Applied Physics A最新文献

This study investigates the mechanical performance of additively manufactured hybrid honeycomb structures, incorporating hexagonal and re-entrant geometries, fabricated from acrylonitrile butadiene styrene (ABS), widely employed thermoplastic material, under bending conditions. Through three-point bending experiments and finite element analysis (FEA), the energy absorption capacity and flexural modulus of these cellular architectures are evaluated. A comparative assessment is conducted between hollow hybrid structures and those reinforced with polyurethane (PU) foam to elucidate the effects of its integration on mechanical properties. The findings indicate that re-entrant hybrid honeycombs exhibit superior reinforcement characteristics compared to hexagonal honeycombs, attributable to their variable cell ratios and dimensions, which allow control over mechanical properties without altering cell geometry. This adaptability facilitates the manufacturing process by enabling the selection of the most straightforward geometry while varying only cell ratios. Additionally, parametric FEA studies explore the influence of structural parameters and bending load configurations on honeycomb performance, revealing that hybrid structures exhibit improved stiffness and energy absorption under three-point bending. Notably, the experimental results closely align with the FEA results, thereby enhancing the reliability of the computational models employed. This research underscores the potential of hybrid designs in the development of advanced lightweight, high-performance materials for diverse engineering applications.

The effects of nano-sized Ni_0.5Zn_0.5Fe₂O₄ (NZFO) addition on the superconducting properties of Bi_1.6Pb_0.4Sr₂CaCu₂O₈ (Bi-2212) were investigated. Samples were prepared using the solid-state reaction method with NZFO addition of 0 to 0.5 wt%. The structural, electrical, and magnetic properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), electrical resistance measurements, and AC susceptibility analysis. All samples exhibited normal metallic characteristics above onset transition temperature, T_c−onset. The resistance versus temperature measurements showed T_c−onset and zero transition temperature, T_c−zero for all samples ranging between 72 and 82 K, and 55 and 70 K, respectively. Scanning electron microscopy (SEM) revealed noticeable microstructural changes with higher additions of nano-sized NZFO. Despite these changes, the addition of nano-sized NZFO did not significantly suppress the intra- and intergrain characteristics of the Bi-2212 phase. The x = 0.06–0.08 wt% samples showed the highest intergrain peak temperatures, Josephson current and Josephson coupling energy even though the transition temperatures and Bi-2212 phase volume fraction were suppressed. This work showed that the appropriate addition of nano-sized NZFO could significantly enhance grain connectivity and critical current density, highlighting its potential as an effective flux pinning center for Bi-based superconductors.

This paper discusses the synthesis of W-type hexaferrite and lanthanum perovskite nanoparticles using the auto-combustion method. Structural analysis conducted through X-ray powder diffraction (XRD) confirms the formation of polycrystalline nanoparticles exhibiting W-type hexaferrite (HF) and orthorhombic perovskite structures. Optical characterization via UV-visible spectroscopy reveals band gaps of 3.2 eV for direct transitions and 2.2 eV for indirect transitions. Scanning electron microscopy (SEM) images illustrate the microstructure, showing grains with prominent hexagonal faces and a spongy morphology, with sizes ranging from 40 to 70 nm. Additionally, antiferromagnetic properties are demonstrated by the hysteresis loop obtained from vibrating sample magnetometer (VSM) measurements. The antibacterial and antifungal activities of the nanosized composite BaCo₂Fe₁₆O₂₇ and LaFeO₃ have been evaluated against various gram-positive and gram-negative bacterial strains.

With the increasing maturity of medical techniques, the implantation of biomaterials into the human body has been identified as a viable solution for treating certain dental and orthopaedic diseases. Titanium (Ti) is typically used as a metallic biomaterial in this process and plays a crucial role in dental and orthopaedic processes. However, these biomaterials still require the use of surface modification techniques. This study aims to apply nanoceramics in metal implants without damaging the substrate and without the need for further heat treatment for the adhesion of composite coatings. Additionally, the effect of using a vitamin (fish oil) as an inhibitor to prevent the corrosion of the titanium implant was investigated. In this study, a Ti substrate was separately coated with composite layers containing polyvinyl alcohol with 3% nano-hydroxyapatite and 3% nano titanium dioxide. The coating process was conducted using a dip coating technique. The prepared specimens were then tested using Fourier-transform infrared spectroscopy, contact angle, atomic force microscopy (AFM), corrosion, antibacterial and cytotoxicity tests. The results demonstrate that the obtained coating layer improved the wettability, antibacterial and cytotoxicity characteristics of the Ti substrate. Additionally, the corrosion resistance improved after coating and increased with increasing corrosion inhibitor concentration. The AFM results revealed that the coating layer was deposited in a thin film with a homogenous morphology. Finally, the obtained results were statistically analysed using an analysis of variance and were found to be statistically significant (P < 0.05). Overall, the results reveal that the modified Ti surface produced metal implants with long-term durability.

We studied the effects of 80 MeV Si(^{8+}) ions on the structural characteristics, surface morphology, optical and electrical properties of 200 nm thick Ga-doped zinc stannate films, fabricated using the pulsed laser deposition technique. The analysis of the glancing incidence X-ray diffraction patterns reveal that the pristine crystalline films became amorphous after Si(^{8+}) ion irradiation, and the surface images from atomic force microscopy display an enhancement in surface roughness with increasing ion fluences. The optical studies show a decrease in the bandgap from 3.62 to 3.42 with irradiation and quenching of the luminescent defects deep in the bandgap. The resistivity of the films decreased with Ga-doping and swift heavy ion (SHI) irradiation. These modifications in the physical properties due to irradiation are understood based on irradiation induced amorphization and thermal spike model. It was found that Ga-doping and SHI irradiation produce similar effects on the electrical and optical properties of the zinc stannate films. These amorphous films may provide a better alternative to the crystalline zinc stannate films, which have potential applications as transparent conducting oxide.

In this study, Ag nanoparticles decorated poly(l-cysteine) (PCs) electrodes (Ag@PCs) were developed for the non-enzymatic determination of H₂O₂. Additionally, the electrochemical synthesis of Ag@PCs nanostructures on the pencil graphite electrode surface was achieved for the first time. Different techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and field emission scanning electron microscopy were used in the analytical and morphological characterization of the produced Ag@PCs modified electrodes. As-prepared Ag@PCs electrodes were examined as electrode materials in the non-enzymatic determination of H₂O₂. Electrochemical determination of H₂O₂ was investigated using cyclic voltammetry and chronoamperometry techniques. While the detection limit of the sensor was 0.26 µM, its sensitivity and linear range were calculated as 142.47 μA μM⁻¹ and 250−3560 µM, respectively. Moreover, high selectivity towards H₂O₂ was achieved in the presence of interfering species at the Ag@PCs electrode. Ag@PCs electrodes have great potential for applications involving the electrochemical detection of H₂O₂.

Bismuth Niobate/polyaniline (Bi₅Nb₃O₁₅(BNO))/PANI nanocomposites were synthesized and studied for use as a supercapacitor electrode. The BNO nanoparticles (NPs) were synthesized using the green route while PANI was synthesized using in-situ polymerization technique. The BNO/PANI nanocomposites were formed with different mass ratios of BNO to PANI, specifically 9:1, 8:2, and 7:3, each totaling 0.5 g for the respective combinations. The physicochemical properties of the composites were obtained using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) spectroscopy, Transmission Electron Microscopy (TEM) and UV–vis spectroscopy. The electrochemical properties were determined using cyclic voltammetry (CV), galvanostatic charge discharge (GCD), and electrochemical impedance spectroscopy (EIS). The XRD pattern indicated the presence of orthorhombic BNO, and the crystalline structure of BNO remained unaffected by the inclusion of PANI. The crystalline sizes of BNO, BNO/PANI-10%, BNO/PANI-20%, and BNO/PANI-30% are 22.58 nm, 26.43 nm, 23.17 nm, and 19.07nm, respectively. Analysis using FTIR confirmed the uniform attachment of PANI on the surface of BNO nanoparticles. SEM imaging revealed a fibrous agglomerated structure in the BNO/PANI composites. TEM results showed well-dispersed nanostructures with clear lattice fringes, indicating high crystallinity. The electrochemical behavior of the BNO/PANI composite electrodes evaluated in a 1M H₂SO₄ solution showed that the BNO/PANI-30% composite electrode exhibited the highest specific capacitance of 216 Fg⁻¹ at a scan rate of 5 mV/s, surpassing the specific capacitance (10.4 Fg⁻¹) of the pristine BNO nanoparticles with more than 20 times. Additionally, the composite retains 69% of its capacitance after 5000 cycles at a current density of 2 Ag⁻¹. An asymmetric supercapacitor device (AC//BNO/PANI-30%) developed using activated carbon (AC) and BNO/PANI-30% as the negative and positive electrode respectively yielded a specific capacitance 475.44 Fg⁻¹ at a current load of 0.1 Ag⁻¹. The device retained 52.87% of its initial capacitance value after 5000 cycles, and also shows 100.14% of coulombic efficiency, indicating the potential of this composite as a promising material for supercapacitors.

Diamond, as an ultra-wide bandgap semiconductor material, exhibits promising properties including strong mechanical stability, fast thermal conductivity, strong radiation resistance and broad-spectrum transmittance. Notably, deep-level defects within the diamond introduce defect-induced energy levels known as color centers. The fluorescence emission from color centers has strong monochromaticity, wavelength stability, and thermal stability, making them great potential for applications in quantum information processing, optical sensing, and biological labeling. Among these, the silicon-vacancy (Siv) color center, characterized by a zero-phonon-line at 738 nm, demonstrates a short excited-state lifetime (1 − 4 ns) and a narrow zero-phonon-line width (≈5 nm) at room temperature, underscoring its superior performance and potential applications. This study investigates the luminescence properties of Siv color centers in silicon-doped single-crystal diamond grown via the microwave plasma chemical vapor deposition (MPCVD) method. Measurements of fluorescence luminescence intensity of Siv color centers were conducted using PL, point-by-point scanning of specific areas to form a mapping image to determine the location of Siv color centers. A strong correlation is established between the distribution of Siv color centers and the surface structural defects existing in the diamond material. The results may support for subsequent research on diamond Siv color-centered single-photon devices such as single-photon detectors, single-photon avalanche diodes.

The magnetocaloric effect(MCE) of the (Fe_0.5Cu_0.5)₆₀Zr₄₀ alloy has been investigated by phenomenological model, estimating magnetic entropy change (∆S_M) and heat capacity change. The results indicate that MCE of (Fe_0.5Cu_0.5)₆₀Zr₄₀ alloy can be controlled and tuned by several magnetic fields. Furthermore, the study of ∆S_M curves predicts how to expand the temperature range for exploiting (Fe_0.5Cu_0.5)₆₀Zr₄₀ in magnetic refrigeration. ∆S_M reaches a peak of about 0.5 J/Kg K at 112 K with δT_FWHM = 227 K and RCP = 102 J/Kg under 5 T applied field variation. (Fe_0.5Cu_0.5)₆₀Zr₄₀ alloy has a potential application for magnetic refrigerants over a wide temperature range, especially its high electrical resistivity leads to decreased eddy current losses, covering a significant range of temperature between 0 K and room temperature. Therefore, these advantages make (Fe_0.5Cu_0.5)₆₀Zr₄₀ alloy potentially practical for efficient cooling devices.

We study the behavior of electromagnetic waves near the interface between two media: a dielectric medium and a conducting medium. Solving this problem within the framework of classical electrodynamics, we obtain results that coincide with the known ones, namely: (1) By comparison of the solution to this problem—when obtained within the framework of classical electrodynamics—with experimental data shows that using the values of electrical conductivity of metals given in physics reference books (the values of the so-called static electrical conductivity), we cannot achieve satisfactory agreement between theory and experiment. (2) We can achieve satisfactory agreement between experimental data and the predictions of classical electrodynamics only if we use values of the so-called optical conductivity that differ by two orders of magnitude from the values of the static conductivity. In addition, we propose a re-evaluation of some well-known facts, namely: (1) According to many literary sources, the permittivity of metals changes by several orders of magnitude depending on frequency and becomes negative at frequencies below the plasma frequency. It turns out that when applying Maxwell’s equations in different frequency ranges, it is necessary to use parameters that differ by two orders of magnitude. (2) At the same time, experimentalists interpret optical experiments by using formulae derived from Maxwell’s equations under the assumption that all parameters are constants. In our opinion, if we interpret experimental data using equations with constant coefficients and as a result we see that the coefficients depend significantly on frequency, we should think about using more complex equations to interpret the experimental data. (3) In this paper, we propose a new approach to interpretation of the experimental data. The novelty is that we use the equations of extended electrodynamics, which are three-dimensional analogues of Kirchhoff’s laws for electrical circuits. We show that extended electrodynamics allows us to describe experimental data using handbook values of conductivity and frequency-independent values of permittivity. Thus, we conclude that extended electrodynamics describes experimental data for metals more accurately than classical electrodynamics.