Nickel valence change

The nickel-based systems include the flowing systems nickel—iron (Ni/Fe), nickel—cadmium (NiCd), nickel—metal hydrides (NiMH), nickel—hydrogen (Ni/ H2), and nickel—zinc (Ni/Zn). All nickel systems are based on the use of a nickel oxide active material (undergoing one valence change from charge to discharge or vice versa). The electrodes can be pocket type, sintered type, fibrous type, foam type, pasted type, or plastic roll-bonded type. All systems use an alkaline electrolyte, KOH. 

Recent studies have involved some fluorinated monothio-jS-diketones with zinc and nickel (195) and palladium and platinum (196). Both nickel and zinc show valence change of the metal. 

An obvious refinement of the simple theory for cobalt and nickel and their alloys can be made which leads to a significant increase in the calculated value of the Curie temperature. The foregoing calculation for nickel, for example, is based upon the assumption that the uncoupled valence electrons spend equal amounts of time on the nickel atoms with / = 1 and the nickel atoms with J = 0. However, the stabilizing interaction of the spins of the valence electrons and the parallel atomic moments would cause an increase in the wave function for the valence electrons in the neighborhood of the atoms with / = 1 and the parallel orientation. This effect also produces a change in the shape of the curve of saturation magnetization as a function of temperature. The details of this refined theory will be published later. 

For metallic iron and nickel electrodes, the transpassive dissolution causes no change in the valence of metal ions during anodic transfer of metal ions across the film/solution interface (non-oxidative dissolution). However, there are some metals in which transpassive dissolution proceeds by an oxidative mode of film dissolution (Sefer to Sec. 9.2.). For example, in the case of chromium electrodes, on whidi the passive film is trivalent chromium oxide (CrgOj), the transpassive dissolution proceeds via soluble hexavalent chromate ions. This process can be... 

The ChemPete bioremediation technology works under buildings, roads, and other structures that would have to be demolished to apply many other technologies. The ChemPete technology can be used in conjunction with soil vapor extraction. Preliminary tests on bioremediation of nickel, in which the valence state is changed rendering it insoluble, have also been conducted. 

For cobalt and iron clusters a mechanism exists for changing the open valence shells to closed shells whereby the reactivity of the cluster is drastically decreased. This mechanism involves the change of an atom in the cluster from a d s to a d s state, which effectively increases the number of valence electrons. The reason this mechanism is effective on iron (in particular) and cobalt is that these atoms have a d s ground state. For nickel, which has a d s ground state, this mechanism will not be as effective. 

It has been demonstrated in earlier sections that the catalytic activity of nickel oxide in the room-temperature oxidation of carbon monoxide is related to the number and the nature of the lattice defects on the surface of the catalyst and that any modification of the surface structure influences the activity of the solid. Changes of catalytic activity resulting from the incorporation of altervalent ions in the lattice of nickel oxide may, therefore, be associated not only with the electronic structure of the semiconductor (principle of controlled valency ) (78) but perhaps also with the presence of impurities in the oxide surface or a modification of the surface structure because of this incorporation. In order to determine the influence of dopants on the lattice defects in the surface of the solid and on its catalytic activity, doped nickel oxides were prepared under vacuum at a low temperature (250°). Bulk doping is not achieved and, thence, one of the basic assumptions of the electronic theory of catalysis (79) is not fulfilled. 

The solid products distributions in SCS process for Ni, Cu and Co SCS systems are presented in Fig 4a, Fig 4b and Fig 4c respectively. In each case, at low cp values, fully oxidized metals are obtained (NiO, CuO and CoO) which gradually reduce to zero valence metals with increasing values. Nickel and Cobalt display only two oxidation states (Ni(0) and Ni(II) and Co(0) and Co(II)) and follow a similar reduction profile. Completely reduced Ni and Co phases can be obtained for tp > 1.25 and tp > 1.5 respectively. Copper on the other hand shows three different phases as the cp value is changed. For (p < 0.5 pure Cu(II) is obtained, while for 1.2 > > 0.5 a mixture of Cu(0), Cu(I) and Cu(II) is obtained and higher values of > 1.2 produce single phase Cu(0). As predicted in other pubhcations [5, 6] the SCS process appears to proceed by producing metal oxide first, and then subsequent reduction of metal oxide to pure metal in presence of higher fuel content. 

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