Preceramic Polymers to HfCN Ceramic Fibers and Matrices

"In this BMDO Phase I SBIR Proposal, we propose to develop and further optimize preceramic polymers to hafnium carbide/nitride (HfCN) for CMC matrices and structural ceramic fibers. Hafnium carbide is the most refractory binary composition known, with amelting point of 3890oC. Hafnium nitride is also the most refractory of all nitrides, with a melting point of 3307oC. For this reason, hafnium carbide and hafnium nitride have been proposed for ultra high temperature applications, such as zero erosionrocket nozzle throats, hypersonic leading edge materials, and combustion liners. Currently, hafnium carbide and nitride is fabricated as monolithic ceramics by hot-pressing and as coatings by chemical vapor deposition and/or infiltration. We have alreadybegun synthesizing poly(propyl)hafnizane (PPHZ) and poly(ethynyl)hafnizane (PEHZ) preceramic polymers with high ceramic yields. Through careful control of molecular weight, as has been demonstrated for our preceramic polymers to SiC and Si3N4, we believewe can tailor the molecular weight and viscosity for structural HfC/HfN ceramic fiber production. We have already synthesized melt-able, high molecular weight HfCN preceramic polymers. In addition, HfC/HfN matrices can also be produced. We have synthesizedlow molecular weight, soluble HfC/HfN preceramic polymers suitable for the polymer impregnation pyrolysis (PIP) method of ceramic matrix fabrication. High temperature ceramic matrix composit