Two-dimensional carbon/carbon(2D C/C)composites are a special class of carbon/carbon composites,generally obtained by combining resin-impregnated carbon fiber clothes,which are then cured and carbonized.This study dea...Two-dimensional carbon/carbon(2D C/C)composites are a special class of carbon/carbon composites,generally obtained by combining resin-impregnated carbon fiber clothes,which are then cured and carbonized.This study deals with the preparation of a protective coating for these materials.This coating,based on graphite,was prepared by the slurry method.The effect of graphite and phenolic resin powders with different weight ratios was examined.The results have shown that the coating slurry can fill the pores and cracks of the composite surface,thereby densifying the surface layer of the material.With the increase of the graphite powder/phenolic resin weight ratio,the coating density is enhanced while the coating surface flatness decreases;moreover,the protective ability of coating against erosion first increases(from 1:3 to 2:2)and then decreases(from 2:2 to 3:1).When the weight ratio is about 1:1,the coating for 2D C/C composites exhibits the best erosion resistance,which greatly aids these materials during gas quenching.In this case,the erosion rate is decreased by approximately 41.5%at the impact angle of 30°and 52.3%at normal impact,respectively.This can be attributed to the ability of the coating slurry to infiltrate into the substrate,thereby bonding the fibers together and increasing the compactness of the 2D C/C composites.展开更多
Common strategies for catalytic graphitization of biochar into graphitic porous carbon(GPC)still face great challenges,such as the realization of simple procedures,energy conservation,and green processes.Controlling o...Common strategies for catalytic graphitization of biochar into graphitic porous carbon(GPC)still face great challenges,such as the realization of simple procedures,energy conservation,and green processes.Controlling over the graphitization degree and pore structure of biochar is the key to its structural diversification.Herein,a clean and energy-efficient method is developed to synthesize adjustable graphitic degree and structure porosity GPC from rice husk-based carbon(RHC)at a relatively low temperature of 800–1000°C with environment-benign organometallic catalyst ethylenediaminetetraacetic acid ferric sodium salt(EDTA-iron)and the recovery ratio of catalyst is as high as 97%.The formed by the organic ligands of EDTA-iron facilitates the etching of RHC surface and pore by iron,resulting in highly graphitized and developed porous GPCs.The pore structure and graphitization degree of GPCs can be adjusted by altering the catalyst loading,temperature,and holding time.The catalyst EDTA-iron with a lower concentration mainly plays the role of etching,which promotes the formation of porous carbon with larger surface area(SBET=1187.2 m^(2)·g^(-1)).The catalyst with higher concentration mainly plays the role of catalyzing graphitization and promotes the obtaining of graphitic carbon with high graphitization degree(ID/IG=0.19).The mechanism of EDTA-iron catalyzed graphitization of RHC is explored by the comprehensive analysis of BET,XRD,Raman,TEM and TGA.This research not only provides an efficient method for the preparation of high-quality biomass-based graphite carbon,but also provides a feasible method for the preparation of biomass-based porous carbon.展开更多
The process of electrodepositing Fe-Cr2O3 composite coating on polyacrylonitrile （PAN）-based carbon fibers and its catalytic graphitization were studied. Carbon fibers with and without electrodeposited Fe-Cr2O3 comp...The process of electrodepositing Fe-Cr2O3 composite coating on polyacrylonitrile （PAN）-based carbon fibers and its catalytic graphitization were studied. Carbon fibers with and without electrodeposited Fe-Cr2O3 composite coating were heat treated at different temperatures and the structural changes were characterized by XRD, Raman spectroscopy and SEM. The results indicate that Fe-Cr2O3 composite coating exhibits a significant catalytic effect on graphitization of carbon fibers at low temperatures. When the Fe-Cr2O3-coated carbon fibers were heat treated at 1 300℃ the interlayer spacing （doo2） and ratio of relative peak area （AD/AG） reach 3.364/k and 0.34, respectively. Whereas, the extent of graphitization of pristine carbon fibers is comparatively low even after heat treatment at 2 800℃ and the values of doo2 and AD/AG are 3.414 A and 0.68, respectively. The extent of graphitization of carbon fibers increases not only with the increase of the catalyst gross but also the Cr2O3 content in Fe-Cr2O3 coating. The catalytic effect of Fe-Cr2O3 composite coating accords with the dissolution-precipitation mechanism.展开更多
A novel carbon fiber pretreatment was proposed.Polyacrylonitrile(PAN)-based carbon fibers were first anodized in H3PO4 electrolyte to achieve an active surface,and then coated with Mo-B catalysts by immersed the carbo...A novel carbon fiber pretreatment was proposed.Polyacrylonitrile(PAN)-based carbon fibers were first anodized in H3PO4 electrolyte to achieve an active surface,and then coated with Mo-B catalysts by immersed the carbon fibers in a uniformly dispersed Mo-B sol.The as-treated carbon fibers were then graphitized at 2 400 ℃ for 2 h.The structural changes were characterized by X-ray diffractometry(XRD),Raman spectroscopy,scanning electron microscopy(SEM) and high-resolution transmission electronic microscopy(HRTEM).The results show that much better graphitization can be achieved in the presence of Mo-B,with an interlayer spacing(d002) of 0.335 8 nm and a crystalline size(Lc) of 28 nm.展开更多
By virtue of the flexibility and safety, polyethylene oxide(PEO) based electrolytes are regarded as an appealing candidate for all-solid-state lithium batteries. However, their application is limited by the poor ionic...By virtue of the flexibility and safety, polyethylene oxide(PEO) based electrolytes are regarded as an appealing candidate for all-solid-state lithium batteries. However, their application is limited by the poor ionic conductivity at room temperature, narrow electrochemical stability window and uncontrolled growth of lithium dendrite. To alleviate these problems, we introduce the ultrathin graphitic carbon nitride nanosheets(GCN) as advanced nanofillers into PEO based electrolytes(GCN-CPE). Benefiting from the high surface area and abundant surface N-active sites of GCN, the GCN-CPE displays decreased crystallinity and enhanced ionic conductivity. Meanwhile, Fourier transform infrared and chronoamperometry studies indicate that GCN can facilitate Li+migration in the composite electrolyte. Additionally, the GCN-CPE displays an extended electrochemical window compared with PEO based electrolytes. As a result, Li symmetric battery assembled with GCN-CPE shows a stable Li plating/stripping cycling performance, and the all-solid-state Li/LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM622) batteries using GCN-CPE exhibit satisfactory cyclability and rate capability in a voltage range of 3-4.2 V at 30 ℃.展开更多
The electrical conductivity and piezoresistivity of carbon fiber graphite cement-matrix composites（CFGCC） with carbon fiber content（1% by the weight of cement）,graphite powder contents （0%-50% by the weight of ce...The electrical conductivity and piezoresistivity of carbon fiber graphite cement-matrix composites（CFGCC） with carbon fiber content（1% by the weight of cement）,graphite powder contents （0%-50% by the weight of cement） and CCCW（cementitious capillary crystalline waterproofing materials,4% by the weight of cement） were studied.The experimental results showed that the relationship between the resistivity of CFGCC and the concentration of graphite powders had typical features of percolation phenomena.The percolation threshold was about 20%.A clear piezoresistive effect was observed in CFGCC with 1wt% of carbon fibers,20wt% or 30wt% of graphite powders under uniaxial compressive tests,indicating that this type of smart composites was a promising candidate for strain sensing.The measured gage factor （defined as the fractional change in resistance per unit strain） of CFGCC with graphite content of 20wt% and 30wt% were 37 and 22,respectively.With the addition of CCCW,the mechanical properties of CFGCC were improved,which benefited CFGCC piezoresistivity of stability.展开更多
Short carbon fiber felts with an initial porosity of 89.5% were deposited by isobaric, isothermal chemical vapor infiltration using natural gas as carbon source. The bulk density of the deposited carbon/carbon （C/C）...Short carbon fiber felts with an initial porosity of 89.5% were deposited by isobaric, isothermal chemical vapor infiltration using natural gas as carbon source. The bulk density of the deposited carbon/carbon （C/C） composites was 1.89 g/cm3 after depositing for 150 h. The microstructure and mechanical properties of the C/C composites were studied by polarized light microscopy, X-ray diffraction, scanning electron microscopy and three-point bending test. The results reveal that high textured pyrolytic carbon is deposited as the matrix of the composites, whose crystalline thickness and graphitization degree highly increase after heat treatment. A distinct decrease of the flexural strength and modulus accompanied by the increase of the toughness of the C/C composites is found to be correlated with the structural changes in the composites during the heat treatment process.展开更多
Three kinds of composite alumina refractories were prepared with tabular alumina （3-1 and 1-0 mm） as aggregates,tabular alumina powder,α-Al2 O3 micropowder,and Si powder as matrix,adding 3 mass％ hexagonal boron ni...Three kinds of composite alumina refractories were prepared with tabular alumina （3-1 and 1-0 mm） as aggregates,tabular alumina powder,α-Al2 O3 micropowder,and Si powder as matrix,adding 3 mass％ hexagonal boron nitride （h-BN）,3 mass％ flake graphite and 10 mass％ flake graphite,respectively.Cold physical properties,hot modulus of rupture,oxidation resistance,thermal shock resistance and slag corrosion resistance of the specimens were compared.The results show that：（1） physical properties and hot modulus of rupture of Al2 O3-h-BN refractories are slightly different from those of low carbon Al2 O3-C refractories,but better than those of traditional Al2 O3-C refractories with 10 mass％ graphite ; （2） Al2 O3-h-BN refractories have better thermal shock resistance and oxidation resistance than the carbon containing refractories,while similar slag resistance with low carbon Al2 O3-C refractories ; （3） h-BN can replace flake graphite as a starting material for the preparation of composite alumina refractories,considering the overall properties of the material.展开更多
A general, simple and economic synthetic method for synthesizing carbon nanofibers was presented. In the method, ethanol was employed as carbon source; metal salts such as nickel nitrate, ferric nitrate and ferric chl...A general, simple and economic synthetic method for synthesizing carbon nanofibers was presented. In the method, ethanol was employed as carbon source; metal salts such as nickel nitrate, ferric nitrate and ferric chloride were used as catalyst precursor respectively; copper plate was employed as the support material. A lot of products were obtained by catalytic combustion deposition of ethanol vapor. Then the as-prepared carbon nanofibers were characterized by field-emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, energy dispersion X-ray spectroscopy and selected-area electron diffractometry. By analyzing the results of characterization, the conclusions are as follows: 1) the large catalyst particles tend to form large-diameter CNFs, small catalyst particles are inclinable to form small-diameter CNFs; 2) the morphology of the catalyst can affect the final morphology of the CNFs. Moreover, the possible growth mechanisms were proposed and the degree of graphitization of samples was estimated by Raman spectroscopy characterization.展开更多
High-density carbon/carbon(C/C)composite plays a critical role in the aerospace industry owing to excellent mechanical properties and resistance to ablation.However,traditional manufacturing relies on pitch precursor ...High-density carbon/carbon(C/C)composite plays a critical role in the aerospace industry owing to excellent mechanical properties and resistance to ablation.However,traditional manufacturing relies on pitch precursor and hot isostatic pressure impregnation and carbonization(HIPIC)technology,which is time-consuming and expensive.In this study,we report an innovative method utilizing polyarylacetylene(PAA)resin and ultra-high pressure impregnation and carbonization(UHPIC)technology.The extremely high char yield of PAA resin(85 wt.%)and high isotropic pressure of UHPIC(over 200 MPa)promote the densification of the composite.As a result,we achieve a high-density(1.90 g/cm^(3))C/C composite with a high degree of graphitization(81%).This composite exhibits impressive properties,including flexural strength of 146 MPa,compressive strength of 187 MPa,and thermal conductivity of 147 W/(m K).When exposed to oxyacetylene flame at 3000 K for 100 s,it displays minimal linear ablation,with a rate of 1.27×10^(-2)mm/s.This study demonstrates the exceptional graphitizable characteristic of PAA resin,setting it apart from conventional resins.Our time-saving and cost-effective approach holds significant promise for aerospace applications,particularly in harsh aerodynamic heating environments.展开更多
Silver matrix composite brushes were fabricated by means of powder metallurgy, which included pressing at 300 MPa and then sintering for 1 h in pure H2 protective atmosphere at 700 ℃ and repressing at 500 MPa. Four k...Silver matrix composite brushes were fabricated by means of powder metallurgy, which included pressing at 300 MPa and then sintering for 1 h in pure H2 protective atmosphere at 700 ℃ and repressing at 500 MPa. Four kinds composites with different compositions were produced, and the mechanical properties and electrical wear performance were investigated. The results showed that the composite added with carbon nanotubes had a higher hardness and strength, a lower contact voltage drop and an excellent anti-wear property in electrical sliding wear, because of the reinforcement ability of carbon nanotubes. Adding graphite to the composite also decreased the wear loss and contact voltage drop, because graphite had an electrical current conducting ability which not only made the current pass the lubricating films easily but also eliminated and reduced the arc and spark effectively.展开更多
To protect carbon materials from oxidation,SiC coatings were prepared on carbon/carbon(C/C)composites and graphite by chemical vapor reaction.SEM and XRD analyses show that the coatings obtained are composed of SiC gr...To protect carbon materials from oxidation,SiC coatings were prepared on carbon/carbon(C/C)composites and graphite by chemical vapor reaction.SEM and XRD analyses show that the coatings obtained are composed of SiC grains and micro-crystals. The influence of different carbon substrates on oxidation behavior of coated samples was investigated,and then their oxidation mechanisms were studied.Oxidation test shows that the SiC coated graphite has a better oxidation resistance than SiC coated C/C composites at high temperatures(1 623 K and 1 823 K).In the oxidation process,the oxidation curves of SiC coated C/C composites are linear,while those of SiC coated graphite follow a quasi-parabolic manner.The oxidation mechanism of the former is controlled by chemical reaction while the latter is controlled by oxygen diffusion based on the experimental results.The variation of oxidation behavior and mechanism of SiC coatings on two kinds of carbon substrates are primarily contributed to their structure differences.展开更多
Uranium removal from aqueous solutions using environmentally friendly photocatalytic technology is a novel approach for resource recovery.Herein,carbon nitride/activated carbon composite materials(CN/AC)were investiga...Uranium removal from aqueous solutions using environmentally friendly photocatalytic technology is a novel approach for resource recovery.Herein,carbon nitride/activated carbon composite materials(CN/AC)were investigated for U(Ⅵ)reduction under visible light.An exceptional boost in photocatalytic activity was observed for CN/AC composites(up to 70 times over the conventional bulk g-C_(3)N_(4)).The strong interactive conjugatedπ-bond structure between g-C_(3)N_(4) and AC accelerated the migration of carriers and then prolonged the electron lifetime.CN/AC composites exhibited excellent compatibility with different water substrates and were resilience to a wide range of p H changes and abundant competitive anions/cations.Quenching experiments and electron microscopy characterization indicated that U(VI)was reduced by photogenerated electrons and deposited on the edge of CN/AC composites.The low-cost,high-performance carbon-based composite material proposed in this work is a potential candidate for the efficient treatment of radioactive wastewater.展开更多
Ir coatings were deposited on the heat-treated C/C composites and graphite by double glow plasma. Microstructure and morphology of the coating and substrate were observed by SEM and TEM. The effect of the surface trea...Ir coatings were deposited on the heat-treated C/C composites and graphite by double glow plasma. Microstructure and morphology of the coating and substrate were observed by SEM and TEM. The effect of the surface treatment for the carbon structural materials on the microstructure of the coating was investigated. Many large gaps and pores appeared on the surface of the substrates after heat treatment. The Ir coating did not fully covered on the surface of heat-treated C/C composite and graphite substrates because of the large gaps and pores on the surface of substrates. The Ir coating exhibited excellent ablation resistance at super-high temperature. After super-high temperature ablation, the coating kept the integrity, but the coating was weekly bonded to the substrates. Some microcracks and micropores appeared on the surface of as-ablated coating. The Ir coating would need thick enough to cover and fill the large microgaps and micropores on the surface of the heat-treated C/C and graphite substrates.展开更多
Carbon/carbon （C/C） composites were deposited with graphite-like carbon （GLC） coating, and then, Arg-Gly- Asp acid （RGD） peptides were successfully immobilized onto the functionalized GLC coating. GLC coating wa...Carbon/carbon （C/C） composites were deposited with graphite-like carbon （GLC） coating, and then, Arg-Gly- Asp acid （RGD） peptides were successfully immobilized onto the functionalized GLC coating. GLC coating was utilized to prevent carbon particles releasing and create a uniform surface condition for C/C composites. RGD peptides were utilized to improve biocompatibility of GLC coating. Surface chemical characterizations of functionalized GLC coating were detected by contact angle measurement, X-ray photoelectron spectroscopy and Raman spectra. Optical morphology of GLC coatings was observed by confocal laser scanning microscopy. In vitro biological performance was determined using samples seeded with MC3T3-E1 osteoblast-like cells and cultured for 1 week. Surface characterizations and morphological analysis indicated that C/C composites were covered by a dense and uniform GLC coating. Contact angle of GLC coating was reduced to 27.2° when it was functionalized by H202 oxidation at 40 ℃ for 1 h. In vitro cytological test showed that the RGD peptides immobilized GLC coating had a significant improvement in biocompatibility. It was suggested that RGD peptides provided GLC coating with a bioactive surface to improve cell adhesion and proliferation on C/C composites.展开更多
A new dual-composition catalyst based on Ni-Mo/MgO with high efficiency of producing carbon nanotubes （CNTs） from methane was reported recently. In the present article, with this type of catalyst, the impact of such...A new dual-composition catalyst based on Ni-Mo/MgO with high efficiency of producing carbon nanotubes （CNTs） from methane was reported recently. In the present article, with this type of catalyst, the impact of such experimental parameters as reaction temperature, reaction time, concentration of H2, flow rate ratio of CH4 to H2 on yield and graphitization were investigated, leading to the following optimal growth conditions： reaction time 60min, reaction temperature 900℃, CH4：H2 about 100：20mL/min, under which high-yield multi-walled CNTs bundles were synthesized. Raman measurement indicated that the as-synthesized product was well-graphitized, and the purity was estimated over 95% by TG-DSC analysis. In terms of the above results, an explanation of high-efficiency formation of CNTs bundles and the co-catalysis mechanism of Ni-Mo/MgO were suggested. 2007 Chinese Societv of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V.展开更多
The complete decomposition of formaldehyde(HCHO) at ambient temperature is the most potential strategy for HCHO elimination from indoor environment.Herein,extra low content of Pt nanoparticles(0.025 wt%)supported on w...The complete decomposition of formaldehyde(HCHO) at ambient temperature is the most potential strategy for HCHO elimination from indoor environment.Herein,extra low content of Pt nanoparticles(0.025 wt%)supported on water-solubility carbon nitride/ceria(Pt/gC_(3)N_(4)@CeO_(2)) was prepared for gaseous HCHO removal at ambient temperature in a simulated indoor environment.Fluorescent light(8 W) illumination could visibly boost the complete decomposition of HCHO into CO_(2) over Pt/gC_(3)N_(4)@CeO_(2).The cooperative effect in the distinct heterostructure and plenty of surface reactive oxygen species contribute primarily to the enhanced catalytic performance of Pt/g-C_(3)N_(4)@CeO_(2).Moreover,the possible mechanism of HCHO oxidation over Pt/g-C_(3)N_(4)@CeO_(2) assisted by the fluorescent light irradiation was proposed based on the physicochemical and optical characterization as well as the result of in situ diffuse reflectance infrared Fourier transform spectra.This work might shed some light on the potential application of the versatile catalysts for ambient-temperature catalytic decomposition of HCHO by making full use of the indoor energies.展开更多
Graphite-phase polymeric carbon nitride （CN） was reported to be a promising material in photoelectrochemical solar energy conversion. However, its high recombination rate of photogenerated carriers limits its potent...Graphite-phase polymeric carbon nitride （CN） was reported to be a promising material in photoelectrochemical solar energy conversion. However, its high recombination rate of photogenerated carriers limits its potential applications. In this article, a heterojunction of CN and sulfur-doped CN （CNS） was constructed through a solution-based processing way. Interestingly, it was observed that the photocatalytic hydrogen production of the as-prepared composite was 32.6 times higher than that of bulk carbon nitride and 2.3 times higher than that of the composites by conventional impregnating method. This study opens a new avenue to construct heterojunction of CN for large-scale industrial applications in environmental remediation.展开更多
基金This paper has obtained the support of the National Natural Science Foundation of China(No.51902039)High-Level Talents Innovation Support Plan of Dalian(No.2020RQ127)Scientific Research Project of Liaoning Provincial Department Education(No.LJKZ0722)。
文摘Two-dimensional carbon/carbon(2D C/C)composites are a special class of carbon/carbon composites,generally obtained by combining resin-impregnated carbon fiber clothes,which are then cured and carbonized.This study deals with the preparation of a protective coating for these materials.This coating,based on graphite,was prepared by the slurry method.The effect of graphite and phenolic resin powders with different weight ratios was examined.The results have shown that the coating slurry can fill the pores and cracks of the composite surface,thereby densifying the surface layer of the material.With the increase of the graphite powder/phenolic resin weight ratio,the coating density is enhanced while the coating surface flatness decreases;moreover,the protective ability of coating against erosion first increases(from 1:3 to 2:2)and then decreases(from 2:2 to 3:1).When the weight ratio is about 1:1,the coating for 2D C/C composites exhibits the best erosion resistance,which greatly aids these materials during gas quenching.In this case,the erosion rate is decreased by approximately 41.5%at the impact angle of 30°and 52.3%at normal impact,respectively.This can be attributed to the ability of the coating slurry to infiltrate into the substrate,thereby bonding the fibers together and increasing the compactness of the 2D C/C composites.
基金the Science and Technology Research Project of Education Department of Jilin Province(JJKH20220683KJ)Natural Science Foundation of Jilin Province(20220101093JC).
文摘Common strategies for catalytic graphitization of biochar into graphitic porous carbon(GPC)still face great challenges,such as the realization of simple procedures,energy conservation,and green processes.Controlling over the graphitization degree and pore structure of biochar is the key to its structural diversification.Herein,a clean and energy-efficient method is developed to synthesize adjustable graphitic degree and structure porosity GPC from rice husk-based carbon(RHC)at a relatively low temperature of 800–1000°C with environment-benign organometallic catalyst ethylenediaminetetraacetic acid ferric sodium salt(EDTA-iron)and the recovery ratio of catalyst is as high as 97%.The formed by the organic ligands of EDTA-iron facilitates the etching of RHC surface and pore by iron,resulting in highly graphitized and developed porous GPCs.The pore structure and graphitization degree of GPCs can be adjusted by altering the catalyst loading,temperature,and holding time.The catalyst EDTA-iron with a lower concentration mainly plays the role of etching,which promotes the formation of porous carbon with larger surface area(SBET=1187.2 m^(2)·g^(-1)).The catalyst with higher concentration mainly plays the role of catalyzing graphitization and promotes the obtaining of graphitic carbon with high graphitization degree(ID/IG=0.19).The mechanism of EDTA-iron catalyzed graphitization of RHC is explored by the comprehensive analysis of BET,XRD,Raman,TEM and TGA.This research not only provides an efficient method for the preparation of high-quality biomass-based graphite carbon,but also provides a feasible method for the preparation of biomass-based porous carbon.
基金Project(2006CB600903) supported by the National Basic Research Program of China
文摘The process of electrodepositing Fe-Cr2O3 composite coating on polyacrylonitrile （PAN）-based carbon fibers and its catalytic graphitization were studied. Carbon fibers with and without electrodeposited Fe-Cr2O3 composite coating were heat treated at different temperatures and the structural changes were characterized by XRD, Raman spectroscopy and SEM. The results indicate that Fe-Cr2O3 composite coating exhibits a significant catalytic effect on graphitization of carbon fibers at low temperatures. When the Fe-Cr2O3-coated carbon fibers were heat treated at 1 300℃ the interlayer spacing （doo2） and ratio of relative peak area （AD/AG） reach 3.364/k and 0.34, respectively. Whereas, the extent of graphitization of pristine carbon fibers is comparatively low even after heat treatment at 2 800℃ and the values of doo2 and AD/AG are 3.414 A and 0.68, respectively. The extent of graphitization of carbon fibers increases not only with the increase of the catalyst gross but also the Cr2O3 content in Fe-Cr2O3 coating. The catalytic effect of Fe-Cr2O3 composite coating accords with the dissolution-precipitation mechanism.
基金Project(2006CB600903) supported by the National Basic Research Program of China
文摘A novel carbon fiber pretreatment was proposed.Polyacrylonitrile(PAN)-based carbon fibers were first anodized in H3PO4 electrolyte to achieve an active surface,and then coated with Mo-B catalysts by immersed the carbon fibers in a uniformly dispersed Mo-B sol.The as-treated carbon fibers were then graphitized at 2 400 ℃ for 2 h.The structural changes were characterized by X-ray diffractometry(XRD),Raman spectroscopy,scanning electron microscopy(SEM) and high-resolution transmission electronic microscopy(HRTEM).The results show that much better graphitization can be achieved in the presence of Mo-B,with an interlayer spacing(d002) of 0.335 8 nm and a crystalline size(Lc) of 28 nm.
基金the National Natural Science Foundation of China (22178120)Guangdong Natural Science Funds for Distinguished Young Scholar (2017A030306022)Guangzhou Technology Project (202002030164)。
文摘By virtue of the flexibility and safety, polyethylene oxide(PEO) based electrolytes are regarded as an appealing candidate for all-solid-state lithium batteries. However, their application is limited by the poor ionic conductivity at room temperature, narrow electrochemical stability window and uncontrolled growth of lithium dendrite. To alleviate these problems, we introduce the ultrathin graphitic carbon nitride nanosheets(GCN) as advanced nanofillers into PEO based electrolytes(GCN-CPE). Benefiting from the high surface area and abundant surface N-active sites of GCN, the GCN-CPE displays decreased crystallinity and enhanced ionic conductivity. Meanwhile, Fourier transform infrared and chronoamperometry studies indicate that GCN can facilitate Li+migration in the composite electrolyte. Additionally, the GCN-CPE displays an extended electrochemical window compared with PEO based electrolytes. As a result, Li symmetric battery assembled with GCN-CPE shows a stable Li plating/stripping cycling performance, and the all-solid-state Li/LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM622) batteries using GCN-CPE exhibit satisfactory cyclability and rate capability in a voltage range of 3-4.2 V at 30 ℃.
基金Funded by the National Natural Science Foundation of China(No.50878170 and No. 10672128)
文摘The electrical conductivity and piezoresistivity of carbon fiber graphite cement-matrix composites（CFGCC） with carbon fiber content（1% by the weight of cement）,graphite powder contents （0%-50% by the weight of cement） and CCCW（cementitious capillary crystalline waterproofing materials,4% by the weight of cement） were studied.The experimental results showed that the relationship between the resistivity of CFGCC and the concentration of graphite powders had typical features of percolation phenomena.The percolation threshold was about 20%.A clear piezoresistive effect was observed in CFGCC with 1wt% of carbon fibers,20wt% or 30wt% of graphite powders under uniaxial compressive tests,indicating that this type of smart composites was a promising candidate for strain sensing.The measured gage factor （defined as the fractional change in resistance per unit strain） of CFGCC with graphite content of 20wt% and 30wt% were 37 and 22,respectively.With the addition of CCCW,the mechanical properties of CFGCC were improved,which benefited CFGCC piezoresistivity of stability.
基金Projects(51221001,50972121)supported by the National Natural Science Foundation of ChinaProject(B08040)supported by the Introducing Talents of Discipline to Universities,ChinaProject(11-BZ-2012)supported by the Research Fund of the State Key Laboratory of Solidification Processing(NWPU),China
文摘Short carbon fiber felts with an initial porosity of 89.5% were deposited by isobaric, isothermal chemical vapor infiltration using natural gas as carbon source. The bulk density of the deposited carbon/carbon （C/C） composites was 1.89 g/cm3 after depositing for 150 h. The microstructure and mechanical properties of the C/C composites were studied by polarized light microscopy, X-ray diffraction, scanning electron microscopy and three-point bending test. The results reveal that high textured pyrolytic carbon is deposited as the matrix of the composites, whose crystalline thickness and graphitization degree highly increase after heat treatment. A distinct decrease of the flexural strength and modulus accompanied by the increase of the toughness of the C/C composites is found to be correlated with the structural changes in the composites during the heat treatment process.
文摘Three kinds of composite alumina refractories were prepared with tabular alumina （3-1 and 1-0 mm） as aggregates,tabular alumina powder,α-Al2 O3 micropowder,and Si powder as matrix,adding 3 mass％ hexagonal boron nitride （h-BN）,3 mass％ flake graphite and 10 mass％ flake graphite,respectively.Cold physical properties,hot modulus of rupture,oxidation resistance,thermal shock resistance and slag corrosion resistance of the specimens were compared.The results show that：（1） physical properties and hot modulus of rupture of Al2 O3-h-BN refractories are slightly different from those of low carbon Al2 O3-C refractories,but better than those of traditional Al2 O3-C refractories with 10 mass％ graphite ; （2） Al2 O3-h-BN refractories have better thermal shock resistance and oxidation resistance than the carbon containing refractories,while similar slag resistance with low carbon Al2 O3-C refractories ; （3） h-BN can replace flake graphite as a starting material for the preparation of composite alumina refractories,considering the overall properties of the material.
基金Project(66167044) supported by the Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing, ChinaProject(66062021) supported by the Science and Technology Activity for Chinese Homecoming Fellow Abroad, Program of Beijing Key Laboratory for Sensor
文摘A general, simple and economic synthetic method for synthesizing carbon nanofibers was presented. In the method, ethanol was employed as carbon source; metal salts such as nickel nitrate, ferric nitrate and ferric chloride were used as catalyst precursor respectively; copper plate was employed as the support material. A lot of products were obtained by catalytic combustion deposition of ethanol vapor. Then the as-prepared carbon nanofibers were characterized by field-emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, energy dispersion X-ray spectroscopy and selected-area electron diffractometry. By analyzing the results of characterization, the conclusions are as follows: 1) the large catalyst particles tend to form large-diameter CNFs, small catalyst particles are inclinable to form small-diameter CNFs; 2) the morphology of the catalyst can affect the final morphology of the CNFs. Moreover, the possible growth mechanisms were proposed and the degree of graphitization of samples was estimated by Raman spectroscopy characterization.
基金supported by the Major Program of National Natural Science Foundation of China(No.52293372).
文摘High-density carbon/carbon(C/C)composite plays a critical role in the aerospace industry owing to excellent mechanical properties and resistance to ablation.However,traditional manufacturing relies on pitch precursor and hot isostatic pressure impregnation and carbonization(HIPIC)technology,which is time-consuming and expensive.In this study,we report an innovative method utilizing polyarylacetylene(PAA)resin and ultra-high pressure impregnation and carbonization(UHPIC)technology.The extremely high char yield of PAA resin(85 wt.%)and high isotropic pressure of UHPIC(over 200 MPa)promote the densification of the composite.As a result,we achieve a high-density(1.90 g/cm^(3))C/C composite with a high degree of graphitization(81%).This composite exhibits impressive properties,including flexural strength of 146 MPa,compressive strength of 187 MPa,and thermal conductivity of 147 W/(m K).When exposed to oxyacetylene flame at 3000 K for 100 s,it displays minimal linear ablation,with a rate of 1.27×10^(-2)mm/s.This study demonstrates the exceptional graphitizable characteristic of PAA resin,setting it apart from conventional resins.Our time-saving and cost-effective approach holds significant promise for aerospace applications,particularly in harsh aerodynamic heating environments.
基金supported by National Natural Science Foundation of China(No50741003)Key Project of Science and Technology of Ministry of Education of China (No107066)Anhui Provincial Natural Science Foundation(No070414181)
文摘Silver matrix composite brushes were fabricated by means of powder metallurgy, which included pressing at 300 MPa and then sintering for 1 h in pure H2 protective atmosphere at 700 ℃ and repressing at 500 MPa. Four kinds composites with different compositions were produced, and the mechanical properties and electrical wear performance were investigated. The results showed that the composite added with carbon nanotubes had a higher hardness and strength, a lower contact voltage drop and an excellent anti-wear property in electrical sliding wear, because of the reinforcement ability of carbon nanotubes. Adding graphite to the composite also decreased the wear loss and contact voltage drop, because graphite had an electrical current conducting ability which not only made the current pass the lubricating films easily but also eliminated and reduced the arc and spark effectively.
基金Project(2006CB600901)supported by the National Basic Research Program of ChinaProjects(50772134,50802115)supported by the National Natural Science Foundation of China
文摘To protect carbon materials from oxidation,SiC coatings were prepared on carbon/carbon(C/C)composites and graphite by chemical vapor reaction.SEM and XRD analyses show that the coatings obtained are composed of SiC grains and micro-crystals. The influence of different carbon substrates on oxidation behavior of coated samples was investigated,and then their oxidation mechanisms were studied.Oxidation test shows that the SiC coated graphite has a better oxidation resistance than SiC coated C/C composites at high temperatures(1 623 K and 1 823 K).In the oxidation process,the oxidation curves of SiC coated C/C composites are linear,while those of SiC coated graphite follow a quasi-parabolic manner.The oxidation mechanism of the former is controlled by chemical reaction while the latter is controlled by oxygen diffusion based on the experimental results.The variation of oxidation behavior and mechanism of SiC coatings on two kinds of carbon substrates are primarily contributed to their structure differences.
基金The financial supports from National Natural Science Foundation of China(No.22176077)Natural Science Foundation of Gansu Province,China(Nos.20JR10RA615,21ZD8JA006)fundamental research funds for the central universities(No.lzujbky-2021-sp29)are acknowledged。
文摘Uranium removal from aqueous solutions using environmentally friendly photocatalytic technology is a novel approach for resource recovery.Herein,carbon nitride/activated carbon composite materials(CN/AC)were investigated for U(Ⅵ)reduction under visible light.An exceptional boost in photocatalytic activity was observed for CN/AC composites(up to 70 times over the conventional bulk g-C_(3)N_(4)).The strong interactive conjugatedπ-bond structure between g-C_(3)N_(4) and AC accelerated the migration of carriers and then prolonged the electron lifetime.CN/AC composites exhibited excellent compatibility with different water substrates and were resilience to a wide range of p H changes and abundant competitive anions/cations.Quenching experiments and electron microscopy characterization indicated that U(VI)was reduced by photogenerated electrons and deposited on the edge of CN/AC composites.The low-cost,high-performance carbon-based composite material proposed in this work is a potential candidate for the efficient treatment of radioactive wastewater.
基金Funded by the National Natural Science Foundation of China (50872055/ E020703)the Funding for Outstanding Doctoral Dissertation in NUAA (BCXJ11-09)+1 种基金the Fundamental Research Funds for the Central Universitiesthe Jiangsu Innovation Program for Graduate Education(CXLX11_0207)
文摘Ir coatings were deposited on the heat-treated C/C composites and graphite by double glow plasma. Microstructure and morphology of the coating and substrate were observed by SEM and TEM. The effect of the surface treatment for the carbon structural materials on the microstructure of the coating was investigated. Many large gaps and pores appeared on the surface of the substrates after heat treatment. The Ir coating did not fully covered on the surface of heat-treated C/C composite and graphite substrates because of the large gaps and pores on the surface of substrates. The Ir coating exhibited excellent ablation resistance at super-high temperature. After super-high temperature ablation, the coating kept the integrity, but the coating was weekly bonded to the substrates. Some microcracks and micropores appeared on the surface of as-ablated coating. The Ir coating would need thick enough to cover and fill the large microgaps and micropores on the surface of the heat-treated C/C and graphite substrates.
基金supported by the National Natural Science Foundation of China under Grant Nos.51202194 and 51221001the Programme of Introducing Talents of Discipline to Universities(‘‘111’’project of China)under Grant No.B08040
文摘Carbon/carbon （C/C） composites were deposited with graphite-like carbon （GLC） coating, and then, Arg-Gly- Asp acid （RGD） peptides were successfully immobilized onto the functionalized GLC coating. GLC coating was utilized to prevent carbon particles releasing and create a uniform surface condition for C/C composites. RGD peptides were utilized to improve biocompatibility of GLC coating. Surface chemical characterizations of functionalized GLC coating were detected by contact angle measurement, X-ray photoelectron spectroscopy and Raman spectra. Optical morphology of GLC coatings was observed by confocal laser scanning microscopy. In vitro biological performance was determined using samples seeded with MC3T3-E1 osteoblast-like cells and cultured for 1 week. Surface characterizations and morphological analysis indicated that C/C composites were covered by a dense and uniform GLC coating. Contact angle of GLC coating was reduced to 27.2° when it was functionalized by H202 oxidation at 40 ℃ for 1 h. In vitro cytological test showed that the RGD peptides immobilized GLC coating had a significant improvement in biocompatibility. It was suggested that RGD peptides provided GLC coating with a bioactive surface to improve cell adhesion and proliferation on C/C composites.
基金This work was supported financially by the National Natural Science Foundation of China （No. 20506010） Beijing Novel Program （2006A74）Natural Science Fund of Shanxi Province （No. 20063004）.
文摘A new dual-composition catalyst based on Ni-Mo/MgO with high efficiency of producing carbon nanotubes （CNTs） from methane was reported recently. In the present article, with this type of catalyst, the impact of such experimental parameters as reaction temperature, reaction time, concentration of H2, flow rate ratio of CH4 to H2 on yield and graphitization were investigated, leading to the following optimal growth conditions： reaction time 60min, reaction temperature 900℃, CH4：H2 about 100：20mL/min, under which high-yield multi-walled CNTs bundles were synthesized. Raman measurement indicated that the as-synthesized product was well-graphitized, and the purity was estimated over 95% by TG-DSC analysis. In terms of the above results, an explanation of high-efficiency formation of CNTs bundles and the co-catalysis mechanism of Ni-Mo/MgO were suggested. 2007 Chinese Societv of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V.
基金financially supported by the National Natural Science Foundation of China(No.21871111)the Excellent Youth Foundation of Hubei Province of China(No.2019CFA078)。
文摘The complete decomposition of formaldehyde(HCHO) at ambient temperature is the most potential strategy for HCHO elimination from indoor environment.Herein,extra low content of Pt nanoparticles(0.025 wt%)supported on water-solubility carbon nitride/ceria(Pt/gC_(3)N_(4)@CeO_(2)) was prepared for gaseous HCHO removal at ambient temperature in a simulated indoor environment.Fluorescent light(8 W) illumination could visibly boost the complete decomposition of HCHO into CO_(2) over Pt/gC_(3)N_(4)@CeO_(2).The cooperative effect in the distinct heterostructure and plenty of surface reactive oxygen species contribute primarily to the enhanced catalytic performance of Pt/g-C_(3)N_(4)@CeO_(2).Moreover,the possible mechanism of HCHO oxidation over Pt/g-C_(3)N_(4)@CeO_(2) assisted by the fluorescent light irradiation was proposed based on the physicochemical and optical characterization as well as the result of in situ diffuse reflectance infrared Fourier transform spectra.This work might shed some light on the potential application of the versatile catalysts for ambient-temperature catalytic decomposition of HCHO by making full use of the indoor energies.
基金financially supported in part by the National Natural Science Foundation of China(No. 21305065)Natural Science Foundation of Jiangsu Province(Nos. BK20160028, BK20170084)+1 种基金the Open Funds of the State Key Laboratory of Electroanalytical Chemistry (No. SKLEAC201703)the Fundamental Research Funds for the Central Universities
文摘Graphite-phase polymeric carbon nitride （CN） was reported to be a promising material in photoelectrochemical solar energy conversion. However, its high recombination rate of photogenerated carriers limits its potential applications. In this article, a heterojunction of CN and sulfur-doped CN （CNS） was constructed through a solution-based processing way. Interestingly, it was observed that the photocatalytic hydrogen production of the as-prepared composite was 32.6 times higher than that of bulk carbon nitride and 2.3 times higher than that of the composites by conventional impregnating method. This study opens a new avenue to construct heterojunction of CN for large-scale industrial applications in environmental remediation.
