Study of the core-shell structure MoSi2@ Al2O3 powder prepared by the sol-gel method in a low-vacuum atmosphere

Abstract

Molybdenum disilicide (MoSi 2 ) is a novel crack-healing material used in the traditional thermal barrier coating , which reacts with ZrO 2 to attain a corresponding volume expansion of approximately 138%. However, the pre-oxidation of MoSi 2 causes the “pesting” phenomenon, which degrades the microstructure and mechanical properties throughout the service. To address this issue, the aluminum oxide was fabricated on the MoSi 2 surface using the sol-gel method and low-pressure post-heat treatment to prevent oxygen penetration. The orthogonal experiment investigated the effect of pH, temperature, and water amount on sol generation. Because the Zeta potential difference has reached its maximum value (about 27 mV) at pH 4, the aluminum sol was notably adsorbed on the MoSi 2 particles. The modified MoSi 2 @Al 2 O 3 particles were characterized to understand their morphologies, surface adsorption energy, and crystal structures. The oxygen adsorption energy on the MoSi 2 (103) surface was lower than that on the Mo 5 Si 3 (411) surface, which indicated that the oxidization process can be divided into two independent steps. The Al 2 O 3 shell was uniformly formed on the MoSi 2 particles, especially in the low-vacuum environment (10 MPa) for 3 h post-treatment. The dense core-shell structure can prevent oxygen penetration into the MoSi 2 surface, thus prolonging the self-healing property of MoSi 2 . • Heterogeneous charge between MoSi 2 and C 9 H 21 AlO 3 is maximum at pH 4.0. • “Pesting” phenomenon occurs by the preferential oxidization of adjacent Mo atoms. • MoSi 2 @Al 2 O 3 core-shell structure is uniformly generated in a low-vacuum atmosphere. • MoSi 2 @Al 2 O 3 can prevent oxygen from reacting with the MoSi 2 surface.