Fracture and Deformation Behavior of Fine Ceramic Particles in In Situ Compression Test for Understanding of Aerosol Deposition Process

Aerosol deposition (AD) method is a dense ceramic coating technology at room temperature. Submicrometer ceramic particles are accelerated to 150-600 m/s by a carrier gas. It has been believed that the ceramic particles were plastically deformed and consolidated by physical energy during collision with the substrate or formerly deposited particles. This phenomenon was called a room temperature impact consolidation (RTIC). When alpha-alumina particles were compressed, micrometer particles exhibited a brittle fracture, while submicrometer particles tended to deform plastically. The fracture strength of fine alumina particles increased as the particle diameter decreased. However, this transition behavior of fracture has not been explained consistently and will be worth to be investigated. Therefore, in this study, we have performed a quasi-static indentation of monocrystalline α-alumina particles over a wide range of diameters. The deformation/fracture behavior was observed in situ during a compression test and evaluated along with the particle diameter. It revealed that micrometer-sized particles were deformed plastically before fracture beyond a bulk elastic limit. Meanwhile, even submicrometer particles were not plastically-deformed completely, accompanied by some brittle fractures. The calculated fracture strength of particles tended to increase with a decrease in diameter as reported.