Fabrication and characterisation of Ni-coated carbon fibre-reinforced alumina ceramic matrix composites using electrophoretic deposition

The present study explores the feasibility of fabricating Ni-coated carbon fibre-reinforced alumina ceramic matrix composites via a single-infiltratio n electrophoretic deposition (EPD) process perfor mcd in vacuum. The nano-s ize boehmite sol was seeded using nano-size delta -alumina powder in order to control the final sintered microstructure and then characterised using t ransmission electron microscopy, differential thermal and thermogravimetric analysis (DTA/TG) and X-ray disc centrifuge system (BI-XDC) in order to de termine the sol microstructure, phase transformation temperatures and parti cle size (also degree of agglomeration), respectively. An EPD manufacturing cell for fabrication of Ni-coated carbon fibre reinforced alumina matrix c omposites was designed and experiments were conducted under vacuum (first t ime to date), resulting in full deposition of the sol material throughout t he voids within/between the fibre tows. Composites with high green density (67% theoretical density) were produced using an applied voltage of 15 V d. c. and deposition time of 400 s. The sintered density after pressureless si ntering at 1250 degreesC for 2 h was 91% theoretical density. Crack path pr opagation test showed that the metallic Ni coating was able to provide a we ak interface, as an indenter induced crack within the alumina matrix was de flected and arrested at the Ni interface. (C) 2001 Acta Materialia Inc. Pub lished by Elsevier Science Ltd. All rights reserved.