Solid Freeforming of Silicon Carbide by Inkjet Printing Using a Polymeric Precursor

Abstract

Preceramic polymers can be dissolved in solvents to form low‐viscosity fluids. This makes them suitable for solid freeforming by direct inkjet printing. Two ways of using polycarbosilane (pcs) were investigated. In the first, it was dissolved in n‐heptane at up to 30 vol% and printed as a single‐phase material. In the second, it was used as an organic binder for silicon carbide powder suspended in an homologous series of hydrocarbon solvents ranging from n‐heptane to n‐decane. Polyisobutene succinimide was used as a surfactant. In both cases, components could be rendered successfully but pyrolysis of the unfilled pcs resulted in cracking. Components printed with powder suspensions did not crack on pyrolysis, retained overall near net shape, and underwent low shrinkage (8.2 vol%). The molecular weight of the n‐paraffin solvents influenced the viscosity and hence the maximum powder loading while the volatility, a property also related to molecular weight, influenced the quiescence time and the drying time needed between layers. Octane gave the best compromise between speed of printing, the quality and knitting of droplet relics, and the avoidance of nozzle blockage caused by too rapid drying.