Deposition of zirconia sols on woven fibre preforms using a dip-coating technique

The technique of depositing zirconia coatings onto woven fibre mats has been investigated in detail. The application of a coating to the fibre is essentially one of the easiest methods of providing a fibre–matrix interface with desired properties. Such coatings can act as reaction barriers or as fibre–matrix debond interfaces. This particular coating method, which is the dip-coating of fibre tows in zirconia sols, does not require sophisticated apparatus and, therefore, has great potential as a standard coating technique for use with woven fibre systems. In this work, an “in-house” produced zirconia sol, synthesised using hydrothermal processing, has been found to be the most successful coating material. Both alumina and alumina-silica woven fibre mats were used as the substrate materials. It has been shown that the zirconia sol employed can be deposited successfully in a single coating step, as a thin (1–2 μm) coating with minimal bridging of the fibre mats. The critical coating parameters when using this dip-coating technique have been discussed in detail.