Biomedical Engineering Reference
In-Depth Information
soot during detonation synthesis strongly depend on conditions
developed during the process.
Compared with the case of soot samples (Fig. 6.6), the TDMS
profiles for the extracted nanodiamonds were substantially modified
(Fig. 6.7). The main components released from nanodiamonds
were CO (500-700°C) and CO
(200-600°C) both arising from
the decomposition of surface oxide groups, and HCl (bimodal at
400-700°C), arising from surfaces contaminated by chlorine used
during chemical extraction. The results indicate a pronounced
difference between surface chemistry of different nanodiamonds,
clearly illustrated by the curves of the ratio between the release
rates of the various species (Fig. 6.7). The whole amount of released
CO
2
is higher in the case of K2-Diam in accordance with the data
for pristine soot (Fig. 6.6). In contrast, the abundance of chlorine-
containing species is highest for CH7-Diam in agreement with our
previous data on chemically treated nanodiamonds CH7 and K2 (see
above). What is more important, the shapes of the ratio curves in Fig.
6.7 (the ratio between release rate from K-2-Diam and CH7-Diam),
consisting of several peaks and shoulders, indicate that the relative
abundances of different surface oxide groups (carboxylic anhydride,
lactone, and carbonyl) decomposed at different temperatures are
not identical for the two types of extracted diamonds. The same is
valid for the chlorine-containing groups.
x
8
Ch7-Diam
6
HCl
+
4
2
CO
+
CO
2
+
0
K2-Diam
12
CO
+
8
CO
2
+
HCl
+
4
0
Ratio
+
CO
2
6
CO
+
3
HCl
+
0
200
400
600
800
1000
TEMPERATURE (
o
C)
Figure 6.7
Thermal desorption of CO, CO
, and HCl from nanodiamonds
CH7-Diam and K2-Diam extracted from detonation soot HCl
ST and K2-ST, respectively.
2
