Preliminary Study of the Applications of Master Curve Model on Simple Chemical Thermal Decomposition Reactions

• Main Authors: Kwei-Fang Shiah, 夏葵芳
• Other Authors: 鄧茂華
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/79133427250292105792

碩士 === 國立臺灣大學 === 地質科學研究所 === 94 === Master Curve Model (MCM) is probably a universal kinetic model, and can be used to predict the variations of various kinetic reactions as long as we can derive the master curves and best apparent activation energy from experimental data. Unlike general chemical kinetic model, which needs all three parameters, i.e. activation energy Q, reaction order n, and collision frequency Ko, to construct the model, MCM is a much simpler and more objective method. Our previous work has shown that MCM can be used to describe and predict complicated ceramic sintering reactions, not only for micron-or submicron powders, but also for nanocrystalline ceramic powders. The purpose of this research is to test the applicability of MCM on some simple chemical thermal decomposition reactions. Four powders, including CaCO3, CuSO4·5H2O, CaSO4·2H2O, and Na2CO3, had been thermally decomposed at various heating rate by thermo gravimetric analysis (TGA). Without grinding and sieving process, no acceptable master curves can be derived from the powders, but after grinding and sieving, three powders (except Na2CO3) gave much better master curves. It indicates that the reaction rates on the surface of the particles are different from that inside the bulk. Below 600oC, Na2CO3 only showed physical desorption reaction, which is not a stable chemical kinetic reaction, therefore no kinetic model is expected to be able to adequately describe the reaction. With some limitations, the preliminary results show that MCM indeed can be used to interpret and predict the thermal decomposition reactions of simple compounds. At least two factors will influence the accuracy of predictions of MCM, i.e. the particle sizes as we have mentioned earlier and the heating rates. In general, a faster heating rate gives a larger apparent activation energy. Therefore, heating rate is a must considered factor when using MCM on the analysis of thermal decomposition reactions.