微波与颗粒物质相互作用的机理及应用研究

【作者】 黄铭；

【导师】 彭金辉；

【作者基本信息】 昆明理工大学 ， 有色冶金， 2006， 博士

【摘要】 本文综述了微波应用的现状，尤其是微波与物质相互作用的机理。根据Maxwell方程组和非Debye弛豫理论，首次导出了微波辐照下材料的吸波公式，并利用该理论公式成功解释了镍铁矿、氧化铝和橡胶的吸波特性；研发了测量工业物料水分的微波设备，并用该设备系统地研究了有色金属和黑色金属精矿水分的微波测量方法；提出了微波检测物质显微结构的方法，并申请了十项专利。本文导出的方程、研发的设备以及提出的方法对促进微波技术在材料和冶金领域的推广应用具有重要意义。本文研究的主要内容和结论归结如下：Ⅰ、对颗粒材料而言，其吸波机理是非Debye的，与材料的显微结构有关。吸波公式为：利用该公式可以从理论上解释了镍铁矿、氧化铝和橡胶的吸波特性，结果表明镍铁矿和氧化铝的弛豫时间与温度成反比，温度越高弛豫时间越小，镍铁矿和氧化铝的吸波性能越好；而橡胶的弛豫时间与温度的关系为τ_T=τ₀exp（-B/（T₀-T）），温度升高时其弛豫时间变化逐步减慢，硫化后的橡胶吸波性能差。Ⅱ、研究微波与物质相互作用机理时，微波场强大小是关键。在微波通信与传统微波检测领域中，微波照射下物质特性不变，微波与物质相互作用是线性时不变的；在微波加热与微波化学领域中，微波照射下物质特性发生了变化，微波与物质相互作用是非线性的和时变的。本文综述了该领域的研究及进展，并进行了初步的分析和计算。Ⅲ、成功研制了检测材料显微结构与吸波性能的微波设备，并用该设备测试了沥青石墨粉混合物及其它矿物的吸波特性，实验结果表明：虽然沥青不吸波，但加入导电的石墨粉后，其吸波性能良好；研究微波技术在材料与冶金领域中的应用时，测量材料吸波特性非常重要，与能耗有关，关系到微波技术在材料与冶金领域应用项目的成败。Ⅳ、在冶金工业中，为了控制颗粒物质的含水量、产品质量和减少能耗，必须测量颗粒物质的含水量。微波水分测量技术已应用于许多工业领域，然而在冶金工业中的应用几乎没有报道。已证明微波穿透深度比红外大，微波能测量体水分。同时，微波测量水分响应快，并且安全。因此本文研制了测量工业物料水分的微波设备，并用该设备系统地研究了有色金属和黑色金属精矿水分的微波测量方法，实验结果表明：微波可以快速测量精矿的水分；微波检测精度高，误差一般小于0.5％；微波快速测量水分时，被检测物粒度和比重等影响检测精度，一般而言，粒度大，精度低，比重小，精度高；微波检测水分受环境温度影响，必须进行温度补偿。Ⅴ、为了检验微波检测物质显微结构方法的普适性，本文系统研究了微波检测技术在其它领域的应用，实验结果表明：微波检测技术可用于精密诊断植物的水分、监测化学反应动态过程、检测烟箱缺条或烟条缺包、测量松散物料流量和检测物质结晶水。例如，微波传感器能用于热分析，与TG、DTG、DTA和DSC比较，微波传感器响应快、测量方便；与IR、Raman和NMR等方法比较，微波传感器价格低。总之，本文导出了微波辐照下材料的吸波公式，并从理论上成功解释了在高温下镍铁矿、氧化铝和橡胶的吸波特性，表明了微波高温技术在材料与冶金领域应用的优势。此外，还提出了微波检测物质显微结构的方法，并用微波方法测量了有色金属和黑色金属精矿水分。以上成果是微波与颗粒物质相互作用机理研究的突破，对促进微波技术在材料和冶金领域的推广应用具有重要的意义。更多还原

【Abstract】 The state of the art of microwave applications, in particular, the mechanism of microwave interaction with matter, was reviewed in this Ph.D thesis. Based on Maxwell’s equation and non-Debye relaxation theory, a new equation for the description of dielectric losses under microwave irradiation was developed for the first time. This equation can be applied to successively explain the microwave absorption properties of nickeliferous limonitic laterite ores, alumina, and rubber compounds, respectively. A microwave setup for measuring the moisture content of industrial materials was also invented. The moisture content of nonferrous and ferrous metals minerals concentrates can be measured accurately by using this microwave setup. In this thesis, the microwave techniques for detecting the microstructure of materials was developed and 10 patents was applied. The equation and the techniques developed in this thesis have been and will be found momentously significant to develop more microwave applications in materials sciences and metallurgical engineering. The main contents and conclusions obtained were as follows:Ⅰ、For granular materials, microwave absorption properties of the materials is a non-Debye relaxation processes which is relevant to the microstructure of materials. The microwave absorption equation of the materials as follows: Based on the above equation, the microwave absorption properties of nickeliferous limonitic laterite ores, alumina, and rubber compound were successively explained. It was found that the relaxation time of nickeliferous limonitic laterite ores and alumina are inversely proportional temperature. Namely, the higher temperature is, the smaller relaxation time of the materials attained and the more microwave power absorbed by nickeliferous limonitic laterite ores and alumina is. It was also found that the relationship between relaxation time r of rubber compound and temperature T as follows:τ（T）=t₀exp（-B/（T₀-T））. Namely, the higher temperature is, the slower relaxation time change of the rubber compound attained. Moreover, the vulcanized rubber absorbed less microwave power.Ⅱ、In order to study mechanism of microwave interaction with materials, microwave field intensity is a key parameter. In the fields of microwave communication and microwave detection, the properties of materials under microwave irradiation are invariant. The microwave interaction with materials is linear. By contrast, in the fields of microwave heating and microwave chemistry, the properties of materials under microwave irradiation are variable and the microwave interaction with materials is non-linear. Development and advance concerning the fields of microwave interaction with materials were reviewed. Preliminary results are obtained by computation and analysis.Ⅲ、A microwave setup for detecting the microstructure and the microwave absorption properties of materials was developed. The microwave absorption properties of graphite powder-pitch mixture and other ore materials were successful studied by this microwave setup. Interestingly, good absorption properties of the graphite powder-pitch mixture could be obtained by adding graphite powder which is a conductor although the pitch do not absorb microwave. To study microwave applications in the fields of material and metallurgical engineering. the properties of materials under microwave irradiation is a key parameter relevant to the efficiency of microwave power which will decide whether microwave power can be applied successfully or not in the fields of materials and metallurgical engineering.Ⅳ、In the metallurgical industry, the exact moisture content of the granular materials has to be determined in order to allow control of the water dosage, of the quality of the product,and of the reduction of applied energy. Moisture determination by microwave is applied in many branches of industry. However, few applications have been reported in the metallurgical industry. It has been shown that the penetration depth of microwaves is much greater than that of infrared radiation, and microwave methods can measure the volume moisture content of the materials. In addition, microwave methods are much safer and faster than ionizing radiation methods. Hence a microwave setup for measuring the moisture content of industrial materials was developed in this Ph.D thesis. And the moisture contents of nonferrous and ferrous metals minerals concentrates were measured by this microwave setup. It was shown that this microwave setup is a practical and accurate technique to measure the moisture content of mineral concentrate with the standard deviation of less than 0.5%. It was also shown that the sizes and the specific gravity of granular materials have influence on the precision of moisture measurement by microwave. Generally speaking, the larger the size of granular matter is. the lower precision of moisture measurement attained, and the lower specific gravity of granular materials is, the higher precision of moisture measurement attained. The environmental temperature has also influence on determination of the water content of granular matter by microwave, thus the value of the moisture content of the materials was compensated for.Ⅴ、In order to explore other applications of the method for detecting the microstructure of materials by microwave, the microwave detecting techniques developed here were also used in other fields. It is clearly shown that the microwave sensor technique can be used to detect plant water status accurately, to monitor the chemical reaction kinetics, to detect a shortage in tobacco box or bar, to measure flux of granular materials and even to acquire the information of various hydration states of salt hydrates. For example, the microwave sensor could be used in thermal analysis accurately and efficiently, which is a key technique in chemistry, metallurgy, mineralogy and geology. Comparing with the method of thermal analysis using TG, DTG, DTA, and DSC, the microwave sensor has the advantages of high accuracy, fast measurement and more convenience. While comparing with the IR spectroscopy, Raman spectroscopy and NMR spectroscopy et al., the microwave sensor has the advantages of low price, low power and more convenience also.In a word, a new equation for the description of dielectric losses under microwave irradiation was developed. This equation can be applied to successively explain the microwave absorption properties of nickeliferous limonitic laterite ores, alumina and rubber compounds at elevated temperature, respectively. The equation implies that the high temperature application of microwave in the fields of materials and metallurgical engineering is preferable. In addition, the microwave techniques for detecting the microstructure of materials were presented. The moisture content of nonferrous and ferrous metals minerals concentrates were measured by the microwave technique. It is a breakthrough in studying mechanism for microwave interaction with materials and it is of momentous significance in studying and developing microwave applications in the fields of materials and metallurgical engineering.更多还原