![]() ![]() ![]() The thermo-oxidative degradation illustrated by Ozawa method shows a stable apparent activation energy (EĪ ≈130 kJ mol−1 ) even though the thermal degradation in nitrogen flow presents a maximum EĪ new type of overhead conductor with a polymer composite core is evaluated in terms of the mechanical properties and operating characteristics. Apparent activation energy calculated by Kissinger method in oxidative atmosphere for each step is between 40–50 kJ mol−1 upper than E A kinetic model described by the Kissinger method or by the Ozawa method gives the kinetic parameters of the composite decomposition. To elucidate this difference, a kinetic analysis is carried on. A three-step loss is observed during dynamic TG in air while mass loss proceeded as a two step process in nitrogen at fast heating rate. Curves obtained by TG in air are quite different from those obtained in nitrogen. The degradation is investigated by means of dynamic thermogravimetric analysis (TG) in air and inert atmosphere at heating rates from 0.5 to 20☌ min−1. In this work, a kinetic study on the thermal degradation of carbon fibre reinforced epoxy is presented. This was substantiated by a comparison of the rate constants, k, derived isothermally with those calculated in terms of the kinetic compensation effect for nonisothermal dehydration at various heating rates. Under nonisothermal conditions, the single-step dehydration could also be described by a contracting geometry model with the exponent n being slightly different from that in the isothermal analysis. The isothermal dehydration of the powdered material, which proceeded in a single step, was described by a contracting geometry law, 1 - (1 - α)1/n = kt, with 1 < n < 2. Nonisothermal dehydration of single crystals proceeds in three stages: (1) surface nucleation and growth of nuclei, followed by the advancement of reaction fronts inward, (2) random nucleation and growth near the reaction front as well as in the bulk, and (3) the rapid escape of water vapor through the cracks formed by crystallization of the solid product in the bulk. The mass-change traces for the isothermal dehydration of the powdered material were recorded at different temperatures. The dehydration of single crystals was followed by observing, microscopically in polarized light, thin sections of the sample dehydrated to different fractions reacted, α. ![]() Thermogravimetry (TG) complemented by differential scanning calorimetry (DSC) has been used to study the kinetics of the dehydration of powdered and single-crystal samples of K2CuCl4♲H2O. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |