Omran Mamdouh, Fabritius Timo, Heikkinen Eetu-Pekka, Chen Guo
Process Metallurgy Research Group, Faculty of Technology, University of Oulu, Oulu, Finland.
Mineral Processing and Agglomeration Laboratory, Central Metallurgical Research and Development Institute, Cairo, Egypt.
R Soc Open Sci. 2017 Sep 20;4(9):170710. doi: 10.1098/rsos.170710. eCollection 2017 Sep.
This paper aims to study the dielectric properties and carbothermic reduction of zinc oxide (zincite, ZnO) and zinc ferrite (franklinite, ZnFeO) by microwave heating. To achieve this aim, the dielectric properties were measured with an open-ended coaxial method to understand the behaviour of the samples under microwave irradiation. The effects of microwave power, duration time and sample mass on the heating rate, and the effects of the stoichiometric amount of graphite on the reduction of ZnO and decomposition of ZnFeO were investigated. The results show that ZnFeO has significantly higher dielectric properties compared to ZnO. Generally, for both samples, the dielectric values at room temperature were quite low, indicating that both ZnO and ZnFeO are poor microwave absorbers. It was found that the temperatures have a more significant effect on the imaginary permittivities than on the real permittivities. The heating rate showed that the sample temperature increased with increase in microwave power and sample mass. Using 700 W of microwave power and two times the stoichiometric amount of graphite, almost complete reduction of ZnO was achieved in 12 min, while ZnFeO completely decomposed to zincite and wustite in 3 min.
本文旨在研究微波加热下氧化锌（锌铁矿，ZnO）和铁酸锌（锌铁尖晶石，ZnFeO）的介电性能及碳热还原。为实现这一目标，采用开口同轴法测量介电性能，以了解样品在微波辐射下的行为。研究了微波功率、持续时间和样品质量对加热速率的影响，以及石墨化学计量比对ZnO还原和ZnFeO分解的影响。结果表明，与ZnO相比，ZnFeO具有显著更高的介电性能。一般来说，对于这两种样品，室温下的介电值都相当低，表明ZnO和ZnFeO都是较差的微波吸收体。研究发现，温度对虚部介电常数的影响比对实部介电常数的影响更大。加热速率表明，样品温度随微波功率和样品质量的增加而升高。使用700W的微波功率和两倍化学计量比的石墨，12分钟内实现了ZnO的几乎完全还原，而ZnFeO在3分钟内完全分解为锌铁矿和浮氏体。
