Synthesis of ZnO Nanograins by Immersing Zn Powders in Oxalic Acid Solution Plus Thermal Decomposition.A simple and inexpensive method to synthesize ZnO nanograin powders from Zn powders is reported in this paper and phase change from Zn powders to ZnO nanograins during the process is studied in detail.  The phase transitions from Zn powders to ZnO nanograins during the two-step synthesis are analyzed thermodynamically. 
THERM