Search Results (11,967)

Organic/silicon hybrid solar cells have attracted much interest due to their cheap fabrication process and simple device structure. A category of organic substances, Dibenzothiophene–Spirobifluorene–Dithiophene (DBBT-mTPA-DBT), comprises dibenzo [d,b] thiophene and 3-(3-methoxyphenyl)-6-(4-methoxyphenyl)-9H-Carbazole, which function as electron donors. In contrast, methanone is an electron acceptor, with an ∆Est of 3.19 eV. This work focused on hybrid solar cells based on the guest–host phenomena of DBBT-mTPA-DBT and CBP. Using a Si/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) hybrid solar cell with an ultra-thin Dibenzothiophene–Spirobifluorene–Dithienothiophene (DBBT-mTPA-DBT) interlayer between Si and Al led to a PCE of 17.5 ± 2.5%. The DBBT-mTPA-DBT interlayer substantially improved the Si/Al interface, reducing contact resistance from 6.5 × 10⁻¹ Ω·cm² to 3.5 × 10⁻² Ω·cm². This improvement increases electron transport efficiency from silicon to aluminum and reduces carrier recombination. The solar cell containing the DBBT-mTPA-DBT/Al double-layer cathode shows a 10.85% increase in power conversion efficiency relative to the standard Al cathode device. Full article

The paper presents the results of a comparative microfluidic study of the oil displacement process from a microfluidic chip simulating rock. Suspensions of spherical nanoparticles of silicon oxide (22 nm) and aluminum oxide (11 nm), as well as aluminum oxide nanofibers (8.7 nm in diameter and with an aspect ratio of 58), were used as displacing liquids. The nanofibers represent a unique new-generation crystalline material with a high aspect ratio. This work presents the first consideration of the use of aluminum oxide nanofibers as an additive for enhanced oil recovery. The comparative analysis has demonstrated that the addition of nanofibers can markedly enhance the oil recovery factor relative to the addition of spherical nanoparticles, other things being equal. Thus, in particular, it was demonstrated that the addition of nanofibers into the system allows for the greatest enhancement of the oil recovery factor, reaching a value of 25%, whereas the addition of spherical nanoparticles results in a maximum increment of approximately 10%. This is due to the fact that nanofiber additives have a tenfold stronger effect on the viscosity of nanosuspensions compared to similar additives of spherical particles. Nanosuspensions of aluminum oxide nanofibers exhibit non-Newtonian behavior at low concentrations. This opens the possibility of their extensive use in enhanced oil recovery. Full article

The commercial use of Si₃N₄ ceramics in the biomedical field dates back to the early 1980s and, initially, did not show promising results, which is why their biocompatibility was not then investigated further until about 10 years later. Over the years, a change in trend has been observed; more and more studies have shown that this material could possess high biocompatibility and antibacterial properties. However, the relevant literature struggles to find mechanisms that can incontrovertibly explain the reasons behind the biological activity of Si₃N₄. The proposed mechanisms are often pure hypotheses or are not substantiated by comprehensive analyses. This review begins by studying the early references to the biological activity of Si₃N₄ and then reviews the literature regarding the bioactivity of this ceramic over time. An examination of the early insights into surface chemistry and biocompatibility lays the foundation for a detailed examination of the chemical reactions that Si₃N₄ undergoes in biological environments. Next, the analysis focuses on the mechanisms of bioactivity and antipathogenicity that the material exhibits both alone and in combination with modern bioglass. However, it is highlighted that despite the general consensus on the biocompatibility and bioactivity of Si₃N₄ ceramics, sometimes the proposed biological mechanisms behind its behavior are discordant or unsupported by the direct evaluation of specific biochemical activities. This review highlights both the reliable information in the literature and the gaps in research that need to be filled in order to fully understand the reasons behind the biological properties of this material. Full article

SiC particle reinforced aluminum matrix composites (SiCp/Al) are widely used in aviation, weaponry, and automobiles because of their excellent service performance. Wire electrical discharge machining (WEDM) regardless of workpiece hardness has become an alternative method for processing SiCp/Al composites. In this paper, the temperature distribution and the discharge crater size of the SiCp/Al composite are simulated by a thermophysical model during a single-pulse discharge process (SPDP) based on the random distribution of SiC particles. The material removal mechanism of the SiCp/Al composite during the multi-pulse discharge process (MPDP) is revealed, and the surface roughness (Ra) of the SiCp/Al composite is predicted during the MPDP. The thermophysical model simulation results during the MPDP and experimental characterization data indicate that the removal mechanism of SiCp/Al composite material consists of the melting and vaporization of the aluminum matrix, as well as the heat decomposition and shedding of silicon carbide particles. Pulse-on time (T_on), pulse-off time (T_off), and servo voltage (SV) have a great influence on surface roughness. The Ra increases with an increase in T_on and SV, but decreases slightly with an increase in T_off. Moreover, compared with experimental data, the relative error of Ra calculated from the thermophysical model is 0.47–7.54%. This means that the developed thermophysical model has a good application and promotion value for the WEDM of metal matrix composite material. Full article

Red mud is a by-product of alumina production, which is largely stored in landfills that can endanger the environment. Red mud, or bauxite residue, is a mixture of inorganic compounds of iron, aluminum, sodium, titanium, calcium and silicon mostly, as well as a large number of rare earth elements in small quantities. Although certain methods of using red mud already exist, none of them have been widely implemented on a large scale. This paper proposes a combination of two methods for the utilization of red mud, first by carbothermic reduction and then, by leaching under high pressure in an autoclave in order to extract useful components from it with a focus on titanium. In the first part of the work, the red mud was reduced with carbon at 1600 °C in an electric arc furnace, with the aim of removing as much iron as possible using magnetic separation. After separation, the slag is leached in an autoclave at different parameters in order to obtain the highest possible yield of titanium, aiming for the formation of titanium oxysulfate and avoiding silica gel formation. A maximal leaching efficiency of titanium of 95% was reached at 150 °C using 5 mol/L sulfuric acid with 9 bar oxygen in 2 h. We found that high-pressure conditions enabled avoiding the formation of silica gel during leaching of the slag using 5 mol/L sulfuric acid, which is a big problem at atmospheric pressure. Previously silica gel formation was prevented using the dry digestion process with 12 mol/L sulfuric acid under atmospheric pressure. Full article

This study explores electrochemical etching to form porous silicon (PS), which has diverse biomedical and energy applications. Our objective is to gain new insights and drive significant scientific and technological advancements. Specifically, we study the effect of electrochemical etching of P-type silicon using laser irradiation in a hydrofluoric acid (HF) solution. The formation of the nanoscale PS structure can be successfully controlled by incorporating laser irradiation into the electrochemical etching process. The wavelength and power of the laser influence the formation of nanoporous silicon (NPS) on the surface during the electrochemical etching process. The luminous flux is monitored with the help of a customized integrating sphere system and an LED-based excitation source to find the light flux values distributed across the P-type nanolayer PS wafers. Analysis of the NPS and luminescence characteristics shows that the laser bandwidth controls the band gap energy absorption (BEA) phenomenon during the electrothermal reaction. It is demonstrated that formation of the NPS layer can be controlled in this combined laser irradiation and electrochemical etching technique by adjusting the range of the laser wavelength. This also allows for further precise control of the numerical trend of the luminous flux. Full article

The Brazilian Pantanal region experiences intense biomass burning during the dry season, releasing large quantities of gasses and particles into the atmosphere, which have serious implications on both the climate system and public health. Understanding the dynamics of these emissions is crucial for mitigating the impact on the ecosystem, its functioning, and potential anthropogenic disturbances. This study focused on analyzing emissions in the northern Pantanal during the 2022 drought. Concentrations of fine particulate matter (PM_2.5), black carbon (BC), and 25 chemical elements were measured using gravimetry, reflectance analysis, and X-Ray fluorescence, respectively, from samples collected between August and October 2022. The average concentrations of PM_2.5 and BC increased approximately 4-fold and 2.5-fold, respectively, compared to averages from a decade ago. Significant increases were also observed in elements such as sulfur (S), potassium (K), iron (Fe), and silicon (Si). The maximum concentrations were comparable to values typical of the southern Amazon, a region known for high deforestation rates and land use changes. Elemental analysis revealed substantial shifts in concentrations, primarily associated with biomass burning (BB) and soil suspension. Additionally, enrichment factor (Ef) analysis showed that lead (Pb) levels, correlated with human activities, were 200 times higher than those found under clean atmospheric conditions. Full article

Soft actuators have enabled the growth of soft robotics, overcoming several drawbacks of rigid robotics by providing devices with many degrees of freedom and the ability to grasp, bend, move, jump, and more. The reconfiguration of the workspace is still a limitation of these actuators. Indeed, once the actuator is designed and developed, it is used for a specific task. This work presents a reconfigurable soft pneumatic actuator with a novel reconfigurable modular reinforcement. The latter is wrapped around an inner tube in silicone rubber and is made of components whose assembly can be configured based on the task. A formulation is identified by a hybrid approach based on finite element analysis and response surface methodology for predicting and designing the behavior of the actuator. The prototyping revealed the ease of fabrication and reconfigurability as the strength of this new actuator. The experimental tests demonstrated the feasibility of adopting the actuator as a finger in a gripper for handling and moving objects of different shapes, masses, and stiffness. Furthermore, the evaluated performance shows a good trade-off between mass, developed force, implementation time, easy reconfigurability, and cost-effectiveness. Full article

The computer-assisted inverse design of photonic computing, especially by leveraging artificial intelligence algorithms, offers great convenience to accelerate the speed of development and improve calculation accuracy. However, traditional thickness-based modulation methods are hindered by large volume and difficult fabrication process, making it hard to meet the data-driven requirements of flexible light modulation. Here, we propose a diffractive deep neural network (D²NN) framework based on a three-layer all-dielectric phased transmitarray as hidden layers, which can perform the classification of handwritten digits. By tailoring the radius of a silicon nanodisk of a meta-atom, the metasurface can realize the phase profile calculated by D²NN and maintain a relative high transmittance of 0.9 at a wavelength of 600 nm. The designed image classifier consists of three layers of phase-only metasurfaces, each of which contains 1024 units, mimicking a fully connected neural network through the diffraction of light fields. The classification task of handwriting digits from the ‘0’ to ‘5’ dataset is verified, with an accuracy of over 90% on the blind test dataset, as well as demonstrated by the full-wave simulation. Furthermore, the performance of the more complex animal image classification task is also validated by increasing the number of neurons to enhance the connectivity of the neural network. This study may provide a possible solution for practical applications such as biomedical detection, image processing, and machine vision based on all-optical computing. Full article

The optical characterization of non-absorbing, homogeneous, isotropic polymer-like thin films with correlated, differently rough boundaries is essential in optimizing their performance in various applications. A central aim of this study is to derive the general formulae necessary for the characterization of such films. The applicability of this theory is illustrated through the characterization of a polymer-like thin film deposited by plasma-enhanced chemical vapor deposition onto a silicon substrate with a randomly rough surface, focusing on the analysis of its rough boundaries over a wide range of spatial frequencies. The method is based on processing experimental data obtained using variable-angle spectroscopic ellipsometry and spectroscopic reflectometry. The transition layer is considered at the lower boundary of the polymer-like thin film. The spectral dependencies of the optical constants of the polymer-like thin film and the transition layer are determined using the Campi–Coriasso dispersion model. The reflectance data are processed using a combination of Rayleigh–Rice theory and scalar diffraction theory in the near-infrared and visible spectral ranges, while scalar diffraction theory is used for the processing of reflectance data within the ultraviolet range. Rayleigh–Rice theory alone is sufficient for the processing of the ellipsometric data across the entire spectral range. We accurately determine the thicknesses of the polymer-like thin film and the transition layer, as well as the roughness parameters of both boundaries, with the root mean square (rms) values cross-validated using atomic force microscopy. Notably, the rms values derived from optical measurements and atomic force microscopy show excellent agreement. These findings confirm the reliability of the optical method for the detailed characterization of thin films with differently rough boundaries, supporting the applicability of the proposed method in high-precision film analysis. Full article

Silicone rubber (SIR) is a crucial insulating material in cable accessories, but it is also susceptible to faults. In practical applications, mechanical pressure from bending or shrinking can impact the degradation of SIR, necessitating the study of its electrical tree and partial discharge (PD) characteristics under such pressure. This work presents the construction of a test platform for electrical trees under varying pressures to observe their growth process. A high-frequency current transformer is used to measure PD patterns during tree growth, enabling analysis of the effect of PD on tree initiation and propagation under pressure. The experimental results demonstrate a significant decrease in tree inception probability and increase in PD inception voltage under pressure. The pressure also influences the tree structure and PD during the treeing process, where the longest tree with a branch-like structure appears under 800 kPa. The effect of pressure on electrical tree and PD characteristics can be attributed to changes in free volume, alterations in air pressure within the tree channels, and the affected charge accumulation. Full article

Objective: The study aimed to optimize protocols for the joint extraction of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) from 0.025 × 10⁶ CFU of Candida albicans, targeting to overcome the challenges in the extraction of these genetic materials. Materials and methods: From this, treated silicon carbide (SiC) granules were added to fungal samples from methods 1, 2, and 3 obtained from aliquots of BHI or Sabouraud medium to cause cell lysis and enable the isolation of these macromolecules by phenol and chloroform. The concentration and integrity of the extracted nucleic acids were analyzed, respectively, by spectrophotometry using the A₂₆₀/A₂₈₀ ratios and 1% agarose gel electrophoresis. Results: Therefore, method 3 is the one that most comprises samples considered pure of both DNA and RNA, simultaneously. Furthermore, the presence of intact RNAs corresponding to the base pair size such as 5.8 S rRNA and tRNA was verified during electrophoresis, considering the particularities of RNA, which makes it very unstable and easily degraded. Conclusions: Thus, it results in a faster and simpler method in addition to obtain promising results using minimal amounts of biological sample and offering a valuable alternative for small laboratories to work with molecular biology. Full article

The excellent mechanical properties of alkaline-activated tailings are essential for their increased use in building materials. While numerous studies have been conducted on activated tailings, the strength of alkaline-activated tungsten slag has not been extensively explored due to the low reactivity of silicon and aluminum in these tailings. This research delves into the early unconfined compressive strength of tungsten tailings activated by two alkali solutions (NaOH and KOH) at three different alkali concentrations (mass ratio of alkali to tungsten tailings), cured at 80 °C over periods of one day, three days, and seven days. The study finds significant improvements in the stability of tungsten tailings when forming (C, N)-A-S-H or (C, K)-A-S-H gels with both alkalis. Scanning Electron Microscope (SEM) results show that the morphology of the (C, N)-A-S-H gels transitions from membranous to flocculated and then to a three-dimensional network as the NaOH content and curing time increase. Conversely, the (C, K)-A-S-H gels primarily exhibit thin-film morphology with some three-dimensional network structures. The presence of flocculation and three-dimensional mesh in the gels fosters the formation of a robust skeletal structure, enhancing the strength of the samples. Furthermore, specimens treated with NaOH solution exhibit a higher gel content compared to those treated with KOH solution. These factors contribute to the superior efficacy of sodium hydroxide in enhancing the strength of tungsten tailings compared to potassium hydroxide. X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) results identify the formation of new phases such as pirssonite, buetschliite, potassium bicarbonate, and potassium carbonate. The first new phase results from the carbonization of excess NaOH solution, while the latter phases arise from the carbonization of excess KOH solution. These carbonization processes negatively impact the strength of the materials. Full article

Highly-effective non-halogenated flame retardants have received widespread attention because they are environmentally friendly, with low toxicity and low smoke density. In this work, interlayer-functionalized graphene (fRGO) containing silicon and phosphorus elements was synthesized via hydrolytic condensation with 3-(methacryloyloxy)propyltrimethoxysilane and addition reaction with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. Interlayer spacing and oxygen-containing groups of reduced graphene oxide (RGO) were regulated by controlling the hydrazine hydrate dosage. Then, phosphorus–silicon-containing organic molecules were inserted into RGO interlayers; this was verified by FTIR, XPS, TEM, etc. The fRGO was added to a polyacrylonitrile (PAN) matrix using a solution blending method to prepare polyacrylonitrile (PAN) composites. The fRGO addition caused the significant decrease in cyclization heat and the considerable increase in char residues, indicating improved thermal stability. Importantly, PAN composites exhibited outstanding flame-retardant properties, with the peak heat release rate reduced by 45%, which is ascribed to the dense graphitic carbon layers induced by phosphorus–silicon-containing organics and the 2D barrier effect of RGO layers to prevent the heat and mass transfer. Full article

The purification and removal of polar impurities in olefin feedstocks is crucial for downstream deep processing, and adsorption is the main method for deep purification of such impurities. This article takes dimethyl ether, a typical oxygen-containing compound impurity in MTOs, as a polar impurity molecule, and LTA and FAU topological zeolites as research objects. The influence of zeolite topology, morphology, skeleton silicon–aluminum (Si/Al) ratio, and ion type on the adsorption and removal of trace dimethyl ether was investigated by XRD, SEM, XRF, and nitrogen adsorption–desorption methods. The FAU topological zeolites show a better adsorption performance for dimethyl ether owing to their larger specific surface area and unobstructed pores compared with LTA zeolites. Among FAU topological zeolites, the NaX zeolite a with lower framework silica–alumina ratio has the highest adsorption capacity for dimethyl ether. Magnesium ion exchange on NaX zeolites (MgNaX) reduce the specific surface area and adsorption capacity of the NaX zeolite. However, after forming with alumina as a binder, the adsorption capacity of the MgNaX–Al₂O₃ adsorbent is about 13% higher than that of the NaX–Al₂O₃ adsorbent without Mg ion exchange. This may be due to the decomposition of residual organic Mg salts in the Mg ion exchange samples during high-temperature calcination, resulting in a larger specific surface area for the formed adsorbent. Further characterization of NH₃–TPD and CO₂–TPD shows that Mg ion exchange weakens the acid–base active sites on the adsorbent surface. The reduction in acid–base sites reduces the occurrence of side reactions such as polymerization and isomerization caused by the exothermic adsorption of olefins on adsorbents. Repeated adsorption data show that the formed adsorbent has excellent regeneration–adsorption performance. Full article