| 1. |
- Abad, Manuel David, et al.
(författare)
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Identification of Ternary Phases in TiBC/a-C Nanocomposite Thin Films : Influence on the Electrical and Optical Properties
- 2011
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Ingår i: Plasma Processes and Polymers. - : Wiley. - 1612-8850 .- 1612-8869. ; 8:7, s. 579-588
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Tidskriftsartikel (refereegranskat)abstract
- The local structure of TiBC and amorphous carbon (a-C) nanocomposite films (TiBC/a-C) was correlated with their optical and electrical properties. TiBC/a-C films with increasing C content were deposited by magnetron co-sputtering from TiC:TiB(2) (60: 40) and graphite targets. Chemical composition is determined by electron energy-loss spectroscopy. Grazing incidence X-ray diffraction reveals that the microstructure of the films is amorphous with small nanocrystallites emerging by increasing the C content that could be attributed to the formation of ternary (TiB(x)C(y)) or mixed binary (TiB(2) and TiC) phases. Further information was then obtained by studying the chemical bonding by measuring the near-edge fine structure (NES) by electron energy-loss (B K-, C K-, and Ti L-edges) and X-ray absorption (B K-and Ti L-edges) spectroscopies. The NES analysis indicates the formation of a nanocrystalline ternary TiB(x)C(y) compound concomitant with the segregation of an a-C phase as the carbon content is increased. The optical properties were studied by spectroscopic ellipsometry and the electrical resistivity was measured by the Van der Pauw method between 20 and 300 K. The films continuously lose their metallic character in terms of optical constants and resistivity with increasing carbon content. Theoretical fitting of the electrical properties using the grain-boundary scattering model supported the formation of a nanocomposite structure based on a ternary TiB(x)C(y) phase embedded in a matrix of a-C. The electron transport properties are mainly limited by the high density of point defects, grain size, and transmission probability.
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| 2. |
- Bárdoš, Ladislav, et al.
(författare)
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Cold Atmospheric Plasma Deposition of Diamond
- 2007
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Ingår i: Plasma Processes and Polymers. - : Wiley. - 1612-8850 .- 1612-8869. ; 4:5, s. 511-514
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Tidskriftsartikel (refereegranskat)abstract
- Nanocluster diamonds can be synthesized in open air on stainless steel and molybdenum substrates with a hybrid cold atmospheric plasma source using air plasma and an air + alcohol mixture. At microwave powers below 300 W and at gas flow rates below 300 sccm the temperature of a thermally insulated steel substrate placed 1.5 cm from the hollow cathode caused by the air plasma were less than 600 °C. 200 nm thick coatings with nanocluster diamond grains and aggregates exhibiting diamond peaks in the Raman spectra at 1 325 cm-1 on stainless steel and at 1 322 cm-1 on Mo were formed after 1 h on untreated substrates.
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| 3. |
- Bárdos, Ladislav, et al.
(författare)
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Cold Atmospheric Plasma Treatment of Steel Buoys for Wave Energy Converters
- 2011
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Ingår i: Plasma Processes and Polymers. - : Wiley. - 1612-8850 .- 1612-8869. ; 8:7, s. 658-663
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Tidskriftsartikel (refereegranskat)abstract
- Steel sheets used for ocean buoys in the linear wave energy converters have been treated by cold atmospheric plasmas in Ar, Ne, and the wet air. The contact angle has decreased from about 48 degrees at an untreated surface to a minimum of about 248, depending on the plasma and the treatment time. This corresponds to an increase of the surface energy from about 57 to 69 mN/m. Comparison of the XPS spectra before and after plasma treatment confirmed important role of the plasma activated oxygen. The hydrophilicity of treated surfaces deteriorates within about 120 min. Immediate painting of treated surfaces has lead to considerable better paint adhesion than on untreated surfaces. The plasma treatment of buoys before painting is, therefore, expected to improve their corrosion resistance and lifetime.
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| 4. |
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| 5. |
- Chappuis, S, et al.
(författare)
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Photocatalytically active titania layers: Production at ambient temperature and characterisation of biological properties
- 2009
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Ingår i: Plasma Processes and Polymers. - : Wiley. - 1612-8850 .- 1612-8869. ; 6:6-7, s. 440-445
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Tidskriftsartikel (refereegranskat)abstract
- The production of phase-pure, photocatalytically active titania layers at ambient temperature is described. This novel synthesis route has been achieved by using direct-current reactive magnetron sputtering as well as plasma-enhanced chemical vapour deposition processes. As a consequence substrates degrading under increased temperature such as, e.g., polymers, biological fibres, tissues, etc., may be coated. The obtained titania coatings are characterised with respect to structure, morphology, phase purity and biological activity. The results of these investigations confirm promising and reproducible photocatalytic, biocompatible as well as bioactive properties. A figure is presented.
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| 6. |
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| 7. |
- Kubart, Tomas, et al.
(författare)
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Modelling of Magnetron Sputtering of Tungsten Oxide with Reactive Gas Pulsing
- 2007
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Ingår i: Plasma Processes and Polymers. - : Wiley. - 1612-8850 .- 1612-8869. ; 4, s. S522-S526
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Tidskriftsartikel (refereegranskat)abstract
- Reactive sputtering is one of the most commonly employed processes for the deposition of thin films. However, the range of applications is limited by inherent instabilities, which necessitates the use of a complex feedback control of reactive gas (RG) partial pressure. Recently pulsing of the RG has been suggested as a possible alternative. In this report, the concept of periodically switching the RG flow between two different values is applied to the deposition of tungsten oxide. The trends in the measured time dependent RG pressure and discharge voltage are reproduced by a dynamical model developed for this process. Furthermore, the model predicts the compositional depth profile of the deposited film reasonably well, and in particular helps to understand the formation of the interfaces in the resulting multi-layer film.
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| 8. |
- Snyders, Rony, et al.
(författare)
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Influence of the chemical composition on the phase constitution and the elastic properties of RF sputtered hydrozyapatite coatings
- 2008
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Ingår i: Plasma Processes and Polymers. - : Wiley. - 1612-8850 .- 1612-8869. ; 5:2, s. 168-174
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the influence of chemical composition on the constitution and elastic properties of dense radio-frequency (RF)-sputtered hydroxyapatite (HA) coatings. The chemical composition was modified by varying the RF sputtering power density (P-D). As the P-D was increased by 240%, the Ca/P ratio measured by X-ray photoelectron spectroscopy increased from approximate to 1.51 to approximate to 1.82. X-ray diffraction indicates phase pure hexagonal HA except for the sample prepared at the highest P-D where CaO and Ca-3(PO4)(2) also form. Deviations from the stoichiometric Ca/P ratio result in reduction of the elastic modulus. For Ca/P = 1.51 +/- 0.02, the elastic modulus decreases by approximate to 15%. This maybe due to incorporation of Ca vacancies in the lattice, while for Ca/P = 1.82 +/- 0.02, the average elastic modulus decreases by approximate to 10% due to formation of additional phases.
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| 9. |
- Eklund, Per, 1977-, et al.
(författare)
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Thermal Stability and Phase Transformations of γ-/Amorphous-Al2O3 Thin Films
- 2009
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Ingår i: Plasma processes and polymers. - : Wiley. - 1612-8850. ; 6:1, s. 907-911
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Tidskriftsartikel (refereegranskat)abstract
- Magnetron-sputtered Al2O3 thin films were annealed in ambient air. The phase compositions of the as-deposited Al2O3 films were (i) fully amorphous, (ii) nanocrystalline γ-Al2O3 in an amorphous Al2O3 matrix, and (iii) fully crystalline γ. For all samples, annealing to 1 100-1 150 °C resulted in a transformation to α-alumina. The transformation paths depend on the phase fraction of γ in the as-deposited films. For amorphous films and films with low initial γ fraction, the intermediate phase θ-Al2O3 appeared in the range of 1 000-1 100 °C. For predominantly crystalline γ-Al2O3 as-deposited films no intermediate Al2O3 phases were observed, indicating a direct γ-to-α phase transformation at ≈1 100 °C.
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| 10. |
- Lewin, Erik, et al.
(författare)
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Industrialisation Study of Nanocomposite nc-TiC/a-C Coatings for Electrical Contact Applications
- 2009
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Ingår i: Plasma Processes and Polymers. - : WILEY-VCH Verlag GmbH & Co. - 1612-8850. ; 6:S1, s. S928-S934
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposite nc-TiC/a-C coatings were prepared by non-reactive magnetron sputtering in industrial scale equipment, under varying deposition conditions in order to investigate upscaling and possible industrialisation. The coatings were found to have similar microstructure and performance compared to previous laboratory scale experiments. The samples were characterised with XRD, XPS and SEM as well with ball-on-disc, nanoindentation and electrical measurements. Coatings containing a small fraction of a-C matrix phase were found to have promising both electrical properties (rho < 400 mu Omega cm and contact resistances down to 0.34 m Omega at 40 N) and tribological properties (f < 0.3 for 10 000 laps).
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