Pore structure characteristic and properties of porous Ti3(Al,Si)C2 solid solution prepared by pressureless sintering

MAX phase solid solutions obtained by alloying at M-, A- and X-sites have attracted much attention recently to adjust the lattices and control the properties of MAX phases. In this work, a series of porous Ti3(Al,Si)C2 solid solutions were fabricated by pressureless sintering with Ti/Al/Si/TiC powder mixtures. Pore structures and effects of Si content were systematically characterized. The Si substitution affected the pore structure of porous Ti3(Al,Si)C2 following a V-shaped law: when xSi≤0.4, the porosity decreased together with the reduced pore size, narrow distribution and increased tortuosity factor; when xSi>0.4, the porosity and pore size increased together with the decreased tortuosity factor. Considering the specific application as capillary wick materials, the capillary performance, compressive strength and thermal conductivity of porous Ti3(Al,Si)C2 solid solution were further measured. The results showed that the larger porosity improved the capillary performance, but decreased the compressive strength and thermal conductivity. Compared with porous Ti3AlC2 of similar porosity, porous Ti3Al0.4Si0.6C2 had smaller pore size with more concentrated distribution, but better overall performances (the much better capillary performance, higher compressive strength and lower thermal conductivity). It was demonstrated that the adapt Si substitution achieved the overall promotions of porous Ti3AlC2, and porous Ti3Al0.4Si0.6C2 solid solution could act as the novel wick materials and show broad prospects in loop heat pipes (LHPs).