The Neck to Particle Ratio Effect on the Mechanical and Morphological Sintering Features of Porous Stainless Steel (SS) Hollow Fibers

The SS hollow fibers are prepared by extruding a mixture of SS particles and a polymeric binder in a phase inversion process followed by sintering at various temperatures (950–1100 °C), resulting in the formation of void structures with a finger‐like inner shell and a sponge‐like outer shell. The mechanical strength increases by over 1000% as the SS particle size decreases from D 50 = 32 to 4 μm, and by ≈150% as the sintering temperature increases from 950 to 1100 °C. The best mechanical strength reached is 820 MPa for the D 50 = 4 μm SS hollow fiber sintered at 1100 °C. The neck to particle (N/P) ratio proves to be a morphological measurement with good correlation with the mechanical properties of the SS hollow fibers. The mechanical strength increases by ≈44% (sintering effect) and ≈92% (particle size effect) from a N/P ratio of ≈0.8 to 0.9 for the smaller SS particle hollow fiber. At this ratio, the necks for the particles are in close contact and at the boundary of full coalescence, thus at the onset of fast mass transfer and grain formation/growth as diffusion increases significantly by six order of magnitude.