Biomedical Engineering Reference
In-Depth Information
In this case the nanodiamond samples were heated in vacuum at a
rate of 7°C/min up to 1600°C. Temperature profiles of evolved noble
gases were measured by means of quadruple mass spectrometer. A
Ti-getter was used to remove a lot of active gases desorbed during
pyrolysis of nanodiamonds, keeping the total pressure of the vacuum
chamber below 10
−
5
torr during the heating runs. The released noble
gases were pumped at a low rate through a calibrated orifice. This
dynamic mode of operation allowed to measure the evolved active
gases as well. This procedure was successfully applied to measure
noble gases in UDD and MND [81] and to clarify the mechanism of
high temperature release of these gases [82].
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TEMPERATURE,
o
C
°C
Figure 6.10
Temperature profiles of helium release from nanodiamonds.
(1) Stepped pyrolysis (static mode) of UDD after implantation
of He-ions (700 eV); (2) linear heating (dynamic mode)
of the same sample; and (3) linear heating of “presolar”
nanodiamonds extracted from Murchison meteorite. The
curves are normalized to the maximum intensity.
An example of the release patterns of helium in different
nanodiamonds is shown in Fig. 6.10. Please note that, due to small
available amount of meteoritic diamonds, only helium could be
measured. The temperature profiles of helium from ion implanted
UDD measured in static (Fig. 6.10, curve 1) and dynamic (Fig. 6.10,
