Iron Surface Research Articles

Influence of adding Nb on oxidation resistance of hypoeutectic high-chromium cast iron

This experiment investigates the effect of Nb on the oxidation resistance of high-chromium cast iron by adding different contents of Nb to high-chromium cast iron. The experimental results show that the oxidation resistance of high-chromium cast iron with the addition of 1 wt% Nb is increased by 43% compared with high-chromium cast iron without the addition of Nb, which may be related to the formation of a large area of weak oxidation area on the surface of high-chromium cast iron. When more than 2.5 wt% Nb is added to high-chromium cast iron, the oxidation resistance of high-chromium cast iron deteriorates significantly due to a large amount of Fe oxide formed around the Nb2O5. However, as the subsequent Nb content continues to increase to 5 wt%, the oxidation resistance of high-chromium cast iron is improved compared to 2.5 wt% Nb because the dispersion of NbC in the matrix decreases.

Microelectrode evaluation of in situ oxidant reactivity and pH variability at new ductile iron and copper coupon surfaces.

Thirty-two short term (∼7.5h) abiotic experiments were conducted with new ductile iron and copper coupons exposed to various water qualities, including pH (7 or 9), dissolved inorganic carbon (DIC, 10 or 50mgCL-1) and phosphate (0 or 3mgPL-1) concentrations and 4mgCl2L-1 free chlorine or monochloramine. To quantify oxidant reactivity with the new metal coupons, microelectrodes were used to obtain oxidant (free chlorine or monochloramine and dissolved oxygen (DO)) concentration and pH microprofiles from the bulk water to near the metal coupon surface. From the microprofiles, apparent surface reaction rate constants (k) were determined for each oxidant. An ANOVA analysis evaluated if the five variables (Material, Oxidant, Phosphate, DIC, and pH) significantly affected estimates of k, finding that the Material and Oxidant variables and their interaction were statistically significant (p<0.05), but the effect of variables of Phosphate, DIC, and pH on k values were not significant in this study. In general, both ductile iron and copper coupons showed significant surface reactivity towards free chlorine and monochloramine. For ductile iron, DO consumption was greater than for copper, which showed minimal DO reactivity, and DO was less reactive towards the copper surface than either free chlorine or monochloramine. Furthermore, pH microprofiles provided insight into the complexity that might exist near corroding metal surfaces where the bulk water pH may be substantially different from that measured near metal surfaces which is significant as pH is a controlling variable in terms of scale formation and metal solubility. This study represents an important first step towards using microelectrodes to (1) understand and provide direct measurement of oxidant microprofiles from the bulk water to the metal surface; (2) determine pipe wall reactivity using the directly measured concentrations profiles versus estimated pipe wall reactivity from bulk water measurements, and (3) understand how variables measured by bulk water samples (e.g., pH) may be drastically different from what is occurring at and near the metal surface. Together, these insights will assist in understanding disinfectant residual maintenance, corrosion, and metal release.

Understanding of selective oxidation of Fe-Mn binary alloys during continuous annealing through X-ray photoelectron spectroscopy

Selective oxidation of Fe-Mn alloys was characterizied through X-ray photoelectron spectroscopy and scanning/transmission electron microscopy during industrial continuous annealing (in an atmosphere of N2–5 vol.% H2 with traces of water at 800 °C). After annealing, only MnO oxides are formed on and below the surface and few iron oxides appear on the top surface due to oxidation of ambient air or the formation of FeO-MnO solid solutions. Mn concentration profiles exhibit typical selective oxidation and show similar features. Mn concentration first increases to a peak value at a depth of 5–10 nm from surface, and then decreases to the minimum at the oxidation front, following with a floating up and down to bulk composition. According to XPS spectra and Mn concentration profiles as a function of depth, the annealed alloy surfaces can be divided into four zones: ambient air contaminated zone, MnO enrichment zone (external and internal oxidation coexisting here), Mn depletion zone and bulk composition zone. Mn concentration reaches a minimum value at the oxidation front, whose position is deeper with annealing temperature and time increasing. The value of Mn diffusion coefficient in ferrite estimated using diffusion flux at the oxidation front is 2.9 × 10−15 m2 s−1 at 800 °C, which is slightly greater than that in literature.

Temperature effect on sulphur adsorption on iron surface: A molecular dynamics simulations study

The effect of temperature on the adsorption of a sulphur atom on the Fe(110) surface has been investigated using molecular dynamics simulations at a temperature of 353[Formula: see text]K, 373[Formula: see text]K and 398[Formula: see text]K. The most favorable adsorption site for a sulphur atom on the Fe(110) is found at a hollow site. The perpendicular height of the sulphur atom position is 4.017[Formula: see text]Å above the Fe surface at a temperature of 398[Formula: see text]K. The Fe–S bonding strength was affected by temperature, it becomes weaker with increasing temperature. The adsorption energy is calculated to be −6.640[Formula: see text]eV, −6.579[Formula: see text]eV and −1.841[Formula: see text]eV for the system at a temperature of 353[Formula: see text]K, 373[Formula: see text]K and 398[Formula: see text]K, respectively. This condition is confirmed by experimental results where the corrosion rate of the samples began to appear at 353[Formula: see text]K, with darker physical characteristics of the corrosion.

Significance of temperature as a key driver in ZVI PRB applications for PCE degradation

We report on the potential of elevated groundwater temperatures and zero-valent iron permeable reactive barriers (ZVI PRBs), for example, through a combination with underground thermal energy storage (UTES), to achieve enhanced remediation of chlorinated hydrocarbon (CHC) contaminated groundwater. Building on earlier findings concerning deionized solutions, we created a database for mineralized groundwater based on temperature dependence of tetrachloroethylene (PCE) degradation using two popular ZVIs (i.e., Gotthart–Maier cast iron [GM] and ISPAT sponge iron [IS]) in column experiments at 25 °C–70 °C to establish a temperature-dependent ZVI PRB dimensioning approach. Scenario analysis revealed that a heated ZVI PRB system in a moderate temperature range up to 40 °C showed the greatest efficiency, with potential material savings of ~55% to 75%, compared to 10 °C, considering manageability and longevity. With a 25 °C–70 °C temperature increase, rate coefficients of PCE degradation increased from 0.4 ± 0.0 h−1 to 2.9 ± 2.2 h−1 (GM) and 0.1 ± 0.1 h−1 to 1.8 ± 0.0 h−1 (IS), while TCE rate coefficients increased from 0.6 ± 0.1 h−1 to 5.1 ± 3.9 h−1 at GM. Activation energies for PCE degradation yielded 32 kJ mol−1 (GM) and 56 kJ mol−1 (IS). Temperature-dependent anaerobic iron corrosion was key in regulating mineral precipitation and passivation of the iron surface as well as porosity reduction due to gas production.

Enhanced hydrogen embrittlement of steel by the premature hydrogen dissociation with the increasing inert gas pressure in hydrogen-containing mixtures

Regarding hydrogen embrittlement (HE) in the mixtures of hydrogen and inert gas, the results were understood mainly based on the partial hydrogen gas pressure. On the other hand, the effect of the total gas pressure has not been fully investigated. In this study, fatigue crack growth rate (FCGR) tests were conducted in high-purity hydrogen gas at different gas pressures. Also, the FCGR tests were conducted in hydrogen and nitrogen mixtures at different total gas pressures. The hydrogen partial pressure in the mixture was the same as the high-purity hydrogen. This was the first time that acceleration of the FCGR in the mixtures compared to that in the high-purity hydrogen was observed. To elucidate the mechanism of the enhanced HE in the mixtures, hydrogen permeation and hydrogen desorption experiments were carried out. Based on the results of these tests, the acceleration of the FCGR in the mixtures could be interpreted by the fast hydrogen entry rate, which may result in a higher local hydrogen concentration near the crack tip during a limited time. Density functional theory (DFT) calculations were performed to consider the total gas pressure effect on an atomic scale. The thrust force of other gas molecules in the mixtures made the hydrogen molecules enter the potential field of the iron surface sooner, advancing the dissociation of the hydrogen. This will increase the surface concentration of the hydrogen atoms.

Structure and energetics of FeO/Fe(001) interfaces

We report results of density functional theory calculations of structure and properties of 1–5 monolayer thin FeO(001) films and their interactions with the Fe(001) surface. It is found that deposition of an iron-oxide film affects weakly geometry of the Fe(001) support, causing small 2% expansion of the first interplanar distance compared to clean iron surface. Analysis of the electronic structure of the FeO/Fe system shows that after interface formation, the oxide layer remains semiconducting and the substrate metallic. Electronic structure of the FeO(001) layer in direct contact with the Fe(001) surface exhibits metallic character. Magnetism of the metal/semiconductor interface is only slightly disturbed compared to that of isolated components. The FeO adlayers preserve antiferromagnetic (AFM) nature of the oxide and the sharp boundary between higher AFM phase of FeO and lower ferromagnetic phase of Fe is observed at the interface.

Experimental and simulation study on the estimation of surface relaxivity of clay minerals

Nuclear Magnetic Resonance (NMR) is an important tool for the evaluation of pore structure and petrophysical properties of reservoir rocks. Pore Surface relaxivity (ρ2), which controls the relaxation decay due to the interaction between the spins and the pore surface, is an important parameter that impacts the interpretation of NMR for petrophysical properties. Sandstone rocks have complex minerology and consist of different clay minerals. Earlier efforts have reported the surface relaxivity of different rock types such as sandstone or carbonate, but less attention was given to the estimation of individual clay minerals surface relaxivity. The surface complexity and variable mineralogy (especially paramagnetic and ferromagnetic minerals) of clays can both impact the surface relaxivity and relaxation times in clays and porous media containing clays. This study, using for the first time both simulation and experimental approaches, aims to systematically investigate the surface relaxivity of clays characterized by variable mineralogy and iron content. A glass beads sample (iron free) and 5 different pure clay minerals samples (ranked by increasing iron content: Kaolinite, Smectite, Illite, Chlorite, and Nontronite) were prepared with similar average grain sizes (500 μm). The determination of surface relaxivity requires prior measurement of pore surface-to-volume ratio (S/V) using an independent method in addition to obtaining T2 relaxation time. Two methods, among the most widely used, were used here for S/V determination including BET N2 gas adsorption and 3D micro CT imaging. The 3D images were also used to conduct NMR simulations to reproduce the experimental data. The estimated surface relaxivity values from both methods were compared and correlated to the iron content of the different clays. The surface relaxivity values obtained based on BET-derived S/V showed reasonable values (29–343 μm/s) that have a strong positive relationship with iron content of the clays. The documented equation relating surface relaxivity and iron content can be potentially utilized to predict surface relaxivity based on the compositional analysis of clays. On the other hand, digital images did not capture the surface complexity of clays thus significantly underestimated S/V which consequently resulted in overestimated surface relaxivity (898–11000 μm/s) that were physically non-feasible. Supporting the same argument, the simulated T2 relaxation distribution showed significant mismatch with the experimental data for the clay samples while an excellent match was observed for the glass beads sample. This can be attributed to the smooth surface of the glass beads, unlike the complex clays. The reported surface relaxivity values (based on BET-derived S/V) for the individual clay minerals can be used to perform NMR simulation and interpretation studies conducted on sandstone or shale formations. Careful attention should be given when performing NMR simulation on micro-CT digital images of samples containing clay due to the inadequacy of such images in capturing the complex surface and microporous nature of clays. The outcomes from this study can improve the interpretation of NMR T2 data and the determination of NMR-derived pore size distribution and petrophysical properties. The reported surface relaxivity values for clay can also inform the NMR simulation.

Multiprotein Adsorption from Human Serum at Gold and Oxidized Iron Surfaces Studied by Atomic Force Microscopy and Polarization-Modulation Infrared Reflection Absorption Spectroscopy.

Multiprotein adsorption from complex body fluids represents a highly important and complicated phenomenon in medicine. In this work, multiprotein adsorption from diluted human serum at gold and oxidized iron surfaces is investigated at different serum concentrations and pH values. Adsorption-induced changes in surface topography and the total amount of adsorbed proteins are quantified by atomic force microscopy (AFM) and polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS), respectively. For both surfaces, stronger protein adsorption is observed at pH 6 compared to pH 7 and pH 8. PM-IRRAS furthermore provides some qualitative insights into the pH-dependent alterations in the composition of the adsorbed multiprotein films. Changes in the amide II/amide I band area ratio and in particular side-chain IR absorption suggest that the increased adsorption at pH 6 is accompanied by a change in protein film composition. Presumably, this is mostly driven by the adsorption of human serum albumin, which at pH 6 adsorbs more readily and thereby replaces other proteins with lower surface affinities in the resulting multiprotein film.

Characterization and Adsorption Capacity of Modified Biochar for Sulfamethylimidine and Methylene Blue in Water.

In this study, a composite of pond mud and lanthanum- and nano-zero valent iron-modified-biochar was investigated for its ability to adsorb methylene blue (MB) and sulfamethazine (SMZ). La-modified attapulgite and nano-zero valent iron (surface area enhanced by 43.7% via Brunauer-Emmett-Teller analysis) were successfully loaded onto the straw-sediment biochar (BC) surface. With the increase in pyrolysis temperature, the biocompatibility yield, the H, O, and N content, and the ratio of carbon elements decreased, while the pH value, surficial micropores, C element, and ash content increased. The biocarbon small molecules were gradually and tightly ordered, and the organic groups such as hydroxyl, carboxyl groups, and carbon oxygen double bonds were gradually lost or disappeared. The original Fe-BC had more phenolic hydroxyl groups forming an intermolecular hydrogen bond than others with a higher adsorption capacity possibly through the Schiff base reaction. The effect of various pH (2-9), temperature (15-35 °C), and initial concentration (1-25 mg L-1) on adsorption was investigated. pH and temperature were the main factors governing the adsorption process. The maximum adsorption capacity was observed at pH 4. The adsorption performances for MB followed the order Fe-BC > La-BC > BC, and the maximum removal rate was over 98.45% with pH = 7. The three types of BC dosages between 0.2 (6.67 g L-1) and 0.4 g showed a removal rate of 99% for MB. The adsorption capacity of Fe-BC, La-BC, and BC for MB was 2.201, 1.905, and 2.401 mg L-1 with pH = 4, while 4.79, 4.58, and 5.55 mg g-1 were observed with BC dosage at 0.025 g. For SMZ, the higher the temperature, the better the adsorption effect, and it reaches saturation at approximately 25 °C. To further evaluate the nature of adsorption, Langmuir/Freundlich/Temkin models were tested and the adsorption capacities were evaluated on the surface of the BC composite. The three modified materials were physisorbed to SMZ, while MB was chemisorbed. For MB, the adsorption performance of BC is the best < 0.2 g (6.67 g L-1) at pH 7.0 at 35 °C. The Elovich model was more suitable for MB, while the Freundlich and Temkin models could better fit the adsorption process of MB. The preparatory secondary dynamics equation and Langmuir equation were more compliant for SMZ, and the saturated adsorption capacities of straw-modified, La-BC, and Fe-BC reached 5.699, 6.088, and 5.678 mg L-1, respectively.

Laser Melting of Prefabrication AlOOH-Activated Film on the Surface of Nodular Cast Iron and Its Associated Properties.

This study aimed to improve the absorption rate of laser energy on the surface of nodular cast iron and further improve its thermal stability and wear resistance. After a 0.3 mm thick AlOOH activation film was pre-sprayed onto the polished surface of the nodular cast iron, a GWLASER 6 kw fiber laser cladding system was used to prepare a mixed dense oxide layer mainly composed of Al2O3, Fe3O4, and SiO2 using the optimal laser melting parameters of 470 W (laser power) and 5.5 mm/s (scanning speed). By comparing and characterizing the prefabricated laser-melted surface, the laser-remelted surface with the same parameters, and the substrate surface, it was found that there was little difference in the structure, composition, and performance between the laser-remelted surface and the substrate surface except for the morphology. The morphology, structure, and performance of the laser-melted surface underwent significant changes, with a stable surface line roughness of 0.9 μm and a 300-400 μm deep heat-affected zone. It could undergo two 1100 °C thermal shock cycles; its average microhardness increased by more than one compared to the remelted and substrate surfaces of 300 HV, with a maximum hardness of 900 HV; and the average friction coefficient and wear quantity decreased to 0.4370 and 0.001 g, respectively. The prefabricated activated film layer greatly improved the thermal stability and wear resistance of the nodular cast iron surface while reducing the laser melting power.

Mechanical Properties of Iron Plating Layer after Nitriding

A certain thickness of the iron plating layer without impurities was fabricated on the surface of pure iron by employing electroplating treatment. The thickness of the iron plating layer was measured by approximately 23 μm. SEM studies demonstrated the microstructure of the surface of the iron plating layer before and after nitriding. According to XRD analysis, the compound layer was mostly composed of Fe2-3N with high supersaturation of nitrogen. After nitriding, the microhardness of the sample was 555 HV with the depth of the matrix at 30 μm, which was four times the hardness of the matrix. Under the same experimental conditions, the wear volume loss and friction coefficient of the nitrided iron plating layer was lower, showing that nitriding can significantly improve the poor wear resistance of the iron plating layer. The Salt spray corrosion experiment showed that nitriding can significantly improve the corrosion resistance of the iron plating layer.

Absence of photophysiological response to iron addition in autumn phytoplankton in the Antarctic sea-ice zone

Abstract. The high nutrient–low chlorophyll condition of the Southern Ocean is generally thought to be caused by the low bioavailability of micronutrients, particularly iron, which plays an integral role in phytoplankton photosynthesis. Nevertheless, the Southern Ocean experiences seasonal blooms that generally initiate in austral spring, peak in summer, and extend into autumn. This seasonal increase in primary productivity is typically linked to the seasonal characteristics of nutrient and light supply. To better understand the potential limitations on productivity in the Antarctic sea-ice zone (SIZ), the photophysiological response of phytoplankton to iron addition (2.0 nM FeCl3) was investigated during autumn along the Antarctic coast off Dronning Maud Land. Five short-term (24 h) incubation experiments were conducted around Astrid Ridge (68∘ S) and along a 6∘ E transect, where an autumn bloom was identified in the region of the western SIZ. Surface iron concentrations ranged from 0.27 to 1.39 nM around Astrid Ridge, and 0.56 to 0.63 nM along the 6∘ E transect. Contrary to expectation, the photophysiological response of phytoplankton to iron addition, measured through the photosynthetic efficiency and the absorption cross-section for photosystem II, showed no significant responses. It is thus proposed that since the autumn phytoplankton in the SIZ exhibited a lack of an iron limitation at the time of sampling, the ambient iron concentrations may have been sufficient to fulfil the cellular requirements. This provides new insights into extended iron replete post-bloom conditions in the typically assumed iron deficient high nutrient–low chlorophyll Southern Ocean.

The Role of Fe in Ni-Fe/TiO2 Catalysts for the Dry Reforming of Methane

A series of nickel- and iron-modified titanium dioxide (Ni-Fe/TiO2) are studied for the dry reforming of methane (DRM) at 550 °C. Temperature-programmed surface reactions using CH4 and CO2 as probe molecules, as well as activity results, confirmed that both CO2 and CH4 conversion decreased with the addition of Fe. The XPS results obtained from reduced and used catalysts suggested changes in the surface nickel and iron species. Characterizations, particularly thermogravimetric analysis (TGA) and Raman spectroscopy over used catalysts, revealed that the addition of Fe can greatly inhibit the coke formation. In situ DRIFTS further identified that the addition of Fe favored the formation of carbonate species, which can facilitate the removal of coke deposited on the surface.

Chitosan/tannic acid phenamine networks-hollow mesoporous silica capsules with reversible pH response: Controlled-releasing amino acid derivatives as “green” corrosion inhibitor

A novel amino acid derivative (SM) was synthesized through Schiff base reaction between syringaldehyde (SA) and methionine (MTI), and loaded to obtain a reversible pH-responsive releasing corrosion inhibitor silica capsule (CS/TA@SM@HMSs) with chitosan/tannic acid phenamine networks on the surface. The corrosion inhibition effect of SM and CS/TA@SM@HMSs on Q235 was studied using electrochemical techniques and surface analysis. The results showed the maximum inhibition efficiency of SM reached to 93.2 % at 200ppm by immersing Q235 in 3.5 wt% NaCl solution. The theoretically calculated electron parameter (the energy gap ΔE = 4.492 eV) indicated that SM molecules were more susceptible to electron transfer with iron surfaces therefore allowing better adsorption on carbon steel surfaces to prevent corrosion. Meanwhile, UV–visible measurements showed that the chitosan/tannic acid phenamine network on the capsule surface responded to changes in pH. The reversible pH-responsive corrosion inhibitor capsule can be switched on and off several times to release SM, demonstrating reversible release and efficient corrosion protection. This study proposes a novel class of “green” amino acid derivative corrosion inhibitors, and establishes a controllable, efficient and reversible pH-responsive release system. A new approach is provided to stimulating the release of corrosion inhibitors in response to long-term corrosion protection of metals.

A combined experimental and theoretical approach effect of Curcuma. L extract as a corrosion inhibitor on iron in acidic solution

ABSTRACT Inhibition performance of the aqueous Curcuma.L extract as a corrosion inhibitor for an iron surface in a 0.1 M HCl solution was investigated using the ac impedance technique. The inhibition efficiency for iron was determined in the presence of the Curcuma.L extract in a 0.1 M HCl solution and reached 81.1% at the optimum concentration. The corrosion inhibitive effect was achieved through the adsorption of Curcuma.L molecules onto the iron surface, which followed the Langmuir adsorption isotherm model. The inhibitive strength of the main compounds in the Curcuma.L extract, namely Curcumin (Inh A), demethoxycurcumin (Inh B), and bis-demethoxycurcumin (Inh C), might have a direct relationship with the electron-donating ability of the molecules, as revealed by quantum chemical parameters. Theoretical investigations were conducted using DFT methods with the B3LYP/6-311G++(d,p) basis set. Mulliken charge and ESP calculations were performed to illustrate the mechanism of inhibition of this extract on the iron surface. The interaction energies derived from Monte Carlo simulations followed the order Inh A > Inh B > Inh C. The aqueous extract of Curcuma.L has been shown to effectively inhibit iron corrosion in acidic environments.

Synthesis of magnetic biochar with high iron content and large specific surface area: Synergistic effect of Fe doping and KOH activation

Magnetic biochar has promising applications in environmental remediation, catalysts, electrode materials, etc. The influence of the sequence of iron doping process and KOH activation process on the properties of magnetic biochar is significant and has not been studied yet. In this work, the properties of magnetic biochar were evaluated by changing the order of iron doping and KOH activation, accompanied by the comparison of simultaneous these two processes. Following the doping of biochar with iron, the oxide clusters of iron distributed in the surface of the carbon skeleton protect the interior from etching by KOH, resulting in low specific surface area (SSA). The advantages of the synergy strategy were evident in the high surface iron content and large SSA of the synthesized magnetic biochar. Further, batch adsorption and recovery experiments were performed on Fe/KOH-C obtained by a simple and low-cost synergistic synthesis strategy, and the results showed that the maximum adsorption capacity of tetracycline was up to 375 mg g−1, with advantages in terms of recovery. Pore filling, electrostatic attraction, π-π interaction, and complexation reaction of the surface functional groups were proved to be the adsorption mechanism of Fe/KOH-C.

First-principles explain the anodic dissolution corrosion of stainless steel surface

The electrochemical corrosion on the face-centred cubic Fe (111) surface is studied on the basis of first-principles calculations when the lead–bismuth eutectic and the second phase precipitates coexist. The precipitates on the iron surface have a great effect on the surface properties, which can form the micro galvanic cell to cause electrochemical corrosion of the anode under corrosive conditions. The electrochemical corrosion was assessed by calculating the electrode potential of the half electrode (Fe surface). In addition, the effect of various alloy combinations on corrosion resistance was studied and a theoretical scheme for experimental design was proposed. Finally, in order to determine the electrochemical corrosion mechanism, the energetic, microstructural and electronic properties were analysed. The results show that the influence of Bi atoms on the surface electrode potential is greater than that of Pb atoms, and the existence of Al and Si atoms slows down the electrochemical corrosion of the anode to a great extent.

Adsorbate-Induced Adatom Formation on Lithium, Iron, Cobalt, Ruthenium, and Rhenium Surfaces.

Recent experimental and theoretical studies have demonstrated the reaction-driven metal-metal bond breaking in metal catalytic surfaces even under relatively mild conditions. Here, we construct a density functional theory (DFT) database for the adsorbate-induced adatom formation energy on the close-packed facets of three hexagonal close-packed metals (Co, Ru, and Re) and two body-centered cubic metals (Li and Fe), where the source of the ejected metal atom is either a step edge or a close-packed surface. For Co and Ru, we also considered their metastable face-centered cubic structures. We studied 18 different adsorbates relevant to catalytic processes and predicted noticeably easier adatom formation on Li and Fe compared to the other three metals. The NH3- and CO-induced adatom formation on Fe(110) is possible at room temperature, a result relevant to NH3 synthesis and Fischer-Tropsch synthesis, respectively. There also exist other systems with favorable adsorbate effects for adatom formation relevant to catalytic processes at elevated temperatures (500-700 K). Our results offer insight into the reaction-driven formation of metal clusters, which could play the role of active sites in reactions catalyzed by Li, Fe, Co, Ru, and Re catalysts.

Effect of chromic acid anodization on the corrosion resistance of Fe-based alloy coatings by high-speed laser cladding

Fe-based alloy coatings were coated on surface of ductile cast iron by high-speed laser cladding, and the effects of chromic acid anodization on corrosion resistance of coatings were analyzed. The results show that as chromic acid anodization time increases, corrosion rate falls and then rises. After 20 min, the coating had Cr and Fe oxide passivation film, maximum impedance value (5.40 × 105 Ω·cm2) and polarization resistance (50.6 kΩ·cm2), and minimum self-corrosion current (0.77 μA/cm2). Its corrosion resistance had improved significantly.