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Direct methanol fuel cells (DMFC) are a promising new energy source. However, the lack of high-performance and low-cost methanol oxidation electrocatalysts hinders their commercial application. Firstly, we successfully prepared NENU-5-derived molybdenum carbide material (Cu-MoC) via a co-precipitation and high-temperature carbonization method using a material composed of a copper-based metal–organic skeleton and a molybdenum-based carbide as the main body. Secondly, PtCu nano-alloy catalysts (Pt/Cu-MoC) were prepared using a unique, spontaneous single replacement reaction after metal–organic skeleton (MOF) carbonization. Through the synergistic effect between Pt and Cu and the strong interaction between Mo2C and PtCu, the electronic structure of the Pt is modified, the energy of the d-band center is reduced, electron exchange is accelerated, and catalytic activity is enhanced. Compared with a commercial Pt/C catalyst in alkaline environments, the Pt0.10/Cu-MoC catalyst has a better MOR catalytic activity (563.25 mA mgPt−1), which is 1.5 times higher than that of commercial Pt/C (376.67 mA mgPt−1). The Pt0.10/Cu-MoC catalyst has an onset potential for CO oxidation that is 16 mV lower than that of commercial Pt/C, indicating better resistance to CO poisoning. Exploring carbon materials derived from MOFs with excellent junction support and using them as carriers to prepare Pt-based catalysts is a practical and feasible approach. It provides a way to develop new Pt-based catalysts that perform efficient MOR. [ABSTRACT FROM AUTHOR]

The aging of asphalt-binder during long-term use is an important reason for the decline in road performance of asphalt mixtures. In this study, waste vegetable oil (fried for 1-2h) was investigated as a rejuvenator of asphalt-binder. The optimisation effect of waste vegetable oil on the performance of asphalt-binder with different aging degrees (RTFOT, PAV15/20/48h) was evaluated by testing their conventional physical properties, high-temperature properties, and low-temperature properties. The molecular dynamics method was used to construct models, and the diffusion properties, solubility properties, adsorption energy, and asphaltene aggregation were calculated. The influences of linoelaidic acid and oleic acid molecules on aged asphalt-binder molecules were evaluated. The changes in the functional groups of the aged asphalt-binder after the addition of waste vegetable oil were analyzed by infrared spectrometry, and the changes in the microstructure of the aged asphalt-binder surface were observed by scanning electron microscopy. The results revealed that waste vegetable oil could regenerate aged asphalt-binder and significantly improve their physical and high-/low-temperature properties. Waste vegetable oil molecules are compatible with aged asphalt-binder molecules, improve their diffusion behaviour, enhance their adsorption capacity, and slightly reduce the aggregation of asphaltenes. Overall, waste vegetable oil shows great potential for the regeneration of aged asphalt-binder. [ABSTRACT FROM AUTHOR]

High-performance anode electrocatalysts for direct methanol fuel cells (DMFCs) have drawn great attention due to their promising commercial applications. Carbon materials derived from metal–organic frameworks (MOFs) are widely used in catalysts as supports. Herein, Ni-embedded nitrogen-doped carbon (Ni–NC) derived from MOFs was synthesized using Ni-PBA via pyrolysis at an optimized temperature of 500 °C. The presence of Ni–NC confirmed the doping of nitrogen and the large specific surface area of the support materials formed at high temperatures. The Pt0.13/Ni–NC sample prepared by the displacement deposition of platinum (Pt) on Ni–NC at the defined mass ratio exhibited an improved mass activity of 1.90 A mg−1Pt in the methanol oxidation reaction (MOR), which is five times higher than that of commercial Pt/C (0.38 A mg−1Pt). The improvement in the activity is ascribed to the synergetic effect of Pt, Ni and NC. Moreover, the Pt0.13/Ni–NC sample demonstrated high stability. This is due to the synergistic effect between Pt and Ni (electron charge donor effect of Ni to Pt), which changes the surface electronic structure of Pt atoms and can maximize the utilization of noble metals while weakening the adsorption of COads at the active site of Pt. This work provides a flexible strategy to construct advanced MOR electrocatalysts using MOF-derived carbon materials. [ABSTRACT FROM AUTHOR]

Due to the excellent comprehensive properties, Si3N4 ceramics have been widely studied and applied in the field of engineering structures. Conventional processing of Si3N4 ceramics faces a series of challenges, and laser processing has become an effective processing technology for hard and brittle materials. In this paper, a new type of dual-beam coupled nanosecond pulsed laser was used to carry out a series of ablation experiments on Si3N4 ceramic at various powers, and the laser ablation mechanism was analyzed. The equivalent diameter method and the equivalent area method were used to calculate the corresponding laser ablation threshold, and influence of laser power on surface roughness of the ablation hole edge, hole depth, removal volume and hole taper were explored. The results show that when the repetition frequency f = 10 kHz, wavelength λ = 532 nm and ablation time t = 6 s, the laser ablation thresholds of Si3N4 ceramic calculated by the equivalent diameter method and the equivalent area method are 0.55 J/cm2 and 0.59 J/cm2, respectively. In a certain power range, surface roughness of the ablation hole edge, hole depth and removal volume increase with the increase of laser power, while the ablation hole taper decreases with the increasing laser power. This innovative work is helpful to expand the scope of laser processing technology for hard and brittle materials, and has guiding significance for the optimization of laser processing technology parameters of Si3N4 ceramics. [ABSTRACT FROM AUTHOR]

Afforestation is beneficial to improving soil carbon pools. However, due to the lack of deep databases, the variations in soil carbon and the combined effects of multiple factors after afforestation have yet to be adequately explored in >1 m deep soils, especially in areas with deep-rooted plants and thick vadose zones. This study examined the multivariate controls of soil organic carbon (SOC) and inorganic carbon (SIC) in 0–18 m deep under farmland, grassland, willow, and poplar in loess deposits. The novelty of this study is that the factors concurrently affecting deep soil carbon were investigated by multiwavelet coherence and structural equation models. On average, the SOC density (53.1 ± 5.0 kg m−2) was only 12% of SIC density (425.4 ± 13.8 kg m−2), with depth-dependent variations under different land use types. In the soil profiles, the variations in SOC were more obvious in the 0–6 m layer, while SIC variations were mainly observed in the 6–12 m layer. Compared with farmland (SOC: 17.0 kg m−2; SIC: 122.9 kg m−2), the plantation of deciduous poplar (SOC: 28.5 kg m−2; SIC: 144.2 kg m−2) increased the SOC and SIC density within the 0–6 m layer (p < 0.05), but grassland and evergreen willow impacted SOC and SIC density insignificantly. The wavelet coherence analysis showed that, at the large scale (>4 m), SOC and SIC intensities were affected by total nitrogen-magnetic susceptibility and magnetic susceptibility-water content, respectively. The structural equation model further identified that SOC density was directly controlled by total nitrogen (path coefficient = 0.64) and indirectly affected by magnetic susceptibility (path coefficient = 0.36). Further, SOC stimulated the SIC deposition by improving water conservation and electrical conductivity. This study provides new insights into afforestation-induced deep carbon cycles, which have crucial implications for forest management and enhancing ecosystem sustainability in arid regions. [Display omitted] • Soil organic and inorganic carbon varied with land use types and soil depths. • Combined effects of multiple factors on soil carbon were studied at various scales. • Magnetic susceptibility increased the coherence between SOC and total nitrogen. • Water content increased the coherence between SIC and magnetic susceptibility. • We revealed the internal relationship between soil organic and inorganic carbon. [ABSTRACT FROM AUTHOR]

Due to the excellent properties of high hardness, oxidation resistance, and high-temperature resistance, silicon carbide fiber reinforced silicon carbide ceramic matrix composite (CMC-SiCf/SiC) is a typical difficult-to-process material. In this paper, according to the relationship between the spatial posture of dual beams and the direction of the machining path, two kinds of scanning methods were set up. The CMC-SiCf/SiC grooving experiments were carried out along different feeding directions (transverse scanning and longitudinal scanning) by using a novel dual-beam coupling nanosecond laser, and the characteristics of grooving morphology were observed by Laser Confocal Microscope, Scanning Electron Microscopy (SEM), and Energy Dispersive Spectrometer (EDS). The results show that the transverse scanning grooving section morphology is V shape, and the longitudinal scanning groove section morphology is W shape. The grooving surface depth and width of transverse scanning are larger and smaller than that of longitudinal scanning when the laser parameters are the same. The depth of the transverse grooving is greater than that of the longitudinal grooving when the laser beam is transverse and longitudinal scanning, the maximum grooving depth is approximately 145.39 μm when the laser energy density is 76.73 J/cm2, and the minimum grooving depth is approximately 83.76 μm when the laser energy density is about 29.59 J/cm2. The thermal conductivity of fiber has a significant effect on the local characteristics of the grooved morphology when using a medium energy density grooving. The obvious recasting layer is produced after the laser is applied to CMC-SiCf/SiC when using a high energy density laser grooving, which directly affects the grooved morphology. [ABSTRACT FROM AUTHOR]

• The ablation threshold of silicon carbide ceramics at different incidence angles was calculated. • The energy density distribution function for the tilted incident laser was derived and established. • The surface morphologies and element distributions of silicon carbide ceramics under different incident angles and powers were systematically discussed and analyzed. Due to their excellent physical and chemical properties, silicon carbide ceramics have become representative high-performance materials in aerospace, energy power, biomedical, and other fields. However, as a typical hard and brittle material, silicon carbide ceramics possess incredibly high hardness and brittleness, which pose challenges to traditional mechanical processing methods. Laser processing, as a non-contact method, offers a wide processing range and high processing efficiency and has broad application prospects in the field of hard and brittle material processing. In this paper, laser ablations of silicon carbide ceramics with various combinations of process parameters were carried out by using a five-axis infrared femtosecond laser processing system. The changes in the ablation morphology with different incidence angles and laser power were discussed. The results demonstrate that the ablation threshold of silicon carbide ceramics initially increases, then decreases, and finally increases with the increase of laser incident angle. This trend may be attributed to the effect of the incidence angle on the laser absorption rate of silicon carbide ceramics. The ablation morphology of silicon carbide ceramics can be divided into three zones based on color and oxygen distribution: the ablation removal zone, ablation edge zone, and ablation affected zone. At the same laser incidence angle, the ablation range and depth gradually increase with the increase in laser power, but the growth rate gradually decreases. Furthermore, at the same laser power, as the incident angle increases, the laser energy density gradually decreases, and the long axis of the actual ablation area gradually lengthens while the short axis gradually shortens. This work could provides technical and theoretical support for laser surface processing at multiple incidence angles, which is conducive to multi-axis processing of complex curved parts. [ABSTRACT FROM AUTHOR]

• Estimated potential recharge vary with methods and vegetation types. • Recharge estimated by CMB and CP is problematic under deep-rooted plants. • CMB performs the best in estimating recharge under shallow-rooted plants. • CWMB present the best results for recharge estimation under deep-rooted plants. • Uncertainties in methods originate from the requirements of methodological theory. Chloride (Cl)-based tracing methods are popular for deep drainage (or potential groundwater recharge) estimation in the unsaturated zone, but uncertainties in various such methods have rarely been investigated. We collected 1827 samples from 24 soil profiles under plants with shallow or deep root systems in the thick unsaturated loess deposits of China, and measured soil water, Cl, and tritium contents. With the drainage estimated with the tritium peak method as reference, we evaluated the applicability of several Cl-based approaches for drainage estimation under shallow- and deep-rooted plants, including the chloride mass balance method (CMB), chloride storage method (CS), chloride peak method (CP) and chloride-water mass balance method (CWMB). The estimated deep drainages varied with methods, and the uncertainties were large with a coefficient of variation of 0.71. Compared to the drainage obtained from tritium-based methods (33.6 ± 11.2 and 9.6 ± 14.5 mm year−1 under shallow- and deep-rooted plants, respectively), CMB and CS (38.0 ± 16.6 and 36.7 ± 17.6 mm year−1) performed better than CP (23.2 ± 17.8 mm year−1) under shallow-rooted plants, while CWMB (7.6 ± 13.9 mm year−1) performed better under deep-rooted plants. The large discrepancy in estimated drainage originates from methodological theory such as the time scales of representation and sensitivity to exogenous Cl inputs. The root water uptake-induced soil water depletion can enrich soil Cl concentration and greatly influence CMB and CP. Our findings provide insights for how to estimate deep drainage through appropriate methods. [ABSTRACT FROM AUTHOR]

Due to the excellent properties of high hardness, oxidation resistance and high temperature resistance, silicon carbide fiber silicon carbide ceramic matrix composite (CMC-SiC f /SiC) is a typical difficult-to-process material, and is a high-performance advanced material in the aerospace field. In this paper, two groups of ablation experiments (experiment 1 and experiment 2) were performed on CMC-SiC f /SiC using a dual-beam coupling nanosecond laser, and the ablation morphology was observed by confocal laser microscope. The dual-beam coupling angle of experiment 2 is obtained by experimental method. And through the method of calculation, we get the dual-beam coupling angle of experiment 1 and experiment 2. According to the dual-beam coupling ablation mechanism, based on the theoretical calculation model of non-destructive method D 2-ln P 0 , combined with the Equivalent Diameter Calculation Method (EDCM) and Equivalent Area Calculation Method (EACM), the laser ablation threshold corresponding to different beam waist size was calculated and compared. The results show that the ablation region of CMC-SiC f /SiC surface can be divided into three parts: ablation boundary, recast layer area and SiO 2 coverage area. When the pulse energy increases gradually from 300 μJ to 1500 μJ, the variation trend of hole depth is first increase, second decrease, increase again, and finally decrease. The angle between two laser beams affects the waist radius, which in turn affect the laser ablation threshold. The waist of the dual-beam coupling is elliptical, and the orifice of the ablation hole is elliptical. When the waist radius of nanosecond laser is 57 μm, the laser ablation threshold is calculated to be 3.12 J/cm2. The main factors affecting the laser ablation threshold are laser pulse repetition frequency (f), beam waist radius (ω 0), laser pulse width (τ), minimum laser power (P th), and laser wavelength (λ). [ABSTRACT FROM AUTHOR]