Search

A new in situ thermal piezocone penetration test (T-CPTU) system is developed to determine the thermal properties of soil. It is expected to overcome most of the shortcomings observed in existing in situ test techniques. Based on Fourier's heat conduction equation and pore pressure dissipation theoretical equation, a method for calculating the thermal conductivity, namely the predicted temperature method, was proposed. The accuracy of the T-CPTU probe testing process and thermal conductivity calculation results were verified by numerical simulation, laboratory large-scale model tank tests, and thermal needle tests. Finally, the field data of T-CPTUs at three sites in Nanjing, China, were collected and compared with the laboratory thermal needle tests. The results indicated that the thermal conductivities obtained using T-CPTU were accurate and closer to those of laboratory thermal needle tests for most soils. The thermal conductivities of the undisturbed soil samples measured in the laboratory were lower than those obtained by T-CPTU.

Phase change energy storage materials are widely used in the field of renewable energy. Paraffin is one of the common phase change energy storage materials. As a multi-component hydrocarbon mixture, the melting of paraffin is different from that of pure substance. In addition the solid and liquid zones, there is also a fuzzy zone in which solid and liquid coexist. In this paper, the melting characteristics of paraffin in phase transition zone are studied by multi-scale experiments. Through the visualization experiment of square cavity paraffin melting, the solid zone, fuzzy zone and liquid zone are determined, and the moving process of phase interface is tracked by digital pictures and infrared heat maps. The evolution process of the pore structure in the fuzzy zone under different temperatures is photographed by means of the micro-experiment, and it is revealed that there are two areas in the fuzzy zone, porous media area and multi-phase flow area. The results show that the melting process of paraffin can be divided into four zones: liquid zone, multi-phase flow zone, porous media zone, and solid phase zone. According to the polarizing optical microscopy picture, the continuous phase and discrete phase transition relationship between solid wax crystal and liquid paraffin is captured. The polarizing optical microscopy picture is statistically analyzed, and the critical liquid phase ratio of the transition from porous media area to multi-phase flow area is given under experimental conditions.

Understanding the phase regulation mechanism of BaTiO3 synthesized by a hydrothermal method is a complicated and challenging task. Here, we successfully prepared cubic and tetragonal BaTiO3 single nanocrystals by changing the ratio of water and ethanol in the solvent. We confirm that the BaTiO3 phase is mainly affected by the hydroxylation process due to the reaction with solvent. In particular, ethanol can be catalytically oxidized by titanium atoms, cause BaTiO3 hydroxylation and promote the formation of a cubic phase. In the mixed solution of ethanol and water, the hydroxylation process is suppressed, which facilitates the formation of the tetragonal phase. The relationship framework between the solvent ratio, phase structure and hydroxyl defects of BaTiO3 is established. Tetragonal BaTiO3 with fewer hydroxyl defects can promote charge transfer and surface reaction after polarization, thereby enhancing their photoelectric catalytic performance. This work provides references for the controllable synthesis of ferroelectric nanocrystals by hydrothermal methods and new insight for the utilization of polarization in photoelectrocatalysis applications.

Cost-efficient and durable oxygen evolution catalysts are in great demand, which are dominated not only by the component of the electrocatalysts but also by their molecular structure and crystallinity. Herein, we developed an efficient cobalt–vanadium spinel-type electrocatalyst with an extremely high concentration of Co 3+ ions by tuning the balanced vanadium ions’ concentration in crystallinity-modulated Co 2–xV xO 4 nanoplates. This resulted in the lowest overpotential of 240 mV at 10 mA/cm 2, the smallest Tafel slope of 45 mV dec –1, and a current density of 100 mA/cm 2 at an overpotential of 280 mV for water oxidation, which is remarkably 20 times better than that of the benchmark RuO 2 catalyst, along with excellent stability. Such excellent performance is due to the very high Co 3+/Co 2+ ratio of 2.84 achieved in situ in the low-crystallinity Co 2–xV xO 4 (LC-Co 2–xV xO 4) sample, which is 40% higher than that of the widely reported Co 3O 4, as evidenced by both operando X-ray absorption near-edge spectroscopy and in situ X-ray photoelectron spectroscopy. These findings stimulate the opportunities to explore Co 2–xV xO 4 as a class of nonprecious-metal-based efficient OER electrocatalysts.

Tungsten diselenide (WSe2) possesses extraordinary electronic properties for applications in electronics, optoelectronics, and emerging exciton physics. The synthesis of monolayer WSe2 film is of topmost for device arrays and integrated circuits. The monolayer WSe2 film has yet been reported by thermal chemical vapor deposition (CVD) approach, and the nucleation mechanism remains unclear. Here, we report a pre-seeding strategy for finely regulating the nuclei density at an early stage and achieving a fully covered film after chemical vapor deposition growth. The underlying mechanism is heterogeneous nucleation from the pre-seeding tungsten oxide nanoparticles. At first, we optimized the precursor concentration for pre-seeding. Besides, we confirmed the superiority of the pre-seeding method, compared with three types of substrate pretreatments, including nontreatment, sonication in an organic solvent, and oxygen plasma. Eventually, the high-quality synthetic WSe2 monolayer film exhibits excellent device performance in field-effect transistors and photodetectors. We extracted thermodynamic activation energy from the nucleation and growth data. Our results may shed light on the wafer-scale production of homogeneous monolayer films of WSe2, other 2D materials, and their van der Waals heterostructures. Web of Science

In the Cu/diamond composites modified by metal matrix alloying, the interfacial thermal conductance depends on the in-situ formed interfacial carbide layer that further depends on the diamond particle size. We fix boron alloying content as 0.3 wt% and vary diamond particle size from 66 to 701 µm to tune interfacial carbide layer with an attempt to separate the two dependences of diamond particle size and interfacial thermal conductance. The Cu-0.3 wt% B/diamond composite exhibits a slowing increase in thermal conductivity as the diamond particle size is larger than 300 µm because of a simultaneous decrease in the interfacial thermal conductance. A high thermal conductivity of 904 W/(m K) is obtained with diamond particle size of 701 μm. The findings emphasize the importance of tailoring interfacial carbide layer to attain high thermal conductivity in the Cu/diamond composites modified by metal matrix alloying.

Graphene foam (GF) has grabbed considerable attention for microwave absorption (MA) due to its high specific surface area, rich micro-nano structures and versatile processing. However, restricted by the intrinsic electromagnetic properties of graphene, the MA property of GF is usually unsatisfactory. To further improve the absorption strength of GF, groundbreakingly, the thermoelectric material Bi2Te2.7Se0.3 (BTS) and graphene are combined to form Bi2Te2.7Se0.3/GF (BTSGF) composites through a solvothermal self-assembly method. BTSGF composites have achieved much enhanced MA properties. The minimal reflection loss (RLmin) and the qualified absorption bandwidth of BTS9GF-200 (90 wt% BTS, annealed at 200 °C) reaches improved −73.0 dB and 5.32 GHz, respectively. Meanwhile, BTS3GF-300 (30 wt% BTS, annealed at 300 °C) exhibits an impressive qualified absorption bandwidth of 8.9 GHz and achieves an enhanced RLmin of −58 dB. The enhanced MA performance of BTSGF stems from various synergistic effects of BTS and GF, such as conduction loss and polarization. More importantly, BTS's thermal energy-electric energy conversion capability is believed to can quickly convert heat into electricity and strengthen the attenuation of electromagnetic waves. Therefore, a new electromagnetic wave-thermo-electric loss MA mechanism is proposed, which is of great significance to the study of thermoelectric materials as high-efficiency MA materials.

Polymers containing catechol groups have gained a large interest, as they mimic an essential feature of mussel adhesive proteins that allow strong binding to a large variety of surfaces under water. This feature has made this class of polymers interesting for surface modification purposes, as layer functionalities can be introduced by a simple adsorption process, where the catechol groups should provide a strong anchoring to the surface. In this work, we utilize an AFM-based method to evaluate the wear resistance of such polymer layers in water and compare it with that offered by electrostatically driven adsorption. We pay particular attention to two block copolymer systems where the anchoring group in one case is an uncharged catechol-containing block and in the other case a positively charged and catechol-containing block. The wear resistance is evaluated in terms of wear volume, and here, we compare with data for similar copolymers with statistical distribution of the catechol groups. Monitoring of nanomechanical properties provides an alternative way of illustrating the effect of wear, and we use modeling to show that the stiffness, as probed by an AFM tip, of the soft layer residing on a hard substrate increases as the thickness of the layer decreases. The stick−slip characteristics are also evaluated.

Peripheral arterial disease (PAD) is a progressive atherosclerotic disorder characterized by blockages of the arteries supplying the lower extremities. Ischemia initiates oxidative damage and mitochondrial dysfunction in the legs of PAD patients, causing injury to the tissues of the leg, significant decline in walking performance, leg pain while walking, and in the most severe cases, nonhealing ulcers and gangrene. Current clinical trials based on cells/stem cells, the trophic factor, or gene therapy systems have shown some promising results for the treatment of PAD. Biomaterial matrices have been explored in animal models of PAD to enhance these therapies. However, current biomaterial approaches have not fully met the essential requirements for minimally invasive intramuscular delivery to the leg. Ideally, a biomaterial should present properties to ameliorate oxidative stress/damage and failure of angiogenesis. Recently, we have created a thermosensitive hyaluronic acid (HA) hydrogel with antioxidant capacity and skeletal muscle-matching stiffness. Here, we further optimized HA hydrogels with the cell adhesion peptide RGD to facilitate the development of vascular-like structures in vitro. The optimized HA hydrogel reduced intracellular reactive oxygen species levels and preserved vascular-like structures against H2O2-induced damage in vitro. HA hydrogels also provided prolonged release of the vascular endothelial growth factor (VEGF). After injection into rat ischemic hindlimb muscles, this VEGF-releasing hydrogel reduced lipid oxidation, regulated oxidative-related genes, enhanced local blood flow in the muscle, and improved running capacity of the treated rats. Our HA hydrogel system holds great potential for the treatment of the ischemic legs of patients with PAD.

Considerably slow H2O2 evaporation leads to a decrease in the oxidation ratio of NO through H2O2 thermal decomposition. Therefore, the metal surfaces of Copper h62, Aluminium 5052, Steel 201, and Steel q235 were used to promote H2O2 thermal decomposition and NO oxidation. The effects of reaction temperature, H2O2 solution concentrations, H2O2:NO ratios, and metal surface inclination angles on NO oxidation were explored through H2O2 thermal decomposition. The evaporation and decomposition rates of H2O2 significantly influenced NO oxidation. After the addition of metal surfaces to the reactor, the NO oxidation ratio considerably enhanced, and NO concentration fluctuations disappeared under most conditions. The hydrophilicity of the metal surfaces can help the H2O2 solution spread rapidly on metal surfaces. The liquid film thickness decreased, which led to an increase in the H2O2 evaporation rate. Consequently, NO oxidation ratios improved. Metal surfaces promoted H2O2 decomposition to produce OH, and relatively more NO was oxidised. The highest NO oxidation ratio was 87 %, which was acquired using the 15 % H2O2 solution at 500 ℃. When temperature was higher than 300 ℃, NO oxidation ratios on different metal surfaces were similar. The inclination angle θ of metal surfaces can considerably affect NO oxidation ratios. When the metal surface was horizontal, the NO oxidation ratio was higher than that when metal surface was placed at other angles, and the oxidation effect of NO was relatively more stable. The longer the droplets stayed on metal surfaces, the smaller were the NO concentration fluctuations.

With the advancement of nanomaterials for surface-enhanced Raman scattering(SERS) detection, a deeper understanding of the chemical mechanism(CM) and further applications has been achieved. Herein, we prepared a porous tungsten trioxide(WO3) film by the pulse electrodeposition method, and constructed a WO3 film SERS aptasensor. With methylene blue(MB) as the adsorption molecule, the developed WO3 film SERS aptasensor revealed remarkable Raman activity. Through experimental data and theoretical calculations, we found that the significant SERS enhancement[enhancement factor(EF)=1.5× 106] was due to the CM based on charge transfer and molecular resonance. Utilizing the Raman response of MB on the WO3 film and specific aptamers, we successfully developed the aptamer sensor by covalently attaching the MB modified aptamer to the WO3 film. The sensor realized the specific and sensitive determination of vascular endothelial growth factor(VEGF) with the detection limit down to 8.7 pg/mL. In addition, the developed aptasensor indicated the excellent selectivity among other interferences, such as metal ions, reactive oxygen species(ROS), and proteins. This WO3 film SERS aptasensor not only contributed to the study of the enhancement mechanism of semiconductor material, but also provided a powerful platform for the sensitive detection of VEGF, possessing a great potential in the real-time monitoring of biomarkers of glioblastoma in vitro.

In this letter, a new method based on the temperature dependence of gate leakage current for accurately characterizing thermal crosstalk is proposed and performed on the advanced silicon-on-insulator (SOI) MOSFETs. The developed technique enables to capture the pure thermal crosstalk effect as it excludes the self-heating impact during the measurement. Moreover, it is proven robust over a large range of gate voltages regardless of the difference of device types, which is demonstrated on a pair of devices with a shared port. The accuracy of the thermal crosstalk measurement benefits in determining the overall thermal performance of the nano-scaled circuits under the mutual heating impacts. It offers a possible hardware solution to thermal monitor and management.

The conversion of biomass-derived products to fine chemicals and fuels is extremely important for the utilization of renewable energy sources. Water is not only a by-product formed during the hydrogenation of biomass-derived oxygenated chemicals, but also an inexpensive and nontoxic solvent. The instability of solid catalysts for aqueous-phase reactions caused by metal leaching and the collapse of a catalyst support represents a significant challenge. In this work, various catalyst stabilization strategies including the nanospace and interfacial confinements that prevent sintering and leaching of metal nanoparticles as well as modification methods for increasing the support stability are summarized and systemically discussed. In addition, feasible approaches to designing stable and efficient heterogeneous catalysts for aqueous-phase reactions are proposed.

A series of high oil-absorption resins with low cross-linking degree were synthesized by suspension polymerization using stearyl methacrylate (SMA), 2-Ethylhexyl methacrylate (EHMA), and styrene (St) as monomers. Response surface methodology (RSM) with central composite design (CCD) was also applied to determine the optimal parameters that are mainly known to affect their synthesis. Thus, the effects of the monomer mass ratio (EHMA:SMA), the rigid monomer (St) dosage, the porous agent (acetone) dosage, and their pairwise interaction on the resin's oil-absorption capacity were analyzed, highlighting PSES-R2 as the resin with the optimum performance. The pure oil-absorption rates of PSES-R2 for gasoline, diesel, and kerosene were 11.19 g·g−1, 16.25 g·g−1, and 14.84 g·g−1, respectively, while the oil removal rates from oily wastewater were 98.82%, 65.11%, and 99.63%, respectively.

We herein develop a concentration gradient generator (CGG) on a microfluidic chip for diluting different nanoparticles. Specifically designed compact disk (CD)-shaped microchannels in the CGG module could thoroughly mix the flowing solutions and generate a linear concentration gradient of nanoparticles without aggregation. We combine the CGG with a single-cell trapper array (SCA) on microfluidics to evaluate the concentration-dependent bioeffects of the nanoparticles. The precise control of the spatiotemporal generation of nanoparticle concentration on the CGG module and the single-cell-level monitoring of the cell behaviors on the SCA module by a high-content system in real time, render the CGG-SCA system a highly precise platform, which can exclude the average effect of cell population and reflect the response of individual cells to the gradient concentrations accurately. In addition, the CGG-SCA system provides an automated platform for high-throughput screening of nanomedicines with high precision and low sample consumption.

Silica (SiO2) aerogels are widely used in high-temperature insulation materials due to their low thermal conductivity. The hydrophobicity of SiO2 aerogels is considerably important for maintaining high-thermal insulation performance for a long duration. Traditional methods for the hydrophobic modification of SiO2 aerogels involve the modification of organic functional groups present on aerogel surfaces to replace original hydrophilic hydroxyl functional groups. However, due to the thermal damage of functional groups, SiO2 aerogels lose their hydrophobicity at high temperatures (400 °C), which limits the aerogel application in high-temperature fields. This study proposed a new hydrophobic method, chemical vapour deposition, to deposit a layer of hydrophobic boron nitride (BN) on the SiO2 aerogel surface. The surface hydrophobic angle of the BN-modified SiO2 aerogel reached 144.3°, and hydrophobic destruction temperature increased to 700 °C, indicating stable hydrophobicity. The method can be used to a decrease in aerogel surface energy through the deposition of a nano-BN film on the aerogel surface layer while maintaining the porous structure of the unmodified aerogel. The deposited BN layer protects the silica skeleton. This layer inhibits silica crystallisation and improves the thermal stability of aerogels.

To solve the disadvantages of weak bonding between the carbon fiber (CF) and the cement matrix, as well as the poor dispersion performance of multi-walled carbon nanotubes (MCNT) in cement paste, h...

Ferroelectric-semiconductor nanostructures can exhibit enhanced photocatalytic activity benefiting from charge separation and transport facilitated by a spontaneous polarization-induced electric fi...

We investigated the gelation of cellulose nanocrystals (CNCs) in polyelectrolyte and neutral polymer solutions. Cellulose nanocrystals (CNCs) with half-ester sulfate groups produced by acid hydrolysis of wood pulp were used in this study. The microstructure of CNCs/polymer suspensions was investigated in semidilute concentration regimes by selecting carboxymethyl cellulose (CMC700) as an anionic polymer and poly(ethylene oxide) (PEO600) as a neutral polymer solution. Together with quartz crystal microbalance with dissipation monitoring (QCM-D), rheology, scanning electron microscopy (SEM), and cryo-transmission electron microscopy (cryo-TEM), we characterized CNCs-polymer interactions, the suspension microstructure, and the macroscopic gel flow. Significant viscosity increases at low shear rates coupled with high shear-thinning behaviors were observed in CNC colloid-CMC700 polymer mixtures, but not those CNCs in PEO600 solutions. The apparent differences between CNCs-CMC700 and CNCs-PEO600 mixtures were due to their chain confirmations. On the basis of the evaluations from STEM, cryo-TEM, and polarized optical microscopy, we proposed that the excess CMC700 molecules in solutions result in the depletion of CNCs and the formation of anisotropic domains.

Transition metal carbide/nitride (MXenes) have attracted widespread attention in recent years due to their unique structure and excellent electrochemical performance. In addition, MXene materials have adjustable interlayer spacing as well as rich functional groups on the bonding end, which provides great potential to enhance the performance of energy devices. However, three-atoms V2C-based MXene was rarely investigated for memristors and its effects on devices are still unknown. In this work, we synthesized V2C MXene and fabricated Ag/V2C/TiO2/W structural memristors. The advantages of V2C on memristors were explored including the coexistence of volatile threshold switching (TS) and non-volatile memory switching (MS) behaviors, low Set and Reset voltages, and small cycle-to-cycle and device-to-device variations. Moreover, the space charge limited current (SCLC) model is the dominant switching mechanism. Additionally, two types of synaptic plasticity, i.e., long-term potentiation/depression (LTP/LTD), have been achieved by continuous pulse stimulations. These results in this study are of great significance for disclosing the possibilities of low power electronic synapses with V2C.

The safe transportation of waxy crude oil is a key in the field of pipeline gathering and transportation. The motion characteristics of an oil droplet in water for safe transportation are numerically analyzed in this paper. The mathematical model of oil-water two-phase flow under pipeline transportation conditions is established and solved by LBM (lattice Boltzmann method). The influences of interfacial tension, contact angle and the viscosity of oil on the flow characteristics of oil droplets, such as deformation and fracture were investigated after validating the model. The results indicate that deformation of the oil droplet is mainly determined by interfacial tension and oil viscosity, while the affect of contact angle is not substantial. With the increase of interfacial tension and the viscosity of oil, the maximum deformation of droplets before fracture decreases. It is found that the contact angle has a significant effect on the number of broken droplets and the shape of the oil droplets. While the critical time of the initial fracture is mainly defined by the viscosity. In addition, the interfacial tension also has a slight influence on the critical time of the initial fracture.

The nanoscale effect enables the unique magnetic, optical, thermal and electrical properties of nanostructured materials and has attracted extensive investigation for applications in catalysis, biomedicine, sensors, and energy storage and conversion. The widely used synthesis methods, such as traditional hydrothermal reaction and calcination, are bulk heating processes based on thermal radiation. Differing from traditional heating methods, non-thermal radiation heating technique is a local heating mode. In this regard, this review summarizes various non-thermal radiation heating methods for synthesis of nanomaterials, including microwave heating, induction heating, Joule heating, laser heating and electron beam heating. The advantages and disadvantages of these non-thermal radiation heating methods for the synthesis of nanomaterials are compared and discussed. Finally, the future development and challenges of non-thermal radiation heating method for potential synthesis of nanomaterials are discussed.

Direct methane conversion (DMC) to high value-added chemicals (such as methanol, etc. ) is one of the most important ways to efficiently utilize methane. Because methane is very stable, it is quite challenging to be activated especially under mild conditions (reaction temperature ≤150 °C without strong acid). Recently, single-atom catalysts (SACs) have attracted wide attention in many reactions for their high utilization of active species and high selectivity for target products. It has been reported that SACs exhibited unique catalytic properties in the activation of methane. In this review, we focused on the research progress of DMC reaction on SACs under mild conditions. We mainly summarized the SACs of the precious and base metal and the reaction route of methane activation in the field of thermal catalysis. Besides, the DMC reaction over the SACs in the photocatalysis process was also briefly summarized. Finally, we prospected the research on the DMC over the SACs under mild conditions in the future.

Fiber breakage is found to be a ubiquitous phenomenon during the thermal treatments for electrospun nanofibers, because of the presence of solvent molecules and unrelaxed assembly of polymer chains. Here a strengthening strategy is designed by introducing a pre-heating stage for the as-spun nanofibers. At a temperature above the polymer’s glass transition temperature, the chains can get sufficiently relaxed by the aid of hot solvent, and at the same time, the solvent confined in the entangled chains can fully and steadily evaporate, but not erupt, off the nanofiber, when the temperature is just as high as the boiling point. Therefore, the nanofibers become more uniform in structure and can withstand the subsequent thermal reactions. For polyacrylonitrile-based electrospinning, such strategy can improve the final tensile strength from 42 to 112 MPa for the nanofiber films.

Lithium sulfur (Li–S) batteries have been investigated as ideal candidates for future high-density energy storage systems with the advantages of abundant reserves, high energy density and competitive cost. The key issues are the severe shuttling of polysulfides and sluggish redox kinetics. Herein, we report a novel metal–organic framework-derived Co2P–ZnS/ZnS–C nanocomposite constructed from inner Co2P–ZnS and outer ZnS–C heterostructures. Both the experimental results and theoretical calculations demonstrated that these dual electrocatalytic heterostructures enabled strong affinity with polysulfides and facilitated the reaction kinetics. Meanwhile, the hollow carbon polyhedron provided fast electron/ion transfer channels and effectively buffered volume expansion during cycling. As anticipated, a high initial capacity of 1503 mA h g−1 was achieved at 0.2C with Co–Zn/Zn–C/S as a cathode, together with excellent stability after 500 cycles at 1C. Even a high reversible capacity of 540 mA h g−1 was achieved at 1C after 200 cycles under an elevated sulfur loading of 3.65 mg cm−2. This work presents a new strategy for designing dual electrocatalytic hosts for immobilization and conversion of polysulfides, which may offer more opportunities as cathodes in stable Li–S batteries with high energy density.

Accurately obtaining the temperature distribution of the medium in the shutdown pipe-line of waxy crude-oil has important guiding significance for making maintenance plan and restart plan. The phase transition process of waxy crude-oil involves complex problems such as natural-convection heat transfer, latent heat release, and difficulty in tracing liquid-solid interface. In this paper, the concept and significance of breaking point were proposed. Taking the breaking point and the freezing point as dividing point, a new zonal partition model was established based on the influence of phase change of crude-oil wax crystal on heat transfer mode, with the corresponding governing equations being established for different regions. With the proposed model, the effects of natural-convection on heat transfer, latent heat release, location change of condensate reservoir, heat transfer mechanism, and other key issues in the process of oil phase transition were analyzed.

The exploitation of low-cost, efficient and stable electrocatalysts for overall water splitting in alkaline media is critical for future renewable energy systems, yet still remains a great challenge. Herein, we report the in situ growth of porous NiCoSe nanosheet arrays derived from 2D MOFs on Ni foam through a simple ion-exchange reaction followed by a hydrothermal process. Benefiting from the unique 2D multi-porous framework with high electrochemical active surface area, conductivity and open channels for the release of gaseous products, the as-prepared NiCoSe nanosheet arrays exhibit excellent electrochemical activity with a low overpotential of 170 mV for the hydrogen evolution reaction (HER) at 10 mA cm−2 and 278 mV for the oxygen evolution reaction (OER) at 20 mA cm−2 and long-term stability. Furthermore, the full cell only requires 1.51 V to drive the current density of 10 mA cm−2 when the NiCoSe nanosheet arrays are used as both anode and cathode, which also exhibits distinguished durability for over 48 h. The present work presents a general strategy for the rational design and synthesis of multifunctional 2D porous electrocatalysts, which is also expected to extend to other noble-metal-free catalysts.

We investigated the structural and photocatalytic properties of tungsten-doped Bi2Mo1−xWxO6 (x = 0, 0.01, 0.03, 0.05 and 0.10) nanosheets. X-ray diffraction patterns showed that the preferred growth orientation of the (020) and (060) planes was suppressed with the increase of tungsten doping. Scanning electron microscopy photos showed that the thickness of the Bi2Mo1−xWxO6 nanosheets gradually diminished when x increases. UV-vis spectra showed that the optical band gap of Bi2Mo1−xWxO6 was gradually enlarged with the increase of tungsten doping. X-ray photoelectric spectra of the Bi2Mo1−xWxO6 revealed that the doped tungsten ions successfully replaced some Mo ions in the Bi2Mo1−xWxO6 nanosheets and the valence band maximum of the different Bi2Mo1−xWxO6 also decreased gradually. When the doped tungsten increased from 0.01, 0.03, and 0.05 to 0.10, the photocatalytic performance of rhodamine B and tetracycline removal was enhanced compared with pristine Bi2MoO6 nanosheets. However, the Bi2Mo0.95W0.05O6 sample possessed the best photocatalytic performance, not the Bi2Mo0.90W0.10O6 sample, which could be explained by the effect of the oxygen vacancy induced electron traps.

MXene is a hot family of transition metal carbides or nitrides demonstrating promising potentials in the fields of batteries, supercapacitors, and memristive devices. One of MXenes, i.e., five-atoms-type MXene (Ti3C2), has been reported to fabricate memristive devices and show resistive switching. However, MXene has another big group of three-atoms-type rather than five-atoms-type based on fundamental chemical structure. Besides, the group of three-atoms-type MXene is rarely investigated to fabricate memristive devices. Moreover, the effect of three-atoms-type Mxene (i.e., V2C) on the performance of memristive devices and the physical mechanisms behind have not been explored. In this work, we constructed the lattice structure and compared the fundamental properties of V2C with Ti3C2 using the first-principles calculation. Moreover, the diffusion coefficient and the conductivity of Ag+ in V2C and Ti3C2 have been checked by the density functional theory (DFT). It can be revealed that V2C has a more stable atomic structure, a higher conductivity, and a superior diffusion coefficient of Ag+ in V2C. In addition, we fabricated memristive devices of the Ag/V2C/W and Ag/Ti3C2/W based on the simulation results for comparison. Next, electrical characteristics of V2C and Ti3C2 of memristive devices were tested including the variation of device-to-device and cycle-to-cycle, the endurance, and the ratio of Roff / Ron . The experimental data indicate that the memristive devices with V2C have achieved more stable resistive switching behaviors. The results of this work provide a useful guideline and methodology for exploring and determining various types of MXenes in advance of the experimental fabrication of memristive devices.

Although direct formic acid fuel cell (DFAFC) is regarded as one of the most promising energy-conversion systems, its commercialization process is impeded by the high costs of electrode catalysts as well as the sluggish catalytic reaction kinetics. Herein, we present a convenient bottom-up method to the synthesis of nanosized Pd crystals grown on 3D porous hybrid nanoarchitectures constructed from MXene (Ti3C2Tx) and reduced graphene oxide nanosheets (Pd/MX-rGO) through a co-assembly process. The as-derived 3D Pd/MX-rGO nanoarchitecture is equipped with a number of attractive textural features, such as 3D cross-linked porous networks, large specific surface area, uniform Pd dispersion, optimized electronic structure, and good electron conductivity. As a result, unusual formic acid oxidation properties in terms of high catalytic activity, strong poison tolerance, and reliable long-term stability are achieved for the 3D Pd/MX-rGO catalyst, significantly superior to those for conventional Pd catalysts supported by carbon black, graphene, and Ti3C2Tx matrixes.

Conduction mechanisms of ferroelectric tunnel junction (FTJ) using metal-ferroelectric-insulator- semiconductor (MFIS) on n- and p-type semiconductor is clarified by a new developed model, which is verified by the experimental results. In the model, electron tunneling from conduction band and valence band, and hole tunneling from valence band are included to calculate the read current in ON/OFF-state of MFIS-FTJ. The model explains the unexpected polarization polarity of ON/OFF-state in p-type and the difference of tunneling electroresistance (TER) ratio between n- and p-type MFIS-FTJ, which cannot be understood just by the depletion/accumulation for majority carriers in semiconductor.

An instrument to detect atmospheric HO2 radicals using fluorescence assay by gas expansion (FAGE) technique has been developed. HO2 is measured by reaction with NO to form OH and subsequent detection of OH by laser-induced fluorescence at low pressure. The system performance has been improved by optimizing the expansion distance and pressure, the influence factors of HO2 conversion efficiency are also studied. The interferences of RO2 radicals were investigated by determining the conversion efficiency of RO2 to OH during the measurement of HO2. The dependence of the conversion of HO2 on NO concentration was investigated, and low HO2 conversion efficiency was selected to realize the ambient HO2 measurement, where the conversion efficiency of RO2 derived by propane, ethene, isoprene and methanol to OH has been reduced to less than 6% in the atmosphere. Furthermore, no significant interferences from PM2.5 and NO were found in the ambient HO2 measurement. The detection limits for HO2 (S/N = 2) are estimated to 4.8 × 105 cm−3 and 1.1 × 106 cm−3 ( ρ H O 2 = 20%) under night and noon conditions, with 60 sec signal integration time. The instrument was successfully deployed during STORM-2018 field campaign at Shenzhen graduate school of Peking University. The concentration of atmospheric HOx radical and the good correlation of OH with j(O1D) was obtained here. The diurnal variation of HOx concentration shows that the OH maximum concentration of those days is about 5.3 × 106 cm−3 appearing around 12:00, while the HO2 maximum concentration is about 4.2 × 108 cm−3 appearing around 13:30.

The effective activation and utilization of O2 have always been the focus of scientists because of its wide applications in catalysis, organic synthesis, life and medical science. Here, a novel method for activating O2 spontaneously via interfacial oxygen vacancies on carbon-coated TiO2-x to generate reactive oxygen species (ROS) with versatile applications is reported. The interfacial oxygen vacancies can be stabilized by the carbon layer and hold its intrinsic properties for spontaneous oxygen activation without light irradiation, while common surface oxygen vacancies on TiO2-x are always consumed by the capture of H2O to form the surface hydroxyls. Thus, O2 absorbed at the interface of carbon and TiO2-x can be directly activated into singlet oxygen (1O2) or superoxide radicals (·O2-), confirmed both experimentally and theoretically. These reactive oxygen species exhibit excellent performance in oxidation reactions and inhibition of MCF-7 cancer cells, providing new insight into the effective utilization of O2 via oxygen vacancies on metal oxides.

As a typical cell structure, the cylindrical ferroelectric capacitor (CFE-cap) has been widely used in 3-D ferroelectric memories. Unlike planar ferroelectric capacitor, the CFE-cap has nonuniform electric field and polarization distribution. In this article, we investigate the impacts of the radius on the capacitance, field distribution, electrode charge densities of both the isotropic and anisotropic CFE-caps. As the inner radius increases, the CFE-cap behaves more like the planar capacitor with the same ferroelectric thickness. The results indicate that CFE-cap has an additional knob of inner radius ${R}_{\text {in}}$ to tune its ferroelectric and electric characteristics. We have considered two kinds of CFE-caps, isotropic and anisotropic CFE-caps. The former is found to have stronger ferroelectric response than the latter, such as higher normalized capacitance and larger polarization.

Bi2Te3 was incorporated in carbon fiber-reinforced cement composites (CFRCs) as thermoelectric-reinforced component via three different doping methods (uniformity volume mixing, gradient volume mix...

Buffer/backfill material is an important engineering barrier in a deep geological repository of high-level radioactive waste (HLW). Its thermo-hydro-mechanical (THM) performance is very important for the safe and stable operation of the HLW repository system. Natural graphite powder mixed with sodium bentonite forms a buffer/backfill material that can dissipate heat quickly and provide strong isolation. In this paper, the THM characteristics of bentonite–sand–graphite–polypropylene fiber (BSGF) mixtures, used as a buffer/backfill material, were studied through a series of laboratory tests. The influence of graphite and polypropylene fiber contents on thermal conductivity, swelling pressure, hydraulic conductivity, and strength properties of BSGF mixtures with different sand contents was analyzed. Experimental results indicated that the graphite content, the maximum graphite mesh number, and the initial dry density of bentonite–graphite mixtures influenced the thermal conductivity of bentonite–graphite mixtures. The addition of polypropylene fiber was found to enhance the shear strength and inhibit cracking without significantly affecting the expansivity, permeability, and thermal conductivity of the BSGF mixtures. This study provides a new buffer/backfill material that can improve the stability, functionality, and thermal efficiency of the HLW repository.

Restraining the shuttle effects of lithium polysulfides is the key to improve the cycling reversibility and stability of lithium-sulfur (Li-S) batteries for which design of robust sulfur hosts has been regarded as the most effective strategy. In this work, we report a new type of hybrid sulfur host which is composed of Al2O3 homogenously decorated in nitrogen-rich mesoporous carbon framework (NMC-Al2O3). The NMC-Al2O3 hybrid host features a poly-dispersed spherical morphology and a mesoporous configuration with high surface area and large pore volume that can accommodate a high sulfur content up to 73.5 wt.%. As a result, the fabricated NMC-Al2O3-S cathode exhibits all-round improvements in electrochemical properties in term of capacities (1,212 mAh·g−1 at 0.2 C; 755 mAh·g−1 at 2 C), cycling charge-discharge reversibility (sustainably 100% efficiencies) and stability (1,000 cycles with only 0.023% capacity decay per cycle at 0.5 C). By contrast, the Al2O3-free NMC-S cathode shows both decreased capacities and rapidly descending Coulombic efficiencies during cycling. Density functional theory (DFT) calculations further reveal that the implanted Al2O3 can greatly enhance the chemical adsorption and catalytic conversion for various lithium polysulfides and thereby effectively prevent the polysulfide shuttling and significantly improve the utilizability, reversibility and stability of sulfur cathode.

The performance of YBa0.5Sr0.5Co1.4Cu0.6O5+δ(YBSCCO)–Sm0.2Ce0.8O1.9 (SDC) composite cathode for SOFC is investigated in this paper. YBSCCO and SDC oxides are synthesized by the sol–gel method. The XRD result reveals that no obvious chemical reaction occurs after sintering the mixture of the YBSCCO and SDC at 850 °C for 20 h. The thermal expansion behavior shows that the YBSCCO–xSDC composite cathode has the suitable TEC values (13.3–11.2 × 10−6 K−1) for the common electrolyte. In different proportions of the composite cathode, YBSCCO–30SDC shows the lowest polarization resistance values, which are only about 0.022 Ω cm2 at 850 °C and 0.034 Ω cm2 at 800 °C. The electrolyte-supported single cell using YBSCCO–30SDC cathode is fabricated, and the peak power densities values are 567 and 432 mW cm−2 at 850 and 800 °C, respectively.

Tuning CO2 hydrogenation selectivity to obtain targeted value-added chemicals and fuels has attracted great yet everincreasing attention. How ever, a fundamental understanding of the nature to control the selectivity is still lacking, posing a challenge in catalyst design and development. Here, w e report our new discovery in ambient pressure CO2 hydrogenation reaction where selectivity canbe completely reversed by simply changing the crystal phases of TiO2 support (anatase- or rutile-TiO2) or changing metal loadings on anatase-TiO2. Operando spectroscopy and NAP-XPS studies reveal the determining factor is dif ferent electron transfer from metal to support under reaction conditions most probably as a result of the different extents of hydrogen spillover, which changes the adsorption and activation of the intermediate of CO. Based on this new finding, we can not only regulate CO2 hydrogenation selectivity but also tune catalytic performance in other important reactions, thus opening up a door for efficient catalyst development by rational design. Fil: Li, Xiaoyu. University Of Chinese Academy Of Sciences; China. Dalian Institute Of Chemical Physics Chinese Academy Of Sciences; China Fil: Lin, Jian. Dalian Institute Of Chemical Physics Chinese Academy Of Sciences; China Fil: Li, Lin. Dalian Institute Of Chemical Physics Chinese Academy Of Sciences; China Fil: Huang, Yike. University Of Chinese Academy Of Sciences; China. Dalian Institute Of Chemical Physics Chinese Academy Of Sciences; China Fil: Pan, Xiaoli. Dalian Institute Of Chemical Physics Chinese Academy Of Sciences; China Fil: Collins, Sebastián Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Ren, Yujing. University Of Chinese Academy Of Sciences; China. Dalian Institute Of Chemical Physics Chinese Academy Of Sciences; China Fil: Su, Yang. Dalian Institute Of Chemical Physics Chinese Academy Of Sciences; China Fil: Kang, Leilei. Dalian Institute Of Chemical Physics Chinese Academy Of Sciences; China Fil: Liu, Xiaoyan. Dalian Institute Of Chemical Physics Chinese Academy Of Sciences; China Fil: Zhou, Yanliang. University Of Chinese Academy Of Sciences; China. Dalian Institute Of Chemical Physics Chinese Academy Of Sciences; China Fil: Wang, Hua. Dalian Institute Of Chemical Physics Chinese Academy Of Sciences; China Fil: Wang, Aiqin. Dalian Institute Of Chemical Physics Chinese Academy Of Sciences; China Fil: Qiao, Botao. Dalian Institute Of Chemical Physics Chinese Academy Of Sciences; China Fil: Wang, Xiaodong. Dalian Institute Of Chemical Physics Chinese Academy Of Sciences; China Fil: Zhang, Tao. Dalian Institute Of Chemical Physics Chinese Academy Of Sciences; China

In this review, I summarize recent experimental investigations of surface and friction forces between bottlebrush structure macromolecules including biolubricants and biomimetic ones by direct force measurements. I also discuss recent experimental investigations of synergy in lubrication in which a question, ‘How do lubricants act together?’, is aimed to be answered. Lastly, challenges and opportunities for developing efficient lubricating systems are outlined.

Photo-thermo catalysis, which integrates photocatalysis on semiconductors with thermocatalysis on supported nonplasmonic metals, has emerged as an attractive approach to improve catalytic performance. However, an understanding of the mechanisms in operation is missing from both the thermo- and photocatalytic perspectives. Deep insights into photo-thermo catalysis are achieved via the catalytic oxidation of propane (C3 H8 ) over a Pt/TiO2 -WO3 catalyst that severely suffers from oxygen poisoning at high O2 /C3 H8 ratios. After introducing UV/Vis light, the reaction temperature required to achieve 70 % conversion of C3 H8 lowers to a record-breaking 90 °C from 324 °C and the apparent activation energy drops from 130 kJ mol-1 to 11 kJ mol-1 . Furthermore, the reaction order of O2 is -1.4 in dark but reverses to 0.1 under light, thereby suppressing oxygen poisoning of the Pt catalyst. An underlying mechanism is proposed based on direct evidence of the in-situ-captured reaction intermediates.

Strong metal-support interaction (SMSI) has gained great attention in the field of heterogeneous catalysis. However, whether single-atom catalysts can exhibit SMSI remains unknown. Here, we demonstrate that SMSI can occur on TiO2 -supported Pt single atoms but at a much higher reduction temperature than that for Pt nanoparticles (NPs). Pt single atoms involved in SMSI are not covered by the TiO2 support nor do they sink into its subsurface. The suppression of CO adsorption on Pt single atoms stems from coordination saturation (18-electron rule) rather than the physical coverage of Pt atoms by the support. Based on the new finding it is revealed that single atoms are the true active sites in the hydrogenation of 3-nitrostyrene, while Pt NPs barely contribute to the activity since the NP sites are selectively encapsulated. The findings in this work provide a new approach to study the active sites by tuning SMSI.

This article presents an evaluation of the photoelectric characteristic of different structured ultrathin body and buried oxide (UTBB) MOSFETs. The UTBB MOSFETs can achieve photoelectric conversion by integrating a doped well or photodiode beneath the BOX. With lightly doped well, the well-UTBB (W-UTBB) image sensor is more sensitive to illumination. On the other hand, the photodiode-UTBB (PD-UTBB) image sensor has a larger full well capacity. The influence of well doped concentration and interface traps at BOX/well on the photoelectric characteristics of both devices has been investigated. The well doped concentration has great impacts on the light sensitivity of the W-UTBB. The interface traps would increase the dark current of the W-UTBB and reduce the internal quantum efficiency (IQE) of the PD-UTBB.

Diamond particle-reinforced copper matrix (Cu/diamond) composites are currently considered as a promising thermal management material due to their high thermal conductivity and matching coefficient of thermal expansion (CTE) with the semiconductor. In this article, the Cu– $x\text{B}$ /diamond ( $x = 0.1$ –1.0 wt%) composites with 67% diamond volume fraction were produced by gas-pressure infiltration. The thermal conductivity of the Cu–B/diamond composites decreases with the increasing temperature from 323 to 673 K, owing to the property change of the composite components. The samples were subjected to 100 thermal cycles from 218 to 423 K to investigate the long-term stability of the Cu–B/diamond composites. The results suggest that the interface structure evolution plays a critical role in determining the high-temperature thermal conductivity and thermal cycling behavior of the Cu–B/diamond composites. By measuring the thermal properties before and after thermal cycling, we found that the Cu–0.5wt%B/diamond composite has the best thermal stability. After 100 thermal cycles, the room temperature thermal conductivity remains almost unchanged at ~740 W/mK, and the CTE increases slightly from 4.88 to 4.97 ppm/K. This article expands the understanding of the thermal properties of the Cu-B/diamond composites and provides a fundamental basis for their electronics packaging applications.

Nanostructure is effective to improve thermoelectric performance by reducing the thermal conductivity. However, electrical conductivity is always synchronously deteriorated due to the scattering of charge carriers. Here, we introduce SiC nanoparticles into the matrix of Pb0.98Na0.02Te doped with SrTe. The two-phased heterostructure causes strong scattering of phonons with multiscale wavelengths, resulting in the decreased lattice thermal conductivity. The electrical conductivity is reduced while Seebeck coefficient is improved. As a result, a peak thermoelectric figure of merit (zT) of 1.73 with a calculated device efficiency of ~10.6% is achieved for the nanocomposites under the temperature range of 300–750 K.

The limited mechanical properties of carbon nanofibers (CNFs) have become a severe problem hindering their wide range applications. The restricting issues are found in the whole fabrication process, including the precursor design, spinning and collection techniques, post treatments like stretching and aligning, and complicated thermal treatments involving stabilization and carbonization. Here we access the CNF development by focusing on the mechanical properties, and systematically discuss the strengthening strategies during the different fabrication stages.

Graphitic carbon nitride (g-C3N4), with a moderate band gap (∼2.7 eV), high chemical and thermal stability, has been the hotspot in environmental photocatalysis. However, its performance is still u...

Single-atom catalysts (SACs) have attracted extensive attention in the field of heterogeneous catalysis. However, the fabrication of SACs with high loading and high-temperature stability remains a grand challenge, especially on oxide supports. In this work, we have demonstrated that through strong covalent metal-support interaction, high-loading and thermally stable single-atom Pt catalysts can be readily prepared by using Fe modified spinel as support. Better catalytic performance in N2O decomposition reaction is obtained on such SACs than their nanocatalyst counterpart and low-surface-area Fe2O3 supported Pt SACs. This work provides a strategy for the fabrication of high-loading and thermally stable SACs for applications at high temperatures.