The Structure Stability of Metal Diffusion Membrane-Filters in the Processes of Hydrogen Absorption/Desorption

The evolution of a nanostructured state of palladium—lead membrane alloys during their interaction with hydrogen was studied using precision X-ray diffraction with synchrotron radiation (SR) and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDXS). The importance of this topic is due to the need and demand for improving the performance characteristics of dense metal diffusion filters for high purity hydrogen separation processes. Palladium-based membrane filters with lead concentrations of 5 and 20 wt.% were prepared via electric arc melting from high purity metals (99.95%). The thickness of the filters was 50 μm. Hydrogenation was carried out from a gas medium at 573 K and the pressure of 16 atm. within 150 min. The focus of the study is on the structural state of diffusion filter membranes depending on the content of the palladium-alloying element—lead—and on analysis of the substructure of alloys before and 5300 h relaxation after hydrogenation is carried out. Specific features of the surface morphology and the structure of the membrane filters depending on the concentration of lead in the alloys are determined. The formation and development of deformation processes in metal systems upon the hydrogenation is shown. The establishment of peculiarities of hydrogen interaction with metals will contribute to obtaining new potentially important characteristics of membrane filters

CALCULATION OF ELASTICALLY STRESSED QUANTUM WELLS HETEROSTRUCTURE AlXGaYIn1-X-YAs/InP FOR EFFICIENT DIODE LASERS

The compositions of epitaxial layers forming quantum-well heterostructures AlxGayIn1-x-yAs / InP for laser diodes with the radiation wavelength of 1.55 μm are calculated. When carrying out the calculations, the problem was to provide the maximum height of the energy barriers for effective limitation of charge carriers in the quantum wells. Along with taking care of the effects of the dimensional quantization of the energy of free charge carriers in allowed zones, the effect of elastic stress in epitaxial layers on the displacement of the edges of the energy bands were taken into account in the calculation. It is shown that in order to solve the posed problems it is necessary to form heterostructures with elastic compression stress in a quantum well and elastic tensile stress in the barrier layers. As a result of the calculations the authors suggest a structure that includes a barrier layer of Al0.28Ga0.30In0.42As with a thickness of 110 Å and a quantum well Al0.03Ga0.23In0.74As in a layer with a thickness of 55Å (with the mismatch between the parameters of the crystal lattice and the InP substrate - 0.8% and + 1.4 %, respectively). According to the calculation results, the indicated thicknesses of epitaxial layers do not exceed the critical values that can lead to the formation of imperfect dislocations at heterointerfaces

Alcoxotechnology for obtaining heat-resistant materials based on rhenium and ruthenium

Objectives. To develop physical and chemical bases and methods to obtain rhenium–ruthenium isoproxide Re4-yRuyO6(OPri)10 —a precursor for obtaining a high-temperature alloy—from ruthenium acetylacetonate and rhenium isoproxide acquired by electrochemical methods.Methods. IR spectroscopy (EQUINOX 55 Bruker, Germany), X-ray phase and elemental analyses, energy-dispersive microanalysis (EDMA, SEM JSM5910-LV, analytical system AZTEC), powder X-ray diffraction (diffractometer D8 Advance Bruker, Germany), experimental station XSA beamline at the Kurchatov Synchrotron Radiation Source.Results. The isoproxide complex of rhenium–ruthenium Re4-yRuyO6(OPri)10 was obtained, and its composition and structure were established. Previously conducted quantum chemical calculations on the possibility of replacing rhenium atoms with ruthenium atoms in the isopropylate complex were experimentally proven, and the influence of the electroconductive additive on the composition of the obtained alloy was revealed.Conclusions. Physical and chemical bases and methods for obtaining rhenium–ruthenium isoproxide Re4-yRuyO6(OPri)10 were developed. The possibility of using rhenium–ruthenium Re4-yRuyO6(OPri)10 as a precursor in the production of ultra- and nanodisperse rhenium–ruthenium alloy powders at a record low temperature of 650°C were shown

Conformation controlled hydrogen storage in the CAU 1 metal organic framework

We have studied the mechanism of hydrogen storage in the aluminium based metal organic framework CAU 1 or [Al4 OH 2 OCH3 4 O2C C6H3NH2 CO2 3] using a complementary multidisciplinary approach of volumetric gas sorption analysis, in situ neutron diffraction and spectroscopy and ab initio calculations. The structure of CAU 1 forms two different types of microporous cages i an octahedral cage with a diameter of about 10 and ii a tetrahedral cage with a diameter of about 5 . Though all metal sites of CAU 1 are fully coordinated, the material exhibits relatively high storage capacities, reaching 4 wt at a temperature of 70 K. Our results reveal that hydrogen sorption is dominantly driven by cooperative guest guest interactions and interactions between guest hydrogen molecules and organic linkers. The adsorption of hydrogen on the organic linkers leads to the contraction of the host framework structure and as a result to changes in the electronic potential surface inside the pores. This, in turn, leads to cooperative rearrangement of the molecules inside the pores and to the formation of additionally occupied positions, increasing hydrogen uptake. At the final stage we observe the formation of solid amorphous hydrogen inside the pore

Алкоксотехнология получения жаропрочных материалов на основе рения и рутения

Objectives. To develop physical and chemical bases and methods to obtain rhenium–ruthenium isoproxide Re4-yRuyO6(OPri)10 —a precursor for obtaining a high-temperature alloy—from ruthenium acetylacetonate and rhenium isoproxide acquired by electrochemical methods.Methods. IR spectroscopy (EQUINOX 55 Bruker, Germany), X-ray phase and elemental analyses, energy-dispersive microanalysis (EDMA, SEM JSM5910-LV, analytical system AZTEC), powder X-ray diffraction (diffractometer D8 Advance Bruker, Germany), experimental station XSA beamline at the Kurchatov Synchrotron Radiation Source.Results. The isoproxide complex of rhenium–ruthenium Re4-yRuyO6(OPri)10 was obtained, and its composition and structure were established. Previously conducted quantum chemical calculations on the possibility of replacing rhenium atoms with ruthenium atoms in the isopropylate complex were experimentally proven, and the influence of the electroconductive additive on the composition of the obtained alloy was revealed.Conclusions. Physical and chemical bases and methods for obtaining rhenium–ruthenium isoproxide Re4-yRuyO6(OPri)10 were developed. The possibility of using rhenium–ruthenium Re4-yRuyO6(OPri)10 as a precursor in the production of ultra- and nanodisperse rhenium–ruthenium alloy powders at a record low temperature of 650°C were shown.Цели. Разработка физико-химических основ и способов получения изопроксида рения-рутения Re4-yRuyO6(OPri)10 из ацетилацетоната рутения и изопроксида рения, полученного электрохимическим методом – прекурсора получения высокотемпературного сплава.Методы. ИК-спектроскопия (EQUINOX 55 Bruker, Германия), рентгенофазовый и элементный анализ, энергодисперсионный микроанализ (ЭДМА, СЭМ JSM5910–LV, аналитическая система AZTEC), порошковая рентгеновская дифракция (дифрактометр D8 Advance Bruker, Германия), экспериментальная станция «РСА» Курчатовского источника синхротронного излучения.Результаты. Получен изопроксидный комплекс рения-рутения Re4-yRuyO6(OPri)10 , подтверждены его состав и строение. Экспериментально подтверждены ранее проведенные квантово-химические расчеты, свидетельствующие о возможности замещения атомов рения атомами рутения в изопропилатном комплексе. Выявлено влияние электропроводящей добавки на состав получаемого сплава.Выводы. Разработаны физико-химические основы и предложены способы получения изопроксида рения-рутения Re4-yRuyO6(OPri)10 , который может найти применение в качестве предшественника при получении ультра- и нанодисперсных порошков сплавов рений-рутений при рекордно низкой температуре 650 °C

Synthesis, X-ray structure analysis, and Raman spectroscopy of R2TiO5R_{2}TiO_{5}-based (R = Sc, Y) solid solutions

Order–disorder transitions in $xR_{2}O_{3} · (1 − x)TiO_{2}$ (R = Sc, 0.4 ≤ x ≤ 0.5; R = Y, 0.5 ≤ x ≤ 0.6) solid solutions with highly imperfect fluorite-derived structures have been studied using monochromatic synchrotron X-ray diffraction and Raman spectroscopy. The results demonstrate that the synthesis process leads to the formation of a fluorite-like (Fm$_3$m) disordered phase and a nanoscale (~10–100 nm) pyrochlore-like (Fd$_3$m) ordered phase of the same composition, coherent with the disordered phase. We have determined their lattice parameters. The Raman spectra of $Sc_{2}TiO_{5}(Y_{2}TiO_{5})$ contain broad lines in low- and high-frequency regions: at 190, 350, and 775 (134, 188, 365, 404, and 727) cm−1. These lines are characteristic of a pyrochlore-like phase with a varying degree of order and a disordered fluorite-like phase, respectively. The pyrochlore-like phase $Y_{2}Ti_{2}O_7$ has two strong Raman peaks in the low-frequency region: at 312 and 527 cm$^{−1}$. The formation of nanodomains with different degrees of order is caused by the internal stress that arises from the high density of structural defects in the unit cells of the solid solutions