Abstract
The limited oxidation resistance of MoSi(2) between 400 °C and 600 °C restricts its aerospace applications. This study develops a silica-sol derived core-shell MoSi(2)@SiO(2) composite to enhance the low-temperature oxidation resistance of MoSi(2). Acidic, neutral, and basic silica sols were systematically applied to coat MoSi(2) powders through sol-adsorption encapsulation. Two pathways were used, one was ethanol-mediated dispersion, and the other was direct dispersion of MoSi(2) particles in silica sol. Analysis demonstrated that ethanol-mediated dispersion significantly influenced the coating efficiency and oxidation resistance, exhibited significantly decreased coating weight gains (maximum 27%) and increased oxidation weight gains (10-20%) between 340 °C and 600 °C compared with direct dispersion of MoSi(2) particles with silica sol, ascribe to the kinetic inhibition of hydroxyl group condensation and steric hindrance of MoSi(2)-silica sol interface interactions of ethanol. Systematic investigation of silica sol encapsulation of MoSi(2) revealed critical correlations between colloid properties and oxidation resistance of MoSi(2)@SiO(2). Basic silica sol coated MoSi(2) (BS-MoSi(2)) exhibits the lowest coating efficiency (coating weight gain of 7.74 ± 0.06%) as well as lowest oxidation weight gain (18.45%) between 340 °C and 600 °C compared with those of acid and neutral silica sol coated MoSi(2) (AS-MoSi(2) and NS-MoSi(2)), arises from optimal gelation kinetics, enhanced surface coverage via reduced agglomeration, and suppressed premature nucleation through controlled charge interactions under alkaline conditions.