In microwave processing, energy is supplied by an electromagnetic field directly to the material. This results in rapid heating throughout the material thickness with reduced thermal gradients. Volumetric heating can also reduce processing times and save energy. The microwave field and the dielectric response of a material govern its ability to heat with microwave energy. A knowledge of electromagnetic theory and dielectric response is essential to optimize the processing of materials through microwave heating. The fundamentals of electromagnetic theory, dielectric response, and applications of microwave heating to materials processing, especially fiber composites, are reviewed in this article.

Microwave processing: fundamentals and applications

This review has presented the principles underlying the dielectric heating effects observed for chemical compounds in solution and in the solid state. The applications of the technique to a wide range of chemical syntheses have also been indicated. The field is in its infancy and therefore much of the effort to date has been directed towards understanding the rate enhancements of known reactions. The next few years should see the isolation of new compounds using microwave heating techniques

Tilden Lecture. Applications of microwave dielectric heating effects to synthetic problems in chemistry

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

The use of microwaves to process absorbing materials was studied intensively in the 1970s and 1980s, and has now been applied to a wide variety of materials1,2,3,4. Initially, success in microwave heating and sintering was confined mainly to oxide and some non-oxide ceramics5,6,7,8,9,10,11; but recently the technique has been extended to carbide semimetals12,13,14 used in cutting tools. Here we describe the microwave sintering of powdered metals to full density. We are able to sinter a wide range of standard powdered metals from commercial sources using a 2.45-GHz microwave field, yielding dense products with better mechanical properties than those obtained by conventional heating. These findings are surprising in view of the reflectivity of bulk metals at microwave frequencies. The ability to sinter metals with microwaves should assist in the preparation of high-performance metal parts needed in many industries, for example, in the automotive industry.

Full sintering of powdered-metal bodies in a microwave field

Use of microwaves in the synthesis of materials is gaining importance. Microwave-assisted synthesis is generally much faster, cleaner, and more economical than the conventional methods. A variety of materials such as carbides, nitrides, complex oxides, silicides, zeolites, apatite, etc. have been synthesized using microwaves. Many of these are of industrial and technological importance. An understanding of the microwave interaction with materials has been based on concepts of dielectric heating and of the resonance absorption due to rotational excitation. This review presents a summary of recent reports of microwave synthesis of inorganic materials. Various observations regarding microwave interaction with materials are also briefly discussed.

Synthesis of inorganic solids using microwaves

Article de synthese sur les avantages de l'utilisation d'hyperfrequences pour les traitements thermiques des ceramiques

W. H Sutton

Papers

Microwave Processing of Ceramic Materials