Abstract
Microwave-assisted sintering materials have been proven to deliver improvements in the mechanical and physicochemical properties of the materials, compared with conventional sintering methods. Accurate values of dielectric properties of materials under high temperatures are essential for microwave-assisted sintering. In view of this, this paper, proposes an on-line system to measure the high temperature dielectric properties of materials under microwave processing at a frequency of 2450 MHz. A custom-designed ridge waveguide is utilized, where samples are heated and measured simultaneously. An artificial neural network (ANN) trained with the corresponding simulation data is integrated into this system to reverse the permittivity of the measured materials. This whole system is tested at room temperature with different materials. Accuracies of measuring dielectric property with an error lower than 9% with respect to theoretical data have been achieved even for high loss media. The functionality of the dielectric measurement system has also been demonstrated by heating and measuring Macor and Duran ceramic glass samples up to 800 °C. All the preliminary experiments prove the feasibility of this system. It provides another method for dielectric property measurement and improves the understanding of the mechanism between microwave and media under high temperatures, which is helpful for optimizing the microwave-assisted sintering of materials.
Highlights
Considerable interest has been drawn to the processes of materials sintering by microwave power and many potential merits have been recognized in applications [1,2,3,4,5,6]
The accuracy of reversed dielectric property reached by the transmission /reflection method
The accuracy of reversed dielectric property reached by the transmission /reflection method with with a custom-designed ridge waveguide must be evaluated first
Summary
Considerable interest has been drawn to the processes of materials sintering by microwave power and many potential merits have been recognized in applications [1,2,3,4,5,6]. Yang Li et al employed microwave power to sinter the metallic matrix diamond tool bits. The relative density, the flexural strength and the abrasive ratio of the sintered sample were increased by 6.75%, 20.3% and 22.2%, respectively [7]. Application of microwave power on sintering the Cu based metallic binder conducted by Guo Shenghui et al showed that the relative density, hardness and flexural strength increased respectively 1.25%, 3.86% and 6.28% [8]. They obtained LiBa1−x PO4:xTm3+ phosphors with more uniform grain size distributions and enhanced emission intensity [9]. Leonelli Cristina et al sintered green metal parts with microwave powers and obtained results with comparable microstructure and shape retention to the conventional sintering methods in much shorter time [10]
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