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采用熔盐电解法以CaCl_2-NaCl为电解质还原Na_2WO_4及NiO合成由W,Ni及NixWy相构成的W-Ni复合金属粉体。通过三电极系统以循环伏安法分析W(VI)和Ni(II)离子的电极还原过程,并通过X射线衍射(XRD)、扫描电镜(SEM)及能谱分析(EDS)表征和分析阴极电解产物的形貌及组成。结果表明:以石墨为电极,在温度800℃,恒电位2.5 V的外部条件下,直接混合Na_2WO_4-NiO电解,容易导致复合金属粉末产物中Ni偏析而形成Ni_(17)W_3相,产物颗粒容易团聚,其中Ni的质量分数高于14%,易形成复杂Ni_xW_y相;而通过先后分时加入Na_2WO_4和NiO方法,可以有效控制W-Ni复合金属粉体的中的Ni偏析并形成NiW相,产物颗粒分散性好,粒径均匀,使Ni质量百分比低于5%,并能有效避免复杂NixWy相的析出;电解过程中W(VI)的主要来源为Na_2WO_4与CaCl_2前置反应而形成的CaWO_4,W(VI)和Ni(II)离子的电极还原过程均为不可逆过程,Na_2WO_4加入后体系活性离子在熔盐中的扩散系数整体减慢了接近10倍,W(VI)离子的引入是制约电极反应速率的控制步骤。
The W-Ni composite metal powders consisting of W, Ni and NixWy phases were synthesized by molten salt electrolysis using Na 2 WO 4 as the electrolyte and CaCl 2 -NCl as electrolyte. Electrode reduction of W (VI) and Ni (II) ions was analyzed by cyclic voltammetry using a three-electrode system and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) Electrolysis product morphology and composition. The results showed that the direct mixing of Na_2WO_4-NiO with graphite as electrode at a temperature of 800 ℃ and constant potential of 2.5 V could lead to the segregation of Ni in the composite metal powder to form Ni_ (17) W_3 phase. Reunion, in which the mass fraction of Ni is higher than 14%, easy to form a complex Ni_xW_y phase; and by successively adding Na_2WO_4 and NiO method can effectively control the W-Ni composite metal Ni in the segregation and the formation of NiW phase, the product The particle dispersion is good, the particle size is uniform, the mass percent of Ni is less than 5%, and the precipitation of complex NixWy phase can be effectively avoided. The main source of W (VI) during electrolysis is CaWO 4 formed by the pre-reaction of Na 2 WO 4 and CaCl 2, The electrode reduction process of W (VI) and Ni (II) ions are both irreversible. The diffusion coefficient of the active ions in the molten salt slowed nearly by 10 times after the addition of Na_2WO_4. The introduction of W (VI) Reaction rate control steps.