Papers by Keyword: XPS Analysis

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Authors: Nikolay Petkov, Totka Bakalova, Hristo Bahchedzhiev, Petr Louda, Pavel Kejzlar, Pavla Capkova, Martin Kormunda, Petr Rysanek
Abstract: TiCN thin coatings with various different carbon contents were deposited using cathode arc evaporation of pure titanium in a mixture of N2 and C2H2 gasses at a constant pressure of 1.5 Pa. The analyses show a transition from a stoichiometric to a non-stoichiometric coating structure with an increasing C2H2 content. Moreover, the increase in the acetylene in the gas mixture leads to a decrease in the crystal phase from pure polycrystalline to pure amorphous. Nanohardness changes from 30.4 to 4.4 GPa and the cohesive failure of the coatings is in the range of 61 - 72 N. The tribology is estimated by the Ball-on-Disc method and an Si3N4 ball as the counterpart. The measured coefficient of friction is in the range of 0.2 - 0.56.
Authors: Enrique Otero, A. Pardo, F.J. Pérez, F.J. Perosanz, A. Parra, T.P. Levi
Authors: Tao Zeng, Hou Juan Liu, Zhan Shu
Abstract: Environmental pollution has become one of the most serious problems with the development of the world. TiO2 has caused great concern due to its excellent effort on the environmental purification and solar energy conversion. N, S-doped titania were prepared by a one-pot hydrothermalmethod using urea and sulfourea as precursor of nitrogen and sulfur. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of them was evaluated for the degradation of methylene blue under xenon lamp which has similar spectra to solar light. The preparation methods and doping mechanism of the nitrogen-doped TiO2 are discussed. Morever, N, S-codoped titania can further enhacnce the photocatalytic activity effectively, This excellent performance could endow the as-prepared P-doped titania potential in purifying wastewater.
Authors: Lilyana Kolaklieva, Roumen Kakanakov, Ts. Marinova, G. Lepoeva
Abstract: X-ray photoelectron spectroscopy is used to study the effect of the metal composition on the electrical and thermal properties of Au/Pd/Ti/Pd contacts to SiC. No reactions and interdiffusion between the contact components and SiC are found for the as-deposited contact layer. The steep metal/SiC interface corresponds to the Schottky behaviour observed before the annealing. Annealing at 900 oC causes Pd2Si formation at the SiC interface and ohmic properties appearance. Due to the addition of Ti to the contact composition the carbon resulting from the SiC dissociation during annealing is completely consumed, which leads to improvement of the thermal stability.
Authors: Xian Lan Chen, Na Wu, Gao Zhang Gou, Ling Shi, Shan Qin Pan, Wei Liu
Abstract: Theoretical studies predicted that doping graphene with nitrogen can tailor its electronic properties and chemical reactivity. We develop here a novel method for synthesis N-doped graphene via solvothermal synthesis process with urea as both reductant and nitrogen sources. The resulting N-doped graphene were characterized by various methods (UV-vis spectra, SEM and XPS). XPS analysis shows a predominant graphitic C 1s peak at ca. 285 eV, an O 1s peak at ca. 532 eV and N 1s peak at ca. 410 eV. Moreover, the atomic ratio of N/C is 5.0% for N-doped graphene, demonstrating nitrogen species have been successfully incorporated into N-doped graphene.
Authors: Ruslan Shvab, Eduard Hryha, Petro Shykula, Eva Dudrová, Ola Bergman, Sven Bengtsson
Abstract: Study of microstructure of high Cr-alloyed sintered austenitic stainless steel was performed in few stages XPS analysis of powder surface, theoretical prediction of microstructure by Thermo-Calc and JMatPro software and metallographic observation of sintered material. XPS analysis showed presence of thin iron oxide layer on the surface of powder particles and oxide islands formed by Si, Mn and Cr. Theoretical prediction made by Thermo-Calc and JMatPro calculations showed presence of austenite with chromium carbides and carbonitrides in equilibrium state. Both predictions are in good agreement. Metallographic observation of sintered material showed that microstructure contains small austenitic grains with size of 3-5 μm with fine carbides (1-2 μm) and carbonitrides distributed mostly on grain boundaries. Metallographic study of material confirmed theoretical predictions.
Authors: Gustavo Henrique Denzin Tonoli, M.N. Belgacem, G. Siqueira, J. Bras, Lourival M. Mendes, F.A. Rocco Lahr, H. Savastano Jr.
Abstract: Fibre-cement products had been widely used in the world due to their versatility as corrugated and flat roofing materials, cladding panels and water containers presented in large number of building and agriculture applications. The main reason for incorporating fibres into the cement matrix is to improve the toughness, tensile strength, and the cracking deformation characteristics of the resultant composite. One of the drawbacks associated with cellulose fibres in cement application is their dimensional instability in the presence of changing relative humidity. The objective of the present work is to evaluate the effect of surface treatment of eucalyptus cellulose pulp fibres on the processing and dimensional changes of fibre-cement composites. Surface modification of the cellulose pulps was performed with methacryloxypropyltri-methoxysilane (MPTS), aminopropyltri-ethoxysilane (APTS) and n-octadecyl isocyanate, an aliphatic isocyanate (AI), in an attempt to improve their dimensional instability into fibre-cement composites. X-ray photoelectron spectroscopy (XPS) showed the chemical changes occurred at the surface, and contact angle measurements showed the changes in the surface energy. MPTS-and AI-treated fibres presented lower hydrophilic character than untreated fibres, which led to lower water retention values (WRV). APTS increased the water retention value of the pulp and improved the capacity of hydrogen bonding of the fibres. MPTS-and AI-treated fibres led to low final water/cement ratios and reduced volume changes after pressing. MPTS-treated fibres decreased the water and dimensional instability of the fibre-cement composites, while the contrary occurred with APTS-modified and AI-modified fibres.These results are promising and contribute for new strategy to improve processing and stability of natural fibres-reinforced cement products.
Authors: Yan Zhang, Cun Bo Gong, Gui Mei Shi, Sheng Gang Wang
Abstract: Potentiodynamic and potentiostatic polarization experiments showed that the nanocrystallized bulk 304 stainless steel (nano304SS) exhibited a superior pitting resistance in 0.5 mol/L HCl solution, in comparison to the bulk 304 austenitic stainless steel (304SS). X-ray photoelectron spectroscopy characterization indicated that a passive film was formed on the nano304SS which was richer in Cr and denser than that on the 304SS
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