F₂-laser-induced surface modification of iron thin films to obtain corrosion resistance

Abstract

Rustproof, chemical-resistant pure-iron thin films were successfully fabricated by the 157 nm F2-laser-induced surface modification of 50-nm-thick iron thin films. An approximately 2-nm-thick Fe3O4 layer underneath a native Fe2O3 layer of approximately 0.6 nm in thickness was formed on the iron thin films after F2 laser irradiation, as confirmed by X-ray photoelectron spectroscopy. The anodic polarization measurement in a 3 wt % NaCl aqueous solution (quasi-seawater) was conducted; the F2-laser-irradiated samples showed high corrosion resistance to the quasi-seawater. Moreover, no rust was observed on the samples after the immersion test in quasi-seawater for 48 h and longer. The measurement also revealed that the F2-laser-irradiated samples showed high corrosion resistance to a HNO3 aqueous solution. Thus, the micropatterning of iron thin films was demonstrated by the combination of F2 laser irradiation and subsequent HNO3 chemical etching.

Synthesis and Characterization of Chemically Pure Nanometer-Thin Zero-Valent Iron Films and Their Surfaces

“…Fe(III) signals are expected given that it is well understood that Fe 0 oxidizes to Fe 2+ and Fe 3+ upon exposure to air. , When compared to α-Fe 2 O 3 , the XPS spectra of the thin iron films studied here do not exhibit the small step in the low energy binding side of the Fe 2p 3/2 peak that is characteristic of hematite, , suggesting the presence of a different Fe(III) oxide. In addition to the Fe 3+ peaks, the XPS spectra of the iron film surface also show Fe 0 (ZVI) peaks at 706.5 and 719.5 eV, , which have not been observed before. Peak fitting of the Fe 3+ , Fe 0 , and O 1s peaks (Supporting Information Figure S3) for all deposition rates shows that the average atomic percentage of Fe 0 on the surface of the sample is 11(4)%.…”

“…Iron films of nanometer thickness are of interest because of a variety of potential applications in catalysis, environmental remediation, optics, data storage, corrosion inhibition, as well as their potential relevance in consumer electronics and coatings products. While many processes that render thin iron films functional occur at their surfaces, their interrogation by spectroscopic probes is often limited by the “strong-absorber” problem associated with macroscopically thick samples of iron and its oxides, , especially in situations where one would like to probe the surface from the iron side.…”

“…Of the PVD methods used to prepared thin iron films, magnetron sputtering can provide the highest sputtering rates. The deposition of corrosion-resistant iron films has been thought to require the use of iron sources having a purity of at least 5N (99.999% Fe), which are difficult to obtain and handle. , Moreover, because of iron’s high boiling point (2862 °C), impurities with lower boiling points, such as zinc or alkali elements, if present in the iron source, are expected to be enriched in the gas phase during low-temperature PVD processes and to therefore coat the substrate to a disproportionally larger extent when compared to their abundance in the bulk iron source. Yet, a comprehensive characterization of the impurities present and a method to minimize them in the thin iron films has not been conducted.…”

Dendritic Oxide Growth in Zerovalent Iron Nanofilms Revealed by Atom Probe Tomography

“…This high level of purity is attributed to the E-beam evaporation method described in our prior work, 22 in which evaporation rates are set high enough to exceed the iron melting point of our 99.95% purity iron boules (~1540 °C). Our method circumvents the need for iron sources having a purity of at least 5N (99.999% Fe), which are considerably more expensive and difficult to obtain 46 and handle [46][47] than the commonly available 99.95% purity iron boules used here. 3D-reconstruction of the ZVI tips including the inert Cr capping shows three defined layers (see Fig.…”

“…Films of Fe(0) having nanometer thickness have potential applications in environmental remediation, catalysis, optics, data storage, consumer electronics, and coatings products, and can serve as models for corrosion studies of Fe(0)-bearing engineered building and construction materials. Of particular importance for the continued and sustainable supply of clean and safe water, the formation of passivation layers of oxidized iron over zerovalent iron (ZVI) materials can significantly curtail the long-term effectiveness of the permeable reactive barriers (PRBs) − that are widely used to remediate legacy pollution of groundwater by toxic metals.…”