[en] An equation is obtained for calculating the rate of molybdenum precipitation from the MoF₆+H₂+HF mixture, and the effect of HF content on the precipitant structures is investigated at 870 deg C. It is shown that presence of hydrogen fluoride in the gas mixture decreases the rate of molybdenum precipitation, reducing the range of conditions for formation of dendrite precipitants

[en] Regularities for reduction of molybdenum hexafluoride on the inner surface of tubular articles are described and possibilities of the fluoride method to resolve this problem are analyzed. It is shown that the change in the composition of a gas mixture, resulting from the reduction of molybdenum hexafluoride with hydrogen, is accompanied by formation of various types of molybdenum precipitates along the reaction zone length. For obtaining compact, structuraly homogeneous precipitates with a high utilization efficiency of MoF₆, temperatures of 850-900 deg C and a content of MoF₆ in its starting hydrogen mixture of 20-27 mole % are recommended. A possibility is shown of obtaining homogeneous molybdenum coatings (+-15%) over the inner surface of tubular articles with lengths of up to 600 mm at the temperature gradient of approx. 1 degree/cm and reversibility of the gas mixture motion direction

[en] The effect of the generated hydrogen fluoride on the kinetics of the heterogeneous reduction of the gaseous MoF₆ with hydrogen has been studied. Molybdenum deposited on the inner surface of the externally heated up copper tube (550-900 deg C). The deposition rate has been measured in several points of the tube length, where the reactive surface temperature was being taken simultaneously. The gaseous mixture composition in each point has been calculated on the basis of the known composition of the initial mixture and with respect to the amount of the deposited molybdenum in the section between the inlet of gas and the point under study. A generalized equation of the chemical kinetics for the heterogeneous reduction in the presence of HF has been worked out

[en] The quantitative analysis of kinetic characteristics of the heterogeneous process of molybdenum hexafluoride reduction with hydrogen has been made. The experimental data of the effect of the molybdenum precipitation rate on MoF₆ concentration in the gas mixture are given at different temperatures and the atmospheric pressure. The chemical kinetics equation evolved for the interaction between adsorbed components in the MoF₆-H₂-Mo system gives an adequate description of the molybdenum precipitation rate in MoF₆+H₂ atmosphere

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[en] Presented are results of a thermodynamic analysis of possible chemical reactions in heterogeneous reduction of molybdenum hexafluoride by hydrogen. Investigated are the kinetic characteristics of the process as a whole and its separate stages with a view to revealing the patterns of chemical transformations of initial product to final ones. The heterogeneous reduction of molybdenum hexafluoride in the presence of hydrogen takes place in two stages. The first stage is the reduction of molybdenum hexafluoride by hydrogen and metallic molybdenum with formation of molybdenum trifluoride. The second stage is the reduction of molybdenum trifluoride to a lower fluoride which disproportionated subsequently with the evolution of metal

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[en] Described is a physical model and presented is a mathematical analysis of operations of devices for gaseous-phase precipitation of niobium and tantalum. The calculation of equilibrium in systems and the use of kinetic characteristics of the processes have permitted to establish a quantitative interconnection of the main process indices (yield and productivity) with parameters of its performance and the sizes of apparature used

No abstract available