The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification proc...The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification process,which cannot provide sufficient protection.In the current study,we design a double-layer epoxy composite coating on Mg alloy with enhanced anti-corrosion/wear properties,via the spin-assisted assembly technique.The outer layer is functionalized graphene(FG)in waterborne epoxy resin(WEP)and the inner layer is Ce-based conversion(Ce)film.The FG sheets can be homogeneously dispersed within the epoxy matrix to fill the intrinsic defects and improve the barrier capability.The Ce film connects the outer layer with the substrate,showing the transition effect.The corrosion rate of Ce/WEP/FG composite coating is 2131 times lower than that of bare Mg alloy,and the wear rate is decreased by~90%.The improved corrosion resistance is attributed to the labyrinth effect(hindering the penetration of corrosive medium)and the obstruction of galvanic coupling behavior.The synergistic effect derived from the FG sheet and blocking layer exhibits great potential in realizing the improvement of multi-functional integration,which will open up a new avenue for the development of novel composite protection coatings of Mg alloys.展开更多
Buckling and postbuckling characteristics of laminated graphene-enhanced composite(GEC)truncated conical shells exposed to torsion under temperature conditions using finite element method(FEM)simulation are presented ...Buckling and postbuckling characteristics of laminated graphene-enhanced composite(GEC)truncated conical shells exposed to torsion under temperature conditions using finite element method(FEM)simulation are presented in this study.In the thickness direction,the GEC layers of the conical shell are ordered in a piece-wise arrangement of functionally graded(FG)distribution,with each layer containing a variable volume fraction for graphene reinforcement.To calculate the properties of temperaturedependent material of GEC layers,the extended Halpin-Tsai micromechanical framework is used.The FEM model is verified via comparing the current results obtained with the theoretical estimates for homogeneous,laminated cylindrical,and conical shells,the FEM model is validated.The computational results show that a piece-wise FG graphene volume fraction distribution can improve the torque of critical buckling and torsional postbuckling strength.Also,the geometric parameters have a critical impact on the stability of the conical shell.However,a temperature rise can reduce the crucial torsional buckling torque as well as the GEC laminated truncated conical shell’s postbuckling strength.展开更多
In this study,the first-order shear deformation theory(FSDT)is used to establish a nonlinear dynamic model for a conical shell truncated by a functionally graded graphene platelet-reinforced composite(FG-GPLRC).The vi...In this study,the first-order shear deformation theory(FSDT)is used to establish a nonlinear dynamic model for a conical shell truncated by a functionally graded graphene platelet-reinforced composite(FG-GPLRC).The vibration analyses of the FG-GPLRC truncated conical shell are presented.Considering the graphene platelets(GPLs)of the FG-GPLRC truncated conical shell with three different distribution patterns,the modified Halpin-Tsai model is used to calculate the effective Young’s modulus.Hamilton’s principle,the FSDT,and the von-Karman type nonlinear geometric relationships are used to derive a system of partial differential governing equations of the FG-GPLRC truncated conical shell.The Galerkin method is used to obtain the ordinary differential equations of the truncated conical shell.Then,the analytical nonlinear frequencies of the FG-GPLRC truncated conical shell are solved by the harmonic balance method.The effects of the weight fraction and distribution pattern of the GPLs,the ratio of the length to the radius as well as the ratio of the radius to the thickness of the FG-GPLRC truncated conical shell on the nonlinear natural frequency characteristics are discussed.This study culminates in the discovery of the periodic motion and chaotic motion of the FG-GPLRC truncated conical shell.展开更多
Graphene oxide has been used widely as a starting precursor for applications that cater to the needs of tunable graphene. However, the hydrophilic characteristic limits their application, especially in a hydrophobic c...Graphene oxide has been used widely as a starting precursor for applications that cater to the needs of tunable graphene. However, the hydrophilic characteristic limits their application, especially in a hydrophobic condition. Herein, a novel non-covalent surface modification approach towards graphene oxide was conducted via a UV-induced photo-polymerization technique that involves two major routes; a UV-sensitive initiator embedded via pi-pi interactions on the graphene planar rings, and the polymerization of hydrophobic polymeric chains along the surface. The functionalized graphene oxide successfully achieved the desired hydrophobicity as it displayed the characteristic of being readily dissolved in organic solvent. Upon its addition into a polymeric solution and subjected to an electrospinning process,non-woven random nanofibers embedded with graphene oxide sheets were obtained. The prepared polymeric nanofibers were subjected to two-step thermal treatments that eventually converted the polymeric chains into a carbon-rich conductive structure. A unique morphology was observed upon the addition of the functionalized graphene oxide, whereby the sheets were embedded and intercalated within the carbon nanofibers and formed a continuous structure. This reinforcement effectively enhanced the electrochemical performance of the carbon nanofibers by recording a specific capacitance of up to 140.10 F/g at the current density of 1 A/g, which was approximately three folds more than that of pristine nanofibers.It also retained the capacitance up to 96.2% after 1000 vigorous charge/discharge cycles. This functionalization technique opens up a new pathway in tuning the solubility nature of graphene oxide towards the synthesis of a graphene oxide-reinforced polymeric structure.展开更多
Supercapacitors(SCs) have attracted much attention as one of the alternative energy devices due to their high power performance,long cycle life,and low maintenance cost.Graphene is considered as an innovative and pr...Supercapacitors(SCs) have attracted much attention as one of the alternative energy devices due to their high power performance,long cycle life,and low maintenance cost.Graphene is considered as an innovative and promising material due to its large theoretical specific surface area,high electrical conductivity,good mechanical properties and chemical stability.Herein,we report an effective strategy for elaborately constructing rationally functionalized self-standing graphene(SG) obtained from giant graphene oxide(GGO) paper followed by an ultrarapid thermal-processing.This treatment results in both the exfoliation of graphene sheets and the reduction of GGO by elimination of oxygencontaining groups.The as-prepared SG electrode materials without additive and conducting agent provide an excellent combination of the electrical double layer capacitor(EDLC) and pseudocapacitor(PC) functions and exhibit superior electrochemical performance,including high specific capacitance,good rate capability and excellent cycling stability when investigated in three-electrode electrochemical cells.展开更多
In this research,to remove sulfur and nitrogen compounds from heavy naphtha,various nanocatalysts were prepared through supporting NiMo over nanoporous graphene and evaluated in hydrodesulfurization and hydrodenitroge...In this research,to remove sulfur and nitrogen compounds from heavy naphtha,various nanocatalysts were prepared through supporting NiMo over nanoporous graphene and evaluated in hydrodesulfurization and hydrodenitrogenation reactions.The nanoporous graphene was initially functionalized in order to facilitate the metal being loaded on it.Three different methods were used to functionalize the nanoporous graphene.The NiMo/nanoporous graphene nanocatalysts were characterized by field emission scanning electron microscopy,Fourier transform infrared spectroscopy,X-ray diffraction,inductively coupled plasma optical emission spectrometry,temperature-programmed reduction,nitrogen adsorption-desorption isotherms and transmission electron microscopy techniques.Catalyst performance was evaluated in terms of conversions of sulfur,mercaptans(R-SH)and nitrogen compounds.It was found that the functionalized nanoporous graphene support could significantly enhance the catalytic performance in comparison with the industrial NiMo/alumina catalyst.Among the functionalized graphene supports,amine-functionalized graphene exhibited the best results.By using NiMo supported over amine-functionalized graphene,the conversions of total sulfur and R-SH reached 97.8%and 98.1%,respectively.展开更多
Functionalized graphene nano-platelets(FGN) were obtained via treating graphene nanoplatelets(GN) with HNO3, and served as adsorbent for the removal of Pb2+from solutions. We investigated the FGN adsorption capacity f...Functionalized graphene nano-platelets(FGN) were obtained via treating graphene nanoplatelets(GN) with HNO3, and served as adsorbent for the removal of Pb2+from solutions. We investigated the FGN adsorption capacity for Pb2+at different initial concentrations, varying pH, contact time and temperature. The characterization results of scanning electron microscopy(SEM), thermal analysis(TG/DTG), Fourier transform infrared spectroscopy(FT-IR) and Brunauer-Emmett-Teller(BET) method indicated that FGN layers were thin and possess large specific area with oxygen-containing functional groups grafted onto their surface. Meanwhile, the determined equilibrium adsorption capacity of FGN for Pb2+was 57.765 mg/g and adsorption isotherms well confirmed to Langmuir isotherms models. The results reveals that the FGN has better effect of water treatment.展开更多
In this paper, we investigate the selection rule for desalinating seawater using functionalized graphene sheet as a semi-permissible membrane. Both the applied mathematical modeling and MD simulations will be used to ...In this paper, we investigate the selection rule for desalinating seawater using functionalized graphene sheet as a semi-permissible membrane. Both the applied mathematical modeling and MD simulations will be used to determine the acceptance conditions for water molecule or sodium ion permeating into the functionalized graphene. Both the Lennard-Jones potential and Coulomb forces are considered by taking into accounts the major molecular and ionic interactions between molecules, ions and functionalized graphene sheet. The continuous approximation will then be used to coarse grain most significant molecular and ionic interactions so that the multi-body problems could be simplified into several two-body problems and the 3D motions are reduced into degenerated 1D motion. Our mathematical model and simulations show that the negatively charged graphene always accepts sodium ions and water;however the permeability of water molecules and sodium ions becomes very sensitive to the presence of positive charges on the graphene.展开更多
We address the electrical conductivity of bilayer graphene as a function of temperature, impurity concentration, and scattering strength in the presence of a finite bias voltage at finite doping, beginning with a desc...We address the electrical conductivity of bilayer graphene as a function of temperature, impurity concentration, and scattering strength in the presence of a finite bias voltage at finite doping, beginning with a description of the tight-binding model using the linear response theory and Green's function approach. Our results show a linear behavior at high doping for the case of high bias voltage. The effects of electron doping on the electrical conductivity have been studied via changing the electronic chemical potential. We also discuss and analyze how the bias voltage affects the temperature behavior of the electrical conductivity. Finally, we study the behavior of the electrical conductivity as a function of the impurity concentration and scattering strength for different bias voltages and chemical potentials respectively. The electrical conductivity is found to be monotonically decreasing with impurity scattering strength due to the increased scattering among electrons at higher impurity scattering strength.展开更多
We present the behaviors of both dynamical and static charge susceptibilities of undoped armchair graphene nanoribbon using the Green's function approach in the context of tight binding model Hamiltonian.Specifically...We present the behaviors of both dynamical and static charge susceptibilities of undoped armchair graphene nanoribbon using the Green's function approach in the context of tight binding model Hamiltonian.Specifically,the effects of magnetic field on the the plasmon modes of armchair graphene nanoribbon are investigated via calculating the correlation function of charge density operators.Our results show that the increase of magnetic field makes the high-frequency plasmon mode for both metallic and insulating cases disappear.We also show that low-frequency plasmon mode for metallic nanoribbon appears due to increase of magnetic field.Furthermore,the number of collective excitation modes increases with ribbon width at zero magnetic field.Finally,the temperature dependence of the static charge structure factor of armchair graphene nanoribbon is studied.The effects of both magnetic field and ribbon width on the static charge structure factor are discussed in detail.展开更多
Formaldehyde(HCHO)is formed through the oxidation of volatile organic compounds(VOCs)and can cause human cancer.Bismuth oxide and titanium oxide nanoparticles-functionalized nanographene oxide(Bi_(2)O_(3)/TiO_(2)@NGO)...Formaldehyde(HCHO)is formed through the oxidation of volatile organic compounds(VOCs)and can cause human cancer.Bismuth oxide and titanium oxide nanoparticles-functionalized nanographene oxide(Bi_(2)O_(3)/TiO_(2)@NGO)were used to rapidly remove the HCHO from the air by a photocatalytic degradation-adsorption process(PC-DAP).The formaldehyde vapor in pure air was generated in a dynamic system within a chamber,and flowed over Bi_(2)O_(3)/TiO_(2)@NGO adsorbent inside a fixed-bed quartz reactor(FBQR)under UV irradiation at optimized conditions(250C).At atmospheric pressure,the flow rate and gas hourly space velocity(GHSV)were adjusted to 300 mL/min and 100-450 L/h,respectively.The radicals of HCHO and nanographene oxide(NGO)were generated through the UV-photochemical process,enhancing the chemical adsorption through the radicals’interactions.On the other hand,the semi-degradation process by catalytic oxidation process converted some HCHO into raw materials of CO_(2)and H_(2)O,while the unconverted HCHO was physically absorbed by NGO.Finally,the HCHO concentration in the outlet system was measured by gas chromatography with a flame ionization detector(GC-FID)after derivatizing formaldehyde with 2,4-dinitrophenylhydrazine(DNPH)and acetonitrile.Therefore,efficient removal of HCHO from the air,the removal efficiency of more than 95%,was achieved through physical/chemical adsorption and the semi-degradation.The mean removal efficiencies for HCHO with Bi_(2)O_(3)-TiO_(2)@NGO,TiO_(2)@NGO,Bi_(2)O_(3)@NGO,and NGO were 98.7%,73.6%,61.8%,and 11.4%,respectively(n=10,RSD<5%).The methodology was validated by spiking different concentrations of standard HCHO into pure air.展开更多
The electrochemical behaviors of shikonin at a poly(diallyldimethylammonium chloride) functionalized graphene sheets modified glass carbon electrode(PDDA-GS/GCE) have been investigated. Shikonin could exhibit a pa...The electrochemical behaviors of shikonin at a poly(diallyldimethylammonium chloride) functionalized graphene sheets modified glass carbon electrode(PDDA-GS/GCE) have been investigated. Shikonin could exhibit a pair of well-defined redox peaks at the PDDA-GS/GCE located at 0.681 V(Epa) and 0.662 V(Epc)[vs. saturated calo- mel electrode(SCE)] in 0.1 mol/L phosphate buffer solution(pH=2.0) with a peak-to-peak separation of about 20 mV, revealing a fast electron-transfer process. Moreover, the current response was remarkably increased at PDDA- GS/GCE compared with that at the bare GCE. The electrochemical behaviors of shikonin at the modified electrode were investigated. And the results indicate that the reaction involves the transfer of two electrons, accompanied by two protons and the electrochemical process is a diffusional-controlled electrode process. The electrochemical para- meters of shikonin at the modified electrode, the electron-transfer coefficient(a), the electron-transfer number(n) and the electrode reaction rate constant(ks) were calculated to be as 0.53, 2.18 and 3.6 s^-1, respectively. Under the optimal conditions, the peak current of differential pulse voltammetry(DPV) increased linearly with the shikonin concentra- tion in a range from 9A72×10^-8 mol/L to 3,789×10^-6 mol/L with a detection limit of 3,157× 10^-8 mol/L. The linear regression equation was Ip=O.7366c+0.7855(R=0.9978; lp: 10-7 A, c: 10-8 mol/L). In addition, the modified glass carbon electrode also exhibited good stability, selectivity and acceptable reproducibility that could be used for the sensitive, simple and rapid determination of shikonin in real samples. Therefore, the present work offers a new way to broaden the analytical application of graphene in pharmaceutical analysis.展开更多
Main observation and conclusion Detection of hydrazine originated from electrochemical media has recently gained considerable attention in the sensing field.Herein,to improve electron transfer capacity,a polyoxometala...Main observation and conclusion Detection of hydrazine originated from electrochemical media has recently gained considerable attention in the sensing field.Herein,to improve electron transfer capacity,a polyoxometalate metal-organic framework(POMOF,NENU-3)is in-situ nucleated onto the carboxyl functionalized reduced graphene oxide(CFG)(NENU-3/CFG,abbreviation N3/CFG).The N3/CFG supported onto carbon cloth electrodes(CCEs)has been investigated for hydrazine detection.The amperometric results display that the POMOF/CFG to hydrazine has a broad linear range(0.09—362.5μmol/L)and low detection limit(24 nmol/L).In addition,the POMOF/CFG-based sensors possess good anti-interference capability,boosted stability and feasibility.Furthermore,when applied to the detection of practical samples,acceptable relative recoveries of 96.26%—107.30%are obtained.展开更多
A series of β-cyclodextrin (CDs) functionalized graphene nanohybrids have been successfully fabricated utilizing the classical covalent modification methods at different reaction temperatures. It is very interesti...A series of β-cyclodextrin (CDs) functionalized graphene nanohybrids have been successfully fabricated utilizing the classical covalent modification methods at different reaction temperatures. It is very interesting that although both CDs and graphene oxide (GO) could he easily decomposed, the effective combination of GO with CDs leads to significantly enhanced thermal stability of graphene derivatives (GO-CDs). Moreover, the introduction of CDs could dramatically improve the dispersibility promotion of our products in both polar/protic and nonpolar/aprotic solvents, which will contribute to the preparation of polymer nanocomposites and increase of their thermal stability. The improved thermal degradation temperatures can be obtained for polyvinyl alcohol after filling with as little as 1 wt.% of the hybrid. The obtained products could be potentially used in heat-retardant or thermal-control materials.展开更多
In this study,the wave propagation properties of piezoelectric sandwich nanoplates deposited on an orthotropic viscoelastic foundation are analyzed by considering the surface effects(SEs).The nanoplates are composed o...In this study,the wave propagation properties of piezoelectric sandwich nanoplates deposited on an orthotropic viscoelastic foundation are analyzed by considering the surface effects(SEs).The nanoplates are composed of a composite layer reinforced by graphene and two piezoelectric surface layers.Utilizing the modified Halpin-Tsai model,the material parameters of composite layers are obtained.The displacement field is determined by the sinusoidal shear deformation theory(SSDT).The Euler-Lagrange equation is derived by employing Hamilton’s principle and the constitutive equations of piezoelectric layers considering the SEs.Subsequently,the nonlocal strain gradient theory(NSGT)is used to obtain the equations of motion.Next,the effects of scale parameters,graphene distribution,orthotropic viscoelastic foundation,and SEs on the propagation behavior are numerically examined.The results reveal that the wave frequency is a periodic function of the orthotropic angle.Furthermore,the wave frequency increases with the increase in the SEs.展开更多
Controlling the spatial distribution of functional groups on two-dimensional(2D)materials on a micrometer scale and below represents a fascinating opportunity to achieve anisotropic(opto)electronic properties of these...Controlling the spatial distribution of functional groups on two-dimensional(2D)materials on a micrometer scale and below represents a fascinating opportunity to achieve anisotropic(opto)electronic properties of these materials.Periodic patterns of covalent functionalization can lead to pericxJic potentials in the monolayer;however,creating such superstructures is very challenging.Here,we describe an original approach to the periodic functionalization of graphene induced by substrate patterning using a pulsed laser.Laser-induced periodic surface structures(LIPSS)are produced on silicon wafers with thermally-grown oxide layers.The irradiation conditions for the formation of UPSS confined at the SiO2/Si interface have been unravelled.LIPSS imprint their periodicity to the reactivity of the monolayer graphene placed on the substrate via modulation of its local doping level.This method is clean,straightforward and scalable with high spatial resolution.展开更多
To overcome two obstacles in graphene functionalization—the random distribution of functional groups and substantial lattice defects,in this contribution,we rationally bypass the universal yet destructive graphene ox...To overcome two obstacles in graphene functionalization—the random distribution of functional groups and substantial lattice defects,in this contribution,we rationally bypass the universal yet destructive graphene oxide(GO)-derived methodologies and adopt reductive covalent functionalization of natural graphite.In this strategy,ultrahigh density graphene sheets with evenly distributed negative charges were intermediately yielded by potassium reduction to graphite.Subsequently,they were regioregularly and efficiently brominated by the benchmark electrophile of molecular bromine.The combined characterizations determined the graphene bromide derivative to have a molecular formula of C_(24)-Br,corresponding well with the brominated entity of the inseparable C_(24)-K^(+)graphite intercalation compounds.Due to the regular distribution of Br groups and intact hexagonal lattice of the graphene matrix,the C_(24)-Br_GBr delivers exceptional electrical properties although theπ-conjugation is partially blocked by C(sp^(3))-Br sites and greatly outperforms its counterparts derived from GO bromination.In both model applications of quickly switchable electrochromic devices and all-solid-state supercapacitors,C_(24)-Br_GBr exhibits impressive performance,which highlights the great significance and prospect of regioregular and lattice-nondestructive graphene functionalization.展开更多
It is well-known that chemical functionalization of graphene has the great significance.We report the development of a new synthesis method of chloro-functionalized reduced graphene oxide(rGOCl).The rGOCl was prepar...It is well-known that chemical functionalization of graphene has the great significance.We report the development of a new synthesis method of chloro-functionalized reduced graphene oxide(rGOCl).The rGOCl was prepared by radical reaction,and treatment of carboxyl graphene oxide(GOCOOH) with N-chlorosuccinimide(NCS) at 90℃ for 10 h under an atmosphere of nitrogen,using silver nitrate as catalyst.The morphologies and structures of the prepared materials were investigated by field-emission scanning electron microscopy(FESEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),Raman spectroscopy and the thermal gravimetric.Results indicated that the rGOCl can be readily obtained from graphene oxide(GO) in three steps.展开更多
It is promising to apply quantum-mechanically confined graphene systems in field-effect transistors. High stability, superior performance, and large-scale integration are the main challenges facing the practical appli...It is promising to apply quantum-mechanically confined graphene systems in field-effect transistors. High stability, superior performance, and large-scale integration are the main challenges facing the practical application of graphene transistors. Our understandings of the adatom-graphene interac- tion combined with recent progress in the nanofabrication technology indicate that very stable and high-quality graphene nanostripes could be integrated in substrate-supported functionalized (hydro- genated or fluorinated) graphene using electron-beam lithography. We also propose that parallelizing a couple of graphene nanostripes in a transistor should be preferred for practical application, which is also very useful for transistors based on graphene nanoribbon.展开更多
Development of multifunctional and high-performance silicone aerogel is highly required for various promising applications.However,unstable cross-linking structure and poor thermal stability of silicone network as wel...Development of multifunctional and high-performance silicone aerogel is highly required for various promising applications.However,unstable cross-linking structure and poor thermal stability of silicone network as well as complicated processing restrict the practical use significantly.Herein,we report a facile and versatile ambient drying strategy to fabricate lightweight,wide-temperature flexible,super-hydrophobic and flame retardant silicone composite aerogels modified with low-content functionalized graphene oxide(FGO).After optimizing silane molecules,incorporation ofγ-aminopropyltriethoxysilane functionalization is found to promote the dispersion stability of GO during the hydrolysis-polymerization process and thus produce the formation of unique strip-like co-cross-linked network.Consequently,the aerogels containing∼2.0 wt%FGO not only possess good cyclic compressive stability under strain of 70%for 100 cycles and outstanding mechanical reliability in wide temperature range(from liquid nitrogen to 350℃),but also display excellent flame resistance and super-hydrophobicity.Further,the optimized silicone/FGO aerogels display exceptional thermal insulating performance superior to pure aerogel and hydrocarbon polymer foams,and they also show efficient oil absorption and separation capacity for var-ious solvents and oil from water.Clearly,this work provides a new route for the rational design and development of advanced silicone composite aerogels for multifunctional applications.展开更多
基金the National Natural Science Foundation of China(Grant number 51771178)Shaanxi Outstanding Youth Fund project(Grant number 2021JC-45)+2 种基金Key international cooperation projects in Shaanxi Province(Grant number 2020KWZ-007)the Major Program of Science and Technology in Shaanxi Province(Grant number20191102006)Open Fund of State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body(Grant number 32115019)。
文摘The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification process,which cannot provide sufficient protection.In the current study,we design a double-layer epoxy composite coating on Mg alloy with enhanced anti-corrosion/wear properties,via the spin-assisted assembly technique.The outer layer is functionalized graphene(FG)in waterborne epoxy resin(WEP)and the inner layer is Ce-based conversion(Ce)film.The FG sheets can be homogeneously dispersed within the epoxy matrix to fill the intrinsic defects and improve the barrier capability.The Ce film connects the outer layer with the substrate,showing the transition effect.The corrosion rate of Ce/WEP/FG composite coating is 2131 times lower than that of bare Mg alloy,and the wear rate is decreased by~90%.The improved corrosion resistance is attributed to the labyrinth effect(hindering the penetration of corrosive medium)and the obstruction of galvanic coupling behavior.The synergistic effect derived from the FG sheet and blocking layer exhibits great potential in realizing the improvement of multi-functional integration,which will open up a new avenue for the development of novel composite protection coatings of Mg alloys.
文摘Buckling and postbuckling characteristics of laminated graphene-enhanced composite(GEC)truncated conical shells exposed to torsion under temperature conditions using finite element method(FEM)simulation are presented in this study.In the thickness direction,the GEC layers of the conical shell are ordered in a piece-wise arrangement of functionally graded(FG)distribution,with each layer containing a variable volume fraction for graphene reinforcement.To calculate the properties of temperaturedependent material of GEC layers,the extended Halpin-Tsai micromechanical framework is used.The FEM model is verified via comparing the current results obtained with the theoretical estimates for homogeneous,laminated cylindrical,and conical shells,the FEM model is validated.The computational results show that a piece-wise FG graphene volume fraction distribution can improve the torque of critical buckling and torsional postbuckling strength.Also,the geometric parameters have a critical impact on the stability of the conical shell.However,a temperature rise can reduce the crucial torsional buckling torque as well as the GEC laminated truncated conical shell’s postbuckling strength.
基金Project supported by the National Natural Science Foundation of China(Nos.12002057,11872127,11832002)the Scientific Research Project of Beijing Educational Committee(No.KM202111232023)the Qin Xin Talents Cultivation Program,Beijing Information Science&Technology University(Nos.QXTCP C202102,A201901)。
文摘In this study,the first-order shear deformation theory(FSDT)is used to establish a nonlinear dynamic model for a conical shell truncated by a functionally graded graphene platelet-reinforced composite(FG-GPLRC).The vibration analyses of the FG-GPLRC truncated conical shell are presented.Considering the graphene platelets(GPLs)of the FG-GPLRC truncated conical shell with three different distribution patterns,the modified Halpin-Tsai model is used to calculate the effective Young’s modulus.Hamilton’s principle,the FSDT,and the von-Karman type nonlinear geometric relationships are used to derive a system of partial differential governing equations of the FG-GPLRC truncated conical shell.The Galerkin method is used to obtain the ordinary differential equations of the truncated conical shell.Then,the analytical nonlinear frequencies of the FG-GPLRC truncated conical shell are solved by the harmonic balance method.The effects of the weight fraction and distribution pattern of the GPLs,the ratio of the length to the radius as well as the ratio of the radius to the thickness of the FG-GPLRC truncated conical shell on the nonlinear natural frequency characteristics are discussed.This study culminates in the discovery of the periodic motion and chaotic motion of the FG-GPLRC truncated conical shell.
文摘Graphene oxide has been used widely as a starting precursor for applications that cater to the needs of tunable graphene. However, the hydrophilic characteristic limits their application, especially in a hydrophobic condition. Herein, a novel non-covalent surface modification approach towards graphene oxide was conducted via a UV-induced photo-polymerization technique that involves two major routes; a UV-sensitive initiator embedded via pi-pi interactions on the graphene planar rings, and the polymerization of hydrophobic polymeric chains along the surface. The functionalized graphene oxide successfully achieved the desired hydrophobicity as it displayed the characteristic of being readily dissolved in organic solvent. Upon its addition into a polymeric solution and subjected to an electrospinning process,non-woven random nanofibers embedded with graphene oxide sheets were obtained. The prepared polymeric nanofibers were subjected to two-step thermal treatments that eventually converted the polymeric chains into a carbon-rich conductive structure. A unique morphology was observed upon the addition of the functionalized graphene oxide, whereby the sheets were embedded and intercalated within the carbon nanofibers and formed a continuous structure. This reinforcement effectively enhanced the electrochemical performance of the carbon nanofibers by recording a specific capacitance of up to 140.10 F/g at the current density of 1 A/g, which was approximately three folds more than that of pristine nanofibers.It also retained the capacitance up to 96.2% after 1000 vigorous charge/discharge cycles. This functionalization technique opens up a new pathway in tuning the solubility nature of graphene oxide towards the synthesis of a graphene oxide-reinforced polymeric structure.
基金supported by 100 Talents Programme of the Chinese Academy of SciencesNational Program on Key Basic Research Project of China(973 Program,Grant No.2012CB215500)+1 种基金Foundation for Innovative Research Groups of the National Natural Science Foundation of China(Grant No.20921002 and No.21101147)the Science and Technology Development Program of Jilin Province(Grant No.20100102 and 20116008)
文摘Supercapacitors(SCs) have attracted much attention as one of the alternative energy devices due to their high power performance,long cycle life,and low maintenance cost.Graphene is considered as an innovative and promising material due to its large theoretical specific surface area,high electrical conductivity,good mechanical properties and chemical stability.Herein,we report an effective strategy for elaborately constructing rationally functionalized self-standing graphene(SG) obtained from giant graphene oxide(GGO) paper followed by an ultrarapid thermal-processing.This treatment results in both the exfoliation of graphene sheets and the reduction of GGO by elimination of oxygencontaining groups.The as-prepared SG electrode materials without additive and conducting agent provide an excellent combination of the electrical double layer capacitor(EDLC) and pseudocapacitor(PC) functions and exhibit superior electrochemical performance,including high specific capacitance,good rate capability and excellent cycling stability when investigated in three-electrode electrochemical cells.
文摘In this research,to remove sulfur and nitrogen compounds from heavy naphtha,various nanocatalysts were prepared through supporting NiMo over nanoporous graphene and evaluated in hydrodesulfurization and hydrodenitrogenation reactions.The nanoporous graphene was initially functionalized in order to facilitate the metal being loaded on it.Three different methods were used to functionalize the nanoporous graphene.The NiMo/nanoporous graphene nanocatalysts were characterized by field emission scanning electron microscopy,Fourier transform infrared spectroscopy,X-ray diffraction,inductively coupled plasma optical emission spectrometry,temperature-programmed reduction,nitrogen adsorption-desorption isotherms and transmission electron microscopy techniques.Catalyst performance was evaluated in terms of conversions of sulfur,mercaptans(R-SH)and nitrogen compounds.It was found that the functionalized nanoporous graphene support could significantly enhance the catalytic performance in comparison with the industrial NiMo/alumina catalyst.Among the functionalized graphene supports,amine-functionalized graphene exhibited the best results.By using NiMo supported over amine-functionalized graphene,the conversions of total sulfur and R-SH reached 97.8%and 98.1%,respectively.
基金Funded by the National Natural Science Fundation of China(Nos.51678111 and 51478082)
文摘Functionalized graphene nano-platelets(FGN) were obtained via treating graphene nanoplatelets(GN) with HNO3, and served as adsorbent for the removal of Pb2+from solutions. We investigated the FGN adsorption capacity for Pb2+at different initial concentrations, varying pH, contact time and temperature. The characterization results of scanning electron microscopy(SEM), thermal analysis(TG/DTG), Fourier transform infrared spectroscopy(FT-IR) and Brunauer-Emmett-Teller(BET) method indicated that FGN layers were thin and possess large specific area with oxygen-containing functional groups grafted onto their surface. Meanwhile, the determined equilibrium adsorption capacity of FGN for Pb2+was 57.765 mg/g and adsorption isotherms well confirmed to Langmuir isotherms models. The results reveals that the FGN has better effect of water treatment.
文摘In this paper, we investigate the selection rule for desalinating seawater using functionalized graphene sheet as a semi-permissible membrane. Both the applied mathematical modeling and MD simulations will be used to determine the acceptance conditions for water molecule or sodium ion permeating into the functionalized graphene. Both the Lennard-Jones potential and Coulomb forces are considered by taking into accounts the major molecular and ionic interactions between molecules, ions and functionalized graphene sheet. The continuous approximation will then be used to coarse grain most significant molecular and ionic interactions so that the multi-body problems could be simplified into several two-body problems and the 3D motions are reduced into degenerated 1D motion. Our mathematical model and simulations show that the negatively charged graphene always accepts sodium ions and water;however the permeability of water molecules and sodium ions becomes very sensitive to the presence of positive charges on the graphene.
文摘We address the electrical conductivity of bilayer graphene as a function of temperature, impurity concentration, and scattering strength in the presence of a finite bias voltage at finite doping, beginning with a description of the tight-binding model using the linear response theory and Green's function approach. Our results show a linear behavior at high doping for the case of high bias voltage. The effects of electron doping on the electrical conductivity have been studied via changing the electronic chemical potential. We also discuss and analyze how the bias voltage affects the temperature behavior of the electrical conductivity. Finally, we study the behavior of the electrical conductivity as a function of the impurity concentration and scattering strength for different bias voltages and chemical potentials respectively. The electrical conductivity is found to be monotonically decreasing with impurity scattering strength due to the increased scattering among electrons at higher impurity scattering strength.
文摘We present the behaviors of both dynamical and static charge susceptibilities of undoped armchair graphene nanoribbon using the Green's function approach in the context of tight binding model Hamiltonian.Specifically,the effects of magnetic field on the the plasmon modes of armchair graphene nanoribbon are investigated via calculating the correlation function of charge density operators.Our results show that the increase of magnetic field makes the high-frequency plasmon mode for both metallic and insulating cases disappear.We also show that low-frequency plasmon mode for metallic nanoribbon appears due to increase of magnetic field.Furthermore,the number of collective excitation modes increases with ribbon width at zero magnetic field.Finally,the temperature dependence of the static charge structure factor of armchair graphene nanoribbon is studied.The effects of both magnetic field and ribbon width on the static charge structure factor are discussed in detail.
基金the Science and Research Branch,Islamic Azad Universitythe Research Institute of Petroleum Industry(RIPI)for supporting this work
文摘Formaldehyde(HCHO)is formed through the oxidation of volatile organic compounds(VOCs)and can cause human cancer.Bismuth oxide and titanium oxide nanoparticles-functionalized nanographene oxide(Bi_(2)O_(3)/TiO_(2)@NGO)were used to rapidly remove the HCHO from the air by a photocatalytic degradation-adsorption process(PC-DAP).The formaldehyde vapor in pure air was generated in a dynamic system within a chamber,and flowed over Bi_(2)O_(3)/TiO_(2)@NGO adsorbent inside a fixed-bed quartz reactor(FBQR)under UV irradiation at optimized conditions(250C).At atmospheric pressure,the flow rate and gas hourly space velocity(GHSV)were adjusted to 300 mL/min and 100-450 L/h,respectively.The radicals of HCHO and nanographene oxide(NGO)were generated through the UV-photochemical process,enhancing the chemical adsorption through the radicals’interactions.On the other hand,the semi-degradation process by catalytic oxidation process converted some HCHO into raw materials of CO_(2)and H_(2)O,while the unconverted HCHO was physically absorbed by NGO.Finally,the HCHO concentration in the outlet system was measured by gas chromatography with a flame ionization detector(GC-FID)after derivatizing formaldehyde with 2,4-dinitrophenylhydrazine(DNPH)and acetonitrile.Therefore,efficient removal of HCHO from the air,the removal efficiency of more than 95%,was achieved through physical/chemical adsorption and the semi-degradation.The mean removal efficiencies for HCHO with Bi_(2)O_(3)-TiO_(2)@NGO,TiO_(2)@NGO,Bi_(2)O_(3)@NGO,and NGO were 98.7%,73.6%,61.8%,and 11.4%,respectively(n=10,RSD<5%).The methodology was validated by spiking different concentrations of standard HCHO into pure air.
文摘The electrochemical behaviors of shikonin at a poly(diallyldimethylammonium chloride) functionalized graphene sheets modified glass carbon electrode(PDDA-GS/GCE) have been investigated. Shikonin could exhibit a pair of well-defined redox peaks at the PDDA-GS/GCE located at 0.681 V(Epa) and 0.662 V(Epc)[vs. saturated calo- mel electrode(SCE)] in 0.1 mol/L phosphate buffer solution(pH=2.0) with a peak-to-peak separation of about 20 mV, revealing a fast electron-transfer process. Moreover, the current response was remarkably increased at PDDA- GS/GCE compared with that at the bare GCE. The electrochemical behaviors of shikonin at the modified electrode were investigated. And the results indicate that the reaction involves the transfer of two electrons, accompanied by two protons and the electrochemical process is a diffusional-controlled electrode process. The electrochemical para- meters of shikonin at the modified electrode, the electron-transfer coefficient(a), the electron-transfer number(n) and the electrode reaction rate constant(ks) were calculated to be as 0.53, 2.18 and 3.6 s^-1, respectively. Under the optimal conditions, the peak current of differential pulse voltammetry(DPV) increased linearly with the shikonin concentra- tion in a range from 9A72×10^-8 mol/L to 3,789×10^-6 mol/L with a detection limit of 3,157× 10^-8 mol/L. The linear regression equation was Ip=O.7366c+0.7855(R=0.9978; lp: 10-7 A, c: 10-8 mol/L). In addition, the modified glass carbon electrode also exhibited good stability, selectivity and acceptable reproducibility that could be used for the sensitive, simple and rapid determination of shikonin in real samples. Therefore, the present work offers a new way to broaden the analytical application of graphene in pharmaceutical analysis.
基金support from the National Natural Science Foundation of China(Nos.21771047,21403048 and 21401147)the Natural Science Foundation of Heilongjiang Province,China(Nos.JJ2020TD0027 and JJ2020YX0209)+1 种基金the Excellent Scientific Research Team Project of Harbin Normal University(No.XKYT202001)the Postgraduate Innovation Project of Harbin Normal University,China(Nos.HSDSSCX2019-38 and HSDSSCX2019-39).
文摘Main observation and conclusion Detection of hydrazine originated from electrochemical media has recently gained considerable attention in the sensing field.Herein,to improve electron transfer capacity,a polyoxometalate metal-organic framework(POMOF,NENU-3)is in-situ nucleated onto the carboxyl functionalized reduced graphene oxide(CFG)(NENU-3/CFG,abbreviation N3/CFG).The N3/CFG supported onto carbon cloth electrodes(CCEs)has been investigated for hydrazine detection.The amperometric results display that the POMOF/CFG to hydrazine has a broad linear range(0.09—362.5μmol/L)and low detection limit(24 nmol/L).In addition,the POMOF/CFG-based sensors possess good anti-interference capability,boosted stability and feasibility.Furthermore,when applied to the detection of practical samples,acceptable relative recoveries of 96.26%—107.30%are obtained.
基金supported by China Postdoctoral Science Foundation Funded Project(No.20100481146)Jiangsu Planned Projects for Postdoctoral Research Funds(No.1002015C)+2 种基金Natural Science Foundation of Jiangsu Province(No.BK2011712, BK20130575)National University Student Innovation Program(No.201210288036)NJUST Opening Measuring Fund of Large Precious Apparatus(No.2012-01-15)
文摘A series of β-cyclodextrin (CDs) functionalized graphene nanohybrids have been successfully fabricated utilizing the classical covalent modification methods at different reaction temperatures. It is very interesting that although both CDs and graphene oxide (GO) could he easily decomposed, the effective combination of GO with CDs leads to significantly enhanced thermal stability of graphene derivatives (GO-CDs). Moreover, the introduction of CDs could dramatically improve the dispersibility promotion of our products in both polar/protic and nonpolar/aprotic solvents, which will contribute to the preparation of polymer nanocomposites and increase of their thermal stability. The improved thermal degradation temperatures can be obtained for polyvinyl alcohol after filling with as little as 1 wt.% of the hybrid. The obtained products could be potentially used in heat-retardant or thermal-control materials.
基金supported by the National Natural Science Foundation of China(Nos.11502218,11672252,11602204,and 12102373)the Fundamental Research Funds for the Central Universities of China(No.2682020ZT106)。
文摘In this study,the wave propagation properties of piezoelectric sandwich nanoplates deposited on an orthotropic viscoelastic foundation are analyzed by considering the surface effects(SEs).The nanoplates are composed of a composite layer reinforced by graphene and two piezoelectric surface layers.Utilizing the modified Halpin-Tsai model,the material parameters of composite layers are obtained.The displacement field is determined by the sinusoidal shear deformation theory(SSDT).The Euler-Lagrange equation is derived by employing Hamilton’s principle and the constitutive equations of piezoelectric layers considering the SEs.Subsequently,the nonlocal strain gradient theory(NSGT)is used to obtain the equations of motion.Next,the effects of scale parameters,graphene distribution,orthotropic viscoelastic foundation,and SEs on the propagation behavior are numerically examined.The results reveal that the wave frequency is a periodic function of the orthotropic angle.Furthermore,the wave frequency increases with the increase in the SEs.
基金The work was supported by project No.18-09055Y and 20-08633X awarded by Czech Science FoundationThe research of I.M.,J.S.,T.J.-Y.D.,and N.M.B.is financed by the European Regional Development Fund and the state budget of the Czech Republic(project BIATRI,No.CZ.02.1.01/0.0/0.0/15_003/0000445,project HiLASE CoE,No.CZ.02.1.01/0.0/0.0/15_006/0000674,programme NPU I,project No.LO1602)+3 种基金The work was further supported by European Regional Development Fund,OP RDE,Project:“Carbon allotropes with rationalized nanointerfaces and nanolinks for environmental and biomedical applications”(No.CZ.02.1.01/0.0/0.0/16_026/0008382)The authors also acknowledge the assistance provided by the Research Infrastructures NanoEnviCz(No.LM2015073)supported by the Ministry of EducationYouth and Sports of the Czech Republic and the project Pro-NanoEnviCz(No.CZ.02.1.01/0.0/0.0/16_013/0001821)supported by the Ministry of EducationYouth and Sports of the Czech Republic and the European Union-European Structural and Investments Funds in the frame of Operational Programme Research Development and Education.
文摘Controlling the spatial distribution of functional groups on two-dimensional(2D)materials on a micrometer scale and below represents a fascinating opportunity to achieve anisotropic(opto)electronic properties of these materials.Periodic patterns of covalent functionalization can lead to pericxJic potentials in the monolayer;however,creating such superstructures is very challenging.Here,we describe an original approach to the periodic functionalization of graphene induced by substrate patterning using a pulsed laser.Laser-induced periodic surface structures(LIPSS)are produced on silicon wafers with thermally-grown oxide layers.The irradiation conditions for the formation of UPSS confined at the SiO2/Si interface have been unravelled.LIPSS imprint their periodicity to the reactivity of the monolayer graphene placed on the substrate via modulation of its local doping level.This method is clean,straightforward and scalable with high spatial resolution.
基金The authors gratefully acknowledge financial support from the National Natural Science Foundation of China(no.21504080)the Natural Science Foundation of Zhejiang Province(no.LQ15B040003)the Fundamental Research Funds of Zhejiang Sci-Tech University(no.2020Q040).
文摘To overcome two obstacles in graphene functionalization—the random distribution of functional groups and substantial lattice defects,in this contribution,we rationally bypass the universal yet destructive graphene oxide(GO)-derived methodologies and adopt reductive covalent functionalization of natural graphite.In this strategy,ultrahigh density graphene sheets with evenly distributed negative charges were intermediately yielded by potassium reduction to graphite.Subsequently,they were regioregularly and efficiently brominated by the benchmark electrophile of molecular bromine.The combined characterizations determined the graphene bromide derivative to have a molecular formula of C_(24)-Br,corresponding well with the brominated entity of the inseparable C_(24)-K^(+)graphite intercalation compounds.Due to the regular distribution of Br groups and intact hexagonal lattice of the graphene matrix,the C_(24)-Br_GBr delivers exceptional electrical properties although theπ-conjugation is partially blocked by C(sp^(3))-Br sites and greatly outperforms its counterparts derived from GO bromination.In both model applications of quickly switchable electrochromic devices and all-solid-state supercapacitors,C_(24)-Br_GBr exhibits impressive performance,which highlights the great significance and prospect of regioregular and lattice-nondestructive graphene functionalization.
基金financially supported by the Natural Science Foundation of Inner Mongolia (No. 2014BS0202)Inner Mongolia University of Science and Technology Innovation Fund (No. 2014QDL018)Talent Incubation Funding of School of Materials and Metallurgy (No. 2014CY012)
文摘It is well-known that chemical functionalization of graphene has the great significance.We report the development of a new synthesis method of chloro-functionalized reduced graphene oxide(rGOCl).The rGOCl was prepared by radical reaction,and treatment of carboxyl graphene oxide(GOCOOH) with N-chlorosuccinimide(NCS) at 90℃ for 10 h under an atmosphere of nitrogen,using silver nitrate as catalyst.The morphologies and structures of the prepared materials were investigated by field-emission scanning electron microscopy(FESEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),Raman spectroscopy and the thermal gravimetric.Results indicated that the rGOCl can be readily obtained from graphene oxide(GO) in three steps.
文摘It is promising to apply quantum-mechanically confined graphene systems in field-effect transistors. High stability, superior performance, and large-scale integration are the main challenges facing the practical application of graphene transistors. Our understandings of the adatom-graphene interac- tion combined with recent progress in the nanofabrication technology indicate that very stable and high-quality graphene nanostripes could be integrated in substrate-supported functionalized (hydro- genated or fluorinated) graphene using electron-beam lithography. We also propose that parallelizing a couple of graphene nanostripes in a transistor should be preferred for practical application, which is also very useful for transistors based on graphene nanoribbon.
基金financially supported by the National Natural Science Foundation of China (Nos. 51973047 and 12002112)the Science Foundation and Technology Project of Zhejiang Province (No. Z22E035302)+1 种基金the Science Foundation and Technology Project of Shandong Province (No. ZR2020LFG004)the Project for Science and Technology Program of Hangzhou (Nos. 20191203B16 and 20201203B136)
文摘Development of multifunctional and high-performance silicone aerogel is highly required for various promising applications.However,unstable cross-linking structure and poor thermal stability of silicone network as well as complicated processing restrict the practical use significantly.Herein,we report a facile and versatile ambient drying strategy to fabricate lightweight,wide-temperature flexible,super-hydrophobic and flame retardant silicone composite aerogels modified with low-content functionalized graphene oxide(FGO).After optimizing silane molecules,incorporation ofγ-aminopropyltriethoxysilane functionalization is found to promote the dispersion stability of GO during the hydrolysis-polymerization process and thus produce the formation of unique strip-like co-cross-linked network.Consequently,the aerogels containing∼2.0 wt%FGO not only possess good cyclic compressive stability under strain of 70%for 100 cycles and outstanding mechanical reliability in wide temperature range(from liquid nitrogen to 350℃),but also display excellent flame resistance and super-hydrophobicity.Further,the optimized silicone/FGO aerogels display exceptional thermal insulating performance superior to pure aerogel and hydrocarbon polymer foams,and they also show efficient oil absorption and separation capacity for var-ious solvents and oil from water.Clearly,this work provides a new route for the rational design and development of advanced silicone composite aerogels for multifunctional applications.