Preceramic Polymers Grafted to SiO2 Nanoparticles via Metal Coordination Pyrolyzing with High Ceramic Yields: Implications for Aerospace Propulsion and Biomedical Coatings

Processable preceramic materials are critically important to a range of applications, especially with regard to biomedical coatings and filling interstitial spaces in preform materials to produce ceramic matrix composites useful for aerospace propulsion. Preceramic polymers (PCPs) with added nanoparticle (NP) components are an attractive way to influence the final ceramic composition and reduce the changes in density and volume during PCP conversion to inorganic material. Cross-linking a polymer to an NP surface is one potential route to mitigating phase separation and potentially improving char yields for the combined materials. In this report, two pyridine-functionalized PCPs were studied by linking the polymers to pyridine-terminated SiO2 nanoparticle (NP) surfaces via a zirconium metal center. The polymer-metal-nanoparticle (PMN) system was studied in an assembled, polymeric form during pyrolysis (i.e., via thermogravimetric analysis) and post-conversion (at 1600 degrees C) by X-ray diffraction, Raman spectroscopy, scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM) with EDS. A dramatic 57% increase in char yield of the PMN relative to the summed char yields of the individual components is observed, showing a significant synergistic effect and yielding a SiO2-ZrO2 nanocomposite.