Iron Oxide Layer Research Articles

A slow-release reduction material of Escherichia sp. F1 coupled with micron iron powder achieves the remediation of trichloroethylene-contaminated soil

Trichloroethylene (TCE) is a prevalent organic pollutant found in soil. The oxide passivation layer on the surface of micron iron powder inhibits the release of its reducing components, leading to ineffective reduction and purification of TCE in soil. To enhance TCE degradation, a slow-release reduction material "Escherichia sp. F1-micron iron powder" was developed. A novel iron-reducing bacterium, Escherichia sp. F1, was isolated from soil contaminated with chlorinated hydrocarbons. This bacterium demonstrated a sustained iron reduction capability, achieving a reduction rate of 38.7% for Fe(Ⅲ) within 15 days. Genome sequencing revealed that strain F1 harbors 53 functional iron reduction genes and 2 dehalogenation genes. Single-factor experiments identified the optimal conditions for TCE degradation in soil using the coupling material: glucose concentration at 40 mmol/kg, soil water content at 50%, and bacterial inoculum at 1% (v:w). Under these optimal conditions, the coupled material achieved 86.86% degradation of TCE in soil within 28 days. Further analysis using X-ray photoelectron spectroscopy of micron iron powder, soil Fe(Ⅱ) concentration, and soil physicochemical properties demonstrated that the addition of strain F1 to the soil could disrupt the passivation layer of iron oxide on the surface of micron iron powder, promoting the exposure of its reactive sites and internal reducing active components. This resulted in an in situ self-actuated activation of passivated micron iron powder, leading to an improved removal rate and complete dechlorination of TCE in the soil. Soil microbial high-throughput sequencing revealed that the addition of strain F1 regulated the soil bacterial community, significantly enriching of Escherichia-Shigella species associated with iron-reducing functions. This enrichment facilitated the degradation of TCE in the soil through coupling materials. The functional material plays a crucial role in achieving green treatment and risk control of sites contaminated with chlorinated organic pollutants.

Ab initio molecular dynamics simulations on the combustion mechanism of Al/Fe2O3 nanothermite at various temperatures

Acquiring a comprehensive understanding of the combustion mechanism of nanothermites is crucial for elucidating phenomena and enhancing performance. The ab initio molecular dynamics method was employed to investigate the reaction process of the Al/Fe2O3 nanothermite at various temperatures. The complex combustion behavior and reaction mechanism were qualitatively described in terms of dynamic morphologies, potential energy, atomic density distribution, etc. Results suggest the initial reaction of Al/Fe2O3 is initiated by the migration of interfacial O atoms and the dissociation of Fe-O bonds, subsequently leading to the formation of alumina at the interface, which impedes the further progression of the thermite reaction. The increase in temperature enhances atomic diffusion and provides sufficient energy for the reaction. The interfacial metal Al layer undergoes melting and diffuses into the iron oxide layer, while vacancies generated during the reaction process sustain the continuous migration of internal oxygen atoms. At 2000 K and 3200 K, the initial structures completely collapse, facilitating the inward propagation of the thermite reaction, which subsequently results in the formation of alumina, iron clusters, and intermetallic compounds (AlFe, AlFe3, and Al6Fe). These findings offer significant insights into the combustion reaction mechanisms of nanothermites.

Tuning the toughness, strength, and biological properties of functionally graded alumina/titania-based composites for use in bone repair applications

In this study, functionally graded composite (FGC) was prepared using a high-energy ball mill by fabricating five layers of alumina (Al2O3), titania (TiO2), hydroxyapatite (HA), and iron oxide (Fe3O4), which were sintered at 1100 °C to create an FGC sample. Scanning electron microscopy (SEM), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and weight loss measurements were used to assess bioactivity and biodegradation after immersing samples in simulated body fluid (SBF). Also, the antimicrobial activity and biocompatibility of these layers were evaluated. Furthermore, their electrical, dielectric, and mechanical properties were examined. The results revealed that all sintered layers were bioactive, and adding HA and Fe3O4 enhanced this desired property. Also, S. aureus bacterial growth was inhibited by TiO2 and Fe3O4. Fortunately, the sintered layers showed no cytotoxic effect, validating the ICP findings that demonstrated acceptable biodegradation. Adding HA and Fe3O4 enhanced fracture toughness in another hopeful outcome, which is crucial for biomaterial efficacy and long-term therapeutic success. Moreover, the compressive strength of all the layers and the FGC sample was 191.7, 182.2, 171.18, 159.8, 142.5, and 171.1 MPa. Layers 3, 4, and 5 notably had a compressive strength similar to cortical bone. This means that implanting these layers into human bone will protect the bone around them from stress-shielding action. Finally, the successive increase in HA/Fe3O4 contents increased the electrical conductivity. Accordingly, the prepared FGC sample and its layers are attractive bone substitute materials.

Sulfidation of Nanoscale Zero-Valent Iron by Sulfide: The Dynamic Process, Mechanism, and Role of Ferrous Iron.

Sulfidation of nanoscale zerovalent iron (nZVI) can enhance particle performance. However, the underlying mechanisms of nZVI sulfidation are poorly known. We studied the effects of Fe2+ on 24-h dynamics of nZVI sulfidation by HS- using a dosed S to Fe molar ratio of 0.2. This shows that in the absence of Fe2+, HS- rapidly adsorbed onto nZVI particles and reacted with surface iron oxide to form mackinawite and greigite (<0.5 h). As nZVI corrosion progressed, amorphous FeSx in solution deposited on nZVI, forming S-nZVI (0.5-24 h). However, in the initial presence of Fe2+, the rapid reaction between HS- and Fe2+ produced amorphous FeSx, which deposited on the nZVI and corroded the surface iron oxide layer (<0.25 h). This was followed by redeposition of colloidal iron (hydr)oxide on the particle surface (0.25-8 h) and deposition of residual FeSx (8-24 h) on S-nZVI. S loading on S-nZVI was 1 order of magnitude higher when Fe2+ was present. Surface characterization of the sulfidated particles by TEM-SAED, XPS, and XAFS verified the solution dynamics and demonstrated that S2- and S22-/Sn2- were the principal reduced S species on S-nZVI. This study provides a methodology to tune sulfur loading and S speciation on S-nZVI to suit remediation needs.

Mixed phase iron oxides thin layers by atmospheric-pressure chemical vapor deposition method

This paper provides a simple method for producing a metal oxide thin layer methodology by atmospheric pressure chemical vapor deposition (APCVD) synthesis over stainless steel substrates. This methodology enables the formation of thin iron oxide layers at its performance at various temperatures of 330 °C, 430 °C, and 530 °C. The deposition arises from thermal decomposition of the iron organometallic precursor Fe3(CO)12, forming a thin layer of iron oxide is, by the ozone present in the reaction chamber promoting the deposition of the iron oxide particles over the substrate. The Raman characterization suggest that at 330 °C, a mixture of hematite and magnetite is predominant on the as deposited substrates, also hematite modes show to be more pronounced as the band at 300 cm-1 narrows. Conversely, magnetite is prominent at higher synthesis temperatures, exhibiting a more intense Eg5 mode at 680 cm-1. The particles exhibit a uniform morphology, with both metal oxide phases coexisting. The average diameter of the particles is 50 nanometers as scanning electronic microscopy shows in a transversal sample section.•The formation of particles is attributed to the combination of iron ions +2 and +3 in the deposition process and their interaction with oxygen in the given synthesis parameters at atmospheric pressure chemical vapor deposition (APCVD).

Iron extraction from copper slag by additive-free activation roasting-magnetic separation

Iron grain growth during deep reduction roasting is important for iron enrichment from copper slag (CS) through magnetic separation. In this work, a novel method of additive-free activation roasting, including oxidation and subsequent reduction roasting, was proposed to increase the iron grain size, then the iron was extracted by magnetic separation. The phase transformation of CS during activation roasting was studied by TG, XRD, SEM, and EDS. Results showed that the main mineral of fayalite in CS was decomposed into iron oxides and silica during oxidation roasting, and the thickness of iron oxide layer on the particle surface increased with the oxidation temperature. During reduction roasting, the CS and oxidized copper slag (OCS) were ultimately converted into metallic iron and cristobalite solid solution. In the reduced product obtained at 1150 °C, the iron grain sizes were 6.42 μm and 16.62 μm from CS and OCS-1100 °C, respectively. Furthermore, the Fe content in the magnetic concentrate was 72.86 % in the reduced product of CS while that was 87.85 % in the reduced product of OCS-1100 °C with an Fe recovery of ∼ 85 %. This study opens a new direction for iron enrichment from copper slag.

Predicting Low Sliding Friction in Al-Steel Reciprocating Sliding Experiment after a Controlled Grinding of the Steel Counterface

The aim of this study was to identify the areal surface parameters that correlated with lowering of sliding friction. Different ground surfaces were created on stainless steel and the lubricated sliding friction generated at the contact interface with a flat-faced aluminum pin was studied. The frictional force encountered is an order of magnitude lower for a P1200-finished surface than the other ground surfaces. Using 3D surface profilometry, a unique surface parameter ratio “Spk/Sk” was found to predict the frictional performance of these surfaces. When this surface parameter ratio was less than 1, average sliding friction was close to 0.1. When this ratio was greater than 1, the coefficient was an order of magnitude lower. Using energy dispersive spectrometry, such surfaces after wear showed the presence of a uniform dispersed layer of iron oxide on the surface of the pin. This was absent on the surfaces having high friction, indicating the role of the steel counter surface in building this beneficial transfer layer. Scanning electron microscopy provided topography images to visualize the surface wear. The motivation for the authors was to use a commercially scaled process like precision grinding for the surface modifications on stainless steel.

The use of amines as steel corrosion inhibitors in butanol-gasoline blends

Butanol is an interesting component used for blending gasoline fuels. However, the polar nature of butanol allows the solubility of water and ionic compounds in butanol-gasoline blends (BGBs) making them aggressive to mild steel. Amines, such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentaamine, morpholine, piperazine, and hexamethylenediamine, were tested as corrosion inhibitors for mild steel in BGBs. Additionally, the influence of the acetic acid and sodium chloride concentrations on the inhibition efficiency was examined. Electrochemical impedance spectroscopy andpotentiodynamic polarization were employed for the measurements, complemented by static immersion testing and an XPS surface analysis. The highest inhibition efficiency was demonstrated for diethylenetriamine, triethylenetetramine, andhexamethylenediamine, achieving a value of 95 % or more at aconcentration of 100 mg/L. The formation of ionic pairs involving protonated amines andchlorides was also confirmed. The XPS analysis revealed a very thin passive layer of iron oxides, which may form in the presence of amines, protecting mild steel in BGBs.

Characteristics of zero-valent iron surface oxide films under the catalytic interface reactions by assisting ligands in nitrate-contaminated groundwater

The surface passivation layer coating on zero-valent iron (ZVI) particles impedes the electron transfer from ZVI to nitrate. To enhance the efficiency of nitrate reduction by Fe(0), we tested the chemical process and the thickness of the iron oxide film on the surface of Fe(0) particles, utilizing Fe2+aq in aqueous solution and wheat straw as ligands. A novel principal surface catalyzing reaction was formulated as follows: NO3−+0.67Fe2++2.2Fe0+2.33H2O→NH4++1.18Fe3O4+0.64OH−. When Fe2+aq concentration increased from 0 - 200 mg·L−1, the NO3- removal rate increased from 6.95% to 82.6% respectively during 12 h and it was 48%, 72%, 79% and 94% respectively in Fe0/WS ratio of 0, 0.25, 0.5 and 1 system. Uniform surface iron oxide films formed around the Fe(0) particles within 12 h after the adding Fe2+aq or wheat straw to the Fe(0) system. The composition and thickness of these films were dependent on the quantity of added materials. X-ray diffraction (XRD) analysis revealed that surface oxide iron mainly consisted of Fe2+ or Fe3+ oxides, with Fe3O4 being predominant. The X-ray photoelectron spectroscopy (XPS) etching indicated that the addition of Fe(0)/straw at mass ratios of 1 or system with 20 mg·L−1 Fe2+aq resulted in the thinnest surface iron oxide layer. The study demonstrated that reducing the oxide layer’s thickness was achieved through partial catalysis and enhanced complexation capacity. This reduction was facilitated by the introduction of Fe2+aq or wheat straw into the Fe(0) system, potentially improving proton dissociation and promoting the ligand-assisted dissolution of Fe3+ oxides.

WLI, XPS and SEM/FIB/EDS Surface Characterization of an Electrically Fluted Bearing Raceway

Electrical bearing currents may disturb the performance of the bearings via electro-corrosion if they surpass a limit of ca. 0.1 to 0.3 A/mm2. A continuous current flow, or, after a longer time span, an alternating current or a repeating impulse-like current, damages the raceway surface, leading in many cases to a fluting pattern on the raceway. Increased bearing vibration, audible noise, and decreased bearing lubrication as a result may demand a replacement of the bearings. Here, an electrically corroded axial ball bearing (type 51208) with fluting patterns is investigated. The bearing was lubricated with grease lubrication and was exposed to 4 A DC current flow. It is shown that the electric current flow causes higher concentrations of iron oxides and iron carbides on the bearing raceway surface together with increased surface roughness, leading to a mixed lubrication also at elevated bearing speeds up to 1500 rpm. The “electrically insulating” iron oxide layer and the “mechanically hard” iron carbide layer on the bearing steel are analysed by WLI, XPS, SEM, and EDS. White Light Interferometry (WLI) is used to provide an accurate measurement of the surface topography and roughness. X-ray Photoelectron Spectroscopy (XPS) measurements are conducted to analyze the chemical surface composition and oxidation states. Scanning Electron Microscopy (SEM) is applied for high-resolution imaging of the surface morphology, while the Focused Ion Beam (FIB) is used to cut a trench into the bearing surface to inspect the surface layers. With the Energy Dispersive X-ray spectrometry (EDS), the presence of composing elements is identified, determining their relative concentrations. The electrically-caused iron oxide and iron carbide may develop periodically along the raceway due to the perpendicular vibrations of the rolling ball on the raceway, leading gradually to the fluting pattern. Still, a simulation of this vibration-induced fluting-generation process from the start with the first surface craters—of the molten local contact spots—to the final fluting pattern is missing.

Cable bacteria delay euxinia and modulate phosphorus release in coastal hypoxic systems.

Cable bacteria are long, filamentous bacteria with a unique metabolism involving centimetre-scale electron transport. They are widespread in the sediment of seasonally hypoxic systems and their metabolic activity stimulates the dissolution of iron sulfides (FeS), releasing large quantities of ferrous iron (Fe2+) into the pore water. Upon contact with oxygen, Fe2+ oxidation forms a layer of iron(oxyhydr)oxides (FeOx), which in its turn can oxidize free sulfide (H2S) and trap phosphorus (P) diffusing upward. The metabolism of cable bacteria could thus prevent the release of H2S from the sediment and reduce the risk of euxinia, while at the same time modulating P release over seasonal timescales. However, experimental support for this so-called 'iron firewall hypothesis' is scarce. Here, we collected natural sediment in a seasonally hypoxic basin in three different seasons. Undisturbed sediment cores were incubated under anoxic conditions and the effluxes of H2S, dissolved iron (dFe) and phosphate (PO4 3-) were monitored for up to 140 days. Cores with recent cable bacterial activity revealed a high stock of sedimentary FeOx, which delayed the efflux of H2S for up to 102 days. Our results demonstrate that the iron firewall mechanism could exert an important control on the prevalence of euxinia and regulate the P release in coastal oceans.

High temperature oxidation behavior of CoCrFeNiMo0.2 high-entropy alloy coatings produced by laser cladding

The oxidation behavior of CoCrFeNiMo0.2 high-entropy alloy laser cladding coatings at 700°C and 900°C was investigated. The oxidation kinetics of the alloys at all temperatures followed a parabolic behavior, with the oxidation rates increasing significantly with increasing temperature. The alloy exhibits excellent oxidation resistance at 700 °C. Compared with the original alloy structure, the segregation of Mo element in the alloy is more serious after high-temperature treatment. Compared with 700 °C, the oxidation degree of the alloy is more intense at 900 °C. The reaction between iron and chromium oxides forms a chromite layer, and the rapid diffusion of iron ions in the layer forms an outer layer of iron oxides. As the oxidation proceeds, the oxide film is separated from the metal, and the chromium oxide layer grows between the spinel layer and the metal. The thermodynamics of the reaction was calculated, the oxidation mechanism of the alloy was explored, and a high-temperature model of the alloy was developed. This study expands the potential applications of high entropy alloys in surface engineering.

Performance and Surface Modification of Cast Iron Corrosion Products by a Green Rust Converter (Mimosa tenuiflora Extract)

One of the alternative materials used for conducting conservation treatment of iron artifacts is the rust converter, since it generates barrier properties and more stable oxides. The protective properties and surface modifications from using Mimosa tenuiflora extract as a green rust converter on a gray iron oxide layer were studied. The surface characterization was carried out using a Scanning Electron Microscope coupled to an energy-dispersive X-ray spectrometer (SEM-EDS), along with infrared spectroscopy (IR), Raman spectroscopy, X-ray Diffraction (XRD), and Water Contact Angle (WCA). Electrochemical characterization was performed with an Electrochemical Impedance Spectroscope (EIS) using 3.5 wt.% NaCl as the electrolyte. According to the results of the Raman spectroscopy and XRD, the layer of corrosion products formed after 90 days in the atmosphere was composed of goethite, lepidocrocite, maghemite, hematite, and magnetite. The surface of the corrosion products was transformed with the rust converter into an amorphous and microcracked layer. By IR, the Fe-O and C-O-Fe bonds associated with the iron chelate were found with absorption bands at 1540 and 1567 cm−1, respectively. By XRD, a modification of the magnetite crystallinity was observed. Finally, the Water Contact Angle and the protective capacity of the corrosion products were improved by the presence of the rust converter.

A Review of Oxide Layer Formation and Corrosion Dynamics in Reinforced Concrete

Corrosion is a natural phenomenon that threatens the durability of steel reinforcement in reinforced concrete. Initially, the reinforcement is protected by a layer of iron oxides known as the passivation layer, formed due to the high alkalinity of the concrete medium. This passivation layer acts as a barrier, preventing the progression of corrosion by isolating the steel from corrosive elements. However, the incorporation of corrosion catalysts such as chlorides or carbon dioxide can destroy this protective layer. Once the passivation layer is compromised, reinforcement corrosion begins, leading to the formation of more complex iron oxides, such as rust (Fe2O3). These corrosion products influence the characteristics of the environment around the reinforcement, creating cracks in the concrete and facilitating the penetration of water and other corrosive agents. This process promotes the spread of corrosion within the reinforced concrete structure, accelerating its deterioration. An extensive analysis of the development of the oxide layer on steel reinforcement is given in this article, and its impact on the interface between reinforcement and concrete. It explores the mechanisms by which the passivation layer is formed and the conditions that lead to its failure.

Decorative Coatings of the Saint Demetrius Basarabov Reliquary’s Wooden Pedestal

This study presents the results and information revealed by in-depth physicochemical investigations carried out on an 18th-century polychrome wooden pedestal of the holy relics of Saint Demetrius Basarabov preserved at the Romanian Patriarchy of Bucharest. The preliminary stylistic observations and examinations on its present state of conservation were followed by optical microscopy, X-ray fluorescence (XRF) spectrometry, and attenuated total reflectance Fourier-transform infrared spectroscopy (FTIR-ATR) analysis performed in order to adopt an appropriate restoration treatment for bringing the artifact, as close as possible, to its original appearance as well as for dating/attributing the artifact and assessing its state of conservation. It was revealed that several interventions were subsequently undertaken on the original gilded surface consisting of a gypsum support layer with an iron oxide layer of bolus on which a silver foil or a gold foil and a natural resin on top of it as a protective layer were applied. The regilding and later restoration interventions consisted in applying, over the original, layers of a copper–zinc alloy foil (Dutch metal as an imitation of gold) with a resin layer of vernis over it. The final decision on the restoration intervention was taken based on the scientific analysis outcome. This work attempts also to highlight the importance of the interdisciplinary collaboration between researchers, conservation scientists, restorers/conservators, and curators for the preservation and valorization of the historical religious Romanian heritage artifacts, largely unknown worldwide.

Oxalate-modified microscale zero-valent iron for trichloroethylene elimination by adsorption enhancement and accelerating electron transfer

Trichloroethylene (TCE) with trace concentrations is often detected in soils and groundwater, posing potential damages to public health. The elimination of TCE can be achieved through reductive dechlorination using zero-valent iron (ZVI). However, ZVI usually suffers from the presence of passive iron (hydro)oxides layer and low electron transfer rate, thus leading to the unsatisfactory reactivity. Herein, we fabricated oxalated ZVI (Ox-ZVIbm) by mechanical ball-milling of micro-scale ZVI and H2C2O4·2H2O to modify the ZVI surface composition. To be specific, the modification of the iron oxide shell by oxalic acid facilitated the generation of unsaturated coordination Fe(II), enhancing TCE adsorption. Furthermore, the formed FeC2O4 on the iron oxide shell improved electron transfer efficiency, contributing to the enhanced TCE reductive dechlorination. Impressively, the rate of TCE degradation by Ox-ZVIbm was 10-fold higher than that of ZVIbm without oxalate modification. Moreover, Ox-ZVIbm samples were filled in a laboratory Permeable Reactive Barriers (PRB) column to treat actual underground wastewater containing TCE pollutants. The effluent concentration of TCE maintained steadily below 0.21 mg/L for over 10 days, complying with the National Groundwater Class IV standard (GBT 14848–2017). This marks a significant step toward practical groundwater treatment.

Seeded growth synthesis, reshaping, and damping of the localized surface plasmon resonance in Au@Fe2O3 nanoparticles

Core@shell Au@Fe2O3 nanoparticles with different iron oxide content were synthesized by a seeded-growth approach. The morphology and structural analysis were carried out by transmission electron microscopy (TEM and HR-TEM) and X-ray diffraction (XRD). The oxidation state of the iron was determined through cyclic voltammetry measurements. The plasmonic resonance modes were investigated by Infrared (IR) and UV–vis spectroscopy. The morphology analysis of Au nanowires (AuNW’s) shows a modification from NW’s (seeds) to faceted nanoparticles, while spectroscopic studies show a disappearance of the Propagation Surface Plasmon Resonance (PSPR) due to this change. Localized Surface Plasmon Resonance (LSPR) is damped due to the aggregation of the iron oxide layer.

Effect of Nitrocarburizing and Post-oxidation Processes on the Microstructure and Surface Properties of AISI 4140 Steel

AISI 4140 çeliği, orta karbonlu düşük alaşımlı çelikler sınıfında yer almakta olup, yüksek sertleşebilirliğe sahip olması ve nispeten ekonomik bir çelik olması nedeniyle endüstride yaygın olarak kullanılmaktadır. AISI 4140 çeliği aynı zamanda nitrürlebilen çelikler arasında yer almaktadır. Nitrürleme işlemiyle, yüzeyde elde edilen sert nitrür tabakası sayesinde sadece aşınmaya dirençli bir yüzey değil aynı zamanda yorulma dayanımında da artış sağlanmaktadır. Bu çalışmada, düşük basınçlı gaz nitrokarbürleme işlemi ve farklı sürelerde son oksidasyon işlemi uygulanmış AISI 4140 çeliğinin mikroyapısal ve yüzey özellikleri araştırılmıştır. Bu amaçla, AISI 4140 çelik numuneler, 850 °C'de 60 dk östenitlenmiş 60 °C’de yağda soğutulmuştur. Soğutma sonrası numuneler 630 °C’de 60 dk temperlenmiştir. Gaz nitrokarbürleme işlem basamakları; 350 °C’de 45 dk ön oksidasyon, 550 °C’de 90 dk nitrürleme ve 550°C’de 480 dk nitrokarbürleme uygulanmış ve ardından numuneler 45-180 dakika aralığında su buharı kullanılarak son oksidasyon işlemine tabi tutulmuştur. Mikroyapısal karakterizasyon çalışmaları optik mikroskop, tarama elektron mikroskobu (SEM), enerji dağılımlı X ışını spektrum analizi (EDX), X ışını kırınımı (XRD) analizi, mikrosertlik ve yüzey pürüzlülüğü ölçümleriyle gerçekleştirildi. X ışını analiz sonuçlarından, numunelerin yüzey katmanının demir nitrür, ɛ-Fe2-3N ve ɣ’-Fe4N fazlarını ve demir oksit (Fe3O4) içerdiği tespit edilmiştir. Son oksidasyon süresi arttıkça, demir oksit (Fe3O4) tabaka kalınlığını arttığı belirlendi. Nitrokarbürlenmiş ve son oksidasyon işlemi uygulanmış AISI 4140 çelik numuneler içerisinde, en iyi sertlik derinliği, yüzey sertliği ve yüzey pürüzlülüğü birleşimi 150 dakikada son oksidasyon uygulanmış elde edilmiştir.

Iron-doped cobalt nitride as an efficient electrocatalyst towards energy saving hydrazine assisted seawater splitting in near neutral to highly alkaline pH achieving industry level current density

Replacing sluggish anodic oxygen evolution reaction by hydrazine oxidation reaction in seawater electrolysis is one of the smartest ways of getting multiple benefits as it offers an energy saving route for hydrogen production keeping the cell voltage way smaller than responsible voltage for corrosive chloride oxidation. Here, we report iron-doped Co3N as highly active electrocatalyst towards hydrazine oxidation reaction and hydrogen evolution reaction in wide pH range of 7–14. The two-electrode electrolyser system reached industry scale current density of 1000 mA cm−2 at ultralow cell voltage of 0.65 V, and found sustainable at 500 mA cm−2 over 95 h in hydrazine assisted alkaline seawater splitting. The electrolyser system also achieved 200 mA cm−2 current density at 0.75 V in hydrazine assisted neutral seawater medium. Interestingly, a thin amorphous iron oxide layer formed in Fe-doped Co3N provided much needed protection during electrocatalysis offering long term stability at industry level current density.

Influence of Artificially Altered Engine Oil on Tribofilm Formation and Wear Behaviour of Grey Cast Cylinder Liners

This work investigates the influence of altered engine oil on the tribological performance, focusing in particular on wear and interconnected tribofilm formation. For this purpose, Zinc dialkyldithiophosphate (ZDDP) additivated engine oils of different degradation levels, produced in an artificial oil alteration process, were used in tribometer tests with a nitride steel piston ring against a grey cast iron cylinder liner model contact. Parameters were chosen to simulate the boundary and mixed lubrication regime typical for the top dead centre conditions of an internal combustion engine of a passenger car. Wear of the cylinder liner specimens was continuously monitored during the tribometer tests by the radio-isotope concentration (RIC) method, and tribofilms were posteriorly investigated by X-ray photoelectron spectroscopy (XPS). The results clearly show that the steady-state wear rates for experiments with altered lubricants were significantly lower than for the experiments with fresh lubricants. XPS analysis on the formed tribofilms revealed a decrease in sulphide and an increase in sulphate states for altered oils evaluated at 120 °C oil temperature, correlating with a decrease in steady-state wear rate. This finding emphasizes the role of sulphate species in the tribofilm formation process and its anti-wear capabilities, in contrast to the sulphide species and the (poly-)phosphate species, as outlined in most of the ZDDP literature. Moreover, the RIC signal that represents the amount of wear in the engine oil showed a decrease over time for specific altered lubricants and test conditions. These “negative” trends in the wear signal are remarkable and have been identified as an incorporation of wear particles from the lubricant into the tribofilm. This finding is supported by XPS results that detected an iron-oxide layer with a remarkably similar quantity within the tribofilm on the surface. Based on these findings, an assessment of the minimum film formation rate and particle incorporation rate was achieved, which is an important basis for adequate tribofilm formation and wear models.