Cathodes iron materials

For the cathode seal material, there is a criterion that the thermal expansion coefficient of the metal component must be lower than that of the a-alumina header. A nickel-cobalt-iron alloy (NiloK) with a... 

Cathode Iron is a very cheap cathode material with a relatively low hydrogen overvoltage (e.g. [25]). It is of interest for industrial applications. In order to avoid corrosion during interruption of the current, stainless steel may be suitable, especially in laboratory cells where the increased electrical resistance and hydrogen overvoltage are irrelevant. 

Nickel-cadmium (Ni-Cd) batteries were invented in 1899 by Jungner. They use nickel hydroxide as cathode active material, cadmium and iron as anode, and an aqueous solution of potassium hydroxide as electrolyte. Materials such as polystyrene, nonwoven nylon, and cellulose are used as... 

Fig. 9.5 Theoretical capacities of various iron-based cathode active materials...

LiCo02 and LiNi02 have been used as a cathode active material for Li-ion battery (LIB) of mobile phone, personal computer, and so on. LiFeP04 of olivine type has attracted much interest as a new cathode active material for LIB. LiFeP04 of olivine type has an outstanding characteristic feature that it is rare-earth free, less toxic, and highly abundant on the Earth [8,9] the abundance of iron on the Earth amounts to 50,000 ppm (5%). 

Mossbauer spectra (Fig. 27.1) of LIB (coin cell type) in which FeP04 was used as a cathode active material showed a quantitative reduction of iron from Fe " to Fe" after full discharge, while a reverse oxidation from Fe" to Fe " was... 

Recently, an iron oxide, having a high valence state, has been reported for use as a cathode active material. " Iron normally exists as a metal or in the valence states of Fe(II) and Fe(III). The new cathode material is an Fe(VI)-containing compound which has a high specific capacity due to a 3-electron change in its reduction reaction, as follows ... 

G. Cheruvally, Lithium Iron Phosphate A Promising Cathode-Active Material for Lithium Secondary Batteries, Trans Tech Publications Inc., Switzerland [2008). 

The cell for this process is unlike the cell for the electrolysis of aluminum which is made of carbon and also acts as the cathode. The cell for the fused-salt electrolysis is made of high temperature refractory oxide material because molten manganese readily dissolves carbon. The anode, like that for aluminum, is made of carbon. Cathode contact is made by water-cooled iron bars that are buried in the wall near the hearth of the refractory oxide cell. 

It is not certain whether Sir Humphrey Davy (Fig. 1-7) knew of these considerations. He accepted a commission from the Admiralty for the protection of copper-clad wooden ships, which had been introduced in 1761. During his numerous laboratory experiments, he discovered the cathodic protection of copper by zinc or iron [3]. Davy had already put forward the hypothesis in 1812 that chemical and electrical changes are identical or at least arise from the same material property. He believed that chemical reaction forces could be reduced or increased by altering the electric state of the material. Materials can combine only if they have different electric charges. If an originally positive material can be artificially negatively... 

The cathodic protection of plain carbon and low-alloy steels can be achieved with galvanic anodes of zinc, aluminum or magnesium. For materials with relatively more positive protection potentials (e.g., stainless steels, copper, nickel or tin alloys), galvanic anodes of iron or of activated lead can be used. 

Wrapped nanocrystals. Metal crystallites covered with well-developed graphitic layers are found in soot-like material deposited on the outer surface of a cathode slag. Figure 6 shows a TEM picture of an a(bcc)-Fe particle grown in the cathode soot. Generally, iron crystallites in the tv-Fe phase are faceted. The outer shell is uniform in thickness, and it usually con-... 

As is well known, high-purity zinc corrodes much less rapidly in dilute acids than commercial purity material in the latter instance, impurities (particularly copper and iron) are exposed on the surface of the zinc to give local cathodes with low hydrogen overpotentials this result is of practical significance only in the use of zinc for sacrificial anodes in cathodic protection or for anodes in dry cells. In neutral environments, where the cathodic... 

---