Novel Method for Cost-Effective Manufacturing of Single Crystal YAG Fibers from Nanosize Particles

"Yttrium-aluminum garnet (YAG) single crystal fibers, 50 micron in diameter, of 100% Y3Al5O12 (YAG) composition, having either [111] or [001] orientations along the axis the fibers, will be fabricated utilizing a novel, versatile approach based on theTemplated Grain Growth of Seeded Nanoparticles (TGGSN) method. Nanocrystalline powders of YAG will be synthesized and dispersed in organic binders and seeded with small elongated single crystals of YAG of [111] or [001] orientations, 10 to 20 microns insmallest dimension and an aspect ratio of 50 to 100 (1 to 2 mm). Continuous fibers will be spun from the seeded suspensions to produce ~50%-dense nanoparticle fibers containing the elongated single crystals oriented along the fiber axis. The pre-cursorfibers will undergo a series of heat treating steps to remove the binder, sinter the nanosize particles into a fully-dense nanograin material, and then, by using unique sintering facilities at the University of Illinois, induce the Templated Grain Growthprocess, during which the large oriented single crystals will grow along the axis of the fibers by consuming the nanosize particles.The resulting single crystal YAG fibers are expected to be a major step in the development of YAG fiber-based composites,because their small diameter should make them amenable to weaving, which is currently impossible with commercially-available YAG fibers of >100 micron diameter. In addition, the TGGSN approach is inherently very economical, as opposed to theprohibitively expensive Edge-Defined Growth method that is the only currently available method for manufacturing YAG fibers."