Abstract
The thermal decomposition process of Pb2O(OH)2 and the phase transformation of the decomposed PbO were studied by using T.G.A., D.T.A. and X-ray diffraction.
The thermogravimetric curves of the samples heated in air, nitrogen and vacuum showed the three stages in the decompostition process and in the oxygen atmosphere the four stages. The temperature of the complete dehydration shifted to higher with increasing the partial pressure of the oxygen. apparent activation energy and the reaction order for the dehydration process in the various atmospheres were determined as follows.
The rate constants for the three dehydration stages in air were represented by K= 107.4 exp (-17000/RT), K = 108.5 exp (-28000/RT) and K = 1016 exp (-45000/RT), respectively.
The phase transformation from litharge to massicot was the second order reaction. The rate determining step of this transformation may be linear growth of the new phase of massicot and the apparent activation energy was about 58 kcal/mol.
