材料性质和环境因素对微波加热特性的影响

Influence of Materials Properties and Environment Conditions on Microwave Heating Behaviors

微波是一种较为新颖的制备材料的技术,材料性质和环境因素对微波的影响还缺乏足够研究。本文在前期工作基础之上,通过数值方法计算研究了材料介电损耗和材料表面物性参数(主要是黑度)及环境条件变化等对材料微波加热行为的影响。材料表面黑度越大,材料向外散热越多,物体升温越缓慢,材料内部温度均匀性越差。材料介电损耗越大,材料吸收微波的能力越强,物体可以达到的最高升温温度越高;在给定材料的条件下,通过调节微波功率,可以实现好的烧结实践。环境温度越低,材料内部温差越大,温度均匀性越差。材料与环境间温差越低,材料表面与环境的传热越小。因此,在加热早、中期阶段采用辐射加热,后期用微波加热的混合加热是一种能保持微波加热和传统加热模式各自优点的一种良好方式。

Microwave heating is an important material processing technology.Up to now it is still lack of study on influence of materials properties and environment conditions.In the present paper based on the previous work,numerical method and computer calculations have been used to investigate the effects of material properties and environmental temperatures on microwave heating behaviors.With the increase of materials emissivity,the heat loss from the material surface increases and the temperature rising rate and equilibrium temperature are lower.The homogeneity of temperatures within materials is worse.With the increase of dielectric loss,the materials absorb more microwave energy and the equilibrium temperature increases as well as the homogeneity of temperature within materials is getting better.Through adjusting microwave power the material dielectric properties are able to realize a better sintering process.The higher the environmental temperature is,the better the homogeneity of temperature within materials would be.The single microwave heating has an advantage of possibility of fast heating rate at the early stage and the weakness of big heat difference between the surface and the center at the medium stage,and the single radiative heating is with the merits of fast temperature rising rate,and the drawback of inhomogeneous temperature distribution within the materials.Therefore,the combined heating of microwave heating and radiative heating would be a good trying.