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Suspension of carbon nanotubes in natural humic acid water
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Abstracts / Carbon 124 (2017) 725e727
100049, China; c Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China; d Institute of Molecular Science, Shanxi University, Taiyuan 030006, China Abstract: Free-standing graphene films (GFs) as functional materials require high mechanical performance for a convenient industrial processing. GFs were prepared from graphene oxide films by annealing temperatures from 1300 to 1700 C, and were characterized by AFM, XRD, SEM, Raman spectroscopy and mechanical testing. Results indicate that the samples have a maximum tensile strength and fracture strain of 22.41 MPa and 2.44%, respectively and a minimum thermal conductivity of 744 W m 1 K 1 for an annealing temperature at 1500 C. This is related to physical interlocking which results, from surface wrinkles of the graphene layers. [New Carbon Materials 2017, 32(3): 227-233] PERFORMANCE OF PITCH AND GLUCOSE REVERSIBLE SODIUM STORAGE
PYROCARBONS
FOR
Wei Dong a, Shao-bin Yang b, Ding Shen b, Xiao-liang Wang b, Si-nan Li a, Wen Sun b. a College of Material Science and Engineering, Liaoning Technical University, Fuxin 123000, China; b College of Mining, Liaoning Technical University, Fuxin 123000, China Abstract: Pitch and glucose pyrocarbons were prepared by the carbonization of petroleum pitch and glucose at 800 C under a nitrogen flow and were used as the electrodes of sodium ion batteries. Results show that the carbon interlayer spacing, and the oxygen content of the glucose carbon are much larger than those of the pitch carbon, while the degree of crystallinity is smaller. The first discharge capacities of the glucose and pitch carbons are 171.9 and 79.2 mAh/g, and their capacity retention rates after 20 cycles are 94.6 and 68.2%, respectively. Cyclic voltammetry analysis shows that the potential of the irreversible reduction peak in the low potential range of the pitch pyrocarbon is lower than that of the glucose pyrocarbon. AC impedance analysis shows that the impedance of a solid-electrolyte interface film, the interface impedance and the diffusion resistance of the glucose pyrocarbon are significantly lower than that of the pitch pyrocarbon. [New Carbon Materials 2017, 32(3): 234-241] PREPARATION OF DIAMETER-CONTROLLED MULTI-WALL CARBON NANOTUBES BY AN IMPROVED FLOATING-CATALYST CHEMICAL VAPOR DEPOSITION METHOD Ya-juan Li a, Chang Ma a, Jian-li Kang a, Jing-li Shi a, Qiang Shi b, Da-heng Wu a. a School of Material Science and Engineering, Tianjin Polytechnic University, Tianjin 300387, China; b Sichuan Innovation and Surpassing Carbon Materials Co., LTD, Langzhong 637400, Sichuan, China Abstract: Multi-wall carbon nanotubes (MWCNTs) with controlled diameters were synthesized by an improved-floating catalyst chemical vapor deposition method, using toluene and ferrocene as a carbon source and catalyst precursor, respectively. Ferrocene was sublimed in a heater and carried as a gas mixed with toluene vapor into a reactor where MWCNTs were formed. The effects of the sublimation temperature, hydrogen content in the gas mixture and gas flow rate on the diameter and diameter distribution of the CNTs formed were investigated. Results indicated that the CNT diameter distributions could be controlled by changing the sublimation temperature. The higher the sublimation temperature, the narrower the distribution of CNT diameters. The average CNT diameter decreased and levelled off with increasing hydrogen content in the gas mixture from 0 to 40 vol%. The CNT diameter decreased with increasing gas flow rate. [New Carbon Materials 2017, 32(3): 242-251] AN INSIGHT INTO THE SUPERIOR PERFORMANCE OF A GOLD NANOCATALYST ON SINGLE WALL CARBON NANOTUBES TO THAT ON TITANIUM DIOXIDE AND AMORPHOUS CARBON FOR THE GREEN AEROBIC OXIDATION OF AROMATIC ALCOHOLS Anne E. Shanahan a, Mary McNamara a, James A. Sullivan b, Hugh J. Byrne a. a FOCAS Research Institute, Dublin Institute of Technology, Camden Row, Dublin 8, Ireland; b UCD School of Chemistry and Chemical Biology, Belfield, Dublin 4, Ireland
Abstract: Gold nanocomposites based on three supports, single wall carbon nanotubes, carbon black and TiO2, were prepared using an in-situ reduction technique and characterized. They were tested for their suitability as heterogeneous catalysts in the green aerobic oxidation of 1phenylethanol, 2-phenylethanol and benzylalcohol of industrial importance. For all reactions, the use of single wall carbon nanotubes as supports resulted in superior reaction efficiency and specificity for aldehyde to that of TiO2 and carbon black. The gold nanocatalysts can be reused over several reaction cycles with a minimal degeneration in catalytic activity. The activity of the gold nanoparticle catalyst was related to the shape and size of the gold particles and the properties of the support. The selectivity was ascribed to the functional groups on the substrate, the properties of the supports and the particle size distributions of the gold nanoparticles. [New Carbon Materials 2017, 32(3): 252-257] SUSPENSION OF CARBON NANOTUBES IN NATURAL HUMIC ACID WATER Chao-xian Wei a, Huang Zhang b, Di Zhang a, Xiao-lei Yang a. a Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China; b Yunnan Institute of Food Safety, Kunming University of Science & Technology, Kunming 650500, China Abstract: The widespread use of carbon nanotubes (CNTs) may cause them to be released into the environment. Their interaction with natural organic matter enhances their dispersion in water, leading to a severe environmental threat. In this study, the effect of dissolved humic acid (HA) on the dispersion of graphitized or hydroxylated CNTs in water was investigated by repeated dispersion of both CNTs in HA water with a concentration of 100 mg/L for 19 times. Results showed that the cumulative adsorption amounts of HA on the graphitized CNTs increased and leveled off, but those on the hydroxylated ones increased continually with the number of dispersions. The amounts of graphitized CNTs suspended in HA water were always lower than those of the hydroxylated ones, which reached a maximum after 4 of 5 dispersions. TEM images showed that hydroxylated CNTs were shorter than the graphitized ones and the suspended CNTs were shorter than the un-suspended ones for both types of CNTs, indicating that CNTs with more defects are easily suspended. [New Carbon Materials 2017, 32(3): 258-264] SYNTHESIS AND CHARACTERIZATION OF Al2O3-C HYBRID AEROGELS BY A ONE-POT SOL-GEL METHOD Rui Zhang a, Ning Jiang a, Xiao-jia Duan a, b, Shuang-ling Jin a, Ming-lin Jin a. a School of Materials Sciences and Engineering, Shanghai Institute of Technology, Shanghai 2001418, China; b Chemical Engineering College, East China University of Science and Technology, Shanghai 200237, China Abstract: Al2O3-C hybrid aerogels were prepared by a one-pot sol-gel method, supercritical n-hexane drying and carbonization using Al(NO3)3$9H2O as the Al2O3 source, resorcinol (R) and furfural (F) as carbon precursors, and propylene oxide (PO) as a gelation initiator. The effects of the Al2O3 contents, the R+F concentrations and the PO/Al molar ratios on the porosity of the hybrid aerogels were investigated using a constant R/F molar ratio of 0.5. It was found that the hybrid aerogels are all mesoporous with an average pore size below 20 nm. The crystalline structure of Al2O3 is g-type, but its diffraction peaks are quite broad. The hybrid aerogels are monolithic when the Al2O3 content is below 5.31 wt% with an R+F concentration of 10 g/100 mL. The mesopore volume and size, BET surface area and external surface area all increase with increasing PO/Al molar ratio under otherwise identical conditions. The volume shrinkage decreases, carbonization yield increases and the density of the hybrid aerogel exhibits a maximum with an Al2O3 content of 4.93 wt%. The size and volume of the mesopores, and the external surface area decrease with the increasing R+F concentration at PO/Al ratios of 5 and 6, but increase with increasing R+F concentration at a PO/ Al ratio of 4.
Abstracts / Carbon 124 (2017) 725e727
100049, China; c Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China; d Institute of Molecular Science, Shanxi University, Taiyuan 030006, China Abstract: Free-standing graphene films (GFs) as functional materials require high mechanical performance for a convenient industrial processing. GFs were prepared from graphene oxide films by annealing temperatures from 1300 to 1700 C, and were characterized by AFM, XRD, SEM, Raman spectroscopy and mechanical testing. Results indicate that the samples have a maximum tensile strength and fracture strain of 22.41 MPa and 2.44%, respectively and a minimum thermal conductivity of 744 W m 1 K 1 for an annealing temperature at 1500 C. This is related to physical interlocking which results, from surface wrinkles of the graphene layers. [New Carbon Materials 2017, 32(3): 227-233] PERFORMANCE OF PITCH AND GLUCOSE REVERSIBLE SODIUM STORAGE
PYROCARBONS
FOR
Wei Dong a, Shao-bin Yang b, Ding Shen b, Xiao-liang Wang b, Si-nan Li a, Wen Sun b. a College of Material Science and Engineering, Liaoning Technical University, Fuxin 123000, China; b College of Mining, Liaoning Technical University, Fuxin 123000, China Abstract: Pitch and glucose pyrocarbons were prepared by the carbonization of petroleum pitch and glucose at 800 C under a nitrogen flow and were used as the electrodes of sodium ion batteries. Results show that the carbon interlayer spacing, and the oxygen content of the glucose carbon are much larger than those of the pitch carbon, while the degree of crystallinity is smaller. The first discharge capacities of the glucose and pitch carbons are 171.9 and 79.2 mAh/g, and their capacity retention rates after 20 cycles are 94.6 and 68.2%, respectively. Cyclic voltammetry analysis shows that the potential of the irreversible reduction peak in the low potential range of the pitch pyrocarbon is lower than that of the glucose pyrocarbon. AC impedance analysis shows that the impedance of a solid-electrolyte interface film, the interface impedance and the diffusion resistance of the glucose pyrocarbon are significantly lower than that of the pitch pyrocarbon. [New Carbon Materials 2017, 32(3): 234-241] PREPARATION OF DIAMETER-CONTROLLED MULTI-WALL CARBON NANOTUBES BY AN IMPROVED FLOATING-CATALYST CHEMICAL VAPOR DEPOSITION METHOD Ya-juan Li a, Chang Ma a, Jian-li Kang a, Jing-li Shi a, Qiang Shi b, Da-heng Wu a. a School of Material Science and Engineering, Tianjin Polytechnic University, Tianjin 300387, China; b Sichuan Innovation and Surpassing Carbon Materials Co., LTD, Langzhong 637400, Sichuan, China Abstract: Multi-wall carbon nanotubes (MWCNTs) with controlled diameters were synthesized by an improved-floating catalyst chemical vapor deposition method, using toluene and ferrocene as a carbon source and catalyst precursor, respectively. Ferrocene was sublimed in a heater and carried as a gas mixed with toluene vapor into a reactor where MWCNTs were formed. The effects of the sublimation temperature, hydrogen content in the gas mixture and gas flow rate on the diameter and diameter distribution of the CNTs formed were investigated. Results indicated that the CNT diameter distributions could be controlled by changing the sublimation temperature. The higher the sublimation temperature, the narrower the distribution of CNT diameters. The average CNT diameter decreased and levelled off with increasing hydrogen content in the gas mixture from 0 to 40 vol%. The CNT diameter decreased with increasing gas flow rate. [New Carbon Materials 2017, 32(3): 242-251] AN INSIGHT INTO THE SUPERIOR PERFORMANCE OF A GOLD NANOCATALYST ON SINGLE WALL CARBON NANOTUBES TO THAT ON TITANIUM DIOXIDE AND AMORPHOUS CARBON FOR THE GREEN AEROBIC OXIDATION OF AROMATIC ALCOHOLS Anne E. Shanahan a, Mary McNamara a, James A. Sullivan b, Hugh J. Byrne a. a FOCAS Research Institute, Dublin Institute of Technology, Camden Row, Dublin 8, Ireland; b UCD School of Chemistry and Chemical Biology, Belfield, Dublin 4, Ireland
Abstract: Gold nanocomposites based on three supports, single wall carbon nanotubes, carbon black and TiO2, were prepared using an in-situ reduction technique and characterized. They were tested for their suitability as heterogeneous catalysts in the green aerobic oxidation of 1phenylethanol, 2-phenylethanol and benzylalcohol of industrial importance. For all reactions, the use of single wall carbon nanotubes as supports resulted in superior reaction efficiency and specificity for aldehyde to that of TiO2 and carbon black. The gold nanocatalysts can be reused over several reaction cycles with a minimal degeneration in catalytic activity. The activity of the gold nanoparticle catalyst was related to the shape and size of the gold particles and the properties of the support. The selectivity was ascribed to the functional groups on the substrate, the properties of the supports and the particle size distributions of the gold nanoparticles. [New Carbon Materials 2017, 32(3): 252-257] SUSPENSION OF CARBON NANOTUBES IN NATURAL HUMIC ACID WATER Chao-xian Wei a, Huang Zhang b, Di Zhang a, Xiao-lei Yang a. a Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China; b Yunnan Institute of Food Safety, Kunming University of Science & Technology, Kunming 650500, China Abstract: The widespread use of carbon nanotubes (CNTs) may cause them to be released into the environment. Their interaction with natural organic matter enhances their dispersion in water, leading to a severe environmental threat. In this study, the effect of dissolved humic acid (HA) on the dispersion of graphitized or hydroxylated CNTs in water was investigated by repeated dispersion of both CNTs in HA water with a concentration of 100 mg/L for 19 times. Results showed that the cumulative adsorption amounts of HA on the graphitized CNTs increased and leveled off, but those on the hydroxylated ones increased continually with the number of dispersions. The amounts of graphitized CNTs suspended in HA water were always lower than those of the hydroxylated ones, which reached a maximum after 4 of 5 dispersions. TEM images showed that hydroxylated CNTs were shorter than the graphitized ones and the suspended CNTs were shorter than the un-suspended ones for both types of CNTs, indicating that CNTs with more defects are easily suspended. [New Carbon Materials 2017, 32(3): 258-264] SYNTHESIS AND CHARACTERIZATION OF Al2O3-C HYBRID AEROGELS BY A ONE-POT SOL-GEL METHOD Rui Zhang a, Ning Jiang a, Xiao-jia Duan a, b, Shuang-ling Jin a, Ming-lin Jin a. a School of Materials Sciences and Engineering, Shanghai Institute of Technology, Shanghai 2001418, China; b Chemical Engineering College, East China University of Science and Technology, Shanghai 200237, China Abstract: Al2O3-C hybrid aerogels were prepared by a one-pot sol-gel method, supercritical n-hexane drying and carbonization using Al(NO3)3$9H2O as the Al2O3 source, resorcinol (R) and furfural (F) as carbon precursors, and propylene oxide (PO) as a gelation initiator. The effects of the Al2O3 contents, the R+F concentrations and the PO/Al molar ratios on the porosity of the hybrid aerogels were investigated using a constant R/F molar ratio of 0.5. It was found that the hybrid aerogels are all mesoporous with an average pore size below 20 nm. The crystalline structure of Al2O3 is g-type, but its diffraction peaks are quite broad. The hybrid aerogels are monolithic when the Al2O3 content is below 5.31 wt% with an R+F concentration of 10 g/100 mL. The mesopore volume and size, BET surface area and external surface area all increase with increasing PO/Al molar ratio under otherwise identical conditions. The volume shrinkage decreases, carbonization yield increases and the density of the hybrid aerogel exhibits a maximum with an Al2O3 content of 4.93 wt%. The size and volume of the mesopores, and the external surface area decrease with the increasing R+F concentration at PO/Al ratios of 5 and 6, but increase with increasing R+F concentration at a PO/ Al ratio of 4.