Fe Substrate Research Articles

Fabrication of composite coatings with core-shell nanofibers and their mechanical properties, anticorrosive performance, and mechanism in seawater

Maintaining or even improving the anti-corrosion performance of coatings while enhancing their mechanical properties is an active research area. Here, polyacrylonitrile nanofibers (PAN-NFs) filled with benzotriazole (BTA) as an inhibitor were created via a coaxial electrospinning technique and directly deposited on a metal surface. The epoxy resin was then covered to form composited coatings. The as-prepared coatings revealed better mechanical properties and high protective ability than unprocessed coatings. The PAN-NFs/BTA system offered long-term sealing function when the coatings were damaged. Molecular dynamic models were then employed to further confirm that the healing agent releasing from the composite coating could prevent Fe substrate from eroding by water molecules.

Synthesis of Monocrystalline Graphite on Ni and Fe Substrates

Synthesis of Monocrystalline Graphite on Ni and Fe Substrates

Enhanced adsorption of graphene oxide on iron surface induced by functional groups

Recent experiments have shown that graphene (Gr) and graphene oxide (GO) as coatings can be adsorbed on steel to effectively protect the surface. In this study, the density functional theory calculations have been carried out to investigate the effect of functional groups (hydroxyl and epoxy groups) on the adsorption of GO on iron surface. Our results show that the increased functional groups make the adsorption of GO on iron surface more favorable, which originates from the enhancement of localized C–Fe bonds around the functional groups. Within the maximum coverage of functional group on GO studied in this work, the maximum binding energy between GO (the ratio of oxygen to carbon is 0.09) and the Fe(1 1 0) surface is more than twice that of Gr/Fe model, suggesting that the introduction of functional groups on graphene basal plane can significantly improve the interaction strength of GO with the Fe substrate. This work provides an atomic-level insight into the adsorption mechanism of graphene-based materials on steel.

Intermetallic formation of Al-Fe and Al-Ni phases by ultrafast slurry aluminization (flash aluminizing)

Aluminizing of Fe and Ni-based substrates is a conventional process often made by gas phase related techniques (CVD, pack cementation and above the pack), whereby the coating thickness is controlled by solid-state diffusion. Similar coatings can be achieved by slurry aluminizing where self-propagating high temperature synthesis and solid-state diffusion mechanisms are involved. The present work investigates ultrafast (5 min annealing) aluminization to reduce coating time and compares the results on pure iron and nickel substrates with a conventional slurry aluminizing treatment (2 and 5 h). The use of fast heating ramps (25 and 100 °C/min) led to outwardly diffused coatings even with very high Al slurry activities. On nickel, the coatings were homogeneous while on iron, Kirkendall porosity occurred in the outermost layers due to the great dissolution of Fe in the Al melt and its subsequent outward diffusion towards to the Al source.

Improved epitaxial growth of TbAs film on III–V semiconductors

In order to achieve high epitaxial quality of rocksalt TbAs, the authors studied the molecular beam epitaxy growth of TbAs films on zincblende (001) GaAs and (001) InP:Fe wafers. Despite the opposite strain condition of TbAs on these two substrates, mixed-orientation TbAs growth was observed on both substrates. However, the nucleation time and the continuing growth of the TbAs misoriented domains were influenced by the substrate type. By suppressing the growth of misoriented domains in the TbAs film, enhanced single-crystal orientation of TbAs grown on the (001) InP:Fe substrate was observed as compared to the (001) GaAs substrate. In addition, the cube-on-cube epitaxial arrangement of (001) TbAs with a thick film of up to ∼1150 nm is maintained on the (001) InP:Fe substrate but not on the (001) GaAs substrate. The improved TbAs film growth on the InP:Fe substrate exhibited enhanced optical properties when compared to that grown on the GaAs substrate, including a threefold reduction in the scattering rate. This largely improved optical property highlights the importance of increasing the epitaxial quality of TbAs films for future optoelectronic as well as other applications.

Microstructures, interface reaction, and properties of Sn–Ag–Cu and Sn–Ag–Cu–0.5CuZnAl solders on Fe substrate

In this paper, microstructures, interface reaction, and stress–strain response of Sn–3.8Ag–0.7Cu and Sn–3.8Ag–0.7Cu–0.5CuZnAl solders on Fe substrate were investigated systematically. The interface reaction and the growth behavior of FeSn2 intermetallic compounds (IMC) at two solder joints interface after 250 °C soldering with 1 min, 10 min, and 60 min are shown. The results indicate that the growth rate of FeSn2 IMC of Sn–3.8Ag–0.7Cu/Fe solder joints was higher than that of Sn–3.8Ag–0.7Cu–0.5CuZnAl/Fe solder joints, the addition of 0.5% CuZnAl particles can decrease the growth rate of interfacial FeSn2 IMC layer with the reduction of elements diffusion coefficient. Based on finite element simulation, it is demonstrated that the addition of CuZnAl particles can decrease the von Mises stress and equivalent creep strain of Sn–3.8Ag–0.7Cu/Fe solder joints, due to the decrease of FeSn2 thickness with the addition of CuZnAl particles, which can enhance the reliability of Sn–3.8Ag–0.7Cu/Fe solder joints.

Growth of High-Quality Superconducting FeSe0.5Te0.5 Films on Pb(Mg1/3Nb2/3)0.7Ti0.3O3 and Electric-Field Modulation of Superconductivity.

Heterostructures composed of superconductor and ferroelectrics (SC/FE) are very important for manipulating the superconducting property and applications. However, growth of high-quality superconducting iron chalcogenide films is challenging because of their volatility and FE substrate with rough surface and large lattice mismatch. Here, we report a two-step growth approach to get high-quality FeSe0.5Te0.5 (FST) films on FE Pb(Mg1/3Nb2/3)0.7Ti0.3O3 with large lattice mismatch, which show superconductivity at only around 10 nm. Through a systematic study of structural and electric transport properties of samples with different thicknesses, a mechanism to grow high-quality FST is discovered. Moreover, electric-field-induced remarkable change of Tc (superconducting transition temperature) is demonstrated in a 20 nm FST film. This work paves the way to grow high-quality films which contain volatile element and have large lattice mismatch with the substrate. It is also helpful for manipulating the superconducting property in SC/FE heterostructures.

Surface Interactions between Water-in-Oil Emulsions with Asphaltenes and Electroless Nickel-Phosphorus Coating.

Surface interactions between emulsion drops and substrate surfaces play an important role in many phenomena in industrial processes, such as fouling issues in oil production. Investigating the interaction forces between the water-in-oil emulsion drops with interfacially adsorbed asphaltenes and various substrates is of fundamental and practical importance in understanding the fouling mechanisms and developing efficient antifouling strategies. In this work, the surface interactions between water drops with asphaltenes and Fe substrates with or without an electroless nickel-phosphorus (EN) coating in organic media have been directly quantified using the atomic force microscope drop probe technique. The effects of asphaltene concentration, organic solvent type, aging time, contact time, and loading force were investigated. The results demonstrated that the adhesion between water drops and the substrates was enhanced with higher asphaltene concentration, better organic solvent to asphaltenes, longer aging time, longer contact time, and stronger loading force, which was due to the growing amount and conformational change of asphaltenes adsorbed at the water/oil interface. Meanwhile, the adhesion between the water drop and the EN substrate was much weaker than that with the Fe substrate. The bulk fouling tests also showed that EN coating had a very good antifouling performance, which was in consistence with the force measurement results. Our work sheds light on the fundamental understanding of emulsion-related fouling mechanisms in the oil industry and provides useful information for developing new coatings with antifouling performances.

In situ electrodeposition of conducting polymer/metal oxide composites on iron electrode for energy storage applications

Conducting polymers and their metals or metal oxides-based composites are promising for applications in aerospace engineering, construction, computer chips, electronic circuits, energy storage systems, catalysis of reaction and so on. Supercapacitor electrodes and devices comprising polymers/metal oxides composites are envisaged to bridge the gap between existing carbon-based supercapacitors and batteries to form units of intermediate specific energy. In this work, polyaniline (PAni) and its composite with MnO2 were successfully deposited by electrochemical method. Simultaneous polymerization of aniline to PAni, and in situ formation and incorporation of MnO2 into the PAni matrix, and their deposition on Fe substrate took place during the cycling of potential in oxalic acid solution containing aniline and a salt of manganese. Elemental characterization and investigation of morphology and microstructure of the deposits were performed by infra-red, UV–visible reflectance and energy dispersive X-ray spectroscopy and scanning electron microscopy. The band gap energy of PAni was substantially higher compared to PAni/MnO2 composite. The specific capacitance of the electrodes prepared was investigated using cyclic voltammetry and charge–discharge test by chronopotentiometry. Fe-PAni and Fe-PAni/MnO2 composite modified electrodes exhibited excellent supercapacitive property, energy density and power density compared to their bulk Fe electrodes in aqueous sodium sulfate solution.

Effect of Surface Roughness on the Formation of Nano-to-Mirco Patterns Using Pattern Transfer Printing

The ability to form high quality nano-/micro- patterns is very important for the nanofabrication of high-density electronic devices. However, remaining challenges have yet to be resolved, including low quality roughness, low pattern resolution, and the highly complex process. In this study, we suggest a novel and simple method for creating high quality patterns, controlling the surface roughness of the target substrates with a polishing process. We systematically investigated the effect of surface roughness on pattern generation, using a nanotransfer printing (nTP) process on target Al2O3 substrates. We successfully formed highly ordered nanoscale functional patterns on well-defined surfaces, using a mirror-polishing process, compared to normally-polished substrates. In addition, we demonstrated well-printed Sn nanopatterns on various metal (Cu and Fe) substrates. Close-up scanning electron microscope (SEM) images clearly show welldefined patterns on the mirror-polished substrates. Based on these results, we expect that by mechanically modifying substrate surfaces, the yield and quality of pattern formation can be improved, and that this approach can be extended to other patterning methods. Key words: surface modification, polishing, nanotransfer printing

Visible-light-assisted condensation of ultrasonically atomized water vapor on LiNbO3:Fe crystals.

Optically massive trapping of the moisture in the air into an adjacent surface is a potential technique in the fields of bacterial adhesion and microfluidic generation, which is quite important to the development of LN-based biological lab-on-chips. Here we demonstrate on a LiNbO3:Fe substrate the visible-light-assisted condensation of the water vapor in a flowing stream created by an ultrasonic atomizer. Through analyzing the dynamic processes of the visible-light-assisted water condensation at different illumination intensities, it is found that the extent of the water condensation, the bending angle of water vapor trails and the interaction range of the condensation effect are highly dependent on the illumination intensity. According to these findings and the simulated trajectories of the water vapor stream at different illumination intensities, we propose that this visible-light-assisted water condensation is an aggregation process of tiny water droplets driven by the dielectrophoretic interaction of inhomogeneous photovoltaic field and also an electrostatic screening course of photovoltaic charges through the charged evaporation of condensed water. The prolonged condensation of water vapor after a high-intensity illumination and that of oil vapor at a super-low evaporation rate are also studied, and the agreement between the simulation and experimental results reinforces the above mechanism. The reported technique, employing the inexpensive, safe-for-cell visible laser beam, is quite convenient for the controllable generation of various biological microdroplets, and thus it is promising for the microfluidic functionality integration of LN-based biological lab-on-chips.

Spin-flip excitations induced by dehydrogenation in a magnetic single-molecule junction.

Recent scanning tunneling microscopy experiments on electron transport through iron(ii) phthalocyanine (FePc) molecules adsorbed on Au(111) surfaces have revealed that the measured differential conductance signals can be modulated through a selective dehydrogenation process [R. Li et al., Chem. Commun. 54, 9135 (2018)]. To understand the physical origin of the variation of line shapes in the measured dI/dV spectra, we employ a first-principles-based quantum transport simulation to calculate the electronic structures and transport properties in the dehydrogenated FePc/Au(111) composite system. Theoretical results indicate that the removal of eight outermost hydrogen atoms in the FePc molecule distorts the planar molecular conformation by increasing the distance between the Fe center and substrate and thus breaks the ligand field exerted on the Fe 3d orbitals. Such variations lead to a weaker coupling with the substrate along with a different local electronic configuration of the Fe center compared with that of the intact case, which is responsible for the suppression of Kondo resonance and the appearance of spin-flip excitation in the system. The simulated dI/dV plots are consistent with the experimental observations, showing the typical step features at finite bias associated with spin-flip excitations of a spin-1 quantum magnet. These findings provide important insights into the electron correlation effects modulated by the structural and chemical environment of the molecular spin center.

Ferroelectric films on metal substrates: The role of thermal expansion mismatch on dielectric, piezoelectric, and pyroelectric properties

We present here a comprehensive analysis of the effect of thermal stresses on the functional properties of ferroelectric oxides on metal substrates. We use a Landau-Devonshire formalism to quantitatively assess the role of in-plane thermal strains that arise from the coefficient of thermal expansion (CTE) mismatch between lead zirconate titanate [PbZrxTi1–xO3, PZT x/(1 – x)] films and Al, Cu, Fe, Ni, and Ti-based substrates. Specifically, we compute Curie transition temperatures, spontaneous polarizations, dielectric permittivities, piezoelectric coefficients, and pyroelectric responses of tetragonal PZT compositions as a function of the growth/processing temperature. To provide a rapid evaluation, we also develop Ashby diagrams of property coefficients as a function of PZT composition, processing temperature, and CTE of the substrate. Our results show that thermal strains in PZT may significantly alter the ferroelectric transition temperature, dielectric, piezoelectric, and pyroelectric properties. For example, for PZT 50/50 films on Ni-based superalloys processed/annealed at 700 °C, we predict monodomain intrinsic dielectric, piezoelectric, and pyroelectric responses to be 234, 152 pC/N, and 0.021 μC cm−2 °C−1, respectively, compared to bulk PZT 50/50 values of 381, 326 pC/N, and 0.045 μC cm−2 °C−1. These are substantial variations which show that thermal strains must be considered in the design and development of built-in functionality obtained through ferroelectric films in structural, aerospace components.

All-optical splitting of dielectric microdroplets by using a y-cut-LN-based anti-symmetrical sandwich structure.

We demonstrate an all-optical active mode of dielectric microdroplet splitting in a sandwich structure consisting of two anti-symmetrical y-cut LN:Fe substrates. The dynamic process of the microdroplet splitting and the simulation of the electrostatic interaction inside the sandwich gap show that the combination of two anti-symmetrical substrates are capable to provide a sufficient dielectrophoretic force and to reduce the unbalance of the drag forces for a stable and efficient splitting of the microdroplet. The dependences of the splitting time on the illumination intensity and the initial microdroplet size are also studied, and the results show that the microdroplet splitting process is fully governed by the establishment of the superposed photovoltaic field inside the sandwich gap. A key ratio Er/E0, representing the microdroplet splitting difficulty for a given sandwich structure, is found linearly dependent on the initial microdroplet size. These points are quite important to the integration of splitting functionality on the LN-based microfluidic chip.

Waterborne bio-based epoxy coatings for the corrosion protection of metallic substrates

Corrosion of engineering metals and alloys poses a threat to the safety and reliability of engineering structures. In this work, an environmentally-friendly hydrophobic coating was developed based on a bio-based epoxy with addition of nanoparticles, a silane coupling agent (3-glycidyloxypropyl) trimethoxysilane (GLYMO), and a hydrophobic curing agent. This coating was applied onto Fe substrates via spin-coating. The water contact angle of ˜153.0° and sliding angle of ˜14.3° were obtained for an optimal coating with 25.0 wt.% nanoparticles loading. The prepared coating exhibited high hydrophobic performance when immersed in water and common solvents including ethanol and acetone for 48 h. Besides, after exposure to continuous cycles of UV irradiation and water condensation for 24 h, this optimal coating was able to retain a high hydrophobicity at contact angle of ˜142.7°, indicating its good weathering resistance. Furthermore, the electrochemical measurements demonstrated that the optimized coating displayed a 2-orders-of-magnitude reduction in its corrosion current density and a positive shift of 0.344 V in its corrosion potential. The corresponding inhibition efficiency was 93.75%. The adsorption energy and diffusion coefficient were calculated using molecules dynamic simulation to further understand the corrosion inhibition behavior at the molecular scale. This green and bio-based water-repellent epoxy coating holds great potential towards corrosion inhibition for other metallic structures in harsh working environment.

Real‐Time Operation of Photovoltaic Optoelectronic Tweezers: New Strategies for Massive Nano‐object Manipulation and Reconfigurable Patterning

AbstractOptical and optoelectronic techniques for micro‐ and nano‐object manipulation are becoming essential tools in nano‐ and biotechnology. Among optoelectronic manipulation platforms, photovoltaic optoelectronic tweezers (PVOTs) are an emergent technique that are particularly successful at producing permanent nanoparticle microstructures. New strategies to enhance the capabilities of PVOT, based on real‐time operation, are investigated. This optoelectronic platform uses z‐cut LiNbO3:Fe substrates under excitation by a Gaussian light beam. Unexpected results show that during illumination, metallic particles previously deposited on the substrate are ejected from the light spot region. This behavior differs from the trapping phenomenon observed in previous work on PVOT operation, using a sequential method in which illumination is prior to particle manipulation. To discuss the results, a novel mechanism of charge exchange between particles and the ferroelectric substrate is proposed. Applications of this repulsion behavior are investigated. On the one hand, either particle repulsion or trapping in the illuminated region can be obtained by simply light switching on/off. On the other hand, by moving the light spot, different kinds of arbitrarily shaped tracks along the light path, either empty or filled with particles, are obtained. The results demonstrate new key capabilities of PVOT, such as pattern drawing, erasure, and reconfiguration.

Synthesis and structural control of Fe-based porous layer on Fe substrate for joining with resin parts using combustion reaction

A porous Fe/TiB2 composite layer was synthesized on an Fe substrate by a powder metallurgy process using combustion reactions among Fe, Ti, and B to achieve Fe/resin joints through interpenetrating phase layers. The effects of Fe particle size and the blending ratio of the raw powder mixture on the porous structure, roughness of the top surface of the porous layer, and adhesiveness between the porous layer and Fe substrate were investigated. The peak temperature measured with a thermocouple increased with increasing Fe particle size and blending ratio of Ti and B. An increase in the peak temperature does not affect the porosity of the porous layer. Higher peak temperatures increase the pore size and change the pore morphology from open to semi-closed (although pores are not completely isolated). The change in pore morphology prevents the exposure of pores on the top surface of the porous layer, resulting in decreasing surface roughness. Moreover, an increase in the maximum temperature promotes bonding between the Fe substrate and porous layer. These results are discussed in view of the thermodynamic assessment using the calculated equilibrium phase diagram.

Influence of tip adhesion on nanoindentation and scratching

Using molecular dynamics simulation, we study the influence of tip adhesion on nanoindentation and scratching. By using a model pair potential between tip atoms and substrate atoms, we can arbitrarily change the adhesion strength. For the prototypical case of a diamond tip and a bcc Fe substrate, we find that with increasing adhesion strength, the indentation hardness and also the normal hardness during scratching decreases. Even more pronounced is a strong increase of the transverse force and hence of the friction coefficient during scratching. The indent pit becomes atomically rough, and the pileup produced during scratch increases with increasing adhesion strength. On the other hand, the length of the dislocations produced and the spatial extent of the plastic zone shrinks.

Surface‐enhanced Raman scattering studies of gold‐coated ripple‐like nanostructures on iron substrate achieved by femtosecond laser irradiation in water

AbstractDuring the past several years, numerous efforts have been accomplished on designing efficient surface‐enhanced Raman scattering (SERS) substrates with high sensitivity, good reproducibility, and recyclable nature. However, it still remains a significant challenge to realize all these qualities in a single substrate. We have fabricated ripple‐like nanostructures (NSs) on Iron (Fe) substrate using femtosecond (fs) laser irradiation of Fe target in distilled water. These ripple‐like structures had periodicities in the range of ~90–190 nm, which was confirmed from the analysis of field emission scanning electron microscope (FESEM) data. We subsequently deposited a thin layer of gold on these ripple‐like Fe NSs using thermal evaporation. Later, these coated NSs were effectively utilized as SERS substrates for methylene blue (MB) detection and were found to be sensitive evident from the data obtained at a very low concentration of 500pM. Furthermore, we observed that the SERS signal variations on the substrate were <11.2% indicating the reproducible nature of these substrates. Additionally, we demonstrate that these substrates can be reused (we establish this for three times consecutively) by detecting malachite green (MG) and an explosive molecule (picric acid, PA) followed by the mixture compound (Rhodamine 6G+MB) through employment of simple cleaning procedures. The detected molecular concentrations in terms of masses were found to be 3.2 pg, 36.5 pg, and 23 ng for MB (for a concentration of 500pM), MG (for a concentration of 5nM), and PA (for a concentration of 5μM), respectively. Furthermore, these Fe NSs exhibited superior batch‐to‐batch reproducibility with a relative standard deviation (RSD) value of ~l4%. The proposed method of fabricating ripple structures as SERS platforms are highly feasible, reliable, and have great potential for on‐site detection of several analyte molecules with an easily transportable Raman spectrometer.

Fabrication and characterization of the stable Ag-Au-metal-organic-frameworks: An application for sensitive detection of thiabendazole

Thiabendazole is likely to cause thyroid hormone imbalances and liver damage at high doses. Conventional detection methods are time-consuming with cumbersome pretreatment or insufficient sensitivity. Herein, Metal-organic framework (MOF, Mil-101(Fe))modified with inositol hexaphosphate (IP6)is fabricated by a solvothermal method and thenAg-Au-IP6-Mil-101(Fe) is obtained by in original position of MOF surface with the aid of IP6. The as-prepared Ag-Au-IP6-Mil-101(Fe) substrate exhibits high stability. Certain target molecules containing atoms of N or S could access the proximity to the surface of Au-IP6-Mil-101(Fe) substrate by the strong interaction with Fe3+ in the MOF, leading to improvement of SERS detection sensitivity. As a real application, Ag-Au-IP6-Mil-101 based Raman strategy is developed to achieve rapid detection of thiabendazole in juice and has good linearity in the range of 1.5 ppm˜75 ppm with correlation coefficient (R2) of 0.986. The detection limit for TBZ reached 50 ppb in juice sample, which meets the requirement of the national standard. In addition, the Ag-Au-IP6-Mil-101(Fe)substrate possessing peroxidase-like activity could degrade organic dyes within a short time.