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Microstructures and mechanical properties of pyrocarbons produced from phenolic resin with added Ni(NO3)2
Abstracts / Carbon 124 (2017) 722e724
(WAXD) and small-angle X-ray scattering (SAXS). Microvoids were characterized by the classical SAXS method, and were compared with simulation results obtained by fitting 2D SAXS patterns to a model based on a dilute system of cylindrical microvoids randomly distributed and preferentially orientated along the fiber axis and having a log-normal size distribution. The WAXD results showed that the crystal size, d-spacing and preferred orientation decreased during pre-oxidation, and increased during carbonization. A diffraction peak for PAN fibers at 2q¼13.6 disappeared during the final stage of pre-oxidation, meanwhile a new peak at 2q¼23.6 appeared, whose intensity increased during carbonization, indicating the formation of the graphite structure. The average length of the microvoids increased, and new microvoids were formed, which became oriented along the fiber axis as the fiber manufacturing process proceeded. The length of microvoids from simulation results is consistent with that from the classical method, indicating that the model is valid to describe the microvoid structure of fibers. [New Carbon Materials 2017, 32(2): 137-142] MICROSTRUCTURES AND MECHANICAL PROPERTIES OF PYROCARBONS PRODUCED FROM PHENOLIC RESIN WITH ADDED Ni(NO3)2 Tian-fei Ma 1, Xiao-xian Wu 2, Hong-xia Li 1, Guo-qi Liu 1, Wen-gang Yang 1. 1 State Key Laboratory of Advanced Refractories, Sinosteel Luoyang Institute of Refractories Research, Luoyang 471039, Henan, China; 2 Zhe Jiang Institute of Geology and Mineral Resource, Hangzhou 310007, Zhejiang, China Abstract: A refractory containing graphite is commonly used in the metallurgical industry in locations subject to severe thermal shock because of the high thermal conductivity and good thermal shock resistance of graphite. However, a refractory that uses phenolic resin as the carbon precursor is brittle, and to improve its strength and toughness, Ni(NO3)2 is added to the resin to catalyze the in-situ formation of carbon nanofibers/nanotubes. The microstructure and mechanical properties of the Ni(NO3)2-modified phenolic resin carbons were characterized by XRD, SEM, TEM and mechanical tests. Results indicate that carbon nanofibers/ nanotubes (2% by volume) were formed within the pyrocarbons as a result of the nickel catalyst and these are interconnected to form a network structure. The nanocarbon fibers/tubes significantly improve the bend strength, elastic modulus, tensile strength and fracture toughness of the pyrocarbons and their fracture energies are increased accordingly. [New Carbon Materials 2017, 32(2): 143-150] ABLATION CHARACTERISTICS OF A 4D CARBON/CARBON COMPOSITE UNDER A HIGH FLUX OF COMBUSTION PRODUCTS WITH A HIGH CONTENT OF PARTICULATE ALUMINA IN A SOLID ROCKET MOTOR Yang Liu, Jing-qiu Pei, Jiang Li, Guo-qiang He. Science and Technology on Combustion, Internal Flow and Thermal-structure Laboratory, Northwestern Polytechnical University, Xi'an 710072, China Abstract: The ablation behavior of a four-directional carbon/carbon (C/C) composite was examined in a lab-scale solid rocket motor under a high flux of combustion products containing a high content of particulate alumina. The composite consisted of three braided carbon fiber bundles at 120 to each other in the XY plane and a hexagonal array of carbon rods in the Z direction, all in a pitch carbon matrix. The rods consisted of a unidirectional array of the same carbon fibers in a pitch carbon matrix The composite was placed in the rocket motor with its XY plane perpendicular to the gas flow and its ablation rate, ablation behavior and microstructure were investigated. The flow field of the combustion products was simulated by solving the Reynolds-averaged NaviereStokes equations. A deep pit was formed on the surface of the composite, the center of which coincides with the simulated particle accumulation area. The mechanical erosion was significantly increased when the particle impact velocity exceeded 96.82m/s. The carbon rods were more susceptible to erosion than the surrounding fiber bundles. The maximum ablation rates of the carbon rod and bundles were increased almost by an order of magnitude by increasing the particle impact velocity by a factor of two. Numerous crater-like pores on the ends of the carbon rods were formed by alumina particle impaction, and the tips of the fibers in the carbon rods were almost
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flat and lower than the surrounding matrix. Heating caused by the particle impact increased the thermal oxidization and hence the overall ablation rate of the composite. [New Carbon Materials 2017, 32(2): 151-159] PREPARATION AND PROPERTIES OF GRAPHENE/CARBON POLY(ETHER ETHER KETONE) COMPOSITES
FIBER/
Ya-nan Su 1, 2, Shou-chun Zhang 1, Xing-hua Zhang 1, Zhen-bo Zhao 1, Cheng-meng Chen 1, De-qi Jing 1. 1 National Engineering Laboratory for Carbon Fiber Technology, Institute of Coal Chemistry, Chinese Academy of Science, Taiyuan 030001, China; 2 University of Chinese Academy of Science, Beijing 100049, China Abstract: Graphene/carbon fiber/poly(ether ether ketone) (GR/CF/PEEK) composites were prepared by directly spraying a GR dispersion onto CF/ PEEK prepregs, followed by hot-pressing the stacked prepregs. The structure of the prepregs and cross-section of the composites were characterized by SEM. The mechanical, thermal and electrical properties of the composites were measured to evaluate the influence of GR on their performance. Results showed that the addition of 0.1 wt% GR increases the interlaminar shear strength, the flexural strength and flexural modulus of the composites from 57.3 MPa, 1 226.2 MPa and 64.5 GPa to 77.6 MPa, 1 512.3 MPa and 73.6 GPa, respectively. DSC analysis showed that the crystallinity of the composites increased with the GR content. The thermal conductivity and electrical conductivity of the composites were increased by 15.5 and 73.1%, respectively after 0.5 wt% GR was added. The GR/CF/ PEEK composites have much better mechanical, thermal and electrical performance than the CF/PEEK composites. [New Carbon Materials 2017, 32(2): 160-167] GRAPHENE OXIDE: A NOVEL ACID CATALYST FOR THE SYNTHESIS OF 2,5-DIMETHYL-N-PHENYL PYRROLE BY THE PAALeKNORR CONDENSATION Chun-yan Chen 1, 2, Xiao-ya Guo 1, Guang-qiang Lu 2, Christian Marcus Pedersen 3, Yan Qiao 4, Xiang-lin Hou 2, Ying-xiong Wang 2. 1 Department of Chemical Engineering, Shanghai University, Shanghai, 200444, China; 2 Shanxi Engineering Research Center of Biorefinery, Institute of Coal Chemistry, Chinese Academy of Sciences, 27 South Taoyuan Road, Taiyuan, 030001, China; 3 Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100, Copenhagen Ø, Denmark; 4 State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, 27 South Taoyuan Road, Taiyuan, 030001, China Abstract: Graphene oxide (GO) was used as an efficient and recyclable catalyst for the synthesis of N-substituted pyrrole using a PaaleKnorr condensation reaction between 2,5-hexanedione and aniline. The effects of reaction time, reaction temperature, solvent, catalyst loading and molar ratio of aniline to 2,5-hexanedione on the yield of 2,5-dimethyl-N-phenyl pyrrole were investigated. In situ NMR was used to follow the PaaleKnorr reaction at the molecular level. Results revealed that the oxygen-containing groups of GO, such as sulfonic acid and carboxyl groups, played a key role in this catalytic reaction. Polar protic solvents were favorable for the reaction. The catalytic activity increased with temperature without any side reaction. The GO could be easily recovered and showed remarkable reusability and excellent catalytic performance allowing it to be reused 5 times. [New Carbon Materials 2017, 32(2): 168-173] INVESTIGATION OF DEFECTS IN A MESOPHASE PITCH-BASED GRAPHITE AT THE ATOMIC SCALE Ju Rong 1, 2, Yuan-yuan Zhu 1, Zhen Fan 3, Zhi-hai Feng 3, Lian-long He 1. 1 Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China; 2 University of Chinese Academy of Sciences, Beijing 100049, China; 3 National Key Laboratory of Advanced Functional Composite Materials, Aerospace Research Institute of Materials & Processing Technology, Beijing 100076, China
(WAXD) and small-angle X-ray scattering (SAXS). Microvoids were characterized by the classical SAXS method, and were compared with simulation results obtained by fitting 2D SAXS patterns to a model based on a dilute system of cylindrical microvoids randomly distributed and preferentially orientated along the fiber axis and having a log-normal size distribution. The WAXD results showed that the crystal size, d-spacing and preferred orientation decreased during pre-oxidation, and increased during carbonization. A diffraction peak for PAN fibers at 2q¼13.6 disappeared during the final stage of pre-oxidation, meanwhile a new peak at 2q¼23.6 appeared, whose intensity increased during carbonization, indicating the formation of the graphite structure. The average length of the microvoids increased, and new microvoids were formed, which became oriented along the fiber axis as the fiber manufacturing process proceeded. The length of microvoids from simulation results is consistent with that from the classical method, indicating that the model is valid to describe the microvoid structure of fibers. [New Carbon Materials 2017, 32(2): 137-142] MICROSTRUCTURES AND MECHANICAL PROPERTIES OF PYROCARBONS PRODUCED FROM PHENOLIC RESIN WITH ADDED Ni(NO3)2 Tian-fei Ma 1, Xiao-xian Wu 2, Hong-xia Li 1, Guo-qi Liu 1, Wen-gang Yang 1. 1 State Key Laboratory of Advanced Refractories, Sinosteel Luoyang Institute of Refractories Research, Luoyang 471039, Henan, China; 2 Zhe Jiang Institute of Geology and Mineral Resource, Hangzhou 310007, Zhejiang, China Abstract: A refractory containing graphite is commonly used in the metallurgical industry in locations subject to severe thermal shock because of the high thermal conductivity and good thermal shock resistance of graphite. However, a refractory that uses phenolic resin as the carbon precursor is brittle, and to improve its strength and toughness, Ni(NO3)2 is added to the resin to catalyze the in-situ formation of carbon nanofibers/nanotubes. The microstructure and mechanical properties of the Ni(NO3)2-modified phenolic resin carbons were characterized by XRD, SEM, TEM and mechanical tests. Results indicate that carbon nanofibers/ nanotubes (2% by volume) were formed within the pyrocarbons as a result of the nickel catalyst and these are interconnected to form a network structure. The nanocarbon fibers/tubes significantly improve the bend strength, elastic modulus, tensile strength and fracture toughness of the pyrocarbons and their fracture energies are increased accordingly. [New Carbon Materials 2017, 32(2): 143-150] ABLATION CHARACTERISTICS OF A 4D CARBON/CARBON COMPOSITE UNDER A HIGH FLUX OF COMBUSTION PRODUCTS WITH A HIGH CONTENT OF PARTICULATE ALUMINA IN A SOLID ROCKET MOTOR Yang Liu, Jing-qiu Pei, Jiang Li, Guo-qiang He. Science and Technology on Combustion, Internal Flow and Thermal-structure Laboratory, Northwestern Polytechnical University, Xi'an 710072, China Abstract: The ablation behavior of a four-directional carbon/carbon (C/C) composite was examined in a lab-scale solid rocket motor under a high flux of combustion products containing a high content of particulate alumina. The composite consisted of three braided carbon fiber bundles at 120 to each other in the XY plane and a hexagonal array of carbon rods in the Z direction, all in a pitch carbon matrix. The rods consisted of a unidirectional array of the same carbon fibers in a pitch carbon matrix The composite was placed in the rocket motor with its XY plane perpendicular to the gas flow and its ablation rate, ablation behavior and microstructure were investigated. The flow field of the combustion products was simulated by solving the Reynolds-averaged NaviereStokes equations. A deep pit was formed on the surface of the composite, the center of which coincides with the simulated particle accumulation area. The mechanical erosion was significantly increased when the particle impact velocity exceeded 96.82m/s. The carbon rods were more susceptible to erosion than the surrounding fiber bundles. The maximum ablation rates of the carbon rod and bundles were increased almost by an order of magnitude by increasing the particle impact velocity by a factor of two. Numerous crater-like pores on the ends of the carbon rods were formed by alumina particle impaction, and the tips of the fibers in the carbon rods were almost
723
flat and lower than the surrounding matrix. Heating caused by the particle impact increased the thermal oxidization and hence the overall ablation rate of the composite. [New Carbon Materials 2017, 32(2): 151-159] PREPARATION AND PROPERTIES OF GRAPHENE/CARBON POLY(ETHER ETHER KETONE) COMPOSITES
FIBER/
Ya-nan Su 1, 2, Shou-chun Zhang 1, Xing-hua Zhang 1, Zhen-bo Zhao 1, Cheng-meng Chen 1, De-qi Jing 1. 1 National Engineering Laboratory for Carbon Fiber Technology, Institute of Coal Chemistry, Chinese Academy of Science, Taiyuan 030001, China; 2 University of Chinese Academy of Science, Beijing 100049, China Abstract: Graphene/carbon fiber/poly(ether ether ketone) (GR/CF/PEEK) composites were prepared by directly spraying a GR dispersion onto CF/ PEEK prepregs, followed by hot-pressing the stacked prepregs. The structure of the prepregs and cross-section of the composites were characterized by SEM. The mechanical, thermal and electrical properties of the composites were measured to evaluate the influence of GR on their performance. Results showed that the addition of 0.1 wt% GR increases the interlaminar shear strength, the flexural strength and flexural modulus of the composites from 57.3 MPa, 1 226.2 MPa and 64.5 GPa to 77.6 MPa, 1 512.3 MPa and 73.6 GPa, respectively. DSC analysis showed that the crystallinity of the composites increased with the GR content. The thermal conductivity and electrical conductivity of the composites were increased by 15.5 and 73.1%, respectively after 0.5 wt% GR was added. The GR/CF/ PEEK composites have much better mechanical, thermal and electrical performance than the CF/PEEK composites. [New Carbon Materials 2017, 32(2): 160-167] GRAPHENE OXIDE: A NOVEL ACID CATALYST FOR THE SYNTHESIS OF 2,5-DIMETHYL-N-PHENYL PYRROLE BY THE PAALeKNORR CONDENSATION Chun-yan Chen 1, 2, Xiao-ya Guo 1, Guang-qiang Lu 2, Christian Marcus Pedersen 3, Yan Qiao 4, Xiang-lin Hou 2, Ying-xiong Wang 2. 1 Department of Chemical Engineering, Shanghai University, Shanghai, 200444, China; 2 Shanxi Engineering Research Center of Biorefinery, Institute of Coal Chemistry, Chinese Academy of Sciences, 27 South Taoyuan Road, Taiyuan, 030001, China; 3 Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100, Copenhagen Ø, Denmark; 4 State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, 27 South Taoyuan Road, Taiyuan, 030001, China Abstract: Graphene oxide (GO) was used as an efficient and recyclable catalyst for the synthesis of N-substituted pyrrole using a PaaleKnorr condensation reaction between 2,5-hexanedione and aniline. The effects of reaction time, reaction temperature, solvent, catalyst loading and molar ratio of aniline to 2,5-hexanedione on the yield of 2,5-dimethyl-N-phenyl pyrrole were investigated. In situ NMR was used to follow the PaaleKnorr reaction at the molecular level. Results revealed that the oxygen-containing groups of GO, such as sulfonic acid and carboxyl groups, played a key role in this catalytic reaction. Polar protic solvents were favorable for the reaction. The catalytic activity increased with temperature without any side reaction. The GO could be easily recovered and showed remarkable reusability and excellent catalytic performance allowing it to be reused 5 times. [New Carbon Materials 2017, 32(2): 168-173] INVESTIGATION OF DEFECTS IN A MESOPHASE PITCH-BASED GRAPHITE AT THE ATOMIC SCALE Ju Rong 1, 2, Yuan-yuan Zhu 1, Zhen Fan 3, Zhi-hai Feng 3, Lian-long He 1. 1 Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China; 2 University of Chinese Academy of Sciences, Beijing 100049, China; 3 National Key Laboratory of Advanced Functional Composite Materials, Aerospace Research Institute of Materials & Processing Technology, Beijing 100076, China