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Twinning is an essential plastic deformation mechanism in hexagonal-close-packed (HCP) metals, where the number of operative dislocation slip systems is limited. Twinning plays an important role in governing the balance between strength and ductility of the materials. The {10-12} and {11-21} twinning are two commonly observed tension twins, and will be the focus of this dissertation. The nucleation and growth are the two stages of the twin formation process, understanding the mechanisms behind which facilitates the study of the mechanical properties of the HCP metals and gives guidance to the alloy design strategies.Grain boundaries and dislocation pile-ups have always been thought of as the most possible twin nucleation sites, but there is a lack of experimental evidence and theoretical understanding of the twin nucleation mechanism from a single lattice dislocation. In this dissertation, a combined experimental and theoretical study of twin nucleation from a single dislocation in HCP crystals is presented. Specifically, high-resolution transmission electron microscopy has been used to identify {11-21} twin nuclei in HCP rhenium, and provided evidence of their nucleation from a dislocation. An anisotropic elasticity model of dislocation dissociation, parametrized by density functional theory calculations, provides conditions for twinning disconnection nucleation and propagation, necessary for the {11-21} twinning mechanism to be operative. The analysis serves to advance our understanding of the origin of the unique predominance of {11-21} twinning in rhenium, which correlates with the high strength and ductility of this metal. The model also provides new insights into design strategies that may be effective in activating this twinning mode and enhancing the balance between strength and ductility in HCP alloys more broadly.This dissertation also explores twin thickening. Twin thickening requires that the twin grows normal to the K1 plane. Molecular dynamics simulations are used to investigate {10-12} and {11-21} twin thickening processes through spontaneous twinning disconnection (TD) formation under applied shear deformation with a constant strain rate, based on an embedded-atom-method potential model of Zr. The stress responses and twin boundary (TB) structure changes verify that both twins thicken through TD formation. However, the thickening process of {10-12} and {11-21} twins differ in significant ways. While {10-12} TD loops were observed to form and expand during the twin thickening process, the {11-21} TB exhibits a more structurally disordered interface throughout the simulation and no sharp boundary corresponding a {11-21} TD ‘loop’ can be recognized, i.e., the TD for this TB is structurally rough. Moreover, the {11-21} twin requires a much lower critical shear stress for twin thickening. The low critical shear stress of {11-21} twin thickening also indicates that these twins should grow easily once nucleated. To the extent that these results apply to HCP materials more generally, the promotion of {11-21} twin nucleation may be an effective way to enhance twinning deformation and twin boundary related work hardening in HCP materials, with the potential to enhance the strength and ductility combination.

In order to investigate the seismic behavior of the hybrid coupled partially encased composite (PEC) wall system, two 2/3-scale three-story specimens with different elastic coupling ratios (CRelastic) were tested under cyclic loading. The results showed that the hysteretic curves of the two specimens were full and stable, indicating their robust cyclic performance and excellent energy dissipation capacity. Under reversed cyclic lateral loading, the specimens exhibited a two-stage yielding energy dissipation mechanism, in accordance with theoretical expectations. Both specimens dissipated a large amount of energy during loading, with the equivalent viscous damping ξeq reaching 0.32 and 0.35 at the maximum displacement level, respectively. Based on the experimental results, the refined finite element model for the hybrid coupled PEC wall was established in ABAQUS and validated. A parametric analysis demonstrated that the CRelastic and the design axial compression ratio (n) had significant influences on the seismic behavior of the hybrid coupled PEC wall. With increasing CRelastic, the lateral stiffness, strength, and yield displacement of the hybrid coupled PEC wall gradually increased, while its ductility deteriorated. Moreover, the ductility of the hybrid coupled PEC wall decreased with increasing n owing to the strong coupling action of the steel coupling beams. In order to ensure the good seismic performance and form a reasonable failure mode, the CRelastic and n in the hybrid coupled PEC wall should not exceed 65% and 0.5, respectively.

In this work, Sentaurus TCAD was used to study the transient surge current mechanism of the 4H-SiC merged pin and schottky (MPS) diode. For the first time, a structure combining multicells with transition region was used to analyze the transient surge current mechanism of the MPS diode. The electrothermal simulation analysis of the surge characteristics of the MPS diode is carried out. Internal carrier distribution and lattice temperature in the surge current transient process of the device are mainly studied. The simulation results show that the hole current distribution and the electron current distribution in the MPS diode are not uniform. In the transient process of surge current, the transition region first enters the bipolar conduction mode, and then, the cells in the active region enter the bipolar conduction mode in the order from outside (close to transition region) to inside. The voltage-time (V-t), maximum temperature-time ( $T_{max}$ -t), and I-V curves of MPS diode in surge current events are obtained by simulation. Combined with the current density distribution diagram, the device behavior of multiple critical time nodes is analyzed in detail, and a reasonable explanation is given. In addition, the influence of different transition region contact types on the internal current distribution of the MPS diode is studied, and the simulation results are reasonably explained.

The ${I}$ – ${V}$ characteristics of 4H-SiC N/P-channel MOSFETs have been carried out at high temperatures up to 300 °C. Different scattering mechanisms of surface mobility for 4H-SiC N-channel MOSFETs have been studied in this article. Moreover, the temperature dependencies of various scattering mobilities for P-channel MOSFETs are given for the first time. Their temperature dependencies were simulated and analyzed at a temperature ranging from 27 °C to 300 °C. Furthermore, an improved method of extracting trapped charge from transfer characteristic is proposed, such that the density of occupied interface traps in a strong inversion can be extracted. The analysis of experimental results shows that sacrificial oxidation can decrease the occupied interface traps at high temperatures but not much effective at room temperature, and the Coulomb scattering in 4H-SiC P-channel MOSFETs has always been the main mechanism from 27 °C to 300 °C, which is different from 4H-SiC N-channel MOSFETs.

Mg-air batteries are explored as the next-generation power systems for wearable and implantable electronics as they could work stably in neutral electrolytes and are also biocompatible. However, high corrosion rate and low utilization of Mg anode largely impair the performance of Mg-air battery with low discharge voltage, poor specific capacity and low energy density. Here, to the best of our knowledge, we first report a dual-layer gel electrolyte to simultaneously solve the above two problems by preventing the corrosion of Mg anode and the production of dense passive layer, respectively. The resulting Mg-air batteries produced an average specific capacity of 2190 mAh g-1 based on the total Mg anode (99.3 % utilization rate of Mg anode) and energy density of 2282 Wh kg-1 based on the total anode and air electrode, both of which are the highest among the reported Mg-air batteries. Besides, our Mg-air batteries could be made into a fiber shape, and they were flexible to work stably under various deformations such as bending and twisting.

SiC MOSFET integrated with Schottky barrier diode (SBD) can handle the reverse current during switching operation and reduce the package cost. However, the integrated SBD weakens the high-voltage-withstanding capability of the SiC MOSFET. In this article, a novel 4H-SiC trench MOSFET integrated with mesa-sidewall SBD (TMS-SBD) is proposed and studied with the 2-D simulation. Compared with the trench MOSFET integrated with the SBD locating on the mesa (TM-SBD), the TMS-SBD shows a larger breakdown voltage (BV), a lower electric field in the gate oxide, and a better tradeoff between BV and specific ON-resistance. The TMS-SBD also shows the same current capability as that of the TM-SBD. Due to the removal of one sidewall overlap between the gate electrode and drain electrode, the reverse capacitance of TMS-SBD is lower than that of the TM-SBD. In double-pulse test simulation, the turn-on loss and turn-off loss of the TMS-SBD reduce by 30% and 56% than those of the TM-SBD, respectively. Therefore, the TMS-SBD is a more attractive device in high-voltage, high-reliability, and low-switching-loss applications.

This paper proposes an innovative externally-hung self-centering rocking wall (ESRW) structural system for retrofitting existing reinforced concrete structures. Reinforced corbels are installed on the columns of an existing structure to which rocking walls having unbonded post-tensioned tendons are connected using H-shaped connectors. The seismic performance and self-centering ability of the ESRW were investigated through a series of shaking table tests. For comparison, an unretrofit control structure (UCS) was also tested. The UCS was severely damaged under peak ground acceleration (PGA) = 1.2 g test conditions: some reinforcing bars were fractured and the UCS was close to collapse. For the ESRW, the damage was significantly reduced: there were only minor cracks appearing at PGA = 1.5 g test conditions and no damage appeared at the corners of the rocking walls. The maximum story drift and residual deformation of the ESRW were reduced 88% and 92%, respectively, relative to the UCS test. The ESRW structure showed desirable seismic performance and self-centering characteristics during shaking table tests.

In this article, the single-event response of the 1.2-kV silicon-carbide (SiC) power MOSFETs with varied buffer layer designs is investigated by the 2-D numerical simulations. The structural parameters of the buffer layers are compared and analyzed to understand the transient response after the heavy ion strike and the related physical mechanisms comprehensively. Simulation results reveal that an optimized single buffer structure can be acquired by using a relatively thicker buffer layer (T $\mu \text{m}$ ) and a moderate doping concentration (D cm−3). It demonstrates that the single-event-burnout (SEB) performance can be improved significantly under the worst case bias conditions [a drain bias voltage of 1.2 kV and a linear energy transfer (LET) of 1 pC/ $\mu \text{m}$ ]. In addition, the optimized structural combinations adopted in the dual or triple buffer layers can strengthen the SEB performance further. The simulation results show that a step electric field distribution is established inside the optimized dual or triple buffers, where the electric field peak is mitigated from 3 to 2.2 MV/cm. Moreover, the excess carrier generation is suppressed and the local temperature rise is weakened during the transient electrothermal process. Consequently, the structure with the optimal buffer layer designs can enlarge the SEB safe operating area (SOA) from 30%–50% to 100% rated breakdown voltage at high LET bias, which makes the SiC power MOSFETs used in aerospace and aviation power electronic systems become possible.

This paper proposes a hybrid coupled partially encased composite (PEC) wall system, obtained through the connection of two PEC walls by means of the shear critical steel coupling beams with an innovative welded connection. This structural solution is designed to take advantage of both the stiffness of the PEC walls (required to limit building damage under frequent earthquakes) and the ductility of the steel coupling beams (necessary to dissipate energy under medium-intensity and high-intensity earthquakes). The connection performance of an innovative rigid joint with different configurations in this system is studied through pseudostatic analysis, and the seismic performance of the proposed hybrid coupled PEC wall system is evaluated through multirecord nonlinear dynamic analysis of a set of case studies. Adopted finite element models are developed and validated against the available experimental results. A summary of the results is presented and discussed to highlight the potential of the proposed hybrid coupled PEC wall systems. The key feature of this system is development of a reasonable two-level yielding mechanism (the first level is the yielding of the coupling beams, and the second level is the yielding of the PEC wall) without damage to the welded joints.

Economical and highly effective catalysts are crucial to the electrocatalytic hydrogen evolution reaction (HER), and few-layer black phosphorus (phosphorene) is a promising candidate because of the high carrier mobility, large specific surface area, and tunable physicochemical characteristics. However, the HER activity of phosphorene is limited by the weak hydrogen adsorption ability on the basal plane. In this work, optimal active sites are created to modulate the electronic structure of phosphorene to improve the HER activity and the effectiveness is investigated theoretically by density-functional theory calculation and verified experimentally. The edges and defects affect the electronic density of states, and a linear relationship between the HER activity and lowest unoccupied states (ε

Poor calculation efficiency is a major issue in the investigation of time-domain aerodynamics of turbomachinery bladings by fluid–structure coupling. In this work, a numerical methodology f...

In this Letter, a 1.2 kV SiC power MOSFET with a partially widened retrograde P-well (RP) structure and N-implanting region is proposed to enhance the device's reliability. Compared with the conventional SiC power MOSFET, the short circuit (SC) ability of the proposed structure can be improved effectively without sacrificing other performance. Simulation results reveal that a 40% reduction of the SC saturation current can be achieved, resulting in the SC withstand time increase from 7 to 10 μs at the DC-link voltage 800 V. Moreover, a better gate oxide reliability at 1.2 kV blocking condition also can be achieved. The peak electric field at the gate oxide interface is decreased by ∼48% owing to the shielding effect of the RP structure. In addition, the fabrication technology of the proposed structure is compatible with the standard planar SiC MOSFET manufacture process only with a few additional implanting steps. Therefore, this new MOSFET structure provides a simple and effective way to optimise the reliability of the planar SiC power MOSFET.

A buried gate fin p-body insulated gate bipolar transistor (BG-Fin-P IGBT) is proposed to achieve ultralow on-state voltage drop (V CE(sat)) and good short-circuit (SC) ruggedness simultaneously. A buried gate is introduced at the bottom part of the fin structure, forming a local region with the nanoscale mesa width, which enhances the conductivity modulation effectively. Meanwhile, a relatively wide mesa width (>0.5 μm) can be adopted at the main fin structure to maintain a good SC capability. Compared to the previously reported ultra-narrow-mesas fin p-body IGBT, simulation results reveal that the V CE(sat) of the BG-Fin-P IGBT is reduced from 1.39 to 1.03 V at the current density of 100 A/cm2 without SC ability degradation. Meanwhile, more than 10 μs short circuit withstand time is enabled at the junction temperature of 423 K for all structures. Moreover, the proposed structure can avoid a fabrication difficulty of the emitter contact when a very narrow mesa width (∼30 nm) is required to achieve the ultralow V CE(sat), which brings design freedom on the device's structure.

A multi-functional polymer with aggregation-induced emission (AIE)-active salicylaldehyde azine (SA) functionality and reactive oxygen species (ROS)-responsive thioether groups is readily prepared via thiol-ene click polymerization of SA derivative diacrylate monomer, poly(ethylene glycol) diacrylate, and 3,6-dioxa-1,8-octanedithiol. The obtained AIE-active polymer exhibited an unexpected strong emission in amide solvents compared to that in other common organic solvents that was dramatically decreased by adding a trace amount of water, suggesting that the polymer could be utilized as a water trace indicator in amide solvents. In the backbone, the PEG segments make the polymer well dispersed in water and the ROS-responsive thioether groups enable this polymer as a promising ROS scavenger, with embedded SA moieties as a fluorescent indicator for the hemolysis determination. Due to the ability of SA moieties to complex with Cu2+, this AIE polymer can also be utilized as a fluorescent sensor for selective Cu2+ detection in real-world water samples. Thus, this multi-functional polymer is anticipated to be well applied in biological and environmental applications.

The static and dynamic characteristics of the 15 kV 4H-silicon carbide (SiC) p-channel insulated gate bipolar transistor (IGBT) are investigated by the numerical simulation. The effect of the JFET width $(L_{\mathrm{JFET}})$ on the blocking voltage, the on-state performance and the capacitance characteristic are analyzed particularly. As the $L_{\mathrm{JFET}}$ is 10 µm, a high blocking voltage of -15.94 kV and a forward voltage drop of -7.5 V at the forward current of -10 A can be achieved. Meanwhile, the $C_{\mathrm{ge}}$ is 1.4 nF and the $C_{\mathrm{gc}}$ is about 4 pF at the $V_{\mathrm{ce}}$ of -5 kV. Furthermore, the turn-on time is about 120 ns and the turn-off time is about 620 ns at -5 kV voltage, respectively.

The heat load caused by windage heating effect of labyrinth seals seriously influences the sealing of shaft air flow. To reveal the windage heating effect of labyrinth seals to reasonably d...

To develop wearable and implantable bioelectronics accommodating the dynamic and uneven biological tissues and reducing undesired immune responses, it is critical to adopt batteries with matched mechanical properties with tissues as power sources. However, batteries available cannot reach the softness of tissues due to high Young's moduli of components (e. g., metals, carbon materials, conductive polymers or composite materials). The fabrication of tissue-like soft batteries thus remains a challenge. Here we report the first ultrasoft batteries totally based on hydrogels. The ultrasoft batteries exhibited Young's moduli of 80 kPa, perfectly matching skin and organs (e. g., heart). The high specific capacities of 82 mAh·g-1 in all-hydrogel lithium-ion batteries and 370 mAh·g-1 in all-hydrogel zinc-ion batteries at a current density of 0.5 A·g-1 were achieved. Both high stability and biocompatibility of the all-hydrogel batteries has been demonstrated upon the applications of wearable and implantable. This work illuminates a pathway for designing power sources for wearable and implantable electronics with matched mechanical properties. This article is protected by copyright. All rights reserved.

While microbial spore production and germination of bacteria have been widely studied for their applications in animal husbandry, aquatic products, medicine, and food, few studies have investigated their use for the crack-healing of concrete. To effectively heal the cracks in concrete, studies suggest that the rate of sporulation and the germination of bacteria should be sufficiently high. This study investigates the effects of different carbon sources, nitrogen sources, Mn2+ concentrations, and external culture conditions on the sporulation rate and analyzes the effects of the pH value, heat activation, germinants, various cations, and nutrients on the germination of spores. Bacillus cohnii (B. cohnii) is chosen as the bacterium to be mixed in concrete because of its alkalophilic nature. The mineralization activity of spores after germination and the crack-healing capacity of concrete are studied. The optimal culture medium and the optimum external conditions for spore production are obtained. The total cell count and sporulation rate of bacteria obtained on this medium are 3.14 × 109 CFU/mL and 92.6%, respectively, under the optimum external conditions. The optimal pH value for the spore germination of B. cohnii is 9.7. While the cation Na+ strongly stimulates the germination of B. cohnii spores, other cations (such as K+, NH4+, and Ca2+) do not stimulate spore germination. The optimal concentration of Na+ is 200 mM. The germination rate of spores in the control group concrete specimen (room temperature 24°C) was more than 50%, thus suggesting that B. cohnii bacteria can be used in the self-healing of concrete cracks. The mineralization activity test proves that the spores of B. cohnii have a mineralizing function after germination, and the crystals produced by microbial-induced carbonate precipitation (MICP) are of pure calcite. When the crack width of the concrete specimen with spores of B. cohnii is less than 1.2 mm, it can be completely repaired after 28 days of healing.

Titanium alloys are widely used in various fields for its high strength, good corrosion resistance and high heat resistance. Many countries in the world have recognized the importance of titanium alloy materials, and have developed and applied them in practice. In order to accurately describe uniaxial tensile behavior and ratcheting behavior of material, a series of experiments of TA17 were conducted at room temperature and 350 ℃, including the uniaxial tensile experiments of TA17 with different processing techniques, the strain controlled cyclic experiments and the stress controlled cyclic experiments. The uniaxial tensile curves of materials with different processing techniques are discussed. The effects of different strain amplitudes of cyclic straining were analyzed. The effects of different combinations of mean stress and stress amplitude were analyzed. Finally, the uniaxial stress and strain curves with different processing techniques, cyclic stress and strain curves under different strain amplitudes and stress amplitude were obtained. The results show that the stress and strain curves of longitudinal plates and forgings are the lowest, while the stress and strain curves of transverse plates and bars are the highest. TA17 exhibited significant cyclic stability under different strain amplitudes and has obvious ratcheting behavior under asymmetric stress control. The obtained conclusions are helpful to improve the mechanical properties of TA17 and establish the cyclic constitutive model in the following work.

TA16 is a new type of titanium alloy material, which is widely used in pipeline systems of aerospace, ship and nuclear reactor with high temperature and high pressure. In this paper, the basic mechanical properties and cyclic deformation characteristics of TA16 were obtained by uniaxial tensile test and cyclic loading test at room temperature and high temperature. The Chaboche constitutive model can reasonably describe the cyclic plastic cumulative effect of materials and is provided in ANSYS which is a commercial finite element analysis software. The constitutive model of Chaboche presents a very important evolution criterion of follow-up hardening for ratchet simulation. Based on steady cyclic stress-strain curves which is got by strain control at different temperatures, the material parameters of Chaboche model are obtained by least multiplication fitting for TA16 at room and high temperatures. The constitutive model can used in elastic and elastic finite element analysis of TA16 materials. The experiment results show that TA16 exhibits slight cyclic softening under symmetrical strain cycles, and obvious ratcheting behavior under asymmetric stress cycles. When ratcheting strain of the structure reaches a certain saturation state, plastic accumulation will lead to accidental damage of the structure and lead to serious consequences. The stable cyclic stress-strain curves of TA16 at room temperature and high temperature are simulated by Chaboche model. The simulation results are in good agreement with the experimental results, which provides the basic data for the finite element simulation of cyclic deformation behavior of TA16 titanium alloy structure.

In this paper, the clamped inductive turn-off ruggedness of a novel Trench Insulated Gate Bipolar Transistor (TIGBT) at overcurrent condition is studied by numerical simulation. This proposed structure is optimized by using split gate structure to improve the turn-off reliability. Simulation result shows that the maximum turn-off critical current of the proposed TIGBT increases for about 42.8% compared with the conventional TIGBT structure. The main reason is that the electric field of the proposed structure is redistributed by RESURF effect at the trench bottomed area, resulting to attenuate the current filament at local area. In addition, the hole which concentrated at the trench bottom area is less because the bottom part of split gate polysilicon is shorted with the emitter. Therefore, the local dynamic avalanche effect which triggered by the excessive carriers concentration and high peak electric filed accumulation is weakened. The turn-off ruggedness of the proposed structure is enhanced effectively and the electrical parameters are not compromised but even better compared with conventional structure.

The crystal phase field (PFC) method is used to simulate the propagation of the nano-crack of samples with different crystal orientations under the strain of the uniaxial tensile. The results show that the different crystal orientations have a significant effect on the initiation and propagation of the cracks. For the samples with the orientation angles of 5° and 20°, the notch is directly cracked due to the strain concentration at the dislocation of the crack tip. The cracks mainly show a mode of the brittle expansion, and its edges show smooth planar features. For the samples with the orientation angles of 10° and 15°, the dislocation is firstly emitted at the notch to generate vacancies by dislocation slipping. The vacancies grow and connect to form cracks. This process of the crack propagation belongs to the mode of the ductile crack with the rough edges. The results are consistent with that of the molecular dynamic and experimental results.

The solid solution alloys containing short-range order (SRO) structure, such as CuNi alloys, are not well structurally described using conventional quasi-disordered models. Based on the first-principles calculations, the optimal cluster-plus-glue-atom (CPGA) models of six typical solid solution CuNi alloys were demonstrated. These CPGA models are better to be used to describe the microstructure of the six CuNi alloys at the atomic scale from the viewpoint of energy. Our further study shown that the stabilities of CPGA models are highly related to the symmetry of initial CPGA models and the aggregation degree of solute atoms in CPGA models. In the condition of low solute Ni concentration, the stability of CPGA model is mostly determined by the symmetry of initial CPGA model, the CPGA model with high symmetry is more stable. As the concentration of solute Ni increasing, the aggregation degree of solute Ni atoms in CPGA models plays more and more important role. The CPGA model with higher aggregation degree of solute Ni is more stable. The simple selection method of optimal CPGA models, therefore is proposed, and which can be extended to other bielement solid solution AB alloys with positive mixing enthalpy of A-B. Using the selected CPGA models, we found the third additive atoms having negative mixing enthalpy with solvent and solute atoms prefer to reside the central site of characteristic principal cluster (CPC) of CPGA, and thereby enhancing the stability of alloys. Our studies provide a distinctive perspective to select the optimal CPGA models of solid solution alloys containing SRO structure and design alloy using the optimal CPGA model.

Zinc (Zn) metal is considered the promising anode for “post-lithium” energy storage due to its high volumetric capacity, low redox potential, abundant reserve, and low cost. However, extravagant Zn is required in present Zn batteries, featuring low Zn utilization rate and device-scale energy/power densities far below theoretical values. The limited reversibility of Zn metal is attributed to the spontaneous parasitic reactions of Zn with aqueous electrolytes, that is, corrosion with water, passive by-product formation, and dendrite growth. Here, a new ion-selective polymer glue coated on Zn anode is designed, isolating the Zn anode from the electrolyte by blocking water diffusion while allowing rapid Zn2+ ion migration and facilitating uniform electrodeposition. Hence, a record-high Zn utilization of 90% is realized for 1000 h at high current densities, in sharp contrast to much poorer cyclability (usually

An innovative externally-hung rocking wall (ERW) with shape memory alloy (SMA) and disc spring self-centering devices for retrofitting existing structures was proposed in this paper. By arranging steel corbels on the columns of an existing structure, the rocking walls were connected to the corbel using H-shaped connectors. Two types of self-centering devices, using disc spring and SMA separately, were installed between rocking wall and foundation to prevent collision damage, and can provide self-centering capability for the structure. The seismic performance characteristic of the ERW structure was studied via a shaking table test. For comparison, an unretrofit control (UC) structure was also tested. The UC structure was severely damaged and nearly collapsed after PGA = 1.2 g test cases: some steel bars at the bottom of the beam were fractured, and concrete at the beam end and column foot were crushed. For the ERW structure, the damage was significantly reduced after PGA = 1.5 g test cases: there were some cracks appeared in the structure, and concrete at the column foot were slightly crushed. However, no obvious damage was observed in the self-centering devices. The maximum story drift and residual deformation of the ERW structure are reduced 86.7% and 91.2%, respectively, relative to the UC structure.

In this paper, a novel CSTBT with very narrow mesa structure is proposed by numerical simulation. The floating pwell region in the proposed structure is connected with the cathode through the very narrow mesa structure to deplete the very high dose concentration of the CS layer. Therefore, the conductivity modulation effect of the proposed structure can be enhanced significantly. It can help the proposed structure to achieve ultra-low on-state saturation voltage closed to the theoretical limit. In addition, there is no degeneration of the short-circuit behavior due to the relatively normal active cell mesa region. It can avoid the CIBL behavior induced by the very narrow conductive channel structure.

A ultrahigh voltage p-channel 4H-SiC (Silicon Carbide) IGBT (Insulated Gate Bipolar Transistor) with CSL (Current Spreading Layer) structure is designed and optimized. The static and dynamic characteristics of the IGBT is improved by adjusting the CSL doping concentration $N_{CSL}$, the CSL thickness $D_{CSL}$ and the width of JFET region $L_{JFET}$. Through numerical simulations, when $N_{CSL}$ is (1×10)$^{16}$ cm$^{-3}$, $D_{CSL}$ is 1.5$\mu$ m and $L_{JFET}$ is 3$\mu$ m, the blocking voltage can reach 15.6kV, and the maximum of gate oxide field $E_{OX,max}$ is less than 3MV/cm. When the on-state current is 10A, the on-state voltage is only 8.2V. The turn-on time is about 120ns and the turn-off time is about 440ns at 5kV dc-link voltage.

In this work, a simple and effective thermal deposition method is described to enhance the stability and achieve n-doping of two-dimensional black phosphorus (BP), resulting in the successful fabrication of logic devices. By doping with Al adatoms, the stability of BP against oxidation is enhanced and the transfer characteristics are maintained for several days under ambient conditions. Furthermore, the resulting BP is n-doping showing a negative-shifted threshold voltage and enhanced electron mobility. The mechanism of Al-doping is investigated by first-principles calculation and Al induces a downward shift of the conduction band minimum and increases the Fermi level. In addition, integration of bare BP and Al-doped BP enables the fabrication of various logic devices such as inverters and p-n diodes. This work reveals a facile strategy to simultaneously enhance the stability and regulate the conductivity of BP by doping with metal adatoms boding well for device applications.

A novel edge termination structure with Four-Region Multistep Field Limiting Rings (FRM-FLRs) is proposed and investigated for 10kV 4H-SiC IGBTs. The structure with FRM-FLRs terminal technology exhibits a good blocking performance with 30% less terminal area and 23% higher blocking voltage compared with the conventional Filed limiting Rings (Con-FLRs) structure. Moreover, the structure with FRM-FLRs can decrease the sensitivity of the interface charges, which greatly improves the reliability of the device at the off-state.

An optimized edge termination structure by increasing the coverage rate of metal plates at termination area is presented for 3.3kV IGBTs. This structure indicates a better stability after 168 hours High temperature reverse bias (HTRB) experiment. The electric potential contours and the surface electric field distribution with the variation of oxide charge are analyzed through numerical simulation. It is realized that the optimized termination structure is less sensitive with oxide charge. Thus the surface electric field is more uniform at each ring location to weaken the electric field concentration. Therefore, the breakdown voltage of the optimized structure is more stable than the conventional structure, which is in good agreement with the experiment results.

Effective improvement in electrical properties of NO passivated SiC/SiO2 interface after being irradiated by electrons is demonstrated. The density of interface traps after being irradiated by 100-kGy electrons decreases by about one order of magnitude, specifically, from 3×1012 cm−2⋅eV−1 to 4×1011 cm−2⋅eV−1 at 0.2 eV below the conduction band of 4H-SiC without any degradation of electric breakdown field. Particularly, the results of x-ray photoelectron spectroscopy measurement show that the C–N bonds are generated near the interface after electron irradiation, indicating that the carbon-related defects are further reduced.

Memory polymers capable of remembering their shape or thermal history have attracted increasing interest due to their potential applications in smart and medical devices. Memory polymers established are mechanically based, which suffer from some inherent limitations such as low sensitivity and bulky size. Here, we develop a general platform for sensitive memory polymers. Incorporating crystallizable polymers with solid-state fluorescent dyes results in crystallizable fluorescent polymers. Such polymers show remarkably temperature-dependent fluorescence emission. Interestingly, fluorescence of the polymers shows a hysteresis between heating and subsequent cooling scans, which offers them a valuable thermally stimulated recording function. Both off-on and on-off recording functions can be achieved. Characters recorded on the polymer films can be erased and rewritten. Moreover, thermal history subjected to the polymers can be memorized and retrieved by measuring fluorescence intensity. With the merit of easy synthesis, recording function, remarkably thermoresponsive fluorescence with memory function, superior flexibility, and biocompatibility inherited from polymers, crystallizable fluorescent polymers offer a general platform for memory fluorescent polymers that are potentially useful for biosensing, recording materials, and smart devices.

First-principles phase diagram calculations based on density functional theory within the generalized gradient approximation in combination with Monte Carlo (MC) techniques and cluster expansion were performed for the ZnSe1−xSx alloys. Formation energies were used as a basis for fitting cluster expansion Hamiltonians. All formation energies of ZnSe1−xSx alloys are positive, showing that ZnSe1−xSx alloys is a miscibility gap system and has a tendency to phase separation. For ZnSe1−xSx alloys the phase diagram computed with conventional cluster expansion shows a miscibility gap with consolute temperature Tc=327 K. The contributions of lattice vibration reduce Tc to 281 K (about 15%). We presented a MC study of the spatial distribution of S and Se in ZnSe0.5S0.5 alloys. We found that, the system becomes more homogeneous including lattice vibration at lower temperature. It is consistence with the calculation of phase diagram of ZnSe1−xSx alloys.

Using wool fibers as template and Ce (NO3)3•6H2O, PEG and NH3·H2O as precursors, micron-scale CeO2tubes composed of well-crystalline CeO2nanoparticles have been synthesized. Cerium oxide was first precipitated on the wool fibers by vapor deposition method, then the fibers were removed by a two-step calcination. The obtained products were characterized by scanning electron microscopy (SEM), thermogravimetric Analyzer (TGA), powder X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). The results show that intact tubes with a diameter of 8~12μm have been successfully prepared.

Cloud mixing and droplet evolution When clouds mix with drier air because of atmospheric turbulence, some of the cloud droplets evaporate. Beals et al. developed an airborne holographic imaging system to look at changes in the spatial structure and sizes of these droplets (see the Perspective by Bodenschatz). Turbulent mixing of clouds with clear air caused dramatic fluctuations in the number density of water droplets but left their mean diameter essentially unchanged. This finding should help models better represent these hard-to-parameterize cloud processes. Science , this issue p. 87 ; see also p. 40

Generalized gradient approximation (GGA) exchange-correlation functional was used in the first-principles method to calculate thermal emittance of La 1− x Sr x MnO 3 (LSMO). The effects of structure and magnetism on thermal emittance of LSMO were systematically investigated by the complex dielectric function. It is found that the LSMO with orthorhombic structure has a higher thermal emittance than that with rhombohedral structure at the same temperature. When the magnetism varying with temperature of LSMO is put into consideration, the magnetic different make a significant change on thermal emittance and the variation of thermal emittance of La 0.75 Sr 0.25 MnO 3 is the biggest among x =0, 0.2, 0.25, 0.5. It is found that thermal emittance have a low value at the low temperature and have a high value at the high temperature, due to the unique feature of variable thermal emittance based on metal-insulator transition, which makes LSMO attractive as potential thermal control materials.

A novel 1200 V 4H-SiC MOSFET, which features a current spreading layer, a split-gate and a central P+ implant in JFET region (CSI-MOSFET), is proposed. The CSI-MOSFET achieves a better trade-off among specific on-resistance, maximum electric field in gate oxide and switching loss. The CSI-MOSFET is comprehensively optimized with numerical simulation, and then two kinds of CSI-MOSFETs (FCSI-MOSFET and GCSI-MOSFET with a floating/grounded central P+ implant) are further investigated. Compared with the conventional double implanted MOSFET (VDMOSFET), both FCSI-MOSFET and GCSI-MOSFET demonstrate a smaller on-resistance, a smaller gate charge. Moreover, a maximum electric field in the gate oxide of 0.92 MV/cm is realized in GCSI-MOSFET, without breakdown voltage degradation. To our best knowledge, it is the lowest electric field among reported on 1200 V SiC MOSFETs. For dynamic characteristics, the FCSI-MOSFET has the largest switching loss and the largest on-state voltage drop, due to the negative charges stored in the floating P+ implant region. On the contrary, the GCSI-MOSFET achieves a same low switching loss as that of the split-gate MOSFET (SG-MOSFET) with an extreme short gate length (0.2 μm), because there is no charge in the grounded P+ implant region. Therefore, the GCSI-MOSFET is much superior for low switching loss and high reliability applications.

With the improvement of thermal insulation performance of building exterior walls, the proportion of heat loss caused by thermal bridges is increasing rapidly, especially for those buildings with a self-insulation wall. Currently, the Chinese government is boosting the use of self-insulation walls due to its advantages in long service life and convenient construction. However, energy loss through thermal bridges is a crucial problem. Wall-to-floor (beam included) thermal bridge (WFTB) is a primary form of the thermal bridge with the most massive heat flux. In this study, the thermal performance of WFTB was investigated with real scale (1:1) experiments and numerical models. On the basis of the distance between the beam and exterior wall surface (D), three types of WFTB structures are defined, i.e., exposed beam structure (EB, D = 0), entirely wrapped beam structure (EW, D = Dwall, the wall thickness) and partially wrapped beam structure (PW, D = 0-Dwall). The energy-saving potential of different WFTBs is ranked as PW (when D = 0.67Dwall) >EW > EB. The temperature spatial variation, which is related to the thermal stress of WFTB, is reduced by both the increases of D in PW and the thickness of the insulation layer at the overhanging structure (δ). Moreover, if expanded polystyrene board (EPS), one commonly used insulation material, is used as the insulation layer material, the δ is suggested to be 0.06–0.07Dwall, considering the effectiveness of the thermal insulation, structure safety, and the insulation material saving.

The liquid water transfer in porous building materials has a great influence on the hygrothremal properties of the materials. The capillary water absorption coefficient a key parameter characterizing the water absorption capability of porous building materials, which is essential to the simulations of moisture transfer. However, the traditional standard measurement (partial impregnation method) which has been widely used today has some disadvantages, such as human error and discontinuous testing. In this paper, an improved continuous measurement method, which is still based on the partial impregnation strategy, was proposed, featuring continuous and automatic data acquisition during the adsorption tests without interruption by an operator. As a typical porous building material, autoclave aerated concrete (AAC) featuring lightweight and high porosity was taken as an example to study the effects of the method on the measured results of capillary water absorption coefficient. Comparisons were made between the results of traditional standard and continuous measurement methods. It was shown that this improved continuous method avoids the process of intermittent sample extraction and weighing, making it more convenient than the standard method. The continuous method was deemed to have the advantages of high precision, simple operation, and high repeatability.

Parabolic antennas, which are wildly used as high-gain antennas for point-to-point communications, need many iterations of design-fabrication-test in parabolic antenna development. However, traditional molding via mechanical processing takes a long manufacturing cycle and high cost. In this paper, a 3D-printed CF/nylon composite parabolic mold for CF/epoxy parabolic antenna is studied. It’s found that the coefficient of thermal expansion (CTE) of 3D-printed CF/nylon composite is usually anisotropic due to the low adhesion between printed layers and the aligned short carbon fiber along the printing trace. Here an inclined mode of 3D printing could uniform the CTE of the antenna mold and solve the problems of large printing steps and the separation of supports and mold occurred in horizontal and vertical modes, respectively. The parabolic mold also reveals high profile precision with a low root mean square (RMS) deviation of 0.14 mm. Utilizing the 3D-printed CF/nylon composite mold, parabolic antenna skin with low surface RMS deviation of 0.16 mm was successfully fabricated by laying CF/epoxy prepreg and curing in autoclave. This research about isotropic and smooth 3D-printed CF/nylon mold may support the low-cost and rapid mold development for microwaves relay links on ground and satellite communication antennas.

Herein, we applied a coaxial cable type polyvinyl alcohol-wrapped silver nanowire (Ag-PVAs) composite sponge as adsorbent material for oil/water separation. The Ag-PVAs sponge was prepared by two steps of hydrothermal and freeze-drying, and then modified with polydimethylsiloxane (PDMS) to reduce its surface energy. The modified Ag-PVAs sponge (f-PDMS) displayed superhydrophobic property due to its porous structure and low surface energy. Importantly, the f-PDMS has 14 times of maximum stress, compared with that of Ag-PVAs. Meanwhile, the maximum compressive stress of the f-PDMS sponge can still be maintained at 87.3% after 50 stress-strain cycles at 70% strain. Moreover, the f-PDMS sponge exhibits good adsorption properties for various oils with different densities and can be reused by extrusion and evaporation. Continuous oil/water separation can also be achieved with the aid of a vacuum pump, which will make it a powerful competitor for large-scale industrial separation of oil/organic solvents and water mixtures.

The paper describes the manufacturing, testing and modelling of a class of open cell polyurethane foams doped with multi-walled carbon nanotubes and nano polyurethane dispersions and subjected to quasi-static cycling compressive loading at large deformations. The doped nano-ink foams areproduced using a multiple steps dip coating technique that makes possible the development of nanobased porous materials by post-processing existing off-the-shelf open cell foams. Tests are carried out up to 18.5% of compressive strain to identify loading/unloading moduli and energy absorbedafter 5 cycles of stabilization. Hyperelastic Ogden models also considering the Mullins effect for cyclic loading are used to identify the constitutive parameters for these foams. The results show that the use of the multi-walled carbon nanotube layers provide an effective increase of the stiffness andenergy absorbed compared to pristine and nano polyurethane dispersions-treated foams. The volume average energy absorbed after the stabilization cycles is increased by 200% compared to thepristine foam when the multi-walled carbon nanotube layers are used. The parameters of the constitutive models extracted from the tests show that these nano-ink foams can be modelled following state-of-the-art hyperelastic representations

Black phosphorus (BP) possesses unique physical properties and, owing to its intrinsic instability, the proper surface and chemical coordination is the key point in many applications. Herein, a facile and efficient surface lanthanide-coordination strategy based on lanthanide (Ln) sulfonate complexes is designed to passivate and functionalize different BP-based nanostructures including quantum dots, nanosheets, and microflakes. By means of Ln-P coordination, the lone-pair electrons of phosphorus are occupied, thus preventing oxidation of BP, and the LnL3 @BP exhibits excellent stability in both air and water. Furthermore, accompanied by the original photothermal performance of BP nanostructures, the Gd-coordinated BP has high R1 relativities in magnetic resonance (MR) imaging, and other Ln (Tb, Eu, and Nd) coordinated BP structures exhibit fluorescence spanning the visible to near-infrared regions. Not only is LnL3 surface passivation an efficient method to enhance the stability of BP, but also the MR or fluorescence derived from lanthanide ions extends the application of BP to optoelectronics and biomedical engineering.

The dispersion polymerization of methyl methacrylate (MMA) with fluorescent monomer tris[2-((8-hydroxyquinolin-5-yl)methoxy)ethyl methacrylate]aluminium (Al-HQHEMA) was investigated to obtain fluorescent microspheres under varying conditions (such as composition of dispersion medium, and content of stabilizer polyvinylpyrrolidone (PVP) and Al-HQHEMA) in methanol–water at 70 °C with 2,2′-azoisobutyronitrile as the initiator. Fluorescent microspheres with particle size of 2.039 µm and uniformity of 0.171 were obtained under the following conditions: methanol–water, 7:3 (v/v); PVP, 15 wt% of MMA; Al-HQHEMA solution, 1.5 mL. Maleic monoester of monomethoxyl poly(ethylene glycol) (Mal-MPEG) was used as a comonomer to simultaneously incorporate carboxyl groups and PEG chains. With Mal-MPEG, no aggregation was observed in the measurements of particle size and size distribution for the obtained microspheres after cleaning off PVP, indicating that self-stabilized fluorescent microspheres were obtained. While without Mal-MPEG, obvious aggregation was observed. The determination of surface carboxyl content using aqueous acid–base titration showed that most of the carboxyl groups of Mal-MPEG were located on the surface of the microspheres. © 2015 Society of Chemical Industry

Using first-principles plane-wave calculations within density functional theory, we theoretically studied the atomic structure, bonding energy and electronic properties of the perfect Mo (110)/MoSe 2 (100) interface with a lattice mismatch less than 4.2%. Compared with the perfect structure, the interface is somewhat relaxed, and its atomic positions and bond lengths change slightly. The calculated interface bonding energy is about −1.2 J/m 2 , indicating that this interface is very stable. The MoSe 2 layer on the interface has some interface states near the Fermi level, the interface states are mainly caused by Mo 4d orbitals, while the Se atom almost have no contribution. On the interface, Mo-5s and Se-4p orbitals hybridize at about −6.5 to −5.0 eV, and Mo-4d and Se-4p orbitals hybridize at about −5.0 to −1.0 eV. These hybridizations greatly improve the bonding ability of Mo and Se atom in the interface. By Bader charge analysis, we find electron redistribution near the interface which promotes the bonding of the Mo and MoSe 2 layer.

We report a novel interpenetrating three-dimentional (3D) macroporous graphene aerogels (GAs) composite consisting of MnO2 wrapping for potential supercapacitor applications. In this article, the macroporous GAs holds abundant of interconnected macroporous and has excellent intrinsic high electrical conductivity resulting from the graphene. Therefore, employing the GAs as the substrates to combine with MnO2 will exhibit excellent electronic conductivity and effective ion-transport capability. The 3D macroporous MnO2/GAs composite has a specific capacitance of 200 F g-1. Thus, the corresponding 3D porous hierarchical GAs/MnO2 materials have a great potential to be used in the field of supercapacitors. This strategy could also be used for other materials to improve the performance of supercapacitors.

To meet the requirements of the energy storage materials for high energy density and high power density, porous silicon carbide/derived carbon-spherical natural graphite (SiC-CDCs@NG) composites were prepared. The composites were composed of tailored porous carbide-derived carbon and graphitized carbon with excellent conductivity and a high energy storage capacity. The composition, structure, morphology, pore structure, and specific surface area of the composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and N2 adsorption/ desorption analysis. The composites exhibited a high and adjustable specific surface area and micro-pore volume, with a micro-pore size of between 0.5 and 0.7 nm. Varying the molar ratio of NG and Si allowed optimization of the micro-pore volume, pore size distribution, specific surface area, and composition and content of the CDCs shell and NG core.