Porous silicon & titanium dioxide coatings prepared by atmospheric pressure plasma jet chemical vapour deposition technique-a novel coating technology for photovoltaic modules

Atmospheric Pressure Plasma Jet (APPJ) is an alternative for wet processes used to make anti reflection coatings and smooth substrate surface for the PV module. It is also an attractive technique because of it’s high growth rate, low power consumption, lower cost and absence of high cost vacuum systems. This work deals with the deposition of silicon oxide from hexamethyldisiloxane (HMDSO) thin films and titanium dioxide from tetraisopropyl ortho titanate using an atmospheric pressure plasma jet (APPJ) system in open air conditions. A sinusoidal high voltage with a frequency between 19-23 kHz at power up to 1000 W was applied between two tubular electrodes separated by a dielectric material. The jet, characterized by Tg ~ 600-800 K, was mostly laminar (Re ~ 1200) at the nozzle exit and became partially turbulent along the jet axis (Re ~ 3300). The spatially resolved emission spectra showed OH, N2, N2+ and CN molecular bands and O, H, N, Cu and Cr lines as well as the NO2 chemiluminescence continuum (450-800 nm). Thin films with good uniformity on the substrate were obtained at high deposition rate, between 800 -1000 nm.s-1, and AFM results revealed that coatings are relatively smooth (Ra ~ 2 nm). The FTIR and SEM analyses were better used to monitor the chemical composition and the morphology of the films in function of the different experimental conditions. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2790

Enhancement of NMP degradation under UV light by nitrogen-doped TiO2 thin films using a design of experiment

Doping nitrogen within TiO2 is an effective way to enhance visible light photocatalysis due to a direct electron excitation from the N2p states within the band gap. However, nitrogen doping is not always efficient for UV photocatalytic activity. Here, different structures of N-doped TiO2 (TiOxNy) have been prepared by reactive RF (13.56 MHz) magnetron sputtering. The morphological, optical, structural, and photocatalytic properties of the films have been studied in order to investigate the competitive effect of the morphology and the chemical composition on the efficiency of the photocatalytic activity. The variation of surface wettability of the film over time in the dark and under visible and UV irradiation was also studied. The reduction in wettability by dark storage can be explained by the adsorption of hydrocarbon contamination on the thin film’s surface. Additionally, from water contact angle experiments, it was found that these films developed hydrophilic properties upon UV and visible illumination. The photoinduced change in the contact angle of water was due to the removal of hydrocarbon contamination on the surface and also the photo-oxidation of the water droplet. Samples prepared at high pressure gave the best photocatalytic activity, even though the deposition rate was lower at higher pressures (lower film thicknesses), due to the high specific surface area and the optimal presence of TiOxNy crystals in the lattice. However, at low pressure, the TiN crystals became more predominant, and acted as recombination centers for the photo-generated charge carriers. A design of experiments was used in order to optimize the deposition parameters to have the best photocatalytic activity. The high photocatalytic activity under UV light was found to be due to the introduction of discrete energy levels within the band gap, the increased sample wettability, and the higher specific surface area. However, the post annealing process did not effect the activity under UV irradiation. Using the response surface methodology, RSM, based on a design of experiment, DOE, we are able to achieve a good understanding of the complex processes involved in the deposition of the thin films and their effect on the photocatalytic activity. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/930

Improvement of the stability of plasma polymerized acrylic acid coating deposited on PS beads in a fluidized bed reactor

The present study deals with the deposition of plasma polymerized acrylic acid (PPAA) coatings on the surface of polystyrene beads. XPS analysis showed that the COOH content of the unwashed surface decreased by increasing the power, whereas the resistance to washing was improved weakly. The results showed that the use of an argon pretreatment of PS beads before plasma deposition of AA leads to a strong adhesion between PPAA coating and the underlying PS, reinforcing its stability. The study of the influence of the plasma deposition time clearly showed that the COOH content increased with the plasma treatment time, due to a better coverage of the PS beads. However, the stability of such coatings decreased inversely with the plasma treatment time due to their delamination

Study of plasmas in He–O

The characteristics of a low frequency (70 kHz) discharge with non-symmetrical configuration of electrodes in He–O2 mixtures were investigated. The Langmuir probe technique, emission spectroscopy, mass spectrometry and absorption spectroscopy were used for plasma diagnostics. The physicochemical properties of PET (polyethylene terephtalate) were analyzed via contact angle measurements and XPS spectroscopy. The presence of the oxygen is shown to modify both the densities of the helium metastable states and also the energetic character of the discharge. The very efficient loss of He excited species and in particularly the metastables, for amounts of O2 higher than a few percents, affects the surface modification in terms of crosslinking, and therefore the stability. This work has shown that one of the important species responsible for the crosslinking process leading to stable surface properties could be the helium metastables

Stable Polymerized Acrylic Acid coating deposited on Polyethylene (PE) films in a low frequency discharge

Plasma polymerized acrylic acid (PPAA) coatings were deposited on PE films, in a 70 kHz low pressure plasma reactor, at various plasma powers. The COOH retention of PPAA coatings and its stability to washing in water were investigated by XPS, WCA (water contact angle), FTIR, ellipsometry and SEM analyses. The results have shown that the use of higher powers leads to an increase of the stability of the coating due to a high degree of cross-linking. Under optimized conditions, it is possible to obtain stable PPAA coatings which resist to washing with a COOH retention rate of 15% on PE, which is much higher than the coating deposited in a 13.56 MHz discharge. This high stability of the coatings observed in the low frequency discharge, which is somewhat similar to DC glow discharges, is probably due to the ions which play an important role in the cross linking process of the coatings. Optical emission spectroscopy measurements (OES) have shown good correlation between the CO density in the gas phase and the carboxylic content of PPAA coating

Cell repellent coatings on inner walls of tubes by means of transporting discharge in atmospheric pressure.

www.springerlink.comInternational audienceWe report a method to obtain biocompatible PEG copolymer coatings inside High Density Polyethylene (HDPE) and Pyrex tubes, which was successfully developed by using a transporting discharge. The latter being a dry process, it is easier to apply as compared to the conventional multistep wet chemical techniques. The results presented in this paper show that for a 70 cm tube good cell repellent properties as compared to the control was obtained for the entire length of the tube. The best nonfouling properties with respect to CT-26 (colon cancer) were obtained for coatings presenting the best retention of ether functionalities from the DEGME monomer i.e. between 5-25 cm downstream of the tube. These results are interesting for surface modification of biomaterial and biomedical devices which present hollow bodies