Nanomaterials最新文献

The progression of SiC MOSFET technology from planar to trench structures requires optimized gate oxide layers within the trench to enhance device performance. In this study, we investigated the interface characteristics of HfO₂ and SiO₂/HfO₂ gate dielectrics grown by atomic layer deposition (ALD) on SiC trench structures. The trench structure morphology was revealed using scanning electron microscopy (SEM). Atomic force microscopy (AFM) measurements showed that the roughness of both films was below 1nm. Spectroscopic ellipsometry (SE) indicated that the physical thicknesses of HfO₂ and SiO₂/HfO₂ were 38.275 nm and 40.51 nm, respectively, demonstrating their comparable thicknesses. X-ray photoelectron spectroscopy (XPS) analysis of the gate dielectrics revealed almost identical Hf 4f core levels for both HfO₂ and the SiO₂/HfO₂ composite dielectrics, suggesting that the SiO₂ interlayer and the SiC substrate had minimal impact on the electronic structure of the HfO₂ film. The breakdown electric field of the HfO₂ film was recorded as 4.1 MV/cm, with a leakage current at breakdown of 1.1 × 10^-3A/cm². The SiO₂/HfO₂ stacked film exhibited significantly better performance, with a breakdown electric field of 6.5 MV/cm and a marked reduction in leakage current to 3.7 × 10^-4 A/cm². A detailed extraction and analysis of the leakage current mechanisms were proposed, and the data suggested that the introduction of thin SiO₂ interfacial layers effectively mitigated small bandgap offset issues, significantly reducing leakage current and improving device performance.

Three-dimensional electrospun foams are emerging in a diversity of applications. However, their characterisation involves procedures to calculate fibre diameter and porosity, which take considerable time. Hence, in this paper, an in situ characterisation method is presented based on signal features of the grounding voltage. These features are combined into the in situ evaluation parameter S_r for each run r. The L9 Taguchi method was utilised to minimise the total number of experiments. Moreover, to prove the accuracy of this method, the traditional post-fabrication analysis was conducted, and the post-fabrication evaluation parameter was retrieved Q_r for each run r. The analysis shows that both parameters detected the same experiment run as the optimal one (with an adjusted R² = 0.84) for polystyrene electrospun foams for two solution concentrations: 15%wv (run 3 with mean S₃ = 54.49 and mean Q₃ = 0.248) and 20%wv (mean S₅ = 2.49 and Q₅ = 0.248), respectively. Also, the statistical analysis shows low standard deviations for the optimal and near-optimal runs, proving the method's repeatability. Furthermore, a theoretical explanation is provided for selecting signal features based on the Maxwellian equivalent circuit approach for the electrospun jet. Finally, this fast in situ evaluation method can replace the post-fabrication time-consuming one. It can be used as a fundamental step for an intelligent artificial intelligence tool that predicts optimal foam formation.

The primary extraction way for unconventional oil/gas resources is hydraulic fracturing to alter the reservoir for commercial production. However, hydraulic fracturing technology consumes a large amount of water, and the flowback water can easily be mixed with hydrocarbon substances to form emulsions. To achieve the recycling of water, it is necessary to develop an efficient continuous demulsification method for treating the flowback fluid. In this study, a composite filtration layer with superhydrophilic and superoleophilic properties was successfully prepared using water-based polyurethane as a binder. The g-C₃N₄ was used to improve the affinity of the filtration layer to water and oil. The diatomite and rice husk carbon were used as an adsorbent and a filter aid, respectively. The contact angles (CA) of both oil and water on the surface of the filtration layer were measured to be 0°. During the demulsification process, vacuum filtration was employed to increase the pressure difference across the filtration layer, thereby improving the treatment flux of flowback fluid. The experimental results showed that the filtration flux with the addition of rice husk charcoal increased from 160.58 L∙m^-2∙h^-1 to 174.68 L∙m^-2∙h^-1 compared to the filter layer without rice husk charcoal. Based on the composite filtration layer, the apparent demulsification efficiency exceeded 90.6% for various types of emulsion. The mechanism of demulsification was investigated by the molecular dynamics method. The results showed that the adsorption layer density of water molecules reached 1.5 g/cm³, and the adsorption layer density of oil molecules exceeded 2.5 g/cm³. The porous structure wall has a strong adsorption effect on both oil and water molecules, resulting in deformation and destruction of the oil-water interface, so that the dispersed phase is adsorbed and aggregated by the filter layer at the same time and permeates from the filter layer after reaching saturation, thus separating the two phases.

The effects of abrasion on the heating performance of carbon nanotube (CNT)/epoxy composites were investigated in terms of Joule's heat, convective heat, and radiative heat under moderate-to-severe and localized abrasive conditions. While the overall heating behavior was characterized by the heating rate and the curvature of the transient response, a numerical solution of the heat equation was used to quantify convective and radiative heat transfers, incorporating the specific heat of each component, the convective heat transfer coefficient, and the Biot number. CNT reinforcement significantly improved wear resistance at a CNT concentration of 0.31 vol. %, but the presence of micro-voids led to a slight increase in wear rate with additional CNT inclusion. Using an equivalent circuit model, local and severe abrasion scenarios were analyzed to determine the variation in electrical conductivity with temperature at different degrees of abrasion, indicating the impact of scattering effects. This analysis provides valuable insights for estimating both wear resistance and the heating performance of self-heated surface materials, with potential applications in future space technologies.

We propose a simple and innovative configuration consisting of a quantum dot and micro-optical resonator that emits single photons with good directionality in a plane parallel to the substrate. In this device, a single quantum dot is placed as a light source between the slits of a triangular split-ring micro-optical resonator (SRR) supported in an optical polymer film with an air-bridge structure. Although most of the previous single photon emitters in solid-state devices emitted photons upward from the substrate, operation simulations confirmed that this configuration realizes lateral light emission in narrow regions above, below, left, and right in the optical polymer film, despite the absence of a light confinement structure such as an optical waveguide. This device can be fabricated using silica-coated colloidal quantum dots, focused ion beam (FIB) lithography, and wet etching using an oxide layer on a silicon substrate as a sacrificial layer. The device has a large tolerance to the variation in the position of the SRR in the optical polymer film and the height of the air-bridge. We confirmed that Pt-SRRs can be formed on the optical polymer film using FIB lithography. This simple lateral photon emitter is suitable for coupling with optical fibers and for fabricating planar optical quantum solid-state circuits, and is useful for the development of quantum information processing technology.

Bismuth vanadate (BiVO₄), a well-known semiconductor photocatalyst with various advantages, has shown great potential in addressing energy and environmental issues. However, its inherent drawbacks restrict the photocatalytic performance of pure BiVO₄. In the past few years, many efforts have been devoted to improving the catalytic activity of BiVO₄ and revealing the degradation mechanism in depth. In this review, we summarized the recent progress on BiVO₄ in the field of photocatalytic degradation, including the strategies which enhance light absorption ability and suppress the recombination of charge carriers of BiVO₄, as well as the related degradation mechanism. Finally, future prospects and challenges are summarized, which may provide new guidelines for designing more effective BiVO₄-based photocatalysts for the degradation of persistent organic pollutants.

Exoskeletons play a crucial role in joint healthcare by providing targeted support and rehabilitation for individuals with musculoskeletal diseases. As an assistive device, the accurate monitoring of the user's joint signals and exoskeleton status using wearable sensors is essential to ensure the efficiency of conducting complex tasks in various scenarios. However, balancing sensitivity and stretchability in wearable devices for exoskeleton applications remains a significant challenge. Here, we introduce a wearable strain sensor for detecting finger and knee joint motions. The sensor utilizes a stretchable elastic conductive network, incorporating multi-walled carbon nanotubes (MWCNTs) into Ecoflex. The concentration of MWCNTs has been meticulously optimized to achieve both a high gauge factor (GF) and stability. With its high sensitivity, the sensor is enabled to be applied in the angle monitoring of finger joints. By integrating the sensor with human knee joints and an exoskeleton device, it can simultaneously detect the flexion and extension movements in real-time. This sensor holds significant potential for enhancing exoskeleton performance and improving joint healthcare technologies.

The fabrication of laser-induced graphene (LIG) electrodes by direct laser writing techniques has received considerable attention due to its simplicity, versatility, and cost-effectiveness for electrochemical applications in both sensing and energy storage. In general, a single-lasing irradiation process is used to prepare LIG electrodes. However, the intrinsic features of LIG can be further improved by taking advantage of additional lasing processes, even without any chemical treatments. In this work, we investigated the potential enhancement of LIG's electrochemical performance through a double-lasing irradiation process. This process does not require any chemical modification of the LIG to improve its electrochemical performance. Importantly, we revealed the correlation between laser irradiation and the properties of LIG electrodes prepared through the lasing process. We evaluated the characteristics of LIG electrodes prepared by the single-lasing and double-lasing irradiation regarding their microstructures and electrochemical features, including the sheet resistance (R_S), specific areal capacitance (C_A), peak-to-peak separation (ΔE_P), and peak current. The double-lasing LIG exhibited improved electrochemical properties, especially low R_S and ΔE_P values. This improvement results from a higher degree of graphitization, making them advantageous for developing electrochemical sensors. This was demonstrated by the improved electrochemical sensing of H₂O₂ using the double-lasing LIG.

Nanofluids have emerged as an advanced media in many applications, particularly thermal management and energy efficiency applications, with extensive research focusing on their thermophysical properties and thermal performances [...].

Iron-based metal-organic frameworks (Fe-MOFs) are widely used for agricultural chemical delivery due to their high loading capacity, and they also have the potential to provide essential iron for plant growth. Therefore, they hold significant promise for agricultural applications. Evaluating the plant biotoxicity of Fe-MOFs is crucial for optimizing their use in agriculture. In this study, we used the natural biomacromolecule carboxymethyl cellulose (CMC) to encapsulate the Fe-MOF NH₂-MIL-101 (Fe) (MIL). Through hydroponic experiments, we investigated the biotoxic effects of Fe-MOFs on rice before and after CMC modification. The results show that the accumulation of iron in rice is dependent on the dose and the exposure concentration of Fe-MOFs. CMC modification (MIL@CMC) can reduce the release rate of Fe ions from Fe-MOFs in aqueous solutions with different pH values (5 and 7). Furthermore, MIL@CMC treatment significantly increases the absorption of iron by both the aboveground and root parts of rice. MIL@CMC significantly alleviated the growth inhibition of rice seedlings and increased the aboveground biomass of rice under medium- to high-exposure conditions. Specifically, in rice roots, MIL induced a more intense oxidative stress response, with significant increases in the activities of related antioxidant enzymes (CAT, POD, and SOD) and MDA content. Our results demonstrated that the encapsulation of NH₂-MIL-101(Fe) using CMC effectively alleviated oxidative damage and promoted the uptake and growth of iron in rice. These findings suggest that rational modification can have a positive effect on reducing the potential phytotoxicity of MOFs and improving their biosafety in agricultural applications.