| 摘要 |
<p>The invention relates to a nanostructured composite material which contains metallic Pd, tungsten carbide WC and carbon and to a process for direct synthesis thereof which allows the control of composition and the crystalline phase of metal carbides and achieves particle sizes of less than 100 nm. According to the invention, the composite material has the following chemical composition: Pd- (WC)- C, where a =0.01...0.9 and b=0.05...0.92, the Pd and WC nanoparticles having sizes in the range of 1...100 nm and an a:b ratio of 0.01...18 and the average size of Pd and WC nanoparticles ranges between 5...40 nm. The process, as claimed by the invention, comprises the following stages: a. preparing a material which consists of a solid homogeneous mixture of Pd and W salts deposited on porous carbon, where the material can be obtained by evaporation, lyophilization of precursor solutions, by impregnation of metal salts in the solution or melt on porous carbon or by physical mixing achieved by crushing in mortars, by grinding in ball mills or by mixing in ultrasound bath for a time interval ranging between 1...120 min; b. pyrolysis of the resulting material in an oven, under N, Ar or He inert gas-protected atmosphere, at a temperature of 600...1500°C, for a time interval ranging from 5 min to 48 hours, the Pd salt being so selected that its decomposition temperature is lower than the carburization temperature of the W precursor, the WC and Pd nanoparticles being obtained directly, at sizes of 1...100 nm, without requiring any other treatment in solution.</p> |
