Microarc Oxidation of Metal Surfaces: Coating Properties and Applications

Russian Physics Journal - The paper deals with one of the most promising, intensively developing methods of depositing functional oxide coatings onto aluminum and titanium alloys, namely microarc...     

Origin and spectral composition of the luminescence associated with the fatigure fracture of polymers

The nature of the luminescence associated with the fatigue fracture of polymers, accompanied by intense cracking, and with the growth of an artificial crack has been subjected to analysis. As a result of a comparison of the spectral composition of the luminescence associated with fracture with that of the luminescence produced by other modes of excitation it is concluded that the emission is chiefly attributable to gas-discharge phenomena.Institute of Chemical Physics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 515–518, May–June, 1972.     

From spontaneous dispersion to mechanical alloying

Phenomena of spontaneous dispersion, mechanical alloying, and plastic deformation of metals and ionic crystals in the air and in the presence of surfactants within a wide range of thermodynamic and mechanical forces are compared. Various manifestations of Rehbinder’s effect and the role of the main mechanisms of mass transfer (diffusion, dislocation, and interstitial) in the aforementioned processes at stresses both lower and much higher than the yield stress are demonstrated.     

Mechanical activation of aluminum: 2. Size,shape, and structure of particles

The structure of active Al/C composite prepared by the mechanochemical method from aluminum and graphite powders (10–30 wt % C) is studied by scanning and transmission electron microscopies, atomic force microscopy, local elemental analysis, X-ray diffraction, as well as by adsorption and sedimentation measurements. It is established that the particles of chemically active Al/C composite represent porous plate-like aggregates with a mean size smaller than 2.5–5 m and composed of nanocrystalline aluminum blocks with a size of 15–60 nm distributed in a loose amorphous carbon. Single aluminum particles with a size of up to 10 nm are also observed; however, their weight fraction is small.Translated from Kolloidnyi Zhurnal, Vol. 66, No. 6, 2004, pp. 819–828.Original Russian Text Copyright © 2004 by Streletskii, Pivkina, Kolbanev, Borunova, Leipunskii, Pshechenkov, Lomaeva, Polunina, Frolov, Butyagin.     

Amorphization of Silicon during Mechanical Treatment of Its Powders: 1. Process Kinetics

The kinetics of silicon amorphization in the process of mechanical treatment of powders in a vibrating micromill was studied by the X-ray diffraction. The treatment was carried out in the argon atmosphere, the apparatus energy intensity was equal to 18 W/g, and the amount of consumed energy (dose) was as high as 510 kJ/g (14 MJ/mol). The analysis of the shape of X-ray diffraction patterns and the dynamics of the changes in silicon atomic structure were described within the framework of three-fraction model. Fraction 1 composed of large crystalline blocks comprising particles of initial powder; the second fraction is represented by nanocrystalline blocks with the dimensions of not less than 8 nm; and the third fraction is an amorphous phase. A decrease in the content and sizes (from 10²to 25 nm) of initial microcrystals of fraction 1 is accompanied by the formation of X-ray amorphous phase 3. Nanocrystalline blocks of fraction 2 are none other than the intermediate products. They are first accumulated synchronously with the amorphous phase and then disintegrated with a decrease in their sizes from 8 to 4 nm. At the initial stage of experiment, at the dose up to 15 kJ/g and the degree of amorphization up to 40%, the energy yield of the formation of amorphous phase amounts to 1 ± 0.1 mol/MJ. At the end of experiment (the dose varies from 20 to 510 kJ/g), the yield drops by tens of times, and the content of amorphous phase reaches 70–80%.