Carbohydrate Polymers 81 (2010) 919–924
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Carbohydrate Polymers
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Preparation of nanofibrillar carbon from chitin nanofibers
M. Nogi
a,∗
, F. Kurosaki
b
, H. Yano
a
, M. Takano
b
a
Research Institute of Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
b
Institute for Integrated Cell-Material Sciences, Kyoto University, Kyoto 606-8501, Japan
article info
Article history:
Received 21 August 2009
Received in revised form 27 January 2010
Accepted 7 April 2010
Available online 13 May 2010
Keywords:
Carbon nanofiber
Chitin
Wood cellulose
Surface area
TGA
abstract
Nanofibrillar carbons were prepared by the carbonization of prawn chitin and wood cellulose nanofibers.
Chitin and cellulose nanofibers with the average width of 10 nm were obtained by a grinder treatment
from prawn shells and wood cell walls, respectively. Nanofiber aerogels prepared from nanofiber-
water suspensions by solvent exchange and freeze-drying were used as carbon precursors. Since chitin
nanofibers did not flocculate in organic solvents due to their low hydrophilicity, the aerogels of chitin
nanofibers did not form wide bundles of coalesced nanofibers. Furthermore, chitin nanofibers had higher
thermal stability than wood cellulose nanofibers. Thus, after the carbonization of chitin nanofibers, the
original fine and individual nanofiber network was maintained in the chitin carbon. In contrast, after the
carbonization of wood cellulose nanofibers, the original nanofiber morphology was destroyed due to the
aggregations of wood cellulose nanofibers and their low thermal stability.
© 2010 Elsevier Ltd. All rights reserved.
1. Introduction
Chitin and cellulose are the most abundant bioresources on
earth—the former is found in arthropods, mollusks, and fungi, and
the latter is found in plants. Chitins are a yearly production of
approximately 10
10
–10
12
tons. However, most of them are dis-
carded as industrial waste without effective utilization (Shahidi &
Synowiecki, 1991). Thus, it is important to make efficient use of
this biomass resource as a natural and environmentally friendly
material.
Recently, chitin and cellulose nanofibers (also known as bio-
nanofibers) with a diameter of 4–20 nm were obtained from squid
pens, crustacean exoskeletons, and wood cell walls (Abe, Iwamoto,
& Yano, 2007; Fan, Saito, & Isogai, 2008, 2009; Ifuku et al., 2009;
Iwamoto, Nakagaito, Yano, & Nogi, 2005; Saito, Nishiyama, Putaux,
Vignon, & Isogai, 2006). Moreover, chemical modifications of bio-
nanofibers have also succeeded in the improvement of mechanical
properties of bionanofiber materials (Ifuku et al., 2007; Nogi et al.,
2006). The bionanofiber materials are the perfect candidate for con-
tinuous roll-to-roll processing in the future production of electronic
devices, such as flexible displays, solar cells, e-papers, and a myriad
of new flexible circuit technologies (Nogi, Iwamoto, Nakagaito, &
Yano, 2009; Nogi & Yano, 2008, 2009; Yano et al., 2005).
∗
Corresponding author. Present address: Institute of Science and Industrial
Research, Osaka University, Ibaraki 567-0047, Japan. Tel.: +81 6 6879 8521;
fax: +81 6 6879 8522.
E-mail address: nogi@eco.sanken.osaka-u.ac.jp (M. Nogi).
Thermal transformation of bionanofibers without changing
their morphology via calcinations at elevated temperatures is effec-
tive procedure to impart new functionalities such as superior
mechanical properties, electrical and thermal conductivity, heat
and chemical resistance and so on. These properties of carbon
fiber make it very popular in aerospace, civil engineering, filter
medium, wind generator blades, and sporting goods. However,
since most biomasses would be destroyed during carbonization, it
is difficult to preserve their nanostructures (Deng, Liao, & Shi, 2008;
Paris, Zollfrank, & Zickler, 2005; Polarz, Smarsly, & Schattka, 2002;
Yoshino, Matsuoka, & Nogami, 1990). For example, Yoshino et al.
(1990) found that when hydrogels of bacterial cellulose nanofibers
were oven-dried, the nanofiber morphology was destroyed after
graphitization. However, when bacterial and tunicate cellulose
nanofiber aerogels with large surface areas, obtained by solvent
exchange (water–ethanol–t-butyl alcohol) and freeze-drying, were
carbonized or graphitized, the nanofiber morphology was main-
tained without melting (Ishida, Kim, Kuga, Nishiyama, & Brown,
2004; Kim, Nishiyama, Wada, & Kuga, 2001; Kuga, Kim, Nishiyama,
& Brown, 2002). Therefore, to carbonize bionanofibers without
damaging their nanostructures, it is important to prepare nanofiber
aerogels having large surface areas.
To fabricate an aerogelwith a large surface area, it is important to
disperse bionanofibers homogeneously in organic solvents, in order
to prevent fiber flocculation. Chitin is a linear polysaccharide of -
(1-4)-2-acetamido-2-deoxy-d-glucose. The chemical structure of
chitin is slightly dissimilar to that of cellulose with a hydroxyl group
replaced by an acetamido group. Therefore, chitin appears to have
an advantage over cellulose in that chitin nanofibers disperse more
homogeneously in organic solvents than cellulose nanofibers do.
0144-8617/$ – see front matter © 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carbpol.2010.04.006