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Titanium alloys are difficult-to-machine materials that exhibit a low machining efficiency, yielding its restricted applications. The combination of micro-textures and a cemented carbide surface cutter can effectively improve the cutting performance and enhance titanium alloys' machining quality. Therefore, this manuscript investigates a cemented carbide ball-end milling cutter with surface modifications. Firstly, we prepared micro-textures with a variable distribution density on the surface of a cemented carbide cutter and revealed its properties from the microscopic aspect based on the simulation and test methods. Secondly, a milling test was done to reveal the anti-wear and anti-friction properties accuracy. Finally, based on the test data, the Lasso regression prediction models were established. Based on the Matlab particle swarm optimization algorithm, the parameters of micro-textures with a variable distribution density were optimized.

Wettability modification is an effective way in tailoring hotspots in surface Raman scattering (SERS) nowadays. However, due to the theoretical contradiction between hydrophobic and hydrophilic strategies, opposite views are usually put forward in building SERS structures. To realize the integration of hydrophobicity and hydrophilia in the same substrate, a wettability-switchable SERS architecture composed of heterostructured CuO@ZnO@Ag biomimetic nano Setaria (NS) has been designed and prepared in this paper. Experimentally, the structure shows impressive SERS performance under both hydrophobic and hydrophilic states. The limit of detection approaches even to single-molecule level and the lowest relative standard deviation is only ca 9.8%. Finite-different time-domain simulations and experimental analyses were systemically made to unearth the mechanism deep behind. Besides, owing to fine quantifiability, the CuO@ZnO@Ag NS shows promising potential in the detection of trace pesticide and deoxyribonucleic acid. This work provides a new idea for integrating the strategies of ‘concentration’ and ‘decentralization’, endowing SERS structure with wider application, and is also meaningful for other surface sciences.

Gate reliability and its degradation mechanism were studied for the normally off high-electron-mobility transistors (HEMTs) with regrown p-GaN gate and AlN/SiN x stack passivation. Through comparing the forward leakage current in two designed structures, the conduction mechanism is determined to be Fowler-Nordheim tunneling whose current is independent of temperature when the Pd/p-GaN Schottky junction is under high electric field. Even for the regrown p-GaN gates, this Schottky junction fails at first, resulting in an abrupt increase in gate current. The maximum gate operation voltage with a failure rate of 1% for 10-year lifetime is estimated to be about 6.87 and 6.07 V at room temperature by adopting power law and exponential law as extrapolation fitting, respectively. Degradation process monitoring reveals that the net acceptor concentration $N_{\mathrm {A}}$ extracted through $C$ – $V$ fitting presents an apparent decreasing trend from $3.8\times 10^{19}$ to $1.1\times 10^{19}$ cm−3 with the stress time increased from 30 to 2600 s. This is assumed to be related with the defects generation in the Schottky depletion region under high tunneling current and high electric field. These analyses show the feasibility of the normally off HEMTs with a regrown p-GaN gate and AlN/SiN x stack passivation for practical applications, giving directions for further improving the gate breakdown voltage and lifetime.

A high-performance quasi-vertical GaN Schottky barrier diode (SBD) was successfully fabricated by using a high-quality n−-GaN drift layer with a precisely-controlled n-type doping. A high current on/off ratio of 1010, an ideality factor of 1.03, a low specific on-resistance of 1.41 $\text{m}\Omega \cdot $ cm2, and a relatively high breakdown voltage (BV) of 250 V have been achieved for the SBD without edge termination. Furthermore, with an Argon-implanted termination, the as-fabricated GaN-on-Si SBD shows a record high BV of 405 V, yielding a critical electric field of ~ 2 MV/cm, while the forward conduction characteristics are well maintained.

In this study, aluminum borate whiskers were prepared on the zirconia-toughened alumina (ZTA) substrates for the first time. This result was achieved by calcining a mixture of B2O3 powders with and without adding the MnO2 flux in air. The morphologies of as-prepared whiskers were carefully characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The length-diameter ratio of whiskers prepared by adding MnO2 flux is larger than those prepared by using only B2O3 powders, and the growth mechanisms of whiskers follow solid–liquid–solid theory. In addition, aluminum borate whiskers were successfully used to join ZTA ceramics. By adding the MnO2 flux in the interlayer, the strength of the joints can be significantly improved. The highest flexural strength for the ZTA/whiskers/ZTA joints bonded using B2O3 + 5 wt% MnO2 powders reached 162 ± 11 MPa at 1100 °C after holding for 4 h.

The control variable method is a method to study the influence of a certain factor on the result quantity by artificially controlling other factors. Some researches have shown that a micro-texture can effectively reduce the surface work-hardening degree of the tool surface. Therefore, in this study, based on the control variable method, a micro-texture ball-end milling cutter was used to mill titanium alloy. The influence rules of micro-texture distance from edge, micro-texture distribution type and mode and cutting stroke on work hardening degree were analysed. The results show that the surface work-hardening degree was the smallest(118%) at a distance of 90 μm from the cutting edge and at a 0.3° offset angle. When the micro-texture is micro-pit texture, the work hardening degree is 121% and is minimum. The content of the O element in the surface modification layer of the micro-textured tool is 6.97%, which is less than 16.17% of that of the non-textured tool, and the content of the C element is 4.95% and 4.97% respectively. The results show that the micro-texture placement can effectively reduce the oxidation degree and work hardening degree of the machined surface of the milled titanium alloy.

Given the serious work hardening phenomenon, high chemical activity, severe tool wear, and poor workpiece surface quality during the cutting of titanium alloys, placing micro-texture on the tool surface decreases the tool-chip contact area and friction and plays the role of wear resistance and friction reduction. In order to improve the cutting performance of cutting tools, the present study examins the effect of micro-texture parameters of a cemented carbide ball-end milling cutter on cutting force, tool wear, and workpiece surface roughness and establishes a regression analysis model via regression analysis. We consider the cutting performance of a cemented carbide micro-texture ball-end milling cutter as an evaluation standard. A genetic algorithm is applied to the multi-objective optimization of micro-texture parameters, and a regression analysis model of micro-texture design criteria is established. This provides a standardised reference to select standard micro-texture parameters in the design and preparation of a cemented carbide micro-texture ball-end milling cutter.

Titanium alloys is a typical difficult-to-cut material with many machining problems, build-up-edge, large cutting force, and high cutting heat. Previous research has shown that micro-texture on the tool surface can solve the above problems potentially, and that a blunt round edge of the cutting tool can enhance its strength and improve the tool wear resistance. Therefore, towards an optimal parameter of micro-texture and blunt round radius, a finite element method (FEM) simulation and an experiment are carried out, where the test result provides a set of data for a genetic algorithm–based prediction model. The optimized parameter combinations of the micro-textured ball-end milling cutter with a blunt round edge are obtained and compared in a set of experiments. The optimized parameters refer to a 40-μm radius of the blunt round edge, a 40-μm micro-texture diameter, a 175-μm spacing, a 120-μm distance from the cutting edge, and an 80-μm depth.

Normally-off HEMTs have been fabricated with regrown p-GaN gate and SiNx passivation by Low-pressure chemical vapor deposition (LPCVD) using an AlN pre-layer, featuring a high-temperature passivation-first technique with no incompatibility issues. Through careful surface treatments, high-quality interfaces (regrown p-GaN/AlGaN and SiNx/AlGaN), as well as a stable p-GaN contact, can be achieved, enabling a robust gate operation and improved dynamic performance. The as-fabricated device exhibits a low reverse gate leakage of 2 nA/mm @ VGD = −200 V, a stable forward gate current of $10~\mu \text{A}$ /mm @ VGS = 5 V, a positive threshold voltage of +1.7 V @ ${I}_{\text {DS}} = {10}\,\,\mu \text{A}$ /mm with a high saturation current of 435 mA/mm, a high Ion/Ioff ratio of ${5}\times {10}^{10}$ , and a low Ron,d/Ron,s ratio of 1.5. The as-developed technique with the LPCVD SiNx passivation and p-GaN gate regrowth may provide a way to enhance the performance of p-GaN E-HEMTs.

In this letter, a composite barrier heterostructure containing a “10-nm-thick GaN insertion” was specially designed and produced for normally-off GaN high-electron-mobility transistor. Based on this structure, a novel self-terminated gate recessing technology by thermal decomposition combined with a dry etching has been successfully developed to achieve a low density of interface states and a high uniformity across the wafer. Compared with the conventional dry etching approach, the uniformity of the gate recessing self-terminated at the bottom AlGaN surface was greatly improved with the standard deviation (Std. Dev.) reduced from 1.42 to 0.5 nm. Moreover, this technology almost completely removed the surface damage induced by the dry etching and effectively reduced the surface oxygen contamination. As a result, the frequency-dispersion of C-V characteristics has been significantly suppressed, and the density of interface states was reduced from $\sim 10^{13}$ to $10^{11}\sim 10^{12}\mathrm{e}\mathrm{V}^{-1}\cdot \mathrm{c}\mathrm{m}^{-2}$. This novel technology with a further optimization paves the way for preparing high performance normally-off GaN HEMTs with a gate dielectric or p-GaN gate.

When precision cutting titanium alloy, the cutting part of cutting tool is mainly concentrated in the cutting edge area, so there is a strong emphasis upon the cutting edge’s geometric parameters. Studies have found that putting a micro-texture on the cutting surface can reduce the cutting force. This article looks at the milling force involved in cutting titanium alloy with a micro-textured ball-end milling cutter with different shaped cutting edges. First, a milling model relating to different cutting edges is established based on the traditional model of milling force. Then, the effects of different cutting edge geometry parameters and micro-texture parameters on milling force are simulated and tested using a finite element method. With milling force serving as the evaluation index, the optimum micro-texture parameters for a blunt circular cutting edge are a micro-pit diameter of 40 μm, a distance between micro-pits of 175 μm, a distance from the cutting edge of 110 μm, and a blunt circle radius of 60 μm. For a negative chamfer edge, the optimum parameters were a micro-pit diameter of 50 μm, a distance between micro-pits of 175 μm, a distance from the cutting edge of 120 μm, an edge width of 200 μm, and an edge angle of 10°.

A high temperature is produced in the process of precision milling of titanium alloy, and the cutting temperature can be effectively reduced by placing a micro-texture on the tool surface. In order to study the milling temperature of micro-textured ball-end milling cutter in milling titanium alloy under the combined action of a blunt radius with different edges and a micro-texture with different parameters, a new method based on micro-element theory and the generation and transmission of cutting heat has been established. At the same time, the influence of different radii of blunt edges on the milling temperature is simulated by the finite element method and experimentally verified to explore the influence of different radii of a blunt edge and micro-texture parameters on the milling temperature. Taking the milling temperature as the evaluation index, the optimum parameters of micro-circular pit texture are as follows: the diameter of micro-circular pit is 40 micron, pit spacing is 225 micron, distance from cutting edge is 100 microns, and radius of the blunt edge is 60 microns.

This experimental study presents the rheological properties and strength characteristics of cemented unclassified tailings backfill (CUTB). The particle size distribution and chemical properties of tailings from the Shizhuyuan lead-zinc mine were examined experimentally. A series of rheological properties and uniaxial compressive strength (UCS) tests were conducted to study the relations between the rheological properties of CUTB and two factors of cement-tailings ratio (c/t) and solid content (SD). The two-factor nonrepetitive analysis of variance (ANOVA) method was used to study the sensitivity of rheological properties to two factors of c/t and SD. Relations between UCS performance of CUTB and c/t, SD, and curing time (CT) were discussed. Results indicate that CUTB samples exhibit obvious shear thinning characteristics and the rheological process is the result of multiple rheological model composites. Yield stress and viscosity of CUTB increase with the increase of SD and c/t as quadratic. The solid content is the most important factor for the rheological properties of CUTB, followed by c/t. UCS of CUTB increases exponentially with the increase of SD and increases with c/t as quadratic. The larger the ratio of c/t, the greater the influence of the CT on the increasing strength of CUTB. The smaller the c/t, the slower the increase of the CUTB’s strength with the increase of the SD. The findings of this study can provide the efficient mix proportion of backfill slurry for the backfill mining design, so as to have better performance of the underground mining structure and reduce the cost of backfill mining.

The aim of this investigation was to study the formation of white etching layer (WEL) induced by rolling contact fatigue (RCF) in a bearing steel. Through sectioning a failed bearing, the microstructure of the WEL was investigated using optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and micro indentation test. The result showed that the WEL is harder than the matrix. It consists of refined grains of martensite, austenite and carbides. In contrast to the thermally-induced WELs, where the austenite is the result of phase transformation due to austenitization, the austenite in the WELs of the current study comes from the original retained austenite. No phase transformation occurred, indicating that the WEL was formed under deformation induced the mechanism. WELs and white etching areas (WEAs) were compared in detail. The result suggested that WELs and WEAs are actually the similar responses to large shear deformation in RCF of martensitic bearing steels.

We put forward a novel strategy for joining zirconia-toughened alumina (ZTA) ceramics using whiskers reinforced borosilicate glasses for high-temperature (HT) applications. Herein, the robust joining of ZTA ceramics by using B2O3-Al2O3-SiO2 (BAS) glasses as an interlayer was achieved in air at 1400 °C. The Al18B4O33 whiskers were generated in the joining seam during the joining process, thus strongly improving the HT strength. The flexural strength of the joint after the thermal cycle test at 1200 °C could still reach 84 % of that at room temperature (RT). The joining mechanism was mainly addressed from the perspective of the in-situ growth of whiskers.

Wind turbine gearbox bearings fail with the service life is much shorter than the designed life. Gearbox bearings are subjected to rolling contact fatigue (RCF) and they are observed to fail due to axial cracking, surface flaking, and the formation of white etching areas (WEAs). The current study reviewed these three typical failure modes. The underlying dominant mechanisms were discussed with emphasis on the formation mechanism of WEAs. Although numerous studies have been carried out, the formation of WEAs remains unclear. The prevailing mechanism of the rubbing of crack faces that generates WEAs was questioned by the authors. WEAs were compared with adiabatic shear bands (ASBs) generated in the high strain rate deformation in terms of microstructural compositions, grain refinement, and formation mechanism. Results indicate that a number of similarities exist between them. However, substantial evidence is required to verify whether or not WEAs and ASBs are the same matters.

The influence of traps on the reverse gate leakage has been studied for two kinds of normally-off high-electron-mobility transistors with regrown p-GaN gate. Different acceptor traps in the p-GaN/AlGaN/GaN junction dramatically impact carrier behaviors, affecting the leakage mechanisms. The reverse gate current of the normal devices with a low density of traps which located at EV + 0.6 eV is dominated by Poole-Frenkel process. For the abnormal devices, a high density of new traps have been confirmed with an energy level of ~ 0.8 eV, resulting in a trap-assisted tunneling thus a relatively high reverse gate leakage.

This Letter studies the reverse leakage and breakdown mechanisms of vertical GaN-on-Si Schottky barrier diodes (SBDs) with and without argon-implanted termination (ArIT). The electrical leakage characteristics in the vertical GaN-on-Si SBD without edge termination sequentially go through the thermionic field emission, variable range hopping (VRH), and trap-assisted tunneling conduction mechanisms as the reverse bias increases gradually. Its leakage and breakdown mechanisms are limited by the edge electric field crowding effect. While for the vertical GaN-on-Si SBD with ArIT (ArIT-SBD), the electrons conduction at a low reverse bias, following the space-charge-limited conduction (SCLC) model, is limited by the damage-induced traps in the implanted GaN. As the reverse bias increases up to the occurrence of breakdown, the VRH and SCLC dominate the leakage mechanism of the ArIT-SBD, which stem from intrinsic traps in GaN grown on Si. A rapidly growing leakage under a low reverse bias and enhanced breakdown voltage performance in the ArIT-SBD is attributed to the charging of the damage-induced traps in implanted GaN. This Letter not only gives in-depth insights of vertical GaN-on-Si SBDs but also provides a useful design guidance of implanted termination for high-voltage power devices.

The influences of porosity on thermal radiation were studied for enhancement of light absorption in porous silicon (pSi) photonic crystal (PhCs). A 2D concept of unit-cell for square and triangular lattice of circular air holes was formulated and solved using plane wave expansion (PWE) technique and Fourier expansion method. The spectral energy density (SED) of the thermal radiation at different porosity consideration of silicon PhC was investigated for both mentioned lattices including the effect of these lattice structures in the creation of photonic band gaps. It revealed useful to increase the number of frequency band gaps by subjecting the PhC to a square lattice at low porosity. Moreover, a triangular lattice beyond 50% of porosity would be suitable in thermal radiation control where the band gap stabilization applications are required.

The purpose of this investigation was to study microstructural evolution leading to the formation of wear debris and white etching areas (WEA) in the subsurface of AISI 52100 steel during rolling contact fatigue (RCF). The specimens were tested using a roller-on-roller geometry testing machine. Surface damage was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Lamellar structures generated during the rubbing of crack faces give a clear picture of how wear debris is formed. In contrast to the previously reported WEA, which is composed of nano-ferrites generated under the mechanism of recrystallization, the WEA produced in the current RCF condition consists of an amorphous phase with nanocrystallites dispersed. Based on this, it is proposed that WEA can be classified into deformed WEA and transformed WEA depending on whether phase transformation occurs. In addition, the relationship between white etching crack (WEC) and WEA was discussed in detail. The result suggests that WEC does not initiate WEAs as it has been accepted. Instead, they form under different mechanisms.

This work studied the effect of thermal cleaning in metal–organic chemical vapor deposition (MOCVD) prior to p-GaN gate regrowth for normally off high-electron-mobility transistors. X-ray photoelectron spectroscopy, capacitance–voltage measurement, and atomic force microscopy were employed to identify the effects of thermal cleaning before p-GaN regrowth. It was found that the residual damage was hardly repaired at a relatively low thermal cleaning temperature, while GaN decomposition would occur at an excessively high temperature. Thermal cleaning at 850 °C for 2 min in MOCVD can effectively remove the surface contamination and alleviate the etch damage without causing any significant deterioration of the AlGaN barrier. In addition, the density of interface states (Dit) in the p-GaN gate was reduced from 1012–1013 to 1011–1012 eV–1·cm–2, resulting in a low gate reverse leakage of 0.1 nA/mm @ VDS-OFF = 180 V, a high Ion/Ioff ratio of 4 × 1010, and a relatively high threshold voltage of +1.7 V @ ID = 10 μA/mm.

Failure analysis of cracking of a GIS aluminum shell which causes SF6 gas leak in a 220 kV substation was present. Visual inspection, microstructure observation, chemical composition and mechanical properties characterization were performed to reveal the forming mechanism of the crack. It is found that the crack is located in the region of the aluminum alloy shell that undergone welding repair. The crack is continuous and develops within the weld metal. Detailed investigation reveals that the crack initiates by the defect of lack of fusion in the welding repaired zone. The working stress induced by gas pressure, combined with the residual stress and vibration stress, results in the extension of the crack and the final leaking of SF6 gas.

White etching area (WEA) has become a big challenge for bearing failure under rolling contact fatigue. Despite of the extensive investigations, the origin of the WEA has not yet been well understood. This work attempts to elucidate the origin based on a new perspective that both the WEA and the shear band (SB) can be the common responses under shear plastic deformation in bearing steel, rather than the unique phenomenon in rolling contact fatigue. First, the SB is generated under quasi-static compression loading, indicating that the SB does not necessarily have to be adiabatic and is not limited to high strain rate loading. Second, the WEA is produced under rolling contact fatigue. The SB is compared with the WEA in terms of shear localization, microstructures, formation mechanism and crack development. The results suggest that both the SB and the WEA can be regarded as the shear localization under large plastic deformation. The SB consists of either nanocrystallines or well-developed equiaxed grains with transformed austenite. The WEA consists of either nanocrystallines or a mixed structure of amorphous phase and nanocrystallines with transformed austenite. Connecting the WEA with the SB provides a new insight into interpreting the origin and formation mechanism of the WEA, and help the further understanding of bearing failure under rolling contact fatigue.

A room-temperature method to determine the trap energy levels in the carbon-doped (Al)GaN buffers is developed via a transient current measurement on the AlGaN/GaN high electron mobility transistors under back-gate voltages combined with a measurement of the buffer vertical leakage. Under high back-gate voltages, a linear relationship is obtained between the trap energy levels and the square roots of electric field strength, suggesting that the vertical conduction in the C-doped buffer follows the Poole–Frenkel law. The trap energy level in C-doped Al0.07Ga0.93N is finally determined to be 1.1 eV through the established room-temperature approach, while that in C-doped GaN is extracted to be 0.9 eV, both of which are related to the carbon impurities.

In the study of metal surface friction, microtextured surfaces have been shown to reduce the surface friction coefficient, However, the influence of microtexture preparation parameters on its surface wear rate is rarely considered. In this paper, the effects of microtexture preparation parameters were studied by detecting elements in the area around the microtexture. Through friction experiments, the relationship between different microtexture preparation parameters and the surface wear rate of cemented carbide was studied. After three stages of experiments, it is concluded that the laser power has an important effect on the surface wear rate of microtextures. In addition, the interaction between laser power and microtexture diameter has a great effect, but gradually decreases with increasing friction distance. Finally, a wear prediction model for carbide microtextured surfaces with different preparation parameters was established, the results can provide a reference for the application of microtextured surfaces in cutting tools.

The sliding wear-induced grain coarsening of nano laminated structure in a martensite steel was investigated by using Transmission Electron Microscopy (TEM) and transmission Kikuchi diffraction (TKD). Microstructure was initially refined into nano laminated structure by dry sliding. In the subsequent lubricated sliding, the nano laminated structure became coarsened instead of being continuously refined. Equiaxed grains and subgrains were observed in the laminated structure under 60 min dry + 60 min lubricated sliding, as compared to the coarsened but still remained lamellar structure under 120 min dry + 60 min lubricated sliding. In contrast to the grain refinement, which was mechanically driven but thermally assisted, the grain coarsening was mechanically dominated without involving the thermal effect. The nano laminated structure did not show strong texture before and after coarsening. The continuous grain growth occurred even if the stress was reduced in the lubricated sliding. The high density of triple junctions in the nano laminated structure promotes grain boundary motion, facilitating the grain coarsening.

Reliable joining of ZrO2 ceramic to TiAl alloy is crucial for the success of the engine industrial application. However, there have been few systematic investigations on joining of ZrO2 ceramic and TiAl alloy. In this study, reliable brazing of ZrO2 ceramic and TiAl alloy was achieved using inactive AgCu filler metal. The interfacial microstructure of the joints was characterized by SEM, XRD and TEM. Effects of holding time on the microstructure and mechanical properties of the joints were investigated in details. The results revealed that Cu3Ti3O + TiO layers were formed adjacent to ZrO2 ceramic while AlCu2Ti layer was formed at TiAl substrate. The thickness of Cu3Ti3O + TiO layers increased and the granular AlCu2Ti coarsened gradually with the prolongation of holding time. The hardness and Young's modulus of reaction phases were characterized by nano-indentation to reveal the plastic deformability. The highest shear strength of 48.4 MPa was achieved when brazed at 880 °C for 10 min. Keywords: TiAl alloy, ZrO2 ceramic, Brazing, Interfacial microstructure, Mechanical properties

Six machine learning methods, including artificial neural network, gradient boosting regression, random forest, etc. were used to conduct a comparative study of building chemical composition-hardenability model for wear resistant steel. The results indicated that artificial neural network method with 32 × 32 × 32 structure had the highest prediction accuracy among the six machine learning methods based on our study. Through Pearson’ s linear correlation heat map and the feature importance parameter in the gradient boosting regression method, the contributions of different alloying elements on hardenability could be predicted, which guided us to design the further chemical composition. Finally, a reverse microalloying design based on the target performance was carried out with the artificial neural network model and an end quenching experiment using actual steel was used to evaluate the performance of model. The predicted results, calculated results and experimental results were consistent. The combination of material data base and machine learning provided an efficient approach to design the chemical composition of steels.

Magnetic ferrite/biochar composites are a kind of promising adsorbents due to their high adsorption efficiency and facile magnetic separation; however, their synthesis is associated with high cost and secondary environmental impacts. In this study, a novel Mn–Zn ferrite/biochar composite (MZF-BC) is synthesized via a green two-step biocheaching and hydrothermal method using waste batteries and pine sawdust. Characterization results indicate that the introduced Mn–Zn ferrite particles are successfully embedded and coated on biochar (BC), and synthesized MZF-BC50 with 50% BC content exhibits best performance with a specific surface area of 138.5 m2 g−1, the saturation magnetization of 27.5 emu g−1 and CEC value of 53.2 mmol 100 g−1. The maximum adsorption capacity of Pb2+ is 99.5 mg g−1 based on the Langmuir sorption isotherm study at 298 K, and pseudo-second-order model accurately describes the adsorption process. Regeneration test suggests that MZF-BC50 can be efficiently reused for 6 cycles. In addition, it exhibits a good selective Pb2+ and Cd2+ removal performance in lead-acid battery wastewater. The results illustrate that this newly developed material has low cost and rapid remediation of Pb2+ as good application potential.

It is a big challenge to identify whether or not a high temperature rise at high strain rate is a prerequisite for shear instability in crystalline materials. In contrast to the prevailing report of shear instability at high strain rate loading, the shear band (SB) was generated at quasi-static loading in a martensite steel. This gives strong evidence that the high temperature rise is not essential as the quasi-static loading is not able to generate enough heat to initiate the shear instability. Different from the conventional narrow SB at high strain rate loading, a large patch of SB was firstly observed. Considerably localized melting occurred due to the abrupt fracture of SB. SB displays different TEM microstructures at melting and no-melting places. This indicates the significance of distinguishing the microstructure formed during shear instability from the one affected by the fracture of SB. The result suggests that the strain localization mechanism in this material is attributed to the microstructural change instead of the thermal softening. The findings provide a new insight into understanding the formation mechanism of SB from the perspective of microstructural evolution in crystalline materials.

The evolution of nano-laminated structure generated in dry sliding wear of a high strength martensite steel was investigated by using Scanning Electronic Microscopy (SEM) and Transmission Electron Microscopy (TEM). Gradient microstructure along the depth was observed with the top layer consisting of nano-laminated structure. During the sliding wear-induced plastic deformation, grains were refined and lamellar structures were formed as a result of generation of dislocation cell blocks bounded by geometrically necessary boundaries (GNBs) and incidental dislocation boundaries (IDBs). With increasing plastic shear strain and strain gradient, there is a continuous reduction in the spacing and length in dislocation cell blocks, leading to nano-laminated structures. The ultrafine nano-laminated structure with laminate spacing of 20 nm was observed at the sliding time of 120 min. However, the grain refinement is not a merely mechanical deformation process. The formation of Fe3O4 and FeO gave direct evidence that the highest temperature due to frictional heat could reach up to 600 °C. The result suggested that the formation of nano-laminated structure was governed by thermally-assisted plastic deformation.

With the rapid development of the supersonic aircraft technology, the aircraft Mach number continues increasing, but on the other hand, the working condition becomes progressively poor. The photonic crystals (PCs) material could reflect the energy of the thermal radiation effectively and prevent heat transferring into the substrate due to its low thermal conductivity. Consequently, the PCs material could be applied to thermal protection for the supersonic aircraft. In this paper, the aircraft state of Mach 5 is set as the target operating condition, and the PC thermal protection ability is simulated by the method of computational fluid dynamics. Based on the theory of the electromagnetics, the characteristics of the photonic band gaps for three-dimensional PCs are calculated and the effects of PCs' medium radius, refractive index, and lattice constant are fully taken into account. For the three-dimensional diamond PCs' structure, two major categories and totally five optimized design schemes are proposed, through combining the condition of supersonic aircraft aerodynamic heating. Results show that the temperature is reduced by 948.4 K when the heat passes through thermal protection layer and reduced by 930.4 K when the heat passes through PC layer. By the method of “coupled optimization strategy (COS),” the energy density which enters into substrate material would decrease by 7.99%. In conclusion, the thermal protection capacity for supersonic aircraft could be effectively improved by using the PCs.

The electronic interaction between metal and supports can regulate the activity of heterogeneous nanomaterials. We designed four supported Pd catalysts (Pd/ZnO, Pd/TiO2, Pd/Al2O3 and Pd/SiO2) for the electrocatalytic activity toward the formic acid oxidation reaction (FAOR). The electrochemical results demonstrate that Pd/ZnO exhibits superior electrocatalytic activity toward FAOR, which can be attributed to the decreased electron density of ZnO-supported Pd nanoparticles, as further confirmed by X-ray photoelectron spectroscopic characterization and CO stripping electrochemical measurement. This study provides an effective method for the design of high-efficiency electrocatalysts, which could be also useful for studying the surface electronics of supported metal-nanoparticle. Keywords: Electronic metal–support interaction, Pd nanoparticles, Electron density, Formic acid oxidation reaction, Electrocatalysis

In this letter, the Ta/HfO x /BN/TiN resistive switching devices are fabricated and they exhibit low power consumption and high uniformity each. The reset current is reduced for the HfO x /BN bilayer device compared with that for the Ta/HfO x /TiN structure. Furthermore, the reset current decreases with increasing BN thickness. The HfO x layer is a dominating switching layer, while the low-permittivity and high-resistivity BN layer acts as a barrier of electrons injection into TiN electrode. The current conduction mechanism of low resistance state in the HfO x /BN bilayer device is space-charge-limited current (SCLC), while it is Ohmic conduction in the HfO x device.

Transport in porous media is common in nature, attracting many attentions for a long time. Tree-like network model is often used as a simplification for porous space, expressing the complexity of pore spaces instead of capillary bundle. To investigate spontaneous imbibition characteristics in this network, a dynamic asymmetric branch-like capillary model is used to represent basic network structure, using fractal method to represent tortuosity. This work investigates the influence of parameters on imbibition process in the branch-like capillary model. An analytical equation for the imbibition mass versus time is derived. Parameters from capillary structures to liquid properties are taken into account and analyzed based on the numerical solution of the equation. It is found that the imbibition process in asymmetric branch-like capillary model can be recognized by four sections and brunching tubes are positive for imbibition process. Concomitantly, meniscus arrest event is simulated and discussed. Moreover, the influence of parameters on imbibition process is discussed. These parameters can be classified as static and dynamic. Static parameters mainly change the capillary force, which are related to the ultimate imbibition mass or imbibition ability, while dynamic parameters mainly have influence on resistance of flowing fluid, which are related to the imbibition speed in the imbibition process.

A novel biomass-coated Ag nanoparticle-modified TiO2 composite was prepared and used as a photoanode in a dye-sensitized solar cell with a high surface area, strong light scattering and efficient electron transport. It was found that syzygium extract has an appreciable effective function as a reducing and stabilizing agent simultaneously. The mean size of the synthesized silver nanoparticles is 4.0 ± 0.7 nm measured on the TEM images. Residual hydroxyl groups of the biomass on the photoanode improve dye absorption and electron injection efficiency. The syzygium-Ag–TiO2 DSSC exhibits the best performance with a short-circuit current of 11.8 mA cm−2 corresponding to a photoelectric conversion efficiency of 5.12%, which is higher than the glucose-Ag–TiO2 and UV-Ag–TiO2 DSSCs, and much higher than the blank DSSC.