Biomedical Engineering Reference
In-Depth Information
substantially different. In particular, the maxima of thermal CO
desorption were observed at 530 and 590°C for the chemically
treated samples K-2 and CH-7, respectively, and the total quantity
of desorbed carbon oxides differed by more than twice for these
samples. The difference of the surface chemistry of chemically
treated samples of two types was confirmed also by the data of FTIR
spectroscopy l [62, 60].
Another important observation was the detection of chlorine
desorbed in the form of HCl from chemically treated UDD in the
temperature range 400-700°C [62]. Chlorine was likely introduced
during treatment by chlorine-containing acids used in chemical
treatment. The contents of chlorine in the treated CH-7 and
K-2 samples differed by more than order magnitude [62]. This
is an evidence of substantially different chemical activities of
nanodiamonds of different types.
These results indicate that, even though the chemical extraction
procedure affects the surface chemistry of synthetic diamond
nanograins, there is a distinct “memory” of surface properties
behind the origin of UDD. Some surface features of treated UDD
are controlled by their initial “biographic” properties. Thus, the
unification of surface properties of UDD by additional acid treatment
is possible, if at all, only when “severe” and prolonged treatments
are performed, and can hardly be used in practice.
6.3.6 Surface Properties of Nanodiamonds Extracted
from Detonation Carbon Soot of Different Types
Another possible way to obtain the standardized nanodiamond
product could be the application of identical procedure of extraction
in the production nanodiamond from carbon soot (the primary
product of explosion synthesis) of different types.
This possibility was checked using two types of diamond-
containing soot, namely, CH7-ST and K2-ST (“raw material” for
obtaining nanodiamond CH-7 and K-2, respectively), synthesized by
explosion in ice and carbon dioxide atmosphere, respectively. The
UDD extraction was performed using a multistage procedure [61],
which includes microwave treatments a mixture of acids HCl, HNO
,
3
and HF, washing in solutions of AlCl
and HCl, colloidal separation
3
into H
. The high efficiency of this procedure was confirmed
by the experiments of extraction of nanodiamond from meteorites
[72].
O/CH
Cl
2
2
2
