Search Results (107)

The complex dielectric permittivity has been studied with the waves of millimeter wavelength for rare earth manganate and titanate and LiCoPO₄ and LiNi_0.5Co_0.5PO₄ orthophosphate composites. The measurements are carried out at frequencies of 26 to 38 GHz via measurements of transmission and reflection coefficients through a plate. A special method on how to extract the real and imaginary parts of dielectric permittivity is applied. Discussion is conducted on a nonmonotonic type of the frequency dependences for both real and imaginary parts of permittivity, and it has been shown that relaxation is non-Debye. The Cole–Cole, Havriliak–Negami, and Kohlrausch–Williams–Watts models cannot also explain the nonmonotonic frequency dependence of the real part of dielectric permittivity. Investigation of the structure and phase composition of nanocomposites has been carried out. Full article

Using the Bridgman technique, GaSe single crystals were obtained which were mechanically split into plane-parallel plates with a wide range of thicknesses. By heat treatment in air at 820 °C and 900 °C, for 30 min and 6 h, micro- and nanocomposite layers of Ga₂Se₃–Ga₂O₃ and β–Ga₂O₃ (native oxide) with surfaces made of nanowires/nanoribbons were obtained. The obtained composite Ga₂Se₃–Ga₂O₃ and nanostructured β–Ga₂O₃ are semiconductor materials with band gaps of 2.21 eV and 4.60 eV (gallium oxide) and photosensitivity bands in the green–red and ultraviolet-C regions that peaked at 590 nm and 262 nm. For an applied voltage of 50 V, the dark current in the photodetector based on the nanostructured β–Ga₂O₃ layer was of 8.0 × 10⁻¹³ A and increased to 9.5 × 10⁻⁸ A upon 200 s excitation with 254 nm-wavelength radiation with a power density of 15 mW/cm². The increase and decrease in the photocurrent are described by an exponential function with time constants of τ_1r = 0.92 s, τ_2r = 14.0 s, τ_1d = 2.18 s, τ_2d = 24 s, τ_1r = 0.88 s, τ_2r = 12.2 s, τ_1d = 1.69 s, and τ_2d = 16.3 s, respectively, for the photodetector based on the Ga₂Se₃–Ga₂S₃–GaSe composite. Photoresistors based on the obtained Ga₂Se₃–Ga₂O₃ composite and nanostructured β–Ga₂O₃ layers show photosensitivity bands in the spectral range of electronic absorption bands of ozone in the same green–red and ultraviolet-C regions, and can serve as ozone sensors (detectors). Full article

Ni-W-Al₂O₃ nanocomposite coatings were fabricated using ultrasonic-assisted jet electrodeposition (UAJED) to improve the wear resistance of agricultural machinery parts. To find the best combination of process parameters, the response surface plotter, contour plotter, and pre-set plotter in the JMP (version Pro 14.3.0) software were employed to investigate the effects of various process parameters (jet rate, Al₂O₃ content, and ultrasonic power) on the microhardness of the nanocomposite coatings. The surface morphology, microstructure, and properties of the coatings, which were prepared under various combinations of process parameters, were studied through scanning electron microscopy (SEM), an X-ray diffractometer (XRD), transmission electron microscopy (TEM), a microhardness tester, and tribemates to determine the optimal process parameters for creating Ni-W-Al₂O₃ nanocomposite coatings. The results indicated that the jet rate, Al₂O₃ content, ultrasonic power, interaction terms, and quadratic terms significantly influenced the microhardness of the coatings. The optimized process parameters using the JMP software were a jet rate of 3.71 m/s, Al₂O₃ content of 15.38 g/L, and ultrasonic power of 210 W. Furthermore, the coatings produced under these optimal conditions showed low wear rates and friction coefficients, a refined grain size, a dense surface topology, and a high microhardness (724.9 HV). Full article

The hygrothermal deformation of nanocomposite piezoelectric plates containing internal pores lying on elastic foundations is illustrated in this paper by utilizing a novel quasi-3D plate theory (Q3DT). This nanocomposite plate has been strengthened by functionally graded graphene platelets (FG GPLs). For the purpose of identifying the FG porous materials, four alternative patterns of porosity distribution are employed, with the first pattern having a uniform distribution and the others having an uneven one. The material properties of the reinforced plate are estimated based on the Halpin–Tsai model. From the proposed theory and the virtual work principle, the basic differential equations are derived. The Levy method is used to convert the deduced partial differential equations to ordinary ones. The differential quadrature method (DQM) as a fast-converging method is utilized to solve these equations for various boundary conditions. The minimal number of grid points needed to obtain the converging solution is found by introducing a convergence study. After validating the obtained results with the studies of other researchers, this study’s findings are provided tabularly and graphically with numerous comprehensive discussions to examine the impact of the various factors of the proposed responding system. Full article

This paper considers the free vibration and flutter of carbon nanotube (CNT) reinforced nanocomposite plates subjected to supersonic flow. From the literature review, a great deal of research has been conducted on the free vibration and flutter response of high-volume CNT/nanocomposite structures; however, there is little research on the flutter instability of low-volume CNT/nanocomposite structures. In this study, free vibration and flutter analysis of classical CNT/nanocomposite thin plates with aligned and uniformly distributed reinforcement and low CNT volume fraction are performed. The geometry of the CNTs and the definition of the nanocomposite material properties are considered. The nanocomposite properties are estimated based on micromechanical modeling, while the governing relations of the nanocomposite plates are derived according to Kirchhoff’s plate theory with von Karman nonlinear strains. Identification of vibrational modes for nanocomposite thin plates and analytical/graphical evaluation of flutter are presented. The novel contribution of this work is the analysis of the eigenfrequencies and dynamic instabilities of nanocomposite plates with a low fraction of CNTs aligned and uniformly distributed in the polymer matrix. This article is helpful for a comprehensive understanding of the influence of a low-volume fraction and uniform distribution of CNTs and boundary conditions on the dynamic instabilities of nanocomposite plates. Full article

A variety of NiP-TiC-SiC nanocomposite coatings were deposited to acrylonitrile–butadiene–styrene (ABS) substrates at varying plating periods and bath temperatures using electroless plating. A field emission scanning electron microscope (FESEM) demonstrates the production of various coating morphologies. Morphology analysis of the deposit coatings shows homogenous, compact, and nodular structured coatings free of any apparent defects in most deposition conditions, except at extra high-temperature deposition baths, some gas bubbles under the coating layers were seen. The patterns of X-ray diffraction (XRD) illustrate nickel peaks at 44.5 which relates to Ni (111). Energy-dispersive X-ray spectroscopy (EDX) data show that the coating’s main constituents are nickel, phosphorus, and nanoparticles. According to the results of the contact angle test, the potentiodynamic polarization, and the impedance spectroscopy (EIS) tests conducted in (3.5%) of NaCl by weight at (25 °C), the nanocomposite coating that was created at 90 min and 75 °C exhibited the best hydrophobic qualities and corrosion resistance. The coating formed at 30 min and 75 °C illustrates the best hardness value. The adhesion force was calculated using the ASTM D 3359 method (B). The findings demonstrate that the coating made under the following deposition conditions, 30 min at 75 °C, 30 min at 95 °C, and 90 min at 75 °C, produces the best bonding strength between the coating and ABS substrate (standard classification 5B); however, the complete gas bubble rejection process from the substrate is rendered difficult by deposition times longer than 30 min in a bath over 85 °C, which decreases the adhesion between NiP-TiC-SiC and the acrylonitrile–butadiene–styrene substrate. The wear rate shows a direct relationship with the coefficient of friction rather than hardness, and the coated prepared at 90 min at 75 °C offers a lower wear rate and coefficient of friction. Full article

To improve the service life of continuous casting crystallizer, the NiCo-ZrB₂ coating was prepared using nanocomposite plating technology. Uniformly dispersed nano-ZrB₂ particles significantly enhanced the hardness and wear resistance of the coating. Upon testing, the hardness of the coating exceeded 700 HV, with a friction coefficient below 0.2, which was superior to those of pure NiCo or other nanocomposite NiCo coatings reported previously. Microscopic analysis revealed that the addition of dispersants and ultrasonic vibration treatment had facilitated the homogeneous distribution of nano-ZrB₂ within the matrix, thereby promoting the formation of numerous nano-twins. Due to dispersion strengthening, fine grain strengthening, and twinning strengthening, the wear behavior of the coating changed from fatigue wear to abrasive wear, and the wear volume was significantly reduced by 82%. The above findings could potentially extend the service life of the coating, reduce the cost of steel loss per ton, and have broad application prospects in other surface protection fields. Full article

In this research, silver-loaded biochar (C-Ag) was acquired from a waste fish scale, and nanocellulose (CNF) was prepared from the waste wheat stalk. Then C-Ag was loaded into chitosan-polyvinyl alcohol hydrogel (CTS-PVA) with CNC as a reinforcement agent, and a novel nanocomposite material was acquired, which could be efficiently applied for antibacterial and dye removal. By plate diffusion analysis, the inhibition areas of C-Ag-CTS-PVA-CNF (C/CTS/PVA/CNF) hydrogel against E. coli ATCC25922, S. aureus ATCC6538, and P. aeruginosa ATCC9027 could reach 22.5 mm, 22.0 mm, and 24.0 mm, respectively. It was found that the antibacterial rate was 100% in the water antibacterial experiment for 2 h, and the antibacterial activity was more than 90% within 35 days after preparation, and the antibacterial rate was more than 90% after repeated antibacterial tests for five times. Through swelling, water adsorption, water loss rate, and water content tests, the hydrogel manifested good moisturizing properties and could effectually block the loss of water and improve the stability of the C/CTS/PVA/CNF hydrogel. The pseudo-first-order and pseudo-second-order models were built, and the adsorption capacity of hydrogel to dye was analyzed, and the dye removal was more consistent with the pseudo-first-order kinetic model. The best removal effect for Congo red was 96.3 mg/g. The C/CTS/PVA/CNF hydrogel had a remarkable removal efficacy on Malachite green, Methyl orange, Congo red, and Methylene blue. As a result, the C/CTS/PVA/CNF hydrogels had robust antibacterial properties and reusability. In addition, the present research developed a facile strategy for effectual dyes removal from the aqueous medium. Full article

The demand for more efficient and sustainable electrical systems has driven research in the quest for innovative materials that enhance the properties of electrical conductors. This study investigated the influence of copper (Cu) coating and multi-walled carbon nanotubes (MWCNTs) on aluminum metal substrate through the pulsed electrodeposition technique. Parameters such as the concentration of chemical elements, current, voltage, temperature, time, and electrode spacing were optimized in search of improving the nanocomposite coating. The metallic substrate underwent anodization as surface preparation for coating. Characterization techniques employed included Field Emission Gun—Scanning Electron Microscopy (FEG-SEM) for analyzing coating morphology, Energy-Dispersive X-Ray Spectroscopy (EDS), Raman spectroscopy, and Kelvin probe for obtaining surface electrical conductivity values. Homogeneous dispersion of the Cu-MWCNTs film coating was achieved across the entire surface of the aluminum plate, creating a complex morphology. The doping effect was highlighted by changes in the vibrational characteristics of the nanocomposite, which affected the Raman spectrum dispersion bands. An increase in surface electrical conductivity by ≈52.33% compared to the control sample was obtained. Therefore, these results indicate that the improvement in the material’s electrical properties is intrinsically related to the complex morphology achieved with the adopted Cu-MWCNT nanocomposite coating process. Full article

TiN/TiAlSiN nanocomposite multilayer coatings were deposited on a titanium alloy by multi-arc ion plating. The investigation of the wear behavior of TiN/TiAlSiN multilayer coatings against Si₃N₄ was conducted at temperatures of 25 °C, 300 °C, and 500 °C using a ball-on-disk tribometer. Additionally, to gain a deeper understanding of medium-temperature oxidation products, an oxidation test was performed at 500 °C for 10 h. The microstructure and chemical composition of the coatings were evaluated by X-ray diffraction and scanning electron microscopy. The primary peak in the XRD pattern of the multilayer coating changed from TiN (111) to Ti₃AlN (111) after the oxidation test. The hardness of the TiN/TiAlSiN multilayer coating was 1540 HV_0.1, representing a notable five times improvement compared to the substrate. The critical load in the scratch test was 52.3 N, indicating robust adhesion performance. The wear rate exhibited a sharp increase from 25 °C to 300 °C, compared to the rise from 300 °C to 500 °C. Furthermore, the friction coefficient of the coated sample was more stable than the substrate, with different scratch track morphologies between the samples before and after the oxidation test. Full article

A binary Fe₂O₃/Fe₃O₄ mixed nanocomposite was prepared by phyto-mediated avenue to be suited in the photo-Fenton photodegradation of methylene blue (MB) in the presence of H₂O₂. XRD and SEM analyses illustrated that Fe₂O₃ nanoparticles of average crystallite size 8.43 nm were successfully mixed with plate-like aggregates of Fe₃O₄ with a 15.1 nm average crystallite size. Moreover, SEM images showed a porous morphology for the binary Fe₂O₃/Fe₃O₄ mixed nanocomposite that is favorable for a photocatalyst. EDX and elemental mapping showed intense iron and oxygen peaks, confirming composite purity and symmetrical distribution. FTIR analysis displayed the distinct Fe-O assignments. Moreover, the isotherm of the developed nanocomposite showed slit-shaped pores in loose particulates within plate-like aggregates and a mesoporous pore-size distribution. Thermal gravimetric analysis (TGA) indicated the high thermal stability of the prepared Fe₂O₃/Fe₃O₄ binary nanocomposite. The optical properties illustrated a narrowing in the band gab (Eg = 2.92 eV) that enabled considerable absorption in the visible region of solar light. Suiting the developed binary Fe₂O₃/Fe₃O₄ nanocomposite in the photo-Fenton reaction along with H₂O₂ supplied higher productivity of active oxidizing species and accordingly a higher degradation efficacy of MB. The solar-driven photodegradation reactions were conducted and the estimated rate constants were 0.002, 0.0047, and 0.0143 min⁻¹ when using the Fe₂O₃/Fe₃O₄ nanocomposite, pure H₂O₂, and the Fe₂O₃/Fe₃O₄/H₂O₂ hybrid catalyst, respectively. Therefore, suiting the developed binary Fe₂O₃/Fe₃O₄ nanocomposite and H₂O₂ in photo-Fenton reaction supplied higher productivity of active oxidizing species and accordingly a higher degradation efficacy of MB. After being subjected to four photo-Fenton degradation cycles, the Fe₂O₃/Fe₃O₄ nanocomposite catalyst still functioned admirably. Further evaluation of Fe₂O₃/Fe₃O₄ nanocomposite in photocatalytic remediation of contaminated water using a mixture of MB and pyronine Y (PY) dyestuffs revealed substantial dye photodegradation efficiencies. Full article

The spinning cup, a crucial component of textile equipment, relies heavily on 2A12 aluminum alloy as its primary raw material. Commonly, electroplating and chemical nickel–phosphorus (Ni-P) plating are employed to improve the surface characteristics of the object. Nevertheless, due to the growing expectations for the performance of aluminum alloys, the hardness and wear resistance of Ni-P coatings are no longer sufficient to fulfill industry standards. This study primarily focuses on the synthesis of Ni-B-PTFE nanocomposite chemical plating and its effectiveness when applied to the surface of 2A12 aluminum alloy. We examine the impact of the composition of the plating solution, process parameters, and various other factors on the pace at which the coating is deposited, the hardness of the surface, and other indicators of the coating. The research findings indicate that the composite co-deposited coating achieves its optimal surface morphology when the following conditions are met: a nickel chloride concentration of 30 g/L, an ethylenediamine concentration of 70 mL, a sodium borohydride concentration of 0.6 g/L, a sodium hydroxide concentration of 90 g/L, a lead nitrate concentration of 30 mL, a pH value of 12, a temperature of 90 °C, and a PTFE concentration of 10 mL/L. The coating exhibits consistency, density, a smooth surface, and an absence of noticeable pores or fissures. The composite co-deposited coating exhibits a surface hardness of 1109 HV_0.1, which significantly surpasses the substrate’s hardness of 232.38 HV_0.1. The Ni-B-PTFE composite coating exhibits an average friction coefficient of around 0.12. It has a scratch width of 855.18 μm and a wear mass of 0.05 mg. This coating demonstrates superior wear resistance when compared to Ni-B coatings. The Ni-B-PTFE composite coating specimen exhibits a self-corrosion potential of −6.195 V and a corrosion current density of 7.81 × 10⁻⁷ A/cm², which is the lowest recorded. This enhances its corrosion resistance compared to Ni-B coatings. Full article

This study aims to develop Ni-P coatings with high P content (≥11 wt.%) reinforced with WC nanoparticles on F22 steel substrates. The introduction of conductive WC in the plating solution dramatically increases reactivity of the plating solution, and consequently a tuning of deposition parameters, in terms of temperature and WC concentration, is required to obtain nanocomposite coatings with improved mechanical properties. The coatings’ porosity and incorporation and dispersion of the reinforcing phase as a function of temperature and WC concentration were analyzed by quantitative image analysis from Scanning Electron Microscopy (SEM) micrographs. Increasing the temperature and concentration of nanoparticles leads to a faster plating rate and a dramatic increase in both porosity and agglomeration of the reinforcing phase, with detrimental effects on the coatings’ microhardness. The best compromise between coating parameters was obtained by deposition at 70 °C and 6.5 g/L of WC, with a plating rate ≈ 12 μm/h, porosity lower than 1.5%, and a good combination between particle incorporation and agglomeration. In these conditions, a hardness increase by 34% is achieved in comparison to standard Ni-P. Coatings were then heat treated in air at 200 °C for 2 h, to induce growing stress relaxation, or 400 °C for 1 h, to study effects of crystallization and precipitation. X-Ray Diffraction (XRD) analysis demonstrated that WC introduction does not alter the microstructure of Ni-P coatings, but delays grain growth coarsening of precipitates. Hardness improvement by 6.5% and 45% is registered after treatment at 200 °C and 400 °C, respectively. An increase in elastic modulus, measured by instrumented indentation, was found in WC-reinforced coatings compared with Ni-P. Potentiodynamic polarization tests revealed that both introduction of WC nanoparticles and heat treatment also enhance corrosion resistance. Full article

A comprehensive study was performed on the supramolecular ordering and optical properties of thin nanostructured glycerohydrogel sol-gel plates based on chitosan L- and D-aspartate and their individual components in the X-ray, UV, visible, and IR ranges. Our comparative analysis of chiroptical characteristics, optical collimated transmittance, the average cosine of the scattering angle, microrelief and surface asymmetry, and the level of structuring shows a significant influence of the wavelength range of electromagnetic radiation and the enantiomeric form of aspartic acid on the functional characteristics of the sol-gel materials. At the macrolevel of the supramolecular organization, a complex topography of the surface layer and a dense amorphous–crystalline ordering of polymeric substances were revealed, while at the nanolevel, there were two forms of voluminous scattering domains: nanospheres with diameters of 60–120 nm (L-) and 45–55 nm (D-), anisometric particles of lengths within ~100–160 (L-) and ~85–125 nm (D-), and widths within ~10–20 (L-) and ~20–30 nm (D-). The effect of optical clearing on glass coated with a thin layer of chitosan L-(D-)aspartate in the near-UV region was discovered (observed for the first time for chitosan-based materials). The resulting nanocomposite shape-stable glycerohydrogels seem promising for sensorics and photonics. Full article

Low friction and high wear resistance are critical properties for sliding bearings. In this research, advanced Cu/GO nanocomposite coatings have been developed by a brush plating method to improve the tribological performance of brass-based sliding bearings. A series of brush plating studies under voltages from 2 to 6 V with different GO concentrations (0.2–0.8 g/L) was conducted, and the coating microstructures were characterised by SEM, EDX, GDOES and XRD and the tribological behaviour of the Cu/GO composite coatings were evaluated using dry ball-on-plane tribological tests The experimental results have demonstrated that GO can be successfully introduced into the whole composite coating layer; the Cu/GO composite coatings can reduce the friction of brass and increase its wear resistance by two orders of magnitude, mainly due to the self-lubricating GO added into the coatings. Full article