【作者】 杨雪蛟；

【导师】 李玉平；

【作者基本信息】 湖南大学 ， 材料学， 2010， 硕士

【摘要】 微波烧成技术是利用微波具有的特殊波段与材料的基本细微结构耦合而产生热量,材料的介质损耗使其材料整体加热至烧结温度而实现致密化的方法,是快速制备高质量的新材料和制备具有新的性能的传统材料的重要技术手段。它具有烧结温度低、烧结时间短、能源利用率和加热效率高、安全卫生无污染等优点。本文采用4个1.5kW的微波源叠加,通过谐振腔和保温装置的优化,设计了一台工业微波炉。当输入功率为1.5kW微波能量时,炉腔内的功率密度为30kW/m3,输入最大功率6kW时,炉腔内的功率密度已经达到120kW/m3。该设备有待改进的地方在于：微波源功率只能四级可调,难以精确控制升温速度,只适用于对升温速度要求不太严格的材料,如粉体材料的合成等。采用自行设计的工业微波炉合成了K0.5Na0.5NbO3(简称KNN)系无铅压电陶瓷粉体。设计了合理的保温装置和微波合成工艺升温曲线,考察了不同微波合成温度对KNN粉体性能和微观形貌的影响。结果发现：传统电热法的固相合成温度需要800℃以上,而微波法的固相合成温度在600℃保温5min,就可得到处于准同型相界(MPB)的粉体,至少降低了200℃的合成温度,且总体合成时间不到电热合成的1/20。微波合成法所得到的粉体形状规则、大小均匀、团聚较少,具有更好的烧结性能,是一种具有很好应用前景的材料合成方法。分别采用电热和微波烧结法制备了(Zr0.8Sn0.2)TiO4 (ZST)微波介质陶瓷,研究了不同方法中烧结工艺制度对介质陶瓷材料密度、微观结构、相组成和微波介电性能的影响。结果表明：与电热烧结相比,在所得材料密度近似的情况下,微波烧结能降低烧结温度约70℃、缩短烧结时间2.5h,所获材料密度分布的标准差大大减小；微波烧结所得材料的晶粒尺寸均匀、结构致密；材料的介电常数和品质因数随着微波烧结温度的提高而增大,对应数值分别比传统烧结方式提高17.5%和14.3%左右。并对微波烧结介质陶瓷的致密化机理以及性能进行了较系统的理论分析。更多还原

【Abstract】 The technology of microwave sintering is the method which use the special band of microwave to couple the basic fine structure of materials to arising heat, and the dielectric loss of materials make itself heated to the sintering temperature to achieve densification. It is an important technical means that can be used to prepare materials which have high quality or new properties fast. It has many benefits such as lower sintering temperature, shorten sintering time, and improve the energy efficiency and security, etc.In this paper, four 1.5kW microwave sources are added to 6 kW, through optimizing the resonant cavity and the insulation device, we designed an industrial microwave oven. When the input microwave power is 1.5kW, the power density of the furnace cavity 30kW/m3, and when the input microwave power is 6kW, the power density of the furnace cavity has reached 120kW/m3. Deficiency is that the microwave source power only four levels adjustable, so it is difficult to control the rate of rising temperature accurately, and it just only applies to material which have less stringent requirements on the heating rate, Such as the synthesis of ceramic powders, etc.In this paper, the self-designed industrial microwave was used to synthesis K0.5Na0.5NbO3 (abbreviated as KNN) Lead-free piezoelectric ceramic powder. A reasonable insulation device and a microwave heating curve are designed, the influence of different microwave synthesis temperature to the powder properties and microstructure of KNN are studied. The results showed that microwave synthesis can lower the synthesis temperature about 200℃and cut down the processing time to about 1/20, comparing to electric heating method need synthesis temperature above 800℃. The powders obtained by microwave synthesis exhibit fine morphology, uniform granularity and less reunion, microwave synthesis is a kind of good prospects for the development of materials process method.Microwave sintering and electrical-thermal sintering techniques were used to prepare the (Zr0.8Sn0.2)TiO4 (ZST) ceramics whose densification, component, microstructure and dielectric performance were characterized by Archimedes method, X-ray diffraction (XRD), scanning electron microscopy (SEM) and HP8720ES network analyzer, etc. The results show that the microwave sintering method can decrease the sintering temperature about 70℃and the sintering time about 150min and can enhance the densification. The value of sr and Q of ZST increased with the increasing of sintering temperature, and the corresponded value increase 17.5% and 14.3% respectively, compared with electrical-thermal sintering. The densification mechanic and performance were analysised more systematically in theoretically.更多还原