Nickel-copper alloys preparation

Thus nickel and nickel-copper alloy films evaporated in vacuo onto the inner walls of the reaction vessel have been chosen for further investigations. The films were deposited onto the inner wall of a glass tube kept at 450°C their thickness amounted to approximately 2000 A. After annealing at the same temperature in vacuo they were transferred into the side-arm of the Smith-Linnett apparatus in order for the recombination coefficients to be determined. The bulk homogeneity of alloy films prepared in this way was confirmed by X-ray diffraction (65, 65a, 66). 

Each alloy catalyst was prepared by a coprecipitation method in which ammonium bicarbonate was added to an aqueous solution of nickel and copper nitrates. The resulting precipitate was dried and heated in air at 370°C to form a mixture of nickel and copper oxides. The mixed oxides were then reduced in hydrogen in several stages over a range of temperatures to produce the nickel-copper alloy. The reduction was completed at 400°C. 

The nickel-copper alloys discussed in the previous chapter were prepared under conditions of complete miscibility of the two components. In our exploratory studies on the chemisorption and catalytic properties of other bimetallic systems comprising a Group VIII and a Group IB metal, an interesting discovery was made Systems which exhibit evidence of marked interaction between the components are not limited to combinations of metallic elements that form bulk alloys (1-5). 

The phase rule is a mathematical expression that describes the behavior of chemical systems in equilibrium. A chemical system is any combination of chemical substances. The substances exist as gas, liquid, or solid phases. The phase rule applies only to systems, called heterogeneous systems, in which two or more distinct phases are in equilibrium. A system cannot contain more than one gas phase, but can contain any number of liquid and solid phases. An alloy of copper and nickel, for example, contains two solid phases. The rule makes possible the simple correlation of very large quantities of physical data and limited prediction of the behavior of chemical systems. It is used particularly in alloy preparation, in chemical engineering, and in geology. 

Surfaces of finely divided nickel also promote the formation of aniline. A practical route to tlie preparation of electrodes coaled with a finely divided metal involves electroplating nickel onto a cathode from a solution containing a suspension of finely divided Raney nickel (Ni 50% A1 50%) or Devarda copper alloy (Cu 50% A1 45% Zn 5%), Some alloy particles stick to the cathode surface which is then activated by leaching out the aluminium using hot aqueous sodium hydroxide... 

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. 

One form of nickel is an important catalyst known as Raney nickel that is prepared by the reduction of NiO with hydrogen. Nickel also is used in several alloys that have wide application. For example, Monel is a type of alloy that contains nickel and copper in a ratio of about 2 1. It is frequently used in making bathroom fixtures. 

Copper salt-amine complexes can also be used for the reduction of aromatic compounds to the corresponding amine.A more general and convenient method for reducing nitroso compounds to amines involves the use of a nickel/aluminum alloy. The low cost and ready commercial availability of nickel/aluminum alloy are important features of this reduction procedure which may find wide acceptance as a preparative method. 

Raney copper is prepared from the commercially available copper aluminum alloy. It does not have much to offer the synthetic chemist as only a few reactions are reported to be affected by this catalyst. Raney copper, as well as Raney cobalt, generally produces fewer side reactions than Raney nickel even though they usually require higher reaction temperatures for the same reaction. Raney copper is, however, quite usefiil for the selective hydrogenation of substituted dinitro benzenes (Eqn. 8.6) with its activity apparently increasing with continued reuse. Raney copper can also be used for the catalytic hydrolysis of hindered nitriles to the amides (Eqn. 12.13). "2... 

Before data are considered on rates of reactions occurring on the alloys, information is presented on the properties of the nickel-copper catalysts themselves. The lattice constants of the alloys were determined as a function of the composition by means of X-ray diffraction, as shown in Figure 2.5. Data on a number of metallurgical preparations taken from the work of Coles... 

The crystal structures of metallic ruthenium and copper are different, ruthenium having a hexagonal close-packed structure and copper a face-centered cubic structure (7). Although the ruthenium-copper system can hardly be considered one which forms alloys, bimetallic ruthenium-copper aggregates can be prepared that are similar in their catalytic behavior to alloys such as nickel-copper (3,4,8). 

Mr. Raney continued to research on his catalyst from the time it was discovered until he died. He was granted a total of six U. S. Patents and five foreign patents. In addition to the two basic patents that issued prior to 1930, he obtained a patent for the preparation of granular catalysts made from aluminum and silicon alloys containing metals such as iron, cobalt, copper and nickel (15), a method for reclaiming spent catalyst (16), the production of a nonpyrophoric catalyst (17) and a catalyst prepared from a mixture of nickel and a nickel-aluminum alloy (18). A list of his inventions is given in Table 1. Over the... 

Ziewiec et al. [24] reported on the preparation, thermal stability and glass-forming ability of copper-nickel-phosphorus alloys. They found that, depending on the composition, melt spinning may result in either amorphous or partially crystalline systems, whose thermal behaviour was characterized by DSC, DTA, andXRD. 

Meites (174) has used controlled-potential reduction of nickel for the purification of electrolytes and the precise determination of nickel in the 10 to 10 per cent range (177). Ultra-pure nickel compounds have been prepared by Lingane and Page (172) using this technique. Applications of controlled-potential coulometry to the determination of nickel in plutonium solutions and copper alloys have been reported by Bergstresser (178) and Tanaka (173), respectively. 

Nickel-copper particles were prepared by Maskos and van Hooff [229] by reduction of Y zeolite co-exchanged with Ni and Cu cations and characterized by ferromagnetic resonance. Formation of alloys was detected, but the bimetallic particles were large and located on the external surface. 

Fluorine cannot be prepared directly by chemical methods. It is prepared in the laboratory and on an industrial scale by electrolysis. Two methods are employed (a) using fused potassium hydrogen-fluoride, KHFj, ill a cell heated electrically to 520-570 K or (b) using fused electrolyte, of composition KF HF = 1 2, in a cell at 340-370 K which can be electrically or steam heated. Moissan, who first isolated fluorine in 1886, used a method very similar to (b) and it is this process which is commonly used in the laboratory and on an industrial scale today. There have been many cell designs but the cell is usually made from steel, or a copper-nickel alloy ( Monel metal). Steel or copper cathodes and specially made amorphous carbon anodes (to minimise attack by fluorine) are used. Hydrogen is formed at the cathode and fluorine at the anode, and the hydrogen fluoride content of the fused electrolyte is maintained by passing in... 

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