工程科学与技术2024，Vol.56Issue(2)：118-128,11.DOI:10.15961/j.jsuese.202201198
氮化硼的介电特性及其在微波加热中的热透波性能
Dielectric Properties of Boron Nitride and Its Thermal Wave-transparent Properties in Microwave Heating
摘要
Abstract
The thermal wave propagation characteristics within refractory structures significantly affect the efficiency and method of microwave heating.Therefore,understanding the dynamic thermal wave propagation within these structures during microwave heating is crucial.This study focuses on boron nitride ceramic(BN)to explore its behavior under microwave heating.The dielectric properties of BN in a wide temperature range(25～1 000 ℃)at frequencies of 915 MHz and 2 450 MHz are tested experimentally.The power transmission coefficient of BN is calculated by transmission line theory.The temperature characteristics of dielectric constant,dielectric loss factor and other parameters of BN are analyzed.The results show that the dielectric constant changes little at two frequencies from 25 to 1 000 ℃,and the dielectric constant only changes by about 1.8％.However,the dielectric loss factor fluctuates with temperature,exhibiting an exponential increase beyond 900 ℃.Concurrently,both the wavelength and penetration depth of microwaves within BN diminish as temperature rises.Additionally,an increase in frequency leads to a re-duction in penetration depth.Notably,the study reveals significant disparities in BN's wave transmission performance between two polarization modes,with horizontal polarization markedly outperforming vertical polarization.At the frequency of 915 MHz,a material thickness of approx-imately 0.08 meters is identified as the optimal,yielding a a transmission performance(PTC≥0.7)in the range of θi≤67°.At the frequency of 2 450 MHz,the optimal material thickness reduces to 0.06 meters.For microwaves in the TE polarization mode at this frequency,the incident angle should ideally belimited to the range of θi≤58°.In the TM polarization mode,it is recommended that the incident angle of θi≤77° has a good wave transmission effect(PTC≥0.9).This study has important practical guiding significance for the selection of lining materials in microwave heating equipment,the setting of process parameters and the effective improvement of microwave energy utilization.关键词
微波加热/氮化硼/透波性能/介电常数/耐火结构Key words
microwave heating/boron nitride/wave-transparent properties/dielectric constant/refractory structure分类
通用工业技术引用本文复制引用
张利,尚小标,白永珍,李广超,肖利平..氮化硼的介电特性及其在微波加热中的热透波性能[J].工程科学与技术,2024,56(2):118-128,11.基金项目
国家自然科学基金项目(51864030) （51864030）
云南省科技厅重点项目(202101AS070023) （202101AS070023）
