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Effect of graphitization on the kinetics and mechanism of thermal oxidation of carbon microcoils
CARBON
4 8 ( 20 1 0 ) 1 6 9 3–16 9 6
1695
Multi-walled carbon nanotubes (MWCNTs) were modified by
catalyst can produce both flat CMCs and circular CMCs depending
grafting an amphiphilic polymer, which were characterized by
on its relative orientation to the fiber axis. A cubic Ni catalyst can
Fourier transform infrared spectroscopy and thermogravimetric
only produce a circular CMC, and can only change the coil diam-
analysis. The modified MWCNTs were added to an intumescent
eter upon changing the reaction conditions. The model will give
fire-retardant coating and their effects on the performance of
more insight into the formation of CMCs and provide information
the coating were studied. Results show that the amphiphilic poly-
on the controlled synthesis of CMCs and carbon fibers.
mer can be attached to the surface of MWCNTs by appropriate processing, and the modified MWCNTs exhibit a remarkable solubility in butyl acetate and distilled water. The modified MWCNTs
[New Carbon Materials 2009;24(4):354–8]. doi:10.1016/j.carbon.2009.12.017
added to the coating can strengthen the carbonized layers, increase intumescent times and decrease the increasing rate of the rear temperature when the coating was exposed to a fire.
Modification of a LiFePO4 cathode for lithium ion batteries by
The modified MWCNTs can also enhance the crack resistance of
carbon coating and copper doping
the coating.
Yi-biao Guan, Feng Wu, Ying Bai, Chuan Wu
[New Carbon Materials 2009;24(4):344–8]. doi:10.1016/j.carbon.2009.12.015
School of Chemical Engineering and the Environment, Beijing Institute of Technology, Beijing 100081, China National Development Center of High Technology Green Materials, Beijing 100081, China
Carbon matrices with different pore structures as heat transfer
The effects of a carbon coating and copper doping on the elec-
intensifier in paraffin wax/carbon thermal energy storage system
trochemical performance and tap density of a LiFePO4 cathode for
Ya-juan Zhonga,b, Si-zhong Lia,b, Xing-hai Weia,b, Xiao-qing Gaoa, Jing-li Shia, Quan-gui Guoa, Lang Liua a
Key Laboratory of Carbon Materials, Institute of Coal Chemistry,
lithium ion batteries were investigated by XRD, SEM, charge/discharge cycle tests, rate tests and tap density tests. Results showed that the average discharge capacity of LiFePO4/C and LiFe0.95-
Chinese Academy of Sciences, Taiyuan 030001, China
Cu0.05PO4 were 147 mAh/g and 131 mAh/g, respectively. The
b
capacity fading rate of LiFe0.95Cu0.05PO4 was much larger than
Graduate University of Chinese Academy of Sciences, Beijing 100049,
China
that of LiFePO4/C in a high-rate discharging test. The electrochemical performance of LiFePO4/C was better than that of
Graphite foam, carbon felt and compressed expanded natural graphite (CENG) were used to increase the heat transfer ability of paraffin wax as latent heat storage (LHS) medium. Structure and thermal properties of the paraffin wax-carbon LHS system were characterized using the scanning electron microscopy, laser flash
LiFe0.95Cu0.05PO4, but the tap density of the latter was 1.5 times as large as that of the former. [New Carbon Materials 2009;24(4):359–63]. doi:10.1016/j.carbon.2009.12.018
technique and differential scanning calorimetry. Results indicated that the thermal conductivities of paraffin wax-graphite foam, paraffin wax-carbon felt and paraffin wax-CENG systems
Effect of graphitization on the kinetics and mechanism of
were enhanced by a factor of 437, 14 and 25 times, respectively,
thermal oxidation of carbon microcoils
compared with pure paraffin wax and their latent heats were
Hui Bi, Kai-chang Kou, Zhao-di Wang *, Zhi-chao Wang,
42.34 J/g, 48.38 J/g and 57.82 J/g, respectively.
Jiao-qiang Zhang
[New Carbon Materials 2009;24(4):349–53]. doi:10.1016/j.carbon.2009.12.016
Department of Applied Chemistry, School of Science, Northwestern Polytechnical University, Xi’an 710072, China Carbon microcoils were prepared by catalytic chemical vapor deposition, using acetylene as carbon source, Ni powder as cata-
Growth mechanism of carbon microcoils with changing fiber
lyst, and a sulfur-containing compound (thiophene) as growth
cross-section shape
promoter. The microcoils were graphitized under an argon atmo-
Jing-bao Cheng, Jin-hong Du, Shuo Bai
sphere at 2500 °C. The morphology and microstructure of the oxi-
Shenyang National Laboratory for Materials Science, Institute of Metal
dized carbon microcoils were investigated by scanning electron
Research, Chinese Academy of Sciences, Shenyang 110016, China
microscopy, and their oxidation resistance was studied by thermogravimetric analysis. Results reveal that oxidation resistance
Carbon microcoils (CMCs) with a fiber cross-section changing
of the carbon microcoils is improved through graphitization,
from flat to circular along with a coil diameter changing from
and the graphitized carbon microcoils retain their microcoil mor-
4.2 to 6.0 lm, which may develop a novel spring for micromechan-
phology after oxidation. Oxidation is a first order reaction and the
ical systems, were obtained by controlling the acetylene flow rate
activation energies are 263 and 297 kJ/mol before and after graph-
using Ni catalyst at a temperature of 1013–1053 K. A growth
itization, respectively.
model for these changes was proposed in which catalytic anisotropy is considered to be the possible factor changing the fiber cross-sectional shape of the CMCs. Owing to the change of catalytic anisotropy caused by reaction conditions, the same slender
[New Carbon Materials 2009;24(4):364–8]. doi:10.1016/j.carbon.2009.12.019
4 8 ( 20 1 0 ) 1 6 9 3–16 9 6
1695
Multi-walled carbon nanotubes (MWCNTs) were modified by
catalyst can produce both flat CMCs and circular CMCs depending
grafting an amphiphilic polymer, which were characterized by
on its relative orientation to the fiber axis. A cubic Ni catalyst can
Fourier transform infrared spectroscopy and thermogravimetric
only produce a circular CMC, and can only change the coil diam-
analysis. The modified MWCNTs were added to an intumescent
eter upon changing the reaction conditions. The model will give
fire-retardant coating and their effects on the performance of
more insight into the formation of CMCs and provide information
the coating were studied. Results show that the amphiphilic poly-
on the controlled synthesis of CMCs and carbon fibers.
mer can be attached to the surface of MWCNTs by appropriate processing, and the modified MWCNTs exhibit a remarkable solubility in butyl acetate and distilled water. The modified MWCNTs
[New Carbon Materials 2009;24(4):354–8]. doi:10.1016/j.carbon.2009.12.017
added to the coating can strengthen the carbonized layers, increase intumescent times and decrease the increasing rate of the rear temperature when the coating was exposed to a fire.
Modification of a LiFePO4 cathode for lithium ion batteries by
The modified MWCNTs can also enhance the crack resistance of
carbon coating and copper doping
the coating.
Yi-biao Guan, Feng Wu, Ying Bai, Chuan Wu
[New Carbon Materials 2009;24(4):344–8]. doi:10.1016/j.carbon.2009.12.015
School of Chemical Engineering and the Environment, Beijing Institute of Technology, Beijing 100081, China National Development Center of High Technology Green Materials, Beijing 100081, China
Carbon matrices with different pore structures as heat transfer
The effects of a carbon coating and copper doping on the elec-
intensifier in paraffin wax/carbon thermal energy storage system
trochemical performance and tap density of a LiFePO4 cathode for
Ya-juan Zhonga,b, Si-zhong Lia,b, Xing-hai Weia,b, Xiao-qing Gaoa, Jing-li Shia, Quan-gui Guoa, Lang Liua a
Key Laboratory of Carbon Materials, Institute of Coal Chemistry,
lithium ion batteries were investigated by XRD, SEM, charge/discharge cycle tests, rate tests and tap density tests. Results showed that the average discharge capacity of LiFePO4/C and LiFe0.95-
Chinese Academy of Sciences, Taiyuan 030001, China
Cu0.05PO4 were 147 mAh/g and 131 mAh/g, respectively. The
b
capacity fading rate of LiFe0.95Cu0.05PO4 was much larger than
Graduate University of Chinese Academy of Sciences, Beijing 100049,
China
that of LiFePO4/C in a high-rate discharging test. The electrochemical performance of LiFePO4/C was better than that of
Graphite foam, carbon felt and compressed expanded natural graphite (CENG) were used to increase the heat transfer ability of paraffin wax as latent heat storage (LHS) medium. Structure and thermal properties of the paraffin wax-carbon LHS system were characterized using the scanning electron microscopy, laser flash
LiFe0.95Cu0.05PO4, but the tap density of the latter was 1.5 times as large as that of the former. [New Carbon Materials 2009;24(4):359–63]. doi:10.1016/j.carbon.2009.12.018
technique and differential scanning calorimetry. Results indicated that the thermal conductivities of paraffin wax-graphite foam, paraffin wax-carbon felt and paraffin wax-CENG systems
Effect of graphitization on the kinetics and mechanism of
were enhanced by a factor of 437, 14 and 25 times, respectively,
thermal oxidation of carbon microcoils
compared with pure paraffin wax and their latent heats were
Hui Bi, Kai-chang Kou, Zhao-di Wang *, Zhi-chao Wang,
42.34 J/g, 48.38 J/g and 57.82 J/g, respectively.
Jiao-qiang Zhang
[New Carbon Materials 2009;24(4):349–53]. doi:10.1016/j.carbon.2009.12.016
Department of Applied Chemistry, School of Science, Northwestern Polytechnical University, Xi’an 710072, China Carbon microcoils were prepared by catalytic chemical vapor deposition, using acetylene as carbon source, Ni powder as cata-
Growth mechanism of carbon microcoils with changing fiber
lyst, and a sulfur-containing compound (thiophene) as growth
cross-section shape
promoter. The microcoils were graphitized under an argon atmo-
Jing-bao Cheng, Jin-hong Du, Shuo Bai
sphere at 2500 °C. The morphology and microstructure of the oxi-
Shenyang National Laboratory for Materials Science, Institute of Metal
dized carbon microcoils were investigated by scanning electron
Research, Chinese Academy of Sciences, Shenyang 110016, China
microscopy, and their oxidation resistance was studied by thermogravimetric analysis. Results reveal that oxidation resistance
Carbon microcoils (CMCs) with a fiber cross-section changing
of the carbon microcoils is improved through graphitization,
from flat to circular along with a coil diameter changing from
and the graphitized carbon microcoils retain their microcoil mor-
4.2 to 6.0 lm, which may develop a novel spring for micromechan-
phology after oxidation. Oxidation is a first order reaction and the
ical systems, were obtained by controlling the acetylene flow rate
activation energies are 263 and 297 kJ/mol before and after graph-
using Ni catalyst at a temperature of 1013–1053 K. A growth
itization, respectively.
model for these changes was proposed in which catalytic anisotropy is considered to be the possible factor changing the fiber cross-sectional shape of the CMCs. Owing to the change of catalytic anisotropy caused by reaction conditions, the same slender
[New Carbon Materials 2009;24(4):364–8]. doi:10.1016/j.carbon.2009.12.019