SnSe thin films synthesized by solid state reactions

Thin SnSe films were synthesized by solid state reactions on glass substrates. X-ray diffraction data, electrical transport properties and optical absorption coefficient data were measured. The grain length, conductivity and Hall mobility were higher than those of evaporated SnSe thin films by factors of 20, 5 and 7 respectively. An exponential-inverse-temperature law is observed for the variations in resistivity, Hall mobility and carrier density. The results are explained in terms of a grain boundary potential barrier mechanism. The optical absorption results indicate the absorption edge of the synthesized SnSe thin films is due to an allowed direct transition of energy about 1.195 eV.     

Theoretical model of the interfacial reactions between solid iron and liquid zinc-aluminium alloy

Steel strip is often coated with a layer of zinc in order to protect it against corrosion. One of the most commonly used coating processes is continuous hot dip galvanizing. In this process, the steel strip is immersed in a molten zinc bath containing small amounts of aluminium (less than 1 wt%). A model has been developed describing the kinetics of the galvanizing reactions that occur at the steel/liquid zinc interface (dissolution of iron, heterogeneous nucleation and growth of the intermetallic phase designated Fe₂Al₅Zn _x ). The model has been validated using experimental data available in the literature for a classical galvanizing treatment that lasts three seconds.     

Obtaining nanodimensional layers of GaAsP solid solutions on GaAs by solid-state substitution reactions

A new method based on solid-state substitution reactions is proposed for obtaining nanodimensional layers of GaAsP solid solutions on the surface of GaAs semiconductor crystals. The processed GaAs wafers exhibit a wide-bandgap optical window effect, whereby their room-temperature photoluminescence intensity increases by a factor of up to 25.     

Specific heat measurements in superconducting and normal state Ta-Nb-V ternary solid solutions

Specific heat measurements between 2 and 6 K on three bulk isoelectronic Ta _x Nb _y V_1–x–y bcc solid solutions have been performed above and below their superconducting transition temperatures in and out of a 46-kOe field. The behavior of T _c with alloying is well predicted by Miedema's charge-transfer method, which uses measured _D, but which has no adjustable parameters. Miedema's model also predicts correctly. Hopfield's method for T _c fails in these alloys, and probably over the entire V-Nb-Ta system except very near the Nb-Ta line.Work supported in part by a grant from the Ohio University Research Committee No. 503.     

Theoretical equation of state for aluminum

Theoretical methods for calculating equations of state are discussed and applied to aluminum. The model includes a treatment of melting, vaporization, and thermal electronic excitation. The thermal electronic terms are shown to cause a plasma phase transition in the hot expanded fluid, affecting the unloading behavior from shocked states. The calculations give good agreement with experimental Hugoniot data, the melting curve, and isobaric expansion measurements.     

Quantitative size-factors for interstitial solid solutions

Quantitative size-factors have been calculated from the initial slopes of volume/ concentration plots for interstitial solid solutions, using data available in the literature. Solutions extending beyond 5 at.% are found to occur only in alloy systems for which the volume size-factor is less than 30×10^–4. In order of relative importance, the factors which inhibit the formation of extensive solutions are: the electronic structure, the misfit strains and the elastic coefficients. These factors are discussed for the solutions based on BCC, FCC and HCP structures.     

Assessment of reactions occurring during the solid state processing of iron-based titanium diboride composites

The reactions occurring during the solid-state processing of Fe-C/TiB₂ composite materials have been assessed. Optical microscopy and X-ray diffraction have been used to identify the products of reaction after sintering and hot isostatic pressing of such materials in the temperature range 1000–1200 °C. TiC has been seen to form readily at the TiB₂/Fe interface: an apparently continuous layer of TiC forms on the surface of the TiB₂, hindering further reaction. Solid state processing appears to be a potentially viable route for the production of iron-based TiB₂ composite materials.     

Quantitative size-factors for metallic solid solutions

Quantitative size-factors, defined in terms of the effective atomic volume of the solute, have been calculated for 469 substitutional solid solutions using precision lattice parameter data available in the literature. Values of the volume size-factor, its linear derivative and a parameter expressing the deviation from Vegard's law, are tabulated in alphabetical order of the solvents. The application of these size-factors is discussed in relation to a number of physical, chemical and mechanical properties of solid solution alloys.     

Structure analysis on Ni and V co-doped zinc oxide prepared by solid state reactions

Powder samples of ZnO co-doped with Ni and V have been grown by standard solid state reaction technique with varying concentrations 2, 4 and 6 %. The grown samples were found to be dilute magnetic in nature along with semiconducting property. The structure of the grown material was solved using powder X-ray diffraction refinements and the electronic structure of the material was determined by maximum entropy method. Magnetic properties of the samples were studied using vibrating sample magnetometry and the samples exhibited ferromagnetic characteristics at room temperature. Inductively coupled-atomic emission spectroscopy was employed to identify the elemental composition of the grown samples. Direct band gap of the material was calculated using UV–vis studies.     

Prospects of solid state lasers for material processing

Since the invention of LASER in 1960, lasers have made a great impact in a wide range of scientific and technological applications. The first half of this paper discusses the basic differences between lasers and conventional heat sources and the second half is devoted to solid state lasers with specific reference to ‘high average power’ solid state lasers used in material processing. The various physical processes that influence their operation and the role of focusing optics are also discussed.     

Nucleation of solid solutions crystallizing from aqueous solutions

The study of nucleation and growth mechanisms of salts from aqueous solutions, as a function of supersaturation, is described using both macroscopic and microscopic experiments. In situ observations in a fluid cell in an atomic force microscope (AFM) reveal phenomena not accounted for in standard crystal-growth theories, specifically on the role of the crystal structure of the substrate in controlling spiral growth and two-dimensional nucleation. As a model example, the crystallization of two isostructural salts, BaSO(4) and SrSO(4), is described. The growth of solid-solution crystals is considerably more complex. The supersaturation of a given aqueous solution relative to a solid solution is different with respect to each solid composition, and it leads to the possibility that different compositions can simultaneously grow by different mechanisms on the same crystal face. Oscillatory compositional zoning is another consequence of the interplay between the thermodynamics and the kinetics of nucleation. The factors which control nucleation and growth of the solid solution (Ba,Sr)SO(4) from an aqueous solution are described. The predictions made from the theory are compared with direct observations of crystal growth in an AFM.     

Nepheline gradient solid solutions

Nepheline solid solutions having high thermal expansion coefficients ranging from 1.2 to 1.8×10⁻⁵°C⁻¹ were prepared from the systems NaAlSiO₄-LiAlSiO₄ and NaAlSi₄-KAlSiO₄. The thermal expansion coefficient decreased by substituting Li⁺ for Na⁺, and increased by substituting K⁺ for Na⁺. By forming a series of the nepheline solid solutions in a single ceramic body, a functionally gradient material with respect to thermal expansion was prepared. The thermal expansion coefficient should gradually vary with position according to the composition x in Na_1−x M_xAlSiCO₄ (M=Li and K).     

Some estimates on solutions of mixed problems for mixtures

Abstract

Our study is dedicated to a composite, which, in fact, is a mixture of two thermoelastic micropolar bodies. We formulate the mixed initial boundary value problem in this context and define the domain of influence for given data. For any solution of the mixed problem we associate a measure and prove a second-order differential inequality for it. Based on the maximum principle for the heat equation and on the second-order differential inequality, we establish an estimate which proves that the thermal and the mechanical effects, at large distance from the domain of influence, are dominated by an exponential decay.     

Relevance of liquid state to solid state properties

We outline in this talk the beginning of a new programme to study physical properties of crystalline solids. It is based on considering the latter, a broken symmetry phase, in terms of the higher symmetry liquid phase. The solid is a calculable perturbation on the fluid. This is exactly opposite to the standard approach which relates mechanical properties to the behaviour of defects (mainly dislocations) etc., in an otherwise perfect crystalline solid. However, most other broken symmetry phases (e.g. ferromagnets) are discussed starting from a symmetric Hamiltonian or a free energy functional, and earlier work by one of the authors shows that the liquid-solid transition is well described, qualitatively and quantitatively, by this approach. On the other hand, defect theories of melting have a long record of nonsuccess. In the first part of the talk, the density wave theory of freezing will be outlined, and it will be shown how properties such as Debye Waller factor, entropy change of freezing etc. can be calculated with no or one free parameter. The problem of calculating shear elastic constants and dislocation core structures as well as energies in terms only of observable liquid state properties will be set up, and results presented. The method will be contrasted with zero temperature ‘atomistic’ models which obscure the essential dependence on structure and flounder in a mass of detail. The concluding part will describe further proposed applications, some suggestive experimental results extant in the literature, and some speculations. Only a summary is presented.     

Quantum nonlocality for a mixed entangled coherent state

Quantum nonlocality is tested for an entangled coherent state, interacting with a dissipative environment. A pure entangled coherent state violates Bell's inequality regardless of its coherent amplitude. The higher the initial nonlocality, the more rapidly quantum nonlocality is lost. The entangled coherent state can also be investigated in the framework of 2 X 2 Hilbert space. The quantum nonlocality persists longer in 2 X 2 Hilbert space. When it decoheres it is found that the entangled coherent state fails the nonlocality test, which contrasts with the fact that the decohered entangled state is always entangled.     

InAs based multicomponent solid solutions for thermophotovoltaic converters

Photoelectric converters based on InAsSbP and GaInAsSbP solid solutions were obtained by liquid phase epitaxy. The new devices are promising elements for thermophotovoltaic generators operating at a reduced emitter temperature (∼1000°C).