Grafting of organic molecular precursors onto ZrC(100)//t-ZrO₂(001) surfaces: When experimental and theoretical studies meet

To control ZrC oxidation, one method is to coat the surface with SiC. This work therefore aims at grafting polymeric precursors on functionalized ZrC surfaces en-route to synthesizing ZrC/SiC core/shell composites. The exposed surface on the zirconia side of t-ZrO₂(001) (tetragonal ZrO₂) on top of a ZrC(100) substrate is first modified in presence of water. Water preferentially adsorbs molecularly and a subsequent functionalization with allylchlorodimethylsilane (ACDMS) in a S_N reaction, appeared quite weak. However, the following grafting of a repetitive unit of the polymeric precursor, built from diphenylsilane and 1,4-diethynylbenzene monomers through a hydrosilylation reaction, is a highly favorable and exothermic reaction. As the main problem occurs during the nucleophilic substitution reaction between ACDMS and hydroxyl groups on the surface, two bifunctional organic molecules, but-3-enoic acid as well as glycolic acid, were also exploited. But-3-enoic acid adsorbed strongly to the Zr atoms of the surface, through chelating effects of the carboxylic acid group. The subsequent hydrosilylation reaction with a repetitive unit of the preceramic precursor was also a favorable exothermic reaction, indicating a promising approach for the grafting of organic macromolecules. In parallel, to associate experimental results, methyldiphenylsilane was grafted onto functionalized ZrC using but-3-enoic acid.