preparation of high purity graphite by an alkaline roasting–leaching method

Abstracts of New Carbon Materials, 2010(1)

Catalyst-free synthesis of onion-like carbon nanoparticles

M. Bystrzejewskia, M.H. Rummelib, T. Gemmingb, H. Langea,

A. Huczkoa

a Department of Chemistry, Warsaw University, Pasteur 1 Str., 02-093

Warsaw, Polandb IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany

A one-step process for the synthesis of onion-like carbon

nanoparticles is described. The process is based on a thermolysis

of a NaN3–C6Cl6 mixture. The effect of buffer gas (Ar or air) on the

yield, morphology, and structure of the carbon products was

investigated by electron microscopy, X-ray diffraction, and

Raman spectroscopy. The products contained carbon-onions,

amorphous carbon nanoparticles, and NaCl. The byproducts were

completely removed using a simple purification process. The for-

mation of onion-like nanoparticles is likely caused by a shock

wave, a rapid increase of pressure, during thermolysis, which

induced the coalescence of phenyl radicals.

[New Carbon Materials 2010;25(1):1–8].

doi:10.1016/j.carbon.2010.01.036

Synthesis of carbon foams with a high compressive strength

from arylacetylene

Shu-ping Zhanga, Ming-xian Liub, Li-hua Gana, Fang-rui Wub,

Zi-jie Xub, Zhi-xian Haob, Long-wu Chenb

a College of Urban Construction and Environmental Engineering, Uni-

versity of Shanghai for Science and Technology, Shanghai 200093, Chinab Department of Chemistry, Tongji University, Shanghai 200092, China

Carbon foams with high mechanical strength were prepared

by polymerization of arylacetylene using sulfuric acid as a cata-

lyst, pentane as a blowing agent and Tween 80 as a bubble stabi-

lizer, followed by carbonization. Through controlling the

preparation conditions such as the proportion of blowing agent,

the concentration and volume of the catalyst, and the amount

of the bubble stabilizer, carbon foams with good porous structure,

smooth ligaments, and junctions without microcracks could be

fabricated. The representative carbon foam possesses a high

compressive strength of 25.8 MPa and a high strength/density

ratio of 43.0 MPa/(g cm�3), owing to a high char yield of the aryl-

acetylene polymer, which is up to 86% after carbonization, and

a good pore structure of the products.


doi:10.1016/j.carbon.2010.01.037

The electromagnetic loss characteristics of SiC/C materials with a

three-dimensionally connected porous structure

Zhi-gang Fanga,b, Chu-sen Lia, Jia-yan Suna, Hong-tao Zhanga

Jin-song Zhanga

a Institute of Metal Research, Chinese Academy of Sciences,

Shenyang 110016, Chinab Schools of Machine Engineering, Taizhou University, Taizhou 318000,

China

SiC/C foams and their monoliths of the same compositions,

with various electrical conductivities were prepared by polymer

sponge replication/carbonization and hot-press solidification/car-

bonization, respectively. Both materials have a three-dimension-

ally connected pore structure with the former on a macroscopic

scale and the latter a microscopic scale. The electromagnetic

parameters of the SiC/C foams and the monoliths versus their elec-

tric conductivities were measured at a frequency of 2450 MHz by

the TE10 resonant cavity perturbation method. Results show that

when the electrical conductivities of the SiC/C foams and the

monoliths increase gradually, their dielectric constants e0r increase

gradually and their dielectric losses tgde exhibit a maximum. The

magnetic loss tgdm of the SiC/C foams increases continually while

that of the monoliths first increases quickly then decreases slowly

with increasing electric conductivities. When the effective electric

conductivities of the SiC/C foams and the monoliths are the same,

the e0r values of the SiC/C foams are about a half and the tgde values

are at least two times larger than those of the monoliths, while the

tgdm values of the monoliths are more than four times those of the

SiC/C foams. The SiC/C foams and the monoliths are both non-

magnetic, and their magnetic losses are found to be caused by their

special structures interacting with the incident electromagnetic

waves. Thus it is apparent that this kind of magnetic loss is

extrinsic.


doi:10.1016/j.carbon.2010.01.038

Preparation of high purity graphite by an alkaline roasting–

leaching method

Peng Ge, Hua-jun Wang, Jing Zhao, Lin Xie, Qiang Zhang

The Ministry of Education Key Laboratory of High Efficiency Mining and

Safety for Metal Mines, University of Science and Technology Beijing,

Beijing 100083, China

An alkaline roasting–leaching method was used to prepare

high purity graphite from flake graphite from Hubei Jinchang

doi:10.1016/S0008-6223(10)00058-8

C A R B O N 4 8 ( 2 0 1 0 ) 2 1 2 3 – 2 1 2 6

ava i lab le a t www.sc iencedi rec t . com

journal homepage: www.elsevier .com/ locate /carbon

instead of the commonly-used alkaline-acid method. The process

parameters were optimized. Results showed that the fixed carbon

mass fraction achieved by this method could be as high as 99.9%

under the optimal conditions while that by the alkaline-acid

method was only 85.8%, indicating that the alkaline roasting–

leaching method was very effective to improve the fixed carbon

content of the graphite.


doi:10.1016/j.carbon.2010.01.039

Pitch spheres stabilized by HNO3 oxidation and their carboniza-

tion behavior

Xiao-jun Liu, Xiao-yi Liang, Chao-jun Liu, Liang Zhan,

Wen-ming Qiao, Li-cheng Ling

State Key Laboratory of Chemical Engineering, East China University of

Science and Technology, Shanghai 200237, China

Pitch spheres were stabilized by HNO3 oxidation at room tem-

perature using HNO3 solutions of 10, 20, 30, and 40 wt%. The

chemical structure and morphology changes of the oxidized pitch

spheres and their carbonized samples were investigated by FT-IR,

XPS, elemental analysis, and SEM. Results showed that the pitch

spheres oxidized by 30% HNO3 for 12 h could be carbonized at

900 �C to produce carbonized spheres without any change in

shape. The successful carbonization can be ascribed to the contri-

bution of nitrogen functional groups in the form of –NO2, which

were introduced in the HNO3 oxidation process. In the early stage

of the heat treatment around 400 �C, the transformation of –NO2

groups to amine groups occurred, which promoted the cross-link-

ing of pitch molecules. As the pitch spheres were carbonized at

900 �C, cyclization and aromatization reactions led to the forma-

tion of pyridine and quaternary nitrogen groups.


doi:10.1016/j.carbon.2010.01.040

Gas products and carbon deposition kinetics in chemical vapor

deposition from propylene

Cui-ying Lua,b, Lai-fei Chenga, Li-tong Zhanga, Chun-nian Zhaoa

a National Key Laboratory of Thermostructural Composite Materials,

Northwestern Polytechnical University, Xi’an 710072, Chinab School of Chemistry and Chemical Engineering, Yulin College, Yulin

719000, China

Gas products and chemical vapor deposition kinetics of pyro-

carbon (PyC) formed during pyrolysis of a propylene/argon mix-

ture in the range 700–1200 �C were analyzed by out-line gas

chromatography coupled with mass spectrometry and by an

in situ magnetic suspension balance, respectively. More than 30

components were identified. Benzene was the main product,

substituting for naphthalene as the temperature increased. PyC

was formed with an apparent activation energy of 137 ± 25 kJ/

mol, assumed to be controlled by the acetylene-forming reaction

from 800 �C to 1000 �C. Whereas, above 1000 �C, the deposition

behavior was representative of a combination between gas phase

diffusion from the bulk flow to the solid surface and gas phase

nucleation. Reaction models describing homogeneous gas phase

PyC deposition reactions were derived. On the basis of these

results, a reaction path scheme of PyC formation from propylene

was proposed.


doi:10.1016/j.carbon.2010.01.041

Evolution of microvoids in PAN-based carbon fibers

Deng-hua Lia,b, Gang-ping Wua, Chun-xiang Lua, Yong-hong Lia,

Fu Hea, Zhi-hai Fengc, Xiu-tao Lic, Yu-ming Guoa

a Key Laboratory of Carbon Materials, Institute of Coal Chemistry,

Chinese Academy of Sciences, Taiyuan 030001, Chinab Graduate University of the Chinese Academy of Sciences, Beijing

100049, Chinac Aerospace Research Institute of Materials and Processing Technology,

China Academy of Launch Vehicle Technology, China Aerospace Science

and Technology Corporation, Beijing 100076, China

Microvoids, formed in spinning, oxidation and carbonization

during the preparation of PAN-based carbon fibers, were investi-

gated by two-dimensional small angle X-ray scattering. Results

indicated that microvoids in PAN fibers had a preferred elonga-

tion and orientation along the fiber axis with an average length

of 24.3 nm, diameter of 19.2 nm and aspect ratio of around 1.27.

The size of the microvoids remained almost unchanged during

oxidation, while their aspect ratio increased to 1.85, possibly

due to a crystalline transformation from a linear structure in

PAN fibers to a heat-resistant ladder structure in oxidized fibers.

However, the size of the microvoids decreased dramatically to

about 3.56 nm in the long axis and 2.85 nm in the short axis dur-

ing carbonization. The surface fractal dimension (Ds) increased in

these processes from 2.42 to 2.88 and the most severe change

occurred in low-temperature carbonization, indicating that sur-

face roughness increased during processing, and carbonization

was the most important process for such a transformation.


doi:10.1016/j.carbon.2010.01.042

Preparation of SiCN crystals using microwave plasma CVD

assisted by pulsed nitrogen ion beam sputtering

Jun Wan, Zhi-bin Ma, Hong Cao, Zhen-hui Wu, Jian-hua Wang

School of Material Science and Engineering, Wuhan Institute of

Technology, Key Laboratory of Plasma Chemical and Advanced Materials

of Hubei Province, Wuhan 430073, China

Crystalline silicon carbon nitrides were synthesized on quartz

glass substrates by microwave plasma chemical vapor deposition,

using precursors produced from a pulsed nitrogen ion beam sput-

tering dicyandiamide target. The effects of deposition tempera-

ture on the morphology, composition and structure of the

samples were investigated by scanning electron microscopy,

energy dispersive X-ray, X-ray diffraction and X-ray photoelectron

spectroscopy. It is found that the surface morphologies of the

deposits change from well crystallized hexagonal crystals at

800 �C to semi-developed multi-sheet crystals at 700 �C and to

2124 C A R B O N 4 8 ( 2 0 1 0 ) 2 1 2 3 – 2 1 2 6

preparation of high purity graphite by an alkaline roasting–leaching method

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