Nanostructured mullite steam oxidation resistant coatings for silicon carbide deposited via atomic layer deposition

Abstract

Oxidation resistant, thin, pinhole‐free, crystalline mullite coatings were deposited on zirconia and silicon carbide particles using atomic layer deposition (ALD). The composition of the films was confirmed with inductively coupled plasma optical emission spectroscopy (ICP OES), and the conformality and elemental dispersion of the films were characterized with transmission electron microscopy (TEM) and energy dispersive X‐ray spectroscopy (EDS), respectively. The films are deposited on the particle surface with a deposition rate of ~1 Å/cycle. The elemental concentration of aluminum relative to silicon in the film was determined to be 2.68:1 which agrees closely with the ratio of stable 3:2 mullite (2.88:1). A high‐temperature anneal for 5 hours at 1500°C was used to crystallize the films into the mullite phase. This work represents the first deposition of mullite films by ALD. The mullite and alumina‐coated particles were exposed to high‐temperature steam for 20 hours at 1000°C to assess the oxidation resistance of the films, which reduced the oxidation of silicon carbide by up to 62% relative to uncoated particles under these conditions. The activation energy of oxygen diffusion in the films was determined with density functional theory, and the computational results aligned well with the experimental outcomes.

Powder Coatings via Atomic Layer Deposition for Batteries: A Review

“…All the particle coating applications are derived either by the need to passivate an active surface or by functionalization of the surface for a particular purpose. Passivation is generally applied in the case of metallic powders to cease their spontaneous oxidation in air or to protect nonmetal powder particles from certain environmental attacks . On the other hand, surface-functionalized particles are finding numerous applications such as in pharmaceutics, biomedical engineering, UV-absorbance, catalysis, photocatalysis, thermite materials, electroluminescent materials, and sintering aid to ceramic particle processing .…”

Surface modification and functionalization of powder materials by atomic layer deposition: a review

“…5b ). 26 Trimethyl aluminum (TMA), water, tris -dimethylaminosilane (TDMAS), and H 2 O 2 were used as the reactants, and the films were annealed at 1500 °C for 5 hours to be converted to the mullite phase. Reduced oxidation of silicon carbide by up to 62% could be obtained with a 10 nm ALD alumina film.…”

Particle atomic layer deposition

“…Recently, Hoskins et al ( 2018 ) have shown that an Al 2 O 3 or mullite (3Al 2 O 3 :2SiO 2 ) coating on SiC can reduce steam oxidation of the SiC at 1000 °C (20 h) by up to 62% for a 10-nm-thick ALD film on micron-sized SiC particles. These results are comparable to CVD films that are three orders of magnitude thicker and support the conclusion that the superior ECB properties using ALD films is the result of the films being free of pin-holes.…”