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The research on graphene-based anode materials for high-performance lithium-ion batteries (LIBs) has been prevalent in recent years. In the present work, carbon-coated SnO2 riveted on a reduced graphene oxide sheet composite (C@SnO2/RGO) was fabricated using GO solution, SnCl4, and glucose via a hydrothermal method after heat treatment. When the composite was exploited as an anode material for LIBs, the electrodes were found to exhibit a stable reversible discharge capacity of 843 mA h g−1 at 100 mA g−1 after 100 cycles with 99.5% coulombic efficiency (CE), and a specific capacity of 485 mA h g−1 at 1000 mA g−1 after 200 cycles; these values were higher than those for a sample without glucose (SnO2/RGO) and a pure SnO2 sample. The favourable electrochemical performances of the C@SnO2/RGO electrodes may be attributed to the special double-carbon structure of the composite, which can effectively suppress the volume expansion of SnO2 nanoparticles and facilitate the transfer rates of Li+ and electrons during the charge/discharge process.

Surface micro/nano processing is an important method and research hotspot for enhancing the boiling heat transfer process. However, the effects of a structural gradient on a boiling surface have not been systematically studied. In this paper, we review researches that focus on porous surfaces with a structural gradient and their effects on the enhancement of boiling heat transfer and performance of phase-change devices from two main aspects: Geometric gradient and wettability gradient. Porous surfaces with a geometric (structural) gradient were divided into four series: single-layer geometric gradient structure, multi-layer geometric gradient structure, surface covered with a micro/nanolayer, and surface with a radial gradient. In addition, the surface with a wettability gradient also has a considerable improvement in boiling heat transfer. Especially, we present some of the work related to the improvement in boiling heat transfer for porous surfaces with structural gradient, which has been carried out by our research group. Honeycomb-like and forest-like porous copper surfaces are typical single-layer geometric gradient porous surfaces with excellent boiling heat transfer performance. They have abundant microstructures and sub-microstructures/nanostructures, which are favorable for vapor escaping and liquid rewetting, respectively. For all the mentioned single-layer geometry gradient porous surfaces, the critical heat flux increases as the sample thickness increases. Furthermore, we fabricated a two-layer composite porous surface (TLCS) with a honeycomb-like porous copper surface on top of a forest-like porous copper surface. This TLCS is a multilayer geometric gradient structure porous surface that can further enhance the boiling heat transfer process. The heat transfer coefficient (HTC) of TLCS is 1.5 and 1.2 times larger than those of the biomimetic copper forest and honeycomb structures, respectively. When a small current is applied to the honeycomb-like porous copper surface, the dendrites on the pore wall transferred to micro balls and a surface with a structural gradient is obtained. The modified surface is a microstructural porous surface covered by a nanolayer that further enhances the HTC (1.7 times). The diameter of the honeycomb-like porous copper surface can be controlled with a radial diameter gradient. A sample in which the diameter around the center is much smaller than that around the edge enhances the HTC 1.4 times compared with a sample with uniform diameter. When the TLCS was modified with polytetrafluoroethylene (PTFE), it became a hybrid wetting surface. The experimental results show that the wall superheat temperature at the same heat flux during the heat flux decreasing can repeat that during the heat flux increasing well within 0.5°C, demonstrating that the boiling hysteresis was successfully eliminated. As the porous surface with a structural gradient has excellent performance in boiling heat transfer, it has been widely used in phase-change devices, such as loop and flat heat pipes, to improve their functioning. An ultra-thin flat heat pipe (UTHP), which is only 0.6 mm thick, can significantly reduce the evaporator temperature by 10°C under a 6 W heat load compared with a copper plate. This paper summarizes the most relevant features related to boiling heat transfer enhancement when using structural-gradient porous surfaces and the improvements in phase-change devices that use such surfaces. Despite the advances in this aspect, the porous surfaces can be further optimized to achieve a better heat transfer performance.

A MnCO₃ /Multiwalled carbon nanotube (MnCO₃/MWCNT) composite has been successfully fabricated by an in-suit hydrothermal method. When the MnCO₃/MWCNT composite is applied as anode materials in lithium-ion batteries (LIBs), the electrodes exhibit a reversible capacity of 645 mA h g-1 at 100 mA g-1 after 80 cycles, reaching an initial coulombic efficiency (CE) of up to 60.6%. Furthermore, the as-prepared MnCO₃/MWCNT composite displays more excellent rate performances than the pure multiwalled carbon nanotube (MWCNT) and pure MnCO₃ particles. The reason is that the MnCO₃ particles can be effectively connected by the MWCNT, thus enhancing the electrochemical performance of the MnCO₃/MWCNT composite.

A NiO flake and reduced graphene oxide sheet (NiO/RGO) composite was synthesized via an in situ ultrasonic agitation method after heat calcination in a nitrogen atmosphere. The NiO/RGO composite displayed a high reversible capacity of 825 mA h/g after 50 cycles at 100 mA/g, which was higher than the pure NiO flakes (197 mA h/g). The RGO sheets (115 mA h/g) used in lithium-ion batteries as anode materials. The NiO/RGO electrode showed excellent rate capacities that were higher than the pure NiO flakes and the RGO sheets electrodes within the same experimental conditions. These improvements could be attributed to the RGO sheets improved the electrical conductivity of NiO flakes and buffered the volume expansion of the NiO/RGO composite electrode during lithium cycling.

In this paper, a type of macroporous carbon (MPC) material was produced using water-soluble sodium carbonate (Na2CO3) as the template and glucose as the carbon precursor. After annealing in an argon atmosphere (Ar) at 700 °C, the samples exhibited specific surface areas up to 600 m2 g−1 with different proportions of sodium carbonate and glucose. When the samples were employed as anode materials in lithium-ion batteries, the electrodes delivered a stable reversible capacity at 200 mA g−1 and favourable cycling stability at 500 mA g−1. Moreover, all MPC samples exhibited excellent rate performances at 5000 mA g−1.

An N-doped MnO/rGO composite (N-MnO/rGO) was successfully fabricated by a one-step hydrothermal method in which histidine and potassium permanganate (KMnO4) reacted in water containing graphene oxide, and the product was then calcinated in a nitrogen (N2) atmosphere. The N-MnO/rGO presents an excellent lithium-storage capability. It shows a high reversible specific capacity of 1020 mA h g−1 at a current density of 200 mA g−1 after 150 cycles and 760 mA h g−1 at a current density of 500 mA g−1 after 200 cycles. Meanwhile, the N-MnO/rGO sample presents a stable rate capability from 100 to 2000 mA g−1. Even at 2000 mA g−1, the electrode delivers 335 mA h g−1, which is higher than the capability for the pure MnO particles and rGO sheets. The outstanding electrochemical performances of the N-MnO/rGO electrodes may be attributed to the combined effect of the rGO with N-doping that can effectively buffer the large volume expansion of the MnO particles and can enhance the transport rates of lithium ions and electrons during lithium cycling.

A mulberry-like MnO specimen was prepared using a MnCO3 sample under nitrogen (N2) protection at 700 °C (denoted as MnO-700). When the specimen was used in lithium-ion batteries (LIBs) as anode material, the reversible capacity of 702 mAh g−1 was displayed after 120 cycles at a current density 200 mA g−1, and 365 mAh g−1 of discharge capacity was obtained at 1000 mA g−1 at the 200th cycle. Meanwhile, the sample also exhibited an excellent rate capacity (224 mAh g−1 at 2000 mA g−1). The MnO-700 sample displayed a favorable electrochemical performance that may be ascribed to the unique mulberry-like structure of the MnO microparticles, which can provide enough space to satisfy the volume change of the MnO microparticles during lithium cycling, and also lead to more transfer paths for Li+ insertion/extraction during charge/discharge processes.

NiO-ZnO/RGO composite was obtained by the annealing of an Ni (OH) 2 -Zn (OH) 2 /RGO precursor, which has been fabricated by in situ ultrasonic agitation. Moreover, the NiO-ZnO nanoflakes are evenly distributed on the RGO sheets based on the scanning electron microscope (SEM) and transmission electron microscope (TEM) characterization results. When the NiO-ZnO/RGO composite was used as an anode material in lithium-ion batteries (LIBs), the electrodes exhibited a high reversible capacity of 1017 mA h/g at a current density of 100 mA/g after 200 cycles and a specific capacity of 458 mA h/g at 500 mA/g even after 400 cycles. The electrode even reached a capacity of 185 mA h/g at a current density of 2000 mA/g. The excellent electrochemical properties of the NiO-ZnO/RGO composite might be attributable to the NiO-ZnO nanoflakes offering rich electrochemical reaction sites and shortening the diffusion length for lithium ion (Li + ), as well as the RGO sheets improving the transfer rates of Li + and electron during the charge-discharge process.

The research on graphene-based anode materials for high-performance lithium-ion batteries (LIBs) has been prevalent in recent years. In the present work, carbon-coated SnO

Fusiform shape MnO/C composite was fabricated for the first time by heat calcining of MnCO3/C precursor, which was produced via a two-step hydrothermal method using glycine, KMnO4 and glucose as reagents. When the composite applied in LIBs as anode materials, the electrodes deliver a reversible capacity as high as 691 mA h g−1 after 120 cycles at a current density of 100 mA g−1 and can retain a stable capacity of 187 mA h g−1 at 1000 mA g−1. Compared with pure MnO particles sample, the enhanced electrochemical performances of MnO/C electrodes were attributed to the carbon layers can effectively improve the transfer rate of electrons and buffer the volume expansion of MnO particles during the charge/discharge process.

Micro pin fin arrays have been widely used in electronic cooling, micro reactors, catalyst support, and wettability modification and so on, and a facile way to produce better micro pin fin arrays is demanded. Herein, a simple electrochemical method has been developed to fabricate copper vertical micro dendrite fin arrays (Cu-VMDFA) with controllable shapes, number density and height. High copper sulphate concentration is one key point to make the dendrite stand vertically. Besides, the applied current should rise at an appropriate rate to ensure the copper dendrite can grow vertically on its own. The Cu-VMDFA can significantly enhance the heat transfer coefficient by approximately twice compared to the plain copper surface. The Cu-VMDFA may be widely used in boiling heat transfer areas such as nuclear power plants, electronic cooling, heat exchangers, and so on.

Janus effect has been studied for emerging materials like Janus membranes, Janus nanoparticles, etc., and the applications including fog collection, oil/water separation, CO 2 removal and stabilization of multiphasic mixtures. However, the Janus effect on oil/water separation is still unclear. Herein, Janus Cu mesh decorated with Ni-NiO/Ni(OH) 2 core-shell nanoparticles is synthesized via selective electrodeposition, in which we keep one side of Cu mesh (Janus A) to be superhydrophilic, while manipulate the wettability of another side (Janus B) from hydrophobic to superhydrophilic. Experimental results indicate that Cu mesh with both-side superhydrophilic shows the superior oil/water separation performance (separation efficiency >99.5%), which is mainly due to its higher water capture percentage as well as larger oil intrusion pressure. Further, we demonstrate the orientation of Janus membranes for oil/water separation, and summarize that the wettability of the upper surface plays a more important role than the lower surface to achieve remarkable performance. Our work provides a clear insight of Janus effect on oil/water separation, it is significative to design high-performance membranes for oil/water separation and many other applications.

Nowadays, new emerging two-dimensional (2D) materials have become a hot topic in the field of theoretical physics, material science, and nanotechnology engineering due to their high surface area, planar structure, and quantum confinement effect. Within a two-dimensional framework, we systematically concentrate on the buckled and puckered systems consisting of the VA group elements (denoted as arsenene, antimonene, and bismuthene). Among these studied systems, the buckled antimonene harbors a thermoelectric figure of merit (ZT) of 2.15 at room temperature. This is probably the highest value that has ever been reported in pristine 2D materials. By simple biaxial strain engineering, the ZT can even get enhanced to 2.9 under 3% tensile strain. The enhancement mainly results from both tuning the electronic structures and reducing the thermal conductance. This work predicts a new promising candidate in thermoelectric devices, based on the fact that buckled antimonene has been lately fabricated and proved to be ...

A MnCO₃ /Multiwalled carbon nanotube (MnCO₃/MWCNT) composite has been successfully fabricated by an in-suit hydrothermal method. When the MnCO₃/MWCNT composite is applied as anode materials in lithium-ion batteries (LIBs), the electrodes exhibit a reversible capacity of 645 mA h g

In this work, we investigate the droplet bouncing on the hierarchical branched nanotube (BNT) arrays surface above and below 0 °C. By anodization, we fabricate large-area arrays of BNT with the BNT spacing controlled from adjacent to sparse. We evaluate the influence of the BNT spacing on the droplet bouncing. The adjacently distributed BNT (A-BNT) outperforms the sparsely distributed BNT (S-BNT). We find that the A-BNT can repel up to 3.1 m/s droplet at 20 °C and 2.3 m/s droplet at −18 °C, while the maximum bouncing velocity on the S-BNT is below 2.3 m/s at 20 °C and below 0.9 m/s at −10 °C. For the bouncing on the supercooled A-BNT surface, the droplet bouncing contact time increases as the substrate temperature decreases for the same droplet velocity, while the bouncing contact time decreases as the droplet velocity increases for the same substrate temperature. We discuss the influence of the nanosized air cushion entrapped amid the branched-arms of the BNT on the three-phase contact line on the BNT walls and bouncing performance under supercooled conditions.

Graphene-based composite materials have attracted much attention as anodes for lithium-ion batteries (LIBs). Herein, TiO2 nanorods anchored on reduced graphene oxide (R-TiO2/rGO) composite were fabricated by hydrothermal method after annealing treatment and then explored as anode material for LIBs. The resultant R-TiO2/rGO samples possess TiO2 nanorods (with a section width of ~5 nm) on the surface of RGO sheets and a specific surface area of 149.5 m2 g−1. Notably, the electrodes deliver high reversible capacities of 267 mA h g−1 at 1 C after 100 cycles and 151 mA h g−1 at 10 C after 500 cycles (1 C = 168 mA g−1, voltage window: 0.01–3 V), respectively. Furthermore, the electrodes exhibit a remarkable rate capability of 55 mA h g−1 at 30 C, and a high coulombic efficiency (~99.5%). Moreover, the sample displays 96 mA h g−1 at 10 C after 1000 cycles ranged from 1 to 3 V. Such a favorable performance can be ascribed to the RGO sheets that facilitate the transport of Li+ and electrons during the lithium cycling process while, the pseudo-capacitance contribution may also be partially responsible for the excellent energy storage performance. This suggests the R-TiO2/rGO composite as a promising anode material for long-term LIBs.

Transition metal oxide/reduced graphene oxide (TMO/RGO) composites have been explored for development as anode materials for lithium-ion batteries (LIBs); TMOs have high theoretical capacities, and the oxidation degrees of RGO sheets can directly affect the lithium storage performance of TMO/RGO composites. In this work, several NiO/reduced graphene oxide composites (NiO/RGO) are prepared based on oxidation degrees of graphite oxide sheets (GOs) through an ultrasonic agitation method. These composites are then explored as anodes for LIBs. Results show that the reversible capacity of NiO/RGO composites increases gradually to 1046 mA h/g and then declines to 956 mA h/g after 50 cycles at 100 mA/g. The variation rule of lithium storage properties of NiO/RGO samples can be attributed to the surface functional groups of RGO sheets, which can affect interfacial interaction between NiO and RGO sheets due to the different oxidation degrees of GO. Different RGO sheets also show distinct abilities to hinder NiO pulverisation and promote lithium-ion/electron diffusion during repeated charge and discharge processes.

MnO micrometer particles with a two-stage structure (composed of mass nanoparticles) were produced via a one-step hydrothermal method using histidine and potassium permanganate (KMnO4) as reagents, with subsequent calcination in a nitrogen (N2) atmosphere. When the MnO micrometer particles were utilized in lithium-ion batteries (LIBs) as anode materials, the electrode showed a high reversible specific capacity of 747 mA h g−1 at 100 mA g−1 after 100 cycles, meanwhile, the electrode presented excellent rate capability at various current densities from 100 to 2000 mA g−1 (∼203 mA h g−1 at 2000 mA g−1). This study developed a new approach to prepare two-stage structure micrometer MnO particles and the sample can be a promising anode material for lithium-ion batteries.

Graphene-epoxy thermal conductive adhesive was obtained using few-layer graphene sheets as additives which were fabricated by a re-expansion and exfoliation method. The experimental results show that graphene sheets can effectively enhance the thermal conductivity of epoxy matrix, with 4.01 W m −1 K −1 for the maximum filling loading of weight 10.10%, which is enhanced by more than 22 times of the pure epoxy resin, about 2.2 times higher than that of the same resin with the maximum weight 16.81% filled with graphite nanoflakes, and approximately 2.4 times higher than that of the same resin with the maximum weight 44.3% filled with the natural graphite powder.

A new family of two-dimensional topological insulator, hydrogenated monolayer Pb2XY (X = Ga/In, Y = Sb/Bi), has been predicted using first-principles density functional theory. The electronic bulk band gap of the proposed systems can be induced in the presence of a spin-orbit coupling effect and its highest value (0.25 eV) was observed in the hydrogenated monolayer Pb2GaBi, which is suitable for practical application. Our simulation study points out that the nanoribbons derived from this new family harbor gapless edge channels. The non-trivial topological nature was further confirmed by calculating the Z2 topological invariant. These novel systems provide a new platform for topological phenomena observation and spintronic applications.

Heat dissipation is an important issue for electronic devices. In the present work, we prepared eight kinds of thermal adhesives by filling the epoxy resin with natural graphite, copper, aluminum, zinc oxide, boron nitride, aluminum oxide, diamond and silver powders, and measured the thermal conductivity of all samples. The results show the eight fillers can efficiently improve the thermal conductivity of the epoxy resin. Meanwhile, we found the layer-shape filler is more favorable than the ball-shape filler and the sharp-corner-shape filler to enhance the thermal conductivity of epoxy resin, and the low price layer-shape natural graphite-epoxy adhesive had the highest thermal conductivity up to 1.68 W m −1 K −1 at weight 44.3% of the eight thermal adhesives. All the fillers and the cross sections of thermal adhesives morphologies images were characterized by scanning electron microscopy, and the thermal conductivities of all the samples were measured by Hot Disk TPS-2500 thermal constants analyzer.

AIP Advances 9(8), 085106 - (2019). doi:10.1063/1.5113973, Published by American Inst. of Physics, New York, NY

Mass graphene sheets were obtained by a re-expansion and exfoliation method which uses the commercially available graphite intercalation compounds as the starting materials. The as-prepared samples have been characterized by scanning electronic microscopy, transmission electron microscope, atomic force microscope, Fourier transform infrared spectrometer spectroscopies, and Raman microscope. Using high resolution transmission electron microscopy on 60 samples, it was shown that the final samples exhibit 8 % monolayer, 19 % bilayer, and 77 % less than or equal to five layers, and the sheets are largely free of defects and chemical functional groups after thermal reduction.

Direct reduced iron (DRI) shaft furnace flow field has important influence to the DRI production process, and the ventilation is a key factor for the velocity and pressure distribution of the gas flow in the furnace. At present works, the direct reducing gas velocity distribution and pressure distribution of DRI shaft furnace were studied with different ventilation. By the analysis of numerical simulation, the result was found that the direct reducing gas velocity increase with height in the shaft furnace reduction section. The velocity of the direct reducing gas augment with the increase of ventilation. The direct reducing gas pressure add with increasing height in the shaft furnace reduction section. With ventilation increasing, the pressure of the shaft furnace ventral part increase, and the pressure gradient increase in the direction of height in the DRI shaft furnace.

The sandwich structure core–shell–shell nanospheres SiO2@(Y,Gd)BO3:Eu3+@SiO2 (SiO2@YGB@SiO2) have been synthesized by depositing YGB nanoparticles on silica core surface through the precipitation method, followed by sol–gel processing of tetraethoxysilane (TEOS) to form smooth silica shell over the surface of YGB. The phosphors were characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), transmission electronic microscope (TEM) and photoluminescence spectra. The results showed that the phosphors with spherical morphology can be produced easily by assembling the core–shell or core–shell–shell structure, and the XRD patterns indicated that the crystallinity of YGB is weakened due to the core–shell structure, which resulting from the local site symmetry of Eu3+ was decreased. The photoluminescence properties of the product are compared with those of the pure YGB, the core–shell structure SiO2@YGB and YGB@SiO2. The emission intensity, relative luminous efficiency and Red/Orange values of phosphors are increased in the order SiO2@YGB@SiO2>SiO2@YGB>YGB@SiO2>YGB; and the chromaticity coordinates of the phosphors are shifted from orange of pure YGB to red of SiO2@YGB@SiO2.

Monodispersed SiO2 @ Y2O3:Eu3+ and SiO2 @ Y2O3:Eu3+ @ SiO2 nanospheres contain SiO2 as core and Y2O3:Eu3+ as shell or another SiO2 shell coated on the surface of SiO2 @ Y2O3:Eu3+ particles were synthesized, respectively. The synthesis of core–shell particles SiO2 @ Y2O3:Eu3+ involved the SiO2 core ultrasonically dispersed into a certain amount of polyethylene glycol solution, and the deposition of Y2O3:Eu3+ on the surface of SiO2 core through homogeneous precipitation of Y3+ and Eu3+ using urea as precipitator. More over, the particles SiO2 @ Y2O3:Eu3+ as core was ultrasonically dispersed into a certain amount of ethanol and followed by sol–gel processing of tetraethoxysilane to form another silica shell. The morphology structures and sizes of the resulting particles were analyzed by SEM and TEM, which indicated that the resulting particles dispersed regularly and the microstructures of the particles are clearly core–shell or core–shell–shell structures. XRD patterns characterized the crystal structures of deposited Y2O3:Eu3+ shell or SiO2 shell after heat treatment at 900 °C. Photoluminescence determination showed that both the phosphors can be excited by ultra violet at 254 nm which showed red-shift. Under the excitation at 254 nm, the Eu3+ ion mainly shows its characteristic red (612 nm, 5D0–7F2) emission in the particles from Y2O3:Eu3+ shell. The emission intensity of Eu3+ was affected by the SiO2 core or shell in some extent.