[en] Some effects produced by substitution of Vanadium to niobium, in memority addition, in FeCo alloy in equiatomic composition are studied. The alteration of microscopic parameters such as the hyperfine field and the parameter of range of far-reaching in function of thermal treatments carried out and their effects over the macroscopic properties of the material are discussed. The analysis of the Moessbauer spectre revealed that the dissolution of until 2 at%v in magnetic matrix reduce significantly the medium hyperfine field of the material while one limit of solubility not higher than 0,4 at%Nb no permit that this element produce observable alterations of that parameter. The addition of quantity of soluto higher than of that limits arouse the appearing of paramagnetic precipitates that together with the reduction of the hiperfine field are able of to alter macroscopic parameters such as magnetic saturation and the coercive power. In this aspect the addition of Nb demonstrated to be more promissing that the V. The evolution of the parameter of range of far-reaching in time function to thermal treatments to 550⁰C showed that the addition of 0,62 at% Nb to FeCO reduce the velocity of arrangement of the alloy in two ranges of magnitude when compared with the of the alloy that contain 2,45 at%V. (V.R.B.)

No abstract available

[en] This study sought to investigate the reaction of Co-binder containing tungsten with molten zinc. Four kinds of Co-W alloys (pure, 10%W, 20%W, 30%W) were prepared using the powder metallurgy method. The specimens were immersion-tested in molten pure zinc baths at 460 .deg. C. To evaluate the corrosion property in molten zinc, the weight loss of the specimen was measured after the immersion tests at different immersion times (10∼300 min.). Co-10%W alloys, compared with pure cobalt, showed no effect of tungsten addition on the reaction rate in molten zinc. The relationship between the weight loss and the square root of immersion period represents a straight line in both pure cobalt and Co-10%W alloy. The Co-Zn reaction layer in Co-10%W alloy consists of γ 2, γ 1, γ and β 1 phases. The rate of weight loss significantly increases and the weight loss behavior is not well accord with the linear relationship as the tungsten content in the Co-W alloy increases. The β 1 layer was not formed on the Co-20%W alloy and neither was a stable Co-Zn intermetallic compound layer found on the Co-30%W alloy. The main cause of increase in reaction rate with increasing tungsten content is related with the instability of the Co-Zn reaction phases as seen on micro-structural analysis

No abstract available

[en] The heats of mixing of binary liquid alloys of cobalt with dysprosium were measured by isoperibolic calorimetry. The experimental data show the exothermic effect of alloys formation. The minimum integral enthalpy of mixing is -22.3 kJmol^-1 at 45 at.% of dysprosium. (orig.)

[en] For a system of spherical particles in a matrix, a relationship is derived between the equilibrium degree of particle contact and the ratio of the interfacial energies, i.e., the energy of the contact boundary between particles and of the particle--matrix interface. The degree of particle contact is expressed in terms of the contiguity and the average number of contacts per particle, both of which can be measured by counting on planar sections. Thus the relationship provides an alternative to the measurement of dihedral angle for the determination of the energy ratio. The method is applied to the systems TiC--Co, TaC--Co, and WC--Co and, in combination with wetting data, is used to estimate the surface and interfacial energies in these systems

[en] We investigated the perpendicular magnetic anisotropy and the Hall resistivity of CoSiB/Pd multilayers. The CoSiB/Pd multilayers consisted of CoSiB (7-Å thickness) and Pd (Pd thickness t_Pd = 10, 12, 14, 16, 18, and 20 -Å), and a CoSiB/Pd bilayer was stacked five times. The coercivity shows oscillating values between t_Pd = 12 -Å and t_Pd = 20 -Å. The value of the saturation magnetization increased between t_Pd = 10 -Å and t_Pd = 12 -Å and then decreased after t_Pd = 12 -Å. The perpendicular magnetic anisotropy constant depended on the thickness of Pd-layer and the values repeatedly increased and decreased. All CoSiB/Pd multilayers exhibited a positive Hall effect, and the Hall resistivity was not proportional to the magnetic moment.

No abstract available

[en] The rates of hydrogen desorption from the β- and γ-phases of Dy₂Co₇ hydride, as well as hydrogen absorption into the α- and β-phases were measured and compared. This represents the first time that such comparisons have been made of two-phase transitions within the same intermetallic hydride. Experiments were designed so that constant pressure thermodynamic driving forces were established and nearly isothermal conditions were maintained. Under these conditions, the rates of hydrogen evolution from the γ-phase were approximately 7 times faster than that from the β-phase. Hydrogen absorption by the β-phase was approximately 8 times faster than that by the α-phase. One possible explanation for the observed differences is that hydrogen atoms in the β- and γ-phases are in different types of lattice sites and this causes them to have different stability and mobility. This explanation would require that diffusion of hydrogen atoms within the crystal lattice have some role in the rate-controlling process. Enthalpies of formation, reaction orders, rate constants and activation energies were determined for each phase transition. (orig.)

[en] Curves of induced magnetic anisotropy in time function of isothermal treatment, to H=0, are obtained to amorphous film of composition Co₇₀,₄Fe₄,₆Si₁₅B₁₀, of magnetostriction almost nule, to samples in natura and pre-treated. A spectre of actived energy was obtained to reversible processes by use of a micromagnetic theory about induced anisotropy, based in distribution of two level systems. This spectra of actived energy also respond by evolution of the value of the coercive field during the isothermal treatment. (V.R.B.)