Igor Rodionov

The comparison of direct and indirect methods for determining the magnetocaloric parameters in the Heusler alloy Ni50Mn34.8In14.2B

The magnetocaloric properties of the Ni50Mn34.8In14.2B Heusler alloy have been studied by direct measurements of the adiabatic temperature change (ΔTAD(T,H)) and indirectly by magnetization (M(T,H)), differential scanning calorimetry, and specific heat (C(T,H)) measurements. The presence of a first-order ferromagnetic-paramagnetic transition has been detected for Ni50Mn34.8In14.2B at 320 K. The magnetocaloric parameters, i.e., the magnetic entropy change (ΔSM = (2.9-3.2) J/kgK) and the adiabatic temperature change (ΔTAD = (1.3-1.52) K), have been evaluated for ΔH = 1.8 T from CP(T,H) and M(T,H) data and from direct ΔTAD(T,H) measurements. The extracted magnetocaloric parameters are comparable to those of Gd.

Nanocrystalline structure of surface layer of technical-purity titanium subjected to induction-thermal oxidation

Metal-oxide coatings on a smooth technical-purity titanium surface were produced that were characterized by lamellar, needled, and prismatic shapes of crystals. Regularities of variations in nanometer morphology characteristics of the titanium surface subjected to induction-thermal oxidation are determined.

Structure of Composite Biocompatible Titania Coatings Modified with Hydroxyapatite Nanoparticles

The article describes prospective composite biocompatible titania coatings modified with hydroxyapatite nanoparticles and obtained on intraosseous implants fabricated from commercially pure titanium. Consistency changes of morphological characteristics and crystalline structure, mechanical properties and biocompatibility of experimental titanium implant coatings obtained by the combination of oxidation and surface modification with hydroxyapatite during induction heat treatment are defined.

Nanostructure of biocompatible titania/hydroxyapatite coatings

The article describes prospective composite biocompatible titania coatings modified with hydroxyapatite nanoparticles and obtained on intraosseous implants fabricated from commercially pure titanium VT1-00. Consistency changes of morphological characteristics, crystalline structure, physical and mechanical properties and biocompatibility of experimental titanium implant coatings obtained by the combination of oxidation and surface modification with hydroxyapatite during induction heat treatment are defined.

The Adiabatic Temperature Changes in the Vicinity of the First-Order Paramagnetic-Ferromagnetic Transition in the Ni-Mn-In-B Heusler Alloy

The magnetocaloric properties of Ni-Mn-In-B Heusler alloy have been studied using direct measurements of the adiabatic temperature change (Δ<i>T</i>_AD(<i>T</i>,<i>H</i>)) , and indirectly by magnetization (<i>M</i>(<i>T</i>,<i>H</i>)), differential scanning calorimetry, and specific heat (<i>C</i>_P(<i>T</i>,<i>H</i>)) measurements. The presence of a first-order ferromagnetic-paramagnetic transition has been detected for Ni₅₀Mn_34.8In_14.2B at 320 K. The magnetocaloric parameters, i.e., the magnetic entropy change, Δ<i>S</i>_M = (2.9-3.2) J/kgK, and the adiabatic temperature change, Δ<i>T</i>_AD = (1.3-1.52) K, have been evaluated for Δμ₀<i>H</i> = 1.8 T from <i>C</i>_P(<i>T</i>,<i>H</i>) and M(T,H), and from <i>C</i>_P(<i>T</i>,<i>H</i>) and direct Δ<i>T</i>_AD(<i>T</i>,<i>H</i>) measurements, respectively, in the vicinity of the first-order transition temperature. The extracted magnetocaloric parameters are comparable to that of Gd.

Induction heat treatment device and technique of bioceramic coatings production on titanium implants

A construction of laboratory apparatus for heat treatment of titanium implants by high-frequency currents is described. Dependencies of heating of titanium implant samples at different power consumption were defined. Novel matrix coatings of titanium dioxide with colloidal hydroxyapatite (nanophase filler) were produced on the surface of medical items, which are made of commercially pure titanium VT1-00 and titanium alloy VT16 (Ti-2.5Al-5Mo-5V). Consistency changes of morphological characteristics, hardness and biological compatibility of titanium intraosseous implants with coatings produced by the above-mentioned technique using induction heating were defined. Technological recommendations for obtaining bioceramic coatings with extremely high strength on titanium items surface were given.

Magneto-Optical Study of Martensitic Transition in Ni45Mn36.7In13.3Co5 (at. %) Single Crystals

Transverse Kerr effect (TKE) was used to study magneto-optical (MO) properties of Ni45Mn36.7In13.3Co5 (at.%) single crystals. A single crystalline ingot of such composition was grown by the Czochralski method. One series of samples was quenched into cold water (WQ) and the other series after quenching was heated at 770 K for 20 min and slowly cooled to assure a complete atomic order (SC). Accordingly to differential scanning calorimetry (DSC), magnetic and magneto-optical (MO) measurements, WQ samples exhibit well-defined martensitic transition (MT), but the SC samples do not show MT. It is found that TKE for WQ samples shows the following features (i) MO signal is well pronounced far below the martensitic transition in spite of a weak magnetization of martensitic phase; (ii) the characteristic temperatures of martensitic transition differ from those for the bulk and depend on annealing conditions; (iii) MO spectra profile do not change significantly during the martensitic transition and is similar but not identical with that for Ni50Mn35In15 thin films and Ni43.7Mn43.6In12.7 ribbons measured before; (iv) MO signal is anisotropic.

Micro- and nanostructure of a titanium surface electric-spark-doped with tantalum and modified by high-frequency currents

We have studied the characteristics of the porous microstructure of tantalum coatings obtained by means of electric spark spraying on the surface of commercial grade titanium. It is established that, at an electric spark current within 0.8–2.2 A, a mechanically strong tantalum coating microstructure is formed with an average protrusion size of 5.1–5.4 µm and pore sizes from 3.5 to 9.2 µm. On the nanoscale, a structurally heterogeneous state of coatings has been achieved by subsequent thermal modification at 800–830°C with the aid of high-frequency currents. A metal oxide nanostructure with grain sizes from 40 to 120 nm is formed by short-time (~30 s) thermal modification. The coating hardness reaches 9.5–10.5 GPa at an elastic modulus of 400–550 GPa.

Superhard oxide coatings formed on titanium treated by high-frequency currents

We have studied the hardness and elastic modulus of rutile (TiO2) oxide coatings formed on the surface of commercial grade VT1-00 titanium treated by high-frequency current (HFC). The mechanism of formation of superhard oxide coatings with thicknesses within 2–3 μm and submicron-grained structure consisting of prismatic crystallites with dimensions of 200–400 nm. It is established that, at high temperatures (within 1000–1200°C) and short HFC treatment durations (30–300 s), the oxide coatings are characterized by hardnesses of about 61–78 GPa and elastic moduli within 330–680 GPa.

Induction heat treatment and technique of bioceramic coatings production on medical titanium alloys

Prospective composite bioceramic titania coatings were obtained on intraosseous implants fabricated from medical titanium alloy VT16 (Ti-2.5Al-5Mo-5V). Consistency changes of morphological characteristics, physico-mechanical properties and biocompatibility of experimental titanium implant coatings obtained by oxidation during induction heat treatment are defined. Technological recommendations for obtaining bioceramic coatings with extremely high strength on titanium items surface are given.