M. A. Sevost’yanov

Materials science aspects of the production, treatment, and properties of titanium nickelide for application in endovascular surgery

The physicochemical properties and application of titanium nickelide TiNi as a biocompatible material for producing stents of various purposes are studied and reviewed. The biochemical factors that require protective coatings on stents are presented. Recommendations for the materials of coatings on titanium nickelide and for its treatment are made.

Properties of nanostructured titanium nickelide and composite based on it

The properties of nanostructured nitinol (Ni, 55.91 wt %; Ti, 44.03 wt %) in the initial state and after mechanical and the thermal treatment and a composite of nitinol with a tantalum surface layer obtained by magnetron sputtering have been studied. Compared with microstructured nitinol, the use of nanostructured nitinol for medical appliances, like stent, has great opportunities due to better corrosion resistance in solutions that model the physiological media of a human organism and the decreased diffusion of nickel ions into solution below the admitted average dietary intake of 200–300 mg/day in solutions of any acidity. Surface mechanical polishing increases its corrosion resistance by two to three times more. Compared with nitinol, the composite of nitinol with a tantalum surface layer is ∼7–11% better by strength, plasticity, and surface microhardness and characterized by the absence of a corrosion processes and diffusion of metal ions into solution.

Mechanical properties of nanostructured nitinol/chitosan composite material

The mechanical properties and degradation behavior of a composite material based on nanostructured nitinol and a biodegradable polymer surface coating of chitosan of various molecular weights are studied. The formation of a biodegradable surface layer of any composition does not change the properties of the base material. The created biodegradable polymer surface coating disintegrates upon applying the yield stress, i.e., within the operating range of loadings on medical items. The base disintegrates with the formation of a neck. Surface layer cracking is observed only near the fracture.

Long-term corrosion tests of nanostructural nitinol of (55.91 wt % Ni, 44.03 wt % Ti) composition under static conditions: Ion release

The corrosion resistance of nanostructural nitinol in solutions with pH from 1.68 to 9.18 for a long time is investigated. The metal concentration in solution was determined using atomic emission spectrometry with inductively coupled plasma. The ion yield is inhibited in NaCl and hardly so in acidic media, and corrosion is not observed in alkaline medium. The corrosion resistance increases by polishing and deteriorates with annealing. The nanostructure promotes a lower yield of nickel ions.

Long-term corrosion tests of nanostructural nitinol of (55.91 wt % Ni, 44.03 wt % Ti) composition under static conditions: Composition and structure before and after corrosion

Nanostructural nitinol is investigated before and after storage for a long time in solutions simulating pH of physiological liquids. The structure and composition are determined by SEM, TEM, and Auger spectroscopy. The material base is the B2 phase in the form of fibers 30–70 nm in diameter. Polishing promotes the formation of a thin homogeneous surface layer of titanium oxide, which thickens after solution storage; and annealing, the layer unchanging, thick, and heterogeneous.

Preparation of a nanostructured shape-memory composite material for biomedical applications

We have obtained nanoscale and microscopic surface tantalum layers on NiTi flat substrates and wires. The structure and composition of the samples were determined by scanning electron microscopy, Auger electron spectroscopy, and X-ray diffraction. With increasing sputtering time, the thickness of the surface layer increases nonlinearly. The transition layer ensures strong adhesion of the surface layer to the substrate.

Kinetics of the release of antibiotics from chitosan-based biodegradable biopolymer membranes

A process for manufacture of chitosan-based biodegradable biopolymer membranes suitable for medical applications was developed. A technology for inclusion of broad spectrum antibiotics into the chitosan membranes was elaborated. The effects of pH of the solution surrounding the membranes and the initial solvent chosen for chitosan on the kinetics of release of antibiotics from the membranes were studied. It was demonstrated that the kinetics of drug release from the chitosan-based biodegradable biopolymer membranes depends on the properties of substance immobilized in the membrane, the membrane manufacture process, and extraction conditions.

Influence of the Surface Modification on the Mechanical Properties of NiTi (55.8 wt % Ni) Alloy Wire for Medical Purposes

The mechanical characteristics of a titanium nickelide alloy are studied depending on the surface machining. The additional processing improves the characteristics.

Effect of heat treatment on the mechanical properties and the structure of a high-nitrogen austenitic 02Kh20AG10N4MFB steel

The effect of heat treatment on the mechanical properties of a high-nitrogen austenitic 02Kh20AG10N4MFB steel has been studied in the temperature region 550—1200°C. The yield strength and the ultimate tensile strength are shown to change nonmonotonically as a function of the heat treatment temperature. They sharply decrease in the annealing temperature range 850—900°C, which can demonstrate a change in the character of the structure–phase state of this steel. After annealing at 850—900°C, aging occurs with the precipitation of embrittling phases; at higher annealing temperatures, these particles dissolve and austenite recrystallizes. The study of the stress–strain diagrams makes it possible to find the laws of strain hardening of the 02Kh20AG10N4MFB steel as a function of the heat treatment temperature.

Temperature dependence of the fracture strength of composite corundum materials reinforced with Ni and NiAl particles

The mechanical properties (fracture strength and Vickers microhardness HV) of corundum-based composite materials containing disperse Ni and NiAl particles are studied. The material samples are prepared by sintering in vacuum at 1500°C or through hot compaction at a temperature ranging from 1470 to 1570°C. The fracture strength of the samples based on Al2O3-Ni (2.2 vol %) and prepared through hot compaction at 1570°C varies from 3.4 to 5.4 MPa m1/2 at 20°C as the NiAl content varies from 5 to 40 vol %, respectively. When the Ni content is increased to 6.5 vol %, the fracture strength values vary from 3.1 MPa m1/2 (5 vol % of NiAl) to 5.1 MPa m1/2 (40 vol % of NiAl). The maximum fracture strength for the Al2O3-Ni (6.5 vol %)-NiAl (40 vol %) samples is 7.36 MPa m1/2 at 500°C.