Papers by Author: A. Maričić

Abstract: The Ni92.8Mo7.2 alloy powder was obtained by electrochemical codeposition from an ammonium solution of NiSO4 and (NH4)6 Mo7O24 at j = 100 mA m-2, on a titanium cathode. DSC measurements and determination of the dependence of electrical resistivity on temperature did not reveal any changes in powder structure in the temperature range from 293 to 460 K. Therefore, in this range, there was no significant change in magnetic susceptibility either. Structural relaxation took place in the temperature interval from 460 to 560 K causing an increase in magnetic susceptibility. At temperatures higher than 570 K, magnetic susceptibility rapidly decreased. The Curie temperature of the powder was 660 K. With the increasing powder pressing pressure the magnetic susceptibility increased while the electric resistivity decreased. With the pressing pressure increase, the pore size was decreased and a better contact between powder particles was established. This caused electrical resistivity decrease and magnetic susceptibility increase.

Abstract: The magnetoimpedance (MI) effect in magnetically soft Fe89.8Ni1.5Si5.2B3C0.5 metallic glass ribbons is studied in this paper. As soft magnetic properties were determined by field induced anisotropy (and therefore by magnetic domain structure), ribbon samples were annealed under tensile stress in order to enhance induction of transverse anisotropy and to improve magnetoimpedance effect. Stress-annealing (SA) technique up to 420 0C/475 MPa/30 min. was used for tailoring electrical resistivity (ρ) and magnetic permeability (μ), i.e. two material properties that in classical skin effect determine the penetration depth δm and therefore have influence on MIeffect. The critical frequency of about 600 kHz was observed as the point with the initial increase of MI. Significant improvement of MI-response reaching the value Z/Z ≈ 25 %, after annealing at 420 0C, was recorded at driving frequency 4 MHz. The highest MI-element sensitivity was found for low magnetic field intensity where values of about 12 % / kA/m were attained.

Abstract: Structural, magnetic and electrical properties of iron oxide nano-sized powders synthesised electrochemically under various conditions are presented. The influence of the temperature and current density of synthesis on particular powder characteristics is established. Possibilities for co-existence of various phases and their impact on powder properties, as well as feasible paths of phase relaxation and transition during non-isothermal heating are investigated, too. In this way, optimal procedures for the preparation and stabilisation of iron oxides nano-sized powders of different characteristics are evaluated.