为了制备MLCC电极用超细铜粉,克服CuSO_4 直接水合肼还原法制备的铜粉存在粒度分布不均匀、振实密度小的问题,提出了两步液相还原新工艺,即以CuSO_4 溶液为原料,首先采用NaOH沉淀-葡萄糖预还原制备Cu_2O,然后用水合肼还原Cu_2O制备超细铜粉.针对实现铜晶体的成核与长大过程的分离,研究了水合肼加入方式对铜粉性能的影响,发现较慢的水合肼滴加速度和将水合肼还原Cu_2O阶段分为升温均匀成核与水合肼连续滴加长大两个过程有利于得到粒度均匀的铜粉.在最佳试验条件下制得的铜粉呈类球形,粒度分布均匀,分散性好,平均粒径为1.8μm,振实密度达4.2 g/ml.
Against the the wide size distribution and low tap density of uhrafine copper powder prepared via direct reduction of CuSO_4 by hydrazine hydrate, a novel two-step-reduction process has been proposed to pre-pare the uhrafine copper powder used for MLCC electrode, in which Cu_2O was prepared via glucose pre-reduc-tion under alkaline conditions firstly, and then uhrafine copper powder was prepared by hydrazine hydrate re-duction of Cu_2O. To separate the nucleation and growth stage of copper crystal, the influence of adding mode of hydrazine hydrate on copper powder was investigated. It has been found that the copper powder with narrow size distribution can be formed by adding hydrazine hydrate slowly, and by separating the hydrazine hydrate re-duction of Cu_2O into a homogeneous nucleation stage during the heating of solution from 45 ℃ to 80 ℃ and a crystal growth stage. For the well-dispersed uniform spherical copper powder prepared under optimized condi-tions, its average particle size is 1.8 μm and its tap density is 4. 2 g/ml.
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