Goethite electron micrographs

Fig. 3.4 Electron micrographs of goethites with Al substitution increasing from 0 to 0.167 mol mol" (produced from 2-line ferri-hydrite in alkaline solution at 70°C.

Fig. 4.5 High resolution electron micrograph of synthetic goethite crystals cut perpendicular to the needle axis [010]. The crystals are bounded by 101 faces. The large crystal contains faults and some of the smaller, fault-free crystals show ca. 1 nm lattice fringes corresponding to the c -parameter of the unit cell (0.9956 nm) (Schwertmann, 1984, with permission, courtesy H. Vali, Schwertmann Cornell, 2000, with permission).

Fig. 4.6 High resolution electron micrograph of natural goethite a) Diamond-shaped cross sections of domains running along [010] and bounded by 101 faces. Lattice fringes correspond to the c -parameter. b) Higher magnification shows the a fringes (ca. 1 nm) and structural distortions. (Smith Eggleton, 1983 with permission courtesy R.A. Eggleton).

Fig. 4.8 High resolution electron micrograph of two goethite domains and their interdomai-nic zone. The lattice fringes at 0.5 nm correspond to the (200) spacing (courtesy S. Mann, Bristol).

Fig. 4.n Replica (upper) and scanning force electron micrograph (lower) of goethite grown epitaxically on hematite cores ( upper see Cornell, 1985 lower Barron et al. 1997,with permission). 

Fig. 14.3 High resolution electron micrographs of the thermal transformation of goethite to hematite showing (Gt[001]//[Hm[210] orientation. Upper Gradual development (a d) of slit pores along Hm[001]. Lower Largely transformed region along the (Gt[001]//[Hm[210] orientation. Electron diffraction patterns in the in-...

Fig. 16.2 Scanning electron micrograph of an association between goethite (go) and hematite (he) in laterite from Cameroon (Muller, 1987 courtesy).P. Muller with permission).

As lepidocrocite is metastable relative to goethite, it can be expected that lepidocrocite may transform into goethite. As demonstrated in the laboratory, this transformation proceeds via solution (see Chap. 14). Electron micrographs from a redoxi-morphic soil in Australia indicate that the same process seems to occur in soils (Fig. 16.5). The lepidocrocite crystals show dissolution features and there are small, acicu-lar, goethite crystals in their neighbourhood. Feroxyhyte was reported in two allopha-... 

Fig. 16.5 Electron micrographs of an association of lepidocrocite (Lp) with goethite (Gt) from a redoximorphic soil, Natal, South Africa (courtesy P. Self).

Fig. 16.7 Electron micrographs of soil goethites. a) Acicular crystals from an Oxisol on peridotite. New Caledonia (Schwertmann, Latham, 1986 with permission), b) Starlike crystals from a redoximorphic paddy soil, China, c) Irregular crystals from an Ultisol on basalt, South Brazil (see also Schwertmann, Kampf,...

Fig. 16.19 Electron micrographs of natural associations between iron oxides and other soil minerals, a) Goethite (Co) crystals epitaxially grown on kaolinite (K) flakes (TEM) from a late-rite in Cameroon (courtesy J.P. Muller see also Boudeulle, Muller, 1988). b) Association of kaolinite (k), goethite (go) and hematite (he) in an Oxisol, Cameroon (SEM) (1987 courtesy J.P. Muller see Muller, Bocquier, 1986). c) Goethite accumulation between kaolinite...

Fig. 17.1 Electron micrograph of the cusp tip of a limpet tooth showing the alignment of acicu-lar goethite parallel to the tooth posterior edge and the changing orientation within the central region (courtesy S. Mann).

Fig. 18.5 Scanning electron micrograph of a tubercle from a corroded water pipe showing large hexagonal plates or prisms of green rust and small Fe " oxide crystals, probably lepidocrocite and goethite formed from oxidation of green rust (Bigham and Tuovinen, 1985, with permission, courtesy J. M. Bigham).

Fig. 22. (A) Transmission electron micrograph showing phosphatidylcholine vesicles containing intravesicular Fe(III) ions at pH 2.0. Bar = 75 nm. (B) Electron micrograph showing discrete intravesicular precipitates 30 min after the addition of NaOH to FedID-containing vesicles. The particles were identified as poorly ordered goethite (a-FeOOH) by electron diffraction. Bar = 30 nm.

Fig. 5-1. Electron micrographs of Al-substituted acicular goethites illustrating the decrease in crystal size with increasing degree of Al-substitution (given as Al/(AI+Fe) moEmoI). The goethites were produced by aging 2-Iine Al-contain-ing-ferrihydrites in 0.35-0.4 M KOH for 14 days at 70 °C (Cornell and Schwert-marm 1996 with permission)..

Fig. 5-2. Electron micrographs of pure and Al-substituted goethites grown in strongly alkaline conditions at 70 °C (a, b) or 25 C (c, d). a no substitution b 7.9 mol% substitution c no substitution d 11.6 mol% substitution. Bar = 100 nm (see also Schulze and Schwertmann, 1984).

This method produces ca. 9 g goethite with a surface area of ca. 20 m / g. The crystals are acicular and consist of several domains along the needle (a-)axis. An electron micrograph is shown in Fig. 5-2 a, an X-ray diffractogram in Fig. 5-6 and an IR spectrum in Fig. 5-7. The crystals are bounded mainly by 101 faces (Fig. 5-3). 

Fig. 5-10. Electron micrographs of goethites with and without A1 substitution produced from Fe systems. For explanation see Fig. 5-9.

Fig. 5-15. Electron micrograph replica of acicular goethite outgrowths on a hematite eore. The crystals grew from ferrihydrite at pH 11.7 and 70 °C in the presence of 10 M maltose in 24 h. Bar =100 nm. (see Cornell, 1985).

Fig. 15-1. Scanning electron micrographs of goethite- (upper) and hematite-eoated (lower) cristobalite produced at pH 2.5. The amounts of iron oxide at-taehed are 14.4 (goethite) and ca. 1 mg (hematite) per g cristobalite sand. (Courtesy A. Scheidegger). (From Scheidegger et al., 1993 with permission.)...

Oxidation ofthe Product of Reaction Between FeSO and NHfiH Properties Goethite, detailed chemical analysis and electron micrograph available, BET specific surface area 24 rn7g [547,1117],... 

Figure 5. Electron micrograph taken after 298 days aging of Run 5, showing lath-like lepidocrocite crystals and smaller needle-like goethite crystals...

Figure 7. Electron micrograph taken after 302 days9 aging at Run 4, showing compact crystalline intergrowth of goethite and lepidocrocite...

The left side of Figure 5 shows a scaniting electron micrograph of iron oxide deposited on sulfonated polystyrene the right side of the figure shows a transmission electron micrograph of the film in cross section. The minei was identified as goethite... 

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