Nataliya Skryabina

Mechanical instability in amorphous metal alloys–hydrogen systems

In the present study, we report the hydrogenation and deuteration of amorphous iron-, cobalt- and nickel-based alloys. Hydrogenation of these materials leads to a multiple acceleration of the creep deformation at room temperature. After hydrogenation, an almost full reduction of the shear resistance was observed on the iron-based alloys. The physical and mechanical characteristics of the alloys return to the initial values after a complete evacuation of hydrogen from the samples.

Ab initio calculations of the stability of disordered Ti-V-Cr solid solutions and their hydrides

The electronic structure of Ti-V-Cr alloys is calculated using the Korringa-Kohn-Rostoker method in the coherent potential approximation. The phase stability of the alloys is investigated as a function of the stoichiometry, the composition, and the hydrogen concentration. The results obtained are in good agreement with the available experimental data and provide an adequate description of the transition from the A2 phase to the A1 phase upon saturation of the alloys with hydrogen. For hydrogen-saturated hydrides with a high chromium concentration, the calculations predict magnetic polarization at chromium atoms with a magnetic moment of up to 2μB.

Spin-lattice relaxation and mobility of protons in the lattice of the TiV0.8Cr1.2 alloy

Titanium-vanadium-chromium alloys are promising materials for hydrogen storage. They can absorb up to 3.8 wt % of hydrogen with a variable (depending on the composition) temperature of hydrogen release in a convenient range. This paper reports on the results of investigations of the TiV0.80Cr1.20H5.29 hydride by continuous-wave (cw) and pulsed 1H nuclear magnetic resonance spectroscopy. It has been revealed that the hydrogen atoms occupy tetrahedral positions of the face-centered cubic lattice. A model that takes into account the exchange between two states of hydrogen, i.e., mobile hydrogen and hydrogen bound to the lattice, has been proposed for interpreting the temperature dependences of the relaxation times T1 and T2 of 1H nuclei. The assumption that the exchange occurs in these alloys has made it possible, in particular, to explain the strong difference between the relaxation times T1 and T2 in the high-temperature range.

The Barkhausen effect in a hydrogen-saturated Fe-B-Si-Ni amorphous alloy

Is is established that saturation of a Fe78B12Si9Ni1 amorphous alloy ribbon with hydrogen leads to a several-fold increase in the emf observed under the Barkhausen effect conditions. The magnitude of the observed effect is related to the hydrogen content in the alloy.

Interaction of Hydrogen with Amorphous Alloys in Open Thermodynamic Systems

In the present study, we report the hydrogenation of amorphous or nanocrystalline iron, cobalt and titanium-nickel based alloys. Hydrogenation of these materials leads to a multiple acceleration of the creep deformation at room temperature. After hydrogenation, an almost full reduction of the shear resistance was observed on the iron-based alloys. The physical and mechanical characteristics of the alloys return to the initial values after a complete evacuation of hydrogen from the samples.

Crystal Structure Analysis of the Mg2Si1-xSnx System Having Potential Thermoelectric Properties at High Temperature

Laves phases of C15 type of the system Mg2Si1-xSnx with x = 0, 0.4, 0.6 and 1 were synthesized in polycrystalline state in tantalum ampoule heated by high frequency coupling. The as-cast materials were analysed first at room temperature by X-ray diffraction (XRD). Systematically, XRD patterns were recorded up to 700 °C and Differential Scanning Calorimetry analysis was performed up to 1200°C to control the chemical and structural phase transformations. From these experiments, a C15 to C36 structure transformation was pointed out around 600°C in Mg2Si1-xSnx.solid solutions.

The effect of hydrogen on crystallization of a Ti50Ni25Cu25 amorphous alloy

Two effects not reported previously for the interaction of hydrogen with amorphous metal alloys were observed in a Ti50Ni25Cu25 alloy: (i) hydrogen-induced increase in the crystallization temperature and (ii) suppression of the reverse martensitic transition B19→B2 in the alloy samples hydrogenated upon crystallization.

The effect of hydrogen on the shear modulus of quasibinary alloys of the TiNi-TiCu system

Hydrogen saturation of amorphous quasibinary alloys of the TiNi-TiCu system is accompanied by a catastrophic decrease in their shear moduli. The effect is not related to the formation of new phases or structural components during hydrogenation.

The Barkhausen effect and percolation threshold in amorphous metal-dielectric nanocomposites

A new percolation situation has been found in metal-dielectric nanocomposites containing ferromagnetic components. For a certain concentration of metal atoms, the vectors of spontaneous magnetization of individual nanoparticles exhibit a correlated behavior. As a result, a structure containing a very large number of ferromagnetic nanoparticles shows magnetization reversal in a macroscopic nanocomposite volume in a single giant Barkhausen jump.

Improvement of hydrogen storage properties of magnesium alloys by cold rolling and forging

In this talk we show that cold rolling (CR) could be used to enhance hydrogen sorption properties of magnesium and magnesium alloys. In particular, cold rolling could reduce the first hydrogenation time, the so-called activation. Pure magnesium, commercial AZ91D alloy, and an experimental creep resistant magnesium alloy MRI153 in the as-cast and die-cast states were investigated. We found that both MRI and AZ91 alloys present faster activation kinetic than pure magnesium. This could be explained by the texture, higher number of defects, and nanostructure in CR materials but also precipitates at the grain boundaries. The effect of filing was also investigated.