Processing and characterization of three-dimensional carbon fiber-reinforced Si–O–C composites via precursor pyrolysis

The cure and pyrolysis of hydrogen-containing polysiloxane (PSO) and divinylbenzene (DVB) were investigated in this paper. It was found that (chloroplatinic acid) H2PtCl6 was an effective catalyst for the cure of DVB/PSO. The mass ratio of DVB/PSO had great effect on ceramic yield. The cured DVB/PSO with a mass ratio of 0.5:1 had the highest ceramic yield (76%) at temperature up to 1000 °C, and its pyrolyzates consisted of 38.3 wt.% silicon, 27.4 wt.% oxygen, and 34.3 wt.% carbon of which 26.3 wt.% was free carbon. The structures of the products pyrolyzed at different temperatures were characterized by FTIR. Three-dimensional braided carbon fiber-reinforced silicon oxycarbide composites (3D-B Cf/Si–O–C) were fabricated via precursor infiltration and pyrolysis using DVB/PSO as precursor. The results showed that the mechanical properties of 3D-B Cf/Si–O–C could be increased if the first pyrolysis was assisted by hot-pressing. The flexural strength and fracture toughness of the composite, which was hot-pressed at 1600 °C for 5 min with a pressure of 10 MPa in the first pyrolysis cycle and treated subsequently with six cycles of vacuum infiltration and pyrolysis under atmospheric pressure, were 502 MPa and 23.7 MPa m1/2, respectively. The high mechanical properties were mainly attributed to the desirable interfacial structure.