Biomedical Engineering Reference
In-Depth Information
curve 2) mode were very much alike, confirming the reliability of the
latter mode of operation. Similar fine features (peaks and shoulders
near 520, 750, 950, and 1150°C) in the release curves were observed
for both UDD and MND. This fine structure indicates the presence of
different (at least five) states (or processes leading to desorption) of
trapped He-atoms in nanodiamonds.
The method of TDMS was used to clarify the mechanism of
noble gas release from nanodiamond, an important issue for
the interpretation of data concerning noble gases in meteoritic
diamonds. The curves in Fig. 6.11 represent the results of noble
gas analysis in UDD sample after simultaneous implantation of ion
mixture (He, Ar, Kr, and Xe) with energy of 1000 eV. The release
profiles for the heavier gases (Ar, Kr, and Xe) measured under linear
heating have bimodal character (LT an HT peaks) as in the case of
stepped pyrolysis (Fig. 6.9).
132Xe
84Kr
4He
40Ar
200
200
200
200
400
400
400
400
600
600
600
600
800
800
800
800
1000
1000
1000
1000
1200
1200
1200
1200
1400
1400
1400
1400
1600
1600
1600
1600
Temperature,
o
C
°C
Figure 6.11
High-resolution temperature-programmed release curves
for He-Xe implanted into UDD at 1000 eV.
However, some fine features, such as peaks and shoulders near
550, 700, and 800°C, can be solved in the LT range. This fine structure
is similar for Ar, Kr, and Xe. On the other hand, a clear shift of the HT-
peak to higher temperatures has been observed in the raw from Ar
(1490°C) to Xe (1550°C).
The LT-peak of noble gas desorption cannot be caused by thermal
decomposition of surface layer as we did not find any correlation
