Relaxation and Dielectric Characteristics of Zn Substituted Copper-gallate Ferrite

The dielectric permittivities(ε'&ε")and dielectric loss tangent(tan)are studied for the prepared samples CuFe2O4 and Cu1-xZnxGa0.1 Fe1.9 O4 spinel ferrites with (0.0≤x≤0.5)from room temperature up to 700K in the frequency range(102～105Hz).Dielectric anomaly at the transition temperature Tc is pronounced in the relations of dielectric permittivitties with temperature where,the obtained Tc is found to decrease linearly with increasing Zn concentration.The relation of tan with frequency at different temperatures shows relaxation spectra where the relaxation time and the maximum frequency of the hopping conduction mechanism are determined.The variation of(ε',ε"and tanδ)with frequency and temperature displays a strong dependence on both gallium and zinc concentrations.The results are explained in light of the cation-anion-cation and cation-cation interactions over the octahedral sites in the spinel structure.     

Gas release from an E125 zirconium alloy under hydrogenation and deformation conditions

The degassing from a hydrogen-saturated E125 zirconium alloy is studied as a function of its deformation. Zirconium alloy samples are subjected to tension at a relative elongation of 2.5, 5, and 10%. Undeformed and deformed samples were saturated with hydrogen by a galvanic method at a current density of 0.5 A/cm²; that is, they are hydrogen saturated and then deformed. As a result, the defects at which hydrogen is trapped in zirconium are identified. The quantity of hydrogen trapped by defects depends on the strain and the sequence of deformation and hydrogen saturation. This is a technical result of the investigations, which can be used to find optimum operation conditions for hydrogen-saturated zirconium articles.     

Crystallographic and Low Frequency Conductivity Studies of the Spinel Systems CuFe_2O_4 and Cu_（1-x）Zn_xGa_（0.1）Fe_（1.9）O_4

Spinel solid solutions of CuFe2O4 and Cu1-xZnxGa0.1Fe1.9O4 with (0.0≤x≤0.5) are synthesized. Crystallographic phase transformation from tetragonal-to-cubic occurred at x=0.2. The derived structural parameters manifest that Zn occupies the tetrahedral A-site while Cu and Ga occupy the octahedral B-site and Fe distributes among A- and B-sites. Electrical conductivity measurements of these materials as a function of temperature and frequency revealed semiconducting behavior except CuFe2O4 sample, which has a metallic behavior at low frequency and at high frequency, metallic -to- semiconductor transition occurred as temperature increases. The metallic behavior in this sample is attributed to cation-cation interactions at B-site while, the semiconductor behavior in Cu1-xZnxGa0.1Fe1.9O4 compounds is due to the cation- anion -cation interactions at the same site in the spinel lattice. All compositions exhibit transition with change in the slope of conductivity versus temperature curve. This transition temperature (Tc) decreases linearly with increasing Zn content x. The relation of the universal exponent s with temperature gives evidence that over large polaron OLP and correlated barrier hopping CBH conduction mechanisms are presented in CuFe2O4 and Cu1-xZnxGa0.1Fe1.9O4 compounds respectively.     

Study and modeling of hydrogen release from Ti,Zr, Ni,Pd, Pt during linear heating

New the experimental results of thermally stimulated hydrogen release (TCHR) from plane-parallel plates of Ti, Zr, Ni, Pd, Pt metals with various thicknesses (0.05–1 mm), pre-saturated with hydrogen, under linear heating (1 °C s^?1) presented. The electrolytic and Sieverts method for saturate were used. Theoretical models for diffusion and desorption hydrogen release from flat metal samples into vacuum with linear heating were developed. In this case, the processes of diffusion and thermal desorption were taken into account to select the optimal conditions and experimental methods. The TSHR spectra simulated using the MATLAB software package to test the consistency of theory with experiment. By modeling in MATLAB using both the developed models and experimental TSHR spectra, the activation energies of desorption, diffusion and decomposition of hydrides, as well as the preexponential factors in the diffusion and kinetic equations, were determined.     

A laboratory device for measuring the diffusion coefficient of hydrogen in metals during their simultaneous hydrogenation and electron irradiation

An upgraded high-vacuum installation and procedure for studying diffusion of hydrogen in a BT1-0 titanium alloy membrane during irradiation of a sample by an electron beam with an energy of 10-120 keV in the scanning and stationary modes and with simultaneous electrolytic saturation are described. For this purpose, deflecting electrodes intended for scanning the beam are additionally integrated into the installation. The mass spectrum of the residual gases was recorded by the partial pressure sensors with a sensitivity as high as 10^-13 Pa. The diffusion coefficient of hydrogen measured under the scanning action of the electron beam on the titanium membrane is given.     

Superparamagnetism in Zn Substituted Copper-gallate Ferrite

Solid solution of spinel ferrite Cu1-xZnxFe2-yGayO4 with (0.0≤x≤0.5 and y=0.1) are synthesized. XRD measurements confirm the presence of single-phase tetragonal structure with c/a>1 for CuFe2O4 and samples with (x=0.0 and 0.1). The tetragonal phase is attributed to the presence of the cooperative Jahn-Teller Cu ions in the octahedral B-site in the spinel lattice. Tetragonal-to-cubic transformation is occurred at the compositional parameter x≥0.2 and the lattice parameter a is found to decrease with increasing Zn content x. 57Fe M(o)ssbauer measurements at 293K for these compounds reveal superparamagnetic phase for samples with (0.0≤x≤0.2). In contrast, M(o)ssbauer spectra at 12K for these materials show well ordered spectra where, the cation distribution and the hyperfine parameters are determined.     

Hydrogen absorption by Ti-implanted Zr-1Nb alloy

This paper describes the hydrogenation behavior of Zr-1Nb alloy Ti-implanted by plasma immersion ion implantation (PIII). Hydrogen sorption kinetics of the Ti-modified alloy was investigated under gas-phase hydrogenation at 400 °C for 1 h. The influence of implantation time on the protective properties of the modified layer was shown. The lowest hydrogen absorption as well as the highest hydrogen trapping efficiency was achieved after PIII for 30 min. The main contribution to the reduction of hydrogen permeation is the formation of an oxide layer consisting of mixed TiO₂ and ZrO₂ on the modified surface of the alloy. X-ray photoelectron spectroscopy (XPS) revealed that PIII titanium oxide exists on the surface in the form of TiO₂, which transforms to mixed Ti₂O₃ and TiO₂ after hydrogenation. The thickness of the modified layer increases with implantation time that improves the efficiency of hydrogen trapping. All the absorbed hydrogen is gradually distributed in the modified layer and no hydrides are formed after hydrogenation in Ti-modified Zr-1Nb for 15 and 30 min.