알루미늄 테르밋 반응의 환원제로서 알루미늄 분말은 200 메쉬 이하의 미분이 필요하나, 알루미늄의 높은 인성과 분말 제조비 때문에 경제적으로 용이하지 않다. 그러므로 Mn3O4 분진 환원용 알루미늄 미분의 제조 코스트를 낮추기 위해, 알루미늄 합금분말의 제특성이 검토되었다. 망간을 다량 함유한 알루미늄 합금괴는 취성이 큰 금속간 화합물을 함유하고 있기 때문에 쉽게 파쇄할 수 있다. 또 망간은 망간 합금철의 주성분이다. Al-15%Mn 합금분말을 기계적 파쇄법으로 저렴하게 제조할 수 있다. Al 분말 대신에 Al-15%Mn 합금분말을 사용한 테르밋 반응 결과는 환원제로 순 알루미늄 분말을 사용한 경우와 같이 고순도 망간 합금철을 얻을 수 있었다. Al-15%Mn 합금분말를 이용한 Mn3O4 분진의 망간 회수율은 알루미늄 분말을 이용한 경우의 약 65% 보다 높은 약 70%의 높은 수준을 보였으며, 이는 비산이 적은 것에 기인한다.

We aimed to examine the co-doping effects of 1/6mol% Mn3O4 and 1/4mol% Cr2O3 (Mn:Cr=1:1) on the reaction,microstructure, and electrical properties, such as the bulk defects and grain boundary properties, of ZnO-Bi2O3-Sb2O3 (ZBS;Sb/Bi=0.5, 1.0, and 2.0) varistors. The sintering and electrical properties of Mn,Cr-doped ZBS, ZBS(MnCr) varistors werecontrolled using the Sb/Bi ratio. Pyrochlore (Zn2Bi3Sb3O14), α-spinel (Zn7Sb2O12), and δ-Bi2O3 (also β-Bi2O3 at Sb/Bi≤1.0)were detected for all of the systems. Mn and Cr are involved in the development of each phase. Pyrochlore was decomposedand promoted densification at lower temperature on heating in Sb/Bi=1.0 system by Mn rather than Cr doping. A morehomogeneous microstructure was obtained in all systems affected by α-spinel. In ZBS(MnCr), the varistor characteristics wereimproved dramatically (non-linear coefficient, α=40~78), and seemed to form Vo.(0.33eV) as a dominant defect. Fromimpedance and modulus spectroscopy, the grain boundaries can be seen to have divided into two types, i.e. one is tentativelyassigned to ZnO/Bi2O3 (Mn,Cr)/ZnO (0.64~1.1eV) and the other is assigned to the ZnO/ZnO (1.0~1.3eV) homojunction.

In order to make high-purity ferro-manganese from Mn3O4 waste dust, the application of aluminothermite process to the reduction of the waste dust was investigated. The mixture from Mn3O4 dust as metallic source and Al metal powder as the reductant ignited, and reduced with an extremely intense exothermic reaction. The rapid propagation of the aluminothermite reaction occurred spontaneously and stably by ignition of the mixture. The Manganese having some alloy elements emerged as liquids due to the high temperatures reached up to about 2,500℃ and separated from the liquid by their differences of specific gravity. The result of thermite reaction showed the fact that can be obtained high purity ferro-manganese which have over about 90% of manganese content and lower impurities such as C, P, S than those of KS D3712 specification. The recovery of manganese from Mn3O4 dust was lower level of about 65% than about 75% from manganese ore by electric furnace process, that is due to spatter loss because of its extremely intense thermite reaction. But it will be improved by the process designed to provide CaO as the cooler or to use the Al metal powder having larger particle size distribution.