Structural and optical properties of (100-x)Li2B4O7 center dot x(Ba5Li2Ti2Nb8O30) glasses and glass nanocrystal composites

Optically clear glasses of various compositions in the system (100-x)Li2B4O7 center dot x(Ba5Li2Ti2Nb8O30) (5 <= x <= 20, in molar ratio) were fabricated by splat quenching technique. Controlled heat-treatment of the as-quenched glasses at 500 degrees C for 8 h yielded nanocrystallites embedded in the glass matrix. High Resolution Transmission Electron Microscopy (HRTEM) of these samples established the composition of the nano-crystallites to be that of Ba5Li2Ti2Nb8O30. B-11 NMR studies revealed the transformation of BO4 structural units into BO3 units owing to the increase in TiO6 and NbO6 structural units as the composition of Ba5Li2Ti2Nb8O30 increased in the glass. This, in turn, resulted in an increase in the density of the glasses. The influence of the nominal composition of the glasses and glass nanocrystal composites on optical band gap (E-opt), Urbach energy (Delta E), refractive index (n), molar refraction (R-m), optical polarizability (alpha(m)) and third order non-linear optical susceptibility (chi(3)) were studied.

Analysis of Dynamic Heterogeneity in a Glass Former from the Spatial Correlations of Mobility

The growth of characteristic length scales associated with dynamic heterogeneity in glass-forming liquids is investigated in an extensive computational study of a four-point, time-dependent structure factor defined from spatial correlations of mobility, for a model liquid for system sizes extending up to 351 232 particles, in constant-energy and constant-temperature ensembles. Our estimates for dynamic correlation lengths and susceptibilities are consistent with previous results from finite size scaling. We find scaling exponents that are inconsistent with predictions from inhomogeneous mode coupling theory and a recent simulation confirmation of these predictions.

Epitaxial growth of Co3O4 films by low temperature, low pressure chemical vapour deposition

The growth of strongly oriented or epitaxial thin films of metal oxides generally requires relatively high growth temperatures or infusion of energy to the growth surface through means such as ion bombardment. We have grown high quality epitaxial thin films of Co3O4 on different substrates at a temperature as low as 400 degreesC by low-pressure metalorganic chemical vapour deposition (MOCVD) using cobalt(II) acetylacetonate as the precursor. With oxygen as the reactant gas, polycrystalline Co3O4 films are formed on glass and Si (100) in the temperature range 400-550 degreesC. Under similar conditions of growth. highly oriented films of Co3O4 are formed on SrTiO3 (100) and LaAlO3 (100). The activation energy for the growth of polycrystalline films on glass is significantly higher than that for epitaxial growth on SrTiO3 (100). The film on LaAlO3 (100) grown at 450 degreesC shows a rocking curve FWHM of 1.61 degrees, which reduces to 1.32 degrees when it is annealed in oxygen at 725 degreesC. The film on SrTiO3 (100) has a FWHM of 0.33 degrees (as deposited) and 0.29 (after annealing at 725 degreesC). The phi -scan analysis shows cube-on-cube epitaxy on both these substrates. The quality of epitaxy on SrTiO3 (100) is comparable to the best of the perovskite-based oxide thin films grown at significantly higher temperatures. A plausible mechanism is proposed for the observed low temperature epitaxy. (C) 2001 Published by Elsevier Science B.V.

Temperature and pressure dependence of direct current electrical resistivity in the Na2O-ZnO-B2O3 glass system

Two series of glasses were prepared, xNa2O, yZnO, 100 - x - yB2O3 and 30 - xNa2O, xZnO, 70B2O3 (mol%). The temperature dependence of the direct current resistivity was measured from room temperature to about 700 K and in both series of glasses we observed a simple Arrhenius type of temperature dependence. However, the resistivity of the binary alkali glass increased steeply by as much as two orders of magnitude with the addition of even a small quantity of ZnO and remained virtually unaffected by further addition of ZnO. The resistivity decreases gradually with increasing pressure in Na2O-B2O3 but increases with increasing pressure with the addition of ZnO.

Photoacoustic Investigation of Glass Transition in AsxTe1-x Glasses

Photoacoustic (PA) technique is used to study glass transition and temperature dependence of thermal diffusivity in AsxTe1-x glasses with 0.25 0.60. PA amplitude goes through a minimum and the phase shows a maximum at glass transition temperature Tg. The variation of thermal diffusivity with temperature shows sharp decrease near Tg. The variation of thermal diffusivity with composition shows maximum at = 0.40 for all temperatures T Tg.

On the hardness and elastic modulus of bulk metallic glass matrix composites

The influences of the amorphous matrix and crystalline dendrite phases on the hardness and elastic moduli of Zr/Ti-based bulk metallic glass matrix composites have been assessed. While the moduli of the composites correspond to those predicted by the rule of mixtures, the hardness of the composites is similar to that of the matrix, suggesting that the plastic flow in the composites under constrained conditions such as indentation is controlled by the flow resistance of the contiguous matrix. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The elastic manifestation of a spin-glass transition: a low-frequency study

The authors report here the first measurements of low-frequency dynamic elastic properties of a spin glass (Fe59Ni21Cr20) across the transition temperature (Tg approximately=16 K). A minimum in the sound velocity (V) and a maximum in the internal friction (Q-1) were found at temperatures close to but below Tg. The elastic data were compared with the AC susceptibility data taken at similar frequency.

Structural, optical and electrical characteristics of transparent bismuth vanadate films deposited on indium tin oxide coated glass substrates

Bismuth vanadate (BVO) thin films were fabricated on indium tin oxide (ITO) coated glass substrates using pulsed laser ablation technique and investigated their structural, optical and electrical properties. The use of the indium tin oxide coated glass substrate resulted in reducing the leakage current characteristics of crystalline BVO thin films. The X-ray diffraction (XRD) studies confirmed the monophasic nature of the post annealed (500 A degrees C/1 h) films. The atomic force microscopy indicated the homogeneous distribution of crystallites in the as-deposited films. The as-deposited and the post annealed films were almost 90% transparent (380-900 nm) as confirmed by optical transmission studies. Dielectric constant of around 52 was attained accompanied by the low dielectric loss of 0.002 at 10 kHz for post annealed films. The leakage current of the post annealed BVO films on ITO coated glass substrates measured at room temperature was 8.1 x 10(-8) A at an applied electric field of 33 kV/cm, which was lower than that of the films with platinum and SrRuO3 as the bottom electrodes.

Formation of lead pyrophosphate glass and the role of anion disproportionation

Thermal, spectroscopic and electrical properties of lead pyrophosphate glass prepared by melt quenching have been examined. A model based on the structural disproportionation of the P2O 7 4− ions has been proposed and is shown to consistently explain all the observations. The equilibrium of various anionic species has been discussed on the basis of their electronegativities which are in turn related to their basicities.

Low-temperature internal friction of glass ceramics

Low-temperature internal-friction measurements have been used to study the universal low-energy excitations in glasses before and after crystallization in two glass ceramics, one based on MgO-Al2O3-SiO2 (Corning Code 9606) and one based on Li2O-Al2O3-SiO2 (Corning Code 9623). In the Code 9606 sample, the number density of excitations is greatly reduced, while in the Code 9623 sample, their number density remains practically unaltered in the crystallized state. These measurements confirm the conclusions reached by Cahill et al. (preceding paper), which were based on thermal measurements up to room temperature. These measurements also demonstrate the usefulness of internal friction as a tool for the study of these low-energy excitations, since internal friction is less sensitive to defects common to glass ceramics, like magnetic impurities and grain boundaries, which tend to dominate low-temperature specific heat and thermal conductivity, respectively.

Deformation and structural densification in Al2O3-Y2O3 glass

In this article, we examine the unusual plastic deformation under uniaxial compression of an Al2O3-15 mol % Y2O3 (A15Y) glass synthesized by a wet chemical route At a low temperature of 650-725 degrees C, plastic deformation of this glass is largely non-viscous through shear instabilities In contrast deformation near the crystallization temperature (850 degrees C) occurs homogeneously with work hardening and with a monotonic increase in the true density of the glass by 10-12% accompanied by an increase in hardness (H) and elastic modulus (E) of up to 100% We hypothesize a phenomenon of molecular densification of the amorphous structure through a hierarchy of multiple phases, analogous to density- or entropy-driven amorphous to-amorphous phase transitions (polyamorphism) These results suggest that the present method of preparation and the unusual behavior can trigger a search for many more systems that display such behavior (C) 2010 Acta Materialia Inc Published by Elsevier Ltd All rights reserved

Looking-Glass Reflections : Norms in translating Lewis Carroll

This thesis in the field of translation studies focusses on the role of norms in the work of a literary translator. Norms are seen as guidelines for the translator; they also reflect the way the target audience either accepts or rejects the translation. Thus they are of an intersubjective nature. The theoretical background of the study is based on the views on norms of Andrew Chesterman and Gideon Toury. The writer makes use of her own editing and publishing experience, as well as her experience in translating Lewis Carroll, considering these in respect to theoretical views of norms and vice versa. The aim is also to bring to light some of the tacit knowledge related to translating, editing and publishing in Finland. The study has three angles. First, the writer introduces the norms of Finnish literary translation as gathered from her own working experience. The sources from which these norms arise and which affect them are briefly described. Six central translation norms emerge; they are described and exemplified through cases of Carroll translation. Secondly, a small-scale questionnaire study is presented. This was carried out in order to sound the normative views of other translators and to limit the role of subjectivity. The views of the informants largely support the set of norms presented by the writer, although the norms of quotability and harmony between translation and illustration do not arise. Instead, the answers give rise to a seventh, ethical norm, which is labelled the norm of integrity. Thirdly, there is a brief presentation of Lewis Carroll, his Alice books and their translation history in Finland. The retranslation hypothesis and the motives of retranslation are considered in the light of the work of Outi Paloposki and Kaisa Koskinen. The final part of the thesis plunges into actual translation work. It includes one and a half chapters of Through the Looking-Glass (Alicen seikkailut peilintakamaassa) as translated into Finnish by the writer. The translation commentary first discusses a number of recurring and general translation points; the running commentary then analyses 77 individual translation solutions and their justifications. The writer uses introspection as a way of reflecting on her own translation process, its decisive points and the role of norms therein. Keywords: Translation studies, Carroll, norms

Local texture and microstructure in cube-oriented nickel single crystal deformed by equal channel angular extrusion

Local texture and microstructure was investigated to study the deformation mechanisms during equal channel angular extrusion of a high purity nickel single crystal of initial cube orientation. A detailed texture and microstructure analysis by various diffraction techniques revealed the complexity of the deformation patterns in different locations of the billet. A modeling approach, taking into account slip system activity, was used to interpret the development of this heterogeneous deformation.

A molecular dynamics study of a PbO.SiO2 glass and melt

The structures of a PbO.SiO2 glass and melt have been studied using molecular dynamics simulation employing Born-Mayer-Huggins pair potentials. Various pair distribution functions are presented and discussed. Pb-Pb correlations persist in the melt, in agreement with experimental observations. The calculated and experimental radial distribution functions are compared.

Role of alumina in flexure of glass/epoxy composites

The influence of particulate additions of alumina on the flexural properties of glass-fabric/epoxy composites was studied. The additions improved translaminar flexural strength, while decreasing interlaminar strength. The translaminar bending modulus showed an increasing trend whereas its interlaminar value showed a decrease, up to additions of 3 vol%. The mechanisms of deformation and the fracture features have been discussed with the aid of scanning electron microscopy.