Pure Nickel Powders Research Articles

Electrodeposition of catalytically active nickel powders from sulphate baths. I. Effect of bath constituents

A detailed study was made of the influence of the sulphate bath constituents: 0.3 - 0.0125 NiSO 4·7H 2O (I), 0.05 – 0.23 (NH 4) 2SO 4 (II), 0.1 – 0.4 H 3BO 3 (III) and 0.07 – 0.35 mol l −1 Na 2SO 4·10H 2O (IV) on the electrodeposition of nickel powder. The cathodic polarization, current efficiency, growth morphology, crystallite size and catalytic activity of the electrodeposited nickel powders were affected to different extents by the bath constituents. A highly pure nickel powder characterized by a small crystallite size (776 Å) and moderate catalytic activity was obtained from a bath containing: 0.0125 (I), 0.23 (II), 0.1 (III) and 0.07 mol l −1 (IV) at a current density of 10 A dm −2 and electrolysis time 60 min. at 25 °C. Structural studies with a scanning electron microscope are given and a reaction mechanism for the electrolytic powder deposition is discussed.

STUDY ON THE HOT PRESSED POWDER METALLURGY OF A TiNi SHAPE MEMORY ALLOY

A TiNi shape-memory alloy was experimentally manufactured by the vacuum hot pressing method, using pure titanium and nickel powders. The homogeneity and density of the TiNi alloy obtained by this method varies according to the temperature and pressure applied during vacuum hot pressing as well as the holding time. The results of studies of mechanical and physical properties confirmed that the alloys obtained show extremely effective shape-memory characteristics. Thus, it was demonstrated that the TiNi shape-memory alloys can indeed also be produced by the vacuum hot pressing method using elemental titanium and nickel powders.

Kinetics of Sintering and Diffusion in Cu-Al-Fe-Ni Quaternary Mixed Compacts

In the present paper the authors studied the kinetics of sintering and diffusion in the Cu-Al-Fe-Ni quaternary mixed compacts, where pure aluminium powder was not mixed but alloy powder of Al-Fe or Al-Ni binary system was used in order to prevent the exothermic expansion reported already in the previous papers, and aluminium contents were always kept 10%.As the present work attaches special importance to examine the diffusivities of nickel contained in different types, i.e., pure nickel, 10AI.3, 7 Ni binary and electroless nickel plated Cu powders, the three different types of Cu-10Al-3, 7 Fe-3, 7 Ni quaternary mixed compacts sintered at 900°C for 1hr were subjected to the X-ray microanalyser, and then we, confirmed that the electroless nickel plated Cu powder showed the best diffusivity of nickel in the sintered compacts, followed by compacts which contained the pure nickel powder. Judging from. the results of X-ray microanalysis and from the dilatometric measurement, it may be proved that the compacts expanded in volume by diffusion of nickel.When the electroless nickel double-plated Cu powder was used in the quaternary mixed compacts, its chemical composition automatically amounted to Cu-lOAl-6, 9Fe-6, 9Ni, where the rank of Ni-diffusivity reversed the order in Cu-10Al-3, 7 Fe-3, 7 Ni quaternary system above described.

Line Shapes, Saturation Behavior, and Temperature Studies in the Nuclear Resonance of Nickel

The nuclear magnetic resonance of ${\mathrm{Ni}}^{61}$ has been studied in pure nickel powders. Both natural nickel (1.25% abundant in ${\mathrm{Ni}}^{61}$) and enriched nickel (99.9% abundant in ${\mathrm{Ni}}^{61}$) were used. The signal observed with a circuit sensitive to the absorption of power is a combination of absorption and dispersion modes. The amount of mode mixing is found to depend on the applied rf field, ambient temperature, annealing temperature, and external magnetic-field intensity. The mode mixing of the resonance is related to electronic losses in the sample. The saturation behavior of the individual absorption and dispersion modes is that of an inhomogeneously broadened line. From the saturation behavior an estimate of the enhancement of the applied rf level for nuclei in domain walls of about 7\ifmmode\times\else\texttimes\fi{}${10}^{3}$ is made. An additional broadening mechanism is observed in the enriched nickel, particularly at 77\ifmmode^\circ\else\textdegree\fi{}K. Application of Redfield's theory of saturation at high rf levels leads to the conclusion that the additional broadening can be attributed to strong indirect exchange between nuclei. Frequency measurements from room temperature to 4.2\ifmmode^\circ\else\textdegree\fi{}K made with a marginal oscillator in both the enriched and unenriched nickel are presented. A temperature-dependent frequency shift is found between the enriched and unenriched nickel which appears to be a maximum at about 200\ifmmode^\circ\else\textdegree\fi{}K where the enriched nickel frequency is about 30 kc/sec higher. From room temperature to 536\ifmmode^\circ\else\textdegree\fi{}K, frequency measurements made with super-regenerative circuits are reported. A comparison of the temperature dependence of the resonance frequency with the saturation magnetization is made.

Roll-compacting produces pure nickel strip

Nickel strip with excellent mechanical properties has been prepared by roll-compacting pure nickel powders, sintering, and re-rolling the sintered compact This study of processing variables and their effect on properties indicates good possibilities for adoption of this technique on a commercial basis.