Calcium carbonate, decomposition diffusion

A classic example of a solid—fluid ceramic powder synthesis reaction is that of calcination and dehydration of natural or synthetic raw materials. Calcination reactions are common for the production of many oxides from carbonates, hydrates, sulfates, nitrates, acetates, oxalates, citrates, and so forth. In general, the reactions produce an oxide and a volatile gaseous reaction product, such as CO2, SOg, or HgO. The most extensively studied reactions of this type are the decompositions of magnesium hydroxide, magnesium carbonate, and calcium carbonate. Depending on the particular conditions of time, temperature, ambient pressure of CO2, relative humidity, particle size, and so on, the process may be controlled by a surface reaction, gas diffusion to the reacting... 

The thermal stability of calcium carbonate (CaC03) nanoparticles on polybutadiene rubber (PBR) were studied by Shimpi and Mishra [105]. They observed that the incorporation of nano CaCOs in PBR shows better thermal stability. At 12 wt% of nano CaCOs (21, 15, and 9 nm) filled in PBR shows decomposition temperature at 491, 483, and 472 °C, respectively. At 4 wt% loading of filler, decomposition temperature is observed to be 488,480,450 °C for nano CaCOs (21, 15, and 9 nm), respectively. This enhancement in thermal stability is due to uniform dispersion of nano CaCOs throughout the matrix that keeps the rubber chains intact on cross-linking, which prevent out diffusion of the volatile decomposition product [106]. The presence of nanoinorganic particles in between the mbber chains is responsible for preventing the diffusion of the volatile decomposition products firom the mbber nanocomposites at same time. It is clear that nanoinorganic filler provides better thermal stability as compared with commercial micron size filler. 

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