OBTAINING OF SPATIAL FORMATIONS FULLERENES TYPE,  MADE UP OF CARBON ATOMS, BY APPLYING DISCHARGES PULSED ELECTRIC PROCESS - EDI - OVER METALLIC SURFACES, WITH GRAPHITE CATHODE

Marin Laurentiu^1,*, Topala Pavel²

¹National Institute for Research and Development in Chemistry and Petrochemistry ICECHIM Bucharest, Romania, Splaiul Independentei Street, no. 202, sect. 6, 060021;  ²State University "Alecu Russo", Balti, Street Puskin, Republic Moldova

abstract

Metal surface treatment, is performed  by chemical procedures e.g. treatment with oxidizing substances -potassium  permanganate, potassium  chloride mixed with oxidizing acids HNO₃ , H₂SO₄, or by physical procedures e.g. such as irradiation or corona treatment.  The surface treatment is made to modify the chemical composition of the metal surface in a superficial depth on the order of a few microns, thus obtaining the oxides, nitrides or metal salts. A special surface treatment consists of applying a film of graphite by pulsed electrical discharges, using a graphite electrode connected to the negative pole-the cathode. This treatment is designed to reduce the metallic surface polarity to prevent subsequently affinities with metal or non-metallic materials with which it can come into contact.

This paper,  presents the results obtained after a laborious  scientific research, undertaken to establish the enforcement technology of graphite films on metallic surfaces with pulsed electrical discharges procedure.

Microscopy SEM analyzes of the graphite film layed with pulsed electrical discharges showed also globular formations made up of carbon atoms

The samples submitted to thermo-gravimetric analysis were small portions of graphite powder, collected from the surface of the metal. The samples submitted to SEM were small metal plates  on whose surface it was deposited a film of graphite. Following the thermo-gravimetric analysis were found the addition of mass insignificant values, 1,365-2.769 %. although thermo-gravimetric analysis was conducted under nitrogen atmosphere.

TG characterization was conducted in nitrogen atmosphere and not in  usual atmosphere containing 22% O₂ , because the results could be distorted, the mass addition may occur as a  result of an oxidation process.

As compared, the study of the graphite samples collected from the electrode does not present this phenomenon. The additions of mass takes place at elevated temperatures and have the following values 222, 99 Cº (1,99 %), 476,12 Cº (1,365 %), 614,73 Cº (2,769 %). The metal plates on whose surface a graphite pellicle was deposited  submitted to an electron microscopic analysis SEM, revealed a number of regular globular formations which are not part of graphite film. This observation corroborated with thermo-gravimetric analysis results, leads to the conclusion that the procedure for obtaining the graphite film also results formation of  carbon atoms type fullerenes, able to incorporate in a reversible process small molecules (Buckminsterfullerene and Buckyballs, 2006) (N₂, HOH) (Howard Jack B. et al., 1991).

Keywords: electric discharges in pulse, graphite, fullerenes.