Fabrication of Carbon Nanofiber and Silicon Carbonitride Ceramic Nanomposites by <i>In Situ</i> Growth during Ceramic Formation

Abstract

Carbon nanofiber (CNF) and silicon carbonitride (SiCN) ceramic nanocomposites (SiCN/CNF) are fabricated by in-situ growth of CNFs in SiCN ceramics during ceramic transformation of polymeric precursors of polysilazanes (PSZ). Metal catalyst precursors are mixed into the polysilazane liquid forming metal particles from decomposition under heating during the pyrolysis. At certain temperatures, ethylene was introduced as a carbon source to induce the growth of CNFs over the metal particles in the ceramic body followed by heating to higher temperatures to complete the pyrolysis. In this way, bulk nanocomposites of SiCN/CNF are obtained as crack-free bodies although some pores are left in the sample. Scanning electron microscopy (SEM) analysis performed on the cross-section of nanocomposites revealed the distribution of needle-like nanofibers of diameter ~ 200 nm and exposed length of ~ 2 μm. The CNFs exhibited the unique multiscale nanostructure in micron hollow tubes with branched nanofiber walls. Energy dispersive X-ray spectrometer (EDX) detected carbon as the major element from the nanofibers confirming the formation of carbon nanofibers. Moreover, clusters of nanoparticles are formed on the ceramic surface from carbon depositions. The in-situ growth of CNFs in SiCN ceramics provides a one-step process potentially to be developed for fabrication of structural and functional SiCN/CNF nanocomposites.