Effect of atomic layer deposited aluminium oxide on mechanical properties of porous silicon carbide

Silicon carbide nanopowder was coated with amorphous alumina by atomic layer deposition (ALD), using trimethylaluminium Al(CH3)3 (TMA) and water as precursors. The ALD experiments were carried out at 300 °C, using variable cycle count or changing pulse times at constant cycle count. Depending on deposition conditions, hardness averaging at 14.8 GPa and corresponding reduced elastic modulus of 114 GPa were measured. Maximum hardness values and reduced moduli of elasticity reached 25–30 and 134–202 GPa, respectively, improving the mechanical properties of composites. Increased precursor flow had positive effect on mechanical properties – maximum values of hardness and elastic module reached 35–45 and 218–261 GPa, respectively. In the composites, the mechanical properties were improved compared to pure alumina films or silicon carbide and the brittleness characteristic of SiC particle tablets was decreased.