V. T. Zabolotnyi

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.

On the problem of the maximum strength of metals and alloys in crystalline, amorphous, and nanocrystalline states

The true breaking stresses and the ultimate tensile strengths of 11 metals with various structures are calculated. Moreover, the fracture strengths of these metals at 0 and 298 K are calculated in the amorphous (σf, a) and nanocrystalline (σf,nanomax) states formed upon severe plastic deformation. The temperature dependences of these properties are also determined. These properties are obtained for a number of alloys (TiNi, NiNb, Pd80Si20, Ni60Nb40). The values of σf, a are shown to correlate with yield strength σy, nano of nanocrystalline substances, and a hypothesis of a deviation from the Hall-Petch relation is advanced. This hypothesis is supported by the calculation of the properties and diffusion characteristics. The obtained numerical results agree satisfactorily with the experimental data and the results of other approaches to estimating these properties.

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.

Strength and plastic properties of amorphous cobalt alloy wires produced by various melt quenching methods

The strength and plastic properties of amorphous wires produced by melt spinning, in-rotatingwater spinning (INROWASP), and the Taylor-Ulitovskii method are studied. The wire produced by the Taylor-Ulitovskii method is found to have the highest level of strength and plasticity. The fracture and lateral surfaces of the amorphous wires are subjected to fractographic analysis. The high plasticity of this wire is shown to be caused by sequential formation of various families of shear bands and their interaction. The structure of the surface layer in an amorphous wire is assumed to be controlled by thermomechanical treatment to form a one-dimensional nanoamorphous composite material.

Nanocrystallization and change in the properties of an Fe80.2P17.1Mo2.7 amorphous alloy during heat or photon treatment

The changes in the phase composition and the mechanical and magnetic properties resulting from the nanocrystallization of an Fe80.2P17.1Mo2.7 amorphous alloy activated by heat or fast photon (xenon lamp radiation) treatment are compared using X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy, and hardness measurements. The initial stages of crystallization of the amorphous alloy have been detected.

Mechanical properties of “Thick” amorphous metallic wires produced by the Ulitovskii-Taylor method

The strength and plastic characteristics of thick (d = 40–120 μm) amorphous wires made of a model Co-based alloy and fabricated by the Ulitovskii-Taylor method are studied. They are found to have stable strength and plastic characteristics along the length. The plasticity of the thick wires is high, and they can form a full knot and undergo a load of 0.5 ultimate tensile strength in this state. The surface state and fracture surfaces of the amorphous wires are analyzed by scanning electron and optical microscopy. The wires are found to have a smooth lustrous lateral surface almost free of defects and to retain stable geometrical parameters along their length. Zones with different positions and frequencies of shear bands can form on the wire surface depending on the type of deformation action. The fracture surfaces of the thick amorphous wires are specific: a venous zone consists of several large pronounced principal “veins” and a rare network of adjoining secondary veins.

Analysis of the character of phase equilibrium in the Fe–P–Si system, nanocrystallization of amorphous alloys, and the choice of optimum composition

The study is devoted to the choice of the optimum composition of a soft magnetic amorphous Fe–P–Sialloy, which is comparable with the (Fe77Si13B7Nb2.1Cu0.9) FINEMET alloy in corrosion resistance and is passivated at lower critical currents in a 0.1 M Na2SO4 solution. The alloy can be prepared from naturally alloyed ferrophosphorus.

Glass ceramic and polymer impact-resistant materials and protective constructions based on them (Review)

The behavior of protective impact-resistant transparent constructions based on glass ceramic and polymer materials during an impact action is studied. Technological solutions are suggested to increase the functional properties of such materials and constructions.

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.