期刊
CHEMICAL ENGINEERING JOURNAL
卷 405, 期 -, 页码 -出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.cej.2020.126609
关键词
Microwave-assisted material processing; Electromagnetic resonators; Ceramic matrix composites; Chemical vapor infiltration
资金
- European Union [280464]
The use of high-quality resonant cavities in microwave-assisted reactors is desirable for high energy efficiency. A general design method has been proposed to achieve defined mode density and high microwave power dissipation in the sample, with the most efficient heating mode determined through rigorous numerical analysis.
The use of high-quality resonant cavities in microwave-assisted reactors is highly desirable. Thanks to the low losses in the cavity walls and to the possibility to reach critical coupling conditions, high energy efficiency can indeed be achieved. This paper describes the design, building, and test of a microwave-assisted Chemical Vapor Infiltration reactor at a pilot scale, based on an overmoded resonant cavity operating at 2.45 GHz. First, a general design method is proposed, in which the dimensions of the cavity are chosen in order to obtain a defined mode density and a high fraction of microwave power dissipated in the sample. Among the modes of this cavity, the most efficient one for the microwave heating of the sample is then determined by means of rigorous numerical analysis. In the graphite reactor cavity built using this approach, the condition of critical coupling is met in a large variety of samples and operating conditions. Moreover, a good agreement between experimental and simulated heating dynamics is obtained, which confirms the validity of the proposed method. As a result, disc-shaped samples with a diameter of the order of 10 cm and a thickness of the order of 1 cm can be brought to an infiltration temperature of about 900 degrees C within 5 min, using a microwave power of 1000 W, with a well controllable and reproducible temperature variation. In the infiltration of Nicalon preforms, more than 60% of the microwave power is dissipated in the sample.
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