The electrical resistivity of Ni–Cu alloys has been measured in the temperature range from 4.2 to 1100 K. By using the numbers of conduction electrons and hole-carriers estimated in this study, the anomalous magnetic resistivity in ferromagnetic Ni–Cu alloys, which has a maximum around 25 at%Cu notwithstanding the linear decrease of magnetization or Curie temperature with increasing Cu content, is explained as a result of the coexistence of scattering processes of spin disorder and s-d transitions. The anomalous variation of the residual resistivity with concentration in Ni–Cu alloys is due mainly to the magnetic clusters, which have the maximum influence at the critical concentration for ferromagnetism.
When a low-carbon aluminium-killed steel which has been quenched from the solution temperature and hardened by preageing at a low temperature is subsequently aged at higher temperatures, reversion and re-age-hardening are circumstantially found to occur before the final softening by overageing. In the present work, the processes of reversion, re-age-hardening and overageing are traced by the displacement of data-points in the thermoelectric power versus electrical conductivity plots. The reversion can be represented by the reverse displacement of data-points back to the original point of as-quenched state. This implies that the coherency strains generated by preageing remain unchanged during the reversion. If the reversion is incomplete, subsequent precipitation of epsilon carbide particles gives rise to re-age-hardening. The coherency strains generated during the re-age-hardening are nearly the same in magnitude as those in the case of direct ageing at the same temperature. During the coarsening of epsilon carbide particles, the coherency strains decline gradually.
A simple preparation method of metallic single crystal plates for X-ray examinations was developed, and thin and flat single crystal plates of cadmium, zinc and tin of low dislocation density were prepared. The as-grown metallic plates contained a few subgrain boundaries, and the dislocation density varied from less than 107 m/m3 in the most perfect region to 109 m/m3 in a less perfect region. Subsequent heat treatment decreased the dislocation density to less than 106 m/m3. By using these crystal plates, evolution of dislocations due to oxidation, expansion and contraction of dislocation loops and dislocation motions in the initial stage of plastic deformation were investigated by means of X-ray transmission topography. In addition, zinc plates containing a few dislocations were used for determining the atomic scattering factors by the Pendellösung-beat method. The present crystal plates were confirmed to be used effectively for solid state researches.
Deformability by hot rolling of Sendust alloy and magnetic properties of hot rolled sheets have been investigated as a function of composition of the alloy. With increasing silicon at a constant aluminum content, deformability decreases, while it is not changed by increasing aluminum at a constant silicon content. These results are qualitatively explained on the basis of mechanical tests at lower strain rates. Magnetic properties are improved by hot rolling, and especially the initial permeability is raised in the low frequency range. Molding and μi-temperature characteristics of cast and hot rolled Sendust are quite sensitive to composition. Segregation of alloying elements introduced during solidification is homogenized by hot rolling.
Oxidation of a dense Cu–Fe sulfide sample composed of a mixture of bornite (Cu5FeS4) and troilite (FeS) was investigated in a N2–O2 gas mixture at 1173 K. The oxygen partial pressure in the gas mixture was between 1.0×103 and 5.0×104 Pa. In the initial stage of oxidation, iron was preferentially oxidized to form magnetite, and the rate of oxidation was controlled by mass transfer of oxygen through a gas boundary film on the sample surface. When the partial pressure of oxygen was higher than 1.0×104 Pa, the oxidation proceeded in accordance with the parabolic rate law at the later stage of oxidation, and a dense Fe3O4 film was formed. At the oxygen partial pressure lower than 5.0×103 Pa, the oxidation was accompanied by the evolution of SO2 gas at the later stage, and porous oxide was formed. During the oxidation, the sulfide was partly melted. Temperature variation of the sample during the oxidation was also studied.
The activity coefficient of oxygen in liquid Ag–Pb alloys, γo, was determined at 1273 and 1473 K by means of a modified coulometric titration technique using the following electrochemical cell: O in liquid Ag–Pb alloys/ZrO2(+CaO)/Air, Pt. The measured lnγo values at both temperatures, plotted in terms of alloy composition, lie on up-wardly concave curves. The data were found to be in close agreement with those calculated from a quasi-chemical equation of Jacob and Alcock. However, the enthalpy and entropy values for oxygen dissolution, evaluated from the present data, were significantly different from those which were predicted from the equation.
The present study was undertaken to find any available solid reference electrode for SO2 sensor employing β-alumina solid electrolyte. We proposed two reference electrodes, Au+Au2Na and (β+β″)-alumina, for such a sensor. Emf measurements of the following cells were performed to investigate the characteristics of the two sodium reference electrodes: Mo, Na(l) / β″-alumina / Au+Au2Na(s), Mo Pt, Au+Au2Na(s) / β″-alumina / SO2+SO3+O2, Pt Pt, (β+β″)-alumina in air / β″-alumina / SO2+SO3+O2, Pt The results indicate that constant sodium activities in these reference electrodes are maintained for a long duration of the experiment. It is concluded that the use of Au+Au2Na and(β+β″)-alumina reference electrodes is recommended for the SO2 sensor employing β″-alumina, β-alumina or other sodium ion solid electrolytes.
Characteristics of superconductivity in Nb–Ti alloys (Nb-41–55 mass%Ti) are studied through electrical resistivity measurements. The superconducting transition temperature Tc and the electron-phonon resistivity at 273 K, ρep (273 K), are obtained with the measurements. From the experimental values of Tc, the electron-phonon coupling parameter λ is determined as a function of concentration. The density of states at Fermi level N(Ef) is estimated by using the relation between the values of λ obtained here and the coefficient of electronic specific heat γ. The results lead to a conclusion that the increase of Tc is mainly caused by the rise of N(Ef) with concentration. The electron-phonon coupling parameter in electronic transport λtr is also determined from the experimental values of ρep (273 K), and compared with λ.