Effect of Diameter on Apparent Activation Energy of Non-isothermal Decomposition Reaction of Nano-Mg(OH)2 Powder

The nano-Mg(OH)2 powders of different diameter were prepared by chemical precipitation. Its DTA-TG curves were obtained by SDT-2960 simultaneous DSC-TGA analysis with rising temperature rate of 15°C·min-1 in air. The kinetics of its non-isothermal decomposition was calculated by DTA-TG curves and dα dt = k 3 2 (1 - α)[- ln(1- α )] 1 3 kinetics model. The results showed that the shape of nano-Mg(OH)2 powders were stick-like or spherical, and their diameters were 7, 12, 20, 40 and 70nm, respectively. Their apparent activation energies for thermal decomposition reaction were 106.817, 109.899, 139.174, 158.170 and 167.639 KJ·mol-1,respectively. The apparent activation energy increased with Mg(OH)2 diameter. Their pre-exponential factors were 1.41x109, 2.47x109, 7.95x1011, 8.78x1012, 3.82x1013, the pre-exponential factor increased with diameter of Mg(OH)2.