Influence of surface modification of nitinol with silicon using plasma-immersion ion implantation on the alloy corrosion resistance in artificial physiological solutions

Cyclic voltammetry and potentiostatic polarization have been applied to study electrochemical behavior and to determine corrosion resistance of nitinol, which surface was modified with silicon using plasma-immersion ion implantation, in 0.9% NaCl solution and in artificial blood plasma. It was found out that continuous, and also homogeneous in composition, thin Si-containing layers are resistant to corrosion damage at high positive potentials in artificial physiological solutions due to formation of stable passive films. Breakdown potential Eb of Si-modified NiTi depends on the character of silicon and Ni distribution at the alloy surface, Eb values amounted to 0.9–1.5 V (Ag/AgCl/KCl sat.) for the alloy samples with continuous Si-containing surface layers and with decreased Ni surface concentration

Structural phase states in nickel-titanium surface layers doped with silicon by plasma immersion ion implantation

The paper reports on a study of NiTi-based alloys used for manufacturing self-expanding intravascular stents to elucidate how the technological modes of plasma immersion ion implantation with silicon influence the chemical an

Plasma immersion ion implantation for surface treatment of complex branched structures

The paper presents experimental results demonstrating the capabilities of plasma immersion ion implantation of silicon (Si) for surface treatment of complex branched structures such are self-expanding intravascular nickel-titanium (NiTi) stents. Using NiTi stents of diameter 4 and 8 mm, it is shown that plasma immersion ion implantation can provide rather homogeneous doping of their outer and inner surfaces with Si atoms. Also presented are research data on the processes that determine the thickness, composition, and structure of surface layers subjected to this type of treatment

Influence of surface modification of nitinol with silicon using plasma-immersion ion implantation on the alloy corrosion resistance in artificial physiological solutions

Cyclic voltammetry and potentiostatic polarization have been applied to study electrochemical behavior and to determine corrosion resistance of nitinol, which surface was modified with silicon using plasma-immersion ion implantation, in 0.9% NaCl solution and in artificial blood plasma. It was found out that continuous, and also homogeneous in composition, thin Si-containing layers are resistant to corrosion damage at high positive potentials in artificial physiological solutions due to formation of stable passive films. Breakdown potential Eb of Si-modified NiTi depends on the character of silicon and Ni distribution at the alloy surface, Eb values amounted to 0.9–1.5 V (Ag/AgCl/KCl sat.) for the alloy samples with continuous Si-containing surface layers and with decreased Ni surface concentration

Cross-sectional TEM analysis of structural phase states in TiNi alloy treated by a low-energy high-current pulsed electron beam

The paper reports on a study of structural phase states and their cross-sectional in-depth evolution from the surface of TiNi specimens treated by low-energy high-current electron beams with surface melting at a beam energy density E = 10 J/cm2, number of pulses N = 10, and pulse duration = 50 s. After treatment,the modified TiNi surface zone takes on a layered structure in which each layer differs in phase composition and structural phase state. Itis found thatthe melted layer is 8–10 m thick. This layer is in a single-B2 phase state with distorted structure, lattice parameters a = b = 3.003–3.033A, ˚ c = 3.033–3.063A˚ and ˛= 89.3–90◦, ˇ = = 90◦, quasihomogeneous chemical composition corresponding to Ti51.7Ni48.3, the preferred orientations ofthe crystallites in a direction close to 4 1 0B2, and inhomogeneous lattice strain. The intermediate layer contains, in addition to the B2 phase, a B19 martensite phase. The structural state of the B2 phase in this layer is close to equilibrium and its parameters approximate those of the initial B2 phase in nonirradiated TiNi specimens.

Cross-sectional TEM analysis of structural phase states in TiNi alloy treated by a low-energy high-current pulsed electron beam

The paper reports on a study of structural phase states and their cross-sectional in-depth evolution from the surface of TiNi specimens treated by low-energy high-current electron beams with surface melting at a beam energy density E = 10 J/cm2, number of pulses N = 10, and pulse duration = 50 s. After treatment,the modified TiNi surface zone takes on a layered structure in which each layer differs in phase composition and structural phase state. Itis found thatthe melted layer is 8–10 m thick. This layer is in a single-B2 phase state with distorted structure, lattice parameters a = b = 3.003–3.033A, ˚ c = 3.033–3.063A˚ and ˛= 89.3–90◦, ˇ = = 90◦, quasihomogeneous chemical composition corresponding to Ti51.7Ni48.3, the preferred orientations ofthe crystallites in a direction close to 4 1 0B2, and inhomogeneous lattice strain. The intermediate layer contains, in addition to the B2 phase, a B19 martensite phase. The structural state of the B2 phase in this layer is close to equilibrium and its parameters approximate those of the initial B2 phase in nonirradiated TiNi specimens.