RELATIONSHIP BETWEEN PRECIPITATION RATE AND SPHERICAL CUO PARTICLE-SIZE IN HIGH-TEMPERATURE HYDROLYSIS OF CU(II) AMMINE SOLUTION

In a previous paper, the present authors reported that the preparation of spherical fine CuO powders was achievable by applying hydrolysis m ethod at elevated temperature to Cu(II) ammine solution. Based on this finding, the effect of hydrolysis reaction rate on CuO particulate di ameter was investigated in this study. It was elucidated that the prec ipitation of spherical CuO particulates proceeds according to a typica l building up mode: super-saturation, nuclear formation and crystal gr owth. Generally, the increase in NH3 concentration, Cu(II) concentrati on under the constant ratio of [CuSO4]/[Ammonia] = 8.5, and (NH4)(2)SO 4 concentration at the constant ratio of [Ammonia] + 2[(NH4)(2)SO4] = 1.7 x 10(2) mol.m(-3) resulted in the decrease of crystallization rate . The concentration-dependence in crystallization rate was more sensit ive at 353 K than 373 K. The apparent activation energy of 11.7 kJ.mol (-1) obtained in the temperature range 363 similar to 378 K suggested mass transfer mechanism. Mean diameter of CuO spherical particles and their size distribution increased with an increasing ammonia, CuSO4 an d (NH4)(2)SO4 concentrations, on the contrary, the yield of CuO decrea sed. No differences of particle size were detected by the change of te mperature from 353 to 373 K. There existed a correlation among crystal liration rate, mean particle size and size distribution range when the temperature was kept constant. The increase in crystallization rate r esulted in the decrease in particle size.