Papers by Author: Oleg V. Tolochko

Abstract: Crystal structures and shape memory properties of Ti-rich Ti52Ni23Cu25 (at.%) ribbon annealed at 450°C for 10 min and 1 h were investigated by X-ray diffraction and dynamic mechanical analyzer. As-spun ribbon was full amorphous and its crystalline peak temperature is 455.4°C. The annealed ribbon is crystallized with strong preferential (110)-B2 orientation. It shows a well-defined shape memory effect and the transformation hysteresis for the annealed ribbon under an external load in the range of 3-9 N is about 38.5°C. With annealing time increasing from 10 min to 1 h, the maximum of transformation strain under the external stress decreases from 1.93% to 1.7%. The temperature dependence of the external stress increases from 0.3 N/°C to 0.43 N/°C. The residual plastic strain is up to about 0.4% at a load of 9 N.

Abstract: Martensitic transformation (MT) and the internal friction (IF) behavior of the initially amorphous Ti-rich Ti-Ni-Cu melt-spun ribbon annealed at 400°C for 10 h were investigated by using DSC and dynamic mechanical analysis (DMA). The annealed ribbon shows B2 structure with strong preferential (110) orientation and exhibits B2↔B19 MT with the temperature hysteresis of 13°C. DMA tests show that the internal friction is frequencies dependence at 1-50 Hz. The tanδ values decrease with the increasing frequency, but it does not meet the 1/f dependence. Isothermal DMA tests show that the tanδ value at a temperature of 15°C in the MT zone increases quickly from 0.005 to 0.045 with the increasing isothermal intervals and keep stable subsequently. The isothermal time to complete the MT can be determined by the DMA tanδ curve directly.

Abstract: Nanostructured Lanthanum hexaboride (LaB6) powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectra (XPS). The average size of LaB6 nanoparticles is about 35nm, which are well crystallized with ball or ellipsoid with inconspicuous corners and covered by a 3-5nm thick amorphous layer containing oxygen and carbon. The absorption of LaB6 nanoparticles in visible and near infrared spectrum (NIR) was measured and compared with micron scale particles. The surface plasmon responance (SPR) of nanoparticles was very efficient at NIR blocking, which almost covered the whole NIR region. The influence of nanoparticles concentration on spectrum absorption was comparatively evident. Meanwhile, micron particles almost haven’t NIR blocking function.

Abstract: Magnetic oxide-coated iron nanoparticles with the mean size ranging from 6 to 75 nm were synthesized by aerosol method using iron carbonyl as a precursor under the flowing inert gas atmosphere. Oxide shells were formed by passivation of as-prepared iron particles. The influence of experimental parameters on the nanoparticles’ microstructure, phase composition and growth behavior as well as magnetic properties were investigated and discussed in this study.