Search

Superconducting energy pipeline (SEP) is a new type of electrical energy transmission. It contains high‐temperature superconducting cables and liquefied natural gas pipelines and can simultaneously transmit electricity and liquefied natural gas (LNG). However, when the superconducting tapes in the superconducting cables in SEP quench and generate heat, bubbles will generate in the butt‐gaps of the insulation layer of superconducting cables, which can reduce the insulation strength of the cables significantly. In addition, the effects of bubbles in the butt‐gap of the insulation layer on the insulation properties of the superconducting cables are unknown. The objective here is to obtain the influences of bubbles in the insulation layer of superconducting cables in capacitive field, transitional field, and resistive field. Simulation results show that: Compared with the absence of bubbles, the big bubbles can increase the capacitive field strength of the PP film, the butt‐gap, and the kraft by 37.54%, 30.89%, and 18.5%, and increase the transition time from the capacitive field to the resistive field, but has almost no effect on the butt‐gap in the resistive field.

Large polarons are known to form in lead halide perovskites (LHPs). Photoinduced isolated polarons at low densities have been well-researched, but many-body interactions at elevated polaron densities, exceeding the Mott criterion (i.e., Mott polaron density), have remained elusive. Here, employing ultrafast terahertz spectroscopy, we identify a stable Mott polaron state in LHPs at which the polaron wavefunctions start to overlap. The Mott polaron density is determined to be ∼1018 cm-3, in good agreement with theoretical calculations based on the Feynman polaron model. The electronic phase transition across the Mott density is found to be universal in LHPs and independent of the constituent ions. Exceeding the Mott polaron density, excess photoinjected charge carriers annihilate quickly within tens to hundreds of picoseconds, before reaching the stable and long-lived Mott state. These results have considerable implications for LHP-based devices and for understanding exotic phenomena reported in LHPs. ispartof: ACS ENERGY LETTERS vol:8 issue:1 pages:420-428 ispartof: location:United States status: published

Solid-state bonding of heterogeneous materials is one of the effective ways to achieve light weight. An extrusion forming process for Mg/Al thickness-oriented bonding sheet was carried out. Due to triaxial compressive stress in the extrusion container, the AZ31 and AA6061 billets were deformed and the bonding and forming of Mg/Al thickness-oriented sheet can be realized by this method. The observation results of the bonding position by using XRD, SEM and EDS showed that: at the forming temperature with 360–420 °C, it had a good bonding interface, and the width of the transition layer increased with the increase of the forming temperature. The presence of brittle intermetallic compounds in the transition layer indicated that metallurgical bonding had occurred at the interface. Considering all factors comprehensively, when the forming temperature was 390 °C, the bonding quality was appropriate. Its tensile-shear strength was 42 MPa, the width of the interface transition layer was about 10 μm, and the microhardness was about 164.3 HV. This method provided scientific guidance and technical reserves for green forming of Mg/Al sheets.

An Fe-abundant solid waste, fabric filter dust (FFD) was used as the starting material for the preparation of metal-doped Fe2O3 (M−Fe2O3) nanoparticles for the photocatalytic degradation of MO aqueous solution. Valuable elements including Fe, Ti, Al, Na, Si, Ca, and Mg were extracted from the dust by hydrochloric acid leaching, transformed into sediments by increasing the pH of the lixivium orderly, and converted into M−Fe2O3 nanoparticles by the sol–gel technology. The effects of pH for the precipitation process and firing temperature for the sol–gel method were investigated systematically. The M−Fe2O3 samples were characterised using X-ray diffraction, field emission scanning electron microscopy, Brunauer–Emmett–Teller analysis, UV–vis spectra, and energy dispersive spectroscopy. The performances of the dust-derived nanoparticles during photocatalytic process were appraised by visible light photodegradation of methyl orange (MO) aqueous solution, indicating that the M−Fe2O3 (M = Ti and Al) sample prepared with a precipitation pH of 4 and a firing temperature of 500 °C exhibits the most impressive photocatalytic behaviour. The product produces a degradation rate of 82.99% for 100 mL of MO solution (10 mg/L) after visible-light degradation for 180 min, which is increased from 38.94% achieved by an undoped Fe2O3 sample prepared under the same conditions.

2.5D Cf/SiC composite has been a key heat-resistant ceramic matrix composite (CMC) in aerospace field due to the special structure characteristics. Against the existing research almost focus on 'ablation behavior' in laser processing of CMC, this paper put forward the 'ablation evolution behavior' for the first time, and reveals the 'ablation evolution behavior' in micro-hole machining of 2.5D Cf/SiC composites with millisecond laser. The results show that 0° fiber experiences the ablation evolution from filiform connection, flat ellipse, needle-like to convex structure. And the 90° fiber suffers the ablation evolution from cylindrical structure, lotus lead shape, bud-shape to closed shape. The core of the 90° fibers undergoes the topography structures from cylindrical protrusion, spherical protrusion to needle-like. Except for the honeycomb structure studied in existing research, four new recast layer structures, named transverse strip, longitudinal strip, shell structure, and multi-layer structure are found and analyzed. Further, the mechanism analysis reveals that the recast layer contains both oxidized characteristics and highly carbonized characteristics. In addition, the microstructural analysis shows that three types of particle topography adhere to the recast layer, that are spherical micro-protrusion (20–48 μm), bubble particles (5–15 μm), and sub-micron particles (

The high conduction loss of solid-state circuit breakers blocks the HTS electrical system implementation for future aircraft. An LN2 switch marries the low conduction loss with good DC interruption performance in the cryogenic circumstance. It shows a fascinating prospect in the HTS electrical system. However, the possible applications of such a novel switch have never been discussed. This paper proposed two potential strategies for applying the LN2 switch into the HTS electrical system. A low voltage experiment is conducted to validate the combination of the SFCL with an LN2 switch. Heat loss is also calculated based on the experimental results. Same level solid-state circuit breakers with cryogenic parameters are set as a fair comparison. A 10 kA prospective short circuit current is limited to 1.4 kA by SFCL within 580 μs and then interrupted by the LN2 switch within 12 ms. The fast response of SFCL compensates for the long clear time of the LN2 switch. Heat loss of this combination is 1/120 of the heat generated by the same level SSCB in an assumed 2-hour flight. With proper design, such a combination could meet the protection requirements of any specific HTS electrical system. Refrigeration system size and weight can be significantly reduced.

Impulse breakdown voltage is one of the most important factors for the designation of the R-SFCLs. However, no research about the polarity effect on standard lightning impulse in LN2/insulation barrier composite systems has been reported. The objective of this paper is to study the polarity effect on the standard lightning impulse in the LN2/insulation barrier composite systems. The 50% impulse breakdown voltage was measured with a pair of the needle to plane electrodes with the 0.05 mm thick PTFE film. The gap length of the two electrodes was 10 mm. The distance between the needle electrode and the insulation barrier was varied. The time delays during the breakdown progress were recorded by the oscilloscope. The breakdown path was determined by the arc traces on the PTFE films. The results showed that the 50% impulse breakdown voltage of the LN2/insulation barrier composite increased with the insulation barrier get closer to the needle electrode. The results of the time delays reflect that in negative polarity, all the breakdowns occurred in the tail of the waveform. In positive polarity, most of the breakdowns occurred in the head of the waveform. With the barrier get closer to the insulation barrier, the longer time delay T delay was in both polarities. And the probability of wave tail breakdown increased in positive polarities. The arc traces on the PTFE showed that all the breakdowns were occurred through the PTFE film.

The appearance of porous asphalt (PA) pavement is to solve the problem of road ponding in rainy days. The internal air voids in PA pavement are the main functional structure that determines its drainage performance. It is of great practical significance to find out the relationship between void drainage capacity and air voids. This paper is aimed at researching the relationship between three-dimensional (3D) pore structures and drainage performance of PA concrete. Four samples were formed and scanned by CT equipment to obtain the internal cross-sectional CT images. Image dodging algorithm and OTSU method were conducted to deal with these CT images for segmenting them into three subimages (void image, asphalt mortar image, and aggregate image) according to the three components of PA concrete. The voids on void images were identified and classified into three groups according to the three kind of pores (interconnected pore, semi-interconnected pore, and closed pore) and reshaped them into 3D pore structures according to the overlapping principle. Then, the volume and size distribution of the pores was analyzed. Besides, this research mainly focused on the influence of several parameters obtained from interconnected pores on the drainage performance of PA concrete at last. The permeability coefficient of PA concrete samples was tested, and equations between permeability coefficient and void content were fitted linearly. The distribution of hydraulic radius and cross-sectional area ratio was calculated and researched by statistical methods. A new parameter, perimeter variation coefficient, is proposed to study the influence of boundary wall roughness on the drainage performance. At last, equivalent drainage channel was drawn to reflect the drainage capacity of PA concrete.

In this paper, 3 mol% yttria-doped tetragonal zirconia polycrystal material (3 mol% Y2O3–ZrO2) was prepared using an optimised pressureless sintering process. The phase change and particle size distribution of Y2O3–ZrO2 during sintering were studied, and the effect of sintering temperature on the properties of Y2O3–ZrO2 was analysed. The raw materials and prepared samples were analysed using XRD, Raman spectroscopy, SEM, and Gaussian mathematical fitting. The results show that sintering encourages the transformation of the monoclinic phase into the tetragonal phase, thus improving the crystallinity of the sample. The relative content of the tetragonal phase in the sample increased from 57.43% to 99.80% after sintering at 1200 °C for 1 h. In the range of sintering temperatures studied in this paper (800–1200 °C), the zirconia material sintered at 1000 °C presented the lowest porosity and the best density.

The successful applications of two-dimensional (2D) transition metal dichalcogenides highly rely on rational regulation of their electronic properties. The nondestructive and controllable doping strategy is of great importance to implement 2D materials in electronic devices. Herein, we propose a straightforward and effective method to realize controllable n-type doping in WSe2 monolayer by electron beam irradiation. Electrical measurements and photoluminescence (PL) spectra verify the strong n-doping in electron beam-treated WSe2 monolayers. The n-type doping arises from the generation of Se vacancies and the doping degree is precisely controlled by irradiation fluences. Due to the n-doping-induced narrowing of the Schottky barrier, the current of back-gated monolayer WSe2 is enhanced by an order of magnitude and a ∼8× increase in the electron filed-effect mobility is observed. Remarkably, it is a moderate method without significant reduction in electrical performance and severe damage to lattice structures even under ultra-high doses of irradiation.

Nanosized CeO2–ZrO2 powders prepared by atmospheric pressure pyrolysis were used as raw materials to prepare CeO2–ZrO2 ceramics using microwave sintering. The samples were characterised using bulk density measurements, X-ray diffraction (XRD), Fourier Transform Infrared Spectrometer (FT-IR), Raman, and scanning electron microscopy (SEM). The purpose was to determine the optimised microwave sintering process for CeO2–ZrO2 ceramics and reveal the corresponding mechanism. The results show that with a CeO2 addition content above 5 mol%, the tetragonal phase peak appeared obviously in the sample. The results show that the tetragonal phase peak appears when the CeO2 content is more than 5 mol%. The dopants, namely CeO2, have reduced the solid solution's phase transformation temperature with the assistance of microwave heating. Additionally, the grain size of the CeO2–ZrO2 ceramics has shown a negative relationship with Ce content at a temperature of 900 °C. The reason is that the rapid sintering due to microwave sintering and the oxygen vacancies generated by CeO2 can effectively inhibit grain growth. The regulation mechanism on microwave sintering of CeO2–ZrO2 ceramic was clarified, and the technical prototype of controlled prepared CeO2–ZrO2 ceramics by microwave sintering was constructed.

As a new ceramics matrix composite, 2.5D Cf/SiC composite has been a key material in high-temperature parts of aerospace field. However, the commonly used fiber laser drilling process tends to cause ablation damage to composite structures, which subsequently affects their fatigue lives and in-service performance. Understanding the ablation damage mechanism is crucial in controlling the fiber laser drilling process for achieving desired micro-hole quality. This paper studies the damage characteristics and correspondingly reveals the ablation mechanism in fiber laser trepan drilling of 2.5D Cf/SiC composites. It is found that there are obvious cone angles in the exit of the micro-hole at low laser scanning speed. Aiming at the special needle-punched structures of the 2.5D Cf/SiC composites, the ablation damage of the transverse fiber (0°, and 90° fiber) and needle-punched fiber bundles is analyzed by ways of scanning electron microscope (SEM) and energy dispersion spectrum (EDS) elemental analysis. Specifically, the transverse fiber is prone to needle-like, tapered, transverse fracture, longitudinal crack, and bending damage, and the needle-punched fiber bundles easily appear to interfacial debonding and extrusion fracture during the fiber laser drilling. More importantly, the results show that the layered accumulation, adherent morphology, thin shell, and bubble-like morphology are found to be four main mechanisms of recasting layers. The research provides a theoretical basis for achieving the high-quality micro-hole machining of 2.5D Cf/SiC composites with the fiber laser drilling.

As an eco-friendly thermoelectric material, SnTe has attracted extensive attention. In this study, we use a stepwise strategy to enhance the thermoelectric performance of SnTe. Firstly, AgCl is doped into SnTe to realize band convergence and enlarge the band gap of AgCl-doped SnTe. AgCl-doping also induces dense point defects, strengthens the phonon scattering, and reduces the lattice thermal conductivity. Secondly, Sb is alloyed into AgCl-doped SnTe to further optimize the carrier concentration and simultaneously reduce the lattice thermal conductivity, leading to improved thermoelectric dimensionless figure of merit, ZT. Finally, (Sn0.81Sb0.19Te)0.93(AgCl)0.07 has approached the ZT value as high as ∼0.87 at 773 K, which is 272 % higher than that of pristine SnTe. This study indicates that stepwise AgCl-doping and Sb-alloying can significantly improve thermoelectric performance of SnTe due to synergistic band engineering, carrier concentration optimization and defect engineering.

Increasing helium (He) demand in fundamental research, medical, and industrial processes necessitates efficient He purification from natural gas. However, most theoretically available membranes focus on the separation of two or three kinds of gas molecules with He and the underlying separation mechanism is not yet well understood. Using molecular dynamic (MD) and first-principle density function theory (DFT) simulations, we systematically demonstrated a novel porous carbon nitride membrane (g-C9N7) with superior performance for He separation from natural gas. The structure of g-C9N7 monolayer was optimized first, and the calculated cohesive energy confirmed its structural stability. Increasing temperature from 200 to 500 K, the g-C9N7 membrane revealed high He permeability, as high as 1.48 × 107 GPU (gas permeation unit, 1 GPU = 3.35 × 10−10 mol∙s−1∙Pa−1∙m−2) at 298 K, and also exhibited high selectivity for He over other gases (Ar, N2, CO2, CH4, and H2S). Then, the selectivity of He over Ne was found to decrease with increasing the total number of He and Ne molecules, and to increase with increasing He to Ne ratio. More interestingly, a tunable He separation performance can be achieved by introducing strain during membrane separation. Under the condition of 7.5% compressive strain, the g-C9N7 membrane reached the highest He over Ne selectivity of 9.41 × 102. It can be attributed to the low energy barrier for He, but increased energy barrier for other gases passing through the membrane, which was subject to a compressive strain. These results offer important insights into He purification using g-C9N7 membrane and opened a promising avenue for the screening of industrial grade gas separation with strain engineering.

The effects of microwave power and sample quality on microwave drying kinetics and characteristics of zirconia were studied. It is found that by increasing the microwave power and decreasing the sample mass, the surface diffusion coefficient (Deff) appears to an upward tendency. The corresponding value Deff at a sample mass of 10, 20, 30, and 40g are 1.849E-14, 2.443E-14, 3.210E-14, and 3.278E-14 m2/s, respectively. The corresponding value Deff at a microwave power of 300, 400, 500, 600, and 700W are 1.270E-14, 1.784E-14, 2.619E-14, 3.392E-14, and 4.497E-14 m2/s, respectively. Besides, the materials were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR) to evaluate the changes of materials before and after drying. The results show that microwave accelerates the drying of zirconia and increases its dispersibility. The heat conduction direction of microwave drying is the same as that of moisture diffusion, which avoids being affected by heat inertia and heat transfer loss. The drying process is fast and efficient, and the microwave directly penetrates the product, avoiding the disadvantage of slow evaporation caused by the temperature gradient.

In this paper, the stability of CaO doped partially stabilised zirconia (CaO-PSZ) prepared by electrofusion method was improved from 88.14% to 95% within 1 h using the microwave heating method. The increase of the stability rate was because of the microwave heating method's advantages, including selective heating and fast heating. Analysis techniques, namely X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Raman spectroscopy, and scanning electron microscopy (SEM), were used to analysis the influences of the holding time (1–4 h) on the CaO doped PSZ samples at a heating temperature of 1100 °C to understand the fundamental mechanism of the optimisation process. The Raman and XRD spectra were fitted by the Gaussian method to further analysis the effect of holding time on the microstructure evolution of the samples. The fitting results indicated that the sample's crystal quality and stability were improved after microwave heating, and the optimised holding time is 2 h.

Graphene nanoribbons (GNRs) not only share many superlative properties of graphene but also display an exceptional degree of tunability of their electronic properties. The bandgaps of GNRs depend greatly on their widths, edges, etc. Herein, we report the synthesis path and the physical properties of atomic accuracy staggered narrow N = 8 armchair graphene nanoribbons (sn-8AGNR) with alternating “Bite” defects on the opposite side. The intermediate structures in the surface physicochemical reactions from the precursors to the sn-8AGNR are characterized by scanning tunneling microscopy. The electronic properties of the sn-8AGNR are characterized by scanning tunneling spectroscopies and d//dV mappings. Compared with the perfect N = 8 armchair graphene nanoribbons (8AGNR), the sn-8AGNR has a larger bandgap, indicating that the “Bite” edges can effectively regulate the electronic structures of GNRs.

Vanadium pentoxide (V2O5) is one of the fundamental materials applied in the productions of batteries, vanadium-aluminium alloys, biomedicine, catalysis, etc. High purity V2O5 can be prepared from an intermediate product, namely ammonium polyvanadate (APV), using roasting after a drying process. In this paper, microwave heating was used as an alternative drying option for APV, which has advantages including selective heating, high heating efficiency, energy-saving, and environmental protection. The authors investigated the microwave heating characteristics of APV and discussed the effects of microwave power, the mass of APV, and initial water content on the efficiency of microwave drying. The dynamic analysis of the APV microwave drying process was also carried out. Four groups of thin-layer drying dynamic models, namely Modified-Page model, Verma model, Sickmplified-Fick's-diffusion model, and Two-term-exponential model, were fitted with the experimental data. Through comparison, the Modified Page model could better describe the microwave drying process of APV.

All-solid-state lithium-metal batteries, with their high energy density and high-level safety, are promising next-generation energy storage devices. Their current performance is however compromised by lithium dendrite formation. Although using 3D-structured metal-based electrode materials as hosts to store lithium metal has the potential to suppress the lithium dendrite growth by providing a high surface area with lithiophilic sites, their rigid and ragged interface with solid-state electrolytes is detrimental to the battery performance. Herein, we show that Li2OHBr-containing poly(ethylene oxide) (PEO) polymer electrolytes can be used as a flexible solid-state electrolyte to mitigate the interfacial issues of 3D-structured metal-based electrodes and suppress the lithium dendrite formation. The presence of Li2OHBr in a PEO matrix can simultaneously improve the mechanical strength and lithium ion conductivity of the polymer electrolyte. It is confirmed that Li2OHBr does not only induce the PEO transformation of a crystalline phase to an amorphous phase but also serves as an anti-perovskite superionic conductor providing additional lithium ion transport pathways and hence improves the lithium ion conductivity. The good interfacial contact and high lithium ion conductivity provide sufficient lithium deposition sites and uniform lithium ion flux to regulate the lithium deposition without the formation of lithium dendrites. Consequently, the Li2OHBr-containing PEO polymer electrolyte in a lithium-metal battery with a 3D-structured lithium/copper mesh composite anode is able to improve the cycle stability and rate performance. The results of this study provide the experimental proof of the beneficial effects of the Li2OHBr-containing PEO polymer electrolyte on the 3D-structured lithium metal anode.

Early spontaneous detection of thrombin activation benefits precise theranostics for thrombotic vascular disease. Herein, a thrombin-responsive nanoprobe conjugated by a FITC dye, PEGylated Fe3O4 nanoparticles, and a thrombin-sensitive peptide (LASG) was constructed to visualize thrombin activation and subsequent thrombosis in vivo. The FITC dye was linked to the LASG coated on the Fe3O4 nanoparticles for sensing the thrombin activity via the Forster resonance energy transfer effect. In vitro fluorescence imaging showed that the fluorescence signal intensity increased significantly after incubation with thrombin in contrast to that of the control group (p < 0.05), and the signal intensity was enhanced with the increase in thrombin concentration. Further in vivo fluorescence imaging also revealed that the signal elevated markedly in the left common carotid artery (LCCA) lesion of the mice thrombosis model after nanoprobe injection, in contrast to that of the control + nanoprobe group (p < 0.05). Moreover, the thrombin inhibitor bivalirudin could decrease the filling defect of the LCCA. Three-dimensional fusion images of micro-CT and fluorescence confirmed that filling defects in the LCCA were nicely colocalized with fluorescence signal caused by nanoprobes. The nanoplatform based on a thrombin-activatable visualization system could provide smart responsive and dynamic imaging of thrombosis in vivo.

Two-dimensional semiconductors (2DSCs) with appropriate band gaps and high mobilities are highly desired for future-generation electronic and optoelectronic applications. Here, using first-principles calculations, we report a novel class of 2DSCs, group-11-chalcogenide monolayers (M2X, M = Cu, Ag, Au; X = S, Se, Te), featuring with a broad range of energy band gaps and high carrier mobilities. Their energy band gaps extend from 0.49 to 3.76 eV at a hybrid density functional level, covering from ultraviolet-A, visible light to near-infrared region, which are crucial for broadband photoresponse. Significantly, the calculated room-temperature carrier mobilities of the M2X monolayers are as high as thousands of cm2·V−1·s−1. Particularly, the carrier mobilities of η-Au2Se and e-Au2Te are up to 104 cm2·V−1·s−1, which is very attracitive for electronic devices. Benefitting from the broad range of energy band gaps and superior carrier mobilities, the group-11-chalcogenide M2X monolayers are promising candidates for future-generation nanoelectronics and optoelectronics.

In the present study, controllable microwave sintering was applied to prepare partially stabilised zirconia ceramics with enhanced phase composition and a more uniform structure. To reveal the phase interface properties and structural changes of PSZ ceramics during the microwave sintering process, XRD, FT-IR, Raman, and SEM characterisations were utilised. XRD analysis and Raman analysis demonstrated that the increase of sintering temperature promoted the martensite conversion. However, prolonging duration time was unconducive to the retention of the stable phase. Additionally, the FT-IR characteristic peak movement caused by the reversible phase martensite transformation was observed. Furthermore, SEM analysis found that microwave treatment improved the grain size and structure distribution of the as-received MgO-PSZ sample. This work constructed a controllable technical prototype of preparing PSZ ceramics via microwave sintering, which can provide a theoretical basis and experimental basis for further industrial production.

Topological Hall effect (THE) has been used as a powerful tool to unlock spin chirality in novel magnetic materials. Recent focus has been widely paid to THE and possible chiral spin textures in two-dimensional (2D) layered magnetic materials. However, the room-temperature THE has been barely reported in 2D materials, which hinders its practical applications in 2D spintronics. In this paper, we report a possible THE signal featuring antisymmetric peaks in a wide temperature window up to 320 K in Cr1.2Te2, a new quasi-2D ferromagnetic material. The temperature, thickness, and magnetic field dependences of the THE lead to potential spin chirality origin that is associated with the spin canting under external magnetic fields. Our work holds promise for practical applications in future chiral spin-based vdW spintronic devices.

Traditional cancer therapeutics have been criticized due to various adverse effects and insufficient damage to targeted tumors. The breakthrough of nanoparticles provides a novel approach for upgrading traditional treatments and diagnosis. Actually, nanoparticles can not only solve the shortcomings of traditional cancer diagnosis and treatment, but also create brand-new perspectives and cutting-edge devices for tumor diagnosis and treatment. However, most of the research about nanoparticles stays in vivo and in vitro stage, and only few clinical researches about nanoparticles have been reported. In this review, we first summarize the current applications of nanoparticles in cancer diagnosis and treatment. After that, we propose the challenges that hinder the clinical applications of NPs and provide feasible solutions in combination with the updated literature in the last two years. At the end, we will provide our opinions on the future developments of NPs in tumor diagnosis and treatment.

Stoichiometry modulation in transition-metal perovskite oxides is a pivotal process that can give rise to unprecedented structures and new functionalities. Despite intensive study, the atomic mecha...

A series of polytetrafluoroethylene (PTFE) composites filled with CF (carbon fiber) and MoS2 (molybdenum disulfide) were prepared by cold-pressing sintering. The tensile strength and elongation at ...

Achieving high detection accuracy of pavement cracks with complex textures under different lighting conditions is still challenging. In this context, an encoder-decoder network-based architecture named CrackResAttentionNet was proposed in this study, and the position attention module and channel attention module were connected after each encoder to summarize remote contextual information. The experiment results demonstrated that, compared with other popular models (ENet, ExFuse, FCN, LinkNet, SegNet, and UNet), for the public dataset, CrackResAttentionNet with BCE loss function and PRelu activation function achieved the best performance in terms of precision (89.40), mean IoU (71.51), recall (81.09), and F1 (85.04). Meanwhile, for a self-developed dataset (Yantai dataset), CrackResAttentionNet with BCE loss function and PRelu activation function also had better performance in terms of precision (96.17), mean IoU (83.69), recall (93.44), and F1 (94.79). In particular, for the public dataset, the precision of BCE loss and PRelu activation function was improved by 3.21. For the Yantai dataset, the results indicated that the precision was improved by 0.99, the mean IoU was increased by 0.74, the recall was increased by 1.1, and the F1 for BCE loss and PRelu activation function was increased by 1.24.

Partially stabilised zirconia has advantages for the applications in the metallurgical processes which have special requirements in corrosion resistance and high-temperature performance. In the present work, controllable microwave heating was used for the uniform thermal field and consequent microstructure improvement to further improve the stability of partially stabilised zirconia, which was 88.14% prepared by electric arc melting. Analyses including X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy (Raman) were used to study the effect of temperature change on the phase composition and structure of the samples. After heating at temperatures of 900 °C, 1000 °C, 1100 °C, 1200 °C and 1300 °C for 1h, the stabilities of the heated product were 88.51%, 95.02%, 95.17%, 96.31% and 97.64%, respectively. From the phase transformations based on the experimental results, the discussion indicates that the martensitic transformation temperature of zirconia from m-ZrO2 to t-ZrO2 during the heating stage was reduced under the radiation of microwave energy.

In this work, microwave heating approach was introduced into the preparation process of zirconia materials to overcome the tricky technical defects during the traditional electric arc furnace method. Magnesia-partially stabilised zirconia (MgO-PSZ) with enhanced stability and a uniform microstructure was prepared via microwave heating of a ZrO2 sample manufactured by the electric arc furnace method. The effects of microwave heating on the phase stability properties, microstructure, and surface morphology of the prepared MgO-PSZ sample were evaluated via X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and Scanning electron microscopy, and the obtained results suggested that the stability rate of the MgO-PSZ sample improved from the initial value of 81.19%–94.82% after microwave heating at 1300 °C for 1 h. As a result of the martensitic conversion of ZrO2 material, the m-ZrO2 diffraction peaks were suppressed at the same time. Additionally, a similar changing trend was noticed in the XRD pattern, Raman spectrum, and FT-IR spectrum, indicating a decrease in the m-ZrO2 phase content in the microwave treated products. Furthermore, the microstructure on the surface of the microwave-sintered MgO-PSZ sample was improved in contrast to the raw MgO-PSZ sample, and became relatively more uniform and smooth. This study determined the optimal microwave heating conditions for the preparation of MgO-PSZ material with enhanced performance, and can provided as a good foundation for developing the further related research on zirconia materials preparing by microwave heating technology.

Synthesis of the unconventional phase of noble metal nanocrystals may create new opportunities in exploring intriguing physicochemical properties but remains challenging. In the research field of thin film growth, the interface strain offers a general driving force to stabilize the metastable phase of epitaxial film. Herein we extend this concept to the field of noble metal nanocrystals and report the solution synthesis of metastable face-centered tetragonal Au that has not been discovered before. The successful synthesis relies on the formation of intermetallic AuCu3@Au core-shell structure, where the interface strain stabilizes the metastable fct Au overlayer. Compared with the face-centered cubic Au counterpart, the metastable fct Au shows greatly improved catalytic activity toward CO2 reduction to CO. The density functional theory calculations and spectroscopic studies reveal that the metastable fct Au upshifts the d-band center, which lowers the energy barrier of key intermediate COOH* formation and thus facilitates the reaction kinetics.

Stimuli-responsive molecular crystals are fascinating for their potential as adaptive smart materials. However, achieving crystals that could respond to multiple stimuli and perform multiple functionalities simultaneously is still a challenging task. Herein, we report the fabrication and preparation of polymorphic crystals with multiple stimuli of a photoactive azobenzene derivative, trans-4-cyano-4′-oxethyl azobenzene (AzC2). Different polymorphic forms of AzC2 exhibit remarkable different photoinduced deformations, mechanical behaviors and photoluminescence properties. Upon UV irradiation, although both polymorphic forms undergo reversible photomechanical bending motions, Form I bent away from the light source while Form II bent towards the light source. Upon exertion of external mechanical stress, Form I tended to break whereas Form II exhibited elastic deformation. Furthermore, being excited at 325 nm, the block crystal of Form I exhibited a relatively strong green-yellow emission while a very weak red fluorescence emission was observed from the thicker Form II crystal. These different properties can be attributed to different molecular packings rather than molecular conformations. The present work provides an effective strategy to construct multiple stimuli-responsive crystal materials with potential applications in actuators, switches and sensors.

C–H bond activation and dehydrogenative coupling reactions have always been significant approaches to construct microscopic nanostructures on surfaces. By using scanning tunneling microscopy/spectroscopy (STM/STS) and non-contact atomic force microscopy (nc-AFM) combined with density functional theory (DFT), we systematically characterized the atomically precise topographies and electronic properties of H2TPP cyclodehydrogenation products on Au(111). Through surface-assisted thermal excitation, four types of cyclodehydrogenation products were obtained and clearly resolved in the nc-AFM images. The electronic characterization depicts the predominant resonances and their spatial distributions of the four products.

Polytetrafluoroethylene (PTFE) composites filled with glass fibre (GF) and graphite were prepared by internal mixer and moulded using compression mould to produce test samples. A high-speed mixer w...

Recent years have witnessed the chalcopyrite compound CuGaTe2 receiving widespread attention as a promising thermoelectric material. In the work, we calculated the band structure of Zn substitution...

This study proposes a hybrid voltage harmonic injection circuit at the DC link of the traditional series-connected 12-pulse rectifier to improve the harmonic suppression performance of the rectifier, which contains an injection transformer and the auxiliary circuit. The optimum turn ratio of the injection transformer and the optimal conduction angle of the switch are designed from the viewpoint of minimising the total harmonic distortion (THD) of the input voltage in the isolated transformer. Under the optimal design, the proposed series-connected rectifier operates as a 36-pulse rectifier. Experimental results indicate that the THD of input voltage reduces to ∼3.19% and that of the input current is only ∼2%.

M-ZnFe2O4 (M = Al, Zn, Cu, Mn) nanoparticles, which are potential photocatalysts, were prepared from Fe-bearing solid waste, namely Waelz slag. The valuable elements, namely Fe, Al, Zn, Cu, and Mn, were extracted from the slag simultaneously through sulfuric acid leaching. The extracted elements were converted into sediments in a controlled fashion by manipulating the pH of the lixivium and subsequently transformed into metal-doped ZnFe2O4 nanoparticles using the sol-gel method. The as-synthesised products were characterised using X-ray diffraction, Brunauer-Emmett-Teller analysis, field emission scanning electron microscopy, energy dispersive spectroscopy, UV–vis spectroscopy, and photoluminescence spectroscopy. The photocatalytic performances of the slag-derived M-ZnFe2O4 nanoparticles in photocatalytic methyl orange degradation under visible light were compared with that of undoped ZnFe2O4 nanoparticles. The results indicated that the slag-derived nanoparticles gave better photocatalytic performances than did the undoped sample, with the M-ZnFe2O4 (M = Al, Zn, Cu) sample, which was prepared with precipitates obtained at pH 7, exhibiting the best photocatalytic activity. The enhancement can be attributed to grain refinement and doping.

The coordination of resistive-type superconducting fault current limiters (R-SFCLs) and DC circuit breakers (DCCBs) have been investigated. However, the use of R-SFCLs with mechanical DCCBs (M-DCCBs) in hybrid transmission systems has not been studied. The objective of this paper is to investigate the parameter requirements of R-SFCLs and M-DCCBs for a detailed system protection strategy in a hybrid AC/DC system considering the influence of AC faults and three types of DC faults. When the AC fault is far from all MMCs, its impact on the DC system is weak. If the AC fault is close to one MMC, it will produce a strong transient response in the DC part. Therefore, a bypass switch in parallel with an R-SFCL is used to remove the R-SFCL from the system if it quenches during the AC fault. Then, the parameters of the protection devices are designed based on pole-to-pole DC fault. System restoration can be achieved within 200 ms after the fault. For pole-to-neutral and pole-to-ground faults, except for the R-SFCLs at the faulty pole, the R-SFCLs at the healthy pole will also quench, but the resistances are very low. The system may be restored within 250 ms after the DC fault.

Infrared radiation is a primary mechanism for heat exchange between the human body and the environment. In the framework of Mie scattering theory, we investigate the infrared absorption of a graphene-coated silk composite. We found that by coating graphene, the infrared absorption efficiency of silk fibrils is five orders larger than that without graphene coating. The observed significant enhancement in infrared absorption arises from the electromagnetic coupling between graphene and the silk. The effects of graphene's chemical potential and silk fibril diameter are also explored. Our results open a pathway to develop biological nanocomposites with tunable optical and thermal properties.

Manganese sulfate is widely used in electrolytic manganese production, catalysts, batteries, and other fields. However, the preparation of manganese sulfate from conventional roasting process of pyrolusite with additive of pyrite has disadvantages including long roasting time and low efficiency. Thus, microwave heating is used as an alternative for the preparation of manganese sulfate instead of traditional heating to destroy the dense structure of minerals and to further improve the heating efficiency which is dominating by dielectric properties of the material. Therefore, to evaluate the mechanism of preparation of manganese sulfate with microwave heating, experiments were carried out to explore the dielectric and thermochemical properties of pyrolusite-pyrite mixture at high temperature. The dielectric properties of pyrolusite-pyrite mixtures with different ratios were measured at high temperature using the resonant cavity perturbation technique, which has been widely used to study the dielectric properties of different metallurgical materials. It was found that with the increase of temperature, the microwave absorption properties of pure pyrolusite decreased from 28.173 F/M to 25.931 F/M. The wave-absorbing property of the soft pyrite/pyrite mixture increased to 41.218 F/M, indicating that pyrite can obviously improve the wave-absorbing property of the mixture. In addition, the characteristics of pyrolysis and reduction were studied systematically, and the pyrolysis and reduction process was divided into four stages according to the difference of temperature: 30 ℃-200 ℃, 200 ℃-400 ℃, 400 ℃-600 ℃, 600 ℃-900 ℃, corresponding to the separation of adsorbed water and bound water, MnO2 decomposition, desulfurization redox reaction of FeS2 and desulfurization redox reaction of Fe(1-x) S, respectively. This work highlights the possibility of reducing manganese ore by microwave heating with an additive of pyrite and finds that pyrite can modify the microwave absorption properties of pyrolusite.

The precipitation of niobium carbide (NbC) is a superior approach to mitigating hydrogen embrittlement (HE). The role of the semi-coherent interface between NbC and α-Fe on hydrogen trapping and HE resistance in high-strength tempered martensitic steel was investigated in this study. High-resolution transmission electron microscopy observations are performed to reveal the atomic-scale crystallographic orientation relationship, atomic arrangements, and associated crystalline defects in the NbC/α-Fe semi-coherent interface. We observed the Kurdjumov–Sachs orientation relationship with ( 1 1 ¯ 1 ¯ ) NbC / / ( 101 ) α − Fe and [ 0 1 ¯ 1 ] NbC / / [ 1 ¯ 11 ] α − Fe between the NbC and α-Fe phases. Noticeably, two sets of misfit dislocations with Burgers vectors of b ( 1 ) = a b / 2 [ 111 ] on ( 01 1 ¯ ) α-Fe planes and b ( 2 ) = a b / 2 [ 1 1 ¯ 1 ] on (110) α-Fe planes (ab is the lattice constant of α-Fe), which would be the deep hydrogen trapping sites, were characterized in the NbC/α-Fe semi-coherent diffuse interface. In addition, density functional theory-based first-principles calculations revealed that the deep binding energy between the NbC/α-Fe semi-coherent interface and hydrogen is 0.80 eV, which well matches the hydrogen desorption activation energy of 81.8 kJ/mol determined via thermal desorption spectroscopy experiments. These demonstrate that the nature of the deep hydrogen trapping sites of the NbC/α-Fe semi-coherent interface is the misfit dislocation core. Distinguished HE resistance was obtained and ascribed to the deep hydrogen trapping of uniformly dispersed NbC nanoprecipitates with an average diameter of 10.0 ± 3.3 nm. The strategy of deep hydrogen trapping in the NbC/α-Fe semi-coherent interface is beneficial for designing HE-resistant steels.

A 30-pulse rectifier using passive voltage harmonic injection method at dc link is proposed in this article. The passive voltage harmonic injection circuit has a function to reduce the characteristic harmonics of the input voltage. Through injecting square wave voltage whose frequency is six times of the supply frequency into the dc link of the rectifier, some existing harmonic at the input voltage of the rectifier is reduced, so that the steps number of the rectifier increases from 18 to 30. The equivalent model of the rectifier bridges is established. The switching functions of the harmonic injection circuit and the rectifier bridges are analyzed, the operation modes of the rectifier are obtained, then the formation processes of the input voltage are analyzed, the quantitative relationship between the input voltage of the rectifier and the turn ratio of the injection transformer is obtained. The simulation and experimental results show that the total-harmonic distortion values of the input voltage and input current are reduced after using the harmonic injection circuit. In unbalanced conditions, the harmonic injection circuit still has good harmonic suppression performance.

The objective of this study is to determine the effect of different barrier positions on the DC breakdown characteristics of liquid nitrogen (LN 2 ), with and without bubbles. The DC breakdown voltage is measured of a needle-to-plane electrode, with 9 mm gap distance, with and without PTFE barrier insulation of 40 μm thickness. The presence of bubbles lowers the breakdown voltage and the effect of have the barrier at various distances from the tip of the needle electrode is studied. The results show that with and without bubbles, the closer the barrier to the needle electrode, the higher the breakdown voltage. Observations using a high-speed camera show that the presence of the insulation barrier triggers the breakdown of the LN 2 /insulation barrier composite system.

Density functional theory (DFT) calculations have been carried out to investigate the hydrogen trap characteristics of a serial of nano-precipitates (VC, VN, TiN, NbN, NbC, and NiAl) in α-Fe. The H atom solution energies calculations in bulk nano-precipitates indicate that ideal nano-precipitates could not trap H atoms, while the vacancies in nano-precipitates could reduce the H atom solution energies. With respect to the coherent interfaces between α-Fe and nano-precipitates, tetrahedral sites are possible hydrogen traps. Volume evolutions and Bader charge analyses have been performed and it was found the strain at the coherent interface benefits to the hydrogen trap. In addition, the vacancies near the coherent interfaces could be fine hydrogen traps, which is attributed to the combined effect of strain and vacancy. This study could provide guidance to design nano-precipitates in steel to suppress the hydrogen embrittlement.

Organometal halide perovskites (OHPs) have been considered as promising materials for light-emission devices. However, the factors influencing the luminescent property of OHPs are intricate. It is not only affected by the intrinsic crystalline quality but also depends on the surrounding environment. Here we demonstrate that the luminescence of CH3NH3PbI3 (MAPbI3) is governed by light-irradiation-induced oxygen curing and vacancy-mediated ion migration. The luminescence increases under continuous irradiation because of the curing of iodine vacancies (VI) by oxygen. While, it decreases with enhanced ion migration, which would induce excess trap states. The existence of VI is proved by low-temperature photoluminescence (PL) spectra, the hysteresis effect in J-V curves, and the excitation density dependence of the PL lifetime. Different oxygen environments and applied biases are employed to control the degree of oxygen curving and ion migration. These results provide a perception of the correlation of the complicated influencing factors affecting the luminescence of OHPs.