Crystal structure and temperature-dependent properties of Na2H4Ga2GeO8 – a novel gallogermanate

Synthesis, crystal structure and temperature-dependent behavior of Na2H4Ga2GeO8 are reported. This novel gallogermanate crystallizes in space group I41/acd with room-temperature powder diffraction lattice parameters of a = 1298.05(1) pm and c = 870.66(1) pm. The structure consists of MO4 (M = Ga, Ge) tetrahedra in four-ring chains, which are connected by two different (left- and right-handed) helical chains of NaO6 octahedra. Protons coordinating the oxygen atoms of the GaO4 tetrahedra not linked to germanium atoms ensure the charge balance. Structure solution and refinement are based on single crystal X-ray diffraction measurements. Proton positions are estimated using a combined approach of DFT calculations and NMR, FTIR and Raman spectroscopic techniques. The thermal expansion was examined in the range between T = 20(2) K and the compound’s decomposition temperature at 568(5) K, in which no phase transition could be observed, and Debye temperatures of 266(11) and 1566(65) K were determined for the volume expansion.

Synthesis, structural, W-H plot and size-strain analysis of nano cobalt doped MgFe2O4 ferrite

In this study we have investigated structural attribute of Co+2 doped MgFe2O4. Synthesis of Mg1-xCoxFe2O4 ferrite was carried out using co-precipitation method. The formation of spinal ferrite was confirmed through X-ray diffraction. Lattice parameter found to be 8.376748 ? and crystallite sizes in the range 180-365 ? are observed. Various parameters like dislocation density (?D); mechanical properties (strain), Hopping length {tetrahedral site (LA) and octahedral site (LB)}, Bond length (A-O and B-O), and Ionic radii (rA and rB) were reported. The W-H plot and Size-Strain plots were extensively studied and the results have been correlated.

CONTROL OF THE MOUNTAINOUS AREA STRESS-STRAINED STATE BY THE SOUND RANGING AND GEOPHYSICAL METHODS

Уровень промышленной безопасности в горнодобывающей отрасли остается одним из низких, что обусловлено, в первую очередь, недостаточной изученностью геотектонических условий разреза, отсутствием инновационных разработок в предупреждении чрезвычайных ситуаций при горнопроходческих и добычных работах, слабой автоматизацией опасных операций производственного цикла. Главной же причиной высокой аварийности в горной отрасли является низкий уровень организации контроля проявления и развития в массиве деформационных процессов, недостаточная разрешающая способность используемых методов контроля, сложность и дороговизна проведения наблюдений, помехонезащищенность используемых радиосхем и электролиний измерительных установок. В работе рассмотрены основные звукометрические и геофизические методы контроля динамики напряженно-деформированного состояния горных пород, физико-механические изменения матрицы горной породы на уровне структурно-текстурной упаковки и кристаллической решетки. Дается обоснование эффективности использования волоконно-оптических материалов, как линий связи и детекторов давления на основе дифракционных решеток Брэгга. The level of industrial safety in the mining branch remains one of the low, which is caused, in the first place, by the insufficient mastery of the geotectonic conditions for section, by the absence of innovation developments in warning of extraordinary situations with the mine-constructing and mining works, by the weak automation of the dangerous operations of production process. However, the main reason for high accident rate in the mountain branch is the low level of the of the manifestation and development control organization in the massif of deformation processes, the insufficient resolution of the utilized methods of control, complexity and high costs of conducting observations, lack of interference defense of the utilized radio circuits and power lines of measuring units. Work examines the basic sound ranging and geophysical methods of the stress-strained state dynamics of the rocks checking, physicomechanical changes in the matrix of the rock at the level of structural-textural packing and crystal lattice. The effectiveness substantiation of the fiber-optic materials use as the communications lines and detectors of pressure on the basis of the Bragg diffraction lattice is given.

A Comparative Study between the Effects of Oxidizing and Reducing Atmospheres on the Properties of ZnO-Bi2O3-Mn2O3 Varistor Fabricated from Micro and Nanoparticles Size of ZnO

Zinc oxide-based varistors are semiconductor ceramics. Their excellent nonlinear electrical behaviors are induced from their grain boundaries and depend on their microstructural characteristics. From a theoretical aspect, finer primary particles with narrow size distributions provide better electrical and optical properties. Thus, these properties are related to the morphology and size of ZnO grains. In this study, ZnO-Bi2O3-Mn2O3 varistors fabricated from ZnO micro-and nanoparticle powders are prepared via conventional ceramic processing. The effects of ZnO particle size and different annealing ambients on the properties of ZnO varistors are also investigated. The strong solid-state reaction during sintering may be attributed to the high surface area of the 20 nm ZnO nanoparticles that promote strong surface reaction. The annealing process also improves grain crystallinity, as shown in the decrease in intrinsic compressive stress based on the X-ray diffraction lattice constant and full-width at half-maximum (FWHM) data. The reduced particle size significantly influences the electrical properties, showing a sharp drop in the breakdown voltage. Thus, the ZnO nanoparticles can be used to manufacture of varistors with superior properties and lower breakdown voltage compared with commercial ones.

Thermal Expansion of Oxyarsenides (LaO)TAs; T = Transition Metal

We have investigated the precise crystal structure and their temperature dependences of oxyarsenides (LaO)TAs; T = Mn, Fe, Co, as the Fe based superconductor’s parent material family using high energy synchrotron radiation x-ray powder diffraction. Lattice constants a and c decrease with decreasing temperature. Focusing the ratios of the changes normalized by room temperature lattice constants, we have found anisotropic shrinks for the superconductor’s parent material of (LaO)FeAs and the ferromagnetic metal (LaO)CoAs. The shrinkage of the lattice constant c along the stacking direction will be discussed by the temperature dependence of the divided three components of the LaO layer, TAs layer, and the interlayer distance.

Determining Ti-17 β-Phase Single-Crystal Elasticity Constants through X-Ray Diffraction and Inverse Scale Transition Model

The scope of this work is the determination of single-crystals elastic constants (SEC) from X-ray diffraction lattice strains measurements performed on multi-phase polycrystals submitted to mechanical load through a bending device. An explicit three scales inverse self-consistent model is developed in order to express the SEC of a cubic phase, embedded in a multi-phase polycrystal, as a function of its X-ray Elasticity Constants. Finally, it is applied to a two-phases (α+β) titanium based alloy (Ti-17), in order to estimate Ti-17 β-phase unknown SEC. The purpose of the present work is to account the proper microstructure of the material. In particular, the morphologic texture of Ti-17 a-phase, i.e. the relative disorientation of the needle-shaped grains constituting this phase, is considered owing to the so-called Generalized Self-Consistent model.