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Sample records for jahn-teller glass formation

  1. 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.

  2. Reactions of trivacant Wells-Dawson heteropolytungstates. Ionic strength and Jahn-Teller effects on formation in multi-iron complexes.

    PubMed

    Anderson, Travis M; Zhang, Xuan; Hardcastle, Kenneth I; Hill, Craig L

    2002-05-06

    Reaction of alpha-P(2)W(15)O(56)(12-) and Fe(III) in a saturated NaCl solution produces a trisubstituted Wells-Dawson structure with three low-valent metals, alpha-(Fe(III)Cl)(2)(Fe(III)OH(2))P(2)W(15)O(59)(11-) (1). Dissolution of this species into 1 M NaBr (Br(-) is non-coordinating) gives the triaquated species alpha-(Fe(III)OH(2))(3)P(2)W(15)O(59)(9-) (2). Ionic strength values of 1 M or greater are necessary to avoid decomposition of 1 or 2 to the conventional sandwich-type complex, alpha beta beta alpha-(Fe(III)OH(2))(2)Fe(III)(2)(P(2)W(15)O(56))(2)(12-) (3). If the pH is greater than 5, a new triferric sandwich, alpha alpha beta alpha-(NaOH(2))(Fe(III)OH(2))Fe(III)(2)(P(2)W(15)O(56))(2)(14-) (4), forms rather than 3. Like the previously reported Wells-Dawson-derived sandwich-type structures with three metals in the central unit ([TM(II)Fe(III)(2)(P(2)W(15)O(56))(P(2)TM(II)(2)W(13)O(52))],(16-) TM = Cu, Co), this complex has a central alpha-junction and a central beta-junction. Thermal studies suggest that 4 is more stable than 3 over a wide range of temperatures and pH values. The intrinsic Jahn-Teller distortion of d-electron-containing metal ions incorporated into the external sites of the central multi-metal unit impacts the stoichiometry of their incorporation (with a consequent change in the inter-POM-unit connectivity, where POM = polyoxometalate). Reaction of non-distorting Ni(II) with the diferric lacunary sandwich-type POM alpha alpha alpha alpha-(NaOH(2))(2)Fe(III)(2)(P(2)W(15)O(56))(2)(16-) (5) produces alpha beta beta alpha-(Ni(II)OH(2))(2)Fe(III)(2)(P(2)W(15)O(56))(2)(14-) (6), a Wells-Dawson sandwich-type structure with two Ni(II) and two Fe(III) in the central unit. All structures are characterized by (31)P NMR, IR, UV-vis, magnetic susceptibility, and X-ray crystallography. Complexes 4 and 6 are highly selective and effective catalysts for the H(2)O(2)-based epoxidation of alkenes.

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

    PubMed

    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

    2015-04-01

    Understanding the relationship between the superconducting, the neighboring insulating, and the normal metallic state above T c 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 C60 (3-) 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 T c with interfulleride separation, demonstrating molecular electronic structure control of superconductivity.

  4. 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

  5. Cooperative Jahn-Teller phase transition of icosahedral molecular units

    NASA Astrophysics Data System (ADS)

    Nasrollahi, Seyed H.; Vvedensky, Dimitri D.

    2017-02-01

    Non-linear molecules undergo distortions when the orbital degeneracy of the highest occupied level is lifted by the Jahn-Teller effect. If such molecules or clusters of atoms are coupled to one another, the system may experience a cooperative Jahn-Teller effect (CJTE). In this paper, we describe a model of how the CJTE leads to the crystallization of the disordered phase. The model Hamiltonian is based on a normal mode decomposition of the clusters in order to maintain the symmetry labels. We take account of the electron-strain and the electron-phonon couplings and, by displacing the coordinates of the oscillators, obtain a term that explicitly couples the Jahn-Teller centers, enabling us to perform a mean-field analysis. The calculation of the free energy then becomes straightforward, and obtaining phase diagrams in various regimes follows from the minimization of this free energy. The results show that the character of the phase transition may change from strong to weak first order and even to second-order, depending on the coupling to the vibrational modes. Taken together, these results may serve as a paradigm for crystallization near the transition temperature, where the atoms tend to form clusters of icosahedral symmetry.

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

    PubMed

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

    2016-02-05

    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 Pb2_{1}m 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.

  7. The Jahn-Teller plus pseudo-Jahn-Teller vibronic problem in the C3 radical and its topological implications

    NASA Astrophysics Data System (ADS)

    Rocha, C. M. R.; Varandas, A. J. C.

    2016-02-01

    The combined Jahn-Teller plus pseudo-Jahn-Teller [ ( E ' + A1 ' ) ⊗ e ' ] problem is discussed for the tricarbon radical (C3) by means of ab initio calculations at the multireference configuration interaction level of theory. For the 1E' electronic state arising from a e'2 valence configuration, three additional symmetry-equivalent C2v seams are found to lie in close proximity to the D3h symmetry-required seam over the entire range of the breathing coordinate here considered. As the perimeter of the molecule increases, the C2v disjoint seams approach the D3h one almost linearly and ultimately coalesce with it at Q1 = 5.005 a0, thence forming an intersection node or confluence. By further increasing the size of the molecular triangle, the C2v seams get rotated by ±π in the g-h plane. A three-state vibronic Hamiltonian is also proposed to model locally the title system and shown to accurately mimic the calculated data over the region close to the minimum energy crossing point. No net geometric phase effect is observed when the associated electronic wave functions are adiabatically transported along closed paths encircling the four singularity points. For all paths enclosing the intersection node, the sign reversal criterion is shown to be not fulfilled, even for infinitesimal loops. The results so obtained are expected to be valid for other ring systems experiencing similar topological attributes.

  8. The Jahn-Teller plus pseudo-Jahn-Teller vibronic problem in the C3 radical and its topological implications.

    PubMed

    Rocha, C M R; Varandas, A J C

    2016-02-14

    The combined Jahn-Teller plus pseudo-Jahn-Teller [(E'+A1')⊗e'] problem is discussed for the tricarbon radical (C3) by means of ab initio calculations at the multireference configuration interaction level of theory. For the (1)E' electronic state arising from a e'(2) valence configuration, three additional symmetry-equivalent C2v seams are found to lie in close proximity to the D3h symmetry-required seam over the entire range of the breathing coordinate here considered. As the perimeter of the molecule increases, the C2v disjoint seams approach the D3h one almost linearly and ultimately coalesce with it at Q1 = 5.005 a0, thence forming an intersection node or confluence. By further increasing the size of the molecular triangle, the C2v seams get rotated by ±π in the g-h plane. A three-state vibronic Hamiltonian is also proposed to model locally the title system and shown to accurately mimic the calculated data over the region close to the minimum energy crossing point. No net geometric phase effect is observed when the associated electronic wave functions are adiabatically transported along closed paths encircling the four singularity points. For all paths enclosing the intersection node, the sign reversal criterion is shown to be not fulfilled, even for infinitesimal loops. The results so obtained are expected to be valid for other ring systems experiencing similar topological attributes.

  9. 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.

  10. 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

    2014-07-24

    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.

  11. Jahn-Teller distortion and magnetic ordering in layered nickelates

    NASA Astrophysics Data System (ADS)

    Johannes, Michelle; Mazin, Igor; Bernstein, Noam

    2006-03-01

    One of the long-standing challenges in the theory of layered nickelates is that NaNiO2 is antiferromagnetic and has a strong Jahn-Teller induced orbital ordering, while LiNiO2 has none. A variety of hypothesis have been proposed to explain this mystery: a difference in Li/Na ionic radii, differences in the underlying electronic structure, the zero-point motion of Li ions, etc. One of the most viable propositions is that the difference is due to the presence of Na2^+ ions (1% or more) on the Li sites. It remains unclear whether the magnetic interaction of Na2^+ with the in-plane Na3^+ is strong enough to cancel the Li-assisted antiferromagnetic superexchange even for 1% of Na2^+, and what effect it has on orbital ordering. We provide quantitative arguments, based on first principles calculations and atomistic simulations, that spin and orbital orderings are unrelated, and that both are destroyed (the latter in a rather unusual way) by Na2^+ impurities, but for entirely separate reasons.

  12. 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.

  13. Pseudo-Jahn-Teller origin of the low barrier hydrogen bond in N2H7+

    NASA Astrophysics Data System (ADS)

    García-Fernández, P.; García-Canales, L.; García-Lastra, J. M.; Junquera, J.; Moreno, M.; Aramburu, J. A.

    2008-09-01

    The microscopic origin and quantum effects of the low barrier hydrogen bond (LBHB) in the proton-bound ammonia dimer cation N2H7+ were studied by means of ab initio and density-functional theory (DFT) methods. These results were analyzed in the framework of vibronic theory and compared to those obtained for the Zundel cation H5O2+. All geometry optimizations carried out using wavefunction-based methods [Hartree-Fock, second and fourth order Möller-Plesset theory (MP2 and MP4), and quadratic configuration interaction with singles and doubles excitations (QCISD)] lead to an asymmetrical H3N-H+⋯NH3 conformation (C3v symmetry) with a small energy barrier (1.26kcal/mol in MP4 and QCISD calculations) between both equivalent minima. The value of this barrier is underestimated in DFT calculations particularly at the local density approximation level where geometry optimization leads to a symmetric H3N⋯H+⋯NH3 structure (D3d point group). The instability of the symmetric D3d structure is shown to originate from the pseudo-Jahn-Teller mixing of the electronic A1g1 ground state with five low lying excited states of A2u symmetry through the asymmetric α2u vibrational mode. A molecular orbital study of the pseudo-Jahn-Teller coupling has allowed us to discuss the origin of the proton displacement and the LBHB formation in terms of the polarization of the NH3 molecules and the transfer of electronic charge between the proton and the NH3 units (rebonding). The parallel study of the H5O2+ cation, which presents a symmetric single-well structure, allows us to analyze why these similar molecules behave differently with respect to proton transfer. From the vibronic analysis, a unified view of the Rudle-Pimentel three-center four-electron and charge transfer models of LBHBs is given. Finally, the large difference in the N-N distance in the D3d and C3v configurations of N2H7+ indicates a large anharmonic coupling between α2u-α1g modes along the proton

  14. 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.

  15. Jahn-Teller effect for short-lived states: Study of the complex potential energy surfaces

    NASA Astrophysics Data System (ADS)

    Feuerbacher, Sven; Cederbaum, Lorenz S.

    2004-07-01

    The Jahn-Teller effect for bound electronic states has been investigated for many decades. In contrast, nothing is known regarding its occurrence for short-lived electronic states. Here we investigate the linear and the quadratic E⊗e Jahn-Teller effect for degenerate resonance states with special regard to the complex potential energy surfaces. We find many new phenomena for both the real and imaginary parts of the potential energy surfaces including additional minima and intersections. Possible simplifications of the equations describing the adiabatic potential energy surfaces are discussed. We also briefly investigate other Jahn-Teller effects in linear approximation. The theoretical concepts are exemplified by calculating ab initio data for the degenerate Π*-type resonance states of the tris(boramethyl)amin anion along two different doubly degenerate vibrational modes.

  16. 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.

  17. 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.

  18. 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.

    2016-12-01

    By combining the results of elastic moduli, electrical resistivity, and magnetization measurements for La_{1-x}SrxMnO3 ( 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.

  19. Seams near seams: the Jahn-Teller effect in the 1E" state of N3+.

    PubMed

    Dillon, Joseph J; Yarkony, David R

    2007-03-28

    The (1)E(") electronic state of cyclic N(3) (+) arising from the singly excited electron configuration e('3)e(") is studied using multireference configuration interaction wave functions and a quadratic Jahn-Teller Hamiltonian determined from those calculations. It is shown that these two states have both a symmetry-required seam of conical intersections at D(3h) geometries and three proximal symmetry equivalent C(2v) seams, located on a circle with radius rho(0) from the D(3h) intersection. rho(0), a function of Q(s), the breathing mode, is quite small but only attains a value of zero at Q(s) (crit)=1.252 A, resulting in a confluence or intersection node of the three C(2v) seams with the D(3h) seam. At this point only, g= parallelg(Q(s)) parallel, the norm of half the energy difference gradient, the linear Jahn-Teller term, vanishes and the intersection is of the Renner-Teller type. The close proximity of the previously unreported C(2v) seams to the D(3h) seam over the range of Q(s) considered is a consequence of the small values of g, compared to the quadratic Jahn-Teller term. The present analysis has important implications in the study of Jahn-Teller effects in ring systems and provides insight into a recent report that characterized this D(3h) seam as a Renner-Teller or glancing intersection.

  20. Jahn Teller effect of cations in water: The cupric ion in water

    SciTech Connect

    Halley, J.W.; Wang, X.R.; Curtiss, L.A.

    1993-02-01

    We report a molecular dynamics model for the Jahn Teller effect in the solvation shell of a cation in solution in an aqueous liquid. We apply the model to the cupric ion and compare results with results of neutron scattering experiments on copper chlorate solutions. We conclude that the original interpretation of the experiments in terms of a Jan Teller effect may require modification.

  1. Model study of coexistence of Jahn-Teller distortion, antiferromagnetism and superconductivity in iron pnictide superconductors

    NASA Astrophysics Data System (ADS)

    Pradhan, B.; Goi, S. K.; Behera, Srikanta; Parida, P. K.; Mishra, R. N.

    2016-12-01

    We have proposed a theoretical model for the coexistence of superconductivity (SC), antiferromagnetism (AFM) and Jahn-Teller (JT) effect in the mean field approximation for iron based superconductors. The model is solved by using Zubarev's double-time Green's function technique to get their selfconsistent gap equations. Then these gap equations are solved numerically.

  2. Jahn-Teller / Kondo Interplay in a Three-Terminal Quantum Dot

    NASA Astrophysics Data System (ADS)

    Toonen, R. C.; Qin, H.; Huettel, A. K.; Goswami, S.; van der Weide, D. W.; Eberl, K.; Blick, R. H.

    2006-03-01

    The Jahn-Teller effect is the spontaneous geometric distortion of a nonlinear molecular entity. The Kondo effect, an expression of asymptotic freedom, arises from the hybridization between localized states of a magnetic impurity and the itinerant states of its environment. The interplay of these two phenomena has attracted the attention of theorists studying the growth and interactions of heavy-fermion systems. Because of the technical difficulties associated with probing isolated impurities in bulk materials, this composite effect has remained experimentally unexplored. We have investigated co-tunneling transport phenomena in a three-terminal quantum dot with triangular symmetry. Our measurements of anomalous spectral signatures reveal interplay between the Jahn-Teller and Kondo effects. This discovery suggests a means of controlling the correlation of spatially separated pairs of entangled electrons (EPR pairs)---a necessary condition for the physical realization of a quantum computer (DiVincenzo's 7th requirement).

  3. Time-dependent Jahn-Teller problem: phonon-induced relaxation through conical intersection.

    PubMed

    Pae, Kaja; Hizhnyakov, Vladimir

    2014-12-21

    A theoretical study of time-dependent dynamical Jahn-Teller effect in an impurity center in a solid is presented. We are considering the relaxation of excited states in the E⊗e-problem through the conical intersection of the potential energy. A strict quantum-mechanical treatment of vibronic interactions with both the main Jahn-Teller active vibration and the nontotally symmetric phonons causing the energy loss is given. The applied method enables us to calculate the time-dependence of the distribution function of the basic configurational coordinate. We have performed a series of numerical calculations allowing us, among other relaxation features, to visualise the details of the relaxation through the conical intersection. In particular, we elucidate how the Slonczewski quantization of the states in the conical intersection affects the relaxation.

  4. Time-dependent Jahn-Teller problem: Phonon-induced relaxation through conical intersection

    SciTech Connect

    Pae, Kaja Hizhnyakov, Vladimir

    2014-12-21

    A theoretical study of time-dependent dynamical Jahn-Teller effect in an impurity center in a solid is presented. We are considering the relaxation of excited states in the E⊗e-problem through the conical intersection of the potential energy. A strict quantum-mechanical treatment of vibronic interactions with both the main Jahn-Teller active vibration and the nontotally symmetric phonons causing the energy loss is given. The applied method enables us to calculate the time-dependence of the distribution function of the basic configurational coordinate. We have performed a series of numerical calculations allowing us, among other relaxation features, to visualise the details of the relaxation through the conical intersection. In particular, we elucidate how the Slonczewski quantization of the states in the conical intersection affects the relaxation.

  5. Jahn-Teller effects in transition-metal compounds with small charge-transfer energy

    NASA Astrophysics Data System (ADS)

    Mizokawa, Takashi

    2013-04-01

    We have studied Jahn-Teller effects in Cs2Au2Br6, ACu3Co4O12(A=Ca or Y), and IrTe2 in which the ligand p-to-transition-metal d charge-transfer energy is small or negative. The Au+/Au3+ charge disproportionation of Cs2Au2Br6 manifests in Au 4f photoemission spectra. In Cs2Au2Br6 with negative Δ and intermediate U, the charge disproportionation can be described using effective d orbitals constructed from the Au 5d and Br 4p orbitals and is stabilized by the Jahn-Teller distortion of the Au3+ site with low-spin d8 configuration. In ACu3Co4O12, Δs for Cu3+ and Co4+ are negative and Us are very large. The Zhang-Rice picture is valid to describe the electronic state, and the valence change from Cu2+/Co4+ to Cu3+/Co3+ can be viewed as the O 2p hole transfer from Co to Cu or d9 + d6L → d9L + d6. In IrTe2, both Δ and U are small and the Ir 5d and Te 5p electrons are itinerant to form the multi-band Fermi surfaces. The ideas of band Jahn-Teller transition and Peierls transition are useful to describe the structural instabilities.

  6. 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

  7. The Jahn Teller and pseudo-Jahn Teller effect in the dark Ãstate of the nitrate radical NO3

    NASA Astrophysics Data System (ADS)

    Takematsu, Kana; Robichaud, David; Okumura, Mitchio; Stanton, John

    2007-03-01

    Despite its apparent simple molecular structure, the lowest electronic states of the nitrate radical NO3 remain poorly understood. In particular, the three lowest states of the radical provide a benchmark for testing models of the Jahn-Teller (JT) and pseudo-JT effects. The dark Ãstate of NO3 undergoes strong JT distortion, suggesting that models with only linear and quadratic vibronic couplings are inadequate. We present cavity ringdown (CRD) and integrated cavity output (ICOS) spectra of the forbidden A&˜circ; ^2E"<-X&˜circ; ^2A2' transition (preliminary report in Deev, et. al. J.Chem. Phys., 2005. 122:224305) and compare them to a simulation based on a model Hamiltonian developed by Koppel, Domcke and Cederbaum that incorporates both JT and PJT couplings. New insights into the pseudo-JT effect among the lowest states are gained by examination of intensity-borrowing mechanisms for the observed vibronic bands.

  8. 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(+) .

  9. First-principles study of the dynamic Jahn-Teller distortion of the neutral vacancy in diamond

    NASA Astrophysics Data System (ADS)

    Prentice, Joseph C. A.; Monserrat, Bartomeu; Needs, R. J.

    2017-01-01

    First-principles density functional theory methods are used to investigate the structure, energetics, and vibrational motions of the neutral vacancy defect in diamond. The measured optical absorption spectrum demonstrates that the tetrahedral Td point group symmetry of pristine diamond is maintained when a vacancy defect is present. This is shown to arise from the presence of a dynamic Jahn-Teller distortion that is stabilized by large vibrational anharmonicity. Our calculations further demonstrate that the dynamic Jahn-Teller-distorted structure of Td symmetry is lower in energy than the static Jahn-Teller distorted tetragonal D2 d vacancy defect, in agreement with experimental observations. The tetrahedral vacancy structure becomes more stable with respect to the tetragonal structure by increasing temperature. The large anharmonicity arises mainly from quartic vibrations, and is associated with a saddle point of the Born-Oppenheimer surface and a minimum in the free energy. This study demonstrates that the behavior of Jahn-Teller distortions of point defects can be calculated accurately using anharmonic vibrational methods. Our work will open the way for first-principles treatments of dynamic Jahn-Teller systems in condensed matter.

  10. A Practical Computational Approach to Study Molecular Instability Using the Pseudo-Jahn-Teller Effect.

    PubMed

    García-Fernández, Pablo; Aramburu, Jose Antonio; Moreno, Miguel; Zlatar, Matija; Gruden-Pavlović, Maja

    2014-04-08

    Vibronic coupling theory shows that the cause for spontaneous instability in systems presenting a nondegenerate ground state is the so-called pseudo-Jahn-Teller effect, and thus its study can be extremely helpful to understand the structure of many molecules. While this theory, based on the mixing of the ground and excited states with a distortion, has been long studied, there are two obscure points that we try to clarify in the present work. First, the operators involved in both the vibronic and nonvibronic parts of the force constant take only into account electron-nuclear and nuclear-nuclear interactions, apparently leaving electron-electron repulsions and the electron's kinetic energy out of the chemical picture. Second, a fully quantitative computational appraisal of this effect has been up to now problematic. Here, we present a reformulation of the pseudo-Jahn-Teller theory that explicitly shows the contributions of all operators in the molecular Hamiltonian and allows connecting the results obtained with this model to other chemical theories relating electron distribution and geometry. Moreover, we develop a practical approach based on Hartree-Fock and density functional theory that allows quantification of the pseudo-Jahn-Teller effect. We demonstrate the usefulness of our method studying the pyramidal distortion in ammonia and its absence in borane, revealing the strong importance of the kinetic energy of the electrons in the lowest a2″ orbital to trigger this instability. The present tool opens a window for exploring in detail the actual microscopic origin of structural instabilities in molecules and solids.

  11. Impurities in noncubic crystals: stabilization mechanisms for Jahn-Teller ions in layered perovskites.

    PubMed

    García-Lastra, J M; Aramburu, J A; Barriuso, M T; Moreno, M

    2004-11-26

    Mechanisms responsible for the local geometry around Jahn-Teller impurities in K2NiF4 type lattices are shown to be different from those generating the warping in cubic crystals. The present density functional theory calculations reveal that the elastic anisotropy of the host lattice (visible for closed shell impurities) and the electric field created by the rest of lattice ions upon active electrons make it possible to have d(9) ions in an elongated geometry but with a A(1g) ground state. The puzzling difference between equilibrium geometries for Cu2+ and Ni+ in layered perovskites can reasonably be understood.

  12. 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.

  13. Vacuum ultraviolet mass-analyzed threshold ionization spectroscopy of hexafluorobenzene: The Jahn-Teller effect and vibrational analysis

    NASA Astrophysics Data System (ADS)

    Kwon, Chan Ho; Kim, Myung Soo

    2004-06-01

    One-photon mass-analyzed threshold ionization (MATI) spectrum of hexafluorobenzene was obtained by using vacuum ultraviolet radiation generated by four-wave difference frequency mixing in Kr. The ionization energy of hexafluorobenzene determined from the position of the 0-0 band was 9.9108±0.0006 eV. To aid the spectral analysis, the Jahn-Teller coupling parameters for four e2g modes of C6F6+ in the ground electronic state were calculated from the topographical data of the potential energy surface obtained at the density functional theory (DFT) level. These were used in the initial calculation of the energies of the Jahn-Teller states and upgraded through the multimode fit to the experimental data. Excellent agreement between the experimental and calculated frequencies was achieved. The vibrations which are not linear Jahn-Teller active were observed and could be assigned by referring to the frequencies obtained at the DFT level.

  14. Stability of Jahn-Teller distortion ordering in LaM n1 -xS cxO3

    NASA Astrophysics Data System (ADS)

    Cuartero, V.; Blasco, J.; Subías, G.; García, J.; Meneghini, C.; Aquilanti, G.

    2015-09-01

    We have investigated the role of M n3 + Jahn-Teller distortion in driving ferromagnetism in the LaM n1 -xS cxO3 series. The replacement of Mn by Sc in LaMn O3 decreases the orthorhombic distortion of the Pbnm cell, but the unit cell remains distorted even in the LaSc O3 sample. The analysis of the x-ray diffraction patterns indicates a continuous evolution from the typical Jahn-Teller distorted octahedron in LaMn O3 into a nearly regular one in LaSc O3 . Surprisingly, x-ray absorption spectroscopy measurements at the Mn and Sc K edges reveal the stability of both Jahn-Teller distorted Mn O6 octahedron and nearly regular Sc O6 octahedron along the whole Sc-substituted series. Moreover, the structure is described as a random distribution of Jahn-Teller distorted Mn O6 octahedra spatially ordered as in LaMn O3 and nearly regular Sc O6 octahedra. This result contrasts with the pseudocubic phase and the appearance of regular Mn O6 octahedra in LaM n1 -xG axO3 for x >0.5 . Thus the occurrence of Jahn-Teller distortion strongly depends on the distorted orthorhombic crystallographic structure of the matrix in which the M n3 + atom is allocated. Besides, a ferromagnetic ground state is observed for x >0.5 in both series independently of the presence (or not) of Jahn-Teller distortions around M n3 + , which discards either the spin flipping or the vibronic superexchange models proposed for the ferromagnetism in LaM n1 -xBxO3 (B =Sc or Ga) .

  15. Effect of Jahn-Teller distortion on the short range magnetic order in copper ferrite

    NASA Astrophysics Data System (ADS)

    Abdellatif, M. H.; Innocenti, Claudia; Liakos, Ioannis; Scarpellini, Alice; Marras, Sergio; Salerno, Marco

    2017-02-01

    Copper ferrite of spinel crystal structure was synthesized in the form of nano-particles using citrate-gel auto-combustion method. The sample morphology and composition were identified using scanning electron microscopy, X-ray diffraction, and X-ray spectroscopy. The latter technique reveals an inverse spinel structure with Jahn-Teller tetragonal distortion. The static magnetization was measured using vibrating sample magnetometer. Magnetic force microscopy was used in combination with the magnetization data to demonstrate the finite size effect of the magnetic spins and their casting behavior due to the introduction of copper ions in the tetrahedral magnetic sub-lattices, which results in tetragonal distorting the spinel structure of the copper ferrite. The magnetic properties of materials are a result of the collective behavior of the magnetic spins, and magnetic force microscopy can probe the collective behavior of the magnetic spins in copper ferrite, yet providing a sufficient resolution to map the effects below the micrometer size scale, such as the magnetic spin canting. A theoretical study was done to clarify the finite size effect of Jahn-Teller distortion on the magnetic properties of the material. When the particles are in the nano-scale, below the single domain size, their magnetic properties are very sensitive to their size change.

  16. Dynamical Jahn-Teller effect and Berry phase in positively charged fullerenes: Basic considerations

    NASA Astrophysics Data System (ADS)

    de Los Rios, Paolo; Manini, Nicola; Tosatti, Erio

    1996-09-01

    We study the Jahn-Teller effect of positive fullerene ions 2C+60 and 1C2+60. The aim is to discover if this case, in analogy with the negative ion, possesses a Berry phase or not, and what are the consequences on dynamical Jahn-Teller quantization. Working in the linear and spherical approximation, we find no Berry phase in 1C2+60, and presence/absence of Berry phase for coupling of one L=2 hole to an L=4/L=2 vibration. We study in particular the special equal-coupling case (g2=g4), which is reduced to the motion of a particle on a five-dimensional sphere. In the icosahedral molecule, the final outcome assesses the presence and/or absence of a Berry phase of π for the hu hole coupled to Gg/Hh vibrations. Some qualitative consequences on ground- state symmetry, low-lying excitations, and electron emission from C60 are spelled out.

  17. 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.

  18. 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.

  19. Jahn-Teller Coupling in the Methoxy Radical: Insights Into the Infrared Spectrum of Molecules with Vibronic Coupling

    NASA Astrophysics Data System (ADS)

    Johnson, Britta; Sibert, Edwin

    2015-06-01

    The ground tilde{X}^2E vibrations of the methoxy radical have intrigued both experimentalists and theorists alike due to the presence of a conical intersection at the C3v molecular geometry. This conical intersection causes methoxy's vibrational spectrum to be strongly influenced by Jahn-Teller coupling which leads to large amplitude vibrations and extensive mixing of the two lowest electronic states. The spectrum is further complicated due to spin-orbit and Fermi couplings. The standard diabatic normal mode quantum numbers are poor labels due to this vibronic mixing. Using the potential energy force field and calculated spectra of the methoxy radical by Nagesh and Sibert^1 as a starting point, we look to develop a method for assigning states to a spectrum with vibronic coupling. We simplify the analysis by considering only the lowest two e modes of methoxy (the rock and the bend). When we include first-order Jahn-Teller coupling between these two modes in a new zero-order Hamiltonian, we are able to use an expanded version of the linear Jahn-Teller quantum numbers to assign the states.^2 This zeroth order representation is nontrivial; therefore, we study the properties of its eigenstates using correlation diagrams with respect to the strength of the Jahn-Teller coupling constant. [^1] Nagesh, J.; Sibert, E. L. J. Phys. Chem. A 2012, 116, 3846-3855. [^2] Barckholtz, T. A.; Miller, T. A. Int. Revs. in Phys. Chem. 1998, 17, 435-524.

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

    DOE PAGES

    Skoulatos, M.; Toth, S.; Roessli, B.; ...

    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

  1. Proposal for observing dynamic Jahn-Teller effect by single solid-state defects

    NASA Astrophysics Data System (ADS)

    Xiao, Xing; Zhao, Nan

    2016-10-01

    The Jahn-Teller effect (JTE) widely exists in polyatomic systems including organic molecules, nano-magnets, and solid-state defects. Detecting the JTE at single-molecule level can provide unique properties about the detected individual object. However, such measurements are challenging because of the weak signals associated with a single quantum object. Here, we propose that the dynamic JTE of single defects in solids can be observed with nearby quantum sensors. With numerical simulations, we demonstrate the real-time monitoring of JT axis jumps between different stable configurations of single substitutional nitrogen defect centers (P1 centers) in diamond. This is achieved by measuring the spin coherence of a single nitrogen-vacancy (NV) center near the P1 center with the double electron-electron resonance technique. Our work extends the ability of NV center as a quantum probe to sense the rich physics in various electron-vibrational coupled systems.

  2. Orbital Ordering in Frustrated Jahn-Teller Systems with 90° Exchange

    NASA Astrophysics Data System (ADS)

    Mostovoy, M. V.; Khomskii, D. I.

    2002-11-01

    We show that superexchange interactions in frustrated Jahn-Teller systems with transition metal ions connected by the 90° metal-oxygen-metal bonds (e.g., NaNiO2, LiNiO2, and ZnMn2O4) are much different from those in materials with the 180° bonds. In the 90°-exchange systems spins and orbitals are decoupled: the spin exchange is much weaker than the orbital one and it is ferromagnetic for all orbital states. Though the mean-field orbital ground state is strongly degenerate, quantum orbital fluctuations select particular ferro-orbital states. We explain the orbital and magnetic ordering observed in NaNiO2 and show that LiNiO2 is not a spin-orbital liquid.

  3. Orbital ordering in frustrated Jahn-Teller systems with 90 degrees exchange.

    PubMed

    Mostovoy, M V; Khomskii, D I

    2002-11-25

    We show that superexchange interactions in frustrated Jahn-Teller systems with transition metal ions connected by the 90 degrees metal-oxygen-metal bonds (e.g., NaNiO2, LiNiO2, and ZnMn2O4) are much different from those in materials with the 180 degrees bonds. In the 90 degrees -exchange systems spins and orbitals are decoupled: the spin exchange is much weaker than the orbital one and it is ferromagnetic for all orbital states. Though the mean-field orbital ground state is strongly degenerate, quantum orbital fluctuations select particular ferro-orbital states. We explain the orbital and magnetic ordering observed in NaNiO2 and show that LiNiO2 is not a spin-orbital liquid.

  4. Nonadiabaticity in a Jahn-Teller system probed by absorption and resonance Raman scattering.

    PubMed

    Pae, K; Hizhnyakov, V

    2013-03-14

    A theory of absorption and resonance Raman scattering of impurity centers in crystals with E⊗e-type Jahn-Teller effect in the excited state is presented. The vibronic interaction with non-totally symmetric local or pseudolocal modes and with a continuum of bath modes (phonons) is considered. A number of specific quantum effects, such as the nonadiabaticity-induced enhancement of the Raman scattering at high-energy excitation, the size effect of the final state, the interference of different channels of scattering, the Fermi resonances in the conical intersection, and others, were shown to become apparent in the calculated spectra. The vibronic interaction with phonons essentially determines the structure of the spectra.

  5. Jahn-Teller coupling and magnetic ground state in vanadium spinels^1

    NASA Astrophysics Data System (ADS)

    Chern, Gia-Wei; Tchernyshyov, Oleg

    2008-03-01

    The interplay of orbital, lattice, and spin degrees of freedom in vanadium spinels has attracted much interest among researchers. The V^3+ ion has two electrons occupying three degenerate t2g orbitals and is thus Jahn-Teller active. It also has a total spin S=1 in accordance with Hund's rules. Moreover, the V^3+ ions sitting on the B-site of spinel form a pyrochlore lattice, the interactions between these localized spin and orbital degrees of freedom are thus geometrically frustrated [1]. Here we present a theoretical model for the ground states of vanadium spinels. We view all of the vanadates (Cd, Zn, Mg on the one hand and Mn on the other) within the same model in which the influence of Mn is simulated by a magnetic field. In the case of MnV2O4, our calculation yields a ground state with antiferro-orbital ordering accompanied by a tetragonal structural distortion with lattice constants a=b>c. In addition, the V spins develop an orthogonal antiferromagnetic order in the ab plane on top of a ferromagnetic moment along the c axis. The results are consistent with a recent experimental characterization of MnV2O4 [2]. In particular, we will discuss the important role played by cooperative Jahn-Teller interaction and spin-orbital coupling in stabilizing the orthogonal spin configuration. [1] O. Tchernyshyov, Phys. Rev. Lett., 93, 157206 (2004). [2] V. O. Garlea et al., cond-mat/0711.1844. ,1NSF Grant No. DMR-0348679

  6. 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

  7. CuN6 Jahn-Teller centers in coordination frameworks comprising fully condensed Kuratowski-type secondary building units: phase transitions and magneto-structural correlations.

    PubMed

    Grzywa, Maciej; Denysenko, Dmytro; Hanss, Jan; Scheidt, Ernst-Wilhelm; Scherer, Wolfgang; Weil, Matthias; Volkmer, Dirk

    2012-04-14

    The metal-organic framework [Cu(ta)(2)] (Hta = 1H-1,2,3-triazole), containing Jahn-Teller active Cu(II) ions and 1,2,3-triazolate ligands, is prepared under solvothermal reaction conditions. The compound shows a reversible phase transition from the tetragonal crystal system (α-[Cu(ta)(2)]: space group I4(1)/amd (no. 141), a = 11.8447(7) Å, c = 18.9782(13) Å, V = 2662.6(3) Å(3)) to the cubic crystal system (β-[Cu(ta)(2)]: space group Fd3m (no. 227), a = 17.4416(15) Å, V = 5305.9(8) Å(3)) within the temperature range of 120-160 °C. Both [Cu(ta)(2)] polymorphs have identical bonding topologies that might be described as fully condensed Kuratowski-type pentanuclear secondary building units of local T(d) point group symmetry in which four Cu(II) ions occupy the vertices of an imaginary tetrahedron. α-[Cu(ta)(2)], as opposed to the high-temperature β-phase, shows a strong tetragonal Jahn-Teller distortion of CuN(6) coordination octahedra. The compounds are characterized by elemental and thermogravimetric analyses, single crystal and powder X-ray diffraction, FTIR-, UV-vis and fluorescence spectroscopy. Magnetic susceptibility investigations reveal two different Cu(II) sites at a ratio of 1 : 2, in agreement with the solid state structure of [Cu(ta)(2)]. At low temperatures the formation of antiferromagnetically coupled Cu(II) dimers is observed, leading to a spin frustration of roughly 1/3 of all magnetically active Cu(II) sites.

  8. A valence bond analysis of electronic degeneracies in Jahn-Teller systems: low-lying states of the cyclopentadienyl radical and cation.

    PubMed

    Zilberg, Shmuel; Haas, Yehuda

    2002-09-11

    The lowest doublet electronic state of the cyclopentadienyl radical (CPDR) and the lowest singlet state of the cyclopentadienyl cation (CPDC) are distorted from the highly symmetric D(5h) structure due to the Jahn-Teller effect. A valence bond analysis based on the phase-change rule of Longuet-Higgins reveals that in both cases the distortion is due to the first-order Jahn-Teller effect. It is shown that, while for the radical an isolated Jahn-Teller degeneracy is expected, in the case of the cation the main Jahn-Teller degeneracy is accompanied by five satellite degeneracies. The method offers a chemically oriented way for identifying the distortive coordinates.

  9. Jahn-Teller effect in LiMn2O4: influence on charge ordering, magnetoresistance and battery performance.

    PubMed

    Ragavendran, K; Xia, H; Mandal, P; Arof, A K

    2017-01-18

    The phase transition near room temperature in LiMn2O4 was studied using thermal expansion measurements, and directly compared with the electrochemical performance of the material. Studies based on thermal expansion indicate the onset of a first-order phase transition at Tc ∼ 220 K for the nearly half-doped material, with [Mn(3+)]/[Mn(4+)] ≈ 1. The Tc shifts to a higher temperature, ∼290 K, and signatures for Verwey-type charge ordering at 290 K can be observed when the fraction of Jahn-Teller Mn(3+) in LiMn2O4 is increased, i.e., [Mn(3+)]/[Mn(4+)] > 1. These studies show that the first-order phase transition near room temperature in LiMn2O4 is associated with charge ordering, which ultimately is a consequence of the Jahn-Teller effect. In addition, the Jahn-Teller effect is proven to be an important cause of magnetoresistance and electrochemical capacity fading in LiMn2O4. Electrochemical measurements show that both materials, either with a Tc ∼ 220 K or Tc ∼ 290 K, exhibit capacity fading to almost the same extent. Electrochemical capacity retention is observed only in nanosized LiMn2O4, for which the phase transition anomalies are completely absent.

  10. Raman phonon study of Jahn-Teller distortion in Ba3CuSb2O9

    NASA Astrophysics Data System (ADS)

    Drichko, Natalia; Broholm, Collin; Kimura, Kenta; Ishii, Rieko; Nakatsuju, Satoru

    2013-03-01

    The frustrated magnet Ba3CuSb2O9 does not exhibit either structural or magnetic ordering down to the lowest measured temperatures and is of great current interest as a spin-liquid candidate. It has been proposed recently that the lack of ordering is due to a static or dynamic Jahn-Teller distortion that leads to orbital disorder. We use phonon Raman scattering at temperatures between 20 and 380 K to investigate Jahn-Teller distortion in crystals with different Sb:Cu stoichiometry. We focus on phonons in the range of 500-800 cm-1 attributable to oxygen vibrations. In addition to signatures of the strong disorder due to Cu-Sb site mixing present in these materials, we observe mode-splitting due to a static Jahn-Teller distortion below 200 K in samples that undergo a transition to an orthorhombic phase. In contrast, samples that remain hexagonal to the lowest temperatures do not show such mode splitting. We are thankful to O. Tchernyshyov and Zihao Hao for discussions. This work was supported in part by the U.S. DoE, Office of Basic Energy Science, DMSE under Award DE-FG02-08ER46544 and H. Blewett Fellowship from APS

  11. Structural ground states of (A ,A')Cr2O4(A = Mg, Zn; A' = Co, Cu) spinel solid solutions: Spin-Jahn-Teller and Jahn-Teller effects

    NASA Astrophysics Data System (ADS)

    Kemei, Moureen C.; Moffitt, Stephanie L.; Darago, Lucy E.; Seshadri, Ram; Suchomel, Matthew R.; Shoemaker, Daniel P.; Page, Katharine; Siewenie, Joan

    2014-05-01

    We examine the effect of small amounts of magnetic substituents in the A sites of the frustrated spinels MgCr2O4 and ZnCr2O4. Specifically, we look for the effects of spin and lattice disorder on structural changes accompanying magnetic ordering in these compounds. Substitution of Co2+ on the nonmagnetic Zn2+ site in Zn1-xCoxCr2O4 where 0 < x ≤ 0.2 completely suppresses the spin-Jahn-Teller distortion of ZnCr2O4 although these systems remain frustrated, and magnetic ordering occurs at very low temperatures of T < 20 K. On the other hand, the substitution of Jahn-Teller active Cu2+ for Mg2+ and Zn2+ in Mg1-xCuxCr2O4 and Zn1-xCuxCr2O4 where 0 < x ≤ 0.2 induce Jahn-Teller ordering at temperatures well above the Néel temperatures of these solid solutions, and yet spin interactions remain frustrated with long-range magnetic ordering occurring below 20 K without any further lattice distortion. The Jahn-Teller distorted solid solutions Mg1-xCuxCr2O4 and Zn1-xCuxCr2O4 adopt the orthorhombic Fddd structure of ferrimagnetic CuCr2O4. Total neutron scattering studies of Zn1-xCuxCr2O4 suggest that there are local AO4 distortions in these Cu2+-containing solid solutions at room temperature and that these distortions become cooperative when average structure distortions occur. Magnetism evolves from compensated antiferromagnetism in MgCr2O4 and ZnCr2O4 to uncompensated antiferromagnetism with substitution of magnetic cations on the nonmagnetic cation sites of these frustrated compounds. The sharp heat capacity anomalies associated with the first-order spin-Jahn-Teller transitions of MgCr2O4 and ZnCr2O4 become broad in Mg1-xCuxCr2O4, Zn1-xCoxCr2O4, and Zn1-xCuxCr2O4 when x > 0. We present a temperature-composition phase diagram summarizing the structural ground states and magnetic properties of the studied spinel solid solutions.

  12. 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.

  13. Dynamic Jahn-Teller viewpoint for generation mechanism of asymmetric modes of coherent phonons

    NASA Astrophysics Data System (ADS)

    Kayanuma, Yosuke; Nakamura, Kazutaka G.

    2017-03-01

    We propose a dynamic Jahn-Teller approach to elucidate the generation mechanism of asymmetric modes of coherent phonons induced in crystals by irradiation with a short optical pulse in the opaque energy region. This is a natural extension of the impulsive excitation model of symmetric modes to multi dimensions in the configuration coordinate space. We show that the two generation mechanisms of coherent phonons coexist in this case, namely the impulsive absorption (IA) mechanism and impulsive stimulated Raman scattering (ISRS) mechanism. The dependence of the phonon amplitude on the polarization of the pump pulse is exactly the same in IA and ISRS processes and is in agreement with the prediction of the argument based on Raman tensors. The dependence of the excitation efficiency of the coherent phonons on the frequency of the pump pulse is calculated using a simplified model of the optical response function of the crystal. Generally, the IA mechanism predominates in the opaque region, although ISRS makes a comparable contribution to phonon generation in the near-edge opaque region. The initial phase of the coherent phonon is always cosine-like in IA but depends on the excitation frequency in ISRS.

  14. Quantum friction of pseudorotation in Jahn-Teller system: Passage through conical intersection

    NASA Astrophysics Data System (ADS)

    Pae, Kaja; Hizhnyakov, Vladimir

    2016-08-01

    A theoretical study of the relaxation of an excited impurity center with strong E × e-type Jahn-Teller effect, caused by the emission of phonons to the bulk, is presented. The dependence of the passing the system through the conical intersection of the potential surface on the momentum of the pseudorotation is figured out. An analytical description of the quantum states of the conical intersection (Slonczewski resonances) is given. It is found that for realistic vibronic interactions with phonons, the characteristic time of the energy loss is several tenths of mean periods of phonons, i.e., it is in the picosecond range. It is also found that there is a finite probability of the speeding-up of the pseudorotation of the system at the intermediate stage of relaxation. In particular, this probability increases close to the Slonczewski resonances. During the relaxation, the system may change the direction of the pseudomoment; the probability of such a change also increases near the resonances.

  15. 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.

  16. Using EPR spectroscopy to go from the Jahn-Teller effect to nuclear waste disposal

    NASA Astrophysics Data System (ADS)

    Boatner, L. A.

    2003-02-01

    Electron paramagnetic resonance (EPR) spectroscopy is a powerful technique for elucidating the fundamental solid-state-chemical and crystal-field ground-state electronic properties of rare-earth and actinide ions that are incorporated into single-crystal host materials. In the case of rare-earth or rare-earth-like ions that are characterized by a degenerate orbital doublet ground state when placed in a cubic crystal field, EPR has proven to be an extremely valuable approach to the study of various manifestations of the Jahn-Teller (J-T) effect. The contributions of EPR spectroscopy to the study of the J-T effect in ions such as La 2+, Y 2+ and Sc 2+ include the discovery of quadrupolar effects in J-T systems and a verification of Frank Ham's theory of the dynamic J-T effect. Such basic studies can often have unforeseen consequences—like leading to the discovery of new scintillators for gamma-ray detection or the development of a matrix for the disposal of radioactive waste.

  17. 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

  18. 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.

  19. 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

  20. Jahn-Teller-like origin of the tetragonal distortion in disordered Fe-Pd magnetic shape memory alloys

    NASA Astrophysics Data System (ADS)

    Opahle, Ingo; Koepernik, Klaus; Nitzsche, Ulrike; Richter, Manuel

    2009-02-01

    The electronic structure and magnetic properties of disordered FexPd100-x alloys (50Jahn-Teller-like effect, which allows the system to reduce its band energy in a narrow composition range. Prospects for an optimization of the alloys' properties by adding third elements are discussed.

  1. 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.

  2. 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.

  3. Local ordering of Jahn-Teller orbitals in LiNiO2 by neutron powder diffraction

    NASA Astrophysics Data System (ADS)

    Chung, Jae-Ho; Egami, Takeshi; Shamoto, Shin-Ichi; Proffen, Thomas; Ghorayeb, Andre

    2004-03-01

    The orbital state of LiNiO2 has been controversial, since there is no signature of long-range Jahn-Teller distortion, unlike NaNiO2 that shows ferromagnetic orbital order. We have neutron pair distribution function analysis to reveal important features, such as the local J-T distortion, the sharp oxygen-oxygen distance correlations, and unusual temperature dependence. These observations can be explained by a local ordering of Ni^3+ Jahn-Teller orbitals, where three neighboring 3d_z^2-r^2/3 orbitals share an oxygen site to form a trimer. Under this arrangement, it is expected that a medium-range elastic field will induce a curvature on NiO2 layers, which frustrates long-range order and is consistent with the systematic peak broadening observed in the neutron diffraction profiles. We propose that this local ordering is the basis for the complex magnetic properties observed in this material.

  4. 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…

  5. Dynamics of photo-induced changes in the elastic characteristics of lithium niobate crystals doped with Jahn-Teller Fe2+ ions

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

    The effect of admixture Jahn-Teller Fe2+ ions on the elastic characteristics of lithium niobate was studied. The appearance of photostrains and a change in elastic moduli under the influence of laser radiation was established, thus enabling the creation of device elements with optically controlled elastic characteristics.

  6. 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…

  7. Pulsed magnetic field synchrotron X-ray powder diffraction of the Jahn-Teller distortion in TbVO4

    NASA Astrophysics Data System (ADS)

    Vanacken, J.; Frings, P.; Detlefs, C.; Duc, F.; Lorenzo, J. E.; Nardone, M.; Billette, J.; Zitouni, A.; Bras, W.; Rikken, G.

    2006-11-01

    X-ray powder diffraction experiments under pulsed magnetic fields were carried out at the DUBBLE beam line at the ESRF. A mobile generator delivered 110 kJ to the load coil, which was sufficient to generate peak fields of 30 T. A liquid He flow cryostat allowed us to vary the sample temperature accurately between 8 K and 300 K. Powder diffraction patterns of TbVO4 were recorded in a broad temperature range using 21 keV monochromatic X-rays and an on-line image plate detector. We present results on the suppression of the Jahn-Teller structural distortion in TbVO4by to the magnetic field.

  8. 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.

  9. Absence of Jahn-Teller transition in the hexagonal Ba3CuSb2O9 single crystal

    DOE PAGES

    Katayama, Naoyuki; Kimura, Kenta; Han, Yibo; ...

    2015-07-13

    With decreasing temperature, liquids generally freeze into a solid state, losing entropy in the process. However, exceptions to this trend exist, such as quantum liquids, which may remain unfrozen down to absolute zero owing to strong quantum entanglement effects that stabilize a disordered state with zero entropy. Examples of such liquids include Bose-Einstein condensation of cold atoms, superconductivity, quantum Hall state of electron systems, and quantum spin liquid state in the frustrated magnets. Furthermore, recent studies have clarified the possibility of another exotic quantum liquid state based on the spin-orbital entanglement in FeSc2S4. To confirm this exotic ground state, experimentsmore » based on single-crystalline samples are essential. However, no such single-crystal study has been reported to date. Here, we report, to our knowledge, the first single-crystal study on the spin-orbital liquid candidate, 6H-Ba3CuSb2O9, and we have confirmed the absence of an orbital frozen state. In strongly correlated electron systems, orbital ordering usually appears at high temperatures in a process accompanied by a lattice deformation, called a static Jahn-Teller distortion. By combining synchrotron X-ray diffraction, electron spin resonance, Raman spectroscopy, and ultrasound measurements, we find that the static Jahn-Teller distortion is absent in the present material, which indicates that orbital ordering is suppressed down to the lowest temperatures measured. Lastly, we discuss how such an unusual feature is realized with the help of spin degree of freedom, leading to a spin-orbital entangled quantum liquid state.« less

  10. 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.

  11. Pseudo-Jahn-Teller and relaxation-rate analyses of a model for the hydride ion at the E' 4 center in alpha quartz

    NASA Astrophysics Data System (ADS)

    Georgiev, M.; Manov, A.

    1988-02-01

    Calculated cluster data on the energy vs hydride-ion displacement for the E' 4 center, as reported by Isoya, Weil, and Halliburton, are re-analyzed in terms of the Pseudo-Jahn-Teller effect. Realistic values are obtained of the vibronic-mixing parameters giving credibility to our interpretation. Relaxation rates are computed of hydrogen transfer between two opposite off-center sites.

  12. Dependence of the Jahn-Teller distortion in LaMn 1-x ScxO3 on the isovalent Mn-site substitution

    NASA Astrophysics Data System (ADS)

    Subías, G.; Cuartero, V.; Blasco, J.; García, J.; Meneghini, C.; Aquilanti, G.

    2016-05-01

    We investigated the relative importance of removing the Mn3+ Jahn-Teller distortion in driving ferromagnetism in LaMn1-xScxO3 combining x-ray powder diffraction and x-ray absorption spectroscopy at the Mn and Sc K-edges. By increasing the Sc content, the orthorhombic distortion of the Pbnm cell in LaMnO3 decreases but the unit-cell remains slightly distorted in LaScO3. Besides, the nearly tetragonal-distorted MO6 in LaMnO3 continuously evolves into a nearly regular one in LaScO3. On the other hand, x-ray absorption spectra show that the MnO6 octahedron remains Jahn-Teller distorted and the ScO6 octahedron is nearly regular along the whole series. Moreover, the ordering of the Mn3+ Jahn-Teller distortion is not disrupted in the ab plane for any Sc concentration. This contrasts with the Ga- substituted compounds, where a regular MnO6 is found for x>0.5. However, both LaMn0.5Sc0.5O3 and LaMn0.5Ga0.5O3 show ferromagnetic behavior independently of the presence (or not) of Jahn-Teller distorted Mn3+. Thus, our results point to the Mn-sublattice dilution as the main effect in driving ferromagnetism in these manganites over local structure effects previously proposed by the spin flipping or the vibronic superexchange models.

  13. The Phase Transitions in Double Tungstate in Extremely Low-Dimensional and Low-Symmetry Compounds with Cooperative Jahn-Teller Effect

    DTIC Science & Technology

    2001-01-01

    UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADPO 11897 TITLE: The Phase Transitions in Double Tungstate in Extremely...report: ADP011865 thru ADP011937 UNCLASSIFIED Invited Paper The phase transitions in double tungstate - in extremely low-dimensional and low-symmetry...Warsaw, Poland ABSTRACT The rare earth double tungstates are of special interest because of manifestation of cooperative Jahn-Teller effect (CJTE) for low

  14. First-Principles Study of the Jahn-Teller Distortion in the Ti1-XVXH2 and Zr1-XNbxH2 Alloys

    NASA Astrophysics Data System (ADS)

    Quijano, Ramiro; de Coss, Romeo; Singh, David

    2008-03-01

    The transition metal dihydrides TiH2 and ZrH2 present the fluorite structure (CaF2) at high temperature but undergoes a tetragonal distortion with c/a<1 at low temperature. Electronic band structure calculations have shown that TiH2 and ZrH2 in the cubic phase display a very flat band at the Fermi level. Thus the low temperature tetragonal distortion has been associated to a Jahn-Teller effect. In order to understand the role of band filling in controlling the structural instability of the transition metal dihydrides, we have performed a first-principles total energy study of the Ti1-XVxH2 and Zr1-xNbxH2 alloys. The calculations were performed using FP-LAPW method within the (DFT) and we use the GGA for exchange correlation functional energy. The critical concentration for which the Jahn-Teller effect is suppressed, was determined from the evolution of the tetragonal-cubic energy barrier. We discuss the electronic mechanism of the structural-instability, in terms of the band filling. From the obtained results we conclude that the tetragonal distortion in TiH2 and ZrH2 is not produced only by a Jahn-Teller Effect. This research was supported by Consejo Nacional de Ciencia y Tecnolog'ia (Conacyt) under Grant No. 43830-F.

  15. Manifestation of the Jahn-Teller active vibrations in the vibronic spectra of tetracoordinate Cu 2+, Ni 2+ and Zn 2+ chlorides

    NASA Astrophysics Data System (ADS)

    Trendafilova, N.; Nikolov, G. St.; Kellner, R.; Mikosch, H.; Bauer, G.; Bogatchev, G.

    1990-11-01

    An attempt is made to track the changes in the vibrational modes that are Jahn-Teller active of some pseudotetrahedral MCl 42- ions. The infrared and Raman spectra of powder (Et 4N) 2MCl 4, M=Ni, Cu, Zn and of Cu- and Ni-doped (Et 4N) 2ZnCl 4 were recorded both at room temperature and at 77, 100 and 170 K. The room temperature spectra show that for NiCl 42- and CuCl 42- if present the Jahn-Teller distortions are dynamically averaged and the transitions can be accounted for as intrasheet vibronic transitions. The low-temperature spectra however show splittings that are indicative of a low symmetry field thus suggestingthat at 77 K the NiCl 42- and CuCl 42- are vibronically stabilized in a static C 2v field. The doped compound spectra reveal that the Zn matrix effect overrides the static Jahn-Teller distortions present in the free ion spectra. In the CuCl 42- spectrum a band at 2700 cm -1 with side bands + v(a 1), - v(t 2s) was detected and it was assigned to the 2B 2g→ 2B 1g transition arising from the split 2T 2 term in D 2h site symmetry.

  16. Model of the interplay of band Jahn-Teller effect with magnetic order mediated by exchange interactions

    NASA Astrophysics Data System (ADS)

    Reddy, G. Gangadhar; Ramakanth, A.; Ghatak, S. K.; Behera, S. N.; Nolting, W.; Rao, T. Venkatappa

    2006-10-01

    A model calculation is presented with the aim to study the interplay between magnetic and structural transitions. The model consists of an orbitally doubly degenerate conduction band and a periodic array of local moments. The band electrons interact with the local spins via the s-f interaction. The interaction of the band electrons with phonons is introduced by including band Jahn-Teller (J-T) interaction. The model Hamiltonian, including the above terms, is solved for the single particle Greens function. In doing this an ansatz for self-energy of electrons, which was developed earlier, has been utilized. The quasiparticle density of states (QDOS) and hence the orbital populations are calculated treating the ferromagnetism of local moments in the mean field approximation. The critical value of electron-phonon interaction (G) for the appearance of the band J-T distortion is higher in the ferromagnetic state. The strain appears at a critical temperature (Ts) when G is greater than the critical value. The onset of ferromagnetism at TC (

  17. On the Jahn-Teller effect in the X∼2E electronic ground state of CH3F+

    NASA Astrophysics Data System (ADS)

    Sarkar, Rudraditya; Rajagopala Reddy, S.; Mahapatra, S.; Köppel, H.

    2017-01-01

    In view of recent experimental and theoretical developments, we revisit our earlier theoretical studies (Mahapatra et al., 2004, 2005) on the Jahn-Teller effect in the degenerate X∼2E electronic ground state of CH3F+. The electronic potential energy surfaces and the coupling surfaces are re-calculated employing state-of-the-art ab initio quantum chemistry methods. The vibronic Hamiltonian, constructed with the aid of multimode vibronic coupling theory and symmetry selection rules, is systematically extended to higher order in the Taylor series expansion and the parameters are carefully revised in the present study. First principles quantum dynamics study is carried out to calculate the vibronic eigenvalue spectrum of this degenerate electronic state of CH3F+. The vibronic energy levels are assigned and compared with the experimental pulsed-field-ionization zero-electron-kinetic energy (PFI-ZEKE) and one photon ZEKE spectra of CH3F+ and also with the earlier theoretical results reported in the literature.

  18. Time-resolved luminescence from Jahn-Teller split states of self-trapped excitons in PbWO4

    NASA Astrophysics Data System (ADS)

    Itoh, Minoru; Sakurai, Takaaki

    2006-06-01

    This paper reports the observation of time-resolved luminescence from a self-trapped exciton (STE) localized at tetrahedral (WO4)2- complex anion in PbWO4 . The results clearly reveal that the STE luminescence is composed of three emission bands peaking at 407, 425, and 450nm . Such a composite nature is explained well by assuming that the lowest triplet states of the STE split into three sublevels owing to the symmetry lowering from Td to C3v due to the Jahn-Teller effect. This assumption is in accordance with the theoretical prediction of Bacci [M. Bacci, S. Porcinai, E. Mihóková, M. Nikl, and K. Polák, Phys. Rev. B 64, 104302 (2001); M. Bacci, E. Mihóková, and L. S. Schulman, ibid. 66, 132301 (2002)]. The decay curve of each component and its temperature dependence are investigated in the range of 77to300K . These results are discussed on the basis of an adiabatic potential energy diagram of the triplet STE state. Time-resolved luminescence spectra are also measured for Mo-doped PbWO4 crystals. From a comparison with the spectra of undoped PbWO4 crystals, the Mo-related luminescence is clearly separated from the intrinsic luminescence due to STEs.

  19. THz and infrared excitation spectrum below the Jahn-Teller transition in Sr3Cr2O8

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Schmidt, Michael; Günther, Axel; Schaile, Sebastian; Pascher, Nikola; Mayr, Franz; Goncharov, Yurii; Krug von Nidda, Hans-Albrecht; Loidl, Alois; Quintero-Castro, Diana; Islam, A. T. M. N.; Lake, Bella; Deisenhofer, Joachim

    2012-02-01

    We report on optical excitations observed recently in Sr3Cr2O8 by THz and infrared spectroscopy. Low-energy excitations below 3 THz are detected by THz time domain spectroscopy. These excitations can be divided into two different classes according to the temperature-dependent properties. One is emergent right below the Jahn-Teller transition temperature, which is determined by specific heat measurement to occur at 285 K [1, 2]. The other appears only below 100 K, where the fluctuations are sufficiently suppressed, consistent with the temperature dependence of low-energy Raman modes [3]. Infrared transmission measurements reveal a broad crystal-field excitation, which can be associated with an electronic transition from E to T2 orbital states. [4pt] [1] Zhe Wang et al., Phys. Rev. B 83, 201102 (2011) [0pt] [2] D. L. Quintero-Castro et al., Phys. Rev. B 81, 014415 (2010) [0pt] [3] D. Wulferding et al., Phys. Rev. B 84, 064419 (2011)

  20. Dielectric anomaly and structural change related to the Jahn-Teller transition in DyVO4

    NASA Astrophysics Data System (ADS)

    Kishimoto, Kazumasa; Ishikura, Taishi; Nakamura, Hiroyuki; Wakabayashi, Yusuke; Kimura, Tsuyoshi

    2010-03-01

    RVO4 system has been studied as dielectrics for several decades. Among them, DyVO4 having Dy^3+ ( 4f^9) and V^5+ (3d^0) ions shows the Jahn-Teller (JT) transition at TD =14 K due to the interaction between 4f electrons on Dy sites and the lattice. As a result, the lattice distorts from the I41amd tetragonal to the Imma orthorhombic structure and ferroquadrupolar ordering occurs below TD. We measured the dielectric constant of a single crystal of DyVO4 and observed a distinct dielectric anomaly around TD. To clarify the origin of the dielectric anomaly, we performed detailed single crystal structure analyses. Our results suggest that the JT distortion shifts the position of oxygen ions relative to a V ion and then local polarization of a VO4 tetrahedron is induced below TD. We also report the structural domain control causing remarkable magnetocapacitance effects by applying a relatively small magnetic field (˜0.1 T), which is attributed to the strong spin-orbit coupling of Dy 4f electrons.

  1. Numerical Estimation of the Pseudo-Jahn-Teller Effect Using Nonadiabatic Coupling Integrals in Monocyclic and Bicyclic Conjugated Molecules.

    PubMed

    Koseki, Shiro; Toyota, Azumao; Muramatsu, Takashi; Asada, Toshio; Matsunaga, Nikita

    2016-12-29

    The pseudo-Jahn-Teller (pJT) effect in monocyclic and bicyclic conjugated molecules was investigated by using the state-averaged multiconfiguration self-consistent field (MCSCF) method, together with the 6-31G(d,p) basis sets. Following the perturbation theory, the force constant along a normal mode Q is given by the sum of the classical force constant and the vibronic contribution (VC) resulting from the interaction of the ground state with excited states. The latter is given as the sum of individual contributions arising from vibronic interactions between the ground state and excited states. In the present work, each VC was calculated on the basis of nonadiabatic coupling (NAC) integrals. Furthermore, the classical force constant was estimated by taking advantage of the VC and the force constant obtained by vibrational analyses. For pentalene and heptalene, the present method seems to overestimate the VC in absolute value because of the small energy gap between the ground state and the lowest excited state. However, we are confident that the VC and the classical force constant for the other molecules are reasonable in magnitude in comparison with available literature information. Thus, it is proved that the present method is applicable and useful for numerical estimation of pJT effect.

  2. Density functional theory study of the multimode Jahn-Teller problem in the open-shell corannulenes and coronenes

    NASA Astrophysics Data System (ADS)

    Andjelković, Ljubica; Gruden-Pavlović, Maja; Zlatar, Matija

    2015-10-01

    Analysis of the multimode Jahn-Teller (JT) distortion in anions and cations of corannulene and coronene is presented, combining multideterminantal-DFT (MD-DFT) and Intrinsic Distortion Path (IDP) methods. The JT distortion is derived from the sum of contributions of all possible JT active normal modes. The Csbnd C stretching modes play the most important role in the stabilization of the systems, in all investigated species, pushing the nuclei toward the minima on the potential energy surface. The further inspection of the IDP revealed that the relaxation of the geometry arrives in the final part of the path and is encountered by the softest vibrational modes. The same trend was observed in cyclopentadienyl radical, benzene anion, benzene cation and fullerene ions. This gives microscopic origin into the mechanism of the distortion and provides general behavior of the JT effect in these similar molecules. Moreover, MD-DFT and IDP, as fast and fully non-empirical approaches, can be considered as a reliable tool for better understanding of the JT effect.

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    The crystal structure of chromite FeCr2O4 was investigated to 13.7 GPa and ambient temperature with single-crystal X-ray diffraction techniques. The unit-cell parameter decreases continuously from 8.3832 (5) to 8.2398 (11) Å up to 11.8 GPa. A fit to the Birch-Murnaghan equation of state (EoS) based on the P-V data gives: K 0 = 209 (13) GPa, K' = 4.0 (fixed), and V 0 = 588 (1) Å3. The FeO4 tetrahedra and CrO6 octahedra are compressed isotropically with pressure with their Fe-O and Cr-O bond distances decreasing from 1.996 (6) to 1.949 (7) Å and from 1.997 (3) to 1.969 (7) Å, respectively. The tetrahedral site occupied by the Fe2+ cation is more compressible than the octahedral site occupied by the Cr3+ cation. The resulting EoS parameters for the tetrahedral and the octahedral sites are K 0 = 147 (9) GPa, K' = 4.0 (fixed), V 0 = 4.07 (1) Å3 and K 0 = 275 (24) GPa, K' = 4.0 (fixed), V 0 = 10.42 (2) Å3, respectively. A discontinuous volume change is observed between 11.8 and 12.6 GPa. This change indicates a phase transition from a cubic (space group Fd-{overline{3}} m) to a tetragonal structure (space group I41 /amd). At the phase transition boundary, the two Cr-O bonds parallel to the c-axis shorten from 1.969 (7) to 1.922 (17) Å and the other four Cr-O bonds parallel to the ab plane elongate from 1.969 (7) to 1.987 (9) Å. This anisotropic deformation of the octahedra leads to tetragonal compression of the unit cell along the c-axis. The angular distortion in the octahedron decreases continuously up to 13.7 GPa, whereas the distortion in the tetrahedron rises dramatically after the phase transition. At the pressure of the phase transition, the tetrahedral bond angles along the c-axis direction of the unit cell begin decreasing from 109.5° to 106.6 (7)°, which generates 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

  4. Suppression of Jahn-Teller Distortions and Origin of Piezochromism and Thermochromism in Cu-Cl Hybrid Perovskite.

    PubMed

    Gupta, Sunny; Pandey, Tribhuwan; Singh, Abhishek Kumar

    2016-07-05

    While pressure-induced changes in the electronic, magnetic, and optical properties of Cu-Cl hybrid perovskites have been studied intensively, the correlation between these properties and pressure-induced structural changes is still vaguely understood. Here, by first-principles calculations on a model system (EDBE)[CuCl4] (EDBE = 2,2'-(ethylenedioxy)bis(ethylammonium)) (a Cu-Cl hybrid perovskite), we correlate the evolution of a series of exciting physical properties with pressure while resolving some of the long-standing debates on the fundamental electronic nature of this important class of material. The material shows two structural phase transitions and an anisotropy in compressibility with increasing pressure. After a critical pressure of 17 GPa, the structure becomes highly symmetric, thereby suppressing the Jahn-Teller distortions. At zero pressure, mapping the optical transitions with the Laporte selection rules, lower and higher energy excitations are found to be of Mott-Hubbard (MH) and charge transfer (CT) type, respectively, signifying the material to be a Mott insulator. The material shows a red shift in the charge transfer band edge with increasing pressure and temperature, demonstrating the piezochromism and the thermochromism, respectively. Piezochromism originates from the changes in mixing of Cl-Cu p-d states, while thermochromism is due to broadening of conduction band states, thereby showing different electronic and structural evolution with pressure and temperature. Furthermore, the magnetic ordering in the material was found to be stable up to higher pressures, making pressure a tool to tune the electronic property without perturbing the magnetic property.

  5. Interaction of spin-orbital-lattice degrees of freedom: Vibronic state of the corner-sharing-tetrahedral frustrated spin system HoBaFe4O7 by dynamical Jahn-Teller effect

    NASA Astrophysics Data System (ADS)

    Kamazawa, Kazuya; Ishikado, Motoyuki; Ohira-Kawamura, Seiko; Kawakita, Yukinobu; Kakurai, Kazuhisa; Nakajima, Kenji; Sato, Masatoshi

    2017-03-01

    A powder inelastic neutron-scattering study of HoBaFe4O7 (HBFO) revealed characteristic magnetic excitations associated with geometrical spin frustration. Dispersionless excitations in energy (ω ) and wave-vector (Q ) space are observed at several discrete energies. Some of them can be attributed to crystal-field excitations of Ho3 + in octahedral symmetry, but the others are explained instead by the vibronic state of the Fe2 + dynamical Jahn-Teller effect with orbit-spin coupling, indicating interaction among the spin, the orbital, and the lattice degree of freedom. The antiferromagnetic HBFO lattice has cubic symmetry, and both Fe2 + and Fe3 + reside on corner-sharing tetrahedra with a number ratio of 3:1. Even though Fe2 + is a Jahn-Teller active ion in tetrahedral symmetry, the system does not exhibit any static lattice distortion to the lowest temperature studied (4 K). The observed excitations can be understood by considering the dynamical interaction among spin-orbital-lattice degrees of freedom, indicating that spin fluctuation due to the frustration effect induces the dynamical Jahn-Teller effect, although in most cases a Jahn-Teller active ion Fe2 + takes the static Jahn-Teller effect in a magnetic oxide system.

  6. Jahn-Teller effect in CH2DO∕CHD2O(X̃(2)E): vibronic coupling of all vibrational modes.

    PubMed

    Shao, Zhuo; Mo, Yuxiang

    2013-06-28

    For the Jahn-Teller active methoxy radical CH3O∕CD3O(X̃(2)E), only the degenerate vibrational modes break the C3v geometric symmetry. For the isotopologues CH2DO∕CHD2O, all their normal vibrational motions break the C3v geometric symmetry, which results in a splitting of the adiabatic potential energy surfaces (APESs), that is, all vibrational modes are Jahn-Teller active. Therefore, each fundamental vibrational energy level of CH2DO∕CHD2O splits into two levels due to a combination of Jahn-Teller and spin-orbit interactions. In this work we report an ab initio calculation of the spin-vibronic energy levels of CH3O∕CH2DO∕CHD2O∕CD3O using a diabatic model. The APESs were calculated at the UCCSD(T)-F12a∕cc-pVQ(T)Z-F12a level. The vibronic parameters in the diabatic model Hamiltonian of CD3O were first determined using the least-squares fitting to the APESs. The vibronic parameters of the other three isotopologues were derived from those of CD3O using the Duschinsky rotation method. The calculated spin-vibronic energy splittings for the vibrational ground states of CH3O∕CH2DO∕CHD2O∕CD3O are 61.8∕73.5∕70.2∕54.5 cm(-1), respectively, in good agreement with the reported experimental results.

  7. First-principle investigation of Jahn-Teller distortion and topological analysis of chemical bonds in LiNiO{sub 2}

    SciTech Connect

    Chen Zhenlian; Zou Huamin; Zhu Xiaopeng; Zou Jie; Cao Jiefeng

    2011-07-15

    First-principle GGA+U calculations were performed on the undistorted rhombohedral R3-bar m model, the collinear Jahn-Teller distorted monoclinic C2/m model, and six non-collinear Jahn-Teller distortion ordering models of LiNiO{sub 2}. The zigzag and C2/m models are found to be the most stable and the next most stable structural models, respectively. An energy gap appears for the C2/m and zigzag structures, whereas no energy gap appears for the R3-bar m structure. Topological analyses were performed on the R3-bar m, C2/m and zigzag models using the atoms-in-molecules theory and the electron localization function. The results show that the Ni-O interaction is the transit closed-shell interaction, in which the net electron transfer occurs from the Ni ion to the ligand O ions. The Ni-O bond possesses the {sigma} dative bond character and is polarized toward the O ions. In the distorted structures, the bonding electrons around the oxygen atom are strongly polarized toward the long Ni-O bond. - Graphical abstract: Isosurfaces of the difference charge density and the electron localization function for the zigzag structure of LiNiO{sub 2}. Highlights: > Using ELF and AIM, topological analyses were carried out on different structures. > The zigzag Jahn-Teller distortion ordering is the most stable structure. > Semiconductor gap emerges in the C2/m and zigzag structures. > The Ni-O bonds are dative bonds. > In the distorted structures, bond electrons accumulate in the long Ni-O bond basins.

  8. Quadratic coupling treatment of the Jahn-Teller effect in the triply-degenerate electronic state of CH4(+): can one account for floppiness?

    PubMed

    Mondal, T; Varandas, A J C

    2012-12-07

    The Jahn-Teller (JT) coupling effects in the triply degenerate ground electronic state of methane radical cation are investigated theoretically within a quadratic vibronic coupling approach. The underlying potential energy surfaces over the two-dimensional space of nuclear coordinates, subject to the T(2) ⊗ (e + t(2) + t(2)) Jahn-Teller effect, are established from extensive ab initio calculations using the multi-reference configuration interaction method and then employed to determine the various parameters of a diabatic Hamiltonian of this system. Our previous investigation [T. Mondal and A. J. C. Varandas, J. Chem. Phys. 135, 174304 (2011)], relying on the linear vibronic coupling approach augmented by only a diagonal second-order term of the totally symmetric mode, are extended here by including all possible quadratic coupling constants of JT active e and t(2) modes. Inclusion of these quadratic couplings is found to be important to reproduce correctly the broad vibrational structure and for a better description of dynamical JT effect in the first vibronic band of this radical cation. The impact of large amplitude motions (which are responsible for floppiness of the molecule) on the vibronic structure and dynamics of the first photoelectron band have been examined via readjustment of their linear coupling parameters up to ±10%.

  9. 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.

  10. Anomalous multi-order Raman scattering in LaMnO3: a signature of quantum lattice effects in a Jahn-Teller crystal.

    PubMed

    Kovaleva, N N; Kusmartseva, O E; Kugel, K I; Maksimov, A A; Nuzhnyy, D; Balbashov, A M; Demikhov, E I; Dejneka, A; Trepakov, V A; Kusmartsev, F V; Stoneham, A M

    2013-04-17

    The multi-order Raman scattering is studied up to fourth order for a detwinned LaMnO3 crystal. Based on a comprehensive data analysis of the polarization-dependent Raman spectra, we show that the anomalous features in the multi-order scattering could be the sidebands on the low-energy mode at about 25 cm(-1). We suggest that this low-energy mode stems from the tunneling transition between the potential energy minima arising near the Jahn-Teller Mn(3+) ion due to the lattice anharmonicity and that the multi-order scattering is activated by this low-energy electronic motion. The sidebands are dominated by the oxygen contribution to the phonon density-of-states, however, there is an admixture of an additional component, which may arise from coupling between the low-energy electronic motion and the vibrational modes.

  11. Anomalous multi-order Raman scattering in LaMnO3: a signature of quantum lattice effects in a Jahn-Teller crystal

    NASA Astrophysics Data System (ADS)

    Kovaleva, N. N.; Kusmartseva, O. E.; Kugel, K. I.; Maksimov, A. A.; Nuzhnyy, D.; Balbashov, A. M.; Demikhov, E. I.; Dejneka, A.; Trepakov, V. A.; Kusmartsev, F. V.; Stoneham, A. M.

    2013-04-01

    The multi-order Raman scattering is studied up to fourth order for a detwinned LaMnO3 crystal. Based on a comprehensive data analysis of the polarization-dependent Raman spectra, we show that the anomalous features in the multi-order scattering could be the sidebands on the low-energy mode at about 25 cm-1. We suggest that this low-energy mode stems from the tunneling transition between the potential energy minima arising near the Jahn-Teller Mn3+ ion due to the lattice anharmonicity and that the multi-order scattering is activated by this low-energy electronic motion. The sidebands are dominated by the oxygen contribution to the phonon density-of-states, however, there is an admixture of an additional component, which may arise from coupling between the low-energy electronic motion and the vibrational modes.

  12. Charge disproportionation and Jahn-Teller distortion in LiNiO2 and NaNiO2: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Chen, Hungru; Freeman, Colin L.; Harding, John H.

    2011-08-01

    Density functional theory calculations have been performed on three potential ground-state configurations of LiNiO2 and NaNiO2. These calculations show that, whereas NaNiO2 shows the expected cooperative Jahn-Teller distortion (and therefore a crystal structure with C2/m symmetry), LiNiO2 shows at least two possible crystal structures very close in energy (within 3 meV/formula unit): P21/c and P2/c. Moreover, one of them (P2/c) shows charge disproportionation of the (expected) Ni3+ cations into Ni2+ and Ni4+. We discuss the implications of this complex ground state for the interpretation of the available electron and neutron structure data, its electronic and complex magnetic behavior.

  13. Electron spin relaxation in pseudo-Jahn-Teller low-symmetry Cu(II) complexes in diaqua(L-aspartate)Zn(II).H(2)O crystals.

    PubMed

    Hoffmann, S K; Hilczer, W; Goslar, J; Massa, M M; Calvo, R

    2001-11-01

    Low-temperature (4-55 K) pulsed EPR measurements were performed with the magnetic field directed along the z-axis of the g-factor of the low-symmetry octahedral complex [(63)Cu(L-aspartate)(2)(H2O)2] undergoing dynamic Jahn-Teller effect in diaqua(L-aspartate)Zn(II) hydrate single crystals. Spin-lattice relaxation time T(1) and phase memory time T(M) were determined by the electron spin echo (ESE) method. The relaxation rate 1/T(1) increases strongly over 5 decades in the temperature range 4-55 K. Various processes and mechanisms of T(1)-relaxation are discussed, and it is shown that the relaxation is governed mainly by Raman relaxation processes with the Debye temperature Theta(D)=204 K, with a detectable contribution from disorder in the doped Cu(2+) ions system below 12 K. An analytical approximation of the transport integral I(8) is given in temperature range T=0.025-10Theta(D) and applied for computer fitting procedures. Since the Jahn-Teller distorted configurations differ strongly in energy (delta(12)=240 cm(-1)), there is no influence of the classical vibronic dynamics mechanism on T(1). Dephasing of the ESE (phase relaxation) is governed by instantaneous diffusion and spectral diffusion below 20 K with resulting rigid lattice value 1/T(0)(M)=1.88 MHz. Above this temperature the relaxation rate 1/T(M) increases upon heating due to two mechanisms. The first is the phonon-controlled excitation to the first excited vibronic level of energy Delta=243 cm(-1), with subsequent tunneling to the neighbor potential well. This vibronic-type dynamics also produces a temperature-dependent broadening of lines in the ESEEM spectra. The second mechanism is produced by the spin-lattice relaxation. The increase in T(M) is described in terms of the spin packets forming inhomogeneously broadened EPR lines.

  14. Absence of Jahn-Teller transition in the hexagonal Ba3CuSb2O9 single crystal

    SciTech Connect

    Katayama, Naoyuki; Kimura, Kenta; Han, Yibo; Nasu, Joji; Drichko, Natalia; Nakanishi, Yoshiki; Halim, Mario; Ishiguro, Yuki; Satake, Ryuta; Nishibori, Eiji; Yoshizawa, Masahito; Nakano, Takehito; Nozue, Yasuo; Wakabayashi, Yusuke; Ishihara, Sumio; Hagiwara, Masayuki; Sawa, Hiroshi; Nakatsuji, Satoru

    2015-07-13

    With decreasing temperature, liquids generally freeze into a solid state, losing entropy in the process. However, exceptions to this trend exist, such as quantum liquids, which may remain unfrozen down to absolute zero owing to strong quantum entanglement effects that stabilize a disordered state with zero entropy. Examples of such liquids include Bose-Einstein condensation of cold atoms, superconductivity, quantum Hall state of electron systems, and quantum spin liquid state in the frustrated magnets. Furthermore, recent studies have clarified the possibility of another exotic quantum liquid state based on the spin-orbital entanglement in FeSc2S4. To confirm this exotic ground state, experiments based on single-crystalline samples are essential. However, no such single-crystal study has been reported to date. Here, we report, to our knowledge, the first single-crystal study on the spin-orbital liquid candidate, 6H-Ba3CuSb2O9, and we have confirmed the absence of an orbital frozen state. In strongly correlated electron systems, orbital ordering usually appears at high temperatures in a process accompanied by a lattice deformation, called a static Jahn-Teller distortion. By combining synchrotron X-ray diffraction, electron spin resonance, Raman spectroscopy, and ultrasound measurements, we find that the static Jahn-Teller distortion is absent in the present material, which indicates that orbital ordering is suppressed down to the lowest temperatures measured. Lastly, we discuss how such an unusual feature is realized with the help of spin degree of freedom, leading to a spin-orbital entangled quantum liquid state.

  15. Bcc and Fcc transition metals and alloys: a central role for the Jahn-Teller effect in explaining their ideal and distorted structures.

    PubMed

    Lee, Stephen; Hoffmann, Roald

    2002-05-01

    Transition metal elements, alloys, and intermetallic compounds often adopt the body centered cubic (bcc) and face centered cubic (fcc) structures. By comparing quantitative density functional with qualitative tight-binding calculations, we analyze the electronic factors which make the bcc and fcc structures energetically favorable. To do so, we develop a tight-binding function, DeltaE(star), a function that measures the energetic effects of transferring electrons within wave vector stars. This function allows one to connect distortions in solids to the Jahn-Teller effect in molecules and to provide an orbital perspective on structure determining deformations in alloys. We illustrate its use by considering first a two-dimensional square net. We then turn to three-dimensional fcc and bcc structures, and distortions of these. Using DeltaE(star), we rationalize the differences in energy of these structures. We are able to deduce which orbitals are responsible for instabilities in seven to nine valence electron per atom (e(-)/a) bcc systems and five and six e(-)/a fcc structures. Finally we demonstrate that these results account for the bcc and fcc type structures found in both the elements and binary intermetallic compounds of group 4 through 9 transition metal atoms. The outline of a theory of metal structure deformations based on loss of point group operation rather than translational symmetry is presented.

  16. Valence and spin states in delafossite AgNiO2 and the frustrated Jahn-Teller system ANiO2 (A=Li,Na)

    NASA Astrophysics Data System (ADS)

    Kang, J.-S.; Lee, S. S.; Kim, G.; Lee, H. J.; Song, H. K.; Shin, Y. J.; Han, S. W.; Hwang, C.; Jung, M. C.; Shin, H. J.; Kim, B. H.; Kwon, S. K.; Min, B. I.

    2007-11-01

    Electronic structures of delafossite oxides AgNi1-xCoxO2 and the frustrated Jahn-Teller (JT) system ANiO2 (A=Li,Na) have been investigated by employing soft x-ray absorption spectroscopy and photoemission spectroscopy (PES). It is found that Ni ions are in the Ni2+-Ni3+ mixed-valent states and that the low-spin (LS) Ni3+ component increases from LiNiO2 to AgNiO2 and NaNiO2 , in agreement with the presence of the JT transition in NaNiO2 and the absence of the JT transition in LiNiO2 and AgNiO2 . In AgNi1-xCoxO2 , the Ni3+ component increases with x , while Co ions are in the LS Co3+ states for all x , which is consistent with the metallic nature for low values of x . A good agreement is found between the measured PES spectra and the calculated local spin density approximation (LSDA) electronic structures of AgNiO2 and AgCoO2 , but the pseudogap feature in PES of AgNiO2 is not described by the LSDA.

  17. 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.

  18. 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.

  19. 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.

  20. Cooperative Jahn-Teller effect in a 2D mesoscopic C{60/n-} system with D5d symmetry adsorbed on buffer layers using Ising EFT model

    NASA Astrophysics Data System (ADS)

    Abou Ghantous, M.; Moujaes, E. A.; Dunn, J. L.; Khater, A.

    2012-06-01

    Fullerene molecules adsorbed on surfaces often show macroscopic average distortions. As charged ions C60n- are known to be Jahn-Teller (JT) active, it is suggested that these distortions could be a manifestation of cooperative JT effects (CJTE) due to interactions between neighbouring fullerene ions. In order to understand the distortion properties it is necessary to take correlations between different distortions into account. However, this can't easily be done in the mean field approximation usually used to describe the CJTE. We therefore propose an alternative procedure to describe 2D mesoscopic islands of C60 ions in which a pseudo vector spin overrightarrow{S} is evoked to represent degenerate JT-distorted states when the quadratic JT coupling is considered. This approach is analogous to methods used for 2D magnetic systems. We then use the differential operator technique in effective field theory within the Ising approach. We include the effects of weak surface interactions and dynamic motion between equivalent distortions via terms equivalent to anisotropy and a transverse field in magnetism respectively. For distortions to D5d symmetry, we determine single site correlations as a function of temperature, the macroscopic average distortion describing a structural phase transition, and the isothermal response function. Phase diagrams are presented for relevant cases of the system parameters.

  1. Ti3+ on Nb site: A paramagnetic Jahn-Teller center in vacuum-reduced LiNbO3:Mg:Ti single crystals

    NASA Astrophysics Data System (ADS)

    Corradi, G.; Zaritskii, I. M.; Hofstaetter, A.; Polgár, K.; Rakitina, L. G.

    1998-10-01

    An axial EPR signal observed in vacuum annealed LiNbO3 single crystals doped with 8 mol % Mg and 0.05 mol % Ti has been attributed to Ti3+ on Nb site. The g tensor components (g||=1.760+/-0.005 and g⊥=1.786+/-0.005 for T=5 K and g||=g⊥=1.893+/-0.005 for T=74 K), resulting in outstandingly low values of the orbital reduction factor (from k=0.16 to 0.13), can be explained by a dynamic pseudo-Jahn-Teller effect. The vibronic coupling of the center is much stronger than that reported for other nd1 centers with similar trigonally distorted octahedral coordination in LiNbO3 like the Ti3+ on Li site and trapped Nb4+ polarons on both cation sites. Stronger coupling for ions on or near the Nb site is understood as a result of smaller trigonal splitting of the ground state due to the more central position of the Nb site in the oxygen octahedron. Electron transfer from the observed Ti3+ center to lattice niobiums, resulting in Nb4+ trapped polarons, has been stimulated by illumination in the near UV region. The average energy difference of the involved Ti4+/3+ and Nb5+/4+ donor levels has been estimated to be 70+/-23 meV depending also on the distance of compensating Mg2+ ions on nearby Li sites.

  2. High-pressure behavior of cuprospinel CuFe2O4: Influence of the Jahn-Teller effect on the spinel structure

    SciTech Connect

    Kyono, Atsushi; Gramsch, Stephen A.; Nakamoto, Yuki; Sakata, Masafumi; Kato, Masato; Tamura, Tomoya; Yamanaka, Takamitsu

    2015-08-14

    The Jahn-Teller-effect at Cu2+ in cuprospinel CuFe2O4 was investigated using high-pressure, single crystal synchrotron x-ray diffraction (XRD) techniques at beamline BL10A at the Photon Factory, KEK, Japan. Six data sets were collected in the pressure range from ambient to 5.9 GPa at room temperature. Structural refinements based on the data were performed at 0.0, 1.8, 2.7, and 4.6 GPa. The unit cell volume of cuprospinel decreases continuously from 590.8 (6) Å3 to 579.5 (8) Å3 up to 3.8 GPa. Leastsquares fitting to a third-order Birch-Murnaghan equation of state yields zero-pressure volume V0 = 590.7 (1) Å3 and bulk modulus K0 = 188.1 (4.4) GPa with K’ fixed at 4.0. The crystal chemical composition determined by electron-probe analysis and x-ray site-occupancy refinement is represented as [Cu0.526Fe0.474][6][Cu0.074Fe1.926]O4. Most of the Cu2+ are preferentially distributed onto the tetrahedral (T) site of the spinel structure. At 4.6 GPa, a cubic-tetragonal phase transition is indicated by a splitting of the a axis of the cubic structure into a smaller a axis and a longer c axis, with unit cell parameters a = 5.882 (1) Å and c = 8.337 (1) Å. The tetragonal crystal structure with space group I41/amd was refined to R1 = 0.0182 and wR2 = 0.0134 using observed 35 x-ray reflections. At the T site, the tetrahedral O-T-O bond angles along the c-axis direction of the unit cell decreases slightly from 109.47 ° to 108.7 (4) °, which generates a stretched tetrahedral geometry along the c-axis. The cubic-totetragonal transition induced by the Jahn-Teller effect at Cu2+ is attributable to the angular distortion at the tetrahedral site. At the octahedral (M) site, on the other hand, the two M-O bonds parallel to the caxis are shortened with respect to the four M-O bonds parallel to

  3. High-pressure behavior of cuprospinel CuFe2O4: Influence of the Jahn-Teller effect on the spinel structure

    DOE PAGES

    Kyono, Atsushi; Gramsch, Stephen A.; Nakamoto, Yuki; ...

    2015-08-14

    The Jahn-Teller-effect at Cu2+ in cuprospinel CuFe2O4 was investigated using high-pressure, single crystal synchrotron x-ray diffraction (XRD) techniques at beamline BL10A at the Photon Factory, KEK, Japan. Six data sets were collected in the pressure range from ambient to 5.9 GPa at room temperature. Structural refinements based on the data were performed at 0.0, 1.8, 2.7, and 4.6 GPa. The unit cell volume of cuprospinel decreases continuously from 590.8 (6) Å3 to 579.5 (8) Å3 up to 3.8 GPa. Leastsquares fitting to a third-order Birch-Murnaghan equation of state yields zero-pressure volume V0 = 590.7 (1) Å3 and bulk modulus K0more » = 188.1 (4.4) GPa with K’ fixed at 4.0. The crystal chemical composition determined by electron-probe analysis and x-ray site-occupancy refinement is represented as [Cu0.526Fe0.474][6][Cu0.074Fe1.926]O4. Most of the Cu2+ are preferentially distributed onto the tetrahedral (T) site of the spinel structure. At 4.6 GPa, a cubic-tetragonal phase transition is indicated by a splitting of the a axis of the cubic structure into a smaller a axis and a longer c axis, with unit cell parameters a = 5.882 (1) Å and c = 8.337 (1) Å. The tetragonal crystal structure with space group I41/amd was refined to R1 = 0.0182 and wR2 = 0.0134 using observed 35 x-ray reflections. At the T site, the tetrahedral O-T-O bond angles along the c-axis direction of the unit cell decreases slightly from 109.47 ° to 108.7 (4) °, which generates a stretched tetrahedral geometry along the c-axis. The cubic-totetragonal transition induced by the Jahn-Teller effect at Cu2+ is attributable to the angular distortion at the tetrahedral site. At the octahedral (M) site, on the other hand, the two M-O bonds parallel to the caxis are shortened with respect to the four M-O bonds parallel to the ab-plane, which are lengthened as a result of the phase transition, leading to a compressed octahedral geometry along the c-axis. With the competing distortions between the

  4. 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.

  5. 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

  6. 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.

  7. The Jahn-Teller effect in the lower electronic states of benzene cation. III. The ground-state vibrations of C6H6+ and C6D6+

    NASA Astrophysics Data System (ADS)

    Burrill, Andrew B.; Chung, You K.; Mann, Heather A.; Johnson, Philip M.

    2004-05-01

    New mass analyzed threshold ionization (MATI) spectra of the molecules C6H6+ and C6D6+ have been collected using tunable vacuum ultraviolet (VUV) single photon excitation from the neutral ground state and also using two-photon excitation through the 61 vibration of the 1B2u S1 state. Emphasis was placed on obtaining accurate relative intensities of the vibrational lines in order to use this information in the vibronic analysis. The MATI spectra collected from VUV (S0 originating state), triplet (T1), and resonant two photon (S1) excitation schemes were compared with Jahn-Teller calculations employing the classical model of Longuet-Higgins and Moffitt to obtain the Jahn-Teller coupling parameters of 3 of the 4 linearly active modes (e2g modes 6-9 in Wilson's notation). Franck-Condon factors, including the effects of geometry changes, were calculated from the vibronic wave functions and used to identify the lines in the various spectra. It is found that most of the lines with substantial intensity can be understood using only the modes 1, 6, 8, and 9. Weaker peaks are due to various non-e2g modes, but these do not derive intensity through Jahn-Teller coupling. When the effects of geometry change were included, simulations of the spectra from the calculated vibrational energies and intensities were close to the experimental spectra. This verifies the applicability of the model to the understanding of the vibrational structure of this type of molecule, but some variations indicate directions for further improvement of the model.

  8. Jahn-Teller Effect in the Phonon Properties of Defective SrTiO3 from First Principles

    SciTech Connect

    Evarestov, Robert; Blokhin, Evgeny; Gryaznov, D.; Kotomin, Eugene Alexej; Merkle, R.; Maier, Joachim

    2012-05-17

    Using a hybrid density functional theory method combined with linear combination of atomic orbitals basis set and periodic supercell approach, the atomic, electronic structure, and phonon properties were calculated for SrTiO3 containing either Fe4+ substituting host Ti4+ ions or neutral oxygen vacancies Vo. For both defects, the Jahn–Teller effect occurs, thus reducing the cubic symmetry of a perfect crystal and leading to the appearance of both Raman- and infrared-active vibrational modes. The calculated phonon densities of states and group-theoretical analysis of defect-induced phonon frequencies were used for the interpretation of the relevant experimental data, once defect-induced local modes are identified. The temperature dependence of the Vo formation energy based on the calculated Gibbs free energy was also compared with experiments, and the phonon contribution therein estimated.

  9. Multiconfiguration Self-Consistent Field Study on Formonitrile Imine and N-Substituted Nitrile Imines HCN2-R: Energy Component Analysis of the Pseudo-Jahn-Teller Effect.

    PubMed

    Toyota, Azumao; Muramatsu, Takashi; Koseki, Shiro

    2017-03-23

    Stable geometrical structures for formonitrile imine (1) and N-substituted nitrile imines HCN2-R (R = Li, BeH, BH2, CH3, CN, CCH, C6H5, NH2, OH, and F) (2-11) were examined by using the multiconfiguration self-consistent-field (MCSCF) method followed by second-order configuration interaction (SOCI) calculations and second-order multiconfiguration quasi-degenerate perturbation theory (MCQDPT2) calculations, together with the aug-cc-pVTZ basis sets. The results show that 1 suffers a pseudo-Jahn-Teller (JT) distortion from a linear C∞v structure to a C1 structure via a planar bent Cs structure. Each of the others is found to undergo pseudo-JT distortion from a symmetrical structure to a planar bent Cs structure for 2, 3, and 7 and to a C1 structure for 4, 5, 6, 8, 9, 10, and 11. At the stationary structures of 1-11, the structural characteristics were briefly discussed in terms of allenic and propargylic. To elucidate the nature of pseudo-JT distortions, energy component analyses were carried out at the MCSCF+SOCI level of theory at all of the stationary structures for the relevant molecules. In most of the molecules examined, pseudo-JT stabilizations were classified into two groups, one in which the stability arises from a lowering of the energy of the attractive term Ven and the other in which the stability results from a lowering of the energy of the repulsive terms Vnn and Vee. In addition to the above two groups, it was also found that the following three groups are responsible for the pseudo-JT stabilizations in a certain stage of the structural changes. Namely, one is a lowering of the energy of the term Vee observed in 6, another is a lowering of the energy of the terms Vee and Ven observed in 9-11, and the other is a lowering of the energy of the terms Ven and Vnn observed in 10. These energetic behaviors were accounted in terms of an elongation or a contraction of the molecular skeleton, a migration of electrons from one part of the molecule to other parts

  10. Nonadiabatic effects in a generalized Jahn-Teller lattice model: Heavy and light polarons, pairing, and the metal-insulator transition

    NASA Astrophysics Data System (ADS)

    Majerníková, Eva; Riedel, J.; Shpyrko, S.

    2002-05-01

    The self-consistent ground state polaron potential of one-dimensional lattice of two-level molecules with spinless electrons and two dispersionless phonon modes with linear coupling and quantum phonon-assisted (nonadiabatic) transitions between the levels is found anharmonic in phonon displacements. As a function of these, the potential shows a crossover from two nonequivalent broad minima to a single narrow minimum which correspond to the positions of the levels in the ground state. Generalized variational approach respecting the mixing of levels (reflection) via a variational parameter implies prominent nonadiabatic effects: (i) In the limit of the symmetric E⊗e Jahn-Teller situation they cause transition between the regime of the predominantly one-level ``heavy'' polaron and a ``light'' polaron oscillating between the levels due to phonon assistance with almost vanishing polaron displacement. Vanishing polaron selflocalization implies enhancement of the electron transfer due to decrease of the ``heavy'' polaron mass (undressing) at the point of the transition. There can occur pairing of ``light'' polarons due to exchange of virtual phonons. Continuous transition to new energy ground state close to the transition from ``heavy'' polaron phase to ``light'' (bi)polaron phase occurs. In the ``heavy'' phase, we have found anomalous (anharmonic) enhancements of quantum fluctuations of the phonon coordinate, conjugated momentum and their product in the ground state as functions of the effective coupling which reach their maxima at E⊗e JT symmetry. They decrease rapidly to their harmonic values as soon as the ``light'' phase is stabilized. (ii) Nonadiabatic dependence of the polaron mass (Debye-Waller screening) on the optical phonon frequency appears. (iii) The contribution of Rabi oscillations to the transfer enhances significantly quantum shift of the insulator-metal transition line to higher values of the critical effective electron-phonon coupling supporting so

  11. Origin of small barriers in Jahn-Teller systems: quantifying the role of 3d-4s hybridization in the model system NaCl:Ni+.

    PubMed

    Barriuso, M T; Ortiz-Sevilla, B; Aramburu, J A; García-Fernández, P; García-Lastra, J M; Moreno, M

    2013-08-19

    Despite its relevance, the microscopic origin of the energy barrier, B, between the compressed and elongated geometries of Jahn-Teller (JT) systems is not well understood yet because of a lack of quantitative data about its various contributions. Seeking to clear up this matter, we have carried out both periodic and cluster ab initio calculations on the model system NaCl:Ni(+). This system is particularly puzzling because, according to experimental data, its barrier is much smaller than that for other d(9) and d(7) ions in similar lattices. All calculations performed on the model system lead, in fact, to values |B| ≤ 160 cm(-1), which are certainly smaller than B = 500 cm(-1) derived for NaCl:M(2+) (M = Ag, Rh) or B = 1024 cm(-1) obtained for KCl:Ag(2+). As a salient feature, analysis of calculations carried out as a function of the Qθ (∼3z(2) - r(2)) coordinate unveils the microscopic origin of the barrier. It is quantitatively proven that the elongated geometry observed for NaCl:Ni(+) is due to the 3d-4s vibronic admixture, which is slightly larger than the anharmonicity in the eg JT mode that favors a compressed geometry. The existence of these two competing mechanisms explains the low value of B for the model system, contrary to cases where the complex formed by d(9) or d(7) ions is elastically decoupled from the host lattice. Although the magnitude of B for NaCl:Ni(+) is particularly small, the tunneling splitting, 3Γ, is estimated to be below 9 cm(-1), thus explaining why the coherence is easily destroyed by random strains and thus a static JT effect is observed experimentally. As a main conclusion, the barrier in JT systems cannot be understood neglecting the tiny changes of the electronic density involved in small distortions. The present calculations reasonably explain the experimental g tensor of NaCl:Ni(+), pointing out that the d-d transitions in NiCl6(5-) are much smaller than those for CuCl6(4-) and the optical electronegativity of Ni(+) is only

  12. Magnetic structure of the high-density single-valent eg Jahn-Teller system LaMn7O12

    NASA Astrophysics Data System (ADS)

    Prodi, Andrea; Gilioli, Edi; Cabassi, Riccardo; Bolzoni, Fulvio; Licci, Francesca; Huang, Qingzhen; Lynn, Jeff W.; Affronte, Marco; Gauzzi, Andrea; Marezio, Massimo

    2009-02-01

    We studied the structural and physical properties of powder samples of the high-pressure LaMn7O12 compound by means of neutron diffraction, dc magnetization, specific-heat, and dc electrical resistivity measurements. Our structural refinement shows that LaMn7O12 is the counterpart with quadruple perovskite structure of the well-known simple-perovskite LaMnO3 because both compounds are single-valent Mn3+ systems sharing a similar pseudocubic network of buckled corner-sharing MnO6 octahedra distorted by the Jahn-Teller (JT) effect. Besides this similarity, LaMn7O12 exhibits the following structural differences: (i) a monoclinic I2/m , instead of orthorhombic Pnma , structure; (ii) a much larger buckling of the MnO6 octahedra, corresponding to a Mn-O-Mn bond angle as small as ψ=180°-ϕ=136° . At TN,B=78K , the neutron data show evidence of an antiferromagnetic (AFM) structure of the octahedral Mn3+ ions ( B sites), which consists of ferromagnetically coupled antiferromagnetic ac planes. This structure, commonly referred to as C type, markedly differs from the A -type structure of LaMnO3 , which consists of antiferromagnetically coupled ferromagnetic ac planes. We argue that this difference may be due not only to the different buckling, because the magnetic superexchange interaction is sensitive to ϕ , but also to the existence of two distinct JT distorted B sites, a characteristic feature of the quadruple perovskite structure not found in LaMnO3 . A further feature of this structure is the presence of a pseudocubic sublattice of JT Mn3+ ions with square coordination ( A' site) in addition to the B -site sublattice. At TN,A'=21K , the A' sublattice of LaMn7O12 is found to form a second AFM structure consisting of AFM coupled ferromagnetic planes. This additional ordering appears to occur independently of that of the B sublattice. Finally, we observed a thermally activated insulating behavior of the resistivity similar to that previously reported for LaMnO3 , which

  13. 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

  14. Geometrical and electronic structure of the molybdenum and tungsten halides MX3 and MX4 (M = Mo, W; X = F, Cl): Jahn-Teller effect and spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Sliznev, Valery V.; Belova, Natalya V.

    2017-03-01

    The ground and lower-lying excited electronic states of MX3 and MX4 (M = Mo, W; X = F, Cl) molecules were systematically studied by the complete active space self-consistent field (CASSCF) and multiconfigurational quasi-degenerate second-order perturbation (XMCQDPT2) methods. Scalar-relativistic effects and spin-orbit coupling were taken into account employing the third-order Douglas-Kroll-Hess (DKH) Hamiltonian and full Breit-Pauli operator. The ground orbital state of MoF3 and MoCl3 complexes is quadruplet 4A2‧ state in the equilibrium configuration with D3h symmetry. If the spin-orbit interaction is taken into account the calculations result in two 4E1/2 and 4E3/2 spin-orbit states with 11-14 cm-1 energy differences instead of one 4A2‧ state. Spin-orbit interaction quenches the Jahn-Teller effect in 2E″ ground orbital state of WF3 complex in D3h configuration, and C2v configuration with (4E1/2 + 4E3/2) spin-mixed state corresponds to the minimum on the PES. The WCl3 complex reveals strong interaction of the spin-orbit states of different multiplicity. For WCl3 complex the configuration with D3h symmetry corresponds to the minimum on the PES for four lowest spin-mixed electronic states. The MoF4, MoCl4 and WCl4 complexes possess the tetrahedral equilibrium configuration with 3A2 orbital electronic state. If the spin-orbit interaction is taken into account the ground state changes to the threefold degenerated 3T2 spin-orbit state with weak Jahn-Teller effect. In the case of WF4 complex the strong Jahn-Teller effect has been discovered in the first excited 1E singlet electronic state of the tetrahedral structure, and D2d configuration with 1A1 electronic state possesses the lowest energy. The comparison with available experimental data has been performed. The tendencies in molecular parameters of complexes studied were analyzed.

  15. Investigations of the spin-Hamiltonian parameters and defect structure due to Jahn-Teller effect for the tetragonal Nb4+ center in cubic Cs2ZrCl6 crystal

    NASA Astrophysics Data System (ADS)

    Wu, Xiao-Xuan; Zheng, Wen-Chen

    2015-06-01

    The spin-Hamiltonian parameters (g factors g//, ?, and hyperfine structure constants A//, ?) of the tetragonally compressed Nb4+ center in cubic Cs2ZrCl6 crystal are calculated from two theoretical methods: one is the complete diagonalization (of energy matrix) method and another is the perturbation theory method. Both methods are based on the two-spin-orbit-parameter model where the contributions to spin-Hamiltonian parameters from the spin-orbit parameter of central dn ion (in the conventional crystal field theory) and that of ligand ion via covalence effect are contained. The calculated results from the two methods are in reasonable agreement with the experimental values. The tetragonal distortion of (NbCl6)2- octahedral cluster due to the Jahn-Teller effect for Nb4+ at the cubic Zr4+ site in Cs2ZrCl6 is also acquired. The results are discussed.

  16. Density functional theory analysis of the interplay between Jahn-Teller instability, uniaxial magnetism, spin arrangement, metal-metal interaction, and spin-orbit coupling in Ca3CoMO6 (M = Co, Rh, Ir).

    PubMed

    Zhang, Yuemei; Kan, Erjun; Xiang, Hongjun; Villesuzanne, Antoine; Whangbo, Myung-Hwan

    2011-03-07

    In the isostructural oxides Ca(3)CoMO(6) (M = Co, Rh, Ir), the CoMO(6) chains made up of face-sharing CoO(6) trigonal prisms and MO(6) octahedra are separated by Ca atoms. We analyzed the magnetic and electronic properties of these oxides on the basis of density functional theory calculations including on-site repulsion and spin-orbit coupling, and examined the essential one-electron pictures hidden behind results of these calculations. Our analysis reveals an intimate interplay between Jahn-Teller instability, uniaxial magnetism, spin arrangement, metal-metal interaction, and spin-orbit coupling in governing the magnetic and electronic properties of these oxides. These oxides undergo a Jahn-Teller distortion, but their distortions are weak, so that their trigonal-prism Co(n+) (n = 2, 3) ions still give rise to strong easy-axis anisotropy along the chain direction. As for the d-state split pattern of these ions, the electronic and magnetic properties of Ca(3)CoMO(6) (M = Co, Rh, Ir) are consistent with d(0) < (d(2), d(-2)) < (d(1), d(-1)) but not with (d(2), d(-2)) < d(0) < (d(1), d(-1)). The trigonal-prism Co(3+) ion in Ca(3)Co(2)O(6) has the L = 2 configuration (d(0))(1)(d(2), d(-2))(3)(d(1), d(-1))(2) because of the metal-metal interaction between adjacent Co(3+) ions in each Co(2)O(6) chain, which is mediated by their z(2) orbitals, and the spin-orbit coupling of the trigonal-prism Co(3+) ion. The spins in each CoMO(6) chain of Ca(3)CoMO(6) prefer the ferromagnetic arrangement for M = Co and Rh but the antiferromagnetic arrangement for M = Ir. The octahedral M(4+) ion of Ca(3)CoMO(6) has the (1a)(1)(1e)(4) configuration for M = Rh but the (1a)(2)(1e)(3) configuration for M = Ir, which arises from the difference in the spin-orbit coupling of the M(4+) ions and the Co···M metal-metal interactions.

  17. Effects of Lattice Distortion and Jahn-Teller Coupling on the Magnetoresistance of La(sub 0.7)Ca(sub 0.3)MnO(sub 3) and La(sub 0.5)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, J.; Beach, G.

    1996-01-01

    Studies of La(sub 0.7)Ca(sub 0.3)MnO(sub 3) epitaxial films on substrates with a range of lattice constants reveal two dominant contributions to the occurence of colossal negative magnetoresistance (CMR) in these manganites:...We therefore suggest that lattice polaron conduction associated with Jahn-Teller coupling is essential for the occurence of CMR, and that lattice distortion further enhances the CMR effect in the manganites.

  18. Sr3Bi2(SeO3)6·H2O: A novel anionic layer consisting of second-order Jahn-Teller (SOJT) distortive cations

    NASA Astrophysics Data System (ADS)

    Ahn, Hyun Sun; Lee, Eun Pyo; Chang, Hong-Young; Lee, Dong Woo; Ok, Kang Min

    2015-01-01

    A new layered bismuth selenite hydrate material, Sr3Bi2(SeO3)6·H2O has been synthesized through a hydrothermal reaction using SrCO3, Bi2O3, SeO2, and water as reagents. The crystal structure of the reported material has been determined by single crystal X-ray diffraction analysis. The anionic layered framework of Sr3Bi2(SeO3)6·H2O consists of polyhedra of second-order Jahn-Teller (SOJT) distortive cations, Bi3+ and Se4+. Attributable to the variable and asymmetric coordination geometry of the constituent cations, a rich structural chemistry including uni-dimensional bands and linkers is observed in the layer. The material is thermally stable up to about 390 °C and starts decomposing due to the sublimation of SeO2 above the temperature. The UV-vis diffuse reflectance spectrum suggests a band gap of 3.3 eV. Elemental analysis, infrared spectrum, local dipole moment calculations, and electronic structure calculations are also reported.

  19. Hydrothermal Synthesis and Characterization of Novel Brackebuschite-Type Transition Metal Vanadates: Ba2M(VO4)2(OH), M = V(3+), Mn(3+), and Fe(3+), with Interesting Jahn-Teller and Spin-Liquid Behavior.

    PubMed

    Sanjeewa, Liurukara D; McGuire, Michael A; Garlea, Vasile O; Hu, Longyu; Chumanov, George; McMillen, Colin D; Kolis, Joseph W

    2015-07-20

    A new series of transition metal vanadates, namely, Ba2M(VO4)2(OH) (M = V(3+), Mn(3+), and Fe(3+)), was synthesized as large single crystals hydrothermally in 5 M NaOH solution at 580 °C and 1 kbar. This new series of compounds is structurally reminiscent of the brackebuschite mineral type. The structure of Ba2V(VO4)2(OH) is monoclinic in space group P21/m, a = 7.8783(2) Å, b = 6.1369(1) Å, c = 9.1836(2) Å, β = 113.07(3)°, V = 408.51(2) Å(3). The other structures are similar and consist of one-dimensional trans edge-shared distorted octahedral chains running along the b-axis. The vanadate groups bridge across edges of their tetrahedra. Structural analysis of the Ba2Mn(VO4)2(OH) analogue yielded a new understanding of the Jahn-Teller effect in this structure type. Raman and infrared spectra were investigated to observe the fundamental vanadate and hydroxide vibrational modes. Single-crystal temperature-dependent magnetic studies on Ba2V(VO4)2(OH) reveal a broad feature over a wide temperature range with maximum at ∼100 K indicating that an energy gap could exist between the antiferromagnetic singlet ground state and excited triplet states, making it potentially of interest for quantum magnetism studies.

  20. 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.

  1. Highly stable cooperative distortion in a weak Jahn-Teller d2 cation: perovskite-type ScVO3 obtained by high-pressure and high-temperature transformation from bixbyite.

    PubMed

    Castillo-Martínez, Elizabeth; Bieringer, Mario; Shafi, Shahid P; Cranswick, Lachlan M D; Alario-Franco, Miguel Ángel

    2011-06-08

    A novel ScVO(3) perovskite phase has been synthesized at 8 GPa and 1073 K from the cation-disordered bixbyite-type ScVO(3). The new perovskite has orthorhombic symmetry at room temperature, space group Pnma, and lattice parameters a = 5.4006(2) Å, b = 7.5011(2) Å, and c = 5.0706(1) Å with Sc(3+) and V(3+) ions fully ordered on the A and B sites of the perovskite cell. The vanadium oxygen octahedra [V-O(6)] display cooperative Jahn-Teller (JT) type distortions, with predominance of the tetragonal Q(3) over the orthorhombic Q(2) JT modes. The orthorhombic perovskite shows Arrhenius-type electrical conductivity and undergoes a transition to triclinic symmetry space group P-1 close to 90 K. Below 60 K, the magnetic moments of the 4 nonequivalent vanadium ions undergo magnetic long-range ordering, resulting in a magnetic superstructure of the perovskite cell with propagation vector (0.5, 0, 0.5). The magnetic moments are confined to the xz plane and establish a close to zigzag antiferromagnetic mode.

  2. Influence of Jahn-Teller Cu2+ (3d9) ion on structural and magnetic properties of Al-Cr co-substituted CuFe2O4

    NASA Astrophysics Data System (ADS)

    Tanna, A. R.; Trivedi, U. N.; Chhantbar, M. C.; Joshi, H. H.

    2013-11-01

    Four specimens of two compositions of the spinel oxide system CuAlxCrxFe2-2xO4 with x = 0.2 and 0.6 have been synthesized by double sintering ceramic technique with different thermal history i.e. quenched and slow-cooled. X-ray diffractometry has confirmed that tetragonal distortion is present in slow-cooled sample, while it is absent in quenched sample. The lower value of saturation moment compared to Neel's moment for each composition is explained by invoking random canting of spins model. Hyperfine interaction parameters: nuclear hyperfine field, quadrupole splitting (shifts), isomer shift and Fe3+ ion distribution are deduced through computer simulation of Mössbauer spectra. 57Fe Mössbauer spectra recorded at room temperature show the effect of magnetic dilution of inter-sublattice ( A- B) interaction (frustration) more in case of quenched-sample compared to slow-cooled one. FTIR spectra also corroborate the influence of Jahn-Teller (J-T) distortion of octahedral void arising due to larger Cu2+ ion occupancy at octahedral sites. The force constants are also estimated from FTIR spectra.

  3. Glass formation in microgravity

    NASA Technical Reports Server (NTRS)

    Ray, C. S.; Day, D. E.

    1987-01-01

    An account is given of containerless glass-forming experiments conducted aboard the Space Shuttle in 1985, using a single-axis acoustic levitator furnace apparatus. An attempt was made to obtain quantitative evidence for the suppression of heterogeneous nucleation/crystallization in containerless melts under microgravity conditions, as well as to study melt homogenization in the absence of gravity-driven convection and assess the feasibility of laser fusion target glass microsphere preparation with a microgravity apparatus of the present type. A ternary calcia-gallia-silica glass thus obtained indicated a 2-3-fold increase in glass-formation tendency for this material composition in microgravity, by comparison with 1g.

  4. Phase Transition and Second Harmonic Generation in Thiophosphates Ag2Cd(P2S6) and AgCd3(PS4)S2 Containing Two Second-Order Jahn-Teller Distorted Cations.

    PubMed

    Fan, Yu-Hang; Jiang, Xiao-Ming; Liu, Bin-Wen; Li, Shu-Fang; Guo, Wei-Huan; Zeng, Hui-Yi; Guo, Guo-Cong; Huang, Jin-Shun

    2017-01-03

    Two new phases in the Ag-Cd-P-S system containing two second-order Jahn-Teller (SOJT) distorted d(10) cations (Cd(2+) and Ag(+)), namely, Ag2Cd(P2S6) (1) and AgCd3(PS4)S2 (2), are obtained via medium-temperature solid-state synthesis. Compound 1 exhibits a two-dimensional layered structure and undergoes a first-order structural phase transition at approximately 280 °C. This outcome can be ascribed to the significant mismatch in the expansion coefficients between Cd-S (Ag-S) and P-P (P-S) bonds evaluated through bond valence theory. The three-dimensional non-centrosymmetric (NCS) framework of 2 is constructed by two types of tetrahedral layers consisting of corner-shared CdS4, AgS4, and PS4 tetrahedra. Compound 2 exhibits second harmonic generation (SHG) intensity of 0.45 times that of commercial AgGaS2 (AGS) at a laser irradiation of 1.85 μm and an optical band gap of 2.56 eV, and no intrinsic vibrational absorption of chemical bonds is observed in the range of 2.5-18.2 μm. Both phase transition in 1 and SHG properties in 2 are closely related to the SOJT distorted d(10) cations and diverse phosphorus-sulfur polyanions (PaSb)(n-), which together can easily result in NCS distorted structures and interesting properties.

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

    SciTech Connect

    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 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. As a result, their magnitude and subnanometer spatial extent remain unchanged.

  6. 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.; ...

    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

  7. Glass formation - A contemporary view

    NASA Technical Reports Server (NTRS)

    Uhlmann, D. R.

    1983-01-01

    The process of glass formation is discussed from several perspectives. Particular attention is directed to kinetic treatments of glass formation and to the question of how fast a given liquid must be cooled in order to form a glass. Specific consideration is paid to the calculation of critical cooling rates for glass formation, to the effects of nucleating heterogeneities and transients in nucleation on the critical cooling rates, to crystallization on reheating a glass, to the experimental determination of nucleation rates and barriers to crystal nucleation, and to the characteristics of materials which are most conducive to glass formation.

  8. Orbital Dimer Model for the Spin-Glass State in Y_{2}Mo_{2}O_{7}.

    PubMed

    Thygesen, Peter M M; Paddison, Joseph A M; Zhang, Ronghuan; Beyer, Kevin A; Chapman, Karena W; Playford, Helen Y; Tucker, Matthew G; Keen, David A; Hayward, Michael A; Goodwin, Andrew L

    2017-02-10

    The formation of a spin glass generally requires that magnetic exchange interactions are both frustrated and disordered. Consequently, the origin of spin-glass behavior in Y_{2}Mo_{2}O_{7}-in which magnetic Mo^{4+} ions occupy a frustrated pyrochlore lattice with minimal compositional disorder-has been a longstanding question. Here, we use neutron and x-ray pair-distribution function (PDF) analysis to develop a disorder model that resolves apparent incompatibilities between previously reported PDF, extended x-ray-absorption fine structure spectroscopy, and NMR studies, and provides a new and physical explanation of the exchange disorder responsible for spin-glass formation. We show that Mo^{4+} ions displace according to a local "two-in-two-out" rule on each Mo_{4} tetrahedron, driven by orbital dimerization of Jahn-Teller active Mo^{4+} ions. Long-range orbital order is prevented by the macroscopic degeneracy of dimer coverings permitted by the pyrochlore lattice. Cooperative O^{2-} displacements yield a distribution of Mo-O-Mo angles, which in turn introduces disorder into magnetic interactions. Our study demonstrates experimentally how frustration of atomic displacements can assume the role of compositional disorder in driving a spin-glass transition.

  9. Orbital Dimer Model for the Spin-Glass State in Y2 Mo2 O7

    NASA Astrophysics Data System (ADS)

    Thygesen, Peter M. M.; Paddison, Joseph A. M.; Zhang, Ronghuan; Beyer, Kevin A.; Chapman, Karena W.; Playford, Helen Y.; Tucker, Matthew G.; Keen, David A.; Hayward, Michael A.; Goodwin, Andrew L.

    2017-02-01

    The formation of a spin glass generally requires that magnetic exchange interactions are both frustrated and disordered. Consequently, the origin of spin-glass behavior in Y2 Mo2 O7 —in which magnetic Mo4 + ions occupy a frustrated pyrochlore lattice with minimal compositional disorder—has been a longstanding question. Here, we use neutron and x-ray pair-distribution function (PDF) analysis to develop a disorder model that resolves apparent incompatibilities between previously reported PDF, extended x-ray-absorption fine structure spectroscopy, and NMR studies, and provides a new and physical explanation of the exchange disorder responsible for spin-glass formation. We show that Mo4 + ions displace according to a local "two-in-two-out" rule on each Mo4 tetrahedron, driven by orbital dimerization of Jahn-Teller active Mo4 + ions. Long-range orbital order is prevented by the macroscopic degeneracy of dimer coverings permitted by the pyrochlore lattice. Cooperative O2 - displacements yield a distribution of Mo-O-Mo angles, which in turn introduces disorder into magnetic interactions. Our study demonstrates experimentally how frustration of atomic displacements can assume the role of compositional disorder in driving a spin-glass transition.

  10. 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.

  11. 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.

  12. Nanogratings formation in multicomponent silicate glasses

    NASA Astrophysics Data System (ADS)

    Lancry, M.; Zimmerman, F.; Desmarchelier, R.; Tian, J.; Brisset, F.; Nolte, S.; Poumellec, B.

    2016-03-01

    We demonstrate the formation of porous nanogratings in various oxide glasses including TiO2-doped silica, GeO2 and alumino-borosilicate by near-IR femtosecond laser radiation. ULE and GeO2 glasses exhibit similar birefringence to pure silica, whereas Borofloat 33 reveals twice weaker amplitude. Using quantitative birefringence measurements, small-angle X-ray scattering and scanning electron microscopy, we correlate birefringence and porous nanolayers formation according to laser repetition rate and glass composition. We show that heat accumulation is a crucial parameter limiting the glass decomposition and thus nanogratings formation.

  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. Symmetry and degeneracy manifolds in Jahn-Teller molecules

    NASA Astrophysics Data System (ADS)

    Mead, C. A.

    2013-04-01

    We consider problems in dealing with molecular systems of n identical nuclei. One problem is that of finding suitable internal coordinates. For n <= 4, these can be simply the internuclear distances. For n > 4, it is shown that, with perhaps one exception, there is no internal coordinate system that treats all nuclei equivalently. We also consder the properties of conical intersections between two Born-Oppenheimer electronic energy surfaces, in particular the problem of identifying the two coordinates that remove the degeneracy to first order in the near neighborhoods of symmetry manifolds.

  15. Spin-singlet state formation in the cluster Mott insulator GaNb4S8 studied by μSR and NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Waki, T.; Kajinami, Y.; Tabata, Y.; Nakamura, H.; Yoshida, M.; Takigawa, M.; Watanabe, I.

    2010-01-01

    Muon spin relaxation (μSR) and nuclear magnetic resonance experiments revealed that the spin-singlet state with an excitation gap of ˜200K is realized from S=1/2Nb4 tetrahedral clusters in a cluster Mott insulator GaNb4S8 . The intercluster cooperative phenomenon to the singlet state at TS=32k is triggered by intracluster Jahn-Teller type structural instability developed from ˜3TS . Referring to the lattice symmetry, the formation of Nb8 octamer ( Nb4-Nb4 bond) is suggested.

  16. The formation kinetics of lunar glasses

    NASA Technical Reports Server (NTRS)

    Uhlmann, D. R.; Handwerker, C. A.; Onorato, P. I. K.; Salomaa, R.; Goncz, D.

    1978-01-01

    The kinetic treatment of crystallization and glass formation, involving the construction of time-temperature-transformation curves (TTT) corresponding to a given degree of crystallinity, is extended to permit the description of crystallization of a body initially cooled to a glassy state. The key assumption is that if at any time and temperature a crystallite is smaller than the critical size corresponding to that temperature, it will melt completely and can be ignored in any further calculations of the crystal distribution. This approach is used to predict the temperature of maximum crystallization rate for the matrix composition of lunar breccia 67975; results are shown to be in excellent agreement with experiment. Theoretical results obtained for anorthite indicate a barrier to nucleation in the range of 75 kT when the ratio of the undercooling to the liquidus temperature is 0.2. Measured nucleation barriers for the 67975 matrix composition are in the range of 42 to 45 kT.

  17. Film formation of CdSe quantum dot embedded phosphate glass on an FTO glass substrate

    NASA Astrophysics Data System (ADS)

    Han, Karam; Kim, Yoon Hwa; Im, Won Bin; Chung, Woon Jin

    2015-07-01

    A thick film with CdSe quantum dot (QD) embedded glass was formed on a fluorine-doped tin oxide (FTO) glass substrate. Phosphate glasses with different CdO and ZnSe concentrations were synthesized, and the heat treatment conditions were varied to determine the appropriate QD and film formation conditions. Phosphate glass with 1 mol. % CdO and 1.5 mol. % ZnSe showed controlled crystallization of CdSe QDs when they were heat treated at 550℃ for 1 hr. Absorption spectra and Raman spectroscopy identified the QD formation. Precursor glass was ground into powder and pasted onto FTO only and TiO2/FTO glass substrates via the screen printing method. Glass film embedded with QDs was successfully formed after sintering, thus demonstrating its potential for film applications. [Figure not available: see fulltext.

  18. Tuning polymer glass formation with additives and ions

    NASA Astrophysics Data System (ADS)

    Simmons, David

    2015-03-01

    A polymer's glass transition and associated dynamic and mechanical properties are among the most important factors determining its performance in engineering applications. For this reason, decades of research have aimed to establish methods of tuning polymers' glass formation behavior. Here I describe molecular simulations providing new insight into two approaches to altering a polymer's glass formation behavior: introduction of small-molecule diluents; and introduction of charged moieties to form an ionomer. In the first case, we explore how diluent molecular properties control modifications to the host polymer's glass transition and mechanical response. Results indicate that diluents can induce a rich array of effects, necessitating development of an expanded classification beyond the usual plasticizer/antiplasticizer dichotomy. In the second case, simulations indicate that ionomer glass formation is indistinguishable from that in polymer nanocomposites, in contrast to the longstanding assumption that covalent grafting of chains to ionic aggregates in these systems leads to a qualitatively distinct effect. Taken together, these results provide new guidance towards the rational understanding and control of polymer glass-formation in a range of materials. In collaboration with Jayachandra Hari Mangalara and Dihui Ruan, The University of Akron. This material is based in part on work supported by the W.M. Keck Foundation.

  19. Substrate effects on glass formation in simple monatomic supercooled liquids

    NASA Astrophysics Data System (ADS)

    Hoang, Vo Van; Thoa, Dao Kim; Odagaki, Takashi; Qui, Le Ngoc

    2015-02-01

    Glass formation in simple monatomic supercooled liquids on substrate is studied via molecular dynamics simulations. We find that glass formation in thin films on substrate exhibits a 'heterogeneous' behavior, i.e. solidlike atoms initiate/enhance simultaneously in the near substrate region and in the interior of the system, then solidlike domain grows outward to the free surface. Substrate causes strong layering of the near substrate region of liquid and glass. Layering is enhanced with decreasing temperature and layering region exhibits a glassy behavior instead of crystalline one. We find that structure and dynamics of liquid and glass in the near substrate region is different from those of the remaining part of thin films. This means that thin films formed on substrate can be divided into three distinct parts: near substrate region, interior and free surface region. We find a significant amount of liquidlike atoms even at T

  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. Potassium Chloride Nanowire Formation Inside a Microchannel Glass Array

    SciTech Connect

    Zhang, Daqing; Moore, Sam; Wei, Jiang; Alkhateeb, Abudullah I.; Gangadean, Dev; Mahmood, Hasan; Lantrips, Justin; McIlroy, David N.; LaLonde, Aaron D.; Norton, M G.; Young, James S.; Wang, Chong M.

    2005-06-27

    The synthesis of KCl nanowires has been achieved by atomic layer deposition inside high aspect ratio channels of microchannel glass. The average diameter of the KCl nanowires is 250 nm, with a minimum observed diameter of 50 nm, and lengths up to 5 {micro}m. The Cl precursor was TaCl5, while the source of K was determined to be impurities in the microchannel glass substrate. The process for KCl nanowire formation is a three-step chemical process that simultaneously etches K from the substrate concomitant with the formation of chlorine gas. It is postulated that the curvature of the channels may influence the diameters of the KCl nanowires.

  5. The descent into glass formation in polymer fluids.

    PubMed

    Freed, Karl F

    2011-03-15

    Glassy materials have been fundamental to technology since the dawn of civilization and remain so to this day: novel glassy systems are currently being developed for applications in energy storage, electronics, food, drugs, and more. Glass-forming fluids exhibit a universal set of transitions beginning at temperatures often in excess of twice the glass transition temperature T(g) and extending down to T(g), below which relaxation becomes so slow that systems no longer equilibrate on experimental time scales. Despite the technological importance of glasses, no prior theory explains this universal behavior nor describes the huge variations in the properties of glass-forming fluids that result from differences in molecular structure. Not surprisingly, the glass transition is currently regarded by many as the deepest unsolved problem in solid state theory. In this Account, we describe our recently developed theory of glass formation in polymer fluids. Our theory explains the origin of four universal characteristic temperatures of glass formation and their dependence on monomer-monomer van der Waals energies, conformational energies, and pressure and, perhaps most importantly, on molecular details, such as monomer structure, molecular weight, size of side groups, and so forth. The theory also provides a molecular explanation for fragility, a parameter that quantifies the rate of change with temperature of the viscosity and other dynamic mechanical properties at T(g). The fragility reflects the fluid's thermal sensitivity and determines the manner in which glass-formers can be processed, such as by extrusion, casting, or inkjet spotting. Specifically, the theory describes the change in thermodynamic properties and fragility of polymer glasses with variations in the monomer structure, the rigidity of the backbone and side groups, the cohesive energy, and so forth. The dependence of the structural relaxation time at lower temperatures emerges from the theory as the Vogel

  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 kinetics of lunar glass formation, revisited

    NASA Technical Reports Server (NTRS)

    Klein, L. C.; Uhlmann, D. R.

    1976-01-01

    The nucleation frequency of Lunar Composition 70019, a lithified soil breccia from the center of a small crater in the Taurus-Littrow Valley, is determined using a relation that describes nucleation throughout the volume of a liquid together with measurements of the time required at temperatures of 780 to 930 C to obtain sensibly crystalline bodies. Curves indicating the time required at a given temperature to reach a particular fraction crystallized are shown to have the general form predicted by kinetic analysis. Nucleation frequencies are evaluated by applying such analysis to a curve representing the transition between glassy material and material with a sensible degree of crystallinity. The results obtained are found to be in excellent agreement with the values expected from the classical theory of homogeneous nucleation, indicating that such nucleation represents the dominant contribution to crystal formation, at least over the range of undercoolings covered (250 to 400 C).

  8. 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

  9. Glass formation, chemical properties and surface analysis of Cu-based bulk metallic glasses.

    PubMed

    Qin, Chunling; Zhao, Weimin; Inoue, Akihisa

    2011-01-01

    This paper reviews the influence of alloying elements Mo, Nb, Ta and Ni on glass formation and corrosion resistance of Cu-based bulk metallic glasses (BMGs). In order to obtain basic knowledge for application to the industry, corrosion resistance of the Cu-Hf-Ti-(Mo, Nb, Ta, Ni) and Cu-Zr-Ag-Al-(Nb) bulk glassy alloy systems in various solutions are reported in this work. Moreover, X-ray photoelectron spectroscopy (XPS) analysis is performed to clarify the surface-related chemical characteristics of the alloy before and after immersion in the solutions; this has lead to a better understanding of the correlation between the surface composition and the corrosion resistance.

  10. Transition from Orbital Liquid to Jahn-Teller Insulator in Orthorhombic Perovskites RTiO3

    NASA Astrophysics Data System (ADS)

    Cheng, J.-G.; Sui, Y.; Zhou, J.-S.; Goodenough, J. B.; Su, W. H.

    2008-08-01

    Following the same strategy used for RVO3, thermal conductivity measurements have been made on a series of single-crystal perovskites RTiO3 (R=La,Nd,…,Yb). Results reveal explicitly a transition from an orbital liquid to an orbitally ordered phase at a magnetic transition temperature, which is common for both the antiferromagnetic and ferromagnetic phases in the phase diagram of RTiO3. This spin/orbital transition is consistent with the mode softening at TN in antiferromagnetic LaTiO3 and is supported by an anomalous critical behavior at Tc in ferromagnetic YTiO3.

  11. Time-dependent pseudo Jahn-Teller effect: Phonon-mediated long-time nonadiabatic relaxation

    SciTech Connect

    Vaikjärv, Taavi Hizhnyakov, Vladimir

    2014-02-14

    Our system under theoretical consideration is an impurity center in a solid. We are considering the time evolution of the center in a quasi-degenerate electronic state. Strict quantum mechanical treatment of non-adiabadicity of the state is used. The phonon continuum is taken into account in addition to the vibration responsible for the main vibronic interaction. To describe the dynamics of the excited state a master equation has been used. The theoretical considerations are illustrated by the calculations of the long-time evolution of vibrations of the center, influenced by the emission of phonons to the bulk.

  12. Jahn-Teller-induced femtosecond electronic depolarization dynamics of the nitrogen-vacancy defect in diamond

    PubMed Central

    Ulbricht, Ronald; Dong, Shuo; Chang, I-Ya; Mariserla, Bala Murali Krishna; Dani, Keshav M.; Hyeon-Deuk, Kim; Loh, Zhi-Heng

    2016-01-01

    Single-photon emission from the nitrogen-vacancy defect in diamond constitutes one of its many proposed applications. Owing to its doubly degenerate 3E electronic excited state, photons from this defect can be emitted by two optical transitions with perpendicular polarization. Previous measurements have indicated that orbital-selective photoexcitation does not, however, yield photoluminescence with well-defined polarizations, thus hinting at orbital-averaging dynamics even at cryogenic temperatures. Here we employ femtosecond polarization anisotropy spectroscopy to investigate the ultrafast electronic dynamics of the 3E state. We observe subpicosecond electronic dephasing dynamics even at cryogenic temperatures, up to five orders of magnitude faster than dephasing rates suggested by previous frequency- and time-domain measurements. Ab initio molecular dynamics simulations assign the ultrafast depolarization dynamics to nonadiabatic transitions and phonon-induced electronic dephasing between the two components of the 3E state. Our results provide an explanation for the ultrafast orbital averaging that exists even at cryogenic temperatures. PMID:27848938

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Universal non-Landau, self-organized, lattice disordering percolative dopant network sub-T(c) phase transition in ceramic superconductors.

    PubMed

    Phillips, J C

    2009-09-15

    Ceramic superconductors (cuprates, pnictides, etc.) exhibit universal features in both T(c)(max) and in their planar lattice disordering measured by EXAFS, as reflected by three phase transitions. The two highest temperature transitions are known to be associated with formation of Jahn-Teller pseudogaps and superconductive gaps, with corresponding Landau order parameters, but no new gap is associated with the third transition below T(c), and its origin is mysterious. It is argued that the third subT(c) transition is a dopant glass transition, which is remarkably similar to topological transitions previously observed in chalcogenide and oxide alloy network glasses (like window glass).

  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. Investigation of the local structure of Cu2+ ions doped in alkali lead tetraborate glasses by their electron paramagnetic resonance and optical spectra

    NASA Astrophysics Data System (ADS)

    Wu, Ying; Chen, Zhi

    2014-06-01

    The local structure of the Cu2+ centers in alkali lead tetraborate glasses was theoretically studied based on the optical spectra data and high-order perturbation formulas of the spin Hamiltonian parameters (electron paramagnetic resonance g factors g∥, g⊥ and hyperfine structure constants A∥, A⊥) for a 3d9 ion in a tetragonally elongated octahedron. In these formulas, the relative axial elongation of the ligand O2- octahedron around the Cu2+ due to the Jahn-Teller effect is taken into account by considering the contributions to the g factors from the tetragonal distortion which is characterized by the tetragonal crystal-field parameters Ds and Dt. From the calculations, the ligand O2- octahedral around Cu2+ is determined to suffer about 19.2% relative elongation along the C4 axis of the alkali lead tetraborate glass system, and a negative sign for A∥ and a positive sign for A⊥ for these Cu2+ centers are suggested in the discussion.

  3. Glass formation and Raman spectra of CaO-SiO2 glasses towards the orthosilicate limit

    NASA Astrophysics Data System (ADS)

    Retsinas, A.; Kalampounias, A. G.; Papatheodorou, G. N.

    2016-12-01

    A series of silicate glasses formed in the binary system (1-X)CaO-XSiO2with silica mole fractions X ranging from 0.61to 0.38have been prepared using container-less aerodynamic levitation techniques and CO2-laser heating. Glasses with X<0.45were prepared for the first time but, no glass formation was possible at compositions X<0.38. Ambient temperature polarized and depolarized Raman spectra were measured for all these glasses. Qi-speciation analysis of the isotropic Raman spectra shows that near X∼0.38the predominant structures present are the SiO44- tetrahedra and the single bridged Q1species. Oxygen bridging was present at all compositions studied while at X<0.45 small amounts of free oxygen anions was present. The data are compared with the resent NMR measurements obtained with the same glass samples used in the present study. Stokes and anti-Stokes Raman spectra were measured in low frequencies revealing the Boson peak (BP) at ∼50 and ∼70 cm-1 for the corresponding polarized and depolarized configurations. On the Stokes side the BP frequencies exhibit a fictional shift due to contributions from the low frequency vibrational modes of the glass.

  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

    2013-08-09

    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.

  9. Glass formation and crystallization of high lead content PbO-B2O3 compositions

    NASA Technical Reports Server (NTRS)

    Weinberg, Michael C.; Smith, Gary L.; Neilson, George F.

    1986-01-01

    The glass-forming and undercooling ability of PbO-B2O3 melts in the 2PbO.B2O3 to 4PbO.B2O3 composition range were studied. The glass formation propensities were investigated as a function of cooling rate and sample mass. A qualitative investigation of the crystallization process(es) preventing glass formation was made, and it was concluded that under normal circumstances heterogeneous nucleation was the common occurrence. Hence, it was concluded that such compositions are prime candidates for containerless experiments aboard the Space Shuttle.

  10. 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.

  11. Formation of nanostructured metallic glass thin films upon sputtering.

    PubMed

    Ketov, Sergey V; Joksimovic, Rastko; Xie, Guoqiang; Trifonov, Artem; Kurihara, Kazue; Louzguine-Luzgin, Dmitri V

    2017-01-01

    Morphology evolution of the multicomponent metallic glass film obtained by radio frequency (RF) magnetron sputtering was investigated in the present work. Two modes of metallic glass sputtering were distinguished: smooth film mode and clustered film mode. The sputtering parameters, which have the most influence on the sputtering modes, were determined. As a result, amorphous Ni-Nb thin films with a smooth surface and nanoglassy structure were deposited on silica float glass and Si substrates. The phase composition of the target appeared to have a significant influence on the chemical composition of the deposited amorphous thin film. The differences in charge transport and nanomechanical properties between the smooth and nanoglassy Ni-Nb film were also determined.

  12. Computation assisted design of favored composition for ternary Mg-Cu-Y metallic glass formation.

    PubMed

    Wang, Q; Li, J H; Liu, B X

    2015-06-14

    With the aid of ab initio calculations, a realistic interatomic potential was constructed for the Mg-Cu-Y ternary system under the proposed formalism of smoothed and long-range second-moment approximation of tight-binding. Taking the potential as the starting base, an atomistic computation/simulation route was developed for designing favored and optimized compositions for Mg-Cu-Y metallic glass formation. Simulations revealed that the physical origin of metallic glass formation is the collapse of crystalline lattice when solute concentration exceeds a critical value, thus leading to predict a hexagonal region in the Mg-Cu-Y composition triangle, within which metallic glass formation is energetically favored. It is proposed that the hexagonal region can be defined as the intrinsic glass formation region, or quantitative glass formation ability of the system. Inside the hexagonal region, the driving force for formation of each specific glassy alloy was further calculated and correlated with its forming ability in practice. Calculations pinpointed the optimized stoichiometry in the Mg-Cu-Y system to be Mg64Cu16Y20, at which the formation driving force reaches its maximum, suggesting that metallic glasses designed to have compositions around Mg64Cu16Y20 are most stable or easiest to obtain. The predictions derived directly from the atomistic simulations are supported by experimental observations reported so far in the literature. Furthermore, Honeycutt-Anderson analysis indicated that pentagonal bipyramids (although not aggregating to form icosahedra) dominate in the local structure of the Mg-Cu-Y metallic glasses. A microscopic picture of the medium-range packing can then be described as an extended network of the pentagonal bipyramids, entangled with the fourfold and sixfold disclination lines, jointly fulfilling the space of the metallic glasses.

  13. 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.

  14. 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.

  15. 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.

  16. Thermal dehydration of magnesium acetate tetrahydrate: formation and in situ crystallization of anhydrous glass.

    PubMed

    Koga, Nobuyoshi; Suzuki, Yasumichi; Tatsuoka, Tomoyuki

    2012-12-13

    The kinetics and mechanism of the thermal dehydration of magnesium acetate tetrahydrate were investigated as a typical example of the glass formation process via the thermal decomposition of solids. Formation of an intermediate fluid phase was identified as the characteristic phenomenon responsible for the formation of anhydrous glass. Thermal dehydration from the surface fluid layer regulates the zero-order-like rate behavior of the mass-loss process with an apparent activation energy E(a) ≈ 70-80 kJ mol(-1). Because of variations in the mechanism of release of the water vapor with changes in the reaction temperature range, the mass-loss behavior is largely dependent on the particle size of the sample and heating conditions. The formation of hollow anhydrous glass is the novel finding of the present study. The mechanism of formation is discussed in terms of complementary interpretations of the morphological changes and kinetic behavior of the thermal dehydration. On further heating, the as-produced anhydrous glass exhibits a glass transition phenomenon at approximately 470 K with an E(a) ≈ 550-560 kJ mol(-1), and subsequently crystallizes via the three-dimensional growth of nuclei controlled by diffusion. The crystallization process is characterized by an E(a) ≈ 280 kJ mol(-1) and an enthalpy change ΔH = -13.3 kJ mol(-1), resulting in the formation of smaller, rounded particles of crystalline anhydrate.

  17. Does fragility of glass formation determine the strength of Tg-nanoconfinement effects?

    NASA Astrophysics Data System (ADS)

    Mangalara, Jayachandra Hari; Marvin, Michael D.; Wiener, Nicholas R.; Mackura, Mark E.; Simmons, David S.

    2017-03-01

    Nanoscale confinement has been shown to alter the glass transition and associated mechanical and transport properties of glass-forming materials. Inspired by expected interrelations between nanoconfinement effects, cooperative dynamics in supercooled liquids, and the "fragility" (or temperature-abruptness) of the glass transition, it is commonly expected that nanoconfinement effects on Tg should be more pronounced for more fragile glass formers. Here we employ molecular dynamics simulations of glass formation in the bulk and under nanoconfinement of model polymers in which we systematically tune fragility by several routes. Results indicate that a correlation between fragility and the strength of nanoconfinement effects is weak to modest at best when considering all systems but can appear to be stronger when considering a subset of systems. This outcome is consistent with a reanalysis of the Adam-Gibbs theory of glass formation indicating that fragility does not necessarily track in a universal way with the scale of cooperative motion in glass-forming liquids. Finally, we find that factors such as composition gradients or variability in measurement sensitivity to different parts of the dynamic gradient have the potential to significantly confound efforts to identify trends in Tg-nanoconfinement effects with variables such as fragility, emphasizing the importance of employing diverse data sets and multiple metrologies in the study of this problem.

  18. Probing Toluene and Ethylbenzene Stable Glass Formation Using Inert Gas Permeation.

    PubMed

    Smith, R Scott; May, R Alan; Kay, Bruce D

    2015-09-17

    Inert gas permeation is used to investigate the formation of stable glasses of toluene and ethylbenzene. The effect of deposition temperature (T(dep)) 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 T(dep) = 0.92 T(g), although glasses with a kinetic stability within 50% of the most stable glass were found with deposition temperatures from 0.85 to 0.95 T(g). Similar results were found for ethylbenzene, which formed its most stable glass at 0.91 T(g) and formed stable glasses from 0.81 to 0.96 T(g). 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.

  19. Glass formation and the third harmonic generation of Cu2Se-GeSe2-As2Se3 glasses

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    We have performed the investigation of the nonlinear optical properties namely the third harmonic generation (THG) of the glass-formation region in the Cu2Se-GeSe2-As2Se3 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 Cu2Se 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.

  20. Glass formation and structure of calcium antimony phosphate glasses and those doped with tellurium oxide

    NASA Astrophysics Data System (ADS)

    Li, Jun; Zhang, Yin; Nian, Shangjiu; Wu, Zhenning; Cao, Weijing; Zhou, Nianying; Wang, Danian

    2017-03-01

    An approximate glass-forming region in the P2O5-Sb2O3-CaO ternary system was determined. The properties and structure of two compositional series of (A) (75- x)P2O5- xSb2O3-25CaO ( x = 20, 25, 30, 35 mol%) and (B) 45P2O5-30Sb2O3-(25- x)CaO- xTeO2 ( x = 5, 10, 15, 20 mol%) were studied systematically. Thermal properties were investigated by means of differential scanning calorimetry (DSC). The densities of all samples were measured by Archimedes' method using distilled water as the immersion liquid. The water durability of the glasses was described by their dissolution rate (DR) in the distilled water at 90 °C for some time periods. Density, thermal stability and water durability were improved with the addition of Sb2O3 and TeO2. Structural studies were carried out by X-ray diffraction (XRD), infrared spectroscopy and Raman spectroscopy. The phosphate chain depolymerization occurred with the increase of Sb2O3 and the Q2 structural units transformed to the Q1 and Q0 structural units with the addition of TeO2.

  1. 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.

  2. Formation of periodic structures on glass with laser irradiation

    NASA Astrophysics Data System (ADS)

    Peng, Ying Zi; An, Cheng Wu; Wu, Dong Jiang; Hong, Ming Hui; Lu, Yong Feng; Chong, Tow Chong

    2003-07-01

    Regular and tidy periodic structures hae been directly induced on glasses using a CW CO2 laser beam with linear polarization. It is experimentally shown that precise periodic structures with the period of several microns can be formed by means of well-set laser parameters. The orientation of the periodic structures formed is the same as that of the laser polarization no matter what the scanning direction is. The occurrence of periodic structures is very sensitive to laser power level and scanning velocity. To obtain appropriate periodic patterns, a combined condition of laser energy and scanning velocity must be satisfied. The period, width and height of the structures are dependent on processing parameters. An interesting phenomenon is that the period decreases with increasing scanning velocity. Permanent relieves with periods, widths and heights varied with the laser parameters are also studied.

  3. 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.

  4. 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).

  5. Fluoride-containing bioactive glasses: effect of glass design and structure on degradation, pH and apatite formation in simulated body fluid.

    PubMed

    Brauer, Delia S; Karpukhina, Natalia; O'Donnell, Matthew D; Law, Robert V; Hill, Robert G

    2010-08-01

    Bioactive glasses are able to bond to bone through formation of carbonated hydroxyapatite in body fluids, and fluoride-releasing bioactive glasses are of interest for both orthopaedic and, in particular, dental applications for caries inhibition. Melt-derived glasses in the system SiO(2)-P(2)O(5)-CaO-Na(2)O with increasing amounts of CaF(2) were prepared by keeping network connectivity and the ratio of all other components constant. pH change, ion release and apatite formation during immersion of glass powder in simulated body fluid at 37 degrees C over up to 2 weeks were investigated. Crystal phases formed in SBF were characterized using infrared spectroscopy, X-ray diffraction with Rietveld analysis and solid-state nuclear magnetic resonance spectroscopy ((19)F and (31)P MAS-NMR). Results show that incorporation of fluoride resulted in a reduced pH rise in aqueous solutions compared to fluoride-free glasses and in formation of fluorapatite (FAp), which is more chemically stable than hydroxyapatite or carbonated hydroxyapatite and therefore is of interest for dental applications. However, for increasing fluoride content in the glass, fluorite (CaF(2)) was formed at the expense of FAp. Apatite formation could be favoured by increasing the phosphate content in the glass, as the release of additional phosphate into the SBF would affect supersaturation in the solution and possibly favour formation of apatite.

  6. 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).

  7. 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.

  8. 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.

  9. 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.

  10. Effect of calcium phosphate glass on bone formation in calvarial defects of Sprague-Dawley rats.

    PubMed

    Moon, Hyun-Ju; Kim, Kyoung-Nam; Kim, Kwang-Mahn; Choi, Seong-Ho; Kim, Chong-Kwan; Kim, Kee-Deog; LeGeros, Racquel Z; Lee, Yong-Keun

    2006-09-01

    The purpose of this study was to investigate the bone regenerative effect of calcium phosphate glass in vivo. We prepared two different sizes of calcium phosphate glass powder using the system CaO-CaF2-P2O5-MgO-ZnO; the particle size of the powders were 400 microm and 40 microm. 8 mm calvarial critical-sized defects were created in 60 male Sprague-Dawley rats. The animals were divided into 3 groups of 20 animals each. Each defect was filled with a constant weight of 0.5 g calcium phosphate glass powder mixed with saline. As controls, the defect was left empty. The rats were sacrificed 2 or 8 weeks after postsurgery, and the results were evaluated using radiodensitometric and histological studies; they were also examined histomorphometrically. When the bigger powders with 400 microm particle were grafted, the defects were nearly completely filled with new-formed bone in a clean healing condition after 8 week. When smaller powders with 40 microm particle were transplanted, new bone formation was even lower than the control group due to a lot of inflammatory cell infiltration. It was concluded that the prepared calcium phosphate glass enhanced the new bone formation in the calvarial defect of Sprague-Dawley rats and it is expected to be a good potential materials for hard tissue regeneration. The particle size of the calcium phosphate was crucial; 400 microm particles promoted new bone formation, while 40 microm particles inhibited it because of severe inflammation.

  11. Thermochromic effects in a Jahn-Teller active CuCl(4-)6 layered hybrid system.

    PubMed

    Caretta, A; Miranti, R; Arkenbout, A H; Polyakov, A O; Meetsma, A; Hidayat, R; Tjia, M O; Palstra, T T M; van Loosdrecht, P H M

    2013-12-18

    The hybrid material copper (II) tetrachloro-bis(phenyl ethyl ammonium) (C6H5CH2CH2NH3)2CuCl4, or PEACuCl, has been investigated by temperature-dependent spectroscopic absorption experiments. The absorption bands observed in the near-infrared region (1.3-1.9 eV) generally exhibit redshifts with increasing temperature. The temperature-induced energy shifts of the spectral components are shown to be consistently related to temperature-induced Cu-Cl bond length changes. Additionally, the thermochromic color change is caused by a charge transfer band edge redshifting (in the visible region 2.0-2.8 eV) with increasing temperature. By comparison with similar Cu-based systems, it is suggested that this shift is caused by broadening and strengthening of the band.

  12. Thermochromic effects in a Jahn-Teller active {{CuCl}}_{6}^{4-} layered hybrid system

    NASA Astrophysics Data System (ADS)

    Caretta, A.; Miranti, R.; Arkenbout, A. H.; Polyakov, A. O.; Meetsma, A.; Hidayat, R.; Tjia, M. O.; Palstra, T. T. M.; van Loosdrecht, P. H. M.

    2013-12-01

    The hybrid material copper (II) tetrachloro-bis(phenyl ethyl ammonium) (C6H5CH2CH2NH3)2CuCl4, or PEACuCl, has been investigated by temperature-dependent spectroscopic absorption experiments. The absorption bands observed in the near-infrared region (1.3-1.9 eV) generally exhibit redshifts with increasing temperature. The temperature-induced energy shifts of the spectral components are shown to be consistently related to temperature-induced Cu-Cl bond length changes. Additionally, the thermochromic color change is caused by a charge transfer band edge redshifting (in the visible region 2.0-2.8 eV) with increasing temperature. By comparison with similar Cu-based systems, it is suggested that this shift is caused by broadening and strengthening of the band.

  13. Generalized entropy theory of glass-formation in fully flexible polymer melts

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    The generalized entropy theory (GET) offers many insights into how molecular parameters influence polymer glass-formation. Given the fact that chain rigidity often plays a critical role in understanding the glass-formation of polymer materials, the GET was originally developed based on models of semiflexible chains. Consequently, all previous calculations within the GET considered polymers with some degree of chain rigidity. Motivated by unexpected results from computer simulations of fully flexible polymer melts concerning the dependence of thermodynamic and dynamic properties on the cohesive interaction strength (ɛ), the present paper employs the GET to explore the influence of ɛ on glass-formation in models of polymer melts with a vanishing bending rigidity, i.e., fully flexible polymer melts. In accord with simulations, the GET for fully flexible polymer melts predicts that basic dimensionless thermodynamic properties (such as the reduced thermal expansion coefficient and isothermal compressibility) are universal functions of the temperature scaled by ɛ in the regime of low pressures. Similar scaling behavior is also found for the configurational entropy density in the GET for fully flexible polymer melts. Moreover, we find that the characteristic temperatures of glass-formation increase linearly with ɛ and that the fragility is independent of ɛ in fully flexible polymer melts, predictions that are again consistent with simulations of glass-forming polymer melts composed of fully flexible chains. Beyond an explanation of these general trends observed in simulations, the GET for fully flexible polymer melts predicts the presence of a positive residual configurational entropy at low temperatures, indicating a return to Arrhenius relaxation in the low temperature glassy state.

  14. 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.

  15. Bone formation in calvarial defects of Sprague-Dawley rats by transplantation of calcium phosphate glass.

    PubMed

    Moon, Hyun-Ju; Kim, Kyoung-Nam; Kim, Kwang-Mahn; Choi, Seong-Ho; Kim, Chong-Kwan; Kim, Kee-Deog; LeGeros, Racquel Z; Lee, Yong-Keun

    2005-09-01

    The purpose of this study was to investigate the bone-regenerative effect of calcium phosphate glass in vivo. We prepared amorphous calcium phosphate glass powder having a mean particle size of 400 microm in the system CaO-CaF2-P2O5-MgO-ZnO. Calvarial critical-sized defects (8 mm) were created in 60 male Sprague-Dawley rats. The animals were divided into an experimental group and control group of 30 animals each. Each defect was filled with a constant weight of 0.5 g calcium phosphate glass powder mixed with saline. As a control, the defect was left empty. The rats were sacrificed 2, 4, or 8 weeks postsurgery, and the results evaluated using radiodensitometric and histological studies; they were also examined histomorphometrically. When the calcium phosphate glass powders with 400-microm particles were grafted, the defects were nearly completely filled with new-formed bone in a clean healing condition after 8 weeks. It was observed that the prepared calcium phosphate glass enhanced new bone formation in the calvarial defect of Sprague-Dawley rats and could be expected to have potential for use as a hard tissue regeneration material.

  16. 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.

  17. A photo-oxidation mechanism for patterning and hologram formation in conjugated polymer/glass composites

    NASA Astrophysics Data System (ADS)

    Levi, Ofer; Perepelitsa, Galina; Davidov, Dan; Shalom, Shoshy; Benjamin, Iris; Neumann, Ronny; Agranat, Aharon J.; Avny, Yair

    2000-08-01

    Improved diffraction efficiency was observed in holograms stored in disordered conjugated polymer/glass composites. The conjugated polymers used were alkoxy substituted poly(phenylenevinylne) analogs and the glass matrices were zirconia-organosilica xerogels. Investigation of the mechanism of hologram formation revealed evidence of a photochromic process consisting of light induced photo-oxidation (bleaching) of the embedded conjugated polymer resulting in the formation of an absorption grating and a phase grating. Investigation of the hologram formation revealed that the process was oxygen dependent. Oxygen removal increases hologram formation time by more than an order of magnitude and halves the total hologram efficiency. The oxygen dependence was also highly correlated with photobleaching of the samples and beam interaction of the writing beams. The chemical transformations upon photobleaching were shown by infrared and Raman spectroscopy to involve chain scission and oxidation of the polymer at the vinylic position of the conjugated polymer. Film preparation of the composites was optimized showing a tenfold improvement in the holographic properties compared to our previous results. The optimized treatment method allows for a high, >20%, diffraction efficiency, η, to be obtained for the 2.5-μm-thick polymer/glass films. Light sensitivity was compared for several polymer/glass composites and was correlated to the absorption curves and holographic diffraction efficiency showing that the new composites and film preparation techniques are promising for holographic materials sensitive in the blue and ultraviolet spectral regions. A method of information fixing by preventing oxygen entry to the composite film resulted in a fourfold increase of the erasure time. These findings suggest that holograms can be fixed for a long term by nonoxygen permeable coating, applied after hologram formation.

  18. Evolutions of Molecular Oxygen Formation and Sodium Migration in Xe Ion Irradiated Borosilicate Glasses

    SciTech Connect

    Chen, Liang; Zhang, Duofei F.; Lv, Peng; Zhang, Jiandong; Du, Xing; Yuan, Wei; Nan, Shuai; Zhu, Zihua; Wang, Tieshan

    2016-07-23

    The modifications of a commercial borosilicate glass induced by Xe ion irradiation have been studied by Raman spectroscopy and ToF-SIMS depth profiling. A decrease in the average Si–O–Si angle, an increase in the population of three-membered rings and an increase of the glass polymerization are evidenced. The molecular oxygen appears in the irradiated glasses after the irradiation fluence reaches approximately 1015 ions/cm2. The O2 concentration decreaseswith the depth of irradiated glass at the ion fluence of 2 × 1016 ions/cm2. A sodiumdepleted layer at the surface and a depleted zone at around the penetration depth of 5 MeV Xe ions are observed. The thickness of the sodium depleted layer increases with the irradiation fluence. Moreover, comparing with previous results after electron and Ar ion irradiation, it can be concluded that the nuclear energy deposition can partially inhibit the formation of molecular oxygen and increase the threshold value of electron energy deposition for the molecular oxygen formation.

  19. 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.

  20. 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.

  1. 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

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

    DOEpatents

    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.

  3. Synthesis, Direct Formation under High Pressure, Structure, and Electronic Properties of LiNbO3-type Oxide PbZnO3.

    PubMed

    Mori, Daisuke; Tanaka, Kie; Saitoh, Hiroyuki; Kikegawa, Takumi; Inaguma, Yoshiyuki

    2015-12-07

    A novel LiNbO3-type (LN-type) lead zinc oxide, PbZnO3, was successfully synthesized under high pressure and temperature. Rietveld structure refinement using synchrotron powder X-ray diffraction (XRD) data demonstrated that LN-type PbZnO3 crystallized into a trigonal structure with a polar space group (R3c). The bond valence sum estimated from the interatomic distances indicated that the sample possesses a Pb(4+)Zn(2+)O3 valence state. Polarization could evolve as a result of the repulsion between constituent cations because PbZnO3 does not contain a stereochemical 6s(2) cation or a Jahn-Teller active d(0) cation. Distortion of ZnO6 octahedra resulting from cation shift is comparable with that of d(0) TiO6 in ZnTiO3 and MnTiO3 with LN-type oxides, which leads to stabilization of the polar structure. PbZnO3 exhibited metallic behavior and temperature-independent diamagnetic character. In situ XRD measurement revealed that the formation of LN-type PbZnO3 occurred directly without the formation of a perovskite phase, which is unusual among LN-type materials obtained by high-pressure synthesis.

  4. 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.

  5. Recent advances with generalized entropy theory of glass-formation in polymers

    NASA Astrophysics Data System (ADS)

    Freed, Karl

    The generalized entropy theory (GET) of glass-formation in polymers is a combination of the lattice cluster theory (LCT) for the configurational entropy density with the Adam-Gibbs (AG) theory for the structural relaxation time. A greatly simplified form of the GET (whose expression for the free energy is roughly double that of Flory-Huggins theory) accurately reproduces the four characteristic temperatures of glass-formation (the onset, crossover, glass transition, and Kauzmann temperatures) of the full GET to within 4K for a series of models of polymers composed of semi-flexible chains having the structure of poly(n-alpha olefins). The theory is now simple enough to be used in courses in polymer physics. Although the successes of the GET provide a strong validation of the final form of the AG theory provided the configurational entropy is used, the physical basis of the AG theory has remained an enigma. Hence, we have developed a new, more general, statistical mechanical derivation of AG theory that explains the previously perplexing observations that the string-like elementary excitations have the mass and temperature dependence of systems undergoing equilibrium self-assembly. This work is supported by the (U.S.) Department of Energy (DOE), Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award No. DE- SC0008631.

  6. 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)

  7. 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.

  8. 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.

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

    PubMed

    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.

  10. Induced rupture of vesicles adsorbed on glass by pore formation at the surface-bilayer interface.

    PubMed

    Kataoka-Hamai, Chiho; Yamazaki, Tomohiko

    2015-02-03

    Supported lipid bilayers (SLBs) are often formed by spontaneous vesicle rupture and fusion on a solid surface. A well-characterized rupture mechanism for isolated vesicles is pore nucleation and expansion in the solution-exposed nonadsorbed area. In contrast, pore formation in the adsorbed bilayer region has not been investigated to date. In this work, we studied the detailed mechanisms of asymmetric rupture of giant unilamellar vesicles (GUVs) adsorbed on glass using fluorescence microscopy. Asymmetric rupture is the pathway where a rupture pore forms in a GUV near the edge of the glass-bilayer interface with high curvature and then expansion of the pore yields a planar bilayer patch. We show that asymmetric rupture occasionally resulted in SLB patches bearing a defect pore. The defect formation probability depended on lipid composition, salt concentration, and pH. Approximately 40% of negatively charged GUVs under physiological conditions formed pore-containing SLB patches, while negatively charged GUVs at low salt concentration or pH 4.0 and positively charged GUVs exhibited a low probability of defect inclusion. The edge of the defect pore was either in contact with (on-edge) or away from (off-edge) the edge of the planar bilayer. On-edge pores were predominantly formed over off-edge defects. Pores initially formed in the glass-adsorbed region before rupture, most frequently in close contact with the edge of the adsorbed region. When a pore formed near the edge of the adsorbed area or when the edge of a pore reached that of the adsorbed area by pore expansion, asymmetric rupture was induced from the defect site. These induced rupture mechanisms yielded SLB patches with an on-edge pore. In contrast, off-edge pores were produced when defect pore generation and subsequent vesicle rupture were uncoupled. The current results demonstrate that pore formation in the surface-adsorbed region of GUVs is not a negligible event.

  11. Interplay between spinodal decomposition and glass formation in proteins exhibiting short-range attractions.

    PubMed

    Cardinaux, Frédéric; Gibaud, Thomas; Stradner, Anna; Schurtenberger, Peter

    2007-09-14

    We investigate the competition between spinodal decomposition and dynamical arrest using aqueous solutions of the globular protein lysozyme as a model system for colloids with short-range attractions. We show that quenches below a temperature Ta lead to gel formation as a result of a local arrest of the protein-dense phase during spinodal decomposition. The rheological properties of these gels allow us to use centrifugation experiments to determine the local densities of both phases and to precisely locate the gel boundary and the attractive glass line close to and within the unstable region of the phase diagram.

  12. CO2 Photoreduction by Formate Dehydrogenase and a Ru-Complex in a Nanoporous Glass Reactor.

    PubMed

    Noji, Tomoyasu; Jin, Tetsuro; Nango, Mamoru; Kamiya, Nobuo; Amao, Yutaka

    2017-02-01

    In this study, we demonstrated the conversion of CO2 to formic acid under ambient conditions in a photoreduction nanoporous reactor using a photosensitizer, methyl viologen (MV(2+)), and formate dehydrogenase (FDH). The overall efficiency of this reactor was 14 times higher than that of the equivalent solution. The accumulation rate of formic acid in the nanopores of 50 nm is 83 times faster than that in the equivalent solution. Thus, this CO2 photoreduction nanoporous glass reactor will be useful as an artificial photosynthesis system that converts CO2 to fuel.

  13. Alkylated glass partition allows formation of solvent-free lipid bilayer by Montal-Mueller technique.

    PubMed

    Batishchev, Oleg V; Indenbom, Andrey V

    2008-11-01

    Formation of bilayer lipid membrane (BLM) by Montal-Mueller technique across a small aperture in a partition film traditionally requires coating of the aperture with a hydrophobic substance, often just an organic solvent. However, we demonstrate here that the most effective coating is not strictly hydrophobic but rather provides water/oil repellent properties. BLM were formed from diphytanoylphosphatidylcholine (DPhPC) on small 0.1-0.8 mm apertures made in specially prepared alkylated glass coverslips. The coverslips were either fluorosiliconized by 3,3,3-Trifluoropropyl-trimethoxysilane, which reduces adsorption of DPhPC in addition to creation of hydrophobic surface, or silanized, which promote adsorption of DPhPC. At fluorosiliconized surfaces stable BLM were formed. Specific capacitance of these BLM was 0.86 microF/cm(2)+/-5%, while their lateral tension was estimated as 4.3+/-0.4 mN/m. BLM were stable for hours under moderate voltage applied. At silanized surfaces stable BLM were formed only in acidic medium (3 glass can be robustly used for formation of model lipid membranes under physiological conditions.

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

    PubMed

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

    2016-09-28

    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 Zn(2+) enhance the disproportionation of metaborate to polyborate and pyroborate units. Pb(2+) and Bi(3+) 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

  15. 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

  16. High-throughput Exploration of Glass Formation via Laser Deposition and the Study of Heterogeneous Microstructure in a Bulk Metallic Glass Alloy

    NASA Astrophysics Data System (ADS)

    Tsai, Peter T.

    Bulk metallic glasses are a relatively novel class of engineering alloys characterized by a "disordered" atomic structure devoid of long-range translational symmetry. Compared to crystalline alloys, the confluence of metallic bonding and amorphous structure imbues bulk metallic glasses with a unique set of properties that makes them particularly attractive for a wide variety of structural applications. Such properties include exceptional yield strengths, high elastic resilience, resistance to corrosion, and in particular, the unparalleled ability among metals to be thermoplastically formed across a wide range of length scales when heated above the glass transition temperature. Formation of metallic glass from a molten liquid depends on whether cooling is sufficiently rapid to bypass crystallization and vitrify into an amorphous solid; for a given alloy composition, the ease with which full vitrification can occur upon cooling from the liquid state is termed the alloy's "glass forming ability". Unfortunately, relatively few excellent glass formers have been reported in the vast, multicomponent composition space in which they reside. The apparent slowness of progress may be attributed largely to the inefficiency of the one-at-a-time experimental approach to discovery and design. In this thesis work, a high-throughput combinatorial methodology was developed to expedite the discovery process of new bulk metallic glasses. Laser deposition was used to fabricate continuously-graded composition libraries of Cu-Zr and Cu-Zr-Ti alloys. By processing the libraries with a range of laser heat input, the best glass formers in each alloy system could be efficiently and systematically deduced. Furthermore, instrumented nanoindentation performed on the libraries enabled rapid evaluation of mechanical property trends. Despite boasting high strengths, monolithic bulk metallic glasses generally suffer from an intrinsic lack of damage tolerance compared to other high performance alloys

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. Non-textured laser modification of silica glass surface: Wettability control and flow channel formation

    NASA Astrophysics Data System (ADS)

    Aono, Yuko; Hirata, Atsushi; Tokura, Hitoshi

    2016-05-01

    Local wettability of silica glass surface is modified by infrared laser irradiation. The silica glass surface exhibits hydrophobic property in the presence of sbnd CF3 or sbnd (CH3)2 terminal functional groups, which are decomposed by thermal treatment, and degree of the decomposition depends on the applied heat. Laser irradiation can control the number of remaining functional groups according to the irradiation conditions; the contact angle of deionized water on the laser modified surfaces range from 100° to 40°. XPS analysis confirms that the variation in wettability corresponds to the number of remaining sbnd CF3 groups. The laser irradiation achieves surface modification without causing any cracks or damages to the surface, as observed by SEM and AFM; moreover, surface transparency to visible light and surface roughness remains unaffected. The proposed method is applied to plane flow channel systems. Dropped water spreads only on the hydrophilic and invisible line modified by the laser irradiation without formation of any grooves. This indicates that the modified line can act as a surface channel. Furthermore, self-transportation of liquid is also demonstrated on a channel with gradually-varied wettability along its length. A water droplet on a hydrophobic side is self-transported to a hydrophilic side due to contact-angle hysteresis force without any actuators or external forces.

  3. The processes of modified microareas formation in the bulk of porous glasses by laser radiation

    NASA Astrophysics Data System (ADS)

    Kostyuk, G. K.; Sergeev, M. M.; Yakovlev, E. B.

    2015-06-01

    The possibility of the formation of modified microareas (MAs) with changed optical properties in the bulk of porous glasses (PGs) with laser radiation is investigated. A laser module of continuous action with wavelength λ = 800 nm and power P = 120 mW was used as the source of radiation. The material used in the experiment was PG of 94.73 SiO2-4.97 B2O3-0.30 Na2O. A model that describes the processes taking place under laser radiation that lead to a modification of the glass is proposed. Our evaluation results based on experimental data are given. The results of an additional PG plate of the same composition impregnated with glycerol—a substance with a high degree of polarizability—during exposure experiments are also given. A fiber laser of continuous action with wavelength λ = 1070 nm and power P = 16.5 W was used as a source of radiation.

  4. Phase formation and mechanical properties of Cu-Zr-Ti bulk metallic glass composites

    NASA Astrophysics Data System (ADS)

    Kim, Byoung Jin; Yun, Young Su; Kim, Won Tae; Kim, Do Hyang

    2016-11-01

    The effect of the type of the crystalline phase and its volume fraction on the mechanical property of Cu50Zr50-xTix alloys (x = 0-10) bulk metallic glass composites has been investigated in this study. Up to 6 at% of Ti, B19' phase particles distributed in the glassy matrix, while at 8 and 10% of Ti, B2 phase particles are retained in the glass matrix due to suppression of the eutectoid transformation of B2 phase and by avoidance of martensitic transformation of B2 into B19'. The volume fraction of crystalline phase is strongly dependent on the cooling rate. The larger volume fraction of the crystalline phases results in the lower yield stress, the higher plastic strain, and the more pronounced work hardening behavior. At the crystalline volume fraction below 30%, the variation of the yield strength can be described by the rule of mixture model (ROM), while at the crystalline volume fraction higher than 50% by the load-bearing model (LBM). At the crystal fractions between 30 and 50%, there is a yield strength drop and a transition from the ROM to the LBM. This transition is due to the formation of the crystalline structural framework at higher crystal fraction.

  5. Formation of alkali-metal nanoparticles in alkali-silicate glasses under electron irradiation and thermal processing

    NASA Astrophysics Data System (ADS)

    Bochkareva, E. S.; Sidorov, A. I.; Ignat'ev, A. I.; Nikonorov, N. V.; Podsvirov, O. A.

    2017-02-01

    Experiments and numerical simulation show that the irradiation of alkali-containing glasses using electrons at an energy of 35 keV and the subsequent thermal processing at a temperature above the vitrification point lead to the formation of spherical metal (lithium, sodium, and potassium) nanoparticles with oxide sheaths that exhibit plasmon resonances in the visible spectral range. Glasses containing two alkali metals exhibit mutual effect of metals on the formation of nanoparticles with two compositions due to the difference of ion radii and mobilities of metal ions.

  6. Formation of cylindrical micro-lens array on fused silica glass surface using CO2 laser assisted reshaping technique

    NASA Astrophysics Data System (ADS)

    Choi, Hun-Kook; Ahsan, Md. Shamim; Yoo, Dongyoon; Sohn, Ik-Bu; Noh, Young-Chul; Kim, Jin-Tae; Jung, Deok; Kim, Jin-Hyeok; Kang, Ho-Min

    2015-12-01

    This paper demonstrates the laser assisted formation of plano-convex cylindrical and flat-top curved micro-lens array on fused silica glass surface. Initially, femtosecond laser pulses are irradiated on the sample glass to fabricate periodic linear micro-gratings on the glass surface. Afterwards, we reshape the micro-gratings by several times irradiation of a CO2 laser beam by focusing the laser beam on top of the micro-gratings. As a consequence, plano-convex cylindrical micro-lens array with a period varying from 20 to 40 μm are formed on fused silica glass surface. However, flat-top curved gratings' array is observed on the glass surface for a gratings' period of 50 μm. The fabricated micro-lenses show great consistency in size and shape throughout the sample area. Furthermore, we analyze the formation mechanism of micro-lens array on glass surface using the CO2 laser assisted reshaping technique. The proposed reshaping technique exhibits great potential for forming a large variety of micro-lens arrays on the surface of various transparent materials.

  7. 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.

  8. 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.

  9. 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.

  10. Yielding of glass under shear: A directed percolation transition precedes shear-band formation

    NASA Astrophysics Data System (ADS)

    Shrivastav, Gaurav Prakash; Chaudhuri, Pinaki; Horbach, Jürgen

    2016-10-01

    Under external mechanical loading, glassy materials, ranging from soft matter systems to metallic alloys, often respond via formation of inhomogeneous flow patterns, during yielding. These inhomogeneities can be precursors to catastrophic failure, implying that a better understanding of their underlying mechanisms could lead to the design of smarter materials. Here, extensive molecular dynamics simulations are used to reveal the emergence of heterogeneous dynamics in a binary Lennard-Jones glass, subjected to a constant strain rate. At a critical strain, this system exhibits for all considered strain rates a transition towards the formation of a percolating cluster of mobile regions. We give evidence that this transition belongs to the universality class of directed percolation. Only at low shear rates, the percolating cluster subsequently evolves into a transient (but long-lived) shear band with a diffusive growth of its width. Finally, the steady state with a homogeneous flow pattern is reached. In the steady state, percolation transitions also do occur constantly, albeit over smaller strain intervals, to maintain the stationary plastic flow in the system.

  11. 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.

  12. 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.

  13. Effects of halogen substitutions on the formation of copper colloids by hydrogen reduction in sodium borate glasses

    NASA Astrophysics Data System (ADS)

    Edson, Daniel Lee

    2002-01-01

    The substitution of small amounts of halogens (< 1 mol%) for oxygen in sodium borate glasses with 10 to 35 mol% soda that contain 0.1 or 0.2 wt% CuO dramatically influences the ligand environment around copper in these glasses and the formation of copper colloids during hydrogen treatment near Tg. The suppression of copper colloid formation in glasses that contain halogen ions has not previously been reported. The interaction of halogen ions and copper depends on the identity of the halogen ion, the ratio of the molar concentrations halogen to copper ions and the soda content of the glass. The heavier halogen ions, Cl, Br and I, preferentially associate with copper ions in the melt. Four bromine ions associate with each cupric ion, reducing it to the cuprous state. The reduction power of the ions increases in the order Cl- < Br- < I-. Cl, Br and I associate with cupric ions in combination with oxygen ions in the glass. These mixed anion complexes, which probably contain multiple halogen ions, give rise to intense charge transfer absorption bands in the UV-Vis spectra which cause a color change in the glass. The concentration of the mixed anion complexes is very small and depends on the ratio of halogen to copper. The reduction of cupric ions has been separated from the growth of copper colloids during hydrogen reduction through use of the ESR. The reduction of cupric ions by hydrogen is described by the tarnishing model. The presence of Cl, Br and I completely prevents the formation of copper colloids during hydrogen reduction near Tg. CuBr nanoparticles form in glasses with ratios of Br:Cu of 1:1 or 2:1. Support for the view that cuprous ions are the diffusing species in these glasses following hydrogen reduction is presented, with a requirement that hydrogen be present at the growing nuclei to further reduce the ion to the atomic state. Bonding between mobile cuprous ions and halogen ions is suggested to slow or prevent the formation of copper colloids and the

  14. Accelerated formation of sodium depletion layer on soda lime glass surface by corona discharge treatment in hydrogen atmosphere

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Keiga; Ikeda, Hiroshi; Sakai, Daisuke; Funatsu, Shiro; Uraji, Keiichiro; Yamamoto, Kiyoshi; Suzuki, Toshio; Harada, Kenji; Nishii, Junji

    2014-05-01

    Formation of a sodium depletion layer on a soda lime glass surface was accelerated efficiently using a corona discharge treatment in H2 atmosphere. One origin of such acceleration was the preferential generation of H+ with a larger mobility at an anode needle end with a lower applied voltage than that in air. The second origin was the applied voltage across the glass plate during the corona discharge treatment, which was estimated theoretically as 2.7 times higher than that in air. These two effects doubled the depletion layer thickness compared with that in air.

  15. 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.

  16. 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.

  17. Secondary caries formation in vitro around glass ionomer-lined amalgam and composite restorations.

    PubMed

    Dionysopoulos, P; Kotsanos, N; Papadogianis, Y

    1996-08-01

    The aim of this in vitro secondary caries study was to examine the glass-ionomer liner's effect on wall-lesion inhibition when a conventional and a light-cured glass ionomer liner was placed under amalgam and composite resin restorations. Class V preparations in extracted upper premolars were used and ten restorations were used for each of the following groups: (i) two layers of copal varnish and amalgam; (ii) conventional glass-ionomer and amalgam; (iii) light-cured glass-ionomer and amalgam; (iv) bonding agent and light-cured composite resin; (v) conventional glass-ionomer, bonding agent and light-cured composite resin; (vi) light-cured glass-ionomer, extended 0.3 mm short of the enamel margin bonding agent and light-cured composite resin; and (vii) light-cured glass-ionomer, extended 1 mm short of the enamel margin, bonding agent and light-cured composite resin. The teeth were thermocycled and artificial caries were created using an acid-gel. The results of this study showed that artificial recurrent caries can be reduced significantly (P < 0.05) with a glass-ionomer liner under amalgam restorations. The results also showed that when the light-cured glass-ionomer liner was placed 0.3 mm from the cavosurface margin under composite resin restoration, the artificial recurrent caries reduced significantly (P < 0.05).

  18. 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.

  19. 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.

  20. Electroless porous silicon formation applied to fabrication of boron-silica-glass cantilevers

    NASA Astrophysics Data System (ADS)

    Teva, J.; Davis, Z. J.; Hansen, O.

    2010-01-01

    This work describes the characterization and optimization of anisotropic formation of porous silicon in large volumes (0.5-1 mm3) of silicon by an electroless wet etching technique. The main goal is to use porous silicon as a sacrificial volume for bulk micromachining processes, especially in cases where etching of the full wafer thickness is needed. The porous silicon volume is formed by a metal-assisted etching in a wet chemical solution composed of hydrogen peroxide (30%), hydrofluoric acid (40%) and ethanol. This paper focuses on optimizing the etching conditions in terms of maximizing the etching rate and reproducibility of the etching. In addition to that, a study of the morphology of the pore that is obtained by this technique is presented. The results from the characterization of the process are applied to the fabrication of boron-silica-glass cantilevers that serve as a platform for bio-chemical sensors. The porous silicon volume is formed in an early step of the fabrication process, allowing easy handling of the wafer during all of the micromachining processes in the process flow. In the final process step, the porous silicon is quickly etched by immersing the wafer in a KOH solution.

  1. Biomimetic formation of apatite on the surface of porous gelatin/bioactive glass nanocomposite scaffolds

    NASA Astrophysics Data System (ADS)

    Mozafari, Masoud; Rabiee, Mohammad; Azami, Mahmoud; Maleknia, Saied

    2010-12-01

    There have been several attempts to combine bioactive glasses (BaGs) with biodegradable polymers to create a scaffold material with excellent biocompatibility, bioactivity, biodegradability and toughness. In the present study, the nanocomposite scaffolds with compositions based on gelatin (Gel) and BaG nanoparticles in the ternary SiO 2-CaO-P 2O 5 system were prepared. In vitro evaluations of the nanocomposite scaffolds were performed, and for investigating their bioactive capacity these scaffolds were soaked in a simulated body fluid (SBF) at different time intervals. The scaffolds showed significant enhancement in bioactivity within few days of immersion in SBF solution. The apatite formation at the surface of the nanocomposite samples confirmed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray powder diffraction (XRD) analyses. In vitro experiments with osteoblast cells indicated an appropriate penetration of the cells into the scaffold's pores, and also the continuous increase in cell aggregation on the bioactive scaffolds with increase in the incubation time demonstrated the ability of the scaffolds to support cell growth. The SEM observations revealed that the prepared scaffolds were porous with three dimensional (3D) and interconnected microstructure, pore size was 200-500 μm and the porosity was 72-86%. The nanocomposite scaffold made from Gel and BaG nanoparticles could be considered as a highly bioactive and potential bone tissue engineering implant.

  2. In vitro surface reaction layer formation and dissolution of calcium phosphate cement-bioactive glass composites.

    PubMed

    Liu, Changsheng; Chen, Chien-Wen; Ducheyne, Paul

    2008-09-01

    Composites of hydrated calcium phosphate cement (CPC) and bioactive glass (BG) containing Si were immersed in vitro to study the effect of chemical composition on surface reaction layer formation and dissolution/precipitation behavior. The solutions used were 0.05 M tris hydroxymethyl aminomethane/HCl (tris buffer), tris buffer supplemented with plasma electrolyte (TE) with pH 7.4 at 37 degrees C, and this solution complemented with 10% newborn bovine serum (TES). The post-immersion solutions were analyzed for changes in Ca, PO(4) and Si concentrations. The reacted surfaces were analyzed using Fourier transform infrared (FTIR), and scanning electron microscopy with energy dispersive x-ray analysis. The sample weight variations after immersion were also determined. The results showed that the composition of the bioactive composite CPCs greatly affected their behavior in solution and the formation of apatite bioactive surface reaction layers. After immersion in the TE solution, Ca ions were taken up by all samples during the entire immersion duration. Initially, the P ion concentration increased sharply, and then decreased. This reaction pattern reveals the formation of an amorphous calcium phosphate layer on the surface of these composite CPCs. FTIR revealed that the layer was, in fact, poorly crystallized Ca-deficient carbonate apatite. The thickness of the layer was 12-14 microm and it was composed of rod-like apatite with directional arrangement. For immersion in the TES solution, the Ca and Si ion concentrations showed a similar behavior to that in TE, but the release rate of Si ions was higher. FTIR revealed that after TES immersion, not only did the typical, poorly crystallized, Ca-deficient carbonated apatite form, as it did in TE, but also the serum proteins co-adsorbed on the surface and thereby affected the surface reaction layer formation. A thinner apatite layer was formed and was composed of a micro-porous layer comprising rounded particles in a glue

  3. Effects of minor Sn addition on the glass formation and properties of Fe-metalloid metallic glasses with high magnetization and high glass forming ability

    NASA Astrophysics Data System (ADS)

    Shi, Minjie; Liu, Zengqian; Zhang, Tao

    2015-03-01

    Effects of minor Sn addition on the glass-forming ability (GFA) as well as thermal, magnetic, and mechanical properties of Fe-P-C-B-Si bulk metallic glasses (BMGs) with compositions of Fe80-xSnxP9C8B2Si1 (x=0, 1, 2 and 3 at%) were investigated. The minor Sn substitution for Fe effectively enhances the GFA. The fully glassy rods can be produced up to 3 and 3.5 mm in diameter for the alloys with 1 and 2 at% Sn addition, respectively. Moreover, these Sn-containing BMGs exhibit good soft magnetic properties including high saturation magnetization (Ms) of 1.46-1.51 T, low coercivity (Hc) of 3.8-5.0 A/m and good mechanical properties, i.e., high fracture strength (σf) above 3.2 GPa and limited plastic strain (εp) above 0.4%. The combination of large GFA, good soft magnetic and mechanical properties as well as low cost makes the Fe-Sn-P-C-B-Si BMGs promising as soft magnetic materials for industrial applications.

  4. Rare earth dependent formation of PbF2 nanocrystals and its effect on the emission properties in oxyfluoride glasses

    NASA Astrophysics Data System (ADS)

    Kim, Kyoung Hoon; Choi, Yong Gyu; Im, Won Bin; Chung, Woon Jin

    2013-03-01

    Oxyfluoride glasses doped with rare earth ions (Dy3+, Er3+ or Ho3+) were fabricated, and their visible and near infrared emissions were evaluated before and after the formation of β-PbF2 nanocrystals. Upon heat treatment of the parent glass to precipitate β-PbF2 nanocrystals, both the intensity and lifetime of radiative emissions from the Dy3+ ion were improved conspicuously, whereas changes in the emissions from Er3+ and Ho3+ turned out to be relatively insignificant. In addition to the hypersensitive nature of some 4 f↔4 f transitions of Dy3+, its spatial distribution inside the heat-treated oxyfluoride samples is believed to be responsible for this interesting observation. Our finding thus exemplifies the chemical effects of rare earth ions on the formation of nanocrystals via heat treating oxyfluoride glasses. Various probes including X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy and Judd-Ofelt analysis were applied to elucidate the rare earth dependence of the fluoride nanocrystals within the oxyfluoride glasses.

  5. 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.

  6. Formation of cylindrical micro-lens array in fused silica glass using laser irradiations

    NASA Astrophysics Data System (ADS)

    Choi, Hun-Kook; Ahsan, Md. Shamim; Yoo, Dongyoon; Sohn, Ik-Bu; Noh, Young-Chul; Kim, Jin Tae; Jung, Deok; Kim, Jin Hyeok

    2013-12-01

    In this article, we report the development of plano-convex cylindrical micro-lens array on the surface of fused silica glass using laser processing technology. Initially, femtosecond laser pulses are irradiated on the target fused silica glass substrate to pattern periodic micro-grooves. Afterwards, laser beam from CO2 laser source is applied several times on the previously micro-patterned fused silica glass surface, the purpose of which is to polish the micro-patterned glass surface. As a consequence, periodic plano-convex cylindrical micro-lens array is evolved on the glass surface. The micro-lens array shows great consistency in size and shape throughout the sample area. We also investigate various optical properties of the micro-lenses evolved glass substrates including the diffraction pattern and diffraction efficiency of light. The glass sample comprising cylindrical micro-lens array can diffract light with moderate diffraction efficiency. We strongly believe that, it is possible to engineer cylindrical micro-lens array on the surface of a variety of transparent materials including glasses and polymers over a large area.

  7. 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

  8. 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.

  9. Durability of SRP Waste Glass - Effects of Pressure and Formation of Surface Layers

    SciTech Connect

    Wicks, G.G.

    2001-10-17

    This report discusses results of an assessment of pressure at anticipated storage temperature on the chemical durability of Savannah River Plant waste glass. Surface interactions were also examined and corrosion mechanisms discussed.

  10. Formation of void array inside transparent and absorptive glasses by femtosecond laser irradiation.

    PubMed

    Jang, Wooyoung; Kim, Daejin; Kim, Taehong; Moon, Ayoung; Lim, Ki-Soo; Lee, Myeongkyu; Sohn, Ik-Bu

    2012-06-01

    We demonstrate self-fabrication of void arrays in a fused silica transparent in the visible and a color-filter borosilicate glass strongly absorptive at 800 nm using tightly focused Ti-sapphire femtosecond laser pulses at 1 kHz without scanning. The period, the size, the number of voids, and the length of the aligned void structure were controlled by changing the laser pulse energy, and the position of the focal point inside two materials. The void arrays were observed by an optical microscope and also estimated by an optical diffraction experiment. The void size and period were smaller in the absorptive glass than in the transparent glass. The submicrometer-sized void was observed by a scanning electron microscope. The smaller and clearer void arrays were formed in the color filter than the fused silica glass. With increasing the laser focal depth, the void-array length increased in the fused silica and decreased in the color filter.

  11. Electron irradiation effect on bubble formation and growth in a sodium borosilicate glass

    SciTech Connect

    Chen, X.; Birtcher, R. C.; Donnelly, S. E.

    2000-02-08

    In this study, the authors studied simultaneous and intermittent electron irradiation effects on bubble growth in a simple sodium borosilicate glass during Xe ion implantation at 200 C. Simultaneous electron irradiation increases the average bubble size in the glass. This enhanced diffusion is also shown by the migration of Xe from bubbles into the matrix when the sample is irradiated by an electron beam after the Xe implantation.

  12. In-situ probing of metallic glass formation and crystallization upon heating and cooling via fast differential scanning calorimetry

    NASA Astrophysics Data System (ADS)

    Pogatscher, S.; Uggowitzer, P. J.; Löffler, J. F.

    2014-06-01

    The crystallization of small-scale Au-based metallic glass samples was investigated by fast differential scanning calorimetry. Rapid cooling and heating makes possible in-situ probing of glass formation from the supercooled liquid state or direct transition from the glassy state to the equilibrium liquid and, thereby, the determination of a critical cooling (Φc ˜ 600 Ks-1) and heating rate (Φh ˜ 6 × 103 Ks-1) for crystallization. Crystallization kinetics was studied in the whole supercooled liquid region by linear heating and isothermal calorimetry. We show that the temperature dependence of crystal growth is reflected in a "Kissinger plot" for Au49Ag5.5Pd2.3Cu26.9Si16.3 and compares well with a model for crystal growth in a glassy system. Linear heating and isothermal measurements after heating the glass show that its crystallization is always growth-controlled up to its temperature of melting. In contrast, for a low degree of direct undercooling from the equilibrium liquid isothermal crystallization is nucleation-controlled, whereas it is again growth-controlled at large undercooling. The overall crystallization behavior of the metallic glass is presented in a complete time-temperature-transformation map on cooling and, so far not accessible, on heating after various cooling procedures.

  13. Trace phase formation, crystallization kinetics and crystallographic evolution of a lithium disilicate glass probed by synchrotron XRD technique

    PubMed Central

    Huang, Saifang; Huang, Zhaohui; Gao, Wei; Cao, Peng

    2015-01-01

    X-ray diffraction technique using a laboratory radiation has generally shown limitation in detectability. In this work, we investigated the in situ high-temperature crystallization of a lithium disilicate glass-ceramic in the SiO2–Li2O–CaO–P2O5–ZrO2 system with the aid of synchrotron radiation. The formation of lithium metasilicate and other intermediate phases in trace amount was successfully observed by synchrotron X-ray diffraction (SXRD). The crystallization mechanism in this glass was thus intrinsically revised to be the co-nucleation of lithium metasilicate and disilicate, instead of the nucleation of lithium disilicate only. The phase content, crystallite size and crystallographic evolutions of Li2Si2O5 in the glass-ceramic as a function of annealing temperature were studied by performing Rietveld refinements. It is found that the growth of Li2Si2O5 is constrained by Li2SiO3 phase at 580–700°C. The relationship between the crystallographic evolution and phase transition was discussed, suggesting a common phenomenon of structural response of Li2Si2O5 along its c axis to other silicon-related phases during glass crystallization. PMID:25778878

  14. Effect of chain stiffness on the competition between crystallization and glass-formation in model unentangled polymers

    NASA Astrophysics Data System (ADS)

    Nguyen, Hong T.; Smith, Tyler B.; Hoy, Robert S.; Karayiannis, Nikos Ch.

    2015-10-01

    We map out the solid-state morphologies formed by model soft-pearl-necklace polymers as a function of chain stiffness, spanning the range from fully flexible to rodlike chains. The ratio of Kuhn length to bead diameter (lK/r0) increases monotonically with increasing bending stiffness kb and yields a one-parameter model that relates chain shape to bulk morphology. In the flexible limit, monomers occupy the sites of close-packed crystallites while chains retain random-walk-like order. In the rodlike limit, nematic chain ordering typical of lamellar precursors coexists with close-packing. At intermediate values of bending stiffness, the competition between random-walk-like and nematic chain ordering produces glass-formation; the range of kb over which this occurs increases with the thermal cooling rate | T ˙ | implemented in our molecular dynamics simulations. Finally, values of kb between the glass-forming and rodlike ranges produce complex ordered phases such as close-packed spirals. Our results should provide a useful initial step in a coarse-grained modeling approach to systematically determining the effect of chain stiffness on the crystallization-vs-glass-formation competition in both synthetic and colloidal polymers.

  15. Defect formation of gamma irradiated MoO3-doped borophosphate glasses

    NASA Astrophysics Data System (ADS)

    Abdelghany, A. M.; Ouis, M. A.; Azooz, M. A.; EllBatal, H. A.

    2013-10-01

    Borophosphate glasses of the basic composition (50P2O5, 30B2O3, 20Na2O mol%) containing different doping molybdenum oxide percents (0.16-0.98) were prepared by melting and annealing method. Infrared and UV-visible absorption spectroscopic measurements before and after gamma irradiation were carried out. The base undoped borophosphate glass reveals strong UV absorption bands but with no visible bands and these UV bands are related to unavoidable trace iron impurities contaminated within the raw materials used for the preparation of this glass. The introduction of MoO3 (in doping ratio) into this glass produces an additional UV band and a broad visible band and their intensities increase with the MoO3 content. These additional bands are related to both Mo6+ and Mo5+ ions. The base undoped borophosphate glass shows retardation effect towards gamma irradiation. Gamma irradiation produces marked changes in the UV-visible spectra of Mosbnd O3-doped glasses. Such changes can be related to the production of induced defects from photochemical reactions and the generation of positive holes. Infrared absorption spectrum of the undoped borophosphate glass reveals complex vibrational bands due to the presence of both phosphate groups beside borate groups with triangular and tetrahedrally coordinated units. The introduction of MoO3 causes some limited variations in the FTIR spectra. Gamma irradiation produces minor changes in the intensities of some IR bands. Such changes are related to the changes in the bond angles and/or bond lengths of few structural groups upon irradiation while the main structural groups remain unchanged in their number and position.

  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.

  17. Formation of metallic nanoislands in the process of electron irradiation of a thin gold film on glass

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

    It has been demonstrated experimentally that the local irradiation of a thin gold film on glass with electrons with an energy of 5 keV led to an increase in the thickness of the irradiated area. When the film was subjected to local irradiation with electrons with an energy of 25 keV, the irradiated region became thinner and a gold ring was formed along the perimeter of this region. At high densities of the electron current, thickened regions of the film assumed the shape of fractal nanostructures. The observed effects were induced by the formation of a negative charge region on the surface of glass (or in the bulk of it) and the migration of positive gold ions into this region.

  18. NEPHELINE FORMATION POTENTIAL IN SLUDGE BATCH 4 AND ITS IMPACT ON DURABILITY: SELECTING GLASSES FOR A PHASE 3 STUDY

    SciTech Connect

    Fox, K

    2006-01-27

    Savannah River National Laboratory's frit development effort for SB4 is being driven by the most current CBU option for this sludge, referred to as Case 15C Blend 1. Candidate frits have been identified for this option via a paper study approach developed by Peeler and Edwards with the intent of down-selecting to a set of key frits whose operating windows (i.e., WL intervals that meet PCCS MAR criteria) are robust to and/or selectively optimal for this sludge option. The primary frits that appear attractive on paper (i.e., down-selected via the paper study) are now being incorporated into this experimental study. The potential for the formation of a nepheline primary crystalline phase is an important factor in frit development for SB4, due to the high Al{sub 2}O{sub 3} content of this sludge. Based upon earlier work by Li et al., glasses that do not satisfy the constraint: (SiO{sub 2}/SiO{sub 2} + Na{sub 2}O + Al{sub 2}O{sub 3}) > 0.62 where the oxides are expressed as mass fractions in the glass, will precipitate nepheline as their primary crystalline phase, hindering the durability of the glass. Based on the most recent compositional projection from the CBU for SB4 (Case 15C Blend 1), 16 glasses have been selected to complement the earlier work by continuing the investigation into the ability of the above constraint to predict the occurrence of a nepheline primary crystalline phase for SB4 glasses and into the impact of such phases on the durability of the SB4 glasses. Glasses were selected to cover WLs which tightly bound the nepheline discriminator value of 0.62, with the intent of refining this value to a level of confidence where it can be incorporated into offline administrative controls and/or the PCCS to support SME acceptability decisions. In addition, glass specimens at WLs of 35 and 40% will be prepared and analyzed to contribute needed data to the ComPro{trademark} database in anticipation of a variability study for SB4. The glasses in Table 4-3 are to

  19. Effect of Etching Condition on the Formation of Bioactive Surface of Hydroxyapatite-Glass-Titanium Composite

    NASA Astrophysics Data System (ADS)

    Ban, Seiji; Maruno, Shigeo; Hasegawa, Jiro

    1991-07-01

    X-ray diffraction study shows that an etching solution of 3% HF and 5% HNO3 is the most suitable solution for preparing a bioactive surface layer of HA-glass-titanium composite, since the glass is removed, a great number of HA particles are exposed, and little CaF2 is produced by the etching. Anodic polarization measurement demonstrates that the 3-min etching gives an electrochemically active surface of the composites. These results and SEM observations suggest that this solution provides an adequate surface of the composite for the dental and medical implants.

  20. Local and Cooperative Jahn-Teller Effect and Resultant Magnetic Properties of M2AgF4 (M = Na-Cs) Phases.

    PubMed

    Kurzydłowski, Dominik; Jaroń, Tomasz; Ozarowski, Andrew; Hill, Stephen; Jagličić, Zvonko; Filinchuk, Yaroslav; Mazej, Zoran; Grochala, Wojciech

    2016-11-07

    The crystal structure, magnetic properties, heat capacity, and Raman spectra of double-perovskite M2AgF4 (M = K, K3/4Rb1/4, K1/2Rb1/2, K1/4Rb3/4, and Rb) phases have been examined, adding to the body of previous results for the M = Na, Cs derivatives. The results suggest that double-perovskite K2AgF4 adopts a disordered orthorhombic Bmab structure with an antiferrodistortive arrangement of the elongated and tilted [AgF6] octahedra rather than the structure with the ferrodistortive arrangement of compressed octahedra, as suggested previously (Mazej, Z.; Goreshnik, E.; Jagličić, Z.; Gaweł, B.; Łasocha, W.; Grzybowska, D.; Jaroń, T.; Kurzydłowski, D.; Malinowski, P. J.; Koźmiński, W.; Szydłowska, J.; Leszczyński, P. J.; Grochala, W. KAgF3, K2AgF4 and K3Ag2F7: important steps towards a layered antiferromagnetic fluoroargentate(II). CrystEngComm 2009, 11, 1702-1710). A re-examination of the previously collected single-crystal X-ray diffraction data confirms the current structure assignment, and it is also in agreement with recent theoretical calculations. High-field electron paramagnetic resonance spectra reaffirm the presence of elongated [AgF6] octahedra in the crystal structure of all M2AgF4 phases studied. The local structure of the M = K derivative is most complex, with regions of the sample that are quite orthorhombically distorted, whereas other regions more closely resemble the tetragonal phase. The mixed-cation K/Rb phases are also inhomogeneous, containing regions of the pure K compound and regions of another high-symmetry phase (likely tetragonal) of a mixed (Rb-richer) compound with unknown composition. The temperature-resolved phase diagram of all K/Rb phases has been established and positioned within the entire M = Na, K, Rb, Cs series.

  1. Effect of Jahn-Teller ion in zinc sodium sulphate hexahydrate: a case of low hyperfine coupling constant for Cu(II) ion

    NASA Astrophysics Data System (ADS)

    Naidu, K. C.; Shiyamala, C.; Mithira, S.; Natarajan, B.; Venkatesan, R.; Rao, P. S.

    2005-06-01

    Single crystal electron paramagnetic resonance (EPR) studies of Cu(II) doped zinc sodium sulphate hexahydrate are carried out from room temperature (RT) to 123 K. The RT spectra show unresolved hyperfine lines and hence angular variation studies are also carried out at 123 K to obtain spin Hamiltonian parameters. The spin Hamiltonian parameters calculated from the 123 K spectra are: g(11)=2.039, g(22)=2.232, g(33)=2.394, A(11)=5.64 mT, A(22)=4.20 mT, and A(33)=7.94 mT. The g-matrix values at RT and 123 K have matched fairly well with each other. The low hyperfine value (A(33)), obtained at 123 K, has been explained by considering considerable admixture of d(x 2-y 2) ground state with d(z 2) excited state and the delocalization of the unpaired spin density onto the ligands. The admixture coefficients of ground state wave function are: a=0.346, b=0.935, c=0.055, d=0.040, e=-0.040, where a and b correspond to admixture coefficients for d(z 2) and d(x 2-y 2), respectively. Angular variation of Cu(II) resonances in the three orthogonal axes shows that the impurity has entered a substitutional site in the host lattice in place of Zn(II). Bonding parameters, kappa=0.295, P=245.4x10(-4), alpha(2)=0.709, alpha=0.8421 and alpha'=0.6034, have also been calculated to fully characterize the EPR.

  2. An unusual stable mononuclear Mn(III) bis-terpyridine complex exhibiting Jahn-Teller compression: electrochemical synthesis, physical characterisation and theoretical study.

    PubMed

    Romain, Sophie; Duboc, Carole; Neese, Frank; Rivière, Eric; Hanton, Lyall R; Blackman, Allan G; Philouze, Christian; Leprêtre, Jean-Claude; Deronzier, Alain; Collomb, Marie-Noëlle

    2009-01-01

    The mononuclear manganese bis-terpyridine complex [Mn(tolyl-terpy)(2)](X)(3) (1(X)(3); X=BF(4), ClO(4), PF(6); tolyl-terpy=4'-(4-methylphenyl)-2,2':6',2"-terpyridine), containing Mn in the unusual +III oxidation state, has been isolated and characterised. The 1(3+) ion is a rare example of a mononuclear Mn(III) complex stabilised solely by neutral N ligands. Complex 1(3+) is obtained by electrochemical oxidation of the corresponding Mn(II) compound 1(2+) in anhydrous acetonitrile. Under these conditions the cyclic voltammogram of 1(2+) exhibits not only the well-known Mn(II)/Mn(III) oxidation at E(1/2)=+0.91 V versus Ag/Ag(+) (+1.21 V vs. SCE) but also a second metal-based oxidation process corresponding to Mn(III)/Mn(IV) at E(1/2)=+1.63 V (+1.93 V vs. SCE). Single crystals of 1(PF(6))(3)2 CH(3)CN were obtained by an electrocrystallisation procedure. X-ray analysis unambiguously revealed its tetragonally compressed octahedral geometry and high-spin character. The electronic properties of 1(3+) were investigated in detail by magnetic measurements and theoretical calculations, from which a D value of +4.82 cm(-1) was precisely determined. Density functional and complete active space self consistent field ab initio calculations both correctly predict a positive sign of D, in agreement with the compressed tetragonal distortion observed in the X-ray structure of 1(PF(6))(3)2 CH(3)CN. The different contributions to D were calculated, and the results show that 1) the spin-orbit coupling part (+2.593 cm(-1)) is predominant compared to the spin-spin interaction (+1.075 cm(-1)) and 2) the excited triplet states make the dominant contribution to the total D value.

  3. 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.

  4. 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

  5. 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

  6. Design rules for rational control of polymer glass formation behavior and mechanical properties with small molecular additives

    NASA Astrophysics Data System (ADS)

    Mangalara, Jayachandra Hari; Simmons, David

    Small molecule additives have long been employed to tune polymers' glass formation, mechanical and transport properties. For example, plasticizers are commonly employed to suppress polymer Tg and soften the glassy state, while antiplasticizers, which stiffen the glassy state of a polymer while suppressing its Tg, are employed to enhance protein and tissue preservation in sugar glasses. Recent literature indicates that additives can have a wide range of possible effects, but all of these have not been clearly understood and well appreciated. Here we employ molecular dynamics simulations to establish design rules for the selection of small molecule additives with size, molecular stiffness, and interaction energy chosen to achieve targeted effects on polymer properties. We furthermore find that a given additive's effect on a polymer's Tg can be predicted from its Debye-Waller factor via a function previously found to describe nanoconfinement effects on the glass transition. These results emphasize the potential for a new generation of targeted molecular additives to contribute to more targeted rational design of polymers. We acknowledge the Keck Foundation and the Ohio Supercomputing Center for financial and computational support of this effort, respectively.

  7. 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.

  8. The Formation of the Second-Order Nonlinearity in Thermally Poled Fused Silica Glass

    DTIC Science & Technology

    2007-11-02

    NONIINEARITY IN THERMALLY POLED FUSED SILICA GLASS 6. AUTHOR(S) THOMAS GUSTAVE ALLEY 5. FUNDING NUMBERS 7. PERFORMING ORGANIZATION NAME(S) AND...ADDRESS(ES) The University of New Mexico 8. PERFORMING ORGANIZATION REPORT NUMBER 98-020D 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES...self- organized , photoinduced, second-order nonlinearity. The most widely accepted explanation attributes the nonlinearity to an asymmetric

  9. Formation and Structure of AL(PO3)3 System Glasses,

    DTIC Science & Technology

    1982-08-06

    only the systems con- taining LiF or MgF2 that formed glass. 3) In the four-component systems that only contained NaF, KF, Ca?2 , SrF2 , or BaF2...a joining effect upon networks. Other single valued and dual valued chemicals such as NaF, KF, CaF2, SrF2 9 and BaF2 , belong to the out- er part of

  10. 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.

  11. 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.

  12. Formation of luminescent and nonluminescent silver nanoparticles in silicate glasses by near-infrared femtosecond laser pulses and subsequent thermal treatment: the role of halogenides

    NASA Astrophysics Data System (ADS)

    Klyukin, Dmitry A.; Dubrovin, Victor D.; Pshenova, Alisa S.; Putilin, Sergey E.; Shakhverdov, Teimur A.; Tsypkin, Anton N.; Nikonorov, Nikolay V.; Sidorov, Alexander I.

    2016-06-01

    It is shown experimentally that the near-infrared femtosecond laser irradiation and subsequent thermal treatment of silver-containing silicate glasses result in the formation of luminescent silver molecular clusters (MCs) and silver nanoparticles (NPs). In glasses doped also with halides (mostly Br), the nonluminescent silver NPs are formed because of the presence of halogenide shells on their surfaces, whereas, in glasses with no Br ions, the luminescent silver nanoparticles provides an emission in the 600- to 750-nm range. Two possible mechanisms of luminescence of glass with silver NPs are considered: (i) luminescence of silver NPs without halogenide shell and (ii) the luminescence of silver MCs Agm (m=1 to 4) remaining even after the formation of silver NPs.

  13. 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.

  14. Effect of aluminum on the formation of silver metal quantum dots in sol-gel derived alumino-silicate glass film.

    PubMed

    Kim, Bok Hyeon; Son, Dong Hoon; Ju, Seongmin; Jeong, Chaehwan; Boo, Seongjae; Kim, Cheol Jin; Hanl, Won-Taek

    2006-11-01

    The effect of aluminum incorporation on silver metal quantum dots formation in the alumino-silicate glass film processed by sol-gel process was investigated. The sol-gel derived glass was coated onto the silica glass plate by spin coating with the mixture solution of tetraethyl orthosilicate (TEOS), C2H5OH, H2O, AgNO3, Al(NO3)3. 39H2O, and HNO3 with the molar ratios of Ag/Si = 0.12 and Al/Si varying from 0 to 0.12. The formation of the silver metal quantum dots was confirmed by the measurements of the UV/VIS optical spectra, the X-ray diffraction patterns, and the transmission electron microscope images. While the radius of silver metal quantum dots increased with the increase of aluminum concentration, the concentration of the silver metal quantum dots decreased. The formation of the silver metal quantum dots was found strongly suppressed by incorporation of aluminum ions in the glass. The change in the glass structure due to the aluminum incorporation was investigated by the analysis of the Raman spectra. The silver ions in the glass contributed to form stable (Al:Ag)O4 tetrahedra by pairing with aluminum ions and thus clustering of silver metal quantum dots was hindered.

  15. Short-pulse laser formation of monatomic metallic glass in tantalum nanowire

    NASA Astrophysics Data System (ADS)

    Gan, Yong; Sun, Zheng; Shen, Yaogen

    2017-01-01

    The short-pulse laser heating of a tantalum nanowire is simulated by a hybrid method coupling the two-temperature model into the molecular dynamics. It is shown that the monatomic metallic glasses can be formed by short-pulse lasers. The critical cooling rate for vitrifying the pure metallic liquids in tantalum nanowire is estimated to be on the order of 1013 K s-1. Further simulations with different laser parameters and heated spot size are performed, demonstrating that the short-pulse laser quenching is a robust and promising alternative to the vitrification of monatomic metallic liquids into glassy state.

  16. 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

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

    DOE PAGES

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

    2014-09-18

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

  18. 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.

  19. Formation of hollow microcylinders from sputtered erbium-doped glass films

    NASA Astrophysics Data System (ADS)

    Krishnaswamy, Madhu; McMullin, James N.; Keyworth, B. P.; Broughton, James N.

    1997-05-01

    A planar sputter-deposited erbium-doped glass ridge was re- shaped into a hollow microcylinder using only photolithography, wet-etching and annealing. It is believed that selective build-up of gas is primarily responsible for this phenomenon, which is similar to glass-blowing. Other factors, such as the width and depth of the original ridge, the adhesion of the ridge to the underlying surface and the duration of the anneal, influence the eventual shape of the hollow microcylinder. By varying the processing parameters, a wide range of microcylinder shapes and sizes were obtained: circular and semi-circular profiles with 9.0 micrometers diameter or flatter 'tunnel-shaped' profiles ranging u pt o 25 micrometers in height and 100 micrometers in width. Microcylinders up to 1 cm long were fabricated. Water was sen to enter these hollow devices through capillary action. He-Ne light propagation through the hollow portion of the device was observed. These observations confirm that the microcylinders are hollow over their entire length. Hollow microcylinders or microchannels may find application in microfluidics and micro-optics.

  20. Specific heat of hydrated lysozyme, water's contribution to its dynamics, and criteria for glass formation of biomaterials.

    PubMed

    Tombari, Elpidio; Johari, G P

    2013-09-14

    Previous studies of the dynamics of hydrated proteins had shown a feature resembling an exceptionally broad glass-softening endotherm. Its onset temperature, denoted as T(g), was indefinable in one calorimetric study of hydrated lysozyme and was in the 148-218 K range in another study, depending upon hydration. Other methods reported this T(g) as ~170 K. We argue that glass-formation of biomaterials should be studied by measuring a property on both the cooling and heating paths and it should be ascertained (i) that there is thermal hysteresis of the measured property, (ii) that the real and imaginary components of a dynamic property obey the Kramers-Kronig relations, and (iii) that there is an effect of annealing that is consistent with the glass phenomenology. We report the real and imaginary components of the dynamic specific heat, C(p)' and C(p)", of dry and two hydrated lysozyme samples on the cooling and the heating paths as well as the effects of annealing and changing the frequency. For the most hydrated (34.6 g water per 100 g lysozyme) sample, C(p,app) does not show thermal hysteresis in the 160-230 K range, C(p)' varies in a sigmoid-shape manner with T while C(p)" remains close to zero, and there is no effect of annealing. We interpret these findings in terms of continuous development of ice-like aggregates of immobile H2O as more H-bonds form on cooling, and continuous deterioration of the aggregates on heating. As the equilibrium constant between the aggregates and mobile H2O increases on cooling, configurational degrees of freedom of H2O molecules and lysozyme segments decrease. Consequently, the net change in enthalpy is small but the change in C(p) is large. Mobility of the lysozyme segments still depends upon the mobility of H2O molecules.

  1. Specific heat of hydrated lysozyme, water's contribution to its dynamics, and criteria for glass formation of biomaterials

    NASA Astrophysics Data System (ADS)

    Tombari, Elpidio; Johari, G. P.

    2013-09-01

    Previous studies of the dynamics of hydrated proteins had shown a feature resembling an exceptionally broad glass-softening endotherm. Its onset temperature, denoted as Tg, was indefinable in one calorimetric study of hydrated lysozyme and was in the 148-218 K range in another study, depending upon hydration. Other methods reported this Tg as ˜170 K. We argue that glass-formation of biomaterials should be studied by measuring a property on both the cooling and heating paths and it should be ascertained (i) that there is thermal hysteresis of the measured property, (ii) that the real and imaginary components of a dynamic property obey the Kramers-Kronig relations, and (iii) that there is an effect of annealing that is consistent with the glass phenomenology. We report the real and imaginary components of the dynamic specific heat, Cp' and Cp″, of dry and two hydrated lysozyme samples on the cooling and the heating paths as well as the effects of annealing and changing the frequency. For the most hydrated (34.6 g water per 100 g lysozyme) sample, Cp,app does not show thermal hysteresis in the 160-230 K range, Cp' varies in a sigmoid-shape manner with T while Cp″ remains close to zero, and there is no effect of annealing. We interpret these findings in terms of continuous development of ice-like aggregates of immobile H2O as more H-bonds form on cooling, and continuous deterioration of the aggregates on heating. As the equilibrium constant between the aggregates and mobile H2O increases on cooling, configurational degrees of freedom of H2O molecules and lysozyme segments decrease. Consequently, the net change in enthalpy is small but the change in Cp is large. Mobility of the lysozyme segments still depends upon the mobility of H2O molecules.

  2. 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.

  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).

  4. Can alteration experiments on impact melts from El'gygytgyn and volcanic glasses shed new light on the formation of the Martian surface?

    NASA Astrophysics Data System (ADS)

    Hellevang, Helge; Dypvik, Henning; Kalleson, Elin; Pittarello, Lidia; Koeberl, Christian

    2013-07-01

    This investigation involved three specimens: an altered felsic sample of impactite from the ICDP El'gygytgyn drill core D1c, and two reference volcanics from Iceland, namely a rhyolitic glass and a basaltic glass. The goal of this work was to better understand the alteration of impact melt and volcanic glass, and to apply the results to an investigation of alteration processes below the surface of Mars. Hydrothermal batch alteration experiments with the El'gygytgyn sample showed formation of various silica phases such as cristobalite, opal, and quartz. According to geochemical modeling, zeolites were also expected, but zeolite minerals already present in the impactite prior to the experiment may have masked possible experimental zeolite growth. Basaltic glass was altered to smectite, talc, and opal. The accompanying numerical modeling gave results that were similar or comparable to the laboratory experiments. Rhyolitic glass was kinetically more stable than basaltic glass, and showed only minor formation of calcite and feldspar during the 3-week experiment. The study showed that closed-system isochemical alteration of both siliceous and mafic glasses and melts results in the formation of smectites and zeolites. Therefore, to link alteration features on Mars to specific physical conditions, the exact identity of the mineral phases present in surface rocks must be known. Moreover, our simulations on closed-system isochemical alteration showed that the fraction of zeolites and silica formed relative to smectite depends on the source mineral altered. Therefore, fractions of these mineral groups present in the Martian soil may be used to better predict source rock characteristics.

  5. Formation and characterization of hydrophobic glass surface treated by atmospheric pressure He/CH4 plasma

    NASA Astrophysics Data System (ADS)

    Noh, Sooryun; Youn Moon, Se

    2014-01-01

    Atmospheric pressure helium plasmas, generated in the open air by 13.56 MHz rf power, were applied for the glass surface wettability modification. The plasma gas temperature, measured by the spectroscopic method, was under 400 K which is low enough to treat the samples without thermal damages. The hydrophobicity of the samples determined by the water droplet contact angle method was dependent on the methane gas content and the plasma exposure time. Adding the methane gas by a small amount of 0.25%, the contact angle was remarkably increased from 10° to 83° after the 10 s plasma treatment. From the analysis of the treated surface and the plasma, it was shown that the deposition of alkane functional groups such as C-H stretch, CH2 bend, and CH3 bend was one of the contributing factors for the hydrophobicity development. In addition, the hydrophobic properties lasted over 2 months even after the single treatment. From the results, the atmospheric pressure plasma treatment promises the fast and low-cost method for the thermally-weak surface modification.

  6. Multispectroscopic methodology to study Libyan desert glass and its formation conditions.

    PubMed

    Gomez-Nubla, Leticia; Aramendia, Julene; Fdez-Ortiz de Vallejuelo, Silvia; Alonso-Olazabal, Ainhoa; Castro, Kepa; Zuluaga, Maria Cruz; Ortega, Luis Ángel; Murelaga, Xabier; Madariaga, Juan Manuel

    2017-03-27

    Libyan desert glass (LDG) is a melt product whose origin is still a matter of controversy. With the purpose of adding new information about this enigma, the present paper analyzes the inner part of LDG specimens and compares them with the results of LDG surfaces. An integrated analytical methodology was used combining different techniques such as Raman spectroscopy, in point-by-point and imaging modes, scanning electron microscopy with X-ray microanalysis (SEM-EDS), energy-dispersive micro X-ray fluorescence spectrometry (μ-EDXRF), electron probe micro analyzer (EPMA), and optical cathodoluminescence (Optical-CL). According to our results, flow structures of the melt and the amorphous nature of the matrix could be discerned. Moreover, the observed displacement of Raman bands, such as in the cases of quartz and zircon, and the identification of certain compounds such as coesite (the most clarifying phase of high pressures), α-cristobalite, gypsum, anhydrite, corundum, rutile, amorphous calcite, aragonite, and calcite allowed us to know that LDGs could be subjected to shock pressures between 6 and more than 30 GPa, and temperatures between 300 and 1470 °C. The differences of temperature and pressure would be provoked by different cooling processes during the impact. Besides, in most cases the minerals corresponding to high pressure and temperatures were located in the inner part of the LDGs, with some exceptions that could be explained because they were trapped subsequently to the impact; there was more than one impact or heterogeneous cooling.Furthermore, nitrogen and oxygen gases were identified inside bubbles, which could have been introduced from the terrestrial atmosphere during the meteorite impact.These data helped us to clarify some clues about the origin of these enigmatic samples.

  7. 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

  8. Formation and spectral probing of transparent oxyfluoride glass-ceramics containing (Eu2+, Eu3+:BaGdF5) nano-crystals

    NASA Astrophysics Data System (ADS)

    Biswas, Kaushik; Balaji, S.; Karmakar, Prantik; Annapurna, K.

    2015-01-01

    In the present study, we report the formation of transparent glass-ceramics containing BaGdF5 nanocrystals under optimum ceramization of SiO2-BaF2-K2O-Sb2O3-GdF3-Eu2O3 based oxyfluoride glass and the energy transfer mechanisms in Eu2+ → Eu3+ and Gd3+ → Eu3+ has been interpreted through luminescence study. The modification of local environment surrounding dopant ion in glass and glass ceramics has been studied using Eu3+ ion as spectral probe. The optimum ceramization temperature was determined from the differential scanning calorimetry (DSC) thermogram which revealed that the glass transition temperature (Tg), the crystallization onset temperature (Tx), and crystallization peak temperature (Tp) are 563 °C, 607 °C and 641 °C, respectively. X-ray diffraction pattern of the glass-ceramics sample displayed the presence of cubic BaGdF5 phase (JCPDS code: 24-0098). Transmission electron microscopy image of the glass-ceramics samples revealed homogeneous distribution of spherical fluoride nanocrystals ranging 5-15 nm in size. The emission transitions from the higher excited sates (5DJ, J = 1, 2, and 3) as well as lowered asymmetry ratio of the 5D0 → 7F2 transition (forced electric dipole transition) to that of the 5D0 → 7F1 transition (magnetic dipole) of Eu3+ in the glass-ceramics when compared to glass sample demonstrated the incorporation of dopant Eu3+ ions into the cubic BaGdF5 nanocrystals with higher local symmetry with enhanced ionic nature. The presence of absorption bands of Eu2+ ions and Gd3+ ions present in the glass matrix or fluoride nanocrystals in the excitation spectra of Eu3+ by monitoring emission at 614 nm indicated energy transfer from (Eu2+ → Eu3+) and (Gd3+ → Eu3+) in both glass and glass-ceramics samples.

  9. 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

  10. 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

  11. 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)

  12. Spin Glass Freezing and Ferromagnetic Cluster Formation in LiNiO_2

    NASA Astrophysics Data System (ADS)

    van Duijn, Joost; Gaulin, Bruce; Park, Sungil; Lee, Seung-Hun; Copley, John

    2003-03-01

    LiNiO2 displays a layered structure that consists of alternating triangular nets of magnetic Ni and non-magnetic Li ions. Its magnetic properties have been a longstanding source of debate, having been proposed as a candidate for many exotic magnetic ground states. Recent detailed characterization studies have shown that some Ni ions always occupy sites in the Li layers and vice versa. We have carried out inelastic neutron scattering studies on a well characterized sample of LiNiO2 using the new Disk Chopper Spectrometer at NIST. Diffuse inelastic scattering is observed in the forward direction and around (1,0,0) in reciprocal space, indicative of short range, dynamic ferromagnetic order. Spin freezing is directly observed by a decrease in the inelastic scattering and concomitant increase in the elastic scattering below ˜15 K, consistent with bulk susceptibility measurements. Our neutron measurements are interpreted as arising from ferromagnetic correlations within the triangular net and 3D ferromagnetic clusters surrounding Ni sites within the Li sublattice. Such ferromagnetic clusters interupt the formation of a 3D Neel state in which ferromagnetic sheets stack antiferromagnetically, as is believed to be the case in NaNiO2.

  13. 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.

  14. 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.

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

    PubMed

    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.

  16. 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.

  17. 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

  18. 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

  19. Formation of hydroxyapatite onto glasses of the CaO-MgO-SiO2 system with B2O3, Na2O, CaF2 and P2O5 additives.

    PubMed

    Agathopoulos, S; Tulyaganov, D U; Ventura, J M G; Kannan, S; Karakassides, M A; Ferreira, J M F

    2006-03-01

    New bioactive glasses with compositions based on the CaO-MgO-SiO(2) system and additives of B(2)O(3), P(2)O(5), Na(2)O, and CaF(2) were prepared. The in vitro mineralization behaviour was tested by immersion of powders or bulk glasses in simulated body fluid (SBF). Monitoring of ionic concentrations in SBF and scanning electron microscopy (SEM) observations at the surface of the glasses were conducted over immersion time. Raman and infrared (IR) spectroscopy shed light on the structural evolution occurring at the surface of the glasses that leads to formation of hydroxyapatite.

  20. Formation of an ensemble of silver nanoparticles in the process of surface evaporation of glass optical waveguides doped with silver ions by the radiation of a pulsed CO{sub 2} laser

    SciTech Connect

    Egorov, V I; Sidorov, A I; Nashchekin, A V

    2015-09-30

    It is shown that pulsed irradiation (a wavelength of 10.6 μm and an energy density of 0.6 – 8.5 J cm{sup -2}) of glass with a waveguide layer containing silver ion leads to the formation of a ring, surrounding the irradiated zone and consisting of silver nanoparticles deposited on the glass surface. The possible process of formation of silver nanoparticles under laser irradiation is discussed. (optics and technology of nanostructures)

  1. 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.

  2. Effects of Cooling Rates on Glass Formation and Magnetic Behavior for the Fe73.0C7.0Si3.3B5.0P8.7Mo3.0 Bulk Metallic Glass

    NASA Astrophysics Data System (ADS)

    Gao, J. E.; Li, H. X.; Jiang, F.; Winiarski, B.; Withers, P. J.; Liaw, P. K.; Lu, Z. P.

    2013-05-01

    In this paper, effects of cooling rates on glass formation and magnetic behavior of the Fe73.0C7.0Si3.3B5.0P8.7Mo3.0 (at. pct) alloy were investigated via different purging gases ( i.e., helium and argon) during suction casting. X-ray diffraction patterns and transmission electron microscopy characterization confirmed that the maximum attainable diameter for glass formation is increased from 5 to 7 mm with the helium as the purging gas, relative to the argon. Meanwhile, the coercivity value ( H c) of the sample cast in helium is almost 5 times larger than that fabricated in argon, although the magnetization saturation in these two alloys is similar. Our pair distribution function analysis, density, and positron annihilation lifetime spectroscopy measurements indicated that the sample cast in helium possesses more free volume; however, the difference between them is insubstantial. Further, experimental results revealed that the residual stress in the samples cast under helium is much larger than that in those prepared in Argon, which could be responsible for the abrupt change in the coercivity.

  3. 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.

  4. Ectopic bone formation by gel-derived bioactive glass-poly-L-lactide-co-glycolide composites in a rabbit muscle model.

    PubMed

    Filipowska, Joanna; Cholewa-Kowalska, Katarzyna; Wieczorek, Jarosław; Semik, Danuta; Dąbrowski, Zbigniew; Łączka, Maria; Osyczka, Anna M

    2017-01-17

    In this study we aimed to assess the in vivo osteoinductive properties of two composite scaffolds made of PLGA (poly-L-lactide-co-glycolide) and two types of gel-derived bioactive glasses, namely a high silica S2 bioactive glass (S2-PLGA composites) or high lime A2 bioactive glass (A2-PLGA composites). To achieve that, the potential of the composites to induce ectopic bone formation in a rabbit muscle has been examined along with the control PLGA scaffold. Cylinder-like scaffolds of 7  ×  3 mm (width  ×  height) were implanted into pouches created in the latissimus dorsi muscle of 18 New Zealand rabbits. The tissue sections were obtained at 6, 12 or 24 weeks post-surgery (six rabbits per each time point) and stained with hematoxylin-eosin. The process of wound healing, the formation of collagen-rich connective tissue and its transition to cartilage were examined by Sirius red and Alcian blue histological stainings. We also performed immunohistochemical verification of the presence of osteoblast- and osteoclast- like cells in the vicinity of the scaffolds. A typical foreign body reaction and wound healing process was observed for all implanted scaffolds. Osteoblast- and osteoclast-like cells were observed in the vicinity of the scaffolds as determined by the immunohistochemical staining for Osteocalcin, BMP-2 and Cathepsin K. Compared to plain PLGA scaffolds, numerous osteoblast-like cells were observed 12 weeks post implantation near the composites and the scaffolds gradually degraded as bone formation proceeded. S2-PLGA and A2-PLGA composites display osteoinductive properties in vivo. Furthermore, they are more effective at inducing ectopic bone formation in a rabbit muscle compared to plain PLGA. Thus these SBG-PLGA composite scaffolds have potential for clinical applications in dental and/or orthopedic-bone tissue engineering.

  5. Formation of molecular glasses and the aggregation in solutions for lanthanum(III), calcium(II), and yttrium(III) complexes of octanoyl-DL-alaninate.

    PubMed

    Naren, Gerile; Masuda, Rie; Iida, Masayasu; Harada, Masafumi; Kurosu, Hiromichi; Suzuki, Toshiharu; Kimura, Takayoshi

    2008-04-07

    Octanoylalaninato-metal (metal = calcium(II), yttrium(III), lanthanum(III), and zinc(II)) complexes were prepared and the first three metal complexes were found to readily form transparent and stable molecular glasses from methanol and chloroform solutions. The process of glass formation from solution was studied in detail. The effect of the central metal ions on the formation of glassy states was remarkable: the lanthanum and calcium complexes assumed glassy or crystalline states depending on the isolation method and the yttrium complex had a large tendency to assume an amorphous state, whereas the zinc complex did not assume a pure and stable glassy-state. The glass transition temperatures were 50 degrees C for the yttrium complex and 70-75 degrees C for the lanthanum and calcium complexes when these complexes are monohydrates prepared by a solvent-cast method, whereas they increase by 10-30 degrees for the hemihydrates which were obtained by an annealing treatment at 110 degrees C. The coordinated water was eliminated from the solid above the glass transition temperature. The glassy state was regarded as a result of the self-aggregation of the metal complex in solution by an entanglement of the methylene chains with one another. SAXS showed the presence of two disordered bilayer structures with 2.2 nm and 4.5 nm periods in the glassy states. The structures of the molecular assemblies in the solid states and solutions were compared by SAXS and NMR studies. EXAFS studies confirmed the coordination numbers of oxygen atoms around the yttrium and lanthanum atoms in the glassy states for the yttrium and lanthanum complexes to be about 7.

  6. Technologies for Use in the Formation of a Differentiated Structure in Iron Billets Used in Glass Molds

    NASA Astrophysics Data System (ADS)

    Leushin, I. O.; Chistyakov, D. G.

    2016-09-01

    Causes for the failure of pig iron press molds that are parts of a glass mold are described. Criteria for differentiating the structure of pig iron are established. Ways of obtaining a differentiated structure of a casting product are outlined. A heat treatment regime for the billets is determined.

  7. Synchrotron X-Ray Diffraction to Detect Glass or Ice Formation in the Vitrified Bovine Cumulus-Oocyte Complexes and Morulae

    PubMed Central

    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. PMID:25536435

  8. 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.

  9. Bioactive glasses and glass-ceramics.

    PubMed

    Rawlings, R D

    1993-01-01

    Bioactive materials are designed to induce a specific biological activity; in most cases the desired biological activity is one that will give strong bonding to bone. A range of materials has been assessed as being capable of bonding to bone, but this paper is solely concerned with bioactive glasses and glass-ceramics. Firstly, the structure and processing of glasses and glass-ceramics are described, as a basic knowledge is essential for the understanding of the development and properties of the bioactive materials. The effect of composition and structure on the bioactivity is then discussed, and it will be shown that bioactivity is associated with the formation of an apatite layer on the surface of the implant. A survey of mechanical performance demonstrates that the structure and mechanical properties of glass-ceramics depend upon whether the processing involves casting or sintering and that the strength and toughness of glass-ceramics are superior to those of glasses. Attempts to further improve the mechanical performance by the use of non-monolithic components, i.e. bioactive coatings on metal substrates and glass and glass-ceramic matrix composites, are also reviewed and are shown to have varying degrees of success. Finally, some miscellaneous applications, namely bioactive bone cements and bone fillers, are briefly covered.

  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

    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.

  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

    DOE PAGES

    Kim, J. S.; Kim, S. Y.; Kim, D. 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

  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. The effects of 3D bioactive glass scaffolds and BMP-2 on bone formation in rat femoral critical size defects and adjacent bones.

    PubMed

    Liu, Wai-Ching; Robu, Irina S; Patel, Rikin; Leu, Ming C; Velez, Mariano; Chu, Tien-Min Gabriel

    2014-08-01

    Reconstruction of critical size defects in the load-bearing area has long been a challenge in orthopaedics. In the past, we have demonstrated the feasibility of using a biodegradable load-sharing scaffold fabricated from poly(propylene fumarate)/tricalcium phosphate (PPF/TCP) loaded with bone morphogenetic protein-2 (BMP-2) to successfully induce healing in those defects. However, there is limited osteoconduction observed with the PPF/TCP scaffold itself. For this reason, 13-93 bioactive glass scaffolds with local BMP-2 delivery were investigated in this study for inducing segmental defect repairs in a load-bearing region. Furthermore, a recent review on BMP-2 revealed greater risks in radiculitis, ectopic bone formation, osteolysis and poor global outcome in association with the use of BMP-2 for spinal fusion. We also evaluated the potential side effects of locally delivered BMP-2 on the structures of adjacent bones. Therefore, cylindrical 13-93 glass scaffolds were fabricated by indirect selective laser sintering with side holes on the cylinder filled with dicalcium phosphate dehydrate as a BMP-2 carrier. The scaffolds were implanted into critical size defects created in rat femurs with and without 10 μg of BMP-2. The x-ray and micro-CT results showed that a bridging callus was found as soon as three weeks and progressed gradually in the BMP group while minimal bone formation was observed in the control group. Degradation of the scaffolds was noted in both groups. Stiffness, peak load and energy to break of the BMP group were all higher than the control group. There was no statistical difference in bone mineral density, bone area and bone mineral content in the tibiae and contralateral femurs of the control and BMP groups. In conclusion, a 13-93 bioactive glass scaffold with local BMP-2 delivery has been demonstrated for its potential application in treating large bone defects.

  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. β-Irradiation Effects on the Formation and Stability of CaMoO4 in a Soda Lime Borosilicate Glass Ceramic for Nuclear Waste Storage.

    PubMed

    Patel, Karishma B; Boizot, Bruno; Facq, Sébastien P; Lampronti, Giulio I; Peuget, Sylvain; Schuller, Sophie; Farnan, Ian

    2017-02-06

    Molybdenum solubility is a limiting factor to actinide loading in nuclear waste glasses, as it initiates the formation of water-soluble crystalline phases such as alkali molybdates. To increase waste loading efficiency, alternative glass ceramic structures are sought that prove resistant to internal radiation resulting from radioisotope decay. In this study, selective formation of water-durable CaMoO4 in a soda lime borosilicate is achieved by introducing up to 10 mol % MoO3 in a 1:1 ratio to CaO using a sintering process. The resulting homogeneously dispersed spherical CaMoO4 nanocrystallites were analyzed using electron microscopy, X-ray diffraction (XRD), Raman and electron paramagnetic resonance (EPR) spectroscopies prior to and post irradiation, which replicated internal β-irradiation damage on an accelerated scale. Following 0.77 to 1.34 GGy of 2.5 MeV electron radiation CaMoO4 does not exhibit amorphization or significant transformation. Nor does irradiation induce glass-in-glass phase separation in the surrounding amorphous matrix, or the precipitation of other molybdates, thus proving that excess molybdenum can be successfully incorporated into a structure that it is resistant to β-irradiation proportional to 1000 years of storage without water-soluble byproducts. The CaMoO4 crystallites do however exhibit a nonlinear Scherrer crystallite size pattern with dose, as determined by a Rietveld refinement of XRD patterns and an alteration in crystal quality as deduced by anisotropic peak changes in both XRD and Raman spectroscopy. Radiation-induced modifications in the CaMoO4 tetragonal unit cell occurred primarily along the c-axis indicating relaxation of stacked calcium polyhedra. Concurrently, a strong reduction of Mo(6+) to Mo(5+) during irradiation is observed by EPR, which is believed to enhance Ca mobility. These combined results are used to hypothesize a crystallite size alteration model based on a combination of relaxation and diffusion

  20. Nanoscale bit formation in highly (111)-oriented ferroelectric thin films deposited on glass substrates for high-density storage media.

    SciTech Connect

    Kim, D. H.; Kim, Y. K.; Hong, S.; Kim, Y.; Baik, S.

    2011-04-21

    PbTiO{sub 3} (PTO) ferroelectric films on Pt(111) bottom electrode layers covering Ta/glass were prepared using pulsed laser deposition. X-ray diffraction patterns revealed that the PTO films were preferentially (111)-oriented. The films were highly crystalline and had a smooth surface with root mean square (RMS) roughness of 1.5 nm. Ferroelectric properties of the PTO films were characterized using piezoresponse force microscopy (PFM). PFM techniques achieved ferroelectric polarization bits with a minimum width of 22 nm, which corresponds to a potential recording density of 1.3 Tbit/in{sup 2} in ferroelectric storage devices.

  1. Morphology and interphase formation in epoxy/PMMA/glass fiber composites: effect of the molecular weight of the PMMA.

    PubMed

    Olmos, D; Bagdi, K; Mózcó, J; Pukánszky, B; González-Benito, J

    2011-08-01

    In this work ternary composites based on an epoxy thermoset modified with a thermoplastic polymer and reinforced with glass fibers were prepared. The aim of this study is to analyze the influence of the molecular weight of the thermoplastic polymer on the final morphologies. To obtain tailor made interphases four poly(methylmethacrylate), PMMA, which differ in their molecular weight (34,000, 65,000, 76,000 and 360,000 g/mol) were chosen to modify the epoxy resin. The amount of PMMA in the composites was fixed to 5 wt.%. Neat polymer matrices (epoxy-PMMA without fibers) were also prepared for comparison. To study all systems dynamic mechanical analysis (DMA), atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used. Although all the systems showed the typical phase separation in the epoxy/PMMA blend, DMA experiments revealed a new phase with more restricted mobility when the glass fibers are present. The amount of this phase increases as molecular weight of PMMA does. The morphologies as well as the fracture surface in the immediate surroundings of the fibers were found to be different from those observed further away from the surface of the fiber, suggesting therefore that, in this case, different fracture mechanism operates. These observations allow us to conclude that an interphase with specific properties is formed. This interphase is based on a polymer or a polymer blend (epoxy-PMMA) enriched in the component with lower mobility.

  2. 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

    2016-06-02

    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.

  3. Lattice vacancies in silicon film exposed to external electric field

    NASA Astrophysics Data System (ADS)

    Mao, Yuliang; Caliste, Damien; Pochet, Pascal

    2013-07-01

    Density functional calculations based on wavelet basis set are performed to investigate the structure, internal electric-charge distribution, and formation energy of lattice vacancies in silicon film under electric fields. It was found that the formation energies of vacancies both in JT⊥ (Jahn-Teller distortion orthogonal to electric field) and JT‖ (Jahn-Teller distortion parallel to electric field) distortions are decreased with the increasing of field strength, due to the charge polarization in the whole space of silicon film. For the split vacancy, it can lower its energy by moving further away from the split space to form a tetragonal JT⊥ vacancy under electric field. Our results also demonstrate the importance of the potential fluctuations induced by the electric fields on the charge redistribution within the vacancy defects.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. Evidence of photo-induced dynamic competition of metallic and insulating phase in a layered manganite.

    PubMed

    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, La0.99Sr2.01Mn2O7, 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.

  10. 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; ...

    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

  11. 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.

  12. 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.

  13. 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.

  14. Glass formation and magnetic properties in the Co and Fe-based amorphous alloy with small Mo or Nb additions

    NASA Astrophysics Data System (ADS)

    Jo, Hye-In; Choi-Yim, Haein

    2012-02-01

    The ferromagnetic metallic glass alloys in the Co-Fe-B-Si-M (M = Mo or Nb) system were investigated. Ingots of [(Co1- x Fe x )0.75B0.2Si0.05]96Mo4 ( x = 0, 0.2, 0.5, 0.8, 1.0) and [(Co1- x Fe x )0.75 B0.2Si0.05]96Nb4 ( x = 0, 0.2, 0.5, 0.8, 1.0) alloys were cast into about 30 µm-thick ribbons by using a melt spinning method. As-spun ribbons were identified as being fully amorphous by using X-ray diffraction (XRD). The thermal stability parameters, such as the supercooled liquid region (Δ T x = T g - T x ) and the exothermic heat (Δ H Exo ), were measured by using differential scanning calorimetry (DSC). For Co-Fe-B-Si-Mo alloys, Δ T x and Δ H Exo were in the range of 41.4-81.7 K and 23.40-104.21 J/g, and for Co-Fe-B-Si-Nb alloys, Δ T x and Δ H Exo were in the range of 60.4-88.0 K and 18.45-62.05 J/g, respectively. These glassy ribbons also exhibited semi-hard magnetic properties, i.e., a coercive force ( H c ) of 67.26-100.68 Oe and a saturation magnetization ( M s ) of 341.288-746.176 emu·cm3.

  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. 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

  17. 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

  18. 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

  19. Glass recycling

    SciTech Connect

    Dalmijn, W.L.; Houwelingen, J.A. van

    1995-12-31

    Glass recycling in the Netherlands has grown from 10,000 to 300,000 tonnes per annum. The various advantages and problems of the glass cycle with reference to the state of the art in the Netherlands is given. Special attention is given to new technologies for the automated sorting of cullet with detection systems. In Western Europe the recycling of glass has become a success story. Because of this, the percentage of glass cullet used in glass furnaces has increased. To meet the quality demands of the glass industry, automated sorting for the removal of stones, non-ferrous metals and other impurities had to be developed and incorporated in glass recycling plants. In Holland, Germany and other countries, the amount of glass collected has reached a level that color-sorting becomes necessary to avoid market saturation with mixed cullet. Recently, two systems for color-sorting have been developed and tested for the separation of bottles and cullet in the size range of 20--50 mm. With the increased capacity of the new glass recycling plants, 120,000--200,000 tpy, the quality systems have also to be improved and automated. These quality control systems are based on the automated sorting technology developed earlier for the glass recycling plants. The data obtained are automatically processed and printed. The sampling system and its relation to the theory of Gy will be described. Results of both developments in glass recycling plants will be described.

  20. 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

  1. 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.

  2. Enzymatically induced formation of neodymium hexacyanoferrate nanoparticles on the glucose oxidase/chitosan modified glass carbon electrode for the detection of glucose.

    PubMed

    Sheng, Qinglin; Luo, Kai; Zheng, Jianbin; Zhang, Hongfang

    2008-11-15

    The formation of neodymium hexacyanoferrate (NdHCF) nanoparticles (NPs) on the surface of glucose oxidase/chitosan (GOx/CHIT) modified glass carbon electrode induced by enzymatic reaction was described and characterized. CHIT can be used not only as enzyme immobilizer, but also to provide active sites for NPs growth. Results showed that the optimized conditions of the GOx/CHIT film induced NdHCF NPs for the biosensing of glucose were 1.0mM Nd(3+) and 20.0mM Fe(CN)(6)(3-). The biocatalyzed generation of NdHCF NPs enabled the development of an electrochemical biosensor for glucose. The calculated apparent Michaelis-Menten constant was 7.5mM. The linear range for glucose detection was 0.01-10.0mM with the correlation coefficient of 0.9946, and the detection limit was 5 microM (S/N=3). Furthermore, this system avoids the interferences of other species during the biosensing process and can be used for the determination of glucose in human plasma samples.

  3. 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.

  4. 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)

  5. 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.

  6. 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.

  7. 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.

  8. Self-assembly and glass-formation in a lattice model of telechelic polymer melts: Influence of stiffness of the sticky bonds.

    PubMed

    Xu, Wen-Sheng; Freed, Karl F

    2016-06-07

    Telechelic polymers are chain macromolecules that may self-assemble through the association of their two mono-functional end groups (called "stickers"). A deep understanding of the relation between microscopic molecular details and the macroscopic physical properties of telechelic polymers is important in guiding the rational design of telechelic polymer materials with desired properties. The lattice cluster theory (LCT) for strongly interacting, self-assembling telechelic polymers provides a theoretical tool that enables establishing the connections between important microscopic molecular details of self-assembling polymers and their bulk thermodynamics. The original LCT for self-assembly of telechelic polymers considers a model of fully flexible linear chains [J. Dudowicz and K. F. Freed, J. Chem. Phys. 136, 064902 (2012)], while our recent work introduces a significant improvement to the LCT by including a description of chain semiflexibility for the bonds within each individual telechelic chain [W.-S. Xu and K. F. Freed, J. Chem. Phys. 143, 024901 (2015)], but the physically associative (or called "sticky") bonds between the ends of the telechelics are left as fully flexible. Motivated by the ubiquitous presence of steric constraints on the association of real telechelic polymers that impart an additional degree of bond stiffness (or rigidity), the present paper further extends the LCT to permit the sticky bonds to be semiflexible but to have a stiffness differing from that within each telechelic chain. An analytical expression for the Helmholtz free energy is provided for this model of linear telechelic polymer melts, and illustrative calculations demonstrate the significant influence of the stiffness of the sticky bonds on the self-assembly and thermodynamics of telechelic polymers. A brief discussion is also provided for the impact of self-assembly on glass-formation by combining the LCT description for this extended model of telechelic polymers with the

  9. Potentially improved glasses from space environment

    NASA Technical Reports Server (NTRS)

    Nichols, R.

    1977-01-01

    The benefits of processing glasses in a low-gravity space environment are examined. Containerless processing, the absence of gravity driven convection, and lack of sedimentation are seen as potential advantages. Potential applications include the formation of glass-ceramics with a high content of active elements for ferromagnetic devices, the production of ultrapure chalcogenide glasses for laser windows and IR fiber optics, and improved glass products for use in optical systems and laser fusion targets.

  10. GLASS FIBER REINFORCED PLASTICS,

    DTIC Science & Technology

    Contents: Fibrous glass fillers Binders used in the glass plastic industry Method of manufacturing glass plastics and glass plastic articles Properties of fiberglass Primary areas for use of glass fibre reinforced plastics

  11. Waste glass melting stages

    SciTech Connect

    Anderson, L.D.; Dennis, T.; Elliott, M.L.; Hrma, P.

    1993-04-01

    Three different simulated nuclear waste glass feeds, consisting of dried waste and glass frit, were heat treated for 1 hour in a gradient furnace at temperatures ranging from approximately 600[degrees]C--1000[degrees]C. Simulated melter feeds from the Hanford Waste Vitrification Plant (HWVP), the Defense Waste Processing Facility (DWPF), and Kernforschungszentrum Karlsruhe (KfK) in Germany were used. The samples were thin-sectioned and examined by optical microscopy to investigate the stages of the conversion from feed to glass. Various phenomena were seen, such as frit softening, bubble formation, foaming, bubble motion and removal, convective mixing, and homogenization. Behavior of different feeds was similar, although the degree of gas generation and melt homogenization varied.

  12. Waste glass melting stages

    SciTech Connect

    Anderson, L.D.; Dennis, T.; Elliott, M.L.; Hrma, P.

    1993-04-01

    Three different simulated nuclear waste glass feeds, consisting of dried waste and glass frit, were heat treated for 1 hour in a gradient furnace at temperatures ranging from approximately 600{degrees}C--1000{degrees}C. Simulated melter feeds from the Hanford Waste Vitrification Plant (HWVP), the Defense Waste Processing Facility (DWPF), and Kernforschungszentrum Karlsruhe (KfK) in Germany were used. The samples were thin-sectioned and examined by optical microscopy to investigate the stages of the conversion from feed to glass. Various phenomena were seen, such as frit softening, bubble formation, foaming, bubble motion and removal, convective mixing, and homogenization. Behavior of different feeds was similar, although the degree of gas generation and melt homogenization varied.

  13. Tempered glass

    SciTech Connect

    Bunnell, L.R.

    1991-11-01

    This document describes a demonstration for making tempered glass using minimal equipment. The demonstration is intended for a typical student of materials science, at the high school level or above. (JL)

  14. 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.

  15. 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.

  16. Modelling aqueous corrosion of nuclear waste phosphate glass

    NASA Astrophysics Data System (ADS)

    Poluektov, Pavel P.; Schmidt, Olga V.; Kascheev, Vladimir A.; Ojovan, Michael I.

    2017-02-01

    A model is presented on nuclear sodium alumina phosphate (NAP) glass aqueous corrosion accounting for dissolution of radioactive glass and formation of corrosion products surface layer on the glass contacting ground water of a disposal environment. Modelling is used to process available experimental data demonstrating the generic inhibiting role of corrosion products on the NAP glass surface.

  17. 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.

  18. Secondary phase formation and the microstructural evolution of surface layers during vapor phase alteration of the French SON 68 nuclear waste glass at 200{degrees}C

    SciTech Connect

    Gong, W.L.; Ewing, R.C.; Wang, L.M.

    1995-12-31

    The SON 68 inactive {open_quotes}R7T7{close_quotes} composition is the French reference glass for the LWR nuclear waste glass. Vapor phase alteration was used to accelerate the reaction progress of glass corrosion and to develop the characteristic suite of secondary, alteration phases. Extensive solid-state characterization (AEM/SEM/HRTEM) was completed on six inactive R7T7 waste glasses which were altered in the presence of saturated water vapor (200{degrees}C) for 91, 241, 908, 1000, 1013, and 1021 days. The AEM samples were examined in cross-section (lattice-fringe imaging, micro-diffraction, and quantitative thin-film EDS analysis). The glass monoliths were invariably covered with a thin altered rind. The layer became thicker with time: 0.5 {mu}m for 22 days; 4 {mu}m for 91 days; 6 {mu}m for 241 days; 10 {mu}m for 908 days; 26 {mu}m for 1013 days; and <35 {mu}m for 1021 days. The composite alteration layer of the SON 68 samples is at least four time less thick than that of the SRL 131 glass composition. Six distinctive zones, based on phase chemistry and microstructure, were distinguished within the well-developed surface layers. Numerous crystalline phases such as analcime, tobermorite, apatite, and weeksite were identified on the surfaces of the reacted glasses as precipitates. Two crystalline phases, Ag{sub 2}TeO{sub 3} and (Ca,Sr)Mo{sub 3}O{sub 9}(OH){sub 2}, were found within the inner zones of surface layers, and they must have nucleated in situ, indicating that Ag, Te, Sr, and Mo can be retained within the surface layer. The majority of the surface layer volume is composed of two morphologically and chemically different structures: one consists of well-crystallized fibrous smectite aggregates occurring along with cavities, the A-domain; and the other consists of poorly-crystallized regions containing needle-like smectite (montmorillonite) crystallites, a silica-rich amorphous matrix, and possibly ZrO{sub 2} particles, the B-domain.

  19. 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.

  20. Zn incorporation and (CuIn)1-xZn2xSe2 thin film formation during the selenization of evaporated Cu and In precursors on Al:ZnO coated glass substrates

    NASA Astrophysics Data System (ADS)

    Guillén, C.; Herrero, J.

    2011-11-01

    CuInSe2 thin films with typical 1.0 eV gap energy and tetragonal chalcopyrite structure have been obtained on soda-lime glass substrates by the reaction of sequentially evaporated Cu and In layers with elemental selenium vapor, at 500 °C in flowing Ar. When analogous deposition and reaction processes were performed on Al:ZnO coated glasses, some increment in the band gap energy and diminution in the crystalline interplanar spacings have been detected for the resulting films with an extent that depends on the Cu/In atomic ratio of the evaporated precursor layers. This fact has been related to Zn incorporation into the selenized film, with quaternary (CuIn)1-xZn2xSe2 compound formation that is influenced by the presence of copper selenide phases during the reaction process. Such deductions are supported by the optical, structural and compositional characterizations that have been performed comparatively on samples prepared by selenization of evaporated metallic precursors with two different Cu/In ratios (0.9 and 1.1) on bare and Al:ZnO coated glass substrates.

  1. Degradable borate glass polyalkenoate cements.

    PubMed

    Shen, L; Coughlan, A; Towler, M; Hall, M

    2014-04-01

    Glass polyalkenoate cements (GPCs) containing aluminum-free borate glasses having the general composition Ag2O-Na2O-CaO-SrO-ZnO-TiO2-B2O3 were evaluated in this work. An initial screening study of sixteen compositions was used to identify regions of glass formation and cement compositions with promising rheological properties. The results of the screening study were used to develop four model borate glass compositions for further study. A second round of rheological experiments was used to identify a preferred GPC formulation for each model glass composition. The model borate glasses containing higher levels of TiO2 (7.5 mol %) tended to have longer working times and shorter setting times. Dissolution behavior of the four model GPC formulations was evaluated by measuring ion release profiles as a function of time. All four GPC formulations showed evidence of incongruent dissolution behavior when considering the relative release profiles of sodium and boron, although the exact dissolution profile of the glass was presumably obscured by the polymeric cement matrix. Compression testing was undertaken to evaluate cement strength over time during immersion in water. The cements containing the borate glass with 7.5 mol % TiO2 had the highest initial compressive strength, ranging between 20 and 30 MPa. No beneficial aging effect was observed-instead, the strength of all four model GPC formulations was found to degrade with time.

  2. 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.

  3. 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.

  4. In situ observation of the formation, diffusion, and reactions of hydrogenous species in F{sub 2}-laser-irradiated SiO{sub 2} glass using a pump-and-probe technique

    SciTech Connect

    Kajihara, Koichi; Hirano, Masahiro; Skuja, Linards; Hosono, Hideo

    2006-09-01

    We quantitatively studied the formation, diffusion, and reactions of mobile interstitial hydrogen atoms (H{sup 0}) and molecules (H{sub 2}) in F{sub 2}-laser-irradiated silica (SiO{sub 2}) glass between 10 and 330 K. Two key techniques were used: single-pulse F{sub 2} laser photolysis of silanol (SiOH) groups to selectively create pairs of H{sup 0} and oxygen dangling bonds (nonbridging oxygen hole centers, NBOHC), and in situ photoluminescence measurements of NBOHCs to monitor their reactions with H{sup 0} and H{sub 2} as a function of time and temperature. A smaller quantum yield of the photolysis of the SiO-H bond (0.15{+-}0.05) compared with values reported for gas molecules containing O-H bonds ({approx}1) suggests that the separation of photogenerated H{sup 0} from NBOHC is hindered by the cage effect of the SiO{sub 2} glass network. Distribution functions for the diffusion coefficients of H{sup 0} and H{sub 2} in the structurally disordered SiO{sub 2} glass were evaluated by numerical analysis of the concentration changes of NBOHC based on diffusion-limited reaction theory. The average diffusion coefficient of H{sub 2} obtained by integrating the distribution agrees well with the values measured by the permeation of H{sub 2} through SiO{sub 2} glass plates. In contrast, the average diffusion coefficient of H{sup 0} significantly decreases with time because the distribution of the diffusion coefficient of H{sup 0} is broad and H{sup 0}s with greater mobility disappear at a faster rate. We suggest that the efficient conversion of H{sup 0} into H{sub 2} in SiO{sub 2} glass is due to dissipation of the excess energy of the reaction intermediate via inelastic collisions with the glass network. The fraction of H{sup 0} that forms H{sub 2} is determined by the ratio of the capture radii of H{sup 0} and NBOHC, and it is independent of the diffusion coefficient and the initial concentration of H{sup 0}.

  5. 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…

  6. 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.

  7. 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

  8. Electrochromic Glasses.

    DTIC Science & Technology

    1980-07-31

    Li20-B203 and Na20-B203 or Te02 . These glasses exhibit for the first time, electrochromic and photochromic behaviour and have potential for use in...the complete spectral distribution of the absorption at levels of 10- cm- I for the first time. In the past, it was only possible to measure low...distribution of the absorption at levels at 10 -cm it was possible, for the first time, to identify extrinsic impurities in highly transparent solids. This

  9. Glass-formers vs. Assemblers

    NASA Astrophysics Data System (ADS)

    Glotzer, Sharon

    2015-03-01

    In most instances, the formation of a glass signifies an inability of the constituents of a system to self-organize into a well-defined, thermodynamically preferred ordered structure. Thus good ''assemblers'' may make poor glass-formers, and good glass-formers tend to be poor assemblers. How good or bad a system is in assembling or vitrifying/jamming depends on many features of the constituent building blocks, including shape and interactions. In many cases, building blocks whose shapes make them good glass-formers can, through almost imperceptible perturbations, become good assemblers, and vice versa. We examine these issues through consideration of several model systems, including colloidal ''rocks'' and foldable nets. *with E.R. Chen, P. Damasceno, P. Dodd, M. Engel, A.S. Keys, D. Klotsa, E. Teich, and G. van Anders

  10. 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.

  11. 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.

  12. 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

    2016-05-07

    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.

  13. 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.

  14. 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.

  15. Petrography and geochemistry of achnelithic tephra from Las Herrerías Volcano (Calatrava volcanic field, Spain): Formation of nephelinitic achneliths and post-depositional glass alteration

    NASA Astrophysics Data System (ADS)

    Carracedo-Sánchez, M.; Sarrionandia, F.; Arostegui, J.; Errandonea-Martin, J.; Gil-Ibarguchi, J. I.

    2016-11-01

    We present the results of a petrographic and geochemical study carried out on a layer of achnelithic tephra outcropping at the base of the volcanic cone of Las Herrerías (Miocene-Quaternary volcanic region of Campo de Calatrava, Spain). The tephra, with a composition of nephelinite and ash (< 1 mm) to coarse lapilli (ca. 1 cm) in size, is made of intact isolated achneliths (mostly elongated and spheroidal, including Pele's tears), achnelith fragments and rare welded achneliths. The achneliths at Las Herrerías were generated in a gas-rich fire fountain that fragmented the magma into micro- to nanometre particles. The low viscosity of the nephelinitic blebs (< 1235 Pa.s) inside the hottest (ca. 900 °C), inner zone of the fountain allowed the development of the characteristic fluidal shapes of these pyroclasts and their welding above the glass transition temperature (533-669 °C). The sideromelane glass of the achneliths, also nephelinitic in composition, is variably altered to palagonite. The palagonitization was isovolumetric and took place in a near closed system at the achnelith scale. Palagonitization involved depletion in the concentration (g/cm3) of all major elements and notable increase in H2O content. The elements liberated by this process formed smectite with an average structural formula comprised between those of beidellite and nontronite end terms: (Na0.01K0.03Ca0.18) (Mg0.22Fe0.16)2 + (Fe0.48Al1.02)3 + (Ti0.18)4 + (Si3.58Al0.42) O10(OH)2. The degree of palagonitization in each achnelith was likely related to the amount of water incorporated by individual clasts at the moment of their deposition in a volcanic maar lake. Afterwards, there was no more water circulation through the achnelithic tephra, which was sealed from water by overlying hydrovolcanic tuff deposits. It was this isolation that made possible the preservation of glass to the present day.

  16. 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.

  17. 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.

  18. On formation of CaO-Al(2)O(3)-SiO2 glass-ceramics by vitrification of incinerator fly ash.

    PubMed

    Cheng, T W; Chen, Y S

    2003-06-01

    CaO-Al(2)O(3)-SiO(2) system glass ceramics of incinerator fly ash have been prepared by vitrification and then heat-treated in different conditions. The thermal molten process (TMP) was applied to heat treat vitrified samples at high temperatures whereas in the powder sintering process water-quenched vitrified samples were ground into powder and then sintered at high temperatures. Gehlenite was found present as the major phase in all treated samples. Treated samples in general exhibited good leachability characteristics as well as chemical durability, except in the HCl solution. Microstructure and physical properties varied with the treatment condition. Fine and relatively high dense structures with desirable properties were obtained for samples treated by the TMP. For both processes, higher temperature treatments caused crystal growth and thus poor properties were attained. Good physical and mechanical properties achieved at 900-950 degrees C in this study imply the treated samples have attractive potential for engineering applications.

  19. 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.

  20. 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.

  1. 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

    2011-09-06

    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.

  2. 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.

  3. GlassForm

    SciTech Connect

    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-day product consistency test (PCT).

  4. Stress enhanced self-diffusion in Si: Entropy effect in anisotropic elastic environment

    NASA Astrophysics Data System (ADS)

    Rushchanskii, Konstantin Z.; Pochet, Pascal; Lançon, Frédéric

    2008-04-01

    We present a multiscale analysis on stress enhanced vacancy-mediated diffusion in strained Si that explicitly includes the Jahn-Teller structural distortion around vacancies. The resulting anisotropy combined with biaxial deformations applied to (100)-oriented films lead to an orientational dependency of the vacancy formation energy. At finite temperatures, it results in a strong entropy effect when thermal activation allows occupancy of high energy defect states. Kinetic Lattice Monte Carlo simulations reveal that the effective activation energy is a strongly nonlinear function of strain at small deformations. At larger deformations, it becomes linear where as the occupancy of the excited states becomes insignificant.

  5. Structure and magnetism of low-doped monoclinic crystals of (Ga{sub 1-x}Mn{sub x}){sub 2}Se{sub 3}

    SciTech Connect

    Dubinin, S. F. Maksimov, V. I.; Parkhomenko, V. D.

    2011-12-15

    The influence that doping with Mn{sup 3+} ions has on the fine crystal structure of the monoclinic compound Ga{sub 2}Se{sub 3} was studied by single-crystal neutron diffraction and the measurements of magnetic properties. It was found that the structural state of the crystals changes even at relatively low doping levels (x = 0.04). Local Jahn-Teller distortions were shown to be responsible for the formation of the fine structure and magnetism in this type of compounds.

  6. 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

  7. Strength of inorganic glass

    SciTech Connect

    Kurkjian, C.R.

    1985-01-01

    This book presents information on the following topics: a look at the history of glass strength; atomistic theory of fracture; surface chemistry in relation to the strength and fracture of silicate glasses; high-speed photographic investigations of the dynamic localized loading of some oxide glasses; a correction for measurements of contact area using Newton's rings; envionmentally enhanced crack growth; fatigue in glass; behavior of flaws in fused silica fibers; fracture toughness of chalcogenide glasses and glass-ceramics; fracture analysis of glass surfaces; and fracture mechanics parameters for glasses - a compilation and correlation.

  8. 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.

  9. Luminescent properties of cadmium selenide quantum dots in fluorophosphate glasses

    NASA Astrophysics Data System (ADS)

    Lipatova, Zh. O.; Kolobkova, E. V.; Babkina, A. N.

    2016-11-01

    The optical properties of fluorophosphate glasses with CdSe quantum dots are studied. Secondary heat treatment at a temperature exceeding the glass transition temperature resulted in the formation of quantum dots with sizes of 3.7-6.2 nm. The influence of the semiconductor component concentration on the spectral-luminescent characteristics of glasses is shown. It is experimentally demonstrated that glasses with a lower CdSe concentration have a higher absolute luminescence quantum yield.

  10. 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.

  11. 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.

  12. 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

  13. 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)

  14. Chemical constraints on fly ash glass compositions

    SciTech Connect

    John H. Brindle; Michael J. McCarthy

    2006-12-15

    The major oxide content and mineralogy of 75 European fly ashes were examined, and the major element composition of the glass phase was obtained for each. Correlation of compositional trends with the glass content of the ash was explored. Alkali content was deduced to have a major influence on glass formation, and this in turn could be related to the probable chemistry of clay minerals in the source coals. Maximal glass content corresponded to high aluminum content in the glass, and this is in accordance with the theoretical mechanism of formation of aluminosilicate glasses, in which network-modifying oxides are required to promote tetrahedral coordination of aluminum in glass chain structures. Iron oxide was found to substitute for alkali oxides where the latter were deficient, and some indications of preferred eutectic compositions were found. The work suggests that the proportion of the glass phase in the ash can be predicted from the coal mineralogy and that the utility of a given ash for processing into geopolymers or zeolites is determined by its source. 23 refs., 7 figs., 1 tab.

  15. 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.

  16. Hydration process of nuclear-waste glass: an interim report

    SciTech Connect

    Bates, J.K.; Jardine, L.J.; Steindler, M.J.

    1982-07-01

    Aging of simulated nuclear waste glass by contact with a controlled-temperature, humid atmosphere results in the formation of a double hydration layer penetrating the glass, as well as the formation of minerals on the glass surface. The hydration process can be described by Arrhenius behavior between 120 and 240/sup 0/C. Results suggest that simulated aging reactions are necessary for demonstrating that nuclear waste forms can meet projected Nuclear Regulatory Commission regulations. 16 figures, 4 tables.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Collescipoli - An unusual fusion crust glass. [chondrite

    NASA Technical Reports Server (NTRS)

    Nozette, S.

    1979-01-01

    An electron microprobe study was conducted on glass fragments taken from the fusion crust and an internal glass-lined vein in the H-5 chondrite Collescipoli. Microprobe analyses of the glasses revealed an unusual fusion crust composition, and analyses of glass from inside the meteorite showed compositions expected for a melt of an H-group chondrite. Studies of fusion crusts by previous workers, e.g., Krinov and Ramdohr, showed that fusion crusts contain large amounts of magnetite and other oxidized minerals. The Collescipoli fusion crusts do contain these minerals, but they also contain relatively large amounts of reduced metal, sulphide, and a sodium-rich glass. This study seems to indicate that Collescipoli preserved an early type of fusion crust. Oxidation was incomplete in the fusion crust melt that drained into a crack. From this study it is concluded that fusion crust formation does not invariably result in complete oxidation of metal and sulphide phases.

  2. 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.

  3. 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.

  4. Glasses in the D'Orbigny angrite

    NASA Astrophysics Data System (ADS)

    Varela, Maria Eugenia; Kurat, Gero; Zinner, Ernst; Métrich, Nicole; Brandstätter, Franz; Ntaflos, Theodoros; Sylvester, Paul

    2003-12-01

    The angrites are a small and heterogeneous group of achondritic meteorites with highly unusual chemical and mineralogical features. The abundant presence of glasses in D'Orbigny makes this rock a unique member of the angrite group. Glasses fill open spaces, form pockets, and occur as inclusions in olivines. Their physical settings exclude an incorporation from an external source. Major and trace element (rare earth elements [REE], Li, B, Be, transition elements, N and C) contents of these glasses and host olivines were measured combining laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), secondary-ion mass spectrometry (SIMS), Nuclear Reaction Analysis (NRA), and EMP techniques. Based on the major element composition, glasses filling voids could represent either a melt formed by melting an angritic rock or a melt from which angrites could have crystallized. Trace element contents of these glasses strongly indicate a direct link to the D'Orbigny bulk meteorite. They are incompatible with the formation of the glasses by partial melting of a chondritic source rock or by shock melting. The refractory elements (e.g., Al, Ti, Ca) have about 10 × CI abundances with CaO/TiO 2 and FeO/MnO ratios being approximately chondritic. Trace element abundances in the glasses appear to be governed by volatility and suggest that the refractory elements in the source had chondritic relative abundances. Although the glasses (and the whole rock) lack volatile elements such as Na and K, they are rich in some moderately volatile elements such as B, V, Mn, Fe (all with close to CI abundances), and Li (about 3-5 × CI). These elements likely were added to the glass in a sub-solidus metasomatic elemental exchange event. We have identified a novel mechanism for alteration of glass and rock compositions based on an exchange of Al and Sc for Fe and other moderately volatile elements in addition to the well-known metasomatic exchange reactions (e.g., Ca-Na and Mg

  5. 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).

  6. Strain accommodation in inelastic deformation of glasses

    SciTech Connect

    Murali, P.; Ramamurty, U.; Shenoy, Vijay B.

    2007-01-01

    Motivated by recent experiments on metallic glasses, we examine the micromechanisms of strain accommodation including crystallization and void formation during inelastic deformation of glasses by employing molecular statics simulations. Our atomistic simulations with Lennard-Jones-like potentials suggests that a softer short range interaction between atoms favors crystallization. Compressive hydrostatic strain in the presence of a shear strain promotes crystallization whereas a tensile hydrostatic strain is found to induce voids. The deformation subsequent to the onset of crystallization includes partial reamorphization and recrystallization, suggesting important atomistic mechanisms of plastic dissipation in glasses.

  7. '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.

  8. 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.

  9. 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

  10. 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.

  11. Interaction between bioactive glasses and human dentin.

    PubMed

    Efflandt, S E; Magne, P; Douglas, W H; Francis, L F

    2002-06-01

    This study explores the interaction between bioactive glasses and dentin from extracted human teeth in simulated oral conditions. Bioactive glasses in the Na(2)O-CaO-P(2)O(5)-SiO(2) and MgO-CaO-P(2)O(5)-SiO(2) systems were prepared as polished disks. Teeth were prepared by grinding to expose dentin and etching with phosphoric acid. A layer of saliva was placed between the two, and the pair was secured with an elastic band and immersed in saliva at 37 degrees C for 5, 21 or 42 days. The bioactive glasses adhered to dentin, while controls showed no such interaction. A continuous interface between the bioactive glass and dentin was imaged using cryogenic-scanning electron microscopy (SEM). However, after alcohol dehydration and critical point drying, fracture occurred due to stresses from dentin shrinkage. SEM investigations showed a microstructurally different material at the fractured interface. Chemical analyses revealed that ions from the glass penetrated into the dentin and that the surface of the glass in contact with the dentin was modified. Microdiffractometry showed the presence of apatite at the interface. Bonding appears to be due to an affinity of collagen for the glass surface and chemical interaction between the dentin and glass, leading to apatite formation at the interface.

  12. Magnetic Excitations in the Stacked Quantum Magnets NaNiO2 and LiNiO2

    NASA Astrophysics Data System (ADS)

    Clancy, J. P.; Gaulin, B. D.; Ruff, J. P. C.; Ross, K. A.; van Gastel, G. J.; Abernathy, D. L.; Stone, M. B.

    2009-03-01

    NaNiO2 and LiNiO2 are isostructural stacked triangular lattice quantum magnets, in which magnetism is conventionally thought to arise due to spin 1/2 moments carried by Ni^3+ ions. Surprisingly, while NaNiO2 undergoes a cooperative Jahn-Teller transition at 480K and magnetically orders below TN ˜ 23K, LiNiO2 undergoes a glass transition at Tg ˜ 9K and remains disordered down to the lowest measured temperatures. The absence of long-range magnetic order in LiNiO2 has been attributed to either geometric frustration caused by mixing of the Li and Ni sublattices, or orbital degeneracy due to the absence of a coherent Jahn-Teller distortion. We have performed time of flight neutron scattering measurements on polycrystalline samples of NaNiO2 and LiNiO2 using the wide Angular-Range Chopper Spectrometer (ARCS) at the SNS. Our measurements reveal previously unobserved magnetic excitations at relatively high energy transfers, which we associate with ferromagnetic spin waves mediated by in-plane interactions. We also find evidence of critical scattering in NaNiO2 near the magnetic phase transition at TN. These results will be compared with previous measurements collected using the DCS at NIST.

  13. The photoexcited triplet state as a probe of chromophore-protein interaction in myoglobin.

    PubMed Central

    Angiolillo, P J; Vanderkooi, J M

    1998-01-01

    The photoexcited metastable triplet state of Mg(2+)-mesoporphyrin IX (MgMPIX) or Mg(2+)-protoporphyrin IX (MgPPIX) located in the heme pocket of horse myoglobin (Mb) was investigated by optical and electron paramagnetic resonance (EPR) spectroscopy, and its properties were compared with the model complexes, MgMPIX, MgPPIX, and Mg2+ etioporphyrin I (MgETIOI), in noncoordinating and coordinating organic glasses. Zero-field splitting parameters, line shape, and Jahn-Teller distortion in the temperature range of 3.8-110 K are discussed in terms of porphyrin-protein interactions. The triplet line shapes for MgMPIXMb and MGPPIXMb show no temperature-dependent spectral line shape changes suggestive of Jahn-Teller dynamics, and it is concluded that the energy splitting is >> 150 cm-1, suggesting symmetry breaking from the anisotropy of intermal electric fields of the protein, and consistent with previous predictions (Geissinger et al. 1995. J. Phys. Chem. 99:16527-16529). Both MgMPIXMb and MgPPIXMb demonstrate electron spin polarization at low temperature, and from the polarization pattern it can be concluded that intersystem crossing occurs predominantly into in-plane spin sublevels of the triplet state. The splitting in the Q0.0 absorption band and the temperature dependence and splitting of the photoexcited triplet state of myoglobin in which the iron was replaced by Mg2+ are interpreted in terms of effects produced by electric field asymmetry in the heme pocket. PMID:9726951

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  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. Failure in glass

    NASA Technical Reports Server (NTRS)

    Keeton, S. C.

    1972-01-01

    Review of state of the art concerning glass failure mechanisms and fatigue theories discusses brittle fracture in glass, fatigue mechanisms, fatigue behavior, environmental effects on failure rate, and aging.

  1. Design of Bulk Metallic Glasses and Glass Matrix Composites Near Intermetallic Composition by the Principle of Competitive Growth

    NASA Astrophysics Data System (ADS)

    Ma, G. Z.; Chen, D.

    2016-11-01

    A Cu49Zr51 intermetallic is used as a base for synthesizing metallic glasses and composites with glass matrixes [(Cu49Zr51)100 - x Al x , where x = 0, 2, 4, 6, 8, 10 and 12 at.%]. The introduction of aluminum raises the microhardness and the ultimate compressive strength. In addition, the suppression of formation of crystalline phase upon the introduction of 8 at.% Al provides a glass-like structure in alloy (Cu49Zr51)92Al8. The formation of the glass-like structure is discussed within the concept of competitive nucleation of different intermetallics.

  2. Weakly supervised glasses removal

    NASA Astrophysics Data System (ADS)

    Wang, Zhicheng; Zhou, Yisu; Wen, Lijie

    2015-03-01

    Glasses removal is an important task on face recognition, in this paper, we provide a weakly supervised method to remove eyeglasses from an input face image automatically. We choose sparse coding as face reconstruction method, and optical flow to find exact shape of glasses. We combine the two processes iteratively to remove glasses more accurately. The experimental results reveal that our method works much better than these algorithms alone, and it can remove various glasses to obtain natural looking glassless facial images.

  3. Containerless Processing of a Lithium Disilicate Glass

    NASA Technical Reports Server (NTRS)

    Ranasinghe, Kisa; Ray, Chandra S.; Day, Delbert E.; Rogers, Jan R.; Hyers, Robert W.; Rathz, Thomas

    2004-01-01

    Glasses of Li2O.2SiO2 (LS2), and LS2 doped with 0.001wt% platinum (LS2 + 0.001 wt% Pt) compositions were melted, cooled and reheated at controlled rates while levitated (containerless) inside an Electrostatic Levitator (ESL) furnace at the NASA Marshall Space Flight Center, Huntsville, AL. The experiments were conducted in vacuum (approximately 10(exp -5) Pa) using spherical, 2.5 to 3 millimeter diameter, glass samples. The measured critical cooling rate for glass formation, R(sub c), for the LS2 and LS2+0.001 wt% Pt glasses processed at ESL were 14 plus or minus 2 Celsius per minute and 130 plus or minus 5 Celsius per minute, respectively. The values of R(sub c), for the same LS2 and LS2 + 0.001 wt% Pt glasses processed in a container were 62 plus or minus 3 Celsius per minute and 162 plus or minus 5 Celsius per minute, respectively. The effective activation energy for crystallization, E, for this LS2 glass processed without a container at ESL, 392 plus or minus 15 kiloJoules per mole, was higher than that, 270 plus or minus 15 kiloJoules per mole, for an identical glass processed in a container. These results suggest that the glass formation tendency for a containerless LS2 melt is significantly increased compared to an identical melt in contact with a container. The absence of heterogeneous nucleation sites that are inherently present in all melts held in containers, and or a change in the surface composition due to evaporation of Li2O during processing at ESL are likely reasons for the increased glass forming tendency of this containerless LS2 melt.

  4. 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.

  5. 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…

  6. 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

  7. 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.

  8. 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.

  9. A predictive structural model for bulk metallic glasses.

    PubMed

    Laws, K J; Miracle, D B; Ferry, M

    2015-09-15

    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.

  10. Application of the model of delocalized atoms to metallic glasses

    NASA Astrophysics Data System (ADS)

    Sanditov, D. S.; Darmaev, M. V.; Sanditov, B. D.

    2017-01-01

    The parameters of the model of delocalized atoms applied to metallic glasses have been calculated using the data on empirical constants of the Vogel-Fulcher-Tammann equation (for the temperature dependence of viscosity). It has been shown that these materials obey the same glass-formation criterion as amorphous organic polymers and inorganic glasses. This fact qualitatively confirms the universality of the main regularities of the liquid-glass transition process for all amorphous materials regardless of their origin. The energy of the delocalization of an atom in metallic glasses, Δɛ e ≈ 20-25 kJ/mol, coincides with the results obtained for oxide inorganic glasses. It is substantially lower than the activation energies for a viscous flow and for ion diffusion. The delocalization of an atom (its displacement from the equilibrium position) for amorphous metallic alloys is a low-energy small-scale process similar to that for other glass-like systems.

  11. 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.

  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. 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.

  14. 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.

  15. 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.

  16. Developing photorefractive glass composites

    NASA Astrophysics Data System (ADS)

    Duignan, Jason P.; Taylor, Lesley L.; Cook, Gary

    2002-01-01

    The production of a transparent photorefractive glass composite would offer a useful alternative to bulk crystal materials. We aim to produce such a material by incorporating single domain photorefractive Fe:LiNbO3 particles into a refractive index matched glass host. This glass host is also required to be chemically compatible with the photorefractive material. This compatibility will ensure that the Fe:LiNbO3 particles added to the host glass will remain in the intended crystalline phase and not simply dissolve in the glass. Due to the high refractive index of the Fe:LiNbO3 (no equals 2.35 532 nm), producing a chemically compatible and refractive index matched glass host is technically challenging. By examining common Tellurite, Bismuthate, and Gallate glasses as a starting point and then developing new and hybrid glasses, we have succeeded in producing a chemically compatible glass host and also a refractive index matched glass host. We have produced preliminary glass composite samples which contain a large amount of Fe:LiNbO3. We are currently able to retain nearly 90% of the incorporated Fe:LiNbO3 in the correct crystalline phase, a substantial improvement over previous work conducted in this area in recent years. In this paper we present our progress and findings in this area.

  17. 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 .

  18. 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.

  19. Acoustics of glass harmonicas

    NASA Astrophysics Data System (ADS)

    Rossing, Thomas D.

    2004-05-01

    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.

  20. 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.

  1. Topological principles of borosilicate glass chemistry.

    PubMed

    Smedskjaer, Morten M; Mauro, John C; Youngman, Randall E; Hogue, Carrie L; Potuzak, Marcel; Yue, Yuanzheng

    2011-11-10

    Borosilicate glasses display a rich complexity of chemical behavior depending on the details of their composition and thermal history. Noted for their high chemical durability and thermal shock resistance, borosilicate glasses have found a variety of important uses from common household and laboratory glassware to high-tech applications such as liquid crystal displays. In this paper, we investigate the topological principles of borosilicate glass chemistry covering the extremes from pure borate to pure silicate end members. Based on NMR measurements, we present a two-state statistical mechanical model of boron speciation in which addition of network modifiers leads to a competition between the formation of nonbridging oxygen and the conversion of boron from trigonal to tetrahedral configuration. Using this model, we derive a detailed topological representation of alkali-alkaline earth-borosilicate glasses that enables the accurate prediction of properties such as glass transition temperature, liquid fragility, and hardness. The modeling approach enables an understanding of the microscopic mechanisms governing macroscopic properties. The implications of the glass topology are discussed in terms of both the temperature and thermal history dependence of the atomic bond constraints and the influence on relaxation behavior. We also observe a nonlinear evolution of the jump in isobaric heat capacity at the glass transition when substituting SiO(2) for B(2)O(3), which can be accurately predicted using a combined topological and thermodynamic modeling approach.

  2. Influence of glass composition on the properties of glass polyalkenoate cements. Part III: influence of fluorite content.

    PubMed

    De Barra, E; Hill, R G

    2000-03-01

    The influence of fluorite content of the glass on the formation and properties of glass polyalkenoate cements was investigated. A series of glass powders based on 1.5SiO2 x 0.5P2O5 x Al2O3 x CaO x XCaF2 were synthesised. The glass transition temperature of the glass fell with increasing fluorite content. Setting and working times of the cement pastes decreased with increasing fluorite content of the glass. Compressive strength and un-notched fracture strength increased with increasing fluorite content of the glass. Fracture toughness and toughness of the cements were relatively insensitive to fluorite content.

  3. In-vitro bioactivity of zirconia doped borosilicate glasses

    SciTech Connect

    Samudrala, Rajkumar; Azeem, P. Abdul E-mail: drazeem2002@yahoo.com

    2015-06-24

    Glass composition 31B{sub 2}O{sub 3}-20SiO{sub 2}-24.5Na{sub 2}O-(24.5-x) CaO-xZrO{sub 2} x=1,2,3,4,5 were prepared by melt-quenching Technique. The formation of hydroxyapatite layer on the surface of glasses after immersion in simulated body fluid (SBF) was explored through XRD, Fourier transform infrared (FTIR) and Scanning electron microscopy (SEM-EDX) analyses. In this report, we observed that hydroxyapatite formation for 5days of immersion time. Also observed that with increasing the immersion time up to 15days, higher amount of hydroxyapatite layer formation on the surface of glasses. The varying composition of zirconia in glass samples influences shown by XRD, FTIR studies. The present results indicate that, in-vitro bioactivity of glasses decreased with increasing zirconia incorporation.

  4. Quenching Effects on Iron Site Partitioning in the Apollo 17 Orange Glass Composition

    NASA Technical Reports Server (NTRS)

    Dyar, M. D.

    1985-01-01

    Mare petrogenesis and the structure of the lunar interior were studied. Analyses of the spectral signatures of glasses was useful to remote sensing applications in areas of the moon where glass is in significant proportions in the lunar soil. The studies provided information on Fe site occupancies in glasses, which are used to construe oxygen fugacities at the lunar surface. Data were obtained through work on synthetic analogues of lunar glasses. However, recent Mossbauer studies of an Apollo 15 green glass composition have shown that synthetic glasses are extremely sensitive to variations in quenching media. Glass structure and Fe(3+)/Fe(2+) ratios are strongly controlled by quenching conditions, which may mask the effects of the original glass' formation temperature or oxygen partial pressure. Synthetic glasses were often run at low fugacities on Pt wires. The effects of quench media on the Apollo 17 orange glass composition are considered.

  5. Computational studies of the glass-forming ability of model bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Wang, Minglei; Papanikolaou, Stefanos; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D.; O'Hern, Corey S.

    2013-09-01

    Bulk metallic glasses (BMGs) are produced by rapidly thermally quenching supercooled liquid metal alloys below the glass transition temperature at rates much faster than the critical cooling rate Rc below which crystallization occurs. The glass-forming ability of BMGs increases with decreasing Rc, and thus good glass-formers possess small values of Rc. We perform molecular dynamics simulations of binary Lennard-Jones (LJ) mixtures to quantify how key parameters, such as the stoichiometry, particle size difference, attraction strength, and heat of mixing, influence the glass-formability of model BMGs. For binary LJ mixtures, we find that the best glass-forming mixtures possess atomic size ratios (small to large) less than 0.92 and stoichiometries near 50:50 by number. In addition, weaker attractive interactions between the smaller atoms facilitate glass formation, whereas negative heats of mixing (in the experimentally relevant regime) do not change Rc significantly. These results are tempered by the fact that the slowest cooling rates achieved in our simulations correspond to ˜1011 K/s, which is several orders of magnitude higher than Rc for typical BMGs. Despite this, our studies represent a first step in the development of computational methods for quantitatively predicting glass-formability.

  6. Computational studies of the glass-forming ability of model bulk metallic glasses.

    PubMed

    Zhang, Kai; Wang, Minglei; Papanikolaou, Stefanos; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D; O'Hern, Corey S

    2013-09-28

    Bulk metallic glasses (BMGs) are produced by rapidly thermally quenching supercooled liquid metal alloys below the glass transition temperature at rates much faster than the critical cooling rate R(c) below which crystallization occurs. The glass-forming ability of BMGs increases with decreasing R(c), and thus good glass-formers possess small values of R(c). We perform molecular dynamics simulations of binary Lennard-Jones (LJ) mixtures to quantify how key parameters, such as the stoichiometry, particle size difference, attraction strength, and heat of mixing, influence the glass-formability of model BMGs. For binary LJ mixtures, we find that the best glass-forming mixtures possess atomic size ratios (small to large) less than 0.92 and stoichiometries near 50:50 by number. In addition, weaker attractive interactions between the smaller atoms facilitate glass formation, whereas negative heats of mixing (in the experimentally relevant regime) do not change R(c) significantly. These results are tempered by the fact that the slowest cooling rates achieved in our simulations correspond to ~10(11) K/s, which is several orders of magnitude higher than R(c) for typical BMGs. Despite this, our studies represent a first step in the development of computational methods for quantitatively predicting glass-formability.

  7. 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

  8. 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.

  9. 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.

  10. Reversing Glass Wettability

    NASA Technical Reports Server (NTRS)

    Frazier, D. O.; Smith, J. E., Jr.; Kaukler, W. F.

    1985-01-01

    Treatment reverses wettability of glassware: Liquids that normally wet glass no longer do, and those that do not wet glass are made to do so. Useful in research on container effects in nucleation and growth of secondary phase from solution. Treatment consists of spreading 3 percent (by weight) solution of silicone oil in hexane isomers over glass, drying in air, and curing at 300 degrees C in vacuum for one hour.

  11. 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

  12. 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

  13. 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.

  14. Chalcogenide glass microsphere laser.

    PubMed

    Elliott, Gregor R; Murugan, G Senthil; Wilkinson, James S; Zervas, Michalis N; Hewak, Daniel W

    2010-12-06

    Laser action has been demonstrated in chalcogenide glass microsphere. A sub millimeter neodymium-doped gallium lanthanum sulphide glass sphere was pumped at 808 nm with a laser diode and single and multimode laser action demonstrated at wavelengths between 1075 and 1086 nm. The gallium lanthanum sulphide family of glass offer higher thermal stability compared to other chalcogenide glasses, and this, along with an optimized Q-factor for the microcavity allowed laser action to be achieved. When varying the pump power, changes in the output spectrum suggest nonlinear and/or thermal effects have a strong effect on laser action.

  15. Photoprotection: clothing and glass.

    PubMed

    Almutawa, Fahad; Buabbas, Hanan

    2014-07-01

    Ultraviolet (UV) radiation (UVR) has well-known adverse effects on the skin and eyes. Little attention is given to physical means of photoprotection, namely glass, window films, sunglasses, and clothing. In general, all types of glass block UV-B. For UV-A, the degree of transmission depends on the type, thickness, and color of the glass. Adding window films to glass can greatly decrease the transmission of UV-A. Factors that can affect the transmission of UVR through cloth include tightness of weave, thickness, weight, type of fabrics, laundering, hydration, stretch, fabric processing, UV absorbers, color, and fabric-to-skin distance.

  16. 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.

  17. 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.

  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. Fast Surface Dynamics of Metallic Glass Enable Superlatticelike Nanostructure Growth

    NASA Astrophysics Data System (ADS)

    Chen, L.; Cao, C. R.; Shi, J. A.; Lu, Z.; Sun, Y. T.; Luo, P.; Gu, L.; Bai, H. Y.; Pan, M. X.; Wang, W. H.

    2017-01-01

    Contrary to the formation of complicated polycrystals induced by general crystallization, a modulated superlatticelike nanostructure, which grows layer by layer from the surface to the interior of a Pd40Ni10Cu30P20 metallic glass, is observed via isothermal annealing below the glass transition temperature. The generation of the modulated nanostructure can be solely controlled by the annealing temperature, and it can be understood based on the fast dynamic and liquidlike behavior of the glass surface. The observations have implications for understanding the glassy surface dynamics and pave a way for the controllable fabrication of a unique and sophisticated nanostructure on a glass surface to realize the properties' modification.

  20. Theoretical study of production of unique glasses in space

    NASA Technical Reports Server (NTRS)

    Larsen, D. C.

    1974-01-01

    Analytical functional relationships describing homogeneous nucleation and crystallization in various supercooled liquids were developed. The time and temperature dependent relationships of nucleation and crystallization (intrinsic properties) are being used to relate glass forming tendency to extrinsic parameters such as cooling rate through computer simulation. Single oxide systems are being studied initially to aid in developing workable kinetic models and to indicate the primary materials parameters affecting glass formation. The theory and analytical expressions developed for simple systems is then extended to complex oxide systems. A thorough understanding of nucleation and crystallization kinetics of glass forming systems provides a priori knowledge of the ability of a given system to form a glass.

  1. 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.

  2. Structure-property relations in lanthanide borate glasses

    NASA Technical Reports Server (NTRS)

    Chakraborty, I. N.; Day, D. E.; Lapp, J. C.; Shelby, J. E.

    1985-01-01

    Glass formation in the system Ln2O3-B2O3 (Ln = Nd, Sm) was studied. Glasses could be formed in the range from 0 to 28 mol pct rare-earth oxide (Ln2O3), but liquid immiscibility in these systems limits the range of homogeneous glasses to 0 to 1.5 and 25 to 28 mol pct Ln2O3. The infrared spectra indicate that the rare-earth-rich glasses are structurally similar to rare-earth metaborates (LnB3O6) which contain (B3O6)-infinity chains. The variation in density, transformation temperature, thermal expansion coefficient, and transformation-range viscosity of these glasses with the size of the rare-earth ion is discussed. Glasses near the metaborate composition have a transformation temperature of about 700 C, which is high for binary borate glasses. Glasses could not be formed in the systems Eu2O3-, Gd2O3-, Ho2O3-, and Er2O3-B2O3, even by quenching at 1300 C/s. The sudden lack of glass formation in the system Ln2O3-B2O3 with Ln(3+) ions smaller than Sm(3+) is explained on the basis of the size effect of the Ln(3+) ion on the stability of (B3O6)-infinity chains in these metaborates.

  3. 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.

  4. Surface modification of bioactive glasses and preparation of PDLLA/bioactive glass composite films.

    PubMed

    Gao, Yuan; Chang, Jiang

    2009-08-01

    In order to improve the homogeneous dispersion of particles in the polymeric matrix, 45S5, mesoporous 58S, and 58S bioactive glasses were surface modified by esterification reactions with dodecyl alcohol at reflux temperature of 260 degrees C (named as m-45S5, m-mesoporous 58S, and m-58S, respectively). The modified particles showed better hydrophobicity and longer time of suspension in organic matrix. The PDLLA/bioactive glass composite films were fabricated using surface modified bioactive glass particles through solvent casting-evaporation method. Surface morphology, mechanical property, and bioactivity were investigated. The results revealed that the inorganic particle distribution and tensile strength of the composite films with modified bioactive glass particles were significantly improved while great bioactive properties were maintained. Scanning electron microscopy (SEM) observation illustrated that the modified bioactive glass particles were homogeneously dispersed in the PDLLA matrix. The maximum tensile strengths of composite films with modified bioactive glass particles were higher than that of composite films with unmodified bioactive glass particles. The bioactivity of the composite films were evaluated by being soaked in the simulated body fluid (SBF) and the SEM observation of the films suggested that the modified composite films were still bioactive in that they could induce the formation of HAp on its surface and the distribution of HAp was even more homogeneous on the film. The results mentioned above indicated that the surface modification of bioactive glasses with dodecyl alcohol was an effective method to prepare PDLLA/bioactive glass composites with enhanced properties. By studying the comparisons of modification effects among the three types of bioactive glasses, we could get the conclusion that the size and morphology of the inorganic particles would greatly affect the modification effects and the properties of composites.

  5. Rare Earth Phosphate Glass and Glass-Ceramic Proton Conductors

    SciTech Connect

    De Jonghe, Lutgard C.; Ray, Hannah L.; Wang, Ruigang

    2008-12-03

    The structure and conductivity of cerium and lanthanum phosphate glasses and glass-ceramics were investigated. The effects of varying the metal to phosphate ratio in the glasses, doping LaP3O9 glasses with Ce, and recrystallization of CeP3O9 glasses, on the glasses' microstructure and total conductivity were investigated using XRD, SEM, and AC impedance techniques. Strong increases in conductivity occurred when the glasses were recrystallized: the conductivity of a cerium metaphosphate glass increased conductivity after recrystallization from 10-7.5 S/cm to 10-6 S/cm at 400oC.

  6. Lanthanoides in Glass and Glass Ceramics

    NASA Astrophysics Data System (ADS)

    Meinhardt, Jürgen; Kilo, Martin; Somorowsky, Ferdinand; Hopp, Werner

    2017-03-01

    Many types of glass contain lanthanoides; among them, special glass for optical applications is the one with the highest content of lanthanoides. The precise determination of the lanthanoides' concentration is performed by inductively coupled plasma-optical emission spectrometry (ICP-OES). However, up to now, there are no established standard processes guaranteeing a uniform approach to the lanthanoide analysis. The knowledge of the lanthanoides' concentrations is necessary on the microscale in some cases, especially if a suitable separation and recycling procedure is to be applied. Here, the analysis is performed by energy-dispersive X-ray (EDX) or wavelength-dispersive X-ray (WDX) analytics in the scanning electron microscope.

  7. 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.

  8. 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…

  9. Glasses and Contact Lenses

    MedlinePlus

    ... about special eyewear you can wear on the field. With glasses, you'll also want to find out how to clean them properly. And it helps if you have a glasses case and put them in it when you're not wearing them. The last thing you want is to sit on your ...

  10. Glasses and Contact Lenses

    MedlinePlus

    ... dientes Video: Getting an X-ray Glasses and Contact Lenses KidsHealth > For Kids > Glasses and Contact Lenses Print A A A What's in this ... together the way they should. But eyeglasses or contact lenses, also called corrective lenses, can help most ...

  11. 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)

  12. Dramatic Stained Glass.

    ERIC Educational Resources Information Center

    Prater, Michael

    2002-01-01

    Describes an art project that is appropriate for students in fifth through twelfth grade in which they create Gothic-style stained-glass windows. Discusses how college students majoring in elementary education created stained-glass windows. Addresses how to adapt this lesson for younger students. (CMK)

  13. 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

    2016-01-05

    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.

  14. 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.

  15. Reluctant glass formers and their applications in optical lens design

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin C.; Johnson, R. Barry; Feng, Chen

    1990-01-01

    Over ten years ago, it was shown that glasses with high index of refraction and some with low dispersion could be produced from a number of pure refractory oxides, including the lanthanides, by containerless processing. By containerless processing it is possible to minimize surface heterogeneous nucleation and produce larger glass samples of the materials than by other methods. The use of proposed high temperature containerless processing facilities in space permits the fabrication of benchmark samples of new unique glass compositions for optical property determination as well as for glass formation. It was shown that glasses with high refractive indices and large Abbe numbers can be formulated using this technology. These glasses lie in the classical forbidden region of the glass map. Preliminary study of the impact of having such unusual glasses available for the lens designer was made. Results indicate that significant improvements can be realized over the use of only conventional glasses. A cursory survey of a number of nationally recognized lens designers indicated a general agreement that such glasses would be highly desired and could be expected to lead to completely new designs as well as simplifying existing designs.

  16. Indium fluoride glass fibers

    NASA Astrophysics Data System (ADS)

    Saad, Mohammed

    2012-03-01

    Fluoride glasses are the only material that transmit light from ultraviolet to mid-infrared and can be drawn into industrial optical fibers. The mechanical and optical properties of new indium fluoride glass fibers have been investigated. Multimode fiber 190 microns, has very high mechanical strength greater than 100 kpsi and optical loss as low as 45 dB/km between 2 and 4 microns. Unlike chalcogenide glass fibers, indium fluoride fiber has a wide transmission window from 0.3 to 5.5 microns without any absorption peak. Indium fluoride glass fibers are the technology of choice for all application requiring transmission up to 5 micron such as infrared contour measure (IRCM) and chemical sensing. Furthermore, Indium fluoride glasses have low phonon energy and can be heavily doped and co-doped whit rare-earth elements. Therefore they are very promising candidates for infrared fiber lasers.

  17. 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

  18. Glass transition in binary eutectic systems: best glass-forming composition.

    PubMed

    Wang, Li-Min; Li, Zijing; Chen, Zeming; Zhao, Yue; Liu, Riping; Tian, Yongjun

    2010-09-23

    The glass transition and glass-forming ability in a binary eutectic system of methyl o-toluate (MOT) versus methyl p-toluate (MPT) are studied across the whole composition range. The phase diagram is constructed to explore the best glass-forming composition as the characteristic temperatures of the glass transition, crystallization, eutectic, and liquidus are determined. The best vitrification region is found to locate between the eutectic and the midpoint compositions of the eutectic line, indicating a remarkable deviation from the eutectic composition. The compilation of various simple binary eutectic systems covering inorganic, metallic, ionic, and molecular glass-forming liquids reproduces the rule. Kinetics and thermodynamics in binary systems are investigated to associate with the rule. The composition dependence of the structural relaxation time and the kinetic fragility are presented with dielectric measurements. It is found that whereas mixing of binary miscible liquids kinetically favors glass formation, thermodynamic contribution to the deviation of the best glass-forming composition from eutectics is implied.

  19. Photoprotection by window glass, automobile glass, and sunglasses.

    PubMed

    Tuchinda, Chanisada; Srivannaboon, Sabong; Lim, Henry W

    2006-05-01

    In daily activity, much time is spent indoors and in vehicles. Although the adverse effect of ultraviolet (UV) radiation is now well recognized and active public education programs on photoprotection have been undertaken, the role of window glass in photoprotection has been rarely addressed. It has been known for some time that window glass filters out UVB and transmits UVA and visible light. Recent developments in the glass industry have resulted in glass that provides broad UV protection without the historically associated loss of visible light transmission. Factors affecting UV-protective properties of glass are glass type, glass color, interleave between glass, and glass coating. In this article, photoprotection by window glass, automobile glass, and sunglasses is reviewed.

  20. 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.

  1. New insights on P-related paramagnetic point defects in irradiated phosphate glasses: Impact of glass network type and irradiation dose

    NASA Astrophysics Data System (ADS)

    Pukhkaya, V.; Trompier, F.; Ollier, N.

    2014-09-01

    P-related paramagnetic point defects were studied in irradiated Yb-doped phosphate glasses by electron paramagnetic resonance spectroscopy (X and Q-bands). A strong impact of the glass network type on the defect nature is shown. In all glasses, r-POHC defects formation is in strong correlation with Q2 tetrahedra amount supporting the structure of r-POHC. Ultra-phosphate glasses contain the larger defect type: Peroxy radicals, P1, P2, and P4 defects whose formation is linked to Q3 tetrahedra presence. In meta-phosphate and poly-phosphate glasses, peroxy radicals appear with r-POHC thermal recovery. In meta-phosphate glasses, a combination of P1 and P3 defects was evidenced for the first time, whereas in poly-phosphate glasses, only P3 defects were identified. Dose effect as well as defect recovery were analyzed.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. Metal coated glasses by sputtering and their microfouling properties

    NASA Astrophysics Data System (ADS)

    Kougo, T.; Kanematsu, H.; Wada, N.; Hihara, T.; Minekawa, M.; Fujita, Y.

    2014-02-01

    Some elements as contaminant tend to be concentrated in biofilm. In order to prevent the fogging of glass, it is very important to control biofilm formation by metal dissolution. In this study, Metals were deposited on glass substrate by Helicon-wave-excited-plasma sputtering process. Sample was very thin metals layer like as half mirror, it could transmit light. The results of biofilm formation test, biofilm formation were inhibited on Cu, Sn and Cr, and light transmission of these samples was not degradation. It could be said that inhibition of biofilm formation was effective to suppressing cloudiness.

  8. 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

  9. Effect of different glasses in glass bonded zeolite

    SciTech Connect

    Lewis, M.A.; Ackerman, J.P.; Verma, S.

    1995-05-01

    A mineral waste form has been developed for chloride waste salt generated during the pyrochemical treatment of spent nuclear fuel. The waste form consists of salt-occluded zeolite powders bound within a glass matrix. The zeolite contains the salt and immobilizes the fission products. The zeolite powders are hot pressed to form a mechanically stable, durable glass bonded zeolite. Further development of glass bonded zeolite as a waste form requires an understanding of the interaction between the glass and the zeolite. Properties of the glass that enhance binding and durability of the glass bonded zeolite need to be identified. Three types of glass, boroaluminosilicate, soda-lime silicate, and high silica glasses, have a range of properties and are now being investigated. Each glass was hot pressed by itself and with an equal amount of zeolite. MCC-1 leach tests were run on both. Soda-lime silicate and high silica glasses did not give a durable glass bonded zeolite. Boroaluminosilicate glasses rich in alkaline earths did bind the zeolite and gave a durable glass bonded zeolite. Scanning electron micrographs suggest that the boroaluminosilicate glasses wetted the zeolite powders better than the other glasses. Development of the glass bonded zeolite as a waste form for chloride waste salt is continuing.

  10. Devitrification of ionomer glass and its effect on the in vitro biocompatibility of glass-ionomer cements.

    PubMed

    Hurrell-Gillingham, K; Reaney, I M; Miller, C A; Crawford, A; Hatton, P V

    2003-08-01

    The effects of devitrification of an ionomer glass with a molar composition 4.5SiO(2).3Al(2)O(3).1.5P(2)O(5).3CaO.2CaF(2) on cement formation and in vitro biocompatibility were investigated. Differential thermal analysis was used to study the phase evolution in the glass, and to determine the heat treatments for production of glass-ceramics. X-ray diffraction patterns from glass frit heat-treated at 750 degrees C for 2h contained peaks corresponding to apatite (JCPDS 15-876), whereas for samples heat-treated at 950 degrees C for 2h apatite and mullite (JCPDS 15-776) were the major phases detected. Transmission electron microscopy (TEM) confirmed that apatite and apatite-mullite phases were present after heat treatments at 750 degrees C and 950 degrees C respectively. Glass and glass-ceramics were ground to prepare <45microm powders and glass ionomer cements were produced using a ratio of 1g powder: 0.2g PAA: 0.3g 10% m/v tartaric acid solution in water. In vitro biocompatibility was evaluated using cultured rat osteosarcoma (ROS) cells. Scanning electron microscopy (SEM) showed that cells colonised the surfaces of cements prepared using untreated ionomer glass and glass crystallised to form apatite (750 degrees C/2h). However, quantitative evaluation using MTT and total protein assays indicated that more cell growth occurred in the presence of cements prepared using ionomer glasses crystallised to apatite than cements prepared using untreated glass. The least cell growth and respiratory activity was observed on cements made with crystallised glass containing both apatite and mullite. It was concluded that the controlled devitrification of ionomer glasses could be used to produce GIC bone cements with improved biocompatibility.

  11. Structural analysis and thermal behavior of diopside-fluorapatite-wollastonite-based glasses and glass-ceramics.

    PubMed

    Kansal, Ishu; Tulyaganov, Dilshat U; Goel, Ashutosh; Pascual, Maria J; Ferreira, José M F

    2010-11-01

    Glass-ceramics in the diopside (CaMgSi2O6)-fluorapatite (Ca5(PO4)3F)-wollastonite (CaSiO3) system are potential candidates for restorative dental and bone implant materials. The present study describes the influence of varying SiO2/CaO and CaF2/P2O5 molar ratio on the structure and thermal behavior of glass compositions in the CaO-MgO-SiO2-P2O5-Na2O-CaF2 system. The structural features and properties of the glasses were investigated by nuclear magnetic resonance (NMR), infrared spectroscopy, density measurements and dilatometry. Sintering and crystallization behavior of the glass powders were studied by hot-stage microscopy and differential thermal analysis, respectively. The microstructure and crystalline phase assemblage in the sintered glass powder compacts were studied under non-isothermal heating conditions at 825 °C. X-ray diffraction studies combined with the Rietveld-reference intensity ratio (R.I.R) method were employed to quantify the amount of amorphous and crystalline phases in the glass-ceramics, while scanning electron microscopy was used to shed some light on the microstructure of resultant glass-ceramics. An increase in CaO/SiO2 ratio degraded the sinterability of the glass powder compacts, resulting in the formation of akermanite as the major crystalline phase. On the other hand, an increase in P2O5/CaF2 ratio improved the sintering behavior of the glass-ceramics, while varying the amount of crystalline phases, i.e. diopside, fluorapatite and wollastonite.

  12. 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.

  13. 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.

  14. 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.

  15. Crystallization of baria-titania-silica glasses

    NASA Technical Reports Server (NTRS)

    Ray, Chandra S.; Day, Delbert E.

    1986-01-01

    The critical cooling rate for glass formation, Rc, and the crystallization kinetics of the compositions (1/2)(100-x)BaO-(1/2)(100-x)TiO2-(x)SiO2 with x = 20, 25, 30, 33.3, and 40 mol pct were studied using a thermal image furnace. Crystallization was studied under nonisothermal conditions, and the data were analyzed using the Johnson-Mehl-Avrami equation. The Rc and activation energy for crystallization both decrease with increasing silica content. Fresnoite, Ba2TiSi2O8, crystallized from all of the glasses when they were reheated. The infrared absorption spectra of the glasses and crystals show that they both contain (Si2O7) and square pyramidal (TiO5) groups.

  16. Cooling rates for glass containing lunar compositions

    NASA Technical Reports Server (NTRS)

    Fang, C. Y.; Yinnon, H.; Uhlmann, D. R.

    1983-01-01

    Cooling rates required to form glassy or partly-crystalline bodies of 14 lunar compositions have been estimated using a previously introduced, simplified model. The calculated cooling rates are found to be in good agreement with cooling rates measured for the same compositions. Measurements are also reported of the liquidus temperature and glass transition temperature for each composition. Inferred cooling rates are combined with heat flow analyses to obtain insight into the thermal histories of samples 15422, 14162, 15025, 74220, 74241, 10084, 15425, and 15427. The critical cooling rates required to form glasses of 24 lunar compositions, including the 14 compositions of the present study, are suggested to increase systematically with increasing ratio of total network modifiers/total network formers in the compositions. This reflects the importance of melt viscosity in affecting glass formation.

  17. 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.

  18. 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.

  19. 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.

  20. Seeing Glass Contractors Clearly.

    ERIC Educational Resources Information Center

    Deliberato, Jerry

    2003-01-01

    Offers seven tips for finding and working with an effective glass contractor. For example, schools should consider the company's reputation and longevity of service, and whether it has in-house engineering capabilities. (EV)