水热还原制备镍包人造金刚石

Preparation of nickel-coated diamond powder by hydrogen reduction under hydrothermal conditions

采用水热加氢还原法制备了镍包金刚石(Ni/Dia.)复合粉末。制备过程包括预处理和包覆两个阶段。对表面活化剂氯化钯(PdCl2)的用量、溶液的组分、操作温度、氢分压以及搅拌速度等因素对反应过程和涂层质量的影响进行了详细的研究。结果表明,表面活化剂PdCl2是获得良好镍包覆层的关键。水热还原的最佳条件是:NH3/Ni摩尔比为2.4/1,氢分压为2.5MPa,温度165℃和搅拌速度为800r/min。

The composite powder of nickel-coated diamond was prepared from an aqueous solution of ammoniacal nickel sulfate by hydrothermal reduction with hydrogen. The process comprised a pretreatment step of activating the surface of the diamond powder, and a coating step of depositing nickel onto the activated diamond. The effects of the composition of solutions, the activator （PdCl2 ）, the partial pressure of hydrogen, temperature and agitation on the coating results were investigated. The pretreatment and the quantity of PdCl2 were shown to be the key point for getting a nice nickel layer on the diaraond surface. The optimum conditions were proposed as follows： 2.4/1 of the molar ratio of NH3/Ni, 2.5MPa of the hydrogen pressure, 800 r/min of the stirring speed, and 165℃ of the reaction temperature.