Iron-oxide particle

Figure Bl.17.8. Iron oxide particles coated with 4 nm of Pt in an m-planar magnetron sputter coater (Hennann and Mtiller 1991). Micrographs were taken in a Hitachi S-900 in-lens field emission SEM at 30,000 primary magnification and an acceleration voltage of 30 kV. Image width is 2163 nm.

Wet preparation of red iron oxides can involve either a hydrothermal process (see Hydrothermal processing) or a direct precipitation and growth of iron oxide particles on specially prepared nucleating seeds of Fe202- In the hydrothermal process, iron(II) salt is chemically oxidized to iron(III) salt, which is further treated by alkahes to precipitate a hydrated iron(III) oxide gel. The gel can be dehydrated to anhydrous hematite under pressure at a temperature around 150°C. 

As shown in Figure 2, adsorption of dispersants on particle surfaces can increase 2eta potential further, enhancing electrostatic repulsion. Increased repulsion between particles is evidenced by lower viscosity in concentrated slurries, or decreased settling rates in dilute suspensions. The effect of added dispersants on settling of (anhydrous) iron oxide particles is shown in Figure 3. 

Co304 with an excess of n-butyl lithium results in further lithiation of the oxide particles, but with a concomitant extrusion of very finely divided transition metal from the rock salt structure. Highly lithiated iron oxide particles are pyrophoric if exposed to air [100]. 

As with the basic pretreatment of MU water for smaller boiler plants applications, various sieves, screens, cyclones, and strainers may sometimes be used for filtering condensate, essentially to remove iron oxide particles. Also bag, cartridge, and candle filters (with or without a filter aid) are employed (see section 9.2.4.4). 

The effect of oxidation pretreatment and oxidative reaction on the graphitic structure of all CNF or CNF based catalysts has been studied by XRD and HRTEM. From the diffraction patterns as shown in Fig. 2(a), it can be observed the subsequent treatment do not affect the integrity of graphite-like structure. TEM examination on the tested K(0.5)-Fe(5)/CNF catalysts as presented in Fig.2(b), also indicates that the graphitic structure of CNF is still intact. The XRD and TEM results are in agreement with TGA profiles of fi-esh and tested catalyst there is no obviously different stability in the carbon dioxide atmosphere (profiles are not shown). Moreover, TEM image as shown in Fig. 2(b) indicates that the iron oxide particle deposited on the surface of carbon nanofibcr are mostly less than less than 10 nm. 

Interestingly, free nano-iron oxide particles are active catalysts for the selective oxidation of alcohols to yield the corresponding aldehydes/ketones [72, 73]. Different aromatic alcohols and secondary aliphatic alcohols were oxidized with high selectivity, but at low conversion. Here, further improvement should be possible (Scheme 25). 

Characterization of Supported Iron Oxide Particles Using Mdssbauer Spectroscopy and Magnetic Susceptibility... 

Two different methods were used to produce Iron oxide (Fe203) particles on Grafoll. One method was a simple Impregnation-calcination based on the method of Bartholomew and Boudart (20). The exact method used 1s described elsewhere (27). The second method used was a two step process. First, metallic iron particles were produced on the Grafoll surface via the thermal decomposition of Iron pentacarbonyl. This process Is also described in detail elsewhere (25). Next, the particles were exposed to air at room atmosphere and thus partially oxidized to 2 3 Following the production of Iron oxide particles (by... 

PHILLIPS ETAL. Supported Iron Oxide Particles... 

Water is pumped upward through a bed of 1 mm diameter iron oxide particles (SG = 5.3). If the bed porosity is 0.45, over what range of superficial water velocity will the bed be fluidized ... 

Iron oxide particles Micellar iron oxide in water... 

Figure 2.15b depicts the continuous flow reactor (designed by the Institute of Gas Technology), consisting of four fluidized beds of iron oxide particles within a single pressurized... 

Mattisson, T., Johansson, M., and Lyngfelt, A., Multicycle reduction and oxidation of different types of iron oxide particles-application to chemical-looping combustion, Energy Fuels, 18(3), 628, 2004. 

In the case of roasting, the pretreatment process destroys the sulfide matrix by driving off sulfur from the structure. This results in the formation of iron oxide particles that are made of concentrically zoned and porous hematite and maghemite (Paktunc et al. 2006). Arsenic is volatilized as As203 and oxidised to... 

Monitoring solid state reactions that play a role in catalyst activation forms a useful application of XRD. The example discussed above concerns a catalyst with large iron oxide particles as is used in the water gas shift reaction, and represents a particularly favorable system for XRD analysis. Similar studies with small particles are certainly also feasible, although it may be advisable to use laboratory X-ray sources of higher energy, such as Mo Ka, or a synchrotron [13]. 

The most direct evidence for surface precursor complex formation prior to electron transfer comes from a study of photoreduc-tive dissolution of iron oxide particles by citrate (37). Citrate adsorbs to iron oxide surface sites under dark conditions, but reduces surface sites at an appreciable rate only under illumination. Thus, citrate surface coverage can be measured in the dark, then correlated with rates of reductive dissolution under illumination. Results show that initial dissolution rates are directly related to the amount of surface bound citrate (37). Adsorption of calcium and phosphate has been found to inhibit reductive dissolution of manganese oxide by hydroquinone (33). The most likely explanation is that adsorbed calcium or phosphate molecules block inner-sphere complex formation between metal oxide surface sites and hydroquinone. 

Brain JD, Bloom SD, Valberg PA, Gehr P (1984) Correlation between the behavior of magnetic iron oxide particles in the lungs of rabbits and phagocytosis. Exp Lung Res 6 115-131. 

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