Paper number 428

PROCESSING OF NEXTEL 720/MULLITE COMPOSITION COMPOSITE USING ELECTROPHORETIC DEPOSITION

S. Kooner, W.S. Westby, P.M. Farries, C.M.A. Watson, P. Boother and R.A. Shatwell

Structural Materials Centre, MSS, DERA, Farnborough, Hampshire, GU14 0LX, UK.

Summary

A technique for electrophoretic deposition (EPD) of alumina, silica and alumina/silica mixtures has been developed. These matrices have been successfully infiltrated into electrically non-conducting 2D alumina/mullite fibre weaves. Surfactants based on carboxylic acid/amine combinations in ethanol were assessed. The objective was the co-deposition of alumina and silica at mullite ratio by tailoring electrophoretic mobilities. Aluminium and silicon contents were measured and the distribution of species within samples monitored via elemental mapping in SEM. Fibres were heat treated in air at 1400°C to assess tolerance to proposed sintering temperatures. Sintering studies were carried out at 1400°C and 1600°C on powder compacts containing alumina and silica in the mullite ratio. Compacts were seeded with mullite with the aim of reducing the temperature required for mullite formation. Infiltrated weaves were assembled with a high powder concentration aqueous suspension to form a composite block which were densified without the application of pressure at 1400°C.

Keywords

electrophoresis, mullite, ceramic-matrix-composite, CMC, oxide fibre, oxide matrix, processing, sintering.