Constrained sintering of an air-plasma-sprayed thermal barrier coating

International Nuclear Information System (INIS)

Cocks, A.C.F.; Fleck, N.A.

2010-01-01

A micromechanical model is presented for the constrained sintering of an air-plasma-sprayed, thermal barrier coating upon a thick superalloy substrate. The coating comprises random splats with intervening penny-shaped cracks. The crack faces make contact at asperities, which progressively sinter in-service by interfacial diffusion, accommodated by bulk creep. Diffusion is driven by the reduction in interfacial energy at the developing contacts and by the local asperity contact stress. At elevated operating temperature, both sintering and creep strains accumulate within the plane of the coating. The sensitivities of sintering rate and microstructure evolution rate to the kinetic parameters and thermodynamic driving forces are explored. It is demonstrated that the sintering response is governed by three independent timescales, as dictated by the material and geometric properties of the coating. Finally, the role of substrate constraint is assessed by comparing the rate of constrained sintering with that for free sintering.

Hydrogen diffusion along grain boundaries in erbium oxide coatings

International Nuclear Information System (INIS)

Mao, Wei; Chikada, Takumi; Suzuki, Akihiro; Terai, Takayuki

2014-01-01

Diffusion of interstitial atomic hydrogen in erbium oxide (Er 2 O 3 ) was investigated using density functional theory (DFT) and molecular dynamics (MD) methods. Hydrogen diffusivity in bulk, on (0 0 1) surface, and along Σ13 (4–3–1)/[1 1 1] symmetric tilt grain boundaries (GBs) were evaluated in a temperature range of 673–1073 K, as well as hydrogen diffusion barriers. It was found that H diffusion shows the faster on (0 0 1) surface than along GBs and in bulk. Also, energy barrier of H diffusion in bulk estimated by DFT and MD methods is somewhat higher than that along GBs evaluated in the experiments. This suggests that H diffusion in Er 2 O 3 coatings depends on GBs rather than bulk. In addition, with a correction of GB density, the simulated diffusivity along GBs in MD simulations is in good agreement with the experimental data within one order of magnitude. The discrepancy of H diffusivity between the experiments and the simulations should be reduced by considering H concentration, H diffusion direction, deviations of the initial configuration, vacancy defects, etc

Vanadium diffusion coating on HT-9 cladding for mitigating the fuel cladding chemical interactions

Science.gov (United States)

Lo, Wei-Yang; Yang, Yong

2014-08-01

Fuel cladding chemical interaction (FCCI) has been identified as one of the crucial issues for developing Ferritic/Martensitic (F/M) stainless steel claddings for metallic fuels in a fast reactor. The anticipated elevated temperature and high neutron flux can significantly aggravate the FCCI, in terms of formation of inter-diffusion and lower melting point eutectic phases. To mitigate the FCCI, vanadium carbide coating as a diffusion barrier was deposited on the HT-9 substrate using a pack cementation diffusion coating (PCDC) method, and the processing temperature was optimized down to 730 °C. A solid metallurgical bonding between the coating layer and substrate was achieved, and the coating is free from through depth cracks. The microstructural characterizations using SEM and TEM show a nanostructured grain structure. EDS/WDS and XRD analysis confirm the phase of coating layer as V2C. Diffusion couple tests at 660 °C for 100 h demonstrate that V2C layer with a thickness of less than 5 μm can effectively eliminate the inter-diffusion between the lanthanide cerium and HT-9 steel.

Vanadium diffusion coating on HT-9 cladding for mitigating the fuel cladding chemical interactions

Energy Technology Data Exchange (ETDEWEB)

Lo, Wei-Yang; Yang, Yong, E-mail: yongyang@ufl.edu

2014-08-01

Fuel cladding chemical interaction (FCCI) has been identified as one of the crucial issues for developing Ferritic/Martensitic (F/M) stainless steel claddings for metallic fuels in a fast reactor. The anticipated elevated temperature and high neutron flux can significantly aggravate the FCCI, in terms of formation of inter-diffusion and lower melting point eutectic phases. To mitigate the FCCI, vanadium carbide coating as a diffusion barrier was deposited on the HT-9 substrate using a pack cementation diffusion coating (PCDC) method, and the processing temperature was optimized down to 730 °C. A solid metallurgical bonding between the coating layer and substrate was achieved, and the coating is free from through depth cracks. The microstructural characterizations using SEM and TEM show a nanostructured grain structure. EDS/WDS and XRD analysis confirm the phase of coating layer as V{sub 2}C. Diffusion couple tests at 660 °C for 100 h demonstrate that V{sub 2}C layer with a thickness of less than 5 μm can effectively eliminate the inter-diffusion between the lanthanide cerium and HT-9 steel.

Thermal Diffusivity Measurement for Thermal Spray Coating Attached to Substrate Using Laser Flash Method

Science.gov (United States)

Akoshima, Megumi; Tanaka, Takashi; Endo, Satoshi; Baba, Tetsuya; Harada, Yoshio; Kojima, Yoshitaka; Kawasaki, Akira; Ono, Fumio

2011-11-01

Ceramic-based thermal barrier coatings are used as heat and wear shields of gas turbine blades. There is a strong need to evaluate the thermal conductivity of coating for thermal design and use. The thermal conductivity of a bulk material is obtained as the product of thermal diffusivity, specific heat capacity, and density above room temperature in many cases. Thermal diffusivity and thermal conductivity are unique for a given material because they are sensitive to the structure of the material. Therefore, it is important to measure them in each sample. However it is difficult to measure the thermal diffusivity and thermal conductivity of coatings because coatings are attached to substrates. In order to evaluate the thermal diffusivity of a coating attached to the substrate, we have examined the laser flash method with the multilayer model on the basis of the response function method. We carried out laser flash measurements in layered samples composed of a CoNiCrAlY bond coating and a 8YSZ top coating by thermal spraying on a Ni-based superalloy substrate. It was found that the procedure using laser flash method with the multilayer model is useful for the thermal diffusivity evaluation of a coating attached to a substrate.

Methods to improve the PVD coatability of brass by using diffusion barriers

Science.gov (United States)

Langer, Bernd

Previous work involving PVD coatings on brass has used a combination of multilayers consisting of electroplated films like nickel or chromium and deposited decorative PVD coatings like TiN, TiAIN or ZrN systems. The disadvantages of these systems are the combination of wet electrochemistry and high tech vacuum processes. Furthermore the allergic reaction to nickel and the toxic nature of Cr(VI) must be considered.There is a need for intermediate layers to 'seal-off the brass in order to avoid the evaporation of zinc in vacuum using a diffusion barrier. Furthermore the intermediate layers are required to act as a corrosion barrier.This thesis reports on the development of PVD coatings on heat sensitive brass substrate materials utilising ABS technology with Al, CuAl8 and Nb targets as vapour sources.The brass pretreatment includes careful grinding, polishing and cleaning steps as well as steered arc metal ion etching using the above target materials. The coatings are produced at temperatures between 100 and 250°C in the unbalanced magnetron mode, including layers made from Al, Al-Nb, CuA18, CuAl8-Nb and Nb.Scratch adhesion and Rockwell indentation tests are found not to be directly applicable to the system of soft brass and ductile coating(s). Therefore a new classification for both scratch and indentation tests was defined. The best adhesion was shown by the CuA18 coatings on brass. Corrosion tests showed good results for the Al coatings and poor results for the pure Nb coatings directly applied on brass. The best corrosion result was obtained with a CuAl8-Nb layer system. This layer system also offers very good barrier behaviour concerning Zn diffusion.Other investigations like Glow Discharge Optical Emission Spectroscopy (GDOES), Scanning Electron Microscopy (SEM) imaging, Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) were undertaken to characterise the new coating systems for brass.

SOUND FIELD DIFFUSIVITY AT THE TOP SURFACE OF SCHROEDER DIFFUSER BARRIERS

OpenAIRE

M. R. Monazzam

2006-01-01

Reactive barriers are one of the most promising and novel environmental noise barriers. In this case using Schroeder diffusers (e.g. quadratic residue diffusers) on the top surface of the T-shape barrier was shown to significantly improve the performance of absorbent T-shape barriers. The reasons behind the high performance of diffuser barriers are considered in this investigation. A question about the diffusivity behavior of Schroeder diffusers when they are utilized on the top of barrier wa...

SOUND FIELD DIFFUSIVITY AT THE TOP SURFACE OF SCHROEDER DIFFUSER BARRIERS

Directory of Open Access Journals (Sweden)

M. R. Monazzam

2006-10-01

Full Text Available Reactive barriers are one of the most promising and novel environmental noise barriers. In this case using Schroeder diffusers (e.g. quadratic residue diffusers on the top surface of the T-shape barrier was shown to significantly improve the performance of absorbent T-shape barriers. The reasons behind the high performance of diffuser barriers are considered in this investigation. A question about the diffusivity behavior of Schroeder diffusers when they are utilized on the top of barrier was raised. Diffusion coefficients of a diffuser in different conditions at some receiver locations were predicted by using a 2D boundary element method. It was found that the diffusion coefficient of diffuser at the top of barrier is so small that the diffusivity of the structure is almost the same as rigid T-shape barrier. To find the barrier’s cap behavior, the total field above the top surface of profile barriers was also predicted. It was found that the lowest total energy is at the receiver side of the cap very close to the top surface,which could demonstrate the effect of top surface on absorbing the energy as wave transfers from source edge toward the receiver side of the cap. In this case the amount of minimum total energy depends on the frequency and the configuration of the top surface. A comparison between the reductions of total field at the source side of the cap with the improvements of barrier’s performance was also done. It was shown that the amount of decrease in total field compared to that of an absorbent barrier “Ref” is directly associated to the amount of improvement in the insertion loss made by the diffuser barrier compared to the “Ref” barrier in the wide area on the ground at the shadow zone. Finally it was concluded that the diffuser on the top of barrier does not act as a diffuser and a kind of similarity between the contribution of diffuser and absorbent material on the top of T-profile barrier is seen.

High quality aluminide and thermal barrier coatings deposition for new and service exposed parts by CVD techniques

Energy Technology Data Exchange (ETDEWEB)

Pedraza, F.; Tuohy, C.; Whelan, L.; Kennedy, A.D. [SIFCO Turbine Components, Carrigtwohill, Cork (Ireland)

2004-07-01

In this work, the performance of CVD aluminide coatings is compared to that of coatings deposited by the classical pack cementation technique using standard SIFCO procedures. The CVD coatings always seem to behave better upon exposure to isothermal and cyclic oxidation conditions. This is explained by a longer term stability of CVD coatings, with higher Al amounts in the diffusion zone and less refractory element precipitation in the additive layer. The qualities of Pt/Al coatings by out-of-pack and CVD are also compared as a previous step for further thermal barrier coating deposition. As an example, YSZ thermal barrier coatings are deposited by MO-CVD on Pt/Al CVD bond coats rendering adherent and thick coatings around the surface of turbine blades. This process under development does not require complex manipulation of the component to be coated. (orig.)

Surface and interface analysis of PVD Al-O-N and {gamma}-Al{sub 2}O{sub 3} diffusion barriers

Energy Technology Data Exchange (ETDEWEB)

Cremer, R.; Witthaut, M.; Reichert, K.; Neuschuetz, D. [Technische Hochschule Aachen (Germany). Lehrstuhl fuer Metallurgie der Kernbrennstoffe und Theoretische Huettenkunde

1999-10-01

The suitability of PVD films of {gamma}-Al{sub 2}O{sub 3} and of ternary Al-O-N as diffusion barriers between a nickel based superalloy CMSX-4 and NiCoCrAlY for a possible application in gas turbines was investigated. Therefore, an Al{sub 2}O{sub 3} film and, alternatively, an Al-O-N film were deposited on CMSX-4 at 100 C substrate temperature by means of reactive magnetron sputtering ion plating (MSIP). After characterization of composition and structure of the films by X-ray photoelectron spectroscopy (XPS) and grazing incidence X-ray diffraction (XRD), a NiCoCrAlY coating was deposited onto the diffusion barriers and, for comparison, directly onto CMSX-4 by MSIP as well. The composites were annealed for 4 h at 1100 C under inert atmosphere. Wavelength dispersive X-ray (WDX) element mappings and line-scans of the cross-sectional cut served to evaluate the suitability of the films as diffusion barriers. After detachment of the coatings from the substrate, the phase stabilities of the two metastable phases {gamma}-Al{sub 2}O{sub 3} and Al-O-N were determined by means of grazing incidence XRD. Without a diffusion barrier, enhanced interdiffusion was observed. Analyses of the composite with the {gamma}-Al{sub 2}O{sub 3} interlayer revealed diffusion of Ti and Ta from the substrate into the NiCoCrAlY coating. No interdiffusion of Ni, Ti, Ta, and Cr could be detected in case of the ternary Al-O-N film. Whereas the ternary Al-O-N film remained in the as-deposited X-ray amorphous structure after annealing, a phase change from the {gamma} to the {alpha} modification could be observed in case of the Al{sub 2}O{sub 3} film, presumably responsible for its lower efficiency as a diffusion barrier. (orig.)

Performance of Nb protective diffusion coating on U-Mo/Al dispersion fuel

Energy Technology Data Exchange (ETDEWEB)

Kim, Ji-Hyeon; Sohn, Dong-Seong [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of); Kim, Sunghwan; Nam, Ji Min; Lee, Kyu Hong; Park, Jong Man [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2014-10-15

To achieve this aim, it is necessary to increase the volume fraction of fuel particles inside the meat. However, the technical limit is reached at approximately 55 vol.% of fuel particles in the aluminum matrix. As a solution, an uranium compound with an higher uranium density than existing U3Si2 fuel has to be selected. Also alloying the uranium must stabilize γ-phase of uranium at room temperature because adequate properties of the γ -phase of uranium showed a good irradiation behavior in the past. Hence, U-Mo alloys were selected as the best candidates. The formation of interaction phase is a critical problem to apply U-Mo alloys to the high performance research reactor. Different means have been proposed to reduce the interaction between U-Mo fuel and Al matrix. There are three means. : 1. Addition of a diffusion limiting element to the matrix 2. Insertion of a diffusion barrier at the interface between the U-Mo and the Al 3. Alloying of the U-Mo with a third element Here we present the effect of Nb coating as diffusion barrier on formation of interaction layers between UMo powders and Al matrix. We present the effect of Nb coating on formation of interaction layers between U-Mo powders and Al matrix. Centrifugally atomized U-7 wt.% Mo powders were used, and Nb was coated on the surface of U-7 wt.% Mo by sputtering. Subsequently, the Nb-coated U-7 wt.% Mo powders were mixed with pure Al powders, and were made into compacts. The compacts were annealed at 550 .deg. C for 1, 3, 5 hours, respectively, and the result showed that the Nb coating on U-7 wt.% Mo effectively suppressed the growth of interaction layers between U-7 wt.% Mo and Al matrix.

Experimental evaluation of optimization method for developing ultraviolet barrier coatings

Science.gov (United States)

Gonome, Hiroki; Okajima, Junnosuke; Komiya, Atsuki; Maruyama, Shigenao

2014-01-01

Ultraviolet (UV) barrier coatings can be used to protect many industrial products from UV attack. This study introduces a method of optimizing UV barrier coatings using pigment particles. The radiative properties of the pigment particles were evaluated theoretically, and the optimum particle size was decided from the absorption efficiency and the back-scattering efficiency. UV barrier coatings were prepared with zinc oxide (ZnO) and titanium dioxide (TiO2). The transmittance of the UV barrier coating was calculated theoretically. The radiative transfer in the UV barrier coating was modeled using the radiation element method by ray emission model (REM2). In order to validate the calculated results, the transmittances of these coatings were measured by a spectrophotometer. A UV barrier coating with a low UV transmittance and high VIS transmittance could be achieved. The calculated transmittance showed a similar spectral tendency with the measured one. The use of appropriate particles with optimum size, coating thickness and volume fraction will result in effective UV barrier coatings. UV barrier coatings can be achieved by the application of optical engineering.

Atomic layer deposition on polymer based flexible packaging materials: Growth characteristics and diffusion barrier properties

International Nuclear Information System (INIS)

Kaeaeriaeinen, Tommi O.; Maydannik, Philipp; Cameron, David C.; Lahtinen, Kimmo; Johansson, Petri; Kuusipalo, Jurkka

2011-01-01

One of the most promising areas for the industrial application of atomic layer deposition (ALD) is for gas barrier layers on polymers. In this work, a packaging material system with improved diffusion barrier properties has been developed and studied by applying ALD on flexible polymer based packaging materials. Nanometer scale metal oxide films have been applied to polymer-coated papers and their diffusion barrier properties have been studied by means of water vapor and oxygen transmission rates. The materials for the study were constructed in two stages: the paper was firstly extrusion coated with polymer film, which was then followed by the ALD deposition of oxide layer. The polymers used as extrusion coatings were polypropylene, low and high density polyethylene, polylactide and polyethylene terephthalate. Water vapor transmission rates (WVTRs) were measured according to method SCAN-P 22:68 and oxygen transmission rates (O 2 TRs) according to a standard ASTM D 3985. According to the results a 10 nm oxide layer already decreased the oxygen transmission by a factor of 10 compared to uncoated material. WVTR with 40 nm ALD layer was better than the level currently required for most common dry flexible packaging applications. When the oxide layer thickness was increased to 100 nm and above, the measured WVTRs were limited by the measurement set up. Using an ALD layer allowed the polymer thickness on flexible packaging materials to be reduced. Once the ALD layer was 40 nm thick, WVTRs and O 2 TRs were no longer dependent on polymer layer thickness. Thus, nanometer scale ALD oxide layers have shown their feasibility as high quality diffusion barriers on flexible packaging materials.

Atomic layer deposition on polymer based flexible packaging materials: Growth characteristics and diffusion barrier properties

Energy Technology Data Exchange (ETDEWEB)

Kaeaeriaeinen, Tommi O., E-mail: tommi.kaariainen@lut.f [ASTRaL, Lappeenranta University of Technology, Prikaatinkatu 3 E, 50100 Mikkeli (Finland); Maydannik, Philipp, E-mail: philipp.maydannik@lut.f [ASTRaL, Lappeenranta University of Technology, Prikaatinkatu 3 E, 50100 Mikkeli (Finland); Cameron, David C., E-mail: david.cameron@lut.f [ASTRaL, Lappeenranta University of Technology, Prikaatinkatu 3 E, 50100 Mikkeli (Finland); Lahtinen, Kimmo, E-mail: kimmo.lahtinen@tut.f [Tampere University of Technology, Paper Converting and Packaging Technology, P.O. Box 541, 33101 Tampere (Finland); Johansson, Petri, E-mail: petri.johansson@tut.f [Tampere University of Technology, Paper Converting and Packaging Technology, P.O. Box 541, 33101 Tampere (Finland); Kuusipalo, Jurkka, E-mail: jurkka.kuusipalo@tut.f [Tampere University of Technology, Paper Converting and Packaging Technology, P.O. Box 541, 33101 Tampere (Finland)

2011-03-01

One of the most promising areas for the industrial application of atomic layer deposition (ALD) is for gas barrier layers on polymers. In this work, a packaging material system with improved diffusion barrier properties has been developed and studied by applying ALD on flexible polymer based packaging materials. Nanometer scale metal oxide films have been applied to polymer-coated papers and their diffusion barrier properties have been studied by means of water vapor and oxygen transmission rates. The materials for the study were constructed in two stages: the paper was firstly extrusion coated with polymer film, which was then followed by the ALD deposition of oxide layer. The polymers used as extrusion coatings were polypropylene, low and high density polyethylene, polylactide and polyethylene terephthalate. Water vapor transmission rates (WVTRs) were measured according to method SCAN-P 22:68 and oxygen transmission rates (O{sub 2}TRs) according to a standard ASTM D 3985. According to the results a 10 nm oxide layer already decreased the oxygen transmission by a factor of 10 compared to uncoated material. WVTR with 40 nm ALD layer was better than the level currently required for most common dry flexible packaging applications. When the oxide layer thickness was increased to 100 nm and above, the measured WVTRs were limited by the measurement set up. Using an ALD layer allowed the polymer thickness on flexible packaging materials to be reduced. Once the ALD layer was 40 nm thick, WVTRs and O{sub 2}TRs were no longer dependent on polymer layer thickness. Thus, nanometer scale ALD oxide layers have shown their feasibility as high quality diffusion barriers on flexible packaging materials.

Metallographic techniques for evaluation of thermal barrier coatings

Science.gov (United States)

Brindley, William J.; Leonhardt, Todd A.

1990-01-01

The performance of ceramic thermal barrier coatings is strongly dependent on the amount and shape of the porosity in the coating. Current metallographic techniques do not provide polished surfaces that are adequate for a repeatable interpretation of the coating structures. A technique recently developed at NASA-Lewis for preparation of thermal barrier coating sections combines epoxy impregnation, careful sectioning and polishing, and interference layering to provide previously unobtainable information on processing-induced porosity. In fact, increased contrast and less ambiguous structure developed by the method make automatic quantitative metallography a viable option for characterizing thermal barrier coating structures.

Phase characterization of Re-based diffusion barrier layer on Nb substrate

International Nuclear Information System (INIS)

Sugiarti, Eni; Wang, Youngmin; Hashimoto, Naoyuki; Ohnuki, Somei; Narita, Toshio

2011-01-01

An electron microscopy phase characterization was carried out for a Re-based diffusion barrier layer, which was deposited on the Nb substrate used as an ultra high temperature material. The coating process produced three layers; an outer Cr(Re) layer, an intermediate Cr-Nb-Re layer, and an inner Nb(Re) layer. The Cr-Nb-Re layer is considered to act as a diffusion barrier layer between the substrate and the outer Cr(Re) reservoir layer. The Cr(Re) and Nb(Re) layers are in single phase with a similar bcc structures, but they are different in structure from the intermediate layer, which is composed of a dual phase of Re 63 Cr 20 Nb 17 with a cubic structure and Nb 42 Re 33 Cr 25 with a hexagonal structure determined by transmission electron microscopy (TEM) in this study. (author)

Diffusion barrier performances of thin Mo, Mo-N and Mo/Mo-N films between Cu and Si

International Nuclear Information System (INIS)

Song Shuangxi; Liu Yuzhang; Mao Dali; Ling Huiqin; Li Ming

2005-01-01

In this work, we have studied the diffusion barrier performances of Mo, Mo-N and Mo/Mo-N metallization layers deposited by sputtering Mo in Ar/N 2 atmospheres, respectively. Samples were subsequently annealed at different temperatures ranging from 400 to 800 deg C in vacuum condition. The film properties and their suitability as diffusion barriers and protective coatings in silicon devices were characterized using four-point probe measurement, X-ray diffractometry, scanning electron microscopy, Auger electron spectroscopy and transmission electron microscopy analyses. Experimental results revealed that the Mo (20 nm)/Mo-N (30 nm) layer was able to prevent the diffusion reaction between Cu and Si substrate after being annealed at 600 deg C for 30 min. The adhesion between layers and the content of N atoms are the key parameters to improve the properties of Mo-based barrier materials. The Mo layer interposed between Cu and Mo-N diluted the high nitrogen concentration of the barrier and so enhanced the barrier performances

Roll-to-roll vacuum deposition of barrier coatings

CERN Document Server

Bishop, Charles A

2015-01-01

It is intended that the book will be a practical guide to provide any reader with the basic information to help them understand what is necessary in order to produce a good barrier coated web or to improve the quality of any existing barrier product. After providing an introduction, where the terminology is outlined and some of the science is given (keeping the mathematics to a minimum), including barrier testing methods, the vacuum deposition process will be described. In theory a thin layer of metal or glass-like material should be enough to convert any polymer film into a perfect barrier material. The reality is that all barrier coatings have their performance limited by the defects in the coating. This book looks at the whole process from the source materials through to the post deposition handling of the coated material. This holistic view of the vacuum coating process provides a description of the common sources of defects and includes the possible methods of limiting the defects. This enables readers...

Evaluation of Erosion Resistance of Advanced Turbine Thermal Barrier Coatings

Science.gov (United States)

Zhu, Dongming; Kuczmarski, Maria A.; Miller, Robert A.; Cuy, Michael D.

2007-01-01

The erosion resistant turbine thermal barrier coating system is critical to aircraft engine performance and durability. By demonstrating advanced turbine material testing capabilities, we will be able to facilitate the critical turbine coating and subcomponent development and help establish advanced erosion-resistant turbine airfoil thermal barrier coatings design tools. The objective of this work is to determine erosion resistance of advanced thermal barrier coating systems under simulated engine erosion and/or thermal gradient environments, validating advanced turbine airfoil thermal barrier coating systems based on nano-tetragonal phase toughening design approaches.

Corrosion resistant coatings suitable for elevated temperature application

Science.gov (United States)

Chan, Kwai S [San Antonio, TX; Cheruvu, Narayana Sastry [San Antonio, TX; Liang, Wuwei [Austin, TX

2012-07-31

The present invention relates to corrosion resistance coatings suitable for elevated temperature applications, which employ compositions of iron (Fe), chromium (Cr), nickel (Ni) and/or aluminum (Al). The compositions may be configured to regulate the diffusion of metals between a coating and a substrate, which may then influence coating performance, via the formation of an inter-diffusion barrier layer. The inter-diffusion barrier layer may comprise a face-centered cubic phase.

Erosion and foreign object damage of thermal barrier coatings

International Nuclear Information System (INIS)

Nicholls, J.R.; Jaslier, Y.; Rickerby, D.S.

1997-01-01

Thermal barrier coating technology is used in the hot sections of gas turbines to extend component life. To maximise these benefits, the thermal barrier coating has to remain intact throughout the life of the turbine. High velocity ballistic damage can lead to total thermal barrier removal, while erosion may lead to progressive loss of thickness during operation. This paper particularly addresses the erosion resistance and resistance to foreign object damage of thermal barrier coatings. It was found that EB-PVD thermal barriers are significantly more erosion resistant when impacted with alumina or silica, than the equivalent plasma spray coating, both at room temperature and 910 C. Examination of tested hardware, reveals that cracking occurs within the near surface region of the columns for EB-PVD ceramic and that erosion occurs by removal of these small blocks of material. In stark contrast, removal of material for plasma sprayed ceramic occurs through poorly bonded splat boundaries. Large particle impact results in severe damage to the EB-PVD thermal barrier, with cracks penetrating through the ceramic coating to the ceramic/bond coat interface. Material removal, per particle impact, increases with increased particle size. (orig.)

An overview of the oxidation performance of silicide diffusion coatings for vanadium-based alloys for generation IV reactors

International Nuclear Information System (INIS)

Chaia, N.; Mathieu, S.; Cozzika, T.; Rouillard, F.; Desgranges, C.; Courouau, J.L.; Petitjean, C.; David, N.; Vilasi, M.

2013-01-01

Highlights: ► Diffusion barrier to oxygen were manufactured by pack cementation diffusion process. ► The use of CrSi 2 + Si and TiSi 2 + Si as masteralloys increased the quality of the coating. ► Thermodynamic stability (coatings/vanadium) was obtained at the operating temperature. ► MSi 2 coatings developed low growing oxide scale in air and at low oxygen pressure. ► Coatings presented high compatibility with liquid sodium ( 2 ) for 360 h. - Abstract: This study focuses on the development of new protective coatings for the vanadium-based alloy V-4Cr-4Ti. Halide-activated pack-cementation (HAPC) technique was used to develop V x Si y multilayered diffusive silicide coatings. The outer layers (coatings) were formed of VSi 2 doped with 27 at.% Cr or TiSi 2 . These compounds exhibited a very low oxidation rate at 650 °C, both in air and at a low oxygen pressure (He, 5 ppm O 2 ). The coatings formed mainly of MSi 2 were found to be insensitive to pesting and largely unreactive to liquid sodium ( 2 ) during a 360 h compatibility test at 550 °C.

Material Barriers to Diffusive Mixing

Science.gov (United States)

Haller, George; Karrasch, Daniel

2017-11-01

Transport barriers, as zero-flux surfaces, are ill-defined in purely advective mixing in which the flux of any passive scalar is zero through all material surfaces. For this reason, Lagrangian Coherent Structures (LCSs) have been argued to play the role of mixing barriers as most repelling, attracting or shearing material lines. These three kinematic concepts, however, can also be defined in different ways, both within rigorous mathematical treatments and within the realm of heuristic diagnostics. This has lead to a an ever-growing number of different LCS methods, each generally identifying different objects as transport barriers. In this talk, we examine which of these methods have actual relevance for diffusive transport barriers. The latter barriers are arguably the practically relevant inhibitors in the mixing of physically relevant tracers, such as temperature, salinity, vorticity or potential vorticity. We demonstrate the role of the most effective diffusion barriers in analytical examples and observational data. Supported in part by the DFG Priority Program on Turbulent Superstructures.

Property Evaluation and Damage Evolution of Environmental Barrier Coatings and Environmental Barrier Coated SiC/SiC Ceramic Matrix Composite Sub-Elements

Science.gov (United States)

Zhu, Dongming; Halbig, Michael; Jaskowiak, Martha; Hurst, Janet; Bhatt, Ram; Fox, Dennis S.

2014-01-01

This paper describes recent development of environmental barrier coatings on SiC/SiC ceramic matrix composites. The creep and fatigue behavior at aggressive long-term high temperature conditions have been evaluated and highlighted. Thermal conductivity and high thermal gradient cyclic durability of environmental barrier coatings have been evaluated. The damage accumulation and complex stress-strain behavior environmental barrier coatings on SiCSiC ceramic matrix composite turbine airfoil subelements during the thermal cyclic and fatigue testing of have been also reported.

Application of diffusion barriers to high modulus fibers

Science.gov (United States)

Veltri, R. D.; Douglas, F. C.; Paradis, E. L.; Galasso, F. S.

1977-01-01

Barrier layers were coated onto high-modulus fibers, and nickel and titanium layers were overcoated as simulated matrix materials. The objective was to coat the high-strength fibers with unreactive selected materials without degrading the fibers. The fibers were tungsten, niobium, and single-crystal sapphire, while the materials used as barrier coating layers were Al2O3, Y2O3, TiC, ZrC, WC with 14% Co, and HfO2. An ion-plating technique was used to coat the fibers. The fibers were subjected to high-temperature heat treatments to evaluate the effectiveness of the barrier layer in preventing fiber-metal interactions. Results indicate that Al2O3, Y2O3, and HfO2 can be used as barrier layers to minimize the nickel-tungsten interaction. Further investigation, including thermal cycling tests at 1090 C, revealed that HfO2 is probably the best of the three.

Creation of leak-proof silicon carbide diffusion barriers by means of pulsed laser deposition

Energy Technology Data Exchange (ETDEWEB)

Reinecke, A.-M.; Lustfeld, M.; Lippmann, W., E-mail: wolfgang.lippmann@tu-dresden.de; Hurtado, A.

2014-05-01

TRISO (tristructural isotropic) coated fuel particles are a crucial element of the HTR safety concept. While TRISO coated particles have been proven as a very efficient barrier for a large range of fission products in HTR experimental reactors, some particular fission products could still diffuse at a considerable rate. Most importantly, radioactive silver {sup 110m}Ag was found to be released from coated particles. In future HTRs with active components like a gas turbine in the primary circuit, such silver contamination may severely limit maintainability of these parts with the result of reduced life-time performance. So far, experimental analyses on silver diffusion through silicon carbide have led to contradictory results. In this work, an alternative method was used to generate silicon carbide layers as a basis for analysis of silver diffusion. With pulsed laser deposition (PLD), it is possible to generate coatings of different materials and various kinds of compounds. In particular, this technology allows the generation of layers very well defined with respect to their composition, purity and density. The microstructure can precisely be manipulated through various parameters. Based on different silicon carbide coatings with well-defined properties, we are going to investigate the silver diffusion process. Our goal is to derive the properties of an ideal silicon carbide coating preventing silver diffusion entirely. In this paper we present the major aspects of our work creating crystalline SiC layers as well as silver and CsI layers both on plane and spherical substrates. Analyses with X-ray diffraction, X-ray spectrometry and secondary ion mass spectrometry show that complex multilayer systems comprising a graphite substrate, a crystalline SiC layer and an intermediate silver layer were successfully created. Major challenges to approach in the future are the handling of high-level intrinsic stresses forming in the layer structure as well as the high vapour

Electrolyte diffusion in compacted montmorillonite engineered barriers

International Nuclear Information System (INIS)

Jahnke, F.M.; Radke, C.J.

1985-09-01

The bentonite-based engineered barrier or packing is a proposed component of several designs conceived to dispose of high-level nuclear waste in geologic repositories. Once radionuclides escape the waste package, they must first diffuse through the highly impermeable clay-rich barrier before they reach the host repository. To determine the effectiveness of the packing as a sorption barrier in the transient release period and as a mass-transfer barrier in the steady release period over the geologic time scales involved in nuclear waste disposal, a fundamental understanding of the diffusion of electrolytes in compacted clays is required. We present, and compare with laboratory data, a model quantifying the diffusion rates of cationic cesium and uncharged tritium in compacted montmorillonite clay. Neutral tritium characterizes the geometry (i.e., tortuosity) of the particulate gel. After accounting for cation exchange, we find that surface diffusion is the dominant mechanism of cation transport, with an approximate surface diffusion coefficient of 2 x 10 -6 cm 2 /s for cesium. This value increases slightly with increasing background ionic strength. The implications of this work for the packing as a migration barrier are twofold. During the transient release period, K/sub d/ values are of little importance in retarding ion migration. This is because sorption also gives rise to a surface diffusion path, and it is surface diffusion which controls the diffusion rate of highly sorbing cations in compacted montmorillonite. During the steady release period, the presence of surface diffusion leads to a flux through the packing which is greatly enhanced. In either case, if surface diffusion is neglected, the appropriate diffusion coefficient of ions in compacted packing will be in considerable error relative to current design recommendations. 11 refs., 4 figs., 1 tab

Application of polycrystalline diffusion barriers

International Nuclear Information System (INIS)

Tsymbal, V.A.; Kolupaev, I.N.

2010-01-01

Degradation of contacts of the electronic equipment at the raised temperatures is connected with active diffusion redistribution of components contact - metalized systems (CMS) and phase production on interphase borders. One of systems diffusion barriers (DB) are polycrystalline silicide a film, in particular silicides of the titan. Reception disilicide the titan (TiSi 2 ) which on the parameters is demanded for conditions of microelectronics from known silicides of system Ti-Si, is possible as a result of direct reaction of a film of the titan and a substrate of silicon, and at sedimentation of layer Ti-Si demanded stoichiometric structure. Simultaneously there is specific problem polycrystalline diffusion a barrier (PDB): the polycrystalline provides structural balance and metastability film disilicide, but leaves in it borders of grains - easy local ways of diffusion. In clause the analysis diffusion permeability polycrystalline and polyphase DB is made and recommendations for practical methods of increase of blocking properties PDB are made.

Experimental study of radon and thoron diffusion through barriers

Energy Technology Data Exchange (ETDEWEB)

Durcik, M; Havlik, F [Inst. of Preventive and Clinical Medicine, 83301 Bratislava (Slovakia)

1996-12-31

The measurement results of diffusion parameters for radon (radon-222) and thoron (radon-220) through barriers, experimental equipment and theoretical background of diffusion are presented in this paper. The diffusion barriers are used for measuring radon and thoron by passive detectors in order to test the reduction techniques in houses. Six samples (filter paper, rubber, polyethylene, glass laminate, polypropylene) were studied for radon diffusion. The thickness barriers were from 0.012 mm to 2 mm, the diffusion area was 16 cm{sup 2} and the volume V{sub 2} was 30 dm{sup 3}. The diffusion constants D were obtained using given expressions and the data from measurements. The procedures used in experiments are useful for study of diffusion ability of radon and thoron in barriers and determination diffusion parameters from short term measurements. (J.K.). 2 figs., 1 tab., 3 refs.

Experimental study of radon and thoron diffusion through barriers

International Nuclear Information System (INIS)

Durcik, M.; Havlik, F.

1995-01-01

The measurement results of diffusion parameters for radon (radon-222) and thoron (radon-220) through barriers, experimental equipment and theoretical background of diffusion are presented in this paper. The diffusion barriers are used for measuring radon and thoron by passive detectors in order to test the reduction techniques in houses. Six samples (filter paper, rubber, polyethylene, glass laminate, polypropylene) were studied for radon diffusion. The thickness barriers were from 0.012 mm to 2 mm, the diffusion area was 16 cm 2 and the volume V 2 was 30 dm 3 . The diffusion constants D were obtained using given expressions and the data from measurements. The procedures used in experiments are useful for study of diffusion ability of radon and thoron in barriers and determination diffusion parameters from short term measurements. (J.K.). 2 figs., 1 tab., 3 refs

Thermal barrier coatings application in diesel engines

Science.gov (United States)

Fairbanks, J. W.

1995-01-01

Commercial use of thermal barrier coatings in diesel engines began in the mid 70's by Dr. Ingard Kvernes at the Central Institute for Industrial Research in Oslo, Norway. Dr. Kvernes attributed attack on diesel engine valves and piston crowns encountered in marine diesel engines in Norwegian ships as hot-corrosion attributed to a reduced quality of residual fuel. His solution was to coat these components to reduce metal temperature below the threshold of aggressive hot-corrosion and also provide protection. Roy Kamo introduced thermal barrier coatings in his 'Adiabatic Diesel Engine' in the late 70's. Kamo's concept was to eliminate the engine block water cooling system and reduce heat losses. Roy reported significant performance improvements in his thermally insulated engine at the SAE Congress in 1982. Kamo's work stimulates major programs with insulated engines, particularly in Europe. Most of the major diesel engine manufacturers conducted some level of test with insulated combustion chamber components. They initially ran into increased fuel consumption. The German engine consortium had Prof. Woschni of the Technical Institute in Munich. Woschni conducted testing with pistons with air gaps to provide the insulation effects. Woschni indicated the hot walls of the insulated engine created a major increase in heat transfer he refers to as 'convection vive.' Woschni's work was a major factor in the abrupt curtailment of insulated diesel engine work in continental Europe. Ricardo in the UK suggested that combustion should be reoptimized for the hot-wall effects of the insulated combustion chamber and showed under a narrow range of conditions fuel economy could be improved. The Department of Energy has supported thermal barrier coating development for diesel engine applications. In the Clean Diesel - 50 Percent Efficient (CD-50) engine for the year 2000, thermal barrier coatings will be used on piston crowns and possibly other components. The primary purpose of the

Improved Metallography Of Thermal-Barrier Coatings

Science.gov (United States)

Brindley, William J.; Leonhardt, Todd A.

1991-01-01

New technique for preparation of metallographic samples makes interpretation of images of pores and microcracks more reliable. Involves use of vacuum epoxy infiltration and interference-film coating to reduce uncertainty. Developed for inspection of plasma-sprayed ceramic thermal-barrier coatings on metals but applicable to other porous, translucent materials, including many important ceramics.

Modeling of Thermal Barrier Coatings

Science.gov (United States)

Ferguson, B. L.; Petrus, G. J.; Krauss, T. M.

1992-01-01

The project examined the effectiveness of studying the creep behavior of thermal barrier coating system through the use of a general purpose, large strain finite element program, NIKE2D. Constitutive models implemented in this code were applied to simulate thermal-elastic and creep behavior. Four separate ceramic-bond coat interface geometries were examined in combination with a variety of constitutive models and material properties. The reason for focusing attention on the ceramic-bond coat interface is that prior studies have shown that cracking occurs in the ceramic near interface features which act as stress concentration points. The model conditions examined include: (1) two bond coat coefficient of thermal expansion curves; (2) the creep coefficient and creep exponent of the bond coat for steady state creep; (3) the interface geometry; and (4) the material model employed to represent the bond coat, ceramic, and superalloy base.

Thermophysical and Thermomechanical Properties of Thermal Barrier Coating Systems

Science.gov (United States)

Zhu, Dongming; Miller, Robert A.

2000-01-01

Thermal barrier coatings have been developed for advanced gas turbine and diesel engine applications to improve engine reliability and fuel efficiency. However, the issue of coating durability under high temperature cyclic conditions is still of major concern. The coating failure is closely related to thermal stresses and oxidation in the coating systems. Coating shrinkage cracking resulting from ceramic sintering and creep at high temperatures can further accelerate the coating failure process. The purpose of this paper is to address critical issues such as ceramic sintering and creep, thermal fatigue and their relevance to coating life prediction. Novel test approaches have been established to obtain critical thermophysical and thermomechanical properties of the coating systems under near-realistic temperature and stress gradients encountered in advanced engine systems. Emphasis is placed on the dynamic changes of the coating thermal conductivity and elastic modulus, fatigue and creep interactions, and resulting failure mechanisms during the simulated engine tests. Detailed experimental and modeling results describing processes occurring in the thermal barrier coating systems provide a framework for developing strategies to manage ceramic coating architecture, microstructure and properties.

High speed PVD thermal barrier coatings

Energy Technology Data Exchange (ETDEWEB)

Beele, W. [Sulzer Metco Coatings BV (Netherlands); Eschendorff, G. [Sulzer Metco Coatings BV (Netherlands); Eldim BV (Netherlands)

2006-07-15

The high speed PVD process (HS-PVD) combines gas phase coating synthesis with high deposition rates. The process has been demonstrated for high purity YSZ deposited as a chemically bonded top thermal barrier with columnar structure of EB-PVD features. The process can manufacture EB-PVD like coatings that match in regards to their TGO-formation and columnar structure. Coatings with a columnar structure formed by individual columns of 1/4 of the diameter of a classical EB-PVD type TBC have been deposited. These coatings have the potential to prove a significant reduction in thermal conductivity and in erosion performance. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

High speed PVD thermal barrier coatings

International Nuclear Information System (INIS)

Beele, W.; Eschendorff, G.

2006-01-01

The high speed PVD process (HS-PVD) combines gas phase coating synthesis with high deposition rates. The process has been demonstrated for high purity YSZ deposited as a chemically bonded top thermal barrier with columnar structure of EB-PVD features. The process can manufacture EB-PVD like coatings that match in regards to their TGO-formation and columnar structure. Coatings with a columnar structure formed by individual columns of 1/4 of the diameter of a classical EB-PVD type TBC have been deposited. These coatings have the potential to prove a significant reduction in thermal conductivity and in erosion performance. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

Identifying barriers in the diffusion of renewable energy sources

International Nuclear Information System (INIS)

Eleftheriadis, Iordanis M.; Anagnostopoulou, Evgenia G.

2015-01-01

Rapid diffusion of renewable energy sources (RES) in the electricity power sector is crucial if the EU wants to fulfill its 2050 CO 2 reduction commitments. For this reason, identifying and alleviating all barriers that hinder the development of RES is necessary to the successful deployment of these technologies. This paper discusses the main barriers in the diffusion of wind and photovoltaic (PV) solar power in the Greek electricity sector by drawing on the literature of technological innovation systems and system functions. Furthermore, we provide an explanation of the different diffusion rates between the two technologies. Inadequate financial resources, low grid capacity, delays in the issuance of building permits, opposition from local communities to the construction of wind farms and the lack of a stable institutional framework are among the most important barriers that inhibit the diffusion of the wind and PV solar power. The nature of the barriers identified in this study calls for policy intervention. - Highlights: • Firms in the Greek wind and solar power sectors assess RES barriers. • Lack of financial resources is the most important RES barrier. • Lack of a stable institutional framework negatively affects RES deployment. • The support of the public sector is crucial to the diffusion of RES. •Wind power faces strong legitimization barriers

Kinetic Monte Carlo Simulation of Oxygen and Cation Diffusion in Yttria-Stabilized Zirconia

Science.gov (United States)

Good, Brian

2011-01-01

Yttria-stabilized zirconia (YSZ) is of interest to the aerospace community, notably for its application as a thermal barrier coating for turbine engine components. In such an application, diffusion of both oxygen ions and cations is of concern. Oxygen diffusion can lead to deterioration of a coated part, and often necessitates an environmental barrier coating. Cation diffusion in YSZ is much slower than oxygen diffusion. However, such diffusion is a mechanism by which creep takes place, potentially affecting the mechanical integrity and phase stability of the coating. In other applications, the high oxygen diffusivity of YSZ is useful, and makes the material of interest for use as a solid-state electrolyte in fuel cells. The kinetic Monte Carlo (kMC) method offers a number of advantages compared with the more widely known molecular dynamics simulation method. In particular, kMC is much more efficient for the study of processes, such as diffusion, that involve infrequent events. We describe the results of kinetic Monte Carlo computer simulations of oxygen and cation diffusion in YSZ. Using diffusive energy barriers from ab initio calculations and from the literature, we present results on the temperature dependence of oxygen and cation diffusivity, and on the dependence of the diffusivities on yttria concentration and oxygen sublattice vacancy concentration. We also present results of the effect on diffusivity of oxygen vacancies in the vicinity of the barrier cations that determine the oxygen diffusion energy barriers.

Permeation Barrier Coatings for the Helical Heat Exchanger

International Nuclear Information System (INIS)

Korinko, P.S.

1999-01-01

A permeation barrier coating was specified for the Helical Heat Exchanger (HHE) to minimize contamination through emissions and/or permeation into the nitrogen system for ALARA reasons. Due to the geometry of the HHE, a special coating practice was needed since the conventional method of high temperature pack aluminization was intractable. A survey of many coating companies was undertaken; their coating capabilities and technologies were assessed and compared to WSRC needs. The processes and limitations to coating the HHE are described. Slurry coating appears to be the most technically sound approach for coating the HHE

Corrosion-Mitigating, Bondable, Fluorinated Barrier Coating for Anodized Magnesium

Science.gov (United States)

2016-05-01

ARL-TR-7669 ● MAY 2016 US Army Research Laboratory Corrosion -Mitigating, Bondable, Fluorinated Barrier Coating for Anodized...ARL-TR-7669 ● MAY 2016 US Army Research Laboratory Corrosion -Mitigating, Bondable, Fluorinated Barrier Coating for Anodized...TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) May 2016 2. REPORT TYPE Final 3. DATES COVERED (From - To) January–December 2015 4. TITLE

Surface coatings as xenon diffusion barriers on plastic scintillators : Improving Nuclear-Test-Ban Treaty verification

OpenAIRE

Bläckberg, Lisa

2011-01-01

This thesis investigates the ability of transparent surface coatings to reduce xenon diffusion into plastic scintillators. The motivation for the work is improved radioxenon monitoring equipment, used with in the framework of the verification regime of the Comprehensive Nuclear-Test-Ban Treaty. A large part of the equipment used in this context incorporates plastic scintillators which are in direct contact with the radioactive gas to be detected. One problem with such setup is that radioxenon...

Design of barrier coatings on kink-resistant peripheral nerve conduits

Directory of Open Access Journals (Sweden)

Basak Acan Clements

2016-02-01

Full Text Available Here, we report on the design of braided peripheral nerve conduits with barrier coatings. Braiding of extruded polymer fibers generates nerve conduits with excellent mechanical properties, high flexibility, and significant kink-resistance. However, braiding also results in variable levels of porosity in the conduit wall, which can lead to the infiltration of fibrous tissue into the interior of the conduit. This problem can be controlled by the application of secondary barrier coatings. Using a critical size defect in a rat sciatic nerve model, the importance of controlling the porosity of the nerve conduit walls was explored. Braided conduits without barrier coatings allowed cellular infiltration that limited nerve recovery. Several types of secondary barrier coatings were tested in animal studies, including (1 electrospinning a layer of polymer fibers onto the surface of the conduit and (2 coating the conduit with a cross-linked hyaluronic acid-based hydrogel. Sixteen weeks after implantation, hyaluronic acid-coated conduits had higher axonal density, displayed higher muscle weight, and better electrophysiological signal recovery than uncoated conduits or conduits having an electrospun layer of polymer fibers. This study indicates that braiding is a promising method of fabrication to improve the mechanical properties of peripheral nerve conduits and demonstrates the need to control the porosity of the conduit wall to optimize functional nerve recovery.

Aspects of fatigue life in thermal barrier coatings

Energy Technology Data Exchange (ETDEWEB)

Brodin, H.

2001-08-01

Thermal barrier coatings (TBC) are applied on hot components in airborne and land based gas turbines when higher turbine inlet temperature, meaning better thermal efficiency, is desired. The TBC is mainly applied to protect underlying material from high temperatures, but also serves as a protection from the aggressive corrosive environment. Plasma sprayed coatings are often duplex TBC's with an outer ceramic top coat (TC) made from partially stabilised zirconia - ZrO{sub 2} + 6-8% Y{sub 2}O{sub 3}. Below the top coat there is a metallic bond coat (BC). The BC is normally a MCrAlX coating (M=Ni, Co, Fe... and X=Y, Hf, Si ... ). In gas turbine components exposed to elevated temperatures nickel-based superalloys are commonly adopted as load carrying components. In the investigations performed here a commercial wrought Ni-base alloy Haynes 230 has been used as substrate for the TBC. As BC a NiCoCrAlY serves as a reference material and in all cases 7% Yttria PS zirconia has been used. Phase development and failure mechanisms in APS TBC during service-like conditions, have been evaluated in the present study. This is done by combinations of thermal cycling and low cycle fatigue tests. The aim is to achieve better knowledge regarding how, when and why thermal barrier coatings fail. As a final outcome of the project a model capable of predicting fatigue life of a given component will help engineers and designers of land based gas turbines for power generation to better optimise TBC's. In the investigations it is seen that TBC life is strongly influenced by oxidation of the BC and interdiffusion between BC and the substrate. The bond coat is known to oxidise with time at high temperature. The initial oxide found during testing is alumina. With increased time at high temperature Al is depleted from the bond coat due to inter-diffusion and oxidation. Oxides others than alumina start to form when the Al content is reduced below a critical limit. It is here believed

Effect of Suspension Plasma-Sprayed YSZ Columnar Microstructure and Bond Coat Surface Preparation on Thermal Barrier Coating Properties

Science.gov (United States)

Bernard, Benjamin; Quet, Aurélie; Bianchi, Luc; Schick, Vincent; Joulia, Aurélien; Malié, André; Rémy, Benjamin

2017-08-01

Suspension plasma spraying (SPS) is identified as promising for the enhancement of thermal barrier coating (TBC) systems used in gas turbines. Particularly, the emerging columnar microstructure enabled by the SPS process is likely to bring about an interesting TBC lifetime. At the same time, the SPS process opens the way to a decrease in thermal conductivity, one of the main issues for the next generation of gas turbines, compared to the state-of-the-art deposition technique, so-called electron beam physical vapor deposition (EB-PVD). In this paper, yttria-stabilized zirconia (YSZ) coatings presenting columnar structures, performed using both SPS and EB-PVD processes, were studied. Depending on the columnar microstructure readily adaptable in the SPS process, low thermal conductivities can be obtained. At 1100 °C, a decrease from 1.3 W m-1 K-1 for EB-PVD YSZ coatings to about 0.7 W m-1 K-1 for SPS coatings was shown. The higher content of porosity in the case of SPS coatings increases the thermal resistance through the thickness and decreases thermal conductivity. The lifetime of SPS YSZ coatings was studied by isothermal cyclic tests, showing equivalent or even higher performances compared to EB-PVD ones. Tests were performed using classical bond coats used for EB-PVD TBC coatings. Thermal cyclic fatigue performance of the best SPS coating reached 1000 cycles to failure on AM1 substrates with a β-(Ni,Pt)Al bond coat. Tests were also performed on AM1 substrates with a Pt-diffused γ-Ni/γ'-Ni3Al bond coat for which more than 2000 cycles to failure were observed for columnar SPS YSZ coatings. The high thermal compliance offered by both the columnar structure and the porosity allowed the reaching of a high lifetime, promising for a TBC application.

Active bio-based food-packaging: Diffusion and release of active substances through and from cellulose nanofiber coating toward food-packaging design.

Science.gov (United States)

Lavoine, Nathalie; Guillard, Valérie; Desloges, Isabelle; Gontard, Nathalie; Bras, Julien

2016-09-20

Cellulose nanofibers (CNFs) were recently investigated for the elaboration of new functional food-packaging materials. Their nanoporous network was especially of interest for controlling the release of active species. Qualitative release studies were conducted, but quantification of the diffusion phenomenon observed when the active species are released from and through CNF coating has not yet been studied. Therefore, this work aims to model CNF-coated paper substrates as controlled release system for food-packaging using release data obtained for two model molecules, namely caffeine and chlorhexidine digluconate. The applied mathematical model - derived from Fickian diffusion - was validated for caffeine only. When the active species chemically interacts with the release device, another model is required as a non-predominantly diffusion-controlled release was observed. From caffeine modeling data, a theoretical active food-packaging material was designed. The use of CNFs as barrier coating was proved to be the ideal material configuration that best meets specifications. Copyright © 2016. Published by Elsevier Ltd.

Ion-plasma diffusion aluminide coatings for gas turbine blades (structure and properties)

International Nuclear Information System (INIS)

Muboyadzhyan, S.A.; Budinovskij, S.A.; Terekhova, V.V.

2003-01-01

A consideration is given to the ion-plasma method of heart resisting alloy diffusion coating with alloyed aluminides offering some advantages over routine techniques. Specific features of ion-plasma diffusion coatings production at the surface of heart resisting alloys using one- and multistage techniques are studied. The process of formation of coatings (Al-Si-Y, Al-Si-Ni-B, Al-Si-Cr-Y) along with coating effects on long-term heat resistance of nickel base alloys (ZhS6U, VZhL12U, ZhS26VNK) is investigated. The advantages of the new method of diffusion aluminide coatings are reported [ru

Thermal barrier coatings: Coating methods, performance, and heat engine applications. (Latest citations from the EI Compendex*plus database). Published Search

Energy Technology Data Exchange (ETDEWEB)

NONE

1997-02-01

The bibliography contains citations concerning conference proceedings on coating methods, performance evaluations, and applications of thermal barrier coatings as protective coatings for heat engine components against high temperature corrosions and chemical erosions. The developments of thermal barrier coating techniques for high performance and reliable gas turbines, diesel engines, jet engines, and internal combustion engines are presented. Topics include plasma sprayed coating methods, yttria stabilized zirconia coatings, coating life models, coating failure and durability, thermal shock and cycling, and acoustic emission analysis of coatings. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

Thermal barrier coatings: Coating methods, performance, and heat engine applications. (Latest citations from the EI Compendex*plus database). Published Search

Energy Technology Data Exchange (ETDEWEB)

NONE

1995-11-01

The bibliography contains citations concerning conference proceedings on coating methods, performance evaluations, and applications of thermal barrier coatings as protective coatings for heat engine components against high temperature corrosions and chemical erosions. The developments of thermal barrier coating techniques for high performance and reliable gas turbines, diesel engines, jet engines, and internal combustion engines are presented. Topics include plasma sprayed coating methods, yttria stabilized zirconia coatings, coating life models, coating failure and durability, thermal shock and cycling, and acoustic emission analysis of coatings. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

Comparison of different models for the determination of the absorption and scattering coefficients of thermal barrier coatings

International Nuclear Information System (INIS)

Wang, Li; Eldridge, Jeffrey I.; Guo, S.M.

2014-01-01

The thermal radiative properties of thermal barrier coatings (TBCs) are becoming more important as the inlet temperatures of advanced gas-turbine engines are continuously being pushed higher in order to improve efficiency. To determine the absorption and scattering coefficients of TBCs, four-flux, two-flux and Kubelka–Munk models were introduced and used to characterize the thermal radiative properties of plasma-sprayed yttria-stabilized zirconia (YSZ) coatings. The results show that the absorption coefficient of YSZ is extremely low for wavelengths 200 μm suggests that when the coating thickness is larger than around twice the average scattering distance, the collimated flux can be simply treated as a diffuse flux inside the coating, and thus the two-flux model can be used to determine the absorption and scattering coefficients as a simplification of the four-flux model

Beeswax–chitosan emulsion coated paper with enhanced water vapor barrier efficiency

International Nuclear Information System (INIS)

Zhang, Weiwei; Xiao, Huining; Qian, Liying

2014-01-01

Graphical abstract: - Highlights: • The water vapor barrier efficiency of paper was enhanced via green-based emulsion coating. • Extremely high lipid content in the emulsion coating layer was firstly utilized to reduce WVTR in emulsion-based film. • A controlled WVTR of beeswax–chitosan emulsion coating could be obtained by dying at specific temperature. - Abstract: For lipid–hydrocolloid emulsion based film, the increase of lipid amount would improve its water vapor barrier property, but also reduce the mechanical strength of the film in the meantime thus leading to a compromised lipid content in the film. However, when the emulsion is coated on paper surface, more lipid could be used for emulsion preparation to enhance the moisture resistance without considering the weakened strength of the film induced by lipid, because the mechanical properties of emulsion coated paper is mainly governed by the strength of base paper instead of the coating layer. In this study, beeswax–chitosan emulsion was first prepared and then coated on paper surface to improve paper's water vapor barrier and water resistance properties. The range and variance analysis of orthogonal test design showed that the order of priorities of the factors accordingly was beeswax solid content, drying temperature and chitosan concentration. The effect of drying temperature on water vapor transmission rate (WVTR) and water contact angle of coated paper was further investigated using 1.2 wt% chitosan and 96% beeswax solid content in the coating layer. The results indicated that water vapor barrier property was in accordance with the density of the coating layer. Atomic force microscope (AFM) was also used to characterize the surface morphology and explain the hydrophobicity of beeswax–chitosan coated paper. It was found that surface beeswax particles melted to wrinkle at high drying temperatures, while roughness values maintained at micro-scale over the temperature range investigated

Application of aluminum diffusion coatings to mitigate the KCl-induced high-temperature corrosion

DEFF Research Database (Denmark)

Kiamehr, Saeed; Lomholt, T. N.; Dahl, Kristian Vinter

2017-01-01

Pack cementation was used to produce Fe1−xAl and Fe2Al5 diffusion coatings on ferritic-martensitic steel P91 and a Ni2Al3 diffusion coating on pure nickel. The performance of diffusion coatings against high-temperature corrosion induced by potassium chloride (KCl) was evaluated by exposing...

Transport phenomena in sharply contrasting media with a diffusion barrier

International Nuclear Information System (INIS)

Dvoretskaya, O A; Kondratenko, P S

2011-01-01

Using the advection–diffusion equation, we analytically study contaminant transport in a sharply contrasting medium with a diffusion barrier due to localization of a contaminant source in a low-permeability medium. Anomalous diffusion behavior and a crossover between different transport regimes are observed. The diffusion barrier results in exponential attenuation of the source power, retardation of the contaminant plume growth and modification of the concentration distribution at large distances. (paper)

Thermal barrier coatings issues in advanced land-based gas turbines

Science.gov (United States)

Parks, W. P.; Lee, W. Y.; Wright, I. G.

1995-01-01

The Department of Energy's Advanced Turbine System (ATS) program is aimed at forecasting the development of a new generation of land-based gas turbine systems with overall efficiencies significantly beyond those of current state-of-the-art machines, as well as greatly increased times between inspection and refurbishment, improved environmental impact, and decreased cost. The proposed duty cycle of ATS turbines will require the use of different criteria in the design of the materials for the critical hot gas path components. In particular, thermal barrier coatings will be an essential feature of the hot gas path components in these machines. While such coatings are routinely used in high-performance aircraft engines and are becoming established in land-based turbines, the requirements of the ATS turbine application are sufficiently different that significant improvements in thermal barrier coating technology will be necessary. In particular, it appears that thermal barrier coatings will have to function on all airfoil sections of the first stage vanes and blades to provide the significant temperature reduction required. In contrast, such coatings applied to the blades and vances of advanced aircraft engines are intended primarily to reduce air cooling requirements and extend component lifetime; failure of those coatings can be tolerated without jeopardizing mechanical or corrosion performance. A major difference is that in ATS turbines these components will be totally reliant on thermal barrier coatings which will, therefore, need to be highly reliable even over the leading edges of first stage blades. Obviously, the ATS program provides a very challenging opportunity for TBC's, and involves some significant opportunities to extend this technology.

Coatings for fast breeder reactor components

International Nuclear Information System (INIS)

Johnson, R.N.

1984-04-01

Several types of metallurgical coatings are used in the unique environments of the fast breeder reactor. Most of the coatings have been developed for tribological applications, but some also serve as corrosion barriers, diffusion barriers, or radionuclide traps. The materials that have consistently given the best performance as tribological coatings in the breeder reactor environments have been coatings based on chromium carbide, nickel aluminide, or Tribaloy 700 (a nickel-base hard-facing alloy). Other coatings that have been qualified for limited applications include chromium plating for low temperature galling protection and nickel plating for radionuclide trapping

Thermal barrier coatings - Technology for diesel engines

International Nuclear Information System (INIS)

Harris, D.H.; Lutz, J.

1988-01-01

Thermal Barrier Coatings (TBC) are a development of the aerospace industry primarily aimed at hot gas flow paths in turbine engines. TBC consists of zirconia ceramic coatings applied over (M)CrAlY. These coatings can provide three benefits: (1) a reduction of metal surface operating temperatures, (2) a deterrent to hot gas corrosion, and (3) improved thermal efficiencies. TBC brings these same benefits to reciprocal diesel engines but coating longevity must be demonstrated. Diesels require thicker deposits and have challenging geometries for the arc-plasma spray (APS) deposition process. Different approaches to plasma spraying TBC are required for diesels, especially where peripheral edge effects play a major role. Bondcoats and ceramic top coats are modified to provide extended life as determined by burner rig tests, using ferrous and aluminum substrates

Thermal Conductivity of Ceramic Thermal Barrier and Environmental Barrier Coating Materials

Science.gov (United States)

Zhu, Dong-Ming; Bansal, Narottam P.; Lee, Kang N.; Miller, Robert A.

2001-01-01

Thermal barrier and environmental barrier coatings (TBC's and EBC's) have been developed to protect metallic and Si-based ceramic components in gas turbine engines from high temperature attack. Zirconia-yttria based oxides and (Ba,Sr)Al2Si2O8(BSAS)/mullite based silicates have been used as the coating materials. In this study, thermal conductivity values of zirconia-yttria- and BSAS/mullite-based coating materials were determined at high temperatures using a steady-state laser heat flux technique. During the laser conductivity test, the specimen surface was heated by delivering uniformly distributed heat flux from a high power laser. One-dimensional steady-state heating was achieved by using thin disk specimen configuration (25.4 mm diam and 2 to 4 mm thickness) and the appropriate backside air-cooling. The temperature gradient across the specimen thickness was carefully measured by two surface and backside pyrometers. The thermal conductivity values were thus determined as a function of temperature based on the 1-D heat transfer equation. The radiation heat loss and laser absorption corrections of the materials were considered in the conductivity measurements. The effects of specimen porosity and sintering on measured conductivity values were also evaluated.

Influence of creep and cyclic oxidation in thermal barrier coatings

Energy Technology Data Exchange (ETDEWEB)

Seiler, Philipp; Baeker, Martin; Roesler, Joachim [Technische Univ. Braunschweig (Germany). Inst. fuer Werkstoffe

2012-01-15

The lifetime of thermal barrier coating systems is limited by cracks close to the interfaces, causing delamination. To study the failure mechanisms, a simplified model system is analysed which consists of a bond-coat bulk material, a thermally grown oxide, and an yttria-stabilised zirconia topcoat. The stresses in the model system are calculated using a finite element model which covers the simulation of full thermal cycles, creep in all layers, and the anisotropic oxidation during dwelling. Creep in the oxide and the thermal barrier coating is varied with the use of different creep parameter sets. The influence of creep in the bondcoat is analysed by using two different bond-coat materials: fast creeping Fecralloy and slow creeping oxide dispersion strengthened MA956. It is shown that creep in the bondcoat influences the lifetime of the coatings. Furthermore, a fast creeping thermally grown oxide benefits the lifetime of the coating system. (orig.)

Estimates for diffusion barriers and atomic potentials in MGO

International Nuclear Information System (INIS)

Skala, L.; Kenkre, V.M.

1991-01-01

In this paper, as part of a program of investigation of microwave sintering, self-consistent CNDO/2 calculations are presented for diffusion barriers and potentials for the motion of interstitial atoms and vacancies in MgO. Clusters of 30 atoms are used in the calculations. Activation energies, diffusion barriers, shape of the potentials and electron densities are obtained

Analyses on the U-Mo/Al Chemical Interaction and the Effects of Diffusion Barrier Coatings

Energy Technology Data Exchange (ETDEWEB)

Ryu, Ho Jin; Kim, Woo Jeong; Cho, Woo Hyung; Jeong, Yong Jin; Lee, Yoon Sang; Park, Jong Man; Kim, Chang Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2012-05-15

While many HEU-fueled research reactors have been converted by adopting LEU U{sub 3}Si{sub 2} fuel in harmony with the Reduced Enrichment for Research and Test Reactors (RERTR) program, some high performance research reactors still need the development of advanced fuels with higher uranium densities. Currently, gamma-phase U-Mo alloys are considered promising candidates to be used as high uranium density fuel for the high performance reactors. For the production of UMo alloy powder, the centrifugal atomization technology developed by KAERI has been considered the most promising way because of high yield production and excellent powder quality when compared with other possible methods such as grinding, machining or hydriding-dehydriding. However, severe pore formation associated with an extensive interaction between the U-Mo and Al matrix, although the irradiation performance of U-Mo itself showed most stable, delay the fuel qualification of UMo fuel for high performance research reactors. Because the reaction products, i.e. uranium aluminides (UAlx), is less dense than the mixed reactants, the volume of the fuel meat increases after formation of interaction layer(IL). In addition to the impact on the swelling performance, the reaction layers between the U-Mo and Al matrix induces a degradation of the thermal conductivities of the U-Mo/Al dispersion fuels. The chemical interaction between the U-Mo and Al matrix are analyzed in this study to find remedies to reduce the growth of the interaction layers during irradiation. In addition, various coating technologies for the formation of diffusion barriers on U-Mo particles are proposed as a result of the analyses

Development and Life Prediction of Erosion Resistant Turbine Low Conductivity Thermal Barrier Coatings

Science.gov (United States)

Zhu, Dongming; Miller, Robert A.; Kuczmarski, Maria A.

2010-01-01

Future rotorcraft propulsion systems are required to operate under highly-loaded conditions and in harsh sand erosion environments, thereby imposing significant material design and durability issues. The incorporation of advanced thermal barrier coatings (TBC) in high pressure turbine systems enables engine designs with higher inlet temperatures, thus improving the engine efficiency, power density and reliability. The impact and erosion resistance of turbine thermal barrier coating systems are crucial to the turbine coating technology application, because a robust turbine blade TBC system is a prerequisite for fully utilizing the potential coating technology benefit in the rotorcraft propulsion. This paper describes the turbine blade TBC development in addressing the coating impact and erosion resistance. Advanced thermal barrier coating systems with improved performance have also been validated in laboratory simulated engine erosion and/or thermal gradient environments. A preliminary life prediction modeling approach to emphasize the turbine blade coating erosion is also presented.

Effect of Layer-Graded Bond Coats on Edge Stress Concentration and Oxidation Behavior of Thermal Barrier Coatings

Science.gov (United States)

Zhu, Dongming; Ghosn, Louis J.; Miller, Robert A.

1998-01-01

Thermal barrier coating (TBC) durability is closely related to design, processing and microstructure of the coating Z, tn systems. Two important issues that must be considered during the design of a thermal barrier coating are thermal expansion and modulus mismatch between the substrate and the ceramic layer, and substrate oxidation. In many cases, both of these issues may be best addressed through the selection of an appropriate bond coat system. In this study, a low thermal expansion and layer-graded bond coat system, that consists of plasma-sprayed FeCoNiCrAl and FeCrAlY coatings, and a high velocity oxyfuel (HVOF) sprayed FeCrAlY coating, is developed to minimize the thermal stresses and provide oxidation resistance. The thermal expansion and oxidation behavior of the coating system are also characterized, and the strain isolation effect of the bond coat system is analyzed using the finite element method (FEM). Experiments and finite element results show that the layer-graded bond coat system possesses lower interfacial stresses. better strain isolation and excellent oxidation resistance. thus significantly improving the coating performance and durability.

Investigations of thermal barrier coatings of turbine parts using gas flame heating

Science.gov (United States)

Lepeshkin, A. R.; Bichkov, N. G.; Ilinskaja, O. I.; Nazarov, V. V.

2017-09-01

The development of methods for the calculated and experimental investigations thermal barrier coatings and thermal state of gas-turbine engine parts with a thermal barrier coatings is actual work. The gas flame heating was demonstrated to be effectively used during investigations of a thermal ceramic barrier coatings and thermal state of such gas-turbine engine parts with a TBC as the cooled turbine blades and vanes and combustion liner components. The gas-flame heating is considered to be preferable when investigating the gas-turbine engine parts with a TBC in the special cases when both the convective and radiant components of thermal flow are of great importance. The small-size rig with gas-flame flow made it possible to conduct the comparison investigations with the purpose of evaluating the efficiency of thermal protection of the ceramic deposited thermal barrier coatings on APS and EB techniques. The developed design-experiment method was introduced in bench tests of turbine blades and combustion liner components of gas turbine engines.

Oxide growth and damage evolution in thermal barrier coatings

NARCIS (Netherlands)

Hille, T.S.; Turteltaub, S.R.; Suiker, A.S.J.

2011-01-01

Cracking in thermal barrier coatings (TBC) is triggered by the development of a thermally-grown oxide (TGO) layer that develops during thermal cycling from the oxidation of aluminum present in the bond coat (BC). In the present communication a numerical model is presented that describes the

The Development of Environmental Barrier Coatings for SiCSiC Ceramic Matrix Composites: Challenges and Opportunities

Science.gov (United States)

Zhu, Dongming

2014-01-01

Environmental barrier coatings (EBCs) and SiC/SiC ceramic matrix composites (CMCs) systems will play a crucial role in future turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures, reduce engine weight and cooling requirements. The development of prime-reliant environmental barrier coatings is a key to enable the applications of the envisioned CMC components to help achieve next generation engine performance and durability goals. This paper will primarily address the performance requirements and design considerations of environmental barrier coatings for turbine engine applications. The emphasis is placed on current candidate environmental barrier coating systems for SiCSiC CMCs, their performance benefits and design limitations in long-term operation and combustion environments. Major technical barriers in developing advanced environmental barrier coating systems, the coating integrations with next generation CMC turbine components having improved environmental stability, cyclic durability and system performance will be described. The development trends for turbine environmental barrier coating systems by utilizing improved compositions, state-of-the-art processing methods, and simulated environment testing and durability modeling will be discussed.

Functionally gradient materials for thermal barrier coatings in advanced gas turbine systems

Energy Technology Data Exchange (ETDEWEB)

Banovic, S.W.; Barmak, K.; Chan, H.M. [Lehigh Univ., Bethlehem, PA (United States)] [and others

1995-10-01

New designs for advanced gas turbine engines for power production are required to have higher operating temperatures in order to increase efficiency. However, elevated temperatures will increase the magnitude and severity of environmental degradation of critical turbine components (e.g. combustor parts, turbine blades, etc{hor_ellipsis}). To offset this problem, the usage of thermal barrier coatings (TBCs) has become popular by allowing an increase in maximum inlet temperatures for an operating engine. Although thermal barrier technology is over thirty years old, the principle failure mechanism is the spallation of the ceramic coating at or near the ceramic/bond coat interface. Therefore, it is desirable to develop a coating that combines the thermal barrier qualities of the ceramic layer and the corrosion protection by the metallic bond coat without the detrimental effects associated with the localization of the ceramic/metal interface to a single plane.

Effects of Thermal Exposure on Structures of DD6 Single Crystal Superalloy with Thermal Barrier Coatings

Directory of Open Access Journals (Sweden)

DONG Jianmin

2016-10-01

Full Text Available In order to investigate the effect of water grit-blasting and high temperature thermal exposure on the microstructures of DD6 alloy with TBCs, DD6 single crystal superalloy specimens were water grit-blasted with 0.3 MPa pressure, then the specimens were coated with thermal barrier coatings by electron beam physical vapor deposition (EB-PVD. Specimens with TBCs were exposed at 1100℃ for 50 and 100 hours in the air respectively, and then these specimens were subjected to stress-rupture tests under the condition of 1100℃/130 MPa. The results show that grit-blasting doesn't lead into the recrystallization, thermal exposure can induce element interdiffusion between the bond coat and alloy substrate, the residual stress and element diffusion lead into the changes of γ' phase coarsing direction. After stress rupture tests, the secondary reaction zone emerges into a local area.

Verification of the integrity of barriers using gas diffusion

International Nuclear Information System (INIS)

Ward, D.B.; Williams, C.V.

1997-06-01

In-situ barrier materials and designs are being developed for containment of high risk contamination as an alternative to immediate removal or remediation. The intent of these designs is to prevent the movement of contaminants in either the liquid or vapor phase by long-term containment, essentially buying time until the contaminant depletes naturally or a remediation can be implemented. The integrity of the resultant soil-binder mixture is typically assessed by a number of destructive laboratory tests (leaching, compressive strength, mechanical stability with respect to wetting and freeze-thaw cycles) which as a group are used to infer the likelihood of favorable long-term performance of the barrier. The need exists for a minimally intrusive yet quantifiable methods for assessment of a barrier's integrity after emplacement, and monitoring of the barrier's performance over its lifetime. Here, the authors evaluate non-destructive measurements of inert-gas diffusion (specifically, SF 6 ) as an indicator of waste-form integrity. The goals of this project are to show that diffusivity can be measured in core samples of soil jet-grouted with Portland cement, validate the experimental method through measurements on samples, and to calculate aqueous diffusivities from a series of diffusion measurements. This study shows that it is practical to measure SF 6 diffusion rates in the laboratory on samples of grout (Portland cement and soil) typical of what might be used in a barrier. Diffusion of SF 6 through grout (Portland cement and soil) is at least an order of magnitude slower than through air. The use of this tracer should be sensitive to the presence of fractures, voids, or other discontinuities in the grout/soil structure. Field-scale measurements should be practical on time-scales of a few days

On the compatibility of single crystal superalloys with a thermal barrier coating system

Energy Technology Data Exchange (ETDEWEB)

Wu, R.T. [Department of Materials, Imperial College London, Prince Consort Road, London SW7 2BP (United Kingdom); Reed, R.C. [Department of Materials, Imperial College London, Prince Consort Road, London SW7 2BP (United Kingdom)], E-mail: r.reed@birmingham.ac.uk

2008-02-15

The compatibility of three Co-containing prototype single crystal nickel-based superalloys with a thermal barrier coating (TBC) system is examined. These contain 2.1, 8.4 and 12.6 at.% Co; the concentrations of Al, Cr, Ta, W, Re, Hf are identical and chosen to be representative of advanced grades of these alloys. The TBC consists of an yttria-stabilized zirconia (YSZ) layer formed by electron beam physical vapour deposition (EB-PVD) and a bond coat made by electrodeposited platinum with a subsequent interdiffusion heat treatment - a so-called 'platinum-diffused' bond coat. The resistance to spallation of the TBC system is degraded as the Co content of the substrate increases. Wavelength-dispersive X-ray analysis and secondary ion mass spectrometry indicate that quantities of Co are present in the thermally grown oxide (TGO) by the time that failure occurs, this effect being most pronounced when the Co content of the substrate is high; the TGO is then more wavy and convoluted. The bond coat consists exclusively of the {gamma} and {gamma}' phases, with the balance shifting towards {gamma} with increasing thermal exposure; the loss of Al from the bond coat due to TGO formation means that the TGO is eventually in contact with the {gamma} phase solely, which is enriched in Co.

Anti-browning and barrier properties of edible coatings prepared with electrospraying

NARCIS (Netherlands)

Khan, M.K.I.; Cakmak, I.; Tavman, S.; Schutyser, M.A.I.; Schroen, C.G.P.H.

2014-01-01

Electrospraying is a novel technique for the application of coating to foods. In this study, thin lipid-based coatings were prepared by electrospraying on model surface and evaluated for their moisture barrier functionality. Sunflower oil and chocolate based coating materials were electrosprayed at

Design and Performance Optimizations of Advanced Erosion-Resistant Low Conductivity Thermal Barrier Coatings for Rotorcraft Engines

Science.gov (United States)

Zhu, Dongming; Miller, Robert A.; Kuczmarski, Maria A.

2012-01-01

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future rotorcraft engine higher fuel efficiency and lower emission goals. For thermal barrier coatings designed for rotorcraft turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability, because the rotorcraft are often operated in the most severe sand erosive environments. Advanced low thermal conductivity and erosion-resistant thermal barrier coatings are being developed, with the current emphasis being placed on thermal barrier coating toughness improvements using multicomponent alloying and processing optimization approaches. The performance of the advanced thermal barrier coatings has been evaluated in a high temperature erosion burner rig and a laser heat-flux rig to simulate engine erosion and thermal gradient environments. The results have shown that the coating composition and architecture optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic oxidation durability

Structural characterisation of oxygen diffusion hardened alpha-tantalum PVD-coatings on titanium.

Science.gov (United States)

Hertl, C; Koll, L; Schmitz, T; Werner, E; Gbureck, U

2014-08-01

Titanium substrates were coated with tantalum layers of 5 μm thickness using physical vapour deposition (PVD). The tantalum layers showed a (110)-preferred orientation. The coated samples were hardened by oxygen diffusion. Using X-ray diffraction the crystallographic structure of the tantalum coatings was characterised, comparing untreated and diffusion hardened specimen conditions. Oxygen depth profiles were determined by glow discharge spectrometry. The hardening effect of the heat treatment was examined by Vickers microhardness testing. The increase of surface hardness caused by oxygen diffusion was at least 50%. Copyright © 2014 Elsevier B.V. All rights reserved.

Optimization of Heat Transfer on Thermal Barrier Coated Gas Turbine Blade

Science.gov (United States)

Aabid, Abdul; Khan, S. A.

2018-05-01

In the field of Aerospace Propulsion technology, material required to resist the maximum temperature. In this paper, using thermal barrier coatings (TBCs) method in gas turbine blade is used to protect hot section component from high-temperature effect to extend the service life and reduce the maintenance costs. The TBCs which include three layers of coating corresponding initial coat is super alloy-INCONEL 718 with 1 mm thickness, bond coat is Nano-structured ceramic-metallic composite-NiCoCrAIY with 0.15 mm thickness and top coat is ceramic composite-La2Ce2O7 with 0.09 mm thickness on the nickel alloy turbine blade which in turn increases the strength, efficiency and life span of the blades. Modeling a gas turbine blade using CATIA software and determining the amount of heat transfer on thermal barrier coated blade using ANSYS software has been performed. Thermal stresses and effects of different TBCs blade base alloys are considered using CATIA and ANSYS.

ANALISIS STRUKTUR MIKRO LAPISAN BOND COAT NIAL THERMAL BARRIER COATING (TBC PADA PADUAN LOGAM BERBASIS CO

Directory of Open Access Journals (Sweden)

Toto Sudiro

2012-11-01

Full Text Available Kehandalan dan umur pakai sistem Thermal Barrier Coating (TBC ditentukan oleh kestabilan lapisan bond coat dan thermal grown oxide (TGO. Sehingga sangatlah penting untuk memahami mekanisme pembentukan dan degradasi lapisan ini. Pada makalah ini akan dibahas analisis struktur mikro lapisan bond coat NiAl yang dideposisikan pada substrat CoCrNi dengan menggunakan gabungan metoda electroplating dan pack-cementation. Pada makalah ini juga dibahas mekanisme pembentukan void disepanjang interface bond coat¬-substrat setelah tes oksidasi.

Evaluation of bond strength of isothermally aged plasma sprayed thermal barrier coating

Energy Technology Data Exchange (ETDEWEB)

Kim, Dae Jin; Lee, Dong Hoon; Koo, Jae Mean; Song, Sung Jin; Seok, Chang Sung [Sungkyunkwan University, Suwon (Korea, Republic of); Kim, Mun Young [Korea Plant Service and Engineering Co., Ltd., Seongnam (Korea, Republic of)

2008-07-15

In this study, disk type of thermal barrier coating system for gas turbine blade was isothermally aged in the furnace changing exposure time and temperature. For each aging condition, bond tests for three samples were conducted for evaluating degradation of adhesive or cohesive strength of thermal barrier coating system. For as-sprayed condition, the location of fracture in the bond test was in the middle of epoxy which have bond strength of 57 MPa. As specimens are degraded by thermal aging, bond strength gradually decreased and the location of failure was also changed from within top coat at the earlier stage of thermal aging to the interface between top coat and TGO at the later stage due to the delamination in the coating.

Thermo-mechanical Fatigue Failure of Thermal Barrier Coated Superalloy Specimen

Science.gov (United States)

Subramanian, Rajivgandhi; Mori, Yuzuru; Yamagishi, Satoshi; Okazaki, Masakazu

2015-09-01

Failure behavior of thermal barrier coated (TBC) Ni-based superalloy specimens were studied from the aspect of the effect of bond coat material behavior on low cycle fatigue (LCF) and thermo-mechanical fatigue (TMF) at various temperatures and under various loading conditions. Initially, monotonic tensile tests were carried out on a MCrAlY alloy bond coat material in the temperature range of 298 K to 1273 K (25 °C to 1000 °C). Special attention was paid to understand the ductile to brittle transition temperature (DBTT). Next, LCF and TMF tests were carried out on the thermal barrier coated Ni-based alloy IN738 specimen. After these tests, the specimens were sectioned to understand their failure mechanisms on the basis of DBTT of the bond coat material. Experimental results demonstrated that the LCF and TMF lives of the TBC specimen were closely related to the DBTT of the bond coat material, and also the TMF lives were different from those of LCF tests. It has also been observed that the crack density in the bond coat in the TBC specimen was significantly dependent on the test conditions. More importantly, not only the number of cracks but also the crack penetration probability into substrate were shown to be sensitive to the DBTT.

Diffusive Barrier and Getter Under Waste Packages VA Reference Design Feature Evaluations

International Nuclear Information System (INIS)

MacNeil, K.

1999-01-01

This technical document evaluates those aspects of the diffusive barrier and getter features which have the potential for enhancing the performance of the Viability Assessment Reference Design and are also directly related to the key attributes for the repository safety strategy of that design. The effects of advection, hydrodynamic dispersion, and diffusion on the radionuclide migration rates through the diffusive barrier were determined through the application of the one-dimensional, advection/dispersion/diffusion equation. The results showed that because advective flow described by the advection-dispersion equation dominates, the diffusive barrier feature alone would not be effective in retarding migration of radiocuclides. However, if the diffusive barrier were combined with one or more features that reduced the potential for advection, then transport of radionuclides would be dominated by diffusion and their migration from the EBS would be impeded. Apatite was chosen as the getter material used for this report. Two getter configurations were developed, Case 1 and Case 2. As in the evaluation of the diffusive barrier, the effects of advection, hydrodynamic dispersion, and diffusion on the migration of radionuclides through the getter are evaluated. However, in addition to these mechanisms, the one-dimensional advection/dispersion/diffusion model is modified to include the effect of sorption on radionuclide migration rates through the sorptive medium (getter). As a result of sorption, the longitudinal dispersion coefficient, and the average linear velocity are effectively reduced by the retardation factor. The retardation factor is a function of the getter material's dry bulk density, sorption coefficient and moisture content. The results of the evaluation showed that a significant delay in breakthrough through the getter can be achieved if the thickness of the getter barrier is increased

Electron grafted barrier coatings for packaging film modification

International Nuclear Information System (INIS)

Rangwalla, I.J.; Nablo, S.V.

1993-01-01

The O 2 barrier performance of organosilane films, coated, dried and electron beam grafted to polyolefin film has been studied. Excellent anti-scalping properties based upon limonene (dipentene) transmission measurements have also been observed. Results are also reported on O 2 permeability reduction when the process is applied to common barrier polymers such as EVOH and acrylonitrile. Experience with its in-line application on LDPE is discussed. (author)

TECHNOLOGICAL PECULIARITIES OF THERMAL BARRIER COATINGS BASED ON ZIRCONIUM DIOXIDE

Directory of Open Access Journals (Sweden)

V. V. Okovity

2016-01-01

Full Text Available A technology for formation of thermal barrier coatings (TBC based on zirconium dioxide has been developed in the paper. The paper investigates structures of phase composition and thermal stability of such developed coatings. Investigation results pertaining to formation of an oxide system ZrO2 – Y2O3, while using plasma spraying and subsequent high-energy processing, which allows to increase resistance of a thermal barrier coating to thermal cycling heat resistance of the coating at temperature of 1100 °C. This leads to longer protection of bottom layer against high-temperature exposure. The methodology is based on complex metallographic, X-ray diffraction and electron microscopy investigations of structural elements in composite plasma coatings of the ZrO2 – Y2O system. Resistance of plasma coatings (Мe – Cr – Al – Y/ZrO2 – Y2O3-type, used as TBC to protect gas turbine engine blades under conditions of frequent thermal cyclings is limited by cleavage of an outer ceramic layer. Structural and electron microprobe investigations have shown that as a result of thermal cycling an outer atmosphere due to porous structure of the ceramic coating layer, migrates to the surface of lower metal coating, causing its oxidation. As a result, the metal-ceramic Al2O3 layer is formed at a metal-ceramic interface and it changes a stress state of the coating that causes a reduction of protective properties. Thus, a high heat resistance of thermal barrier coatings depends on processes occurring at the interface between metal and ceramic coating layers. A laser impact on samples with TBC leads to changes in the structure of the oxide layer of ZrO2 – Y2O3. In this case its initial surface characterized by considerable relief is significantly flattened due to processing and the coating is fractured and it is separated in fragments. As the oxide coating has low thermal conductivity, and the time of laser exposure is about 10–3 sec, a heat flux

Influence of Experimental Parameters Using the Dip-Coating Method on the Barrier Performance of Hybrid Sol-Gel Coatings in Strong Alkaline Environments

Directory of Open Access Journals (Sweden)

Rita B. Figueira

2015-04-01

Full Text Available Previous studies have shown that the barrier effect and the performance of organic-inorganic hybrid (OIH sol-gel coatings are highly dependent on the coating deposition method as well as on the processing conditions. However, studies on how the coating deposition method influences the barrier properties in alkaline environments are scarce. The aim of this experimental research was to study the influence of experimental parameters using the dip-coating method on the barrier performance of an OIH sol-gel coating in contact with simulated concrete pore solutions (SCPS. The influence of residence time (Rt, a curing step between each dip step and the number of layers of sol-gel OIH films deposited on hot-dip galvanized steel to prevent corrosion in highly alkaline environments was studied. The barrier performance of these OIH sol-gel coatings, named U(400, was assessed in the first instants of contact with SCPS, using electrochemical impedance spectroscopy and potentiodynamic methods. The durability and stability of the OIH coatings in SCPS was monitored during eight days by macrocell current density. The morphological characterization of the surface was performed by Scanning Electronic Microscopy before and after exposure to SCPS. Glow Discharge Optical Emission Spectroscopy was used to investigate the thickness of the U(400 sol-gel coatings as a function of the number of layers deposited with and without Rt in the coatings thickness.

Sintering and microstructure evolution in columnar thermal barrier coatings

International Nuclear Information System (INIS)

Krishnamurthy, Ramanathan; Srolovitz, David J.

2009-01-01

Sintering of thermal barrier coatings changes their key properties, such as thermal conductivity and thermal shock resistance, thus adversely impacting their reliability. We present a novel modeling approach to study the evolution of coating structure during sintering. We model the sintering of individual columns using a thermodynamic principle, and incorporate the center-to-center approach rates for the columns calculated using this principle in a larger scale discrete dynamics model for the evolution of a large number of columns. Surface energies, grain boundary energies and strain energies associated with the deformation of the columns are all included in this framework, while sintering is assumed to occur by the concerted action of surface and grain boundary diffusion. Two sets of initial conditions corresponding to different extents of pre-sintering among neighboring columns are considered. When the extent of pre-sintering is small, we observe that small clusters containing 5-20 columns are formed. In contrast, where a larger amount of pre-sintering exists, we observe, especially at large column densities, that clusters containing 50-100 columns separated by large inter-cluster pores/channels that appear to organize themselves into a network are formed. These observations are in good agreement with recently published experimental observations. We also explain how these results can explain the development of a 'mud-crack'-like pattern

Barrier and mechanical properties of plasticized and cross-linked nanocellulose coatings for paper packaging applications

OpenAIRE

Herrera, M. A. (Martha A.); Mathew, A. P. (Aji P.); Oksman, K. (Kristiina)

2017-01-01

Abstract Barrier, mechanical and thermal properties of porous paper substrates dip-coated with nanocellulose (NC) were studied. Sorbitol plasticizer was used to improve the toughness, and citric acid cross-linker to improve the moisture stability of the coatings. In general, the addition of sorbitol increased the barrier properties, maximum strength and toughness as well as the thermal stability of the samples when compared to the non-modified NC coatings. The barrier properties significan...

Calcium-Magnesium-Aluminosilicate (CMAS) Reactions and Degradation Mechanisms of Advanced Environmental Barrier Coatings

Science.gov (United States)

Ahlborg, Nadia L.; Zhu, Dongming

2013-01-01

The thermochemical reactions between calcium-magnesium-aluminosilicate- (CMAS-) based road sand and several advanced turbine engine environmental barrier coating (EBC) materials were studied. The phase stability, reaction kinetics and degradation mechanisms of rare earth (RE)-silicates Yb2SiO5, Y2Si2O7, and RE-oxide doped HfO2 and ZrO2 under the CMAS infiltration condition at 1500 C were investigated, and the microstructure and phase characteristics of CMAS-EBC specimens were examined using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). Experimental results showed that the CMAS dissolved RE-silicates to form crystalline, highly non-stoichiometric apatite phases, and in particular attacking the silicate grain boundaries. Cross-section images show that the CMAS reacted with specimens and deeply penetrated into the EBC grain boundaries and formed extensive low-melting eutectic phases, causing grain boundary recession with increasing testing time in the silicate materials. The preliminary results also showed that CMAS reactions also formed low melting grain boundary phases in the higher concentration RE-oxide doped HfO2 systems. The effect of the test temperature on CMAS reactions of the EBC materials will also be discussed. The faster diffusion exhibited by apatite and RE-doped oxide phases and the formation of extensive grain boundary low-melting phases may limit the CMAS resistance of some of the environmental barrier coatings at high temperatures.

Co-sputtered amorphous Nb–Ta, Nb–Zr and Ta–Zr coatings for corrosion protection of cyclotron targets for [{sup 18}F] production

Energy Technology Data Exchange (ETDEWEB)

Skliarova, Hanna, E-mail: Hanna.Skliarova@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell’Università, 2, 35020 Legnaro, Padua (Italy); University of Ferrara, Ferrara (Italy); Azzolini, Oscar, E-mail: Oscar.Azzolini@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell’Università, 2, 35020 Legnaro, Padua (Italy); Johnson, Richard R., E-mail: richard.johnson@teambest.com [BEST Cyclotron Systems Inc., 8765 Ash Street Unit 7, Vancouver, BC V6P 6T3 (Canada); Palmieri, Vincenzo, E-mail: Vincenzo.Palmieri@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell’Università, 2, 35020 Legnaro, Padua (Italy); University of Padua, Padua (Italy)

2015-08-05

Highlights: • Nb–Ta, Nb–Zr and Ta–Zr alloy films were deposited by co-sputtering. • Co-sputtered Nb–Zr and Nb–Ta alloy coatings had crystalline microstructures. • Diffusion barrier efficiency of Nb–Zr and Nb–Ta decreased with the increase of Nb %. • Co-sputtered Ta–Zr films with 30–73 at.% Ta were amorphous. • Sputtered amorphous Ta–Zr films showed superior diffusion barrier efficiency. - Abstract: Protective corrosion resistant coatings serve for decreasing the amount of ionic contaminants from Havar® entrance foils of the targets for [{sup 18}F] production. The corrosion damage of coated entrance foils is caused mainly by the diffusion of highly reactive products of water radiolysis through the protective film toward Havar® substrate. Since amorphous metal alloys (metallic glasses) are well-known to perform a high corrosion resistance, the glass forming ability, microstructure and diffusion barrier efficiency of binary alloys containing chemically inert Nb, Ta, Zr were investigated. Nb–Ta, Nb–Zr and Ta–Zr films of different alloy composition and ∼1.5 μm thickness were co-deposited by magnetron sputtering. Diffusion barrier efficiency tests used reactive aluminum underlayer and protons of acid solution and gallium atoms at elevated temperature as diffusing particles. Though co-sputtered Nb–Ta and Nb–Zr alloy films of different contents were crystalline, Ta–Zr alloy was found to form dense amorphous microstructures in a range of composition with 30–73% atomic Ta. The diffusion barrier efficiency of Nb–Zr and Nb–Ta alloy coatings decreased with increase of Nb content. The diffusion barrier efficiency of sputtered Ta–Zr alloy coatings increased with the transition from nanocrystalline columnar microstructure to amorphous for coatings with 30–73 at.% Ta.

Advanced Environmental Barrier Coating Development for SiC/SiC Ceramic Matrix Composites: NASA's Perspectives

Science.gov (United States)

Zhu, Dongming

2016-01-01

This presentation reviews NASA environmental barrier coating (EBC) system development programs and the coating materials evolutions for protecting the SiC/SiC Ceramic Matrix Composites in order to meet the next generation engine performance requirements. The presentation focuses on several generations of NASA EBC systems, EBC-CMC component system technologies for SiC/SiC ceramic matrix composite combustors and turbine airfoils, highlighting the temperature capability and durability improvements in simulated engine high heat flux, high pressure, high velocity, and with mechanical creep and fatigue loading conditions. The current EBC development emphasis is placed on advanced NASA 2700F candidate environmental barrier coating systems for SiC/SiC CMCs, their performance benefits and design limitations in long-term operation and combustion environments. Major technical barriers in developing environmental barrier coating systems, the coating integrations with next generation CMCs having the improved environmental stability, erosion-impact resistance, and long-term fatigue-environment system durability performance are described. The research and development opportunities for advanced turbine airfoil environmental barrier coating systems by utilizing improved compositions, state-of-the-art processing methods, and simulated environment testing and durability modeling are discussed.

Environmental Barrier Coatings for Turbine Engines: A Design and Performance Perspective

Science.gov (United States)

Zhu, Dongming; Fox, Dennis S.; Ghosn, Louis; Smialek, James L.; Miller, Robert A.

2009-01-01

Ceramic thermal and environmental barrier coatings (TEBC) for SiC-based ceramics will play an increasingly important role in future gas turbine engines because of their ability to effectively protect the engine components and further raise engine temperatures. However, the coating long-term durability remains a major concern with the ever-increasing temperature, strength and stability requirements in engine high heat-flux combustion environments, especially for highly-loaded rotating turbine components. Advanced TEBC systems, including nano-composite based HfO2-aluminosilicate and rare earth silicate coatings are being developed and tested for higher temperature capable SiC/SiC ceramic matrix composite (CMC) turbine blade applications. This paper will emphasize coating composite and multilayer design approach and the resulting performance and durability in simulated engine high heat-flux, high stress and high pressure combustion environments. The advances in the environmental barrier coating development showed promise for future rotating CMC blade applications.

Influence of Food with High Moisture Content on Oxygen Barrier Property of Polyvinyl Alcohol (PVA)/Vermiculite Nanocomposite Coated Multilayer Packaging Film.

Science.gov (United States)

Kim, Jung Min; Lee, Min Hyeock; Ko, Jung A; Kang, Dong Ho; Bae, Hojae; Park, Hyun Jin

2018-02-01

This study investigates the potential complications in applying nanoclay-based waterborne coating to packaging films for food with high moisture content. Multilayer packaging films were prepared by dry laminating commercially available polyvinyl alcohol (PVA)/vermiculite nanocomposite coating films and linear low-density polyethylene film, and the changes in oxygen barrier properties were investigated according to different relative humidity using 3 types of food simulants. When the relative humidity was above 60%, the oxygen permeability increased sharply, but this was reversible. Deionized water and 3% acetic acid did not cause any large structural change in the PVA/vermiculite nanocomposite but caused a reversible deterioration of the oxygen barrier properties. In contrast, 50% ethanol, a simulant for the semifatty food, induced irreversible structural changes with deterioration of the oxygen barrier property. These changes are due to the characteristics of PVA rather than vermiculite. We believe this manuscript would be of interest to the wide group of researchers, organizations, and companies in the field of developing nanoclay-based gas barrier packaging for foods with high moisture content. Hence, we wish to diffuse our knowledge to the scientific community. © 2018 Institute of Food Technologists®.

Energy barriers for diffusion on heterogeneous stepped metal surfaces: Ag/Cu(110)

International Nuclear Information System (INIS)

Sbiaai, K.; Boughaleb, Y.; Mazroui, M.; Hajjaji, A.; Kara, A.

2013-01-01

In this paper we investigated the diffusion of Ag adatom by computing the energy barriers for many elementary diffusive processes which are likely to happen near to the step edge on Cu (110). The barriers are calculated by means of molecular dynamics simulation by using embedded atom potentials. The proximity to steps alters these barriers considerably, and very different results may be expected. In fact, our numerical calculations show that the diffusion via jump process along step edge is predominant for Ag/Cu(110) and the diffusion over the step occurs sometimes, but only via exchange mechanisms. The adatom diffusion across channels is difficult due to the high value of activation energy required (around 1 eV). Furthermore, we found the Ehrlich–Schwoebel barrier for diffusion around 120 meV in order to descend via exchange process and of the order of 170 meV via hopping mode. This aspect may have a strong influence on the growth character. In general our results suggest that, for our metal system, diffusion mechanism may be important for mass transport across the steps. Implications of these findings are discussed. - Highlights: • Study of adatom diffusion near the step edge • The diffusion along channel is enhanced through jump process. • Arrhenius law is satisfied for a wide range of temperature (310–600 K)

Calcium-Magnesium-Aluminosilicate (CMAS) Infiltration and Cyclic Degradations of Thermal and Environmental Barrier Coatings in Thermal Gradients

Science.gov (United States)

Zhu, Dongming; Harder, Bryan; Smialek, Jim; Miller, Robert A.

2014-01-01

In a continuing effort to develop higher temperature capable turbine thermal barrier and environmental barrier coating systems, Calcium-Magnesium-Aluminosilicate (CMAS) resistance of the advanced coating systems needs to be evaluated and improved. This paper highlights some of NASA past high heat flux testing approaches for turbine thermal and environmental barrier coatings assessments in CMAS environments. One of our current emphases has been focused on the thermal barrier - environmental barrier coating composition and testing developments. The effort has included the CMAS infiltrations in high temperature and high heat flux turbine engine like conditions using advanced laser high heat flux rigs, and subsequently degradation studies in laser heat flux thermal gradient cyclic and isothermal furnace cyclic testing conditions. These heat flux CMAS infiltration and related coating durability testing are essential where appropriate CMAS melting, infiltration and coating-substrate temperature exposure temperature controls can be achieved, thus helping quantify the CMAS-coating interaction and degradation mechanisms. The CMAS work is also playing a critical role in advanced coating developments, by developing laboratory coating durability assessment methodologies in simulated turbine engine conditions and helping establish CMAS test standards in laboratory environments.

Ion Diffusion-Directed Assembly Approach to Ultrafast Coating of Graphene Oxide Thick Multilayers.

Science.gov (United States)

Zhao, Xiaoli; Gao, Weiwei; Yao, Weiquan; Jiang, Yanqiu; Xu, Zhen; Gao, Chao

2017-10-24

The layer-by-layer (LbL) assembly approach has been widely used to fabricate multilayer coatings on substrates with multiple cycles, whereas it is hard to access thick films efficiently. Here, we developed an ion diffusion-directed assembly (IDDA) strategy to rapidly make multilayer thick coatings in one step on arbitrary substrates. To achieve multifunctional coatings, graphene oxide (GO) and metallic ions were selected as the typical building blocks and diffusion director in IDDA, respectively. With diffusion of metallic ions from substrate to negatively charged GO dispersion spontaneously (i.e., from high-concentration region to low-concentration region), GO was assembled onto the substrate sheet-by-sheet via sol-gel transformation. Because metallic ions with size of subnanometers can diffuse directionally and freely in the aqueous dispersion, GO was coated on the substrate efficiently, giving rise to films with desired thickness up to 10 μm per cycle. The IDDA approach shows three main merits: (1) high efficiency with a μm-scale coating rate; (2) controllability over thickness and evenness; and (3) generality for substrates of plastics, metals and ceramics with any shapes and morphologies. With these merits, IDDA strategy was utilized in the efficient fabrication of functional graphene coatings that exhibit outstanding performance as supercapacitors, electromagnetic interference shielding textiles, and anticorrosion coatings. This IDDA approach can be extended to other building blocks including polymers and colloidal nanoparticles, promising for the scalable production and application of multifunctional coatings.

Niobium–niobium oxide multilayered coatings for corrosion protection of proton-irradiated liquid water targets for ["1"8F] production

International Nuclear Information System (INIS)

Skliarova, Hanna; Renzelli, Marco; Azzolini, Oscar; Felicis, Daniele de; Bemporad, Edoardo; Johnson, Richard R.; Palmieri, Vincenzo

2015-01-01

Chemically inert coatings on Havar"® entrance foils of the targets for ["1"8F] production via proton irradiation of enriched water at pressurized conditions are needed to decrease the amount of ionic contaminants released from Havar"®. During current investigation, magnetron sputtered niobium and niobium oxide were chosen as the candidates for protective coatings because of their superior chemical resistance. Aluminated quartz substrates allowed us to verify the protection efficiency of the desirable coatings as diffusion barriers. Two modeling corrosion tests based on the extreme susceptibility of aluminum to liquid gallium and acid corrosion were applied. As far as niobium coatings obtained by magnetron sputtering are columnar, the grain boundaries provide a fast diffusion path for active species of corrosive media to penetrate and to corrode the substrate. Amorphous niobium oxide films obtained by reactive magnetron sputtering showed superior barrier properties according to the corrosion tests performed. In order to prevent degrading of brittle niobium oxide at high pressures, multilayers combining high ductility of niobium with superior diffusion barrier efficiency of niobium oxide were proposed. The intercalation of niobium oxide interlayers was proved to interrupt the columnar grain growth of niobium during sputtering, resulting in improved diffusion barrier efficiency of obtained multilayers. The thin layer multilayer coating architecture with 70 nm bi-layer thickness was found preferential because of higher thermal stability. - Highlights: • Diffusion barrier efficiency of niobium, niobium oxide and their multilayers was studied. • The intercalation of niobium oxide layers interrupted the columnar grain growth of niobium. • The bilayer architectures influenced the stability of the multilayer coatings. • The thin layer multilayer coating with 70 nm double-layer was found superior.

Niobium–niobium oxide multilayered coatings for corrosion protection of proton-irradiated liquid water targets for [{sup 18}F] production

Energy Technology Data Exchange (ETDEWEB)

Skliarova, Hanna, E-mail: Hanna.Skliarova@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell' Università, 2, 35020 Legnaro, Padua (Italy); University of Ferrara, Ferrara (Italy); Renzelli, Marco, E-mail: marco.renzelli@uniroma3.it [University of Rome “Roma TRE”, Via della Vasca Navale, 79, 00146 Rome (Italy); Azzolini, Oscar, E-mail: Oscar.Azzolini@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell' Università, 2, 35020 Legnaro, Padua (Italy); Felicis, Daniele de, E-mail: daniele.defelicis@uniroma3.it [University of Rome “Roma TRE”, Via della Vasca Navale, 79, 00146 Rome (Italy); Bemporad, Edoardo, E-mail: edoardo.bemporad@uniroma3.it [University of Rome “Roma TRE”, Via della Vasca Navale, 79, 00146 Rome (Italy); Johnson, Richard R., E-mail: richard.johnson@teambest.com [BEST Cyclotron Systems Inc., 8765 Ash Street Unit 7, Vancouver BC V6P 6T3 (Canada); Palmieri, Vincenzo, E-mail: Vincenzo.Palmieri@lnl.infn.it [National Institute of Nuclear Physics, Legnaro National Laboratories, Viale dell' Università, 2, 35020 Legnaro, Padua (Italy); University of Padua, Padua (Italy)

2015-09-30

Chemically inert coatings on Havar{sup ®} entrance foils of the targets for [{sup 18}F] production via proton irradiation of enriched water at pressurized conditions are needed to decrease the amount of ionic contaminants released from Havar{sup ®}. During current investigation, magnetron sputtered niobium and niobium oxide were chosen as the candidates for protective coatings because of their superior chemical resistance. Aluminated quartz substrates allowed us to verify the protection efficiency of the desirable coatings as diffusion barriers. Two modeling corrosion tests based on the extreme susceptibility of aluminum to liquid gallium and acid corrosion were applied. As far as niobium coatings obtained by magnetron sputtering are columnar, the grain boundaries provide a fast diffusion path for active species of corrosive media to penetrate and to corrode the substrate. Amorphous niobium oxide films obtained by reactive magnetron sputtering showed superior barrier properties according to the corrosion tests performed. In order to prevent degrading of brittle niobium oxide at high pressures, multilayers combining high ductility of niobium with superior diffusion barrier efficiency of niobium oxide were proposed. The intercalation of niobium oxide interlayers was proved to interrupt the columnar grain growth of niobium during sputtering, resulting in improved diffusion barrier efficiency of obtained multilayers. The thin layer multilayer coating architecture with 70 nm bi-layer thickness was found preferential because of higher thermal stability. - Highlights: • Diffusion barrier efficiency of niobium, niobium oxide and their multilayers was studied. • The intercalation of niobium oxide layers interrupted the columnar grain growth of niobium. • The bilayer architectures influenced the stability of the multilayer coatings. • The thin layer multilayer coating with 70 nm double-layer was found superior.

Improving the Corrosion Resistance of Biodegradable Magnesium Alloys by Diffusion Coating Process

Science.gov (United States)

Levy, Galit Katarivas; Aghion, Eli

Magnesium alloys suffer from accelerated corrosion in physiological environment and hence their use as a structural material for biodegradable implants is limited. The present study focuses on a diffusion coating treatment that amplifies the beneficial effect of Neodymium on the corrosion resistance of magnesium alloys. The diffusion coating layer was obtained by applying 1 µm Nd coating on EW10X04 magnesium alloy using Electron-gun evaporator and PVD process. The coated alloy was heat treated at 350°C for 3 hours in a protective atmosphere of N2+0.2%SF6. The micro structure characteristics were evaluated by SEM, XRD, and XPS; the corrosion resistance was examined by potentiodynamic polarization and EIS analysis. The corrosion resistance of the diffusion coated alloy was significantly improved compared to the uncoated material. This was related to: (i) formation of Nd2O3 in the outer scale, (ii) integration of Nd in the MgO oxide layer, and (iii) formation of secondary phase Mg41Nd5 along the grain boundaries of α-Mg.

Diffusion barrier performance of novel Ti/TaN double layers for Cu metallization

International Nuclear Information System (INIS)

Zhou, Y.M.; He, M.Z.; Xie, Z.

2014-01-01

Highlights: • Novel Ti/TaN double layers offering good stability as a barrier against Cu metallization have been made achievable by annealing in vacuum. • The Ti/TaN double layers improved the adhesion with Cu thin films and showed good diffusion barrier between Cu and SiO 2 /Si up to the annealing condition. • The failure mechanism of Ti/TaN bi-layer is similar with the Cu/TaN/Si metallization system in which Cu atoms diffuse through the grain boundary of barrier and react with silicon to form Cu 3 Si. - Abstract: Novel Ti/TaN double layers offering good stability as a barrier against Cu metallization have been made achievable by annealing in vacuum better than 1 × 10 −3 Pa. Ti/TaN double layers were formed on SiO 2 /Si substrates by DC magnetron sputtering and then the properties of Cu/Ti/TaN/SiO 2 /Si film stacks were studied. It was found that the Ti/TaN double layers provide good diffusion barrier between Cu and SiO 2 /Si up to 750 °C for 30 min. The XRD, Auger and EDS results show that the Cu–Si compounds like Cu 3 Si were formed by Cu diffusion through Ti/TaN barrier for the 800 °C annealed samples. It seems that the improved diffusion barrier property of Cu/Ti/TaN/SiO 2 /Si stack is due to the diffusion of nitrogen along the grain boundaries in Ti layer, which would decrease the defects in Ti film and block the diffusion path for Cu diffusion with increasing annealing temperature. The failure mechanism of Ti/TaN bi-layer is similar to the Cu/TaN/Si metallization system in which Cu atoms diffuse through the grain boundary of barrier and react with silicon to form Cu 3 Si

Thermal barrier coatings with a double-layer bond coat on Ni{sub 3}Al based single-crystal superalloy

Energy Technology Data Exchange (ETDEWEB)

Zhou, Xin [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Beijing Institute of Aeronautical Materials, Department 5, P.O. Box 81-5, Beijing 100095 (China); Xu, Zhenhua; Mu, Rende [Beijing Institute of Aeronautical Materials, Department 5, P.O. Box 81-5, Beijing 100095 (China); He, Limin, E-mail: he_limin@yahoo.com [Beijing Institute of Aeronautical Materials, Department 5, P.O. Box 81-5, Beijing 100095 (China); Huang, Guanghong [Beijing Institute of Aeronautical Materials, Department 5, P.O. Box 81-5, Beijing 100095 (China); Cao, Xueqiang, E-mail: xcao@ciac.ac.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

2014-04-05

Highlights: • Thermal barrier coatings with a double-layer bond coat of (Ni,Pt)Al and NiCrAlYSi. • Good adherence at all interfaces within TBC system. • The underlying (Ni,Pt)Al layer can supply abundant Al content for the upper NiCrAlYSi layer. • Crack nucleation, propagation and coalescence lead to the failure of coating. -- Abstract: Electron-beam physical vapor deposited thermal barrier coatings (TBCs) with a double-layer bond coat of (Ni,Pt)Al and NiCrAlYSi were prepared on a Ni{sub 3}Al based single-crystal superalloy. Phase and cross-sectional microstructure of the developed coatings were studied by using X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The experimental results show good adherence at all interfaces within this system. Furthermore, oxidation resistance and elements interdiffusion behavior of the double-layer bond coat were also investigated. The double-layer bond coat system exhibits a better scale adherence than the single layer bond coat systems since the underlying (Ni,Pt)Al layer can supply abundant Al for the upper NiCrAlYSi layer. Finally, thermal cycling behavior of the double-layer bond coat TBC was evaluated and the failure mechanism was discussed. Crack nucleation, propagation and coalescence caused by TGO growth stress and the thermal expansion mismatch stress between TGO and bond coat can be mainly responsible for the spallation of this coating.

Review of hot corrosion of thermal barrier coatings of gas turbine

Directory of Open Access Journals (Sweden)

LIU Yongbao

2017-03-01

Full Text Available The review was done in order to make clear the problem of the hot corrosion of the Thermal Barrier Coatings(TBCsduring gas turbine serving. This paper summarizes the factors resulting from the hot corrosion of TBCs during turbine service and classifies methods for enhancing the corrosive resistance of TBCs. A prospective methodology for improving corrosion resistance is also formulated. The main types of corrosion coating include phase reaction, oxidizing of the bond coating, salt-fog corrosion, CMAS corrosion and fuel impurity corrosion. So far, methods for improving the corrosion resistance of TBCs include developing new coating materials, anticorrosive treatment on the surface of TBCs, modifying the stacking configuration and improving the cleansing functions of the gas turbines. In the future, developing new materials with excellent performance will still be the main direction for boosting the improvement of the hot corrosion resistance of TBCs. Simultaneously, improving the tacking configuration and nanotechnology of TBC coatings are potential approaches for improving corrosion resistance. With the development of a Ceramic Matrix Composite (CMC, the focus of the hot corrosion of TBCs may turn to that of Environmental Barrier Coatings (EBCs.

Comparison of some coating techniques to fabricate barrier layers on packaging materials

Energy Technology Data Exchange (ETDEWEB)

Hirvikorpi, Terhi, E-mail: terhi.hirvikorpi@vtt.f [VTT Technical Research Centre of Finland, Biologinkuja 7, Espoo, P.O. Box 1000, FI-02044 VTT (Finland); Vaehae-Nissi, Mika, E-mail: mika.vaha-nissi@vtt.f [VTT Technical Research Centre of Finland, Biologinkuja 7, Espoo, P.O. Box 1000, FI-02044 VTT (Finland); Harlin, Ali, E-mail: ali.harlin@vtt.f [VTT Technical Research Centre of Finland, Biologinkuja 7, Espoo, P.O. Box 1000, FI-02044 VTT (Finland); Karppinen, Maarit, E-mail: maarit.karppinen@tkk.f [Laboratory of Inorganic Chemistry, Department of Chemistry, Aalto University School of Science and Technology, Kemistintie 1, P.O. Box 16100, FI-00076 AALTO (Finland)

2010-07-30

Atomic layer deposition (ALD), electron beam evaporation, magnetron sputtering and a sol-gel method were used to deposit thin aluminum oxide coatings onto two different fiber-based packaging materials of commercial board grades coated with synthetic and biodegradable polymers. Significant decreases in both the water vapor and oxygen permeation rates were observed. With each technique the barrier performance was improved. However, among the techniques tested ALD was found to be most suitable. Our results moreover revealed that biodegradable polylactic acid-coated paperboard with a 25-nm thick layer of aluminum oxide grown by ALD on top of it showed promising barrier characteristics against water vapor and oxygen.

Comparison of some coating techniques to fabricate barrier layers on packaging materials

International Nuclear Information System (INIS)

Hirvikorpi, Terhi; Vaehae-Nissi, Mika; Harlin, Ali; Karppinen, Maarit

2010-01-01

Atomic layer deposition (ALD), electron beam evaporation, magnetron sputtering and a sol-gel method were used to deposit thin aluminum oxide coatings onto two different fiber-based packaging materials of commercial board grades coated with synthetic and biodegradable polymers. Significant decreases in both the water vapor and oxygen permeation rates were observed. With each technique the barrier performance was improved. However, among the techniques tested ALD was found to be most suitable. Our results moreover revealed that biodegradable polylactic acid-coated paperboard with a 25-nm thick layer of aluminum oxide grown by ALD on top of it showed promising barrier characteristics against water vapor and oxygen.

Nanocomposite Coatings: Preparation, Characterization, Properties, and Applications

Directory of Open Access Journals (Sweden)

Phuong Nguyen-Tri

2018-01-01

Full Text Available Incorporation of nanofillers into the organic coatings might enhance their barrier performance, by decreasing the porosity and zigzagging the diffusion path for deleterious species. Thus, the coatings containing nanofillers are expected to have significant barrier properties for corrosion protection and reduce the trend for the coating to blister or delaminate. On the other hand, high hardness could be obtained for metallic coatings by producing the hard nanocrystalline phases within a metallic matrix. This article presents a review on recent development of nanocomposite coatings, providing an overview of nanocomposite coatings in various aspects dealing with the classification, preparative method, the nanocomposite coating properties, and characterization methods. It covers potential applications in areas such as the anticorrosion, antiwear, superhydrophobic area, self-cleaning, antifouling/antibacterial area, and electronics. Finally, conclusion and future trends will be also reported.

Deposition stress effects on thermal barrier coating burner rig life

Science.gov (United States)

Watson, J. W.; Levine, S. R.

1984-01-01

A study of the effect of plasma spray processing parameters on the life of a two layer thermal barrier coating was conducted. The ceramic layer was plasma sprayed at plasma arc currents of 900 and 600 amps onto uncooled tubes, cooled tubes, and solid bars of Waspalloy in a lathe with 1 or 8 passes of the plasma gun. These processing changes affected the residual stress state of the coating. When the specimens were tested in a Mach 0.3 cyclic burner rig at 1130 deg C, a wide range of coating lives resulted. Processing factors which reduced the residual stress state in the coating, such as reduced plasma temperature and increased heat dissipation, significantly increased coating life.

Highly conformal SiO2/Al2O3 nanolaminate gas-diffusion barriers for large-area flexible electronics applications

International Nuclear Information System (INIS)

Choi, Jin-Hwan; Kim, Young-Min; Park, Young-Wook; Park, Tae-Hyun; Jeong, Jin-Wook; Choi, Hyun-Ju; Song, Eun-Ho; Ju, Byeong-Kwon; Lee, Jin-Woo; Kim, Cheol-Ho

2010-01-01

The present study demonstrates a flexible gas-diffusion barrier film, containing an SiO 2 /Al 2 O 3 nanolaminate on a plastic substrate. Highly uniform and conformal coatings can be made by alternating the exposure of a flexible polyethersulfone surface to vapors of SiO 2 and Al 2 O 3 , at nanoscale thickness cycles via RF-magnetron sputtering deposition. The calcium degradation test indicates that 24 cycles of a 10/10 nm inorganic bilayer, top-coated by UV-cured resin, greatly enhance the barrier performance, with a permeation rate of 3.79 x 10 -5 g m -2 day -1 based on the change in the ohmic behavior of the calcium sensor at 20 deg. C and 50% relative humidity. Also, the permeation rate for 30 cycles of an 8/8 nm inorganic bilayer coated with UV resin was beyond the limited measurable range of the Ca test at 60 deg. C and 95% relative humidity. It has been found that such laminate films can effectively suppress the void defects of a single inorganic layer, and are significantly less sensitive against moisture permeation. This nanostructure, fabricated by an RF-sputtering process at room temperature, is verified as being useful for highly water-sensitive organic electronics fabricated on plastic substrates.

The Barrier Properties of PET Coated DLC Film Deposited by Microwave Surface-Wave PECVD

Science.gov (United States)

Yin, Lianhua; Chen, Qiang

2017-12-01

In this paper we report the investigation of diamond-like carbon (DLC) deposited by microwave surface-wave plasma enhanced chemical vapor deposition (PECVD) on the polyethylene terephthalate (PET) web for the purpose of the barrier property improvement. In order to characterize the properties of DLC coatings, we used several substrates, silicon wafer, glass, and PET web and KBr tablet. The deposition rate was obtained by surface profiler based on the DLC deposited on glass substrates; Fourier transform infrared spectroscope (FTIR) was carried out on KBr tablets to investigate chemical composition and bonding structure; the morphology of the DLC coating was analyzed by atomic force microscope (AFM) on Si substrates. For the barrier properties of PET webs, we measured the oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) after coated with DLC films. We addressed the film barrier property related to process parameters, such as microwave power and pulse parameter in this work. The results show that the DLC coatings can greatly improve the barrier properties of PET webs.

Thermal Barrier Coatings Resistant to Glassy Deposits

Science.gov (United States)

Drexler, Julie Marie

Engineering of alloys has for years allowed aircraft turbine engines to become more efficient and operate at higher temperatures. As advancements in these alloy systems have become more difficult, ceramic thermal barrier coatings (TBCs), often yttria (7 wt %) stabilized zirconia (7YSZ), have been utilized for thermal protection. TBCs have allowed for higher engine operating temperatures and better fuel efficiency but have also created new engineering problems. Specifically, silica based particles such as sand and volcanic ash that enter the engine during operation form glassy deposits on the TBCs. These deposits can cause the current industrial 7YSZ thermal barrier coatings to fail since the glass formed penetrates and chemically interacts with the TBC. When this occurs, coating failure may occur due to a loss of strain tolerance, which can lead to fracture, and phase changes of the TBC material. There have been several approaches used to stop calcium-magnesium aluminio-silcate (CMAS) glasses (molten sand) from destroying the entire TBC, but overall there is still limited knowledge. In this thesis, 7YSZ and new TBC materials will be examined for thermochemical and thermomechanical performance in the presence of molten CMAS and volcanic ash. Two air plasma sprayed TBCs will be shown to be resistant to volcanic ash and CMAS. The first type of coating is a modified 7YSZ coating with 20 mol% Al2O3 and 5 mol% TiO2 in solid solution (YSZ+20Al+5Ti). The second TBC is made of gadolinium zirconate. These novel TBCs impede CMAS and ash penetration by interacting with the molten CMAS or ash and drastically changing the chemistry. The chemically modified CMAS or ash will crystallize into an apatite or anorthite phase, blocking the CMAS or ash from further destroying the coating. A presented mechanism study will show these coatings are effective due to the large amount of solute (Gd, Al) in the zirconia structure, which is the key to creating the crystalline apatite or

Multilayer TiC/TiN diffusion barrier films for copper

International Nuclear Information System (INIS)

Yoganand, S.N.; Raghuveer, M.S.; Jagannadham, K.; Wu, L.; Karoui, A.; Rozgonyi, G.

2002-01-01

TiC/TiN thin films deposited by reactive magnetron sputtering on Si (100) substrates were investigated by transmission electron microscopy for microstructure and by deep level transient spectroscopy (DLTS) for diffusion barrier against copper. TiN thin films deposited on Si substrates at a substrate temperature of 600 deg. C were textured, and TiC thin films deposited at the same temperature were polycrystalline. TiC/TiN multilayer films also showed the same characteristics with the formation of an additional interaction layer. The diffusion barrier characteristics of the TiC/TiN/Si were determined by DLTS and the results showed that the films completely prevented diffusion of copper into Si

The oxidation behavior of classical thermal barrier coatings exposed to extreme temperature

Directory of Open Access Journals (Sweden)

Alina DRAGOMIRESCU

2017-03-01

Full Text Available Thermal barrier coatings (TBC are designed to protect metal surfaces from extreme temperatures and improve their resistance to oxidation during service. Currently, the most commonly used systems are those that have the TBC structure bond coat (BC / top coat (TC layers. The top coat layer is a ceramic layer. Oxidation tests are designed to identify the dynamics of the thermally oxide layer (TGO growth at the interface of bond coat / top coat layers, delamination mechanism and the TBC structural changes induced by thermal conditions. This paper is a short study on the evolution of aluminum oxide protective layer along with prolonged exposure to the testing temperature. There have been tested rectangular specimens of metal super alloy with four surfaces coated with a duplex thermal barrier coating system. The specimens were microscopically and EDAX analyzed before and after the tests. In order to determine the oxide type, the samples were analyzed using X-ray diffraction. The results of the investigation are encouraging for future studies. The results show a direct relationship between the development of the oxide layer and long exposure to the test temperature. Future research will focus on changing the testing temperature to compare the results.

Robust ultra-thin RuMo alloy film as a seedless Cu diffusion barrier

International Nuclear Information System (INIS)

Hsu, Kuo-Chung; Perng, Dung-Ching; Wang, Yi-Chun

2012-01-01

Highlights: ► A 5 nm-thick Mo added Ru film has been investigated as a Cu diffusion barrier layer. ► RuMo film provides over 175 °C improvement in thermal stability than that of pure Ru layer. ► The 5 nm-thick RuMo film shows excellent barrier performance against Cu diffusion upon 725 °C. - Abstract: This study investigated the properties of 5 nm-thick RuMo film as a Cu diffusion barrier. The sheet resistance variation and X-ray diffraction patterns show that the RuMo alloy film has excellent barrier performance and that it is stable upon annealing at 725 °C against Cu. The transmission electron microscopy micrograph and diffraction patterns show that the RuMo film is an amorphous-like structure, whereas pure Ru film is a nano-crystalline structure. The elements’ depth profiles, analyzed by X-ray photoelectron spectroscopy, indicate no inter-diffusion behavior between the Cu and Si layer, even annealing at 700 °C. Lower leakage current has been achieved from the Cu/barrier/insulator/Si test structure using RuMo film as the barrier layer. A 5 nm ultrathin RuMo film provided two orders of magnitude improvement in leakage current and also exhibited a 175 °C improvement in thermal stability than that of the pure Ru film. It is a potential candidate as a seedless Cu diffusion barrier for advanced Cu interconnects.

Performance Testing of Suspension Plasma Sprayed Thermal Barrier Coatings Produced with Varied Suspension Parameters

Directory of Open Access Journals (Sweden)

Nicholas Curry

2015-07-01

Full Text Available Suspension plasma spraying has become an emerging technology for the production of thermal barrier coatings for the gas turbine industry. Presently, though commercial systems for coating production are available, coatings remain in the development stage. Suitable suspension parameters for coating production remain an outstanding question and the influence of suspension properties on the final coatings is not well known. For this study, a number of suspensions were produced with varied solid loadings, powder size distributions and solvents. Suspensions were sprayed onto superalloy substrates coated with high velocity air fuel (HVAF -sprayed bond coats. Plasma spray parameters were selected to generate columnar structures based on previous experiments and were maintained at constant to discover the influence of the suspension behavior on coating microstructures. Testing of the produced thermal barrier coating (TBC systems has included thermal cyclic fatigue testing and thermal conductivity analysis. Pore size distribution has been characterized by mercury infiltration porosimetry. Results show a strong influence of suspension viscosity and surface tension on the microstructure of the produced coatings.

Dielectric and diffusion barrier multilayer for Cu(In,Ga)Se{sub 2} solar cells integration on stainless steel sheet

Energy Technology Data Exchange (ETDEWEB)

Amouzou, Dodji, E-mail: dodji.amouzou@fundp.ac.be [Research Centre in Physics of Matter and Radiation (PMR), University of Namur (FUNDP), Rue de Bruxelles, 61, 5000 Namur (Belgium); Guaino, Philippe; Fourdrinier, Lionel; Richir, Jean-Baptiste; Maseri, Fabrizio [CRM-Group, Boulevard de Colonster, B 57, 4000 Liège (Belgium); Sporken, Robert [Research Centre in Physics of Matter and Radiation (PMR), University of Namur (FUNDP), Rue de Bruxelles, 61, 5000 Namur (Belgium)

2013-09-02

For the fabrication of monolithically integrated flexible Cu(In, Ga)Se{sub 2}, CIGS modules on stainless steel, individual photovoltaic cells must be insulated from metal substrates by a barrier layer that can sustain high thermal treatments. In this work, a combination of sol–gel (organosilane-sol) and sputtered SiAlxOy forming thin diffusion barrier layers (TDBL) was prepared on stainless steel substrates. The deposition of organosilane-sol dielectric layers on the commercial stainless steel (maximal roughness, Rz = 500 nm and Root Mean Square roughness, RMS = 56 nm) induces a planarization of the surface (RMS = 16.4 nm, Rz = 176 nm). The DC leakage current through the dielectric layers was measured for the metal-insulator-metal (MIM) junctions that act as capacitors. This method allowed us to assess the quality of our TDBL insulating layer and its lateral uniformity. Indeed, evaluating a ratio of the number of valid MIM capacitors to the number of tested MIM capacitors, a yield of ∼ 95% and 50% has been reached respectively with non-annealed and annealed samples based on sol–gel double layers. A yield of 100% was achieved for sol–gel double layers reinforced with a sputtered SiAlxOy coating and a third sol–gel monolayer. Since this yield is obtained on several samples, it can be extrapolated to any substrate size. Furthermore, according to Glow Discharge Optical Emission Spectroscopy and Time of Flight Secondary Ion Mass Spectroscopy measurements, these barrier layers exhibit excellent barrier properties against the diffusion of undesired atoms which could otherwise spoil the electronic and optical properties of CIGS photovoltaic cells. - Highlights: • We functionalize steel for monolithically integrated Cu(In,Ga)Se{sub 2} solar cells • Thin dielectric and diffusion barrier layers (TDDBL) prepared on steel • Reliability and breakdown voltage of dielectric layers have been studied. • Investigation of thermal treatment effect on dielectric

Evaluation of Degradation of Isothermally Aged Plasma-Sprayed Thermal Barrier Coating

Energy Technology Data Exchange (ETDEWEB)

Koo, Jae Mean; Seok, Chang Sung; Kang, Min Sung; Kim, Dae Jin [Sungkyunkwan University, Seoul (Korea, Republic of); Lee, Dong Hoon [HYUNDAI STEEL CO., Incheon (Korea, Republic of); Kim, Mun Young [KPS Gas Turbine Technology Service Center, Seongnam (Korea, Republic of)

2010-04-15

The thermal barrier coating of a gas turbine blade was degraded by isothermal heating in a furnace and by varying the exposure time and temperature. Then, a micro-Vickers hardness test was conducted on the cross section of the bond coat and Ni-based superalloy substrate. Further, the thickness of TGO(Thermally Grown Oxide) was measured by using an image analyzer, and the changes in the microstructure and element contents in the coating were analyzed by using an optical microscope and by performing SEM-EDX analysis. No significant change was observed in the Vickers hardness of the bond coat when the coated specimen was degraded at a high temperature: delamination was observed between the top coat and the bond coat when the coating was degraded for 50 h at a temperature 1,151 .deg. C.

Environmental Barrier Coating Development for SiC/SiC Ceramic Matrix Composites: Recent Advances and Future Directions

Science.gov (United States)

Zhu, Dongming

2016-01-01

This presentation briefly reviews the SiC/SiC major environmental and environment-fatigue degradations encountered in simulated turbine combustion environments, and thus NASA environmental barrier coating system evolution for protecting the SiC/SiC Ceramic Matrix Composites for meeting the engine performance requirements. The presentation will review several generations of NASA EBC materials systems, EBC-CMC component system technologies for SiC/SiC ceramic matrix composite combustors and turbine airfoils, highlighting the temperature capability and durability improvements in simulated engine high heat flux, high pressure, high velocity, and with mechanical creep and fatigue loading conditions. This paper will also focus on the performance requirements and design considerations of environmental barrier coatings for next generation turbine engine applications. The current development emphasis is placed on advanced NASA candidate environmental barrier coating systems for SiC/SiC CMCs, their performance benefits and design limitations in long-term operation and combustion environments. The efforts have been also directed to developing prime-reliant, self-healing 2700F EBC bond coat; and high stability, lower thermal conductivity, and durable EBC top coats. Major technical barriers in developing environmental barrier coating systems, the coating integrations with next generation CMCs having the improved environmental stability, erosion-impact resistance, and long-term fatigue-environment system durability performance will be described. The research and development opportunities for turbine engine environmental barrier coating systems by utilizing improved compositions, state-of-the-art processing methods, and simulated environment testing and durability modeling will be briefly discussed.

A high performance ceria based interdiffusion barrier layer prepared by spin-coating

DEFF Research Database (Denmark)

Plonczak, Pawel; Joost, Mario; Hjelm, Johan

2011-01-01

A multiple spin-coating deposition procedure of Ce0.9Gd0.1O1.95 (CGO) for application in solid oxide fuel cells (SOFCs) was developed. The thin and dense CGO layer can be employed as a barrier layer between yttria stabilised zirconia (YSZ) electrolyte and a (La, Sr)(Co, Fe)O3 based cathode....... The decomposition of the polymer precursor used in the spin-coating process was studied. The depositions were performed on anode supported half cells. By controlling the sintering temperature between each spin-coating process, dense and crack-free CGO films with a thickness of approximately 1 μm were obtained....... The successive steps of dense layer production was investigated by scanning electron microscopy. X-ray diffraction was employed to monitor the crystal structure of the CGO layer sintered at different temperatures. The described spin coated barrier layer was evaluated using an anode supported cell...

Tritium permeation characterization of Al{sub 2}O{sub 3}/FeAl coatings as tritium permeation barriers on 321 type stainless steel containers

Energy Technology Data Exchange (ETDEWEB)

Yang, Feilong; Xiang, Xin; Lu, Guangda; Zhang, Guikai, E-mail: zhangguikai@caep.cn; Tang, Tao; Shi, Yan; Wang, Xiaolin

2016-09-15

Accurate tritium transport properties of prospective tritium permeation barriers (TPBs) are essential to tritium systems in fusion reactors. By passing a temperature and rate-controlled sweeping gas over specimen surfaces to carry the permeated tritium to an ion chamber, the gas-driven permeation of tritium has been performed on 321 type stainless steel containers with Al{sub 2}O{sub 3}/FeAl barriers, to determine the T-permeation resistant performance and mechanism of the barrier. The tritium permeability of the Al{sub 2}O{sub 3}/FeAl coated container was reduced by 3 orders of magnitude at 500–700 °C by contrast with that of the bare one, which meets the requirement of the tritium permeation reduction factor (PRF) of TPBs for tritium operating components in the CN-HCCB TBM. The Al{sub 2}O{sub 3}/FeAl barrier resists the tritium permeation by the diffusion in the bulk substrate at a limited number of defect sites with an effective area and thickness, suggesting that the TPB quality is a very important factor for efficient T-permeation resistance. - Highlights: • T-permeation has been measured on bare and coated type 321 SS containers. • Al{sub 2}O{sub 3}/FeAl coating give a reduction of T-permeability of 3 orders of magnitude. • Mechanism of Al{sub 2}O{sub 3}/FeAl barrier resisting T-permeation has obtained. • Quality of TPB is a very important factor for efficient T-permeating reduction.

A sphingolipid-dependent diffusion barrier confines ER stress to the yeast mother cell

Science.gov (United States)

Clay, Lori; Caudron, Fabrice; Denoth-Lippuner, Annina; Boettcher, Barbara; Buvelot Frei, Stéphanie; Snapp, Erik Lee; Barral, Yves

2014-01-01

In many cell types, lateral diffusion barriers compartmentalize the plasma membrane and, at least in budding yeast, the endoplasmic reticulum (ER). However, the molecular nature of these barriers, their mode of action and their cellular functions are unclear. Here, we show that misfolded proteins of the ER remain confined into the mother compartment of budding yeast cells. Confinement required the formation of a lateral diffusion barrier in the form of a distinct domain of the ER-membrane at the bud neck, in a septin-, Bud1 GTPase- and sphingolipid-dependent manner. The sphingolipids, but not Bud1, also contributed to barrier formation in the outer membrane of the dividing nucleus. Barrier-dependent confinement of ER stress into the mother cell promoted aging. Together, our data clarify the physical nature of lateral diffusion barriers in the ER and establish the role of such barriers in the asymmetric segregation of proteotoxic misfolded proteins during cell division and aging. DOI: http://dx.doi.org/10.7554/eLife.01883.001 PMID:24843009

Evaluation of Defects of Thermal Barrier Coatings by Thermal Shock Test Using Eddy Current Testing

Energy Technology Data Exchange (ETDEWEB)

Heo, Tae Hoon; Cho, Youn Ho; Lee, Joon Hyun [Pusan National University, Busan (Korea, Republic of); Oh, Jeong Seok; Lee, Koo Hyun [KIMM, Daejeon (Korea, Republic of)

2009-10-15

Periodical thermal shock can introduce defects in thermal barrier coating made by layers of CoNiCrAlY bond coating(BC) and ZrO{sub 2}-8wt%Y{sub 2}O{sub 3} ceramic top coating(TC) on Inconel-738 substrate using plasma spraying. Thermal shock test is performed by severe condition that is to heat until 1000 .deg. C and cool until 20 .deg. C. As the number of cycle is increased, the fatigue by thermal shock is also increased. After test, the micro-structures and mechanical characteristics of thermal barrier coating were investigated by SEM, XRD. The TGO layer of is Al{sub 2}O{sub 3} formed between BC and TC by periodical thermal shock test, and its change in thickness is inspected by eddy current test(ECT). By ECT test, it is shown that TGO and micro-crack can be detected and it is possible to predict the life of thermal barrier coating

Microstructure Evolution and Durability of Advanced Environmental Barrier Coating Systems for SiC/SiC Ceramic Matrix Composites

Science.gov (United States)

Zhu, Dongming; Evans, Laura J.; McCue, Terry R.; Harder, Bryan

2016-01-01

Environmental barrier coated SiC-SiC ceramic matrix composites (CMCs) systems will play a crucial role in next generation turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures with improved efficiency, reduce engine weight and cooling requirements. Advanced HfO2 and rare earth silicate environmental barrier coatings (EBCs), along with multicomponent hafnium and rare earth silicide EBC bond coats have been developed. The coating degradation mechanisms in the laboratory simulated engine thermal cycling, and fatigue-creep operating environments are also being investigated. This paper will focus on the microstructural and compositional evolutions of an advanced environmental barrier coating system on a SiC-SiC CMC substrate during the high temperature simulated durability tests, by using a Field Emission Gun Scanning Electron Microscopy, Energy Dispersive Spectroscopy (EDS) and Wavelength Dispersive Spectroscopy (WDS). The effects of Calcium-Magnesium-Alumino-Silicate (CMAS) from road sand or volcano-ash deposits on the degradation mechanisms of the environmental barrier coating systems will also be discussed. The detailed analysis results help understand the EBC-CMC system performance, aiming at the durability improvements to achieve more robust, prime-reliant environmental barrier coatings.

Damage and Performance Assessment of Protective Coatings on Turbine Blades

OpenAIRE

Pokluda, Jaroslav; Kianicová, Marta

2010-01-01

Protective coatings on blades serve as physical barriers between the underlying substrate and the outer environment. This article presents an overview of damage mechanisms leading to failure of all basic types of coatings (diffusion, overlay and thermal barrier) on turbine blades of aircraft engines during service. Although a special emphasize is devoted to destructive effects of thermo-mechanical fatigue and overheating, the severe effects of hot corrosion, oxidation and erosion effects are ...

Evaluation of a Degradation of Thermal Barrier Coating for Gas Turbine Blade

Energy Technology Data Exchange (ETDEWEB)

Kim, Dae Jin; Lee, Dong Hoon; Koo, Jae Mean; Seok, Chang Sung [Sungkyunkwan Univ., Seoul (Korea, Republic of); Kim, Mun Young; Yang, Sung Ho; Park, Sang Yoel [Korea Power Engineering Company, Inc., Yongin (Korea, Republic of)

2007-07-01

Thermal barrier coating system for gas turbine blade were thermally aged by isothermal heating in the furnace varing aging time and temperature. Then, micro Vickers hardness test was done for the cross section of bond coat and Ni-based superalloy substrate. Also, the thickness of TGO was measured by image analyzer and the changes in the microstructure and element distributions in the coating were analyzed by optical microscope and SEM-EDX analysis. No significant changes in the Vickers hardness of the bond coat were observed as the coated specimen was aged at high temperature and delaminations near between top coat and bond coat occurred when the coatings were aged for 50 hr at over 1,151 .deg. C.

Sub-barrier capture with quantum diffusion approach

Directory of Open Access Journals (Sweden)

Scheid W.

2011-10-01

Full Text Available With the quantum diffusion approach the behavior of capture cross sections and mean-square angular momenta of captured systems are revealed in the reactions with deformed and spherical nuclei at sub-barrier energies. With decreasing bombarding energy under the barrier the external turning point of the nucleus-nucleus potential leaves the region of short-range nuclear interaction and action of friction. Because of this change of the regime of interaction, an unexpected enhancement of the capture cross section is found at bombarding energies far below the Coulomb barrier. This effect is shown its worth in the dependence of mean-square angular momentum on the bombarding energy. From the comparison of calculated capture cross sections and experimental capture or fusion cross sections the importance of quasifission near the entrance channel is demonstrated for the actinidebased reactions and reactions with medium-heavy nuclei at extreme sub-barrier energies.

Effect of the top coat on the phase transformation of thermally grown oxide in thermal barrier coatings

Energy Technology Data Exchange (ETDEWEB)

Zhao, X. [Materials Science Centre, School of Materials, University of Manchester, Manchester M1 7HS (United Kingdom); Hashimoto, T. [Materials Science Centre, School of Materials, University of Manchester, Manchester M1 7HS (United Kingdom); Xiao, P. [Materials Science Centre, School of Materials, University of Manchester, Manchester M1 7HS (United Kingdom)]. E-mail: ping.xiao@manchester.ac.uk

2006-12-15

The phase transformation of the thermally grown oxide (TGO) formed on a Pt enriched {gamma} + {gamma}' bond coat in electron beam physical vapour deposited thermal barrier coatings (TBCs) was studied by photo-stimulaluminescence spectroscopy. The presence of the TBC retards the {theta} to {alpha} transformation of the TGO and leads to a higher oxidation rate. The reasons for these phenomena are discussed.

Thermal barrier coatings on gas turbine blades: Chemical vapor deposition (Review)

Science.gov (United States)

Igumenov, I. K.; Aksenov, A. N.

2017-12-01

Schemes are presented for experimental setups (reactors) developed at leading scientific centers connected with the development of technologies for the deposition of coatings using the CVD method: at the Technical University of Braunschweig (Germany), the French Aerospace Research Center, the Materials Research Institute (Tohoku University, Japan) and the National Laboratory Oak Ridge (USA). Conditions and modes for obtaining the coatings with high operational parameters are considered. It is established that the formed thermal barrier coatings do not fundamentally differ in their properties (columnar microstructure, thermocyclic resistance, thermal conductivity coefficient) from standard electron-beam condensates, but the highest growth rates and the perfection of the crystal structure are achieved in the case of plasma-chemical processes and in reactors with additional laser or induction heating of a workpiece. It is shown that CVD reactors can serve as a basis for the development of rational and more advanced technologies for coating gas turbine blades that are not inferior to standard electron-beam plants in terms of the quality of produced coatings and have a much simpler and cheaper structure. The possibility of developing a new technology based on CVD processes for the formation of thermal barrier coatings with high operational parameters is discussed, including a set of requirements for industrial reactors, high-performance sources of vapor precursors, and promising new materials.

Environmental Barrier Coatings for Ceramic Matrix Composites - An Overview

Science.gov (United States)

Lee, Kang; Zhu, Dongming; Wiesner, Valerie Lynn; van Roode, Mark; Kashyap, Tania; Zhu, Dongming; Wiesner, Valerie

2016-01-01

Ceramic Matrix Composites (CMCs) are increasingly being considered as structural materials for advanced power generation equipment. Broadly speaking the two classes of materials are oxide-based CMCs and non-oxide based CMCs. The non-oxide CMCs are primarily silicon-based. Under conditions prevalent in the gas turbine hot section the water vapor formed in the combustion of gaseous or liquid hydrocarbons reacts with the surface-SiO2 to form volatile products. Progressive surface recession of the SiC-SiC CMC component, strength loss as a result of wall thinning and chemical changes in the component occur, which leads to the loss of structural integrity and mechanical strength and becomes life limiting to the equipment in service. The solutions pursued to improve the life of SiC-SiC CMCs include the incorporation of an external barrier coating to provide surface protection to the CMC substrate. The coating system has become known as an Environmental Barrier Coating (EBC). The relevant early coatings work was focused on coatings for corrosion protection of silicon-based monolithic ceramics operating under severely corrosive conditions. The development of EBCs for gas turbine hot section components was built on the early work for silicon-based monolithics. The first generation EBC is a three-layer coating, which in its simplest configuration consists of a silicon (Si) base coat applied on top of the CMC, a barium-strontium-aluminosilicate (BSAS) surface coat resistant to water vapor attack, and a mullite-based intermediate coating layer between the Si base coat and BSAS top coat. This system can be represented as Si-Mullite-BSAS. While this baseline EBC presented a significant improvement over the uncoated SiC-SiC CMC, for the very long durations of 3-4 years or more expected for industrial operation further improvements in coating durability are desirable. Also, for very demanding applications with higher component temperatures but shorter service lives more rugged EBCs

The Development of 2700-3000 F Environmental Barrier Coatings for SiC/SiC Ceramic Matrix Composites: Challenges and Opportunities

Science.gov (United States)

Zhu, Dongming

2015-01-01

Environmental barrier coatings (EBCs) and SiCSiC ceramic matrix composites (CMCs) systems will play a crucial role in future turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures, reduce engine weight and cooling requirements. The development of prime-reliant environmental barrier coatings is a key to enable the applications of the envisioned 2700-3000F EBC - CMC systems to help achieve next generation engine performance and durability goals. This paper will primarily address the performance requirements and design considerations of environmental barrier coatings for turbine engine applications. The emphasis is placed on current NASA candidate environmental barrier coating systems for SiCSiC CMCs, their performance benefits and design limitations in long-term operation and combustion environments. The efforts have been also directed to developing prime-reliant, self-healing 2700F EBC bond coat; and high stability, lower thermal conductivity, and durable EBC top coats. Major technical barriers in developing environmental barrier coating systems, the coating integrations with next generation CMCs having the improved environmental stability, cyclic durability, erosion-impact resistance, and long-term system performance will be described. The research and development opportunities for turbine engine environmental barrier coating systems by utilizing improved compositions, state-of-the-art processing methods, and simulated environment testing and durability modeling will be discussed.

Oxidation and thermal shock behavior of thermal barrier coated 18/10CrNi alloy with coating modifications

Energy Technology Data Exchange (ETDEWEB)

Guergen, Selim [Vocational School of Transportation, Anadolu University, Eskisehir (Turkmenistan); Diltemiz, Seyid Fehmi [Turkish Air Force1st Air Supply and Maintenance Center Command, Eskisehir (Turkmenistan); Kushan, Melih Cemal [Dept. of Mechanical Engineering, Eskisehir Osmangazi University, Eskisehir (Turkmenistan)

2017-01-15

In this study, substrates of 18/10CrNi alloy plates were initially sprayed with a Ni-21Cr-10Al-1Y bond coat and then with an yttria stabilized zirconia top coat by plasma spraying. Subsequently, plasma-sprayed Thermal barrier coatings (TBCs) were treated with two different modification methods, namely, vacuum heat treatment and laser glazing. The effects of modifications on the oxidation and thermal shock behavior of the coatings were evaluated. The effect of coat thickness on the bond strength of the coats was also investigated. Results showed enhancement of the oxidation resistance and thermal shock resistance of TBCs following modifications. Although vacuum heat treatment and laser glazing exhibited comparable results as per oxidation resistance, the former generated the best improvement in the thermal shock resistance of the TBCs. Bond strength also decreased as coat thickness increased.

Stability of tritium permeation prevention barrier with TiC and TiN + TiC coating

International Nuclear Information System (INIS)

Shan Changqi; Chen Qingwang; Dai Shaoxia; Jiang Weisheng

1999-01-01

The stability of tritium permeation prevention barrier of 316L stainless steel with coating TiC and TiN + TiC under the conditions of very large thermal gradient, thermal cycling and plasma irradiation is researched. The research includes two aspects: one is the study on the stability resisting H + plasma irradiation; another is on the ability of two coating materials when they are used in long term under the condition of very large thermal gradient and cycling. The results show that TiC and TiN + TiC composite coating materials, after chemical heat treatment and forming tritium permeation prevention barrier, can resist H + ion irradiation, and also can resist very large thermal gradient and thermal cycling. The long time experiments show that tritium permeation prevention barrier of those coating materials is stable when they are used in long term

Lower-Conductivity Ceramic Materials for Thermal-Barrier Coatings

Science.gov (United States)

Bansal, Narottam P.; Zhu, Dongming

2006-01-01

Doped pyrochlore oxides of a type described below are under consideration as alternative materials for high-temperature thermal-barrier coatings (TBCs). In comparison with partially-yttria-stabilized zirconia (YSZ), which is the state-of-the-art TBC material now in commercial use, these doped pyrochlore oxides exhibit lower thermal conductivities, which could be exploited to obtain the following advantages: For a given difference in temperature between an outer coating surface and the coating/substrate interface, the coating could be thinner. Reductions in coating thicknesses could translate to reductions in weight of hot-section components of turbine engines (e.g., combustor liners, blades, and vanes) to which TBCs are typically applied. For a given coating thickness, the difference in temperature between the outer coating surface and the coating/substrate interface could be greater. For turbine engines, this could translate to higher operating temperatures, with consequent increases in efficiency and reductions in polluting emissions. TBCs are needed because the temperatures in some turbine-engine hot sections exceed the maximum temperatures that the substrate materials (superalloys, Si-based ceramics, and others) can withstand. YSZ TBCs are applied to engine components as thin layers by plasma spraying or electron-beam physical vapor deposition. During operation at higher temperatures, YSZ layers undergo sintering, which increases their thermal conductivities and thereby renders them less effective as TBCs. Moreover, the sintered YSZ TBCs are less tolerant of stress and strain and, hence, are less durable.

Preparation and characterization of enamel coating on pure titanium as a hydrogen penetration barrier

Energy Technology Data Exchange (ETDEWEB)

Tao, Jie, E-mail: taojie@nuaa.edu.cn [College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China); Guo, Xunzhong [College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China); Huang, Zhendong [Graduate School of Human and Environmental Studies, Kyoto University, oshida-Nihonmatsu-Cho, Sakyo-Ku, Kyoto shi 606-8501 (Japan); Liu, Hongbing [Shanghai Aircraft Manufacturing Co,. Ltd, Shanghai 200436 (China); Wang, Tao [College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China)

2013-06-15

Highlights: ► The enamel coating was prepared by spin-coating and enameling method. ► The dense enamel coatings were chemically bonded with TA1 substrate. ► The coatings possessed better thermal shock resistance property. ► The coatings had excellent ball-dropping impact properties. ► The enamel coating exhibited a good barrier effect to hydrogen isotope penetration. -- Abstract: The enamel coating with a thickness of 90–110 × 10{sup −6} m was prepared on TA1 substrate by spin-coating and enameling to solve the problems of hydrogen isotope penetration for commercial pure titanium TA1. The microstructure and the interfacial morphology of the samples were characterized respectively by X-ray diffraction, optical and scanning electron microscopy. The profiles of main elements at the interface were analyzed by EDS line-scanning. The experimental results indicated that the dense enamel coatings were chemically bonded with TA1 substrate, and possessed better thermal shock resistance and ball-dropping impact properties. It was concluded from the results of hydrogen charging test with Vickers microhardness measurement and deuterium penetration experiments that the as-prepared dense enamel coating exhibited a good barrier effect to hydrogen isotope penetration.

A density functional theory study of the carbon-coating effects on lithium iron borate battery electrodes.

Science.gov (United States)

Loftager, Simon; García-Lastra, Juan María; Vegge, Tejs

2017-01-18

Lithium iron borate (LiFeBO 3 ) is a promising cathode material due to its high theoretical specific capacity, inexpensive components and small volume change during operation. Yet, challenges related to severe air- and moisture-induced degradation have prompted the utilization of a protective coating on the electrode which also improves the electronic conductivity. However, not much is known about the preferential geometries of the coating as well as how these coating-electrode interfaces influence the lithium diffusion between the coating and the electrode. Here, we therefore present a density functional theory (DFT) study of the anchoring configurations of carbon coating on the LiFeBO 3 electrode and its implications on the interfacial lithium diffusion. Due to large barriers associated with Li-ion diffusion through a parallel-oriented pristine graphene coating on the FeBO 3 and LiFeBO 3 electrode surfaces, large structural defects in the graphene coating are required for fast Li-ion diffusion. However, such defects are expected to exist only in small concentrations due to their high formation energies. Alternative coating geometries were therefore investigated, and the configuration in which the coating layers were anchored normal to the electrode surface at B and O atoms was found to be most stable. Nudged elastic band (NEB) calculations of the lithium diffusion barriers across the interface between the optimally oriented coating layers and the electrode show no kinetic limitations for lithium extraction and insertion. Additionally, this graphite-coating configuration showed partial blocking of electrode-degrading species.

Diffusion mechanism in molten salt baths during the production of carbide coatings via thermal reactive diffusion

Institute of Scientific and Technical Information of China (English)

Aliakbar Ghadi; Hassan Saghafian; Mansour Soltanieh; Zhi-gang Yang

2017-01-01

The diffusion mechanism of carbide-forming elements from a molten salt bath to a substrate surface was studied in this research, with particular focus on the processes occurring in the molten bath at the time of coating. Metal, oxide, and metal-oxide baths were investi-gated, and the coating process was performed on H13 steel substrates. Scanning electron microscopy and electron-probe microanalysis were used to study the coated samples and the quenched salt bath. The thickness of the carbide coating layer was 6.5 ± 0.5, 5.2 ± 0.5, or 5.7 ± 0.5μm depending on whether it was deposited in a metal, oxide, or metal-oxide bath, respectively. The phase distribution of vanadium-rich regions was 63%, 57%, and 74% of the total coating deposited in metal, oxide, and metal-oxide baths, respectively. The results obtained using the metal bath indicated that undissolved suspended metal particles deposited onto the substrate surface. Then, carbon subsequently diffused to the sub-strate surface and reacted with the metal particles to form the carbides. In the oxide bath, oxide powders dissolved in the bath with or without binding to the oxidative structure (Na2O) of borax; they were then reduced by aluminum and converted into metal particles. We concluded that, in the metal and oxide baths, the deposition of metal particles onto the sample surface is an important step in the formation of the coating.

Thermal Shock Property of Al／Ni-ZrO2 Gradient Thermal Barrier Coatings

Institute of Scientific and Technical Information of China (English)

FANJin-juan; WANGQuan-sheng; ZHANGWei-fang

2004-01-01

Al/Ni-ZrO2 gradient thermal barrier coatings are made on aluminum substrate using plasma spraying method and one direction thermal shock properties of the coatings are studied in this paper. The results show that pores in coatings link to form cracks vertical to coating surface. They go through the whole ZrO2 coating once vertical cracks form. When thermal shock cycles increase, horizontal cracks that result in coatings failure forms in the coatings and interface. And vertical cracks delay appearance of horizontal cracks and enhance thermal shock property of coatings. Failure mechanisms of coating thermal shock are discussed using experiments and finite element method.

Thermal Conductivity Analysis and Lifetime Testing of Suspension Plasma-Sprayed Thermal Barrier Coatings

Directory of Open Access Journals (Sweden)

Nicholas Curry

2014-08-01

Full Text Available Suspension plasma spraying (SPS has become an interesting method for the production of thermal barrier coatings for gas turbine components. The development of the SPS process has led to structures with segmented vertical cracks or column-like structures that can imitate strain-tolerant air plasma spraying (APS or electron beam physical vapor deposition (EB-PVD coatings. Additionally, SPS coatings can have lower thermal conductivity than EB-PVD coatings, while also being easier to produce. The combination of similar or improved properties with a potential for lower production costs makes SPS of great interest to the gas turbine industry. This study compares a number of SPS thermal barrier coatings (TBCs with vertical cracks or column-like structures with the reference of segmented APS coatings. The primary focus has been on lifetime testing of these new coating systems. Samples were tested in thermo-cyclic fatigue at temperatures of 1100 °C for 1 h cycles. Additional testing was performed to assess thermal shock performance and erosion resistance. Thermal conductivity was also assessed for samples in their as-sprayed state, and the microstructures were investigated using SEM.

Durability and CMAS Resistance of Advanced Environmental Barrier Coatings Systems for SiC/SiC Ceramic Matrix Composites

Science.gov (United States)

Zhu, Dongming

2015-01-01

Environmental barrier coatings (EBCs) and SiCSiC ceramic matrix composites (CMCs) systems will play a crucial role in next generation turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures with improved efficiency, reduce engine weight and cooling requirements. This paper will emphasize advanced environmental barrier coating developments for SiCSiC turbine airfoil components, by using advanced coating compositions and processing, in conjunction with mechanical and environment testing and durability validations. The coating-CMC degradations and durability in the laboratory simulated engine fatigue-creep and complex operating environments are being addressed. The effects of Calcium-Magnesium-Alumino-Silicate (CMAS) from road sand or volcano-ash deposits on the degradation mechanisms of the environmental barrier coating systems will be discussed. The results help understand the advanced EBC-CMC system performance, aiming at the durability improvements of more robust, prime-reliant environmental barrier coatings for successful applications of the component technologies and lifing methodologies.

Tritium breeders and tritium permeation barrier coatings for fusion reactor

International Nuclear Information System (INIS)

Yamawaki, Michio; Kawamura, Hiroshi; Tsuchiya, Kunihiko

2004-01-01

A state of R and D of tritium breeders and tritium permeation barrier coatings for fusion reactor is explained. A list of candidate for tritium breeders consists of ceramics containing lithium, for examples, Li 2 O, Li 2 TiO 3 , Li 2 ZrO 3 , Li 4 SiO 4 and LiAlO 2 . The characteristics and form are described. The optimum particle size is from 1 to 10 μm. The production technologies of tritium breeders in the world are stated. Characteristics of ceramics with lithium as tritium breeders are compared. TiC, TiN/TiC, Al 2 O 3 and Cr 2 O 3 -SiO 2 -P 2 O 5 are tritium permeation barrier coating materials. These production methods and evaluation of characteristics are explained. (S.Y.)

Microstructural development in physical vapour-deposited partially stabilized zirconia thermal barrier coatings

Energy Technology Data Exchange (ETDEWEB)

Sohn, Y. H. (Center for Intelligent Processing of Materials, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609-2280 (United States)); Biederman, R.R. (Center for Intelligent Processing of Materials, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609-2280 (United States)); Sisson, R.D. Jr. (Center for Intelligent Processing of Materials, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609-2280 (United States))

1994-10-01

The effects of processing parameters of physical vapour deposition on the microstructure of partially stabilized zirconia (PSZ) thermal barrier coatings have been experimentally investigated. Emphasis has been placed on the crystallographic texture of the PSZ coatings and the microstructure of the top surface of the PSZ coatings as well as the metal-ceramic interface. The variations in the deposition chamber temperature, substrate thickness, substrate rotation and vapour incidence angle resulted in the observation of significant differences in the crystallographic texture and microstructure of the PSZ coatings. ((orig.))

Simulation of thermo-Elastics Properties of Thermal Barrier Coatings ...

African Journals Online (AJOL)

Thermal barrier coatings are used to protect different parts in compressors and turbines from heat. They are generally composed of two layers, one metallic layer providing resistance to heat corrosion and oxidation, and one thermally insulating ceramic layer. Two different techniques are industrially used. Plasma spray ...

Where Diffusion of Clean Technologies and Barriers to Innovation Clash: Application to the Global Diffusion of the Electrical Arc Furnace

Directory of Open Access Journals (Sweden)

José Antonio Moya

2017-01-01

Full Text Available This paper analyses the role of barriers preventing the worldwide take-up of a clean technology: the electrical arc furnace. It also identifies which barriers affect a parameter that summarises the combined effect of all of them. The first step, determination of the combined effect of the barriers, is carried out using a novel approach to model the diffusion of innovations. This new approach is composed only by terms that account for the driver of innovations and the parameter that summarises the effect of barriers. The objective quantification of the effect of barriers in the diffusion of innovations opens up new opportunities for designing policies to overcome the barriers identified as the most relevant, for identifying the effect of existing policies, for relating innovation indicators with those barriers or for better incorporating the effect of barriers in bottom-up models that forecast the technological evolution of the economy.

Plasma Spray and Pack Cementation Process Optimization and Oxidation Behaviour of Novel Multilayered Coatings

Science.gov (United States)

Gao, Feng

The hot section components in gas turbines are subjected to a harsh environment with the temperature being increased continuously. The higher temperature has directly resulted in severe oxidation of these components. Monolithic coatings such as MCrAIY and aluminide have been traditionally used to protect the components from oxidation; however, increased operating temperature quickly deteriorates the coatings due to accelerated diffusion of aluminum in the coatings. To improve the oxidation resistance a group of multilayered coatings are developed in this study. The multilayered coatings consist of a Cr-Si co-deposited layer as the diffusion barrier, a plasma sprayed NiCrA1Y coating as the middle layer and an aluminized top layer. The Cr-Si and aluminized layers are fabricated using pack cementation processes and the NiCrA1Y coatings are produced using the Mettech Axial III(TM) System. All of the coating processes are optimized using the methodology of Design of Experiments (DOE) and the results are analyzed using statistical method. The optimal processes are adopted to fabricate the multilayered coatings for oxidation tests. The coatings are exposed in air at 1050°C and 1150°C for 1000 hr. The results indicate that a Cr layer and a silicon-rich barrier layer have formed on the interface between the Cr-Si coating and the NiCrA1Y coating. This barrier layer not only prevents aluminum and chromium from diffusing into the substrate, but also impedes the diffusion of other elements from the substrate into the coating. The results also reveal that, for optimal oxidation resistance at 1050°C, the top layer in a multilayered coating should have at least Al/Ni ratio of one; whereas the multilayered coating with the All Ni ratio of two in the top layer exhibits the best oxidation resistance at 1150°C. The DOE methodology provides an excellent means for process optimization and the selection of oxidation test matrix, and also offers a more thorough understanding of the

Improvement of Silicide Coating Method as Diffusion Barrier for U-Mo Dispersion Fuel

Energy Technology Data Exchange (ETDEWEB)

Nam, Ji Min; Kim, Sunghwan; Lee, Kyu Hong; Park, Jong Man [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2014-10-15

The excessive interaction between the U-Mo alloys and their surrounding Al matrix lead to excessive local swelling called 'pillowing'. For this reason, KAERI suggested several remedies such as alloying U-Mo with Ti, or Al matrix with Si. In addition, silicide or nitride coatings on the surface of U-Mo particles have also been proposed to hinder the growth of the interaction layer. In this study, centrifugally atomized U-Mo-Ti alloy powders were coated with silicide layers. The coating process was improved when compared to the previous coating in terms of the ball milling and heat treatment conditions. Subsequently, silicide coated U-Mo-Ti powders and pure aluminum powders were mixed and made into a compact for the annealing test. The compacts were annealed at 550 .deg. C for 2hr, and characterized using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). 1. Uniform, homogeneous, thickness controllable silicide layers were successfully coated on the surface of U-7wt%Mo-1wt%Ti powders. 2. U{sub 3}Si, U{sub 3}Si{sub 2} silicide layers formed on the surface of U-7wt%Mo-1wt%Ti powders, and were identified by XRD and EDS analyses.

A chromia forming thermal barrier coating system

Energy Technology Data Exchange (ETDEWEB)

Taylor, M.P.; Evans, H.E. [Metallurgy and Materials, The University of Birmingham, Birmingham, B15 2TT (United Kingdom); Gray, S.; Nicholls, J.R. [Surface Science and Engineering Centre, Cranfield University, Cranfield, MK43 0AL (United Kingdom)

2011-07-15

Conventional thermal barrier coating (TBC) systems consist of an insulating ceramic topcoat, a bond coat for oxidation protection and the underlying superalloy designed to combat the oxidising conditions in aero- and land-based gas turbines. Under high-temperature oxidation, the use of an alumina forming bond coat is warranted, thus all current TBC systems are optimised for the early formation of a dense, protective thermally grown oxide (TGO) of alumina. This also offers protection against Type I hot corrosion but a chromia layer gives better protection against Type II corrosion and intermediate temperatures, the conditions found in land-based gas turbines. In this paper the authors present the first known results for a chromia forming TBC system. Tests have been performed under oxidising conditions, up to 1000 h, at temperatures between 750 C and 900 C, and under Type I (900 C) and Type II (700 C) hot corrosion conditions up to 500 h. Under all these conditions no cracking, spallation or degradation was observed. Examination showed the formation of an adherent, dense chromia TGO at the bond coat / topcoat interface. These initial results are very encouraging and the TGO thicknesses agree well with comparable results reported in the literature. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Next Generation Thermal Barrier Coatings for the Gas Turbine Industry

Science.gov (United States)

Curry, Nicholas; Markocsan, Nicolaie; Li, Xin-Hai; Tricoire, Aurélien; Dorfman, Mitch

2011-01-01

The aim of this study is to develop the next generation of production ready air plasma sprayed thermal barrier coating with a low conductivity and long lifetime. A number of coating architectures were produced using commercially available plasma spray guns. Modifications were made to powder chemistry, including high purity powders, dysprosia stabilized zirconia powders, and powders containing porosity formers. Agglomerated & sintered and homogenized oven spheroidized powder morphologies were used to attain beneficial microstructures. Dual layer coatings were produced using the two powders. Laser flash technique was used to evaluate the thermal conductivity of the coating systems from room temperature to 1200 °C. Tests were performed on as-sprayed samples and samples were heat treated for 100 h at 1150 °C. Thermal conductivity results were correlated to the coating microstructure using image analysis of porosity and cracks. The results show the influence of beneficial porosity on reducing the thermal conductivity of the produced coatings.

Polymeric hydrogen diffusion barrier, high-pressure storage tank so equipped, method of fabricating a storage tank and method of preventing hydrogen diffusion

Science.gov (United States)

Lessing, Paul A [Idaho Falls, ID

2008-07-22

An electrochemically active hydrogen diffusion barrier which comprises an anode layer, a cathode layer, and an intermediate electrolyte layer, which is conductive to protons and substantially impermeable to hydrogen. A catalytic metal present in or adjacent to the anode layer catalyzes an electrochemical reaction that converts any hydrogen that diffuses through the electrolyte layer to protons and electrons. The protons and electrons are transported to the cathode layer and reacted to form hydrogen. The hydrogen diffusion barrier is applied to a polymeric substrate used in a storage tank to store hydrogen under high pressure. A storage tank equipped with the electrochemically active hydrogen diffusion barrier, a method of fabricating the storage tank, and a method of preventing hydrogen from diffusing out of a storage tank are also disclosed.

Microstructural effect on radiative scattering coefficient and asymmetry factor of anisotropic thermal barrier coatings

Science.gov (United States)

Chen, X. W.; Zhao, C. Y.; Wang, B. X.

2018-05-01

Thermal barrier coatings are common porous materials coated on the surface of devices operating under high temperatures and designed for heat insulation. This study presents a comprehensive investigation on the microstructural effect on radiative scattering coefficient and asymmetry factor of anisotropic thermal barrier coatings. Based on the quartet structure generation set algorithm, the finite-difference-time-domain method is applied to calculate angular scattering intensity distribution of complicated random microstructure, which takes wave nature into account. Combining Monte Carlo method with Particle Swarm Optimization, asymmetry factor, scattering coefficient and absorption coefficient are retrieved simultaneously. The retrieved radiative properties are identified with the angular scattering intensity distribution under different pore shapes, which takes dependent scattering and anisotropic pore shape into account implicitly. It has been found that microstructure significantly affects the radiative properties in thermal barrier coatings. Compared with spherical shape, irregular anisotropic pore shape reduces the forward scattering peak. The method used in this paper can also be applied to other porous media, which designs a frame work for further quantitative study on porous media.

Method of coating the interior surface of hollow objects with a diffusion coating

Science.gov (United States)

Knowles, Shawn D.; Senor, David J.; Forbes, Steven V.; Johnson, Roger N.; Hollenberg, Glenn W.

2005-03-15

A method for forming a diffusion coating on the interior of surface of a hollow object wherein a filament, extending through a hollow object and adjacent to the interior surface of the object, is provided, with a coating material, in a vacuum. An electrical current is then applied to the filament to resistively heat the filament to a temperature sufficient to transfer the coating material from the filament to the interior surface of the object. The filament is electrically isolated from the object while the filament is being resistively heated. Preferably, the filament is provided as a tungsten filament or molybdenum filament. Preferably, the coating materials are selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Ge, Hg, In, K, Li, Mg, Mn, Na, Ni P, Pb, Pd, Pr, S, Sb, Sc, Se, Si, Sn, Sr, Te, Tl, Y, Yb, Zn, and combinations thereof. The invention additionally allows for the formation of nitrides, hydrides, or carbides of all the possible coating materials, where such compounds exist, by providing a partial pressure of nitrogen, hydrogen, hydrocarbons, or combination thereof, within the vacuum.

Mechanical Properties and Durability of Advanced Environmental Barrier Coatings in Calcium-Magnesium-Alumino-Silicate Environments

Science.gov (United States)

Miladinovich, Daniel S.; Zhu, Dongming

2011-01-01

Environmental barrier coatings are being developed and tested for use with SiC/SiC ceramic matrix composite (CMC) gas turbine engine components. Several oxide and silicate based compositons are being studied for use as top-coat and intermediate layers in a three or more layer environmental barrier coating system. Specifically, the room temperature Vickers-indentation-fracture-toughness testing and high-temperature stability reaction studies with Calcium Magnesium Alumino-Silicate (CMAS or "sand") are being conducted using advanced testing techniques such as high pressure burner rig tests as well as high heat flux laser tests.

Chemical vapor deposition of refractory ternary nitrides for advanced diffusion barriers

Energy Technology Data Exchange (ETDEWEB)

Custer, Jonathan S.; Fleming, James G.; Roherty-Osmun, Elizabeth; Smith, Paul Martin

1998-09-22

Refractory ternary nitride films for diffusion barriers in microelectronics have been grown using chemical vapor deposition. Thin films of titanium-silicon-nitride, tungsten-boron-nitride, and tungsten-silicon-nitride of various compositions have been deposited on 150 mm Si wafers. The microstructure of the films are either fully amorphous for the tungsten based films, or nauocrystalline TiN in an amorphous matrix for titanium-silicon-nitride. All films exhibit step coverages suitable for use in future microelectronics generations. Selected films have been tested as diffusion barriers between copper and silicon, and generally perform extremely weH. These fiIms are promising candidates for advanced diffusion barriers for microelectronics applications. The manufacturing of silicon wafers into integrated circuits uses many different process and materials. The manufacturing process is usually divided into two parts: the front end of line (FEOL) and the back end of line (BEOL). In the FEOL the individual transistors that are the heart of an integrated circuit are made on the silicon wafer. The responsibility of the BEOL is to wire all the transistors together to make a complete circuit. The transistors are fabricated in the silicon itself. The wiring is made out of metal, currently aluminum and tungsten, insulated by silicon dioxide, see Figure 1. Unfortunately, silicon will diffuse into aluminum, causing aluminum spiking of junctions, killing transistors. Similarly, during chemical vapor deposition (CVD) of tungsten from ~fj, the reactivity of the fluorine can cause "worn-holes" in the silicon, also destroying transistors. The solution to these problems is a so-called diffusion barrier, which will allow current to pass from the transistors to the wiring, but will prevent reactions between silicon and the metal.

High temperature oxidation behavior of hafnium modified NiAl bond coat in EB-PVD thermal barrier coating system

Energy Technology Data Exchange (ETDEWEB)

Guo Hongbo; Sun Lidong; Li Hefei [Department of Material Science and Engineering, Beijing University of Aeronautics and Astronautics, No.37 Xueyuan Road, Beijing 100083 (China); Gong Shengkai [Department of Material Science and Engineering, Beijing University of Aeronautics and Astronautics, No.37 Xueyuan Road, Beijing 100083 (China)], E-mail: gongsk@buaa.edu.cn

2008-06-30

NiAl coatings doped with 0.5 at.% and 1.5 at.% Hf were produced by co-evaporation of NiAl and Hf ingots by electron beam physical vapor deposition (EB-PVD), respectively. The addition of 0.5 at.% Hf significantly improved the cyclic oxidation resistance of the NiAl coating. The TGO layer in the 1.5 at.% Hf doped NiAl coating is straight; while that in the 0.5 at.% Hf doped coating became undulated after thermal cycling. The doped NiAl thermal barrier coatings (TBCs) revealed improved thermal cycling lifetimes at 1423 K, compared to the undoped TBC. Failure of the 0.5 at.% Hf doped TBC occurred by cracking at the interface between YSZ topcoat and bond coat, while the 1.5 at.% Hf doped TBC cracked at the interface between bond coat and substrate.

Effect of diffuse roof cover with anti-reflection coating for roses; Effect van diffuus kasdek met Anti Reflectie coating bij Roos

Energy Technology Data Exchange (ETDEWEB)

Garcia Victoria, N.; Kempkes, F.

2012-10-15

The rose Red Naomi was cultivated in two greenhouses at Wageningen UR Greenhouse Horticulture in Bleiswijk, Netherlands (August 2010 - September 2011). One greenhouse covered with normal float glass; the other with AR coated diffuse glass (70% haze). This Anti-Reflection coating on both glass sides compensated for the loss in light transmission caused by the diffusing structure in the glass. The diffuse AR glass lead to a 5.2% higher production (>6.1% fresh weight). Sunscreens were necessary in spring and summer to avoid high light levels on the flower buds, as they cause very high bud temperatures leading to quality problems (blue petal edges and burnt leaf tips). The diffuse greenhouse cover allowed a 100 W/m{sup 2} higher screening threshold than the reference glass. This caused a 2.7% higher daily light integral, able to explain part of the extra production obtained. Part of the extra production achieved can not be explained by the measured factors as no differences were found in the amount of light intercepted by the crop or in leaf photosynthesis under both cover types. The light under the diffuse AR cover was nevertheless much smoother, so the crop seemed to suffer less (lower bud temperatures and less burned leaf tips), and this should provide an explanation for the rest of the extra production. The cover properties did not influence disease development (powdery mildew). The obtained extra production makes the tempered, diffuse glass with Anti Reflection coating on both sides economically feasible [Dutch] Tussen augustus 2010 en september 2011 is bij Wageningen UR Glastuinbouw het effect van diffuus glas, met dubbelzijdige AR coating, op de productie en energiegebruik van roos 'Red Naomi' onderzocht. Onder het diffuse glas werden 5,2% meer bloemtakken geproduceerd, deze rozen waren ook iets langer en zwaarder (6,1% meer versgewicht). Dit verschil kan deels verklaard worden doordat er onder het diffuse glas pas bij hogere stralingsniveau

Microstructure of oxides in thermal barrier coatings grown under dry/humid atmosphere

International Nuclear Information System (INIS)

Zhou Zhaohui; Guo Hongbo; Wang Juan; Abbas, Musharaf; Gong Shengkai

2011-01-01

Graphical abstract: The presence of water vapor promoted the formation of spinels in the TBC. Highlights: → Thermal barrier coatings are produced by electron beam physical vapour deposition. → Oxidation behaviour of the coatings at 1100 deg. C has been investigated in dry/humid O 2 . → Thermally grown oxides formed in the coatings are characterized. → The presence of water vapour promotes the formation of spinel in the TBCs. - Abstract: The microstructure of thermally grown oxide (TGO) in thermal barrier coatings (TBCs) oxidized under dry/humid atmosphere at 1100 deg. C has been characterized by transmission electron microscopy. A thin and continuous oxide layer is formed in the as-deposited TBCs produced by electron beam physical vapor deposition. The TGO formed in dry atmosphere consists of an outer layer of fine α-alumina, zirconia grains and an inner layer of columnar α-alumina grains. However, a small amount of spinel is observed in the TGO under humid atmosphere. The presence of water vapour promotes the formation of spinel.

Migration mechanisms and diffusion barriers of vacancies in Ga2O3

Science.gov (United States)

Kyrtsos, Alexandros; Matsubara, Masahiko; Bellotti, Enrico

2017-06-01

We employ the nudged elastic band and the dimer methods within the standard density functional theory (DFT) formalism to study the migration of the oxygen and gallium vacancies in the monoclinic structure of β -Ga2O3 . We identify all the first nearest neighbor paths and calculate the migration barriers for the diffusion of the oxygen and gallium vacancies. We also identify the metastable sites of the gallium vacancies which are critical for the diffusion of the gallium atoms. The migration barriers for the diffusion of the gallium vacancies are lower than the migration barriers for oxygen vacancies by 1 eV on average, suggesting that the gallium vacancies are mobile at lower temperatures. Using the calculated migration barriers we estimate the annealing temperature of these defects within the harmonic transition state theory formalism, finding excellent agreement with the observed experimental annealing temperatures. Finally, we suggest the existence of percolation paths which enable the migration of the species without utilizing all the migration paths of the crystal.

The diffusion permeability to water of the rat blood-brain barrier

DEFF Research Database (Denmark)

Bolwig, T G; Lassen, N A

1975-01-01

The diffusion permeability to water of the rat blood-brain-barrier (BBB) was studied. Preliminary data obtained with the Oldendorf tissue uptake method (Oldendorf 1970) in seizure experiments suggested that the transfer from blood to brain of labelled water is diffusion-limited. More definite...... passage increased from 0.26 to 0.67 when the arterial carbon dioxide tension was changed from 15 to 85 mm Hg, a change increasing the cerebral blood flow about sixfold. This finding suggests that water does not pass the blood-brain barrier as freely as lipophilic gases....

Phase Stability and Thermal Conductivity of Composite Environmental Barrier Coatings on SiC/SiC Ceramic Matrix Composites

Science.gov (United States)

Benkel, Samantha; Zhu, Dongming

2011-01-01

Advanced environmental barrier coatings are being developed to protect SiC/SiC ceramic matrix composites in harsh combustion environments. The current coating development emphasis has been placed on the significantly improved cyclic durability and combustion environment stability in high-heat-flux and high velocity gas turbine engine environments. Environmental barrier coating systems based on hafnia (HfO2) and ytterbium silicate, HfO2-Si nano-composite bond coat systems have been processed and their stability and thermal conductivity behavior have been evaluated in simulated turbine environments. The incorporation of Silicon Carbide Nanotubes (SiCNT) into high stability (HfO2) and/or HfO2-silicon composite bond coats, along with ZrO2, HfO2 and rare earth silicate composite top coat systems, showed promise as excellent environmental barriers to protect the SiC/SiC ceramic matrix composites.

Atomic diffusion induced degradation in bimetallic layer coated cemented tungsten carbide

International Nuclear Information System (INIS)

Peng, Zirong; Rohwerder, Michael; Choi, Pyuck-Pa; Gault, Baptiste; Meiners, Thorsten; Friedrichs, Marcel; Kreilkamp, Holger; Klocke, Fritz; Raabe, Dierk

2017-01-01

Highlights: • We study the temporal degradation of PtIr/Cr/WC and PtIr/Ni/WC systems. • Short cut diffusion, segregation, oxidation and interdiffusion reactions occurred. • Outward diffusion of Cr (Ni) via PtIr grain boundaries triggered the degradation. • The microstructure of the PtIr layer controlled the systems stability. • We propose an atomic diffusion induced degradation mechanism. - Abstract: We investigated the temporal degradation of glass moulding dies, made of cemented tungsten carbide coated with PtIr on an adhesive Cr or Ni interlayer, by electron microscopy and atom probe tomography. During the exposure treatments at 630 °C under an oxygen partial pressure of 1.12 × 10"−"2"3 bar, Cr (Ni) was found to diffuse outwards via grain boundaries in the PtIr, altering the surface morphology. Upon dissolution of the interlayer, the WC substrate also started degrading. Extensive interdiffusion processes involving PtIr, Cr (Ni) and WC took place, leading to the formation of intermetallic phases and voids, deteriorating the adhesion of the coating.

Optimization of High Porosity Thermal Barrier Coatings Generated with a Porosity Former

Czech Academy of Sciences Publication Activity Database

Medřický, J.; Curry, N.; Pala, Zdeněk; Vilémová, Monika; Chráska, Tomáš; Johansson, J.; Markocsan, N.

2015-01-01

Roč. 24, č. 4 (2015), s. 622-628 ISSN 1059-9630 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61389021 Keywords : gas turbine s * high temperature application * porosity of coatings * stabilized zirconia * thermal barrier coatings (TBCs) Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 1.568, year: 2015

FAILURE MECHANISMS OF THERMAL BARRIER COATINGS INTERNAL COMBUSTION ENGINES AND llMPROVEMENTS

Directory of Open Access Journals (Sweden)

ADNAN PARLAK

2003-04-01

Full Text Available MechanicaJ properties of high performance ceramics have been improved to the point where their use in heat engines is possible. The high temperature strength and low thermal expansion properties of bigh performance ceramics offer an advantage over metals in the development of non-water cooling engine. However, because bard environment in diesel engine combustion chamber, solving the problem of durabiUty of TBC is important. DurabiUty of thermal barrier coatings(TBC is liınited by two main failure mechanisms: Therınal expansion nlİsmatch betwcen bond coat and top coat and bond coat oxidation. Both of these can cause failure of the ceramic top coat. Developments of recent years sholv that bond coats \\Vith higher oxidation resistance tend to have better coating system cyclic lives

Oscillatory shear response of moisture barrier coatings containing clay of different shape factor.

Science.gov (United States)

Kugge, C; Vanderhoek, N; Bousfield, D W

2011-06-01

Oscillatory shear rheology of barrier coatings based on dispersed styrene-butadiene latex and clay of various shape factors or aspect ratio has been explored. Barrier performance of these coatings when applied to paperboard has been assessed in terms of water vapour transmission rates and the results related to shape factor, dewatering and critical strain. It has been shown that a system based on clay with high shape factor gives a lower critical strain, dewatering and water vapour transmission rate compared with clays of lower shape factor. The dissipated energy, as calculated from an amplitude sweep, indicated no attractive interaction between clay and latex implying a critical strain that appears to be solely dependent on the shape factor at a constant volume fraction. Particle size distribution was shown to have no effect on the critical strain while coatings of high elasticity exhibited high yield strains as expected. The loss modulus demonstrated strain hardening before the elastic to viscous transition. The loss modulus peak was identified by a maximum strain which was significantly lower for a coating based on clay with a high shape factor. The characteristic elastic time was found to vary between 0.6 and 1.3s. The zero shear viscosity of barrier dispersion coatings were estimated from the characteristic elastic time and the characteristic modulus to be of the order of 25-100 Pa s. Copyright © 2011 Elsevier Inc. All rights reserved.

Evaluation of properties and thermal stress field for thermal barrier coatings

Institute of Scientific and Technical Information of China (English)

王良; 齐红宇; 杨晓光; 李旭

2008-01-01

In order to get thermal stress field of the hot section with thermal barrier coating (TBCs), the thermal conductivity and elastic modulus of top-coat are the physical key properties. The porosity of top-coat was tested and evaluated under different high temperatures. The relationship between the microstructure (porosity of top-coat) and properties of TBCs were analyzed to predict the thermal properties of ceramic top-coat, such as thermal conductivity and elastic modulus. The temperature and stress field of the vane with TBCs were simulated using two sets of thermal conductivity data and elastic modulus, which are from literatures and this work, respectively. The results show that the temperature and stress distributions change with thermal conductivity and elastic modulus. The differences of maximum temperatures and stress are 6.5% and 8.0%, respectively.

Durability and Design Issues of Thermal/environmental Barrier Coatings on Sic/sic Ceramic Matrix Composites Under 1650 C Test Conditions

Science.gov (United States)

Zhu, Dong-Ming; Choi, Sung R.; Ghosn, Louis J.; Miller, Robert A.

2004-01-01

Ceramic thermal/environmental barrier coatings for SiC-based ceramics will play an increasingly important role in future gas turbine engines because of their ability to effectively protect the engine components and further raise engine temperatures. However, the coating durability remains a major concern with the ever-increasing temperature requirements. Currently, advanced T/EBC systems, which typically include a high temperature capable zirconia- (or hahia-) based oxide top coat (thermal barrier) on a less temperature capable mullite/barium-strontium-aluminosilicate (BSAS)/Si inner coat (environmental barrier), are being developed and tested for higher temperature capability Sic combustor applications. In this paper, durability of several thermal/environmental barrier coating systems on SiC/SiC ceramic matrix composites was investigated under laser simulated engine thermal gradient cyclic, and 1650 C (3000 F) test conditions. The coating cracking and delamination processes were monitored and evaluated. The effects of temperature gradients and coating configurations on the ceramic coating crack initiation and propagation were analyzed using finite element analysis (FEA) models based on the observed failure mechanisms, in conjunction with mechanical testing results. The environmental effects on the coating durability will be discussed. The coating design approach will also be presented.

Thermal fatigue behavior of thermal barrier coatings by air plasma spray

Energy Technology Data Exchange (ETDEWEB)

Lee, Han Sang; Kim, Eui Hyun [Korea Electric Power Research Institute, Daejeon (Korea, Republic of); Lee, Jung Hyuk [Korea Plant Service and Engineering Co. Ltd., Incheon (Korea, Republic of)

2008-06-15

Effects of top coat morphology and thickness on thermal fatigue behavior of Thermal Barrier Coatings (TBC) were investigated in this study. Thermal fatigue tests were conducted on three coating specimens with different top coat morphology and thickness, and then the test data were compared via microstructures, cycles to failure, and fracture surfaces. In the air plasma spray specimens (APS1, APS2), top coat were 200 and 300 {mu}m respectively. The thickness of top coat was about 700 {mu}m in the Perpendicular Cracked Specimen (PCS). Under thermal fatigue condition at 1,100 .deg. C, the cycles to top coat failure of APS1, APS2, and PCS were 350, 560 and 480 cycles, respectively. The cracks were initiated at the interface of top coat and Thermally Grown Oxide (TGO) and propagated into TGO or top coat as the number of thermal fatigue cycles increased. For the PCS specimen, additive cracks were initiated and propagated at the starting points of perpendicular cracks in the top coat. Also, the thickness of TGO and the decrease of aluminium concentration in bond coat do not affect the cycles to failure.

Graphene Oxide Bionanocomposite Coatings with High Oxygen Barrier Properties

Directory of Open Access Journals (Sweden)

Ilke Uysal Unalan

2016-12-01

Full Text Available In this work, we present the development of bionanocomposite coatings on poly(ethylene terephthalate (PET with outstanding oxygen barrier properties. Pullulan and graphene oxide (GO were used as main polymer phase and nanobuilding block (NBB, respectively. The oxygen barrier performance was investigated at different filler volume fractions (ϕ and as a function of different relative humidity (RH values. Noticeably, the impermeable nature of GO was reflected under dry conditions, in which an oxygen transmission rate (OTR, mL·m−2·24 h−1 value below the detection limit of the instrument (0.01 mL·m−2·24 h−1 was recorded, even for ϕ as low as 0.0004. A dramatic increase of the OTR values occurred in humid conditions, such that the barrier performance was totally lost at 90% RH (the OTR of coated PET films was equal to the OTR of bare PET films. Modelling of the experimental OTR data by Cussler’s model suggested that the spatial ordering of GO sheets within the main pullulan phase was perturbed because of RH fluctuations. In spite of the presence of the filler, all the formulations allowed the obtainment of final materials with haze values below 3%, the only exception being the formulation with the highest loading of GO (ϕ ≈ 0.03. The mechanisms underlying the experimental observations are discussed.

Combined Thermomechanical and Environmental Durability of Environmental Barrier Coating Systems on SiC/SiC Ceramic Matrix Composites

Science.gov (United States)

Zhu, Dongming; Harder, Bryan; Bhatt, Ramakrishna

2016-01-01

Environmental barrier coatings (EBCs) and SiC/SiC ceramic matrix composites (CMCs) will play a crucial role in next generation turbine engines for hot-section component applications. The development of prime-reliant environmental barrier coatings is essential to the EBC-CMC system durability, ensuring the successful implementations of the high temperature and lightweight engine component technologies for engine applications.This paper will emphasize recent NASA environmental barrier coating and CMC developments for SiC/SiC turbine airfoil components, utilizing advanced coating compositions and processing methods. The emphasis has been particularly placed on thermomechanical and environment durability evaluations of EBC-CMC systems. We have also addressed the integration of the EBCs with advanced SiC/SiC CMCs, and studied the effects of combustion environments and Calcium-Magnesium-Alumino-Silicate (CMAS) deposits on the durability of the EBC-CMC systems under thermal gradient and mechanical loading conditions. Advanced environmental barrier coating systems, including multicomponent rare earth silicate EBCs and HfO2-Si based bond coats, will be discussed for the performance improvements to achieve better temperature capability and CMAS resistance for future engine operating conditions.

A Study on Silicide Coatings as Diffusion barrier for U-7Mo Dispersion Fuel

Energy Technology Data Exchange (ETDEWEB)

Won, Ju Jin; Kim, Sung Hwan; Lee, Kyu Hong; Jeong, Yong Jin; Kim, Ki Nam; Park, Jong Man; Lee, Chong Tak [KAERI, Daejeon (Korea, Republic of)

2016-05-15

Gamma phase U-Mo alloys are regarded as one of the promising candidates for advanced research reactor fuel when it comes to the irradiation performance. However, it has been reported that interaction layer formation between the UMo alloys and Al matrix degrades the irradiation performance of U-Mo dispersion fuel. The excessive interaction between the U-Mo alloys and their surrounding Al matrix lead to excessive local swelling called 'pillowing'. For this reason, KAERI suggested several remedies such as alloying U-Mo with Al matrix with Si. In addition, silicide or nitride coatings on the surface of U-Mo particles have also been proposed to hinder the growth of the interaction layer. In this study, centrifugally atomized U-7Mo alloy powders were coated with silicide layers at 900 .deg. C for 1hr. U-Mo alloy powder was mixed with MoSi{sub 2}, Si and ZrSi{sub 2} powders and subsequently heat-treated to form uranium-silicide coating layers on the surface of U-Mo alloy particles. Silicide coated U-Mo powders and characterized using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS) and X-ray diffractometer (XRD). The ZrSi{sub 2} coating layers has a thickness of about 1∼ 2μm. The surface of a silicide coated particle was very rough and silicide powder attached to the surface of the coating layer. 3. The XRD analysis of the coating layers showed that, they consisted of compounds such as U3Si{sub 2}, USi{sub 2}.

Robust Superhydrophobic Graphene-Based Composite Coatings with Self-Cleaning and Corrosion Barrier Properties.

Science.gov (United States)

Nine, Md J; Cole, Martin A; Johnson, Lucas; Tran, Diana N H; Losic, Dusan

2015-12-30

Superhydrophobic surfaces for self-cleaning applications often suffer from mechanical instability and do not function well after abrasion/scratching. To address this problem, we present a method to prepare graphene-based superhydrophobic composite coatings with robust mechanical strength, self-cleaning, and barrier properties. A suspension has been formulated that contains a mixture of reduced graphene oxide (rGO) and diatomaceous earth (DE) modified with polydimethylsiloxane (PDMS) that can be applied on any surface using common coating methods such as spraying, brush painting, and dip coating. Inclusion of TiO2 nanoparticles to the formulation shows further increase in water contact angle (WCA) from 159 ± 2° to 170 ± 2° due to the structural improvement with hierarchical surface roughness. Mechanical stability and durability of the coatings has been achieved by using a commercial adhesive to bond the superhydrophobic "paint" to various substrates. Excellent retention of superhydrophobicity was observed even after sandpaper abrasion and crosscut scratching. A potentiodynamic polarization study revealed excellent corrosion resistance (96.78%) properties, and an acid was used to provide further insight into coating barrier properties. The ease of application and remarkable properties of this graphene-based composite coating show considerable potential for broad application as a self-cleaning and protective layer.

CONTRIBUTION OF QUADRATIC RESIDUE DIFFUSERS TO EFFICIENCY OF TILTED PROFILE PARALLEL HIGHWAY NOISE BARRIERS

Directory of Open Access Journals (Sweden)

M. R. Monazzam ، P. Nassiri

2009-10-01

Full Text Available This paper presents the results of an investigation on the acoustic performance of tilted profile parallel barriers with quadratic residue diffuser (QRD tops and faces. A 2D boundary element method (BEM is used to predict the barrier insertion loss. The results of rigid and with absorptive coverage are also calculated for comparisons. Using QRD on the top surface and faces of all tilted profile parallel barrier models introduced here is found to improve the efficiency of barriers compared with rigid equivalent parallel barrier at the examined receiver positions. Applying a QRD with frequency design of 400 Hz on 5 degrees tilted parallel barrier improves the overall performance of its equivalent rigid barrier by 1.8 dB(A. Increase in the treated surfaces with reactive elements shifts the effective performance toward lower frequencies. It is found that by tilting the barriers from 0 to 10 degrees in parallel set up, the degradation effects in parallel barriers is reduced but the absorption effect of fibrous materials and also diffusivity of the quadratic residue diffuser is reduced significantly. In this case all the designed barriers have better performance with 10 degrees tilting in parallel set up. The most economic traffic noise parallel barrier which produces significantly high performance, is achieved by covering the top surface of the barrier closed to the receiver by just a QRD with frequency design of 400 Hz and tilting angle of 10 degrees. The average A-weighted insertion loss in this barrier is predicted to be 16.3 dB (A.

Deposition and characterization of plasma sprayed Ni-5A1/ magnesia stabilized zirconia based functionally graded thermal barrier coating

International Nuclear Information System (INIS)

Baig, M N; Khalid, F A

2014-01-01

Thermal barrier coatings (TBCs) are employed to protect hot section components in industrial and aerospace gas turbine engines. Conventional TBCs frequently fail due to high residual stresses and difference between coefficient of thermal expansion (CTE) of the substrate and coatings. Functionally graded thermal barrier coatings (FG-TBCs) with gradual variation in composition have been proposed to minimize the problem. In this work, a five layered functionally graded thermal barrier coating system was deposited by atmospheric plasma spray (APS) technique on Nimonic 90 substrates using Ni-5Al as bond coat (BC) and magnesia stabilized zirconia as top coat (TC). The coatings were characterized by SEM, EDS, XRD and optical profilometer. Microhardness and coefficient of thermal expansion of the five layers deposited as individual coatings were also measured. The deposited coating system was oxidized at 800°C. SEM analysis showed that five layers were successfully deposited by APS to produce a FG-TBC. The results also showed that roughness (Ra) of the individual layers decreased with an increase in TC content in the coatings. It was found that microhardness and CTE values gradually changed from bond coat to cermet layers to top coat. The oxidized coated sample revealed parabolic behavior and changes in the surface morphology and composition of coating

Production of Transitional Diffused Layers by Electrospark Coating

Science.gov (United States)

Smolentsev, Vladislav P.; Boldyrev, Alexander I.; Smolentsev, Evgeniy V.; Boldyrev, Alexander A.; Mozgalin, Vladislav L.

2018-03-01

The article presents a new method for production of diffused transitional layers with nano- and microthickness by local removal of nanofilms on aluminum alloys. This allows procuring of high-quality coatings on fusible alloys (for example, on aluminum ones) by materials, the melting point of which is 2-3 times higher than that of the basis (for example, of cast iron). This permits imparting new useful properties to workpieces made from light alloys with decent values for electrochemical working. The authors show that application of coatings provides minimum heating of workpieces. This enables the regulation in temperature condition of operating environment and permits efficiency improving during the process of electrochemical working by means of higher density current supply.

Polymer-Derived Ceramics as Innovative Oxidation Barrier Coatings for Mo-Si-B Alloys

Science.gov (United States)

Hasemann, Georg; Baumann, Torben; Dieck, Sebastian; Rannabauer, Stefan; Krüger, Manja

2015-04-01

A preceramic polymer precursor, perhydropolysilazane, is used to investigate its function as a new type of oxidation barrier coating on Mo-Si-B alloys. After dip-coating and pyrolysis at 1073 K (800 °C), dense and well-adhering SiON ceramic coatings could be achieved, which were investigated by SEM and cyclic oxidation tests at 1073 K and 1373 K (800 °C and 1100 °C). The coating is promising in reducing the mass loss during the initial stage of oxidation exposure at 1373 K (1100 °C) significantly.

Creep Behavior of Hafnia and Ytterbium Silicate Environmental Barrier Coating Systems on SiC/SiC Ceramic Matrix Composites

Science.gov (United States)

Zhu, Dongming; Fox, Dennis S.; Ghosn, Louis J.; Harder, Bryan

2011-01-01

Environmental barrier coatings will play a crucial role in future advanced gas turbine engines because of their ability to significantly extend the temperature capability and stability of SiC/SiC ceramic matrix composite (CMC) engine components, thus improving the engine performance. In order to develop high performance, robust coating systems for engine components, appropriate test approaches simulating operating temperature gradient and stress environments for evaluating the critical coating properties must be established. In this paper, thermal gradient mechanical testing approaches for evaluating creep and fatigue behavior of environmental barrier coated SiC/SiC CMC systems will be described. The creep and fatigue behavior of Hafnia and ytterbium silicate environmental barrier coatings on SiC/SiC CMC systems will be reported in simulated environmental exposure conditions. The coating failure mechanisms will also be discussed under the heat flux and stress conditions.

Diffusion of Cr, Fe, and Ti ions from Ni-base alloy Inconel-718 into a transition alumina coating

Energy Technology Data Exchange (ETDEWEB)

Dressler, M., E-mail: martin.dressler@bam.de; Nofz, M.; Doerfel, I.; Saliwan-Neumann, R.

2012-04-30

Heat treating metals at high temperatures trigger diffusion processes which may lead to the formation of oxide layers. In this work the diffusion of Cr, Fe and Ti into an alumina coating applied to Inconel-718 is being investigated. Mass gain measurements, UV-vis spectroscopy and transmission electron microscopy were applied in order to study the evolution of the diffusion process. It was found that mainly Cr as well as minor amounts of Fe and Ti are being incorporated into the alumina coating upon prolonged heat treatment at 700 Degree-Sign C. It could be shown that alumina coatings being void of Cr have the same oxidation related mass gain as uncoated samples. However, incorporation of Cr into the alumina coating decreased their mass gain below that of uncoated substrates forming a Cr oxide scale only. - Highlights: Black-Right-Pointing-Pointer We investigated the diffusion of Cr into alumina coatings applied on IN-718. Black-Right-Pointing-Pointer The ingress of Cr led to the formation of mixed alumina/chromium coatings. Black-Right-Pointing-Pointer The mass gain of mixed alumina/chromium coatings was compared to uncoated IN-718. Black-Right-Pointing-Pointer The mixed alumina/chromium coatings improved the oxidation resistance of IN-718.

Investigation on the suitability of plasma sprayed Fe-Cr-Al coatings as tritium permeation barrier

International Nuclear Information System (INIS)

Fazio, C.; Serra, E.; Benamati, G.

1999-01-01

Results on the fabrication of a tritium permeation barrier by spraying Fe-Cr-Al powders are described. The sprayed coatings were deposited at temperatures below the A c1 temperature of the ferritic-martensitic steel substrate and no post-deposition heat treatment was applied. The aim of the investigation was the determination of the efficiency of the coatings to act as tritium permeation barrier. Metallurgical investigations as well as hydrogen isotope permeation measurements were carried out onto the produced coatings. The depositions were performed on ferritic-martensitic steels by means of three types of spray techniques: high velocity oxy fuel, air plasma spray and vacuum plasma spray. (orig.)

How thin barrier metal can be used to prevent Co diffusion in the modern integrated circuits?

International Nuclear Information System (INIS)

Dixit, Hemant; Konar, Aniruddha; Pandey, Rajan; Ethirajan, Tamilmani

2017-01-01

In modern integrated circuits (ICs), billions of transistors are connected to each other via thin metal layers (e.g. copper, cobalt, etc) known as interconnects. At elevated process temperatures, inter-diffusion of atomic species can occur among these metal layers, causing sub-optimal performance of interconnects, which may lead to the failure of an IC. Thus, typically a thin barrier metal layer is used to prevent the inter-diffusion of atomic species within interconnects. For ICs with sub-10 nm transistors (10 nm technology node), the design rule (thickness scaling) demands the thinnest possible barrier layer. Therefore, here we investigate the critical thickness of a titanium–nitride (TiN) barrier that can prevent the cobalt diffusion using multi-scale modeling and simulations. First, we compute the Co diffusion barrier in crystalline and amorphous TiN with the nudged elastic band method within first-principles density functional theory simulations. Later, using the calculated activation energy barriers, we quantify the Co diffusion length in the TiN metal layer with the help of kinetic Monte Carlo simulations. Such a multi-scale modelling approach yields an exact critical thickness of the metal layer sufficient to prevent the Co diffusion in IC interconnects. We obtain a diffusion length of a maximum of 2 nm for a typical process of thermal annealing at 400 °C for 30 min. Our study thus provides useful physical insights for the Co diffusion in the TiN layer and further quantifies the critical thickness (∼2 nm) to which the metal barrier layer can be thinned down for sub-10 nm ICs. (paper)

How thin barrier metal can be used to prevent Co diffusion in the modern integrated circuits?

Science.gov (United States)

Dixit, Hemant; Konar, Aniruddha; Pandey, Rajan; Ethirajan, Tamilmani

2017-11-01

In modern integrated circuits (ICs), billions of transistors are connected to each other via thin metal layers (e.g. copper, cobalt, etc) known as interconnects. At elevated process temperatures, inter-diffusion of atomic species can occur among these metal layers, causing sub-optimal performance of interconnects, which may lead to the failure of an IC. Thus, typically a thin barrier metal layer is used to prevent the inter-diffusion of atomic species within interconnects. For ICs with sub-10 nm transistors (10 nm technology node), the design rule (thickness scaling) demands the thinnest possible barrier layer. Therefore, here we investigate the critical thickness of a titanium-nitride (TiN) barrier that can prevent the cobalt diffusion using multi-scale modeling and simulations. First, we compute the Co diffusion barrier in crystalline and amorphous TiN with the nudged elastic band method within first-principles density functional theory simulations. Later, using the calculated activation energy barriers, we quantify the Co diffusion length in the TiN metal layer with the help of kinetic Monte Carlo simulations. Such a multi-scale modelling approach yields an exact critical thickness of the metal layer sufficient to prevent the Co diffusion in IC interconnects. We obtain a diffusion length of a maximum of 2 nm for a typical process of thermal annealing at 400 °C for 30 min. Our study thus provides useful physical insights for the Co diffusion in the TiN layer and further quantifies the critical thickness (~2 nm) to which the metal barrier layer can be thinned down for sub-10 nm ICs.

Role of high-temperature creep stress in thermally grown oxide growth of thermal barrier coatings

Energy Technology Data Exchange (ETDEWEB)

Ogawa, K.; Nakao, Y.; Seo, D.; Miura, H.; Shoji, T. [Tohoku Univ., Sendai (Japan)

2008-07-01

Thermally grown oxide (TGO) grows at the top / bond coating interface of the thermal barrier coating (TBC) in service. It is supposed that the failures of the TBC occur due to thermal stress and the decrease of adhesive strength caused by the TGO growth. Recently, large local stress has been found to change both the diffusion constant of oxygen through an existing oxide and the rate of chemical reaction at the oxide / oxidized material interface. Since high thermal stress occurs in the TBC, the volume expansion of the newly grown oxide, and centrifugal force, the growth rate of the TGO may change depending on not only temperature but also the stress. The aim of this study is to make clear the influence of stress on the growth rate of the TGO quantitatively. As a result, the thickness of the TGO clearly increases with increase of the amplitude of the applied stress and temperature. The increase rate of the TGO thickness is approximately 23% when the applied stress is increased from 0 to 205 MPa at 900 C, and approximately 29% when the stress is increased from 0 to 150 MPa at 950 C. (orig.)

Thermally induced atomic diffusion at the interface between release agent coating and mould substrate in a glass moulding press

Energy Technology Data Exchange (ETDEWEB)

Masuda, Jun; Fukase, Yasushi [Toshiba Machine Co., Ltd, Ooka 2068-3, Numazu-Shi, Shizuoka-Ken, 410-8510 (Japan); Yan Jiwang; Zhou Tianfeng; Kuriyagawa, Tsunemoto, E-mail: yanjw@pm.mech.tohoku.ac.jp [Department of Mechanical Systems and Design, Graduate School of Engineering, Tohoku University, Aoba 6-6-01, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

2011-06-01

In a glass moulding press (GMP) for refractive/diffractive hybrid lenses, to improve the service life of nickel-phosphorus (Ni-P) plated moulds, it is necessary to control the diffusion of constituent elements from the mould into the release agent coating. In this study, diffusion phenomena of constituents of Ni-P plating are investigated for two types of release agent coatings, iridium-platinum (Ir-Pt) and iridium-rhenium (Ir-Re), by cross-sectional observation, compositional analysis and stress measurements. The results show that Ni atoms in the plating layer flow from regions of compressive stress to regions of tensile stress. In the case of the Ir-Pt coated mould, the diffusion of Ni is promoted from the grain boundaries between the Ni and Ni{sub 3}P phases in the plating towards the surface of the Ir-Pt coating. However, in the Ir-Re coated mould, the diffusion of Ni is suppressed because the diffusion coefficient of Ni in the Ir-Re alloy is smaller than that in the Ir-Pt alloy, although the stress state is similar in both cases. By controlling the diffusion of Ni atoms, the use of Ir-Re alloy as a release agent coating for Ni-P plated moulds is expected to lead to a high degree of durability.

Contribution of diffuser surfaces to efficiency of tilted T shape parallel highway noise barriers

Directory of Open Access Journals (Sweden)

N. Javid Rouzi

2009-04-01

Full Text Available Background and aimsThe paper presents the results of an investigation on the acoustic  performance of tilted profile parallel barriers with quadratic residue diffuser tops and faces.MethodsA2D boundary element method (BEM is used to predict the barrier insertion loss. The results of rigid and with absorptive coverage are also calculated for comparisons. Using QRD on the top surface and faces of all tilted profile parallel barrier models introduced here is found to  improve the efficiency of barriers compared with rigid equivalent parallel barrier at the examined  receiver positions.Results Applying a QRD with frequency design of 400 Hz on 5 degrees tilted parallel barrier  improves the overall performance of its equivalent rigid barrier by 1.8 dB(A. Increase the treated surfaces with reactive elements shifts the effective performance toward lower frequencies. It is  found that by tilting the barriers from 0 to 10 degrees in parallel set up, the degradation effects in  parallel barriers is reduced but the absorption effect of fibrous materials and also diffusivity of thequadratic residue diffuser is reduced significantly. In this case all the designed barriers have better  performance with 10 degrees tilting in parallel set up.ConclusionThe most economic traffic noise parallel barrier, which produces significantly  high performance, is achieved by covering the top surface of the barrier closed to the receiver by  just a QRD with frequency design of 400 Hz and tilting angle of 10 degrees. The average Aweighted  insertion loss in this barrier is predicted to be 16.3 dB (A.

Diffusion barriers for Cu metallisation in Si integrated circuits : deposition and related thin film properties

NARCIS (Netherlands)

van Nieuwkasteele-Bystrova, Svetlana Nikolajevna

2004-01-01

In modern integrated circuits with Cu interconnects a diffusion barrier is used between the dielectric and Cu in order to prevent diffusion of Cu through the dielectrics. The choice of such a barrier requires a material exploration and a study of the material reactivity with both Cu and the

Stress controlled gas-barrier oxide coatings on semi-crystalline polymers

International Nuclear Information System (INIS)

Rochat, G.; Leterrier, Y.; Fayet, P.; Manson, J.-A.E.

2005-01-01

Thin silicon oxide (SiO x ) barrier coatings formed by plasma enhanced chemical vapor deposition on poly(ethylene terephthalate) (PET) substrates were subjected to post-deposition annealing treatments in the temperature range for orientation relaxation of the polymer. The resulting change in coating internal stress state was measured by means of thermo-mechanical analyses, and its effect on the coating cohesive properties and coating/polymer adhesion was determined from the analysis of uniaxial fragmentation tests in situ in a scanning electron microscope, assuming a Weibull-type probability of failure and a perfectly plastic stress transfer at the SiO x /PET interface. The strain to failure and intrinsic fracture toughness of the ultrathin oxide coating were found to be as high as 5.7% and 10 J/m 2 , respectively, and its interfacial shear strength with PET was found to be close to 100 MPa. Annealing for 10 min at 150 deg. C did not modify the oxygen permeation properties of the SiO x /PET film, which suggests that the defect population of the oxide was not affected by the thermal treatment. In contrast, the coating internal compressive stress resulting from annealing was shown to increase by 40% the apparent coating cohesive properties and adhesion to the polymer

Influence of Bondcoat Spray Process on Lifetime of Suspension Plasma-Sprayed Thermal Barrier Coatings

Science.gov (United States)

Gupta, M.; Markocsan, N.; Li, X.-H.; Östergren, L.

2018-01-01

Development of thermal barrier coatings (TBCs) manufactured by suspension plasma spraying (SPS) is of high commercial interest as SPS has been shown capable of producing highly porous columnar microstructures similar to the conventionally used electron beam-physical vapor deposition. However, lifetime of SPS coatings needs to be improved further to be used in commercial applications. The bondcoat microstructure as well as topcoat-bondcoat interface topography affects the TBC lifetime significantly. The objective of this work was to investigate the influence of different bondcoat deposition processes for SPS topcoats. In this work, a NiCoCrAlY bondcoat deposited by high velocity air fuel (HVAF) was compared to commercial vacuum plasma-sprayed NiCoCrAlY and PtAl diffusion bondcoats. All bondcoat variations were prepared with and without grit blasting the bondcoat surface. SPS was used to deposit the topcoats on all samples using the same spray parameters. Lifetime of these samples was examined by thermal cyclic fatigue testing. Isothermal heat treatment was performed to study bondcoat oxidation over time. The effect of bondcoat deposition process and interface topography on lifetime in each case has been discussed. The results show that HVAF could be a suitable process for bondcoat deposition in SPS TBCs.

Thermal Gradient Cyclic Behavior of a Thermal/Environmental Barrier Coating System on SiC/SiC Ceramic Matrix Composites

Science.gov (United States)

Zhu, Dongming; Lee, Kang N.; Miller, Robert A.

2002-01-01

Thermal barrier and environmental barrier coatings (TBCs and EBCs) will play a crucial role in future advanced gas turbine engines because of their ability to significantly extend the temperature capability of the ceramic matrix composite (CMC) engine components in harsh combustion environments. In order to develop high performance, robust coating systems for effective thermal and environmental protection of the engine components, appropriate test approaches for evaluating the critical coating properties must be established. In this paper, a laser high-heat-flux, thermal gradient approach for testing the coatings will be described. Thermal cyclic behavior of plasma-sprayed coating systems, consisting of ZrO2-8wt%Y2O3 thermal barrier and NASA Enabling Propulsion Materials (EPM) Program developed mullite+BSAS/Si type environmental barrier coatings on SiC/SiC ceramic matrix composites, was investigated under thermal gradients using the laser heat-flux rig in conjunction with the furnace thermal cyclic tests in water-vapor environments. The coating sintering and interface damage were assessed by monitoring the real-time thermal conductivity changes during the laser heat-flux tests and by examining the microstructural changes after the tests. The coating failure mechanisms are discussed based on the cyclic test results and are correlated to the sintering, creep, and thermal stress behavior under simulated engine temperature and heat flux conditions.

Comparative study on the deposition of silicon oxide permeation barrier coatings for polymers using hexamethyldisilazane (HMDSN) and hexamethyldisiloxane (HMDSO)

Science.gov (United States)

Mitschker, F.; Schücke, L.; Hoppe, Ch; Jaritz, M.; Dahlmann, R.; de los Arcos, T.; Hopmann, Ch; Grundmeier, G.; Awakowicz, P.

2018-06-01

The effect of the selection of hexamethyldisiloxane (HMDSO) and hexamethyldisilazane (HMDSN) as a precursor in a microwave driven low pressure plasma on the deposition of silicon oxide barrier coatings and silicon based organic interlayers on polyethylene terephthalate (PET) and polypropylene (PP) substrates is investigated. Mass spectrometry is used to quantify the absolute gas density and the degree of depletion of neutral precursor molecules under variation of oxygen admixture. On average, HMDSN shows a smaller density, a higher depletion and the production of smaller fragments. Subsequently, this is correlated with barrier performance and chemical structure as a function of barrier layer thickness and oxygen admixture on PET. For this purpose, the oxygen transmission rate (OTR) is measured and Fourier transformed infrared (FTIR) spectroscopy as well as x-ray photoelectron spectroscopy (XPS) is performed. HMDSN based coatings exhibit significantly higher barrier performances for high admixtures of oxygen (200 sccm). In comparison to HMDSO based processes, however, a higher supply of oxygen is necessary to achieve a sufficient degree of oxidation, cross-linking and, therefore, barrier performance. FTIR and XPS reveal a distinct carbon content for low oxygen admixtures (10 and 20 sccm) in case of HMDSN based coatings. The variation of interlayer thickness also reveals significantly higher OTR for HMDSO based coatings on PET and PP. Barrier performance of HMDSO based coatings improves with increasing interlayer thickness up to 10 nm for PET and PP. HMDSN based coatings exhibit a minimum of OTR without interlayer on PP and for 2 nm interlayer thickness on PET. Furthermore, HMDSN based coatings show distinctly higher bond strengths to the PP substrate.

Design of a Nickel-Based Bond-Coat Alloy for Thermal Barrier Coatings on Copper Substrates

Directory of Open Access Journals (Sweden)

Torben Fiedler

2014-11-01

Full Text Available To increase the lifetime of rocket combustion chambers, thermal barrier coatings (TBC may be applied on the copper chamber wall. Since standard TBC systems used in gas turbines are not suitable for rocket-engine application and fail at the interface between the substrate and bond coat, a new bond-coat material has to be designed. This bond-coat material has to be chemically compatible to the copper substrate to improve the adhesion and needs a coefficient of thermal expansion close to that of copper to reduce thermal stresses. One approach to achieve this is to modify the standard NiCrAlY alloy used in gas turbines by adding copper. In this work, the influence of copper on the microstructure of NiCrAlY-alloys is investigated with thermodynamical calculations, optical microscopy, SEM, EDX and calorimetry. Adding copper leads to the formation of a significant amount of \\(\\beta\\ and \\(\\alpha\\ Reducing the aluminum and chromium content leads furthermore to a two-phase fcc microstructure.

Anisotropic Lithium Insertion Behavior in Silicon Nanowires: Binding Energy, Diffusion Barrier, and Strain Effect

KAUST Repository

Zhang, Qianfan; Cui, Yi; Wang, Enge

2011-01-01

Silicon nanowires (SiNWs) have recently been shown to be promising as high capacity lithium battery anodes. SiNWs can be grown with their long axis along several different crystallographic directions. Due to distinct atomic configuration and electronic structure of SiNWs with different axial orientations, their lithium insertion behavior could be different. This paper focuses on the characteristics of single Li defects, including binding energy, diffusion barriers, and dependence on uniaxial strain in [110], [100], [111], and [112] SiNWs. Our systematic ab initio study suggests that the Si-Li interaction is weaker when the Si-Li bond direction is aligned close to the SiNW long axis. This results in the [110] and [111] SiNWs having the highest and lowest Li binding energy, respectively, and it makes the diffusion barrier along the SiNW axis lower than other pathways. Under external strain, it was found that [110] and [001] SiNWs are the most and least sensitive, respectively. For diffusion along the axial direction, the barrier increases (decreases) under tension (compression). This feature results in a considerable difference in the magnitude of the energy barrier along different diffusion pathways. © 2011 American Chemical Society.

Anisotropic Lithium Insertion Behavior in Silicon Nanowires: Binding Energy, Diffusion Barrier, and Strain Effect

KAUST Repository

Zhang, Qianfan

2011-05-19

Silicon nanowires (SiNWs) have recently been shown to be promising as high capacity lithium battery anodes. SiNWs can be grown with their long axis along several different crystallographic directions. Due to distinct atomic configuration and electronic structure of SiNWs with different axial orientations, their lithium insertion behavior could be different. This paper focuses on the characteristics of single Li defects, including binding energy, diffusion barriers, and dependence on uniaxial strain in [110], [100], [111], and [112] SiNWs. Our systematic ab initio study suggests that the Si-Li interaction is weaker when the Si-Li bond direction is aligned close to the SiNW long axis. This results in the [110] and [111] SiNWs having the highest and lowest Li binding energy, respectively, and it makes the diffusion barrier along the SiNW axis lower than other pathways. Under external strain, it was found that [110] and [001] SiNWs are the most and least sensitive, respectively. For diffusion along the axial direction, the barrier increases (decreases) under tension (compression). This feature results in a considerable difference in the magnitude of the energy barrier along different diffusion pathways. © 2011 American Chemical Society.

Structural stability of diffusion barriers in thermoelectric SbTe: From first-principles calculations to experimental results

International Nuclear Information System (INIS)

Hsu, Hsiao-Hsuan; Cheng, Chun-Hu; Chiou, Shan-Haw; Huang, Chiung-Hui; Liu, Chia-Mei; Lin, Yu-Li; Chao, Wen-Hsuan; Yang, Ping-Hsing; Chang, Chun-Yen; Cheng, Chin-Pao

2014-01-01

Highlights: • The diffusion behavior was originated from high-vapor-pressure Te atom. • Te out-diffusion is main driving force to cause inter-diffusion effect. • Mid-band Ta and TaN with favored ohmic-like contact showed small diffusion tail. • Strong Ta-N bonding and high total energy suppressed interfacial layer formation. -- Abstract: This study involved developing robust diffusion barrier for n-type antimony telluride (SbTe) thermoelectric devices. Compared to conventional Ni barrier, the mid-band metals of Ta and TaN with favored ohmic-like contact exhibited smaller diffusion tail because of structurally stable interface on SbTe, which have been supported by first-principles calculations and demonstrated by experimental results. Furthermore, the TaN barrier has strong ionic Ta–N bonding and a high total energy of −4.7 eV/atom that could effectively suppress the formation of SbTe-compounds interfacial layer

Thermal shock behavior of platinum aluminide bond coat/electron beam-physical vapor deposited thermal barrier coatings

Energy Technology Data Exchange (ETDEWEB)

Xu, Zhenhua, E-mail: zhxuciac@163.com [Beijing Institute of Aeronautical Materials, Department 5, P.O. Box 81-5, Beijing 100095 (China); Dai, Jianwei [Beijing Institute of Aeronautical Materials, Department 5, P.O. Box 81-5, Beijing 100095 (China); Niu, Jing [Shenyang Liming Aero-engine (Group) Corporation Ltd., Institute of Metallurgical Technology, Technical Center, Shengyang 110043 (China); Li, Na; Huang, Guanghong; He, Limin [Beijing Institute of Aeronautical Materials, Department 5, P.O. Box 81-5, Beijing 100095 (China)

2014-12-25

Highlights: • TBCs of (Ni, Pt)Al bond coat with grit blasting process and YSZ ceramic coating. • Grain boundary ridges are the sites for spallation damage initiation in TBCs. • Ridges removed, cavities formation appeared and the damage initiation deteriorated. • Damage initiation and progression at interface lead to a buckling failure. - Abstract: Thermal barrier coating systems (TBCs) including of chemical vapor deposited (Ni, Pt)Al bond coat with grit blasting process and electron beam physical vapor deposited Y{sub 2}O{sub 3}-stabilized-ZrO{sub 2} (YSZ) ceramic coating were investigated. The phase structures, surface and cross-sectional morphologies, thermal shock behaviors and residual stresses of the coatings were studied in detail. Grain boundary ridges still remain on the surface of bond coat prior to the deposition of the ceramic coating, which are shown to be the major sites for spallation damage initiation in TBCs. When these ridges are mostly removed, they appear some of cavities formation and then the damage initiation mode is deteriorated. Damage initiation and progression occurs at the bond coat to thermally grown oxide (TGO) interface leading to a buckling failure behavior. A buckle failure once started may be arrested when it runs into a region of high bond coat to TGO interface toughness. Thus, complete failure requires further loss in toughness of the bond coat to TGO interface during cooling. The suppressed cavities formation, the removed ridges at the grain boundaries, the relative high TGO to bond coat interface toughness, the uniform growth behavior of TGO thickening and the lower of the residual stress are the primary factors for prolonging the lifetime of TBCs.

Design and Characterization of High-strength Bond Coats for Improved Thermal Barrier Coating Durability

Science.gov (United States)

Jorgensen, David John

High pressure turbine blades in gas turbine engines rely on thermal barrier coating (TBC) systems for protection from the harsh combustion environment. These coating systems consist of a ceramic topcoat for thermal protection, a thermally grown oxide (TGO) for oxidation passivation, and an intermetallic bond coat to provide compatibility between the substrate and ceramic over-layers while supplying aluminum to sustain Al2O 3 scale growth. As turbine engines are pushed to higher operating temperatures in pursuit of better thermal efficiency, the strength of industry-standard bond coats limits the lifetime of these coating systems. Bond coat creep deformation during thermal cycling leads to a failure mechanism termed rumpling. The interlayer thermal expansion differences, combined with TGO-imposed growth stresses, lead to the development of periodic undulations in the bond coat. The ceramic topcoat has low out-of-plane compliance and thus detaches and spalls from the substrate, resulting in a loss of thermal protection and subsequent degradation of mechanical properties. New creep resistant Ni3Al bond coats were designed with improved high-temperature strength to inhibit this type of premature failure at elevated temperatures. These coatings resist rumpling deformation while maintaining compatibility with the other layers in the system. Characterization methods are developed to quantify rumpling and assess the TGO-bond coat interface toughness of experimental systems. Cyclic oxidation experiments at 1163 °C show that the Ni3Al bond coats do not experience rumpling but have faster oxide growth rates and are quicker to spall TGO than the (Pt,Ni)Al benchmark. However, the Ni 3Al coatings outperformed the benchmark by over threefold in TBC system life due to a higher resistance to rumpling (mechanical degradation) while maintaining adequate oxidation passivation. The Ni3Al coatings eventually grow spinel NiAl2O4 on top of the protective Al2O3 layer, which leads to the

Deposition stress effects on the life of thermal barrier coatings on burner rigs

Science.gov (United States)

Watson, J. W.; Levine, S. R.

1984-01-01

A study of the effect of plasma spray processing parameters on the life of a two layer thermal barrier coating was conducted. The ceramic layer was plasma sprayed at plasma arc currents of 900 and 600 amps onto uncooled tubes, cooled tubes, and solid bars of Waspalloy in a lathe with 1 or 8 passes of the plasma gun. These processing changes affected the residual stress state of the coating. When the specimens were tested in a Mach 0.3 cyclic burner rig at 1130 deg C, a wide range of coating lives resulted. Processing factors which reduced the residual stress state in the coating, such as reduced plasma temperature and increased heat dissipation, significantly increased coating life.

Thermal barrier coatings (TBC's) for high heat flux thrust chambers

Science.gov (United States)

Bradley, Christopher M.

The last 30 years materials engineers have been under continual pressure to develop materials with a greater temperature potential or to produce configurations that can be effectively cooled or otherwise protected at elevated temperature conditions. Turbines and thrust chambers produce some of the harshest service conditions for materials which lead to the challenges engineers face in order to increase the efficiencies of current technologies due to the energy crisis that the world is facing. The key tasks for the future of gas turbines are to increase overall efficiencies to meet energy demands of a growing world population and reduce the harmful emissions to protect the environment. Airfoils or blades tend to be the limiting factor when it comes to the performance of the turbine because of their complex design making them difficult to cool as well as limitations of their thermal properties. Key tasks for space transportation it to lower costs while increasing operational efficiency and reliability of our space launchers. The important factor to take into consideration is the rocket nozzle design. The design of the rocket nozzle or thrust chamber has to take into account many constraints including external loads, heat transfer, transients, and the fluid dynamics of expanded hot gases. Turbine engines can have increased efficiencies if the inlet temperature for combustion is higher, increased compressor capacity and lighter weight materials. In order to push for higher temperatures, engineers need to come up with a way to compensate for increased temperatures because material systems that are being used are either at or near their useful properties limit. Before thermal barrier coatings were applied to hot-section components, material alloy systems were able to withstand the service conditions necessary. But, with the increased demand for performance, higher temperatures and pressures have become too much for those alloy systems. Controlled chemistry of hot

The Role of Diffusion Media in Nitriding Process on Surface Layers Characteristics of AISI 4140 with and without Hard Chrome Coatings

Directory of Open Access Journals (Sweden)

K.A. Widi

2016-09-01

Full Text Available The surface layer characteristics of the AISI 4140 tool steel treated by nitriding gas before and after hard chrome plating utilizing pure nitrogen diffusion media (fluidized bed reactor and the without gas (muffle reactor has been studied experimentally. The result shows that nitriding substrate with hard chrome layers has nitrogen atoms concentration almost twice greater than that without hard chrome layers. After being given a hard chrome plating, nitriding on AISI 4140 steel generally has a nitrogen concentration of up to 4 times more than the substrate without hard chrome coating. Almost the entire specimen showed the highest concentration of N atoms in the area below the surface (hardening depth of 200 to 450 µm. N atoms diffusion depth profile has a correlation with hardening depth profile, especially on the specimens layered with hard chromium. The substrate without hard chrome plating tends to have higher surface hardness than the sub-surface. The results show that the effectiveness and efficiency of the gas nitriding diffusion process can be produced without the use of gas in the muffle reactor but the specimens must be hard chromium coated first. This phenomenon can be explained by the role of the passive layer formation that works as a barrier to keeps the spreading of N atoms concentrated in sub-surface areas.

Barrier capability of Zr-N films with titanium addition against copper diffusion

International Nuclear Information System (INIS)

Wang Ying; Cao Fei; Yang Xiaodong; Ding Minghui

2009-01-01

Zr-Ti-N film prepared by sputtering deposition has been employed as a potential diffusion barrier for Cu metallization. It is thought that the existing states of Ti and Zr in the films are Ti-N and Zr-N phase in Zr-Ti-N films. Material analysis by XRD, XPS and sheet resistance measurement reveal that the failure of Zr-N film is mainly due to the formation of Cu 3 Si precipitates at the Zr-N/Si interface by Cu diffusion through the grain boundaries or local defects of the Zr-N barrier layer into Si substrate. In conjunction with sheet resistance measurement, XRD and XPS analyses, the Cu/Zr-Ti-N/Si contact system has high thermal stability at least up to 700 deg. C. The incorporation of Ti atoms into Zr-N barrier layer was shown to be beneficial in improving the thermal stability of the Cu/barrier/Si contact system.

Design of Thermal Barrier Coatings Thickness for Gas Turbine Blade Based on Finite Element Analysis

OpenAIRE

Li, Biao; Fan, Xueling; Li, Dingjun; Jiang, Peng

2017-01-01

Thermal barrier coatings (TBCs) are deposited on the turbine blade to reduce the temperature of underlying substrate, as well as providing protection against the oxidation and hot corrosion from high temperature gas. Optimal ceramic top-coat thickness distribution on the blade can improve the performance and efficiency of the coatings. Design of the coatings thickness is a multiobjective optimization problem due to the conflicts among objectives of high thermal insulation performance, long op...

Shear strength of a thermal barrier coating parallel to the bond coat

International Nuclear Information System (INIS)

Cruse, T.A.; Dommarco, R.C.; Bastias, P.C.

1998-01-01

The static and low cycle fatigue strength of an air plasma sprayed (APS) partially stabilized zirconia thermal barrier coating (TBC) is experimentally evaluated. The shear testing utilized the Iosipescu shear test arrangement. Testing was performed parallel to the TBC-substrate interface. The TBC testing required an innovative use of steel extensions with the TBC bonded between the steel extensions to form the standard Iosipescu specimen shape. The test method appears to have been successful. Fracture of the TBC was initiated in shear, although unconstrained specimen fractures propagated at the TBC-bond coat interface. The use of side grooves on the TBC was successful in keeping the failure in the gage section and did not appear to affect the shear strength values that were measured. Low cycle fatigue failures were obtained at high stress levels approaching the ultimate strength of the TBC. The static and fatigue strengths do not appear to be markedly different from tensile properties for comparable TBC material

A study of the barrier properties of polyethylene coated with a nanocellulose/magnetite composite film

Directory of Open Access Journals (Sweden)

Đorđević Nenad

2016-01-01

Full Text Available The morphological, thermal and barrier properties of low-density polyethylene/polycaprolactone-modified nanocellulose hybrid materials were investigated in this paper. Nanonocelulose/magnetite (NC-Fe3O4 nanocomposite and maleic acid functionalized NC/magnetite (NCMA-Fe3O4 nanocomposite were prepared and used as filler at various concentrations (5, 10 and 15 wt. % in polycaprolactone (PCL layer. PE was coated with PCL/NC/magnetite layer. The addition of the filler did not unfavorably affect the inherent properties of the polymer, especially its barrier properties. Oxygen permeation measurements show that the oxygen barrier properties of magnetite enriched PCL film were improved due to chemical activity of added material. The highest level of barrier capacity was observed for PE samples coated with PCL based composite with NCMA-Fe3O4 micro/-nanofiller, which implies the significant contribution of nanocellulose surface modification with maleic anhydride residue to improved barrier properties. [Projekat Ministarstva nauke Republike Srbije, br. III45019 i br. OI172013

Inter-diffusion of carbon into niobium coatings deposited on graphite

International Nuclear Information System (INIS)

Barzilai, S.; Raveh, A.; Frage, N.

2006-01-01

The inter-diffusion of carbon (originating from a graphite substrate) into a niobium coating and the fabrication of its carbides by heat treatment in the temperature range of 1073-1773 K was studied. The thickness of the Nb 2 C and Nbc phases formed after heat treatment as well as the inter-diffusion coefficients for the formation of the carbide layers were also studied. It was found that the carbide layer growth displayed parabolic behavior patterns inherent in the growth rate constants (K) of Nb 2 C and NbC layers. By assuming that the inter-diffusion coefficients are independent of concentration, it was possible to determine the inter-diffusion coefficients of carbon D c into Nb 2 C and NbC layers as a function of temperature

Gas barrier properties of hydrogenated amorphous carbon films coated on polyethylene terephthalate by plasma polymerization in argon/n-hexane gas mixture

Energy Technology Data Exchange (ETDEWEB)

Polonskyi, Oleksandr; Kylián, Ondřej, E-mail: ondrej.kylian@gmail.com; Petr, Martin; Choukourov, Andrei; Hanuš, Jan; Biederman, Hynek

2013-07-01

Hydrogenated amorphous carbon thin films were deposited by RF plasma polymerization in argon/n-hexane gas mixture on polyethylene terephthalate (PET) foils. It was found that such deposited films may significantly improve the barrier properties of PET. It was demonstrated that the principal parameter that influences barrier properties of such deposited films towards oxygen and water vapor is the density of the coatings. Moreover, it was shown that for achieving good barrier properties it is advantageous to deposit coatings with very low thickness. According to the presented results, optimal thickness of the coating should not be higher than several tens of nm. - Highlights: • a-C:H films were prepared by plasma polymerization in Ar/n-hexane atmosphere. • Barrier properties of coatings are dependent on their density and thickness. • Highest barrier properties were observed for films with thickness 15 nm.

Determination of diffusion factors according to the distribution of coating components at isothermal hold-up

International Nuclear Information System (INIS)

Shatinskij, V.F.; Nesterenko, A.I.

1980-01-01

Calculation equations for estimate of coating metal diffusion coefficients are derived. The experimental checking of derived dependences is carried out. Studies have been made on flat samples of 2x10x15 mm dimensions made of armco iron with W,Mo,Cr, Ga, Ge coatings. The initial distribution of saturation elements determined experimentally, and approximated by functions, is presented. By the method of placing of values of initial distributions into the calculated dependences determined are the coefficients of diffusion for above elements in armco iron. For experimental ckecking of the problem made is a program of computer calculation for two-phase chromium coating on armco iron. Cr diffusion coefficients in α- and γ-phase are determined at 950 deg, which constitute 5.692x10 -10 cm 2 /s and 1.365x10 -10 cm 2 /s. respectively. The control tests have shown that the application of calculated diffusion coefficients permits to describe with high accuracy the redistribution of saturation element in matrix of the saturating metal

Roll-to-roll DBD plasma pretreated polyethylene web for enhancement of Al coating adhesion and barrier property

Energy Technology Data Exchange (ETDEWEB)

Zhang, Haibao; Li, Hua; Fang, Ming; Wang, Zhengduo; Sang, Lijun; Yang, Lizhen; Chen, Qiang, E-mail: lppmchenqiang@hotmail.com

2016-12-01

Graphical abstract: The images of Al coating adhesion testes for (a) untreated and (b) roll-to-roll DBD plasma treated PE. - Highlights: • Over three-months ageing a high surface energy was still existed in roll-to-roll DBD plasma-treated PE surface. • The adhesion and barrier property of Al-coated PE web were greatly improved. • The mechanism of plasma grafting to improve the properties of Al-coated PE web was found. - Abstract: In this paper the roll-to-roll atmospheric dielectric barrier discharge (DBD) was used to pre-treat polyethylene (PE) web surface before the conventional thermal evaporation aluminum (Al) was performed as a barrier layer. We emphasized the plasma environment effect based on the inlet three kinds of reactive monomers. The cross hatch test was employed to assess the Al coating adhesion; and the oxygen transmission rate (OTR) was used to evaluate gas barrier property. The results showed that after roll-to-roll DBD plasma treatment all Al coatings adhered strongly on PE films and were free from pinhole defects with mirror morphology. The OTR was reduced from 2673 cm{sup 3}/m{sup 2} day for Al-coated original PE to 138 cm{sup 3}/m{sup 2} day for Al-coated allyamine (C{sub 3}H{sub 7}N) modified PE. To well understand the mechanism the chemical compositions of the untreated and DBD plasma pretreated PE films were analyzed by X-ray photoelectron spectroscopy (XPS). The surface topography was characterized by atomic force microscopy (AFM). For the property of surface energy the water contact angle measurement was also carried out in the DBD plasma treated samples with deionized water.

Roll-to-roll DBD plasma pretreated polyethylene web for enhancement of Al coating adhesion and barrier property

International Nuclear Information System (INIS)

Zhang, Haibao; Li, Hua; Fang, Ming; Wang, Zhengduo; Sang, Lijun; Yang, Lizhen; Chen, Qiang

2016-01-01

Graphical abstract: The images of Al coating adhesion testes for (a) untreated and (b) roll-to-roll DBD plasma treated PE. - Highlights: • Over three-months ageing a high surface energy was still existed in roll-to-roll DBD plasma-treated PE surface. • The adhesion and barrier property of Al-coated PE web were greatly improved. • The mechanism of plasma grafting to improve the properties of Al-coated PE web was found. - Abstract: In this paper the roll-to-roll atmospheric dielectric barrier discharge (DBD) was used to pre-treat polyethylene (PE) web surface before the conventional thermal evaporation aluminum (Al) was performed as a barrier layer. We emphasized the plasma environment effect based on the inlet three kinds of reactive monomers. The cross hatch test was employed to assess the Al coating adhesion; and the oxygen transmission rate (OTR) was used to evaluate gas barrier property. The results showed that after roll-to-roll DBD plasma treatment all Al coatings adhered strongly on PE films and were free from pinhole defects with mirror morphology. The OTR was reduced from 2673 cm 3 /m 2 day for Al-coated original PE to 138 cm 3 /m 2 day for Al-coated allyamine (C 3 H 7 N) modified PE. To well understand the mechanism the chemical compositions of the untreated and DBD plasma pretreated PE films were analyzed by X-ray photoelectron spectroscopy (XPS). The surface topography was characterized by atomic force microscopy (AFM). For the property of surface energy the water contact angle measurement was also carried out in the DBD plasma treated samples with deionized water.

Development of Reliability Based Life Prediction Methods for Thermal and Environmental Barrier Coatings in Ceramic Matrix Composites

Science.gov (United States)

Shah, Ashwin

2001-01-01

Literature survey related to the EBC/TBC (environmental barrier coating/thermal barrier coating) fife models, failure mechanisms in EBC/TBC and the initial work plan for the proposed EBC/TBC life prediction methods development was developed as well as the finite element model for the thermal/stress analysis of the GRC-developed EBC system was prepared. Technical report for these activities is given in the subsequent sections.

Failure mechanism for thermal fatigue of thermal barrier coating systems

Energy Technology Data Exchange (ETDEWEB)

Giolli, C.; Scrivani, A.; Rizzi, G. [Turbocoating S.p.A., Rubbiano di Solignano (Italy); Borgioli, F. [Firenze Univ., Sesto Fiorentino (Italy); Bolelli, G.; Lusvarghi, L. [Univ. di Modena e Reggio Emilia, Modena (Italy)

2008-07-01

High temperature thermal fatigue causes the failure of Thermal Barrier Coating (TBC) systems. Due to the difference in thickness and microstructure between thick TBCs and traditional thin TBCs, they cannot be assumed a-priori to possess the same failure mechanisms. Thick TBCs, consisting of a CoNiCrAlY bond coat and Yttria Partially Stabilised Zirconia top coat with different values of porosity, were produced by Air Plasma Spray. Thermal fatigue resistance limit of TBCs was tested by Furnace Cycling Tests (FCT) according to the specifications of an Original Equipment Manufacturer (OEM). TBC systems were analyzed before and after FCT. The morphological and chemical evolution of CoNiCrAlY/TGO microstructure was studied. Sintering effect, residual stress, phase transformation and fracture toughness were evaluated in the ceramic Top Coat. All the tested samples passed FCT according to the specification of an important OEM. Thermal fatigue resistance increases with the amount of porosity in the top coat. The compressive in-plane stresses increase in the TBC systems after thermal cycling, nevertheless the increasing rate has a trend contrary to the porosity level of top coat. The data suggest that the spallation happens at the TGO/Top Coat interface. The failure mechanism of thick TBCs subjected to thermal fatigue was eventually found to be similar to the failure mechanism of thin TBC systems made by APS. (orig.)

Tribological and wear behavior of yttria stabilized zirconia thermal barrier coatings on mild steel

International Nuclear Information System (INIS)

Farooq, M.; Pervez, A.

2012-01-01

The perfection of the temperature confrontation of the engine essentials can be obtained by claim of a single ceramic thermal barrier coating (TBC) or several composite layers. Engine elements protected by TBC can work safely in elevated temperature range above 1000 degree C. Continuous endeavor to increase thermal resistance of engine the elements requires, apart from laboratory investigations, also numerical study of the different engine parts. The high temperatures and stress concentrations can act as the local sources of damage initiation and defects propagation in the form of cracks. The current study focuses the development of Yttria stabilized zirconia thermal barrier coating by Thermal spray technique. Mild steel was used as a substrate and the coating was then characterized for tribological analysis followed by the optical analysis of wear tracks and found the TBC behavior more promising then steel. (author)

Oxidation behavior of niobium aluminide intermetallics protected by aluminide and silicide diffusion coatings

International Nuclear Information System (INIS)

Li, Y.; Soboyejo, W.; Rapp, R.A.

1999-01-01

The isothermal and cyclic oxidation behavior of a new class of damage-tolerant niobium aluminide (Nb 3 Al-xTi-yCr) intermetallics is studied between 650 C and 850 C. Protective diffusion coatings were deposited by pack cementation to achieve the siliciding or aluminizing of substrates with or without intervening Mo or Ni layers, respectively. The compositions and microstructures of the resulting coatings and oxidized surfaces were characterized. The isothermal and cyclic oxidation kinetics indicate that uncoated Nb-40Ti-15Al-based intermetallics may be used up to ∼750 C. Alloying with Cr improves the isothermal oxidation resistance between 650 C and 850 C. The most significant improvement in oxidation resistance is achieved by the aluminization of electroplated Ni interlayers. The results suggest that the high-temperature limit of niobium aluminide-based alloys may be increased to 800 C to 850 C by aluminide-based diffusion coatings on ductile Ni interlayers. Indentation fracture experiments also indicate that the ductile nickel interlayers are resistant to crack propagation in multilayered aluminide-based coatings

Evaluation of magnetostrictive composite coated fabric as a fragment barrier material

International Nuclear Information System (INIS)

Son, Kwon Joong; Fahrenthold, Eric P

2012-01-01

Over the last decade a surge in fragment barrier research has led to investigation of numerous materials and material augmentations in the attempt to improve the ballistic performance of systems designed to protect personnel, vehicles or infrastructure from impact and blast loads. One widely studied material augmentation approach is the use of coatings, often polymers, to enhance the performance of protection systems constructed from metal, concrete, composite and fabric materials. In recent research the authors have conducted the first experimental study of the ballistic performance of fabrics coated with a magnetically responsive polymer. Zero field impact experiments on coated fabric targets showed a 61% increase in impact energy dissipation, although the coated targets were not competitive with neat fabrics on a protection per unit mass basis. Under an applied field of 110 kA m −1 , the ballistic performance of the coated fabric was reduced. The reduction in performance may be attributed to a reduction in material damping and an increase in material modulus for the magnetostrictive component of the coating. Analysis of the coated fabric response to magnetic preloads suggests that coating tensile stresses and coating–fabric interface stresses induced by the applied field may also adversely affect ballistic performance. (paper)

Efficacy of Tantalum Tungsten Alloys for Diffusion Barrier Applications

Science.gov (United States)

Smathers, D. B.; Aimone, P. R.

2017-12-01

Traditionally either Niobium, Tantalum or a combination of both have been used as diffusion barriers in Nb3Sn Multi-filament wire. Vanadium has also been used successfully but the ultimate RRR of the copper is limited unless an external shell of Niobium is included. Niobium is preferred over Tantalum when alternating current losses are not an issue as the Niobium will react to form Nb3Sn. Pure Tantalum tends to deform irregularly requiring extra starting thickness to ensure good barrier qualities. Our evaluations showed Tantalum lightly alloyed with 3 wt% Tungsten is compatible with the wire drawing process while deforming as well as or better than pure Niobium. Ta3wt%W has been processed as a single barrier and as a distributed barrier to fine dimensions. In addition, the higher modulus and strength of the Tantalum Tungsten alloy improves the overall tensile properties of the wire.

Properties of Whey-Protein-Coated Films and Laminates as Novel Recyclable Food Packaging Materials with Excellent Barrier Properties

Directory of Open Access Journals (Sweden)

Markus Schmid

2012-01-01

Full Text Available In case of food packaging applications, high oxygen and water vapour barriers are the prerequisite conditions for preserving the quality of the products throughout their whole lifecycle. Currently available polymers and/or biopolymer films are mostly used in combination with barrier materials derived from oil based plastics or aluminium to enhance their low barrier properties. In order to replace these non-renewable materials, current research efforts are focused on the development of sustainable coatings, while maintaining the functional properties of the resulting packaging materials. This article provides an introduction to food packaging requirements, highlights prior art on the use of whey-based coatings for their barriers properties, and describes the key properties of an innovative packaging multilayer material that includes a whey-based layer. The developed whey protein formulations had excellent barrier properties almost comparable to the ethylene vinyl alcohol copolymers (EVOH barrier layer conventionally used in food packaging composites, with an oxygen barrier (OTR of <2 [cm³(STP/(m²d bar] when normalized to a thickness of 100 μm. Further requirements of the barrier layer are good adhesion to the substrate and sufficient flexibility to withstand mechanical load while preventing delamination and/or brittle fracture. Whey-protein-based coatings have successfully met these functional and mechanical requirements.

Investigations of surface coatings to reduce memory effect in plastic scintillator detectors used for radioxenon detection

Science.gov (United States)

Bläckberg, L.; Fay, A.; Jõgi, I.; Biegalski, S.; Boman, M.; Elmgren, K.; Fritioff, T.; Johansson, A.; Mårtensson, L.; Nielsen, F.; Ringbom, A.; Rooth, M.; Sjöstrand, H.; Klintenberg, M.

2011-11-01

In this work Al2O3 and SiO2 coatings are tested as Xe diffusion barriers on plastic scintillator substrates. The motivation is improved beta-gamma coincidence detection systems, used to measure atmospheric radioxenon within the verification regime of the Comprehensive Nuclear-Test-Ban Treaty. One major drawback with the current setup of these systems is that the radioxenon tends to diffuse into the plastic scintillator material responsible for the beta detection, resulting in an unwanted memory effect. Here, coatings with thicknesses between 20 and 900 nm have been deposited onto plastic scintillators, and investigated using two different experimental techniques. The results show that all tested coatings reduce the Xe diffusion into the plastic. The reduction is observed to increase with coating thickness for both coating materials. The 425 nm Al2O3 coating is the most successful one, presenting a diffusion reduction of a factor 100, compared to uncoated plastic. In terms of memory effect reduction this coating is thus a viable solution to the problem in question.

Investigations of surface coatings to reduce memory effect in plastic scintillator detectors used for radioxenon detection

International Nuclear Information System (INIS)

Blaeckberg, L.; Fay, A.; Jogi, I.; Biegalski, S.; Boman, M.; Elmgren, K.; Fritioff, T.; Johansson, A.; Martensson, L.; Nielsen, F.; Ringbom, A.; Rooth, M.; Sjoestrand, H.; Klintenberg, M.

2011-01-01

In this work Al 2 O 3 and SiO 2 coatings are tested as Xe diffusion barriers on plastic scintillator substrates. The motivation is improved beta-gamma coincidence detection systems, used to measure atmospheric radioxenon within the verification regime of the Comprehensive Nuclear-Test-Ban Treaty. One major drawback with the current setup of these systems is that the radioxenon tends to diffuse into the plastic scintillator material responsible for the beta detection, resulting in an unwanted memory effect. Here, coatings with thicknesses between 20 and 900 nm have been deposited onto plastic scintillators, and investigated using two different experimental techniques. The results show that all tested coatings reduce the Xe diffusion into the plastic. The reduction is observed to increase with coating thickness for both coating materials. The 425 nm Al 2 O 3 coating is the most successful one, presenting a diffusion reduction of a factor 100, compared to uncoated plastic. In terms of memory effect reduction this coating is thus a viable solution to the problem in question.

Optimization of High Porosity Thermal Barrier Coatings Generated with a Porosity Former

Science.gov (United States)

Medřický, Jan; Curry, Nicholas; Pala, Zdenek; Vilemova, Monika; Chraska, Tomas; Johansson, Jimmy; Markocsan, Nicolaie

2015-04-01

Yttria-stabilized zirconia thermal barrier coatings are extensively used in turbine industry; however, increasing performance requirements have begun to make conventional air plasma sprayed coatings insufficient for future needs. Since the thermal conductivity of bulk material cannot be lowered easily; the design of highly porous coatings may be the most efficient way to achieve coatings with low thermal conductivity. Thus the approach of fabrication of coatings with a high porosity level based on plasma spraying of ceramic particles of dysprosia-stabilized zirconia mixed with polymer particles, has been tested. Both polymer and ceramic particles melt in plasma and after impact onto a substrate they form a coating. When the coating is subjected to heat treatment, polymer burns out and a complex structure of pores and cracks is formed. In order to obtain desired porosity level and microstructural features in coatings; a design of experiments, based on changes in spray distance, powder feeding rate, and plasma-forming atmosphere, was performed. Acquired coatings were evaluated for thermal conductivity and thermo-cyclic fatigue, and their morphology was assessed using scanning electron microscopy. It was shown that porosity level can be controlled by appropriate changes in spraying parameters.

Microstructural Analysis and Transport Properties of Thermally Sprayed Multiple-Layer Ceramic Coatings

Science.gov (United States)

Wang, Hsin; Muralidharan, Govindarajan; Leonard, Donovan N.; Haynes, J. Allen; Porter, Wallace D.; England, Roger D.; Hays, Michael; Dwivedi, Gopal; Sampath, Sanjay

2018-02-01

Multilayer, graded ceramic/metal coatings were prepared by an air plasma spray method on Ti-6Al-4V, 4140 steel and graphite substrates. The coatings were designed to provide thermal barriers for diesel engine pistons to operate at higher temperatures with improved thermal efficiency and cleaner emissions. A systematic, progressive variation in the mixture of yttria-stabilized zirconia and bondcoat alloys (NiCoCrAlYHfSi) was designed to provide better thermal expansion match with the substrate and to improve thermal shock resistance and cycle life. Heat transfer through the layers was evaluated by a flash diffusivity technique based on a model of one-dimensional heat flow. The aging effect of the as-sprayed coatings was captured during diffusivity measurements, which included one heating and cooling cycle. The hysteresis of thermal diffusivity due to aging was not observed after 100-h annealing at 800 °C. The measurements of coatings on substrate and freestanding coatings allowed the influence of interface resistance to be evaluated. The microstructure of the multilayer coating was examined using scanning electron microscope and electron probe microanalysis.

Environmental Barrier Coatings for Ceramic Matrix Composites - An Overview

Science.gov (United States)

Lee, Kang; van Roode, Mark; Kashyap, Tania; Zhu, Dongming; Wiesner, Valerie

2017-01-01

SiC/SiC Ceramic Matrix Composites (CMCs) are increasingly being considered as structural materials for advanced power generation equipment because of their light weight, higher temperature capability, and oxidation resistance. Limitations of SiC/SiC CMCs include surface recession and component cracking and associated chemical changes in the CMC. The solutions pursued to improve the life of SiC/SiC CMCs include the incorporation of coating systems that provide surface protection, which has become known as an Environmental Barrier Coating (EBC). The development of EBCs for the protection of gas turbine hot section CMC components was a continuation of coating development work for corrosion protection of silicon-based monolithics. Work on EBC development for SiC/SiC CMCs has been ongoing at several national laboratories and the original gas turbine equipment manufacturers. The work includes extensive laboratory, rig and engine testing, including testing of EBC coated SiC/SiC CMCs in actual field applications. Another EBC degradation issue which is especially critical for CMC components used in aircraft engines is the degradation from glassy deposits of calcium-magnesium-aluminosilicate (CMAS) with other minor oxides. This paper addresses the need for and properties of external coatings on SiC/SiC CMCs to extend their useful life in service and the retention of their properties.

Surface diffusion of long chainlike molecules: The role of memory effects and stiffness on effective diffusion barriers

DEFF Research Database (Denmark)

Hjelt, T.; Vattulainen, Ilpo Tapio

2000-01-01

stiffness. Our primary aim is to consider the role played by chain stiffness and the resulting memory effects in tracer diffusion, and in particular their role in the effective tracer diffusion barrier E-A(T) extracted from the well-known Arrhenius form. We show that the memory effects in tracer diffusion......, for a single diffusing chain, about 20% of E-A(T) arises from temperature variations in the memory effects, while only the remaining part comes from thermally activated chain segment movements. At a finite coverage, the memory contribution in E-A(T) is even larger and is typically about 20%-40%. Further...... of recent experimental work as regards surface diffusion of long DNA molecules on a biological interface. (C) 2000 American Institute of Physics....

Advanced Environmental Barrier Coating Development for SiC-SiC Ceramic Matrix Composite Components

Science.gov (United States)

Zhu, Dongming; Harder, Bryan; Hurst, Janet B.; Halbig, Michael Charles; Puleo, Bernadette J.; Costa, Gustavo; Mccue, Terry R.

2017-01-01

This presentation reviews the NASA advanced environmental barrier coating (EBC) system development for SiC-SiC Ceramic Matrix Composite (CMC) combustors particularly under the NASA Environmentally Responsible Aviation, Fundamental Aeronautics and Transformative Aeronautics Concepts Programs. The emphases have been placed on the current design challenges of the 2700-3000F capable environmental barrier coatings for low NOX emission combustors for next generation turbine engines by using advanced plasma spray based processes, and the coating processing and integration with SiC-SiC CMCs and component systems. The developments also have included candidate coating composition system designs, degradation mechanisms, performance evaluation and down-selects; the processing optimizations using TriplexPro Air Plasma Spray Low Pressure Plasma Spray (LPPS), Plasma Spray Physical Vapor Deposition and demonstration of EBC-CMC systems. This presentation also highlights the EBC-CMC system temperature capability and durability improvements under the NASA development programs, as demonstrated in the simulated engine high heat flux, combustion environments, in conjunction with high heat flux, mechanical creep and fatigue loading testing conditions.

Thermal shock behavior of toughened gadolinium zirconate/YSZ double-ceramic-layered thermal barrier coating

International Nuclear Information System (INIS)

Zhong, Xinghua; Zhao, Huayu; Zhou, Xiaming; Liu, Chenguang; Wang, Liang; Shao, Fang; Yang, Kai; Tao, Shunyan; Ding, Chuanxian

2014-01-01

Highlights: • Gd 2 Zr 2 O 7 /YSZ DCL thermal barrier coating was designed and fabricated. • The Gd 2 Zr 2 O 7 top ceramic layer was toughened by addition of nanostructured 3YSZ. • Remarkable improvement in thermal shock resistance of the DCL coating was achieved. - Abstract: Double-ceramic-layered (DCL) thermal barrier coating system comprising of toughened Gadolinium zirconate (Gd 2 Zr 2 O 7 , GZ) as the top ceramic layer and 4.5 mol% Y 2 O 3 partially-stabilized ZrO 2 (4.5YSZ) as the bottom ceramic layer was fabricated by plasma spraying and thermal shock behavior of the DCL coating was investigated. The GZ top ceramic layer was toughened by addition of nanostructured 3 mol% Y 2 O 3 partially-stabilized ZrO 2 (3YSZ) to improve fracture toughness of the matrix. The thermal shock resistance of the DCL coating was enhanced significantly compared to that of single-ceramic-layered (SCL) GZ-3YSZ composite coating, which is believed to be primarily attributed to the two factors: (i) the increase in fracture toughness of the top ceramic layer by incorporating nanostructured YSZ particles and (ii) the improvement in strain tolerance through the utilization of 4.5YSZ as the bottom ceramic layer. In addition, the failure mechanisms are mainly attributed to the still low fracture toughness of the top ceramic layer and oxidation of the bond-coat

High temperature oxidation interfacial growth kinetics in YSZ thermal barrier coatings with bond coatings of NiCoCrAlY with 0.25% Hf

Energy Technology Data Exchange (ETDEWEB)

Soboyejo, W.O. [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States); Mensah, P., E-mail: mensah@engr.subr.edu [Department of Mechanical Engineering, Southern University and A and M College, Baton Rouge, LA 70813 (United States); Diwan, R. [Department of Mechanical Engineering, Southern University and A and M College, Baton Rouge, LA 70813 (United States); Crowe, J. [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States); Akwaboa, S. [Department of Mechanical Engineering, Southern University and A and M College, Baton Rouge, LA 70813 (United States)

2011-03-15

Research highlights: {yields} Isothermal oxidation of standard (STD) and vertically cracked (VC) TBCs has been investigated. {yields} The temporal TGO growth kinetics is parabolic in the temperature range between 900 and 1100 deg. C. {yields} Activation energies correspond to growth kinetics controlled by the diffusion of O{sub 2} in Al{sub 2}O{sub 3}. {yields} Variation in oxidation of TBCs is attributed to its microstructure and in-situ oxygen ingression. {yields} Doping TBC bond coat with Hf appears to have potential for enhancing the development of robust TBCs. - Abstract: The results of an experimental study of the high-temperature isothermal oxidation behavior and microstructural evolution in two variations of air plasma sprayed ceramic thermal barrier coatings (TBCs) are discussed in the paper. Two types of TBC specimens were produced for testing. These include a standard and vertically cracked APS. High temperature oxidation was carried out at 900, 1000, 1100 and 1200 deg. C. The experiments were performed in air under isothermal conditions. At each temperature, the specimens were exposed for 25, 50, 75 and 100 h. The corresponding microstructures and microchemistries of the TBC layers were examined using scanning electron microscopy and energy dispersive X-ray spectroscopy. Changes in the dimensions of the thermally grown oxide layer were determined as functions of time and temperature. The evolution of bond coat microstructures/interdiffusion zones and thermally grown oxide layers were compared in the TBC specimens with standard and vertically cracked microstructures.

Self-healing thermal barrier coatings; with application to gas turbine engines

NARCIS (Netherlands)

Ponnusami, S.A.

2013-01-01

Thermal Barrier Coating (TBC) systems have been applied in turbine engines for aerospace and power plants since the beginning of the 1980s to increase the energy efficiency of the engine, by allowing for higher operation temperatures. TBC systems on average need to be replaced about four times

A density functional theory study of the carbon-coating effects on lithium iron borate battery electrodes

DEFF Research Database (Denmark)

Loftager, Simon; García Lastra, Juan Maria; Vegge, Tejs

2017-01-01

a density functional theory (DFT) study of the anchoring configurations of carbon coating on the LiFeBO3 electrode and its implications on the interfacial lithium diffusion. Due to large barriers associated with Li-ion diffusion through a parallel-oriented pristine graphene coating on the FeBO3 and LiFeBO3......Lithium iron borate (LiFeBO3) is a promising cathode material due to its high theoretical specific capacity, inexpensive components and a small volume change during operation. Yet, challenges relating to severe air- and moisture-induced degradation necessitate the application of a protective...... coating on the electrode which also improves the electronic conductivity. However, not much is known about the preferential geometries of the coating as well as how these coating–electrode interfaces influence the lithium diffusion between the coating and the electrode. Here, we therefore present...

A novel method for calculating the energy barriers for carbon diffusion in ferrite under heterogeneous stress

Science.gov (United States)

Tchitchekova, Deyana S.; Morthomas, Julien; Ribeiro, Fabienne; Ducher, Roland; Perez, Michel

2014-07-01

A novel method for accurate and efficient evaluation of the change in energy barriers for carbon diffusion in ferrite under heterogeneous stress is introduced. This method, called Linear Combination of Stress States, is based on the knowledge of the effects of simple stresses (uniaxial or shear) on these diffusion barriers. Then, it is assumed that the change in energy barriers under a complex stress can be expressed as a linear combination of these already known simple stress effects. The modifications of energy barriers by either uniaxial traction/compression and shear stress are determined by means of atomistic simulations with the Climbing Image-Nudge Elastic Band method and are stored as a set of functions. The results of this method are compared to the predictions of anisotropic elasticity theory. It is shown that, linear anisotropic elasticity fails to predict the correct energy barrier variation with stress (especially with shear stress) whereas the proposed method provides correct energy barrier variation for stresses up to ˜3 GPa. This study provides a basis for the development of multiscale models of diffusion under non-uniform stress.

A novel method for calculating the energy barriers for carbon diffusion in ferrite under heterogeneous stress

International Nuclear Information System (INIS)

Tchitchekova, Deyana S.; Morthomas, Julien; Perez, Michel; Ribeiro, Fabienne; Ducher, Roland

2014-01-01

A novel method for accurate and efficient evaluation of the change in energy barriers for carbon diffusion in ferrite under heterogeneous stress is introduced. This method, called Linear Combination of Stress States, is based on the knowledge of the effects of simple stresses (uniaxial or shear) on these diffusion barriers. Then, it is assumed that the change in energy barriers under a complex stress can be expressed as a linear combination of these already known simple stress effects. The modifications of energy barriers by either uniaxial traction/compression and shear stress are determined by means of atomistic simulations with the Climbing Image-Nudge Elastic Band method and are stored as a set of functions. The results of this method are compared to the predictions of anisotropic elasticity theory. It is shown that, linear anisotropic elasticity fails to predict the correct energy barrier variation with stress (especially with shear stress) whereas the proposed method provides correct energy barrier variation for stresses up to ∼3 GPa. This study provides a basis for the development of multiscale models of diffusion under non-uniform stress

A novel method for calculating the energy barriers for carbon diffusion in ferrite under heterogeneous stress

Energy Technology Data Exchange (ETDEWEB)

Tchitchekova, Deyana S. [IRSN, PSN, SEMIA, LPTM, Saint-Paul-Lez-Durance (France); Univ. Lyon, INSA Lyon, MATEIS, UMR CNRS 5510, Villeurbanne (France); Morthomas, Julien; Perez, Michel [Univ. Lyon, INSA Lyon, MATEIS, UMR CNRS 5510, Villeurbanne (France); Ribeiro, Fabienne [IRSN, PSN, SEMIA, LPTM, Saint-Paul-Lez-Durance (France); Ducher, Roland [IRSN, PSN, SAG, LETR, Saint-Paul-Lez-Durance (France)

2014-07-21

A novel method for accurate and efficient evaluation of the change in energy barriers for carbon diffusion in ferrite under heterogeneous stress is introduced. This method, called Linear Combination of Stress States, is based on the knowledge of the effects of simple stresses (uniaxial or shear) on these diffusion barriers. Then, it is assumed that the change in energy barriers under a complex stress can be expressed as a linear combination of these already known simple stress effects. The modifications of energy barriers by either uniaxial traction/compression and shear stress are determined by means of atomistic simulations with the Climbing Image-Nudge Elastic Band method and are stored as a set of functions. The results of this method are compared to the predictions of anisotropic elasticity theory. It is shown that, linear anisotropic elasticity fails to predict the correct energy barrier variation with stress (especially with shear stress) whereas the proposed method provides correct energy barrier variation for stresses up to ∼3 GPa. This study provides a basis for the development of multiscale models of diffusion under non-uniform stress.

Drug diffusion and biological responses of arteries using a drug-eluting stent with nonuniform coating

Directory of Open Access Journals (Sweden)

Saito N

2016-03-01

Full Text Available Noboru Saito, Yuhei Mori, Sayaka Uchiyama Terumo Corporation R&D Center, Inokuchi, Nakai-machi, Ashigarakami-gun, Kanagawa, Japan Abstract: The purpose of this study was to determine the effect of a nonuniform coating, abluminal-gradient coating (AGC, which leaves the abluminal surface of the curves and links parts of the stent free from the drug coating, on the diffusion direction of the drug and the biological responses of the artery to drug-eluting stent (DES by comparing the AGC-sirolimus stent and the conventional full-surface coating (CFC sirolimus stent. The study aimed to verify whether the AGC approach was appropriate for the development of a safer DES, minimizing the risks of stent thrombosis due to delayed endothelialization by the drug and distal embolization due to cracking of the coating layer on the hinge parts of the DES on stent expansion. In the in vitro local drug diffusion study, we used rhodamine B as a model drug, and rhodamine B released from the AGC stent diffused predominantly into the abluminal side of the alginate artery model. Conversely, rhodamine B released from the CFC stent quickly spread to the luminal side of the artery model, where endothelial cell regeneration is required. In the biological responses study, the luminal surface of the iliac artery implanted with the AGC-sirolimus stent in a rabbit iliac artery for 2 weeks was completely covered with endothelial-like cells. On the other hand, the luminal surface of the iliac artery implanted with the CFC-sirolimus stent for 2 weeks only showed partial coverage with endothelial-like cells. While thrombosis was observed in two of the three CFC-sirolimus stents, it was observed in only one of the three AGC-sirolimus stents. Taken together, these findings indicate that the designed nonuniform coating (AGC is an appropriate approach to ensure a safer DES. However, the number of studies is limited and a larger study should be conducted to reach a statistically

Plasma sprayed thermal barrier coatings for industrial gas turbines: morphology, processing and properties

International Nuclear Information System (INIS)

Gruenling, H.W.; Mannsmann, W.

1993-01-01

Thermal barrier coatings out of fully or partially stabilized zirconia offer a unique chance in gas turbines to increase the gas inlet temperature significantly while keeping the temperature of the structural material of the component within conventional limits. The protection of combustor parts and transition pieces as well as of some stationary gas turbine parts however is state of the art. As a consequence of still insufficient reliability, the application for hot rotating parts is very limited. The introduction as a design element requires safe life within defined time intervals. These depend on the overhaul and repair intervals of the engines. For large land based industrial or utility gas turbines, for example, coating life between 25.000 and 30.000 hrs. is a minimum requirement. Premature failure of a coating by e.g. local spalling causes local overheating of the component with the consequence of its total destruction or even more expensive secondary damages. Life limiting is the corrosion rate at the ceramic-metal interface and the behavior of the coated system under transient operating conditions, where multiaxial strain and stress distributions are generated. Sufficient strain tolerance of the coating both under tensile as well as compressive conditions is required. The properties of thermal barrier coating systems depend strongly on the structure and phase composition of the coating layers and the morphology of and the adhesion at the ceramic-metal interface. They have to be controlled by the process itself, the process parameters and the characteristics of the applied materials (e.g. chemical composition, processing, morphology, particle size and size distribution). It will be reviewed, how properties and structures of coating systems correlate and how structures can be modified by careful control of the process parameters. (orig.)

Effects of barrier composition and electroplating chemistry on adhesion and voiding in copper/dielectric diffusion barrier films

Energy Technology Data Exchange (ETDEWEB)

Birringer, Ryan P.; Dauskardt, Reinhold H. [Department of Materials Science and Engineering, Stanford University, Durand Building, Stanford, California 94305-4034 (United States); Shaviv, Roey [Novellus Systems Inc., 4000 North First Street, San Jose, California 95134 (United States); Geiss, Roy H.; Read, David T. [National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305 (United States)

2011-08-15

The effects of electroplating chemistry and dielectric diffusion barrier composition on copper voiding and barrier adhesion are reported. Adhesion was quantified using the four-point bend thin film adhesion technique, and voiding in the Cu films was quantified using scanning electron microscopy. A total of 12 different film stacks were investigated, including three different Cu electroplating chemistries and four different barrier materials (SiN, N-doped SiC, O-doped SiC, and dual-layer SiC). Both plating chemistry and barrier composition have a large effect on interface adhesion and voiding in the Cu film. X-ray photoelectron spectroscopy was used to investigate the segregation of Cu electroplating impurities, such as S and Cl, to the Cu/barrier interface. Secondary ion mass spectrometry was used to quantify oxygen content at the Cu/barrier interface in a subset of samples. This interface oxygen content is correlated with measured adhesion values.

Microstructure Analysis of Laser Remelting for Thermal Barrier Coatings on the Surface of Titanium Alloy

Directory of Open Access Journals (Sweden)

Lu Bin

2016-01-01

Full Text Available In this paper, the preparation and organization performance of thermal barrier coatings (TCBs on the surface of titanium were studied experimentally. Nanostructured 8 wt% yttria partially stabilized zirconia coatings were deposited by air plasma spraying. The microstructure of nanostructured and the conventional coating was studied after laser remelting. It has shown that formed a network of micro-cracks and pits after laser remelting on nanostructured coatings. With the decrease of the laser scanning speed, mesh distribution of micro cracks was gradually thinning on nanostructured coatings. Compared with conventional ceramic layers, the mesh cracks of nanostructured coating is dense and the crack width is small.

Robust TaNx diffusion barrier for Cu-interconnect technology with subnanometer thickness by metal-organic plasma-enhanced atomic layer deposition

International Nuclear Information System (INIS)

Kim, H.; Detavenier, C.; Straten, O. van der; Rossnagel, S.M.; Kellock, A.J.; Park, D.-G.

2005-01-01

TaN x diffusion barriers with good barrier properties at subnanometer thickness were deposited by plasma-enhanced atomic layer deposition (PE-ALD) from pentakis(dimethylamino)Ta. Hydrogen and/or nitrogen plasma was used as reactants to produce TaN x thin films with a different nitrogen content. The film properties including the carbon and oxygen impurity content were affected by the nitrogen flow during the process. The deposited film has nanocrystalline grains with hydrogen-only plasma, while the amorphous structure was obtained for nitrogen plasma. The diffusion barrier properties of deposited TaN films for Cu interconnects have been studied by thermal stress test based on synchrotron x-ray diffraction. The results indicate that the PE-ALD TaN films are good diffusion barriers even at a small thickness as 0.6 nm. Better diffusion barrier properties were obtained for higher nitrogen content. Based on a diffusion kinetics analysis, the nanocrystalline microstructure of the films was responsible for the better diffusion barrier properties compared to polycrystalline PE-ALD TaN films deposited from TaCl 5

BARRIERS TO THE USE OF RADIATION-CURABLE ADHESIVES IN THE COATED AND LAMINATED SUBSTRATE MANUFACTURING INDUSTRY

Science.gov (United States)

The paper gives results of an investigation of barriers to the use of radiation-cured technology in the coated and laminated substrate manufacturing industry. t presents information gathered from radiation-curable coating and equipment suppliers as well as technical publications....

Thermal failure of nanostructured thermal barrier coatings with cold sprayed nanostructured NiCrAlY bond coat

Energy Technology Data Exchange (ETDEWEB)

Zhang, Q.; Li, Y.; Zhang, S.L.; Wang, X.R.; Yang, G.J.; Li, C.X.; Li, C.J. [Xi' an Jiaotong Univ., Xi' an (China)

2008-07-01

Nanostructured YSZ is expected to exhibit a high strain tolerability due to its low Young's modulus and consequently high durability. In this study, a porous YSZ as the thermal barrier coating was deposited by plasma spraying using an agglomerated nanostructured YSZ powder on a Ni-based superalloy Inconel 738 substrate with a cold-sprayed nanostructured NiCrAlY as the bond coat. The heat treatment in Ar atmosphere was applied to the cold-sprayed bond coat before deposition of YSZ. The isothermal oxidation and thermal cycling tests were applied to examine failure modes of plasma-sprayed nanostructured YSZ. The results showed that YSZ coating was deposited by partially melted YSZ particles. The nonmelted fraction of spray particles retains the porous nanostructure of the starting powder into the deposit. YSZ coating exhibits a bimodal microstructure consisting of nanosized particles retained from the powder and micro-columnar grains formed through the solidification of the melted fraction in spray particles. The oxidation of the bond coat occurs during the heat treatment in Ar atmosphere. The uniform oxide at the interface between the bond coat and YSZ can be formed during isothermal test. The cracks were observed at the interface between TGO/BC or TGO/YSZ after thermal cyclic test. However, the failure of TBCs mainly occurred through spalling of YSZ within YSZ coating. The failure characteristics of plasma-sprayed nanostructured YSZ are discussed based on the coating microstructure and formation of TGO on the bond coat surface. (orig.)

The Development of Environmental Barrier Coating Systems for SiC-SiC Ceramic Matrix Composites: Environment Effects on the Creep and Fatigue Resistance

Science.gov (United States)

Zhu, Dongming; Ghosn, Louis J.

2014-01-01

Topics covered include: Environmental barrier coating system development: needs, challenges and limitations; Advanced environmental barrier coating systems (EBCs) for CMC airfoils and combustors; NASA EBC systems and material system evolutions, Current turbine and combustor EBC coating emphases, Advanced development, processing, testing and modeling, EBC and EBC bond coats: recent advances; Design tool and life prediction of coated CMC components; Advanced CMC-EBC rig demonstrations; Summary and future directions.

A modelling approach to designing microstructures in thermal barrier coatings

International Nuclear Information System (INIS)

Gupta, M.; Nylen, P.; Wigren, J.

2013-01-01

Thermomechanical properties of Thermal Barrier Coatings (TBCs) are strongly influenced by coating defects, such as delaminations and pores, thus making it essential to have a fundamental understanding of microstructure-property relationships in TBCs to produce a desired coating. Object-Oriented Finite element analysis (OOF) has been shown previously as an effective tool for evaluating thermal and mechanical material behaviour, as this method is capable of incorporating the inherent material microstructure as input to the model. In this work, OOF was used to predict the thermal conductivity and effective Young's modulus of TBC topcoats. A Design of Experiments (DoE) was conducted by varying selected parameters for spraying Yttria-Stabilised Zirconia (YSZ) topcoat. The microstructure was assessed with SEM, and image analysis was used to characterize the porosity content. The relationships between microstructural features and properties predicted by modelling are discussed. The microstructural features having the most beneficial effect on properties were sprayed with a different spray gun so as to verify the results obtained from modelling. Characterisation of the coatings included microstructure evaluation, thermal conductivity and lifetime measurements. The modelling approach in combination with experiments undertaken in this study was shown to be an effective way to achieve coatings with optimised thermo-mechanical properties.

TGO growth and crack propagation in a thermal barrier coating

Energy Technology Data Exchange (ETDEWEB)

Chen, W.R.; Archer, R.; Huang, X. [National Research Council of Canada, Ottawa, ON (Canada); Marple, B.R. [National Research Council of Canada, Boucherville, PQ (Canada)

2008-07-01

In thermal barrier coating (TBC) systems, a continuous alumina layer developed at the ceramic topcoat/bond coat interface helps to protect the metallic bond coat from further oxidation and improve the durability of the TBC system under service conditions. However, other oxides such as spinel and nickel oxide, formed in the oxidizing environment, are believed to be detrimental to TBC durability during service at high temperatures. It was shown that in an air-plasma-sprayed (APS) TBC system, post-spraying heat treatments in low-pressure oxygen environments could suppress the formation of the detrimental oxides by promoting the formation of an alumina layer at the ceramic topcoat/bond coat interface, leading to an improved TBC durability. This work presents the influence of post-spraying heat treatments in low-pressure oxygen environments on the oxidation behaviour and durability of a thermally sprayed TBC system with high-velocity oxy-fuel (HVOF)-produced Co-32Ni-21Cr-8Al-0.5Y (wt.%) bond coat. Oxidation behaviour of the TBCs is evaluated by examining their microstructural evolution, growth kinetics of the thermally grown oxide (TGO) layers, as well as crack propagation during low frequency thermal cycling at 1050 C. The relationship between the TGO growth and crack propagation will also be discussed. (orig.)

Detection of thermally grown oxides in thermal barrier coatings by nondestructive evaluation

Science.gov (United States)

Fahr, A.; Rogé, B.; Thornton, J.

2006-03-01

The thermal-barrier coatings (TBC) sprayed on hot-section components of aircraft turbine engines commonly consist of a partially stabilized zirconia top-coat and an intermediate bond-coat applied on the metallic substrate. The bond-coat is made of an aluminide alloy that at high engine temperatures forms thermally grown oxides (TGO). Although formation of a thin layer of aluminum oxide at the interface between the ceramic top-coat and the bond-coat has the beneficial effect of protecting the metallic substrate from hot gases, oxide formation at splat boundaries or pores within the bond-coat is a source of weakness. In this study, plasma-sprayed TBC specimens are manufactured from two types of bond-coat powders and exposed to elevated temperatures to form oxides at the ceramic-bond-coat boundary and within the bond-coat. The specimens are then tested using nondestructive evaluation (NDE) and destructive metallography and compared with the as-manufactured samples. The objective is to determine if NDE can identify the oxidation within the bond-coat and give indication of its severity. While ultrasonic testing can provide some indication of the degree of bond-coat oxidation, the eddy current (EC) technique clearly identifies severe oxide formation within the bond-coat. Imaging of the EC signals as the function of probe location provides information on the spatial variations in the degree of oxidation, and thereby identifies which components or areas are prone to premature damage.

Mechanisms of oxygen permeation through plastic films and barrier coatings

International Nuclear Information System (INIS)

Wilski, Stefan; Wipperfürth, Jens; Jaritz, Montgomery; Kirchheim, Dennis; Dahlmann, Rainer; Hopmann, Christian; Mitschker, Felix; Awakowicz, Peter

2017-01-01

Oxygen and water vapour permeation through plastic films in food packaging or other applications with high demands on permeation are prevented by inorganic barrier films. Most of the permeation occurs through small defects (<3 µ m) in the barrier coating. The defects were visualized by etching with reactive oxygen in a capacitively coupled plasma and subsequent SEM imaging. In this work, defects in SiO x -coatings deposited by plasma-enhanced chemical vapour deposition on polyethylene terephthalate (PET) are investigated and the mass transport through the polymer is simulated in a 3D approach. Calculations of single defects showed that there is no linear correlation between the defect area and the resulting permeability. The influence of adjacent defects in different distances was observed and led to flow reduction functions depending on the defect spacing and defect area. A critical defect spacing where no interaction between defects occurs was found and compared to other findings. According to the superposition principle, the permeability of single defects was added up and compared to experimentally determined oxygen permeation. The results showed the same trend of decreasing permeability with decreasing defect densities. (paper)

Conjugate heat transfer investigation on the cooling performance of air cooled turbine blade with thermal barrier coating

Science.gov (United States)

Ji, Yongbin; Ma, Chao; Ge, Bing; Zang, Shusheng

2016-08-01

A hot wind tunnel of annular cascade test rig is established for measuring temperature distribution on a real gas turbine blade surface with infrared camera. Besides, conjugate heat transfer numerical simulation is performed to obtain cooling efficiency distribution on both blade substrate surface and coating surface for comparison. The effect of thermal barrier coating on the overall cooling performance for blades is compared under varied mass flow rate of coolant, and spatial difference is also discussed. Results indicate that the cooling efficiency in the leading edge and trailing edge areas of the blade is the lowest. The cooling performance is not only influenced by the internal cooling structures layout inside the blade but also by the flow condition of the mainstream in the external cascade path. Thermal barrier effects of the coating vary at different regions of the blade surface, where higher internal cooling performance exists, more effective the thermal barrier will be, which means the thermal protection effect of coatings is remarkable in these regions. At the designed mass flow ratio condition, the cooling efficiency on the pressure side varies by 0.13 for the coating surface and substrate surface, while this value is 0.09 on the suction side.

Life Prediction Issues in Thermal/Environmental Barrier Coatings in Ceramic Matrix Composites

Science.gov (United States)

Shah, Ashwin R.; Brewer, David N.; Murthy, Pappu L. N.

2001-01-01

Issues and design requirements for the environmental barrier coating (EBC)/thermal barrier coating (TBC) life that are general and those specific to the NASA Ultra-Efficient Engine Technology (UEET) development program have been described. The current state and trend of the research, methods in vogue related to the failure analysis, and long-term behavior and life prediction of EBCITBC systems are reported. Also, the perceived failure mechanisms, variables, and related uncertainties governing the EBCITBC system life are summarized. A combined heat transfer and structural analysis approach based on the oxidation kinetics using the Arrhenius theory is proposed to develop a life prediction model for the EBC/TBC systems. Stochastic process-based reliability approach that includes the physical variables such as gas pressure, temperature, velocity, moisture content, crack density, oxygen content, etc., is suggested. Benefits of the reliability-based approach are also discussed in the report.

Characterization and evaluation of EB-PVD thermal barrier coatings by impedance spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Zhang Chunxia; Liu Fushun; Gong Shengkai; Xu Huibin [School of Materials Science and Engineering, Beihang Univ., Beijing, BJ (China)

2005-07-01

Two layer thermal barrier coatings (TBCs) were prepared by EB-PVD (electron beam-physical vapor deposition) at different substrate temperatures in the range of 823 to 1123 K, and their microstructure was investigated with SEM and AC impedance as a function of substrate temperature and thermal cycling time. YSZ layer of all TBCs samples is in column structure, but the grain size and growth orientation are different with substrate. In this research, impedance spectra (IS) was measured as a function of thermal cycling between 1323 K and 298 K for these thermal barrier coatings. Grain boundary and bulk can be distinguished from analysis of AC impedance spectroa to provide information about the relation between microstructure and electric properties. The change in IS until failure was found to be related with the thickness, microcracks and macrocracks of TGO and the change in the interfacial of TGO/YSZ. (orig.)

Evolution of pore microstructure in thermal barrier coatings studied by SANS

Czech Academy of Sciences Publication Activity Database

Haug, J.; Wiedenmann, A.; Flores, A.; Saruhan-Brings, B.; Strunz, Pavel

2006-01-01

Roč. 385, č. 1 (2006), s. 617-619 ISSN 0921-4526 R&D Projects: GA ČR GA202/06/0601 Institutional research plan: CEZ:AV0Z10480505 Keywords : thermal barrier coatings * electron beam physical vapor deposition * SANS Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.872, year: 2006

Influence of coatings on the corrosion fatigue behaviour on 13% chromium steel

Energy Technology Data Exchange (ETDEWEB)

Schmitt-Thomas, K G; Meisel, H; Sessler, W

1986-01-01

The influence of coatings on the corrosion fatigue behaviour of 13% chromium steel has been studied. There have been selected different coating systems: Barrier coating (enamel), diffusion coatings, (aluminizing, chromizing) and anodic coating, (aluminium, zinc, tin, cadmium). The corrosion fatigue limits of coated with uncoated specimens in neutral NaCl-solution are compared. Salt-concentrations were 0,01 and 22% (=0,38 M) NaCl at 80/sup 0/C and 150/sup 0/C. The tests were carried out with alternating tensions and a constant frequency of 50 Hz. Only the use of anodic coatings improved the corrosion fatigue behaviour of the chromium steel.

Diffusion chamber system for testing of collagen-based cell migration barriers for separation of ligament enthesis zones in tissue-engineered ACL constructs.

Science.gov (United States)

Hahner, J; Hoyer, M; Hillig, S; Schulze-Tanzil, G; Meyer, M; Schröpfer, M; Lohan, A; Garbe, L-A; Heinrich, G; Breier, A

2015-01-01

A temporary barrier separating scaffold zones seeded with different cell types prevents faster growing cells from overgrowing co-cultured cells within the same construct. This barrier should allow sufficient nutrient diffusion through the scaffold. The aim of this study was to test the effect of two variants of collagen-based barriers on macromolecule diffusion, viability, and the spreading efficiency of primary ligament cells on embroidered scaffolds. Two collagen barriers, a thread consisting of a twisted film tape and a sponge, were integrated into embroidered poly(lactic-co-caprolactone) and polypropylene scaffolds, which had the dimension of lapine anterior cruciate ligaments (ACL). A diffusion chamber system was designed and established to monitor nutrient diffusion using fluorescein isothiocyanate-labeled dextran of different molecular weights (20, 40, 150, 500 kDa). Vitality of primary lapine ACL cells was tested at days 7 and 14 after seeding using fluorescein diacetate and ethidium bromide staining. Cell spreading on the scaffold surface was measured using histomorphometry. Nuclei staining of the cross-sectioned scaffolds revealed the penetration of ligament cells through both barrier types. The diffusion chamber was suitable to characterize the diffusivity of dextran molecules through embroidered scaffolds with or without integrated collagen barriers. The diffusion coefficients were generally significantly lower in scaffolds with barriers compared to those without barriers. No significant differences between diffusion coefficients of both barrier types were detected. Both barriers were cyto-compatible and prevented most of the ACL cells from crossing the barrier, whereby the collagen thread was easier to handle and allowed a higher rate of cell spreading.

SiC fiber and yttria-stabilized zirconia composite thick thermal barrier coatings fabricated by plasma spray

Science.gov (United States)

Ma, Rongbin; Cheng, Xudong; Ye, Weiping

2015-12-01

Approximately 4 mm-thick SiC fiber/yttria-stabilized zirconia (YSZ) composite thermal barrier coatings (TBCs) were prepared by atmospheric plasma spray (APS). The composite coatings have a 'reinforced concrete frame structure', which can protect the coating from failure caused by increasing thickness of coating. The SiC fiber plays an important role in reducing the residual stress level of the composite coatings. The thermal conductivity (TC) value of the composite coatings is 0.632 W/m K, which is about 50% reduction compared to that of typical APS YSZ TBCs. And the composite coatings have higher fracture toughness and better thermal shock resistance than the YSZ TBCs.

Tritium/hydrogen barrier development

International Nuclear Information System (INIS)

Hollenberg, G.W.; Simonen, E.P.; Kalinen, G.; Terlain, A.

1994-06-01

A review of hydrogen permeation barriers that can be applied to structural metals used in fusion power plants is presented. Both implanted and chemically available hydrogen isotopes must be controlled in fusion plants. The need for permeation barriers appears strongest in Li17-Pb blanket designs, although barriers also appear necessary for other blanket and coolant systems. Barriers that provide greater than a 1000 fold reduction in the permeation of structural metals are desired. In laboratory experiments, aluminide and titanium ceramic coatings provide permeation reduction factors, PRFS, from 1000 to over 100,000 with a wide range of scatter. The rate-controlling mechanism for hydrogen permeation through these barriers may be related to the number and type of defects in the barriers. Although these barriers appear robust and resistant to liquid metal corrosion, irradiation tests which simulate blanket environments result in very low PRFs in comparison to laboratory experiments, i.e., <150. It is anticipated from fundamental research activities that the REID enhancement of hydrogen diffusion in oxides may contribute to the lower permeation reduction factors during in-reactor experiments

Thermal Fatigue Behavior of Air-Plasma Sprayed Thermal Barrier Coating with Bond Coat Species in Cyclic Thermal Exposure

Directory of Open Access Journals (Sweden)

Ungyu Paik

2013-08-01

Full Text Available The effects of the bond coat species on the delamination or fracture behavior in thermal barrier coatings (TBCs was investigated using the yclic thermal fatigue and thermal-shock tests. The interface microstructures of each TBC showed a good condition without cracking or delamination after flame thermal fatigue (FTF for 1429 cycles. The TBC with the bond coat prepared by the air-plasma spray (APS method showed a good condition at the interface between the top and bond coats after cyclic furnace thermal fatigue (CFTF for 1429 cycles, whereas the TBCs with the bond coats prepared by the high-velocity oxygen fuel (HVOF and low-pressure plasma spray (LPPS methods showed a partial cracking (and/or delamination and a delamination after 780 cycles, respectively. The TBCs with the bond coats prepared by the APS, HVOF and LPPS methods were fully delaminated (>50% after 159, 36, and 46 cycles, respectively, during the thermal-shock tests. The TGO thickness in the TBCs was strongly dependent on the both exposure time and temperature difference tested. The hardness values were found to be increased only after the CFTF, and the TBC with the bond coat prepared by the APS showed the highest adhesive strength before and after the FTF.

A heating and diffusion barrier based on TaSiN x for miniaturized IC devices

International Nuclear Information System (INIS)

Cheng, H.-Y.; Chen, Y.-C.; Lee, C.-M.; Wang, S.-H.; Chin, T.-S.

2006-01-01

Highly resistive TaSiN x films investigated as candidates for heating and diffusion-barrier layers for miniaturized IC devices such as a sensor or a phases-change random access memory (PCRAM). The obtained resistivity, between 0.069-1.21 Ω cm, increases with increasing nitrogen content up to 52.83%, and fulfills the requirements as a suitable heating layer. All the as-deposited films were amorphous, and the films with substantial nitrogen content showed excellent thermal stability The amorphous structure had a very smooth surface which was stable at temperatures up to 800 deg. C. In addition to its heating capability, the amorphous structure with no grain boundaries was found to also act as a good diffusion barrier effect in contact with a tungsten electrode as determined by AES an TEM analysis. The barrier effect was evaluated by an annealing at 500 and 600 deg. C in Ar atmosphere for 30 min, respectively. The highly resistive TaSiN x heating layer successfully obstructed the diffusion of tungsten atoms from the W electrodes even when the layer was only 10 nm thick. With increasing N content, the heating and diffusion-barrier layer for PCRAM was proposed as a typical example of many potential applications

Preparation and enhanced oxidation performance of a Hf-doped single-phase Pt-modified aluminide coating

International Nuclear Information System (INIS)

Yang, Y.F.; Jiang, C.Y.; Yao, H.R.; Bao, Z.B.; Zhu, S.L.; Wang, F.H.

2016-01-01

Graphical abstract: Tiny Hf particles were successfully incorporated into Pt plating via simple electro-plating method. The hafnium particles were either nipped at Pt grain boundaries or wrapped inside Pt grains, and most of them were below 3 μm in size, showing a uniform distribution within the Pt plating. - Highlights: • A Hf-rich belt formed between outer (Ni,Pt)Al and IDZ after aluminisation. • Hf-doped coating showed much decreased mass gain and oxidation rate constant k_p. • Hf-rich belt acted as diffusion barrier by restraining diffusions of Al and W. • Degradation of β was effectively postponed by the unique Hf addition. • Hf-doped coating exhibited lighter oxide scale rumpling tendency. - Abstract: A Hf-doped β-(Ni,Pt)Al coating was prepared by co-deposition of a Pt-Hf composite plating and successive aluminisation. Then, a distinct Hf-rich belt was formed internally between the outer additive (Ni,Pt)Al coating and interdiffusion zone. An isothermal oxidation test at 1100 °C revealed a relatively lower oxidation rate constant and decreased oxide scale rumpling tendency for the Hf-doped coating during which the Hf-rich belt partly acted as an effective diffusion barrier. The unique addition of Hf into a β-(Ni,Pt)Al coating can delay the transitional oxidation period from transient alumina to stable one and postpone the degradation from β to γ'.

Kinetic Monte Carlo Simulation of Cation Diffusion in Low-K Ceramics

Science.gov (United States)

Good, Brian

2013-01-01

Low thermal conductivity (low-K) ceramic materials are of interest to the aerospace community for use as the thermal barrier component of coating systems for turbine engine components. In particular, zirconia-based materials exhibit both low thermal conductivity and structural stability at high temperature, making them suitable for such applications. Because creep is one of the potential failure modes, and because diffusion is a mechanism by which creep takes place, we have performed computer simulations of cation diffusion in a variety of zirconia-based low-K materials. The kinetic Monte Carlo simulation method is an alternative to the more widely known molecular dynamics (MD) method. It is designed to study "infrequent-event" processes, such as diffusion, for which MD simulation can be highly inefficient. We describe the results of kinetic Monte Carlo computer simulations of cation diffusion in several zirconia-based materials, specifically, zirconia doped with Y, Gd, Nb and Yb. Diffusion paths are identified, and migration energy barriers are obtained from density functional calculations and from the literature. We present results on the temperature dependence of the diffusivity, and on the effects of the presence of oxygen vacancies in cation diffusion barrier complexes as well.

A bilayer diffusion barrier of Ru/WSi{sub x}N{sub y} for advanced Cu interconnects

Energy Technology Data Exchange (ETDEWEB)

Eom, Tae-Kwang; Sari, Windu [School of Materials Science and Engineering, Yeungnam University 214-1, Dae-dong, Gyeongsan-si, Gyeongsangbuk-do, 712-749 (Korea, Republic of); Cheon, Taehoon [Center for Core Research Facilities, Daegu Gyeongbuk Institute of Science and Technology, Sang-ri, Hyeonpung-myeon, Dalseong-gun, Daegu, 711-873 (Korea, Republic of); Kim, Soo-Hyun, E-mail: soohyun@ynu.ac.kr [School of Materials Science and Engineering, Yeungnam University 214-1, Dae-dong, Gyeongsan-si, Gyeongsangbuk-do, 712-749 (Korea, Republic of); Kim, Woo Kyoung [School of Chemical Engineering, Yeungnam University 214-1, Dae-dong, Gyeongsan-si, Gyeongsangbuk-do, 712-749 (Korea, Republic of)

2012-10-30

Bilayers of Ru (7 nm)/WSi{sub x}N{sub y} (8 nm) prepared by sputtering were investigated as diffusion barriers between Cu and Si for direct-platable Cu interconnects. Four different WSi{sub x}N{sub y} films were prepared by using various N{sub 2}/Ar flow rate ratios during sputtering of a WSi{sub 2.7} target. Sheet resistance measurements and X-ray diffractometry analysis showed that Ru/WSi{sub x}N{sub y} bilayer diffusion barriers prevented Cu diffusion during 30 min of annealing at temperatures of up to 550-750 Degree-Sign C, while the Ru single layer of the same thickness (15 nm) failed after annealing at 400 Degree-Sign C by the formation of copper silicide due to the diffusion of Cu into Si. It was shown that the performances of bilayer diffusion barriers were improved as the nitrogen content in the WSi{sub x}N{sub y} films was increased, which can be explained based on the results from transmission electron microscopy and X-ray photoelectron spectroscopy analysis of WSi{sub x}N{sub y} films deposited with different N{sub 2}/Ar flow rate ratios. From the results, the Si-N and W-N chemical bonds are strengthened as the N contents in the WSi{sub x}N{sub y} films are increased by increasing the N{sub 2} flow rate during the deposition. The results indicate that the formation of both Si-N and W-N bonds will give an effective diffusion barrier against Cu diffusion.

DEVELOPMENT AND ASSESSMENT OF COATINGS FOR FUTURE POWER GENERATION TURBINES

Energy Technology Data Exchange (ETDEWEB)

Alvin, Maryanne; Klotz, K.; McMordie, B.; Gleeson, B.; Zhu, D.; Warnes, B.; Kang, B.; Tannenbaum, J.

2012-01-01

The NETL-Regional University Alliance (RUA) continues to advance technology development critical to turbine manufacturer efforts for achieving DOE Fossil Energy (FE's) Advanced Turbine Program Goals. In conjunction with NETL, Coatings for Industry (CFI), the University of Pittsburgh, NASA GRC, and Corrosion Control Inc., efforts have been focused on development of composite thermal barrier coating (TBC) architectures that consist of an extreme temperature coating, a commercially applied 7-8 YSZ TBC, a reduced cost bond coat, and a diffusion barrier coating that are applied to nickel-based superalloys or single crystal airfoil substrate materials for use at temperatures >1450 C (> 2640 F). Additionally, construction of a unique, high temperature ({approx}1100 C; {approx}2010 F), bench-scale, micro-indentation, nondestructive (NDE) test facility at West Virginia University (WVU) was completed to experimentally address in-situ changes in TBC stiffness during extended cyclic oxidation exposure of coated single crystal coupons in air or steam containing environments. The efforts and technical accomplishments in these areas are presented in the following sections of this paper.

NASA's Advanced Environmental Barrier Coatings Development for SiC/SiC Ceramic Matrix Composites: Understanding Calcium Magnesium Alumino-Silicate (CMAS) Degradations and Resistance

Science.gov (United States)

Zhu, Dongming

2014-01-01

Environmental barrier coatings (EBCs) and SiCSiC ceramic matrix composites (CMCs) systems will play a crucial role in next generation turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures with improved efficiency, reduce engine weight and cooling requirements. The development of prime-reliant environmental barrier coatings is essential to the viability and reliability of the envisioned CMC engine component applications, ensuring integrated EBC-CMC system durability and designs are achievable for successful applications of the game-changing component technologies and lifing methodologies.This paper will emphasize recent NASA environmental barrier coating developments for SiCSiC turbine airfoil components, utilizing advanced coating compositions, state-of-the-art processing methods, and combined mechanical and environment testing and durability evaluations. The coating-CMC degradations in the engine fatigue-creep and operating environments are particularly complex; one of the important coating development aspects is to better understand engine environmental interactions and coating life debits, and we have particularly addressed the effect of Calcium-Magnesium-Alumino-Silicate (CMAS) from road sand or volcano-ash deposits on the durability of the environmental barrier coating systems, and how the temperature capability, stability and cyclic life of the candidate rare earth oxide and silicate coating systems will be impacted in the presence of the CMAS at high temperatures and under simulated heat flux conditions. Advanced environmental barrier coating systems, including HfO2-Si with rare earth dopant based bond coat systems, will be discussed for the performance improvements to achieve better temperature capability and CMAS resistance for future engine operating conditions.

Novel thermal barrier coatings based on La{sub 2}(Zr{sub 0.7}Ce{sub 0.3}){sub 2}O{sub 7}/8YSZ double-ceramic-layer systems deposited by electron beam physical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Xu Zhenhua, E-mail: zhxuciac@yahoo.com.cn [Beijing Institute of Aeronautical Materials, Department 5, P.O. Box 81-5, Beijing 100095 (China); He Shimei; He Limin; Mu Rende; Huang Guanghong [Beijing Institute of Aeronautical Materials, Department 5, P.O. Box 81-5, Beijing 100095 (China); Cao Xueqiang [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

2011-03-17

Research highlights: > LZ7C3 and YSZ have good chemical compatibility for the formation of DCL coating. > DCL coating has a longer lifetime than that of single layer coating of LZ7C3 or YSZ. > Similar TECs of LZ7C3 with YSZ coatings and YSZ coating with TGO layer. > Unique growth modes of columns within DCL coating. > Outward diffusion of Cr element (bond coat) into LZ7C3 layer. - Abstract: Double-ceramic-layer (DCL) thermal barrier coatings (TBCs) of La{sub 2}(Zr{sub 0.7}Ce{sub 0.3}){sub 2}O{sub 7} (LZ7C3) and yttria stabilized zirconia (YSZ) were deposited by electron beam-physical vapor deposition (EB-PVD). The thermal cycling test at 1373 K in an air furnace indicates the DCL coating has a much longer lifetime than the single layer LZ7C3 coating, and even longer than that of the single layer YSZ coating. The superior sintering-resistance of LZ7C3 coating, the similar thermal expansion behaviors of YSZ interlayer with LZ7C3 coating and thermally grown oxide (TGO) layer, and the unique growth modes of columns within DCL coating are all very helpful to the prolongation of thermal cycling life of DCL coating. The failure of DCL coating is mainly a result of the reduction-oxidation of cerium oxide, the crack initiation, propagation and extension, the abnormal oxidation of bond coat, the degradation of t'-phase in YSZ coating and the outward diffusion of Cr alloying element into LZ7C3 coating.

The role of oxygen in the deposition of copper–calcium thin film as diffusion barrier for copper metallization

Energy Technology Data Exchange (ETDEWEB)

Yu, Zhinong, E-mail: znyu@bit.edu.cn [School of Optoelectronics and Beijing Engineering Research Center of Mixed Reality and Advanced Display, Beijing Institute of Technology, Beijing 100081 (China); Ren, Ruihuang [School of Optoelectronics and Beijing Engineering Research Center of Mixed Reality and Advanced Display, Beijing Institute of Technology, Beijing 100081 (China); Xue, Jianshe; Yao, Qi; Li, Zhengliang; Hui, Guanbao [Beijing BOE Optoelectronics Technology Co., Ltd, Beijing 100176 (China); Xue, Wei [School of Optoelectronics and Beijing Engineering Research Center of Mixed Reality and Advanced Display, Beijing Institute of Technology, Beijing 100081 (China)

2015-02-15

Highlights: • The CuCa film as the diffusion barrier of Cu film improves the adhesion of Cu film. • The introduction of oxygen into the deposition of CuCa film is necessary to improve the adhesion of Cu film. • The CuCa alloy barrier layer deposited at oxygen atmosphere has perfect anti-diffusion between Cu film and substrate. - Abstract: The properties of copper (Cu) metallization based on copper–calcium (CuCa) diffusion barrier as a function of oxygen flux in the CuCa film deposition were investigated in view of adhesion, diffusion and electronic properties. The CuCa film as the diffusion barrier of Cu film improves the adhesion of Cu film, however, and increases the resistance of Cu film. The introduction of oxygen into the deposition of CuCa film induces the improvement of adhesion and crystallinity of Cu film, but produces a slight increase of resistance. The increased resistance results from the partial oxidation of Cu film. The annealing process in vacuum further improves the adhesion, crystallinity and conductivity of Cu film. X-ray diffraction (XRD) and Auger electron spectroscopy (AES) show that the CuCa alloy barrier layer deposited at oxygen atmosphere has perfect anti-diffusion between Cu film and substrate due to the formation of Ca oxide in the interface of CuCa/substrate.

Effect of thermal barrier coating with various blends of pumpkin seed oil methyl ester in DI diesel engine

Science.gov (United States)

Karthickeyan, V.; Balamurugan, P.

2017-10-01

The rise in oil prices, dependency on fossil fuels, degradation of non-renewable energy resources and global warming strives to find a low-carbon content alternative fuel to the conventional fuel. In the present work, Partially Stabilized Zirconia (PSZ) was used as a thermal barrier coating in piston head, cylinder head and intake and exhaust valves using plasma spray technique, which provided a rise in combustion chamber temperature. With the present study, the effects of thermal barrier coating on the blends of Pumpkin Seed Oil Methyl Ester (PSOME) were observed in both the coated and uncoated engine. Performance and emission characteristics of the PSOME in coated and uncoated engines were observed and compared. Increased thermal efficiency and reduced fuel consumption were observed for B25 and diesel in coated and uncoated engine. On comparing with the other biodiesel samples, B25 exhibited lower HC, NOx and smoke emissions in thermally coated engine than uncoated engine. After 100 h of operation, no anamolies were found in the thermally coated components except minor cracks were identified in the edges of the piston head.

Development of Advanced Environmental Barrier Coatings for SiC/SiC Ceramic Matrix Composites: Path Toward 2700 F Temperature Capability and Beyond

Science.gov (United States)

Zhu, Dongming; Harder, Bryan; Hurst, Janet B.; Good, Brian; Costa, Gustavo; Bhatt, Ramakrishna T.; Fox, Dennis S.

2017-01-01

Advanced environmental barrier coating systems for SiC-SiC Ceramic Matrix Composite (CMC) turbine and combustor hot section components are currently being developed to meet future turbine engine emission and performance goals. One of the significant coating development challenges is to achieve prime-reliant environmental barrier coating systems to meet the future 2700F EBC-CMC temperature stability and environmental durability requirements. This presentation will emphasize recent NASA environmental barrier coating system testing and down-selects, particularly the development path and properties towards 2700-3000F durability goals by using NASA hafnium-hafnia-rare earth-silicon-silicate composition EBC systems for the SiC-SiC CMC turbine component applications. Advanced hafnium-based compositions for enabling next generation EBC and CMCs capabilities towards ultra-high temperature ceramic coating systems will also be briefly mentioned.

Deactivation of SCR catalysts by potassium: A study of potential alkali barrier materials

DEFF Research Database (Denmark)

Olsen, Brian Kjærgaard; Kügler, Frauke; Castellino, Francesco

2017-01-01

The use of coatings in order to protect vanadia based SCR catalysts against potassium poisoning has been studied by lab- and pilot-scale experiments. Three-layer pellets, consisting of a layer ofa potential coating material situated between layers of fresh and potassium poisoned SCR catalyst, were...... the coating process. Potassium had to some extent penetrated the MgO coat, and SEM analysis revealed it to be rather thick and fragile. Despite these observations, the coating did protect the SCR catalyst against potassium poisoning to some degree, leaving promise of further optimization....... used to test the ability of the barrier layer to block the diffusion of potassium across the pellet. Of MgO, sepiolite and Hollandite manganese oxide, MgO was the most effective potassium barrier, and no potassium was detected in the MgO layer upon exposure to SCR conditions for 7 days. Two monoliths...

Thermal analysis of the effect of thick thermal barrier coatings on diesel engine performance

International Nuclear Information System (INIS)

Hoag, K.L.; Frisch, S.R.; Yonushonis, T.M.

1986-01-01

The reduction of heat rejection from the diesel engine combustion chamber has been the subject of a great deal of focus in recent years. In the pursuit of this goal, Cummins Engine Company has received a contract from the Department of Energy for the development of thick thermal barrier coatings for combustion chamber surfaces. This contract involves the analysis of the impact of coatings on diesel engine performance, bench test evaluation of various coating designs, and single cylinder engine tests. The efforts reported in this paper center on the analysis of the effects of coatings on engine performance and heat rejection. For this analysis the conventional water cooled engine was compared with an engine having limited oil cooling, and utilizing zirocnia coated cylinder had firedecks and piston crowns. The analysis showed little or no benefits of similarly coating the valves or cylinder liner

Glial diffusion barriers during aging and pathological states

Czech Academy of Sciences Publication Activity Database

Syková, Eva

2001-01-01

Roč. 132, - (2001), s. 339-363 ISSN 0079-6123 R&D Projects: GA MŠk VS96130; GA ČR GV307/96/K226; GA ČR GV309/97/K048; GA ČR GA309/99/0657; GA ČR GA305/99/0655; GA ČR GA309/00/1430 Institutional research plan: CEZ:AV0Z5039906 Keywords : diffusion barriers volume transmission Subject RIV: FH - Neurology Impact factor: 1.409, year: 2001

Application of Nanofibrillated Cellulose on BOPP/LDPE Film as Oxygen Barrier and Antimicrobial Coating Based on Cold Plasma Treatment

Directory of Open Access Journals (Sweden)

Peng Lu

2018-05-01

Full Text Available The application of nanofibrillated cellulose (NC films in packaging industry has been hindered by its lack of heat-sealing ability. Incorporation of NC films with the biaxially oriented polypropylene/low density polyethylene (BOPP/LDPE laminates can take advantage of each material and endow the films with novel functions for food packaging applications. In this study, a coating that consists of NC and nisin was applied onto a cold plasma treated BOPP/LDPE film to fabricate a novel active packaging with an improved oxygen barrier performance and an added antimicrobial effect. The results showed that cold plasma treatment improved the surface hydrophilicity of BOPP/LDPE films for better attachment of the coatings. NC coatings significantly enhanced oxygen barrier property of the BOPP/LDPE film, with an oxygen transmission rate as low as 24.02 cc/m2·day as compared to that of the non-coated one (67.03 cc/m2·day. The addition of nisin in the coating at a concentration of 5 mg/g caused no significant change in barrier properties but imparted the film excellent antimicrobial properties, with a growth inhibition of L. monocytogenes by 94%. All films exhibit satisfying mechanical properties and transparency, and this new film has the potential to be used as antimicrobial and oxygen barrier packaging.

A Septin-Dependent Diffusion Barrier at Dendritic Spine Necks.

Directory of Open Access Journals (Sweden)

Helge Ewers

Full Text Available Excitatory glutamatergic synapses at dendritic spines exchange and modulate their receptor content via lateral membrane diffusion. Several studies have shown that the thin spine neck impedes the access of membrane and solute molecules to the spine head. However, it is unclear whether the spine neck geometry alone restricts access to dendritic spines or if a physical barrier to the diffusion of molecules exists. Here, we investigated whether a complex of septin cytoskeletal GTPases localized at the base of the spine neck regulates diffusion across the spine neck. We found that, during development, a marker of the septin complex, Septin7 (Sept7, becomes localized to the spine neck where it forms a stable structure underneath the plasma membrane. We show that diffusion of receptors and bulk membrane, but not cytoplasmic proteins, is slower in spines bearing Sept7 at their neck. Finally, when Sept7 expression was suppressed by RNA interference, membrane molecules explored larger membrane areas. Our findings indicate that Sept7 regulates membrane protein access to spines.

Improved Thermally Grown Oxide Scale in Air Plasma Sprayed NiCrAlY/Nano-YSZ Coatings

International Nuclear Information System (INIS)

Daroonparvar, M.; Yajid, M.A.M.; Yusof, N.M.; Hussain, M.S.

2013-01-01

Oxidation has been considered as one of the principal disruptive factors in thermal barrier coating systems during service. So, oxidation behavior of thermal barrier coating (TBC) systems with nano structured and micro structured YSZ coatings was investigated at 1000 degree c for 24 h, 48 h, and 120 h. Air plasma sprayed nano-YSZ coating exhibited a tri modal structure. Microstructural characterization also demonstrated an improved thermally grown oxide scale containing lower spinels in nano-TBC system after 120 h of oxidation. This phenomenon is mainly related to the unique structure of the nano-YSZ coating, which acted as a strong barrier for oxygen diffusion into the TBC system at elevated temperatures. Nearly continues but thinner Al 2 O 3 layer formation at the NiCrAlY/nano-YSZ interface was seen, due to lower oxygen infiltration into the system. Under this condition, spinels formation and growth on the Al 2 O 3 oxide scale were diminished in nano-TBC system compared to normal TBC system.

High-Performance Ink-Synthesized Cu-Gate Thin-Film Transistor with Diffusion Barrier Formation

Science.gov (United States)

Woo, Whang Je; Nam, Taewook; Oh, Il-Kwon; Maeng, Wanjoo; Kim, Hyungjun

2018-05-01

The improved electrical properties of Cu-gate thin-film transistors (TFTs) using an ink-synthesizing process were studied; this technology enables a low-cost and large area process for the display industry. We investigated the film properties and the effects of the ink-synthesized Cu layer in detail with respect to device characteristics. The mobility and reliability of the devices were significantly improved by applying a diffusion barrier at the interface between the Cu gate and the gate insulator. By using a TaN diffusion barrier layer, considerably improved and stabilized ink-Cu gated TFTs could be realized, comparable to sputtered-Cu gated TFTs under positive bias temperature stress measurements.

High-Performance Ink-Synthesized Cu-Gate Thin-Film Transistor with Diffusion Barrier Formation

Science.gov (United States)

Woo, Whang Je; Nam, Taewook; Oh, Il-Kwon; Maeng, Wanjoo; Kim, Hyungjun

2018-02-01

The improved electrical properties of Cu-gate thin-film transistors (TFTs) using an ink-synthesizing process were studied; this technology enables a low-cost and large area process for the display industry. We investigated the film properties and the effects of the ink-synthesized Cu layer in detail with respect to device characteristics. The mobility and reliability of the devices were significantly improved by applying a diffusion barrier at the interface between the Cu gate and the gate insulator. By using a TaN diffusion barrier layer, considerably improved and stabilized ink-Cu gated TFTs could be realized, comparable to sputtered-Cu gated TFTs under positive bias temperature stress measurements.

Evaluation of diffusion barrier and electrical properties of tantalum oxynitride thin films for silver metallization

International Nuclear Information System (INIS)

Misra, E.; Wang, Y.; Theodore, N.D.; Alford, T.L.

2004-01-01

The thermal stability and the diffusion barrier properties of DC reactively sputtered tantalum oxynitride (Ta-O-N) thin films, between silver (Ag) and silicon (Si) p + n diodes were investigated. Both materials characterization (X-ray diffraction analysis, Rutherford backscattering spectrometry (RBS), Auger depth profiling) and electrical measurements (reverse-biased junction leakage current-density) were used to evaluate diffusion barrier properties of the thin films. The leakage current density of p + n diodes with the barrier (Ta-O-N) was approximately four orders of magnitude lower than those without barriers after a 30 min, 400 deg. C back contact anneal. The Ta-O-N barriers were stable up to 500 deg. C, 30 min anneals. However, this was not the case for the 600 deg. C anneal. RBS spectra and cross-sectional transmission electron microscopy of as-deposited and vacuum annealed samples of Ag/barrier (Ta-O-N)/Si indicate the absence of any interfacial interaction between the barrier and substrate (silicon). The failure of the Ta-O-N barriers has been attributed to thermally induced stresses, which cause the thin film to crack at elevated temperatures

Design of durability and lifetime assessment method under thermomechanical stress for thermal barrier coatings

Energy Technology Data Exchange (ETDEWEB)

Shin, Hyun Gyoo; Choi, Young Kue; Jeon, Seol; Lee, Hee Soo [Pusan National University, Busan (Korea, Republic of); Jeon, Min Seok [Korea Testing Laboratory, Seoul (Korea, Republic of)

2014-01-15

A durability testing method under thermo-mechanical stress for thermal barrier coatings (TBC) specimens was designed by a combination of an electric furnace and a tensile testing machine, which was done on TBCs on NIMONIC 263 substrates by an atmospheric plasma spraying (APS) deposition method. The testing conditions were chosen according to a preliminary experiment that identified the elastic deformation region of the top coating and the substrate during mechanical loading. Surface cracking and a decrease in the thickness of the top coating, which are typical degradation behaviors under conventional thermal shock testing, were observed after the designed thermal fatigue test, and delamination at the top coating-bond coating interface occurred by the mechanical load. Lifetime assessment was conducted by statistical software using life cycle data which were obtained after the thermal fatigue test.

Calcium-Magnesium-Alumino-Silicates (CMAS) Reaction Mechanisms and Resistance of Advanced Turbine Environmental Barrier Coatings for SiC/SiC Ceramic Matrix Composites

Science.gov (United States)

Zhu, Dongming; Costa, Gustavo; Harder, Bryan J.; Wiesner, Valerie L.; Hurst, Janet B.; Puleo, Bernadette J.

2017-01-01

Environmental barrier coatings (EBCs) and SiC/SiC ceramic matrix composites (CMCs) systems will play a crucial role in future turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures, reduce engine weight and cooling requirements. The development of prime-reliant environmental barrier coatings is an essential requirement to enable the applications of the 2700-3000 F EBC - CMC systems. This presentation primarily focuses on the reaction mechanisms of advanced NASA environmental barrier coating systems, when in contact with Calcium-Magnesium Alumino-Silicates (CMAS) at high temperatures. Advanced oxide-silicate defect cluster environmental barrier coatings are being designed for ultimate balanced controls of the EBC temperature capability and CMAS reactivity, thus improving the CMAS resistance. Further CMAS mitigation strategies are also discussed.

Valence and atomic size dependent exchange barriers in vacancy-mediated dopant diffusion

International Nuclear Information System (INIS)

Nelson, J.S.; Schultz, P.A.; Wright, A.F.

1998-01-01

First-principles pseudopotential calculations of dopant-vacancy exchange barriers indicate a strong dependency on dopant valence and atomic size, in contrast to current models of vacancy-mediated dopant diffusion. First-row elements (B, C, N) are found to have exchange barriers which are an order of magnitude larger than the assumed value of 0.3 eV (the Si vacancy migration energy). copyright 1998 American Institute of Physics

Novel Functionally Graded Thermal Barrier Coatings in Coal-Fired Power Plant Turbines

Energy Technology Data Exchange (ETDEWEB)

Zhang, Jing [Indiana Univ., Indianapolis, IN (United States)

2016-11-01

This project presents a detailed investigation of a novel functionally graded coating material, pyrochlore oxide, for thermal barrier coating (TBC) in gas turbines used in coal-fired power plants. Thermal barrier coatings are refractory materials deposited on gas turbine components, which provide thermal protection for metallic components at operating conditions. The ultimate goal of this research is to develop a manufacturing process to produce the novel low thermal conductivity and high thermal stability pyrochlore oxide based coatings with improved high-temperature durability. The current standard TBC, yttria stabilized zirconia (YSZ), has service temperatures limited to <1200°C, due to sintering and phase transition at higher temperatures. In contrast, pyrochlore oxide, e.g., lanthanum zirconate (La₂Zr₂O₇, LZ), has demonstrated lower thermal conductivity and better thermal stability, which are crucial to high temperature applications, such as gas turbines used in coal-fired power plants. Indiana University – Purdue University Indianapolis (IUPUI) has collaborated with Praxair Surface Technologies (PST), and Changwon National University in South Korea to perform the proposed research. The research findings are critical to the extension of current TBCs to a broader range of high-temperature materials and applications. Several tasks were originally proposed and accomplished, with additional new opportunities identified during the course of the project. In this report, a description of the project tasks, the main findings and conclusions are given. A list of publications and presentations resulted from this research is listed in the Appendix at the end of the report.

Environmental/Thermal Barrier Coatings for Ceramic Matrix Composites: Thermal Tradeoff Studies

Science.gov (United States)

Murthy, Pappu L. M.; Brewer, David; Shah, Ashwin R.

2007-01-01

Recent interest in environmental/thermal barrier coatings (EBC/TBCs) has prompted research to develop life-prediction methodologies for the coating systems of advanced high-temperature ceramic matrix composites (CMCs). Heat-transfer analysis of EBC/TBCs for CMCs is an essential part of the effort. It helps establish the resulting thermal profile through the thickness of the CMC that is protected by the EBC/TBC system. This report documents the results of a one-dimensional analysis of an advanced high-temperature CMC system protected with an EBC/TBC system. The one-dimensional analysis was used for tradeoff studies involving parametric variation of the conductivity; the thickness of the EBC/TBCs, bond coat, and CMC substrate; and the cooling requirements. The insight gained from the results will be used to configure a viable EBC/TBC system for CMC liners that meet the desired hot surface, cold surface, and substrate temperature requirements.

Electroless deposition of NiCrB diffusion barrier layer film for ULSI-Cu metallization

Energy Technology Data Exchange (ETDEWEB)

Wang, Yuechun [School of Materials Science and Engineering, Yunnan University, Kunming (China); Chen, Xiuhua, E-mail: chenxh@ynu.edu.cn [School of Materials Science and Engineering, Yunnan University, Kunming (China); Ma, Wenhui [National Engineering Laboratory of Vacuum Metallurgy, Kunming University of Science and Technology, Kunming (China); Shang, Yudong; Lei, Zhengtao; Xiang, Fuwei [School of Materials Science and Engineering, Yunnan University, Kunming (China)

2017-02-28

Highlights: • In this paper, the electroless deposited NiCrB thin film was mainly in the form of NiB, CrB{sub 2} compounds and elementary Ni. • The sheet resistance of NiCrB thin film was 3.043 Ω/□, it is smaller than that of the widely used Ta, TaN and TiN diffusion barrier layers. • Annealing experiments showed that the failure temperature of NiCrB thin film regarding Cu diffusion was 900 °C. • NiCrB barrier layer crystallized after 900 °C annealing, Cu grains arrived at Si-substrate through grain boundaries, resulting in the formation of Cu{sub 3}Si. • Eelectroless deposited NiCrB film also had good oxidation resistance, it is expected to become an anti-oxidant layer of copper interconnection. - Abstract: NiCrB films were deposited on Si substrates using electroless deposition as a diffusion barrier layer for Cu interconnections. Samples of the prepared NiCrB/SiO{sub 2}/Si and NiCrB/Cu/NiCrB/SiO{sub 2}/Si were annealed at temperatures ranging from 500 °C to 900 °C. The reaction mechanism of the electroless deposition of the NiCrB film, the failure temperature and the failure mechanism of the NiCrB diffusion barrier layer were investigated. The prepared samples were subjected to XRD, XPS, FPP and AFM to determine the phases, composition, sheet resistance and surface morphology of samples before and after annealing. The results of these analyses indicated that the failure temperature of the NiCrB barrier film was 900 °C and the failure mechanism led to crystallization and grain growth of the NiCrB barrier layer after high temperature annealing. It was found that this process caused Cu grains to reach Si substrate through the grain boundaries, and then the reaction between Cu and Si resulted in the formation of highly resistive Cu{sub 3}Si.

In situ SANS study of pore microstructure in YSZ thermal barrier coatings

Czech Academy of Sciences Publication Activity Database

Strunz, Pavel; Schumacher, G.; Vassen, R.; Wiedenmann, A.

2004-01-01

Roč. 52, č. 11 (2004), s. 3305-3312 ISSN 1359-6454 R&D Projects: GA ČR GA202/03/0891 Institutional research plan: CEZ:AV0Z1048901 Keywords : plasma spraying * thermal barrier coatings * ceramics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.490, year: 2004

Evaluation of Thermal Barrier and PS-200 Self-Lubricating Coatings in an Air-Cooled Rotary Engine

Science.gov (United States)

Moller, Paul S.

1995-01-01

This project provides an evaluation of the feasibility and desirability of applying a thermal barrier coating overlaid with a wear coating on the internal surfaces of the combustion area of rotary engines. Many experiments were conducted with different combinations of coatings applied to engine components of aluminum, iron and titanium, and the engines were run on a well-instrumented test stand. Significant improvements in specific fuel consumption were achieved and the wear coating, PS-200, which was invented at NASA's Lewis Research Center, held up well under severe test conditions.

Hafnia-Based Nanostructured Thermal Barrier Coatings for Advanced Hydrogen Turbine Technology

Energy Technology Data Exchange (ETDEWEB)

Ramana, Chintalapalle; Choudhuri, Ahsan

2013-01-31

Thermal barrier coatings (TBCs) are critical technologies for future gas turbine engines of advanced coal based power generation systems. TBCs protect engine components and allow further increase in engine temperatures for higher efficiency. In this work, nanostructured HfO{sub 2}-based coatings, namely Y{sub 2}O{sub 3}-stabilized HfO{sub 2} (YSH), Gd{sub 2}O{sub 3}-stabilized HfO{sub 2} (GSH) and Y{sub 2}O{sub 3}-stabilized ZrO{sub 2}-HfO{sub 2} (YSZH) were investigated for potential TBC applications in hydrogen turbines. Experimental efforts are aimed at creating a fundamental understanding of these TBC materials. Nanostructured ceramic coatings of YSH, GSH and YSZH were grown by physical vapor deposition methods. The effects of processing parameters and ceramic composition on the microstructural evolution of YSH, GSH and YSZH nanostructured coatings was studied using combined X-ray diffraction (XRD) and Electron microscopy analyses. Efforts were directed to derive a detailed understanding of crystal-structure, morphology, and stability of the coatings. In addition, thermal conductivity as a function of composition in YSH, YSZH and GSH coatings was determined. Laboratory experiments using accelerated test environments were used to investigate the relative importance of various thermo-mechanical and thermo-chemical failure modes of TBCs. Effects of thermal cycling, oxidation and their complex interactions were evaluated using a syngas combustor rig.

Surface Cracking and Interface Reaction Associated Delamination Failure of Thermal and Environmental Barrier Coatings

National Research Council Canada - National Science Library

Zhu, Dongming

2003-01-01

...%Y2O3 and mullite/BSAS/Si thermal and environmental barrier coating system on SiC/SiC ceramic matrix composites were characterized after long-term combined laser thermal gradient and furnace cyclic...

Experimental concrete coating application on the median barrier of I 65 in Louisville.

Science.gov (United States)

2008-06-01

The objectives of this research were to evaluate the experimental protective coating that was applied to approximately 1,200 linear feet of concrete median barrier along the paving project on a section of I 65 between mile points 131.289 and 136.421 ...

Development of a Nondestructive Evaluation Technique for Degraded Thermal Barrier Coatings Using Microwave

Science.gov (United States)

Sayar, M.; Ogawa, K.; Shoji, T.

2008-02-01

Thermal barrier coatings have been widely used in gas turbine engines in order to protect substrate metal alloy against high temperature and to enhance turbine efficiency. Currently, there are no reliable nondestructive techniques available to monitor TBC integrity over lifetime of the coating. Hence, to detect top coating (TC) and TGO thicknesses, a microwave nondestructive technique that utilizes a rectangular waveguide was developed. The phase of the reflection coefficient at the interface of TC and waveguide varies for different TGO and TC thicknesses. Therefore, measuring the phase of the reflection coefficient enables us to accurately calculate these thicknesses. Finally, a theoretical analysis was used to evaluate the reliability of the experimental results.

Thermal barrier coatings of rare earth materials deposited by electron beam-physical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Xu Zhenhua [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Beijing Institute of Aeronautical Materials, Department 5, P.O. Box 81-5, Beijing 100095 (China); He Limin, E-mail: he_limin@yahoo.co [Beijing Institute of Aeronautical Materials, Department 5, P.O. Box 81-5, Beijing 100095 (China); Chen Xiaolong; Zhao Yu [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Cao Xueqiang, E-mail: xcao@ciac.jl.c [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

2010-10-15

Thermal barrier coatings (TBCs) have very important applications in gas turbines for higher thermal efficiency and protection of components at high temperature. TBCs of rare earth materials such as lanthanum zirconate (La{sub 2}Zr{sub 2}O{sub 7}, LZ), lanthanum cerate (La{sub 2}Ce{sub 2}O{sub 7}, LC), lanthanum cerium zirconate (La{sub 2}(Zr{sub 0.7}Ce{sub 0.3}){sub 2}O{sub 7}, LZ7C3) were prepared by electron beam-physical vapor deposition (EB-PVD). The composition, crystal structure, cross-sectional morphology and cyclic oxidation behavior of these coatings were studied. These coatings have partially deviated from their original compositions due to the different evaporation rates of oxides, and the deviation could be reduced by properly controlling the deposition condition. A double ceramic layer-thermal barrier coatings (DCL-TBCs) of LZ7C3 and LC could also be deposited with a single LZ7C3 ingot by properly controlling the deposition energy. LaAlO{sub 3} is formed due to the chemical reaction between LC and Al{sub 2}O{sub 3} in the thermally grown oxide (TGO) layer. The failure of DCL-TBCs is a result of the sintering-induced of LZ7C3 coating and the chemical incompatibility of LC and TGO. Since no single material that has been studied so far satisfies all the requirements for high temperature applications, DCL-TBCs are an important development direction of TBCs.

Blocking germanium diffusion inside silicon dioxide using a co-implanted silicon barrier

Science.gov (United States)

Barba, D.; Wang, C.; Nélis, A.; Terwagne, G.; Rosei, F.

2018-04-01

We investigate the effect of co-implanting a silicon sublayer on the thermal diffusion of germanium ions implanted into SiO2 and the growth of Ge nanocrystals (Ge-ncs). High-resolution imaging obtained by transmission electron microscopy and energy dispersive spectroscopy measurements supported by Monte-Carlo calculations shows that the Si-enriched region acts as a diffusion barrier for Ge atoms. This barrier prevents Ge outgassing during thermal annealing at 1100 °C. Both the localization and the reduced size of Ge-ncs formed within the sample region co-implanted with Si are observed, as well as the nucleation of mixed Ge/Si nanocrystals containing structural point defects and stacking faults. Although it was found that the Si co-implantation affects the crystallinity of the formed Ge-ncs, this technique can be implemented to produce size-selective and depth-ordered nanostructured systems by controlling the spatial distribution of diffusing Ge. We illustrate this feature for Ge-ncs embedded within a single SiO2 monolayer, whose diameters were gradually increased from 1 nm to 5 nm over a depth of 100 nm.

Effects of a Chitosan Coating Layer on the Surface Properties and Barrier Properties of Kraft Paper

Directory of Open Access Journals (Sweden)

Shanhui Wang

2016-01-01

Full Text Available Biodegradable chitosan can be applied as a coating on the surface of kraft paper in order to improve its barrier properties against water vapor and air. The food packaging industry can benefit from the addition of chitosan to its current packaging, and in turn reduce pollution from plastic packaging plants. This paper discusses the film formation of chitosan, the permeability of paper coated with a chitosan layer, and the influence on the paper’s surface and barrier properties under different process conditions. SEM (scanning electron microscope, AFM (atomic force microscope, ATR-FTIR (Fourier transmission infrared spectroscope with attenuated total reflection, and PDA (penetration dynamics analysis were used to analyze the properties of chitosan’s film formation and permeability. A controlled experiment showed that the chitosan layer was smoother than the surface of the uncoated kraft paper, had better film formation, and that there was no chitosan penetration through the kraft paper. The barrier properties against water vapor were strongest when there was a higher concentration of chitosan solution at the optimum pH, stirring speed, and those with a thicker coating on the kraft paper.

CMAS Interactions with Advanced Environmental Barrier Coatings Deposited via Plasma Spray- Physical Vapor Deposition

Science.gov (United States)

Harder, B. J.; Wiesner, V. L.; Zhu, D.; Johnson, N. S.

2017-01-01

Materials for advanced turbine engines are expected to have temperature capabilities in the range of 1370-1500C. At these temperatures the ingestion of sand and dust particulate can result in the formation of corrosive glass deposits referred to as CMAS. The presence of this glass can both thermomechanically and thermochemically significantly degrade protective coatings on metallic and ceramic components. Plasma Spray- Physical Vapor Deposition (PS-PVD) was used to deposit advanced environmental barrier coating (EBC) systems for investigation on their interaction with CMAS compositions. Coatings were exposed to CMAS and furnace tested in air from 1 to 50 hours at temperatures ranging from 1200-1500C. Coating composition and crystal structure were tracked with X-ray diffraction and microstructure with electron microscopy.

Microtexture of the thermally grown alumina in commercial thermal barrier coatings

Energy Technology Data Exchange (ETDEWEB)

Karadge, M. [School of Materials, University of Manchester, Grosvenor St., Manchester M1 7HS (United Kingdom); Zhao, X. [School of Materials, University of Manchester, Grosvenor St., Manchester M1 7HS (United Kingdom); Preuss, M. [School of Materials, University of Manchester, Grosvenor St., Manchester M1 7HS (United Kingdom); Xiao, P. [School of Materials, University of Manchester, Grosvenor St., Manchester M1 7HS (United Kingdom)]. E-mail: Ping.Xiao@manchester.ac.uk

2006-02-15

otextures of the thermally grown {alpha}-alumina (TGO) in isothermally treated and thermal cycled electron beam physical vapor deposited thermal barrier coatings (EB-PVD-TBC) and isothermally treated air plasma sprayed (APS-TBC) specimens were studied by high resolution electron back-scattered diffraction. The TGO in EB-PVD specimens exhibited a basal microtexture. The TGO in APS specimens, however, did not show any significant microtexture development.

The influence of creep properties on crack propagation in thermal barrier coatings

International Nuclear Information System (INIS)

Baeker, Martin

2010-01-01

Thermal barrier coatings are used to protect turbine blades from the high temperature of the process gas inside a turbine. They consist of a metallic bond coat and of a ceramic top coat with low thermal conductivity. During service, an additional oxide layer forms between bond coat and top coat that eventually causes failure. Finite element simulations show that the roughness of the interface between top and bond coat is crucial for determining the stress state. Lifetime models have been inferred that assume that cracks form in the peak positions at small oxide thickness and propagate when the oxide layer grows and the stress field shifts. A two-dimensional finite element model of crack propagation in the TBC layer is presented. Since the cracks propagate near a material interface and since plasticity may occur in the bond coat, standard tools of fracture mechanics for predicting the crack propagation direction are difficult to apply. This problem is circumvented in a very simple way by propagating short 'test cracks' in different directions and optimising to find the crack direction with the maximum energy release rate. It is shown that the energy release rate and the crack propagation direction are sensitive to the details of the stress state and especially to the creep properties of the materials. Implications for failure models are discussed.

Thin coatings in packaging: Fundamental and practical aspects

International Nuclear Information System (INIS)

Thorne, N.A.

1996-01-01

A beverage or food can is very much a functionalized product, the overall performance characteristics being achieved by the use of several materials each of which provides a specific property. Schematically, the metal substrate provides the mechanical and barrier properties, whereby the chemical resistance is provided by specific surface treatments to the metal surface and the application of a thin organic coating. Between about 4 endash 15 μm in thickness, this organic coating has a double protective role, as it must protect the substrate from the foodstuff (corrosion) and the foodstuff from the substrate (taste..) over the required shelflife of the product. To give an idea of the industrial importance of this application, over 100 billion beverage cans per year are produced worldwide, each being individually sprayed with a protective organic layer. To perform correctly these coatings need to possess the following characteristics: emdash ability to be applied in thin, homogeneous layers without macroscopic or microscopic defects, emdash sufficient adhesion with the substrate and possess considerable interface stability emdash mechanical properties sufficient to withstand the can forming operations emdash intrinsic diffusion barrier properties necessary to prevent significant interaction with the substrate emdash sufficient chemical resistance to withstand any significant modification of the coating structure and hence intrinsic properties induced by the foodstuff Whereas a considerable amount of scientific attention has been applied to ''bulk'' systems, such as the mechanical properties of epoxies used for composite materials, diffusion in polymer packaging..., little published work is available concerning the specific properties of these thin coatings. The task is not helped by the commercial nature of the resin formulations used, the need to adapt these formulations to the multitude of industrial operations and the physical size of the coatings

Oxidation resistance of CrN/(Cr,V)N hard coatings deposited by DC magnetron sputtering

Energy Technology Data Exchange (ETDEWEB)

Panjan, P., E-mail: peter.panjan@ijs.si [Jožef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Drnovšek, A.; Kovač, J.; Gselman, P. [Jožef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Bončina, T. [University of Maribor, Faculty of Mechanical Engineering, Smetanova 17, 2000 Maribor (Slovenia); Paskvale, S.; Čekada, M.; Kek Merl, D.; Panjan, M. [Jožef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia)

2015-09-30

In recent years vanadium-doped hard coatings have become available as possible candidates for self-lubrication at high temperatures. Their low coefficient of friction has mainly been attributed to the formation of the V{sub 2}O{sub 5} phase. However, the formation of vanadium oxides must be controlled by the out-diffusion of vanadium in order to achieve the combination of a low coefficient of friction and good mechanical properties for the protective coatings. In this work the application of a nanolayer of CrN/(Cr,V)N hard coating was proposed as a way to better control the out-diffusion of vanadium, while the topmost chromium oxide layer acts as barrier for the vanadium diffusion. However, the aim of this investigation was not only to focus on the formation of the oxide layer. Special attention was given to the oxidation process that takes place at the growth defects, where we observed a strong diffusion of vanadium taking place. The CrN/(Cr,V)N nanolayer coatings were deposited by DC unbalanced magnetron sputtering in an CC800/9 (CemeCon) industrial unit. The vanadium concentration in the (Cr,V)N layers was varied in the range 1.0–11.5 at.%. - Highlights: • Oxidation processes of CrN/(Cr,V)N nanolayers with vanadium content were investigated. • The CrN/(Cr,V)N hard layers were oxidized at high temperature in O2 atm. • The top chromium oxide layer acts as a diffusion barrier for vanadium ions during oxidation. • Important role of growth defects during the oxidation process is demonstrated.

Oxidation resistance of CrN/(Cr,V)N hard coatings deposited by DC magnetron sputtering

International Nuclear Information System (INIS)

Panjan, P.; Drnovšek, A.; Kovač, J.; Gselman, P.; Bončina, T.; Paskvale, S.; Čekada, M.; Kek Merl, D.; Panjan, M.

2015-01-01

In recent years vanadium-doped hard coatings have become available as possible candidates for self-lubrication at high temperatures. Their low coefficient of friction has mainly been attributed to the formation of the V_2O_5 phase. However, the formation of vanadium oxides must be controlled by the out-diffusion of vanadium in order to achieve the combination of a low coefficient of friction and good mechanical properties for the protective coatings. In this work the application of a nanolayer of CrN/(Cr,V)N hard coating was proposed as a way to better control the out-diffusion of vanadium, while the topmost chromium oxide layer acts as barrier for the vanadium diffusion. However, the aim of this investigation was not only to focus on the formation of the oxide layer. Special attention was given to the oxidation process that takes place at the growth defects, where we observed a strong diffusion of vanadium taking place. The CrN/(Cr,V)N nanolayer coatings were deposited by DC unbalanced magnetron sputtering in an CC800/9 (CemeCon) industrial unit. The vanadium concentration in the (Cr,V)N layers was varied in the range 1.0–11.5 at.%. - Highlights: • Oxidation processes of CrN/(Cr,V)N nanolayers with vanadium content were investigated. • The CrN/(Cr,V)N hard layers were oxidized at high temperature in O2 atm. • The top chromium oxide layer acts as a diffusion barrier for vanadium ions during oxidation. • Important role of growth defects during the oxidation process is demonstrated.

Thermal diffusivity of samarium-gadolinium zirconate solid solutions

International Nuclear Information System (INIS)

Pan, W.; Wan, C.L.; Xu, Q.; Wang, J.D.; Qu, Z.X.

2007-01-01

We synthesized samarium-gadolinium zirconate solid solutions and determined their thermal diffusivities, Young's moduli and thermal expansion coefficients, which are very important for their application in thermal barrier coatings. Samarium-gadolinium zirconate solid solutions have extremely low thermal diffusivity between 20 and 600 deg. C. The solid solutions have lower Young's moduli and higher thermal expansion coefficients than those of pure samarium and gadolinium zirconates. This combination of characteristics is promising for the application of samarium and gadolinium zirconates in gas turbines. The mechanism of phonon scattering by point defects is discussed

Physical barrier effect of geopolymeric waste form on diffusivity of cesium and strontium

Energy Technology Data Exchange (ETDEWEB)

Jang, J.G.; Park, S.M.; Lee, H.K., E-mail: haengki@kaist.ac.kr

2016-11-15

Highlights: • Physical immobilization of radionuclides in geopolymer was quantitatively assessed. • Fly ash-based geopolymer showed excellent immobilization performance. • Diffusivity of soluble Cs and Sr was highly correlated with critical pore diameter. - Abstract: The present study investigates the physical barrier effect of geopolymeric waste form on leaching behavior of cesium and strontium. Fly ash-based geopolymers and slag-blended geopolymers were used as solidification agents. The leaching behavior of cesium and strontium from geopolymers was evaluated in accordance with ANSI/ANS-16.1. The diffusivity of cesium and strontium in a fly ash-based geopolymer was lower than that in Portland cement by a factor of 10{sup 3} and 10{sup 4}, respectively, showing significantly improved immobilization performance. The leaching resistance of fly ash-based geopolymer was relatively constant regardless of the type of fly ash. The diffusivity of water-soluble cesium and strontium ions were highly correlated with the critical pore diameter of the binder. The critical pore diameter of the fly ash-based geopolymer was remarkably smaller than those of Portland cement and slag-blended geopolymer; consequently, its ability physically to retard the diffusion of nuclides (physical barrier effect) was superior.

Protective coatings for commercial particulates

DEFF Research Database (Denmark)

Kindl, B.; Teng, Y.H.; Liu, Y.L.

1994-01-01

SiC/Al composites are in large-scale production with Al-Si alloy matrices. The same composites with pure Al or low Si matrices need diffusion barriers on the SiC reinforcement to control the interfacial reaction. The present paper describes various approaches taken to obtain protective coatings...... of alumina and zirconia on SiC particulates by sol-gel techniques. Aqueous and organic precursors have been used. The extent of the reaction, i.e., the Si and Al4C3 content in the matrix, was determined by differential thermal analysis and X-ray diffraction. The reaction rates of some coated particulates...... in liquid Al are decreased by as much as one order of magnitude during the first 15 min of immersion. Pretreatments of the SiC surface, the composition and thickness of the coating interphase and heat treatments of the coated materials have been studied, and are discussed in relation to their effect...

Thermal cycling behaviour of lanthanum zirconate as EB-PVD thermal barrier coating

International Nuclear Information System (INIS)

Bobzin, K.; Lugscheider, E.; Bagcivan, N.

2006-01-01

Thermal cycling tests with two different EB-PVD thermal barrier coatings (TBC) were performed in a furnace cycle test. The results of these tests showed an increase of endurable cycle number when pyrochloric La 2 Zr 2 O 7 was used as TBC. 1865 cycles were reached with La 2 Zr 2 O 7 and 1380 cycles with 7 weigth-% yttria stabilised zirconia (YSZ) EB-PVD TBC. Additional investigation was made with scanning electron microscope (SEM) to investigate morphology and to determine chemical composition by electron dispersive x-ray spectroscopy (EDS) analysis. X-Ray diffraction was performed to analyze structural constitution of deposited coatings. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

Measurement of interfacial shear mechanical properties in thermal barrier coating systems by a barb pullout method

International Nuclear Information System (INIS)

Guo, S.Q.; Mumm, D.R.; Karlsson, A.M.; Kagawa, Y.

2005-01-01

A test technique has been developed to facilitate evaluation of the fracture characteristics of coatings and interfaces in thermal barrier coating (TBC) systems. The methodology has particular application in analyzing delamination crack growth, where crack propagation occurs under predominantly mode II loading. The technique has been demonstrated by quantitatively measuring the effective delamination fracture resistance of an electron-beam physical vapor deposition TBC

Thermal Cycling and High-Temperature Corrosion Tests of Rare Earth Silicate Environmental Barrier Coatings

Science.gov (United States)

Darthout, Émilien; Gitzhofer, François

2017-12-01

Lutetium and yttrium silicates, enriched with an additional secondary zirconia phase, environmental barrier coatings were synthesized by the solution precursor plasma spraying process on silicon carbide substrates. A custom-made oven was designed for thermal cycling and water vapor corrosion testing. The oven can test four specimens simultaneously and allows to evaluate environmental barrier performances under similar corrosion kinetics compared to turbine engines. Coatings structural evolution has been observed by SEM on the polished cross sections, and phase composition has been analyzed by XRD. All coatings have been thermally cycled between 1300 °C and the ambient temperature, without spallation, due to their porosity and the presence of additional secondary phase which increases the thermal cycling resistance. During water vapor exposure at 1200 °C, rare earth disilicates showed a good stability, which is contradictory with the literature, due to impurities—such as Si- and Al-hydroxides—in the water vapor jets. The presence of vertical cracks allowed the water vapor to reach the substrate and then to corrode it. It has been observed that thin vertical cracks induced some spallation after 24 h of corrosion.

Ordering of Self-Diffusion Barrier Energies on Pt(110)-1x2

International Nuclear Information System (INIS)

Feibelman, Peter J.

1999-01-01

Bond-counting arguments, supported by ab-initio calculations, predict a lower barrier for ''leapfrog'' diffusion of Pt addimers on Pt(llO)-lx2 than for adatom dif- fusion or addimer dissociation. This conflicts with experiment, possibly signaling contaminant influence

Electroless Ni-Mo-P diffusion barriers with Pd-activated self-assembled monolayer on SiO2

International Nuclear Information System (INIS)

Liu Dianlong; Yang Zhigang; Zhang Chi

2010-01-01

Ternary Ni-based amorphous films can serve as a diffusion barrier layer for Cu interconnects in ultralarge-scale integration (ULSI) applications. In this paper, electroless Ni-Mo-P films deposited on SiO 2 layer without sputtered seed layer were prepared by using Pd-activated self-assembled monolayer (SAM). The solutions and operating conditions for pretreatment and deposition were presented, and the formation of Pd-activated SAM was demonstrated by XPS (X-ray photoelectron spectroscopy) analysis and BSE (back-scattered electron) observation. The effects of the concentration of Na 2 MoO 4 added in electrolytes, pH value, and bath temperature on the surface morphology and compositions of Ni-Mo-P films were investigated. The microstructures, diffusion barrier property, electrical resistivity, and adhesion were also examined. Based on the experimental results, the Ni-Mo-P alloys produced by using Pd-activated SAM had an amorphous or amorphous-like structure, and possessed good performance as diffusion barrier layer.

TiO2 as diffusion barrier at Co/Alq3 interface studied by x-ray standing wave technique

Science.gov (United States)

Phatak Londhe, Vaishali; Gupta, A.; Ponpandian, N.; Kumar, D.; Reddy, V. R.

2018-06-01

Nano-scale diffusion at the interfaces in organic spin valve thin films plays a vital role in controlling the performance of magneto-electronic devices. In the present work, it is shown that a thin layer of titanium dioxide at the interface of Co/Alq3 can act as a good diffusion barrier. The buried interfaces of Co/Alq3/Co organic spin valve thin film has been studied using x-ray standing waves technique. A planar waveguide is formed with Alq3 layer forming the cavity and Co layers as the walls of the waveguide. Precise information about diffusion of Co into Alq3 is obtained through excitation of the waveguide modes. It is found that the top Co layer diffuses deep into the Alq3 resulting in incorporation of 3.1% Co in the Alq3 layer. Insertion of a 1.7 nm thick barrier layer of TiO2 at Co/Alq3 interface results in a drastic reduction in the diffusion of Co into Alq3 to a value of only 0.4%. This suggests a better performance of organic spin valve with diffusion barrier of TiO2.

The oxidation of aluminide diffusion coatings containing platinum used for the protection of IN738 superalloy

International Nuclear Information System (INIS)

Hanna, M.D.; Haworth, C.W.

1993-01-01

Aluminide coatings, as used for the protection against oxidation of most nickel-base superalloy components in modern jet engines, have been formed by a diffusion process on IN738 to give a coating that is essentially NiAl containing Al-rich precipitates. Aluminide coatings containing platinum have also been produced by initially depositing a thin layer (several microns thick) of Pt on the superalloy prior to the aluminisation process. Depending upon the details of the processing (such as the thickness of the Pt or the Al flux during the diffusion process) the structure of the coating on being formed was essentially either PtAl/sub 2/, PtAl or NiAl, or a mixture of these phases, but after some hours heat treatment at a high temperature (equivalent to service) was converted to either NiAl (containing Pt), or PtAl (containing Ni) or a mixture of PtAl and NiAl. The oxidation rate of these coatings at different temperatures between 800 and 1000 deg. C was studied using an automatic recording micro-balance and compared with the oxidation rate of a simple aluminide coating and of uncoated IN738. Further longer-term oxidation tests, including cyclic tests, were also undertaken. The Pt containing coatings gave approximately the same performance, and some were slightly better than the simple aluminide coatings, (and much better than the uncoated IN738). Both sections through the oxidised surface of the Al/sub 2/O/sub 3/ scale formed on the coatings were examined using optical microscopy and the SEM. The coating/scale interface on the platinum aluminide was seen to be slightly convoluted. It was more adherent and showed less tendency to spall than that formed on the simple aluminide coating. (author)

Selection of design parameters of diffusion barrier in a passive 222Rn sampler based on activated charcoal adsorption

International Nuclear Information System (INIS)

Wei Suxia

1992-01-01

A method concerning selection of design parameters of diffusion barrier in a passive 222 Rn sampler based on activated charcoal adsorption. The proper parameter value of diffusion barrier is obtained by means of linearization of 222 Rn adsorption versus the exposure time. Thus, the influence of temperature on measured results may be greatly decreased, and higher sensitivity of the detector may be maintained

Investigation on the Interface Characteristics of the Thermal Barrier Coating System through Flat Cylindrical Indenters

Directory of Open Access Journals (Sweden)

Shifeng Wen

2014-01-01

Full Text Available Thermal barrier coating (TBC systems are highly advanced material systems and usually applied to insulate components from large and prolonged heat loads by utilizing thermally insulating materials. In this study, the characteristics of the interface of thermal barrier coating systems have been simulated by the finite-element method (FEM. The emphasis was put on the stress distribution at the interface which is beneath the indenter. The effect of the interface roughness, the thermally grown oxide (TGO layer's thickness, and the modulus ratio (η of the thin film with the substrate has been considered. Finite-element results showed that the influences of the interface roughness and the TGO layer's thickness on stress distribution were important. At the same time, the residual stress distribution has been investigated in detail.

Advanced thermal barrier coatings for operation in high hydrogen content fueled gas turbines.

Energy Technology Data Exchange (ETDEWEB)

Sampath, Sanjay [Stony Brook Univ., NY (United States)

2015-04-02

The Center for Thermal Spray Research (CTSR) at Stony Brook University in partnership with its industrial Consortium for Thermal Spray Technology is investigating science and technology related to advanced metallic alloy bond coats and ceramic thermal barrier coatings for applications in the hot section of gasified coal-based high hydrogen turbine power systems. In conjunction with our OEM partners (GE and Siemens) and through strategic partnership with Oak Ridge National Laboratory (ORNL) (materials degradation group and high temperature materials laboratory), a systems approach, considering all components of the TBC (multilayer ceramic top coat, metallic bond coat & superalloy substrate) is being taken during multi-layered coating design, process development and subsequent environmental testing. Recent advances in process science and advanced in situ thermal spray coating property measurement enabled within CTSR has been incorporated for full-field enhancement of coating and process reliability. The development of bond coat processing during this program explored various aspects of processing and microstructure and linked them to performance. The determination of the bond coat material was carried out during the initial stages of the program. Based on tests conducted both at Stony Brook University as well as those carried out at ORNL it was determined that the NiCoCrAlYHfSi (Amdry) bond coats had considerable benefits over NiCoCrAlY bond coats. Since the studies were also conducted at different cycling frequencies, thereby addressing an associated need for performance under different loading conditions, the Amdry bond coat was selected as the material of choice going forward in the program. With initial investigations focused on the fabrication of HVOF bond coats and the performance of TBC under furnace cycle tests , several processing strategies were developed. Two-layered HVOF bond coats were developed to render optimal balance of density and surface roughness

High Temperature Multilayer Environmental Barrier Coatings Deposited Via Plasma Spray-Physical Vapor Deposition

Science.gov (United States)

Harder, Bryan James; Zhu, Dongming; Schmitt, Michael P.; Wolfe, Douglas E.

2014-01-01

Si-based ceramic matrix composites (CMCs) require environmental barrier coatings (EBCs) in combustion environments to avoid rapid material loss. Candidate EBC materials have use temperatures only marginally above current technology, but the addition of a columnar oxide topcoat can substantially increase the durability. Plasma Spray-Physical Vapor Deposition (PS-PVD) allows application of these multilayer EBCs in a single process. The PS-PVD technique is a unique method that combines conventional thermal spray and vapor phase methods, allowing for tailoring of thin, dense layers or columnar microstructures by varying deposition conditions. Multilayer coatings were deposited on CMC specimens and assessed for durability under high heat flux and load. Coated samples with surface temperatures ranging from 2400-2700F and 10 ksi loads using the high heat flux laser rigs at NASA Glenn. Coating morphology was characterized in the as-sprayed condition and after thermomechanical loading using electron microscopy and the phase structure was tracked using X-ray diffraction.

Multiple-diffusion flame synthesis of pure anatase and carbon-coated titanium dioxide nanoparticles

KAUST Repository

Memon, Nasir; Anjum, Dalaver H.; Chung, Suk-Ho

2013-01-01

A multi-element diffusion flame burner (MEDB) is useful in the study of flame synthesis of nanomaterials. Here, the growth of pure anatase and carbon-coated titanium dioxide (TiO2) using an MEDB is demonstrated. Hydrogen (H2), oxygen (O2), and argon

Electron microscopy characterization of a molybdenum diffusion barrier in metallizations for chip carriers

International Nuclear Information System (INIS)

He Anqiang; Ivey, Douglas G.

2004-01-01

Mo layers have been studied as potential diffusion barriers for Au-Sn solder bonds in micro/optoelectronic device packaging. Solder was electroplated as alternating AuSn and Au 5 Sn multi-layers on wafers covered with Ti as an adhesion layer, followed by Mo as the diffusion barrier and Au as a capping layer. Samples were annealed at 340-420 deg. C for as long as 20 min. Scanning and transmission electron microscopy (SEM and TEM) were utilized to characterize interfacial reactions. Mo was found to be metallurgically stable, relative to the Au-Sn solder and the other metallization components, at temperatures up to at least 420 deg. C. However, the effectiveness of Mo as a barrier can be compromised by two factors. One of these is related to surface roughness associated with AlN or Al 2 O 3 carriers. Non-uniform metallization coverage can lead to breaks in the Mo barrier, resulting in contact between the carrier and molten solder during bonding applications. In addition, thermal stresses generated during heating and cooling can lead to cracking and spalling of the Mo and adhesion layers, exposing the carrier material to molten solder. Pre-annealing can help to relieve the thermal stresses and prevent spalling

Design of Thermal Barrier Coatings Thickness for Gas Turbine Blade Based on Finite Element Analysis

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Biao Li

2017-01-01

Full Text Available Thermal barrier coatings (TBCs are deposited on the turbine blade to reduce the temperature of underlying substrate, as well as providing protection against the oxidation and hot corrosion from high temperature gas. Optimal ceramic top-coat thickness distribution on the blade can improve the performance and efficiency of the coatings. Design of the coatings thickness is a multiobjective optimization problem due to the conflicts among objectives of high thermal insulation performance, long operation durability, and low fabrication cost. This work developed a procedure for designing the TBCs thickness distribution for the gas turbine blade. Three-dimensional finite element models were built and analyzed, and weighted-sum approach was employed to solve the multiobjective optimization problem herein. Suitable multiregion top-coat thickness distribution scheme was designed with the considerations of manufacturing accuracy, productivity, and fabrication cost.

Thermal Conductivity and Wear Behavior of HVOF-Sprayed Fe-Based Amorphous Coatings

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Haihua Yao

2017-10-01

Full Text Available To protect aluminum parts in vehicle engines, metal-based thermal barrier coatings in the form of Fe59Cr12Nb5B20Si4 amorphous coatings were prepared by high velocity oxygen fuel (HVOF spraying under two different conditions. The microstructure, thermal transport behavior, and wear behavior of the coatings were characterized simultaneously. As a result, this alloy shows high process robustness during spraying. Both Fe-based coatings present dense, layered structure with porosities below 0.9%. Due to higher amorphous phase content, the coating H-1 exhibits a relatively low thermal conductivity, reaching 2.66 W/(m·K, two times lower than the reference stainless steel coating (5.85 W/(m·K, indicating a good thermal barrier property. Meanwhile, the thermal diffusivity of amorphous coatings display a limited increase with temperature up to 500 °C, which guarantees a steady and wide usage on aluminum alloy. Furthermore, the amorphous coating shows better wear resistance compared to high carbon martensitic GCr15 steel at different temperatures. The increased temperature accelerating the tribological reaction, leads to the friction coefficient and wear rate of coating increasing at 200 °C and decreasing at 400 °C.

Physical barrier effect of geopolymeric waste form on diffusivity of cesium and strontium.

Science.gov (United States)

Jang, J G; Park, S M; Lee, H K

2016-11-15

The present study investigates the physical barrier effect of geopolymeric waste form on leaching behavior of cesium and strontium. Fly ash-based geopolymers and slag-blended geopolymers were used as solidification agents. The leaching behavior of cesium and strontium from geopolymers was evaluated in accordance with ANSI/ANS-16.1. The diffusivity of cesium and strontium in a fly ash-based geopolymer was lower than that in Portland cement by a factor of 10(3) and 10(4), respectively, showing significantly improved immobilization performance. The leaching resistance of fly ash-based geopolymer was relatively constant regardless of the type of fly ash. The diffusivity of water-soluble cesium and strontium ions were highly correlated with the critical pore diameter of the binder. The critical pore diameter of the fly ash-based geopolymer was remarkably smaller than those of Portland cement and slag-blended geopolymer; consequently, its ability physically to retard the diffusion of nuclides (physical barrier effect) was superior. Copyright © 2016 Elsevier B.V. All rights reserved.

Diffusion barrier characteristics of co monolayer prepared by Langmuir Blodgett technique

Energy Technology Data Exchange (ETDEWEB)

Sharma, Sumit, E-mail: sumitelsd2007@gmail.com [Electronic Science Department, Kurukshetra University, Kurukshetra, Haryana 136119 (India); Kumar, Mukesh, E-mail: kumarmukesh@gmail.com [Department of Electrical Engineering, College of Engineering at Wadi Aldawasir, Prince Sattam Bin Abdulaziz University, Wadi Aldawasir 11991 (Saudi Arabia); Rani, Sumita [Electronic Science Department, Kurukshetra University, Kurukshetra, Haryana 136119 (India); Kumar, Dinesh, E-mail: dineshelsd@gmail.com [Electronic Science Department, Kurukshetra University, Kurukshetra, Haryana 136119 (India)

2016-04-30

Graphical abstract: Thermal stability of structures (a) Cu/SiO{sub 2}/Si and (b) Cu/Co/SiO{sub 2}/Si, indicating that presence of thin cobalt layer improves the thermal stability of the structure up to 600 °C. - Highlights: • Monolayers of cobalt were deposited on SiO{sub 2}/Si substrates using LB technique. • Copper layers were deposited on this structures using thermal evaporation method. • Thermal stability was determined by annealing the structures at various temperatures. • The structure was found to be stable up to 650 °C. - Abstract: Monolayers of Co over SiO{sub 2}/Si substrate were deposited using Langmuir Blodgett (LB) technique. The diffusion barrier capability of Co layer was evaluated against copper diffusion. The structure of the deposited Co layer was analyzed using X-ray photoelectron spectroscopy (XPS), Energy Dispersive X-ray Spectroscopy (EDS) and Atomic force microscopy (AFM) techniques. Thermal stability of Cu/SiO{sub 2}/Si and Cu/Co/SiO{sub 2}/Si test structures was studied and compared using X-ray diffraction (XRD), scanning electron microscope (SEM) and four probe techniques. The samples were annealed at different temperatures starting from 200 °C up to 700 °C in vacuum for 30 min. XRD results indicated that combination of Co/SiO{sub 2} worked as diffusion barrier up to 550 °C whereas SiO{sub 2} alone could work as barrier only up to 300 °C. Sheet resistance of these samples was measured as a function of annealing temperature which also supports XRD results. C–V curves of these structures under the influence of Biased Thermal Stress (BTS) were analyzed. BTS was applied at 2.5 MV cm{sup −1} at 150 °C. Results showed that in the presence of Co barrier layer there was no shift in the C–V curve even after 90 min of BTS while in the absence of barrier there was a significant shift in the C–V curve even after 30 min of BTS. Further these test structures were examined for leakage current density (j{sub L}) at same BTS

Oxidation behaviour of a Ti2AlN MAX-phase coating

International Nuclear Information System (INIS)

Wang Qimin; Kim, Kwangho; Garkas, W; Renteria, A Flores; Leyens, C; Sun Chao

2011-01-01

In this paper, we reported the oxidation behaviour of Ti 2 AlN coatings on a -TiAl substrate. The coatings composed mainly of Ti 2 AlN MAX phase were obtained by magnetron sputtering and subsequent vacuum annealing. Isothermal oxidation tests at 700-900 deg. C were performed in air. The results indicated that the oxidation resistance of the -TiAl alloy can be improved by depositing a Ti 2 AlN layer on the alloy surface, especially at high temperatures. An Al-rich oxide scale formed on the coating surfaces during oxidation. This scale acts as diffusion barrier blocking the ingress of oxidation, and effectively protects the coated alloys from further oxidation attack.

Performance of the diffusion barrier in the metallic fuel in sodium-cooled fast reactor

International Nuclear Information System (INIS)

Kim, Jun Hwan; Ryu, Ho Jin; Yang, Seong Woo; Lee, Byoung Oon; Oh, Seok Jin; Lee, Chan Bock; Hahn, Dohee

2009-01-01

The objectives in this study are to propose several kinds of barrier materials and to evaluate their performance to prevent a fuel-clad interaction situation between the metallic fuel and the clad material in the Sodium-cooled Fast Reactor (SFR). Metallic foil made from refractory element, electrodeposition of the Cr on the clad surface, and the vapor deposition of the Zr were used as the barrier layers. The diffusion couple test was performed at the temperature of 800degC for 25 hour. The results showed that considerable amount of reaction occurred at the specimen without barrier, whereas excellent performance was observed in that neither reaction nor inter-diffusion occurred in the case of metallic foil made of Cr or V. Electrodeposition was revealed to be excellent provided that optimum deposition condition can be found. Similar to the electro-deposition result, excellent performance observed in the case of vapor deposition condition. (author)

The influence of the structures and compounds of DLC coatings on the barrier properties of PET bottles

International Nuclear Information System (INIS)

Li, Yang; Zhen-Duo, Wang; Shou-Ye, Zhang; Li-Zhen, Yang; Qiang, Chen

2009-01-01

To reduce the oxygen transmission rate through a polyethylene terephthalate (PET) bottle (an organic plastic) diamond-like carbon (DLC) coatings on the inner surface of the PET bottle were deposited by radio frequency plasma-enhanced chemical vapour deposition (RF-PECVD) technology with C 2 H 2 as the source of carbon and Ar as the diluted gas. As the barrier layer to humidity and gas permeation, this paper analyses the DLC film structure, composition, morphology and barrier properties by Fourier transform infrared, atomic force microscopy, scanning electron microscopy and oxygen transmission rate in detail. From the spectrum, it is found that the DLC film mainly consists of sp 3 bonds. The barrier property of the films is significantly relevant to the sp 3 bond concentration in the coating, the film thickness and morphology. Additionally, it is found that DLC film deposited in an inductively coupled plasma enhanced capacitively coupled plasma source shows a compact, homogeneous and crack-free surface, which is beneficial for a good gas barrier property in PET bottles. (fluids, plasmas and electric discharges)

Laser Cladding of Embedded Sensors for Thermal Barrier Coating Applications

Directory of Open Access Journals (Sweden)

Yanli Zhang

2018-05-01

Full Text Available The accurate real-time monitoring of surface or internal temperatures of thermal barrier coatings (TBCs in hostile environments presents significant benefits to the efficient and safe operation of gas turbines. A new method for fabricating high-temperature K-type thermocouple sensors on gas turbine engines using coaxial laser cladding technology has been developed. The deposition of the thermocouple sensors was optimized to provide minimal intrusive features to the TBC, which is beneficial for the operational reliability of the protective coatings. Notably, this avoids a melt pool on the TBC surface. Sensors were deposited onto standard yttria-stabilized zirconia (7–8 wt % YSZ coated substrates; subsequently, they were embedded with second YSZ layers by the Atmospheric Plasma Spray (APS process. Morphology of cladded thermocouples before and after embedding was optimized in terms of topography and internal homogeneity, respectively. The dimensions of the cladded thermocouple were in the order of 200 microns in thickness and width. The thermal and electrical response of the cladded thermocouple was tested before and after embedding in temperatures ranging from ambient to approximately 450 °C in a furnace. Seebeck coefficients of bared and embedded thermocouples were also calculated correspondingly, and the results were compared to that of a commercial standard K-type thermocouple, which demonstrates that laser cladding is a prospective technology for manufacturing microsensors on the surface of or even embedded into functional coatings.

Investigation of Top/Bottom electrode and Diffusion Barrier Layer for PZT Thick Film MEMS Sensors

DEFF Research Database (Denmark)

Hindrichsen, Christian Carstensen; Pedersen, Thomas; Thomsen, Erik Vilain

2008-01-01

Top and bottom electrodes for screen printed piezoelectric lead zirconate titanate, Pb(ZrxTi1 - x)O3 (PZT) thick film are investigated with respect to future MEMS devices. Down to 100 nm thick E-beam evaporated Al and Pt films are patterned as top electrodes on the PZT using a lift-off process...... with a line width down to 3 μ m. A 700 nm thick ZrO2 layer as insolating diffusion barrier layer is found to be insufficient as barrier layer for PZT on a silicon substrate sintered at 850°C. EDX shows diffusion of Si into the PZT layer....

Sintering Characteristics of Multilayered Thermal Barrier Coatings Under Thermal Gradient and Isothermal High Temperature Annealing Conditions

Science.gov (United States)

Rai, Amarendra K.; Schmitt, Michael P.; Bhattacharya, Rabi; Zhu, Dongming; Wolfe, Douglas E.

2014-01-01

Pyrochlore oxides have most of the relevant attributes for use as next generation thermal barrier coatings such as phase stability, low sintering kinetics and low thermal conductivity. One of the issues with the pyrochlore oxides is their lower toughness and therefore higher erosion rate compared to the current state-of-the-art TBC material, yttria (6 to 8 wt%) stabilized zirconia (YSZ). In this work, sintering characteristics were investigated for novel multilayered coating consisted of alternating layers of pyrochlore oxide viz Gd2Zr2O7 and t' low k (rare earth oxide doped YSZ). Thermal gradient and isothermal high temperature (1316 C) annealing conditions were used to investigate sintering and cracking in these coatings. The results are then compared with that of relevant monolayered coatings and a baseline YSZ coating.

Mueller matrix polarimetry on plasma sprayed thermal barrier coatings for porosity measurement.

Science.gov (United States)

Luo, David A; Barraza, Enrique T; Kudenov, Michael W

2017-12-10

Yttria-stabilized zirconia (YSZ) is the most widely used material for thermal plasma sprayed thermal barrier coatings (TBCs) used to protect gas turbine engine parts in demanding operation environments. The superior material properties of YSZ coatings are related to their internal porosity level. By quantifying the porosity level, tighter control on the spraying process can be achieved to produce reliable coatings. Currently, destructive measurement methods are widely used to measure the porosity level. In this paper, we describe a novel nondestructive approach that is applicable to classify the porosity level of plasma sprayed YSZ TBCs via Mueller matrix polarimetry. A rotating retarder Mueller matrix polarimeter was used to measure the polarization properties of the plasma sprayed YSZ coatings with different porosity levels. From these measurements, it was determined that a sample's measured depolarization ratio is dependent on the sample's surface roughness and porosity level. To this end, we correlate the depolarization ratio with the samples' surface roughness, as measured by a contact profilometer, as well as the total porosity level, in percentage measured using a micrograph and stereological analysis. With the use of this technique, a full-field and rapid measurement of porosity level can be achieved.

New Bond Coat Materials for Thermal Barrier Coating Systems Processed Via Different Routes

Science.gov (United States)

Soare, A.; Csaki, I.; Sohaciu, M.; Oprea, C.; Soare, S.; Costina, I.; Petrescu, M. I.

2017-06-01

This paper aims at describing the development of new Ru-based Bond Coats (BC) as part of Thermal Barrier Coatings. The challenge of this research was to obtain an adherent and uniform layer of alumina protective layer after high temperature exposure. We have prepared a RuAl 50/50 at% alloy in an induction furnace which was subsequently subjected to oxidation in an electric furnace, in air, at 1100C, for 10h and 100h. Mechanical alloying of Ru and Al powders was another processing route used in an attempt to obtain a stoichiometric RuAl. The alloy was sintered by Spark Plasma Sintering (SPS) and then oxidized at 1100C for 1 and10h. The alloys obtained as such were analysed before and after oxidation using advanced microscopy techniques (SEM and TEM). The encouraging results in case of RuAl alloys prepared by induction melting reveal that we obtained an adherent and uniform layer of alumina, free of delta-Ru. The results for the samples processed by powder metallurgy were positive but need to be further investigated. We should note here the novelty of this method for this particular type of application - as a BC part of a TBC system.

Thermal Conductivity of EB-PVD Thermal Barrier Coatings Evaluated by a Steady-State Laser Heat Flux Technique

Science.gov (United States)

Zhu, Dongming; Miller, Robert A.; Nagaraj, Ben A.; Bruce, Robert W.

2000-01-01

The thermal conductivity of electron beam-physical vapor deposited (EB-PVD) Zr02-8wt%Y2O3 thermal barrier coatings was determined by a steady-state heat flux laser technique. Thermal conductivity change kinetics of the EB-PVD ceramic coatings were also obtained in real time, at high temperatures, under the laser high heat flux, long term test conditions. The thermal conductivity increase due to micro-pore sintering and the decrease due to coating micro-delaminations in the EB-PVD coatings were evaluated for grooved and non-grooved EB-PVD coating systems under isothermal and thermal cycling conditions. The coating failure modes under the high heat flux test conditions were also investigated. The test technique provides a viable means for obtaining coating thermal conductivity data for use in design, development, and life prediction for engine applications.

Effect of H2O and Y(O on Oxidation Behavior of NiCoCrAl Coating Within Thermal Barrier Coating

Directory of Open Access Journals (Sweden)

WANG Yi-qun

2017-04-01

Full Text Available NiCoCrAl coatings containing Y and Y oxide were made using vacuum plasma deposition and high-velocity oxygen fuel respectively, high temperature oxidation dynamics and cross-section microstructures of NiCoCrAl+Y and NiCoCrAl+Y(O coatings in Ar-16.7%O2, Ar-3.3%H2O and Ar-0.2%H2-0.9%H2O at 1100℃ were investigated by differential thermal analysis (DTA and optical and electron microscope. The influencing mechanism of Y oxide on the oxidation of coatings at different atmosphere was compared by computation using First-Principles. The results show that Al2O3 layer on NiCoCrAl+Y coatings has more holes for internal oxidation on account of the element Y diffusion and enrichment on the interface. In addition, steam can promote the internal oxidation. While a thinner and uniform alumina form on NiCoCrAl+Y(O coatings because element Y is pinned by oxygen atoms during the preparation of coatings. Water vapor has less influence on protective alumina formation on the NiCoCrAl+Y(O coating. Therefore, oxidation behavior of NiCoCrAl coatings vary in composition and structure in different oxidizing atmosphere. Besides, Y and Y-enrichment oxides have key influences on the microstructure and the growth rate.

Convective diffusion of nanoparticles from the epithelial barrier toward regional lymph nodes.

Science.gov (United States)

Dukhin, Stanislav S; Labib, Mohamed E

2013-11-01

Drug delivery using nanoparticles as drug carriers has recently attracted the attention of many investigators. Targeted delivery of nanoparticles to the lymph nodes is especially important to prevent cancer metastasis or infection, and to diagnose disease stage. However, systemic injection of nanoparticles often results in organ toxicity because they reach and accumulate in all the lymph nodes in the body. An attractive strategy would be to deliver the drug-loaded nanoparticles to a subset of draining lymph nodes corresponding to a specific site or organ to minimize systemic toxicity. In this respect, mucosal delivery of nanoparticles to regional draining lymph nodes of a selected site creates a new opportunity to accomplish this task with minimal toxicity. One example is the delivery of nanoparticles from the vaginal lumen to draining lymph nodes to prevent the transmission of HIV in women. Other known examples include mucosal delivery of vaccines to induce immunity. In all cases, molecular and particle transport by means of diffusion and convective diffusion play a major role. The corresponding transport processes have common inherent regularities and are addressed in this review. Here we use nanoparticle delivery from the vaginal lumen to the lymph nodes as an example to address the many aspects of associated transport processes. In this case, nanoparticles penetrate the epithelial barrier and move through the interstitium (tissue) to the initial lymphatics until they finally reach the lymph nodes. Since the movement of interstitial liquid near the epithelial barrier is retarded, nanoparticle transport was found to take place through special foci present in the epithelium. Immediately after nanoparticles emerge from the foci, they move through the interstitium due to diffusion affected by convection (convective diffusion). Specifically, the convective transport of nanoparticles occurs due to their convection together with interstitial fluid through the

Oxidation behaviour of a Ti{sub 2}AlN MAX-phase coating

Energy Technology Data Exchange (ETDEWEB)

Wang Qimin; Kim, Kwangho [National Core Research Center for Hybrid Materials Solution, Pusan National University, Busan 609-735 (Korea, Republic of); Garkas, W; Renteria, A Flores [Chair of Physical Metallurgy and Materials Technology, Technical University of Brandenburg at Cottbus, 03046 Cottbus (Germany); Leyens, C [Institute of Materials Science, Technical University of Dresden, Helmholtzstrasse 7, 01069 Dresden (Germany); Sun Chao, E-mail: qmwang@pusan.ac.kr, E-mail: kwhokim@pusan.ac.kr [Division of Surface Engineering of Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

2011-10-29

In this paper, we reported the oxidation behaviour of Ti{sub 2}AlN coatings on a -TiAl substrate. The coatings composed mainly of Ti{sub 2}AlN MAX phase were obtained by magnetron sputtering and subsequent vacuum annealing. Isothermal oxidation tests at 700-900 deg. C were performed in air. The results indicated that the oxidation resistance of the -TiAl alloy can be improved by depositing a Ti{sub 2}AlN layer on the alloy surface, especially at high temperatures. An Al-rich oxide scale formed on the coating surfaces during oxidation. This scale acts as diffusion barrier blocking the ingress of oxidation, and effectively protects the coated alloys from further oxidation attack.

Few-layer MoS2 as nitrogen protective barrier

Science.gov (United States)

Akbali, B.; Yanilmaz, A.; Tomak, A.; Tongay, S.; Çelebi, C.; Sahin, H.

2017-10-01

We report experimental and theoretical investigations of the observed barrier behavior of few-layer MoS2 against nitrogenation. Owing to its low-strength shearing, low friction coefficient, and high lubricity, MoS2 exhibits the demeanor of a natural N-resistant coating material. Raman spectroscopy is done to determine the coating capability of MoS2 on graphene. Surface morphology of our MoS2/graphene heterostructure is characterized by using optical microscopy, scanning electron microscopy, and atomic force microscopy. In addition, density functional theory-based calculations are performed to understand the energy barrier performance of MoS2 against nitrogenation. The penetration of nitrogen atoms through a defect-free MoS2 layer is prevented by a very high vertical diffusion barrier, indicating that MoS2 can serve as a protective layer for the nitrogenation of graphene. Our experimental and theoretical results show that MoS2 material can be used both as an efficient nanocoating material and as a nanoscale mask for selective nitrogenation of graphene layer.

Photoluminescence studies of organic phosphor coated diffusing surface using blue inorganic light-emitting diode as excitation source

International Nuclear Information System (INIS)

Singh, Gyanendra; Mehta, Dalip Singh

2013-01-01

We report the studies on photoluminescence (PL) of organic phosphor coated on a diffusing surface using a blue inorganic light-emitting diode (LED) array as an excitation source. The organic phosphor composite coated diffuser was used to scatter the directional blue light from the LED array. Some of the blue light is absorbed by the organic phosphor composite and the phosphor molecules are excited and re-emit light at longer wavelengths due to the PL process. The output light consists of scattered blue light plus phosphor generated broadband yellow light, thus making white light. The diffuser was made up of a plastic substrate coated with an organic composite of small molecule fluorescent material zinc(II)bis(8-hydroxyquinoline) (Znq 2 ) doped with different percentages of electro-phosphorescent metal complex iridium(III)bis(2-methyldibenzo-[f, h] quinoxaline) (acetylacetonate) ([Ir(MDQ) 2 (acac)]). By means of changing the concentration and the thickness of the phosphor composite material the colour coordinates of white light were achieved. The CIE coordinates and correlated colour temperature were calculated for various thicknesses and phosphor composite concentrations and the results are reported. (paper)

Na effect on flexible Cu(In,Ga)Se{sub 2} photovoltaic cell depending on diffusion barriers (SiOx, i-ZnO) on stainless steel

Energy Technology Data Exchange (ETDEWEB)

Lee, Woo-Jung; Cho, Dae-Hyung; Wi, Jae-Hyung; Han, Won Seok [Electronics and Telecommunications Research Institute, Daejeon 305-700 (Korea, Republic of); Kim, Jeha [Insitute of Photovoltaics, Cheongju University, Cheongju 360-764 (Korea, Republic of); Chung, Yong-Duck, E-mail: ydchung@etri.re.kr [Electronics and Telecommunications Research Institute, Daejeon 305-700 (Korea, Republic of); Department of Advanced Device Engineering, Korea University of Science and Technology, Daejeon 305-350 (Korea, Republic of)

2014-10-15

Cu(In,Ga)Se{sub 2} (CIGS) based-photovoltaic (PV) cells with different diffusion barriers of SiOx and i-ZnO were fabricated on stainless steel (STS) substrate and their electrical characteristics were investigated by measuring J–V curves under illuminated and dark conditions. The physical properties of the CIGS film depending on type of diffusion barrier were also analyzed using X-ray diffraction and secondary ion mass spectroscopy. The efficiency of the CIGS-PV cell with i-ZnO barrier was approximately 2% higher than that with the SiOx barrier. Through the analysis of dark J–V curves, we discovered that distinctive defects were formed in the band gap of CIGS based on which diffusion barrier contacted the STS. The diffraction pattern showed a slightly different tendency of the peak intensity ratio of (220/204)/(112) in the PV cell with the i-ZnO barrier, which was slightly higher than that in the PV cell with SiOx barrier. In elemental depth profile, a deficient Ga profile was observed near the surface of the CIGS film with the SiOx barrier, and an abundant Na profile within the CIGS film with the i-ZnO barrier was detected. This is attributed to a difference in thermal conduction through the diffusion barriers during CIGS film growth, originating from the larger thermal conductivity of ZnO compared with SiOx. - Highlights: • We fabricated CIGS-PV cells with diffusion barriers of SiOx and i-ZnO on STS. • The efficiency of CIGS-PV cell with i-ZnO was ∼2% higher than that with SiOx. • Distinctive defects were formed into CIGS absorber depending on diffusion barrier.

Electrochemical characterization of V{sub x}Nb{sub y}C{sub z}/Bi{sub x}Ti{sub y}O{sub z} coatings produced through thermo-reactive diffusion and the sputtering technique

Energy Technology Data Exchange (ETDEWEB)

Castro H, S. A.; Alfonso, J. E.; Olaya, J. J., E-mail: jealfonso@unal.edu.co [Universidad Nacional de Colombia, Departamento de Fisica, Grupo de Ciencia de Materiales y Superficies, AA-14490 Bogota (Colombia)

2016-11-01

We present and experimental study of the structural evolution of a bilayer V{sub x}Nb{sub y}C{sub z}/Bi{sub x}Ti{sub y}O{sub z} coating produced via thermo-reactive diffusion (TRD) and the RF sputtering process on D-2 steel substrate. The TRD treatments were carried out in a molten mixture consisting of borax, ferro-niobium, ferro-vanadium, and aluminum, at 1313 K for 3 hours, using a resistance-heating furnace. Bi{sub x}Ti{sub y}O{sub z} coatings were deposited using RF magnetron sputtering on TRD coatings, in order to carry out a study of the corrosion behavior of this compound. The crystallographic structure of the coatings was determined via X-ray diffraction, the corrosion resistance was analyzed through the potentiodynamic polarization test (Tafel Extrapolation) and electrochemical impedance spectroscopic analysis (EIS). X-ray diffraction patterns showed that the ternary coating (VNbC{sub 2}) was preferentially oriented along the [200] direction with a cubic-centered face structure, and the Bi{sub x}Ti{sub y}O{sub z} coatings were amorphous. The electrochemical studies showed that the resistance corrosion of the coatings increased with respect to the bare substrate, and that polarization resistance in the bilayer coatings increased with respect to the ternary coatings, suggesting that the titanate has anti corrosive barrier effects. (Author)

Acoustic Emission Analysis of Damage Progression in Thermal Barrier Coatings Under Thermal Cyclic Conditions

Science.gov (United States)

Appleby, Matthew; Zhu, Dongming; Morscher, Gregory

2015-01-01

Damage evolution of electron beam-physical vapor deposited (EBVD-PVD) ZrO2-7 wt.% Y2O3 thermal barrier coatings (TBCs) under thermal cyclic conditions was monitored using an acoustic emission (AE) technique. The coatings were heated using a laser heat flux technique that yields a high reproducibility in thermal loading. Along with AE, real-time thermal conductivity measurements were also taken using infrared thermography. Tests were performed on samples with induced stress concentrations, as well as calcium-magnesium-alumino-silicate (CMAS) exposure, for comparison of damage mechanisms and AE response to the baseline (as-produced) coating. Analysis of acoustic waveforms was used to investigate damage development by comparing when events occurred, AE event frequency, energy content and location. The test results have shown that AE accumulation correlates well with thermal conductivity changes and that AE waveform analysis could be a valuable tool for monitoring coating degradation and provide insight on specific damage mechanisms.

Thermomechanical and Environmental Durability of Environmental Barrier Coated Ceramic Matrix Composites Under Thermal Gradients

Science.gov (United States)

Zhu, Dongming; Bhatt, Ramakrishna T.; Harder, Bryan

2016-01-01

This paper presents the developments of thermo-mechanical testing approaches and durability performance of environmental barrier coatings (EBCs) and EBC coated SiCSiC ceramic matrix composites (CMCs). Critical testing aspects of the CMCs will be described, including state of the art instrumentations such as temperature, thermal gradient, and full field strain measurements; materials thermal conductivity evolutions and thermal stress resistance; NDE methods; thermo-mechanical stress and environment interactions associated damage accumulations. Examples are also given for testing ceramic matrix composite sub-elements and small airfoils to help better understand the critical and complex CMC and EBC properties in engine relevant testing environments.

Method and Process Development of Advanced Atmospheric Plasma Spraying for Thermal Barrier Coatings

Science.gov (United States)

Mihm, Sebastian; Duda, Thomas; Gruner, Heiko; Thomas, Georg; Dzur, Birger

2012-06-01

Over the last few years, global economic growth has triggered a dramatic increase in the demand for resources, resulting in steady rise in prices for energy and raw materials. In the gas turbine manufacturing sector, process optimizations of cost-intensive production steps involve a heightened potential of savings and form the basis for securing future competitive advantages in the market. In this context, the atmospheric plasma spraying (APS) process for thermal barrier coatings (TBC) has been optimized. A constraint for the optimization of the APS coating process is the use of the existing coating equipment. Furthermore, the current coating quality and characteristics must not change so as to avoid new qualification and testing. Using experience in APS and empirically gained data, the process optimization plan included the variation of e.g. the plasma gas composition and flow-rate, the electrical power, the arrangement and angle of the powder injectors in relation to the plasma jet, the grain size distribution of the spray powder and the plasma torch movement procedures such as spray distance, offset and iteration. In particular, plasma properties (enthalpy, velocity and temperature), powder injection conditions (injection point, injection speed, grain size and distribution) and the coating lamination (coating pattern and spraying distance) are examined. The optimized process and resulting coating were compared to the current situation using several diagnostic methods. The improved process significantly reduces costs and achieves the requirement of comparable coating quality. Furthermore, a contribution was made towards better comprehension of the APS of ceramics and the definition of a better method for future process developments.

Facile approach in the development of icephobic hierarchically textured coatings as corrosion barrier

Energy Technology Data Exchange (ETDEWEB)

Momen, G., E-mail: gmomen@uqac.ca; Farzaneh, M.

2014-04-01

Highlights: • A superhydrophobic coating is developed via a simple environmental-friendly method. • This coating can be used on the surface of various metals such as copper, magnesium. • The superhydrophobic aluminum surface showed the excellent corrosion resistance. • The fabricated surface revealed a drastically reduction of ice adhesion strength. • Such surfaces can advantageously be used in cold climate regions. - Abstract: An anti-corrosion superhydrophobic film with water contact angle greater than 160° on aluminum alloy 6061 substrate was fabricated simply through the spin-coating method applied to Al{sub 2}O{sub 3} nanoparticles doped in silicone rubber solution. The as-obtained sample was characterized by scanning electron microscopy (SEM) and water contact angle/surface energy measurement. The corrosion behaviour of such coating in the NaCl solutions was investigated using the potentiodynamic polarization. The results show that the corrosion resistance of the developed superhydrophobic surface is improved greatly due to the composite wetting states or interfaces with numerous air pockets between its surface and the NaCl solution. This superhydrophobic coating could serve as an effective barrier against aggressive medium. Ice adhesion strength of the as-prepared superhydrophobic coating was also evaluated by measuring its ice adhesion force which was found to have reduced by 4.8 times compared to that of aluminum substrate as reference test.

Effects of variations in coating materials and process conditions on the thermal cycle properties of NiCrAlY/YSZ thermal barrier coatings

Energy Technology Data Exchange (ETDEWEB)

Tang Feng [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616 (United States)]. E-mail: ftang@ucdavis.edu; Ajdelsztajn, Leonardo [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616 (United States); Kim, George E. [Perpetual Technologies, Montreal, Que., H3E 1T8 (Canada); Provenzano, Virgil [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Schoenung, Julie M. [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616 (United States)

2006-06-15

Thermal cycle tests were conducted on a variety of thermal barrier coating (TBC) specimens with bond coats that had been prepared in different ways. Variables include: (1) different thermal spray processes (high velocity oxy-fuel (HVOF) spray and low pressure plasma spray (LPPS)) (2) different feedstock powder (gas-atomized and cryomilled) (3) the introduction of nano-sized alumina additives (particles and whiskers) and (4) with and without a post-spray vacuum heat treatment. The results show that the cryomilling of the NiCrAlY powder and the post-spray heat treatment in vacuum can both lead to significant improvement in the thermal cycle lifetime of the TBCs. The TBC specimens with LPPS bond coats also generally showed longer lifetimes than those with HVOF bond coats. In contrast, the intentional dispersion of alumina particles or whiskers in the NiCrAlY powders during cryomilling did not result in the further improvement of the lifetime of the TBCs. Microstructural evolution, including the thermally grown oxide (TGO) formation, the distribution of the dispersoids in the bond coat, the internal oxidation of the bond coat, the bond coat shrinkage during the thermal cycle tests and the reduction of the ZrO{sub 2} in the top coat during the heat treatment in vacuum, was investigated.

Delamination Mechanisms of Thermal and Environmental Barrier Coatings on SiC/SiC Ceramic Matrix Composites

Science.gov (United States)

Zhu, Dongming; Choi, Sung R.; Lee, Kang N.; Miller, Robert A.

2003-01-01

Advanced ceramic thermal harrier coatings will play an increasingly important role In future gas turbine engines because of their ability to effectively protect the engine components and further raise engine temperatures. However, the coating durability issue remains a major concern with the ever-increasing temperature requirements. In this paper, thermal cyclic response and delamination failure modes of a ZrO2-8wt%Y2O3 and mullite/BSAS thermaVenvironmenta1 barrier coating system on SiC/SiC ceramic matrix composites were investigated using a laser high-heat-flux technique. The coating degradation and delamination processes were monitored in real time by measuring coating apparent conductivity changes during the cyclic tests under realistic engine temperature and stress gradients, utilizing the fact that delamination cracking causes an apparent decrease in the measured thermal conductivity. The ceramic coating crack initiation and propagation driving forces under the cyclic thermal loads, in conjunction with the mechanical testing results, will be discussed.

Microstructural characterization of thermal barrier coating on Inconel 617 after high temperature oxidation

Directory of Open Access Journals (Sweden)

Mohammadreza Daroonparvar

2013-06-01

Full Text Available A turbine blade was protected against high temperature corrosion and oxidation by thermal barrier coatings (TBCsusing atmospheric plasma spraying technique (APS on a Ni-based superalloy (Inconel 617. The coatings (NiCr6AlY/ YSZ and NiCr10AlY/YSZ consist of laminar structure with substantial interconnected porosity transferred oxygen from Yittria stabilized Zirconia (YSZ layer toward the bond coat (NiCrAlY. Hence, a thermally grown oxide layer (TGO was formed on the metallic bond coat and internal oxidation of the bond coat occurred during oxidation. The TBC systems were oxidized in a normal electrically heated furnace at 1150 °C for 18, 22, 26, 32 and 40h.Microstructural characterization of coatings demonstrated that the growth of the TGO layer on the nickel alloy with 6wt. % Al is more rapid than TGO with 10wt. % Al. In addition, many micro-cracks were observed at the interface of NiCr6AlY/YSZ. X-ray diffraction analysis (XRD showed the existence of detrimental oxides such as NiCr2O4, NiCrO3 and NiCrO4 in the bond coat containing 6wt. % Al, accompanied by rapid volume expansion causing the destruction of TBC. In contrast, in the bond coat with 10wt. % Al, NiO, Al2O3and Cr2O3 oxides were formed while very low volume expansion occurred. The oxygen could not penetrate into the TGO layer of bond coat with 10 wt. % Al during high temperature oxidation and the detrimental oxides were not extensively formed within the bond coat as more oxygen was needed. The YSZ with higher Al content showed higher oxidation resistance.

Passivation coating for flexible substrate mirrors

Science.gov (United States)

Tracy, C. Edwin; Benson, David K.

1990-01-01

A protective diffusion barrier for metalized mirror structures is provided by a layer or coating of silicon nitride which is a very dense, transparent, dielectric material that is impervious to water, alkali, and other impurities and corrosive substances that typically attack the metal layers of mirrors and cause degradation of the mirrors' reflectivity. The silicon nitride layer can be deposited on the substrate before metal deposition thereon to stabilize the metal/substrate interface, and it can be deposited over the metal to encapsulate it and protect the metal from corrosion or other degradation. Mirrors coated with silicon nitride according to this invention can also be used as front surface mirrors. Also, the silver or other reflective metal layer on mirrors comprising thin, lightweight, flexible substrates of metal or polymer sheets coated with glassy layers can be protected with silicon nitride according to this invention.

Tensile toughness test and high temperature fracture analysis of thermal barrier coatings

International Nuclear Information System (INIS)

Qian, G.; Nakamura, T.; Berndt, C.C.; Leigh, S.H.

1997-01-01

In this paper, an effective fracture toughness test which uses interface fracture mechanics theory is introduced. This method is ideally suited for determining fracture resistance of multilayered thermal barrier coatings (TBCs) consisting of ceramic and bond layers and, unlike other fracture experiments, requires minimal set-up over a simple tensile adhesion test. Furthermore, while other test methods usually use edge cracked specimens, the present test models a crack embedded within the coatings, which is more consistent with actual TBCs where failure initiates from internal voids or defects. The results of combined computational and experimental analysis show that any defects located within the ceramic coating can significantly weaken a TBC, whereas the debonding resistances of the bond coating and its interfaces are found to be much higher. In a separate analysis, the authors have studied fracture behavior of TBCs subjected to thermal loading in a high temperature environment. The computed fracture parameters reveal that when the embedded crack size is on order of the coating thickness, the fracture driving force is comparable to the fracture resistance of the coating found in the toughness test. In addition, the major driving force for fracture derives from the thermal insulating effect across the crack faces rather than the mismatch in the coefficients of thermal expansion. The authors have also investigated the effects of functionally graded material (FGM) within TBCs and found its influences on the fracture parameters to be small. This result implies that the FGM may not contribute toward enhancing the fracture toughness of the TBCs considered here

Time-to-failure analysis of 5 nm amorphous Ru(P) as a copper diffusion barrier

International Nuclear Information System (INIS)

Henderson, Lucas B.; Ekerdt, John G.

2009-01-01

Evaluation of chemical vapor deposited amorphous ruthenium-phosphorous alloy as a copper interconnect diffusion barrier is reported. Approximately 5 nm-thick Ru(P) and TaN films in Cu/Ru(P)/SiO 2 /p-Si and Cu/TaN/SiO 2 /p-Si stacks are subjected to bias-temperature stress at electric fields from 2.0 MV/cm to 4.0 MV/cm and temperatures from 200 deg. C to 300 deg. C . Time-to-failure measurements suggest that chemical vapor deposited Ru(P) is comparable to physical vapor deposited TaN in preventing Cu diffusion. The activation energy of failure for stacks using Ru(P) as a liner is determined to be 1.83 eV in the absence of an electric field. Multiple models of dielectric failure, including the E and Schottky-type √E models indicate that Ru(P) is acceptable for use as a diffusion barrier at conditions likely in future technology generations

Analysis and experimental study on formation conditions of large-scale barrier-free diffuse atmospheric pressure air plasmas in repetitive pulse mode

Science.gov (United States)

Li, Lee; Liu, Lun; Liu, Yun-Long; Bin, Yu; Ge, Ya-Feng; Lin, Fo-Chang

2014-01-01

Atmospheric air diffuse plasmas have enormous application potential in various fields of science and technology. Without dielectric barrier, generating large-scale air diffuse plasmas is always a challenging issue. This paper discusses and analyses the formation mechanism of cold homogenous plasma. It is proposed that generating stable diffuse atmospheric plasmas in open air should meet the three conditions: high transient power with low average power, excitation in low average E-field with locally high E-field region, and multiple overlapping electron avalanches. Accordingly, an experimental configuration of generating large-scale barrier-free diffuse air plasmas is designed. Based on runaway electron theory, a low duty-ratio, high voltage repetitive nanosecond pulse generator is chosen as a discharge excitation source. Using the wire-electrodes with small curvature radius, the gaps with highly non-uniform E-field are structured. Experimental results show that the volume-scaleable, barrier-free, homogeneous air non-thermal plasmas have been obtained between the gap spacing with the copper-wire electrodes. The area of air cold plasmas has been up to hundreds of square centimeters. The proposed formation conditions of large-scale barrier-free diffuse air plasmas are proved to be reasonable and feasible.

Computing the blood brain barrier (BBB) diffusion coefficient: A molecular dynamics approach

Energy Technology Data Exchange (ETDEWEB)

Shamloo, Amir, E-mail: shamloo@sharif.edu; Pedram, Maysam Z.; Heidari, Hossein; Alasty, Aria, E-mail: aalasti@sharif.edu

2016-07-15

Various physical and biological aspects of the Blood Brain Barrier (BBB) structure still remain unfolded. Therefore, among the several mechanisms of drug delivery, only a few have succeeded in breaching this barrier, one of which is the use of Magnetic Nanoparticles (MNPs). However, a quantitative characterization of the BBB permeability is desirable to find an optimal magnetic force-field. In the present study, a molecular model of the BBB is introduced that precisely represents the interactions between MNPs and the membranes of Endothelial Cells (ECs) that form the BBB. Steered Molecular Dynamics (SMD) simulations of the BBB crossing phenomenon have been carried out. Mathematical modeling of the BBB as an input-output system has been considered from a system dynamics modeling viewpoint, enabling us to analyze the BBB behavior based on a robust model. From this model, the force profile required to overcome the barrier has been extracted for a single NP from the SMD simulations at a range of velocities. Using this data a transfer function model has been obtained and the diffusion coefficient is evaluated. This study is a novel approach to bridge the gap between nanoscale models and microscale models of the BBB. The characteristic diffusion coefficient has the nano-scale molecular effects inherent, furthermore reducing the computational costs of a nano-scale simulation model and enabling much more complex studies to be conducted. - Highlights: • Molecular dynamics simulation of crossing nano-particles through the BBB membrane at different velocities. • Recording the position of nano-particle and the membrane-NP interaction force profile. • Identification of a frequency domain model for the membrane. • Calculating the diffusion coefficient based on MD simulation and identified model. • Obtaining a relation between continuum medium and discrete medium.

Mechanical Properties of Air Plasma Sprayed Environmental Barrier Coating (EBC) Materials

Science.gov (United States)

Richards, Bradley; Zhu, Dongming; Ghosn, Louis; Wadley, Haydn

2015-01-01

Development work in Environmental Barrier Coatings (EBCs) for Ceramic Matrix Composites (CMCs) has focused considerably on the identification of materials systems and coating architectures to meet application needs. The evolution of these systems has occurred so quickly that modeling efforts and requisite data for modeling lag considerably behind development. Materials property data exists for many systems in the bulk form, but the effects of deposition on the critical properties of strength and fracture behavior are not well studied. We have plasma sprayed bulk samples of baseline EBC materials (silicon, ytterbium disilicate) and tested the mechanical properties of these materials to elicit differences in strength and toughness. We have also endeavored to assess the mixed-mode fracture resistance, Gc, of silicon in a baseline EBC applied to SiCSiC CMC via four point bend test. These results are compared to previously determined properties of the comparable bulk material.

Performance and Durability of Environmental Barrier Coatings on SiC/SiC Ceramic Matrix Composites

Science.gov (United States)

Zhu, Dongming; Harder, Bryan; Bhatt, Ramakrishna

2016-01-01

This presentation highlights advanced environmental barrier coating (EBC) and SiC-SiC Ceramic Matrix Composites (CMC) systems for next generation turbine engines. The emphasis will be placed on fundamental coating and CMC property evaluations; and the integrated system performance and degradation mechanisms in simulated laboratory turbine engine testing environments. Long term durability tests in laser rig simulated high heat flux the rmomechanical creep and fatigue loading conditions will also be presented. The results can help improve the future EBC-CMC system designs, validating the advanced EBC-CMC technologies for hot section turbine engine applications.

Load rate dependence of the mechanical properties of thermal barrier coating systems

Energy Technology Data Exchange (ETDEWEB)

Zotov, Nikolay; Eggeler, Gunther [Institut fuer Werkstoffe, Ruhr Universitaet Bochum, 44780 Bochum (Germany); Bartsch, Marion [Institut fuer Werkstoff-Forschung, DLR Koeln, 51147 Koeln (Germany)

2009-07-01

Thermal barrier coatings (TBC), composed of yttrium-stabilized zirconia (YSZ) ceramic top coat (TC) and intermetallic NiCoCrAlY bond coat (BC) are commonly used as protective coatings of Ni-based high temperature gas engine components. Nanoindentation techniques are increasingly applied for determining the TBC mechanical properties on a nanometre scale. However, little is known about the load-rate dependence of the mechanical properties, which is important for better understanding of cyclic thermal fatigue experiments. Nanoindentations with different load rates omega were performed on polished cross-sections of TBC, deposited by EB-PVD on IN625 substrates (S), using a XP Nanoindenter (MTS) equipped with Berkovich diamond tip. The Young's modulus (E) of the TC is independent of omega, while E for the BC and the S decreases with omega. The hardness (H) of the TC and the BC increases, while H for the S decreases with omega. From the dependence of H on omega, creep power-law exponents c = 0.24(11) and c = 0.023(6) for the TC and the BC were determined. For all TBC components, a decrease with omega of the power-law exponents n and m, describing the loading and unloading nanoindentation curves, is observed.

Design and optimization of coating structure for the thermal barrier coatings fabricated by atmospheric plasma spraying via finite element method

Directory of Open Access Journals (Sweden)

L. Wang

2014-06-01

Full Text Available The first prerequisite for fabricating the thermal barrier coatings (TBCs with excellent performance is to find an optimized coating structure with high thermal insulation effect and low residual stress. This paper discusses the design and optimization of a suitable coating structure for the TBCs prepared by atmospheric plasma spraying (APS using the finite element method. The design and optimization processes comply with the rules step by step, as the structure develops from a simple to a complex one. The research results indicate that the suitable thicknesses of the bond-coating and top-coating are 60–120 μm and 300–420 μm, respectively, for the single ceramic layer YSZ/NiCoCrAlY APS-TBC. The embedded interlayer (50 wt.%YSZ + 50 wt.%NiCoCrAlY will further reduce the residual stress without sacrificing the thermal insulation effect. The double ceramic layer was further considered which was based on the single ceramic layer TBC. The embedded interlayer and the upper additional ceramic layer will have a best match between the low residual stress and high thermal insulation effect. Finally, the optimized coating structure was obtained, i.e., the La2Ce2O7(LC/YSZ/Interlayer/NiCoCrAlY coating structure with appropriate layer thickness is the best choice. The effective thermal conductivity of this optimized LC/YSZ/IL/BL TBC is 13.2% lower than that of the typical single ceramic layer YSZ/BL TBC.

High Speed, Low Cost Fabrication of Gas Diffusion Electrodes for Membrane Electrode Assemblies

Energy Technology Data Exchange (ETDEWEB)

DeCastro, Emory S.; Tsou, Yu-Min; Liu, Zhenyu

2013-09-20

Fabrication of membrane electrode assemblies (MEAs) depends on creating inks or pastes of catalyst and binder, and applying this suspension to either the membrane (catalyst coated membrane) or gas diffusion media (gas diffusion electrode) and respectively laminating either gas diffusion media or gas diffusion electrodes (GDEs) to the membrane. One barrier to cost effective fabrication for either of these approaches is the development of stable and consistent suspensions. This program investigated the fundamental forces that destabilize the suspensions and developed innovative approaches to create new, highly stable formulations. These more concentrated formulations needed fewer application passes, could be coated over longer and wider substrates, and resulted in significantly lower coating defects. In March of 2012 BASF Fuel Cell released a new high temperature product based on these advances, whereby our customers received higher performing, more uniform MEAs resulting in higher stack build yields. Furthermore, these new materials resulted in an “instant” increase in capacity due to higher product yields and material throughput. Although not part of the original scope of this program, these new formulations have also led us to materials that demonstrate equivalent performance with 30% less precious metal in the anode. This program has achieved two key milestones in DOE’s Manufacturing R&D program: demonstration of processes for direct coating of electrodes and continuous in-line measurement for component fabrication.

Sputtering an exterior metal coating on copper enclosure for large-scale growth of single-crystalline graphene

DEFF Research Database (Denmark)

Luo, Birong; Caridad, José M; Whelan, Patrick Rebsdorf

2017-01-01

growth. The sputtered coating suppresses nucleation density by acting as both a diffusion barrier and as a sink for excess carbon during the growth, reducing the carbon concentration in the interior of the enclosure. Field effect mobility of hBN-templated devices fabricated from graphene domains grown...

Enhanced Corrosion Resistance of PVD-CrN Coatings by ALD Sealing Layers

Science.gov (United States)

Wan; Zhang, Teng Fei; Ding, Ji Cheng; Kim, Chang-Min; Park, So-Won; Yang, Yang; Kim, Kwang-Ho; Kwon, Se-Hun

2017-04-01

Multilayered hard coatings with a CrN matrix and an Al2O3, TiO2, or nanolaminate-Al2O3/TiO2 sealing layer were designed by a hybrid deposition process combined with physical vapor deposition (PVD) and atomic layer deposition (ALD). The strategy was to utilize ALD thin films as pinhole-free barriers to seal the intrinsic defects to protect the CrN matrix. The influences of the different sealing layers added in the coatings on the microstructure, surface roughness, and corrosion behaviors were investigated. The results indicated that the sealing layer added by ALD significantly decreased the average grain size and improved the corrosion resistance of the CrN coatings. The insertion of the nanolaminate-Al2O3/TiO2 sealing layers resulted in a further increase in corrosion resistance, which was attributed to the synergistic effect of Al2O3 and TiO2, both acting as excellent passivation barriers to the diffusion of corrosive substances.

Low Thermal Conductivity, High Durability Thermal Barrier Coatings for IGCC Environments

Energy Technology Data Exchange (ETDEWEB)

Jordan, Eric [Univ. of Connecticut, Storrs, CT (United States); Gell, Maurice [Univ. of Connecticut, Storrs, CT (United States)

2015-01-15

Advanced thermal barrier coatings (TBC) are crucial to improved energy efficiency in next generation gas turbine engines. The use of traditional topcoat materials, e.g. yttria-stabilized zirconia (YSZ), is limited at elevated temperatures due to (1) the accelerated undesirable phase transformations and (2) corrosive attacks by calcium-magnesium-aluminum-silicate (CMAS) deposits and moisture. The first goal of this project is to use the Solution Precursor Plasma Spray (SPPS) process to further reduce the thermal conductivity of YSZ TBCs by introducing a unique microstructural feature of layered porosity, called inter-pass boundaries (IPBs). Extensive process optimization accompanied with hundreds of spray trials as well as associated SEM cross-section and laser-flash measurements, yielded a thermal conductivity as low as 0.62 Wm⁻¹K⁻¹ in SPPS YSZ TBCs, approximately 50% reduction of APS TBCs; while other engine critical properties, such as cyclic durability, erosion resistance and sintering resistance, were characterized to be equivalent or better than APS baselines. In addition, modifications were introduced to SPPS TBCs so as to enhance their resistance to CMAS under harsh IGCC environments. Several mitigation approaches were explored, including doping the coatings with Al₂O₃ and TiO₂, applying a CMAS infiltration-inhibiting surface layer, and filling topcoat cracks with blocking substances. The efficacy of all these modifications was assessed with a set of novel CMAS-TBC interaction tests, and the moisture resistance was tested in a custom-built high-temperature moisture rig. In the end, the optimal low thermal conductivity TBC system was selected based on all evaluation tests and its processing conditions were documented. The optimal coating consisted on a thick inner layer of YSZ coating made by the SPPS process having a thermal conductivity 50% lower than standard YSZ coatings topped with a high temperature tolerant CMAS resistant gadolinium

Diffusion barrier characteristics and shear fracture behaviors of eutectic PbSn solder/electroless Co(W,P) samples

International Nuclear Information System (INIS)

Pan, Hung-Chun; Hsieh, Tsung-Eong

2012-01-01

Highlights: ► Diffusion barrier features, activation energies of IMC growth and mechanical behaviors of electroless Co(W,P)/PbSn joints. ► Amorphous Co(W,P) is a sacrificial- plus stuffed-type barrier while polycrystalline Co(W,P) is a sacrificial-type barrier. ► Ductile mode dominates the failure of Co(W,P)/PbSn joints. ► Phosphorus content of Co(W,P) is crucial to the barrier capability and microstructure evolution at Co(W,P)/PbSn interface. ► Diffusion barrier capability is governed by the nature of chemical bonds, rather than the crystallinity of materials. - Abstract: Diffusion barrier characteristics, activation energy (E a ) of IMC growth and bonding properties of amorphous and polycrystalline electroless Co(W,P) (termed as α-Co(W,P) and poly-Co(W,P)) to eutectic PbSn solder are presented. Intermetallic compound (IMC) spallation and an nano-crystalline P-rich layer were observed in PbSn/α-Co(W,P) samples subjected to liquid-state aging at 250 °C. In contrast, IMCs resided on the P-rich layer in PbSn/α-Co(W,P) samples subjected to solid-state aging at 150 °C. Thick IMCs neighboring to an amorphous W-rich layer was seen in PbSn/poly-Co(W,P) samples regardless of the aging type. α-Co(W,P) was found to be a sacrificial- plus stuffed-type barrier while poly-Co(W,P) is mainly a sacrificial-type barrier. The values of E a 's for PbSn/α-Co(W,P) and PbSn/poly-Co(W,P) systems were 338.6 and 167.5 kJ/mol, respectively. Shear test revealed the ductile mode dominates the failure in both α- and poly-Co(W,P) samples. Analytical results indicated the high P content in electroless layer might enhance the barrier capability but degrade the bonding strength.

Effect of thermal barrier coatings on the performance of steam and water-cooled gas turbine/steam turbine combined cycle system

Science.gov (United States)

Nainiger, J. J.

1978-01-01

An analytical study was made of the performance of air, steam, and water-cooled gas-turbine/steam turbine combined-cycle systems with and without thermal-barrier coatings. For steam cooling, thermal barrier coatings permit an increase in the turbine inlet temperature from 1205 C (2200 F), resulting in an efficiency improvement of 1.9 percentage points. The maximum specific power improvement with thermal barriers is 32.4 percent, when the turbine inlet temperature is increased from 1425 C (2600 F) to 1675 C (3050 F) and the airfoil temperature is kept the same. For water cooling, the maximum efficiency improvement is 2.2 percentage points at a turbine inlet temperature of 1683 C (3062 F) and the maximum specific power improvement is 36.6 percent by increasing the turbine inlet temperature from 1425 C (2600 F) to 1730 C (3150 F) and keeping the airfoil temperatures the same. These improvements are greater than that obtained with combined cycles using air cooling at a turbine inlet temperature of 1205 C (2200 F). The large temperature differences across the thermal barriers at these high temperatures, however, indicate that thermal stresses may present obstacles to the use of coatings at high turbine inlet temperatures.

MnCo{sub 2}O{sub 4} spinel chromium barrier coatings for SOFC interconnect by HVOF

Energy Technology Data Exchange (ETDEWEB)

Lagerbom, J.; Varis, T.; Pihlatie, M.; Himanen, O.; Saarinen, V.; Kiviaho, J.; Turunen, E. [VTT Technical Research Centre of Finland, Espoo (Finland); Puranen, J. [Tampere Univ. of Technology (Finland). Inst. of Materials Science

2010-07-01

Chromia released from steel parts used for interconnect plates by evaporation and condensation can quickly degrade the cell (cathode) performance in solid oxide fuel cell SOFC. Coatings on top of the IC plate can work as a chromium evaporation barrier. The coating material should have good electrical conductivity, high temperature stability and nearly the same coefficient of thermal expansion as the cell materials. One candidate for the coating material is MnCo{sub 2}O{sub 4} spinel because of its suitable properties. High velocity oxy fuel (HVOF) spraying was used for the coating application on Crofer 22 APU steel samples. Using commercial and self made spray dried powders together with an HV2000 spray gun it was possible to successfully manufacture, well adhering, dense and reasonably uniform coatings. The samples were tested in oxidation exposure tests in air followed by post analysis in SEM. Powders and coatings microstructures are presented here, both before and after exposure. It was found out that together with spraying parameters the powder characteristics used influence clearly to the coating quality. Especially as very thin coatings was aimed with dense structure fine powders was found to be essential. (orig.)

Pack cementation diffusion coatings for Fe-base and refractory alloys. Final report

Energy Technology Data Exchange (ETDEWEB)

Rapp, R.A. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering

1998-03-10

With the aid of computer-assisted calculations of the equilibrium vapor pressures in halide-activated cementation packs, processing conditions have been identified and experimentally verified for the codeposition of two or more alloying elements in a diffusion coating on a variety of steels and refractory metal alloys. A new comprehensive theory to treat the multi-component thermodynamic equilibria in the gas phase for several coexisting solid phases was developed and used. Many different processes to deposit various types of coatings on several types of steels were developed: Cr-Si codeposition for low- or medium-carbon steels, Cr-Al codeposition on low-carbon steels to yield either a Kanthal-type composition (Fe-25Cr-4Al in wt.%) or else a (Fe, Cr){sub 3}Al surface composition. An Fe{sub 3}Al substrate was aluminized to achieve an FeAl surface composition, and boron was also added to ductilize the coating. The developmental Cr-lean ORNL alloys with exceptional creep resistance were Cr-Al coated to achieve excellent oxidation resistance. Alloy wires of Ni-base were aluminized to provide an average composition of Ni{sub 3}Al for use as welding rods. Several different refractory metal alloys based on Cr-Cr{sub 2}Nb have been silicided, also with germanium additions, to provide excellent oxidation resistance. A couple of developmental Cr-Zr alloys were similarly coated and tested.

Thermal conductivity issues of EB-PVD thermal barrier coatings

Energy Technology Data Exchange (ETDEWEB)

Schulz, U.; Raetzer-Scheibe, H.J.; Saruhan, B. [DLR - German Aerospace Center, Institute of Materials Research, 51170 Cologne (Germany); Renteria, A.F. [BTU, Physical Metallurgy and Materials Technology, Cottbus (Germany)

2007-09-15

The thermal conductivity of electron-beam physical vapor deposited (EB-PVD) thermal barrier coatings (TBCs) was investigated by the Laser Flash technique. Sample type and methodology of data analyses as well as atmosphere during the measurement have some influence on the data. A large variation of the thermal conductivity was found by changes in TBC microstructure. Exposure at high temperature caused sintering of the porous microstructure that finally increased thermal conductivity up to 30 %. EB-PVD TBCs show a distinct thickness dependence of the thermal conductivity due to the anisotropic microstructure in thickness direction. Thin TBCs had a 20 % lower thermal conductivity than thick coatings. New compositions of the ceramic top layer offer the largest potential to lower thermal conductivity. Values down to 0.8W/(mK) have been already demonstrated with virgin coatings of pyrochlore compositions. (Abstract Copyright [2007], Wiley Periodicals, Inc.) [German] Die Waermeleitfaehigkeit von elektronenstrahl-aufgedampften (EB-PVD) Waermedaemmschichten (TBCs) wurde mittels Laser-Flash untersucht. Probentyp, Messmethodik und die Atmosphaere waehrend der Messung haben einen Einfluss auf die Ergebnisse. Aenderungen in der Mikrostruktur der TBC fuehrten zu grossen Unterschieden der Waermeleitfaehigkeit. Eine Hochtemperaturbelastung verursachte Sintervorgaenge in der poroesen Mikrostruktur, was die Waermeleitfaehigkeit um bis zu 30 % ansteigen liess. EB-PVD TBCs zeigen eine deutliche Dickenabhaengigkeit der Waermeleitfaehigkeit durch die Anisotropie der Mikrostruktur in dieser Richtung. Duenne TBCs haben eine um 20 % geringere Waermeleitfaehigkeit als dicke Schichten. Neue Zusammensetzungen der keramischen Deckschicht bieten die groessten Moeglichkeiten fuer eine Reduktion der Waermeleitfaehigkeit. Werte bis zu 0,8 W/(mK) wurden damit bereits erreicht. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

Thermocyclic behaviour of microstructurally modified EB-PVD thermal barrier coatings

International Nuclear Information System (INIS)

Schulz, U.; Fritscher, K.; Raetzer-Scheibe, H.-J.; Kaysser, W.A.; Peters, M.

1997-01-01

This paper focuses on the combined effects of substrate temperature and rotation during electron-beam physical vapor deposition (EB-PVD) on the columnar microstructure of yttria partially stabilized zirconia (YPSZ) thermal barrier coatings. Diameter and degree of ordering of the columns and the density of the coatings are sensitive to the processing parameters. Results are discussed in the frame of common structural zone models for PVD processes. The models are extended to consider the rotational effect. EB-PVD YPSZ TBCs of different column diameters were deposited on top of an EB-PVD NiCoCrAlY bondcoat on IN 100 superalloy test bars. The performance of the TBCs was investigated in a cyclic oxidation furnace test rig between 1100 C and 130 C and in a burner rig under hot gas corrosion conditions at a maximum temperature of 900 C. Results showed a correlation between cyclic lifetime and the various microstructures of the TBCs. Samples having a non-regular arrangement of columns performed best in both tests. (orig.)

Simultaneous cell death and desquamation of the embryonic diffusion barrier during epidermal development

International Nuclear Information System (INIS)

Saathoff, Manuela; Blum, Barbara; Quast, Thomas; Kirfel, Gregor; Herzog, Volker

2004-01-01

The periderm is an epithelial layer covering the emerging epidermis in early embryogenesis of vertebrates. In the chicken embryo, an additional cellular layer, the subperiderm, occurs at later embryonic stages underneath the periderm. The questions arose what is the function of both epithelial layers and, as they are transitory structures, by which mechanism are they removed. By immunocytochemistry, the tight junction (TJ) proteins occludin and claudin-1 were localized in the periderm and in the subperiderm, and sites of close contact between adjacent cells were detected by electron microscopy. Using horseradish peroxidase (HRP) as tracer, these contacts were identified as tight junctions involved in the formation of the embryonic diffusion barrier. This barrier was lost by desquamation at the end of the embryonic period, when the cornified envelope of the emerging epidermis was formed. By TUNEL and DNA ladder assays, we detected simultaneous cell death in the periderm and the subperiderm shortly before hatching. The absence of caspases-3, -6, and -7 activity, key enzymes of apoptosis, and the lack of typical morphological criteria of apoptosis such as cell fragmentation or membrane blebbing point to a special form of programmed cell death (PCD) leading to the desquamation of the embryonic diffusion barrier

The role that bond coat depletion of aluminum has on the lifetime of APS-TBC under oxidizing conditions

Energy Technology Data Exchange (ETDEWEB)

Renusch, D.; Schorr, M.; Schuetze, M. [Karl-Winnacker-Institut der DECHEMA e.V., D-60486 Frankfurt am Main (Germany)

2008-07-15

Bond coat oxidation as well as bond coat depletion of Al are still believed to be a major degradation mechanism with respect to the lifetime of thermal barrier coating (TBC) systems. In this study the top coat lifetime is described as being limited by both bond coat depletion of Al and mechanical failure of the top coat. The empirical results are introduced by considering three spallation cases, namely, Al depletion failure, thermal fatigue failure, and thermal aging failure. Al depletion failure occurs when the Al content within the bond coat reaches a critical value. In this paper bond coat depletion of Al is modeled by considering the diffusion of Al into both the thermally grown oxide (TGO) and substrate. The diffusion model results are compared to Al concentration profiles measured with an electron beam microprobe. These measured results are from oxidized air plasma sprayed TBC systems (APS-TBC) with vacuum plasma sprayed (VPS) bond coats for exposures up to 5000 h in the temperature range of 950-1100 C. This paper focuses on the Al depletion failure and how it relates to top coat spallation. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

Corrosion and Fatigue Behavior of High-Strength Steel Treated with a Zn-Alloy Thermo-diffusion Coating

Science.gov (United States)

Mulligan, C. P.; Vigilante, G. N.; Cannon, J. J.

2017-11-01

High and low cycle fatigue tests were conducted on high-strength steel using four-point bending. The materials tested were ASTM A723 steel in the as-machined condition, grit-blasted condition, MIL-DTL-16232 heavy manganese phosphate-coated condition, and ASTM A1059 Zn-alloy thermo-diffusion coated (Zn-TDC). The ASTM A723 steel base material exhibits a yield strength of 1000 MPa. The effects of the surface treatments versus uncoated steel were examined. The fatigue life of the Zn-TDC specimens was generally reduced on as-coated specimens versus uncoated or phosphate-coated specimens. Several mechanisms are examined including the role of compressive residual stress relief with the Zn-TDC process as well as fatigue crack initiation from the hardened Zn-Fe alloy surface layer produced in the gas-metal reaction. Additionally, the effects of corrosion pitting on the fatigue life of coated specimens are explored as the Zn-TDC specimens exhibit significantly improved corrosion resistance over phosphate-coated and oiled specimens.

Diffusion barrier and adhesion properties of SiO(x)N(y) and SiO(x) layers between Ag/polypyrrole composites and Si substrates.

Science.gov (United States)

Horváth, Barbara; Kawakita, Jin; Chikyow, Toyohiro

2014-06-25

This paper describes the interface reactions and diffusion between silver/polypyrrole (Ag/PPy) composite and silicon substrate. This composite material can be used as a novel technique for 3D-LSI (large-scale integration) by the fast infilling of through-silicon vias (TSV). By immersion of the silicon wafer with via holes into the dispersed solution of Ag/PPy composite, the holes are filled with the composite. It is important to develop a layer between the composite and the Si substrate with good diffusion barrier and adhesion characteristics. In this paper, SiOx and two types of SiOxNy barrier layers with various thicknesses were investigated. The interface structure between the Si substrate, the barrier, and the Ag/PPy composite was characterized by transmission electron microscopy. The adhesion and diffusion properties of the layers were established for Ag/PPy composite. Increasing thickness of SiOx proved to permit less Ag to transport into the Si substrate. SiOxNy barrier layers showed very good diffusion barrier characteristics; however, their adhesion depended strongly on their composition. A barrier layer composition with good adhesion and Ag barrier properties has been identified in this paper. These results are useful for filling conductive metal/polymer composites into TSV.

Nanoparticle/Polymer Nanocomposite Bond Coat or Coating

Science.gov (United States)

Miller, Sandi G.

2011-01-01

This innovation addresses the problem of coatings (meant to reduce gas permeation) applied to polymer matrix composites spalling off in service due to incompatibility with the polymer matrix. A bond coat/coating has been created that uses chemically functionalized nanoparticles (either clay or graphene) to create a barrier film that bonds well to the matrix resin, and provides an outstanding barrier to gas permeation. There is interest in applying clay nanoparticles as a coating/bond coat to a polymer matrix composite. Often, nanoclays are chemically functionalized with an organic compound intended to facilitate dispersion of the clay in a matrix. That organic modifier generally degrades at the processing temperature of many high-temperature polymers, rendering the clay useless as a nano-additive to high-temperature polymers. However, this innovation includes the use of organic compounds compatible with hightemperature polymer matrix, and is suitable for nanoclay functionalization, the preparation of that clay into a coating/bondcoat for high-temperature polymers, the use of the clay as a coating for composites that do not have a hightemperature requirement, and a comparable approach to the preparation of graphene coatings/bond coats for polymer matrix composites.

Gas barrier properties of diamond-like carbon films coated on PTFE

International Nuclear Information System (INIS)

Ozeki, K.; Nagashima, I.; Ohgoe, Y.; Hirakuri, K.K.; Mukaibayashi, H.; Masuzawa, T.

2009-01-01

Diamond-like carbon (DLC) films were deposited on polytetrafluoroethylene (PTFE) using radio frequency (RF) plasma-enhanced chemical vapour deposition (PE-CVD). Before the DLC coating, the PTFE substrate was modified with a N 2 plasma pre-treatment to enhance the adhesive strength of the DLC to the substrate. The influences of the N 2 plasma pre-treatment and process pressure on the gas permeation properties of these DLC-coated PTFE samples were investigated. In the Raman spectra, the G peak position shifted to a lower wave number with increasing process pressure. With scanning electron microscopy (SEM), a network of microcracks was observed on the surface of the DLC film without N 2 plasma pre-treatment. The density of these cracks decreased with increasing process pressure. In the film subjected to a N 2 plasma pre-treatment, no cracks were observed at any process pressure. In the gas barrier test, the gas permeation decreased drastically with increasing film thickness and saturated at a thickness of 0.2 μm. The DLC-coated PTFE with the N 2 plasma pre-treatment exhibited a greater reduction in gas permeation than did the samples without pre-treatment. For both sample types, gas permeation decreased with increasing process pressure.

Multiple-diffusion flame synthesis of pure anatase and carbon-coated titanium dioxide nanoparticles

KAUST Repository

Memon, Nasir

2013-09-01

A multi-element diffusion flame burner (MEDB) is useful in the study of flame synthesis of nanomaterials. Here, the growth of pure anatase and carbon-coated titanium dioxide (TiO2) using an MEDB is demonstrated. Hydrogen (H2), oxygen (O2), and argon (Ar) are utilized to establish the flame, whereas titanium tetraisopropoxide is used as the precursor for TiO2. The nanoparticles are characterized using high-resolution transmission electron microscopy, with elemental mapping (of C, O, and Ti), X-ray diffraction, Raman spectroscopy, and thermogravimetric analysis. The growth of pure anatase TiO2 nanoparticles occurs when Ar and H2 are used as the precursor carrier gas, while the growth of carbon-coated nanoparticles ensues when Ar and ethylene (C2H4) are used as the precursor carrier gas. A uniform coating of 3-5nm of carbon is observed around TiO2 particles. The growth of highly crystalline TiO2 nanoparticles is dependent on the gas flow rate of the precursor carrier and amorphous particles are observed at high flow rates. Carbon coating occurs only on crystalline nanoparticles, suggesting a possible growth mechanism of carbon-coated TiO2 nanoparticles. © 2013 The Combustion Institute.

Effects of angular dependence of surface diffuseness in deformed nuclei on Coulomb barrier

International Nuclear Information System (INIS)

Adamian, G.G.; Antonenko, N.V.; Malov, L.A.; Scamps, G.; Lacroix, D.

2014-01-01

The angular dependence of surface diffuseness is further discussed. The results of self-consistent calculations are compared with those obtained with the phenomenological mean-field potential. The rather simple parametrizations are suggested. The effects of surface polarization and hexadecapole deformation on the height of the Coulomb barrier are revealed. (authors)

Method of moments approach to pricing double barrier contracts in polynomial jump-diffusion models

NARCIS (Netherlands)

Eriksson, B.; Pistorius, M.

2011-01-01

Abstract: We present a method of moments approach to pricing double barrier contracts when the underlying is modelled by a polynomial jump-diffusion. By general principles the price is linked to certain infinite dimensional linear programming problems. Subsequently approximating these by finite

Isothermal oxidation behaviour of thermal barrier coatings with CoCrAlY bond coat irradiated by high-current pulsed electron beam

Energy Technology Data Exchange (ETDEWEB)

Cai, Jie [School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Guan, Qingfeng, E-mail: guanqf@mail.ujs.edu.cn [School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Hou, Xiuli [School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Wang, Zhiping; Su, Jingxin; Han, Zhiyong [College of Science, Civil Aviation University of China, Tianjin 300300 (China)

2014-10-30

Highlights: • The original coarse surface was re-melted by pulsed electron beam irradiation. • Very fine grains were homogeneously dispersed on the irradiated coat surface. • A compact Al{sub 2}O{sub 3} scale was formed in irradiated TBCs at the onset of oxidation. • The selective oxidation of Al element avoided the formation of other oxides. • The irradiated coating has a much higher oxidation resistance. - Abstract: Thermal sprayed CoCrAlY bond coat irradiated by high-current pulsed electron beam (HCPEB) and thermal barrier coatings (TBCs) prepared with the irradiated bond coat and the ceramic top coat were investigated. The high temperature oxidation resistance of these specimens was tested at 1050 °C in air. Microstructure observations revealed that the original coarse surface of the as-sprayed bond coat was significantly changed as the interconnected bulged nodules with a compact appearance after HCPEB irradiation. Abundant Y-rich alumina particulates and very fine grains were dispersed on the irradiated surface. After high temperature oxidation test, the thermally grown oxide (TGO) in the initial TBCs grew rapidly and was comprised of two distinct layers: a large percentage of mixed oxides in the outer layer and a relatively small portion of Al{sub 2}O{sub 3} in the inner layer. Severe local internal oxidation and extensive cracks in the TGO layer were discovered as well. Comparatively, the irradiated TBCs exhibited thinner TGO layer, slower TGO growth rate, and homogeneous TGO composition (primarily consisting of Al{sub 2}O{sub 3}). The results indicate that TBCs with the irradiated bond coat have a much higher oxidation resistance.

Synchrotron X-ray measurement techniques for thermal barrier coated cylindrical samples under thermal gradients

Energy Technology Data Exchange (ETDEWEB)

Siddiqui, Sanna F.; Knipe, Kevin; Manero, Albert; Raghavan, Seetha [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, Florida 32816 (United States); Meid, Carla; Wischek, Janine; Bartsch, Marion [German Aerospace Center (DLR), Institute of Materials Research, 51147 Cologne (Germany); Okasinski, John; Almer, Jonathan [X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Karlsson, Anette M. [Cleveland State University, 2121 Euclid Avenue, Cleveland, Ohio 44115 (United States)

2013-08-15

Measurement techniques to obtain accurate in situ synchrotron strain measurements of thermal barrier coating systems (TBCs) applied to hollow cylindrical specimens are presented in this work. The Electron Beam Physical Vapor Deposition coated specimens with internal cooling were designed to achieve realistic temperature gradients over the TBC coated material such as that occurring in the turbine blades of aeroengines. Effects of the circular cross section on the x-ray diffraction (XRD) measurements in the various layers, including the thermally grown oxide, are investigated using high-energy synchrotron x-rays. Multiple approaches for beam penetration including collection, tangential, and normal to the layers, along with variations in collection parameters are compared for their ability to attain high-resolution XRD data from the internal layers. This study displays the ability to monitor in situ, the response of the internal layers within the TBC, while implementing a thermal gradient across the thickness of the coated sample. The thermal setup maintained coating surface temperatures in the range of operating conditions, while monitoring the substrate cooling, for a controlled thermal gradient. Through variation in measurement location and beam parameters, sufficient intensities are obtained from the internal layers which can be used for depth resolved strain measurements. Results are used to establish the various techniques for obtaining XRD measurements through multi-layered coating systems and their outcomes will pave the way towards goals in achieving realistic in situ testing of these coatings.

Production of atmospheric pressure diffuse nanosecond pulsed dielectric barrier discharge using the array needles-plate electrode in air

International Nuclear Information System (INIS)

Yang Dezheng; Wang Wenchun; Jia Li; Nie Dongxia; Shi Hengchao

2011-01-01

In this paper, a bidirectional high pulse voltage with 20 ns rising time is employed to generate an atmospheric pressure diffuse dielectric barrier discharge using the array needles-plate electrode configuration. Both double needle and multiple needle electrode configurations nanosecond pulsed dielectric barrier discharges are investigated. It is found that a diffuse discharge plasma with low gas temperature can be obtained, and the plasma volume increases with the increase of the pulse peak voltage, but remains almost constant with the increase of the pulse repetition rate. In addition to showing the potential application on a topographically nonuniform surface treatment of the discharge, the multiple needle-plate electrode configuration with different needle-plate electrode gaps are also employed to generate diffuse discharge plasma.

A Review of Tribological Coatings for Control Drive Mechanisms in Space Reactors

International Nuclear Information System (INIS)

CJ Larkin; JD Edington; BJ Close

2006-01-01

Tribological coatings must provide lubrication for moving components of the control drive mechanism for a space reactor and prevent seizing due to friction or diffusion welding to provide highly reliable and precise control of reflector position over the mission lifetime. Several coatings were evaluated based on tribological performance at elevated temperatures and in ultrahigh vacuum environments. Candidates with proven performance in the anticipated environment are limited primarily to disulfide materials. Irradiation data for these coatings is nonexistent. Compatibility issues between coating materials and structural components may require the use of barrier layers between the solid lubricant and structural components to prevent deleterious interactions. It would be advisable to consider possible lubricant interactions prior to down-selection of structural materials. A battery of tests was proposed to provide the necessary data for eventual solid lubricant/coating selection

Ultrathin Cr added Ru film as a seedless Cu diffusion barrier for advanced Cu interconnects

Science.gov (United States)

Hsu, Kuo-Chung; Perng, Dung-Ching; Yeh, Jia-Bin; Wang, Yi-Chun

2012-07-01

A 5 nm thick Cr added Ru film has been extensively investigated as a seedless Cu diffusion barrier. High-resolution transmission electron microscopy micrograph, X-ray diffraction (XRD) pattern and Fourier transform-electron diffraction pattern reveal that a Cr contained Ru (RuCr) film has a glassy microstructure and is an amorphous-like film. XRD patterns and sheet resistance data show that the RuCr film is stable up to 650 °C, which is approximately a 200 °C improvement in thermal stability as compared to that of the pure Ru film. X-ray photoelectron spectroscopy depth profiles show that the RuCr film can successfully block Cu diffusion, even after a 30-min 650 °C annealing. The leakage current of the Cu/5 nm RuCr/porous SiOCH/Si stacked structure is about two orders of magnitude lower than that of a pristine Ru sample for electric field below 1 MV/cm. The RuCr film can be a promising Cu diffusion barrier for advanced Cu metallization.

Suppression of interfacial reactions between Li4Ti5O12 electrode and electrolyte solution via zinc oxide coating

International Nuclear Information System (INIS)

Han, Cuiping; He, Yan-Bing; Li, Hongfei; Li, Baohua; Du, Hongda; Qin, Xianying; Kang, Feiyu

2015-01-01

Graphical abstract: The Li 4 Ti 5 O 12 (LTO) based batteries have severe gassing behavior due to the strong interfacial reactions between LTO and the electrolyte solution, which hampers the practical application of LTO in high power LIBs. The ZnO coating on LTO particles as a barrier layer can effectively suppress the interfacial reactions between LTO and the electrolyte solution. Simultaneously, the ZnO coating significantly reduces the charge-transfer resistance and increases the lithium ion diffusion coefficient, which leads to great improvement of rate and cyclic performance of LTO electrode. - Highlights: • A ZnO coating layer was constructed on the LTO particles by a chemical process as a barrier layer between LTO and surrounding electrolyte solution. • The ZnO coating can effectively stabilize the electrode/electrolyte interface and suppress interfacial reactions between LTO and electrolyte solution. • The ZnO coating can improve the electronic conductivity and lithium ion diffusion coefficient, which contributes to a great improvement in cyclic and high rate capabilities of LTO electrode. • The ZnO coating on LTO may be an effective method to solve the gassing behavior of LTO based battery and promote its wide application in lithium ion power battery. - Abstract: Li 4 Ti 5 O 12 (LTO) based batteries have severe gassing behavior during charge/discharge and storage process. The interfacial reactions between LTO and electrolyte solution may be the main reason. In this work, the LTO spinel particles are modified with ZnO coating using a chemical process to reduce the surface reactivity of LTO particles. Results show that the ZnO coating can effectively stabilize the electrode/electrolyte interface and suppress the formation of a solid electrolyte interface (SEI) film. Simultaneously, this ZnO modification can improve the electronic conductivity and lithium ion diffusion coefficient, which contributes to a great improvement in cyclic and high rate

Laser surface modification of Yttria Stabilized Zirconia (YSZ) thermal barrier coating on AISI H13 tool steel substrate

Science.gov (United States)

Reza, M. S.; Aqida, S. N.; Ismail, I.

2018-03-01

This paper presents laser surface modification of plasma sprayed yttria stabilized zirconia (YSZ) coating to seal porosity defect. Laser surface modification on plasma sprayed YSZ was conducted using 300W JK300HPS Nd: YAG laser at different operating parameters. Parameters varied were laser power and pulse frequency with constant residence time. The coating thickness was measured using IM7000 inverted optical microscope and surface roughness was analysed using two-dimensional Mitutoyo Surface Roughness Tester. Surface roughness of laser surface modification of YSZ H-13 tool steel decreased significantly with increasing laser power and decreasing pulse frequency. The re-melted YSZ coating showed higher hardness properties compared to as-sprayed coating surface. These findings were significant to enhance thermal barrier coating surface integrity for dies in semi-solid processing.

Characterization of Secondary Mineral Grain Coatings and their Role as Diffusion-controlled Sinks and Sources for Metal Contaminants

Science.gov (United States)

Davis, J. A.; Guo, H.; Lai, B.; Kemner, K. M.; Ercius, P.; Fox, P. M.; Singer, D. M.; Minor, A.; Waychunas, G.

2012-12-01

Many important geochemical reactions occur at the mineral-water interface, including sorption and desorption reactions of contaminants. Fundamental knowledge of the kinetics of these processes is based primarily on experimental observations of reactions at faces of single crystals or macroscopic data from pure mineral powder suspensions. Sorption reactions at crystal faces are generally very fast, on the order of microseconds or less, with reaction times often limited only by film diffusion at the mineral-water interface. In well-stirred suspensions of aquifer sediments, however, sorptive equilibrium can take many hours or days to achieve steady-state concentrations. We have examined the potential reasons for sorption rate limitation using uranium(VI) sorption by sediments from a sandy aquifer in Savannah River, South Carolina (USA). U(VI) sorption by sand-sized grains from the aquifer is dominated by reaction with secondary mineral coatings on quartz and feldspar grains. The coatings studied were on the order of 15 microns in thickness (i.e., from quartz grain to aqueous solution) and composed primarily of clay minerals and hematite of varying particle size. Microfocused-XRF imaging of elemental concentrations (e.g., U, Fe) of polished cross-sections of the grain/coating contact showed strong spatial correlations of U and Fe within the coatings, regardless of the length of reaction time (30 minutes to 4 weeks). The spatial resolution of the μ-XRF technique is of the order of 2 microns in horizontal directions, but the uncertainty of the observed spatial gradients is high due to grain curvature away from the polished surface and fluorescence contributed from the entire 30 micron thickness of a typical grain/epoxy thin section. TEM characterization of focused-ion-beam (FIB), vertically-extracted samples of the grain-coating contact shows that complex pore networks exist within the coatings of variable dimensions and unknown connectivity. Using scanning TEM (STEM

Effects of humidity and filter material on diffusive sampling of isocyanates using reagent-coated filters