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The stressed-oxidation behaviors of 2D woven SiCf/BN/SiC composites were investigated at 950 °C and 1100 °C in air. The different proportions (60%–90%) of the ultimate tensile strength (UTS) at corresponding temperatures were chosen as constant stress. The stressed-oxidation experiments were taken to failure or interrupted (240h). The UTS decreases by 20.75% at 950 °C and 30.71% at 1100 °C. The composites did not fail during stressed oxidation when subjected to constant stress corresponding to the initial linear and the beginning of nonlinear segments of the tensile curve, above which the composites failed with a maximum failure life of about 10h. Fiber degradation due to the thermal exposure and the fiber cracks caused by the oxidation of BN interface coating and SiC fiber could be responsible for the strength degradation and failure of the composites during stressed oxidation.

The tensile-tension fatigue behavior of minicomposite SiC/(PyC/SiC)2/SiC at room temperature was studied, and the residual mechanical properties of specimens were tested after 106 pre-fatigue cycles under different levels of stress. The results show that the residual strength first increases owing to the release of stress concentration and then decreases owing to excessive fiber wear. In addition, it is worth noting that the tensile curve of pre-fatigue specimens deflects twice; the first occurrence correlates with matrix crack reopening, and the second occurs when the uniaxial tensile load exceeds the pre-fatigue stress, and the degree of deflection also gradually decreases or almost disappears.

In this study, a kind of honeycomb-structured woven fabric was investigated and the effect of yarn size and fabric layer on the compression property of the fabric-reinforced polyurethane elastomer composites was discussed. The honeycomb-structured fabric was analyzed from the cross-sectional view of combined regular hexagonal cells. The three-layer fabric and four-layer fabric were designed and fabricated using three different finenesses of weft yarns. After that, polyurethane elastomer was used as matrix resin and the 3D honeycomb-structured fabrics were composited. In-plane compression test was conducted to investigate the cushioning property. For samples with doubled weft yarns, such as 3L-2W, the stress value when compressed to 65% of its initial thickness (CV65%), energy absorption (EA), and specific energy absorption (SEA) showed higher values than 3L-1W and 3L-1.5W. It was concluded that the weft yarn fineness had an important effect on the compression property of fabric composites. The thicker yarn size, the stronger cell wall, and the lightweight honeycomb-structure composite was difficult to be compressed. As to the fabric layers, three-layer composites showed a higher compression property than four-layer ones. The reason for this was considered to be the fiber volume content, which was the key parameter affecting composite mechanical properties. As the real fiber volume content in a three-layer fabric composite was higher than that of a four-layer fabric composite, it was resulted in a higher allowable safe stress and energy absorption ability. It can be concluded that the yarn fineness and fabric layers had an influence on the compression property, which can be seemed as the design parameters of honeycomb-structured fabrics for cushion applications.

Some textiles and apparel cannot be laundered, such as astronauts’ clothes on the space station, smart textiles that contain optical fiber electronic devices. Thus, self-cleaning technology can be considered as a potential technique that can be used to remove sebum, which is secreted by the human body, from such textiles and apparel. In this study, the photocatalytic self-cleaning properties of cotton fabrics coated with TiO2 nanoparticles were evaluated for their efficacy in removing the sebum that is transferred from human skin to the fabric. Cotton fabric was treated with four different weight ratios of the TiO2 photocatalyst, and the surface morphology, elemental composition, and thermogravimetric analysis were determined and evaluated. For the self-cleaning properties, the color changes of the photographic images and the differences in the colors were recorded and obtained using oleic acid as the pollutant and Oil Red O as the coloring agent before and after simulated sunlight irradiation. The results showed that, compared to 0 wt% coated fabric, the 20 wt% coated fabric decolorized in the shortest time, and it showed a higher initial speed in color difference. For the lower weight ratios, such as 1 wt%, much more time was required to obtain the same color difference as the 20 wt% coated fabric. It meant that increasing the weight ratio and irradiation time provided enhanced self-cleaning properties. In addition, Fourier Transform Infrared Spectroscopy (FTIR) spectra were evaluated in order to obtain a quantitative evaluation of the pollutants. Examination of the peaks of oleic acid clarified that the self-cleaning properties increased as the weight ratio and irradiation time increased. Moreover, results of the high performance liquid chromatography (HPLC) showed that besides 0 wt% coated fabric, it cannot detect the contaminant on the other samples after irradiation, which were found to concide with the results showed by FTIR. Based on this study, we found that the color changes from photographs and the colorimeter can be used as references, but they do not provide decisive evidence of degradation, especially for colorless pollutants. The FTIR spectra and liquid chromatography can be used to make decisive judgements concerning the self-cleaning properties of photocatalysis. The findings in this study identified a potential application for textiles and apparel that cannot be washed in liquid media, such as astronauts’ suits on the station, smart textiles for actuators and sensors.

The theoretical Shockley-Queisser limit of photon-electricity conversion in a conventional p-n junction could be potentially overcome by the bulk photovoltaic effect that uniquely occurs in non-centrosymmetric materials. Using strain-gradient engineering, the flexo-photovoltaic effect, that is, the strain-gradient-induced bulk photovoltaic effect, can be activated in centrosymmetric semiconductors, considerably expanding material choices for future sensing and energy applications. Here we report an experimental demonstration of the flexo-photovoltaic effect in an archetypal two-dimensional material, MoS2, by using a strain-gradient engineering approach based on the structural inhomogeneity and phase transition of a hybrid system consisting of MoS2 and VO2. The experimental bulk photovoltaic coefficient in MoS2 is orders of magnitude higher than that in most non-centrosymmetric materials. Our findings unveil the fundamental relation between the flexo-photovoltaic effect and a strain gradient in low-dimensional materials, which could potentially inspire the exploration of new optoelectronic phenomena in strain-gradient-engineered materials.

Polyethylene (PE) membrane has poor wettability and poor thermal stability, which results in insufficient wetting by liquid electrolytes, thermal shrinkage, and no guarantee of safety. In addition, polyethylene terephthalate (PET) nonwoven fabric has inhomogeneous pores and no shutdown function. Therefore, it may cause some problems for independent use, either in the assembly or in usage. In this study, a hybrid separator used in lithium-ion batteries was investigated. The separator was fabricated by laminating a PE membrane and PET nonwoven fabric with or without a ceramic coating on the PET nonwoven. The morphology, wettability, thermal stability, and battery performance were evaluated, and the results showed that the homogeneous distribution of pores can be obtained from the hybrid separators. The wettability properties were also improved in terms of contact angle, liquid electrolyte absorption height, and the decrease in the spreading area. Moreover, with laminated PET nonwoven fabric, the hybrid separators kept the dimensional shape at 180°C for 1 hour of heating, but the PE membrane shrank and became a small wad. The difference between the shutdown and meltdown temperatures ensured that the battery was safe to use. In addition, the evaluation of the battery’s performance indicated that the hybrid separators can be used instead of a PE membrane. This study showed a facile method for the preparation of a hybrid composite separator with improved wettability, thermal stability, and safety for lithium-ion batteries, and it has the potential to be used extensively in the future.

Single crystals of LiCaAlF6:Eu and LiCaAlF6:Ce with a diameter of 25.4 mm were grown by the Bridgman method in a nonvacuum atmosphere. The as-grown crystals are highly transparent and crack- and in...

Carbon fiber-reinforced polymer composites (CFRPs) have many features, such as lightweight, high specific strength, and excellent chemical resistance. However, the adhesion at the interface of the CFRPs, which are composed of fiber and resin, is poor. Thus, de-lamination and interfacial peeling occur, and the mechanical properties, such as intrinsic strength and rigidity, decrease. Fiber surface modification by plasma and silane coupling treatments has attracted much attention to improve these properties. In this study, argon and oxygen mixed gas plasma treatment was used as pretreatment to introduce hydroxyl group on the fiber surface. This method was utilized to improve the adhesion between the fiber and resin. A silane coupling treatment was conducted to bond the carbon fiber and epoxy resin by chemical covalent bonding. The effect of silane coupling treatment on the interfacial property of CFRPs was investigated. Elemental analysis of the surface modified carbon fiber was explored through energy dispersive X-ray spectrometry. The functional groups of different carbon fiber surfaces were analyzed through X-ray photoelectron spectroscopy. The wettability of the treated carbon fiber was examined with a contact angle meter. The interlaminar shear strength was determined with a short beam method.

Defects in strongly correlated materials such as V2O3 play influential roles on their electrical properties. Understanding the defects' structure is of paramount importance. In this project, we investigate defect structures in V2O3 grown via a flux method. We use AFM to see surface features in several large flake-like particles that exhibit characteristics of spiral growth. We also use Bragg coherent diffractive imaging (BCDI) to probe in 3 dimensions a smaller particle without flake-like morphology and note an absence of the pure screw dislocation characteristic of spiral growth. We identified and measured several defects by comparing the observed local displacement of the crystal, measured via BCDI to well-known models of the displacement around defects in the crystal. We identified two partial dislocations in the crystal. We discuss how defects of different types influence the morphology of V2O3 crystals grown via a flux method.

Realizing high-efficiency solar evaporation has great potential for purification of sewage and seawater desalination. However, continuous water supply, solar energy conversion, and thermal manageme...

Separation and recovery of high-purity Si powder from kerf-loss Si slurry waste is a critical challenge for the photovoltaic industry. A green surfactant poly (propylene glycol) bis (2-aminopropyl ether) (PEA) was employed as a collector to facilitate the separation of Si and SiC from kerf-loss Si waste during flotation process. Single flotation tests of Si and SiC were conducted using 5 × 10−6 mol/L PEA, respectively. The separation efficiencies of Si and SiC in conjunction with PEA adsorption mechanism were investigated. It was found that the maximum recoveries rate of SiC and Si were 90.59% (pH 9.00) and 80.93% (pH 1.96), respectively. Furthermore, the maximum Si grade was determined as 92.31% at pH 8.95 for the sinking part of the mixture generating excellent floatability and selectivity. Zeta potential measurements, FT-IR spectra, and XPS analyses demonstrated that PEA was present on the surface of Si and SiC through electrostatic and hydrogen-bond interactions. The adsorption mechanism was explained based on the results. This research provides an efficient and environmentally friendly route for the separation and recovery of high purity silicon from kerf-loss Si waste.

Ultrasonic vibration–assisted EDM (UEDM) has excellent performance on difficult-to-machine materials processing such as titanium alloy, stellite, and nickel-based alloy, and it was hard to describe the material removal process and surface generation mechanism due to the complex physiochemical reactions during UEDM. In the present study, the material removal mechanism is fundamentally studied based on heat transfer theory. The model of microscopic removal volume of single pulse in UEDM is established according to the characteristics of EDM removal mechanism and the interference of ultrasonic vibration energy. The micro-surface topography generating process is described and the influence of ultrasonic vibration on the machined surface is analyzed. Both simulation calculation and experiment validation are executed in order to verify the accuracy of the theoretical derivation. As the experimental results have shown, the surface-generating process is matching well with the theoretical deduction; the carbon deposit area is reduced and the surface roughness is decreased due to the ultrasonic vibration interference. The machined surface quality can be modified by adjusting the matching performance of ultrasonic vibration energy and EDM energy.

The temperature-induced variation in operating force of flow control valves may result in performance degradation or even jam faults of fuel metering unit (FMU), which significantly affects the safety of aircrafts. In this work, an analytical modeling approach of temperature-sensitive operating-force of servo valve is proposed to investigate the temperature characteristics in varying temperature conditions. Considering the temperature effects, a new extended model of flow force is built and an analytical model of valve friction is also derived theoretically based on the dynamic clearance induced by thermal effects. The extremum condition of friction is obtained to analyze the characteristic-temperature points where jam faults occur easily. The numerical results show that flow force increases firstly and then decreases as temperature increases under a constant valve opening. The maximum friction of flow servo valve can be uniquely determined when the structural parameters and ambient temperature are given. The worst situation just happens at the characteristic-temperature points, which are linearly related to the axial temperature gradients of valve spool. Such evaluations may give an explanation for the temperature-induced jam faults of vulnerable valves and provide a reference for designers to determine a suitable working-temperature range of valves in practice.

In the search for chemically stable two-dimensional (2D) materials with high in-plane mobility, proper bandgap, and compatibility with vapor-based fabrication, van der Waals semiconductor SiP has become a potential candidate as a robust variation of black phosphorous. While bulk SiP crystals were synthesized in the 1970s, the vapor-based synthesis of SiP nanostructures or thin films is still absent. We here report the first chemical vapor growth of SiP nanostructures on SiO2/Si substrate. SiP islands with lateral size up to 20 µm and showing well-defined Raman signals were grown on SiO2/Si substrate or on SiP-containing concentric rings. The presence of SiP phase is confirmed by XRD. The formation of rings and islands is explained by a multiple coffee ring growth model where a dynamic fluctuation of droplet growth front induces the topography of concentric ring surfaces. This new growth method might shed light on the controlled growth of group IV-III high-mobility 2D semiconductors.

Summary Two-dimensional materials with abundant in-plane pores (porous 2D materials) have shown high performances as catalysts, especially for photocatalysis and electrocatalysis, owing to their distinct microstructural advantages originating from both 2D materials and porous materials. Here, the recent progress in porous 2D materials in photocatalysis and electrocatalysis is reviewed. We first highlight the influence of their special structural merits on the processes of photocatalysis and electrocatalysis, including transport of ion and/or charge carriers, surface active sites, stability, modifications, electronic band structure, and light absorption properties. Representative synthetic methods for porous 2D materials are also introduced classified by top-down and bottom-up routes. In addition, their applications in different aspects of photocatalysis and electrocatalysis are presented systematically. In conclusion, we propose some opportunities and challenges for the development of porous 2D materials, with the hope of further facilitating the applications of these emerging advanced materials in photocatalysis and electrolysis.

In this paper, an ultrahigh sensitive hydrazine electrochemical sensor based on gold nanoparticles integrated into a reduced graphene oxide/nickel foam (AuNPs-rGO@NF) hybrid structure was synthesized using a facile coating and electrochemical deposition method. The morphology and elemental composition of the as-synthesized AuNPs-rGO@NF structure was comprehensively investigated. Both cyclic voltammetry and potential amperometry results show the optimum AuNPs-rGO@NF sensor exhibits excellent electrochemical performances including higher sensitivity (14.635 μA μM−1 cm−2), lower limit of detection (0.056 μM; S/N = 3), wider linear detection range (0.2–200 μM), good selectivity and long-term stability. Meanwhile, the results of real sample analysis indicate the AuNPs-rGO@NF sensor has great potential for practical electrochemical hydrazine sensing applications.

Most high-quality CdTe thin films are epitaxially grown on single-crystalline substrates through chemical bondings by either molecular beam epitaxy or metalorganic chemical vapor deposition. The ep...

With the influx of flexible electronics as well as the emergence or prediction of unique phenomena in two dimensional forms of materials, epitaxy at weakly-coupled interfaces is gaining momentum as...

The reconfigurability of the electrical heterostructure featured with external variables, such as temperature, voltage, and strain, enabled electronic/optical phase transition in functional layers has great potential for future photonics, computing, and adaptive circuits. VO2 has been regarded as an archetypal phase transition building block with superior metal-insulator transition characteristics. However, the reconfigurable VO2-based heterostructure and the associated devices are rare due to the fundamental challenge in integrating high-quality VO2 in technologically important substrates. In this report, for the first time, we show the remote epitaxy of VO2 and the demonstration of a vertical diode device in a graphene/epitaxial VO2/single-crystalline BN/graphite structure with VO2 as a reconfigurable phase-change material and hexagonal boron nitride (h-BN) as an insulating layer. By diffraction and electrical transport studies, we show that the remote epitaxial VO2 films exhibit higher structural and electrical quality than direct epitaxial ones. By high-resolution transmission electron microscopy and Cs-corrected scanning transmission electron microscopy, we show that a graphene buffered substrate leads to a less strained VO2 film than the bare substrate. In the reconfigurable diode, we find that the Fermi level change and spectral weight shift along with the metal-insulator transition of VO2 could modify the transport characteristics. The work suggests the feasibility of developing a single-crystalline VO2-based reconfigurable heterostructure with arbitrary substrates and sheds light on designing novel adaptive photonics and electrical devices and circuits.

In this research, a high-boron-content composite material with both neutron and γ rays shielding properties was developed by an optimized design and manufacture. It consists of 304 stainless steel as the matrix and spherical boron carbide (B4C) particles as the functional particles. The content of B4C is 24.68 wt%, and the particles’ radius is 1.53 mm. The density of the newly designed material is 5.17 g·cm−3, about 68.02% of that of traditional borated stainless steel containing 1.7 wt% boron, while its neutrons shielding performance is much better. Firstly, focusing on shielding properties and material density, the content and the size of B4C were optimized by the Genetic Algorithm (GA) program combined with the MCNP program. Then, some samples of the material were manufactured by the infiltration casting technique according to the optimized results. The actual density of the samples was 5.21 g cm−3. In addition, the neutron and γ rays shielding performance of the samples and borated stainless steel containing 1.7 wt% boron was tested by using an 241Am–Be neutron source and 60Co and 137Cs γ rays sources, respectively, and the results were compared. It can be concluded that the new designed material could be used as a material for nuclear power plants or spent-fuel storage and transportation containers with high requirements for mobility.

Hydrophobic deep eutectic solvents (DESs) emerge as candidates to extract organic substrates from aqueous solutions. The DES-aqueous liquid-liquid interface plays a vital role in the extraction ability of hydrophobic DES because the non-bulk structure of molecules at the interface could cause thermodynamic and kinetic barriers. One question is how the DES compositions affect the structural features of the DES-aqueous liquid-liquid interface. We investigate the density profile, dipole moment and hydrogen bonds of eight hydrophobic DES-aqueous liquid-liquid interfaces using molecular dynamics simulations. The eight DESs are composed of four organic compounds: decanoic acid, menthol, thymol, and lidocaine. The simulation results show the variations of dipole moment and hydrogen bond structure and dynamics at the liquid-liquid interfaces. Such variations could influence the extraction ability of DES through adjusting the partition and kinetics of organic substrates in the DES-aqueous biphasic systems.

Wear phenomenon occurring in the slipper/swashplate pair of the high-speed piston pump is investigated in this paper. Analytical model along with the finite difference method is adopted to solve the transient thermo-elasto-hydrodynamic (TEHD) lubrication process. The proposed approach considers the slipper wear clearance and deformations caused by thermal deflection and hydrostatic pressure. The results show that the lubricating oil film is unevenly distributed. Consequently, discrete friction area wear model is proposed to account for the partial abrasion characteristics. In addition, the slipper wear profile is dynamically updated with the pump working time extended. The simulation results indicate that the wear of the slipper pair can be reduced by operating the pump within the high-speed/low pressure/small displacement zone.

Many published models can be used to analyse the sealing performance of rotary lip seal. The surfaces are normally assumed to be periodic variation. However, the quasi-randomness of surface height distribution should be considered, especially the non-Gaussian distribution. Hence, a mixed elastohydrodynamic lubrication model with non-Gaussian surfaces is proposed and used to analyse the effects of sealed fluid pressure on the seal performance in this paper. Based on digital filter and Johnson’s translator system, a rough surface simulation method is introduced to simulate non-Gaussian rough surface. Based on this method the mixed lubrication model with non-Gaussian surfaces is built. The proposed model is verified by comparing the simulation results to experimental observations. Furthermore, it is hardly to find the research focused on the effects of sealed pressure. Hence, the effects of sealed fluid pressure on the seal performance is focused.

Hydrophobic deep eutectic solvents (DESs) emerge as candidates to extract organic substrates from aqueous solutions. The DES-aqueous liquid-liquid interface plays a vital role in the extraction ability of hydrophobic DES because the non-bulk structure of molecules at the interface could cause thermodynamic and kinetic barriers. One question is how the DES compositions affect the structural features of the DES-aqueous liquid-liquid interface. We investigate the density profile, dipole moment and hydrogen bonds of eight hydrophobic DES-aqueous liquid-liquid interfaces using molecular dynamics simulations. The eight DESs are composed of four organic compounds: decanoic acid, menthol, thymol, and lidocaine. The simulation results show the variations of dipole moment and hydrogen bond structure and dynamics at the liquid-liquid interfaces. Such variations could influence the extraction ability of DES through adjusting the partition and kinetics of organic substrates in the DES-aqueous biphasic systems.

Highlighted by the discovery of high-temperature superconductivity, strongly correlated oxides with highly distorted perovskite structures serve as intriguing model systems for pursuing emerging materials physics and testing technological concepts. While 3d correlated oxides with a distorted perovskite structure are not uncommon, their 4d counterparts are unfortunately rare. In this work, we report the tuning of the electrical and optical properties of a quasi-2D perovskite niobate CsBiNb2O7 via hydrogenation. It is observed that hydrogenation induces drastic changes of lattice dynamics, optical transmission, and conductance. It is suggested that changing the orbital occupancy of Nb d orbitals could trigger the on-site Coulomb interaction in the NbO6 octahedron. The observed hydrogen doping-induced electrical plasticity is implemented for simulating neural synaptic activity. Our finding sheds light on the role of hydrogen in 4d transition metal oxides and suggests a new avenue for the design and development of novel electronic phases.

Understanding the domain structure of two-dimensional materials is of paramount importance for the design of next generation microelectronic devices. Here, the authors employ a Dion--Jacobson layered oxide as a model system to study the ferroelectric domain structure with atomic scale analysis. They reveal the existence of a unit-cell-thick ferroelectric domain size as well as both 180\ifmmode^\circ\else\textdegree\fi{} and 90\ifmmode^\circ\else\textdegree\fi{} domain walls in a free-standing ferroelectric oxide. This may suggest ways to achieve unit-cell-thick domain structures and shed light on promising material solutions for emerging nonvolatile high-density memories and synaptic devices.

Spintronic device is promising due to their potential merits of low power consumption and fast operation. In this work, we present the effect of persistent spin helix, barrier resistance, spin polarization and channel resistance on the magnetoresistance of spin field effect transistor (FET) when the channel material carries strong spin-orbit coupling (SOC) and persistent spin helix (PSH). Our device shows promising spintronic performance with current device technologies.

Biomass deconstruction and lignin depolymerization was performed using three different deep eutectic solvents. Various temperature (110°, 130°, and 150 °C) and time (1, 5, 10, 15 min) conditions were tested in a 2450 MHz microwave reactor. Oxalic acid (130 °C, 15 min) and formic acid DES (150 °C, 15 min) gave the highest lignin yield. Microwave heating reduced the processing time significantly. NMR characterization shows that microwave heating promotes selective bond cleavage during lignin depolymerization and has a narrow molecular weight distribution compared to conventional heating techniques. Molecular dynamic simulations showed that certain lignin bonds are stretched under the electric field imparted during microwave irradiation, increasing its probability of breaking.

Crystallographic dislocation has been well-known to be one of the major causes responsible for the unfavorable carrier dynamics in conventional semiconductor devices. Halide perovskite has exhibited promising applications in optoelectronic devices. However, how dislocation impacts its carrier dynamics in the ‘defects-tolerant’ halide perovskite is largely unknown. Here, via a remote epitaxy approach using polar substrates coated with graphene, we synthesize epitaxial halide perovskite with controlled dislocation density. First-principle calculations and molecular-dynamics simulations reveal weak film-substrate interaction and low density dislocation mechanism in remote epitaxy, respectively. High-resolution transmission electron microscopy, high-resolution atomic force microscopy and Cs-corrected scanning transmission electron microscopy unveil the lattice/atomic and dislocation structure of the remote epitaxial film. The controlling of dislocation density enables the unveiling of the dislocation-carrier dynamic relation in halide perovskite. The study provides an avenue to develop free-standing halide perovskite film with low dislocation density and improved carried dynamics., Crystallographic dislocation has proven harmful to the carrier dynamics in conventional semiconductors but it is unexplored in metal halide perovskites. Here Jiang et al. grow remote epitaxial perovskite films on graphene with density-controlled dislocations and confirm their negative impact.

A series of phase change materials (PCMs) microcapsules based on industrial paraffin core and calcium carbonate (CaCO3) shell were successfully synthesized for thermal energy storage. The SEM results revealed that the composites are mainly of spherical morphology. The FT-IR and XRD confirmed that the composites were mainly composed of the vaterite CaCO3, paraffin, and a small amount of calcite CaCO3. Compared with the composites prepared with sodium dodecyl sulfonate (SDS) as anionic surfactant, DSC and TG results of composites prepared with sodium dodecyl benzene sulfonate (SDBS) demonstrated that the encapsulation efficiency increased but the thermal stability decreased. Besides, with the different concentrations of CaCl2, the influence of anionic surfactants on the performance of microcapsules had been discussed. The results exhibited higher encapsulation efficiency of microcapsules with SDBS than that with SDS, even up to ten times. When the mass of CaCl2 is about 0.05 mol, encapsulation efficiency with SDBS can reach up to 20.80%. Accordingly, the super-cooling of PCM was significantly suppressed. From all results, it is worth developing the PCMs microcapsules with CaCO3 shell modulated by different anionic surfactants for thermal energy storage and SDBS is more suitable for preparing PCM@CaCO3 microcapsules.

A simple one-step interfacial polymerization method without special requirements for fabrication of paraffin@ polymethyl methacrylate (PCM@PMMA) nanocapsules is developed. Moreover, all the raw materials are cheap, innocuous and rich in resource. The influences of the mass ratio of methyl methacrylate/Paraffin (MMA/PCM) and stirring speed are studied. Scanning electron microscope (SEM), Fourier transformed infrared spectroscopy (FT-IR), Differential scanning calorimetric (DSC) and Thermo gravimetric analysis (TGA) are employed to characterize the as-prepared PCM@PMMA nanocapsules. Nano-encapsulated PCM could be successfully obtained under the stirring speed of 800 rpm for 2.5 h. The surface of the spherical nano-encapsulated PCMs is homogeneous, smooth and compact, and the particle size is in the range of 200–400 nm. The nano-encapsulated PCM are stable and reliable with the melting enthalpy of about 64.93 J/g and crystallization enthalpy of about 66.45 J/g. TGA results indicate that the nano-encapsulated PCM degraded in three steps and have good thermal stability with the content of the PCM about 52.95%. The PCM@PMMA nanocapsules could be promising for thermal energy storage application.

Atmospheric pressure chemical vapor deposition (APCVD) is employed for the synthesis of layered vanadium disulfide. By tuning several critical growth parameters, we achieve VS2 flakes with lateral ...

Traditionally, a high-quality CdTe film can only be grown on a single crystal substrate with a small lattice mismatch. Herein, we report the epitaxy of CdTe films on monolayer single crystal graphene buffered amorphous SiO2/Si(100) substrates, despite a 86% lattice mismatch between CdTe(111) and graphene. X-ray pole figure, electron backscatter diffraction mapping and transmission electron microscopy all confirm that the epitaxial CdTe films are composed of two domains: the primary and the Σ3 twin. The crystal quality of films is shown to improve as the post-deposition annealing temperature increases. However, the rotational misalignment in CdTe remains large even after annealing. Through density functional theory calculations on the charge transfer distribution at the interface of CdTe and graphene, it is found that the interface is dominated by the weak van der Waals interaction, which explains the large spread of in-plane orientation in CdTe films. Furthermore, the rotational misalignment in graphene itself is also confirmed to produce the large in-plane orientation spread in CdTe films. Although imperfect in epitaxy quality, this work demonstrates that monolayer single crystal graphene can buffer amorphous substrates for growing epitaxial films, and hence hints an opportunity for developing advanced thin film devices using graphene as a template.

Unlike the vast majority of transition metal dichalcogenides which are semiconductors, vanadium disulfide is metallic and conductive. This makes it particularly promising as an electrode material in lithium-ion batteries. However, vanadium disulfide exhibits poor stability due to large Peierls distortion during cycling. Here we report that vanadium disulfide flakes can be rendered stable in the electrochemical environment of a lithium-ion battery by conformally coating them with a ~2.5 nm thick titanium disulfide layer. Density functional theory calculations indicate that the titanium disulfide coating is far less susceptible to Peierls distortion during the lithiation-delithiation process, enabling it to stabilize the underlying vanadium disulfide material. The titanium disulfide coated vanadium disulfide cathode exhibits an operating voltage of ~2 V, high specific capacity (~180 mAh g−1 @200 mA g−1 current density) and rate capability (~70 mAh g−1 @1000 mA g−1), while achieving capacity retention close to 100% after 400 charge−discharge steps., VS2 is a promising cathode material for lithium-ion batteries, but is susceptible to Peierls distortion during (de)lithiation. Here the authors show that VS2 cathodes can be stabilized by conformally coating them with a nanoscale TiS2 protective layer, leading to impressive electrochemical performance.

The discovery of hydrogen-induced electronic phase transitions in strongly correlated materials such as rare-earth nickelates has opened up a new paradigm in regulating materials’ properties for both fundamental study and technological applications. However, the microscopic understanding of how protons and electrons behave in the phase transition is lacking, mainly due to the difficulty in the characterization of the hydrogen doping level. Here, we demonstrate the quantification and trajectory of hydrogen in strain-regulated SmNiO3 by using nuclear reaction analysis. Introducing 2.4% of elastic strain in SmNiO3 reduces the incorporated hydrogen concentration from ~1021 cm−3 to ~1020 cm−3. Unexpectedly, despite a lower hydrogen concentration, a more significant modification in resistivity is observed for tensile-strained SmNiO3, substantially different from the previous understanding. We argue that this transition is explained by an intermediate metastable state occurring in the transient diffusion process of hydrogen, despite the absence of hydrogen at the post-transition stage., Nature Communications, 10 (1), ISSN:2041-1723

The functionality and performance of a semiconductor is determined by its bandgap. Alloying, as for instance in InxGa1-xN, has been a mainstream strategy for tuning the bandgap. Keeping the semiconductor alloys in the miscibility gap (being homogeneous), however, is non-trivial. This challenge is now being extended to halide perovskites – an emerging class of photovoltaic materials. While the bandgap can be conveniently tuned by mixing different halogen ions, as in CsPb(BrxI1-x)3, the so-called mixed-halide perovskites suffer from severe phase separation under illumination. Here, we discover that such phase separation can be highly suppressed by embedding nanocrystals of mixed-halide perovskites in an endotaxial matrix. The tuned bandgap remains remarkably stable under extremely intensive illumination. The agreement between the experiments and a nucleation model suggests that the size of the nanocrystals and the host-guest interfaces are critical for the photo-stability. The stabilized bandgap will be essential for the development of perovskite-based optoelectronics, such as tandem solar cells and full-color LEDs., The bandgap of mixed-halide perovskites can be continuously tuned by changing the halide ratio, but the crystals have poor photo-stability. Here the authors show that photoinduced phase separation is suppressed when perovskite nanocrystals are embedded in a non-perovskite endotaxial matrix.

As a promising anode material with a graphite-like layered structure for lithium ion batteries (LIBs), molybdenum disulfide (MoS2) suffers from poor electrical conductivity and rapid capacity fading. A heterostructure with conductive phases is considered as an effective solution to tackle these challenges, while rational construction and elaborate engineering of the heterostructure with maximized advantages from each component is highly desirable. Herein, we report the fabrication of a unique heterostructure composed of MoS2/Mo2N with nitrogen doped carbon (MoS2/Mo2N/C) via a stepwise cooperative assembly-directed strategy. Instead of using traditional NH3, a Mo2N based heterostructure was formed by in situ stepwise nitridation of Mo sources with dopamine and thiourea. The hierarchical porous tubular nanostructure with high electrical conductivity showed a remarkable electrochemical performance with a high specific capacity (945 mA h g−1 at 0.1 A g−1) and excellent cycling stability, which makes it one of the best Mo-based materials. Confirmed by density functional theory (DFT) calculations, introduction of Mo2N with abundant nitrogen vacancies generated an interfacial electric field in MoS2/Mo2N heterojunctions, which promotes charge transfer and electrochemical reaction kinetics. This work provides possible strategies for the development of high performance heterostructured electrodes for LIBs and other energy storage devices.

In this study, a new design method for a three-dimensional hollow structure woven fabric was proposed and the effect of cellular size on the cushioning property of the fabric-reinforced polyurethane elastomer composite was investigated. The fabric structure was analyzed from a cross-section view and the theoretical equations for the warp and weft yarns were proposed, using the fabric layer and cellular size as parameters. Nine kinds of fabrics with different layers and cellular size were fabricated with a Jacquard loom and reinforced with polyurethane elastomer to yield fabric composites. Then the effect of cellular size on the cushioning property of the fabric composites was discussed. The results showed that upon increasing the cellular size, the cellular fabric composite exhibited lower compression resistance. Moreover, the stress at a strain of 65% and the energy absorbed in the loading process were increased with decreasing cellular size. Moreover, the compression resilience was also changed with the cellular size. It can be concluded that the cellular size had an important effect on the cushioning property of the fabric composite, which can be considered as a design parameter for cushion material based on its usages.

Despite their weak nature, van der Waals (vdW) interactions have been shown to effectively control the optoelectronic and vibrational properties of layered materials. However, how vdW effects exist in Ruddlesden–Popper layered halide perovskites remains unclear. Here we reveal the role of interlayer vdW force in Ruddlesden–Popper perovskite in regulating phase-transition kinetics and carrier dynamics based on high-quality epitaxial single-crystalline (C4H9NH3)2PbI4 flakes with controlled dimensions. Both substrate–perovskite epitaxial interaction and interlayer vdW interaction play significant roles in suppressing the structural phase transition. With reducing flake thickness from ∼100 to ∼20 nm, electron–phonon coupling strength decreases by ∼30%, suggesting the ineffectiveness of phonon confinement of the natural quantum wells. Therefore, the conventional understanding that vdW perovskite is equivalent to a multiple quantum well has to be substantially amended due to significant nonlocal phononic effect...

Biophysical and biochemical properties of the extracellular matrix (ECM) are important for regulation of cell behaviors and tissue functions. In this study, we fabricated monolayers of gelatin nanofibers on both sides of a honeycomb micro-frame by electrospinning and chemical crosslinking, resulting in tri-layer patches with adjustable thickness and pore size. Fibroblast cells were cultured on this tri-layer scaffold, showing an enhanced cell proliferation. More importantly, our results showed an efficient cell infiltration into the space between the two fiber layers and 3D cell distribution suitable for cell based assays.

Hexagonal-phase NaYF4:Yb3+/Ho3+ nanocrystals (with size of 20 nm) were successfully prepared by a modified solution-based method. Under 980 nm near- infrared (NIR) excitation, the upconversion (UC) emission was tuned from green to red in NaYF4:Yb3+/Ho3+ nanocrystals by introducing Ce3+ ions. The corresponding red to green (R/G) emission ratio of Ho3+ increased by approximately 10-fold as the Ce3+ concentration increased to 14%. However, the overall UC emission intensity gradually decreased. A series of core–shell structures for NaYF4:Yb3+/Ho3+/Ce3+@NaYF4:Yb3+ nanocrystals codoped with different Yb3+ ion concentrations in the shell was successfully fabricated by a sequential growth process to further enhance the red UC emission intensity. When the Yb3+ concentration from the shell of NaYF4:Yb3+ was increased from 0% to 20%, the UC emission intensity of the core–shell nanocrystals first increased and then decreased. Moreover, the highest UC emission intensity was obtained in the core–shell nanocrystals with 10% Yb3+. Experimental results indicated red UC was enhanced due to the resonance energy transfer between adjacent Ho3+ and Ce3+ and Yb3+ and Ho3+ ions. These nanocrystals with red UC emission have great potential in the biological field and multicolor applications.

Hydrophobic deep eutectic solvents (DESs) have emerged as excellent extractants. Their performance depends on the heterogeneous hydrogen bond environment formed by multiple hydrogen bond donors and acceptors. An understanding of this heterogeneous hydrogen bond environment can be used to develop principles for designing high-performance DESs for extraction and other separation applications. We investigate the structure and dynamics of hydrogen bonds in eight hydrophobic DESs formed by decanoic acid, menthol, thymol, and Lidocaine using molecular dynamics simulations. The results show the diversity of hydrogen bonds in the eight DESs and their impact on diffusivity and molecular association. Each DES possesses four-six types of hydrogen bonds and one or two of them overwhelm the others in quantity and lifetime. The dominating hydrogen bonds determine whether the DESs are governed by intra- or inter-component associations. The component diffusivity presents an inverse relationship with the hydrogen bond strength.

The excessive use and disposal of plastic packaging materials have drawn increasing concerns from the society because of the detrimental effect on environment and ecosystems. As the most widely used fruit packing material, polyethylene (PE) film is not suitable for long-term preservation of some tropical fruits, such as mangos, due to its inferior gas permeability. Cellulose based film can be made from renewable resources and is biodegradable and environmental-friendly, which makes it a promising alternative to PE as a packaging material. In this study, cellulose film synthesized from delignified banana stem fibers via an ionic liquid 1-Allyl-3-methylimidazolium chloride ([AMIm][Cl]) were evaluated as packing material for mangos preservation. The moisture vapor transmission rate and gas transmission rate of the synthesized cellulose film were 1,969.1 g/(m2⋅24 h) and 10,015.4 ml/(m2⋅24 h), respectively, which are significantly higher than those of commercial PE films. The high permeability is beneficial to the release of ethylene so that contribute to extend fruit ripening period. As a result, cellulose film packaging significantly decreased the disease and color indexes of mangos, while prolonged the storage and shelf life of marketable fruits. In addition, the cellulose film was decomposed in soils in 4 weeks, indicating an excellent biodegradability as compared to the PE plastic film.

The dose uniformity and penumbra in the treatment field are important factors in radiotherapy, which affects the outcomes of radiotherapy. In this study, the integrated depth-dose-distributions (IDDDs) of 190 MeV/u and 260 MeV/u carbon beams in the active spot-scanning delivery system were measured and calculated by FLUKA Monte Carlo simulation based on the Heavy Ion Medical Machine (HIMM). Considering the dose distributions caused by secondary particles and scattering, we also used different types of pencil beam (PB) models to fit and compare the spatial distributions of PB. We superposed a bunch of PB to form a 20×20 cm2 treatment field with the double Gaussian and double Gaussian logistic beam models and calculated the influence of beam delivery error on the field flatness and penumbra, respectively. The simulated IDDDs showed good agreement with the measured values. The triple Gaussian and double Gaussian logistic beam models have good fitness to the simulated dose distributions. There are different influences on dose uniformity and penumbra resulting from beam uncertainties. These results would be helpful for understanding carbon ion therapy, and physical therapists are more familiar with beam characteristics for active scanning therapy, which provides a reference for commissioning and optimization of treatment plans in radiotherapy.

A numerical analysis of the effect of roughness interface on the thermal stress in the environmental barrier coatings for ceramic matrix composites was performed. Based on the concept of representative volume elements, a micromechanical finite element model of the coated composites was established. The rough interfaces between the coating layers were described using sine curves. The cooling process after preparation and the typical service conditions for the CMCs component were simulated, respectively. The results show that the rough interface has little effect on the temperature distribution along the depth direction for the studied T/EBC coatings for SiC/SiC composites. The stress concentration occurs at the rough EBC/BC interface, which is prone to cause delamination cracking. Under typical service conditions, the high temperature can eliminate part of the thermal residual stress. Meanwhile, the thermal gradient will cause large thermal stress in the TBC layer and the stress will result in surface cracks. The stress concentrations appear at the peaks and valleys of rough interfaces. The variation range of thermal stress increases with the roughness amplitude and decreases with the wavelength.