Nickel dendrites

One of the major problems with the MCFC is that the state-of-the-art nickel oxide cathode material shows a weak, but significant, solubility in molten carbonates [13, 95, 114-119]. Through dissolution, some Ni + ions are formed in the electrolyte and diffuse toward the anode, leading to precipitation of metallic nickel dendrites. This precipitation can cause internal short circuits with subsequent loss of power. It has been reported [13] that solubility is reduced if the more basic, carbonates are used in the electrolyte. The addition of some alkaline earth oxides (CaO, SrO, and BaO) to the electrolyte has also been found to be beneficial [13]. 

Miscellaneous. Electron beams can be used to decompose a gas such as silver chloride and simultaneously deposit silver metal. An older technique is the thermal decomposition of volatile and extremely toxic gases such as nickel carbonyl [13463-39-3] Ni(CO)4, to form dense deposits or dendritic coatings by modification of coating parameters. 

EDA and other alkylene amines react readily with acrylonitrile or acrylate esters. EDA reacts with acrylonitrile to give tetrakis(2-cyanoeth5i)-ethylenediamine which is reduced over Raney nickel to give tetralds(3-anainoprop5i)-ethyl-enediainine (52). With methyl acrylate and EDA under controlled conditions, a new class of starburst dendritic macromolecules forms (53,54). 

S, Albanesi C, Girolomoni G Human CD4+ T lymphocytes with remarkable regulatory functions on dendritic cells and nickel-specific Thl immune responses. J Invest Dermatol 2000 114 295-302. 

There are two broad classes of separators employed in nickel—zinc batteries a main separator, which exhibits resistance to dendrite penetration, and an interseparator, which principally acts as an electrolyte reservoir and wicking layer. Both main and interseparator should be resistant to chemical attack by the alkaline electrolyte and resistant to oxidative attack by nascent oxygen, permanently wettable by the electrolyte, flexible, heat sealable, tear resistant, and inexpensive. 

To address the zinc dendrite problem in nickel-zinc cells, eVionyx claims to have developed a proprietary membrane system that is nonporous, has very high ionic conductivity, is of low cost, and can block zinc dendrite penetration even in high concentrations of KOH. The polymeric membrane has an ionic species contained in a solution phase thereof. The ionic species behaves like a liquid electrolyte, while at the same time the polymer-based solid gel membrane provides a smooth impenetrable surface that allows the exchange of ions for both discharging and charging of the cell. 

Fig. 14. Dendritic dodeca-nickel catalyst, 47, for Kharasch reaction...

An early example of a dendritic catalyst was reported by Knapen et al. 24), who functionalized GO and G1 carbosilane dendrimers with up to 12 NCN pincer-nickel(II) groups (7a) and applied them as catalysts in the Kharasch addition of organic halides to alkenes (Scheme 3). 

Fig. 6.27 Nickel-loaded carbosilane dendrimers 1-3 of increasing generation number (GO—C2) and a corresponding non-dendritic reference substance 4...

Fig. 6.29 Dendritic carbosilane-nickel complexes with decreasing catalytic activity owing to mixed complex formation...

In this system, the catalyst G3-I9 showed a similar reaction rate and turnover number as observed with the parent unsupported NCN-pincer nickel complex under the same conditions. This result is in contrast to the earlier observations for periphery-functionalized Ni-containing carbosilane dendrimers (Fig. 4), which suffer from a negative dendritic effect during catalysis due to the proximity of the peripheral catalytic sites. In G3-I9, the catalytic active center is ensconced in the core of the dendrimer, thus preventing catalyst deactivation by the previous described radical homocoupling formation (Scheme 4). 

Although strictly not a dendritic system, Agar et al.[75] have reported the preparation of copper(n) phthalocyaninate substituted with eight 12-membered tetraaza macrocycles as well as its nickel(n), copper(n), cobalt(n), and zinc(n) complexes. Thus, the use of the l,4,7-tritosyl-l,4,7,10-tetraazacyclododecane offers a novel approach to the 1 — 3 branching pattern and a locus for metal ion encapsulation. 

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