Protection of Metals and Physical Chemistry of Surfaces最新文献

The present work focusses on the fabrication of new Ni–Co electrolyte for the development of Ni–Co electrocatalysts for water splitting application. All the Ni–Co alloy coatings were deposited from an acid sulphate bath and their electrocatalytic activity was tested in 1 M KOH. The Ni–Co alloys developed at range of current density from 3.0 to 6.0 A dm^–2 were found to be good electrode materials for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), as demonstrated by cyclic voltammetry (CV) and chronopotentiometry (CP) methods. The Ni–Co alloy deposits which are catalytically active for HER are found to be inactive for OER and vice versa. The change in surface appearance, composition, and the phase structure of all developed coatings were analysed using instrumental techniques like scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD), respectively.

Corrosion is one of the key technical problems impeding the widespread use of magnesium (Mg) and its alloys. Consequently, enhancing the corrosion resistance of Mg alloys is an urgent issue that necessitates immediate attention in their applications. Polytetrafluoroethylene (PTFE), often termed the ‘king of plastics’ because of its exceptional chemical inertness and non-reactivity, forms coatings that effectively shield metal substrates from corrosive environments. This capability substantially reduces corrosion rates, underscoring its considerable potential in corrosion prevention. In this study, PTFE coatings were successfully prepared on Mg–3Al–1Zn (AZ31) alloy sheets through electrophoretic deposition (EPD). The coatings underwent sintering treatments of varying durations, and their corrosion resistance properties were systematically evaluated. The results indicate that sintering duration critically influences the microstructural morphology of the PTFE coatings; extending the sintering duration within a specific range enhances the microstructure’s compactness. Furthermore, the study examined the corrosion behavior of Mg alloys coated with sintered PTFE in a 3.5 wt % NaCl solution, where the corrosion resistance of the sintered PTFE-coated AZ31 was significantly enhanced. Notably, coatings sintered for 14 h exhibited the highest corrosion resistance, with the corrosion current density decreasing from 4.05 × 10^–5 A cm^–2 for the bare AZ31 to 1.20 × 10^–7 A cm^–2 for the sintered PTFE-coated AZ31. Concurrently, the charge transfer resistance increased significantly from 227 to 2.72 × 10⁵ Ω cm². The coatings achieved a contact angle exceeding 123° and an adhesion rating of 5B. This offers a novel approach for mitigating corrosion in Mg and its alloys.

This study investigates the effect of an aluminized coating on the oxidation resistance of GH3039 superalloy. A powder embedding technique at 900°C with 60 wt % aluminum was employed to prepare the coating. The phase composition and surface morphology of oxidation products were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Untreated and aluminized samples were subjected to oxidation at 800, 900, and 1000°C for 100 h. Post-treatment, the GH3039 alloy exhibited a uniformly distributed aluminized layer about 90 μm thick. This layer comprised three distinct sub-layers: a top layer with Ni₂Al₃ and minor NiAl₃ phases, a middle layer of mainly Ni₂Al₃, and a β-NiAl phase-rich bottom layer. Oxide weight measurements indicated an initial rapid increase followed by a significant reduction at high temperatures, primarily due to Cr₂O₃ volatilization into gaseous CrO₃. Oxidation curves for the aluminized samples showed reduced and stable weight gain patterns, adhering mostly to the parabolic law with no further increase at advanced stages. The untreated samples presented a porous oxide film with complex components including Cr₂O₃, NiCr₂O₄, TiO₂, which adversely affected their oxidation resistance. In contrast, the aluminized samples predominantly displayed an Al₂O₃ film that transitioned from flaky θ-Al₂O₃ to a compact α-Al₂O₃ structure at increased temperatures, thereby significantly enhancing the alloy’s resistance against high-temperature oxidation.

The electrodeposition technique was successfully used for the co-deposition of Mn and Co metals and Y₂O₃ particles on Corofer 22 APU interconnects. The uncoated and Mn–Co–Y₂O₃-coated samples were oxidized in an electric furnace for 500 h at 800°C. The surface morphology and phase structure of these samples were examined by field emission scanning electron microscopy (FESEM) and XRD analysis, respectively. The electrical conductivity of the samples was investigated by measuring area specific resistance. The results showed that the weight gain of uncoated and Mn–Co–Y₂O₃-coated samples after isothermal oxidation for 500 h was 0.52 and 0.4 mg cm^–2, respectively. Microscopic investigations demonstrated that a non-continuous thin oxide scale forms underneath the applied coating, while high outward diffusion of Fe, Mn, and Cr occurred in uncoated steel after 500 h of oxidation at 800°C. Findings also implied that the applied coating significantly improve the electrical conductivity of steel interconnects after long-term oxidation at high temperatures.

This work focuses on the characterization and fabrication of iron–nickel–sulfide (FeNiS₂) thin films made via chemical spray pyrolysis. The quality of the films was assessed using a variety of physicochemical characterization methods, including optical and electrical characteristics, energy dispersive X-ray analysis (EDX), X-ray diffraction, and scanning electron microscopy. The purity of the NiFeS₂ thin films and their good structure in accordance with the cubic structure (Fm3m) were determined by the structural studies. Finally, after examining the practical results of optical and electrical properties, it was determined that NiFeS₂ thin film has a number of benefits and can be applied in a number of settings, including metal-air batteries, supercapacitors, solar cells, and electrocatalysts.

The as-extracted Tamarindus indica fiber (TIF) extract and its structural insights were analyzed successfully by spectral, electrochemical, analytical and theoretical techniques. The maximum corrosion inhibition efficiency (90.16%) was found by weight loss technique at 308 K. Monolayer adsorption was found and it obeyed the Langmuir adoption model. The –∆H* values support an exothermic process and –∆S* values confirm TIF adsorbed on mild steel surface. The –∆G° values reveal that the TIF adsorption on mild steel is a spontaneous process. Mixed type inhibition behavior was confirmed by Tafel plots. Increased trend of charge transfer resistance (R_ct) and decreased trend of double layer capacitance (C_dl) with increasing TIF (0–25 mg/L) concentration by Nyquist plots. FTIR and UV-Visible result confirms the mild steel-TIF extract complex formation. FE-SEM, EDAX, mapping analysis and XPS study supports the adsorption of TIF extract on mild steel surface. DFT study suggests that the biomolecules present in TIF extract is responsible for the formation mono adsorption layer on mild steel surface. An appropriate mechanism for mild steel corrosion inhibition with TIF extract in 0.5 M TCA was proposed.

This work addresses the modelling of growth kinetics for FeB, Fe₂B, and the diffusion zone formed after the solid boriding of the iron-based A286 superalloy. A novel kinetic model was developed to analyze the boron diffusion in this multi-layer system, with a non-linear boron distribution in each phase. The boron concentration profile within each phase was expressed as a function expanded in a second-order Taylor series. Subsequently, the proposed model was used to assess the boron diffusion coefficients in the FeB and Fe₂B layers, as well as in the diffusion zone (DZ), using experimental data from the literature. As a result, the boron activation energies in the FeB, Fe₂B, and DZ layers were determined to be 176.69, 201.05, and 207.80 kJ mol^–1, respectively. Additionally, the experimentally measured layer thicknesses were compared with the predicted values, validating the developed model.

A new series of Schiff base derivatives of quinazoline core were synthesized through the reaction of quinazoline derivative A with different substituted aromatic aldehydes to produce compounds 1–4. The new Schiff base derivatives 1–4 were obtained in high yields and characterized using various techniques including FTIR, ¹H‑NMR, and ¹³C-NMR. Compounds 1–4 were studied as corrosion inhibitors for carbon steel 45 using polarization curves. Various thermal and kinetic parameters were also examined to better understand the corrosion process and inhibition mechanism of these compounds. All compounds demonstrated excellent corrosion inhibition properties, and the results were corroborated by X-ray diffraction and AFM techniques.

In this study, acrylic emulsion was made using the emulsion polymerization technique with butyl acrylate (BA) and methyl meth acrylate (MMA) monomers. MMA provides rigidity and durability, while BA imparts flexibility to the polymer. To enhance its antibacterial capabilities, the acrylic emulsion was polymerized in-situ using 1.5% (relative to the monomers) magnesium oxide (MgO) nanoparticles. In-situ polymerization helps in the uniform dispersion of nanoparticles within the polymer matrix, enhancing the properties of the final product. The synthesised acrylic emulsion was evaluated using Fourier-transform infrared (FTIR) spectroscopy to determine its structural characteristics, an E. coli test to determine its antibacterial qualities and a Brookfield viscometer to determine its viscosity. The prepared acrylic emulsions were applied as a coating on mild steel (MS) panels and tested for its adherence, gloss, drying time, and flexibility. The study demonstrates that MgO nanoparticles can effectively enhance the antimicrobial properties of acrylic emulsions without compromising other essential coating properties like gloss, adhesion, and flexibility, making them suitable for protective coatings in various applications.

As-plated and heat-treated Ni–P, Ni–B, and Ni–P/Ni–B coatings (Ni–P as an internal layer) on steel by electroless plating and their morphology, microstructure, and corrosion performance were evaluated in this study. Scanning electron microscopy analysis demonstrated that all coatings are uniform and adhesion between the substrate and coating was good. Ni–P and Ni–B coatings were amorphous-like structures in their as-plated condition, and by applying heat treatment nickel fully crystallized, nickel borides and nickel phosphides were formed. Immersion tests in 10% HCl and 5% H₂SO₄ solutions and potentiodynamic polarisation measurements in 3.5% NaCl aqueous solution were applied to investigate the corrosion resistance of the coatings. The results demonstrated that all coatings exhibit better corrosion performance than the substrate steel. Applying heat treatment did not change the corrosion resistance of Ni–P coating, conversely, heat treatment had a dominant positive effect on the corrosion performance of Ni–B and a minor effect on Ni–P/Ni–B duplex coatings.