610 Journal of Donghua University(Eng．Ed，)Vot．24。No．5(2007)

Stress and Strain During the Process of Thermal Stabilization of

Modified Pan Precursors

ZHANG Wang-xi(张旺玺)，WANG Yan—zhi(ZF艳芝)，PAN Wei(潘玮)

School of Materials＆Chemical Engineering，Zhongyuan University of Technology，Zhengzhou 450007，China

Abstract：Thermal mechanical analysis，FT一Ⅱt，Ⅵ煳andsoftie convemional measurements， such as densities and

mechanical properties，were used to characterize the effect of

the modification usmgⅪU以and SnCh on the thermal

naechanical behaviors and stnlctural changes during the process

of thermal stabilization of roodified PAN precursors．C(m删to the unmodified original P，虹呵p代ql巧。璐，salne conclusions

were drawn that the thermal stabilization starts at a lower哪ture for modified PAN fibers，for example，the peak of

thermal stress changes for modified pAN pr阳l麟髂using

KMR04 displays a d‘xa'ease of 20℃and a increase of 30％in

the ultimate thermal stress。that chemical mediflcation nlak鼯

st丌lctIl阳l transformation pc晾妞and increases by 25％0f the

tll咖nI s协嘟at the ten．113eratllre哗of 230℃一31)0℃，that

the modified PAN fibers display an increase of 100％in the

thennal strain，oglce after佴簪嘲dized，show all increase of

7．8％in orientation index。and a decrease of 9．9％in crystal

size for identical preload in the region of 13．1—14．S胁．Itwas also concluded that the modification using SnCh would

alleviate the cIl2mges in physical and chereacal s打鸭s咒萄m瞎

and result in improvement in$tnlctuge and decrease in defects．

Key words：carbon fibers；carbon precursor；chemical

treatment；mechanical properties

CLC nmnber：TQ 342+．74 Document cede：A

Article ID：1672—5220(2007)05—0610一04

Carbon fibers，especially for polyacrylonitrile(PAN)一

based ones，offer the highest specific strength and modulus of

"all reinforcing fibers，which are mainly selected as

reinforcements in composite materials．In order to meet

eglYd／Kled USe in some high-tech sectors。many hovel

approaches，such as dry-wet spinniI醇”，steam drawin誊2]，

increasing the molecular weight of precursors polymerL引，

modifying the precursors prior to stabilizationr“，ere．have

been performed to increase the tensile strength of PAN—basedc{arbon fibers．Studies on the physical，mechanical and thermal

characteristics of different PAN precursors have led to the

basic understanding that these characteristies vary markedly for

different precursors and the mechanicaI properties of the

resultant carbon fihers a'lso establish a direct correlation with

characteristics of the starting precursor．There are，however，

some limitations during spinning，which do not permit to

produce a precursor with alI the desired characteristics

combined togetherE“．Therefore·post spinning modifications

on PAN have been used as usef,ll methods which have resulted

in certain improvements inthg properties of resulting carbon

fibers：“．Post spinning modification using KMn04 has been

studied in detail and it is observed that with KMnO,treatment

of PAN fibers。resultant carbon fibers display an improvement

of 20％一40％in the tensile strength i11 comparison to the

carbon fibers developea from unmodified fibers because of the

plasticizing effect，eatalytic effect of l(1咖Q例．

However，it is not fully to understand the relationship

between different modification results and the structure and

properties of刚precursor fibers or earbon fibers，especially，

the thermal stress and strain changes of modified fibers during

the thermal．oxidation stabilization were not reported within

our knowledge．This paper is mainly concentrated on

comparative studies on the changes of thermal stress"and strain

of original and modified PAN precursor fibers upon different

heat treatment temperature．

1 Experimental

A special grade of polyacrylonitrile precursor with．Aa'q／

MA／IA(92．8／1．2／6、Ⅳt．％)was selected，which was辄ppHed

by Courtaulds Ltd．(United Kingdom)．田k origin'd,that is

unmodified，洲precursor fibers were named as U samples，

the modified PAN precursor fibers using 5 wt．％aqueous

KMn04 solution were named as K samples，and the modified

PAN precursor fibers using 4 wt．％aqueous SnCh solution

were designated as S samples．

The thermal．oxidation stabilization of the original and

different modified PAN precursor fibers were carried out in

a 3一ternperature-zone furnace in air with a flow rate of

Received date：2006一01—11

Foundation itern：HAIPURT(No．2006KYCX009)；National Natural Science Foundation of Henan，China(No．200510465008)；

Henan Innovation PrMect of China(No．0523021300)

Biography：ZHANG Wang-xi(1967一)，male,prof．E-mail：zhangwx@zzti．edu．ca

万方数据

Journal of Donghua University(Eng．Ed．)V01．24．No．5(2007) 61 1

1 L／min from 50C to 350C．

The mechanical properties of the various fibers were

determined with a YG001一A tensile testing machine at a

crosshead speed of 1 0 mm／min and 20 mm of testing gauge．

In each specimen，at least 50 filaments were tested and

their average value was reported here．Densities of various

fibers were obtained at 25C by the use of density gradient

colulnn metho【1．FT—lR measurements were made for the KBr

disks(O．5 mg sample with 200 mg KBr)for the specimens by

the uSe of a Nicolet750 Magna—IR．Elemental analysis(EA)

was carried out with a Carto Erba Azione 1 106 model elemental

analyzer．A gigaku X-my diffractorneter，providing Ni-filtered

Oa Ko(A=0．154 178 nm)radiation。was used to record the

wide-angie diffraction pattern of the oriel fibers and their

rncdified countewm'ts．The step-scan method was selected to

皿leaSure the stacldng size(L。)using the foUowing equation：

Lc=K百AcosO (1)

where．；I is the wavelength of Cu K。X—ray；B is the width

at half maximum intensity of the peak at 20=1 7。and 25。

for PAN precursors and carbon fibers，respectively；and K

is the apparatus constant(2 0．89)．The step-interval was

set at 0．02。．The preferred orientation of the precursors

(001)and the resultant carbon fibers(002)were

determined by an X·-ray diffractmeter with a special fiber·-

specimen attachment．The width at half-maximum

intensity was used as an index of orientation，which may be

used to calculate the parallelism of the crystalline part of

structure by the following equation：

丌=紫×100％ (2)

where丌is the orientation index．H is the width at half-

maximum intensity．

2 Results and Discussion

2．1 The thermal stress change in a fixed—iength

stabilization process

Fig．1 shows the changes of thermal stress of original and

modified PAN precursor fibets upon different heat treatment

temperature in a fixed-length thermal-oxidation stabilization

process．It has been shown that some黝sily discernible regimes

can be seen．In the first regime．when the heat treatment

temperature is up to t，no more than 120℃，the

macromolecules are inelined to shrink with the result of

thermal motion of chains owing to their conformational

changes．When the temperature is up to 150℃一210℃．the

maeromolecules can undergo enough stretching because of a

great deal of chain motion resulting in slippage among the PAN

macromolecules。hence，the thermal stregs of original PAN

fibers starts to lower and the thermal stress of U fibers has a

valley at 200C．The lowest valley of thermal stress of

rno【Jified S fibers tends to a higher temperature at 240℃．

However，those modified K fibers all the蛆me display various

increase trends，the rr划ified K fibers show higher thermaJ

stress than that of S fibers．This is because of much inclusion

of oxygen for modified K fibers during their modification

process，the oxygen content of mollified K fibers has increased

by 71％compared to original ones，as a result of active

reaction site，much includ。d oxygen makes the cyclization and

oxidation start earlier at 175℃。other than 21 O℃for original

fibers．

Temperature(*C)

Fig．1 The thermal stress of various fibers in

a fixed-length stabilization process

Fig．2 is the FT-IR spectra of U，K，S fibers and their

stabilized fibers．The vibration characteristics of渊structureare those of CN nitrile groups at 2 243—2 241 on～，the strong

trand at l 732 em．1 is attributed to C—o stretching due to the

presence of ester or acid．The most prominent structural

changes are the decrease in the intensities of CEN band and

the decrease of those for aliphatic C—H ones once the

precursor fibers are heated to an adequate elevated

temperature，especially for modified K"and S fibers．

Wavenumber(em‘J)

Fig．2 The FT—IR spectra ofl．U，3．K，5．S andtheir

stabilized fibers of 2．U。4．K，6．S after 250℃

2．2 3he strain eha,l窖e in a fixed-preload stabilization

process

Fig．3 shows the strain changes of U and modified K

fibers in a various fixed．preload stabilization process．Both

U and K fibers show shrinkage when a preload is

1．75 MPa，and K fibers have higher shrinkage than

万方数据

612 Journal of Donghua University(Eng．Ed．)V01．24．No．5(2007)

original U fibers，which is in agreement with higher

thermal stress for K fibers in a fixed．1ength stabilization

process when they undergo constraint heat treatment．

When the preload iS uD to 13．1 MPa，both U and K fibers

display elongation trends，the higher the preload is，the

larger the elongation of fibers is．But，the K fibers always

display lower elongation，especially in a higher temperature

region．Because the K fibers have been modified for a 5％

stretch，the results of differences in element composition，

later 0rder。crystal size and orientation index from the

original U fibers。are listed in Table 1．The catalytic effect

of KMnO,causes lower initiating cyclization temperatureand much ladder structure。which results in lower tensile

strength。as shown in Table 2．

Temperature(℃)

Fig．3 The strain of U and K fibers in different

preload VS．temperature

Table 1 The lateral structure index of

modified and unmodified fibers

Table 2 The properties of sample U。K，S and their

stabilized fibers after different temperature

2．3 Effect of preload on the changes of thermal

stress

Both U and K fibers undergo thermal stress relaxation

when a higher preload(≥8．73 MPa)is imposed at the

temperature no more than 90℃，as illustrated in Figs．4

and 5．Modified K fibers undergo higher thermal stress

relaxation than original U fibers．When upon heating to

90℃一1 60℃。thermal stress iS increased owing to the

physical chains mobility，the original U fibers show faster

increase in thermaI stress．When the tem【perature iS beyond

130℃．the changes of thermal stress are mainly resulted

from chemical reaction，such cyclization and oxidation，the

sizes of new formed ladder molecules mainly determined

the changes of thermal stress．As a result。the thermaI stress

is aII】曝ost independent on the imposed preload when the heat

treat temperature is up to 225'C．In the same thermal stress，

tmxtified K fibers need lower preload than original U fibers at

identical thermal-oxidation stabilization conditions．

Temperature(℃)

Fig．4 The thermal stress of U fibers in different

preload Vs．temperature

Temperature(*(；)

Fig．5 The thermal stress of K fibers in

different preload Vs．temperature

3 Conclusion

Compared with the original U fibers，the modified K

fibers have increased by 71％in oxygen content，which

makes the chemical-reaction-induced changes of thermal

stress start earlier by 20"C．The modified K fibers display

一日l至一∞∞3J1s

一目山芝一∞∞3JlS

万方数据

Journal ofDonghua University(Eng．Ed．)V01．24．No．5(2007) 613

easy shrinkage and difficult stretch．which can be imposed

larger preload．In the same thermal stress．modified K

fibers need Iower preload than original U fibers at identieal

thermal—oxidation stabilization conditions．The change

inflexions of thermal stress and strain take place at similar

temperature regions，which means that they can be used as

an indication of chemical and physical changes of PAN

precursor fibers upon heat treatment．

References

[1-I Baiai P，Streekumar T V，Sen K．Structure Development

During Dry-Jet—Wet Spinning of Acrylonitrile／Vinyl Acids

and Acrylonitrile／Methyl Acrylate Copolymers[J]．

Journal ofApplied PolymerScience。2002，86，773—787．

L 2]Mitsubishi Rayon Co，Ltd．Acrylonitrile-Based Precursor

Fibcr for Carbon Fiber and Method for Production

Thereof：EP l 230140A1rP]．2001一05一09．

L 3] Wilkinson K．Process and Product of Acrylonitrile

Copelymer：W0 96／39552[P]．1996一12—12．

L 4]Wilkinson K．Process for the Preparation of Carbon Fiber：

US 605，1211l P1．2000—04—25．

[5]Jean B D，TongK W，Jimmy C M P．Carbon Fibers[M]，

3rd．New York：Marcel Dekker PreSS，1998：13．

[6]Zhang Wang-xi，Wang Yan-zhi．Manufacture of Carbon Fibers

from PAN Precursors Treated with CoS04[J]．Journal 0厂

Applied PolFncrScience，2002，85(1)，153—158．

[7]Tse-hao Ko．The Influence of Pyrolysis On Physical

Properties and Microstructure of Modified PAN Fibers

during Carbonization[J]．Journal of Applied Polymer

Science，1991，43(7)，589—600．

万方数据

Stress and Strain During the Process of Thermal

Stabilization of Modified Pan Precursors作者： ZHANG Wang-xi， WANG Yan-zhi， PAN Wei

作者单位： School of Materials & Chemical Engineering, Zhongyuan University of Technology,

Zhengzhou 450007, China

刊名：东华大学学报（英文版）

英文刊名： JOURNAL OF DONGHUA UNIVERSITY(ENGLISH EDITION)

年，卷(期)： 2007，24(5)

引用次数： 0次

参考文献(7条)

1.Bajaj P.Streekumar T V.Sen K Structure Development During Dry-Jet-Wet Spinning of

Acrylonitrile/Vinyl Acids and Acrylonitrile/Methyl Acrylate Copolymers 2002

2.Mitsubishi Rayon Co Ltd Acrylonitrile-Based Precursor Fiber for Carbon Fiber and Method for

Production Thereof 2001

3.Wilkinson K Process and Product of Acrylonitrile Copolymer 1996

4.Wilkinson K Process for the Preparation of Carbon Fiber 2000

5.Jean B D.Tong K W.Jimmy C M P Carbon Fibers 1998

6.ZhangWang-xi.WangYan-zhi Manufacture of Carbon Fibers from PAN Precursors Treated with COSO4

2002(1)

7.Tse-hao Ko The Influence of Pyrolysis on Physical Properties and Microstructure of Modified PAN

Fibers during Carbonization 1991(7)

相似文献(10条)

1.期刊论文 ZHANG Wangxi.LIU Jie Effect of Post-spinning Modification on the PAN Precursors andResulting Carbon Fibers -武汉理工大学学报（材料科学版）英2006,21(3) The impregnation of a special grade PAN precursor fibers was carried out in a 8 wt% KMnO4 aqueous solution to obtain modified PAN

precursor fibers. The effects of modification on the chemical structure and the mechanical properties of precursor fibers thermally

stabilized and their resulting carbon fibers were characterized by the combination use of densities, wide-angle X-ray diffraction

(WAXD), X-ray photoelectron spectroscopy (XPS), elemental analysis (EA), Fourier transform infrared spectroscopy (FT-IR) and scanning

electron microscope (SEM), etc. KMnO4 as a strong oxidizer can swell, oxidize and corrode the skin of a precursor fiber,and transform

C(=)N groups to C=N ones, meanwhile, it can decrease the crystal size increase the orientation index and the crystallinity index,

furthermore it can increase the densities of modified PAN precursors and resulting thermally stabilized fibers. As a result, the

carbon fibers developed from modified PAN fibers show an improvement in tensile strength of 31.25 % and an improvement in elongation

of 77.78 %, but a decrease of 16.52 % in Young's modulus.

2.外文期刊 Zhang Wangxi.Liu Jie.Wu Gang Evolution of structrue and properties of PAN precursorsduring their conversion to carbon fibers The formation and evolution of structure,and the changes of properties during the preoxidation,precarbonization,and carbonization

of different PAN precursors were studied by the combination of DSC,FT-IR,SEM and some traditional measurements,such as density and

mecahanical properties of various fibers.The exothermic regime of polyacrylonitrile-based precursors made of acrylonitrile/itaconic

acid (AN/IA) copolymers or acrylonitrile/acrylamide (AN/AM) copolymers is much broader and the cyclizationreaction starts at lower

temperature,compared to that of PAN homopholymer precursors,but AM appears to be more effective in separation the exothermic

reactions corresponding to preoxidation stages in DSC curves as compared to IA.If AN/IA (97.5/2.5 w/w)precursors are designated as P1

and P2,respectively,the AM-containing commercial precursors (P3) are thermally more stable than the P2 ones,and the density of P3 is

higher than that of P1 or P2.This may result from the difference of aggregation morphology among the original precursors,since it is

dense for P3 precursors,whereas P2 and P1 precursors have some voids.The tensile strength of resultant carbon fibers from P3

precursors was better than that of carbon fibers from P2 or P1 after identical conditions of preoxidation are employed.

3.外文期刊 ZHANG Wangxi.LIU Jie Effect of Post-spinning Modification on the PAN Precursors andResulting Carbon Fibers The impregnation of a special grade PAIS precursor fibers was carried out in a 8 wt percent KMnO_4 aqueous solution to obtain

modified PAIS precursor fibers. The effects of modification on the chemical structure and the mechanical properties of precursor

fibers thermally stabilized and, their resulting carbon fibers were characterized by the combination use of densities, wide-angle X-

ray diffraction (WAXD), X-ray photoelectron spectroscopy (XPS), elemental analysis (EA), Fourier transform infrared spectroscope (FT-

IR) and scanning electron microscope (SEM), etc. KMnO_4 as a strong oxidizer can swell, oxidize and coir ode the skin of a precursor

fiber, and transform C ident to N groups to C velence N ones, meanwhile, it can decrease the crystal size increase the orientation

index and the crystallinity index, furthermore it can increase the densities of modified PAN precursors and resulting thermally

stabilized fibers. As a, result, the carbon fibers developed from modified PAN fibers show an improvement in tensile strength of

31.25 percent and an improvement in elongation of 11.78 percent, but a decrease of 16.52 percent in Young's modulus.

4.外文期刊 Christian L. Mangun.Kelly R. Benak.James Economy.Kenneth L. Foster Surface chemistry,pore sizes and adsorption properties of activated carbon fibers and proecursors treated with ammonia

A series of activated carbon fibers (ACFs) were produced by treatment with ammonia to yield a basic surface. The micropore sizes

of these chemically modified fibers were determined with nitrogen adsorption experiments and they were shown to increaseiwth

increasing activation time and temeprature. The types of groups present were analyzed by Fourier transform infrared spectroscopy

(FTIR), X-ray photoelectron spectroscopy (XPS), and temperature programmed desorption (TPD). The adsorption isotherms of an acidic

gas (HCl) show a great improvement in capacity over an untreated acidic fiber. The adsorption is completely reversible and must

therefore invlove enhanced phydical adosorption instead of chemisorption. This demonstrates that ACFs can be tailored to selectively

remove a specific contaminant based on the chemical modification of their pore surfaces.

5.外文期刊 W. M. Qiao.Y. Song.M. Huda Development of carbon precursor from bamboo tar Bamboo is a renewable resource that can provide an available energy source when cycle of Its plantation and use is properly,

scheduled Us pyrolysis In the bsence of air provides bamboo tar as well as bamboo charcoal. The charcoal is used as an effective

adsorbent for removal of humidity and odors as well as a convenient solid fuel. The by-product tar with high oxygen content contains

a mixture of phenols [1-3] and may be applied as a precursor for carbon products, considering its molecular structural

characteristics. The pre-treatment and carbonization properties of eucalyptus pitch have been reported to yield an interesting

precursor for this possible application [4.5]. Generally, polymerization of phenols with formaldehyde is employed to synthesize

phenolic resin, an important precursor for many carbon products. The composition of bamboo tar suggests its suitability as a

competitive and renewable substitute for phenolic resin in the manufacture of carbon materials. In the present study, our target is

to prepare bamboo tar based resin through a chemical modification of bamboo tar. Such biomass resin is expected to be used as a new

carbon precursor for carbon materials.

6.外文期刊 Byung G. Min.T.V. Sreekumar.Tetsuya Uchida Oxidative stabilization of PAN/SWNT compositefiber PAN/SWNT composite fibers have been spun with 0, 5, and 10 wt percent single wall carbon nanotubes (SWNTs). Tensile fracture

surfaces of polyacrylonitrile (PAN) fibers exhibited extensive fibrillation, while for PAN/SWNT composite fibers, tendency

tofibrillate decreased with increasing SWNT content. The reinforcing effect of SWNTs on the oxidized polyacrylonitrile (PAN) fiber

has been studied. At 10wt percent SWNTs, breaking strength, modulus, and strain to failure of the oxidized composite fiber increased

by 100 percent, 160 percent, and 115 percent, respectively. Tensile fracture surfaces of thermally stabilized PAN and the PAN/SWNT

fibers exhibited brittle behavior and well distributed SWNT ropes covered with the oxidized matrix can beobserved in the tensile

fracture surfaces of the fibers. No de-bonding has been observed between unoxidized or the oxidized PAN matrix and the nanotube

ropes. Higher strain to failure of the oxidized composite fiber as compared to that of the oxidized control PAN fiber also suggests

good adhesion/interaction between SWNT and the oxidized matrix. Thermal stresses generated on the composite fiber during the

oxidation process were lower than those for the control fiber. The potential of PAN/SWNT composite fiber as the precursor material

for the carbon fiber has been discussed.

7.外文期刊 J.C.Chen.I.R.Harrison Modfiication of polyacrylonitrile (PAN) carbon fiber precursor viapost-spinning plasticization and stretching in dimethyl formamide (DMF) This study investigates the possibility of using a post-spinning plasticization and stretching process to eliminate suspected

property-limiting factors in polyacrylonitrile-based carbon fibers. This process was performed with the intention of removing surface

defects (to improve tensile strength), attenuating fiber diameter (to promote more uniform heat treatment), and reducing molecular

dipole interactions (to facilitate further molecular orientation). Among the various organic and inorganic solutions tested,

treatment using aqueous dimethyl formamide (DMF) offered far and away the best properties and was therefore selected for further

testing. Tested individually (as single filaments), fibers exposed to 80% DMF for 10 s gave the highest precursor values of elastic

modulus (9.07 GPa) and tensile strength (675 MPa). While fibers treated in 80% DMF gave a 73% improvement in elastic modulus and a

53% improvement in tensil estrength over as-received PAN, limitations in sample preparationand carbonization necessitated a reduction

in DMF concentration (to 30%) to allow extraction of individual carbon fibers for tensile testing. Despite this compromise, results

for fibers carbonized at 1000 deg C ultimately showed a 32% improvement incarbon fiber elastic modulus and a 14% improvement in

carbon fiber tesnile strength over egularly prepared carbon fibers. These results show that, to a certain extent, improvements in PAN

precursor properties can translate to corresponding improvements in subsequently produced carbon fibers. Additional characterization

using wide angle X-ray scattering (WAXS) and scanning electron microscopy (SEM) suggests that these improvements are due in part to

improved lateral order as well as the successful elimination fo surface defects and prevention of skin-core formation.

8.外文期刊 Young-Jae Lee Formation of Silicon carbide on carbon fibers by carbothermal reduction ofsilica Both PAN- and pitch-based carbon fibers were reacted at different temperature by carbothermal reduction of silica with the

objectives of understanding texture and oxidation behavior changes of both carbon fibers, and the role of carbon precursor

andreaction temperature. The reduction at 1800 deg C resulted in the SiC coating on the fibers as expected, but the microtextures

were different with carbon precursors. Unexpectedly, both carbon fibers were completely converted into SiC fibers at 1500 deg C but

with different microtextures: PAN-based carbon fibers were composed of approximately 1-mu m size of grains; in contrast, pitch-based

carbon fibers consisted of 100-nm size of particles. Oxidation resistance of the fibers increased as the reduction temperature

increased, but it was overturned at 1800 deg C due to the remaining unreacted carbon.

9.外文期刊 W.M. Qiao.S.H. Yoon.I. Mochida Waste polyvinylchloride derived pitch as a precursor todevelop carbon fibers and activated carbon fibers Polyvinylchloride (PVC) was successfully recycled through the solvent extraction from waste pipe with an extraction yield of ca.

86 percent. The extracted PVC was pyrolyzed by a two-stage process (260 and 410 deg C) to obtain free-chlorine PVC based pitch

through an effective removal of chlorine from PVC during the heat-treatment. As-prepared pitch (softening point: 220 deg C) was spun,

stabilized, carbonized into carbon fibers (CFs), and further activated into activated carbon fibers (ACFs) in a flow of CO_2. As-

prepared CFs show comparable mechanical properties to commercial CFs, whose maximum tensile strength and modulus are 862 MPa and 62

GPa, respectively. The resultant ACFs exhibit a high surface area of 1200 m~2/g, narrow pore size distribution and a low oxygen

content of 3 percent. The study provides an effective insight to recycle PVC from waste PVC and develop a carbon precursor for high

performance carbon materials such as CFs and ACFs.

10.外文期刊 Soshi SHIRAISHI.Yuriko IDA.Asao OYA Application of Thin Carbon Fibers Prepared byPolymer-Blend Technique for Lithium-Ion Battery Negative Electrode Thin carbon fibers (TCF) were prepared by the spinning/stabilization/carbonization process of the polymer blend, which consists

of phenolic resin (carbon precursor) and polyethylene (pyrolysing polymer without carbon residue). TCF had the diameter of100 approx

400 nm and microporous structure. The conventional carbon fibers (Ref-CF) with 10 approx 20 mum diameter were also obtained from

phenolic resin in the same process. The TCF electrode showed different properties for electrochemical Li~+ insertion/extraction

compared with the Ref-CF electrode. The cycleability and the rate properties for TCF were better than those for Ref-CF. TCF and Ref-

CF had the similar carbon structure for pore structure and crystallinity. Therefore, the characteristic properties for TCF can be

attributed to the size dimension effect.

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