Decay Of Solid Solution Research Articles

SCINTILLATION CHARACTERISTICS OF HEAVILY DOPED CsI:Tl, IO3 CRYSTALS

The effect of 3 IO− ions on spectrometric characteristic of CsI:Tl crystal has been considered. It has been shown that co-doping of CsI:Tl crystal by 3 IO− anions permits to obtain clear ingots with increased thallium concentration up to CTl ~ 0.9 mole % in which the concentration quenching of photo- or radioluminescence do not observed. It has been shown that the decay of solid solution in CsI:Tl, 3 IO crystals is not observed, at least up to CTl ~ 0.5 mole %, as evidenced by a good energy resolution (R = 6.3%) of samples with the specified Tl concentration and this also evidenced by a larger segregation coefficient of thallium in CsI:Tl, 3 IO crystals (k = 0.24 contrary to k = 0.19 in CsI:Tl). An explanation of thallium solid solution stability in CsI matrix has been proposed which based on experimental fact of complex formation. Compensation of elastic stresses of opposite sign due to complex formation results in preventing of nucleation for solid solution decay.

Influence of Temperature of Severe Plastic Deformation and Aging on Microstructure, Mechanical Properties and Electrical Conductivitiy of the Cu-Cr-Zr Alloy

The article studies an influence of temperature of severe plastic deformation (SPD) and post-deformation heat treatment on microstructure, mechanical properties and thermal stability of the Cu-0.5Cr-0.2Zr alloy. The results demonstrate that strength is considerably increased to 900 MPa by high pressure torsion (HPT) at room temperature. Subsequent ageing at 450 °С during 1 hour leads to a decay of solid solution and an allocation of dispersion particles that further incrises strength to 900 MPa, restores electrical conductivity to 70% IACS (International annealed copper standard) and enhances thermal stability of the alloy. When deformation temperature is increased to 300°С, strength is 690 MPa that is lower than in the case of deformation at room temperature that is related to reversion process at deformation. Additional a aging does not lead to an increase of strength characteristics.

Control of the solid solution decay by heat treatments of deformed niobium-titanium alloys

Control of the solid solution decay by heat treatments of deformed niobium-titanium alloys

Structural features of Ag-Cu alloy films produced by the codeposition of sputtered metals

Solid solutions in the form of alloy coatings are obtained in the entire concentration range of binary system using ion-plasma sputtering and the codeposition of Ag and Cu ultrafine particles. Sstudying the structure of solid solutions shows a change in the FCC-lattice parameters from silver to copper with a characteristic bend corresponding to the eutectic composition of the equilibrium phase diagram. Solid-solution decay begins at 100°C, and their complete decomposition occurs at 250°C. The surface structure of the initial solutions is presented by crystallites 20–30 nm in cross section; after decomposition, their size is less than 100 nm. For the latter, the distortions of the lattice parameters are 0.32% for a solution of Cu in Ag and 0.29% for a solution of Ag in Cu. The method of alloy production can be extended to the systems of metals immiscible in the solid phase.

Effect of Thermal Annealing in Vacuum and in Air on Nanograin Sizes in Hard and Superhard Coatings Zr–Ti–Si–N

Zr-Ti-Si-N coating had high thermal stability of phase composition and remained structure state under thermal annealing temperatures reached 1180 degrees C in vacuum and 830 degrees C in air. Effect of isochronous annealing on phase composition, structure, and stress state of Zr-Ti-Si-N-ion-plasma deposited coatings (nanocomposite coatings) was reported. Below 1000 degrees C annealing temperature in vacuum, changing of phase composition is determined by appearing of siliconitride crystallites (beta-Si3N4) with hexagonal crystalline lattice and by formation of ZrO2 oxide crystallites. Formation of the latter did not result in decay of solid solution (Zr, Ti)N but increased in it a specific content of Ti-component. Vacuum annealing increased sizes of solid solution nanocrystallites from (12 to 15) in as-deposited coatings to 25 nm after annealing temperature reached 1180 degrees C. One could also find macro- and microrelaxations, which were accompanied by formation of deformation defects, which values reached 15.5 vol.%. Under 530 degrees C annealing in vacuum or in air, nanocomposite coating hardness increased. When Ti and Si concentration increased and three phases nc-ZrN, (Zr, Ti)N-nc, and alpha-Si3N4 were formed, average hardness increased to 40.8 +/- 4 GPa. Annealing to 500 degrees C increased hardness and demonstrated lower spread in values H = 48 +/- 6 GPa and E = (456 +/- 78) GPa. Zr-Ti-Si-N coatings has high wear resistance and low friction coefficient in comparison at a temperature of 500 degrees C possess with coatings TiN, Ti-Si-N.

Defect Generation during Plastic Deformation of Si-Rich Cz-Grown SiGe Crystals

The IR absorption spectra and kinetics of the oxygen solid solution decay were studied in the Si1¡xGex crystals (0 · x · 0:055) plastically deformed at 680±C up to the 2{5% residual strain. It is found that the defects of non-dislocation nature, the dislocation trails, are formed during the plastic deformation of all studied SiGe crystals. The ¯ne structure of the IR absorption spectra around the 1000 cm¡1 wave number is found to be nearly identical in the pure Si (no Ge) samples and Si1¡xGex crystals with x · 0:02. At higher x the ¯ne structure was not detected due to the alloy-related broadening. In all studied crystals, the decay of the supersaturated oxygen solid solution at 650±C is determined by oxygen agglomeration at the dislocation trails as shown by the comparison with the samples annealed at 1150±C.

Features of Swelling in Modified Austenitic Steels

Results of analysis of swelling behaviour of alloying austenitic steels are described from the point of view of the cooperative interaction of defect structure, solid solution decay and precipitates evolution.

Peculiarities of solid solution decay of hydride-forming and non-hydride-forming systems with close-packed crystal structure

The most precise structure-sensitive methods (electron—positron annihilation, electroresistivity and internal friction measurements) yield for the existence of hydrogen-induced lattice vacancies, and hydrogen-stimulated diffusion in HCP and FCC Me-H systems which were accompanied by the formation of “H atom—excess (non-intrinsic) vacancy” pair defects (clusters). A new method for analysing the high-temperature dependence of Me-H system electroresistivity and a model for clusterization of the structure in solid solutions of Me-H, oversaturated with excess vacancies were developed. It was established that partial thermally activated dissociation (decay) of clusters with low bonding energy (0.2 eV) appears to be a controlling mechanism for hydrogen-stimulated diffusion in hydride-forming systems (Ti-H, Zr-H). Thermally activated association of clusters with high bonding energy (0.5-0.6 eV) was found to be a controlling mechanism for hydrogen-stimulated diffusion in non-hydride-forming systems (AlH). Clusterization of excess defects simplifies formation of hydrides at significantly lower temperature.

Influence of carbon and nitrogen on solid solution decay and “475 °C Embrittlement” of High-Chromium Ferritic Steels

“475 °C embrittlement” of high-chromium ferritic steels with Cr content from 15 to 35 wt pct and different commercial impurities (C, N) has been investigated. The influence of preliminary treatment (600 °C to 1250 °C) and chemical composition of the alloy (Cr, C, N, Mo, Ti, Nb) on kinetics has been established. Internal friction (IF) was used to determine the contribution of interstitial atoms to the formation of Cr-modulated structure during different stages of embrit- tlement of high-chromium steels. By use of IF, static and dynamic (impact) mechanical tests with different states of stress, transmission and scanning electron microscopy of structures and fracture surfaces, and the application of diffraction methods, thermodynamic diagrams of the aging of high-chromium steels have been obtained. In the temperature range of 475 °C em- brittlement, the following sequence of processes has been established: (1) decay of solid solution supersaturated with interstitial atoms by dislocation pinning, (2) formation of substitutional- interstitial (s-i) complexes of interstitial (C, N) and substitutional (Cr) atoms, and (3) formation of zones enriched in Cr.

Superconductivity and Decay Phenomena of Nb3AlNb3Ge Solid Solutions

The dependences of lattice parameter, critical temperature of superconducting transition, and the derivative (∂Hc2/∂T)Tc on composition of the solid solutions Nb3AlNb3Ge are investigated. Specimens of the solid solutions are obtained by the method of controlled synthesis. It is shown that the main peculiarities of the change of properties at the composition transformation may be explained by the development of processes of solid solution decay, when the concentration of Nb3Ge exceeds 30 to 35 mol%. It is also shown that “stoichiometric” Nb3Ge may be regarded as a solid solution, capable for decay into two components with different Nb/Ge-ratio. [Russian Text Ignored.]

Electron localization on defects and optical nuclear polarization in disordered and semimagnetic semiconductors

AbstractUsing optical nuclear polarization (ONP) and nuclear magnetic resonance (NMR) techniques silicon single crystal solid solutions containing impurity defects of more than one kind are studied. The application of the ONP techniques to the investigation of nonuniformly doped silicon is demonstrated. The concentration and energy fluctuations of donor levels are determined in silicon doped with elements of III to V and transition groups. Solid solution decay processes are studied by ONP techniques in silicon crystals doped with deep‐level impurities. Finally, the ONP technique is applied to the investigations of semimagnetic semiconductors.

Electron localization on defects and optical nuclear polarization in disordered and semimagnetic semiconductors

Using optical nuclear polarization (ONP) and nuclear magnetic resonance (NMR) techniques the silicon single crystal solid solutions containing impurity defects of a few rather than one kind have been studied. Application of the ONP techniques to the investigation of nonuniformly doped silicon has been demonstrated. The concentrations and energy fluctuations of donor levels have been determined in silicon doped with elements of III–V and transition groups. Solid solution decay processes have been studied by ONP techniques in silicon crystals doped with deep level impurities. Finally, ONP techniques have been applied to the investigations of semimagnetic semiconductors.

Dynamical Scattering of X-Rays in Gallium Arsenide Crystals Containing Dislocation Loops

A method is developed for the discrimination of the diffuse scattering absorption coefficient μDS from the experimental interference absorption coefficient (IAC) μie by the investigation of the dynamical scattering of X-rays for wavelengths near the K absorption edges of Ga and As in GaAs crystals heavily doped with Te. Conclusions are made about the appearance of dislocation loops after the Te solid solution decay comparing the IAC increments ratios measured at different hkl reflections for Cuα and CuKβ radiations and those values calculated by means of formulae obtained from Dederichs's theory for μDS. The conclusions of this theory are experimentally proved with the dependences of μDS on the wavelength λ and diffraction vector H. [Russian Text Ignored].

Structural vacancies and solid solution decay in ferrospinels

The formation of vacancies in nonstoichiometric ferrospinels and their effect, upon solid solution stability are considered. On the basis of a solution model including vacancies of both signs, the interdependency of cation and anion vacancy concentrations, and of degree of inversion and magnetite content in solutions of Mg 1− a Fe 2+ a O 4 at a fixed temperature are obtained. It is shown that vacancy concentration can be considered as a parameter determining the structure stability. Exceeding a critical value of this parameter in a given solution leads to instability. Within the temperature range considered, this critical vacancy concentration is not temperature-dependent. The estimated interdependencies are verified by X-ray, chemical and magnetic data.