Gap Density Research Articles

Flower like Ni doped BiVO4 composite with efficient visible light photocatalytic performance for the removal of Naproxen: A detailed mechanism and DFT study

BiVO4 and Ni doped BiVO4 (Ni-BiVO4) photocatalysts were synthesised by the co-precipitation method. BiVO4 and Ni-BiVO4 photocatalysts were characterized by various analytical techniques. PXRD studies of the BiVO4 and Ni-BiVO4 catalysts shows monoclinic-scheelite structure. Density functional theory calculations were carried out to predict the density of states and band gaps. The flower bunch is arrayed in a rod-like pattern on the HRTEM images, and the particle size was estimated using d-spacing and found to be in the range of 98-415 nm. Furthermore, the charge separation mechanism of photogenerated charge carriers of BiVO4 and Ni-BiVO4 photocatalysts were studied by photoelectrochemical response and impendence spectroscopy. The result shows that the Ni-BiVO4 photocatalyst possess the higher photocatalytic performance, and this can be attributed to the enhanced absorption of visible light, and lower recombination of electron and holes. Further, enhanced photocatalytic activity of Ni-BiVO4 photocatalyst was observed by addition of hydrogen peroxide (H2O2). The order of photocatalytic activity for the degradation of Naproxen under visible light: Ni-BiVO4 +H2O2 > Ni-BiVO4 > BiVO4 > Ni-BiVO4 + IPA. The investigation of degradation products was carried out utilising liquid chromatography mass spectroscopy coupled UV-visible absorption spectrum technique. Radical quenching is studied to reveal the substantial contribution of hydroxyl free radicals in the Ni-BiVO4 with H2O2 system.

Improving radio frequency heating uniformity in cauliflower by changing density in different zones

Radio frequency (RF) treatment is one of the most promising approaches for disinfesting, drying, and pasteurizing agricultural products. However, the inhomogeneous heating of RF treatment is the primary barrier for practical applications. To improve the RF heating uniformity, a 27.12 MHz, 6 kW pilot-scale RF system was applied to heat the cauliflower by changing its density in different zones of a rectangular container. The results proved that the RF heating rate and the average mass change rate of the cauliflower decreased with increasing electrode gap and bulk density of the cauliflower. The RF heating uniformity of the cauliflower was improved by increasing the electrode gap and the bulk density of the cauliflower during RF heating. With increasing of the bulk density of sample at the edges in the container, the RF heating rate and heating uniformity index of the sample firstly decreased and then increased when the sample density at the center and the corners were 405.5 and 516.8 kg/m3, respectively. The mass change rate of the sample presented an inverse relationship with the heating rate and heating uniformity index during RF treatment. The best heating uniformity and highest mass change rate were obtained when the bulk density of the cauliflowers at the center, edges, and corners in the container was 405.5, 461.1, and 516.8 kg/m3, respectively. The results of this study can offer effective method for improving the RF heating uniformity in high moisture products.

Defect related photocatalytic and photoluminescent characteristics of Gd-doped SnO2 nanoparticles with different shapes

A new method for the preparation of Gd-doped SnO2 nanoparticles based on the precipitation method followed by hydrothermal treatment has been developed. Two different shape series of nanoparticles with different Gd content were obtained and fully characterized. Wide number of parameters, including lattice parameters, crystallite size, particle size, surface composition, oxygen vacancies, structural defects, band gap energy, luminescent spectra, band structure and density of states were determined.It was shown that the mechanism of oriented attachment of nanoparticle growth is stimulated during hydrothermal treatment. Quantum computer calculations of the interaction energies of oriented nanoparticles were performed and the role of ions in the reaction media was revealed.A study of the photoluminescence of the obtained nanoparticles was carried out, showing a blue photoluminescence corresponding to the oxygen vacancies, indicating their presence.Photocatalytic activity of nanoparticles when irradiated with visible light was shown, which is explained by quantum chemical calculations and demonstrated in the example of a colored solution of the organic dye methylene blue. The relation between the morphological and structural properties of nanoparticles and their photocatalytic properties has been studied in detail. A high degradation percentage is achieved using a regular commercially available LED lamp with a visible light spectrum.Novelty of the work lies in obtaining series of samples with various parameters, detailed studies of oriented attachment mechanism and impact of the nanoparticle parameters on photocatalytic properties. A concept for the development of efficient photocatalysts based on chemical and computational experiments is proposed.

Design and Simulation of an Environment-Friendly ZrS2/CuInS2 Thin Film Solar Cell Using SCAPS 1D Software

In this research, we proposed new inorganic ZrS2/CuInS2 heterojunction solar cells based on 2D dichalcogenides material using SCAPS-1D software. Transition metal dichalcogenides (TMDs) are two-dimensional materials with outstanding semiconducting properties due to their high optical absorption coefficients, nontoxic nature, significant charge carrier mobility, and tunable energy band structures. In this study, eco-friendly solar cells having the arrangement Al/ZrS2/CuInS2/Au have been quantitatively analyzed. This simulation employed the absorber layer CuInS2 and the buffer layer ZrS2 with aluminum as the front contact and gold as the back contact. The impact of the absorber layer thickness, band gap, buffer layer thickness, acceptor density, defect density, series and shunt resistances, C-V, Mott–Schottky, and the operating temperature has been studied for the proposed solar cell structure. The best performance of proposed solar cell structure thickness, band gap, and donor density for n-ZrS2 is 0.3 µm, 1.7 eV, 1 × 1019 cm−3, and for p-CuInS2, respectively, 4 µm, 1.43 eV, 2 × 1017 cm−3. The suggested solar cell has a power conversion efficiency of 21.1% with 0.81 V Voc, 30.5 mA/cm2 Jsc, and 85.78% FF. The analysis reveals that CuInS2 absorber material and ZrS2 semiconducting transition metal dichalcogenides (TMDs) are potential materials for photovoltaic applications.

Disorder effects in NbTiN superconducting resonators

Disordered superconducting materials like NbTiN possess a high kinetic inductance fraction and an adjustable critical temperature, making them a good choice for low-temperature detectors. Their energy gap (Δ), critical temperature (T c), and quasiparticle density of states (QDOS) distribution, however, deviate from the classical BCS theory due to the disorder effects. The Usadel equation, which takes account of elastic scattering, non-elastic scattering, and electro–phonon coupling, can be applied to explain and describe these deviations. This paper presents numerical simulations of the disorder effects based on the Usadel equation to investigate their effects on the Δ, T c, QDOS distribution, and complex conductivity of the NbTiN film. Furthermore, NbTiN superconducting resonators with coplanar waveguide (CPW) structures are fabricated and characterized at different temperatures to validate our numerical simulations. The pair-breaking parameter α and the critical temperature in the pure state TcP of our NbTiN film are determined from the experimental results and numerical simulations. This study has significant implications for the development of low-temperature detectors made of disordered superconducting materials.

Monocrystalline silicon materials with the group IVA elements doped: A first-principles analysis

In this paper, the changes of lattice constant, stability and electronic structural properties of Si64−xMx (M=C, Ge, Sn, Pb; x=0, 1, 2, 3, 4) doped system under various doping types and concentrations were studied by using first principles calculation to determine the influence of doped IVA family elements on the properties of monocrystalline silicon materials. The results have shown that, the Ge, Sn and Pb doped systems will produce an expansion effect, and the lattice constant of the C doped system will decrease with the increasing of the number of doped atoms, and will have the greatest impact on the lattice constant of the system. The increase in defect formation energy is Pb¿C¿Sn¿Ge, the Ge doped system is the easiest to synthesize; and as the doping concentration increases, the defect formation energy of each doping system also increases, indicating that high concentration doping systems are more difficult to synthesize. There are no virtual frequencies in the phonon spectra of all doped systems, and the systems are thermally stable. In addition, doping will gradually reduce the bandgap width as the doping concentration increases. The band gap characteristics will also change: when doped with C, the system will become Metalloid; when doped with Ge, the system remains unchanged; when doped with Sn and Pb, the system will become a direct band gap semiconductor. From the perspective of band gap and charge differential density, the effect of different doping elements on enhancing electronic transitions is C¿Pb¿Sn¿Ge. This means that C doping system has the best improvement in conductivity.

Ab initio calculations of structural, electronic, optical, and magnetic properties of delafossite SMoO2 (S = Na, K, Rb, Cs) for spintronics

Half metallic ferromagnetic (HMF) are key materials for quantum computing information storage devices and green energy. So, the structural, electronic, optical, and magnetic properties of SMoO2 (S = Na, K, Rb, Cs) are studied by quantum simulations based on density functional theory (DFT) within WIEN2K code. The Perdew − Burke − Ernzerhof (PBE + GGA) was used for the exchange correlation potential to study the said compounds. The volume optimization properties indicated that these compounds have minimum ground state energy in monoclinic crystal structure with space group 12 C2/m. Moreover, electronic band gap properties and density of states (DOS) graphs depicted the metallic nature for spin up a channel and semiconductor nature for spin down channel. This confirms the half-metallic ferromagnetism (HMF), and Heisenberg's classical model confirms the 100% spin polarization. Various frequency dependent optical parameters explain the optical properties. The double exchange process, crystal field energy ∆Ecry, direct Δx(d), and indirect exchange energies Δx(pd), is demonstrated by the quantum ferromagnetic behavior. The negative value of Δx(pd) and magnetic exchange constants confirm the ferromagnetism due to the quantum exchange mechanism of electrons. In addition to the above, it has been noted from the density of states that Mo d-states are responsible for the response of half metallic nature of these compounds. The magnetic parameter values of SMoO2 (S = Na, K, Rb, and Cs) show higher magnetic moment and major contribution coming from the Mo atom. Hence the studied results show that these compounds are valuable materials for spintronic applications.

Evaluation of the efficacy of horizontal distraction osteogenesis using expansion screws in the repair of the acquired jaw bone defects.

A total of eight patients ( age 17-36 years) who came with atrophy of the maxilla were treated by horizontal DO. The used device consisted of two parts: one was an orthodontic expander and the other was a screw-ring. The expansion screws were set on the transport bone, which was osteotomized and fixed to the segments using microscrews. Radiographical documentation of the patients was obtained with cone beam computed tomography prior to the surgery and after 4 months of the distraction phase. The average of the actual bone gain at the end of the consolidation period was 7mm (range 5-9mm). Intraoral DO failed in one patient. The average bone density in the distraction gap after 4 months of the DO was 460.40. The average bone density of the bone defect region after 4 months of the DO was 487.90. Our results confirm that horizontal DO using expansion screws is a predictable and effective regenerative procedure for patients with acquired bone defects in the jaw.

Investigation of p-CuNb2O6 for use as photocathodes for photoelectrochemical water splitting

P-type copper niobate (CuNb2O6) was prepared for the first time by a two-step spray pyrolysis method on FTO glass substrates. Its feasibility in photoelectrochemical (PEC) decomposition water was systematically evaluated. The physical and photophysical properties of the thin film, including band edge position, bandgap energy, carrier lifetime, and incident photo-to-current efficiency (IPCE), were characterized and analyzed. The optical band gap of the prepared gray CuNb2O6 film is ∼1.41 eV, which indicates that it can absorb visible light and achieve sunlight-driven water splitting. The photocurrent density under simulated sunlight at AM1.5 was 0.25 mA/cm2, and the IPCE value could reach up to 3% at 400 nm in an aqueous solution (pH = 6.8) when applying a bias of 0.4 V vs. RHE. Despite exhibiting a good optical band gap and photocurrent density, the fabricated p-CuNb2O6 thin films remained unstable under illumination in aqueous solutions due to the reduction reaction of copper. Based on these findings, this study provides a new opinion on the applicability of CuNb2O6 as a photocathode material for PEC water splitting.

Alkaline earth based antiperovskite AsPX3 (X = Mg, Ca, and Sr) materials for energy conversion efficient and thermoelectric applications

Antiperovskite were created by swapping ionic positions in the perovskite ABX3 crystal composition. These have great potential for renewable energy devices owing to their low band gap, low cost, and high absorption with Pm-3m space group. Herein, the authors have investigated inherent properties such as bulk modulus and its pressure derivatives, lattice constant, the density of states, band gap, effective mass, refractive index, dielectric constant, extinction coefficient, and absorption coefficient, thermoelectric parameters etc of antiperovskite materials by using density functional theory-based first-principles calculations. These materials exhibit high absorption in the Visible, Ultraviolet region and also in the Near Infrared region which is the most admirable property acquired by various Optoelectronic devices. The proposed compounds have been found mechanically and thermodynamically stable. Their high figure of merit makes them a potential candidate for thermoelectric devices. The proposed material AsPCa3 with a theoretical efficiency of 34% is expected to be a good photovoltaic absorber material.

Local density of states fluctuations in a two-dimensional superconductor as a probe of quantum diffusion

The interplay of superconductivity and disorder generates a wealth of complex phenomena. In particular, the peculiar structure of diffusive electronic wavefunctions is predicted to increase the superconducting critical temperature in some range of disorder. In this work, we use an epitaxial monolayer of lead showing a simple band structure and homogenous structural disorder as a model system of a 2D superconductor in the weak-antilocalization regime. Then, we perform an extensive study of the emergent fluctuations of local density of states (LDOS) and spectral energy gap in this material and compare them with both analytical results and numerical solution of the attractive Hubbard model. We show that mesoscopic LDOS fluctuations allow to probe locally both the elastic and inelastic scattering rates which are notoriously difficult to measure in transport measurements.

AcesExperimental and theoretical study on photocatalytic nitrogen reduction catalyzed by Fe doped MoO2

Transition metal oxides are suitable for photocatalytic nitrogen reduction (pNRR) due to their properties of narrow band gap and high energy density. Still, it is also limited by the defects of high photogenerated carrier recombination and low adsorption capacity of nitrogen molecules, which hinder the further improvement of the activity. For high carrier recombination and low activation rate of the nitrogen molecule, herein, Fe-doped MoO2 catalyst (Fe−MoO2) was synthesized for pNRR. Combined with the experimental characterization and theoretical calculation, it shows that the doping of Fe atoms, one hand, improves the conduction band position of MoO2 and enhances the reduction ability, which is favorable to nitrogen reduction. On the other hand, it not only enhances the adsorption of Mo sites and N2 molecules, but also changes the surface electronic structure and promotes the electron transfer from MoO2 to Fe sites, and the two act synergistically to adsorb and activate nitrogen more effectively. The activity of Fe−MoO2 for pNRR is as high as 96.62 μmol g−1h−1, which is about 2.5 times that of pristine MoO2, and the activity decreases by only 10% after three cycles.

Lead-Free FACsSnI3 Based Perovskite Solar Cell: Designing Hole and Electron Transport Layer.

In recent years, lead-based perovskites solar cells have demonstrated excellent power-conversion efficiency. Despite their remarkable progress, the commercialization of lead-based perovskites is hampered by lead toxicity concerns. The recently discovered non-toxic FACsSnI3 perovskite has the potential to replace lead-based perovskites in solar cell applications. Since the perovskite material FACsSnI3 (FA0.85Cs0.15SnI3) is relatively new, there is a lack of information, particularly regarding the design features required for electron and hole-transport layers for efficient photovoltaic responses. The important variables, such as electron affinity, energy band gap, film thickness, and doping density of both electron and hole-transport layers, were simulated and modeled separately and iteratively in this study to achieve the most efficient photovoltaic response. Finally, the absorber layer thickness of FACsSnI3 perovskite is tuned to achieve a maximum power-conversion efficiency of slightly more than 24%. We hope that the findings of this study will serve as a strong guideline for future research and the design of lead-free perovskite solar cells for efficient photovoltaic responses.

Explainable Artificial Intelligence (XAI) Model for Earthquake Spatial Probability Assessment in Arabian Peninsula

Among all the natural hazards, earthquake prediction is an arduous task. Although many studies have been published on earthquake hazard assessment (EHA), very few have been published on the use of artificial intelligence (AI) in spatial probability assessment (SPA). There is a great deal of complexity observed in the SPA modeling process due to the involvement of seismological to geophysical factors. Recent studies have shown that the insertion of certain integrated factors such as ground shaking, seismic gap, and tectonic contacts in the AI model improves accuracy to a great extent. Because of the black-box nature of AI models, this paper explores the use of an explainable artificial intelligence (XAI) model in SPA. This study aims to develop a hybrid Inception v3-ensemble extreme gradient boosting (XGBoost) model and shapely additive explanations (SHAP). The model would efficiently interpret and recognize factors’ behavior and their weighted contribution. The work explains the specific factors responsible for and their importance in SPA. The earthquake inventory data were collected from the US Geological Survey (USGS) for the past 22 years ranging the magnitudes from 5 Mw and above. Landsat-8 satellite imagery and digital elevation model (DEM) data were also incorporated in the analysis. Results revealed that the SHAP outputs align with the hybrid Inception v3-XGBoost model (87.9% accuracy) explanations, thus indicating the necessity to add new factors such as seismic gaps and tectonic contacts, where the absence of these factors makes the prediction model performs poorly. According to SHAP interpretations, peak ground accelerations (PGA), magnitude variation, seismic gap, and epicenter density are the most critical factors for SPA. The recent Turkey earthquakes (Mw 7.8, 7.5, and 6.7) due to the active east Anatolian fault validate the obtained AI-based earthquake SPA results. The conclusions drawn from the explainable algorithm depicted the importance of relevant, irrelevant, and new futuristic factors in AI-based SPA modeling.

Influence of Curing Agents Molecular Structures on Interfacial Characteristics of Graphene/Epoxy Nanocomposites: A Molecular Dynamics Framework

AbstractThis paper presents a comprehensive molecular dynamics study on the effects of the stoichiometric ratio of epoxy:hardener, hardener's linear and cyclic structure, and number of aromatic rings on the interfacial characteristics of graphene/epoxy nanocomposite. The van der Waals gap and polymer peak density as a function of the type of the hardener is calculated by analyzing the local mass density profile. Additionally, steered molecular dynamics are used to conduct normal pull‐out of graphene to study the effect of the mentioned features of hardeners on the interfacial mechanical properties of nanocomposites, including traction force, separation distance, and distribution quality of reacted epoxide rings in the epoxy. Influence of the hardeners on the damage mechanism and its initiation point are also studied by analyzing the evolution of local mass density profile during the normal pull‐out simulation. It is seen that stoichiometric ratio and geometrical structure of the hardeners affect the interfacial strength. It is also revealed that the hardener type can change the epoxy damage initiation point. The damage occurs in the interphase region for a higher stoichiometric ratio or cyclic structure of hardener. In comparison, for hardener's lower stoichiometric ratio and non‐cyclic structure, failure begins in the epoxy near graphene layers.

Design and analysis of in-wheel motor with sinusoidal permanent magnet shape for electrical vehicles

This paper deals with the design and analysis of a surface-mounted outer rotor in-wheel motor (IWM) with the aim of reducing cogging torque and torque ripple for electric vehicles. The proposed IWM is equipped with axial sinusoidal surface-mounted permanent magnets (PMs), with the purpose of producing sinusoidal air gap flux density distribution, thus to realize sinusoidal back electromotive force (EMF) and smooth electromagnetic torque. To highlight the advantage of the proposed IWM, the conventional IWM with tile-shaped PMs and the IWM with stepwise-shaped PMs are also studied for comparison. The finite element method in the commercial software package is utilized to analyze the performance of the three motors, including the radial flux density of air gap, back EMF, cogging torque, and electromagnetic torque. Through the quantitative comparison, it is found that the proposed IWM greatly reduces the cogging torque, highly improves the sinusoidality of back EMF, and nearly eliminates the torque ripple.

Sessile drop evaporation in a gap – crossover between diffusion-limited and phase transition-limited regime

We consider the time evolution of a sessile drop of volatile partially wetting liquid on a rigid solid substrate. The drop evaporates under strong confinement, namely, it sits on one of the two parallel plates that form a narrow gap. First, we develop an efficient mesoscopic long-wave description in gradient dynamics form. It couples the diffusive dynamics of the vertically averaged vapour density in the narrow gap to an evolution equation for the profile of the volatile drop. The underlying free energy functional incorporates wetting, interface and bulk energies of the liquid and gas entropy. The model allows us to investigate the transition between diffusion-limited and phase transition-limited evaporation for shallow droplets. Its gradient dynamics character allows for a long-wave as well as a full-curvature formulation. Second, we compare results obtained with the mesoscopic long-wave model to corresponding direct numerical simulations solving the Stokes equation for the drop coupled to the diffusion equation for the vapour as well as to selected experiments. In passing, we discuss the influence of contact line pinning.

Modeling liquid droplet impact on a micropillar-arrayed viscoelastic surface via mechanically averaged responses

Droplet impact on a substrate is an intriguing phenomenon that widely exists in our daily life and a broad range of industrial processes. However, droplet impact dynamics on soft textured surfaces are less explored and the underlying mechanisms remain elusive. Here, we report numerical simulation of droplet impact dynamics on a micropillar-arrayed soft surface using BASILISK, which involves a multiscale geometric domain containing the micropillars and droplet that are in the order of μm and mm, respectively. As such, the volume of fluid (VOF) method is coupled with the finite volume method (FVM) to build the fluid fields and track their interface. From a conceptual point of view, the micropillared substrate is formed by imposing interstitial gaps into the otherwise intact soft material, whose viscoelastic properties can be quantified by gap density ϵ. Via a five-parameter generalized Maxwell model, the viscoelastic properties of the micropillared substrate can be approximated by its equivalent elastic response in the Laplace–Carson (LC) space, and the averaged bulk strain of the micropillared substrate in the real space is obtained by the inverse LC transform. Moreover, through parametric studies of splash extent, it turns out that for a specific ϵ, the splash is dramatically intensified with increasing impact velocity Ui. The splash also turns more violent with increasing ambient pressure Pa, which is evidenced by a larger splash angle of 114.44∘ between the ejected sheet and the horizontal substrate at 5 atm. Conversely, the splash becomes more depressed with increasing surface tension σ. Overall, the splash magnitudes of our simulations agree well with those predicted by the Kelvin-Helmholtz instability theory. By leveraging the LC transform in the fluid-viscoelastic solid interactions, our simulation methodology captures the main features of droplet impact dynamics on microstructured viscoelastic surfaces by means of the mechanically averaged responses while avoiding the predicament of domain scale inconsistency.

Design and Optimization of Synchronous Motor Using PM Halbach Arrays for Rim-Driven Counter-Rotating Pump

This document deals with the design of a Permanent Magnet Synchronous Motor (PMSM) to peripherally drive a counter-rotating pump inducer. The motor/pump is associated using a rim-driven principle where the motor’s active parts are located at the periphery of the inducer blades. It proposes using a Halbach array of permanent magnets for the active rotor of the motor. This solution allows the generation of a Sinusoidal Electromotive Force (EMF). Therefore, a more stable electromagnetic torque is reached. An optimum geometry suitable for the inducer specifications while respecting operational constraints is determined. The obtained geometry is then simulated using the Finite Element Method. The results are satisfactory in terms of average torque and EMF waveform. Use of the Halbach array allows a significant improvement of the flux density in the air gap compared to a designed surface-mounted machine. The experimental validation will be performed once the prototype is realized in the Laboratory of Fluid Engineering and Energy systems (LISFE).

Observation of the Superconducting Proximity Effect from Surface States in SmB_{6}/YB_{6} Thin Film Heterostructures via Terahertz Spectroscopy.

The ac conduction of epitaxially grown SmB_{6} thin films and superconducting heterostructures of SmB_{6}/YB_{6} are investigated via time-domain terahertz spectroscopy. A two-channel model of thickness-dependent bulk states and thickness-independent surface states accurately describes the measured conductance of bare SmB_{6} thin films, demonstrating the presence of surface states in SmB_{6}. While the observed reductions in the simultaneously measured superconducting gap, transition temperature, and superfluid density of SmB_{6}/YB_{6} heterostructures relative to bare YB_{6} indicate the penetration of proximity-induced superconductivity into the SmB_{6} overlayer; the corresponding SmB_{6}-thickness independence between different heterostructures indicates that the induced superconductivity is predominantly confined to the interface surface state of the SmB_{6}. This study demonstrates the ability of terahertz spectroscopy to probe proximity-induced superconductivity at an interface buried within a heterostructure, and our results show that SmB_{6} behaves as a predominantly insulating bulk surrounded by conducting surface states in both the normal and induced-superconducting states in both terahertz and dc responses, which is consistent with the topological Kondo insulator picture.