Iron continued transformation

The term channel induction furnace is appHed to those in which the energy for the process is produced in a channel of molten metal that forms the secondary circuit of an iron core transformer. The primary circuit consists of a copper cod which also encircles the core. This arrangement is quite similar to that used in a utdity transformer. Metal is heated within the loop by the passage of electric current and circulates to the hearth above to overcome the thermal losses of the furnace and provide power to melt additional metal as it is added. Figure 9 illustrates the simplest configuration of a single-channel induction melting furnace. Multiple inductors are also used for appHcations where additional power is required or increased rehabdity is necessary for continuous operation (11). 

Townes s academic life continued. He served as provost of MIT from 1961 to 1966. In 1964, Townes received the Nobel Prize in physics for work in quantum electronics leading to construction of oscillators and amplifiers based on the maser-laser principle. He was named university professor at the University of California-Berkeley in 1967. There he worked for more than 20 years in astrophysics. Ironically, this field is one of many that were transformed by die laser, and Townes often tised lasers in his subsequent research. 

The Industrial Revolution was made possible by iron in the form of steel, an alloy used for construction and transportation. Other d-block metals, both as the elements and in compounds, are transforming our present. Copper, for instance, is an essential component of some superconductors. Vanadium and platinum are used in the development of catalysts to reduce pollution and in the continuing effort to make hydrogen the fuel of our future. 

Figure 5.26. Iron binary alloys. Examples of the effects produced by the addition of different metals on the stability of the yFe (cF4-Cu type) field are shown. In the Fe-Ge and Fe-Cr systems the 7 field forms a closed loop surrounded by the a-j two-phase field and, around it, by the a field. Notice in the Fe-Cr diagram a minimum in the a-7 transformation temperature. The iron-rich region of the Fe-Ru diagram shows a different behaviour the 7 field is bounded by several, mutually intersecting, two (and three) phase equilibria. The Fe-Ir alloys are characterized, in certain temperature ranges, by the formation of a continuous fee solid solution between Ir and yFe. Compare with Fig. 5.27 where an indication is given of the effects produced by the different elements of the Periodic Table on the stability and extension of the yFe field.

This work was supported by "JUNTA DE ANDALUCIA" (Res. SEPT.88). One of us (M.G.G.) wishes to thank the Ministry of Education and Science of Spain for the award of a scholarship.Authors are very gratefull to Mr. F.J.Marchena (Universi ty of Sevilla,Spain) for the preparation of iron-doped titania catalysts. Fina lly, we are gratefull to Dr. Pierre Pichat (CNRS.Ecole Centrale de Lyon,France) for helpful discussions and continuing collaboration on this and related photo catalytic transformations. 

However, spectroscopic studies of activated BLM indicate that it is not an Fev=0 species. It exhibits an S - 1/2 EPR spectrum with g values at 2.26, 2.17, and 1.94 [15], which is typical of a low-spin Fe111 center. This low-spin Fem designation is corroborated by Mossbauer and x-ray absorption spectroscopy [16,19], Furthermore, EXAFS studies on activated BLM show no evidence for a short Fe—0 distance, which would be expected for an iron-oxo moiety [19], These spectroscopic results suggest that activated BLM is a low-spin iron(III) peroxide complex, so the two oxidizing equivalents needed for the oxidation chemistry would be localized on the dioxygen moiety, instead of on the metal center. This Fe(III)BLM—OOH formulation has been recently confirmed by electrospray ionization mass spectrometry [20] and is supported by the characterization of related synthetic low-spin iron(III) peroxide species, e.g., [Fe(pma)02]+ [21] and [Fe(N4py)OOH]2+ [22], The question then arises whether the peroxide intermediate is itself the oxidant in these reactions or the precursor to a short-lived iron-oxo species that effects the cytochrome P-450-like transformations. This remains an open question and the subject of continuing interest. 

Fig. 5. Young s modulus versus temperature in iron. Notice the continuous decrease as a function of temperature. The abrupt change in modulus when bcc iron transforms to fee.

The unique versatility of ruthenium as an oxidation catalyst continues to provide a stimulus for research on a variety of oxidative transformations. Its juxtaposition in the periodic table and close similarity to the biological redox elements, iron and manganese, coupled with the accessibility of various high-valent oxo species by reaction of lower-valent complexes with dioxygen make ruthenium an ideal candidate for suprabiotic catalysis. 

Figure 3. Mossbauer spectrum of the iron sulfide obtained from the high-tempera-ture transformation of Fe7S8. Continuous line is the least-square fit to the spectrum.

On the basis of these in vitro observations, it seems probable that the immature bacterial crystals develop through phase transformation processes involving a solution interface between the crystalline and amorphous phases. Initially, the amorphous phase is the kinetically favored product resulting from iron(II) oxidation. Continual flux of iron(II) across the magnetosome membrane will result either in additional ferric oxide formation or reaction of iron(II) with the preexisting iron(III) phase to give magnetite within the vesicle. The second pathway becomes competitive with a continual increase in iron(II) influx. 

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