Applied Physics A最新文献

This study presents a comprehensive fabrication process for dielectric ceramic capacitor derived from lead-free Bi_0.5(Na_0.8K_0.2)_0.5TiO₃ (BNKT) in bulk and powder form, synthesized by sol–gel method. Both the BNKT powder and the bulk ceramic were rigorously analyzed and compared for their crystal structure, morphology, magnetic and optical properties. Through XRD and Raman results, the structure in the form of morphological phase boundary (MPB) was detected. In addition, the morphological structure, grain size evolution and purity of the samples were also confirmed by SEM and EDX. The weak ferromagnetic property of the BNKT powder sample was replaced by the diamagnetic property of the bulk ceramic sample and a decrease in the band gap (E_g) from 3.33 eV to 3.13 eV was also observed in the corresponding samples. At room temperature, the dielectric constant (ε_r) of the bulk ceramic reached 2193 with a dielectric loss (tanδ) of 0.332 at 1 kHz. It also exhibits typical ferroelectric behavior with slim P–E loop, a recoverable energy density (W_rec) of 12.541 mJ/cm³, and a high energy storage efficiency (η) of 46.44% under a low electric field of 15 kV/cm. Furthermore, the charge–discharge properties of BNKT dielectric ceramic capacitor were also characterized by a time constant (τ) of 8.452 μs. With this simple production process, it is possible to expand large-scale production while still ensuring the quality of ceramic capacitors, contributing to the development of BNKT lead-free material applications in electronic devices.

Herein, we present the luminescence-emission properties of (Ce³⁺, Eu³⁺) doped Li₂O-CaO-Bi₂O₃-B₂O₃ glasses fabricated via melt-quenching. The density of glasses was found to increase from 3.551 to 3.655 g/cm³ with dopant concentration, owing to the formation of non-bridging oxygens, resulting in enhanced luminescence by facilitating radiative transitions of Eu³⁺-ions. On the other hand, slight decreases in molar volume, refractivity, polarizability, optical basicity, and electronic polarizability suggest a more localised charge distribution and reduced polarizability. nevertheless, the stability in reflection loss, dielectric constant, and transmission coefficient indicates consistent optical quality and stable glass material. Raman analysis reveals the structural changes induced by the dopants due to Bi-O bonds, B-O-B linkages, and BO₃ and BO₄ units. The excitation spectra revealed broad Ce³⁺ (300–350 nm) bands and sharp peaks for Eu³⁺ (393 and 464 nm), indicating distinct optical behaviours. Emission spectra showed broad Ce³⁺ emission (400–450 nm) and sharp Eu³⁺ emission (592 and 615 nm), highlighting effective energy transfer between Ce³⁺-Eu³⁺ ions and improved luminescent properties. Decay kinetics demonstrated increased lifetime values with higher Eu³⁺ concentrations under 328 nm excitation, and consistent lifetime values were observed under 394 nm excitation due to the interplay of energy transfer dynamics, quenching effects, and the availability of non-radiative decay channels influenced by Eu³⁺ concentration and excitation wavelength. Among the prepared glasses, the LCBBCe_0.1Eu_0.5 glass exhibits the highest emission intensity in the deep red region, with an emission purity of 98.3% when excited at 394 nm.

Metal oxide layer removal is an important part of steel processing in the automotive and mechanical engineering industry. Laser cleaning of metal oxide layer has attracted extensive attention for its selectivity and environmental protection. However, laser cleaning efficiency and high cleaning threshold remain challenges for industrial applications. To address these issues, a new electromagnetic induction heating assisted laser cleaning method is proposed. This innovative approach increases the cleaning efficiency and reduces the laser cleaning threshold via elevating surface temperature. With this novel technology, the laser cleaning threshold of metal oxide layer is reduced from 5.5 J/cm² to 3.3 J/cm². Oxygen content also decreases by 68.1% with the assistance of electromagnetic induction heating at the laser fluence of 3.3 J/cm². To validate the industrial applications of the electromagnetic heating assisted laser cleaning, a rusty steel plate is used as a sample. At the same laser fluence, the time for the rust layer reaches its evaporation temperature is shortened when assisted by the electromagnetic induction heating. The cleaning time is reduced by approximately 50% at the laser fluence of 3.3 J/cm².

In recent years, Bismuth Ferrite (BiFeO₃, BFO) has emerged as a promising multiferroic material due to its high antiferromagnetic Néel temperature (T_N ~ 623–643 K) and ferroelectric Curie temperature (T_C ~ 1083–1103 K). These properties make BFO a strong candidate for exhibiting a magnetoelectric effect even at room temperature. Understanding the temperature-dependent ferroelectric behavior of BFO is crucial for optimizing its performance in applications where stable ferroelectric behavior at operational temperatures is essential for enhancing device efficiency, stability, and functionality. This study investigates the impact of temperature on the crystallographic characteristics (unit cell type, bond lengths, and dimensions) and ferroelectric performance of BFO. X-ray diffraction and electrical hysteresis measurements confirm the presence of a ferroelectric phase with a rhombohedral R3c structure, along with two phase transitions: the first around 600 K from ferroelectric to paraelectric, and the second near 1050 K from paraelectric back to ferroelectric.

Surface roughness plays a critical role in ultrashort pulse laser ablation, particularly for industrial applications using burst mode operations, multi-pulse laser processing, and the generation of laser-induced periodic surface structures. Hence, we address the impact of surface roughness on the resulting laser ablation topography, comparing predictions from a simulation model to experimental results. We present a comprehensive multi-scale simulation framework that first employs finite-difference-time-domain simulations for calculating the surface fluence distribution on a rough surface measured by atomic-force-microscopy followed by the two-temperature model coupled with hydrodynamic/solid mechanics simulation for the initial material heating. Lastly, a computational fluid dynamics model for material relaxation and fluid flow is developed and employed. Final state results of aluminum and AISI 304 stainless steel simulations demonstrated alignment with established ablation models and crater dimension prediction. Notably, Al exhibited significant optical scattering effects due to initial surface roughness of 15 nm—being 70 times below the laser wavelength -leading to localized, selective ablation processes and substantially altered crater topography compared to idealized conditions. Contrary, AISI 304 with ({R}_{text{q}}) surface roughness of 2 nm showed no difference. Hence, we highlight the necessity of incorporating realistic, material-specific surface roughness values into large-scale ablation simulations. Furthermore, the induced local fluence variations demonstrated the inadequacy of neglecting lateral heat transport effects in this context.

A new hybrid composite has been synthesized from partially unzipped multi-walled carbon nanotubes and graphite-like carbon nitride. This composite was thermochemically synthesized from urea and melamine with partially unzipped carbon nanotubes obtained by electrochemical synthesis. The resulting hybrid composite was characterized by X-ray diffraction, selected area electron diffraction, transmission electron microscopy and Fourier-transform infrared and Raman spectroscopy. These methods have proven the production of a hybrid composite of partially unzipped multi-walled carbon nanotubes and graphite-like carbon nitride. As evident from the voltammograms, the hybrid composite material exhibits the highest activity compared to the original components such as g-C₃N₄ and unzipped multi-walled carbon nanotubes. Electrochemical studies have demonstrated that the resulting hybrid composite is a promising material for use as a metal-free catalyst in oxygen electrodes for fuel cells, with performance characteristics approaching those of Pt-based oxygen electrodes. The resulting composites remained stable in operation for six months as an oxygen electrode in a fuel half-cell.

A series of α-, β-unsaturated ketone derivatives of four substituted pyrazoles were synthesised using Claisen-Schmidt condensation reaction and were characterised using Fourier-transform infrared (FTIR) spectroscopy, ¹H nuclear magnetic resonance (NMR) and ¹³C NMR spectroscopy. Further, these derivatives were studied under application as an oxidising agent in a compost-based microbial fuel cell (cMFC) to enhance its reduction efficiency. Characterisation methods of cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and chrono-amperometry (CS) were employed to analyse the behaviour of the coin-cell device with and without pyrazoles at the cathode. Concentration dependence of the best pyrazole out of the series was studied to optimise the device performance. The results indicate the enhancement in bio-electro-catalytic activity and output power density when the cathode of the cMFC is laced with pyrazoles. In addition, sustainability and stability of the device was also investigated, and study to confirm the role of micro-organisms in the compost was also performed.

Optical vortex induced forward transfer (OV-LIFT) allows the crystallization of magnetic nanoparticles enabling the fabrication of a 2-dimensional array of monocrystalline structures with a high spatial resolution. We herein investigate the optimum experimental conditions, such as the viscosity range of the donor and the energy range of the optical vortex pulse required for the crystallization of magnetic nanoparticles through a cavitation processes, including the flight dynamics of donor.

One effective way to prevent toxicity and improve the stability of materials for photovoltaic applications is to exclude lead and organic molecules from perovskite materials. Specifically, the CsSn_1−xGe_xI₃ appears to be a promising contender; nonetheless, it requires optimization, particularly bandgap tuning by doping concentration modifications. In this study, density functional theory (DFT) was employed to comprehensively analyze the electronic properties of CsSn_1−xGe_xI₃ that influenced light-matter interactions tuning of the perovskite materials by varying composition in B site atoms. We use the solar cell capacitance (SCAPS-1D) simulator to compute device performance; however, it computes the absorption spectrum using a simplified mathematical function that approximates the actual spectrum. To achieve a quantum-mechanical level of accuracy DFT extracted parameters like absorption spectra and bandgap were fed into SCAPS-1D. We find that increasing the Ge concentration leads to a higher bandgap and improved absorption profile, thereby enhancing solar energy conversion efficiency. Thermal and field distribution analyses were also done for the optimized device through a finite-difference time-domain (FDTD) framework. By optimizing the absorber layer with a 75% Ge concentration, we achieve a remarkable PCE of 23.55%. Our findings guide future research in designing high-performance non-leaded halide PSCs, paving the way for low-cost, stable, and highly efficient solar cells through atomic doping-tuned perovskite absorber layers.

Reduced graphite oxide (rGO) based smart sensor is promising for the detection of structural strain sensing, fatigue monitoring, impact drop sensing, crack sensing and human physiological sensing action owing to its extremely large surface to volume ratio, high sensitivity and tensile strength. However, maximum commercial based sensors suffered from non-uniformity and sensitivity in their response towards dynamic and human physiological action. Such a reliable and high sensitize reduced graphite oxide polymer nanocomposite spray coated sensor shows good piezo-resistive behaviour and it is reported that the green synthesis of photo reduction-based graphite oxide shows good sensitivity in their response towards dynamic sensing and wearable devices. Such a reliable and highly sensitize based solar assisted green technology sensor has not yet studied in deeper level for multi-sensing applications. In this study, graphite oxide is obtained by intercalating graphite with molecular diffusion to KMnO₄-H₂SO₄₋NaNO₃, called as Hummer’s method. Then graphite oxide is made up to undergo solar exfoliation for conversion into reduced graphite oxide. This is the latest and most unique clean green synthesis method for smart piezo-sensor development approach. Electrical and piezoresistive behaviour of these sensor is studied upon structures and body locomotion. I report the comparative study of rGO/PMMA with SEM, Raman Spectroscopy, XRD-analysis, EDAX with commercial based GNP (graphene nano-platelet) sensor in terms of morphology confirmation. A unique design for solar exfoliation has been implemented with the help of steeper motor control mounted with convex lens. Our solar reduction-based sensor may replace commercial based low sensitive sensor in future.