新型炭材料

H+, N+, and Ar+ ion irradiation induced structure changes of carbon nanostructures

A Ishaq1, 　Shahid Iqbal1, 2, 　Naveed Ali1, 　A A Khurram1, 　A U Akrajas3

2013, 28(2): 81-87. doi: 10.1016/S1872-5805(13)60068-2

Abstract(1260)

PDF(1127)

Abstract:
The effects of H+, N+, and Ar+ ion irradiation on structural changes in multi-walled carbon nanotubes (MWCNTs) and amorphous carbon nanowires (a-CNWs) were investigated at room and elevated temperatures with different irradiation doses. It is found that at room temperature, defects were introduced in MWCNTs under 70 keV N+ ion beam irradiation at a low dose of 1×1016 ions/cm2 while MWCNTs transformed into a-CNWs at a high dose of 7×1016 ions/cm2. At 1 000 K, the 70 keV N+ ion beam irradiation of defective MWCNTs causes the curling of carbon clusters to an onion-like structure at a dose of 4×1016 ions/cm2 and the formation of a low density onion-like structure at 7×1016 ions/cm2. Irradiation of the defective MWCNTs by 70 keV Ar+ ion at 1 000 K and 7×1016 ions/cm2 leads to the formation of a high density onion-like structure. Irradiation of a-CNWs with 70 keV H+ ion at 1 000 K gradually increases the fraction of material with a diamond structure with increasing dose from 1×1016 to 1×1017 ions/cm2.

High electrical sensitivity of polyurethane carbon nanotube composites to tensile strain

ZENG You1, 2, 　LIN Peng-fei1

2013, 28(2): 88-93.

Abstract(1307)

PDF(1264)

Abstract:
Carbon nanotube/polyurethane (CNT/PU) composites were prepared by using an in-situ polymerization method, and their electrical sensitivity to tensile strain was investigated. The addition of CNTs can remarkably enhance both the mechanical strength and electrical conductivity of the composite. The CNT/PU composite exhibits a high sensitivity of electrical resistance to changes in tensile strain. The electrical resistance of the CNT/PU composite increases by six orders of magnitude in the enlongation range 0-200%, which can be attributed to the decrease of CNT volume fraction, expansion of total volume, and changes in the CNT-network structure under the high strain. The dependence of electrical resistivity of the composites on tensile strain can be well explained by a percolation threshold theory. The high electrical sensitivity of the CNT/PU composites to tensile strain can be used as an intelligent material and strain sensors in the field of construction safety.

Solubility increase of multi-walled carbon nanotubes in water

SHEN Qian-jin1

2013, 28(2): 94-100.

Abstract(1301)

PDF(1205)

Abstract:
Water-soluble hydroxylated multi-wall carbon nanotubes (MWCNTols) were synthesized by the NaOH/H2O2 oxidation method. A L9(34) orthogonal experimental design was used to optimize the preparation conditions, and TEM, SEM and Raman spectroscopy were used to characterize the products. The solubility of as-prepared MWCNTols in water was 0.72 mg/mL. Furthermore, MWCNTols were wrapped by polyvinylpyrrolidone (PVP) by solution blending. Good water-solubility of PVP further increases the stability and dispersibility of MWCNTols in water. The content of MWCNTols in PVP-MWCNTols is calculated to be as high as 41 mass%. The solubility of PVP-MWCNTols in water was up to 2.34 mg/mL. No aggregation or sedimentation was observed for a saturated solution during more than 2 month storage at room temperature.

Alignment of carbon nanotubes in ultra-long carbon nanotube polymethylmethacrylate composite nanofibers by electrospinning

DAI Yi-le1, 　DAI Jian-feng1, 2, 　SUN Yi-bin1

2013, 28(2): 101-107.

Abstract(1667)

PDF(1483)

Abstract:
Carboxylated carbon nanotube-filled polymethylmethacrylate (CNT/PMMA) ultra-long composite nanofibers were prepared by electrospinning of in-situ polymerized CNT/PMMA bulk composites under shear flow in a quartz capillary tube. They were characterized by SEM, TEM and FT-IR. The degree of orientation of the CNTs in the nanofibers was investigated by polarized Raman spectroscopy. The force imposed on CNTs by the poiseuille flow was analyzed. Results indicate that the nanofibers are smooth with a diameter of around 100 nm and a uninterrupted length of several meters. The CNTs in them are well dispersed and highly aligned parallel to the fiber axis. Chemical bonding between the carboxylated CNTs and PMMA is found. The electrical conductivity of the nanofibers is increased by 10 orders of magnitude by adding 8 mass% of CNTs. The alignment of CNTs in the nanofbers was induced by the shear force of PMMA on CNTs during the electrospinning.

Preparation of porous carbons from non-metallic fractions of waste printed circuit boards by chemical and physical activationKE

KE Yi-hu

2013, 28(2): 108-114.

Abstract(1220)

PDF(1230)

Abstract:
Non-metallic fractions of FR-3 type waste printed circuit boards were pyrolyzed at high temperatures. The resultant char at 600℃ was used to prepare activated carbons by physical and chemical activation. The influence of pyrolysis temperature on char yields, and activation conditions on the burn-off and porous properties of the activated carbons were investigated. Results show that char yields decrease with pyrolysis temperature. A granular activated carbon with a surface area of 1 019 m2·g-1 and a pore volume of 1.1 cm3·g-1 can be obtained by moulding, pyrolysis and physical activation using H2O as an activation agent. An activated carbon powder with a surface area of 3 112 m2·g-1and a pore volume of 1.13 cm3·g-1 can be achieved by KOH activation.

Monolithic porous carbon prepared by Na2CO3 templating as a substrate for a nickel hydroxide electrode

CHEN Dong1, 2

2013, 28(2): 115-120.

Abstract(1302)

PDF(1194)

Abstract:
Monolithic porous carbon (MPC) was synthesized by a templating method using Na2CO3 as template, novolac-type phenolic resin as carbon precursor and hexamethylenetetramine as hardening agent. The template, carbon precursor and hardening agent were mechanically mixed in a grinding machine, hardened at 150 ℃, crushed into fine particles, compacted into a disc, carbonized at 800℃ and finally washed with deionized water to form MPC. MPC-Ni(OH)2 electrodes were prepared by loading Ni(OH)2 into the MPC by cathodic deposition. The MPC is hierarchically porous, has an electric conductivity of 20.40 S·cm-1 and a specific surface area of 576 m2·g-1.Charge-discharge characterization of the MPC-Ni(OH)2 electrodes shows that the specific capacities based on active material and the whole electrode are 230 mAh·g-1 and 131 mAh·g-1, respectively. This suggests that the MPC is a promising lightweight matrix to host nickel hydroxide to achieve a high specific energy in nickel-based alkaline batteries.

Synthesis of highly graphitic mesoporous carbon using Ni-Fe double-layered hydroxide as both template and catalyst precursor

ZENG Fu-long

2013, 28(2): 121-126. doi: 10.1016/S1872-5805(13)60070-0

Abstract(1131)

PDF(1247)

Abstract:
A graphitic mesoporous carbon was prepared using sucrose as carbon precursor and Ni-Fe (Ni/Fe=2) double-layered hydroxide (DLH) as template and catalyst precursor by a solid-phase method. The material was characterized by X-ray diffraction, Raman spectroscopy and high-resolution transmission electron microscopy. Results indicated that the graphitic mesoporous carbon has a uniform mesopore size and a high degree of graphitization. The mesoporous structure of the carbon is generated by templating from the mesoporous DLH. The catalytic metallic Ni was formed by reduction of Ni ions in the pore walls of the DLH with carbon during carbonization, and this caused graphitized carbon to be formed at a quite low temperature of 900℃.

Synthesis of carbon foam with high compressive strength from an asphaltite pitch

Deniz Baran1, 　Mehmet Ferhat Yardim2, 　Hüsnü Atakül2, 　Ekrem Ekinci3

2013, 28(2): 127-133.

Abstract(1175)

PDF(1385)

Abstract:
Carbon foams were synthesized using an asphaltite pitch as a carbon precursor. The effects of foaming conditions and carbonization on the pore structures and physical properties of carbon foams were investigated. Results indicate that the average pore size and density of as-synthesized carbon foams were about 150 μm and 800 kg/m3, respectively. The compressive strength of the carbon foam increased from 10 to 18.7 MPa after carbonization at 1323K. The high ash content of (41.76%) the pitch plays an important role on the density and compressive strength of carbon foams.

Growth of ultrananocrystalline diamond films in an Ar-rich CH4/H2/Ar atmosphere with varying H2 concentrations

LIU Jie, 　HEI Li-fu, 　CHEN Guang-chao, 　LI Cheng-ming, 　TANG Wei-zhong, 　LU Fan-xiu

2013, 28(2): 134-139. doi: 10.1016/S1872-5805(13)60072-4

Abstract(1253)

PDF(1297)

Abstract:
Ultrananocrystalline diamond (UNCD) films were prepared by microwave plasma chemical vapor deposition using argon-rich CH4/H2/Ar plasmas with different H2 concentrations from 5 to 20%. The influence of the H2 concentration on the microstructure, morphology and phase composition of the UNCD films was investigated by SEM, XRD, surface profilometry and Raman spectroscopy. It is found that the grain size and surface roughness increase with the H2 concentration. The grain size of the UNCD is less than 6 nm when the H2 concentration is less than 10% and it is still less than 10 nm even when the concentration is 20%. The thickness of the UNCD films is 1.75, 1.80, 1.65 and 2.9 μm using H2 concentrations of 5, 10, 15 and 20%, respectively. All the films are dense and compact in the cross section, and smooth on the top surface.

A comparative study of the characteristics and carbonization behaviors of three modified coal tar pitches

ZHANG Wen-juan

2013, 28(2): 140-145. doi: 10.1016/S1872-5805(13)60073-6

Abstract(1349)

PDF(1255)

Abstract:
Coal tar pitch (CTP) was modified either with 10g cinnamaldehyde (CMA) per 100 g CTP, 7 g p-toluene sulfonic acid (PTS) per 100g CTP, or a mixture of 10g CMA and 7 g PTS per 100g CTP. The parent CTP and the modified CTPs were characterized by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis. The four samples were carbonized at different temperatures and the products were characterized by FT-IR and polarized-light microscopy. Results show that the modifications have a large influence on the characteristics and carbonization behavior of the CTP. The distillation of CMA occurs at a temperature lower than 300 ℃ during the carbonization of the CMA-modified CTP. Methyl and methylene groups of the parent CTP and the modified CTPs gradually disappear with increasing temperature during carbonization. The modification of the CTP with the mixture of CME and PTS results in a highest increase (5.08%) of carbonization yield and the most abundant mesophase sphere formation during carbonization

The influence of pretreatment on multi-wall carbon nanotubes for electrochemical capacitors

GENG Xin1, 2

2013, 28(2): 146-150.

Abstract(1130)

PDF(1143)

Abstract:
Multi-wall carbon nanotubes (MWCNTs) prepared by chemical vapor deposition, were pretreated by ball milling, chemical activation and ammoxidation and the influence of the pretreatment on their electrochemical capacitance was investigated. Results show that MWCNTs can be shortened and broken by ball milling and chemical activation, and as a result their surface area and pore volume are increased. However, ammoxidation decreases the surface area of the activated MWCNTs. The electrical conductivity of the ball-milled MWCNTs is the smallest while that of the ammoxidated is the largest. The specific capacitances of the ball-milled and the activated MWCNTs are close, but higher than that of the ammoxidated MWCNTs. The capacitances of the MWCNTs pretreated by ball milling, chemical activation and ammoxidation are reduced by 17, 27 and 13% respectively when the discharge current density is increased from 5 to 100mA/g.

The simple preparation of a hierarchical porous carbon with high surface area for high performance supercapacitors

ZHENG Dong-fang 1

2013, 28(2): 151-155.

Abstract(1265)

PDF(1671)

Abstract:
A simple method was proposed to prepare a high surface area and hierarchical porous carbon for supercapacitors by one step carbonization-activation of poly(vinylidene chloride) with NaOH. The porous carbon has hierarchical micropores, mesopores and macropores with a high surface area of 2815m2 · g-1. Its capacitance reaches 376 and 215F · g-1at current densities of 0.05 and 50A · g-1 respectively in 6 mol · L-1 KOH aqueous electrolyte. The capacitance is 170 and 124F · g-1 at 0.05 and 20A · g-1, respectively in 1 mol · L-1 Et4NBF4/AN non-aqueous electrolyte. The high capacitance and its high retention ratios at high current density in both electrolytes could be ascribed to its hierarchically porous structure and high surface area.

Modification of activated carbon using sodium citrate and its effect on the adsorption of copper ions

ZHONG Kai-kai1, 2　HUANG Zhang-gen1|　HAN Xiao-jin1|　ZHANG Chang-ming1

2013, 28(2): 156-160.

Abstract(1245)

PDF(1690)

Abstract:
Activated carbon (AC) was modified with sodium citrate at a concentration of 5-15% by impregnation to develop a new type of adsorbent, named (Nx-AC where x is the concentration. Their pore structures and surface chemical properties were characterized by N2 adsorption, Boehm titration and FT-IR. The adsorption of copper ions by the (Nx-AC and the regenerated ones were investigated through a static adsorption method. Results showed that the carboxyl content had a great influence in the adsorption properties of (Nx-AC for copper with the adsorption capacity of N15-AC being 1.76 times higher than the parent AC, which was higher than those of the N5-AC. and the (N10-AC. The adsorption capacity of the regenerated N15-AC s for copper can reach 98.2 and 95.9% of the original N15-AC for the first and second regenerations respectively.

2013 Vol. 28, No. 2

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