The synergy effect of bimetallic oxide shell and high electrically conductive metallic core enables the dendritic Cu-Ni/ nickel foam (NF) for detecting non-enzymatic glucose.
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...•Binder-free Cu-Ni alloys@metal oxide was prepared by facile electrodeposition method.•The dendritic structure promotes glucose diffusion and provides rich active sites.•The bimetallic oxide shell and metallic core enable highly effective glucose sensing.
A success has been achieved in the synthesis of dendritic core-shell copper-nickel alloy@metal oxide on nickel foam (Cu-Ni/NF) electrode for non-enzymatic glucose detection by going through a facile electrodeposition process followed by oxidation in NaOH solution. The direct electrodeposition approach facilitates the transfer of electrons in the binder-free electrode, and the dendritic structure promotes glucose diffusion while providing sufficient active sites required for the process of glucose electrocatlysis. Moreover, the unique core-shell structure promotes the catalytic activity towards glucose oxidation due to the synergistic effect caused by the bimetallic oxide shell and the metallic core that is conductive to electron transport. Accordingly, the Cu-Ni/NF electrode exhibits a high sensitivity of 11.34 mA mM−1 cm-2, a low detection limit of 2 μM (S/N = 3), and a wide linear range of 1–600 μM for glucose detection. In addition, the electrode demonstrates such advantages as high selectivity, fast response time, and long duration stability. The designed Cu-Ni/NF electrode shows its massive potential of application for non-enzymatic glucose detection.
Nickel base hardfacing alloys serve to mitigate corrosion losses at elevated temperatures. Efficacy of Nickel base hardfacing alloys can be compromised when applied onto Fe base substrates due to ...iron dilution in hardfacing. The degree of Fe dilution can be reduced by using advanced deposition methods and optimized deposition parameters. Gas Tungsten Arc Welding (GTAW) method is commonly employed for its cost-effectiveness and versatility, but it tends to induce higher Fe dilution due to increased heat input. This study aims to reduce the degree of Fe dilution and enhance corrosion resistance by introducing a nickel base buffer layer (alloy 625) between the nickel base hardfacing alloy and AISI 316L stainless steel substrate. For comparative purposes, Ni base hardfacing alloy was deposited on the substrate without any buffer layer. Hardfacing depositions were prepared using manual GTAW process. Process parameters namely, deposition current, voltage, travelling speed, pre-heating temperature, and cooling method were kept constant. Samples underwent aging at 1123 K for 4 h, followed by microstructural examination via optical and scanning electron microscopes. Iron (Fe) dilution quantification was performed using energy dispersive spectroscopy (EDS). The EDS analysis showed that the use of buffer layer between the hardfaced deposit and the substrate decreased the degree of Fe dilution in the hardfaced deposit. X-Ray diffraction (XRD) analysis was performed to identify various phases formed in the hardfaced deposit. Potentiodynamic polarization test was performed to assess the corrosion resistance of hardfaced deposit in 3.5 wt% NaCl solution. Results show significant improvement in corrosion resistance of hardfacings deposited sample with buffer layer as compared to those without buffer layer. Aging treatment further enhanced corrosion resistance. The corrosion resistance data is correlated with the microstructure and phases formed in various samples.
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•The impact of buffer layer on hardness, microstructure, Fe dilution, and corrosion resistance in Ni-based hardfacing using the GTAW method.•Higher Ni concentration in the hardfacing deposition reduces Fe dilution, improving the Ni/Fe ratio in Ni-based hardfacing.•Presence of Mo and Nb in the hardfacing refine microstructure and improve corrosion resistance.•Solidification analysis performed to assess the impact of Mo and Nb addition using phase and Scheil diagrams.
Dielectric fluids affect not only the discharge status but also the structure and composition of recast layer in the electrical discharge machining (EDM) process. In order to reduce the thickness of ...recast layer and improve the surface quality of film cooling holes of nickel alloy, in this paper, the effects of four different types of dielectric fluids on surface integrity of the recast layer formed during high speed EDM drilling process were investigated; the formation mechanism of the recast layer on nickel alloy was discussed by comparing the surface characters of the bulk and those of the recast layer using various characterization methods. The dielectric fluids with larger electric conductivity (emulsion and water solution) were found to have higher sensitivity to the single pulse discharge energy. With the increase in electric conductivity of dielectric fluids, the recast layer became thicker accordingly. The thickness of the recast layer when using kerosene fluid was the smallest (4.8 μm), which was nearly one third of the that of using water-based fluid. The cooling rate of the dielectric fluid affected the microstructure of the recast layer, where the surface of recast layer was apt to form fine grain zone and the bottom formed columnar grain.
•Larger electric conductivity dielectric has higher sensibility to discharge energy.•The slower servo voltage enhances the electro chemical reaction to thin the recast layer.•The surface of recast layer was prone to form fine grain due to the fast cooling rates.•Kerosene dielectric can result in thin recast layer, but a low machining speed.
Laser powder bed fusion (L-PBF) as an additive manufacturing process produces nearly fully dense nickel alloy 625 (IN625) parts with complex features. L-PBF generates surfaces and microstructure ...through directional solidification that can be controlled by scan strategies and selection of process parameters. This study provides experimental investigations on microstructure formation including sizes of cellular grains and growth directions of columnar grains on the nickel alloy 625 test coupons. The effects of process parameters including laser power, scan velocity, hatch distance, and scan strategy that produce various solidification cooling rates and thermal gradients during the process, which also contribute to resultant microstructure, have been analyzed. Optimization studies are conducted on several objectives to improve the productivity while controlling the process effects on the resultant microstructure using response surface regression, desirability functions, and multi-objective genetic algorithm optimization.
Nickel alloy X-750 which is difficult-to-machine material, is employed in many critical fields owing to its superior mechanical and thermal properties. However, these superior features lead to some ...difficulties in its machinability especially when using carbide tool materials. Hence, ceramic cutting tools (CCTs) having excellent hardness, heat and abrasion resistance, and poor chemical proximity to workpiece material are a perfect choice in machining operations of such materials. Considering this, the current study focused on the influence of various cutting environment, i.e., dry, base fluid-MQL without any mixed nanoparticles (BF-MQL) and hBN dispersed nanofluid-MQL (NF-MQL) on surface roughness, 2D-surface topography, maximum cutting temperature, cutting force, micro-hardness, flank wear and its mechanism when milling of alloy X-750 with Sialon ceramic tools. As a result, surface roughness was reduced by about 39% and 47.2% with BF-MQL (0 vol% additive) and hBN mixed NF-MQL, respectively compared to dry machining environment. Also the noticeable improvement with NF-MQL environment in 2D-surface topography of workpice, cutting temperature and cutting force has been achieved, the dry machining offered less tool wear for CCT than both BF-MQL and NF-MQL.
•Dry, BF-MQL and hBN mixed nanofluid-MQL were used in experiments.•Nickel alloy X-750 was milled with SiAlON tool under different machining modes.•Wear performance of SiAlON ceramic tool was investigated.•Microhardness, surface roughness/topography, force and temperature were studied.•NF-MQL exhibited good performance in surface condition, force and temperature.
The microstructural evolution of a nickel-based heat resistant alloy during long term aging (10000 h) at 700 °C was systematically investigated. Experimental results showed that the main precipitates ...after pre-aging treatments were MC, M23C6 and homogeneous γ’. The weight fraction of γ′ increased continuously with the aging time up to 5000 h, while an obvious coarsening was observed after aging for 100 h. The grain sizes of γ′ precipitates from all aged samples exhibited unimodal distributions, and their coarsening behavior showed good agreement with the LSW model. Compared to the MC carbides, the weight fraction of the M23C6 carbides increased significantly with the increase of the aging time. This could be attributed to their precipitation from the supersaturated matrix. Due to the precipitation and coarsening of γ′, the hardness of the aged samples increased sharply during the first 100 h of aging and then decreased with the increase of the aging time (up to 10000 h).
•All aged samples were quantitatively studied by the phase analysis.•The sizes of γ′ precipitates from all aged samples exhibited unimodal distributions.•The increase of M23C6 during the aging time could be attributed mainly to their precipitation from the supersaturated matrix.
In this study, we report the synthesis and application of palladium-nickel nanoparticles decorated on functionalized-multiwall carbon nanotube Pd–Ni@f-MWCNT and employed as a sensitive non-enzymatic ...electrochemical glucose sensor. The composition and crystal structure was characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman spectroscopy. The surface morphology of Pd–Ni@f-MWCNT was investigated by a transmission electron microscopy (TEM). The electrochemical response of the Pd–Ni@f-MWCNT to glucose was examined via the cyclic voltammetry. Results revealed that the prepared electrode exhibits high electrocatalytic activity for the oxidation of glucose into gluconolactone. The amperometric response of the Pd–Ni@f-MWCNT electrode to glucose was investigated at a potential of 0.5 V that demonstrated an extended linear range of from 0.01 to 1.4 mM, very low detection limit of 0.026 μM, very high sensitivity at 71 μA mM−1 cm−2, as well as good reproducibility, high stability and applicability for the real sample analysis. The reliability of the developed sensor was verified by comparison with a commercially available glucometer. The obtained results indicate that Pd–Ni@f-MWCNT is a promising candidate for electrochemical glucose sensing.
•The synthesis of novel conductive nanomaterials.•The fully characterization of novel bio-sensor.•High efficiency and stability of novel biosensor towards glucose.•Real time measurements of novel biosensor.
