Effect of process for producing Al2O3 particles on deposition efficiency in aerosol deposition method

The aerosol deposition method (ADM) is a technique to form dense films by impacting solid particles on a substrate. Dense ceramic films with thicknesses of over several µm can be formed directly on substrates even at room temperature by the ADM. In this study, to improve the deposition efficiency of the ADM, the effect of the process for producing Al2O3 particles on the deposition efficiency was investigated. Two types of commercially available α-Al2O3 particles produced by sintering Al(OH)3 (sintered particle) and chemical vapor deposition (CVD particle) were used. The average deposition efficiency of the sintered particles ranged from 0.067 to 0.088% and was much higher than that of the CVD particles, which ranged from 0.005 to 0.012%. When the sintered particles were used, the AD films grew about 30 µm. In contrast, when the CVD particles were used, the AD films didn’t grow over several µm. The morphologies of the AD films suggested that the deformed volume of the sintered particles was larger than that of the CVD particles. The specific fracture energy of each particle was estimated from a compression test. The average specific fracture energy of the sintered particles was 7.3 × 107 J/m3, which was about 32% of that of the CVD particles (2.3 × 108 J/m3). Comparing this specific fracture energy with the specific kinetic energy, which was estimated to range from 4.4 × 107 to 1.8 × 108 J/m3, there is a possibility that the sintered particles showed higher deposition efficiency because they could deform by their kinetic energy and easily form activated surface promoting the bonding between the ceramic particles. We conclude that the specific fracture energy of the particle depends on the process for producing it and could be the crucial property to focus on to improve the deposition efficiency.