Papers by Keyword: GIXRD

Abstract: Article presents results of measurements of vital parameters of PVD coatings of potential application in medicine (joint replacements or medical tools). The phase identification, level of residual stresses and texture were determined for various coatings by X-ray diffraction method. Chemical composition of coatings was verified by means of XRF. A set of measurements reveled the existence of advantageous compressive stresses in coatings, the texture determination showed undesirable fiber texture in TiN coating and advantageous uniformity of TiCN ones. XRF analysis pointed out the necessity of careful preparation of samples during PVD process during which phenomena of inhomogeneity in chemical can be present as it is presented in the paper.

Abstract: Transparent thin film of TiO2 is deposited on glass substrate by e-beam evaporation method with the pressure, deposition rate, and substrate temperature of 3.0 x 10-6m.bar, 3 nm/s and 100 0C respectively. The film is annealed at 500 0C for about 1 hour. The structural property of the films has been studied using GIXRD. The optical property of the film has been studied using UV-Visible and Photoluminescence spectroscopy (PL). Photoluminescence spectra shows intense and sharp peak at 440 nm. The dielectric property of the film is studied by measuring capacitance at different frequencies at room temperature. It is observed that the capacitance decreases with increase in frequency but at high frequency, the capacitance becomes constant. GIXRD data indicates the crystalline property of the film.

Abstract: We recently synthesized different composition polycrystalline Ho2+xTi2-xO7-x/2 (x=0, 0.4 and 0.67), which is derivative fluorite compounds known as and pyrochlore phases in Ho3O2-TiO2 phase diagram by using conventional solid state synthesis methods. The samples were irradiated with 400 keV Ne2+ ions at cryogenic temperature (~77 K), using the Danfysik ion accelerator at the Ion Beam Materials Laboratory (IBML) of Los Alamos National Laboratory (LANL). The irradiation fluences in the experiments ranged from 5×10¹⁴-5×10¹⁵ ions/cm². An order-to-disorder (O-D) transformation was observed for α, β and pyrochlore phases, as determined using grazing incidence X-ray diffraction (GIXRD) at an incident angle of 0.25°. The O-D transformation threshold fluence for α phase was found to be noticeably lower than those for β phase and pyrochlore, and the O-D transformation threshold fluence for β phase was the highest. The O-D transformation threshold fluence was found to be coherent with the phase transformation temperature in the Ho₃O₂-TiO₂ temperature-composition (T-C) phase diagram.

Abstract: Roughness influence on the residual stress gradient evaluation in the case of a grazing incidence X-ray diffraction setup is considered. In this geometry the surface roughness changes essentially the X-ray wave fields of the transmitted and diffracted beams inside the coatings and subsurface regions of bulk samples, and thus influences the refractive properties of the investigated sample area. In turn, the change in the refraction index enforces the re-scale of the informational depth and, consequently, the evaluated stress depth profile. The diffracted amplitude from the crystalline grain located beneath the surface is calculated. The surface roughness is shown to contribute into reconstruction of the real stress gradient profile of the coating.

Abstract: Oxidation kinetic of a Zr55Cu30Al10Ni5 bulk metallic glass (BMG) and its crystalline counterpart were studied under dry artificial air (20% of O2 and 80% of N2) at 673 K by thermogravimetry analysis (TGA) method. According to TGA profiles, the oxidation kinetic in both amorphous and crystalline states followed a protective parabolic law. However, the oxidation rates for the amorphous alloy were obviously higher than those for the crystalline alloy. Pseudo-grazing incident X-Ray diffraction (GIXRD) has been carried out to identify the oxides nature and their crystalline structure. Tetragonal-ZrO2 dominated the oxide scale formed on both alloys (BMG and crystalline) at T = 673 K; meanwhile, a slight amount of Cu was detected on the oxide surface of studied BMG alloy. The atomic diffusion mechanism was investigated using a two-stage oxidation treatment to study oxide scale growth kinetics. The studied specimens were oxidized firstly under dry artificial air and then under 18O2 isotopic tracer gas for 1.5 hours respectively at 673 K. The evident solute penetration zone and ion diffusion characteristic through the oxide scale were determined by Cs+ secondary ion mass spectrometry (SIMS) depth profile. The results showed the mechanism of the oxide layer formation of both alloys was not only due to Oxygen ions diffusion from oxide surface to interior scale, but also to an outward diffusion of Zirconium ions from substrate to oxide layer and the ZrO2 oxide growth seemed to occur at the oxide/gas interface in our studied case.

Abstract: This paper is a review of the thermal stability of nanostructured nitride coatings synthesised by reactive magnetron sputtering technique. In the last three decade, nitride based coatings have been widely applied as hard wear-protective coatings in mechanical components. More recently, a larger interest has been addressed to evaluate the thermal stability of such coatings, as their mechanical and tribological properties are deteriorated at high working temperatures. This study describes the microstructural, mechanical and compositional stability of nano-crystalline Cr-N and nano-composited Ti-N based coatings (Ti-Al-Si-B-N and Ti-Cr-B-N) after air and vacuum annealing. For Cr-N coatings annealing in vacuum induces phase transformation from CrN to Cr2N, while after annealing in air only Cr2O3 phase is present. For Ti-N based coatings, a well-definite multilayered structure was shown after air annealing. Degradation of mechanical properties was observed for all the nitride coatings after thermal annealing in air.

Abstract: Two austenitic stainless steels have been implanted at 150 keV with Mo at a fluence of 3.5x1015 ions/cm2. The effects of ion implantation in the chemical composition of the passive films was evaluated by x-ray photoelectron spectroscopy (XPS) and glancing angle x-ray diffraction (GAXRD) was used to determine the induced structural modifications. The results of the pitting corrosion studies carried out in neutral chloride medium as well as the morphology of the localized attack are discussed.

Abstract: The isothermal oxidation behavior of Zr58Nb3Cu16Ni13Al10 bulk metallic glass (BMG) under dry air in the glassy state and the supercooled liquid state (SLS) was studied by the thermogravimetric method. The oxidation rate and thickness growth speed in the SLS were both hugely higher than in the glassy state. The oxidation kinetics of BMG in both states for 1.5 hours was different, the parabolic law was followed in the glassy state at 300°C and 350°C, contrarily the linear law was followed in SLS at 400 °C. After the oxidation for 126 hours in SLS, the oxidation kinetics possessed two stages, the linear stage and the parabolic stage. The diffusion of the Cu2+ ion and CuZr intermetallic alloys were detected by GIXRD.

Abstract: Subsurface residual stresses of tungsten films induced by Chemical Mechanical Polishing (CMP) processes were investigated by the Grazing Incident X-Ray Diffraction (GIXRD). Basis of the GIXRD measurement was introduced and the experiments were conducted for residual stress of tungsten film measurements. Experimental procedures of the GIXRD measurements were presented. The obtained residual stresses value of tungsten films from 800 nm to 400 nm varies from 1086.1 ± 105.2 MPa to 1670.6±103.4 MPa prior and after CMP process.