Wet Chemical Method - A Reduction Of Hydrogen Preparation Of Molybdenum Copper Composite Powder And Sintering Performance Of The Research

In the investigation, preparation of ultra-fine Mo-Cu nanocomposites by the technique of one-stage reduction of liquid reduction was studied with the aid of differential scanning calorimetry and thermal gravimetric analysis (DSC-TG), X-ray diffraction (XRD), scanning electron microcopy (SEM), transmission electron microcopy (TEM). The influence of the liquid reduction temperature, magnetic stirring and surfactant on the microstructure and size of the Mo-Cu powders was studied and the thermodynamical conditions at different stages of hydrogen reduction of Mo-Cu nanocomposite powders were analyzed. The possible mechanism of one-stage reduction was also proposed. Finally, the technique of Mo-Cu composite powders sintering and influence of sintering temperature on properties of Mo-Cu composites were researched.CuMoO4N0.42H1.26·H2O and Cu mixtures can be obtained by ammonium heptamolybdate, copper chloride and hydrazine hydrate with water bath. Then it was accompanied by a transformation from CuMoO4N0.42H1.26·H20to Cu3Mo2O9and Cu2MoO5, which can decompose into Mo02, MoO3and CuO at a low temperature (200℃) during the H2reduction process, giving rise to the Mo-Cu nanocomposites with particle size ranging from50nm to100nm at800℃. Because of the Cu3Mo2O9and Cu2Mo05, the reduction processe in H2is the one-stage reduction from the precipitates to the Mo-Cu composite powders. The prepared Mo-Cu powders have a coating structure, which causes a homogeneous distribution of Mo and Cu phases and controls the growing of Cu phase effectively.Sintering temperature has critical effects on the microstructures and properties of Mo-30Cu composites. The liquid sintering method was not ideal way to fabricate the Mo-Cu composite materials, because after liquid sintering the phenomena of copper exudation was observed, which has a negative effect on properties of Mo-Cu composites. It is shown that specimens sintered at1050℃for120min obtained good complex properties. The density, hardness, electrical conductivity, thermal conductivity and coefficient of thermal expansion are9.52g·cm-3,214.7MPa,28.1MS·m-1,153.65Wm-1K-1,8.6×10-6K-1.