Carbonyl Nickel Powder Research Articles

Gas Carburizing and Quenching of Sintered Iron-Nickel

Sintered iron-3%nickel specimens prepared from the mixture of reduced iron and carbonyl nickel powders were gas carburized and oil-quenched. The effects of nickel addition were examined. The results obtained are as follows :1) The increase in sintered density by nickel addition was found to be effective in reducing the penetration of carburizing gas to the interior of the sintered specimens. The carbon decrease in the carburized specimens is remarkable owing to the high density of the specimen obtained by the prolonged sintering.2) The surface carbon content of carburized specimens tends to decrease as compared with sintered and carburized iron specimens owing to the density increase and the change of the carbon activity in austenite by the nickel addition.3) The increase in quench-hardening ability by the nickel addition depends on the diffusion of nickel into iron during the sintering. The depth of the hardened case increases in the early stage, and then decreases, with increasing sintering time. This decrease of depth is due to the above mentioned carbon decrease during the prolonged sintering.

Storage battery electrodes made by rolling carbonyl nickel powder

1. It is shown that, by rolling a mixture of carbonyl nickel and urea powders, it is possible to produce sintered electrode strip reinforced with gauze or a grid, having a porosity of about 75% after sintering. 2. The rolled strip may have the following constructional features: a) the powder mass layer may extend 1.0–2.0 mm beyond the edge of the grid strip; b) the grid strip may protrude from the powder layer along the length of the strip. 3. Sintered strip produced by rolling is superior to pressed strip lengths in respect to thickness and porosity uniformity.

Elektrolytisch hergestelltes nickelpulver und dessen verwendung zur erzeugung von porösen gesinterten platten

The experimental results on the application's possibility of nickel-powder, obtained on the electrolytical way, for the formation of electrodes for fuel cells and active material's skeletons for alkaline storage-batteries, have been presented. The size-grading, electrolytic precipitates and sinters structure, catalytic properties, overpotential of hydrogen evolution, porosity and sintering conditions of the powder in the temperature of 500 and 700°C has been investigated. Comparative tests of the powders of other origin (powder obtained from nickel carbonyl and nickel formate) were performed too, in order to determine the differences between their physical and electrochemical properties. The results of the investigations carried out entitle to state, that the light powder obtained electrolytically, may be successfully applied for the sintered electrodes production, instead of commonly used carbonyl nickel powder.

On the Activated Sintering of Iron Powder Compacts with Nickel

This paper deals with the sintering mechanism of iron powder compacts containing nickel. Nickel-coated iron powder by electroless plating and iron powder mixed with carbonyl nickel powder are used. The shrinkage during sintering is examined using the theory of liquid phase sintering. In the case of coated powder, the circumferential diffusion of iron through the nickel layer of constant thickness is the rate controlling step, and the shrinkage is independent of nickel content. In the case of mixed powder, the thickness of diffusion layer is dependent on nickel content, and the shrinkage is also dependent on nickel content. The activation energy for the sintering process is about 48, 000cal/mole.

Study of the sintering of nickel powders produced by different methods

It was established in this investigation that, in the temperature range 500–700°C, carbonyl nickel powder is subject to more intensive sintering than electrolytic nickel powder. The theory of diffusional viscous flow is unsuitable for this case, and needs revision.

THE STRUCTURE AND PROPERTIES OF SINTERED CARBONYL-NICKEL POWDERS

Four carbonyl-nickel powders with bulk densities between 0.6 and 1.0 g/c.c. have been examined and their behaviour on loose sintering in dry hydrogen between 700 and 1000°C assessed. The properties of the porous plates produced were determined from porosity, pore-spectrum, fibre-strength, and electrical-resistivity measurements.It is shown that the majority of shrinkage occurs in the vertical direction by collapse of the powder bed in the first stage of sintering and that sub-sequent densification in the second stage is considerably slower. The increase in strength and decrease in electrical resistivity is more rapid in the second stage. The strength and resistivity are related to porosity, indicating a slight preference for a low-bulk-density powder when considering porosities in the range between 80 and 90%.Limited consideration is given to the effects of restraint and of atmospheres other than dry hydrogen, but although these modify the sintering behaviour the relationships with porosity obtained with dry hydrogen appear to hold.

Pressed-oxide nickel-matrix cathode below apertured electrodes

Carbonyl-nickel powder pressed and sintered with alkaline-earth triple carbonates serves as an experimental emitter. The general behaviour of this dispenser-type cathode under the severe field and ion-focusing conditions below closely spaced and apertured electrodes is investigated.Locally confined ionization processes in the alkaline vapour components will develop. The ion-focusing ability of the aperture, particularly if the surface-protecting space charge is removed, enhances evaporation. A spontaneous rise in cathode temperature accompanies this effect, leading to more vapour generation.Deep pit formations will invalidate the advantage believed to exist in a well-determinable surface profile. Negative grid control produces similar ionization effects because of the large centre field below the aperture.The self-sustaining discharge, starting just beyond the saturation bend, will last as long as sufficient alkaline metal is available on the surface. Three discharge peaks were measured with gradually increased anode voltage, indicating the replenishing ability from within the matrix. A faster recovery from the discharge state at higher temperatures is explained by a higher deionization rate, owing to a more intense vaporization of nickel.Under the severe aperturing conditions the cathode is inferior to oxide-coated cathodes and also to dispenser-type cathodes with built-in chemical reaction and vapour controls.

CONTINUOUS COMPACTION BY CYCLIC PRESSING

AbstractA process recently developed produces wide, thick bars of unlimited length from powder, granular, or sponge raw materials by a cyclic pressing operation. The process can be adapted readily for laboratory study or for large-scale production.Many materials have been pressed by this technique, and in all cases compaction was similar to that experienced in conventional pressing. Work on the pressing, sintering, and subsequent working of various nickel powders and of a nickel-iron-molybdenum magnetic alloy has been carried out. Carbonyl nickel powder produces nickel strip of high quality. A high-permeability alloy containing nickel 79, iron 17, and molybdenum 4% can be made into strip with good magnetic properties by compacting the powders with the cyclic-pressing technique and then sintering and rolling the pressed bar into strip.

PRODUCTION OF PURE NICKEL STRIP BY THE DIRECT-ROLLING PROCESS

AbstractResults are presented of an investigation into the production of pure nickel strip, 6 in. wide × 0·030 in. thick, from carbonyl-nickel powder, using compacting rolls 7 ⅝ in. in dia., arranged in a horizontal plane. Special reference is made to the factors affecting the quality and output of green strip: roll-gap dimensions, the head of powder above the roll gap, rolling speed, and raw-material properties. It is shown that for a given compacting mill, the thickness of green strip that can be produced is strictly limited and that it becomes progressively more difficult to achieve the limiting thickness with increase in rolling speed. A method of reducing the detrimental effect of high rolling speeds is described.The continuous sintering and subsequent processing of directly rolled strip, using conventional cold-rolling and annealing plant, are then considered, and the properties of fully processed material are compared with those of strip produced from melted and cast carbonyl-nickel pellet. It is c...

Sintered Plates for Nickel‐Cadmium Batteries

Porous plaques are prepared by sintering carbonyl nickel powder of low apparent density. The plaques are impregnated with nickel or cadmium salt solutions and the heavy metal ions precipitated in the pores of the plaque by cathodic polarization in alkali hydroxide solution. Sintered plates made by this procedure have been assembled into experimental cells for study. A typical set of discharge curves is shown for a five plate experimental cell covering the range from the twenty hour rate to the three minute rate.

IV.—THE FORM OF PARTICLES OF NICKEL PRODUCED BY THE CARBONYL PROCESS

Summary.Electron microscopical examination of (carbonyl) nickel powders consisting of particles a few microns in diameter has revealed two types of powder consisting respectively of (a) a mixture of irregularly shaped and cube‐shaped particles each with rough surfaces and (b) characteristically shaped particles with smooth surfaces. The form of the smooth surfaced particles could not be determined until evidence from the electron microscope was combined with evidence from the light microscope. It was then inferred that the smooth‐surfaced particles were single crystals in the form of icositetrahedra, probable indices of faces {544}.