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The exploration for low-cost bifunctional materials for highly efficient overall water splitting has drawn profound research attention. Here, we present a facile preparation of Mo–P dual-doped Co/o...

Large-size flexible biomass carbon membranes have been prepared by using inexhaustible chitosan (CS) as carbon source. The microstructure of carbon membranes depends on the pyrolysis temperature, and the resulting membrane has a porous honeycomb-like architecture with N-doping content of 6.3% after the pyrolysis at 1000 °C. The flexible carbon membranes can be directly used as self-standing electrodes for various batteries, that is, with no current collectors, organic binders, or additional conductive agents. The carbon membranes as anodes for potassium-ion batteries exhibit excellent rate performance and a stable reversible capacity of 146 mAh g−1 at 2 A g−1 after 500 cycles, and its sodium-ion storage remains 236 mAh g−1 after 70 cycles. The kinetic analysis of carbon membranes in batteries shows that the surface-controlled mechanism plays a decisive role in the potassium/sodium storage because the honeycomb structure and high proportion of pyridine N-doping can improve the adsorption of K+/Na+ ions and the conductivity. In addition, the main reasons for the capacity degradation of the carbon membrane under long cycle and different current densities are discussed. The CS-derived flexible carbon membranes show a promising application as cost-effective, binder-free electrodes in flexible batteries.

Control of the shape and uniformity of colloid particles is essential for realizing their functionality in various applications. Herein, we report a facile approach for the synthesis of narrowly dispersed anisotropic microparticles with well-defined raspberry-like and golf ball-like surface patterns. First, we demonstrate that hybrid raspberry-like particles can be achieved through a one-pot polymerization method using glycidyl polyhedral oligomeric silsesquioxane (GPOSS) and pentaerythritol tetra(3-mercaptopropionate) (PETMP) as monomers. Varying the polymerization parameters such as catalyst loading, monomer concentration, and the molar ratio of monomers, we are able to regulate the sizes and surface protrusion numbers of these raspberry-like microparticles. The formation mechanism is attributed to a competition balance between thiol-epoxy reaction and thiol-thiol coupling reaction. The former promotes rapid formation of large core particles between PETMP and GPOSS droplets (which can serve as core particles), while the latter allows for generation of surface protrusions by PETMP self-polymerization, leading to the formation of raspberry-like surface patterns. Based on the different POSS contents in the surface protrusions and cores of the raspberry-like microparticles, we demonstrate that they can be used as precursors to produce microporous silica (sub)microparticles with golf ball-like morphology via pyrolysis subsequently. Overall, this work provides a facile yet controllable approach to synthesize narrowly dispersed anisotropic microparticles with diverse surface patterns.

Adding fumed silica (SiO2) has been considered as an effective method for tailoring the phase morphology and performance of elastomer-toughened plastic binary blends. It has been demonstrated that the selective distribution of SiO2 plays a decisive role in the mechanical properties of plastic/elastomer/SiO2 nanocomposites, especially for the impact toughness. In this work, we aim to illuminate the role of specific surface area in controlling their selective distribution of fumed SiO2 and consequent mechanical properties of plastic/elastomer binary blends. Three types of SiO2 with different specific surface areas were incorporated into polylactide/ethylene-co-vinyl-acetate (PLA/EVA) model blends by melt blending directly. It was found that the selective distribution of SiO2 is largely determined by their specific surface areas, i.e. SiO2 nanoparticles with low specific surface area has a stronger tendency to be located at the interface between PLA matrix and EVA dispersed phase as compared to those with high specific surface area. The specific surface area-dependent interfacial selective distribution of SiO2 is mainly attributed to the extent of increased viscosity of EVA dispersed phase in which SiO2 nanoparticles are initially dispersed and resultant migration rate of SiO2 nanoparticles. The interfacial localized SiO2 nanoparticles induce an obvious enhancement in the impact toughness with strength and modulus well maintained. More importantly, in the case of the same interfacial distribution, toughening efficiency is increased with the specific surface area of SiO2. Therefore, this is an optimum specific surface area of SiO2 for the toughening. This work not only provides a novel way to manipulate the selective distribution of SiO2 in elastomer-toughened plastic blends toward high-performance, but also gives a deep insight into the role of interfacial localized nanoparticles in the toughening mechanism.

The development of highly efficient transition metal-based catalysts for overall water splitting is of extreme significance for promoting large-scale sustainable utilization of hydrogen energy and energy conversion. Herein, we report a novel 3D Ni3S2/Cu-NiCo LDH heterostructure nanosheet arrays grown on nickel foam as a promising bifunctional electrocatalyst for OER and HER. In this design, copper ions are firstly doped into NiCo LDH to tune the electronic structure and enhance the inherent activity of pristine LDH. Metallic Ni3S2 is then introduced to establish a coupling heterostructure interface with Cu-NiCo LDH to boost the conductivity and activity. The incorporation of Cu ions and Ni3S2 into NiCo LDH also creates more active sites through crystal structure disorder and interface defects. Moreover, the 3D hierarchical nanosheet arrays can accelerate the electrolyte diffusion, promote the rapid release of gas bubbles, and ensure fast electron/mass transport along with strong electrochemical stability. All these merits endow the materials with a superior overall water splitting ability in alkaline environment, showing the low overpotentials of 119 and 218 mV for OER and overpotentials of 156 and 304 mV for HER at 10 and 100 mA cm-2, respectively. Furthermore, the overall water electrolytic cell using Ni3S2/Cu-NiCo LDH as both electrodes can reach 100 mA cm-2 at 1.75 V with outstanding durability. This study provides new strategy and insights for the exploration of high activity non-noble metal catalysts for overall water splitting.

The introduction of a dual-functional interlayer into lithium-sulfur batteries (LSBs) provides many opportunities for restraining the "shuttle effect" and enhancing sluggish sulfur conversion kinetics. Tuning the band structure of the metal sulfide provides an opportunity to enhance its catalytic activity, which plays an important role in suppressing the "shuttle effect" of lithium polysulfides (LiPSs) in LSBs. Here were present a Co9S8@MoS2 core-shell heterostructure anchored to a carbon nanofiber (Co9S8@MoS2/CNF), developed as an interlayer for suppressing the shuttle effect of LiPSs. The fabricated composite heterostructure is determined to be an effective alternative material that combines the synergistic relationship between chemisorption and electrochemical catalysis. We find that the band structure of the MoS2 shell can be effectively tuned by the Co9S8 core and that the Co9S8@MoS2/CNF can capture the LiPSs, providing excellent catalytic ability to convert LiPSs into Li2S2, with subsequent transformation from Li2S2 to Li2S. Importantly, high capacities of 1002 and 986 mAh g-1 can be retained after 50 cycles with high-sulfur loadings of 6 and 10 mg cm-2. Our results highlight the design of an atomic-scale heterostructure as a multifunctional interlayer providing a synergistic relationship between adsorption and catalysis. The net result is an effective retardation of the shuttling of LiPSs and an enhancement of the electrochemical redox reactions of LiPSs. This work shows great promise toward the development of practical applications of LSBs.

Previously, much attention has been paid to prepare porous magnetic silica micro/nanoparticles, but most of the reported methods are limited by sophisticated procedures and strict synthetic conditi...

Gallium nitride (GaN) high electron mobility transistor (HEMT) has a lateral device structure with wafer-level packaging, which is advantageous in minimizing parasitic parameters and overall device size. This type of packaging also has better thermal performance than conventional packaging due to low junction-to-bottom thermal resistances. It indicates copper layers in printed circuit boards can effectively serve as heat dissipation channels for the switching devices. When these copper traces and pours in the vicinity of the switching devices are carefully designed and shaped, they can also be utilized as an integrated output filter. In this article, a synchronous buck converter with a single-turn air-core integrated planar inductor is proposed to achieve both zero-voltage switching and high thermal performance of the GaN HEMTs. A new planar inductor design flowchart is introduced, and analytically estimated inductance and resistance are verified with simulation and experiment. Three different inductors are designed and fabricated to prove the improved thermal performance of the proposed converters.

Manual visual inspection for thermistor wire solder joints used in satellite circuits always results in inefficiency and low accuracy. A method based on improved YOLOv5s model is proposed to automatically inspect defections in thermistor wire solder joints through infrared images. In order to enhance feature extraction capability, ECA module is introduced to the backbone of YOLOv5s network. Image database is built through infrared image shooting platform for model training and testing. The experiment result indicates that precision, recall and mAP of improved model reach 64.1%, 92.0% and 88.4% respectively, which are all superior to original model. This work paves the way for automatically defect detection of thermistor wire solder joints based on infrared thermography.

Three-dimensional microstructures fabricated by origami, including folding, rolling and buckling, gain great interests in mechanics, optics and electronics. We propose a general strategy on on-demand and spontaneous rolling origami for artificial microstructures aiming at massive and intelligent production. Deposited nanomembranes are rolled-up in great amount triggered by the intercalation of tiny droplet, taking advantage of a creative design of van der Waals interaction with substrate. The rolling of nanomembranes delaminated by liquid permits a wide choice in materials as well as precise manipulation in rolling direction by controlling the motion of microdroplet, resulting in intelligent construction of rolling microstructures with designable geometries. Moreover, this liquid-triggered delamination phenomenon and constructed microstructures are demonstrated in the applications among vapor sensing, microresonators, micromotors, and microactuators. This investigation offers a simple, massive, low-cost, versatile and designable construction of rolling microstructures for fundamental research and practical applications., Rolling microstructures have great potential among optics and micromechanics but on-demand construction with versatile materials remains challenging. Here Xu et al. precisely construct 3D rolling microstructures by liquid-triggered delamination in predictable manner and demonstrate their applications.

We report the symmetry-dictated mesophase formation and phase diagram of a series of T8-polyhedral oligomeric silsesquioxane (POSS) derivatives bearing perfluoroalkyl chains and hydroxyl alkyl groups. The phase structures and phase behaviors of these molecular Janus particles were studied by DSC, POM, FT-IR, and WAXD experiments. It was found that introducing one hydroxyl alkyl group leads to a decreased crystal melting point, and incorporating two hydroxyl alkyl groups at different POSS positions causes the formation of lamellar liquid crystal mesophases with feature sizes and transition temperatures that depend on the symmetry of these regioisomers. Interestingly, installing only one substituent with two hydroxyl groups leads to monotropic phase transitions, where the mesophase appears only upon cooling from the isotropic melt within the narrow supercooling window. Phase diagrams were systematically constructed for these compounds and understood based on the fine influence of symmetry on their possible ...

Radiative cooling is a passive technology that lowers surface temperatures, which has shown great potential in temperate regions. However, cooling performance characterised by high solar irradiance and humidity under tropical climate still lacks exploration. Herein, we propose a highly reflective polymeric coating with BaSO4 particles dispersed in P(VdF-HFP) matrix for radiative cooling. Through the strong Mie scattering of sunlight and intrinsic bond vibration, the average substrate-independent solar reflectance and infrared emittance within the 8 to 13 μm atmospheric window could reach 97% and 94.2%, respectively. Under direct exposure to the sky, surfaces could maintain close to ambient temperatures even when the solar intensity was as high as 1000 W/m 2 , while separately achieving 5.7 °C below ambient during night-time with an effective cooling power of 54.4 W/m2. With a scalable fabrication-process, our cost-effective single-layer coating can be easily applied to diverse substrates, which is suitable for real-world applications in the tropics.

The authors show the onset of an asymmetrically coupled cavity-waveguide system to enable pseudospin modulation in graphene through the mechanism of chaos-assisted tunneling.

Organic field effect transistors based on blended polymer insulators were fabricated. The effects of polystyrene (PS), poly (vinyldifluoride) (PVDF) and poly (vinylphenyl) (PVP) blended with poly (methylmethacrylate) (PMMA) on the properties of insulating layers were studied. The PMMA:PS films have spherical grains, the PMMA:PVP films exhibit porous pit morphology, and the PMMA:PVDF films still show plane morphology. The morphology of insulating layers can affect the crystallization of organic semiconductors. Meanwhile, the performance of OFET devices indicates that polymer doping decreases the threshold voltage of devices. When the mass ratio of PMMA:PVDF is 10:5, the threshold voltage of OFET devices is about -14.7 V, which is significant lower than that of pure PMMA devices. This is attributed to the larger capacitance and lower roughness of the insulating layers. Therefore, it is a convenient and effective method to optimize the threshold voltage of OFET devices by applying blended polymer insulating layers.

Expanded graphite (EG) films with low oxidation degree exhibit excellent thermal, electric properties and electromagnetic interference (EMI) shielding. However, the mechanical brittleness is the major limitation for their applications. To meet this challenge, in this work, a small amount of flexible graphene (GE) is introduced to endow EG films with good flexibility and mechanical properties by forming simulate shell structure. Moreover, the influence of oxidation degree and sheet thickness for carbon sheets as well as the lateral size of GE on the film performance is carefully discussed. As a result, a 431% enhancement of tensile strength from 7.7 Mpa to 40.9 Mpa and little sacrifice of electric, thermal conductivities up to 1467 S cm−1 and 348 W m−1 K−1 are observed with the loading of only 10% large GE (LGE) sheets in EG films. Besides, high EMI shielding of 48.3 dB is achieved as the film thickness reaches 43 μm. The excellent flexibility of prepared EG/LGE films can be retained even after more than 1000 times of direct folding. These excellent properties of light-weight EG/LGE films, together with their advantages of environmentally friendly and facile large-scale fabrication, endow the films with great potential applications in next-generation commercial portable flexible electronics.

Modified castor oil-based epoxy resin (EP)/polyurethane (PU) grafted copolymer by glycidyl polyhedral oligomeric silsesquioxane (glycidyl POSS) was synthesized. The damping properties, thermal stability, mechanical properties and morphology of the grafted copolymer modified by glycidyl POSS were studied systematically. The results revealed that the incorporation of glycidyl POSS improved the damping performance evidently and broadened damping temperature range, especially when the glycidyl POSS content was 0.2%–1%. At the same time, there was a slight increase in thermal stability with the increase of POSS content. The tensile properties changed with the change of the copolymer’s Tg, decreased at low POSS contents and increased at high POSS contents. This modified copolymer has the potential to be used as film damping material or constrained damping layer.

Bramble-like NaVMoO6/C nanofibers with remarkable lithium-storage property are fabricated via a simple electrospinning method. The NaVMoO6 nanoparticles with average size of 84 nm are uniformly embedded into the carbon nanofibers at loading of 77.2 wt%. The unique architecture of the resulting nanocomposite has great advantages like enhanced surface-to-volume ratio, reduced ion transport lengths and strengthened electron transfer along the longitudinal direction. As a new-type anode for lithium-ion batteries (LIBs), NaVMoO6/C composite demonstrates a stable capacity of 1013 and 682 mAh g−1 at the current density of 0.1 and 1 A g−1, respectively. Furthermore, the structure evolution mechanism during the first discharge process is carefully researched by ex-situ X-ray diffraction and X-ray photoelectron spectroscopy. It is found that the NaVMoO6 crystals begin to change after being embedded with a few equivalent Li+ when discharging to 2.2 V. With the continuous intercalation of Li+ ions, the main crystal form of the electrode is V2O5 at the potential of about 2.0 V. At low potential (≈ 1.2 V vs. Li/Li+), the formed V2O5 is transformed into LiVO2. In addition, the volume expansion of the NaVMoO6 particles is alleviated due to the confining effect of carbon nanofibers. Consequently, NaVMoO6/C nanofibers demonstrate a high reversible capacity even at high rate.

The lithium-sulfur (Li-S) batteries involve intricate electrochemical processes containing the formation and conversion of polysulfides, in which the shuttle effect and slow reaction kinetics impair its practical performance. Exploring new electrocatalyst with strong catalytic ability can greatly accelerate the conversion of polysulfides in Li-S batteries. Herein, BiOI/carbon fibers (BiOI/CFs) core–shell composite has been prepared by a facile electrospinning combined with solvothermal method and used as a promising electrocatalyst. The BiOI nanosheets are cross-linked to form a porous three-dimensional network on the surface of carbon fibers. This architecture not only has the advantage of large aspect ratio, but also has a high specific surface area, which provides abundant active sites and ensures high electron/ion transfer for the electrocatalysis of lithium polysulfides. As expected, BiOI/CFs electrode presents a superior bidirectional oxidation–reduction ability for polysulfides. The first-principles calculations also prove the strong interaction between BiOI and polysulfides. Due to these advantages, BiOI/CFs can effectively inhibit the shuttle effect of polysulfides, and possesses excellent electrochemical performance in Li-S batteries. The specific capacity of the BiOI/CFs-S electrode is stable at 1020 mAh g−1 after 200 cycles at 0.2C and 598 mAh g−1 after 1000 cycles at 5C. This work provides new insights for the development of high-performance electrocatalysts for polysulfide conversion.

Synthesis of hybrid hetero-arms star polymer with precisely defined arms distribution in three dimensional (3D) space is still a challenge. Herein, we have employed cubic polyhedral oligomeric silsesquioxane (POSS) nanoparticle as a scaffold to synthesize a biodegradable Janus POSS star polymer (oom-T8PLLA5PCL3), which contains an inorganic rigid POSS core, three poly(e-caprolactone) (PCL) arms and five poly( l -lactide) (PLLA) arms on the POSS cage two sides, respectively. The chemical structure of oom-T8PLLA5PCL3 was confirmed by NMR, SEC, and FTIR spectra. As an example of application for the Janus POSS star polymer, oom-T8PLLA5PCL3 was used for the compatibilization of biodegradable PLLA/PCL (w/w = 70/30) blends. It was found that oom-T8PLLA5PCL3 could reduce the dispersed PCL phase size in PLLA matrix and enhance the properties of PLLA/PCL polymer blends, which was reflected in the increase of Izod impact strength and tensile performance of the polymer blends.

Recently, safety issues in conventional organic liquid electrolytes and the interface resistance between the electrode and electrolyte have been the most challenging barriers for the expansion of lithium batteries to a wide range of applications. Here, an ion-conductive PVDF-based composite polymer electrolyte (CPE) consisting of lithium aluminum germanium phosphate (Li1.3Al0.3Ti1.7(PO4)3) and polyvinylidene fluoride (PVDF) is prepared on a Li metal anode via a facile casting method. The ionic conductivity and electrochemical stability were enhanced by incorporating an appropriate amount of LATP into the PVDF-based composite polymer electrolyte, and the optimum content of LATP in the hybrid solid electrolyte was approximately 90 wt%. The corresponding solid-state battery based on an SEI-protected Li anode, the PVDF–LATP electrolyte, and a LiMn2O4 (LMO) cathode exhibited excellent rate capability and long-term cycling performance, with an initial discharge capacity of 107.4 mA h g−1 and a retention of 91.4% after 200 cycles.

Silicon carbide (SiC) MOSFETs and gallium nitride (GaN) high-electron mobility transistors are perceived as future replacements for Si IGBTs and MOSFETs in medium- and low-voltage drives due to their low conduction and switching losses. However, it is widely believed that the already significant conducted common-mode (CM) electromagnetic interference (EMI) emission of motor drives will be further exacerbated by the high-speed switching operation of these new devices. Hence, this paper investigates and quantifies the increase in the conducted CM EMI emission of a pulse width modulation inverter-based motor drive when SiC and GaN devices are adopted. Through an analytical approach, the results reveal that the influence of dv/dt on the conducted CM emission is generally limited. On the other hand, the influence of switching frequency is more significant. Lab tests are also conducted to verify the analysis.

Wide bandgap semiconductors, such as gallium nitride (GaN)-based power devices have become increasingly popular in the automotive industry due to their low on-state resistance and fast switching capabilities. These devices are sought to replace silicon (Si) devices in power electronics converters for vehicular applications. GaN devices dissipate less energy during each switching event, thus, GaN converter designers can significantly increase the switching frequency without increasing switching losses, relative to Si converters. However, one item of concern is that the high $dv/dt$ of GaN devices, due to the increased switching speed, has the potential to deteriorate the electromagnetic interference (EMI) emission of power converters, and thus may fail the corresponding regulations for vehicles. To understand these effects, this paper presents an experimental case study on the switching characteristics and common mode (CM) noise generation of a GaN-based half-bridge configuration operating in the synchronous boost mode. A comprehensive comparison has been made between the chosen GaN high electron mobility transistors (HEMTs) and Si MOSFET in terms of switching voltage waveforms, ground leakage currents, and CM noise spectrum. By parametrically increasing the gate resistance of GaN HEMT and Si MOSFET, the tradeoff between converter efficiency and CM noise generation is also quantified.

Sub-ambient cooling can be achieved through radiative coolers that selectively emit radiation within the atmospheric window (8–13 μm) to outer space and suppress absorption/emission of other wavelengths. This study explores the feasibility of adopting radiative cooling in the hot and humid climate of Singapore through both numerical and experimental approaches. A theoretical simulation based on the heat transfer balance is first proposed to obtain the cooling power of the radiative cooler considering different solar spectral irradiance and total water vapor column. The larger solar irradiance in Singapore, especially within the ultraviolet and visible light spectrum where the absorbance of the material is relatively high, could counteract its cooling effects. Moreover, the increased atmospheric radiation induced by higher humidity and temperatures in Singapore could worsen cooling performances of the radiative material. Next, experimental investigations were conducted by measuring the steady-state temperatures of two radiative coolers (photonic radiative cooler and enhanced specular reflector film) under three typical weather conditions in Singapore, namely clear, partly cloudy and cloudy skies. While both radiative coolers were unable to achieve daytime cooling performance on a clear day, the enhanced specular reflector (ESR) film with higher solar reflectance can reach sub-ambient temperatures on a cloudy day. When it comes to night-time, the steady-state temperature of the photonic radiative cooler and ESR film was about 3.5 °C and 5 °C lower than ambient, respectively. Ministry of Education (MOE) Nanyang Technological University Accepted version This study was funded by the Singapore Ministry of Education through grant no. 2018-T1-001-070 and supported through a start-up grant by Nanyang Technological University M408202

To enhance the treatment efficiency in tumor therapy, we developed a tumor-targeting protein-based delivery system, DOX&ICG@BSA-KALA/Apt, to efficiently integrate multimodal therapy with tumor imaging and realize synchronous photodynamic therapy/photothermal therapy/chemotherapy. In the delivery system, a chemotherapeutic drug (doxorubicin, DOX) and an optotheranostic agent (indocyanine green, ICG) were co-loaded in bovine serum albumin (BSA) via a hydrophobic-interaction-induced self-assembly to form stable DOX&ICG@BSA nanoparticles. After the decoration of a surface layer composed of a tumor-targeting aptamer (AS1411) and a cell-penetrating peptide (KALA), the obtained DOX&ICG@BSA-KALA/Apt nanoparticles exhibit a significantly improved multimodal cancer therapeutic efficiency due to the enhanced cancer cellular uptake mediated by AS1411 and KALA. In vitro and in vivo studies show that the multimodal theranostic system can efficiently inhibit tumor growth. In addition, the near-infrared fluorescent/photothermal dual-mode imaging enables accurate visualization of the therapeutic action in tumor sites. This study provides a facile strategy to construct self-assembled multimodal theranostic systems, and the functional protein-based theranostic system prepared holds great promise in multimodal cancer therapeutics.

We report that variation of a single regio-configuration in molecular Janus particles leads to divergent self-assembly behaviors where each isomer gives a distinct morphology as guided by their molecular symmetry. The differences in their phase diagrams were rationalized based on the proposed molecular packing and relevant interfacial energies.

Gallium nitride (GaN) high electron mobility transistor (HEMT) has a lateral device structure with a wafer-level packaging, which is advantageous in minimizing parasitic parameters and the overall device size. The wafer-level packaging also provides better thermal performance than the conventional packaging due to low junction-to-case and junction-to-bottom thermal resistances. When a printed circuit board layout is optimally designed, copper traces and pours in the vicinity of the switching devices can serve as effective heat dissipation channels. In this paper, a synchronous buck converter with a single-turn air-core integrated planar inductor is proposed to achieve both quasisquare wave zero-voltage switching (QSW ZVS) and high thermal performance of the GaN HEMTs in high-frequency operation. The integrated planar inductor which is directly connected to the GaN HEMTs serves as a heat dissipation channel to maintain the device temperature low enough without any additional heat sink. Three different inductor designs with two different copper thicknesses have been investigated and compared to verify the effective thermal performance of the proposed converters.

One-dimensional zinc molybdate (ZnMoO4) nanotubes with excellent sodium-storage performance are controllably and delicately prepared by a facile electrospinning method. The as-prepared nanotubes are systematically characterized. The charge-discharge cycling curves, cyclic voltammetry and rate performance further reveal the electrochemical properties of the samples when used as the new Sodium-ion batteries (SIBs) anode material. In the charge-discharge process, the initial discharge capacity of the electrode is 548 mAh g−1, and remains a reversible capacity of about 190 mAh g−1 after 500 cycles at the current density of 100 mA g−1. ZnMoO4 nanotubes also deliver an excellent rate capability. In addition, the sodium-storage reaction mechanism of ZnMoO4 nanotubes is revealed via ex-situ XRD and TEM analysis. The results suggest the transformation of ZnMoO4 to Zn and NaMoO4 at the potential of ∼1.0 V during the first discharge, which is subsequently converted to Zn and Mo nanograins of 3–5 nm with the deepening of the discharge. This study provides an in-depth understanding of the electrochemical mechanism of molybdates-type anode materials.

With low loss, fast switching speed, and high-temperature capabilities, silicon carbide (SiC)-based devices are beneficial to automotive power converters in terms of efficiency increase and size reduction. Nevertheless, as a result of fast switching transitions and low on-state resistance of SiC devices, SiC-based converters are prone to overshoots and oscillations on switching waveforms, with the presence of parasitic inductances in the circuit. The overshoots and oscillations further contribute to increased converter loss and EMI emissions. This paper aims to study the influence of parasitic inductances on the performance of SiC MOSFETs for automotive dc–dc converters from the loss and electromagnetic interference perspective.

Oily wastewater has caused serve environmental pollution in nowadays, and it is highly urgent to develop an effective method for disposing of it. The development superhydrophilic and underwater superoleophobic (SUS) membranes bring hope of solving this global challenge. Previously, deformable hydrogels/hydrophilic polymers, brittle and chemically weak inorganic/metal oxides have been widely employed for fabricating SUS membranes, while most of these materials are likely to be corroded under practical severe conditions. In this work, we report a novel SUS membrane with excellent durability as achieved by introducing polyhedral oligomeric silsesquioxane (POSS) nanoparticles on cotton fabric (CF) followed by thiol-ene functionalization to graft hydrophilic carboxyl group. It is found that the prepared SUS membrane can withstand long-term mechanical abrasion, ultrasonic washing, UV light irradiation and corrosive aqueous solutions without reducing the underwater superoleophobicity. This SUS membrane is also able to separate various oil/water and oil/corrosive aqueous solution mixtures, and only water phase is allowed to permeate through it. The measured water fluxes are very high (up to 88,214 L m−2 h−1), the initial separation efficiencies of this membrane for various oil/water mixtures are over 99% and those values are still maintained at high level (around 98%) after 50 separation cycles even in severe conditions. We believe that this work would be helpful for fabrication of advanced SUS membranes with excellent durability.

Polymer dielectrics have been considered as an ideal choice for preparation of advanced power and electronic systems as their good comprehensive performances. However, it remains a challenge to obtain polymer dielectrics with high dielectric constant ( e r ), low dielectric loss (tan δ) and high temperature capability. Although adding high permittivity inorganic nanofillers has become a promising approach to improve the e r of polymers, it usually causes the adverse increment tan δ. Herein, we demonstrate that fluoride ion encapsulated polyhedral oligomeric silsesquioxane (POSS@F−) can be regarded as a novel filler to enhance the e r and reduce the tan δ of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) simultaneously. Compared with the pristine PPO, the e r of PPO/POSS@F− composite can be enhanced from 2.81 to 5.31, while its tan δ is still relatively low (0.0011 at 1 kHz). Meanwhile, the breakdown strength of PPO can also be slightly reinforced from 334.9 kV/mm to 394.0 kV/mm. Owing to the good thermal properties of PPO and POSS@F−, these composites exhibit good dielectric properties and improved dimension stability at high temperature. We believe that these results are particularly important for the preparation of advanced dielectric materials for desirable applications.

We design and fabricate a simple self-powered system to collect analyte molecules in fluids for surface-enhanced Raman scattering (SERS) detection. The system is based on catalytic Au/SiO/Ti/Ag-layered microengines by employing rolled-up nanotechnology. Pronounced SERS signals are observed on microengines with more carrier molecules compared with the same structure without automatic motions.

Herein, we report a novel strategy to use Janus polyhedral oligomeric silsesquioxane (POSS)–[60]fullerene (C60) (JPC) giant molecules as compatibilizer for immiscible polystyrene (PS)/polymethyl methacrylate (PMMA) blends. It was found that the domain sizes of the dispersed PMMA phase decrease in PS matrix, and tensile strength and elongation of PS/PMMA blends were largely enhanced by adding a small amount of JPC. More importantly, both interfacial tension analyses and elemental Si distribution in the blends suggest a possible location of the JPC at the PS/PMMA interfaces. Our studies provide not only a new idea for the compatibilization of polymer blends, but also for precisely controlling the positions of nanoparticles in a polymer matrix, which is also of great importance for the preparation of polymer nanocomposites with high-performance and excellent functionality.

Gallium nitride (GaN)-based power switching devices, such as high-electron-mobility transistors (HEMT), provide significant performance improvements in terms of faster switching speed, zero reverse recovery, and lower on-state resistance compared with conventional silicon (Si) metal–oxide–semiconductor field-effect transistors (MOSFET). These benefits of GaN HEMTs further lead to low loss, high switching frequency, and high power density converters. Through simulation and experimentation, this research thoroughly contributes to the understanding of performance characterization including the efficiency, loss distribution, and thermal behavior of a 160-W GaN-based synchronous boost converter under various output voltage, load current, and switching frequency operations, as compared with the state-of-the-art Si technology. Original suggestions on design considerations to optimize the GaN converter performance are also provided.

Graphene oxide (GO)/chitosan composite membrane with a thickness of several hundred nanometers was prepared through an interfacial self-assembly process. Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectra and X-ray photoelectron spectroscopy (XPS) were employed to study the interactions that induced the assembly of GO nanosheets and chitosan and identified that the results showed that the major interactions were from electrostatic interactions. The surface morphology of synthesized membrane can be further tuned by adjusting the concentration of the chitosan solution. This new method is very effective to improve the GO/chitosan composite membrane production and may promote its broad potential applications in battery industry and life sciences.

A convenient technique is reported to fabricate Ag-SiOx hyperbolic metamaterials (HMMs) as robust surface-enhanced Raman scattering (SERS) substrates based on roll-up nanotechnology. As an illustration, dramatic enhancement is achieved using Rhodamine 6G as a molecular probe, which indicates that a larger plasmonic density of states exist, leading to a greatly enhanced local electromagnetic (EM) field when the sample is irradiated with a laser beam. Optimized results are obtained by controlling the thickness of alumina coating onto Ag-SiOx HMMs using atomic layer deposition. Finite-difference time-domain simulations further illustrate the excitation of localized surface plasmon modes by calculating the EM field properties on the surface of Ag-SiOx HMMs. This efficient method of producing Ag-SiOx HMMs with highly SERS-active properties could spur expanding applications in metamaterials and bioanalysis.

A convenient technique was developed to fabricate gold-capped TiO 2 nanocomposites as robust, cost-efficient and recyclable surface-enhanced Raman scattering (SERS) substrates. The morphologies of obtained nanocomposites exhibit nanotube, nanolace, and nanopore nanostructures by adjusting TiO 2 anodization parameters. As an illustration, dramatic enhancement is achieved using Rhodamine 6G as a molecular probe. Owing to activation by the incident laser beam, the localized electromagnetic field on the nanocomposite surface can be enhanced subsequently amplifying the Raman signal. The topography can be further tuned to optimize the enhancement factor by adjusting the time of gold evaporation. Finite-difference time-domain calculations indicate the nanopore structure may possess excellent SERS characteristic due to the high density of hot spots. In addition, the substrate can be self-cleaned under ultraviolet irradiation due to the superior photocatalytic capacity of the Au–TiO 2 nanocomposites. Our Au–TiO 2 nanocomposites with highly SERS-active properties and recyclability shows promising applications in the detection and treatment of pollutants.

In this study, we first synthesised dumbbell-shaped Janus molecular nanoparticles (MNPs) based on polyhedral oligomeric silsesquioxane (POSS) and [60]fullerene (C60) (POSS–C60) via Bingel–Hirsch cyclopropanation, with the goal of combining their unique physical and chemical characteristics. The successful preparation of this new Janus POSS–C60 was confirmed by NMR, FT-IR and MALDI-TOF MS experiments. Then a co-precipitation method was used to prepare four kinds of polystyrene (PS) nanocomposites, namely, PS/POSS, PS/C60, PS/POSS/C60 (which is a physical mixture of PS, POSS and C60) and PS/POSS–C60. The effect of POSS, C60, POSS/C60 and POSS–C60 on the properties of PS was investigated. SEM results suggest a good and similar dispersion for all of the four prepared PS nanocomposites. The glass transition temperature (Tg) of PS is decreased with increasing filler content in a similar way for the four kinds of PS nanocomposites. Rheological result suggests a similar trend of the storage modulus change with increasing filler content, disregarding the chemical structure of fillers and combination of fillers. However, it was interesting to find that POSS alone is good for mechanical property reinforcement and C60 alone is good for thermal stability reinforcement for PS, while POSS–C60, which is a particle with chemically bonded POSS and C60, exhibit better reinforcement of both mechanical properties and thermal stability compared with pristine POSS, C60 and POSS/C60. Our work provides some new ideas for the preparation of polymer nanocomposites with novel particle shapes and unique properties.

Due to the introduction of wide bandgap (WBG) devices such as silicon carbide and gallium nitride devices, the power inverters with ultra-low loss, high temperature, and compact size are made possible for various applications. However, the increased dv/dt and switching frequency of WBG devices also aggravate the common-mode (CM) voltage related issues of the PWM inverter based systems. In the past few years, the magnified CM EMI emission and ground leakage currents in WBG based inverter systems are starting to draw attentions and becoming a concern among researchers and engineers. In this paper, the four-leg topology is investigated as a potential solution to the CM voltage generation of WBG inverters. Detailed design and implantation considerations of a GaN-based four-leg inverter are presented, and the performance of the inverter is also evaluated.

The use of gallium nitride (GaN) high-electron mobility transistors (HEMTs) is a promising solution for a highly efficient motor drive design due to their high-switching speed and low on-state resistance. However, the higher reverse voltage drop of GaN HEMTs than that of the conventional silicon (Si) devices generates significant reverse conduction loss during the freewheeling period. This phenomenon can be exacerbated especially when regenerative braking or bipolar PWM is utilized since the reverse conduction period increases. It can also lead to a device failure when high freewheeling current flows through the reverse conduction channel. This paper suggests a critical design consideration of GaN HEMT-based high-speed permanent magnet brushless DC motor drive regarding the reverse conduction and switching losses minimization. A diode-free GaN-HEMT-based single-phase brushless DC motor has been designed to quantify the effect of reverse conduction loss on the overall motor drive efficiency. Three different solutions to reduce the reverse conduction loss are applied and compared in detail. The switching characteristics are also investigated to quantify the effect of the additional antiparallel diode in GaN HEMT-based motor drive.

We design and fabricate a simple micro-system to collect analyte molecules in fluids for surface-enhanced Raman scattering (SERS) detection. The system is based on catalytic Au/SiO/Ti/Ag layered microengines by employing roll-up nanotechnology [1] and the Raman spectrum. Finite-difference time-domain method is employed to illustrate the excitation of localized surface plasmon modes by calculating the electromagnetic field on the rough microengine surface. The bubble-propelled microengines [2] adsorb analyte molecules in fluids, acting as molecule carriers. Pronounced SERS signals are observed on microengines with more carrier molecules compared with the same structure without automatic motions, which indicates outstanding molecule collection performance. Furthermore, optimized collection efficiency of the system is obtained by controlling the fuel concentration. This facile system for molecule collection and detection could spur expanding applications in bioanalysis and lab-on-a-chip research. [3]

Due to low loss and fast switching capabilities of gallium nitride (GaN) based power devices; there has been a strong interest in the replacement of silicon (Si) devices in power electronics converters for various applications. However, one of the concerns is that the high switching speed (dv/dt and di/dt) of GaN devices will deteriorate the EMI emission of power converters. Hence, this paper studies the common mode EMI emission of GaN based devices by taking a synchronous boost converter as a case study. It will be shown that, exploiting the full switching speed of GaN devices increases the EMI in very high frequency range by up to 10dB comparing to a Si counterpart, while slowing down the switching transition completely offsets the advantage on switching loss. Based on the above observation, two solutions are proposed to mitigate EMI generation of GaN converter without compromising its benefits on low switching loss.

Nowadays, oil contamination has become a major source of water pollution and results in the global environmental challenge. Although numerous efforts have been made on the fabrication of oil/water separation materials, their practical applications are still hindered by the low preparation efficiency, weak mechanical durability, poor chemical tolerance and environmental resistance, as well as low permeation flux. To overcome these drawbacks, herein, we directly anchor hydrophobic/oleophilic polyhedral oligomeric silsesquioxane (POSS) onto the surface of cotton fabric by one-step dipping strategy to yield a robust POSS based hydrophobic oil/water separation membrane. At First, commercially available octavinyl-POSS (VPOSS) was functionalized by 3-mercaptopropyltrimethoxysilane (MPTMS) via thiol-ene click reaction to afford a novel POSS derivate, named POSS-MPTMS. Then, it was used for modification of the cotton fabric by one-step dip-coating method to form a stable and robust POSS layer. The formed POSS layer endow modified cotton fabric become hydrophobic with the water contact angle higher than 142°. More importantly, the POSS modified fabric can withstand UV irradiation, chemical corrosion, ultrasonic washing as well as repeatedly mechanical abrasion for a long time. Solely driven by gravity, the modified fabric can enable separation of oil/water mixture with a permeation flux as high as 114,744 L·m−2·h−1. Moreover, it maintains excellent stability and effective separation property even in harsh environments with high concentration of acid, alkali, and salt solutions. We believe this facile strategy is a good solution for construction of advanced filtration materials for practical oil/water separation.

Silicon carbide (SiC)-based switching devices provide significant performance improvements in many aspects, including lower power dissipation, higher operating temperatures, and faster switching, compared with conventional Si devices. However, tradeoffs in efficiency, size, and weight between Si- and SiC-based converters are still unclear in the literature. In this paper, a bidirectional dc-dc converter that is suitable for hybrid or electric vehicle application is studied based on three sets of device combinations, e.g., all-silicon [conventional silicon insulated-gate bipolar transistors (IGBTs) and silicon PN diodes], hybrid (silicon IGBTs with SiC Schottky diodes), and all-SiC (SiC metal-oxide-semiconductor field-effect transistors with SiC Schottky diodes). At the switching frequency of 20 kHz, comparative analyses regarding the power loss reduction of power devices and efficiency improvements are carried out for the converters. Possible size and weight reduction is also investigated by increasing the operating frequencies of hybrid and all-SiC converters while reducing the capacitance and inductance values.

Polyhedral oligomeric silsesquioxane (POSS) is an attractive nano-building block for the preparation of organic-inorganic hybrid materials with diverse applications. However, hybrid microparticles based on POSS have rarely been reported as their preparation remains a challenge. In this work, we describe a facile approach for the fabrication of monodispersed organic-inorganic hybrid microparticles based on POSS (MBOPs) through thiol-Michael dispersion polymerization method. By adjusting the polymerization conditions and the monomer combinations, not only the size and uniformity, but also the POSS content of MBOPs can be tuned. The varied POSS content result in the enhanced UV resistance and thermal stability of hybrid MBOPs compared to purely organic microparticles. In addition, MBOPs could be regarded as precursors for formation of the inorganic SiOC ceramic microparticles with uniform size, well-defined micropore and good alkali resistance after high temperature removing the organic components. Considering the vast selection of POSS derivatives and the vast adaptability of chemical conversion that are possible, we believe that this work provides a platform for material chemists to fabrication of advanced microparticles with unique structures and performances from organic to inorganic.

In this paper, a silicon-carbide based capacitor-switched phase-shifted full bridge DC-DC converter circuit for electrical vehicles is investigated. The state-of-the-art silicon-carbide components were used as switching power devices. The reduction of conduction and switching losses has been achieved by using silicon-carbide devices. As a consequence, the performance of the converter is increased and weight and volume of the circuit are reduced.

The adoption of silicon carbide (SiC) MOSFETs in variable speed motor drives makes it possible to increase the inverter switching frequency up to several hundred kilohertz without incurring excessive inverter loss. As a result, the harmonic currents and related losses in the machine can be significantly reduced, and the dynamic performance of motor will also be improved. However, the increased switching frequency of SiC drives will increase the ground leakage current in the common mode (CM) path, presenting new challenges on CM choke design. This paper aims at understanding the CM choke design under this new circumstance. First, a simple and accurate frequency domain CM circuit modeling approach suitable for SiC motor drives is proposed and subsequently verified through experimental tests. Based on the model, required choke parameters are then determined through analytical calculation. Through comparative analysis, the impact of increased switching frequency on CM choke design is studied.

Titanium alloy Ti6Al4V, as difficult-to-cut material, has poor machinability. Conventional cutting fluid serves as a coolant and lubricant. In green drilling, water vapor is recognized as an effective coolant; however, its lubrication properties are not well known in drilling. This paper investigates the friction characteristics between chip and tool in green drilling Ti6Al4V, compared with that in sliding and turning process. A friction evaluation model is developed based on the equivalent model of drilling, then is used to calculate the effective friction coefficient. Results indicate that the friction coefficient on the tool-chip interface is considerably reduced in drilling by water vapor, so the drilling forces decrease, too. The friction coefficient decreases as velocity increases in drilling, which is different from the law of sliding tests; the friction coefficient increases when the distance to chisel edge increases.