RESUMO
In this study, the joining of silicon carbide (SiC) ceramics was achieved via a Si-C reaction bonding method using the phenolic resin (PF)-MgCl2 system as the carbon precursor. Specifically, by adding MgCl2 to the phenolic resin mixture, the average pore size of the product of carbonization of the PF resin mixture increased from 14 ± 5 nm to 524 ± 21 nm, which was beneficial for the infiltration of molten silicon at high temperature. The microstructure of the joined specimens and the effect of the inert filler on the joint strength were investigated. It was demonstrated that SiC-SiC joints with strong interfacial bonding and high flexural strength could be obtained by the Si-C reaction bonding method using a phenol formaldehyde resin/alcohol sol-gel system as the carbon precursor. The flexural strength of the joined specimens reached the highest value, i.e., 308 ± 27 MPa when the solid loading of the inert filler was 26%. Overall, stable joining of silicon carbide ceramics was achieved by the proposed method, which has significance for realizing the preparation of complex-shaped or large silicon carbide ceramic parts.
RESUMO
Boric acid was used as a source of complexing agent to change phase separation kinetics and dynamics of the resin-glycol system to regulate the pore structure of porous carbon. The results show that the addition of H3BO3 in the resin mixtures can change the polymerization dynamics during curing of resin-glycol mixtures. For the complexation of H3BO3 to diols, the size of the ethylene glycol-rich phase produced during the curing of the resin mixture increase with the increase of the content of H3BO3. Similarly, the pore size of porous carbon after pyrolysis increases with the increase of H3BO3 content. The average pore size of resulting porous carbon can be regulated in the range from 15 to 2754 nm. These results reveal that H3BO3 exhibited obvious effects in changing the pore structure of resin-glycol system during pyrolysis.