High char yield BPR modified with ZrSi2 and B4C: Pyrolysis kinetic behavior and structure evolution

BPR has been widely used as ablative material for thermal protection on aircraft surface. In this study, model-free method was employed to study the kinetic models of BPR and ZrSi 2 /B 4 C-Ph composite. In addition, the thermal stability, chemical reaction and structure evolution during pyrolysis of ZrSi 2 /B 4 C-Ph composite were characterized by TGA, XRD, XPS, GC–MS and TG-MS. The results indicated that the pyrolysis of BPR includes three consecutive and overlapping stages. And the kinetic mechanism function f(α) , apparent activation energy E a and pre-exponential factor A of each stage were confirmed. Besides, the high char yield of ZrSi 2 /B 4 C-Ph composite is mainly attributed to the reaction of ZrSi 2 and B 4 C with gases released during BPR pyrolysis, which formed solid phases such as amorphous carbon, ZrO 2 , SiO 2 and B 2 O 3 .