PRIMARY STUDY OF CREATION OF FINE METALLIC PARTICLES DISPERSED ON METAL OXIDES BY UTILIZING PROPERTIES OF NON-EQUILIBRIUM ALLOYS

研究了非平衡Cu-Zr、Cu-Ta和Ni-Zr合金的氧化行为和Co-Zr合金对NO直接分解的催化性能，发现急冷Cu-Zr合金表面形成的ZrO_2膜很薄，具有保护作用，但与大气中的水分反应后失去保护作用，导致合金氧化。与水分反应形成了金属铜层和ZrO_2层的层状结构。在70 ℃、相对湿度为70%的空气中暴露60小时，使沉积法制备的Cu-Ta合金着色成各种颜色。颜色取决于合金成分。着色试样的最上表面由金属铜组成，其下为含Ta的氧化层，着色主要取决于初始氧化膜的保护性，约20 μ m厚的非晶态Ni-33 Zr合金在高温空气中表现出Zr的完全优先氧化。在完全的Zr氧化之后，镍被氧化。含少量Pt族元素的非晶态Co-Zr合金在HF溶液中处理后氧化，可形成Pt族金属的细小颗粒，分散在氧化物上，对NO的分解反应具有较高的催化活性，而二元Co-Zr合金对上述反应无催化活性。在添加的Pt族金属中，Pd的催化效果最好，Co-Zr-Pd合金由于Co_3O_4、ZrO_2和金属Pd的协同作用，具有与Pd黑相当的催化活性，并成功地制备了纳米级的非晶态Fe-Cr-P-C合金粉末。

Oxidation behavior of non-equilibrium Cu-Zr, Cu-Ta and Ni-Zr alloys and catalytic properties of Co-Zr alloys for NO direct decomposition were examined in details.The initial surface ZrO_2 film formed on the rapidly quenched Cu-Zr alloy surface was very thin and protective, but it lost its protectiveness by reaction with moisture in atmosphere, resulting in oxidation of the alloy. The reaction with moisture developed a sandwich-structure of metallic copper layrs and ZrO_2 layrs. Two types of ZrO_2 oxide, tetragonal and monoclinic phases were formed ; the former transformes to the latter phase by reaction with the atmospheric moisture.Cu-Ta alloys prepared by sputter-deposition were colored to various colors by exposure to an air with relative humidities of 70% at 70ﾟC for 60 hours. The color depends on the alloy composition. The topmost surface of the colored specimens consisted of metallic copper, under which oxide layr containing Ta, and the coloration depends mostly on the protectiveness of the initial oxide film.A morphous Ni-33Zr alloy about 20mum thick showed complete preferential oxidation of Zr in air at high temperature. Nickel was oxidized after the complete Zr oxidation. The formed ZrO_2 was mainly tetragonal on high Ni alloys and monoclinic on low Ni alloys.Treatment of amorphous Co-Zr alloys containing small amount of Pt-group elements in HF solutions followed by oxidation formed fine particles of Pt-group metals dispersed and supported on oxides and showed high activity to the decomposition reaction of NO.On the other hand, binary Co-Zr alloys had no catalytic activity to the above reaction. Among the additive Pt-group metals, palladium was most effective, and Co-Zr-Pd alloys had almost the same high catalytic activity with that of Pd-black because of synergistic action of Co_3O_4, ZrO_2 and metallic Pd for the catalytic reaction.Amorphous Fe-Cr-P-C alloy powder of nanometer-size was also successfully formed.