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The pyrolysis kinetic behaviors and reaction mechanism of polycarbosilane (PCS) were characterized by means of XRD, SEM and on-line TG-DSC-FTIR-MS coupling technique, which showed that the pyrolysis process accorded with the F2 integral model (300-600°C), and the values of apparent activation energy (Ea) and pre-exponential factor (A) were 56.10KJ/mol and 10.84, respectively. During the pyrolysis process, PCS was converted into amorphous inorganic solid from organic polymer with breakage and rearrangement of chemical bonds, then to well-defined crystal structure of good thermal stability. Furthermore, the weight loss occurred mainly among 300°C and 800°C with CH4, (CH3)4Si,(CH3)3SiH,(CH3)2SiH2and other silane gases releasing from pyrolysis product leading to the conversion from organic polymers to inorganic ceramic. The pyrolysis product was converted into β-SiC crystal completely at 1400°C, and the crystallization of α-SiC phase occurred after 1550°C which might influence the stability of SiC matrix. Key words:polycarbosilane, organic precursor, pyrolysis kinetic behavior

The pyrolysis dynamic process of ZrB2 organic precursor,soluble in benzene homologues with polycarbosilane, was characterized by means of on-line TG-DSC-FTIR-MS coupling technique. The conversion mechanism of ZrB2 ceramic was investigated based on EDS, SEM and XRD. The results show that methylamine, methane, acetone and propene were given off before heat treatment at 1000°C, and the pyrolysis product of ZrB2 precursor existed in the form of ZrO2, B2O3 and amorphous carbon. ZrB2 crystals are obtained completely by the carbothermal reduction process with the release of carbon dioxide at 1500°C. Key words:ZrB2 organic precursor, pyrolysis kinetic behavior, carbothermal reduction process.