Iron oxide layer

In a similar study, Zhang and Wang (1997) studied the reaction of zero-valent iron powder and palladium-coated iron particles with trichloroethylene and PCBs. In the batch scale experiments, 50 mL of 20 mg/L trichloroethylene solution and 1.0 g of iron or palladium-coated iron were placed into a 50 mL vial. The vial was placed on a rotary shaker (30 rpm) at room temperature. Trichloroethylene was completely degraded by palladium/commercial iron powders (<2 h), by nanoscale iron powder (<1.7 h), and nanoscale palladium/iron bimetallic powders (<30 min). Degradation products included ethane, ethylene, propane, propene, butane, butene, and pentane. The investigators concluded that nanoscale iron powder was more reactive than commercial iron powders due to the high specific surface area and less surface area of the iron oxide layer. In addition, air-dried nanoscale iron powder was not effective in the dechlorination process because of the formation of iron oxide. 

The open circuit potential data for the B210/NVP system mirrors the behavior of the rust ratings over the temperature range examined. A plausible explanation of the change of the open circuit potential is as follows. As temperature is increased, the composition of the various oxides and hydroxides which make up the zinc phosphate conversion layer and the base iron oxide layer undergo changes. 

Weiss W, Ranke W. Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers. Prog Surf Sci. 2002 70 1-151. 

Re-immersion of the ordered oxide films into HC104 or HC1 solutions led to the disappearance of the LEED beams of Type 2. That is, the CrO phase was not stable in acid solutions. This is an indication that acidic electrolytes, particularly HC1, attacked the passive layer at the comparatively thin CrO regions, replacing or covering those regions with a thin, hydrated amorphous iron oxide layer. 

Busch M, Gruyters M, Winter H (2006) Spin polarization and structure of thin iron oxide layers prepared by oxidation of Fe(110). Surf Sci 600 4166-4169... 

Other substitution reactions lead to more crystalline phases. Reaction of (4-aminopyridine)i/4FeOCl with methanol at 100 °C, for example, gives crystalline FeOOMe. Reactions with aliphatic and aromatic alkoxides and acids, of the type shown in equations (13) and (14), have also been studied. More rigid and longer molecules, such as 4-hydroxybenzoic acid, can crosslink the iron oxide layers. An initial intercalation step that causes an expansion of the FeOCl interlayer distance is followed by a second substitntion step leading to layer crosslinking. 

The components of the layers of the film chip (Fig. 29) placed under the spreader are as follows The top coat contains buffer components, surfactants, etc. The optical screen contains an iron oxide layer which serves to block the... 

Air and water can eat away iron and steel Oxygen binds to IY1°F6 jron molecules to make iron oxide. Layer by layer, the metal changes to a red powder called rust. When painted, rusting slows on cars, bicycles, and tricycles. 

Complex surface processes during HC1 etching (acidic dissolution of oxides, electrochemical oxidation) lead to the formation of a porous, chloride-containing iron oxide layer while nickel remains in the zero-valent state. Subsequent reduction, facilitated also by hydrogen atoms formed on nickel sites, results in an increased number of surface iron and nickel atoms and an enhanced catalytic activity. The larger concentration of atomic hydrogen on the surface and the presence of surface Ni are observations that are supported by the decreased selectivity of olefin formation. 

Corrosion near a crack in an iron oxide layer can give rise to the phenomenon of "tuberculation". Fig. 10.9 shows a cross section of a tubercle consisting of various... 

The passive iron oxide layer is destroyed when pH is reduced to about 11.0 or below, causing the porous oxide layer (rust) to form during corrosion. 

It was only in 1992-1993 that we finally found out after an in-depth evaluation of the interactions between various metal surfaces and coatings of polyaniline (applied as pure dispersion or as dispersion paints) that together with a remarkable corrosion potential shift (ermobling) and an iron oxide layer formation (passivation) lead to a significant anticorrosion effect [71]. In a study together with Elsenbaumer et al. [72], we discovered that the corrosion rate was reduced by a factor of up to 10,000. The iron oxide that formed between the metal surface and the polyaniline primer coating was determined to be Fe203, later confirmed with even clearer x-ray photoelectron spectra (XPS) [23b]. 

At 150 °C, tribofilms of 6 nm or thicker were formed on the disc. When the layers had a thickness higher than 6 nm no signal from the iron oxide layer was detected and the reaction layer has to be assumed to be semi-infinite and the... 

S. -H., Baek, I.-H., Choy, J.-H., and Hwang, S.-J. (2008) Mesoporous iron oxide-layered titanate nanohybrids soft-chemical synthesis, characterization, and photocatalyst application. /. Phys. Chem. 

Mass transport-control Mass transport-controlled corrosion implies that the rate of corrosion is dependent on the convective mass-transfer processes at the metal/fluid interface. When steel is exposed to oxygenated water, the initial corrosion rate will be closely related to the convective flux of dissolved oxygen toward the surface, and later by the oxygen diffusion through the iron oxide layer. Corrosion by mass transport will often be streamlined and smooth. 

If a steel shell is overheated, the oxidation of the steel shell may give an iron oxide layer up to 30 mm thick [150] that may become an additional thermal barrier, but it also may give additional strain to the SiC block. 

Fig. 19.68 X-ray photoelectron spectroscopic (XPS) analysis of passive iron oxide layers form in the presence of doped polyaniline. (From Ref. 83.)...

Fig. 31.36 XPS spectrum of the passive iron oxide layer formed on steel under doped polyaniline coating. (From Ref. 26.)...

The use of de-icing salts on concrete pavements has a deleterious effect on reinforced concrete. Many bridges and parking garages with cast-in-place concrete and reinforced steel develop cracks by allowing corrosive chemicals to react with the steel. In normal concrete, the water in the pores is highly alkaline and a protective iron oxide layer forms on the steel. This... 

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