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Molybdenum carbide (Mo2C) is one of most widely used transition metal carbides due to its remarkable physical and chemical properties, such as outstanding catalytic properties, good thermal stability, high hardness, excellent corrosion, and wear resistances. In the current work, a facile and feasible method was proposed to synthesize ultrafine molybdenum carbide powders with a high purity. Firstly, molybdenum trioxide (MoO3) powder was reduced with insufficient carbon black powder to remove oxygen from MoO3 and generate a mixture of Mo2C and Mo. Then, the mixture was further carbided at 1100 °C or 1200 °C by carbon black to obtain pure Mo2C with an average particle size of 230 nm or 250 nm, respectively. A complete deoxidation at the first step is of significant importance for the precisely determining the amount of carbon addition in the carbonization step. The currently proposed method is a low-cost and efficient method to produce high purity and ultrafine Mo2C in a large scale.

In this work, high pure Mo-10 wt% Cu composite powders with a ultrafine particle size are prepared by a two-step reduction process (first carbothermal reduction and then hydrogen reduction). Ammonium heptamolybdate and copper nitrate trihydrate powders are used as molybdenum and copper source, respectively. The mixtures of raw materials are calcined at 400 °C firstly to form the composite oxides which are then reacted with insufficient carbon black at 1050 °C for 2 h. The as-prepared powders are further reduced by hydrogen at 750 °C for 2 h to obtain the ultrafine Mo-10 wt% Cu composite powders. The experimental results show that the residual carbon of the Mo-10 wt% Cu powders can be decreased to 0.015 wt%, and the composite powders have an average particle size of 200 nm. The sintering behavior of ultrafine Mo Cu powders and the properties (vickers hardness and thermal conductivity) of samples after sintering are investigated. High sintering temperature is beneficial to increase the density of the compact. At 1200 °C, the relative density of the Mo Cu compacts is 98.8%. The vickers hardness and thermal conductivity of the Mo-10 wt% Cu composites sintered at 1200 °C for 3 h are 233 HV and 130 (W/m·k), respectively.

Industrial grade MoO2 powders have a plenty of advantages relative to MoO3 in the direct alloying steelmaking processes. In this work, the reduction of industrial grade MoO3 powder with CO gas or the mixed gases of CO and CO2 has been investigated in detail in order to prepare industrial grade MoO2 powder. It is found that reaction temperature has a significant effect on the product composition. Using pure CO as the reducing gas, for temperatures below 868 K (595 °C), the main product is MoO2 with some whisker carbon; for temperatures above 868 K (595 °C) the main reaction products are MoC and amorphous carbon; as the reaction temperature further increased, the final reaction product is Mo2C. In addition, Mo4O11 is always formed as an intermediate product during the reaction processes both at lower and higher temperatures, which is similar to that observed on reduction of MoO3 by H2. It is found that adding CO2 to the reducing gases eliminated carbon formation but still allows the formation of MoO2 during the reaction process. This method may be applied to produce industrial grade MoO2.

In this paper, high quality Mo-(10–40) wt% Cu and W-(10–40) wt% Cu alloys were prepared by powder metallurgy using the ultrafine molybdenum and tungsten powders as raw materials. The molybdenum powder with the size of 100–200 nm and tungsten powder with the size of 50–100 nm were prepared by a two-step reduction-process composed of an insufficient carbothermal reduction reaction and the following deep reduction reaction by hydrogen. From the experimental results, it was concluded that at the sintering temperature of 1200 °C to 1300 °C, relative densities of the Mo-(10–40) wt% Cu and W-(10–40) wt% Cu sintered blocks can reach >98%, and at the same time, excellent physical and mechanical properties were achieved. Meanwhile, the larger the content of copper in the alloy, the lower the temperature required for densification. At 1300 °C, the relative density, microhardness and thermal conductivity of the Mo-10 wt% Cu and W-10 wt% Cu sintered blocks are 98.83% and 99.36%, 167 HV and 283 HV, 138.38 W·m−1·k−1 and 154.15 W·m−1·k−1, respectively. Whereas, at 1200 °C, the relative density, microhardness and thermal conductivity of the Mo-40 wt% Cu and W-40 wt% Cu sintered block are 99.68% and 98.87%, 150 HV and 207 HV, 138.38 W·m−1·k−1 and 154.15 W·m−1·k−1, respectively. The present method was much more convenient relative to the traditional infiltration method.

In the present study, the solid state reactions between molybdenum disulfide (MoS2) and molybdenum trioxide (MoO3) under different mixing molar ratios and different reaction temperatures have been investigated in order to produce industrial grade molybdenum dioxide (MoO2). It was found that it was difficult to react completely when the temperature was less than 873 K. However, when the temperature was up to 923 K or 973 K, the final product MoO2 with low residual sulfur can be obtained. Results of the residual sulfur levels at different conditions show that the content of residual sulfur decreases with the increase of temperature. In addition, the excess additions of MoO3 are effective and necessary in order to decrease the residual sulfur level. When the mixing molar ratio of MoS2 to MoO3 is 1:6.5, the content of residual sulfur can decrease down to 0.075% at 973 K. It was also found that the reaction between MoS2 and MoO3 obeyed the shrinking core model.

The principle and process of producing molybdenum powder via reduction reaction of molybdenum trioxide at lower temperature in a N2-H2 system were researched. The effects of hydrogen concentration, temperature, and volatilization rate of molybdenum trioxide on particle size were analyzed. The experimental results showed that the optimal process parameters were 770°C-790°C in 60min when the hydrogen flow rate was 700mL/min. Particle size of superfine molybdenum powder was less than 4μm. The concentrations of hydrogen, temperature and volatilization rate of molybdenum trioxide have great effect on the particle size of superfine molybdenum powder.