Investigation of Nanometer- and Submicron-Size Dispersed Phases in Titanium Pseudo- β -Alloys using Scattering and Diffraction of Neutrons,Electrons, and X-Ray Radiation

Metal Science and Heat Treatment - The size and volume fraction of fine particles of secondary β -phase formed during hardening heat treatment of pseudo-β-titanium alloy VT22 are...     

Investigation into the formation of phases with a Ba<Subscript>2</Subscript>Ti<Subscript>9</Subscript>O<Subscript>20</Subscript>-type structure in the BaO-TiO<Subscript>2</Subscript> and BaO-SrO-TiO<Subscript>2</Subscript> systems

The mechanism of formation of barium titanate Ba₂Ti₉O₂₀ in the BaO-TiO₂ and BaO-SrO-TiO₂ systems is investigated using initial mixtures prepared by three methods, namely, mechanical grinding of the initial reactants, coprecipitation from aqueous solutions of salts, and the sol-gel technique. It is established that, irrespective of the preparation procedure, the formation of Ba₂Ti₉O₂₀ proceeds through the formation of the intermediate phases BaTi₄O₉ and BaTi₅O₁₁. The nature of the intermediate phases is determined by the homogeneity and dispersion of the initial mixture, as well as by the stability of the intermediate phase. The most optimum conditions for the synthesis of Ba₂Ti₉O₂₀ are provided by the formation of BaTi₅O₁₁ as an intermediate phase upon heat treatment of the coprecipitation products in the nanocrystalline state. The metastability and structural defects in the BaTi₅O₁₁ intermediate phase encourage a decrease in the temperature of the final heat treatment by 100–150°C in the course of the preparation of Ba₂Ti₉O₂₀ single-phase ceramics.     

基于新标准的俄罗斯釆金业职业风险评估

当前俄罗斯正在进行立法改革以实现治理体系现代化，其中改革的重点是国家管理体系中的劳动保护、工业安全和突发事件的应急处理。过去的立法体系侧重于对受伤员工提供健康补偿和医疗救护，而新的立法体系则以预防为主，以期通过建立完善的风险管理机制和运行规则，提高安全生产水平、普及安全文化教育，保障员工的生命安全。新标准强调企业必须进行职业风险评估，并将职业风险评估纳入企业工作管理体系。论文以采金业为例，选取伊尔库茨克州波戴波区金矿露天采场为研究案例，探讨了现代化职业风险评估的方法，明确了职业风险评估首先要进行危害鉴别，编制了风险源管理档案清单。采用实测员工风险因素的“记分法”和数学模拟“矩阵法”完成了伊尔库茨克州波戴波区金矿露天采场主要职业的风险评估。研究表明: 在钻井爆破作业场所，由碎石的喷射、粉尘的排放和噪声效应引起的危险为不可接受风险，通过实施安全生产制度（即遵守安全标准和技术要求、为工人提供防护装备）,可将高风险和不可接受风险化解为可接受风险；阐述了高风险职业，编制了风险手册，提出了改善工作条件的首要措施是消除影响爆破手和钻机操作员的有害因素，并为员工提供能更有效预防噪音和振动的个人防护用品。     

Rapid determination of zinc in soils by laser-induced breakdown spectroscopy

The possibility of quantitative detection of trace zinc levels in soils per single laser pulse using laser-induced breakdown spectroscopy is shown. The development of laser plasma and the signal-to-noise ratio are studied when evaporating soils by the second (532 nm) and the third (355 nm) harmonics of an Nd:YAG pulse laser. The use of the third harmonics permits one to reach the zinc detection limit (18 ppm) below Occupational Exposure Limits (OEL) in soil (150 ppm) and below the mean abundance in the earth’s crust of zinc (83 ppm). This allows the use of the suggested technique for the rapid determination of soil pollution with zinc and searching for geochemical anomalies.     

Nonequilibrium Diamond Growth during the High-Temperature High-Pressure Synthesis of a Composite Material Made of a Mixture of Cobalt and Fullerene Powders

A composite material (CM) reinforced by diamond particles is fabricated from a mixture of cobalt and 10 wt % C₆₀ powders at a pressure of 8 GPa and a temperature of 1200–1300°C, which is close to the melting temperature of the metastable Co–C eutectic. The results of X-ray diffraction, Raman spectroscopy, and electron-probe microanalysis demonstrate that the CM consists of diamond and the Co₃C carbide. Diamond crystals are shown to grow as plates parallel to a {100} plane according to the mechanism of nonequilibrium normal growth during liquid-phase CM synthesis. The diamond particles have a hardness of 82 GPa at an elastic recovery of 95%. The structure of the synthesized cobalt-based CM with diamond inclusions ensures its ultrahigh wear resistance and antifriction properties.     

Photoresponse recovery in silicon photodiodes upon VUV irradiation

The spatial homogeneity of the photoresponse is studied for silicon photodiodes based on p-n and n-p junctions a year after their irradiation at a wavelength of 121.6 nm and those based on n-p junctions four years after their irradiation with soft X-rays. It is demonstrated that silicon photodiodes based on p-n junctions exhibit a photoresponse recovery effect on being irradiated at a wavelength of 121.6 nm. No recovery effect is observed for silicon photodiodes based on n-p structures.     

Formation of Mg3Si2O5(OH)4 Nanotubes under Hydrothermal Conditions

The formation of nanotubes of magnesium hydrosilicate Mg₃Si₂O₅(OH)₄ with a chrysotile structure is investigated. It is found that the nanotubes of magnesium hydrosilicate Mg₃Si₂O₅(OH)₄ are formed through different mechanisms depending on the initial state of reactants, the composition of the hydrothermal solution, and temperature. It is shown that the rate of formation of nanotubes is determined by the stability of intermediate compounds, the chemical composition of the reaction mixture, and the synthesis temperature.     

Thin Films of Cadmium and Dysprosium Oxides as Gas-Sensitive Elements of Sensors

Polycrystalline nanofilms of Dy₂O₃ and CdO are prepared by hydropyrolysis from aqueous solutions of dysprosium and cadmium nitrate salts. The surface morphology of the films and their polycrystalline structure are investigated by X-ray diffraction and electron microscopy. The synthesis of powders is performed by thermolysis of aqueous solutions of cadmium and dysprosium nitrates. The sequence of formation and crystallization of oxide phases of CdO and Dy₂O₃ is ascertained from the X-ray powder diffraction data. The temperature dependence of the electrical resistance of the films obtained is studied in air and argon atmosphere.     

Low-flow membrane oxygenation of blood in patients with diffuse purulent peritonitis

Small-flow membranous oxygenation of the blood was used in 45 patients with peritonitis in the multiple organ failure phase. In ten cases blood oxygenation was combined with hemofiltration. MOCT 19-03 (Kvant Research and Production Unit) and Gambro FH hemofilters (Sweden) were employed. Combination of small-flow membranous oxygenation of the blood combined with hemofiltration appreciably improved the oxygen-transporting function of the blood in adult patients with the respiratory distress syndrome, which was due to mutual potentiation of the two methods' effects. Small-flow membraneous oxygenation alone improved cellular immunity and decreased the laboratory manifestations of endogenous intoxication due to biotransformation of toxic products.