Papers by Author: C.T. Dervos

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Authors: T.G. Argyropoulos, Jelica Novakovic, M.D. Athanassopoulou, P. Vassiliou, J.A. Mergos, C.T. Dervos
Abstract: Electrolytical deposition of CdSe on Ti substrates from CdSO4 - SeO2 solutions is investigated. The effect of the bath temperature was investigated and how it affects the CdSe deposits. According to the XRD spectra, the obtained CdSe films exhibit the cubic zinc-blende structure that remains unaffected by vacuum heat treatment (650°C). The surface morphology of the films differs significantly with bath solution temperatures. When Au contacts are used, the Ti/CdSe/Au structure may exhibit rectifying properties depending on the temperature during the electrodeposition. High temperature baths make the deposits to obtain ohmic properties.
Authors: Jelica Novakovic, M. Delagrammatikas, P. Vassiliou, C.T. Dervos
Abstract: The study of composite electroless Ni-P coatings is pursued in order to obtain coatings on a metal substrate with advanced properties i.e. with high wear and corrosion resistance for particular engineering uses. Composite NiP-ZrO2 layers were prepared by simultaneous electroless co-deposition of Ni-P and ZrO2 on steel, from a reducing solution in which ZrO2 particles were kept in suspension by stirring. The particles load in the bath was 0, 0.5, 1.0, 2.0 and 5.0 g/l. The deposits of 30 m in thickness, were characterized for structure, morphology and hardness by scanning electron microscopy and microanalysis as well as X-ray diffraction. It was found that the maximum ZrO2 particle incorporation attained was 7-10% of Zr. Vickers microhardness was measured for the plain deposit and found to be 720 HV and for the maximum zirconia content of 10%, 820 HV. After a vacuum heat treatment for 10 min, the microhardness of the composite is found to be 1500 HV. The electrochemical linear polarization measurements in a corrosive NaCl 3.5% solution shows at 2.0 g/l bath load favourable conditions for the formation of a defects free composite deposit could be created.
Authors: C.G. Karagiannopoulos, P.D. Bourkas, C.T. Dervos, C.A. Kagarakis
Authors: A.X. Moronis, P.G. Halaris, P.D. Bourkas, C.T. Dervos, C.A. Kagarakis
Authors: M.D. Athanassopoulou, T.G. Argyropoulos, G.T. Paparoupas, J.A. Mergos, C.T. Dervos
Abstract: The utilization of Al2O3 and Li2O as dopants that promote the anatase-to-rutile (A-R) phase transition in TiO2 nanoparticles during calcinations is studied. X-Ray Diffraction and SEM techniques were employed for the evaluation of phase transformation and particle size coarsening in pure TiO2, TiO2-Al2O3 and TiO2-Li2O mixtures. For the Li-Ti-O pseudobinary systems some complex oxides may be formed during phase transformation that occurs at significantly lower temperatures compared to pure TiO2 or TiO2-Al2O3 mixtures. Al2O3 doping in TiO2 only increases the anatase-to-rutile transition rate once the phase transformation has been initiated.
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