Laser pyrolysis offers a means of extending solid free-form fabrication to polymeric precursors. Laser pyrolysis of polycarbosilane (PCS) produces controlled P-SiC shapes with nanometer grain size although properties are currently limited by high porosity. By the addition of filler powders, either inert or reactive, ceramic-metal and ceramic-ceramic composite shapes are possible. The results of laser pyrolysis of PCS alone and in mixtures with p-Sic, Al, Si, Ti, and Zr are presented showing that the technique has the potential to produce a range of materials and shapes customized to particular design requirements.

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The microstructure of silicon carbide fabricated from the gas‐phase‐based, laser‐driven selective area laser deposition (SALD) process has been characterized by X‐ray diffraction and solid‐state 29Si NMR techniques with magic angle spinning (MAS). X‐ray patterns reveal the characteristic spectrum of pure ß, cubic silicon carbide polytype while NMR shows a ß‐SiC pattern with additional peaks. To determine the source of the extra peaks, a comparative evaluation of commercially available silicon carbide powders, both alpha‐ and ß‐SiC, was undertaken with NMR. Spin‐lattice relaxation time measurements (T1) were also carried out to determine the polytype morphology of the SALD deposit. The results showed an NMR spectrum that appears to be a combination of alpha and ß polytypes. Microtwinning is advanced as a possible explanation for this phenomenon.

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