II International Symposium on Carbon for Catalysis ABSTRACTS

PP-I-48
Table 1 Characteristics of various solvents and measured relative wetting contact angles
Solvent
Surface
tension
(mN/m)
Density
(kg/m 3 )
Viscosity
(mpa.s)
Dielectric
constant(ε0)
RWCA/°
Water 72.8 998.2 1.005 80 81.6
Ethannol 22.8 789 1.15 24.3 24.8
Acetone 23.7 792 0.32 20.7 45.2
Cyclohexane 25.3 778.6 0.97 2.016 0
Further studies revealed that both the nature of the functional groups on the CNF surfaces
and the wettability of the CNF in different solvents could be tailored by different surface
modification methods. Fig.1 shows that CNF wettability was increased both in water and in
cyclohexane, when it was treated in concentrated nitric acid. When it was treated in peroxide
hydrogen, however, its wettability was decreased in both solvents. Interestingly, when it was
treated in argon, its wettability was increased in water but decreased in cyclohexane.
Temperature programmed desorption analysis of the modified CNFs revealed that the surface
affinity changes could be attributed to the surface chemistry changes during modification.
w 2 /g 2
5
4
3
4
2
2
M
Ar900
1
H2O2
HNO3felux
0
0 100 200 300 400 500
1
time/s
3
w 2 /g 2
2.5
2.0
1.5
1.0
0.5
4
1
2
0.0
0 100 200 300 400 500
time/s
3
M
Ar900
H2O2
HNO3reflux
a
Fig 1 Influence of surface modification on wettability of CNFs in water(a) and in cyclohexane
(b)
as-synthesized CNF; 2. CNF after heated in argon at 900 o C for 4 h; 3. CNF after treatment in
H 2 O 2 for 24 h; 4. CNF after being refluxed in concentrated HNO 3 for 0.5 h.
In summary, wicking kinetic measurement is a successful method to determine the CNF’s
wettability. The described results are important for CNF synthesis and modification as well as
its application in carbon-nanofiber-supported catalysts.
References
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173:75-98.
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3 Tijmen G.. Ros, Adrianus J. van Dillen, John W. Geus et al. Chem. Eur. J. 2002,
8(5):1151-1162.
4 Grundke K. Boerner M. and Jacobasch H. J., Colloids and Surfaces, 1991, 58, 47-59.
b
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