RUI: Studies of the Heating and Sintering of Powdered Metals in Separate Electric and Magnetic Fields Using a Single Mode Microwave Cavity

这项由宾夕法尼亚州立大学材料研究部颁发的RUI奖解决了两个问题：第一，金属粉末压块是如何通过微波辐射如此有效地加热的；第二，烧结的初始阶段是否符合传统模型，或者是否需要微波特定模型来解释？这两个问题将由Zimmerman教授和位于Altoona的宾夕法尼亚州立大学的团队从三个方面来解决：(a)使用谐振腔技术对粉末金属压实物的复杂介电常数和磁导率作为温度、粒度、颗粒氧化和填充密度的函数进行经验研究；(b)利用单模微波系统分别确定电场和磁场对加热和烧结的贡献；(c)通过使用光学和扫描或透射电子显微镜（SEM或TEM）直接检查加热（烧结）样品来评估烧结的第一阶段。由于这些材料的工业意义，重点将放在铜、金、钨的过渡金属粉末和铁、钴的铁磁粉末上。从这些研究中获得的温度分布和能量沉积的知识将促进对微波烧结过程的理解。该项目将为粉末金属的电磁特性和微波加热烧结提供新的知识，具有广泛的工业应用价值。此外，该项目还包括学生的培训和发展，以及教师和博士后研究员的专业发展。这项工作是为准备研究生学习或应用科学和工程领域的工业工作的本科生提供的研究环境。大学的理学学士学位，机电工程技术和材料应用科学的学位课程将从这个本科研究项目中受益匪浅。学生将在为研究的成功做出重大贡献的同时获得教育效益。他们的经验最终将在区域或国家会议上以口头和海报介绍的方式传播成果。这些研究补充了宾夕法尼亚州立大学材料研究所的工作，本科生将从与宾夕法尼亚州立大学其他学生、博士后研究人员和教职员工的思想交流中受益。

This RUI award by the Division of Materials Research to Pennsylvania State University at University Park addresses two questions: first, how metal powder compacts are heated so efficiently by microwave radiation and, second, if the initial stage of sintering fits conventional models or does the explanation require a microwave-specific model? These two questions will be addressed by Professor Zimmerman and the team at Pennsylvania State University at Altoona on three fronts: (a) an empirical study of the complex permittivity and permeability of powder metal compacts as a function of temperature, particle size, particle oxidation, and packing density using resonant cavity techniques; (b) identification of the separate contributions of the electric and magnetic fields to the heating and sintering using a single-mode microwave system; and (c) evaluation of the first stage of sintering by direct examination of heated (sintered) samples by inspection with both optical and scanning or transmission electron microscopy (SEM or TEM). The focus will be on transition metal powders of copper, gold, and tungsten and ferromagnetic powders of iron and cobalt, due to the industrial significance of these materials. The knowledge of the temperature distribution and energy deposition gained from these present studies would advance understanding of the microwave sintering process.This project would provide new knowledge on the electromagnetic properties and microwave heating and sintering of powdered metals, which could have wide applications in industry. In addition, the project includes training and development of students and enables professional development of faculty and a postdoctoral researcher. This work is in a research environment for undergraduate students who are preparing for graduate studies or industrial work in the applied sciences and engineering. The universities B.S. degrees in Science, Electromechanical Engineering Technology and a proposed degree program in Applied Science of Materials will benefit greatly from this undergraduate research program. The students will reap educational benefits while making significant contributions to the success of the research. Their experience will culminate in the dissemination of results with oral and poster presentations at regional or national meetings. The studies complement work at the Materials Research Institute at Penn State University in University Park and the undergraduate students will benefit from an exchange of ideas with other students, post- doctoral researchers, and faculty at Penn State University in University Park.