Salt Heat Treatment and Passivation to Improve the Corrosion Resistance of Nitinol (Ni-Ti)

Corrosion of nitinol (NiTi) is a major factor in the failure of implantable materials. Recently, as the importance of corrosion of metals has increased, testing according to international guidelines is essential. The purpose of this study was to evaluate the corrosion resistance of NiTi wire through heat treatment and passivation process. In this study, NiTi wire used two commercially available products and a self-manufactured stent. Experimental consideration was carried out according to ASTM standards. Heat treatment was carried out in an air or a salt furnace, and the corrosion was measured after additional process, such as passivation and scratch tests. As a result, the metal potential was rapidly decreased in the air furnace group. On the other hand, the potential of wires was dramatically increased in the salt furnace group compared to the air furnace group. The dislocation decreased below the acceptance criteria (>600 mV) within 60 s of heat treatment time in the air furnace. Moreover, the potential was dramatically improved, even after only 20 min of passivation treatment (1076 mV, 442% compared to the non-passivated group), and it continued to rise until 180 min. This phenomenon was similarly observed in the group of self-manufactured stents. The potential slightly decreased by the scratch process (93.1%) was significantly reduced by the air furnace process (315 mV, 24.4% of the nontreated group). In the passivated group of the air furnace sample with reduced potential, the potential was restored to the level before the air furnace (scratch stage) (1032 mV). In conclusion, the heat treatment is preferably carried out in a salt furnace rather than an air furnace, and the passivation process can be an advantageous tool to improve corrosion resistance by suppressing the oxidation process.

Two-dimensional or passivation treatment: the effect of Hexylammonium post deposition treatment on 3D halide perovskite-based solar cells

Much effort has been made to push the power conversion efficiency of perovskite solar cells (PSCs) towards the theoretical limit. Recent studies have shown that post deposition treatment of barrier...

A synergistic Cs2CO3 ETL treatment to incorporate Cs cation into perovskite solar cells via two-step scalable fabrication

Cs incorporation into perovskite film via a thin Cs2CO3 layer ETL passivation treatment.

Effects of Steaming and SiO2 Surface Passivation on SSZ-13 Zeolites in the Ethylene to Propylene Reaction

SSZ-13 zeolite was modified by two kinds of post-treatment methods such as steaming and SiO2 surface passivation (silylation) for ETP catalyst with high activity. The former steaming treatment was conducted in the range of 400–700 °C, whereas the latter surfaces passivation was applied to a chemical liquid deposition (CLD) technique that uses various silylation agents such as tetramethylorthosilicate (TMOS), tetraethylorthosilicate (TEOS), and tetrabuthylorthosilicate (TBOS). Catalysts were characterized by powder-XRD, ICP, Ar-phsisorption, solid-state 27Al MAS NMR, and NH3-TPD, and their activities were tested in fixed bed reaction system. Regarding the effects of steaming temperature, the results show that a relatively higher selectivity is observed in SSZ-13 catalysts treated at proper steaming temperatures such as 450 and 500 °C compared to parent and other steam treated catalysts. For optimum surface passivation treatments for ETP reactions, one-step surface passivation using TEOS agents among various passivation agents led to enhanced propylene selectivity to 80% when compared with parent and other silylated SSZ-13 catalysts. However, a sequential passivation treatment with a TEOS agent was not highly affected by the reaction activity.