A.R. Boccaccini et al. Composites: Part A 32(2001)997-1006 preforms has been studied theoretically and experimentally Sol particles In the present work, a complete literature review focusing on the particular use of EPd to infiltrate ceramic and metallic fibre preforms with the ultimate goal of fabricating composite materials is presented. Typical EPD experimen- tal procedures and the results achieved are described in detail, taking as example a model alumina matrix composite reinforced by Ni-coated carbon fibres Literature review fbre ureter Table 1 presents an overview of the published work deal- ing with the application of the EPD technique for the fabri Fig. 1 Schematic diagram of the epd cell for obtaining cation of fibre reinforced ceramic and glass matrix conductive fibre mats. The fibre mat the positive ele the composites. Other types of ceramic composite systems. particles in the suspension are negatively charged (e.g. silica such as whisker reinforced composites [16, 17], laminated composites [18-20), composite coatings [21], composites with porous layers [22]and functionally graded materials recent years simple and inexpensive method for [22-24]have been fabricated by the EPD technique More- infiltration of tightly woven fibre over, the use of electrodeposition to coat ceramic fibres with preforms omplete in chnique is based on using nanoscale metals with the aim to fabricate metal matrix composites has ceramic particles in a stable non-agglomerated form(such also been investigated [25, 26]. However, research on these as in a sol or colloidal suspension) and exploiting their net areas will not be reviewed here, this paper being restricted to surface electrostatic charge characteristics while in suspen the use of epd for the fabrication of fibre reinforced sion. On application of an electric field the particles will ceramic and glass matrix composites migrate towards and deposit on an electrode. If the deposi- The feasibility of infiltrating ceramic woven fibre tion electrode is replaced by a conducting fibre preform, the preforms by EPD has been demonstrated for a variety of suspended particles will be attracted into and deposited single and mixed component ceramic sols, as summarised in within it, providing an appropriate means of effectively Table 1. Mainly graphite [22, 27-32, SiC-based infiltrating densely packed fibre bundles. A schematic [4, 7, 22, 33-40], alumina [35, 41-43]and aluminosilicate diagram of the basic Epd cell is shown in Fig. 1 (mullite)37, 44, 45] woven fibre mats have been employed The movement of ceramic sol particles in an aqueous es investigated have been silica, alumina, suspension within an electric field is governed by the field mullite, SiC, Si3 N4 and borosilicate glass. Both aqueous strength, and the pH, ionic strength and viscosity of the and non-aqueous suspensions have been used, although solution [4]. The electrophoretic mobility(EM) of the aqueous colloidal suspensions or sols are preferred due to harged particles in suspension is given by [8] environmental and cost advantages [46]. The experiments U have been invariably carried out in laboratory scale, using EM= E (1) EPD cells of small dimensions, i.e. the gap between the electrodes was between 1 and 5 cm in most studies. and where U is the velocity, E the field strength, e the dielectric the area of the fibre preforms infiltrated was smaller than constant,s the zeta potential and n the viscosity. Accord- 100 cm". When EPD is used as a ceramic forming techni ingly, a suitable suspension for EPD should have high- que, it is possible to use either constant current or constant particle surface charge, high dielectric constant of the liquid voltage conditions. An analysis of the literature showed, phase and low viscosity. Moreover, low conductivity of the however, that all investigations have been conducted by suspending medium to minimise solvent transport is using constant voltage conditions, the reason being most probably that this is the simplest mode of operation The phenomenon of electrophoresis has been known In the case of non-conductive fibres, such as aluminosis since the beginning of the last century [9] and has found ate(mullite)fibres of the type Nextel 720(3M Co., MN extended application in ceramic technology. In available USA)or alumina fibres(e.g. Almax, Mitsui Mining Co comprehensive review articles, complete descriptions of Japan), a modification of the basic EPD cell must the basics of the EPD technique and its applications in conducted. This has been called electrophoretic filtration ceramics have been presented [8, 10-12]. 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