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Material deformation due to nanoindentation is well known. However, the deformation of a material, indentation cavity, and piled-up region drastically increases and nanohardness significantly decreases if the nanoindentation is performed in such a way that the deformation of one nanoindentation affects the others. This situation arises in various materials when they are subjected to tribological application such as pantograph assembly in electric trains and contact between the electrical power supply plug and pins. This situation has been addressed in this study and the quantitative reduction in nanohardness has been evaluated in detail. In this work, the nanoindentation was performed on the laser powder bed fusion (LPBF) CuCrZr alloy specimen under a load condition of 4500$\mu$N. This test was conducted at 100 points with an array of $10\times 10$ at a 1$\mu$m pitch value. Two significant findings were identified in this work. First, the indentation impression was smaller and the corresponding nanohardness and contact stiffness values were higher in the first column of 10 nanoindentations and the first row of 10 nanoindentations. The remaining 80 nanoindentations displayed contrasting behavior compared to the initial 20 nanoindentations due to the prior deformation of nearer regions. Nanohardness value decreased parabolically from the low deformation to the high deformation region. This finding was validated by increasing the pitch to 15$\mu$m under the 4500$\mu$N load conditions. The piled-up region around the impression of indentation changed from a semi-circular shape at a 15$\mu$m pitch value to a cone shape at a 1$\mu$m pitch value. These findings will be beneficial for industries during the design of materials and will help reduce material failures resulting from tribological activities.

In this study, the effects of Cu nanoparticles on the melting characteristics, wettability, interfacial reaction and mechanical properties of $\mathrm{\text{Sn}}$–$\mathrm{\text{xCu}}$$(x=0$, $0.3$, $0.7$, $1.0$, $1.5$, $2.0)$ composite solders were investigated. Results show that the properties of the composite solder containing Cu nanoparticles were improved effectively. With the addition of Cu nanoparticles, the melting point of $\mathrm{\text{Sn}}$–$\mathrm{\text{xCu}}$ solder decreased significantly, and the spreading area and the shear strength were increased by 10.3% and 23.2%, respectively. For the performance, the optimal addition of Cu nanoparticles was 0.7%. In addition, the growth of interfacial intermetallic compounds in $\mathrm{\text{Sn}}$–$\mathrm{\text{xCu/Cu}}$ solder joints was inhibited by adding Cu nanoparticles.

In this paper, fully developed forced convective flow properties of hybrid nanofluid through annular sector duct are discussed. The studies of hybrid nanofluid, i.e. the combination of a nanofluid (nanoparticles plus water) with another nanoparticles’ volume fraction, are considered. Hybrid nanofluids become most important due to enhancement in the heat transfer rate. Copper oxide (CuO)–water is taken as the nanofluid. The volume fraction of CuO nanoparticles in water is kept fixed at 4%, whereas the volume fractions of Cu nanoparticles are taken in the range of 0–4% in this study. Under the assumption of hydrodynamically and thermally fully developed flow, the deviation in the velocity components along the axial direction vanishes in the case of momentum equations; however, the deviation in the temperature becomes constant in the case of energy equation. After dimensionless analysis, the finite volume method is applied to find the numerical solutions for velocity, temperature, heat transfer rate and fanning friction factor. During physical analysis, it has been concluded that the percentage enhancement in heat transfer rate is comparably more than fanning friction factor when we increase the volume fraction of Cu nanoparticles in the CuO–water nanofluid. Furthermore, the same observation has been noticed in the case of heat transfer rate when the platelet shape factor of the nanoparticles has been used instead of brick and cylinder shape factors. Increase in fRe is 8.01% when we increase the Cu nanoparticles’ volume fraction from 1% to 4%, whereas the increments in Nu are 15.09%, 18.56% and 20.81% for the brick-, cylinder- and platelet-shaped nanoparticles, respectively, for all values of the ratio of radii, $\widehat{R}$, and apex angle, $2\alpha$, in both thermal cases.

Metallic nanoparticles have attracted intense interest for the potential applications in biocompatibility due to the reduced particle size. However, the methods to produce metallic nanoparticles usually produce an inhomogeneous size distribution. In this work, Cu nanoparticles were generated using a gas-aggregation cluster source technique, employing a specially designed quadrupole mass filter to control the size of the nanoparticles with a mass resolution (m/$\mathrm{\Delta }$m) of 5. Transmission electron microscopic (TEM) analysis was used to confirm the size control of our technique. The generally high angular electronic scattering analysis revealed the spherical shapes of the Cu nanoparticles. We used beams of these nanoparticles to prepare nano-granular films on a Si substrate. Their antibacterial effect of the modified materials on Escherichia coli was assessed by means of a bacterial adhesion test. Our results may not only reveal the cluster technique to produce the uniform metallic nanoparticles, but also form the basis of antibacterial applications.

Copper nanoparticles frequently exhibit unique electrocatalytic activity for the electrochemical reduction of carbon dioxide. However, the synthesis of Cu nanoparticles in aqueous systems remains rare. Herein, we report the synthesis of copper nanoparticles by using a zinc(II) porphyrin-based photocatalytic method in the presence of polyacrylic acid sodium salt (PAA) in water under visible light irradiation, leading to a series of Cu nanoparticles with relatively small average sizes ranging from 69 to 97 nm. PAA molecules adsorbed on Cu nanoparticles were simply removed by washing with copious amount of water. The purified Cu nanoparticles show some activity toward the electrochemical reduction of carbon dioxide as evidenced by linear sweep voltammetry (LSV) and gas chromatography (GC).

WO₃/Cu composite film electrodes were synthesized by hydrothermal combined electrodeposition method. Characterization of samples was conducted by SEM, XRD and XPS, which showed WO₃/Cu composite films had been synthesized. The diffusion coefficient, reversibility, response time, coloration efficiency and transmission rate of the samples were obtained by electrochemical and spectral measurements. The photocurrent and photoelectric catalysis degradation efficiency of the samples were obtained by photocurrent and photoelectric catalysis measurements. The WO₃/Cu composite films improve electrochromic performance, photocurrent and photoelectric catalytic activity compared with pure WO₃ nanoblocks, and the WO₃/Cu composite film obtained by depositing Cu nanoparticles at 50 s shows the highest electrochromic performance, photocurrent and photoelectric catalytic activity. Meanwhile, the direct photocatalytic and electric catalytic activity of the composite film are also discussed. The combined effects of the lower band gap and the Schottky junction lead to significant enhancement in the electrochromic and photoelectrochemical properties of the WO₃/Cu composite film.

In the past several years, the widespread utility of copper nanoparticles (CuNPs) has spurred global interest in streamlining synthesis methodologies. Notably, this study introduces an environmentally conscious strategy for synthesizing CuNPs using the extract of Alocasia indica. Employing a chemical reduction process, A. indica, abundant in phenolics and flavonoids, acts as a potent reducing agent. The nanoparticles (NPs) synthesized by A. indica have been carefully characterized by Ultraviolet–Visible (UV–Viz) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD) analysis and antimicrobial analysis. UV testing, spanning wave length, elucidates light absorption attributed to the newly formed CuNPs by showcasing a surface plasmonic resonance peak at 204 nm. The evolution of the FTIR spectrum of the produced CuNPs confirms the presence of diverse biomolecules. TEM delineates the synthesis of irregularly shaped particles. Elemental composition analysis via EDX identifies the presence of various elements, including C, O, Al, Cl, K and Cu, with detailed insights into their mass percentages, standard deviations, atom percentages and characteristic X-ray energy levels. The successful synthesis of CuNPs is validated by XRD, which reveals characteristic copper peaks at 2$𝜃$ = 43.375${}^{\circ }$, 50.520${}^{\circ }$ and 74.165${}^{\circ }$. The synthesized NP showed 98.99% inhibition against Staphylococcus aureus and 99.99% inhibition against Escherichia coli. This research presents an easy, economical and ecologically friendly process for producing CuNPs utilizing A. indica extracts.