Z.C. Zhong

Microstructure, mechanical properties and superelasticity of biomedical porous NiTi alloy prepared by microwave sintering.

Porous NiTi alloys were prepared by microwave sintering using ammonium hydrogen carbonate (NH4HCO3) as the space holder agent to adjust the porosity in the range of 22-62%. The effects of porosities on the microstructure, hardness, compressive strength, bending strength, elastic modulus, phase transformation temperature and superelasticity of the porous NiTi alloys were investigated. The results showed that the porosities and average pore sizes of the porous NiTi alloys increased with increasing the contents of NH4HCO3. The porous NiTi alloys consisted of nearly single NiTi phase, with a very small amount of two secondary phases (Ni3Ti, NiTi2) when the porosities are lower than 50%. The amount of Ni3Ti and NiTi2 phases increased with further increasing of the porosity proportion. The porosities had few effects on the phase transformation temperatures of the porous NiTi alloys. By increasing the porosities, all of the hardness, compressive strength, elastic modulus, bending strength and superelasticity of the porous NiTi alloys decreased. However, the compressive strength and bending strength were higher or close to those of natural bone and the elastic modulus was close to the natural bone. The superelastic recovery strain of the trained porous NiTi alloys could reach between 3.1 and 4.7% at the pre-strain of 5%, even if the porosity was up to 62%. Moreover, partial shape memory effect was observed for all porosity levels under the experiment conditions. Therefore, the microwave sintered porous NiTi alloys could be a promising candidate for bone implant.

Magnetic and Magnetocaloric Properties in Ferrimagnetic Mn 2− x Co x Sb (

The ferrimagnetic Mn2-xCoxSb (x = 0.15 and 0.20) alloys were prepared by arc-melting technique. The structure, magnetic, and magnetocaloric properties on these compounds were investigated. The tetragonal Cu2Sb-type structure (P4/nmm space group) was confirmed by X-ray powder diffraction measurements at room temperature for these two alloys. The Co-introduction results in a first-order magnetic transition between the antiferromagnetic and the ferrimagnetic state. Adopting the standard and loop process method, respectively, the measurements of isothermal magnetization were performed and the magnetic entropy changes were evaluated for these alloys.