The phase composition of Si6 – zAlzOzNg8 – z β-sialon samples Si5AlON7 (z = 1) and Si4Al2O2N6 (z = 2) before and after two-stage firing at 900°C in air and at 1650°C in a nitrogen flow without sintering additives and with addition of 0.5 and 2.0 wt

This paper presents results on the synthesis, phase composition, and optical properties of Al5O6N aluminum oxynitride doped with Fe ions in a broad concentration range: from 0.01 to 5.0 at

The article presents a comprehensive study of the synthesis, phase formation, electronic structure, and optical properties of cobalt-doped aluminum oxynitride Al5O6N (AlON) in the concentration range of 0.01-5 at%. The solubility limit of cobalt in AlON is found to be 0.1-0.2 at% compared to Al. No corundum is detected even at the lowest cobalt content (0.01 at%), but a low amount of AlN and Co or Co4N is observed. Cobalt ions are incorporated into AlON with the typical oxidation state of Co2+ and form Co-O and Co-N bonds in a ratio of 92/8. The bandgap (Eg) and lattice parameters of AlON:Co are found to be in the range of 5.72-5.84 eV and 7.9411-7.9539 & Aring;, respectively, and are influenced by the oxygen content. Pulsed cathodoluminescence spectra show five emission bands, with some attributed to (VAl-ON)-type defects. The luminescence intensity of AlON:Co decreases with higher contents of cobalt ions.

A new approach for simulation of the interaction of space and lunar dust with the surface of spacecrafts has been proposed. The approach is based on creating a dusty plasma cloud when the substance imitating the space or lunar dust is treated with high-power pulsed microwave radiation in the developed experimental facility. The facility consists of a high-power gyrotron (75 GHz, 0.8 MW); a plasma-chemical reactor; and a diagnostic complex, which includes optical emission spectrometers and a high-speed camera. The approach has been tested using the substance of the Tsarev meteorite, which represents a typical substance of meteorites. It was found that the substance mainly keeps the phase composition; however, the particles change their morphology due to rapid heating and melting.

В эксперименте получены плазменно-пылевые облака из вещества метеорита Царев, имитатора лунного реголита LMS-1D и ильменитового концентрата с помощью микроволнового разряда в порошковых средах. Для каждого из образцов зарегистрирована динамика развития разряда и образования плазменно-пылевого облака с последующей релаксацией после окончания микроволнового импульса. По спектрам излучения плазмы и поверхности твердого тела определены температуры газа, электронов и поверхности. Проведенное сравнение фазового и элементного состава исходных образцов и образцов после воздействия плазмы показало, что существенного изменения состава не происходит. Однако результаты сканирующей электронной микроскопии четко указывают на сфероидизацию исходных угловатых частиц и частиц неправильной формы. Также наблюдается появление сферических частиц, размеры которых больше, чем линейные размеры частиц в исходном образце. Полученные результаты указывают на возможность использования таких экспериментов для исследования химических и плазмохимических процессов синтеза и модификации веществ в условиях плазменно-пылевых облаков, встречающихся в космических явлениях.

An original plasma chemical process initiated by microwave discharge in a mixture of metal and dielectric powders was applied to prepare specific materials, which consisted of microsized spherical particles of aluminum oxide covered with silver nanoparticles. The prepared materials are highly uniform in shape, size distribution, and composition. Their cytotoxicity was investigated using the human cell lines MCF7, HEK293T, A549, and VA-13 and the bacterial strains E. coli JW5503 (ΔtolC) and E. coli K12. Their cytotoxicity was found not to exceed the cytotoxicity of the starting materials. Thus, the prepared materials can be considered highly promising for catalysis and biotechnology applications.

In the experiment, plasma–dust clouds were obtained from the substance of the Tsarev meteorite, a simulant of lunar regolith LMS-1D and ilmenite concentrate using a microwave discharge in powder media. For each of the samples, the dynamics of the development of the discharge and the formation of a plasma–dust cloud with subsequent relaxation after the end of the microwave pulse were recorded. From the emission spectra of the plasma and the surface of a solid body, the temperatures of the gas, electrons and surface were determined. A comparison of the phase and elemental composition of the initial samples and samples after exposure to plasma showed that there is no significant change in the composition. However, scanning electron microscopy results clearly indicate spheroidization of the original angular and irregularly shaped particles. The appearance of spherical particles is also observed, the dimensions of which are larger than the linear dimensions of the particles in the original sample. The results obtained indicate the possibility of using such experiments to study chemical and plasma-chemical processes of synthesis and modification of substances under conditions of plasma–dust clouds encountered in space phenomena.

This review summarizes the studies on the palladium carboxylate π-complexes with unsaturated hydrocarbons (alkenes, alkynes, and arenes) as well as with N -heterocyclic carbenes, phosphonyl-substituted ferrocene ligands, etc . In these complexes the palladium atoms are coordinated with unsaturated hydrocarbons via the carbon atoms forming the multiple bonds. These complexes are traditional objects in fundamental coordination chemistry including chemistry of polynuclear compounds. They are also applied as pre-catalysts and as model intermediates for catalytic transformations of unsaturated hydrocarbons, e.g. , oxidation and isomerization of alkenes, hydrogenation and coupling reactions of alkenes, alkynes, and arenes.

We present a description of a plasma-chemical facility designed for synthesis of micro- and nanoparticles using the radiation of a high-power gyrotron. The facility has been developed at the Plasma Physics Division of A.M.Prokhorov General Physics Institute of the Russian Academy of Sciences. The facility includes a plasma-chemical reactor, a gyrotron unit, an in-line calorimeter, a diagnostic system, which ensures video and spectroscopic measurements, balance measurements of the microwave radiation, and thermal imagery measurements, a chemical unit for specimen preparation and analysis of synthesis products, an electronic logging unit, and a specimen labeling system for organization and storage of a large amount of experimental data and specimens.

We have studied the effect of sodium fluoride as a sintering aid for β-sialons on the phase composition and physicomechanical properties of Si5AlON7 and Si4Al2O2N6. Two-step high-temperature firing of the β-sialons in the presence of NaF under a nitrogen atmosphere has been shown to cause no significant changes in the phase composition of the materials. The density and microhardness of the materials prepared using 0.5 and 5.0 wt

Представлены экспериментальные результаты по осаждению заряженных частиц, имитирующих левитирующую пыль реголита (пылевую плазму) на Луне, на металлические пластины. Эксперимент основан на аналогии физико-химических процессов, развивающихся в реголите при микроволновом разряде, возбуждаемом излучением мощного гиротрона, в лабораторном эксперименте в порошке реголита (лунной пыли) с процессами, которые происходят на Луне при бомбардировке ее поверхности микрометеоритами. Исследуется воздействие левитирующего облака пыли на пластины из молибдена и тантала. Результаты сравниваются с экспериментом по воздействию пыли на пластины из нержавеющей стали. Показано, что на пластины металлов (размер которых составляет 10 мм × 40 мм) осаждаются частицы пыли в виде сфероидов различной величины. Распределение этих частиц по размерам и химический состав покрытия соответствовал лунному реголиту. Установлено, что на равномерность осаждения пыли возможно повлиять, произведя предварительную обработку пластин металлов с помощью низкотемпературной плазмы прямого пьезоразряда. Продемонстрировано, что полученная в лабораторных условиях левитирующая пыль (ансамбли заряженных частиц реголита) может быть использована для имитационных экспериментов для изучения модификации поверхности разных материалов и разработки способов очистки космической техники в условиях лунных экспедиций.

The article presents a method to synthesize aluminum oxynitride (AlON) doped with cobalt ions at concentrations ranging from 0.01 at.% to 5 at.%. The phase and elemental composition of the samples and their optical properties have been studied upon variation of the cobalt content. Five emission bands in the pulsed cathodoluminescence spectra are attributed to intrinsic defects and impurities in AlON. The optical gap of AlON:Co estimated using the Tauc method are in the range of 5.72–5.84 eV and are significantly influenced by the oxygen content in the AlON host.

Изучено влияние фторида натрия как спекающей добавки для β-сиалонов на фазовый состав и физико-механические свойства Si 5 AlON 7 и Si 4 Al 2 O 2 N 6 . Показано, что двухстадийный высокотемпературный обжиг β-сиалонов в атмосфере азота с добавлением NaF не приводит к значимым изменениям в фазовом составе образцов. Плотность и микротвердость полученных с добавлением 0.5 и 5.0 мас. % NaF образцов оказываются ниже, чем для образцов без спекающих добавок, однако прочность на изгиб демонстрирует рост на величину до +14.3% для Si 5 AlON 7 при содержании NaF 0.5 мас. % и до +4.9% для Si 4 Al 2 O 2 N 6 при содержании NaF 5.0 мас. %.

Gold(III) complexation with the octadecahydrido-eicosaborate anion [B20H18]2− was studied for the first time. It was found that when gold(III) complexes [Au(L)Cl2]BF4 (L = bipy, phen) reacted with [B20H18]2−, complexes [Au(L)Cl2]2[B20H18] were isolated. The compounds consisted of a cationic gold(III) complex [Au(L)Cl2]+ and the hydridoborate cluster as a counterion. X-ray diffraction studies revealed weak B–H...Au interactions for both compounds. Note that more reactive anions [BnHn]2− (n = 10, 12) in similar reactions with gold(III) complexes resulted in gold mirror reactions.

Formation of Si6-zAlzOzN8-z from Si3N4/Al2O3/AlN mixtures was studied in a wide range of z value. Mixtures were annealed under 1 bar nitrogen flow at 1550, 1650 and 1750 degrees C for 1.5 and 3 h. The annealed samples were characterized with X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that in general formation of beta-SiAlON phases with higher z value requires lower temperature but longer annealing time. XRD analysis revealed a high yield of beta-SiAlONs (>= 75 wt%) in the whole range of z value (1, 2, 3 and 4) at 1550-1650 degrees C (from 77% (z = 4) up to 93% (z = 3)). For z = 1 and 2 formation of beta-SiAlON with z = 2 and 3 respectively was observed at 1550 degrees C with the yields up to similar to 59 and similar to 74%. At 1750 degrees C decomposition and sublimation of Si3N4 leads to formation of silicon poor phases derived from AlN including 12H, 15R and 21R. The only exception is a formation of Si3Al7O3N9-zeta phase with quite a high yield (similar to 68%) in the system relating to z = 3 at 1750 degrees C. As a result, some conclusions about formation of SiAlON phases in a broad Si/Al ratio range were made.

Министерство науки и высшего образования Российской Федерации Российская академия наук Научный совет по неорганической химии РАН Научный совет по аналитической химии РАН Научный совет по химической технологии РАН Российское химическое общество имени Д.И

Министерство науки и высшего образования Российской Федерации Российская академия наук Научный совет по неорганической химии РАН Научный совет по аналитической химии РАН Научный совет по химической технологии РАН Российское химическое общество имени Д.И

The high-temperature interactions of β-SiAlONs with sodium fluoride NaF at 1650 °C under a nitrogen atmosphere are described in this paper. It was found that in case of Si5AlON7 the formation of phases enriched with aluminum occurred, including Si4Al2O2N6 at an NaF loading of 0.5 wt.% and Si4Al2O2N6 and Si3.1Al2.9O2.9N5.1 at an NaF loading of 2.0 wt.%, although Si5AlON7 still was a major phase. For Si4Al2O2N6, a kind of disproportionation was observed, and Si5AlON7 formed together with Si3Al3O3N5 and Si3.1Al2.9O2.9N5.1. Moreover, the initial phase Si4Al2O2N6 was not identified at all, while Si5AlON7 was found to be a major phase at an NaF loading of 0.5 wt.% and Si3.1Al2.9O2.9N5.1 prevailed at an NaF loading of 2.0 wt.%. All the samples showed a high degree of densification when studied with scanning electronic microscopy.

Herein we describe the results of our study of plasma chemical process initiated by high-power microwave pulses generated by 75/0.8 gyrotron (frequency 75 GHz, pulse duration up to 12 ms, power up to 550 kW) in mixtures of metal (Mg, Ti, Mo) and dielectric (Al2O3, AlN, B) powders. The process leads to formation of microand nanostructured materials and the yield is strongly affected by hydrogen-containing additives (C2B10H12, H3BO3, NaBH4) in the mixture. It was found that the process occurs in three main stages. The first initiation stage is very short (just slightly exceeds the pulse duration) and includes the absorption of microwave irradiation and the discharge proceeded as coulombic explosion. The main stage is much longer and includes decomposition of starting materials and reactions between all the components. All the tested additives prolong the main stage, in some cases by an order of magnitude or even more, and turn it into self-sustaining oscillating mode. The last one is realized most likely due to autothermic effect. As a result, the yield increases sufficiently. Finally, the decay stage is relatively short stage (up to 200 ms) following the main stage and includes irreversible cooling down of the reaction zone and deposition of the particles. The decay stage is not affected by additives. Owing to use the additives we were able to decrease the energy consumption for preparation of the materials below 1 kJ/g, which is 2-3 times lower compared to our previous results. The prepared materials were characterized by SEM, EDS and X-ray diffraction analysis and found to be mainly oxides, nitrides and borides.