Irreversible thermal transformations of optical constants of petroleum compounds thin layers on the metal surfaces
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EVTODIEV, Silvia, DMITROGLO, Liliana, EVTODIEV, Igor, GURĂU, Nicolae, POPOVICI, Tudor, CARAMAN, Mihail. Irreversible thermal transformations of optical constants of petroleum compounds thin layers on the metal surfaces. In: Central and Eastern European Conference on Thermal Analysis and Calorimetry, Ed. 4, 28-31 august 2017, Chişinău. Germany: Academica Greifswald, 2017, Editia 4, p. 254. ISBN 978-3-940237-47-7.
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Central and Eastern European Conference on Thermal Analysis and Calorimetry
Editia 4, 2017
Conferința "Central and Eastern European Conference"
4, Chişinău, Moldova, 28-31 august 2017

Irreversible thermal transformations of optical constants of petroleum compounds thin layers on the metal surfaces


Pag. 254-254

Evtodiev Silvia12, Dmitroglo Liliana1, Evtodiev Igor13, Gurău Nicolae4, Popovici Tudor2, Caraman Mihail1
 
1 Moldova State University,
2 University of European Political and Economic Studies „Constantin Stere”,
3 Institute of the Electronic Engineering and Nanotechnologies "D. Ghitu" of the Academy of Sciences of Moldova,
4 National Center for Judicial Expertise
 
Disponibil în IBN: 3 octombrie 2019


Rezumat

The influence of the temperature on the structure of absorption and photoluminescence spectra of the M-40 and M-60 oil layers on the granular surface of the Al, Fe and textolite plates are studied in this paper . The non-destructive identification of the thin film composition of natural oils on metallic or dielectric surfaces (asphalt, ceramics, soil etc.) is mainly made by spectroscopy and photoluminescence methods. The structure of the optical spectra depends on the thermal treatment to which the sample is subjected. As a result of heat treatment at temperatures (-20 ÷ 40)°C, in the thin oil layers the composite changes occur due to the chemical composition of the object, the substrate nature and the temperature. The refractive index and absorption coefficient spectra of the thin layers of internal combustion engine oil obtained on smooth metal surfaces (granulation less than the wavelength of the probe) and on micro granulated metal or dielectric surfaces subjected to long term heat treatment were studied in this paper. The optical constants at the given wavelength of the thin layers on the metal surfaces were determined by the ellipsometry method. From measurements of the radiation diffuse reflectance spectra of the micro granulate surface coated with a thin layer of natural oil, the spectral distribution of the absorption coefficient of both the substrate and the oil layer on this surface, was determined. The thermal kinetics of the absorption coefficient was studied in the temperature range from -20°C to 60°C, at wavelengths corresponding to the absorption bands maximum. The results of the absorption coefficient thermal kinetics measurements are compared with the photoluminescence thermal kinetics of the studied objects. The absorption spectrum of the M-30 oil layer on the aluminum plate surface at the normal temperature contains two wide-band bands: one in the ultraviolet-blue region of the spectrum and the other in the orange region. The time dependence of the absorption coefficient on the wavelength of 410 nm after the laser impulse heating of the oil layer on the surface of the aluminum plate to the temperature of 60°C is well described by an exponential dependence with the time constant in the range from 0,7s to 3s. The time constant is increasing with the thickness of the oil layer. The surface temperature of the investigated sample was determined by the dependence of photoluminescence intensity of 3,0% Eu doped GaSe micro-crystallites.