Precipitation Coating of Monazite on Woven Ceramic Fibers: I. Feasibility

Monazite coatings were deposited on woven cloths and tows of Nextel™ 610 fibers by heterogeneous nucleation and growth using solution precursors. Initial experiments revealed two coating regimes in which monazite was either precipitated both in solution and onto the fiber surfaces or only onto the fiber surfaces depending on the precursor solution concentration and fiber surface area. In both cases, regions of tightly packed fibers within cloth were uncoated. Image analysis of coated fiber cross sections revealed a strong correlation between fiber separation and coating thickness, suggesting that the coating of tightly packed fibers was limited by transport of the reactants in solution to these areas. By adopting a coating procedure in which the tightly packed regions are saturated with reactants before precipitation, more uniform coatings of monazite were obtained throughout the cloth; however, the strength of as-coated and heat-treated fibers was degraded and remains problematic.