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Production cost, capacitance, and electrode materials safety are the key factors to be concerned about for supercapacitors. In this work, a type of carbon nanosheets was produced through the carbonization of tripotassium citrate monohydrate and nitric acidification. Subsequently, a well-designed manganese dioxide/carbon nanosheets composite was synthesized through hydrothermal treating. The carbon nanosheets served as the substrate for growing the manganese dioxide, regulating its distribution, and preventing it from inhomogeneous dimensions and severe agglomeration. Many manganese dioxide nanosheets grew vertically on the numerous functional groups generated on the surface of the carbon nanosheets during acidification. The synergistic combination of carbon nanosheets and manganese dioxide tailors the electrochemical performance of the composite, which benefits from the excellent conductivity and stability of carbon nanosheets. The carbon nanosheets derived from tripotassium citrate monohydrate are conducive to the remarkable performance of manganese dioxide/carbon nanosheets electrode. Finally, an asymmetric supercapacitor with active carbon as the cathode and manganese dioxide/carbon nanosheets as the anode was assembled, achieving an outstanding energy density of 54.68 Wh·kg−1 and remarkable power density of 6399.2 W·kg−1 superior to conventional lead-acid batteries. After 10000 charge-discharge cycles, the device retained 75.3% of the initial capacitance, showing good cycle stability. Two assembled asymmetric supercapacitors in series charged for 3 min could power a yellow light emitting diode with an operating voltage of 2 V for 2 min. This study may provide valuable insights for applying carbon materials and manganese dioxide in the energy storage field. [ABSTRACT FROM AUTHOR]

The hot deformation characteristics, microstructure evolution, and dynamic recrystallization (DRX) mechanism of the newly developed austenitic heat-resistant steel Fe–18Cr–10Ni–0.3Nb–2.5Cu were systematically investigated by thermal compression tests combined with microstructure characterizations. The activation energy (Q) map, Zener–Hollomon parameter (Z) map, and processing map were plotted according to the stress–strain curves to reveal the inherent connection between the three maps and the hot deformation characteristics of this alloy. The high η region in the processing map does not precisely correspond to the region where DRX developed. Nevertheless, the flow instability map accurately predicts the microstructure. The variation pattern of Z corresponded more closely to the hot deformation microstructure evolution than did the variation pattern of Q. The degree of DRX increases with decreasing Z. The optimal process parameters are 1000 °C/0.01 s−1/0.8 and 1100 °C/10 s−1/0.8 (temperature/strain rate/strain), and they result in complete DRX and a narrow range of Z values. The DRX mechanism at high strain rate is characterized by the combined enhancement of discontinuous DRX (DDRX), continuous DRX (CDRX), and twin-DRX (TDRX). The dominance of the particle-stimulated nucleation (PSN) mechanism at intermediate strain rate results in the formation of incompletely recrystallized microstructures with approximate orientation. Sufficient time at low strain rate promotes the development of DDRX and CDRX. [ABSTRACT FROM AUTHOR]

The hot working performance and microstructure evolution of an innovative GH1059 superalloy are investigated via Gleeble-3500 simulator under the deformation parameters of 950–1100 ℃ and 0.01–5 s−1. Through the true stress-true strain curves, the Arrhenius high temperature constitutive model is established, which is able to describe the influence of deformation parameters on deformation resistance. The processing map based on the dynamic materials model is constructed for the GH1059 superalloy. Along with the optical microscopy and electron backscattered diffraction microstructure analyses, the processing map is classified into three typical domains: unstable domain, safety transition domain and optimal domain. The optimal processing domain covers the deformation parameters of 1030–1100 ℃ and 0.01–0.1 s−1, where DRX occurs, leading to the best hot working performance for GH1059, while the absence of DRX is responsible for the unstable behavior. Furthermore, from the comprehensive analyses of crystallographic orientation and dislocation density, the major dynamic recrystallization (DRX) mechanism for this GH1059 superalloy is determined as the discontinuous dynamic recrystallization while the continuous dynamic recrystallization plays the minor role. [ABSTRACT FROM AUTHOR]

The flow stress behavior of an innovative spray-formed aluminum–copper–lithium (Al–Cu–Li) alloy was successfully investigated via isothermal compression tests under a deformation temperature range of 350–450 °C (25 °C interval) and a strain rate range of 0.01, 0.1, 1, 5, 10 s−1. The constitutive relationship was established based on backpropagation artificial neural network (BP-ANN) algorithm. And the 3D processing maps were constructed as well. The results show that the constitutive model is in great agreement with the experiment data where the correlation coefficient goes up to 0.99963 and the average residual error lies only 1.06%. Moreover, from the 3D processing maps, the area of the instable regions tends to enlarge by virtue of the increasing strain, and the optimum processing domain is advised to be 440–450 °C. The microstructure evolution is found consistent with the prediction of the processing map. [ABSTRACT FROM AUTHOR]

Highlights: The multiple thermal treatments strategy is proposed for preparing the hollow oxygen-incorporated g-C3N4 nanosheets (OCN). Oxygen-adsorption creates a lot of defects to the formation of hollow and monolayered structure, while oxygen-doping reduces the band gap significantly. OCN exhibits stable and high photocatalytic hydrogen evolution with increased surface area, enhanced charge transport, and reduced band gap.Graphitic carbon nitride (g-C3N4)-based photocatalysts have shown great potential in the splitting of water. However, the intrinsic drawbacks of g-C3N4, such as low surface area, poor diffusion, and charge separation efficiency, remain as the bottleneck to achieve highly efficient hydrogen evolution. Here, a hollow oxygen-incorporated g-C3N4 nanosheet (OCN) with an improved surface area of 148.5 m2 g−1 is fabricated by the multiple thermal treatments under the N2/O2 atmosphere, wherein the C–O bonds are formed through two ways of physical adsorption and doping. The physical characterization and theoretical calculation indicate that the O-adsorption can promote the generation of defects, leading to the formation of hollow morphology, while the O-doping results in reduced band gap of g-C3N4. The optimized OCN shows an excellent photocatalytic hydrogen evolution activity of 3519.6 μmol g−1 h−1 for ~ 20 h, which is over four times higher than that of g-C3N4 (850.1 μmol g−1 h−1) and outperforms most of the reported g-C3N4 catalysts. [ABSTRACT FROM AUTHOR]

The hot deformation behavior of an alumina-forming austenitic (AFA) stainless steel was investigated on a Gleeble-3500 simulator. Moreover, the critical dynamic recrystallization model was established, and the critical stress was determined. Microstructural characterization was analyzed using electron backscattered diffraction (EBSD) and transmission electron microscope (TEM). The microstructure evolution showed that the degree of dynamic recrystallization (DRX) and the content of high-angle grain boundaries increased significantly with the increasing temperature and the decreasing strain rate. For recrystallization mechanisms, the bulging mechanism was found dominating, while the sub-grain rotation mechanism played an assisting role. Furthermore, discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) coexisted during the hot deformation. [ABSTRACT FROM AUTHOR]

MoO3, as a potential electrode material in energy storage, has recently been attracted increasing attention in supercapacitor. However, due to the poor electrical conductivity of MoO3, its practical application is limited. In this work, the electronic conductivity and the electrochemical performances of MoO3 electrode have been improved by introducing carbon on the surface of MoO3 nanobelt. The novel C@MoO3 nanocomposite was successfully prepared by hydrothermal in this study. The as-prepared samples were characterized by XRD, Raman, Fourier transform infrared, X-ray photoelectron spectroscopy, scanning electron microscope and transmission electron microscope. The electrochemical measurement results showed that the C@MoO3 nanocomposite exhibits superior electrochemical properties. The specific capacitance of C@MoO3 is 179 F g− 1 at current density of 1 A g− 1, which is 2.8 times than MoO3 at the same current density. The outstanding electrochemical performance could be attributed to these reasons including the advantages of the synergistic effect and good conductivity of carbon layer. This work will facilitate the application of other transition metal oxides with similar structures in energy storage. [ABSTRACT FROM AUTHOR]

A novel and unique MoS2 nanosheets-coated Bi2S3 nanorods composite was successfully prepared by a facile hydrothermal method. The crystal structure and morphology of MoS2/Bi2S3 nanocomposite were confirmed by X-ray diffraction photoelectron spectroscopy, laser Raman mapping, scanning electron microscope and transmission electron microscope. Bi2S3 nanorods are uniform with an average length of about 200 nm, and MoS2 nanosheets are closely attached to Bi2S3 nanorods. The electrochemical performance of MoS2/Bi2S3 nanocomposite was characterized by a conventional three-electrode test in 1 M KOH electrolyte solution. The as-prepared MoS2/Bi2S3 electrode exhibits rapid electron transfer, long-time cycle stability, high specific capacitance of about 120.2 F g−1 (at a current density of 1 A g−1) and long-term cycling stability with nearly 87.7% capacity retention after 2000 cycles. The improved electrochemical performance should be attributed to the synergistic effect of Bi2S3 nanorods and MoS2 nanosheets. The MoS2/Bi2S3 nanocomposite with excellent electrochemical performance will have promising application in supercapacitor electrode materials. [ABSTRACT FROM AUTHOR]

A cobalt sulfide decorated reduced graphene oxide (CoS/rGO) nanocomposite was successfully synthesized via a facile one-step hydrothermal route assisted by ethylenediamine. The crystalline phase, structure and morphology of the products were systematically characterized by x-ray diffraction, transmission electron microscopy, scanning electron microscopy, x-ray photoelectron spectroscopy, nitrogen (N2) absorption-desorption isotherm, Raman spectra and thermogravimetric analysis. The results show that CoS nanoparticles with the size of 30-100 nm are well dispersed on or anchored in the creasy rGO sheets substrate. Combining the CoS compound nature with the rGO outstanding characteristics, the as-obtained CoS/rGO as an electrode for a supercapacitor harvests high specific capacitance, excellent long-cycle stability and remarkable high-rate capability, which are all superior to those of pristine CoS. Importantly, this nanocomposite possesses a specific capacitance of 813 F g−1 at 0.5 A g−1 (about 2 times that of pure CoS) and excellent cycling stability with 91.2% capacitance retention after 1000 repetitive charge-discharge cycles. It is noteworthy that this approach can be readily applicable to the nanoparticle decoration of graphene sheets and the preparation of other graphene-based nanocomposites for supercapacitors. [ABSTRACT FROM AUTHOR]

Abstract: Materials with yolk-shell structure have attracted wide attention and they have been applied in energy storage devices with long cycle life. Carbon (yolk)-MoS2 (shell) hierarchical microspheres were successfully prepared in this study by a facile one-step hydrothermal method. Scanning electron microscope and transmission electron microscope images showed that the carbon-MoS2 microspheres were obviously made up of carbon yolk and MoS2 shell. The diameter of the yolk and thickness of shell were 2.1 and 0.26 µm, respectively. The as-prepared carbon-MoS2 yolk-shell hierarchical microspheres displayed charge capacity of 120 F g−1 after 3000 charge and discharge cycles at the current density of 1 A g−1. The superior electrochemical performance of the as-prepared materials was attributed to the yolk-shell structure and smart combination between carbon and MoS2. The yolk-shell structure provided sufficient void space for expansion without causing shell damage, leading to stable structure with long cycle life. The possible formation mechanism for the carbon-MoS2 yolk-shell microsphere was also discussed according to the characterization results.Graphical Abstract: Carbon (yolk)-MoS2 (shell) hierarchical microspheres were successfully prepared by a facile hydrothermal method with only one step. Materials with yolk-shell structure have been attracted wide attention and could be applied for long-cycle-life energy storage devices. When it was used as the electrode materials, it shown excellent electrochemical properties. Because the yolk-shell microsphere has sufficient void space for expansion without causing the shell to be destroyed, leading to stable structure and cycling. [ABSTRACT FROM AUTHOR]

Porous SiOC composites for efficient treatment of dye wastewater were prepared using polysiloxane preceramic polymer mixed with wood biomass by pyrolysis under Ar atmosphere. The influences of the pyrolysis temperature on the microstructure, pore feature and adsorption behavior were investigated. The composites contain the α-quartz, cristobalite, nanosized β-SiC and free carbon embedded in a SiOC matrix. The composite obtained at 1300 °C presents a high specific surface area up to 463 m/g. The adsorption capacity is enhanced by increasing pyrolysis temperature. The adsorption for the removal of methylene blue on the composites follows the pseudo second-order kinetics, and the adsorption data can be described by the Langmuir and Freundlich adsorption isotherms very well. The composite at 1300 °C displays a maximum adsorption capacity up to 173.5 mg/g caused by the enhancement of specific surface area and the existence of sp carbons, resulting in many favorable adsorption sites and strong electrostatic attraction. [ABSTRACT FROM AUTHOR]

A nanocomposite consisted of Ag nanoparticles and WS nanosheets was prepared by a two-step procedure, in which Ag sol was generated at first, then added into WS nanosheet dispersion to form the nanocomposite via self-assembly. The nanocomposites with different content of Ag nanoparticles were successfully prepared. The results show that Ag nanoparticles with the diameter of 10-20 nm are uniformly distributed on WS nanosheets and not oxidized. All nanocomposites are mesoporous. The specific surface area and the mesoporosity of WS are improved due to the existence of Ag nanoparticles. The specific capacitance of the nanocomposite increases with the increasing content of Ag nanoparticles. The 2000 cycles of charging and discharging were carried out on 20%AgNPs@WS nanocomposite, proving its good cycling performance. It has smaller transfer resistance and internal series resistance than WS nanosheets. This nanocomposite has potential application in supercapacitors. [ABSTRACT FROM AUTHOR]

Cubic ZrMoVO (0 ≤ x ≤ 0.5) compounds, with well-defined nanorods morphology, were synthesized by a facile sol-gel process without using any surfactant or template. The resulting products were characterized by the X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermal mechanical analyzer and UV-vis diffuse reflectance spectra (UV-vis DRS). The results indicated that V-doping did not influence the crystal structure and negative thermal expansion (NTE) property, but made rods size increase. Narrowed band gap was observed in V-doped ZrMoO. The resultant V-doped ZrMoO samples, as compared with pure ZrMoO, exhibited improved UV-light photocatalytic activity, during the photocatalytic degradation of rhodamine B. The mechanism was supposed that the V-doping gave rise to the formation of oxygen vacancies which could enhance photocatalytic performance by reducing the recombination of electrons and holes. In addition, cubic ZrMoVO also displayed reliable recycling photocatalytic performance and satisfying UV-light catalytic activity for the organic pollutant. Furthermore, all of the resulting cubic ZrMoVO showed excellent NTE property from 25 to 450 °C. Graphical Abstract: TEM images of (a) pure ZrMoO and (b) ZrMoVO; (c) RhB degradation under UV-light illumination for 180 min in the presence of cubic ZrMoVO ( x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) photocatalysts.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Novel ZrVO fibers with negative thermal expansion were prepared via combination of sol-gel process and thermal decomposition. The as-prepared fibers were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy and Raman spectroscopy. The results showed that the synthetic pH value had little influence on the crystal structure of products while showed significant effect on morphology. The fibers obtained at pH = 9 exhibited cylindrical morphology and its mean diameter was about 1 μm. The thermal expansion property of the as-prepared fibers was investigated by in situ XRD and thermal mechanical analyzer. All of the as-prepared fibers showed positive thermal expansion first and then negative thermal expansion, resulting from a phase transition from 3 × 3 × 3 superstructure to 1 × 1 × 1 cubic structure. The macro thermal expansion coefficients of ZrVO ceramic rods increased with decreasing of fiber diameter. The mechanism of the phase transition was also discussed. [ABSTRACT FROM AUTHOR]

Graphene-based silver nanoparticles (Ag NPs-GE) material has been developed and demonstrated antibacterial effect against Escherichia coli and Pseudomonas aeruginosa. In this study, the antibacterial activity and mechanism on P. aeruginosa were investigated. The experiments results showed the minimum bactericidal concentration of Ag NPs-GE to P. aeruginosa is 20 μg/ml. When P. aeruginosa were exposed to 20 μg/ml Ag NPs-GE for 1 h, the cell wall was breakdown. In order to study the mechanism of antibacterial effect of Ag NPs-GE, two-dimensional electrophoresis was carried out to compare the protein expressional profiles of P. aeruginosa exposed to 5 μg/ml Ag NPs-GE or 5 μg/ml AgNO with the untreated bacteria. Identification of differentially expressed protein was performed by MALDI-TOF/TOF MS. The change of proteomic profile induced by Ag NPs-GE was distinct from that induced by AgNO. Seven identified proteins were found induced and nine proteins were suppressed by Ag NPs-GE. Five identified proteins were found induced and twenty proteins were suppressed by AgNO. In addition, either Ag NPs-GE or AgNO suppressed the expression of eight proteins, amidotransferase, 30S ribosomal protein S6, bifunctional proline dehydrogenase/pyrroline-5-carboxylate dehydrogenase, arginyl-tRNA synthetase, nitroreductase, acetolactate synthase 3, methionyl-tRNA synthetase and periplasmic tail-specific protease. Furthermore, gene ontology analysis and KEGG pathway analysis were used to characterize the functions of those proteins. [ABSTRACT FROM AUTHOR]

A free-standing and flexible silver nanoparticles-graphene (Ag NPs-GE) film with high surface-enhanced Raman scattering (SERS) sensitivity has been developed. First, the high stable and dispersive Ag NPs-GE composite was fabricated by in situ reduction using graphene oxide sheets as substrates and the hydrazine hydrate as a reducing agent in the solvothermal environment. Second, the Ag NPs-GE films can be fabricated through vacuum filtration of the Ag NPs-GE suspension. Transmission electron microscope (TEM) images show that the Ag NPs with an average size of 22 nm and a narrow particle size distribution are uniformly distributed on GE sheets. The coverage density of Ag NPs onto the surface of GE sheets can be successfully controlled by tuning the concentration of silver ion precursor. As-prepared Ag NPs-GE substrates have good SERS sensitivity due to the high SERS-active of Ag NPs. The enhancement factor for 1 × 10 M of rhodamine 6G molecules adsorbed onto the surface of substrate is about 2.7 × 10. The SERS activity toward crystal violet and Escherichia coli was also investigated. [ABSTRACT FROM AUTHOR]

A free-standing and flexible silver nanoparticle-graphene (Ag NP-GE) film with high surface-enhanced Raman scattering (SERS) sensitivity has been synthesized. Firstly, the highly stable and dispersive Ag NP-GE nanocomposite was fabricated by an in situ reduction method using graphene oxide sheets as substrates and ethylene glycol as a reduction agent in a solvothermal environment. Secondly, the Ag NP-GE films can be fabricated through vacuum filtration of the Ag NP-GE suspension. The highly SERS-active Ag nanoparticles and Ag nanoparticle aggregates make a significant contribution to the high sensitivity of SERS to rhodamine 6G molecules with an enhancement factor of 5.6 × 10. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A novel one-pot catalytic synthesis of 1-benzoylpyrene through acylation of pyrene with benzoic anhydride catalyzed by several heteropoly acids (HPAs) was investigated. Pure 1-benzoylpyrene was obtained and its structure was identified by GC/MS, FT-IR and H NMR spectra. Silica-supported phosphotungstic heteropoly acid (PW/SiO) was found to be the most active catalyst in the acylation. The yield and the selectivity of 1-benzoylpyrene were up to 62.5% and 100%, respectively. The effects of experimental parameters on the catalytic acylation reaction, and the possibility of reusability of PW/SiO catalyst were studied. PW/SiO catalyst is easily separable from the reaction mixture and reusable without loss of its activity. [ABSTRACT FROM AUTHOR]

ZrWMoO8 powders with different morphologies were obtained using ammonium tungstate, molybdate tungstate and zirconium tungstate as the starting materials by dehydrating the precursor ZrWMoO7(OH)2(H2O)2. The precursor was studied by thermo-gravimetric and differential scanning calorimetry (TG-DSC). The influence of the gelling agents (HCl, HClO4, HNO3, H2SO4 and H3PO4) on the crystallization process and crystal morphology of the products prepared was investigated by X-ray powder diffraction (XRD), scanning electron micrograph (SEM) and X-ray fluorescence spectrometer (XRF). Results showed that the morphology of the ZrWMoO8 particles can be simply adjusted by changing the gelling agents, and the thermal expansion coefficients of cubic ZrWMoO8 prepared in HCl solution are −3.84 × 10−6 K−1 from 100°C to 700°C. [ABSTRACT FROM AUTHOR]