Abstract
The homogeneous precipitation of hydrous zinc oxide colloids using hexamethylenetetramine (HMTA) as the precipitant was investigated. Depending upon the precipitation conditions, the precipitates can be made into various shapes such as rod, needle, globular or aggregates. It was found that the starting pH value, the reaction temperature and the addition of alcohol all have quite significant effects on particle morphology. However, after prolonged aging, all precipitates would transform into crystalline rod-shaped particles. The role of HMTA as well as the formation mechanism of these particles were also discussed.