Sintered nickel

Uses. Nickel nitrate is an intermediate in the manufacture of nickel catalysts, especially those that are sensitive to sulfur and therefore preclude the use of the less expensive nickel sulfate. Nickel nitrate also is an intermediate in loading active mass in nickel—alkaline batteries of the sintered plate type (see Batteries, SECONDARY cells). Typically, hot nickel nitrate symp is impregnated in the porous sintered nickel positive plates. Subsequendy, the plates are soaked in potassium hydroxide solution, whereupon nickel hydroxide [12054-48-7] precipitates within the pores of the plate. 

The other type of nickel electrode involves constmctions in which the active material is deposited in situ. This includes the sintered-type electrode in which nickel hydroxide is chemically or electrochemically deposited in the pores of a 80—90% porous sintered nickel substrate that may also contain a reinforcing grid. 

Some y-NiOOH has been shown to be formed in sintered nickel electrodes (38), and changes in water and KOH concentration during the cycling of nickel electrodes has been studied (12,39—41). Although there is some disagreement on the movement of water, KOH is adsorbed on the nickel electrode when the cell is charged and desorbed from the electrode when the cell is discharged. 

Sintered Cells. Tlie fabrication of sintered electrode batteries can be divided into fwe principal operations preparation of sintering-grade nickel powder preparation of the sintered nickel plaque impregnation of the plaque with actwe material assembly of the impregnated plaques (often called plates) into electrode groups and into cells and assembly of cells into batteries. 

Sintering is a thermal process through which a loose mass of particles is transformed to a coherent body. It usually takes place at a temperature equal to two-thirds the melting point, or ca 800—1000°C for nickel. The sintered nickel stmcture without active material is called a plaque and it can be prepared by either dry or wet processes (see Metallurgy, powder). 

To reduce labor and other expenses, most sintered nickel plaques are produced by a wet-slurry method. A nickel slurry is prepared by mixing a low density nickel powder with a viscous aqueous solution such as carboxymethylceUulose [9004-42-6] (CMC). Pure nickel gau2e, a nickel-plated gau2e, or a nickel-plated perforated steel strip is continuously carried through a container filled with the nickel paste and sintering is done in a hori2ontal furnace. The time of the sinter in the furnace is ca 10—20 min. 

Eor the negative electrolyte, cadmium nitrate solution (density 1.8 g/mL) is used in the procedure described above. Because a small (3 —4 g/L) amount of free nitric acid is desirable in the impregnation solution, the addition of a corrosion inhibitor prevents excessive contamination of the solution with nickel from the sintered mass (see Corrosion and corrosion inhibitorsCorrosion and corrosion control). In most appHcations for sintered nickel electrodes the optimum positive electrode performance is achieved when one-third to one-half of the pore volume is filled with active material. The negative electrode optimum has one-half of its pore volume filled with active material. 

For many years, sintered-nickel electrodes have been used as the positive electrodes for sealed-type nickel-cadmium batteries. With an increase in the demand for high energy density, this type of elec-... 

Although one of the most common storage batteries is called the nickel/cadmium system ( NiCad ), correctly written (-)Cd/KOH/NiO(OH)(+), cadmium is not usually applied as a metal to form a battery anode. The same can be said with regard to the silver/cadmium [(-) Cd / KOH / AgO (+)] and the MerCad battery [(-)Cd/KOH/HgO(+)]. The metallic negative in these cases may be formed starting with cadmium hydroxide, incorporated in the pore system of a sintered nickel plate or pressed upon a nickel-plated steel current collector (pocket plates), which is subsequently converted to cadmium metal by electrochemical reduction inside the cell (type AB2C2). This operation is done by the customers when they start the application of these (storage)... 

Sintered Electrodes In these electrodes the active materials are present in pores of a sintered nickel support plate. This plate is manufactured by sintering of highly disperse nickel powder produced by thermal decomposition of nickel pentacarbonyl Ni(CO)5. The plates are filled by impregnating them in alternation with concentrated solutions of salts of the corresponding metals (Ni or Cd) and with an alkali solution serving to precipitate insoluble oxides or hydroxides. 

It has been found for sintered nickel films (72) that the surface area a... 

Before leaving the nickel experiments, it may be well to refer to the experiments on hydrogen adsorption variously reported in the literature. As an example, the work of Maxted and Hassid (13) had as its main objective the measurement of the slow activated adsorption of hydrogen on reduced nickel oxide catalysts. It has been proved by the foregoing that the slow adsorption is actually absorption. When plotting their data as isobars, as was done in Fig. 9, the similarity between these isobars and those obtained with sintered nickel films is evident. 

Nickel salts are used in electroplating, ceramics, pigments, and as catalysts. Sinter nickel oxide is used as charge material in the manufacture of alloy steel and stainless steel. Nickel is also used in alkaline (nickel-cadmium) batteries. 

Cell construction is mainly confined to two types, using either pocket plate electrodes (vented cells) or sintered , bonded or fibre plate electrodes (vented and sealed cells). In the former, the active materials are retained within pockets of finely perforated nickel-plated sheet steel which are interlocked to form a plate. Positive and negative plates are then interleaved with insulating spacers placed between them. In sintered plate electrodes, a porous sintered nickel mass is formed and the active materials are distributed within the pores. In sintered plate vented cells, cellulose or other membrane materials are used in combination with a woven nylon separator. In sealed or recombining cells, special nylon separators are used which permit rapid oxygen diffusion through the electrolyte layer. 

Recently, cells employing thick sintered nickel plates on nickel-plated porous steel substrates have been developed which have greatly improved energy densities. The active material is introduced by electroprecipitation. Electrodes based on nickel fibre supports are also being studied. 

Sintered nickel electrodes used in nickel iron cells are usually thicker than those used in Ni-Cd cells. These result in high energy density cells, because very high discharge rates are usually not required. 

Performance Characteristics. The sintered nickel-sintered iron design battery has outstanding power characteristics at all states of discharge. making them attractive to the design of electric vehicles (EV) which must accelerate with traffic even when almost completely discharged. 

Diffraction patterns from a nickel-alumina steam reforming—methanation catalyst and a sample of sintered nickel recorded on a LIN AC source... 

Another disadvantage of vertical decomposition towers is that the caustic solution contains a certain amount of fine graphite powder formed by abrasion of the graphite lumps. The hydroxide solution also contains a considerable quantity of mercury (approx. 5 mg per litre). In order to remove these impurities from the solution it is passed through candle filters made of sintered nickel powder and carbon. 

Derivation Nickel ores are of two types, sulfide and oxide, the former accounting for two-thirds of the world s consumption. Sulfide ores are refined by flotation and roasting to sintered nickel oxide, and... 

The electrodes are flat. The anode is composed of porous sintered nickel along with additives, which inhibit the loss of surface area during operation. The anode is in direct contact with the electrolyte matrix. The cathode is a porous nickel oxide, which is initially fabricated in the form of a porous sintered nickel and is subsequently oxidized during the cell operation. 

The MCFC anodes are made from a porous sintered nickel with a thickness of 0.8-1.0 mm and a porosity of 55-70% with a mean pore diameter of 5pm. This porosity range provides adequate interconnected pores for mass transport of gaseous reactants and adequate surface area for the anodic electrocatalytic reactions. Because the anode kinetics is faster than that of the cathode, less active surface area is sufficient for the anodic process. Partial flooding of the comparatively thick anode is therefore acceptable at the anode interface. 

We did run a quick comparison test with another electrolyzer. This particular electrolyzer weighed in at about 30 pounds, used sintered nickel plates, and was about three times as large as our P41. The P41 weighs a little more than a pound and was less than half the size of the commercial electrolyzer. 

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