Oxidation iron foil

In Fig. 2.35, a set of He I (top) and He II (bottom) excited UPS data for a reduction experiment inside the analysis chamber is shown. The He I spectra are dominated by a feature at 6.5 eV and an additional structure around 10.8 eV. The most significant change as reduction proceeds is the appearance of a new feature at the Fermi level (compare the spectra after 1 h and 70 h). The formation of a Fermi edge indicates that the chemical reaction produces a species of metallic iron, even at the low partial pressure of hydrogen used in the reduction experiment. A comparative experiment using an oxidized iron foil under the same reaction conditions did not lead to the formation of an equivalent feature at the Fermi edge. 

Fig. 35. Mossbauer spectra of an iron foil after various oxidation times, (a) 3.2, (b) 15.5, (c) 30.9 hr. Reproduced from Channing and Graham (233) with permission from The Electrochemical Society.

The kinetics of a similar oxidation reaction was studied by Pritchard and Dobson (236). These authors studied the oxidation between 450 and 560 K of a metallic-iron foil (0.02 mm thick electroplated with 1 mg cm 2 57Fe) by deoxygenated water. The resulting Mossbauer spectra (at room temperature) showed Fe304 to be the only detectable reaction product, and from the ratio of the Fe304 spectral area to that of metallic iron, the magnetite film thickness y can be calculated. Assuming that the rate law is of the form... 

Figure 4.65 shows the 57Fe Mossbauer transmission spectra of thin iron foils oxidized with nitric oxide (NO) at 500°C and 600°C [146], In the spectra, the lines corresponding to the position of the Mossbauer transmission spectra of Fe, Fe203, and Fe304 are indicated. 

If both substrates to be bonded are nonconducting, then the adhesive formulation must contain a susceptor material. Susceptors can have a small percentage of magnetic iron oxide, iron filings, or carbon additives. A susceptor can also be a steel screen or perforated steel foil that is embedded in the adhesive bond line. It has been found that graphite fiber composites used in the automotive and aerospace industries are sufficiently conductive that they can be successfully heated with induction. Design considerations must be taken into account in placement of the graphite reinforcement, so that the material heats uniformly. 

Filters for Co K radiation are usually made of iron oxide (Fe203) powder rather than iron foil. If a filter contains 5 mg Fe203/cm, what is the transmission factor for the Co Ka line What is the intensity ratio of Co Ka to Co Kfi in the filtered beam ... 

The above ideas that anion-cation pair sites are the surface sites for CO and CO2 adsorption on magnetite was verified directly by Udovic and Dumesic (43 ). These authors prepared films of magnetite on polycrystalline iron foils and varied the oxidation state of the surface by vacuum-annealing at different temperatures. In short, it was shown by Auger electron spectroscopy and X-ray photo-... 

Figure 6. Oxide nuclei on (111) iron foil after oxidation at 540°C and 1.1 X 10" ...

The situation during the oxidation was illustrated also by measuring the emf during the oxidation of an Fe-foil, fixed on a plate of Zr02 + CaO, versus a reference electrode [73] (Fig. 6). The iron foil is held at first in a nonoxidizing CO2—CO mixture, then at 7=0, it is changed to an oxidizing CO2/CO ratio. After adsorption of 0(ad) and nucleation of FeO, the emf is constant at the value for equilibrium Fe—FeO, until at 7b the thin... 

Fig. 6 Use of a solid electrolyte cell for measurement of oxygen transfer reactions [78] (a) schematic setup and (b) emf versus time curve for the oxidation of an iron foil (5 pm) in COj—CO at 960 °C, periods I Fe in reducing gas, II nucleation of Fe, III oxidation Fe Fe till consumption of Fe,...

Despite the poor performance of the nanowire arrays prepared by this technique it remains an intriguing morphology for hematite photoanodes. Another facile method to produce hematite nanowires by the simple thermal oxidation of iron foils has been reported by many groups [78, 81-84]. Due to the increased volume of the oxide over the metal, when foils of iron are thermally oxidized under the right... 

Spectra similar to the top trace in Fig. 2.37, showing the characteristic distortion of the conduction band feature, were obtained after exposure of the iron foil to 2 L (L is the Langmuir unit, 1 L = 10" Torr sec) of oxygen at 300 K. The shoulder around 4 eV is indicative of the presence of ferrous ions. These are not normally formed in the initial phase of oxidation of elemental iron. The catalyst surface is... 

Both catalysts exhibit a broader iron 3d band than that of elemental iron. A large fraction of the total valence band intensity arises from these iron 3d states (cross section of Fe3d 4.5 x 10" compared to O 2p with 5 x lO " ). This reflects the presence of covalently bonded iron compounds in the mixed surface of the catalysts. The broad feature at 5.5 eV in the top spectrum arises largely from oxygen, since a similar structure with low intensity at the Fermi edge was found for iron foil exposed to 8 L oxygen at room temperature. The shoulder around 10 eV, indicative of iron oxides, was not observed in the chemisorption experiment. 

Spectra from surfaces prepared under dry reduction conditions are dominated by the peak for elemental iron. They all, however, showed a shoulder at 710 eV, characteristic of the presence of unreduced material in, presumably, both ferrous and ferric oxidation states. The position and linewidth of the zero-valent iron peak are different from those of iron foil. A shift of 0.2-0.3 eV to higher binding energy was typical as well as a broader linewidth (2.2 eV for ion foil and ca 3.0 eV for the catalyst). There was no detectable relaxation shift in the iron spectrum. Therefore, the possibility of small-particle effects seems unlikely. The presence of large concentrations of local defects, in addition to possible spectroscopic effects of local variations in the position of the Fermi level, offer plausible explanations for the differences in spectral parameters. 

Thin films of a composite nickel-iron (9 1 Ni/Fe ratio) and iron-free oxyhydroxides were deposited from metal nitrate solutions onto Ni foils by electroprecipitation at constant current density. A comparison of the cyclic voltammetry of such films in 1M KOH at room temperature (see Fig. 6) shows that the incorporation of iron in the lattice shifts the potentials associated formally with the Ni00H/Ni(0H)2 redox processes towards negative potentials, and decreases considerably the onset potential for oxygen evolution. The oxidation peak, as shown in the voltammo-gram, is much larger than the reduction counterpart, providing evidence that within the time scale of the cyclic voltammetry, a fraction of the nickel sites remains in the oxidized state at potentials more negative than the reduction peak. 

Shin, Oxidation resistance of iron and copper foils coated with reduced graphene oxide multilayers, Acs Nano, vol. 6, pp. 7763-7769, 2012. 

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