Effective fugitive carbon coatings for the strength improvement of 3D Nextel™ 440/aluminosilicate composites

• CVD carbon coatings were introduced into 3D N440/AS composites.
• 3D N440/AS composites were prepared by a sol–gel process.
• The composite strength was improved remarkably by fugitive carbon coatings.

Three-dimensional (3D) Nextel™ 440 fiber-reinforced aluminosilicate (N440/AS) ceramic matrix composites with fugitive carbon coatings were fabricated by a sol–gel process. Effects of the coatings on the strength improvement of the composites were investigated. Three-point bending tests were performed on samples in three conditions (as-received, with carbon interface, and with carbon removal, i.e., with fugitive interface). Results showed that the carbon/fugitive interface played a key role in the strength improvement of the composites. Three-point flexural strength of the composites with carbon interface was approximately 3.5 times that of as-received ones. Microstructure analysis revealed that the interfacial gaps formed following carbon removal were distinct, and the strength of the composites with fugitive interface was about 3.3 times that of as-received ones.