Sintering of nanoceramics

AbstractAbstractThere are two challenges in nanoceramic sintering: fully densifying the sintered body and maintaining the sintered grains at <100 nm size. This review examines the fundamental factors underlying nanoceramic sintering and the approaches to effectively utilise the sintering factors to advantage. Nanoceramic sintering techniques are divided into four categories: pressureless sintering, pressure sintering, electrically assisted sintering, and other sintering related techniques. Pressureless sintering has mainly evolved around modifying sintering schedules, improving nanoparticle packing characteristics, and using additives to tailor the diffusion rates. Pressure sintering, which includes hot pressing, hot isostatic pressing, and sinter forging, can effectively achieve full densification for nanostructured ceramics but microstructural inhomogeneity and sintered shape limitation are difficult to overcome. For electrically assisted sintering, many nanoceramics have been sintered to full density with spark plasma even though the atomic diffusion process is not well understood; microwave sintering can achieve fast heating but has limited ability in reaching full density or controlling grain growth. Plasma spray forming and dynamic compaction are drastically different from the mainstream sintering concepts and so are briefly reviewed. Finally, the remaining issues in nanoceramic sintering are summarised and the future directions are projected.Keywords: NANOCERAMICSSINTERINGGRAIN GROWTHDENSIFICATIONPRESSURESPARK PLASMAMICROWAVE