Nano-scale γ-AlOOH with various morphologies, such as whisker, bar, ball, and sheet, was synthesized successfully and controllably through a facile hydrothermal method just by adjusting the pH value of the solvent. Based on the analysis of the experimental data, the growth mechanism of nano-scale γ-AlOOH in the hydrothermal process was established. It is proposed that the growth unit and the growth direction are determined by the pH value of the solution and the growth unit, respectively. One-dimensional γ-AlOOH, such as whisker and bar, is formed in lower pH ranges, while two-dimensional γ-AlOOH such as sheet is formed only in high pH environment following the plane expansion crystallization mechanism.

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