Biomedical Engineering Reference
In-Depth Information
-1
CA250 and it becomes weaker at about 1340 cm
when the sample
is further heated to 500°C.
In Fig. 3.3a, the bands at 1012 and 974 cm
-1
and the bands at
739 cm
were
assigned to aromatic and furan −CH− out-of-plane bending vibrations.
These peaks become weaker when heated at higher temperatures,
the second set of absorbance bands almost disappear for CA500;
however, the C=C bonds remain in the samples above 500°C, i.e.,
1104 cm
-1
and its accompanying peaks at 806 and 837 cm
-1
for CA900, respectively. This
means that the −CH− bond will be broken after carbonization at
temperatures above 500°C. Therefore the FTIR spectra indicates
that the hydroxyl groups of mixed furfural break away from the
aromatic ring between 250°C and 500°C and the graphitization
temperature begins above 500°C.
The BET surface area was measured on aerogel powders that
were first out gassed at 110°C, by means of N
-1
for CA750 and 1092 cm
-1
adsorption/desorption
at 77 K. The BET surface area of CA900 was calculated as 1005 ±
18 m
2
2
/g, which is nearly double that of CAs prepared by ambient
pressure drying with BET (550-660 m
/g) [25] and is very close to
other CA obtained under supercritical conditions [27-29]. Moreover,
the BET surface area of CA900-A was 1539 ± 20 m
2
2
/g. The mesopore
volume (per gram of sample) was calculated via the BJH method for
CA900 as 0.66 ± 0.03 cm
3
3
/g.
Micropore information was calculated using the D - R equation
[30]:
/g and CA900-A as 0.99 ± 0.05 cm
2
2
 
 
RT
P
0
ln
V
ln
V
-
ln
 
(3.5)
   
ads
mic
E
P
where
V
is the volume of adsorbed gas at a relative pressure of
P
/
P
,
ads
0
V
is the micropore volume and
E
is the interaction energy. The
mic
micropore radius of gyration (
R
) can be related to
E
via [31, 32]:
Gmic
ER
Gmic
14.8±0.6(kJ nm/mol)
(3.6)
where
).
The surface area per molecule used to determine the BET surface
area from the monolayer capacity is 0.1620 nm
β
denotes the affinity coefficient (
β
= 0.33 for N
2
2
(TriStar 3000 V6.04
A manual). The micropore radius of gyration and micropore volume
can be obtained by the slope and intercept of a ln
2
V
vs. (ln
P
/
P
)
ads
0
plot. The micropore volume (per gram of sample) as calculated by
 
Search WWH ::




Custom Search