The dispersion effect of carbon nanofibers （CNFs） in aqueous solution and the mechanical properties, porosity, pore size distribution and microstructure of CNFs reinforced cement-based composites were investigated i...The dispersion effect of carbon nanofibers （CNFs） in aqueous solution and the mechanical properties, porosity, pore size distribution and microstructure of CNFs reinforced cement-based composites were investigated in this paper. To achieve effective dispersion of CNFs, a method utilizing ultrasonic processing and a commercially surfactant were employed. CNFs were incorporated to cementitious materials with the addition of 0.1 wt% and 0.2 wt% of cement with a water/cement ratio of 0.35. The mechanical properties of CNFs/ cement composites were analyzed, the porosity and pore size distribution were characterized by ^1H low field nuclear magnetic resonance （NMR）, and the microstructure was observed by scanning electron microscopy （SEM）. The results indicate that the optimum concentration ratio of MC to CNFs is 2：1 for dispersing in aqueous solution. Moreover, in the field of mechanical properties, CNFs can improve the flexural strength and compressive strength. The increased mechanical properties and the decreased porosity of the matrices correspond to the increasing CNFs content and CNFs act as bridges and networks across cracks and voids.展开更多
Biodegradable polymers are highly attractive as potential alternatives to petroleum-based polymers in an attempt to achieve carbon neutrality whilst maintaining the mechanical properties of the structures.Among these ...Biodegradable polymers are highly attractive as potential alternatives to petroleum-based polymers in an attempt to achieve carbon neutrality whilst maintaining the mechanical properties of the structures.Among these polymers,polylactic acid(PLA)is particularly promising due to its good mechanical properties,biocompatibility and thermoplasticity.In this work,we aim to enhance the mechanical properties of PLA using mechanically-defibrated cellulose nanofibers(CNFs)that exhibit remarkable mechanical properties and biodegradability.We also employ fused deposition modeling(FDM),one of the three-dimensional printing methods for thermoplastic polymers,for the low-cost fabrication of the products.Mechanically-defibrated CNF-reinforced PLA matrix composites are fabricated by FDM.Their tensile properties are investigated in two printing directions(0°/90°and+45°/-45°).The discussion about the relationship between printing direction and tensile behavoir of mechanically-defibrated CNF-reinforced PLA matrix composite is the unique point of this study.We further discuss the microstructure and fracture surface of mechanically-defibrated CNF-reinforced PLA matrix composite by scanning electron microscope.展开更多
Carbon materials have the advantages of good electrical conductivity and excellent chemical stability, so many carbon materials have been introduced as electrodes for the capacitive deionization (CDI) process. Due to ...Carbon materials have the advantages of good electrical conductivity and excellent chemical stability, so many carbon materials have been introduced as electrodes for the capacitive deionization (CDI) process. Due to the low surface area compared to the other nanocarbonaceous materials, CNFs performance as electrode in the CDI units is comparatively low. This problem has been overcome by preparing high surface area carbon nanofibers and by creating numerous long pores on the nanofibers surface. The modified CNFs have been synthesized using low cost, high yield and facile method;electrospinning technique. Stabilization and graphitization of electrospun nanofiber mats composed of polyacrylonitrile (PAN) and poly (methyl methacrylate) (PMMA) leads form longitudinal pores CNFs. The utilized characterizations indicated that the CNFs obtained from electrospun solution having 50% PMMA have surface area of 181 m2/g which are more than the conventional CNFs. Accordingly, these nanofibers revealed salt removal efficiency of ~90% and specific capacitance of 237 F/g.展开更多
In this study, the surface chemical properties of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) grown by catalytic decomposition of methane on nickel and cobalt based catalysts were studied by DRIFT (Diffuse Re...In this study, the surface chemical properties of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) grown by catalytic decomposition of methane on nickel and cobalt based catalysts were studied by DRIFT (Diffuse Reflectance Infrared Fourier Transform) and transmission Infrared (IR) spectroscopy. The results show that the surface exists not only carbon-hydrogen groups, but also carboxyl, ketene or quinone (carbonyl) oxygen-containing groups. These functional groups were formed in the process of the material growth, which result in large amount of chemical defect sites on the walls.展开更多
Chitin nanofibers (CNFs) processed from second most abundant biomolecule chitin were loaded with gold metallic nanoparticles (Au NPs) to obtained hybrid organic-inorganic composite which was molded in different forms ...Chitin nanofibers (CNFs) processed from second most abundant biomolecule chitin were loaded with gold metallic nanoparticles (Au NPs) to obtained hybrid organic-inorganic composite which was molded in different forms dispersion, flakes, powder, and transparent thin film. First pre-organized Au NPs were prepared in soluble triblock copolymer poly (methyl vinyl ether) (PMVE) by reduction of gold precursor salt (HAuCl43H2O) by NaBH4 then NPs were mixed with diluted CNFs suspension to obtain CNFs-Au NPs composite. CNFs of width 25 - 40 nm were prepared by combination of chemical and mechanical processing in wet acidic condition from 1 wt% crab shell chitin slurry. When polymer stabilized Au NPs blended with CNF suspension, all Au NPs and 56% polymer were found mass transferred from water phase to entangle with more polar moieties of chitin. Composite’s suspension and compressed dried film were characterized by recording digital images, UV-vis, TEM, SEM, and XRD spectroscopies. When 70 m thin non transparent composite film was impregnated with tricyclodecane dimethanol dimethacrylate (TCDDMA) resin and subsequent polymerized with photoinitiator 2-hydroxy-2-methylpropiophenone, the film became transparent due to filling of nanosized CNFs in the cages of the resin.展开更多
Rational construction of active components has been the biggest challenge in preparing efficient bifunctional oxygen electrocatalysts.Herein,electrospinning and chemical vapor deposition(CVD)were employed to embed act...Rational construction of active components has been the biggest challenge in preparing efficient bifunctional oxygen electrocatalysts.Herein,electrospinning and chemical vapor deposition(CVD)were employed to embed active species including FeCo nanoparticles,MNx(M=Fe,Co),and FePx in porous and graphitized carbon nanotubes(CNTs)/carbon nanofiber(CNF).The as-prepared FeCo@CoNx@FePx/C exhibited a half-wave potential as high as 0.86 V in oxygen reduction reaction(ORR)and low oxygen evolution reaction(OER)overpotential of 368 mV at 10 mA·cm^(−2),which are superior to Pt/C(0.83 V)and IrO_(2)(375 mV)respectively.The assembled Zn-air battery(ZAB)showed a high energy efficiency(Edischarge/Echarge)of 65%at 20 mA·cm^(−2)and stabilized for 700 charge-discharge cycles.The spectroscopic and microscopic characterizations evidenced that the outstanding bifunctionality of the electrocatalyst can be ascribed to three main reasons:First,FeCo nanoparticles are rich in MOH/MOOH active sites for OER,and FePx/CNTs constructed with CVD also modulate electronic structure to improve electron transfer;second,both MNx in carbon matrix and FePx/CNTs are highly active towards ORR;third,the CNTs/CNF are highly porous and graphitized,which promotes mass transport and improves electrical conductivity and stability of the electrocatalysts.This work gives important implications on the design of bifunctional electrocatalysts.展开更多
Cobalt selenide(CoSe_(2))has become a promising anode material for sodium-ion batteries(SIBs)due to its stable chemical properties,environmental friendliness,and high theoretical capacity.However,the undesirable rate ...Cobalt selenide(CoSe_(2))has become a promising anode material for sodium-ion batteries(SIBs)due to its stable chemical properties,environmental friendliness,and high theoretical capacity.However,the undesirable rate capacity and cycle stability of the anode materials largely limit its applications for SIBs due to the relatively low electronic conductivity and huge volume change during the Na+insertion/extraction.In this study,electrostatic spinning combined with a wet chemical method is employed to synthesize coral-like composite material(CNF@c-CoSe_(2)/C),which is composed of CoSe_(2)/carbon nanosheet arrays(CoSe_(2)/C)and carbon nanofibers(CNFs).CoSe_(2)/C nanoflakes derived from metal-organic frameworks(MOFs)with high surface area and the porous structure can inhibit the pulverization and amorphization of CoSe_(2) during charge and discharge processes,thus significantly keeping the stability of the microstructure.CNF can limit the overgrowth of nanosheets and serve as a conductive skeleton.Compared to two-dimensional CoSe_(2)/C nanoflakes and pure CoSe_(2) nanoparticles,the composite can expose more active sites and effectively accelerate the diffusion of Na+,which displays enhanced rate capability(266.5 mAh·g^(-1) at 5.0 A·g^(-1))and cycling stability(268.3 mAh·g^(-1) after 100 cycles at 1.0 A·g^(-1)).Moreover,the rational preparation strategy for metal selenide-based heterostructure material presents a new way for high-performance SIB s.展开更多
For harsh real-world service settings,it is essential to build corrosion-resistant,diverse,and effective microwave absorbers.Herein,we successfully prepared a 3D NiAl-layered double hydroxide/carbon nanofibers(NiAl-LD...For harsh real-world service settings,it is essential to build corrosion-resistant,diverse,and effective microwave absorbers.Herein,we successfully prepared a 3D NiAl-layered double hydroxide/carbon nanofibers(NiAl-LDH/CNFs)composite material as an anticorrosive microwave absorber assisted by an atomic layer deposition(ALD)method.The size,coating thickness,and content of NiAl-LDH can be readily adjusted by changing the ALD cycling numbers.The optimized NiAl-LDH/CNFs demonstrates prominent microwave absorbing properties including the strongest reflection loss of–55.65 dB and the widest effective absorption bandwidth of 4.80 GHz with only 15 wt%loading.The reasons for performance improvement are the cooperative effect of interfacial polarization loss,conduction loss,and three-dimensional porous structure.Moreover,due to the synergistic effects between the excellent impermeability of CNFs and the trapping ability of NiAl-LDH for chloride ions,NiAl-LDH/CNFs exhibits strong corrosion resistances under acidic,neutral,and alkaline conditions.NiAl-LDH/CNFs should be a potential candidate to simultaneously use for microwave absorption and corrosion resistance,and this work provides a certain guiding significance for designing microwave absorbers that satisfy the corrosion resistance.展开更多
基金Funded by the the National Natural Science Foundation of China(No.51278086)the Program for New Century Excellent Talents in University by Ministry of Education of the People’s Republic of China(No.NCET-12-0084)+2 种基金Liaoning BaiQianWan Talents Program(No.2012921073)Dalian Plan Projects of Science and Technology(Nos.2012A13GX024 and 2013A16GX113)the Construction Safety and Environment State Key Laboratory Open Fund(No.201202)
文摘The dispersion effect of carbon nanofibers （CNFs） in aqueous solution and the mechanical properties, porosity, pore size distribution and microstructure of CNFs reinforced cement-based composites were investigated in this paper. To achieve effective dispersion of CNFs, a method utilizing ultrasonic processing and a commercially surfactant were employed. CNFs were incorporated to cementitious materials with the addition of 0.1 wt% and 0.2 wt% of cement with a water/cement ratio of 0.35. The mechanical properties of CNFs/ cement composites were analyzed, the porosity and pore size distribution were characterized by ^1H low field nuclear magnetic resonance （NMR）, and the microstructure was observed by scanning electron microscopy （SEM）. The results indicate that the optimum concentration ratio of MC to CNFs is 2：1 for dispersing in aqueous solution. Moreover, in the field of mechanical properties, CNFs can improve the flexural strength and compressive strength. The increased mechanical properties and the decreased porosity of the matrices correspond to the increasing CNFs content and CNFs act as bridges and networks across cracks and voids.
基金supported by the Program for Creation of Interdisciplinary Research and Ensemble Program of Frontier Research Institute for Interdisciplinary Sciences,Tohoku University。
文摘Biodegradable polymers are highly attractive as potential alternatives to petroleum-based polymers in an attempt to achieve carbon neutrality whilst maintaining the mechanical properties of the structures.Among these polymers,polylactic acid(PLA)is particularly promising due to its good mechanical properties,biocompatibility and thermoplasticity.In this work,we aim to enhance the mechanical properties of PLA using mechanically-defibrated cellulose nanofibers(CNFs)that exhibit remarkable mechanical properties and biodegradability.We also employ fused deposition modeling(FDM),one of the three-dimensional printing methods for thermoplastic polymers,for the low-cost fabrication of the products.Mechanically-defibrated CNF-reinforced PLA matrix composites are fabricated by FDM.Their tensile properties are investigated in two printing directions(0°/90°and+45°/-45°).The discussion about the relationship between printing direction and tensile behavoir of mechanically-defibrated CNF-reinforced PLA matrix composite is the unique point of this study.We further discuss the microstructure and fracture surface of mechanically-defibrated CNF-reinforced PLA matrix composite by scanning electron microscope.
文摘Carbon materials have the advantages of good electrical conductivity and excellent chemical stability, so many carbon materials have been introduced as electrodes for the capacitive deionization (CDI) process. Due to the low surface area compared to the other nanocarbonaceous materials, CNFs performance as electrode in the CDI units is comparatively low. This problem has been overcome by preparing high surface area carbon nanofibers and by creating numerous long pores on the nanofibers surface. The modified CNFs have been synthesized using low cost, high yield and facile method;electrospinning technique. Stabilization and graphitization of electrospun nanofiber mats composed of polyacrylonitrile (PAN) and poly (methyl methacrylate) (PMMA) leads form longitudinal pores CNFs. The utilized characterizations indicated that the CNFs obtained from electrospun solution having 50% PMMA have surface area of 181 m2/g which are more than the conventional CNFs. Accordingly, these nanofibers revealed salt removal efficiency of ~90% and specific capacitance of 237 F/g.
文摘In this study, the surface chemical properties of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) grown by catalytic decomposition of methane on nickel and cobalt based catalysts were studied by DRIFT (Diffuse Reflectance Infrared Fourier Transform) and transmission Infrared (IR) spectroscopy. The results show that the surface exists not only carbon-hydrogen groups, but also carboxyl, ketene or quinone (carbonyl) oxygen-containing groups. These functional groups were formed in the process of the material growth, which result in large amount of chemical defect sites on the walls.
文摘Chitin nanofibers (CNFs) processed from second most abundant biomolecule chitin were loaded with gold metallic nanoparticles (Au NPs) to obtained hybrid organic-inorganic composite which was molded in different forms dispersion, flakes, powder, and transparent thin film. First pre-organized Au NPs were prepared in soluble triblock copolymer poly (methyl vinyl ether) (PMVE) by reduction of gold precursor salt (HAuCl43H2O) by NaBH4 then NPs were mixed with diluted CNFs suspension to obtain CNFs-Au NPs composite. CNFs of width 25 - 40 nm were prepared by combination of chemical and mechanical processing in wet acidic condition from 1 wt% crab shell chitin slurry. When polymer stabilized Au NPs blended with CNF suspension, all Au NPs and 56% polymer were found mass transferred from water phase to entangle with more polar moieties of chitin. Composite’s suspension and compressed dried film were characterized by recording digital images, UV-vis, TEM, SEM, and XRD spectroscopies. When 70 m thin non transparent composite film was impregnated with tricyclodecane dimethanol dimethacrylate (TCDDMA) resin and subsequent polymerized with photoinitiator 2-hydroxy-2-methylpropiophenone, the film became transparent due to filling of nanosized CNFs in the cages of the resin.
基金the grants from the National Natural Science Foundation of China(No.22004085)Regional Joint Fund of Guangdong Province(No.2019A1515111054).
文摘Rational construction of active components has been the biggest challenge in preparing efficient bifunctional oxygen electrocatalysts.Herein,electrospinning and chemical vapor deposition(CVD)were employed to embed active species including FeCo nanoparticles,MNx(M=Fe,Co),and FePx in porous and graphitized carbon nanotubes(CNTs)/carbon nanofiber(CNF).The as-prepared FeCo@CoNx@FePx/C exhibited a half-wave potential as high as 0.86 V in oxygen reduction reaction(ORR)and low oxygen evolution reaction(OER)overpotential of 368 mV at 10 mA·cm^(−2),which are superior to Pt/C(0.83 V)and IrO_(2)(375 mV)respectively.The assembled Zn-air battery(ZAB)showed a high energy efficiency(Edischarge/Echarge)of 65%at 20 mA·cm^(−2)and stabilized for 700 charge-discharge cycles.The spectroscopic and microscopic characterizations evidenced that the outstanding bifunctionality of the electrocatalyst can be ascribed to three main reasons:First,FeCo nanoparticles are rich in MOH/MOOH active sites for OER,and FePx/CNTs constructed with CVD also modulate electronic structure to improve electron transfer;second,both MNx in carbon matrix and FePx/CNTs are highly active towards ORR;third,the CNTs/CNF are highly porous and graphitized,which promotes mass transport and improves electrical conductivity and stability of the electrocatalysts.This work gives important implications on the design of bifunctional electrocatalysts.
基金financially supported by the National Natural Science Foundation of China(Nos.51603092 and 21706103)the Natural Science Foundation of Jiangsu Province(Nos.BK20160537 and BK20170549)China Postdoctoral Science Foundation(No.2019T120393)。
文摘Cobalt selenide(CoSe_(2))has become a promising anode material for sodium-ion batteries(SIBs)due to its stable chemical properties,environmental friendliness,and high theoretical capacity.However,the undesirable rate capacity and cycle stability of the anode materials largely limit its applications for SIBs due to the relatively low electronic conductivity and huge volume change during the Na+insertion/extraction.In this study,electrostatic spinning combined with a wet chemical method is employed to synthesize coral-like composite material(CNF@c-CoSe_(2)/C),which is composed of CoSe_(2)/carbon nanosheet arrays(CoSe_(2)/C)and carbon nanofibers(CNFs).CoSe_(2)/C nanoflakes derived from metal-organic frameworks(MOFs)with high surface area and the porous structure can inhibit the pulverization and amorphization of CoSe_(2) during charge and discharge processes,thus significantly keeping the stability of the microstructure.CNF can limit the overgrowth of nanosheets and serve as a conductive skeleton.Compared to two-dimensional CoSe_(2)/C nanoflakes and pure CoSe_(2) nanoparticles,the composite can expose more active sites and effectively accelerate the diffusion of Na+,which displays enhanced rate capability(266.5 mAh·g^(-1) at 5.0 A·g^(-1))and cycling stability(268.3 mAh·g^(-1) after 100 cycles at 1.0 A·g^(-1)).Moreover,the rational preparation strategy for metal selenide-based heterostructure material presents a new way for high-performance SIB s.
基金supported by the National Natural Science Foundation of China(Grant Nos.22068010,22278101,and 22168016)the Finance Science and Technology Project of Hainan Province(Grant Nos.ZDYF2020009)the Natural Science Foundation of Hainan Province(Grant Nos.2019RC142 and 519QN176).
文摘For harsh real-world service settings,it is essential to build corrosion-resistant,diverse,and effective microwave absorbers.Herein,we successfully prepared a 3D NiAl-layered double hydroxide/carbon nanofibers(NiAl-LDH/CNFs)composite material as an anticorrosive microwave absorber assisted by an atomic layer deposition(ALD)method.The size,coating thickness,and content of NiAl-LDH can be readily adjusted by changing the ALD cycling numbers.The optimized NiAl-LDH/CNFs demonstrates prominent microwave absorbing properties including the strongest reflection loss of–55.65 dB and the widest effective absorption bandwidth of 4.80 GHz with only 15 wt%loading.The reasons for performance improvement are the cooperative effect of interfacial polarization loss,conduction loss,and three-dimensional porous structure.Moreover,due to the synergistic effects between the excellent impermeability of CNFs and the trapping ability of NiAl-LDH for chloride ions,NiAl-LDH/CNFs exhibits strong corrosion resistances under acidic,neutral,and alkaline conditions.NiAl-LDH/CNFs should be a potential candidate to simultaneously use for microwave absorption and corrosion resistance,and this work provides a certain guiding significance for designing microwave absorbers that satisfy the corrosion resistance.
