II International Symposium on Carbon for Catalysis ABSTRACTS

PP-I-31
suspensions of UFD had low values of surface tension and could easily wet different
substrates to form films by dipping technique. The films were deposited on silicon, quartz and
other substrates arranged upright by dip coating technique. The surface of the substrates and
the effects of the organic medium stimulated a structural organization. The following
evaporation of organic phase on the substrate was carried out at the temperature 300-350 °C,
which did not exceed the temperature of diamond oxidation and by thermograph
investigations of UFD powders, the mass loss in air started at 500 °C. The choice of organic
liquids was determined from their ability to wet the substrate completely and their low
temperatures of evaporation. The second factor provided the ability to preserve the
nanodiamond without oxidation or graphitization during the film formation. The adhesion of
this layer is improved by further process of pyrolysis at a temperature greater than that of the
boiling point of dispersion medium. The processes of wetting and pyrolysis were repeated for
the preparation of films with desired thickness.
By a method of the fast electron diffraction it was found that the coatings prepared from
nanosuspensions of UFD do not show the crystal reflection. The surface of coatings was
uniform without ant cracks and voids resembling amorphous structure.
The spectral investigation in UV-VIS-IR region showed that the films have the diamondlike
optical properties. It was found that the glasses became more transparent with these UFD
coatings on them. In the IR-spectrum (400 - 4000 cm -1 ) no absorption was observed. Films
were transparent through out the whole range of measurement. But for powders of UFD in
KBr pellets, the absorption for nitric - extrinsic structures could be identified. In the
UV-visible range (200-800 nm) in the reflection spectra of the UFD-coatings on silicon and
glass, the absorption below 225 nm was observed. The corresponding band gap would be
≥ 5.6 eV. This would mean that the films would contain higher percentage of sp 3 bonded
carbon. Thus, the spectral investigations in IR, UV and visible ranges confirm the formation
diamond-like structure of UFD-coatings.
From Auger spectrum of film surface indicated the presence of carbon and a small
amount of oxygen.
The results of X-ray diffraction measurements on Mo substrate and Mo coated with the UFDcoatings
(after examination on internal friction) are shown in Fig.1a and 1b respectively. Fig.1b
indicates shows that thermal load on these materials lead to form a carbide phase on the surface of
the samples. Formation of carbide is usually favored at high temperatures. Efficiency of cutting
tools was found to increase significantly with the use of UFD coating on them.
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