Nickel fibres

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. 

The liquid lithium anode is held in a stainless steel case or nickel fibre pleated wick, and chlorine gas is fed under pressure from external storage... 

Rosenow MWK, Long nickel fibres for EMI shielding, ETP 99 World Congress Engineering Thermoplastics, Zurich, Jun 7-9, 1999. 

Figure 3.22 The effect of orientation on the pull-out force and work generated by the bending across the crack of a ductile nickel fibre in a brittle polyester matrix (after Morton and Groves [53]).

As Fig. 20.7 shows, if DS eutectics ( DSEs ) prove successful, they will allow the metal temperature to be increased by =100°C above conventional DS nickel alloys, and the inlet temperature by =200°C (because of a temperature scaling effect caused by the blade cooling). Further improvements in alloy design are under way in which existing nickel alloys and DS eutectics are being blended to give a fibre-reinforced structure with precipitates in the matrix. 

The use of quenching agents in polymers is a recent development. Of particular interest are the nickel(II) chelates in polypropylene film and fibre and the even newer hindered amines which appear to combine the roles of antioxidant cmd quenching agent. 

To improve the resistance to ultraviolet light carbon black is often useful as a light screen. Its use in fibres and films is clearly very restricted and in these instances ultraviolet absorbers and/or quenching agents are used. Recent developments include the greater use of hindered amine and nickel compounds. 

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. 

Iron-nickel oxide cells are always vented. Tubular/pocket plate electrodes are constructed as described above and are generally housed in nickel-plated steel cases. Cells with sintered plate electrodes have smaller inter-electrode spacings. They use synthetic fibre fabrics as separators, and plastic containers. 

Batteries based on the iron-nickel oxide system are now being developed for electric vehicle applications. These use fibre-plaque electrodes, as described above for the nickel-cadmium system, and incorporate electrolyte circulation systems to permit removal of gases evolved during charge... 

The most important azo compounds employed in the manufacture of dyes of this type are those containing the < ,o -dihydroxyazo-, the o-hydroxy-o -carboxyazo- and the o-hydroxy-o -amino-diarylazo systems. It is well established3 33-0 that these form four-coordinate copper and nickel complexes (35) in which the coordination sphere of the metal can be completed by a variety of neutral ligands. In both cases the light-fastness of the parent azo compound is improved as a result of complex formation but the nickel complexes are insufficiently stable towards acid to be of commercial interest as dyestuffs. The history of copper complexes has already been discussed (Section 58.1) and will not be considered further here, although it is worthy of mention that currently the most important copper complex dyestuffs are those containing fibre-reactive systems, e.g. (36), for application on cellulosic fibres. 

Interestingly, complexes of the type (189) were prepared by the interaction of o-aminophenols and arylazomalondialdehydes in the presence of copper(II) or nickel(II) salts. Replacement of the o-aminophenol by an acyl hydrazide resulted in the formation of complexes of the type (190), which are reported134 to be suitable for dyeing synthetic fibres. 

Table 7 7.7 Nickel absorption and reduction by sodium dithionite and rongalite for different types of fibres and their electroconductive capacity...

The results of this analysis are shown in Table 11.1. It is clear that absorption of nickel in all fibres is reasonably high, but the amount of metallic nickel is considerably higher in PAN fibres and, to a lesser extent, in natural silk. This indicates that the structure of the fibres (pore size and permeability as well as functional groups) plays an important role. Sodium dithionite and rongalite are known as good reducing agents, but their stability is fairly limited. One of their decomposition products (particularly in acidic solutions) is sulphide, which explains why an important fraction of... 

Table 11.2 Nickel and cobalt absorption capacity and their diffusion coefficient as a function of precipitation-bath parameters during PAN-fibre production...

Table 11.9 Relative variations of amount of nickel and specific electrical resistance in individually cut PAN-fibre pieces obtained through chemical metallisation and galvanisation...

The program, AXIS, was specifically designed to analyse fibre diffraction patterns similar to that shown in Figure 1, although some of the methods described in this chapter may be extended to other types of pattern if required. The fibre patterns are recorded on flat film using pinhole collimated, nickel-filtered CuKor radiation, and finely powdered calcite is dusted onto the specimen to provide a calibration ring of spacing 0.3035 nm. 

The solution of the gem-dihalide and the olefin in DMF CH2C12 (v/v = 1 9) containing Bu4NX (X = I, Br) was electrolysed at 40°C with a zinc anode and a carbon fibre or a nickel foam cathode. The method compares favourably with the usual route involving CH2I2 and Cu/Zn. 

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