Effect of Si content on the phase transformation and pore structure evolution of porous Mo–Al–Si–B ceramics

抄録

Porous Mo–Al–Si–B ceramics were prepared by activation reaction sintering method utilizing Mo, Al, Si and B elemental particles as starting materials, and the pore forming mechanism of the porous materials with different Si contents was investigated by characterizing the phase constitution, volume expansion rate, pore structure and pore morphology. The results show that the volume expansion, porosity, maximum pore size and permeability of the porous ceramics tended to decrease and then increase with the addition of Si atomic ratio, and the volume expansion, overall porosity, maximum pore size and permeability reached the maximum values of 26.64, 56.21 %, 14.16 µm and 169.48 m³·m⁻²·kPa⁻¹·h⁻¹ at Si atomic ratio of 1.3, respectively. The phase components with different Si contents were characterized by X-ray diffraction (XRD), and the results showed that the phase constitution gradually changed from MoAlB to MoSi₂ as the Si atomic ratio increased. The pore forming mechanism of porous Mo–Al–Si–B was investigated, mainly: interstitial pores generated by the powder pressing process; contraction of the pore structure due to the surface tension of the Al–Si molten liquid phase; and pore forming by the Kirkendall effect caused by the partial diffusion of different solid-state atoms.