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Fretting wear has an adverse impact on the fatigue life of turbine blade roots. The current work is to comparatively investigate the fretting wear behaviour of the nickel-based superalloy surfaces produced by polishing and creep-feed profile grinding, respectively, in terms of surface/subsurface fretting damage, the friction coefficient, wear volume and wear rate. Experimental results show that the granulated tribolayer aggravates the workpiece wear, while the flat compacted tribolayer enhances the wear resistance ability of workpiece, irrespective of whether the workpiece is processed by polishing or grinding. However, the wear behaviors of tribolayers are different. For the polished surface, when the normal load exceeds 100 N, the main defects are crack, rupture, delamination and peeling of workpiece materials; the wear mechanism changes from severe oxidative wear to fatigue wear and abrasive wear when the loads increase from 50 to 180 N. As for the ground surface, the main wear mechanism is abrasive wear. Particularly, the ground surface possesses better wear-resistant ability than the polished surface because the former has the lower values in coefficient friction (0.23), wear volume (0.06×106 μm3) and wear rate (0.25×10-16 Pa-1). Finally, an illustration is given to characterize the evolution of wear debris on such nickel-based superalloy on the ground surface.

Considerable studies on processed pure titanium and titanium alloys have proved the possibility of property anisotropy induced by crystallographic textures, but limited information is available for the intrinsic coupling of matrix and reinforcement textures and their synergistic effect on property anisotropy in titanium matrix composite (TMCs). In the present work, an advanced EBSD/EDS coupling method was used to investigate the formation mechanism of primary α and secondary α textures in the matrix alloy. It is revealed for the first time that the reinforcement TiBw displays a { 100 } 〈 010 〉 texture after hot rolling and has little effect on the matrix texture component but weakens texture intensity. Significant anisotropies in the tensile strength and ductility can be all noted at room- and high- temperatures, which is the synergistic effect of the matrix texture and the aligned TiBw. The mean Schmid factor of each slip system was calculated to evaluate the influence of matrix texture on the minimum active stress of slip deformation in the different tensile directions. The analysis shows that the strong T-type matrix texture results in higher strength but lower ductility when loaded in the transverse direction. Moreover, a generalized shear-lag model was modified to quantitatively evaluate the strengthening contribution of aligned TiBw, which decreases with increasing off-axis angle and test temperature. A new parameter, defined as the critical aspect ratio of the off-axis whisker, was proposed to rationalize why the TiBw failure mechanism converts from TiBw fracture to TiBw/matrix interfacial debonding with increasing off-axis angle and test temperature.

Wide application of NCM (LiNiₓCoyMnzO₂) lithium-ion batteries (LIBs) for electric vehicles indicates their high scrap amount in the near future. Thus, spent NCM LIBs must be recycled from the economic and environment viewpoint. In this context, a novel process was developed to achieve efficient extraction of valuable metals and harmless treatment of organics in NCM LIBs through full-component pyrolysis. Organic substances, such as a separator and a binder, were recovered in the form of pyrolytic oil and gas, whereas the cathode material was simultaneously dissociated and reduced, realizing the subsequent extraction of valuable metals by acid leaching without a reducing agent. The leaching efficiencies of lithium, nickel, cobalt, and manganese were over 99.5% under optimum conditions: a pyrolysis temperature of 450 °C, a pyrolysis time of 60 min, and a nitrogen flow rate of 100 mL/min. In addition, the reduction mechanism of the cathode material was investigated by experimental design and analysis of pyrolytic gas.

Abstract In this study, the fatigue crack growth rate (FCGR) of Ti-6Al-4V alloy at 723 K was measured by direct current potential drop (DCPD) method, and exceptional nano-α phases and {10 $$ \bar{1} $$ 1 ¯ 2} deformation twins were newly found at the crack tip in Ti-6Al-4V alloy. The results showed that nano-α phases have Burgers orientation relationships (OR) (0001) α //(110) β , [ $$ \bar{2} $$ 2 ¯ 110] α //[ $$ \bar{1} $$ 1 ¯ 11] β with β phases. The terraced-structure interface consisted of (0 $$ \bar{1} $$ 1 ¯ 10) α //(1 $$ \bar{1} $$ 1 ¯ 2) β and (10 $$ \bar{1} $$ 1 ¯ 0) α //(1 $$ \bar{1} $$ 1 ¯ 0) β . Numerous dislocations accumulated in the β phase and became the diffused channels of O and V atoms. The α stabilizers (O element) diffused into the crystal lattice and β stabilizers (V element) spread out of the crystal lattice which accelerated the nano-α phases nucleation. and dislocations piled up at the primary α grain, interface and low angle grain boundaries (LAGBs), and dissociated into twinning dislocations to promote the twin nucleation. Dislocation transformation enabled nano-twins to grow through the primary α/β interface and strain transfer led that deformation twins nucleated in the adjacent primary α grains. With the effects of nano-α phases, LAGBs and twins, the resistance of crack propagation increased and the driving force decreased, and resulted in the low FCGR. Graphic Abstract

Corrosion of metals in atmospheric environments is a worldwide problem in industry and daily life. Traditional anticorrosion methods including sacrificial anodes or protective coatings have performance limitations. Here, we report atomically thin, polycrystalline few-layer graphene (FLG) grown by chemical vapor deposition as a long-term protective coating film for copper (Cu). A six-year old, FLG-protected Cu is visually shiny and detailed material characterizations capture no sign of oxidation. The success of the durable anticorrosion film depends on the misalignment of grain boundaries between adjacent graphene layers. Theoretical calculations further found that corrosive molecules always encounter extremely high energy barrier when diffusing through the FLG layers. Therefore, the FLG is able to prevent the corrosive molecules from reaching the underlying Cu surface. This work highlights the interesting structures of polycrystalline FLG and sheds insight into the atomically thin coatings for various applications.

High-alumina coal fly ash (HAFA) is an important aluminum and silicon resource. In terms of its comprehensive utilization, how to efficiently separate aluminum and silicon must be resolved. In this work, a mechanochemical activation method in the desilication process is adopted and investigated. Desilication ratio, efficient desilicated ratio, microscopic appearance, and coordination structure change in aluminum-silicon atoms are investigated during mechanochemical activation process. Results indicate that the Al-O-Si coordination structure in HAFA can be transformed from Q4 (3Al) and Q4 (2Al) to reactive Q2 (1Al) structure, and the radio of Q2 (1Al) with high activity increased from 6.93% to 14.47%, which can improve HAFA reaction activity obviously. During the desilication process, the aluminum-silicon mass ratio (A/S) can be elevated from 1.23 to 2.56 after the process optimization, which provides a high-quality raw material for further high-valued utilization of HAFA.

Metallic lithium is regarded as the “Holy Grail” among various anode materials for the next-generation rechargeable batteries. Unfortunately, the inhomogeneous Li deposition and uncontrolled dendrite growth during repeated cycling lead to low Coulombic efficiency, poor performance, and serious safety issues. Herein, a novel two-pronged strategy is proposed to effectively guide Li nucleation and suppress the unwanted Li dendrites growth, by a synergized approach of combining the laser-machined 3D holey Cu matrix (3D Cu) and lithiophilic polydopamine (PDA) surface coating layer. The PDA@3D Cu scaffold is shown to exhibit the wanted dendrite-free Li plating/stripping behavior. It delivers a remarkable Coulombic efficiency of 96.4% after 150 cycles (2.0 ​mA ​cm−2 ​at 1.0 mAh cm−2), and achieves an excellent lifespan of over 1000 ​h operation tested in Li/Li symmetric cells, together with good stability for Li//FePO4 full batteries. Our molecular dynamics (MD) simulations, density functional theory (DFT) calculations, and in-situ real-time monitoring using optical microscopy together have established the direct correlation between reversible Li electrodeposition and lithiophilic 3D holey structure scaffold. Significantly, the new findings suggest that a synergistic combination of 3D Cu with lithiophilic PDA coating layer represents an effective pathway to regulate metallic Li anodes towards practical applications.

Semiconductor-sensitized TiO2 thin films with long-term air stability are attractive for optoelectronic devices and applications. Herein, we demonstrate the potential of the TiO2 thin film (∼800 nm...

We propose and discuss a compact and tunable plasmonic terahertz (THz) metamaterial switch based on graphene microcavity. Due to the joint effect of graphene plasmon resonances and Fabry–Perot oscillations, this metamaterial structure can be switched from the ON state to OFF state with the maximum intensity attenuation larger than 95% (ON–OFF ratio larger than 30 dB). The central frequency of the switch could be tuned in a wide frequency range from 3.6 to 9.6 THz by tuning the Fermi energies of the graphene patterns. Moreover, the metamaterial structure is valid for a wide range of incident angles of both transverse electric (TE) and transverse magnetic (TM) polarizations with the highest Q factor of 15.5. This investigation promises the development of high-performance, widely tunable THz switch in chip integrated photonic circuits without reconstructing the physical structures.

Surface oxidation frequently occurs in non-oxide antimony chalcogenides, which is a double-edged sword for their (opto)electronic properties and applications. Here we report that the photoelectronic performance of Sb2Se3 nanorods (NRs) can be improved through an appropriate degree of surface oxidation. During the synthesis, the volume ratio of oleic acid (OA)/oleylamine (OLA) was varied to control the oxidation degrees of the Sb2Se3 NRs, which span 1.20–51.49% with increasing OA ratio as revealed by X-ray photoelectron spectroscopy (XPS) analysis. A medium level of surface oxidation, typically 20–30% found here, is beneficial to the enhancement of the photocurrent, on/off ratios and photostability of the Sb2Se3 NRs when evaluated in a sandwich-type ITO/Sb2Se3/ITO photoconductor device. Surface hydroxylation, which is boosted by the presence of Sb–oleate and trace H2O remaining in the reaction system, is suggested to facilitate the formation of Sb–OH bonds and the OA-volume dependent oxidation at the surface of Sb2Se3.

Fabrication of a stable dendrite-free Li metal anode that accommodates very large volume changes is urgently needed for the development of advanced lithium metal batteries. Herein, an integrated Li/TiN/carbon textile anode (LTNC) is fabricated in which lithium is hosted in a self-supported TiN nanorod array with high surface area, excellent electrical conductivity, and porous structure. The as-prepared LTNC anode achieves outstanding electrochemical performance with a low overpotential of 50 mV and stable cycling for 1000 h at 1 mA cm−2, 1 mA h cm−2, and even at a high current density of 10 mA cm−2 it shows highly stable performance with a low overpotential. When paired with a LiNi0.8Mn0.1Co0.1O2 cathode, the assembled cells display enhanced capacity retention of 85% after 500 cycles at 1C and improved coulombic efficiency. Furthermore, a high capacity of 2.3 mA h cm−2 with a capacity retention of 92% is maintained at 1 mA cm−2 after 100 cycles when the negative to positive electrode capacity ratio is only ∼3.5. This work indicates that the structural engineering of Li metal is highly applicable for lithium metal batteries with high rates and long cycle life.

The preparation and functionalization of biomass-based hydrogels that can be used in the field of biomedicine have received an increasing amount of attention. Carbon dots are a kind of fluorescent carbon nanomaterial with stable fluorescence emission and low biotoxicity, therefore the introduction of carbon dots into the biomass-based hydrogel can make it have a broader application prospect. In this work, fluorescent nitrogen-doped carbon dots/cellulose nanofibril composite hydrogel (NCDs/CNF-gel) with exceptional mechanical properties was successfully fabricated by a facile one-pot green hydrothermal treatment. The properties of NCDs/CNF-gel prepared at different temperatures and CNF concentrations were investigated by electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, fluorescence spectroscopy, rheology, and mechanical tests. NCDs/CNF-gel with injectable, pressure-resistance and excellent fluorescence properties can be obtained by controlling the hydrothermal treatment temperature. Furthermore, the self-assembly mechanism of NCDs in the hydrogel network and the improvement mechanism of hydrogel compressive strength were explored. The NCDs/CNF-gel exhibited acid-resistant and alkaline sensitive blue-green fluorescent emission. The outstanding biocompatibility, excellent fluorescence and mechanical properties of NCDs/CNF-gels, and their facile fabrication render these so-prepared gels promising candidates for future biomedical applications.

Selective hydrodeoxygenation of biomass-derived aromatic alcohols to value-added chemical or fuel is of great importance for sustainable biomass upgrading, and hydrodeoxygenation of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) is one of the most attractive reactions. Achieving the conversion of HMF to DMF using H2 at ambient temperature is challenging. In this work, we used PdCu nanoalloys to catalyze the selective hydrodeoxygenation reaction of HMF to DMF using H2 as the reducing agent. The reaction path and the product selectivity are governed by the crystallographic phase of the PdCu nanoalloys. It was discovered that body-centered cubic (BCC) PdCu nanoalloys supported on activated carbon (AC) exhibited outstanding performance with 93.6% yield of DMF at room temperature (PdCu/AC-BCC). A combination of experimental and density functional theory (DFT) studies showed that the tilted adsorption modes of furanic intermediates on PdCu-BCC nanoalloy surfaces accounted for the high selectivity of DMF; however, furan ring was activated on PdCu face-centered cubic (FCC) nanoalloy surfaces. Furthermore, PdCu/AC-BCC could also catalyze the hydrodeoxygenation of other aromatic alcohols at room temperature while maintaining the aromatic structures. This work opens the way for selective hydrodeoxygenation of the aromatic alcohols at room temperature with the aromatic ring intact., Graphical abstract, Public summary • Selectively cleaving of C–O bonds in lignocellulosic biomass is very difficult. The PdCu nanoalloys can catalyze the selective hydrodeoxygenation reaction of HMF to DMF • The PdCu nanoalloys with specific crystallographic phases can improve the selectivity of hydrodeoxygenation reaction • The body-centered cubic (BCC) PdCu nanoalloys exhibited outstanding performance with 93.6% yield of DMF at room temperature • PdCu/AC-BCC could also catalyze other aromatic alcohols at room temperature

Aqueous zinc ion hybrid supercapacitors (ZHSCs) have emerged and are regarded as promising candidates for energy storage due to their environmental friendlessness and cost‐effectiveness. However, the development of a satisfying positive electrode with high performance still poses challenges. Herein, a hierarchical porous carbon with a fast‐ion‐transport feature is rationally reported via a facile template modification strategy. By adjusting the content of the template, the physiochemical characteristics and microstructures of carbon can be reasonably optimized. As proof of concept, the produced carbon electrode can deliver a high specific capacitance of 294.8 F g−1 at a current density of 0.2 A g−1, long cycling stability with ≈100% capacitance retention over 20 000 cycles, and a maximum power density of 13.2 kW kg−1 at 30.8 W h kg−1. Significantly, a superior areal capacitance of 3390 mF cm−2 is offered with a mass loading of 21 mg cm−2. When coupled with a unique antifreezing hydrogel electrolyte, the constructed quasi‐solid‐state ZHSC can not only endure −15 °C, but also exhibits outstanding durability and an ultralow self‐discharging rate, demonstrating its potential prospect for extreme conditions. This work may bring light on the preparation of carbon materials and the fabrication of multifunctional devices.

Wet-process phosphoric acid is a fundamental process in the fertilizer industry. The influence of impurities on crystallization kinetics of CaSO4 was investigated in the Ca(H2PO4)2–H2SO4–H3PO4–H2O system using a mixed suspension mixed product removal crystallizer. Effects of Si, Al, Fe, Mg, K, and Na on crystal morphology and structure were examined in the highly acidic system through scanning electron microscopy and high-resolution transmission electron microscopy. Results show that the increase of Mg, K, and Na content facilitates crystal growth. Si, Al, and Fe are beneficial to CaSO4 crystal growth at a certain concentration range. Impurities also affect the crystal morphology, and the addition of Si, Fe, and Na promotes the formation of needle-like crystals compared with other impurities. X-ray diffraction results show that the preferred crystal growth direction is (020), and the interplanar spacing of the crystals is affected by the element radius of the impurities.

The Chinese Accelerator Driven Sub-critical system (C-ADS) is an important strategic research that is based on a high energy proton beam for nuclear waste transmutation. To meet the requirements of stability and reliability of the lower energy part, two identical Injectors are operated in parallel. The Injector-I is designed and constructed by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS) in Beijing, China. The Injector-I linac with two accelerating cryomodules (named CM1 and CM2) successfully accelerated the proton beam to 10.67 MeV with the beam current of 10.11 mA in pulse mode and 10.0 MeV with a beam current of 1.6 mA in CW (continuous wave) mode. The cryomodules have been designed, fabricated, assembled and commissioned at IHEP since the beginning of 2012. The thermal performances of the cryomodules were analyzed with numerical simulations and the empirical calculations take into account all the main contributors (support posts, multilayer insulation, current leads, power couplers and cavities) to the static and dynamic heat loads at various temperature levels. Two designs of current leads are developed and analyzed, and the case 2 current leads are tested and used in the CM2. The estimated static heat loads by analysis have been compared with the available experimental measurements. The operation experiences including the cool down, operating parameters and heat load measurements are reported, and the results were shown that the cryomodules can keep in a stable operation at 2 K and 30 mbar ±10 Pa.

The vortex-induced vibration behavior and mechanism of an asymmetrical composite beam cable-stayed bridge is investigated by means of aerodynamic sectional tests and computational fluid dynamics me...

Spinel-type lithium manganese oxides (LMOs) are the most promising lithium-adsorption materials. LMOs can be in the form of solid solutions of LiMn2O4, Li1.33Mn1.67O4, and Li1.6Mn1.6O4. However, uncertainty about the lithium-desorption mechanism restricts material development. The synthesis of intermediate products of spinel-type LMOs during acid treatment is important to investigate such a mechanism. In this work, precisely controlled acid treatment experiments were performed to successfully obtain the intermediate products of LiMn2O4, Li1.33Mn1.67O4, and Li1.6Mn1.6O4. For LiMn2O4, lithium was desorbed with the dissolution of manganese. For Li1.33Mn1.67O4 and Li1.6Mn1.6O4, the lithium-desorption mechanism was an ion-exchange reaction, where lithium ions (Li+) in the 8a sites were prioritized for the ion-exchange reaction compared with Li+ in the 16d sites. Density functional theory (DFT) calculation results confirmed the experimental results and explained that the prioritization of Li+ in the 8a sites arose from its lower reaction-energy barrier, thereby revealing that Li+ preferred to move to the nearest vacant 8a sites when lithium was desorbed because of the lower diffusion-energy barrier. This work is the first to clarify the lithium-desorption mechanism through experiments and DFT calculations, and thus lays a foundation for the further exploitation of LMOs.

A three-dimensional (3D) printing method has been developed for preparing a lithium anode base on 3D-structured copper mesh current collectors. Through in situ observations and computer simulations, the deposition behavior and mechanism of lithium ions in the 3D copper mesh current collector are clarified. Benefiting from the characteristics that the large pores can transport electrolyte and provide space for dendrite growth, and the small holes guide the deposition of dendrites, the 3D Cu mesh anode exhibits excellent deposition and stripping capability (50 mAh cm-2), high-rate capability (50 mA cm-2), and a long-term stable cycle (1000 h). A full lithium battery with a LiFePO4 cathode based on this anode exhibits a good cycle life. Moreover, a 3D fully printed lithium-sulfur battery with a 3D printed high-load sulfur cathode can easily charge mobile phones and light up 51 LED indicators, which indicates the great potential for the practicability of lithium-metal batteries with the characteristic of high energy densities. Most importantly, this unique and simple strategy is also able to solve the dendrite problem of other secondary metal batteries. Furthermore, this method has great potential in the continuous mass production of electrodes.

High-alumina coal fly ash (HAFA) is an important aluminum and silicon resource. In the process of preparing aluminum–silicon materials from HAFA, the influence of impurity elements on its performance must be considered. In this work, the occurrence state of impurities in HAFA, micro morphology, and the bond energy of different impurity coordination were studied. Sulfuric acid leaching method and density functional theory were used to study the leaching behavior of impurities to verify the difficulty of removing different impurity elements. The results show that iron existed in the form of magnetic particles (34.78%), amorphous phase (49.24%), and crystalline phase (15.96%) in HAFA. Titanium mainly existed in amorphous phase (29.34%) and crystalline phase (69.4%). In sulfuric acid leaching, titanium was more difficult to leach, and the content of TiO2 decreased from 2.30% to 2.25%, whereas that of Fe2O3 decreased from 1.50% to 0.86%. The actual leaching behavior of impurity elements was consistent with the simulation results, with more energy required to remove Ti than Fe. These studies of impurity elements in HAFA will provide theoretical support for the preparation of aluminum–silicon materials.

2D van der Waals materials are crystals composed of atomic layers, which have atomic thickness scale layers and rich distinct properties, including ultrafast optical response, surface effects, light-mater interaction, small size effects, quantum effects and macro quantum tunnel effects. With the exploration of saturable absorption characteristic of 2D van der Waals materials, a series of potential applications of 2D van der Waals materials as high threshold, broadband and fast response saturable absorbers (SAs) in ultrafast photonics have been proposed and confirmed. Herein, the photoelectric characteristics, nonlinear characteristic measurement technique of 2D van der Waals materials and the preparation technology of SAs are systematically described. Furthermore, the ultrafast pulsed fiber lasers based on classical 2D van der Waals materials including graphene, transition metal chalcogenides, topological insulators and black phosphorus have been fully summarized and analyzed. On this basis, opportunities and directions in this field, as well as the research results of ultrafast pulsed fiber lasers based on the latest 2D van der Waals materials (such as PbO, FePSe3, graphdiyne, bismuthene, Ag2S and MXene etc), are reviewed and summarized.

One of the most important devices for the High Energy Photon Source Test Facility project, the 2.6 T 32-pole 3W1 superconducting wiggler, was designed by the Institute of High Energy Physics (IHEP); its magnetic gap is 68 mm, and its storage energy is 286 kJ. It will be installed at the storage ring of the Beijing Electron Positron Collider Upgrade Project at the IHEP to replace the old permanent wiggler. The primary purpose of the cryostat is to create a safe and reliable system and realize long-term operation with zero liquid helium consumption. To maintain liquid helium temperature, four identical two-stage cryocoolers are placed symmetrically at the wiggler ends. The cryostat has only one 60 K thermal shield, which is used to reduce the heat load to the liquid helium vessel. The cryostat has several novel features, including a suspension system with little heat leakage that is self-centered during cooling of the cryostat, a special copper liner and high-efficiency condensers, three pairs of binary current leads, and three-level safety design. The cryogenic system has been cooled three times, and the residual cooling capacity is approximately 0.41 W at 4.2 K without current.

In this study, titanium matrix composites (TMCs) reinforced with hybrid TiB, TiC and RexOy (rare earth oxides) were successfully fabricated by vacuum arc melting technique. Subsequently thermomechanical processing was carried out to optimize the microstructure and investigate the synergistic strengthening behavior. It is found that the optimized microstructure mainly contained two typical regions: Region 1, reinforcement-lean region with coarse lamellar grains. Region 2, reinforcement-rich region containing fine equiaxed α grains comparing with reinforcement-lean region, all hybrid reinforcements distributed homogeneously at their grain boundaries and TiB fibers are perpendicular to the forging direction. It is shown that the reinforcement can stimulate the dynamic/static recrystallization during the thermomechanical processing. The tensile strength was significantly enhanced by the ternary reinforcements and the thermomechanical processing. A well-matched relationship between microstructure and mechanical properties is obtained. When the reinforcement content is 2.5 vol%, the tensile strength at room temperature and high temperature (700 °C) increased to 1214 MPa and 552 MPa, while the TMCs maintained a good elongation of 5.1% and 58% respectively. The strengthening mechanism could be attributed to the refinement of the matrix grain, the solid solution strengthening of C element and the load-bearing capability of TiB and ternary oxide clusters.

TiC crystals are an ideal and irreplaceable reinforcement in metal matrix composites (MMCs). The C, Ti vacancies and dislocations provide elemental diffusion channels, and thermal processing provides sufficient activation energy to induce a special rod-like α-Ti phase, even the phase transformation of β-Ti→α-Ti within the in situ TiC crystals. The ultimate tensile strength of the 8 vol. % TiC/Ti6Al4V at 723K increase by approximately 12.6%, and the fatigue crack at 723K grows much faster than the Ti6Al4V matrix, which is nearly 2 times. The rod-like α-Ti imposes an additive effect on the stress concentration within the TiC crystals during deformation, and results in the formation of microcracks and microvoids within the TiC crystals, ultimately, the premature fracture of TiC crystals, thus, reducing the strengthening effect on the TMCs and accelerating the fatigue crack propagation. To prevent effectively rod-like α-Ti precipitates within the TiC crystals and improve the tensile properties and fatigue performances, the TiC content should be reduced as much as possible (lower than 2.5 vol. %), and its size should be as small as possible (smaller than 10 μm). Our work provides strong evidence for atomic diffusion within the in situ TiC crystals and paves the way to make full use of the strengthening effect of TiC crystals on MMCs.

For the simultaneous photocatalytic reduction of hexavalent chromium (Cr(VI)) and the degradation of rhodamine B (RhB), directional charge-transfer channels and efficient separation of photogenerated holes and electrons are important. Herein, a Z-scheme heterojunction photocatalyst, protonated g-C3N4/BiVO4 decorated with wood flour biochar (pCN/WFB/BiVO4), was prepared through a hydrothermal reaction and electrostatic self-assembly for Cr(VI) photoreduction and RhB photodegradation. The morphological features, crystalline structure, chemical composition, optical properties, specific surface area, and photoelectrochemical properties of the prepared samples were investigated. The pCN/WFB/BiVO4 photocatalyst exhibited superior removal performance when used to remove Cr(VI) and RhB separately or RhB-Cr(VI) system. The biochar bridge served as a charge-transfer channel between two semiconductors, and the electrons in protonated g-C3N4 (pCN) and BiVO4 achieved a charge balance. This led to the formation of a Z-scheme heterojunction, fast photogenerated charge separation, and a powerful redox ability. The pCN/WFB/BiVO4 photocatalyst provides new insight into the mechanisms responsible for boosting multicomponent photocatalytic reactions, while constituting a promising candidate for wastewater treatment.

During sustainable high-value utilization of coal-based solid wastes, a kind of characteristic silicon-rich lye (SRL) generated, and its comprehensive recovery and recycling remains an important subject. Through a simple and facile strategy of mild caustic-crystallization method, SRL was favorably utilized through calcium silicate hydrate (C − S − H) synthesis with silicon conversion efficiency over 97.33%. The micro-morphology of C − S − H presented a typical “honeybee hive”−like porous structure with numerous exchangeable activity cations and combination sites in the silicate chain structure. The amorphous C − S − H products possessed marvelous recovery abilities for typical heavy metals as Cu (II), Zn (II), and Cr (III) in industrial wastewater with recovery efficiency all above 99.6% in quite a short period. The recovery mechanism of C − S − H toward heavy metals was revealed as calcium ions exchange and interlayer structure combination with SiO4 and AlO4 tetrahedron through the analysis of characterization technologies and DFT simulation calculation. C − S − H synthesized in SRL contributes to achieving valuable resources conversion and recycling for guiding sustainable development of coal-based solid waste comprehensive utilization.

This work creatively planted nano-TiB fibers (10∼50 nm in width) as a novel ultra-fine network in pre-alloyed Ti-composite powder based on the rapid eutectic reaction method, constitutional supercooling would limit the ultra-fine network skeletons to micro-scale (2∼5 μm), which were thermal stabilized below 900 °C. The new configuration structure of ultra-fine network loaded the nano TiB-fibers is expected to improve the high temperature properties. However, high temperature would coarsen the nano-TiB fibers, resulting in the destruction of the ultra-fine network. The decomposition and growth of the TiB nano-fibers followed the Ostwald ripening mechanism and then coarsened following the merging mechanism, obtaining random distribution of two-scale TiB. It provided a new guidance for optimizing the nano-TiB size-scale and distribution by controlling the sintering temperature, which was useful for constructing multistage network structure enhanced Ti-composites based on pre-planted nano-TiB in alloy powders.

To solve the precision forming problem of titanium matrix composites (TMCs) precision components with variable cross-sections, isothermal compression model of (TiB + La2O3)/IMI834 composite was established to investigate the deformation behaviors, determine forming strategy, predict and optimize the local microstructure. The subsequent isothermal precision forming experiment proved the precision forgings can be successfully fulfilled with good surface quality in one step using a cylindrical billet following the simulation strategy. Referring to simulation results, the local microstructure and performance were successfully optimized by controlling the deformation degree in different section regions to meet the service requirements. Fine-grained regions and reinforcement-rich regions were formed in the small cross-section (large deformation) regions due to the rotation and directional arrangement of the reinforcements and the dynamic recrystallization stimulated by the reinforcements, where the engineering strength and elongation were both improved from 1137 MPa and 2.55% to 1176.5 MPa and 4.0%, respectively, compared with the large cross-section (small deformation) regions. This research provided an important guidance for improving the fabrication efficiency and optimizing the local microstructure and performance of TMCs precision components by isothermal forming.

Surface-grafted polymer brushes have been long reported as a desired matrix for biosensing applications, owing to enhanced immobilization capacity and anti-fouling properties. However, simultaneous optimizing binding signal and minimizing non-specific adsorption using polymer matrix is still a challenge, due to the lack of systematic structural and composition optimization at molecular level. In this research, a series of block copolymer brushes with controlled hierarchical architectures, poly [oligo (ethylene glycol) methacrylate-b-glycidyl methacrylate] (POEMGA-b-PGMA) were prepared by two-stage surface-initiated polymerization. Surface plasmon resonance imaging (SPRi), as a real-time and label-free biosensing technology, was used as means to evaluate their detecting performances of bio-interactions. In contrast to one-layer poly (glycidyl methacrylate) (PGMA), 4.7-fold enhancement of signal-to-background (S/B) was achieved in bi-layer POEGMA-b-PGMA surface, by using rabbit IgG (R-IgG, in 10% serum) and a microarray of goat-anti-rabbit IgG (G-R-IgG) as the system of study. Interestingly, the binding signals and anti-fouling performances of the polymer brushes could be enhanced simultaneously by increasing the length of the monomer in the primary layer. Theoretically, it mainly owed to the formation of a densely packing protective primary layer against non-specific physical adsorption and a spatially optimized secondary layer of minimized steric hindrance that allowed optimum binding of analytes.

To develop photocatalysts with desirable compositions and structures for improving the efficiency and selectivity of CO2 conversion to CH4 under mild conditions is of great importance. Here, we design an effective photocatalyst of bimetal (Ag/Pd) nanoalloys supported on nitrogen-doped TiO2 nanosheet for CO2 conversion. Such a novel photocatalyst combines multiple advantages of abundant Ti3+ ions, oxygen vacancies, and substitutional nitrogen that are favorable for catalyzing CO2 reduction. It was found that CO2 could be efficiently transformed to CH4 under mild conditions, i.e., in aqueous solution and at atmospheric pressure and room temperature. The maximum production rate of CH4 can reach 79.0 μmol g–1 h–1. Moreover, the Ag/Pd bimetals supported on N-doped TiO2 nanosheet exhibit high selectivity to CH4. The as-synthesized photocatalyst can be well recycled for CO2 reduction.

In this paper, we proposed a multi-band metamaterial absorber for sensing thin film, which consists of tri-layer structure: patterned multi-split electric ring resonators layer, dielectric spacer l...

The cryostat chiefly consists of external vacuum housing, 60 K shield screens, liquid helium vessel with an SC multipole magnet inside, vacuum chamber (beam duct) with copper liner inside, and four two-stage cryocoolers with a stage temperature of 4.2 K/60 K. Current leads have heat in-leak interception in vacuum using cryocoolers. The helium vessel is suspended with four vertical and four horizontal CFRP (T300) tension rods connected to the external cryostat vessel. These tension rods pass throughout the 60 K shield screens and attach to bolts on the external housing walls and are used for precise alignment of the vertical magnet position.

High-alumina coal fly ash (HAFA) is a special solid waste due to the existence of more than 45% alumina and 35% silica, which can be applied to prepare Al-Si series ceramics if the impurities can be removed and the Al/Si mass ratio can exceed 2.55 (Mullite: 3Al2O3.2SiO2). In this work, a new mechanical–chemical synergistic activation–desilication process is proposed, and the contents of different impurities can be lowered up to less than 1%, and the Al/Si mass ratio can be elevated from 1.26 to 2.71. Especially, the mechanism of this process is investigated in detail. The analysis of the mechanism shows that the decrease of Q4(3Al) and the increase of Q4(0Al), Q4(1Al), and Q4(2Al) improve amorphous silicate reactivity through synergistic activation, and the exposed amorphous Si-O-/Si-O-Si can be removed by OH- during the desilication process (desilicated ratio>55%), which help the fine mullite to exhibit excellent properties (bulk density > 2.85 g/cm3, apparent porosity < 0.5%) during the sintering process. Finally, this process not only decreases the pollution but also alleviates the shortage of Al/Si resources and promotes the clean development of coal-fired power generation.

High-alumina-coal fly ash (HAFA) with a high Li content is regarded as a potential resource for Li production. To support the development of Li recovery technology from HAFA, the distribution and modes of occurrence of Li in HAFA were investigated. HAFA was separated into magnetic particles, glass, and mullite+corundum+quartz (MCQ) using an acid-alkali combination method. 79–94% of the Li was found in glass, with the remaining 5–16% and 3(0Al) and Q3(1Al) structures by reacting with Q4(0Al) and Q4(1Al). Based on the experimental and simulation results, we propose extracting Li during the pre-desilication process by dissolving the glass phase.

Li1.6Mn1.6O4 is a representative ion sieve material that is used to recover lithium from salt brines and bitterns owing to its high lithium ion adsorption capacity reaching 11.9–44 mg g−1. However, manganese dissolution during acid treatment hinders the industrial application of the material. For investigating the mechanism of manganese dissolution, the precursor Li1.6Mn1.6O4 and ion sieve H1.6Mn1.6O4 were prepared and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), chemical content analyses, diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS), and X-ray photoelectron spectroscopy (XPS). The results of XRD, SEM, and FT-IR showed that the bulk phase of Li1.6Mn1.6O4 retained the spinel structure, whereas the lattice diminished during acid treatment. The results of chemical content analyses showed that the bulk phase of Li1.6Mn1.6O4 contained a few trivalent manganese atoms and that the mean valence of manganese in the material increased during acid treatment. DRIFTS and XPS exhibited that the surface of Li1.6Mn1.6O4 was mostly full of tetravalent manganese and retained the spinel structure during acid treatment. In the proposed mechanism of manganese dissolution, an electron of trivalent manganese in the bulk phase transfers to the surface and is captured by tetravalent manganese within the acidic environment. Then, tetravalent manganese is converted to bivalent manganese after acquiring sufficient electrons, and dissolution occurs simultaneously.

We report a method to support Pt sub-nanoparticles on TiO2. The feature of this route was that N,N′-(ethane-1,2-diyl)diformamide (ED) acted as both the reducing agent and stabilizing agent. The yield of 1,2,3,4-tetrahydroquinoline could be higher than 99% at room temperature. In addition, the catalyst can be recycled at least 4 times.

Superconducting 499.8 MHz β single cell ellipsoidal cavities of quarter-wave geometry have been chosen for the High Energy Photon Source (HEPS). The cooling process of the superconducting cavity from the room temperature to 4.2 K is an unsteady forced convective heat transfer process. Its heat transfer mechanism analysis and efficient cooling strategy in the cooldown process is insufficient in present studies. In this paper, a three-dimensional coupled heat-flow model of 499.8 MHz superconducting cavity was built. The unsteady temperature distributions of the superconducting cavity in different inlet temperature condition were studied, serving as the training samples for the neural networks. The agent models based on the two sets of Back-Propagation (BP) neural networks (BPNet1 and BPNet2) were designed to obtain a set of quick calculation model. Genetic algorithm (GA) was used to perform the results optimization. The cooling time of the optimized cooling method could be reduced from 480 min to 290 min, with a reduction of about 40% compared the traditional cooling method. The standard deviation σ sk of the modified cooling method was 0.56. The maximum temperature difference in each cooling stage approximately approached the allowed temperature difference 20 K, indicating the potential of the cooling method was maximized. The modified cooling method could shorten the total cooling time and greatly improve the efficiency during the cooldown process.

Enhancing the critical heat flux (CHF) of external reactor vessel cooling (ERVC) to achieve the strategy of in-vessel retention (IVR) has been deemed as an essential requirement for the security of modern commercial PWR nuclear power plants. A new type of multi-scale conical pin fin structures had been designed to meet this need. These conical structures of four different axial heights (1.0, 1.5, 2.0 & 2.5mm) and similar radial geometric parameters were fabricated on four heating surfaces of copper substrates by supersonic cold gas spray technique (SCGS), and the conical pin fin structures were combined with a thin layer of micro porous structures. Transient-state (quenching) and steady-state (heating) pool boiling experiments had been respectively conducted on 6 different downward-facing surfaces under different inclination angles including 5°, 30°, 45°, 60°, 75° & 90° (in vertical), which included above-mentioned four pin fin surfaces, a plain surface and a coated surface covered with a 1mm-thick layer of uniform porous coating fabricated by SCGS with copper particles. The experimental results showed that the CHF increased with the inclination angles. The CHF of all the SCGS-modified surfaces were significantly enhanced compared with those of the plain surface. The maximum CHF value and the maximum CHF enhancement belonged to the 2.0mm-height pin fin surface whose CHF values were more than 1.7 times of those of the plain surface, and up to 2.1 times in 90°. The 1.0mm pin fin surface had the greatest performance in boiling heat transfer coefficient (HTC) and its CHF-enhancing performance also greatly exceeded that of 1.0mm uniform porous coating surface. Remarkable performances of multi-scale conical pin fin structures had been experimentally confirmed, hence the safety margin of IVR-ERVC will be greatly enhanced after adopting them. In addition, the CHF enhancement mechanism of the multi-scale conical pin fin structures was analyzed.

In this work, a novel cellulose based fluorescent carbon dots (CDs) doped ZnO composite, ZnO/CDs-x (x = 10, 20, 30, 40), was developed as a photocatalyst for the photocatalytic degradation of four dyes. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV visible diffuse reflectance spectroscopy (UV–Vis DRS), and transient photocurrent measurements were carried out to study the effects of different concentrations of CDs on the morphology and photocatalytic properties of ZnO/CDs−x (x = 10, 20, 30, 40) composites. When the concentration of CDs increased, the structure of ZnO/CDs−x (x = 10, 20, 30, 40) changed from a peony like structure (x = 10, 20) to a hexagonal prism like structure (x = 30, 40) and assembled into a flower like structure. Flower like ZnO/CDs-20 showed the best photocatalytic performance and good durability under UV light, and three types of excitation effects were observed: mixed light > sunlight > visible light. It was found that the addition of CDs with a concentration of 20 mL in ZnO can significantly enhance the photoabsorption and the separation of photogenerated carriers, which is beneficial to improve the photocatalytic performance.

Five 166.6 MHz beta = 1 quarter-wave resonator (QWR) superconducting cavities (SC) have been chosen for the High Energy Photon Source (HEPS), a 6 GeV kilometer-scale diffraction-limited storage light source to be built in Beijing suburb. Each cavity is equipped with one high power input coupler to deliver over 180 kW RF power in continuous mode (cw). Overheating and the result in excessive heat load, even quench were observed during the horizontal test of the first proof-of principle (PoP) cavity. To find the overheating reason, a dedicated two-way coupled electromagnetic-fluid-thermal simulation of the helium gas-cooled coupler was carried out by Ansys solver. This paper presents some key parameters of the coupler calculated by the two-way coupled electromagnetic-fluid-thermal numerical simulation and the accuracy of the simulation was proved by comparing with the horizontal test results. Based on the electromagnetic-fluid-thermal coupling analysis, this paper takes into account the inlet gas temperature and flow rate on the temperature distribution, electromagnetic loss distribution, and 4.2 K heat load of the coupler. Furthermore, the occurrence conditions of overheating and quench are explored and some improvement suggestions of the coupler structure are given.

As an insertion device, the superconducting wiggler has been developed for about 40 years, the superconducting magnet of which is usually made of NbTi and set in a cryostat. The performance of the cryostat is vital to the success of the superconducting wiggler. In this paper, a cryostat of the superconducting wiggler with 32 poles and 2.6 T field for the High Energy Photon Source Test Facility (HEPS-TF) was developed in the Institute of High Energy Physics (IHEP). In the cryostat, a novel design of thermal structure and cooling capacity distribution was proposed. Compared with the conventional two thermal shields, the single thermal shield was adopted to simplify the mechanical design, which was extended to the outside of the vacuum chamber to decrease the heat loads at 4.2 K. The current leads were optimized to minimize the heat loads at 60 K. After the systematic thermal analysis and optimization, the total heat load was covered by the four Gifford-Mcmahon cryocoolers successfully. In the experiment, the measured heat load was 3.85 W with magnet current of 320 A and beam of 250 mA. And the residual cooling power was 0.65 W.

In Na2O–CaO–SiO2–H2O system, systematic investigations of phase and morphology of calcium silicate in hydrothermal conditions were concisely conducted for high-value utilization of silicon resource in high-alumina fly ash (HAFA). The results show that crystal composition and phase may be affected by relatively low concentration of NaOH, and sodium ions are rearranged into the structure to form NaCaHSiO4 and Na2Ca3H8Si2O12 with different C/S ratio at high concentration of NaOH. In addition, phases in wollastonite group possess the morphology of nanofiber. Formation of nanofiber is attributed to the difference of surface energies between axial and radial direction, and higher temperatures lead to easier growth along radial direction. The preparation of C–S–H with different phases and morphologies can guide for the application of silicate solution with high alkalinity with different purposes.

High-alumina coal fly ash (HAFA) is a special solid waste because it contains more than 45% alumina and 35% silica. This material can be applied to prepare Al–Si series ceramics if the impurities can be removed and the Al/Si mass ratio can be elevated to a high level. In this work, a new mechanical–chemical synergistic activation–desilication process is proposed and optimized. During the synergistic activation, the morphology, ironic leaching ratios, efficient desilicated ratio (EDR), and mineral phases of different treatments are investigated. The reactivity of amorphous silica can be elevated to a high level (EDR>11%). After the desilication process, the contents of different impurities can be lowered up to less than 1%, and the Al/Si mass ratio can be elevated from 1.26 to 2.71. Mullite refractories are prepared from desilicated HAFA by forming and sintering process, and the bulk density and apparent porosity can reach to 2.85 g/cm3 and 2.07%, respectively.

In this paper, we proposed a voltage-tunable terahertz metamatrial, which is composed of the circular-ring deep-slot array fabricated by UV-LIGA process to form a controlled cavity embedded with the liquid crystal (LC). By changing the biased voltage, the transmission peak of the terahertz metamaterial can be continuously tuned within a frequency range of 38 GHz. Moreover, this metamaterial can work over a wide range of incident and polarization angle for both TE and TM waves due structure symmetry. In addition, a differential phase of 74° is obtained at 0.45 THz by tuning the biased voltage. Therefore, our results open new opportunities for the tunable THz bandpass filters and phase shifters.

Recently, resonance sensing based on the terahertz metamaterials has attracted considerable attentions due to the enhancement and confinement of local fields in microsize gap of resonant structures. Here, a high-sensitive dual-band sensor based on the complementary terahertz metamaterial composed of microsize circular ring gap array is proposed to detect the thickness and refractive index of thin film. The structure of this sensor is polarization insensitive dual-band operating mode and can be easily filled by the biomolecules. Simulation results demonstrate that the dual-band resonances are very sensitive to the dielectric variation, and the sensitivity levels of 99 GHz/refractive index unit (RIU) for mode f1 and 242 GHz/RIU for mode f2 are obtained and further enhanced by optimizing structures. Therefore, this structure can exhibit promising application for monitoring thin film thickness.

Superconducting cavity is usually needed to be gradually cooled from room temperature to the superconducting temperature zone (4.2 K and below) in the testing and sophisticated operation process of superconducting cavity. The purpose of this paper is to study the cooling law on the helium cooldown process for the 650 MHz two-cell superconducting cavity with the unsteady numerical simulation. A three-dimensional coupled heat-flow model of 650 MHz two-cell superconducting cavity was established. The unsteady numerical simulation of different inlet temperatures, flow rates and pressure conditions was carried out. The equivalent convective heat transfer coefficient and temperature distribution of 650 MHz two-cell superconducting cavity during cooldown process were obtained. The effects of cooling time and entrance parameters on the cooldown process were analyzed. The temperature distribution of the lower intersection lines has a large drop in the initial stage of cooldown process (120 s), while the temperature near the flanges at the both ends is still higher (remaining at the initial temperature of 300 K). With the passage of time, the temperature of the upper and lower intersection lines decreases. The maximum temperature difference on the lower intersections is within 2 K in the final stage of cooldown process (3600 s). The maximum temperature difference increases by 180%, and the difference between the maximum temperature and the minimum temperature (dT) at the end of a cooldown stage increases by 130% after 1 h, respectively, when the inlet temperature drops from 290 to 270 K (under the condition of the initial temperature of 300 K). The maximum temperature difference and the dT at the end of a cooldown stage increase with the decrease in the inlet temperature. The maximum temperature difference increases with the increase in the inlet flow rate, while the dT at the end of a cooldown stage decreases with the increase in the inlet flow rate. The effect of changing the inlet flow rate on the cooling rate is not as obvious as changing the inlet temperature. Once there is a certain flow rate, the advantage of further increasing the flow rate to reduce the temperature of the superconducting cavity is not so great.

The current insertion anode chemistries are approaching their capacity limits; thus, alloying reaction anode materials with high theoretical specific capacity are investigated as potential alternatives for lithium-ion batteries. However, their performance is far from being satisfactory because of the large volume change and severe capacity decay that occurs upon lithium alloying and dealloying processes. To address these problems, we propose and demonstrate a versatile strategy that makes use of the electronic reaction confinement via the synthesis of ultrasmall Ge nanoparticles (10 nm) uniformly confined in a matrix of larger spherical carbon particles (Ge⊂C spheres). This architecture provides free pathways for electron transport and Li+ diffusion, allowing for the alloying reaction of the Ge nanoparticles. The thickness change of electrodes containing such a material, monitored byan in situ electrochemical dilatometer, is rather limited and reversible, confirming the excellent mechanical integrity of the confined electrode. As a result, these electrodes exhibit high reversible capacity (1310 mAh g-1, 0.1C) and very impressive cycling ability (92% after 1000 cycles at 2C). A prototype device employing such an alloying electrode material in combination with LiNi0.8Mn0.1Co0.1O2 offers a high energy density of 250 Wh kg-1.

Lithium metal is considered to be one of the most potential anode materials on account of its high theoretical specific capacity and lowermost electrochemical potential. Nevertheless, the critical challenges of dendrite growth and low Coulombic efficiency (CE) of the lithium metal anode during cycling prevent the commercial application of the lithium metal battery. Herein, rubidium fluoride (RbF) as additives is utilized to inhibit the lithium dendrite growth. Benefiting from the stronger electropositive property of Rb+, it can adsorb on the surface of protuberances during the lithium deposition process, form an electrostatic shielding field of the surface, and guide the uniform deposition of Li+. The CE can maintain above 90% with the additives of RbF in the carbonate electrolyte. Besides that, RbF improves the cycle life and decreases the polarization, a stable cycling performance of more than 1000 h is obtained, and the overvoltage is controlled below 100 mV in the cycling test of Li∥Li symmetrical cel...