Composite particles cobalt-nickel alloy

Alloys are prepared commercially and in the laboratory by melting the active metal and aluminum in a crucible and quenching the resultant melt which is then crushed and screened to the particle size range required for a particular application. The alloy composition is very important as different phases leach quite differently leading to markedly different porosities and crystallite sizes of the active metal. Mondolfo [14] provides an excellent compilation of the binary and ternary phase diagrams for aluminum alloys including those used for the preparation of skeletal metal catalysts. Alloys of a number of compositions are available commercially for activation in the laboratory or plant. They include alloys of aluminum with nickel, copper, cobalt, chromium-nickel, molybdenum-nickel, cobalt-nickel, and iron-nickel. 

In recent years, we have seen an explosive interest in nanomaterials, in particular in nanofibers, nanofilaments, and nanotubes of the very different chemical composition. The interest arises from the specific mechanical and physicochemical properties of these nano objects, which allow them to be used, for example, as specific adsorbents, catalyst supports, reinforcing components of composite materials, and so on. The most cited generic types of nanomaterials are carbon nanofilaments and nanotubes. Numerous methods for preparing these carbon materials are known. However, the simplest method seems to be thermal pyrolysis of various carbon contain ing precursors (e.g., carbon monoxide, saturated and unsaturated hydro carbons, etc.) in the presence of special catalysts that are typically nanosized particles of nickel, cobalt, iron metals, or their alloys with different metals. 

The composition of the codeposition bath is defined not only by the concentration and type of electrolyte used for depositing the matrix metal, but also by the particle loading in suspension, the pH, the temperature, and the additives used. A variety of electrolytes have been used for the electrocodeposition process including simple metal sulfate or acidic metal sulfate baths to form a metal matrix of copper, iron, nickel, cobalt, or chromium, or their alloys. Deposition of a nickel matrix has also been conducted using a Watts bath which consists of nickel sulfate, nickel chloride and boric acid, and electrolyte baths based on nickel fluoborate or nickel sulfamate. Although many of the bath chemistries used provide high current efficiency, the effect of hydrogen evolution on electrocodeposition is not discussed in the literature. 

We speak of a direct conversion when there is an alteration of the chemical structure of the material in the wake of a reaction of decomposition of the original material, MX, in a composite electrode comprising nanoparticles of metal M° encapsulated in a LiX matrix. There is no formation of a lithiated metal alloy as before, but rather of metal particles which are inactive in comparison to lithium. The reaction leads to the formation of a metastable compound LiX (essentially Li20). In theory, this compound which is formed is not stable, but it is considered to be so because of its very slow rate of transformation. Many transition-metal oxides are involved oxides of cobalt CoO and C03O4, of copper CuO, of nickel NiO and of iron FeO and Fc203. Other compounds such as NiPs and FeS2 can also be considered. 

The term cemented carbides, also called hardmetals, refers to powder-composite materials consisting of carbide particles bonded with metals or alloys. Extensive treatments are given in [ 1.94,95]. The most common cemented carbide is WC bonded with Co. Cobalt is used as a binder since it wets the angular WC particles particularly well. Nickel is added to increase corrosion and oxidation resistance of the Co binder phase. The metals Ta, Nb, and Ti may be added to form a (W, Ta, Nb, or Ti) C solid solution carbide phase which is an additional microstructural constituent in the form of rounded particles in the so-called complex grade, multigrade, or steel-cutting grade cemented carbides. Table 3.1-90 lists representative materials. 

Metallic particles such as chromium can be introduced into a metal plating electrolyte (for example, nickel and cobalt), and the deposited composite can be subsequently heat treated to form high-temperature oxidation-resistant alloys. MCrAlY composites have been made by depositing 10 p,m CrAlY powder in a cobalt or nickel matrix. Heat treatment bonds... 

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