新型炭材料

Fabrication of well-dispersed, multiwall carbon nanotube-reinforced
aluminum matrix composites

A.H.Javadi, Sh.Mirdamadi, M. A. Faghihisani, S. Shakhesi|　R.Soltani

2012, 27(3): 161-165. doi: 10.1016/S1872-5805(12)60010-9

Abstract(1629)

PDF(1229)

Abstract:
Mechanical alloying was used to disperse multiwall carbon nanotubes (MWCNTs) in an aluminum (Al) matrix. Mixtures consisting of 99% pure Al powder and a mass fraction of 2% MWCNTs were sonicated. Then, horizontal ball milling was used to generate mechanical bonding between the Al particles and the MWCNTs. The structure observed by a field-emission scanning electron microscope revealed an attachment of MWCNTs to the surface of the Al-flakes. FESEM results showed that particle size and morphology varied with milling time. Finally, the composite powders were processed into bulk material by compaction and sintering. The macro-hardness confirmed the improvement in the mechanical properties due to the addition of MWCNTs to the Al matrix

Synthesis of CdS/CNT-TiO₂ with a high photocatalytic activity in the photodegradation of methylene blue

朱　雷, 孟则达, CHO Kwang-youn, 吴沅春

2012, 27(3): 166-174. doi: 10.1016/S1872-5805(12)60011-0

Abstract(1894)

PDF(1066)

Abstract:
Novel CdS/CNT-TiO₂ photocatalysts were synthesized by a simple chemical routine through the drop-wise addition of Na₂S · 5H₂O solutions to cadmium acetate solutions containing purified multiwall carbon nanotubes (MWCNTs). The CdS/CNT materials obtained were treated with titanium (IV) n-butoxide to form CdS/CNT-TiO₂ composites which were characterized by N₂ adsorption, XRD, TEM, SEM, and energy-dispersive X-ray analysis. The composites were found to be porous, and the MWCNTs were homogenously dispersed in the composites without any apparent agglomeration of TiO₂ nanoparticles and CdS nanoparticles. The CdS/CNT-TiO₂ composites exhibited excellent activity for the degradation of methylene blue under UV and visible-light irradiation. This was attributed not only to the photocatalysis of the supported TiO₂ for the radical reaction and the adsorptivity of MWCNTs, but also to the introduction of the narrow-band gap semiconductor CdS that increases the transfer rate of photogenerated electrons through the surface of the MWCNTs.

Carbon nanotubes produced by chemical vapor depositionusing natural biomass-based catalysts

SHI Jian-hua, ZHAO Jian-guo, XING Bao-yan, ZHAO Ren

2012, 27(3): 175-180.

Abstract(2051)

PDF(870)

Abstract:
Carbon nanotubes (CNTs) were prepared by chemical vapor deposition, using carbonized iron-rich biomass, mushrooms, seaweed, black fungus and black sesame seeds as catalysts, and methane as the carbon source. It was found that CNT arrays with narrow diameter distributions were formed on the catalysts derived from mushrooms, seaweed and black sesame seeds because they have a high carbon yield and as a result iron-based nanoparticles are well dispersed in these catalysts. The diameter distribution of the CNTs prepared using black fungus based catalyst was also narrow, but not well distributed, owing to the fact that black fungus has a low carbon yield and the iron-based nanoparticles are not well dispersed in the catalyst derived from them.

The spin-dependent transport properties of a zigzag graphene nanoribbon edge-defect junction

AN Li-ping

2012, 27(3): 181-187. doi: 10.1016/S1872-5805(12)60012-2

Abstract(1819)

PDF(1059)

Abstract:
First-principles calculation was performed to investigate the transport properties of edge-defect junctions of graphene with H-terminated or bare edges, which were generated by removing edge carbon atoms from a perfect ribbon. The edge defect changes the electronic transport behavior of a zigzag graphene nanoribbon from spin-degenerated for a perfect ribbon to highly spin-polarized for edge-defective ones at the Fermi level. The electronic local density of states isosurface calculations could help understand the transport results. These junctions could generate spin-polarized currents. Especially, the bare edge-defect junction has a high spin filter efficiency regardless of the external bias. This behavior suggests a possible use of the edge-defective graphene in a spin filter system.
Keywords:　Graphene nanoribbon; Edge-defect junction; Spin-dependent transport

Preparation and characterization of graphene-reinforced polyacrylonitrile-based carbon nanofibers

KONG Qing-qiang, YANG Mang-guo, CHEN Cheng-meng, YANG Yong-gang

2012, 27(3): 188-193.

Abstract(2369)

PDF(1869)

Abstract:
Graphene was obtained by vacuum-assisted thermal expansion of graphite oxide followed by a further thermal annealing. A series of polyacrynitrile (PAN)-based nanofibers with different graphene contents were prepared by electrospinning, using the graphene as the reinforcement. SEM, XRD, FT-IR, TG-DSC and elemental analysis were used to investigate the microstructure evolution of the PAN nanofibers during stabilization and carbonization. Results show that the addition of graphene improves the orientation of the PAN molecules, but decreases their crystallinity. This inhibits oxidation, cyclization and dehydrogenation during the oxidative stabilization of PAN fibers. Graphene acts as nucleation sites for the growth of graphite crystals along the graphene plane during carbonization.

Synthesis of porous carbons from metal-organic coordination polymers and their adsorption performance for carbon dioxide

DENG Hong-gui, JIN Shuang-ling, ZHAN Liang, WANG Yan-li

2012, 27(3): 194-199. doi: 10.1016/S1872-5805(12)60013-4

Abstract(1701)

PDF(923)

Abstract:
A series of porous carbons (PCs) was synthesized from nonporous metal-organic coordination polymers (MOCPs), using in-situ polymerized phenol resin as a carbon precursor. The optimized PC has a BET surface area of 2368m²/g and an equilibrium CO₂ adsorption capacity of 2.9mmol/g at 300K and atmospheric pressure. The porous structure of the PCs can be controlled by the formulations of the carbon precursors and gelation/aging time. Meanwhile, the evaporated Zn from the thermal decomposition of the MOCPs acts as an activation agent during carbonization, which eventually improves the microporosity of the PCs. The CO₂ equilibrium adsorption capacity increases with increasing Brunauer-Emmett-Teller surface area of the PCs.

Transmission electron microscope identification of a hexagonal porous arrangement in ordered mesoporous carbon

LIN Qing-yun, LI Peng, SONG Yan, HE Lian-long, GUO Quan-gui, YE Heng-qiang

2012, 27(3): 200-204.

Abstract(1693)

PDF(1029)

Abstract:
The overall properties of ordered mesoporous carbons (OMCs) are essentially influenced by the pore structure. However, neither X-ray diffraction analysis nor transmission electron microscopy (TEM) micrographs can identify the pore structure correctly. Therefore, a three-dimensional (3D) reconstruction method from TEM was carefully developed to investigate the structure and parameters of OMCs. Characteristic pore images of OMCs can be obtained by separately tilting along the two vertical axes using a 3D specimen holder. Pore parameters and a model of their arrangement can be readily obtained by analyzing the geometrical relationship of pore images of OMCs with different azimuths. As an example, OMCs synthesized from resin using an organic template method were investigated. It is concluded that the OMCs have an ordered hexagonal arrangement with a uniform pore size of 11 nm. It is demonstrated that a series of tiltings about two vertical axes can easily confirm whether the arrangement of OMCs is hexagonal or not. The structure model and parameters of OMCs with hexagonal symmetry can also be easily identified by this method.

Synthesis, structure and adsorption properties of bagasse-based carbon molecular sieves

GUO Hai-rong, WANG Guo-mei, MA Shao-ying, LI Bin

2012, 27(3): 205-210.

Abstract(1879)

PDF(1244)

Abstract:
Bagasse-based carbon molecular sieves (BCMS) were synthesized by a two-stage carbonization method, using bagasse as the raw material, and phenol-formaldehyde resin and carboxymethyl cellulose as the binders. The BCMS were characterized by N₂ adsorption, X-ray powder diffraction differential thermal analysis, scanning and transmission electron microscopy and adsorptive de-coloring tests. Results showed that the BCMS had mainly micropores with the size centered at 0.72 nm, a micropore volume of 0.11cm³/g and a Brunauer-Emmett-Teller surface area of 269m²/g. XRD showed that apart from the broad peaks at 2θ values of 23^o and 44^o, ascribed to amorphous carbon, there are peaks ascribed to a monoclinic single crystal belonging to C2/c(15) space group, with size of 57.7nm and cell parameters of a=2.0437nm，b=0.3497nm，c=1.0345nm， α=90.000°， β=106.439°， γ=90.000°. The BCMS had developed pores with a hierarchical structure, which afforded them a high adsorption capacity of 1.296g/g for coloring substances in a clear sugarcane liquor.

The secondary growth of mesocarbon microbeads

DING Han-yang, WANG Cheng-yang, CHEN Ming-ming, ZHENG Jia-ming

2012, 27(3): 211-218.

Abstract(1715)

PDF(1154)

Abstract:
A small quantity of mesocarbon microbeads (MCMBs) derived from a coal tar pitch were added to another coal tar pitch to investigate the formation and growth mechanism of MCMBs. It was found that new MCMBs were also observed. A further analysis of particle size distributions, morphology and cross-section texture of the new and added MCMBs as well as their total yields showed that the secondary growth of the added MCMBs was mainly driven by physical interactions. The thermal condensation of the pitch included nucleation of raw pitch to form the new MCMBs and secondary growth of the added MCMBs. The two parallel processes competed with each other and the dominating one was determined by the fraction of the added MCMBs. It was concluded that the basic structural units of MCMBs moved from the parent pitch onto the surface of MCMBs during the growth.

Studies on the adsorption of cadmium ions by micro-size carbon fibers in aqueous solution

2012, 27(3): 219-225.

Abstract(1680)

PDF(1212)

Abstract:
Micro-size carbon fibers (MCFs) with a diameter of 0.4-0.6 μm and a length of tens of micrometers were prepared on a coal-based anode by dc arc discharge in a mixture of helium and acetylene. The adsorption of cadmium ions by the MCFs in solution was studied. The effect of the functional groups, time, pH value and initial concentration of solution on the adsorption of cadmium ions was investigated. Results showed that the acid oxidation resulted in an increase in the number of oxygen-containing groups. The adsorption capacity of the oxidized MCFs increased significantly. The pH value has a great influence on the adsorption of cadmium ions. A kinetic study showed that the adsorption followed the pseudo-second order kinetic adsorption model. Both Langmuir and Freundlich models described the adsorption isotherms well at pH<7.00, while the surface precipitation model showed good agreement with the experiment data when deposition occurred. The adsorption capacity, based on the unit weight and the unit surface area, was the larger for the oxidized MCFs than those for the un-oxidized ones. When the equilibrium concentration was 2 mg · L^-1 and pH=5.50, the adsorption capacities were 5.7 mg · g^-1 or 0.058 mg · m^-2. These suggested that the MCFs have potential applications in environmental protection.

Boron-doped glassy carbon fabricated by chemical vapor deposition

XU Li, WU Jun-feng, BAI Shuo

2012, 27(3): 226-232. doi: DOI: 10.1016/S1872-5805(12)600

Abstract(1542)

PDF(1000)

Abstract:
A boron-doped glassy carbon was fabricated by chemical vapor deposition from a gaseous CH₄/BCl₃ mixture. It was characterized by X-ray diffraction, Raman spectroscopy, scanning, and transmission electron microscopy. Results show that the deposited carbon is characteristic of a glass-like carbon but with boron carbide nanocrystals around 20 nm in diameter uniformly distributed in its matrix. In contrast to the conventional non-graphitizable glassy carbon, the product behaved similarly to a graphitizable carbon on high-temperature treatment because of the strong catalytic graphitization effect of the boron. The glass carbon was transformed into lamellar carbon structures, probably by a dissolution-precipitation mechanism.

C364 carbon black pigment as a reinforcement in plastics

XU Yan-lian|　CHEN Qin-hui|　HU Bing-huan, LIN Jin-hou, XIA Jian-rong|

2012, 27(3): 233-240.

Abstract(2103)

PDF(1057)

Abstract:
Three samples, C364 carbon black, C364 carbon black pigment after a two step ozone oxidation, and MA100 from Mitsubishi Corporation, were characterized by XPS, IR, SEM, PY-GC/MS spectroscopy and elemental analysis. The processing parameters, mechanical properties, aging resistance and micro-morphology of the oxidized C364 carbon black pigment and its composites with polyethylene, polyvinyl chloride and poly(acrylonitrile-butadiene-styrene) resins were characterized by a HAAKE torque rheometer, scanning electron microscopy and an aging test chamber. Results show that oxidized C364 carbon black pigment contains more hydroxyl, carbonyl, carboxyl and other functional groups than the original C364 sample. The mechanical properties of the composites with oxidized C364 carbon black pigment were almost the same as those of MA100-based ones. Oxidation of the C364 carbon black pigment significantly increased the photo aging lifetime of the polyethylene-based composite 10 times.

2012 Vol. 27, No. 3

Classified CollectionMORE

Information Notice MORE MORE

DownloadMORE

LinksMORE