RECOMMENDATIONS

  • For particular materials, define the conditions under which microwaves provide uniform, stable processing. These may be developed through appropriate numerical modeling techniques and should be presented as processing charts that contain information on material properties, processing conditions, and specimen size and geometry. This modeling requires characterization of the thermal and physical properties of materials, including thermal conductivity and diffusivity, thermal expansion, and the temperature-dependent dielectric properties. Hybrid heating schemes, in which traditional heating is augmented with microwave heat, should be considered.

  • Emphasize research work that facilitates the transition of developmental processes to production scale. This may include materials property characterization, process simulation, control schemes, equipment prototyping, and pilot-scale production.

  • Establish multidisciplinary teams, consisting of materials and process engineers, microwave engineers, equipment designers, and manufacturing specialists, to properly develop microwave processes and procedures.

  • Provide training in fundamentals of microwave processing technology, including microwave interactions with materials.

  • Define general specifications for applicator design, and characterize the resulting electromagnetic field to enable users to successfully apply microwaves to materials processing.

  • Compile existing material-property information on dielectric, magnetic, and thermal properties (including dependence on frequency and temperature) in the range useful in the processing of materials.

  • Provide more-complete and more-consistent measurements of basic dielectric properties of materials to be processed using microwaves, and develop calibration standards for comparing the various techniques for dielectric properties measurements.

  • Develop empirically simplified models and ''microwave heating diagrams'' based on measurements and on the extensive data collected from results of numerical simulation to make numerical techniques more accessible to processors.

  • Establish standards for measurement of temperature to ensure reproducibility. In addition, the techniques and procedures used to measure temperature should be reported in detail, so an evaluation of accuracy can be made. The level of uncertainty in temperature measurements should also be reported. Perform experiments using several techniques for measuring temperature to determine the relative accuracy and reproducibility of the various techniques against a known standard (melting point, phase transition temperature, etc., of well characterized materials).

  • Develop practical methods to monitor or determine internal temperature and thermal profiles (thermal gradients) within a material during the process cycle.

  • Conduct detailed and controlled experiments to determine if the "microwave effect" reported for materials is valid. Care should be taken to use a microwave source with predictable and reproducible fields and to have an internal temperature calibration to avoid temperature measurement uncertainties.



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