Felt base carbon/carbon composites fabricated by super-high pressure impregnation carbonization process (SPIC) were heat treated at high temperature 2773K. The oxidation properties of felt base carbon/carbon composite...Felt base carbon/carbon composites fabricated by super-high pressure impregnation carbonization process (SPIC) were heat treated at high temperature 2773K. The oxidation properties of felt base carbon/carbon composites were investigated at different temperatures (773-1173K), and the microstructures of carbon/carbon composites were studied by SEM and X-ray diffraction. The experimental results showed that the inter-laminar distance of (002) plane (d002) deceased while the microcrystalline stack height (Lc) increased. The oxidation rate of felt base carbon/carbon composites was invari-able at certain temperatures. The oxidation mechanism of carbon/carbon composites changed remarkably at the oxidation temperature 973K. At the initial oxidation stage of carbon/carbon composites, carbon matrix was oxidized much more rapidly than carbon felt.展开更多
Nitrogen removal from domestic sewage is usually limited by insufficient carbon source and electron donor.An economical solid carbon source was developed by composition of polyvinyl alcohol,sodium alginate,and corncob...Nitrogen removal from domestic sewage is usually limited by insufficient carbon source and electron donor.An economical solid carbon source was developed by composition of polyvinyl alcohol,sodium alginate,and corncob,which was utilized as external carbon source in the anaerobic anoxic oxic(AAO)-biofilter for the treatment of low carbon-to-nitrogen ratio domestic sewage,and the nitrogen removal was remarkably improved from 63.2%to 96.5%.Furthermore,the effluent chemical oxygen demand maintained at 35 mg/L or even lower,and the total nitrogenwas reduced to less than 2mg/L.Metagenomic analysis demonstrated that the microbial communities responsible for potential denitrification and organic matter degradation in both AAO and the biofilter reactors were mainly composed of Proteobacteria and Bacteroides,respectively.The solid carbon source addition resulted in relatively high abundance of functional enzymes responsible for NO_(3)^(−)-N to NO_(2)^(−)-N con-version in both AAO and the biofilter reactors,thus enabled stable reaction.The carbon source addition during glycolysis primarily led to the increase of genes associated with the metabolic conversion of fructose 1.6P2 to glycerol-3P The reactor maintained high abun-dance of genes related to the tricarboxylic acid cycle,and then guaranteed efficient carbon metabolism.The results indicate that the composite carbon source is feasible for denitri-fication enhancement of AAO-biofilter,which contribute to the theoretical foundation for practical nitrogen removal application.展开更多
Carbon Carbon(C/C)composites in thermal-protection system are exposed to severe thermochemical ablation and mechanical erosion,and their thermal-protection performance is of vital importance to the structural safety a...Carbon Carbon(C/C)composites in thermal-protection system are exposed to severe thermochemical ablation and mechanical erosion,and their thermal-protection performance is of vital importance to the structural safety and flight status of hypersonic vehicles.We numerically analyzes the mesoscopic ablation-erosion of C/C Composites with Inclined Fibers(CCIF).First,a thermochemical ablation model describing the reaction-diffusion coupled problem of C/C composites on mesoscale is employed to analyze ablative process,and the corresponding surface ablation morphology is obtained.Then,the ablation morphology of CCIF is taken as the geometrical model for mechanical erosion analysis,and their damage and failure behavior under high-speed airflow shear is analyzed by using progressive damage method.Moreover,the effects of fiber inclined angle and airflow direction on the mechanical erosion of CCIF are investigated,and the ablationerosion behavior is analyzed and discussed.The results show that the failure modes of mechanical erosion in inner and edge regions are obviously different,showing granular and block erosion phenomena respectively.The mechanical erosion of CCIF in the direction of reverse flow is easier than that in the direction of forward flow.These results can provide a theoretical basis for the design and optimization of thermal protection system materials.展开更多
Insufficient interfacial activity and poor wettability between fibers and matrix are the two main factors limiting the improvement of mechanical properties of Carbon Fiber Reinforced Plastics(CFRP).Owl feathers are kn...Insufficient interfacial activity and poor wettability between fibers and matrix are the two main factors limiting the improvement of mechanical properties of Carbon Fiber Reinforced Plastics(CFRP).Owl feathers are known for their unique compact structure;they are not only lightweight but also strong.In this study,an in-depth look at owl feathers was made and it found that owl feathers not only have the macro branches structure between feather shafts and branches but also have fine feather structures on the branches.The presence of these fine feather structures increases the specific surface area of the plume branches and allows neighboring plume branches to hook up with each other,forming an effective mechanical interlocking structure.These structures bring owl feathers excellent mechanical properties.Inspired by the natural structure of owl feathers,a weaving technique and a sizing process were combined to prepare bionic Carbon Fiber(CF)fabrics and then to fabricate the bionic CFRP with structural characteristics similar to owl feathers.To evaluate the effect of the fine feather structure on the mechanical properties of CFRP,a mechanical property study on CFRP with and without the fine feather imitation structure were conducted.The experimental results show that the introduction of the fine feather branch structure enhance the mechanical properties of CFRP significantly.Specifically,the tensile strength of the composites increased by 6.42%and 13.06%and the flexural strength increased by 8.02%and 16.87%in the 0°and 90°sample directions,respectively.These results provide a new design idea for the improvement of the mechanical properties of the CFRP,promoting the application of CFRP in engineering fields,such as automotive transportation,rail transit,aerospace,and construction.展开更多
The advancement of planar micro-supercapacitors(PMSCs)for micro-electromechanical systems(MEMS)has been significantly hindered by the challenge of achieving high energy and power densities.This study addresses this is...The advancement of planar micro-supercapacitors(PMSCs)for micro-electromechanical systems(MEMS)has been significantly hindered by the challenge of achieving high energy and power densities.This study addresses this issue by leveraging screen-printing technology to fabricate high-performance PMSCs using innovative composite ink.The ink,a synergistic blend of few-layer graphene(Gt),carbon black(CB),and NiCo_(2)O_(4),was meticulously mixed to form a conductive and robust coating that enhanced the capacitive performance of the PMSCs.The optimized ink formulation and printing process result in a micro-supercapacitor with an exceptional areal capacitance of 18.95 mF/cm^(2)and an areal energy density of 2.63μW·h/cm^(2)at a current density of 0.05 mA/cm^(2),along with an areal power density of 0.025 mW/cm^(2).The devices demonstrated impressive durability with a capacitance retention rate of 94.7%after a stringent 20000-cycle test,demonstrating their potential for long-term applications.Moreover,the PMSCs displayed excellent mechanical flexibility,with a capacitance decrease of only 3.43%after 5000 bending cycles,highlighting their suitability for flexible electronic devices.The ease of integrating these PMSCs into series and parallel configurations for customized power further underscores their practicality for integrated power supply solutions in various technologies.展开更多
Solar interfacial evaporation(SIE),is currently one of the most potential water supply technologies in the remote,insular,and disaster-stricken areas.However,the existence of volatile organic compounds(VOCs)in water d...Solar interfacial evaporation(SIE),is currently one of the most potential water supply technologies in the remote,insular,and disaster-stricken areas.However,the existence of volatile organic compounds(VOCs)in water deteriorates the distillate quality,threatening human health.Herein,we constructed a carbonbased bimetallic(C/FeCo)photothermal membrane by electrospinning technique.Results illustrated that the membrane can catalytically degrade VOCs during SIE with persulfate(PDS)mediation.PDS,as well as phenol,was mainly reacted on the interface of the photothermal membrane instead of in the bulk solution.The interception efficiency of phenol achieved nearly 100%using the C/FeCo membrane during SIE.Hydroxyl radical(•OH),sulfate radical(SO_(4)•−),superoxide radical(O_(2)•−),and singlet oxygen(^(1)O_(2))were identified as the main active substances to degrade VOCs.We also conducted SIE experiments using actual river water to evaluate the practical performance of the C/FeCo membrane.This work holds the promise of VOCs interception during SIE and enlarges the application of solar distillation in water/wastewater treatment.展开更多
Activated carbon(AC)is considered to be an excellent adsorbent due to its high specific surface area and various functional groups.AC powders are available in sizes ranging from 44 to 150 μm.Its particle size prevent...Activated carbon(AC)is considered to be an excellent adsorbent due to its high specific surface area and various functional groups.AC powders are available in sizes ranging from 44 to 150 μm.Its particle size prevent its separation from the soil.Therefore,when AC powder is applied to Cd-contaminated soil,it only reduces the bioavailability of Cd and Cd is not necessarily removed but semi-immobilized.Recovery of adsorbent materials from the soil is therefore a preferred soil remediation method.In order to achieve the separation of Cd from soil and the recovery and reuse of AC,a batch of phenolic resin(PR)-carboxymethyl cellulose(CMC)-activated carbon(AC)composite(PCC-800)with uniform particle diameter(diameter 0.8 mm)and high compressive strength was prepared.PCC-800 composites were made of PR/CMC/AC calcined at 800℃ in a certain ratio.The Barrett-Joyner-Halender results showed that the PCC-800 spheres own a mesoporous structure.The compressive strength of PCC-800 pellets was 20.6 N.After first adsorption cycle,total Cd in the soil decreased by 52.18%while bioavailable Cd decreased to 25.68%of the original soil.After three cycles,the recovery rates of PCC-800 were 90.37%and the adsorption regeneration was 72.73%.The PCC-800 immobilized Cd by adsorption,precipitation and complexation reaction.This study demonstrates the potential for developing adsorbents that are both easily separable from soil and highly effective in adsorption.展开更多
Herein,nanosized Hf_(6)Ta_(2)O_(17) encapsulated graphite flakes were firstly constructed using the sol-gel method,then deposited on the surface of carbon/carbon(C/C)composites by plasma spraying technique to prolong ...Herein,nanosized Hf_(6)Ta_(2)O_(17) encapsulated graphite flakes were firstly constructed using the sol-gel method,then deposited on the surface of carbon/carbon(C/C)composites by plasma spraying technique to prolong their service span in critical environments.Nanoindentation results affirmed the active influ-ence of graphite flakes on elevating the toughness of the Hf_(6)Ta_(2)O_(17) coating.Besides,after being exposed to the oxyacetylene torch with a peak temperature of about 2000℃,the sample achieved near zero ab-lation(0.06 mg/s),meanwhile its porosity and mass ablation rate showed 39.5%and 60.0%reduction when compared to pure Hf_(6)Ta_(2)O_(17) sample.During exposure,the external Hf_(6)Ta_(2)O_(17) served as an oxy-gen barrier for internal graphite flakes,inversely internal graphite flakes provided a“pinning”effect on external Hf_(6)Ta_(2)O_(17),which accounted for its exceptional ablation performance.This work offers a new insight into the design of surface modification of C/C composites and other high-temperature structural materials.展开更多
Silicon-based anode is a promising candidate for all-solid-state batteries(ASSBs).However,it must be further improved because of its tremendous volume change.In this study,various interface treatment strategies for Si...Silicon-based anode is a promising candidate for all-solid-state batteries(ASSBs).However,it must be further improved because of its tremendous volume change.In this study,various interface treatment strategies for SiO/carbon composite anodes in ASSBs were investigated using a multiphysics modeling framework.By evaluating the effects of active(carbon)and inactive coating materials,as well as the geometric and mechanical parameters,this research provides critical insights into optimizing their electrochemical performance and mechanical stability.Computational results indicate that carbon coatings can greatly enhance lithiation kinetics by regulating the interfacial electrochemical potential gradients,reducing the residual lithium concentration,and homogenizing the lithium-ion distribution compared with uncoated or inactive-coated configurations.In addition,thinner carbon coatings further improve capacity retention and stress management by balancing shorter lithium diffusion pathways with mitigated interfacial stress accumulation.Despite their ability to mechanically stabilize the anode,inactive coatings exhibit tradeoffs between lithium transport kinetics and stress modulation,with optimal performance achieved at lower Young’s moduli.Mechanical analyses highlight distinct failure mechanisms at the anode–electrolyte(shear driven)and particle-coating(tension driven)interfaces,emphasizing the need for tailored adhesion strategies.These findings provide actionable guidelines for designing robust SiO-based anodes,emphasizing the interplay among electrochemical efficiency,stress regulation,and interfacial durability in ASSBs.展开更多
The automobile industry is the first to form a typical representative of the global industry in modern industry,with the increase of the national emphasis on the environment,the automobile industry was regarded as an ...The automobile industry is the first to form a typical representative of the global industry in modern industry,with the increase of the national emphasis on the environment,the automobile industry was regarded as an important energy consumption and one of the sources of environmental pollution,the policy of energy conservation and emission reduction requirements for the automobile industry are becoming stricter over the years,energy conservation and emission reduction has becomes the main direction of product optimization in the automobile industry in recent years.Due of a series of excellent properties such as light weight and high strength,composite materials have become the main material for the development of lightweight vehicles.With the development of material technology and the update and iteration of manufacturing technology,composite materials are currently popular being adopted in the automotive field.展开更多
A mesh-free method is presented to investigate the static bending properties of functionally graded carbon nanotube-reinforced composite(FG-CNTRC)plates.The curvature of the plate is directly interpolated with the nod...A mesh-free method is presented to investigate the static bending properties of functionally graded carbon nanotube-reinforced composite(FG-CNTRC)plates.The curvature of the plate is directly interpolated with the nodal deflections due to the higher-order continuity property of the moving leastsquares approximation,establishing a mesh-free computational scheme where the nodal deflections are the only unknowns.The convergence and efficiency of the proposed method are studied based on a homogeneous square plate.The FG-CNTRC plates are modeled with continuously varying Young’s moduli along the thickness direction according to the volume fraction of the carbon nanotubes(CNTs).Detailed studies have been conducted on the effects of different boundary conditions,CNT volume fractions,geometric shapes,and width-to-thickness ratios on bending behavior.CNT efficiency parameters are introduced to account for load transfer between the nanotubes and the matrix,treating the nanocomposites as orthotropic materials.However,in the actual structure,arranging the CNTs in the desired direction is more difficult compared to other fibers.Therefore,in the present study,CNTs in the composites are considered to be arranged randomly,resulting in the composite properties being treated as isotropic.The study includes second-order derivatives of deflections,and the finite element method typically requires C1 continuity for interpolation,which introduces challenges in building elements and constructing interpolation functions.The distinct advantage of the mesh-free method is that it requires only C0 weight functions.A mesh-free computational scheme based on moving leastsquares approximations for composite plates using Kirchhoffplate theory is established.Bending analyses of homogeneous and FG-CNTRC plates are conducted using the proposed method.Aspects such as boundary conditions,CNT volume fractions,geometric shapes,and width-to-thickness ratios are also discussed.Regular node arrangements and background meshes are adopted in the present study.Results are computed using different scalar parameters and numbers of nodes.Convergence properties for the central deflection of isotropic plates are analyzed in terms of the number of nodes and different scalar parameters.The normalized central deflection is defined and examined under various boundary conditions.展开更多
Carbon fiber reinforced carbon aerogel matrix(C/CA)composites have been considered as attractive candidates for thermal protection system owing to their excellent thermal insulation and superior thermal stability.Howe...Carbon fiber reinforced carbon aerogel matrix(C/CA)composites have been considered as attractive candidates for thermal protection system owing to their excellent thermal insulation and superior thermal stability.However,they still suffer from challenges with insufficient oxidation resistance in practical application.Herein,a series of novel SiBCN-modified C/CA are developed for the first time through matrix modification by introducing precursors with different molecular weights in order to control residual stress.Resultantly,the C/CA-SiBCN composites derived from a high molecular weight precursor show the large residual tensile stress even with the low ceramic contents of 10%(mass fraction)due to the severe shrinkage mismatch during pyrolysis caused by the large SiBCN clusters and their inhomogeneous distribution,as well as the mismatched coefficients of thermal expansion.Comparatively,the composites derived from a low molecular weight precursor have the small carbon-ceramic particles with uniform distribution even though the ceramic content is up to 30%,thus resulting in the favorable residual compressive stress.Accordingly,the C/CA-SiBCN containing a 30%ceramic content demonstrates the significantly enhanced performance with low residual compressive stress of 0.31 GPa,52%mechanical improvement and reduction in oxidation rate by 39.21%-60.35%at 800-1100℃compared to the original C/CA.This work offers a new avenue for enhancing oxidation resistance of C/CA applied as thermal insulators to cope with the harsh operating environments.展开更多
Carbon fiber-reinforced composites(CFRCs)have a wide range of applications in the aerospace,automotive,and energy sectors.A higher specific strength-to-weight ratio is desired in high-performance applications.The fail...Carbon fiber-reinforced composites(CFRCs)have a wide range of applications in the aerospace,automotive,and energy sectors.A higher specific strength-to-weight ratio is desired in high-performance applications.The failure mechanism of CFRCs involves multiscale phenomena,such as failure that can occur at the matrix,fibers,interface,layers,lamina,and laminates.When an impactor hits the CFRCs,the design involves analyzing each of these stages to prevent failure and optimize the properties of CFRCs under various loading conditions.A numerical model was employed to predict the fracture toughness of CFRCs with varying weight fractions and orientations.Finite Element Analysis(FEA)was conducted at the fiber level on a micrometer scale for the CFRCs against an impact loading.Epoxy composite samples at the coupon level were prepared using the hand layup technique with carbon fibers laid at three different angles,i.e.,longitudinal,transverse,and angular orientations.Samples with five different weight percentages of carbon fibers were prepared and investigated.An Izod impact tester was used to fracture the samples and characterize the energy absorption.The fractured surfaces were observed with a scanning electron microscope(SEM).The numerical and experimental results show that crack propagation is inhibited at higher loading fractions at an angular orientation by creating obstacles for the crack to propagate and arresting the dislocation motion.The fractography analysis through a scanning electron microscope exhibits how the angular orientations of the fibers are reoriented after fracture to prevent further crack propagation.展开更多
In thermal protection structures,controlling and optimizing the surface roughness of carbon/phenolic(C/Ph)composites can effectively improve thermal protection performance and ensure the safe operation of carriers in ...In thermal protection structures,controlling and optimizing the surface roughness of carbon/phenolic(C/Ph)composites can effectively improve thermal protection performance and ensure the safe operation of carriers in high-temperature environments.This paper introduces a machine learning(ML)framework to forecast the surface roughness of carbon-phenolic composites under various thermal conditions by employing an ML algorithm derived from historical experimental datasets.Firstly,ablation experiments and collection of surface roughness height data of C/Ph composites under different thermal environments were conducted in an electric arc wind tunnel.Then,an ML model based on Ridge regression is developed for surface roughness prediction.The model involves incorporating feature engineering to choose the most concise and pertinent features,as well as developing an ML model.The ML model considers thermal environment parameters and feature screened by feature engineering as inputs,and predicts the surface height as the output.The results demonstrate that the suggested ML framework effectively anticipates the surface shape and associated surface roughness parameters in various heat flow conditions.Compared with the conventional 3D confocal microscope scanning,the method can obtain the surface topography information of the same area in a much shorter time,thus significantly saving time and cost.展开更多
The icing characteristics of supercooled large droplet(SLD)impacting carbon fiber-reinforced composites(CFRCs)remain poorly understood,hindering the enhancement of ice protection capabilities and the certification of ...The icing characteristics of supercooled large droplet(SLD)impacting carbon fiber-reinforced composites(CFRCs)remain poorly understood,hindering the enhancement of ice protection capabilities and the certification of ice-accreted composite aircraft.The paper systematically investigates the effects of the supercooling degree,the surface temperature,and the impact velocity on the ice accretion behavior of SLDs impacting carbon fiber-reinforced epoxy composite surfaces.To address the ice-prone nature of CFRCs,nanoparticle-modified anti-icing coatings are developed,and the icing characteristics of SLD-impacted modified carbon fiber-reinforced epoxy composite surfaces are analyzed.Results demonstrate that surface-modified carbon fiber-reinforced epoxy composite exhibits significantly delayed ice formation.Under conditions of droplet temperature(−15℃)and surface temperature(−18℃),the icing time of hydrophobic-modified CFRCs was delayed by over 1100 ms,representing a 5.4-fold improvement compared to the unmodified carbon fiber-reinforced epoxy composite.展开更多
3D printing has emerged as an advanced manufacturing technique for carbon fiber reinforced composites and relevant structures that endure significant dynamic loads in engineering applications.The dynamic behavior of t...3D printing has emerged as an advanced manufacturing technique for carbon fiber reinforced composites and relevant structures that endure significant dynamic loads in engineering applications.The dynamic behavior of these materials,primarily influenced by the dynamic fiber pullout interface strength necessitates investigation into the rate-dependent fiber/matrix interfacial strength.This study modifies a Hopkinson tension bar to conduct dynamic pullout tests on a single fiber bundle,utilizing a low-impedance bar and an in-situ calibrated semiconductor strain gauge to capture weak stress signals.Stress equilibrium analyses are performed to validate the transient dynamic loading on single fiber bundle specimens.The results reveal that the fiber/matrix interfacial strength is rate-dependent,increasing with the loading rate,while remaining unaffected by the embedded length.Fracture microstructural analyses show minimal fiber pullout due to high interfacial stresses induced by longer embedded lengths.Lastly,suggestions are made for the efficient design of fiber pullout experiments.展开更多
The poor surface antibacterial properties are one of the important factors limiting the application of Carbon Fibers Reinforced Polyetheretherketone (CFR-P) composites as artificial bone replace materials. Some of the...The poor surface antibacterial properties are one of the important factors limiting the application of Carbon Fibers Reinforced Polyetheretherketone (CFR-P) composites as artificial bone replace materials. Some of the Two-Dimensional (2D) nanomaterials with unique lamellar structures and biological properties have been demonstrated to have excellent antibacterial properties. Antibacterial properties can be improved by feasible chemical strategies for preparing 2D nanomaterials coating on the surface of CFR-P. In this work, Black Phosphorus (BP) coating was prepared on the originally chemically inert CFR-P surface based on wet chemical pretreatment. The physical and chemical properties, including surface microstructure, chemical composition and state, roughness and hydrophilicity were characterized. The antibacterial ratios against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Streptococcus mutans (S. mutans) were evaluated. The results indicated that hydrophilicity of BP coating on CFR-P was significantly higher compared to that of the pure CFR-P. Wet chemical pretreatment using mixed acid reagents (concentrated sulfuric acid and concentrated nitric acid) introduced hydroxyl, carboxyl and nitro groups on CFR-P. The BP coating exhibited the antibacterial rate of over 98% against both S. aureus and E. coli. In addition, the antibacterial rate of BP coating against the main pathogenic bacteria of dental caries, Streptococcus mutans, reached 45%.展开更多
Carbon fiber/phenolic resin composites have great potential application in the field of electronic information,where excellent structural-functional integration is required.In this work,the establishment of interfacia...Carbon fiber/phenolic resin composites have great potential application in the field of electronic information,where excellent structural-functional integration is required.In this work,the establishment of interfacial structures consisting of carbon nanotubes with different morphologies at the fiber/matrix interface is conducive to the further modulation of the mechanical,tribological,electromagnetic interference(EMI)shielding and thermal conductivity properties of carbon fiber/phenolic resin composites.Specially,array carbon nanotubes can deep into the resin matrix,effectively hindering crack extension,and constructing an electrically and thermally conductive network.Compared with the carbon fiber/phenolic composites,the tensile strength and modulus of elasticity(163.86±9.60 MPa,5.06±0.25 GPa)of the array carbon nanotubes reinforced carbon fiber/phenolic composites were enhanced by 57.09%and 22.22%.The average friction coefficient and wear rate(0.20±0.02,1.11×10^(-13)±0.13×10^(-13)m^(3)N^(−1)m^(−1))were reduced by 39.39%and 74.31%.EMI shielding effectiveness up to 40 dB in the X-band at 0.4 mm sample thickness,diffusion coefficient(0.39±0.003 mm^(2)/s)and thermal conductivity(0.54±0.004 W/(m K))were enhanced by up to 14.37%and 50.42%.This study reveals the beneficial effects of morphological changes of carbon nanotubes on the design of interfacial structure,proposes the reinforcement mechanism of array carbon nanotubes,and opens up the prospect of carbon fiber/phenolic composites for electronic applications.展开更多
To improve the oxidation resistance of C/C composites, a double SiC protective coating was prepared by a two-step technique. Firstly, the inner SiC layer was prepared by a pack cementation technique, and then an outer...To improve the oxidation resistance of C/C composites, a double SiC protective coating was prepared by a two-step technique. Firstly, the inner SiC layer was prepared by a pack cementation technique, and then an outer uniform and compact SiC coating was obtained by low pressure chemical vapor deposition. The microstructures and phase compositions of the coatings were characterized by SEM, EDS and XRD analyses. Oxidation behaviour of the SiC coated C/C composites was also investigated. It was found that the double SiC coating could protect C/C composites against oxidation at 1773 K in air for 178 h with a mass loss of 1.25%. The coated samples also underwent thermal shocks between 1773 K and room temperature 16 times. The mass loss of the coated C/C composites was only 2.74%. Double SiC layer structures were uniform and dense, and can suppress the generation of thermal stresses, facilitating an excellent anti-oxidation coating.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
文摘Felt base carbon/carbon composites fabricated by super-high pressure impregnation carbonization process (SPIC) were heat treated at high temperature 2773K. The oxidation properties of felt base carbon/carbon composites were investigated at different temperatures (773-1173K), and the microstructures of carbon/carbon composites were studied by SEM and X-ray diffraction. The experimental results showed that the inter-laminar distance of (002) plane (d002) deceased while the microcrystalline stack height (Lc) increased. The oxidation rate of felt base carbon/carbon composites was invari-able at certain temperatures. The oxidation mechanism of carbon/carbon composites changed remarkably at the oxidation temperature 973K. At the initial oxidation stage of carbon/carbon composites, carbon matrix was oxidized much more rapidly than carbon felt.
基金supported by the Special Funds for Chengde national innovation demonstration area construction of science and technology special project sustainable development agenda(No.202104F001)the National Basic Research Program of China(No.2019YFC0408602).
文摘Nitrogen removal from domestic sewage is usually limited by insufficient carbon source and electron donor.An economical solid carbon source was developed by composition of polyvinyl alcohol,sodium alginate,and corncob,which was utilized as external carbon source in the anaerobic anoxic oxic(AAO)-biofilter for the treatment of low carbon-to-nitrogen ratio domestic sewage,and the nitrogen removal was remarkably improved from 63.2%to 96.5%.Furthermore,the effluent chemical oxygen demand maintained at 35 mg/L or even lower,and the total nitrogenwas reduced to less than 2mg/L.Metagenomic analysis demonstrated that the microbial communities responsible for potential denitrification and organic matter degradation in both AAO and the biofilter reactors were mainly composed of Proteobacteria and Bacteroides,respectively.The solid carbon source addition resulted in relatively high abundance of functional enzymes responsible for NO_(3)^(−)-N to NO_(2)^(−)-N con-version in both AAO and the biofilter reactors,thus enabled stable reaction.The carbon source addition during glycolysis primarily led to the increase of genes associated with the metabolic conversion of fructose 1.6P2 to glycerol-3P The reactor maintained high abun-dance of genes related to the tricarboxylic acid cycle,and then guaranteed efficient carbon metabolism.The results indicate that the composite carbon source is feasible for denitri-fication enhancement of AAO-biofilter,which contribute to the theoretical foundation for practical nitrogen removal application.
基金supported by the National Natural Science Foundation of China(Nos.U2241240,12172045 and 12221002)the Opening Fund of State Key Laboratory of Explosion Science and Technology of Beijing Institute of Technology,China(No.ZDKT23-02)。
文摘Carbon Carbon(C/C)composites in thermal-protection system are exposed to severe thermochemical ablation and mechanical erosion,and their thermal-protection performance is of vital importance to the structural safety and flight status of hypersonic vehicles.We numerically analyzes the mesoscopic ablation-erosion of C/C Composites with Inclined Fibers(CCIF).First,a thermochemical ablation model describing the reaction-diffusion coupled problem of C/C composites on mesoscale is employed to analyze ablative process,and the corresponding surface ablation morphology is obtained.Then,the ablation morphology of CCIF is taken as the geometrical model for mechanical erosion analysis,and their damage and failure behavior under high-speed airflow shear is analyzed by using progressive damage method.Moreover,the effects of fiber inclined angle and airflow direction on the mechanical erosion of CCIF are investigated,and the ablationerosion behavior is analyzed and discussed.The results show that the failure modes of mechanical erosion in inner and edge regions are obviously different,showing granular and block erosion phenomena respectively.The mechanical erosion of CCIF in the direction of reverse flow is easier than that in the direction of forward flow.These results can provide a theoretical basis for the design and optimization of thermal protection system materials.
基金supported by the Science and Technology Development Program of Jilin Province(No.20240101122JC)and(No.20240101143JC)the Key Scientific and Technological Research and Development Projects of Jilin Provincial Science and Technology Department(Grant Number 20230201108GX)。
文摘Insufficient interfacial activity and poor wettability between fibers and matrix are the two main factors limiting the improvement of mechanical properties of Carbon Fiber Reinforced Plastics(CFRP).Owl feathers are known for their unique compact structure;they are not only lightweight but also strong.In this study,an in-depth look at owl feathers was made and it found that owl feathers not only have the macro branches structure between feather shafts and branches but also have fine feather structures on the branches.The presence of these fine feather structures increases the specific surface area of the plume branches and allows neighboring plume branches to hook up with each other,forming an effective mechanical interlocking structure.These structures bring owl feathers excellent mechanical properties.Inspired by the natural structure of owl feathers,a weaving technique and a sizing process were combined to prepare bionic Carbon Fiber(CF)fabrics and then to fabricate the bionic CFRP with structural characteristics similar to owl feathers.To evaluate the effect of the fine feather structure on the mechanical properties of CFRP,a mechanical property study on CFRP with and without the fine feather imitation structure were conducted.The experimental results show that the introduction of the fine feather branch structure enhance the mechanical properties of CFRP significantly.Specifically,the tensile strength of the composites increased by 6.42%and 13.06%and the flexural strength increased by 8.02%and 16.87%in the 0°and 90°sample directions,respectively.These results provide a new design idea for the improvement of the mechanical properties of the CFRP,promoting the application of CFRP in engineering fields,such as automotive transportation,rail transit,aerospace,and construction.
基金supported by the Shanxi Province Central Guidance Fund for Local Science and Technology Development Project(YDZJSX2024D030)the National Natural Science Foundation of China(22075197,22278290)+2 种基金the Shanxi Province Key Research and Development Program Project(2021020660301013)the Shanxi Provincial Natural Science Foundation of China(202103021224079)the Research and Development Project of Key Core and Common Technology of Shanxi Province(20201102018).
文摘The advancement of planar micro-supercapacitors(PMSCs)for micro-electromechanical systems(MEMS)has been significantly hindered by the challenge of achieving high energy and power densities.This study addresses this issue by leveraging screen-printing technology to fabricate high-performance PMSCs using innovative composite ink.The ink,a synergistic blend of few-layer graphene(Gt),carbon black(CB),and NiCo_(2)O_(4),was meticulously mixed to form a conductive and robust coating that enhanced the capacitive performance of the PMSCs.The optimized ink formulation and printing process result in a micro-supercapacitor with an exceptional areal capacitance of 18.95 mF/cm^(2)and an areal energy density of 2.63μW·h/cm^(2)at a current density of 0.05 mA/cm^(2),along with an areal power density of 0.025 mW/cm^(2).The devices demonstrated impressive durability with a capacitance retention rate of 94.7%after a stringent 20000-cycle test,demonstrating their potential for long-term applications.Moreover,the PMSCs displayed excellent mechanical flexibility,with a capacitance decrease of only 3.43%after 5000 bending cycles,highlighting their suitability for flexible electronic devices.The ease of integrating these PMSCs into series and parallel configurations for customized power further underscores their practicality for integrated power supply solutions in various technologies.
基金the National Natural Science Foundation of China(No.52070052)the National Natural Science Foundation of China(No.52300082)+3 种基金National Key Research and Development Program of China(No.2022YFB3805903)the State Key Laboratory of Urban Water Resource and Environment in HIT of China(No.2022TS14)the China Postdoctoral Science Foundation(No.2023M730881)Postdoctoral Fellowship Program of CPSF(No.GZB20230964)。
文摘Solar interfacial evaporation(SIE),is currently one of the most potential water supply technologies in the remote,insular,and disaster-stricken areas.However,the existence of volatile organic compounds(VOCs)in water deteriorates the distillate quality,threatening human health.Herein,we constructed a carbonbased bimetallic(C/FeCo)photothermal membrane by electrospinning technique.Results illustrated that the membrane can catalytically degrade VOCs during SIE with persulfate(PDS)mediation.PDS,as well as phenol,was mainly reacted on the interface of the photothermal membrane instead of in the bulk solution.The interception efficiency of phenol achieved nearly 100%using the C/FeCo membrane during SIE.Hydroxyl radical(•OH),sulfate radical(SO_(4)•−),superoxide radical(O_(2)•−),and singlet oxygen(^(1)O_(2))were identified as the main active substances to degrade VOCs.We also conducted SIE experiments using actual river water to evaluate the practical performance of the C/FeCo membrane.This work holds the promise of VOCs interception during SIE and enlarges the application of solar distillation in water/wastewater treatment.
文摘Activated carbon(AC)is considered to be an excellent adsorbent due to its high specific surface area and various functional groups.AC powders are available in sizes ranging from 44 to 150 μm.Its particle size prevent its separation from the soil.Therefore,when AC powder is applied to Cd-contaminated soil,it only reduces the bioavailability of Cd and Cd is not necessarily removed but semi-immobilized.Recovery of adsorbent materials from the soil is therefore a preferred soil remediation method.In order to achieve the separation of Cd from soil and the recovery and reuse of AC,a batch of phenolic resin(PR)-carboxymethyl cellulose(CMC)-activated carbon(AC)composite(PCC-800)with uniform particle diameter(diameter 0.8 mm)and high compressive strength was prepared.PCC-800 composites were made of PR/CMC/AC calcined at 800℃ in a certain ratio.The Barrett-Joyner-Halender results showed that the PCC-800 spheres own a mesoporous structure.The compressive strength of PCC-800 pellets was 20.6 N.After first adsorption cycle,total Cd in the soil decreased by 52.18%while bioavailable Cd decreased to 25.68%of the original soil.After three cycles,the recovery rates of PCC-800 were 90.37%and the adsorption regeneration was 72.73%.The PCC-800 immobilized Cd by adsorption,precipitation and complexation reaction.This study demonstrates the potential for developing adsorbents that are both easily separable from soil and highly effective in adsorption.
基金supported by the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(Grant No.CX2021006)the National Natural Science Foundation of China(Grant Nos.91860203,51727804,and 52130205)the Fundamental Research Funds for the Central Universities(Grant No.3102019TS0409).
文摘Herein,nanosized Hf_(6)Ta_(2)O_(17) encapsulated graphite flakes were firstly constructed using the sol-gel method,then deposited on the surface of carbon/carbon(C/C)composites by plasma spraying technique to prolong their service span in critical environments.Nanoindentation results affirmed the active influ-ence of graphite flakes on elevating the toughness of the Hf_(6)Ta_(2)O_(17) coating.Besides,after being exposed to the oxyacetylene torch with a peak temperature of about 2000℃,the sample achieved near zero ab-lation(0.06 mg/s),meanwhile its porosity and mass ablation rate showed 39.5%and 60.0%reduction when compared to pure Hf_(6)Ta_(2)O_(17) sample.During exposure,the external Hf_(6)Ta_(2)O_(17) served as an oxy-gen barrier for internal graphite flakes,inversely internal graphite flakes provided a“pinning”effect on external Hf_(6)Ta_(2)O_(17),which accounted for its exceptional ablation performance.This work offers a new insight into the design of surface modification of C/C composites and other high-temperature structural materials.
基金supported by the startup funding from Shanghai Jiao Tong University(Grant No.WH220402052).
文摘Silicon-based anode is a promising candidate for all-solid-state batteries(ASSBs).However,it must be further improved because of its tremendous volume change.In this study,various interface treatment strategies for SiO/carbon composite anodes in ASSBs were investigated using a multiphysics modeling framework.By evaluating the effects of active(carbon)and inactive coating materials,as well as the geometric and mechanical parameters,this research provides critical insights into optimizing their electrochemical performance and mechanical stability.Computational results indicate that carbon coatings can greatly enhance lithiation kinetics by regulating the interfacial electrochemical potential gradients,reducing the residual lithium concentration,and homogenizing the lithium-ion distribution compared with uncoated or inactive-coated configurations.In addition,thinner carbon coatings further improve capacity retention and stress management by balancing shorter lithium diffusion pathways with mitigated interfacial stress accumulation.Despite their ability to mechanically stabilize the anode,inactive coatings exhibit tradeoffs between lithium transport kinetics and stress modulation,with optimal performance achieved at lower Young’s moduli.Mechanical analyses highlight distinct failure mechanisms at the anode–electrolyte(shear driven)and particle-coating(tension driven)interfaces,emphasizing the need for tailored adhesion strategies.These findings provide actionable guidelines for designing robust SiO-based anodes,emphasizing the interplay among electrochemical efficiency,stress regulation,and interfacial durability in ASSBs.
文摘The automobile industry is the first to form a typical representative of the global industry in modern industry,with the increase of the national emphasis on the environment,the automobile industry was regarded as an important energy consumption and one of the sources of environmental pollution,the policy of energy conservation and emission reduction requirements for the automobile industry are becoming stricter over the years,energy conservation and emission reduction has becomes the main direction of product optimization in the automobile industry in recent years.Due of a series of excellent properties such as light weight and high strength,composite materials have become the main material for the development of lightweight vehicles.With the development of material technology and the update and iteration of manufacturing technology,composite materials are currently popular being adopted in the automotive field.
基金supported by the National Natural Science Foundation of China(No.52374110)Key scientific and technological projects of Henan province(No.242102320337)Basic Research Fund of Zhongyuan University of Technology(No.K2022QN008).
文摘A mesh-free method is presented to investigate the static bending properties of functionally graded carbon nanotube-reinforced composite(FG-CNTRC)plates.The curvature of the plate is directly interpolated with the nodal deflections due to the higher-order continuity property of the moving leastsquares approximation,establishing a mesh-free computational scheme where the nodal deflections are the only unknowns.The convergence and efficiency of the proposed method are studied based on a homogeneous square plate.The FG-CNTRC plates are modeled with continuously varying Young’s moduli along the thickness direction according to the volume fraction of the carbon nanotubes(CNTs).Detailed studies have been conducted on the effects of different boundary conditions,CNT volume fractions,geometric shapes,and width-to-thickness ratios on bending behavior.CNT efficiency parameters are introduced to account for load transfer between the nanotubes and the matrix,treating the nanocomposites as orthotropic materials.However,in the actual structure,arranging the CNTs in the desired direction is more difficult compared to other fibers.Therefore,in the present study,CNTs in the composites are considered to be arranged randomly,resulting in the composite properties being treated as isotropic.The study includes second-order derivatives of deflections,and the finite element method typically requires C1 continuity for interpolation,which introduces challenges in building elements and constructing interpolation functions.The distinct advantage of the mesh-free method is that it requires only C0 weight functions.A mesh-free computational scheme based on moving leastsquares approximations for composite plates using Kirchhoffplate theory is established.Bending analyses of homogeneous and FG-CNTRC plates are conducted using the proposed method.Aspects such as boundary conditions,CNT volume fractions,geometric shapes,and width-to-thickness ratios are also discussed.Regular node arrangements and background meshes are adopted in the present study.Results are computed using different scalar parameters and numbers of nodes.Convergence properties for the central deflection of isotropic plates are analyzed in terms of the number of nodes and different scalar parameters.The normalized central deflection is defined and examined under various boundary conditions.
基金financially supported by the National Natural Science Foundation of China(Nos.52272075 and 52472053)the Research Fund of Youth Innovation Promotion Association of CAS,China(No.2021190)the Directional Institutionalized Scientific Research Platform relying on China Spallation Neutron Source of Chinese Academy of Sciences and the Defense Industrial Technology Development Program(No.JCKY2021130B007).
文摘Carbon fiber reinforced carbon aerogel matrix(C/CA)composites have been considered as attractive candidates for thermal protection system owing to their excellent thermal insulation and superior thermal stability.However,they still suffer from challenges with insufficient oxidation resistance in practical application.Herein,a series of novel SiBCN-modified C/CA are developed for the first time through matrix modification by introducing precursors with different molecular weights in order to control residual stress.Resultantly,the C/CA-SiBCN composites derived from a high molecular weight precursor show the large residual tensile stress even with the low ceramic contents of 10%(mass fraction)due to the severe shrinkage mismatch during pyrolysis caused by the large SiBCN clusters and their inhomogeneous distribution,as well as the mismatched coefficients of thermal expansion.Comparatively,the composites derived from a low molecular weight precursor have the small carbon-ceramic particles with uniform distribution even though the ceramic content is up to 30%,thus resulting in the favorable residual compressive stress.Accordingly,the C/CA-SiBCN containing a 30%ceramic content demonstrates the significantly enhanced performance with low residual compressive stress of 0.31 GPa,52%mechanical improvement and reduction in oxidation rate by 39.21%-60.35%at 800-1100℃compared to the original C/CA.This work offers a new avenue for enhancing oxidation resistance of C/CA applied as thermal insulators to cope with the harsh operating environments.
基金supported by the University of Texas(UT)system STARs grant,Semester Undergraduate Research Experience(SURE)program at the College of Engineering at the University of Texas Permian Basin(UTPB)EM-STEP(Engineering Minority Student Engagement Project)at UTPB College of Engineering,funded by Department of Education.
文摘Carbon fiber-reinforced composites(CFRCs)have a wide range of applications in the aerospace,automotive,and energy sectors.A higher specific strength-to-weight ratio is desired in high-performance applications.The failure mechanism of CFRCs involves multiscale phenomena,such as failure that can occur at the matrix,fibers,interface,layers,lamina,and laminates.When an impactor hits the CFRCs,the design involves analyzing each of these stages to prevent failure and optimize the properties of CFRCs under various loading conditions.A numerical model was employed to predict the fracture toughness of CFRCs with varying weight fractions and orientations.Finite Element Analysis(FEA)was conducted at the fiber level on a micrometer scale for the CFRCs against an impact loading.Epoxy composite samples at the coupon level were prepared using the hand layup technique with carbon fibers laid at three different angles,i.e.,longitudinal,transverse,and angular orientations.Samples with five different weight percentages of carbon fibers were prepared and investigated.An Izod impact tester was used to fracture the samples and characterize the energy absorption.The fractured surfaces were observed with a scanning electron microscope(SEM).The numerical and experimental results show that crack propagation is inhibited at higher loading fractions at an angular orientation by creating obstacles for the crack to propagate and arresting the dislocation motion.The fractography analysis through a scanning electron microscope exhibits how the angular orientations of the fibers are reoriented after fracture to prevent further crack propagation.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2241240,12172045,and 12221002).
文摘In thermal protection structures,controlling and optimizing the surface roughness of carbon/phenolic(C/Ph)composites can effectively improve thermal protection performance and ensure the safe operation of carriers in high-temperature environments.This paper introduces a machine learning(ML)framework to forecast the surface roughness of carbon-phenolic composites under various thermal conditions by employing an ML algorithm derived from historical experimental datasets.Firstly,ablation experiments and collection of surface roughness height data of C/Ph composites under different thermal environments were conducted in an electric arc wind tunnel.Then,an ML model based on Ridge regression is developed for surface roughness prediction.The model involves incorporating feature engineering to choose the most concise and pertinent features,as well as developing an ML model.The ML model considers thermal environment parameters and feature screened by feature engineering as inputs,and predicts the surface height as the output.The results demonstrate that the suggested ML framework effectively anticipates the surface shape and associated surface roughness parameters in various heat flow conditions.Compared with the conventional 3D confocal microscope scanning,the method can obtain the surface topography information of the same area in a much shorter time,thus significantly saving time and cost.
基金supported by the National Key Laboratory of Advanced Composite Materials(No.KZ42191814)。
文摘The icing characteristics of supercooled large droplet(SLD)impacting carbon fiber-reinforced composites(CFRCs)remain poorly understood,hindering the enhancement of ice protection capabilities and the certification of ice-accreted composite aircraft.The paper systematically investigates the effects of the supercooling degree,the surface temperature,and the impact velocity on the ice accretion behavior of SLDs impacting carbon fiber-reinforced epoxy composite surfaces.To address the ice-prone nature of CFRCs,nanoparticle-modified anti-icing coatings are developed,and the icing characteristics of SLD-impacted modified carbon fiber-reinforced epoxy composite surfaces are analyzed.Results demonstrate that surface-modified carbon fiber-reinforced epoxy composite exhibits significantly delayed ice formation.Under conditions of droplet temperature(−15℃)and surface temperature(−18℃),the icing time of hydrophobic-modified CFRCs was delayed by over 1100 ms,representing a 5.4-fold improvement compared to the unmodified carbon fiber-reinforced epoxy composite.
基金supported by the Key Research and Development Plan of Shaanxi Province(No.2023-GHZD-12)the Chinese Aeronautical Establishment Aeronautical Science Foundation(No.20230041053006)the National Natural Science Foundation of China(Nos.12472392 and 12172304).
文摘3D printing has emerged as an advanced manufacturing technique for carbon fiber reinforced composites and relevant structures that endure significant dynamic loads in engineering applications.The dynamic behavior of these materials,primarily influenced by the dynamic fiber pullout interface strength necessitates investigation into the rate-dependent fiber/matrix interfacial strength.This study modifies a Hopkinson tension bar to conduct dynamic pullout tests on a single fiber bundle,utilizing a low-impedance bar and an in-situ calibrated semiconductor strain gauge to capture weak stress signals.Stress equilibrium analyses are performed to validate the transient dynamic loading on single fiber bundle specimens.The results reveal that the fiber/matrix interfacial strength is rate-dependent,increasing with the loading rate,while remaining unaffected by the embedded length.Fracture microstructural analyses show minimal fiber pullout due to high interfacial stresses induced by longer embedded lengths.Lastly,suggestions are made for the efficient design of fiber pullout experiments.
基金support of the National Natural Science Foundation of China(61971301)In part by the Central Guidance on Local Science and Technology Development Fund of Shanxi Province under Grant YDZJSX2021A018+1 种基金Shanxi Province Higher Education Science and Technology Innovation Plan Project(2022L060)the Fundamental Research Program of Shanxi Province(Nos.202203021212227,202303021212082).
文摘The poor surface antibacterial properties are one of the important factors limiting the application of Carbon Fibers Reinforced Polyetheretherketone (CFR-P) composites as artificial bone replace materials. Some of the Two-Dimensional (2D) nanomaterials with unique lamellar structures and biological properties have been demonstrated to have excellent antibacterial properties. Antibacterial properties can be improved by feasible chemical strategies for preparing 2D nanomaterials coating on the surface of CFR-P. In this work, Black Phosphorus (BP) coating was prepared on the originally chemically inert CFR-P surface based on wet chemical pretreatment. The physical and chemical properties, including surface microstructure, chemical composition and state, roughness and hydrophilicity were characterized. The antibacterial ratios against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Streptococcus mutans (S. mutans) were evaluated. The results indicated that hydrophilicity of BP coating on CFR-P was significantly higher compared to that of the pure CFR-P. Wet chemical pretreatment using mixed acid reagents (concentrated sulfuric acid and concentrated nitric acid) introduced hydroxyl, carboxyl and nitro groups on CFR-P. The BP coating exhibited the antibacterial rate of over 98% against both S. aureus and E. coli. In addition, the antibacterial rate of BP coating against the main pathogenic bacteria of dental caries, Streptococcus mutans, reached 45%.
基金supported by the National Natural Science Foundation of China(No.51872232)the Key Scientific and Technological Innovation Research Team of Shaanxi Province(No.2022TD-31)the Key R&D Program of Shaanxi Province(No.2021ZDLGY14-04).
文摘Carbon fiber/phenolic resin composites have great potential application in the field of electronic information,where excellent structural-functional integration is required.In this work,the establishment of interfacial structures consisting of carbon nanotubes with different morphologies at the fiber/matrix interface is conducive to the further modulation of the mechanical,tribological,electromagnetic interference(EMI)shielding and thermal conductivity properties of carbon fiber/phenolic resin composites.Specially,array carbon nanotubes can deep into the resin matrix,effectively hindering crack extension,and constructing an electrically and thermally conductive network.Compared with the carbon fiber/phenolic composites,the tensile strength and modulus of elasticity(163.86±9.60 MPa,5.06±0.25 GPa)of the array carbon nanotubes reinforced carbon fiber/phenolic composites were enhanced by 57.09%and 22.22%.The average friction coefficient and wear rate(0.20±0.02,1.11×10^(-13)±0.13×10^(-13)m^(3)N^(−1)m^(−1))were reduced by 39.39%and 74.31%.EMI shielding effectiveness up to 40 dB in the X-band at 0.4 mm sample thickness,diffusion coefficient(0.39±0.003 mm^(2)/s)and thermal conductivity(0.54±0.004 W/(m K))were enhanced by up to 14.37%and 50.42%.This study reveals the beneficial effects of morphological changes of carbon nanotubes on the design of interfacial structure,proposes the reinforcement mechanism of array carbon nanotubes,and opens up the prospect of carbon fiber/phenolic composites for electronic applications.
基金Projects(51221001,51222207)supported by the National Natural Science Foundation of ChinaProject(090677)supported by the Program for New Century Excellent Talents in University of Ministry of Education of ChinaProject(B08040)supported by the Program of Introducing Talents of Discipline to Universities (111 Project) of China
文摘To improve the oxidation resistance of C/C composites, a double SiC protective coating was prepared by a two-step technique. Firstly, the inner SiC layer was prepared by a pack cementation technique, and then an outer uniform and compact SiC coating was obtained by low pressure chemical vapor deposition. The microstructures and phase compositions of the coatings were characterized by SEM, EDS and XRD analyses. Oxidation behaviour of the SiC coated C/C composites was also investigated. It was found that the double SiC coating could protect C/C composites against oxidation at 1773 K in air for 178 h with a mass loss of 1.25%. The coated samples also underwent thermal shocks between 1773 K and room temperature 16 times. The mass loss of the coated C/C composites was only 2.74%. Double SiC layer structures were uniform and dense, and can suppress the generation of thermal stresses, facilitating an excellent anti-oxidation coating.
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.
