The Effect of Pore Structure on the Electrical Conductivity of Ti

Open-pore Ti foam samples with porosity in the range of 10-70% and average pore size of 150-400 mu m was fabricated by powder metallurgy method using polymethyl methacrylate (PMMA) as space holder initially. The resulting foam is anisotropic: the pores are spheroidal, being shorter along the pressing direction than in the pressing plane. The pore anisotropy decreases as the size of the polymethyl methacrylate (PMMA) particles used increases and hence with pore size, which leads to a higher conductivity in the plane of the pressing. As the porosity increases, the conductivity of porous Ti decreases dramatically. The porosity dependence of the electrical conductivity sigma could be well described by Maxwell approximation, while the differential effective medium approximation is only suitable to porous Ti with finite size of 400 mu m in the porosity range of 40-70%, i.e., high porosity metal with randomly oriented spheroids.