We research the adsorption geometries graphene （Li-GR） before and after CO and electronic structures of pristine graphene （p-GR） and Li-doped adsorption by first-principles. The adsorption energies Ead of CO on p-...We research the adsorption geometries graphene （Li-GR） before and after CO and electronic structures of pristine graphene （p-GR） and Li-doped adsorption by first-principles. The adsorption energies Ead of CO on p-GR and Li-GR are calculated. The results demonstrate that Ead of CO on Li-GR is from -3.3 eV to -3.5 eV, meanwhile Q is up to 0.13e, which indicate that strong electrostatic attractions occur between CO and Li-GR, while CO is physically adsorbed on p-GR. The obvious accumulated charge in electron density difference and increasing carrier density suggest that the conductivity of Li-GR is improved considerably after CO adsorp- tion. An adsorption mechanism is also proposed. Our results provide a path to achieving CO sensors with high performance.展开更多
Few-layer graphenes were fabricated from expandable graphite by rapid microwave exfoliation. Expandable graphite was irradiated in a domestic microwave in full power for 3 min, then soaked in mixed strong hydrogen nit...Few-layer graphenes were fabricated from expandable graphite by rapid microwave exfoliation. Expandable graphite was irradiated in a domestic microwave in full power for 3 min, then soaked in mixed strong hydrogen nitrate and sulfuric acid with volume ratio of 1：1 for 24 h and re-irradiated, thus few-layer graphene sheets were obtained. Specimens gained from every step were selectively characterized by different techniques, such as SEM, XRD, Raman, AFM, XPS, FTIR and combustion elemental analysis. The results show that expandable graphite with loose, porous and worm-like morphology forms instantaneously in microwave irradiation with crackling sound and sparkles, which manifests physical exfoliation of graphene sheets. Few-layer graphene sheets with a dozen or more layers and average thickness of about 4.7 nm are obtained eventually after sequential treatment of microwave irradiation, mixed acid soaking and second microwave irradiation. The as-prepared few-layer graphenes still have high crystallinity and high purity with traces of oxide groups and without serious unrecoverable oxidation damage.展开更多
Adsorption and desorption of hydrogen on/from single-vacancy and double-vacancy graphenes were studied by means of first-principles calculations. The structure and stability of continuous hydrogenation in single vacan...Adsorption and desorption of hydrogen on/from single-vacancy and double-vacancy graphenes were studied by means of first-principles calculations. The structure and stability of continuous hydrogenation in single vacancy were investigated. Several new stable structures were found, along with their corresponding energy barriers. In double-vacancy graphene, the preferred sites of H atoms were identified, and H2 molecule desorption and adsorption of from/on were calculated from the energy barriers. This work provides a systematic and comprehensive understanding of hydrogen behavior on defected graphene.展开更多
In this work we report that when ferromagnetic metals （Fe, Co and Ni） are thermMly evaporated onto n-layer graphenes and graphite, a metal nanowire and adjacent nanogaps can be found along the edges regardless of it...In this work we report that when ferromagnetic metals （Fe, Co and Ni） are thermMly evaporated onto n-layer graphenes and graphite, a metal nanowire and adjacent nanogaps can be found along the edges regardless of its zigzag or armchair structure. Similar features can also be observed for paramagnetic metals, such as Mn, Al and Pd. Meanwhile, metal nanowires and adjacent nanogaps cannot be found for diamagnetic metals （Au and Ag）. An external magnetic field during the evaporation of metals can make these unique features disappear for ferromagnetic and paramagnetic metal; and the morphologies of diamagnetic metal do not change after the application of an external magnetic field. We discuss the possible reasons for these novel and interesting results, which include possible one-dimensional ferromagnets along the edge and edge-related binding energy.展开更多
The effects of graphene oxide（GO） with polar groups and functionalized GO（f GO） with nonpolar groups on the isothermal crystallization of poly（L-lactide）（PLLA） were compared. Functionalized GO was obtained by ...The effects of graphene oxide（GO） with polar groups and functionalized GO（f GO） with nonpolar groups on the isothermal crystallization of poly（L-lactide）（PLLA） were compared. Functionalized GO was obtained by grafting octadecylamine and characterized by FTIR, WAXD and TGA. Isothermal crystallization kinetics of PLLA/GO and PLLA/f GO nanocomposites were investigated by combining DSC data and Avrami equation. The results showed that f GO could improve PLLA crystallization rate more obviously than GO. By analyzing the morphology obtained from POM, SEM and TEM, it was found f GO with large layer space dispersed better in PLLA and supplied more nucleation sites than GO. Therefore, for the multilayer graphene, increasing the layer spaces is important to improve its dispersion in polymers, which will cause the crystal kinetics changing of polymers.展开更多
Friction plays a critical role in the function and maintenance of small-scale structures, where the conventional Coulomb friction law often fails. To probe the friction at small scales, here we present a molecular dyn...Friction plays a critical role in the function and maintenance of small-scale structures, where the conventional Coulomb friction law often fails. To probe the friction at small scales, here we present a molecular dynamics study on the process of dragging graphene nanoribbons on waved graphene substrates. The simulation shows that the induced friction on graphene with zero waviness is ultra-low and closely related to the surface energy barrier. On waved graphenes, the friction generally increases with the amplitude of the wave at a fixed period, but anomalously increases and then decreases with the period at a fixed amplitude. These findings provide the insights into the ultraqow friction at small scales, as well as some guidelines into the fabrication ofgraphene-based nano-composites with high performance.展开更多
The adsorption of hydrogen molecules on titanium-decorated （Ti-decorated） single-layer and bilayer graphenes is studied using density functional theory （DFT） with the relativistic effect. Both the local density ap...The adsorption of hydrogen molecules on titanium-decorated （Ti-decorated） single-layer and bilayer graphenes is studied using density functional theory （DFT） with the relativistic effect. Both the local density approximation （LDA） and the generalized gradient approximation （GGA） are used for obtaining the region of the adsorption energy of H2 molecules on Ti-decorated graphene. We find that a graphene layer with titanium （Ti） atoms adsorbed on both sides can store hydrogen up to 9.51 wt% with average adsorption energy in a range from -0.170 eV to 0.518 eV. Based on the adsorption energy criterion, we find that chemisorption is predominant for H2 molecules when the concentration of H2 molecules absorbed is low while physisorption is predominant when the concentration is high. The computation results for the bilayer graphene decorated with Ti atoms show that the lower carbon layer makes no contribution to hydrogen adsorption.展开更多
Graphene prepared by non-covalent modification of sulfonated poly(ether-ether-ketone)(SPG)was combined with polyvinylidene fluoride(PVDF)/Al to improve the PVDF/Al thermal conductivity while reducing the effect of the...Graphene prepared by non-covalent modification of sulfonated poly(ether-ether-ketone)(SPG)was combined with polyvinylidene fluoride(PVDF)/Al to improve the PVDF/Al thermal conductivity while reducing the effect of the thermal resistance at the graphene-polymer interface.The regulation rule of SPG with different contents on the energy release of fluorine-containing system was studied.When the content of SPG is 4%,the peak pressure and rise rate of SPG/PVDF/Al composite powder during ignition reach the maximum of 4845.28 kPa and 8683.58 kPa/s.When the content of SPG is 5%,the PVDF/Al composite powder is completely coated by SPG,and the calorific value of the material reachs the maximum of 29.094 kJ/g.Through the design and micro-control of the composite powder,the calorific value of the material can be effectively improved,but the improvement of the mass release rate still depends on the graphene content and surface modification state.展开更多
In this paper, the epitaxial graphene layers grown on Si- and C-face 6H-SiC substrates are investigated under a low pressure of 400 Pa at 1600℃ By using atomic force microscopy and Raman spectroscopy, we find that th...In this paper, the epitaxial graphene layers grown on Si- and C-face 6H-SiC substrates are investigated under a low pressure of 400 Pa at 1600℃ By using atomic force microscopy and Raman spectroscopy, we find that there are distinct differences in the formation and the properties between the epitaxial graphene layers grown on the Si-face and the C-face substrates, including the hydrogen etching process, the stacking type, and the number of layers. Hopefully, our results will be useful for improving the quality of the epitaxial graphene on SiC substrate.展开更多
In this paper,the epitaxial graphene layers grown on Si-and C-face 6H-SiC substrates are investigated under a low pressure of 400 Pa at 1600 C.By using atomic force microscopy and Raman spectroscopy,we find that there...In this paper,the epitaxial graphene layers grown on Si-and C-face 6H-SiC substrates are investigated under a low pressure of 400 Pa at 1600 C.By using atomic force microscopy and Raman spectroscopy,we find that there are distinct differences in the formation and the properties between the epitaxial graphene layers grown on the Si-face and the C-face substrates,including the hydrogen etching process,the stacking type,and the number of layers.Hopefully,our results will be useful for improving the quality of the epitaxial graphene on SiC substrate.展开更多
A highly efficient catalyst of graphene-supported mixed-valent Mn_(16)-containing polyoxometalate is reported here by electrochemical strategy. The modified electrode with the catalyst exhibits an excellent electrocat...A highly efficient catalyst of graphene-supported mixed-valent Mn_(16)-containing polyoxometalate is reported here by electrochemical strategy. The modified electrode with the catalyst exhibits an excellent electrocatalytic performance for water oxidation, which will contribute to the development of highly efficient catalysts for oxygen evolution.展开更多
The existence of nanographene in cluster form is discussed in organic solvents. Theories are developed based on the columnlet, bundlet and droplet models describing the size-distribution functions. Phenomena present a...The existence of nanographene in cluster form is discussed in organic solvents. Theories are developed based on the columnlet, bundlet and droplet models describing the size-distribution functions. Phenomena present a unified explanation in the columnlet model in which free energy of Cgraphene involved in cluster is combined from a volume part proportional to the number of molecules n in cluster and a constant. The columnlet model enables describing distribution function of Cgraphene clusters by size. From purely geometrical considerations the columnlet （Cgraphene）, bundlet （single-wall carbon nanotube）, CNT （carbon nanotube）, SWNT （single-wall C-nanotube）, and carbon nanobud, CNB （carbon nanobud）） and droplet （fullerene） models predict dissimilar behaviours. The interaction-energy parameters of Cgraphene are taken from C60. An CNB behaviour or further is expected. The decay of solubility with rising temperature is smaller for Cgraphene than for SWNT and CNB and, furthermore, than for C60, in agreement with lesser numbers of units in Cgraphene clusters. The discrepancy between the experimental data of the heat of solution of fullerenes, CNTs, CNBs and graphenes is ascribed to the sharp concentration dependence of the heat of solution. The diffusion coefficient drops with temperature result greater for Cgraphene than CNB and SWNT than C60 corresponding to lesser number of units in clusters. The aggregates near （C60）13, SWNT/CNB7 and （Cgraphene）3 could be representative of the droplet, bundlet and columnlet models.展开更多
Vertically oriented graphenes(VGs)have attracted tremendous attention in a variety of energy storage-related applications.However,the high cost of preparing VGs significantly hinders their practical applications.Herei...Vertically oriented graphenes(VGs)have attracted tremendous attention in a variety of energy storage-related applications.However,the high cost of preparing VGs significantly hinders their practical applications.Herein we introduce the Ar-plasma-enhanced chemical vapor deposition to demonstrate the cost-effective,environmentally-sustainable,and scale-up synthesis of VGs from waste oil.In our system,Ar gas can improve the electron energy and ionization rate of plasma,which breaks down the chemical bonding of waste oil into essential species to etch the amorphous carbon,yielding large-area VGs(12×3.5 cm^(2))with highly-oriented structure and superior growth efficiency beyond VGs from hydrocarbon precursors.In the supercapacitor applications,the VG-based electrode exhibits significantly enhanced capacitance(~4 times that from conventional hydrocarbon gases)and efficient AC(alternating current)filtering capability RC(resistor-capacitor)(time constant of of 163μs at 120 Hz),which is obviously superior to the non-oriented counterpart.Besides,MnO_(2)/VGs composite electrode is prepared to deliver a maximum energy density of~33.2 Wh/kg at 1.0 kW/kg and a power density of 10.2 kW/kg at 22.9 Wh/kg.In the end,the economic analysis suggests that the total cost of VGs can be reduced by~32%.This work provides an environment-friendly and low-cost avenue for preparing VGs for advanced energy storage applications.展开更多
We develop here a simple wet chemistry to prepare covalent functionalized graphenes （FGs） through epoxide aminolysis espe- cially under alkaline aqueous condition. Remarkably, a series of typical monoamines, such as...We develop here a simple wet chemistry to prepare covalent functionalized graphenes （FGs） through epoxide aminolysis espe- cially under alkaline aqueous condition. Remarkably, a series of typical monoamines, such as industrial Huntsman Jeffamine M-2070 and M-2005 polymer with hydrophilic or hydrophobic polyetheramine chains, positively-charged 2-amino-N,N,N- trimethylpropanaminium, negatively-charged sulfanilic acid, even oligopeptide sequence, can be effectively grafted on the platelets of graphene oxide precursor with covalent functionalization and partially reduced features. This strategy provides the researchers a facile and convenient approach to design and synthesize solution processable, biocompatible and functionalized graphenes for the potent applications in electronic inks, drug carriers and biomedicines. Expansion of the current study is actively ongoing in our laboratory.展开更多
Graphene/copper-based composite heat sinks demonstrate extensive application potential in military equipment thermal management,high-power electronic packaging,new energy vehicles,and 5G communication systems,due to t...Graphene/copper-based composite heat sinks demonstrate extensive application potential in military equipment thermal management,high-power electronic packaging,new energy vehicles,and 5G communication systems,due to their outstanding properties,including high thermal conductivity,tunable thermal expansion coefficients,excellent mechanical strength,and low density.However,the industrial-scale application of these composites faces critical challenges during the fabrication of components with complex structures,such as inhomogeneous dispersion of graphene within the copper matrix and poor interfacial bonding between the two phases,which substantially undermine the overall performance of graphene/copper-based composites.To address these issues,the preparation methods for graphene/copper-based composite heat sinks were reviewed.For each method,a rigorous analysis was presented to clarify its inherent advantages and unavoidable restrictions.Furthermore,the latest research progress in addressing three core scientific challenges was synthesized,including uniform dispersion of graphene,interfacial optimization mechanisms,and molecular dynamics simulations for elucidating the structure-property relationships.Finally,the future development directions of graphene/copper-based composite heat sinks in engineering applications were prospected.展开更多
Graphite,encompassing both natural graphite and synthetic graphite,and graphene,have been extensively utilized and investigated as anode materials and additives in lithium-ion batteries(LIBs).In the pursuit of carbon ...Graphite,encompassing both natural graphite and synthetic graphite,and graphene,have been extensively utilized and investigated as anode materials and additives in lithium-ion batteries(LIBs).In the pursuit of carbon neutrality,LIBs are expected to play a pivotal role in reducing CO_(2)emissions by decreasing reliance on fossil fuels and enabling the integration of renewable energy sources.Owing to their technological maturity and exceptional electrochemical performance,the global production of graphite and graphene for LIBs is projected to continue expanding.Over the past decades,numerous researchers have concentrated on reducing the material and energy input whilst optimising the electrochemical performance of graphite and graphene,through novel synthesis methods and various modifications at the laboratory scale.This review provides a comprehensive examination of the manufacturing methods,environmental impact,research progress,and challenges associated with graphite and graphene in LIBs from an industrial perspective,with a particular focus on the carbon footprint of production processes.Additionally,it considers emerging challenges and future development directions of graphite and graphene,offering significant insights for ongoing and future research in the field of green LIBs.展开更多
Two-dimensional materials for flexible energy storage commonly facehuge challenges in limited active surface and hindered charge transport.Herein,wereport an innovative asymmetric pseudocapacitor based on synergistic ...Two-dimensional materials for flexible energy storage commonly facehuge challenges in limited active surface and hindered charge transport.Herein,wereport an innovative asymmetric pseudocapacitor based on synergistic design of modifiedMXene and graphene,integrating gas-induced rapid expansion technology andprecise surface chemical regulation methods.For graphene modification,rapid vaporizationinduces exfoliation and expansion of graphene oxide layers.Subsequently,pseudocapacitiveoxygen-containing groups were selectively introduced through acid oxidation,yielding expanded-and-oxidized graphene(OEG)for positive porous-nanopaperelectrode.For MXene modification,alkali-treated MXene underwent hydrazine assistance to facilitate gas expansion and-NH_(2)grafting,producing MXene-NH_(2)(NOM)for negative porous-nanopaper electrode.Density functional theory calculations show that-COOH moreeffectively modulate graphene’s electronic structure by inducing charge redistribution and creating active sites,thereby enhancing H^(+)adsorption and ion interactions compared to-OH.Meanwhile,-NH_(2)on MXene enable electron delocalization and dynamic Ti-N-H^(+)interactions,speeding up proton adsorption/desorption and boosting both pseudocapacitance and conductivity.Through collaborativeoptimized spatial architecture and surface properties,flexible OEGB and NOMB exhibited of 333.6 and 500.5 F g^(-1)at high mass loading,respectively.The assembled proton pseudocapacitor readily achieved energy and power densities of 58.9 Wh kg^(-1)and 3802 W kg^(-1),respectively,with excellent stability for potential applications.展开更多
Improving device efficiency is fundamental for advancing energy harvesting technology,particularly in systems designed to convert light energy into electrical output.In our previous studies,we developed a basic struct...Improving device efficiency is fundamental for advancing energy harvesting technology,particularly in systems designed to convert light energy into electrical output.In our previous studies,we developed a basic structure light pressure electric generator(Basic-LPEG),which utilized a layered configuration of Ag/Pb(Zr,Ti)O_(3)(PZT)/Pt/GaAs to generate electricity based on light-induced pressure on the PZT.In this study,we sought to enhance the performance of this Basic-LPEG by introducing Ag nanoparticles/graphene oxide(AgNPs/GO)composite units(NP-LPEG),creating upgraded harvesting device.Specifically,by depositing the AgNPs/GO units twice onto the Basic-LPEG,we observed an increase in output voltage and current from 241 mV and 3.1μA to 310 mV and 9.3μA,respectively,under a solar simulator.The increase in electrical output directly correlated with the intensity of the light pressure impacting the PZT,as well as matched the Raman measurements,finite-difference time-domain simulations,and COMSOL Multiphysics Simulation.Experimental data revealed that the enhancement in electrical output was proportional to the number of hot spots generated between Ag nanoparticles,where the electric field experienced substantial amplification.These results underline the effectiveness of AgNPs/GO units in boosting the light-induced electric generation capacity,thereby providing a promising pathway for high-efficiency energy harvesting devices.展开更多
Artificial intelligence(AI)based models have been used to predict the structural,optical,mechanical,and electrochemical properties of zinc oxide/graphene oxide nanocomposites.Machine learning(ML)models such as Artific...Artificial intelligence(AI)based models have been used to predict the structural,optical,mechanical,and electrochemical properties of zinc oxide/graphene oxide nanocomposites.Machine learning(ML)models such as Artificial Neural Networks(ANN),Support Vector Regression(SVR),Multilayer Perceptron(MLP),and hybrid,along with fuzzy logic tools,were applied to predict the different properties like wavelength at maximum intensity(444 nm),crystallite size(17.50 nm),and optical bandgap(2.85 eV).While some other properties,such as energy density,power density,and charge transfer resistance,were also predicted with the help of datasets of 1000(80:20).In general,the energy parameters were predicted more accurately by hybrid models.The hydrothermal method was used to synthesize graphene oxide(GO)and zinc oxide(ZnO)nanocomposites.The increased surface area,conductivity,and stability of graphene oxide in zinc oxide nanoparticles make the composite an ideal option for energy storage.X-ray diffraction(XRD)confirmed the crystallite size of 17.41 nm for the nanocomposite and the presence of GO(12.8○)peaks.The scanning electron microscope(SEM)showed anchored wrinkled GO sheets on zinc oxide with an average particle size of 2.93μm.Energy-dispersive X-ray spectroscopy(EDX)confirmed the elemental composition,and Fouriertransform infrared spectroscopy(FTIR)revealed the impact of GO on functional groups and electrochemical behavior.Photoluminescence(PL)wavelength of(439 nm)and band gap of(2.81 eV)show that the material is suitable for energy applications in nanocomposites.Smart nanocomposite materials with improved performance in energy storage and related applications were fabricated by combining synthesis,characterization,fuzzy logic,and machine learning in this work.展开更多
In this study,multilayer lamination welding was employed to prepare graphene/copper(Gr/Cu)composite billets from graphene-coated copper foils,followed by multi-pass cold drawing to produce Φ1 mm Gr/Cu composite wires...In this study,multilayer lamination welding was employed to prepare graphene/copper(Gr/Cu)composite billets from graphene-coated copper foils,followed by multi-pass cold drawing to produce Φ1 mm Gr/Cu composite wires.Microstructure and property analyses in both the cold-drawn and annealed states show that the incorporation of graphene significantly improves the ductility and electrical conductivity of the copper wire.After annealing at 350℃ for 30 minutes,the composite wire demonstrates a tensile strength of 270 MPa and an electrical conductivity of 102.74%IACS,both superior to those of pure copper wire under identical conditions.At 150℃,the electrical conductivity of the annealed composite wire reaches 72.60%IACS,notably higher than the 68.19%IACS of pure copper.The results suggest that graphene is uniformly distributed within the composite wire,with minimal impact on conductivity,while effectively refining the copper grain structure to enhance ductility.Moreover,graphene suppresses copper lattice vibrations at elevated temperatures,reducing the rate of conductivity degradation.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 51372282,51072024 and 51132002the National College Students’Innovative and Entrepreneurial Training Program of Beijing Institute of Technology under Grant No201410007050
文摘We research the adsorption geometries graphene （Li-GR） before and after CO and electronic structures of pristine graphene （p-GR） and Li-doped adsorption by first-principles. The adsorption energies Ead of CO on p-GR and Li-GR are calculated. The results demonstrate that Ead of CO on Li-GR is from -3.3 eV to -3.5 eV, meanwhile Q is up to 0.13e, which indicate that strong electrostatic attractions occur between CO and Li-GR, while CO is physically adsorbed on p-GR. The obvious accumulated charge in electron density difference and increasing carrier density suggest that the conductivity of Li-GR is improved considerably after CO adsorp- tion. An adsorption mechanism is also proposed. Our results provide a path to achieving CO sensors with high performance.
基金Project(51274248)supported by the National Natural Science Foundation of China
文摘Few-layer graphenes were fabricated from expandable graphite by rapid microwave exfoliation. Expandable graphite was irradiated in a domestic microwave in full power for 3 min, then soaked in mixed strong hydrogen nitrate and sulfuric acid with volume ratio of 1：1 for 24 h and re-irradiated, thus few-layer graphene sheets were obtained. Specimens gained from every step were selectively characterized by different techniques, such as SEM, XRD, Raman, AFM, XPS, FTIR and combustion elemental analysis. The results show that expandable graphite with loose, porous and worm-like morphology forms instantaneously in microwave irradiation with crackling sound and sparkles, which manifests physical exfoliation of graphene sheets. Few-layer graphene sheets with a dozen or more layers and average thickness of about 4.7 nm are obtained eventually after sequential treatment of microwave irradiation, mixed acid soaking and second microwave irradiation. The as-prepared few-layer graphenes still have high crystallinity and high purity with traces of oxide groups and without serious unrecoverable oxidation damage.
基金supported by the National Natural Science Foundation of China(Grant No.5160121211475082)‘‘Strategic Priority Research Program of Chinese Academy of Sciences’’ Thorium Molten Salts Reactor Fund
文摘Adsorption and desorption of hydrogen on/from single-vacancy and double-vacancy graphenes were studied by means of first-principles calculations. The structure and stability of continuous hydrogenation in single vacancy were investigated. Several new stable structures were found, along with their corresponding energy barriers. In double-vacancy graphene, the preferred sites of H atoms were identified, and H2 molecule desorption and adsorption of from/on were calculated from the energy barriers. This work provides a systematic and comprehensive understanding of hydrogen behavior on defected graphene.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10774032,90921001 and 50952009)
文摘In this work we report that when ferromagnetic metals （Fe, Co and Ni） are thermMly evaporated onto n-layer graphenes and graphite, a metal nanowire and adjacent nanogaps can be found along the edges regardless of its zigzag or armchair structure. Similar features can also be observed for paramagnetic metals, such as Mn, Al and Pd. Meanwhile, metal nanowires and adjacent nanogaps cannot be found for diamagnetic metals （Au and Ag）. An external magnetic field during the evaporation of metals can make these unique features disappear for ferromagnetic and paramagnetic metal; and the morphologies of diamagnetic metal do not change after the application of an external magnetic field. We discuss the possible reasons for these novel and interesting results, which include possible one-dimensional ferromagnets along the edge and edge-related binding energy.
基金financially supported by the National Natural Science Foundation of China(Nos.51503117 and 51403119)Promotive Research Fund for Excellent Young and Middle-aged Scientisits of Shandong Province(No.BS2013CL032)
文摘The effects of graphene oxide（GO） with polar groups and functionalized GO（f GO） with nonpolar groups on the isothermal crystallization of poly（L-lactide）（PLLA） were compared. Functionalized GO was obtained by grafting octadecylamine and characterized by FTIR, WAXD and TGA. Isothermal crystallization kinetics of PLLA/GO and PLLA/f GO nanocomposites were investigated by combining DSC data and Avrami equation. The results showed that f GO could improve PLLA crystallization rate more obviously than GO. By analyzing the morphology obtained from POM, SEM and TEM, it was found f GO with large layer space dispersed better in PLLA and supplied more nucleation sites than GO. Therefore, for the multilayer graphene, increasing the layer spaces is important to improve its dispersion in polymers, which will cause the crystal kinetics changing of polymers.
基金support of the Science and Technology Development Fund from Macao SAR (FDCT-068/2014/A2 and FDCT-132/2014/A3) Multi-Year Research Grants (MYRG201400159-FST and MYRG2015-00017-FST) from Research & Development Office at University of Macaosupport of the National Natural Science Foundation of China (Grant No.11372279)
文摘Friction plays a critical role in the function and maintenance of small-scale structures, where the conventional Coulomb friction law often fails. To probe the friction at small scales, here we present a molecular dynamics study on the process of dragging graphene nanoribbons on waved graphene substrates. The simulation shows that the induced friction on graphene with zero waviness is ultra-low and closely related to the surface energy barrier. On waved graphenes, the friction generally increases with the amplitude of the wave at a fixed period, but anomalously increases and then decreases with the period at a fixed amplitude. These findings provide the insights into the ultraqow friction at small scales, as well as some guidelines into the fabrication ofgraphene-based nano-composites with high performance.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10974076,11047020,and 11204120)the Natural Science Foundation of Shandong Province,China (Grant No. ZR2012AM022)
文摘The adsorption of hydrogen molecules on titanium-decorated （Ti-decorated） single-layer and bilayer graphenes is studied using density functional theory （DFT） with the relativistic effect. Both the local density approximation （LDA） and the generalized gradient approximation （GGA） are used for obtaining the region of the adsorption energy of H2 molecules on Ti-decorated graphene. We find that a graphene layer with titanium （Ti） atoms adsorbed on both sides can store hydrogen up to 9.51 wt% with average adsorption energy in a range from -0.170 eV to 0.518 eV. Based on the adsorption energy criterion, we find that chemisorption is predominant for H2 molecules when the concentration of H2 molecules absorbed is low while physisorption is predominant when the concentration is high. The computation results for the bilayer graphene decorated with Ti atoms show that the lower carbon layer makes no contribution to hydrogen adsorption.
基金Funded by the National Natural Science Foundation of China(No.52104363)。
文摘Graphene prepared by non-covalent modification of sulfonated poly(ether-ether-ketone)(SPG)was combined with polyvinylidene fluoride(PVDF)/Al to improve the PVDF/Al thermal conductivity while reducing the effect of the thermal resistance at the graphene-polymer interface.The regulation rule of SPG with different contents on the energy release of fluorine-containing system was studied.When the content of SPG is 4%,the peak pressure and rise rate of SPG/PVDF/Al composite powder during ignition reach the maximum of 4845.28 kPa and 8683.58 kPa/s.When the content of SPG is 5%,the PVDF/Al composite powder is completely coated by SPG,and the calorific value of the material reachs the maximum of 29.094 kJ/g.Through the design and micro-control of the composite powder,the calorific value of the material can be effectively improved,but the improvement of the mass release rate still depends on the graphene content and surface modification state.
基金Project supported by the Key Research Foundation from the Ministry of Education of China （Grant No. JY10000925016）.
文摘In this paper, the epitaxial graphene layers grown on Si- and C-face 6H-SiC substrates are investigated under a low pressure of 400 Pa at 1600℃ By using atomic force microscopy and Raman spectroscopy, we find that there are distinct differences in the formation and the properties between the epitaxial graphene layers grown on the Si-face and the C-face substrates, including the hydrogen etching process, the stacking type, and the number of layers. Hopefully, our results will be useful for improving the quality of the epitaxial graphene on SiC substrate.
基金Project supported by the Key Research Foundation from the Ministry of Education of China (Grant No. JY10000925016)
文摘In this paper,the epitaxial graphene layers grown on Si-and C-face 6H-SiC substrates are investigated under a low pressure of 400 Pa at 1600 C.By using atomic force microscopy and Raman spectroscopy,we find that there are distinct differences in the formation and the properties between the epitaxial graphene layers grown on the Si-face and the C-face substrates,including the hydrogen etching process,the stacking type,and the number of layers.Hopefully,our results will be useful for improving the quality of the epitaxial graphene on SiC substrate.
基金supported by the National Natural Science Foundation of China(No.21371173,51402298,91545125)the China Postdoctoral Foundation(No.2014M550846)
文摘A highly efficient catalyst of graphene-supported mixed-valent Mn_(16)-containing polyoxometalate is reported here by electrochemical strategy. The modified electrode with the catalyst exhibits an excellent electrocatalytic performance for water oxidation, which will contribute to the development of highly efficient catalysts for oxygen evolution.
文摘The existence of nanographene in cluster form is discussed in organic solvents. Theories are developed based on the columnlet, bundlet and droplet models describing the size-distribution functions. Phenomena present a unified explanation in the columnlet model in which free energy of Cgraphene involved in cluster is combined from a volume part proportional to the number of molecules n in cluster and a constant. The columnlet model enables describing distribution function of Cgraphene clusters by size. From purely geometrical considerations the columnlet （Cgraphene）, bundlet （single-wall carbon nanotube）, CNT （carbon nanotube）, SWNT （single-wall C-nanotube）, and carbon nanobud, CNB （carbon nanobud）） and droplet （fullerene） models predict dissimilar behaviours. The interaction-energy parameters of Cgraphene are taken from C60. An CNB behaviour or further is expected. The decay of solubility with rising temperature is smaller for Cgraphene than for SWNT and CNB and, furthermore, than for C60, in agreement with lesser numbers of units in Cgraphene clusters. The discrepancy between the experimental data of the heat of solution of fullerenes, CNTs, CNBs and graphenes is ascribed to the sharp concentration dependence of the heat of solution. The diffusion coefficient drops with temperature result greater for Cgraphene than CNB and SWNT than C60 corresponding to lesser number of units in clusters. The aggregates near （C60）13, SWNT/CNB7 and （Cgraphene）3 could be representative of the droplet, bundlet and columnlet models.
基金This work is financially supported by Royal Society Newton Advanced Fellowship(Grant No.52061130218)the National Natural Science Foundation of China(No.51906211)China Postdoctoral Science Foundation(Nos.2020T130574 and 2019M662048).Z.B.thanks the National Program for Support of Top-notch Young Professionals.
文摘Vertically oriented graphenes(VGs)have attracted tremendous attention in a variety of energy storage-related applications.However,the high cost of preparing VGs significantly hinders their practical applications.Herein we introduce the Ar-plasma-enhanced chemical vapor deposition to demonstrate the cost-effective,environmentally-sustainable,and scale-up synthesis of VGs from waste oil.In our system,Ar gas can improve the electron energy and ionization rate of plasma,which breaks down the chemical bonding of waste oil into essential species to etch the amorphous carbon,yielding large-area VGs(12×3.5 cm^(2))with highly-oriented structure and superior growth efficiency beyond VGs from hydrocarbon precursors.In the supercapacitor applications,the VG-based electrode exhibits significantly enhanced capacitance(~4 times that from conventional hydrocarbon gases)and efficient AC(alternating current)filtering capability RC(resistor-capacitor)(time constant of of 163μs at 120 Hz),which is obviously superior to the non-oriented counterpart.Besides,MnO_(2)/VGs composite electrode is prepared to deliver a maximum energy density of~33.2 Wh/kg at 1.0 kW/kg and a power density of 10.2 kW/kg at 22.9 Wh/kg.In the end,the economic analysis suggests that the total cost of VGs can be reduced by~32%.This work provides an environment-friendly and low-cost avenue for preparing VGs for advanced energy storage applications.
基金supported by the Ministry of Science and Technology of China (2014CB239402, 2013CB834505, 2013CB834804)the National Natural Science Foundation of China (91427303, 21372232, 21204052)+1 种基金the Key Research Programme of the Chinese Academy of Sciences (KGZD-EW-T05)the Foundation of Director of TIPC
文摘We develop here a simple wet chemistry to prepare covalent functionalized graphenes （FGs） through epoxide aminolysis espe- cially under alkaline aqueous condition. Remarkably, a series of typical monoamines, such as industrial Huntsman Jeffamine M-2070 and M-2005 polymer with hydrophilic or hydrophobic polyetheramine chains, positively-charged 2-amino-N,N,N- trimethylpropanaminium, negatively-charged sulfanilic acid, even oligopeptide sequence, can be effectively grafted on the platelets of graphene oxide precursor with covalent functionalization and partially reduced features. This strategy provides the researchers a facile and convenient approach to design and synthesize solution processable, biocompatible and functionalized graphenes for the potent applications in electronic inks, drug carriers and biomedicines. Expansion of the current study is actively ongoing in our laboratory.
基金Research Start-Up Fund Project of Anhui Polytechnic University(S022023017)University Research Project of Anhui Province(2023AH050937)+1 种基金Anhui Polytechnic University Research Foundation for Introducing Talents(2022YQQ003)Anhui Province Key Laboratory of Intelligent Vehicle Chassis by Wire。
文摘Graphene/copper-based composite heat sinks demonstrate extensive application potential in military equipment thermal management,high-power electronic packaging,new energy vehicles,and 5G communication systems,due to their outstanding properties,including high thermal conductivity,tunable thermal expansion coefficients,excellent mechanical strength,and low density.However,the industrial-scale application of these composites faces critical challenges during the fabrication of components with complex structures,such as inhomogeneous dispersion of graphene within the copper matrix and poor interfacial bonding between the two phases,which substantially undermine the overall performance of graphene/copper-based composites.To address these issues,the preparation methods for graphene/copper-based composite heat sinks were reviewed.For each method,a rigorous analysis was presented to clarify its inherent advantages and unavoidable restrictions.Furthermore,the latest research progress in addressing three core scientific challenges was synthesized,including uniform dispersion of graphene,interfacial optimization mechanisms,and molecular dynamics simulations for elucidating the structure-property relationships.Finally,the future development directions of graphene/copper-based composite heat sinks in engineering applications were prospected.
基金supported by European Union's Horizon Europe,UK Research and Innovation(UKRI).
文摘Graphite,encompassing both natural graphite and synthetic graphite,and graphene,have been extensively utilized and investigated as anode materials and additives in lithium-ion batteries(LIBs).In the pursuit of carbon neutrality,LIBs are expected to play a pivotal role in reducing CO_(2)emissions by decreasing reliance on fossil fuels and enabling the integration of renewable energy sources.Owing to their technological maturity and exceptional electrochemical performance,the global production of graphite and graphene for LIBs is projected to continue expanding.Over the past decades,numerous researchers have concentrated on reducing the material and energy input whilst optimising the electrochemical performance of graphite and graphene,through novel synthesis methods and various modifications at the laboratory scale.This review provides a comprehensive examination of the manufacturing methods,environmental impact,research progress,and challenges associated with graphite and graphene in LIBs from an industrial perspective,with a particular focus on the carbon footprint of production processes.Additionally,it considers emerging challenges and future development directions of graphite and graphene,offering significant insights for ongoing and future research in the field of green LIBs.
基金supported by the National Nature Science Foundation of China(No.52402126)Shaanxi Province Qin Chuangyuan general window four chain integration project(No.2024PT-ZCK-09)+3 种基金Shaanxi Province military-civilian integration project(Shaanxi finance office【2024】22nd)Qinchuangyuan introducing high-level innovation and entrepreneurship talent projects(NO.QCYRCXM-2022-343)the China Postdoctoral Science Foundation(Grant Number:2025M772524)National Nature Science Foundation of China(22508239).
文摘Two-dimensional materials for flexible energy storage commonly facehuge challenges in limited active surface and hindered charge transport.Herein,wereport an innovative asymmetric pseudocapacitor based on synergistic design of modifiedMXene and graphene,integrating gas-induced rapid expansion technology andprecise surface chemical regulation methods.For graphene modification,rapid vaporizationinduces exfoliation and expansion of graphene oxide layers.Subsequently,pseudocapacitiveoxygen-containing groups were selectively introduced through acid oxidation,yielding expanded-and-oxidized graphene(OEG)for positive porous-nanopaperelectrode.For MXene modification,alkali-treated MXene underwent hydrazine assistance to facilitate gas expansion and-NH_(2)grafting,producing MXene-NH_(2)(NOM)for negative porous-nanopaper electrode.Density functional theory calculations show that-COOH moreeffectively modulate graphene’s electronic structure by inducing charge redistribution and creating active sites,thereby enhancing H^(+)adsorption and ion interactions compared to-OH.Meanwhile,-NH_(2)on MXene enable electron delocalization and dynamic Ti-N-H^(+)interactions,speeding up proton adsorption/desorption and boosting both pseudocapacitance and conductivity.Through collaborativeoptimized spatial architecture and surface properties,flexible OEGB and NOMB exhibited of 333.6 and 500.5 F g^(-1)at high mass loading,respectively.The assembled proton pseudocapacitor readily achieved energy and power densities of 58.9 Wh kg^(-1)and 3802 W kg^(-1),respectively,with excellent stability for potential applications.
基金supported by Korea Evaluation Institute of Industrial Technology(KEIT)grant funded by the Korea Government(MOTIE)(RS-2022-00154720,Technology Innovation Program Development of next-generation power semiconductor based on Si-on-SiC structure)the National Research Foundation of Korea(NRF)by the Korea government(RS-2023-NR076826)Global-Learning&Academic Research Institution for Master's·PhD students,and Postdocs(LAMP)Program of the National Research Foundation of Korea(NRF)by the Ministry of Education(No.RS-2024-00443714).
文摘Improving device efficiency is fundamental for advancing energy harvesting technology,particularly in systems designed to convert light energy into electrical output.In our previous studies,we developed a basic structure light pressure electric generator(Basic-LPEG),which utilized a layered configuration of Ag/Pb(Zr,Ti)O_(3)(PZT)/Pt/GaAs to generate electricity based on light-induced pressure on the PZT.In this study,we sought to enhance the performance of this Basic-LPEG by introducing Ag nanoparticles/graphene oxide(AgNPs/GO)composite units(NP-LPEG),creating upgraded harvesting device.Specifically,by depositing the AgNPs/GO units twice onto the Basic-LPEG,we observed an increase in output voltage and current from 241 mV and 3.1μA to 310 mV and 9.3μA,respectively,under a solar simulator.The increase in electrical output directly correlated with the intensity of the light pressure impacting the PZT,as well as matched the Raman measurements,finite-difference time-domain simulations,and COMSOL Multiphysics Simulation.Experimental data revealed that the enhancement in electrical output was proportional to the number of hot spots generated between Ag nanoparticles,where the electric field experienced substantial amplification.These results underline the effectiveness of AgNPs/GO units in boosting the light-induced electric generation capacity,thereby providing a promising pathway for high-efficiency energy harvesting devices.
基金extend their gratitude to the Deanship of Scientific Research,Vice Presidency for Graduate Studies and Scientific Research,King Faisal University,Saudi Arabia,for funding the publication of this work under the Ambitious Researcher program(Project No.KFU253806).
文摘Artificial intelligence(AI)based models have been used to predict the structural,optical,mechanical,and electrochemical properties of zinc oxide/graphene oxide nanocomposites.Machine learning(ML)models such as Artificial Neural Networks(ANN),Support Vector Regression(SVR),Multilayer Perceptron(MLP),and hybrid,along with fuzzy logic tools,were applied to predict the different properties like wavelength at maximum intensity(444 nm),crystallite size(17.50 nm),and optical bandgap(2.85 eV).While some other properties,such as energy density,power density,and charge transfer resistance,were also predicted with the help of datasets of 1000(80:20).In general,the energy parameters were predicted more accurately by hybrid models.The hydrothermal method was used to synthesize graphene oxide(GO)and zinc oxide(ZnO)nanocomposites.The increased surface area,conductivity,and stability of graphene oxide in zinc oxide nanoparticles make the composite an ideal option for energy storage.X-ray diffraction(XRD)confirmed the crystallite size of 17.41 nm for the nanocomposite and the presence of GO(12.8○)peaks.The scanning electron microscope(SEM)showed anchored wrinkled GO sheets on zinc oxide with an average particle size of 2.93μm.Energy-dispersive X-ray spectroscopy(EDX)confirmed the elemental composition,and Fouriertransform infrared spectroscopy(FTIR)revealed the impact of GO on functional groups and electrochemical behavior.Photoluminescence(PL)wavelength of(439 nm)and band gap of(2.81 eV)show that the material is suitable for energy applications in nanocomposites.Smart nanocomposite materials with improved performance in energy storage and related applications were fabricated by combining synthesis,characterization,fuzzy logic,and machine learning in this work.
基金Funded by Hunan Provincial Natural Science Foundation(No.2023JJ40074)Hunan Provincial Education Department Excellent Youth Project(No.21B0757)Hunan Provincial Engineering Technology Center(No.2022TP2036)。
文摘In this study,multilayer lamination welding was employed to prepare graphene/copper(Gr/Cu)composite billets from graphene-coated copper foils,followed by multi-pass cold drawing to produce Φ1 mm Gr/Cu composite wires.Microstructure and property analyses in both the cold-drawn and annealed states show that the incorporation of graphene significantly improves the ductility and electrical conductivity of the copper wire.After annealing at 350℃ for 30 minutes,the composite wire demonstrates a tensile strength of 270 MPa and an electrical conductivity of 102.74%IACS,both superior to those of pure copper wire under identical conditions.At 150℃,the electrical conductivity of the annealed composite wire reaches 72.60%IACS,notably higher than the 68.19%IACS of pure copper.The results suggest that graphene is uniformly distributed within the composite wire,with minimal impact on conductivity,while effectively refining the copper grain structure to enhance ductility.Moreover,graphene suppresses copper lattice vibrations at elevated temperatures,reducing the rate of conductivity degradation.
