ICMCTF2005 Session AP: Symposium A Poster Session

Thursday, May 5, 2005 5:00 PM in Room Town & Country

Thursday Afternoon

Time Period ThP Sessions | Topic A Sessions | Time Periods | Topics | ICMCTF2005 Schedule

AP-1 Corrosion Behavior of Cr(N,O)/CrN Double-Layered Coatings by Cathodic Arc Deposition
W.-Y. Ho (Mingdao University, Taiwan); C.-H. Hsu (Tatung University, R.O.C.); D.-H. Huang, Y.-P. Cheng, Y.-C. Lin (Tatung University, Taiwan)

CrN coatings deposited by PVD techniques exhibit excellent corrosion and wear properties, and have better oxidation resistance, as well as better adhesion to tool steel. Earlier work concluded that Cr(N,O) films deposited by cathodic arc deposition exhibit better mechanical properties when compared to CrN. However, it is expected that macroparticles accompanied with cathodic arc deposition result in defects of the films. Increasing amount of researches found that multilayers combined the properties of the constituent materials had led to improved properties when compared to the individual single layer films.

In this study, the Cr(N,O)/CrN double-layered coatings on tool steel was conducted using cathodic arc deposition process. CrN layer was first deposited on tool steel as an interlayer to ensure better adhesion. The following procedure was deposited with Cr(N,O) as a surface layer. The Cr(N,O) was designed with various composition by various O/N gas flow ratio during the process. The chemical composition, structure and morphology of coatings was analyzed by XRD, XPS and SEM, respectively. The corrosion behavior of Cr(N,O)/CrN double-layered coatings was investigated using polarization and immersion tests. Polarization properties of coatings were carried out under the condition of 3.5 wt% NaCl solution. In the immersion test, Cr(N,O)/CrN double-layered coatings were exposed under H2SO4, HCl, NaOH environment for 25, 50 and 50 hours, respectively. The results show that the corrosion resistance of Cr(N,O)/CrN coating is similar to diamond like carbon (DLC) films, but better than that of CrN single layer.

AP-3 Thermal Stability of Ta-Al Thin Film Resistor by Magnetron Sputtering
C.K. Chung, Y.L. Chang, T.C. Chen, P.J. Su (National Cheng Kung University, Taiwan)
The Ta-Al thin film resistor has been used as a heating element of the micro-droplet injector or thermal bubble inkjet printhead with several millions of thermal cycle operation between room temperature and about 350°C. Materials with higher thermal stability generally have longer lifetime of operation. In this paper, the thermal stability of Ta-Al alloy materials is investigated by the variation of phase composition and resistivity at annealing temperature of 450- 650°C. The composition, phase, and resistivity of Ta-Al films are characterized by grazing incident angle X-ray diffractometer (GIAXRD), Rutherford backscattering spectrometry (RBS), Auger electron spectroscopy (AES) depth profile and four-point probe instrument, respectively. Three kinds of Ta-Al films are sputtered by different Al powers of 1kW, 2kW and 4kW, while Ta power is fixed at 2.68kW. The corresponding average Ta/Al composition ratios of Ta-Al films are 2/1, 1/1 and 1/2, respectively. As the Al power increases, the microstructure and composition of Ta-Al alloy are changed. The resistivity of Ta-Al film is related to the Ta/Al composition ratio and annealing temperature. The Ta-Al film obtained at Al power of 2kW has pure microstructure in X-ray diffracted spectra than others Ta-Al film at Al power of 1 or 4 kW. This film is stable in the microstructure and resistivity at thermal annealing up to 550°C in the vacuum and air annealing. It is good for the thermal bubble inkjet application with thermal cycle at maximum temperature below 400°C.
AP-5 Evaluation of the Effect of Ni-P Coating on the Corrosion Resistance of the Aluminium 7075-T6 Alloy
L. Jimenez (Corrosion Studies Center, Venezuela); L. Gil (UNEXPO, Venezuela); M.H. Staia (Central University of Venezuela)
The aluminium alloy 7075-T6 is a structural alloy widely used for aeronautical applications due to its high relationship between mechanical resistance and weight. Depending upon the environmental conditions, many types of corrosion mechanisms such as intergranular, exfoliation, pitting, crevice, fretting, microbiologically influenced corrosion, stress corrosion cracking, and hydrogen embrittlement have been found to occur in aircraft structural aluminum alloys. Moreover, the synergistic effects of corrosion and the loading conditions have been found to initiate the corrosion fatigue failure process and the stress corrosion cracking failure process of aluminum alloy aircraft structural components. A significant advance in order to improve the behavior of this alloy is related to the application of the autocatalytic Ni-P coating, which could present an amorphous structure, conferring thus an excellent corrosion resistance coupled with both reduced erosive wear and high hardness. The purpose of this work was to investigate the effect of the application of a Ni-P coating on the corrosion resistance aluminum 7075-T6 alloy. Pitting corrosion resistance was evaluated by conducting cyclic potentiodynamic polarization curves in a 3.0% NaCl solution under the standard ASTM G61-86 The exfoliation corrosion resistance was evaluated according to the ASTM G-34-72 standard. Optical microscopy and scanning electron microscopy (SEM) techniques were employed for the coatings microstructural characterization before and after the corrosion test to identify the possible mechanisms of corrosion. The results obtained indicated that the application of the Ni-P coatings diminishes the susceptibility to the pitting and increases the exfoliation corrosion resistance of the aluminum 7075 T6 alloy.
AP-6 Correlation between Microstructural Characteristics and the Abrasion Wear Resistance of Sealed Thermal Sprayed Coatings
S. Liscano, L. Gil (UNEXPO, Venezuela); M.H. Staia (Central University of Venezuela)
Plasma sprayed aluminum oxide coatings (Al2O3) are mainly used as a wear-resistant coating in mechanical applications. Previous studies have shown that both the abrasion wear resistance and the corrosion resistance of these coatings can be significantly improved by applying a sealing treatment. It was reported that this improvement it is mainly due to the microstructural modifications which take place during the post treatment process. Therefore, this study was conducted in order to determine the influence of the microstructural characteristics on the wear resistance of these coatings when different sealing treatments were applied to AISI 1020 thermal sprayed specimens coated with alumina + 13% titania. Abrasion wear resistance of these coatings was evaluated employing the standard rubber wheel abrasion test and the ball-on-disc test. The coatings microstructure was characterized and their wear mechanisms were analyzed by using SEM. Porosity and microhardness values were also reported. It was shown that the abrasion wear resistance of both the phosphoric acid sealed coatings and the epoxy sealed coatings is significantly better than that of the unsealed coatings.
AP-7 The Influence of the Period Size on the Corrosion and the Wear Abrasion Resistance of TiN/Ti Multilayers
M. Flores (Universidad de Guadalajara, Mexico); S. Muhl, L. Huerta (IIM-UNAM, Mexico); E. Andrade (IF-UNAM, Mexico)
Metal-ceramic multilayers were deposited by reactive magnetron sputtering with the aim to simultaneously improve the corrosion and wear resistance of metallic substrates. In this paper we report the results of studies of the influence of the period size on the corrosion and the wear abrasion resistance of TiN/Ti multilayers deposited on H13 steel substrates. The Ti layers were deposited for between 4 - 0.5 minutes and TiN deposited for 10 - 1.5 min; the number of periods was from 1 to 60. The wear was studied using a commercial ball cratering system and the corrosion with potentiodinamyc polarizations in an electrolyte of NaCl 0.5M. It was found that reducing the period also decreased the grain size and that the wear resistance of multilayer was improved; however the results of the corrosion testing were somewhat mixed. The results obtained for the periodic multilayers are compared with those for both monolithic coatings and relatively thicker (5-10 microns) multilayers. XRD analysis was used to study the influence of the period size on the texture of multilayers. The composition of the films was determined by RBS and Auger depth analysis.
AP-8 Growth of Ti/TiN/DLC Multilayers using a Pulsed Vacuum Arc System
D. Devia (Universidad Nacional de Colombia Sede Manizales, Colombia)
Ti/TiN/DLC multilayers were deposited on stainless steel samples, by employing a PAPVD pulsed vacuum arc system. The Ti films were produced by using a target of Ti by using Argon as gas of work The TiN films were produced by using a target of Ti and Nitrogen as gas of work. These films were studied by means of X ray Diffraction (XRD) identifying the crystalline structure with orientations in planes (111), (200) and (220), present phases, crystallite size and micro-strain. Also their stoichiometry and composition were determined by analyzing the binding energy Ti2p doublet with X Photoelectron Spectroscopy (XPS). DLC (Diamond Like Carbon) films were grown on the TiN coating by using a target of HOPG (High Oriented Pyrolitic Graphite) and a mixture of Argon/Hydrogen as gas of work. These coatings were studied employing Fourier Transform Infrared Spectroscopy (FTIR) techniques in order to obtain the presence of sp3 y sp2 bonding and their relative concentration by the line-base method. These results were corroborated by studying the binding energy C1s line with XPS technique. Moreover, depth profiles were carried out in order to observe the behavior of the bilayer as a function of the thickness. Energy Disperse Spectroscopy (EDS) spectra were realized to identified the elements present in the bilayers. Other morphological properties of the coatings like roughness and grain size were analyzed by means of Scanning electron Microscopy (SEM) and Scanning Probe Microscopy (SPM).
AP-9 Comparison between Graded and Multilayer Coatings of Ti/TiN/TiCN Grown by Sputtering DC
E. Restrepo (Universidad Nacional de Colombia Sede Manizales, Colombia)
Ti/TiN/TiCN films were grown in multilayers, with abrupt interphases and in graded way, with diffuse interphases, on stainless steel samples with a previous plasma nitriding process, in order to improve the adherence and the mechanical behavior of the coatings as it has been reported. Both coatings were produced in a sputtering DC system, because it is important to have total control on the deposition rate and thickness. The films were grown by using a target of Ti, and filling the reaction chamber with different gases depending of the coatings to be produced, i.e. Ti is grown in argon atmosphere, TiN with a mixture of Ar/ N2 and TiCN with a mixture of Ar/N2/CH4. The graded coatings were produced changing gradually the concentration of gases, beginning with Ar, then increasing N2 and decreasing Ar and finally, decreasing N2 and increasing CH4. The films are characterizing in chemical composition by X photoelectron spectroscopy (XPS) identifying the stoichiometry. Depth profile of both, multilayer and graded coatings were realized, in order to observe the behavior of the interphases. Mechanical properties like nanohardness and friction coefficient were studied by using an scanning probe microscopy (SPM) technique. Morphology and thickness were determined by atomic force microscopy (AFM) and scanning electron microscopy (SEM).
AP-10 Heat Treatment of Co-Deposited Aluminium'SiliconCoating on Ferritic Steels by CVD=FBR Technology
F.J. Pérez, M.P. Hierro, J.A. Trilleros, M.C. Carpintero, F.J. Bolívar, L. Sánchez (Universidad Complutense de Madrid, Spain)

The co-deposition of Al-Si coatings on ferritic steels (P-91, P-92 and HCM-12A) were produced by Chemical Vapour Deposition in Fluidized Bed Reactors (CVD-FBR). The initial parameters of the processes were determined by means of thermochemical calculations using the Themo Calc Sofware. Metal sub-halide chemistry was used to produce the gas precursors for the deposition. The thermodynamic analysis of system consists of Al and Si powder as donator, HCl as activator, H2 as reducing agent and Ar as inert gas. The most important precursors for Al and Si in a range o temperature from 450°C up to 600°C were AlCl3, Al2Cl6, AlHCl2, AlCl, and Cl1H3Si, respectively. With this method Al-Si coatings 4 μm thick were obtained at low deposition temperatures and short deposition time.

The effect of diffusion heat treatment that was performed under argon flow a 700°C for 2 hours on coating was studied in order to allow the phase transformation from Fe2Al5 to another iron aluminides. The coating morphology, composition and mechanical properties were characterized using optical microscopy (OM), Scanning Electron Microscopy (SEM), Electron Probe Microanalysis, X-ray diffraction and the mechanical properties were measurement using Vickers microhardness tester. The heat treatment at 700°C brings about transport of different elements, which in turn give rise to thicker coatings and phase change of intermetallic compounds.

AP-12 Residual Stress and Crystallographic Texture in Thermally Grown Oxide (TGO) on FeCr Alloy
X.F. Zhao, X. Wang, P. Xiao (University of Manchester, United Kingdom)
The residual stresses in thermally grown oxide (TGO) layer formed on Fecralloy were measured using Cr3+ fluorescence spectroscopy. The spectroscopic R lines shifted as a function of the heat treatment temperature, but the stresses obtained from R1 line shift were different from that obtained from R2 line shift. This difference can be attributed to the non-hydrostatic nature of the stress field and the preferred orientation of alpha-alumina in the TGO. The piezo-spectroscopic measurement on the cross-section was systemically conducted with various laser excitation directions relative to TGO growth direction (along the thickness). The changes of fluorescence intensity and intensity ratio I(R2)/I(R1) with different directions indicate c-axis of the alpha-alumina in the TGO layer is preferentially orientated in parallel to TGO growth direction, which has been confirmed by subsequent XRD measurements. The changes in other spectroscopic parameters, such as peak width (FWHM), peak splitting (R2-R1), as a function of stress level were also presented and discussed.
AP-13 Electrochemical and Structural Characterization on PEM Fuel Cell Enhanced with Pt/Pt-Ru Multilayered Catalysts Prepared by Unbalanced Magnetron Sputtering Method
C.-L. Chang, T.-C. Chang, J.-Y. Jao, D.-Y. Wang (Mingdao University, Taiwan)
In the preparation of electrodes for proton exchange membrane fuel cell (PEMFC), the influence of the catalyst loading and layered structure on the electrochemical properties of Nafion 117 membrane was investigated. The deposition of Pt/Pt-Ru multilayer catalysts was prepared by unbalanced magnetron sputter method. The Nafion solution was impregnated using brushing method. The goal of this work is to reduce the catalyst loading and to increase the carbon monoxide tolerance by the advantage of unbalanced magnetron sputtering technology. The effects of loading and layer design of the Pt/Pt-Ru catalyst is discussed in light of porosimetry and I-V polarization curves. The microstructure of layered Pt/Pt-Ru catalyst was analyzed by scanning electron microscopy, energy dispersive X-ray, and X-ray diffraction.
AP-14 Characterization of Surface Characteristics and Interfacial Structure in Lithium Nickel Oxides
P.-Y. Liao, J.G. Duh (National Tsing Hua University, Taiwan); S.-R. Sheen (Academia Sinica, Taiwan)
Due to the lower cost and higher discharge capacity, LiNiO2 is the most attractive cathode material to replace LiCoO2 in lithium-ion batteries. Nevertheless, stoichiometric LiNiO2 is difficult to synthesize, and it is necessary to substitute Ni partially with other elements to stabilize the structure. In this work, the newly developed LiNi1-x-yCoyMnxO2 cathode materials with excellent electrochemical performance were successfully synthesized by the mixing hydroxide method. X-ray diffraction patterns showed that the samples exhibited a typical hexagonal α-NaFeO2 structure. The scanning electron microscopy (SEM) micrograph revealed that Mn doping had effects on both morphology and structural properties of the materials. To further investigate the effect of Mn content on the surface properties of LiNi0.75-xCo0.25MnxO2, the oxidation states of Ni, Co and Mn were evaluated. X-ray photoelectron spectroscopy (XPS) measurements revealed that predominant valence state of Ni ion in the near-surface region was +3 and the ratio of Ni+2/Ni+3 increased with the Mn doping concentration. Since the interface structure of the particles between the electrodes and electrolyte might change during the cycling test, the transmission electron microscopy (TEM) with combined techniques of imaging and diffraction was performed on LiNi1-x-yCoyMnxO2 before and after charge/discharge tests. It exhibited that the changes of unit cell dimension gave rise to cracks on the surface of the particles, which deteriorated the electrochemical performance of the cathode materials.
AP-15 Plasma Surface Modification of TiO2 Photocatalysts for Improvement of Catalytic Efficiency
C.K. Jung, I.S. Bae, Y.H. Song, J.-H. Boo (Sungkyunkwan University, South Korea)
We have deposited titanium dioxide (TiO2) thin films on glass and honeycom using a single molecular precursor such as titanium (IV) iso-propoxide (Ti[OCH(CH3) 2] 4, 97%) by sol-gel processing. In order to elevate photocatalytic activity of the as-grown TiO2 films, Argon and oxygen plasmas ignited by redio-frequency (RF) and microwave (MW) under both vacuum and atmosphere conditions were also used in the range of 50 ~ 200 W within 0.5 hr at room temperature. Photocatalytic activity was evaluated by the measurements of the contact angle, UV/vis. irradiation, and toluene removal test. TiO2 films were also investigated using SEM and XPS for detail analysis of relationship between film compositions. In this work, the effect of the plasma with photocatalyst (TiO2) on the improvement of hydrophilic properties has mainly been investigated. A superhydrophilic property and surface morphology change appeared in the light irradiation with O2 plasma treatment. Based on this work, we confirmed that the plasma treatment method was very reliable method for the synthesis of TiO2 thin films with high catalytic performance.
AP-16 Influence of Nitrogen on the Photocatalytic Properties of Titanium Dioxide Reactively Sputter-Deposited Coatings
E. Aubry, V. Demange, A. Billard (Ecole des Mines-Parc de Saurupt, France)

Titanium dioxide is a widely studied material due its numerous applications in optics, optoelectronics or photocatalysis, in relation with its favourable physical, chemical and optoelectronical properties associated with a high stability. Extensive efforts have been made by several authors for the development of titanium dioxide coatings that can efficiently use solar or indoor light [1, 2]. Numerous techniques are available to synthesise photocatalytic anatase thin films, such as sol-gel, chemical vapour deposition, pulsed laser deposition or physical vapour deposition.

In this paper, we present results of nitrogen doped titanium dioxide coatings deposited on glass slides by reactive magnetron sputtering of a titanium target in the presence of various reactive argon-oxygen-nitrogen mixtures. In a first part, we investigate the influence of the deposition pressure and of the annealing temperature in case of TiO2 coatings in relation with their morphology and their grain size, determined respectively by scanning and transmission electron microscopy. The second part is ascribed to the nitrogen substitution in the TiO2-xNx anatase structure as a function of the N2 to O2 ratio in the reactive atmosphere. Finally, photocatalytic measurements, performed by irradiating samples covered by orange-G, are discussed in relation with the films composition, microstructure and morphology.

[1] Y. Suda, H. Kawasaki, T. Ueda, T. Ohshima, Thin Solid Films 453-454 (2004), 162

[2] L. Shivalingappa, J. Sheng, T. Fukami, Vacuum 48 5 (1997), 413.

AP-17 Sputter Deposition of Pt Nanocluster and Thin Film on PEM Fuel Cell Electrodes
M. Alvisi (Enea Cr Brindisi, Italy); V. Contini (ENEA CR CASACCIA, Italy); G. Galtieri (ENEA CR BRINDISI, Italy); L. Giorgi, R. Giorgi, A. Pozio, E. Serra (ENEA CR CASACCIA, Italy); M.A. Signore (ENEA CR BRINDISI, Italy)

Sputter deposition has been investigated as a tool for manufacturing proton-exchange membrane fuel cell (PEMFC) elecrodes with improved performance and catalyst utilization vs. commercial and metal chemical electrode. Nanosize (diameter 2-5 nm) platinum cluster has been deposited on gas diffusion electrode (carbon paper + PTFE/C diffusive layer) and the activity for methanol oxidation resulted highly increased (about 30 times) compared to commercial catalyst, with loading of 0.006 mg/cm2.

We measured and studied the electrochemical performance also of nanosized films deposited on Nafion membrane and of the entire cell (membrane electrode assembly, MEA), prepared by bonding the catalysed electrodes to the catalysed proton exchange polymer membrane.

SEM-FEG, XRD and XPS measurements were carried out to understand the performaces and beahvior of the Pt electrocatalyst as both cathode and anode of a polymer electrolyte fuel cell.

AP-18 Structure-Electrical Properties of Lanthanum Manganite Coatings Obtained by Magnetron Sputtering of Two Targets in Argon-Oxygen Reactive Mixtures
E. Seminskaya (Laboratoire de Science et Génie des Surfaces, France); A. Billard (École des Mines Parc de Saurupt, France)

Lanthanum manganite of perovskite structure are potential candidates for numerous applications in energy generation [1] or environmental applications [2] due to their catalytic properties. Their use as thin films should constitute a useful way to improve devices functionality such as solid oxide fuel cells or air cleaning systems using the concept of electrochemical promotion of catalysis. In this paper, we investigate the deposition of La1-x√sub xMnO3 coatings by co-sputtering of La0.9√sub 0.1and Mn metallic targets on a rotating substrate-holder in the presence of reactive argon-oxygen mixtures. After a short description of the reactor equipped with a conventional optical emission spectroscopy (OES) system and an original optical transmittance interferometry (OTI) device developed at the laboratory, the structure of the as-deposited coatings is investigated by X-ray diffraction as a function of their composition, measured by electron probe micro analysis (EPMA), resulting from the power dissipated on each target. The structural evolution of the coatings, initially amorphous, is then presented as a function of the annealing temperature. Finally, electrical conductivity measurements performed by the four probe method are presented in relation with the coatings structure.

[1] M. Gaudon, C. Laberty-Robert, F. Ansart, P. Stevens, A. Rousset, Solid State sciences 4 (2002) 125.

[2]J.J. Spivey, Ind. Eng. Chem. Res., 26 (1987) 2165.

AP-19 Characterization of YSZ Thin Film for SOFCs by XPS.
E.B. Ramirez, L. Huerta, A. Huanosta, A. Ortiz, J.C. Alonso (Instituto de Investigaciones en Materiales, Mexico)
In order to make solid oxide fuel cells (SOFCs) with reduced operation temperature, the thickness of the electrolyte should be as thin as possible. Yttrium stabilized zirconia (YSZ) thin films deposited by different techniques are being considered as the best candidates to achieve this purpose. In general, it is found that the electrical properties of these films depends strongly on their composition and crystallographic structure, which in turn depends on the deposition method and conditions used for film deposition. In this work we present an X-ray photoelectron spectroscopy investigation of the composition of YSZ thin films deposited by ultrasonic spray pyrolisis using start solutions with different yttrium concentrations. All the XPS spectra exhibited dominant peaks of Zr, Y and O along with C 1s peak due to contamination coming from the precursors materials and/or solvent. The binding energies of the Zr 3d5/2 and Zr 3d3/2 peaks which were around 183.4 and 186.2 eV, respectively, indicates that zirconium is fully oxidized in its Zr4+ state. The position of the peaks in the original spectra appear shifted from its expected position due to surface charge up, which confirms the insulating character of the films. The Zr, Y, and O atomic concentration was determined by normalizing the integrated photoemission intensity using the relative sensitive factors (RSF) determined for each element from ZrO2 and Y2O3 standards. The chemical uniformity of the films along the substrate surface was checked by collecting the data in three different points. Depth composition profiles were also obtained and they revealed homogeneous concentrations of Zr and O, and a small gradient (increase) in the concentration of Y toward the substrate. YSZ films with yttrium concentrations varying from 3 to 22 percent were studied as part of a more general characterization by XRD and impedance spectroscopy measurements to know the correlation between composition, crystallographic structure and electrical properties.
AP-20 New Surface Modification Material for LiMn2O4 Cathode Material in Li-ion Battery
H.-W. Chan, J.G. Duh (National Tsing Hua University, Taiwan); S.-R. Sheen (Academia Sinica, Taiwan); S.Y. Tsai, C.R. Lee (Minghsin University of Science and Technology, Taiwan)
The LiMn2O4 cathode powders derived from co-precipitation method was calcined with various weight percent of the surface modified material to form fine powder of single spinel phase with different particle size, size distribution and morphology. The structure of both substrate and coating material were confirmed by X-ray diffractometry (XRD) along with the composition measured by the electron probe microanalyzer (EPMA). From the field emission scanning electron microscope (FE-SEM) image and Laser Scattering measurements, the average particle size of surface treatment cathode powder was in the range of 7-8 µm. The film thickness and phase of coating material were observed by transition electron microscope (TEM). Cyclic charge/discharge testing of the coin cells, fabricated by both coated and uncoated cathode material, provided that the fading rate of lithium manganese oxide cathode powder was reduced significantly through the employment of surface modification.
AP-21 Method of Resolution to Inhibit the Growth of Alumina in the Intermetallic NiAl FG 75 Alloy to Increase TBC Lifetime
K. Lackner, L. Lugscheider, K. Bobzin, M. Maes (Aachen University, Germany)
The thermal cycling behaviour of the developed Thermal Barrier Coating (TBC) systems (Monolayer, Bilayer) based on Lanthanzirconate and yttria stabilized zirconia (YSZ) is reported. In the last preceding investigations Lanthanzirconate with pyrochlor structure shows a promising performance for application as TBC. The TBCs are deposited on modified intermetallic NiAl FG 75 alloy substrates by the Electron Beam Physical Vapour Deposition (EB-PVD). The modifications of substrates differ in the Thermal Grown Oxide (TGO) growth conditions. Two methods of resolution have been persecuted to reduce the amount of aluminum in NiAl FG 75 for the first 50 µm in the surface border area. The influence of both methods on the TGO growth is examined. The phase structure of the modified NiAl FG 75 are analyzed by x-ray diffraction (XRD). The amount of aluminium and nickel is examined by energy-dispersive x-ray diffraction (EDX). The TGO growth during the thermal cyle test is examined by scanning electron microscopy (SEM). Cycling is stopped when a visible spallation of the coating occurs. By means of that procedure the thermal cycling behavior of the developed TBCs has been improved. The aim is the development of new material concepts for the next generation of EB-PVD-TBCs for the application in the gas turbine.

Keywords: Lanthanzirconate, TGO growth, EB-PVD-technique, thermal cycle test.

AP-22 Evaluation of Laser-Glazed Plasma-Sprayed Thermal Barrier Coatings Under High Temperature Exposure to Molten Salts
C. Batista, A. Portinha, R.M. Ribeiro, Vasco Teixeira (University of Minho, Portugal); C.R. Oliveira (IDIT - Institute for Development and Tecnological Inovation, Portugal)

Under a severe gas turbine environment it is expected from thermal barrier coatings (TBCs) to provide not only thermal insulation to the metallic components by preserving a low thermal conductivity but also to protect them from oxidation, hot corrosion and wear damage.

In this paper, a TBC system is investigated with regard to performance under high temperature corrosion exposure in molten salts. The investigated TBC system comprises an atmospheric plasma-sprayed ZrO2-8wt%Y2O3 top coat and a vacuum plasma-sprayed NiCoCrAlY bond coat deposited on a stainless steel substrate. The surface of the ceramic top coat has been previously laser-glazed by a high power continuous wave CO2 laser to generate an external dense layer.

The hot corrosion investigation was carried out by subjecting the specimens to an isothermal air furnace testing under Na2SO4 and/or V2O5 deposits in a temperature of approximately 1000°C for 1 hour cycles. The corrosion mechanisms were investigated from post-test image analysis using scanning electron microscopy (SEM) and from structural changes by X-ray diffraction (XRD). Energy dispersive X-ray analysis (EDX) was also used to map the elements deriving from the corrosive compounds along through-thickness. Bond coat corrosion and top coat destabilization mechanisms are discussed.

AP-23 Characterization of Aluminized Layer Formation on Ti-5Al-3Mo-1V Alloy Coated by Al Film During Annealing
S.E. Romankov, E. Ermakov (Institute of Physics & Technology, Kazakhstan)
Intermetallic compounds of the Ti-Al system and alloys based on such compounds have been considered extensively for high-temperature structural applications because they offer a combination of low density, good oxidation resistance, and useful mechanical properties at temperatures higher than those possible with more conventional titanium alloys. The available experimental data show that aluminide phases can be used as a protective coating for industrial titanium alloys. In order to develop the processing strategy for protective coating based on aluminide phases for titanium alloys it is necessary to understand the interdiffusion growth of aluminide phases and to study kinetics of structural formation. In present work we have studied the kinetics of structural formation of aluminized layers on the surface of industrial titanium alloy. The Ti-5Al-3Mo-1V alloy has been used as a substrate. The different phase composition and grain structure have been formed by quenching. The Al layer on the surface of substrate has been formed by the thermal deposition. During annealing on the surface Al3Ti, Al2Ti, TiAl, Ti3Al and a solid solution of Al in -Ti are formed successively. The kinetic of the structural formation is function of annealing temperature and exposure time. The kinetics of structural formation depends on the grain structure and phase composition of the initial substrates. During annealing quenched samples coated by aluminum film the decomposition of metastable phases of substrate takes place. This process influences strongly interdiffusion growth and the morphology of forming aluminize layers.
AP-24 Evaulation of SiN as a Diffusion Barrier for Gd-Si-Ge Films on Silicon
S.N. Sambandam, B. Bethala, S. Bhansali (University of South Florida); D.K. Sood (Royal Melbourne Institute of Technology, Australia)
A search for a suitable diffusion barrier layer for annealing Gd-Si-Ge films on silicon has been presented. Gd-Si-Ge alloy thin films are investigated for use in magnetic microcooling applications and are synthesized by RF sputtering on to Si(100) substrates. Films are further subjected to ex-situ high temperature annealing in the range of 600 to 1300°C in order to form required phases. Platinum and Silicon Nitride have been studied as diffusion barrier layers between Gd-Si-Ge and Si to avoid reaction during annealing. Films of Si/1000Å Pt/ 1000 Å GdSiGe and Si/3000 Å SiN/ 1000 Å GdSiGe have been synthesized and annealed in vacuum in the range of 600 to 1300°C. The structure and morphology of films were analyzed by X-ray diffraction (XRD), optical microscope and scanning electron microscopy (SEM). XRD analysis revealed absence of Pt reaction with the film at low temperature (600°C), however, at high temperatures (1300°C) severe reaction of Pt occurred with substrate. Pt was also observed to diffuse through the substrate to backside of the wafer. Silicon nitride was found to be a suitable diffusion barrier at high temperatures (1300°C) and no reaction with film was observed. The interface of silicon nitride and Gd-Si-Ge was probed by secondary ion mass spectrometry (SIMS) and was observed to have minimal reaction between them.
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