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HCN evolution from thermal and oxidative degradation of poly(diphenyl methane pyromellitimide) at high temperatures

HCN evolution from thermal and oxidative degradation of poly(diphenyl methane pyromellitimide) has been investigated over a range of temperatures from 500 to 1000°C; rate constants and Arrhenius equations have been determined. Kinetics and mechanisms have been proposed and quantitatively evaluated. They account well for the experimental results. The rate determining steps are C? N scission for thermal degradation and H abstraction from the methylene bridge by O₂ for oxidative degradation, respectively. At high temperatures, oxidation and thermal decomposition of the evolved HCN take place on its passage through the hot zone of the furnace in the highest range of temperatures (800–1000°C). Additional HCN is produced (>800°C) from the char obtained during thermal and oxidative degradation.     

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Structure and shape variations in intermediate-size copper clusters

Using extensive, unbiased searches based on density-functional theory, we explore the structural evolution of Cu(n) clusters over the size range n=8-20. For n=8-16, the optimal structures are plateletlike, consisting of two layers, with the atoms in each layer forming a trigonal bonding network similar to that found in smaller, planar clusters (n相似文献