Comparing thermal and mechanochemical decomposition of ammonium paratungstate (APT)

In this research, the possibility of mechanochemical decomposition of ammonium paratungstate (APT) has been studied, and compared with thermal decomposition method. For this purpose, APT powders were milled using a planetary ball mill up to 36 h and under air atmosphere. For thermal decomposition, APT powders were heated for 30 minutes at 300 and 450 degrees C in air atmosphere. X-ray diffraction (XRD), differential scanning calorimeter (DSC), and thermo gravimetric analyzer (TGA) were used to study the decomposition progress, and products. The XRD results showed that APT completely decomposed to WO(3) by thermal decomposition, while the final product of mechanochemical decomposition was WO(3) (H(2)O)(0.5). According to DSC and TGA results, during thermal decomposition, ammonia and water released in four steps, and leaved WO(3). By mechanochemical decomposition crystal water and ammonia liberated from APT structure, but structural water of APT remained. In both methods, an X-ray amorphous phase was the intermediate product of APT decomposition. (C) 2011 Elsevier Ltd. All rights reserved.