Preparation of Metal-Oxide Composites using Solid-State Displacement Reaction

本文研究了NiO、CoO、Cu_2O和Ti以及Cu_2O和Fe混合粉末的固相置换反应，制备了金属-氧化物复合材料。在NiO和CoO与Ti的反应中，1000 ℃退火25 h后，TiO_2相和金属相均得到了很好的结合。所用Ti粉的粒径为50~100 μ m，但置换反应后，TiO_2相和金属相以微米级的尺寸交织在一起。在Cu_2O与Ti的反应中，通过铝热剂反应，在600 - 800 ℃的温度下爆炸熔化芯块。ZrO_2粉末作为惰性物质加入到混合物中，对反应只有动力学影响。添加至少2重量%的极细粉末ZrO_2含量超过30wt. %的试样，烧结性变差，不利于铝热反应的进行没有烧结。烧结样品具有Cu和TiO_2相交织的结构，ZrO_2分布在Cu相的晶界上。在Cu_2O与Fe的反应中，Cu_2O + Fe = 2Cu + FeO和4Cu_2O +3Fe = 8Cu + Fe_3O_4两种反应均发生，且在Fe/Cu_2O混合比较高时，前者占主导地位。增加模具压力和退火温度可降低孔隙率。

Preparation of metal-and oxide composites was examined for the solid-state displacement reactions between powders of NiO, CoO Cu_2O and Ti and between Cu_2O and Fe, using pellets obtained by die-pressing their mixed powders. In the both reactions of NiO and CoO with Ti, TiO_2 phases and metallic phases were finely combined after annealing at 1000ﾟC for 25 h. Diameter of Ti powder used was ranging form 50 to 100mum, but, after displacement reaction, TiO_2 phases and metallic phases were interwoven in micron size. In the reaction of Cu_2O with Ti, pellets were explosively fused at temperatures of 600 to 800ﾟC by thermit reaction. The powder of ZrO_2 was added to the mixtures as an inert substance, which had only a kinetic influence to a reaction. The addition of very fine powder by at least 2 wt.% pevented the thermit reaction the increase of ZrO_2 lead to bad sinterability ; samples containing ZrO_2 above 30 wt.% were not sintered. Sintered sample had interwove n structures of Cu and TiO_2 phases ; ZrO_2 was distributed at grain boundaries of Cu phases. In the reaction of Cu_2O and Fe, both the reactions Cu_2O + Fe = 2Cu + FeO and 4Cu_2O + 3Fe = 8Cu + Fe_3O_4 proceeded and the former reaction was predominant at higher mixing ratios of Fe/Cu_2O.Composites obtained by the displacement reaction had porosities of 20 to 40 vol.%. The increase of the pressure applied to a die and of the annealing temperature were lowered porosity.