Reaction characteristics of combustion synthesis of β-SiAlON using different additives

• Reaction characteristics of the combustion synthesis of β-SiAlON were investigated.
• Kinetic of the reaction on propagation was analyzed using Boddington’s model.
• The addition of NaCl gave slower conversion rate than that of β-SiAlON.
• NaCl additive yielded β-SiAlON rod-like crystals.
• Self-sintering occurred with the addition of β-SiAlON.

Reaction characteristics of combustion synthesis (CS) of β-SiAlON powders in a horizontal CS chamber were compared by including two types of additives (β-SiAlON and NaCl) in Si, SiO2, and Al powder raw materials. The results showed that the reaction characteristics were influenced by the additives, which exerted a strong effect on the reaction rate and the morphology of the products. At the respective maximum combustion temperatures, a relatively slow conversion rate, with a reacted fraction (η) of 58.7%, was achieved with the addition of 12 mass% NaCl to the raw materials, whereas the addition of 45 mass% β-SiAlON powders afforded η = 88%. The NaCl additive yielded rod-like crystals, which were well developed by a long after-burn time. However, self-sintering occurred in the presence of β-SiAlON powders. The results indicate that some degree of control over the conversion rate of the reaction and the microstructures of the product can be achieved by varying the type of additives.