Ni(OH)₂ hollow spheres have been prepared by solvent displacement crystallization using a micro-injection device, and the effect of process parameters such as concentration and the relative ratio of the injection speed of the precursor solution, which is an aqueous solution of NiSO₄·6H₂O, to isopropyl alcohol of displacement solvent have been investigated. The crystal phases after NaOH treatment are in the β-phase for all process parameters. A higher concentration of NiSO₄·6H₂O aqueous solution is injected by a micro-injection device and bigger Ni(OH)₂ hollow spheres with a narrower particle size distribution are formed. The crystallinity and hardness of the as-obtained powder are so poor that hydrothermal treatment of the as-obtained Ni(OH)₂ at 120°C for 24 h in distilled water is performed in order to greatly improve the crystallinity. It is thought that a relative ratio of the injection speed of NiSO₄·6H₂O to that of isopropyl alcohol of at least more than 1 is preferable to synthesize Ni(OH)₂ hollow spheres. It is confirmed that this solution- based process is very effective in synthesizing ceramic hollow spheres by simple adjustment of the process parameters such as the concentration and the injection speed.

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• The Effects of Hexamethylenetetramine Concentration on the Structural and Electrochemical Performances of Ni(OH)₂ Powder for Pseudocapacitor Applications
  Dong Yeon Kim, Young-Min Jeong, Seong-Ho Baek, Injoon Son
  Journal of Korean Powder Metallurgy Institute.2019; 26(3): 231.     CrossRef