Search Results (2,808)

When grinding silicon carbide, surface and subsurface damage have a significant impact on the product’s surface quality. One method to control the crack dimensions is laser irradiation on the SiC surface. The effect of this method on the grinding process is analyzed in this study. A series of experiments was carried out based on an orthogonal experimental design, with systematic adjustments made to laser parameters, including pulse energy (current), laser spot spacing, scanning times, and grinding process parameters. During the experiments, the grinding force was monitored by a dynamometer, and the specific grinding energy was calculated accordingly. Pulsed engraving laser modification effectively reduced the hardness of the ceramic surface layer by about 20%. The median and radial crack sizes induced by the laser in the subsurface layer ranged from 20.4 μm to 54.3 μm. This effectively inhibited further propagation of median and radial cracks during the grinding processes. Simultaneously, the tangential grinding force F_t was reduced by 30%. These conclusions were obtained through corresponding experiments that link surface roughness to laser power and grinding parameters. Using laser-induced controllable crack characteristics in the grinding process allow damage from surface and subsurface grinding to be controlled in brittle materials. Full article

The microstructure and wear behaviors of Mg₂Si/Al composites with 0 wt.%, 5 wt.%, and 10 wt.% SiC particles were studied using XRD, OM observation, SEM observation, EDS analysis, an extraction experiment, a hardness test, and the dry sliding wear test. It is shown by the results that after the addition of 10 wt.% SiC particles, the population of primary Mg₂Si particles increased, while the mean size of these particles reduced from 40 ± 10 μm (in the SiC-free composite) to 25 ± 8 μm. Both the matrix and the eutectic structure were refined. The tetrakaidecahedral morphologies of Mg₂Si crystals were confirmed by the results of extraction tests. The wear test results with GCr15 steel as the friction pair show that the Mg₂Si/Al composite with 10 wt.% SiC particles displayed more favorable wear resistance than the specimens with 0 wt.% and 5 wt.% SiC particle additions under both constant load and constant sliding velocity conditions. Under applied loads of 10 N, 20 N, and 30 N at a fixed sliding speed of 300 r/min, the wear rate of the Mg₂Si-Al composites reinforced with 10 wt.% SiC particles was 36.01%, 48.29%, and 23.32% lower than that of the SiC-free composites, respectively. When the sliding speed was set to 300 r/min, 550 r/min, 750 r/min, and 1000 r/min under a constant applied load of 20 N, the wear rate of the 10 wt.% SiC-reinforced Mg₂Si-Al composites was reduced by 40.37%, 40.87%, 26.20%, and 25.78%, respectively, compared with the SiC-free counterparts. The wear failure mechanisms of (Mg₂Si + SiC_P)/Al composites were mainly adhesive wear and abrasive wear, but the proportion of oxidation wear increased after the addition of the SiC particles. Full article

In the context of tightening sustainability regulations and rising demands for transparent and responsible capital allocation, understanding how digital financial innovations influence market efficiency has become increasingly important. This study examines the impact of Financial Technology (FinTech) solutions and crowdfunding platforms on sustainable market efficiency, volatility dynamics, and risk structures in the United Kingdom. Using weekly data for the Financial Times Stock Exchange 100 (FTSE 100) index from January 2010 to June 2025, the analysis applies the Lo–MacKinlay variance ratio test to assess compliance with the Random Walk Hypothesis as a proxy for informational efficiency. Firm-level proxies for FinTech and crowdfunding activity are constructed using the Nomenclature of Economic Activities (NACE) and Standard Industrial Classification (SIC) systems. The empirical results indicate substantial deviations from random-walk behavior in crowdfunding-related market segments, where persistent positive autocorrelation and elevated volatility reflect liquidity constraints and informational frictions. By contrast, FinTech-dominated segments display milder inefficiencies and faster information absorption, pointing to more stable price-adjustment mechanisms. After controlling for structural distortions through heteroskedasticity-consistent corrections and volatility adjustments, variance ratios converge toward unity, suggesting a restoration of informational efficiency. The results provide relevant insights for investors, regulators, and policymakers seeking to align financial innovation with the objectives of sustainable financial systems. Full article

Recognizing the critical role of polar Sea Ice Concentration (SIC) in climate feedback mechanisms, this study presents the first comprehensive investigation of China’s Fengyun-3E(FY-3E) GNOS-II Global Navigation Satellite System Reflectometry (GNSS-R) for bipolar SIC retrieval. Specifically, reflected signals from multiple Global Navigation Satellite Systems (GNSS) are utilized to extract characteristic parameters from Delay Doppler Maps (DDMs). By integrating regional partitioning and dynamic thresholding for sea ice detection, a Random Forest Regression (RFR) model incorporating a rolling-window training strategy is developed to estimate SIC. The retrieved SIC products are generated at the native GNSS-R observation resolution of approximately 1 × 6 km, with each SIC estimate corresponding to an individual GNSS-R observation time. Owing to the limited daily spatial coverage of GNSS-R measurements, the retrieved SIC results are further aggregated into monthly composites for spatial distribution analysis. The model is trained and validated across both polar regions, including targeted ice–water boundary zones. Retrieved SIC estimates are compared with reference data from the OSI SAF Special Sensor Microwave Imager Sounder (SSMIS), demonstrating strong agreement. Based on an extensive dataset, the average correlation coefficient (R) reaches 0.9450 in the Arctic and 0.9602 in the Antarctic for the testing set, with corresponding Root Mean Squared Error (RMSE) of 0.1262 and 0.0818, respectively. Even in the more challenging ice–water transition zones, RMSE values remain within acceptable ranges, reaching 0.1486 in the Arctic and 0.1404 in the Antarctic. This study demonstrates the feasibility and accuracy of GNSS-R-based SIC retrieval, offering a robust and effective approach for cryospheric monitoring at high latitudes in both polar regions. Full article

Sea ice concentration (SIC) is crucial to the global climate. In this study, a new single-channel SIC retrieval algorithm utilizing spaceborne L-band brightness temperature (TB) measurements is developed based on a microwave radiative transfer model. Additionally, its four uncertainties are quantified and constrained: (1) variations in seawater reference TB under warm water conditions, (2) variations in sea ice reference TB under extremely low-temperature conditions, (3) the freeze–thaw dynamics of sea ice captured by Diurnal Amplitude Variation (DAV) signals, and (4) Land mask imperfections. It is found that DAV has the most pronounced effect: eliminating its influence reduces RMSE from 10.51% to 8.43%, increases R from 0.92 to 0.94, and minimizes Bias from -0.68 to 0.13. Suppressing all four uncertainties lowers RMSE to 7.42% (a 3% improvement). Furthermore, the algorithm exhibits robust agreement with the seasonal variability of SSM/I SIC, with R mostly exceeding 0.9, RMSE mostly below 10%, and Biases mostly within 5% throughout the year. Compared to ship-based and SAR SIC data, the new L-band algorithm’s Bias and RMSE are only 2% and 2% (ship-based)/2% and 1% (SAR) higher, respectively, than those of the SSM/I product. Future algorithms can integrate the DAV signal more effectively to better understand sea ice freeze–thaw processes and ice-atmosphere interactions. Full article

Interannual climate changes and increasing atmospheric CO₂ (AtmCO₂) have significantly altered sea surface partial pressure of CO₂ (pCO₂) in the Beaufort Sea (BS). Yet, their decadal variability and underlying mechanisms remain inadequately understood. Using observational data and the Regional Arctic System Model (RASM), a decreasing trend transition of the BS summer surface pCO₂ was identified at around 2010–2012. Sensitivity cases reveal that the decadal trend transition in surface pCO₂ (early: 4.12 ± 0.80 μatm/yr, p < 0.05 and late: 1.23 ± 2.22 μatm/yr, p > 0.05) is driven by interannual climate changes. While the long-term increase in AtmCO₂ does not directly drive surface pCO₂ trend transition, it reduces its magnitude. The sensitivity experiment with no interannual AtmCO₂ changes from 1990 reveals that the statistically significant contributor of the decadal trend transition in surface pCO₂ is the concurrent transition in sea ice concentration (SIC, early: −0.0120 ± 0.0037/yr, p < 0.05 and late: 0.0101 ± 0.0063/yr, p > 0.05). The decadal trend transitions in the subsurface and deep layer pCO₂ are negligible compared to that in the sea surface pCO₂ due to the insignificant influence of interannual climate changes on subsurface and deep layer pCO₂. The surface pCO₂ decadal trend transition is significantly correlated with a trend transition of CO₂ sink. On seasonal timescales, the effects of SIC on the decadal trend transition of pCO₂ occur primarily within the duration of open-water (DOW), and align with the decadal trend transitions in the open-water start day, end day, and DOW. The magnitude of sea surface pCO₂ trend transition increases as the magnitude of the DOW trend transition increases. Full article

Wide-bandgap (WBG) semiconductor materials such as silicon carbide (SiC) and gallium nitride (GaN) are key enablers of power-electronics converters for aerospace platforms, where high efficiency, weight reduction, and thermal robustness are critical requirements. This paper presents the main challenges associated with the use of these technologies, including protection requirements, electromagnetic compatibility, and thermal management, as well as the material advantages that enable higher switching frequencies and lower losses compared to conventional Si technologies. A comparative analysis of semiconductor technologies and suitable power-conversion topologies for the aerospace context is provided. Representative laboratory-scale experimental validation is presented, including the development of a DC–DC boost converter and a DC–AC full-bridge inverter, which are linked through the common DC-link and are used for interfacing batteries and an electrical motor, both based on GaN and SiC diodes. The results demonstrated the correct operation, with stable high-frequency performance under controlled laboratory conditions, supporting aerospace-oriented development, although evaluated in a laboratory environment, confirming the potential of WBG technologies for future power-conversion architectures. Full article

Silicon carbide (SiC) has emerged as a robust and tunable semiconductor for advanced photocatalytic applications. This review provides a comprehensive overview of recent progress in the development of SiC-based materials for environmental remediation and solar-driven hydrogen production. Key aspects discussed include morphological engineering, heterostructure design, doping strategies, and plasmonic enhancement. Emphasis is placed on structure–activity relationships, insights from density functional theory (DFT) and machine learning (ML) models, and synergistic effects in composite systems. This review concludes with a critical analysis of current challenges and future research directions, highlighting the potential of SiC implementation as a sustainable platform for next-generation photocatalytic technologies. Full article

Silicon carbide (SiC) MOSFETs, as one of the representative power electronic devices, have faced reliability challenges due to threshold voltage (V_th) instability under dynamic gate stress. To explore the underlying mechanisms, this work investigates 4H-SiC MOS structures (P-MOS and N-MOS) under AC bias temperature instability (AC BTI) stress, utilizing a laser to generate minority carriers and simulate realistic switching conditions. Through combined capacitance–voltage (C-V) and gate current–voltage (J_g-V_g) characterizations on P-MOS and N-MOS devices before and after degradation at different temperatures, we reveal a critical temperature dependence in defect interactions. At room temperature, degradation is dominated by electron trapping in shallow interface states and near-interface traps (NITs). In contrast, high-temperature stress activates charge exchange with deep-level, slow states. Notably, a positive V_FB shift is consistently observed in both N-MOS and P-MOS devices under AC stress, confirming that electron trapping is the dominant cause of the commonly observed positive V_th shift in SiC MOSFETs. These findings clarify the distinct defect-mediated mechanisms governing dynamic V_th instability in SiC devices, providing fundamental insights for interface engineering and reliability assessment. Full article

This work presents the fabrication and characterization of a bow-tie antenna integrated uni-traveling carrier photodiode (UTC-PD) on a silicon carbide (SiC) substrate for efficient terahertz (THz) wave generation. The proposed device exploits the superior thermal conductivity and mechanical robustness of SiC to overcome the self-heating limitations associated with conventional indium phosphide (InP)-based photodiodes. An epitaxial layer transfer technique was utilized to bond InP/InGaAs UTC-PD structures onto SiC. The study systematically examines the influence of critical geometric parameters, specifically the mesa diameter and length between the antenna arms, on the emitted THz intensity in the 300 GHz frequency band. Experimental results show that the THz radiation efficiency is primarily governed by the mesa diameter, reflecting the trade-off between light absorption, device capacitance, and bandwidth, while the length between the antenna arms exhibits only a weak influence within the investigated parameter range. The fabricated device demonstrates strong linearity between photocurrent and THz output power up to 7.5 mA, after which saturation occurs due to space-charge effects. This work provides crucial insights for optimizing SiC-based bow-tie antenna integrated UTC-PD devices to realize robust, high-power THz sources vital for future high-data-rate wireless communication systems such as beyond 5G and 6G networks. Full article

Sea ice concentration (SIC) and thickness (SIT) are critical variables for polar research. In this study, the potential of Tianmu-1 GNSS-R observations for retrieving Arctic SIC and SIT is explored using machine learning algorithms. XGBoost demonstrated superior accuracy and efficiency in the comparison of the three methods. For SIC retrieval, 14 parameters from Tianmu-1 were employed directly, whereas SIT retrieval incorporated additional auxiliary parameters, including SIC, sea ice salinity (S), and temperature (T). Among the different GNSS systems, GLO achieved the lowest RMSE for SIC, at 7.750%, whereas GAL performed comparatively poorly, with an RMSE of 10.475%. In SIT retrieval, the GPS and BDS yielded the smallest RMSE values of 0.276 m and 0.278 m, respectively, while GLO resulted in a slightly higher RMSE of 0.309 m. Daily retrievals of both the SIC and SIT were conducted from 18 October 2023 to 12 April 2024, with consistently stable evaluation metrics throughout the freezing season. In high-concentration regions, the retrieved SIC and SIT closely matched the reference data, whereas larger errors occurred in marginal ice zones and coastal areas. This study reveals the potential of Tianmu-1 to complement existing satellite missions in Arctic sea ice monitoring during the freezing period. Full article

In this study, the microstructural, mechanical, wear, and corrosion behavior of Ni-Al-Cr and Ni–Al–Cr/SiC composite coatings with different composition ratios, produced by electric arc melting on Inconel 600 substrates, was systematically investigated. Microhardness measurements revealed a significant and consistent increase in the hardness values of the coatings depending on the increase in SiC reinforcement ratio (1%, 3%, and 5%). Wear tests showed that the coated samples exhibited significantly higher wear resistance compared to the pure Inconel 600 substrate. A significant improvement in wear resistance was achieved with the addition of SiC at 1% and 3% weight percentages; the width and depth of wear tracks were significantly reduced with SiC reinforcement. In contrast, increasing the SiC ratio to 5% weight percentage led to a decrease in wear resistance. This was attributed to particle aggregation at high SiC content, weakening of bonds at the matrix-reinforcement interface, and the behavior of SiC particles separated from the matrix as third-body abrasives. Electrochemical corrosion tests have shown that SiC-reinforced coatings form a more stable and permanent passive film, and corrosion resistance increases as the SiC content increases (1%, 3%, and 5%). The results indicate that the SiC reinforcement ratio affects the mechanical and electrochemical properties of Ni-Al-Cr/SiC composite coatings produced by electric arc melting. Full article

This study investigated the fabrication and characterization of polylactic acid (PLA)-based ceramic composite filaments for fused deposition modeling (FDM) 3D printing. Boron carbide (B₄C) and silicon carbide (SiC) were incorporated into PLA at various weight fractions (1–40 wt. % for B₄C and 1–20 wt. % for SiC) to produce composite filaments using a commercial extruder. The rheological properties, thermal stability, and printability of the filaments were evaluated. Filaments with low ceramic content exhibited satisfactory quality, whereas those with higher loadings required reprocessing to improve their dimensional stability and surface morphology. Successful printing was achieved with SiC contents of up to 8 wt. % using single-extruded filaments and up to 20 wt. % using double-extruded filaments. Rheological tests revealed that filaments with low ceramic content exhibited shear-thinning behavior, whereas those with higher loadings displayed nearly Newtonian-like behavior. Thermal analysis using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) determined the optimal processing temperature range for the composite filaments to be between 200 °C and 270 °C. High-temperature microscopy was used to study the temperature behavior of the B₄C-containing filaments and set the optimum printing temperature. The results demonstrate the feasibility of producing PLA-based ceramic composite filaments for FDM 3D printing with the potential to tailor the thermal and functional properties of the printed parts for specific applications. Full article

Binder jetting additive manufacturing (BJAM) offers an effective approach for fabricating silicon carbide (SiC) parts with complex geometries; however, part quality is strongly influenced by process variables. Binder saturation and drying time are key process variables in BJAM, yet their individual influences on the density and dimensional deviation of SiC green parts remain underexplored. To address this gap, this study systematically investigates the effects of binder saturation and drying time on the dimensional deviation and density of SiC green parts by evaluating four binder saturation levels (60%, 80%, 100%, and 120%) and three drying times (15, 30, and 45 s). The results show that increasing binder saturation reduces green part density and increases dimensional deviation, whereas increasing drying time improves density and reduces dimensional deviation. Excessive drying, however, causes severe warpage, preventing the fabrication of dimensionally accurate parts. These findings highlight the need to optimize binder saturation and drying time to improve the density of printed parts while minimizing dimensional deviation. Full article

Freshwater scarcity is increasing day by day and has already reached a threatening level, especially in remotely populated areas. One of the technological solutions to this rising concern could be the use of the solar-based humidification–dehumidification (SHDH) method for water desalination. This technology is a promising solution but has challenges such as solar intermittency. This challenge can be solved by integrating SHDH with the phase change material as a solar energy storage medium. Therefore, a novel nano-enhanced binary eutectic phase change material (NEPCM) was developed in this project. PCM consisting of 70 wt.% stearic acid (ST) and 30 wt.% suberic acid (SBU) with a varying concentration of silicon carbide (SiC) nanoparticles (NPs) (0.1 to 3 wt.%) was synthesized specifically considering the need of SHDH application. The systematic thermophysical characterization was conducted to investigate their energy storage capacity, thermal durability, and performance consistency over repeated cycles. DSC analysis revealed that the addition of SiC NPs preserved the thermal stability of the NEPCM, while the phase transition temperature remained nearly unchanged with a variation of less than 0.74%. The value of latent heat is inversely related to the nanoparticle concentration, i.e., from 142.75 kJ/kg for the base PCM to 131.24 kJ/kg at 3 wt.% loading. This corresponds to reductions in latent heat ranging between 0.98% and 8.06%. The FTIR measurement confirms that no chemical reactions or no new functional groups were formed. All original functional groups of ST and SBU remained intact, showing that incorporating the SiC NP to the PCM lead to physical interactions (e.g., hydrogen bonding or surface adsorption). The TGA analysis showed that the SiC NPs in the NEPCM act as supporting material, and its nano-doping enhanced the final degradation temperature and thermal stability. There was negligible change in thermal conductivity for nanoparticle loadings of 0.1% and 0.4%; however, it increased progressively by 5.2%, 10.8%, 23.12%, and 25.8% at nanoparticle loadings of 0.7%, 1%, 2%, and 3%, respectively, at 25 °C. Thermal reliability was analyzed through a DSC thermal cycling test which confirmed the suitability of the material for the desired applications. Full article