Particles magnetite

Kato (K3) measured so-called critical gas velocities corresponding to the complete suspension of solids, and presents a graphical correlation of the results for glass spheres (diameters from 0.074 to 0.295 mm), magnetite particles (particle size from 0.038 to 0.175 mm), and sand particles (particle size 0.147 to 0.295 mm). 

Catalyst Production. Supported magnetite particles were produced on Grafoll (Union Carbide), a high surface area form of graphite. The nature of Grafoll and the reasons It is convenient to use In MCssbauer spectroscopy experiments eu e described elsewhere (25). Grafoll is also well suited for magnetic susceptibility experiments. 

In Figure 2, the MCssbauer spectrum of sample 2 (Table I) and a matching computer-simulated model spectrum are shown. This spectrum was recorded over a period of 30 hours while sample 2 was under a flowing CO/CO2 (15 85) gas mixture at 613 K. Following the completion of the experiment, the average magnetite particle... 

MSssbauer spectroscopy and magnetic susceptibility were used to demonstrate that magnetite particles supported on a Grafoil substrate sinter very slowly under water-gas shift reaction conditions. 

External stimuli have also been used to further target liposomes. In one such study magnetite particles were incorporated in radiolabeled liposomes and a magnet positioned over the right kidney of a test animal. The liposomes were selectively targeted to that kidney in concentrations that were viewed as significantly high for relevant clinical applications [66],... 

PEG is hydrophilic and is widely used in biological research because it protects surfaces from interacting with cells or proteins. Thus, coated particles may result in increased blood circulation time. For their preparation, 10-mg magnetite particles were dispersed in 1.0 mU of deoxygenated water by sonication for 30 min. The aqueous dispersion of MNPs was dissolved in the aqueous cores of reverse micelles... 

The first one is the bulk magneto crystalline anisotropy field. It depends on the chemical composition and crystallographic structure of the material. For instance, the anisotropy constant is 30 times larger in cobalt ferrite particles than in magnetite particles. 

As the radical tends to disproportionate, the rate of dissolution gradually decreases. Addition of EDTA to the system greatly enhances the dissolution owing to the formation of Fe -EDTA which dissolves the oxide via a thermal pathway. In the presence of 2-propanol, the Fe -EDTA is continually regenerated and thus acts as a catalyst. Similar behaviour has been observed for magnetite particles (Segal Sellers, 1984). 

Gorichev and Kipriyanov (1984, and references therein) found that dissolution of powdered magnetite particles in HCl, H2SO4, H3PO4 and Na2EDTA at temperatures of up to 80 °C displayed sigmoidal dissolution curves that could be described by. 

In acid media (pH 2) magnetite crystals ca. 10 nm across transform topotactically to maghemite via an adsorption reaction which traps mobile electrons from the bulk material and reduces interfacial Fe the Fe ions that form are selectively leached into solution (Jolivet Tronc, 1988). Electron delocalization also induces ferrihydrite in contact with small magnetite particles to transform into a spinel layer (Belleville etal., 1992). 

Stable, nanometre magnetite particles form by boiling a mixture of Fe" sulphate and bispyridoxylidene hydrazine phthalazine for 10 min. at pH 7 (Sarel et al., 1989). 

Holding a very dilute suspension of magnetite particles in sodium silicate solution at room temperature for 4 days produces magnetite with a uniform, 3 nm Si02 coating (Philipse et al., 1994 Correa-Duarte et al., 1998). 

Boron nitride capsules containing 10-20 nm particles of magnetite were produced by forming pellets of boron nitride magnetite in a ratio of 8 2 and arc melting the pellets in an Ar/N2 atmosphere for a few minutes. HRTEM confirmed that the magnetite particles were encapsulated in the boron nitride (Hirano et al., 1999). 

Sugimoto,T. Matijevic, E. (1980) Formation of uniform spherical magnetite particles by crystallization from ferrous hydroxide gels. 

Tamura, H. Matijevic, E. Meites, L. (1983) Adsorption of Co " ions on spherical magnetite particles. J. Colloid Interface Sci. 92 303-314... 

Stripped magnetite particles. Applications of the double surfactant layer. Principle in the preparation of water based magnetic fluids. J. Colloid Interface Sci. 149 98-104 Wuehn, M, JosephJ., Bagus, P.S. Niklewski.A., Puettner, R., Reis,S., Weiss,W., Martins, M.,... 

Sugimoto and Matijevic (3) prepared uniform spherical particles of magnetite (Fe,04) as well by partial oxidation of ferrous hydroxide gel with nitrate. The uniform magnetite particles were obtained at a slight excess of Fe2+, and the mean size critically depended on the excess concentration of Fe2+ or pH. 

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