Bulletin of Materials Science最新文献

Li₂ZnGe₃O₈:Er³⁺ and Li₂ZnGe₃O₈:Er³⁺/Yb³⁺ phosphors were successfully synthesized via a high-temperature solid-state reaction method, and the upconversion luminescence properties and mechanisms of both Er³⁺-doped and Er³⁺/Yb³⁺ co-doped systems under 980 and 1550 nm excitation were systematically investigated. Additionally, the optical temperature sensing performance of the Li₂ZnGe₃O₈:Er³⁺/Yb³⁺ phosphor was explored in detail. To enhance temperature sensitivity and self-calibration features, a dual-mode temperature sensing method was designed and implemented based on fluorescence intensity ratio from thermally coupled energy levels (TCELs) and non-thermally coupled energy levels (NTCELs). Experimental results show that in the TCELs mode, the maximum absolute sensitivity under 980 nm excitation is 0.003197 K^–1 (462 K), and under 1550 nm excitation is 0.0028 K^–1 (303 K); while in the NTCELs mode, the maximum absolute sensitivity under 980 nm excitation is 0.003059 K^–1 (529 K), and under 1550 nm excitation is 0.0013 K^–1 (303 K). These findings indicate that Li₂ZnGe₃O₈:Er³⁺/Yb³⁺ phosphors exhibit excellent dual-mode optical temperature sensing potential under dual-excitation conditions.

The pursuit of nanomaterials with desirable properties including excellent reflection loss (RL), reduced thickness, wide bandwidth, facile fabrication process and low density has garnered significant attention. In this study, we explore the potential of new nanocomposite samples through the incorporation of copper oxide nanoparticles into epoxy resin matrices. The investigation further delves into the thermal, morphological and electrical characteristics of these samples. This study evaluates the electromagnetic properties of the composites, including permittivity (ε), permeability (μ), RL and shielding effectiveness. The microwave characterization and shielding effectiveness assessments were conducted across the X-band frequency range (8–12 GHz). The findings are promising where the epoxy/10% CuO composite exhibits strong absorption with a spectrum below −10 dB in the 8.5–9 GHz and 9.75–11.25 GHz ranges. Notably, the 20% CuO composite consistently achieves a spectrum below −10 dB across all frequencies, indicating a remarkable 90% absorption capability at varying thicknesses.

This study investigates the effect of nanoclay (NC) and alumina on improving the thermo-mechanical properties of high-density polyethylene (HDPE) and polypropylene (PP) blends, compatibilized with polyethylene-grafted maleic anhydride (pEMAH). The modulus of the sample containing 1.5% and 3% NC are 893 MPa and 786 MPa, respectively. The ratio of the modulus of composites to that of the matrix increase proportionally with an increase in the composition of NC for various micromechanical models studied. The fracture energy release rate for Run 1 and Run 2 start at 2.08 and 2.35 kJ m^–2 before aging, and once aged, they increase to 6.17 and 5.82 kJ m^–2. High heat on tensile samples leads to bonding in the polymer. The bonding makes a polymer firm, prevents bending and increases the tensile strength. The COMSOL models predict the tensile strength of simulated values at 27 MPa for the 1.5% NC-reinforced matrix, which is the same as the experimental tensile value. Maximum mass loss rates show an increasing trend, with heating rates for the samples containing NC. For instance, the polymer blend containing 1.5% NC has peak mass loss rates of 15% at 5°C, 26% at 10°C and 43% at 15°C as the temperature increases. Adding NC particles to the blend improves its temperature resistance. The activation energy found using Horowitz and Metzger plots for HDPE/PP is 113 kJ mol^–1, which increases to 141 kJ mol^–1 for the 1.5% NC blend.

Ni–P-based composite coatings have been widely used in the field of surface protection of metal materials due to their excellent physical and chemical properties. This study selected hard Al₂O₃ and SiO₂ nanoparticles as strengthening phases and uniformly doped them into the Ni–P matrix using pulsed electrodeposition technology. The surface quality and mechanical properties of the composite coating were improved by optimizing the duty cycle parameters, and the effect of duty cycle on the deposition behaviour of the composite coating was revealed. The microstructure, composition, wear resistance and elastoplasticity of the composite coatings were characterized by scanning electron microscope, energy dispersive spectrometer, X-ray diffraction analyzer and nano-indentation instrument. The research results indicate that the reduction of pulse duty cycle has significant grain refinement and concentration polarization reduction effects, but this seriously sacrifices the deposition rate. Under direct current conditions, there are numerous defects such as pores and micro cracks on the surface of composite coatings. When the duty cycle is 40%, the surface of the composite coating is smooth and dense, and its micro hardness and elastic recovery ratio (h_e/h_max) reach their maximum values of 806 HV and 0.48, respectively, while the average friction coefficient reaches its minimum value of 0.27, which indicates that it has good mechanical properties. This study provides a theoretical basis for the efficient preparation of Ni–P–based composite coatings and improve its application value in surface engineering.

TiN coating prepared by physical vapour deposition on additively manufactured Ti-6Al-4V alloy was studied from the perspective of residual stress to improve adhesion strength. The growth mechanism of TiN coatings was analysed and the coating adhesions were evaluated using a scratch tester. The results showed that the crystal nucleus grew under the surface diffusion and grain boundary migration to form a continuous coating. The preferred directions for crystal growth were the (111), (200) and (220) planes. The compressive stress value has a negative correlation with the bonding strength between the coating and the substrate. Specimen with larger tensile stresses had a more regular cross-section and more compact connection, and protected the coating integrity.

Electrochemical synthesis of graphene is an established process with high consistency and scalable potential. However, information on the effect of types of waveform on the quality of graphene nanoplatelets (NPs) is scanty. In this study, different types of waveform, namely direct current (DC), pulsed direct current (PDC) and bipolar waveform (BP) were used for the electrochemical exfoliation of graphite. All experiments were performed keeping other process parameters constant, such as electrolyte concentration (0.05 M KOH solution), temperature (303 K), distance between electrodes (6 cm) and stirring speed (200 rpm). It is observed that the type of waveform plays a significant effect on the defect concentration and size of the as-synthesized graphene NPs. The size of graphene NPs synthesized using PDC, BP and DC waveforms was in the range of 1–5, 60–220 and 250–450 nm, respectively. Raman spectroscopic analysis confirmed that multilayer graphene consisting of 4–5 layers of C atoms was successfully synthesized irrespective of the type of waveform. Further, the calculated defect concentration of graphene synthesized using PDC waveform was 1.64 ± 0.41 × 10⁹ cm^–2, which is significantly less than those prepared by DC and BP waveforms. The X-ray photoelectron spectroscopic (XPS) analysis showed that the highest C/O ratio (i.e., less oxygen) was noted in graphene synthesized using the PDC waveform. A proof-of-concept study showed a 50% increase in the specific capacitance of Al-doped ZnO nanopowder using graphene quantum dots.

Carbon-based materials are in high demand due to their advanced high-tech applications. In contrast to traditional synthesis methods, a single-step green method is demonstrated for reducing graphene oxide. A simple one-step hydrothermal method successfully synthesized reduced graphene oxide (rGO)-multi-walled carbon nanotube (MWCNT). The composite was characterized using X-ray diffraction (XRD), micro-Raman, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), fourier transform infrared spectroscopy (FTIR), UV-visible absorption spectroscopy (UV-Vis) and zeta potential measurements. The present work aims to investigate the feasibility of utilizing nonlinear optical properties of reduced graphene oxide-carbon nanotube (rGO-CNT) composite as an optical limiter. The Z-scan technique was used to study the composite nonlinear absorption properties at a laser intensity of 532 nm. The result displayed that the composite material exhibits strong nonlinear absorption properties, chiefly resulting from the synergistic impact of rGO and CNT. The optical limiting behaviour of the rGO-CNT composite was evaluated, and it demonstrated excellent performance with a limiting threshold of 0.70 × 10¹² W m^–2. Combining MWCNT tubular shape, homogeneous decorating and strong visible absorption with rGO’s extensive conjugation for charge transfer leads to a highly improved nonlinear optical (NLO) response. The excellent optical limiting performance of rGO-CNT composite makes it an ideal candidate for laser safety and energy stabilizer devices operating in the 532 nm, 9 ns laser domain.

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The processes occurring on the friction surface of polymer composite materials (PCMs) based on polytetrafluoroethylene (PTFE) and layered (LS) silicates such as serpentine and phlogopite are described in the article. The studies were carried out with a scanning electron microscope and X-ray photoelectron microscopy and indicated the occurrence of tribo-oxidative processes in the polymer/metal contact zone. The investigation of the elemental composition of the friction surface by energy dispersive analysis revealed the appearance of new peaks corresponding to Fe and Cr. This fact indicates the interaction of the counterbody metal with the polymer during friction. The occurrence of defluorination and hydroxylation reactions of PTFE macromolecules on the friction surface of PCM was recorded based on the results of X-ray photoelectron spectroscopy. A possible mechanism is proposed for the tribochemical processes that occur on the friction surface of composites, regardless of the composition of the fillers. It has been established that a protective layer is formed consisting of filler particles and tribodestruction products due to tribochemical reactions on the friction surface. The formation of a secondary layer is not observed in the case of a composite with phlogopite. Thus, the main factor in increasing the wear resistance of PTFE-based PCM is the formation of new secondary structures on the friction surface in the friction zone due to the occurrence of tribo-oxidative processes. The generated secondary structures provide a protective surface that contributes to the shear friction stress.

This study was performed on a hot extruded titanium alloy (Ti6Al4V) of circular cross-section. The alloy was deformed at different temperatures and strain rates using the uniaxial tension test. Subsequently, a comprehensive microstructure analysis using an electron back-scattered diffraction technique was performed to investigate the microstructure of the alloy. The study revealed the formation of hard-orientated regions during deformation that adversely affected the ductility of the alloy. This study also highlights the reasons responsible for the evolution of hard orientations at different temperatures.

Resource utilization of food waste and fly ash has been a significant challenge for managing the environment, building a ‘waste-free city’ and achieving the ‘dual-carbon’ goal. In the present study, a high-strength food waste/fly ash/acrylamide composite hydrogel was developed by combining food waste and fly ash into functionalized particles using free radical cross-linking polymerization, with acrylamide used as the monomer, N, N′-methylene bisacrylamide as the cross-linking agent and sodium persulphate as the initiator. After one-factor experiments by changing the dosages of acrylamide, N, N′-methylene bisacrylamide, sodium persulphate, fly ash and polymerization temperature, the process conditions for the hydrogel to have the optimum mechanical property were obtained using response surface optimization. The experimental results showed that Young’s modulus of the produced hydrogels was as high as 2913 kPa at the dosages of acrylamide, N, N′-methylene bisacrylamide, sodium persulphate and fly ash of 4.349, 0.012, 0.540 and 1.181 g, respectively. Subsequently, the morphology and structure of the hydrogels were characterized using a Fourier transform infrared spectrometer, scanning electron microscope and X-ray diffractometer. The results showed that the interactions among polymer chains in the network structure of the hydrogel, the filling of fly ash and the hydrogen bonding combined to give the hydrogel excellent mechanical property. Meanwhile, Young’s modulus of composite hydrogel increased by 30.16% compared to that of the single-phase food waste hydrogel.