Experimental Study of Porous Titaniumzirconium alloys fabricated by Liquid Metal Dealloying for Biomedical Applications

This research aims to develop porous titaniumzirconium (TiZr) alloys for implant applications by the liquid metal dealloying (LMD) method. Alloy ingot of Ti۲۰Zr۲۰Cu۶۰ was manufactured by arc melting the mixtures of pure metals of titanium, zirconium and copper on a water-cooled copper plate under a purified argon atmosphere. Then, cylindrical rods with diameter of ۱ mm were made from the ingot by suction casting into a copper mold in a high-vacuum chamber. The as-cast Ti۲۰Zr۲۰Cu۶۰ precursors were dealloyed in pure magnesium melt electrically heated in a graphite crucible at a temperature of ۱۰۲۳ K for various durations of ۶۰, ۱۸۰, ۳۰۰ and ۶۰۰ s under the coverage of a protecting gas (mixture of CO + SF۶). The LMD occurred based on preferential corrosion of Ti۲۰Zr۲۰Cu۶۰ precursors in magnesium melt and sporadic arrangement of titanium and zirconium atoms by surface diffusion mechanism. Afterwards, magnesium with corrosion resistance so much weaker than titanium and zirconium was dissolved in ۳ M HNO۳ for ۵ h, leaving porous TiZr alloys of different densities. Cross sections of dealloyed and etched samples were characterized using a field-emission scanning electron microscope (FESEM, Tescan Mira۳) equipped with an energy dispersive X-ray Spectroscopy (EDS). Crystal structure was determined by X-ray diffraction (XRD) in Bragg-Brentano. Static compression test was conducted in a standard universal testing machine (Santam STM۲۰) with a load capacity of ۲۰ kN at a nominal strain rate of ۱۰(-۳)s according to ISO ۱۳۳۱۴ standard. Finally, the human osteoblast cell line (MG۶۳, NCBI; National Cell Bank of Iran) was used to evaluate the biological properties of synthesized samples. MTT assay was utilized to analyze the biocompatibility of different powder extracts. The resultant porous materials exhibit the ligament size, density and porosity lie in the range of ۱۳۰ to ۲۸۰ nm, ۲.۸ to ۳.۲ g/cm۳ and ۰.۴۳ to ۰.۵, respectively. The porous scaffolds prove fulfillment of unique mechanical features in these new biomaterials. The highest values of ligament size (۲۸۰ nm), density (۳.۲ g/cm۳) and compressive strength (۶۲۰ MPa) belong to immersion time of ۶۰۰ s. The biocompatibility analysis also proposes the immersion time of ۶۰۰ s to better facilitate the extension and growth of MG-۶۳ osteoblastic line. The astonishing compressive properties along with sufficient cell proliferation of TiZr@۵۷vol% (porosity of ۰.۴۳) scaffold make it appropriate for bone tissue engineering. The porous TiZr alloy produced by the LMD method provides the promising opportunity to minimize the stress shielding of dental implants, and the tunable microstructure, mechanical behavior and biocompatibility are fulfilled by controlling the immersion time.

کلیدواژه ها:

Liquid metal dealloying ، porous TiZr ، dental implant ، immersion time