DEVELOPMENT OF A PROCESS FOR DIRECTLY PRODUCING Zr-Ni-Mn ALLOY POWDERS FOR HYDROGEN STORAGE BY METALLOTHERMIC REDUCTION METHOD

以锆锰氧化物为原料，以金属钙为还原剂，直接制备Zr-Ni-Mn合金粉末，研究了合金的吸放氢性能及合金的形成机理。采用电弧熔炼法合成了50多种Zr-Ni-Mn合金，并研究了合金的显微组织和成分对合金性能的影响。结果表明，在两相分离前的单相合金中，成分为42.2%Zr，29.9%Ni，27.9%Mn或44.4%Zr，34.3%Ni，21.3%Mn的合金具有最好的储氢性能;其次，成分为44.4%Zr，用金属热还原法制备了34.3%Ni和21.3%Mn的合金。结果表明，合金是由液态Ni-Ca合金相中的Ni与固态Zr、Mn相发生非均相反应形成的。这一机理与用同样方法制备镍-稀土合金的机理有很大不同。所生产的合金的储氢性能被发现是略劣于那些由电弧熔炼生产的合金。认为要提高合金的性能，必须去除合金粉末表面形成的阻碍氢原子通过的氧化层。

Aiming at the development of an efficient process to make Zr-Ni-Mn alloy powders directly from the oxide resources of zirconium and manganese by using metallic calcium as a reductant, the hydrogen-absorbing and -desorbing properties of the synthesized alloys and the mechanism of formation of the alloy were studied.Firstly, more than 50 kinds of Zr-Ni-Mn alloys were synthesized by arc-melting and their properties were investigated in relation to the microstructure and the compositions. It was clarified that the alloys with a single phase just before separating into two-phases have most favorable properties for hydrogen storage, with the compositions of 42.2%Zr, 29.9%Ni and 27.9%Mn or 44.4%Zr, 34.3%Ni and 21.3%Mn.Secondly, the alloy powders with the compositions of 44.4%Zr, 34.3%Ni and 21.3%Mn were prepared by the metallothermic reduction method. It was found that the alloys were formed through a heterogeneous reaction between nickel in the liquid Ni-Ca alloy phase and the solid Zr and Mn phases. This mechanism was quite defferent from that in making Ni-rare earth alloys by the same method. The properties of the produced alloys for hydrogen storage was found to be a little inferior to those of the alloys produced by the arc-melting. It was considered that the properties must improve by removing the oxide layr formed on the alloy powder which makes the transit of hydrogen atom difficult.