The gelation mechanism of carbon aerogel spheres

CARBON

4 7 ( 20 0 9 ) 2 1 4 3–21 4 6

2145

Effect of different oxide additives on the properties of a SiC

microscopy, N2 adsorption, thermal gravimetric, and aqueous

coating on carbon/carbon composites

adsorption. Results showed that PACS with BET surface areas

Xiao-Hong Shi, He-Jun Li, Qian-Gang Fu, Jin-Hua Lu, Ke-Zhi Li

up to 979–1672 m2/g were obtained. The BET surface areas and

C/C Composites Research Center, Key Laboratory of Ultrahigh Composites, Northwestern Polytechnical University, Xi’an 710072, China

pore volumes increased with activation time and steam flow rate except for the volume of narrow micropores (<0.7 nm). The maximum adsorption capacity of PACS to DBT was 109.36 mg/g and

Double-layer SiC-based coatings on carbon/carbon composites

the adsorption capacity was related to the volume of narrow

were prepared by a wrapping cementation method with different

micropores, independent of surface area and total pore volume.

oxides (MgO, Al2O3 or B2O3) as additives to the inner layer. The

Irreversible adsorption existed between DBT and PACS. The larger

phase morphologies and antioxidation properties of the SiC

the volume of the narrow micropores, the higher the desorption

coated carbon/carbon composites were investigated by SEM,

temperature and the larger the amount of sulfur retained after

EDS and XRD. Results show that the SiC coating with B2O3 as an

heating.

additive to the inner layer is more compact than those with

[New Carbon Materials 2009;24(1):55–60]

MgO or Al2O3 as the additive. Different phases exist in the three

doi:10.1016/j.carbon.2009.03.018

different inner layer SiC coatings. The double-layer SiC coating modified by B2O3 is dense and uniform with few flaws and holes, and can protect carbon/carbon composites from oxidation at 1500 °C for 200 h in air.

Bubble growth in the preparation of mesophase-pitch-based

[New Carbon Materials 2009;24(1):45–9]

carbon foams

doi:10.1016/j.carbon.2009.03.016

Mei-Xian Wanga, Cheng-Yang Wanga, Ming-Ming Chena, Tong-Qi Lia, Zi-Jun Hua,b a

Key Laboratory for Green Chemical Technology of State Education

A eutectic effect in the formation of coal based mesophase pitch

Ministry, School of Chemical Engineering and Technology, Tianjin

Xiang-Lin Cheng, Qing-Fang Zha, Xue-Jun Li, Xiao-Jun Yang

University, Tianjin 300072, China

State Key Laboratory of Heavy Oil, China University of Petroleum,

Aerospace Research Institute of Materials and Processing Technology,

Dongying 257061, China

Beijing 100076, China

The toluene soluble part of coal tar pitch (TS) was co-carbonized with waste polystyrene (WPS) to produce mesophase pitch. Results showed that the properties of the mesophase were improved greatly due to the eutectic effect. The solubilities of the TS mesophase pitch and TS-WPS mesophase pitch were 10 and 52 wt.%, respectively. The anisotropic volume fractions of the TS mesophase pitch and TS-WPS mesophase pitch were 65% (coarse mosaic texture) and 100% (flow domain texture) respectively. Apparent viscosities showed that the mesophase pitch was changed from thixotropic to unthixotropic by adding 1

WPS to TS. FT-IR and H NMR spectroscopy showed that an alkylation reaction took place accompanied by an increase of methylene groups when WPS was added to TS. The increase of alkyl groups led to an assembly of mesogen molecules, resulting in a eutectic effect. [New Carbon Materials 2009;24(1):50–4] doi:10.1016/j.carbon.2009.03.017

Preparation of polystyrene-based activated carbon spheres and their adsorption of dibenzothiophene Qin Wang, Xiao-Yi Liang, Rui Zhang, Chao-Jun Liu, Xiao-Jun Liu, Wen-Ming Qiao, Liang Zhan, Li-Cheng Ling State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China

b

National Key Laboratory of Advanced Functional Composite Materials,

A synthetic mesophase pitch from naphthalene was used as a precursor to prepare carbon foams under different temperatures in order to study the bubble growth process and the effect of temperature on the bubble shape during the formation of carbon foams. Scanning electron microscopy and optical microscopy were used to analyze the microstructure of the as-prepared foams. Results show that the bubble size increases from 500 lm to 800 lm when the temperature increases from 480 °C to 540 °C. The initial bubbles are not uniformly dispersed in the molten pitch, but start to grow at the upper section of the pitch. The cross-section bubble shape in the direction of the gravitational force is elliptical but perpendicular to the direction it is circular. The non-spherical shape of the bubble is closely related to the bulk density of the mesophase-pitch based carbon foams, and there is a bulk density gradient in the Z direction of the as-prepared foam. [New Carbon Materials 2009;24(1):61–6] doi:10.1016/j.carbon.2009.03.019

The gelation mechanism of carbon aerogel spheres Ning Liua,b, Ming-Yuan Lia, Ruo-Wen Fua a

Materials Science Institute, PCFM Lab, Zhongshan (Sun Yat-sen)

University, Guangzhou 510275, China b

College of Pharmacy, GuangDong Pharmaceutical University, Guangz-

hou 510006, China

Polystyrene-based activated carbon spheres (PACS) were prepared by steam activation and their adsorption performance to

Carbon aerogel (CA) spheres were prepared by an inverse

a sulfur-containing dibenzothiophene (DBT) was studied. The

phase suspension polymerization of resorcinol and formaldehyde

textural structure of PACS was characterized by scanning electron

(RF) monomers with hexadecyltrimethylammonium bromide as

2146

CARBON

4 7 ( 2 0 0 9 ) 2 1 4 3 –2 1 4 6

catalyst. The gelation mechanism of RF gel was investigated by

fraction of mesophase that is aligned upon spinning, and ali-

analyzing the changes of viscosity, pH, temperature and the UV

phatic side chains that are beneficial to spinning. The carbon

spectra of the as-formed sol. Results indicate that the gelation

fibers have a radial core structure with a linear and bent type

of resorcinol and formaldehyde is a condensation polymeriza-

anisotropic texture. The maximum tensile strength of the carbon

tion, which can be divided into four stages including linear con-

fiber is 650 MPa.

densation, cross-linking, growth of colloidal particles and

[New Carbon Materials 2009;24(1):83–8]

macroscopic gelation. [New Carbon Materials 2009;24(1):67–72]

doi:10.1016/j.carbon.2009.03.022

doi:10.1016/j.carbon.2009.03.020 Effect of surface treatments of short carbon fibers on the properties of pitch-based C/C composites The dispersion of SWCNT bundles on interaction with pterphenyl Theresa G. Heddermana, Anika S. Mostaertb, Anne E. Shanahana, Hugh J. Byrnea a

Ling-Jun Guo, He-Jun Li, Ke-Zhi Li State Key Lab of Thermostructure Composite Materials, Northwestern Polytechnical University, Xi’an 710072, China C/C composites were fabricated in air using mold pressing and

Focas Institute, Dublin Institute of Technology, Kevin Street, Dublin 8,

Ireland

semi-carbonization shaping technology. The effects of surface

b

treatment methods for short carbon fibers on the density and

Conway Institute of Biomolecular and Biomedical Research, University

College Dublin, Dublin 4, Ireland

mechanical properties of the C/C composites were investigated by an electronic universal testing machine and a scanning elec-

The interaction and dispersion of single-walled carbon nano-

tron microscope. Results showed that the compressive strength

tube (SWCNT) bundles were investigated. SWCNTs were pro-

of the as-fabricated C/C composites increased with an enhance-

duced by arc discharge and by the high pressure decomposition

ment in intensity of surface treatment for short carbon fibers.

of carbon monoxide (HiPco method), in the presence of the mol-

The compressive strength of the C/C composites with surface-

ecule p-terphenyl. The dispersion of SWCNT bundles and their

treated carbon fibers was increased by 138.5% compared with that

interaction with p-terphenyl in their as-produced state and after

of the C/C composites without surface treatment.

purification were compared. A number of spectroscopic and

[New Carbon Materials 2009;24(1):89–92]

microscopic techniques were used to probe the SWCNTs and their interaction with p-terphenyl. X-ray energy dispersive analy-

doi:10.1016/j.carbon.2009.03.023

sis was used to give an elemental analysis of the SWCNT samples before and after purification. Fluorescence and atomic force microscopy are used as techniques to assess the degree of inter-

The influence of nickel nitrate on the structure of mesoporous

action and dispersion of the SWCNT bundles. Results show that

carbon prepared by a template method

the extent of bundle dispersion and the degree of interaction with

Zhi-Hong Tanga,b, Yan Songa, Lang Liua, Quan-Gui Guoa, Yuan-Li

p-terphenyl is related to the purity of the SWCNTs.

Zhanga

[New Carbon Materials 2009;24(1):73–82]

a

doi:10.1016/j.carbon.2009.03.021

Chinese Academy of Sciences, Taiyuan 030001, China b

Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Graduate University of the Chinese Academy of Sciences, Beijing

100049, China Mesoporous carbons (MCs) were synthesized using thermosetPreparation and characterization of pitch-based carbon fibers

ting phenol resin as carbon precursor, commercial nanometer

Arshad Hussain Wazir, Lutfullah Kakakhel

sized silica dioxide particles as template and nickel nitrate as additive. The pore structure as well as the crystalline structure

National Centre of Excellence in Physical Chemistry, University of

of the as-prepared carbons before and after the addition of nickel

Peshawar, Peshawar-25120, Pakistan

nitrate was investigated by nitrogen adsorption and X-ray diffrac-

A petroleum pitch was heated at 420 °C for 7 h in nitrogen to prepare a carbon fiber precursor with a softening point of 295 °C. The precursor was successfully melt-spun into fibers through a circular nozzle of a monofilament spinning apparatus, and these were then stabilized at 320 °C in air and finally carbonized at 1000 °C in nitrogen to produce carbon fibers. SEM, TGA, FTIR, and XRD were performed to characterize the petroleum pitch, the precursor, the as-spun fibers, the stabilized fibers, and the carbon fibers. It is found that the precursor contains 70.5% mass

tion. Results indicated that the addition of an appropriate amount of nickel nitrate not only increased the BET specific surface area, but also led to the formation of graphite crystallite. At the same time, bimodal pores with the size of about 4 nm and 10 nm were developed by adjusting the content of nickel nitrate. [New Carbon Materials 2009:24(1):93–6] doi:10.1016/j.carbon.2009.03.024