High temperature hydrolysis of the mixed aqueous solution consisting of 5.0×10
−3∼5.0×10
−2 kmol·m
−3 Cu(II), Zn(II), Co(II) or Ni(II) sulfate, 0∼0.5 kmol·m
−3 (NH
4)
2SO
4 and 0.1∼1.2 kmol·m
−3 NH
3 were studied at 373 K for 3.6 ks to examine the effects of solution composition on the shape, particle size and precipitation degree of the hydrolyzed particles. Particles precipitated were identified as spherical CuO, cylinder shape ZnO, spherical Ni(OH)
2 and spherical Co
3O
4.
The increase in the concentration of metal ions, NH
3 and (NH
4)
2SO
4 in the high temperature hydrolyses of Cu(II) and Zn(II) results in the increase of particle size, while the precipitation degree decreases. In contrast, the increase in the concentration of Co(II) ions results in a slight increase in the particle size, but there was no significant effect on controlling particle size expected from changing NH
3 and (NH
4)
2SO
4 concentrations.
As mentioned above, the particle shape as well as the particle size can be controlled by changing the composition of ammine solution in the case of Cu(II) and Zn(II), whereas it is difficult for Co(II). The control of particle size of Cu(II) is far easier than that of Zn(II). The change in precipitation degree by changing the solution composition was the smallest with Cu(II). Controlling the particle size of Co
3O
4 was almost impossible by changing solution composition.
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