THE PHYSICAL BASES OF ELECTROLYTIC FORMATION OF CHROMIUM- SILICON DIOXIDE NANOCOMPOSITE SYSTEMS IN ELECTROLYTIC COATINGS

11th International Multidisciplinary Scientific GeoConference SGEM2011, www.sgem.org, SGEM2011 Conference Proceedings/ ISSN 1314-2704, June 20-25, 2011, Vol. 2, 753-758 pp

ABSTRACT

The main aim of the work is theoretical and experimental research of
nanocomposite systems formation process on the model of chromium electrolytic
coatings, ascertainment of laws and mechanisms of silicon dioxide nano-sized particles
influence on the structure and properties of metal. We researched the process of
electrolytic formation of chrome - silicon dioxide nanocomposite systems and
nanostructured composite electrolytic coatings with silicon dioxide (3-50 nm) used as a
dispersed phase. Methods of the research: atomic-force, raster electronic, optical
microscopy, as well as IR-spectrometry, and roentgen-structural analysis. Estimation of
endurance and corrosion resistance was made by weight.

Main results and findings of the present research:

 Analysis of contemporary state and perspective ways of nanotechnology development
has made it possible to propose a new scientific approach for the solving the problem of
Cr-SiO2 nanocomposite systems formation in electrolytic coatings.

 On the basis of the research it has become possible to determine the electrolyte
compositions for chrome - silicion dioxide nanocomposite systems formation, and it has
been established that optimal content of silicon dioxide in the electrolyte is 20 g/l. A
larger content of the second phase will cause sludging, dramatic lessening of current
output, while lower content of SiO2 will not bring marked changes of the microstructure
and getting the required properties of the nanocomposite system.

 Mechanisms and natural laws were ascertained to determine influence of temperature,
current density and ultrasonic exposure modes on the parameters of metal plating by
nano-CEC. It has been shown, that increase of temperature and current density causes
decrease of current output, and periodical ultrasonic exposure enables formation of
nanocomposite systems with dense, finely crystalline and porous chromium matrix.

 Researches with atomic-force, electronic and optical microscopy have revealed
uncharacteristic for metals (chromium in particular) petal-like, globular structures
predetermined by high activity of nano-sized particles of silicon dioxide.

 Radiographic studies of nanocomposite systems formed at different temperatures
established that changes of microhardness depend on the fact that within 298-323 K
hexagonal chromium hydride (CrH) having microhardness 10,5-12 GPa deposits. In the
temperature interval of 338-348 K mainly FCC chromium hydride with microhardness about 6-10 GPa deposits.

Keywords: nanocomposite systems, atom-force microscopy, nano-sized particles, nano-composition electrolytic coatings (nano-CEC), microhardness.