Porous NbAl3/TiAl3 intermetallic composites with controllable porosity and pore morphology prepared by two-step thermal explosion

Abstract

Porous NbAl3/TiAl3 with adjustable porosity was prepared by the thermal explosion (TE) mode of combustion synthesis (CS). This was achieved by using NaCl as temporary space holder, which was completely removed from specimens before TE reaction. The combustion image of this process provided the visual evidence for the observation of TE. The temperature profile, course of reaction as well as the effect of NaCl content on the phase composition, pore morphology and open porosity of porous NbAl3/TiAl3 were investigated. The results showed that the addition of TiH2 prevent the samples from cracking and deforming, and in situ synthesis of NbAl3/TiAl3 intermetallic composites. The interconnected channel was formed when using NaCl as space holder, which made the porous NbAl3/TiAl3 an open cellular structure. The open porosity can be improved from 48% to 79% by adding 70 vol.% NaCl particles. The small pores (<20 μm) in porous NbAl3/TiAl3 originated from the intergranular pores in green compact and the decomposition of TiH2, whereas the large pores (200–300 μm) were attributed to the replication of NaCl particles. This leachable space holder route provides a flexible way to adjust the pore morphology and porosity to multifarious applications. Keywords: Porous material, Niobium–aluminum, Intermetallics, Thermal explosion