Obtaining of powders of tungsten and molybdenum aluminothermy of oxides in a melt of chloride of alkali metals

摘要

A assessment of the current state of research in the field of physico-chemical bases production of powders of tungsten and molybdenum are given. It was noted that traditional technology hydrogen reduction of oxides does not fully meet modern requirements. The problem of producing metal powders of tungsten and molybdenum is offered to solve using the new approach: reduction of oxides of metals is necessary to conduct in the environment of melts of salts of alkali metals. The conditions for producing fine powders of molybdenum and tungsten by reduction of oxygen compounds of aluminum in NaCl-KCl melts are studied at temperature of 1100-1200K. Thermal analysis showed that the restoration in the melt, with a deficiency of oxygen occurs less intensively than in air, and fits into the range 700-850°C. Products of restoration showed that monophase powders of molybdenum and tungsten are formed. It was shown that the yield of the powders reaches 96-98% due to 25% excess aluminum concentration in the melt. Purity of powders makes 98,5-99%. The microstructure of the powder is presented by the agglomerates, consisting of particles of round shape less than 2 μm. It is shown that under equal conditions of synthesis powders of molybdenum have a greater value of specific surface area (45,3·105 m-1) than tungsten (32,4·105 m-1). It is shown that with increasing concentrations of the reactants in the melt in 4 times, the fraction of particles finer fractions powders increases and as a result, the specific surface area becomes more in 2 times.