Residual stress of as-deposited coatings may cause bending of the coating/substrate system. If residual stresses are
present and the overall deflection is small compared with the substrate thickness, then by symmetry the coated substrate
will take up a spherical curvature in the region away from the edges. Near the edges a complex stress state will be
present. However away from the edges this reverts to a simple stress state where stresses normal to the substrate and
shear stresses are zero The three-dimensional inspection of thin films deposited in thin substrates allows the assessment
of film's residual stress. In this communication we report on the use of this method illustrating it by performing the
residual stress evaluation PVD onto glass deposited thin films using optical non-destructive and non-invasive
microtopographic inspection using an active optical triangulation sensor developed by the first author at the Universidade
do Minho. It allows depth measures with resolutions down to 2nm and lateral resolutions down to 1μm. The three
dimensional map and corresponding coordinate set obtained allow the calculation of the stress distribution over the film.
Thermal barrier coatings (TBCs) are extremely useful in gas turbine engines. The quality of these coatings can be improved by subjecting their surface to laser glazing. A reduction in surface roughness, eliminating open porosity on the surface, and the generation of a controlled segmented crack network, can be achieved. TBCs consisting of atmospheric plasma sprayed (APS) ZrO2-8%wtY2O3 are subjected to a CO2 continuous wave laser glazing process to seal their surface porosity, generating an external dense layer. Different amounts of irradiation are applied to the specimens. The microtopograpic inspection of the samples reveal a significant decrease of the surface roughness after laser treatment. However, a network of surface cracks, dependent on the laser scanning speed and track overlapping, are noticed. The cracks have a tendency to be oriented in two perpendicular directions, one in the direction of the laser beam travel direction, the other perpendicular to it. Cracks parallel to the beam scanning direction are found to be at the overlapping zone, in the edge of the subsequent track.
The refractive index (n), the extinction coefficient (κ), dielectric constant ε, free carrier density (nc) and the carrier mobility (μ) of the ITO (Indium-Tin-Oxide) films with different deposition time (or thickness), oxygen partial pressure ratio (PO2) and annealing temperature were measured and studied. The calculated optical parameter-extinction coefficient (κ) was obtained from the diffuse reflectance spectra using "scattering model". The Lorentz oscillator classical model has also been used for fitting the ellipsometric spectra in order to obtain both n and κ values. As comparing the Swanepoel method was used for the refractive index. Clearly the results of the "scattering model", Swanepoel method and Ellipsometric method agree in magnitude. The films prepared at different PO2 show different behaviour of the refractive index and extinction coefficient. The electrical characteristic parameter nc and μ were compared and studied by experimental measurements and calculations using an equation that relates the dielectric function and photo-energy (Drude theory) by Mathematic-4.1 software. Both measured and calculated values coincide in magnitude.
TiO2 thin films were deposited on the glass substrates by dc reactive magnetron sputtering technique at different sputtering pressures. The films prepared at low pressures have an anatase phase, and the films prepared at high pressures have an amorphous phase. The optical properties were studied by measuring the transmittance and the ellipsometric spectra. The optical constants of the films in the visible range were obtained by fitting the transmittance combined with the ellipsometry measurements using the classical model with one oscillator. The films prepared at the pressure higher than 6 x 10-3 mbar show a volume inhomogeneity. This volume inhomogeneity has been calculated by fitting the transmittance and the ellipsometric spectra.
In order to control the roughness of the surfaces of thin titanium films applied on different kinds of substrates, a treatment with CO2 laser is used. The main characteristics of the films' deposition conditions and the treatment employed will be presented. Results of the coatings roughness will be presented. (Summary only available)
Electrochromic coatings are finding a large array of interesting applications in a wide range of fields. The possibility of controlling the transparency of WO3 thin films by the application of small electrical voltages in a reversible way is quite promising and was explored in the work herein reported.
An increasing effort is put our days on the development of new efficient solar energy collectors either for quantum or thermal conversion as the conventional energy sources availability diminishes and its use environmental impact builds up to alarming levels. On this communication we will refer to thermal converters focusing on the roughness and microtopographic inspection of surface thin films and spectrally selective coatings. Physically Vapor Deposited coatings like sputter deposited metal oxide and nitride thin multilayered and graded ones can be used in spectrally selective surfaces for thermal collectors and energy- efficient windows. The energy conversion efficiency of Cr- Cr2O3 cermet solar absorbers depends on its chemical and physical structural characteristics and related optical properties like reflectance, emittance, absorptance and transmittance. The roughness and topographic characteristics of the produced coatings will greatly condition its relevant properties. A careful integral evaluation of the micro- relief structure, and not only the roughness values and roughness regimes, of these Cr-Cr2O3 cermet coatings needs to be performed.
The importance of renewable energy sources is currently attracting widespread attention due to the limited
availability of fuels and major environmental impacts. A great deal of effort is put our days on the development of new
efficient solar energy collectors either by quantum or thermal conversion. On this communication we will focus on the
roughness and microtopographic inspection of surface thin films and spectrally selective coatings for these types of
applications.
Physically Vapour Deposited (PVD) coatings like sputter deposited metal oxide and nitride thin multilayered and
graded ones can be used in spectrally selective surfaces for thermal collectors and energy-efficient windows. The efficiency
of Cr-Cr2O3 cermet solar absorbers for both static and dynamic control of radiative heat transfer through absorbing surfaces
will depend Ofl the chemical and physical structural characteristics and related optical properties like reflectance, emittance,
absorbance and transmittance.
The topographic characteristics of the produced coatings will greatly condition its relevant properties. A careful
integral evaluation of the micro-relief structure of these Cr-Cr203 cermet coatings needs to be performed in a nondestructive,
non-invasive way. Two optical inspection system suitable for the type of surfaces and range of roughness
involved were employed: the MICROTOP.03.MFC an active optical triangulation sensor developed by the principal author
at the Universidade do Minho; and, the Rodenstock' RM1 00 focus sensing based system. Not only the roughness values and
roughness regimes of the surfaces are meaningful but also all other microtopographic characteristics including lay and form.
The Fourier analysis of the different obtained profiles was performed and frequency filtering and extracting applied as a
major source of meaningful microtopographic information.
KEYWORDS: Inspection, Optical coatings, Solar energy, Linear filtering, Solar cells, Oxides, Thin film coatings, Metals, Multilayers, Sputter deposition
The importance of renewable energy sources is currently attracting widespread attention due to the limited availability of fuels and major environmental impacts. A great deal of effort is put our days on the development of new efficient solar energy collectors either by quantum or thermal conversion. On this communication we will refers just to thermal converters focusing on the roughness and microtopographic inspection of surface thin films and spectrally selective coatings. Physically Vapor Deposited coatings like sputter deposited metal oxide and nitride thin multilayered and graded ones can be used in spectrally selective surfaces for thermal collectors and energy- efficient windows.
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