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In this paper, a Ni coating was deposited on the surface of the A356 aluminum alloy by high velocity oxygen fuel spraying to improve the performance of the AZ91D magnesium/A356 aluminum bimetal prepared by a compound casting. The effects of the Ni coating as well as its thickness on microstructure and mechanical properties of the AZ91D/A356 bimetal were systematically researched for the first time. Results demonstrated that the Ni coating and its thickness had a significant effect on the interfacial phase compositions and mechanical properties of the AZ91D/A356 bimetal. The 10µm's Ni coating cannot prevent the generation of the Al-Mg intermetallic compounds (IMCs) at the interface zone of the AZ91D/A356 bimetal, while the Ni coating with the thickness of 45 µm and 190 µm can avoid the formation of the Al-Mg IMCs. When the Ni coating was 45 µm, the Ni coating disappeared and transformed into Mg-Mg2Ni eutectic structures+Ni2Mg3Al particles at the interface zone. With a thickness of 190µm's Ni coating, part of the Ni coating remained and the interface layer was composed of the Mg-Mg2Ni eutectic structures+ Ni2Mg3Al particles, Mg2Ni layer, Ni solid solution (SS) layer, Al3Ni2 layer, Al3Ni layer and sporadic Al3Ni+Al-Al3Ni eutectic structures from AZ91D side to A356 side in sequence. The interface layer consisting of the Mg-Ni and Al-Ni IMCs obtained with the Ni coating had an obvious lower hardness than the Al-Mg IMCs. The shear strength of the AZ91D/A356 bimetal with a Ni coating of 45 µm thickness enhanced 41.4% in comparison with that of the bimetal without Ni coating, and the fracture of the bimetal with 45µm's Ni coating occurred between the Mg matrix and the interface layer with a mixture of brittle fracture and ductile fracture.

Hypereutectic Al-Si-Cu coatings were prepared by supersonic atmospheric plasma spraying to enhance the surface performance of lightweight alloys. To find out optimum process conditions and achieve desirable coatings, this work focuses on the influence of three important parameters (in-flight particle temperature, impact velocity, and substrate temperature) on the collected splats morphology, coatings microstructure and microhardness. Results show that appropriate combinations of temperature and velocity of in-flight particles cannot only completely melt hypereutectic Al-Si-Cu particles, especially the primary Si phase, but also provide the particles with sufficient kinetic energy. Thus, the optimized coating consists of 98.6 % of fully-melted region with nanosized coupled eutectic and 0.9 % of porosity. Increasing the substrate deposition temperature promotes the transition from inhomogeneous banded microstructure to homogeneous equiaxed microstructure with a lower porosity level. The observations are further interpreted by a newly developed phase-change heat transfer model on quantitatively revealing the solidification and remelting behaviors of several splats deposited on substrate. Besides, phase evolutions including the formation of supersaturated α-Al matrix solid solution, growth of Si and Al2Cu phases at different process conditions are elaborated. An ideal microstructure (low fractions of unmelted/partially-melted regions and defects) together with solid solution, grain refinement, and second phase strengthening effects contributes to the enhanced microhardness of coating. This integrated study not only provides a framework for optimizing Al-Si based coatings via thermal spraying but also gives valuable insights into the formation mechanisms of this class of coating materials.

In order to improve mechanical properties of 6082 aluminum alloy, the SiCp/Al 6082 composites were prepared by the addition of the micron-sized SiC particles combined with the squeeze casting. The effects of the SiCp content and squeeze casting on the microstructure and mechanical properties of the 6082 aluminum alloy were investigated by SEM, EDS, TEM, tensile testing and hardness testing analysis methods. Research results exhibited that the SiCp content and squeeze casting had a significant impact on the microstructure and mechanical properties of the 6082 aluminum alloy. The addition of the SiCp refined the grain size of the 6082 aluminum alloy while caused the increase of the porosity with increasing the SiCp content, especially in the permanent mold casting condition. Compared to the permanent mold casting, the squeeze casting obviously reduced pore defects, refined grain size and made the SiCp distribute evenly as well as bond tightly with the Al matrix. The tensile strength, yield strength, elongation, elastic modulus and hardness of the 6082 aluminum alloy obtained with the SiCp and squeeze casting were remarkably improved, and the optimal mechanical properties were obtained with a 2 wt.% SiCp, and they increased 10.73 %, 72.7 %, 193.9 %, 23.5 % and 25.2 %, respectively, compared to those of the 6082 aluminum alloy obtained without SiCp and squeeze casting. The fracture surface of the SiCp/Al 6082 composites obtained with the squeeze casting was dense and exhibited a ductile fracture mode.

Donor-acceptor co-doped rutile TiO2 ceramics with colossal permittivity (CP) have been extensively investigated in recent years due to their potential applications in modern microelectronics. In addition to CP and low dielectric loss, voltage stability is an essential property for CP materials utilized in high-power and high-energy density storage devices. Unfortunately, the voltage stability of CP materials based on co-doped TiO2 does not catch enough attention. Here, we propose a strategy to enhance the voltage stability of co-doped TiO2, where different ionic defect clusters are formed by two acceptor ions with different radii to localize free carriers and result in high performance CP materials. The (Ta + Al + La) co-doped TiO2 ceramic with suitable La/Al ratio exhibits colossal permittivity with excellent temperature stability as well as outstanding dc bias stability. The density functional theory analysis suggests that L a 3 + A l 3 + V O • • T i 3 + defect clusters and Ta5+-Al3+ pairs are responsible for the excellent dielectric properties in (Ta + Al + La) co-doped TiO2. The results and mechanisms presented in this work open up a feasible route to design high performance CP materials via defect engineering.

Catalysts of Ni supported on home-made mesoporous alumina (Ni/M-Al2O3) were prepared via facile incipient impregnation method and calcined under different temperature (500–800 °C). Compared with catalysts of Ni supported on commercial alumina, they showed much higher conversion and lower carbon deposition in methane dry reforming (DRM). Among the catalysts, Ni/M-Al2O3-700 exhibited the highest DRM activity, with 77.6% CH4 conversion and 85.4% CO2 conversion at 700 °C. TPR revealed that almost all the Ni was in the form of NiAl2O4 spinel after calcination at 700 °C. Due to the strong metal-support interaction of NiAl2O4 structure, the Ni crystal size of Ni/M-Al2O3-700 after reduction was around 5 nm. TGA and TEM results showed its carbon deposition after 20 h DRM test was only 3.8% and mainly in the form of amorphous carbon. This work indicates that the formation of NiAl2O4 spinel is beneficial to activity and stability towards DRM reaction and controlling calcination temperature is crucial.

A novel virtual material layer model based on the fractal theory was proposed to predict the natural frequencies of carbon fiber reinforced plastic composite bolted joints. Rough contact surfaces of composite bolted joints are modeled with this new proposed approach. Numerical and experimental modal analyses were conducted to validate the effectiveness of the proposed model. A good consistence is noted between the numerical and experimental results. To demonstrate the necessity of accurately modeling the rough contact surfaces in the prediction of natural frequencies, virtual material layer model was compared with the widely used traditional model based on the Master-Slave contact algorithm and experiments, respectively. Results show that the proposed model has a better agreement with experiments than the widely used traditional model (the prediction accuracy is raised by 8.77% when the pre-tightening torque is 0.5 N∙m). Real contact area ratio A* of three different virtual material layers were calculated. Value of A* were discussed with dimensionless load P*, fractal dimension D and fractal roughness G. This work provides a new efficient way for accurately modeling the rough contact surfaces and predicting the natural frequencies of composite bolted joints, which can be used to help engineers in the dynamic design of composite materials.

Germanium selenide attracts emerging attention for applications in high-performance field-effect transistors and photodetector, due to its unique photoelectric performances and tunable bandgap. Herein, the germanium selenide-reduced graphene oxide (GeSe-RGO) hybrid is successfully synthesized by loading liquid-phase exfoliated GeSe nanosheets on the 2D graphene via a hydrothermal reduction process. It is demonstrated that the photoresponse performance of the photoelectrochemical (PEC) device constructed by the synthesized GeSe-RGO hybrid is significantly enhanced in comparison to the one built by the sole GeSe nanosheets. The results of the PEC tests display the photocurrent density can reach to 8.45 μA/cm2 at the bias of 0.8 V, which is approximately 4 times that of sole GeSe nanosheets. Meanwhile, with the increase of illumination intensity, the photocurrent density of the GeSe-RGO photodetector almost presents a linear increase. When the illumination intensity is 90 mW/cm2, the photoresponsivity value is up to 116 μA/W. In addition, the GeSe-RGO hybrid shows a durable photoresponse capability under the bias of 0 V, revealing that such a hybrid has the excellent self-powered ability in the PEC system. There is no evident degradation on the photoresponsive performance of GeSe-RGO photodetector after 50 light on-off cycling, indicating the good stability of the hybrids. The enhanced performance of the GeSe-RGO hybrid is attributed to the outstanding photoresponsive capability of RGO and the effective separation of photo-generated electron-hole pairs. Our work indicates that the GeSe-RGO hybrid has great prospects for future applications in PEC-type photodetector devices.

Anion redox chemistry plays a crucial role in Na-deficient or Na-rich oxide cathodes for sodium-ion batteries (SIBs). But the oxygen redox chemistry has been rarely reported in O3-type (Na-full) layered oxides for SIBs. Herein, we reveal the anion redox chemistry in O3-type NaMn1/3Fe1/3Ni1/3O2 (MFN) cathode material, and propose an integrated strategy combining ZrO2 coating and Zr4+ doping to tune the anionic redox chemistry and crystal structures which improves the activity, reversibility, and stability of O2−. Oxygen redox reactions with high reversibility and cyclic stability mainly occur between 4.0 V and 4.3 V. The structure of Na-O-TM is regulated by Zr4+ doping, and the electronic state of O-2p occupies a higher energy level by the regulation of Na-O-TM structure. The electrons can migrate from O2- more easily and O2−/O− contribute more capacity. Zr4+ doping optimizes the lattice structure, enlarges the Na layer, and decreases TMO2 layer, which reduces the diffusion resistance of Na+ and increases the structural stability. ZrO2 layer effectively mitigates the corrosion of the electrolyte and ensures the integrity of the structure, which inhibits the formation of Na2CO3 on the surface and decreases CO2 release. This study not only reveals the anion redox chemistry in O3-type layered oxide cathode material but also is available for insights into regulating the redox activity, reversibility, and stability of oxygen.

Carbon-molybdenum disulfide (C-MoS2) ultrathin nanosheets were prepared by a hydrothermal process, and then AgI/C-MoS2 were synthesized via an in-situ deposition method. This ternary heterojunction composite exhibited better photocatalytic activity compared with those of one-component (pristine MoS2) and bicomponent (AgI/MoS2 and C-MoS2) materials for the degradation of organic dyes under the visible-light irradiation. In particular, by comparing with AgI/MoS2, the significant role of conductive amorphous carbon in AgI/C-MoS2 in enhancing the charge transfer during the photocatalytic degradation of dyes was first confirmed by photocurrent response and electrochemical impedance spectroscopy (EIS). A possible photocatalytic mechanism was proposed based on the capture experiment results. Furthermore, a straightforward and interesting way had been applied to test the recycled/newly-prepared AgI/C-MoS2 composite for revealing its distinctive self-cleaning performance and recyclability characteristic besides its good photocatalytic activity. This work could provide a reference for the design of other new ternary heterojunction composite materials with special structures and properties.

Oxygen release and irreversible cation migration are the main causes of voltage fade in Li-rich transition metal oxide cathode. But their correlation is not very clear and voltage decay is still a bottleneck. Herein, we modulate the oxygen anionic redox chemistry by constructing Li2ZrO3 slabs into Li2MnO3 domain in Li1.21Ni0.28Mn0.51O2, which induces the lattice strain, tunes the chemical environment for redox-active oxygen and enlarges the gap between metallic and anionic bands. This modulation expands the region in which lattice oxygen contributes capacity by oxidation to oxygen holes and relieves the charge transfer from anionic band to antibonding metal–oxygen band under a deep delithiation. This restrains cation reduction, metal–oxygen bond fracture, and the formation of localized O2 molecule, which fundamentally inhibits lattice oxygen escape and cation migration. The modulated cathode demonstrates a low voltage decay rate (0.45 millivolt per cycle) and a long cyclic stability., Voltage fade is a critical issue for Li-rich transition metal oxide cathode. Here, the authors modulate the oxygen anionic redox chemistry and enlarges the gap between metallic and anionic states by constructing Li2ZrO3 slabs into Li2MnO3 domain in Li1.21Ni0.28Mn0.51O2 which fundamentally suppresses the voltage decay.

In this work, cabon nanofiber supported cobalt ferrite composites (C/CFO) were prepared by electrospinning combined with hydrothermal method. The morphology, structure and microwave absorption properties were discussed in detail. The results revealed that the C/CFO composites with 3 D network structure exhibited excellent microwave absorption properties, which were linked to the composite compositions and synergistic effect between C NFs and CFO NPs. When the content of CFO NPs was 10 wt %, the C/CFO sample showed RLmax of −137 dB at 11.36 GHz and the EAB (RL

The argon power cycle is one of the most promising technologies for high efficiency and low emission hydrogen-fueled internal combustion engines. The application of coaxial injection technology in the hydrogen-fueled argon engine can improve the mixing process and the combustion performance of the H2/O2 mixture. In this study, an innovative H2–O2 coaxial injection combustion system was designed to investigate the jet flame characteristics of oxygen coaxially wrapped by hydrogen in a controllable argon thermal atmosphere. The findings of this study could provide a new perspective for designing hydrogen-fueled argon engines in the future. The influences of co-flow temperature, jet injection pressure, and excess oxygen coefficient were all determined. Observations of the flame showed a bright blue flame with a reddish glow in the far-burner region. Experimental results show that the flame length, cross-sectional area, and area/perimeter ratio first decrease with increasing jet injection pressure and subsequently increase, reaching maximum values at 0.4–0.6 MPa. When increasing the co-flow temperature from 1023 K to 1223 K, the cross-sectional area of the flame increases significantly by 61.1% at an excess oxygen coefficient of 0.4. Furthermore, the liftoff flame height shrinks when the co-flow temperature and the excess oxygen coefficient increase, while it rises along with an increasing jet injection pressure.

Geosynthetic clay liners (GCLs), which have a very low permeability to water and a considerably high self-healing capacity, are widely used in liner systems of landfills. In this study, a series of experimental tests were carried out under complex conditions on typical commercial GCLs from China. In particular, the effects of pH values and lead ions (Pb2+) were tested in addition to other factors. The swelling properties of natural bentonite encapsulated between geotextile components in the GCLs were tested first. The swelling capacity was reduced rapidly at pH values 40 mM. Permeability tests on GCLs with different concentrations of lead ions were then performed by using the self-developed multi-link flexible wall permeameter, and data showed that increases in lead ion concentrations greatly improved the permeability. Finally, self-healing capacity tests were conducted on needle-punched GCLs under different levels of damage. Results showed that the GCLs have a good self-healing capacity with small diameter damage holes (2 mm, close to three times the original aperture), but with a damage aperture larger than 15% of the sample area, the self-healing capacity could not prevent leakage; hence, in certain situations it will be necessary to repair the damage to meet the anti-seepage requirement.

The bionic porous zirconia fiber was prepared by the microemulsion electrospinning method. The phase, morphology and pore structure of the fibers were tested by X-ray diffraction, FTIR, RAMAN, SEM, TEM, and BET. The results show that the fiber was t-ZrO2 phase and its average fiber diameter was about 120 nm. There was obvious multi-cavity hollow structure like the polar bear hair in the zirconia fiber. The BET specific surface area and BJH average pore diameter of the fiber was 23.8 m2/g, and 11 nm, respectively. As a result, the bionic porous zirconia fiber had low thermal conductivity of 0.075 W/m k and low infrared emissivity of 0.598 at 3–5 μm. Therefore, the bionic porous zirconia fiber could be used as infrared stealth material.

By increasing the charging voltage, a cell specific energy of >400 W h kg−1 is achievable with LiNi0.8Mn0.1Co0.1O2 in Li metal batteries. However, stable cycling of high-nickel cathodes at ultra-high voltages is extremely challenging. Here we report that a rationally designed sulfonamide-based electrolyte enables stable cycling of commercial LiNi0.8Co0.1Mn0.1O2 with a cut-off voltage up to 4.7 V in Li metal batteries. In contrast to commercial carbonate electrolytes, the electrolyte not only suppresses side reactions, stress-corrosion cracking, transition-metal dissolution and impedance growth on the cathode side, but also enables highly reversible Li metal stripping and plating leading to a compact morphology and low pulverization. Our lithium-metal battery delivers a specific capacity >230 mA h g−1 and an average Coulombic efficiency >99.65% over 100 cycles. Even under harsh testing conditions, the 4.7 V lithium-metal battery can retain >88% capacity for 90 cycles, advancing practical lithium-metal batteries. Charging at high voltages in principle makes batteries energy dense, but this is often achieved at the cost of the cycling stability. Here the authors design a sulfonamide-based electrolyte to enable a Li metal battery with a state-of-the-art cathode at an ultra-high voltage of 4.7 V while maintaining cyclability.

To investigate the mutual effect of hydrogen, microstructures and stress concentration on the fatigue failure, fatigue behaviors of X65 steel welded joints in both air and saturated H2S solution were investigated at high cycle regime. The experimental result demonstrates that due to lower dislocation density observed by electron backscattered diffraction (EBSD), the fine grain heat affected zone (FGHAZ) is prone to induce cyclic strain localization and further lead to fatigue crack propagating along the FGHAZ in air. Furthermore, the quasi-cleavage with brittle-like fatigue striations and secondary crack on the fracture surface in saturated H2S solution is attributed to hydrogen embrittlement. Moreover, compared with base metal (BM) and FGHAZ, the weld metal (WM) and coarse grain heat affected zone (CGHAZ) are composed of bainite and martensite/austenite (M/A) phase, and more sensitive to hydrogen. Therefore, the fatigue crack is prone to grow along the interface between WM and CGHAZ under the normal applied stress.

Lithium-metal batteries (LMBs) are promising electrochemical energy storage devices with high energy densities. However, the extreme reactivity of metallic lithium, the large volumetric change of the electrode during cycling, and the notorious dendrite formation issues lead to low cyclic stability and safety concerns, hindering the practical application of LMBs. In particular, the intrinsic tendency of uneven lithium deposition and the large internal electrode stress lead to the piecing of solid electrolyte interphases (SEIs), thereby resulting in fast decay of the anode. We develop a facile laser processing technique to fabricate laser-structured copper foils (LSCFs) that are able to regulate the lithium deposition kinetics and increase the cycle life of LMBs. By simply scribing commercial foils using a 355 nm laser, microstructural features with fish-scale patterns are obtained. The lithium deposition follows a drastically different mode on the LSCF compared with commercial planar copper foils which relieves the internal stress of lithium and prohibits the piecing of SEI. A high Coulombic efficiency of >96% of the lithium metal anode is maintained for over 100 cycles on the LSCF at a current density of 1 mA cm-2 and an areal capacity of 1 mAh cm-2 while the benchmark decayed to below 80% after 50 cycles. Full cells based on LiFePO4 cathodes display a reasonable specific capacity of 125 mAh g-1 over 300 cycles at a rate of 1 C. This work provides a fast yet effective laser-based approach to construct highly stable lithium metal anodes.

Magnetic liquid metal is regarded as a promising material due to its integration of fluidic, metallic, and magnetic properties simultaneously. Previously, few methods of fabricating magnetic liquid metal have been proposed. However, either the alloying reaction inside the matrix or the poor performance in electrical and thermal conduction is troublesome in practical applications. Here, inspired by the mussel in nature, polydopamine is introduced to in situ reduce and immobilize silver shells on the surface of iron particles, and then the modified particles mix with liquid metal to prepare liquid metal-based magnetic suspensions (LMMSs). The silver shells can prevent iron particles from alloying with liquid metal and enhance the electrical and thermal conductivities of the LMMS concurrently. Besides, the LMMS thus obtained can keep its magnetism intact for a long period, at least during the 60 days of the test. Compared to directly mixing bare iron particles with liquid metal, the maximum electrical conductivities increase by at least 13.69% and the thermal conductivities increase by almost 4 times in the LMMS. The LMMS also exhibits potential applications in patterning and magnetic manipulation. This work puts forward a new strategy for preparing a LMMS with appealing properties and its broad applications are expected in the future.

Surface enhanced Raman spectroscopy (SERS) is a promising sensing technique that can provide unique chemical and structural fingerprint information, but gaining reliable SERS quantitative data with high sensitivity and stability still remains a challenge. Although using a molecule as an internal standard (IS) can improve the SERS quantitative capability, the reliability and SERS measuring conditions for signal fluctuations during calibration based on IS are yet to be explored when the embedded IS molecules and target objects are located in different environments. Herein, a 3D hotspot matrix SERS platform based on Au@4-MPy@AgNPs was constructed in water with the assistance of glycerol and the dynamic signal changes from the IS, i.e. 4-Mpy, and target molecules were monitored during the process of evaporation with high sensitivity and stability. In contrast to the traditional water-dispersed drying film system, the variation trends of IS and target molecules were consistent in the glycerol-assisted liquid film protection system. Therefore, it is reasonable to calibrate the signal fluctuation by utilizing the embedded IS based on the construction strategy of a glycerol-assisted 3D hotspot platform. This work demonstrates a rational, reliable and precise SERS quantitative technique for testing analyte concentrations in practical systems and has great application prospects in the field of analytical chemistry.

P2-type Na2/3Ni1/3Mn2/3O2 is one of the most promising cathode candidates for sodium-ion batteries due to its high specific capacity and high working voltage. However, a detrimental P2–O2 phase transition usually occurs at a high voltage (>4.2 V) leading to poor cycle stability. Herein, we propose to mitigate this critical issue through a controlled F−/Ca2+ dual-doping strategy with CaF2 as a dopant. The divalent Ca2+ ion doped in the Na layer stabilizes the layered structure at a high voltage when excessive Na+ is extracted. The more electronegative F− ion forms a stronger transition metal (TM)–F bond and reduces the electrostatic repulsion between the oxygen layers impeding the gliding of TMO2 layers. The Ca2+/F− co-doping successfully suppresses the unfavorable P2–O2 phase transition, and significantly improves the structural stability and cycling performance (27.1% vs. 87.2% after 500 cycles at 1C). Furthermore, density functional theory calculations combined with experimental tests reveal that the incorporation of Ca2+ and F− in Na sites and O sites facilitates the electronic and ionic conductivity owing to Na+/vacancy disordering, which enhances the high-rate capability. This study provides some insights into the design of long-life and high-rate cathode materials for sodium-ion batteries.

Reusable electronics have received widespread attention and are urgently needed. Here, nanocellulose-based liquid metal (NC-LM) printed circuit has been fabricated by the evaporation-induced transfer printing technology. In this way, the liquid metal pattern is embedded into the nanocellulose membrane, which is beneficial for the stability of the circuit during use. Besides, the NC-LM circuit is ultrathin with just tens of microns. In particular, the finished product is environmentally friendly because it can be completely dissolved by water, and both the liquid metal ink and the nanocellulose membrane can be easily recollected and reused, thereby reducing waste and pollution to the environment. Several examples of flexible circuits have been designed to evaluate their performance. The mechanism of evaporation-induced transfer printing technology involves the deposition, aggregation, and coverage tightly of the nanosized cellulose fibrils as the water evaporated. This study provides an economical and environmentally friendly way for the fabrication of renewable flexible electronics.

The water–gas shift (WGS) reaction is a key chemical process for CO removal and hydrogen generation in which CO and H2O are converted to CO2 and H2. The activation of H2O at the oxygen vacancy sites of a reducible oxide-supported catalyst is widely viewed as the critical step for this reaction. However, the strategy of rational fabrication of oxygen vacancies in reducible oxides to boost catalytic activity is rarely reported. Here, we report a facile method to fabricate oxygen vacancies through assembling an amorphous titanate overlayer on the surface of TiO2 support via alkali doping, aiming to improve its activity in WGS reaction. TEM, EPR, H2-TPR and XPS results verified that the titanate overlayer is in situ formed via alkali doping, where oxygen vacancies can be rationally regulated during reduction through tuning the amount of alkali. The ease of oxygen vacancy formation induced by alkali doping could be attributed to the lower Ti–O bond energy in titanate. It is shown that sodium-doped Ni/TiO2 with titanate overlayer on the support exhibited superior activity in WGS reaction compared with undoped catalyst, i.e., around threefold greater activity compared with undoped catalyst was achieved at 300 °C. Furthermore, the formation of CH4, a common side reaction in WGS on Ni-based catalysts, is suppressed on the sodium-doped Ni/TiO2. More importantly, the titanate overlayer strategy is successfully extended to other reducible oxide-supported catalysts, which provides a universal method to fabricate oxygen vacancies in reducible oxide-supported catalysts.

Until now, there is no effective method to detect the early weak structural damage of the aero engine intershaft bearing. In this article, an online method based on acoustic emission technology is used to detect the early weak structural damage of aeroengine intershaft bearing. The combination of maximum correlated kurtosis deconvolution and bandpass filter is proposed to enhance and denoise fault characteristic signals of the aero engine intershaft bearing. The Hilbert envelope demodulation is used to extracting the bear fault characteristic frequency. Under aeroengine working conditions, the experiment of an intershaft bearing with outer ring fault is carried out. The result shows that bearing outer ring fault characteristic frequency and bearing vibration frequencies clearly appear in the envelope spectrum of the acoustic emission signal. Therefore, online detection of early weak structure damage of aeroengine intershaft bearing is realized by acoustic emission technology under the background of strong noise.

Understanding self-crystallization characteristics of calcium-magnesium-alumina- silicate (CMAS) glass is of great significance for seeking for solution to its corrosion to thermal barrier coatings (TBCs). Here, we design a series of experiments to investigate the relationship between CMAS self-crystallization behavior and cooling/heating rates and dwell temperature, and emphasize the potential influence of self-crystallization on CMAS corrosion behavior to TBCs. With the cooling rate decreasing, crystalline phases formed in a sequence of diopside, wollastonite and anorthite, and the thickness of the crystalline layer increased. During the heating process, diopside and melilite phases formed when the temperature was lower than 1050 °C; while at higher temperatures, melilite transformed to anorthite and wollastonite, independent on the heating rate. Although self-crystallization can slow molten CMAS penetration, the function on protecting TBCs from damage is limited, and other strategies alleviating CMAS corrosion are necessitated to be developed.

Lattice oxygen undergoes redox reaction to achieve high specific capacity of the material in lithium-rich cathode oxides. However, irreversible oxygen loss causes a change in the crystal structure, and the cations migrate in the transition metal layer, resulting in a rearrangement of the electronic structure and ultimately a severe voltage decay. Herein, we introduce Pt nanoparticles with good catalytic activity and electrical conductivity into lithium-rich cathode materials to improve the loss of lattice oxygen for the first time. We have revealed that the evolution of the lattice structure after the lattice oxygen redox reaction is relatively stable in the lithium-rich oxide with Pt nanoparticles, which is in stark contrast to the apparently deformed crystal structure in the lithium-rich oxide without Pt. Pt-containing electrodes exhibit excellent high-capacity retention rate (more than 80% after 200 cycles), and voltage decay is significantly reduced (less than 0.4 V after 200 cycles). Our results highlight the role of Pt nanoparticles in alleviating the loss of lattice oxygen and stabilizing the crystal structure, which opens up the field of vision for the design of high-energy-density lithium rich cathode oxides with stable structure.

The flexible energy storage film based on PVDF matrix has very extensive application. The electrical properties of PVDF composite films doped by nanometer MnO2 was studied in this research, and the influences of MnO2 content on dielectric constant, breakdown strength and energy storage properties were systematic investigated. The results indicated that using MnO2 as fillers is an effective approach to improve the dielectric constant and breakdown strength of PVDF matrix composites. The dielectric constant is 18.1 and the breakdown electric field is 100 kV/mm when the content of MnO2 is 10 wt%. In addition, both large energy storage density (1.67 J/cm3) and high energy storage efficiency (81.9%) are obtained in composite film with 10 wt% MnO2. The enhancement of dielectric constant and energy storage efficiency are due to the ionic polarization of MnO2 under applied electric field. Moreover, the effect of MnO2 on electron trapping improves the breakdown strength and energy storage density of MnO2/PVDF composite films. This work provides a feasible route for designing flexible composites with excellent energy storage performance.

A new and simple strategy towards electric-field-driven multiple chirality switching device has been designed and fabricated by combining a newly synthesized base-responsive chiroptical polymer switch (R-FLMA) and p-benzoquinone (p-BQ) via proton-coupled electron transfer (PCET) mechanism. Clear and stable triple chirality states (silence, positive, negative) of this device in visible band can be regulated reversibly (>1000 cycles) by adjusting voltage programs. Furthermore, such chiral switching phenomena are also accompanied by apparent changes of color and fluorescence. More importantly, the potential application of this device for a spatial light modulator has also been demonstrated.

With the advantage of high surface-roughness tolerance, the pillar–concave Cu–Cu direct bonding without chemical-mechanical planarization (CMP) is investigated in detail, including the mechanism of thermal compensation, analysis of roughness, bonding strength, and bonding reliability. With the special design of Cu bond structure, excellent bonding results can be achieved under low thermal budget (150 °C for 1 min, atmosphere) with even high roughness of bonding surface. In addition, the pillar–concave scheme applied to fan-out panel-level package (FOPLP) has been demonstrated, showing the high feasibility of this scheme to realize applications in heterogeneous integration.

The development of effective but earth-abundant electrocatalysts for hydrogen evolution is still a great challenge. Non-noble metal-based multi-phase nanocomposites are regarded as emerging catalysts for efficient catalysts, but their practical application is still hindered by the lack of both satisfying activity and cost-effective synthesis. In this work, ternary CoSe2/MoO2/MoSe2 nanocomposites with controllable phases have been successfully synthesized by simply direct selenization of cobalt molybdate (CoMoO4) nanorods. Compared with related pure Mo-based and Co-based counterparts, the electric conductivity and the active sites of the as-prepared ternary nanocomposites have been both increased due to the synergistic effects. The as-prepared ternary CoSe2/MoO2/MoSe2 nanocomposites electrocatalysts demonstrated superior HER performance which only requiring an overpotential of 229 mV for reaching 10 mA/cm2 current density in acidic media.

High power piezoelectric ceramics 0.04Bi(Ni1/2Ti1/2)O3-xPb(Mn1/3Nb2/3)O3-(0.96-x)Pb(ZryTi1-y)O3 (BNT-xPMnN-PZyT) with various contents of PMnN from 0 to 12 mol% (keep y = 0.50) and Zr/Ti ratio gradually increasing from 48/52 to 52/48 (keep x = 0.06) were prepared by solid-state method. X-ray diffraction (XRD) results show a single phase of polycrystalline perovskite and indicate that the phase structure transforms from tetragonal phase to rhombohedral with x and y increasing. The optimal comprehensive properties of BNT-xPMnN-PZyT ceramic, d33 (355 pC/N), kp (0.58), er (1512), tanδ (0.40%), Tc (336 °C) and Qm (2010), are obtained at x = 0.06 and y = 0.50, which are apparently superior to typical or commercial Pb(Zr,Ti)O3 (PZT) based power ceramics. Within the range from room temperature to 200 °C, the variation of electric-field induced strains is less than 8.3%, indicating its good temperature stability. The maximum vibration velocity of the ceramic at temperature rise of 20 °C is measured to be 0.92 m/s, which is about 2 times higher than that of commercial hard PZT ceramics, suggesting the BNT-xPMnN-PZyT ceramic is a competitive and potential candidate for power piezoelectric transduction and actuation applications.

BiScO3-PbTiO3 ceramics are attractive for high-temperature piezoelectric applications while their high dielectric loss has to be substantially reduced. In this paper, a ternary perovskite system of xBi(Mn1/2Zr1/2)O3-(1-x-y)BiScO3-yPbTiO3 (abbreviated as xBMZ-BS-yPT) with x = 0.02, 0.04 and y = 0.62–0.67 were fabricated by conventional solid-phase method, and their ceramics were systematically studied with regards to phase structure, microstructure, dielectric and piezoelectric properties. X-ray diffraction results indicate a gradual change from rhombohedral to tetragonal phase with increasing PT composition. Morphotropic phase boundary (MPB) is revealed for the system with x = 0.02, y = 0.64, at which ultralow dielectric loss factor (0.58 %), almost unchanged Curie temperature (449 °C), high electromechanical properties (d33 = 360 pC/N, kp = 0.53), and stable strain output below 200 °C are observed. With such excellent piezoelectric properties and high-temperature stability, BMZ modified BS-PT ceramics are promising candidates for power electromechanical devices, especially operating in high-temperature environments.

The corrosion behavior and passive film properties of CrMnFeCoNi and CrFeCoNi coatings in 0.5 mol/L H2SO4 solution were investigated by potentiodynamic and potentiostatic measurements, electrochemical impedance spectroscopy and Mott-Schottky tests. The chemical compositions of passive film were characterized by X-ray photoelectron spectroscopy (XPS). Results indicated that CrFeCoNi coating possessed lower passive current density, higher polarization resistance, lower donor and acceptor density compared with CrMnFeCoNi coating, which determined CrFeCoNi coating has higher corrosion resistance than CrMnFeCoNi coating. The excellent resistance to corrosion could be attributed to the structure and chemical compositions of passive film

We present a comprehensive composition analysis of calcium phosphate cements (CPCs) incorporating increasing amounts of bioactive pyrophosphate species (up to 17 wt% P2O7). These cements comprise p ...

Ceria has been used for catalyst support for long time due to its unique structural properties resulting from oxygen vacancies and reversible valence change (Ce4+ and Ce3+). In this report, ceria nanorods (NR) and nanocubs (NC) were prepared with hydrothermal method and 5 wt% nickel was loaded on it. The effect of morphology of ceria supports for CO2 methanation reaction was studied. Characterization including TPR, TEM, XRD and XPS shows that Ni/CeO2-NR had a higher number of Ce3+ proportion compared with Ni/CeO2-NC. Both catalysts showed high conversion and selectivity for methane at low temperature range at200–250 °C and interestingly Ni/CeO2-NR exhibited a higher activity than Ni/CeO2–NC. A kinetic study and DRIFTs investigation were carried out to formulate the mechanism. It turned out that CO2 methanation on Ni/CeO2 goes through a formate route instead of CO2 dissociation and the oxygen vacant sites are supposed to be the active sites for the formate formation in this mechanism.

Storing hydrogen efficiently in condensed materials is a key technical challenge. Tremendous efforts have been given to inorganic hydrides containing B–H, Al–H and/or N–H bonds, while organic compounds with a great variety and rich chemistry in manipulating C–H and unsaturated bonds, however, are undervalued mainly because of their unfavourable thermodynamics and selectivity in dehydrogenation. Here, we developed a new family of hydrogen storage material spanning across the domain of inorganic and organic hydrogenous compounds, namely metallo-N-heterocycles, utilizing the electron donating nature of alkali or alkaline earth metals to tune the electron densities of N-heterocyclic molecules to be suitable for hydrogen storage in terms of thermodynamic properties. Theoretical calculations reveal that the enthalpies of dehydrogenation (ΔHd) of these metallo-N-heterocycles are dependent on the electronegativity of the metals. In line with our calculation results, sodium and lithium analogues of pyrrolides, imidazolides and carbazolides of distinct structures were synthesized and characterized for the first time, where the cation-π interaction was identified. More importantly, a reversible hydrogen absorption and desorption can be achieved over lithium carbazolide which has a hydrogen capacity as high as 6.5 ​wt% and a suitable enthalpy of dehydrogenation of 34.2 ​kJ ​mol−1-H2 for on-board hydrogen storage.

This paper investigated the combustion instability of spanwise positions in a hydrogen fueled scramjet combustor with a cavity flame holder. High-speed OH-PLIF technique was performed on a direct-connect supersonic combustion facility, and dynamic mode decomposition (DMD) as postprocessing. Combustion instability was investigated by characterizing the dominant frequencies and growth factors. By changing the equivalence ratio of hydrogen, the peak frequencies of scramjet mode and ramjet mode were obtained. Scramjet mode tended to have small oscillation at 150–200 Hz reflected by negative growth factors due to the stable flame structure. At ram-to-scram transition, oscillations at 80–120 Hz were remarkably enhanced due to the positive growth factors. In ramjet mode, the large differences of frequency characteristics in spanwise positions were observed. The dominant DMD modes near the cavity wall appeared to have negative growth factors leading to a stable flame with small oscillations. Besides, the characteristics of frequency-shift were affected by the positions of injector.

Donor-acceptor co-doped rutile TiO 2 ceramics with colossal permittivity have been paid more attention recent years. However, the application of the ceramics in high-energy-density storage devices was limited by the low breakdown strength of co-doped TiO 2 colossal permittivity ceramics, therefore the dielectric properties of Nb x La 0.004 Ti 0996-x O 2 (x:0.004=1:1, 1.02:1, 1.04:1, 1.06:1, 1.08:1) ceramics were investigated. Colossal permittivity with low dielectric loss and high dielectric strength was found in Nb x La 0.004 Ti 0.996-x O 2 (x:0.004=1.04:1) ceramics. The enhancement dielectric properties with larger Nb5+ doping concentration in co-doped ceramics provide the colossal permittivity mechanism in (Nb+La) co-doped TiO 2 ceramics could be attribute to the electron-pinned defect-dipole effect. Furthermore, finding the proper donor concentration is a feasible way to enhance the dielectric strength to satisfy the condition for application in high-energy-density storage devices.

Electronic phase separation in complex oxides is the inhomogeneous spatial distribution of electronic phases, involving length scales much larger than those of structural defects or nonuniform distribution of chemical dopants. While experimental efforts focused on phase separation and established its correlation with nonlinear responses under external stimuli, it remains controversial whether phase separation requires quenched disorder for its realization. Early theory predicted that if perfectly “clean” samples could be grown, both phase separation and nonlinearities would be replaced by a bicritical-like phase diagram. Here, using a layer-by-layer superlattice growth technique we fabricate a fully chemically ordered “tricolor” manganite superlattice, and compare its properties with those of isovalent alloyed manganite films. Remarkably, the fully ordered manganite does not exhibit phase separation, while its presence is pronounced in the alloy. This suggests that chemical-doping-induced disorder is crucial to stabilize the potentially useful nonlinear responses of manganites, as theory predicted.

The oxygen reduction reaction (ORR) plays an irreplaceable role in many energy-conversion processes. Low-cost catalysts with high activity and stability are eagerly needed to improve the sluggish O...

For the development of advanced flexible and wearable electronic devices, functional electrolytes with excellent conductivity, temperature tolerance, and desirable mechanical properties need to be engineered. Herein, an alkaline double-network hydrogel with high conductivity and superior mechanical and antifreezing properties is designed and promisingly utilized as the flexible electrolyte in all-solid-state zinc-air batteries. The conductive hydrogel is comprised of covalently cross-linked polyelectrolyte poly(2-acrylamido-2-methylpropanesulfonic acid potassium salt) (PAMPS-K) and interpenetrating methyl cellulose (MC) in the presence of concentrated alkaline solutions. The covalently cross-linked PAMPS-K skeleton and interpenetrating MC chains endow the hydrogel with good mechanical strength, toughness, an extremely rapid self-recovery capability, and an outstanding antifatigue property. Gratifyingly, the entrapment of a concentrated alkaline solution in the hydrogel matrix yields an extremely high ionic conductivity (105 mS cm-1 at 25 °C) and an excellent antifreezing capacity. The hydrogel retains comparable conductivity and eligible strength to withstand various mechanical deformations at -20 °C. The all-solid-state zinc-air batteries using PAMPS-K/MC hydrogels as flexible alkaline electrolytes exhibit comparable values of specific capacity (764.7 mAh g-1), energy capacity (850.2 mWh g-1), cycling stability, and mechanical flexibility. The batteries still possess competitive electrochemical performances even when the operating temperature drops to -20 °C.

The thermal conductivity (TC) of gutta-percha, zinc oxide, and carbon nanotubes nanocomposites (GP/ZnO@CNTs) is improved greatly by the oriented CNTs, which is induced by shear field of the capillary rheometer. Furthermore, the effects of shear rate and temperature on the orientation of CNTs and the TC of the nanocomposites are investigated. The results of Raman show that the degree of orientation of CNTs increases with the increment of shear rate and/or temperature, which greatly improves the thermal conductance of the nanocomposites when the orientation degree is equal to 10.8. Compared with the GP/ZnO@CNTs nanocomposites with random CNTs, the highest TC of GP/ZnO@CNTs nanocomposites with oriented CNTs is increased by 81.2%, which is up to 2.50 W m−1K−1.

Understanding and controlling parasitic reactions at the electrode–electrolyte interface (EEI) in Li-ion batteries is essential to enhance and predict the battery cycle life. Recent work has shown ...

Flow battery technology offers a promising low-cost option for stationary energy storage applications. Aqueous zinc–nickel battery chemistry is intrinsically safer than non-aqueous battery chemistry (e.g. lithium-based batteries) and offers comparable energy density. In this work, we show how combining high power density and low-yield stress electrodes can minimize energy loss due to pumping, and have demonstrate methods to achieve high energy and power density for ZnO/Ni(OH)2 electrodes by changing composition and optimizing testing protocols. Firstly, mechanically stable and homogeneous Ni(OH)2/carbon and ZnO/Zn flowable electrodes in 7 M KOH electrolyte were designed using a microgel dispersion as the suspending matrix. By determining the critical volume fractions for conductivity percolation, colloidal suspensions with 6.2 vol% of carbon and 23.1 vol% of Zn were selected for preparing catholytes and anolytes to ensure that these semi-solid electrodes possess high voltage and high coulombic efficiencies. The resulting flowable electrodes exhibited non-Newtonian rheology with a yield stress of approximately ∼200 Pa, which assists in maintaining mechanical stability of the suspensions. An energy density of up to 134 W h Lcatholyte−1 and power density up to ∼159 mW cmgeo.−2 was demonstrated for semi-solid ZnO/Ni(OH)2 electrodes, and coulombic efficiency of 94% was achieved during cycling by optimizing the charging protocol to 60% SOC of Ni(OH)2. Lastly, semi-solid ZnO and Ni(OH)2 flow cells were built and tested using an intermittent mode of operation. The high energy and power densities, high coulombic efficiency, and negligible pumping loss of the Zn–Ni semi-solid electrodes developed in the present work present a promising system for further development.

Carbon nanofibers (CNFs) were prepared by electrospinning, and silver (Ag) ions were grown on the surface of the CNFs by in situ solution synthesis. The structure and morphology of obtained Ag-doped CNFs (Ag-CNFs) were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The gas sensibility of the composite fiber was investigated by ammonia (NH3) obtained by natural volatilization from 1 to 4 mL of NH3 solution at room temperature. It was found that the fibers exhibited a sensitive current corresponding to different NH3 concentrations and a greater response at high concentrations. The sensing mechanism was discussed, and the good absorptivity was demonstrated. The results show that Ag-CNF is a promising material for the detection of toxic NH3.

Silicon germanium (SiGe) alloys hold promise for thermoelectric power generation at high temperatures and have been applied in deep-space missions. However, enhancement of the dimensionless thermoelectric figure-of-merit (ZT) is still needed for practical civil applications of SiGe. In this work, we report high-performance oxide/SiGe bulk composites that were obtained via hot-press sintering of mixed powders composed of phosphorus (P)-doped SiGe prepared via mechanical alloying, using a ball-milling technique and La-Nb-doped SrTiO3 (La-Nb-STO). The La-Nb-STO powder was obtained from ball milling of a bulk La-Nb-STO sample that was sintered via hot pressing of hydrothermally synthesized La-Nb-STO powder. Controlling the amount of La-Nb-STO nanoparticles added to SiGe matrix increased the power factor by optimizing the electron concentration and mobility in the composite. In addition, compared with single-phase P-doped SiGe, the second phase decreased the thermal conductivity because of additional phonon scattering at the interface. As a result, a high ZT of 0.91 was realized in the n-type oxide/SiGe bulk composite at 1000 K, which was 18% larger than that for the typical materials used in space flight missions and 5% higher than the single-phase SiGe alloys obtained in the present study. The strategy used in this study could also be viable to further enhance the ZT of nanostructured n-type SiGe and SrTiO3-based oxide materials.

Due to the unique properties of flexible electronic devices, various microelectromechanical systems (MEMS) devices based on flexible substrate have been proposed for miniaturization, lightweight, and intelligent applications. Obviously, the deformation of flexible substrate inevitably affects the performance of flexible MEMS devices. This article first investigates the static modeling of bending characteristics on the flexible V-shaped beam actuator, which is the most representative MEMS thermal actuator. This article focused on a comprehensive static analysis of bending mechanical property based on the flexible substrate. The innovation of static modeling is obtaining variation regularity of bending characteristics by establishing the deformation coupling model of V-beam structure and flexible substrate. The V-shaped beam thermal actuators are designed and fabricated on flexible liquid crystal polymer (LCP) substrate, and the influence of bending substrate on the actuation performance of the device is revealed by calculation, simulation, and experiment. The experimental results demonstrate that the actuation current of the V-shaped beam actuator rises up proportionally with the increase of angle and the decrease of beam length. When flexible substrate bends gradually from curvature 0 to 33.3 (1/m), the rates of measured actuation current change are 17.05%, 13.70%, and 10.24%, corresponding to different angles of 13°, 20°, and 27° at $600~\mu \text{m}$ length of V-shaped beams. Meanwhile, the rates of measured actuation current change are 9.22%, 13.22%, and 13.70%, corresponding to different lengths of 400, 500, and $600~\mu \text{m}$ at 20° angle of V-shaped beams. The experimental results are consistent with the theoretical calculation results of static modeling, and the error is less than 3.7%.

Low temperature stability has limited the applications at elevated temperature for ABO3-type lead-free ceramics. And multi-grade resonances of piezoelectric ceramics are hardly obtained although the resonances are very important in some applications such as filter and resonator. High piezoelectric properties and large mechanical quality factors with multi-grade resonances can be obtained in (Li+-La3+) co-doped BaTiO3 ceramics, and excellent temperature stabilities are achieved in the ceramics. It has been shown that the thermal treatments both with and without electric field at 200 °C improve the piezoelectric properties and thermal stability further. Large piezoelectric constant (272 pC N1) and huge mechanical quality factor (2010) was obtained after thermal-electrical treatment, which is caused by Li+-La3+ ionic pair aligning along the external electric filed during thermal-electrical treatment. Moreover, the present study provides an effective method to design combination properties with high temperature stability for ABO3 perovskite ferroelectric ceramics.

The Al0.3CoCrFeNi high-entropy alloy (HEA) particles reinforced Cu matrix composites (CMCs) were fabricated by mechanical alloying and sintering. Transition layer structure was obtained by multi-step ball milling to investigate the related influence on element diffusion behavior and wear properties of CMCs. The results indicate that a new Cu transition layer is generated, and the thickness is about 5 μm. Cr element diffuses into the interface via the transition layer, which forms the complex oxide. Because of the structure of Cu transition layer, the diffusion rates of Ni, Co and Fe increase, especially the Ni element. The wear resistance of CMCs is improved by 30%, which is due to the improvement of interface bonding strength, compared with the CMCs without transition layer. This method is applicable to the development of advanced HEA reinforced metallic matrix composites.

From a suite of advanced magic-angle spinning (MAS) NMR spectroscopy and powder X-ray diffraction (PXRD) experiments, we present a comprehensive structural analysis of pyrophosphate-bearing calcium ...

Design of hollow carbon structure by using metal-organic-frameworks (MOFs) precursors has come under the spotlight in electrochemical energy related applications due to its structure advantages. Here, a bimetal-based MOF (Zn and Fe) is adopted to synthesize hollow carbon nanobox with encapsulation of FeP nanoparticles. An unique core-shell architecture consisting of Zn-Fe Prussian blue analogue (PBA) core and polydopamine shell is first synthesized, followed by pyrolysis-oxidation-phosphorization process to prepare monodispersed FeP nanoparticles encapsulated in hollow carbon nanobox (denoted as FeP/HCNB). Electrochemical hydrogen evolution activity is chosen to investigate the structure advantage of FeP/HCNB. It achieves overpotentials of −88 mV and −180 mV at 10 mA cm−2 in acidic and alkaline solutions, respectively, and continuous operation for 15 h (start at 20 mA cm−2). It is therefore expected that the synthetic strategy of nanobox would enlighten the preparation of various nanostructures for different applications.