shell structure of polyacrylonitrile fibers during preoxidation

ARTICLE IN PRESS 4

CARBON

x x x ( 2 0 0 8 ) x x x –x x x

Effect of a Ni–P coating on the tensile strength of carbon fibers

Preparation and surface structures of carbon nanofibers pro-

evaluated by a Weibull statistical method

duced from electrospun PAN precursors

Ying-Lu

Ji a,b, Chun-Xiang Lu a, Pu-Cha Zhou a,b, Yu Yang a,

Xiao-Xuan Lu a

a,b

a

a

, Yong-Hong Li , Shu-Xia Yuan , Fu He

Shu-Ying Gu a, Qi-Lin Wu b, Jie Ren a

a

Key Laboratory of Carbon Materials, Institute of Coal Chemistry,

a

Institute of Nano- and Bio-Polymeric Materials, School of Materials

Science and Engineering, Tongji University, Shanghai 200092, China

Chinese Academy of Sciences, Taiyuan 030001, China

b

b

Materials, Donghua University, Shanghai 200051, China

Graduate University, Chinese Academy of Sciences, Beijing 100049,

State Key Laboratory for Modification of Synthetic Fibers and Polymer

China Carbon nanofibers with diameters in the range of 100–300 nm Ni–P coated carbon fibers were prepared by a chemical plating

were obtained by stabilizing and carbonizing electrospun polyac-

method. The microstructures of uncoated and coated carbon

rylonitrile (PAN) precursors. The morphologies and structures of

fibers were investigated by SEM and XRD, and the surface atom

the nanofibers and PAN precursors were investigated by scanning

compositions were studied by EDS. The tensile strength of the

electron microscopy, scanning tunneling microscopy, and differ-

carbon fibers was analyzed by a Weibull statistical method.

ential scanning calorimetry. The diameters of the PAN precursors

Results show that the number of defects on the carbon fiber sur-

and carbon nanofibers showed a log-normal distribution. The

faces decreases after Ni–P coating. When the thickness of the Ni–

cyclization exothermic peak shifted to a lower temperature for

P coating reaches 0.149 lm, the tensile strength of carbon fibers

electrospun fibers, which suggested that cyclization could be

exhibits a maximum value of 3.10 GPa, a 8.77% increase com-

more easily initiated. Pits 10 nm in length and 5 nm in width

pared to the uncoated carbon fibers, which might be ascribed to

formed on the surface of the carbon nanofibers, caused by the

the elimination of a number of surface defects by the Ni–P

rough surface of the electrospun precursors and their shrinkage

coating.

during heat treatment.

[New Carbon Materials 2008;23(2):159–64.]

[New Carbon Materials 2008;23(2):171–6.]

doi:10.1016/j.carbon.2008.06.013

doi:10.1016/j.carbon.2008.06.015

Preparation and microstructure control of carbon aerogels pro-

The evolution of the core/shell structure of polyacrylonitrile

duced using m-cresol mediated sol–gel polymerization of phenol

fibers during preoxidation

and furfural

Jie Liu, Jia Li, Lei Wang, Jie-ying Liang

Dong-Hui

Long a, Jie Zhang a, Jun-He Yang b, Zi-Jun Hu c,

Tong-Qi Li c, Guo Cheng a, Rui Zhang a, Li-Cheng Ling a a

State Key Laboratory of Chemical Engineering, East China University of

The Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials, Beijing University of Chemical Technology, Beijing 100029, China

Science and Technology, Shanghai 200237, China b

Shanghai Institute of Technology, Shanghai 200235, China

c

Aerospace Institute of Materials and Processing Technology, Beijing

100076, China

The core/shell structure of polyacrylonitrile (PAN) fibers formed during preoxidation was investigated by DSC, FT-IR, SEM, optical microscopy and density measurement. Five precursors were used to correlate the core/shell structure with their

Carbon aerogels rich in mesopores were prepared by the sol-

thermo-chemical reactivity. It was found that the morphologies

gel polycondensation of phenol, m-cresol, and furfural by an acid

of the core/shell structures are highly relevant to the reactivity,

catalyst in a 1-propanol solution, followed by supercritical 1-pro-

microstructure and density of PAN fibers, and the quality of the

panol drying and pyrolysis. The effect of the ratios of m-cresol to

resultant carbon fibers depends strongly on the degree of pre-

phenol (m-C/P) on the properties of aerogels was investigated.

oxidation.

The aerogels were characterized by infrared spectroscopy, N2 adsorption, scanning and transmission electron microscopy. It was found that the microstructure of carbon aerogels could be adjusted by the m-C/P ratio. The average mesopore size of carbon aerogels decreased from 47 to 13 nm with increasing

[New Carbon Materials 2008;23(2):177–84.] doi:10.1016/j.carbon.2008.06.016

m-C/P ratio. The surface area calculated using the Brunauer– Emmett–Teller method, external surface area, and mesopore volume of carbon aerogels, all exhibited maxima at the m-C/P ratio

Preparation of bromine intercalated pyrolytic carbon

of 0.33.

Jin-Hua Lu, He-Jun Li, Ke-Zhi Li C/C Composites Technology Research Center, Northwestern Polytechnical

[New Carbon Materials 2008;23(2):165–70.] doi:10.1016/j.carbon.2008.06.014

University, Xi’an 710072, China Pyrolytic carbon prepared by chemical vapor deposition was intercalated by bromine in the liquid phase at 20 °C for 48 h with