Segregation in Porous NiTi Made by SHS in Flow Reactor

Abstract

The research considers the contribution of gases to the surface formation during self-propagating high-temperature synthesis (SHS) of porous titanium nickelide based alloys. The structure of the obtained porous alloys was analyzed using the methods of secondary ion mass spectrometry (SIMS), optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM).Nanocrystalline intermetallic oxycarbonitrides of a complicated structure were found on the porous titanium nickelide surface. A dense double gradient layer was found under the outer loose deposits. It is concluded that the dense gradient layer of intermetallic oxycarbonitride provides chemical passivity of the investigated porous alloys. Loose surface deposits of intermetallic oxycarbonitrides ensure successful integration of the alloy into the biological tissue in case of implantation.

Study of Structural Features of Porous TINI-Based Materials Produced by SHS and Sintering

“…Depending on the SHS modes, porous materials with micro-and nano-sized pores can be produced. Studies made using mercury injection technique for measuring of pore size have shown that nano-sized pores, 1-100 nm, are also found in the alloy along with open pores [12].…”

Biocompatibility and Clinical Application of Porous TiNi Alloys Made by Self-Propagating High-Temperature Synthesis (SHS)

“…The given shell comprises amorphous-nanocrystalline phases of intermetallic oxycarbonitrides in the form of epitaxial strata (foamy onlay and dense bisubstrate), as reported in References [20,21]. Considering the chemical composition and structure, the shell can be classified as a cermet Ti 4 Ni 2 (O,N,C) layer [42,43,44]. In fact, such amorphous-nanocrystalline phases are implied to exhibit high corrosion resistance.…”

“…Turning to the issue of the PTN enhanced corrosion resistance highlighted earlier, we were bound to note the superficial amorphous-nanocrystalline layer of intermetallic oxycarbonitrides, which entirely conceal the pore walls. It was denoted that the SHS process in itself is the rationale for this layer appearance resulting from retrograde gas streams interacting with the surface melt [43,54]. In our experience, we have studied the surface structures of high-porous PTN using a confocal laser scanning instrument [55].…”

“…Potentiodynamic polarization was used in a comparative study of the surface susceptibility of PTN and dense Ti, TiNi, and in a 1% HCl solution, as reported in Reference [43]. Figure 6 illustrates the anodic behavior of unwrought PTN, dense Ti, and TiNi samples, modified by electropolishing, followed by N ion implantation.…”

“…Anodic behavior of ( a ) unwrought PTN sample and ( b ) dense Ti and TiNi samples modified by anodic polishing and subsequent N ion implantation [43]. …”