新型炭材料

A method for coating carbon nanotubes with titaniumH.

Omidvar1, 　F. K. Mirzaei2, 　M. H. Rahimi1, 　Z. Sadeghian3

2012, 27(6): 401-408. doi: 10.1016/S1872-5805(12)60023-7

Abstract(1373)

PDF(1886)

Abstract:
The surfaces of acid-functionalized carbon nanotubes (CNTs) were coated by TiO₂ produced by the hydrolysis of TiCl₄, which was converted into Ti through temperature-programmed reduction (TPR) equipment. SEM, TEM, XRD, and EDAX analyses were used to characterize the primary CNTs, as-prepared TiO₂-coated CNTs and the Ti-coated CNTs. It was found that after the functionalization of CNTs by ultrasonic-assisted acid treatment, TiO₂ was successfully coated onto the CNTs, which was reduced in TPR under H₂/Ar flow at 850℃ to metal Ti. The Ti transition layer is important for the formation of composites of CNTs with other metals.

Study of thallium(III) adsorption onto multiwall carbon nanotubes

Saeed ur Rehman1, 　Najeeb Ullah1, 2, 　Ali Reza Kamali2

2012, 27(6): 409-415. doi: 10.1016/S1872-5805(12)60024-9

Abstract(1416)

PDF(2088)

Abstract:
Multiwall carbon nanotubes (MWCNTs) oxidized by H2SO4, KMnO4, and HNO3 were used as sorbents and their sorption abilities for Tl(III) were compared with raw MWCNTs. The Langmuir model was used for the calculation of the amount of Tl(III) sorbed on the surface of MWCNTs. The acidic oxidation treatment of MWCNTs yielded a large number of functional groups, leading to a sharp increase in Tl(III) adsorption. Maximum adsorption of Tl(III) was recorded at a pH value of 7. The maximum amounts of Tl(III) sorbed on raw MWCNTs, H2SO4-oxidized, KMnO4-oxidized and HNO3-oxidized MWCNTs calculated by the Langmuir model were 3.0, 11.7, 21.6 and 31.5 mg/g, respectively. The MWCNTs oxidized by HNO3 showed the best sorption performance for Tl (III) ions.

Synthesis of short multi-walled carbon nanotubes by molecular self-assembly

CHEN Yong1

2012, 27(6): 416-420. doi: 10.1016/S1872-5805(12)60025-0

Abstract(1425)

PDF(1068)

Abstract:
Short multiwall carbon nanotubes (MWCNTs) were synthesized by pyrolysis of a polysilazane-polyvinyl pyrrolidone mixture that was characterized by dynamic light scattering. It was found that the polymer mixture had a tube-shaped aggregate at the nanometer scale. The MWCNTs are ~30nm in diameter and ~500nm in length. Structural characterization revealed that they have a well-developed tubular structure with a uniform wall thickness, but are not well graphitized. The formation of the MWCNTs can be accounted for by the self-assembly of polyvinyl pyrrolidone in the solution to form polymeric nanotubes that were converted to MWCNTs by subsequent pyrolysis.

The distribution of intravenously administered functionalized carbon nanotubes in rabbit tissue and their urinary excretion

YU Shi-ping1, 2

2012, 27(6): 421-426.

Abstract(2165)

PDF(1081)

Abstract:
Diethylenetriaminepentaacetic acid-functionalized multi-wall carbon nanotubes (MWCNT-DTPA) were labeled by 99mTc and intravenously administered to rabbits, the radioactivity in different organs was scanned by single photon emission computed tomography and a well-type γ counter. Results showed that the administered MWCNT-DTPA-99mTc was mainly distributed in heart, liver, spleen and kidney. Centrifugate from urine was subjected to transmission electron microscopy analysis which showed that MWCNTs could be excreted through the urinary system.

Synergetic effect of conductive additives on the performance of high power lithium ion batteries

WANG Qi1, 2, 　SU Fang-yuan3, 　TANG Zhi-yuan1

2012, 27(6): 427-432. doi: 10.1016/S1872-5805(12)60026-2

Abstract(1506)

PDF(1691)

Abstract:
Two commercial conductive additives, carbon black (super P, SP) and vapor grown carbon fibers (VGCFs), were used to construct an effective conducting network in the cathode of commercial LiFePO4 lithium ion batteries (LIBs). Results suggest that the LIB with SP possesses a higher discharge capacity than that with VGCFs with the same mass fraction of the additives. The high-rate capacity of LIB with SP is much higher than that with VGCFs. Furthermore, the LIB with a mixture of these two additives has an apparently improved performance in low and high rate discharge capacity compared with the LIBs with a single component additive with the same mass fraction due to the synergetic effect. The same conclusion can be reached for the larger-capacity batteries (10 Ah or 50 Ah packs). Therefore, the use of two different fillers is important for the high power LIBs used in the electric vehicle and mass energy-storage industry.

Preparation of a direct methanol fuel cell tubular cathode support from mesocarbon microbeads and graphite

NI Hong-jun1, 　TANG Dong2, 　YIN Ming-qiang1, 2, 　WANG Xing-xing1, 　LIAO Ping1

2012, 27(6): 433-439.

Abstract(1303)

PDF(815)

Abstract:
A tubular cathode support green body for tubular direct methanol fuel cell was prepared by a gel casting molding method using a mixture of mesocarbon microbeads and natural graphite powder with a mass ratio of 3∶2 as carbon precursor. It was sintered at 1 000 ℃ for 5 h in a graphite boat covered by graphite powder. Subsequently, a tubular cathode and a planar anode were obtained by coating the supports with slurry containing a catalyst and a Nafion membrane in a PTFE suspension. The catalysts for the cathode and anode are Pt/C and Pt-Ru/C, respectively. Results show that the surface of the tubular cathode support is smooth with no distortion. Both the gas diffusion layer and catalyst layer of the cathode show a similar porous structure with most of the holes in the sub-micron scale, which is favorable for decreasing mass transfer resistance and improving catalytic efficiency. A single cell performance test indicates that the sintered cathode bodies from the mixture of mesocarbon microbeads and graphite can be used as a special-shaped cathode support.

Preparation and characterization of activated carbons from spirit lees by physical activation

LI Qiang1

2012, 27(6): 440-447.

Abstract(1670)

PDF(1293)

Abstract:
Spirit lees was carbonized and then activated by steam and CO2 to prepare activated carbons. The effect of carbonization temperature, type and amount of activator, activation temperature and time on the pore structure, and the adsorption of methylene blue and iodine were investigated. The gas products during activation were analyzed online to reveal the activation mechanism. Results showed that steam activation was rather more active than CO2. Regardless of the activation agent, a low carbonization temperature of 450 ℃ and a medium activation temperature of 800 ℃ favored the iodine adsorption. For the methylene blue adsorption, the same low carbonization temperature of 450 ℃, however, medium/high activation temperatures (850 to 900 ℃) are favorable.. The best activated carbon was prepared with a steam activator using a carbonization temperature of 450℃ and an activation temperature of 800 ℃, which had a surface area and pore volume of 371.6 m2/g and 0.34 cm3/g, and iodine and methylene blue adsorption capacities of 580 mg/g and 90 mg/g respectively. O- and H-containing functional groups in the carbonized spirit lees reacted with the activation regent (steam or CO2) to form the initial pores, then the accessible active sites reacted with the activation regent to generate secondary pores.

Effect of high temperature treatment on the topological microstructure of micro-coil carbon fibers

WU Fa-yu1, 　ZHOU Yan-wen1, 　ZHANG Jun-wei1, 　DU Jin-hong2

2012, 27(6): 448-454.

Abstract(1195)

PDF(1196)

Abstract:
The topological microstructure of micro-coiled carbon fibers (MCFs) before and after high temperature treatment (HTT) was explored and characterized. Results suggested that as-grown MCFs had an annular ring-like structure in the cross section and a herringbone-like structure in the longitudinal section, but the orientation range of graphitic domains was wide. After HTT, the coiled fibers consisted of stacked pyramidal prisms of ordered graphitic domains. The apparent morphology of the coiled fibers is a uniform spiral prism. The evolvement of the microstructure of MCFs after HTT was also confirmed by X-ray diffraction and Raman spectroscopy. The topological microstructure provides a reliable reference for the prediction of properties and projected applications of the MCFs.

Effects of carbon nanotubes grafted on a carbon fiber surface on their interfacial properties with the matrix in composites

LIU Xiu-ying

2012, 27(6): 455-461.

Abstract(1881)

PDF(1282)

Abstract:
Carbon fibers (CFs) were oxidized by concentrated HNO3 and then reacted with polyamidoamine dendrimers (PAMAM) with an average molecular weight of 157 to form CF-PAMAM. The CF-PAMAM was further reacted with oxidized carbon nanotubes (CNTs) to form CF-PAMAM-CNTs that were used as the reinforcement for epoxy resin-based composites. The functional groups and structure of the CF-PAMAM-CNTs were examined by XPS, SEM and AFM, and their wettability and the tensile strength were investigated by contact angle measurements and single strand extension respectively. The interfacial shear strength of the composites was measured by a micro-debonding method. Results showed that, compared with CFs, the surface roughness, surface energy and tensile strength of the CF-PAMAM-CNTs were increased by 180%, 300% and 22%, respectively when the CNT content was 15 mass%. The interfacial shear strength of the composite reinforced with CF-PAMAM-CNTs was increased by 178% for the same CNT content, which showed that the grafted nanotubes improved the interfacial properties of the filler with the matrix.

Preparation of carbon aerogels at room temperature using acetonitrile as solvent

WU Pei-di, 　ZHOU Bin

2012, 27(6): 462-468.

Abstract(1525)

PDF(1059)

Abstract:
Carbon aerogels were synthesized at room temperature by a sol-gel polymerization route using resorcinol and formaldehyde as precursors, acetonitrile as solvent and hydrochloric acid as catalyst, followed by CO2 supercritical drying and carbonization. FT-IR, SEM, XRD and nitrogen adsorption were used to characterize the microstructure of the aerogels. Results showed that the carbon aerogels are graphite-like amorphous materials with nano-skeleton networks formed by nanoparticles around 40-70 nm in diameter, whose specific surface area is up to 1 300 m2·g-1 and lowest density about 0.050 g/cm3. The heat of condensation and the catalytic action of hydrochloric acid made it possible to form gels at room temperature. The high surface area and low density of the as-prepared carbon aerogels were ascribed to a strong interaction between acetonitrile and —OH groups by hydrogen bonding.

Synthesis and characterization of condensed poly-nuclear aromatic resin using heavy distillate from ethylene tar

WU Ming-bo1

2012, 27(6): 469-475. doi: 10.1016/S1872-5805(12)60027-4

Abstract(1427)

PDF(1449)

Abstract:
Heat-resistant condensed poly-nuclear aromatic resin (COPNAR) was prepared using heavy distillate (>250℃, named DO) from distilled ethylene tar (ET). The basic properties of ET, DO and COPNAR were investigated by FT-IR, 1H-NMR, TGA and elemental analysis. The structural parameters of DO and ET were obtained by the improved Brown - Ladner method and the formation mechanism of the COPNAR from DO was deduced. Results show that a superior heat-resistant COPNAR can be obtained from DO. The distillation of ET increases the heat resistance of the COPNAR, and the reaction mechanism is confirmed to be an acid-catalyzed positive ion-type polymerization.

Purification of natural graphite by microwave assisted acid leaching

LI Yu-feng1, 2

2012, 27(6): 476-480.

Abstract(1530)

PDF(1252)

Abstract:
Natural graphite was leached under microwave irradiation by acid mixtures containing HCl (12 mol/L) and HNO3 (16 mol/L). It was found that the purification efficiency was affected by microwave power, reaction pressure, reaction time and the acid ratio. The carbon content of the graphite increased from 95.84 to 99. 43% under optimized leaching conditions with an acid volume ratio of 1∶1, pressure of 1.0 MPa, reaction time of 25 min and microwave power of 800 W. SEM indicated that the morphology remained unchanged and XRD indicated that there was no apparent change in the 2θ peak position, peak height and full width at half maximum after the leaching.

2012 Vol. 27, No. 6

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