Anton S. Konopatsky

Manufacturing, Structure Control, and Functional Testing of Ti–Nb-Based SMA for Medical Application

This paper focuses on the development and characterization of Ni-free shape memory alloys, more specifically, Ti–Nb-based alloys for biomedical applications. It starts by describing the smelting technology used to produce small and medium size ingots of selected compositions. Thermomechanical treatments: structure interrelations are discussed next. Finally, the results of their mechanical, electrochemical, and in vitro cytotoxicity testing are presented to allow a general assessment of the mechanical, chemical, and biological aspects of compatibility of these alloys, and of the methods to control their functional properties.

BN nanoparticle/Ag hybrids with enhanced catalytic activity: theory and experiments

Hexagonal boron nitride nanoparticles (BNNPs) with different amounts of boron oxide on their surfaces were used as catalyst carriers. BNNPs/Ag nanohybrids were produced via ultraviolet (UV) decomposition of AgNO3 in a mixture of polyethylene glycol and BNNPs. High temperature (1600 °C, 1.5 h) vacuum annealing of BNNPs promoted small size (5–10 nm) Ag nanoparticle (AgNPs) formation on BN surfaces with narrow size distribution, whereas using BNNPs in their as-produced state resulted in large AgNPs with various sizes. An increase in the B2O3 content on the BNNPs surfaces (up to a certain point) during BNNP pre-annealing in air led to larger amounts of AgNPs on their surfaces. Experimental results were confirmed by theoretical calculations of the adhesion energy of the (111)Ag with (0001)h-BN and (100)B2O3 surfaces. In contrast to the nonwettability of the h-BN surface by AgNPs, silver bound well to B2O3 with the formation of a covalent bond at the interface. Excessive fraction of B2O3, however, was not beneficial in terms of obtaining the optimal contents of AgNPs. Results of catalytic activity tests demonstrated that BNNPs/Ag nanohybrids synthesized using BNNPs with an optimized amount of B2O3 possess significantly enhanced catalytic activity compared to BNNPs without or with excess amounts of oxide. Finally, the catalytic activity of nanohybrids was theoretically analyzed using density functional theory (DFT) calculations.

Investigation of Electrochemical Behavior of Novel Superelastic Biomedical Alloys in Simulated Physiological Media

This paper focuses on study of the kinetics and the mechanism of passive film formation on novel superelastic biomedical Ti-22Nb-6Ta and Ti-21.8Nb-6Zr (at.%) alloys in simulated physiological solutions using XPS and electrochemical techniques in comparison with commercially pure titanium and Nitinol. In vitro biocompatibility study of Ti-22Nb-6Ta alloy was carried out as well. Ti-22Nb-6Ta alloy manifests a strong trend to protective passive film formation during the first stage of oxidation in simulated physiological solutions. It is shown that Ti-22Nb-6Ta and Ti-21.8Nb-6Zr electrochemical characteristics are comparable to those of titanium and Nitinol, and the alloy can be recommended for use in implantology.