Pore control in SMA NiTi scaffolds via space holder usage

Porous NiTi shape memory alloy (SMA) was fabricated by sintering of compressed constituent elements pre-mixed with NaCl or urea spacer holders. Effect of spacer to metal volume-ratio (rS) on shape, size, distribution and openness of the voids was probed by optical metallography, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) was used to determine the SMA transformation temperatures. Controllable void geometry helping osteoblast proliferation and bone cell growth was gained by addition of the spacers. At rS = 0.7, percentage of the open pores reached 52% while at rS = 1.43, interconnected pores with 200 to 500 μm diameter were produced. Although trace of microstructural chlorine was observed in NaCl treated samples, no remains were detectable in the urea made specimens. The latter had a greater advantage of being more homogeneous as well.