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The emitted noise and vibration induced by the unsteady flow of the centrifugal pump are always focused during its running, which is also associated with the high amplitude pressure pulsations. How to reduce pressure pulsations remains a crucial problem for the researcher considering low noise design of the centrifugal pump. In the current research, a special staggered impeller is proposed to reduce intense pressure pulsations of a centrifugal pump with ns = 69 based on alleviating rotor‐stator interaction. The numerical simulation method is conducted to illustrate the influence of staggered impeller on the pump performance and pressure pulsations, and three typical flow rates (0.8ФN–1.2ФN) are simulated. Results show that the staggered impeller will lead to the pump head increasing, and at the design working condition, the increment reaches about 3% compared with the original impeller. Meanwhile, the pump efficiency is little affected by the staggered impeller, which is almost identical with the original impeller. From comparison of pressure spectra at 20 monitoring points around the impeller outlet, it is validated that the staggered impeller contributes significantly to decreasing pressure pulsations at the concerned working conditions. At the blade passing frequency, the averaged reduction of 20 points reaches 89% by using the staggered impeller at 1.0ФN. The reduction reaches to 90%, 80% at 0.8ФN, 1.2ФN, respectively. Caused by the rib within the staggered impeller, the internal flow field in the blade channel will be affected. Finally, it is concluded that the proposed staggered impeller surely has a significant effect on alleviating intense pressure pulsation of the model pump and does not obviously alter the global performance of the pump, which is very promising during the low noise pump design considering its feasibility for manufacturing.

Monolayer MoS2 has emerged as one of the most promising candidate materials for future semiconductor devices because of its fascinating physical properties and optoelectronic performance. Recently, the utilization of alkali metal compounds as promoters in CVD growth has been demonstrated to be a facile strategy for growing monolayer MoS2 and other 2D TMDs with large domain sizes. In this work, we systematically investigated the residues derived from alkali metal compounds and the spontaneous n-doping effect on monolayer MoS2 in alkali metal compound-promoted CVD growth. When using NaOH and other alkali metal compounds as promoters, it is found that the Raman peak of the A1g mode red shifted with a broadening width and the PL intensity of the A peak decreased with a red shift, which was attributed to the spontaneous n-doping effect during growth. Moreover, the growth using varying amounts of NaOH promoter suggests that the n-doping level could be controlled by the amount of promoter. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary-ion mass spectroscopy (TOF-SIMS) showed the existence of cation-derived residues in the form of a Na-O cluster physiosorbed on top of monolayer MoS2, which was also confirmed by the transfer experiment. The NaOH treatment experiment and density functional theory (DFT) calculations demonstrate that sodium hydroxide clusters, which could be converted from a combination of Na-O clusters and water vapor, could produce an n-doping effect on monolayer MoS2. This study provides a facile route to controllably grow monolayer 2D materials with a desired doping level without further treatment.

In recent years, lithium-containing ceramic materials have attracted considerable research attention as high-temperature adsorbents of carbon dioxide. The recycling of electrode materials from spent lithium-ion batteries for use as photocatalysts in recovering CO2 and degrading organic pollutants is worthy of exploration. Solid, magnetic ferrite-containing photocatalysts are easily separated from reaction solutions by using magnetic devices. Solid catalysts (e.g., LiFeO2, LiFe5O8, NaFeO2, and K2Fe2O4) were prepared through the calcination of Fe2O3 and M2CO3. CO2 was photoreduced and crystal violet (CV) and 2-hydroxybenzoic acid (2-HBA) were photodegraded under visible light irradiation. The optimized K2Fe2O4 photocatalyst increased the rate of photocatalytic conversion from CO2 to methane at 20.9 µmol g−1 h−1. The catalytic efficiency indicated that the optimized reaction rate constants of CV with LiFeO2, NaFeO2, and K2Fe2O4 were 2.98 × 10−1, 5.32 × 10−1, and 4.36 × 10−1 h−1, respectively. The quenching effect achieved through the use of various scavengers and the electron paramagnetic resonance in CV degradation revealed the substantial contribution of the reactive superoxide anion radical O2 − and the minor roles of h+ and the OH radical. Its usefulness in the synthesis of solid-base catalyst MFeO2 is promising for environmental control and relevant applications, particularly in solar energy manufacturing.

A series of novel negative temperature coefficient thermistor materials based on SrCexNbxWO4+4x (0.1 ≤ x ≤ 0.8) ceramics was synthesized by the solid-state route. X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy revealed that the SrCexNbxWO4+4x ceramics were composed of scheelite structural solid solution based on the SrWO4 phase and a CeNbO4.08 secondary phase that exhibited a fergusonite structure. The resistance-temperature analysis demonstrated that the resistivity ρ800 of the SrCexNbxWO4+4x ceramics decreased from 8.25 ± 0.08 × 106 to 2.52 ± 0.11 × 102 with the increase of x value, along with a decrease in the thermal constant B from 11,102 ± 97–4137 ± 37 K. It was observed that the SrCexNbxWO4+4x ceramics exhibited high resistivity and excellent aging characteristics as well as suitable B values at elevated temperatures, making it a promising candidate that can be used for the fabrication of high-temperature NTC thermistors with a wide operating temperature range.

A functional Fe3O4/SiO2 core–shell abrasive was synthesized via hydrolysis of tetraethyl orthosilicate. A silica shell was successfully coated on a Fe3O4 core, resulting in a core-shell particle with an average diameter of 140 nm. The prepared core–shell abrasives was utilized for ultrasound-assisted magneto-rheological polishing (UAMP) of sapphire substrate. The experimental results showed that the Fe3O4/SiO2 core–shell abrasives exhibited a remarkable polishing performance for the sapphire material, resulting in smooth and detect-free surfaces with a high material removal rate (MRR) compared to mixed abrasives (Fe3O4 and SiO2) and pure Fe3O4 particles. The application of ultrasonic vibration to the sapphire wafer further improved the MRR, which was approximately 3.4 times higher than that of traditional magneto-rheological polishing. The largest MRR (1.974 μm/h) and comparatively low surface roughness (0.442 nm) of the polished sapphire wafer were achieved by UAMP with the Fe3O4/SiO2 core–shell abrasives. The polishing mechanism of the sapphire wafer is discussed in terms of chemical reactions and mechanical polishing.

Lithium-sulfur batteries (LSBs) suffer from sluggish reaction kinetics of sulfur-containing species and loss of soluble polysulfides (PSs) during cycling, especially in the case of liquid electrolytes. Here, we improve the kinetics of sulfur species by decorating Mo2C nanoparticles on carbon nanotubes (CNTs) as the host for sulfur active mass. In addition, by use of gel polymer electrolytes (GPEs) derived from in situ polymerization of 1,3-dioxolane (DOL) to mitigate the diffusion of PSs and improve the stability of Li stripping/plating. As a result, the sulfur cathodes are endowed with enhanced initial specific capacity and suppressed dissolution of sulfur species. The cells with CNT/Mo2C/S cathodes and GPE exhibit excellent electrochemical performance. The anodes cycled with GPE show remarkably enhanced lithium plating-stripping behavior. Benefitting from the synergistic effect, LSBs with higher energy density and improved durability are obtained, demonstrating a new approach for developing high-performance quasi-solid-state Li metal batteries.

A series of Mn1.2Co1.5Ni0.3O4 spinel polycrystalline negative temperature coefficient (NTC) thin films on amorphous (SiO2 and Al2O3) and crystalline (Si3N4 and AlN) substrates was prepared using the direct current sputtering technique. Electron microscopy studies reveal the morphology–substrate dependence of films grown at the optimum temperature of 200 °C, with grain size increasing in the order of Si3N4

Electrical-based self-sensing methods for damage monitoring of carbon fiber reinforced polymer are promising for online and in-situ damage monitoring. Multi-frequency electrical impedance fusion will be used to realize damage sensing and damage mode identification. In order to correlate the electrical impedance response with damage, monotonic tensile tests were performed on 0°-orientation, 45°-orientation and woven fabric laminates. Electrodes configurations were optimally selected for effective detection of damage. The electrical impedance characteristics of the laminates over a wide frequency range were studied and the corresponding macroscopic equivalent circuit models were established. A manifold learning algorithm was applied for multi-frequency electrical impedance fusion and damage-related features extraction. Results showed that there is a linear relationship between electrical impedance of the laminates and their mechanical damage. Different damage modes including matrix cracking, fiber-matrix debonding and fiber breakage can be distinguished in the measured data. The damage mode identification method based on electrical impedance is validated by acoustic emission test results and microscopic images, making this method preferable for online monitoring.

As one of the main reasons for the deterioration of Nomex paper and charge migration, partial discharge (PD) plays a critical role during PD degradation. In this study, the PD characteristics of multilayer oil paper are focused on. In order to explore the characteristics of charge migration, the experiments of the relative permittivity, conductivity, isothermal surface potential decay, scanning electron microscopy and Fourier infrared spectroscopy have been carried out. The results show that the discharge branches of the second layer are two and three times longer than those in the first layer. In addition, the trap level of the first layer for PD degradation samples increases with the degree of PD degradation. The charges captured by deep traps provide seed charges for PD on the surface of the first layer. The charge transportation will accelerate the formation of shallow traps. The charge distribution and shallow traps contribute to the expansion of discharge branches.

Micro-scale combustion is facing the problems of ignition difficulty, combustion instability, and low combustion efficiency. Therefore, it is necessary to improve the combustion characteristics in micro-combustor to expand the application range of micro-combustor. Focusing on the problem of the weak preheating effect of the micro cavity-combustor, the guide vanes are constructed to enhance the combustion near the cavity, and further combine with the bluff body to enhance combustion. The combustion characteristics of three types of cavity combustors with guide vanes (CCGV), bluff body (CCBB), bluff body, and guide vanes (CCGB) respectively are compared and analyzed under different inlet velocities (8–32 m/s), equivalence ratios (0.6–1.4), and wall materials (quartz glass, steel, and SiC). Results show that the guide vanes can greatly improve the combustion intensity near the cavity and improve the combustion stability of the cavity combustor. The combustion efficiency of CCGV and CCGB are increased by 43.04% and 85.96% respectively than CCBB when the inlet velocity is 32 m/s. The reaction heat of CCGV is 244.5 W when inlet velocity is 32 m/s, which is 0.55 times and 1.57 times that of CCGV and CCBB, respectively. The temperature uniformity and mean temperature of the outer wall of CCGV and CCGB both are better than that of CCGB. The combustion efficiency of CCGB is the highest among three combustors under the same equivalence ratio, especially when the equivalence ratio is less than 1. The reaction intensity in the cavity of the CCGV and CCGB with steel wall material is highest than that of the combustor with the other two wall materials. Wall materials with high thermal conductivity have a better preheating effect. Compared with quartz as the wall material, the mean temperature of the external wall of CCGV and CCGB using steel and silicon carbide as the wall material both increase by more than 130 K, and the wall heat loss both increase by more than 50%.

3D woven fabric has great application potential in military armor systems. Here we report numerical simulation of 3 D angle interlock woven fabric(3DAWF) subjected to the ballistic impact using LS-...

The rolling force model is the core of rolling model, and the prediction accuracy of the Zr-4 alloy cold rolling force model directly affects the control accuracy of the thickness and shape of the Zr-4 alloy strip. In this paper, the cold rolling force model of the nuclear power Zr-4 alloy is studied based on the adaptive Particle Swarm Optimization (PSO) algorithm. The cold rolling deformation resistance model of the nuclear power Zr-4 alloy was obtained by field actual sampling and tensile test. The friction coefficient model of the nuclear power Zr-4 alloy was studied based on the Particle Swarm Optimization (PSO) algorithm according to the field measured rolling force value. According to the Hill model, a simplified method of external friction stress state coefficient model based on global variables is proposed by using the Particle Swarm Optimization (PSO) algorithm. Finally, the cold rolling force model of the Zr-4 alloy is established. Industrial test proves that the average cold rolling force prediction accuracy of the nuclear power Zr-4 alloy is 95.36%, which can effectively guide the rolling control of the nuclear power Zr-4 alloy cold rolling production process.

A mathematical model of the particle heating process in the reaction shaft of flash smelting furnace was established and the calculation was performed. The results indicate that radiation plays a significant role in the heat transfer process within the first 0.6 m in the upper part of the reaction shaft, whilst the convection is dominant in the area below 0.6 m for the particle heating. In order to accelerate the particle ignition, it is necessary to enhance the convection, thus to speed up the particle heating. A high-speed preheated oxygen jet technology was then suggested to replace the nature gas combustion in the flash furnace, aiming to create a lateral disturbance in the gaseous phase around the particles, so as to achieve a slip velocity between the two phases and a high convective heat transfer coefficient. Numerical simulation was carried out for the cases with the high-speed oxygen jet and the normal nature gas burners. The results show that with the high-speed jet technology, particles are heated up more rapidly and ignited much earlier, especially within the area of the radial range of R=0.3–0.6 m. As a result, a more efficient smelting process can be achieved under the same operational condition.

A hydrofoil blade design (HBD) is proposed to suppress the unsteady pressure pulsations in a centrifugal pump. Numerical simulation is carried out using the SST k‐ω model to obtain the unsteady flow field in the pump both with HBD and the conventional blade design (CBD). The pressure pulsations with the two types of blade profiles are compared at the nominal flow rate, whereas the jet‐wake flow patterns and vortex structures are analyzed to clarify the effect of the HBD on the flow field. The pressure pulsation amplitudes at the blade frequency (fBPF) are significantly reduced with the HBD, especially near the volute tongue, with a reduction of 72%. It is evident that HBD can effectively suppress the pressure pulsation. It is for these reasons that the relative velocities in the jet region at the impeller outlet are reduced, and the velocity gradients between the pressure and suction side are decreased, which contributes to improving the flow uniformity at the impeller outlet. Besides, the vorticities at the impeller outlet are reduced, and the high energy vortices shedding from the blade trailing edge are restrained. The combined effects of the uniform flow field and low vorticities contribute to the reduction of pressure amplitude with the HBD. The findings would serve as a reference for the pump designs with low noise and vibration.

High interfacial resistance between electrode and solid electrolyte (SE) is one of the major challenges for the commercial application of all-solid-state batteries (ASSBs), and coating at the interface is an effective way for decreasing the resistance. However, microscopic electrochemistry especially for the electrochemical potential and the distribution of Li+ at the interface has not been well established yet, impeding the in-depth understanding of interfacial Li+ transport. Herein, we have introduced a potential energy profile for Li+, ηLi+, and demonstrated that the interfacial ηLi+ can be evaluated from the calculated interfacial Li vacancy formation energy or the bulk vacancy formation energy and the interface band alignment. Through computational analysis of the representative LiCoO2 cathode/LiNbO3 coating/β-Li3PS4 SE interfaces using the novel interface structure prediction scheme based on the CALYPSO method, we found that ηLi+ at the LiCoO2/β-Li3PS4 interface is highly disordered under the influence of the interface reconstruction and is rather electronic conductive. Insertion of LiNbO3 coating can effectively decrease the preference of ion mixing. Besides, the appropriate changes in band alignments lead to a decrease of difference in the interfacial ηLi+ and lower resistances at the interfaces. The results provide a reliable explanation for the effectiveness of the coating layer observed experimentally. Furthermore, our study provides a guidance for the future simulation of the microscopic electrochemistry at the electrode/SE interfaces in ASSBs.

Effects of the staggered blades on unsteady pressure pulsations of a centrifugal pump with a specific speed ns=147 are investigated by the numerical simulation method. The obtained results are compared with the original blades. To clarify the resulting effects, eight monitoring points are used to extract pressure signals at three typical working conditions, and component at the blade passing frequency fBPF is emphasized. Results show that the pump efficiency and head will be reduced by the staggered blades, and at the nominal flow rate, the reduction is about 1.5% from comparison with the original blades. For all the eight points, the staggered blades contribute to the reduction of pressure amplitudes at fBPF when the pump works at three flow rates. The averaged reduction is 15.5% at the nominal flow rate. However, the negative effect on the second harmonic of fBPF will be caused by the staggered blades, and the corresponding pressure amplitude will increase at 2fBPF. It means that the pressure pulsation energy will be redistributed among the discrete components in pressure spectrum by the staggered blades. From the TKE distribution, it is found that the TKE values on the blade pressure side will be significantly affected by the staggered blades.

Titania nanotubes (TNTs) with high length–diameter ratio are incorporated into reduced graphene oxide (rGO) aerogel to modify the porous structure of the obtained rGO/TNTs aerogel for efficient methylene blue (MB) adsorption. A hydrothermal method along with freeze drying is applied for the preparation of the rGO/TNTs composite aerogel. The uniformly dispersed TNTs in rGO matrix can effectively support the network structure and hinder the π–π bonding interaction between graphene sheets, thus resulting in a three-dimensional mesoporous network with high specific surface area. The rGO/TNTs aerogel shows favorable adsorption property toward MB and the maximum adsorption capacity can be 380.7 mg g−1 with the adsorption efficiency of 92.2%. Besides, the adsorption kinetic analysis reveals that a dispersion process is found to be the rate-limiting step when the adsorbent dosage is low. With the increase of adsorbent content, chemical sorption such as the π–π interaction or the reaction of the polar functional groups between MB and rGO–TNTs-C aerogel becomes the rate-limiting step.

Monolayer semiconducting two-dimensional (2D) materials are strongly emerging materials for exploring the spin-valley coupling effect and fabricating novel optoelectronic devices due to their unique structural symmetry and band structures. Due to their atomic thickness, their excitonic optical response is highly sensitive to the dielectric environment. In this work, we present a novel approach to reversibly modulate the optical properties of monolayer molybdenum disulfide (MoS2) via changing the dielectric properties of the substrate by laser irradiation and thermal annealing. We chose LiNbO3 as the substrate and recorded the PL spectra of monolayer MoS2 on LiNbO3 substrates with positive (P+) and negative (P-) ferroelectric polarities. A distinct PL intensity of the A peak was observed due to opposite doping by surface charges. Under light irradiation, the PL intensity of monolayer MoS2 on P+ Fe2O3-doped LiNbO3 gradually decreased with time due to the reduction of intrinsic p-doping, which originated from the drift of photo-excited electrons under a spontaneous polarization field and accumulation on the surface. The PL intensity was found to be restored by thermal annealing which could erase the charge redistribution. This study provides a strategy to reversibly modulate the optical properties of monolayer 2D materials on top of ferroelectric materials.

AlGaN/GaN-Si based MIS-HEMTs are considered as the popular candidates for application in the 5G communication system due to their competitive characteristics and low cost. Ohmic contact, as an important fabrication process, significantly affects the performance of the device. In this study, the ohmic contact process, including the SiN passivation layer etching, surface treatment, and barrier layer etching, was studied in detail in order to effectively optimize the device performance. It is observed that the sample with the SiN passivation layer etched by the magnetic neutral loop discharge (NLD) resulted in a lower contact resistance as compared to the reaction ion etching (RIE). The sample surface treated with the O plasma and pickled in the HCl:H2O = 1:10 liquid could effectively remove the pollutants and oxides from the surface, thus, correspondingly presenting a lower ohmic contact resistance as compared to the N2 plasma. Meanwhile, an optimum etching depth was developed with the ICP process for 6 min with an etching speed of 1.6 nm/min. A contact resistance of $0.76~\Omega \cdot \text {mm}$ and square resistance of 274.63 ohm/sq were observed under the above-mentioned optimized ohmic contact process. The AlGaN/GaN-Si MIS-HEMT with gate length of $0.5~\mu \text{m}$ , gate-source space of $1~\mu \text{m}$ , gate-drain space of $2.5~\mu \text{m}$ , and gate width of $100~\mu \text{m}$ was fabricated using the optimized process. A saturation current density of 794.30 mA/mm and the maximum transconductance of 16.86 mS were observed. The findings in this study provide the experimental basis for the manufacturing of AlGaN/GaN-Si based MIS-HEMTs for RF applications.

Hydrogen (H2) is a clean energy carrier and its cost-effective separation is important for future H2 energy deployment. Currently, H2 is mainly produced from high temperature methane steam reforming reactions and thus the availability of membrane separation technology that can work at elevated temperatures can reduce the production cost. In this work, a cross-linked polybenzimidazole (PBI)-triglycidylisocyanurate (TGIC) and sulfonated graphene (SG) composite membrane was developed using a mixed proton–electron conducting concept. In such a membrane, protons diffuse by hopping along the cross-linking sites between the sulfonic groups of SG and the pyrrole rings of PBI, while electrons are transported via highly electron conductive SG. Following the addition of SG, the membrane became more compact, given the reduced interlayer spacing and swelling ratio. The thermal stability and oxidative resistance are comparable to those of other PBI-based membranes. For H2/CO2 separation, H2 can permeate through a 132 μm-thick membrane with 99.99% selectivity and a high flux of up to 0.22 mL min−1 cm−2 at 300 °C. The stable operation at 280 °C for 160 hours proves the membrane robustness at such an elevated temperature. Compared to the previously reported mixed conducting ceramic membranes exhibiting equivalent H2 fluxes requiring operation temperatures above 800 °C, the polymer and graphene composite membrane presented herein can reduce the operation temperature by 500 °C. This is an important requirement to ensure a more practical integration of membrane technology into industrial processes.

In this paper, iron and nitrogen co-doped carbon material with nanotube structure (Fe/N-CCM-T) was synthesized by pyrolyzing a mixture of Fe salt, chitosan and melamine and displayed high electrocatalytic performance for oxygen reduction reaction (ORR). The structure of the Fe/N-CCM-T was characterized and their ORR performance in alkaline media was investigated by linear sweep voltammetry, cyclic voltammetry and chronoamperometry. Fe/N-CCM-T displayed better ORR performance than other carbon materials like Fe/N-CC-800. The Fe/N-CCM-800 with a large surface area (302.5 m2/g) especially exhibited the best ORR electrocatalytic performance among the prepared carbon materials, which was also proved by its similar Tafel slope (76 mV decade−1) to Pt/C catalyst (74 mV decade−1). Fe/N-CCM-800 showed similar ORR activity as commercial Pt/C catalyst, but superior tolerance to methanol and stability. Such high ORR performance of the Fe/N-CCM-T can be attributed to its nanotube structure, high specific surface area (SSA), high graphitic-N and pyridinic-N contents.

Metallic phase molybdenum disulfides exhibit impressive charge transfer ability and this has made them interesting candidates for use in the field of nano-science and heterogeneous catalysis. However, the synthesis of 100% pure bare 1T-MoS2 is difficult due to its kinetic instability. In the past, the phase transition mechanism from a semiconductor (2H) to a metallic (1T) phase has been explained only by theoretical calculations. Herein, we used magnetron sputtering to deposit a series of MoS2 films containing various metal heteroatoms as the dopants. Density functional theory (DFT) calculations revealed that the single-doped Cu-MoS2, Au-MoS2, Ag-MoS2, and Al-MoS2 exhibited distinct phase transitions compared to Cr-MoS2, Hf-MoS2, Ta-MoS2, and Zr-MoS2, due to the introduction of additional charge. Furthermore, the hydrogen evolution reaction (HER) activities of the series of MoS2 films were explored, and the adsorption free energy of H atoms was evaluated by DFT calculations.

As an intrigued layered 2D semiconductor material, indium selenide (In2Se3) has attracted widespread attention due to its excellent properties. So far, the carrier dynamics of α-In2Se3 and β-In2Se3 are still lacking a comprehensive understanding, which is essential to enhancing the performance of In2Se3-based optoelectronic devices. In this study, we explored the ultrafast carrier dynamics in thin α-In2Se3 and β-In2Se3via transient absorption microscopy. For α-In2Se3 with a narrower bandgap, band filling and bandgap renormalization jointly governed the time evolution of the differential reflectivity signal, whose magnitude and sign at different delays were determined by the weights between the band filling and bandgap renormalization, depending on the carrier density. For β-In2Se3, whose bandgap is close to the probe photon energy, only positive differential reflectivity was detected, which was attributed to strong band filling effect. In both materials, the lifetime decreased and the relative amplitude of the Auger process increased, when the pump fluence was increased. These findings could provide further insights into the optical and optoelectronic properties of In2Se3-based devices.

In order to harvest more light wavelengths to improve the light-assisted electrochemical water splitting capacity, we developed a novel heterostructure of three-dimensional (3D) flower-like CuS architecture with accompanying SnS2 nanoparticles and reduced graphene oxide (rGO) aerogel for outstanding light-assisted electrocatalytic OER performance and good stability. The excellent catalytic kinetics, effective capturing of visible light, and rapid charge transfer of the CuS/SnS2/rGO (CSr) heterostructure were demonstrated. The overpotential (264 mV@10 mA cm-2) under light-assisted conditions is 20% lower than that under light-chopped conditions. SnS2 can harvest more light wavelengths and this boosts its intrinsic activity. However, with the increase of the SnS2 content, the OER activity decreases. The combination of the CS heterostructure and the rGO conductive aerogel achieves rapid charge transfer. Furthermore, the possible mechanism of the light-assisted electrocatalytic OER was also proposed. Overall, this work provides new insights into the simple and scalable fabrication of a highly efficient, low-cost, and stable non-noble-metal-based electrocatalyst.

Organic–inorganic hybrid perovskites have emerged as promising light harvesting materials for many optoelectronic devices. Here, we present a facile mechanochemical synthesis (MCS) route for the preparation of a series of pure phase mixed-cation/anion (FAPbI3)x(MAPbBr3)1−x (0 ≤ x ≤ 1) hybrid perovskite materials for high-efficiency thin-film perovskite solar cells (PSCs). The use of (α-FAPbI3)0.95(MAPbBr3)0.05 perovskite prepared by MCS for the thin-film PSCs achieves a maximum PCE of 15.9% from a current–voltage (J–V) scan, which stabilises at 15.4% after 120 s of the maximum power point output. Furthermore, PSCs based on (KPbI3)0.05(FAPbI3)0.9(MAPbBr3)0.05 perovskite prepared by MCS exhibit higher photovoltaic performance and lower hysteresis compared with (α-FAPbI3)0.95(MAPbBr3)0.05, with a maximum PCE of 16.7%. These results indicate that the use of mechanochemically synthesised perovskites provides a promising strategy for high performance PSCs and superior control in optoelectronic properties, leading to improved control in fabrication approaches and facilitating the development of efficient and stable PSCs in the future.

In order to quantitatively understand the residual strain distributions and benefits of engineering components following special technique treatment, such as Autofrettaging, Hot Isostatic Pressing (HIP) and Dissimilar Material Welding (DMW), the Neutron Diffraction Technique (NDT) has been employed recently to measure residual strain and stress distributions on following three cases of (a) Autofrettaged Aluminum 7075 high pressure vessels; (b) Hot Isostatic Pressed (HIPPED) heavy metals of tungsten clad in tantalum plate and (c) Dissimilar Material Welding (DMW) of 316L austenitic stainless steel and ferritic steel AS508 with Alloy 52 weld filler. This paper reports the recent research findings, including (a) NDT can identify optimal Autofrettage pressure level, by which load bearing capacity of the Autofrettaged pressure vessel increased by 215MPa; (b) NDT is able to reveal residual strains within heavy metals of Tungsten clad in Tantalum plate HIPPED and (c) NDT revealed a maximum residual tensile hoop stress value of about 494MPa in the interface between parent material SA508 and the weld seam. This is vital information for the post weld process and subsequent safe use of the dissimilar materials weld. Other researchers’ successful examples of working with NDT are also briefly reviewed. Future prospective of Engineering Materials Diffractometer (EMD) at CSNS is described too with a view to demonstrating the application and importance of NDT in revealing residual strain-stresses that are inevitable within engineering materials and engineering components following any manufacturing process.

An atmospheric pressure microwave plasma tubular furnace apparatus (MPTF) for the rapid synthesis of carbon nanotubes (CNTs) has been developed. CNTs have been synthesized by an Argon-Hydrogen microwave plasma using ethanol vapor as carbon source with the furnace temperature of 800 °C at the atmospheric pressure. The synthesized CNTs have been analyzed by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and are shown to be multi-walled and tangled and chemically connected to form a high-density network with the diameter at the range of 25–70 nm. The measurement of X-ray photoelectron spectroscopy (XPS) indicates that a large number of oxygenated functional groups grown on the surface of CNTs. These properties proved that the CNTs could be utilized as nanoscale templates for various applications.

The flashover voltage of high temperature vulcanised (HTV) silicone rubber will be decreased after corona ageing, and it further decreases under the effect of mineral oil. The mechanisms for the phenomena can be explained by considering the role of trap level distribution. In this study, the corona ageing of silicone rubber was conducted and the flashover voltage was tested. The isothermal surface potential decay was tested to explore the internal relationship between trap distribution and flashover voltage. Besides, the surface microtopography and chemical structure of silicone rubber were gained by scanning electron microscopy and Fourier infrared spectroscopy to explain the change of trap distribution. The test results show that the flashover voltage of HTV silicone rubber decreases with AC corona ageing time, the reduction of flashover voltage for an oil-impregnated sample is more serious. The density of shallow electron traps increases at first and then decreases, while the density of shallow hole traps increases with ageing time. The density of deep traps decreases after corona ageing. These trap level distribution characteristics are beneficial to promote the development of flashover, leading to lower flashover voltage. The effect of mineral oil can be regarded as an accelerated ageing effect.

Phonon polaritons in van der Waals materials show the strong electric confinement and low energy loss. Combining with the materials hexagonal boron nitride, hyperbolic phonon polaritons can be excited in two RS bands, which changes a lot in electric field distribution and transmission characteristics. In order to increase the tunability of hyperbolic phonon polaritons, a structure based on graphene/h-BN heterostructure has been formed in previous studies. In this paper, the electric field distribution and transmissivity characteristics are calculated and discussed based on grapheme–h-BN–graphene heterostructure. The results illustrate the excellent transmissivity tunability in 780 cm−1 incident wavenumber of type-I band and poor transmissivity tunability in 1368 cm−1 of type-II band. In addition, superior field-enhanced characteristic (115.76% transmissivity in 6 V external voltage) is shown in the structure. These excellent properties make such structure a promising component in future optoelectronic devices design.

In the present work, we report the observation of deformation kinking bands in β-treated commercial pure zirconium sheets during impact experiments. Crystallography analyses based on electron backscatter diffraction (EBSD) technique reveal that these kinking bands exhibit a common rotation axis of 〈 10 1 ¯ 0 〉 with misorientation angles varying in a wide range and are not belonging to anyone of the well-established twinning modes in Zr. Based on the combination of Schmid factor calculation and in-grain misorientation axes (IGMA) determination, the underlying mechanisms accounting for their formation are proposed and discussed.

Magnetic impurities in metallic superconductors are important for both fundamental and applied sciences. In this study, we focused on dilute Mn-doped aluminum (AlMn) films, which are common superconducting materials used to make transition edge sensors and other superconducting devices. We developed a multi-energy ion-implantation technique to make AlMn films. Compared with frequently used sputtering techniques, ion-implantation provides more precise control of the Mn doping concentration in the AlMn films. It enables us to fabricate reliably AlMn films with a different superconducting transition temperature (Tc) that can match a variety of application needs. We also found that the superconducting transition temperature drops with increasing film thickness for samples with the same nominal concentration of Mn dopants. The dependence of Tc on the film thickness is attributed to the increasing implantation energy. By quantitatively analyzing the curves of Tc versus the Mn doping concentration, we propose that Mn dopants act as magnetic impurities and suppression of superconductivity is counteracted by the antiferromagnetic Ruderman–Kittel–Kasuya–Yosida interaction among Mn dopants, which is influenced by the defects induced in the ion-implantation process.

As monolayer graphene comprises only one single atomic layer, its physical and chemical properties could be easily tuned by the underlying substrate. However, it is still unknown how the distinct s...

The aim of this paper is to present a novel negative temperature coefficient (NTC) thermistor based on A2Zr2O7 (A = Nd, Sm, Gd, Yb) zirconate ceramics with pyrochlore-type structure for high-temperature application. The zirconate ceramics were synthesized via a solid-state reaction method where rare-earth oxides and ZrO2 were used as starting materials. The physical structures were characterized by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. It was confirmed that Nd2Zr2O7 and Sm2Zr2O7 are pyrochlore phases, while Yb2Zr2O7 and Gd2Zr2O7 are defect fluorite phases. The electrical property investigated by using resistance–temperature measurements demonstrated that the prepared A2Zr2O7 zirconate ceramics exhibit a typical characteristic of NTC over a wide temperature range between 673 and 1273 K. Particularly, A2Zr2O7, in addition to having high activation energy to ensure better sensitivity, can still maintain higher resistivity under high-temperature environments. Furthermore, the resistivity of A2Zr2O7 is almost independent of the change in oxygen partial pressure. These properties are superior to the classical spinel-type or perovskite-type NTC thermistor, providing valuable information to explore new NTC thermistor for high-temperature applications.

Lithium sulfur battery (LSB) is widely considered as a next-generation battery system due to its high theoretical energy density of 2567 Wh kg−1. However, several inherent issues obstruct the business application of LSB. To address these issues, we assemble core–shell structure Fe3O4@C nanodots with 5 nm diameter as a valid sulfur host via a convenient organic pyrolysis treatment followed by calcination. The nanosized Fe3O4 particles could expose more chemisorption sites and inhibit the polysulfides shuttle. Moreover, the carbon layer could not only increase the conductivity but also ensure structural integrity during cyclic process. Furthermore, the mesoporous channels around Fe3O4@C could supply sufficient space to load sulfur and physically restrict the shuttle of polysulfides. Thus, the resultant S/Fe3O4@C cathode shows a highly initial capacity of 1089 mAh g−1 at 0.2 C, even retains 655 mAh g−1 over 200 cycles at 1 C.

Bifunctional Ni-15 at.% Zn/rGO catalyst was fabricated by a two-step electrodeposition to be used for efficient alkaline water-to-hydrogen conversion via hydrazine electrolysis. Experiments show that the as-deposited Ni-15 at.% Zn/rGO nanosheet arrays with porous structure possesses excellent catalytic activity and stability towards both hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR). A small overpotential of 49 mV at 10 mA cm−2 with a low Tafel slope of 26.3 mV dec−1, and a retention rate of 91.4% after 12 h at 10 mA cm−2 are observed for Ni-15 at.% Zn/rGO towards HER. Moreover, Ni-15 at.% Zn/rGO also shows an extra-high current density of 1097 mA cm−2 at 0.6 V vs RHE with a low Tafel slope of 33.5 mV dec−1, and a high durability of 90.5% after 5000 s towards HzOR. Moreover, two-electrode cell was constructed using Ni-15 at.% Zn/rGO as both cathode and anode for HER and HzOR, achieving 100 mA cm−2 at an ultralow cell voltage of 0.418 V. The above outstanding bifunctional catalytic performance should be attributed to its large ECSA, high electrical conductivity and most importantly, its superaerophobic surface induced by the porous structure with nanosheet arrays.

To solve the severe flow‐induced vibration during the pump operation, the impeller cut is a reasonable and operable approach. In the present study, effects of cutting the blade on the pump performance, especially for pressure pulsations, are conducted by experiments, and numerical results are used to discuss the relation between the internal flow and pressure pulsation. Three cutting angles are investigated, and the obtained results are compared with the original pump. Pressure transducers are mounted on the volute wall and outlet to capture pressure signals of different pumps. Results show that at the cutting angle φ = 15°, pump heads at low flow rates are decreased, which are little affected at high flow rates. With the cutting angles increasing to φ = 25° and φ = 35°, cutting the blade contributes to the reductions of pump heads at all the measured flow rates. Pressure pulsations are significantly affected by cutting the blade. For major measuring points on the volute wall, pressure amplitudes at the blade passing frequency fBPF are attenuated by cutting the blade, especially at high flow rates. Mean pressure amplitude at fBPF is decreased by 38.6% at φ = 15°, which is caused by the increasing gap between the tongue and the blade. From comparison, it is suggested that the cut angle φ = 15° can be used to reduce pressure pulsation considering its little influence on the pump head during application. The obtained results will be useful during the pump operation to reduce pressure pulsations by the blade cut approach.

Noble gas (NG) is often used as a hydrostatic pressure-transmitting medium in high-pressure experiments. However, the NG atoms under compression are found to be readily trapped in the voids of some...

The garnet-type Li7La3Zr2O12 (LLZO) solid electrolyte is of particular interest because of its good chemical stability under atmospheric condition, suitable for practical all-solid-state batteries (ASSBs). However, recent works observed electrochemical instability at the LLZO/Li interfaces. Herein, we have revealed the origin of the instability by performing a comprehensive first-principles investigation with a high-throughput interface structure search scheme, based on the density functional theory framework. Based on the constructed phase diagrams of low-index surfaces, we found that the coordinatively unsaturated (i.e. coordination number < 6) Zr sites exist widely on the low-energy LLZO surfaces. These undercoordinated Zr sites are reduced once the LLZO surface is in contact with the Li metal, leading to chemical instability of the LLZO/Li interface. Besides, the calculated formation and adhesion energies of interfaces suggest that the Li wettability on the LLZO surface is dependent on the termination structure. The employment of the approaches such as by controlling the synthesis atmosphere are needed for preventing the reduction of LLZO against the Li metal. The present analysis with comprehensive first-principles calculations provides a novel perspective for the rational optimization of the interface between LLZO electrolyte and Li metal anode in the ASSB.

Oil-paper insulation of higher voltage winding and traction winding in on-board traction transformers frequently withstand large AC fluctuation voltages mainly combined with AC and inter-harmonic components. This paper presents the characteristics of partial discharge (PD) of oil-paper insulation under superimposed inter-harmonic AC voltages. The experimental results show that the addition of the inter-harmonic to the fundamental sinusoidal component results in variation of peak voltage and dv/dt along the phase. This superimposed inter-harmonic AC voltages has a significant impact on PD including partial discharge inception voltage (PDIV), breakdown voltage, PD repetition rate, and phase resolved partial discharge (PRPD). In addition, a dynamic characterization method of PD statistical parameters is proposed to determine the developing trend. The critical values and inflection points of PD are obtained. Besides, the theoretical mechanism is expounded to better interpret and understand the influence of inter-harmonic component on PD properties. These methods will provide the dynamic datasets and more information for insulation condition assessment of on-board traction transformer.

Environmental pollution, especially air pollution, seriously endangers public health globally. Due to severe air pollution, air filters still face many challenges, especially in terms of filtration...

The main dielectric medium in converter transformers is the oil-pressboard. The valve windings of converter transformers are subjected to AC-DC combined voltage. Creepage discharge is a common defect of oil-pressboard insulation. The degree of the oil-immersed pressboard (OIP) damage is directly affected by different creepage discharge paths. In this study, a needle-plate model was developed to explore different creepage discharge paths in oil-pressboard insulation under AC-DC combined voltage. A high-speed camera was used to record the developmental process of white marks on the OIP. We explored reasons behind the different creepage discharge paths under different voltage types. Results revealed that the creepage discharge path and the degree of OIP damage were influenced by the DC component. Although the damaged OIP in converter transformers may cause catastrophic flashover inside the transformers, it is difficult to replace it. This implies that transformer insulation designers should pay attention to the influence of the DC component on OIP damage. In this study, we used pulse current method to detect discharge patterns. Discharge parameters were then extracted from discharge patterns. We observed that developmental process of white marks corresponded to developmental process of discharge parameters. This suggests that creepage discharges can be diagnosed based on discharge parameters. Based on these conclusions, important information was provided for the on-line monitoring design of transformer insulation status.

Understanding phase evolutions and the underlying mechanism under external stimuli is of fundamental importance for novel material discovery. Herein, combining angular dispersive X-ray diffraction and first-principles pathway sampling, we found that the ZnTe alloy undergoes a quasi-reconstructive transition to a metastable rocksalt phase under deviatoric stress. The rocksalt ZnTe has reconstructed chemical bonds and dendrite crystal morphology. It also suffers more severe thermodynamic hysteresis compared with the same experiments under hydrostatic pressure. However, the phase transition towards the rock-salt phase is still described by relatively small atomic displacements and is slightly first order; thus, it is neither fully displacive nor fully reconstructive. The quasi-reconstructive transition in ZnTe narrows its electronic bandgap and may provide insights into the semiconductor–metal transition in II–VI alloys in general.

Hybrid perovskites have recently received much attention in optoelectronic applications. However, hybrid perovskites are unstable in a humid environment. Mixed halide perovskites (MHPs) show enhanced stability and band-gap tunability upon engineering of their halide composition. Here, MHPs are prepared through a solvent-free mechanochemical synthesis (MCS) route that allows superior control over halide compositions than the solvent synthesis routes (SS). The MCS route eliminates the problem in the preparation of MAPb(Ix Br1-x )3 with continuously varying x, while maintaining the material properties and suppressing phase segregation present in SS routes. UV-vis absorption and X-ray diffraction patterns confirm the production of the desired pure-phase MHPs. For MAPb(Ix Br1-x )3 (0≤x≤1), with increased ratio of halide (x), the cubic phase gradually transforms into the tetragonal phase and band-gap tunability is accomplished. The MCS route for the preparation of MHPs is a very promising and efficient technique for superior control in optoelectronic properties, leading to improved control in fabrication approaches.

Metallic 1T-phase MoS2 is considered to be the ideal electrocatalyst to carry out hydrogen evolution reaction (HER) because of favorable conductivity and sufficient active site compared with 2H-pha...

Determination of the structures of materials involving more light elements such as boron-rich compounds is challenging and technically important in understanding their varied compositions and super...