Submicron size single crystal MeIVB2 (Me = Ti, Zr, Hf) fibers

Submicron diameter ZrB2, TiB2 and HfB2 fibers were produced in single crystal form. Directional solidification of diboride eutectics followed by matrix phase removal was utilized to fabricate single crystal fibers. LaB6 was utilized as the matrix phase for crystal growth. Fiber diameter ranged from 0.4 to 0.8 μm for all compositions investigated. The length-to diameter aspect ratio exceeded 500 for all compositions. Fibers were uniform and had smooth surfaces along the entire length. Transmission electron microscopy characterization showed that the fibers were single crystals with a high degree of perfection and preferential growth direction along the 〈1 1 1〉 orientation of the diboride lattice. Porous structures were formed by pressing the diboride fibers and sintering at temperatures up to 2200 K in vacuum. The level of porosity, average pore size distribution, and specific surface area could be controlled to some extent by mechanical pressing. The diborides in small fiber form may have technical applications in structural components and functional devices, i.e., industrial filters, thermal protection systems, and possibly for reinforcement.