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A novel thiol‐ene photopolymerization reaction involving copolymerization of tetrathiol monomer with vinyl silazane is experimentally characterized and is modeled successfully. The overall polymerization rate is found to be controlled by the ratio of the propagation to chain transfer kinetic parameters. The polymerization rate of this mixture, in the presence of added photoinitiator, is approximately first order in ene functionality and is independent of thiol functional group concentration. Initiation rates in this system, when cured utilizing a light centered around 365 nm light, and in the presence of no added photoinitiator, are shown to be proportional to the ene monomer concentration. When the mixture is polymerized utilizing light centered at 254 nm light, and without photoinitiator, the initiation rates are proportional to the thiol monomer concentrations. This novel reaction scheme is further utilized to form ultra rapidly polymerizable polymer derived ceramic structures with high aspect ratios.

A novel reaction scheme for rapidly fabricating polymer-derived ceramic structures with high aspect ratios and with controlled shape and structure is described. The reaction scheme is based largely upon a thiol-ene photopolymerization mechanism. Thiol-ene photopolymerizations offer unique advantages including high polymerization speed in the presence of little or no photoinitiator, the ability to delay gelation, and the ability to achieve high double bond conversions. The addition of thiols to polymerizable vinyl-containing ceramic precursors further enables the formation of thicker structures than traditionally achieved. Structures formed using this mechanism exhibit little warping, and upon pyrolysis the polymer structures are transformed into ceramic structures of a self-similar shape. In the pyrolysis step, structures formed using this novel mechanism exhibit shrinkage and mass loss values similar to those produced from typical ceramic precursors. Further, the photolithographic process described here is readily extendable to make complex three-dimensional ceramic microstructures and microdevices.

Polymer-derived ceramics (PDCs) are a new class of ceramics that are obtained from direct pyrolysis of densely crosslinked polymers. In this article, we report the mechanical and tribological properties of silicon-based PDCs. The density, the elastic modulus, the hardness, and the fracture toughness of silicon oxycarbonitride ceramics are related to their tribological (friction and wear) behavior. The mechanical properties show a strong relationship with the oxygen/nitrogen ratio in the ceramic, which was varied by annealing the specimens in nitrogen at high temperatures and pressure. The properties are enhanced by a higher nitrogen-to-oxygen ratio. In dry environments, the tribological behavior is divided into two regimes: a low-friction regime with a coefficient of friction, l, of about 0.2, and a highfriction regime with lB0.7. The transition occurs at a critical value of contact stress. This transition stress appears to be related to the onset of fracture of the ceramic, and moves to a higher value with higher modulus and hardness of the ceramic. The transition stress is successfully analyzed in terms of the influence of the elastic modulus on the fracture stress. The analysis leads to the suggestion of a residual tensile stress in the surface of the specimens of approximately 1 GPa equivalent of the contact stress. In a humid environment, the transition stress apparently moves beyond the experimentally accessible regime. In this environment, the coefficient of friction remains unchanged at lB0.2. Two hypotheses, one related to the effect of humidity on the work of fracture, and the other to the formation of a hydrated film on the surface of silicon nitride, the counterface in the tribological experiments, are proposed for this behavior.