From Phenylsiloxane Polymer Composition to Size-Controlled Silicon Carbide Nanocrystals

2009-01-21T00:00:00Z (GMT) by Eric J. Henderson Jonathan G. C. Veinot
Silicon carbide (SiC) has become a very important material for many high-performance applications as a result of its exceptional material properties. The emergence of size-dependent properties in SiC nanocrystals (SiC-NCs), together with the increased surface area intrinsic to nanocrystals, has led to a variety of new possible applications, including optoelectronics and hybrid materials. Here we report the straightforward preparation of size-controlled oxide-embedded and freestanding SiC-NCs from the reductive thermal processing of compositionally controlled phenylsiloxane polymers. Compositional tuning of the polymers is achieved by varying the relative amounts of phenyl trichlorosilane (C<sub>6</sub>H<sub>5</sub>SiCl<sub>3</sub>) and silicon tetrachloride (SiCl<sub>4</sub>) during hydrolysis and cocondensation. Thermal processing of the resulting compositionally controlled condensation copolymers yields oxide-embedded SiC-NCs whose average diameter is dependent on the relative C<sub>6</sub>H<sub>5</sub>SiCl<sub>3</sub> concentration in the initial precursor mixture. A liberation procedure for preparing size-controlled freestanding SiC-NCs that involves oxidation of matrix carbon and subsequent chemical etching of the matrix is also presented.