Complex ferrites

Fig. 5. Complex magnetic permeabihty vs frequency for a series of ferrites used for power transformers and inductors at 25°C, S <0.1 mT (—) represents real parts ]l (-----------------------) show the imaginary parts ]l". The arrows indicate the frequencies where tan6 = fi/fi = 1 (57).

The magnetic properties of ferrites are intricately related to composition, microstmcture, and processing much more so than in the case of metals primarily because of the complex chemistry of the oxides and because of the ceramic processing requited to produce the finished parts. 

For maximum temperatures below 800°F, suitable ferritic steels are usually good selections. Above 800°F their loss of strength must be considered carefully and balanced against their lower thermal expansion. It should be recognized that if they are heated through the ferrite to austenite transformation temperature their behavior will become more complex and the results probably adverse. 

Irons of the compositions indicated above all have structures similar to that shown in Fig. 3.52, that is, a uniform dispersion of chromium-iron complex carbides in a matrix of chromium-containing ferrite. The chromium content of the ferrite is not known, although it is assumed to be about 10-13%. The... 

The high-chromium irons undoubtedly owe their corrosion-resistant properties to the development on the surface of the alloys of an impervious and highly tenacious film, probably consisting of a complex mixture of chromium and iron oxides. Since the chromium oxide will be derived from the chromium present in the matrix and not from that combined with the carbide, it follows that a stainless iron will be produced only when an adequate excess (probably not less than 12% of chromium over the amount required to form carbides is present. It is commonly held, and with some theoretical backing, that carbon combines with ten times its own weight of chromium to produce carbides. It has been said that an increase in the silicon content increases the corrosion resistance of the iron this result is probably achieved because the silicon refines the carbides and so aids the development of a more continuous oxide film over the metal surface. It seems likely that the addition of molybdenum has a similar effect, although it is possible that the molybdenum displaces some chromium from combination with the carbon and therefore increases the chromium content of the ferrite. 

The most extensively studied rate processes in this group are those which yield spinels [1] (ferrites, chromites, etc.), molybdates and tungstates, and complex iodides. These types are conveniently exemplified by the representative systems... 

The chemistry of waste treatment processes and the development of new processes are fertile areas of research work. The speciation of plutonium in basic and laundry wastes is needed. For example, if soluble plutonium complexes in basic wastes can be destroyed, perhaps ultrafiltration could replace the flocculent-carrier precipitation process. The chemistry of plutonium(VII) and of ferrites—a candidate waste treatment process—needs to be explored.(23)... 

Using a similar procedure, based on the thermal decomposition of a metal-surfactant complex followed by mild oxidation, we synthesized highly crystalline and monodisperse nanocrystals of cobalt ferrite (CoFc204), manganese ferrite (MnFe204) MnO, and Ni [5]. 

The thermal decomposition of iron complexes leading to the formation of different ferrites (MFe204, M = Fe, Co, Mn, etc.) is one of the most commonly used protocols to obtain magnetic NPs with control of size and shape [39]. However, some of them cannot be considered as green processes since the iron precursor, the Fe(CO)5 complex, is expensive, toxic, and flammable. Therefore, researchers have looked for non-toxic and less expensive iron precursors to be used in the thermal decomposition reactions. The first precursor in substitution of Fe(CO)5 was the FeCup3... 

Chemical reagents are primarily concerned with dielectric liquids or solids. For metal oxides such as ferrites, however, magnetic losses occur in the microwave region. As for a dielectric material, a complex magnetic permeability is defined as given by Eq. (16) ... 

Nickel dioxide, 77 107 Nickel double salts, 77 113 Nickel electrodes, 3 430 72 216 Nickel electroplating solutions, 9 818t Nickel extraction, 70 791 Nickel ferrite brown spinel, formula and DCMA number, 7 348t Nickel fibers, 77 108 Nickel fluoride complexes, 77 111 Nickel fluoride tetrahydrate, 77 109-110 Nickel fluoroborate, 77 111 Nickel fluoroborate hexahydrate, 4 157t, 158, 159... 

Validation of the database. This is the final part in producing an assessed database and must be undertaken systematically. There are certain critical features such as melting points which are well documented for complex industrial alloys. In steels, volume fractions of austenite and ferrite in duplex stainless steels are also well documented, as are 7 solvus temperatures (7 ) in Ni-based superalloys. These must be well matched and preferably some form of statistics for the accuracy of calculated results should be given. 

To understand the principle of operation of important non-reciprocal (see below) microwave devices, consider what occurs when a plane-polarized microwave is propagated through a ferrite in the direction of a saturating field Ht. The wave can be resolved into two components of equal amplitude but circularly polarized in opposite senses, i.e. into a right-polarized and a left-polarized component. These two components interact very differently with the material, leading to different complex relative permeabilities H r+ = n r+ - j/r" i and /r - = /T- — j/r"-, as shown in Fig. 9.40. Because of the... 

A soft ferrite with complex relative permeability fi T = 2000 — 7j is in the form of a toroid of cross-sectional area 0.5 cm2 and inner radius 3 cm. A primary winding... 

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