The thermodynamic properties of the components in the Cu-Ni-S ternary system have been measured by means of the H₂S/H₂ ratio in a gas phase equilibrated with the molten matte at 1200°C. The measured sulphur potentials were integrated to establish the activities in the Cu₂S-Ni₃S₂ pseudobinary and the isoactivity lines over the ternary system. The resultant activity pattern suggests the presence of a pseudocomponent at approximately the composition 0.02 N Ni, 0.63 NCu, and 0.35 NS . The influence exerted by the pseudocomponent causes the activity of Cu₂S to be nearly constant in the miscibility gap. In this same region the activity of Ni₃S₂ is restricted to low values. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The surface tension of solid commercially pure nickel was determined by the force measurement technique using fine wires as proposed by Udin, Shaler, and Wulff. Grain boundary measurements were also made on the same metal. After finding experimentally that tests in a vacuum of approximately 5 x 10⁻⁵ mm Hg were unsuccessful because of the high power vapour pressure of nickel at high temperatures, similar tests were made in helium and argon atmospheres, the pressure being kept constant at 760 mm Hg during the experiments. The average surface tension of nickel in argon was found to be 2220 ± 300 dynes per centimeter for a temperature range from 1370°C to 1390°C. The relative grain boundary energy of solid nickel was determined by measuring the dihedral grain boundary groove angles of thermally etched nickel. The interferometric method developed by Hilliard and Harrold was used for this purpose. An average value of 161 degrees was found for the dihedral angle. The grain boundary energy was calculated to be 740± 300 dynes per centimeter. Examination of thermally etched nickel surfaces was inconclusive with respect to physical evidence for dislocation. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

Kinetics of the Dissolution of Copper in Aqueous Aliphatic Amines. An investigation was made of the dissolution of copper metal in aqueous solutions of methyl, ethyl and n-butyl amine and ammonia, as well as in solutions of their aminium and ammonium ions, under oxygen pressure. Study of the kinetics of the dissolution was carried out over a wide range of concentrations. It was observed that there are two regions of oxygen pressure dependency of the rate. The range of oxygen pressure, where rate is independent of oxygen pressure, was investigated in detail. The rate process has been established to obey the relation R = [formula omitted] [k₂(A) + k₃ (AH⁻⁺)] for all the systems studied. A mechanism for the dissolution reaction has been proposed. Catalytic Reduction of Nickel Ion by Molecular Hydrogen. The rate of precipitation of nickel from salt solution by molecular hydrogen in the presence of catalyst has been investigated over a wide range of concentrations. The variables studied are concentration of nickel, hydrogen pressure, amount of catalyst, concentration of- hydrogen ion and temperature. The rate of reduction is found to obey an equation of the form: [formula omitted] = -k₁[S][PH₂]½[Ni⁺⁺] + k₂[S][H⁺] The activation energy is found to be 25±2 kcal/mol. The equilibrium constant k for the reaction Ni⁺⁺ H2 Ni° + H₂ ⇌ Nº + 2 H⁺ is found to be 4.65 x 10⁻⁶ atm⁻¹ at 140°C. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

An investigation of ferromagnetism in nickel manganese alloys up to forty atomic percent manganese has been carried out. Twenty alloys within this composition range were subjected to three heat treatments such that the conditions within the alloys varied from atomic disorder to a high degree of long range order. The degree of order of Ni₃Mn calculated from measured saturation magnetisation using the Ising model of ferromagnetism was consistent with the value calculated from the ratio of measured integrated intensity of the (110) x-ray diffraction superlattice line to that of line (111). The relationship between saturation magnetisation and concentration for the disordered alloys can be explained adequately by the existence of short range order. A value of 3.4 Bohr magnetons was obtained for the effective magnetic moment of manganese atoms in a nickel lattice. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This study is carried out to find the effect of nickel on the beginning of isothermal transformation of austenite in an iron-carbon-molybdenum alloy containing 0.55 carbon and 0.35 molybdenum. An introduction describes the iron-carbon equilibrium system, the products of slow cooling of austenite, the relation between slow cooling and isothermal transformation at temperatures below equilibrium, and a full discussion of terminology used. A literature review discusses theories of transformation and previous work on the effect of nickel on austenite transformation. Development of experimental technique in isothermal transformation and melting of pure alloys is discussed. The isothermal transformation diagrams are shown for beginning of transformation of austenite of base composition 0.55 carbon and 0.35 molybdenum, relatively free from impurities (silicon, manganese, etc.), showing the effect of nickel on the beginning of transformation. Nickel additions used are 0, 2.13, 3.69, and 5.31 percent. Isothermal transformation is shown by photomicrographs which are discussed fully. The effect of increasing nickel on the isothermal transformation of an alloy containing 0.55 carbon and 0.35 molybdenum is as follows: (1) the pearlite reaction is delayed appreciably: (2) ferrite formed at intermediate temperatures (880 to 1000 deg. F.) becomes more prominently acicular, the acicular ferrite reaction taking the place of the upper bainite reaction of low nickel alloys: (3) the acicular ferrite reaction is followed first by rejection of carbide particles, and later by agglomeration and growth of the carbide phase: (4) the acicular ferrite and feathery bainite reactions as represented on the isothermal transformation diagram become separated by the appearance of a bay in the isothermal transformation curve. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The extraction of nickel and cobalt, from nickeliferous laterite, together with the hydrothermal precipitation of hematite has been investigated. In order to emphasize the relevance and significance of this process, an appraisal is made of the state of the nickel, cobalt and iron industries. A compilation of the annual production of the respective ores on the world market is included with an examination of the future uses and demand of nickel and cobalt. Solubility relationships for iron (III) compounds in aqueous solution are reviewed in terms of pH, solution composition and temperature. The thermodynamic data used at elevated temperatures between 60°C (333°K) and 200°C (473°K) have been estimated by using the "Entropy correspondence principle" method of Criss and Coble. A sample calculation is shown in Appendix A. The effects of (a) temperature; (b) ferric chloride concentration, (c) hydrochloric acid concentration and (d) pulp density were studied in order to evaluate extraction conditions. Generally, metal extraction increased with temperature and ferric chloride concentration. At 423°K, over 90 percent of the nickel was extracted with a ferric chloride concentration greater than 1M. Since appreciable amounts of gangue dissolved under most conditions, thereby consuming acid, a discussion on the recovery of hydrochloric acid is presented. Filtration of the precipitated hematite has proved difficult, because of the very fine nature of the particles. An overview of the nucleation and growth of particles in supersaturated solutions has therefore been included. This phenomenon is used to describe the phase changes which occurred during leaching experiments, and to propose an approach by which coarser particles might be achieved. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The importance of the direct and indirect mechanisms in the bacterial leaching of a synthetic nickel sulphide is investigated using an electrochemical leaching model. Sterile controls runs, in which only ferric leaching took place, are compared with runs in the presence of an active, adapted bacterial culture. The direct mechanism occurs when bacteria attach to the sulphide mineral and catalyze the oxidation of the mineral, presumably with enzymes (biological catalysts). No evidence was found of the direct mechanism, in fact ferric leaching appeared to be inhibited as the bacterial presence increased due to growth. Considering evidence obtained by the fitting of the electrochemical model, it is tentatively suggested that leaching of the mineral is largely due to chemical ferric leaching, with the leaching role of bacteria restricted to re-oxidizing the resulting ferrous ions. Whether this is the case for other minerals remains to be established.

No description available.

No description available.

The purpose of this study is to investigate the varying conditions in types of solutions, concentrations of solutions, hydrogen-ion concentration, current densities and potentials in the electro deposition of nickel.