Global insight into microwave stoneware firing: Macro and microstructural changes |
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Authors: | Tiago Santos Celso S. F. Gomes Luc Hennetier Vítor A. F. Costa Luís C. Costa |
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Affiliation: | 1. Department of Physics and I3N, University of Aveiro, Aveiro, Portugal;2. GeoBioTec, Research Unit of FCT, University of Aveiro, Aveiro, Portugal;3. Technological Centre for Ceramic and Glass Industries, Coimbra, Portugal;4. Centre for Mechanical Technology and Automation, Department of Mechanical Engineering, University of Aveiro, Aveiro, Portugal |
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Abstract: | Industrial competition and environmental concerns lead to the exploration of alternative and energy-efficient technologies for ceramic materials processing. The main objective of this work was to present microwave heating as a viable option for stoneware processing. Stoneware functional properties are presented and discussed, with emphasis on impact strength, water absorption, porosity, and color. Microstructure analyses show that microwave- and gas-fired samples have higher densifications than electrically fired samples. A relevant finding for processing conditions is that microwave firing requires temperatures approximately 100°C lower than those required by conventional firing. Microwave-fired samples’ rupture energies are approximately twice (0.57 ± 0.06 (J)) those of the reference samples (0.26 ± 0.03 (J)), and their water absorptions are approximately one-half (1.5% at 1170°C and 0.8% at 1190°C) of those of the reference samples (2.0%), whereas the water absorption of electrically fired samples at 1180°C has been estimated to be 7.5%. Color analysis also evidences a shift to lower microwave firing temperatures, what is attributed to the enhanced transformations promoted by microwave heating when comparing with the transformations promoted by conventional (gas or electric) heating. |
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Keywords: | color analysis conventional firing macro and microstructure changes microwave firing stoneware |
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