Manganese oxide scale

Figure 6.7 reveals no new products at the Crofer22APU/SACNZn glass-ceramic interface indicating no reaction between the chromium—manganese oxide scale and... 

Since Mn is both soluble in iron oxides and mobile to the same extent as Fe, the addition of Mn to steels has little effect on the overall scaling rate in air or oxygen. Jackson and Wallwork have shown that between 20% and 40% manganese must be added to steel before the iron oxides are replaced by manganese oxides. However, Mn supresses breakaway oxidation in CO/CO2 possibly by reducing the coalescence of pores in the oxide scale. 

Fig. 6. Thin section of Leptothrix sp. which is precipitating manganese oxide on its outermost structure called a sheath (McLean et al. 2002). The arrows point to the manganese mineral phase identified by EDS. Scale bar = 150 nm. 

NMR time scale (ca. 10 s), the lithium spins see an average manganese oxidation state of 3.5 (i.e., Mn 5+ ions), and thus there is only one magnetically inequivalent lithium site (the 8a site). The NMR spectra are clearly sensitive to this hopping mechanism, and NMR spectroscopy may be used to follow the partial charge-ordering process that occurs just below room temperature in the stoichiometric material. 

Coarse (dP = 50-100 pm) porous disks are the most frequently applied diffusers in large-scale drinking water treatment systems (Masschelein, 1994). They are seldom used in industrial waste water treatment applications. The reason is that blocking or clogging can easily occur, e. g. by means of precipitation of chemicals, like carbonates, aluminum or ferrous oxides, manganese oxides, calcium oxalate or organic polymers. This is also valid for ceramic filter tubes, which are sometimes used as mass transfer systems in drinking water applications. 

In other cases, the oxidation reaction may not be asymmetric, but stereogenic centers within the substrate are preserved in the product allowing for an asymmetric reaction. An example of this type of reaction is provided by ozonolysis, which is discussed in Chapter 11. The use of ozone also overcomes one of the major problems that has been associated with oxidations at scale—the use of toxic, heavy metals their separation from the reaction product and waste disposal. However, there are still some useful reactions that use metals without chiral ligands and provide stereodifferentiation. An example is provided by the manganese oxide oxidation of ferrocenyl amino alcohols (Scheme 9.2).14... 

Early antisealants used sodium hexametaphosphate (SHMP) as a threshold agent to inhibit the growth of calcium carbonate and sulfate-based scales.6 Most antisealants on the market today contain sulfonate, phosphate, or carboxylic acid functional groups. Perhaps the most effective antisealants today contain and blend of polyacrylic acid (PAA) and phosphoric acid or polyacrylate and a hydroyethylidene diphosphonate (HEDP).12 The polyacrylate-HEDP blends also claim to have good dispersion qualities toward silts and clays.12 Some new inhibitors include a chelant and disper-ant to keep suspended solids such as iron and manganese oxides in solution. These newer antisealants are generally more effective than SHMP for a variety of potential scales.6... 

A more long term goal is to explore the use of OMS and OL systems for other selective oxidations. Conventional manganese oxide reagents are typically used as oxidizing agents for stoichiometric oxidations on a laboratory scale. 51 Specific examples include oxidation of primary and secondary alcohols,10 transformation of vitamin A to retinene, l02 overoxidation of aldehydes to acids and esters, 03 etc. Radical intermediates and specific stereochemistries are important in these systems. We expect that these reactions can be carried out catalyticaiiy using our OMS and OL materials. 

JW Harvey, CC FuUer. Effect of enhanced manganese oxidation in the hyporheic zone on basin-scale geochemical mass balance. Water Res Res 34 623-636,... 

When alloyed with small percentages of certain metals (e.g., aluminum, beryllium, iron, silicon, manganese, tin, titanium, and zinc), copper oxidizes with precipitation of oxide particles within the body of the metal as well as forming an outer oxide scale. Oxidation within the metal is called subscale formation or internal oxidation. Similar behavior is found for many silver alloys, but without formation of an outer scale. Internal oxidation is not observed, in general, with cadmium-, lead-, tin-, or zinc-based alloys. A few exceptions have been noted, such as for alloys of sodium-lead, aluminum-tin, and magnesium-tin [44]. Internal oxidation is usually not pronounced for any of the iron alloys. 

Shin, Y. and Manthiram, A. (2004). Factors Influencing the Capacity Fade of Spinel Lithium Manganese Oxides,. Electrochem. Soc., Vol.151, (2), pp. A204-A208 Tanaka, T. Ohta, K. and Arai, N. (2001). Year 2000 R D Status Of Large Scale Lithiinn Ion Secondary Batteries In the National Project Of Japan, /. of Power Sources, Vol.97-98,... 

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