Abstract

A characteristic of obtaining metal powders by direct current electrolysis is changes in the morphology of particles over the loose deposit layer thickness up to the formation of large spherulites. Deposits should be periodically removed from the cathode in order to obtain a powder with homogeneous composition. This paper justifies the choice of the parameter describing the change in loose deposit properties and proposes a method for determining the periodicity of its removal from the cathode. Loose zinc deposits were obtained at 25°C from zincate electrolyte containing 0.3 mol L^–1 of ZnO and 4 mol L^–1 of NaOH at a current setpoint exceeding six times the limiting diffusion current calculated using the smooth electrode. Electrode potential, deposit thickness and evolved hydrogen volume were measured directly in the process of electrolysis. Current redistribution between the metal reduction and hydrogen evolution leads to a change in the structure of loose deposit particles. It is shown that the differential current efficiency of zinc is the parameter describing the change in the loose zinc deposit density. Its value should not exceed 0.96, in order to ensure deposition of loose deposit with homogeneous properties. A further increase in current efficiency will lead to the formation of aggregates at the deposit growth front. It is proposed to determine the periodicity of loose deposit removal from the cathode using the empirical equation for the time dependency of differential current efficiency of zinc. The mathematical and statistical analysis of the data obtained in six replicates was carried out. The interval approach made it possible to significantly narrow the range of permissible differential current efficiency values and, as a consequence, to determine empirical equation coefficients with acceptable accuracy and calculate the growth time period of a deposit with homogeneous structure. The obtained approach can be used to estimate the time period of loose metal deposition accompanied by hydrogen evolution.

中文翻译：

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区间分析法确定松散锌矿床的生长期

摘要

通过直流电解获得金属粉末的特征是，在整个沉积层厚度上直至形成大球晶之前，颗粒的形态都会发生变化。为了获得具有均匀组成的粉末，应当定期从阴极去除沉积物。本文论证了描述疏松沉积物特性变化的参数的合理选择，并提出了一种确定从阴极去除其周期性的方法。在25°C下，从含0.3 mol L ^–1的ZnO和4 mol L ^–1的锌酸盐电解质中获得的锌沉积较松散电流设定点的NaOH超过使用光滑电极计算的极限扩散电流的六倍。在电解过程中直接测量电极电位，沉积物厚度和析出的氢气量。金属还原和氢放出之间的电流重新分布导致疏松的沉积颗粒结构的变化。结果表明，锌的差动电流效率是描述疏松的锌沉积密度变化的参数。其值不应超过0.96，以确保沉积具有均一性质的疏松沉积物。电流效率的进一步提高将导致在沉积物生长前沿形成聚集体。建议根据经验公式确定锌的差分电流效率与时间的相关性，以确定从阴极去除松散沉积物的周期。对六次重复获得的数据进行了数学和统计分析。间隔方法可以显着缩小允许的差分电流效率值的范围，从而可以确定具有可接受精度的经验方程系数，并计算具有均质结构的沉积物的生长时间。所获得的方法可用于估计伴随氢放出的松散金属沉积的时间。间隔方法可以显着缩小允许的差分电流效率值的范围，从而可以确定具有可接受精度的经验方程系数，并计算具有均质结构的沉积物的生长时间。所获得的方法可用于估计伴随氢放出的松散金属沉积的时间。间隔方法可以显着缩小允许的差分电流效率值的范围，从而可以确定具有可接受精度的经验方程系数，并计算具有均质结构的沉积物的生长时间。所获得的方法可用于估计伴随氢放出的松散金属沉积的时间。