Sintered Nickel Powder

This electrode structure was also used in the Apollo mission fuel cells. Such structures may or may not be combined with catalysts. In the Apollo and Bacon cells, the anode was formed from the straightforward nickel powder as described above, whereas the cathode was partially lithiated and oxidised.  

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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. 

In 1932, Shlecht and Ackermann invented the sintered plate. In those days, conventional plates involved a system in which the active materials were packed into a metal container called a pocket or tube. However, with the sintered-plate method, the active materials are placed inside a porous electrode formed of sintered nickel powder. In 1947, Neumann achieved a completely sealed stracture. This idea of protection against overcharge and overdischarge by proper capacity balance is illustrated in Figure 2.5. 

Dispersions of flake aluminum powders having surface oxide up to 14 wt % Al O have been pressed, sintered, and worked to a material known as sintered aluminum powder (SAP). This product exhibits high strength at elevated temperatures. Nickel containing small additions of thoria, known as TD-nickel, is also a high temperature cermet. 

Ma.nufa.cture. Several nickel oxides are manufactured commercially. A sintered form of green nickel oxide is made by smelting a purified nickel matte at 1000°C (30) a powder form is made by the desulfurization of nickel matte. Black nickel oxide is made by the calcination of nickel carbonate at 600°C (31). The carbonate results from an extraction process whereby pure nickel metal powder is oxidized with air in the presence of ammonia (qv) and carbon dioxide (qv) to hexaamminenickel(TT) carbonate [67806-76-2], [Ni(NH3)3]C03 (32). Nickel oxides also ate made by the calcination of nickel carbonate or nickel nitrate that were made from a pure form of nickel. A high purity, green nickel oxide is made by firing a mixture of nickel powder and water in air (25). 

Sintering Datafordnco Nickel Powder A-129 3, The International Nickel Co., Inc., New York, 1979. 

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. 

Steam forms a protective white film at temperatures up to about 250°C, but above this temperature steam can, under some conditions, react with aluminium progressively to form aluminium oxide and hydrogen. Sintered aluminium powder (S. A.P.) has relatively good resistance to steam at 500°C, but at about 300°C an addition of 1% nickel to the S.A.P. is needed to prevent rapid disintegration. 

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. 

Similar reactions are known to take place in sintering of powder mixtures consisting of an intermetallic compound and an elementary substance.393 394 For example, I.F. Martynova et al394 found the Fe2Ti and TiNi3 layers to grow at the interface between FeTi and nickel (Fig. 5.25). 

K The hot mixture disintegrates filter paper the nickel oxide, nickel powder, and fine carbon residues rapidly block a sintered-glass frit or Celite filter bed. 

Deposition of a nickel layer hy fluidized bed CVD can improve sintering in powder metallurgy applications. The process can he used as a premixing step of the composite, for example on W particles. A similar technique can also he used to improve the wettabilty of ceramics like SiC hy the molten A1 during the fabrication of metal matrix composites. ... 

The purified nickel and cobalt sulfates, with low concentrations of ammonium sulfate, are reduced with hydrogen in agitated autoclaves at 375°F and 650 psig. By controlling the pH between 0.9-1.8 by continuous addition of aqueous ammonia, 95% of the Ni is preferentially reduced. The nickel powder is washed, filtered, dried, and packaged or is briquetted and sintered at 1750°F in hydrogen before shipment to alloy manufacturers. 

Pure nickel tends to sinter at the fuel cell operating conditions, resulting in loss of surface area and pore growth. Additives have been used to control the sintering. For example, the addition of Cr203 to nickel has been shown to effectively prevent anode sintering, by the formation of submicrometer LiCr02 on the nickel surface. Additions of Co, Cr, and Cu metals to nickel powder have also been tried and a Ni-10% Cr alloy has become the standard anode. ... 

Composite membranes also employ dense cermets fabricated by sintering together mixed powders of metal and ceramic [10-12], Examples include powders of Pd and its alloys sintered with powders of perovskites [11,12], niobium sintered together with AI2O3 [12], and nickel sintered with proton-conducting perovskites. Layers of dense cermets, 25-100 xm thick, are supported by porous ceramic tubes. Cermets employing chemically reactive metals, Nb, Ta, U, V, Zr, and their alloys, are typically coated with Pd and alloys thereof [11,12],... 

The sintered-type electrode was developed in Germany in 1932. This electrode is characterized by filling up active materials by an impregnation method into a porous sintered plaque in which carbonyl nickel powder having an average particle diameter of several microns is sintered. 

The production method of the porous sintered plaque includes a dry method and a wet method. With respect to the dry method, carbonyl nickel powder is spread to a Ni wire grid with a sieve or the like, adjusted to a predetermined thickness, and then sintered at 800-1,000° [Celsius] in a reducible gas atmospheres, such as hydrogen gas or butane reformed gas. With respect to the wet method, carbonyl nickel powder, a binder such as CMC or MC, and water are mixed to prepare a slurry. The slurry is applied to a nickel-plated iron thin sheet (perforated sheet) which has an open area ratio of about 50 %, and the thickness is adjusted in a scratching pcrtimi. Then, after drying with a drying furnace, it is sintered at a temperature of 800-1,000° [Celsius] in a reducible gas atmosphere. The typical porosity of the porous sintered plaque is 80-87 %. 

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