Applied Surface Science Advances最新文献

This paper investigates the impact of duplex plasma nitriding and diamond-like carbon (DLC) coatings on the pure fatigue and fretting fatigue properties of 16MnCr5 steel extracted from industrial piston pins used in combustion engines. Two different nitriding and DLC coating processes were performed: "DLC-A" and "DLC-B". The Raman spectrometry and microhardness tests were utilized to evaluate the formation of DLC coating on the sample. Subsequently, the pure and fretting fatigue tests (at 350 MPa and under 100 Hz of the frequency) were performed on as-cast and DLC-coated specimens to obtain the effect of coatings on the fatigue behaviors of the 16MnCr5 steel. Finally, the formation of the DLC layer and the fracture mechanisms were also briefly investigated using field-emission scanning electron microscopy. Then, the obtained results demonstrated that DLC coating ("DLC-B") increased the fatigue lifetime of 16MnCr5 steel by 47.7 % and 85.3 % in pure and fretting fatigue conditions, respectively. This layer can improve the surface properties of engineering materials and components, which can enhance the fatigue lifetime by increasing microhardness and compressive residual stress, reducing wear and friction, and improving adhesion between the substrate and coating. However, due to the white layer, the “DLC-A” improperly enhanced the material performance.

Superhydrophobic/Icephobic tin oxide honeycomb-like nanostructures were synthesized on copper surfaces via facile controlled hydrothermal method. Effects of two crucial fabrication parameters including etching treatment variables and presence the seed layer, on the morphology and wettability of the resulted coating were determined. The chemical composition, wettability characteristics, and topographical properties of the samples were characterized by FE-SEM, stylus profilometry, contact angle measurement, and ATR-FTIR analyses. The wettability evaluations confirmed that the tin oxide deposited on the copper oxide (seed layer) exhibited excellent superhydrophobic properties. The prepared hierarchical surfaces showed high water contact angles (CA) as well as 169. $5^{\circ }\pm 1^{\circ }$ with a contact angle hysteresis (CAH) of 5°± 1°. Moreover, the results confirmed that the etching treatment and the presence of the seed layer can promote the morphology to a uniform state. The ice adhesion strength of the obtained superhydrophobic surfaces reached to 30.4 kPa, showing an excellent ice-phobicity. The mechanical resistance and/or sustainability of the optimized sample was also passed successfully under 10 abrasion test cycles.

In this work, oxygen reduction reaction (ORR) catalysts were developed from a precursor of spent coffee ground-based biochar. Nitrogen doping was achieved via urea addition preceding a pyrolysis synthesis process, yielding nitrogen-doped biochar (NDB). Cobalt was deposited onto the NDB surface using a non-conventional ball-milling procedure. The microstructure of the synthesized samples was studied through Scanning Electron Microscopy (SEM), where a rather distorted surface, highlighted by prominent wrinkles (which doubled the surface area at 50.58 m²/g), was shown for nitrogen-doped samples. Moreover, the high energy ball-milling technique shows an almost perfect coverage of cobalt nanoparticles on the biochar surface through SEM/EDS and Raman results. Additionally, electrochemical testing was conducted using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Cyclic voltammetry measurements conducted under nitrogen (inert) and oxygen-saturated alkaline solution (0.1 M KOH) conditions showed that nitrogen doping enhances the oxygen reduction reaction current (-1 vs -0.59 mA.cm⁻¹ at -0.3 V vs Hg/HgO) and slightly reduces the onset potential compared to pristine biochar. Depositing cobalt onto the NDB surface had a minor adverse effect on the onset potential, but significantly increased the oxygen reduction reaction current, reaching a value of -2.09 mA.cm⁻² at -0.3 V vs Hg/HgO. All catalysts were compared to a commercial carbon supported platinum catalyst (Pt10%C) to showcase the potential room of improvement for the developed catalysts.

In this study the heavy metals (Cu²⁺, Pb²⁺, Hg⁺²) were removed from waste water using two types of sorbents, namely, MoO₃ and MoO₃ doped with 12 %Y₂O₃ were synthesized by solgel method. The as-prepared oxides were characterized using X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS). A combination of quantitative and qualitative analysis techqnieus, portable X-ray fluorescence (pXRF) and laser-induced breakdown spectroscopy (LIBS) were used to evaluate the removing efficency. Calibration curves were performed to elucidate the limit of detection (LOD) of the Laser-Induced Breakdown Spectroscopy (LIBS) technique for the removal process The LOD were 1.65, 2–21 and 0.98 ppm for Cu, Pb and Hg respectively. The results indicated that the Y₂O₃-doped α-MoO₃ has a consistently greater removal efficiency compared to MoO₃. The removal effecieny of Hg²⁺, Pb²⁺ and Cu²⁺ was 95 %, 33 % and 21 % respectively with MoO₃ while it was 98 % 63 % 35 % for MoO₃ doped Y₂O₃, The results proved also that MoO₃ and MoO₃ doped Y₂O₃ nanoparticles can be utilized as cost effective adsorbent material for heavy metal removal in wastewater. The study showed the potential of using Laser-Induced Breakdown Spectroscopy (LIBS) in environmental applications.

The study focuses on an innovative process for the use of a ZrN coating on Ti6Al4V alloy for orthopaedic bone implants. The preparation process combines the technology of physical vapour deposition (PVD) and micro-arc oxidation (MAO) to achieve hydrophobic properties, improved corrosion resistance and enhanced coating adhesion to Ti6Al4V alloy. An alkaline electrolyte and different microarc discharge intensities were used to prepare MAO coatings. The evaluation of the structure and topography of the coatings was performed using SEM with XRPD, EDX, and XPS analysis. The prepared oxide coatings Zr, ZrSiO₄, and ZrTiO₄ increase the corrosion potential depending on the applied source frequency and thus increase the corrosion resistance of the hybrid system. At the same time, the formation of oxide phases leads to changes in surface topography associated with increasing friction coefficient and better wear resistance.

Magnetic nanomaterials (MNMs) with metallic and semiconducting properties are useful in energy conversion, energy storage, environmental, biomedical, agricultural applications thanks to their large surface area, charge carrier mobility, optical band structure, non-toxic nature, and ability to recover and recycle. However, their poor stability, agglomeration, lack of biocompatibility, fast electron-hole recombination, and leaching in acidic environments restrict bare MNMs for real-time applications. There are several approaches employed to overcome these issues, such as elemental doping, defect formation, nanocomposites, and surface functionalization. Among them, functionalization is one of the promising techniques to alter various properties of MNMs such as specific morphology, size, facet, crystalline phase, and electron mobility. Functionalized MNMs have been explored for various areas of research, including biomedical and environmental applications such as MRI, drug delivery, catalysis, solar hydrogen production, sensors, water and air purification. In this short perspective, promising advances in various functionalization strategies such as surface modification, amino functionalization, polymer functionalization, and biomolecule functionalization, techniques were consolidated, reviewed and their various applications are discussed in detail.

In this work the interface between a Pt film and a Bi₂Se₃ (0001) surface is investigated using electron microscopy and microanalysis, in order to characterize the structure of the interface and verify if it is chemically stable or an interaction occurs. At room temperature, the Pt film is composed of small clusters (∼10 nm) and the interface is stable. However, already upon mild annealing (200 °C) the interface displays instability and forms an interfacial phase. The interfacial phase, not previously reported in literature, is a long-range ordered ternary Pt:Bi:Se phase aligned with the Bi₂Se₃ crystal, most probably an intermetallic compound. The presence of a new phase at Pt/Bi₂Se₃ interface, together with the possible effects on the topological surface states, has to be considered in all the applied studies where this interface is present, as well as in the models for theoretical studies.

In the present work, the corrosion inhibition of AA2024 by lithium salts (nitrate, oxalate and carbonate) is investigated by using both global and local electrochemical techniques. With LiNO₃ (0.1 M), the anodic and cathodic current densities are lower and the impedance values higher by comparison with the results obtained in the presence of 0.1 M Li₂C₂O₄ or 0.1 M Li₂CO₃. After 20 h of immersion in the electrolyte, SEM observations reveal the formation of thick films on the AA2024 surface in the presence of carbonate or oxalate, whereas a thin and denser film is formed in the presence of nitrate. Specifically, the Li₂C₂O₄ addition, by increasing the pH of the electrolyte, induces significant alloy dissolution from the very beginning of immersion which contributes to the growth of a protective layer on the alloy surface, combining lithium, carbonate species and metal cations.

A self-healing effect by Li₂C₂O₄ or Li₂CO₃ is shown by local impedance measurements on artificial scratches made on a water-based epoxy coating deposited on AA2024 plates, confirming their potential use, as inhibitive species, in organic coatings.

The development of electrocatalysts with high catalytic performance and low costs for oxygen reduction reaction (ORR) is still challenging. Herein, an overall solution for ORR in alkaline media, from the catalyst synthesis to catalyst regeneration and to the development of a rapid, reliable and easy approach for electrode surface evaluation, is presented. We focused on the development and characterization of an efficient material for ORR in alkaline media, α-Fe₂O₃ N-doped graphene (Fe-N-Gr). The associative pathway for the four electron transfer ORR mechanism is sustained by the Raman spectra recorded from the electrode surface. We highlighted the possibility of catalyst regeneration by a simple electrochemical method. After two regeneration rounds and 1500 cycles in O₂-saturated 1 M NaOH, the catalyst still retains 40.8 % catalytic activity. Finally, as a part of the overall solution, we demonstrated that a methodology based on Raman spectroscopic measurements and machine learning algorithms can be applied for graphene-based catalysts lifetime investigation.

Mg-based alloys are used in various industrial sectors due to the unique combination of mechanical and biomedical behaviors. However, they are challenging in terms of corrosion protection and do not produce a protective oxide layer on their surface. The unregulated corrosion rate of these alloys restricts their application. One of the strategies that can provide a protective coating that prevents the direct contact of corrosive media with the substrates is coating on magnesium and its alloys. In recent years, MOF‒MOF-containing coatings have been investigated as a means of protecting various metal alloys against corrosion. The results show that these inhibitors have significantly reduced the rate of metal dissolution by affecting the kinetics of electrochemical reactions and greatly increasing corrosion resistance. So, these coatings are useful for increasing the corrosion resistance of magnesium alloys. Also, the anti-corrosion mechanisms and performance of MOFs in the coating matrix are discussed accordingly. This review article attempts to highlight the importance of MOFs for coating applications and enhancing corrosion resistance.