Microwave versus conventional sintering: A review of fundamentals, advantages and applications

Microwave processing has been emerging as an innovative sintering method for many traditional ceramics, advanced ceramics, specialty ceramics and ceramic composites as well as polymer and polymer composites. Development of functionally gradient materials: joining; melting; fibre drawing; reaction synthesis of ceramics; synthesis of ceramic powder, phosphor materials, whiskers, microtubes and nanotubes; sintering of zinc oxide varistors; glazing of coating surface and coating development have been performed using microwave heating. In addition, microwave energy is being explored for the sintering of metal powders also. Ceramic and metal nanopowders have been sintered in microwave. Furthermore, initiatives have been taken to process the amorphous materials (e.g. glass) by microwave heating. Besides this, attempt has been made to study the heating behaviour of materials in the electric and magnetic fields at microwave frequencies. The research is now focused on the use of microwave processing for industrial applications.

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Prospects of microwave processing: An overview

A review on the susceptor assisted microwave processing of materials

The effects of a microwave heating method on the production of activated carbon from agricultural waste: A review

https://repositorium.sdum.uminho.pt/bitstream/1822/44365/1/document_46583_1.pdf

Microwave heating processing as alternative of pretreatment in second-generation biorefinery: An overview

Microwave sintering behaviors of three kinds of ceramics with different dielectric loss [Al 2 O 3 , Ce–Y–ZrO 2 and lead-based relaxor ferroelectrics (PMZNT)] in 2·45 GHz microwave furnace were described. Measurement of sample densities showed an enhancement of the sintering processing for all materials studied. For PMZNT and Ce–Y–ZrO 2 with high dipolar loss or ionic conductive loss, the associated microstructure examined using scanning electron microscopy showed that microwave-sintered compacts produced much finer grain sizes at near theoretical density compared to conventional sintering. Resulting material properties, such as flexure strength and breakdown strength, were also increased due to developed microstructure in microwave processing. However, a comparable grain size and properties were observed for high pure Al 2 O 3 with low dielectric loss in microwave and conventional methods. ©

Microwave processing and properties of ceramics with different dielectric loss

Microwave processing of \(O_3 - yPb(Zn_{1/3} Nb_{2/3} )O_3 - zPbTiO_3 Pb(Fe_{1/2} Ta_{1/2} )O_3 \) relaxor ferroelectric ceramics was investigated in a 2.45 GHz multimode cavity. The microwave-sintered samples were densified more rapidly and in a shorter time than the conventional sintered sample. A much smaller grain size and more uniform microstructure was developed in microwave heating. Dielectric measurement showed microwave sintered samples could obtain comparable dielectric properties (high pemittivity of 20,000) to the conventional. It was found that a high breakdown strength of 10 kV/mm and mechanical strength of 90 MPa can be achieved by the microwave method. It shows the potential to improve the figure of merit for the materials. The results reveal that microwave processing is a promising method for sintering the high dielectric ceramics.

Xiangdong Huang

Papers

Microwave processing and properties of ceramics with different dielectric loss

Characterization of lead-based relaxor ferroelectric ceramics sintered in a 2.45 GHz microwave radiation