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The inconsistencies regarding the fundamental correlation between Gd content and slip (twinning) activities of Mg alloys appeal further investigations. However, the traditional slip dislocations analysis by TEM is time-consuming, and that by SEM/EBSD cannot recognize the partial slip modes. These urge a more efficient and comprehensive approach to easily distinguish all potential slip modes occurred concurrently in alloy matrix. Here we report a modified lattice rotation analysis that can distinguish all slip systems and provide statistical results for slip activities in Mg alloy matrix. Using this method, the high ductility of Mg-Gd alloy ascribed to the enhanced non-basal slips, cross-slip, and postponed twinning activities by Gd addition is quantitatively clarified.

The design of efficient and robust non-precious metal electrocatalysts towards oxygen evolution reaction (OER) is of great value for developing green energy technologies. The in-situ formed high-valence (oxy)hydroxides species during the reconstruction process of pre-catalysts are recognized as the real contributing sites for OER. However, pre-catalysts generally undergo a slow and inadequate self-reconstruction. Herein, we reported a PO43− optimized CoFe-based OER catalysts with amorphous structure, which enables a fast and deep reconstruction during the OER process. The amorphous structure induced by ligands PO43− is prone to evolution and further form active species for OER. The electron interaction between metal sites can be modulated by electron-rich PO43−, which promotes generation of high active CoOOH. Simultaneously, the etching of PO43− from the pre-catalysts during the catalytic process is in favor of accelerating the self-reconstruction. As a result, as-prepared pre-catalyst can generate high active CoOOH at a low potential of 1.4 V and achieve an in-depth reconstructed nanosheet structure with abundant OER active sites. Our work provides a promising design of pre-catalysts for realizing efficient catalysis of water oxidation.

Direct conversion of syngas to aromatics (STA) over oxide-zeolite composite catalysts is promising as an alternative method for aromatics production. However, the structural effect of the oxide component in composite catalysts is still ambiguous. Herein, we investigate the size effect by selecting ZnCr2O4 spinel, as a probe oxide, mixing with H-ZSM-5 zeolite as a composite catalyst for STA reaction. The CO conversion, aromatics selectivity and space-time yield (STY) of aromatics are all significantly improved with the crystal size of ZnCr2O4 oxide decreases, which can mainly attribute to the higher oxygen vacancy concentration and thus the rapid generation of more C1 oxygenated intermediate species. Based on the understanding of the size–performance relationship, ZnCr2O4-400 with a smaller size mixing with H-ZSM-5 can achieve 32.6% CO conversion with 76% aromatics selectivity. The STY of aromatics reaches as high as 4.79 mmol gcat−1 h−1, which outperforms the previously reported some typical catalysts. This study elucidates the importance of regulating the size of oxide to design more efficient oxide-zeolite composite catalysts for conversion of syngas to value-added chemicals.

SnO2 has been extensively used in the detection of various gases. As a gas sensing material, SnO2 has excellent physical-chemical properties, high reliability, and short adsorption-desorption time. The application of the traditional SnO2 gas sensor is limited due to its higher work-temperature, low gas response, and poor selectivity. Nanomaterials can significantly impact gas-sensitive properties due to the quantum size, surface, and small size effects of nanomaterials. By applying nanotechnology to the preparation of SnO2, the SnO2 nanomaterial-based sensors could show better performance, which greatly expands the application of SnO2 gas sensors. In this review, the preparation method of the SnO2 nanostructure, the types of gas detected, and the improvements of SnO2 gas-sensing performances via elemental modification are introduced as well as the future development of SnO2 is discussed.

Rechargeable aqueous zinc ion batteries (AZIBs) were considered as one of the most promising candidates for large-scale energy storage due to the merits of high safety and inexpensiveness. As AZIBs cathode material, MnO2 possesses great merits but was greatly hindered due to the sluggish diffusion kinetic of Zn2+ during electrochemical operations. Herein, deep Zn2+ ions intercalated δ-MnO2 (Zn-MnO2) was achieved by the in situ electrochemical deposition route, which significantly enhanced the diffusion ability of Zn2+ due to the synergistic effects of Zn2+ pillars and structural H2O. The resultant Zn-MnO2 based AZIBs delivers a record capacity of 696 mAh/g (0.5 mAh/cm2) based on the initial mass loading, which is approaching the theoretical capacity of MnO2 with a two-electrons reaction. In-situ Raman studies reveal highly reversible Zn2+ ions insertion/extraction behaviors and here the Zn-MnO2 plays the role of a container during the charge–discharge process. Further charge storage mechanism investigations point out the insertion/extraction of Zn2+ and H+ coincides, and such process is significantly facilitated results from superior interlayered configurations of Zn-MnO2. The excellent electrochemical performance of Zn-MnO2 achieved in this work suggests the deep ions pre-intercalation strategy may aid in the future development of advanced cathodes for AZIBs.

It is an inevitable trend of sustainable manufacturing to replace flood and dry machining with minimum quantity lubrication (MQL) technology. Nevertheless, for aeronautical difficult-to-machine materials, MQL couldn’t meet the high demand of cooling and lubrication due to high heat generation during machining. Nano-biolubricants, especially non-toxic carbon group nano-enhancers (CGNs) are used, can solve this technical bottleneck. However, the machining mechanisms under lubrication of CGNs are unclear at complex interface between tool and workpiece, which characterized by high temperature, pressure, and speed, limited its application in factories and necessitates in-depth understanding. To fill this gap, this study concentrates on the comprehensive quantitative assessment of tribological characteristics based on force, tool wear, chip, and surface integrity in titanium alloy and nickel alloy machining and attempts to answer mechanisms systematically. First, to establish evaluation standard, the cutting mechanisms and performance improvement behavior covering antifriction, antiwear, tool failure, material removal, and surface formation of MQL were revealed. Second, the unique film formation and lubrication behaviors of CGNs in MQL turning, milling, and grinding are concluded. The influence law of molecular structure and micromorphology of CGNs was also answered and optimized options were recommended by considering diverse boundary conditions. Finally, in view of CGNs limitations in MQL, the future development direction is proposed, which needs to be improved in thermal stability of lubricant, activity of CGNs, controllable atomization and transportation methods, and intelligent formation of processing technology solutions.

This paper demonstrates the developments toward a high performance monolithic wheeled structure horizontal dual-axis (pitch (X-axis) and roll (Y-axis)) microelectromechanical system (MEMS) gyroscope based on off-plane coupling suppression silicon gratings. Gyroscopes have been fabricated with a silicon-on-glass fabrication process with vacuum-sealed in a metal packaging. The featured gyroscope operates in split-mode with the bandwidths of two axes devices both ~70Hz. By unitizing two individual active restraining control loops that adjust the quadrature amplitude via differentially biasing the silicon gratings in real-time, the off-plane mechanical couplings of the two sense modes are significantly reduced by ~95 and ~30 times, which enables ~25-fold and ~56-fold improvements in the bias instability for a typical dual-axis device. Tactical-grade performances are achieved for both the X-axis and Y-axis gyroscopes with angle random walk (ARW) of 0.02 deg/h and 0.045 deg/h along with in-run bias instability (BI) of 0.26 deg/h and 0.65 deg/h respectively without any temperature compensation. The current preliminary results show great potential to achieve navigation grade precision by employing the mode-matching technique in the future. The use of silicon gratings for out-of-plane coupling reduction also provides an effective way to build a high performance planar monolithic chip inertial measurement unit (IMU).

Online condition monitoring of winding insulation has been proved to be an effective means to improve the reliability of an inverter-fed machine, but little work has been done on the insulation of line-end coil subjected to much higher transient voltage stress with a higher risk of premature insulation break down. In this paper, the inverter self-excited high-frequency switching oscillations are utilized for the line-end coil insulation condition monitoring. To improve the condition monitoring sensitivity and its robustness to dynamic operating conditions, a switching oscillation mode decomposition (SOMD) method is proposed. Firstly, the condition-sensitive mode, i.e. high-frequency common-mode (HFCM) current is selected and separated by the variation mode decomposition (VMD) algorithm among three dominant modes in switching oscillation current. Then, the amplitude-frequency features of HFCM current are extracted for condition monitoring. Finally, the overall insulation condition of three-phase line-end coils and the degree of asymmetric degradation are quantitatively evaluated by the frequency and amplitude features respectively. Experimental work was carried out and the results demonstrate the good performance of high sensitivity, good robustness, and non-contract safety.

Corrosion behavior of AZ31 magnesium alloy in NH4+-bearing chloride solution with controlled pH was investigated by weight loss experiment, hydrogen collection, and electrochemical test combined with surface morphology and topography observation. The results show that NH4+ and pH of the solution can affect the corrosion of AZ31 magnesium alloy. The existence of NH4+ affects the formation and dissolution of corrosion products, which makes the protective effect of the corrosion product layer weaker. The change of pH value not only affects the corrosion mechanism of AZ31, but also alters the concentration of NH4+ ions in the solution, which further influences the corrosion product layer of AZ31, and finally makes the corrosion of AZ31 change significantly.

The microstructure of primary Mg 2 Si and the interface of Mg 2 Si / α -Mg modified by Sn and Sb elements in an as-cast Mg-5Sn-2Si-1.5Al-1Zn-0.8Sb (wt.%) alloy were investigated. In the primary Mg 2 Si phase not only the Si atoms but also the Mg atoms could be substituted by Sn and Sb atoms, resulting in the slightly reduced lattice constant a of 0.627 nm. An OR of Mg 2 Si phase and α -Mg in the form of [ 001 ] Mg 2 Si ∥ [ 01 1 ¯ 1 ] α , ( 220 ) Mg 2 Si ∥ ( 0 1 ¯ 12 ) α was discovered. Between primary Mg 2 Si phase and α -Mg matrix two transitional nano-particle layers were formed. In the rim region of primary Mg 2 Si particle, Mg 2 Sn precipitates sizing from 5 nm to 50 nm were observed. Adjacent to the boundary of primary Mg 2 Si particle, luxuriant columnar crystals of primary Mg 2 Sn phase with width of about 25 nm and length of about 100 nm were distributed on the α -Mg matrix. The lattice constant of the Mg 2 Sn precipitate in primary Mg 2 Si particle was about 0.756 nm. Three ORs between Mg 2 Sn and Mg 2 Si were found, in which the Mg 2 Sn precipitates had strong bonding interfaces with Mg 2 Si phase. Three new minor ORs between Mg 2 Sn phase and α -Mg were found. The lattice constant of primary Mg 2 Sn phase was enlarged to 0.813 nm owing to the solution of Sn and Sb atoms. Primary Mg 2 Sn had edge-to-edge interfaces with α -Mg. Therefore, the primary Mg 2 Si particle and α -Mg were united and the interfacial adhesion was improved by the two nano-particles layers of Mg 2 Sn phase.

Magnetic nanoparticles (MNPs) have been widely studied for use in biomedical and industrial applications. The frequency dependence of the magnetization of magnetic nanoparticles is analyzed for different AC excitation fields. We employ a Fokker-Planck equation, which accurately describes AC magnetization dynamics and analyze the difference in AC susceptibility between Fokker-Planck equation and Debye model. Based on these results we proposed a simple, empirical AC susceptibility model. Simulation and experimental results showed that the proposed empirical model accurately describes AC susceptibility, and the AC susceptibility constructed with the proposed empirical equation based on Debye model agrees well with the measured results. Therefore, we can utilize the proposed empirical model in biomedical applications, such as the estimation of the hydrodynamic size and temperature, which is expected to apply to biologicals assays and hyperthermia.

Multi-direction impact forging (MDIF) was applied to the as-extruded ZK60 Mg alloy, and the microstructure, texture evolution and yield strength symmetry were investigated in the current study. The results showed that the average grain size of forged piece was greatly refined to 5.3 μm after 120 forging passes, which was ascribed to the segmenting effect of {10–12} twins and the subsequent multiple rounds of dynamic recrystallization (DRX). A great deal of {10–12} twins were activated at the beginning of MDIF process, which played an important role in grain refinement. With forging proceeding, continuous and discontinuous DRX were successively activated, resulting in the fully DRXed microstructure. Meanwhile, the forged piece exhibited a unique four-peak texture, and the initial //ED fiber texture component gradually evolved into multiple texture components composed of //FFD (first forging direction) and //FFD texture. The special strain path was the key to the formation of the unique four-peak texture. The {10–12} twinning and basal slip were two dominant factors to the evolution of texture during MDIF process. Grain strengthening and dislocation strengthening were two main strengthening mechanisms of the forged piece. Besides, the symmetry of yield strength was greatly improved by MDIF process.

Twinning-detwinning (TDT) behavior in a strongly basal-textured Mg-Li alloy during two-step compression (RD)-compression (ND) process was investigated using quasi-in-situ EBSD. TDT behavior and TDT variants selection were statistically discussed with the loading path for the first time. Non-Schmid twinning behavior was observed in the first step compression, owing to the local stress fluctuations by neighboring twins; in contrast, Schmid's law well predicted the detwinning variants selection. This asymmetrical TDT behavior was first investigated to date related with the strong basal texture and loading path. Besides, with the progress of compression, Schmid factors for twinning demonstrated a decreasing tendency; however, those for detwinning during the second step displayed an abnormally increasing trend, fundamentally stemming from prior twinning behavior.

Due to the remarkable performance of SiC MOSFET on high temperature, it is promising in the future applications in various of applications. The accurate online junction temperature based on dynamic temperature sensitive electrical parameters (TSEPs) is significant for the protection and condition monitoring, which can prolong or monitor the lifetime of SiC MOSFET devices. In this paper, four different dynamic TSEPs including turn-on delay time, turn-off delay time, maximum current turn-on and turn-off switching rate are theoretical analyzed taking the parasitic parameters into consideration. The experimental analysis of the influence of parasitic parameters dynamic TSEPs are carried on using a buck converter test setup. Based on the theoretical and experiments analysis, a junction temperature correction method is proposed for SiC MOSFET. The online junction temperature monitoring experiments are used to verify the accuracy and effectiveness of the proposed method. The results show that the proposed correction method can largely eliminate the junction temperature monitoring error at different parasitic parameters. The maximum measurement error is reduced from 147 °C to 4.7 °C after correction.

Using first-principles calculations, hydrogen evolution reaction (HER) activity on two-dimensional (2D) gallium chalcogenides monolayers GaX (X = O, S, Se, and Te) as well as the derived Janus monolayers Ga2XY (X≠Y, X/Y = O, S, Se, and Te) were systematically examined. It was found that Ga2OSe Janus monolayer with a 0.3% strain has the lowest ΔGH∗ of 0.19 eV (modified to −0.01 eV including the solvation effect) because (i) O is the most electronegative among X/Y atoms, (ii) the Ga2OSe monolayer has a larger lattice parameter with respect to GaO monolayer, and (iii) the built-in electric field is enhanced after H adsorption. The enhanced H adsorption with the lattice stretching is a result of the weaker Ga–O bond strength before H adsorption and the reduced electron fillings of anti-bonding molecular orbital formed by H 1s and O 2pz orbitals after H adsorption. The O-pz band center can be served as a descriptor to describe the HER activity trend for these p-block materials. Moreover, Ga2OSe monolayer has appropriate band alignment, distinguished optical absorption coefficient (105 cm−1), low exciton binding energy (0.71 eV), and the spontaneous HER process, indicating that it is a highly potential candidate for near-infrared photocatalyst for hydrogen production. Our research provides a novel paradigm that forming Janus structure can effectively tune the HER activity, which would guide the searching for excellent HER photocatalysts for clean hydrogen production.

SiC MOSFET is a promising power device for electric drive system due to its various advantages such as high switching frequency and low loss. However, fast switching speed results in high voltage stress and can potentially cause insulation damage of the winding. Few studies have analyzed and evaluated the voltage stress, especially for the hairpin winding, which is the mainstream winding type for electric vehicle traction machines. For this purpose, this paper proposes a high-frequency equivalent circuit model to predict the inter-turn voltage stress of hairpin windings driven by SiC MOSFETs. Firstly, the working principle of the overvoltage at the winding ends is analyzed and validated by experiments. Then, the parasitic parameters are calculated before building the high-frequency equivalent circuit. A field-circuit coupled finite element method is used to consider the nonlinear parameters and to evaluate the voltage stress. Finally, a prototype is built, and the voltage stress is tested. The resultant error between the calculated and experimental maximum inter-turn voltage stress is only 1.3%, which supports the inference on the validity of the presented equivalent circuit and the method. Based on the above, a novel winding connection scheme is proposed to reduce effectively the voltage stress of hairpin winding.

Ultrathin conversion coatings, made from aligned graphene derivatives and ammonium zirconium carbonate (AZC), were fabricated on stainless steel by electrodeposition. Sulfonated graphene oxide (SGO) provided electron pathways and physical barriers to corrosive molecules. Electrodeposition ensured the alignment of SGO and the facile fabrication of the coatings. AZC is an environmental-friendly crosslinking agent, water-repellent and corrosion inhibitor. Upon dehydration reactions, AZC improved the cohesion between SGO layers and anchored the conversion coatings on metal substrates. When the mass ratio of SGO to AZC was 2:1, the corrosion current density of the composite coatings reached 0.098 ​μA ​cm−2, while that of the bared stainless steel was 1.04 ​μA ​cm−2, given a coating thickness of only 500 ​nm. The electrical conductivity of SGO/AZC composite coatings can be tailored from 3.84 ​× ​10−5 to 2.28 ​× ​10−3 ​S‧cm−1 by heat treatment and HI reduction, which satisfied the electrical conductivity requirement of wide applications in electronic industry, office appliances and petroleum storage.