(152e) Radio Frequency and Microwave Heating of Preceramic Polymers and Its Application in Silicon Carbide Processing

Here, we demonstrate microwave and noncontact Radio Frequency heating methods for mold free processing of silicon carbides (SiC) via preceramic polymer (polycarbosilane) route using carbon nanotube susceptors as fillers. This results in volumetric heating of polycarbosilanes and has applications in 3D printing of SiC and fiber processing.

We show that polycarbosilanes have minimum response to RF and addition of electromagnetic susceptors like MWCNT results in rapid heating and curing of these polymers. We perform dielectric characterizations on the polycarbosilane-MWCNT composites at room temperature. We were able to achieve 95 % extent of curing for polycarbosilane-MWCNT composite using RF in range of 76-78 MHz at 100 W. Microwave pyrolysis of polycarbosilane-MWCNT composites results in formation of cubic SiC structure. We used noncontact RF heating method for 3D printing ink composed of polycarbosilane and SiC nanoparticles with iterative deposition and curing to form a cross-linked structure. We also report for the first time change in dielectric constant and ac conductivity of the 3D printing ink as it heats and transforms while curing. We have studied rheological properties of the ink and its shear thinning behavior. We have also shown that RF/microwave heating results in molecular heating and avoids puddle formation while curing polycarbosilane fibers to SiC fibers.