Manchili Swathi K, Wendel Johan, Hryha Eduard, Nyborg Lars
Department of Industrial and Materials Science, Chalmers University of Technology, Gothenburg 41296, Sweden.
Nanomaterials (Basel). 2020 Jun 30;10(7):1276. doi: 10.3390/nano10071276.
Iron nanopowder could be used as a sintering aid to water-atomised steel powder to improve the sintered density of metallurgical (PM) compacts. For the sintering process to be efficient, the inevitable surface oxide on the nanopowder must be reduced at least in part to facilitate its sintering aid effect. While appreciable research has been conducted in the domain of oxide reduction of the normal ferrous powder, the same cannot be said about the nanometric counterpart. The reaction kinetics for the reduction of surface oxide of iron nanopowder in hydrogen was therefore investigated using nonisothermal thermogravimetric (TG) measurements. The activation energy values were determined from the TG data using both isoconversional Kissinger-Akahira-Sunose (KAS) method and the Kissinger approach. The values obtained were well within the range of reported data. The reaction kinetics of FeO as a reference material was also depicted and the reduction of this oxide proceeds in two sequential stages. The first stage corresponds to the reduction of FeO to FeO, while the second stage corresponds to a complete reduction of oxide to metallic Fe. The activation energy variation over the reduction process was observed and a model was proposed to understand the reduction of surface iron oxide of iron nanopowder.
铁纳米粉末可作为水雾化钢粉的烧结助剂，以提高冶金（粉末冶金）压块的烧结密度。为使烧结过程高效进行，纳米粉末上不可避免的表面氧化物必须至少部分被还原，以促进其烧结助剂效果。虽然在普通铁粉的氧化物还原领域已开展了大量研究，但对于纳米级铁粉则并非如此。因此，利用非等温热重（TG）测量研究了铁纳米粉末在氢气中表面氧化物还原的反应动力学。使用等转化率基辛格-赤平-ose（KAS）方法和基辛格方法从TG数据确定活化能值。所得值完全在报道数据范围内。还描述了作为参考材料的FeO的反应动力学，该氧化物的还原分两个连续阶段进行。第一阶段对应于FeO还原为FeO，而第二阶段对应于氧化物完全还原为金属Fe。观察了还原过程中的活化能变化，并提出了一个模型来理解铁纳米粉末表面氧化铁的还原。
