Mechanisms governing tribochemical reduction of metals and non-metals from their oxides

The paper describes the physical and chemical mechanisms governing the tribochemical reduction of metals and non-metals from their oxides. The reduction was started by a tribochemical activation of initial constituents in a vibrating mill used as a reactor. Powders of oxides of copper, iron, molybdenum, tungsten, vanadium, titanium and boron and also such chemically pure metals as magnesium, aluminium and titanium were used as reaction constituents. The triboactivation energy contribution needed to start the explosive mechanism reduction is found to increase as the heat of reaction decreases and the heat of formation of the associated product rises. Introducing oxygen into the reactor during the tribochemical activation of powders of oxides together with magnesium causes the intense oxidation of magnesium and stimulates the reduction process. To increase the yield of tungsten monocarbide from tungsten concentrate, the reduction process should be implemented in an atmosphere of hydrogen or hydrocarbons.     

Stability Criteria of Underground Workings under Zonal Disintegration of Rocks

Using the energy approach as the base, the criteria are developed for brittle rock failure in outcropping in the workings driven in the rock masses of different degree of disturbance. A method is presented for estimating the stability of workings under conditions of zonal disintegration.     

Calculations of the Probability of Positron Trapping by a Vacancy in a Metal and the Estimation of the Vacancy Contribution to the Work Function of Electrons and Positrons

The probabilities of the localization of positrons in monovacancies of Al and Cu have been calculated as functions of the energy and temperature. The vacancy was simulated by a void with a radius equal to the radius of the Wigner—Seitz cell in the model of stable jellium. Using the Fermi—Dirac golden rule for transitions, the formula for the rate of positron trapping by a vacancy has been derived as the function of the positron energy. For the thermalized positrons, the rate of localization near the triple point proved to be, on the order of magnitude, close to the rate of annihilation. Within the framework of our previously proposed models, the contribution of vacancies to the work function of electrons and positrons has been demonstrated based on the example of Al. The physical situations where the vacancy effect can manifest have been considered.     

Tin- and copper-based electrochemical coatings for sliding bearings

Copper- and tin-based electrochemical coatings are obtained. The results of disk-shoe couple tests show the wear and wear rate of the coatings; their structure is studied demonstrating that bi- and tricomponental electrochemical coatings boost considerably the copper and bronze wear resistance, making them useful for the manufacture of sliding bearings.     

Processing of sphagnum moss to produce carbon nanotubes

Attention focuses on the processing of sphagnum moss and the sequence by which multiwalled carbon nanotubes are formed in the mechanical activation of amorphous carbon. Nanotube formation occurs within a mass of carbon particles.     

Factors influencing the mechanochemical synthesis of tungsten and titanium carbides

Nanometer-sized tungsten monocarbide and titanium carbide are produced by mechanical activation. The formation of the former carbide is shown to be promoted by the introduction of polymethylmethacrylate into the initial charge for synthesizing tungsten carbide. It is found that the main limiting factors of the mechanochemical synthesis in the titanium-carbon system are the structure of carbon modifications and the degree of their aromaticity.     

Mechanochemical processing of wastes from high-speed steel machining

The manufacture of cutting plates on the basis of powder produced by the disintegration of wastes from the machining of P6M5 high-speed steel is considered. The use of high-molecular compounds in the processing of waste chips is promising. The performance of plates made from high-speed steel powder is investigated.