Spark plasma sintering kinetics of pure α-alumina
Résumé
The microstructure development of sintered alumina at different stages in the spark plasma sintering process has been investigated. Based on classical kinetics laws and adapted Coble creep models of hot pressing, the densification and grain growth kinetics were analyzed as a function of various parameters such as heating rate, sintering temperature, and dwell duration. It is found that sintering kinetics are greatly influenced by heating rates. The local temperature gradients at interparticle contacts during high heating rate can be from three to 10 times higher than in low heating rate cycles. Plastic yield might lead to instantaneous densification at an early stage of sintering. However, grain-boundary diffusion probably dominates at low heating rate whereas grain coarsening, in respect of thermal equilibrium establishment, is unavoidable with high heating rate during the initial-stage sintering at low temperatures. During the final-stage sintering, fast grain growth mechanisms such as surface diffusion and pore-controlled grain-boundary migration may dominate over densification controlled by grain-boundary sliding or lattice diffusion. The grain size-density trajectory corroborates that low heating rate is much favorable to achieve near full density with fine grain size at low sintering temperatures. © 2011 The American Ceramic Society.
Mots clés
Coble creep
Fine grains
Grain boundary migrations
Grain coarsening
Grain-boundary diffusion
Grain-boundary slidings
Growth mechanisms
High heating rates
Interparticle contacts
Lattice diffusion
Local temperature
Low sintering temperature
Low temperatures
Microstructure development
Plastic yield
Sintering kinetics
Sintering temperatures
Spark plasma
Spark plasma sintering process
Thermal equilibriums
Densification
Diffusion
Electric sparks
Grain boundary sliding
Grain size and shape
Growth kinetics
Heating
Heating rate
Hot pressing
Kinetics
Sintered alumina
Spark plasma sintering
Superconducting materials
Grain growth