Ferrite reds

Ferrite grain size, 23 294 Ferrite precipitates, 23 275 Ferrite reds, 19 399 Ferrites, 5 583-584 11 55-91 14 543 ... 

Dehydroxylation of goethite produces the ferrite reds - extremely colour fast and pure hematite. With low temperature calcination the acicular shape of the goethite precursor is retained, whereas high temperatures lead to a sintered product. 

Fuller (1973a) describes a number of processes that result in synthetic iron oxides and hydroxides. For red iron oxides he details calcination of iron(II) sulfate hydrate (copperas reds), calcination of synthetic yellow iron oxides (ferrite reds), aqueous precipitation from iron(III) hydroxide nucleation in solutions of iron(II) salts and calcination of magnetite at about 370°C. For... 

Unfortunately considerably less is known about MMCT in other solids. This does not mean that it is not of importance. Consider for example, the ferrites. Those with only Fe(III) are brown-red colored like Fe203, LiFcgOg, MgFe204. However, MnFe204, CoFe204 and NiFe204 are black. This is undoubtedly due to a MMCT transition of the type M(II) + Fe(III) M(III) -1- Fe(II) in the near infrared. 

Accurate production figures for natural and synthetic iron oxide pigments are difficult to obtain, because statistics also include nonpigmentary oxides (e.g., red mud from bauxite treatment, intermediate products used in ferrite production). World production of synthetic iron oxides in 1995 was estimated to be 600000 t ... 

An increasing number of colored inorganic pigments are FDA-compliant. Historically, yellow iron oxide, red iron oxide, black iron oxide, zinc ferrite, burnt umber, raw and burnt sienna, channel carbon black, chromium oxide green, ultramarine blue, cobalt blue and copper chrome black have enjoyed FDA—compliant status, under 21 CFR 178.3297, Colorants for Polymers . More recently, the FDA has been successfully petitioned with regard to nickel titanium yellow, chrome titanium yellow, and cobalt green under 21 CFR 170.39, Threshold of Regulation for Substances Used in Food-Contact Articles . 

Fig. 4.2 shows a polished and etched section of a production clinker. Crystals of alite and belite are embedded in a matrix of aluminate and ferrite phases. If HF vapour is properly used, the alite is yellowish brown, the belite is blue or red, and the aluminate is grey the ferrite, which is unattacked, is... 

Plumbo-ferrite, (Pb, Fe, Cu) 0.Fc203, occurs in Sweden and elsewhere as hexagonal plates, in appearance like molybdenite, but yielding a pale red streak.2... 

Calcium ferrite, Ca(Fe02)2, is formed as deep red or nearly black crystals 2 by heating together ferric oxide and calcium oxide. 

Zinc ferrite, Zn(Fe02)2 or Zn0.Fe203, occurs in nature as frank-linite (see p. 14) and may be artificially prepared in the laboratory in a variety of ways,5 such as by fusing an intimate mixture of the sulphates of sodium, zinc, and ferric iron at cherry-red heat, and extracting the melt with boiling water. Any basic zinc sulphate is removed with dilute acetic acid. Crystalline zinc ferrite also results when zinc chloride is heated in moist air with ferric chloride or haematite. The zinc chloride may be replaced by the corresponding fluoride.6... 

SYNS FERROUS ferrite IRON OXIDE IRON OXIDE RED 130B IRON SPONGE, spent obtained from coal gas purification (DOT) MIO 40GN SIFERRIT... 

Iron oxides (synthetic), red-maroon Zinc ferrite tan... 

Ferrosoferric oxide. See Iron oxide black Ferric oxide Ferrous ferrite. See Iron oxide red Ferrous phosphide. See Di-iron phosphide Ferrous sulfate. See Ferrous sulfate heptahydrate... 

Synonyms Burnt sienna Cl 77491 Copperas red Ferrous ferrite Gulf red Indian red Iron mass, spent Iron oxide Iron oxide, spent Iron sponge, spent Pigment red 101 Pigment red 102 Red haematite Red iron oxide Red oxide Turkey red Definition Sienna, siderite, Persian red, Spanish red, and red ochre are natural iron oxide ores used as red pigments Empirical FejOj... 

Photograph 7-70 Strongly pleochroic red ferrite in clinker containing partially consumed chrome-magnesia refractory brick (not shown). Belite with abundant exsolved impurities. Belite crystals in other parts of this clinker nodule are pale green. (S A6688)... 

Photograph 7-94 Isotropic glass matrix (arrows) in clinker formed at near-melting temperature. Belite shows prominent lamellar extensions ferrite is red and strongly pleochroic. Numerous exsolved dots in belite. (S A6712)... 

Figure 15.1 shows the Nio.5Zno.5Fe204 ferrite structure with octahedral sites in red and tetrahedral sites in dark yellow. This ferrite is formed by a solid solution of Ni203 (nickel oxide), ZnO (zinc oxide) and iron oxide (Fe203) in haematite form (a-Fc203), where this last oxide contains about 70% by weight of ferrite composition. 

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