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Sample records for jahn-teller glass formation

  1. Theory of the Jahn-Teller Soliton

    NASA Astrophysics Data System (ADS)

    Clougherty, Dennis

    2006-03-01

    It is demonstrated that under common conditions a molecular solid subject to Jahn-Teller interactions supports stable Q- ball-like non-topological solitons. Such solitons represent a localized lump of excess electric charge in periodic motion accompanied by a time-dependent shape distortion of a set of adjacent molecules. The motion of the distortion can correspond to a true rotation or to a pseudo-rotation about the symmetric shape configuration. These solitons are stable for Jahn-Teller coupling strengths below a critical value; however, as the Jahn- Teller coupling approaches this critical value, the size of the soliton diverges signaling an incipient structural phase transition. The soliton phase mimics features commonly attributed to phase separation in complex solids.

  2. The Jahn-Teller effect in triptycene

    NASA Astrophysics Data System (ADS)

    Furlan, Alan; Riley, Mark J.; Leutwyler, Samuel

    1992-05-01

    The irregular vibronic structure resolved in the S1←S0 resonant two-photon ionization (R2PI) spectrum of supersonically cooled triptycene (9,10-dihydro-9,10[1'2']benzenoanthracene) is assigned in terms of a single-mode E'⊗e' Jahn-Teller vibronic Hamiltonian for the excited state, with linear and quadratic coupling terms. The Jahn-Teller active vibrational mode is a benzene wagging framework mode. To fit to the observed vibronic levels yields a very low frequency νe' =47.83 cm-1 and linear and quadratic terms are k=1.65 and g=0.426. This fit accounts for ≊98% of the observed absorption band intensities over the observable range 0-350 cm-1. The quadratic term is unusually large, leading to localization of the lowest vibronic levels in the three symmetry-equivalent minima. Emission spectra from 13 vibronic levels in the excited E' state show extended vibrational progressions with up to 25 members in the analogous e' ground state vibration, which is highly harmonic in the electronic ground state. The Franck-Condon factors of the fluorescence emission spectra calculated with the E' state Jahn-Teller parameters fitted to the absorption spectrum also yield a quantitative fit to observed emission intensities. The eigenvectors of the E' state vibronic levels are hence determined to great precision; the lowest five can be classified as radial oscillator and/or hindered rotor states, while higher levels have mixed character. Several eigenvectors are strongly localized in the upper sheet of the adiabatic Jahn-Teller surface, corresponding to ``cone'' states.

  3. Fullerene anions: Jahn-Teller or pseudo-Jahn-Teller effects?

    SciTech Connect

    Borshch, S.A. |; Prassides, K.

    1996-05-30

    The vibronic problems appearing in manifolds of the electronic terms of C{sub 60} anions are studied. It is shown that the vibronic coupling of the t{sub 1u} molecular orbital with the h{sub g} vibrations induces pseudo-Jahn-Teller and Jahn-Teller coupling within the electronic terms. The resulting vibronic distortions are determined by the interplay of interelectronic and vibronic interactions. In certain cases the vibronic interaction of excited electronic terms can change the spin multiplicity of the ground state. 31 refs.

  4. Quantum simulation of the cooperative Jahn-Teller transition in 1D ion crystals.

    PubMed

    Porras, Diego; Ivanov, Peter A; Schmidt-Kaler, Ferdinand

    2012-06-01

    The Jahn-Teller effect explains distortions and nondegenerate energy levels in molecular and solid-state physics via a coupling of effective spins to collective bosons. Here we propose and theoretically analyze the quantum simulation of a many-body Jahn-Teller model with linear ion crystals subjected to magnetic field gradients. We show that the system undergoes a quantum magnetic structural phase transition which leads to a reordering of particle positions and the formation of a spin-phonon quasicondensate in mesoscopic ion chains. PMID:23003971

  5. Jahn-Teller effect: its history and applicability

    SciTech Connect

    Teller, E.

    1981-08-31

    The interactions between Teller, Renner, Jahn and Landau which led to the formulation of the Jahn-Teller effect are discussed. The applicability of Jahn-Teller type of theory to superconductivity and the explanation proposed by the use of Goldstone particles are assessed.

  6. Jahn-Teller Effect: Its History and Applicability

    DOE R&D Accomplishments Database

    Teller, E.

    1981-08-31

    The interactions between Teller, Renner, Jahn and Landau which led to the formulation of the Jahn-Teller effect are discussed. The applicability of Jahn-Teller type of theory to superconductivity and the explanation proposed by the use of Goldstone particles are assessed.

  7. Jahn-Teller and pseudo-Jahn-Teller effects in trifluoromethane radical cation

    NASA Astrophysics Data System (ADS)

    Ghanta, Susanta

    2016-08-01

    Jahn-Teller (JT) and pseudo-Jahn-Teller (PJT) effects in the ground, first and second excited electronic states of the trifluoromethane radical cation are theoretically examined here. Extensive ab initio computation of electronic potential energy surfaces and their coupling surfaces are performed. Full quantum dynamics are obtained by both time-independent and time-dependent quantum mechanical methods. This system belongs to (E+A)⊗e JT-PJT family. Our results compare well with the experimental data. JT interactions are fairly strong in the second excited B˜2 E electronic state and the PJT interaction between A˜2A2 - B˜2 E electronic states is stronger which cause an increase of the spectral line density of the vibronic spectrum.

  8. Polarons and solitons in Jahn Teller systems

    NASA Astrophysics Data System (ADS)

    Clougherty, Dennis P.

    2007-07-01

    Using a semiclassical continuum model of an electron in a deformable molecular crystal, some properties of multicomponent generalizations of the polaron - "vector polarons" - are elucidated. Analytical solutions for the case of two electronic bands coupled to two vibrational modes are given in detail. Within the model considered, the vector polaron can be classified by its wavefunction into several types and can have features that include: (1) a spatial variation in the electronic and vibrational character, and (2) low-energy internal degrees of freedom. For the case of electronic and vibrational degeneracy, local Jahn-Teller interactions can also lead to a novel spatiotemporal soliton, a long-lived excited state of the many-electron system stabilized by the conservation law resulting from degeneracy.

  9. Dynamical Jahn-Teller instability in metallic fullerides

    NASA Astrophysics Data System (ADS)

    Iwahara, Naoya; Chibotaru, Liviu

    2015-03-01

    Dynamical Jahn-Teller effect has escaped so far direct observation in metallic systems. It is particularly believed to be quenched also in correlated conductors with orbitally degenerate sites such as cubic fullerides. Here the Gutzwiller approach is extended to treat electron correlation over metals with Jahn-Teller active sites and applied to the investigation of the ground state of K3C60. It is shown that dynamical Jahn-Teller instability fully develops in this material when the interelectron repulsion U on C60 sites exceeds some critical value. The latter is found to be lower than the current estimates of U, meaning that dynamical Jahn-Teller effect takes place in all cubic fullerides. This leads to strong splitting of LUMO orbitals on C60 sites and calls for reconsideration of the role of orbital degeneracy in the Mott-Hubbard transition in fullerides.

  10. Dynamical Jahn-Teller instability in metallic fullerides

    NASA Astrophysics Data System (ADS)

    Iwahara, Naoya; Chibotaru, Liviu F.

    2015-01-01

    Dynamical Jahn-Teller effect has escaped so far direct observation in metallic systems. It is particularly believed to be quenched also in correlated conductors with orbitally degenerate sites such as cubic fullerides. Here, the Gutzwiller approach is extended to treat electron correlation over metals with Jahn-Teller active sites and applied to the investigation of the ground state of K3C60 . It is shown that dynamical Jahn-Teller instability fully develops in this material when the interelectron repulsion U on C60 sites exceeds some critical value. The latter is found to be lower than the current estimates of U , meaning that dynamical Jahn-Teller effect takes place in all cubic fullerides. This leads to strong splitting of LUMO orbitals on C60 sites and calls for reconsideration of the role of orbital degeneracy in the Mott-Hubbard transition in fullerides.

  11. Photophysics of barrelene: The Jahn-Teller and pseudo-Jahn-Teller effects

    NASA Astrophysics Data System (ADS)

    Ghanta, Susanta

    2016-04-01

    The static and dynamic aspects of Jahn-Teller(JT) and pseudo-Jahn-Teller(PJT) interactions between ground (X˜2A2‧) and first three excited electronic states (A˜2E‧ , B˜2E″ and C˜2A‧1) of bicyclo- [2,2,2]-octa-2,5,7-triene (barrelene) radical cation (Bl+) are theoretically investigated here. This belongs to the (E + E) ⊗ e and (E + A) ⊗ e JT-PJT class of compounds as described by the symmetry of the electronic states and the molecular point group. The complex vibronic dynamics on the coupled electronic states of the cation is simulated by both time-independent and time-dependent wave packet propagation method using multi configuration time-dependent Hartree scheme. The JT effects in the A˜ and B˜ electronic states and the PJT coupling between the B˜ and C˜ electronic states of Bl+ are found very strong. The final theoretical results are compared with the experimental results.

  12. Jahn-Teller solitons, structural phase transitions, and phase separation.

    PubMed

    Clougherty, Dennis P

    2006-02-01

    It is demonstrated that under common conditions a molecular solid subject to Jahn-Teller interactions supports stable Q-ball-like nontopological solitons. Such solitons represent a localized lump of excess electric charge in periodic motion accompanied by a time-dependent shape distortion of a set of adjacent molecules. The motion of the distortion can correspond to a true rotation or to a pseudorotation about the symmetric shape configuration. These solitons are stable for Jahn-Teller coupling strengths below a critical value; however, as the Jahn-Teller coupling approaches this critical value, the size of the soliton diverges signaling an incipient structural phase transition. The soliton phase mimics features commonly attributed to phase separation in complex solids. PMID:16486846

  13. Jahn-Teller Solitons, Structural Phase Transitions, and Phase Separation

    NASA Astrophysics Data System (ADS)

    Clougherty, Dennis P.

    2006-02-01

    It is demonstrated that under common conditions a molecular solid subject to Jahn-Teller interactions supports stable Q-ball-like nontopological solitons. Such solitons represent a localized lump of excess electric charge in periodic motion accompanied by a time-dependent shape distortion of a set of adjacent molecules. The motion of the distortion can correspond to a true rotation or to a pseudorotation about the symmetric shape configuration. These solitons are stable for Jahn-Teller coupling strengths below a critical value; however, as the Jahn-Teller coupling approaches this critical value, the size of the soliton diverges signaling an incipient structural phase transition. The soliton phase mimics features commonly attributed to phase separation in complex solids.

  14. Dynamic Jahn-Teller coupling and high T c superconductivity

    NASA Astrophysics Data System (ADS)

    Clougherty, Dennis P.; Johnson, Keith H.; McHenry, Michael E.

    1989-12-01

    Based on the cooperative dynamic Jahn-Teller effect, a universal model of superconductivity is sketched which accounts for many aspects of conventional BCS and high T c superconductors. Within the quasi-molecular approximation, a real space vibronic coupling of degenerate (or nearly degenerate) electronic states to anharmonically mixed nuclear distortions is shown to lead to electron pairing. The crossover from electron-phonon behavior to electronic behavior as a function of Jahn-Teller coupling and anharmonic mixing is illustrated for the case of a CuO 4 cluster having D 4 h symmetry.

  15. Optimized unconventional superconductivity in a molecular Jahn-Teller metal

    PubMed Central

    Zadik, Ruth H.; Takabayashi, Yasuhiro; Klupp, Gyöngyi; Colman, Ross H.; Ganin, Alexey Y.; Potočnik, Anton; Jeglič, Peter; Arčon, Denis; Matus, Péter; Kamarás, Katalin; Kasahara, Yuichi; Iwasa, Yoshihiro; Fitch, Andrew N.; Ohishi, Yasuo; Garbarino, Gaston; Kato, Kenichi; Rosseinsky, Matthew J.; Prassides, Kosmas

    2015-01-01

    Understanding the relationship between the superconducting, the neighboring insulating, and the normal metallic state above Tc is a major challenge for all unconventional superconductors. The molecular A3C60 fulleride superconductors have a parent antiferromagnetic insulator in common with the atom-based cuprates, but here, the C603– electronic structure controls the geometry and spin state of the structural building unit via the on-molecule Jahn-Teller effect. We identify the Jahn-Teller metal as a fluctuating microscopically heterogeneous coexistence of both localized Jahn-Teller–active and itinerant electrons that connects the insulating and superconducting states of fullerides. The balance between these molecular and extended lattice features of the electrons at the Fermi level gives a dome-shaped variation of Tc with interfulleride separation, demonstrating molecular electronic structure control of superconductivity. PMID:26601168

  16. Electric Field Control of Jahn-Teller Distortions in Bulk Perovskites

    NASA Astrophysics Data System (ADS)

    Varignon, Julien; Bristowe, Nicholas C.; Ghosez, Philippe

    2016-02-01

    The Jahn-Teller distortion, by its very nature, is often at the heart of the various electronic properties displayed by perovskites and related materials. Despite the Jahn-Teller mode being nonpolar, we devise and demonstrate, in the present Letter, an electric field control of Jahn-Teller distortions in bulk perovskites. The electric field control is enabled through an anharmonic lattice mode coupling between the Jahn-Teller distortion and a polar mode. We confirm this coupling and quantify it through first-principles calculations. The coupling will always exist within the P b 21m space group, which is found to be the favored ground state for various perovskites under sufficient tensile epitaxial strain. Intriguingly, the calculations reveal that this mechanism is not only restricted to Jahn-Teller active systems, promising a general route to tune or induce novel electronic functionality in perovskites as a whole.

  17. Synchronization of networked Jahn-Teller systems in SQUIDs

    NASA Astrophysics Data System (ADS)

    Gül, Yusuf

    2016-06-01

    We consider the nonlinear effects in a Jahn-Teller (JT) system of two coupled resonators interacting simultaneously with a flux qubit using coupled SQUIDs. A two-frequency description of JT system that inherits the networked structure of both nonlinear Josephson junctions and harmonic oscillators is employed to describe the synchronous structures in a multifrequency scheme. Eigenvalue spectrum is used to show the switch between the effective single mode and two mode configuration in terms of frequency difference. The Rabi supersplitting is investigated by the spectral response of JT systems in different coupling regimes. Second-order coherence functions are employed to investigate antibunching effects in resonator mode. Synchronous structure between correlations of privileged mode and qubit is obtained in localization-delocalization and photon blockade regime controlled by the population imbalance.

  18. Jahn-Teller instability in dissipative quantum systems

    SciTech Connect

    Meaney, Charles P.; Duty, Tim; McKenzie, Ross H.; Milburn, G. J.

    2010-04-15

    We consider the steady states of a harmonic oscillator coupled so strongly to a two-level system (a qubit) that the rotating wave approximation cannot be made. The Hamiltonian version of this model is known as the E x {beta} Jahn-Teller model. The semiclassical version of this system exhibits a fixed-point bifurcation, which in the quantum model leads to a ground state with substantial entanglement between the oscillator and the qubit. We show that the dynamical bifurcation survives in a dissipative quantum description of the system, amidst an even richer bifurcation structure. We propose an experimental implementation of this model based on a superconducting cavity: a superconducting junction in the central conductor of a coplanar waveguide.

  19. Jet-Cooled Laser Spectroscopy of a Jahn-Teller and Pseudo Jahn-Teller Active Molecule: the Nitrate Radical

    NASA Astrophysics Data System (ADS)

    Chen, Ming-Wei; Takematsu, Kana; Okumura, Mitchio; Miller, Terry A.

    2009-06-01

    Well-known as an important intermediate in atmospheric chemistry, the nitrate radical (NO_3) has been extensively studied both experimentally and theoretically. The three energetically lowest electronic states (tilde{X} ^{2}A_{2}^', tilde{A} ^{2}E^'', and tilde{B} ^{2}E^') are strongly coupled by vibronic interactions and hence it is a textbook molecule for understanding the coupling between nearby potential energy surfaces. Such coupling has been treated in considerable detail theoretically. However, corresponding experimental characterization of the interaction is much less detailed. The experimental results primarily consist of IR measurements of vibrational transitions in the ground state. In addition, the electronically forbidden tilde{A}-tilde{X} transition has been observed in ambient temperature CRDS studies. To understand both the Jahn-Teller and pseudo Jahn-Teller coupling in the molecule, further measurements are required with different selection rules and/or higher resolution to resolve the rotational structures of different transitions. In our group, a high-resolution (source Δν≈ 100 MHz in NIR region), jet-cooled CRDS system can be applied to rotationally resolve the electronically forbidden tilde{A}-tilde{X} transition. Furthermore, our high-resolution LIF/SEP system (source Δν≈ 100 MHz) can provide the direct, rotationally resolved measurements of the tilde{B}-tilde{X} and tilde{B}-tilde{A} transitions by operating in the LIF and SEP modes respectively. Such data can provide unambiguous spectral assignments in the tilde{X}, tilde{A} and tilde{B} states. J. F. Stanton, J. Chem. Phys., 126, 134309 (2007) K. Kawaguchi, E. Hirota, T. Ishiwata, and I. Tanaka, J. Chem. Phys., 93, 951 (1990) K. Kawaguchi, T. Ishiwata, E. Hirota, and I. Tanaka, Chem. Phys., 231, 193 (1998) A. Deev, J. Sommar, and M. Okumura, J. Chem. Phys., 122, 224305 (2005) S. Wu, P. Dupré, and T. A. Miller, Phys. Chem. Chem. Phys., 8, 1682, (2006)

  20. Jahn-Teller effect and adiabatic cooling in the vicinity of crossover point

    NASA Astrophysics Data System (ADS)

    Rosenfeld, E. V.

    2016-10-01

    It is shown that an ensemble of two-state systems, which commonly works as a refrigerator when the levels adiabatically approach each other, turns into a thermostat as soon as the Jahn-Teller effect emerges.

  1. Unusual ferroelectricity induced by the Jahn-Teller effect: A case study on lacunar spinel compounds

    NASA Astrophysics Data System (ADS)

    Xu, Ke; Xiang, Hongjun

    The Jahn-Teller effect refers to the symmetry-lowering geometrical distortion in a crystal (or nonlinear molecule) due to the presence of a degenerate electronic state. Usually, the Jahn-Teller distortion is not polar. Recently, GaV4S8 with a lacunar spinel structure was found to undergo a Jahn-Teller distortion from a cubic to ferroelectric rhombohedral structure at TJT = 38 K. Here, we carry out a general group theory analysis to show how and when the Jahn-Teller effect gives rise to ferroelectricity. On the basis of this theory, we ?nd that the ferroelectric Jahn-Teller distortion in GaV4S8 is due to the noncentrosymmetric nature of the parent phase and a strong electron-phonon interaction related to two low-energy T2 phonon modes. Interestingly, GaV4S8 is not only ferroelectric, but also ferromagnetic with a magnetic easy axis along the ferroelectric direction. This suggests that GaV4S8 is a multiferroic material in which an external electric ?eld may control its magnetization direction. Our study not only explains the Jahn-Teller physics in GaV4S8, but also paves a way for searching and designing different ferroelectrics and multiferroics.

  2. Relativistic theory of the Jahn-Teller effect: p-orbitals in tetrahedral and trigonal systems

    NASA Astrophysics Data System (ADS)

    Domcke, Wolfgang; Opalka, Daniel; Poluyanov, Leonid V.

    2016-03-01

    A relativistic generalization of Jahn-Teller theory is presented which includes spin-orbit coupling effects beyond low-order Taylor expansions in vibrational coordinates. For the example of a p-electron in tetrahedral and trigonal environments, the matrix elements of the Breit-Pauli spin-orbit-coupling operator are expressed in terms of the matrix elements of the electrostatic electronic potential. Employing expansions of the latter in invariant polynomials in symmetry-adapted nuclear coordinates, the spin-orbit induced Jahn-Teller coupling terms are derived for the T2 × (t2 + e) and (E + A) × (e + a) Jahn-Teller problems up to arbitrarily high orders. The linear G3/2 × (t2 + e) Jahn-Teller Hamiltonian of Moffitt and Thorson [Phys. Rev. 108, 1251 (1957)] for tetrahedral systems is generalized to higher orders in vibrational displacements. The Jahn-Teller Hamiltonians derived in the present work are useful for the interpolation and extrapolation of Jahn-Teller distorted potential-energy surfaces of molecules and complexes with heavy elements as well as for the calculation of vibronic spectra of such systems.

  3. Chemically induced Jahn-Teller ordering on manganite surfaces.

    PubMed

    Gai, Zheng; Lin, Wenzhi; Burton, J D; Fuchigami, K; Snijders, P C; Ward, T Z; Tsymbal, Evgeny Y; Shen, J; Jesse, Stephen; Kalinin, Sergei V; Baddorf, Arthur P

    2014-01-01

    Physical and electrochemical phenomena at the surfaces of transition metal oxides and their coupling to local functionality remains one of the enigmas of condensed matter physics. Understanding the emergent physical phenomena at surfaces requires the capability to probe the local composition, map order parameter fields and establish their coupling to electronic properties. Here we demonstrate that measuring the sub-30-pm displacements of atoms from high-symmetry positions in the atomically resolved scanning tunnelling microscopy allows the physical order parameter fields to be visualized in real space on the single-atom level. Here, this local crystallographic analysis is applied to the in-situ-grown manganite surfaces. In particular, using direct bond-angle mapping we report direct observation of structural domains on manganite surfaces, and trace their origin to surface-chemistry-induced stabilization of ordered Jahn-Teller displacements. Density functional calculations provide insight into the intriguing interplay between the various degrees of freedom now resolved on the atomic level. PMID:25058540

  4. Entanglement and bifurcations in Jahn-Teller models

    SciTech Connect

    Hines, Andrew P.; Milburn, G.J.; Dawson, Christopher M.; McKenzie, Ross H.

    2004-08-01

    We compare and contrast the entanglement in the ground state of two Jahn-Teller models. The Ex{beta} system models the coupling of a two-level electronic system, or qubit, to a single-oscillator mode, while the Ex{epsilon} models the qubit coupled to two independent, degenerate oscillator modes. In the absence of a transverse magnetic field applied to the qubit, both systems exhibit a degenerate ground state. Whereas there always exists a completely separable ground state in the Ex{beta} system, the ground states of the Ex{epsilon} model always exhibit entanglement. For the Ex{beta} case we aim to clarify results from previous work, alluding to a link between the ground-state entanglement characteristics and a bifurcation of a fixed point in the classical analog. In the Ex{epsilon} case we make use of an ansatz for the ground state. We compare this ansatz to exact numerical calculations and use it to investigate how the entanglement is shared between the three system degrees of freedom.

  5. Crystal structure, ferromagnetostructural behavior and evidence of cooperative Jahn-Teller interactions of the complex [CuL]Cl·H 2O (L= N-glycyl-2(aminomethyl)benzimidazol), synthesized by a novel simple method of peptide bond formation.

    NASA Astrophysics Data System (ADS)

    García-Orozco, Ivan; Tapia-Benavides, Antonio Rafael; Alvarez-Toledano, Cecilio; Toscano, Ruben A.; Ramírez-Rosales, Daniel; Zamorano-Ulloa, Rafael; Reyes-Ortega, Yasmi

    2002-01-01

    [CuL]Cl·H 2O 1 (L= N-glycyl-2(aminomethyl)benzimidazol) compound crystallizes in the orthorhombic space group Pna2 1 with unit cell parameters a=7.140(5) Å, b=17.621(5) Å, c=9.941(5) Å. Its structure shows that the copper(II) ion is tetra coordinated with a square planar geometry. The ligand acts as a tridentate and the chloride ion is the fourth ligand. Symmetry related units stack into helicoidal columns along the ā direction producing weakly bonded strips with dihedral angles of 2.6° between two consecutive molecular planes. UV/VIS spectrum of 1 shows one broad and weak band at 622 nm, characteristic of d-d transitions, indicative of low local Cu(II) symmetry. X band ESR spectra of 1 at 300 and 77 K are axial exchange narrow lines with g∥=2.135 and g⊥=2.028. However, the axial spectrum at 6.4 K shows an increment Δ g∥=0.076(6) and Δ g⊥=0.028(4) which suggests a cooperative Jahn-Teller interactions between complexes via the hydrogen-bonding network. Magnetic susceptibility data at 18-300 K and fitted to the modified Bleany-Bowers equation indicate a weak ferromagnetic coupling with 2J≅+17 cm-1, which is compatible with the helium temperature ESR results and with the helicoidal stacking into columns of the molecules along the a-axis with 78.9° Cu'-Cl'-Cu and 81.2° Cu'-N( 1)-Cu bonds angles. The synthesis is a novel, simple and efficient method: in aqueous conditions and heterogeneous phase with basic copper(II) carbonate, which carries out the formation of the stable peptide bond.

  6. Photoluminescence properties of Jahn-Teller transition-metal ions

    NASA Astrophysics Data System (ADS)

    Sanz-Ortiz, Marta N.; Rodríguez, Fernando

    2009-09-01

    This work investigates the influence of electron-phonon coupling associated with E ⊗e and T ⊗e Jahn-Teller (JT) effect in different transition-metal (TM) ions on de-excitation phenomena through nonradiative multiphonon relaxation, i.e., photoluminescence (PL) quenching. We developed a configurational curve model which is able to predict from the absorption spectrum whether a given JT-TM ion is PL or quenched. The prediction is made on the basis of an adapted Dexter-Klick-Russell parameter for JT systems, defined in terms of spectroscopic parameters through ΛJT=αΔeabs/Eabs, where Δeabs refers to the splitting of the parent octahedral Eg states by the JT distortion in E ⊗e (α =3/4) or T ⊗e (α =1/4), and Eabs is the energy of the first absorption band involving electronic transition between Eg and T2g. We show that PL in any JT-TM ion occurs whenever ΛJT<0.1 or is quenched if ΛJT>0.2. This result is noteworthy since it allows us to establish structural requirements for the JT-TM ion and the host crystal to be PL. Although PL properties of materials containing TM ions depend on a variety of structural factors such as the electronic configuration, the site symmetry, and the crystal field produced by neighboring atoms, the present model achieves this goal through a simple spectroscopic parameter: ΛJT. In this work we correlated the PL properties of different sixfold-coordinated JT systems such as Ti3+, Cu2+, Mn3+, Cr2+, Fe2+, Co3+, and Ni3+ in halides and oxides with ΛJT obtained from their respective absorption spectra. From this analysis we conclude that depending on the nature of the JT coupling and its strength, PL is either strongly favored or quenched in T ⊗e while it is mostly quenched in E ⊗e systems due to the larger JT distortion.

  7. Novel aspects of the Jahn-Teller effect in molecular and solid-state systems

    NASA Astrophysics Data System (ADS)

    Ernst, Wolfgang E.; Köppel, Horst

    2015-10-01

    The Jahn-Teller effect continues to be a source of insight and inspiration for the interpretation of structural instabilities and dynamic phenomena in molecules and solids. About two decades passed between the publication of the proof of the Jahn-Teller theorem in 1937 and broad scientific activity in the field (although clear experimental evidence of the effect in the ESR spectra of bivalent copper compounds became available in 1950). Then a rapid development set in, and suitable model treatments were set up in the literature and applied to various kinds of problems in molecular and solid-state spectroscopy. Different possibilities for structural distortions, and the associated dynamical (tunneling) processes, were explored, and consequences for magnetic resonance and optical spectra revealed. Key extensions followed, regarding the structural and also dynamic aspects of the Jahn-Teller effect (JTE): similar distortions may also occur in near-degeneracy situations, termed pseudo JTE, which enhances the importance of the effects.

  8. Angular-overlap calculation of the Jahn-Teller stabilization energie for f-orbital degeneracies

    SciTech Connect

    Warren, K.D.

    1980-03-01

    The angular-overlap model is applied to the calculation of the linear Jahn-Teller coupling constants for f-orbital degeneracies. The MX/sub 6/, O/sub h/, chromophore is treated as representative of the highest symmetry commonly occurring in the lanthanide and actinide series, and it is shown that, even when spin-orbit effects are taken into account, 5f orbital degeneracies may lead to significant Jahn-Teller stabilization energies. The operation of this effect for F/sup 1/ GAMMA/sub 8/ states is considered. 2 tables.

  9. Flattening a puckered cyclohexasilane ring by suppression of the pseudo-Jahn-Teller effect

    NASA Astrophysics Data System (ADS)

    Pokhodnya, Konstantin; Olson, Christopher; Dai, Xuliang; Schulz, Douglas L.; Boudjouk, Philip; Sergeeva, Alina P.; Boldyrev, Alexander I.

    2011-01-01

    We report the experimental and theoretical characterization of neutral Si6X12 (X = Cl, Br) molecules that contain D3d distorted six-member silicon rings due to a pseudo-Jahn-Teller (PJT) effect. Calculations show that filling the intervenient molecular orbitals with electron pairs of adduct suppresses the PJT effect in Si6X12, with the Si6 ring becoming planar (D6h) upon complex formation. The stabilizing role of electrostatic and covalent interactions between positively charged silicon atoms and chlorine atoms of the subject [Si6Cl14]2- dianionic complexes is discussed. The reaction of Si6Cl12 with a Lewis base (e.g., Cl-) to give planar [Si6Cl14]2- dianionic complexes presents an experimental proof that suppression of the PJT effect is an effective strategy in restoring high Si6 ring symmetry. Additionally, the proposed pathway for the PJT suppression has been proved by the synthesis and characterization of novel compounds containing planar Si6 ring, namely, [nBu4N]2[Si6Cl12I2], [nBu4N]2[Si6Br14], and [nBu4N]2[Si6Br12I2]. This work represents the first demonstration that PJT effect suppression is useful in the rational design of materials with novel properties.

  10. The vibrational Jahn-Teller effect in E⊗e systems

    NASA Astrophysics Data System (ADS)

    Thapaliya, Bishnu P.; Dawadi, Mahesh B.; Ziegler, Christopher; Perry, David S.

    2015-10-01

    The Jahn-Teller theorem is applied in the vibrational context where degenerate high-frequency vibrational states (E) are considered as adiabatic functions of low-frequency vibrational coordinates (e). For CH3CN and Cr(C6H6)(CO)3, the global minimum of the non-degenerate electronic potential energy surface occurs at the C3v geometry, but in CH3OH, the equilibrium geometry is far from the C3v reference geometry. In the former cases, the computed spontaneous Jahn-Teller distortion is exceptionally small. In methanol, the vibrational Jahn-Teller interaction results in the splitting of the degenerate E-type CH stretch into what have been traditionally assigned as the distinct ν2 and ν9 vibrational bands. The ab initio vibrational frequencies are fit precisely by a two-state high-order Jahn-Teller Hamiltonian (Viel and Eisfeld, 2004). The presence of vibrational conical intersections, including 7 for CH3OH, has implications for spectroscopy, for geometric phase, and for ultrafast localized non-adiabatic energy transfer.

  11. Interplay Between Structural, Jahn-Teller, and Magnetic States of Slightly Doped Lanthanum Manganites

    NASA Astrophysics Data System (ADS)

    Golenishchev-Kutuzov, V. A.; Golenishchev-Kutuzov, A. V.; Kalimullin, R. I.; Semennikov, A. V.

    2016-03-01

    By combining the results of elastic moduli, electrical resistivity, and magnetization measurements for La_{1-x} Srx MnO3 (x = 0.125, x = 0.15, and x = 0.175), we have constructed a phase diagram that describes the structural, magnetic, transport properties and the relationships among them as a function of the composition and temperature (140-340 K). The local, intermediate, and cooperative Jahn-Teller distortions of the octahedral structural units MnO6 have been studied. It is common for these distortions to be observed using probes of intermediate structures (domains or super-cells), but they are absent in the averaged crystallographic structure. In the cooperative Jahn-Teller distorted phase, the macroscopic sample length is temperature dependent. We presume that the structural transitions from the cooperative Jahn-Teller phase to the charge ordering phase at low temperatures (150 and 180 K at x = 0.125 and x = 0.15) are due to the increase in the spontaneous magnetization with the conservation of the local deformations of separate octahedra. The agreement between the types of the orbital ordering and the local, intermediate, and Jahn-Teller cooperative distortions of octahedra was established.

  12. Experimental evidence of a dynamic Jahn-Teller effect in C-60(+)

    SciTech Connect

    Canton, S.E.; Yencha, A.J.; Kukk, E.; Bozek, J.D.; Lopes, M.C.A.; Snell, G.; Berrah, N.

    2002-05-20

    Detailed analysis of the HOMO bandshape in the photoelectron spectrum of gaseous C60 reveals a dynamic Jahn-Teller effect in the ground state of C60+. The direct observation of three tunneling states asserts a D3d geometry for the isolated cation, originating from a strong vibronic coupling. These results show that the ionic motion of the ions plays an important role in the electron-phonon interaction.

  13. Vibrational Jahn-Teller Effect in Non-Degenerate Electronic States

    NASA Astrophysics Data System (ADS)

    Dawadi, Mahesh B.; Thapaliya, Bishnu P.; Bhatta, Ram; Perry, David S.

    2015-06-01

    The Jahn-Teller theorem states that "All non-linear nuclear configurations are therefore unstable for an orbitally degenerate electronic state." In 1982, Kellman realized that the Jahn-Teller theorem also applies to nonlinear molecular species in non-degenerate electronic states when there are high-frequency vibrations that are degenerate at a symmetrical reference geometry. When those high frequencies can be considered as adiabatic functions of degenerate low-frequency coordinates, there is a spontaneous Jahn-Teller distortion that lifts the degeneracy of the high-frequency vibrations. Kellman applied the vibrational Jahn-Teller (vJT) concept to the Van der Waals dimer (SF6)2. In this talk, the vJT concept is applied to E ⊗ e systems that are small bound molecules in non-degenerate electronic states. The first case considered in systems for which the global minimum of the electronic potential has C3v symmetry.For such systems, including (C6H6)Cr(CO)3 and CH3CN, the vJT effect leads to a significant splitting of the degenerate high-frequency vibrations (CH or CO stretches), but the spontaneous vJT distortion is exceptionally small. The second case in systems for which the global minimum of the electronic potential is substantially distorted from the C3v reference geometry. For the second case systems, including CH3OH and CH3SH, the vJT splitting of the degenerate CH stretches is much larger, on the order of several 10Äôs of cm-1). For both cases, there is the symmetry-required vibrational conical intersection at the C3v reference geometry. For the second case systems, there are additional symmetry-allowed vibrational conical intersections far from the C3v geometry but energetically accessible to the molecule at thermal energies. For both cases, the vibrationally adiabatic surfaces, including the multiple conical intersections, are well described by modest extensions to a high-order Hamiltonian that was developed for the electronic Jahn-Teller problem. H

  14. PREFACE: XXIst International Symposium on the Jahn-Teller Effect 2012

    NASA Astrophysics Data System (ADS)

    Koizumi, Hiroyasu

    2013-04-01

    (The PDF contains the full conference program, the list of sponsors and the conference poster.) The 21st International Symposium on the Jahn-Teller effect was held at the University of Tsukuba, Japan, from 26-31 August 2012. People from 23 different countries participated and the number of registered participants was 118. In this symposium, the phrase 'Jahn-Teller effect' was taken to have a rather broad meaning. We discussed the Jahn-Teller and pseudo Jahn-Teller distortions. We also discussed general vibronic problems, and the problems associated with the conical intersections of the potential energy surfaces. As is indicated in the subtitle of the present symposium, 'Physics and Chemistry of Symmetry Breaking', a number of different topics concerning symmetry breaking were also extensively discussed. In particular, we had many discussions on magnetism, ferroelectricity, and superconductivity. A subtle but important problem that was dealt with was the appearance of multi-valuedness in the use of multi-component wave functions. In the Jahn-Teller problems, we almost always use the multi-component wave functions, thus, the knowledge of the proper handling of multi-valuedness is very important. Digital computers are not good at dealing with multi-valuedness, but we need to somehow handle it in our calculations. A very well known example of successful handling is found in the problem of the molecular system with the conical intersection: we cannot obtain the solution that satisfies the single-valuedness of wave functions (SVWF) just using the potential energy surface generated by a package program, and solving the Schrödinger equation with the quantum Hamiltonian constructed from the classical counterpart by replacing the classical variables with the corresponding operators; however, if a gauge potential is included and the double-valuedness of the electronic wave functions around the conical intersections is taken into account, the solution that satisfies the SVWF

  15. A Genuine Jahn-Teller System with Compressed Geometry and Quantum Effects Originating from Zero-Point Motion.

    PubMed

    Aramburu, José Antonio; García-Fernández, Pablo; García-Lastra, Juan María; Moreno, Miguel

    2016-07-18

    First-principle calculations together with analysis of the experimental data found for 3d(9) and 3d(7) ions in cubic oxides proved that the center found in irradiated CaO:Ni(2+) corresponds to Ni(+) under a static Jahn-Teller effect displaying a compressed equilibrium geometry. It was also shown that the anomalous positive g∥ shift (g∥ -g0 =0.065) measured at T=20 K obeys the superposition of the |3 z(2) -r(2) ⟩ and |x(2) -y(2) ⟩ states driven by quantum effects associated with the zero-point motion, a mechanism first put forward by O'Brien for static Jahn-Teller systems and later extended by Ham to the dynamic Jahn-Teller case. To our knowledge, this is the first genuine Jahn-Teller system (i.e. in which exact degeneracy exists at the high-symmetry configuration) exhibiting a compressed equilibrium geometry for which large quantum effects allow experimental observation of the effect predicted by O'Brien. Analysis of the calculated energy barriers for different Jahn-Teller systems allowed us to explain the origin of the compressed geometry observed for CaO:Ni(+) . PMID:27028895

  16. A Genuine Jahn-Teller System with Compressed Geometry and Quantum Effects Originating from Zero-Point Motion.

    PubMed

    Aramburu, José Antonio; García-Fernández, Pablo; García-Lastra, Juan María; Moreno, Miguel

    2016-07-18

    First-principle calculations together with analysis of the experimental data found for 3d(9) and 3d(7) ions in cubic oxides proved that the center found in irradiated CaO:Ni(2+) corresponds to Ni(+) under a static Jahn-Teller effect displaying a compressed equilibrium geometry. It was also shown that the anomalous positive g∥ shift (g∥ -g0 =0.065) measured at T=20 K obeys the superposition of the |3 z(2) -r(2) ⟩ and |x(2) -y(2) ⟩ states driven by quantum effects associated with the zero-point motion, a mechanism first put forward by O'Brien for static Jahn-Teller systems and later extended by Ham to the dynamic Jahn-Teller case. To our knowledge, this is the first genuine Jahn-Teller system (i.e. in which exact degeneracy exists at the high-symmetry configuration) exhibiting a compressed equilibrium geometry for which large quantum effects allow experimental observation of the effect predicted by O'Brien. Analysis of the calculated energy barriers for different Jahn-Teller systems allowed us to explain the origin of the compressed geometry observed for CaO:Ni(+) .

  17. Dynamic Jahn-Teller effect in the parent insulating state of the molecular superconductor Cs₃C₆₀.

    PubMed

    Klupp, Gyöngyi; Matus, Péter; Kamarás, Katalin; Ganin, Alexey Y; McLennan, Alec; Rosseinsky, Matthew J; Takabayashi, Yasuhiro; McDonald, Martin T; Prassides, Kosmas

    2012-01-01

    The 'expanded fulleride' Cs(3)C(60) is an antiferromagnetic insulator in its normal state and becomes a molecular superconductor with T(c) as high as 38 K under pressure. There is mounting evidence that superconductivity is not of the conventional BCS type and electron-electron interactions are essential for its explanation. Here we present evidence for the dynamic Jahn-Teller effect as the source of the dramatic change in electronic structure occurring during the transition from the metallic to the localized state. We apply infrared spectroscopy, which can detect subtle changes in the shape of the C(60)3- ion due to the Jahn-Teller distortion. The temperature dependence of the spectra in the insulating phase can be explained by the gradual transformation from two temperature-dependent solid-state conformers to a single one, typical and unique for Jahn-Teller systems. These results unequivocally establish the relevance of the dynamic Jahn-Teller effect to overcoming Hund's rule and forming a low-spin state, leading to a magnetic Mott-Jahn-Teller insulator.

  18. Pair correlation and dynamic Jahn-Teller effect: High-Tc in nanoclusters

    NASA Astrophysics Data System (ADS)

    Kresin, Vladimir; Ovchinnikov, Yurii; Friedel, Jacques

    2014-11-01

    Electronic states in metallic nanoclusters form energy shells and degree of their filling depends on the number of delocalized electrons. In the region close to half-filling the cluster's geometry oscillates between the prolate and oblate configurations (dynamic Jahn-Teller effect). For large clusters (N > 102 N is the number of delocalized electrons) this effect competes with pair correlation and, as a result, it is perfectly realistic to observe the transition to the superconducting state. For some clusters (e.g., for Zn76, Al70) the value of the critical temperature is rather high (≳ 140 \\text{K}) .

  19. Lattice modes and the Jahn-Teller ferroelectric transition of GaV4S8

    NASA Astrophysics Data System (ADS)

    Hlinka, J.; Borodavka, F.; Rafalovskyi, I.; Docekalova, Z.; Pokorny, J.; Gregora, I.; Tsurkan, V.; Nakamura, H.; Mayr, F.; Kuntscher, C. A.; Loidl, A.; Bordács, S.; Szaller, D.; Lee, H.-J.; Lee, J. H.; Kézsmárki, I.

    2016-08-01

    Crystal of GaV4S8 , a multiferroic system hosting a Néel-type skyrmion lattice phase, has been investigated by polarized Raman and IR spectroscopy above and below the ferroelectric phase transition. Counts of the observed IR and Raman-active modes belonging to distinct irreducible representations agree quite well with group-theory predictions. Phonon spectra are assigned and interpreted with the aid of ab initio calculations of the phonon spectra in the ferroelectric phase. Results allow appreciation of phonon frequencies of the modes involved in Jahn-Teller distortion and their contribution to the spontaneous polarization.

  20. Competing Jahn-Teller distortions and ferrimagnetic ordering in the geometrically frustrated system N i1 -xC uxC r2O4

    NASA Astrophysics Data System (ADS)

    Reehuis, M.; Tovar, M.; Többens, D. M.; Pattison, P.; Hoser, A.; Lake, B.

    2015-01-01

    with a disordered spin-liquid-like or a reentrant-spin-glass-like state. This paper provides insight into the interplay between the Jahn-Teller effect, geometrical frustration, and long-range magnetic order in these complex systems.

  1. Influence of the ionic size on the evolution of local Jahn-Teller distortions in cobaltites

    NASA Astrophysics Data System (ADS)

    Phelan, D.; Louca, Despina; Kamazawa, K.; Hundley, M. F.; Yamada, K.

    2007-09-01

    The thermodynamic and atomic structure properties of La1-xAxCoO3 ( A=Ba2+ and Ca2+ ) with 0⩽x⩽0.5 , a class of compounds that exhibit magnetoresistance in the presence of an applied magnetic field, have been investigated via magnetic and transport measurements and neutron scattering. While in the parent compound, the Co3+ ion undergoes a spin-state transition from the low-spin ground state to a dynamic intermediate-spin configuration thermally, with hole doping, the intermediate-spin state becomes static as evidenced by the Jahn-Teller octahedral splitting of the Co-O bonds. The size of the split depends strongly on the tolerance factor, where small or no Jahn-Teller distortions are observed in samples with small tolerance factors (i.e., Ca), but as the tolerance factor approaches 1 (i.e., Ba), the bond split can be as much as 0.2Å . At the same time, ferromagnetic ordering is also influenced by the tolerance factor. As it gets closer to 1, ferromagnetic coupling is enhanced due to the straightening of the Co-O-Co bonds, where the angle becomes almost 180° that, in turn, favors double-exchange interactions between Co ions. With the ferromagnetic transition, the system becomes metallic and shows a negative magnetoresistance with field. As the tolerance factor is reduced from 1, the ferromagnetic coupling is weak and the bond angle is about 160°.

  2. Medium effect on the Jahn-Teller distortions of the tetramethylallene radical cation

    SciTech Connect

    Qin, X.Z.; Trifunac, A.D. )

    1991-08-22

    The Jahn-Teller distortion of the delocalized {pi}-radical cation tetramethylallene{sm bullet}{sup +} (TMA{sm bullet}{sup +}) was found to be medium dependent. TMA{sup {sm bullet}} was studied in liquid hydrocarbons (195-295 K) by time-resolved fluorescence-detected magnetic resonance (FDMR) spectroscopy and in freon matrices (80-160 K) and zeolite Na-Y (80-298 K) by EPR spectroscopy. The observed coupling constants for the twelve protons of the four methyl groups of the radical cation are 11.3, 8.1, and 14.4 G, respectively. AM1 and INDO calculations suggest that different coupling constants can be explained by different twist angles in TMA{sup {sm bullet}+}. It is suggested that interaction between TMA{sup {sm bullet}+} and the chlorine or fluorine atoms of freon matrices or between TMA{sup {sm bullet}+} and the sodium atoms of the zeolite can influence the charge and spin distribution in the radical cation so that the structures that differ from that found in hydrocarbon solution can be stabilized. This is the first example of a Jahn-Teller-active radical cation that has been studied in several media.

  3. Rotationally resolved photoelectron spectroscopic study of the Jahn-Teller effect in allene

    NASA Astrophysics Data System (ADS)

    Schulenburg, A. M.; Merkt, F.

    2009-01-01

    The pulsed-field-ionization zero-kinetic-energy photoelectron spectra of allene (C3H4) and perdeuterated allene have been recorded from the first adiabatic ionization energy up to 2200 cm-1 of internal energy in the cations at a resolution sufficient to observe the full rotational structure. The intensity distributions in the spectra are dominated by vibrational progressions in the torsional mode, which were analyzed in the realm of a two-dimensional model of the E ⊗(b1⊕b2) Jahn-Teller effect in the allene cation [C. Woywod and W. Domcke, Chem. Phys. 162, 349 (1992)]. Whereas the rotational structure of the transitions to the lowest torsional levels (00 and 41) are regular and can be qualitatively analyzed in terms of a simple orbital ionization model, the rotational structure of the spectra of the 42 and 43 levels are strongly perturbed. The photoelectron spectrum of C3H4 also reveals several weak vibrational bands in the immediate vicinity of these levels that are indicative of (ro)vibronic perturbations. A slight broadening of the transitions to the 41 levels compared to that of the vibronic ground state and the increase of the number of sharp features in the rotational structure of the spectrum of the 42 level point at the importance of large-amplitude motions not considered in previous treatments of the Jahn-Teller effect in the allene cation.

  4. The hydration of Cu2+: Can the Jahn-Teller effect be detected in liquid solution?

    NASA Astrophysics Data System (ADS)

    Chaboy, Jesús; Muñoz-Páez, Adela; Merkling, Patrick J.; Sánchez Marcos, Enrique

    2006-02-01

    The long elusive structure of Cu(II) hydrate in aqueous solutions, classically described as a Jahn-Teller distorted octahedron and recently proposed to be a fivefold coordination structure [Pasquarello et al., Science 291, 856 (2001)], has been probed with x-ray-absorption spectroscopy by performing a combined theoretical and experimental analysis. Two absorption channels were needed to obtain a proper reproduction of the x-ray-absorption near-edge structure (XANES) region spectrum, as already observed in other Cu(II) complexes [Chaboy et al., Phys. Rev. B 71, 134208 (2005)]. The extended x-ray-absorption fine-structure (EXAFS) spectrum was analyzed as well within this approach. Quite good reproductions of both XANES and EXAFS spectra were attained for several distorted and undistorted structures previously proposed. Nevertheless, there is not a clearly preferred structure among those including four-, five-, and sixfold coordinated Cu(II) ions. Taking into account our results, as well as many more from several other authors using different techniques, the picture of a distorted octahedron for the Cu(II) hexahydrate in aqueous solution, paradigm of the Jahn-Teller effect, is no longer supported. In solution a dynamical view where the different structures exchange among themselves is the picture that better suits the results presented here.

  5. Jahn-Teller assisted polaronic hole hopping as a charge transport mechanism in CuO nanograins

    NASA Astrophysics Data System (ADS)

    Younas, M.; Nadeem, M.; Idrees, M.; Akhtar, M. J.

    2012-04-01

    Impedance spectroscopy has been employed to investigate the dielectric and electric transport phenomena in sol-gel synthesized CuO nanograins. Semiconducting features of the grains and grain boundaries have been endorsed to the thermal activation of the localized charge carriers. On cooling below 303 K, a transition from Jahn-Teller polaron hopping mechanism to the Mott's variable range hopping mechanism has been observed owing to random potential fluctuations among localized sites. Activation energies for conduction and relaxation processes at grain boundaries provide strong signatures for the involvement of Jahn-Teller adiabatic small polarons as a charge transport mechanism in CuO nanograins.

  6. Jahn-Teller stabilization energies for ZnS:Mn and ZnSe:Mn excited states obtained by the angular overlap model

    NASA Astrophysics Data System (ADS)

    Stavrev, K. K.; Kynev, K. D.; Nikolov, G. St.

    1988-06-01

    Linear Jahn-Teller coupling constants are obtained by the angular overlap model. A comparison with the data published recently [Parrot et al., J. Chem. Phys. 87, 1463 (1987)] is made in order to demonstrate the considerable improvement in the calculated Jahn-Teller coefficients when the parameters of the angular overlap model are extracted from a spectral analysis of the systems under consideration.

  7. Soft-acoustic phonon mode at the Jahn-Teller transition in LaMnO 3

    NASA Astrophysics Data System (ADS)

    Saint-Paul, M.; Lejay, P.

    2004-10-01

    The elastic properties of LaMnO3 have been investigated by means of ultrasonic measurements. The longitudinal elastic constant C22Ort propagating along the b-axis exhibits a large softening around the Jahn-Teller transition TJT∼750 K accompanied by the orbital order-disorder transition

  8. Jahn-Teller inactivity and magnetic frustration in GeCo2O4 probed by ultrasound velocity measurements

    NASA Astrophysics Data System (ADS)

    Watanabe, Tadataka; Hara, Shigeo; Ikeda, Shin-Ichi

    2008-09-01

    Ultrasound velocity measurements of cubic spinel GeCo2O4 in single crystal were performed for the investigation of shear and compression moduli. The shear moduli in the paramagnetic state reveal the absence of Jahn-Teller activity despite the presence of orbital degeneracy in the Co2+ ions. Such a Jahn-Teller inactivity indicates that the intersite orbital-orbital interaction is much stronger than the Jahn-Teller coupling. The compression moduli in the paramagnetic state near the Néel temperature TN reveal that the most relevant exchange path for the antiferromagnetic transition lies in the [111] direction. This exchange-path anisotropy is consistent with the antiferromagnetic structure with the wave vector q∥[111] , suggesting the presence of bond frustration due to competition among a direct ferromagnetic interaction and several distant-neighbor antiferromagnetic interactions. In the Jahn-Teller-inactive condition, the bond frustration can be induced by geometrical orbital frustration of t2g-t2g interaction between the Co2+ ions, which can be realized in the pyrochlore lattice of the high-spin Co2+ with t2g -orbital degeneracy. In GeCo2O4 , the tetragonal elongation below TN releases the orbital frustration by quenching the orbital degeneracy.

  9. DFT-based studies on the Jahn-Teller effect in 3d hexacyanometalates with orbitally degenerate ground states.

    PubMed

    Atanasov, Mihial; Comba, Peter; Daul, Claude A; Hauser, Andreas

    2007-09-20

    The topology of the ground-state potential energy surface of M(CN)(6) with orbitally degenerate (2)T(2g) (M = Ti(III) (t(2g)(1)), Fe(III) and Mn(II) (both low-spin t(2g)(5))) and (3)T(1g) ground states (M = V(III) (t(2g)(2)), Mn(III) and Cr(II) (both low-spin t(2g)(4))) has been studied with linear and quadratic Jahn-Teller coupling models in the five-dimensional space of the epsilon(g) and tau(2g) octahedral vibrations (Tg[symbol: see text](epsilon(g)+tau(2g)) Jahn-Teller coupling problem (T(g) = (2)T(2g), (3)T(1g))). A procedure is proposed to give access to all vibronic coupling parameters from geometry optimization with density functional theory (DFT) and the energies of a restricted number of Slater determinants, derived from electron replacements within the t(2g)(1,5) or t(2g)(2,4) ground-state electronic configurations. The results show that coupling to the tau(2g) bending mode is dominant and leads to a stabilization of D(3d) structures (absolute minima on the ground-state potential energy surface) for all complexes considered, except for [Ti(CN)(6)](3-), where the minimum is of D(4h) symmetry. The Jahn-Teller stabilization energies for the D3d minima are found to increase in the order of increasing CN-M pi back-donation (Ti(III) < V(III) < Mn(III) < Fe(III) < Mn(II) < Cr(II)). With the angular overlap model and bonding parameters derived from angular distortions, which correspond to the stable D(3d) minima, the effect of configuration interaction and spin-orbit coupling on the ground-state potential energy surface is explored. This approach is used to correlate Jahn-Teller distortion parameters with structures from X-ray diffraction data. Jahn-Teller coupling to trigonal modes is also used to reinterpret the anisotropy of magnetic susceptibilities and g tensors of [Fe(CN)(6)](3-), and the (3)T(1g) ground-state splitting of [Mn(CN)(6)](3-), deduced from near-IR spectra. The implications of the pseudo Jahn-Teller coupling due to t(2g)-e(g) orbital mixing via

  10. Jahn-Teller versus quantum effects in the spin-orbital material LuVO3

    DOE PAGES

    Skoulatos, M.; Toth, S.; Roessli, B.; Enderle, M.; Habicht, K.; Sheptyakov, D.; Cervellino, A.; Freeman, P. G.; Reehuis, M.; Stunault, A.; et al

    2015-04-13

    In this article, we report on combined neutron and resonant x-ray scattering results, identifying the nature of the spin-orbital ground state and magnetic excitations in LuVO3 as driven by the orbital parameter. In particular, we distinguish between models based on orbital-Peierls dimerization, taken as a signature of quantum effects in orbitals, and Jahn-Teller distortions, in favor of the latter. In order to solve this long-standing puzzle, polarized neutron beams were employed as a prerequisite in order to solve details of the magnetic structure, which allowed quantitative intensity analysis of extended magnetic-excitation data sets. The results of this detailed study enabledmore » us to draw definite conclusions about the classical versus quantum behavior of orbitals in this system and to discard the previous claims about quantum effects dominating the orbital physics of LuVO3 and similar systems.« less

  11. (Bis(terpyridine))copper(II) Tetraphenylborate: A Complex Example for the Jahn-Teller Effect.

    PubMed

    Meyer, Andreas; Schnakenburg, Gregor; Glaum, Robert; Schiemann, Olav

    2015-09-01

    The surprisingly complicated crystal structure of (bis(terpyridine))copper(II) tetraphenylborate [Cu(tpy)2](BPh4)2 (tpy = 2,2':6',2″-terpyridine) consists of six crystallographically independent [Cu(tpy)2](2+) complexes. At ambient temperature, five out of six [Cu(II)N6] chromophores appear to be compressed octahedra, while at 100 K, four exhibit elongated and only two compressed octahedral geometry. Temperature dependent single crystal UV/vis (100, 298 K) and EPR measurements (20, 100, 298 K) as well as AOM calculations suggest that the octahedra which show apparently compressed octahedral geometry (XRD) result from dynamic Jahn-Teller behavior of elongated octahedra [Cu(II)N6]. The detailed correlation of structural and spectroscopic data allows an understanding of the strongly solvent-dependent structures of the [Cu(tpy)2](2+) complex in solution. PMID:26275138

  12. The effect of band Jahn-Teller distortion on the magnetoresistivity of manganites: a model study.

    PubMed

    Rout, G C; Panda, Saswati; Behera, S N

    2011-10-01

    We present a model study of magnetoresistance through the interplay of magnetisation, structural distortion and external magnetic field for the manganite systems. The manganite system is described by the Hamiltonian which consists of the s-d type double exchange interaction, Heisenberg spin-spin interaction among the core electrons, and the static and dynamic band Jahn-Teller (JT) interaction in the e(g) band. The relaxation time of the e(g) electron is found from the imaginary part of the Green's function using the total Hamiltonian consisting of the interactions due to the electron and phonon. The calculated resistivity exhibits a peak in the pure JT distorted insulating phase separating the low temperature metallic ferromagnetic phase and the high temperature paramagnetic phase. The resistivity is suppressed with the increase of the external magnetic field. The e(g) electron band splitting and its effect on magnetoresistivity is reported here.

  13. Paramagnetism of caesium titanium alum and the Jahn-Teller interaction

    NASA Astrophysics Data System (ADS)

    Tregenna-Piggott, Philip L. W.; O'Brien, Mary C. M.; Pilbrow, John R.; Güdel, Hans U.; Best, Stephen P.; Noble, Chris

    1997-11-01

    The magnetic properties of [Ti(OH2)6]3+ within CsTi(SO4)2ṡ12H2O and doped into a range of isostructural diamagnetic lattices, has been reinvestigated using electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. Whereas previous attempts to rationalise the variation of the magnetic susceptibility with temperature have employed a 2Ag trigonal ground term, the data are interpreted within a framework used to describe other tervalent hexa-aqua cations whereby the trigonal field is considerable and of a sign such that the eg orbital set is lower lying, resulting in a 2Eg trigonal ground term. The magnetic susceptibility is then modeled using a novel approach based on the numerical diagonalisation of the vibronic Hamiltonian. Hence, it is shown that the singular magnetic properties of CsTi(SO4)2ṡ12H2O arise from a delicate balance between spin-orbit and Jahn-Teller coupling. Particular use is made of isotopic substitution to obtain information regarding the nature of the vibronic interaction. An excellent fit to both the susceptibility data and ground state g values is provided by a model in which the Jahn-Teller interaction is dominated by coupling to phonon modes involving librational modes of sulphate and water coordinated to titanium(III). This interpretation is further supported by Raman data on the corresponding compounds. This analysis provides the first satisfactory explanation of the magnetic properties of [Ti(OH2)6]3+ in the β-alum lattice.

  14. Quantifying the Effects of Higher Order Jahn-Teller Coupling Terms on a Quadratic Jahn-Teller Hamiltonian in the Case of NO_3 and Li_3.

    NASA Astrophysics Data System (ADS)

    Tran, Henry; Stanton, John F.; Miller, Terry A.

    2016-06-01

    The Jahn-Teller (JT) effect represents an enormous complication in the understanding of many molecules. We have been able to assign ˜20 vibronic bands in the tilde{A}^2E'' ← tilde{X}^2A_2' transition of NO_3 and determine the linear and quadratic JT coupling terms for ν_3 and ν_4, indicating strong and weak JT coupling along these modes respectively. It was found that the experimental results quantitatively disagree with ones determined from a vibronic Hamiltonian based on high-level ab-initio theory. Typical analyses of experimental data use the quadratic JT Hamiltonian because limited measured levels tend to allow fitting only to coupling terms up to quadratic JT coupling. Hence, these analyses may neglect key contributions from cubic and quartic terms. To quantify this limitation, we have fit artificial spectra calculated with up to fourth order terms in the potential using a quadratic JT Hamiltonian and analyzed the results. The parameters chosen for this analysis are determined from ab-initio potentials for the tilde{A} state of NO_3 and tilde{X} state of Li_3 to gain further insight on these molecules. Our initial results concerning the limitations of the quadratic JT Hamiltonian will be presented. T. Codd, M.-W. Chen, M. Roudjane, J. F. Stanton, and T. A. Miller. Jet cooled cavity ringdown spectroscopy of the tilde{A}^2E'' ← tilde{X}^2A'_2 Transition of the NO_3 Radical. J. Chem. Phys., 142:184305, 2015

  15. Deviations from Born-Oppenheimer theory in structural chemistry: Jahn-Teller, pseudo Jahn-Teller, and hidden pseudo Jahn-Teller effects in C3H3 and C3H3(-).

    PubMed

    Kayi, H; Garcia-Fernandez, P; Bersuker, I B; Boggs, J E

    2013-09-12

    The electronic structure and vibronic coupling in two similar molecular systems, radical C3H3 and anion C3H3(-), in ground and excited states, are investigated in detail to show how their equilibrium structures, in deviation from the Born-Oppenheimer approximation, originate from the vibronic mixing of at least two electronic states, producing the Jahn-Teller (JT), pseudo JT (PJT), and hidden PJT effects. Starting with the high-symmetry geometry D3h of C3H3, we evaluated its 2-fold degenerate ground electronic state (2)E″ and two lowest excited states (2)A1' and (2)E' and found that all of them contribute to the distortion of the ground state via the JT vibronic coupling problem E″ ⊗ e' and two PJT problems (E″ + A1') ⊗ e″ and (E″ + E') ⊗ (a2″ + e″); all the three active normal modes e'(1335 cm(-1)), e″(1030 cm(-1)), and a2″(778 cm(-1)) are imaginary, meaning that all the three vibronic couplings are sufficiently strong to cause instability, albeit in different directions. The first of them, the ground state JT effect, enhances one of the C-C bonds (toward an ethylenic form with C2v symmetry), while the two PJT effects produce, respectively, cis (a2″ toward C3v symmetry) and trans (e″) puckering of the hydrogen atoms. As a result, C3H3 has two coexisting equilibrium configurations with different geometry. In the C3H3(-) anion, the ground electronic state in D3h symmetry is an orbitally nondegenerate spin triplet (3)A2' with a group of close in energy singlet and triplet excited states in the order of (1)A1', (3)A1″, (1)E″, (3)E″, and (1)E'. This shows that two PJT couplings, ((3)A2' + (3)A1″) ⊗ a2″ and ((3)A2' + (3)E″) ⊗ e″, may influence the geometry of the equilibrium structure in the (3)A2' state. Indeed, both vibrational modes, a2″(1034 cm(-1)) and e″(1284 cm(-1)), are imaginary in this state. Similar to the radical case, they produce, respectively, cis (a2″) and trans (e″) puckering of the hydrogen atoms

  16. Jahn-Teller, polarity, and insulator-to-metal transition in BiMnO3 at high pressure.

    PubMed

    Guennou, Mael; Bouvier, Pierre; Toulemonde, Pierre; Darie, Céline; Goujon, Céline; Bordet, Pierre; Hanfland, Michael; Kreisel, Jens

    2014-02-21

    The interaction of coexisting structural instabilities in multiferroic materials gives rise to intriguing coupling phenomena and extraordinarily rich phase diagrams, both in bulk materials and strained thin films. Here we investigate the multiferroic BiMnO3 with its peculiar 6s2 electrons and four interacting mechanisms: electric polarity, octahedra tilts, magnetism, and cooperative Jahn-Teller distortion. We have probed structural transitions under high pressure by synchrotron x-ray diffraction and Raman spectroscopy up to 60 GPa. We show that BiMnO3 displays under pressure a rich sequence of five phases with a great variety of structures and properties, including a metallic phase above 53 GPa and, between 37 and 53 GPa, a strongly elongated monoclinic phase that allows ferroelectricity, which contradicts the traditional expectation that ferroelectricity vanishes under pressure. Between 7 and 37 GPa, the Pnma structure remains remarkably stable but shows a reduction of the Jahn-Teller distortion in a way that differs from the behavior observed in the archetypal orthorhombic Jahn-Teller distorted perovskite LaMnO3. PMID:24579610

  17. Collective versus local Jahn-Teller distortion in Ba3CuSb2O9 : Raman scattering study

    NASA Astrophysics Data System (ADS)

    Drichko, Natalia; Broholm, Collin; Kimura, K.; Ishii, R.; Nakasutji, Satoru

    2016-05-01

    We present temperature dependent Raman spectra of single crystals of two different samples of the spin-orbital liquid candidate Ba3CuSb2O9 . The "hexagonal" sample is known to show no magnetic order down to low temperatures, while the "orthorhombic" sample undergoes a crossover into an orthorhombic crystal structure below TJT of approximately 200 K and shows spin freezing at 110 μ K . Our Raman scattering results demonstrate a strong influence of disorder in both samples. The frequencies of stretching vibrations of oxygens associated with CuSbO9 octahedra indicate a difference in the crystal structure between the hexagonal and orthorhombic samples even at room temperature. On cooling below TJT we observe new bands in the spectra of the orthorhombic sample due to a lowering of symmetry of the unit cell and a collective Jahn-Teller distortion. The spectra of the hexagonal sample show that average hexagonal symmetry is maintained at least down to 20 K. An analysis of the band shape of stretching oxygen vibrations suggests a weak disordered local Jahn-Teller distortion in the hexagonal sample of Ba3CuSb2O9 which increases slightly on cooling. This Jahn-Teller distortion is either static or dynamic with a frequency below 1.5 THz.

  18. The role of the Jahn-Teller coupling in dissociative recombination of H3O+ and H ions

    NASA Astrophysics Data System (ADS)

    Douguet, N.; Orel, A.; Mikhailov, I.; Schneider, I. F.; Greene, C. H.; Kokoouline, V.

    2011-07-01

    We discuss the importance of the non Born-Oppenheimer Jahn-Teller coupling in the dissociative recombination of H3O+ and H ions with low energy electrons. The coupling is known to be important for dissociative recombination of H, for which detailed and simplified theoretical models have been previously developed. In this study we discuss how the detailed theoretical model reproduces individual resonances in the experimental spectrum of H. We present a simplified theoretical model of the dissociative recombination of H3O+. Similarly to H, we consider the Jahn-Teller coupling as a key factor responsible for the capture of the electron into a Rydberg state associated with excited vibrational levels of the ion. We use a simplified Jahn-Teller model for highly symmetrical ions (not only for H3O+ and H) and adopt the normal mode approximation for the vibrational states of H3O+. Using the multi-channel quantum defect formalism and accurate ab initio calculations, we derive the cross sections for electron capture by the ion that is initially in the ground vibrational level. In our approximation, once the electron is captured by the ion, the autoionization probability is neglected compared to the predissociation probability. This allows us to evaluate the cross section for the dissociative recombination of H3O+ using just a few parameters obtained from ab initio calculation. The total cross section obtained is in good agreement with data from storage ring experiments.

  19. Geometry, Electronic Structure, and Pseudo Jahn-Teller Effect in Tetrasilacyclobutadiene Analogues

    PubMed Central

    Liu, Yang; Wang, Ya; Bersuker, Isaac B.

    2016-01-01

    We revealed the origin of the structural features of a series of tetrasilacyclobutadiene analogues based on a detailed study of their electronic structure and the pseudo Jahn-Teller effect (PJTE). Starting with the D4h symmetry of the Si4R4 system with a square four-membered silicon ring as a reference geometry, and employing ab initio calculations of energy profiles along lower-symmetry nuclear displacements in the ground and several excited states, we show that the ground-state boat-like and chair-like equilibrium configurations are produced by the PJT interaction with appropriate excited sates. For Si4F4 a full two-mode b1g−b2g adiabatic potential energy surface is calculated showing explicitly the way of transformation from the unstable D4h geometry to the two equilibrium C2h configurations via the D2h saddle point. The PJTE origin of these structural features is confirmed also by estimates of the vibronic coupling parameters. For Si4R4 with large substituents the origin of their structure is revealed by analyzing the PJT interaction between the frontier molecular orbitals. The preferred chair-like structures of Si4R4 analogues with amido substituents, and heavier germanium-containing systems Ge4R4 (potential precursors for semiconducting materials) are predicted. PMID:26996445

  20. Dynamic Jahn-Teller Coupling, Anharmonic Oxygen Vibrations and HIGH-Tc Superconductivity in Oxides

    NASA Astrophysics Data System (ADS)

    Johnson, K. H.; Clougherty, D. P.; McHenry, M. E.

    A universal dynamic Jahn-Teller (DJT) mechanism for superconductivity and its applications to CuO and BaBiO3 high-Tc oxides are reviewed. Dynamical interconversion between the shallow "double-well" potentials of degenerate delocalized oxygen-oxygen "pπ-bonds" at the Fermi energy (EF) induces anharmonic oxygen vibrations, lattice-electron coupling, and Cooper pairing. This mechanism yields high Tc's and small-to-vanishing isotope shifts for cuprates, where O(pπ)-O(pπ) bond overlap at EF is promoted by Cu(dπ*)-O(pπ) hybridization. It yields lower Tc's and larger isotope shifts for BaBiO3's, where O(pπ)-O(pπ) overlap is small. For vanishing bond overlap at EF, DJT coupling reduces to harmonic phonon coupling in BCS theory. Simple formulae for calculating Tc and isotope shifts for any superconductor from the "real-space" chemical bonding at EF are presented, yielding (Tc)max ≈ 230 K.

  1. Geometry, Electronic Structure, and Pseudo Jahn-Teller Effect in Tetrasilacyclobutadiene Analogues

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Wang, Ya; Bersuker, Isaac B.

    2016-03-01

    We revealed the origin of the structural features of a series of tetrasilacyclobutadiene analogues based on a detailed study of their electronic structure and the pseudo Jahn-Teller effect (PJTE). Starting with the D4h symmetry of the Si4R4 system with a square four-membered silicon ring as a reference geometry, and employing ab initio calculations of energy profiles along lower-symmetry nuclear displacements in the ground and several excited states, we show that the ground-state boat-like and chair-like equilibrium configurations are produced by the PJT interaction with appropriate excited sates. For Si4F4 a full two-mode b1g‑b2g adiabatic potential energy surface is calculated showing explicitly the way of transformation from the unstable D4h geometry to the two equilibrium C2h configurations via the D2h saddle point. The PJTE origin of these structural features is confirmed also by estimates of the vibronic coupling parameters. For Si4R4 with large substituents the origin of their structure is revealed by analyzing the PJT interaction between the frontier molecular orbitals. The preferred chair-like structures of Si4R4 analogues with amido substituents, and heavier germanium-containing systems Ge4R4 (potential precursors for semiconducting materials) are predicted.

  2. Symmetry-adapted excited states for the T1u⊗hg Jahn-Teller system

    NASA Astrophysics Data System (ADS)

    Qiu, Q. C.; Dunn, J. L.; Bates, C. A.

    2001-08-01

    Jahn-Teller (JT) systems typically contain a set of equivalent-energy wells in the lowest adiabatic potential-energy surface (APES). Quantum-mechanical tunneling between these wells (the dynamic JT effect) must be allowed for by taking appropriate symmetrized combinations of oscillator-type states associated with the wells. It is important to be able to describe the excited states of such systems for a number of reasons. One particular reason is that they are required for the calculation of second-order vibronic reduction factors, which in turn are useful for modeling experimental data using effective Hamiltonians. In this paper, projection-operator techniques are used to obtain general expressions for the symmetry-adapted excited states of the icosahedral T1u⊗hg JT system for the case of D5d minima in the APES. Analytical expressions for the states and their energies for one-phonon excitation are given explicitly. The energies of a selection of states with two-phonon excitations are also obtained and plotted. The results obtained in this paper are applicable to the C-60 molecule.

  3. Aqua Ions. 2. Structural manifestations of the Jahn-Teller effect in the beta-alums.

    PubMed

    Tregenna-Piggott, Philip L W; Andres, Hans-Peter; McIntyre, Garry J; Best, Stephen P; Wilson, Chick C; Cowan, John A

    2003-02-24

    Variable-temperature single-crystal neutron diffraction structures of the alums CsM(III)(SO(4))(2).12D(2)O, where M(III) = Ti, V, Mn, and Ga, are reported. Structural differences are highlighted by the titanium and manganese alums, which undergo cubic (Pathremacr;) to orthorhombic (Pbca) phase transitions at approximately 13 and approximately 156 K, respectively. The structural instability exhibited by these salts is interpreted as arising from cooperative Jahn-Teller interactions, and these measurements characterize the structural changes that result from the coupling between the electronic and vibrational states. Although the symmetry changes associated with the phase transformations are analogous for the Ti and Mn alums, the low-temperature geometries of the tervalent hexaaqua cations are markedly different. Whereas the MnO(6) framework is subject to a pronounced tetragonal elongation, changes in the Ti-O bond lengths are very modest; but significant changes in the O-Ti-O bond angles and in the disposition of the coordinated water molecules are identified. The large differences in the transition temperatures and in the low-temperature stereochemistries of the [Ti(OD(2))(6)](3+) and [Mn(OD(2))(6)](3+) cations are related to the sensitivity of the energies of the t(2g) (O(h)) and e(g) (O(h)) orbitals to the various asymmetric vibrations of the hexaaqua complex. PMID:12588175

  4. Jahn-Teller Interactions in the Dissociative Recombination of H3^+

    NASA Astrophysics Data System (ADS)

    Pratt, Stephen; Jungen, Christian

    2009-05-01

    A simple analytical approach is presented to describe the dissociative recombination (DR) of an electron with H3^+ and its isotopomers. The principal assumption is that resonant capture mediated by the Jahn-Teller interaction dominates the cross section. The only input required comes from spectroscopic data on the 3pE' Rydberg state of H3 and the ν2 vibrational frequencies of H3^+ and its isotopomers. The approach provides an independent prediction of the low-energy DR cross sections and rates, and is in good agreement with the latest experimental^1 and theoretical^2 determinations. Work at Argonne was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under contract No. DE-AC02-06CH11357. 1. K. Kreckel et al., Phys. Rev. Lett. 95, 263201 (2005); see also, B. J. McCall et al., Nature 422, 500 (2003), and B. J. McCall et al., Phys. Rev. A 70, 052716 (2004). 2. S. Fonseca dos Santos, V. Kokoouline, and C. H. Greene, J. Chem. Phys. 127, 124309 (2007).

  5. Ultrasonic investigations of the Jahn-Teller effect in a ZnSe :Fe2+ crystal

    NASA Astrophysics Data System (ADS)

    Gudkov, V. V.; Lonchakov, A. T.; Zhevstovskikh, I. V.; Sokolov, V. I.; Surikov, V. T.

    2009-01-01

    The temperature dependence of the absorption and velocity of transverse ultrasonic waves propagating in the [110] direction in a ZnSe :Fe2+ crystal with the iron impurity of n=2.2×1019cm-3 is investigated in the temperature interval 1.4-100K at a frequency of 53MHz. For the slow transverse mode an absorption peak at 7.3K and a decrease of the phase velocity below 40K are found, while no such features are observed for the fast mode. The anomalies are interpreted as manifestations of the Jahn-Teller effect. The softening of the elastic modulus (C11-C12)/2 indicates that the local distortions in ZnSe :Fe2+ are tetragonal. Under the assumption that the absorption maximum is of a relaxational nature, the temperature dependence of the relaxation time is recovered from the data, and the values of the potential barrier height and vibronic frequency are obtained.

  6. Symmetry rules and strain/order-parameter relationships for coupling between octahedral tilting and cooperative Jahn-Teller transitions in ABX3 perovskites. II. Application.

    PubMed

    Carpenter, Michael A; Howard, Christopher J

    2009-04-01

    The structural evolution of selected perovskites containing Jahn-Teller cations has been investigated in the light of a formal analysis of symmetry hierarchies for phase transitions driven by octahedral tilting and Jahn-Teller cooperative distortions. General expressions derived from the strain/order-parameter coupling relationships allowed by symmetry are combined with observed changes in lattice parameters to reveal details of order-parameter evolution and coupling. LuVO3, YbVO3, YVO3 and CeVO3 are representative of systems which develop Jahn-Teller ordering schemes associated with irreducible representations M2+ and R3+ of the space group Pm3m. Tilting of their octahedra is associated with M3+ and R4+. The Pnma (M3+ + R4+ tilting) <--> P2(1)/a (M3+ + R4+ tilting, R3+ Jahn-Teller order) transition below room temperature is close to second order in character. Shear strains which depend primarily on tilt angles show little variation, implying that there is only weak coupling between the tilting and Jahn-Teller order parameters. The subsequent P2(1)/a <--> Pnma (M3+ + R4+ tilting, M2+ Jahn-Teller order) is first order in character, and involves either a reduction in the R4+ tilt angle or a change in the strength of tilt/Jahn-Teller order-parameter coupling. In LaMnO3, the isosymmetric Pnma (M3+ + R4+ tilting) <--> Pnma (M3+ + R4+ tilting, M2+ Jahn-Teller order) transition can be described in terms of a classical first-order transition conforming to a 246 Landau expansion with negative fourth-order coefficients. Strain evolution in Ba-doped samples suggests that the transition becomes second order in character and reveals a new strain relaxation mechanism in LaMnO3 which might be understood in terms of local strain heterogeneities due to the disordering of distorted MnO6 octahedra. Transitions in PrAlO3 and La(0.5)Ba(0.5)CoO3 illustrate the transformation behaviour of systems in which the Jahn-Teller ordering scheme is associated with the irreducible representation

  7. A Local Approach to Solid State Problems: Pseudo Jahn-Teller origin of Ferroelectricity and Multiferroicity

    NASA Astrophysics Data System (ADS)

    Bersuker, I. B.

    2013-04-01

    This is a partially review paper in which, in continuation of previous work, it is shown that in perovskite crystals of ABO3 type the spontaneous polarization is triggered by local vibronic interactions, the pseudo Jahn-Teller effect (PJTE). The driving force of the latter is added covalency by distortion, which is essentially of local (chemical) origin. The local origin of polar instability in crystals is confirmed by the theorem of structural instability proved earlier. For crystals of BaTiO3 type local PJT interactions of the metal ion with the oxygen environment results in a peculiar adiabatic potential energy surface (APES) which has eight trigonal [111] type minima, twelve [110] type saddle points between them, six higher in energy [100] type saddle points at the top of the barrier connecting four minima, and a maximum at the cubic symmetry. The temperature dependence of the free energy with this potential explains the origin of all the four phases in such crystals; only the lowest rhombohedral phase is fully ordered, the other two ones at higher temperatures are partially disordered, and the paraelectric phase is fully (three-dimensionally) disordered. For BaTiO3 this picture is confirmed by numerical estimates and ab initio DFT calculations. An important further development of this theory was reached recently by showing that not only B ions with electronic d0 configurations are subject to the PJTE instability to produce ferroelectricity in perovskite crystals ("the d0 mystery"), but some other specific dn configurations with unpaired electrons may be dipolar active too, the crystal being thus both magnetic and ferroelectric (multiferroic), and the necessary conditions for such multiferroicity are formulated for the whole d0-dn variety of perovskites. Moreover, the condition of multiferroicity was shown to depend also on the spin state, high-spin or low-spin, which in conditions of spin crossover leads to a magnetic-ferroelectric crossover that can be

  8. Percolation features of cooperative Jahn-Teller systems: Ising EFT framework

    NASA Astrophysics Data System (ADS)

    Moujaes, Elie A.; Abou Ghantous, Michel

    2014-08-01

    Elastic exchange between two nearest Jahn-Teller (JT) centers in two or three dimensional dense crystals, can give an ordered macroscopic distortion known as cooperative JT effect (CJTE). A very diluted JT crystal does not show this effect. In the dynamic JT effect (DJTE), tunneling between different equivalent distorted wells has a pronounced influence on the CJTE. We investigate this phenomenon using a progressive increase in the concentration of these centers in the JT crystals, based on a bond percolation vector spin analogy technique within the framework of effective field theory (EFT). Mean field theory (MFT) was extensively used in previous studies of CJTE; however it neither includes correlation between JT centers in the lattice due to the complexity of the distortion field in the crystal nor the effect of tunneling between wells. We resort to an alternative procedure, by describing a JT center as a pseudo-spin vector , induced to represent the degenerate JT-distorted states, where two nearest JT centers interact via an elastic exchange described by an Ising type spin interaction. The DJTE is considered to be similar to an elastic transverse field term in the Hamiltonian portraying the effect of tunneling between equivalent wells in the adiabatic potential energy surface (APES). We will be particularly discussing S = 1, S = 3/2 and S = 5/2 spin cases, where 2 S + 1 wells in the APES are present and what JT systems they actually represent, with a percolative mechanism applied to the interactions between different JT centers. The different lattices are distinguished by their coordination numbers. Strong tunneling effects can suppress the CJTE and lead to a new state of criticality. Generalizations to higher spin systems will be obtained using a scaling technique. For the relevant distortions, we determine single site correlations, the macroscopic average distortion describing a structural phase transition and the elastic isothermal susceptibility as a

  9. Further studies of anisotropy in the T1u⊗hg Jahn-Teller system

    NASA Astrophysics Data System (ADS)

    Qiu, Q. C.; Dunn, J. L.; Bates, C. A.; Liu, Y. M.

    1998-08-01

    In the linear T1u⊗hg Jahn-Teller system, the adiabatic potential energy surface (APES) is a trough. However, in real systems, quadratic coupling will be present, which warps the APES to give wells of either D3d or D5d symmetry. The degeneracy of the vibrations within the wells is also lifted. This anisotropy has recently been investigated in the T1u⊗hg system, and expressions for the frequencies in both types of wells obtained in the strong coupling limit using the method of Öpik and Pryce. A scale transformation procedure was then used to incorporate these results into expressions for the states in the wells and their associated energies. However, this calculation did not allow for second-order perturbation effects and is only valid in the strong coupling limit. In this paper, a revised scale transformation procedure is developed for the D5d wells, which allows expressions for the anisotropic frequencies to be obtained without employing the Öpik and Pryce procedure. An expression is obtained for the phonon overlap that is correct to second-order and is not restricted to the strong coupling limit. Results are then obtained for the ground-state energies and inversion splitting. For D3d wells, the previous results are improved by application of a modified scale transformation procedure and overlaps correct to second order obtained. The results obtained in this paper are of interest in studies of the C-60 anion state of the C60 molecule, which is known to occupy a T1u orbital ground state.

  10. Pseudo Jahn-Teller origin of bending instability of triatomic molecules

    NASA Astrophysics Data System (ADS)

    Kayi, Hakan; Bersuker, Isaac B.; Boggs, James E.

    2012-09-01

    For several decades the bending of linear molecules in degenerate states has been assumed to be due to the Renner-Teller effect (RTE), whereas the pseudo Jahn-Teller effect (PJTE) has been completely ignored. But in a recent publication of ab initio calculations performed on a series of triatomics it was shown that the contribution of the PJTE to their bending instability is much larger than that of the RTE. This raised the question of whether the finding of the essential role of the PJTE in the instability is a particular case for the molecules studied or a general trend. The problem is important not only for rationalizing the experimental observations and ab initio calculations of such systems, but also for a correct interpretation of their spectra, as the PJTE, by admixing excited states of different symmetry (opposite parity) to the ground one, influences significantly their spectroscopic properties. To contribute to the solution of this problem we performed ab initio calculations of electronic structure and energy profiles of a group of triatomic systems including CH2+,HO,SiH2+,PH, and HNF which have a Π twofold degenerate state in the linear configuration, but are bent in the equilibrium geometry. For them we formulated the combined RTE and PJTE problem and, by calculating ab initio the Renner-Teller vibronic coupling constant g and estimating the other parameters by fitting the PJTE equations to the ab initio calculated energy profiles, we show that in all the cases under consideration the PJTE contribution is significantly larger than that of the RTE. The parameters of the equilibrium geometry and electronic structure of these systems obtained in our calculations are in good agreement with those reported in other publications.

  11. Ultrasonic evaluation of the Jahn-Teller effect parameters. Application to ZnSe:Cr2 +

    NASA Astrophysics Data System (ADS)

    Gudkov, V. V.; Bersuker, I. B.; Zhevstovskikh, I. V.; Korostelin, Yu V.; Landman, A. I.

    2011-03-01

    A method is constructed that uses ultrasonic experiments to evaluate the parameters of the Jahn-Teller (JT) effect in impurity centers in crystals. The method is based on measurements of temperature dependent attenuation and phase velocity and does not require assumptions about mechanisms of relaxation. The results are illustrated by measurements performed on the impurity system ZnSe:Cr2 + , in which the Cr2 + ion has a threefold degenerate T term in the ground state, subject to the T\\otimes (e+t_2) JT problem. Ultrasound propagation anomalies show that the main JT distortions of the tetrahedral environment of the Cr2 + ion are of tetragonal E type and hence the lowest branch of the adiabatic potential energy surface (APES) is formed in accordance with the T\\otimes e problem. With dopant concentration 3.8 × 1018 cm - 3 the modulus of the constant of linear vibronic coupling to tetragonal E type vibrations is determined by two independent experiments: |FE| = 5.49 × 10 - 5 dyn revealed from attenuation measurements, while a slightly different value |FE| = 5.57 × 10 - 5 dyn emerges from phase velocity measurements. Contributions of other active vibronic modes to the elastic modulus Cl = (C11 + C12 + 2C44)/2 are analyzed and it is shown that the influence of the totally symmetric mode is negligible. Using additional information about this system obtained from independent sources, we also estimated the primary force constant in the E direction (KE≈(1.4-4.2) × 104 dyn cm - 1) and orthorhombic and trigonal saddle points of the APES in the five-dimensional space of the tetragonal and trigonal coordinates, their stabilization energies being EJTO≈81-450 cm - 1 and EJTT≈48-417 cm - 1, respectively (the variations of the KE, EJTO and EJTT values are due to different literature data for EJTE). With these data the APES of the JT linear T\\otimes (e+t_2) problem for the Cr2 + ion in the ZnSe:Cr2 + system is revealed.

  12. Jahn-Teller coupling and fragmentation after core-shell excitation in CF{sub 4} investigated by partial-ion-yield spectroscopy

    SciTech Connect

    Guillemin, Renaud; Stolte, Wayne C.; Lindle, Dennis W.; Piancastelli, Maria Novella

    2010-10-15

    We investigate fragmentation processes induced by core-level photoexcitation in CF{sub 4} at both the carbon and fluorine K edges by means of partial-ion-yield spectroscopy. The molecule CF{sub 4} is a textbook example of systems in which Jahn-Teller coupling strongly manifests itself in the photoabsorption spectrum. Spectral features related to Jahn-Teller and quasi-Jahn-Teller splitting are observed, and important differences in the fragmentation pathways are revealed depending on the symmetries of the core-excited states. We interpret these experimental observations on the grounds of symmetry lowering from the T{sub d} to the C{sub 3v} point group as well as preferential orientation with respect to the polarization vector of the incident radiation.

  13. Teaching the Jahn-Teller Theorem: A Simple Exercise That Illustrates How the Magnitude of Distortion Depends on the Number of Electrons and Their Occupation of the Degenerate Energy Level

    ERIC Educational Resources Information Center

    Johansson, Adam Johannes

    2013-01-01

    Teaching the Jahn-Teller theorem offers several challenges. For many students, the first encounter comes in coordination chemistry, which can be difficult due to the already complicated nature of transition-metal complexes. Moreover, a deep understanding of the Jahn-Teller theorem requires that one is well acquainted with quantum mechanics and…

  14. Using Extended Huckel Theory as a Platform to Introduce Jahn-Teller Distortion: The Spontaneous Distortion of 1,3,5,7-Cyclooctatetraene from a Perfect Octagon

    ERIC Educational Resources Information Center

    Sohlberg, Karl; Liu, Xiang

    2013-01-01

    Herein, a slightly enhanced version of extended Huckel molecular orbital theory is applied to demonstrate the spontaneous distortion of 1,3,5,7-cyclooctatetraene from a perfect octagon, a consequence of the Jahn-Teller effect. The exercise is accessible to students who have been introduced to basic quantum mechanics and extended Huckel molecular…

  15. Jahn-Teller versus quantum effects in the spin-orbital material LuVO3

    SciTech Connect

    Skoulatos, M.; Toth, S.; Roessli, B.; Enderle, M.; Habicht, K.; Sheptyakov, D.; Cervellino, A.; Freeman, P. G.; Reehuis, M.; Stunault, A.; McIntyre, G. J.; Tung, L. D.; Marjerrison, C.; Pomjakushina, E.; Brown, P. J.; Khomskii, D. I.; Rüegg, Ch.; Kreyssig, A.; Goldman, A. I.; Goff, J. P.

    2015-04-13

    In this article, we report on combined neutron and resonant x-ray scattering results, identifying the nature of the spin-orbital ground state and magnetic excitations in LuVO3 as driven by the orbital parameter. In particular, we distinguish between models based on orbital-Peierls dimerization, taken as a signature of quantum effects in orbitals, and Jahn-Teller distortions, in favor of the latter. In order to solve this long-standing puzzle, polarized neutron beams were employed as a prerequisite in order to solve details of the magnetic structure, which allowed quantitative intensity analysis of extended magnetic-excitation data sets. The results of this detailed study enabled us to draw definite conclusions about the classical versus quantum behavior of orbitals in this system and to discard the previous claims about quantum effects dominating the orbital physics of LuVO3 and similar systems.

  16. Breaking the Symmetry in Jahn-Teller Active Molecules by Asymmetric Isotopic Substitution: Splitting the Zero-Point Vibronic Level.

    NASA Astrophysics Data System (ADS)

    Melnik, Dmitry G.; Liu, Jinjun; Miller, Terry A.; Curl, Robert F.

    2011-06-01

    Analysis and understanding of the vibronic spectra of Jahn-Teller active molecules have been challenging tasks due to the complex interaction patterns between vibronic levels even if the density of vibronic states is not too high. An example of a spectral feature that draws attention is the splitting of the ground vibronic level, as reported for degenerate electronic states of asymmetrically deuterated C_6H_6, C_5H_5, CH_4^+, and most recently, the methoxy isotopologues, CH_2DO and CHD_2O. Understanding such splittings plays a crucial role for the analysis of the vibronic spectra of these species. We have developed a simplified model emulating vibronic interactions involving a single doubly-degenerate vibrational mode and one totally symmetric mode in a degenerate electronic state. The extension of this model to more complex, realistic cases and comparison with experiment and quantum chemical calculations will also be presented.

  17. N-Terminal Peptide Sequence Repetition Influences the Kinetics of Backbone Fragmentation: A Manifestation of the Jahn-Teller Effect?

    NASA Astrophysics Data System (ADS)

    Good, David M.; Yang, Hongqian; Zubarev, Roman A.

    2013-11-01

    Analysis of large (>10,000 entries) databases consisting of high-resolution tandem mass spectra of peptide dications revealed with high statistical significance ( P < 1ṡ10-3) that peptides with non-identical first two N-terminal amino acids undergo cleavages of the second peptide bond at higher rates than repetitive sequences composed of the same amino acids (i.e., in general AB- and BA- bonds cleave more often than AA- and BB- bonds). This effect seems to depend upon the collisional energy, being stronger at lower energies. The phenomenon is likely to indicate the presence of the diketopiperazine structure for at least some b2 + ions. When consisting of two identical amino acids, these species should form through intermediates that have a symmetric geometry and, thus, must be subject to the Jahn-Teller effect that reduces the stability of such systems.

  18. The Jahn-Teller-effect on the cuprospinel (CuFe2O4) at high pressure

    NASA Astrophysics Data System (ADS)

    Kyono, A.; Nakamoto, Y.; Sakata, M.

    2013-12-01

    The crystal structure of cuprospinel CuFe2O4 was investigated to 4.6 GPa and ambient temperature with single-crystal x-ray diffraction techniques. The unit-cell parameter decreases continuously from 8.391 (3) Å to 8.351 (4) Å up to 2.7 GPa. A fit to the Birch-Murnaghan equation of state (EoS) based on the P-V data gives: K0 = 178 (3) GPa, K' = 4.0 (fixed), and V0 = 590.8 (1) Å3. The tetrahedral (T) site is filled with 42% Cu2+ cations and 58% Fe3+ cations, whereas, the octahedral (M) site is on the contrary with 42% Fe3+ cations and 58% Cu2+ cations. The polyhedra are compressed isotropically with pressure with their T-O and M-O bond distances decreasing from 1.917 (2) to 1.902 (9) Å and from 2.042 (1) to 2.035 (5) Å, respectively. A discontinuous volume change is observed between 2.7 GPa and 4.6 GPa. This change indicates a phase transition from a cubic (space group Fd-3m) to a tetragonal structure (space group I41/amd). After the phase transition, the two M-O bonds parallel to the c-axis are more shortened than the other four M-O bonds parallel to the ab plane. Consequently, the octahedral coordination changes a 'flattened' octahedral geometry along the c-axis. In the tetragonally distorted cuprospinel with a c/a ratio > 1 at ambient conditions, the octahedral geometry forms a 'stretched' environment with elongated two M-O bonds along the c-axis. With pressure, the anisotropic deformation of the octahedra leads to tetragonal compression of the unit cell (the c/a ratio < 1). On the other hand, the tetrahedral bond angles along the c-axis direction of the unit cell decreases slightly from 109.5° to 108.2 (7)°, which generates a 'stretched' tetrahedral geometry. It is proposed that the large Jahn-Teller effect at the octahedrally-coordinated Cu2+ cation becomes active with compression and gives rise to the angular distortion at the octahedral environments, which induces the cubic-to-tetragonal transition. A qualitative molecular orbital model is proposed to

  19. The effect of oxygen on the Jahn-Teller distortion and magnetization dynamics of Pr0.9Ca0.1MnO3 thin films.

    PubMed

    Majumdar, S; Huhtinen, H; Paturi, P; Palai, R

    2013-02-13

    We report on the effect of oxygen on the Jahn-Teller distortion and dynamic magnetic properties of low hole-doped Pr(0.9)Ca(0.1)MnO(3) thin films, using micro-Raman spectroscopy and the temperature dependent ac susceptibility, as a function of the frequency, dc field bias, and thermal cycles. The as-grown and vacuum annealed thin films show a high amount of magnetic frustration and inferior ferromagnetic ordering compared with the oxygen annealed thin films. It has been found that the amount of magnetic frustration in the film is interlinked with the Jahn-Teller distortion and domain wall dynamics. An attempt has been made to understand the origin and nature of the magnetic frustration.

  20. Remarks on the Phase Change of the Electronic Wave Function upon Going Once around a Jahn-Teller Conical Intersection in Vibrational Coordinate Space

    NASA Astrophysics Data System (ADS)

    Hougen, Jon T.

    2012-06-01

    In this talk we revisit, with pedagogical emphasis for high-resolution spectroscopists, some presently existing discussions of phase factors for fixed-nuclei electronic wavefunctions in the Jahn-Teller problem. We give explicit examples, for a symmetric pyramidal NH_3-like molecular shape, of perfectly reasonable variants of such electronic wavefunctions that do not transform into their negatives upon going once around the conical intersection (i.e., that do not exhibit a Berry phase change of -1), as well as an example calculation for the pseudo-rotational energy levels and wavefunctions near the bottom of a deep Jahn-Teller moat that does not make use of half-integral quantum numbers and that does not require abandoning ordinary C3v point group theory. Some cautionary remarks on drawing inappropriate conclusions from overly hasty Berry phase arguments will also be presented.

  1. Stability of Jahn-Teller distortion in LaMnO{sub 3} under pressure: An x-ray absorption study

    SciTech Connect

    Ramos, Aline Y.; Tolentino, Helio C. N.; Souza-Neto, Narcizo M.; Itie, Jean-Paul; Morales, Liliana; Caneiro, Alberto

    2007-02-01

    The local environment of manganese atoms in LaMnO{sub 3} under pressure up to 15.3 GPa has been studied by x-ray absorption spectroscopy. For pressures below 8 GPa, no change is detected within the MnO{sub 6} octahedra. Above this pressure a continuous reduction of the long Mn-O distance takes place, however, the octahedral distortion persists over the whole pressure range. At 15.3 GPa the average Jahn-Teller splitting of the distances is reduced by about one-third, indicating that a total removal of the local Jahn-Teller distortion would occur only for pressures around 30 GPa, where metallization is reported to take place. A hysteresis in the long distance reduction is observed down to ambient pressure, suggesting the coexistence of MnO{sub 6} distorted and undistorted units.

  2. Effect of lattice constant on pseudo Jahn-Teller polar distortion: Application to search for new multiferroic compounds

    NASA Astrophysics Data System (ADS)

    Song, Guang; Zhang, Weiyi

    2016-08-01

    By analog to Maxwell construction for the first-order phase transition, the pseudo Jahn-Teller polar distortion arises naturally once the local bond length of transition-metal oxygen octahedra is enhanced beyond the inflexion point of pair potential into the concave-down dominated region. This concept is applied to search for the new multiferroic compounds for which we specifically choose the (BaMnO3)1/(BaFeO3)1 superlattice as a candidate. The large Ba radius favors the polar distortion in a BaMnO3 layer, while the orbital-ordering-induced superexchange ferromagnetic coupling among Fe-Fe and double-exchange mediated ferromagnetic coupling among Fe-Mn ions stabilize the overall ferromagnetic insulator. A large magnetic moment of 7 μB per unit cell and electric polarization of 14.4 μ Ccm -2 are obtained. Our study offers an important insight for designing robust multiferroic compounds in the future.

  3. Effect of Jahn-Teller and Spin-Orbit Coupling on tilde{X}2E Infrared Spectrum of CH3O

    NASA Astrophysics Data System (ADS)

    Nagesh, Jayashree; Sibert, Edwin L. Sibert, III

    2011-06-01

    The tilde{X} state is doubly degenerate for the CH3O radical in its highest symmetry, for geometries belonging to C3v point group. The symmetry is lowered and the degeneracy removed by displacements along asymmetric modes of vibration due to Jahn-Teller coupling between electronic and vibrational degrees of freedom. Spin-orbit coupling plays an important role as well, by removing degeneracy at high symmetry and partically quenching Jahn-Teller coupling at displaced geometries or lower symmetries. In this work, we examine the effect of Jahn-Teller and Spin-Orbit coupling on the infrared spectrum of the tilde{X} surface. The selection rules combine symmetries of vibrational and electronic degrees of freedom and are less straightforward. We calculate a 9-D dipole moment surface for x, y and z components using ab initio methods. The components of the vibronic dipole moment operator, obey transformation properties belonging to different symmetry species of the C3v point group and we use group-theoretical arguments to impose constraints on the allowed terms in its functional form, similar to that used in construction of the vibronic Hamiltonian [1]. We construct the dipole moment surface solely using geometries of CS symmetry in a diabatic vibronic representation, using the two electronic states as diabatic basis. We fit only the x and z components for the two diabatic states and derive the rest of the dipole operator based on constraints imposed by three-fold symmetry. The merits and limitations of such an approach will be discussed. The vibronic states are calculated using a 9-D quartic force field as described in [1]., where both Jahn-Teller and spin-orbit coupling are included. The Davidson and Lanczos iterative methods are used to calculate the transitions between the ground vibronic to the higher levels in the infrared spectrum and the calculated transitions are compared to experiment. [1] Jayashree Nagesh and Edwin L. Sibert III it Phys. Chem. Chem. Phys.,12

  4. Pseudo Jahn-Teller coupling in trioxides XO3((0,1,-1)) with 22 and 23 valence electrons.

    PubMed

    Grein, Friedrich

    2013-05-28

    D3h and C2v geometries and energies, vertical excitation energies, as well as minimal energy paths as function of the O(1)(z)-X-O(2) angle α were obtained for XO3((0,1,-1)) (X = B, Al, Ga; C, Si, Ge; N, P, As; S, Se) molecules and ions with 22 and 23 valence electrons (VE), using density functional theory (DFT), coupled cluster with single and double substitutions with noniterative triple excitations (CCSD(T)), equation of motion (EOM)-CCSD, time-dependent DFT, and multi-reference configuration interaction methods. It is shown that pseudo Jahn-Teller (PJT) coupling increases as the central atom X becomes heavier, due to decreases in excitation energies. As is well known for CO3, the excited (1)E' states of the 22 VE systems SiO3, GeO3; NO3(+), PO3(+), AsO3(+); BO3(-), AlO3(-), GaO3(-) have strong vibronic coupling with the (1)A1' ground state via the e' vibrational modes, leading to a C2v minimum around α = 145°. For first and second row X atoms, there is an additional D3h minimum (α = 120°). Interacting excited states have minima around 135°. In the 23 VE systems CO3(-), SiO3(-); NO3, PO3; SO3(+), coupling of the excited (2)E' with the (2)A2' ground state via the e' mode does not generate a C2v state. Minima of interacting excited states are close to 120°. However, due to very strong PJT coupling, a double-well potential is predicted for GeO3(-), AsO3, and SeO3(+), with a saddle point at D3h symmetry. Interaction of the b2 highest occupied molecular orbital with the b2 lowest unoccupied molecular orbital, both oxygen lone pair molecular orbitals, is seen as the reason for the C2v stabilization of 22 VE molecules.

  5. Pseudo Jahn-Teller coupling in trioxides XO3(0,1,-1) with 22 and 23 valence electrons

    NASA Astrophysics Data System (ADS)

    Grein, Friedrich

    2013-05-01

    D3h and C2v geometries and energies, vertical excitation energies, as well as minimal energy paths as function of the O1(z)-X-O2 angle α were obtained for XO3(0,1,-1) (X = B, Al, Ga; C, Si, Ge; N, P, As; S, Se) molecules and ions with 22 and 23 valence electrons (VE), using density functional theory (DFT), coupled cluster with single and double substitutions with noniterative triple excitations (CCSD(T)), equation of motion (EOM)-CCSD, time-dependent DFT, and multi-reference configuration interaction methods. It is shown that pseudo Jahn-Teller (PJT) coupling increases as the central atom X becomes heavier, due to decreases in excitation energies. As is well known for CO3, the excited 1E' states of the 22 VE systems SiO3, GeO3; NO_3 ^ +, PO3+, AsO3+; BO3-, AlO3-, GaO3- have strong vibronic coupling with the 1A1' ground state via the e' vibrational modes, leading to a C2v minimum around α = 145°. For first and second row X atoms, there is an additional D3h minimum (α = 120°). Interacting excited states have minima around 135°. In the 23 VE systems CO3-, SiO3-; NO3, PO3; SO3+, coupling of the excited 2E' with the 2A2' ground state via the e' mode does not generate a C2v state. Minima of interacting excited states are close to 120°. However, due to very strong PJT coupling, a double-well potential is predicted for GeO3-, AsO3, and SeO3+, with a saddle point at D3h symmetry. Interaction of the b2 highest occupied molecular orbital with the b2 lowest unoccupied molecular orbital, both oxygen lone pair molecular orbitals, is seen as the reason for the C2v stabilization of 22 VE molecules.

  6. Jahn-Teller distortion in tris[4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionato]manganese(III) isomers: An X-ray and computational study

    NASA Astrophysics Data System (ADS)

    Gostynski, Roxanne; van Rooyen, Petrus H.; Conradie, Jeanet

    2016-09-01

    The solid state crystal data of a mer isomer of the [Mn(CF3COCHCOC4H3S)3] complex, [Mn(tfth)3], exhibits elongation Jahn-Teller distortion (elongation of the metal-ligand bonds along the z-axis and shortening of the metal-ligand bonds along both the x and y-axes). Density functional theory calculations (DFT) show that one fac and three mer isomers of [Mn(tfth)3] can exist. The difference between the three mer isomers of [Mn(tfth)3] is that the Jahn-Teller elongation of the two trans axial Mn-O bonds along the z-axis occur along three different Otfth-Mn-Otfth bonds. DFT calculations further show that the ground state geometry of all the [Mn(tfth)3] isomers exhibits elongation Jahn-Teller distortion.

  7. High-order expansion of T2×t2 Jahn-Teller potential-energy surfaces in tetrahedral molecules

    NASA Astrophysics Data System (ADS)

    Opalka, Daniel; Domcke, Wolfgang

    2010-04-01

    Methods from Jahn-Teller theory and invariant theory have been combined for the construction of analytic diabatic potential-energy surfaces of triply degenerate states in tetrahedral molecules. The potentials of a threefold degenerate electronic state of T2 symmetry, subject to the T2×t2 or T2×(t2+t2) Jahn-Teller effect in a three-dimensional or six-dimensional space of nuclear coordinates, respectively, are considered. The permutation symmetry of four identical nuclei is taken into account in the polynomial expansion of the diabatic surfaces. Symmetry adapted polynomials up to high orders are explicitly given and a simple combinatorial scheme was developed to express terms of arbitrary order as products of a small number of polynomials which are invariant under the permutation of identical nuclei. The method is applied to the methane cation in its triply degenerate ground state. The parameters of the analytic surfaces have been fitted to accurate ab initio data calculated at the full-valence CASSCF/MRCI/cc-pVTZ level. A three-sheeted six-dimensional analytic potential-energy surface of the T22 ground state of CH4+ is reported, which involves terms up to eighth order in the degenerate stretching coordinate, up to 12th order in the degenerate bending coordinate, and up to fourth order in the stretch-bend coupling.

  8. Symmetry breaking in the planar configurations of disilicon tetrahalides: Pseudo-Jahn-Teller effect parameters, hardness and electronegativity.

    PubMed

    Kouchakzadeh, Ghazaleh; Nori-Shargh, Davood

    2015-11-21

    CCSD(T), MP2, LC-BLYP, LC-ωPBE and B3LYP methods with the Def2-TZVPP basis set and natural bond orbital (NBO) interpretations were performed to investigate the correlations between the Pseudo-Jahn-Teller Effect (PJTE) parameters [i.e. vibronic coupling constant values (F), energy gaps between reference states (Δ) and the primary force constant (K0)], structural and configurational properties, global hardness, global electronegativity, natural bond orders, stabilization energies associated with electron delocalizations and natural atomic charges of disilicon tetrafluoride (1), disilicon tetrachloride (2), disilicon tetrabromide (3) and disilicon tetraiodide (4). All levels of theory showed the trans-bent (C2h) configurations as the energy minimum structures of compounds 1-4, and the flap angles between the X2Si planes and the Si=Si bonds in the distorted (C2h) configurations decrease from compound 1 to compound 4. The negative curvatures of the ground state electronic configurations and the positive curvatures of the excited states of the adiabatic potential energy surfaces (APESs) which resulted from the mixing of the ground Ag and excited B2g states are due to the PJTE (i.e. PJT(Ag + B2g) ⊗ b2g problem). Contrary to the usual expectation, with the decrease of the energy gaps between reference states (Δ), the PJTE stabilization energy, E(PJT), decreases from compound 1 to compound 4. The canonical molecular orbital (CMO) analysis revealed that the contributions of the ψ(HOMO)(b3u) and ψL(UMO)(b1u) molecular orbitals in the vibronic coupling constant (F) decrease from compound 1 to compound 4. This fact clearly justifies the decrease of the vibronic coupling constant (F) and the primary force constant (the force constant without the PJTE) values on going from compound 1 to compound 4, leading to the decrease of the negative curvatures of the ground state electronic configuration curves of their corresponding APESs. The results obtained showed that the

  9. Symmetry breaking in the planar configurations of disilicon tetrahalides: Pseudo-Jahn-Teller effect parameters, hardness and electronegativity.

    PubMed

    Kouchakzadeh, Ghazaleh; Nori-Shargh, Davood

    2015-11-21

    CCSD(T), MP2, LC-BLYP, LC-ωPBE and B3LYP methods with the Def2-TZVPP basis set and natural bond orbital (NBO) interpretations were performed to investigate the correlations between the Pseudo-Jahn-Teller Effect (PJTE) parameters [i.e. vibronic coupling constant values (F), energy gaps between reference states (Δ) and the primary force constant (K0)], structural and configurational properties, global hardness, global electronegativity, natural bond orders, stabilization energies associated with electron delocalizations and natural atomic charges of disilicon tetrafluoride (1), disilicon tetrachloride (2), disilicon tetrabromide (3) and disilicon tetraiodide (4). All levels of theory showed the trans-bent (C2h) configurations as the energy minimum structures of compounds 1-4, and the flap angles between the X2Si planes and the Si=Si bonds in the distorted (C2h) configurations decrease from compound 1 to compound 4. The negative curvatures of the ground state electronic configurations and the positive curvatures of the excited states of the adiabatic potential energy surfaces (APESs) which resulted from the mixing of the ground Ag and excited B2g states are due to the PJTE (i.e. PJT(Ag + B2g) ⊗ b2g problem). Contrary to the usual expectation, with the decrease of the energy gaps between reference states (Δ), the PJTE stabilization energy, E(PJT), decreases from compound 1 to compound 4. The canonical molecular orbital (CMO) analysis revealed that the contributions of the ψ(HOMO)(b3u) and ψL(UMO)(b1u) molecular orbitals in the vibronic coupling constant (F) decrease from compound 1 to compound 4. This fact clearly justifies the decrease of the vibronic coupling constant (F) and the primary force constant (the force constant without the PJTE) values on going from compound 1 to compound 4, leading to the decrease of the negative curvatures of the ground state electronic configuration curves of their corresponding APESs. The results obtained showed that the

  10. Lattice Distortion, Polaron Conduction, and Jahn-Teller Effect on teh Magnetoresistance of La(sub 0.7)Ca(sub 0.5)CoO(sub 3) Epitaxial Films

    NASA Technical Reports Server (NTRS)

    Yeh, N. C.; Vasquez, R. P.; Beam, D. A.; Fu, C. C.; Huynh, H.; Beach, G.

    1996-01-01

    In summary, we have investigated the role of lattice distortion, polaron conduction and Jahn-Teller coupling in the occurrence of the colossal negative magnetoresistance in perovskite oxides. We conclude that larger lattice distortion gives rise to larger zero-field resistivity and larger magnitude of negative magnetoresistance.

  11. Preparation, crystallography and spectroscopic properties of the polymeric {(1-( E)-2-pyridinylmethylidene)semicarbazone)(aqua)copper(II)} sulphate dihydrate complex: Evidence of dynamic Jahn-Teller effect

    NASA Astrophysics Data System (ADS)

    Garbelini, Ellery R.; Ribeiro, Ronny Rocha; Hörner, Manfredo; Locatelli, Aline; Nunes, Fábio S.

    2011-05-01

    Pyridine-2-carbaldehyde semicarbazone ligand (HL) reacts with copper(II) sulphate in water solution to yield the coordination polymer [{Cu II(HL)(H 2O)(SO 4)} n] (1). The crystals are triclinic with space group P(-1) and the metal ion is occupying a distorted octahedral geometry. EPR results show that a dynamic Jahn-Teller (J-T) effect is operative in water solutions and also support the stability of the polymeric chains as they continue to show a characteristic half-field Δ mS = ±2 transitions. UV-visible spectrum analysis allowed access to the J-T stabilization energy of 5995 cm -1 in water. Thermogravimetric/differential thermal analysis curves showed a step-by-step decomposition of complex 1 with loss of water, release of SO 3 and oxidation of the semicarbazone ligand in the 30-422 °C range.

  12. Jahn-Teller-induced crossover of the paramagnetic response in the singly valent eg system LaMn7O12

    NASA Astrophysics Data System (ADS)

    Cabassi, R.; Bolzoni, F.; Gilioli, E.; Bissoli, F.; Prodi, A.; Gauzzi, A.

    2010-06-01

    We investigate the high-temperature magnetic and transport properties of LaMn7O12 , which displays a similar perovskitelike structure and the same single-valent Mn3+ properties of LaMnO3 but a much simpler Jahn-Teller (JT) distortion at TJT=650K . We find that the magnetic response of LaMn7O12 is similar to that of LaMnO3 below TJT , but strikingly different in the undistorted phase above TJT , where the Curie-Weiss susceptibility is strongly suppressed. Electrical resistivity and thermopower measurements unveil a concomitant crossover from nonadiabatic to adiabatic small polaron regime. This suggests that the above suppression is due to low-spin electron-hole dimers formed by the eg charge transfer between Mn sites and stabilized by the slow JT dynamics above TJT .

  13. Unexpected Spin-Crossover and a Low-Pressure Phase Change in an Iron(II)/Dipyrazolylpyridine Complex Exhibiting a High-Spin Jahn-Teller Distortion.

    PubMed

    Kershaw Cook, Laurence J; Thorp-Greenwood, Flora L; Comyn, Tim P; Cespedes, Oscar; Chastanet, Guillaume; Halcrow, Malcolm A

    2015-07-01

    The synthesis of 4-methyl-2,6-di(pyrazol-1-yl)pyridine (L) and four salts of [FeL2]X2 (X(-) = BF4(-), 1; X(-) = ClO4(-), 2; X(-) = PF6(-), 3; X(-) = CF3SO3(-), 4) are reported. Powder samples of 1 and 2 both exhibit abrupt, hysteretic spin-state transitions on cooling, with T1/2↓ = 204 and T1/2↑ = 209 K (1), and T1/2↓ = 175 and T1/2↑ = 193 K (2). The 18 K thermal hysteresis loop for 2 is unusually wide for a complex of this type. Single crystal structures of 2 show it to exhibit a Jahn-Teller-distorted six-coordinate geometry in its high-spin state, which would normally inhibit spin-crossover. Bulk samples of 1 and 2 are isostructural by X-ray powder diffraction, and undergo a crystallographic phase change during their spin-transitions. At temperatures below T1/2, exposing both compounds to 10(-5) Torr pressure inside the powder diffractometer causes a reversible transformation back to the high-temperature crystal phase. Consideration of thermodynamic data implies this cannot be accompanied by a low → high spin-state change, however. Both compounds also exhibit the LIESST effect, with 2 exhibiting an unusually high T(LIESST) of 112 K. The salts 3 and 4 are respectively high-spin and low-spin between 3 and 300 K, with crystalline 3 exhibiting a more pronounced version of the same Jahn-Teller distortion. PMID:26052980

  14. Jahn-Teller phase transition in Cu 0.50TiO(PO 4): Powder structural characterization of the β-variety and thermal study

    NASA Astrophysics Data System (ADS)

    Gravereau, Pierre; Benmokhtar, Saïd; Chaminade, Jean-Pierre; El Jazouli, Abdelaziz; Lebraud, Eric; Denux, Dominique

    2007-03-01

    The thermal study of Cu 0.50TiO(PO 4), by X-ray diffraction and DSC, shows a phase transition α → β with a hysteresis (˜600 °C during heating; ˜300 °C during cooling). Single crystals have been obtained for the α-phase but the β-phase can only be stabilised at room temperature as a powder mixture with α. Structural characterization of the β-variety has been done with diffraction data (X-ray Cu Kα 1 and neutrons) using a powder rich in β-phase (α(20%) + β(80%)). A monoclinic cell ( a = 7.1134(7) Å; b = 7.7282(7) Å; c = 7.3028(7) Å; β=119.30(1)°; V = 350.1(1) Å 3) has been found for β-phase, space group P2 1/ c. An " ab initio" structure determination has been done, and the Rietveld refinement leads to cRwp = 0.150 and RB = 0.041. The results from the X-ray data were confirmed by refinements from neutron data. Similarly to the α-phase, the structure of β-Cu 0.50TiO(PO 4) can be described as a TiOPO 4 framework constituted of chains of tilted corner-sharing [TiO 6] octahedra running parallel to the c axis and cross linked by [PO 4] tetrahedra. Ti atoms are displaced from the centres of the octahedral units, leading to long (2.27 Å) and short (1.73 Å) Ti-O(1) bonds. The [CuO 6] octahedra exhibit a typical Jahn-Teller distorted coordination with four short equatorial Cu-O bonds (2 × 1.93 Å and 2 × 2.06 Å), and two longer apical Cu-O bonds (2 × 2.33 Å). The two longer Cu-O bonds are almost parallel to the b axis. The transition from the α to the β-phase is characterized by a "rocking" of the Jahn-Teller elongation from the ( a, c) plane to the b direction accompanied by a relatively strong expansion of the cell volume.

  15. Pseudo-Jahn-Teller Distortion in Two-Dimensional Phosphorus: Origin of Black and Blue Phases of Phosphorene and Band Gap Modulation by Molecular Charge Transfer.

    PubMed

    Chowdhury, Chandra; Jahiruddin, Sheik; Datta, Ayan

    2016-04-01

    Phosphorene (Pn) is stabilized as a layered material like graphite, yet it possess a natural direct band gap (Eg = 2.0 eV). Interestingly, unlike graphene, Pn exhibits a much richer phase diagram which includes distorted forms like the stapler-clip (black Pn, α form) and chairlike (blue Pn, β form) structures. The existence of these phases is attributed to pseudo-Jahn-Teller (PJT) instability of planar hexagonal P6(6-) rings. In both cases, the condition for vibronic instability of the planar P6(6-) rings is satisfied. Doping with electron donors like tetrathiafulvalene and tetraamino-tetrathiafulvalene and electron acceptors like tetracyanoquinodimethane and tetracyanoethylene convert blue Pn into N-type and black Pn into efficient P-type semiconductors, respectively. Interestingly, pristine blue Pn, an indirect gap semiconductor, gets converted into a direct gap semiconductor on electron or hole doping. Because of comparatively smaller undulation in blue Pn (with respect to black Pn), the van der Waals interactions between the dopants and blue Pn is stronger. PJT distortions for two-dimensional phosphorus provides a unified understanding of structural features and chemical reactivity in its different phases. PMID:26987273

  16. Local Jahn-Teller distortions and orbital ordering in Ba3Cu1 +xSb2 -xO9 investigated by neutron scattering

    NASA Astrophysics Data System (ADS)

    Li, Bing; Louca, Despina; Feygenson, Mikhail; Brown, Craig M.; Copley, John R. D.; Iida, Kazuki

    2016-01-01

    A spin-orbital quantum liquid state is theoretically proposed in the honeycomb lattice of Ba3CuSb2O9 , enabled by dynamic short-range correlations between the spin and orbital degrees of freedom. Using neutron diffraction, the local atomic structure of Ba3Cu1 +xSb2 -xO9 at x =0 and 0.1 is obtained via the pair density function analysis. The results indicate that both compositions exhibit local Jahn-Teller (JT) distortions with the elongated CuO3 octahedral configuration. In Ba3Cu1.1Sb1.9O9 , JT ordering of the distorted CuO3 octahedra gives rise to the orthorhombic symmetry with ferro-orbital order. On the other hand, in Ba3CuSb2O9 , even though the CuO3 octahedra are JT distorted, there is no long-range ordering hence the symmetry is hexagonal. Furthermore, the local singlet excitation at 5.8 meV observed in Ba3CuSb2O9 below 50 K is absent in Ba3Cu1.1Sb1.9O9 . Instead, an excitation at 2.5 meV is observed in the latter, which is likely associated with short-range spin order.

  17. An EPR investigation of the dynamic Jahn-Teller effect in SrCl2:y(2 plus) and SrCl2:Sc(2 plus)

    NASA Technical Reports Server (NTRS)

    Herrington, J. R.; Estle, T. L.; Boatner, L. A.

    1972-01-01

    EPR spectra have been observed for SrCl2:Y(2+) and SrCl2:Sc(2+) at liquid helium temperatures. At 1.2 K the spectra were dominated by anisotropic hyperfine patterns whose lineshapes and angular dependences were explained using second order solutions of the effective Hamiltonian for an isolated 2Eg state split by large random internal strains. Pronounced asymmetries in some of the strin produced lineshapes for Srcl2:Sc(2+) are shown to result from second order terms in the solution of the effective Hamiltonian. Coexisting with the anisotropic hyperfine patterns are weak nearly isotropic hyperfine patterns with typical lineshapes. Variations in the apparent intensity of lines in these weak hyperfine patterns as functions of the applied magnetic field direction and temperature imply that these lines result from averaging by vibronic relaxation of a portion of the anisotropic pattern. The effective Hamiltonian parameters for SrCl2:La(2+), SrCl2:y(2+), and SrCl2:SC(2+) are analyzed in terms of crystal field theory modified to include a dynamic Jahn-Teller effect.

  18. Local Jahn-Teller distortions and orbital ordering in Ba3Cu1+xSb2-xO9 investigated by neutron scattering

    DOE PAGES

    Li, Bing; Feygenson, Mikhail; Brown, Craig M.; Copley, John R. D.; Iida, Kazuki

    2016-01-15

    In this study, a spin-orbital quantum liquid state is theoretically proposed in the honeycomb lattice of Ba3CuSb2O9, enabled by dynamic short-range correlations between the spin and orbital degrees of freedom. Using neutron diffraction, the local atomic structure of Ba3Cu1+xSb2-xO9 at x = 0 and 0.1 is obtained via the pair density function analysis. The results indicate that both compositions exhibit local Jahn-Teller (JT) distortions with the elongated CuO3 octahedral configuration. In Ba3Cu1.1Sb1.9O9, JT ordering of the distorted CuO3 octahedra gives rise to the orthorhombic symmetry with ferro-orbital order. On the other hand, in Ba3CuSb2O9, even though the CuO3 octahedra aremore » JT distorted, there is no long-range ordering hence the symmetry is hexagonal. Furthermore, the local singlet excitation at 5.8 meV observed in Ba3CuSb2O9 below 50 K is absent in Ba3Cu1.1Sb1.9O9. Instead, an excitation at 2.5 meV is observed in the latter, which is likely associated with short-range spin order.« less

  19. Origin of warping in the E⊗e Jahn-Teller problem: Quadratic vibronic coupling versus anharmonicity and application to NaCl: Rh2+ and triangular molecules

    NASA Astrophysics Data System (ADS)

    García-Fernández, P.; Bersuker, I. B.; Aramburu, J. A.; Barriuso, M. T.; Moreno, M.

    2005-05-01

    A general method is suggested which allows one to separate the quadratic, cubic, and pseudo Jahn-Teller contributions to the warping of the adiabatic potential energy surface (APES) of the E⊗e problem employing ab initio calculations. Numerical results were obtained for NaCl:Rh2+ in a cluster approximation and triangular molecules (Na3,K3,Cu3,Ag3) using density functional theory (DFT) and multireference second-order perturbation theory (CASPT2) methods. A largely unexpected result is that the contribution of cubic anharmonicity to the energy barrier between the minima of the lower and upper branches of the APES is dominant in all the systems and amounts for not less than 60% of the total. Another feature is that the three different contributions mentioned above may have different signs, thus either enhancing or diminishing each other, affecting in different ways the lower and upper branches of the APES. Other details of the numerical results are also analyzed.

  20. Symmetry-adapted excited states for the T{sub 1u}(direct-product)h{sub g} Jahn-Teller system

    SciTech Connect

    Qiu, Q. C.; Dunn, J. L.; Bates, C. A.

    2001-08-15

    Jahn-Teller (JT) systems typically contain a set of equivalent-energy wells in the lowest adiabatic potential-energy surface (APES). Quantum-mechanical tunneling between these wells (the dynamic JT effect) must be allowed for by taking appropriate symmetrized combinations of oscillator-type states associated with the wells. It is important to be able to describe the excited states of such systems for a number of reasons. One particular reason is that they are required for the calculation of second-order vibronic reduction factors, which in turn are useful for modeling experimental data using effective Hamiltonians. In this paper, projection-operator techniques are used to obtain general expressions for the symmetry-adapted excited states of the icosahedral T{sub 1u}(direct-product)h{sub g} JT system for the case of D{sub 5d} minima in the APES. Analytical expressions for the states and their energies for one-phonon excitation are given explicitly. The energies of a selection of states with two-phonon excitations are also obtained and plotted. The results obtained in this paper are applicable to the C{sub 60}{sup -} molecule.

  1. Infrared Absorption Spectra of Jahn-Teller Systems: Application to the Transition-Metal Trifluorides MnF3 and NiF3.

    PubMed

    Mondal, Padmabati; Domcke, Wolfgang

    2014-05-14

    The theory for the calculation of vibronic absorption spectra within a Jahn-Teller (JT) active electronic state from first principles has been developed. The infrared absorption spectra of the (5)E' ground state, the low-lying (5)E″ excited state of MnF3, and the (4)E' state of NiF3 have been computed and analyzed. Dipole moment derivatives have been determined by a linear-plus-quadratic expansion of nuclear dipole moment functions in the JT-active coordinates. Electronic transition dipole moments have been taken into account in the Condon approximation in the diabatic representation. The initial and final vibronic states have been expanded in a product of diabatic electronic states and vibrational basis functions. The effect of spin-orbit coupling on the vibronic infrared spectra of these molecules in their JT-active electronic states has been investigated, by employing the Breit-Pauli spin-orbit operator. The effect of temperature on the vibronic infrared spectra has also been explored. These results represent the first theoretical study of vibronic infrared spectra of JT-active states in transition metal compounds.

  2. Competing Jahn-Teller distortions and hydrostatic pressure effects in the quasi-one-dimensional quantum ferromagnet CuAs2O4

    NASA Astrophysics Data System (ADS)

    Caslin, K.; Kremer, R. K.; Razavi, F. S.; Hanfland, M.; Syassen, K.; Gordon, E. E.; Whangbo, M.-H.

    2016-01-01

    CuAs2O4 is a S =1 /2 quasi-one-dimensional ribbon chain compound which orders ferromagnetically at 7.4 K under ambient conditions. CuAs2O4 features nearest- and next-nearest-neighbor spin-exchange interactions along the spin chains with a ratio α =Jnn /Jnnn in close proximity to the quantum critical point at α =-4 . We apply hydrostatic pressure up to ˜11.5 GPa and examine the structural and magnetic properties using Raman spectroscopy, single-crystal synchrotron x-ray diffraction, and magnetic susceptibility measurements. External pressure severely reduces the axial Jahn-Teller elongations of the oxygen octahedra surrounding the Cu2 + cations and stabilizes the ferromagnetic ground state. At 9.2(2) GPa, we detect a structural phase transition leading to an increased twisting of the CuO2 ribbon chains and a large drop of the magnetic ordering temperature. Ab initio density functional theory calculations of the spin-exchange parameters, using the structural parameters as a function of pressure, support the experimental findings.

  3. Optical and magnetic characterisation of Co3+ and Ni3+ in LaAlO3: interplay between the spin state and Jahn-Teller effect

    NASA Astrophysics Data System (ADS)

    Sanz-Ortiz, Marta N.; Rodríguez, Fernando; Rodríguez, Jesús; Demazeau, Gérard

    2011-10-01

    The coordination, the electronic structures and the spin of the ground state of Ni3+ (3d7) and Co3+ (3d6) introduced as impurities in LaAlO3 are investigated through optical spectroscopy and magnetic measurements. The unusual trivalent valence state in both transition-metal ions was stabilised via a sol-gel process followed by high oxygen pressure treatments. We show that the crystal-field strength at the nearly Oh transition-metal site in LaAlO3 locates Ni3+ and Co3+ near the spin state crossover, yielding a low-spin ground state in both cases. We analyse how the interplay between the Jahn-Teller (JT) effect and the spin state affects the magnetic moment of the ion and its temperature dependence. The optical spectra reveal a JT effect associated with a low-spin ground state in Ni3+ and with a thermally populated high-spin low-lying first excited state in Co3+. The corresponding JT distortions are derived from structural correlations. We conclude that the JT effect is unable to stabilise the intermediate spin state in Co3+. A low-spin ground state in thermal equilibrium with a high-spin low-lying first excited state is detected in diluted Co3+-doped LaAlO3. These results are compared with those obtained in the parent pure compounds LaNiO3 and LaCoO3.

  4. Jahn-Teller effect in van der Waals complexes; Ar-C6H6+ and Ar-C6D6+

    NASA Astrophysics Data System (ADS)

    van der Avoird, Ad; Lotrich, Victor F.

    2004-06-01

    The two asymptotically degenerate potential energy surfaces of argon interacting with the X˜ 2E1g ground state benzene+ cation were calculated ab initio from the interaction energy of the neutral Ar-benzene complex given by Koch et al. [J. Chem. Phys. 111, 198 (1999)] and the difference of the geometry-dependent ionization energies of the complex and the benzene monomer computed by the outer valence Green's function method. Coinciding minima in the two potential surfaces of the ionic complex occur for Ar on the C6v symmetry axis of benzene+ (the z axis) at ze=3.506 Å. The binding energy De of 520 cm-1 is only 34% larger than the value for the neutral Ar-benzene complex. The higher one of the two surfaces is similar in shape to the neutral Ar-benzene potential, the lower potential is much flatter in the (x,y) bend direction. Nonadiabatic (Jahn-Teller) coupling was taken into account by transformation of the two adiabatic potentials to a two-by-two matrix of diabatic potentials. This transformation is based on the assumption that the adiabatic states of the Ar-benzene+ complex geometrically follow the Ar atom. Ab initio calculations of the nonadiabatic coupling matrix element between the adiabatic states with the two-state-averaged CAS-SCF(5,6) method confirmed the validity of this assumption. The bound vibronic states of both Ar-C6H6+ and Ar-C6D6+ were computed with this two-state diabatic model in a basis of three-dimensional harmonic oscillator functions for the van der Waals modes. The binding energy D0=480 cm-1 of the perdeuterated complex agrees well with the experimental upper bound of 485 cm-1. The ground and excited vibronic levels and wave functions were used, with a simple model dipole function, to generate a theoretical far-infrared spectrum. Strong absorption lines were found at 10.1 cm-1 (bend) and 47.9 cm-1 (stretch) that agree well with measurements. The unusually low bend frequency is related to the flatness of the lower adiabatic potential in the

  5. Jahn-Teller effect in van der Waals complexes; Ar-C6H6 + and Ar-C6D6 +.

    PubMed

    van der Avoird, Ad; Lotrich, Victor F

    2004-06-01

    The two asymptotically degenerate potential energy surfaces of argon interacting with the X (2)E(1g) ground state benzene(+) cation were calculated ab initio from the interaction energy of the neutral Ar-benzene complex given by Koch et al. [J. Chem. Phys. 111, 198 (1999)] and the difference of the geometry-dependent ionization energies of the complex and the benzene monomer computed by the outer valence Green's function method. Coinciding minima in the two potential surfaces of the ionic complex occur for Ar on the C(6v) symmetry axis of benzene(+) (the z axis) at z(e)=3.506 A. The binding energy D(e) of 520 cm(-1) is only 34% larger than the value for the neutral Ar-benzene complex. The higher one of the two surfaces is similar in shape to the neutral Ar-benzene potential, the lower potential is much flatter in the (x,y) bend direction. Nonadiabatic (Jahn-Teller) coupling was taken into account by transformation of the two adiabatic potentials to a two-by-two matrix of diabatic potentials. This transformation is based on the assumption that the adiabatic states of the Ar-benzene(+) complex geometrically follow the Ar atom. Ab initio calculations of the nonadiabatic coupling matrix element between the adiabatic states with the two-state-averaged CAS-SCF(5,6) method confirmed the validity of this assumption. The bound vibronic states of both Ar-C(6)H(6) (+) and Ar-C(6)D(6) (+) were computed with this two-state diabatic model in a basis of three-dimensional harmonic oscillator functions for the van der Waals modes. The binding energy D(0)=480 cm(-1) of the perdeuterated complex agrees well with the experimental upper bound of 485 cm(-1). The ground and excited vibronic levels and wave functions were used, with a simple model dipole function, to generate a theoretical far-infrared spectrum. Strong absorption lines were found at 10.1 cm(-1) (bend) and 47.9 cm(-1) (stretch) that agree well with measurements. The unusually low bend frequency is related to the flatness

  6. The influence of the Jahn-Teller effect at Fe2+ on the structure of chromite at high pressure

    SciTech Connect

    Kyono, Atsushi; Gramsch, Stephen A; Yamanaka, Takamitsu; Ikuta, Daijo; Ahart, Muhtar; Mysen, Bjørn O; Mao, Ho-kwang; Hemley, Russell J

    2012-03-15

    a 'stretched' tetrahedral geometry. It is proposed that the Jahn-Teller effect at the tetrahedrally coordinated Fe2+ cation becomes active with compression and gives rise to the tetrahedral angular distortion, which in turn induces the cubic-to-tetragonal transition. A qualitative molecular orbital model is proposed to explain the origin and nature of the Jahn-Teller effect observed in this structure and its role in the pressure-induced phase transition.

  7. Pseudo Jahn-Teller origin of ferroelectric instability in BaTiO3 type perovskites: The Green's function approach and beyond

    NASA Astrophysics Data System (ADS)

    Polinger, V.; Garcia-Fernandez, P.; Bersuker, I. B.

    2015-01-01

    The local origin of dipolar distortions in ABO3 perovskite crystals is reexamined by means of a novel approach, the Green's function method augmented by DFT computations. The ferroelectric distortions are shown to be induced by the pseudo Jahn-Teller effect (PJTE). The latter involves vibronic hybridization (admixture) of the ground state to same-spin opposite-parity excited electronic bands. Similar to numerous molecular calculations, the PJT approach provides a deeper insight into the nature of chemical bonding in the octahedral cluster [BO6] and, in particular, reveals the local origin of its polar instability. This allows predicting directly which transition ions can create ferroelectricity. In particular, the necessary conditions are established when an ABO3 perovskite crystal with an electronic dn configuration of the complex ion [BO6] can possess both proper ferroelectric and magnetic properties. Distinguished from the variety of cluster approaches to local properties, the Green's function method includes the influence of the local vibronic-coupling perturbation on the whole crystal via the inter-cell interaction responsible for creation of electronic and vibrational bands. Calculated Green's functions combined with the corresponding numeric estimates for the nine electronic bands, their density of states, and the local adiabatic potential energy surface (APES) confirm the eight-minimum form of this surface and feasibility of the PJT origin of the polar instability in BaTiO3. We show also that multicenter long-range dipole-dipole interactions critically depend on the PJTE largely determining the magnitude of the local dipoles. DFT calculations for the bulk crystal and its clusters confirm that the dipolar distortions are of local origin, but become possible only when their influence on (relaxation of) the whole lattice is taken into account. The results are shown to be in full qualitative and semiquantitative agreement with the experimental data for this

  8. Pseudo Jahn-Teller origin of puckering in cyclohexahomoatomic molecules E6 (E = S, Se, Te) and restoring S6 planar ring configuration

    NASA Astrophysics Data System (ADS)

    Ilkhani, Ali Reza

    2015-10-01

    The pseudo Jahn-Teller effect (PJTE) is employed to explore the origin of the puckering structure of cyclohexasulfur (S6), cyclohexaselenium (Se6) and cyclohexatellurium (Te6) and their nondegenerate and degenerate vibronic excited states and their planar structure instabilities have investigated. The ab initio geometry optimization and frequency calculations show that all these cyclohexahomoatomic molecules chose D6h symmetry in the planar configuration, and according the S6 and Se6 experimental structure, the chair form of the molecules is stable structure. The vibronic coupling between the ground state 1A1g and excited state 1B2g is the cause of chair puckering in all these series compounds and the numerical solutions of the PJTE (1A1g+1B2g)⊗b2g problems describe their instability. The adiabatic potential energy surfaces (APES) cross sections of low-lying electronic states along the b2g puckering normal coordinates have calculated by the state-average complete active space self-consistent field (SA-CASSCF) method. The calculation results show that, the chair puckering instability in the S6 from unstable planar configuration with D6h symmetry to a stable D3d distorted geometry, is stronger than others, whereas it is weaker in Te6. Additionally, coordination two canions (X = H+, He2+) to the S6 chair structure restore the planarity of S6 puckered ring in the S6X2 systems, although the D6h symmetry in S6 planar ring configuration changes to the Cs symmetry in the systems.

  9. Incorporation of Jahn-Teller Cu(2+) Ions into Magnetoelectric Multiferroic MnWO4: Structural, Magnetic, and Dielectric Permittivity Properties of Mn1-xCuxWO4 (x ≤ 0.25).

    PubMed

    Patureau, Pascaline; Josse, Michaël; Dessapt, Rémi; Mevellec, Jean-Yves; Porcher, Florence; Maglione, Mario; Deniard, Philippe; Payen, Christophe

    2015-11-16

    Polycrystalline samples of Mn1-xCuxWO4 (x ≤ 0.5) have been prepared by a solid-state synthesis as well as from a citrate synthesis at moderate temperature (850 °C). The goal is to study changes in the structural, magnetic, and dielectric properties of magnetoelectric type-II multiferroic MnWO4 caused by replacing Jahn-Teller-inactive Mn(2+) (d(5), S = 5/2) ions with Jahn-Teller-active Cu(2+) (d(9), S = 1/2) ions. Combination of techniques including scanning electron microscopy, powder X-ray and neutron diffraction, and Raman spectroscopy demonstrates that the polycrystalline samples with low copper content 0 ≤ x ≤ 0.25 are solid solution that forms in the monoclinic P2/c space group. Rietveld analyses indicate that Cu atoms substitutes for Mn atoms at the Mn crystallographic site of the MnWO4 structure and suggest random distributions of Jahn-Teller-distorted CuO6 octahedra in the solid solution. Magnetic susceptibility reveals that only 5% of Cu substitution suppresses the nonpolar collinear AF1 antiferromagnetic structure observed in pure MnWO4. Type-II multiferroicity survives a weak Cu substitution rate (x < 0.15). Multiferroic transition temperature and Néel temperature increase as the amount of Cu increases. New trends in some of the magnetic properties and in dielectric behaviors are observed for x = 0.20 and 0.25. Careful analysis of the magnetic susceptibility reveals that the incorporation of Cu into MnWO4 strengthens the overall antiferromagnetic interaction and reduces the magnetic frustration. PMID:26502801

  10. High-T c superconductivity in potassium-doped fullerene, K xC 60, via coupled C 60 (pπ) cluster molecular orbitals and dynamic Jahn-Teller coupling

    NASA Astrophysics Data System (ADS)

    Johnson, K. H.; McHenry, M. E.; Clougherty, D. P.

    1991-11-01

    Recently observed superconductivity at 18 K in potassium-doped fullerene, K xC 60, may be due to Cooper pairing of partially occupied icosahedral C 60 cluster t 1u (pπ) molecular orbitals, induced by cooperative dynamic Jahn-Teller coupling of these orbitals to “soft-mode” vibrations of the C 60 molecules, leading to a BCS-like mechanism. Predicted are a nonvanishing isotope effect and Tc increasing to 30 K or more with optimization of doping, and significant effects with pressure.

  11. Nd, Ce(fπ)-O(pπ) Hybridization in Nd2-xCexCuO4 and Dynamic Jahn-Teller Pairing in HIGH-Tc Superconductors

    NASA Astrophysics Data System (ADS)

    Johnson, K. H.; Clougherty, D. P.; McHenry, M. E.

    Hybridization of Nd(fπ) and Ce(fπ) orbitals with composite O(pπ)-O(pπ) bonding/ Cu(dπ*)-O(pπ) antibonding orbitals at the Fermi energy (EF) is shown to promote high-Tc superconductivity in Nd2-xCexCuO4. Dynamic Jahn-Teller coupling of these hybrid molecular orbitals to the lattice leads to Cooper pairing as it does in other high-Tc superconductors, such as La2-xSrxCuO4, where O(pπ) character at EF is dominant.

  12. Numerical adiabatic potentials of orthorhombic Jahn-Teller effects retrieved from ultrasound attenuation experiments. Application to the SrF2:Cr crystal

    NASA Astrophysics Data System (ADS)

    Zhevstovskikh, I. V.; Bersuker, I. B.; Gudkov, V. V.; Averkiev, N. S.; Sarychev, M. N.; Zherlitsyn, S.; Yasin, S.; Shakurov, G. S.; Ulanov, V. A.; Surikov, V. T.

    2016-06-01

    A methodology is worked out to retrieve the numerical values of all the main parameters of the six-dimensional adiabatic potential energy surface (APES) of a polyatomic system with a quadratic T-term Jahn-Teller effect (JTE) from the ultrasound experiments. The method is based on a verified assumption that ultrasound attenuation and speed encounter anomalies when the direction of propagation and polarization of its wave of strain coincides with the characteristic directions of symmetry breaking in the JTE. For the SrF2:Cr crystal, employed as a basic example, we observed anomaly peaks in the temperature dependence of attenuation of ultrasound at frequencies of 50-160 MHz in the temperature interval of 40-60 K for the wave propagating along the [110] direction, for both the longitudinal and the shear modes, the latter with two polarizations along the [001] and [1 1 ¯ 0 ] axes, respectively. We show that these anomalies are due to the ultrasound relaxation by the system of non-interacting Cr2+ JT centers with orthorhombic local distortions. The interpretation of the experimental findings is based on the T2 g⊗(eg+t2 g) JTE problem including the linear and the quadratic terms of vibronic interactions in the Hamiltonian and the same-symmetry modes reduced to one interaction mode. Combining the experimental results with a theoretical analysis, we show that on the complicated six-dimensional APES of this system with three tetragonal, four trigonal, and six orthorhombic extrema points, the latter are global minima, while the former are saddle points, and we estimate numerically all the main parameters of this surface, including the linear and quadratic vibronic coupling constants, the primary force constants, the coordinates of all the extrema points and their energies, the energy barrier between the orthorhombic minima, and the tunneling splitting of the ground vibrational states. To our knowledge, such a based-on-experimental-data numerical reconstruction of the APES

  13. Jahn-Teller effect in the ground and excited states of MnO2 - 4 doped into Cs2SO4

    NASA Astrophysics Data System (ADS)

    Brunold, Thomas C.; Güdel, Hans U.; Riley, Mark J.

    1996-11-01

    The polarized low-temperature absorption spectra of the 3d1 ion MnO2-4 in the Cs2SO4 host consist of a very weak, highly-structured band in the near-infrared (NIR) region corresponding to the 2E→2T2(d→d) transition and a series of intense ligand-to-metal charge transfer (LMCT) excitations above 16 000 cm-1. As a result of the low-symmetry crystal-field (CF) potential in Cs2SO4 the 2T2 ligand-field (LF) state of MnO2-4 is split into its three orbital components at 10 557, 10 848, and 10 858 cm-1 above the ground state. The lowest-energy component serves as initial state for broadband luminescence to the 2E ground state, exhibiting unusually well-resolved fine structure at 15 K. The orbital splitting of 2E is 969 cm-1 and thus larger by more than 1 order of magnitude and of opposite sign compared to the result of a ligand-field calculation within the angular-overlap model (AOM). This discrepancy is explained with the large contribution of the second-nearest neighbor Cs+ ions to the CF potential of MnO2-4 in the Cs2SO4 host lattice. The vibrational progressions in the 2E↔2T2 absorption and luminescence spectra are dominated by O-Mn-O bending modes. This is the result of a weak E⊗e and a stronger T2⊗e Jahn-Teller (JT) effect in the ground and excited LF states, respectively. The observed vibronic levels in the luminescence spectrum are fitted with a single-mode E⊗e JT Hamiltonian with an additional term representing the noncubic CF potential in Cs2SO4. The JT effect in the 2T2 LF state causes a large displacement of the emitting level along the two coordinates of the e mode and thus substantially affects the intensity distribution in the luminescence spectrum. The fitted linear and quadratic vibronic constants for the 2E ground state are 91 and 12 cm-1, respectively, and for the 2T2 excited state the linear coupling constant is -790 cm-1. The corresponding JT stabilization energies are 14 and 925 cm-1 for 2E and 2T2, respectively.

  14. Evidence for a Jahn-Teller distortion in the CMR layered manganite La{sub 1.4}Sr{sub 1.6}Mn{sub 2}O{sub 7}

    SciTech Connect

    Louca, D.; Kwei, G.H.; Mitchell, J.F.

    1998-12-31

    The changes with temperature in the crystallographic structure of the two-layered La{sub 1.4}Sr{sub 1.6}Mn{sub 2}O{sub 7}, are on average quite small but the atomic pair density function analysis of pulsed neutron diffraction data shows that the lattice is locally distorted in accordance with the change in the transport properties. In particular, while no Jahn-Teller (JT) distortion is expected in the layered compounds because the octahedral bilayers are almost cubic, lattice distortions attributed to a large JT effect are present and are of comparable magnitude as in the cubic perovskite system. This could in turn explain the similarity in their properties. The number of the JT distorted sites is reduced with temperature concomitantly with the decrease in resistivity of the ab-plane.

  15. Effects of hydrostatic pressure and temperature on the electron paramagnetic resonance spectrum of off-centre Jahn Teller [CuF4F4]6- complexes in SrF2 crystal

    NASA Astrophysics Data System (ADS)

    Ulanov, V. A.; Krupski, M.; Hoffmann, S. K.; Zaripov, M. M.

    2003-02-01

    Pressure and temperature variations of the spin-Hamiltonian parameters and electron paramagnetic resonance (EPR) linewidths of non-central Jahn-Teller [CuF4F4]6- complexes in SrF2 crystal were studied by continuous-wave EPR. It was found that the static spin-Hamiltonian parameters, found at T = 85 K and at normal pressure (gparallel = 2.491, gbot = 2.083, aparallel = 360, abot = 26, Ax'' = 96, Ay'' = 99, Az'' = 403 and betaexp = 17°), are slightly changed with hydrostatic pressure and, at T = 85 K and P = 550 MPa, become equal to gparallel = 2.489, gbot = 2.083, aparallel = 348, abot = 27, Ax'' = 99, Ay'' = 102, Az'' = 406 and betaexp = 20° (a and A values in megahertz, x''-, y''-and z''-axes are eigenvectors of the super-hyperfine tensor A, betaexp is the experimental value of the angle between the C4 symmetry axis of the complex and the x''-axis). With increasing temperature the well-resolved EPR spectrum of the complex is transformed continuously into a single broad line both at normal pressure and at a hydrostatic pressure of 550 MPa. But in the first case the coalescence point corresponds to 220-230 K while in the second case it is 195-205 K. Treatment using the linear combination of atomic orbitals representation of molecular orbitals (LCAO MO) model was performed to establish some relations between variations of the spin-Hamiltonian parameters and pressure-induced changes in the molecular structure of the complex. To get some additional information about the molecular structure of the complex and variations of its structural parameters with pressure, treatment using the rigid-ion model was performed. Experimental and theoretical results are discussed in the framework of the Jahn-Teller model of the complex.

  16. Investigation of dielectric relaxation, Jahn-Teller distortion, and magnetic ordering in Y substituted Pr1-xYxMnO3 (0.1 ≤ x ≤ 0.4)

    NASA Astrophysics Data System (ADS)

    Yadav, Ruchika; Nair, Harikrishnan S.; Kumar, Amit; Adiga, Shilpa; Bhat, H. L.; Yusuf, S. M.; Elizabeth, Suja

    2015-03-01

    We report structural, magnetic, and dielectric properties of the perovskite compound Pr1-xYxMnO3 (0.1 ≤ x ≤ 0.4) studied using dc magnetization, ac susceptibility, neutron powder diffraction, and dielectric techniques. These compounds crystallize in orthorhombic space group (Pnma) in the temperature range 5-300 K. The Mn-O-Mn bond angle decreases with the Y substitution along with an increase in the Jahn-Teller distortion. The Jahn-Teller distortion for Pr0.9Y0.1MnO3 shows an anomalous change near 50 K, below which it falls sharply. Neutron powder diffraction patterns of all reported compositions at low temperature constitute additional magnetic Bragg peaks that suggest magnetic ordering. Magnetic reflections were indexed in the nuclear lattice with the propagation vector k = (0, 0, 0). Rietveld refinement of powder patterns conform to A type antiferromagnetic ordering where moments are aligned ferromagnetically in a-c plane and coupled nearly antiferromagnetically along b-axis resulting in a net ferromagnetic component along the b-direction. The antiferromagnetic transition temperature was deduced from dc magnetization and ac susceptibility data. The transition temperature decreases by nearly 22 K (from 81 K to 59 K) as yttrium content (x) increases from 0.1 to 0.4. Measurements reveal strong frequency dispersion in dielectric constant and dielectric loss. Activation energy and relaxation time are estimated from the Arrhenius plot. It is further shown that relaxation behaviour is altered with yttrium doping concentration.

  17. Pseudo Jahn-Teller origin of instability of planar configurations of hexa-heterocycles. Application to compounds with 1,2- and 1,4-C4X2 skeletons (X = O, S, Se, Te)

    NASA Astrophysics Data System (ADS)

    Ilkhani, Ali R.; Hermoso, Willian; Bersuker, Isaac B.

    2015-10-01

    The driving force of symmetry breaking in planar molecular-ring systems in nondegenerate states is the pseudo Jahn-Teller effect (PJTE), and the knowledge of the mechanism of the latter allows one to manipulate the molecular properties, in particular, by restoring the planar configuration. We explore the PJTE induced structural nonplanarity in a series of 12 hexa-heterocycles with a C4X2 skeleton, 1,2- and 1,4-dichalcogenins with X = O, S, Se, Te, and a variety of ligands (H, F, Cl, Br). All the structures are optimized in both distorted equilibrium and unstable planar configurations, and the vibrational frequencies of the latter are evaluated. Then the energy profiles of the ground and several excited states in the planar configuration along the coordinate of instability are calculated, the excited states producing the instability of the ground state via the PJTE are revealed, and the vibronic coupling constants are estimated by means of fitting the solutions of the secular equations to the corresponding energy profiles.

  18. Structural characterisation of the perovskite series Sr{sub 0.9-x}Ca{sub x}Ce{sub 0.1}MnO{sub 3}: Influence of the Jahn-Teller effect

    SciTech Connect

    Kennedy, Brendan J.; Ting, Jimmy; Zhou Qingdi; Zhang Zhaoming; Matsuda, Motohide; Miyake, Michihiro

    2009-04-15

    Fifteen perovskite-type compounds Sr{sub 0.9-x}Ca{sub x}Ce{sub 0.1}MnO{sub 3}, x=0-0.9 in steps as fine as 0.05, have been synthesised by solid state methods, and the room temperature structures characterised using X-ray synchrotron powder diffraction. At low Ca contents (x<=0.45) the structures are tetragonal in space group I4/mcm and at high Ca contents (x>=0.55) the compounds are orthorhombic in space group Pbnm. At room temperature these two phases co-exist in the compound with x=0.5. XANES measurements show the Ce to be present as Ce{sup 4+} in all the oxides. High temperature structures are reported for selected members. - Graphical abstract: At room temperature the oxides with x<=0.45 in the series Sr{sub 0.9-x}Ca{sub x}Ce{sub 0.1}MnO{sub 3} are tetragonal in I4/mcm with a large Jahn-Teller distortion, and those with x>=0.55 are orthorhombic, in Pbnm. Heating the tetragonal samples results in two transitions, ultimately the structure becomes cubic.

  19. Evolution of Jahn-Teller distortion, transport and dielectric properties with doping in perovskite NdFe1-xMnxO3 (0 ≤ x ≤ 1) compounds.

    PubMed

    Chakraborty, Tirthankar; Yadav, Ruchika; Elizabeth, Suja; Bhat, H L

    2016-02-21

    We have carried out dielectric and transport measurements in NdFe1-xMnxO3 (0 ≤ x ≤ 1) series of compounds and studied the variation of activation energy due to a change in Mn concentration. Despite similar ionic radii in Mn(3+) and Fe(3+), large variation is observed in the lattice parameters and a crossover from dynamic to static Jahn-Teller distortion is discernible. The Fe/Mn-O-Fe/Mn bond angle on the ab plane shows an anomalous change with doping. With an increase in the Mn content, the bond angle decreases until x = 0.6; beyond this, it starts rising until x = 0.8 and again falls after that. A similar trend is observed in activation energies estimated from both transport and dielectric relaxation by assuming a small polaron hopping (SPH) model. Impedance spectroscopy measurements delineate grain and grain boundary contributions separately both of which follow the SPH model. Frequency variation of the dielectric constant is in agreement with the modified Debye law from which relaxation dispersion is estimated. PMID:26817614

  20. A study of the geometrical phase effect on scattering processes: Validity of the extended-Longuet-Higgins formalism for a four-fold Jahn-Teller type model system

    NASA Astrophysics Data System (ADS)

    Sarkar, B.; Varandas, A. J. C.

    2011-11-01

    The Longuet-Higgins theorem has recently been extended to Jahn-Teller type electronic degeneracy manifolds of arbitrary dimension and suggested to obtain generalized Born-Oppenheimer equations including the geometrical phase effect [A.J.C. Varandas, Chem. Phys. Lett. 487 (2010) 139]. By replacing the traditional sign-change diagnostic of the adiabatic electronic wave vectors (upon adiabatic transportation in configuration space along a loop that encircles the point of degeneracy) with a sign-change criterion based upon their rotation by π in the N-dimensional electronic wave-vector space, it has been shown that only one pair of adiabatic electronic states changes sign upon encircling the degeneracy in configuration space. Here, we examine in detail the four-fold problem and report relevant dynamics studies. The results are compared with those obtained from the simple Born-Oppenheimer approximation (geometrical phase ignored) as well as two- and three-fold single-surface generalized Born-Oppenheimer equations. A rationalization is provided based on the symmetry-allowed reactive probabilities.

  1. Effect of Jahn-Teller interactions on the specific heat and magnetic properties of charge-ordered La1-xCaxMnO3 (0.55⩽x⩽0.87) compounds

    NASA Astrophysics Data System (ADS)

    Qian, T.; Zheng, R. K.; Zhang, T.; Zhou, T. F.; Wu, W. B.; Li, X. G.

    2005-07-01

    The effect of Jahn-Teller (JT) interactions on specific heat and magnetic properties was studied for the series of La1-xCaxMnO3 (0.55⩽x⩽0.87) compounds by measurements of specific heat, ultrasonic velocity, and magnetization. Upon increasing x from 0.55 to 0.75, the enhancement of the JT interactions suppresses the ferromagnetic fluctuation above the charge ordering (CO) transition temperature TCO , increases the change of entropy associated with the charge/orbital ordering transition, and therefore enhances the stability of the CO state. With further increasing x from 0.75 to 0.87, the ferromagnetic fluctuation gradually swells up and the change of entropy almost linearly decreases, due to the reduction of the JT interactions. The magnetic field dependence of TCO was estimated based on the Clausius-Clapeyron equation, which well coincides with that obtained from the transport measurements in high magnetic fields. These results imply that the JT effect is a key ingredient in understanding the essential physics of the CO state.

  2. Relaxation Phenomenon in the Formation of the C-Type Orbital-Ordered State in the Simple Perovskite Manganite Sr1-xNdxMnO3

    NASA Astrophysics Data System (ADS)

    Inoue, Yasuhide; Sato, Hiroki; Koyama, Yasumasa

    2016-02-01

    The formation of the C-type orbital-ordered (COO) state from the disordered cubic (DC) state in Sr1-xNdxMnO3 (SNMO) with the simple perovskite structure has been examined mainly by transmission electron microscopy. As the COO state has tetragonal I4/mcm symmetry, its formation is associated with the cubic-to-tetragonal structural transition. It was found that, when SNMO samples were cooled down from the DC state, the R25-type rotational displacement of MnO6 octahedra was first induced, together with the symmetry change into the tetragonal I4/mcm structure. The C-type orbital ordering then appeared due to the induction of the Jahn-Teller distortion as a response of a lattice system to this orbital ordering. Because no symmetry change occurred in the latter case, the Jahn-Teller distortion can be regarded as a dilatational distortion. One interesting feature is that the appearance of the dilatational Jahn-Teller distortion led to a nanometer-scale banded structure, characterized by an alternating array of two tetragonal variants with different c/a values. In addition, the formation of the COO state from the DC state exhibited a time-relaxation phenomenon. The origin of this relaxation phenomenon is also discussed here in terms of the competition between the tetragonal spontaneous strain for the rotational displacement and the dilatational Jahn-Teller distortion for orbital ordering.

  3. Nonpercolative nature of the metal-insulator transition and persistence of local Jahn-Teller distortions in the rhombohedral regime of La1 -xCaxMnO3

    NASA Astrophysics Data System (ADS)

    Shatnawi, Mouath; Bozin, Emil S.; Mitchell, J. F.; Billinge, Simon J. L.

    2016-04-01

    Evolution of the average and local crystal structure of Ca-doped LaMnO3 has been studied across the metal to insulator (MI) and the orthorhombic to rhombohedral (OR) structural phase transitions over a broad temperature range for two Ca concentrations (x =0.18 ,0.22 ). Combined Rietveld and high real space resolution atomic pair distribution function (PDF) analysis of neutron total scattering data was carried out with aims of exploring the possibility of nanoscale phase separation (PS) in relation to MI transition, and charting the evolution of local Jahn-Teller (JT) distortion of MnO6 octahedra across the OR transition at TS˜720 K. The study utilized explicit two-phase PDF structural modeling, revealing that away from TMI there is no evidence for nanoscale phase coexistence. The local JT distortions disappear abruptly upon crossing into the metallic regime both with doping and temperature, with only a small temperature-independent signature of quenched disorder being observable at low temperature as compared to CaMnO3. The results hence do not support the percolative scenario for the MI transition in La1 -xCaxMnO3 based on PS, and question its ubiquity in the manganites. In contrast to LaMnO3 that exhibits long-range orbital correlations and sizable octahedral distortions at low temperature, the doped samples with compositions straddling the MI boundary exhibit correlations (in the insulating regime) limited to only ˜1 nm with observably smaller distortions. In the x =0.22 sample local JT distortions are found to persist across the OR transition and deep into the R phase (up to ˜1050 K), where they are crystallographically prohibited. Their magnitude and subnanometer spatial extent remain unchanged.

  4. Anisotropic orbital occupation and Jahn-Teller distortion of orthorhombic YMnO{sub 3} epitaxial films: A combined experimental and theoretical study on polarization-dependent x-ray absorption spectroscopy

    SciTech Connect

    Haw, Shu-Chih; Chen, Shin-Ann; Lee, Jenn-Min; Lu, Kueih-Tzu; Lee, Ming-Tao; Pi, Tun-Wen; Chen, Jin-Ming E-mail: Zhiwei.Hu@cpfs.mpg.de; Lin, Pao-An; Lee, Chih-Hao; Hu, Zhiwei E-mail: Zhiwei.Hu@cpfs.mpg.de

    2014-04-21

    The b-axis oriented orthorhombic YMnO{sub 3} (o-YMnO{sub 3}) epitaxial films on a YAlO{sub 3} (010) substrate were fabricated with pulsed-laser deposition. The anisotropic orbital occupation and Jahn-Teller (JT) distortion of an o-YMnO{sub 3} film were investigated with polarization-dependent x-ray absorption spectra and configuration-interaction multiplet-cluster calculations. A significant energy difference, ∼3.8 eV, for the main white line along E//b and E//a in polarization-dependent Mn K-edge spectra of o-YMnO{sub 3} indicates an extraordinary JT distortion and significant anisotropic Mn–O bonding within the ab plane in the o-YMnO{sub 3} film. Most importantly, although the orbital occupation of 3d electrons in o-YMnO{sub 3} films is almost the same as that in single crystalline o-DyMnO{sub 3}, the JT distortion of o-YMnO{sub 3} films is larger than that of single crystalline o-DyMnO{sub 3}, deduced from the multiplet calculations. We speculate that this JT distortion predominantly contributes to the origin of the cycloidal spin deformation in bulk o-YMnO{sub 3}, because of a suppressed nearest-neighbor superexchange interaction and an enhanced next-nearest-neighbor superexchange interaction. These complementary results provide insight into the origin of the E-type magnetic configuration of o-YMnO{sub 3}.

  5. Non percolative nature of the metal-insulator transition and persistence of local Jahn-Teller distortions in the rhombohedral regime of La1-xCaxMnO3

    DOE PAGES

    Shatnawi, Mouath; Bozin, Emil S.; Mitchell, J. F.; Billinge, Simon J. L.

    2016-04-25

    Evolution of the average and local crystal structure of Ca-doped LaMnO3 has been studied across the metal to insulator (MI) and the orthorhombic to rhombohedral (OR) structural phase transitions over a broad temperature range for two Ca concentrations (x = 0.18,0.22). Combined Rietveld and high real space resolution atomic pair distribution function (PDF) analysis of neutron total scattering data was carried out with aims of exploring the possibility of nanoscale phase separation (PS) in relation to MI transition, and charting the evolution of local Jahn-Teller (JT) distortion of MnO6 octahedra across the OR transition at TS~720 K. The study utilizedmore » explicit two-phase PDF structural modeling, revealing that away from TMI there is no evidence for nanoscale phase coexistence. The local JT distortions disappear abruptly upon crossing into the metallic regime both with doping and temperature, with only a small temperature-independent signature of quenched disorder being observable at low temperature as compared to CaMnO3. The results hence do not support the percolative scenario for the MI transition in La1–xCaxMnO3 based on PS, and question its ubiquity in the manganites. In contrast to LaMnO3 that exhibits long-range orbital correlations and sizable octahedral distortions at low temperature, the doped samples with compositions straddling the MI boundary exhibit correlations (in the insulating regime) limited to only ~1 nm with observably smaller distortions. In the x = 0.22 sample local JT distortions are found to persist across the OR transition and deep into the R phase (up to ~1050 K), where they are crystallographically prohibited. As a result, their magnitude and subnanometer spatial extent remain unchanged.« less

  6. Pseudo Jahn-Teller distortion for a tricyclic carbon sulfide (C6S8) and its suppression in S-oxygenated dithiine (C4H4(SO2)2)

    NASA Astrophysics Data System (ADS)

    Pratik, Saied Md.; Chowdhury, Chandra; Bhattacharjee, Rameswar; Jahiruddin, Sk.; Datta, Ayan

    2015-10-01

    The tricyclic carbon-sulfide, C6S8 molecule containing two S-atoms in the 1,4-position of the central six-membered ring and one disulfide (Ssbnd S) and one thione (Cdbnd S) bond on the five membered rings on its either side (1) possesses a "butterfly flapping" type distorted ground state in the gas-phase and also in β-phase of the crystal. For the isolated molecule, better consideration of the S…S non-bonding interactions in the dithiine ring in the bent form at the M06-2X/6-31+G(d,p) level leads to a significant barrier for inversion of 2.4 kcal/mol which is 2-3 times more than that previously obtained by Weber and Dolg at the B3LYP/cc-pVTZ level due to underestimation of dispersion interactions at the B3LYP level. The origin of the distortion leading to lowering of symmetry for 1 (C2h → C2) is traced to vibronic mixing between the ground state (Ag) and the low lying excited states of Au symmetry through the au normal mode, a (1Ag + 1Au + 2Au + 3Au) × au pseudo Jahn-Teller effect (PJTE) problem. Based on fitting of the ground state APES to the lowest root of the 4 × 4 secular determinant, we calculate the linear vibronic coupling constants (F0i) between the relevant states. Similar in class to 1, the S-oxygenated derivative of dithiine, C4H4(SO2)2 (2) unlike most other dithiines, remains planar. The absence of the butterfly-type puckered structure in 2 is traced to the enhanced gap (Δ0) and very small vibronic coupling (F01) between the ground and PJT active state along the au distortion which suppress the PJT instability. Considering the separation of the occupied molecular orbital (OMO) and unoccupied molecular orbitals (UMO) energy levels provide a qualitative understanding for the contrasting behavior of 1 and 2. In effect, the PJT effect is shown to be a fruitful and general tool to describe the presence or lack of molecular distortion.

  7. The Jahn-Teller effect in the excitation and emission spectra of Ba/sub 6/Y/sub 2/Al/sub 4/O/sub 15/:Sn/sup 2+/ and Ba/sub 2/YAlO/sub 5/:Sn/sup 2+/

    SciTech Connect

    Smets, B.M.J.; Verlijsdonk, J.G.; Rutten, J. )

    1989-04-01

    Luminescence measurements are presented for Sn/sup 2+/ doped Ba/sub 6/Y/sub 2/Al/sub 4/O/sub 15/ and Ba/sub 2/YAlO/sub 5/. In these compounds several crystallographic sites are available for Sn/sup 2+/. The luminescence properties of Sn/sup 2+/ in one of these sites can be accounted for by assuming that the Jahn-Teller effect is acting on the /sup 3/P/sub 1/ excited state of the Sn/sup 2+/ ion. The vibronic interaction results in the occurrence of two emission bands in the case of Ba/sub 6/Y/sub 2/Al/sub 4/O/sub 15/:Sn/sup 2+/.

  8. Investigation of dielectric relaxation, Jahn-Teller distortion, and magnetic ordering in Y substituted Pr{sub 1−x}Y{sub x}MnO{sub 3} (0.1 ≤ x ≤ 0.4)

    SciTech Connect

    Yadav, Ruchika Elizabeth, Suja; Nair, Harikrishnan S.; Kumar, Amit; Yusuf, S. M.; Adiga, Shilpa

    2015-03-07

    We report structural, magnetic, and dielectric properties of the perovskite compound Pr{sub 1−x}Y{sub x}MnO{sub 3} (0.1 ≤ x ≤ 0.4) studied using dc magnetization, ac susceptibility, neutron powder diffraction, and dielectric techniques. These compounds crystallize in orthorhombic space group (Pnma) in the temperature range 5–300 K. The Mn-O-Mn bond angle decreases with the Y substitution along with an increase in the Jahn-Teller distortion. The Jahn-Teller distortion for Pr{sub 0.9}Y{sub 0.1}MnO{sub 3} shows an anomalous change near 50 K, below which it falls sharply. Neutron powder diffraction patterns of all reported compositions at low temperature constitute additional magnetic Bragg peaks that suggest magnetic ordering. Magnetic reflections were indexed in the nuclear lattice with the propagation vector k = (0, 0, 0). Rietveld refinement of powder patterns conform to A type antiferromagnetic ordering where moments are aligned ferromagnetically in a–c plane and coupled nearly antiferromagnetically along b-axis resulting in a net ferromagnetic component along the b-direction. The antiferromagnetic transition temperature was deduced from dc magnetization and ac susceptibility data. The transition temperature decreases by nearly 22 K (from 81 K to 59 K) as yttrium content (x) increases from 0.1 to 0.4. Measurements reveal strong frequency dispersion in dielectric constant and dielectric loss. Activation energy and relaxation time are estimated from the Arrhenius plot. It is further shown that relaxation behaviour is altered with yttrium doping concentration.

  9. From spin induced ferroelectricity to dipolar glasses: Spinel chromites and mixed delafossites

    SciTech Connect

    Maignan, A.

    2012-11-15

    Magnetoelectric multiferroics showing coupling between polarization and magnetic order are attracting much attention. For instance, they could be used in memory devices. Metal-transition oxides are provided several examples of inorganic magnetoelectric multiferroics. In the present short review, spinel and delafossite chromites are described. For the former, an electric polarization is evidenced in the ferrimagnetic state for ACr{sub 2}O{sub 4} polycrystalline samples (A=Ni, Fe, Co). The presence of a Jahn-Teller cation such as Ni{sup 2+} at the A site is shown to yield larger polarization values. In the delafossites, substitution by V{sup 3+} at the Cr or Fe site in CuCrO{sub 2} (CuFeO{sub 2}) suppresses the complex antiferromagnetic structure at the benefit of a spin glass state. The presence of cation disorder, probed by transmission electron microscopy, favors relaxor-like ferroelectricity. The results on the ferroelectricity of ferrimagnets and insulating spin glasses demonstrate that, in this research field, transition-metal oxides are worth to be studied. - Graphical abstract: Electric polarization as a function of temperature is measured up to T{sub C} in three chromite ferrimagnetic spinels. Largest values are reached for spinels with Jahn-Teller cations at the A site (Ni or Fe). Highlights: Black-Right-Pointing-Pointer Electric polarization is evidenced in the ferrimagnetic state of the chromite spinels. Black-Right-Pointing-Pointer Jahn-Teller cations at the A site of these spinels lead to larger polarization values. Black-Right-Pointing-Pointer Vanadium substituted at the Cr (or Fe) site of delafossites changes the antiferromagnetic state to spin glass. Black-Right-Pointing-Pointer Electric polarization is not the result of magnetic ordering but magnetic disordering in Cr or Fe delafossites. Black-Right-Pointing-Pointer Relaxor-type ferroelectricity or spin induced ferroelectricity can be observed in the delafossites.

  10. Glass transition and stable glass formation of tetrachloromethane

    NASA Astrophysics Data System (ADS)

    Chua, Y. Z.; Tylinski, M.; Tatsumi, S.; Ediger, M. D.; Schick, C.

    2016-06-01

    Physical vapor deposition (PVD) has been used to prepare organic glasses with very high kinetic stability and it has been suggested that molecular anisotropy is a prerequisite for stable glass formation. Here we use PVD to prepare glasses of tetrachloromethane, a simple organic molecule with a nearly isotropic molecular structure. In situ AC nanocalorimetry was used to characterize the vapor-deposited glasses. Glasses of high kinetic stability were produced by deposition near 0.8 Tg. The isothermal transformation of the vapor-deposited glasses into the supercooled liquid state gave further evidence that tetrachloromethane forms glasses with high kinetic stability, with the transformation time exceeding the structural relaxation time of the supercooled liquid by a factor of 103. The glass transition temperature of liquid-cooled tetrachloromethane is determined as Tg ≈ 78 K, which is different from previously reported values. The frequency dependence of the glass transition was also determined and the fragility was estimated as m ≈ 118. The successful formation of PVD glasses of tetrachloromethane which have high kinetic stability argues that molecular asymmetry is not a prerequisite for stable glass formation.

  11. Effects of dynamic Jahn-Teller distortions by Raman spectroscopy in the layered CMR manganite La{sub 2{minus}2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7}, x = 0.36

    SciTech Connect

    Bordallo, H.N.; Argyriou, D.N.; Mitchell, J.F.; Strouse, G.F.

    1998-12-01

    The close interplay among charge, spin, and lattice degrees of freedom in the colossal magnetoresistive (CMR) manganite oxides is believed to play an important role in the transport mechanism in these itinerant ferromagnets. While the work on CMR materials has concentrated on the 3D perovskite manganites, the discovery of the layered compounds La{sub 2{minus}2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7} as another class of CMR oxides provides a rich opportunity to explore the relationship between structure and transport properties on varying length and time scales in reduced dimensions. The crystal structure of the layered CMR compounds La{sub 2{minus}2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7} is comprised of perovskite bilayers of corner-linked MnO{sub 6} octahedra forming infinite sheets. Doping of divalent cations such as Sr{sup 2+} gives rise to a mixed valent system were Jahn-Teller (JT) active Mn{sup 3+} and JT-inactive Mn{sup 4+} co-exist on the lattice. Among the current theoretical models of transport in the three-dimensional perovskite materials is the role of JT. This transport mechanism plays a fundamental role above the Curie temperature (T{sub c}). Indeed, localized lattice distortions have been observed experimentally above T{sub c} in the (La,Ca)MnO{sub 3} perovskite system. In this communication, the authors report resonant Raman spectroscopic measurements on a micro-crystalline sample of La{sub 1.28}Sr{sub 1.72}Mn{sub 2}O{sub 7} (x = 0.36). The measurements suggest discrete phonon modes for the Mn{sup 3+} and Mn{sup 4+} lattice sites, which may arise from either dynamic or static localization and the presence of Mn{sup 2+} defects in the lattice.

  12. Solid solutions of a Jahn-Teller compound in an undistorted host. 4. Neutron and X-ray single-crystal structures of two Cr/Zn Tutton salt solid solutions and the observation of disorder by low-temperature neutron diffraction

    SciTech Connect

    Cotton, F.A.; Daniels, L.M.; Falvello, L.R.; Schultz, A.J.; Murillo, C.A. |

    1994-11-23

    Solid solutions of the ammonium Cr/Zn Tutton salt with two different compositions, (NH{sub 4}){sub 2}[Cr{sub 0.10}Zn{sub 0.90}(H{sub 2}O){sub 6}]-(SO{sub 4}){sub 2}, 1, and (NH{sub 4}){sub 2}[Cr{sub 0.22}Zn{sub 0.78}(H{sub 2}O){sub 6}](SO{sub 4}){sub 2}, 2, have been studied by single-crystal X-ray diffraction at room temperature and by single crystal time-of-flight neutron diffraction at 11-16 K for 1 and at 11-17 K for 2. Composition was also characterized by atomic absorption, AA, analysis. The solid solutions crystallize in the monoclinic space group P2{sub 1}/c, Z = 2. The structure of 1 was refined to residuals of R = 0.0226 and 0.0670 and quality of fit = 1.099 and 1.165 for X-ray and neutron data, respectively; the corresponding residuals for the X-ray and neutron structures of 2 are R = 0.0215 and 0.0682, and quality-of-fit = 1.057 and 0.994. The anisotropic displacement parameters of the oxygen and hydrogen atoms from the neutron diffraction studies are examined for their implications as to the presence or absence of disorder in the ligands about the composite Cr/Zn metal center. The results for composition 2, x(Cr) = 0.22, clearly indicate the presence of disorder for the aqua ligand affected by Jahn-Teller distortion in the pure chromium complex. For composition 1, x(Cr) = 0.10, the observation of disorder is not clear. The structures of 1 and 2 are isotypic at a given temperature, but the room-temperature and low-temperature structures differ subtly in the hydrogen bonding pattern.

  13. Bubble formation in additive manufacturing of glass

    NASA Astrophysics Data System (ADS)

    Luo, Junjie; Gilbert, Luke J.; Peters, Daniel C.; Bristow, Douglas A.; Landers, Robert G.; Goldstein, Jonathan T.; Urbas, Augustine M.; Kinzel, Edward C.

    2016-05-01

    Bubble formation is a common problem in glass manufacturing. The spatial density of bubbles in a piece of glass is a key limiting factor to the optical quality of the glass. Bubble formation is also a common problem in additive manufacturing, leading to anisotropic material properties. In glass Additive Manufacturing (AM) two separate types of bubbles have been observed: a foam layer caused by the reboil of the glass melt and a periodic pattern of bubbles which appears to be unique to glass additive manufacturing. This paper presents a series of studies to relate the periodicity of bubble formation to part scan speed, laser power, and filament feed rate. These experiments suggest that bubbles are formed by the reboil phenomena why periodic bubbles result from air being trapped between the glass filament and the substrate. Reboil can be detected using spectroscopy and avoided by minimizing the laser power while periodic bubbles can be avoided by a two-step laser melting process to first establish good contact between the filament and substrate before reflowing the track with higher laser power.

  14. A simplified model for glass formation

    NASA Technical Reports Server (NTRS)

    Uhlmann, D. R.; Onorato, P. I. K.; Scherer, G. W.

    1979-01-01

    A simplified model of glass formation based on the formal theory of transformation kinetics is presented, which describes the critical cooling rates implied by the occurrence of glassy or partly crystalline bodies. In addition, an approach based on the nose of the time-temperature-transformation (TTT) curve as an extremum in temperature and time has provided a relatively simple relation between the activation energy for viscous flow in the undercooled region and the temperature of the nose of the TTT curve. Using this relation together with the simplified model, it now seems possible to predict cooling rates using only the liquidus temperature, glass transition temperature, and heat of fusion.

  15. Effect of alteration phase formation on the glass dissolution rate

    SciTech Connect

    Ebert, W.L.

    1997-10-01

    The dissolution rates of many glasses have been observed to increase upon the formation of certain alteration phases. It is important to understand the mechanism by which alteration phases affect glass corrosion behavior and the glass dissolution rate to reliably predict whether or not similar effects will occur in a disposal environment and the impact of phase formation on the long-term performance of waste glass. While solid state transformation of a glass to thermodynamically more stable phases in kinetically prohibitive, contact by water provides an energetically favorable pathway for this transformation to occur by a dissolution-reprecipitation mechanism. The kinetics of the transformation depends on the dissolution kinetics of the glass and the precipitation kinetics of the alteration phases. The rates of these two processes are linked primarily through the solution activity of orthosilicic acid (and perhaps also that of an aluminum-bearing species).

  16. Crystal nucleation and glass formation in metallic alloy melts

    NASA Technical Reports Server (NTRS)

    Spaepen, F.

    1984-01-01

    Homogeneous nucleation, containerless solidification, and bulk formation of metallic glasses are discussed. Homogeneous nucleation is not a limiting factor for metallic glass formation at slow cooling rates if the reduced glass transition temperature is high enough. Such glasses can be made in bulk if heterogeneous nucleants are removed. Containerless processing eleminates potential sources of nucleants, but as drop tube experiments on the Pd-Si alloys show, the free surface may still be a very effective heterogeneous nucleant. Combination of etching and heating in vacuum or fluxing can be effective for cleaning fairly large ingots of nucleants. Reduced gravity processing has a potentially useful role in the fluxing technique, for example to keep large metallic ingots surrounded by a low density, low fluidity flux if this proved difficult under ground conditions. For systems where heterogeneous nucleants in the bulk of the ingot need gravity to segregate to the flux-metal interface, reduced gravity processing may not be appropriate for bulk glass formation.

  17. Glass Formation Ability and Kinetics of the Gd55Al20Ni25 Bulk Metallic Glass

    NASA Astrophysics Data System (ADS)

    Jo, Chol-Lyong; Xia, Lei; Ding, Ding; Dong, Yuan-Da

    2006-03-01

    We report a new bulk glass-forming alloy Gd55Al20Ni25. The bulk sample of the alloy is prepared in the shape of rods in diameter 2 mm by suction casting. The rod exhibits typical amorphous characteristics in the x-ray diffraction pattern, paramagnetic property at 300 K, distinct glass transition and multi-step crystallization behaviour in differential scanning calorimetry traces. The glass formation ability of the alloy is investigated by using the reduced glass transition temperature Trg and the parameter γ. Kinetics of glass transition and primary crystallization is also studied. The fragility parameter m obtained from the Vogel-Fulcher-Tammann dependence of glass transition temperature Tg on ln phi (phi is the heating rate) classifies the bulk metallic glasses into the intermediate category according to Angell's classification.

  18. Glass formation and physical properties of chalcogenide glasses in Ge-S-Pb system

    NASA Astrophysics Data System (ADS)

    Qu, Guoshun; Lin, Changgui; Li, Zhuobin; Zhai, Sumin; Gu, Shaoxuan; Tao, Haizheng; Xu, Tiefeng

    2014-03-01

    Chalcogenide glasses based on Ge-S-Pb system were prepared, and the compositional dependence of their physic-chemical properties and glass structure were investigated. Up to 23 mol% Pb can be dissolved in this glass system and the glass-formation region like a small isolated island was found. The effect of the introduction of Pb on the glass structure is discussed by employing Raman spectra. It is shown that the substitution of Pb for Ge decreases the number of [GeS4] and [S3Ge-GeS3] units, leading to the variation of properties, such as Tg, H‧, and Hv. The knowledge of this structure-properties relationship of Ge-S-Pb glasses would be of significance to select or to design suitable host glass for optoelectronic applications.

  19. Formation and durability of hydrated layers for several oxide glasses

    SciTech Connect

    Nishii, Junji; Akai, Tomoko; Yamashita, Masaru; Yamanaka, Hiroshi; Wakabayashi, Hajimu

    1995-12-31

    Formations and durabilities of hydrated layers were compared between a soda-aluminosilicate (NAS), a soda-lime-aluminosilicate (NCAS) and a soda-lime-alumino-borosilicate (NCABS) glasses. The first step of the study was to prepare the optically transparent hydrated layers on the surface of specimens by an autoclave (400 C, 20 kgf/cm{sup 2}) treatment. Distributions of OH groups in hydrated layers were analyzed by an etch sectioning and FTIR measurement. The rates of hydration of the glasses were in the order NAS {much_gt} NCAS > NCABS. The hydration of the NCABS glass, which is a modified nuclear waste glass, required the treatment longer than those of the NAS and NCAS glasses. In the second step, the authors investigated the durabilities of hydrated layers by immersing the specimens into a distilled water at 100 C. The dissolutions of hydrated layers were confirmed for each glass. The dissolution rates of hydrated layers were in the order NCAS > NCABS {much_gt} NAS. It has become apparent by an XPS analysis that the highest durability of the hydrated NAS glass was due to the formation of a sodium free Al{sub 2}O{sub 3}-SiO{sub 2} layer on the surface. The hydrated layer of the NCAS glass, while the sodium ions were almost leached out during immersion, dissolved to water most quickly than those of other glasses. In the hydrated layer of the NCABS glass, a half amount of sodium and boron ions remained and inhibited the dissolution of hydrated layer.

  20. Glass formation, properties and structure of soda-yttria-silica glasses

    NASA Technical Reports Server (NTRS)

    Angel, Paul W.; Hann, Raiford E.

    1992-01-01

    The glass formation region of the soda yttria silicate system was determined. The glasses within this region were measured to have a density of 2.4 to 3.1 g/cu cm, a refractive index of 1.50 to 1.60, a coefficient of thermal expansion of 7 x 10(exp -6)/C, softening temperatures between 500 and 780 C, and Vickers hardness values of 3.7 to 5.8 GPa. Aqueous chemical durability measurements were made on select glass compositions while infrared transmission spectra were used to study the glass structure and its effect on glass properties. A compositional region was identified which exhibited high thermal expansion, high softening temperatures, and good chemical durability.

  1. Glass formation, properties, and structure of soda-yttria-silicate glasses

    NASA Technical Reports Server (NTRS)

    Angel, Paul W.; Hann, Raiford E.

    1991-01-01

    The glass formation region of the soda yttria silicate system was determined. The glasses within this region were measured to have a density of 2.4 to 3.1 g/cu cm, a refractive index of 1.50 to 1.60, a coefficient of thermal expansion of 7 x 10(exp -6)/C, softening temperatures between 500 and 780 C, and Vickers hardness values of 3.7 to 5.8 GPa. Aqueous chemical durability measurements were made on select glass compositions while infrared transmission spectra were used to study the glass structure and its effect on glass properties. A compositional region was identified which exhibited high thermal expansion, high softening temperatures, and good chemical durability.

  2. Study of the glass formation of high temperature superconductors

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin C.; Kaukler, William F.; Rolin, Terry

    1992-01-01

    A number of compositions of ceramic oxide high T(sub c) superconductors were elevated for their glass formation ability by means of rapid thermal analysis during quenching, optical, and electron microscopy of the quenched samples, and with subsequent DSC measurements. Correlations between experimental measurements and the methodical composition changes identified the formulations of superconductors that can easily form glass. The superconducting material was first formed as a glass; then, with subsequent devitrification, it was formed into a bulk crystalline superconductor by a series of processing methods.

  3. Quantifying the origin of metallic glass formation

    NASA Astrophysics Data System (ADS)

    Johnson, W. L.; Na, J. H.; Demetriou, M. D.

    2016-01-01

    The waiting time to form a crystal in a unit volume of homogeneous undercooled liquid exhibits a pronounced minimum τX* at a `nose temperature' T* located between the glass transition temperature Tg, and the crystal melting temperature, TL. Turnbull argued that τX* should increase rapidly with the dimensionless ratio trg=Tg/TL. Angell introduced a dimensionless `fragility parameter', m, to characterize the fall of atomic mobility with temperature above Tg. Both trg and m are widely thought to play a significant role in determining τX*. Here we survey and assess reported data for TL, Tg, trg, m and τX* for a broad range of metallic glasses with widely varying τX*. By analysing this database, we derive a simple empirical expression for τX*(trg, m) that depends exponentially on trg and m, and two fitting parameters. A statistical analysis shows that knowledge of trg and m alone is therefore sufficient to predict τX* within estimated experimental errors. Surprisingly, the liquid/crystal interfacial free energy does not appear in this expression for τX*.

  4. Quantifying the origin of metallic glass formation

    PubMed Central

    Johnson, W. L.; Na, J. H.; Demetriou, M. D.

    2016-01-01

    The waiting time to form a crystal in a unit volume of homogeneous undercooled liquid exhibits a pronounced minimum τX* at a ‘nose temperature' T* located between the glass transition temperature Tg, and the crystal melting temperature, TL. Turnbull argued that τX* should increase rapidly with the dimensionless ratio trg=Tg/TL. Angell introduced a dimensionless ‘fragility parameter', m, to characterize the fall of atomic mobility with temperature above Tg. Both trg and m are widely thought to play a significant role in determining τX*. Here we survey and assess reported data for TL, Tg, trg, m and τX* for a broad range of metallic glasses with widely varying τX*. By analysing this database, we derive a simple empirical expression for τX*(trg, m) that depends exponentially on trg and m, and two fitting parameters. A statistical analysis shows that knowledge of trg and m alone is therefore sufficient to predict τX* within estimated experimental errors. Surprisingly, the liquid/crystal interfacial free energy does not appear in this expression for τX*. PMID:26786966

  5. Formation of monatomic metallic glasses through ultrafast liquid quenching.

    PubMed

    Zhong, Li; Wang, Jiangwei; Sheng, Hongwei; Zhang, Ze; Mao, Scott X

    2014-08-14

    It has long been conjectured that any metallic liquid can be vitrified into a glassy state provided that the cooling rate is sufficiently high. Experimentally, however, vitrification of single-element metallic liquids is notoriously difficult. True laboratory demonstration of the formation of monatomic metallic glass has been lacking. Here we report an experimental approach to the vitrification of monatomic metallic liquids by achieving an unprecedentedly high liquid-quenching rate of 10(14) K s(-1). Under such a high cooling rate, melts of pure refractory body-centred cubic (bcc) metals, such as liquid tantalum and vanadium, are successfully vitrified to form metallic glasses suitable for property interrogations. Combining in situ transmission electron microscopy observation and atoms-to-continuum modelling, we investigated the formation condition and thermal stability of the monatomic metallic glasses as obtained. The availability of monatomic metallic glasses, being the simplest glass formers, offers unique possibilities for studying the structure and property relationships of glasses. Our technique also shows great control over the reversible vitrification-crystallization processes, suggesting its potential in micro-electromechanical applications. The ultrahigh cooling rate, approaching the highest liquid-quenching rate attainable in the experiment, makes it possible to explore the fast kinetics and structural behaviour of supercooled metallic liquids within the nanosecond to picosecond regimes.

  6. The formation of crystals in glasses containing rare earth oxides

    NASA Astrophysics Data System (ADS)

    Fadzil, Syazwani Mohd; Hrma, Pavel; Crum, Jarrod; Siong, Khoo Kok; Ngatiman, Mohammad Fadzlee; Said, Riduan Mt

    2014-02-01

    Korean spent nuclear fuel will reach the capacity of the available temporary storage by 2016. Pyroprocessing and direct disposal seems to be an alternative way to manage and reuse spent nuclear fuel while avoiding the wet reprocessing technology. Pyroprocessing produces several wastes streams, including metals, salts, and rare earths, which must be converted into stabilized form. A suitable form for rare earth immobilization is borosilicate glass. The borosilicate glass form exhibits excellent durability, allows a high waste loading, and is easy to process. In this work, we combined the rare earths waste of composition (in wt%) 39.2Nd2O3-22.7CeO2-11.7La2O3-10.9PrO2-1.3Eu2O3-1.3Gd2O3-8.1Sm2O3-4.8Y2O3 with a baseline glass of composition 60.2SiO2-16.0B2O3-12.6Na2O-3.8Al2O3-5.7CaO-1.7ZrO2. Crystallization in waste glasses occurs as the waste loading increases. It may produce complicate glass processing and affect the product quality. To study crystal formation, we initially made glasses containing 5%, 10% and 15% of La2O3 and then glasses with 5%, 10% and 15% of the complete rare earth mix. Samples were heat-treated for 24 hours at temperatures 800°C to 1150°C in 50°C increments. Quenched samples were analyzed using an optical microscope, scanning electron microscope with energy dispersive spectroscopy, and x-ray diffraction. Stillwellite (LaBSiO5) and oxyapatite (Ca2La8Si6O26) were found in glasses containing La2O3, while oxyapatite (Ca2La8Si6O26 and NaNd9Si6O26) precipitated in glasses with additions of mixed rare earths. The liquidus temperature (TL) of the glasses containing 5%, 10% and 15% La2O3 were 800°C, 959°C and 986°C, respectively; while TL was 825°C, 1059°C and 1267°C for glasses with 5%, 10% and 15% addition of mixed rare earth oxides. The component coefficients TB2O3, TSiO2, TCaO, and TRE2O3 were also evaluated using a recently published study.

  7. The formation of crystals in glasses containing rare earth oxides

    SciTech Connect

    Fadzil, Syazwani Mohd; Hrma, Pavel; Crum, Jarrod; Siong, Khoo Kok; Ngatiman, Mohammad Fadzlee; Said, Riduan Mt

    2014-02-12

    Korean spent nuclear fuel will reach the capacity of the available temporary storage by 2016. Pyroprocessing and direct disposal seems to be an alternative way to manage and reuse spent nuclear fuel while avoiding the wet reprocessing technology. Pyroprocessing produces several wastes streams, including metals, salts, and rare earths, which must be converted into stabilized form. A suitable form for rare earth immobilization is borosilicate glass. The borosilicate glass form exhibits excellent durability, allows a high waste loading, and is easy to process. In this work, we combined the rare earths waste of composition (in wt%) 39.2Nd{sub 2}O{sub 3}–22.7CeO{sub 2}–11.7La{sub 2}O{sub 3}–10.9PrO{sub 2}–1.3Eu{sub 2}O{sub 3}–1.3Gd{sub 2}O{sub 3}–8.1Sm{sub 2}O{sub 3}–4.8Y{sub 2}O{sub 3} with a baseline glass of composition 60.2SiO{sub 2}–16.0B{sub 2}O{sub 3}–12.6Na{sub 2}O–3.8Al{sub 2}O{sub 3}–5.7CaO–1.7ZrO{sub 2}. Crystallization in waste glasses occurs as the waste loading increases. It may produce complicate glass processing and affect the product quality. To study crystal formation, we initially made glasses containing 5%, 10% and 15% of La{sub 2}O{sub 3} and then glasses with 5%, 10% and 15% of the complete rare earth mix. Samples were heat-treated for 24 hours at temperatures 800°C to 1150°C in 50°C increments. Quenched samples were analyzed using an optical microscope, scanning electron microscope with energy dispersive spectroscopy, and x-ray diffraction. Stillwellite (LaBSiO{sub 5}) and oxyapatite (Ca{sub 2}La{sub 8}Si{sub 6}O{sub 26}) were found in glasses containing La{sub 2}O{sub 3}, while oxyapatite (Ca{sub 2}La{sub 8}Si{sub 6}O{sub 26} and NaNd{sub 9}Si{sub 6}O{sub 26}) precipitated in glasses with additions of mixed rare earths. The liquidus temperature (T{sub L}) of the glasses containing 5%, 10% and 15% La{sub 2}O{sub 3} were 800°C, 959°C and 986°C, respectively; while T{sub L} was 825°C, 1059°C and 1267°C for glasses

  8. Glass formation and thermodynamics of supercooled monatomic liquids.

    PubMed

    Hoang, Vo Van; Odagaki, Takashi

    2011-06-01

    Atomic mechanism of glass formation of a supercooled simple monatomic liquid with Lennard-Jones-Gauss (LJG) interatomic potential is studied by molecular dynamics (MD) simulation. Supercooled and glassy states are obtained by cooling from the melt. Glassy state obtained at low temperatures is annealed for very long time, on the order of microsecond, and we find that glassy state remains unchanged and that the long-lived glassy state of a simple monatomic system in three dimensions is realized. We analyze the spatiotemporal properties of solid-like and liquid-like atoms that are defined by the Lindemann-like freezing criterion. The number of solid-like atoms, distributed throughout the liquid, increases with decreasing temperature toward glass transition and they form clusters. In the deeply supercooled region, almost all solid-like atoms form a single percolation cluster and its characteristic size increases sharply on further cooling. Glass formation in supercooled liquid occurs when a single percolation cluster of solid-like atoms involves a majority of atoms to form a relatively rigid solid phase. We also obtain several physical quantities of the system, including temperature dependence of mass density, Lindemann ratio, incoherent intermediate scattering function, α-relaxation time, evolution of radial distribution function, and local bond-pair orders detected by Honeycutt-Andersen analysis. We identify three characteristic temperatures related to the vitrification: a temperature at which crossover from liquid-like to solid-like dynamics occurs on cooling, the glass transition temperature, and the Vogel-Fulcher-Tammann temperature. Behavior of liquid-like atoms in glassy state has been analyzed and discussed. PMID:21553835

  9. Apatite formation on dental ceramics modified by a bioactive glass.

    PubMed

    Kontonasaki, E; Papadopoulou, L; Zorba, T; Pavlidou, E; Paraskevopoulos, K; Koidis, P

    2003-09-01

    Restorative dental materials are considered biocompatible without exhibiting any bioactive behaviour. The aim of this study was the investigation of surface structure changes on conventional dental ceramics used in metal-ceramic restorations modified by a bioactive glass, after immersion in SBF for various time periods. Bioactive glass powder was mixed with porcelain powder with three different weight ratios: 1:1, 1:2, and 2:1. The two powders were mixed with porcelain modelling liquid and the mixture was transferred and spread on the surface of pre-fabricated ceramic disks. Coated ceramic specimens after being exposed to a specific thermal cycle as it is recommended for dental ceramics were soaked in Simulated Body Fluid (SBF) at 37 degrees C for various periods of time. After soaking, specimens were studied using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Results revealed the development of a non-stoichiometric, biological apatite layer on their surface after exposure in SBF for several time periods. The onset of apatite-layer formation is directly dependent on the amount of bioglass in the coating and its thickness reduces within the specimens of the same bioactive glass-porcelain proportion with time, reaching an average thickness of 15 microm at the longest immersion time, for all the specimens.

  10. Smectite Formation from Basaltic Glass Under Acidic Conditions on Mars

    NASA Technical Reports Server (NTRS)

    Peretyazhko, T. S.; Sutter, B.; Morris, R. V.; Agresti, D. G.; Le, L.; Ming, D. W.

    2015-01-01

    Massive deposits of phyllosilicates of the smectite group, including Mg/Fe-smectite, have been identified in Mars's ancient Noachian terrain. The observed smectite is hypothesized to form through aqueous alteration of basaltic crust under neutral to alkaline pH conditions. These pH conditions and the presence of a CO2-rich atmosphere suggested for ancient Mars were favorable for the formation of large carbonate deposits. However, the detection of large-scale carbonate deposits is limited on Mars. We hypothesized that smectite deposits may have formed under acidic conditions that prevented carbonate precipitation. In this work we investigated formation of saponite at a pH of approximately 4 from Mars-analogue synthetic Adirondack basaltic glass of composition similar to Adirondack class rocks located at Gusev crater. Hydrothermal (200º Centigrade) 14 day experiments were performed with and without 10 millimoles Fe(II) or Mg under anoxic condition [hereafter denoted as anoxic_Fe, anoxic_Mg and anoxic (no addition of Fe(II) or Mg)] and under oxic condition [hereafter denoted as oxic (no addition of Fe(II) or Mg)]. Characterization and formation conditions of the synthesized saponite provided insight into the possible geochemical conditions required for saponite formation on Mars.

  11. Examining the role of canister cooling conditions on the formation of nepheline from nuclear waste glasses

    SciTech Connect

    Christian, J. H.

    2015-09-01

    Nepheline (NaAlSiO₄) crystals can form during slow cooling of high-level waste (HLW) glass after it has been poured into a waste canister. Formation of these crystals can adversely affect the chemical durability of the glass. The tendency for nepheline crystallization to form in a HLW glass increases with increasing concentrations of Al₂O₃ and Na₂O.

  12. Apparatus and process to enhance the uniform formation of hollow glass microspheres

    SciTech Connect

    Schumacher, Ray F

    2013-10-01

    A process and apparatus is provided for enhancing the formation of a uniform population of hollow glass microspheres. A burner head is used which directs incoming glass particles away from the cooler perimeter of the flame cone of the gas burner and distributes the glass particles in a uniform manner throughout the more evenly heated portions of the flame zone. As a result, as the glass particles are softened and expand by a released nucleating gas so as to form a hollow glass microsphere, the resulting hollow glass microspheres have a more uniform size and property distribution as a result of experiencing a more homogenous heat treatment process.

  13. Spectroscopic investigation of a new hybrid glass formed by the interaction between croconate ion and calcium polyphosphate

    NASA Astrophysics Data System (ADS)

    de Oliveira, Carlos Ivan R.; de Oliveira, Luiz Fernando C.; Dias Filho, Francisco A.; Messaddeq, Younes; Ribeiro, Sidney J. L.

    2005-07-01

    In this work, a new organic-inorganic hybrid material has been synthesized by the incorporation of croconate ion into a calcium polyphosphate coacervate. The hybrid so obtained was characterized by means of electronic and vibrational spectroscopies. The material is a homogeneous mixture described by a structural model, which includes helical chains of polyphosphate ions, where the calcium ion occupies the internal vacancies of the structure. The croconate ion appears to be occupying the regions outside the polymeric structure, surrounded by several water molecules. The electronic spectrum of the incorporated material shows a broad band peaking at the same wavelength region (363 nm) observed for the aqueous solution of croconate ion, and manifesting the Jahn-Teller effect as evidenced by the doublet structure of the band. The infrared spectrum is widely dominated by the absorption bands of the polyphosphate ion and the appearance of the carbonyl stretching band at ca. 1550 cm -1 indicates the presence of croconate ion incorporated in the structure. The Raman spectrum of the material shows several vibrational bands related to the oxocarbon moiety; most of them are shifted in comparison with the free ion. These shifts can be understood in terms of strong hydrogen bonding interactions between water molecules and the oxocarbon moiety. The low temperature methodology proposed here can be well used in the preparation of new phosphate glasses containing organic moieties opening the route to an entirely new class of hybrid glasses.

  14. Theoretical Studies of the Spin Hamiltonian Parameters and Local Distortions for Cu2+ in Alkaline Earth Lead Zinc Phosphate Glasses

    NASA Astrophysics Data System (ADS)

    Wang, Bo-Kun; Wu, Shao-Yi; Yuan, Zi-Yi; Liu, Zi-Xuan; Jiang, Shi-Xin; Liu, Zheng; Yao, Zi-Jian; Teng, Bao-Hua; Wu, Ming-He

    2016-08-01

    The spin Hamiltonian parameters and local structures are theoretically studied for Cu2+-doped alkaline earth lead zinc phosphate (RPPZ, R=Mg, Ca, Sr, and Ba) glasses based on the high-order perturbation calculations for a tetragonally elongated octahedral 3d9 cluster. The relative elongation ratios are found to be ρ≈3.2%, 4.4%, 4.6%, and 3.3% for R=Mg, Ca, Sr, and Ba, respectively, because of the Jahn-Teller effect. The whole decreasing crystal-field strength Dq and orbital reduction factor k from Mg to Sr are ascribed to the weakening electrostatic coulombic interactions and the increasing probability of productivity of nonbridge oxygen (and hence increasing Cu2+-O2- electron cloud admixtures) under PbO addition, respectively, with increasing alkali earth ionic radius. The anomalies (the largest Dq and the next highest k among the systems) for R=Ba are attributed to the cross linkage of this large cation in the network. The overall increasing order (Mg≤Baglasses containing copper dopants.

  15. Probing Toluene and Ethylbenzene Stable Glass Formation using Inert Gas Permeation

    SciTech Connect

    Smith, R. Scott; May, Robert A.; Kay, Bruce D.

    2015-09-01

    Inert gas permeation is used to investigate the formation of stable glasses of toluene and ethylbenzene. The effect of deposition temperature (Tdep) on the kinetic stability of the vapor deposited glasses is determined using Kr desorption spectra from within sandwich layers of either toluene or ethylbenzene. The results for toluene show that the most stable glass is formed at Tdep = 0.92 Tg, although glasses with a kinetic stability within 50% of the most stable glass were found with deposition temperatures from 0.85 to 0.95 Tg. Similar results were found for ethylbenzene, which formed its most stable glass at 0.91 Tg and formed stable glasses from 0.81 to 0.96 Tg. These results are consistent with recent calorimetric studies and demonstrate that the inert gas permeation technique provides a direct method to observe the onset of molecular translation motion that accompanies the glass to supercooled liquid transition.

  16. Bulk Formation of Metallic Glasses and Amorphous Silicon from the Melt

    NASA Technical Reports Server (NTRS)

    Spaepen, F.

    1985-01-01

    By using metallic glass compositions with a high relative glass transition temperature, such as Pd40Ni40P20, homogeneous nucleation also becomes negligible. Large (5g) masses of this alloys were obtained using a molten B2O3 flux. Presently, bulk glass formation in iron based glasses is being investigated. It is expected that if an undercooling of about 250K can be achieved in a Ge or Si melt, formation of the amorphous semiconductor phase (rather than the crystal) may be kinetically favored. The volumetric behavior of undercooled liquid Ga droplet dispersion is investigated by dilatometry. A theoretical model (both analytical and numerical) was developed for transient nucleation in glass forming melts. The model, originally designed for isothermal conditions, was extended to continuous quenching. It is being applied to glass formation in various metallic and oxide systems. A further refinement will be the inclusion of diffusion controlled interfacial rearrangements governing the growth of the crystal embryos.

  17. Role of Ti in the formation of Zr-Ti-Cu-Ni-Al glasses

    SciTech Connect

    Kim, T H; Gangopadhyay, A K; Xing, L Q; Lee, G W; Shen, Y T; Kelton, K F; Goldman, A I; Hyers, R W; Rogers, J R

    2010-07-19

    It has been widely reported that glass formation improves in Zr{sub 62}Cu{sub 20}Ni{sub 8}Al{sub 10} alloys when small amounts of Ti are substituted for Zr. Glasses containing greater than 3 at. % Ti crystallize to a metastable icosahedral phase, suggesting that Ti enhances icosahedral short-range order in the liquid/glass, making crystallization more difficult during cooling. However, based on containerless solidification and in situ high-energy synchrotron diffraction studies of electrostatically levitated supercooled liquids of these alloys, we demonstrate that Ti inhibits surface crystallization but neither increases the icosahedral short-range order nor improves glass formation.

  18. Influence of strontium for calcium substitution in bioactive glasses on degradation, ion release and apatite formation.

    PubMed

    Fredholm, Yann C; Karpukhina, Natalia; Brauer, Delia S; Jones, Julian R; Law, Robert V; Hill, Robert G

    2012-05-01

    Bioactive glasses are able to bond to bone through the formation of hydroxy-carbonate apatite in body fluids while strontium (Sr)-releasing bioactive glasses are of interest for patients suffering from osteoporosis, as Sr was shown to increase bone formation both in vitro and in vivo. A melt-derived glass series (SiO(2)-P(2)O(5)-CaO-Na(2)O) with 0-100% of calcium (Ca) replaced by Sr on a molar base was prepared. pH change, ion release and apatite formation during immersion of glass powder in simulated body fluid and Tris buffer at 37°C over up to 8 h were investigated and showed that substituting Sr for Ca increased glass dissolution and ion release, an effect owing to an expansion of the glass network caused by the larger ionic radius of Sr ions compared with Ca. Sr release increased linearly with Sr substitution, and apatite formation was enhanced significantly in the fully Sr-substituted glass, which allowed for enhanced osteoblast attachment as well as proliferation and control of osteoblast and osteoclast activity as shown previously. Studying the composition-structure-property relationship in bioactive glasses enables us to successfully design next-generation biomaterials that combine the bone regenerative properties of bioactive glasses with the release of therapeutically active Sr ions. PMID:21993007

  19. Influence of strontium for calcium substitution in bioactive glasses on degradation, ion release and apatite formation

    PubMed Central

    Fredholm, Yann C.; Karpukhina, Natalia; Brauer, Delia S.; Jones, Julian R.; Law, Robert V.; Hill, Robert G.

    2012-01-01

    Bioactive glasses are able to bond to bone through the formation of hydroxy-carbonate apatite in body fluids while strontium (Sr)-releasing bioactive glasses are of interest for patients suffering from osteoporosis, as Sr was shown to increase bone formation both in vitro and in vivo. A melt-derived glass series (SiO2–P2O5–CaO–Na2O) with 0–100% of calcium (Ca) replaced by Sr on a molar base was prepared. pH change, ion release and apatite formation during immersion of glass powder in simulated body fluid and Tris buffer at 37°C over up to 8 h were investigated and showed that substituting Sr for Ca increased glass dissolution and ion release, an effect owing to an expansion of the glass network caused by the larger ionic radius of Sr ions compared with Ca. Sr release increased linearly with Sr substitution, and apatite formation was enhanced significantly in the fully Sr-substituted glass, which allowed for enhanced osteoblast attachment as well as proliferation and control of osteoblast and osteoclast activity as shown previously. Studying the composition–structure–property relationship in bioactive glasses enables us to successfully design next-generation biomaterials that combine the bone regenerative properties of bioactive glasses with the release of therapeutically active Sr ions. PMID:21993007

  20. Effects of phosphate buffer in parenteral drugs on particle formation from glass vials.

    PubMed

    Ogawa, Toru; Miyajima, Makoto; Wakiyama, Naoki; Terada, Katsuhide

    2013-01-01

    The characteristics of inorganic particles generated in glass vials filled with phosphate buffer solutions were investigated. During storage, particles were visually detected in the phosphate buffer solution in particular glass vials which pass compendial tests of containers for injectable drugs. These particles were considered to be different from ordinal glass delamination, which has been reported in a number of papers because the particles were mainly composed of Al, P and O, but not Si. The formation of the particles accelerated at higher storage temperatures. Among the surface treatments tested for the glass vials, sulfur treatment showed a protective effect on the particle formation in the vials, whereas the SiO(2) coating did not have any protective effects. It was found that the elution ratio of Al and Si in the solution stored in the glass vials after the heating was similar to the ratio of Al and Si in borosilicate glass. However, the Al concentration decreased during storage (5°C, 6 months), and consequently, particle formation was observed in the solution. Adding citrate, which is a chelating agent for Al, effectively suppressed the particle formation in the heated solution. When 50 ppb and higher concentrations of Al ion were added to the phosphate buffer solution, the formation of white particles containing Al, P and O was detected. It is suggested that a phosphate buffer solution in a borosilicate glass vial has the ability to form particles due to interactions with the Al that is eluted from the glass during storage.

  1. Pregrowth and Biofilm formation of Bacillus subtilis on Glass Studied via AFM, SEM and Optical Microsopy

    NASA Astrophysics Data System (ADS)

    Stutzman, Sydney; Otte, Michelle; Calabrese, Joseph; Senevirathne, Reshani; Senevirathne, Indrajith

    2014-03-01

    Lock Haven University of Pennsylvania - Research into surface adhesion properties and the selectivity of bacteria towards glass will provide a better understanding of biofilm formation and how this formation will in turn effect hospital and laboratory settings. Investigation was focused on quantifying the selectivity of non-pathogenic B. subtilis - on soda lime glass substrates. Standardized Corning 2947-75X25 microscope glass slides were used as the surface for bacterial attachment and facilitation of preliminary growth and formation of biofilms. Observations will be discussed both quantitatively and qualitatively. Structure morphology was investigated via Atomic Force Microscopy, Scanning Electron Microscopy and complemented with Optical Microscopy.

  2. Formation of metallic nanostructures on the surface of ion- exchange glass by focused electron beam

    NASA Astrophysics Data System (ADS)

    Komissarenko, F. E.; Zhukov, M. V.; Mukhin, I. S.; Golubok, A. O.; Sidorov, A. I.

    2015-11-01

    This paper presents a new method for formation of metallic nanostructures on the surface of ion-exchange glass. The method is based on the interaction of a focused electron beam with ions in ion-exchange glass. In experiments nanostructures with different shapes were obtained, depending on the electrons irradiation conditions.

  3. Colloid formation during the corrosion of SRL 200 glass

    SciTech Connect

    Buck, E.C.; Bates, J.K.; Feng, X.

    1994-05-01

    Nonradioactive SRL 200S glass and fully radioactive SRL 200R glass were reacted at glass surface areas to leachant volume (SA/V) ratios of 20,000, 2,000, and 340 m{sup {minus}1} for times varying from several days to a few years. The particles present in the leachates of these tests have been examined by analytical electron microscopy (AEM). The major colloidal clay phase was identified as a smectite clay from its characteristic electron diffraction pattern. The clay colloids eventually disappear from the solution and return to the glass; the time at which this occurs depends on the SA/V. Uranium silicate particles and calcium-bearing phases were also sometimes found in the leachates.

  4. THE IMPACT OF KINETICS ON NEPHELINE FORMATION IN NUCLEAR WASTE GLASSES

    SciTech Connect

    Amoroso, J.

    2011-03-07

    Sixteen glass compositions were selected to study the potential impacts of the kinetics of nepheline formation in high-level nuclear waste (HLW) glass. The chosen compositions encompassed a relatively large nepheline discriminator (ND) range, 0.40-0.66, and included a relatively broad range, and amount of, constituents including high aluminum and high boron concentrations. All glasses were fabricated in the laboratory and subsequently exposed to six different cooling treatments. The cooling treatments consisted of three 'stepped' profiles and their corresponding 'smooth' profiles. Included in the cooling treatment was the Defense Waste Processing Facility (DWPF) canister centerline cooling (CCC) profile in addition to a 'faster' and a 'slower' total cooling line. After quenching and heat treating, x-ray diffraction confirmed the type and amount of any resultant crystallization. The target compositions were shown to be consistent with the measured compositions. Two quenched glasses and several treated glasses exhibited minor amounts of spinel and spinel-like phases. Nepheline was not observed in any of the quenched glasses but was observed in many of the treated glasses. The amount of nepheline ranged from approximately 2wt% to 30wt% for samples cooled over shorter times and longer times respectively. Differences were observed in the amount of nepheline crystallization after smooth and stepped cooling and increased with total cooling time. In some glasses, nepheline crystallization appeared to be directly proportional to total cooling time while the total amount of nepheline crystallization varied, suggesting that the nepheline crystallization rate was independent of (or at least faster than) cooling rate but, varied depending on the glass composition. On the contrary, in another glass, nepheline crystallization appeared to be inversely proportional to cooling rate. The high alumina glasses, predicted to form nepheline according to the ND, did not precipitate

  5. Formation of gallium arsenide nanostructures in Pyrex glass.

    PubMed

    Howlader, Matiar M R; Zhang, Fangfang; Deen, M Jamal

    2013-08-01

    In this paper, we report on a simple, low-cost process to grow GaAs nanostructures of a few nm diameter and ∼50 nm height in Pyrex glass wafers. These nanostructures were grown by sequential plasma activation of GaAs and Pyrex glass surfaces using a low-temperature hybrid plasma bonding technology in air. Raman analyses of the activated surfaces show gallium oxide and arsenic oxide, as well as suppressed non-bridging oxygen with aluminate and boroxol chains in glass. The flow of alkaline ions toward the cathode and the replacement of alkaline ions by Ga and As ions in glass result in the growth of GaAs nanostructures in nanopores/nanoscratches in glass. These nanopores/nanoscratches are believed to be the origin of the growth of the nanostructures. It was found that the length of the GaAs nanostructures may be controlled by an electrostatic force. Cross-sectional observation of the bonded interface using high-resolution transmission electron microscopy confirms the existence of the nanostructures. A possible application of the nanostructures in glass is a filtration system for biomolecules.

  6. Entropy Theory of Polymer Glass-Formation in Variable Spatial Dimension

    NASA Astrophysics Data System (ADS)

    Xu, Wen-Sheng; Douglas, Jack; Freed, Karl

    The importance of packing frustration is broadly appreciated to be an important aspect of glass-formation. Recently, great interest has focused on using spatial dimensionality () as a theoretical tool for exploring this and other aspects of glass-forming liquids. We explore glass-formation in variable based on the generalized entropy theory, a synthesis of the Adam-Gibbs model with direct computation of the configurational entropy of polymer fluids using an established analytical statistical thermodynamic model. We find that structural relaxation in the fluid state asymptotically becomes Arrhenius in the limit and that the fluid transforms upon sufficient cooling above a critical dimension near into a dense amorphous state with a finite positive residual configurational entropy. The GET also predicts the variation with of measures of fragility and of the characteristic temperatures of glass-formation demarking the onset , middle , and end , of the broad glass transition. Direct computations of the isothermal compressibility and thermal expansion coefficient, which are physical measures of packing frustration, demonstrate that these fluid properties strongly correlate with the fragility of glass-formation. Back to three dimensions, we deduce apparently universal relationships between , a measure of the breadth of the glass-formation and both the isothermal compressibility and thermal expansion coefficient of polymer melts at .

  7. Glass formation, glass fragility, molecular mobility and longevity of germplasm stored at cryogenic temperatures.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cryogenic storage of living specimens presupposes that viability can be maintained indefinitely when aqueous glasses are formed and maintained. Indeed, constrained mobility within glassy matrices is a thermodynamic barrier to many chemical and physical reactions. However, impeding molecular mobili...

  8. Glass formation in a mixture of hard disks and hard ellipses.

    PubMed

    Xu, Wen-Sheng; Duan, Xiaozheng; Sun, Zhao-Yan; An, Li-Jia

    2015-06-14

    We present an event-driven molecular dynamics study of glass formation in two-dimensional binary mixtures composed of hard disks and hard ellipses, where both types of particles have the same area. We demonstrate that characteristic glass-formation behavior appears upon compression under appropriate conditions in such systems. In particular, while a rotational glass transition occurs only for the ellipses, both types of particles undergo a kinetic arrest in the translational degrees of freedom at a single density. The translational dynamics for the ellipses is found to be faster than that for the disks within the same system, indicating that shape anisotropy promotes the translational motion of particles. We further examine the influence of mixture's composition and aspect ratio on the glass formation. For the mixtures with an ellipse aspect ratio of k = 2, both translational and rotational glass transition densities decrease with increasing the disk concentration at a similar rate, and hence, the two glass transitions remain close to each other at all concentrations investigated. By elevating k, however, the rotational glass transition density diminishes at a faster rate than the translational one, leading to the formation of an orientational glass for the ellipses between the two transitions. Our simulations imply that mixtures of particles with different shapes emerge as a promising model for probing the role of particle shape in determining the properties of glass-forming liquids. Furthermore, our work illustrates the potential of using knowledge concerning the dependence of glass-formation properties on mixture's composition and particle shape to assist in the rational design of amorphous materials. PMID:26071719

  9. Quasi-containerless glass formation method and apparatus

    NASA Technical Reports Server (NTRS)

    Naumann, Robert J. (Inventor); Ethridge, Edwin C. (Inventor)

    1987-01-01

    Glass rods or fibers are prepared from a polycrystalline rod by heating a short section of the rod in a first furnace to form a molten zone of the rod, heating a second short section of the rod in a second furnace to form a second molten zone and gradually moving the furnaces apart from one another to form an elongated molten float zone, which is cooled in its midsection to produce a glass rod between the molten zones. In another embodiment a single moving furnace assembly and a precursor rod with compositional gradient sections, are used, and the moving furnace traverses the rod so that the molten portion is drawn out to a degree whereby a fiber of ultrapure glass is formed.

  10. A deep water turbidity origin for the Altuda Formation (Capitanian, Permian), Northwest Glass Mountains, Texas

    USGS Publications Warehouse

    Haneef, Mohammad; Rohr, D.M.; Wardlaw, B.R.

    2000-01-01

    The Altuda Formation (Capitanian) in the northwestern Glass Mountains is comprised of thin, even bedded limestones, dolostones, mixed clastic-carbonates, and silt/sandstones interbedded with basin-ward dipping wedge-shaped clinoforms of the Captian Limestone. The formation is characterized by graded bedding, planar laminations, flame structures, contorted/convolute bedding, horizontal branching burrows, and shelf-derived normal marine fauna. A detailed study of the Altuda Formation north of Old Blue Mountain, Glass Mountains, reveals that the formation in this area was deposited by turbidity currents in slope to basinal settings.

  11. White spot formation under orthodontic bands cemented with glass ionomer with or without Fluor Protector.

    PubMed

    van der Linden, R P; Dermaut, L R

    1998-06-01

    The purpose of this study was to determine whether an additional application of Fluor Protector before band cementation with glass ionomer cement reduces white spot formation compared with band cementation with glass ionomer cement. In the in vitro study, 80 premolars were divided in half, creating a control and a test group. All specimens were divided into four different groups to simulate different clinical situations and stored in a demineralizing solution to induce white spot formation. In the in vivo investigation, 18 orthodontic patients were incorporated in the study. One lower and one upper first molar band (randomly selected) were coated with Fluor Protector and then cemented with a glass ionomer cement (test group). The other two uncoated first molars were cemented with glass ionomer cement and served as the control group. The application of Fluor Protector in combination with Aquacem did not contribute to a reduction of white spot formation underneath molar bands compared with the use of Aquacem for banding.

  12. Investigation of ruthenium dioxide formation mechanisms in containment glass synthesized by liquid feed

    SciTech Connect

    Sawada, K.; Shimada, T.; Sako, N.; Enokida, Y.; Schuller, S.; Angeli, F.; Charpentier, T.

    2013-07-01

    The presenting paper focuses on the structural configuration of ruthenium in vitreous matrices with the objective of obtaining more insight into ruthenium incorporation and solubilization mechanisms in borosilicate glasses. To determine the structural effect of an increasing RuO{sub 2} in a borosilicate glass, a series of glass samples were selected from a benchmark composition. {sup 11}B NMR shows that the borate network is influenced by the presence of RuO{sub 2} in the glass: the addition of 2% RuO{sub 2} in a borosilicate glass led to a significant rise of BO{sub 4}. RuO{sub 2} precipitated in the glass does not seem to be the cause of this modification because when RuO{sub 2} increase there is no further change of BO{sub 4} fraction. This effect can be therefore attributed to RuO{sub 2} dissolved in the glass. RuO{sub 2} is known to have a very low solubility in borosilicate glasses (50 to 2000 ppm depending on the temperature, sodium concentration and conditions of synthesis). The link between the ruthenium and the borated network is not yet clearly identified, however, assumptions can be made such as the formation of Ru-O-B when a sufficient quantity of Ru is add (> 400 ppm). Ruthenium could play the role of silicon in increasing the possibility of bridging bond formation with boron coordination number IV.

  13. A review of bioactive glasses: Their structure, properties, fabrication and apatite formation.

    PubMed

    Kaur, Gurbinder; Pandey, Om P; Singh, Kulvir; Homa, Dan; Scott, Brian; Pickrell, Gary

    2014-01-01

    Bioactive glass and glass-ceramics are used in bone repair applications and are being developed for tissue engineering applications. Bioactive glasses/Bioglass are very attractive materials for producing scaffolds devoted to bone regeneration due to their versatile properties, which can be properly designed depending on their composition. An important feature of bioactive glasses, which enables them to work for applications in bone tissue engineering, is their ability to enhance revascularization, osteoblast adhesion, enzyme activity and differentiation of mesenchymal stem cells as well as osteoprogenitor cells. An extensive amount of research work has been carried out to develop silicate, borate/borosilicate bioactive glasses and phosphate glasses. Along with this, some metallic glasses have also been investigated for biomedical and technological applications in tissue engineering. Many trace elements have also been incorporated in the glass network to obtain the desired properties, which have beneficial effects on bone remodeling and/or associated angiogenesis. The motivation of this review is to provide an overview of the general requirements, composition, structure-property relationship with hydroxyapatite formation and future perspectives of bioglasses.Attention has also been given to developments of metallic glasses and doped bioglasses along with the techniques used for their fabrication.

  14. Glass formation and crystallization in high-temperature glass-ceramics and Si3N4

    NASA Technical Reports Server (NTRS)

    Drummond, Charles H., III

    1991-01-01

    The softening of glassy grain boundaries in ceramic matrix composites and Si3N4 at high temperatures reduces mechanical strength and the upper-use temperature. By crystallizing this glass to a more refractory crystalline phase, a material which performs at higher temperatures may result. Three systems were examined: a cordierite composition with ZrO2 as a nucleating agent; celsian compositions; and yttrium silicate glasses both in bulk and intergranular in Si3N4. For the cordierite compositions, a series of metastable phases was obtained. The crystallization of these compositions was summarized in terms of metastable ternary isothermal sections. Zircon formed at the expense of ZrO2 and spinel. In SiC composites, the transformations were slower. In celsian, two polymorphs were crystallized. One phase, hexacelsian, which always crystallized, even when metastable, had an undesirable volume change. The other phase, celsian, was very difficult to crystallize. In yttrium silicate bulk glasses, similar in composition to the intergranular glass in Si3N4, a number of polymorphs of Y2Si2O7 were crystallized. The conditions under which these polymorphs formed are compared with crystallization in Si3N4.

  15. Glass formation, magnetic properties and magnetocaloric effect of ternary Ho-Al-Co bulk metallic glass

    NASA Astrophysics Data System (ADS)

    Zhang, Huiyan; Li, Ran; Ji, Yunfei; Liu, Fanmao; Luo, Qiang; Zhang, Tao

    2012-11-01

    A ternary Ho-Al-Co system with high glass-forming ability (GFA) was developed and fully glassy rods with diameters up to 1 cm can be produced for the best glass former of Ho55Al27.5Co17.5 alloy. The thermal stability and low-temperature magnetic properties of the Ho55Al27.5Co17.5 bulk metallic glass (BMG) were studied. The magnetic transition temperature of this alloy is ˜14 K as determined by the thermomagnetic measurement. Two indicators, i.e. isothermal magnetic entropy change (ΔSM) and the relative cooling power (RCP), were adopted to evaluate the magnetocaloric effect (MCE) of the alloy under a low magnetic field up to 2 T, which can be generated by permanent magnets. The values of |ΔSM| and RCP are 7.98 J kg-1 K-1 and 191.5 J kg-1, respectively. The Ho55Al27.5Co17.5 BMG with good MCE and high GFA provides an attractive candidate for magnetic refrigeration applications, like hydrogen liquefaction and storage.

  16. Glass formation processes in mixed inorganic/organic aerosol particles.

    PubMed

    Dette, Hans P; Koop, Thomas

    2015-05-14

    Recent experiments suggest that organic aerosol particles may transform into a glassy state at room temperature under dry conditions. Information on glass forming processes in mixed inorganic/organic aerosol particles is sparse, however, because inorganic crystal nucleation is usually very likely in such mixtures. Here we investigate the glass transition temperatures Tg of various organics (trehalose, sucrose, citric acid, sorbitol, and glycerol as well as 3-MBTCA) in binary mixtures with either NaNO3 or NH4HSO4 at different mass fractions. The glassy samples were prepared with the MARBLES technique by atomizing dilute aqueous solutions into aerosol particles and subsequent diffusion drying. The resulting aerosol particles were collected and their phase behavior was investigated using differential scanning calorimetry. At small and intermediate inorganic mass fractions salt crystallization did not occur. Instead, the single-phase mixtures remained in an amorphous state upon drying such that determination of their Tg was possible. From these measurements the Tg value of pure NaNO3 and pure NH4HSO4 could be inferred through extrapolation, resulting in values of Tg(NaNO3) ≈ 290 K and Tg(NH4HSO4) ≈ 220 K. Upon drying of NH4HSO4/3-MBTCA mixtures, phase-separated samples formed in which the inorganic-rich and organic-rich phases each show an independent glass transition. Our measurements provide a route toward establishing Tg values of inorganic salts that usually crystallize readily, and they may explain the reported contradicting observations of NaNO3 aerosol particles to either crystallize or remain amorphous upon drying at room temperature. PMID:25490407

  17. Crystallization behavior and glass formation of selected lunar compositions.

    NASA Technical Reports Server (NTRS)

    Scherer, G.; Hopper, R. W.; Uhlmann, D. R.

    1972-01-01

    The kinetics of crystal growth have been determined over a wide range of temperature, from 800 to 1219 C, for lunar compositions 14259 and 14310. At all temperatures for both compositions the extent of crystal growth is found to be a linear function of time. For both materials, the growth rate versus temperature relations exhibit the form generally found with glass-forming materials. At all temperatures measured, the crystal growth rate of composition 14259 is smaller than that of composition 14310. The maximum growth rate for both compositions occurs at a temperature of about 1120 C. The growth rate data are combined with viscosity data obtained on the same compositions to construct the reduced growth rate versus undercooling relations.

  18. Modeling Multiple Time Scales during Glass Formation with Phase-Field Crystals

    SciTech Connect

    Berry, Joel; Grant, Martin

    2011-04-29

    The dynamics of glass formation in monatomic and binary liquids are studied numerically using a microscopic field theory for the evolution of the time-averaged atomic number density. A stochastic framework combining phase-field crystal free energies and dynamic density functional theory is shown to successfully describe several aspects of glass formation over multiple time scales. Agreement with mode coupling theory is demonstrated for underdamped liquids at moderate supercoolings, and a rapidly growing dynamic correlation length is found to be associated with fragile behavior.

  19. The formation of silver metal nanoparticles by ion implantation in silicate glasses

    NASA Astrophysics Data System (ADS)

    Vytykacova, S.; Svecova, B.; Nekvindova, P.; Spirkova, J.; Mackova, A.; Miksova, R.; Böttger, R.

    2016-03-01

    It has been shown that glasses containing silver metal nanoparticles are promising photonics materials for the fabrication of all-optical components. The resulting optical properties of the nanocomposite glasses depend on the composition and structure of the glass, as well as on the type of metal ion implanted and the experimental procedures involved. The main aim of this article was to study the influence of the conditions of the ion implantation and the composition of the glass on the formation of metal nanoparticles in such glasses. Four various types of silicate glasses were implanted with Ag+ ions with different energy (330 keV, 1.2 MeV and 1.7 MeV), with the fluence being kept constant (1 × 1016 ions cm-2). The as-implanted samples were annealed at 600 °C for 1 h. The samples were characterised in terms of: the nucleation of metal nanoparticles (linear optical absorption), the migration of silver through the glass matrix during the implantation and post-implantation annealing (Rutherford backscattering spectroscopy), and the oxidation state of silver (photoluminescence in the visible region).

  20. Formation of plasma induced surface damage in silica glass etching for optical waveguides

    NASA Astrophysics Data System (ADS)

    Choi, D. Y.; Lee, J. H.; Kim, D. S.; Jung, S. T.

    2004-06-01

    Ge, B, P-doped silica glass films are widely used as optical waveguides because of their low losses and inherent compatibility with silica optical fibers. These films were etched by ICP (inductively coupled plasma) with chrome etch masks, which were patterned by reactive ion etching (RIE) using chlorine-based gases. In some cases, the etched surfaces of silica glass were very rough (root-mean square roughness greater than 100 nm) and we call this phenomenon plasma induced surface damage (PISD). Rough surface cannot be used as a platform for hybrid integration because of difficulty in alignment and bonding of active devices. PISD reduces the etch rate of glass and it is very difficult to remove residues on a rough surface. The objective of this study is to elucidate the mechanism of PISD formation. To achieve this goal, PISD formation during different etching conditions of chrome etch mask and silica glass was investigated. In most cases, PISD sources are formed on a glass surface after chrome etching, and metal compounds are identified in theses sources. Water rinse after chrome etching reduces the PISD, due to the water solubility of metal chlorides. PISD is decreased or even disappeared at high power and/or low pressure in glass etching, even if PISD sources were present on the glass surface before etching. In conclusion, PISD sources come from the chrome etching process, and polymer deposition on these sources during the silica etching cause the PISD sources to grow. In the area close to the PISD source there is a higher ion flux, which causes an increase in the etch rate, and results in the formation of a pit.

  1. Compositional landscape for glass formation in metal alloys.

    PubMed

    Na, Jong Hyun; Demetriou, Marios D; Floyd, Michael; Hoff, Andrew; Garrett, Glenn R; Johnson, William L

    2014-06-24

    A high-resolution compositional map of glass-forming ability (GFA) in the Ni-Cr-Nb-P-B system is experimentally determined along various compositional planes. GFA is shown to be a piecewise continuous function formed by intersecting compositional subsurfaces, each associated with a nucleation pathway for a specific crystalline phase. Within each subsurface, GFA varies exponentially with composition, wheres exponential cusps in GFA are observed when crossing from one crystallization pathway to another. The overall GFA is shown to peak at multiple exponential hypercusps that are interconnected by ridges. At these compositions, quenching from the high-temperature melt yields glassy rods with diameters exceeding 1 cm, whereas for compositions far from these cusps the critical rod diameter drops precipitously and levels off to 1 to 2 mm. The compositional landscape of GFA is shown to arise primarily from an interplay between the thermodynamics and kinetics of crystal nucleation, or more precisely, from a competition between driving force for crystallization and liquid fragility.

  2. Studies of the Local Distortions and the EPR Parameters for Cu2+ in xLi2O-(30-x)Na2O-69·5B2O Glasses

    NASA Astrophysics Data System (ADS)

    Ding, Chang-Chun; Wu, Shao-Yi; Kuang, Min-Quan; Hu, Xian-Fen; Li, Guo-Liang

    2016-03-01

    The local distortions and electron paramagnetic resonance (EPR) parameters for Cu2+ in lithium sodium borate (LNB) glasses xLi2O·(30-x)·Na2O·69.5B2O3 (5≤x≤25 mol%) are theoretically studied at various concentrations x in a consistent way. Owing to the Jahn-Teller effect, the [CuO6]10- clusters are found to experience the significant tetragonal elongations of 16% along C4 axis. Despite the nearly unchanging observed g factors, measured d-d transition band (or cubic field parameter Dq) shows remarkable linear increases with concentration x, whose influences on g‖ and g⊥ are actually cancelled by the linearly increasing covalency factor N and relative elongation ratio η with x. The almost unvarying hyperfine structure constants are attributed to the fact that the influences of the linearly increasing N and the linearly decreasing core polarisation constant κ largely cancel one another. The microscopic mechanisms of the above concentration dependences for these quantities are illustrated from mixed alkali effect (modification of B2O3 network by transforming some BO3 units into BO4 ones with variations in modifier Li2O concentration).

  3. Influence of the Substrate on the Formation of Metallic Glass Coatings by Cold Gas Spraying

    NASA Astrophysics Data System (ADS)

    Henao, John; Concustell, Amadeu; Dosta, Sergi; Cinca, Núria; Cano, Irene G.; Guilemany, Josep M.

    2016-06-01

    Cold gas spray technology has been used to build up coatings of Fe-base metallic glass onto different metallic substrates. In this work, the effect of the substrate properties on the viscoplastic response of metallic glass particles during their impact has been studied. Thick coatings with high deposition efficiencies have been built-up in conditions of homogeneous flow on substrates such as Mild Steel AISI 1040, Stainless Steel 316L, Inconel 625, Aluminum 7075-T6, and Copper (99.9%). Properties of the substrate have been identified to play an important role in the viscoplastic response of the metallic glass particles at impact. Depending on the process gas conditions, the impact morphologies show not only inhomogeneous deformation but also homogeneous plastic flow despite the high strain rates, 108 to 109 s-1, involved in the technique. Interestingly, homogenous deformation of metallic glass particles is promoted depending on the hardness and the thermal diffusivity of the substrate and it is not exclusively a function of the kinetic energy and the temperature of the particle at impact. Coating formation is discussed in terms of fundamentals of dynamics of undercooled liquids, viscoplastic flow mechanisms of metallic glasses, and substrate properties. The findings presented in this work have been used to build up a detailed scheme of the deposition mechanism of metallic glass coatings by the cold gas spraying technology.

  4. Simulation of an atomistic dynamic field theory for monatomic liquids: freezing and glass formation.

    PubMed

    Berry, Joel; Elder, K R; Grant, Martin

    2008-06-01

    We examine a phase field crystal model for simple liquid-solid systems consisting of a free energy functional related to the Ramakrishnan-Yussouff free energy of classical density functional theory and an equation of motion capable of describing long-time-scale behavior in the deeply supercooled regime. The thermodynamics and dynamics of freezing and glass formation in this model system are studied through large-scale three-dimensional Langevin simulations. At low cooling rates bcc crystals are formed by nucleation and growth from the melt. At large cooling rates no clear glass transition is observed, but a kinetically driven first-order transition from supercooled liquid to a disordered glasslike solid does occur. Despite the peculiarities of the transition, the structure and properties of the resulting disordered solid are shown to strongly resemble those of a typical glass. Consequences of pseudocritical behavior and heterogeneity near the liquid spinodal are also discussed. PMID:18643271

  5. Characterization and Glass Formation of JSC-1 Lunar and Martian Soil Simulants

    NASA Astrophysics Data System (ADS)

    Ray, Chandra S.; Reis, Signo T.; Sen, Subhayu

    2008-01-01

    The space exploration mission of NASA requires human and robotic presence for long duration beyond the low earth orbit (LEO), especially on Moon and Mars. Developing a human habitat or colony on these planets would require a diverse range of materials, whose applications would range from structural foundations, (human) life support, (electric) power generation to components for scientific instrumentations. A reasonable and cost-effective approach for fabricating the materials needed for establishing a self-sufficient human outpost would be to primarily use local (in situ) resources on these planets. Since ancient times, glass and ceramics have been playing a vital role on human civilization. A long term project on studying the feasibility of developing glass and ceramic materials has been undertaken using Lunar and Martian soil simulants (JSC-1) as developed by Johnson Space Center. The first step in this on-going project requires developing a data base on results that fully characterize the simulants to be used for further investigations. The present paper reports characterization data of both JSC-1 Lunar and JSC Mars-1 simulants obtained up to this time via x-ray diffraction analysis, scanning electron microscopy, thermal analysis (DTA, TGA) and chemical analysis. The critical cooling rate for glass formation for the melts of the simulants was also measured in order to quantitatively assess the glass forming tendency of these melts. The importance of the glasses and ceramics developed using in-situ resources for constructing human habitats on Moon or Mars is discussed.

  6. Characterization and Glass Formation of JSC-1 Lunar and Martian Soil Simulants

    NASA Technical Reports Server (NTRS)

    Sen, Subhayu

    2008-01-01

    The space exploration mission of NASA requires long duration presence of human being beyond the low earth orbit (LEO), especially on Moon and Mars. Developing a human habitat or colony on these planets would require a diverse range of materials, whose applications would range from structural foundations, (human) life support, (electric) power generation to components for scientific instrumentation. A reasonable and cost-effective approach for fabricating the materials needed for establishing a self-sufficient human outpost would be to primarily use local (in situ) resources on these planets. Since ancient times, glass and ceramics have been playing a vital role on human civilization. A long term project on studying the feasibility of developing glass and ceramic materials using Lunar and Martian soil simulants (JSC-1) as developed by Johnson Space Center has been undertaken. The first step in this on-going project requires developing a data base on results that fully characterize the simulants to be used for further investigations. The present paper reports characterization data of both JSC-1 Lunar and JSC Mars-1 simulants obtained up to this time via x-ray diffraction analysis, scanning electron microscopy, thermal analysis (DTA, TGA) and chemical analysis. The critical cooling rate for glass formation for the melts of the simulants was also measured in order to quantitatively assess the glass forming tendency of these melts. The importance of the glasses and ceramics developed using in-situ resources for constructing human habitats on Moon or Mars is discussed.

  7. Effects of Oxygen Impurities on Glass-Formation Ability in Zr2Cu Alloy.

    PubMed

    Wang, Zhanyu; Huang, Li; Yue, G Q; Shen, B; Dong, F; Zhang, R J; Zheng, Y X; Wang, S Y; Wang, C Z; Kramer, M J; Ho, K M; Chen, L Y

    2016-09-01

    Using ab initio molecular dynamics simulations, we show that oxygen (O) impurities have a noticeable influence on the glass-formation ability (GFA) in Zr2Cu alloy. Cu-centered icosahedral clusters and Zr-centered Kasper polyhedra are the dominate short-range orders in undercooled Zr2Cu liquid which are most likely to be responsible for the glass formation in Zr2Cu systems. When O is introduced, a Zr octahedron is formed around the O impurity. Most of the Zr atoms in the octahedron also serve as the bridging atoms for cross-linked Kasper polyhedral network, resulting in an O-centered medium range order (MRO) structure. Meanwhile, Cu atoms are moved away from the first shell of O-centered octahedral clusters. With 1 at. % O impurities, the fractions of Zr-centered clusters are less affected, while the increase of ideal icosahedral order and decrease of distorted icosahedral order lead to a more stable atomic structure. This result suggests that a low concentration of O impurities would improve the GFA in Zr2Cu alloy. However, when ∼5 at. % O impurities are included, the ideal icosahedral clusters and Zr-centered Kasper polyhedra are seriously suppressed by the formation of O-centered MRO, which can lead to deterioration of GFA. Our analyses provide useful insight into glass formation behavior in O-doped metallic alloy systems. PMID:27509394

  8. A novel method of natural cryoprotection : intracellular glass formation in deeply frozen populus.

    PubMed

    Hirsh, A G; Williams, R J; Meryman, H T

    1985-09-01

    Correlating measurements from differential scanning calorimetry, freeze-fracture freeze-etch electron microscopy, and survival of twigs after two-step cooling experiments, we provide strong evidence that winter-hardened Populus balsamifera v. virginiana (Sarg.) resists the stresses of freezing below -28 degrees C by amorphous solidification (glass formation) of most of its intracellular contents during slow cooling (glass transitions during slow cooling at about -45 degrees C and below -70 degrees C. This ;three glass' model was then used to predict the results of differential scanning calorimetry, freeze-fracture freeze-etch electron microscopy, and biological experiments. This model is the first definitive explanation for the resistance of a woody plant to liquid N(2) temperatures even if quench cooling (1200 degrees C per minute) begins at temperatures as high as -20 degrees C and warming is very slow (glass formation has been demonstrated.

  9. Structural aspects of glass-formation in Ni-Nb melts

    SciTech Connect

    Holland-Moritz, D.; Yang, F.; Gegner, J.; Meyer, A.; Hansen, T.; Ruiz-Martín, M. D.

    2014-05-28

    We report on investigations of the static structure factors of glass-forming Ni{sub 59.5}Nb{sub 40.5} alloy melts by combination of the containerless processing technique of electrostatic levitation with neutron diffraction. By application of the isotopic substitution method, the full set of partial structure factors was determined. The short-range order in liquid Ni{sub 59.5}Nb{sub 40.5} is characterized by a large nearest neighbor coordination number of Z{sub NN} = 14.3 and a chemical short-range order with an affinity for the formation of heterogeneous Nb-Ni nearest neighbors. The structure factors observed here in the liquid state closely resemble those reported for amorphous Nb-Ni solids. The comparison with earlier results on the short-range structure in Zr-based glass-forming melts suggests that a large local density of packing, chemical order, and structural frustration are, amongst others, common structural properties of these metallic glass-forming systems, which favor glass-formation.

  10. Glass formation and cluster evolution in the rapidly solidified monatomic metallic liquid Ta under high pressure

    NASA Astrophysics Data System (ADS)

    Jiang, Dejun; Wen, Dadong; Tian, Zean; Liu, Rangsu

    2016-12-01

    Molecular dynamics (MD) simulations have been performed to examine the glass formation and cluster evolution during the rapid solidification of monatomic metallic liquid Ta under high pressure. The atomic structures in the systems are characterized by the radical distribution function (RDF), Honeycutt-Anderson (H-A) bond-type index method and cluster-type index method (CTIM). It is observed that the defective icosahedra play the critical role in the formation of Ta monatomic metallic glasses (MGs) rather than (12 0 12 0) perfect icosahedra, which have been identified as the basic local atomic units in many multi-component MGs. With the increase of pressure P, the fraction of icosahedral type clusters decreases remarkably in Ta MGs, while the fraction of bcc type clusters rises evidently. The evolution of vitrification degree (DSRO or DMRO) of the rapidly cooled metal Ta system further reveals that a higher pressure P is disadvantageous to the formation of Ta monatomic MGs. The weaker glass forming ability (GFA) of liquid metal Ta obtained under higher pressure P can be contributed to the decrease of DSRO or DMRO which is induced by increasing high pressure P to some extent.

  11. Recrystallized Impact Glasses of the Onaping Formation and the Sudbury Igneous Complex, Sudbury Structure, Ontario, Canada

    NASA Technical Reports Server (NTRS)

    Dressler, B. O.; Weiser, T.; Brockmeyer, P.

    1996-01-01

    The origin of the Sudbury Structure and of the associated heterolithic breccias of the Onaping Formation and the Sudbury Igneous Complex have been controversial. While an impact origin of the structure has gained wide acceptance over the last 15 years, the origin of the recrystallized Onaping Formation glasses and of the igneous complex is still being debated. Recently the interpretation of the breccias of the Onaping Formation as suevitic fall-back impact breccias has been challenged. The igneous complex is interpreted either as a differentiated impact melt sheet or as a combination of an upper impact melt represented by the granophyre, and a lower, impact-triggered magmatic body consisting of the norite-sublayer formations. The Onaping Formation contains glasses as fluidal and nonfluidal fragments of various shapes and sizes. They are recrystallized, and our research indicates that they are petrographically heterogeneous and span a wide range of chemical compositions. These characteristics are not known from glasses of volcanic deposits. This suggests an origin by shock vitrification, an interpretation consistent with their association with numerous and varied country rock clasts that exhibit microscopic shock metamorphic features. The recrystallized glass fragments represent individual solid-state and liquid-state vitrified rocks or relatively small melt pods. The basal member lies beneath the Gray and Black members of the Onaping Formation and, where not metamorphic, has an igneous matrix. Igneous-textured melt bodies occur in the upper two members and above the Basal Member. A comparison of the chemical compositions of recrystallized glasses and of the matrices of the Basal Member and the melt bodies with the components and the bulk composition of the igneous complex is inconclusive as to the origin of the igneous complex. Basal Member matrix and Melt Bodies, on average, are chemically similar to the granophyre of the Sudbury Igneous Complex, suggesting that

  12. Porous wall hollow glass microspheres as a medium or substrate for storage and formation of novel materials

    SciTech Connect

    Wicks, George G; Serkiz, Steven M.; Zidan, Ragaiy; Heung, Leung K.

    2014-06-24

    Porous wall hollow glass microspheres are provided as a template for formation of nanostructures such as carbon nanotubes, In addition, the carbon nanotubes in combination with the porous wall hollow glass microsphere provides an additional reaction template with respect to carbon nanotubes.

  13. Formation and evolution of ultrashort pulse-induced nanogratings in Borosilicate glass

    NASA Astrophysics Data System (ADS)

    Zimmermann, F.; Plech, Anton; Richter, S.; Tünnermann, Andreas; Nolte, S.

    2014-05-01

    The versatility of ultrashort laser pulses as a tool for laser materials processing has augmented particular interest in the past decade. Especially birefringent modifications, so-called nanogratings, have found to exhibit tremendous potential for manifold photonic functionalities. These self-assembling structures, orienting always perpendicular to the laser polarization, have been up to now extensively studied in bulk fused silica. Commonly it is assumed that the formation of nanogratings is actually limited to anomalous glasses like silica or slightly doped silica. However, we recently found that even in glasses like borosilicate or BK7 nanogratings can be observed within certain parameter regimes. Here we present an extensive study of the fundamental constituents of nanogratings in bulk borosilicate glass using small angle X-ray scattering (SAXS) in combination with focused ion beam milling (FIB) and scanning electron microscopy (SEM). The irradiation produces void-like sheets (10-20 nm wide) as well as elongated cracks of up to 400 nm. In contrast to nanogratings in fused silica, borosilicate shows a significant smaller optical retardance. The cumulative action of several hundreds of laser pulses lead to the formation of individual grating planes with a period of about 60 nm (at an inscribing laser wavelength of 800 nm) while the well-known λ/2n (n-refractive index) period is prevented. This has never been observed for ultrashort pulse induced nanogratings so far.

  14. Thermodynamic calculation and interatomic potential to predict the favored composition region for the Cu-Zr-Al metallic glass formation.

    PubMed

    Cui, Y Y; Wang, T L; Li, J H; Dai, Y; Liu, B X

    2011-03-01

    For the Cu-Zr-Al system, the glass forming compositions were firstly calculated based on the extended Miedema's model, suggesting that the amorphous phase could be thermodynamically favored over a large composition region. An n-body potential was then constructed under the smoothed and long-range second-moment-approximation of tight-binding formulism. Applying the constructed Cu-Zr-Al potential, molecular dynamics simulations were conducted using solid solution models to compare relative stability of crystalline solid solution versus its disordered counterpart. Simulations reveal that the physical origin of metallic glass formation is crystalline lattice collapsing while solute concentration exceeding the critical value, thus predicting a hexagonal composition region, within which the Cu-Zr-Al ternary metallic glass formation is energetically favored. The molecular dynamics simulations predicted composition region is defined as the quantitative glass-forming-ability or glass-forming-region of the Cu-Zr-Al system. PMID:21229150

  15. Effect of variable valence impurities on the formation of bismuth-related optical centres in a silicate glass

    SciTech Connect

    Galagan, B I; Denker, B I; Lili Hu; Sverchkov, S E; Shulman, I L; Dianov, Evgenii M

    2012-10-31

    We have studied the effect of variable valence impurities (cerium and iron) on the formation of bismuth-related IR luminescence centres and the optical loss between 1000 and 1300 nm in a magnesium aluminosilicate glass. The results demonstrate that additional doping of the glass with ceria leads to effective bleaching in a wide spectral range, including the luminescence range of the bismuth centres. At the same time, ceria reduces the concentration of luminescence centres. Gamma irradiation of the glass bleached by cerium restores the luminescence centres but leads to a background loss in a wide spectral range. Iron is shown to be a very harmful impurity in bismuth-doped active media: even trace levels of iron prevent the formation of bismuth-related active centres in the glass and produce a strong, broad absorption band centred near 1 {mu}m. (luminescence of glasses)

  16. A New DTA Method for Measuring Critical Cooling Rate for Glass Formation

    NASA Technical Reports Server (NTRS)

    Ray, Chandra S.; Reis, Signo T.; Brow, Richard K.; Holand, Wolfram; Rheinberger, Volker

    2004-01-01

    A new differential thermal analysis (DTA) experimental method has been developed to determine the critical cooling rate for glass formation, R(sub c). The method, which is found especially suitable for melts that, upon cooling, have a small heat of crystallization or a very slow crystallization rate, has been verified using a 38Na2O-62SiO2 (mol%) melt with a known R(sub c) (-approx. 19 C/min), then used to determine R(sub c) for two complex lithium silicate glass forming melts. The new method is rapid, easy to conduct and yields values for R(sub c) that are in excellent agreement with the R(sub c)-values measured by standard DTA techniques.

  17. Communication: The simplified generalized entropy theory of glass-formation in polymer melts

    SciTech Connect

    Freed, Karl F.

    2015-08-07

    While a wide range of non-trivial predictions of the generalized entropy theory (GET) of glass-formation in polymer melts agree with a large number of observed universal and non-universal properties of these glass-formers and even for the dependence of these properties on monomer molecular structure, the huge mathematical complexity of the theory precludes its extension to describe, for instance, the perplexing, complex behavior observed for technologically important polymer films with thickness below ∼100 nm and for which a fundamental molecular theory is lacking for the structural relaxation. The present communication describes a hugely simplified version of the theory, called the simplified generalized entropy theory (SGET) that provides one component necessary for devising a theory for the structural relaxation of thin polymer films and thereby supplements the first required ingredient, the recently developed Flory-Huggins level theory for the thermodynamic properties of thin polymer films, before the concluding third step of combining all the components into the SGET for thin polymer films. Comparisons between the predictions of the SGET and the full GET for the four characteristic temperatures of glass-formation provide good agreement for a highly non-trivial model system of polymer melts with chains of the structure of poly(n-α olefins) systems where the GET has produced good agreement with experiment. The comparisons consider values of the relative backbone and side group stiffnesses such that the glass transition temperature decreases as the amount of excess free volume diminishes, contrary to general expectations but in accord with observations for poly(n-alkyl methacrylates). Moreover, the SGET is sufficiently concise to enable its discussion in a standard course on statistical mechanics or polymer physics.

  18. Communication: The simplified generalized entropy theory of glass-formation in polymer melts

    NASA Astrophysics Data System (ADS)

    Freed, Karl F.

    2015-08-01

    While a wide range of non-trivial predictions of the generalized entropy theory (GET) of glass-formation in polymer melts agree with a large number of observed universal and non-universal properties of these glass-formers and even for the dependence of these properties on monomer molecular structure, the huge mathematical complexity of the theory precludes its extension to describe, for instance, the perplexing, complex behavior observed for technologically important polymer films with thickness below ˜100 nm and for which a fundamental molecular theory is lacking for the structural relaxation. The present communication describes a hugely simplified version of the theory, called the simplified generalized entropy theory (SGET) that provides one component necessary for devising a theory for the structural relaxation of thin polymer films and thereby supplements the first required ingredient, the recently developed Flory-Huggins level theory for the thermodynamic properties of thin polymer films, before the concluding third step of combining all the components into the SGET for thin polymer films. Comparisons between the predictions of the SGET and the full GET for the four characteristic temperatures of glass-formation provide good agreement for a highly non-trivial model system of polymer melts with chains of the structure of poly(n-α olefins) systems where the GET has produced good agreement with experiment. The comparisons consider values of the relative backbone and side group stiffnesses such that the glass transition temperature decreases as the amount of excess free volume diminishes, contrary to general expectations but in accord with observations for poly(n-alkyl methacrylates). Moreover, the SGET is sufficiently concise to enable its discussion in a standard course on statistical mechanics or polymer physics.

  19. Communication: The simplified generalized entropy theory of glass-formation in polymer melts.

    PubMed

    Freed, Karl F

    2015-08-01

    While a wide range of non-trivial predictions of the generalized entropy theory (GET) of glass-formation in polymer melts agree with a large number of observed universal and non-universal properties of these glass-formers and even for the dependence of these properties on monomer molecular structure, the huge mathematical complexity of the theory precludes its extension to describe, for instance, the perplexing, complex behavior observed for technologically important polymer films with thickness below ∼100 nm and for which a fundamental molecular theory is lacking for the structural relaxation. The present communication describes a hugely simplified version of the theory, called the simplified generalized entropy theory (SGET) that provides one component necessary for devising a theory for the structural relaxation of thin polymer films and thereby supplements the first required ingredient, the recently developed Flory-Huggins level theory for the thermodynamic properties of thin polymer films, before the concluding third step of combining all the components into the SGET for thin polymer films. Comparisons between the predictions of the SGET and the full GET for the four characteristic temperatures of glass-formation provide good agreement for a highly non-trivial model system of polymer melts with chains of the structure of poly(n-α olefins) systems where the GET has produced good agreement with experiment. The comparisons consider values of the relative backbone and side group stiffnesses such that the glass transition temperature decreases as the amount of excess free volume diminishes, contrary to general expectations but in accord with observations for poly(n-alkyl methacrylates). Moreover, the SGET is sufficiently concise to enable its discussion in a standard course on statistical mechanics or polymer physics.

  20. Effects of microalloying with 3d transition metals on glass formation in AlYFe alloys

    SciTech Connect

    Bondi, K.S.; Gangopadhyay, A.K.; Marine, Z.; Kim, T.H.; Mukhopadhyay, Anindita; Goldman, A.I.; Buhro, William E.; Kelton, K.F.

    2008-05-20

    The effects of microalloying on glass formation and stability were systematically investigated by substituting 0.5 at.% of all 3d transition metals for Al in Al{sub 88}Y{sub 7}Fe{sub 5} alloys. X-ray diffraction and isothermal differential scanning calorimetry studies indicate that samples containing microadditions of Ti, V, Cr, Mn, Fe and Co were amorphous, while those alloyed with Ni and Cu were not. The onset temperatures for crystallization (devitrification) of the amorphous alloys were increased with microalloying and some showed a supercooled liquid region ({Delta}T{sub x} = T{sub x} - T{sub g}) of up to 40 C. In addition, microalloying changes the glass structure and the devitrification sequence, as determined by differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA) and high energy X-ray diffraction. The results presented here suggest that the order induced in the alloy by the transition metal microaddition decreases the atomic mobility in the glass and raises the barrier for the nucleation of {alpha}-Al, the primary devitrifying phase in most cases. New intermetallic phases also appear with microalloying and vary for different transition metal additions.

  1. Effects of electric field on the entropy, viscosity, relaxation time, and glass-formation.

    PubMed

    Johari, G P

    2013-04-21

    By using the known formalism for the effect of an externally applied electric field, E, on thermodynamics of a dielectric material, we calculated the field-induced configurational entropy factor, ΔSconf (E)/E(2), of 50 dipolar liquids, including those whose static permittivity, εs, decreases on cooling. The field induced change, ΔSconf (E), is found to be experimentally detectable only when E is on the order of 10(5) V∕cm, a value less than the dielectric breakdown field strength of some liquids but in the range of nonlinear dielectric response. We argue that the dielectric response is formally nonlinear already for E > 0, and then show that the difference between the Langevin-function and the extrapolated linear response is < 0.15% for E in the 10(5) V∕cm range. Therefore, such high E values may be used to estimate ΔSconf (E). We conclude that (i) for E in the 10(5) V∕cm range, ΔSconf (E) is high enough to produce a measurable change in the viscosity and relaxation time of some ultraviscous liquids with prominent dipolar interactions, thereby changing their glass formation temperature, and (ii) application of E would reversibly transform, isothermally, some liquids to glass, and transform some glasses to liquid. Finally, we suggest that the effect of E can be used to determine the merits of the models for non-Arrhenius kinetics.

  2. Interphase formation and environmental degradation in glass fiber/vinyl ester composites

    NASA Astrophysics Data System (ADS)

    Gorowara, Rajeev Lochan

    2002-09-01

    Interphase formation mechanisms are identified, modeled, and correlated with degradation in glass fiber/thermoset polymer composites. This work focused on the effects of glass-fiber-surface coatings (sizings) in free-radical polymerizing vinyl ester/styrene resin. Prior research focused on silane coupling agents, which comprise only 10% of typical commercial sizing formulations. Well-defined models of commercial multi-component glass fiber sizings were formulated and applied to E-glass fibers in a manner consistent with commercial production. Sized fiber were chemically analyzed before and after extraction with acetone, a solubility model for the resin. Solution FTIR, HPLC-MALLS and fiber XPS determined quantity and quality of physically- and chemically-adsorbed layers. In these systems, thermodynamic equilibrium dominates interphase formation and structure, not a diffusion-gradient mechanism. Interphase environmental degradation (durability) was characterized by Interlaminar Shear Strength (ILSS) strength retention after hygrothermal exposure at 80°C, in unidirectional multi-fiber composites. Durability decreased with increasing amount of sizing inert relative to the matrix. Some sizing effects became less distinguished as the matrix degraded. Single fiber-microdroplet testing measuring interfacial shear strength showed similar results. Nonreactive species in the interphase would reduce the final interphase network crosslink density and reduce the durability of the interphase. Species partitioning between the bulk and interphase are described using a multi-component model for polymer chemical potential with a complex non-linear solution. A critical aspect considered is the elastic response of the swollen bound phase. It was found that predicted interphase concentrations were very sensitive to the crosslink density of the bound sizing layer, Mc, which describes the sizing structure. Other physical properties are calculated from the interphase species concentration

  3. Study of hydroxyl carbonate apatite formation on bioactive glass coated dental ceramics by confocal laser scanning microscopy (CLSM)

    NASA Astrophysics Data System (ADS)

    Stanciu, G. A.; Savu, B.; Sandulescu, I.; Paraskevopoulos, K.; Koidis, P.

    2007-03-01

    Some dental ceramics were coated with a bioactive glass and resulted the formation of a stable and well bonded with the ceramic substrate thin layer. After immersion in a solution with ion concentrations similar to those of human blood plasma the development of hydroxy carbonate apatite layer on the surface of bioactive glass may be observed. The objective of this study was to investigate structural surface changes of bioactive glass, after exposure in a simulated body fluid for a different number of days. The roughness and topography of the hydroxyapatite surface were investigated by Confocal Scanning Laser Microscopy. The chemical composition was analyzed by Energy Dispersive Spectroscopy measurements.

  4. Transition and post-transition metal ions in borate glasses: Borate ligand speciation, cluster formation, and their effect on glass transition and mechanical properties

    NASA Astrophysics Data System (ADS)

    Möncke, D.; Kamitsos, E. I.; Palles, D.; Limbach, R.; Winterstein-Beckmann, A.; Honma, T.; Yao, Z.; Rouxel, T.; Wondraczek, L.

    2016-09-01

    A series of transition and post-transition metal ion (Mn, Cu, Zn, Pb, Bi) binary borate glasses was studied with special consideration of the cations impact on the borate structure, the cations cross-linking capacity, and more generally, structure-property correlations. Infrared (IR) and Raman spectroscopies were used for the structural characterization. These complementary techniques are sensitive to the short-range order as in the differentiation of tetrahedral and trigonal borate units or regarding the number of non-bridging oxygen ions per unit. Moreover, vibrational spectroscopy is also sensitive to the intermediate-range order and to the presence of superstructural units, such as rings and chains, or the combination of rings. In order to clarify band assignments for the various borate entities, examples are given from pure vitreous B2O3 to meta-, pyro-, ortho-, and even overmodified borate glass compositions. For binary metaborate glasses, the impact of the modifier cation on the borate speciation is shown. High field strength cations such as Zn2+ enhance the disproportionation of metaborate to polyborate and pyroborate units. Pb2+ and Bi3+ induce cluster formation, resulting in PbOn- and BiOn-pseudophases. Both lead and bismuth borate glasses show also a tendency to stabilize very large superstructural units in the form of diborate polyanions. Far-IR spectra reflect on the bonding states of modifier cations in glasses. The frequency of the measured cation-site vibration band was used to obtain the average force constant for the metal-oxygen bonding, FM-O. A linear correlation between glass transition temperature (Tg) and FM-O was shown for the metaborate glass series. The mechanical properties of the glasses also correlate with the force constant FM-O, though for cations of similar force constant the fraction of tetrahedral borate units (N4) strongly affects the thermal and mechanical properties. For paramagnetic Cu- and Mn-borate glasses, N4 was determined

  5. Radiation effects in moist-air systems and the influence of radiolytic product formation on nuclear waste glass corrosion

    SciTech Connect

    Wronkiewicz, D.J.; Bates, J.K.; Buck, E.C.; Hoh, J.C.; Emery, J.W.; Wang, L.M.

    1997-07-01

    Ionizing radiation may affect the performance of glass in an unsaturated repository site by interacting with air, water vapor, or liquid water to produce a variety of radiolytic products. Tests were conducted to examine the effects of radiolysis under high gas/liquid ratios. Results indicate that nitrate is the predominant radiolytic product produced following both gamma and alpha radiation exposure, with lesser amounts of nitrite and carboxylic acids. The formation of nitrogen acids during exposure to long-lived, alpha-particle-emitting transuranic elements indicates that these acids may play a role in influencing nuclear waste form reactions in a long-term unsaturated disposal scenario. Experiments were also conducted with samples that simulate the composition of Savannah River Plant nuclear waste glasses. Radiolytic product formation in batch tests (340 m{sup {minus}1}, 90 C) resulted in a small increase in the release rates of many glass components, such as alkali and alkaline earth elements, although silicon and uranium release rates were slightly reduced indicating an overall beneficial effect of radiation on waste form stability. The radiolytic acids increased the rate of ion exchange between the glass and the thin film of condensate, resulting in accelerated corrosion rates for the glass. The paragenetic sequence of alteration phases formed on both the irradiated and nonirradiated glass samples reacted in the vapor hydration tests matches closely with those developed during volcanic glass alteration in naturally occurring saline-alkaline lake systems. This correspondence suggests that the high temperatures used in these tests have not changed the underlying glass reaction mechanism relate to that which controls glass reactions under ambient surficial conditions.

  6. Enhanced osteoprogenitor elongated collagen fiber matrix formation by bioactive glass ionic silicon dependent on Sp7 (osterix) transcription.

    PubMed

    Varanasi, Venu G; Odatsu, Tetsurou; Bishop, Timothy; Chang, Joyce; Owyoung, Jeremy; Loomer, Peter M

    2016-10-01

    Bioactive glasses release ions, those enhance osteoblast collagen matrix synthesis and osteogenic marker expression during bone healing. Collagen matrix density and osteogenic marker expression depend on osteogenic transcription factors, (e.g., Osterix (OSX)). We hypothesize that enhanced expression and formation of collagen by Si(4+) depends on enhanced expression of OSX transcription. Experimental bioactive glass (6P53-b) and commercial Bioglass(TM) (45S5) were dissolved in basal medium to make glass conditioned medium (GCM). ICP-MS analysis was used to measure bioactive glass ion release rates. MC3T3-E1 cells were cultured for 20 days, and gene expression and extracellular matrix collagen formation was analyzed. In a separate study, siRNA was used to determine the effect of OSX knockdown on impacting the effect of Si(4+) on osteogenic markers and matrix collagen formation. Each bioactive glass exhibited similar ion release rates for all ions, except Mg(2+) released by 6P53-b. Gene expression results showed that GCM markedly enhanced many osteogenic markers, and 45S5 GCM showed higher levels of expression and collagen matrix fiber bundle density than 6P53-b GCM. Upon knockdown of OSX transcription, collagen type 5, alkaline phosphatase, and matrix density were not enhanced as compared to wild type cells. This study illustrates that the enhancement of elongated collagen fiber matrix formation by Si(±) depends on OSX transcription. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2604-2615, 2016.

  7. The Formation of Boundary Clinopyroxenes and Associated Glass Veins in Type B1 CAIs

    SciTech Connect

    Paque, J M; Beckett, J R; Ishii, H A; Toppani, A; Burnett, D S; Teslich, N; Dai, Z R; Bradley, J P

    2008-05-18

    We used focused ion beam thin section preparation and scanning transmission electron microscopy (FIB/STEM) to examine the interfacial region between spinel and host melilite for three spinel grains, two from the mantle and one from the core of an Allende type B1 inclusion, and a second pair of spinel grains from a type B1 inclusion from the Leoville carbonaceous chondrite. The compositions of boundary clinopyroxenes decorating spinel surfaces are generally consistent with those of coarser clinopyroxenes from the same region of the inclusion, suggesting little movement of spinels between mantle and core regions after the formation of boundary clinopyroxenes. The host melilite displays no anomalous compositions near the interface, and anorthite or other late-stage minerals are not observed, suggesting that crystallization of residual liquid was not responsible for the formation of boundary clinopyroxenes. Allende spinels display either direct spinel-melilite contact or an intervening boundary clinopyroxene between the two phases. In the core, boundary clinopyroxene is mantled by a thin (1-2 {micro}m thick) layer of normally zoned (X{sub Ak} increasing away from the melilite-clinopyroxene contact) melilite with X{sub Ak} matching that of the host melilite at the melilite-melilite contact. In the mantle, X{sub Ak} near boundary spinels is constant. Spinels in a Leoville type B1 inclusion are more complex with boundary clinopyroxene, as observed in Allende, but also variable amounts of glass ({approx}1 {micro}m width), secondary calcite, perovskite, and an unknown Mg-, Al-, OH-rich and Ca-, Si-poor crystalline phase that may be a layered double hydrate. Glass compositions are consistent to first order with a precursor consisting mostly of Mg-carpholite or sudoite with some aluminous diopside. One possible scenario of formation for the glass veins is that open system alteration of melilite produced a porous, hydrated aggregate of Mg-carpholite or sudoite + aluminous

  8. Network topology for the formation of solvated electrons in binary CaO-Al2O3 composition glasses.

    PubMed

    Akola, Jaakko; Kohara, Shinji; Ohara, Koji; Fujiwara, Akihiko; Watanabe, Yasuhiro; Masuno, Atsunobu; Usuki, Takeshi; Kubo, Takashi; Nakahira, Atsushi; Nitta, Kiyofumi; Uruga, Tomoya; Weber, J K Richard; Benmore, Chris J

    2013-06-18

    Glass formation in the CaO-Al2O3 system represents an important phenomenon because it does not contain typical network-forming cations. We have produced structural models of CaO-Al2O3 glasses using combined density functional theory-reverse Monte Carlo simulations and obtained structures that reproduce experiments (X-ray and neutron diffraction, extended X-ray absorption fine structure) and result in cohesive energies close to the crystalline ground states. The O-Ca and O-Al coordination numbers are similar in the eutectic 64 mol % CaO (64CaO) glass [comparable to 12CaO·7Al2O3 (C12A7)], and the glass structure comprises a topologically disordered cage network with large-sized rings. This topologically disordered network is the signature of the high glass-forming ability of 64CaO glass and high viscosity in the melt. Analysis of the electronic structure reveals that the atomic charges for Al are comparable to those for Ca, and the bond strength of Al-O is stronger than that of Ca-O, indicating that oxygen is more weakly bound by cations in CaO-rich glass. The analysis shows that the lowest unoccupied molecular orbitals occurs in cavity sites, suggesting that the C12A7 electride glass [Kim SW, Shimoyama T, Hosono H (2011) Science 333(6038):71-74] synthesized from a strongly reduced high-temperature melt can host solvated electrons and bipolarons. Calculations of 64CaO glass structures with few subtracted oxygen atoms (additional electrons) confirm this observation. The comparable atomic charges and coordination of the cations promote more efficient elemental mixing, and this is the origin of the extended cage structure and hosted solvated (trapped) electrons in the C12A7 glass.

  9. Network topology for the formation of solvated electrons in binary CaO–Al2O3 composition glasses

    PubMed Central

    Akola, Jaakko; Kohara, Shinji; Ohara, Koji; Fujiwara, Akihiko; Watanabe, Yasuhiro; Masuno, Atsunobu; Usuki, Takeshi; Kubo, Takashi; Nakahira, Atsushi; Nitta, Kiyofumi; Uruga, Tomoya; Weber, J. K. Richard; Benmore, Chris J.

    2013-01-01

    Glass formation in the CaO–Al2O3 system represents an important phenomenon because it does not contain typical network-forming cations. We have produced structural models of CaO–Al2O3 glasses using combined density functional theory–reverse Monte Carlo simulations and obtained structures that reproduce experiments (X-ray and neutron diffraction, extended X-ray absorption fine structure) and result in cohesive energies close to the crystalline ground states. The O–Ca and O–Al coordination numbers are similar in the eutectic 64 mol % CaO (64CaO) glass [comparable to 12CaO·7Al2O3 (C12A7)], and the glass structure comprises a topologically disordered cage network with large-sized rings. This topologically disordered network is the signature of the high glass-forming ability of 64CaO glass and high viscosity in the melt. Analysis of the electronic structure reveals that the atomic charges for Al are comparable to those for Ca, and the bond strength of Al–O is stronger than that of Ca–O, indicating that oxygen is more weakly bound by cations in CaO-rich glass. The analysis shows that the lowest unoccupied molecular orbitals occurs in cavity sites, suggesting that the C12A7 electride glass [Kim SW, Shimoyama T, Hosono H (2011) Science 333(6038):71–74] synthesized from a strongly reduced high-temperature melt can host solvated electrons and bipolarons. Calculations of 64CaO glass structures with few subtracted oxygen atoms (additional electrons) confirm this observation. The comparable atomic charges and coordination of the cations promote more efficient elemental mixing, and this is the origin of the extended cage structure and hosted solvated (trapped) electrons in the C12A7 glass. PMID:23723350

  10. Microfacies and depositional environment of the Word Formation (Permian) Glass Mountains, Texas

    SciTech Connect

    Rathjen, J.D. . Dept. of Geological Sciences)

    1993-02-01

    The Word Formation (Permian) crops out in the Glass Mountains of West Texas. The Word is composed of clastics in the southwest, carbonates in the northeast, and a transitional zone of alternating carbonates and clastics separating the two extreme facies. Sediment thickness ranges from 457 meters in the southwest to 91 meters in the northeast. Measured sections and petrographic data have identified six microfacies from the transitional and eastern facies of the Word. These are southwest to northeast: (1) Peloidal Packstones, (2) Bioclastic Wackestones/Packstones, (3) Whole Fossil Wackestones/Packstones, (4) Bioturbated Wackestones, (5) Fusulinid-Crinoid Packstones, and from the eastern facies, (6) Dolostones. Petrographic data indicate that a shallow water lagoonal environment existed in the southwest. This lagoonal environment grades into a more fossiliferous normal marine environment toward the northeast. In the northeast, a very shallow water shelf environment existed which was periodically subaerially exposed, dolomitizing the sediments.

  11. Rough glass surface-mediated formation of vesicles from lauryl sulfobetaine micellar solutions.

    PubMed

    Zhu, Xiaoyu; Du, Na; Song, Ruiying; Hou, Wanguo; Song, Shue; Zhang, Renjie

    2014-10-01

    We report novel vesicles composed of the zwitterionic surfactant lauryl sulfobetaine (LSB), which is a simple single-tailed surfactant (STS). The novel vesicles spontaneously formed from LSB micellar solutions with the mediation of a rough glass surface (RGS) in the absence of any cosurfactants or additives. Importantly, the obtained STS vesicles displayed good stability upon long-term storage, exposure to high temperature, and freeze-thawing after the RGS was removed. The pH of the LSB solution (4.0-9.0) and the presence of NaCl (1.0 × 10(-5) and 1.0 × 10(-4) mol/L) in the LSB solution had no obvious influence on the formation and stability of the vesicles. The adsorption configuration of LSB on the RGS was investigated via water contact angle measurements and atomic force microscope observations. The results showed that LSB adsorption bilayers could form on the RGS, and the bilayer adsorption of LSB on the RGS and the roughness of the solid surface played a key role in the vesicle formation. A possible mechanism for the RGS-mediated formation of LSB vesicles is proposed: LSB micelles and molecules adsorb on the RGS to form curved bilayers, and the curved bilayers are then detached from the RGS and close to form vesicles. To the best of our knowledge, this is the first report of LSB alone forming vesicles. This finding extends our understanding of the nature of vesicle systems.

  12. Investigation of bone formation using calcium phosphate glass cement in beagle dogs

    PubMed Central

    Lee, Seung-Bum; Jung, Ui-Won; Choi, Youna; Jamiyandorj, Otgonbold; Kim, Chang-Sung; Lee, Yong-Keun; Chai, Jung-Kiu

    2010-01-01

    Purpose Among available biomaterials, bioceramics have drawn special interest due to their bioactivity and the possibility of tailoring their composition. The degradation rate and formulation of bioceramics can be altered to mimic the compositions of the mineral phase of bone. The aim of this study was to investigate the bone formation effect of amorphous calcium phosphate glass cement (CPGC) synthesized by a melting and quenching process. Methods In five male beagle dogs, 4 × 4 mm 1-wall intrabony defects were created bilaterally at the mesial or distal aspect of the mandibular second and fourth premolars. Each of the four defects was divided according to graft materials: CPGC with collagen membrane (CM), biphasic calcium phosphate (BCP) with CM, CM alone, or a surgical flap operation only. The dogs were sacrificed 8 weeks post-surgery, and block sections of the defects were collected for histologic and histometric analysis. Results There were significant differences in bone formation and cementum regeneration between the experimental and control groups. In particular, the CPGC and BCP groups showed greater bone formation than the CM and control groups. Conclusions In conclusion, CPGC was replaced rapidly with an abundant volume of new bone; CPGC also contributed slightly to regeneration of the periodontal apparatus. PMID:20607057

  13. Experimental investigation of biofilm formation within a glass porous medium in the presence of carbon dioxide

    NASA Astrophysics Data System (ADS)

    Sygouni, Varvara; Manariotis, Ioannis D.; Chrysikopoulos, Constantinos V.

    2013-04-01

    Capturing CO2 emissions and storing them in properly selected deep geologic formations is considered a promising solution for the reduction of CO2 in the atmosphere. However, if CO2 leakage occurs from geologic storage formations due to permeability increases caused by rock-brine-supercritical CO2 geochemical reactions or reactivation of existing fractures, the impact to groundwater quality could be significant. Dissolved CO2 in groundwater can decrease the pH, which in turn can solubilize undesired heavy metals from the solid matrix with profound and severe implications to public health. Consequently, it is essential to fully understand the potential impact of CO2 to shallow groundwater systems. In this study, a series of visualization experiments in a glass-etched micromodel were performed in order to estimate the effect of CO2 on biofilm formation. All biofilms were developed using Pseudomonas (P.) Putida. Synthetic water saturated with CO2 was injected through the micromodel through an inlet port, and CO2 was measured at the outlet port. The transient growth of the biofilm was monitored by taking high-resolution digital photographs at various times, and the effect of CO2 on biofilm growth was estimated. Furthermore, transient changes of effective permeability and porosity were measured and the effect of solution chemistry (e.g. pH, ionic strength, redox potential) on the rate of biofilm growth was evaluated.

  14. Rough glass surface-mediated formation of vesicles from lauryl sulfobetaine micellar solutions.

    PubMed

    Zhu, Xiaoyu; Du, Na; Song, Ruiying; Hou, Wanguo; Song, Shue; Zhang, Renjie

    2014-10-01

    We report novel vesicles composed of the zwitterionic surfactant lauryl sulfobetaine (LSB), which is a simple single-tailed surfactant (STS). The novel vesicles spontaneously formed from LSB micellar solutions with the mediation of a rough glass surface (RGS) in the absence of any cosurfactants or additives. Importantly, the obtained STS vesicles displayed good stability upon long-term storage, exposure to high temperature, and freeze-thawing after the RGS was removed. The pH of the LSB solution (4.0-9.0) and the presence of NaCl (1.0 × 10(-5) and 1.0 × 10(-4) mol/L) in the LSB solution had no obvious influence on the formation and stability of the vesicles. The adsorption configuration of LSB on the RGS was investigated via water contact angle measurements and atomic force microscope observations. The results showed that LSB adsorption bilayers could form on the RGS, and the bilayer adsorption of LSB on the RGS and the roughness of the solid surface played a key role in the vesicle formation. A possible mechanism for the RGS-mediated formation of LSB vesicles is proposed: LSB micelles and molecules adsorb on the RGS to form curved bilayers, and the curved bilayers are then detached from the RGS and close to form vesicles. To the best of our knowledge, this is the first report of LSB alone forming vesicles. This finding extends our understanding of the nature of vesicle systems. PMID:25220115

  15. Formation mechanism of a silane-PVA/PVAc complex film on a glass fiber surface.

    PubMed

    Repovsky, Daniel; Jane, Eduard; Palszegi, Tibor; Slobodnik, Marek; Velic, Dusan

    2013-10-21

    Mechanical properties of glass fiber reinforced composite materials are affected by fiber sizing. A complex film formation, based on a silane film and PVA/PVAc (polyvinyl alcohol/polyvinyl acetate) microspheres on a glass fiber surface is determined at 1) the nanoscale by using atomic force microscopy (AFM), and 2) the macroscale by using the zeta potential. Silane groups strongly bind through the Si-O-Si bond to the glass surface, which provides the attachment mechanism as a coupling agent. The silane groups form islands, a homogeneous film, as well as empty sites. The average roughness of the silanized surface is 6.5 nm, whereas it is only 0.6 nm for the non-silanized surface. The silane film vertically penetrates in a honeycomb fashion from the glass surface through the deposited PVA/PVAc microspheres to form a hexagonal close pack structure. The silane film not only penetrates, but also deforms the PVA/PVAc microspheres from the spherical shape in a dispersion to a ellipsoidal shape on the surface with average dimensions of 300/600 nm. The surface area value Sa represents an area of PVA/PVAc microspheres that are not affected by the silane penetration. The areas are found to be 0.2, 0.08, and 0.03 μm(2) if the ellipsoid sizes are 320/570, 300/610, and 270/620 nm for silane concentrations of 0, 3.8, and 7.2 μg mL(-1), respectively. The silane film also moves PVA/PVAc microspheres in the process of complex film formation, from the low silane concentration areas to the complex film area providing enough silane groups to stabilize the structure. The values for the residual silane honeycomb structure heights (Ha ) are 6.5, 7, and 12 nm for silane concentrations of 3.8, 7.2, and 14.3 μg mL(-1), respectively. The pH-dependent zeta-potential results suggest a specific role of the silane groups with effects on the glass fiber surface and also on the PVA/PVAc microspheres. The non-silanized glass fiber surface and the silane film have similar zeta potentials ranging

  16. The influence of sodium nanoparticles formation on luminescent properties of fluorophosphate glasses containing molecular clusters and quantum dots of lead selenide

    NASA Astrophysics Data System (ADS)

    Lipatova, Zh. O.; Kolobkova, E. V.; Sidorov, A. I.; Nikonorov, N. V.

    2016-08-01

    The influence of sodium nanoparticles and secondary heat treatment conditions on the spectralluminescent characteristics of fluorophosphate glasses with PbSe molecular clusters and quantum dots is studied. Experiments with glasses containing no sodium nanoparticles show that their thermal treatment leads to the formation of molecular clusters with subsequent formation of quantum dots having an intense luminescence. The results of numerical simulation for glasses with sodium nanoparticles shows that heat treatment leads to formation of a sodium fluoride shell on the nanoparticles surface. It is shown that quenching of the luminescence of PbSe molecular clusters and quantum dots takes place in these glasses.

  17. Glass formation and the third harmonic generation of Cu{sub 2}Se–GeSe{sub 2}–As{sub 2}Se{sub 3} glasses

    SciTech Connect

    Reshak, A. H.; Klymovych, O. S.; Zmiy, O. F.; Myronchuk, G. L.; Zamuruyeva, O. V.; Alahmed, Z. A.; Chyský, J.; Bila, Jiri; Kamarudin, H.

    2014-10-14

    We have performed the investigation of the nonlinear optical properties namely the third harmonic generation (THG) of the glass-formation region in the Cu{sub 2}Se–GeSe{sub 2}–As{sub 2}Se{sub 3} system. The samples were synthesized by direct single-temperature method from high-purity elementary substances. We have found that the value of disorder parameter Δ depends on the composition of the glassy alloys. The measurements show that increasing the Cu{sub 2}Se concentration leads to increased slope of the absorption edge, which may be explained by the decrease of the height of random potential relief for the electrons in the tails of the state density which border the band edges. A very sharp increase in the THG at low temperature was observed. Significant enhancement in THG was obtained with decreasing the energy gap, which agreed well with the nonlinear optical susceptibilities obtained from other glasses.

  18. On the Formation of Nanobubbles in Vycor Porous Glass during the Desorption of Halogenated Hydrocarbons.

    PubMed

    Mitropoulos, A C; Stefanopoulos, K L; Favvas, E P; Vansant, E; Hankins, N P

    2015-01-01

    Vycor porous glass has long served as a model mesoporous material. During the physical adsorption of halogenated hydrocarbon vapours, such as dibromomethane, the adsorption isotherm exhibits an hysteresis loop; a gradual ascent is observed at higher pressures during adsorption, and a sharp drop is observed at lower pressures during desorption. For fully wetting fluids, an early hypothesis attributed the hysteresis to mechanistic differences between capillary condensation (adsorption) and evaporation (desorption) processes occurring in the wide bodies and narrow necks, respectively, of 'ink-bottle' pores. This was later recognized as oversimplified when the role of network percolation was included. For the first time, we present in-situ small angle x-ray scattering measurements on the hysteresis effect which indicate nanobubble formation during desorption, and support an extended picture of network percolation. The desorption pattern can indeed result from network percolation; but this can sometimes be initiated by a local cavitation process without pore blocking, which is preceded by the temporary, heterogeneous formation of nanobubbles involving a change in wetting states. The capacity of the system to sustain such metastable states is governed by the steepness of the desorption boundary. PMID:26047466

  19. On the Formation of Nanobubbles in Vycor Porous Glass during the Desorption of Halogenated Hydrocarbons

    NASA Astrophysics Data System (ADS)

    Mitropoulos, A. C.; Stefanopoulos, K. L.; Favvas, E. P.; Vansant, E.; Hankins, N. P.

    2015-06-01

    Vycor porous glass has long served as a model mesoporous material. During the physical adsorption of halogenated hydrocarbon vapours, such as dibromomethane, the adsorption isotherm exhibits an hysteresis loop; a gradual ascent is observed at higher pressures during adsorption, and a sharp drop is observed at lower pressures during desorption. For fully wetting fluids, an early hypothesis attributed the hysteresis to mechanistic differences between capillary condensation (adsorption) and evaporation (desorption) processes occurring in the wide bodies and narrow necks, respectively, of ‘ink-bottle’ pores. This was later recognized as oversimplified when the role of network percolation was included. For the first time, we present in-situ small angle x-ray scattering measurements on the hysteresis effect which indicate nanobubble formation during desorption, and support an extended picture of network percolation. The desorption pattern can indeed result from network percolation; but this can sometimes be initiated by a local cavitation process without pore blocking, which is preceded by the temporary, heterogeneous formation of nanobubbles involving a change in wetting states. The capacity of the system to sustain such metastable states is governed by the steepness of the desorption boundary.

  20. On the Formation of Nanobubbles in Vycor Porous Glass during the Desorption of Halogenated Hydrocarbons.

    PubMed

    Mitropoulos, A C; Stefanopoulos, K L; Favvas, E P; Vansant, E; Hankins, N P

    2015-01-01

    Vycor porous glass has long served as a model mesoporous material. During the physical adsorption of halogenated hydrocarbon vapours, such as dibromomethane, the adsorption isotherm exhibits an hysteresis loop; a gradual ascent is observed at higher pressures during adsorption, and a sharp drop is observed at lower pressures during desorption. For fully wetting fluids, an early hypothesis attributed the hysteresis to mechanistic differences between capillary condensation (adsorption) and evaporation (desorption) processes occurring in the wide bodies and narrow necks, respectively, of 'ink-bottle' pores. This was later recognized as oversimplified when the role of network percolation was included. For the first time, we present in-situ small angle x-ray scattering measurements on the hysteresis effect which indicate nanobubble formation during desorption, and support an extended picture of network percolation. The desorption pattern can indeed result from network percolation; but this can sometimes be initiated by a local cavitation process without pore blocking, which is preceded by the temporary, heterogeneous formation of nanobubbles involving a change in wetting states. The capacity of the system to sustain such metastable states is governed by the steepness of the desorption boundary.

  1. Discovery of Critical Oxygen Content for Glass Formation in Zr80Pt20 Melt Spun Ribbons

    SciTech Connect

    D.J. Sordelet; E.A. Rozhkova; X. Yang; M.J. Kramer

    2004-09-30

    Zr{sub 80}Pt{sub 20} alloys may form meta-stable quasicrystals either during devitrification of an amorphous phase or directly upon cooling from a liquid depending on processing conditions. To date, little attention has been given to the role of oxygen on the glass formation or devitrification behavior of Zr-Pt and similar alloys. This study reveals that oxygen content during melt spinning indeed strongly influences the formation of the as-quenched structure. A critical amount of oxygen was found to be required to form amorphous ribbons at a fixed quench rate. At lower oxygen levels (i.e., <500 ppm mass), a fully crystallized is formed; the structure is composed mainly of meta-stable {beta}-Zr with a small fraction of a quasicrystalline phase. At higher oxygen levels, the as-quenched structure transitions to a fully amorphous structure ({approx}1000 ppm mass), and with further oxygen addition forms a mixture of amorphous and quasicrystalline ({approx}1500 ppm mass) or crystalline phases (>2500 ppm mass). Details regarding the structure of the meta-stable {beta}-Zr phase in the low-oxygen ribbons are provided along with a discussion of the structural similarity between this phase and the quasicrystal structure that formed in this alloy.

  2. On the Formation of Nanobubbles in Vycor Porous Glass during the Desorption of Halogenated Hydrocarbons

    PubMed Central

    Mitropoulos, A. C.; Stefanopoulos, K. L.; Favvas, E. P.; Vansant, E.; Hankins, N. P.

    2015-01-01

    Vycor porous glass has long served as a model mesoporous material. During the physical adsorption of halogenated hydrocarbon vapours, such as dibromomethane, the adsorption isotherm exhibits an hysteresis loop; a gradual ascent is observed at higher pressures during adsorption, and a sharp drop is observed at lower pressures during desorption. For fully wetting fluids, an early hypothesis attributed the hysteresis to mechanistic differences between capillary condensation (adsorption) and evaporation (desorption) processes occurring in the wide bodies and narrow necks, respectively, of ‘ink-bottle’ pores. This was later recognized as oversimplified when the role of network percolation was included. For the first time, we present in-situ small angle x-ray scattering measurements on the hysteresis effect which indicate nanobubble formation during desorption, and support an extended picture of network percolation. The desorption pattern can indeed result from network percolation; but this can sometimes be initiated by a local cavitation process without pore blocking, which is preceded by the temporary, heterogeneous formation of nanobubbles involving a change in wetting states. The capacity of the system to sustain such metastable states is governed by the steepness of the desorption boundary. PMID:26047466

  3. Investigations on HONO formation from photolysis of adsorbed HNO3 on quartz glass surfaces.

    PubMed

    Laufs, Sebastian; Kleffmann, Jörg

    2016-04-14

    During the last few decades, nitrous acid (HONO) has attracted significant attention as a major source of the OH radical, the detergent of the atmosphere. However, the different daytime sources identified in the laboratory are still the subject of controversial discussion. In the present study, one of these postulated HONO sources, the heterogeneous photolysis of nitric acid (HNO3), was studied on quartz glass surfaces in a photo flow-reactor under atmospherically relevant conditions. In contrast to other investigations, a very low HNO3 photolysis frequency for HONO formation of J(HNO3→ HONO) = 2.4 × 10(-7) s(-1) (0° SZA, 50% r.h.) was determined. If these results can be translated to atmospheric surfaces, HNO3 photolysis cannot explain the significant HONO levels in the daytime atmosphere. In addition, it is demonstrated that even the small measured yields of HONO did not result from the direct photolysis of HNO3 but rather from the consecutive heterogeneous conversion of the primary photolysis product NO2 on the humid surfaces. The secondary NO2 conversion was not photo-enhanced on pure quartz glass surfaces in good agreement with former studies. A photolysis frequency for the primary reaction product NO2 of J(HNO3→ NO2) = 1.1 × 10(-6) s(-1) has been calculated (0° SZA, 50% r.h.), which indicates that renoxification by photolysis of adsorbed HNO3 on non-reactive surfaces is also a minor process in the atmosphere. PMID:26997156

  4. Enhanced osteoprogenitor elongated collagen fiber matrix formation by bioactive glass ionic silicon dependent on Sp7 (osterix) transcription.

    PubMed

    Varanasi, Venu G; Odatsu, Tetsurou; Bishop, Timothy; Chang, Joyce; Owyoung, Jeremy; Loomer, Peter M

    2016-10-01

    Bioactive glasses release ions, those enhance osteoblast collagen matrix synthesis and osteogenic marker expression during bone healing. Collagen matrix density and osteogenic marker expression depend on osteogenic transcription factors, (e.g., Osterix (OSX)). We hypothesize that enhanced expression and formation of collagen by Si(4+) depends on enhanced expression of OSX transcription. Experimental bioactive glass (6P53-b) and commercial Bioglass(TM) (45S5) were dissolved in basal medium to make glass conditioned medium (GCM). ICP-MS analysis was used to measure bioactive glass ion release rates. MC3T3-E1 cells were cultured for 20 days, and gene expression and extracellular matrix collagen formation was analyzed. In a separate study, siRNA was used to determine the effect of OSX knockdown on impacting the effect of Si(4+) on osteogenic markers and matrix collagen formation. Each bioactive glass exhibited similar ion release rates for all ions, except Mg(2+) released by 6P53-b. Gene expression results showed that GCM markedly enhanced many osteogenic markers, and 45S5 GCM showed higher levels of expression and collagen matrix fiber bundle density than 6P53-b GCM. Upon knockdown of OSX transcription, collagen type 5, alkaline phosphatase, and matrix density were not enhanced as compared to wild type cells. This study illustrates that the enhancement of elongated collagen fiber matrix formation by Si(±) depends on OSX transcription. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2604-2615, 2016. PMID:27279631

  5. On the formation of Na nanoparticles in femtosecond-laser irradiated glasses

    SciTech Connect

    Jiang Nan; Su Dong; Spence, John C. H.; Qiu Jianrong

    2010-03-15

    This work discusses the response of Na to both high-energy electrons and femtosecond-laser (fs-laser) pulses in the soda-lime glass. The evidence for different responses of Na to high-energy electron irradiation between glasses with and without fs-laser irradiation suggests that the chemical and/or physical states of Na in the fs-laser irradiated glass are different from those in the original glass. Fs-laser pulses in the glass may be able to neutralize Na, which may form clusters. These results suggest that close attention should be paid to the defects associated with Na when optical or physical data are interpreted in fs-laser irradiated Na glasses.

  6. Formation temperature of ultra-stable glasses and application to ethylbenzene

    NASA Astrophysics Data System (ADS)

    Tournier, Robert F.

    2015-11-01

    Ultra-stable thin glass films are obtained when they are deposited at a temperature Td below the glass transition temperature Tg. An enthalpy excess Δɛ × ΔHm is frozen during deposition inducing an isothermal liquid-glass transition temperature Tsg equal to Td and a liquid-to-liquid transition temperature Tgf above Tg depending on Δɛ. The enthalpy excess, the ultra-stable glass enthalpy saving, and the optimum deposition temperature Tsg leading to the maximum density, are predicted for ethylbenzene, knowing only the molar melting heat ΔHm of crystals, their melting temperature Tm, Tg, and the specific heat jump at Tg.

  7. In-situ observation of bubble formation at silicon melt-silica glass interface

    NASA Astrophysics Data System (ADS)

    Minami, Toshiro; Maeda, Susumu; Higasa, Mitsuo; Kashima, Kazuhiko

    2011-03-01

    The generation mechanism of pinhole defects in the Czochralski (CZ)-grown silicon (Si) single crystals was clarified by in-situ observations of bubble formation at the interface between Si melt and a silica glass crucible in a small experimental apparatus. The nucleation and growth of bubbles were facilitated by creating small cavities on the inner wall of the crucible. Si melting was conducted in an argon (Ar) atmosphere, and the pressure was maintained at either 100 Torr or close to a vacuum (no Ar-gas flow). It was found that in the presence of Ar, bubbles formed in the cavities immediately after the cavities came in contact with the melt. However, no bubbles formed in a vacuum in the experimental apparatus. These results indicate that the bubbles formed in the cavities are largely filled with Ar, and the initial bubble volumes are nearly comparable with those of the cavities. In an initial stage of expansion of a bubble, estimated volumes changed nearly in accordance with the Boyle-Charles law. Further, participation of SiO gas in bubble growth may explain the deviation of the bubble volume from the theoretical value anticipated if only Ar gas was involved in the bubble growth.

  8. Irradiation-induced Ag-colloid formation in ion-exchanged soda-lime glass

    NASA Astrophysics Data System (ADS)

    Caccavale, F.; De Marchi, G.; Gonella, F.; Mazzoldi, P.; Meneghini, C.; Quaranta, A.; Arnold, G. W.; Battaglin, G.; Mattei, G.

    1995-03-01

    Ion-exchanged glass samples were obtained by immersing soda-lime slides in molten salt baths of molar concentration in the range 1-20% AgNO 3 in NaNO 3, at temperatures varying from 320 to 350°C, and processing times of the order of a few minutes. Irradiations of exchanged samples were subsequently performed by using H +m, He +, N + ions at different energies in order to obtain comparable projected ranges. The fluence was varied between 5 × 10 15 and 2 × 10 17 ions/cm 2. Most of the samples were treated at current densities lower than 2 μA/cm 2, in order to avoid heating effects. Some samples were irradiated with 4 keV electrons, corresponding to a range of 250 nm. The formation of nanoclusters of radii in the range 1-10 nm has been observed after irradiation, depending on the treatment conditions. The precipitation process is governed by the electronic energy deposition of incident particles. The most desirable results are obtained for helium implants. The process was characterized by the use of Secondary Ion Mass Spectrometry (SIMS) and nuclear techniques (Rutherford Backscattering (RBS), Nuclear Reactions (NRA)), in order to determine concentration-depth profiles and by optical absorption and Transmission Electron Microscopy (TEM) measurements for the silver nanoclusters detection and size evaluation.

  9. Formation of Nanoporous Anodic Alumina by Anodization of Aluminum Films on Glass Substrates.

    PubMed

    Lebyedyeva, Tetyana; Kryvyi, Serhii; Lytvyn, Petro; Skoryk, Mykola; Shpylovyy, Pavlo

    2016-12-01

    Our research was aimed at the study of aluminum films and porous anodic alumina (PAA) films in thin-film РАА/Al structures for optical sensors, based on metal-clad waveguides (MCWG). The results of the scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies of the structure of Al films, deposited by DC magnetron sputtering, and of PAA films, formed on them, are presented in this work.The study showed that the structure of the Al films is defined by the deposition rate of aluminum and the thickness of the film. We saw that under anodization in 0.3 M aqueous oxalic acid solution at a voltage of 40 V, the PAA film with a disordered array of pores was formed on aluminum films 200-600 nm thick, which were deposited on glass substrates with an ultra-thin adhesive Nb layer. The research revealed the formation of two differently sized types of pores. The first type of pores is formed on the grain boundaries of aluminum film, and the pores are directed perpendicularly to the surface of aluminum. The second type of pores is formed directly on the grains of aluminum. They are directed perpendicularly to the grain plains. There is a clear tendency to self-ordering in this type of pores. PMID:27083584

  10. Bulk formation of metallic glasses and amorphous silicon from the melt

    NASA Technical Reports Server (NTRS)

    Spaepen, F.

    1984-01-01

    Procedures and compositions for producing metallic glasses in bulk at slow cooling rates were investigated. An attempt was made to form the amorphous phase of the tetrahedrally coordinated elements (Si or Ge) by undercooling the melt. The crystal nucleation behavior of pure liquids and glass formers were examined.

  11. The effect of phosphate based glasses on the formation and viability of oral bacterial biofilms

    NASA Astrophysics Data System (ADS)

    Mulligan, April Miranda

    This study considered the antibacterial activity of a series of soluble phosphate-based glasses (based on the Na2O-CaO-P2O5 glass system) doped with increasing amounts of copper or silver against oral bacterial biofilms. Initially, a variety of phosphate-based glass compositions were produced. The dissolution rate of these glasses was determined, and the information obtained was used to decide which glass compositions would be investigated in future experiments for their antibacterial properties. Selected glass compositions were investigated for their antibacterial activity against Streptococcus sanguis biofilms and oral microcosm biofilms. These biofilms were produced on phosphate-based glass discs using a Constant Depth Film Fermenter (CDFF), which allows the conditions found in the oral cavity to be closely mimicked. Following disc removal from the CDFF, various analytical procedures were carried out. Under conditions designed to mimic the supragingival environment of the oral cavity, fewer viable cells of Streptococcus sanguis were detected on both copper and silver-containing glass discs than on control discs, during the initial stages of the experiments, the greatest reduction occurring on the silver-containing glasses. An increase in viable cell number was observed as the experiments continued. Under the same conditions, copper-containing glasses failed to reduce the viability of microcosm biofilms. Viable cell number was initially reduced on the silver-containing glasses, but by the end of the experiments the viability of microcosm biofilms was significantly similar to those observed on the controls. Attempts to determine the efficacy of silver-containing glasses at reducing the viability of microcosm biofilms, under conditions designed to mimic the subgingival environment of the oral cavity, were subsequently made. Viable cells were not detected on any type of disc, including the control discs. Various reasons for this were postulated. In conclusion, the

  12. Alteration of Basaltic Glass to Mg/Fe-Smectite under Acidic Conditions: A Potential Smectite Formation Mechanism on Mars

    NASA Technical Reports Server (NTRS)

    Peretyazhko, Tanya; Sutter, Brad; Ming, Douglas W.

    2014-01-01

    Phyllosilicates of the smectite group including Mg- and Fe-saponite and Fe(III)-rich nontronite have been identified on Mars. Smectites are believed to be formed under neutral to alkaline conditions that prevailed on early Mars. This hypothesis is supported by the observation of smectite and carbonate deposits in Noachian terrain on Mars. However, smectite may have formed under mildly acidic conditions. Abundant smectite formations have been detected as layered deposits hundreds of meters thick in intracrater depositional fans and plains sediments, while no large deposits of carbonates are found. Development of mildly acidic conditions at early Mars might allow formation of smectite but inhibit widespread carbonate precipitation. Little is known regarding the mechanisms of smectite formation from basaltic glass under acidic conditions. The objective of this study was to test a hypothesis that Mars-analogue basaltic glass alters to smectite minerals under acidic conditions (pH 4). The effects of Mg and Fe concentrations and temperature on smectite formation from basaltic glass were evaluated. Phyllosilicate synthesis was performed in batch reactors (Parr acid digestion vessel) under reducing hydrothermal conditions at 200 C and 100 C. Synthetic basaltic glass with a composition similar to that of the Gusev crater rock Adirondack (Ground surface APXS measurement) was used in these experiments. Basaltic glass was prepared by melting and quenching procedures. X-ray diffraction (XRD) analysis indicated that the synthesized glass was composed of olivine, magnetite and X-ray amorphous phase. Samples were prepared by mixing 250 mg Adirondack with 0.1 M acetic acid (final pH 4). In order to study influence of Mg concentration on smectite formation, experiments were performed with addition of 0, 1 and 10 mM MgCl2. After 1, 7 and 14 day incubations the solution composition was analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and the altered glass and formed

  13. Glass transition and composite formation in InF3-containing oxyfluoroniobate system

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    The glasses in the system MnNbOF5-BaF2-InF3 have been firstly synthesized and studied. The thermal parameters of these glasses are analyzed. It was stated that glass of the composition 40MnNbOF5-40BaF2-20InF3 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 Ba3In2F12 and BaNbOF5. 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 in NbO2F-BaF2 system: (NbOnFm) polyhedra joined oxygen bridges. Indium trifluoride forms InF6 polyhedra, which are embeded between oxyfluoroniobate ions, forming a common networks or forms its own layers from InF6 polyhedra. IR-spectroscopy method showed that at devitrification of the sample 30MnNbOF5-50BaF2-20InF3 the band position and shape change in going from glass state to crystalline. The bands in the range 900-700 cm-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.

  14. Computer Modeling of Thermal Convection in Melts to Explain Glass Formation in Low Gravity and on Earth

    NASA Technical Reports Server (NTRS)

    Ray, Chandra S.; Ramachandran, Narayanan

    2006-01-01

    Experiments conducted up to this time on glass forming melts in the low gravity environment of space show that glasses prepared in low-g are more chemically homogeneous and more resistant to crystallization than the comparable glasses prepared at 1-g on Earth. This result is somewhat surprising and opposite to the accepted concept on glass formation for a melt. A hypothesis based on "shear thinning" of a melt, a decrease in viscosity with increasing shear stress, is proposed as an explanation for the observed low-gravity results. This paper describes detailed simulation procedures to test the role of thermal convection in introducing shear stress in glass forming melts, using a lithium disilcate melt as a model. The simulation system in its idealized version consists of a cylinder that is heated at one end and cooled at the other with gravity acting in a transverse direction to the thermal gradient. The side wall of the cylinder is assumed to be insulating. The governing equations of motion and energy are solved using variable properties for viscosity (Arrehenius and non-Arrehenius behaviors) and density (constant and temperature dependent). Other parametric variables in the calculations include gravity level and gravity vector orientation. The shear stress in the system are then computed as a function of gravity from the calculated values of maximum melt velocity, and its effect on melt viscosity (shear thinning) is predicted. Also included and discussed are the modeling efforts related to other potential convective processes in glass forming melts and their possible effects on melt viscosity.

  15. New glasses for graded-index optics: influence of non-linear diffusion in the formation of optical microstructures

    NASA Astrophysics Data System (ADS)

    Liñares, J.; Sotelo, D.; Lipovskii, A. A.; Zhurihina, V. V.; Tagantsev, D. K.; Turunen, J.

    2000-03-01

    We have designed novel glasses for the formation of graded-index diffractive optical structures. In these glasses silver ion exchange and rapid diffusion produce a large refractive-index variation (0.085). We model the non-linearity of the diffusion process by applying the Boltzmann-Matano technique to the optical profiles and use index variation rather than concentration in the second Fick equation. The simulation of graded-index diffraction gratings formed under thermal and electrically assisted diffusion shows that, other conditions being equal, more efficient gratings can be formed when the diffusion coefficient increases with the dopant concentration. According to the simulation, the application of an electric field of about 0.5 V/μm enables one to obtain a phase shift equal to 1.5 π rad if a grating with a period of 4 μm is formed in the novel glass material. For comparison, a phase shift of only 0.9 π is predicted when a similar grating is formed in the commercial BK-7 glass.

  16. Bioactive glasses with improved processing. Part 1. Thermal properties, ion release and apatite formation.

    PubMed

    Groh, Daniel; Döhler, Franziska; Brauer, Delia S

    2014-10-01

    Bioactive glasses, particularly Bioglass® 45S5, have been used to clinically regenerate human bone since the mid-1980s; however, they show a strong tendency to undergo crystallization upon heat treatment, which limits their range of applications. Attempts at improving their processing (by reducing their tendency to crystallize) have included increasing their silica content (and thus their network connectivity), incorporating intermediate oxides or reducing their phosphate content, all of which reduce glass bioactivity. Therefore, bioactive glasses known for their good processing (e.g. 13-93) are considerably less bioactive. Here, we investigated if the processing of 45S5 bioactive glass can be improved while maintaining its network connectivity and phosphate content. The results show that, by increasing the calcium:alkali cation ratio, partially substituting potassium for sodium (thereby making use of the mixed alkali effect) and adding small amounts of fluoride, bioactive glasses can be obtained which have a larger processing window (suggesting that they can be processed more easily, allowing for sintering of scaffolds or drawing into fibres) while degrading readily and forming apatite in aqueous solution within a few hours. PMID:24880003

  17. Chemical durability of glass containing SRP waste: leachability characteristics, protective layer formation, and repository system interactions

    SciTech Connect

    Wicks, G G; Robnett, B M; Rankin, W D

    1982-01-01

    The Repository Systems Program at Savannah River consists of the following elements: (a) static repository tests, (b) slow flow groundwater tests, (c) dynamic leaching experiments, (d) long term leaching tests, and (e) in situ experiments. The scouting tests performed in the static repository program are summarized and a new dynamic leaching concept is introduced in this paper. Abbreviated MCC-1 static leaching tests were used in this static repository program. The tests were conducted at 90/sup 0/C for 7 days with deionized water as well as repository groundwaters as leachants. The static repository program consisted of three phases. Phase 1 of the study evaluated the leachability of SRP waste glass leached in the presence of salt, basalt, shale, granite, and tuff at three different ratios of surface areas of sample to volume of leachant (SA/V). These data were then compared to tests on similar glasses leached in the absence of rock. The second phase of this program evaluated the effects of five simulated groundwaters on the leachability of waste glass both with and without host rock present and compared these results to glass leached by deionized water. The groundwaters included many minor as well as major constituents. The third and final phase of the program evaluated waste glass leachability as a function of tests conducted in the presence of candidate canister and overpack metals, backfill mixtures, and five complete package systems. The sample matrices are given in Table 2 and the data are summarized.

  18. Formation of Cu-Zr-M ternary bulk metallic glasses based on atomic clusters

    NASA Astrophysics Data System (ADS)

    Li, Y. H.; Wang, Q.; Wu, J.; Dong, C.

    2008-02-01

    Ternary Cu-Zr-M (M= Al, Ti and Ag) bulk metallic glasses are investigated using a cluster line approach. New bulk metallic glass rods with compositions lying along the cluster line Cu5Zr6-M were fabricated by copper mould suction, where binary cluster Cu5Zr6 is an Archimedean octahedral antiprism, M being about 4~13.2 at.% for Al, 8.3 at.% for Ti and 9 at.% for Ag. The relevant mechanism was discussed in the light of the cluster-plus-glue-atom model.

  19. Bulk metallic glass formation in Zr-Cu-Fe-Al alloys

    SciTech Connect

    Jin Kaifeng; Loeffler, Joerg F.

    2005-06-13

    We have discovered a series of bulk metallic glass-forming alloys of composition (Zr{sub x}Cu{sub 100-x}){sub 80}(Fe{sub 40}Al{sub 60}){sub 20} with x=68-77 and have investigated them by x-ray diffraction, small-angle neutron scattering, and differential scanning calorimetry. All of these alloys exhibit a calorimetric glass transition temperature of 670 Kglass-forming ability is obtained for x{approx_equal}72.5, i.e., for the alloy Zr{sub 58}Cu{sub 22}Fe{sub 8}Al{sub 12}. In rod shape this alloy has a critical casting thickness of 13 mm, as verified by detailed casting experiments, while alloys with x=68 and 77 can still be cast to a thickness of 5 mm. Furthermore, the region where glassy samples with a thickness of 0.5 mm can be prepared extends from x=62-81. The best glass-former, Zr{sub 58}Cu{sub 22}Fe{sub 8}Al{sub 12}, has a tensile yield strength of 1.71 GPa and shows an elastic limit of 2.25%. This new class of Ni-free Zr-based alloys is potentially very interesting for biomedical applications.

  20. Formation of Fe/mg Smectite Under Acidic Conditions from Synthetic Adirondack Basaltic Glass: an Analog to Fe/mg Smectite Formation on Mars

    NASA Technical Reports Server (NTRS)

    Sutter, B.; Peretyazhko, T.; Morris, R. V.; Ming, D. W.

    2014-01-01

    Smectite has been detected as layered material hundreds of meters thick, in intracrater depositional fans, in plains sediments, and deposits at depth on Mars. If early Mars hosted a dense CO2 atmosphere, then extensive carbonate should have formed in the neutral/alkaline conditions expected for smectite formation. However, large carbonate deposits on Mars have not been discovered. Instead of neutral to moderately alkaline conditions, early Mars may have experienced mildly acidic conditions that allowed for Fe/Mg smectite formation but prevented widespread carbonate formation. The objective of this work is to demonstrate that Fe(II)/Mg saponite and nontronite can form in mildly acidic solutions (e.g., pH 4). Synthetic basaltic glass (< 53 microns) of Adirondack rock class composition was exposed to pH 4 (acetic acid buffer) and N2 purged (anoxic) solutions amended with 0 and 10 mM Mg or Fe(II). Basaltic glass in these solutions was heated to 200 C in batch reactors for 1, 7, and 14 days. X-ray diffraction analysis of reacted materials detected the presence of phyllosilicates as indicated by a approx. 15.03-15.23Angstroms (001) peak. Smectite was confirmed as the phyllosilicate after treatments with glycerol and KCl and heating to 550 C. Trioctahedral saponite was confirmed by the presence of a 4.58 to 4.63 Angstroms (02l) and 1.54Angstroms (060) peaks. Saponite concentration was highest, as indicated by XRD peak intensity, in the 10 mM Mg treatment followed by the 0 mM and then 10 mM Fe(II) treatments. This order of sapontite concentration suggests that Fe(II) additions may have a role in slowing the kinetics of saponite formation relative to the other treatments. Nontronite synthesis was attempted by exposing Adirondack basaltic glass to pH 4 oxic solutions (without N2 purge) at 200 C for 14 days. X-ray diffraction analysis indicated that mixtures of trioctahedral (saponite) and dioctahedral (nontronite) may have formed in these experiments based on the 02l and 060

  1. Formation of Fe/Mg Smectite under acidic conditions from synthetic Adirondack Basaltic Glass: An Analog to Fe/Mg Smectite Formation on Mars.

    NASA Astrophysics Data System (ADS)

    Sutter, B.; Peretyazhko, T.; Morris, R. V.; Ming, D. W.

    2014-12-01

    Smectite has been detected as layered material hundreds of meters thick, in intracrater depositional fans, in plains sediments, and deposits at depth on Mars. If early Mars hosted a dense CO2 atmosphere, then extensive carbonate should have formed in the neutral/alkaline conditions expected for smectite formation. However, large carbonate deposits on Mars have not been discovered. Instead of neutral to moderately alkaline conditions, early Mars may have experienced mildly acidic conditions that allowed for Fe/Mg smectite formation but prevented widespread carbonate formation. The objective of this work is to demonstrate that Fe(II)/Mg-saponite and nontronite can form in mildly acidic solutions (e.g., pH 4). Synthetic basaltic glass (< 53 μm) of Adirondack rock class composition was exposed to pH 4 (acetic acid buffer) and N2 purged (anoxic) solutions amended with 0 and 10 mM Mg or Fe(II). Basaltic glass in these solutions was heated to 200ºC in batch reactors for 1, 7, and 14 days. X-ray diffraction analysis of reacted materials detected the presence of phyllosilicates as indicated by a ~15.03-15.23Ǻ (001) peak. Smectite was confirmed as the phyllosilicate after treatments with glycerol and KCl and heating to 550°C. Trioctahedral saponite was confirmed by the presence of a 4.58 to 4.63 Ǻ (02l) and 1.54Ǻ (060) peaks. Saponite concentration was highest, as indicated by XRD peak intensity, in the 10 mM Mg treatment followed by the 0 mM and then 10 mM Fe(II) treatments. This order of sapontite concentration suggests that Fe(II) additions may have a role in slowing the kinetics of saponite formation relative to the other treatments. Nontronite synthesis was attempted by exposing Adirondack basaltic glass to pH 4 oxic solutions (without N2 purge) at 200ºC for 14 days. X-ray diffraction analysis indicated that mixtures of trioctahedral (saponite) and dioctahedral (nontronite) may have formed in these experiments based on the 02l and 060 peaks. Mössbauer analysis

  2. Role of magnesium during spontaneous formation of a calcium phosphate layer at the periphery of a bioactive glass coating doped with MgO

    NASA Astrophysics Data System (ADS)

    Jallot, E.

    2003-04-01

    The prerequisite for bioactive glasses to bond to living bone is the formation of biologically active apatites on their surface in the body. Reactions and bioactivity mechanisms between bioactive glasses and bone depend on the glass composition. Our results demonstrate this property of bioactivity for the studied bioactive glass. The bioactive glass doped with MgO leads to the formation of a Ca-P-Mg rich layer on top of a pure Si layer. Ca, P and Mg elements diffuse through the Si rich layer which seems to act as a protective diffusion barrier leading to t1/2 leaching kinetics. This paper demonstrates for the first time, the presence of Mg in the Ca-P rich layer at the interface between the bioactive glass and bone. However, magnesium influences the formation and the evolution of the apatite layer. Magnesium has synergistic effects on the crystallinity and solubility of apatites. These phenomena can promote a greater dissolution of the apatite precipitates in the studied bioactive glass. Determination of supersaturations values permits to better understand growth and dissolution of precipitates forming the apatite-Mg layer. Measurements of supersaturations for Ca, P and Mg were consistent before 3 months and after 6 months. Before 3 months, the apatite-Mg layer grows and after 3 months this layer is in dissolution.

  3. Formation of a macro-porous SiO2 layer as an anti-reflective coating on glass substrates.

    PubMed

    Park, No-Kuk; Kim, Yong Sul; Kim, Min Jung; Lee, Tae Jin; Lee, Seung Hyun; Lee, Seung Hun

    2013-11-01

    A macro-porous silica layer, consisting of a silica layer with macro-sized pores, was formed as an antireflective material on glass substrates. The silica layer and macro-pores were formed by the oxidative thermal decomposition of tetra-ethylorthorsilicate (TEOS) used as the precursor and polystyrene (PS) spherical beads used as the polymer template for the macro-pores at high temperatures. The size of pores was determined by the size of PS beads in the antireflective agent solution. The size of the PS spherical beads can be controlled by changing the concentration of styrene monomer, and the porosity of the macro pore in the silica layer could be controlled by the TEOS/PS ratio. The optimal thermal treating temperature for the formation of a macro-porous silica layer was found to be 650 degrees C. The size of the spherical type macro pores formed in the silica layer on the glass substrate was 100-150 nm. UV-Vis spectrophotometry confirmed the improved antireflective properties of the glass substrate with the macro-porous silica layer.

  4. Thermochromism, the Alexandrite effect, and dynamic Jahn-Teller distortions in Ho2Cu(TeO3)2(SO4)2.

    PubMed

    Lin, Jian; Diefenbach, Kariem; Cross, Justin N; Babo, Jean-Marie; Albrecht-Schmitt, Thomas E

    2013-11-18

    A 3d-4f heterobimetallic material with mixed anions, Ho2Cu(TeO3)2(SO4)2, has been prepared under hydrothermal conditions. Ho2Cu(TeO3)2(SO4)2 exhibits both thermochromism and the Alexandrite effect. Variable temperature single crystal X-ray diffraction and UV-vis-NIR spectroscopy reveal that changes in the Cu(II) coordination geometry result in negative thermal expansion of axial Cu-O bonds that plays a role in the thermochromic transition of Ho2Cu(TeO3)2(SO4)2. Magnetic studies reveal an effective magnetic moment of 14.97 μB. which has a good agreement with the calculated value of 15.09 μB.

  5. Thermochromism, the Alexandrite effect, and dynamic Jahn-Teller distortions in Ho2Cu(TeO3)2(SO4)2.

    PubMed

    Lin, Jian; Diefenbach, Kariem; Cross, Justin N; Babo, Jean-Marie; Albrecht-Schmitt, Thomas E

    2013-11-18

    A 3d-4f heterobimetallic material with mixed anions, Ho2Cu(TeO3)2(SO4)2, has been prepared under hydrothermal conditions. Ho2Cu(TeO3)2(SO4)2 exhibits both thermochromism and the Alexandrite effect. Variable temperature single crystal X-ray diffraction and UV-vis-NIR spectroscopy reveal that changes in the Cu(II) coordination geometry result in negative thermal expansion of axial Cu-O bonds that plays a role in the thermochromic transition of Ho2Cu(TeO3)2(SO4)2. Magnetic studies reveal an effective magnetic moment of 14.97 μB. which has a good agreement with the calculated value of 15.09 μB. PMID:24180361

  6. Unexpected Spin-Crossover and a Low-Pressure Phase Change in an Iron(II)/Dipyrazolylpyridine Complex Exhibiting a High-Spin Jahn- Teller Distortion.

    PubMed

    Kershaw Cook, Laurence J; Thorp-Greenwood, Flora L; Comyn, Tim P; Cespedes, Oscar; Chastanet, Guillaume; Halcrow, Malcolm A

    2015-07-01

    The synthesis of 4-methyl-2,6-di(pyrazol-1-yl)pyridine (L) and four salts of [FeL2]X2 (X– = BF(4)(–), 1; X– = ClO(4)(–), 2; X– = PF(6)(–), 3; X– = CF3SO(3)(–), 4) are reported. Powder samples of 1 and 2 both exhibit abrupt, hysteretic spin-state transitions on cooling, with T(1/2)↓ = 204 and T(1/2)↑ = 209 K (1), and T(1/2)↓ = 175 and T(1/2)↑ = 193 K (2). The 18 K thermal hysteresis loop for 2 is unusually wide for a complex of this type. Single crystal structures of 2 show it to exhibit a Jahn–Teller-distorted six-coordinate geometry in its high-spin state, which would normally inhibit spin-crossover. Bulk samples of 1 and 2 are isostructural by X-ray powder diffraction, and undergo a crystallographic phase change during their spin-transitions. At temperatures below T(1/2), exposing both compounds to 10(–5) Torr pressure inside the powder diffractometer causes a reversible transformation back to the high-temperature crystal phase. Consideration of thermodynamic data implies this cannot be accompanied by a low → high spin-state change, however. Both compounds also exhibit the LIESST effect, with 2 exhibiting an unusually high T(LIESST) of 112 K. The salts 3 and 4 are respectively high-spin and low-spin between 3 and 300 K, with crystalline 3 exhibiting a more pronounced version of the same Jahn–Teller distortion. PMID:26351707

  7. Formation of budesonide/α-lactose glass solutions by ball-milling

    NASA Astrophysics Data System (ADS)

    Dudognon, E.; Willart, J. F.; Caron, V.; Capet, F.; Larsson, T.; Descamps, M.

    2006-04-01

    The possibility to obtain amorphous budesonide stabilised by blending with an excipient characterised by a higher glass transition temperature, namely α-lactose, has been studied. We carried out the mixing of the two compounds at room temperature by ball-milling. The four obtained blends (containing, respectively, 10, 30, 50 and 70% w of budesonide) are X-ray amorphous and exhibit a single glass transition located between the ones of pure milled crystalline compounds. This revealed that the two amorphous phases are miscible whatever the composition and sufficiently mixed to relax as a whole. Ball-milling thus appears as a powerful tool to form amorphous molecular alloys with enhanced stability properties.

  8. The configuration exchanging theory for transport properties and glass formation temperature of ionic liquids.

    PubMed

    Hu, Yu-Feng; Zhang, Xian-Ming; Qi, Jian-Guang; Yin, Liu-Yi

    2015-11-28

    Understanding molecular motion in terms of molecular structure is an important issue for microscopic understanding of the nature of transport properties and glass transition, and for design of structured materials to meet specific demands in various applications. Herein, a novel molecular mechanism is proposed to connect macroscopic motion in ionic liquids with molecular structure via conformational conversions of the constituent ions or of the cation-anion pairs. New equations for description of relaxation time, diffusion coefficient, molar conductivity, and viscosity of ionic liquids are established. The equation parameters, which were determined from the temperature dependent heat capacities, self-diffusion coefficients, molar conductivities, and viscosities of typical ionic liquids, were used to produce predictions for the corresponding properties of other ionic liquids and for the glass transition temperatures of representative ionic liquids. All predictions are in nice agreements with the experimental results.

  9. Formation of silver nanoparticles inside a soda-lime glass matrix in the presence of a high intensity Ar{sup +} laser beam

    SciTech Connect

    Niry, M. D.; Khalesifard, H. R.; Mostafavi-Amjad, J.; Ahangary, A.; Azizian-Kalandaragh, Y.

    2012-02-01

    Formation and motion of the silver nanoparticles inside an ion-exchanged soda-lime glass in the presence of a focused high intensity continuous wave Ar{sup +} laser beam (intensity: 9.2 x 10{sup 4} W/cm{sup 2}) have been studied in here. One-dimensional diffusion equation has been used to model the diffusion of the silver ions into the glass matrix, and a two-dimensional reverse diffusion model has been introduced to explain the motion of the silver clusters and their migration toward the glass surface in the presence of the laser beam. The results of the mentioned models were in agreement with our measurements on thickness of the ion-exchange layer by means of optical microscopy and recorded morphology of the glass surface around the laser beam axis by using a Mirau interferometer. SEM micrographs were used to extract the size distribution of the migrated silver particles over the glass surface.

  10. Origin of an Isothermal R -Martensite Formation in Ni-rich Ti-Ni Solid Solution: Crystallization of Strain Glass

    NASA Astrophysics Data System (ADS)

    Ji, Yuanchao; Wang, Dong; Ding, Xiangdong; Otsuka, Kazuhiro; Ren, Xiaobing

    2015-02-01

    We report that R martensite isothermally forms with time in a solution-treated Ti48.7Ni51.3 single crystal. This abnormal formation originates from the growth of a short-range ordered R phase with time, i.e., the "crystallization" of strain glass. The established time-composition-temperature Ti-Ni diagram shows a time evolution of the R phase and composition-temperature phase diagram. The presence or absence of the R phase in this new diagram, as well as in other conditions (like doping Fe or aging), is explained in a unified framework of free-energy landscape. Our finding suggests a new mechanism for the isothermal martensite formation, which could be applied to other metal and ceramic martensitic systems to find new phases and novel properties.

  11. Formation, structural and optical characterization of neodymium doped-zinc soda lime silica based glass

    NASA Astrophysics Data System (ADS)

    Zamratul, M. I. M.; Zaidan, A. W.; Khamirul, A. M.; Nurzilla, M.; Halim, S. A.

    New glass system of neodymium - doped zinc soda lime silica glass has been synthesized for the first time by melt-quenching of glass waste soda lime silica (SLS) with zinc oxide (ZnO) as precursor glass and Nd2O3 as dopant. In order to examine the effect of Nd3+ on the structural and optical properties, the prepared sample of structure [(ZnO)0.5(SLS)0.5](Nd2O3)x (x = 0, 1, 2, 3, 4 and 5 wt%) was characterized through X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-Vis spectroscopy (UV-Vis) and the photoluminescence (PL). XRD pattern justifies the amorphous nature of synthesized glasses. FTIR spectroscopy has been used to observe the structural evolution of ZnO4 and SiO4 groups. The UV-Vis-NIR absorption spectra reveals seven peaks centered at excitation of electron from ground state 4I9/2 to 4D3/2 + 4D5/2 (∼360 nm), 2G9/2 + 2D3/2 + 2P3/2(∼470 nm), 2K13/2 + 4G7/2 + 4G9/2 (∼523 nm), 4G5/2 + 2G7/2 (∼583 nm), 4F9/2 (∼678 nm), 4S3/2 + 4F7/2 (∼748 nm) and 4F5/2 + 2H9/2 (∼801 nm). PL spectra under the excitation of 800 nm display four emission bands centered at 531 nm, 598 nm, 637 nm and 671 nm corresponding to 4G7/2 → 4I9/2, (4G7/2 → 4I11/2, 4G5/2 → 4I9/2), (4G5/2 → 4I11/2) and (4G7/2 → 4I13/2, 4G5/2 → 4I11/2) respectively.

  12. Calculation of alloying effect on formation enthalpy of TiCu intermetallics from first-principles calculations for designing Ti-Cu-system metallic glasses

    NASA Astrophysics Data System (ADS)

    Shirasawa, Naoya; Takigawa, Yorinobu; Uesugi, Tokuteru; Higashi, Kenji

    2016-01-01

    The effect of alloying on the formation enthalpy of TiCu intermetallics was investigated via first-principles calculations to propose a new design method for Ti-Cu-system metallic glasses. The calculation results showed good agreement with the reported experimental results that Ni, Pd, Sn and Zr improve this system's glass-forming ability. According to the calculation results, a Ti-Zr-Cu-Ga system was designed as a potential new bulk Ti-based metallic glass, and a bulk sample with a 2-mm diameter was fabricated.

  13. The formation of frangipane horizons and their influence on physical-chemical properties of soils from glass houses

    NASA Astrophysics Data System (ADS)

    Filipov, F.; Bulgariu, D.; Avarvarei, I.

    2009-04-01

    The pedological, mineralogical and geochemical studies performed by as on soils (s.s hortic antrosols) from Iasi (Copou glass house), Barlad and Bacau glass houses have show that, in most of cases, the profile of hortic antrosols have the following compositions: Aho-AC-C or Ck, and Aho-B/C or Ck, respectively. In function of parental material nature and specific exploitation technologies, can appear the diagnostic horizons of association (hiposalic-sc, hiponatric-ac etc.) and / or of transition (A/B, A/C, C/A, A+C, ABk etc.). Specific for soils from glass houses are intense modifications of soil profile, large variability of mineralogy and chemistry, salinization processes (by progressive accumulation of soluble salts) at superior horizons level and formation, at 50 cm depth, of a compact and impermeable horizon (frangipane horizon). From chemical point of view, the hortic antrosols are generally characterized by high values of saturation in bases, of accessible phosphorus and of ratio between humic and fulvic acids (organic matter is dominant in intense humified fraction). Regarding the formation conditions, the mineralogy and geochemistry of frangipane horizons, in this moment, in literature are not too many data. In case of studied soils, the frangipane horizons appear in specific forms, where their structure, morphology and chemistry varied in large limits. In hortic antrosols where are formed, the frangipane horizons determined a sever pedogeochemical segregation. Thus, the horizons situated above to the frangipane horizon evolutes in weak oxidant conditions, weak acid-neutral pH (5.87 - 6.95), high salinity and humidity, intense biological activity; while the horizons situated below to the frangipane horizon evolutes in weak reduction conditions, neutral - weak alkaline pH (7.61 - 8.04), reduced salinity and humidity, weak biological activity. This determined an important differentiation of micro-elements and organic compounds dynamic, evidenced by the

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

    DOE PAGES

    Zhang, Feng; Ji, Min; Fang, Xiao-Wei; Sun, Yang; Wang, Cai-Zhuang; Mendelev, Mikhail I.; Kramer, M. J.; Napolitano, Ralph E.; Ho, Kai-Ming

    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

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

    SciTech Connect

    Zhang, Feng; Ji, Min; Fang, Xiao-Wei; Sun, Yang; Wang, Cai-Zhuang; Mendelev, Mikhail I.; Kramer, M. J.; Napolitano, Ralph E.; Ho, Kai-Ming

    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 motif 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.

  16. Formation of double glass in binary mixtures of anisotropic particles: Dynamic heterogeneities in rotations and displacements

    NASA Astrophysics Data System (ADS)

    Takae, Kyohei; Onuki, Akira

    2013-10-01

    We study glass behavior in a mixture of elliptic and circular particles in two dimensions at low temperatures using an orientation-dependent Lennard-Jones potential. The ellipses have a mild aspect ratio (˜1.2) and tend to align at low temperatures, while the circular particles play the role of impurities disturbing the ellipse orientations at a concentration of 20%. These impurities have a size smaller than that of the ellipses and attract them in the homeotropic alignment. As a result, the coordination number around each impurity is mostly 5 or 4 in glassy states. We realize double glass, where both the orientations and the positions are disordered but still hold mesoscopic order. We find a strong heterogeneity in the flip motions of the ellipses, which sensitively depends on the impurity clustering. In our model, a small fraction of the ellipses still undergo flip motions relatively rapidly even at low temperatures. In contrast, the nonflip rotations (with angle changes not close to ±π) are mainly caused by the cooperative configuration changes involving many particles. Then, there arises a long-time heterogeneity in the nonflip rotations closely correlated with the dynamic heterogeneity in displacements.

  17. Formation of double glass in binary mixtures of anisotropic particles: dynamic heterogeneities in rotations and displacements.

    PubMed

    Takae, Kyohei; Onuki, Akira

    2013-10-01

    We study glass behavior in a mixture of elliptic and circular particles in two dimensions at low temperatures using an orientation-dependent Lennard-Jones potential. The ellipses have a mild aspect ratio (∼1.2) and tend to align at low temperatures, while the circular particles play the role of impurities disturbing the ellipse orientations at a concentration of 20%. These impurities have a size smaller than that of the ellipses and attract them in the homeotropic alignment. As a result, the coordination number around each impurity is mostly 5 or 4 in glassy states. We realize double glass, where both the orientations and the positions are disordered but still hold mesoscopic order. We find a strong heterogeneity in the flip motions of the ellipses, which sensitively depends on the impurity clustering. In our model, a small fraction of the ellipses still undergo flip motions relatively rapidly even at low temperatures. In contrast, the nonflip rotations (with angle changes not close to ±π) are mainly caused by the cooperative configuration changes involving many particles. Then, there arises a long-time heterogeneity in the nonflip rotations closely correlated with the dynamic heterogeneity in displacements. PMID:24229182

  18. Magnetoelastic evidence for a local structural transformation in Co-rich glasses

    NASA Astrophysics Data System (ADS)

    O'Handley, R. C.; Grant, N. J.

    1983-04-01

    orientation of the local structural units. The electronic origin of the transformations in both crystalline and noncrystalline materials is suggested to be a Jahn-Teller mechanism involving two states close to EF which have orbital character similar to dx2- y2 (near EF- kBT/2) and dz2- r2 (near EF + kBT/2) levels. The ground state of the system is then characterized by an oblate spheroidal d-charge distribution and the ɛ phase (basal plane expansion, λ<0) is stable in the crystal and a similar local order is assumed to obtain in the glass. Increasing temperature (or shifting EF relative to these nearly degenerate levels by alloying) will tend to equalize their populations and drive the system to the higher-symmetry local order seen in the crystal as the γ phase.

  19. Effect of wollastonite ceramics and bioactive glass on the formation of a bonelike apatite layer on a cobalt base alloy.

    PubMed

    Cortés, D A; Medina, A; Escobedo, J C; Escobedo, S; López, M A

    2004-08-01

    A biomimetic method was used to promote a bioactive surface on a cobalt base alloy (ASTM F-75). The metallic substrates were alkali treated and some of the samples were subsequently heat treated. The treated samples were immersed in simulated body fluid (SBF) on granular particles of either bioactive glass or wollastonite. For comparative purposes, no bioactive system was used in some tests. Three different methods were used for the immersion of the samples in SBF: 1) 21 days in SBF, 2) 21 days in 1.5 SBF, and 3) 7 days in SBF followed by 14 days in 1.5 SBF (re-immersion method). A bonelike apatite layer was formed on all the samples placed on wollastonite and bioactive glass particles. The morphology of the apatite layer formed by using the re-immersion method and wollastonite closely resembled the existing bioactive systems. No apatite layer was observed on the samples treated without bioactive material and soaked for 21 days in SBF or 1.5 SBF, apart from the substrates treated by using the re-immersion method. The heat treatment delayed the apatite formation in all the cases studied.

  20. Effect of geometrical constraint condition on the formation of nanoscale twins in the Ni-based metallic glass composite

    SciTech Connect

    Lee, M H; Kim, B S; Kim, D H; Ott, R T; Sansoz, F; Eckert, J

    2014-04-25

    We investigated the effect of geometrically constrained stress-strain conditions on the formation of nanotwins in alpha-brass phase reinforced Ni59Zr20Ti16Si2Sn3 metallic glass (MG) matrix deformed under macroscopic uniaxial compression. The specific geometrically constrained conditions in the samples lead to a deviation from a simple uniaxial state to a multi-axial stress state, for which nanocrystallization in the MG matrix together with nanoscale twinning of the brass reinforcement is observed in localized regions during plastic flow. The nanocrystals in the MG matrix and the appearance of the twinned structure in the reinforcements indicate that the strain energy is highly confined and the local stress reaches a very high level upon yielding. Both the effective distribution of reinforcements on the strain enhancement of composite and the effects of the complicated stress states on the development of nanotwins in the second-phase brass particles are discussed.

  1. Effect of geometrical constraint condition on the formation of nanoscale twins in the Ni-based metallic glass composite

    NASA Astrophysics Data System (ADS)

    Lee, M. H.; Kim, B. S.; Kim, D. H.; Ott, R. T.; Sansoz, F.; Eckert, J.

    2014-06-01

    We investigated the effect of geometrically constrained stress-strain conditions on the formation of nanotwins in α-brass phase reinforced Ni59Zr20Ti16Si2Sn3 metallic glass (MG) matrix deformed under macroscopic uniaxial compression. The specific geometrically constrained conditions in the samples lead to a deviation from a simple uniaxial state to a multi-axial stress state, for which nanocrystallization in the MG matrix together with nanoscale twinning of the brass reinforcement is observed in localized regions during plastic flow. The nanocrystals in the MG matrix and the appearance of the twinned structure in the reinforcements indicate that the strain energy is highly confined and the local stress reaches a very high level upon yielding. Both the effective distribution of reinforcements on the strain enhancement of composite and the effects of the complicated stress states on the development of nanotwins in the second-phase brass particles are discussed.

  2. Cluster formation in Ag{sub 2}O-P{sub 2}O{sub 5}-CdCl{sub 2} glass system

    SciTech Connect

    Das, S.S.; Singh, N.B.

    2008-11-03

    Ag{sub 2}O-P{sub 2}O{sub 5} and Ag{sub 2}O-P{sub 2}O{sub 5}-20 wt% CdCl{sub 2} glasses were prepared by melt quenching method and characterized with the help of several experimental techniques. Powder X-ray diffraction study indicated that the glasses are amorphous in nature. DSC studies showed that CdCl{sub 2} doped glass is chemically more durable. Electrical conductivity and ionic transference number measurements have shown that both the glasses are ionic conductors with Ag{sup +} ions as the charge carriers. The electrical conductivity of the doped glass is found to be higher than the undoped one. Structures of the glasses have been proposed on the basis of IR spectral analysis. From SEM studies it has been inferred that addition of 20 wt% CdCl{sub 2} modifies the morphology of Ag{sub 2}O-P{sub 2}O{sub 5} glass and in its presence formation of clusters composed of nanofibers occur.

  3. The evaluation of Candida albicans biofilms formation on silicone catheter, PVC and glass coated with titanium dioxide nanoparticles by XTT method and ATPase assay.

    PubMed

    Haghighi, F; Mohammadi, Sh R; Mohammadi, P; Eskandari, M; Hosseinkhani, S

    2012-01-01

    Lots of Candida albicans infections involve in biofilm formation on medical devices. This kind of biofilm can impede antifungal therapy and complicates the treatment of infectious diseases particularly in field of chronic diseases associated with implanted devices. This study has investigated the influence of treating silicone catheter, PVC and glass coated with Titanium dioxide (TiO2) nanoparticles on attachment of C. albicans. In this study TiO2 nanoparticles were synthesized from precursor TiCl4 and characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) which showed TiO2 nanoparticles are 70-100 nm in size. In the simplest model of biofilms formation, C. albicans isolates (ATCC10231) and (ATCC 76615) were grown on the surface of small disks of catheter, PVC and glass in a flat-bottomed 12-well plates and evaluated biofilm formation using ATP bioluminescence and tetrazolium salt (XTT) reduction assays. In addition, morphology of C. albicans biofilms after 48 h incubation was observed by SEM. Results indicated that there is a statistical difference between mean of coated samples especially catheter and glass before and after TiO2 nanoparticles coating (p<0.05). In SEM analysis, C. albicans biofilm was more aggregated on the surface of glass and catheter than PVC and control groups and after treatment by these nanoparticles, catheter and glass both showed most significant decrease of C. albicans attachment in comparison to the control groups (Fig. 4, Ref. 23). PMID:23173628

  4. The evaluation of Candida albicans biofilms formation on silicone catheter, PVC and glass coated with titanium dioxide nanoparticles by XTT method and ATPase assay.

    PubMed

    Haghighi, F; Mohammadi, Sh R; Mohammadi, P; Eskandari, M; Hosseinkhani, S

    2012-01-01

    Lots of Candida albicans infections involve in biofilm formation on medical devices. This kind of biofilm can impede antifungal therapy and complicates the treatment of infectious diseases particularly in field of chronic diseases associated with implanted devices. This study has investigated the influence of treating silicone catheter, PVC and glass coated with Titanium dioxide (TiO2) nanoparticles on attachment of C. albicans. In this study TiO2 nanoparticles were synthesized from precursor TiCl4 and characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) which showed TiO2 nanoparticles are 70-100 nm in size. In the simplest model of biofilms formation, C. albicans isolates (ATCC10231) and (ATCC 76615) were grown on the surface of small disks of catheter, PVC and glass in a flat-bottomed 12-well plates and evaluated biofilm formation using ATP bioluminescence and tetrazolium salt (XTT) reduction assays. In addition, morphology of C. albicans biofilms after 48 h incubation was observed by SEM. Results indicated that there is a statistical difference between mean of coated samples especially catheter and glass before and after TiO2 nanoparticles coating (p<0.05). In SEM analysis, C. albicans biofilm was more aggregated on the surface of glass and catheter than PVC and control groups and after treatment by these nanoparticles, catheter and glass both showed most significant decrease of C. albicans attachment in comparison to the control groups (Fig. 4, Ref. 23).

  5. Glass Formation and Primary Solidification in Nd2Fe14B with TiC Additions

    NASA Astrophysics Data System (ADS)

    McCallum, R. W.; Willard, M. A.; Dennis, K. W.; Kramer, M. J.; Branagan, D. J.

    1996-03-01

    In bulk permanent magnets, the extrinsic properties relating to the microstructure determine the level of hard magnetic properties that is actually achieved. Alloy additions which affect the solidification behavior of the melt and then form precipitates which pin grain boundaries and therefor control grain size should be valuable in producing the uniform microstructure required for good magnetic properties. The addition of TiC to 2-14-1 results in a factor of three reduction of the quench rate required to produce amorphous material. In addition, the crystallization temperature of the glass is enhanced leading to enhanced nucleation and finer grain size during crystallization. Given the affect of TiC additions to the stochiometric melt, it is not surprising that the additions affect the range of primary solidification of the 2-14-1 phase. When TiC is added to the limit of liquid solubility, the limit 2-14-1 primary solidification is move farther from the stochiometric composition in the Nd rich region. Work at the Ames Laboratory, was supported by the U. S. Department of Energy under contract No. W-7405-ENG-82.

  6. Sulfamic Acid-Catalyzed Lead Perovskite Formation for Solar Cell Fabrication on Glass or Plastic Substrates.

    PubMed

    Guo, Yunlong; Sato, Wataru; Shoyama, Kazutaka; Nakamura, Eiichi

    2016-04-27

    Lead perovskite materials such as methylammonium triiodoplumbate(II) (CH3NH3PbI3, PV) are promising materials for printable solar cell (SC) applications. The preparation of PV involves a series of energetically costly cleavages of the μ-iodo bridges via conversion of a mixture of PbI2 (PI) and methylammonium iodide (CH3NH3I, MAI) in N,N-dimethylformamide (DMF) into a precursor solution containing a polymeric strip of a plumbate(II) dimer [(MA(+))2(PbI3(-))2·(DMF)2]m, which then produces a perovskite film with loss of DMF upon spin-coating and heating of the substrate. We report here that the PI-to-PV conversion and the PV crystal growth to micrometer size can be accelerated by a small amount of zwitterionic sulfamic acid (NH3SO3, SA) and that sulfamic acid facilitates electron transfer to a neighboring electron-accepting layer in an SC device. As a result, an SC device on indium tin oxide (ITO)/glass made of a 320 nm thick PV film using 0.7 wt % SA showed a higher short-circuit current, open-circuit voltage, and fill factor and hence a 22.5% higher power conversion efficiency of 16.02% compared with the device made without SA. The power conversion efficiency value was reproducible (±0.3% for 25 devices), and the device showed very small hysteresis. The device without any encapsulation showed a respectable longevity on a shelf under nitrogen under ambient light. A flexible device similarly fabricated on ITO/poly(ethylene naphthalate) showed an efficiency of 12.4%. PMID:27054265

  7. Relations among nonbridging oxygen, optical properties, optical basicity, and color center formation in CaO-MgO aluminosilicate glasses

    SciTech Connect

    Novatski, A.; Steimacher, A.; Medina, A. N.; Bento, A. C.; Baesso, M. L.; Andrade, L. H. C.; Lima, S. M.; Guyot, Y.; Boulon, G.

    2008-11-01

    In this study the relations among nonbridging oxygen (NBO), optical properties, optical basicity, and color center formation in CaO-MgO aluminosilicate glasses were studied. Samples containing (in mol %) 35.9-57.5 of CaO, 16-27.7 of Al{sub 2}O{sub 3}, 7.9-41.6 of SiO{sub 2}, and 6.5-6.9 of MgO were measured by optical absorption and excitation, luminescence, and Raman spectroscopy. The results showed that when the SiO{sub 2} content was increased, the absorption edge shifted toward lower wavelengths and the bonds between O{sup 2-} ions and cations became more covalent. These observations were confirmed by Raman results that showed a decrease in the number of NBO per silicon tetrahedron as a function of SiO{sub 2} content. The results indicate that the effects of higher NBO concentration are the narrowing of the band gap energy and the delocalization of O{sup 2-} electrons, which facilitates the O{sup 2-} electrons to be trapped by anion vacancies and, consequently, forming color centers. The relationship between color center formation and SiO{sub 2} content was confirmed by optical spectroscopic measurements under UV radiation.

  8. Effects of surface reaction-type pre-reacted glass ionomer on oral biofilm formation of Streptococcus gordonii.

    PubMed

    Shimazu, Kisaki; Oguchi, Riyo; Takahashi, Yukihiro; Konishi, Kiyoshi; Karibe, Hiroyuki

    2016-09-01

    Streptococcus gordonii, a bacterium involved in the initial colonization of tooth surfaces, contributes to dental biofilm formation and is an important cause of infective endocarditis. This study aimed to investigate the influence of surface reaction-type pre-reacted glass ionomer (S-PRG) filler on oral bacterial growth and aggregation of S. gordonii. The effect of various concentrations of S-PRG eluate on the growth and the biofilm formation of S. gordonii and other oral microorganisms (Streptococcus mutans, Streptococcus oralis, Lactobacillus acidophilus, and Candida albicans) was assessed. In addition, the effect of S-PRG eluate on coaggregation of S. gordonii with both S. oralis and Fusobacterium nucleatum was assessed. The effect of S-PRG eluate treatment on autoaggregation of S. gordonii was also evaluated. Our results indicate that S-PRG eluate treatment reduced both for the growth and for biofilm of all organisms in a dose-dependent manner. Coaggregation of S. gordonii with both S. oralis and F. nucleatum was inhibited by S-PRG eluate, whereas autoaggregation of S. gordonii increased at certain concentrations of S-PRG eluate. These results indicate that the S-PRG filler possesses antimicrobial activity that is mediated by inhibiting growth and biofilm of oral microorganisms, and by suppressing coaggregation of S. gordonii. In addition, these findings indicate that coaggregation of S. gordonii with other bacteria is inhibited by increased autoaggregation of S. gordonii. PMID:26319990

  9. Myotube Formation on Micro-patterned Glass: Intracellular Organization and Protein Distribution in C2C12 Skeletal Muscle Cells

    PubMed Central

    Yamamoto, Daniel L.; Csikasz, Robert I.; Li, Yu; Sharma, Gunjana; Hjort, Klas; Karlsson, Roger; Bengtsson, Tore

    2008-01-01

    Proliferation and fusion of myoblasts are needed for the generation and repair of multinucleated skeletal muscle fibers in vivo. Studies of myocyte differentiation, cell fusion, and muscle repair are limited by an appropriate in vitro muscle cell culture system. We developed a novel cell culture technique [two-dimensional muscle syncytia (2DMS) technique] that results in formation of myotubes, organized in parallel much like the arrangement in muscle tissue. This technique is based on UV lithography–produced micro-patterned glass on which conventionally cultured C2C12 myoblasts proliferate, align, and fuse to neatly arranged contractile myotubes in parallel arrays. Combining this technique with fluorescent microscopy, we observed alignment of actin filament bundles and a perinuclear distribution of glucose transporter 4 after myotube formation. Newly formed myotubes contained adjacently located MyoD-positive and MyoD-negative nuclei, suggesting fusion of MyoD-positive and MyoD-negative cells. In comparison, the closely related myogenic factor Myf5 did not exhibit this pattern of distribution. Furthermore, cytoplasmic patches of MyoD colocalized with bundles of filamentous actin near myotube nuclei. At later stages of differentiation, all nuclei in the myotubes were MyoD negative. The 2DMS system is thus a useful tool for studies on muscle alignment, differentiation, fusion, and subcellular protein localization. (J Histochem Cytochem 56:881–892, 2008) PMID:18574252

  10. Thermodynamic prediction of glass formation tendency, cluster-in-jellium model for metallic glasses, ab initio tight-binding calculations, and new density functional theory development for systems with strong electron correlation

    SciTech Connect

    Yao, Yongxin

    2009-01-01

    Solidification of liquid is a very rich and complicated field, although there is always a famous homogeneous nucleation theory in a standard physics or materials science text book. Depending on the material and processing condition, liquid may solidify to single crystalline, polycrystalline with different texture, quasi-crystalline, amorphous solid or glass (Glass is a kind of amorphous solid in general, which has short-range and medium-range order). Traditional oxide glass may easily be formed since the covalent directional bonded network is apt to be disturbed. In other words, the energy landcape of the oxide glass is so complicated that system need extremely long time to explore the whole configuration space. On the other hand, metallic liquid usually crystalize upon cooling because of the metallic bonding nature. However, Klement et.al., (1960) reported that Au-Si liquid underwent an amorphous or “glassy” phase transformation with rapid quenching. In recent two decades, bulk metallic glasses have also been found in several multicomponent alloys[Inoue et al., (2002)]. Both thermodynamic factors (e.g., free energy of various competitive phase, interfacial free energy, free energy of local clusters, etc.) and kinetic factors (e.g., long range mass transport, local atomic position rearrangement, etc.) play important roles in the metallic glass formation process. Metallic glass is fundamentally different from nanocrystalline alloys. Metallic glasses have to undergo a nucleation process upon heating in order to crystallize. Thus the short-range and medium-range order of metallic glasses have to be completely different from crystal. Hence a method to calculate the energetics of different local clusters in the undercooled liquid or glasses become important to set up a statistic model to describe metalllic glass formation. Scattering techniques like x-ray and neutron have widely been used to study the structues of metallic glasses. Meanwhile, computer simulation

  11. A formation mechanism for concentric ridges in ejecta surrounding impact craters in a layer of fine glass beads

    NASA Astrophysics Data System (ADS)

    Suzuki, Ayako I.; Nakamura, Akiko M.; Kadono, Toshihiko; Wada, Koji; Yamamoto, Satoru; Arakawa, Masahiko

    2013-07-01

    Ejecta patterns are experimentally examined around craters formed in a layer of glass beads by vertical impacts at low velocities. The diameters of the constituent glass beads of three different targets range 53-63 μm, 90-106 μm, and 355-500 μm. The impact velocities and ambient pressures range from a few to 240 m s-1 and from 500 Pa to the atmospheric pressure, respectively. Various ejecta patterns are observed around craters and are classified into two major classes based on whether they have concentric ridges or not. We propose a possible formation model for the ridges in which the wake created by a projectile as it passes through the atmosphere causes the crater rim to collapse: The model can explain the observation that the degree of collapse of the resultant crater rim depends on the impact velocity and ambient pressure. Using the ratio between the hydrodynamic drag of the airflow induced by the wake and the gravitational force of the degraded part of the rim, we calculate the critical conditions of the impact velocity and ambient pressure necessary for the wake to erode the rim. The conditions turn out to be roughly consistent with the boundary between the two morphological classes. As a result, it is possible that the projectile wake triggers the collapse of the crater rim, leading to a ground-hugging flow that settles to form the distal ridge observed in this study. This mechanism may play a role in producing ejecta morphologies on planetary bodies with atmosphere.

  12. The role of superheating in the formation of Glass Mountain obsidians (Long Valley, CA) inferred through crystallization of sanidine

    NASA Astrophysics Data System (ADS)

    Waters, Laura E.; Andrews, Benjamin J.

    2016-10-01

    The Glass Mountain obsidians (Long Valley, CA) are crystal poor (<8 vol%) and highly evolved (high SiO2, low Sr), and therefore, their formation required extremely efficient separation of melts from a crystal-rich source. A petrologic and experimental investigation of the mineral phases in Glass Mountain lavas identifies conditions under which phenocrysts grew and the driving mechanism for crystallization, which places constraints on the possible processes that generated the obsidians. The obsidian in this study (GM-11) is saturated in nine phases (sanidine + quartz + plagioclase + titanomagnetite + ilmenite + zircon + apatite + allanite + biotite), and results of high-resolution SEM compositional mapping and electron microprobe analysis reveal that individual sanidine crystals are normally zoned and span a range of compositions (Or40-78). Sanidines have a "granophyric" texture, characterized by intergrowths of quartz and sanidine. Mineral phases in the natural sample are compared to H2O-saturated phase equilibrium experiments conducted in cold-seal pressure vessels, over a range of conditions (700-850 °C; 75-225 MPa), and all are found to be plausible phenocrysts. Comparison of sanidine compositions from the natural sample with those grown in phase equilibrium experiments demonstrates that sanidine in the natural sample occurs in a reduced abundance. Further comparison with phase equilibrium experiments suggests that sanidine compositions track progressive loss of dissolved melt water (±cooling), suggesting that crystallization in the natural obsidian was driven predominantly by degassing resulting from decompression. It is paradoxical that an effusively (slowly) erupted lava should contain multiple phenocryst phases, including sanidine crystals that span a range of compositions with granophyric textures, and yet remain so crystal poor. To resolve this paradox, it is necessary that the solidification mechanism (degassing or cooling) that produced the sanidine

  13. “Breaking news” on the formation of volcanic ash: Fracture dynamics in silicate glass

    NASA Astrophysics Data System (ADS)

    Dürig, Tobias; Zimanowski, Bernd

    2012-06-01

    In explosive volcanic eruptions magmatic melts behave like brittle solids under rapid loading: volcanic ash particles predominantly are generated by brittle fragmentation, induced within pre-stressed magma in volcanic conduits. Here we present straightforward measurements of fracture area velocity, i.e., surface generation rates in analog materials under "volcanic" time— and deformation rates, using a high resolution high-speed camera at up to 2.5 million frames per second. Surface generation rates are directly linked to energy dissipation and can be related to pyroclast formation during explosive volcanism. According to our findings, pre-existing stress fields play a crucial role for the evolution of cracks, control the dynamics of fracture area growths during fragmentation, and thus strongly modify the production of volcanic ash.

  14. Properties of glass, oil's formation...how to explain it? The secret is to amaze!

    NASA Astrophysics Data System (ADS)

    Merlino, Silvia; Evangelista, Rosaria; Bianucci, Marco; Mantovani, Carlo; Gambarelli, Licia

    2013-04-01

    The design and testing of numerous routes for teaching and dissemination of topics in physics, biology, geology and energy is born from a collaboration between teachers and researchers that lasted for many years in Parma, Italy. These projects are implemented by the association "Parma Casa della Scienza", which promotes the dissemination of scientific culture in schools and among the public. The main purpose of the association is to create a science center in Parma, offering also training opportunities on techniques for teaching science. The funds for the projects come from European competitions and Cariparma Foundation. Currently the association is proposing laboratory activities, with the widespread diffusion of 20 educational programs, included in school curricula. The approach is informal and aims at the stimulation of curiosity and surprise. Students who participate arise so spontaneously in an attitude of research - action, working directly on the phenomena under study. This avoids the clichés of standard passive listening. Our work is a constant search for ideas, ways and means to demonstrate, for the purposes of school education, how useful is the game and the interaction with the phenomena, many of which are usually only seen in books and not lived with awareness. Two in particular are the educational proposals that we would like to present , relating to content of great importance that are rarely addressed in the context of schooling completed First Path: explains the physico-chemical properties and structural properties of glassy materials; enters the details of the molecular structure of "amorphous solid" contrasting it with that of crystalline solid; llustrates the process of formation; gives reason for its peculiar properties from which derive extreme flexibility of working and the many optical properties. This is achieved through the actual processing of a fluid "pseudo glassy" realized at low temperatures, which simulates the processes described

  15. Mechanism of Phase Formation in the Batch Mixtures for Slag-Bearing Glass Ceramics - 12207

    SciTech Connect

    Stefanovsky, Sergey V.; Stefanovsky, Olga I.; Malinina, Galina A.

    2012-07-01

    Slag surrogate was produced from chemicals by heating to 900 deg. C and keeping at this temperature for 1 hr. The product obtained was intermixed with either sodium di-silicate (75 wt.% waste loading) or borax (85 wt.% slag loading). The mixtures were heat-treated within a temperature range of 25 to 1300 deg. C. The products were examined by X-ray diffraction and infrared spectroscopy. The products prepared at temperatures of up to 1000 deg. C contained both phase typical of the source slag and intermediate phases as well as phases typical of the materials melted at 1350 deg. C such as nepheline, britholite, magnetite and matrix vitreous phase. Vitrification process in batch mixtures consisting of slag surrogate and either sodium di-silicate or sodium tetraborate runs through formation of intermediate phases mainly silico-phosphates capable to incorporate Sm as trivalent actinides surrogate. Reactions in the batch mixtures are in the whole completed by ∼1000 deg. C but higher temperatures are required to homogenize the products. If in the borate-based system the mechanism is close to simple dissolution of slag constituents in the low viscous borate melt, then in the silicate-based system the mechanism was found to be much complicated and includes re-crystallization during melting with segregation of newly-formed nepheline type phase. (authors)

  16. Oxidation of Al-containing austenitic stainless steels as related to the formation of strong glass-ceramic to metal seals

    SciTech Connect

    Moddeman, W.E.; Birkbeck, J.C.; Bowling, W.C.; Burke, A.R.; Cassidy, R.T.

    1996-08-01

    In glass-ceramic to metal seals used in pyrotechnic actuators and ignitors, Ni-based alloys and Al-containing austenitic stainless steels are used. Metal attack by the glass is severe if Ni based alloys are used, less so for the Al-containing alloys. In this paper, lithia-alumina-silica glass-ceramic was sealed to Al-containing alloys that were first oxidized prior to sealing (preoxidation). Results show that this preoxidation substantially reduces the probability of glass/metal reactions during seal formation, thus improving the overall quality of the interface without loss of seal bond strength. Mechanism of surface oxide formation of these Al- containing steels is discussed. Auger data show the composition of the resulting oxides to be a function of oxidation temperature. There are two theories on the oxidation mechanism: (1) oxidation occurring at the air/oxide interface (Abderrazik et al, 1987), and (2) oxidation taking place at the oxide/metal interface (Hindam and Smeltzer, 1980). To test the theories, oxidation of the Al-containing alloys was carried out, first in pure oxygen-16, and then followed by pure oxygen-18. SIMS showed no layered structure, but did show a mixture of oxides. Thus, the oxidation mechanism is not simple and must be allowing oxygen to have access at all stages of the oxidation process.

  17. Large low-symmetry polarons of the high-Tc, copper oxides: Formation, mobility and ordering

    NASA Astrophysics Data System (ADS)

    Bersuker, Gennadi I.; Goodenough, John B.

    1997-02-01

    A microscopic model of the evolution from antiferromagnetic insulator to superconductor on oxidation of the parent-phase (CuO 2) 2- sheets of a cuprate superconductor starts with the assumption that strong electron-lattice interactions are dominant and give a heterogeneous electronic distribution. Introduction of pseudo-Jahn-Teller vibronic coupling associated with the δ holes in the (CuO 2) (2-δ) - sheets is shown to stabilize, below a critical temperature Tp ≈ 850 K, large non-adiabatic polarons containing 5 to 7 copper centers; cooperative low-symmetry in-plane vibrations also stabilize an elastic attractive force between polarons that can overcome the longer-range Coulomb repulsion between polarons. Utilizing established parameters for isolated CuO 6 complexes gives a calculated polaron size of 5 to 7 copper centers, which compares with a measured mean size of 5.3 copper centers in underdoped samples 0 < δ ≤ 0.10. A large polaron is shown to move by a piece-wise tunneling of a fraction of itself across a peripheral CuO vibronic bond rather than by an activated hopping. This type of motion, which is not described by conventional transport theories, gives a linear increase of the resistivity with temperature above a temperature Tϱ due to scattering of the polaron at its own border, which separates regions inside and outside the polaron of slightly different mean CuO bond length. At lower temperatures, the polaron mobility becomes activated, but at higher concentrations this change is obscured because the elastic interpolaron attractive force causes the polarons to condense into a “polaron liquid,” and below some critical temperature Td ≥ Tc the polarons undergo long-range ordering into one-dimensional <110> polaronic stripes separated by stripes of the parent phase, which support antiferromagnetic spin fluctuations. The zig-zag polaron stripes consist of polaron pairs oriented alternately along [100] and [010] axes of a CuO 2 sheet. Formation

  18. Innovative approach to the design of low-cost Zr-based BMG composites with good glass formation

    NASA Astrophysics Data System (ADS)

    Cheng, Jia-Lin; Chen, Guang; Liu, Chain-Tsuan; Li, Yi

    2013-06-01

    The high manufacturing cost for metallic glasses hampers actual commercial applications of this class of fascinating materials. In this letter, the effect of oxygen impurity on the glass forming ability and tensile properties of Zr-BMG composites were studied. Our results have demonstrated that oxygen was absorbed and concentrated only in the precipitated β-Zr phase, leading that the remainder molten metal retains good glass forming ability. The high oxygen concentration in the β-Zr phase induces a significant solid-solution strengthening effect, this resulting in an enhanced strength of the BMG composites without sacrificing their overall ductility. Based on this alloying strategy, we have successfully developed the low-cost Zr-based BMG composites with excellent tensile properties and good glass forming ability, using the low grade industrial raw materials processed under industrial vacuum systems. This finding is expected to greatly cut down the manufacturing cost and greatly promote the commercial applications of the BMG composites.

  19. Formation and atomic configuration of binary metallic glasses studied by ion beam mixing and molecular dynamics simulation

    SciTech Connect

    Tai, K. P.; Gao, N.; Dai, X. D.; Li, J. H.; Liu, B. X.

    2007-06-15

    Metallic glasses are obtained in an immiscible Ag-Nb system with overall composition ranging from 25 to 90 at. % of Nb by ion beam mixing. Interestingly, the diffraction analysis shows that the formed Nb-rich metallic glass features are two distinct atomic configurations. In atomistic modeling, an n-body Ag-Nb potential is derived, under the assistance of ab initio calculation, and then applied in molecular dynamics simulations. An atomic configuration is discovered, i.e., an icositetrahedral ordering, and as well as an icosahedral ordering observed in the Ag-Nb metallic glasses and in some previously reported systems. Simulations confirm that the two dominate local atomic packing units are formed through a structural phase transition from the Nb-based bcc and fcc solid solutions, respectively, suggesting a concept of structural heredity that the crystalline structure of the constituent metals play a decisive role in determining the atomic structure of the resultant metallic glasses.

  20. Characterization of Free Volume Changes Associated with Shear Band Formation in Zr- and Cu-Based Bulk Metallic Glasses

    SciTech Connect

    Flores, K M; Glade, S C; Asoka-Kumar, P; Kanungo, B

    2003-11-14

    The free volume model for flow in metallic glasses predicts a significant increase in free volume at the onset of plastic deformation. The details of these structural changes are unclear, however, particularly during strain localization in shear bands. In this study, the free volume changes associated with inhomogeneous plastic deformation of a Cu-based bulk metallic glass were examined using positron annihilation spectroscopy (PAS). PAS results indicated that there was a distribution of free volume site sizes in both the as-quenched and rolled glasses, and that the concentration of larger sites increased with deformation. Differential scanning calorimetry (DSC) was also used to observe the glass transition behaviors of Cu- and Zr-based glasses after rolling and annealing. Annealing resulted in an increase in the height of the endothermic glass transition peak, consistent with structural relaxation relative to the as-quenched material. Deformation resulted in both a lower endothermic peak height and an earlier and deeper exothermic peak associated with structural relaxation, indicating a more disordered structure with more free volume.

  1. Analysis of the effects of microalloying on glass formation in aluminum-yttrium-iron alloys by fluctuation electron microscopy and other techniques

    NASA Astrophysics Data System (ADS)

    Bondi, Karyn Spence

    Metallic glasses offer enhanced properties in processing and wear over their crystalline counterparts. Aluminum-based metallic glasses are further desired for their high strength-to-weight ratio and low cost. It has been observed that additions of very small amounts of additional elements to the base aluminum-based alloys can dramatically improve glass formability. Here, the effects of microalloying on glass formation and stability are systematically investigated by substituting 0.5 atomic percent of all 3-d transition metals for Al in Al88Y7Fe5 alloys. X-ray diffraction, differential scanning calorimetry, differential thermal analysis, and transmission electron microscopy studies demonstrate enhanced glassy characteristics and stability in the microalloys. Further collaborative investigations using high-energy synchrotron X-ray diffraction, extended X-ray absorption fine structure analysis, and atom probe tomography reveal enhanced short- and medium-range order as well as a suppression of phase separation upon microalloying. A novel investigation method, fluctuation electron microscopy, was employed to quantify the extent of medium range order in the alloys by statistical analysis of microdiffraction patterns. Significant enhancements were made to the methodological protocol for this new technique, allowing for greatly enhanced experimental reproducibility.

  2. Nepheline Formation Potential in Sludge Batch 4 (SB4) and Its Impact on Durability: Selecting Glasses for a Phase 2 Study

    SciTech Connect

    Peeler, D

    2005-08-15

    The likelihood for the formation of nepheline in Sludge Batch 4 (SB4) glass systems and the potential impact of nepheline on the durability of these systems is part of the frit development efforts for SB4. The effect of crystallization on glass durability is complex and depends on several interrelated factors including the change in residual glass composition, the formation of internal stress or microcracks, and the preferential attack at the glass-crystal interface. Perhaps one of the most significant effects is the type and extent (or fraction) of crystallization and the change to the residual glass composition. A strong increase in glass dissolution (or decrease in durability) has been observed in previous studies in glasses that formed aluminum-containing crystals, such as NaAlSiO{sub 4} (nepheline) and LiAlSi{sub 2}O{sub 6}, and crystalline SiO{sub 2}. Although it is well known that the addition of Al{sub 2}O{sub 3} to borosilicate glasses enhances the durability of the waste form (through creation of network-forming tetrahedral Na{sup +}-[AlO{sub 4/2}]{sup -} pairs), the combination of high Al{sub 2}O{sub 3} and Na{sub 2}O can lead to the formation of nepheline (NaAlSiO{sub 4}). Given the projected high concentration of Al{sub 2}O{sub 3} in SB4 and the potential use of a high Na{sub 2}O based frit to improve melt rate and a high Na{sub 2}O sludge due to settling problems, the potential formation of nepheline in various SB4 systems continues to be assessed. The most recent compositional projections from the Closure Business Unit (CBU) for SB4 may be framed around three decision areas: the sodium molarity of the sludge (at values of 1M Na and 1.6M Na), the SB3 heel that will be included in the batch (expressed in inches of SB3 sludge with values of 0, 40, and 127''), and the introduction of an ARP stream into the sludge (which is represented by six options: no ARP, ARPa, ARPe, ARPk, ARPm, and ARPv). Candidate frits are being identified for these options via a

  3. Hydrothermal Alteration of Glass from Underground Nuclear Tests: Formation and Transport of Pu-clay Colloids at the Nevada National Security Site

    SciTech Connect

    Zavarin, M.; Zhao, P.; Joseph, C.; Begg, J.; Boggs, M.; Dai, Z.; Kersting, A. B.

    2015-05-27

    The testing of nuclear weapons at the Nevada National Security Site (NNSS), formerly the Nevada Test Site (NTS), has led to the deposition of substantial quantities of plutonium into the environment. Approximately 2.8 metric tons (3.1×104 TBq) of Pu were deposited in the NNSS subsurface as a result of underground nuclear testing. While 3H is the most abundant anthropogenic radionuclide deposited in the NNSS subsurface (4.7×106 TBq), plutonium is the most abundant from a molar standpoint. The only radioactive elements in greater molar abundance are the naturally occurring K, Th, and U isotopes. 239Pu and 240Pu represent the majority of alpha-emitting Pu isotopes. The extreme temperatures associated with underground nuclear tests and the refractory nature of Pu results in most of the Pu (98%) being sequestered in melted rock, referred to as nuclear melt glass (Iaea, 1998). As a result, Pu release to groundwater is controlled, in large part, by the leaching (or dissolution) of nuclear melt glass over time. The factors affecting glass dissolution rates have been studied extensively. The dissolution of Pu-containing borosilicate nuclear waste glasses at 90ºC has been shown to lead to the formation of dioctahedral smectite colloids. Colloid-facilitated transport of Pu at the NNSS has been observed. Recent groundwater samples collected from a number of contaminated wells have yielded a wide range of Pu concentrations from 0.00022 to 2.0 Bq/L. While Pu concentrations tend to fall below the Maximum Contaminant Level (MCL) established by the Environmental Protection Agency (EPA) for drinking water (0.56 Bq/L), we do not yet understand what factors limit the Pu concentration or its transport behavior. To quantify the upper limit of Pu concentrations produced as a result of melt glass dissolution and determine the nature of colloids and Pu associations, we performed a 3 year nuclear melt glass dissolution experiment

  4. Effects of soda-lime-silica waste glass on mullite formation kinetics and micro-structures development in vitreous ceramics.

    PubMed

    Marinoni, Nicoletta; D'Alessio, Daniela; Diella, Valeria; Pavese, Alessandro; Francescon, Ferdinando

    2013-07-30

    The effects of soda-lime waste glass, from the recovery of bottle glass cullet, in partial replacement of Na-feldspar for sanitary-ware ceramic production are discussed. Attention is paid to the mullite growth kinetics and to the macroscopic properties of the final output, the latter ones depending on the developed micro-structures and vitrification grade. Measurements have been performed by in situ high temperature X-ray powder diffraction, scanning electron microscopy, thermal dilatometry, water absorption and mechanical testing. Glass substituting feldspar from 30 to 50 wt% allows one (i) to accelerate the mullite growth reaction kinetics, and (ii) to achieve macroscopic features of the ceramic output that comply with the latest technical requirements. The introduction of waste glass leads to (i) a general saving of fuel and reduction of the CO2-emissions during the firing stage, (ii) a preservation of mineral resources in terms of feldspars, and (iii) an efficient management of the bottle glass refuse by readdressing a part of it in the sanitary-ware manufacturing.

  5. Development of glass-ceramic scaffolds for bone tissue engineering: characterisation, proliferation of human osteoblasts and nodule formation.

    PubMed

    Vitale-Brovarone, C; Verné, E; Robiglio, L; Appendino, P; Bassi, F; Martinasso, G; Muzio, G; Canuto, R

    2007-03-01

    Glass-ceramic macroporous scaffolds for tissue engineering have been developed using a polyurethane sponge template and bioactive glass powders. The starting glass (CEL2) belongs to the system SiO(2)-P(2)O(5)-CaO-MgO-Na(2)O-K(2)O and has been synthesised by a conventional melting-quenching route. A slurry of CEL2 powder, polyvinyl alcohol and water has been prepared in order to coat, by impregnation, the polymeric template. An optimised thermal treatment was then use to remove the sponge and to sinter the glass powders, leading to a glass-ceramic replica of the template. Morphological observations, image analyses, mechanical tests and in vitro tests showed that the obtained devices are good candidates as scaffolds for bone-tissue engineering, in terms of pore-size distribution, pore interconnection, surface roughness, and both bioactivity and biocompatibility. In particular, a human osteoblast cell line (MG-63) seeded onto the scaffold after a standardised preconditioning route in simulated body fluid showed a high degree of cell proliferation and a good ability to produce calcium nodules. The obtained results were enhanced by the addition of bone morphogenetic proteins after cell seeding.

  6. Containerless synthesis of interesting glasses

    NASA Technical Reports Server (NTRS)

    Weinberg, Michael C.

    1990-01-01

    One aspect of containerless glass experimentation was thoroughly examined: glass forming ability. It is argued that although containerless processing will abet glass formation, other ground-based methods can do the job better. However, these methods have limitations, such as sample dimensions and concomitant ability to make property measurements. Most importantly, perhaps, is the observation that glass properties are a function of preparation procedure. Thus, it seems as though there still is an argument for use of containerless processing for glass forming.

  7. Atomic-scale models of early-stage alkali depletion and SiO2-rich gel formation in bioactive glasses.

    PubMed

    Tilocca, Antonio

    2015-01-28

    Molecular dynamics simulations of Na(+)/H(+)-exchanged 45S5 Bioglass® models reveal that a large fraction of the hydroxyl groups introduced into the proton-exchanged, hydrated glass structure do not initially form covalent bonds with Si and P network formers but remain free and stabilised by the modifier metal cations, whereas substantial Si-OH and P-OH bonding is observed only at higher Na(+)/H(+) exchange levels. The strong affinity between free OH groups and modifier cations in the highly fragmented 45S5 glass structure appears to represent the main driving force for this effect. This suggests an alternative direct route for the formation of a repolymerised silica-rich gel in the early stages of the bioactive mechanism, not considered before, which does not require sequential repeated breakings of Si-O-Si bonds and silanol condensations.

  8. Innovative approach to the design of low-cost Zr-based BMG composites with good glass formation

    PubMed Central

    Cheng, Jia-Lin; Chen, Guang; Liu, Chain-Tsuan; Li, Yi

    2013-01-01

    The high manufacturing cost for metallic glasses hampers actual commercial applications of this class of fascinating materials. In this letter, the effect of oxygen impurity on the glass forming ability and tensile properties of Zr-BMG composites were studied. Our results have demonstrated that oxygen was absorbed and concentrated only in the precipitated β-Zr phase, leading that the remainder molten metal retains good glass forming ability. The high oxygen concentration in the β-Zr phase induces a significant solid-solution strengthening effect, this resulting in an enhanced strength of the BMG composites without sacrificing their overall ductility. Based on this alloying strategy, we have successfully developed the low-cost Zr-based BMG composites with excellent tensile properties and good glass forming ability, using the low grade industrial raw materials processed under industrial vacuum systems. This finding is expected to greatly cut down the manufacturing cost and greatly promote the commercial applications of the BMG composites. PMID:23807140

  9. Synchrotron X-ray diffraction to detect glass or ice formation in the vitrified bovine cumulus-oocyte complexes and morulae.

    PubMed

    Anzar, Muhammad; Grochulski, Pawel; Bonnet, Brennan

    2014-01-01

    Vitrification of bovine cumulus-oocyte complexes (COCs) is not as successful as bovine embryos, due to oocyte's complex structure and chilling sensitivity. Synchrotron X-ray diffraction (SXRD), a powerful method to study crystal structure and phase changes, was used to detect the glass or ice formation in water, tissue culture medium (TCM)-199, vitrification solution 2 (VS2), and vitrified bovine COCs and morulae. Data revealed Debye's rings and peaks associated with the hexagonal ice crystals at 3.897, 3.635, 3.427, 2.610, 2.241, 1.912 and 1.878 Å in both water and TCM-199, whereas VS2 showed amorphous (glassy) appearance, at 102K (-171°C). An additional peak of sodium phosphate monobasic hydrate (NaH2PO4.H2O) crystals was observed at 2.064 Å in TCM-199 only. All ice and NaH2PO4.H2O peaks were detected in the non-vitrified (control) and vitrified COCs, except two ice peaks (3.145 and 2.655 Å) were absent in the vitrified COCs. The intensities of majority of ice peaks did not differ between the non-vitrified and vitrified COCs. The non-vitrified bovine morulae in TCM-199 demonstrated all ice- and NaH2PO4.H2O-associated Debye's rings and peaks, found in TCM-199 alone. There was no Debye's ring present in the vitrified morulae. In conclusion, SXRD is a powerful method to confirm the vitrifiability of a solution and to detect the glass or ice formation in vitrified cells and tissues. The vitrified bovine COCs exhibited the hexagonal ice crystals instead of glass formation whereas the bovine morulae underwent a typical vitrification.

  10. Effect of hydrothermal condition on the formation of multi-component oxides of Ni-based metallic glass under high temperature water near the critical point

    DOE PAGES

    Kim, J. S.; Kim, S. Y.; Kim, D. H.; Ott, R. T.; Kim, H. G.; Lee, M. H.

    2015-07-01

    The specific feature of multi-component oxides synthesized by hydrothermal process under high temperature (633 K) and highly pressurized water (18.9 MPa) near critical point. Effects of hydrothermal processing duration times 24 hours and 72 hours, respectively, on the oxide formation of the Ni59Zr20Ti16Si2Sn3 metallic glass synthesized by powder metallurgy process were characterized by X-ray diffractometer, differential scanning calorimeter along with the particle size, morphology and crystalline phase of the oxides. The crystallization of the needle-shape NiTiO3, ZrTiO4 and ZrSnO4 ternary oxide phases observed on the surface of metallic glass at below glass transition temperature and the morphology of oxide phasesmore » changed to plate-shape around 2 μm in diameter by the increase processing time. This hydrothermal processing in subcritical water provides accelerated dense metal oxide crystals due to the reaction medium being at higher pressure than conventional oxidation processing.« less

  11. Effect of hydrothermal condition on the formation of multi-component oxides of Ni-based metallic glass under high temperature water near the critical point

    SciTech Connect

    Kim, J. S.; Kim, S. Y.; Kim, D. H.; Ott, R. T.; Kim, H. G.; Lee, M. H.

    2015-07-01

    The specific feature of multi-component oxides synthesized by hydrothermal process under high temperature (633 K) and highly pressurized water (18.9 MPa) near critical point. Effects of hydrothermal processing duration times 24 hours and 72 hours, respectively, on the oxide formation of the Ni59Zr20Ti16Si2Sn3 metallic glass synthesized by powder metallurgy process were characterized by X-ray diffractometer, differential scanning calorimeter along with the particle size, morphology and crystalline phase of the oxides. The crystallization of the needle-shape NiTiO3, ZrTiO4 and ZrSnO4 ternary oxide phases observed on the surface of metallic glass at below glass transition temperature and the morphology of oxide phases changed to plate-shape around 2 μm in diameter by the increase processing time. This hydrothermal processing in subcritical water provides accelerated dense metal oxide crystals due to the reaction medium being at higher pressure than conventional oxidation processing.

  12. Effect of hydrothermal condition on the formation of multi-component oxides of Ni-based metallic glass under high temperature water near the critical point

    SciTech Connect

    Kim, J. S.; Lee, M. H.; Kim, S. Y.; Kim, D. H.; Ott, R. T.; Kim, H. G.

    2015-07-15

    The specific feature of multi-component oxides synthesized by hydrothermal process under high temperature (633 K) and highly pressurized water (18.9 MPa) near critical point. Effects of hydrothermal processing duration times 24 hours and 72 hours, respectively, on the oxide formation of the Ni{sub 59}Zr{sub 20}Ti{sub 16}Si{sub 2}Sn{sub 3} metallic glass synthesized by powder metallurgy process were characterized by X-ray diffractometer, differential scanning calorimeter along with the particle size, morphology and crystalline phase of the oxides. The crystallization of the needle-shape NiTiO{sub 3}, ZrTiO{sub 4} and ZrSnO{sub 4} ternary oxide phases observed on the surface of metallic glass at below glass transition temperature and the morphology of oxide phases changed to plate-shape around 2 μm in diameter by the increase processing time. This hydrothermal processing in subcritical water provides accelerated dense metal oxide crystals due to the reaction medium being at higher pressure than conventional oxidation processing.

  13. THE GRISM LENS-AMPLIFIED SURVEY FROM SPACE (GLASS). V. EXTENT AND SPATIAL DISTRIBUTION OF STAR FORMATION IN z ∼ 0.5 CLUSTER GALAXIES

    SciTech Connect

    Vulcani, Benedetta; Treu, Tommaso; Malkan, Matthew; Abramson, Louis; Schmidt, Kasper B.; Poggianti, Bianca M.; Dressler, Alan; Fontana, Adriano; Pentericci, Laura; Bradac, Marusa; Hoag, Austin; Huang, Kuan-Han; He, Julie; Brammer, Gabriel B.; Trenti, Michele; Linden, Anja von der; Morris, Glenn

    2015-12-01

    We present the first study of the spatial distribution of star formation in z ∼ 0.5 cluster galaxies. The analysis is based on data taken with the Wide Field Camera 3 as part of the Grism Lens-Amplified Survey from Space (GLASS). We illustrate the methodology by focusing on two clusters (MACS 0717.5+3745 and MACS 1423.8+2404) with different morphologies (one relaxed and one merging) and use foreground and background galaxies as a field control sample. The cluster+field sample consists of 42 galaxies with stellar masses in the range 10{sup 8}–10{sup 11} M{sub ⊙} and star formation rates in the range 1–20 M{sub ⊙} yr{sup −1}. Both in clusters and in the field, Hα is more extended than the rest-frame UV continuum in 60% of the cases, consistent with diffuse star formation and inside-out growth. In ∼20% of the cases, the Hα emission appears more extended in cluster galaxies than in the field, pointing perhaps to ionized gas being stripped and/or star formation being enhanced at large radii. The peak of the Hα emission and that of the continuum are offset by less than 1 kpc. We investigate trends with the hot gas density as traced by the X-ray emission, and with the surface mass density as inferred from gravitational lens models, and find no conclusive results. The diversity of morphologies and sizes observed in Hα illustrates the complexity of the environmental processes that regulate star formation. Upcoming analysis of the full GLASS data set will increase our sample size by almost an order of magnitude, verifying and strengthening the inference from this initial data set.

  14. Origin of an isothermal R-martensite formation in Ni-rich Ti-Ni solid solution: crystallization of strain glass.

    PubMed

    Ji, Yuanchao; Wang, Dong; Ding, Xiangdong; Otsuka, Kazuhiro; Ren, Xiaobing

    2015-02-01

    We report that R martensite isothermally forms with time in a solution-treated Ti(48.7)Ni(51.3) single crystal. This abnormal formation originates from the growth of a short-range ordered R phase with time, i.e., the "crystallization" of strain glass. The established time-composition-temperature Ti-Ni diagram shows a time evolution of the R phase and composition-temperature phase diagram. The presence or absence of the R phase in this new diagram, as well as in other conditions (like doping Fe or aging), is explained in a unified framework of free-energy landscape. Our finding suggests a new mechanism for the isothermal martensite formation, which could be applied to other metal and ceramic martensitic systems to find new phases and novel properties.

  15. Biofilm Formation and Adaptation by Pseudomonas fluorescens on both Biotite and Glass Coupons Under Varying Fe-Nutrient Availability

    NASA Astrophysics Data System (ADS)

    Grant, M.; Helms, G. L.; Shi, Z.; Thomashow, L.; Keller, C. K.; Harsh, J. B.

    2014-12-01

    We isolated an efficient weathering strain of Pseudomonas fluorescens from the rhizosphere of a White Pine (Pinus strobus) seedling. We grew it in a drip-flow biofilm reactor using both Fe-abundant and Fe-deficient media on either a glass or biotite coupon. Our working hypothesis was that the bacterium would respond to Fe deficiency by enhancing biotite weathering through an increase in the relative amount of polysaccharides in the biofilm compared to the Fe-abundant treatment. Because Fe is necessary for biofilm development, we hypothesized that biomass production on the biotite surface would exceed that on a Fe-free glass slide only in the Fe-deficient medium. We quantified total biomass, specific number of viable cells (SNVC), and the concentrations of K, Mg, and Fe in the biofilm. High-resolution magic angle spinning proton nuclear magnetic resonance (HR-MAS 1H-NMR) spectroscopy was used to characterize the biofilm matrix in terms of relative biofilm constituent concentrations. Compared with biofilms grown on glass, biofilms grown on biotite had higher total biomass and SNVC irrespective of Fe supply, with a near doubling of both the biofilm biomass from 0.43 to 0.76 mg cm-2 and SNVC from 1.52 × 107 to 3.24 × 107 CFU cm-2 mg-1 when Fe was deficient, and an increase in biomass from 1.94 to 2.46 mg cm-2 and in SNVC from 8.39 × 107 to 1.96 × 108 CFU cm-2 mg-1 when Fe was sufficient. Similarly with Fe deficient, the cation concentrations in biofilms grown on biotite vs. glass increased 2.14 and 2.46 times for K and Mg, respectively, and 7.01 times for Fe. When Fe was sufficient, the concentrations of cations increased 1.24, 2.07, and 3.77 times for K, Mg, and Fe, respectively. Based on NMR spectra, no significant change in biofilm chemistry occurred between the glass and biotite systems whether Fe was deficient or not. However, we did observe an increase in the ratio of the integrated areas corresponding to the carbohydrate and protein NMR regions, increasing

  16. Measuring the specific surface area of natural and manmade glasses: effects of formation process, morphology, and particle size

    SciTech Connect

    Papelis, Charalambos; Um, Wooyong; Russel, Charles E.; Chapman, Jenny B.

    2003-03-28

    The specific surface area of natural and manmade solid materials is a key parameter controlling important interfacial processes in natural environments and engineered systems, including dissolution reactions and sorption processes at solid-fluid interfaces. To improve our ability to quantify the release of trace elements trapped in natural glasses, the release of hazardous compounds trapped in manmade glasses, or the release of radionuclides from nuclear melt glass, we measured the specific surface area of natural and manmade glasses as a function of particle size, morphology, and composition. Volcanic ash, volcanic tuff, tektites, obsidian glass, and in situ vitrified rock were analyzed. Specific surface area estimates were obtained using krypton as gas adsorbent and the BET model. The range of surface areas measured exceeded three orders of magnitude. A tektite sample had the highest surface area (1.65 m2/g), while one of the samples of in situ vitrified rock had the lowest surf ace area (0.0016 m2/g). The specific surface area of the samples was a function of particle size, decreasing with increasing particle size. Different types of materials, however, showed variable dependence on particle size, and could be assigned to one of three distinct groups: (1) samples with low surface area dependence on particle size and surface areas approximately two orders of magnitude higher than the surface area of smooth spheres of equivalent size. The specific surface area of these materials was attributed mostly to internal porosity and surface roughness. (2) samples that showed a trend of decreasing surface area dependence on particle size as the particle size increased. The minimum specific surface area of these materials was between 0.1 and 0.01 m2/g and was also attributed to internal porosity and surface roughness. (3) samples whose surface area showed a monotonic decrease with increasing particle size, never reaching an ultimate surface area limit within the particle

  17. Use of a Routh-Russel deformation map to achieve film formation of a latex with a high glass transition temperature.

    PubMed

    Gonzalez, Edurne; Paulis, María; Barandiaran, María Jesús; Keddie, Joseph L

    2013-02-12

    In the film formation of latex, particle deformation can occur by processes of wet sintering, dry sintering, or capillary action. When latex films dry nonuniformly and when particles deform and coalesce while the film is still wet, a detrimental skin layer will develop at the film surface. In their process model, Routh and Russel proposed that the operative particle deformation mechanism can be determined by the values of control parameters on a deformation map. Here, the film formation processes of three methyl methacrylate/butyl acrylate copolymer latexes with high glass transition temperatures (T(g)), ranging from 45 to 64 °C, have been studied when heated by infrared radiation. Adjusting the infrared (IR) power density enables the film temperature, polymer viscosity, and evaporation rate during latex film formation to be controlled precisely. Different polymer particle deformation mechanisms have been demonstrated for the same latex under a variety of film formation process conditions. When the temperature is too high, a skin layer develops. On the other hand, when the temperature is too low, particles deform by dry sintering, and the process requires extended time periods. The deduced mechanisms can be interpreted and explained by the Routh-Russel deformation maps. Film formation of hard (high T(g)) coatings is achieved without using coalescing aids that emit volatile organic compounds (VOCs), which is a significant technical achievement.

  18. Containerless processing of fluoride glass

    NASA Technical Reports Server (NTRS)

    Doremus, Robert H.

    1990-01-01

    Ground-based experiments on glass formation, crystallization, surface tension, vaporization, and chemical durability of a zirconium-barium-lanthanum (ZBL) fluoride glass are summarized. In a container large, columnar grains grew out from the container-glass interface during cooling. The main crystalline phase was alpha BaZrF6. A ZBL glass sphere was levitated acoustically during Shuttle flight STS-11. The glass was melted and then cooled while being levitated (containerless). Crystallization in the recovered sample was very fine and mainly beta BaZr2F10, showing the influence of the container on the nucleation and microstructure of crystallization in the glass. Glass formation should be easier for a containerless glass than in a container.

  19. Solubilities and Glass Formation in Aqueous Solutions of the Sodium Salts of Malonic Acid With and Without Ammonium Sulfate.

    PubMed

    Kissinger, Jared A; Buttke, Lukas G; Vinokur, Anastasiya I; Guzei, Ilia A; Beyer, Keith D

    2016-06-01

    The solubility of sodium hydrogen malonate and sodium malonate in water both with and without ammonium sulfate present has been studied using differential scanning calorimetry and infrared spectroscopy. The crystals that form from sodium hydrogen malonate/water solutions were determined to be sodium hydrogen malonate monohydrate by single-crystal X-ray diffractometry. The crystals formed in sodium malonate/water solutions were determined to be sodium malonate monohydrate, a compound whose structure had not been previously known. When ammonium sulfate is added to these respective aqueous systems, the precipitation solids contain sodium sulfate decahydrate under low to moderate ammonium concentrations and lecontite (NaNH4SO4·2H2O) under high ammonium concentrations, which can be found under dry atmospheric conditions. Thus, it appears the presence of malonate and hydrogen malonate ions does not significantly affect the precipitation of inorganic salts in these systems. The glass transition temperatures of all solutions were also determined, and it was observed that the addition of ammonium sulfate slightly lowers the glass transition temperature in these solutions.

  20. Designing new biocompatible glass-forming Ti75-x Zr10 Nbx Si15 (x = 0, 15) alloys: corrosion, passivity, and apatite formation.

    PubMed

    Abdi, Somayeh; Oswald, Steffen; Gostin, Petre Flaviu; Helth, Arne; Sort, Jordi; Baró, Maria Dolors; Calin, Mariana; Schultz, Ludwig; Eckert, Jürgen; Gebert, Annett

    2016-01-01

    Glass-forming Ti-based alloys are considered as potential new materials for implant applications. Ti75 Zr10 Si15 and Ti60 Zr10 Nb15 Si15 alloys (free of cytotoxic elements) can be produced as melt-spun ribbons with glassy matrix and embedded single β-type nanocrystals. The corrosion and passivation behavior of these alloys in their homogenized melt-spun states have been investigated in Ringer solution at 37°C in comparison to their cast multiphase crystalline counterparts and to cp-Ti and β-type Ti-40Nb. All tested materials showed very low corrosion rates as expressed in corrosion current densities icorr  < 50 nA/cm(2). Electrochemical and surface analytical studies revealed a high stability of the new alloys passive states in a wide potential range. This corresponds to low passive current densities ipass  = 2 ± 1 µA/cm(2) based on the growth of oxide films with thickness d <10 nm. A homogeneous constituent distribution in the melt-spun alloys is beneficial for stable surface passivity. The addition of Nb does not only improve the glass-forming ability and the mechanical properties but also supports a high pitting resistance even at extreme anodic polarization up to 4V versus SCE were oxide thickness values of d ∼35 nm are reached. With regard to the corrosion properties, the Nb-containing nearly single-phase glassy alloy can compete with the β-type Ti-40Nb alloy. SBF tests confirmed the ability for formation of hydroxyapatite on the melt-spun alloy surfaces. All these properties recommend the new glass-forming alloys for application as wear- and corrosion-resistant coating materials for implants. PMID:25611821

  1. Designing new biocompatible glass-forming Ti75-x Zr10 Nbx Si15 (x = 0, 15) alloys: corrosion, passivity, and apatite formation.

    PubMed

    Abdi, Somayeh; Oswald, Steffen; Gostin, Petre Flaviu; Helth, Arne; Sort, Jordi; Baró, Maria Dolors; Calin, Mariana; Schultz, Ludwig; Eckert, Jürgen; Gebert, Annett

    2016-01-01

    Glass-forming Ti-based alloys are considered as potential new materials for implant applications. Ti75 Zr10 Si15 and Ti60 Zr10 Nb15 Si15 alloys (free of cytotoxic elements) can be produced as melt-spun ribbons with glassy matrix and embedded single β-type nanocrystals. The corrosion and passivation behavior of these alloys in their homogenized melt-spun states have been investigated in Ringer solution at 37°C in comparison to their cast multiphase crystalline counterparts and to cp-Ti and β-type Ti-40Nb. All tested materials showed very low corrosion rates as expressed in corrosion current densities icorr  < 50 nA/cm(2). Electrochemical and surface analytical studies revealed a high stability of the new alloys passive states in a wide potential range. This corresponds to low passive current densities ipass  = 2 ± 1 µA/cm(2) based on the growth of oxide films with thickness d <10 nm. A homogeneous constituent distribution in the melt-spun alloys is beneficial for stable surface passivity. The addition of Nb does not only improve the glass-forming ability and the mechanical properties but also supports a high pitting resistance even at extreme anodic polarization up to 4V versus SCE were oxide thickness values of d ∼35 nm are reached. With regard to the corrosion properties, the Nb-containing nearly single-phase glassy alloy can compete with the β-type Ti-40Nb alloy. SBF tests confirmed the ability for formation of hydroxyapatite on the melt-spun alloy surfaces. All these properties recommend the new glass-forming alloys for application as wear- and corrosion-resistant coating materials for implants.

  2. The formation of supercooled brines, viscous liquids, and low-temperature perchlorate glasses in aqueous solutions relevant to Mars

    NASA Astrophysics Data System (ADS)

    Toner, J. D.; Catling, D. C.; Light, B.

    2014-05-01

    Salt solutions on Mars can stabilize liquid water at low temperatures by lowering the freezing point of water. The maximum equilibrium freezing-point depression possible, known as the eutectic temperature, suggests a lower temperature limit for liquid water on Mars; however, salt solutions can supercool below their eutectic before crystallization occurs. To investigate the magnitude of supercooling and its variation with salt composition and concentration, we performed slow cooling and warming experiments on pure salt solutions and saturated soil-solutions of MgSO4, MgCl2, NaCl, NaClO4, Mg(ClO4)2, and Ca(ClO4)2. By monitoring solution temperatures, we identified exothermic crystallization events and determined the composition of precipitated phases from the eutectic melting temperature. Our results indicate that supercooling is pervasive. In general, supercooling is greater in more concentrated solutions and with salts of Ca and Mg. Slowly cooled MgSO4, MgCl2, NaCl, and NaClO4 solutions investigated in this study typically supercool 5-15 °C below their eutectic temperature before crystallizing. The addition of soil to these salt solutions has a variable effect on supercooling. Relative to the pure salt solutions, supercooling decreases in MgSO4 soil-solutions, increases in MgCl2 soil-solutions, and is similar in NaCl and NaClO4 soil-solutions. Supercooling in MgSO4, MgCl2, NaCl, and NaClO4 solutions could marginally extend the duration of liquid water during relatively warm daytime temperatures in the martian summer. In contrast, we find that Mg(ClO4)2 and Ca(ClO4)2 solutions do not crystallize during slow cooling, but remain in a supercooled, liquid state until forming an amorphous glass near -120 °C. Even if soil is added to the solutions, a glass still forms during cooling. The large supercooling effect in Mg(ClO4)2 and Ca(ClO4)2 solutions has the potential to prevent water from freezing over diurnal and possibly annual cycles on Mars. Glasses are also

  3. Glass Formation of n-Butanol: Coarse-grained Molecular Dynamics Simulations Using Gay-Berne Potential Model

    NASA Astrophysics Data System (ADS)

    Xie, Gui-long; Zhang, Yong-hong; Huang, Shi-ping

    2012-04-01

    Using coarse-grained molecular dynamics simulations based on Gay-Berne potential model, we have simulated the cooling process of liquid n-butanol. A new set of GB parameters are obtained by fitting the results of density functional theory calculations. The simulations are carried out in the range of 290-50 K with temperature decrements of 10 K. The cooling characteristics are determined on the basis of the variations of the density, the potential energy and orientational order parameter with temperature, whose slopes all show discontinuity. Both the radial distribution function curves and the second-rank orientational correlation function curves exhibit splitting in the second peak. Using the discontinuous change of these thermodynamic and structure properties, we obtain the glass transition at an estimate of temperature Tg=120±10 K, which is in good agreement with experimental results 110±1 K.

  4. Glass formation and high conductivity in the ternary system AgI + Ag/sub 3/AsO/sub 4/ + AgPO/sub 3/: host to glassy AgI

    SciTech Connect

    Martin, S.W.; Schiraldi, A.

    1985-05-09

    Wide regions of glass formation have been found in the ternary system xAgI + yAg/sub 3/AsO/sub 4/ + (1 - x - y)AgPO/sub 3/. Glasses containing up to 75 mol % AgI can be formed in sections greater than 2 cm thick without signs of devitrification. Glass transition temperatures as high as 175/sup 0/C for glasses containing approx. 10 mol% AgI fall to approx. 45/sup 0/C at the highest AgI content. An equivalent ratio of AgI:N is defined and it is found that, for all glass-forming compositions, the electrical data as expressed in the Arrhenius form, sigma = A exp(-E/sub act/RT), log (sigma/omega cm)/sup -1/), log (A/omega cm)/sup -1/), E/sub act//(kcal mol/sup -1/), and additionally T/sub g/K, can be described as linear functions of N. These data are used to give support to the view of these glasses as being hosts to a liquidlike AgI giving rise to the high conductivity they exhibit, as high as 0.0143 (omega cm)/sup -1/ at room temperature for glasses containing the maximum AgI. Finally, from these linear relationships, functions for the mobility ..mu.. and number of the mobile Ag/sup +/ cations n are developed. 29 references, 8 figures, 2 tables.

  5. Glass sealing

    SciTech Connect

    Brow, R.K.; Kovacic, L.; Chambers, R.S.

    1996-04-01

    Hernetic glass sealing technologies developed for weapons component applications can be utilized for the design and manufacture of fuel cells. Design and processing of of a seal are optimized through an integrated approach based on glass composition research, finite element analysis, and sealing process definition. Glass sealing procedures are selected to accommodate the limits imposed by glass composition and predicted calculations.

  6. Properties Of Soda/Yttria/Silica Glasses

    NASA Technical Reports Server (NTRS)

    Angel, Paul W.; Hann, Raiford E.

    1994-01-01

    Experimental study of glass-formation compositional region of soda/ yttria/silicate system and of selected physical properties of glasses within compositional region part of continuing effort to identify glasses with high coefficients of thermal expansion and high softening temperatures, for use as coatings on superalloys and as glass-to-metal seals.

  7. Mapping the spatial distribution of star formation in cluster galaxies at z ~0.5 with the Grism Lens-Amplified Survey from Space (GLASS)

    NASA Astrophysics Data System (ADS)

    Vulcani, B.; Treu, T.; Schmidt, K. B.; Poggianti, B. M.; Dressler, A.; Fontana, A.; Bradač, M.; Brammer, G. B.; Hoag, A.; Huang, K.; Malkan, M.; Pentericci, L.; Trenti, M.; von der Linden, A.; Abramson, L.; He, J.; Morris, G.

    2016-06-01

    What physical processes regulate star formation in dense environments? Understanding why galaxy evolution is environment dependent is one of the key questions of current astrophysics. I will present the first characterization of the spatial distribution of star formation in cluster galaxies at z~0.5, and compare to a field control sample, in order to quantify the role of different physical processes that are believed to be responsible for shutting down star formation (Vulcani et al. 2015, Vulcani et al. in prep). The analysis makes use of data from the Grism Lens-Amplified Survey from Space (GLASS), a large HST cycle-21 program targeting 10 massive galaxy clusters with extensive HST imaging from CLASH and the Frontier Field Initiative. The program consists of 140 primary and 140 parallel orbits of near-infrared WCF3 and optical ACS slitless grism observations, which result in 3D spectroscopy of hundreds of galaxies. The grism data are used to produce spatially resolved maps of the star formation density, while the stellar mass density and optical surface brightness are obtained from multiband imaging. I will describe quantitative measures of the spatial location and extent of the star formation rate. I will show that both in clusters and in the field, Hα is more extended than the rest-frame UV continuum in 60% of the cases, consistent with diffuse star formation and inside out growth. The Hα emission appears more extended in cluster galaxies than in the field, pointing perhaps to ionized gas being stripped and/or star formation being enhanced at large radii. The peak of the Hα emission and that of the continuum are offset by less than 1 kpc. I will also correlate the properties of the Hα maps to the cluster global properties, such as the hot gas density, and the surface mass density. The characterization of the spatial distribution of Halpha provides a new window, yet poorly exploited, on the mechanisms that regulate star formation and morphological

  8. Evidence of photo-induced dynamic competition of metallic and insulating phase in a layered manganite

    SciTech Connect

    Li, Yuelin; Walko, Daonld A.; Li, Qing'an; Liu, Yaohua; Rosenkranz, Stephen; Zheng, Hong; Mitchell, J. F.

    2015-11-17

    We show evidence that the competition between the antiferromagetic metallic phase and the charge- and orbital-ordered insulating phase at the reentrant phase boundary of a layered manganite, LaSr2Mn2O7, can be manipulated using ultrafast optical excitation. The time-dependent evolution of the Jahn-Teller superlattice reflection, which indicates the formation of the charge and orbital order, was measured at different laser fluences. The laser-induced enhancement and reduction the Jahn-Teller reflection intensity shows a reversal of sign between earlier (~10 ns) and later (~150 ns) time delays during the relaxation after photo excitation. This effect is consistent with a scenario whereby the laser excitation modulates the local competition between the metallic and the insulating phases.

  9. Evidence of photo-induced dynamic competition of metallic and insulating phase in a layered manganite

    DOE PAGES

    Li, Yuelin; Walko, Daonld A.; Li, Qing'an; Liu, Yaohua; Rosenkranz, Stephen; Zheng, Hong; Mitchell, J. F.

    2015-11-17

    We show evidence that the competition between the antiferromagetic metallic phase and the charge- and orbital-ordered insulating phase at the reentrant phase boundary of a layered manganite, LaSr2Mn2O7, can be manipulated using ultrafast optical excitation. The time-dependent evolution of the Jahn-Teller superlattice reflection, which indicates the formation of the charge and orbital order, was measured at different laser fluences. The laser-induced enhancement and reduction the Jahn-Teller reflection intensity shows a reversal of sign between earlier (~10 ns) and later (~150 ns) time delays during the relaxation after photo excitation. This effect is consistent with a scenario whereby the laser excitationmore » modulates the local competition between the metallic and the insulating phases.« less

  10. Evidence of Photo-induced Dynamic Competition of Metallic and Insulating Phase in a Layered Manganite.

    SciTech Connect

    Li, Yuelin; Walko, Donald A.; Li, Qing'an; Liu, Yaohua; Rosenkranz, Stephan; Zheng, Hong; Mitchell, J. F.

    2015-12-16

    We show evidence that the competition between the antiferromagetic metallic phase and the charge- and orbital-ordered insulating phase at the reentrant phase boundary of a layered manganite, LaSr2Mn2O7, can be manipulated using ultrafast optical excitation. The time- dependent evolution of the Jahn-Teller superlattice reflection, which indicates the formation of the charge and orbital order, was measured at different laser fluences. The laser-induced enhancement and reduction the Jahn-Teller reflection intensity shows a reversal of sign between earlier (~10 ns) and later (~150 ns) time delays during the relaxation after photo excitation. This effect is consistent with a scenario whereby the laser excitation modulates the local competition between the metallic and the insulating phases.

  11. Glass leaching performance

    SciTech Connect

    Chick, L.A.; Turcotte, R.P.

    1983-05-01

    Current understanding of the leaching performance of high-level nuclear waste (HLW) glass is summarized. The empirical model of waste glass leaching behavior developed shows that at high water flow rates the glass leach rate is kinetically limited to a maximum value. At intermediate water flow rates, leaching is limited by the solution concentration of silica and decreases with decreasing water flow rates. Release of soluble elements is controlled by silica dissolution because silica forms the binding network of the glass. At low water flow rates, mass loss rates reach values controlled by formation rates of alteration minerals, or by diffusion of dissolution products through essentially stagnant water. The parameters reviewed with respect to their quantifiable influence on leaching behavior include temperature, pH, leachant composition, glass composition, thermal history, and radiation. Of these, temperature is most important since the rate of mass loss approximately doubles with each 10/sup 0/C increase in dilute solutions. The pH has small effects within the 4 to 10 range. The chemical composition of the leachant is most important with regard to its influence on alteration product formation. Glass composition exhibits the largest effects at high flow rates where improved glasses leach from ten to thirty times slower than glass 76 to 68. The effects of the thermal history (devitrification) of the glass are not likely to be significant. Radiation effects are important primarily in that radiolysis can potentially drive pH values to less than 4. Radiation damage to the glass causes insignificant changes in leaching performance.

  12. Low-temperature formation of high-quality gate oxide by ultraviolet irradiation on spin-on-glass

    SciTech Connect

    Usuda, R.; Uchida, K.; Nozaki, S.

    2015-11-02

    Although a UV cure was found to effectively convert a perhydropolysilazane (PHPS) spin-on-glass film into a dense SiO{sub x} film at low temperature, the electrical characteristics were never reported in order to recommend the use of PHPS as a gate-oxide material that can be formed at low temperature. We have formed a high-quality gate oxide by UV irradiation on the PHPS film, and obtained an interface midgap trap density of 3.4 × 10{sup 11 }cm{sup −2} eV{sup −1} by the UV wet oxidation and UV post-metallization annealing (PMA), at a temperature as low as 160 °C. In contrast to the UV irradiation using short-wavelength UV light, which is well known to enhance oxidation by the production of the excited states of oxygen, the UV irradiation was carried out using longer-wavelength UV light from a metal halide lamp. The UV irradiation during the wet oxidation of the PHPS film generates electron-hole pairs. The electrons ionize the H{sub 2}O molecules and facilitate dissociation of the molecules into H and OH{sup −}. The OH{sup −} ions are highly reactive with Si and improve the stoichiometry of the oxide. The UV irradiation during the PMA excites the electrons from the accumulation layer, and the built-in electric field makes the electron injection into the oxide much easier. The electrons injected into the oxide recombine with the trapped holes, which have caused a large negative flat band voltage shift after the UV wet oxidation, and also ionize the H{sub 2}O molecules. The ionization results in the electron stimulated dissociation of H{sub 2}O molecules and the decreased interface trap density.

  13. Low-temperature formation of high-quality gate oxide by ultraviolet irradiation on spin-on-glass

    NASA Astrophysics Data System (ADS)

    Usuda, R.; Uchida, K.; Nozaki, S.

    2015-11-01

    Although a UV cure was found to effectively convert a perhydropolysilazane (PHPS) spin-on-glass film into a dense SiOx film at low temperature, the electrical characteristics were never reported in order to recommend the use of PHPS as a gate-oxide material that can be formed at low temperature. We have formed a high-quality gate oxide by UV irradiation on the PHPS film, and obtained an interface midgap trap density of 3.4 × 1011 cm-2 eV-1 by the UV wet oxidation and UV post-metallization annealing (PMA), at a temperature as low as 160 °C. In contrast to the UV irradiation using short-wavelength UV light, which is well known to enhance oxidation by the production of the excited states of oxygen, the UV irradiation was carried out using longer-wavelength UV light from a metal halide lamp. The UV irradiation during the wet oxidation of the PHPS film generates electron-hole pairs. The electrons ionize the H2O molecules and facilitate dissociation of the molecules into H and OH-. The OH- ions are highly reactive with Si and improve the stoichiometry of the oxide. The UV irradiation during the PMA excites the electrons from the accumulation layer, and the built-in electric field makes the electron injection into the oxide much easier. The electrons injected into the oxide recombine with the trapped holes, which have caused a large negative flat band voltage shift after the UV wet oxidation, and also ionize the H2O molecules. The ionization results in the electron stimulated dissociation of H2O molecules and the decreased interface trap density.

  14. Biosilica-glass formation using enzymes from sponges [silicatein]: Basic aspects and application in biomedicine [bone reconstitution material and osteoporosis

    NASA Astrophysics Data System (ADS)

    Wang, Shun-Feng; Wang, Xiao-Hong; Gan, Lu; Wiens, Matthias; Schröder, Heinz C.; Müller, Werner E. G.

    2011-09-01

    In the last 15 years biomineralization, in particular biosilicification (i.e., the formation of biogenic silica, SiO2), has become an exciting source of inspiration for the development of novel bionic approaches, following "Nature as model". Among the silica forming organisms there are the sponges that have the unique property to catalyze their silica skeletons by a specific enzyme termed silicatein. In the present review we summarize the present state of knowledge on silicatein-mediated "biosilica" formation in marine sponges, the involvement of further molecules in silica metabolism and their potential application in biomedicine. Recent advancements in the production of bone replacement material and in the potential use as a component in the treatment of osteoporosis are highlighted.

  15. Synthesis, cytotoxicity, and hydroxyapatite formation in 27-Tris-SBF for sol-gel based CaO-P2O5-SiO2-B2O3-ZnO bioactive glasses

    PubMed Central

    Kaur, Gurbinder; Pickrell, G.; Kimsawatde, G.; Homa, D.; Allbee, H. A.; Sriranganathan, N.

    2014-01-01

    CaO-P2O5-SiO2-B2O3-ZnO bioactive glasses were prepared via an optimized sol–gel method. The current investigation was focused on producing novel zinc based calcium phosphoborosilicate glasses and to evaluate their mechanical, rheological, and biocompatible properties. The morphology and composition of these glasses were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The particle size, mechanical and flexural strength was also determined. Furthermore, the zeta potential of all the glasses were determined to estimate their flocculation tendency. The thermal analysis and weight loss measurements were carried out using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) respectively. For assessing the in-vitro bioactive character of synthesized glasses, the ability for apatite formation on their surface upon their immersion in simulated body fluid (SBF) was checked using SEM and pH measurements. MTS assay cytotoxicity assay and live-dead cell viability test were conducted on J774A.1 cells murine macrophage cells for different glass concentrations. PMID:24637634

  16. Synthesis, cytotoxicity, and hydroxyapatite formation in 27-Tris-SBF for sol-gel based CaO-P2O5-SiO2-B2O3-ZnO bioactive glasses

    NASA Astrophysics Data System (ADS)

    Kaur, Gurbinder; Pickrell, G.; Kimsawatde, G.; Homa, D.; Allbee, H. A.; Sriranganathan, N.

    2014-03-01

    CaO-P2O5-SiO2-B2O3-ZnO bioactive glasses were prepared via an optimized sol-gel method. The current investigation was focused on producing novel zinc based calcium phosphoborosilicate glasses and to evaluate their mechanical, rheological, and biocompatible properties. The morphology and composition of these glasses were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The particle size, mechanical and flexural strength was also determined. Furthermore, the zeta potential of all the glasses were determined to estimate their flocculation tendency. The thermal analysis and weight loss measurements were carried out using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) respectively. For assessing the in-vitro bioactive character of synthesized glasses, the ability for apatite formation on their surface upon their immersion in simulated body fluid (SBF) was checked using SEM and pH measurements. MTS assay cytotoxicity assay and live-dead cell viability test were conducted on J774A.1 cells murine macrophage cells for different glass concentrations.

  17. Synthesis, cytotoxicity, and hydroxyapatite formation in 27-Tris-SBF for sol-gel based CaO-P2O5-SiO2-B2O3-ZnO bioactive glasses.

    PubMed

    Kaur, Gurbinder; Pickrell, G; Kimsawatde, G; Homa, D; Allbee, H A; Sriranganathan, N

    2014-03-18

    CaO-P2O5-SiO2-B2O3-ZnO bioactive glasses were prepared via an optimized sol-gel method. The current investigation was focused on producing novel zinc based calcium phosphoborosilicate glasses and to evaluate their mechanical, rheological, and biocompatible properties. The morphology and composition of these glasses were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The particle size, mechanical and flexural strength was also determined. Furthermore, the zeta potential of all the glasses were determined to estimate their flocculation tendency. The thermal analysis and weight loss measurements were carried out using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) respectively. For assessing the in-vitro bioactive character of synthesized glasses, the ability for apatite formation on their surface upon their immersion in simulated body fluid (SBF) was checked using SEM and pH measurements. MTS assay cytotoxicity assay and live-dead cell viability test were conducted on J774A.1 cells murine macrophage cells for different glass concentrations.

  18. The relationship of dynamical heterogeneity to the Adam-Gibbs and random first-order transition theories of glass formation.

    PubMed

    Starr, Francis W; Douglas, Jack F; Sastry, Srikanth

    2013-03-28

    We carefully examine common measures of dynamical heterogeneity for a model polymer melt and test how these scales compare with those hypothesized by the Adam and Gibbs (AG) and random first-order transition (RFOT) theories of relaxation in glass-forming liquids. To this end, we first analyze clusters of highly mobile particles, the string-like collective motion of these mobile particles, and clusters of relative low mobility. We show that the time scale of the high-mobility clusters and strings is associated with a diffusive time scale, while the low-mobility particles' time scale relates to a structural relaxation time. The difference of the characteristic times for the high- and low-mobility particles naturally explains the well-known decoupling of diffusion and structural relaxation time scales. Despite the inherent difference of dynamics between high- and low-mobility particles, we find a high degree of similarity in the geometrical structure of these particle clusters. In particular, we show that the fractal dimensions of these clusters are consistent with those of swollen branched polymers or branched polymers with screened excluded-volume interactions, corresponding to lattice animals and percolation clusters, respectively. In contrast, the fractal dimension of the strings crosses over from that of self-avoiding walks for small strings, to simple random walks for longer, more strongly interacting, strings, corresponding to flexible polymers with screened excluded-volume interactions. We examine the appropriateness of identifying the size scales of either mobile particle clusters or strings with the size of cooperatively rearranging regions (CRR) in the AG and RFOT theories. We find that the string size appears to be the most consistent measure of CRR for both the AG and RFOT models. Identifying strings or clusters with the "mosaic" length of the RFOT model relaxes the conventional assumption that the "entropic droplets" are compact. We also confirm the

  19. The relationship of dynamical heterogeneity to the Adam-Gibbs and random first-order transition theories of glass formation

    PubMed Central

    Starr, Francis W.; Douglas, Jack F.; Sastry, Srikanth

    2013-01-01

    We carefully examine common measures of dynamical heterogeneity for a model polymer melt and test how these scales compare with those hypothesized by the Adam and Gibbs (AG) and random first-order transition (RFOT) theories of relaxation in glass-forming liquids. To this end, we first analyze clusters of highly mobile particles, the string-like collective motion of these mobile particles, and clusters of relative low mobility. We show that the time scale of the high-mobility clusters and strings is associated with a diffusive time scale, while the low-mobility particles' time scale relates to a structural relaxation time. The difference of the characteristic times for the high- and low-mobility particles naturally explains the well-known decoupling of diffusion and structural relaxation time scales. Despite the inherent difference of dynamics between high- and low-mobility particles, we find a high degree of similarity in the geometrical structure of these particle clusters. In particular, we show that the fractal dimensions of these clusters are consistent with those of swollen branched polymers or branched polymers with screened excluded-volume interactions, corresponding to lattice animals and percolation clusters, respectively. In contrast, the fractal dimension of the strings crosses over from that of self-avoiding walks for small strings, to simple random walks for longer, more strongly interacting, strings, corresponding to flexible polymers with screened excluded-volume interactions. We examine the appropriateness of identifying the size scales of either mobile particle clusters or strings with the size of cooperatively rearranging regions (CRR) in the AG and RFOT theories. We find that the string size appears to be the most consistent measure of CRR for both the AG and RFOT models. Identifying strings or clusters with the “mosaic” length of the RFOT model relaxes the conventional assumption that the “entropic droplets” are compact. We also confirm

  20. The relationship of dynamical heterogeneity to the Adam-Gibbs and random first-order transition theories of glass formation

    NASA Astrophysics Data System (ADS)

    Starr, Francis W.; Douglas, Jack F.; Sastry, Srikanth

    2013-03-01

    We carefully examine common measures of dynamical heterogeneity for a model polymer melt and test how these scales compare with those hypothesized by the Adam and Gibbs (AG) and random first-order transition (RFOT) theories of relaxation in glass-forming liquids. To this end, we first analyze clusters of highly mobile particles, the string-like collective motion of these mobile particles, and clusters of relative low mobility. We show that the time scale of the high-mobility clusters and strings is associated with a diffusive time scale, while the low-mobility particles' time scale relates to a structural relaxation time. The difference of the characteristic times for the high- and low-mobility particles naturally explains the well-known decoupling of diffusion and structural relaxation time scales. Despite the inherent difference of dynamics between high- and low-mobility particles, we find a high degree of similarity in the geometrical structure of these particle clusters. In particular, we show that the fractal dimensions of these clusters are consistent with those of swollen branched polymers or branched polymers with screened excluded-volume interactions, corresponding to lattice animals and percolation clusters, respectively. In contrast, the fractal dimension of the strings crosses over from that of self-avoiding walks for small strings, to simple random walks for longer, more strongly interacting, strings, corresponding to flexible polymers with screened excluded-volume interactions. We examine the appropriateness of identifying the size scales of either mobile particle clusters or strings with the size of cooperatively rearranging regions (CRR) in the AG and RFOT theories. We find that the string size appears to be the most consistent measure of CRR for both the AG and RFOT models. Identifying strings or clusters with the "mosaic" length of the RFOT model relaxes the conventional assumption that the "entropic droplets" are compact. We also confirm the

  1. The relationship of dynamical heterogeneity to the Adam-Gibbs and random first-order transition theories of glass formation.

    PubMed

    Starr, Francis W; Douglas, Jack F; Sastry, Srikanth

    2013-03-28

    We carefully examine common measures of dynamical heterogeneity for a model polymer melt and test how these scales compare with those hypothesized by the Adam and Gibbs (AG) and random first-order transition (RFOT) theories of relaxation in glass-forming liquids. To this end, we first analyze clusters of highly mobile particles, the string-like collective motion of these mobile particles, and clusters of relative low mobility. We show that the time scale of the high-mobility clusters and strings is associated with a diffusive time scale, while the low-mobility particles' time scale relates to a structural relaxation time. The difference of the characteristic times for the high- and low-mobility particles naturally explains the well-known decoupling of diffusion and structural relaxation time scales. Despite the inherent difference of dynamics between high- and low-mobility particles, we find a high degree of similarity in the geometrical structure of these particle clusters. In particular, we show that the fractal dimensions of these clusters are consistent with those of swollen branched polymers or branched polymers with screened excluded-volume interactions, corresponding to lattice animals and percolation clusters, respectively. In contrast, the fractal dimension of the strings crosses over from that of self-avoiding walks for small strings, to simple random walks for longer, more strongly interacting, strings, corresponding to flexible polymers with screened excluded-volume interactions. We examine the appropriateness of identifying the size scales of either mobile particle clusters or strings with the size of cooperatively rearranging regions (CRR) in the AG and RFOT theories. We find that the string size appears to be the most consistent measure of CRR for both the AG and RFOT models. Identifying strings or clusters with the "mosaic" length of the RFOT model relaxes the conventional assumption that the "entropic droplets" are compact. We also confirm the

  2. Structural characterisation of the perovskite series Sr{sub x}Ca{sub 1-x-y}Nd{sub y}MnO{sub 3}: Influence of the Jahn-Teller effect

    SciTech Connect

    Kennedy, Brendan J.; Saines, Paul J.; Ting, Jimmy; Zhou Qingdi; Kimpton, Justin A.

    2009-10-15

    The crystal structures of the perovskite manganites Sr{sub x}Ca{sub 1-x-y}Nd{sub y}MnO{sub 3} with y=0.1 or 0.2 have been investigated using synchrotron X-ray powder diffraction. At room temperature the structures change from Pm3-barmreversibleI4/mcmreversiblePbnm depending on the cation distribution, the different structures exhibiting different tilts of the MnO{sub 6} octahedra. High temperature diffraction measurements demonstrate the presence of, an apparently continuous, isosymmetric I4/mcm to I4/mcm phase transition associated with the removal of long range orbital ordering. Heating the manganites to still higher temperatures results in a continuous transition to the cubic Pm3-barm structure. A feature of such transitions is the continuous evolution of the octahedral tilt angle through the I4/mcm to I4/mcm phase transition. The orthorhombic structures do not exhibit orbital ordering and although a first order transition to the tetragonal structure is observed in Sr{sub 0.4}Ca{sub 0.5}Nd{sub 0.1}MnO{sub 3}, this high temperature tetragonal structure does not exhibit orbital ordering. - Graphical abstract: Structural studies of oxides of the type Sr{sub x}Ca{sub 1-x-y}Nd{sub y}MnO{sub 3} series illustrate the continuous removal of the octahedral tilting, despite the loss of orbital ordering.

  3. Electrical conductivity and glass formation in nitrile-functionalized pyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids: chain length and odd-even effects of the alkyl spacer between the pyrrolidinium ring and the nitrile group.

    PubMed

    Leys, Jan; Tripathi, Chandra Shekhar Pati; Glorieux, Christ; Zahn, Stefan; Kirchner, Barbara; Longuemart, Stéphane; Lethesh, Kallidanthiyil Chellappan; Nockemann, Peter; Dehaen, Wim; Binnemans, Koen

    2014-06-14

    The electrical conductivity of a series of pyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids, functionalized with a nitrile (cyano) group at the end of an alkyl chain attached to the cation, was studied in the temperature range between 173 K and 393 K. The glass formation of the ionic liquids is influenced by the length of the alkyl spacer separating the nitrile function from the pyrrolidinium ring. The electrical conductivity and the viscosity do not show a monotonic dependence on the alkyl spacer length, but rather an odd-even effect. An explanation for this behavior is given, including the potential energy landscape picture for the glass transition.

  4. Plagioclase zonation styles in hornblende gabbro inclusions from Little Glass Mountain, Medicine Lake volcano, California: Implications for fractionation mechanisms and the formation of composition gaps

    USGS Publications Warehouse

    Brophy, J.G.; Dorais, M.J.; Donnelly-Nolan, J.; Singer, B.S.

    1997-01-01

    The rhyolite of Little Glass Mountain (73-74% SiO2) is a single eruptive unit that contains inclusions of quenched andesite liquid (54-61% SiO2) and partially crystalline cumulate hornblende gabbro (53-55% SiO2). Based on previous studies, the quenched andesite inclusions and host rhyolite lava are related to one another through fractional crystallization and represent an example of a fractionation-generated composition gap. The hornblende gabbros represent the cumulate residue associated with the rhyolite-producing and composition gap-forming fractionation event. This study combines textural (Nomarski Differential Interference Contrast, NDIC, imaging), major element (An content) and trace element (Mg, Fe, Sr, K, Ti, Ba) data on the style of zonation of plagioclase crystals from representative andesite and gabbro inclusions, to assess the physical environment in which the fractionation event and composition gap formation took place. The andesite inclusions (54-61% SiO2) are sparsely phyric with phenocrysts of plagioclase, augite and Fe-oxide??olivine, +/-orthopyroxene, +/-hornblende set within a glassy to crystalline matrix. The gabbro cumulates (53-55% SiO2) consist of an interconnected framework of plagioclase, augite, olivine, orthopyroxene, hornblende and Fe-oxide along with highly vesicular interstitial glass (70-74% SiO2). The gabbros record a two-stage crystallization history of plagioclase + olivine + augite (Stage I) followed by plagioclase+orthopyroxene + hornblende + Fe-oxide (Stage II). Texturally, the plagioclase crystals in the andesite inclusions are characterized by complex, fine-scale oscillatory zonation and abundant dissolution surfaces. Compositionally (An content) the crystals are essentially unzoned from core-to-rim. These features indicate growth within a dynamic (convecting?), reservoir of andesite magma. In contrast, the plagioclase crystals in the gabbros are texturally smooth and featureless with strong normal zonation from An74 at the

  5. Fracture of Silicate Glasses: Ductile or Brittle?

    NASA Astrophysics Data System (ADS)

    Guin, Jean-Pierre; Wiederhorn, Sheldon M.

    2004-05-01

    Atomic force microscopy is used to investigate the possibility of cavity formation during crack growth in silicate glasses. Matching areas on both fracture surfaces were mapped and then compared. For silica glass, and soda-lime-silicate glass, the fracture surfaces matched to a resolution of better than 0.3 nm normal to the surface and 5 nm parallel to the surface. We could find no evidence for cavity formation in our study and suggest that completely brittle fracture occurs in glass.

  6. Transient nucleation in glasses

    NASA Technical Reports Server (NTRS)

    Kelton, K. F.

    1991-01-01

    Nucleation rates in condensed systems are frequently not at their steady state values. Such time dependent (or transient) nucleation is most clearly observed in devitrification studies of metallic and silicate glasses. The origin of transient nucleation and its role in the formation and stability of desired phases and microstructures are discussed. Numerical models of nucleation in isothermal and nonisothermal situations, based on the coupled differential equations describing cluster evolution within the classical theory, are presented. The importance of transient nucleation in glass formation and crystallization is discussed.

  7. Glass Artworks

    NASA Technical Reports Server (NTRS)

    1988-01-01

    Several NASA technologies have played part in growth and cost containment of studio glass art, among them a foam type insulation developed to meet a need for lightweight material that would reduce flame spread in aircraft fire. Foam comes in several forms and is widely used by glass artists, chiefly as an insulator for the various types of ovens used in glass working. Another Spinoff is alumina crucibles to contain molten glass. Before alumina crucibles were used, glass tanks were made of firebrick which tended to erode under high temperatures and cause impurities; this not only improved quality but made the process more cost effective. One more NASA technology that found its way into glass art working is a material known as graphite board, a special form of graphite originally developed for rocket motor applications. This graphite is used to exact compound angles and creates molds for poured glass artworks of dramatic design.

  8. Bioactive glass in tissue engineering

    PubMed Central

    Rahaman, Mohamed N.; Day, Delbert E.; Bal, B. Sonny; Fu, Qiang; Jung, Steven B.; Bonewald, Lynda F.; Tomsia, Antoni P.

    2011-01-01

    This review focuses on recent advances in the development and use of bioactive glass for tissue engineering applications. Despite its inherent brittleness, bioactive glass has several appealing characteristics as a scaffold material for bone tissue engineering. New bioactive glasses based on borate and borosilicate compositions have shown the ability to enhance new bone formation when compared to silicate bioactive glass. Borate-based bioactive glasses also have controllable degradation rates, so the degradation of the bioactive glass implant can be more closely matched to the rate of new bone formation. Bioactive glasses can be doped with trace quantities of elements such as Cu, Zn and Sr, which are known to be beneficial for healthy bone growth. In addition to the new bioactive glasses, recent advances in biomaterials processing have resulted in the creation of scaffold architectures with a range of mechanical properties suitable for the substitution of loaded as well as non-loaded bone. While bioactive glass has been extensively investigated for bone repair, there has been relatively little research on the application of bioactive glass to the repair of soft tissues. However, recent work has shown the ability of bioactive glass to promote angiogenesis, which is critical to numerous applications in tissue regeneration, such as neovascularization for bone regeneration and the healing of soft tissue wounds. Bioactive glass has also been shown to enhance neocartilage formation during in vitro culture of chondrocyte-seeded hydrogels, and to serve as a subchondral substrate for tissue-engineered osteochondral constructs. Methods used to manipulate the structure and performance of bioactive glass in these tissue engineering applications are analyzed. PMID:21421084

  9. Bioactive glass in tissue engineering.

    PubMed

    Rahaman, Mohamed N; Day, Delbert E; Bal, B Sonny; Fu, Qiang; Jung, Steven B; Bonewald, Lynda F; Tomsia, Antoni P

    2011-06-01

    This review focuses on recent advances in the development and use of bioactive glass for tissue engineering applications. Despite its inherent brittleness, bioactive glass has several appealing characteristics as a scaffold material for bone tissue engineering. New bioactive glasses based on borate and borosilicate compositions have shown the ability to enhance new bone formation when compared to silicate bioactive glass. Borate-based bioactive glasses also have controllable degradation rates, so the degradation of the bioactive glass implant can be more closely matched to the rate of new bone formation. Bioactive glasses can be doped with trace quantities of elements such as Cu, Zn and Sr, which are known to be beneficial for healthy bone growth. In addition to the new bioactive glasses, recent advances in biomaterials processing have resulted in the creation of scaffold architectures with a range of mechanical properties suitable for the substitution of loaded as well as non-loaded bone. While bioactive glass has been extensively investigated for bone repair, there has been relatively little research on the application of bioactive glass to the repair of soft tissues. However, recent work has shown the ability of bioactive glass to promote angiogenesis, which is critical to numerous applications in tissue regeneration, such as neovascularization for bone regeneration and the healing of soft tissue wounds. Bioactive glass has also been shown to enhance neocartilage formation during in vitro culture of chondrocyte-seeded hydrogels, and to serve as a subchondral substrate for tissue-engineered osteochondral constructs. Methods used to manipulate the structure and performance of bioactive glass in these tissue engineering applications are analyzed.

  10. On photo-expansion and microlens formation in (GeS{sub 2}){sub 0.74}(Sb{sub 2}S{sub 3}){sub 0.26} chalcogenide glass

    SciTech Connect

    Knotek, P.; Tichy, L.

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► Photo-expansion induced by sub-band-gap photons in GeSbS glass. ► One-step microlens formation. ► The topography of the microlenses detected by AFM and DHM. ► The good mechanical characteristics of the microlenses were obtained. ► Local light-induced overheating of the glass. -- Abstract: Photo-expansion of the bulk of (GeS{sub 2}){sub 0.74}(Sb{sub 2}S{sub 3}){sub 0.26} glass induced by sub-gap photons is studied employing specifically atomic force microscopy (AFM) namely an atomic force acoustic microscopy (AFAM) and a force spectroscopy and digital holographic microscopy. The results are discussed with respect to the possible role of light induced overheating in the process of photo-expansion.

  11. Electronic structure of metallic glasses

    SciTech Connect

    Oelhafen, P.; Lapka, R.; Gubler, U.; Krieg, J.; DasGupta, A.; Guentherodt, H.J.; Mizoguchi, T.; Hague, C.; Kuebler, J.; Nagel, S.R.

    1981-01-01

    This paper is organized in six sections and deals with (1) the glassy transition metal alloys, their d-band structure, the d-band shifts on alloying and their relation to the alloy heat of formation (..delta..H) and the glass forming ability, (2) the glass to crystal phase transition viewed by valence band spectroscopy, (3) band structure calculations, (4) metallic glasses prepared by laser glazing, (5) glassy normal metal alloys, and (6) glassy hydrides.

  12. Glass Research

    NASA Technical Reports Server (NTRS)

    Weinberg, M. C.

    1985-01-01

    Research efforts span three general areas of glass science: glass refining, gel-derived glasses, and nucleation and crystallization of glasses. Gas bubbles which are present in a glass product are defects which may render the glass totally useless for the end application. For example, optical glasses, laser host glasses, and a variety of other specialty glasses must be prepared virtually defect free to be employable. Since a major mechanism of bubble removal, buoyant rise, is virtually inoperative in microgravity, glass fining will be especially difficult in space. On the other hand, the suppression of buoyant rise and the ability to perform containerless melting experiments in space allows the opportunity to carry out several unique bubble experiments in space. Gas bubble dissolution studies may be performed at elevated temperatures for large bubbles with negligible bubble motion. Also, bubble nucleation studies may be performed without the disturbing feature of heterogeneous bubble nucleation at the platinum walls. Ground based research efforts are being performed in support of these potential flight experiments.

  13. International Congress on Glass XII

    SciTech Connect

    Doremus, R H; LaCourse, W C; Mackenzie, J D; Varner, J R; Wolf, W W

    1980-01-01

    A total of 158 papers are included under nine headings: structure and glass formation; optical properties; electrical and magnetic properties; mechanical properties and relaxation; mass transport; chemical durability and surfaces; nucleation; crystallization; and glass ceramics; processing; and automatic controls. Separate abstracts were prepared for eight papers; four of the remaining papers had been processed previously for the data base. (DLC)

  14. Formation and X-ray Structures of Eight- and Sixteen-Membered Rings (ArC)(n)()N(2)(n)()(SPh)(n)() [n = 2, Ar = 4-XC(6)H(4) (X = Br, CF(3)); n = 4, Ar = 4-BrC(6)H(4)] and the Electronic Structures of (HC)(2)N(4)(SH)(2) and (HC)(2)N(4)(SH)(2)(2)(-).

    PubMed

    Chivers, Tristram; Parvez, Masood; Vargas-Baca, Ignacio; Ziegler, Tom; Zoricak, Peter

    1997-04-01

    Optimum yields of heterocyclic products are obtained when the reaction of 4-XC(6)H(4)CN(2)(SiMe(3))(3) (X = Br, CF(3)) with PhSCl in a 1:3 molar ratio in CH(2)Cl(2) is carried out at -100 degrees C followed by the mixture being warmed to -70 degrees C for 16 h. Under these conditions the eight-membered rings (4-XC(6)H(4))(2)C(2)N(4)S(2)Ph(2) (1b, X = Br; 1c, X = CF(3)) are obtained in 64 and 80% yields, respectively, in addition to the purple diazenes Z,E,Z-PhSN(4-XC(6)H(4))CN=NC(C(6)H(4)X-4)NSPh (2b, 8%; 2c, 19%) and, in the case of X = Br, the sixteen-membered ring (4-BrC(6)H(4))(4)C(4)N(8)S(4)Ph(4) (3) (8%). With a reaction time of 40 h the yield of 3 is increased to 25%. By contrast, the reaction of 3-BrC(6)H(4)CN(2)(SiMe(3))(3) with 3 equiv of PhSCl at -70 degrees C gives Z,E,Z-PhSN(3-BrC(6)H(4))CN=NC(3-BrC(6)H(4))NSPh in 75% yield. A possible pathway for the formation of cyclic products is proposed. The solid-state structures of 1b, 1c, and 3 were determined by X-ray crystallography. The eight-membered rings 1b and 1c adopt long boat conformations with the phenyl groups (attached to S) in equatorial positions. Density functional theory (DFT) calculations for the model ring system (HC)(2)N(4)(SH)(2) reveal that the observed C(2)(v)() geometry is the result of a second-order Jahn-Teller distortion of the planar (D(2)(h)()) structure. The chair conformer (C(2)(h)()) is only ca. 10 kJ mol(-)(1) higher in energy than the boat conformer. The hypothetical dianion (HC)(2)N(4)(SH)(2)(2)(-) is predicted to have a transannular S.S contact of about 2.5 Å. The sixteen-membered ring 3 has a cradle-like structure with S(4) symmetry.

  15. Glass corrosion in natural environment

    NASA Technical Reports Server (NTRS)

    Thorpe, Arthur N.

    1989-01-01

    A series of studies of the effects of solutes which appear in natural aqueous environments, specifically Mg and Al, under controlled conditions, permit characterization of the retardation of silicate glass leaching in water containing such solutes. In the case of Mg the interaction with the glass appears to consist of exchange with alkali ions present in the glass to a depth of several microns. The effect of Al can be observed at much lower levels, indicating that the mechanism in the case of Al involves irreversible formation of aluminosilicate species at the glass surface.

  16. Glass formation and structure in the MgSiO{sub 3}-Mg{sub 2}SiO{sub 4} pseudobinary system: From degraded networks to ioniclike glasses

    SciTech Connect

    Kalampounias, A. G.; Nasikas, N. K.; Papatheodorou, G. N.

    2009-09-21

    A series of glasses xMgO-(1-x)SiO{sub 2} with compositions from enstatite MgSiO{sub 3} (x=0.5) to forsterite Mg{sub 2}SiO{sub 4} (x=0.667) in mole fraction intervals of x{approx_equal}0.02 have been prepared by containerless levitation techniques and CO{sub 2} laser heating. Polarized and depolarized Raman spectra measured at ambient conditions for all these glasses show systematic and smooth band intensity changes with composition. Analysis of the Raman band contours in terms of vibrations due to different oxygen bridged SiO{sub 4} tetrahedra (Q{sup i}, species analysis) undoubtedly shows that bridging oxygens are present in all glasses studied even in the limit of the forsterite composition where bridged Si{sub 2}O{sub 7}{sup 6-} ionic dimers are formed. Furthermore the relative amounts of the Q{sup i} species change smoothly with composition while at high MgO content 'free' oxygens are present presumably forming Mg-O-Mg bridges, which contribute to the glass stability at these compositions. Raman spectra measurements at different temperature below T{sub g} show small alterations in the Q{sup i} species in the MgSiO{sub 3} region while no changes were observed in the Mg{sub 2}SiO{sub 4} region. The Boson peak frequency is practically invariant on both composition and temperature and this is in contrast to the systematics followed by most silicate glasses. It is suggested that at compositions near the forsterite ioniclike glasses are formed arising from a very fragile liquid.

  17. 2012 Problem 13: Misty Glass

    NASA Astrophysics Data System (ADS)

    Huang, Shan; Li, Xiao; Gao, Wenli; Zhou, Huijun

    2015-10-01

    Based on diffraction theory, we propose a model to explain the formation of colorful rings created by a misty glass. The model is verified by examining the relation between the size of the ring and size of the droplets.

  18. Metallic glasses.

    PubMed

    Greer, A L

    1995-03-31

    Amorphous metallic alloys, relative newcomers to the world of glasses, have properties that are unusual for solid metals. The metallic glasses, which exist in a very wide variety of compositions, combine fundamental interest with practical applications. They also serve as precursors for exciting new nanocrystalline materials. Their magnetic (soft and hard) and mechanical properties are of particular interest.

  19. Melting of Soil Rich in Quartz by Radiation from Aerial Bursts - A Possible Cause of Formation of Libyan Desert Glass and Layered Tektites

    NASA Astrophysics Data System (ADS)

    Svetsov, V. V.; Wasson, J. T.

    2007-03-01

    Impact scenarios with breakup and atmospheric deceleration of meteoroids, in which Libyan Desert Glass and layered tektites could be produced, are considered. Amounts of quartz-rich soil melted by radiation from the bursts are estimated.

  20. Combinatorial development of bulk metallic glasses.

    PubMed

    Ding, Shiyan; Liu, Yanhui; Li, Yanglin; Liu, Ze; Sohn, Sungwoo; Walker, Fred J; Schroers, Jan

    2014-05-01

    The identification of multicomponent alloys out of a vast compositional space is a daunting task, especially for bulk metallic glasses composed of three or more elements. Despite an increasing theoretical understanding of glass formation, bulk metallic glasses are predominantly developed through a sequential and time-consuming trial-and-error approach. Even for binary systems, accurate quantum mechanical approaches are still many orders of magnitude away from being able to simulate the relatively slow kinetics of glass formation. Here, we present a high-throughput strategy where ∼3,000 alloy compositions are fabricated simultaneously and characterized for thermoplastic formability through parallel blow forming. Using this approach, we identified the composition with the highest thermoplastic formability in the glass-forming system Mg-Cu-Y. The method provides a versatile toolbox for unveiling complex correlations of material properties and glass formation, and should facilitate a drastic increase in the discovery rate of metallic glasses.

  1. Sm3+-doped fluorophosphate glass: Formation of Ag nanoparticles via Ag+/K+ ion exchange and their effects on optical and dielectric properties

    NASA Astrophysics Data System (ADS)

    Thomas, Sunil; Sajna, M. S.; Nayab Rasool, Sk.; Gopinath, Manju; Joseph, Cyriac; Unnikrishnan, N. V.

    2015-01-01

    Silver-potassium ion exchange on Sm3+-doped fluorophosphate glass has been carried out via thermal diffusion method. The crystallite size of silver was estimated to be 19 nm from X-ray diffraction pattern and it was confirmed using transmission electron microscopy analysis. Assessment of the optical properties has been carried out by absorption, photoluminescence and lifetime measurements. Present glass system exhibits favorable optical properties for possible uses as optical amplifiers, sensors and planar waveguides. The energy transfer mechanism from silver to samarium and the surface plasmon resonance of silver nanoparticles are discussed for the ion exchanged glass. The dielectric studies have been carried out in order to assess the influence of silver on the dielectric properties and ac conductivity of the ion exchanged glass. Coulomb blockade effects have been discussed to clarify the enhancement in the insulating behavior of the glass by the incorporation of silver nanoparticles. The power-law and Cole-Cole parameters were determined and the influence of silver on these parameters is discussed.

  2. Formation of a plano-convex micro-lens array in fused silica glass by using a CO2 laser-assisted reshaping technique

    NASA Astrophysics Data System (ADS)

    Sohn, Ik-Bu; Yoo, Dongyoon; Noh, Young-Chul; Sung, Jae-Hee; Lee, Seong-Ku; Choi, Hun-Kook; Ahsan, Md. Shamim

    2016-08-01

    We report on fabricating high-fill-factor plano-convex spherical and square micro-lens arrays on fused silica glass surface by using a CO2 laser-assisted reshaping technique. Initially, periodic micro-pillars are encoded on glass surfaces by means of a femtosecond laser beam, afterwards, the micro-pillars are polished several times by irradiating a CO2 laser beam on top of the micro-pillars. Consequently, a spherical micro-lens array with micro-lens size of 50 μm × 50 μm and a square micro-lens array with micro-lens size of 100 μm × 100 μm are formed on the surface of the fused silica glass. We also study the intensity distribution of light passing through the glass sample engraved with a spherical micro-lens array. The simulation result shows that the focal length of the spherical micro-lens array is 35 μm. Furthermore, we investigate the optical properties of glass samples with engraved micro-lens arrays. The proposed CO2-laser-based reshaping technique is simple and fast and shows promises for fabricating arrays of smooth micro-lenses in various transparent materials.

  3. Glass microspheres

    SciTech Connect

    Day, D.E.; Ehrhardt, G.J.

    1988-12-06

    This patent describes a glass microsphere having a diameter of about 54 micrometers or less and adapted for radiation therapy of a mammal. The glass consists of essentially an yttrium oxide-aluminosilicate glass composition lying substantially within a quadrilateral region of the ternary composition diagram of the yttria-alumina-silica system, the quadrilateral region being defined by its four corners having the following combination of weight proportions of the components: 20% silica, 10% alumina, 70% yttria; 70% silica, 10% alumina, 20% yttria; 70% silica, 20% alumina, 10% yttria; and 20% silica, 45% alumina, 35% yttria, the glass having a chemical durability such that subsequent to irradiation and administration of the microsphere to the mammal, the mircosphere will not release a significant amount of yttrium-90 into the mammal's system.

  4. Glass electrolytes

    SciTech Connect

    Not Available

    1984-06-25

    The objective of this research is a glass electrolyte for use in sodium/sulfur batteries that has a low resistivity (100 ohm-cm at 300/sup 0/C) and is stable in the cell environment. Experiments in this program are focussed on glasses in the quaternary system: soda, alumina, zirconia and silica. The FY 1983 research on glass analogs of NASICON, parallel thermodynamic calculations, and a review of the literature in the areas of glass conductivity and corrosion resistance led to selection of this system for more detailed investigation. The main program elements are: (1) conductivity measurements at 300 to 500/sup 0/C; (2) differential thermal analysis for determination of glass-transition and crystallization temperatures; (3) static corrosion tests at 400/sup 0/C using Na, Na/sub 2/S/sub 4/, and S; (4) mechanical strength and fracture toughness measurements; and (5) sodium/sulfur cell tests at 350/sup 0/C. Elements (1) and (2) are nearly completed; element (3) is being initiated using the glasses prepared for (1) and (2), and elements (4) and (5) will begin in the first and second quarters of FY 1985, respectively. Fourteen quaternary glasses having a broad range of compositions have been made. The resistivities of these glasses at 300/sup 0/C extended from 130 to 3704 ohm-cm; the activation energies for conduction extended from 0.488 to 0.684 eV, and the glass transition temperatures extended from 397 to 685/sup 0/C. Through a multiple linear regression analysis of these data response surfaces were generated for resistivity, activation energy for conduction, and glass transition temperature over the composition region within the quaternary system that is bounded by SiO/sub 2/, Na/sub 2/O/sub 3/, Na/sub 2/AlO/sub 4/ and Na/sub 2/ZrO/sub 3/. These response surfaces indicated a new region of high conductivity and high glass transition temperature in the neighborhood of 42% soda, 31% silica and 27% alumina plus zirconia.

  5. Crystallization of copper metaphosphate glass

    NASA Technical Reports Server (NTRS)

    Bae, Byeong-Soo; Weinberg, Michael C.

    1993-01-01

    The effect of the valence state of copper in copper metaphosphate glass on the crystallization behavior and glass transition temperature has been investigated. The crystallization of copper metaphosphate is initiated from the surface and its main crystalline phase is copper metaphosphate (Cu(PO)3),independent of the (Cu sup 2+)/(Cu(total)). However, the crystal morphology, the relative crystallization rates, and their temperature dependences are affected by the (Cu sup 2+)/(Cu (total)) ratio in the glass. On the other hand, the totally oxidized glass crystallizes from all over the surface. The relative crystallization rate of the reduced glass to the totally oxidized glass is large at low temperature, but small at high temperature. The glass transition temperature of the glass increases as the (Cu sup 2+)/(Cu(total)) ratio is raised. It is also found that the atmosphere used during heat treatment does not influence the crystallization of the reduced glass, except for the formation of a very thin CuO surface layer when heated in air.

  6. Effect of MST on Crystallinity of CST/Sludge Glasses

    SciTech Connect

    Andrews, M.K.

    1998-11-18

    In support of the Salt Disposition team, the effects of monosodium titanate (MST) on two glass formulations were investigated. These glass formulations combined a blend-type sludge with Crystalline Silicotitanate (CST) and glass formers (or frit). The objective of the testing was to determine if the MST would lead to crystal formation in the glasses.

  7. High modulus high temperature glass fibers

    NASA Technical Reports Server (NTRS)

    Bacon, J. F.

    1973-01-01

    The search for a new high-modulus, high-temperature glass fiber involved the preparation of 500 glass compositions lying in 12 glass fields. These systems consisted primarily of low atomic number oxides and rare-earth oxides. Direct optical measurements of the kinetics of crystallization of the cordierite-rare earth system, for example, showed that the addition of rare-earth oxides decreased the rate of formation of cordierite crystals. Glass samples prepared from these systems proved that the rare-earth oxides made large specific contributions to the Young's modulus of the glasses. The best glasses have moduli greater than 21 million psi, the best glass fibers have moduli greater than 18 million psi, and the best glass fiber-epoxy resin composites have tensile strengths of 298,000 psi, compressive strengths of at least 220,000 psi, flexural strengths of 290,000 psi, and short-beam shear strengths of almost 17,000 psi.

  8. Molecular glasses for nuclear waste encapsulation

    SciTech Connect

    Ropp, R.C.

    1982-09-28

    A molecular glass based upon a phosphate of aluminum, or other trivalent metal, provides significant improvement over prior art glasses for encapsulation of high level radioactive nuclear waste. When containing a controlled amount of those elemental oxides found in a typical nuclear waste, the waste-glass would not devitrify under conditions which produced devitrification in the non-nuclear-waste-containing glass, exhibited hydrolysis losses lower by an order of magnitude, had high solvency power for those elemental oxides, exhibited little tendency for internal crystallite formation, and possessed other desirable physical characteristics, all in direct antithesis to the properties of the best prior-known glasses used for this application.

  9. Method for manufacturing glass frit

    DOEpatents

    Budrick, Ronald G.; King, Frank T.; Nolen, Jr., Robert L.; Solomon, David E.

    1977-01-01

    A method of manufacturing a glass frit for use in the manufacture of uniform glass microspheres to serve as containers for laser fusion fuel to be exposed to laser energy which includes the formation of a glass gel which is then dried, pulverized, and very accurately sized to particles in a range of, for example, 125 to 149 micrometers. The particles contain an occluded material such as urea which expands when heated. The sized particles are washed, dried, and subjected to heat to control the moisture content prior to being introduced into a system to form microspheres.

  10. Method of determining glass durability

    DOEpatents

    Jantzen, Carol Maryanne; Pickett, John Butler; Brown, Kevin George; Edwards, Thomas Barry

    1998-01-01

    A process for determining one or more leachate concentrations of one or more components of a glass composition in an aqueous solution of the glass composition by identifying the components of the glass composition, including associated oxides, determining a preliminary glass dissolution estimator, .DELTA.G.sub.p, based upon the free energies of hydration for the component reactant species, determining an accelerated glass dissolution function, .DELTA.G.sub.a, based upon the free energy associated with weak acid dissociation, .DELTA.G.sub.a.sup.WA, and accelerated matrix dissolution at high pH, .DELTA.G.sub.a.sup.SB associated with solution strong base formation, and determining a final hydration free energy, .DELTA.G.sub.f. This final hydration free energy is then used to determine leachate concentrations for elements of interest using a regression analysis and the formula log.sub.10 (N C.sub.i (g/L))=a.sub.i +b.sub.i .DELTA.G.sub.f. The present invention also includes a method to determine whether a particular glass to be produced will be homogeneous or phase separated. The present invention is also directed to methods of monitoring and controlling processes for making glass using these determinations to modify the feedstock materials until a desired glass durability and homogeneity is obtained.

  11. Method of determining glass durability

    DOEpatents

    Jantzen, C.M.; Pickett, J.B.; Brown, K.G.; Edwards, T.B.

    1998-12-08

    A process is described for determining one or more leachate concentrations of one or more components of a glass composition in an aqueous solution of the glass composition by identifying the components of the glass composition, including associated oxides, determining a preliminary glass dissolution estimator, {Delta}G{sub p}, based upon the free energies of hydration for the component reactant species, determining an accelerated glass dissolution function, {Delta}G{sub a}, based upon the free energy associated with weak acid dissociation, {Delta}G{sub a}{sup WA}, and accelerated matrix dissolution at high pH, {Delta}G{sub a}{sup SB} associated with solution strong base formation, and determining a final hydration free energy, {Delta}G{sub f}. This final hydration free energy is then used to determine leachate concentrations for elements of interest using a regression analysis and the formula log{sub 10}(N C{sub i}(g/L))=a{sub i} + b{sub i}{Delta}G{sub f}. The present invention also includes a method to determine whether a particular glass to be produced will be homogeneous or phase separated. The present invention is also directed to methods of monitoring and controlling processes for making glass using these determinations to modify the feedstock materials until a desired glass durability and homogeneity is obtained. 4 figs.

  12. Silicate Glass Corrosion Mechanism revisited

    NASA Astrophysics Data System (ADS)

    Geisler, Thorsten; Lenting, Christoph; Dohmen, Lars

    2015-04-01

    Understanding the mechanism(s) of aqueous corrosion of nuclear waste borosilicate glasses is essential to predict their long-term aqueous durability in a geologic repository. Several observations have been made with compositionally different silicate glasses that cannot be explained by any of the established glass corrosion models. These models are based on diffusion-controlled ion exchange and subsequent structural reorganisation of a leached, hydrated residual glass, leaving behind a so-called gel layer. In fact, the common observation of lamellar to more complex pattern formation observed in experiment and nature, the porous structure of the corrosion layer, an atomically sharp boundary between the corrosion zone and the underlying pristine glass, as well as results of novel isotope tracer and in situ, real time experiments rather support an interface-coupled glass dissolution-silica reprecipitation model. In this model, the congruent dissolution of the glass is coupled in space and time to the precipitation and growth of amorphous silica at an inwardly moving reaction front. We suggest that these coupled processes have to be considered to realistically model the long-term performance of silicate glasses in aqueous environments.

  13. Pinhole Glasses

    NASA Astrophysics Data System (ADS)

    Colicchia, Giuseppe; Hopf, Martin; Wiesner, Hartmut; Zollman, Dean

    2008-01-01

    Eye aberrations are commonly corrected by lenses that restore vision by altering rays before they pass through the cornea. Some modern promoters claim that pinhole glasses are better than conventional lenses in correcting all kinds of refractive defects such as myopia (nearsighted), hyperopia (farsighted), astigmatisms, and presbyopia. Do pinhole glasses really give better vision? Some ways to use this question for motivation in teaching optics have been discussed. For this column we include a series of experiments that students can complete using a model of the eye and demonstrate issues related to pinhole vision correction.

  14. Native amorphous nanoheterogeneity in gallium germanosilicates as a tool for driving Ga2O3 nanocrystal formation in glass for optical devices.

    PubMed

    Sigaev, Vladimir N; Golubev, Nikita V; Ignat'eva, Elena S; Champagnon, Bernard; Vouagner, Dominique; Nardou, Eric; Lorenzi, Roberto; Paleari, Alberto

    2013-01-01

    Nanoparticles in amorphous oxides are a powerful tool for embedding a wide range of functions in optical glasses, which are still the best solutions in several applications in the ever growing field of photonics. However, the control of the nanoparticle size inside the host material is often a challenging task, even more challenging when detrimental effects on light transmittance have to be avoided. Here we show how the process of phase separation and subsequent nanocrystallization of a Ga-oxide phase can be controlled in germanosilicates - prototypal systems in optical telecommunications - starting from a Ga-modified glass composition designed to favour uniform liquid-liquid phase separation in the melt. Small angle neutron scattering data demonstrate that nanosized structuring occurs in the amorphous as-quenched glass and gives rise to initially smaller nanoparticles, by heating, as in a secondary phase separation. By further heating, the nanophase evolves with an increase of nanoparticle gyration radius, from a few nm to a saturation value of about 10 nm, through an initial growing process followed by an Ostwald ripening mechanism. Nanoparticles finally crystallize, as indicated by transmission electron microscopy and X-ray diffraction, as γ-Ga(2)O(3)- a metastable gallium oxide polymorph. Infrared reflectance and photoluminescence, together with the optical absorption of Ni ions used as a probe, give an indication of the underlying interrelated processes of the structural change in the glass and in the segregated phase. As a result, our data give for the first time a rationale for designing Ga-modified germanosilicates at the nanoscale, with the perspective of a detailed nanostructuring control.

  15. Alteration layer formation of Ca- and Zn-oxide bearing alkali borosilicate glasses for immobilisation of UK high level waste: A vapour hydration study

    NASA Astrophysics Data System (ADS)

    Cassingham, N. J.; Corkhill, C. L.; Stennett, M. C.; Hand, R. J.; Hyatt, N. C.

    2016-10-01

    The UK high level nuclear waste glass modified with CaO/ZnO was investigated using the vapour phase hydration test, performed at 200 °C, with the aim of understanding the impact of the modification on the chemical composition and microstructure of the alteration layer. Experiments were undertaken on non-modified and CaO/ZnO-modified base glass, with or without 25 wt% of simulant Magnox waste calcine. The modification resulted in a dramatic reduction in gel layer thickness and also a reduction in the reaction rate, from 3.4 ± 0.3 g m-2 d-1 without CaO/ZnO modification to 0.9 ± 0.1 g m-2 d-1 with CaO/ZnO. The precipitated phase assemblage for the CaO/ZnO-modified compositions was identified as hydrated Ca- and Zn-bearing silicate phases, which were absent from the non-modified counterpart. These results are in agreement with other recent studies showing the beneficial effects of ZnO additions on glass durability.

  16. Pinhole Glasses

    ERIC Educational Resources Information Center

    Colicchia, Giuseppe; Hopf, Martin; Wiesner, Hartmut; Zollman, Dean

    2008-01-01

    Eye aberrations are commonly corrected by lenses that restore vision by altering rays before they pass through the cornea. Some modern promoters claim that pinhole glasses are better than conventional lenses in correcting all kinds of refractive defects such as myopia (nearsighted), hyperopia (farsighted), astigmatisms, and presbyopia. Do pinhole…

  17. Glass Ceramic Formulation Data Package

    SciTech Connect

    Crum, Jarrod V.; Rodriguez, Carmen P.; McCloy, John S.; Vienna, John D.; Chung, Chul-Woo

    2012-06-17

    A glass ceramic waste form is being developed for treatment of secondary waste streams generated by aqueous reprocessing of commercial used nuclear fuel (Crum et al. 2012b). The waste stream contains a mixture of transition metals, alkali, alkaline earths, and lanthanides, several of which exceed the solubility limits of a single phase borosilicate glass (Crum et al. 2009; Caurant et al. 2007). A multi-phase glass ceramic waste form allows incorporation of insoluble components of the waste by designed crystallization into durable heat tolerant phases. The glass ceramic formulation and processing targets the formation of the following three stable crystalline phases: (1) powellite (XMoO4) where X can be (Ca, Sr, Ba, and/or Ln), (2) oxyapatite Yx,Z(10-x)Si6O26 where Y is alkaline earth, Z is Ln, and (3) lanthanide borosilicate (Ln5BSi2O13). These three phases incorporate the waste components that are above the solubility limit of a single-phase borosilicate glass. The glass ceramic is designed to be a single phase melt, just like a borosilicate glass, and then crystallize upon slow cooling to form the targeted phases. The slow cooling schedule is based on the centerline cooling profile of a 2 foot diameter canister such as the Hanford High-Level Waste canister. Up to this point, crucible testing has been used for glass ceramic development, with cold crucible induction melter (CCIM) targeted as the ultimate processing technology for the waste form. Idaho National Laboratory (INL) will conduct a scaled CCIM test in FY2012 with a glass ceramic to demonstrate the processing behavior. This Data Package documents the laboratory studies of the glass ceramic composition to support the CCIM test. Pacific Northwest National Laboratory (PNNL) measured melt viscosity, electrical conductivity, and crystallization behavior upon cooling to identify a processing window (temperature range) for melter operation and cooling profiles necessary to crystallize the targeted phases in the

  18. Oxygen miscibility gap and spin glass formation in the pyrochlore Lu{sub 2}Mo{sub 2}O{sub 7}

    SciTech Connect

    Clark, L.; Ritter, C.; Harrison, A.; Attfield, J.P.

    2013-07-15

    Rare earth (R) molybdate pyrochlores, R{sub 2}Mo{sub 2}O{sub 7}, are of interest as frustrated magnets. Polycrystalline samples of Lu{sub 2}Mo{sub 2}O{sub 7−x} prepared at 1600 °C display a coexistence of cubic pyrochlore phases. Rietveld fits to powder neutron diffraction data and chemical analyses show that the miscibility gap is between a stoichiometric x=0 and an oxygen-deficient x≈0.4 phase. Lu{sub 2}Mo{sub 2}O{sub 7} behaves as a spin glass material, with a divergence of field cooled and zero field cooled DC magnetic susceptibilities at a spin freezing temperature T{sub f}=16 K, that varies with frequency in AC measurements following a Vogel–Fulcher law. Lu{sub 2}Mo{sub 2}O{sub 6.6} is more highly frustrated spin glass and has T{sub f}=20 K. - Graphical abstract: The cubic Lu{sub 2}Mo{sub 2}O{sub 7−x} system exhibits a miscibility gap between coexisting pyrochlore phases at 1600 °C. Neutron powder diffraction refinement and chemical analysis shows that the gap separates stoichiometric x=0 and oxygen-deficient x≈0.4 phases. Lu{sub 2}Mo{sub 2}O{sub 7−x} has a frustrated spin glass ground state that is sensitive to the oxygen content. - Highlights: • The cubic Lu{sub 2}Mo{sub 2}O{sub 7−x} system has a miscibility gap between coexisting pyrochlore phases at 1600 °C. • Neutron powder diffraction shows that the gap separates x=0 and oxygen-deficient x≈0.4 phases. • Lu{sub 2}Mo{sub 2}O{sub 7−x} has a frustrated spin glass ground state that is sensitive to the oxygen content.

  19. Children's Glasses

    NASA Astrophysics Data System (ADS)

    Akerskog, Gunnar; Soderlund, Jan

    1980-07-01

    There is a common opinion among eye specialists and opticians that children's glasses often are not shaped for optimal fitting. A fundamental reason for this is the lack of data for the shaping of the bows, with the result that most children's glasses are reduced copies of adult's glasses. This report describes a photogrammetric method for collection of primary data for manufac-turing bows for children. An ordinary amateur camera was equipped with a stereo-adapter. With a few arrangements, such as projecting a pattern on the face and keeping the hair away from the ears, 600 children were photographed. A calibration photograph was exposed at the beginning and end of each film or when the equipment had been transported or otherwise disturbed. The photographs were measured in a stereocomparator and the coordinates analytically corrected for distortion. After determination of model coordinates the requested geometric information, such as pupillar distance, eye-ear distance, location of the bridge of the nose etc, was calculated. The shapes of average noses were presented as profile plots.

  20. Spectroscopic study of biologically active glasses

    NASA Astrophysics Data System (ADS)

    Szumera, M.; Wacławska, I.; Mozgawa, W.; Sitarz, M.

    2005-06-01

    It is known that the chemical activity phenomenon is characteristic for some inorganic glasses and they are able to participate in biological processes of living organisms (plants, animals and human bodies). An example here is the selective removal of silicate-phosphate glass components under the influence of biological solutions, which has been applied in designing glasses acting as ecological fertilizers of controlled release rate of the nutrients for plants. The structure of model silicate-phosphate glasses containing the different amounts of the glass network formers, i.e. Ca 2+ and Mg 2+, as a binding components were studied. These elements besides other are indispensable of the normal growth of plants. In order to establish the function and position occupied by the particular components in the glass structure, the glasses were examined by FTIR spectroscopy (with spectra decomposition) and XRD methods. It has been found that the increasing amount of MgO in the structure of silicate-phosphate glasses causes the formation of domains the structure of which changes systematically from a structure of the cristobalite type to a structure corresponding to forsterite type. Whilst the increasing content of CaO in the structure of silicate-phosphate glasses causes the formation of domains the structure of which changes from a structure typical for cristobalite through one similar to the structure of calcium orthophosphate, to a structure corresponding to calcium silicates. The changing character of domains structure is the reason of different chemical activity of glasses.

  1. Formation of silicon-on-insulator layer with midair cavity for meniscus force-mediated layer transfer and high-performance transistor fabrication on glass

    NASA Astrophysics Data System (ADS)

    Akazawa, Muneki; Sakaike, Kohei; Higashi, Seiichiro

    2015-08-01

    We attempted to transfer a phosphorus ion (P+)-implanted oxidized silicon-on-insulator (SOI) layer with a midair cavity to a glass substrate using meniscus force at a low temperature. The SiO2 column size was controlled by etching time and the minimum column size was 104 nm. The transfer yield of the implanted sample was significantly improved by decreasing the column size, and the maximum transfer yield was 95% when the implantation dose was 1 × 1015 cm-2. The causes of increasing transfer yield are considered to be the tapered SiO2 column shape and the hydrophilicity of the surface of oxidized samples with implantation. N-channel thin-film transistors (TFTs) fabricated using the films on glass at 300 °C showed a field-effect mobility of 505 cm2 V-1 s-1, a threshold voltage of 2.47 V and a subthreshold swing of 324 mV/dec. on average.

  2. Experimental evidence of the formation of a reentrant spin-glass phase in alloying two ferromagnetic CoPt3 and MnPt3 compounds

    NASA Astrophysics Data System (ADS)

    Kim, T. H.; Cadeville, M. C.; Dinia, A.; Rakoto, H.

    1996-01-01

    The magnetic properties and the magnetic phase diagram of the pseudobinary Co1-xMnxPt3 system resulting from alloying two ferromagnetic CoPt3 and MnPt3 compounds have been investigated. Structural and microstructural characterizations added to thorough preparation conditions yield well-ordered samples having the L12 structure, large ordered domains, and a long-range order parameter close to its maximum value. Magnetic properties including ac and dc susceptibilities, zero-field-cooled and field-cooled magnetizations as a function of temperature and field (0-35 T) have been investigated. The resulting magnetic phase diagram displays, below a ferromagnetic region spreading over the whole (0<=x<=1) concentration range, a reentrant spin-glass phase for 0glass orderings. This phase diagram is well described in the theoretical infinite-range model of Gabay and Toulouse. The randomness of the average exchange interaction is suggested to arise from competing magnetic interactions between the positive values of J2ndCoCo and J2ndMnMn and the negative value of J2ndCoMn for 3d atoms in position of second-nearest neighbors.

  3. Glass formability in medium-sized molecular systems/pharmaceuticals. I. Thermodynamics vs. kinetics.

    PubMed

    Tu, Wenkang; Li, Xiangqian; Chen, Zeming; Liu, Ying Dan; Labardi, Massimiliano; Capaccioli, Simone; Paluch, M; Wang, Li-Min

    2016-05-01

    Scrutinizing critical thermodynamic and kinetic factors for glass formation and the glass stability of materials would benefit the screening of the glass formers for the industry of glassy materials. The present work aims at elucidating the factors that contribute to the glass formation by investigating medium-sized molecules of pharmaceuticals. Glass transition related thermodynamics and kinetics are performed on the pharmaceuticals using calorimetric, dielectric, and viscosity measurements. The characteristic thermodynamic and kinetic parameters of glass transition are found to reproduce the relations established for small-molecule glass formers. The systematic comparison of the thermodynamic and kinetic contributions to glass formation reveals that the melting-point viscosity is the crucial quantity for the glass formation. Of more interest is the finding of a rough correlation between the melting-point viscosity and the entropy of fusion normalized by the number of beads of the pharmaceuticals, suggesting the thermodynamics can partly manifest its contribution to glass formation via kinetics. PMID:27155640

  4. Glass formability in medium-sized molecular systems/pharmaceuticals. I. Thermodynamics vs. kinetics

    NASA Astrophysics Data System (ADS)

    Tu, Wenkang; Li, Xiangqian; Chen, Zeming; Liu, Ying Dan; Labardi, Massimiliano; Capaccioli, Simone; Paluch, M.; Wang, Li-Min

    2016-05-01

    Scrutinizing critical thermodynamic and kinetic factors for glass formation and the glass stability of materials would benefit the screening of the glass formers for the industry of glassy materials. The present work aims at elucidating the factors that contribute to the glass formation by investigating medium-sized molecules of pharmaceuticals. Glass transition related thermodynamics and kinetics are performed on the pharmaceuticals using calorimetric, dielectric, and viscosity measurements. The characteristic thermodynamic and kinetic parameters of glass transition are found to reproduce the relations established for small-molecule glass formers. The systematic comparison of the thermodynamic and kinetic contributions to glass formation reveals that the melting-point viscosity is the crucial quantity for the glass formation. Of more interest is the finding of a rough correlation between the melting-point viscosity and the entropy of fusion normalized by the number of beads of the pharmaceuticals, suggesting the thermodynamics can partly manifest its contribution to glass formation via kinetics.

  5. Alteration kinetics of the glass-ceramic zirconolite and role of the alteration film Comparison with the SON68 glass

    NASA Astrophysics Data System (ADS)

    Martin, C.; Ribet, I.; Frugier, P.; Gin, S.

    2007-06-01

    The glass-ceramic zirconolite is being considered for specific conditioning of plutonium or the minor actinides. The actinides are distributed throughout the zirconolite crystals and the residual glass phase. Since zirconolite alteration is extremely limited, actinide release from the glass-ceramic material is mainly attributable to alteration of the residual glass. Specimens corresponding to the residual glass phase alone were therefore altered under different conditions to compare their kinetics with the one of the SON68 glass (inactive R7T7 type glass). Glass-ceramic zirconolite presents a more important rate decrease occuring more rapidly and that induces a quantity of glass altered at least 10 times as small as for SON68 glass. This slowdown of the alteration rate is attributed to the formation of an alteration film that has been the subject of a specific study. We have in particular identified a dense phase enriched in titanium and neodymium that probably influences deeply the kinetics.

  6. Bond Formation and Bond Scission Dynamics in Polyatomic Molecules Revealed by Momentum Imaging Experiments and Electron Scattering Calculations

    NASA Astrophysics Data System (ADS)

    Slaughter, Daniel; Trevisan, Cynthia; Weyland, Marvin; Dorn, Alexander; Douguet, Nicolas; Orel, Ann; Adaniya, Hidehito; McCurdy, Bill; Belkacem, Ali; Rescigno, Tom

    2016-05-01

    We present combined experimental and theoretical studies of dissociative electron attachment (DEA) dynamics in methane and ammonia. DEA in each of these systems proceeds through electronic Feshbach resonances, where a valence electron is excited and captured with the incident electron in the lowest unoccupied orbital. In methane, one triply-degenerate resonance undergoes Jahn-Teller splitting through molecular distortions, leading to four observed final states, each having a 2-body and a 3-body dissociation with anionic products H- and CH2-and neutrals CH3, CH2, H2 or H. In ammonia, one resonance leads to H- + NH2 and NH2-+ H, the latter resulting from non-adiabatic charge transfer. A higher energy resonance leads directly to H- + NH2* and indirectly to NH2-+ H. We examine the dynamics of the transient anion in each of these processes. work supported by Chemical Sciences, Geosciences and Biosciences division of BES/DOE.

  7. Crystallization in high-level waste glass: A review of glass theory and noteworthy literature

    SciTech Connect

    Christian, J. H.

    2015-08-18

    There is a fundamental need to continue research aimed at understanding nepheline and spinel crystal formation in high-level waste (HLW) glass. Specifically, the formation of nepheline solids (K/NaAlSiO4) during slow cooling of HLW glass can reduce the chemical durability of the glass, which can cause a decrease in the overall durability of the glass waste form. The accumulation of spinel solids ((Fe, Ni, Mn, Zn)(Fe, Cr)2O4), while not detrimental to glass durability, can cause an array of processing problems inside HLW glass melters. In this review, the fundamental differences between glass and solid-crystals are explained using kinetic, thermodynamic, and viscosity arguments, and several highlights of glass-crystallization research, as it pertains to high-level waste vitrification, are described. In terms of mitigating spinel in the melter and both spinel and nepheline formation in the canister, the complexity of HLW glass and the intricate interplay between thermal, chemical, and kinetic factors further complicates this understanding. However, new experiments seeking to elucidate the contributing factors of crystal nucleation and growth in waste glass, and the compilation of data from older experiments, may go a long way towards helping to achieve higher waste loadings while developing more efficient processing strategies. Higher waste loadings and more efficient processing strategies will reduce the overall HLW Hanford Tank Waste Treatment and Immobilization Plant (WTP) vitrification facilities mission life.

  8. Crystallization in high-level waste glass: A review of glass theory and noteworthy literature

    SciTech Connect

    Christian, J. H.

    2015-08-01

    There is a fundamental need to continue research aimed at understanding nepheline and spinel crystal formation in high-level waste (HLW) glass. Specifically, the formation of nepheline solids (K/NaAlSiO₄) during slow cooling of HLW glass can reduce the chemical durability of the glass, which can cause a decrease in the overall durability of the glass waste form. The accumulation of spinel solids ((Fe, Ni, Mn, Zn)(Fe,Cr)₂O₄), while not detrimental to glass durability, can cause an array of processing problems inside of HLW glass melters. In this review, the fundamental differences between glass and solid-crystals are explained using kinetic, thermodynamic, and viscosity arguments, and several highlights of glass-crystallization research, as it pertains to high-level waste vitrification, are described. In terms of mitigating spinel in the melter and both spinel and nepheline formation in the canister, the complexity of HLW glass and the intricate interplay between thermal, chemical, and kinetic factors further complicates this understanding. However, new experiments seeking to elucidate the contributing factors of crystal nucleation and growth in waste glass, and the compilation of data from older experiments, may go a long way towards helping to achieve higher waste loadings while developing more efficient processing strategies.

  9. Thermal Analysis Of Reluctant Glass Formers

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin C.; Curreri, Peter A.

    1989-01-01

    Thermocouple holds sample and monitors temperature during cooling. Ellipsoidal furnace provides controlled cooling rates for studies of thermal properties of reluctant glass formers. Glass tube inserted into furnace and used to blow helium on specimen to cool rapidly. Cooling curve analyzed to determine rate of cooling and such properties of sample as nucleation and recalescence temperatures at cooling rate. Continuous-cooling-crystallization boundaries determined empirically from plots of nucleation time vs. nucleation temperature from runs at large number of different rates of cooling. Apparatus used to examine glass-formation ability of material and critical cooling rate to form glass.

  10. Optical Properties of Silver Nanoparticulate Glasses

    NASA Astrophysics Data System (ADS)

    Evans, Rachel N.; Cannavino, Sarah A.; King, Christy A.; Lamartina, Joseph A.; Magruder, Robert H.; Ferrara, Davon W.

    The ion exchange method of embedding metal nanoparticles (NPs) into float glass is an often used technique of fabricating colored glasses and graded-index waveguides. The depth and size of NP formation in the glass depends on the concentration and temperature of metal ions in the molten bath. In this study we explore the dichroic properties of silver metal ion exchange restricted to only one side of a glass microscope slide using reflection and transmission spectroscopy and its dependence on temperature, concentration of silver ions, and length of time in the molten bath.

  11. 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.

  12. Nanometer-size P/K-rich silica glass (former melt) inclusions in microdiamond from the gneisses of Kokchetav and Erzgebirge massifs: Diversified characteristics of the formation media of metamorphic microdiamond in UHP rocks due to host-rock buffering

    NASA Astrophysics Data System (ADS)

    Hwang, Shyh-Lung; Chu, Hao-Tsu; Yui, Tzen-Fu; Shen, Pouyan; Schertl, Hans-Peter; Liou, Juhn G.; Sobolev, Nikolai V.

    2006-03-01

    Nanometer-size P/K-rich silica glass (former melt) inclusions were identified within metamorphic microdiamonds from garnets of ultrahigh-pressure (UHP) gneisses of the Kokchetav and the Erzgebirge massifs by analytical electron microscopy (AEM). The chemical characteristics of these inclusions within microdiamonds are surprisingly similar among various gneissic rocks from both Kokchetav and Erzgebirge, but are significantly different from the Si-poor ultrapotassic fluid inclusions within microdiamonds from garnets of the Kokchetav UHP marble. These contrasting findings not only provide constraints on the characteristics/compositions of the formation media of metamorphic microdiamonds, but also imply that the formation media must have been buffered by the hosting rocks, resulting in the observed diversities as reported here. In addition, depending on the rock types and thus on the nature of the formation media from which metamorphic microdiamonds were formed, the respective characteristic morphologies of the microdiamonds differ. The P/K-rich silica melt tends to form octahedral or cubo-octahedral microdiamonds within garnet in gneissic rocks, whereas the Si-poor ultrapotassic fluid tends to form spheroids/cuboid microdiamonds with rugged surfaces within garnet in marble. Consequently, the buffered media in hosting rocks played a decisive role in determining the different morphologies and growth rates/mechanisms of metamorphic microdiamonds in general.

  13. Coulomb Glass: a Mean Field Study

    NASA Astrophysics Data System (ADS)

    Mandra, Salvatore; Palassini, Matteo

    2012-02-01

    We study the Coulomb glass model of disordered localized electrons with long-range Coulomb interaction, which describes systems such as disordered insulators, granular metals, amorphous semiconductors, or doped crystalline semiconductors. Long ago Efros and Shklovskii showed that the long-range repulsion induces a soft Coulomb gap in the single particle density of states at low temperatures. Recent works suggested that this gap is associated to a transition to a glass phase, similar to the Almeida-Thouless transition in spin glasses. In this work, we use a mean field approach to characterize several physical properties of the Coulomb glass. In particular, following a seminal work of Bray and Moore, we show that the Edward-Anderson parameter qEA and the spin glass susceptibility χSG are directly related to spectrum distribution of the Hessian matrix around free energy minima. Using this result, we show that no glass transition is associated to the gap formation.

  14. Hidden topological order and its correlation with glass-forming ability in metallic glasses.

    PubMed

    Wu, Z W; Li, M Z; Wang, W H; Liu, K X

    2015-01-01

    Unlike the well-defined long-range periodic order that characterizes crystals, so far the inherent atomic packing mode in glassy solids remains mysterious. Based on molecular dynamics simulations, here we find medium-range atomic packing orders in metallic glasses, which are hidden in the diffraction data in terms of structure factors or pair correlation functions. The analysis of the hidden orders in various metallic glasses indicates that the glassy and crystalline solids share a nontrivial structural homology in short-to-medium range, and the hidden orders are formulated by inheriting partial crystalline orders during glass formation. As the number of chemical components increases, more hidden orders are often developed in a metallic glass and entangled topologically. We use this phenomenon to explain the geometric frustration in glass formation and the glass-forming ability of metallic alloys.

  15. Hidden topological order and its correlation with glass-forming ability in metallic glasses

    NASA Astrophysics Data System (ADS)

    Wu, Z. W.; Li, M. Z.; Wang, W. H.; Liu, K. X.

    2015-01-01

    Unlike the well-defined long-range periodic order that characterizes crystals, so far the inherent atomic packing mode in glassy solids remains mysterious. Based on molecular dynamics simulations, here we find medium-range atomic packing orders in metallic glasses, which are hidden in the diffraction data in terms of structure factors or pair correlation functions. The analysis of the hidden orders in various metallic glasses indicates that the glassy and crystalline solids share a nontrivial structural homology in short-to-medium range, and the hidden orders are formulated by inheriting partial crystalline orders during glass formation. As the number of chemical components increases, more hidden orders are often developed in a metallic glass and entangled topologically. We use this phenomenon to explain the geometric frustration in glass formation and the glass-forming ability of metallic alloys.

  16. Thulium-based bulk metallic glass

    SciTech Connect

    Yu, H. B.; Yu, P.; Wang, W. H.; Bai, H. Y.

    2008-04-07

    We report the formation and properties of a thulium-based bulk metallic glass (BMG). Compared with other known rare-earth (RE) based BMGs, Tm-based BMGs show features of excellent glass formation ability, considerable higher elastic modulus, smaller Poisson's ratio, high mechanical strength, and intrinsic brittleness. The reasons for the different properties between the Tm-based and other RE-based BMGs are discussed. It is expected that the Tm-based glasses with the unique properties are appropriate candidates for studying some important issues in BMGs.

  17. Relationship between topological order and glass forming ability in densely packed enstatite and forsterite composition glasses.

    PubMed

    Kohara, S; Akola, J; Morita, H; Suzuya, K; Weber, J K R; Wilding, M C; Benmore, C J

    2011-09-01

    The atomic structures of magnesium silicate melts are key to understanding processes related to the evolution of the Earth's mantle and represent precursors to the formation of most igneous rocks. Magnesium silicate compositions also represent a major component of many glass ceramics, and depending on their composition can span the entire fragility range of glass formation. The silica rich enstatite (MgSiO(3)) composition is a good glass former, whereas the forsterite (Mg(2)SiO(4)) composition is at the limit of glass formation. Here, the structure of MgSiO(3) and Mg(2)SiO(4) composition glasses obtained from levitated liquids have been modeled using Reverse Monte Carlo fits to diffraction data and by density functional theory. A ring statistics analysis suggests that the lower glass forming ability of the Mg(2)SiO(4) glass is associated with a topologically ordered and very narrow ring distribution. The MgO(x) polyhedra have a variety of irregular shapes in MgSiO(3) and Mg(2)SiO(4) glasses and a cavity analysis demonstrates that both glasses have almost no free volume due to a large contribution from edge sharing of MgO(x)-MgO(x) polyhedra. It is found that while the atomic volume of Mg cations in the glasses increases compared to that of the crystalline phases, the number of Mg-O contacts is reduced, although the effective chemical interaction of Mg(2+) remains similar. This unusual structure-property relation of Mg(2)SiO(4) glass demonstrates that by using containerless processing it may be possible to synthesize new families of dense glasses and glass ceramics with zero porosity. PMID:21873237

  18. Relationship between topological order and glass forming ability in densely packed enstatite and forsterite composition glasses.

    PubMed

    Kohara, S; Akola, J; Morita, H; Suzuya, K; Weber, J K R; Wilding, M C; Benmore, C J

    2011-09-01

    The atomic structures of magnesium silicate melts are key to understanding processes related to the evolution of the Earth's mantle and represent precursors to the formation of most igneous rocks. Magnesium silicate compositions also represent a major component of many glass ceramics, and depending on their composition can span the entire fragility range of glass formation. The silica rich enstatite (MgSiO(3)) composition is a good glass former, whereas the forsterite (Mg(2)SiO(4)) composition is at the limit of glass formation. Here, the structure of MgSiO(3) and Mg(2)SiO(4) composition glasses obtained from levitated liquids have been modeled using Reverse Monte Carlo fits to diffraction data and by density functional theory. A ring statistics analysis suggests that the lower glass forming ability of the Mg(2)SiO(4) glass is associated with a topologically ordered and very narrow ring distribution. The MgO(x) polyhedra have a variety of irregular shapes in MgSiO(3) and Mg(2)SiO(4) glasses and a cavity analysis demonstrates that both glasses have almost no free volume due to a large contribution from edge sharing of MgO(x)-MgO(x) polyhedra. It is found that while the atomic volume of Mg cations in the glasses increases compared to that of the crystalline phases, the number of Mg-O contacts is reduced, although the effective chemical interaction of Mg(2+) remains similar. This unusual structure-property relation of Mg(2)SiO(4) glass demonstrates that by using containerless processing it may be possible to synthesize new families of dense glasses and glass ceramics with zero porosity.

  19. Relationship between topological order and glass forming ability in densely packed enstatite and forsterite composition glasses

    PubMed Central

    Kohara, S.; Akola, J.; Morita, H.; Suzuya, K.; Weber, J. K. R.; Wilding, M. C.; Benmore, C. J.

    2011-01-01

    The atomic structures of magnesium silicate melts are key to understanding processes related to the evolution of the Earth’s mantle and represent precursors to the formation of most igneous rocks. Magnesium silicate compositions also represent a major component of many glass ceramics, and depending on their composition can span the entire fragility range of glass formation. The silica rich enstatite (MgSiO3) composition is a good glass former, whereas the forsterite (Mg2SiO4) composition is at the limit of glass formation. Here, the structure of MgSiO3 and Mg2SiO4 composition glasses obtained from levitated liquids have been modeled using Reverse Monte Carlo fits to diffraction data and by density functional theory. A ring statistics analysis suggests that the lower glass forming ability of the Mg2SiO4 glass is associated with a topologically ordered and very narrow ring distribution. The MgOx polyhedra have a variety of irregular shapes in MgSiO3 and Mg2SiO4 glasses and a cavity analysis demonstrates that both glasses have almost no free volume due to a large contribution from edge sharing of MgOx-MgOx polyhedra. It is found that while the atomic volume of Mg cations in the glasses increases compared to that of the crystalline phases, the number of Mg-O contacts is reduced, although the effective chemical interaction of Mg2+ remains similar. This unusual structure-property relation of Mg2SiO4 glass demonstrates that by using containerless processing it may be possible to synthesize new families of dense glasses and glass ceramics with zero porosity. PMID:21873237

  20. Pressure-Induced Amorphization of Small Pore Zeolites—the Role of Cation-H2O Topology and Anti-glass Formation

    PubMed Central

    Chan Hwang, Gil; Joo Shin, Tae; Blom, Douglas A.; Vogt, Thomas; Lee, Yongjae

    2015-01-01

    Systematic studies of pressure-induced amorphization of natrolites (PIA) containing monovalent extra-framework cations (EFC) Li+, Na+, K+, Rb+, Cs+ allow us to assess the role of two different EFC-H2O configurations within the pores of a zeolite: one arrangement has H2O molecules (NATI) and the other the EFC (NATII) in closer proximity to the aluminosilicate framework. We show that NATI materials have a lower onset pressure of PIA than the NATII materials containing Rb and Cs as EFC. The onset pressure of amorphization (PA) of NATII materials increases linearly with the size of the EFC, whereas their initial bulk moduli (P1 phase) decrease linearly. Only Cs- and Rb-NAT reveal a phase separation into a dense form (P2 phase) under pressure. High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM) imaging shows that after recovery from pressures near 25 and 20 GPa long-range ordered Rb-Rb and Cs-Cs correlations continue to be present over length scales up to 100 nm while short-range ordering of the aluminosilicate framework is significantly reduced—this opens a new way to form anti-glass structures. PMID:26455345

  1. Flurbiprofen-loaded nanoparticles prepared with polyvinylpyrrolidone using Shirasu porous glass membranes and a spray-drying technique: nano-sized formation and improved bioavailability.

    PubMed

    Oh, Dong Hoon; Din, Fakhar Ud; Kim, Dong Wuk; Kim, Jong Oh; Yong, Chul Soon; Choi, Han-Gon

    2013-01-01

    A unique flurbiprofen-loaded nanoemulsion was listed earlier using a Shirasu porous glass (SPG) membrane emulsification technique, which gave constant emulsion droplets with a thin size distribution. In this study, a flurbiprofen-loaded nanoemulsion was developed further into a solid form using polyvinylpyrrolidone (PVP) as a carrier by a spray-drying technique. The flurbiprofen-loaded nanoparticles with a weight ratio of flurbiprofen/PVP/surfactant mixture of 1/8/2 were connected with about 130,000-fold enhanced drug solubility and had a mean size of about 70 nm. In these nanoparticles, flurbiprofen was found in an altered amorphous state. Additionally, the nanoparticles gave significantly shorter T(max), and greater AUC and C(max) compared to the commercially available product. Specially, the AUC of the drug from the nanoparticles was about 10-fold greater compared to the commercially available product. Therefore, these flurbiprofen-loaded nanoparticles can be convenient for distributing a poorly water-soluble flurbiprofen with improved bioavailability using uniform nano-sized particles.

  2. Impact Strength of Glass and Glass Ceramic

    NASA Astrophysics Data System (ADS)

    Bless, Stephan; Tolman, John

    2009-06-01

    Bar impact tests, using the techniques described elsewhere in this symposium, were used to measure compressive and tensile strengths of borosilicate glass, soda lime glass, and glass ceramic. The glass ceramic was 25% crystalline spinel, furnished by Corning, Inc. There are two measures of compressive strength: the peak stress that can be transmitted in unconfined compression and the steady-state strength. For both glasses, these values were similar, being about 1.8 and 1.5 GPa, respectively. The glass ceramic was almost 50% stronger. Tensile failure in the glass and glass ceramic takes places via surface flaws, and thus tensile strength is an extrinsic---as opposed to intrinsic---property.

  3. CRYSTALLIZATION IN MULTICOMPONENT GLASSES

    SciTech Connect

    KRUGER AA; HRMA PR

    2009-10-08

    In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glass making are reviewed.

  4. Glass frits coated with silver nanoparticles for silicon solar cells

    NASA Astrophysics Data System (ADS)

    Li, Yingfen; Gan, Weiping; Zhou, Jian; Li, Biyuan

    2015-06-01

    Glass frits coated with silver nanoparticles were prepared by electroless plating. Gum Arabic (GA) was used as the activating agent of glass frits without the assistance of stannous chloride or palladium chloride. The silver-coated glass frits prepared with different GA dosages were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and thermogravimetric analysis (TGA). The characterization results indicated that silver-coated glass frits had the structures of both glass and silver. Spherical silver nanoparticles were distributed on the glass frits evenly. The density and particle size of silver nanoparticles on the glass frits can be controlled by adjusting the GA dosage. The silver-coated glass frits were applied to silver pastes to act as both the densification promoter and silver crystallite formation aid in the silver electrodes. The prepared silver-coated glass frits can improve the photovoltaic performances of solar cells.

  5. IMPACT STRENGTH OF GLASS AND GLASS CERAMIC

    SciTech Connect

    Bless, S.; Tolman, J.

    2009-12-28

    Strength of glass and glass ceramic was measured with a bar impact technique. High-speed movies show regions of tensile and compressive failure. The borosilicate glass had a compressive strength of at least 2.2 GPa, and the glass ceramic at least 4 GPa. However, the BSG was much stronger in tension than GC. In ballistic tests, the BSG was the superior armor.

  6. Impact Strength of Glass and Glass Ceramic

    NASA Astrophysics Data System (ADS)

    Bless, S.; Tolman, J.

    2009-12-01

    Strength of glass and glass ceramic was measured with a bar impact technique. High-speed movies show regions of tensile and compressive failure. The borosilicate glass had a compressive strength of at least 2.2 GPa, and the glass ceramic at least 4 GPa. However, the BSG was much stronger in tension than GC. In ballistic tests, the BSG was the superior armor.

  7. Will it form a stable glass? How the stability of vapor deposited glasses depends on molecular structure

    NASA Astrophysics Data System (ADS)

    Tylinski, Michael; Beasley, Madeleine; Chua, Yeong Zen; Schick, Christoph; Ediger, Mark

    Over the past nine years physical vapor deposition has been used to prepare molecular glasses with exceptional properties. When heated, transformation of these highly stable glasses takes orders of magnitude longer than the transformation of liquid-cooled glasses. Until recently, it appeared that most organic molecules could form stable glasses when vapor deposited. We test the generality of stable glass formation by vapor-depositing a wide range of small organic molecules, including hydroxyl, carbonyl, phosphate, aromatic, and aliphatic functional groups. When prepared under conditions expected to yield highly stable glasses, we observe glasses with a wide range of kinetic stabilities, depending on the functional groups in the molecule. In general, alcohols and molecules with long aliphatic chains do not form highly stable glasses while aromatic molecules do. We also test the hypothesis that the surface mobility during deposition determines if a molecule is able to create highly stable glasses.

  8. Study of PbO - TiO2 - B2O3 glass and glass ceramics

    NASA Astrophysics Data System (ADS)

    Shankar, J.; Deshpande, V. K.

    2015-06-01

    Glass samples with composition (35 - X) B2O3 - (40 + X) PbO - 25 TiO2 (where X=0, 2.5, 5, 7.5 and 10 mol %) were prepared using conventional quenching technique. It was observed that as PbO content increases the value of Tg and Tc decreases. These glass samples were converted to glass ceramics by following two stage heat treatment schedule. The density values of glass ceramic samples are higher than those of corresponding glass samples. It was observed that there was good correlation between the density and CTE results of the glass-ceramics. The XRD results revealed the formation of tetragonal lead titanate as a major crystalline phase in the glass ceramics. The dielectric constant of glass ceramic samples is higher than those of corresponding glasses

  9. Nitridation of organo-silicate glass: A self-limiting process for PVD Ta 1+ xN/Ta barrier formation

    NASA Astrophysics Data System (ADS)

    Wilks, J. A.; Kelber, J. A.

    2009-09-01

    Interfacial reactions of sputter-deposited Ta with a low dielectric constant Si-O-C-H material (SiCOH), and with surface-nitrided SiCOH (N-SiCOH) were investigated using X-ray photoelectron spectroscopy (XPS). The studies were carried out in a system containing a processing chamber attached to an XPS analysis chamber so that sample transport between deposition and analysis environments occurred under ultrahigh vacuum (UHV) conditions. Ta sputter deposition on unmodified SiCOH yielded an interfacial phase ˜3 nm thick composed of Ta oxide/carbide (Ta-O-C), which is known to interact only weakly with Cu. Bombardment of the vicinal SiCOH surface by 500 eV Ar + in the presence of NH 3 resulted in carbon depletion and the self-limiting nitridation of the surface, with N attachment primarily at Si sites. Subsequent Ta sputter deposition yielded reduced Ta oxide and carbide formation, and formation of a Ta-rich nitride layer of 10 Å average thickness. Subsequent deposition resulted in metallic Ta formation.

  10. Crystallization Kinetics in Fluorochloroziroconate Glass-Ceramics

    NASA Astrophysics Data System (ADS)

    Alvarez, Carlos J.

    Annealing fluorochlorozirconate (FCZ) glasses nucleates BaCl2 nanocrystals in the glass matrix, resulting in a nanocomposite glass-ceramic that has optical properties suitable for use as a medical X-ray imaging plate. Understanding the way in which the BaCl¬2 nanocrystal nucleation, growth and phase transformation processes proceed is critical to controlling the optical behavior. However, there is a very limited amount of information about the formation, morphology, and distribution of the nanocrystalline particles in FCZ glass-ceramics. In this thesis, the correlation between the microstructure and the crystallization kinetics of FCZ glass-ceramics, are studied in detail. In situ X-ray diffraction and transmission electron microscopy annealing experiments are used to analyze the crystal structure, size and distribution of BaCl 2 nanocrystals in FCZ glass-ceramics as a function of annealing rate and temperature. Microstructural analysis of the early stages on nucleation identified the formation of both BaCl2 and BaF2 nanocrystals. Annealing FCZ glass-ceramics above 280°C can cause the formation of additional glass matrix phase crystals, their microstructure and the annealing parameters required for their growth are identified. As the crystalline phases grow directly from the glass, small variations in processing of the glass can have a profound influence on the crystallization process. The information obtained from these experiments improves the understanding of the nucleation, growth and phase transformation process of the BaCl¬2 nanocrystals and additional crystalline phases that form in FCZ glass-ceramics, and may help expedite the implementation of FCZ glass-ceramics as next-generation X-ray detectors. Lastly, as these glass-ceramics may one day be commercialized, an investigation into their degradation in different environmental conditions was also performed. The effects of direct contact with water or prolonged exposure to humid environments on the

  11. Chemical Principles Revisited: The Chemistry of Glass.

    ERIC Educational Resources Information Center

    Kolb, Doris; Kolb, Kenneth E.

    1979-01-01

    Presents a detailed discussion on the chemistry of glass. Topics discussed include: natural glass, early history, modern glass composition, raw materials for glass melting, chemically modified glasses, modern glass forming, glass ceramics, and new developments in glass research. (BT)

  12. Surface layer effects on waste glass corrosion

    SciTech Connect

    Feng, X.

    1993-12-31

    Water contact subjects waste glass to chemical attack that results in the formation of surface alteration layers. Two principal hypotheses have been advanced concerning the effect of surface alteration layers on continued glass corrosion: (1) they act as a mass transport barrier and (2) they influence the chemical affinity of the glass reaction. In general, transport barrier effects have been found to be less important than affinity effects in the corrosion of most high-level nuclear waste glasses. However, they can be important under some circumstances, for example, in a very alkaline solution, in leachants containing Mg ions, or under conditions where the matrix dissolution rate is very low. The latter suggests that physical barrier effect may affect the long-term glass dissolution rate. Surface layers influence glass reaction affinity through the effects of the altered glass and secondary phases on the solution chemistry. The reaction affinity may be controlled by various precipitates and crystalline phases, amorphous silica phases, gel layer, or all the components of the glass. The surface alteration layers influence radionuclide release mainly through colloid formation, crystalline phase incorporation, and gel layer retention. This paper reviews current understanding and uncertainties.

  13. Repairing cracked glass

    NASA Technical Reports Server (NTRS)

    Helman, D. D.; Holt, J. W.; Smiser, L. V.

    1979-01-01

    Filing procedure consisting of machined lightweight fused-silica tiles coated with thin-layer of borosilicate glass produces homogeneous seal in thin glass. Procedure is useful in repairing glass envelopes, X-ray tub windows, Dewar flasks, and similar thin glass objects.

  14. The mechanism of borosilicate glass corrosion revisited

    NASA Astrophysics Data System (ADS)

    Geisler, Thorsten; Nagel, Thorsten; Kilburn, Matt R.; Janssen, Arne; Icenhower, Jonathan P.; Fonseca, Raúl O. C.; Grange, Marion; Nemchin, Alexander A.

    2015-06-01

    Currently accepted mechanistic models describing aqueous corrosion of borosilicate glasses are based on diffusion-controlled hydrolysis, hydration, ion exchange reactions, and subsequent re-condensation of the hydrolyzed glass network, leaving behind a residual hydrated glass or gel layer. Here, we report results of novel oxygen and silicon isotope tracer experiments with ternary Na borosilicate glasses that can be better explained by a process that involves the congruent dissolution of the glass, which is spatially and temporally coupled to the precipitation and growth of an amorphous silica layer at an inwardly moving reaction interface. Such a process is thermodynamically driven by the solubility difference between the glass and amorphous silica, and kinetically controlled by glass dissolution reactions at the reaction front, which, in turn, are controlled by the transport of water and solute elements through the growing corrosion zone. Understanding the coupling of these reactions is the key to understand the formation of laminar or more complex structural and chemical patterns observed in natural corrosion zones of ancient glasses. We suggest that these coupled processes also have to be considered to realistically model the long-term performance of silicate glasses in aqueous environments.

  15. Inverted glass harp

    NASA Astrophysics Data System (ADS)

    Quinn, Daniel B.; Rosenberg, Brian J.

    2015-08-01

    We present an analytical treatment of the acoustics of liquid-filled wine glasses, or "glass harps." The solution is generalized such that under certain assumptions it reduces to previous glass harp models, but also leads to a proposed musical instrument, the "inverted glass harp," in which an empty glass is submerged in a liquid-filled basin. The versatility of the solution demonstrates that all glass harps are governed by a family of solutions to Laplace's equation around a vibrating disk. Tonal analyses of recordings for a sample glass are offered as confirmation of the scaling predictions.

  16. Inverted glass harp.

    PubMed

    Quinn, Daniel B; Rosenberg, Brian J

    2015-08-01

    We present an analytical treatment of the acoustics of liquid-filled wine glasses, or "glass harps." The solution is generalized such that under certain assumptions it reduces to previous glass harp models, but also leads to a proposed musical instrument, the "inverted glass harp," in which an empty glass is submerged in a liquid-filled basin. The versatility of the solution demonstrates that all glass harps are governed by a family of solutions to Laplace's equation around a vibrating disk. Tonal analyses of recordings for a sample glass are offered as confirmation of the scaling predictions. PMID:26382336

  17. Glass-silicon column

    DOEpatents

    Yu, Conrad M.

    2003-12-30

    A glass-silicon column that can operate in temperature variations between room temperature and about 450.degree. C. The glass-silicon column includes large area glass, such as a thin Corning 7740 boron-silicate glass bonded to a silicon wafer, with an electrode embedded in or mounted on glass of the column, and with a self alignment silicon post/glass hole structure. The glass/silicon components are bonded, for example be anodic bonding. In one embodiment, the column includes two outer layers of silicon each bonded to an inner layer of glass, with an electrode imbedded between the layers of glass, and with at least one self alignment hole and post arrangement. The electrode functions as a column heater, and one glass/silicon component is provided with a number of flow channels adjacent the bonded surfaces.

  18. Surface Coatings on Lunar Volcanic Glasses

    NASA Technical Reports Server (NTRS)

    Wentworth, Susan J.; McKay, D. S.; Thomas,-Keprta, K. L.; Clemett, S. J.

    2007-01-01

    We are undertaking a detailed study of surface deposits on lunar volcanic glass beads. These tiny deposits formed by vapor condensation during cooling of the gases that drove the fire fountain eruptions responsible for the formation of the beads. Volcanic glass beads are present in most lunar soil samples in the returned lunar collection. The mare-composition beads formed as a result of fire-fountaining approx.3.4-3.7 Ga ago, within the age range of large-scale mare volcanism. Some samples from the Apollo 15 and Apollo 17 landing sites are enriched in volcanic spherules. Three major types of volcanic glass bead have been identified: Apollo 15 green glass, Apollo 17 orange glass, and Apollo 17 "black" glass. The Apollo 15 green glass has a primitive composition with low Ti. The high-Ti compositions of the orange and black glasses are essentially identical to each other but the black glasses are opaque because of quench crystallization. A poorly understood feature common to the Apollo 15 and 17 volcanic glasses is the presence of small deposits of unusual materials on their exterior surfaces. For example, early studies indicated that the Apollo 17 orange glasses had surface enrichments of In, Cd, Zn, Ga, Ge, Au, and Na, and possible Pb- and Zn-sulfides, but it was not possible to characterize the surface features in detail. Technological advances now permit us to examine such features in detail. Preliminary FE-TEM/X-ray studies of ultramicrotome sections of Apollo 15 green glass indicate that the surface deposits are heterogeneous and layered, with an inner layer consisting of Fe with minor S and an outer layer of Fe and no S, and scattered Zn enrichments. Layering in surface deposits has not been identified previously; it will be key to defining the history of lunar fire fountaining.

  19. Bioactive glass coatings for orthopedic metallic implants

    SciTech Connect

    Lopez-Esteban, Sonia; Saiz, Eduardo; Fujino, Sigheru; Oku, Takeo; Suganuma, Katsuaki; Tomsia, Antoni P.

    2003-06-30

    The objective of this work is to develop bioactive glass coatings for metallic orthopedic implants. A new family of glasses in the SiO2-Na2O-K2O-CaO-MgO-P2O5 system has been synthesized and characterized. The glass properties (thermal expansion, softening and transformation temperatures, density and hardness) are in line with the predictions of established empirical models. The optimized firing conditions to fabricate coatings on Ti-based and Co-Cr alloys have been determined and related to the glass properties and the interfacial reactions. Excellent adhesion to alloys has been achieved through the formation of 100-200 nm thick interfacial layers (Ti5Si3 on Ti-based alloys and CrOx on Co-Cr). Finally, glass coatings, approximately 100 mu m thick, have been fabricated onto commercial Ti alloy-based dental implants.

  20. Atomic Dynamics in Metallic Liquids and Glasses

    SciTech Connect

    Egami, Takeshi; Levashov, Valentin A; Aga, Rachel S; Morris, James R

    2007-01-01

    How atoms move in metallic glasses and liquids is an important question in discussing atomic transport, glass formation, structural relaxation and other properties of metallic glasses. While the concept of free-volume has long been used in describing atomic transport, computer simulations and isotope measurements have shown that atomic transport occurs by a much more collective process than assumed in the free-volume theory. We introduce a new approach to describe the atomic dynamics in metallic glasses, in terms of local energy landscapes related to fluctuations in the topology of atomic connectivity. This approach may form the basis for a new paradigm for discussing the structure-properties relationship in metallic glasses.

  1. Investigations on oxyhalide glasses synthesized by microwave assisted process

    NASA Astrophysics Data System (ADS)

    Vijayatha, D.; Viswanatha, R.; Somashekaraiah, C. S.; Reddy, C. Narayana

    2016-05-01

    Glass formation and properties in the system xPbCl2-15PbO-(85-x) PbBr2 (where 0 ≤ x ≤ 25) has been prepared by microwave method. The glass forming tendency of the admixtures was also been studied by determining the Hurby's factor (HR). HR values of the investigated glasses lie in a short range of 0.14 to 0.24; hence preparation of these glasses is very difficult and requires suitable experimental conditions. Lead bromide and lead chloride are inter-substituted by keeping the concentration of PbO at 15 mol%. Properties like glass transition temperature (Tg), jump in heat capacity (ΔCp) at Tg, width of glass transition (ΔT), show a composition dependent trend. The stability indices such as H' and S have also been calculated. These values reveal that PbCl2 rich glasses are less stable while PbBr2 rich glasses are stable, which is well supported by chemical durability studies. The calculated values of glass formation indices fall in right range (G≥20 for glass formers, for conditional glass formers 10≤G≤20 and G<10 for glass modifiers) for compositions studied in the present work.

  2. Glass-ferroic composite caused by the crystallization of ferroic glass

    NASA Astrophysics Data System (ADS)

    Ji, Yuanchao; Ding, Xiangdong; Wang, Dong; Otsuka, Kazuhiro; Ren, Xiaobing

    2015-12-01

    We report a glass-ferroic composite (in short "glass-ferroic") in ferroic materials, an analog of the composite of glassy and crystalline phases (glass-crystal composite, e.g., semicrystalline polymer). The formation of glass-ferroic (i.e., the existence of residual ferroic glass) stems from a time-dependent crystallization of the ferroic glass. Moreover, glass-ferroics show two types of transition characteristics depending on the thermal hysteresis of crystallization transition as exemplified in T i48.7N i51.3 and P b0.87L a0.13Z r0.4T i0.6O3 . Based on experimental results, a generic phase diagram is established to include all ferroic states, i.e., ferroic crystal, ferroic glass, and glass-ferroic. Being the third class of ferroic materials, glass-ferroics may open a new avenue for achieving novel properties and designing ferroic phase-change memory devices.

  3. Characteristics of hydrogen bond formation between sugar and polymer in freeze-dried mixtures under different rehumidification conditions and its impact on the glass transition temperature.

    PubMed

    Imamura, Koreyoshi; Asano, Yoko; Maruyama, Yoshinobu; Yokoyama, Tohru; Nomura, Mayo; Ogawa, Seiji; Nakanishi, Kazuhiro

    2008-03-01

    The characteristics of hydrogen bond formation between trehalose and polyvinylpyrrolidone (PVP) in amorphous mixtures at different hydration states were quantitatively investigated. Amorphous trehalose-PVP mixtures were prepared by freeze-drying and equilibrated at different relative humidities (RH). Infrared (IR) spectra of the trehalose-PVP mixtures were obtained by Fourier transform IR spectroscopy,(FTIR) and the IR band corresponding to C=O groups of PVP was deconvolved into the component bands responsible for C=O groups that were free and restricted by hydrogen bonds, to estimate the degree of the trehalose-PVP interactions. The FTIR analysis indicated that approximately 80% of the C=O groups of PVP formed hydrogen bonds with trehalose in the presence of more than 3 g of trehalose per gramme of PVP, independent of the RH. IR analysis of the O--H stretching vibration of the sugar demonstrated that the presence of PVP lead to an increase in the free hydroxyl groups of trehalose that did not form hydrogen bonds at RH 0%. On the other hand, the water sorption behavior of the trehalose-PVP mixtures suggested that rehumidification diminished the effect of PVP on increasing the free OH groups. Thus a peculiar relationship may exist between Tg, RH and the composition of the mixture: The presence of PVP increased Tg at RHs 0 and above 23% but decreased Tg at 11%.

  4. Containerless preparation of advanced optical glasses: Experiment 77F095

    NASA Technical Reports Server (NTRS)

    Happe, R. A.; Kim, K. S.

    1982-01-01

    Containerless processing of optical glasses was studied in preparation for space shuttle MEA flight experiments. Ground based investigation, experiment/hardware coordination activities and development of flight experiment and sample characterization plans were investigated. In the ground based investigation over 100 candidate glass materials for space processing were screened and promising compositions were identified. The system of Nb2O5-TiO2-CaO was found to be very rich with containerless glass compositions and as extensive number of the oxides combinations were tried resulting in a glass formation ternary phase diagram. The frequent occurrence of glass formation by containerless processing among the compositions for which no glass formations were previously reported indicated the possibility and an advantage of containerless processing in a terrestrial environment.

  5. Picture Wall (Glass Structures)

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Photo shows a subway station in Toronto, Ontario, which is entirely glass-enclosed. The all-glass structure was made possible by a unique glazing concept developed by PPG Industries, Pittsburgh, Pennsylvania, one of the largest U.S. manufacturers of flat glass. In the TVS glazing system, transparent glass "fins" replace conventional vertical support members used to provide support for wind load resistance. For stiffening, silicone sealant bonds the fins to adjacent glass panels. At its glass research center near Pittsburgh, PPG Industries uses the NASTRAN computer program to analyze the stability of enclosures made entirely of glass. The company also uses NASTRAN to simulate stresses on large containers of molten glass and to analyze stress effects of solar heating on flat glass.

  6. Reaction cured glass and glass coatings

    NASA Technical Reports Server (NTRS)

    Goldstein, H. E.; Leiser, D. B.; Katvala, V. W. (Inventor)

    1978-01-01

    The invention relates to reaction cured glass and glass coatings prepared by reacting a compound selected from the group consisting of silicon tetraboride, silicon hexaboride, other boron silicides, boron and mixtures with a reactive glass frit composed of a porous high silica borosilicate glass and boron oxide. The glassy composites of the present invention are useful as coatings on low density fibrous porous silica insulations used as heat shields and for articles such as reaction vessels that are subjected to high temperatures with rapid heating and cooling and that require resistance to temperature and repeated thermal shock at temperatures up to about 1482C (2700PF).

  7. Accelerated glass reaction under PCT conditions

    SciTech Connect

    Ebert, W.L.; Bates, J.K.; Buck, E.C.; Bradley, C.R.

    1992-01-01

    Static leach tests similar to PCT (Product Consistency Test) were performed for up to 2 years to assess long-term reaction behavior of high-level nuclear waste glasses similar to those at Defense Waste Processing Facility. These tests show the reaction rate to decrease with the reaction time from an initially high rate to a low rate, but then to accelerate to a higher rate after reaction times of about 1 year, depending on glass surface area/leachant volume ratio used. Solution concentrations of soluble glass components increase as the reaction is accelerated, while release of other glass components into solution is controlled by secondary phases. Net result is that transformation of glass to stable phases is accelerated while the solution becomes enriched in soluble components not effectively contained in secondary phases. Rate becomes linear in time after the acceleration and may be similar to the initial forward rate. A current model of glass reaction predicts that the glass reaction will be accelerated upon the formation of secondary phases which lower the silicic acid solution concentration. These tests show total Si concentration to increase upon reaction acceleration, however, which may be due to the slightly higher pH attained with the acceleration. The sudden change in the reaction rate is likely due to secondary phase formation. 17 refs, 2 tabs, 3 figs.

  8. Accelerated glass reaction under PCT conditions

    SciTech Connect

    Ebert, W.L.; Bates, J.K.; Buck, E.C.; Bradley, C.R.

    1992-12-31

    Static leach tests similar to PCT (Product Consistency Test) were performed for up to 2 years to assess long-term reaction behavior of high-level nuclear waste glasses similar to those at Defense Waste Processing Facility. These tests show the reaction rate to decrease with the reaction time from an initially high rate to a low rate, but then to accelerate to a higher rate after reaction times of about 1 year, depending on glass surface area/leachant volume ratio used. Solution concentrations of soluble glass components increase as the reaction is accelerated, while release of other glass components into solution is controlled by secondary phases. Net result is that transformation of glass to stable phases is accelerated while the solution becomes enriched in soluble components not effectively contained in secondary phases. Rate becomes linear in time after the acceleration and may be similar to the initial forward rate. A current model of glass reaction predicts that the glass reaction will be accelerated upon the formation of secondary phases which lower the silicic acid solution concentration. These tests show total Si concentration to increase upon reaction acceleration, however, which may be due to the slightly higher pH attained with the acceleration. The sudden change in the reaction rate is likely due to secondary phase formation. 17 refs, 2 tabs, 3 figs.

  9. Ultrahigh stability of atomically thin metallic glasses

    SciTech Connect

    Cao, C. R.; Huang, K. Q.; Zhao, N. J.; Sun, Y. T.; Bai, H. Y.; Gu, L. E-mail: dzheng@iphy.ac.cn Zheng, D. N. E-mail: dzheng@iphy.ac.cn Wang, W. H. E-mail: dzheng@iphy.ac.cn

    2014-07-07

    We report the fabrication and study of thermal stability of atomically thin ZrCu-based metallic glass films. The ultrathin films exhibit striking dynamic properties, ultrahigh thermal stability, and unique crystallization behavior with discrete crystalline nanoparticles sizes. The mechanisms for the remarkable high stability and crystallization behaviors are attributed to the dewetting process of the ultrathin film. We demonstrated a promising avenue for understanding some fundamental issues such as glassy structure, crystallization, deformation, and glass formation through atomic resolution imaging of the two dimensional like metallic glasses.

  10. 'Work-Hardenable' Ductile Bulk Metallic Glass

    SciTech Connect

    Das, Jayanta; Eckert, Juergen; Tang Meibo; Wang Weihua; Kim, Ki Buem; Baier, Falko; Theissmann, Ralf

    2005-05-27

    Usually, monolithic bulk metallic glasses undergo inhomogeneous plastic deformation and exhibit poor ductility (<1%) at room temperature. We present a new class of bulk metallic glass, which exhibits high strength of up to 2265 MPa together with extensive 'work hardening' and large ductility of 18%. Significant increase in the flow stress was observed during deformation. The 'work-hardening' capability and ductility of this class of metallic glass is attributed to a unique structure correlated with atomic-scale inhomogeneity, leading to an inherent capability of extensive shear band formation, interactions, and multiplication of shear bands.

  11. GlassForm

    2011-09-16

    GlassForm is a software tool for generating preliminary waste glass formulas for a given waste stream. The software is useful because it reduces the number of verification melts required to develop a suitable additive composition. The software includes property models that calculate glass properties of interest from the chemical composition of the waste glass. The software includes property models for glass viscosity, electrical conductivity, glass transition temperature, and leach resistance as measured by the 7-daymore » product consistency test (PCT).« less

  12. Control of radioactive waste-glass melters

    SciTech Connect

    Bickford, D.F. ); Hrma, P. ); Bowan, B.W. II )

    1990-01-01

    Slurries of simulated high level radioactive waste and glass formers have been isothermally reacted and analyzed to identify the sequence of the major chemical reactions in waste vitrification, their effect on glass production rate, and the development of leach resistance. Melting rates of waste batches have been increased by the addition of reducing agents (formic acid, sucrose) and nitrates. The rate increases are attributable in part to exothermic reactions which occur at critical stages in the vitrification process. Nitrates must be balanced by adequate reducing agents to avoid the formation of persistent foam, which would destabilize the melting process. The effect of foaming on waste glass production rates is analyzed, and melt rate limitations defined for waste-glass melters, based upon measurable thermophysical properties. Minimum melter residence times required to homogenize glass and assure glass quality are much smaller than those used in current practice. Thus, melter size can be reduced without adversely affecting glass quality. Physical chemistry and localized heat transfer of the waste-glass melting process are examined, to refine the available models for predicting and assuring glass production rate. It is concluded that the size of replacement melters and future waste processing facilities can be significantly decreased if minimum heat transfer requirements for effective melting are met by mechanical agitation. A new class of waste glass melters has been designed, and proof of concept tests completed on simulated High Level Radioactive Waste slurry. Melt rates have exceeded 155 kg m{sup {minus}2} h{sup {minus}1} with slurry feeds (32 lb ft{sup {minus}2} h{sup {minus}1}), and 229 kg kg m{sup {minus}2} h{sup {minus}1} with dry feed (47 lb ft{sup {minus}2} h{sup {minus}1}). This is about 8 times the melt rate possible in conventional waste- glass melters of the same size. 39 refs., 5 figs., 9 tabs.

  13. Glasses for seeing beyond visible.

    PubMed

    Zhang, XiangHua; Bureau, Bruno; Lucas, Pierre; Boussard-Pledel, Catherine; Lucas, Jacques

    2008-01-01

    Conventional glasses based on oxides have a transparency limited by phonon absorption in the near IR region and have a limited interest for analyzing information located far beyond the visible. The IR spectral domain is nevertheless of prime interest, since it covers fundamental wavelength ranges used for thermal imaging as well as molecular vibrational signatures. Besides spectacular advances in the field of IR detectors, the main significant progresses are related to the development of IR glass optics, such as lenses or IR optical fibres. The field of IR glasses is almost totally dominated by glasses formed from heavy atoms such as the chalcogens S, Se and Te. Their transparency extends up to 12, 16 and 28 microm for sulfide-, selenide- and the new generation of telluride-based glasses, respectively. They cover the atmospheric transparency domains, 3-5 and 8-13 microm, respectively, at which the IR radiation can propagate allowing thermal imaging and night-vision operations through thick layers of atmosphere. The development of new glass compositions will be discussed on the basis of structural consideration with the objective of moulding low-cost lenses for IR cameras used, for instance, in car-driving assistance. Additionally, multimode, single-index, optical fibres operating in the 3 to 12 microm window developed for in situ remote evanescent-wave IR spectroscopy will also be mentioned. The detection of molecular IR signatures is applied to environmental monitoring for investigating the pollution of underground water with toxic molecules. The extension of this technique to the investigation of biomolecules in three different studies devoted to liver tissues analysis, bio-film formation, and cell metabolism will also be discussed. Finally we will mention the developments in the field of single-mode fibres operating around 10 mum for the Darwin space mission, which is aiming at discovering, signs of biological life in telluric earth-like exoplanets throughout

  14. Antibacterial properties of laser spinning glass nanofibers.

    PubMed

    Echezarreta-López, M M; De Miguel, T; Quintero, F; Pou, J; Landin, M

    2014-12-30

    A laser-spinning technique has been used to produce amorphous, dense and flexible glass nanofibers of two different compositions with potential utility as reinforcement materials in composites, fillers in bone defects or scaffolds (3D structures) for tissue engineering. Morphological and microstructural analyses have been carried out using SEM-EDX, ATR-FTIR and TEM. Bioactivity studies allow the nanofibers with high proportion in SiO2 (S18/12) to be classified as a bioinert glass and the nanofibers with high proportion of calcium (ICIE16) as a bioactive glass. The cell viability tests (MTT) show high biocompatibility of the laser spinning glass nanofibers. Results from the antibacterial activity study carried out using dynamic conditions revealed that the bioactive glass nanofibers show a dose-dependent bactericidal effect on Sthaphylococcus aureus (S. aureus) while the bioinert glass nanofibers show a bacteriostatic effect also dose-dependent. The antibacterial activity has been related to the release of alkaline ions, the increase of pH of the medium and also the formation of needle-like aggregates of calcium phosphate at the surface of the bioactive glass nanofibers which act as a physical mechanism against bacteria. The antibacterial properties give an additional value to the laser-spinning glass nanofibers for different biomedical applications, such as treating or preventing surgery-associated infections.

  15. DEFENSE HIGH LEVEL WASTE GLASS DEGRADATION

    SciTech Connect

    W. Ebert

    2001-09-20

    provide models and parameter values that can be used to calculate the dissolution rates for the different modes of water contact. The analyses were conducted to identify key aspects of the mechanistic model for glass dissolution to be included in the abstracted models used for PA calculations, evaluate how the models can be used to calculate bounding values of the glass dissolution rates under anticipated water contact modes in the disposal. system, and determine model parameter values for the range of potential waste glass compositions and anticipated environmental conditions. The analysis of a bounding rate also considered the effects of the buildup of glass corrosion products in the solution contacting the glass and potential effects of alteration phase formation. Note that application of the models and model parameter values is constrained to the anticipated range of HLW glass compositions and environmental conditions. The effects of processes inherent to exposure to humid air and dripping water were not modeled explicitly. Instead, the impacts of these processes on the degradation rate were taken into account by using empirically measured parameter values. These include the rates at which water sorbs onto the glass, drips onto the glass, and drips off of the glass. The dissolution rates of glasses that were exposed to humid air and dripping water measured in laboratory tests are used to estimate model parameter values for contact by humid air and dripping water in the disposal system.

  16. 6. Looking glass aircraft in the project looking glass historic ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. Looking glass aircraft in the project looking glass historic district. View to north. - Offutt Air Force Base, Looking Glass Airborne Command Post, Looking Glass Avenue between Comstat Drive & Nightwatch Avenue, Offutt Air Force Base, Bellevue, Sarpy County, NE

  17. Oxynitride glass fibers

    NASA Technical Reports Server (NTRS)

    Patel, Parimal J.; Messier, Donald R.; Rich, R. E.

    1991-01-01

    Research at the Army Materials Technology Laboratory (AMTL) and elsewhere has shown that many glass properties including elastic modulus, hardness, and corrosion resistance are improved markedly by the substitution of nitrogen for oxygen in the glass structure. Oxynitride glasses, therefore, offer exciting opportunities for making high modulus, high strength fibers. Processes for making oxynitride glasses and fibers of glass compositions similar to commercial oxide glasses, but with considerable enhanced properties, are discussed. We have made glasses with elastic moduli as high as 140 GPa and fibers with moduli of 120 GPa and tensile strengths up to 2900 MPa. AMTL holds a U.S. patent on oxynitride glass fibers, and this presentation discusses a unique process for drawing small diameter oxynitride glass fibers at high drawing rates. Fibers are drawn through a nozzle from molten glass in a molybdenum crucible at 1550 C. The crucible is situated in a furnace chamber in flowing nitrogen, and the fiber is wound in air outside of the chamber, making the process straightforward and commercially feasible. Strengths were considerably improved by improving glass quality to minimize internal defects. Though the fiber strengths were comparable with oxide fibers, work is currently in progress to further improve the elastic modulus and strength of fibers. The high elastic modulus of oxynitride glasses indicate their potential for making fibers with tensile strengths surpassing any oxide glass fibers, and we hope to realize that potential in the near future.

  18. 4He glass phase: A model for liquid elements

    NASA Astrophysics Data System (ADS)

    Tournier, Robert F.; Bossy, Jacques

    2016-08-01

    The specific heat of liquid helium confined under pressure in nanoporous material and the formation, in these conditions, of a glass phase accompanied by latent heat are known. These properties are in good agreement with a recent model predicting, in liquid elements, the formation of ultrastable glass having universal thermodynamic properties. The third law of thermodynamics involves that the specific heat decreases at low temperatures and consequently the effective transition temperature of the glass increases up to the temperature where the frozen enthalpy becomes equal to the predicted value. The glass residual entropy is about 23.6% of the melting entropy.

  19. Glass tube splitting tool

    NASA Technical Reports Server (NTRS)

    Klein, J. A.; Murray, C. D.; Stein, J. A.

    1971-01-01

    Tool accurately splits glass tubing so cuts are aligned 180 deg apart and reassembled tube forms low pressure, gastight enclosure. Device should interest industries using cylindrical closed glass containers.

  20. First principles process-product models for vitrification of nuclear waste: Relationship of glass composition to glass viscosity, resistivity, liquidus temperature, and durability

    SciTech Connect

    Jantzen, C.M.

    1991-12-31

    Borosilicate glasses will be used in the USA and in Europe to immobilize radioactive high level liquid wastes (HLLW) for ultimate geologic disposal. Process and product quality models based on glass composition simplify the fabrication of the borosilicate glass while ensuring glass processability and quality. The process model for glass viscosity is based on a relationship between the glass composition and its structural polymerization. The relationship between glass viscosity and electrical resistivity is also shown to relate to glass polymerization. The process model for glass liquidus temperature calculates the solubility of the liquidus phases based on the free energies of formation of the precipitating species. The durability product quality model is based on the calculation of the thermodynamic hydration free energy from the glass composition.

  1. First principles process-product models for vitrification of nuclear waste: Relationship of glass composition to glass viscosity, resistivity, liquidus temperature, and durability

    SciTech Connect

    Jantzen, C.M.

    1991-01-01

    Borosilicate glasses will be used in the USA and in Europe to immobilize radioactive high level liquid wastes (HLLW) for ultimate geologic disposal. Process and product quality models based on glass composition simplify the fabrication of the borosilicate glass while ensuring glass processability and quality. The process model for glass viscosity is based on a relationship between the glass composition and its structural polymerization. The relationship between glass viscosity and electrical resistivity is also shown to relate to glass polymerization. The process model for glass liquidus temperature calculates the solubility of the liquidus phases based on the free energies of formation of the precipitating species. The durability product quality model is based on the calculation of the thermodynamic hydration free energy from the glass composition.

  2. Stabilization of Ca1-dFe2-xMnxO4 (0.44 lt x lt 2) with CaFe2O4-type Structure and Ca2plus Defects in 1D Channels

    SciTech Connect

    T Yang; M Croft; A Ignatov; I Nowik; R Cong; M Greenblatt

    2011-12-31

    Solid solutions of Ca{sub 1-{delta}}Fe{sub 2-x}Mn{sub x}O{sub 4} (0.45 {<=} x {<=} 2) were synthesized from CaCl{sub 2} as flux at 850 C in air. The entire series, even with x = 2, crystallizes in the CaFe{sub 2}O{sub 4}-type structure (Pnma), rather than in the CaMn{sub 2}O{sub 4}-type structure (Pbcm). Rietveld refinements confirmed mixed-valency Mn{sup 3+}/Mn{sup 4+} and a substantial level of Ca{sup 2+} deficiency ({delta} {approx} 0.25) at high x. With increasing x, the unit-cell dimensions a and b decrease, while that of c increases. Detailed structural analyses, together with Mn K-edge X-ray absorption and {sup 57}Fe Moessbauer spectroscopy studies, revealed that the stabilization of CaFe{sub 2}O{sub 4}-type structure, even at high values of x, is due to the existence of non-Jahn-Teller active Mn{sup 4+} (and Fe{sup 3+}), which is compensated by the formation of the Ca{sup 2+} deficiencies in the one-dimensional (1D) channels of Ca{sub 1-{delta}}Fe{sub 2-x}Mn{sub x}O{sub 4} during the flux synthesis. Antiferromagnetic (AFM) long-range ordering is achieved for all compounds at low temperature, because of strong AFM interactions between Mn{sup 3+}/Mn{sup 4+} and Fe{sup 3+}. In addition, a spin (or cluster) glass component was also observed, as expected, because of the extensive Mn/Fe structural and Mn{sup 3+}/Mn{sup 4+} charge disordering.

  3. Technique for Machining Glass

    NASA Technical Reports Server (NTRS)

    Rice, S. H.

    1982-01-01

    Process for machining glass with conventional carbide tools requires a small quantity of a lubricant for aluminum applied to area of glass to be machined. A carbide tool is then placed against workpiece with light pressure. Tool is raised periodically to clear work of glass dust and particles. Additional lubricant is applied as it is displaced.

  4. Glass in Class

    ERIC Educational Resources Information Center

    Greaves, Neville

    2005-01-01

    Glass is reviewed from fabrication to application, laying emphasis on the wide-ranging physics involved. This begins with liquids and solids and the way in which glasses are defined and can be demonstrated in the classroom. At the atomic level the regular structure of crystals and their irregular counterparts in glasses are explained through…

  5. PLUTONIUM SOLUBILITY IN HIGH-LEVEL WASTE ALKALI BOROSILICATE GLASS

    SciTech Connect

    Marra, J.; Crawford, C.; Fox, K.; Bibler, N.

    2011-01-04

    The solubility of plutonium in a Sludge Batch 6 (SB6) reference glass and the effect of incorporation of Pu in the glass on specific glass properties were evaluated. A Pu loading of 1 wt % in glass was studied. Prior to actual plutonium glass testing, surrogate testing (using Hf as a surrogate for Pu) was conducted to evaluate the homogeneity of significant quantities of Hf (Pu) in the glass, determine the most appropriate methods to evaluate homogeneity for Pu glass testing, and to evaluate the impact of Hf loading in the glass on select glass properties. Surrogate testing was conducted using Hf to represent between 0 and 1 wt % Pu in glass on an equivalent molar basis. A Pu loading of 1 wt % in glass translated to {approx}18 kg Pu per Defense Waste Processing Facility (DWPF) canister, or about 10X the current allowed limit per the Waste Acceptance Product Specifications (2500 g/m{sup 3} of glass or about 1700 g/canister) and about 30X the current allowable concentration based on the fissile material concentration limit referenced in the Yucca Mountain Project License Application (897 g/m{sup 3}3 of glass or about 600 g Pu/canister). Based on historical process throughput data, this level was considered to represent a reasonable upper bound for Pu loading based on the ability to provide Pu containing feed to the DWPF. The task elements included evaluating the distribution of Pu in the glass (e.g. homogeneity), evaluating crystallization within the glass, evaluating select glass properties (with surrogates), and evaluating durability using the Product Consistency Test -- Method A (PCT-A). The behavior of Pu in the melter was evaluated using paper studies and corresponding analyses of DWPF melter pour samples.The results of the testing indicated that at 1 wt % Pu in the glass, the Pu was homogeneously distributed and did not result in any formation of plutonium-containing crystalline phases as long as the glass was prepared under 'well-mixed' conditions. The

  6. Bleaching versus poling: Comparison of electric field induced phenomena in glasses and glass-metal nanocomposites

    NASA Astrophysics Data System (ADS)

    Lipovskii, A. A.; Melehin, V. G.; Petrov, M. I.; Svirko, Yu. P.; Zhurikhina, V. V.

    2011-01-01

    By examining the electric field induced processes in glasses and glass-metal nanocomposites (GMN) we propose mechanism of the electric field assisted dissolution (EFAD) of metal nanoparticles in glass. We show that in both glass poling and EFAD processes, the strong (up to 1 V/nm) local electric field in the subanodic region is due to the presence of "slow" hydrogen ions bonded to nonbridging oxygen atoms in glass matrix. However, the origin of these hydrogen ions in glass and GMN is different. Specifically, when we apply the electric field to a virgin glass, the enrichment of the glass with hydrogen species takes place in the course of the poling. In GMN, the hydrogen ions have been incorporated into the glass matrix during metal nanoparticles formation via reduction in a metal by hydrogen, i.e., before the electric field was applied. The EFAD of metal nanoparticles resembles the electric field stimulated diffusion of metal film in glass (the important difference however is that in GMN, there is no direct contact of dissolving metal entity with anodic electrode). This similarity makes it possible to estimate the energy of thermal activated transition of silver atoms from a nanoparticle to glass matrix as ˜1.3 eV. Electroneutrality of the GMN requires emission of electrons from nanoparticles. Photoconductivity spectra of soda-lime glasses and the results of numerical calculations of band structure of fused silica, sodium disilicate and sodium-calcium-silicate glass enable us to evaluate the bandgap and the position of electron mobility edge in soda-lime glass. The evaluated values are ˜6 eV and ˜1.2 eV below vacuum level, respectively. The bent of the glass band structure in strong electric field permits a direct tunneling of Fermi electrons from silver nanoparticle (4.6 eV below the vacuum level) to the glass conductivity band. Evaluated in accordance with the Fowler-Nordheim equation the magnitude of electric field necessary to establish comparable electron

  7. Radiation coloration resistant glass

    DOEpatents

    Tomozawa, M.; Watson, E.B.; Acocella, J.

    1986-11-04

    A radiation coloration resistant glass is disclosed which is used in a radiation environment sufficient to cause coloration in most forms of glass. The coloration resistant glass includes higher proportions by weight of water and has been found to be extremely resistant to color change when exposed to such radiation levels. The coloration resistant glass is free of cerium oxide and has more than about 0.5% by weight water content. Even when exposed to gamma radiation of more than 10[sup 7] rad, the coloration resistant glass does not lose transparency. 3 figs.

  8. Oxynitride glass production procedure

    DOEpatents

    Weidner, Jerry R.; Schuetz, Stanley T.; O'Brien, Michael H.

    1991-01-01

    The invention is a process for the preparation of high quality oxynitride glasses without resorting to high pressures. Nitrogen-containing compounds such as Si.sub.3 N.sub.4 are first encapsulated in a low melting temperature glass. Particles of the encapsulated nitrogen-containing compound are mixed with other oxide glass-formers and melted in an atmosphere of flowing nitrogen and in the presence of buffering gas to form the oxynitride glass. Glasses containing up to 15 at % nitrogen have been prepared by this method.

  9. Radiation coloration resistant glass

    DOEpatents

    Tomozawa, Minoru; Watson, E. Bruce; Acocella, John

    1986-01-01

    A radiation coloration resistant glass is disclosed which is used in a radiation environment sufficient to cause coloration in most forms of glass. The coloration resistant glass includes higher proportions by weight of water and has been found to be extremely resistant to color change when exposed to such radiation levels. The coloration resistant glass is free of cerium oxide and has more than about 0.5% by weight water content. Even when exposed to gamma radiation of more than 10.sup.7 rad, the coloration resistant glass does not lose transparency.

  10. Immobilization of gadolinium in iron borophosphate glasses and iron borophosphate based glass-ceramics: Implications for the immobilization of plutonium(Ⅲ)

    NASA Astrophysics Data System (ADS)

    Wang, Fu; Liao, Qilong; Dai, Yunya; Zhu, Hanzhen

    2016-08-01

    Immobilization of gadolinium (Gd), a nonradioactive surrogate for Pu3+, in iron borophosphate glasses/glass-ceramics (IBP glasses/glass-ceramics) has been investigated. The IBP glass containing 4 mol% Gd2O3 is homogeneously amorphous. At higher Gd2O3 concentrations, additional Gd is retained in the glasses as crystalline inclusions of monazite GdPO4 crystalline phase detected with X-ray diffraction. Moreover, Gd2O3 addition increases the Tg of the IBP glasses in glass formation range, which is consistent with the structural modification of the glasses. The structure of the Gd2O3-loaded IBP glasses/glass-ceramics is mainly based on pyrophosphate units. The chemical durability of Gd2O3-loaded IBP glasses/glass-ceramics is comparable to widely used borosilicate glass waste forms and the existence of monazite GdPO4 crystalline phase does not degrade the aqueous chemical durability of the IBP glasses/glass-ceramics. The Gd-loading results imply that the solubility should not be a limiting factor in processing nuclide Pu3+ if the formed crystalline phase(s) have high chemical durability.

  11. A predictive structural model for bulk metallic glasses

    PubMed Central

    Laws, K. J.; Miracle, D. B.; Ferry, M.

    2015-01-01

    Great progress has been made in understanding the atomic structure of metallic glasses, but there is still no clear connection between atomic structure and glass-forming ability. Here we give new insights into perhaps the most important question in the field of amorphous metals: how can glass-forming ability be predicted from atomic structure? We give a new approach to modelling metallic glass atomic structures by solving three long-standing problems: we discover a new family of structural defects that discourage glass formation; we impose efficient local packing around all atoms simultaneously; and we enforce structural self-consistency. Fewer than a dozen binary structures satisfy these constraints, but extra degrees of freedom in structures with three or more different atom sizes significantly expand the number of relatively stable, ‘bulk' metallic glasses. The present work gives a new approach towards achieving the long-sought goal of a predictive capability for bulk metallic glasses. PMID:26370667

  12. Probing equilibrium glass flow up to exapoise viscosities.

    PubMed

    Pogna, Eva Arianna Aurelia; Rodríguez-Tinoco, Cristian; Cerullo, Giulio; Ferrante, Carino; Rodríguez-Viejo, Javier; Scopigno, Tullio

    2015-02-24

    Glasses are out-of-equilibrium systems aging under the crystallization threat. During ordinary glass formation, the atomic diffusion slows down, rendering its experimental investigation impractically long, to the extent that a timescale divergence is taken for granted by many. We circumvent these limitations here, taking advantage of a wide family of glasses rapidly obtained by physical vapor deposition directly into the solid state, endowed with different "ages" rivaling those reached by standard cooling and waiting for millennia. Isothermally probing the mechanical response of each of these glasses, we infer a correspondence with viscosity along the equilibrium line, up to exapoise values. We find a dependence of the elastic modulus on the glass age, which, traced back to the temperature steepness index of the viscosity, tears down one of the cornerstones of several glass transition theories: the dynamical divergence. Critically, our results suggest that the conventional wisdom picture of a glass ceasing to flow at finite temperature could be wrong.

  13. Electroless plating of copper on surface-modified glass substrate

    NASA Astrophysics Data System (ADS)

    Su, Wei; Yao, Libei; Yang, Fang; Li, Peiyuan; Chen, Juan; Liang, Lifang

    2011-07-01

    This work focuses on developing a novel convenient method for electroless copper deposition on glass material. This method is relied on the formation of amino (NH2)-terminated film on the surface of glass substrate, by coating polyethylenimine (PEI) on glass matrix and using epichlorohydrin (ECH) as cross-linking agent. The introduced amino groups can effectively adsorb the palladium, the catalysts which could initiate the subsequent Cu electroless plating, onto the glass substrate surface. Finally, a copper film is formed on the palladium-activated glass substrate through copper electroless plating and the surface-coppered glass material is therefore acquired. X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscopy (SEM) images combined with energy diffraction X-ray (EDX) analysis demonstrate the successful copper deposition on the surface of glass substrate.

  14. Nanostructures synthesis by femtosecond laser ablation of glasses

    NASA Astrophysics Data System (ADS)

    Vipparty, D.; Tan, B.; Venkatakrishnan, K.

    2012-10-01

    In this article, we investigate the variations in ablation dynamics that result in diverse nanostructures on SiO2 based glass samples. A three-dimensional fibrous nanoparticle agglomerate was observed on sodalime glass when exposed to femtosecond laser irradiation. The fused nanoparticles have diameters ranging from 30 nm to 70 nm. Long continuous nanofibers of extremely high aspect ratio (certain fibers up to 100 000:1) were obtained by exposing silica glass surface to femtosecond laser irradiation at MHz repetition rate in air. A nanostructure assembly comprising of nanofiber and nanoparticle agglomerates was also observed by ablating silica glass. From our experimental analysis, it was determined that variation in bandgap and material composition alters ablation dynamics and dictates the response of glass to femtosecond laser irradiation, ultimately leading to the formation of structures with varying morphology on silica and sodalime glass. The possible underlying mechanisms that produce such nanostructures on glass specimens have also been explored.

  15. Estimation of the critical glass transition rate and the inorganic glass thickness

    NASA Astrophysics Data System (ADS)

    Belousov, O. K.

    2009-12-01

    Procedures are described for calculating the components of a new equation obtained to estimate critical glass transition rate R c . Reported data on R c are used to calculate critical shear frequency ν t, g( m), and a technique of its calculation using absolute entropy and elastic constants is presented. Procedures for calculating the energy of defect formation in amorphous substances H ν and for estimating glass transition temperature T g are described. It is shown that the ratio H ν / q (where q = N A k BΔ T m-g , N A is Avogadro’s number, k B is the Boltzmann constant, and Δ T m-g is the difference between the melting and glass transition temperatures) can be used to estimate critical glass transition rate R c and critical glass thickness h c .

  16. Composition-dependent metallic glass alloys correlate atomic mobility with collective glass surface dynamics.

    PubMed

    Nguyen, Duc; Zhu, Zhi-Guang; Pringle, Brian; Lyding, Joseph; Wang, Wei-Hua; Gruebele, Martin

    2016-06-22

    Glassy metallic alloys are richly tunable model systems for surface glassy dynamics. Here we study the correlation between atomic mobility, and the hopping rate of surface regions (clusters) that rearrange collectively on a minute to hour time scale. Increasing the proportion of low-mobility copper atoms in La-Ni-Al-Cu alloys reduces the cluster hopping rate, thus establishing a microscopic connection between atomic mobility and dynamics of collective rearrangements at a glass surface made from freshly exposed bulk glass. One composition, La60Ni15Al15Cu10, has a surface resistant to re-crystallization after three heating cycles. When thermally cycled, surface clusters grow in size from about 5 glass-forming units to about 8 glass-forming units, evidence of surface aging without crystal formation, although its bulk clearly forms larger crystalline domains. Such kinetically stable glass surfaces may be of use in applications where glassy coatings stable against heating are needed.

  17. Acoustics of glass harmonicas

    NASA Astrophysics Data System (ADS)

    Rossing, Thomas D.

    2001-05-01

    Glass musical instruments are probably as old as glassmaking. At least as early as the 17th century it was discovered that wine glasses, when rubbed with a wet finger, produced a musical tone. A collection of glasses played in this manner is called a glass harp. Another type of glass harmonica, called the armonica by its inventor Benjamin Franklin, employs glass bowls or cups turned by a horizontal axle, so the performer need only touch the rim of the bowls as they rotate to set them into vibration. We discuss the modes of vibration of both types of glass harmonica, and describe the different sounds that are emitted by rubbing, tapping, or bowing them. Rubbing with a wet finger tends to excite only the (2,0) mode and its harmonics through a ``stick-slip'' process, while tapping excites the other modes as well.

  18. A molecular view of vapor deposited glasses

    SciTech Connect

    Singh, Sadanand; Pablo, Juan J. de

    2011-05-21

    Recently, novel organic glassy materials that exhibit remarkable stability have been prepared by vapor deposition. The thermophysical properties of these new ''stable'' glasses are equivalent to those that common glasses would exhibit after aging over periods lasting thousands of years. The origin of such enhanced stability has been elusive; in the absence of detailed models, past studies have discussed the formation of new polyamorphs or that of nanocrystals to explain the observed behavior. In this work, an atomistic molecular model of trehalose, a disaccharide of glucose, is used to examine the properties of vapor-deposited stable glasses. Consistent with experiment, the model predicts the formation of stable glasses having a higher density, a lower enthalpy, and higher onset temperatures than those of the corresponding ''ordinary'' glass formed by quenching the bulk liquid. Simulations reveal that newly formed layers of the growing vapor-deposited film exhibit greater mobility than the remainder of the material, thereby enabling a reorganization of the film as it is grown. They also reveal that ''stable'' glasses exhibit a distinct layered structure in the direction normal to the substrate that is responsible for their unusual properties.

  19. Bioactive ceramic glasses in situ synthesized by laser melting

    NASA Astrophysics Data System (ADS)

    Taca, Mihaela; Vasile, Eugeniu; Boroica, Lucica; Udrea, Mircea; Medianu, Rares; Munteanu, Maria Cristina

    2008-10-01

    The synthesis of bioactive glass from raw materials even during the laser deposition process, could provide formation of a biocompatible layer on the metallic prosthesis. During the laser irradiation melting and ultrarapid solidification of ceramic materials occur and glasses controlled by the process parameters (especially laser power and solidification rate) will be obtained. The aim of the present paper is to study the influence of the processing parameters on the laser synthesized glasses chemical composition, structure and bioactive behaviour.

  20. Viscosity properties of tellurite-based glasses

    SciTech Connect

    Tincher, B.; Massera, J.; Petit, L.; Richardson, K.

    2010-12-15

    The viscosity behavior of glasses with the composition (90-x)TeO{sub 2}-10Bi{sub 2}O{sub 3}-xZnO with x = 15, 17.5, and 20 (TBZ glasses) and 80TeO{sub 2}-(20-y)Na{sub 2}O-yZnO system with y = 0, 5, and 10 (TNZ glasses) have been measured as a function of temperature using a beam-bending (BBV) and a parallel-plate (PPV) viscometer. The structure of the glass' network has been characterized using Raman spectroscopy and has been related to the viscosity temperature behavior and the fragility parameter (m) of the glasses. As the concentration of ZnO in the TBZ system (x) increases, the fragility parameter of the glass increases, whereas it decreases with an increase of the ZnO concentration (y) in the TNZ system. In both glasses, these variations in m have been related to the partial depolymerization of the tellurite network associated with the level of modifier content. The depolymerization of the tellurite network is believed to be the result of a reduction in the number of [TeO{sub 4}] units and the formation of [TeO{sub 3}] and [TeO{sub 3+1}] units that occurs with a change in TeO{sub 2} content in the TBZ system and modifier content in the TNZ system.

  1. Radiation resistance of quartz glass for VUV discharge lamps

    NASA Astrophysics Data System (ADS)

    Schreiber, A.; Kühn, B.; Arnold, E.; Schilling, F.-J.; Witzke, H.-D.

    2005-09-01

    Electrically-fused quartz glass, flame-fused quartz glass and plasma-fused quartz glass as well as synthetic fused silica samples were irradiated stepwise with a high energy Xe barrier discharge excimer lamp at 172 nm. VUV spectra were measured before and after every irradiation step. The results show that the VUV transmittance and the resistance against high energy radiation strongly depend on the quartz glass type, as well as on the thermal pretreatment of the quartz glass samples. In electrically-fused and plasma-fused quartz glass the VUV transmission decreases by the formation of oxygen deficiency and E' centres with absorption bands at 163 nm and 215 nm. Best irradiation resistance is found in synthetic fused silica and in thermally treated flame-fused quartz glass. Photoluminescence spectra measured under excitation with a KrF excimer laser before and after irradiation indicate fundamental differences in the SiO2 network structure of the different quartz glass types. Whereas a poor radiation resistance correlates with a blue photoluminescence band at 390 nm, the photoluminescence of flame-fused quartz glass changes from blue to green by a thermal treatment which is correlated with a significant improvement of radiation resistance. A simplified model is presented referring to hydride and oxygen deficiency centres as precursors to colour centre formation in different types of quartz glass.

  2. Molecular dynamics studies of metallic glasses

    NASA Astrophysics Data System (ADS)

    Lee, Hyon-Jee

    The thermodynamic, structural, and mechanical properties of metallic glasses are studied using molecular dynamics simulations. Molecular dynamics provides a computational framework to simulate the movement of interacting atoms in response to external perturbations, such as changes in temperature or pressure. In this thesis, a Sutton-Chen potential was chosen to describe the many-body interactions in metals and alloys. Our first application for this approach is to develop a simple model to derive the thermodynamic properties of metallic alloys (Chapter 2). Based on this model, we demonstrate that the glass transition is thermodynamically sensitive to differences between atomic radii and that there is an optimal difference for glass formation. Next, we extend these simulations to elucidate the details of structural organization in the glass (Chapter 3). We find that the liquid phase is characterized by a local five-fold symmetry, which becomes more prominent as the glass phase forms. This five-fold symmetry is related to the formation of icosahedral structures. The mechanical properties of glasses are also investigated and it is found that shear localization, which accompanies a sharp drop in the stress-strain curve, occurs at 45 degree with respect to the loading axis (Chapter 4). The generation of free volume is found to be the dominant mechanism that leads to shear localization, rather than adiabatic heating. Finally, generic first principle potentials are constructed to guide the experimental development of AlTiNi based metallic glasses (Chapter 5). Together, the results from these simulations improve our understanding of the thermodynamic, structural, and mechanical properties of metallic glasses and will aid computer-driven materials design.

  3. Random pinning glass model.

    PubMed

    Karmakar, Smarajit; Parisi, Giorgio

    2013-02-19

    Glass transition, in which viscosity of liquids increases dramatically upon decrease of temperature without any major change in structural properties, remains one of the most challenging problems in condensed matter physics despite tremendous research efforts in past decades. On the other hand, disordered freezing of spins in magnetic materials with decreasing temperature, the so-called "spin glass transition," is understood relatively better. A previously found similarity between some spin glass models and the structural glasses inspired development of theories of structural glasses based on the scenario of spin glass transition. This scenario, although it looks very appealing, is still far from being well established. One of the main differences between standard spin systems and molecular systems is the absence of quenched disorder and the presence of translational invariance: it often is assumed that this difference is not relevant, but this conjecture still needs to be established. The quantities, which are well-defined and characterized for spin models, are not easily calculable for molecular glasses because of the lack of quenched disorder that breaks the translational invariance in the system. Thus the characterization of the similarity between spin and the structural glass transition remains an elusive subject. In this study, we introduced a model structural glass with built-in quenched disorder that alleviates this main difference between the spin and molecular glasses, thereby helping us compare these two systems: the possibility of producing a good thermalization at rather low temperatures is one of the advantages of this model. PMID:23382186

  4. Liquid Glass: A Facile Soft Replication Method for Structuring Glass.

    PubMed

    Kotz, Frederik; Plewa, Klaus; Bauer, Werner; Schneider, Norbert; Keller, Nico; Nargang, Tobias; Helmer, Dorothea; Sachsenheimer, Kai; Schäfer, Michael; Worgull, Matthias; Greiner, Christian; Richter, Christiane; Rapp, Bastian E

    2016-06-01

    Liquid glass is a photocurable amorphous silica nanocomposite that can be structured using soft replication molds and turned into glass via thermal debinding and sintering. Simple polymer bonding techniques allow the fabrication of complex microsystems in glass like microfluidic chips. Liquid glass is a step toward prototyping of glass microstructures at low cost without requiring cleanroom facilities or hazardous chemicals. PMID:27060964

  5. Liquid Glass: A Facile Soft Replication Method for Structuring Glass.

    PubMed

    Kotz, Frederik; Plewa, Klaus; Bauer, Werner; Schneider, Norbert; Keller, Nico; Nargang, Tobias; Helmer, Dorothea; Sachsenheimer, Kai; Schäfer, Michael; Worgull, Matthias; Greiner, Christian; Richter, Christiane; Rapp, Bastian E

    2016-06-01

    Liquid glass is a photocurable amorphous silica nanocomposite that can be structured using soft replication molds and turned into glass via thermal debinding and sintering. Simple polymer bonding techniques allow the fabrication of complex microsystems in glass like microfluidic chips. Liquid glass is a step toward prototyping of glass microstructures at low cost without requiring cleanroom facilities or hazardous chemicals.

  6. Radiopaque Strontium Fluoroapatite Glass-Ceramics.

    PubMed

    Höland, Wolfram; Schweiger, Marcel; Dittmer, Marc; Ritzberger, Christian

    2015-01-01

    The controlled precipitation of strontium fluoroapatite crystals was studied in four base glass compositions derived from the SiO2-Al2O3-Y2O3-SrO-Na2O-K2O/Rb2O/Cs2O-P2O5-F system. The crystal phase formation of these glasses and the main properties of the glass-ceramics, such as thermal and optical properties and radiopacity were compared with a fifth, a reference glass-ceramic. The reference glass-ceramic was characterized as Ca-fluoroapatite glass-ceramic. The four strontium fluoroapatite glass-ceramics showed the following crystal phases: (a) Sr5(PO4)3F - leucite, KAlSi2O6, (b) Sr5(PO4)3F - leucite, KAlSi2O6, and nano-sized NaSrPO4, (c) Sr5(PO4)3F - pollucite, CsAlSi2O6, and nano-sized NaSrPO4, and (d) Sr5(PO4)3F - Rb-leucite, RbAlSi2O6, and nano-sized NaSrPO4. The proof of crystal phase formation was possible by X-ray diffraction. The microstructures, which were studied using scanning electron microscopy, demonstrated a uniform distribution of the crystals in the glass matrix. The Sr-fluoroapatites were precipitated based on an internal crystallization process, and the crystals demonstrated a needle-like morphology. The study of the crystal growth of needle-like Sr-fluoroapatites gave a clear evidence of an Ostwald ripening mechanism. The formation of leucite, pollucite, and Rb-leucite was based on a surface crystallization mechanism. Therefore, a twofold crystallization mechanism was successfully applied to develop these types of glass-ceramics. The main focus of this study was the controlled development of glass-ceramics exhibiting high radiopacity in comparison to the reference glass-ceramic. This goal could be achieved with all four glass-ceramics with the preferred development of the Sr-fluoroapatite - pollucite-type glass-ceramic. In addition to this main development, it was possible to control the thermal properties. Especially the Rb-leucite containing glass-ceramic showed the highest coefficient of thermal expansion (CTE). These

  7. Radiopaque Strontium Fluoroapatite Glass-Ceramics.

    PubMed

    Höland, Wolfram; Schweiger, Marcel; Dittmer, Marc; Ritzberger, Christian

    2015-01-01

    The controlled precipitation of strontium fluoroapatite crystals was studied in four base glass compositions derived from the SiO2-Al2O3-Y2O3-SrO-Na2O-K2O/Rb2O/Cs2O-P2O5-F system. The crystal phase formation of these glasses and the main properties of the glass-ceramics, such as thermal and optical properties and radiopacity were compared with a fifth, a reference glass-ceramic. The reference glass-ceramic was characterized as Ca-fluoroapatite glass-ceramic. The four strontium fluoroapatite glass-ceramics showed the following crystal phases: (a) Sr5(PO4)3F - leucite, KAlSi2O6, (b) Sr5(PO4)3F - leucite, KAlSi2O6, and nano-sized NaSrPO4, (c) Sr5(PO4)3F - pollucite, CsAlSi2O6, and nano-sized NaSrPO4, and (d) Sr5(PO4)3F - Rb-leucite, RbAlSi2O6, and nano-sized NaSrPO4. The proof of crystal phase formation was possible by X-ray diffraction. The microstructures, which were studied using scanning electron microscopy, demonstrated a uniform distribution of the crystals in the glass matrix. The Sr-fluoroapatites were precipitated based on an internal crystallization process, and the crystals demonstrated a needle-like morphology. The study of the crystal growth of needle-like Sr-fluoroapatites gave a clear evidence of an Ostwald ripening mechanism. The formation of leucite, pollucite, and Rb-leucite was based on a surface crystallization mechanism. Therefore, a twofold crystallization mechanism was successfully applied to develop these types of glass-ceramics. The main focus of this study was the controlled development of glass-ceramics exhibiting high radiopacity in comparison to the reference glass-ceramic. This goal could be achieved with all four glass-ceramics with the preferred development of the Sr-fluoroapatite - pollucite-type glass-ceramic. In addition to this main development, it was possible to control the thermal properties. Especially the Rb-leucite containing glass-ceramic showed the highest coefficient of thermal expansion (CTE). These

  8. Radiopaque Strontium Fluoroapatite Glass-Ceramics

    PubMed Central

    Höland, Wolfram; Schweiger, Marcel; Dittmer, Marc; Ritzberger, Christian

    2015-01-01

    The controlled precipitation of strontium fluoroapatite crystals was studied in four base glass compositions derived from the SiO2–Al2O3–Y2O3–SrO–Na2O–K2O/Rb2O/Cs2O–P2O5–F system. The crystal phase formation of these glasses and the main properties of the glass-ceramics, such as thermal and optical properties and radiopacity were compared with a fifth, a reference glass-ceramic. The reference glass-ceramic was characterized as Ca-fluoroapatite glass-ceramic. The four strontium fluoroapatite glass-ceramics showed the following crystal phases: (a) Sr5(PO4)3F – leucite, KAlSi2O6, (b) Sr5(PO4)3F – leucite, KAlSi2O6, and nano-sized NaSrPO4, (c) Sr5(PO4)3F – pollucite, CsAlSi2O6, and nano-sized NaSrPO4, and (d) Sr5(PO4)3F – Rb-leucite, RbAlSi2O6, and nano-sized NaSrPO4. The proof of crystal phase formation was possible by X-ray diffraction. The microstructures, which were studied using scanning electron microscopy, demonstrated a uniform distribution of the crystals in the glass matrix. The Sr-fluoroapatites were precipitated based on an internal crystallization process, and the crystals demonstrated a needle-like morphology. The study of the crystal growth of needle-like Sr-fluoroapatites gave a clear evidence of an Ostwald ripening mechanism. The formation of leucite, pollucite, and Rb-leucite was based on a surface crystallization mechanism. Therefore, a twofold crystallization mechanism was successfully applied to develop these types of glass-ceramics. The main focus of this study was the controlled development of glass-ceramics exhibiting high radiopacity in comparison to the reference glass-ceramic. This goal could be achieved with all four glass-ceramics with the preferred development of the Sr-fluoroapatite – pollucite-type glass-ceramic. In addition to this main development, it was possible to control the thermal properties. Especially the Rb-leucite containing glass-ceramic showed the highest coefficient of thermal

  9. Nanophase glass ceramics for capacitive energy storage

    NASA Astrophysics Data System (ADS)

    Rangarajan, Badri

    Glass ceramics are candidate dielectric materials for high energy storage capacitors. Since energy density depends primarily on dielectric permittivity and breakdown strength, glass ceramics with interconnected nano-crystalline particles and low porosity, which leads to high breakdown strength, are expected to have high energy density values. Three glass ceramic systems were investigated. Barium/lead sodium niobate glass ceramics, designated as PNNS (PbO-Na 2O-Nb2O5-SiO2) and BNNS (BaONa 2O- Nb2O5-SiO2), and barium titanate silicate glass ceramic, designated as BTS (BaOTiO2-SiO2), belonging to medium (epsilonr ~ 400-700) and low (epsilon r ~ 20) permittivity regimes, respectively, were fabricated by roller quenching and controlled crystallization. The overall properties of the glass ceramics were controlled by connectivity and volume fraction of crystallites. PNNS and BNNS developed perovskite and tungsten-bronze phases during crystallization with permittivity values between 400 and 700. Microstructural analysis of PNNS glass ceramic revealed grain sizes of the order of 50 nm. The calculated breakdown strengths were ~0.7 and ~075 MV/cm for PNNS and BNNS respectively. The resulting energy densities at breakdown were ~4.5 and ~6.5 J/cm3 for PNNS and BNNS respectively. However, the disadvantages, such as difficult glass formability, less control over crystallization due to multiphase formation and low dielectric breakdown strength values due to high dielectric contrast between the glass and crystal phases, associated with PNNS and BNNS glass ceramics served as the motivating factor for exploring BTS glass ceramic. The major advantage of studying BTS glass ceramic over the other systems is that a single crystalline phase, fresnoite (Ba2TiSi2O 8), grows from the quenched glass and properties can be explored over the whole spectrum ranging from fully amorphous to fully crystalline. Crystallization kinetics of the BTS glass is explored to control the relative volume

  10. Glass science tutorial lecture {number_sign}6: The melting of silicate glasses, a review of selected topics

    SciTech Connect

    Swarts, E.L.

    1995-03-01

    This report summarizes a two-day lecture given at Westinghouse Hanford Company in March, 1995 and includes the data used in the presentation. Topics included the special needs of a low-level waste vitrification process, glass melting, mechanisms of the formation of foam, glass refining (bubble removal), and homogenization (reduction of chemical heterogeneity to acceptable levels). 96 refs.

  11. Optical Basicity and Nepheline Crystallization in High Alumina Glasses

    SciTech Connect

    Rodriguez, Carmen P.; McCloy, John S.; Schweiger, M. J.; Crum, Jarrod V.; Winschell, Abigail E.

    2011-02-25

    The purpose of this study was to find compositions that increase waste loading of high-alumina wastes beyond what is currently acceptable while avoiding crystallization of nepheline (NaAlSiO4) on slow cooling. Nepheline crystallization has been shown to have a large impact on the chemical durability of high-level waste glasses. It was hypothesized that there would be some composition regions where high-alumina would not result in nepheline crystal production, compositions not currently allowed by the nepheline discriminator. Optical basicity (OB) and the nepheline discriminator (ND) are two ways of describing a given complex glass composition. This report presents the theoretical and experimental basis for these models. They are being studied together in a quadrant system as metrics to explore nepheline crystallization and chemical durability as a function of waste glass composition. These metrics were calculated for glasses with existing data and also for theoretical glasses to explore nepheline formation in Quadrant IV (passes OB metric but fails ND metric), where glasses are presumed to have good chemical durability. Several of these compositions were chosen, and glasses were made to fill poorly represented regions in Quadrant IV. To evaluate nepheline formation and chemical durability of these glasses, quantitative X-ray diffraction (XRD) analysis and the Product Consistency Test were conducted. A large amount of quantitative XRD data is collected here, both from new glasses and from glasses of previous studies that had not previously performed quantitative XRD on the phase assemblage. Appendix A critically discusses a large dataset to be considered for future quantitative studies on nepheline formation in glass. Appendix B provides a theoretical justification for choice of the oxide coefficients used to compute the OB criterion for nepheline formation.

  12. Diamond turning of glass

    SciTech Connect

    Blackley, W.S.; Scattergood, R.O.

    1988-12-01

    A new research initiative will be undertaken to investigate the critical cutting depth concepts for single point diamond turning of brittle, amorphous materials. Inorganic glasses and a brittle, thermoset polymer (organic glass) are the principal candidate materials. Interrupted cutting tests similar to those done in earlier research are Ge and Si crystals will be made to obtain critical depth values as a function of machining parameters. The results will provide systematic data with which to assess machining performance on glasses and amorphous materials

  13. Engineering Glass Passivation Layers -Model Results

    SciTech Connect

    Skorski, Daniel C.; Ryan, Joseph V.; Strachan, Denis M.; Lepry, William C.

    2011-08-08

    The immobilization of radioactive waste into glass waste forms is a baseline process of nuclear waste management not only in the United States, but worldwide. The rate of radionuclide release from these glasses is a critical measure of the quality of the waste form. Over long-term tests and using extrapolations of ancient analogues, it has been shown that well designed glasses exhibit a dissolution rate that quickly decreases to a slow residual rate for the lifetime of the glass. The mechanistic cause of this decreased corrosion rate is a subject of debate, with one of the major theories suggesting that the decrease is caused by the formation of corrosion products in such a manner as to present a diffusion barrier on the surface of the glass. Although there is much evidence of this type of mechanism, there has been no attempt to engineer the effect to maximize the passivating qualities of the corrosion products. This study represents the first attempt to engineer the creation of passivating phases on the surface of glasses. Our approach utilizes interactions between the dissolving glass and elements from the disposal environment to create impermeable capping layers. By drawing from other corrosion studies in areas where passivation layers have been successfully engineered to protect the bulk material, we present here a report on mineral phases that are likely have a morphological tendency to encrust the surface of the glass. Our modeling has focused on using the AFCI glass system in a carbonate, sulfate, and phosphate rich environment. We evaluate the minerals predicted to form to determine the likelihood of the formation of a protective layer on the surface of the glass. We have also modeled individual ions in solutions vs. pH and the addition of aluminum and silicon. These results allow us to understand the pH and ion concentration dependence of mineral formation. We have determined that iron minerals are likely to form a complete incrustation layer and we plan

  14. Containerless processing of glass

    NASA Technical Reports Server (NTRS)

    Happe, R. A.

    1981-01-01

    Ground-based research on the containerless melting of glass and experiments performed during a flight on the SPAR 6 are described. Experiments leading to selection of the flight sample composition, a silica-modified gallia/calcia glass, and the preparation of a one quarter inch diameter flight sample are described. During the flight experiment, a sample of the glass was containerless melted and cooled to a clear glass in a single axis acoustic positioning apparatus. The functioning of the flight experimental hardware was evaluated. The evaluation of the sample is presented.

  15. Drugstore Reading Glasses

    NASA Astrophysics Data System (ADS)

    Erlichson, Herman

    2006-03-01

    The occasion for this paper was my reading of a paper in the February 2005 issue of TPT. As one gets older the near point of the eye begins to recede.2 This is called presbyopia.3 An alternative to purchasing glasses from an optometrist is to purchase an inexpensive pair of reading glasses in a pharmacy. The pharmacy has these glasses ordered by diopters corresponding to the strength of the lens needed for a particular presbyopic eye. The glasses are, of course, not available for myopic eyes.

  16. Glass--Sand + Imagination

    NASA Astrophysics Data System (ADS)

    Kolb, Kenneth E.; Kolb, Doris K.

    2000-07-01

    Glass is older than recorded history, and yet it is as new as tomorrow! How, when, or where man first learned to make glass is not known, but we do know that the ancient Egyptians were making glass articles as early as 2,600 B.C.E. (The making of glass beads may have begun as much as 3000 years earlier.) They used it to make jewelry and luxury items, such as decorative bowls and perfume bottles, available only to the wealthy.

  17. Apollo 15 green glasses.

    NASA Technical Reports Server (NTRS)

    Ridley, W. I.; Reid, A. M.; Warner, J. L.; Brown, R. W.

    1973-01-01

    The samples analyzed include 28 spheres, portions of spheres, and angular fragments from soil 15101. Emerald green glasses from other soils are identical to those from 15101. The composition of the green glass is unlike that of any other major lunar glass group. The Fe content is comparable to that in mare basalts, but Ti is much lower. The Mg content is much higher than in most lunar materials analyzed to date, and the Cr content is also high. The low Al content is comparable to that of mare basalt glasses.

  18. Economic manufacturing of bulk metallic glass compositions by microalloying

    DOEpatents

    Liu, Chain T.

    2003-05-13

    A method of making a bulk metallic glass composition includes the steps of:a. providing a starting material suitable for making a bulk metallic glass composition, for example, BAM-11; b. adding at least one impurity-mitigating dopant, for example, Pb, Si, B, Sn, P, to the starting material to form a doped starting material; and c. converting the doped starting material to a bulk metallic glass composition so that the impurity-mitigating dopant reacts with impurities in the starting material to neutralize deleterious effects of the impurities on the formation of the bulk metallic glass composition.

  19. Ion-wake field inside a glass box

    NASA Astrophysics Data System (ADS)

    Chen, Mudi; Dropmann, Michael; Zhang, Bo; Matthews, Lorin S.; Hyde, Truell W.

    2016-09-01

    The confinement provided by a glass box is proving ideal for the formation of vertically aligned structures and a convenient method for controlling the number of dust particles comprising these dust structures as well as their sizes and shapes. In this paper, the electronic confinement of the glass box is mapped, and the particle interactions between the particle pairs inside the glass box are measured. The ion-wake field is shown to exist within the glass box, and its vertical and horizontal extents are measured.

  20. Apatite formation on (2-x)CaO.x/3 M2O3 x 2SiO2 glasses (M = La, Y; 0 < or = x < or = 0.6) in a simulated body fluid.

    PubMed

    Fresa, R; Costantini, A; Buri, A; Branda, F

    1995-11-01

    Glasses were prepared by substituting La2O3 or Y2O3 for CaO in glassy wollastonite composition (CaO.SiO2). Their behaviour when they are soaked in a simulated body fluid (SBF) was studied by means of an electron microscope equipped with an energy dispersive system for elemental analysis, and by means of IR spectroscopy. Electron microscopy and energy dispersive microanalysis were performed on samples soaked as polished bulk samples, and IR analysis was on samples soaked as fine powders. A carbonate-containing hydroxyapatite layer is formed when glasses of low La2O3 content are soaked in SBF. When Y2O3-containing glasses are considered, even in the case of small substitution for CaO, the same layer forms only on fracture surfaces. The experimental results agree with the mechanism reported in the literature. PMID:8589195

  1. Nanoscale self-arranged layers of silver nanoparticles in glass

    NASA Astrophysics Data System (ADS)

    Redkov, Alexey V.; Lipovskii, Andrey A.; Dussauze, Marc; Paraillous, Maxime; Cardinal, Thierry

    2016-05-01

    We characterized changes in the composition of subsurface layer of silver ion-exchanged soda-lime glass during annealing in hydrogen atmosphere. The formation of tens of nanometers distanced layers of silver nanoparticles in the glass at temperature of 300 °C has been revealed. Performed numerical modeling of the process demonstrates a good qualitative agreement with the experiment. This is of interest for simple formation of 3D-optoplasmonic structures, Bragg gratings or photonic crystals.

  2. Glass produced by underground nuclear explosions. [Rainier

    SciTech Connect

    Schwartz, L.; Piwinskii, A.; Ryerson, F.; Tewes, H.; Beiriger, W.

    1983-01-01

    Detonation of an underground nuclear explosive produces a strong shock wave which propagates spherically outward, vaporizing the explosive and nearby rock and melting, the surrounding rock. The vaporized material expands adiabatically, forming a cavity. As the energy is dissipated during the cavity formation process, the explosive and rock debris condense and mix with the melted rock. The melt flows to the bottom of the cavity where it is quenched by fractured rock fragments falling from above as the cavity collapses. Measurements indicate that about 740 tonnes of rock and/or soil are melted for every kiloton (10/sup 12/ calories) of explosive energy, or about 25% of the explosive energy goes to melting rock. The resulting glass composition reflects the composition of the unaltered rock with explosive debris. The appearance ranges from white pumice to dense, dark lava. The bulk composition and color vary with the amount of explosive iron incorporated into the glass. The refractory explosion products are mixed with the solidified melt, although the degree of mixing is variable. Electron microprobe studies of glasses produced by Rainier in welded tuff have produced the following results: glasses are dehydrated relative to the host media, glasses are extremely heterogeneous on a 20 ..mu..m scale, a ubiquitous feature is the presence of dark marble-cake regions in the glass, which were locally enriched in iron and may be related to the debris, optically amorphous regions provide evidence of shock melting, only limited major element redistribution and homogenization occur within the cavity.

  3. Glass Dissolution: Testing and Modeling for Long-Term Behavior.

    SciTech Connect

    Strachan, Denis M. )

    2001-09-01

    The basic concepts of thermodynamics and kinetics are discussed in relationship to glass dissolution testing. While it seems like these subjects are too basic to be discussed in a journal article, it is often the case that we forget these concepts when planning and designing dissolution tests and interpreting the results that come from these tests. The possible connection between the composition of the dissolving glass and its long-term behavior is discussed. Results from a preliminary study suggest that the aluminum content of a glass is important to its long-term behavior. The formation of a zeolite can cause the glass dissolution rate to increase under certain conditions that can be modeled. Results indicate that complex glasses can be modeled with a glass containing as little as six components.

  4. Theory of corrosion of alkali-borosilicate glass

    SciTech Connect

    Clark, D.E.; Hench, L.L.

    1983-01-01

    The alkali-borosilicate (ABS) system provides the basis for a wide variety of commercially important products among which are the nuclear waste glasses. Although a large number of investigations have been undertaken in the last five years, the corrosion mechanisms of the ABS glasses have not been characterized nearly as well as for the soda-lime-silicate (NCS) glasses commonly used for containers. It is well known that the corrosion of the latter glasses involves ion exchange, network dissolution, and precipitation mechanisms resulting in the development of one of five types of surface films. In the present paper we compare the corrosion behavior to the ABS and NCS glasses and discuss our current understanding of ABS glass corrosion in terms of mechanisms, kinetics, surface film formation and thermodynamics.

  5. Getting Started with Glass

    ERIC Educational Resources Information Center

    White, Heather

    2007-01-01

    The metamorphosis of glass when heated is a magical process to students, yet teachers are often reluctant to try it in class. The biggest challenge in working with glass in the classroom is to simplify procedures just enough to ensure student success while maintaining strict safety practices so no students are injured. Project concepts and safety…

  6. Glasses and Contact Lenses

    MedlinePlus

    ... Here's Help White House Lunch Recipes Glasses and Contact Lenses KidsHealth > For Kids > Glasses and Contact Lenses Print A A A Text Size What's ... together the way they should. But eyeglasses or contact lenses, also called corrective lenses, can help most ...

  7. Surface Conductive Glass.

    ERIC Educational Resources Information Center

    Tanaka, John; Suib, Steven L.

    1984-01-01

    Discusses the properties of surface-conducting glass and the chemical nature of surface-conducting stannic (tin) oxide. Also provides the procedures necessary for the preparation of surface-conducting stannic oxide films on glass substrates. The experiment is suitable for the advanced inorganic chemistry laboratory. (JN)

  8. Application of the hydration thermodynamic model for glass durability under saturated tuff repository conditions

    SciTech Connect

    Ramsey, W.G.; Jantzen, C.M.

    1990-12-31

    The effects of tuff repository groundwater on glass dissolution and surface layer formation was examined utilizing the hydration thermodynamic model. A 28 day MCC-1 monolithic durability test was performed on the following glasses: SiO{sub 2}, obsidian, basalt, medieval window glasses, frit glass, and simulated nuclear waste glass. Silica dissolution was compared with the pH corrected free energy of hydration and shown to have the theoretical slope, ln(1/2.303RT), in agreement with MCC-1 tests using deionized water. X-ray diffraction and scanning electron microscopy identified clays of the saponite family and carbonates, on the glass surfaces leached in tuff groundwater. 31 refs.

  9. Role of SrO on the bioactivity behavior of some ternary borate glasses and their glass ceramic derivatives.

    PubMed

    Abdelghany, A M; Ouis, M A; Azooz, M A; ElBatal, H A; El-Bassyouni, G T

    2016-01-01

    Borate glasses containing SrO substituting both CaO and NaO were prepared and characterized for their bioactivity or bone bonding ability. Glass ceramic derivatives were prepared by thermal heat treatment process. FTIR, XRD and SEM measurements for the prepared glass and glass-ceramics before and after immersion in sodium phosphate solution for one and two weeks were carried out. The appearance of two IR peaks within the range 550-680cm(-1) after immersion in phosphate solution indicates the formation of hydroxyapatite or equivalent Sr phosphate layer. X-ray diffraction data agree with the FTIR spectral analysis. The solubility test was carried out for both glasses and glass ceramics derivatives in the same phosphate solution. The introduction of SrO increases the solubility for both glasses and glass ceramics and this is assumed to be due to the formation of Sr phosphate which is more soluble than calcium phosphate (hydroxyapatite). SEM images reveal varying changes in the surfaces of glass ceramics after immersion according to the SrO content.

  10. Role of SrO on the bioactivity behavior of some ternary borate glasses and their glass ceramic derivatives.

    PubMed

    Abdelghany, A M; Ouis, M A; Azooz, M A; ElBatal, H A; El-Bassyouni, G T

    2016-01-01

    Borate glasses containing SrO substituting both CaO and NaO were prepared and characterized for their bioactivity or bone bonding ability. Glass ceramic derivatives were prepared by thermal heat treatment process. FTIR, XRD and SEM measurements for the prepared glass and glass-ceramics before and after immersion in sodium phosphate solution for one and two weeks were carried out. The appearance of two IR peaks within the range 550-680cm(-1) after immersion in phosphate solution indicates the formation of hydroxyapatite or equivalent Sr phosphate layer. X-ray diffraction data agree with the FTIR spectral analysis. The solubility test was carried out for both glasses and glass ceramics derivatives in the same phosphate solution. The introduction of SrO increases the solubility for both glasses and glass ceramics and this is assumed to be due to the formation of Sr phosphate which is more soluble than calcium phosphate (hydroxyapatite). SEM images reveal varying changes in the surfaces of glass ceramics after immersion according to the SrO content. PMID:26204506

  11. Role of SrO on the bioactivity behavior of some ternary borate glasses and their glass ceramic derivatives

    NASA Astrophysics Data System (ADS)

    Abdelghany, A. M.; Ouis, M. A.; Azooz, M. A.; ElBatal, H. A.; El-Bassyouni, G. T.

    2016-01-01

    Borate glasses containing SrO substituting both CaO and NaO were prepared and characterized for their bioactivity or bone bonding ability. Glass ceramic derivatives were prepared by thermal heat treatment process. FTIR, XRD and SEM measurements for the prepared glass and glass-ceramics before and after immersion in sodium phosphate solution for one and two weeks were carried out. The appearance of two IR peaks within the range 550-680 cm-1 after immersion in phosphate solution indicates the formation of hydroxyapatite or equivalent Sr phosphate layer. X-ray diffraction data agree with the FTIR spectral analysis. The solubility test was carried out for both glasses and glass ceramics derivatives in the same phosphate solution. The introduction of SrO increases the solubility for both glasses and glass ceramics and this is assumed to be due to the formation of Sr phosphate which is more soluble than calcium phosphate (hydroxyapatite). SEM images reveal varying changes in the surfaces of glass ceramics after immersion according to the SrO content.

  12. Molecular modeling of vapor-deposited polymer glasses.

    PubMed

    Lin, Po-Han; Lyubimov, Ivan; Yu, Lian; Ediger, M D; de Pablo, Juan J

    2014-05-28

    We have investigated the properties of vapor-deposited glasses prepared from short polymer chains using molecular dynamics simulations. Vapor-deposited polymer glasses are found to have higher density and higher kinetic stability than ordinary glasses prepared by gradual cooling of the corresponding equilibrium liquid. In contrast to results for binary Lennard-Jones glasses, the deposition rate is found to play an important role in the stability of polymer vapor-deposited glasses. Glasses deposited at the slowest deposition rate and at the optimal substrate temperature are found to correspond to the ordinary glasses that one could hypothetically prepare by cooling the liquid at rates that are 4-5 orders of magnitude slower than those accessible in the current simulations. For intermediate-length polymer chains, the resulting vapor-deposited glasses are found to be highly anisotropic. For short chains, however, the glasses are isotropic, showing that structural anisotropy is not a necessary condition for formation of stable glasses by physical vapor deposition.

  13. Applications of physical chemistry to glass technology

    NASA Astrophysics Data System (ADS)

    Stewart, Ogie Gregory

    2001-07-01

    Industrial manufacturing of glass, called float glass, involves a process in which flat pieces of glass are produced by pouring molten glass on a bath of molten tin metal. The glass is then coated with thin film coatings for such applications as solar radiation control and "privacy" glass. In this thesis, principles of physical chemistry are applied to selected aspects of glass production and thin film coatings in an effort to better understand these processes with the hope of improving film and glass quality. The research described here consists of three major studies. Part 1 describes the production of thin films by Atmospheric Pressure Chemical Vapor Deposition (APCVD) and characterization of the films by various analytical techniques. Vanadium oxide films were produced from vanadium (IV) chloride and each of several alcohols to determine the feasibility of this method of deposition and to investigate its use in an electrochromic device. The focus here was to investigate the levels of carbon contamination in the films. It was found that the level of carbon present in the films depend on the type of amine used. Part 2 is an investigation of the flow dynamics that occur during the two thin film deposition processes. APCVD and Powder Spray Pyrolysis (PSP). Information regarding flow dynamics and particle distribution in the region above the films' substrates were obtained and related to film formation and quality. Part 3 is a kinetic study of the gas phase reactions that occur in the vapor region above the glass during float glass production. A kinetic model of the possible reactions was devised and integrated to predict the formation of these impurities with time. An experimental setup to test the model's predictions is also discussed. The research described in this thesis lays the groundwork for several possibilities for future work. Electrochromic films can be produced by APCVD to construct an all-solid-state device. Two dimensional imaging coupled with Laser

  14. Structure of bioactive glass and its application to glass ionomer cement.

    PubMed

    Matsuya, S; Matsuya, Y; Ohta, M

    1999-06-01

    We prepared a new glass ionomer cement using bioactive CaO-P2O5-SiO2(-MgO) glass and investigated its setting process using FT-IR and MAS NMR analyses. The compressive strengths of the cements depended on the glass composition and a maximum strength of 33.3 +/- 4.7 MPa was obtained using cement with the glass composition of MgO:4.6, CaO:44.9, SiO2:34.2 and P2O5:16.3% in weight. FT-IR analysis showed that the COOH group in the polyacrylic acid decreased and carboxylate ion (COO-Ca2+) increased after the setting reaction. A broad signal appeared around -82 ppm in 29Si MAS-NMR spectra of the glass and a new signal corresponding to hydrated silica gel formation appeared around -102 and -111 ppm after setting. This suggests that Ca2+ was released from the glass powder to form carboxylate salt and that a degree of polymerization in the silicate network increased. The setting mechanism of the cement was found to be essentially the same as in conventional glass ionomer cement. PMID:10786128

  15. Defense HLW Glass Degradation Model

    SciTech Connect

    D. Strachan

    2004-10-20

    The purpose of this report is to document the development of a model for calculating the release rate for radionuclides and other key elements from high-level radioactive waste (HLW) glasses under exposure conditions relevant to the performance of the repository. Several glass compositions are planned for the repository, some of which have yet to be identified (i.e., glasses from Hanford and Idaho National Engineering and Environmental Laboratory). The mechanism for glass dissolution is the same for these glasses and the glasses yet to be developed for the disposal of DOE wastes. All of these glasses will be of a quality consistent with the glasses used to develop this report.

  16. Optically responsive supramolecular polymer glasses

    NASA Astrophysics Data System (ADS)

    Balkenende, Diederik W. R.; Monnier, Christophe A.; Fiore, Gina L.; Weder, Christoph

    2016-03-01

    The reversible and dynamic nature of non-covalent interactions between the constituting building blocks renders many supramolecular polymers stimuli-responsive. This was previously exploited to create thermally and optically healable polymers, but it proved challenging to achieve high stiffness and good healability. Here we present a glass-forming supramolecular material that is based on a trifunctional low-molecular-weight monomer ((UPyU)3TMP). Carrying three ureido-4-pyrimidinone (UPy) groups, (UPyU)3TMP forms a dynamic supramolecular polymer network, whose properties are governed by its cross-linked architecture and the large content of the binding motif. This design promotes the formation of a disordered glass, which, in spite of the low molecular weight of the building block, displays typical polymeric behaviour. The material exhibits a high stiffness and offers excellent coating and adhesive properties. On account of reversible dissociation and the formation of a low-viscosity liquid upon irradiation with ultraviolet light, rapid optical healing as well as (de)bonding on demand is possible.

  17. Optically responsive supramolecular polymer glasses.

    PubMed

    Balkenende, Diederik W R; Monnier, Christophe A; Fiore, Gina L; Weder, Christoph

    2016-01-01

    The reversible and dynamic nature of non-covalent interactions between the constituting building blocks renders many supramolecular polymers stimuli-responsive. This was previously exploited to create thermally and optically healable polymers, but it proved challenging to achieve high stiffness and good healability. Here we present a glass-forming supramolecular material that is based on a trifunctional low-molecular-weight monomer ((UPyU)3TMP). Carrying three ureido-4-pyrimidinone (UPy) groups, (UPyU)3TMP forms a dynamic supramolecular polymer network, whose properties are governed by its cross-linked architecture and the large content of the binding motif. This design promotes the formation of a disordered glass, which, in spite of the low molecular weight of the building block, displays typical polymeric behaviour. The material exhibits a high stiffness and offers excellent coating and adhesive properties. On account of reversible dissociation and the formation of a low-viscosity liquid upon irradiation with ultraviolet light, rapid optical healing as well as (de)bonding on demand is possible. PMID:26983805

  18. Optically responsive supramolecular polymer glasses

    PubMed Central

    Balkenende, Diederik W. R.; Monnier, Christophe A.; Fiore, Gina L.; Weder, Christoph

    2016-01-01

    The reversible and dynamic nature of non-covalent interactions between the constituting building blocks renders many supramolecular polymers stimuli-responsive. This was previously exploited to create thermally and optically healable polymers, but it proved challenging to achieve high stiffness and good healability. Here we present a glass-forming supramolecular material that is based on a trifunctional low-molecular-weight monomer ((UPyU)3TMP). Carrying three ureido-4-pyrimidinone (UPy) groups, (UPyU)3TMP forms a dynamic supramolecular polymer network, whose properties are governed by its cross-linked architecture and the large content of the binding motif. This design promotes the formation of a disordered glass, which, in spite of the low molecular weight of the building block, displays typical polymeric behaviour. The material exhibits a high stiffness and offers excellent coating and adhesive properties. On account of reversible dissociation and the formation of a low-viscosity liquid upon irradiation with ultraviolet light, rapid optical healing as well as (de)bonding on demand is possible. PMID:26983805

  19. Waste glass/metal interactions in brines

    SciTech Connect

    Shade, J.W.; Pederson, L.R.; McVay, G.L.

    1983-05-01

    Leaching studies of MCC 76-68 glass in synthetic brines high in NaCl were performed from 50 to 150/sup 0/C and included interactive testing with ductile iron and titanium. Hydrolysis of the glass matrix was generally slower in saturated brines than in deionized water, due to a lower solubility of silica in the brines. Inclusion of ductile iron in the tests resulted in accelerated leach rates because irion-silica reactions occurred which reduced the silica saturation fraction. At 150/sup 0/C, iron also accelerated the rate of crystalline reaction product formation which were primarily Fe-bearing sepiolite and talc. 16 references.

  20. Interaction of water with bioactive glass surfaces

    NASA Astrophysics Data System (ADS)

    Zeitler, Todd R.; Cormack, A. N.

    2006-08-01

    The bioactivity of bioactive glasses is related to their dissolution in the presence of body fluid, or water. The dissolution process involves disruption of the tetrahedral network structure through the formation of silanol groups on the take-up of water by bioactive glasses. Molecular dynamics simulations show that the dissolution energy varies considerably depending on the nature and environment of the Si-O-Si bond being broken. However, no obvious correlation with bioactivity is observed, suggesting that although the network disruption is a necessary process, it is not rate determining.

  1. Two glass transitions in miscible polymer blends?

    SciTech Connect

    Dudowicz, Jacek; Freed, Karl F.; Douglas, Jack F.

    2014-06-28

    In contrast to mixtures of two small molecule fluids, miscible binary polymer blends often exhibit two structural relaxation times and two glass transition temperatures. Qualitative explanations postulate phenomenological models of local concentration enhancements due to chain connectivity in ideal, fully miscible systems. We develop a quantitative theory that explains qualitative trends in the dynamics of real miscible polymer blends which are never ideal mixtures. The theory is a synthesis of the lattice cluster theory of blend thermodynamics, the generalized entropy theory for glass-formation in polymer materials, and the Kirkwood-Buff theory for concentration fluctuations in binary mixtures.

  2. Structural characterization of the metal/glass interface in bioactive glass coatings on Ti-6Al-4V

    SciTech Connect

    Oku, T.; Suganuma, K.; Wallemberg, L.R.; Tomsia, A.P.; Gomez-Vega, J.M.; Saiz, E.

    1999-12-01

    Coating Ti-based implants with bioactive materials promotes joining between the prostheses and the bone as well as increasing long-term implant stability. In the present work, the interface between Ti-6Al-4V and bioactive silicate glass coatings, prepared using a simple enameling technique, is analyzed. High-resolution transmission electron microscopy of the glass/alloy interface shows the formation of a reaction layer ({approx}150 nm thick) composed of Ti5Si3 nanoparticles with a size of {approx}20 nm. This nanostructured interface facilitates the formation of a stable joint between the glass coating and the alloy.

  3. Glass Stability and Kinetic Analysis of Iron-Metalloid Bulk Metallic Glass

    NASA Astrophysics Data System (ADS)

    Santhaweesuk, Charuayporn

    Multicomponent Fe-based bulk metallic glasses (BMGs) with a combination of excellent properties such as good soft magnetic properties, high strength, high hardness, and high corrosion resistance have attracted increasing attention both from a basic science research standpoint and due to their industrial application potential. However, many of the elemental additions which lead to the easiest glass formation are expensive. The identification of alloys composed of abundant and inexpensive elements that still retain excellent properties would promote applications for engineering and industry. In short, the development of the Fe-based BMG without any glass-forming metal elements and with high glass forming ability is desired. This study shows that the thermal stability of the Fe-based alloys can be improved beyond a simple rule of mixtures prediction by utilizing a well-balance multi-metalloid approach. The kinetics aspect of glass-forming ability is studied experimentally for Fe-B-Si-P alloys. The systematic variation in alloy composition gives access to differences in phase selection and the final dimensions of glass formation. Two alloys, representing the best glass-forming composition and the poorest glass-forming composition, were studied in terms of their stability to crystallization, solidification microstructure evolution and thermal history. The utility of the wedge-casting technique is developed to examine bulk glass-forming alloys by combining multiple temperature profiles of the quenching melt with a measurement-based kinetic analysis of the phase selection competition and critical cooling rate conditions. Based upon direct thermal measurement, microstructural analysis and kinetic modeling, it was found that both representative alloys show a board spectrum of solidification microstructures which include a critical cooling rate range. The kinetic competition in the formation of certain phases can enhance or detract from the final dimension of bulk glass

  4. GLASS FABRICATION AND PRODUCT CONSISTENCY TESTING OF LANTHANIDE BOROSILICATE GLASS FOR PLUTONIUM DISPOSITION

    SciTech Connect

    Crawford, C; James Marra, J; Ned Bibler, N

    2007-02-12

    The Department of Energy Office of Environmental Management (DOE/EM) plans to conduct the Plutonium Disposition Project at the Savannah River Site (SRS) in Aiken, SC, to disposition excess weapons-usable plutonium. A plutonium glass waste form is a leading candidate for immobilization of the plutonium for subsequent disposition in a geologic repository. The objectives of this present task were to fabricate plutonium-loaded lanthanide borosilicate (LaBS) Frit B glass and perform testing to provide near-term data that will increase confidence that LaBS glass product is suitable for disposal in the proposed Federal Repository. Specifically, testing was conducted in an effort to provide data to Yucca Mountain Project (YMP) personnel for use in performance assessment calculations. Plutonium containing LaBS glass with the Frit B composition with a 9.5 wt% PuO{sub 2} loading was prepared for testing. Glass was prepared to support glass durability testing via the ASTM Product Consistency Testing (PCT) at Savannah River National Laboratory (SRNL). The glass was characterized with X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) prior to performance testing. This characterization revealed some crystalline PuO{sub 2} inclusions with disk-like morphology present in the as fabricated, quench-cooled glass. A series of PCTs was conducted at SRNL with varying exposed surface area and test durations. Filtered leachates from these tests were analyzed to determine the dissolved concentrations of key elements. The leachate solutions were also ultrafiltered to quantify colloid formation. Leached solids from select PCTs were examined in an attempt to evaluate the Pu and neutron absorber release behavior from the glass and to investigate formation of alteration phases on the glass surface. A series of PCTs was conducted at 90 C in ASTM Type 1 water to compare the Pu LaBS Frit B glass durability to current requirements for High

  5. Glass electrolyte composition

    DOEpatents

    Kucera, Gene H.; Roche, Michael F.

    1985-01-01

    An ionically conductive glass is disclosed for use as electrolyte in a high temperature electrochemical cell, particularly a cell with sodium anode and sulfur cathode. The glass includes the constituents Na.sub.2 O, ZrO.sub.2, Al.sub.2 O.sub.3 and SiO.sub.2 in selected proportions to be a single phase solid solution substantially free of crystalline regions and undissolved constituents. Other advantageous properties are an ionic conductivity in excess of 2.times.10.sup.-3 (ohm-cm).sup.-1 at 300.degree. C. and a glass transition temperature in excess of 500.degree. C.

  6. Glass electrolyte composition

    DOEpatents

    Kucera, G.H.; Roche, M.F.

    1985-01-08

    An ionically conductive glass is disclosed for use as electrolyte in a high temperature electrochemical cell, particularly a cell with sodium anode and sulfur cathode. The glass includes the constituents Na/sub 2/O, ZrO/sub 2/, Al/sub 2/O/sub 3/ and SiO/sub 2/ in selected proportions to be a single phase solid solution substantially free of crystalline regions and undissolved constituents. Other advantageous properties are an ionic conductivity in excess of 2 x 10/sup -3/ (ohm-cm)/sup -1/ at 300/sup 0/C and a glass transition temperature in excess of 500/sup 0/C.

  7. Wetting of metals and glasses on Mo

    SciTech Connect

    Saiz, Eduardo; Tomsia, Antoni P.; Saiz, Eduardo; Lopez-Esteban, Sonia; Benhassine, Mehdi; de Coninck, Joel; Rauch, Nicole; Ruehle, Manfred

    2008-01-08

    The wetting of low melting point metals and Si-Ca-Al-Ti-O glasses on molybdenum has been investigated. The selected metals (Au, Cu, Ag) form a simple eutectic with Mo. Metal spreading occurs under nonreactive conditions without interdiffusion or ridge formation. The metals exhibit low (non-zero) contact angles on Mo but this requires temperatures higher than 1100 C in reducing atmospheres in order to eliminate a layer of adsorbed impurities on the molybdenum surface. By controlling the oxygen activity in the furnace, glass spreading can take place under reactive or nonreactive conditions. We have found that in the glass/Mo system the contact angle does not decrease under reactive conditions. In all cases, adsorption from the liquid seems to accelerate the diffusivity on the free molybdenum surface.

  8. Structural and Magnetic Studies on Nano-crystalline Biocompatible Glass/Glass-ceramic

    NASA Astrophysics Data System (ADS)

    Kothiyal, G. P.; Sharma, K.; Dixit, A.; Srinivasan, A.

    2010-12-01

    Ferrimagnetic glass-ceramics have been derived from bulk CaO-P2O5-SiO2-Fe2O3 glass system containing different additives like MgO, ZnO etc. by controlled crystallization. Phase formation and magnetic behaviour of glass-ceramics samples have been studied using XRD and SQUID magnetometer. The microstructure as seen by scanning electron microscopy exhibits nano sized particles. Nanocrystalline hematite and magnetite along with bone mineral phases constitute the major crystalline phases. Saturation magnetization increases with increase in amount of iron oxide since the volume fraction of magnetite has also increased. Addition of ZnO leads to increase in the saturation magnetization. In vitro response in simulated body fluid shows the formation of hydroxyapatite like layer implying the bioactive nature of the samples.

  9. Magnetic properties of tektites and other related impact glasses

    NASA Astrophysics Data System (ADS)

    Rochette, P.; Gattacceca, J.; Devouard, B.; Moustard, F.; Bezaeva, N. S.; Cournède, C.; Scaillet, B.

    2015-12-01

    We present a comprehensive overview of the magnetic properties of the four known tektite fields and related fully melted impact glasses (Aouelloul, Belize, Darwin, Libyan desert and Wabar glasses, irghizites, and atacamaites), namely magnetic susceptibility and hysteresis properties as well as properties dependent on magnetic grain-size. Tektites appear to be characterized by pure Fe2+ paramagnetism, with ferromagnetic traces below 1 ppm. The different tektite fields yield mostly non-overlapping narrow susceptibility ranges. Belize and Darwin glasses share similar characteristics. On the other hand the other studied glasses have wider susceptibility ranges, with median close to paramagnetism (Fe2+ and Fe3+) but with a high-susceptibility population bearing variable amounts of magnetite. This signs a fundamental difference between tektites (plus Belize and Darwin glasses) and other studied glasses in terms of oxygen fugacity and heterogeneity during formation, thus bringing new light to the formation processes of these materials. It also appears that selecting the most magnetic glass samples allows to find impactor-rich material, opening new perspectives to identify the type of impactor responsible for the glass generation.

  10. Waste glass weathering

    SciTech Connect

    Bates, J.K.; Buck, E.C.

    1993-12-31

    The weathering of glass is reviewed by examining processes that affect the reaction of commercial, historical, natural, and nuclear waste glass under conditions of contact with humid air and slowly dripping water, which may lead to immersion in nearly static solution. Radionuclide release data from weathered glass under conditions that may exist in an unsaturated environment are presented and compared to release under standard leaching conditions. While the comparison between the release under weathering and leaching conditions is not exact, due to variability of reaction in humid air, evidence is presented of radionuclide release under a variety of conditions. These results suggest that both the amount and form of radionuclide release can be affected by the weathering of glass.

  11. Super ionic conductive glass

    DOEpatents

    Susman, Sherman; Volin, Kenneth J.

    1984-01-01

    An ionically conducting glass for use as a solid electrolyte in a power or secondary cell containing an alkali metal-containing anode and a cathode separated by an alkali metal ion conducting glass having an ionic transference number of unity and the general formula: A.sub.1+x D.sub.2-x/3 Si.sub.x P.sub.3-x O.sub.12-2x/3, wherein A is a network modifier for the glass and is an alkali metal of the anode, D is an intermediate for the glass and is selected from the class consisting of Zr, Ti, Ge, Al, Sb, Be, and Zn and X is in the range of from 2.25 to 3.0. Of the alkali metals, Na and Li are preferred and of the intermediate, Zr, Ti and Ge are preferred.

  12. Super ionic conductive glass

    DOEpatents

    Susman, S.; Volin, K.J.

    Described is an ionically conducting glass for use as a solid electrolyte in a power or secondary cell containing an alkali metal-containing anode and a cathode separated by an alkali metal ion conducting glass having an ionic transference number of unity and the general formula: A/sub 1 + x/D/sub 2-x/3/Si/sub x/P/sub 3 - x/O/sub 12 - 2x/3/, wherein A is a network modifier for the glass and is an alkali metal of the anode, D is an intermediate for the glass and is selected from the class consisting of Zr, Ti, Ge, Al, Sb, Be, and Zn and X is in the range of from 2.25 to 3.0. Of the alkali metals, Na and Li are preferred and of the intermediate, Zr, Ti and Ge are preferred.

  13. Glass Stronger than Steel

    DOE R&D Accomplishments Database

    Yarris, Lynn

    2011-03-28

    A new type of damage-tolerant metallic glass, demonstrating a strength and toughness beyond that of steel or any other known material, has been developed and tested by a collaboration of researchers from Berkeley Lab and Caltech.

  14. Whisker reinforced glass ceramic

    SciTech Connect

    Hirschfeld, D.A.; Brown, J.J. Jr.

    1996-06-03

    The process for making an in-situ whisker reinforced glass-ceramic that is up to 1.5 times as strong as conventional glass-ceramics was developed at Virginia Tech and patented in 1993. This technology has been identified as having commercial potential for use in high temperature heat exchanger applications for the electric power generation field by the National Center for Appropriate Technology (NCAT). This technology was licensed by MATVA, Inc., a small Virginia business, for further development. In particular, the goal of this project was to develop a property database and conduct initial testing of heat exchanger prototypes to demonstrate its potential application. This final report describes how the glass precursor was formed, physical properties of the glass-ceramic, techniques for making heat exchanger prototypes.

  15. THE COLOR GLASS CONDENSATE.

    SciTech Connect

    MCLERRAN,L.

    2001-08-26

    The Color Glass Condensate is a state of high density gluonic matter which controls the high energy limit of hadronic interactions. Its properties are important for the initial conditions for matter produced at RHIC.

  16. Electron beam irradiation effects in Trombay nuclear waste glass

    NASA Astrophysics Data System (ADS)

    Mohapatra, M.; Kadam, R. M.; Mishra, R. K.; Dutta, D.; Pujari, P. K.; Kaushik, C. P.; Kshirsagar, R. J.; Tomar, B. S.; Godbole, S. V.

    2011-10-01

    Spectroscopic investigations were carried out on electron beam irradiated sodium barium borosilicate glasses, which is the base glass for immobilization of nuclear high level radioactive waste, generated from the research reactors at Bhabha Atomic Research Centre, Trombay. This was done in order to access the defects generated in it under long term irradiation. Electron paramagnetic resonance was used to identify the defect centers generated in the borosilicate glass after irradiation. In addition, positron annihilation spectroscopy and infrared investigations were done on the samples to evaluate the radiation induced changes in the glass. It was found that, boron-oxygen and silicon based hole centers along with E' centers are getting formed in the glass after irradiation due to the breaking of the Si sbnd O bonds at regular tetrahedron sites of Si sbnd O sbnd Si. The positron annihilation spectroscopy data gave an idea regarding the free volume size and fraction of the glasses before and after irradiation. It was seen that, after irradiation the free volume size in the glass increased with creation of additional sites. Microwave power variation and temperature variation studies suggested the formation of at least five different radicals in the irradiated glasses. The spin Hamiltonian parameter of all the radical species were determined by computer simulation. An electron paramagnetic resonance spin counting technique was employed to evaluate the defect concentration in the glasses after irradiation.

  17. Frangible glass canisters

    NASA Technical Reports Server (NTRS)

    Seifert, R.

    1972-01-01

    The need for a canister that can release its contents without disturbing the contents dynamically is discussed. The solution of this problem by the use of a frangible glass canister is considered. The basic theory applicable to frangible glass and the method of initiating a command flaw are discussed. A brief description of the test program and the results of a flight test are presented.

  18. Metallic glass composition

    DOEpatents

    Kroeger, Donald M.; Koch, Carl C.

    1986-01-01

    A metallic glass alloy that is either iron-based or nickel-based or based on a mixture of iron and nickel, containing lesser amounts of elements selected from the group boron, silicon carbon and phosphorous to which is added an amount of a ductility enhancing element selected from the group cerium, lanthanum, praseodymium and neodymium sufficient to increase ductility of the metallic glass upon annealing.

  19. Display innovations through glass

    NASA Astrophysics Data System (ADS)

    Hamilton, Lori L.

    2016-03-01

    Prevailing trends in thin, lightweight, high-resolution, and added functionality, such as touch sensing, continue to drive innovation in the display market. While display volumes grow, so do consumers’ need for portability, enhanced optical performance, and mechanical reliability. Technical advancements in glass design and process have enabled display innovations in these areas while supporting industry growth. Opportunities for further innovation remain open for glass manufacturers to drive new applications, enhanced functionality, and increased demand.

  20. Glass fiber insulation

    SciTech Connect

    Griffith, E.J.; Ngo, T.M.

    1993-06-29

    A composition for a glass fiber insulation is described comprising a loose mat of glass fibers having at least a portion of the surface coated with a water insoluble, non-hygroscopic, amorphous aluminum phosphate polymer having a molar ratio of Al[sub 2]O[sub 3] to P[sub 2]O[sub 5] of less than 1 and providing a substantial thermal resistance.