Structural evolution during the catalytic graphitization of a thermosetting refractory binder and oxidation resistance of the derived carbons

Talabi, Segun Isaac ; Luz, Ana Paula ; Pandolfelli, Victor Carlos ; Lucas, Alessandra de Almeida (2018-06)


Carbon-containing refractories' (CCRs) thermomechanical properties depend on the presence of carbonaceous phase with a structure and features similar to those of graphite. Based on this, boron oxide and boric acid were used to induce graphite generation during the pyrolysis of novolac resin (binder for CCRs) to provide an additional source of crystalline carbons. In this study, the structural evolution leading to crystallization of the derived carbons was studied via Fourier Transform Infrared (FTIR) spectroscopy. The results showed that the carbons graphitization was as a result of the formation and cleavage of the Bsingle bondOsingle bondC bond during heat treatment. The lower binding energy of this bond compared to plain Csingle bondC bond permits carbon atoms rotation and restructuring necessary for graphite generation during the pyrolysis operation. Furthermore, the research investigated the oxidation resistance of the derived carbon samples with the aid of thermogravimetric (TGA) and differential scanning calorimetry (DSC) equipment. The influence of different mixing routes at the preparation stage and hexamethylenetetramine (HMTA) addition to the resin formulations on the carbons' oxidation resistance was also examined. The analysis provides insight on the parameters that control the oxidizing behavior of the different samples obtained based on these variations. Several factors including graphitization, composition and atoms bond strength were observed to influence their performance when the carbons were exposed to the non-reducing environment at high temperatures up to 1000 °C.