Microwave-induced combustion synthesis of aluminum oxide-titanium carbide powder.

摘要

Microwave heating offers many potential advantages, including synthesizing of material. This advantage results from the unique features of microwave heating which include its internal volumetric heating and subsequent inverted temperature profile. Fundamental knowledge of how reaction parameters influence microwave-ignition behavior is needed in order to provide information required for synthesizing the desired products.;This study was performed to synthesize Al2O3-TiC powders by using microwave heating. The important reaction parameters were identified using the Plackett-Burman design including amount of excess Al and Al2O3, particle size of C and Al2O 3, and heating method. The effect of these reaction parameters on the ignition behavior and characteristics of the resulting powders was then evaluated by the central composite design.;The combustion synthesis of Al2O3-TiC powders using microwave heating (MH) and microwave hybrid heating (MHH) was successfully achieved. The MHH-ignited sample required a longer time to reach ignition temperature and thus resulted in a lower combustion temperature. The results showed no significant difference in characteristics of powders ignition time and temperature, while decreasing the combustion temperature. An increased particle size of Al2O3 lowered the ignition time and temperature. The density of product decreased with increasing amounts of Al. Addition of excess Al2O3 to reactants resulted in decreasing the agglomeration size. The empirical models relating these important parameters and their interactions to the responses were then developed.;The mechanism governing the combustion reaction of Al2O 3-TiC powders under microwave and conventional heating was also investigated. The results suggested that reaction mechanisms using these two methods were similar. The reaction proceeded in a three-stage process where the aluminum melted, then the melting Al reacted with the titania, and finally the titanium reacted with the carbon to produce the Al2O3-TiC. The only difference was the way the reactants were heated. In conventional heating, material was heated by heat transfer process depending on its thermal conductivity. Heating by microwaves is a function of dielectric properties of the material. Depending on the microwave absorption of the materials in question, heat generation by microwave heating occurs internally.