IVa, Va族元素/BN混合粉末層への溶融アルミニウムの浸透による複合材料の反応合成 Synthesis of composite materials by infiltration of IVa, Va metals and BN powder mixtures with molten aluminum
The spontaneous infiltration of BN-base powder mixture with molten aluminum was carried out to produce ceramic/metal composites. Ceramic phases were synthesized by the <i>in situ</i> reaction shown below. 2Al+2BN+<i>Me</i>→<i>Me</i>B<sub>2</sub>+2AlN where <i>Me</i> denotes a metal element (tantalum, niobium, zirconium or hafnium) . Each of these metal elements was mixed with BN powder. The spontaneous infiltration occurred in each system with a 3600 s holding at 1473 K, and neither pores nor cavities were observed in these specimens. After a 3600 s holding, TaB<sub>2</sub> and NbB<sub>2</sub> were completely formed together with AlN for [Ta, BN] and [Nb, BN] systems, respectively. These <i>in situ</i> formed particles were uniformly dispersed in aluminum matrix. In the case of [Zr, BN] and [Hf, BN] systems, however, residual <i>Me</i>B<sub>2</sub> (<i>Me</i>: Zr or Hf) and BN were found. According to the differential thermal analysis, the heat of tantalum-aluminum and niobium-aluminum reactions, initiating at around 1200 K, can ignite a reaction including boron nitride. However, zirconium-aluminum and hafnium-aluminum reactions initiate at around 1000 K, and they do not ignite the reaction including BN. Hence, it took a longer processing time to complete the <i>in situ</i> reaction for specimens with [Zr, BN] and [Hf, BN] powder mixtures. The powder mixture of tantalum and boron nitride was infiltrated with molten aluminum at temperatures above 1173 K, and both tantalum boride and aluminum nitride were present as a result of the <i>in situ</i> reaction.
軽金属 46(12), 638-643, 1996-12-30
The Japan Institute of Light Metals