Electrostatically deposited surface seeding and promotion of crystallization of sol-gel derived LaAl11O18 coating on oxide fibers

For the use as interface material in oxide/oxide-continuous fiber-reinforce d composites, LaAl11O18-fiber coatings have been developed. The magnetoplum bite structure has an attractive property, due to the presence of mechanica lly weak cleavage planes between the stacked spinel blocks. Thus, easy clea vage or crack deflection resulting in reduction in energy release rate at t he fiber/matrix interface can be provided during the fracture of an oxide/o xide-composite. The synthesis of LaAl11O18 via sol-gel route required high processing temperature which causes the instability of fibers. An optimizat ion of the process, in terms of elimination of occurrence of an intermediat e phase and promotion of complete crystallization at temperatures less than or equal to 1200 degrees C was necessary. This study describes a method to obtain continuous and well-crystallized LaAl11O18 fiber-coatings at temper atures as low as 1100 degrees C, benefiting from both the sol-gel-process a nd the seeding concept. (C) 1999 Elsevier Science Ltd. All rights reserved.