A review on combustion synthesis intensification by means of microwave energy

Energy Efficiency in the Microwave-Assisted Solid-State Synthesis of Cobalt Aluminate Pigment

“…Microwave furnaces 3-5 were equipped with directional couplers, which allowed for the real-time measurement of the emitted and reflected power and hence, by difference, the power dissipated into the load (i.e., the sample plus the crucible and the refractory lining). The CEM MAS applicator could mount an optional SiC ring to achieve hybrid heating conditions, i.e., direct microwave absorption by the load and indirect heating of the load by heat transfer from the microwave-heated SiC ring [10]. Temperature was monitored during the microwave processing using a sapphire fiber directly touching the upper free surface of the sample and connected to a signal conditioner (MIKRON M680 Infraducer, Mikron Infrared Inc., Santa Clara, CA, USA).…”

Solution combustion synthesis of La1−xSrxFe1−yCuyO3±w (x=0, 0.2; y=0, 0.2) perovskite nanoparticles: Conventional vs. microwaves ignition

“…Conventional soft-chemistry routes allow operating at lower temperatures with respect to the "ceramic" route, however most of them still suffer from requiring rather long reaction times, tedious work-up procedures, considerable amount of energy and the use of large amounts of organic solvents [20][21][22]. On the other hand solution combustion synthesis (SCS) can easily be considered both more energy and time-efficient [23][24][25], being the energy required limited to the ignition step and being the reaction rate greatly reduced as a consequence of the high exothermicity of the reaction ignited. Indeed, combustion synthesis (CS) exploits exothermic reactions between reactants (usually in powdered form) which ϯ after being heated up to the ignition temperature start reacting in a self-sustaining combustion regime, thus they do not require any additional energy contribution to complete the production of the desired product.…”

“…The use of microwave (MW) energy has been recently recognized as a process intensification promoting ignition strategy due to the unquestionable enhancements in energy transfer efficiency and rapidity due to the strong MWabsorbing abilities of most of the reactive salts solutions, independently on the desired oxide or metal product [23,24,30]. Indeed the long initial heating period (up to the ignition temperature of the exothermic reaction), which may result in inhomogeneous temperature profiles, can be effectively decreased as a consequence of direct microwave-reactants mixture interaction.…”

Estudo da influência da razão combustível/oxidante e da potência do micro-ondas na formação da α-Al 2 O 3 via reação de combustão

“…Em particular, a síntese por combustão assistida por micro-ondas tem se tornado um método de produção de pós cerâmicos cada vez mais eficiente, no sentido de ser uma técnica rápida e prática, além de proporcionar a obtenção de uma estrutura com melhor definição, quando comparada ao método de síntese por combustão convencional ou outros métodos como a coprecipitação [9,10]. No estudo desenvolvido em [1], o método de síntese por combustão assistida por micro-ondas promoveu a formação de α-Al 2 O 3 com tamanhos de cristalito entre 18 e 20 nm, enquanto que o método por combustão convencional produziu o mesmo óxido com cristalitos na faixa de 50 a 90 nm.…”

“…Apesar da sua simplicidade em termos de processo, as características estruturais da cerâmica produzida pelo método de síntese por combustão assistida por micro-ondas são dependentes de vários parâmetros que podem influenciar na reação, tais como tipo de combustível, quantidade de água na solução precursora, potência do micro-ondas e razão combustível/oxidante [9][10][11][12][13][14]. No caso da síntese do Al 2 O 3 , vários trabalhos já relataram o uso de diferentes tipos de combustíveis [15][16][17].…”