higher content of either of the component elements are unstable, inducing agglomeration and coalescence to form elongated structures with uneven morphologies. Au3Zn1 nanoparticles followed a directional growth pattern, producing bimetallic nanorods with multiple crystalline domains. Interestingly, in these rod-like nanostructures, the domains are in well array of solid solution-like bimetallic and pure mono-metallic regions alternatively. Such nanostructures with uneven morphology and compositions might show distinct catalytic selectivity in chemical reactions.

Investigation on Polylactide (PLA)/Poly(butylene adipate-co-terephthalate) (PBAT)/Bark Flour of Plane Tree (PF) Eco-Composites

PubMed Central

Dou, Qiang; Cai, Jun

2016-01-01

Polylactide (PLA)/poly(butylene adipate-co-terephthalate) (PBAT)/bark flour of plane tree (PF) eco-composites were prepared via melt blending. The morphologies, mechanical properties, crystal structures and melting and crystallization behaviors of the eco-composites were investigated by means of scanning electron microscopy (SEM), mechanical tests, polarized light microscopy (PLM), wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC), respectively. It is shown that the interfacial adhesion between PLA matrix and PF is weak and the mechanical properties of PLA/PF eco-composites are poor. The titanate treatment improves the adhesion between the matrix and the filler and enhances the stiffness of the eco-composites. The toughness is improved by PBAT and ductile fractured surfaces can be found. The spherulitic size of PLA is decreased by the addition of PF. The α crystalline form of PLA remains in the composites. Compared with PF, T-PF (PF treated by a titanate coupling agent) and PBAT have negative effects on the crystallization of PLA. PMID:28773515

Flexible and Hierarchical Metal-Organic Framework Composites for High-Performance Catalysis.

PubMed

Huang, Ning; Drake, Hannah; Li, Jialuo; Pang, Jiangdong; Wang, Ying; Yuan, Shuai; Wang, Qi; Cai, Peiyu; Qin, Junsheng; Zhou, Hong-Cai

2018-05-18

The development of new types of porous composite materials is of great significance owing to their potentially improved performance over those of individual components and extensive applications in separation, energy storage, and heterogeneous catalysis. In this work, we integrated mesoporous metal-organic frameworks (MOFs) with macroporous melamine foam (MF) using a one-pot process, generating a series of MOF/MF composite materials with preserved crystallinity, hierarchical porosity, and increased stability over that of melamine foam. The MOF nanocrystals were threaded by the melamine foam networks, resembling a ball-and-stick model overall. As a proof-of-concept study, the resulting MOF/MF composite materials were employed as an effective heterogeneous catalyst for the epoxidation of cholesteryl esters. Combining the advantages of interpenetrative mesoporous and macroporous structures, the MOF/melamine foam composite provided higher dispersibility and more accessibility of catalytic sites, exhibiting excellent catalytic performance. This strategy constitutes an important step forward the development of other MOF composites and exploration of their high-performance catalysis. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of noble metal/carbon nanotube composites in supercritical methanol.

PubMed

Sun, Zhenyu; Fu, Lei; Liu, Zhimin; Han, Buxing; Liu, Yunqi; Du, Jimin

2006-03-01

A simple and efficient route has been employed to deposit noble metal nanoparticles (Pt, Ru, Pt-Ru, Rh, Ru-Sn) onto carbon nanotubes (CNTs) in supercritical methanol solution. In this method, the inorganic metallic salts acted as metal precursors, and methanol as solvent as well as reductant for the precursors. The as-prepared nanocomposites were structurally and morphologically characterized by X-ray diffraction spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy, and X-ray photoelectron spectroscopy analyses. It was demonstrated that the CNTs were decorated by crystalline metal nanoparticles with uniform sizes and a narrow particle size distribution. The size and loading content of the nanoparticles on CNTs could be tuned by manipulating reaction parameters. Furthermore, the formation mechanism of the composites was also discussed.

Silicic volcanism on Mars evidenced by tridymite in high-SiO2 sedimentary rock at Gale crater

NASA Astrophysics Data System (ADS)

Morris, Richard V.; Vaniman, David T.; Blake, David F.; Gellert, Ralf; Chipera, Steve J.; Rampe, Elizabeth B.; Ming, Douglas W.; Morrison, Shaunna M.; Downs, Robert T.; Treiman, Allan H.; Yen, Albert S.; Grotzinger, John P.; Achilles, Cherie N.; Bristow, Thomas F.; Crisp, Joy A.; Des Marais, David J.; Farmer, Jack D.; Fendrich, Kim V.; Frydenvang, Jens; Graff, Trevor G.; Morookian, John-Michael; Stolper, Edward M.; Schwenzer, Susanne P.

2016-06-01

Tridymite, a low-pressure, high-temperature (>870 °C) SiO2 polymorph, was detected in a drill sample of laminated mudstone (Buckskin) at Marias Pass in Gale crater, Mars, by the Chemistry and Mineralogy X-ray diffraction instrument onboard the Mars Science Laboratory rover Curiosity. The tridymitic mudstone has ˜40 wt.% crystalline and ˜60 wt.% X-ray amorphous material and a bulk composition with ˜74 wt.% SiO2 (Alpha Particle X-Ray Spectrometer analysis). Plagioclase (˜17 wt.% of bulk sample), tridymite (˜14 wt.%), sanidine (˜3 wt.%), cation-deficient magnetite (˜3 wt.%), cristobalite (˜2 wt.%), and anhydrite (˜1 wt.%) are the mudstone crystalline minerals. Amorphous material is silica-rich (˜39 wt.% opal-A and/or high-SiO2 glass and opal-CT), volatile-bearing (16 wt.% mixed cation sulfates, phosphates, and chlorides-perchlorates-chlorates), and has minor TiO2 and Fe2O3T oxides (˜5 wt.%). Rietveld refinement yielded a monoclinic structural model for a well-crystalline tridymite, consistent with high formation temperatures. Terrestrial tridymite is commonly associated with silicic volcanism, and detritus from such volcanism in a “Lake Gale” catchment environment can account for Buckskin's tridymite, cristobalite, feldspar, and any residual high-SiO2 glass. These cogenetic detrital phases are possibly sourced from the Gale crater wall/rim/central peak. Opaline silica could form during diagenesis from high-SiO2 glass, as amorphous precipitated silica, or as a residue of acidic leaching in the sediment source region or at Marias Pass. The amorphous mixed-cation salts and oxides and possibly the crystalline magnetite (otherwise detrital) are primary precipitates and/or their diagenesis products derived from multiple infiltrations of aqueous solutions having variable compositions, temperatures, and acidities. Anhydrite is post lithification fracture/vein fill.

Silicic volcanism on Mars evidenced by tridymite in high-SiO2 sedimentary rock at Gale crater

PubMed Central

Morris, Richard V.; Vaniman, David T.; Blake, David F.; Gellert, Ralf; Chipera, Steve J.; Rampe, Elizabeth B.; Ming, Douglas W.; Morrison, Shaunna M.; Downs, Robert T.; Treiman, Allan H.; Yen, Albert S.; Grotzinger, John P.; Achilles, Cherie N.; Bristow, Thomas F.; Crisp, Joy A.; Des Marais, David J.; Farmer, Jack D.; Fendrich, Kim V.; Graff, Trevor G.; Morookian, John-Michael; Stolper, Edward M.; Schwenzer, Susanne P.

2016-01-01

Tridymite, a low-pressure, high-temperature (>870 °C) SiO2 polymorph, was detected in a drill sample of laminated mudstone (Buckskin) at Marias Pass in Gale crater, Mars, by the Chemistry and Mineralogy X-ray diffraction instrument onboard the Mars Science Laboratory rover Curiosity. The tridymitic mudstone has ∼40 wt.% crystalline and ∼60 wt.% X-ray amorphous material and a bulk composition with ∼74 wt.% SiO2 (Alpha Particle X-Ray Spectrometer analysis). Plagioclase (∼17 wt.% of bulk sample), tridymite (∼14 wt.%), sanidine (∼3 wt.%), cation-deficient magnetite (∼3 wt.%), cristobalite (∼2 wt.%), and anhydrite (∼1 wt.%) are the mudstone crystalline minerals. Amorphous material is silica-rich (∼39 wt.% opal-A and/or high-SiO2 glass and opal-CT), volatile-bearing (16 wt.% mixed cation sulfates, phosphates, and chlorides−perchlorates−chlorates), and has minor TiO2 and Fe2O3T oxides (∼5 wt.%). Rietveld refinement yielded a monoclinic structural model for a well-crystalline tridymite, consistent with high formation temperatures. Terrestrial tridymite is commonly associated with silicic volcanism, and detritus from such volcanism in a “Lake Gale” catchment environment can account for Buckskin’s tridymite, cristobalite, feldspar, and any residual high-SiO2 glass. These cogenetic detrital phases are possibly sourced from the Gale crater wall/rim/central peak. Opaline silica could form during diagenesis from high-SiO2 glass, as amorphous precipitated silica, or as a residue of acidic leaching in the sediment source region or at Marias Pass. The amorphous mixed-cation salts and oxides and possibly the crystalline magnetite (otherwise detrital) are primary precipitates and/or their diagenesis products derived from multiple infiltrations of aqueous solutions having variable compositions, temperatures, and acidities. Anhydrite is post lithification fracture/vein fill. PMID:27298370

Electronic and atomic structures of Ti{sub 1-x}Al{sub x}N thin films related to their damage behavior

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

Tuilier, M.-H.; Pac, M.-J.; Girleanu, M.

2008-04-15

Ti and Al K-edge x-ray absorption spectroscopy is used to investigate the electronic structure of Ti{sub 1-x}Al{sub x}N thin films deposited by reactive magnetron sputtering. The experimental near edge spectra of TiN and AlN are interpreted in the light of unoccupied density of state band structure calculations. The comparison of the structural parameters derived from x-ray absorption fine structure and x-ray diffraction reveals segregation between Al-rich and Ti-rich domains within the Ti{sub 1-x}Al{sub x}N films. Whereas x-ray diffraction probes only the crystallized domains, the structural information derived from extended x-ray absorption fine structure analysis turns on both crystalline and grainmore » boundaries. The results are discussed by considering the damage behavior of the films depending on the composition.« less

Polyolefin composites containing a phase change material

DOEpatents

Salyer, Ival O.

1991-01-01

A composite useful in thermal energy storage, said composite being formed of a polyolefin matrix having a phase change material such as a crystalline alkyl hydrocarbon incorporated therein, said polyolefin being thermally form stable; the composite is useful in forming pellets, sheets or fibers having thermal energy storage characteristics; methods for forming the composite are also disclosed.

Structure and Crystallization of Alkaline-Earth Aluminosilicate Glasses: Prevention of the Alumina-Avoidance Principle.

PubMed

Allu, Amarnath R; Gaddam, Anuraag; Ganisetti, Sudheer; Balaji, Sathravada; Siegel, Renée; Mather, Glenn C; Fabian, Margit; Pascual, Maria J; Ditaranto, Nicoletta; Milius, Wolfgang; Senker, Jürgen; Agarkov, Dmitrii A; Kharton, Vladislav V; Ferreira, José M F

2018-05-03

Aluminosilicate glasses are considered to follow the Al-avoidance principle, which states that Al-O-Al linkages are energetically less favorable, such that, if there is a possibility for Si-O-Al linkages to occur in a glass composition, Al-O-Al linkages are not formed. The current paper shows that breaching of the Al-avoidance principle is essential for understanding the distribution of network-forming AlO 4 and SiO 4 structural units in alkaline-earth aluminosilicate glasses. The present study proposes a new modified random network (NMRN) model, which accepts Al-O-Al linkages for aluminosilicate glasses. The NMRN model consists of two regions, a network structure region (NS-Region) composed of well-separated homonuclear and heteronuclear framework species and a channel region (C-Region) of nonbridging oxygens (NBOs) and nonframework cations. The NMRN model accounts for the structural changes and devitrification behavior of aluminosilicate glasses. A parent Ca- and Al-rich melilite-based CaO-MgO-Al 2 O 3 -SiO 2 (CMAS) glass composition was modified by substituting MgO for CaO and SiO 2 for Al 2 O 3 to understand variations in the distribution of network-forming structural units in the NS-region and devitrification behavior upon heat treating. The structural features of the glass and glass-ceramics (GCs) were meticulously assessed by advanced characterization techniques including neutron diffraction (ND), powder X-ray diffraction (XRD), 29 Si and 27 Al magic angle spinning (MAS)-nuclear magnetic resonance (NMR), and in situ Raman spectroscopy. ND revealed the formation of SiO 4 and AlO 4 tetrahedral units in all the glass compositions. Simulations of chemical glass compositions based on deconvolution of 29 Si MAS NMR spectral analysis indicate the preferred formation of Si-O-Al over Si-O-Si and Al-O-Al linkages and the presence of a high concentration of nonbridging oxygens leading to the formation of a separate NS-region containing both SiO 4 and AlO 4 tetrahedra (Si/Al) (heteronuclear) in addition to the presence of Al [4] -O-Al [4] bonds; this region coexists with a predominantly SiO 4 -containing (homonuclear) NS-region. In GCs, obtained after heat treatment at 850 °C for 250 h, the formation of crystalline phases, as revealed from Rietveld refinement of XRD data, may be understood on the basis of the distribution of SiO 4 and AlO 4 structural units in the NS-region. The in situ Raman spectra of the GCs confirmed the formation of a Si/Al structural region, as well as indicating interaction between the Al/Si region and SiO 4 -rich region at higher temperatures, leading to the formation of additional crystalline phases.

Method for making an electrochemical cell

DOEpatents

Tuller, Harry L.; Kramer, Steve A.; Spears, Marlene A.; Pal, Uday B.

1996-01-01

An electrochemical device including a solid electrolyte and solid electrode composed of materials having different chemical compositions and characterized by different electrical properties but having the same crystalline phase is provided. A method for fabricating an electrochemical device having a solid electrode and solid electrolyte characterized by the same crystalline phase is provided.