Self-reinforced materials based on aluminum nitride

Powder Metallurgy and Metal Ceramics -     

Exciton photoluminescence in doped quasi-1D structures based on silicon

The dependence of carrier density in silicon quantum wires sheathed with SiO₂ on the wire diameter and the position of impurity atoms in respect to the wire center is analyzed theoretically. It is shown that, as the diameter of wires and nanocrystals decreases, the ionization energy of a dopant increases; therefore, the free carrier density decreases, and the screening of the Coulomb attraction becomes ineffective. As a result, the photoluminescence is defined by the radiative recombination of excitons even in the case of heavily doped Si. These conclusions are supported by the data of experimental study of spectral, excitation-power, and temperature dependences of photoluminescence in porous silicon structures fabricated on lightly and heavily doped Si substrates.     

Specifics of initial steam condensation and its influence on corrosion damage in turbines

Processes of corrosion cracking of the metal of turbine blades in the region of initial steam condensation are considered. Possible ways of preventing corrosion-fatigue damage to the blades are proposed.     

十年磨一剑——记上海上大玲珀化工科技有限公司董事长朱勇强

穿着朴实，谈吐文雅，举止端庄，从他富有表情的脸上和那对炯炯有神的眼睛，折射出一个青年科技企业家特有的自信、干练、豁达与刚毅。他，就是上海上大玲珀化工科技有限公司的董事长朱勇强博士。在与他寒喧之际，记者感到朱博士是位思维敏捷、善于开拓、好学求进、富有创新精神和管理才能的既懂技术、又会经营的复合型人才。他谈吐中潜在的智慧、才干和创业的理念使记者佩服。     

Temperature Dependence of the Magnetic Properties of Amorphous Fe-Me-Si-B Alloys

Alloying of amorphous Fe-Me-Si-B metallic compositions with nickel and molybdenum results in a decrease in the values of saturation magnetization in fields with a magnetic intensity of 0.72 MA/m. The same alloying additions decrease the temperature of formation of new magnetic Fe₃B-type phases, which are stable up to 873 ± 5 K.     

Dissolution of U,Np, Pu,and Am Oxides and Their Mixtures in Tributyl Phosphate Saturated with HNO3

It was shown for the first time that weighable amounts of uranium dioxide and its mixtures with Np, Pu, and Am in the form of solid solutions can be efficiently and quantitatively dissolved in the presence of tributyl phosphate saturated with HNO₃. Individual PuO₂ and NpO₂ are not dissolved under these conditions. In treatment of a mechanical mixture of UO₂ with PuO₂ or NpO₂, uranium is completely dissolved, while plutonium and neptunium remain in the precipitate.     

Effect of spontaneous polarization on the energy levels in quantum wells formed at the contact between cubic and noncubic silicon carbide polytypes

We have studied the effect of spontaneous polarization, which is inherent in noncubic silicon carbide (SiC) polytypes, on the characteristics of quantum wells (QWs) formed in the cubic region at the heterojunction. The analysis is performed for various QW models, including triangular, parabolic, and exponential. Conditions for the appearance of a two-dimensional electron gas at the interface are briefly discussed.     

The fractal structure of a carbon deposit formed during graphite spraying in an electric arc

Experimental data obtained by atomic force microscopy showing that a carbon deposit formed during graphite spraying in an electric arc possesses a fractal structure. The deposit is composed of clusters with dimensions on the order of 1–5 nm. The surface and profile of the deposit exhibit a self-affine fractal structure. The fractal dimensions of the deposit surface and profile, as well as the Hurst index characterizing the self-affine fractal, are determined.