Processing of Nextel 720/mullite composition composite using electrophoretic deposition

A technique for electrophoretic deposition of alumina, silica and alumina/s ilica mixtures has been developed. Experiments have been carried out to suc cessfully infiltrate these matrices into electrically non-conducting Nextel 720 2D alumina fibre weave. Surfactants based on carboxylic acid/amine com binations in ethanol were assessed. The objective was to enable the co-depo sition of alumina and silica at mullite ratio by tailoring the electrophore tic mobility. Tartaric acid with dibutylamine was identified as the most ef ficient surfactant mix. Aluminium and silicon contents were measured by ato mic emission spectrometry, ensuring that a deposit of mullite composition h ad been achieved. The distribution of species within samples was monitored via elemental mapping in SEM. Fibres were heat treated in air at 1400 degre es C to assess tolerance to proposed sintering temperatures. Resultant comp osite green bodies are densely infiltrated with powder deposited within fib re tows. The ease of preparation of low volume content powder suspensions r educes slurry processing time in comparison to conventional routes. The inf iltration time required is short. These findings indicate that a potentiall y economic electrophoretic composite manufacturing route, not restricted to single powder species or conductive fibre weaves, has been developed. (C) 1999 Kluwer Academic Publishers.