Preparation and Foaming Mechanism of Pyrocarbon Foams Controlled by Activated Carbon as the Transplantation Core

Carbon foams were prepared with walnut shell liquefaction resin (WLP-PF) as precursor and hexane/activated carbon (H/AC) as foaming core. The effect of the particle size of H/AC and the additive amount of H/AC on the microstructure and properties of carbon foams was investigated. Results showed that when the particle size of H/AC was in the range of 75–150 μm, the bulk density of carbon foams was in the range of 0.115–0.218 g/cm3, the compressive strength (4.79 MPa) reached maximum value, and the Brunauer–Emmett–Teller specific surface area was 721m2/g. Use of foaming core of H/AC made resin with lower viscosity foam. Foaming core of H/AC more uniformly dispersed the blowing agent in WLP-PF resin and improved the microstructure of carbon foams while effectively reducing the micropores in the ligaments and joints. Further, the volume shrinkage rate of carbon foams was reduced by using H/AC for foaming. The foaming mechanism using H/AC was considered to be implantation core foaming accompanied by interfacial nucleation foaming. This led to uniform control of the size and distribution of foam cells.