Synthesis and Phase Stability of Scandia, Gadolinia, and Ytterbia Co-doped Zirconia for Thermal Barrier Coating Application

NASA Astrophysics Data System (ADS)

Li, Qi-Lian; Cui, Xiang-Zhong; Li, Shu-Qing; Yang, Wei-Hua; Wang, Chun; Cao, Qian

2015-01-01

Scandia, gadolinia, and ytterbia co-doped zirconia (SGYZ) ceramic powder was synthesized by chemical co-precipitation and calcination processes for application in thermal barrier coatings to promote the durability of gas turbines. The ceramic powder was agglomerated and sintered at 1150 °C for 2 h, and the powder exhibited good flowability and apparent density to be suitable for plasma spraying process. The microstructure, morphology and phase stability of the powder and plasma-sprayed SGYZ coatings were analyzed by means of scanning electron microscope and x-ray diffraction. Thermal conductivity of plasma-sprayed SGYZ coatings was measured. The results indicated that the SGYZ ceramic powder and the coating exhibit excellent stability to retain single non-transformable tetragonal zirconia even after high temperature (1400 °C) exposure for 500 h and do not undergo a tetragonal-to-monoclinic phase transition upon cooling. Furthermore, the plasma-sprayed SGYZ coating also exhibits lower thermal conductivity than yttria stabilized zirconia coating currently used in gas turbine engine industry. SGYZ can be explored as a candidate material of ultra-high temperature thermal barrier coating for advanced gas turbine engines.

Interpenetrating phase ceramic/polymer composite coatings: Fabrication and characterization

NASA Astrophysics Data System (ADS)

Craig, Bradley Dene

The goals of this thesis research were to fabricate interpenetrating phase composite (IPC) ceramic/polymer coatings and to investigate the effect of the interconnected microstructure on the physical and wear properties of the coatings. IPC coatings with an interpenetrating phase microstructure were successfully fabricated by first forming a porous ceramic with an interconnected microstructure using a chemical bonding route (mainly reacting alpha-alumina (0.3 mum) with orthophosphoric acid to form a phosphate bond). Porosity within these ceramic coatings was easily controlled between 20 and 50 vol. % by phosphoric acid addition, and was measured by a new porosity measurement technique (thermogravimetric volatilization of liquids, or TVL) which was developed. The resulting ceramic preforms were infiltrated with a UV and thermally curable cycloaliphatic epoxide resin and cured. This fabrication route resulted in composite coatings with thicknesses ranging from ˜1mum to 100 mum with complete filling of open pore space. The physical properties of the composite coatings, including microhardness, flexural modulus and wear resistance, were evaluated as a function of processing variables, including orthophosphoric acid content and ceramic phase firing temperature, which affected the microstructure and interparticulate bonding between particles in the coatings. For example, microhardness increased from ˜30 on the Vicker's scale to well over 200 as interparticulate bonding was increased in the ceramic phase. Additionally, Taber wear resistance in the best TPC coatings was found to approach that of fully-densified alumina under certain conditions. Several factors were found to influence the wear mechanism in the IPC coating materials. Forming strong connections between ceramic particles led to up to an order of magnitude increase in the wear resistance. Additionally, coating microhardness and ceramic/polymer interfacial strength were studied and found to be important in determining the wear mechanism and wear resistance of IPC composite coatings. A qualitative theory for wear mechanisms in these coatings was developed. Finally, a series of transparent coatings were developed via a similar processing route, using smaller (˜90 nm) boehmite particles instead of 0.3 mum alpha-alumina. Physical property control was found to mimic that found in opaque coatings, and showed increasing surface adsorption characteristics with increasing phosphoric acid content.

Plasma Spray-Physical Vapor Deposition (PS-PVD) of Ceramics for Protective Coatings

NASA Technical Reports Server (NTRS)

Harder, Bryan J.; Zhu, Dongming

2011-01-01

In order to generate advanced multilayer thermal and environmental protection systems, a new deposition process is needed to bridge the gap between conventional plasma spray, which produces relatively thick coatings on the order of 125-250 microns, and conventional vapor phase processes such as electron beam physical vapor deposition (EB-PVD) which are limited by relatively slow deposition rates, high investment costs, and coating material vapor pressure requirements. The use of Plasma Spray - Physical Vapor Deposition (PS-PVD) processing fills this gap and allows thin (< 10 microns) single layers to be deposited and multilayer coatings of less than 100 microns to be generated with the flexibility to tailor microstructures by changing processing conditions. Coatings of yttria-stabilized zirconia (YSZ) were applied to NiCrAlY bond coated superalloy substrates using the PS-PVD coater at NASA Glenn Research Center. A design-of-experiments was used to examine the effects of process variables (Ar/He plasma gas ratio, the total plasma gas flow, and the torch current) on chamber pressure and torch power. Coating thickness, phase and microstructure were evaluated for each set of deposition conditions. Low chamber pressures and high power were shown to increase coating thickness and create columnar-like structures. Likewise, high chamber pressures and low power had lower growth rates, but resulted in flatter, more homogeneous layers

The role of nano-particles in the field of thermal spray coating technology

NASA Astrophysics Data System (ADS)

Siegmann, Stephan; Leparoux, Marc; Rohr, Lukas

2005-06-01

Nano-particles play not only a key role in recent research fields, but also in the public discussions about health and safety in nanotechnology. Nevertheless, the worldwide activities in nano-particles research increased dramatically during the last 5 to 10 years. There are different potential routes for the future production of nano-particles at large scale. The main directions envisaged are mechanical milling, wet chemical reactions or gas phase processes. Each of the processes has its specific advantages and limitations. Mechanical milling and wet chemical reactions are typically time intensive and batch processes, whereas gas phase productions by flames or plasma can be carried out continuously. Materials of interest are mainly oxide ceramics, carbides, nitrides, and pure metals. Nano-ceramics are interesting candidates for coating technologies due to expected higher coating toughness, better thermal shock and wear resistance. Especially embedded nano-carbides and-nitrides offer homogenously distributed hard phases, which enhance coatings hardness. Thermal spraying, a nearly 100 years old and world wide established coating technology, gets new possibilities thanks to optimized, nano-sized and/or nano-structured powders. Latest coating system developments like high velocity flame spraying (HVOF), cold gas deposition or liquid suspension spraying in combination with new powder qualities may open new applications and markets. This article gives an overview on the latest activities in nano-particle research and production in special relation to thermal spray coating technology.

Titanium Dioxide Coating Prepared by Use of a Suspension-Solution Plasma-Spray Process

NASA Astrophysics Data System (ADS)

Du, Lingzhong; Coyle, Thomas W.; Chien, Ken; Pershin, Larry; Li, Tiegang; Golozar, Mehdi

2015-08-01

Titanium dioxide coatings were prepared from titanium isopropoxide solution containing nano TiO2 particles by use of a plasma-spray process. The effects of stand-off distance on coating composition and microstructure were investigated and compared with those for pure solution precursor and a water-based suspension of TiO2. The results showed that the anatase content of the coating increased with increasing stand-off distance and the rate of deposition decreased with increasing spray distance. Anatase nanoparticles in solution were incorporated into the coatings without phase transformation whereas most of the TiO2 in the precursor solution was transformed into rutile. The microstructure of preserved anatase particles bound by rutile improved the efficiency of deposition of the coating. The amount of anatase phase can be adjusted by variation of the ratio of solution to added anatase TiO2 nanoparticles.

Microstructure and wear resistance of laser cladded Ni-Cr-Co-Ti-V high-entropy alloy coating after laser remelting processing

NASA Astrophysics Data System (ADS)

Cai, Zhaobing; Cui, Xiufang; Liu, Zhe; Li, Yang; Dong, Meiling; Jin, Guo

2018-02-01

An attempt, combined with the technologies of laser cladding and laser remelting, has been made to develop a Ni-Cr-Co-Ti-V high entropy alloy coating. The phase composition, microstructure, micro-hardness and wear resistance (rolling friction) were studied in detail. The results show that after laser remelting, the phase composition remains unchanged, that is, as-cladded coating and as-remelted coatings are all composed of (Ni, Co)Ti2 intermetallic compound, Ti-rich phase and BCC solid solution phase. However, after laser remelting, the volume fraction of Ti-rich phase increases significantly. Moreover, the micro-hardness is increased, up to ∼900 HV at the laser remelting parameters: laser power of 1 kW, laser spot diameter of 3 mm, and laser speed of 10 mm/s. Compared to the as-cladded high-entropy alloy coating, the as-remelted high-entropy alloy coatings have high friction coefficient and low wear mass loss, indicating that the wear resistance of as-remelted coatings is improved and suggesting practical applications, like coatings on brake pads for wear protection. The worn surface morphologies show that the worn mechanism of as-cladded and as-remelted high-entropy alloy coatings are adhesive wear.

The Interface Structure of High-Temperature Oxidation-Resistant Aluminum-Based Coatings on Titanium Billet Surface

NASA Astrophysics Data System (ADS)

Xu, Zhefeng; Rong, Ju; Yu, Xiaohua; Kun, Meng; Zhan, Zhaolin; Wang, Xiao; Zhang, Yannan

2017-10-01

A new type of high-temperature oxidation-resistant aluminum-based coating, on a titanium billet surface, was fabricated by the cold spray method, at a high temperature of 1050°C, for 8 h, under atmospheric pressure. The microstructure of the exposed surface was analyzed via optical microscopy, the microstructure of the coating and elemental diffusion was analyzed via field emission scanning electron microscopy, and the interfacial phases were identified via x-ray diffraction. The Ti-Al binary phase diagram and Gibbs free energy of the stable phase were calculated by Thermo-calc. The results revealed that good oxidation resistant 50-μm-thick coatings were successfully obtained after 8 h at 1050°C. Two layers were obtained after the coating process: an Al2O3 oxidation layer and a TiAl3 transition layer on the Ti-based substrate. The large and brittle Al2O3 grains on the surface, which can be easily spalled off from the surface after thermal processing, protected the substrate against oxidation during processing. In addition, the thermodynamic calculation results were in good agreement with the experimental data.

Microstructures and Properties of Plasma Sprayed Ni Based Coatings Reinforced by TiN/C1-xNxTi Generated from In-Situ Solid-Gas Reaction.

PubMed

Wang, Wenquan; Li, Wenmo; Xu, Hongyong

2017-07-11

The strengthening hard phases TiN/C 1- x N x Ti were generated by in-situ solid-gas reaction in Ni-based composite coatings prepared using a plasma spray welding process to reinforce the wear resistance of the coatings. The microstructures and properties of the coatings were investigated. The results showed that the coatings mainly consisted of phases such as TiN, C 1- x N x Ti, TiC, etc. A small amount of CrB, M₇C₃, and M 23 C₆ were also detected in the coatings by micro-analysis method. Compared with the originally pure NiCrBSi coatings, the hardness of the NiCrBSi coatings reinforced by in-situ solid-gas reaction was 900 HV 0.5 , increased by more than 35%. Consequently, the wear resistance of the reinforced coatings was greatly improved due to the finely and uniformly dispersed hard phases mentioned above. The weight losses after wear test for the two kinds of coatings were 15 mg and 8 mg, respectively.

Preparation and characterisation of titania/hydroxyapatite composite coatings obtained by sol-gel process.

PubMed

Milella, E; Cosentino, F; Licciulli, A; Massaro, C

2001-06-01

In the present work a titania network encapsulating a hydroxyapatite particulate phase is proposed as a bioceramic composite coating. The coating on a titanium substrate was produced starting from a sol containing a mixture of titania colloidal particles and hydroxyapatite submicron particles using the dip-coating technique. The microstructure, the morphology and the surface chemical composition of the coating were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. Adhesion tests were also performed. These analyses showed that the obtained coating was chemically clean, homogeneous, rough, porous, with a low thickness and well-defined phase composition as well as a good adhesion to the substrate.

Effect of laser power on the microstructure and mechanical properties of TiN/Ti3Al composite coatings on Ti6Al4V

NASA Astrophysics Data System (ADS)

Liu, Zhengdao; Zhang, Xiancheng; Xuan, Fuzhen; Wang, Zhengdong; Tu, Shandong

2013-07-01

Laser nitriding is one of the effective techniques to improve the surface properties of titanium alloys and has potential application in the life extension of last-stage steam turbine blades. However, cracking of surface coating is a common problem due to heat concentration in laser nitriding process. Conventionally, the cracks can be avoided through heat treatment, which may have an important influence on the mechanical properties of coating. Crack-free TiN/Ti3Al IMC coatings on Ti6Al4V are prepared by plasma spraying and laser nitriding. The microstructures, phase constitutes and compositions of the coating are observed and analyzed with scanning electron microscopy(SEM), X-ray diffraction(XRD) and X-ray energy-dispersive spectroscopy(EDS). Microhardness, elastic modulus, fracture toughness of the coating are measured. The results show that the crack- and pore-free IMC coatings can be made through the proposed method; with increasing laser power, the amount and density of TiN phase in the coating first increased and then decreased, leading to the similar trend of microhardness and elastic modulus and the reverse trend of fracture toughness of the coating. Both the average microhardness and elastic modulus of the coating increase three times higher than those of the substrate. The volume fraction of the TiN reinforced phase in composite can be controlled by varying the laser power and the cracking problem in laser nitriding process is successfully solved.

Numerical and experimental study of electron-beam coatings with modifying particles FeB and FeTi

NASA Astrophysics Data System (ADS)

Kryukova, Olga; Kolesnikova, Kseniya; Gal'chenko, Nina

2016-07-01

An experimental study of wear-resistant composite coatings based on titanium borides synthesized in the process of electron-beam welding of components thermo-reacting powders are composed of boron-containing mixture. A model of the process of electron beam coating with modifying particles of boron and titanium based on physical-chemical transformations is supposed. The dissolution process is described on the basis of formal kinetic approach. The result of numerical solution is the phase and chemical composition of the coating under nonequilibrium conditions, which is one of the important characteristics of the coating forming during electron beam processing. Qualitative agreement numerical calculations with experimental data was shown.

Microstructure and high temperature oxidation resistance of Ti-Ni gradient coating on TA2 titanium alloy fabricated by laser cladding

NASA Astrophysics Data System (ADS)

Liu, Fencheng; Mao, Yuqing; Lin, Xin; Zhou, Baosheng; Qian, Tao

2016-09-01

To improve the high temperature oxidation resistance of TA2 titanium alloy, a gradient Ni-Ti coating was laser cladded on the surface of the TA2 titanium alloy substrate, and the microstructure and oxidation behavior of the laser cladded coating were investigated experimentally. The gradient coating with a thickness of about 420-490 μm contains two different layers, e.g. a bright layer with coarse equiaxed grain and a dark layer with fine and columnar dendrites, and a transition layer with a thickness of about 10 μm exists between the substrate and the cladded coating. NiTi, NiTi2 and Ni3Ti intermetallic compounds are the main constructive phases of the laser cladded coating. The appearance of these phases enhances the microhardness, and the dense structure of the coating improves its oxidation resistance. The solidification procedure of the gradient coating is analyzed and different kinds of solidification processes occur due to the heat dissipation during the laser cladding process.

Investigation of the Phase Formation of AlSi-Coatings for Hot Stamping of Boron Alloyed Steel

NASA Astrophysics Data System (ADS)

Veit, R.; Hofmann, H.; Kolleck, R.; Sikora, S.

2011-01-01

Hot stamping of boron alloyed steel is gaining more and more importance for the production of high strength automotive body parts. Within hot stamping of quenchenable steels the blank is heated up to austenitization temperature, transferred to the tool, formed rapidly and quenched in the cooled tool. To avoid scale formation during the heating process of the blank, the sheet metal can be coated with an aluminium-silicum alloy. The meltimg temperature of this coating is below the austenitization temperature of the base material. This means, that a diffusion process between base material and coating has to take place during heating, leading to a higher melting temperature of the coating. In conventional heating devices, like roller hearth furnaces, the diffusion process is reached by relatively low heating rates. New technologies, like induction heating, reach very high heating rates and offer great potentials for the application in hot stamping. Till now it is not proofed, that this technology can be used with aluminum-silicon coated materials. This paper will present the results of comparative heating tests with a conventional furnace and an induction heating device. For different time/temperature-conditions the phase formation within the coating will be described.

Effect of KOH to Na2SiO3 Ratio on Microstructure and Hardness of Plasma Electrolytic Oxidation Coatings on AA 6061 Alloy

NASA Astrophysics Data System (ADS)

Sharma, Ashutosh; Jang, Yong-Joo; Jung, Jae Pil

2017-10-01

In this study, plasma electrolytic oxidation (PEO) process has been employed to fabricate alumina coatings on AA 6061 aluminum alloy from an electrolyte containing water glass (Na2SiO3) and alkali (KOH). The effect of deposition time and the alkali to water glass (KOH: Na2SiO3) composition ratio on the coating morphology and properties are studied. The different phases of the oxide layer and microstructure are investigated by x-ray diffraction, scanning electron microscopy, and atomic force microscopy. The results indicate that initially γ-Al2O3 forms in the coating, and as the processing time is increased from 5 to 60 minutes, α-Al2O3 phase becomes prominent. Further, higher the content of Na2SiO3, higher is the hardness and coating growth rate due to the formation of stable α-Al2O3 and Al-Si-O phase. It has been reported that the optimum properties of the PEO coatings can be obtained at a ratio of KOH: Na2SiO3 ≈ 15:10 followed by 10:10.

Structure of Biocompatible Coatings Produced from Hydroxyapatite Nanoparticles by Detonation Spraying

NASA Astrophysics Data System (ADS)

Nosenko, Valentyna; Strutynska, Nataliia; Vorona, Igor; Zatovsky, Igor; Dzhagan, Volodymyr; Lemishko, Sergiy; Epple, Matthias; Prymak, Oleg; Baran, Nikolai; Ishchenko, Stanislav; Slobodyanik, Nikolai; Prylutskyy, Yuriy; Klyui, Nickolai; Temchenko, Volodymyr

2015-12-01

Detonation-produced hydroxyapatite coatings were studied by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Raman spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy. The source material for detonation spraying was a B-type carbonated hydroxyapatite powder. The coatings consisted of tetracalcium phosphate and apatite. The ratio depended slightly on the degree of crystallinity of the initial powder and processing parameters of the coating preparation. The tetracalcium phosphate phase was homogeneous; the apatite phase contained defects localized on the sixfold axis and consisted of hydroxyapatite and oxyapatite. Technological factors contributing to the transformation of hydroxyapatite powder structure during coating formation by detonation spraying are discussed.

Structure of Biocompatible Coatings Produced from Hydroxyapatite Nanoparticles by Detonation Spraying.

PubMed

Nosenko, Valentyna; Strutynska, Nataliia; Vorona, Igor; Zatovsky, Igor; Dzhagan, Volodymyr; Lemishko, Sergiy; Epple, Matthias; Prymak, Oleg; Baran, Nikolai; Ishchenko, Stanislav; Slobodyanik, Nikolai; Prylutskyy, Yuriy; Klyui, Nickolai; Temchenko, Volodymyr

2015-12-01

Detonation-produced hydroxyapatite coatings were studied by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Raman spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy. The source material for detonation spraying was a B-type carbonated hydroxyapatite powder. The coatings consisted of tetracalcium phosphate and apatite. The ratio depended slightly on the degree of crystallinity of the initial powder and processing parameters of the coating preparation. The tetracalcium phosphate phase was homogeneous; the apatite phase contained defects localized on the sixfold axis and consisted of hydroxyapatite and oxyapatite. Technological factors contributing to the transformation of hydroxyapatite powder structure during coating formation by detonation spraying are discussed.

Alternative Solvents/Technologies for Paint Stripping: Phase 1.

DTIC Science & Technology

1994-03-01

processes . Three phases of study are defined: Phase I, identify alternate solvents/strippers and screen them; Phase II, field test solvent/ strippers...Section Title Page 1 Metal Refinishing Process - Immersion Method ............... 8 2 Phase Summary Chart ........................ 12 3 The...of the following: (a) nontoxic chemical formulations, (b) new process development, and (c) new coating reformulations. This program consists of three

Ion-plasma protective coatings for gas-turbine engine blades

NASA Astrophysics Data System (ADS)

Kablov, E. N.; Muboyadzhyan, S. A.; Budinovskii, S. A.; Lutsenko, A. N.

2007-10-01

Evaporated, diffusion, and evaporation—diffusion protective and hardening multicomponent ionplasma coatings for turbine and compressor blades and other gas-turbine engine parts are considered. The processes of ion surface treatment (ion etching and ion saturation of a surface in the metallic plasma of a vacuum arc) and commercial equipment for the deposition of coatings and ion surface treatment are analyzed. The specific features of the ion-plasma coatings deposited from the metallic plasma of a vacuum arc are described, and the effect of the ion energy on the phase composition of the coatings and the processes occurring in the surface layer of an article to be treated are discussed. Some properties of ion-plasma coatings designed for various purposes are presented. The ion surface saturation of articles made from structural materials is shown to change the structural and phase states of their surfaces and, correspondingly, the related properties of these materials (i.e., their heat resistance, corrosion resistance, fatigue strength, and so on).

Development of form stable Poly(methyl methacrylate) (PMMA) coated thermal phase change material for solar water heater applications

NASA Astrophysics Data System (ADS)

Munusamy, Y.; Shanmugam, S.; Shi-Ying, Kee

2018-04-01

Phase change material (PCM) is one of the most popular and widely used thermal energy storage material in solar water heater because it able to absorb and release a large amount of latent heat during a phase change process over a narrow temperature range. However the practical application of PCM is limited by two major issues; 1) leakage which leads to material loss and corrosion of tank and 2) large volume change during phase change process which cause pressure build up in the tank. In this work, form-stable PCM was prepared by coating myristic acid with Poly(methyl methacrylate) (PMMA) to prevent leakage of PCM. PMMA was mixed with different weight percentage (0.1, 0.2, 0.3, 0.4 and 0.5 wt%) of dicumyl peroxide (DCP). The purpose of adding DCP to PMMA is to crosslink the polymer and to increase the mechanical strength of PMMA to hold the myristic acid content inside the coating during the phase change process. Leakage test results showed that PMMA mixed with 0.1% DCP exhibit 0% leakage. This result is further supported by Field Emission Scanning Electron Microscopy (FESEM) images and Fourier transform infrared spectroscopy (FTIR) analysis results, where a compact and uniform coating without cracks were formed for PCM coated with PMMA with 0.1% DCP. Differential scanning calorimetry (DSC) results shows that the melting point of form-stable PCM is 55°C, freezing point is 50°C, the latent heat of melting and freezing is 67.59 J/g.

Formation of structure, phase composition and properties of electro explosion resistant coatings using electron-beam processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romanov, Denis A., E-mail: romanov-da@physics.sibsiu.ru, E-mail: kos2906@mail.ru, E-mail: budovskih-ea@physics.sibsiu.ru, E-mail: gromov@physics.sibsiu.ru, E-mail: da-rom@live.ru; Sosnin, Kirill V., E-mail: romanov-da@physics.sibsiu.ru, E-mail: kos2906@mail.ru, E-mail: budovskih-ea@physics.sibsiu.ru, E-mail: gromov@physics.sibsiu.ru, E-mail: da-rom@live.ru; Budovskikh, Evgenij A., E-mail: romanov-da@physics.sibsiu.ru, E-mail: kos2906@mail.ru, E-mail: budovskih-ea@physics.sibsiu.ru, E-mail: gromov@physics.sibsiu.ru, E-mail: da-rom@live.ru

2014-11-14

For the first time, the high intensity electron beam modification of electroexplosion composite coatings of MoCu, MoCCu, WCu, WCCu and TiB{sub 2}Cu systems was done. The studies of phase and elemental composition, defective structure conditions of these coatings were carried out. The regimes of electron-beam processing making possible to form the dense, specular luster surface layers having a submicrocrystalline structure were revealed. It was established that electron-beam processing of elecroexplosion spraying of layer of elecroexplosion spraying carried out in the regime of melting results in the formation of structurally and contrationally homogeneous surface layer. Investigation of the effect of electron-beammore » processing of electroexplosion electroerosion resistant coatings on their tribological properties (wear resistanse and coefficient of friction) and electroerosion resistance was done. It was shown that all the examined costings demonstrate the increase of electroerosion resistance in spark erosion up to 10 times.« less

Formation mechanism of a silicon carbide coating for a reinforced carbon-carbon composite

NASA Technical Reports Server (NTRS)

Rogers, D. C.; Shuford, D. M.; Mueller, J. I.

1975-01-01

Results are presented for a study to determine the mechanisms involved in a high-temperature pack cementation process which provides a silicon carbide coating on a carbon-carbon composite. The process and materials used are physically and chemically analyzed. Possible reactions are evaluated using the results of these analytical data. The coating is believed to develop in two stages. The first is a liquid controlled phase process in which silicon carbide is formed due to reactions between molten silicon metal and the carbon. The second stage is a vapor transport controlled reaction in which silicon vapors react with the carbon. There is very little volume change associated with the coating process. The original thickness changes by less than 0.7%. This indicates that the coating process is one of reactive penetration. The coating thickness can be increased or decreased by varying the furnace cycle process time and/or temperature to provide a wide range of coating thicknesses.

Effects of annealing heat treatment on the corrosion resistance of Zn/Mg/Zn multilayer coatings

NASA Astrophysics Data System (ADS)

Bae, KiTae; La, JoungHyun; Lee, InGyu; Lee, SangYul; Nam, KyungHoon

2017-05-01

Zn coatings alloyed with magnesium offer superior corrosion resistance compared to pure Zn or other Zn-based alloy coatings. In this study, Zn/Mg/Zn multilayer coatings with various Mg layer thicknesses were synthesized using an unbalanced magnetron sputtering process and were annealed to form Zn-Mg intermetallic phases. The effects of the annealing heat treatment on the corrosion resistance of the Zn/Mg/Zn multilayer coatings were evaluated using electrochemical measurements. The extensive diffusion of magnesium species into the upper and lower zinc layer from the magnesium layer in the middle of the coating was observed after the heat treatment. This phenomenon caused (a) the porous microstructure to transition into a dense structure and (b) the formation of a MgZn2 intermetallic phase. The results of the electrochemical measurements demonstrated that the heat treated Zn/Mg/Zn multilayer coatings possessed higher levels of corrosion resistance than the non-heat treated coatings. A Zn/Mg/Zn multilayer coating with MgZn2 and (Zn) phases showed the best corrosion resistance among the heat treated coatings, which could be attributed to the reduced galvanic corrosion effects due to a small potential gradient between the MgZn2 and zinc.

In-situ grown MgO-ZnO ceramic coating with high thermal emittance on Mg alloy by plasma electrolytic oxidation

NASA Astrophysics Data System (ADS)

Li, Hang; Lu, Songtao; Qin, Wei; Wu, Xiaohong

2017-07-01

Intense solar radiation and internal heat generation determine the equilibrium temperature of an in-orbit spacecraft. Thermal control coatings with low solar absorptance and high thermal emittance effectively maintain the thermal equilibrium within safe operating limits for exposed, miniaturized and highly integrated components. A novel ceramic coating with high thermal emittance and good adhesion was directly prepared on the Mg substrate using an economical process of controlled plasma electrolytic oxidation (PEO) in the electrolyte containing ZnSO4. XRD and XPS results showed that this coating was mainly composed of the MgO phase as well as an unusual ZnO crystalline phase. The adhesive strength between the coating and substrate determined by a pull-off test revealed an excellent adhesion. Thermal and optical properties test revealed that the coating exhibited a high infrared emittance of 0.88 (2-16 μm) and low solar absorptance of 0.35 (200-2500 nm). The result indicated that the formation of ZnO during the PEO process played an important role in the improvement of the coating emittance. The process developed provides a simple surface method for improving the thermal emittance of Mg alloy, which presents a promising application prospect in the thermal management of the spacecraft.

High temperature barrier coatings for refractory metals

NASA Technical Reports Server (NTRS)

Malone, G. A.; Walech, T.

1995-01-01

Improvements in high temperature oxidation resistant metal coating technology will allow NASA and commercial entities to develop competitive civil space transport and communication systems. The success of investigations completed in this program will have a positive impact on broadening the technology base for high temperature materials. The work reported herein describes processes and procedures for successfully depositing coherent oxidation barrier coatings on refractory metals to prevent degradation under very severe operating environments. Application of the new technology developed is now being utilized in numerous Phase 3 applications through several prominent aerospace firms. Major achievements have included: (1) development of means to deposit thick platinum and rhodium coatings with lower stress and fewer microcracks than could be previously achieved; (2) development of processes to deposit thick adherent coatings of platinum group metals on refractory substrates that remain bonded through high temperature excursions and without need for intermediate coatings (bonding processes unique to specific refractory metals and alloys have been defined; (3) demonstration that useful alloys of refractory and platinum coatings can be made through thermal diffusion means; (4) demonstration that selected barrier coatings on refractory substrates can withstand severe oxidizing environments in the range of 1260 deg and 1760 deg C for long time periods essential to the life requirements of the hardware; and (5) successful application of the processes and procedures to prototype hardware. The results of these studies have been instrumental in improved thermal oxidation barrier coatings for the NASP propulsion system. Other Phase 3 applications currently being exploited include small uncooled thrusters for spacecraft and microsatellite maneuvering systems.

Infiltration processing of metal matrix composites using coated ceramic particulates

NASA Astrophysics Data System (ADS)

Leon-Patino, Carlos Alberto

2001-07-01

A new process was developed to fabricate particulate metal matrix composites (MMCs). The process involves three steps: (1) modifying the particulate surface by metal coating, (2) forming a particulate porous compact; and (3) introducing metal into the channel network by vacuum infiltration. MMCs with different reinforcements, volume fractions, and sizes can be produced by this technique. Powders of alumina and silicon carbide were successfully coated with nickel and copper in preparation for infiltration with molten aluminum. Electroless Ni and Cu deposition was used since it enhances the wettability of the reinforcements for composite fabrication. While Cu deposits were polycrystalline, traces of phosphorous co-deposited from the electroless bath gave an amorphous Ni-P coating. The effect of metal coating on wetting behavior was evaluated at 800°C on plain and metal-coated ceramic plates using a sessile drop technique. The metallic films eliminated the non-wetting behavior of the uncoated ceramics, leading to equilibrium contact angles in the order of 12° and below 58° for Ni and Cu coated ceramics, respectively. The spreading data indicated that local diffusion at the triple junction was the governing mechanism of the wetting process. Precipitation of intermetallic phases in the drop/ceramic interface delayed the formation of Al4C3. Infiltration with molten Al showed that the coated-particulates are suitable as reinforcing materials for fabricating MMCs, giving porosity-free components with a homogeneously distributed reinforcing phase. The coating promoted easy metal flow through the preform, compared to the non-infiltration behavior of the uncoated counterparts. Liquid state diffusion kinetics due to temperature dependent viscosity forces controlled the infiltration process. Microstructural analysis indicated the formation of intermetallic phases such as CuAl 2, in the case of Cu coating, and Ni2Al3 and NiAl 3 when Ni-coated powders were infiltrated. The overall Ni and Cu content increased from bottom to top of the samples due to dissolution of the metal film by the stream of liquid Al during infiltration. The strengths of the Al/Ni-SiC composites, measured by four-point bending, were 205 and 225 MPa for samples reinforced with 78 mum and 49 mum Ni-SiC, respectively. The mode of fracture was mainly controlled by SiC particle fracture.

Tribological Properties of HVOF-Sprayed TiB2-NiCr Coatings with Agglomerated Feedstocks

NASA Astrophysics Data System (ADS)

Zhao, Zichun; Li, Hui; Yang, Tianlong; Zhu, Hongbin

2018-04-01

Boride materials have drawn great attention in surface engineering field, owing to their high hardness and good wear resistance. In our previous work, a plasma-sprayed TiB2-based cermet coating was deposited, but the coating toughness was significantly influenced by the formation of a brittle ternary phase (Ni20Ti3B6) derived from the reaction between TiB2 and metal binder. In order to suppress such a reaction occurred in the high-temperature spraying process, the high-velocity oxygen-fuel spraying technique was applied to prepare the TiB2-NiCr coating. Emphasis was paid on the microstructure, the mechanical properties, and the sliding wearing performance of the coating. The result showed that the HVOF-sprayed coating mainly consisted of hard ceramic particles including TiB2, CrB, and the binder phase. No evidence of Ni20Ti3B6 phase was found in the coating. The mechanical properties of HVOF-sprayed TiB2-NiCr coating were comparable to the conventional Cr3C2-NiCr coating. The frictional coefficient of the TiB2-NiCr coating was lower than the Cr3C2-NiCr coating when sliding against a bearing steel ball.

Synthesis and Microstructure Evolution of Nano-Titania Doped Silicon Coatings

NASA Astrophysics Data System (ADS)

Moroz, N. A.; Umapathy, H.; Mohanty, P.

2010-01-01

The Anatase phase of Titania (TiO2) in nanocrystalline form is a well known photocatalyst. Photocatalysts are commercially used to accelerate photoreactions and increase photovoltaic efficiency such as in solar cells. This study investigates the in-flight synthesis of Titania and its doping into a Silicon matrix resulting in a catalyst-dispersed coating. A liquid precursor of Titanium Isopropoxide and ethanol was coaxially fed into the plasma gun to form Titania nanoparticles, while Silicon powder was externally injected downstream. Coatings of 75-150 μm thick were deposited onto flat coupons. Further, Silicon powder was alloyed with aluminum to promote crystallization and reduce the amorphous phase in the Silicon matrix. Dense coatings containing nano-Titania particles were observed under electron microscope. X-ray diffraction showed that both the Rutile and Anatase phases of the Titania exist. The influence of process parameters and aluminum alloying on the microstructure evolution of the doped coatings is analyzed and presented.

NASA TEERM Hexavalent Chrome Alternatives Projects

NASA Technical Reports Server (NTRS)

Rothgeb, Matt

2009-01-01

This slide presentation reviews the NASA/DOD projects to select an alternative to hexavalent chrome in the aerospace industry. The Phase I process of the project performed: (1) Evaluation and testing of non-chromated coating systems as replacements for hexavalent chrome coatings in aircraft and aerospace applications. (2) Testing of coating systems to DoD and NASA specifications for corrosion resistance and adhesion. (3) Bare corrosion resistance and atmospheric exposure will be focus areas of Phase II Testing. The description includes a chart that summarizes the 3000 hour salt fog test results. The second phase of the project includes (1) Evaluation and testing of coating systems that do not contain hexavalent chrome as replacements for aerospace applications. (2) Evaluation of coatings at Beach Test Site and Launch Complex 39B (3) Evaluation of non-chrome coatings for electronic housings (bare corrosion resistance and electrical impedance) is a part of this round of testing. This project was performed for the Technology Evaluation for Environmental Risk Mitigation (TEERM)

Formation of Aluminide Coatings on Fe-Based Alloys by Chemical Vapor Deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Ying; Pint, Bruce A; Cooley, Kevin M

2008-01-01

Aluminide and Al-containing coatings were synthesized on commercial ferritic (P91) and austenitic (304L) alloys via a laboratory chemical vapor deposition (CVD) procedure for rigorous control over coating composition, purity and microstructure. The effect of the CVD aluminizing parameters such as temperature, Al activity, and post-aluminizing anneal on coating growth was investigated. Two procedures involving different Al activities were employed with and without including Cr-Al pellets in the CVD reactor to produce coatings with suitable thickness and composition for coating performance evaluation. The phase constitution of the as-synthesized coatings was assessed with the aid of a combination of X-ray diffraction, electronmore » probe microanalysis, and existing phase diagrams. The mechanisms of formation of these CVD coatings on the Fe-based alloys are discussed, and compared with nickel aluminide coatings on Ni-base superalloys. In addition, Cr-Al pellets were replaced with Fe-Al metals in some aluminizing process runs and similar coatings were achieved.« less

Tribological and Corrosion Properties of Coatings Produced by Plasma Electrolytic Oxidation on the ZA27 Alloy

NASA Astrophysics Data System (ADS)

Li, Guangyin; Mao, Yifan; Li, Zhijian; Wang, Linlin; DaCosta, Herbert

2018-05-01

In this paper, a continuous and dense coating was deposited on samples of the ZA27 alloy through the plasma electrolytic oxidation (PEO) process to improve its wear and corrosion performance. A nontoxic and environmentally friendly inorganic salt, Na2SiO3, is chosen as electrolytes with different concentrations. The effect of the concentration of Na2SiO3 aqueous solutions on the coating performances was investigated. The coatings with 3Al2O3·2SiO2 (mullite), Zn2SiO4 and Al2O3 (either crystal phase or with some amorphous SiO2 phases) were formed by the PEO processes. It was found that the coating thickness increased with the increase in electrolyte concentration. However, the wear and corrosion resistance performance of the coatings did not improve as the coating's thickness increased. This was due to the fact that the coating produced with electrolytes of 10 g/L has a porous structure with large pore size. Among all the samples, coating produced by 15 g/L Na2SiO3 has the best wear and corrosion resistance, which is attributed to its continuous and dense structure with thickness of about 47 μm.

Tribological and Corrosion Properties of Coatings Produced by Plasma Electrolytic Oxidation on the ZA27 Alloy

NASA Astrophysics Data System (ADS)

Li, Guangyin; Mao, Yifan; Li, Zhijian; Wang, Linlin; DaCosta, Herbert

2018-04-01

In this paper, a continuous and dense coating was deposited on samples of the ZA27 alloy through the plasma electrolytic oxidation (PEO) process to improve its wear and corrosion performance. A nontoxic and environmentally friendly inorganic salt, Na2SiO3, is chosen as electrolytes with different concentrations. The effect of the concentration of Na2SiO3 aqueous solutions on the coating performances was investigated. The coatings with 3Al2O3·2SiO2 (mullite), Zn2SiO4 and Al2O3 (either crystal phase or with some amorphous SiO2 phases) were formed by the PEO processes. It was found that the coating thickness increased with the increase in electrolyte concentration. However, the wear and corrosion resistance performance of the coatings did not improve as the coating's thickness increased. This was due to the fact that the coating produced with electrolytes of 10 g/L has a porous structure with large pore size. Among all the samples, coating produced by 15 g/L Na2SiO3 has the best wear and corrosion resistance, which is attributed to its continuous and dense structure with thickness of about 47 μm.

Toughening Fe-based Amorphous Coatings by Reinforcement of Amorphous Carbon.

PubMed

Wang, Wei; Zhang, Cheng; Zhang, Zhi-Wei; Li, Yi-Cheng; Yasir, Muhammad; Wang, Hai-Tao; Liu, Lin

2017-06-22

Toughening of Fe-based amorphous coatings meanwhile maintaining a good corrosion resistance remains challenging. This work reports a novel approach to improve the toughness of a FeCrMoCBY amorphous coating through in-situ formation of amorphous carbon reinforcement without reducing the corrosion resistance. The Fe-based composite coating was prepared by high velocity oxy-fuel (HVOF) thermal spraying using a pre-mixed Fe-based amorphous/nylon-11 polymer feedstock powders. The nylon-11 powders were in-situ carbonized to amorphous carbon phase during thermal spraying process, which homogeneously distributed in the amorphous matrix leading to significant enhancement of toughness of the coating. The mechanical properties, including hardness, impact resistance, bending and fatigue strength, were extensively studied by using a series of mechanical testing techniques. The results revealed that the composite coating reinforced by amorphous carbon phase exhibited enhanced impact resistance and nearly twice-higher fatigue strength than that of the monolithic amorphous coating. The enhancement of impact toughness and fatigue properties is owed to the dumping effect of the soft amorphous carbon phase, which alleviated stress concentration and decreased crack propagation driving force.

Gas-Phase Synthesis of Gold- and Silica-Coated Nanoparticles

NASA Astrophysics Data System (ADS)

Boies, Adam Meyer

2011-12-01

Composite nanoparticles consisting of separate core-shell materials are of interest for a variety of biomedical and industrial applications. By combining different materials at the nanoscale, particles can exhibit enhanced or multi-functional behavior such as plasmon resonance combined with superparamagnetism. Gas-phase nanoparticle synthesis processes are promising because they can continuously produce particles with high mass-yield rates. In this dissertation, new methods are investigated for producing gas-phase coatings of nanoparticles in an "assembly-line" fashion. Separate processes are developed to create coatings from silica and gold that can be used with a variety of core-particle chemistries. A photoinduced chemical vapor deposition (photo-CVD) method is used to produce silica coatings from tetraethyl orthosilicate (TEOS) on the surface of nanoparticles (diameter ˜5--70 nm). Tandem differential mobility analysis (TDMA) of the process demonstrates that particle coatings can be produced with controllable thicknesses (˜1--10 nm) by varying system parameters such as precursor flow rate. Electron microscopy and infrared spectroscopy confirm that the photo-CVD films uniformly coat the particles and that the coatings are silica. In order to describe the coating process a chemical mechanism is proposed that includes gas-phase, surface and photochemical reactions. A chemical kinetics model of the mechanism indicates that photo-CVD coating proceeds primarily through the photodecomposition of TEOS which removes ethyl groups, thus creating activated TEOS species. The activated TEOS then adsorbs onto the surface of the particle where a series of subsequent reactions remove the remaining ethyl groups to produce a silica film with an open site for further attachment. The model results show good agreement with the experimentally measured coating trends, where increased TEOS flow increases coating thickness and increased nitrogen flow decreases coating thickness. Gold decoration of nanoparticles is accomplished by evaporation of solid gold in the presence of an aerosol flow. A hot-wire generation method is developed where gold particles are produced from a composite gold-platinum wire. Investigations of the hot-wire generator show that it can produce particles with a range of sizes and that more uniform, non-agglomerated particles are produced when using smaller diameter tubes where gas velocities across the wire are higher and recirculation zones are diminished. When gold is evaporated in the presence of silica nanoparticles, the silica aerosol is decorated by gold through either homogeneous gold nucleation and subsequent scavenging by the silica nanoparticles, or by heterogeneous nucleation on the silica surface in which the gold "balls up" due to the high surface tension of gold on silica. In both cases the resulting particles exhibit a plasmon absorbance resonance typical of gold nanoparticles (lambda˜550 nm). Finally, the silica coating and gold decoration processes are combined with a thermal plasma technique for synthesizing iron-oxide to produce tri-layer nanoparticles.

Effect of microstructure on the zinc phosphate conversion coatings on magnesium alloy AZ91

NASA Astrophysics Data System (ADS)

Van Phuong, Nguyen; Moon, Sungmo; Chang, Doyon; Lee, Kyu Hwan

2013-01-01

The effect of the microstructure, particularly of β-Mg17Al12 phase, on the formation and growth of zinc phosphate conversion coatings on magnesium alloy AZ91 (AZ91) was studied. The zinc phosphate coatings were formed on AZ91 with different microstructures produced by heat treatment. The effect of the microstructure on the zinc phosphate coatings were examined using optical microscope (OM), X-ray diffraction (XRD), coatings weight and etching weight balances, scanning electron microscopy (SEM) and salt immersion test. Results showed that as-cast AZ91 contained a high volume fraction of the β-Mg17Al12 phase and it was dissolved into α-Mg phase during heat treatment at 400 °C. The β-phase became center for hydrogen evolution during phosphating reaction (cathodic sites). The decreased volume fraction of the β-phase caused decreasing both coatings weight and etching weight of the phosphating process. However, it increased the crystal size of the coatings and improved corrosion resistance of AZ91 by immersing in 0.5 M NaCl solution. Results also showed that the structure of the zinc phosphate conversion on AZ91 consisted of two layers: an outer crystal Zn3(PO4)2·4H2O (hopeite) and an inner which was mainly composed of MgZn2(PO4)2 and Mg3(PO4)2. A mechanism for the formation of two layers of the coatings was also proposed in this study.

Self-healing atmospheric plasma sprayed Mn1.0Co1.9Fe0.1O4 protective interconnector coatings for solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Grünwald, Nikolas; Sebold, Doris; Sohn, Yoo Jung; Menzler, Norbert Heribert; Vaßen, Robert

2017-09-01

Dense coatings on metallic interconnectors are necessary to suppress chromium poisoning of SOFC cathodes. Atmospherically plasma sprayed (APS) Mn1.0Co1.9Fe0.1O4 (MCF) protective layers demonstrated reduced chromium related degradation in laboratory and stack tests. Previous analyses revealed strong microstructural changes comparing the coating's as-sprayed and operated condition. This work concentrates on the layer-densification and crack-healing observed by annealing APS-MCF in air, which simulates the cathode operation conditions. The effect is described by a volume expansion induced by a phase transformation. Reducing conditions during the spray process lead to a deposition of the MCF in a metastable rock salt configuration. Annealing in air activates diffusion processes for a phase transformation to the low temperature stable spinel phase (T < 1050 °C). This transformation is connected to an oxygen incorporation which occurs at regions facing high oxygen partial pressures, as there are the sample surface, cracks and pore surfaces. Calculations reveal a volume expansion induced by the oxygen uptake which seals the cracks and densifies the coating. The process decelerates when the cracks are closed, as the gas route is blocked and further oxidation continues over solid state diffusion. The self-healing abilities of metastable APS coatings could be interesting for other applications.

Columnar-Structured Mg-Al-Spinel Thermal Barrier Coatings (TBCs) by Suspension Plasma Spraying (SPS)

NASA Astrophysics Data System (ADS)

Schlegel, N.; Ebert, S.; Mauer, G.; Vaßen, R.

2015-01-01

The suspension plasma spraying (SPS) process has been developed to permit the feeding of sub-micrometer-sized powder into the plasma plume. In contrast to electron beam-physical vapor deposition and plasma spray-physical vapor deposition, SPS enables the cost-efficient deposition of columnar-structured coatings. Due to their strain tolerance, these coatings play an important role in the field of thermal barrier coatings (TBCs). In addition to the cost-efficient process, attention was turned to the TBC material. Nowadays, yttria partially stabilized zirconia (YSZ) is used as standard TBC material. However, its long-term application at temperatures higher than 1200 °C is problematic. At these high temperatures, phase transitions and sintering effects lead to the degradation of the TBC system. To overcome those deficits of YSZ, Mg-Al-spinel was chosen as TBC material. Even though it has a lower melting point (~2135 °C) and a higher thermal conductivity (~2.5 W/m/K) than YSZ, Mg-Al-spinel provides phase stability at high temperatures in contrast to YSZ. The Mg-Al-spinel deposition by SPS resulted in columnar-structured coatings, which have been tested for their thermal cycling lifetime. Furthermore, the influence of substrate cooling during the spraying process on thermal cycling behavior, phase composition, and stoichiometry of the Mg-Al-spinel has been investigated.

Preparation of stir bars for sorptive extraction using sol-gel technology.

PubMed

Liu, Wenmin; Wang, Hanwen; Guan, Yafeng

2004-08-06

A sol-gel coating method for the preparation of extractive phase on bars used in sorptive microextraction is described. The extraction phase of poly(dimethylsiloxane) is partially crosslinked with the sol-gel network, and the most part is physically incorporated in the network. Three aging steps at different temperatures are applied to complete the crosslinking process. Thirty-micrometer-thick coating layer is obtained by one coating process. The improved coating shows good thermal stability up to 300 degrees C. Spiked aqueous samples containing n-alkanes, polycyclic aromatic hydrocarbons and organophosphorus pesticides were analyzed by using the sorptive bars and GC. The results demonstrate that it is suitable for both aploar and polar analytes. The detection limit for chrysene is 7.44 ng/L, 0.74 ng/L for C19 and 0.9 ng/L for phorate. The extraction equilibration can be reached in less than 15 min by supersonic extraction with the bars of 30 microm coating layer.

Comparison of Single-Phase and Two-Phase Composite Thermal Barrier Coatings with Equal Total Rare-Earth Content

NASA Astrophysics Data System (ADS)

Rai, Amarendra K.; Schmitt, Michael P.; Dorfman, Mitchell R.; Zhu, Dongming; Wolfe, Douglas E.

2018-04-01

Rare-earth zirconates have been the focus of advanced thermal barrier coating research for nearly two decades; however, their lack of toughness prevents a wide-scale adoption due to lack of erosion and thermal cyclic durability. There are generally two methods of improving toughness: intrinsic modification of the coating chemistry and extrinsic modification of the coating structure. This study compares the efficacy of these two methods for a similar overall rare-earth content via the air plasma spray process. The extrinsically toughened coatings were comprised of a two-phase composite containing 30 wt.% Gd2Zr2O7 (GZO) combined with 70 wt.% of a tougher t' low-k material (ZrO2-2Y2O3-1Gd2O3-1Yb2O3; mol.%), while a single-phase fluorite with the overall rare-earth content equivalent to the two-phase composite (13 mol.% rare-earth) was utilized to explore intrinsically toughened concept. The coatings were then characterized via x-ray diffraction, energy-dispersive spectroscopy, and scanning electron microscopy, and their performance was evaluated via erosion, thermal conductivity, thermal annealing (500 h), and thermal cycling. It was shown that the extrinsic method provided an improved erosion and thermal conductivity response over the single phase, but at the expense of high-temperature stability and cyclic life.

Nanocoatings for High-Efficiency Industrial and Tooling Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blau, P; Qu, J.; Higdon, C.

This industry-driven project was the result of a successful response by Eaton Corporation to a DOE/ITP Program industry call. It consisted of three phases in which ORNL participated. In addition to Eaton Corporation and ORNL (CRADA), the project team included Ames Laboratory, who developed the underlying concept for aluminum-magnesium-boron based nanocomposite coatings [1], and Greenleaf, a small tooling manufacturer in western Pennsylvania. This report focuses on the portion of this work that was conducted by ORNL in a CRADA with Eaton Corporation. A comprehensive final report for the entire effort, which ended in September 2010, has been prepared by Eatonmore » Corporation. Phase I, “Proof of Concept” ran for one year (September 1, 2006 to September 30, 2007) during which the applicability of AlMgB14 single-phase and nanocomposite coatings on hydraulic material coupons and components as well as on tool inserts was demonstrated.. The coating processes used either plasma laser deposition (PLD) or physical vapor deposition (PVD). During Phase I, ORNL conducted laboratory-scale pin-on-disk and reciprocating pin-on-flat tests of coatings produced by PLD and PVD. Non-coated M2 tool steel was used as a baseline for comparison, and the material for the sliding counterface was Type 52100 bearing steel since it simulated the pump materials. Initial tests were run mainly in a commercial hydraulic fluid named Mobil DTE-24, but some tests were later run in a water-glycol mixture as well. A tribosystem analysis was conducted to define the operating conditions of pump components and to help develop simulative tests in Phase II. Phase II, “Coating Process Scale-up” was intended to use scaled-up process to generate prototype parts. This involved both PLD practices at Ames Lab, and a PVD scale-up study at Eaton using its production capable equipment. There was also a limited scale-up study at Greenleaf for the tooling application. ORNL continued to conduct friction and wear tests on process variants and developed tests to better simulate the applications of interest. ORNL also employed existing lubrication models to better understand hydraulic pump frictional behavior and test results. Phase III, “Functional Testing” focused on finalizing the strategy for commercialization of AlMgB14 coatings for both hydraulic and tooling systems. ORNL continued to provide tribology testing and analysis support for hydraulic pump applications. It included both laboratory-scale coupon testing and the analysis of friction and wear data from full component-level tests performed at Eaton Corp. Laboratory-scale tribology test methods are used to characterize the behavior of nanocomposite coatings prior to running them in full-sized hydraulic pumps. This task also includes developing tribosystems analyses, both to provide a better understanding of the performance of coated surfaces in alternate hydraulic fluids, and to help design useful laboratory protocols. Analysis also includes modeling the lubrication conditions and identifying the physical processes by which wear and friction of the contact interface changes over time. This final report summarizes ORNL’s portion of the nanocomposite coatings development effort and presents both generated data and the analyses that were used in the course of this effort.« less

Sprayable Phase Change Coating Thermal Protection Material

NASA Technical Reports Server (NTRS)

Richardson, Rod W.; Hayes, Paul W.; Kaul, Raj

2005-01-01

NASA has expressed a need for reusable, environmentally friendly, phase change coating that is capable of withstanding the heat loads that have historically required an ablative thermal insulation. The Space Shuttle Program currently relies on ablative materials for thermal protection. The problem with an ablative insulation is that, by design, the material ablates away, in fulfilling its function of cooling the underlying substrate, thus preventing the insulation from being reused from flight to flight. The present generation of environmentally friendly, sprayable, ablative thermal insulation (MCC-l); currently use on the Space Shuttle SRBs, is very close to being a reusable insulation system. In actual flight conditions, as confirmed by the post-flight inspections of the SRBs, very little of the material ablates. Multi-flight thermal insulation use has not been qualified for the Space Shuttle. The gap that would have to be overcome in order to implement a reusable Phase Change Coating (PCC) is not unmanageable. PCC could be applied robotically with a spray process utilizing phase change material as filler to yield material of even higher strength and reliability as compared to MCC-1. The PCC filled coatings have also demonstrated potential as cryogenic thermal coatings. In experimental thermal tests, a thin application of PCC has provided the same thermal protection as a much thicker and heavier application of a traditional ablative thermal insulation. In addition, tests have shown that the structural integrity of the coating has been maintained and phase change performance after several aero-thermal cycles was not affected. Experimental tests have also shown that, unlike traditional ablative thermal insulations, PCC would not require an environmental seal coat, which has historically been required to prevent moisture absorption by the thermal insulation, prevent environmental degradation, and to improve the optical and aerodynamic properties. In order to reduce the launch and processing costs of a reusable space vehicle to an affordable level, refurbishment costs must be substantially reduced. A key component of such a cost effective approach is the use of a reusable, phase change, thermal protection coating.

Deposition of Hydroxyapatite Onto Superelastic Nitinol Using an Ambient Temperature Blast Coating Process

NASA Astrophysics Data System (ADS)

Dunne, Conor F.; Roche, Kevin; Ruddy, Mark; Doherty, Kevin A. J.; Twomey, Barry; O'Donoghue, John; Hodgson, Darel; Stanton, Kenneth T.

2018-06-01

This work investigates the deposition of hydroxyapatite (HA) onto superelastic nickel-titanium (NiTi) using an ambient temperature coating process known as CoBlast. The process utilises a stream of abrasive alumina (Al2O3) and a coating medium (HA) sprayed simultaneously at the surface of the substrate. The use of traditional coatings methods, such as plasma spray, is unsuitable due to the high temperatures of the process. This can result in changes to both the crystallinity of the HA and properties of the thermally sensitive NiTi. HA is a biocompatible, biodegradable and osteoconductive ceramic, which when used as a coating can promote bone growth and prevent the release of nickel from NiTi in vivo. Samples were coated using different blast pressures and abrasive particle sizes and were examined using a variety of techniques. The coated samples had a thin adherent coating, which increased in surface roughness and coating thickness with increasing abrasive particle size. X-ray diffraction analysis revealed that the process gave rise to a stress-induced martensite phase in the NiTi which may enhance mechanical properties. The study indicates that the CoBlast process can be used to deposit thin adherent coatings of HA onto the surface of superelastic NiTi.

Plasma Sprayed Hydroxyapatite Coatings: Influence of Spraying Power on Microstructure

NASA Astrophysics Data System (ADS)

Mohd, S. M.; Abd, M. Z.; Abd, A. N.

2010-03-01

The plasma sprayed hydroxyapatite (HA) coatings are used on metallic implants to enhance the bonding between the implant and bone in human body. The coating process was implemented at different spraying power for each spraying condition. The coatings formed from a rapid solidification of molten and partly molten particles that impact on the surface of substrate at high velocity and high temperature. The study was concentrated on different spraying power that is between 23 to 31 kW. The effect of different power on the coatings microstructure was investigated using scanning electron microscope (SEM) and phase composition was evaluated using X-ray diffraction (XRD) analysis. The coatings surface morphology showed distribution of molten, partially melted particles and some micro-cracks. The produced coatings were found to be porous as observed from the cross-sectional morphology. The coatings XRD results indicated the presence of crystalline phase of HA and each of the patterns was similar to the initial powder. Regardless of different spraying power, all the coatings were having similar XRD patterns.

Facile one-pot transformation using structure-guided combustion waves of micro-nanostructured β-Bi2O3 to α-Bi2O3@C and analysis of electrochemical capacitance

NASA Astrophysics Data System (ADS)

Hwang, Hayoung; Shin, Jung-ho; Lee, Kang Yeol; Choi, Wonjoon

2018-01-01

Precise phase-transformation can facilitate control of the properties of various materials, while an organic coating surrounding inorganic materials can yield useful characteristics. Herein, we demonstrate facile, selective manipulation of micro-nanostructured bismuth oxide (Bi2O3) for phase transformation from microflower-like β-Bi2O3 to micropill-like α-Bi2O3, with carbon-coating layer deposition, using structure-guided combustion waves (SGCWs). Microflower-like β-Bi2O3 are synthesized as core materials and nitrocellulose is coated on their surfaces for the formation of core-shell hybrid structures of Bi2O3 and chemical fuel. The SGCWs, which propagate along the core-material and fuel interfaces, apply high thermal energy (550-600 °C) and deposit incompletely combusted carbonaceous fuel on the microflower-like β-Bi2O3 to enable transformation to α-phase and carbon-coating-layer synthesis. SGCW-induced improvements to the electrochemical characteristics of the developed micropill-like α-Bi2O3@C, compared with the microflower-like β-Bi2O3, are investigated. The enhanced stability from the α-phase Bi2O3 and micropill-like structures during charge-discharge cycling improves the specific capacitance, while the carbon-coating layers facilitate increased electrical conductivity. SGCW-based methods exhibit high potential for selective phase manipulation and synthesis of carbon coatings surrounding micro-nanomaterials. They constitute a low-cost, fast, large-scale process for metal oxides, ceramics, and hybrid materials, implemented through control of the processing parameters by tuning the temperature, chemical fuel, and ambient conditions.

Failure behavior of plasma-sprayed HAp coating on commercially pure titanium substrate in simulated body fluid (SBF) under bending load.

PubMed

Laonapakul, Teerawat; Rakngarm Nimkerdphol, Achariya; Otsuka, Yuichi; Mutoh, Yoshiharu

2012-11-01

Four point bending tests with acoustic emission (AE) monitoring were conducted for evaluating failure behavior of the plasma-sprayed hydroxyapatite (HAp) top coat on commercially pure titanium (cp-Ti) plate with and without mixed HAp/Ti bond coat. Effect of immersion in simulated body fluid (SBF) on failure behavior of the coated specimen was also investigated by immersing the specimen in SBF. The AE patterns obtained from the bending test of the HAp coating specimens after a week immersion in SBF clearly showed the earlier stage of delamination and spallation of the coating layer compared to those without immersion in SBF. It was also found that the bond coating improved failure resistance of the HAp coating specimen compared to that without the bond coat. Four point bend fatigue tests under ambient and SBF environments were also conducted with AE monitoring during the entire fatigue test for investigating the influence of SBF environment on fatigue failure behavior of the HAp coating specimen with the mixed HAp/Ti bond coat. The specimens tested at a stress amplitude of 120 MPa under both ambient and SBF environments could survive up to 10⁷ cycles without spallation of HAp coating layer. The specimens tested under SBF environment and those tested under ambient environment after immersion in SBF showed shorter fatigue life compared to those tested under ambient environment without SBF immersion. Micro-cracks nucleated in the coating layer in the early stage of fatigue life and then propagated into the cp-Ti substrate in the intermediate stage, which unstably propagated to failure in the final stage. It was found from the XRD analysis that the dissolution of the co-existing phases and the precipitation of the HAp phase were taken place during immersion in SBF. During this process, the co-existing phases disappeared from the coating layer and the HAp phase fully occupied the coating layer. The degradation of bending strength and fatigue life of the HAp coating specimens tested under SBF environment would be induced by dissolution of the co-existing phases from the coating layer during immersion in SBF. Copyright © 2012 Elsevier Ltd. All rights reserved.

Investigation of Mixed-Type Craters and the Role of Bifluoride Additives to Produce Zirconia-Toughened Alumina-Based PEO Coating

NASA Astrophysics Data System (ADS)

Ur Rehman, Zeeshan; Shin, Seong Hun; Ahmad, Tanveer; Koo, Bon Heun

2018-05-01

Al2O3-ZrO2 composite ceramic coatings were prepared on Al6061 aluminum alloy by plasma electrolytic oxidation in Na3PO4-K2ZrF6-Na2SiF6-based alkaline electrolyte. Optimum processing time for the coating formation was found to be 50 min. Cross section and surface morphology of the coatings were analyzed using scanning electron microscope. From the phase and elemental composition analysis, the presence of m-ZrO2 and t-ZrO2 phases was confirmed. It was further observed that the peak intensities of t-ZrO2 and α-Al2O3 phases increased with processing time, which was attributed to the enhanced crystallinity caused by the efficient sintering conditions. Corrosion properties were investigated by potentiodynamic polarization test in 3.5 wt.% NaCl solution. The results showed high improvement in corrosion rate with minimum recorded value 0.25 mmy (mm/year) and corrosion current 0.15 × 10-6 A/cm2.

A Study on the Deposition of Al2O3 Coatings on Polymer Substrates by a Plasma Spray/Micro-Arc Oxidation Two-Step Method

NASA Astrophysics Data System (ADS)

Sun, Guanhong; He, Xiaodong; Jiang, Jiuxing; Sun, Yue; Zhong, Yesheng

2013-02-01

To increase the wear resistance of polymer matrix composites, alumina coatings were deposited on polymer substrates by a two-step method combining plasma spraying and micro-arc oxidation. The microstructures and phase compositions of the processed coatings were investigated for different treatment times. Uniformly distributed pores were found in addition to the presence of various coral-like structures and floccules on the surface of the coatings. The presence of α-Al2O3 and γ-Al2O3 phases was identified by XRD. The distribution of alumina was analyzed by EDS and is discussed. The maximum bond strength of the coatings was found to be 5.89 MPa. There was little thermal damage in the polymer substrates after the coatings were produced.

Effects of different binders on microstructure and phase composition of hydroxyapatite Nd-YAG laser clad coatings

NASA Astrophysics Data System (ADS)

Chien, C. S.; Hong, T. F.; Han, T. J.; Kuo, T. Y.; Liao, T. Y.

2011-01-01

The laser clad coating technique can help to produce metallurgical bonding with high bonding strength between the coating layer and the substrate, which has been gradually applied for hydroxyapatite (HA) coating on metallic substrates. In this study, HA powder is mixed with two different binders, namely water glass (WG) and polyvinyl alcohol (PVA), respectively, and is then clad on Ti-6Al-4V substrates using an Nd:YAG laser system under various processing conditions. The microstructure, chemical composition and hardness of the coating layer and transition layer of the various samples are then systematically explored. The experimental results show that the coating layers of the various samples all contain both cellular dendrites and rod-like piled structures, while the transition layers contain only cellular dendrites. For all samples, the coating layer consists mostly of CaTiO 3, Ca 2P 2O 7, CaO and HA phases, whereas the transition layer contains primarily CaTiO 3, Ca 2P 2O 7, Ti 3P, Ti and HA phases. In addition, the transition layer of the WG samples also contains SiO 2 and Si 2Ti phases. In all of the specimens, the transition layer has a higher average hardness than the substrate or coating layer. Moreover, the transition layer in the WG sample is harder than that in the PVA sample.

Nucleation and growth of hydroxyapatite on arc-deposited TiO2 surfaces studied by quartz crystal microbalance with dissipation

NASA Astrophysics Data System (ADS)

Lilja, Mirjam; Butt, Umer; Shen, Zhijian; Bjöörn, Dorota

2013-11-01

Understanding of nucleation and growth kinetics of biomimetically deposited hydroxyapatite (HA) on crystalline TiO2 surfaces is important with respect to the application and performance of HA as functional implant coatings. Arc-evaporation was used to deposit TiO2 coatings dominated by anatase phase, rutile phase or their mixtures. Subsequent formation of HA from phosphate buffered saline solution (PBS) was investigated in real-time using in situ quartz crystal microbalance with dissipation technique (QCM-D). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to characterize the presence, morphology and crystal structure of TiO2 coatings and the formed HA. Increasing temperature of the PBS, increasing flow rate and applying a higher ion concentration in solution were found to accelerate HA nucleation process and hence affect growth kinetics. Lower PBS temperature resulted in the formation of HA coatings with flake-like morphology and increasing HA porosity. All TiO2 coatings under study enabled HA formation at body temperature, while in contrast Ti reference surfaces only supported HA nucleation and growth at elevated temperatures. QCM-D technique is a powerful tool for studying the impact of process parameters during biomimetic coating deposition on coating structure evolution in real time and provides valuable information for understanding, optimizing as well as tailoring the biomimetic HA growth processes.

Stability of whole inactivated influenza virus vaccine during coating onto metal microneedles

PubMed Central

Choi, Hyo-Jick; Bondy, Brian J.; Yoo, Dae-Goon; Compans, Richard W.; Kang, Sang-Moo; Prausnitz, Mark R.

2012-01-01

Immunization using a microneedle patch coated with vaccine offers the promise of simplified vaccination logistics and increased vaccine immunogenicity. This study examined the stability of influenza vaccine during the microneedle coating process, with a focus on the role of coating formulation excipients. Thick, uniform coatings were obtained using coating formulations containing a viscosity enhancer and surfactant, but these formulations retained little functional vaccine hemagglutinin (HA) activity after coating. Vaccine coating in a trehalose-only formulation retained about 40 – 50% of vaccine activity, which is a significant improvement. The partial viral activity loss observed in the trehalose-only formulation was hypothesized to come from osmotic pressure-induced vaccine destabilization. We found that inclusion of a viscosity enhancer, carboxymethyl cellulose, overcame this effect and retained full vaccine activity on both washed and plasma-cleaned titanium surfaces. The addition of polymeric surfactant, Lutrol® micro 68, to the trehalose formulation generated phase transformations of the vaccine coating, such as crystallization and phase separation, which was correlated to additional vaccine activity loss, especially when coating on hydrophilic, plasma-cleaned titanium. Again, the addition of a viscosity enhancer suppressed the surfactant-induced phase transformations during drying, which was confirmed by in vivo assessment of antibody response and survival rate after immunization in mice. We conclude that trehalose and a viscosity enhancer are beneficial coating excipients, but the inclusion of surfactant is detrimental to vaccine stability. PMID:23246470

Effects of laser remelting on microstructures and immersion corrosion performance of arc sprayed Al coating in 3.5% NaCl solution

NASA Astrophysics Data System (ADS)

Sun, Ze; Zhang, Donghui; Yan, Baoxu; Kong, Dejun

2018-02-01

An arc sprayed aluminum (Al) coating on S355 steel was processed using a laser remelting (LR). The microstructures, chemical element composition, and phases of the obtained Al coating were analyzed using a field mission scanning electronic microscope (FESEM), energy dispersive spectrometer (EDS), and X-ray diffractometer (XRD), respectively, and the residual stresses were measured using an X-ray diffraction stress tester. The immersion corrosion tests and potentiodynamic polarization of Al coating in 3.5% NaCl solution were performed to investigate the effects of LR on its immersion corrosion behaviors, and the corrosion mechanism of Al coating was also discussed. The results show that the arc sprayed Al coating is composed of Al phase, while that by LR is composed of Al-Fe and AlO4FeO6 phases, and the porosities and cracks in the arc sprayed Al coating are eliminated by LR, The residual stress of arc sprayed Al coating is -5.6 ± 18 MPa, while that after LR is 137.9 ± 12 MPa, which deduces the immersion corrosion resistance of Al coating. The corrosion mechanism of arc sprayed Al coating is pitting corrosion and crevice corrosion, while that by LR is uniform corrosion and pitting corrosion. The corrosion potential of arc sprayed Al coating by LR shifts positively, which improves its immersion corrosion resistance.

High-Performance Molybdenum Coating by Wire–HVOF Thermal Spray Process

NASA Astrophysics Data System (ADS)

Tailor, Satish; Modi, Ankur; Modi, S. C.

2018-04-01

Coating deposition on many industrial components with good microstructural, mechanical properties, and better wear resistance is always a challenge for the thermal spray community. A number of thermal spray methods are used to develop such promising coatings for many industrial applications, viz. arc spray, flame spray, plasma, and HVOF. All these processes have their own limitations to achieve porous free, very dense, high-performance wear-resistant coatings. In this work, an attempt has been made to overcome this limitation. Molybdenum coatings were deposited on low-carbon steel substrates using wire-high-velocity oxy-fuel (W-HVOF; WH) thermal spray system (trade name HIJET 9610®). For a comparison, Mo coatings were also fabricated by arc spray, flame spray, plasma spray, and powder-HVOF processes. As-sprayed coatings were analyzed using x-ray diffraction, scanning electron microscopy for phase, and microstructural analysis, respectively. Coating microhardness, surface roughness, and porosity were also measured. Adhesion strength and wear tests were conducted to determine the mechanical and wear properties of the as-sprayed coatings. Results show that the coatings deposited by W-HVOF have better performance in terms of microstructural, mechanical, and wear resistance properties, in comparison with available thermal spray process (flame spray and plasma spray).

Characterization of Antisticking Layers for UV Nanoimprint Lithography Molds with Scanning Probe Microscopy

NASA Astrophysics Data System (ADS)

Masaaki Kurihara,; Sho Hatakeyama,; Noriko Yamada,; Takeya Shimomura,; Takaharu Nagai,; Kouji Yoshida,; Tatsuya Tomita,; Morihisa Hoga,; Naoya Hayashi,; Hiroyuki Ohtani,; Masamichi Fujihira,

2010-06-01

Antisticking layers (ASLs) on UV nanoimprint lithography (UV-NIL) molds were characterized by scanning probe microscopies (SPMs) in addition to macroscopic analyses of work of adhesion and separation force. Local physical properties of the ASLs were measured by atomic force microscopy (AFM) and friction force microscopy (FFM). The behavior of local adhesive forces measured with AFM on several surfaces was consistent with that of work of adhesion obtained from contact angle. The ASLs were coated by two different processes, i.e., one is a vapor-phase process and the other a spin-coating process. The homogeneity of the ASLs prepared by the vapor-phase process was better than that of those prepared by the spin-coating process. In addition, we measured the thicknesses of ASL patterns prepared by a lift-off method to investigate the effect of the ASL thicknesses on critical dimensions of the molds with ASLs and found that this effect is not negligible.

Fabrication of Nanosized Lanthanum Zirconate Powder and Deposition of Thermal Barrier Coating by Plasma Spray Process

NASA Astrophysics Data System (ADS)

Mishra, S. K.; Jagdeesh, N.; Pathak, L. C.

2016-07-01

The present manuscript discusses our findings on fabrication of nanosized lanthanum zirconate powder for thermal barrier coating application and its coating by plasma spray on nickel-based superalloy substrate. Single-phase La2Zr2O7 coating of thickness of the order of 45 µm on the Ni-Cr-Al bond coat coated Ni-based superalloy substrate was deposited by plasma spray process. The layers at the interface did not show spallation and inter diffusion was very less. The microstructure, interface, porosity, and mechanical properties of different layers are investigated. The lanthanum zirconate hardness and modulus were 10.5 and 277 GPa, respectively. The load depth curve for lanthanum zirconate showed good elastic recovery around 74%.

The induction of nanographitic phase on Fe coated diamond films for the enhancement in electron field emission properties

NASA Astrophysics Data System (ADS)

Panda, Kalpataru; Sundaravel, B.; Panigrahi, B. K.; Chen, H.-C.; Huang, P.-C.; Shih, W.-C.; Lo, S.-C.; Lin, L.-J.; Lee, C.-Y.; Lin, I.-N.

2013-03-01

A thin layer of iron coating and subsequent post-annealing (Fe-coating/post-annealing) is seen to significantly enhance the electron field emission (EFE) properties of ultrananocrystalline diamond (UNCD) films. The best EFE properties, with a turn on field (E0) of 1.98 V/μm and current density (Je) of 705 μA/cm2 at 7.5 V/μm, are obtained for the films, which were Fe-coated/post-annealed at 900 °C in H2 atmosphere. The mechanism behind the enhanced EFE properties of Fe coated/post-annealed UNCD films are explained by the microstructural analysis which shows formation of nanographitic phase surrounding the Fe (or Fe3C) nanoparticles. The role of the nanographitic phase in improving the emission sites of Fe coated/post-annealed UNCD films is clearly revealed by the current imaging tunneling spectroscopy (CITS) images. The CITS images clearly show significant increase in emission sites in Fe-coated/post-annealed UNCD films than the as-deposited one. Enhanced emission sites are mostly seen around the boundaries of the Fe (or Fe3C) nanoparticles which were formed due to the Fe-coating/post-annealing processes. Moreover, the Fe-coating/post-annealing processes enhance the EFE properties of UNCD films more than that on the microcrystalline diamond films. The authentic factor, resulting in such a phenomenon, is attributed to the unique granular structure of the UNCD films. The nano-sized and uniformly distributed grains of UNCD films, resulted in markedly smaller and densely populated Fe-clusters, which, in turn, induced more finer and higher populated nano-graphite clusters.

Coated electroactive materials

DOEpatents

Amine, Khalil; Abouimrane, Ali

2016-08-30

A process includes suspending an electroactive material in a solvent, suspending or dissolving a carbon precursor in the solvent; and depositing the carbon precursor on the electroactive material to form a carbon-coated electroactive material. Compositions include a graphene-coated electroactive material prepared from a solution phase mixture or suspension of an electroactive material and graphene, graphene oxide, or a mixture thereof.

The effects of plasma spray parameters and atmosphere on the properties and microstructure of WC-Co coatings

NASA Astrophysics Data System (ADS)

Ghosh, D.; Lamy, D.; Sopkow, T.; Smuga-Otto, I.

Wear- and corrosion-resistant coatings deposited by plasma spray process are increasingly used in severe environments in resource industries, such as oil and gas, oil sands, mining, pulp and paper, etc. While there is a large volume of literature in the area of plasma spray coatings, comparatively few papers deal with the co-relation between coating properties and microstructure as a function of plasma spray processing parameters. In this study, the effect of some plasma spray processing variables and atmosphere (air or inert gas) on the microstructure and the properties of WC-Co coatings were studied. The properties of the coatings measured include: microhardness, porosity by image analysis, wear resistance by dry sand/rubber wheel abrasion test (ASTM G 65-91) and corrosion properties by AC impedance technique. Phase analyses of the coatings were also performed by X-ray diffraction. From the above, optimized coatings were developed for oil and gas industry applications.

Furnace Cyclic Oxidation Behavior of Multi-Component Low Conductivity Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dong-Ming; Nesbitt, James A.; Barrett, Charles A.; McCue, Terry R.; Miller, Robert A.

2004-01-01

Ceramic thermal barrier coatings will play an increasingly important role in advanced gas turbine engines because of their ability to further increase engine operating temperatures and reduce cooling, thus helping achieve future engine low emission, high efficiency and improved reliability goals. Advanced multi-component zirconia-based thermal barrier coatings are being developed using an oxide defect clustering design approach to achieve the required coating low thermal conductivity and high temperature stability. Although the new composition coatings were not yet optimized for cyclic durability, an initial durability screening of the candidate coating materials was conducted using conventional furnace cyclic oxidation tests. In this paper, furnace cyclic oxidation behavior of plasma-sprayed zirconia-based defect cluster thermal barrier coatings was investigated at 1163 C using 45 min hot cycles. The ceramic coating failure mechanisms were studied using scanning electron microscopy (SEM) combined with X-ray diffraction (XRD) phase analysis after the furnace tests. The coating cyclic lifetime is also discussed in relation to coating processing, phase structures, dopant concentration, and other thermo-physical properties.

Ultrasonic cavitation erosion of high-velocity oxygen-fuel (HVOF) sprayed near-nanostructured WC-10Co-4Cr coating in NaCl solution.

PubMed

Hong, Sheng; Wu, Yuping; Zhang, Jianfeng; Zheng, Yugui; Qin, Yujiao; Lin, Jinran

2015-09-01

The high-velocity oxygen-fuel (HVOF) spraying process was used to prepare near-nanostructured WC-10Co-4Cr coating. The cavitation erosion behavior and mechanism of the coating in 3.5 wt.% NaCl solution were analyzed in detail. The results showed that the amorphous phase and WC grain were present in the coating. The cavitation erosion resistance of the coating was about 1.27 times that of the stainless steel 1Cr18Ni9Ti under the same testing conditions. The effects of erosion time on the microstructural evolution were discussed. It was revealed that cracks initiated at the edge of pre-existing pores and propagated along the carbide-binder interface, leading to the pull-out of carbide particle and the formation of pits and craters on the surface. The main failure mechanism of the coating was erosion of the binder phases, brittle detachment of hard phases and formation of pitting corrosion products. Copyright © 2015 Elsevier B.V. All rights reserved.

Methylsilane derived silicon carbide particle coatings produced by fluid-bed chemical vapor deposition

NASA Astrophysics Data System (ADS)

Miller, James Henry

This report describes the research effort that was undertaken to develop and understand processing techniques for the deposition of both low and high density SiC coatings from a non-halide precursor, in support of the Generation IV Gas-Cooled Fast Reactor (GFR) fuel development program. The research was conducted in two phases. In the first phase, the feasibility of producing both porous SiC coatings and dense SiC coatings on surrogate fuel particles by fluidized bed chemical vapor deposition (FBCVD) using gas mixtures of methylsilane and argon was demonstrated. In the second phase, a combined experimental and modeling effort was carried out in order to gain an understanding of the deposition mechanisms that result in either porous or dense SiC coatings, depending on the coating conditions. For this second phase effort, a simplified (compared to the fluid bed) single-substrate chemical vapor deposition (CVD) system was employed. Based on the experimental and modeling results, the deposition of SiC from methylsilane is controlled by the extent of gas-phase reaction, and is therefore highly sensitive to temperature. The results show that all SiC coatings are due to the surface adsorption of species that result from gas-phase reactions. The model terms these gas-borne species embryos, and while the model does not include a prediction of coating morphology, a comparison of the model and experimental results indicates that the morphology of the coatings is controlled by the nucleation and growth of the embryos. The coating that results from small embryos (embryos with only two Si-C pairs) appears relatively dense and continuous, while the coating that results from larger embryos becomes less continuous and more nodular as embryo size increases. At some point in the growth of embryos they cease to behave as molecular species and instead behave as particles that grow by either agglomeration or by incorporation of molecular species on their surface. As these particles adhere to the substrate surface and become fixed in place by surface deposition in the interstices between adjacent particles, a low density coating consisting of these particles results.

Interdiffusion behaviors of iron aluminide coatings on China low activation martensitic steel

NASA Astrophysics Data System (ADS)

Zhu, X. X.; Yang, H. G.; Yuan, X. M.; Zhao, W. W.; Zhan, Q.

2014-12-01

The iron aluminide coating on China Low Activation Martensitic (CLAM) steel was prepared by pack cementation and subsequent heat treatment. A surface Fe2Al5 layer was formed on CLAM substrate by pack cementation process with Fe2Al5 donor powder and NH4Cl activator. Diffusion heat treatment was performed in order to allow the phase transformation from Fe2Al5 to a phase with lower aluminum content. Morphology and composition of the coatings were characterized by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), glow discharge optical emission spectroscopy (GDOES) and X-ray diffraction (XRD). There is a need to study the interdiffusion behaviors in these Al containing systems, as a basis for controlling the formation and subsequent degradation of the coating. In this paper, a predictive model was developed to describe the phase transformation of Fe2Al5 as a function of processing parameters. The Wagner's equation was used to calculate the interdiffusion coefficients based on the analysis of the Al concentration profiles. The results showed that the interdiffusion coefficients in the FeAl and α-Fe(Al) phase strongly depends on Al content and showed a maximum at about 28 at.% Al.

Influence of substrate metal alloy type on the properties of hydroxyapatite coatings deposited using a novel ambient temperature deposition technique.

PubMed

Barry, J N; Cowley, A; McNally, P J; Dowling, D P

2014-03-01

Hydroxyapatite (HA) coatings are applied widely to enhance the level of osteointegration onto orthopedic implants. Atmospheric plasma spray (APS) is typically used for the deposition of these coatings; however, HA crystalline changes regularly occur during this high-thermal process. This article reports on the evaluation of a novel low-temperature (<47°C) HA deposition technique, called CoBlast, for the application of crystalline HA coatings. To-date, reports on the CoBlast technique have been limited to titanium alloy substrates. This study addresses the suitability of the CoBlast technique for the deposition of HA coatings on a number of alternative metal alloys utilized in the fabrication of orthopedic devices. In addition to titanium grade 5, both cobalt chromium and stainless steel 316 were investigated. In this study, HA coatings were deposited using both the CoBlast and the plasma sprayed techniques, and the resultant HA coating and substrate properties were evaluated and compared. The CoBlast-deposited HA coatings were found to present similar surface morphologies, interfacial properties, and composition irrespective of the substrate alloy type. Coating thickness however displayed some variation with the substrate alloy, ranging from 2.0 to 3.0 μm. This perhaps is associated with the electronegativity of the metal alloys. The APS-treated samples exhibited evidence of both coating, and significantly, substrate phase alterations for two metal alloys; titanium grade 5 and cobalt chrome. Conversely, the CoBlast-processed samples exhibited no phase changes in the substrates after depositions. The APS alterations were attributed to the brief, but high-intensity temperatures experienced during processing. Copyright © 2013 Wiley Periodicals, Inc.

Industrialization of the mirror plate coatings for the ATHENA mission

NASA Astrophysics Data System (ADS)

Massahi, S.; Christensen, F. E.; Ferreira, D. D. M.; Shortt, B.; Collon, M.; Sforzini, J.; Landgraf, B.; Hinze, F.; Aulhorn, S.; Biedermann, R.

2017-08-01

In the frame of the development of the Advanced Telescope for High-ENergy Astrophysics (Athena) mission, currently in phase A, ESA is continuing to mature the optics technology and the associated mass production techniques. These efforts are driven by the programmatic and technical requirement of reaching TRL 6 prior to proposing the mission for formal adoption (planned for 2020). A critical part of the current phase A preparation activities is addressing the industrialization of the Silicon Pore Optics mirror plates coating. This include the transfer of the well-established coating processes and techniques, performed at DTU Space, to an industrial scale facility suitable for coating the more than 100,000 mirror plates required for Athena. In this paper, we explain the considerations for the planned coating facility including, requirement specification, equipment and supplier selection, preparing the coating facility for the deposition equipment, designing and fabrication.

Preparation of a novel hyperbranched carbosilane-silica hybrid coating for trace amount detection by solid phase microextraction/gas chromatography.

PubMed

Chen, Guowen; Li, Wenjie; Zhang, Chen; Zhou, Chuanjian; Feng, Shengyu

2012-09-21

Phenyl-ended hyperbranched carbosilane (HBC) is synthesized and immobilized onto the inner wall of a fused silica capillary column using a sol-gel process. The hybrid coating layer formed is used as a stationary phase for gas chromatography (GC) and as an adsorption medium for solid phase microextraction (SPME). Trifluoroacetic acid, as a catalyst in this process, helps produce a homogeneous hybrid coating layer. This result is beneficial for better column chromatographic performances, such as high efficiency and high resolution. Extraction tests using the novel hybrid layer show an extraordinarily large adsorption capacity and specific adsorption behavior for aromatic compounds. A 1 ppm trace level detectability is obtained with the SPME/GC work model when both of the stationary phase and adsorption layer bear a hyperbranched structure. A large amount of phenyl groups and a low viscosity of hyperbranched polymers contribute to these valuable properties, which are important to environment and safety control, wherein detection sensitivity and special adsorption behavior are usually required. Copyright © 2012 Elsevier B.V. All rights reserved.

Reactive Fabrication and Effect of NbC on Microstructure and Tribological Properties of CrS Co-Based Self-Lubricating Coatings by Laser Cladding.

PubMed

Fang, Liuyang; Yan, Hua; Yao, Yansong; Zhang, Peilei; Gao, Qiushi; Qin, Yang

2017-12-28

The CrS/NbC Co-based self-lubricating composite coatings were successfully fabricated on Cr12MoV steel surface by laser clad Stellite 6, WS₂, and NbC mixed powders. The phase composition, microstructure, and tribological properties of the coatings ware investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS), as well as dry sliding wear testing. Based on the experimental results, it was found reactions between WS₂ and Co-based alloy powder had occurred, which generated solid-lubricant phase CrS, and NbC play a key role in improving CrS nuclear and refining microstructure of Co-based composite coating during laser cladding processing. The coatings were mainly composed of γ-Co, CrS, NbC, Cr 23 C₆, and CoC x . Due to the distribution of the relatively hard phase of NbC and the solid lubricating phase CrS, the coatings had better wear resistance. Moreover, the suitable balance of CrS and NbC was favorable for further decreasing the friction and improving the stability of the contact surfaces between the WC ball and the coatings. The microhardness, friction coefficient, and wear rate of the coating 4 (Clad powders composed of 60 wt % Stellite 6, 30 wt % NbC and 10 wt % WS₂) were 587.3 HV 0.5 , 0.426, and 5.61 × 10 -5 mm³/N·m, respectively.

Microstructure and Mechanical Properties of Zn-Ni-Al₂O₃ Composite Coatings.

PubMed

Bai, Yang; Wang, Zhenhua; Li, Xiangbo; Huang, Guosheng; Li, Caixia; Li, Yan

2018-05-21

Zn-Ni-Al₂O₃ composite coatings with different Ni contents were fabricated by low-pressure cold spray (LPCS) technology. The effects of the Ni content on the microstructural and mechanical properties of the coatings were investigated. According to X-ray diffraction patterns, the composite coatings were primarily composed of metallic-phase Zn and Ni and ceramic-phase Al₂O₃. The energy-dispersive spectroscopy results show that the Al₂O₃ content of the composite coatings gradually decreased with increasing of Ni content. The cross-sectional morphology revealed thick, dense coatings with a wave-like stacking structure. The process of depositing Zn and Ni particles and Al₂O₃ particles by the LPCS method was examined, and the deposition mechanism was demonstrated to be mechanical interlocking. The bond strength, micro hardness and friction coefficient of the coatings did not obviously change when the Ni content varied. The presence of Al₂O₃ and Ni increased the wear resistance of the composite coatings, which was higher than that of pure Zn coatings, and the wear mechanism was abrasive and adhesive wear.

Novel benzo-15-crown-5 sol-gel coating for solid-phase microextraction.

PubMed

Wang, Danhua; Xing, Jun; Peng, Jiagang; Wu, Caiying

2003-07-11

A novel dihydroxy-terminated benzo-15-crown-5 was synthesized and applied to prepare a solid-phase microextraction (SPME) fiber coating with sol-gel technology. The optimization of the sol-gel process was studied. The coating method with sol-gel was improved and completed in one run, which economized materials and allowed easier control of the fiber thickness. The repeatability of coating fiber to fiber was better than 4.94% (RSD). The surface of the fiber coating was well-distributed and an electron microscopy experiment suggested a porous structure for crown ether coating, providing high surface areas and allowing for high extraction efficiency. The coating has a high thermal stability (350 degrees C), long lifetime and can stand solvent (organic and inorganic) rinsing due to the chemical binding between the coating and the fiber surface. Non-polar benzene, toluene, ethylbenzene, xylenes, chlorobenzenes, polar phenolic compounds and arylamines were used to evaluate the character of the fiber coating by headspace SPME-gas chromatography technology. For phenols, the linear concentrations ranged from 5 to 1000 microg/l, the detection limits were between 0.05 and 1 microg/l, and the RSD was less than 5%. The addition of benzo-crown ether not only increases the thermal stability of the fiber coating, but also enhances the selectivity of the fiber coating. Compared with commercially available SPME fibers poly(dimethylsiloxane) and polyacrylate, the few phases showed better selectivity and sensitivity towards non-polar and polar aromatic compounds.

In-line agglomeration degree estimation in fluidized bed pellet coating processes using visual imaging.

PubMed

Mehle, Andraž; Kitak, Domen; Podrekar, Gregor; Likar, Boštjan; Tomaževič, Dejan

2018-05-09

Agglomeration of pellets in fluidized bed coating processes is an undesirable phenomenon that affects the yield and quality of the product. In scope of PAT guidance, we present a system that utilizes visual imaging for in-line monitoring of the agglomeration degree. Seven pilot-scale Wurster coating processes were executed under various process conditions, providing a wide spectrum of process outcomes. Images of pellets were acquired during the coating processes in a contactless manner through an observation window of the coating apparatus. Efficient image analysis methods were developed for automatic recognition of discrete pellets and agglomerates in the acquired images. In-line obtained agglomeration degree trends revealed the agglomeration dynamics in distinct phases of the coating processes. We compared the in-line estimated agglomeration degree in the end point of each process to the results obtained by the off-line sieve analysis reference method. A strong positive correlation was obtained (coefficient of determination R 2 =0.99), confirming the feasibility of the approach. The in-line estimated agglomeration degree enables early detection of agglomeration and provides means for timely interventions to retain it in an acceptable range. Copyright © 2018 Elsevier B.V. All rights reserved.

Morphology and microstructure evolution of Ti-50 at.% Al cathodes during cathodic arc deposition of Ti-Al-N coatings

NASA Astrophysics Data System (ADS)

Syed, Bilal; Zhu, Jianqiang; Polcik, Peter; Kolozsvari, Szilard; Hâkansson, Greger; Johnson, Lars; Ahlgren, Mats; Jöesaar, Mats; Odén, Magnus

2017-06-01

Today's research on the cathodic arc deposition technique and coatings therefrom primarily focuses on the effects of, e.g., nitrogen partial pressure, growth temperature, and substrate bias. Detailed studies on the morphology and structure of the starting material—the cathode—during film growth and its influence on coating properties at different process conditions are rare. This work aims to study the evolution of the converted layer, its morphology, and microstructure, as a function of the cathode material grain size during deposition of Ti-Al-N coatings. The coatings were reactively grown in pure N2 discharges from powder metallurgically manufactured Ti-50 at.% Al cathodes with grain size distribution averages close to 1800, 100, 50, and 10 μm, respectively, and characterized with respect to microstructure, composition, and mechanical properties. The results indicate that for the cathode of 1800 μm grain size the disparity in the work function among parent phases plays a dominant role in the pronounced erosion of Al, which yields the coatings rich in macro-particles and of high Al content. We further observed that a reduction in the grain size of Ti-50 at.% Al cathodes to 10 μm provides favorable conditions for self-sustaining reactions between Ti and Al phases upon arcing to form γ phase. The combination of self-sustaining reaction and the arc process not only result in the formation of hole-like and sub-hole features on the converted layer but also generate coatings of high Al content and laden with macro-particles.

Dry coating of solid dosage forms: an overview of processes and applications.

PubMed

Foppoli, Anastasia Anna; Maroni, Alessandra; Cerea, Matteo; Zema, Lucia; Gazzaniga, Andrea

2017-12-01

Dry coating techniques enable manufacturing of coated solid dosage forms with no, or very limited, use of solvents. As a result, major drawbacks associated with both organic solvents and aqueous coating systems can be overcome, such as toxicological, environmental, and safety-related issues on the one hand as well as costly drying phases and impaired product stability on the other. The considerable advantages related to solventless coating has been prompting a strong research interest in this field of pharmaceutics. In the article, processes and applications relevant to techniques intended for dry coating are analyzed and reviewed. Based on the physical state of the coat-forming agents, liquid- and solid-based techniques are distinguished. The former include hot-melt coating and coating by photocuring, while the latter encompass press coating and powder coating. Moreover, solventless techniques, such as injection molding and three-dimensional printing by fused deposition modeling, which are not purposely conceived for coating, are also discussed in that they would open new perspectives in the manufacturing of coated-like dosage forms.

Electrochemical corrosion behaviour of nickel chromium-chromium carbide coating by HVOF process

NASA Astrophysics Data System (ADS)

Amudha, A.; Nagaraja, H. S.; Shashikala, H. D.

2018-04-01

To overcome the corrosion problem in marine industry, coatings are one of the most economical solutions. In this paper, the corrosion behaviour of 25(NiCr)-75Cr3C2 cermet coating on low carbon steel substrate by HVOF process is studied. Different phases such as Cr7C3 and Cr3C2, along with Ni and chromium oxide(Cr3O2) constituents present in the coating were revealed by X-Ray Diffraction (XRD) analysis. The morphology of the coating obtained by scanning electron microscope (SEM) gave confirmation for the XRD analysis. Electrochemical corrosion techniques such as Linear Polarization Resistance (LPR) and Electrochemical Impedance Spectroscopy (EIS) were used to study the corrosion behaviour of the cermet in 3.5wt% NaCl electrolyte solution. The corrosion current density of the coated sample and substrate were found to be 6.878µA/cm-2 and 21.091µA/cm-2 respectively. The Nyquist Impedance spectra were used to derive an equivalent circuit to analyze the interaction between the coating and electrolyte. The Bode Impedance plots obtained by EIS for the coating showed a typical passive material capacitive behaviour, indicated by medium to low frequency with phase angle approaching -60o, suggesting that a stable film is formed on the tested material in the electrolyte used.

Conversion Coatings for Aluminum Alloys by Chemical Vapor Deposition Mechanisms

NASA Technical Reports Server (NTRS)

Reye, John T.; McFadden, Lisa S.; Gatica, Jorge E.; Morales, Wilfredo

2004-01-01

With the rise of environmental awareness and the renewed importance of environmentally friendly processes, the United States Environmental Protection Agency has targeted surface pre-treatment processes based on chromates. Indeed, this process has been subject to regulations under the Clean Water Act as well as other environmental initiatives, and there is today a marked movement to phase the process out in the near future. Therefore, there is a clear need for new advances in coating technology that could provide practical options for replacing present industrial practices. Depending on the final application, such coatings might be required to be resistant to corrosion, act as chemically resistant coatings, or both. This research examined a chemical vapor deposition (CVD) mechanism to deposit uniform conversion coatings onto aluminum alloy substrates. Robust protocols based on solutions of aryl phosphate ester and multi-oxide conversion coating (submicron) films were successfully grown onto the aluminum alloy samples. These films were characterized by X-ray Photoelectron Spectroscopy (XPS). Preliminary results indicate the potential of this technology to replace aqueous-based chromate processes.

Bioactive (Si, O, N)/(Ti, O, N)/Ti composite coating on NiTi shape memory alloy for enhanced wear and corrosion performance

NASA Astrophysics Data System (ADS)

Sun, Tao; Xue, Ning; Liu, Chao; Wang, Chao; He, Jin

2015-11-01

In this investigation, (Si, O, N)/(Ti, O, N)/Ti composite coating was synthesized on a NiTi shape memory alloy (SMA) substrate (50.8 at.% Ni) via plasma immersion ion implantation and deposition (PIIID) followed by magnetron sputtering, with the aim of promoting bioactivity and biocompatibility of NiTi SMAs. Nano featured (Si, O, N)/(Ti, O, N)/Ti coating was approximate 0.84 ± 0.05 μm in thickness, and energy dispersive X-ray (EDX) spectroscopy showed that Ni element was depleted from the surface of coated samples. X-ray diffraction (XRD) did not identify the phase composition of the (Si, O, N)/(Ti, O, N)/Ti coating, probably due to its thin thickness and poor crystalline resulting from low-temperature coating processes (<200 °C). X-ray photoelectron spectroscopy (XPS) analyses confirmed that a Ni-free surface was formed and Si element was incorporated into the composite coating via the magnetron sputtering process. Additionally, phase transformation behaviors of uncoated and coated NiTi SMA samples were characterized using differential scanning calorimetry (DSC). Wear and corrosion resistance of uncoated and coated NiTi SMA samples were evaluated using ball-on-disc tests and potentio-dynamic polarization curves, respectively. The (Si, O, N)/(Ti, O, N)/Ti coated NiTi SMA samples showed enhanced wear and corrosion resistance. Furthermore, the (Si, O, N)/(Ti, O, N)/Ti composite coating facilitated apatite formation in simulated body fluid (SBF) and rendered NiTi SMA bioactivity.

Photocatalytic activity of titania coatings synthesised by a combined laser/sol–gel technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adraider, Y.; Pang, Y.X., E-mail: F6098038@tees.ac.uk; Nabhani, F.

2014-06-01

Highlights: • Sol–gel method was used to prepare titania coatings. • Titania thin films were coated on substrate surface by dip coating. • Fibre laser was employed to irradiate the titania coated surfaces. • Photocatalytic efficiency of titania coatings was significantly improved after laser processing. - Abstract: Titania coatings were prepared using sol–gel method and then applied on the substrate surface by dip coating. Fibre laser (λ = 1064 nm) in continuous wave mode was used to irradiate the titania coated surfaces at different specific energies. The ATR-FTIR, XRD, SEM, EDS and contact angle measurement were employed to analyse surfacemore » morphology, phase composition and crystalline structure of laser-irradiated titania coatings, whilst the photocatalytic activity was evaluated by measuring the decomposition of methylene blue (MB) after exposure to the visible light for various illumination times. Results showed that the laser-irradiated titania coatings demonstrate significant different composition and microstructure in comparison with the as-coated from the same sol–gel titania. Photocatalytic efficiency of titania coatings was significantly improved after laser processing. The photocatalytic activity of laser-irradiated titania coatings was higher than that of the as-coated titania. The titania coating processed at laser specific energy of 6.5 J/mm{sup 2} exhibited the highest photocatalytic activity among all titania samples.« less

Development of a special purpose spacecraft coating, phase 4

NASA Technical Reports Server (NTRS)

Gillman, H. D.

1980-01-01

Coating formulations based on a fluorocarbon resin were evaluated for use on spacecraft exteriors. Formulations modified with an acrylic resin were found to have excellent offgassing properties. A much less expensive process for increasing to solid content of the fluorocarbon latex was developed.

Blast Coating of Superelastic NiTi Wire with PTFE to Enhance Wear Properties

NASA Astrophysics Data System (ADS)

Dunne, Conor F.; Roche, Kevin; Twomey, Barry; Hodgson, Darel; Stanton, Kenneth T.

2015-03-01

This work investigates the deposition of polytetrafluoroethylene (PTFE) onto a superelastic NiTi wire using an ambient temperature-coating technique known as CoBlast. The process utilises a stream of abrasive (Al2O3) and a coating medium (PTFE) sprayed simultaneously at the surface of the substrate. Superelastic NiTi wire is used in guidewire applications, and PTFE coatings are commonly applied to reduce damage to vessel walls during insertion and removal, and to aid in accurate positioning by minimising the force required to advance, retract or rotate the wire. The CoBlast coated wires were compared to wire treated with PTFE only. The coated samples were examined using variety of techniques: X-ray diffraction (XRD), microscopy, surface roughness, wear testing and flexural tests. The CoBlast coated samples had an adherent coating with a significant resistance to wear compared to the samples coated with PTFE only. The XRD revealed that the process gave rise to a stress-induced martensite phase in the NiTi which may enhance mechanical properties. The study indicates that the CoBlast process can be used to deposit thin adherent coatings of PTFE onto the surface of superelastic NiTi.

Spray process for in situ synthesizing Ti(C,N)-TiB2-Al2O3 composite ceramic coatings

NASA Astrophysics Data System (ADS)

Zhou, Jian; Liu, Hongwei; Sun, Sihao

2017-12-01

Using core wires with Ti-B4C-C as core and Al as strip materials, Ti(C,N)-TiB2-Al2O3 composite ceramic coatings were prepared on 45 steel substrates by the reactive arc spray technology. The influence of spray voltage, current, gas pressure and distance on the coatings was discussed. The spray parameters were optimized with porosity of the coatings as evaluation standard. The results showed that the most important factor which influences the quality of the coatings was spray distance. Then spray gas pressure, current and voltage followed in turn. The optimum process was spray current of 120A, voltage of 36, gas pressure of 0.7MPa and distance of 160mm. The porosity of coatings prepared in this spray process was only 2.11%. The coatings were composed of TiB2, TiC0.3N0.7, TiN, Al2O3 and AlN. Good properties and uniform distribution of these ceramic phases made the coatings have excellent comprehensive performances.

Laser induced hierarchical calcium phosphate structures.

PubMed

Kurella, Anil; Dahotre, Narendra B

2006-11-01

The surface properties of biomedical implant materials control the dynamic interactions at tissue-implant interfaces. At such interfaces, if the nanoscale features influence protein interactions, those of the microscale and mesoscale aid cell orientation and provide tissue integration, respectively. It seems imperative that the synthetic materials expected to replace natural hard tissues are engineered to mimic the complexity of their hierarchical assembly. However, the current surface engineering approaches are single scaled. It is demonstrated that using laser surface engineering a controlled multiscale surface can be synthesized for bioactive functions. A systematic organization of bioactive calcium phosphate coating with multiphase composition on Ti-alloy substrate ranging from nano- to mesoscale has been achieved by effectively controlling the thermo physical interactions during laser processing. The morphology of the coating consisted of a periodic arrangement of Ti-rich and Ca-P-deficient star-like phases uniformly distributed inside a Ca-P-rich self-assembled cellular structure with the presence of CaO, alpha-tricalcium phosphate, CaTiO(3), TiO(2) and Ti phase in the coating matrix. The cellular structures ranged in diameter from 2.5 microm to 10 microm as an assembly of cuboid shaped particles of dimensions of approximately 200 nm x 1 microm. The multiscale texture also included nanoscale particles that are the precursors for many of these phases. The rapid cooling associated with the laser processing resulted in formation, organization and controlling dimensions of the Ca-P-rich glassy phase into a micron scale cellular morphology and submicron scale clusters of CaTiO(3) phase inside the cellular structures. The self-assembly of the coating into multiscale structure was influenced by chemical and physical interactions among the multiphases that evolved during laser processing.

Microstructures Evolution and Micromechanics Features of Ni-Cr-Si Coatings Deposited on Copper by Laser Cladding.

PubMed

Zhang, Peilei; Li, Mingchuan; Yu, Zhishui

2018-05-23

Three Ni-Cr-Si coatings were synthesized on the surface of copper by laser cladding. The microstructures of the coatings were characterized by optical microscopy (OM), X-ray diffraction (XRD), and scanning electron microscopy (SEM) with an energy dispersive spectrometer (EDS). According to the analysis results of phase compositions, Gibbs free energy change and microstructures, the phases of three coatings appeared were Cr₃Si+γ-Ni+Cu ss (Coating 1, Ni-26Cr-29Si), Cr₆Ni 16 Si₇+Ni₂Si+Cu ss (Coating 2, Ni-10Cr-30Si) and Cr₃Ni₅Si₂+Cr₂Ni₃+Cu ss (Coating 3, Ni-29Cr-16Si). The crystal growth in the solidification process was analyzed with a modified model, which is a combination of Kurz-Giovanola-Trivedi (KGT) and Lipton-Kurz-Trivedi (LKT) models. The dendrite tip undercooling in Coating 2 was higher than those of Coating 1 and Coating 3. Well-developed dendrites were found in Coating 2. A modification of Hunt’s model was adopted to describe the morphological differences in the three coatings. The results show that Coating 1 was in the equiaxed dendrite region, while Coatings 2 and 3 were in the columnar dendrite region. The average friction coefficients of the three coatings were 0.45, 0.5 and 0.4, respectively. Obvious plastic deformation could be found in the subsurface zone of Coatings 2 and 3.

Furnace Cyclic Oxidation Behavior of Multicomponent Low Conductivity Thermal Barrier Coatings

NASA Astrophysics Data System (ADS)

Zhu, Dongming; Nesbitt, James A.; Barrett, Charles A.; McCue, Terry R.; Miller, Robert A.

2004-03-01

Ceramic thermal barrier coatings (TBCs) will play an increasingly important role in advanced gas turbine engines due to their ability to further increase engine operating temperatures and reduce cooling, thus helping achieve future engine low emission, high efficiency, and improved reliability goals. Advanced multicomponent zirconia (ZrO2)-based TBCs are being developed using an oxide defect clustering design approach to achieve the required coating low thermal conductivity and high-temperature stability. Although the new composition coatings were not yet optimized for cyclic durability, an initial durability screening of the candidate coating materials was conducted using conventional furnace cyclic oxidation tests. In this paper, furnace cyclic oxidation behavior of plasma-sprayed ZrO2-based defect cluster TBCs was investigated at 1163°C using 45 min hot-time cycles. The ceramic coating failure mechanisms were studied using scanning electron microscopy (SEM) combined with x-ray diffraction (XRD) phase analysis after the furnace tests. The coating cyclic lifetime is also discussed in relation to coating processing, phase structures, dopant concentration, and other thermo-physical properties.

Automated array assembly task, phase 1

NASA Technical Reports Server (NTRS)

Carbajal, B. G.

1977-01-01

Various aspects of a sensitivity analysis, in particular, the impact of variations in metal sheet resistivity, metal line width, diffused layer sheet resistance, junction depth, base layer lifetime, optical coating thickness and optical coating refractive index and on process reproducibility for A's diffusion from a polymer dopant source and on module fabrication were studied. Model calculations show that acceptable process windows exist for each of these parameters.

Effect of annealing temperature on the properties of copper oxide films prepared by dip coating technique

NASA Astrophysics Data System (ADS)

Raship, N. A.; Sahdan, M. Z.; Adriyanto, F.; Nurfazliana, M. F.; Bakri, A. S.

2017-01-01

Copper oxide films were grown on silicon substrates by sol-gel dip coating method. In order to study the effects of annealing temperature on the properties of copper oxide films, the temperature was varied from 200 °C to 450 °C. In the process of dip coating, the substrate is withdrawn from the precursor solution with uniform velocity to obtain a uniform coating before undergoing an annealing process to make the copper oxide film polycrystalline. The physical properties of the copper oxide films were measured by an X-ray diffraction (XRD), a field emission scanning electron microscope (FESEM), an atomic force microscopy (AFM) and a four point probe instrument. From the XRD results, we found that pure cuprite (Cu2O) phase can be obtained by annealing the films annealed at 200 °C. Films annealed at 300 °C had a combination phase which consists of tenorite (CuO) and cuprite (Cu2O) phase while pure tenorite (CuO) phase can be obtained at 450 °C annealing temperature. The surface microstructure showed that the grains size is increased whereas the surface roughness is increased and then decreases by increasing in annealing temperature. The films showed that the resistivity decreased with increasing annealing temperature. Consequently, it was observed that annealing temperature has strong effects on the structural, morphological and electrical properties of copper oxide films.

Development of refractory armored silicon carbide by infrared transient liquid phase processing

NASA Astrophysics Data System (ADS)

Hinoki, Tatsuya; Snead, Lance L.; Blue, Craig A.

2005-12-01

Tungsten (W) and molybdenum (Mo) were coated on silicon carbide (SiC) for use as a refractory armor using a high power plasma arc lamp at powers up to 23.5 MW/m 2 in an argon flow environment. Both tungsten powder and molybdenum powder melted and formed coating layers on silicon carbide within a few seconds. The effect of substrate pre-treatment (vapor deposition of titanium (Ti) and tungsten, and annealing) and sample heating conditions on microstructure of the coating and coating/substrate interface were investigated. The microstructure was observed by scanning electron microscopy (SEM) and optical microscopy (OM). The mechanical properties of the coated materials were evaluated by four-point flexural tests. A strong tungsten coating was successfully applied to the silicon carbide substrate. Tungsten vapor deposition and pre-heating at 5.2 MW/m 2 made for a refractory layer containing no cracks propagating into the silicon carbide substrate. The tungsten coating was formed without the thick reaction layer. For this study, small tungsten carbide grains were observed adjacent to the interface in all conditions. In addition, relatively large, widely scattered tungsten carbide grains and a eutectic structure of tungsten and silicon were observed through the thickness in the coatings formed at lower powers and longer heating times. The strength of the silicon carbide substrate was somewhat decreased as a result of the processing. Vapor deposition of tungsten prior to powder coating helped prevent this degradation. In contrast, molybdenum coating was more challenging than tungsten coating due to the larger coefficient of thermal expansion (CTE) mismatch as compared to tungsten and silicon carbide. From this work it is concluded that refractory armoring of silicon carbide by Infrared Transient Liquid Phase Processing is possible. The tungsten armored silicon carbide samples proved uniform, strong, and capable of withstanding thermal fatigue testing.

Phase separation in NiCrN coatings induced by N2 addition in the gas phase: A way to generate magnetic thin films by reactive sputtering of a non-magnetic NiCr target

NASA Astrophysics Data System (ADS)

Luciu, I.; Duday, D.; Choquet, P.; Perigo, E. A.; Michels, A.; Wirtz, T.

2016-12-01

Magnetic coatings are used for a lot of applications from data storage in hard discs, spintronics and sensors. Meanwhile, magnetron sputtering is a process largely used in industry for the deposition of thin films. Unfortunately, deposition of magnetic coatings by magnetron sputtering is a difficult task due to the screening effect of the magnetic target lowering the magnetic field strength of the magnet positioned below the target, which is used to generate and trap ions in the vicinity of the target surface to be sputtered. In this work we present an efficient method to obtain soft magnetic thin films by reactive sputtering of a non-magnetic target. The aim is to recover the magnetic properties of Ni after dealloying of Ni and Cr due to the selective reactivity of Cr with the reactive nitrogen species generated during the deposition process. The effects of nitrogen content on the dealloying and DC magnetron sputtering (DCMS) deposition processes are studied here. The different chemical compositions, microstructures and magnetic properties of DCMS thin films obtained by sputtering in reactive gas mixtures with different ratios of Ar/N2 from a non-magnetic Ni-20Cr target have been determined. XPS data indicate that the increase of nitrogen content in the films has a strong influence on the NiCr phase decomposition into Ni and CrN, leading to ferromagnetic coatings due to the Ni phase. XRD results show that the obtained Ni-CrN films consist of a metallic fcc cubic Ni phase mixed with fcc cubic CrN. The lattice parameter decreases with the N2 content and reaches the theoretical value of the pure fcc-Ni, when Cr is mostly removed from the Ni-Cr phase. Dealloying of Cr from a Ni80-Cr20 solid solution is achieved in our experimental conditions and the deposition of Ni ferromagnetic coatings embedding CrN from a non-magnetic target is possible with reactive DC magnetron sputtering.

Induction Plasma Sprayed Nano Hydroxyapatite Coatings on Titanium for Orthopaedic and Dental Implants

PubMed Central

Roy, Mangal; Bandyopadhyay, Amit; Bose, Susmita

2011-01-01

This paper reports preparation of a highly crystalline nano hydroxyapatite (HA) coating on commercially pure titanium (Cp-Ti) using inductively coupled radio frequency (RF) plasma spray and their in vitro and in vivo biological response. HA coatings were prepared on Ti using normal and supersonic plasma nozzles at different plate powers and working distances. X-ray diffraction (XRD) and Fourier transformed infrared spectroscopic (FTIR) analysis show that the normal plasma nozzle lead to increased phase decomposition, high amorphous calcium phosphate (ACP) phase formation, and severe dehydroxylation of HA. In contrast, coatings prepared using supersonic nozzle retained the crystallinity and phase purity of HA due to relatively short exposure time of HA particles in the plasma. In addition, these coatings exhibited a microstructure that varied from porous and glassy structure at the coating-substrate interface to dense HA at the top surface. The microstructural analysis showed that the coating was made of multigrain HA particles of ~200 nm in size, which consisted of recrystallized HA grains in the size range of 15– 20 nm. Apart from the type of nozzle, working distance was also found to have a strong influence on the HA phase decomposition, while plate power had little influence. Depending on the plasma processing conditions, a coating thickness between 300 and 400 μm was achieved where the adhesive bond strengths were found to be between 4.8 MPa to 24 MPa. The cytotoxicity of HA coatings was examined by culturing human fetal osteoblast cells (hFOB) on coated surfaces. In vivo studies, using the cortical defect model in rat femur, evaluated the histological response of the HA coatings prepared with supersonic nozzle. After 2 weeks of implantation, osteoid formation was evident on the HA coated implant surface, which could indicate early implant- tissue integration in vivo. PMID:21552358

Reactive Fabrication and Effect of NbC on Microstructure and Tribological Properties of CrS Co-Based Self-Lubricating Coatings by Laser Cladding

PubMed Central

Fang, Liuyang; Yan, Hua; Yao, Yansong; Zhang, Peilei; Gao, Qiushi; Qin, Yang

2017-01-01

The CrS/NbC Co-based self-lubricating composite coatings were successfully fabricated on Cr12MoV steel surface by laser clad Stellite 6, WS2, and NbC mixed powders. The phase composition, microstructure, and tribological properties of the coatings ware investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS), as well as dry sliding wear testing. Based on the experimental results, it was found reactions between WS2 and Co-based alloy powder had occurred, which generated solid-lubricant phase CrS, and NbC play a key role in improving CrS nuclear and refining microstructure of Co-based composite coating during laser cladding processing. The coatings were mainly composed of γ-Co, CrS, NbC, Cr23C6, and CoCx. Due to the distribution of the relatively hard phase of NbC and the solid lubricating phase CrS, the coatings had better wear resistance. Moreover, the suitable balance of CrS and NbC was favorable for further decreasing the friction and improving the stability of the contact surfaces between the WC ball and the coatings. The microhardness, friction coefficient, and wear rate of the coating 4 (Clad powders composed of 60 wt % Stellite 6, 30 wt % NbC and 10 wt % WS2) were 587.3 HV0.5, 0.426, and 5.61 × 10−5 mm3/N·m, respectively. PMID:29283411

Stress and structure development in polymeric coatings

NASA Astrophysics Data System (ADS)

Vaessen, Diane Melissa

2002-09-01

The main goal of this research is to measure the stress evolution in various polymer coating systems to establish the mechanisms responsible for stress development, stress relaxation, and defect formation. Investigated systems include ultraviolet (UV)-curable coatings, dense and porous coatings from polymer solutions, and latex coatings. Coating stress was measured using a controlled environment stress apparatus based on a cantilever deflection principle. For acrylate coatings, it was found that by cycling a UV-lamp on and off, keeping the total dose constant, coating stress was lowered by 60% by decreasing the cycle period. A stress minimum was also found to exist for a given dose of radiation. The lower stress is attributed to stress relaxation and/or slower reaction during dark periods. A viscoelastic stress model of this process was formulated and predicted stress values close to those observed experimentally. During drying of cellulose acetate (CA) coatings cast in acetone, final stress increased from 10 to 45 MPa as coating thickness decreased from 60 to 10 mum. This thickness dependent coating stress for a solvent-cast polymer coating is a new finding and is attributed to (1) less shrinkage in thicker coatings due to more trapped solvent (from skinning) and (2) greater amounts of polymer stress relaxation in thicker coatings. For porous CA coatings prepared by dry-cast phase separation, final in-plane stresses ranged from 20 MPa for coatings containing small pores (˜1 mum) to 5 MPa for coatings containing small pores and macrovoids (˜200 mum). For these coatings, a small amount of stress relaxation occurs due to capillary pressure relief. A stress plateau for the macrovoid-containing coating is likely caused by stress-induced rupture of the polymer-rich phase. Measured stress in pigment-free latex coatings was much lower (˜0.3 MPa) than UV-curable and solvent-cast polymer coatings and was found to increase with increasing latex glass transition temperature. Observations from infrared spectroscopy, scanning electron microscopy, camera imaging, and indentation were also studied to correlate coating properties to measured stresses. The results obtained in this thesis will lead to strategies for material selection, process optimization, and defect elimination in polymeric coatings.

Estimation of the Friction Coefficient of a Nanostructured Composite Coating

NASA Astrophysics Data System (ADS)

Shil'ko, S. V.; Chernous, D. A.; Ryabchenko, T. V.; Hat'ko, V. V.

2017-11-01

The frictional-mechanical properties of a thin polymer-ceramic coating obtained by gas-phase impregnation of nanoporous anodic alumina with a fluoropolymer (octafluorocyclobutane) have been investigated. The coefficient of sliding friction of the coating is predicted based on an analysis of contact deformation within the framework of the Winkler elastic foundation hypothesis and a three-phase micromechanical model. It is shown that an acceptable prediction accuracy can be obtained considering the uniaxial strain state of the coating. It was found that, on impregnation by the method of plasmachemical treatment, the relative depth of penetration of the polymer increased almost in proportion to the processing time. The rate and maximum possible depth of penetration of the polymer into nanoscale pores grew with increasing porosity of the alumina substrate.

Modified Surface Having Low Adhesion Properties to Mitigate Insect Residue Adhesion

NASA Technical Reports Server (NTRS)

Wohl, Christopher J., Jr. (Inventor); Smith, Joseph G., Jr. (Inventor); Siochi, Emilie J. (Inventor); Penner, Ronald K. (Inventor)

2016-01-01

A process to modify a surface to provide reduced adhesion surface properties to mitigate insect residue adhesion. The surface may include the surface of an article including an aircraft, an automobile, a marine vessel, all-terrain vehicle, wind turbine, helmet, etc. The process includes topographically and chemically modifying the surface by applying a coating comprising a particulate matter, or by applying a coating and also topographically modifying the surface by various methods, including but not limited to, lithographic patterning, laser ablation and chemical etching, physical vapor phase deposition, chemical vapor phase deposition, crystal growth, electrochemical deposition, spin casting, and film casting.

Microstructure and Mechanical Properties of Zn-Ni-Al2O3 Composite Coatings

PubMed Central

Bai, Yang; Wang, Zhenhua; Li, Xiangbo; Huang, Guosheng; Li, Caixia

2018-01-01

Zn-Ni-Al2O3 composite coatings with different Ni contents were fabricated by low-pressure cold spray (LPCS) technology. The effects of the Ni content on the microstructural and mechanical properties of the coatings were investigated. According to X-ray diffraction patterns, the composite coatings were primarily composed of metallic-phase Zn and Ni and ceramic-phase Al2O3. The energy-dispersive spectroscopy results show that the Al2O3 content of the composite coatings gradually decreased with increasing of Ni content. The cross-sectional morphology revealed thick, dense coatings with a wave-like stacking structure. The process of depositing Zn and Ni particles and Al2O3 particles by the LPCS method was examined, and the deposition mechanism was demonstrated to be mechanical interlocking. The bond strength, micro hardness and friction coefficient of the coatings did not obviously change when the Ni content varied. The presence of Al2O3 and Ni increased the wear resistance of the composite coatings, which was higher than that of pure Zn coatings, and the wear mechanism was abrasive and adhesive wear. PMID:29883391

Correlating the properties of different carioca bean cultivars (Phaseolus vulgaris) with their hydration kinetics.

PubMed

Miano, Alberto Claudio; Saldaña, Erick; Campestrini, Luciano Henrique; Chiorato, Alisson Fernando; Augusto, Pedro Esteves Duarte

2018-05-01

This work explained how the intrinsic properties of beans affects the hydration process. For that, different properties of six cultivars of carioca bean (a variety of common bean) were analyzed to verify the correlation with their hydration kinetics characteristics (hydration rate, lag phase time and equilibrium moisture content), using a Multiple Factorial Analysis (MFA): the chemical composition (starch, protein, lipids, minerals (Mg, P, S, K, Ca, Mn, Fe, Cu, Zn), functional groups from the seed coat analyzed by FT-IR), physical properties (size, 1000 grain weight, seed coat thickness, energy to penetrate the bean) and microstructure. Only few properties correlated with the hydration kinetics characteristics of the studied bean, comprising both composition and structure. The fat content, potassium content, specific surface, and the protein to lipids ratio correlated with the lag phase time, which is related with the seed coat impermeability to water. The necessary energy to perforate the seed coat correlated negatively with the hydration rate. It was concluded that the hydration of beans process is a complex phenomenon and that despite being from the same variety of legume, any change due to agronomic enhancement may affect their hydration process kinetics. Copyright © 2018 Elsevier Ltd. All rights reserved.

Processing - microstructure relationships of chemically vapor deposited zirconia fiber coating for environmentally durable silicon carbide/silicon carbide composites

NASA Astrophysics Data System (ADS)

Lee, Jinil

In SiC/SiC ceramic matrix composites, toughness is obtained by adding a fiber coating which provides a weak interface for crack deflection and debonding between the fiber and the matrix. However, the most commonly used fiber coatings, carbon and boron nitride, are unstable in oxidative environments. In the present study, the feasibility of using a chemically vapor deposited zirconia (CVD-ZrO 2) fiber coating as an oxidation-resistant interphase for SiC/SiC composites was investigated. The feasibility of the CVD-ZrO2 coating as a useful interphase for SiC/SiC composites was investigated with emphasis on developing critical processing-microstructure relationships. A study of morphological evolution in the CVD-ZrO2 coating suggested that a size-controlled displacive phase transformation from tetragonal ZrO2 (t-ZrO2) to monoclinic ZrO2 (m-ZrO2) was the key mechanism responsible for the weak interface behavior exhibited by the ZrO2 coating. The pre-delamination occurred as a result of (i) continuous formation of t-ZrO2 nuclei on the deposition surface; (ii) martensitic transformation of the tetragonal phase to a monoclinic phase upon reaching a critical grain size; and (iii) development of significant compressive hoop stresses due to the volume dilation associated with the transformation. We also discovered that low oxygen partial pressure in the CVD reactor was required for the nucleation of t-ZrO2 and was ultimately responsible for the delamination behavior. The effects of oxygen partial pressure on the nucleation behavior of the CVD-ZrO2 coating was systematically studied by intentionally adding the controlled amount of O2 into the CVD chamber. Characterization results suggested that the number density of t-ZrO2 nuclei apparently decreased with increasing the oxygen partial pressure from 0.004 to 1.6 Pa. Also, the coating layer became more columnar and contained larger m-ZrO2 grains. The observed relationships between the oxygen partial pressure and the morphological characteristics of the ZrO 2 coating were explained in the context of the grain size and oxygen deficiency effects which have been previously reported to cause the stabilization of the t-ZrO2 phase in bulk ZrO2 specimens.

Biomedical coatings on magnesium alloys - a review.

PubMed

Hornberger, H; Virtanen, S; Boccaccini, A R

2012-07-01

This review comprehensively covers research carried out in the field of degradable coatings on Mg and Mg alloys for biomedical applications. Several coating methods are discussed, which can be divided, based on the specific processing techniques used, into conversion and deposition coatings. The literature review revealed that in most cases coatings increase the corrosion resistance of Mg and Mg alloys. The critical factors determining coating performance, such as corrosion rate, surface chemistry, adhesion and coating morphology, are identified and discussed. The analysis of the literature showed that many studies have focused on calcium phosphate coatings produced either using conversion or deposition methods which were developed for orthopaedic applications. However, the control of phases and the formation of cracks still appear unsatisfactory. More research and development is needed in the case of biodegradable organic based coatings to generate reproducible and relevant data. In addition to biocompatibility, the mechanical properties of the coatings are also relevant, and the development of appropriate methods to study the corrosion process in detail and in the long term remains an important area of research. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Initiated Chemical Vapor Deposition (iCVD) of Highly Cross-Linked Polymer Films for Advanced Lithium-Ion Battery Separators.

PubMed

Yoo, Youngmin; Kim, Byung Gon; Pak, Kwanyong; Han, Sung Jae; Song, Heon-Sik; Choi, Jang Wook; Im, Sung Gap

2015-08-26

We report an initiated chemical vapor deposition (iCVD) process to coat polyethylene (PE) separators in Li-ion batteries with a highly cross-linked, mechanically strong polymer, namely, polyhexavinyldisiloxane (pHVDS). The highly cross-linked but ultrathin pHVDS films can only be obtained by a vapor-phase process, because the pHVDS is insoluble in most solvents and thus infeasible with conventional solution-based methods. Moreover, even after the pHVDS coating, the initial porous structure of the separator is well preserved owing to the conformal vapor-phase deposition. The coating thickness is delicately controlled by deposition time to the level that the pore size decreases to below 7% compared to the original dimension. The pHVDS-coated PE shows substantially improved thermal stability and electrolyte wettability. After incubation at 140 °C for 30 min, the pHVDS-coated PE causes only a 12% areal shrinkage (versus 90% of the pristine separator). The superior wettability results in increased electrolyte uptake and ionic conductivity, leading to significantly improved rate performance. The current approach is applicable to a wide range of porous polymeric separators that suffer from thermal shrinkage and poor electrolyte wetting.

A study of the physical, chemical and biological properties of TiO2 coatings produced by micro-arc oxidation in a Ca-P-based electrolyte.

PubMed

dos Santos, Amanda; Araujo, Joyce R; Landi, Sandra M; Kuznetsov, Alexei; Granjeiro, José M; de Sena, Lidia Ágata; Achete, Carlos Alberto

2014-07-01

In this work, a porous and homogeneous titanium dioxide layer was grown on commercially pure titanium substrate using a micro-arc oxidation (MAO) process and Ca-P-based electrolyte. The structure and morphology of the TiO2 coatings were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy, and profilometry. The chemical properties were studied using electron dispersive X-ray spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy. The wettability of the coating was evaluated using contact angle measurements. During the MAO process, Ca and P ions were incorporated into the oxide layer. The TiO2 coating was composed of a mixture of crystalline and amorphous structures. The crystalline part of the sample consisted of a major anatase phase and a minor rutile phase. A cross-sectional image of the coating-substrate interface reveals the presence of voids elongated along the interface. An osteoblast culture was performed to verify the cytocompatibility of the anodized surface. The results of the cytotoxicity tests show satisfactory cell viability of the titanium dioxide films produced in this study.

Advanced Microstructural Study of Suspension Plasma Sprayed Hydroxyapatite Coatings

NASA Astrophysics Data System (ADS)

Podlesak, Harry; Pawlowski, Lech; D'Haese, Romain; Laureyns, Jacky; Lampke, Thomas; Bellayer, Severine

2010-03-01

Fine, home-synthesized, hydroxyapatite powder was formulated with water and alcohol to obtain a suspension used to plasma spray coatings onto a titanium substrate. The deposition process was optimized using statistical design of 2 n experiments with two variables: spray distance and electric power input to plasma. X-ray diffraction (XRD) was used to determine quantitatively the phase composition of obtained deposits. Raman microscopy and electron probe microanalysis (EPMA) enabled localization of the phases in different positions of the coating cross sections. Transmission electron microscopic (TEM) study associated with energy-dispersive x-ray spectroscopy (EDS) enabled visualization and analysis of a two-zone microstructure. One zone contained crystals of hydroxyapatite, tetracalcium phosphate, and a phase rich in calcium oxide. This zone included lamellas, usually observed in thermally sprayed coatings. The other zone contained fine hydroxyapatite grains that correspond to nanometric and submicrometric solids from the suspension that were agglomerated and sintered in the cold regions of plasma jet and on the substrate.

Effect of the Platinum Electroplated Layer Thickness on the Coatings' Microstructure

NASA Astrophysics Data System (ADS)

Zagula-Yavorska, Maryana; Gancarczyk, Kamil; Sieniawski, Jan

2017-03-01

CMSX 4 and Inconel 625 superalloys were coated by platinum layers (3 and 7 μm thick) in the electroplating process. The heat treatment of platinum layers (at 1,050 ˚C for 2 h) was performed to increase platinum adherence to the superalloys substrate. The diffusion zone obtained on CMSX 4 superalloy (3 and 7 μm platinum thick before heat treatment) consisted of two phases: γ-Ni(Al, Cr) and (Al0.25Pt0.75)Ni3. The diffusion zone obtained on Inconel 625 superalloy (3 μm platinum thick before heat treatment) consisted of the α-Pt(Ni, Cr, Al) phase. Moreover, γ-Ni(Cr, Al) phase was identified. The X-ray diffraction (XRD) results revealed the presence of platinum in the diffusion zone of the heat-treated coating (7 μm platinum thick) on Inconel 625 superalloy. The surface roughness parameter Ra of heat-treated coatings increased with the increase of platinum layers thickness. This was due to the unequal mass flow of platinum and nickel.

A review on development of solid phase microextraction fibers by sol-gel methods and their applications.

PubMed

Kumar, Ashwini; Gaurav; Malik, Ashok Kumar; Tewary, Dhananjay Kumar; Singh, Baldev

2008-03-03

Solid phase microextraction (SPME) is an innovative, solvent free technology that is fast, economical and versatile. SPME is a fiber coated with a liquid (polymer), a solid (sorbent) or a combination of both. The fiber coating takes up the compounds from the sample by absorption in the case of liquid coatings or adsorption in the case of solid coatings. The SPME fiber is then transferred with the help of a syringe like device into the analytical instrument for desorption and analysis of the target analytes. The sol-gel process provides a versatile method to prepare size, shape and charge selective materials of high purity and homogeneity by means of preparation techniques different from the traditional ones, for the chemical analysis. This review is on the current state of the art and future trends in the developments of solid phase microextraction (SPME) fibers using sol-gel method. To achieve more selective determination of different compound classes, the variety of different coating material for SPME fibers has increased. Further developments in SPME as a highly efficient extraction technique, will greatly depend on new breakthroughs in the area of new coating material developments for the SPME fibers. In sol-gel approach, appropriate sol-gel precursors and other building blocks can be selected to create a stationary phase with desired structural and surface properties. This approach is efficient in integrating the advantageous properties of organic and inorganic material systems and thereby increasing and improving the extraction selectivity of the produced amalgam organic-inorganic stationary phases. This review is mainly focused on recent advanced developments in the design, synthesis, characterisation, properties and application of sol-gel in preparation of coatings for the SPME fibers.

Plasma-Sprayed High Entropy Alloys: Microstructure and Properties of AlCoCrFeNi and MnCoCrFeNi

NASA Astrophysics Data System (ADS)

Ang, Andrew Siao Ming; Berndt, Christopher C.; Sesso, Mitchell L.; Anupam, Ameey; S, Praveen; Kottada, Ravi Sankar; Murty, B. S.

2015-02-01

High entropy alloys (HEAs) represent a new class of materials that present novel phase structures and properties. Apart from bulk material consolidation methods such as casting and sintering, HEAs can also be deposited as a surface coating. In this work, thermal sprayed HEA coatings are investigated that may be used as an alternative bond coat material for a thermal barrier coating system. Nanostructured HEAs that were based on AlCoCrFeNi and MnCoCrFeNi were prepared by ball milling and then plasma sprayed. Splat studies were assessed to optimise the appropriate thermal spray parameters and spray deposits were prepared. After mechanical alloying, aluminum-based and manganese-based HEA powders revealed contrary prominences of BCC and FCC phases in their X-ray diffraction patterns. However, FCC phase was observed as the major phase present in both of the plasma-sprayed AlCoCrFeNi and MnCoCrFeNi coatings. There were also minor oxide peaks detected, which can be attributed to the high temperature processing. The measured porosity levels for AlCoCrFeNi and MnCoCrFeNi coatings were 9.5 ± 2.3 and 7.4 ± 1.3 pct, respectively. Three distinct phase contrasts, dark gray, light gray and white, were observed in the SEM images, with the white regions corresponding to retained multicomponent HEAs. The Vickers hardness (HV0.3kgf) was 4.13 ± 0.43 and 4.42 ± 0.60 GPa for AlCoCrFeNi and MnCoCrFeNi, respectively. Both type of HEAs coatings exhibited anisotropic mechanical behavior due to their lamellar, composite-type microstructure.

Investigation on the relationship between NbC and wear-resistance of Fe matrix composite coatings with different C contents

NASA Astrophysics Data System (ADS)

Zhao, Changchun; Zhou, Yefei; Xing, Xiaolei; Liu, Sha; Ren, Xuejun; Yang, Qingxiang

2018-05-01

The wear resistance of Fe-based composite coating is significantly related with the character of carbides and matrix, which could be strongly affected by C content in it. In this work, the Fe-based composite coatings with different C contents were prepared. The microstructure and phase structure of the coatings were analyzed by scanning electron microscope (SEM) equipped with an energy-dispersive spectroscopy (EDS) and X-ray diffractometer (XRD). The hardness and wear resistance of the coatings were determined. Then the hardness and brittleness of carbon poor niobium carbides were calculated by first principles calculation. The results show that, the phase structures of the coatings are mainly composed of NbC, γ phase (retained austenite) and α phase (martensite). With the increase of C content, the retained austenite appears and C content of martensite is increased. The hardness of the coatings are increased from HRC 22 to HRC 59. The distribution and morphology of NbC are changed with the increase of C content. The NbC precipitated in reticular grain boundary can be observed when C content is 0.4 wt.% C (C-1). NbC turn into granular and small rod morphology when C content increases to 0.8 wt.% C (C-2). The cracks and defects cannot been found on the surface of the coating when C content is 1.2 wt.% C(C-3), whose hardness is HRC 58 and wear loss is 0.27 g/N cm2 in 8 h. The flaky M7C3 carbide precipitates on the coating when C content is 1.4 wt.% C(C-4), which weaken the wear resistance of the matrix. Compared with the hardfacing coatings with different C contents, the C-3 coating processes higher hardness and wear resistance.

Influence of polymer coating morphology on microsensor response

NASA Astrophysics Data System (ADS)

Levit, Natalia; Pestov, Dmitry; Tepper, Gary C.

2004-03-01

Nanoscale polymeric coatings are used in a variety of sensor systems. The influence of polymer coating morphology on sensor response was investigated and it was determined that coating morphology plays a particularly important role in transducers based on optical or acoustic resonance such as surface acoustic wave (SAW) or surface plasmon resonance (SPR) devices. Nanoscale polymeric coatings were deposited onto a number of miniature devices using a "solvent-free" deposition technique known as Rapid Expansion of Supercritical Solutions (RESS). In RESS, the supercritical solvent goes into the vapor phase upon fast depressurization and separates from the polymer. Therefore, dry polymer particles are deposited from the gas phase. The average diameter of RESS precipitates is about two orders of magnitude smaller than the minimum droplet size achievable by the air-brush method. For rubbery polymers, such as PIB and PDMS, the nanoscale solute droplets produced by RESS agglomerate on the surface forming a highly-uniform continuous nanoscale film. For glassy and crstalline polymers, the RESS droplets produce uniform particulate coatings exhibiting high surface-to-volume ratio. The coating morphology can be changed by controlling the RESS processing conditions.

Combined synthesis and in situ coating of nanoparticles in the gas phase

NASA Astrophysics Data System (ADS)

Lähde, Anna; Raula, Janne; Kauppinen, Esko I.

2008-12-01

Combined gas phase synthesis and coating of sodium chloride (NaCl) and lactose nanoparticles has been developed using an aerosol flow reactor. Nano-sized core particles were produced by the droplet-to-particle method and coated in situ by the physical vapour deposition of L-leucine vapour. The saturation of L-leucine in the reactor determined the resulting particle size and size distribution. In general, particle size increased with the addition of L-leucine and notable narrowing of the core particle size distribution was observed. In addition, homogeneous nucleation of the vapour, i.e. formation of pure L-leucine particles, was observed depending on the saturation conditions of L-leucine as well as the core particle characteristics. The effects of core particle properties, i.e. size and solid-state characteristics, on the coating process were studied by comparing the results for coated NaCl and lactose particles. During deposition, L-leucine formed a uniform coating on the surface of the core particles. The coating stabilised the nanoparticles and prevented the sintering of particles during storage.

Plasma Spraying of Ceramics with Particular Difficulties in Processing

NASA Astrophysics Data System (ADS)

Mauer, G.; Schlegel, N.; Guignard, A.; Jarligo, M. O.; Rezanka, S.; Hospach, A.; Vaßen, R.

2015-01-01

Emerging new applications and growing demands of plasma-sprayed coatings initiate the development of new materials. Regarding ceramics, often complex compositions are employed to achieve advanced material properties, e.g., high thermal stability, low thermal conductivity, high electronic and ionic conductivity as well as specific thermo-mechanical properties and microstructures. Such materials however, often involve particular difficulties in processing by plasma spraying. The inhomogeneous dissociation and evaporation behavior of individual constituents can lead to changes of the chemical composition and the formation of secondary phases in the deposited coatings. Hence, undesired effects on the coating characteristics are encountered. In this work, examples of such challenging materials are investigated, namely pyrochlores applied for thermal barrier coatings as well as perovskites for gas separation membranes. In particular, new plasma spray processes like suspension plasma spraying and plasma spray-physical vapor deposition are considered. In some cases, plasma diagnostics are applied to analyze the processing conditions.

Calcium phosphate coatings modified with zinc- or copper- incorporation on Ti-40Nb alloy

NASA Astrophysics Data System (ADS)

Komarova, E. G.; Sedelnikova, M. B.; Sharkeev, Yu P.; Kazakbaeva, A. A.; Glukhov, I. A.; Khimich, M. A.

2017-05-01

The influence of the microarc oxidation parameters and electrolyte composition on the structure, properties and composition of CaP coatings modified with Zn- or Cu- incorporation on the Ti-40mas.%Nb (Ti-40Nb) alloy was investigated. The linear growth of thickness, roughness, and size of structural elements with process voltage increasing has been revealed. It was shown that the CaP coatings have the low contact angles with liquids and, consequently, high free surface energy. This indicates a high hydrophilicity of the coatings. X-ray diffraction analysis showed that the coatings have X-ray amorphous structure. The increase of the process voltage leads to the formation of such crystalline phases as CaHPO4 and β-Ca2P2O7 in the coatings. The maximum Ca/P atomic ratio was equal to 0.4, and Zn or Cu contents was equal to 0.3 or 0.2 at.%, respectively.

Characterization of in situ synthesized TiB 2 reinforcements in iron-based composite coating

NASA Astrophysics Data System (ADS)

Zhang, Panpan; Wang, Xibao; Guo, Lijie; Cai, Lijuan; Sun, Hongling

2011-12-01

TiB2 reinforced iron-based composite coatings can be fabricated on the mild steel substrate with a powder mixture of Ti and B4C by plasma transferred arc (PTA) powder surfacing process. Characterizations of the TiB2 reinforcements in the coated surface were investigated in this paper. The experimental work enables the following findings to be obtained: (i) acicular shaped and blocky formed TiB2 phases could be synthesized in situ using PTA powder surfacing process in the iron-based composite coating. (ii) Gradient distributions of TiB2 reinforcements appeared in the composite coating from both the vertical and horizontal direction of the coating's cross-section. Significant changes of the size, shape and volume fraction for TiB2 particles appeared in different regions of the surface coating, due to the effects of the dilution rate and mass density. (iii) Values of coating dilution could have profound impacts on the characterization of TiB2 reinforcements in the coated surfaces. With the increase of coating dilution, TiB2 grain tends to be acicular shaped at the edge of the surface coating, while it remains to be granular formed in the center of the composite coating.

Ultrasonic semi-solid coating soldering 6061 aluminum alloys with Sn-Pb-Zn alloys.

PubMed

Yu, Xin-ye; Xing, Wen-qing; Ding, Min

2016-07-01

In this paper, 6061 aluminum alloys were soldered without a flux by the ultrasonic semi-solid coating soldering at a low temperature. According to the analyses, it could be obtained that the following results. The effect of ultrasound on the coating which promoted processes of metallurgical reaction between the components of the solder and 6061 aluminum alloys due to the thermal effect. Al2Zn3 was obtained near the interface. When the solder was in semi-solid state, the connection was completed. Ultimately, the interlayer mainly composed of three kinds of microstructure zones: α-Pb solid solution phases, β-Sn phases and Sn-Pb eutectic phases. The strength of the joints was improved significantly with the minimum shear strength approaching 101MPa. Copyright © 2016. Published by Elsevier B.V.

Aluminide coatings for nickel base alloys

NASA Technical Reports Server (NTRS)

Fiedler, H. C.; Sieraski, R. J.

1971-01-01

The metalliding process was used to aluminide IN-100 and TD NiCr. Aluminum was deposited over a broad range of deposition rates, with two types of coating structures resulting. Chromium, silicon, titanium and yttrium were also individually deposited simutaneously with aluminum on IN-100. None of these had a marked effect on the oxidation resistance of the aluminide coating. Porosity-free aluminide coatings with good oxidation resistance were formed on TD NiCr providing the aluminum concentration did not exceed 8 percent, the limit of solubility in the gamma phase.

Preparation of YBa2Cu3O7 High Tc Superconducting Coatings by Plasma Spraying

NASA Astrophysics Data System (ADS)

Danroc, J.; Lacombe, J.

The following sections are included: * INTRODUCTION * THE COMPOUND YBa2Cu3O7-δ * Structure * Critical temperature * Critical current density * Phase equilibria in the YBaCuO system * PREPARATION OF YBa2Cu3O7 COATINGS * General organisation of the preparation process * The powder * Hot plasma spraying of YBa2Cu3O7 * The post-spraying thermal treatment * CHARACTERISTICS OF THE YBa2Cu3O7-δ COATINGS * Chemical composition * Crystalline structure * Morphology of the coatings * Electrical and magnetic characteristics * Conclusion * REFERENCES

DMF as an Additive in a Two-Step Spin-Coating Method for 20% Conversion Efficiency in Perovskite Solar Cells.

PubMed

Wu, Jionghua; Xu, Xin; Zhao, Yanhong; Shi, Jiangjian; Xu, Yuzhuan; Luo, Yanhong; Li, Dongmei; Wu, Huijue; Meng, Qingbo

2017-08-16

DMF as an additive has been employed in FAI/MAI/IPA (FA= CH 2 (NH 2 ) 2 , MA = CH 3 NH 3 , IPA = isopropanol) solution for a two-step multicycle spin-coating method in order to prepare high-quality FA x MA 1-x PbI 2.55 Br 0.45 perovskite films. Further investigation reveals that the existence of DMF in the FAI/MAI/IPA solution can facilitate perovskite conversion, improve the film morphology, and reduce crystal defects, thus enhancing charge-transfer efficiency. By optimization of the DMF amount and spin-coating cycles, compact, pinhole-free perovskite films are obtained. The nucleation mechanisms of perovskite films in our multicycle spin-coating process are suggested; that is, the introduction of DMF in the spin-coating FAI/MAI/IPA solution can lead to the formation of an amorphous phase PbX 2 -AI-DMSO-DMF (X = I, Br; A = FA, MA) instead of intermediate phase (MA) 2 Pb 3 I 8 ·2DMSO. This amorphous phase, similar to that in the one-step method, can help FAI/MAI penetrate into the PbI 2 framework to completely convert into the perovskite. As high as 20.1% power conversion efficiency (PCE) has been achieved with a steady-state PCE of 19.1%. Our work offers a simple repeatable method to prepare high-quality perovskite films for high-performance PSCs and also help further understand the perovskite-crystallization process.

SiAlON COATINGS OF SILICON NITRIDE AND SILICON CARBIDE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jan W. Nowok; John P. Hurley; John P. Kay

2000-06-01

The need for new engineering materials in aerospace applications and in stationary power turbine blades for high-efficiency energy-generating equipment has led to a rapid development of ceramic coatings. They can be tailored to have superior physical (high specific strength and stiffness, enhanced high-temperature performance) and chemical (high-temperature corrosion resistance in more aggressive fuel environments) properties than those of monolithic ceramic materials. Among the major chemical properties of SiAlON-Y ceramics are their good corrosion resistance against aggressive media combined with good thermal shock behavior. The good corrosion resistance results from the yttria-alumina-garnet (YAG), Al{sub 5}Y{sub 3}O{sub 12}, formed during the corrosionmore » process of SiAlON-Y ceramics in combustion gases at 1300 C. The interfacial chemical precipitation of the YAG phase is beneficial. This phase may crystallize in cubic and/or tetragonal modifications and if formed in SiAlON-Y ceramic may simultaneously generate residual stress. Also, this phase can contain a large number of point defects, which is a consequence of the large unit cell and complexity of the YAG structure because it has no close-packed oxygen planes. Therefore, the need exists to elucidate the corrosion mechanism of a multilayered barrier with respect to using SiAlON-YAG as a corrosion-protective coating. Stress corrosion cracking in the grain boundary of a silicon nitride (Si{sub 3}N{sub 4}) ceramic enriched in a glassy phase such as SiAlON can significantly affect its mechanical properties. It has been suggested that the increased resistance of the oxynitride glass to stress corrosion is related to the increased surface potential of the fracture surface created in the more durable and highly cross-linked oxynitride glass network structure. We expect that either increased or decreased surface potential of the intergranular glassy phase is brought about by changes in the residual stress of the SiAlON-Y ceramic and/or creation of a space-charge region at the SiAlON-YAG interface. Both features originate from a secondary phase of YAG formed during the SiAlON-Y glass corrosion process. Conventional oxidation-protection coatings for metallic materials in high-temperature corrosive environments are typically formed by applying a slurry mixture to the surface followed by a high-temperature furnace cure. During the cure, the coating reacts with the alloy to form a layer typically 25 to 50 {micro}m{sup 3} thick. Generally, coating thickness is one critical microstructural parameter that influences its performance; therefore, its optimization is an important aspect of coating technology. The aim of the present research program is (1) to produce a thin SiAlON-YAG ceramic coating with a high quality of interface, (2) to understand the major experimental characteristics for creating a good bonding between a substrate and a thin coating, and (3) to explain why the Al{sub 5}Y{sub 3}O{sub 12} phase increases SiAlON-Y ceramic alkali corrosion resistance. To produce the SiAlON-Y coating on silicon nitride ceramic with a YAG layer, a slurry mixture of SiAlON-Y components was designed. The research program was extended to Y{sub 2}SiO{sub 5} coating to get preliminary information on the Si{sub 3}N{sub 4}-Y{sub 2}SiO{sub 5} interface microstructure. It was expected that this phase would have a very low porosity. Generally, coatings that contain ductile phases such as Y{sub 2}SiO{sub 5} can produce low-porosity coatings.« less

Structure, phases, and mechanical response of Ti-alloy bioactive glass composite coatings.

PubMed

Nelson, G M; Nychka, J A; McDonald, A G

2014-03-01

Porous titanium alloy-bioactive glass composite coatings were manufactured via the flame spray deposition process. The porous coatings, targeted for orthodontic and bone-fixation applications, were made from bioactive glass (45S5) powder blended with either commercially pure titanium (Cp-Ti) or Ti-6Al-4V alloy powder. Two sets of spray conditions, two metallic particle size distributions, and two glass particle size distributions were used for this study. Negative control coatings consisting of pure Ti-6Al-4V alloy or Cp-Ti were sprayed under both conditions. The as-sprayed coatings were characterized through quantitative optical cross-sectional metallography, X-ray diffraction (XRD), and ASTM Standard C633 tensile adhesion testing. Determination of the porosity and glassy phase distribution was achieved by using image analysis in accordance with ASTM Standard E2109. Theoretical thermodynamic and heat transfer modeling was conducted to explain experimental observations. Thermodynamic modeling was performed to estimate the flame temperature and chemical environment for each spray condition and a lumped capacitance heat transfer model was developed to estimate the temperatures attained by each particle. These models were used to establish trends among the choice of alloy, spray condition, and particle size distribution. The deposition parameters, alloy composition, and alteration of the feedstock powder size distribution had a significant effect on the coating microstructure, porosity, phases present, mechanical response, and theoretical particle temperatures that were attained. The most promising coatings were the Ti-6Al-4V-based composite coatings, which had bond strength of 20±2MPa (n=5) and received reinforcement and strengthening from the inclusion of a glassy phase. It was shown that the use of the Ti-6Al-4V-bioactive glass composite coatings may be a superior choice due to the possible osteoproductivity from the bioactive glass, the potential ability to support tissue ingrowth and vascular tissue, and the comparable strength to similar coatings. Copyright © 2013 Elsevier B.V. All rights reserved.

Fabrication and Microstructure of Hydroxyapatite Coatings on Zirconia by Room Temperature Spray Process.

PubMed

Seo, Dong Seok; Chae, Hak Cheol; Lee, Jong Kook

2015-08-01

Hydroxyapatite coatings were fabricated on zirconia substrates by a room temperature spray process and were investigated with regards to their microstructure, composition and dissolution in water. An initial hydroxyapatite powder was prepared by heat treatment of bovine-bone derived powder at 1100 °C for 2 h, while dense zirconia substrates were fabricated by pressing 3Y-TZP powder and sintering it at 1350 °C for 2 h. Room temperature spray coating was performed using a slit nozzle in a low pressure-chamber with a controlled coating time. The phase composition of the resultant hydroxyapatite coatings was similar to that of the starting powder, however, the grain size of the hydroxyapatite particles was reduced to about 100 nm due to their formation by particle impaction and fracture. All areas of the coating had a similar morphology, consisting of reticulated structure with a high surface roughness. The hydroxyapatite coating layer exhibited biostability in a stimulated body fluid, with no severe dissolution being observed during in vitro experimentation.

Oxidation resistant slurry coating for carbon-based materials

NASA Technical Reports Server (NTRS)

Smialek, J. L.; Rybicki, G. C. (Inventor)

1985-01-01

An oxidation resistant coating is produced on carbon-base materials, and the same processing step effects an infiltration of the substrate with silicon containing material. The process comprises making a slurry of nickel and silicon powders in a nitrocellulose lacquer, spraying onto the graphite or carbon-carbon substrate, and sintering in vacuum to form a fused coating that wets and covers the surface as well as penetrates into the pores of the substrate. Optimum wetting and infiltration occurs in the range of Ni-60 w/o Si to Ni-90 w/o Si with deposited thicknesses of 25-100 mg/sq. cm. Sintering temperatures of about 1200 C to about 1400 C are used, depending on the melting point of the specific coating composition. The sintered coating results in Ni-Si intermetallic phases and SiC, both of which are highly oxidation resistant.

Y2O3-MgO Nano-Composite Synthesized by Plasma Spraying and Thermal Decomposition of Solution Precursors

NASA Astrophysics Data System (ADS)

Muoto, Chigozie Kenechukwu

This research aims to identify the key feedstock characteristics and processing conditions to produce Y2O3-MgO composite coatings with high density and hardness using solution precursor plasma spray (SPPS) and suspension plasma spray (SPS) processes, and also, to explore the phenomena involved in the production of homogenized nano-composite powders of this material system by thermal decomposition of solution precursor mixtures. The material system would find potential application in the fabrication of components for optical applications such as transparent windows. It was shown that a lack of major endothermic events during precursor decomposition and the resultant formation of highly dense particles upon pyrolysis are critical precursor characteristics for the deposition of dense and hard Y2O3-MgO coatings by SPPS. Using these principles, a new Y2O3-MgO precursor solution was developed, which yielded a coating with Vickers hardness of 560 Hv. This was a considerable improvement over the hardness of the coatings obtained using conventional solution precursors, which was as low as 110 Hv. In the thermal decomposition synthesis process, binary solution precursor mixtures of: yttrium nitrate (Y[n]) or yttrium acetate (Y[a]), with magnesium nitrate (Mg[n]) or magnesium acetate (Mg[a]) were used in order to study the effects of precursor chemistry on the structural characteristics of the resultant Y2O3-MgO powders. The phase domains were coarse and distributed rather inhomogeneously in the materials obtained from the Y[n]Mg[n] and Y[a]Mg[a] mixtures; finer and more homogeneously-distributed phase domains were obtained for ceramics produced from the Y[a]Mg[n] and Y[n]Mg[a] mixtures. It was established that these phenomena were related to the thermal characteristics for the decomposition of the precursors and their effect on phase separation during oxide crystallization. Addition of ammonium acetate to the Y[n[Mg[n] mixture changed the endothermic process to exothermic and improved the dispersion of the component phases. Two suspension types, made with powders synthesized from the Y[n]Mg[n] and Y[n]Mg[a] precursor mixtures were sprayed by SPS. The densities and hardnesses of the coatings deposited using the two powder types were similar. However, the microstructure of coatings deposited using the Y[n]Mg[a]-synthesized powder exhibited some eutectic configuration which was not observed in the coatings deposited using the Y[n]Mg[n]-synthesized powder.

Opportunities for functional oxides in yttrium oxide-titanium oxide-zirconium oxide system: Applications for novel thermal barrier coatings

NASA Astrophysics Data System (ADS)

Francillon, Wesley

This dissertation is an investigation of materials and processed under consideration for next generation thermal structural oxides with potential applications as thermal barrier coatings; wherein, high temperature stability and mechanical properties affect durability. Two notable next generation materials systems under investigation are pyrochlore and co-doped zirconia oxides. The motivation for this work is based on current limitations of the currently used thermal barrier material of yttria stabilized zirconia (YSZ) deposited by the plasma spray processes. The rapid quenching associated with the plasma spray process, results in a metastable structure that is a non-transformable tetragonal structure in the yttria partially stabilized zirconia system rather than the equilibrium anticipated two phase mixture of cubic and monoclinic phases. It has been shown that this metastable structure offers enhanced toughness and thus durability during thermomechanical cycling from the operating temperatures in excess of 1000C to ambient. However, the metastable oxides are susceptible to partitioning at temperatures greater than 1200C, thus resulting in a transformation of the tetragonal phase oxides. Transformations of the tetragonal prime phase into the parent cubic and tetragonal prime phase result in coating degradation. Several of the emerging oxides are based on rare earth additions to zirconia. However, there is limited information of the high temperature stability of these oxide coatings and more notably these compositions exhibit limited toughness for durable performance. A potential ternary composition based on the YSZ system that offers the ability to tailor the phase structure is based YO1.5-TiO2 -ZrO2. The ternary of YO1.5-TiO2-ZrO 2 has the current TBC composition of seven molar percent yttria stabilized zirconia, pyrochlore phase oxide and zirconia doped with yttria and titania additions (Ti-YSZ). The Ti-YSZ phase field is of interest because at equilibrium it is a single tetragonal phase. Thus, compositions are of single phase tetragonal phase, theoretically, should not undergo high temperature partitioning. Single Tetragonal phase oxides of Ti-YSZ also offer the possibility of enhanced toughness and higher temperature stability akin to those observed in yttria partially stabilized zirconia. Many pyrochlore oxides are under review because they have shown to have lower thermal conductivity than YSZ oxides. This study focused on chemically synthesizing homogeneous starting material compositions in a metastable state (preferably amorphous), following its evolution according to the phase hierarchy under conditions of kinetic constraints. The current equilibrium diagram of YO1.5-TiO2-ZrO 2 is based on theoretical calculations. One of the contributions of this work is the redefined phase fields in YO1.5-TiO2-ZrO 2 based on our experimental results. Investigated compositions were based on tie lines of Y2-xTi2ZrxO7+x/2 and Y2Ti2-yZryO7 representing substitution of Zr4+ for Y3+ and Zr4+ for Ti4+ respectively. More notably, we observed extended metastable phases in pyrochlore and fluorite oxides at low temperature. The significance of this result is that it offers a larger compositional range for investing pyrochlore oxides with associated high temperature phase stability for TBC applications. In tetragonal oxides, our results showed that Ti-YSZ results have slower partitioning kinetics in comparison to YSZ at high temperature. This study also emphasized the deposition of advanced ceramic coatings by plasma spray for tetragonal and pyrochlore systems, compositionally complex functional oxides that may potentially have lower thermal conductivity values compared to current YSZ oxides. Next generation thermal barrier coatings require powders with high chemical purity, chemical homogeneity, controlled particle size/shape and pertinent phase state. Thermal spray offers an avenue to create novel materials and deposits directly from the precursor and compositionally controlled powder feedstock. This study contributed to investigating an unexplored field that offers a variety of opportunities in materials synthesis that would not be possible by conventional methods. Understanding processing-microstructure-property correlations is of considerable importance in thermal spray of functional oxide materials. This thesis demonstrated by radio-frequency thermal spray that the complex pyrochlore oxide Y 2Ti2O7 could be deposited by directly injecting molecularly mixed precursors to form oxide coatings. Structural analysis revealed the metastable fluorite phase; however, with thermal treatments at relatively low temperature of 700°C the pyrochlore phase was obtained. For Ti-YSZ coatings, the tetragonal phase oxides were obtained with unique microstructures, however, the tetragonal prime destabilized at 1200°C. This dissertation explored novel oxide compositions through detailed structural analysis. The approach presented a comprehensive and integrated investigation as it pertains to phase evolution of oxides in powder feedstock to coating characteristics (phase/properties).

Nanoscale Reinforced, Polymer Derived Ceramic Matrix Coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajendra Bordia

The goal of this project was to explore and develop a novel class of nanoscale reinforced ceramic coatings for high temperature (600-1000 C) corrosion protection of metallic components in a coal-fired environment. It was focused on developing coatings that are easy to process and low cost. The approach was to use high-yield preceramic polymers loaded with nano-size fillers. The complex interplay of the particles in the polymer, their role in controlling shrinkage and phase evolution during thermal treatment, resulting densification and microstructural evolution, mechanical properties and effectiveness as corrosion protection coatings were investigated. Fe-and Ni-based alloys currently used in coal-firedmore » environments do not possess the requisite corrosion and oxidation resistance for next generation of advanced power systems. One example of this is the power plants that use ultra supercritical steam as the working fluid. The increase in thermal efficiency of the plant and decrease in pollutant emissions are only possible by changing the properties of steam from supercritical to ultra supercritical. However, the conditions, 650 C and 34.5 MPa, are too severe and result in higher rate of corrosion due to higher metal temperatures. Coating the metallic components with ceramics that are resistant to corrosion, oxidation and erosion, is an economical and immediate solution to this problem. Good high temperature corrosion protection ceramic coatings for metallic structures must have a set of properties that are difficult to achieve using established processing techniques. The required properties include ease of coating complex shapes, low processing temperatures, thermal expansion match with metallic structures and good mechanical and chemical properties. Nanoscale reinforced composite coatings in which the matrix is derived from preceramic polymers have the potential to meet these requirements. The research was focused on developing suitable material systems and processing techniques for these coatings. In addition, we investigated the effect of microstructure on the mechanical properties and oxidation protection ability of the coatings. Coatings were developed to provide oxidation protection to both ferritic and austentic alloys and Ni-based alloys. The coatings that we developed are based on low viscosity pre-ceramic polymers. Thus they can be easily applied to any shape by using a variety of techniques including dip-coating, spray-coating and painting. The polymers are loaded with a variety of nanoparticles. The nanoparticles have two primary roles: control of the final composition and phases (and hence the properties); and control of the shrinkage during thermal decomposition of the polymer. Thus the selection of the nanoparticles was the most critical aspect of this project. Based on the results of the processing studies, the performance of selected coatings in oxidizing conditions (both static and cyclic) was investigated.« less

Thermal Annealing Effect on Optical Properties of Binary TiO₂-SiO₂ Sol-Gel Coatings.

PubMed

Wang, Xiaodong; Wu, Guangming; Zhou, Bin; Shen, Jun

2012-12-24

TiO₂-SiO₂ binary coatings were deposited by a sol-gel dip-coating method using tetrabutyl titanate and tetraethyl orthosilicate as precursors. The structure and chemical composition of the coatings annealed at different temperatures were analyzed by Raman spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy. The refractive indices of the coatings were calculated from the measured transmittance and reflectance spectra. An increase in refractive index with the high temperature thermal annealing process was observed. The Raman and FTIR results indicate that the refractive index variation is due to changes in the removal of the organic component, phase separation and the crystal structure of the binary coatings.

Influence of process parameters on the content of biomimetic calcium phosphate coating on titanium: a Taguchi analysis.

PubMed

Thammarakcharoen, Faungchat; Suvannapruk, Waraporn; Suwanprateeb, Jintamai

2014-10-01

In this study, a statistical design of experimental methodology based on Taguchi orthogonal design has been used to study the effect of various processing parameters on the amount of calcium phosphate coating produced by such technique. Seven control factors with three levels each including sodium hydroxide concentration, pretreatment temperature, pretreatment time, cleaning method, coating time, coating temperature and surface area to solution volume ratio were studied. X-ray diffraction revealed that all the coatings consisted of the mixture of octacalcium phosphate (OCP) and hydroxyapatite (HA) and the presence of each phase depended on the process conditions used. Various content and size (-1-100 μm) of isolated spheroid particles with nanosized plate-like morphology deposited on the titanium surface or a continuous layer of plate-like nanocrystals having the plate thickness in the range of -100-300 nm and the plate width in the range of 3-8 μm were formed depending on the process conditions employed. The optimum condition of using sodium hydroxide concentration of 1 M, pretreatment temperature of 70 degrees C, pretreatment time of 24 h, cleaning by ultrasonic, coating time of 6 h, coating temperature of 50 degrees C and surface area to solution volume ratio of 32.74 for producing the greatest amount of the coating formed on the titanium surface was predicted and validated. In addition, coating temperature was found to be the dominant factor with the greatest contribution to the coating formation while coating time and cleaning method were significant factors. Other factors had negligible effects on the coating performance.

Static adsorptive coating of poly(methyl methacrylate) microfluidic chips for extended usage in DNA separations.

PubMed

Du, Xiao-Guang; Fang, Zhao-Lun

2005-12-01

A simple and robust static adsorptive (dynamic) coating process using 2% hydroxyethylcellulose was developed for surface modification of poly(methyl methacrylate) (PMMA) microfluidic chips for DNA separations, suitable for usage over extended periods, involving hundreds of runs. The coating medium was also used as a sieving matrix for the DNA separations following the coating process. Four consecutive static treatments, by simply filling the PMMA chip channels with sieving matrix once every day, were required for obtaining a stable coating and optimum performance. The performance of the coated chips at different phases of the coating process was studied by consecutive gel electrophoretic separations with LIF detection using a PhiX-174/HaeIII DNA digest sample. The coated chip, with daily renewal of the sieving matrix, showed high stability in performance during a 25-day period of systematic study, involving more than 100 individual runs. The performance of the coated chip also remained almost the same after 3 months of continuous usage, during which over 200 separations were performed. The average precision of migration time for the 603-bp fragment was 1.31% RSD (n = 6) during the 25-day study, with a separation efficiency of 6.5 x 10(4) plates (effective separation length 5.4 cm).

Thermal Spray Deposition, Phase Stability and Mechanical Properties of La2Zr2O7/LaAlO3 Coatings

NASA Astrophysics Data System (ADS)

Lozano-Mandujano, D.; Poblano-Salas, C. A.; Ruiz-Luna, H.; Esparza-Esparza, B.; Giraldo-Betancur, A. L.; Alvarado-Orozco, J. M.; Trápaga-Martínez, L. G.; Muñoz-Saldaña, J.

2017-08-01

This paper deals with the deposition of La2Zr2O7 (LZO) and LaAlO3 (LAO) mixtures by air plasma spray (APS). The raw material for thermal spray, single phase LZO and LAO in a 70:30 mol.% ratio mixture was prepared from commercial metallic oxides by high-energy ball milling (HEBM) and high-temperature solid-state reaction. The HEBM synthesis route, followed by a spray-drying process, successfully produced spherical agglomerates with adequate size distribution and powder-flow properties for feeding an APS system. The as-sprayed coating consisted mainly of a crystalline LZO matrix and partially crystalline LAO, which resulted from the high cooling rate experienced by the molten particles as they impact the substrate. The coatings were annealed at 1100 °C to promote recrystallization of the LAO phase. The reduced elastic modulus and hardness, measured by nanoindentation, increased from 124.1 to 174.7 GPa and from 11.3 to 14.4 GPa, respectively, after the annealing treatment. These values are higher than those reported for YSZ coatings; however, the fracture toughness ( K IC) of the annealed coating was only 1.04 MPa m0.5.

Microencapsulation and Electrostatic Processing Method

NASA Technical Reports Server (NTRS)

Morrison, Dennis R. (Inventor); Mosier, Benjamin (Inventor)

2000-01-01

Methods are provided for forming spherical multilamellar microcapsules having alternating hydrophilic and hydrophobic liquid layers, surrounded by flexible, semi-permeable hydrophobic or hydrophilic outer membranes which can be tailored specifically to control the diffusion rate. The methods of the invention rely on low shear mixing and liquid-liquid diffusion process and are particularly well suited for forming microcapsules containing both hydrophilic and hydrophobic drugs. These methods can be carried out in the absence of gravity and do not rely on density-driven phase separation, mechanical mixing or solvent evaporation phases. The methods include the process of forming, washing and filtering microcapsules. In addition, the methods contemplate coating microcapsules with ancillary coatings using an electrostatic field and free fluid electrophoresis of the microcapsules. The microcapsules produced by such methods are particularly useful in the delivery of pharmaceutical compositions.

Microstructural Characteristics and Oxidation Behavior of Low-Pressure Cold-Sprayed CoNiCrAlY Coatings

NASA Astrophysics Data System (ADS)

Zhang, Lin-wei; Lu, Lei; Wang, Lu; Ning, Xian-jin; Wang, Quan-sheng; Wang, Ri-xin

2017-10-01

CoNiCrAlY coatings were deposited by low-pressure cold spraying and subsequently heat-treated at 1050 °C for 4 h in a vacuum environment. The microstructural characteristics and oxidation behavior of CoNiCrAlY coatings were investigated. The as-sprayed coating exhibited low porosity and oxygen content. The high plastic deformation of the sprayed particles led to significant refinement of γ-matrix and dissolution of β-(Ni,Co)Al phase in the as-sprayed coating. After heat treatment, the single phase (γ) in the as-sprayed coating was converted into a γ/β microstructure, and a continuous single α-Al2O3 scale was formed on the coating surface. Vacuum heat treatment can postpone the formation of spinel oxides within 100 h. After being oxidized at 1050 °C for 400 h, the heat-treated coating exhibited better oxidation resistance than the as-sprayed coating. The reduced growth rate of the oxide scale and the suppression of the formation of spinel oxides can be attributed to the vacuum heat treatment, as well as the intrinsic microstructure of the cold-sprayed coating. Finally, the effects of the microstructural changes induced during the cold spraying process on the growth of the thermally grown oxide and the oxidation mechanisms of the CoNiCrAlY coatings were discussed.

Tribological Properties of TiO2/SiO2 Double Layer Coatings Deposited on CP-Ti

NASA Astrophysics Data System (ADS)

Çomakli, O.; Yazici, M.; Yetim, T.; Yetim, A. F.; Çelik, A.

In the present paper, the influences of different double layer on wear and scratch performances of commercially pure Titanium (CP-Ti) were investigated. TiO2/SiO2 and SiO2/TiO2 double layer coatings were deposited on CP-Ti by sol-gel dip coating process and calcined at 750∘C. The phase structure, cross-sectional morphology, composition, wear track morphologies, adhesion properties, hardness and roughness of uncoated and coated samples were characterized with X-ray diffraction, scanning electron microscopy (SEM), nano-indentation technique, scratch tester and 3D profilometer. Also, the tribological performances of all samples were investigated by a pin-on-disc tribo-tester against Al2O3 ball. Results showed that hardness, elastic modulus and adhesion resistance of double layer coated samples were higher than untreated CP-Ti. It was found that these properties of TiO2/SiO2 double layer coatings have higher than SiO2/TiO2 double layer coating. Additionally, the lowest friction coefficient and wear rates were obtained from TiO2/SiO2 double layer coatings. Therefore, it was seen that phase structure, hardness and film adhesion are important factors on the tribological properties of double layer coatings.

Corrosion Behavior of Yttria-Stabilized Zirconia-Coated 9Cr-1Mo Steel in Molten UCl3-LiCl-KCl Salt

NASA Astrophysics Data System (ADS)

Jagadeeswara Rao, Ch.; Venkatesh, P.; Prabhakara Reddy, B.; Ningshen, S.; Mallika, C.; Kamachi Mudali, U.

2017-02-01

For the electrorefining step in the pyrochemical reprocessing of spent metallic fuels of future sodium cooled fast breeder reactors, 9Cr-1Mo steel has been proposed as the container material. The electrorefining process is carried out using 5-6 wt.% UCl3 in LiCl-KCl molten salt as the electrolyte at 500 °C under argon atmosphere. In the present study, to protect the container vessel from hot corrosion by the molten salt, 8-9% yttria-stabilized zirconia (YSZ) ceramic coating was deposited on 9Cr-1Mo steel by atmospheric plasma spray process. The hot corrosion behavior of YSZ-coated 9Cr-1Mo steel specimen was investigated in molten UCl3-LiCl-KCl salt at 600 °C for 100-, 500-, 1000- and 2000-h duration. The results revealed that the weight change in the YSZ-coated specimen was insignificant even after exposure to molten salt for 2000 h, and delamination of coating did not occur. SEM examination showed the lamellar morphology of the YSZ coating after the corrosion test with occluded molten salt. The XRD analysis confirmed the presence of tetragonal and cubic phases of ZrO2, without any phase change. Formation of UO2 in some regions of the samples was evident from XRD results.

Improvements in Microstructure and Wear Resistance of Plasma-Sprayed Fe-Based Amorphous Coating by Laser-Remelting

NASA Astrophysics Data System (ADS)

Jiang, Chaoping; Chen, Hong; Wang, Gui; Chen, Yongnan; Xing, Yazhe; Zhang, Chunhua; Dargusch, Matthew

2017-04-01

Amorphous coating technology is an attractive way of taking advantage of the superior properties of amorphous alloys for structural applications. However, the limited bonds between splats within the plasma-sprayed coatings result in a typically lamellar and porous coating structure. To overcome these limitations, the as-sprayed coating was treated by a laser-remelting process. The microstructure and phase composition of two coatings were analyzed using scanning electron microscopy with energy-dispersive spectroscopy, transmission electron microscopy, and x-ray diffraction. The wear resistance of the plasma-sprayed coating and laser-remelted coating was studied comparatively using a pin-on-disc wear test under dry friction conditions. It was revealed that the laser-remelted coating exhibited better wear resistance because of its defect-free and amorphous-nanocrystalline composited structure.

Metallization of Kevlar fibers with gold.

PubMed

Little, Brian K; Li, Yunfeng; Cammarata, V; Broughton, R; Mills, G

2011-06-01

Electrochemical gold plating processes were examined for the metallization of Kevlar yarn. Conventional Sn(2+)/Pd(2+) surface activation coupled with electroless Ni deposition rendered the fibers conductive enough to serve as cathodes for electrochemical plating. The resulting coatings were quantified gravimetrically and characterized via adhesion tests together with XRD, SEM, TEM; the coatings effect on fiber strength was also probed. XRD data showed that metallic Pd formed during surface activation whereas amorphous phases and trace amounts of pure Ni metal were plated via the electroless process. Electrodeposition in a thiosulfate bath was the most efficient Au coating process as compared with the analogous electroless procedure, and with electroplating using a commercial cyanide method. Strongly adhering coatings resulted upon metallization with three consecutive electrodepositions, which produced conductive fibers able to sustain power outputs in the range of 1 W. On the other hand, metallization affected the tensile strength of the fiber and defects present in the metal deposits make questionable the effectiveness of the coatings as protective barriers. © 2011 American Chemical Society

Sintered tantalum carbide coatings on graphite substrates: Highly reliable protective coatings for bulk and epitaxial growth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakamura, Daisuke; Suzumura, Akitoshi; Shigetoh, Keisuke

2015-02-23

Highly reliable low-cost protective coatings have been sought after for use in crucibles and susceptors for bulk and epitaxial film growth processes involving wide bandgap materials. Here, we propose a production technique for ultra-thick (50–200 μmt) tantalum carbide (TaC) protective coatings on graphite substrates, which consists of TaC slurry application and subsequent sintering processes, i.e., a wet ceramic process. Structural analysis of the sintered TaC layers indicated that they have a dense granular structure containing coarse grain with sizes of 10–50 μm. Furthermore, no cracks or pinholes penetrated through the layers, i.e., the TaC layers are highly reliable protective coatings. The analysismore » also indicated that no plastic deformation occurred during the production process, and the non-textured crystalline orientation of the TaC layers is the origin of their high reliability and durability. The TaC-coated graphite crucibles were tested in an aluminum nitride (AlN) sublimation growth process, which involves extremely corrosive conditions, and demonstrated their practical reliability and durability in the AlN growth process as a TaC-coated graphite. The application of the TaC-coated graphite materials to crucibles and susceptors for use in bulk AlN single crystal growth, bulk silicon carbide (SiC) single crystal growth, chemical vapor deposition of epitaxial SiC films, and metal-organic vapor phase epitaxy of group-III nitrides will lead to further improvements in crystal quality and reduced processing costs.« less

Highly porous solid-phase microextraction fiber coating based on poly(ethylene glycol)-modified ormosils synthesized by sol-gel technology.

PubMed

da Costa Silva, Raquel Gomes; Augusto, Fabio

2005-04-22

The preparation and characteristics of solid-phase microextraction (SPME) fibers coated with Carbowax 20M ormosil (organically modified silica) are described here. Raw fused silica fibers were coated with Carbowax 20M-modified silica using sol-gel process. Scanning electron micrographs of fibers revealed a highly porous, sponge-like coating with an average thickness of (8 +/- 1) microm. The sol-gel Carbowax fibers were compared to commercial fibers coated with 100 microm polydimethylsiloxane (PDMS) and 65 microm Carbowax-divinylbenzene (DVB). Shorter equilibrium times were possible with the sol-gel Carbowax fiber: for headspace extraction of the test analytes, they ranged from less than 3 min for benzene to 15 min for o-xylene. Extraction efficiencies of the sol-gel Carbowax fiber were superior to those of conventional fibers: for o-xylene, the extracted masses were 230 and 540% of that obtained with 100 microm PDMS and 65 microm Carbowax-DVB fibers, respectively.

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

NASA Technical Reports Server (NTRS)

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.

Experimental Study of the Microstructure and Micromechanical Properties of Laser Cladded Ni-based Amorphous Composite Coatings

NASA Astrophysics Data System (ADS)

Li, Ruifeng; Zheng, Qichi; Zhu, Yanyan; Li, Zhuguo; Feng, Kai; Liu, Chuan

2018-01-01

(Ni0.6Fe0.4)65B18Si10Nb4C3 amorphous composite coating was successfully fabricated on AISI 1045 steel substrate by using laser cladding process with coaxial powder feeding equipment. The microstructure and phase distribution of the coating were investigated by using x-ray diffraction, scanning electron microscopy and transmission electron microscope. The mechanical properties of the coating were examined by using microhardness testing and nanoindentation. The experimental results indicated that the volume fraction of amorphous phase increased with the decrease in laser cladding heat input, leading to an improvement of mean microhardness and nanohardness. NbC particles in a size ranging between 150 and 1650 nm were found embedding in the amorphous composite coatings in all situations. The presence of the NbC particles can contribute to an improvement of 96.7 HV in hardness on the basis of experimental results, while theoretical prediction suggests an improvement of 92.5 HV by using Orowan-Ashby equation.

Microstructural Study on Oxidation Resistance of Nonmodified and Platinum Modified Aluminide Coating

NASA Astrophysics Data System (ADS)

Zagula-Yavorska, Maryana; Sieniawski, Jan

2014-03-01

Platinum electroplating layers (3 and 7 μm thick) were deposited on the surface of the Inconel 713 LC, CMSX 4, and Inconel 625 Ni-base superalloys. Diffusion treatment at 1050°C for 2 h under argon atmosphere was performed after electroplating. Diffusion treated samples were aluminized according to the low activity CVD process at 1050°C for 8 h. The nonmodified aluminide coatings consist of NiAl phase. Platinum modification let to obtain the (Ni,Pt)Al phase in coatings. The coated samples were subjected to cyclic oxidation testing at 1100°C. It was discovered that increase of the platinum electroplating thickness from 3 to 7 μm provides the improvement of oxidation resistance of aluminide coatings. Increase of the platinum thickness causes decreases in weight change and decreases in parabolic constant during oxidation. The platinum provides the pure Al2O3 oxide formation, slow growth oxide layer, and delay the oxide spalling during heating-cooling thermal cycles.

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

NASA Astrophysics Data System (ADS)

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.

Lyotropic liquid crystalline L3 phase silicated nanoporous monolithic composites and their production

DOEpatents

McGrath, Kathryn M.; Dabbs, Daniel M.; Aksay, Ilhan A.; Gruner, Sol M.

2003-10-28

A mesoporous ceramic material is provided having a pore size diameter in the range of about 10-100 nanometers produced by templating with a ceramic precursor a lyotropic liquid crystalline L.sub.3 phase consisting of a three-dimensional, random, nonperiodic network packing of a multiple connected continuous membrane. A preferred process for producing the inesoporous ceramic material includes producing a template of a lyotropic liquid crystalline L.sub.3 phase by mixing a surfactant, a co-surfactant and hydrochloric acid, coating the template with an inorganic ceramic precursor by adding to the L.sub.3 phase tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS) and then converting the coated template to a ceramic by removing any remaining liquids.

Corrosion behavior of magnetic ferrite coating prepared by plasma spraying

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yi; Wei, Shicheng, E-mail: wsc33333@163.com; Tong, Hui

Graphical abstract: The saturation magnetization (M{sub s}) of the ferrite coating is 34.417 emu/g while the M{sub s} value of the ferrite powder is 71.916 emu/g. It can be seen that plasma spray process causes deterioration of the room temperature soft magnetic properties. - Highlights: • Spinel ferrite coatings have been prepared by plasma spraying. • The coating consists of nanocrystalline grains. • The saturation magnetization of the ferrite coating is 34.417 emu/g. • Corrosion behavior of the ferrite coating was examined in NaCl solution. - Abstract: In this study, spray dried spinel ferrite powders were deposited on the surfacemore » of mild steel substrate through plasma spraying. The structure and morphological studies on the ferrite coatings were carried out using X-ray diffraction, scanning electron microscope and Raman spectroscopy. It was showed that spray dried process was an effective method to prepare thermal spraying powders. The coating showed spinel structure with a second phase of LaFeO{sub 3}. The magnetic property of the ferrite samples were measured by vibrating sample magnetometer. The saturation magnetization (M{sub s}) of the ferrite coating was 34.417 emu/g. The corrosion behavior of coating samples was examined by electrochemical impedance spectroscopy. EIS diagrams showed three corrosion processes as the coating immersed in 3.5 wt.% NaCl solution. The results suggested that plasma spraying was a promising technology for the production of magnetic ferrite coatings.« less

Microstructural Effects and Properties of Non-line-of-Sight Coating Processing via Plasma Spray-Physical Vapor Deposition

NASA Astrophysics Data System (ADS)

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

2017-08-01

Plasma spray-physical vapor deposition (PS-PVD) is a unique processing method that bridges the gap between conventional thermal spray and vapor phase methods, and enables highly tailorable coatings composed of a variety of materials in thin, dense layers or columnar microstructures with modification of the processing conditions. The strengths of this processing technique are material and microstructural flexibility, deposition speed, and potential for non-line-of-sight (NLOS) capability by vaporization of the feedstock material. The NLOS capability of PS-PVD is investigated here using yttria-stabilized zirconia and gadolinium zirconate, which are materials of interest for turbine engine applications. PS-PVD coatings were applied to static cylindrical substrates approximately 6-19 mm in diameter to study the coating morphology as a function of angle. In addition, coatings were deposited on flat substrates under various impingement configurations. Impingement angle had significant effects on the deposition mode, and microscopy of coatings indicated that there was a shift in the deposition mode at approximately 90° from incidence on the cylindrical samples, which may indicate the onset of more turbulent flow and PVD-like growth. Coatings deposited at non-perpendicular angles exhibited a higher density and nearly a 2× improvement in erosion performance when compared to coatings deposited with the torch normal to the surface.

Bioceramic coating of hydroxyapatite fabricated on Ti-6Al-4V with Nd-YAG laser

NASA Astrophysics Data System (ADS)

Tlotleng, Monnamme; Akinlabi, Esther T.; Shukla, Mukul; Pityana, Sisa

2015-03-01

This paper presents on the direct laser melted hydroxyapatite coatings achieved by melting the pre-placed powder beds using Nd-YAG laser. The process development and optimized parameters are reported. The results show that by changing the laser power and the beam inclined plane it is possible that a desirable coating of HAP that is rich on the surface can be produced. The microstructures of the coatings showed balling and cracking at beam angles between 0-15° and at 27° a successful coating was achieved with laser power and scanning speed of 750W and 5mm/s respectively. The said coating was pore and crack free while it retained non-decomposed HAP crystallites on the surface (mixed). The microstructure of the transition layer concluded a moderate temperature process since the formed dendrites did not develop or form secondary arms. The Ca/P conducted on the coating using EDS concluded Ca/P ratio of 8.04 and the absence of titanium phosphates phase (TiP2). TiP2 is typically associated with the decomposition of HAP and indicate the presence of high processing temperatures. Even so, the current results indicated that the investigated process was successful in depositing HAP coating with desirable microstructures even though its bio-corrosion properties still need to be ascertained before it could be qualified as suitable for biomedical applications.

Investigation of fragrance stability used in the formulation of cosmetic and hygienic products using headspace solid-phase microextraction by nanostructured materials followed by gas chromatography with mass spectrometry.

PubMed

Masoum, Saeed; Gholami, Ali; Ghaheri, Salehe; Bouveresse, Delphine Jouan-Rimbaud; Cordella, Christophe B Y; Rutledge, Douglas N

2016-07-01

A new composite coating of polypyrrole and sodium lauryl ether sulfate was electrochemically prepared on a stainless-steel wire using cyclic voltammetry. The application and performance of the fiber was evaluated for the headspace solid-phase microextraction of a fragrance in aqueous bleach samples followed by gas chromatography combined with mass spectrometry to assess the fragrance stability in this kind of household cleaning product. To obtain a stable and efficient composite coating, parameters related to the coating process such as scan rate and numbers of cycles were optimized using a central composite design. In addition, the effects of various parameters on the extraction efficiency of the headspace solid-phase microextraction process such as extraction temperature and time, ionic strength, sample volume, and stirring rate were investigated by experimental design methods using Plackett-Burman and Doehlert designs. The optimum values of 53°C and 28 min for sample temperature and time, respectively, were found through response surface methodology. Results show that the combination of polypyrrole and sodium lauryl ether sulfate in a composite form presents desirable opportunities to produce new materials to study fragrance stability by headspace solid-phase microextraction. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Constructing a superhydrophobic surface on polydimethylsiloxane via spin coating and vapor-liquid sol-gel process.

PubMed

Peng, Yu-Ting; Lo, Kuo-Feng; Juang, Yi-Je

2010-04-06

In this study, a superhydrophobic surface on polydimethylsiloxane (PDMS) substrate was constructed via the proposed vapor-liquid sol-gel process in conjunction with spin coating of dodecyltrichlorosilane (DTS). Unlike the conventional sol-gel process where the reaction takes place in the liquid phase, layers of silica (SiO(2)) particles were formed through the reaction between the reactant spin-coated on the PDMS surface and vapor of the acid solution. This led to the SiO(2) particles inlaid on the PDMS surface. Followed by subsequent spin coating of DTS solution, the wrinkle-like structure was formed, and the static contact angle of the water droplet on the surface could reach 162 degrees with 2 degrees sliding angle and less than 5 degrees contact angle hysteresis. The effect of layers of SiO(2) particles, concentrations of DTS solution and surface topography on superhydrophobicity of the surface is discussed.

Predicting the optimal process window for the coating of single-crystalline organic films with mobilities exceeding 7 cm2/Vs.

NASA Astrophysics Data System (ADS)

Janneck, Robby; Vercesi, Federico; Heremans, Paul; Genoe, Jan; Rolin, Cedric

2016-09-01

Organic thin film transistors (OTFTs) based on single crystalline thin films of organic semiconductors have seen considerable development in the recent years. The most successful method for the fabrication of single crystalline films are solution-based meniscus guided coating techniques such as dip-coating, solution shearing or zone casting. These upscalable methods enable rapid and efficient film formation without additional processing steps. The single-crystalline film quality is strongly dependent on solvent choice, substrate temperature and coating speed. So far, however, process optimization has been conducted by trial and error methods, involving, for example, the variation of coating speeds over several orders of magnitude. Through a systematic study of solvent phase change dynamics in the meniscus region, we develop a theoretical framework that links the optimal coating speed to the solvent choice and the substrate temperature. In this way, we can accurately predict an optimal processing window, enabling fast process optimization. Our approach is verified through systematic OTFT fabrication based on films grown with different semiconductors, solvents and substrate temperatures. The use of best predicted coating speeds delivers state of the art devices. In the case of C8BTBT, OTFTs show well-behaved characteristics with mobilities up to 7 cm2/Vs and onset voltages close to 0 V. Our approach also explains well optimal recipes published in the literature. This route considerably accelerates parameter screening for all meniscus guided coating techniques and unveils the physics of single crystalline film formation.

Ni-Flash-Coated Galvannealed Steel Sheet with Improved Properties

NASA Astrophysics Data System (ADS)

Pradhan, D.; Dutta, M.; Venugopalan, T.

2016-11-01

In the last several years, automobile industries have increasingly focused on galvannealed (GA) steel sheet due to their superior properties such as weldability, paintability and corrosion protection. To improve the properties further, different coatings on GA have been reported. In this context, an electroplating process (flash coating) of bright and adherent Ni plating was developed on GA steel sheet for covering the GA defects and enhancing the performances such as weldability, frictional behavior, corrosion resistance and phosphatability. For better illustration, a comparative study with bare GA steel sheet has also been carried out. The maximum electroplating current density of 700 A/m2 yielded higher cathode current efficiency of 95-98%. The performances showed that Ni-coated (coating time 5-7 s) GA steel sheet has better spot weldability, lower dynamic coefficient of friction (0.07 in lubrication) and three times more corrosion resistance compared to bare GA steel sheet. Plate-like crystal of phosphate coating with size of 10-25 µm was obtained on the Ni-coated GA. The main phase in the phosphate compound was identified as hopeite (63.4 wt.%) along with other phases such as spencerite (28.3 wt.%) and phosphophyllite (8.3 wt.%).

PEO of pre-anodized Al-Si alloys: Corrosion properties and influence of sealings

NASA Astrophysics Data System (ADS)

Mohedano, M.; Matykina, E.; Arrabal, R.; Mingo, B.; Pardo, A.

2015-08-01

Voltage-controlled PEO coatings were developed on A356 aluminum alloys (gravity-cast and rheocast) with a pre-anodized layer. The influence of the alloy manufacturing process and the effect of Si-rich phase on the structure and composition of the oxide layers were evaluated using SEM, EDS and XRD. The pre-anodized oxide layer preserves the microstructure of the substrate due to the presence of secondary phases that have a different behavior relative to the matrix during anodizing. PEO coatings consisted of a mixture of α-Al2O3, γ-Al2O3 and mullite. The corrosion behavior and the effectiveness of different sealing techniques based on salts of nickel, cobalt, cerium and phosphonic acid were also studied. Post-treatments improved the hydrophobic properties of the coatings and showed a beneficial effect, significantly increasing the coating impedance and thereby reducing the susceptibility to corrosion.

Development of new solid-phase microextraction fibers by sol-gel technology for the determination of organophosphorus pesticide multiresidues in food.

PubMed

Yu, Jianxin; Wu, Caiying; Xing, Jun

2004-05-21

Allyloxy bisbenzo 16-crown-5 trimethoxysilane was first used as precursor to prepare the sol-gel-derived bisbenzo crown ether/hydroxyl-terminated silicone oil (OH-TSO) SPME coating. The coating procedure involving sol solution composition and conditioning process was presented. Compared with commercial SPME stationary phases, the new coatings showed higher extraction efficiency and therefore could provide higher sensitivity for organphosphorous pesticides (OPs). Limits of detection (LODs) were in the range of 0.003-1.0 ng/g for these OPs in food samples (honey, juice, orange and pakchoi). The optimal extraction conditions of the new coatings to OPs in these samples were investigated by adjusting extraction time, salt addition, extraction temperature, and dilution ratios of samples with distilled water by using SPME coupled with gas chromatography (GC)-flame photometric detection (FPD). The method was applied to determine the concentrations of OPs in real samples.

Microstructural inhomogeneity in plasma-sprayed hydroxyapatite coatings and effect of post-heat treatment

NASA Astrophysics Data System (ADS)

Lu, Yu-Peng; Xiao, Gui-Yong; Li, Shi-Tong; Sun, Rui-Xue; Li, Mu-Sen

2006-01-01

The microstructural inhomogeneity in the plasma-sprayed hydroxyapatite (HA) coatings was characterized by using electron probe microanalyser (EPMA). A simple and artful method was developed to detect the interface characteristics. All the samples for observation were ground and polished along the direction parallel to the coating surfaces. The BSE images directly and clearly showed the inhomogeneity in the as-sprayed coatings with the amorphous regions being bright gray and crystalline regions being dark gray. X-ray diffractometer (XRD) patterns indicated that after immersion in deionized water for 20 days, bone-like apatite and α-Ca 2P 2O 7 precipitated on the polished surfaces of the as-sprayed HA coatings. The post-heat treatment could eliminate the microstructural inhomogeneity in the coatings. Only β-Ca 2P 2O 7 precipitated on the surfaces of the heat-treated HA coatings. The immersed samples were re-polished till tiny substrate was bared to investigate the effect of immersion on interface. It was shown that the immersion decreased the cohesive strength of the as-sprayed coatings. There were more and broader cracks in the splats that came into contact with the substrate and amorphous phase increased toward the coating-substrate interface. Post-heat treatment was proved to reduce the peeling off of coating during re-polishing operation. It was proposed that the distributions of amorphous phase and cracks in as-sprayed coatings are detrimental to coating properties and should be modified through improving the plasma spraying processing.

Development of an Innovative Laser-Assisted Coating Process for Extending Lifetime of Metal Casting Dies. Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Madhav Rao Gonvindaraju

1999-10-18

Die casting dies used in the metal casting industry fail due to thermal fatigue cracking accompanied by the presence of residual tensile stresses, corrosion, erosion and wear of die surfaces. This phase 1 SBIR Final Report summarize Karta Technologies research involving the development of an innovative laser coating technology for metal casting dies. The process involves depositing complex protective coatings of nanocrystalline powders of TiC followed by a laser shot peening. The results indicate a significant improvement in corrosion and erosion resistance in molten aluminum for H13 die casting die steels. The laser-coated samples also showed improved surface finish, amore » homogeneous and uniform coating mircrostructure. The technology developed in this research can have a significant impact on the casting industry by saving the material costs involved in replacing dies, reducing downtime and improving the quality.« less

Effect of Powder-Feeding Modes During Plasma Spray on the Properties of Tungsten Carbide Composite Coatings

NASA Astrophysics Data System (ADS)

Zhong, Yi-ming; Du, Xiao-dong; Wu, Gang

2017-05-01

A WC-reinforced composite coating was fabricated on the surface of 45 steel samples by plasma, cladding process with WC powder added to the molten pool synchronously or in the tail of the molten pool. The microstructure, phase composition, and element distribution in the coating were analyzed. The results show that the undissolved WC particles and crystallized carbide (WC, W2C) were distributed uniformly in the sub-eutectic matrix in both cases. Fewer of the WC particles are dissolved in the matrix when they are injected into the tail of the molten pool. There are fewer needle-like tungsten carbide formations seen in the composite coating fabricated by back-feeding process than in that formed by synchronous feeding. The former results in a finer microstructure and a higher concentration gradient of elements near the interface between the WC particles and the coating matrix.

Mechanism of adaptability for the nano-structured TiAlCrSiYN-based hard physical vapor deposition coatings under extreme frictional conditions

NASA Astrophysics Data System (ADS)

Fox-Rabinovich, G. S.; Endrino, J. L.; Aguirre, M. H.; Beake, B. D.; Veldhuis, S. C.; Kovalev, A. I.; Gershman, I. S.; Yamamoto, K.; Losset, Y.; Wainstein, D. L.; Rashkovskiy, A.

2012-03-01

Recently, a family of hard mono- and multilayer TiAlCrSiYN-based coatings have been introduced that exhibit adaptive behavior under extreme tribological conditions (in particular during dry ultrahigh speed machining of hardened tool steels). The major feature of these coatings is the formation of the tribo-films on the friction surface which possess high protective ability under operating temperatures of 1000 °C and above. These tribo-films are generated as a result of a self-organization process during friction. But the mechanism how these films affect adaptability of the hard coating is still an open question. The major mechanism proposed in this paper is associated with a strong gradient of temperatures within the layer of nano-scaled tribo-films. This trend was outlined by the performed thermodynamic analysis of friction phenomena combined with the developing of a numerical model of heat transfer within cutting zone based on the finite element method. The results of the theoretical studies show that the major physical-chemical processes during cutting are mostly concentrated within a layer of the tribo-films. This nano-tribological phenomenon produces beneficial heat distribution at the chip/tool interface which controls the tool life and wear behavior.Results of x-ray photoelectron spectroscopy studies indicate enhanced formation of protective sapphire- and mullite-like tribo-films on the friction surface of the multilayer TiAlCrSiYN/TiAlCrN coating. Comprehensive investigations of the structure and phase transformation within the coating layer under operation have been performed, using high resolution transmission electron microscopy, synchrotron radiation technique: x-ray absorption near-edge structure and XRD methods.The data obtained show that the tribo-films efficiently perform their thermal barrier functions preventing heat to penetrate into the body of coated cutting tool. Due to this the surface damaging process as well as non-beneficial phase transformation (formation of AlN hex phase) drastically diminishes within the layer of the adaptive coating. Micro-mechanical properties measurements performed at room and elevated temperatures show that the hardness of the multilayer TiAlCrSiYN/TiAlCrN coating appears stable to 500 °C and then drops a little at 600 °C but still remains high. It means that if the surface tribo-films can reduce actual temperature down to this level the coating underneath is able to efficiently withstand heavy loads under operation.

Formation of Microcracks During Micro-Arc Oxidation in a Phytic Acid-Containing Solution on Two-Phase AZ91HP

NASA Astrophysics Data System (ADS)

Zhang, R. F.; Chang, W. H.; Jiang, L. F.; Qu, B.; Zhang, S. F.; Qiao, L. P.; Xiang, J. H.

2016-04-01

Micro-arc oxidation (MAO) is an effective method to produce ceramic coatings on magnesium alloys and can considerably improve their corrosion resistance. The coating properties are closely related with microcracks, which are always inevitably developed on the coating surface. In order to find out the formation and development regularity of microcracks, anodic coatings developed on two-phase AZ91HP after different anodizing times were fabricated in a solution containing environmentally friendly organic electrolyte phytic acid. The results show that anodic film is initially developed on the α phase. At 50 s, anodic coatings begin to develop on the β phase, evidencing the formation of a rough area. Due to the coating successive development, the microcracks initially appear at the boundary between the initially formed coating on the α phase and the subsequently developed coating on the β phase. With the prolonging treatment time, the microcracks near the β phase become evident. After treating for 3 min, the originally rough area on the β phase disappears and the coatings become almost uniform with microcracks randomly distributed on the sample surface. Inorganic phosphates are found in MAO coatings, suggesting that phytate salts are decomposed due to the high instantaneous temperature on the sample surface resulted from spark discharge.

Investigation about the Chrome Steel Wire Arc Spray Process and the Resulting Coating Properties

NASA Astrophysics Data System (ADS)

Wilden, J.; Bergmann, J. P.; Jahn, S.; Knapp, S.; van Rodijnen, F.; Fischer, G.

2007-12-01

Nowadays, wire-arc spraying of chromium steel has gained an important market share for corrosion and wear protection applications. However, detailed studies are the basis for further process optimization. In order to optimize the process parameters and to evaluate the effects of the spray parameters DoE-based experiments had been carried out with high-speed camera shoots. In this article, the effects of spray current, voltage, and atomizing gas pressure on the particle jet properties, mean particle velocity and mean particle temperature and plume width on X46Cr13 wire are presented using an online process monitoring device. Moreover, the properties of the coatings concerning the morphology, composition and phase formation were subject of the investigations using SEM, EDX, and XRD-analysis. These deep investigations allow a defined verification of the influence of process parameters on spray plume and coating properties and are the basis for further process optimization.

Advanced Antireflection Coatings for High-Performance Solar Energy Applications

NASA Technical Reports Server (NTRS)

Pan, Noren

2015-01-01

Phase II objectives: Develop and refine antireflection coatings incorporating lanthanum titanate as an intermediate refractive index material; Investigate wet/dry thermal oxidation of aluminum containing semiconductor compounds as a means of forming a more transparent window layer with equal or better optical properties than its unoxidized form; Develop a fabrication process that allows integration of the oxidized window layer and maintains the necessary electrical properties for contacting the solar cell; Conduct an experimental demonstration of the best candidates for improved antireflection coatings.

Analytical methods to characterize heterogeneous raw material for thermal spray process: cored wire Inconel 625

NASA Astrophysics Data System (ADS)

Lindner, T.; Bonebeau, S.; Drehmann, R.; Grund, T.; Pawlowski, L.; Lampke, T.

2016-03-01

In wire arc spraying, the raw material needs to exhibit sufficient formability and ductility in order to be processed. By using an electrically conductive, metallic sheath, it is also possible to handle non-conductive and/or brittle materials such as ceramics. In comparison to massive wire, a cored wire has a heterogeneous material distribution. Due to this fact and the complex thermodynamic processes during wire arc spraying, it is very difficult to predict the resulting chemical composition in the coating with sufficient accuracy. An Inconel 625 cored wire was used to investigate this issue. In a comparative study, the analytical results of the raw material were compared to arc sprayed coatings and droplets, which were remelted in an arc furnace under argon atmosphere. Energy-dispersive X-ray spectroscopy (EDX) and X-ray fluorescence (XRF) analysis were used to determine the chemical composition. The phase determination was performed by X-ray diffraction (XRD). The results were related to the manufacturer specifications and evaluated in respect to differences in the chemical composition. The comparison between the feedstock powder, the remelted droplets and the thermally sprayed coatings allows to evaluate the influence of the processing methods on the resulting chemical and phase composition.

Optical Constants of Crystallized TiO2 Coatings Prepared by Sol-Gel Process

PubMed Central

Wang, Xiaodong; Wu, Guangming; Zhou, Bin; Shen, Jun

2013-01-01

Titanium oxide coatings have been deposited by the sol-gel dip-coating method. Crystallization of titanium oxide coatings was then achieved through thermal annealing at temperatures above 400 °C. The structural properties and surface morphology of the crystallized coatings were studied by micro-Raman spectroscopy and atomic force microscopy, respectively. Characterization technique, based on least-square fitting to the measured reflectance and transmittance spectra, is used to determine the refractive indices of the crystallized TiO2 coatings. The stability of the synthesized sol was also investigated by dynamic light scattering particle size analyzer. The influence of the thermal annealing on the optical properties was then discussed. The increase in refractive index with high temperature thermal annealing process was observed, obtaining refractive index values from 1.98 to 2.57 at He-Ne laser wavelength of 633 nm. The Raman spectroscopy and atomic force microscopy studies indicate that the index variation is due to the changes in crystalline phase, density, and morphology during thermal annealing. PMID:28811410

Optical Constants of Crystallized TiO₂ Coatings Prepared by Sol-Gel Process.

PubMed

Wang, Xiaodong; Wu, Guangming; Zhou, Bin; Shen, Jun

2013-07-12

Titanium oxide coatings have been deposited by the sol-gel dip-coating method. Crystallization of titanium oxide coatings was then achieved through thermal annealing at temperatures above 400 °C. The structural properties and surface morphology of the crystallized coatings were studied by micro-Raman spectroscopy and atomic force microscopy, respectively. Characterization technique, based on least-square fitting to the measured reflectance and transmittance spectra, is used to determine the refractive indices of the crystallized TiO₂ coatings. The stability of the synthesized sol was also investigated by dynamic light scattering particle size analyzer. The influence of the thermal annealing on the optical properties was then discussed. The increase in refractive index with high temperature thermal annealing process was observed, obtaining refractive index values from 1.98 to 2.57 at He-Ne laser wavelength of 633 nm. The Raman spectroscopy and atomic force microscopy studies indicate that the index variation is due to the changes in crystalline phase, density, and morphology during thermal annealing.

The effect of hydrogen on B4C coatings fabrication in inductively coupled plasma torch

NASA Astrophysics Data System (ADS)

Guo, Q. J.; Zhao, P.; Li, L.; Zhou, Q. J.; Ni, G. H.; Meng, Y. D.

2018-02-01

Boron carbide (B4C) coatings are prepared by an RF inductively coupled plasma (ICP) torch with different amounts of hydrogen introduced into the sheath gas. The effects of the added hydrogen on the characteristics of the plasma are diagnosed by optical emission spectroscopy and high speed photography. The effects on the melting of B4C particles in the plasma are studied by scanning electron microscopy (SEM). The microstructure of the B4C coatings was determined with SEM imaging and x-ray diffraction analysis. The results show that adding hydrogen to the sheath gas leads to plasma contraction, which results in higher gas temperature of plasma. It also enhances B4C particles spheroidizing and improves the compactness of B4C coatings. Plasma processing does not change the main phase of boron carbide. The obtained results on B4C coatings on Cu substrates allows for improving the B4C coatings fabrication process.

Abrasion resistant coating and method of making the same

DOEpatents

Sordelet, Daniel J.; Besser, Matthew F.

2001-06-05

An abrasion resistant coating is created by adding a ductile phase to a brittle matrix phase during spray coating where an Al--Cu--Fe quasicrystalline phase (brittle matrix) and an FeAl intermetallic (ductile phase) are combined. This composite coating produces a coating mostly of quasicrystal phase and an inter-splat layer of the FeAl phase to help reduce porosity and cracking within the coating. Coatings are prepared by plasma spraying unblended and blended quasicrystal and intermetallic powders. The blended powders contain 1, 5, 10 and 20 volume percent of the intermetallic powders. The unblended powders are either 100 volume percent quasicrystalline or 100 volume percent intermetallic; these unblended powders were studied for comparison to the others. Sufficient ductile phase should be added to the brittle matrix to transform abrasive wear mode from brittle fracture to plastic deformation, while at the same time the hardness of the composite should not be reduced below that of the original brittle phase material.

Fundamentals and applications of solar energy. Part 2

NASA Astrophysics Data System (ADS)

Faraq, I. H.; Melsheimer, S. S.

Applications of techniques of chemical engineering to the development of materials, production methods, and performance optimization and evaluation of solar energy systems are discussed. Solar thermal storage systems using phase change materials, liquid phase Diels-Alder reactions, aquifers, and hydrocarbon oil were examined. Solar electric systems were explored in terms of a chlorophyll solar cell, the nonequilibrium electric field effects developed at photoelectrode/electrolyte interfaces, and designs for commercial scale processing of solar cells using continuous thin-film coating production methods. Solar coal gasification processes were considered, along with multilayer absorber coatings for solar concentrator receivers, solar thermal industrial applications, the kinetics of anaerobic digestion of crop residues to produce methane, and a procedure for developing a computer simulation of a solar cooling system.

On-line coating of glass with tin oxide by atmospheric pressure chemical vapor deposition.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allendorf, Mark D.; Sopko, J.F.; Houf, William G.

2006-11-01

Atmospheric pressure chemical vapor deposition (APCVD) of tin oxide is a very important manufacturing technique used in the production of low-emissivity glass. It is also the primary method used to provide wear-resistant coatings on glass containers. The complexity of these systems, which involve chemical reactions in both the gas phase and on the deposition surface, as well as complex fluid dynamics, makes process optimization and design of new coating reactors a very difficult task. In 2001 the U.S. Dept. of Energy Industrial Technologies Program Glass Industry of the Future Team funded a project to address the need for more accuratemore » data concerning the tin oxide APCVD process. This report presents a case study of on-line APCVD using organometallic precursors, which are the primary reactants used in industrial coating processes. Research staff at Sandia National Laboratories in Livermore, CA, and the PPG Industries Glass Technology Center in Pittsburgh, PA collaborated to produce this work. In this report, we describe a detailed investigation of the factors controlling the growth of tin oxide films. The report begins with a discussion of the basic elements of the deposition chemistry, including gas-phase thermochemistry of tin species and mechanisms of chemical reactions involved in the decomposition of tin precursors. These results provide the basis for experimental investigations in which tin oxide growth rates were measured as a function of all major process variables. The experiments focused on growth from monobutyltintrichloride (MBTC) since this is one of the two primary precursors used industrially. There are almost no reliable growth-rate data available for this precursor. Robust models describing the growth rate as a function of these variables are derived from modeling of these data. Finally, the results are used to conduct computational fluid dynamic simulations of both pilot- and full-scale coating reactors. As a result, general conclusions are reached concerning the factors affecting the growth rate in on-line APCVD reactors. In addition, a substantial body of data was generated that can be used to model many different industrial tin oxide coating processes. These data include the most extensive compilation of thermochemistry for gas-phase tin-containing species as well as kinetic expressions describing tin oxide growth rates over a wide range of temperatures, pressures, and reactant concentrations.« less

Galvanizing and Galvannealing Behavior of CMnSiCr Dual-Phase Steels

NASA Astrophysics Data System (ADS)

Lin, Ko-Chun; Chu, Peng-Wei; Lin, Chao-Sung; Chen, Hon-Bor

2013-06-01

Alloying elements, such as Mn, Mo, Si, and Cr, are commonly used to enhance the strength of advanced high-strength steels. Those elements also play an important role in the hot-dip galvanizing (GI) and galvannealing (GA) process. In this study, two kinds of CMnSiCr dual-phase steels were galvanized and galvannealed using a hot-dip simulator to investigate the effect of the alloying elements on the microstructure of the GI and GA coatings. The results showed that the dual-phase steels had good galvanizability because no bare spots were observed and the Fe-Zn phases were readily formed at the interface. However, the alloying reaction during the GA process was significantly hindered. XPS analysis showed that external oxidation occurred under an extremely low dew point [213 K to 203 K (-60 °C to -70 °C)] atmosphere during the annealing prior to hot dipping. However, most of the oxides were reduced during the GI process. After the GI process, the Al was present as solid solutes in the Fe-Zn phase, suggesting that the Fe-Zn phase was formed from the transformation of the Fe-Al inhibition alloy. Meanwhile, the solubility of Si in the ζ phase was extremely low. With continued GA reaction, the ζ phase transformed into the δ phase, which contained approximately 1.0 at.pct Si. The Si also diffused into the Zn layer during the GA reaction. Hence, the ζ phase did not homogeneously nucleate at the steel substrate/Zn coating interface, but was found at the area away from the interface. Therefore, the Fe-Zn phases on the CMnSiCr dual-phase steels were relatively non-uniform compared to those on interstitial-free steel.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jolly, Brian C.; Lindemer, Terrence; Terrani, Kurt A.

In support of fully ceramic matrix (FCM) fuel development, coating development work has begun at the Oak Ridge National Laboratory (ORNL) to produce tri-isotropic (TRISO) coated fuel particles with UN kernels. The nitride kernels are used to increase heavy metal density in these SiC-matrix fuel pellets with details described elsewhere. The advanced gas reactor (AGR) program at ORNL used fluidized bed chemical vapor deposition (FBCVD) techniques for TRISO coating of UCO (two phase mixture of UO 2 and UC x) kernels. Similar techniques were employed for coating of the UN kernels, however significant changes in processing conditions were required tomore » maintain acceptable coating properties due to physical property and dimensional differences between the UCO and UN kernels.« less

Effect of oxygen content of Nd-Fe-B sintered magnet on grain boundary diffusion process of DyH2 dip-coating

NASA Astrophysics Data System (ADS)

Bae, Kyoung-Hoon; Lee, Seong-Rae; Kim, Hyo-Jun; Lee, Min-Woo; Jang, Tae-Suk

2015-11-01

We investigated the effect of oxygen content on the microstructural and magnetic properties of a DyH2 dip-coated Nd-Fe-B sintered magnet. When the magnet had a low oxygen content (1500 ppm), the volume and size of the rare-earth-rich oxide (Nd-Dy-O) phase was reduced, and a uniform and continuous thin Nd-rich grain boundary phase (GBP) was well developed. The grain boundary diffusion depth of Dy increased from 200 to 350 μm with decreasing oxygen content from ˜3000 to 1500 ppm. The coercivity of the low-oxygen magnet increased from 19.98 to 23.59 kOe after grain boundary diffusion process (GBDP) while the remanence reduction was minimized. The formation of an fcc-NdOx Nd-rich phase in the high-oxygen magnet hindered the formation of a Nd-rich triple-junction phase and GBP. In contrast, a metallic dhcp-Nd phase, which was closely related to coercivity enhancement after GBDP, was formed in the low-oxygen magnet.

Fabrication and characterization of flaky core-shell particles by magnetron sputtering silver onto diatomite

NASA Astrophysics Data System (ADS)

Wang, Yuanyuan; Zhang, Deyuan; Cai, Jun

2016-02-01

Diatomite has delicate porous structures and various shapes, making them ideal templates for microscopic core-shell particles fabrication. In this study, a new process of magnetron sputtering assisted with photoresist positioning was proposed to fabricate lightweight silver coated porous diatomite with superior coating quality and performance. The diatomite has been treated with different sputtering time to investigate the silver film growing process on the surface. The morphologies, constituents, phase structures and surface roughness of the silver coated diatomite were analyzed with SEM, EDS, XRD and AFM respectively. The results showed that the optimized magnetron sputtering time was 8-16 min, under which the diatomite templates were successfully coated with uniform silver film, which exhibits face centered cubic (fcc) structure, and the initial porous structures were kept. Moreover, this silver coating has lower surface roughness (RMS 4.513 ± 0.2 nm) than that obtained by electroless plating (RMS 15.692 ± 0.5 nm). And the infrared emissivity of coatings made with magnetron sputtering and electroless plating silver coated diatomite can reach to the lowest value of 0.528 and 0.716 respectively.

Dilation Behavior of Thermal Spray Coatings

NASA Astrophysics Data System (ADS)

Bejarano Lopez, Miryan Lorena

Thermal Spray (TS) is a very versatile manufacturing process to deposit thick coatings on a variety of substrates. Coatings are used in protective (i.e. wear, chemical attack, high temperature, etc.) and functional (i.e. sensors) applications. TS coatings have a unique lamellar microstructure as a result of the overlapping of millions of molten and partially-molten particles. During processing, high deformation by impact, high temperature, and rapid solidification lead to a complex hierarchical material system that contains a high amount of microstructural defects. The presence of defects in the microstructure contribute to differences in property values in comparison to bulk materials. Thermal stresses and residual strains arise from processing, thermal gradients and thermal exposure. Evaluation of thermal properties, in this case, the coefficient of thermal expansion (CTE) is of vital importance to enhance coating performance. In this dissertation, expansion measurements of various metals, alloys, ceramics, and cermet coatings; were carried out using various techniques (push rod dilatometry, x-ray diffraction XRD, digital image correlation DIC, and curvature method) to determine the dilation behavior at the atomic, micro- and macro-scale levels. The main results were. 1) Mathematical models (Turner and Kerner) used for composite materials, successfully predicted the CTE property of a TS coating where the primary phase is the coating material and the secondary phases can be oxides, precipitates, etc. (formed as a byproduct of the spraying process). CTE was found not to be affected by porosity. 2) Despite the anisotropic behavior characteristic of TS coatings, the experimental results shown that CTE results to be reasonable isotropic within the scope of this study. 3) The curvature method was found to be an alternative technique to obtain the CTE, as well as the Young's modulus of coating in a bi-material strip, with good approximation. 4) An anomalous expansion behavior during the first heating exposure was exhibited by all coatings. The effect was named here, as "thermal shakedown", and is magnified in metals and alloys. 5) Non-isothermal rapid annealing of defects was correlated to this first irreversible contraction or expansion behavior. Although observed in most thermal spray materials, two material systems, pure Al and Ni-5Al were evaluated in-depth to quantify the mechanisms contributing to this behavior: vacancy formation, dislocation annealing, grain boundaries annihilation, residual stress relief, inelastic mechanical effects, etc. Correct determination of CTE values are important for design to assure integrity and functionality of coatings. Considerations of appropriate measurements are described in this dissertation.

Effect of applied bias voltage on corrosion-resistance for TiC 1- xN x and Ti 1- xNb xC 1- yN y coatings

NASA Astrophysics Data System (ADS)

Caicedo, J. C.; Amaya, C.; Yate, L.; Aperador, W.; Zambrano, G.; Gómez, M. E.; Alvarado-Rivera, J.; Muñoz-Saldaña, J.; Prieto, P.

2010-02-01

Corrosion-resistance behavior of titanium carbon nitride (Ti-C-N) and titanium niobium carbon nitride (Ti-Nb-C-N) coatings deposited onto Si(1 0 0) and AISI 4140 steel substrates via r.f. magnetron sputtering process was analyzed. The coatings in contact with a solution of sodium chloride at 3.5% were studied by Tafel polarization curves and impedance spectroscopy methods (EIS). Variations of the bias voltage were carried out for each series of deposition to observe the influence of this parameter upon the electrochemical properties of the coatings. The introduction of Nb in the ternary Ti-C-N film was evaluated via X-ray diffraction (XRD) analysis. The structure was characterized by using Raman spectroscopy to identify ternary and quaternary compounds. Surface corrosion processes were characterized using optical microscopy and scanning electron microscopy (SEM). XRD results show conformation of the quaternary phase, change in the strain of the film, and lattice parameter as the effect of the Nb inclusion. The main Raman bands were assigned to interstitial phases and "impurities" of the coatings. Changes in Raman intensities were attributed to the incorporation of niobium in the Ti-C-N structure and possibly to resonance enhancement. Finally, the corrosion data obtained for Ti-C-N were compared with the results of corrosion tests of Ti-Nb-C-N coating. The results obtained showed that the incorporation of niobium to Ti-C-N coatings led to an increase in the corrosion-resistance. On another hand, an increase in the bias voltage led to a decrease in the corrosion-resistance for both Ti-C-N and Ti-Nb-C-N coatings.

Microstructure transformation of Cr-Al coating on carbon steel prepared by ball milling method as a function of tungsten doping

NASA Astrophysics Data System (ADS)

Wismogroho, A. S.; Sudiro, T.; Didik, A.; Ciswandi

2018-03-01

In present work, Cr-Al coatings containing 0, 1, 2, 3, and 5% W have been prepared on the surface of low carbon steel by mechanical alloying technique. The composition of each powder was milled for 2 hour in a stainless steel crucible with a ball to powder ratio of 10:1. Afterward, the Cr-Al-W powder and substrate were mechanically alloyed in air for 1 hour. The heat treatment of coated samples was carried out at 800 °C in a vacuum furnace for 2 hour. In order to characterize the phase composition and microstructure of the coating before and after heat treatment, XRD and SEM-EDX were used. The analysis results reveal that the ball milling process induces the formation of homogeneous Cr-Al-W coating structure with a thickness of about 80 μm. The phase observation shows individual peaks of each starting elements, along with the occurrence of powder refinement and solid solution formation. After heat treatment, AlCr2 and Al8Cr5 phases were formed. The addition of W accelerates the formation of AlCr2, but inhibits the formation of Al8Cr5. The detail of the results was presented in this paper.

The calcium phosphate coating of soy lecithin nanoemulsion with performance in stability and as an oxygen carrier

NASA Astrophysics Data System (ADS)

Han, Kyu B.

This work studied the relationship between surfactant, oil, and water, by building ternary phase diagrams, the goal of which was to identify the oil-in-water phase composition. The resulting nano-sized emulsion was coated with dicalcium phosphate by utilizing the ionic affinity between calcium ions and the emulsion surface. Since the desired function of the particle is as an oxygen carrier, the particle stability, oxygen capacity, and oxygen release rate were investigated. The first step in the process was to construct ternary phase diagrams with 1,2-dioleoyl-sn-glycero-3-phosphate (DOPA) and soy derived lecithin. The results showed that the lecithin surfactant formed an oil-in-water phase region that was 36 times greater than that of DOPA. With the desired phase composition set, the lecithin emulsion was extruded, resulting in a well-dispersed nanosized particle. A pH titration study of the emulsion found an optimized calcium phosphate coating condition at pH 8.8, at which, the calcium ion had a greater affinity for the emulsion surface than phosphate. A Hill plot was used to show calcium cooperativeness on the emulsion surface which suggested one calcium ion binds to one lecithin molecule. The lecithin emulsion particles were then coated with calcium phosphate using a layering technique that allowed for careful control of the coating thickness. The overall particle hydrodynamic radius was consistent with the growth of the calcium phosphate coating, from 8 nm to 28 nm. This observation was further supported with cryo-TEM measurements. The stability of the coated emulsion was tested in conditions that simulate practical thermal, physical, and time-dependent conditions. Throughout the tests, the coated emulsion exhibited a constant mono-dispersed particle size, while the uncoated emulsion size fluctuated greatly and exhibited increased polydispersion. The fast mixing method with the stopped-flow apparatus was employed to test the product as an oxygen carrier, and it was shown that particles with thicker calcium phosphate coatings released smaller amounts of oxygen in a given timeframe. This study proved the hypothesis by showing a fundamental understanding of emulsion science, coating the flexible emulsion surface with a biocompatible material, and a strong particle performance with regard to stability and as an oxygen carrier.

Electrospun Polymer Blend Nanofibers for Tunable Drug Delivery: The Role of Transformative Phase Separation on Controlling the Release Rate.

PubMed

Tipduangta, Pratchaya; Belton, Peter; Fábián, László; Wang, Li Ying; Tang, Huiru; Eddleston, Mark; Qi, Sheng

2016-01-04

Electrospun fibrous materials have a wide range of biomedical applications, many of them involving the use of polymers as matrices for incorporation of therapeutic agents. The use of polymer blends improves the tuneability of the physicochemical and mechanical properties of the drug loaded fibers. This also benefits the development of controlled drug release formulations, for which the release rate can be modified by altering the ratio of the polymers in the blend. However, to realize these benefits, a clear understanding of the phase behavior of the processed polymer blend is essential. This study reports an in depth investigation of the impact of the electrospinning process on the phase separation of a model partially miscible polymer blend, PVP K90 and HPMCAS, in comparison to other conventional solvent evaporation based processes including film casting and spin coating. The nanoscale stretching and ultrafast solvent removal of electrospinning lead to an enhanced apparent miscibility between the polymers, with the same blends showing micronscale phase separation when processed using film casting and spin coating. Nanoscale phase separation in electrospun blend fibers was confirmed in the dry state. Rapid, layered, macroscale phase separation of the two polymers occurred during the wetting of the fibers. This led to a biphasic drug release profile from the fibers, with a burst release from PVP-rich phases and a slower, more continuous release from HPMCAS-rich phases. It was noted that the model drug, paracetamol, had more favorable partitioning into the PVP-rich phase, which is likely to be a result of greater hydrogen bonding between PVP and paracetamol. This led to higher drug contents in the PVP-rich phases than the HPMCAS-rich phases. By alternating the proportions of the PVP and HPMCAS, the drug release rate can be modulated.

Cadmium Alternatives for High-Strength Steel JTP. Phase 2

DTIC Science & Technology

2007-01-24

Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 U.S. AIR FORCE Project Overview Objective Assess DoD- selected cadmium alternatives in...focused) – Phase III (fatigue testing focused) • Down- selection of candidates for further testing after each phase of testing is complete (Phases I...Laboratories – Mr. John Marshall U.S. AIR FORCE Phase I Overview and Selection Process – Traditional plating (primary coatings): • Sputtered Aluminum

Growth and Filling Regularities of Filamentary Channels in Non-Metallic Inorganic Coatings Under Anodic Oxidation of Valve Metals. Mathematical Modeling

NASA Astrophysics Data System (ADS)

Mamaev, A. I.; Mamaeva, V. A.; Kolenchin, N. F.; Chubenko, A. K.; Kovalskaya, Ya. B.; Dolgova, Yu. N.; Beletskaya, E. Yu.

2015-12-01

Theoretical models are developed for growth and filling processes in filamentary channels of nanostructured non-metallic coatings produced by anodizing and microplasma oxidation. Graphical concentration distributions are obtained for channel-reacting anions, cations, and sparingly soluble reaction products depending on the time of electric current transmission and the length of the filamentary channel. Graphical distributions of the front moving velocity for the sparingly soluble compound are presented. The resulting model representation increases the understanding of the anodic process nature and can be used for a description and prediction of porous anodic film growth and filling. It is shown that the character of the filamentary channel growth and filling causes a variety of processes determining the textured metal - nonmetallic inorganic coating phase boundary formation.

An environmentally compliant cerium-based conversion coating for aluminum protection

NASA Astrophysics Data System (ADS)

Lin, Xuan

Chromate conversion coatings have been extensively used in the aircraft industry for the corrosion protection of aluminum alloys. Unfortunately, hexavalent chromium, which is a primary component in the chromating process, is a confirmed carcinogen. Because of rising remediation and disposal costs caused by increasingly strict regulations, the replacement of the traditional chromate conversion process is becoming a top priority in the metal finishing industry. This research focused on the electrodeposition of cerium-based coatings on 7075-T6 aluminum alloy in an electrolyte containing a cerium salt, an oxidizing agent and an organic solvent. The cerium-rich deposits were characterized by phase composition, oxidation state, coating thickness, surface morphology, deposition mechanism and polarization behavior. Chemical and electrochemical tests were utilized to compare the corrosion resistance between cerium-based coatings and chromate conversion coatings. To characterize and simulate the deposition process, a variety of approaches were utilized to study the oxidation states of cerium in various soluble and precipitated forms as a function of hydrogen peroxide and electrolyte pH. The pH ranges where the oxidation and reduction reactions dominate were determined. Further studies were performed to optimize the corrosion performance of cerium-based coatings and to understand the effects of electrolyte constituents and deposition parameters. The optimum levels for these variables were identified. A patent disclosure on the cerium-based coating process was made to the University of Missouri-Rolla and has now been officially filed with the U.S. Patent Office.

Phase analysis of plasma-sprayed zirconia-yttria coatings

NASA Technical Reports Server (NTRS)

Shankar, N. R.; Berndt, C. C.; Herman, H.

1983-01-01

Phase analysis of plasma-sprayed 8 wt pct-yttria-stabilized zirconia (YSZ) thermal barrier coatings and powders was carried out by X-ray diffraction. Step scanning was used for increased peak resolution. Plasma spraying of the YSZ powder into water or onto a steel substrate to form a coating reduced the cubic and monoclinic phases with a simultaneous increase in the tetragonal phase. Heat treatment of the coating at 1150 C for 10 h in an Ar atmosphere increased the amount of cubic and monoclinic phases. The implications of these transformations on coating performance and integrity are discussed.

Surface properties of AZ91 magnesium alloy after PEO treatment using molybdate salts and low current densities

NASA Astrophysics Data System (ADS)

Pezzato, Luca; Brunelli, Katya; Napolitani, Enrico; Magrini, Maurizio; Dabalà, Manuele

2015-12-01

Plasma electrolytic oxidation (PEO) process is a recently developed electrochemical method used to produce on the surface of various metals oxide ceramic coatings that improve corrosion and wear properties of the substrate. In this work, PEO process was applied on AZ91 magnesium alloy using low current densities (0.05 A/cm2) and an alkaline solution of silicates with different concentrations of sodium molybdate (0.3-3 g/l). The effect of the low current densities of process and of molybdate salts on the corrosion resistance of the coatings was studied with potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) in chloride and sulfate environment. The morphology, the phases and the chemical composition of the coatings were examined using a scanning electron microscope equipped with EDS, X-ray diffraction, secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The corrosion properties of the PEO coated samples were remarkably improved if compared with the uncoated samples. The addition of sodium molybdate, in determinate conditions, had a positive effect on the characteristics of the coatings in terms of corrosion resistance.

Influence of heat-pretreatments on the microstructural and mechanical properties of galfan-coated metal bonds

NASA Astrophysics Data System (ADS)

Hordych, Illia; Rodman, Dmytro; Nürnberger, Florian; Schmidt, Hans Christian; Orive, Alejandro Gonzalez; Homberg, Werner; Grundmeier, Guido; Maier, Hans Jürgen

2018-05-01

In the present study, heat-treatment assisted bonding of galfan-coated low-carbon steel sheets was investigated. Steel sheets were bonded by cold rolling subsequently to a heat treatment in the temperature range from 400 °C to 550°C. The reduction ratio during cold rolling was varied in the range from 50% to 80%. Such high reduction ratios were achieved by splitting the bonding process into three stages. By employing heat-treatments, the mechanical properties of the bonds were improved. The heat-pretreatment allowed the formation of brittle intermetallic phases that were easily fractured in the rolling gap during the bonding process. Thus, juvenile non-oxidized surfaces were formed, which facilitated the bonding between the steel layers, and thus increased the bond strength. The intermetallic phases were actively formed at temperatures of 450 °C and above; however increasing temperatures resulted in decreasing mechanical properties due to oxidation processes. The local microstructure was analyzed by scanning electron microscopy in order to characterize the contact zone on the micro level with a focus on the formation of intermetallic phases. The mechanical properties were determined in tensile shear tests. Interestingly, it was found that the galfan coating allowed for bonding at room temperature, and the aluminum fraction was primarily responsible for the enhanced oxide formation during the heat-pretreatment.

Triso coating development progress for uranium nitride kernels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jolly, Brian C.; Lindemer, Terrence; Terrani, Kurt A.

2015-08-01

In support of fully ceramic matrix (FCM) fuel development [1-2], coating development work is ongoing at the Oak Ridge National Laboratory (ORNL) to produce tri-structural isotropic (TRISO) coated fuel particles with UN kernels [3]. The nitride kernels are used to increase fissile density in these SiC-matrix fuel pellets with details described elsewhere [4]. The advanced gas reactor (AGR) program at ORNL used fluidized bed chemical vapor deposition (FBCVD) techniques for TRISO coating of UCO (two phase mixture of UO2 and UCx) kernels [5]. Similar techniques were employed for coating of the UN kernels, however significant changes in processing conditions weremore » required to maintain acceptable coating properties due to physical property and dimensional differences between the UCO and UN kernels (Table 1).« less

Structural and Mechanical Properties of the ZrC/Ni-Nanodiamond Coating Synthesized by the PVD and Electroplating Processes for the Cutting Knifes

NASA Astrophysics Data System (ADS)

Chayeuski, V.; Zhylinski, V.; Cernashejus, O.; Visniakov, N.; Mikalauskas, G.

2018-04-01

In this work, combined gradient ZrC/Ni-nanodiamond ultradispersed diamonds (UDD) coatings were synthesized on the surface of knife blades made of hard alloy WC-2 wt.% Co by electroplating and cathode arc evaporation PVD techniques to increase the durability period of a wood-cutting milling tool. The microstructure, phase and elemental composition, microhardness, and adhesion strength of the coatings were investigated. Ni-UDD layer is not mixed with the ZrC coating and hard alloy substrate. Cobalt is present in Ni-UDD layer after deposition of ZrC. The ZrC/Ni-nanodiamond coating consists of separate phases of zirconium carbide (ZrC), α-Ni, and Ni-UDD. The maximum value of microhardness of the Ni-nanodiamond coating is 5.9 GPa. The microhardness value of the ZrC/Ni-nanodiamond coatings is 25 ± 6 GPa, which corresponds to the microhardness of the hard alloy substrate and ZrC coating. The obtained high values of the critical loads on the scratch track of the ZrC/Ni-nanodiamond coating in 24 N prove a sufficiently high value of the adhesion strength of the bottom Ni-UDD layer with WC-Co substrate. Pilot testing of ZrC/Ni-nanodiamond-coated cutting tools proved their increasing durability period to be 1.5-1.6 times higher than that of bare tools, when milling laminated chipboard.

Development of coatings for ultrasonic additive manufacturing sonotrode using laser direct metal deposition process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sridharan, Niyanth; Dehoff, Ryan R.; Jordan, Brian H.

2016-10-01

ORNL partnered with Fabrisonic, LLC to develop galling resistant hard facing coatings on sonotrodes used to fabricate 3D printed materials using ultrasonic additive manufacturing. The development and deployment of a coated sonotrode is expected to push the existing state of the art to facilitate the solidstate additive manufacturing of hard steels and titanium alloys. To this effect a structurally amorphous stainless steel material and cobalt chrome material were deposited on the sonotrode material. Both the deposits showed good adhesion to the substrate. The coatings made using the structurally amorphous steel materials showed cracking during the initial trials and cracking wasmore » eliminated by deposition on a preheated substrate. Both the coatings show hardness in excess of 600 HVN. Thus the phase 1 of this project has been used to identify suitable materials to use to coat the sonotrode. Despite the fact that successful deposits were obtained, the coatings need to be evaluated by performing detailed galling tests at various temperatures. In addition field tests are also necessary to test the stability of these coatings in a high cycle ultrasonic vibration mode. If awarded, phase 2 of the project would be used to optimize the composition of the deposit material to maximize galling resistance. The industrial partner would then use the coated sonotrode to fabricate builds made of austenitic stainless steel to test the viability of using a coated sonotrode.« less

Antimicrobial activity of silica coated silicon nano-tubes (SCSNT) and silica coated silicon nano-particles (SCSNP) synthesized by gas phase condensation.

PubMed

Tank, Chiti; Raman, Sujatha; Karan, Sujoy; Gosavi, Suresh; Lalla, Niranjan P; Sathe, Vasant; Berndt, Richard; Gade, W N; Bhoraskar, S V; Mathe, Vikas L

2013-06-01

Silica-coated, silicon nanotubes (SCSNTs) and silica-coated, silicon nanoparticles (SCSNPs) have been synthesized by catalyst-free single-step gas phase condensation using the arc plasma process. Transmission electron microscopy and scanning tunneling microscopy showed that SCSNTs exhibited a wall thickness of less than 1 nm, with an average diameter of 14 nm and a length of several 100 nm. Both nano-structures had a high specific surface area. The present study has demonstrated cheaper, resistance-free and effective antibacterial activity in silica-coated silicon nano-structures, each for two Gram-positive and Gram-negative bacteria. The minimum inhibitory concentration (MIC) was estimated, using the optical densitometric technique, and by determining colony-forming units. The MIC was found to range in the order of micrograms, which is comparable to the reported MIC of metal oxides for these bacteria. SCSNTs were found to be more effective in limiting the growth of multidrug-resistant Staphylococcus aureus over SCSNPs at 10 μg/ml (IC 50 = 100 μg/ml).

Liquid phase diffusion bonding of A1070 by using metal formate coated Zn sheet

NASA Astrophysics Data System (ADS)

Ozawa, K.; Koyama, S.; shohji, I.

2017-05-01

Aluminium alloy have high strength and easily recycle due to its low melting point. Therefore, aluminium is widely used in the manufacturing of cars and electronic devices. In recent years, the most common way for bonding aluminium alloy is brazing and friction stir welding. However, brazing requires positional accuracy and results in the formation of voids by the flax residue. Moreover, aluminium is an excellent heat radiating and electricity conducting material; therefore, it is difficult to bond together using other bonding methods. Because of these limitations, liquid phase diffusion bonding is considered to the suitable method for bonding aluminium at low temperature and low bonding pressure. In this study, the effect of metal formate coating processing of zinc surface on the bond strength of the liquid phase diffusion bonded interface of A1070 has been investigated by SEM observation of the interfacial microstructures and fractured surfaces after tensile test. Liquid phase diffusion bonding was carried out under a nitrogen gas atmosphere at a bonding temperature of 673 K and 713 K and a bonding load of 6 MPa (bonding time: 15 min). As a result of the metal formate coating processing, a joint having the ultimate tensile strength of the base aluminium was provided. It is hypothesized that this is because metallic zinc is generated as a result of thermal decomposition of formate in the bonded interface at lower bonding temperatures.

Fabrication of electrically bistable organic semiconducting/ferroelectric blend films by temperature controlled spin coating.

PubMed

Hu, Jinghang; Zhang, Jianchi; Fu, Zongyuan; Weng, Junhui; Chen, Weibo; Ding, Shijin; Jiang, Yulong; Zhu, Guodong

2015-03-25

Organic semiconducting/ferroelectric blend films attracted much attention due to their electrical bistability and rectification properties and thereof the potential in resistive memory devices. During film deposition from the blend solution, spinodal decomposition induced phase separation, resulting in discrete semiconducting phase whose electrical property could be modulated by the continuous ferroelectric phase. However, blend films processed by common spin coating method showed extremely rough surfaces, even comparable to the film thickness, which caused large electrical leakage and thus compromised the resistive switching performance. To improve film roughness and thus increase the productivity of these resistive devices, we developed temperature controlled spin coating technique to carefully adjust the phase separation process. Here we reported our experimental results from the blend films of ferroelectric poly(vinylidene fluoride-trifluoroethylene (P(VDF-TrFE)) and semiconducting poly(3-hexylthiophene) (P3HT). We conducted a series of experiments at various deposition temperatures ranging from 20 to 90 °C. The resulting films were characterized by AFM, SEM, and VPFM to determine their structure and roughness. Film roughness first decreased and then increased with the increase of deposition temperature. Electrical performance was also characterized and obviously improved insulating property was obtained from the films deposited between 50 and 70 °C. By temperature control during film deposition, it is convenient to efficiently fabricate ferroelectric/semiconducting blend films with good electrical bistability.

Elevated Temperature Solid Particle Erosion Performance of Plasma-Sprayed Co-based Composite Coatings with Additions of Al2O3 and CeO2

NASA Astrophysics Data System (ADS)

Nithin, H. S.; Desai, Vijay; Ramesh, M. R.

2017-11-01

In this paper, investigation into solid particle erosion behavior of atmospheric plasma-sprayed composite coating of CoCrAlY reinforced with Al2O3 and CeO2 oxides on Superni 76 at elevated temperature of 600 °C is presented. Alumina particles are used as erodent at two impact angles of 30° and 90°. The microstructure, porosity, hardness, toughness and adhesion properties of the as-sprayed coatings are studied. The effects of temperature and phase transformation in the coatings during erosion process are analyzed using XRD and EDS techniques. Optical profilometer is used for accurate elucidation of erosion volume loss. CoCrAlY/CeO2 coating showed better erosion resistance with a volume loss of about 50% of what was observed in case of CoCrAlY/Al2O3/YSZ coating. Lower erosion loss is observed at 90° as compared to 30° impact angle. The erosion mechanism evaluated using SEM micrograph revealed that the coatings experienced ductile fracture exhibiting severe deformation with unusual oxide cracks. Reinforced metal oxides provide shielding effect for erodent impact, enabling better erosion resistance. The oxidation of the coating due to high-temperature exposure reforms erosion process into oxidation-modified erosion process.

Process for forming a homogeneous oxide solid phase of catalytically active material

DOEpatents

Perry, Dale L.; Russo, Richard E.; Mao, Xianglei

1995-01-01

A process is disclosed for forming a homogeneous oxide solid phase reaction product of catalytically active material comprising one or more alkali metals, one or more alkaline earth metals, and one or more Group VIII transition metals. The process comprises reacting together one or more alkali metal oxides and/or salts, one or more alkaline earth metal oxides and/or salts, one or more Group VIII transition metal oxides and/or salts, capable of forming a catalytically active reaction product, in the optional presence of an additional source of oxygen, using a laser beam to ablate from a target such metal compound reactants in the form of a vapor in a deposition chamber, resulting in the deposition, on a heated substrate in the chamber, of the desired oxide phase reaction product. The resulting product may be formed in variable, but reproducible, stoichiometric ratios. The homogeneous oxide solid phase product is useful as a catalyst, and can be produced in many physical forms, including thin films, particulate forms, coatings on catalyst support structures, and coatings on structures used in reaction apparatus in which the reaction product of the invention will serve as a catalyst.

Heterogeneous ice nucleation on phase-separated organic-sulfate particles: effect of liquid vs. glassy coatings

NASA Astrophysics Data System (ADS)

Schill, G. P.; Tolbert, M. A.

2013-05-01

Atmospheric ice nucleation on aerosol particles relevant to cirrus clouds remains one of the least understood processes in the atmosphere. Upper tropospheric aerosols as well as sub-visible cirrus residues are known to be enhanced in both sulfates and organics. The hygroscopic phase transitions of organic-sulfate particles can have an impact on both the cirrus cloud formation mechanism and resulting cloud microphysical properties. In addition to deliquescence and efflorescence, organic-sulfate particles are known to undergo another phase transition known as liquid-liquid phase separation. The ice nucleation properties of particles that have undergone liquid-liquid phase separation are unknown. Here, Raman microscopy coupled with an environmental cell was used to study the low temperature deliquescence, efflorescence, and liquid-liquid phase separation behavior of 2 : 1 mixtures of organic polyols (1,2,6-hexanetriol and 1 : 1 1,2,6-hexanetriol + 2,2,6,6-tetrakis(hydroxymethyl)cyclohexanol) and ammonium sulfate from 240-265 K. Further, the ice nucleation efficiency of these organic-sulfate systems after liquid-liquid phase separation and efflorescence was investigated from 210-235 K. Raman mapping and volume-geometry analysis indicate that these particles contain solid ammonium sulfate cores fully engulfed in organic shells. For the ice nucleation experiments, we find that if the organic coatings are liquid, water vapor diffuses through the shell and ice nucleates on the ammonium sulfate core. In this case, the coatings minimally affect the ice nucleation efficiency of ammonium sulfate. In contrast, if the coatings become semi-solid or glassy, ice instead nucleates on the organic shell. Consistent with recent findings that glasses can be efficient ice nuclei, the phase-separated particles are nearly as efficient at ice nucleation as pure crystalline ammonium sulfate.

Heterogeneous ice nucleation on phase-separated organic-sulfate particles: effect of liquid vs. glassy coatings

NASA Astrophysics Data System (ADS)

Schill, G. P.; Tolbert, M. A.

2012-12-01

Atmospheric ice nucleation on aerosol particles relevant to cirrus clouds remains one of the least understood processes in the atmosphere. Upper tropospheric aerosols as well as sub-visible cirrus residues are known to be enhanced in both sulfates and organics. The hygroscopic phase transitions of organic-sulfate particles can have an impact on both the cirrus cloud formation mechanism and resulting cloud microphysical properties. In addition to deliquescence and efflorescence, organic-sulfate particles are known to undergo another phase transition known as liquid-liquid phase separation. The ice nucleation properties of particles that have undergone liquid-liquid phase separation are unknown. Here, Raman microscopy coupled with an environmental cell was used to study the low temperature deliquescence, efflorescence, and liquid-liquid phase separation behavior of 2:1 mixtures of organic polyols (1,2,6-hexanetriol, and 1:1 1,2,6-hexanetriol +2,2,6,6-tetrakis(hydroxymethyl)cycohexanol) and ammonium sulfate from 240-265 K. Further, the ice nucleation efficiency of these organic-sulfate systems after liquid-liquid phase separation and efflorescence was investigated from 210-235 K. Raman mapping and volume-geometry analysis indicates that these particles contain solid ammonium sulfate cores fully engulfed in organic shells. For the ice nucleation experiments, we find that if the organic coatings are liquid, water vapor diffuses through the shell and ice nucleates on the ammonium sulfate core. In this case, the coatings minimally affect the ice nucleation efficiency of ammonium sulfate. In contrast, if the coatings become semi-solid or glassy, ice instead nucleates on the organic shell. Consistent with recent findings that glasses can be efficient ice nuclei, the phase separated particles are nearly as efficient at ice nucleation as pure crystalline ammonium sulfate.

Optimizing surface characteristics for cell adhesion and proliferation on titanium plasma spray coatings on polyetheretherketone.

PubMed

Yoon, Byung Jo Victor; Xavier, Fred; Walker, Brendon R; Grinberg, Samuel; Cammisa, Frank P; Abjornson, Celeste

2016-10-01

Titanium plasma spray coating on polyetheretherketone (PEEK) is a recent innovation to interbody spacer technology. The inherent hydrophobic properties of standard, uncoated PEEK implants can hamper cell attachment and bone healing during fusion. The addition of titanium coating not only offers initial stability due to increased surface roughness but also long-term stability due to bony ongrowth created from osteoconductive microenvironment on the device surface. The previously established hydrophilic and osteophilic properties of commercially pure titanium (CPTi) can potentially provide an ideal environment promoting cell attachment and bony ongrowth when applied at the end plate level of the fusion site. Because the surface material composition and topography is what seems to directly affect cell adhesion, it is important to determine the ideal titanium coating for the highest effectiveness. The purpose of the study is to determine whether there is an optimal surface roughness for the titanium coatings and whether different polishing methods have a greater effect than roughness or topography in mediating cell adhesion to the surface. The study was divided into two phases. In Phase 1, the effects of varying surface roughnesses on identical polishing method were compared. In Phase 2, the effect of varying polishing methods was compared on identical surface roughnesses. Coating thickness, porosity, and surface roughness were characterized using an optical microscope as per ASTM F 1854 standards. For both phases, PEEK coupons with plasma-sprayed CPTi were used, and human mesenchymal stem cells (hMSCs) at an initial density of 25,000 cells/cm 2 were seeded and cultured for 24 hours before fixation in 10% formalin. The cultured hMSCs were visualized by 4',6-diamidino-2-phenylindole (DAPI) staining, a fluorescent stain that binds to the DNA of living cells. Samples were imaged using an environmental scanning electron microscope (eSEM) (Carl Zeiss Microscopy, Thornwood, NY, USA) using a backscattered detector. Image analysis of the CPTi coatings showed uniform and rough surfaces. For Phase 1, roughness was evaluated as fine, medium, and coarse. The eSEM image analysis and cell counting by DAPI demonstrated that hMSCs have a tendency to form stronger adhesion and greater pseudopodia extensions on fine roughness surfaces. Individual hMSCs were seen forming cytoplasmic processes extending across the width of a pore. There was a 4- and 20-fold reduction in adhered hMSCs with an increase to medium and coarse roughnesses, respectively. For Phase 2, studied groups are (1) medium CPTi coating with zirconia polishing, (2) medium CPTi coating with CPTi polishing, and (3) fine CPTi coating with CPTi polishing. The eSEM image analysis and cell counting by DAPI demonstrated that hMSCs have a tendency to form stronger adhesion and greater pseudopodia extensions on Group 3 over the other two groups. There was a twofold reduction in adhered hMSCs on medium roughness relative to fine. No difference in cell adhesion was found between Groups 1 and 2. Individual hMSCs were seen forming cytoplasmic processes extending across the width of a pore. Previously, it was accepted without much scrutiny that surface coatings were beneficial. This study begins to discover that surface topography directly affects the potential for cells to adhere and proliferate and lead to greater surgical efficacy. Copyright © 2016 Elsevier Inc. All rights reserved.

Galvanic Liquid Applied Coating Development for Protection of Steel in Concrete

NASA Technical Reports Server (NTRS)

Curran, Joseph John; Curran, Jerry; MacDowell, Louis

2004-01-01

Corrosion of reinforcing steel in concrete is a major problem affecting NASA facilities at Kennedy Space Center (KSC), other government agencies, and the general public. Problems include damage to KSC launch support structures, transportation and marine infrastructures, as well as building structures. A galvanic liquid applied coating was developed at KSC in order to address this problem. The coating is a non-epoxy metal rich ethyl silicate liquid coating. The coating is applied as a liquid from initial stage to final stage. Preliminary data shows that this coating system exceeds the NACE 100 millivolt shift criterion. The remainder of the paper details the development of the coating system through the following phases: Phase I: Development of multiple formulations of the coating to achieve easy application characteristics, predictable galvanic activity, long-term protection, and minimum environmental impact. Phase II: Improvement of the formulations tested in Phase I including optimization of metallic loading as well as incorporation of humectants for continuous activation. Phase III: Application and testing of improved formulations on the test blocks. Phase IV: Incorporation of the final formulation upgrades onto large instrumented structures (slabs).

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

NASA Astrophysics Data System (ADS)

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.

Inorganic-organic hybrid coating material for the online in-tube solid-phase microextraction of monohydroxy polycyclic aromatic hydrocarbons in urine.

PubMed

Wang, ShuLing; Xu, Hui

2016-12-01

An inorganic-organic hybrid nanocomposite (zinc oxide/polypyrrole) that represents a novel kind of coating for in-tube solid-phase microextraction is reported. The composite coating was prepared by a facile electrochemical polymerization strategy on the inner surface of a stainless-steel tube. Based on the coated tube, a novel online in-tube solid-phase microextraction with liquid chromatography and mass spectrometry method was developed and applied for the extraction of three monohydroxy polycyclic aromatic hydrocarbons in human urine. The coating displayed good extraction ability toward monohydroxy polycyclic aromatic hydrocarbons. In addition, long lifespan, excellent stability, and good compression resistance were also obtained for the coating. The experimental conditions affecting the extraction were optimized systematically. Under the optimal conditions, the limits of detection and quantification were in the range of 0.039-0.050 and 0.130-0.167 ng/mL, respectively. Good linearity (0.2-100 ng/mL) was obtained with correlation coefficients larger than 0.9967. The repeatability, expressed as relative standard deviation, ranged between 2.5% and 9.4%. The method offered the advantage of process simplicity, rapidity, automation, and sensitivity in the analysis of human urinary monohydroxy polycyclic aromatic hydrocarbons in two different cities of Hubei province. An acceptable recovery of monohydroxy polycyclic aromatic hydrocarbons (64-122%) represented the additional attractive features of the method in real urine analysis. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Process-Property Relationship for Air Plasma-Sprayed Gadolinium Zirconate Coatings

NASA Astrophysics Data System (ADS)

Dwivedi, Gopal; Tan, Yang; Viswanathan, Vaishak; Sampath, Sanjay

2015-02-01

The continuous need of elevating operating temperature of gas turbine engines has introduced several challenges with the current state-of-the-art yttria-stabilized zirconia (YSZ)-based thermal barrier coatings (TBCs), requiring examination of new TBC material with high temperature phase stability, lower thermal conductivity, and resistance to environmental ash particles. Gadolinium zirconate (Gd2Zr2O7) (GDZ) has been shown to meet many of these requirements, and has, in fact, been successfully implemented in to engine components. However, several fundamental issues related to the process-ability, toughness, and microstructural differences for GDZ when compared to equivalent YSZ coating. This study seeks to critically address the process-structure-property correlations for plasma-sprayed GDZ coating subjected to controlled parametric exploration. Use of in-flight diagnostics coupled with in situ and ex situ coating property monitoring allows examination and comparison of the process-property interplay and the resultant differences between the two TBC compositions. The results indicate that it is feasible to retain material chemistry and fabricate relevant microstructures of interest with GDZ with concomitant performance advantages such as low conductivity, mechanical compliance, sintering resistance, and suppression of environmentally induced damage from ash particles. This study provides a framework for optimal design and manufacturing of emergent multi-layer and multi-material TBCs.

Influence of laser power on microstructure and mechanical properties of laser welded-brazed Mg to Ni coated Ti alloys

NASA Astrophysics Data System (ADS)

Tan, Caiwang; Lu, Qingshuang; Chen, Bo; Song, Xiaoguo; Li, Liqun; Feng, Jicai; Wang, Yang

2017-03-01

AZ31B Magnesium (Mg) and Ti-6Al-4V titanium (Ti) alloys with Ni coating were joined by laser welding-brazing process using AZ92 Mg based filler. The influence of laser power on microstructure and mechanical properties were investigated. Ni coating was found to significantly promote good wetting-spreading ability of molten filler on the Ti sheet. Acceptable joints without obvious defects were obtained within a relatively wide processing window. In the process metallurgical bonding was achieved by the formation of Ti3Al phase at direct irradiation zone and Al-Ni phase followed by a layer of Mg-Al-Ni ternary compound adjacent to the fusion zone at the intermediate zone. The thickness of reaction layers increased slowly with the increasing laser power. The tensile-shear test indicated that joints produced at the laser power of 1300 W reached 2387 N fracture load, representing 88.5% joint efficiency with respect to the Mg base metal. The corresponding failure occurred in the fusion zone of the Mg base metal, while joints fractured at the interface at lower/higher laser power due to the crack or excessive intermetallic compound (IMC) formation along the interface.

On the fate of particles liberated from hydroxyapatite coatings in vivo.

PubMed

Dunne, C F; Gibbons, J; FitzPatrick, D P; Mulhall, K J; Stanton, K T

2015-03-01

Hydroxyapatite (HA) has been used as a coating for orthopaedic implants for over 30 years to help promote the fixation of orthopaedic implants into the surrounding bone. However, concerns exist about the fate of the hydroxyapatite coating and hydroxyapatite particles in vivo, especially in the wake of recent concerns about particulates from metal-on-metal bearings. Here, we assess the mechanisms of particle detachment from coated orthopaedic devices as well as the safety and performance concerns and biomedical implications arising from the liberation of the particles by review of the literature. The mechanisms that can result in the detachment of the HA coating from the implant can be mechanical or biochemical, or both. Mechanical mechanisms include implant insertion, abrasion, fatigue and micro-motion. Biochemical mechanisms that contribute to the liberation of HA particles include dissolution into extra-cellular fluid, cell-mediated processes and crystallisation of amorphous phases. The form the particles take once liberated is influenced by a number of factors such as coating method, the raw powder morphology, processing parameters, coating thickness and coating structure. This review summarises and discusses each of these factors and concludes that HA is a safe biomimetic material to use as a coating and does not cause any problems in particulate form if liberated as debris from an orthopaedic implant.

Influence of frequency on the structure of zirconium oxide coatings deposited from aqueous electrolytes under microplasma oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gubaidulina, Tatiana A., E-mail: goub2002@mail.ru; Sergeev, Viktor P., E-mail: vserg@mail.tomsknet.ru; Fedorischeva, Marina V., E-mail: fmw@ispms.tsc.ru

2015-10-27

The work describes the microplasma oxidation (MPO) of zirconium surface resulting in the formation of zirconium oxide Zr-Al-Nb-O. We have used novel power supply to deposit oxide ceramic coatings by MPO and studied the effect of current density on the phase structure of oxide ceramic coatings. The size of microcracks in the coatings was determined at different frequencies. We have also used EVO50c scanning election microscope with an attachment for elemental analysis to study the morphology and elemental composition of oxide ceramic coating. In addition, we have established the influence of the frequency on the phase composition of the coating:more » at the frequency of 2500 Hz, the fraction of monoclinic phase was 18%, while the fraction of tetragonal phase amounted to 72%. The oxide ceramic coating produced at 250 Hz contained 38% of monoclinic phase and 62% of tetragonal phase; in addition, it had no buildups and craters.« less

Novel Surface Modification Method for Ultrasupercritical Coal-Fired Boilers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, T. Danny

2013-05-22

US Department of Energy seeks an innovative coating technology for energy production to reduce the emission of SOx, NOx, and CO2 toxic gaseous species. To realize this need, Inframat Corporation (IMC) proposed an SPS thermal spray coating technique to produce ultrafine/nanocoatings that can be deposited onto the surfaces of high temperature boiler tubes, so that higher temperatures of boiler operation becomes possible, leading to significantly reduced emission of toxic gaseous species. It should be noted that the original PI was Dr. Xinqing Ma, who after 1.5 year conducting this project left Inframat in December, 2008. Thus, the PI was transferredmore » to Dr. Danny Xiao, who originally co-authored the proposal with Dr. Ma, in order to carry the project into a completion. Phase II Objectives: The proposed technology has the following attributes, including: (1). Dispersion of a nanoparticle or alloyed particle in a solvent to form a uniform slurry feedstock; (2). Feeding of the slurry feedstock into a thermal spray flame, followed by deposition of the slurry feedstock onto substrates to form tenacious nanocoatings; (3). High coating performance: including high bonding strength, and high temperature service life in the temperature range of 760oC/1400oF. Following the above premises, our past Phase I project has demonstrated the feasibility in small scale coatings on boiler substrates. The objective of this Phase II project was to focus on scale-up the already demonstrated Phase I work for the fabrication of SPS coatings that can satisfy DOE's emission reduction goals for energy production operations. Specifically, they are: (1). Solving engineering problems to scale-up the SPS-HVOF delivery system to a prototype production sub-delivery system; (2). Produce ultrafine/nanocoatings using the scale-up prototype system; (3). Demonstrate the coated components using the scale-up device having superior properties. Proposed Phase II Tasks: In the original Phase II proposal, we have six (6) technical tasks plus one (1) reporting task, as described below: Task 1 Scale-up and optimize the SPS process; Task 2 Coating design and fabrication with desired microstructure; Task 3 Evaluate microstructure and physical properties; Task 4 Test performance of long-term corrosion and erosion; Task 5 Test mechanical property and reliability; Task 6 Coating of a prototype boiler tube for evaluation; Task 7 Reporting task. To date, we have already completed all the technical tasks of 1 through 6. Major Phase II Achievements: In this four (4) year working period, Inframat had spent great effort to complete the proposed tasks. The project had been completed; the goals have been accomplished. Major achievements obtained include: (1). Developed a prototype scale-up slurry feedstock delivery system for thermal spray coatings; (2). Successfully coated high performance coatings using this scale-up slurry delivery system; (3). Commercial applications in energy efficiency and clean energy components have been developed using this newly fabricated slurry feedstock delivery system.« less

Influence of free carbon on the characteristics of ZrC and deposition of near-stoichiometric ZrC in TRISO coated particle fuel

NASA Astrophysics Data System (ADS)

Kim, Daejong; Ko, Myeong Jin; Park, Ji Yeon; Cho, Moon Sung; Kim, Weon-Ju

2014-08-01

Advanced TRISO coated particles with a ZrC coating layer as a main pressure boundary were fabricated by a fluidized-bed chemical vapor deposition (FBCVD) method using a chloride process. Experiments were performed to determine the effect of codeposition of graphitic carbon on the hardness and obtain the stoichiometric ZrC phase. The ZrC coating layer was composed of a mixture of ZrC and graphitic carbon phases at a low ZrCl4/CH4 ratio. A near-stoichiometric ZrC without the free carbon can be obtained by employing an impeller-driven ZrCl4 vaporizer. The codeposition of the graphitic carbon significantly lowered the hardness of ZrC while increasing the fraction of the carbon. The hardness reached its maximum when ZrC was in a slight carbon deficit without free carbon. As the graphitic carbon increased up to 12 vol%, the hardness was reduced by approximately 50% compared to the near-stoichiometric ZrC.

Sol-gel titania-coated needles for solid phase dynamic extraction-GC/MS analysis of desomorphine and desocodeine.

PubMed

Su, Chi-Ju; Srimurugan, Sankarewaran; Chen, Chinpiao; Shu, Hun-Chi

2011-01-01

Novel sol-gel titania film coated needles for solid-phase dynamic extraction (SPDE)-GC/MS analysis of desomorphine and desocodeine are described. The high thermal stability of titania film permits efficient extraction and analysis of poorly volatile opiate drugs. The influences of sol-gel reaction time, coating layer, extraction and desorption time and temperature on the SPDE needle performance were investigated. The deuterium labeled internal standard was introduced either during the extraction of analyte or directly injected to GC after the extraction process. The latter method was shown to be more sensitive for the analysis of water and urine samples containing opiate drugs. The proposed conditions provided a wide linear range (from 5-5000 ppb), and satisfactory linearity, with R(2) values from 0.9958 to 0.9999, and prominent sensitivity, LOQs (1.0-5.0 ng/g). The sol-gel titania film coated needle with SPDE-GC/MS will be a promising technique for desomorphine and desocodeine analysis in urine.

Survey of selective solar absorbers and their limitations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mattox, D.M.; Sowell, R.R.

1980-01-01

A number of selective absorber coating systems with high solar absorptance exist which may be used in the mid-temperature range. Some of the systems are more chemically and thermally stable than others. Unfortunately, there are large gaps in the stability data for a large number of the systems. In an inert environment, the principle degradation mechanisms are interdiffusion between the layers or phases and changes in surface morphology. These degradation mechanisms would be minimized by using refractory metals and compounds for the absorbing layer and using refractory materials or diffusion barriers for the underlayer. For use in a reactive environment,more » the choice of materials is much more restrictive since internal chemical reactions can change phase compositions and interfacial reactions can lead to loss of adhesion. For a coating process to be useful, it is necessary to determine what parameters influence the performance of the coating and the limits to these parameters. This process sensitivity has a direct influence on the production process controls necessary to produce a good product. Experience with electroplated black chrome has been rather disappointing. Electroplating should be a low cost deposition process but the extensive bath analysis and optical monitoring necessary to produce a thermally stable produce for use to 320/sup 0/C has increased cost signficantly. 49 references.« less

Encapsulation of thermal energy storage media

DOEpatents

Dhau, Jaspreet; Goswami, Dharendra; Jotshi, Chand K.; Stefanakos, Elias K.

2017-09-19

In one embodiment, a phase change material is encapsulated by forming a phase change material pellet, coating the pellet with flexible material, heating the coated pellet to melt the phase change material, wherein the phase change materials expands and air within the pellet diffuses out through the flexible material, and cooling the coated pellet to solidify the phase change material.

Development and Testing of Ceramic Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Choi, Sung R.; Miller, Robert A.

2004-01-01

Ceramic thermal barrier 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. Durability of the coating systems remains a critical issue with the ever-increasing temperature requirements. Thermal conductivity increase and coating degradation due to sintering and phase changes are known to be detrimental to coating performance. There is a need to characterize the coating behavior and temperature limits, in order to potentially take full advantage of the current coating capability, and also accurately assess the benefit gained from advanced coating development. In this study, thermal conductivity behavior and cyclic durability of plasma-sprayed ZrO2-8wt%Y2O3 thermal barrier coatings were evaluated under laser heat-flux simulated high temperature, large thermal gradient and thermal cycling conditions. The coating degradation and failure processes were assessed by real-time monitoring of the coating thermal conductivity under the test conditions. The ceramic coating crack propagation driving forces and resulting failure modes will be discussed in light of high temperature mechanical fatigue and fracture testing results.

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

NASA Astrophysics Data System (ADS)

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.

Interference lithography for optical devices and coatings

NASA Astrophysics Data System (ADS)

Juhl, Abigail Therese

Interference lithography can create large-area, defect-free nanostructures with unique optical properties. In this thesis, interference lithography will be utilized to create photonic crystals for functional devices or coatings. For instance, typical lithographic processing techniques were used to create 1, 2 and 3 dimensional photonic crystals in SU8 photoresist. These structures were in-filled with birefringent liquid crystal to make active devices, and the orientation of the liquid crystal directors within the SU8 matrix was studied. Most of this thesis will be focused on utilizing polymerization induced phase separation as a single-step method for fabrication by interference lithography. For example, layered polymer/nanoparticle composites have been created through the one-step two-beam interference lithographic exposure of a dispersion of 25 and 50 nm silica particles within a photopolymerizable mixture at a wavelength of 532 nm. In the areas of constructive interference, the monomer begins to polymerize via a free-radical process and concurrently the nanoparticles move into the regions of destructive interference. The holographic exposure of the particles within the monomer resin offers a single-step method to anisotropically structure the nanoconstituents within a composite. A one-step holographic exposure was also used to fabricate self-healing coatings that use water from the environment to catalyze polymerization. Polymerization induced phase separation was used to sequester an isocyanate monomer within an acrylate matrix. Due to the periodic modulation of the index of refraction between the monomer and polymer, the coating can reflect a desired wavelength, allowing for tunable coloration. When the coating is scratched, polymerization of the liquid isocyanate is catalyzed by moisture in air; if the indices of the two polymers are matched, the coatings turn transparent after healing. Interference lithography offers a method of creating multifunctional self-healing coatings that readout when damage has occurred.

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

NASA Technical Reports Server (NTRS)

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.

Stationary phase deposition based on onium salts

DOEpatents

Wheeler, David R [Albuquerque, NM; Lewis, Patrick R [Albuquerque, NM; Dirk, Shawn M [Albuquerque, NM; Trudell, Daniel E [Albuquerque, NM

2008-01-01

Onium salt chemistry can be used to deposit very uniform thickness stationary phases on the wall of a gas chromatography column. In particular, the stationary phase can be bonded to non-silicon based columns, especially microfabricated metal columns. Non-silicon microfabricated columns may be manufactured and processed at a fraction of the cost of silicon-based columns. In addition, the method can be used to phase-coat conventional capillary columns or silicon-based microfabricated columns.

An overview on tritium permeation barrier development for WCLL blanket concept

NASA Astrophysics Data System (ADS)

Aiello, A.; Ciampichetti, A.; Benamati, G.

2004-08-01

The reduction of tritium permeation through blanket structural materials and cooling tubes has to be carefully evaluated to minimise radiological hazards. A strong effort has been made in the past to select the best technological solution for the realisation of tritium permeation barriers (TPB) on complex structures not directly accessible after the completion of the manufacturing process. The best solution was identified in aluminium rich coatings, which form Al 2O 3 at their surface. Two technologies were selected as reference for the realisation of coating in the WCLL blanket concept: the chemical vapour deposition (CVD) process developed on laboratory scale by CEA, and the hot dipping (HD) process developed by FZK. The results obtained during three years of tests on CVD and HD coated specimens in gas and liquid metal phase are summarised and discussed.

Electrodeposition of nanostructured Sn-Zn coatings

NASA Astrophysics Data System (ADS)

Salhi, Y.; Cherrouf, S.; Cherkaoui, M.; Abdelouahdi, K.

2016-03-01

The electrodeposition of Sn-Zn coating at ambient temperature was investigated. The bath consists of metal salts SnCl2·2H2O and ZnSO4·7H2O and sodium citrate (NaC6H5Na3O7·2H2O) as complexing agent. To prevent precipitation, the pH is fixed at 5. Reducing tin and zinc through Sncit2- and ZnHcit- complex respectively is confirmed by the presence of two cathodic peaks on the voltammogram. The kinetic of tin (II) reduction process is limited by the SnCit2- dissociation. The SEM and TEM observations have showed that the coating consists of a uniform Sn-Zn layer composed of fine grains on which tin aggregates grow up. XRD revealed peaks corresponding to the hexagonal Zn phase and the tetragonal β-Sn phase.

Theory, Investigation and Stability of Cathode Electrocatalytic Activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ding, Dong; Liu, Mingfei; Lai, Samson

2012-09-30

The main objective of this project is to systematically characterize the surface composition, morphology, and electro-catalytic properties of catalysts coated on LSCF, aiming to establish the scientific basis for rational design of high-performance cathodes by combining a porous backbone (such as LSCF) with a thin catalyst coating. The understanding gained will help us to optimize the composition and morphology of the catalyst layer and microstructure of the LSCF backbone for better performance. More specifically, the technical objectives include: (1) to characterize the surface composition, morphology, and electro-catalytic properties of catalysts coated on LSCF; (2) to characterize the microscopic details andmore » stability of the LSCF-catalyst (e.g., LSM) interfaces; (3) to establish the scientific basis for rational design of high-performance cathodes by combining a porous backbone (such as LSCF) with a thin catalyst coating; and (4) to demonstrate that the performance and stability of porous LSCF cathodes can be enhanced by the application of a thin-film coating of LSM through a solution infiltration process in small homemade button cells and in commercially available cells of larger dimension. We have successfully developed dense, conformal LSM films with desired structure, composition, morphology, and thickness on the LSCF surfaces by two different infiltration processes: a non-aqueous and a water-based sol-gel process. It is demonstrated that the activity and stability of LSCF cathodes can be improved by the introduction of a thin-film LSM coating through an infiltration process. Surface and interface of the LSM-coated LSCF cathode were systematically characterized using advanced microscopy and spectroscopy techniques. TEM observation suggests that a layer of La and Sr oxide was formed on LSCF surfaces after annealing. With LSM infiltration, in contrast, we no longer observe such La/Sr oxide layer on the LSM-coated LSCF samples after annealing under similar conditions. This was also confirmed by x-ray analyses. For example, soft x-ray XANES data reveal that Co cations displace the Mn cations as being more favored to be reduced. Variations in the Sr-O in the annealed LSCF Fourier-transformed (FT) EXAFS suggest that some Sr segregation is occurring, but is not present in the annealed LSM-infiltrated LSCF cathode materials. Further, a surface enhanced Raman technique was also developed into to probe and map LSM and LSCF phase on underlying YSZ substrate, enabling us to capture important chemical information of cathode surfaces under practical operating conditions. Electrochemical models for the design of test cells and understanding of mechanism have been developed for the exploration of fundamental properties of electrode materials. Novel catalyst coatings through particle depositions (SDC, SSC, and LCC) or continuous thin films (PSM and PSCM) were successfully developed to improve the activity and stability of LSCF cathodes. Finally, we have demonstrated enhanced activity and stability of LSCF cathodes over longer periods of time in homemade and commercially available cells by an optimized LSM infiltration process. Microstructure examination of the tested cells did not show obvious differences between blank and infiltrated cells, suggesting that the infiltrated LSM may form a coherent film on the LSCF cathodes. There was no significant change in the morphology or microstructure of the LSCF cathode due to the structural similarity of LSCF and LSM. Raman analysis of the tested cells indicated small peaks emerging on the blank cells that correspond to trace amounts of secondary phase formation during operation (e.g., CoO{sub x}). The formation of this secondary phase might be attributed to performance degradation. In contrast, there was no such secondary phase observed in the LSM infiltrated cells, indicating that the LSM modification staved off secondary phase formation and thus improved the stability.« less

Carbon-based nanostructured surfaces for enhanced phase-change cooling

NASA Astrophysics Data System (ADS)

Selvaraj Kousalya, Arun

To maintain acceptable device temperatures in the new generation of electronic devices under development for high-power applications, conventional liquid cooling schemes will likely be superseded by multi-phase cooling solutions to provide substantial enhancement to the cooling capability. The central theme of the current work is to investigate the two-phase thermal performance of carbon-based nanostructured coatings in passive and pumped liquid-vapor phase-change cooling schemes. Quantification of the critical parameters that influence thermal performance of the carbon nanostructured boiling surfaces presented herein will lead to improved understanding of the underlying evaporative and boiling mechanisms in such surfaces. A flow boiling experimental facility is developed to generate consistent and accurate heat transfer performance curves with degassed and deionized water as the working fluid. New means of boiling heat transfer enhancement by altering surface characteristics such as surface energy and wettability through light-surface interactions is explored in this work. In this regard, carbon nanotube (CNT) coatings are exposed to low-intensity irradiation emitted from a light emitting diode and the subcooled flow boiling performance is compared against a non-irradiated CNT-coated copper surface. A considerable reduction in surface superheat and enhancement in average heat transfer coefficient is observed. In another work involving CNTs, the thermal performance of CNT-integrated sintered wick structures is evaluated in a passively cooled vapor chamber. A physical vapor deposition process is used to coat the CNTs with varying thicknesses of copper to promote surface wetting with the working fluid, water. Thermal performance of the bare sintered copper powder sample and the copper-functionalized CNT-coated sintered copper powder wick samples is compared using an experimental facility that simulates the capillary fluid feeding conditions of a vapor chamber. Nanostructured samples having a thicker copper coating provided a considerable increase in dryout heat flux while maintaining lower surface superheat temperatures compared to a bare sintered powder sample; this enhancement is attributed primarily to the improved surface wettability. Dynamic contact angle measurements are conducted to quantitatively compare the surface wetting trends for varying copper coating thicknesses and confirm the increase in hydrophilicity with increasing coating thickness. The second and relatively new carbon nanostructured coating, carbon nanotubes decorated with graphitic nanopetals, are used as a template to manufacture boiling surfaces with heterogeneous wettability. Heat transfer surfaces with parallel alternating superhydrophobic and superhydrophilic stripes are fabricated by a combination of oxygen plasma treatment, Teflon coating and shadow masking. Such composite wetting surfaces exhibit enhanced flow-boiling performance compared to homogeneous wetting surfaces. Flow visualization studies elucidate the physical differences in nucleate boiling mechanisms between the different heterogeneous wetting surfaces. The third and the final carbon nanomaterial, graphene, is examined as an oxidation barrier coating for liquid and liquid-vapor phase-change cooling systems. Forced convection heat transfer experiments on bare and graphene-coated copper surfaces reveal nearly identical liquid-phase and two-phase thermal performance for the two surfaces. Surface analysis after thermal testing indicates significant oxide formation on the entire surface of the bare copper substrate; however, oxidation is observed only along the grain boundaries of the graphene-coated substrate. Results suggest that few-layer graphene can act as a protective layer even under vigorous flow boiling conditions, indicating a broad application space of few-layer graphene as an ultra-thin oxidation barrier coating.

Synthesis and chromatographic characterization of dextran-coated zirconia high-performance liquid chromatographic stationary phases.

PubMed

Dunlap, C J; Carr, P W

1996-10-11

Porous zirconia particles made by the oil emulsion (OE) method and the polymerization-induced colloid aggregation (PICA) method have been coated with a small, carboxymethylated (approximately 5%) dextran polymer and crosslinked in place. The parameters of the coating process (dextran concentration, adsorption time and crosslinker concentration) have all been examined and an optimum value for each determined. The coated and uncoated materials were characterized by nitrogen sorptometry and size-exclusion chromatography (SEC) using solutes (polystyrenes and dextrans) of well-defined molecular masses. Nitrogen sorptometry results show that the PICA material has a much lower pore volume and smaller pore diameter than do the OE materials. Despite this, the elution volumes of the SEC probes change very little upon polymer coating the PICA material while the OE material shows a very large change upon coating.

Effects of Current Density on Microstructure and Corrosion Property of Coating on AZ31 Mg Alloy Processed via Plasma Electrolytic Oxidation

NASA Astrophysics Data System (ADS)

Lee, Kang Min; Einkhah, Feryar; Sani, Mohammad Ali Faghihi; Ko, Young Gun; Shin, Dong Hyuk

The effects of the current density on the micro structure and the corrosion property of the coating on AZ31 Mg alloy processed by the plasma electrolytic oxidation (PEO) were investigated. The present coatings were produced in an acid electrolyte containing K2ZrF6 with three different current densities, i.e., 100, 150, and 200 mA/cm2. From the microstructural observations, as the applied current density was increased, the diameter of micro-pores formed by the plasma discharges with high temperature increased. The coatings on AZ31 Mg alloy were mainly composed of MgO, ZrO2, MgF2, and Mg2Zr5O12 phases. The results of potentiodynamic polarization clearly showed that the PEO-treated AZ31 Mg alloy applied at 100 mA/cm2 of current density exhibited better corrosion properties than the others.

Oxidation of Alumina-Forming MAX Phases in Turbine Environments

NASA Technical Reports Server (NTRS)

Smialek, James; Garg, Anita; Harder, Bryan; Nesbitt, James; Gabb, Timothy; Gray, SImon

2017-01-01

Protective coatings for high temperature turbine components are based on YSZ thermal barriers and oxidation resistant, alumina-forming NiAl or NiCoCrAlY bond coats. Ti2AlC and Cr2AlC MAX phases are thus of special interest because of good oxidation resistance and CTE that can match Al2O3 and YSZ. Their alumina scales grow according to cubic kinetics due to grain growth in the scale, with initial heating dominated by fast TiO2 growth. Protective cubic kinetics are also found in high pressure burner rig tests of MAXthal 211 Ti2AlC, but with reduced rates due to volatile TiO(OH)2 formation in water vapor. YSZ-coatings on bulk Ti2AlC exhibit remarkable durability up to 1300C in furnace tests and at least a 25x life advantage compared to superalloys. At another extreme, Cr2AlC is resistant to low temperature Na2SO4 hot corrosion and exhibits thermal cycling stability bonded to a superalloy disk material. Accordingly, sputtered Cr2AlC coatings on disk specimens prevented hot corrosion detriments on LCF. Breakaway oxidation (Ti2AlC), scale spallation (Cr2AlC), interdiffusion, and processing as coatings still present serious challenges. However the basic properties of MAX phases provide some unusual opportunities for use in high temperature turbines.

Thin Film Coating with Highly Dispersible Barium Titanate-Polyvinylpyrrolidone Nanoparticles.

PubMed

Li, Jinhui; Inukai, Koji; Takahashi, Yosuke; Tsuruta, Akihiro; Shin, Woosuck

2018-05-01

Thin BaTiO₃ (BT) coating layers are required in various multilayer ceramic technologies, and fine nanosized BT particles with good dispersion in solution are essential for this coating process. In this work, cubic and tetragonal phase monodispersed BT nanoparticles—which were referred to as LBT and HBT-PVP coated on their surface by polyvinylpyrrolidone (PVP) polymer—were prepared by low temperature synthesis (LTS) and hydrothermal method (HT) at 80 and 230 °C, respectively. They were applied for the thin film coating on polyethylene terephthalate (PET) and Si wafer substrates by a simple bar coating. The thickness of BT, LBT-PVP, and HBT-PVP films prepared by their 5 wt % coating agent on Si are around 268, 308, and 263 nm, and their surface roughness are 104.6, 91.6, and 56.1 nm, respectively. The optical transmittance of BT, LBT-PVP, and HBT-PVP films on PET are 55, 66, and 73% at 550 nm wavelength and the haze values are 34.89, 24.70, and 20.53% respectively. The mechanism of dispersant adsorbed on the BT surface for densification of thin film during the drying process of the film was discussed.

Thin Film Coating with Highly Dispersible Barium Titanate-Polyvinylpyrrolidone Nanoparticles

PubMed Central

Li, Jinhui; Inukai, Koji; Takahashi, Yosuke; Tsuruta, Akihiro; Shin, Woosuck

2018-01-01

Thin BaTiO3 (BT) coating layers are required in various multilayer ceramic technologies, and fine nanosized BT particles with good dispersion in solution are essential for this coating process. In this work, cubic and tetragonal phase monodispersed BT nanoparticles—which were referred to as LBT and HBT-PVP coated on their surface by polyvinylpyrrolidone (PVP) polymer—were prepared by low temperature synthesis (LTS) and hydrothermal method (HT) at 80 and 230 °C, respectively. They were applied for the thin film coating on polyethylene terephthalate (PET) and Si wafer substrates by a simple bar coating. The thickness of BT, LBT-PVP, and HBT-PVP films prepared by their 5 wt % coating agent on Si are around 268, 308, and 263 nm, and their surface roughness are 104.6, 91.6, and 56.1 nm, respectively. The optical transmittance of BT, LBT-PVP, and HBT-PVP films on PET are 55, 66, and 73% at 550 nm wavelength and the haze values are 34.89, 24.70, and 20.53% respectively. The mechanism of dispersant adsorbed on the BT surface for densification of thin film during the drying process of the film was discussed. PMID:29724007

Nanopatterning of metal-coated silicon surfaces via ion beam irradiation: Real time x-ray studies reveal the effect of silicide bonding

DOE Office of Scientific and Technical Information (OSTI.GOV)

El-Atwani, Osman; Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907; Gonderman, Sean

We investigated the effect of silicide formation on ion-induced nanopatterning of silicon with various ultrathin metal coatings. Silicon substrates coated with 10 nm Ni, Fe, and Cu were irradiated with 200 eV argon ions at normal incidence. Real time grazing incidence small angle x-ray scattering (GISAXS) and x-ray fluorescence (XRF) were performed during the irradiation process and real time measurements revealed threshold conditions for nanopatterning of silicon at normal incidence irradiation. Three main stages of the nanopatterning process were identified. The real time GISAXS intensity of the correlated peaks in conjunction with XRF revealed that the nanostructures remain for amore » time period after the removal of the all the metal atoms from the sample depending on the binding energy of the metal silicides formed. Ex-situ XPS confirmed the removal of all metal impurities. In-situ XPS during the irradiation of Ni, Fe, and Cu coated silicon substrates at normal incidence demonstrated phase separation and the formation of different silicide phases that occur upon metal-silicon mixing. Silicide formation leads to nanostructure formation due the preferential erosion of the non-silicide regions and the weakening of the ion induced mass redistribution.« less

Electrochemical Behavior of Biomedical Titanium Alloys Coated with Diamond Carbon in Hanks' Solution

NASA Astrophysics Data System (ADS)

Gnanavel, S.; Ponnusamy, S.; Mohan, L.; Radhika, R.; Muthamizhchelvan, C.; Ramasubramanian, K.

2018-03-01

Biomedical implants in the knee and hip are frequent failures because of corrosion and stress on the joints. To solve this important problem, metal implants can be coated with diamond carbon, and this coating plays a critical role in providing an increased resistance to implants toward corrosion. In this study, we have employed diamond carbon coating over Ti-6Al-4V and Ti-13Nb-13Zr alloys using hot filament chemical vapor deposition method which is well-established coating process that significantly improves the resistance toward corrosion, wears and hardness. The diamond carbon-coated Ti-13Nb-13Zr alloy showed an increased microhardness in the range of 850 HV. Electrochemical impedance spectroscopy and polarization studies in SBF solution (simulated body fluid solution) were carried out to understand the in vitro behavior of uncoated as well as coated titanium alloys. The experimental results showed that the corrosion resistance of Ti-13Nb-13Zr alloy is relatively higher when compared with diamond carbon-coated Ti-6Al-4V alloys due to the presence of β phase in the Ti-13Nb-13Zr alloy. Electrochemical impedance results showed that the diamond carbon-coated alloys behave as an ideal capacitor in the body fluid solution. Moreover, the stability in mechanical properties during the corrosion process was maintained for diamond carbon-coated titanium alloys.

Coating of peanuts with edible whey protein film containing alpha-tocopherol and ascorbyl palmitate.

PubMed

Han, J H; Hwang, H-M; Min, S; Krochta, J M

2008-10-01

Physical properties of whey protein isolate (WPI) coating solution incorporating ascorbic palmitate (AP) and alpha-tocopherol (tocopherol) were characterized, and the antioxidant activity of dried WPI coatings against lipid oxidation in roasted peanuts were investigated. The AP and tocopherol were mixed into a 10% (w/w) WPI solution containing 6.7% glycerol. Process 1 (P1) blended an AP and tocopherol mixture directly into the WPI solution using a high-speed homogenizer. Process 2 (P2) used ethanol as a solvent for dissolving AP and tocopherol into the WPI solution. The viscosity and turbidity of the WPI coating solution showed the Newtonian fluid behavior, and 0.25% of critical concentration of AP in WPI solution rheology. After peanuts were coated with WPI solutions, color changes of peanuts were measured during 16 wk of storage at 25 degrees C, and the oxidation of peanuts was determined by hexanal analysis using solid-phase micro-extraction samplers and GC-MS. Regardless of the presence of antioxidants in the coating layer, the formation of hexanal from the oxidation of peanut lipids was reduced by WPI coatings, which indicates WPI coatings protected the peanuts from oxygen permeation and oxidation. However, the incorporation of antioxidants in the WPI coating layer did not show a significant difference in hexanal production from that of WPI coating treatment without incorporation of antioxidants.

Response of Cr and Cr-Al coatings on Zircaloy-2 to high temperature steam

NASA Astrophysics Data System (ADS)

Zhong, Weicheng; Mouche, Peter A.; Heuser, Brent J.

2018-01-01

The oxidation behavior of chromium (Cr) and chromium-aluminum (CrAl) coatings with various compositions deposited on Zircaloy-2 to 700 °C high-temperature steam (HTS) exposure has been investigated. CrAl coatings with higher Al compositions demonstrate lower oxidation weight gain. A layer of γ-alumina developed on the CrAl coatings with Al composition over 43 at%, while Al2O3 and Cr2O3 developed on CrAl coatings with Al composition below 33 at%. Oxidation of Zircaloy-2 substrate was inhibited by the 1um coatings to 20 h HTS exposure. Coating constituent elements diffused into the substrate and formed intermetallic phases with the Zircaloy substrate. Thicker layers of intermetallic phases developed on the coatings with higher Al composition. The intermetallic phases included Fe and Ni, indicating the dissolution of second phase particles (SPPs) during HTS exposure.

MC3T3-E1 cell response of amorphous phase/TiO2 nanocrystal composite coating prepared by microarc oxidation on titanium.

PubMed

Zhou, Rui; Wei, Daqing; Yang, Haoyue; Feng, Wei; Cheng, Su; Li, Baoqiang; Wang, Yaming; Jia, Dechang; Zhou, Yu

2014-06-01

Bioactive amorphous phase/TiO2 nanocrystal (APTN) composite coatings were fabricated by microarc oxidation (MAO) on Ti. The APTN coatings are composed of much amorphous phase with Si, Na, Ca, Ti and O elements and a few TiO2 nanocrystals. With increasing applied voltage, the micropore density of the APTN coating decreases and the micropore size of the APTN coating increases. The results indicate that less MC3T3-E1 cells attach on the APTN coatings as compared to Ti. However, the APTN coatings greatly enhance the cell proliferation ability and the activity of alkaline phosphatase. The amorphous phase and the concentrations of the released Ca and Si from the APTN coatings during cell culture have significant effects on the cell response. Copyright © 2014 Elsevier B.V. All rights reserved.

A basic study on Thermosyphon-type thermal storage unit (TSU) using Nanofluid as the heat transfer medium

NASA Astrophysics Data System (ADS)

Li, Shuang-Fei; Wang, Ping-Yang; Liu, Zhen-hua

2018-05-01

This study proposed a novel thermosyphon-type thermal storage unit using water-based CuO nanofluid as the phase-change heat transfer medium. Seven tubular canisters containing solid-liquid phase-change material (PCM) with peak melting temperature of 100 °C were placed vertically into the center of the TSU which is a vertical cylindrical vessel made of stainless steel. Coat formed by depositing nanoparticles during the phase-change process was adopted to increase the wettability of the heat transfer surfaces of the canisters. We investigated the phase-change heat transfer, as well as the heat-storage and heat-release properties, of the TSU through experimental and computational analysis. Our results demonstrate that this thermal storage unit construction can propose good heat transfer and heat-storage/heat-release performance. The coating of nanoparticles onto the heat transfer surfaces increases the surface wettability and improves both the evaporation and condensation heat transfer. The main thermal resistance in the TSU results from the conductive heat transfer inside of the PCM. All phase-change thermal resistance of liquid film in charging and discharging processes can be ignored in this TSU.

Development and Fatigue Testing of Ceramic Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

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

2004-01-01

Ceramic thermal barrier 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. Durability of the coating systems remains a critical issue with the ever-increasing temperature requirements. Thermal conductivity increase and coating degradation due to sintering and phase changes are known to be detrimental to coating performance. There is a need to characterize the coating thermal fatigue behavior and temperature limit, in order to potentially take full advantage of the current coating capability. In this study, thermal conductivity and cyclic fatigue behaviors of plasma-sprayed ZrO2-8wt%Y2O3 thermal barrier coatings were evaluated under high temperature, large thermal gradient and thermal cycling conditions. The coating degradation and failure processes were assessed by real-time monitoring of the coating thermal conductivity under the test conditions. The ceramic coating crack initiation and propagation driving forces and failure modes under the cyclic thermal loads will be discussed in light of the high temperature mechanical fatigue and fracture testing results.

Fabrication of Cu2ZnSn(S,Se)4 (CZTSSe) absorber films based on solid-phase synthesis and blade coating processes

NASA Astrophysics Data System (ADS)

Ma, Ruixin; Yang, Fan; Li, Shina; Zhang, Xiaoyong; Li, Xiang; Cheng, Shiyao; Liu, Zilin

2016-04-01

CZTSSe is an important earth abundant collection of materials for the development of low cost and high efficiency thin film solar cells. This work developed a simple non-vacuum-based route to fabricate CZTSSe absorber films. This was demonstrated by first synthesizing Cu2ZnSnS4 (CZTS) nano-crystalline based on solid-phase synthesis. Then a stable colloidal ink composed of CZTS nano-crystalline was blade coated on Mo-coated substrates followed by an annealing process under Ar atmosphere. After CZTS films formation, the films were sintered into CZTSSe absorber films by exposing them under Selenium vapor. The formation of a kesterite type CZTS was confirmed using X-ray diffraction and Raman scattering measurements. The band gap of CZTSSe absorber films was determined to be 1.26 eV, which was appropriate for use as an absorber layer in thin film solar cells. The CZTSSe absorber films showed a good photovoltatic performance, demonstrating this simple approach had great potential for CZTSSe solar cell production.

Characterization and in-situ formation mechanism of tungsten carbide reinforced Fe-based alloy coating by plasma cladding

NASA Astrophysics Data System (ADS)

Wang, Mi-qi; Zhou, Ze-hua; Wu, Lin-tao; Ding, Ying; Wang, Ze-hua

2018-04-01

The precursor carbonization method was first applied to prepare W-C compound powder to perform the in-situ synthesis of the WC phase in a Fe-based alloy coating. The in-situ formation mechanism during the cladding process is discussed in detail. The results reveal that fine and obtuse WC particles were successfully generated and distributed in Fe-based alloy coating via Fe/W-C compound powders. The WC particles were either surrounded by or were semi-enclosed in blocky M7C3 carbides. Moreover, net-like structures were confirmed as mixtures of M23C6 and α-Fe; these structures were transformed from M7C3. The coarse herringbone M6C carbides did not only derive from the decomposition of M7C3 but also partly originated from the chemical reaction at the α-Fe/M23C6 interface. During the cladding process, the phase evolution of the precipitated carbides was WC → M7C3 → M23C6 + M6C.

Sensitivity studies of different aerosol indirect effects in mixed-phase clouds

NASA Astrophysics Data System (ADS)

Lohmann, U.; Hoose, C.

2009-11-01

Aerosols affect the climate system by changing cloud characteristics. Using the global climate model ECHAM5-HAM, we investigate different aerosol effects on mixed-phase clouds: The glaciation effect, which refers to a more frequent glaciation due to anthropogenic aerosols, versus the de-activation effect, which suggests that ice nuclei become less effective because of an anthropogenic sulfate coating. The glaciation effect can partly offset the indirect aerosol effect on warm clouds and thus causes the total anthropogenic aerosol effect to be smaller. It is investigated by varying the parameterization for the Bergeron-Findeisen process and the threshold coating thickness of sulfate (SO4-crit), which is required to convert an externally mixed aerosol particle into an internally mixed particle. Differences in the net radiation at the top-of-the-atmosphere due to anthropogenic aerosols between the different sensitivity studies amount up to 0.5 W m-2. This suggests that the investigated mixed-phase processes have a major effect on the total anthropogenic aerosol effect.

Sensitivity studies of different aerosol indirect effects in mixed-phase clouds

NASA Astrophysics Data System (ADS)

Lohmann, U.; Hoose, C.

2009-07-01

Aerosols affect the climate system by changing cloud characteristics. Using the global climate model ECHAM5-HAM, we investigate different aerosol effects on mixed-phase clouds: The glaciation effect, which refers to a more frequent glaciation due to anthropogenic aerosols, versus the de-activation effect, which suggests that ice nuclei become less effective because of an anthropogenic sulfate coating. The glaciation effect can partly offset the indirect aerosol effect on warm clouds and thus causes the total anthropogenic aerosol effect to be smaller. It is investigated by varying the parameterization for the Bergeron-Findeisen process and the threshold coating thickness of sulfate (SO4-crit), which is required to convert an externally mixed aerosol particle into an internally mixed particle. Differences in the net radiation at the top-of-the-atmosphere due to anthropogenic aerosols between the different sensitivity studies amount up to 0.5 W m-2. This suggests that the investigated mixed-phase processes have a major effect on the total anthropogenic aerosol effect.

Polarization Phase-Compensating Coats for Metallic Mirrors

NASA Technical Reports Server (NTRS)

Balasubramanian, Kunjithapatham

2006-01-01

A method of compensating for or minimizing phase differences between orthogonal polarizations of light reflected from metallic mirrors at oblique incidence, as, for example, from weakly curved mirrors, is undergoing development. The method is intended to satisfy a need to maintain precise polarization phase relationships or minimum polarization differences needed for proper operation of telescopes and other scientific instruments that include single or multiple mirrors. The basic idea of the method is to optimally coat mirrors with thin engineered layers of materials that introduce phase differences that, as nearly precisely as possible, are opposite of the undesired phase differences arising in reflection with non-optimum coatings. Depending on the specific optical system, the method could involve any or all of the following elements: a) Optimization of a single coat on all the mirrors in the system. b) Optimization of a unique coat for each mirror such that the polarization phase effects of the coat on one mirror compensate, to an acceptably high degree over an acceptably wide wavelength range, for those of the coat on another mirror. c) Tapering the coat on each mirror. Optimization could involve the choice of a single dielectric coating material and its thickness, or design of a more complex coat consisting of multiple layers of different dielectric materials and possibly some metallic materials. Such designs and coatings are particularly significant and needed for obtaining very high quality of wavefront required in high-contrast imaging instruments such as the NASA Terrestrial Planet Finder Coronagraph.

High temperature wear performance of HVOF-sprayed Cr3C2-WC-NiCoCrMo and Cr3C2-NiCr hardmetal coatings

NASA Astrophysics Data System (ADS)

Zhou, Wuxi; Zhou, Kesong; Li, Yuxi; Deng, Chunming; Zeng, Keli

2017-09-01

A novel Cr3C2-WC-NiCoCrMo and commercial Cr3C2-NiCr thermal spray-grade powders with particle size of -45 + 15 μm were prepared by an agglomeration and sintering process. Cr3C2-WC-NiCoCrMo and Cr3C2-NiCr coatings were deposited by high velocity oxygen fuel (HVOF) spraying. The fundamental properties of both coatings were evaluated and friction wear test against Al2O3 counterbodies of both coatings at high temperatures (450 °C, 550 °C, 650 °C) were carried out ball-on-disk high temperature tribometer. All specimens were characterized by optical microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) and 3D non-contact surface mapping profiler. The results have shown that the Cr3C2-WC-NiCoCrMo coating exhibited lower porosity, higher micro-hardness compared to the Cr3C2-NiCr coating. The Cr3C2-WC-NiCoCrMo coating also exhibited better wear resistance and higher friction coefficient compared to the Cr3C2-NiCr coating when sliding against the Al2O3 counterpart. Wear rates of both coatings increased with raising temperature. Both coatings experienced abrasive wear; hard phase particles (WC and Cr3C2) with different sizes, distributed in the matrix phase, will effectively improve the resistance against wear at high temperatures.

Ultra-High Temperature Thermal Barrier Coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jordan, Eric; Gell, Maurice; Wang, Jiwen

In this project, HiFunda LLC worked with the University of Connecticut (UConn) to demonstrate an attractive option for thermal barrier coatings (TBCs), namely yttrium aluminum garnet (YAG), which was well known to have proven thermal stability and excellent high-temperature mechanical properties. YAG and other higher temperature TBCs have not been used to date because they exhibit inadequate durability, resulting from (a) poor erosion resistance and (b) greater thermal expansion mismatch strains compared to 7YSZ. UConn had previously demonstrated that the solution precursor plasma spray (SPPS) process could produce a durable 7YSZ TBC resulting from a highly strain tolerant microstructure, consistingmore » of through-coating-thickness vertical cracks. HiFunda/UConn reasoned at the start of Phase I that such a strain-tolerant microstructure could produce durable, higher temperature TBCs. The Phase I work demonstrated the feasibility of that concept and of SPPS YAG TBCs. The Phase II work demonstrated that SPPS YAG coating possessed the necessary range of properties to be a viable high temperature TBC, including cyclic durability and reduced elevated temperature thermal conductivity. The SPPS YAG TBCs were shown to have the potential to be used at temperatures 200°C higher than APS YSZ, based on thermal stability, sinter resistance, and CMAS resistance. The overall technical objectives of this Phase 2A project were to further improve the commercial viability of SPPS by improving their performance capabilities and manufacturing economics. The improved performance capability was to be achieved through: (1) further reductions in thermal conductivity, which allows higher gas temperatures and/or thinner coatings to achieve similar gas temperatures; and (2) improved resistance to calcium magnesium alumnoslicate (CMAS) attack of the TBCs, which can yield improved lifetimes. The improved thermal conductivity and CMAs resistance was to be accomplished through compositional and microstructural optimization. Finally, the key metrics to improve the process economics were increased deposition rate and efficiency. In addition to these technical objectives, there were commercialization objectives of getting key commercialization partners to evaluate and qualify the SPPS YAG technology independently so that the technology readiness level (TRL) of the technology could be sufficiently advanced to facilitate Phase III strategic partnerships, leading to eventual commercialization consistent with the overall objectives of the DOE SBIR/STTR program. All the Phase 2A goals were successfully achieved.« less

Applications of Laser Cladded WC-Based Wear Resistant Coatings

NASA Astrophysics Data System (ADS)

Verwimp, Jo; Rombouts, Marleen; Geerinckx, Eric; Motmans, Filip

Laser cladding is an additive process wherein a laser source is used to melt metal-based powder or wire on to a metal substrate. The technique is frequently used to produce wear resistant coatings consisting of a metal matrix and a ceramic strengthening phase. In this study mixtures of nickel based powders and various amounts of tungsten carbides have been used as feedstock for laser cladding on a range of steel substrates and for different applications. Crack-free low porosity coatings with a thickness of about 1 mm and carbide concentrations up to 50 vol% have been produced. The evaluation of the wear resistance of the different coatings is performed on lab scale or in the application itself.

Method for thermally spraying crack-free mullite coatings on ceramic-based substrates

NASA Technical Reports Server (NTRS)

Spitsberg, Irene T. (Inventor); Wang, Hongyu (Inventor); Heidorn, Raymond W. (Inventor)

2001-01-01

A process for depositing a mullite coating on a silicon-based material, such as those used to form articles exposed to high temperatures and including the hostile thermal environment of a gas turbine engine. The process is generally to thermally spray a mullite powder to form a mullite layer on a substrate, in which the thermal spraying process is performed so that the mullite powder absorbs a sufficient low level of energy from the thermal source to prevent evaporation of silica from the mullite powder. Processing includes deposition parameter adjustments or annealing to maintain or reestablish phase equilibrium in the mullite layer, so that through-thickness cracks in the mullite layer are avoided.

Method for thermally spraying crack-free mullite coatings on ceramic-based substrates

NASA Technical Reports Server (NTRS)

Spitsberg, Irene T. (Inventor); Wang, Hongyu (Inventor); Heidorn, Raymond W. (Inventor)

2000-01-01

A process for depositing a mullite coating on a silicon-based material, such as those used to form articles exposed to high temperatures and including the hostile thermal environment of a gas turbine engine. The process is generally to thermally spray a mullite powder to form a mullite layer on a substrate, in which the thermal spraying process is performed so that the mullite powder absorbs a sufficient low level of energy from the thermal source to prevent evaporation of silica from the mullite powder. Processing includes deposition parameter adjustments or annealing to maintain or reestablish phase equilibrium in the mullite layer, so that through-thickness cracks in the mullite layer are avoided.

Seed defective reduction in automotive Electro-Deposition Coating Process of truck cabin

NASA Astrophysics Data System (ADS)

Sonthilug, Aekkalag; Chutima, Parames

2018-02-01

The case study company is one of players in Thailand’s Automotive Industry who manufacturing truck and bus for both domestic and international market. This research focuses on a product quality problem about seed defects occurred in the Electro-Deposition Coating Process of truck cabin. The 5-phase of Six Sigma methodology including D-Define, M-Measure, A-Analyze, I-Improve, and C-Control is applied to this research to identify root causes of problem for setting new parameters of each significant factor. After the improvement, seed defects in this process is reduced from 9,178 defects per unit to 876 defects per unit (90% improvement)

An update on coating/manufacturing techniques of microneedles.

PubMed

Tarbox, Tamara N; Watts, Alan B; Cui, Zhengrong; Williams, Robert O

2017-12-29

Recently, results have been published for the first successful phase I human clinical trial investigating the use of dissolving polymeric microneedles… Even so, further clinical development represents an important hurdle that remains in the translation of microneedle technology to approved products. Specifically, the potential for accumulation of polymer within the skin upon repeated application of dissolving and coated microneedles, combined with a lack of safety data in humans, predicates a need for further clinical investigation. Polymers are an important consideration for microneedle technology-from both manufacturing and drug delivery perspectives. The use of polymers enables a tunable delivery strategy, but the scalability of conventional manufacturing techniques could arguably benefit from further optimization. Micromolding has been suggested in the literature as a commercially viable means to mass production of both dissolving and swellable microneedles. However, the reliance on master molds, which are commonly manufactured using resource intensive microelectronics industry-derived processes, imparts notable material and design limitations. Further, the inherently multi-step filling and handling processes associated with micromolding are typically batch processes, which can be challenging to scale up. Similarly, conventional microneedle coating processes often follow step-wise batch processing. Recent developments in microneedle coating and manufacturing techniques are highlighted, including micromilling, atomized spraying, inkjet printing, drawing lithography, droplet-born air blowing, electro-drawing, continuous liquid interface production, 3D printing, and polyelectrolyte multilayer coating. This review provides an analysis of papers reporting on potentially scalable production techniques for the coating and manufacturing of microneedles.

Correlation between Hierarchical Structure and Processing Control of Large-area Spray-coated Polymer Solar Cells toward High Performance

PubMed Central

Huang, Yu-Ching; Tsao, Cheng-Si; Cha, Hou-Chin; Chuang, Chih-Min; Su, Chun-Jen; Jeng, U-Ser; Chen, Charn-Ying

2016-01-01

The formation mechanism of a spray-coated film is different from that of a spin-coated film. This study employs grazing incidence small- and wide-angle X-ray Scattering (GISAXS and GIWAXS, respectively) quantitatively and systematically to investigate the hierarchical structure and phase-separated behavior of a spray-deposited blend film. The formation of PCBM clusters involves mutual interactions with both the P3HT crystal domains and droplet boundary. The processing control and the formed hierarchical structure of the active layer in the spray-coated polymer/fullerene blend film are compared to those in the spin-coated film. How the different post-treatments, such as thermal and solvent vapor annealing, tailor the hierarchical structure of the spray-coated films is quantitatively studied. Finally, the relationship between the processing control and tailored BHJ structures and the performance of polymer solar cell devices is established here, taking into account the evolution of the device area from 1 × 0.3 and 1 × 1 cm2. The formation and control of the special networks formed by the PCBM cluster and P3HT crystallites, respectively, are related to the droplet boundary. These structures are favorable for the transverse transport of electrons and holes. PMID:26817585

Controlling initial biodegradation of magnesium by a biocompatible strontium phosphate conversion coating.

PubMed

Chen, X B; Nisbet, D R; Li, R W; Smith, P N; Abbott, T B; Easton, M A; Zhang, D-H; Birbilis, N

2014-03-01

A simple strontium phosphate (SrP) conversion coating process was developed to protect magnesium (Mg) from the initial degradation post-implantation. The coating morphology, deposition rate and resultant phases are all dependent on the processing temperature, which determines the protective ability for Mg in minimum essential medium (MEM). Coatings produced at 80 °C are primarily made up of strontium apatite (SrAp) with a granular surface, a high degree of crystallinity and the highest protective ability, which arises from retarding anodic dissolution of Mg in MEM. Following 14 days' immersion in MEM, the SrAp coating maintained its integrity with only a small fraction of the surface corroded. The post-degradation effect of uncoated Mg and Mg coated at 40 and 80 °C on the proliferation and differentiation of human mesenchymal stem cells was also studied, revealing that the SrP coatings are biocompatible and permit proliferation to a level similar to that of pure Mg. The present study suggests that the SrP conversion coating is a promising option for controlling the early rapid degradation rate, and hence hydrogen gas evolution, of Mg implants without adverse effects on surrounding cells and tissues. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Section 2: Phase transformation studies in mechanically alloyed Fe-Nz and Fe-Zn-Si intermetallics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jordan, A.; Uwakweh, O.N.C.; Maziasz, P.J.

1997-04-01

The initial stage of this study, which was completed in FY 1995, entailed an extensive analysis characterizing the structural evolution of the Fe-Zn intermetallic system. The primary interest in these Fe-Zn phases stems from the fact that they form an excellent coating for the corrosion protection of steel (i.e., automobile body panels). The Fe-Zn coating generally forms up to four intermetallic phases depending on the particular industrial application used, (i.e., galvanization, galvannealing, etc.). Since the different coating applications are non-equilibrium in nature, it becomes necessary to employ a non-equilibrium method for producing homogeneous alloys in the solid-state to reflect themore » structural changes occurring in a true coating. This was accomplished through the use of a high energy/non-equilibrium technique known as ball-milling which allowed the authors to monitor the evolution process of the alloys as they transformed from a metastable to stable equilibrium state. In FY 1996, this study was expanded to evaluate the presence of Si in the Fe-Zn system and its influence in the overall coating. The addition of silicon in steel gives rise to an increased coating. However, the mechanisms leading to the coating anomaly are still not fully understood. For this reason, mechanical alloying through ball-milling of pure elemental powders was used to study the structural changes occurring in the sandelin region (i.e., 0.12 wt % Si). Through the identification of invariant reactions (i.e., eutectic, etc.) the authors were able to explore the sandelin phenomenon and also determine the various fields or boundaries associated with the Fe-Zn-Si ternary system.« less

Continuous API-crystal coating via coacervation in a tubular reactor.

PubMed

Besenhard, M O; Thurnberger, A; Hohl, R; Faulhammer, E; Rattenberger, J; Khinast, J G

2014-11-20

We present a proof-of-concept study of a continuous coating process of single API crystals in a tubular reactor using coacervation as a microencapsulation technique. Continuous API crystal coating can have several advantages, as in a single step (following crystallization) individual crystals can be prepared with a functional coating, either to change the release behavior, to protect the API from gastric juice or to modify the surface energetics of the API (i.e., to tailor the hydrophobic/hydrophilic characteristics, flowability or agglomeration tendency, etc.). The coating process was developed for the microencapsulation of a lipophilic core material (ibuprofen crystals of 20 μm- to 100 μm-size), with either hypromellose phthalate (HPMCP) or Eudragit L100-55. The core material was suspended in an aqueous solution containing one of these enteric polymers, fed into the tubing and mixed continuously with a sodium sulfate solution as an antisolvent to induce coacervation. A subsequent temperature treatment was applied to optimize the microencapsulation of crystals via the polymer-rich coacervate phase. Cross-linking of the coating shell was achieved by mixing the processed material with an acidic solution (pH<3). Flow rates, temperature profiles and polymer-to-antisolvent ratios had to be tightly controlled to avoid excessive aggregation, leading to pipe plugging. This work demonstrates the potential of a tubular reactor design for continuous coating applications and is the basis for future work, combining continuous crystallization and coating. Copyright © 2014 Elsevier B.V. All rights reserved.

Fused Silica Surface Coating for a Flexible Silica Mat Insulation System

NASA Technical Reports Server (NTRS)

Rhodes, W. H.

1973-01-01

Fused silica insulation coatings have been developed for application to a flexible mat insulation system. Based on crystalline phase nucleation and growth kinetics, a 99+% SiO2 glass was selected as the base composition. A coating was developed that incorporated the high emissivity phase NiCr2O4 as a two phase coating with goals of high emittance and minimum change in thermal expansion. A second major coating classification has a plasma sprayed emittance coating over a sealed pure amorphous SiO2 layer. A third area of development centered on extremely thin amorphous SiO2 coatings deposited by chemical vapor deposition. The coating characterization studies presented are mechanical testing of thin specimens extracted from the coatings, cyclic arc exposures, and emittance measurements before and after arc exposures.

Comparison of Physical-chemical and Mechanical Properties of Chlorapatite and Hydroxyapatite Plasma Sprayed Coatings

PubMed Central

Demnati, Imane; Grossin, David; Marsan, Olivier; Bertrand, Ghislaine; Collonges, Gérard; Combes, Christèle; Parco, Maria; Braceras, Inigo; Alexis, Joel; Balcaen, Yannick; Rey, Christian

2015-01-01

Chlorapatite can be considered a potential biomaterial for orthopaedic applications. Its use as plasma-sprayed coating could be of interest considering its thermal properties and particularly its ability to melt without decomposition unlike hydroxyapatite. Chlorapatite (ClA) was synthesized by a high-temperature ion exchange reaction starting from commercial stoichiometric hydroxyapatites (HA). The ClA powder showed similar characteristics as the original industrial HA powder, and was obtained in the monoclinic form. The HA and ClA powders were plasma-sprayed using a low-energy plasma spraying system with identical processing parameters. The coatings were characterized by physical-chemical methods, i.e. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, including distribution mapping of the main phases detected such as amorphous calcium phosphate (ACP), oxyapatite (OA), and HA or ClA. The unexpected formation of oxyapatite in ClA coatings was assigned to a side reaction with contaminating oxygenated species (O2, H2O). ClA coatings exhibited characteristics different from HA, showing a lower content of oxyapatite and amorphous phase. Although their adhesion strength was found to be lower than that of HA coatings, their application could be an interesting alternative, offering, in particular, a larger range of spraying conditions without formation of massive impurities. PMID:25893015

The improvement of moisture resistance and thermal stability of Ca 3SiO 4Cl 2:Eu 2+ phosphor coated with SiO 2

NASA Astrophysics Data System (ADS)

Zhuang, Jiaqing; Xia, Zhiguo; Liu, Haikun; Zhang, Zepeng; Liao, Libing

2011-02-01

Green-emitting phosphors Ca3SiO4Cl2:Eu2+ were prepared by the high temperature solid-state method. Sol-gel process was adopted to encapsulate the as-prepared phosphors with tetraethylorthosilicate (TEOS) as silicon coating reagent. Fluorescence spectrometer, scanning electron microscopy (SEM) and powder X-ray diffraction (XRD) patterns were employed to characterize the emission spectra, the surface morphologies and the phase structures, respectively. The chemical stability testing was operated by the method of soaking the phosphors in deionized water and roasting them at different temperatures. The results indicated that the surfaces of the green phosphors were evenly coated by SiO2 and the phase structure of the coated phosphors remained the same as the uncoated samples. The luminance centre of Eu2+ did not shift after surface treatment and the luminance intensity of coated phosphors was lower than that of the uncoated samples. The results demonstrated that the water-resistance stability of the coated phosphor was improved to some degree because the pH value and the luminance intensity variation were both smaller than the uncoated phosphor after steeping within the same time. Moreover, the thermal stability of coated phosphors was enhanced obviously compared to the original samples based on the temperature dependent emission spectra measurement.

Demands, Potentials, and Economic Aspects of Thermal Spraying with Suspensions: A Critical Review

NASA Astrophysics Data System (ADS)

Toma, Filofteia-Laura; Potthoff, Annegret; Berger, Lutz-Michael; Leyens, Christoph

2015-10-01

Research and development work for about one decade have demonstrated many unique thermal spray coating properties, particularly for oxide ceramic coatings by using suspensions of fine powders as feedstock in APS and HVOF processes. Some particular advantages are direct feeding of fine nano- and submicron-scale particles avoiding special feedstock powder preparation, ability to produce coating thicknesses ranging from 10 to 50 µm, homogeneous microstructure with less anisotropy and lower surface roughness compared to conventional coatings, possibility of retention of the initial crystalline phases, and others. This paper discusses the main aspects of thermal spraying with suspensions which have been taken into account in order to produce these coatings on an economical way. The economic efficiency of the process depends on the availability of suitable additional system components (suspension feeder, injectors), on the development and handling of stable suspensions, as well as on the high process stability for acceptance at industrial scale. Special focus is made on the development and processability of highly concentrated water-based suspensions. While costs and operational safety clearly speak for use of water as a liquid media for preparing suspensions on an industrial scale, its use is often critically discussed due to the required higher heat input during spraying compared to alcoholic suspensions.

Mg Content Dependence of EML-PVD Zn-Mg Coating Adhesion on Steel Strip

NASA Astrophysics Data System (ADS)

Jung, Woo Sung; Lee, Chang Wook; Kim, Tae Yeob; De Cooman, Bruno C.

2016-09-01

The effect of coating thickness and Mg concentration on the adhesion strength of electromagnetic levitation physical vapor deposited Zn-Mg alloy coatings on steel strip was investigated. The phase fraction of Zn, Mg2Zn11, and MgZn2 was determined for a coating Mg concentration in the 0 to 15 wt pct range. Coatings with a Mg content less than 5 pct consisted of an Zn and Mg2Zn11 phase mixture. The coatings showed good adhesion strength and ductile fracture behavior. Coatings with a higher Mg concentration, which consisted of a Mg2Zn11 and MgZn2 phase mixture, had a poor adhesion strength and a brittle fracture behavior. The adhesion strength of PVD Zn-Mg alloy coatings was found to be related to the pure Zn phase fraction. The effect of coating thickness on adhesion strength was found to be negligible. The microstructure of the interface between steel and Zn-Mg alloy coatings was investigated in detail by electron microscopy, electron diffraction, and atom probe tomography.

Characterization of High-Velocity Solution Precursor Flame-Sprayed Manganese Cobalt Oxide Spinel Coatings for Metallic SOFC Interconnectors

NASA Astrophysics Data System (ADS)

Puranen, Jouni; Laakso, Jarmo; Kylmälahti, Mikko; Vuoristo, Petri

2013-06-01

A modified high-velocity oxy-fuel spray (HVOF) thermal spray torch equipped with liquid feeding hardware was used to spray manganese-cobalt solutions on ferritic stainless steel grade Crofer 22 APU substrates. The HVOF torch was modified in such a way that the solution could be fed axially into the combustion chamber through 250- and 300-μm-diameter liquid injector nozzles. The solution used in this study was prepared by diluting nitrates of manganese and cobalt, i.e., Mn(NO3)2·4H2O and Co(NO3)2·6H2O, respectively, in deionized water. The as-sprayed coatings were characterized by X-ray diffraction and field-emission scanning electron microscopy operating in secondary electron mode. Chemical analyses were performed on an energy dispersive spectrometer. Coatings with remarkable density could be prepared by the novel high-velocity solution precursor flame spray (HVSPFS) process. Due to finely sized droplet formation in the HVSPFS process and the use of as delivered Crofer 22 APU substrate material having very low substrate roughness ( R a < 0.5 μm), thin and homogeneous coatings, with thicknesses lower than 10 μm could be prepared. The coatings were found to have a crystalline structure equivalent to MnCo2O4 spinel with addition of Co-oxide phases. Crystallographic structure was restored back to single-phase spinel structure by heat treatment.

Anticorrosive organic/inorganic hybrid coatings

NASA Astrophysics Data System (ADS)

Gao, Tongzhai

Organic/inorganic hybrid coating system was developed for anticorrosion applications using polyurea, polyurethane or epoxide as the organic phase and polysiloxane, formed by sol-gel process, as the inorganic phase. Polyurea/polysiloxane hybrid coatings were formulated and moisture cured using HDI isocyanurate, alkoxysilane-functionalized HDI isocyanurate, and tetraethyl orthosilicate (TEOS) oligomers. Two urethanes were prepared using the same components as abovementioned in addition to the oligoesters derived from either cyclohexane diacids (CHDA) and 2-butyl-2-ethyl-1,3-propanediol (BEPD) or adipic acid (AA), isophthalic acid (IPA), 1,6-hexanediol (HD), and trimethylol propane (TMP). Accelerated weathering and outdoor exposure were performed to study the weatherability of the polyurethane/polysiloxane hybrid coating system. FTIR and solid-state 13C NMR revealed that the degradation of the hybrid coatings occurred at the urethane and ester functionalities of the organic phase. DMA and DSC analyses showed the glass transition temperature increased and broadened after weathering. SEM was employed to observe the change of morphology of the hybrid coatings and correlated with the gloss variation after weathering. Rutile TiO2 was formulated into polyurethane/polysiloxane hybrid coatings in order to investigate the effect of pigmentation on the coating properties and the sol-gel precursor. Chemical interaction between the TiO2 and the sol-gel precursor was investigated using solid-state 29Si NMR and XPS. The morphology, mechanical, viscoelastic, thermal properties of the pigmented coatings were evaluated as a function of pigmentation volume concentration (PVC). Using AFM and SEM, the pigment were observed to be well dispersed in the polymer matrix. The thermal stability, the tensile modulus and strength of the coatings were enhanced with increasing PVC, whereas the pull-off adhesion and flexibility were reduced with increasing PVC. Finally, the pigmented coatings were evaluated by electrochemical impedance spectroscopy (EIS) and the results showed that 10 wt% pigmentation improved the corrosion resistance of the entire coating system. The effect of pigmentation on epoxide/polysiloxane hybrid coatings was also investigated. The epoxide was successfully modified using 3-(triethoxysilyl) propyl isocyanate (TEOSPI) as indicated by FTIR and NMR. Good dispersion of the pigment particles was achieved as revealed by the SEM images. The tensile modulus, tensile strength, pencil hardness and thermal stability of the hybrid coatings were improved while the flexibility and pull-off adhesion were deteriorated when increasing PVC.

Calcium phosphate coating on titanium using laser and plasma spray

NASA Astrophysics Data System (ADS)

Roy, Mangal

Though calcium phosphate (CaP) coated implants are commercially available, its acceptance is still not wide spread due to challenges related to weaker interfacial bonding between metal and ceramic, and low crystallinity of hydroxyapatite (HA). The objectives of this research are to improve interfacial strength, crystallinity, phase purity and bioactivity of CaP coated metallic implants for orthopaedic applications. The rationale is that forming a diffuse and gradient metal-ceramic interface will improve the interfacial strength. Moreover, reducing CaP particles exposure to high temperature during coating preparation, can lead to improvement in both crystallinity and phase purity of CaP. In this study, laser engineered net shaping (LENS(TM)) was used to coat Ti metal with CaP. LENS(TM) processing enabled generation of Ti+TCP (tricalcium phosphate) composite coating with diffused interface, that also increased the coating hardness to 1049+/-112 Hv compared to a substrate hardness of 200+/-15 Hv. In vitro bone cell-material interaction studies confirmed the bioactivity of TCP coatings. Antimicrobial properties of the TCP coatings were improved by silver (Ag) electrodeposition. Along with LENS(TM), radio frequency induction plasma spray, equipped with supersonic plasma nozzle, was used to prepare HA coatings on Ti with improved crystallinity and phase purity. The coating was made of multigrain HA particles of ˜200 nm in size, which consisted of 15--20 nm HA grains. In vitro bone cell-material interaction and in vivo rat model studies confirmed the HA coatings to be bioactive. Furthermore, incorporation of Sr2+ improved bone cell of HA coatings interaction. A combination of LENS(TM) and plasma spray was used to fabricate a compositionally graded HA coatings on Ti where the microstructure varied from pure HA at the surface to pure Ti substrate with a diffused Ti+TCP composite region in between. The plasma spray system was used to synthesize spherical HA nano powder from HA sol, where the production rate was 20 g/h, which is only 16% of the total powder produced. The effects of Sr2+ and Mg2+ doping on bone cell-CaP interaction was further studied with osteoclast cells. Mg2+ doing was found to be an effective way of controlling osteoclast differentiation.

Textile composite fuselage structures development

NASA Technical Reports Server (NTRS)

Jackson, Anthony C.; Barrie, Ronald E.; Chu, Robert L.

1993-01-01

Phase 2 of the NASA ACT Contract (NAS1-18888), Advanced Composite Structural Concepts and Materials Technology for Transport Aircraft Structures, focuses on textile technology, with resin transfer molding or powder coated tows. The use of textiles has the potential for improving damage tolerance, reducing cost and saving weight. This program investigates resin transfer molding (RTM), as a maturing technology for high fiber volume primary structures and powder coated tows as an emerging technology with a high potential for significant cost savings and superior structural properties. Powder coated tow technology has promise for significantly improving the processibility of high temperature resins such as polyimides.

The effect of crystal structure of TiO2 nanotubes on the formation of calcium phosphate coatings during biomimetic deposition

NASA Astrophysics Data System (ADS)

Liu, Yi; Kim, Sun; McLeod, John A.; Li, Jun; Guo, Xiaoxuan; Sham, Tsun-Kong; Liu, Lijia

2017-02-01

The crystallization process of bioactive calcium phosphate (CaP) species via biomimetic deposition onto anodic TiO2 nanotubes is investigated. The porous surface of nanostructured TiO2 provides an ideal substrate for CaP crystallization. The compositions of CaP coatings are studied using X-ray absorption near-edge structures (XANES) at the Ca K-edge. Using detection modes with different probing depths, both the surface of the CaP coating and the CaP-TiO2 interface are simultaneously analyzed. Calcium phosphate (CaP) species, such as hydroxyapatite (HAp), octacalcium phosphate (Ca8(HPO4)2(PO4)4·5H2O, OCP), brushite (CaHPO4·2H2O, DCPD), and amorphous calcium phosphate (ACP), are found in the CaP coatings. TiO2 nanotubes of amorphous and anatase phases are comparatively studied to determine their effect on the efficiency of CaP formation and the phase transformation among CaP species in prolonged deposition time. It is found the composition of CaP coating has a strong dependency on the crystal structure of TiO2 substrate and the kinetics (deposition time).

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications.

PubMed

Eliaz, Noam; Metoki, Noah

2017-03-24

Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs.

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications

PubMed Central

Eliaz, Noam; Metoki, Noah

2017-01-01

Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs. PMID:28772697

The effects of phase transformation on the structure and mechanical properties of TiSiCN nanocomposite coatings deposited by PECVD method

NASA Astrophysics Data System (ADS)

Abedi, Mohammad; Abdollah-zadeh, Amir; Bestetti, Massimiliano; Vicenzo, Antonello; Serafini, Andrea; Movassagh-Alanagh, Farid

2018-06-01

In the present study, the effects of phase transformations on the structure and mechanical properties of TiSiCN coatings were investigated. TiSiCN nanocomposite coatings were deposited on AISI H13 hot-work tool steel by a pulsed direct current plasma-enhanced chemical vapor deposition process at 350 or 500 °C, using TiCl4 and SiCl4 as the precursors of Ti and Si, respectively, in a CH4/N2/H2/Ar plasma as the source of carbon and nitrogen and reducing environment. Some samples deposited at 350 °C were subsequently annealed at 500 °C under Ar atmosphere. Super hard self-lubricant TiSiCN coatings, having nanocomposite structure consisting of TiCN nanocrystals and amorphous carbon particles embedded in an amorphous SiCNx matrix, formed through spinodal decomposition in the specimens deposited or annealed at 500 °C. In addition, it was revealed that either uncomplete or relatively coarse phase segregation of titanium compounds was achieved during deposition at 350 °C and 500 °C, respectively. On the contrary, by deposition at 350 °C followed by annealing at 500 °C, a finer structure was obtained with a sensible improvement of the mechanical properties of coatings. Accordingly, the main finding of this work is that significant enhancement in key properties of TiSiCN coatings, such as hardness, adhesion and friction coefficient, can be obtained by deposition at low temperature and subsequent annealing at higher temperature, thanks to the formation of a fine grained nanocomposite structure.

Microstructure characterization of hypereutectoid aluminium bronze composite coating

NASA Astrophysics Data System (ADS)

Kucita, P.; Wang, S. C.; Li, W. S.; Cook, R. B.; Starink, M. J.

2015-10-01

Hypereutectoid aluminium bronze coating was deposited onto an E.N. 10503 steel substrate using plasma transferred arc welding (PTA). Microstructure characterisation of the coating and a section near the steel substrate joint was carried out using SEM, EBSD, EDS in conjunction with XRD and depth-sensing nano-indentation. The constituent phases in the coating were identified as: martensitic Cu3Al β1' phase, solid solution of Al in Cu α phase and the intermetallic Fe3Al κ1 phase. The region near the steel substrate was characterised by high hardness, large grains and presence of Cu precipitates. No cracks were observed in this region. The coating has high hardness of 4.9GPa and Young's modulus of 121.7GPa. This is attributed to homogeneous distribution of sub microns size Fe3Al intermetallic phase. The implications of the coating to the engineering application of sheet metal forming are discussed.

Process for coating an object with silicon carbide

NASA Technical Reports Server (NTRS)

Levin, Harry (Inventor)

1989-01-01

A process for coating a carbon or graphite object with silicon carbide by contacting it with silicon liquid and vapor over various lengths of contact time. In the process, a stream of silicon-containing precursor material in gaseous phase below the decomposition temperature of said gas and a co-reactant, carrier or diluent gas such as hydrogen is passed through a hole within a high emissivity, thin, insulating septum into a reaction chamber above the melting point of silicon. The thin septum has one face below the decomposition temperature of the gas and an opposite face exposed to the reaction chamber. The precursor gas is decomposed directly to silicon in the reaction chamber. A stream of any decomposition gas and any unreacted precursor gas from said reaction chamber is removed. The object within the reaction chamber is then contacted with silicon, and recovered after it has been coated with silicon carbide.

NASA Astrophysics Data System (ADS)

Wang, Mao-Hua; Ma, Xiao-Yu; Zhang, Bo; Zhou, Fu

2014-11-01

CaCu3Ti4O12 (CCTO) powders coated with carbon were synthesized by using a high-energy ball milling method. The obtained samples were characterized by x-ray diffraction, transmission electron microscopy and scanning electron microscopy. The carbon-coated CCTO particles had a rough surface, which resulted from the growth of the carbon coating on the CCTO particles. It was found that the CCTO phase was observed as the major phase and no reaction occurred between the carbon and CCTO during the sintering process. The grain size of the CCTO ceramics decreased with the increase in carbon content, which indicated that carbon inhibits grain growth of CCTO ceramics. Specially, the dielectric constant decreased with the increase in carbon content. And CCTO1 ceramic (mass ratio of CCTO: carbon = 10:1) showed a lower dielectric constant (3.74 × 104), with the dielectric loss value (0.04) much lower than that of CCTO at 20°C (10 k Hz).

Influence of Heat Treatment on Fracture Toughness and Wear Resistance of Nicral-Zro2 Multilayered Thermal Barrier Coating

NASA Astrophysics Data System (ADS)

Ye, Zibo; Wang, Guanghong

2018-04-01

The chemical composition and fracture toughness of thermal barrier coatings (TBCs) before and after heat treatment were characterized, and the cracks around the interface between the coating and the substrate could be successfully eliminated and meanwhile the porosity of the coatings tended to reduce. The XRD analysis revealed the coatings were composed of non-transformable tetragonal t' phase of ZrO2 and γ -(Ni, Cr) with minor Ni3Al (γ') precipitates. Additionally, the relationship between the heat treatment and wear resistance was systematically studied. The results indicated that both the hardness and fracture toughness increased after quenching process. The oxidation wear became more prominent after heat treatment, which probably resulted from the better bonding strength of coatings. Dense and homogeneous microstructure introduced by vacuum oil-quenching improved stabilization of the weight gain during thermal cycle test.

Design of Aerosol Particle Coating: Thickness, Texture and Efficiency

PubMed Central

Buesser, B.; Pratsinis, S.E.

2013-01-01

Core-shell particles preserve the performance (e.g. magnetic, plasmonic or opacifying) of a core material while modifying its surface with a shell that facilitates (e.g. by blocking its reactivity) their incorporation into a host liquid or polymer matrix. Here coating of titania (core) aerosol particles with thin silica shells (films or layers) is investigated at non-isothermal conditions by a trimodal aerosol dynamics model, accounting for SiO2 generation by gas phase and surface oxidation of hexamethyldisiloxane (HMDSO) vapor, coagulation and sintering. After TiO2 particles have reached their final primary particle size (e.g. upon completion of sintering during their flame synthesis), coating starts by uniformly mixing them with HMDSO vapor that is oxidized either in the gas phase or on the particles’ surface resulting in SiO2 aerosols or deposits, respectively. Sintering of SiO2 deposited onto the core TiO2 particles takes place transforming rough into smooth coating shells depending on process conditions. The core-shell characteristics (thickness, texture and efficiency) are calculated for two limiting cases of coating shells: perfectly smooth (e.g. hermetic) and fractal-like. At constant TiO2 core particle production rate, the influence of coating weight fraction, surface oxidation and core particle size on coating shell characteristics is investigated and compared to pertinent experimental data through coating diagrams. With an optimal temperature profile for complete precursor conversion, the TiO2 aerosol and SiO2-precursor (HMDSO) vapor concentrations have the strongest influence on product coating shell characteristics. PMID:23729833

Control of artificial pinning centers in REBCO coated conductors derived from the trifluoroacetate metal-organic deposition process

NASA Astrophysics Data System (ADS)

Izumi, T.; Nakaoka, K.

2018-07-01

The metal-organic deposition (MOD) process using metal trifluoroacetate salts (TFA) has the advantages of low-cost and high-scalability for the fabrication of REBa2Cu3O y (REBCO, RE: rare earth elements) superconducting coated conductors (CCs) with high critical current density, in principle, because of its non-vacuum process. For the magnetic applications of CCs such as motors, magnetic resonance imaging and superconducting magnetic energy storage, further improvement of superconducting performance under magnetic fields is required. However, the in-field superconducting performance of REBCO CCs derived from the TFA-MOD process had been inferior to those derived from the vapor-phase process. In order to improve the in-field performance, the size control of the artificial pinning centers has been known as an effective way. In the early stage, the BaZrO3 (BZO) material, which was one of the effective materials in the CCs by the vapor-phase process, was also introduced in the TFA-MOD-derived CCs. The unique feature of the BZO material in the TFA-MOD process is the shape. The BZO in the TFA-MOD process formed the particle shape, although in the vapor-phase process it has a rod shape with a long axis elongating along the thickness direction. In addition, a special heat treatment for refining the BZO particles was developed, which is called the ‘interim heat treatment’. This heating profile made the in-field characteristics higher, although they were still lower than those of the vapor-phase process. Then, the new MOD process including ‘ultra-thin once coating’ was recently developed for further refinement of the BZO particles. The characteristics of the new TFA-MOD-derived CCs in magnetic fields have become compatible with those of the CCs derived from the vapor-phase process.

Apparatus and method for measuring the thickness of a coating

DOEpatents

Carlson, Nancy M.; Johnson, John A.; Tow, David M.; Walter, John B

2002-01-01

An apparatus and method for measuring the thickness of a coating adhered to a substrate. An electromagnetic acoustic transducer is used to induce surface waves into the coating. The surface waves have a selected frequency and a fixed wavelength. Interpolation is used to determine the frequency of surface waves that propagate through the coating with the least attenuation. The phase velocity of the surface waves having this frequency is then calculated. The phase velocity is compared to known phase velocity/thickness tables to determine the thickness of the coating.

The effect of heat treatment on structural and electronic properties of niobium nitride prepared by a thermal diffusion method

DOE PAGES

Farha, Ashraf Hassan; Ozkendir, Osman Murat; Elsayed-Ali, Hani E.; ...

2016-11-15

NbN coatings are prepared onto Nb substrate by thermal diffusion at high temperatures. The formation of NbN coating by thermal diffusion was studied in the range of 1250-1500 °C at constant nitrogen background gas pressure (1.3x10 -3 Pa) and processing time (180 min). The electronic and crystal structures of the NbN coatings were investigated. It was found that nitrogen diffuses into Nb forming the Nb-N solid solution (bcc) a-NbN phase that starts to appear above 1250 °C. Increasing the processing temperature gives richer a-phase concentration. Besides, X-ray absorption spectroscopy (XAS) was performed to study the electronic structure of the NbNmore » layer. The results of the electronic structural study corroborate the crystal structural analysis. The Nb M 3,2 edge X-ray absorption spectroscopy (XAS) spectrum shows strong temperature dependence. At the highest processing temperature (1500 °C), the number of d holes increased. Nitrogen diffusion into Nb is resulting to increase electrostatic interaction between d electron and core hole. Lastly, for the studied conditions, only the α-NbN was observed in the X-ray diffraction patterns.« less

The effect of heat treatment on structural and electronic properties of niobium nitride prepared by a thermal diffusion method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farha, Ashraf Hassan; Ozkendir, Osman Murat; Elsayed-Ali, Hani E.

NbN coatings are prepared onto Nb substrate by thermal diffusion at high temperatures. The formation of NbN coating by thermal diffusion was studied in the range of 1250-1500 °C at constant nitrogen background gas pressure (1.3x10 -3 Pa) and processing time (180 min). The electronic and crystal structures of the NbN coatings were investigated. It was found that nitrogen diffuses into Nb forming the Nb-N solid solution (bcc) a-NbN phase that starts to appear above 1250 °C. Increasing the processing temperature gives richer a-phase concentration. Besides, X-ray absorption spectroscopy (XAS) was performed to study the electronic structure of the NbNmore » layer. The results of the electronic structural study corroborate the crystal structural analysis. The Nb M 3,2 edge X-ray absorption spectroscopy (XAS) spectrum shows strong temperature dependence. At the highest processing temperature (1500 °C), the number of d holes increased. Nitrogen diffusion into Nb is resulting to increase electrostatic interaction between d electron and core hole. Lastly, for the studied conditions, only the α-NbN was observed in the X-ray diffraction patterns.« less

Spray Characteristics and Tribo-Mechanical Properties of High-Velocity Arc-Sprayed WC-W2C Iron-Based Coatings

NASA Astrophysics Data System (ADS)

Tillmann, W.; Hagen, L.; Kokalj, D.

2017-10-01

In terms of arc-sprayed coatings, the lamellar coating microstructure is mainly affected by the atomization behavior of the molten electrode tips. When using compressed air, oxide formations occur during atomization, across the particle-laden spray plume and when the molten droplets splash onto the substrate. Within the scope of this study, the potential of a high-velocity arc-spraying process due to elevated atomization gas pressures and its effect on the spray and coating characteristics was analyzed using a cast tungsten carbide (CTC)-reinforced FeCMnSi cored wire. Since the atomization behavior corresponds with the electrode phenomena, the power spectrum and the droplet formation were observed during spraying. The tribo-mechanical properties of CTC-FeCMnSi coatings were examined in dry sliding experiments and indentation tests. In addition, adhesion tests and metallographic investigations were carried out to analyze the bonding strength, cohesive behavior, and lamellar microstructure. The occurrence of oxide phases was evaluated by x-ray diffraction and electron microscopy. Moreover, the oxygen content was determined by using glow discharge optical emission spectroscopy as well as energy-dispersive x-ray spectroscopy. With respect to elevated atomization gas pressures, a dense microstructure with improved adhesion to the substrate and reduced surface roughness was observed. Dry sliding experiments revealed an advanced wear behavior of specimens, when using above average increased atomization gas pressures. Analytic methods verified the existence of oxide phases, which were generated during spraying. A significant change of the extent and type of oxides, when applying an increased flow rate of the atomization gas, cannot be observed. Besides an enhanced coating quality, the use of increased atomization gas pressure exhibited good process stability.

Preparation of nanocrystalline TiN coated cubic boron nitride powders by a sol-gel process.

PubMed

Park, Hee S; Umer, M Adeel; Ryu, Ho J; Hong, Soon H

2011-01-01

Cubic boron nitride (cBN) particles coated with 20 wt% nanocrystalline TiN were prepared by coating the surface of cBN particles with TiO2, followed by nitridation with NH3 gas at 900 degrees C. Coating of TiO2 on cBN powders was accomplished by a sol-gel process from a solution of titanium (IV) isopropoxide and anhydrous ethanol. An amorphous TiO(x) layer of 50 nm thickness was homogenously formed on the surface of the cBN particles by the sol-gel process. The amorphous layer was then crystallized to an anatase TiO2 phase through calcination in air at 400 degrees C. The crystallized TiO2 layer was 50 nm in thickness, and the size of TiO2 particles comprising the layer was nearly 10 nm. The TiO2 on cBN surfaces was completely converted into nanocrystalline TiN of uniform particles 20 nm in size on cBN particles by nitridation under flowing NH3 gas.

Silicanizing Process On Mild Steel Substrate by Using Tronoh Silica Sand: Microstructure, composition and coating growth

NASA Astrophysics Data System (ADS)

Y, Yusnenti F. M.; M, Othman; Mustapha, Mazli; I, MohdYusri

2016-02-01

A new Silicanizing process on formation of coating on mild steel using Tronoh Silica Sand (TSS) is presented. The process was performed in the temperature range 1000- 1100°C and with varying deposition time of 1-4 hours. Influence of the layer and the substrate constituents on the coating compatibility of the whole silicanized layer is described in detail. Morphology and structure of the silicanized layer were investigated by XRF, XRD and SEM. It is observed that diffusion coatings containing high concentrations of silica which profile distribution of SiO2 in the silicanized layer was encountered and the depth from the surface to the substrate was taken as the layer thickness. The results also depicted that a longer deposition time have tendency to produce a looser and larger grain a hence rougher layer. The silicanized layer composed of FeSi and Fe2SiO4 phases with preferred orientation within the experimental range. It is also found that longer deposition time and higher temperature resulted in an increase in SiO2 concentration on the substrate (mild steel).

Apparatus and Method for Increasing the Diameter of Metal Alloy Wires Within a Molten Metal Pool

DOEpatents

Hartman, Alan D.; Argetsinger, Edward R.; Hansen, Jeffrey S.; Paige, Jack I.; King, Paul E.; Turner, Paul C.

2002-01-29

In a dip forming process the core material to be coated is introduced directly into a source block of coating material eliminating the need for a bushing entrance component. The process containment vessel or crucible is heated so that only a portion of the coating material becomes molten, leaving a solid portion of material as the entrance port of, and seal around, the core material. The crucible can contain molten and solid metals and is especially useful when coating core material with reactive metals. The source block of coating material has been machined to include a close tolerance hole of a size and shape to closely fit the core material. The core material moves first through the solid portion of the source block of coating material where the close tolerance hole has been machined, then through a solid/molten interface, and finally through the molten phase where the diameter of the core material is increased. The crucible may or may not require water-cooling depending upon the type of material used in crucible construction. The system may operate under vacuum, partial vacuum, atmospheric pressure, or positive pressure depending upon the type of source material being used.

Milestones in Functional Titanium Dioxide Thermal Spray Coatings: A Review

NASA Astrophysics Data System (ADS)

Gardon, M.; Guilemany, J. M.

2014-04-01

Titanium dioxide has been the most investigated metal oxide due to its outstanding performance in a wide range of applications, chemical stability and low cost. Coating processes that can produce surfaces based on this material have been deeply studied. Nevertheless, the necessity of coating large areas by means of rapid manufacturing processes renders laboratory-scale techniques unsuitable, leading to a noteworthy interest from the thermal spray (TS) community in the development of significant intellectual property and a large number of scientific publications. This review unravels the relationship between titanium dioxide and TS technologies with the aim of providing detailed information related to the most significant achievements, lack of knowhow, and performance of TS TiO2 functional coatings in photocatalytic, biomedical, and other applications. The influence of thermally activated techniques such as atmospheric plasma spray and high-velocity oxygen fuel spray on TiO2 feedstock based on powders and suspensions is revised; the influence of spraying parameters on the microstructural and compositional changes and the final active behavior of the coating have been analyzed. Recent findings on titanium dioxide coatings deposited by cold gas spray and the capacity of this technology to prevent loss of the nanostructured anatase metastable phase are also reviewed.

Apparatus and method for increasing the diameter of metal alloy wires within a molten metal pool

DOEpatents

Hartman, Alan D.; Argetsinger, Edward R.; Hansen, Jeffrey S.; Paige, Jack I.; King, Paul E.; Turner, Paul C.

2002-01-29

In a dip forming process the core material to be coated is introduced directly into a source block of coating material eliminating the need for a bushing entrance component. The process containment vessel or crucible is heated so that only a portion of the coating material becomes molten, leaving a solid portion of material as the entrance port of, and seal around, the core material. The crucible can contain molten and solid metals and is especially useful when coating core material with reactive metals. The source block of coating material has been machined to include a close tolerance hole of a size and shape to closely fit the core material. The core material moves first through the solid portion of the source block of coating material where the close tolerance hole has been machined, then through a solid/molten interface, and finally through the molten phase where the diameter of the core material is increased. The crucible may or may not require water-cooling depending upon the type of material used in crucible construction. The system may operate under vacuum, partial vacuum, atmospheric pressure, or positive pressure depending upon the type of source material being used.

Effect of Particle Morphology on Cold Spray Deposition of Chromium Carbide-Nickel Chromium Cermet Powders

NASA Astrophysics Data System (ADS)

Fernandez, Ruben; Jodoin, Bertrand

2017-08-01

Nickel chromium-chromium carbide coatings provide good corrosion and wear resistance at high temperatures, making them ideal for applications where a harsh environment and high temperatures are expected. Thermal spray processes are preferred as deposition technique of cermets, but the high process temperatures can lead to decarburization and reduction of the coatings properties. Cold spray uses lower temperatures preventing decarburization. Since the metallic phase remains solid, the feedstock powder morphology becomes crucial on the deposition behavior. Six commercially available powders were studied, varying in morphology and metal/ceramic ratios. The powders were categorized into 4 groups depending on their morphology. Spherical powders lead to substrate erosion due to their limited overall ductility. Porous agglomerated and sintered powders lead to severely cracked coatings. For dense agglomerated and sintered powders, the outcome depended on the initial metal/ceramic ratio: powders with 25 wt.% NiCr led to substrate erosion while 35 wt.% NiCr powders led to dense coatings. Finally, blended ceramic-metal mixtures also lead to dense coatings. All coatings obtained had lower ceramic content than the initial feedstock powders. Interrupted spray tests, combined with FEA, helped drawing conclusions on the deposition behavior to explain the obtained results.

A Platinum-Enriched gamma+gamma' Two-Phase Bond Coat on Ni-Base Superalloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Ying; Pint, Bruce A; Haynes, James A

2005-01-01

Pt-enriched {gamma} + {gamma}{prime} two-phase coating was applied to directionally-solidified Ni-based superalloy Ren{acute e} 142 substrates with three different Hf levels (0.02, 0.76, and 1.37 wt.%). The coating was prepared by electroplating a thin layer of Pt on the superalloy followed by a diffusion treatment. The as-deposited coating exhibited a {gamma} + {gamma}{prime} two-phase microstructure with a major composition of Ni-16Al-18Pt-7Cr-9Co (in at.%) along with some incorporation of refractory elements from the substrates. Cyclic oxidation testing at 1100 C in air indicated improved oxidation resistance of the Ren{acute e} 142 alloys with the Pt-enriched {gamma} + {gamma}{prime} coatings. In addition,more » the oxidation resistance of both uncoated and coated alloys was proportional to the Hf content in the substrate. Compared with the single-phase {beta}-(Ni,Pt)Al coating, slightly higher mass gains and localized spallation were observed on the {gamma} + {gamma}{prime} two-phase coating, which might be due to the segregation of refractory elements and high sulfur levels in these superalloy substrates.« less

Parametric Study of Slurry-Erosion of Hydroturbine Steels with and without Detonation Gun Spray Coatings using Taguchi Technique

NASA Astrophysics Data System (ADS)

Grewal, Harpreet Singh; Bhandari, Sanjeev; Singh, Harpreet

2012-09-01

WC-Co-Cr coatings were deposited on some hydroturbine 13Cr4Ni and 16Cr5Ni steels by the detonation-gun spray process. An in-depth characterization of the as-sprayed coating was done using X-ray diffraction (XRD) and scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDS) techniques. Microhardness and porosity measurements were also made. The coating was found to have a typical splat-like morphology with some indications of unmelted carbide particles. The XRD results showed the presence of WC as the primary phase along with W2C and Co6W6C as secondary phases. Furthermore, the slurry erosion behavior of the coatings was investigated to ascertain the usefulness of the coatings to reduce the slurry erosion of the steels. The effect of four operating factors viz. the velocity, impact angle, concentration, and particle size on the slurry erosion of coated and bare steels has been studied using a high-speed jet-type test rig. The sand used as an erodent was collected from a power plant to replicate the actual turbine conditions. It has been observed that the given cermet coating can enhance the erosion resistance of the steel. Velocity was found to be the most significant factor affecting the erosion behavior of the coating, whereas it was the erodent particle size in the case of uncoated steel. As evidenced from the SEM images, the platelet mechanism of erosion seemed to be the prominent one, causing the removal of material from the surface of the steel, whereas for the coating, the formation and interlinking of cracks resulted in the removal of material.

TiC-Fe-Based Composite Coating Prepared by Self-Propagating High-Temperature Synthesis

NASA Astrophysics Data System (ADS)

He, Shen; Fan, Xi'an; Chang, Qingming; Xiao, Lixiang

2017-06-01

TiC-Fe-based composite coatings were prepared in situ by self-propagating high-temperature synthesis combined with vacuum expendable pattern casting process. The band-like TiC phase embedded in a continuous Fe binder. There were no obvious defects and impurities at the interface between coatings and matrices. Fe presented consecutively in the coating zones and substrate zones without interruption and the microhardness in the cross-sectional area of the coating-matrix reduces continuously from the coating to the matrix area, indicating a good metallurgical bonding between the coatings and matrices. The effect of casting temperature on the microstructure and hardness of TiC-Fe-based composite coating was investigated in detail. The TiC particles formed at low casting temperature were nearly spherical in shape, and the size of TiC particles increased with increasing casting temperature due to more agglomeration. The hardness of the coatings increased first and then decreased with increasing casting temperature, and reached the highest value of 68 HRC when the casting temperature was 1773 K (1500 °C), which was twice more than that of the matrix.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Korol, A.A.; Korol, Y.A.; Kasich-Pilipenko, I.Y.

Melted slip coatings were obtained and the structural changes in the coatings and their substrates upon simultaneous heating by concentrated solar radiant energy fluxes were studied. Well known wear and corrosion resistant TiC-Ni-B and WC-Ni-B coatings 50 to 300 microns thick applied by the slip method to flat or cylindrical stainless steel and titanium specimens were examined. The specimens were heated in an SGU-5 solar heating installation with a 2 m diameter parabolic mirror concentrator in a process chamber with a quartz window under a vacuum. Metallographic analysis revealed a finely dispersed heterogeneous structure with no visible porosity, good bondingmore » of coating to substrate, and uniform distribution of carbide phase in the metal matrix of the TiC-Ni-B coatings on titanium. Results were similar for the other coatings, indicating that concentrated solar energy can produce coatings with satisfactory surface quality, good density, and a framework structure. The coating interacted with the substrate by diffusion. Most of the volume of the substrate underwent no significant changes, indicating good bond strength between coatings and substrate.« less

Figure correction of multilayer coated optics

DOEpatents

Chapman; Henry N. , Taylor; John S.

2010-02-16

A process is provided for producing near-perfect optical surfaces, for EUV and soft-x-ray optics. The method involves polishing or otherwise figuring the multilayer coating that has been deposited on an optical substrate, in order to correct for errors in the figure of the substrate and coating. A method such as ion-beam milling is used to remove material from the multilayer coating by an amount that varies in a specified way across the substrate. The phase of the EUV light that is reflected from the multilayer will be affected by the amount of multilayer material removed, but this effect will be reduced by a factor of 1-n as compared with height variations of the substrate, where n is the average refractive index of the multilayer.

Lessons learned from the development and manufacture of ceramic reusable surface insulation materials for the space shuttle orbiters

NASA Technical Reports Server (NTRS)

Banas, R. P.; Elgin, D. R.; Cordia, E. R.; Nickel, K. N.; Gzowski, E. R.; Aguiler, L.

1983-01-01

Three ceramic, reusable surface insulation materials and two borosilicate glass coatings were used in the fabrication of tiles for the Space Shuttle orbiters. Approximately 77,000 tiles were made from these materials for the first three orbiters, Columbia, Challenger, and Discovery. Lessons learned in the development, scale up to production and manufacturing phases of these materials will benefit future production of ceramic reusable surface insulation materials. Processing of raw materials into tile blanks and coating slurries; programming and machining of tiles using numerical controlled milling machines; preparing and spraying tiles with the two coatings; and controlling material shrinkage during the high temperature (2100-2275 F) coating glazing cycles are among the topics discussed.

Final Report: Novel ALD-Coated Nanoparticle Anodes for Enhanced Performance Lithium-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Groner, Markus

2009-04-16

The Phase I effort is described in detail in the Phase I report given below. The key accomplishments of the Phase I project were (1) the demonstration of high stability LiCoO2 cathodes using ALD-coated LiCoO2 particles, as well as on ALD-coated LiCoO2 electrodes and (2) the demonstration of high stability of graphite anodes using ALD-coated graphite electrodes.

Influence of Gas Atmosphere Dew Point on the Galvannealing of CMnSi TRIP Steel

NASA Astrophysics Data System (ADS)

Cho, Lawrence; Kim, Myung Soo; Kim, Young Ha; De Cooman, Bruno C.

2013-11-01

The Fe-Zn reaction occurring during the galvannealing of a Si-bearing transformation-induced plasticity (TRIP) steel was investigated by field-emission electron probe microanalysis and field-emission transmission electron microscopy. The galvannealing was simulated after hot dipping in a Zn bath containing 0.13 mass pct Al at 733 K (460 °C). The galvannealing temperature was in the range of 813 K to 843 K (540 °C to 570 °C). The kinetics and mechanism of the galvannealing reaction were strongly influenced by the gas atmosphere dew point (DP). After the galvannealing of a panel annealed in a N2+10 pct H2 gas atmosphere with low DPs [213 K and 243 K (-60 °C and -30 °C)], the coating layer consisted of δ (FeZn10) and η (Zn) phase crystals. The Mn-Si compound oxides formed during intercritical annealing were present mostly at the steel/coating interface after the galvannealing. Galvannealing of a panel annealed in higher DP [263 K and 273 K, and 278 K (-10 °C, 0 °C, and +5 °C)] gas atmospheres resulted in a coating layer consisting of δ and Г (Fe3Zn10) phase crystals, and a thin layer of Г 1 (Fe11Zn40) phase crystals at the steel/coating interface. The Mn-Si oxides were distributed homogeneously throughout the galvannealed (GA) coating layer. When the surface oxide layer thickness on panels annealed in a high DP gas atmosphere was reduced, the Fe content at the GA coating surface increased. Annealing in a higher DP gas atmosphere improved the coating quality of the GA panels because a thinner layer of oxides was formed. A high DP atmosphere can therefore significantly contribute to the suppression of Zn-alloy coating defects on CMnSi TRIP steel processed in hot dip galvanizing lines.

Array automated assembly task, phase 2. Low cost silicon solar array project

NASA Technical Reports Server (NTRS)

Rhee, S. S.; Jones, G. T.; Allison, K. T.

1978-01-01

Several modifications instituted in the wafer surface preparation process served to significantly reduce the process cost to 1.55 cents per peak watt in 1975 cents. Performance verification tests of a laser scanning system showed a limited capability to detect hidden cracks or defects, but with potential equipment modifications this cost effective system could be rendered suitable for applications. Installation of electroless nickel plating system was completed along with an optimization of the wafer plating process. The solder coating and flux removal process verification test was completed. An optimum temperature range of 500-550 C was found to produce uniform solder coating with the restriction that a modified dipping procedure is utilized. Finally, the construction of the spray-on dopant equipment was completed.

Preparation and characterization of polydimethylsiloxane/poly(vinylalcohol) coated solid phase microextraction fibers using sol-gel technology.

PubMed

Lopes, Alexandre Leite; Augusto, Fabio

2004-11-12

The applicability of a composite composed of polydimethylsiloxane (PDMS) and poly(vinyl alcohol) (PDMS/PVA) as coating sorbent for SPME fibers is demonstrated here. Fused silica (FS) fibers were coated with PDMS/PVA composite through a sol-gel process, using methyltrimethoxysilane as reticulating agent. The chemical and physical properties of the sol-gel PDMS/PVA composite were determined by infrared spectroscopy and thermogravimetric analysis. Electron scanning microscopy of the prepared fibers, showed that the coating obtained was highly microporous, having a thickness of approximately 5 microm. The fibers were tested for the headspace extraction of several organic compounds (o-xylene, naphthalene, ethyl caprate, p-chlorotoluene and PCB) prior to gas chromatographic analysis. The extractive capacity of the PDMS/PVA coating was found to be superior to that of pure conventional PDMS fibers.

Plasma-sprayed self-lubricating coatings

NASA Technical Reports Server (NTRS)

Nakamura, H. H.; Logan, W. R.; Harada, Y.

1982-01-01

One of the most important criterion for acceptable commercial application of a multiple phase composition is uniformity and reproducibility. This means that the performance characteristics of the coat - e.g., its lubricating properties, bond strength to the substrate, and thermal properties - can be readily predicted to give a desired performance. The improvement of uniformity and reproducibility of the coats, the oxidation behavior at three temperature ranges, the effect of bond coat and the effect of preheat treatment as measured by adhesive strength tests, coating examination procedures, and physical property measurements were studied. The following modifications improved the uniformity and reproducibility: (1) changes and closer control in the particle size range of the raw materials used, (2) increasing the binder content from 3.2% to 4.1% (dried weight), and (3) analytical processing procedures using step by step checking to assure consistency.

Effects of Laser Power Level on Microstructural Properties and Phase Composition of Laser-Clad Fluorapatite/Zirconia Composite Coatings on Ti6Al4V Substrates.

PubMed

Chien, Chi-Sheng; Liu, Cheng-Wei; Kuo, Tsung-Yuan

2016-05-17

Hydroxyapatite (HA) is one of the most commonly used materials for the coating of bioceramic titanium (Ti) alloys. However, HA has poor mechanical properties and a low bonding strength. Accordingly, the present study replaces HA with a composite coating material consisting of fluorapatite (FA) and 20 wt % yttria (3 mol %) stabilized zirconia (ZrO₂, 3Y-TZP). The FA/ZrO₂ coatings are deposited on Ti6Al4V substrates using a Nd:YAG laser cladding system with laser powers and travel speeds of 400 W/200 mm/min, 800 W/400 mm/min, and 1200 W/600 mm/min, respectively. The experimental results show that a significant inter-diffusion of the alloying elements occurs between the coating layer (CL) and the transition layer (TL). Consequently, a strong metallurgical bond is formed between them. During the cladding process, the ZrO₂ is completely decomposed, while the FA is partially decomposed. As a result, the CLs of all the specimens consist mainly of FA, Ca₄(PO₄)₂O (TTCP), CaF₂, CaZrO₃, CaTiO₃ and monoclinic phase ZrO₂ (m-ZrO₂), together with a small amount of θ-Al₂O₃. As the laser power is increased, CaO, CaCO₃ and trace amounts of tetragonal phase ZrO₂ (t-ZrO₂) also appear. As the laser power increases from 400 to 800 W, the CL hardness also increases as a result of microstructural refinement and densification. However, at the highest laser power of 1200 W, the CL hardness reduces significantly due to the formation of large amounts of relatively soft CaO and CaCO₃ phase.

Deposition and characterization of magnetron sputtered bcc tantalum

NASA Astrophysics Data System (ADS)

Patel, Anamika

The goal of this thesis was to provide scientific and technical research results for developing and characterizing tantalum (Ta) coatings on steel substrates deposited by DC magnetron sputtering. Deposition of tantalum on steel is of special interest for the protection it offers to surfaces, e.g. the surfaces of gun barrels against the erosive wear of hot propellant gases and the mechanical damage caused by the motion of launching projectiles. Electro-plated chromium is presently most commonly used for this purpose; however, it is considered to be carcinogenic in its hexavalent form. Tantalum is being investigated as non-toxic alternative to chromium and also because of its superior protective properties in these extreme environments. DC magnetron sputtering was chosen for this investigation of tantalum coatings on steel substrates because it is a versatile industrial proven process for deposition of metals. Sputter deposited Ta films can have two crystallographic structures: (1) body center cubic (bcc) phase, characterized by high toughness and high ductility and (2) a tetragonal beta phase characterized by brittleness and a tendency to fail under stress. It was found in this work that the bcc Ta coatings on steel can be obtained reliably by either of two methods: (1) depositing Ta on a submicron, stoichiometric TaN seed layer reactively sputtered on unheated steel and (2) depositing Ta directly on steel heated above a critical temperature. For argon sputtering gas this critical temperature was found to be 400°C at a pressure of 5 mtorr. With the heavier krypton gas, this critical temperature is reduced to 350°C. X-ray diffraction (XRD) was used to investigate the structure of tantalum and nitride films, and the composition of the nitride films was measured by nuclear reaction analyses (NRA), which were used to study in detail the enhancement of the bcc phase of Ta on steel. The scratch adhesion tests performed with a diamond hemispherical tip of radius 200 mum under increasing loads revealed high critical load values for failure (>15 N) for the bcc coatings versus the low load values (<9 N) for the beta coatings. The coating deposited on TaN interlayers on sputter-etched steel had better adhesion than those on steel surface without sputter etching. The results for this work have demonstrated that by controlling the various process parameters of do magnetron sputtering, high quality bcc Ta coatings of multi-micron thickness with excellent adhesion to steel can be made. An important contribution of this dissertation is in the enhancing an understanding of this process. The impact of this research will be in a number of fields where superior protective castings are needed. These include military applications, electronic components, chemical processing, and others.

The effect of annealing on structure and hardness of (Fe-Cr)-50 at.% Al coatings synthesized by mechanical alloying

NASA Astrophysics Data System (ADS)

Ciswandi, Aryanto, Didik; Irmaniar, Tjahjono, Arif; Sudiro, Toto

2018-05-01

In this research, the deposition of (Fe-Cr)-50at.% Al coatings on low carbon steel was carried out by a mechanical alloying (MA) technique. The MA was performed in a shaker mill for 4 hours. Two types of Fe-Cr powders as starting material were used, high purity Fe-Cr powders: (Fe-12.5Cr)-50Al and (Fe-25Cr)-50Al, and Fe-Cr lump powder: (50FeCr)-50Al (in at.%). The coated samples were then annealed in a vacuum furnace at 700°C for 1h. The characterizations of coating structure before and after annealing were studied by XRD and SEM-EDX, while the coating hardness was measured by micro-Vickers hardness tester. Before annealing, all of coating composition were composed mainly of (Fe,Cr)Al phase. After annealing, the FeAl and Fe0.99Cr0.02Al0.99 intermetallic phases was formed in the (Fe-12.5Cr)-50Al and (Fe-25Cr)-50Al coatings. In addition, Fe2CrAlwas also found in the (Fe-25Cr)-50Al coating. Whilethe AlCr2 intermetallic phase was detected as the main phase of (50FeCr)-50Al coating. The cross-sectional microstructure showed that the (Fe-12.5Cr)-50Al and (Fe-25Cr)-50Al coatings have a smoother structure compared to (50FeCr)-50Al coating. The annealing led to intermetallic phase formation and an increasing coating hardness.

Microstructure and Sliding Wear Performance of Cr7C3-(Ni,Cr)3(Al,Cr) Coating Deposited from Cr7C3 In Situ Formed Atomized Powder

NASA Astrophysics Data System (ADS)

Zhu, Hong-Bin; Shen, Jie; Gao, Feng; Yu, Yueguang; Li, Changhai

2017-01-01

This work is aimed at developing a new type of Cr7C3-(Ni,Cr)3(Al,Cr) coating for parts used in heavy-duty diesel engines. The feedstock, in which the stripe-shaped Cr7C3 was in situ formed, was firstly prepared by vacuum melting and gas atomization and then subjected by high-velocity oxy-fuel spraying to form the coatings. The carbon content, microstructure and phase constitution of the powders, as well as the sprayed coatings, were analyzed by chemical analysis, SEM and XRD. The hardness and sliding wear performance of the sprayed coatings were also tested and compared to a commercial Cr3C2-NiCr coating used on piston rings. The results showed that the content of carbon in feedstock was almost the same as designed, and that the volume content of in situ formed Cr7C3 was increased with carbon and chromium added. The major phases of the powders and sprayed coatings are Cr7C3 and Cr-alloyed Ni3Al. Only a small amount of carbon lost during the spraying process. As Cr7C3 content increased in the coatings, the microhardness at room temperature was firstly increased to about 1000Hv0.3. The microhardness of the coatings stayed almost constant, while the testing temperature was raised up to 700 °C for 0.5 h, which illustrates the potential application of the investigated coatings under high temperature conditions. The coatings containing 70 and 77 vol.% Cr7C3 showed the most promising wear resistance, lower friction coefficient and better tribological compatibility to gray cast iron counterpart than other tested Cr7C3-(Ni,Cr)3(Al,Cr) coatings and the reference Cr3C2-NiCr coating.

Superparamagnetism in carbon-coated Co particles produced by the Kratschmer carbon arc process

NASA Astrophysics Data System (ADS)

McHenry, M. E.; Majetich, S. A.; Artman, J. O.; Degraef, M.; Staley, S. W.

1994-04-01

A process based on the Kratschmer-Huffman carbon arc method of preparing fullerenes has been used to generate carbon-coated cobalt and cobalt carbide nanocrystallites. Magnetic nanocrystallites are extracted from the soot with a gradient field technique. For Co/C composites, structural characterization by x-ray diffraction and high-resolution transmission electron microscopy reveals the presence of a fcc Co phase, graphite, and a minority Co2C phase. The majority of Co nanocrystals exists as nominally spherical particles, 0.5-5 nm in radius. Hysteretic and temperature-dependent magnetic response, in randomly and magnetically aligned powder samples frozen in epoxy reveals fine-particle magnetism associated with monodomain Co particles. The magnetization exhibits a unique functional dependence on H/T, and hysteresis below a blocking temperature, TB~=160 K. Below TB, the temperature dependence of the coercivity is given by Hc=Hci[1-(T/TB)1/2], with Hci~=450 Oe.

Bioactive and Porous Metal Coatings for Improved Tissue Regeneration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, A. A.

Our first objective was to develop the SIM process for the deposition of calcium phosphate films. This process is based on the observation that, in nature, living organisms use macromolecules to control the nucleation and growth of mineral phases. These macromolecules act as templates where various charged functional groups, contained within the molecule, can interact with the ions in the surrounding media, thus stimulating crystal nucleation and growth. Rather than using complex proteins or biopolymers, surface modification schemes were developed to place simple functional groups on the underlying substrate using self-assembling monolayers. Once the substrate was chemically modified, it wasmore » then placed into an aqueous solution containing soluble precursors of the desired mineral coating. Solution pH, ionic concentration and temperature is maintained in a regime where the solution is supersaturated with respect to the desired mineral phase, thereby creating the driving force for nucleation and growth.« less

Polymer blend lithography: A versatile method to fabricate nanopatterned self-assembled monolayers.

PubMed

Huang, Cheng; Moosmann, Markus; Jin, Jiehong; Heiler, Tobias; Walheim, Stefan; Schimmel, Thomas

2012-01-01

A rapid and cost-effective lithographic method, polymer blend lithography (PBL), is reported to produce patterned self-assembled monolayers (SAM) on solid substrates featuring two or three different chemical functionalities. For the pattern generation we use the phase separation of two immiscible polymers in a blend solution during a spin-coating process. By controlling the spin-coating parameters and conditions, including the ambient atmosphere (humidity), the molar mass of the polystyrene (PS) and poly(methyl methacrylate) (PMMA), and the mass ratio between the two polymers in the blend solution, the formation of a purely lateral morphology (PS islands standing on the substrate while isolated in the PMMA matrix) can be reproducibly induced. Either of the formed phases (PS or PMMA) can be selectively dissolved afterwards, and the remaining phase can be used as a lift-off mask for the formation of a nanopatterned functional silane monolayer. This "monolayer copy" of the polymer phase morphology has a topographic contrast of about 1.3 nm. A demonstration of tuning of the PS island diameter is given by changing the molar mass of PS. Moreover, polymer blend lithography can provide the possibility of fabricating a surface with three different chemical components: This is demonstrated by inducing breath figures (evaporated condensed entity) at higher humidity during the spin-coating process. Here we demonstrate the formation of a lateral pattern consisting of regions covered with 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS) and (3-aminopropyl)triethoxysilane (APTES), and at the same time featuring regions of bare SiO(x). The patterning process could be applied even on meter-sized substrates with various functional SAM molecules, making this process suitable for the rapid preparation of quasi two-dimensional nanopatterned functional substrates, e.g., for the template-controlled growth of ZnO nanostructures [1].

Aggregation in complex triacylglycerol oils: coarse-grained models, nanophase separation, and predicted x-ray intensities.

PubMed

Quinn, Bonnie; Peyronel, Fernanda; Gordon, Tyler; Marangoni, Alejandro; Hanna, Charles B; Pink, David A

2014-11-19

Triacylglycerols (TAGs) are biologically important molecules which form crystalline nanoplatelets (CNPs) and, ultimately, fat crystal networks in edible oils. Characterizing the self-assembled hierarchies of these networks is important to understanding their functionality and oil binding capacity. We have modelled CNPs in multicomponent oils and studied their aggregation. The oil comprises (a) a liquid component, and (b) components which phase separately on a nano-scale (nano-phase separation) to coat the surfaces of the CNPs impenetrably, either isotropically or anisotropically, with either liquid-like coatings or crystallites, forming a coating of thickness ?. We modelled three cases: (i) liquid?liquid nano-phase separation, (ii) solid?liquid nano-phase separation, with CNPs coated isotropically, and (iii) CNPs coated anisotropically. The models were applied to mixes of tristearin and triolein with fully hydrogenated canola oil, shea butter with high oleic sunflower oil, and cotton seed oil. We performed Monte Carlo simulations, computed structure functions and concluded: (1) three regimes arose: (a) thin coating regime, Δ < 0.0701 u (b) transition regime, 0.0701 u ≤ Δ ≤ 0.0916 u and (c) thick coating regime, Δ > 0.0916 u. (arbitrary units, u) (2) The thin coating regime exhibits 1D TAGwoods, which aggregate, via DLCA/RLCA, into fractal structures which are uniformly distributed in space. (3) In the thick coating regime, for an isotropic coating, TAGwoods are not formed and coated CNPs will not aggregate but will be uniformly distributed in space. For anisotropic coating, TAGwoods can be formed and might form 1D strings but will not form DLCA/RLCA clusters. (4) The regimes are, approximately: thin coating, 0 < Δ < 7.0 nm transition regime, 7.0 < Δ < 9.2 nm and thick coating, Δ > 9.2 nm (5) The minimum minority TAG concentration required to undergo nano-phase separation is, approximately, 0.29% (thin coatings) and 0.94% (thick coatings). Minority components can have substantial effects upon aggregation for concentrations less than 1%.

Surface modification technologies using concentrated solar radiation

NASA Astrophysics Data System (ADS)

Pitts, J. Roland; Stanley, J. T.; Tracy, Ed; Fields, C. L.

Research conducted at the Solar Energy Research Institute (SERI) during the past three years addressed a number of the critical areas and has explored the possibility of using highly concentrated solar radiation to induce beneficial surface transformation. The principal goal is to develop new coatings and processes that improve the performance and lifetime of materials at reduced processing costs. Highly concentrated radiant energy provides a controllable means of delivering large flux densities to solid surfaces, where the resulting thermal energy can cause phase changes, atomic migrations, and chemical reactions on a surface without greatly perturbing the bulk properties; alternatively, the photons may directly interact with species on the surface. These changes may result in improved properties of the materials by making the surface harder, more resistant to corrosion or wear, thermally resistant, or with lower coefficients of friction. In a solar furnace, this flux can be delivered in large quantities over large areas, or it can be tailored to match the demands of a particular process. Furthermore, this occurs without the environmental liability associated with providing power to more conventional light sources. Recent work at SERI has used fluxes in the range from 100 to 250 w/sq cm for inducing such beneficial surface transformations. Significant results have been obtained in the area of phase transformation hardening of steels and melting powders and preapplied coatings to form fully dense, well-bonded coatings on the surface. New directions in coating technology using highly concentrated solar beams to induce chemical vapor deposition processes are described. Application areas that have not been researched in detail but would appear to be good matches to the solar technology are also reviewed.

Developing bioactive composite scaffolds for bone tissue engineering

NASA Astrophysics Data System (ADS)

Chen, Yun

Poly(L-lactic acid) (PLLA) films were fabricated using the method of dissolving and evaporation. PLLA scaffold was prepared by solid-liquid phase separation of polymer solutions and subsequent sublimation of solvent. Bonelike apatite coating was formed on PLLA films, PLLA scaffolds and poly(glycolic acid) (PGA) scaffolds in 24 hours through an accelerated biomimetic process. The ion concentrations in the simulated body fluid (SBF) were nearly 5 times of those in human blood plasma. The apatite formed was characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The apatite formed in 5SBF was similar in morphology and composition to that formed in the classical biomimetic process employing SBF or 1.5SBF, and similar to that of natural bone. This indicated that the biomimetic apatite coating process could be accelerated by using concentrated simulated body fluid at 37°C. Besides saving time, the accelerated biomimetic process is particularly significant to biodegradable polymers. Some polymers which degrade too fast to be coated with apatite by a classical biomimetic process, for example PGA, could be coated with bone-like apatite in an accelerated biomimetic process. Collagen and apatite were co-precipitated as a composite coating on poly(L-lactic acid) (PLLA) in an accelerated biomimetic process. The incubation solution contained collagen (1g/L) and simulated body fluid (SBF) with 5 times inorganic ionic concentrations as human blood plasma. The coating formed on PLLA films and scaffolds after 24 hours incubation was characterized using EDX, XRD, FTIR, and SEM. It was shown that the coating contained carbonated bone-like apatite and collagen, the primary constituents of natural bone. SEM showed a complex composite coating of submicron bone-like apatite particulates combined with collagen fibrils. This work provided an efficient process to obtain bone-like apatite/collagen composite coating. Saos-2 osteoblast-like cells were used to evaluate the cellular behaviors on these biomimetic coatings. Cell morphologies on the surfaces of PLLA films and scaffolds, PLLA films and scaffolds with apatite coating, and PLLA films and scaffolds with apatite/collagen composite coating were studied by SEM. Cell viability was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrasodium bromide (MTT) assay. In addition, differentiated cell function was assessed by measuring alkaline phosphatase activity. These results suggested that the apatite coating and apatite/collagen composite coating fabricated through the accelerated biomimetic processes could improve the interactions between osteoblasts and PLLA. The composite coating was more effective than apatite coating in improving such interactions. PLLA scaffolds coated with submicron collagen fibrils and submicron apatite paticulates are expected to be one of the promising 3D substrates for bone tissue engineering. To facilitate coating into scaffolds, the flowing condition was introduced into the accelerated biomimetic process. The apatite formed in the different sites in the scaffold was characterized using SEM. It was found that the accelerated biomimetic process performed in the flowing condition yielded more uniform spatial distribution of apatite particles than that in the regular shaking condition. This work provides a novel condition for obtaining uniform spatial distribution of bone-like apatite within the scaffolds in a timely manner, which is expected to facilitate uniform distribution of attached cells within the scaffoldsin vitro and in vivo.

Thermal Aging Behavior of Axial Suspension Plasma-Sprayed Yttria-Stabilized Zirconia (YSZ) Thermal Barrier Coatings

NASA Astrophysics Data System (ADS)

Zhao, Yuexing; Wang, Liang; Yang, Jiasheng; Li, Dachuan; Zhong, Xinghua; Zhao, Huayu; Shao, Fang; Tao, Shunyan

2015-02-01

7.5YSZ thermal barrier coatings (TBCs) were deposited onto the stainless steel substrates using axial suspension plasma spraying (ASPS). Free-standing coatings were isothermally aged in air from 1200 to 1600 °C for 24 h and at 1550 °C for 20 to 100 h, respectively. Thermal aging behavior such as phase composition, microstructure evolutions, grain growth, and mechanical properties for thermal-aged coatings were investigated. Results show that the as-sprayed metastable tetragonal (t'-ZrO2) phase decomposes into equilibrium tetragonal (t-ZrO2) and cubic (c-ZrO2) phases during high-temperature exposures. Upon further cooling, the c-ZrO2 may be retained or transform into another metastable tetragonal (t″-ZrO2) phase, and tetragonal → monoclinic phase transformation occurred after 1550 °C/40 h aging treatment. The coating exhibits a unique structure with segmentation cracks and micro/nano-size grains, and the grains grow gradually with increasing aging temperature and time. In addition, the hardness ( H) and Young's modulus ( E) significantly increased as a function of temperature due to healing of pores or cracks and grain growth of the coating. And a nonmonotonic variation is found in the coatings thermal aged at a constant temperature (1550 °C) with prolonged time, this is a synergetic effect of coating sintering and m-ZrO2 phase formation.

Thermal stability and magnetic properties of MgFe2O4@ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Mallesh, S.; Prabu, D.; Srinivas, V.

2017-05-01

Magnesium ferrite, MgFe2O4, (MgFO) nanoparticles (NPs) have been synthesized through sol-gel process. Subsequently, as prepared particles were coated with Zinc-oxide (ZnO) layer(s) through ultrasonication process. Thermal stability, structure and magnetic properties of as-prepared (AP) and annealed samples in the temperature range of 350 °C-1200 °C have been investigated. Structural data suggests that AP MgFO NPs and samples annealed below 500 °C in air exhibit stable ferrite phase. However, α-Fe2O3 and a small fraction of MgO secondary phases appear along with ferrite phase on annealing in the temperatures range 500 °C- 1000 °C. This results in significant changes in magnetic moment for AP NPs 0.77 μB increases to 0.92 μB for 1200 °C air annealed sample. The magnetic properties decreased at intermediate temperatures due to the presence of secondary phases. On the other hand, pure ferrite phase could be stabilized with an optimum amount of ZnO coated MgFO NPs for samples annealed in the temperature range 500 °C-1000 °C with improvement in magnetic behavior compared to that of MgFO samples.

High Critical Current in Metal Organic Derived YBCO Films

DTIC Science & Technology

2010-10-31

process, particularly in reel-to- reel manufacturing equipment. During Phase I, a “three-step” conversion process was developed to de- convolute the...Task 3. After reaction, the 40-mm web was coated on both sides with a silver layer then slit into eight 4-mm width tapes which were laminated between

Solid coatings deposited from liquid methyl methacrylate via Plasma Polymerization

NASA Astrophysics Data System (ADS)

Wurlitzer, Lisa; Maus-Friedrichs, Wolfgang; Dahle, Sebastian

2016-09-01

The polymerization of methyl methacrylate via plasma discharges is well known today. Usually, plasma-enhanced chemical vapor deposition (PECVD) is used to deposit polymer coatings. Solid coatings are formed out of the liquid phase from methyl methacrylate via dielectric barrier discharge. The formation of the coating proceeds in the gas and the liquid phase. To learn more about the reactions in the two phases, the coatings from MMA monomer will be compared to those from MMA resin. Finally, attenuated total reflection infrared spectroscopy, confocal laser scanning microscopy and X-ray photoelectron spectroscopy are employed to characterize the solid coatings. In conclusion, the plasma enhanced chemical solution deposition is compared to the classical thermal polymerization of MMA.

The effect of steel chemistry on the formation of Fe-Zn intermetallic compounds of galvanneal-coated steel sheets

NASA Astrophysics Data System (ADS)

Lin, C. S.; Meshii, M.

1994-10-01

The effects of steel chemistry on the formation of Fe-Zn intermetallic compounds in the galvanneal coatings have been investigated by examining the microstructure of galvanneal coat-ings on extra-low-carbon (ELC) steel, interstitial-free (IF) steel, and interstitial-free rephos-phorized (IFP) steel. The layer structure of the coatings was revealed by chemical etching. Phases present in each layer were then identified using electron diffraction in transmission elec-tron microscopy (TEM). A two-layer structure, one consisting of the δ phase with a small fraction of the ζ, phase dispersed on the surface and Γ phases and another consisting of the δ and Γ1 phases, was observed in the ELC sample and the IFP sample, respectively. A three-layer structure consisting of the δ, Γ1 + δ, and Γ phases was observed in the IF sample. The presence of C in the steel substrate retarded the alloying between Fe and Zn; while P in the steel favored the formation of the Γ1, phase over the Γ phase by its surface segregation in the steel substrate. The orientation relationship between coating and substrate was also studied by electron diffraction. Three α-Fe/Γ orientation relationships were frequently observed.

Automated aray assembly, phase 2

NASA Technical Reports Server (NTRS)

Daiello, R. V.

1979-01-01

A manufacturing process suitable for the large-scale production of silicon solar array modules at a cost of less than $500/peak kW is described. Factors which control the efficiency of ion implanted silicon solar cells, screen-printed thick film metallization, spray-on antireflection coating process, and panel assembly are discussed. Conclusions regarding technological readiness or cost effectiveness of individual process steps are presented.

Investigation of (Ti-Zr-Hf-V-Nb)N Multicomponent Nanostructured Coatings before and after Thermal Annealing by Nuclear Physics Methods of Analysis

NASA Astrophysics Data System (ADS)

Pogrebnjak, A. D.; Beresnev, V. M.; Bondar', A. V.; Kaverin, M. V.; Ponomarev, A. G.

2013-10-01

(Ti-Zr-Hf-V-Nb)N multicomponent nanostructured coatings with thickness of 1.0-1.4 μm synthesized by the method of cathode arc-vapor deposition at temperatures of 250-300°С are investigated by various mutually complementary methods of elemental structural analysis using slow positron beams (SPB), proton microbeam based particle-induced x-ray emission (μ-PIXE), energy-dispersive x-ray spectroscopy (EDS) and scanning electron microscopy (SEM) analyses based on electron micro- and nanobeams, x-ray diffraction (XRD) method of phase structural analysis, and the "a-sin2φ" method of measuring a stressed-strained state (x-ray tensometry). The elemental composition, microstructure, residual stress in nanograins, profiles of defect and atom distributions with depth and over the coating surface in 3D-representation are studied for these coatings, and their phase composition, severely strained state, and composition of coatings before and after annealing at Tann = 600°С for annealing time τ = 30 min are investigated. It is demonstrated that the oxidation resistance of the examined coatings can be significantly increased by high-temperature annealing that leads to the formation of elastic severely strained compression state of the coating. Redistribution of elements and defects, their segregation near the interface boundaries and around grains and subgrains in the process of thermostimulated diffusion, and termination of spinodal segregation without considerable change of the average nanograin size are revealed.

The Effects of Sn Addition on the Microstructure and Surface Properties of Laser Deposited Al-Si-Sn Coatings on ASTM A29 Steel

NASA Astrophysics Data System (ADS)

Fatoba, Olawale S.; Akinlabi, Stephen A.; Akinlabi, Esther T.

2018-03-01

Aluminium and its alloys have been successful metal materials used for many applications like commodity roles, automotive and vital structural components in aircrafts. A substantial portion of Al-Fe-Si alloy is also used for manufacturing the packaging foils and sheets for common heat exchanger applications. The present research was aimed at studying the morphology and surface analyses of laser deposited Al-Sn-Si coatings on ASTM A29 steel. These Fe-intermetallic compounds influence the material properties during rapid cooling by laser alloying technique and play a crucial role for the material quality. Thus, it is of considerable technological interest to control the morphology and distribution of these phases in order to eliminate the negative effects on microstructure. A 3 kW continuous wave ytterbium laser system (YLS) attached to a KUKA robot which controls the movement of the alloying process was utilized for the fabrication of the coatings at optimum laser parameters. The fabricated coatings were investigated for its hardness and wear resistance performance. The field emission scanning electron microscope equipped with energy dispersive spectroscopy (SEM/EDS) was used to study the morphology of the fabricated coatings and X-ray diffractometer (XRD) for the identification of the phases present in the coatings. The coatings were free of cracks and pores with homogeneous and refined microstructures. The enhanced hardness and wear resistance performance were attributed to metastable intermetallic compounds formed.

Controlling the Release of Indomethacin from Glass Solutions Layered with a Rate Controlling Membrane Using Fluid-Bed Processing. Part 1: Surface and Cross-Sectional Chemical Analysis.

PubMed

Dereymaker, Aswin; Scurr, David J; Steer, Elisabeth D; Roberts, Clive J; Van den Mooter, Guy

2017-04-03

Fluid bed coating has been shown to be a suitable manufacturing technique to formulate poorly soluble drugs in glass solutions. Layering inert carriers with a drug-polymer mixture enables these beads to be immediately filled into capsules, thus avoiding additional, potentially destabilizing, downstream processing. In this study, fluid bed coating is proposed for the production of controlled release dosage forms of glass solutions by applying a second, rate controlling membrane on top of the glass solution. Adding a second coating layer adds to the physical and chemical complexity of the drug delivery system, so a thorough understanding of the physical structure and phase behavior of the different coating layers is needed. This study aimed to investigate the surface and cross-sectional characteristics (employing scanning electron microscopy (SEM) and time of flight secondary ion mass spectrometry (ToF-SIMS)) of an indomethacin-polyvinylpyrrolidone (PVP) glass solution, top-coated with a release rate controlling membrane consisting of either ethyl cellulose or Eudragit RL. The implications of the addition of a pore former (PVP) and the coating medium (ethanol or water) were also considered. In addition, polymer miscibility and the phase analysis of the underlying glass solution were investigated. Significant differences in surface and cross-sectional topography of the different rate controlling membranes or the way they are applied (solution vs dispersion) were observed. These observations can be linked to the polymer miscibility differences. The presence of PVP was observed in all rate controlling membranes, even if it is not part of the coating solution. This could be attributed to residual powder presence in the coating chamber. The distribution of PVP among the sample surfaces depends on the concentration and the rate controlling polymer used. Differences can again be linked to polymer miscibility. Finally, it was shown that the underlying glass solution layer remains amorphous after coating of the rate controlling membrane, whether formed from an ethanol solution or an aqueous dispersion.

Conformal coating of amorphous silicon and germanium by high pressure chemical vapor deposition for photovoltaic fabrics

NASA Astrophysics Data System (ADS)

Ji, Xiaoyu; Cheng, Hiu Yan; Grede, Alex J.; Molina, Alex; Talreja, Disha; Mohney, Suzanne E.; Giebink, Noel C.; Badding, John V.; Gopalan, Venkatraman

2018-04-01

Conformally coating textured, high surface area substrates with high quality semiconductors is challenging. Here, we show that a high pressure chemical vapor deposition process can be employed to conformally coat the individual fibers of several types of flexible fabrics (cotton, carbon, steel) with electronically or optoelectronically active materials. The high pressure (˜30 MPa) significantly increases the deposition rate at low temperatures. As a result, it becomes possible to deposit technologically important hydrogenated amorphous silicon (a-Si:H) from silane by a simple and very practical pyrolysis process without the use of plasma, photochemical, hot-wire, or other forms of activation. By confining gas phase reactions in microscale reactors, we show that the formation of undesired particles is inhibited within the microscale spaces between the individual wires in the fabric structures. Such a conformal coating approach enables the direct fabrication of hydrogenated amorphous silicon-based Schottky junction devices on a stainless steel fabric functioning as a solar fabric.

Synthesizing and characterization of titanium diboride for composite bipolar plates in PEM fuel cell

NASA Astrophysics Data System (ADS)

Duddukuri, Ramesh

This research deals with the synthesis and characterization of titanium diboride (TiB2) from novel carbon coated precursors. This work provides information on using different boron sources and their effect on the resulting powders of TiB2. The process has two steps in which the oxide powders were first coated with carbon by cracking of a hydrocarbon gas, propylene (C3H6) and then, mixed with boron carbide and boric acid powders in a stoichiometric ratio. These precursors were treated at temperatures in the range of 1200--1400° C for 2 h in flowing Argon atmosphere to synthesize TiB2. The process utilizes a carbothermic reduction reaction of novel carbon coated precursor that has potential of producing high-quality powders (sub-micrometer and high purity). Single phase TiB2 powders produced, were compared with commercially available titanium diboride using X-ray diffraction and Transmission electron microscopy obtained from boron carbide and boric acid containing carbon coated precursor.

Plasma Processing of Lunar Regolith Simulant for Diverse Applications

NASA Technical Reports Server (NTRS)

Schofield, Elizabeth C.; Sen, Subhayu; O'Dell, J. Scott

2008-01-01

Versatile manufacturing technologies for extracting resources from the moon are needed to support future space missions. Of particular interest is the production of gases and metals from lunar resources for life support, propulsion, and in-space fabrication. Deposits made from lunar regolith could yield highly emissive coatings and near-net shaped parts for replacement or repair of critical components. Equally important is development of high fidelity lunar simulants for ground based validation of potential lunar surface operations. Described herein is an innovative plasma processing technique for insitu production of gases, metals, coatings, and deposits from lunar regolith, and synthesis of high fidelity lunar simulant from NASA issued lunar simulant JSC-1. Initial plasma reduction trials of JSC-1 lunar simulant have indicated production of metallic iron and magnesium. Evolution of carbon monoxide has been detected subsequent to reduction of the simulant using the plasma process. Plasma processing of the simulant has also resulted in glassy phases resembling the volcanic glass and agglutinates found in lunar regolith. Complete and partial glassy phase deposits have been obtained by varying the plasma process variables. Experimental techniques, product characterization, and process gas analysis will be discussed.

Final Report: Superconducting Joints Between (RE)Ba 2Cu 3O 7-x Coated Conductors via Electric Field Assisted Processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwartz, Justin

Here we report the results from a project aimed at developing a fully superconducting joint between two REBCO coated conductors using electric field processing (EFP). Due to a reduction in the budget and time period of this contract, we reduced the project scope and focused first on the key scientific issues for forming a strong bond between conductors, and subsequently focused on improving through-the-joint transport. A modified timeline and task list is shown in Table 1, summarizing accomplishments to date. In the first period, we accomplished initial surface characterization as well as rounds of EFP experiments to begin to understandmore » processing parameters which produce well-bonded tapes. In the second phase, we explored the effects of two fundamental EFP parameters, voltage and pressure, and the limitations they place on the process. In the third phase, we achieved superconducting joints and established base characteristics of both the bonding process and the types of tapes best suited to this process. Finally, we investigated some of the parameters related to kinetics which appeared inhibit joint quality and performance.« less

Preparation of Janus Particles and Alternating Current Electrokinetic Measurements with a Rapidly Fabricated Indium Tin Oxide Electrode Array.

PubMed

Chen, Yu-Liang; Jiang, Hong-Ren

2017-06-23

This article provides a simple method to prepare partially or fully coated metallic particles and to perform the rapid fabrication of electrode arrays, which can facilitate electrical experiments in microfluidic devices. Janus particles are asymmetric particles that contain two different surface properties on their two sides. To prepare Janus particles, a monolayer of silica particles is prepared by a drying process. Gold (Au) is deposited on one side of each particle using a sputtering device. The fully coated metallic particles are completed after the second coating process. To analyze the electrical surface properties of Janus particles, alternating current (AC) electrokinetic measurements, such as dielectrophoresis (DEP) and electrorotation (EROT)- which require specifically designed electrode arrays in the experimental device- are performed. However, traditional methods to fabricate electrode arrays, such as the photolithographic technique, require a series of complicated procedures. Here, we introduce a flexible method to fabricate a designed electrode array. An indium tin oxide (ITO) glass is patterned by a fiber laser marking machine (1,064 nm, 20 W, 90 to 120 ns pulse-width, and 20 to 80 kHz pulse repetition frequency) to create a four-phase electrode array. To generate the four-phase electric field, the electrodes are connected to a 2-channel function generator and to two invertors. The phase shift between the adjacent electrodes is set at either 90° (for EROT) or 180° (for DEP). Representative results of AC electrokinetic measurements with a four-phase ITO electrode array are presented.

Erosion and corrosion resistance of laser cladded AISI 420 stainless steel reinforced with VC

NASA Astrophysics Data System (ADS)

Zhang, Zhe; Yu, Ting; Kovacevic, Radovan

2017-07-01

Metal Matrix Composites (MMC) fabricated by the laser cladding process have been widely applied as protective coatings in industries to improve the wear, erosion, and corrosion resistance of components and prolong their service life. In this study, the AISI 420/VC metal matrix composites with different weight percentage (0 wt.%-40 wt.%) of Vanadium Carbide (VC) were fabricated on a mild steel A36 by a high power direct diode laser. An induction heater was used to preheat the substrate in order to avoid cracks during the cladding process. The effect of carbide content on the microstructure, elements distribution, phases, and microhardness was investigated in detail. The erosion resistance of the coatings was tested by using the abrasive waterjet (AWJ) cutting machine. The corrosion resistance of the coatings was studied utilizing potentiodynamic polarization. The results showed that the surface roughness and crack susceptibility of the laser cladded layer were increased with the increase in VC fraction. The volume fraction of the precipitated carbides was increased with the increase in the VC content. The phases of the coating without VC consisted of martensite and austenite. New phases such as precipitated VC, V8C7, M7C3, and M23C6 were formed when the primary VC was added. The microhardness of the clads was increased with the increase in VC. The erosion resistance of the cladded layer was improved after the introduction of VC. The erosion resistance was increased with the increase in the VC content. No obvious improvement of erosion resistance was observed when the VC fraction was above 30 wt.%. The corrosion resistance of the clads was decreased with the increase in the VC content, demonstrating the negative effect of VC on the corrosion resistance of AISI 420 stainless steel

Linking Precursor Alterations to Nanoscale Structure and Optical Transparency in Polymer Assisted Fast-Rate Dip-Coating of Vanadium Oxide Thin Films

PubMed Central

Glynn, Colm; Creedon, Donal; Geaney, Hugh; Armstrong, Eileen; Collins, Timothy; Morris, Michael A.; Dwyer, Colm O’

2015-01-01

Solution processed metal oxide thin films are important for modern optoelectronic devices ranging from thin film transistors to photovoltaics and for functional optical coatings. Solution processed techniques such as dip-coating, allow thin films to be rapidly deposited over a large range of surfaces including curved, flexible or plastic substrates without extensive processing of comparative vapour or physical deposition methods. To increase the effectiveness and versatility of dip-coated thin films, alterations to commonly used precursors can be made that facilitate controlled thin film deposition. The effects of polymer assisted deposition and changes in solvent-alkoxide dilution on the morphology, structure, optoelectronic properties and crystallinity of vanadium pentoxide thin films was studied using a dip-coating method using a substrate withdrawal speed within the fast-rate draining regime. The formation of sub-100 nm thin films could be achieved rapidly from dilute alkoxide based precursor solutions with high optical transmission in the visible, linked to the phase and film structure. The effects of the polymer addition was shown to change the crystallized vanadium pentoxide thin films from a granular surface structure to a polycrystalline structure composed of a high density of smaller in-plane grains, resulting in a uniform surface morphology with lower thickness and roughness. PMID:26123117

The role of nanocrystalline binder metallic coating into WC after additive manufacturing

NASA Astrophysics Data System (ADS)

Cavaleiro, A. J.; Fernandes, C. M.; Farinha, A. R.; Gestel, C. V.; Jhabvala, J.; Boillat, E.; Senos, A. M. R.; Vieira, M. T.

2018-01-01

Tungsten carbide with microsized particle powders are commonly used embedded in a tough binder metal. The application of these composites is not limited to cutting tools, WC based material has been increasingly used in gaskets and other mechanical parts with complex geometries. Consequently, additive manufacturing processes as Selective Laser Sintering (SLS) might be the solution to overcome some of the manufacturing problems. However, the use of SLS leads to resolve the problems resulting from difference of physical properties between tungsten carbide and the metallic binder, such as laser absorbance and thermal conductivity. In this work, an original approach of powder surface modification was considered to prepare WC-metal composite powders and overcome these constraints, consisting on the sputter-coating of the WC particle surfaces with a nanocrystalline thin film of metallic binder material (stainless steel). The coating improves the thermal behavior and rheology of the WC particles and, at the same time, ensures a binder homogenous distribution. The feasibility of the SLS technology as manufacturing process for WC powder sputter-coated with 13 wt% stainless steel AISI 304L was explored with different laser power and scanning speed parameters. The SLS layers were characterized regarding elemental distribution, phase composition and morphology, and the results are discussed emphasizing the role of the coating on the consolidation process.

A Simple, Cost-Efficient Method to Separate Microalgal Lipids from Wet Biomass Using Surface Energy-Modified Membranes.

PubMed

Kwak, Moo Jin; Yoo, Youngmin; Lee, Han Sol; Kim, Jiyeon; Yang, Ji-Won; Han, Jong-In; Im, Sung Gap; Kwon, Jong-Hee

2016-01-13

For the efficient separation of lipid extracted from microalgae cells, a novel membrane was devised by introducing a functional polymer coating onto a membrane surface by means of an initiated chemical vapor deposition (iCVD) process. To this end, a steel-use-stainless (SUS) membrane was modified in a way that its surface energy was systemically modified. The surface modification by conformal coating of functional polymer film allowed for selective separation of oil-water mixture, by harnessing the tuned interfacial energy between each liquid phase and the membrane surface. The surface-modified membrane, when used with chloroform-based solvent, exhibited superb permeate flux, breakthrough pressure, and also separation yield: it allowed separation of 95.5 ± 1.2% of converted lipid (FAME) in the chloroform phase from the water/MeOH phase with microalgal debris. This result clearly supported that the membrane-based lipid separation is indeed facilitated by way of membrane being functionalized, enabling us to simplify the whole downstream process of microalgae-derived biodiesel production.

Preparation of ceramic coating on Ti substrate by Plasma electrolytic oxidation in different electrolytes and evaluation of its corrosion resistance

NASA Astrophysics Data System (ADS)

Shokouhfar, M.; Dehghanian, C.; Baradaran, A.

2011-01-01

Ceramic oxide coatings (titania) were produced on Ti by micro-arc oxidation in different aluminate and carbonate based electrolytes. This process was conducted under constant pulsed DC voltage condition. The effect of KOH and NaF in aluminate based solution was also studied. The surface morphology, growth and phase composition of coatings were investigated using scanning electron microscope and X-ray diffraction. Corrosion behavior of the coatings was also examined by potentiodynamic polarization and electrochemical impedance spectroscopy. It was found that the sparking initiation voltage (spark voltage) had a significant effect on the form and properties of coatings. Coatings obtained from potassium aluminate based solution had a lower spark voltage, higher surface homogeneity and a better corrosion resistance than the carbonate based solution. Addition of NaF instead of KOH had improper effects on the homogeneity and adhesion of coatings which in turn caused a poor corrosion protection behavior of the oxide layer. AC impedance curves showed two time constants which is an indication of the coatings with an outer porous layer and an inner compact layer.

Easily recycled Bi2O3 photocatalyst coatings prepared via ball milling followed by calcination

NASA Astrophysics Data System (ADS)

Cheng, Lijun; Hu, Xumin; Hao, Liang

2017-06-01

Bi2O3 photocatalyst coatings derived from Bi coatings were first prepared by a two-step method, namely ball milling followed by the calcination process. The as-prepared samples were characterized by XRD, SEM, XPS and UV-Vis spectra, respectively. The results showed that monoclinic Bi2O3 coatings were obtained after sintering Bi coatings at 673 or 773 K, while monoclinic and triclinic mixed phase Bi2O3 coatings were obtained at 873 or 973 K. The topographies of the samples were observably different, which varied from flower-like, irregular, polygonal to nanosized particles with the increase in calcination temperature. Photodegradation of malachite green under simulated solar irradiation for 180 min showed that the largest degradation efficiency of 86.2% was achieved over Bi2O3 photocatalyst coatings sintered at 873 K. The Bi2O3 photocatalyst coatings, encapsulated with Al2O3 ball with an average diameter around 1 mm, are quite easily recycled, which provides an alternative visible light-driven photocatalyst suitable for practical water treatment application.

Characterization of coatings formed on AZX magnesium alloys by plasma electrolytic oxidation

NASA Astrophysics Data System (ADS)

Anawati, Anawati; Gumelar, Muhammad Dikdik

2018-05-01

Plasma Electrolytic Oxidation (PEO) is an electrochemical anodization process which involves the application of a high voltage to create intense plasma on a metal surface to form a ceramic type of oxide. The resulted coating exhibits high wear resistance and good corrosion barrier which are suitable to enhance the performance of biodegradable Mg alloys. In this work, the role of alloying element Ca in modifying the characteristics of PEO layer formed on AZ61 series magnesium alloys was investigated. PEO treatment was conducted on AZ61, AZX611, and AZX612 alloys in 0.5 M Na3PO4 solution at a constant current of 200 A/m2 at 25°C for 8 min. The resulted coatings were characterized by field emission-scanning electron microscope (FESEM), X-ray diffraction spectroscopy (XRD), and X-ray fluorescence spectroscopy (XRF), as well as hardness test. The presence of alloying element Ca in the AZ61 alloys accelerated the PEO coatings formation without altering the coating properties significantly. The coating formed on AZX specimen was slightly thicker ( 14-17 µm) than that of formed onthe AZ specimens ( 13 µm). Longer exposure time to plasma discharge was the reason for faster thickening of the coating layer on AZX specimen. XRD detected a similar crystalline oxide phase of Mg3(PO4)2 in the oxide formed on all of the specimens. Zn was highly incorporated in the coatings with a concentration in the range 24-30 wt%, as analyzed by XRF. Zn compound might exist in amorphous phases. The microhardness test on the coatings revealed similar average hardness 124 HVon all of the specimens.

Evaluation of coating thickness by thermal wave imaging: A comparative study of pulsed and lock-in infrared thermography - Part I: Simulation

NASA Astrophysics Data System (ADS)

Shrestha, Ranjit; Kim, Wontae

2017-06-01

This paper investigates the possibilities of evaluating non-uniform coating thickness using thermal wave imaging method. A comparative study of pulsed thermography (PT) and lock-in thermography (LIT) based on evaluating the accuracy of predicted coating thickness is presented. In this study, a transient thermal finite element model was created in ANSYS 15. A single square pulse heating for PT and a sinusoidal heating at different modulation frequencies for LIT were used to stimulate the sample according to the experimental procedures. The response of thermally excited surface was recorded and data processing with Fourier transform was carried out to obtain the phase angle. Then calculated phase angle was correlated with the coating thickness. The method demonstrated potential in the evaluation of coating thickness and was successfully applied to measure the non-uniform top layers ranging from 0.1 mm to 0.6 mm; within an accuracy of 0.0003-0.0023 mm for PT and 0.0003-0.0067 mm for LIT. The simulation model enabled a better understanding of PT and LIT and provided a means of establishing the required experimental set-up parameters. This also led to optimization of experimental configurations, thus limiting the number of physical tests necessary.

Dissolution behavior and early bone apposition of calcium phosphate-coated machined implants

PubMed Central

Hwang, Ji-Wan; Lee, Eun-Ung; Lee, Jung-Seok; Jung, Ui-Won; Lee, In-Seop

2013-01-01

Purpose Calcium phosphate (CaP)-coated implants promote osseointegration and survival rate. The aim of this study was to (1) analyze the dissolution behavior of the residual CaP particles of removed implants and (2) evaluate bone apposition of CaP-coated machined surface implants at the early healing phase. Methods Mandibular premolars were extracted from five dogs. After eight weeks, the implants were placed according to drilling protocols: a nonmobile implant (NI) group and rotational implant (RI) group. For CaP dissolution behavior analysis, 8 implants were removed after 0, 1, 2, and 4 weeks. The surface morphology and deposition of the coatings were observed. For bone apposition analysis, block sections were obtained after 1-, 2-, and 4-week healing periods and the specimens were analyzed. Results Calcium and phosphorus were detected in the implants that were removed immediately after insertion, and the other implants were composed mainly of titanium. There were no notable differences between the NI and RI groups in terms of the healing process. The bone-to-implant contact and bone density in the RI group showed a remarkable increase after 2 weeks of healing. Conclusions It can be speculated that the CaP coating dissolves early in the healing phase and chemically induces early bone formation regardless of the primary stability. PMID:24455442

Influence of solution conditions on deposition of calcium phosphate on titanium by NaOH-treatment

NASA Astrophysics Data System (ADS)

Feng, Q. L.; Cui, F. Z.; Wang, H.; Kim, T. N.; Kim, J. O.

2000-03-01

The present paper demonstrated a biomimetic method to coat calcium phosphate (Ca-P) on the surface of titanium induced by NaOH-treatment from a simple supersaturated hydroxyapatite solution (SHS). The influence of pH value and calcium ions concentration on the precipitation process was investigated. It is necessary for the solution to be supersaturated than the critical concentration of octacalcium phosphate (OCP) to get Ca-P coatings on titanium surface. In the precipitating process, it seems that amorphous calcium phosphate (ACP) precipitated first, then OCP, and finally hydroxyapatite (HA). The system was in continuous evolution and the phase transitions occurred in sequence.

Environmental Barrier Coatings Having a YSZ Top Coat

NASA Technical Reports Server (NTRS)

Lee, Kang N.; Gray, Hugh (Technical Monitor)

2002-01-01

Environmental barrier coatings (EBCs) with a Si bond coat, a yttria-stabilized zirconia (YSZ) top coat, and various intermediate coats were investigated. EBCs were processed by atmospheric pressure plasma spraying. The EBC durability was determined by thermal cycling tests in water vapor at 1300 C and 1400 C, and in air at 1400 C and 1500 C. EBCs with a mullite (3Al2O3 (dot) 2SiO2) + BSAS (1 - xBaO (dot) xSrO (dot) Al2O3 (dot) 2SiO2) intermediate coat were more durable than EBCs with a mullite intermediate coat, while EBCs with a mullite/BSAS duplex intermediate coat resulted in inferior durability. The improvement with a mullite + BSAS intermediate coat was attributed to enhanced compliance of the intermediate coat due to the addition of a low modulus BSAS second phase. Mullite + BSAS/YSZ and BSAS/YSZ interfaces produced a low melting (less than 1400 C) reaction product, which is expected to degrade the EBC performance by increasing the thermal conductivity. EBCs with a mullite + BSAS / graded mullite + YSZ intermediate coat showed the best durability among the EBCs investigated in this study. This improvement was attributed to diffused CTE (Coefficient of Thermal Expansion) mismatch stress and improved chemical stability due to the compositionally graded mullite+YSZ layer.

Biomimetic whisker-shaped apatite coating of titanium powder.

PubMed

Sim, Young Uk; Kim, Jong Hee; Yang, Tae Young; Yoon, Seog Young; Park, Hong Chae

2010-05-01

Biomimetic apatite coatings on chemically modified titanium powder have been processed and the resulting coating layers evaluated in terms of morphology, composition and structure, using TF-XRD, XPS, SEM, TEM and FTIR analysis. After 7 days immersion in a simulated body fluid (SBF), nanometer-sized fine precipitates with an amorphous whisker-like phase and a Ca/P atomic ratio of 1.94 were obtained on the external surface of the titanium particles. When the immersion time in SBF was extended to 16 days, the coating layer consisted of the whisker-like nanostructured crystals of carbonated hydroxyapatite with a atomic ratio of 3; in such a case, a double coating layer was developed. The double layer could be divided into two regions and could be clearly distinguished: an inner dense region (approximately 200 nm in thickness) which may include hard agglomerated crystals and an outer less dense region (> 500 nm in thickness) in which crystals are loosely distributed.

Tribological Behavior of IN718 Superalloy Coating Fabricated by Laser Additive Manufacturing

NASA Astrophysics Data System (ADS)

Zhang, Yaocheng; Pan, Qiyong; Yang, Li; Li, Ruifeng; Dai, Jun

2017-12-01

The tribological behavior of laser manufactured IN718 superalloy coating are investigated with different applied loads, sliding speeds and lubricating mediums. The wear resistance of laser manufactured IN718 coating is increased by heat treatment due to higher microhardness and homogeneous brittle phase distribution. The principal factors for the wear rate are applied load and lubricating medium. The worn surface of laser manufactured IN718 coating consists of the grooves, crack, wear debris and material delamination generated by the fatigue wear associated with adhesive wear and abrasive wear. The friction coefficients are influenced by the tribological noise decrescence by the tribo-oxidant and the liquid lubricant. The real contact temperature between coating sample and frictional counterpart is higher than the solid-solution temperature of IN718 superalloy, and the effect of surface contact temperature on the orientational microstructure and wear resistance for dry friction and wet friction process is indistinct.

Corrosion behaviors and effects of corrosion products of plasma electrolytic oxidation coated AZ31 magnesium alloy under the salt spray corrosion test

NASA Astrophysics Data System (ADS)

Wang, Yan; Huang, Zhiquan; Yan, Qin; Liu, Chen; Liu, Peng; Zhang, Yi; Guo, Changhong; Jiang, Guirong; Shen, Dejiu

2016-08-01

The effects of corrosion products on corrosion behaviors of AZ31 magnesium alloy with a plasma electrolytic oxidation (PEO) coating were investigated under the salt spray corrosion test (SSCT). The surface morphology, cross-sectional microstructure, chemical and phase compositions of the PEO coating were determined using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction analysis (XRD), respectively. Further, the corrosion process of the samples under the SSCT was examined in a non-aqueous electrolyte (methanol) using electrochemical impedance spectroscopy (EIS) coupled with equivalent circuit. The results show that the inner layer of the coating was destroyed firstly and the corrosion products have significant effects on the corrosion behaviors of the coating. The results above are discussed and an electrochemical corrosion model is proposed in the paper.

Effect of Aluminum Coating on the Surface Properties of Ti-(~49 at. pct) Ni Alloy

NASA Astrophysics Data System (ADS)

Sinha, Arijit; Khan, Gobinda Gopal; Mondal, Bholanath; Majumdar, Jyotsna Dutta; Chattopadhyay, Partha Protim

2015-08-01

Stable porous layer of mixed Al2O3 and TiO2 has been formed on the Ti-(~49 at. pct) Ni alloy surface with an aim to suppress leaching of Ni from the alloy surface in contact with bio-fluid and to enhance the process of osseointegration. Aluminum coating on the Ni-Ti alloy surface prior to the anodization treatment has resulted in enhancement of depth and uniformity of pores. Thermal oxidation of the anodized aluminum-coated Ni-Ti samples has exhibited the formation of Al2O3 and TiO2 phases with dense porous structure. The nanoindentation and nanoscratch measurements have indicated a remarkable improvement in the hardness, wear resistance, and adhesiveness of the porous aluminum-coated Ni-Ti sample after thermal oxidation.

The role of microstructure and phase distribution in the failure mechanisms and life prediction model for PSZ coatings

NASA Technical Reports Server (NTRS)

Sisson, R. D., Jr.; Sone, Ichiro; Biederman, R. R.

1985-01-01

Partially Stabilized Zirconia (PSZ) may become widely used for Thermal Barrier Coatings (TBC). Failure of these coatings can occur due to thermal fatigue in oxidizing atmospheres. The failure is due to the strains that develop due to thermal gradients, differences in thermal expansion coefficients, and oxidation of the bond coating. The role of microstructure and the cubic, tetragonal, and monoclinic phase distribution in the strain development and subsequent failure will be discussed. An X-ray diffraction technique for accurate determination of the fraction of each phase in PSZ will be applied to understanding the phase transformations and strain development. These results will be discussed in terms of developing a model for life prediction in PSZ coatings during thermal cycling.

Methods of Fabricating a Layer of Metallic Glass-Based Material Using Immersion and Pouring Techniques

NASA Technical Reports Server (NTRS)

Hofmann, Douglas (Inventor)

2015-01-01

Systems and methods in accordance with embodiments of the invention implement layers of metallic glass-based materials. In one embodiment, a method of fabricating a layer of metallic glass includes: applying a coating layer of liquid phase metallic glass to an object, the coating layer being applied in a sufficient quantity such that the surface tension of the liquid phase metallic glass causes the coating layer to have a smooth surface; where the metallic glass has a critical cooling rate less than 1000 K/s; and cooling the coating layer of liquid phase metallic glass to form a layer of solid phase metallic glass.

Intelligent process control of fiber chemical vapor deposition

NASA Astrophysics Data System (ADS)

Jones, John Gregory

Chemical Vapor Deposition (CVD) is a widely used process for the application of thin films. In this case, CVD is being used to apply a thin film interface coating to single crystal monofilament sapphire (Alsb2Osb3) fibers for use in Ceramic Matrix Composites (CMC's). The hot-wall reactor operates at near atmospheric pressure which is maintained using a venturi pump system. Inert gas seals obviate the need for a sealed system. A liquid precursor delivery system has been implemented to provide precise stoichiometry control. Neural networks have been implemented to create real-time process description models trained using data generated based on a Navier-Stokes finite difference model of the process. Automation of the process to include full computer control and data logging capability is also presented. In situ sensors including a quadrupole mass spectrometer, thermocouples, laser scanner, and Raman spectrometer have been implemented to determine the gas phase reactants and coating quality. A fuzzy logic controller has been developed to regulate either the gas phase or the in situ temperature of the reactor using oxygen flow rate as an actuator. Scanning electron microscope (SEM) images of various samples are shown. A hierarchical control structure upon which the control structure is based is also presented.

New support for high-performance liquid chromatography based on silica coated with alumina particles.

PubMed

Silveira, José Leandro R; Dib, Samia R; Faria, Anizio M

2014-01-01

A new material based on silica coated with alumina nanoparticles was proposed for use as a chromatographic support for reversed-phase high-performance liquid chromatography. Alumina nanoparticles were synthesized by a sol-gel process in reversed micelles composed of sodium bis(2-ethylhexyl)sulfosuccinate, and the support material was formed by the self-assembly of alumina layers on silica spheres. Spectroscopic and (29)Si nuclear magnetic resonance results showed evidence of chemical bonds between the alumina nanoparticles and the silica spheres, while morphological characterizations showed that the aluminized silica maintained the morphological properties of silica desired for chromatographic purposes after alumina incorporation. Stability studies indicated that bare silica showed high dissolution (~83%), while the aluminized silica remained practically unchanged (99%) after passing one liter of the alkaline mobile phase, indicating high stability under alkaline conditions. The C18 bonded aluminized silica phase showed great potential for use in high-performance liquid chromatography to separate basic molecules in the reversed-phase mode.

ENVIRONMENTALLY SAFE, NO VOC AUTOMOTIVE COATING - PHASE II

EPA Science Inventory

The EPA recognizes that volatile organic compounds (VOCs) must be eliminated from automotive coating formulations to improve worker safety and reduce environmental pollution. The phase I project resulted in the production of a polymer-based coating material that was clear, ...

Atmospheric photochemistry at a fatty acid-coated air-water interface

NASA Astrophysics Data System (ADS)

Rossignol, Stéphanie; Tinel, Liselotte; Bianco, Angelica; Passananti, Monica; Brigante, Marcello; Donaldson, D. James; George, Christian

2016-08-01

Although fatty acids are believed to be photochemically inert in the actinic region, complex volatile organic compounds are produced during illumination of an air-water interface coated solely with a monolayer of carboxylic acid. When aqueous solutions containing nonanoic acid (NA) at bulk concentrations that give rise to just over a monolayer of NA coverage are illuminated with actinic radiation, saturated and unsaturated aldehydes are seen in the gas phase, and more highly oxygenated products appear in the aqueous phase. This chemistry is probably initiated by triplet-state NA molecules excited by direct absorption of actinic light at the water surface. Because fatty acids-covered interfaces are ubiquitous in the environment, such photochemical processing will have a substantial impact on local ozone and particle formation.

Microstructure and wear property of the Ti5Si3/TiC reinforced Co-based coatings fabricated by laser cladding on Ti-6Al-4V

NASA Astrophysics Data System (ADS)

Weng, Fei; Yu, Huijun; Liu, Jianli; Chen, Chuanzhong; Dai, Jingjie; Zhao, Zhihuan

2017-07-01

Ti5Si3/TiC reinforced Co-based composite coatings were fabricated on Ti-6Al-4V titanium alloy by laser cladding with Co42 and SiC mixture. Microstructure and wear property of the cladding coatings with different content of SiC were investigated. During the cladding process, the original SiC dissolved and reacted with Ti forming Ti5Si3 and TiC. The complex in situ formed phases were found beneficial to the improvement of the coating property. Results indicated that the microhardness of the composite coatings was enhanced to over 3 times the substrate. The wear resistance of the coatings also showed distinct improvement (18.4-57.4 times). More SiC gave rise to better wear resistance within certain limits. However, too much SiC (20 wt%) was not good for the further improvement of the wear property.

Electroplating chromium on CVD SiC and SiCf-SiC advanced cladding via PyC compatibility coating

NASA Astrophysics Data System (ADS)

Ang, Caen; Kemery, Craig; Katoh, Yutai

2018-05-01

Electroplating Cr on SiC using a pyrolytic carbon (PyC) bond coat is demonstrated as an innovative concept for coating of advanced fuel cladding. The quantification of coating stress, SEM morphology, XRD phase analysis, and debonding test of the coating on CVD SiC and SiCf-SiC is shown. The residual tensile stress (by ASTM B975) of electroplated Cr is > 1 GPa prior to stress relaxation by microcracking. The stress can remove the PyC/Cr layer from SiC. Surface etching of ∼20 μm and roughening to Ra > 2 μm (by SEM observation) was necessary for successful adhesion. The debonding strength (by ASTM D4541) of the coating on SiC slightly improved from 3.6 ± 1.4 MPa to 5.9 ± 0.8 MPa after surface etching or machining. However, this improvement is limited due to the absence of an interphase, and integrated CVI processing may be required for further advancement.

[Characteristics of electroosmotic flow in open-tubular capillary electrochromatography with magnetic nanoparticle coating as mixed-mode stationary phase].

PubMed

Qin, Sasa; Zhou, Chaoran; Zhu, Yaxian; Ren, Zhiyu; Zhang, Lingyi; Fu, Honggang; Zhang, Weibing

2011-09-01

A novel open-tubular capillary electrochromatography (OT-CEC) column with magnetic nanoparticle coating as mixed-mode stationary phase was prepared. The mixed-mode stationary phases were obtained by mixing C18 and amino modified magnetic nanoparticles with different ratios. The mixed modified magnetic nanoparticles as stationary phase were introduced into the capillary by using external magnetic force. The magnetic nanoparticle coating can be easily regenerated by removing the external magnetic field, and applied to other separation modes. The characteristics of electroosmotic flow (EOF) were theoretically investigated through the effect of physicochemical properties of different stationary phases on EOF. The experiment was conducted under different ratios of mixed-mode stationary phases and coating lengths, and it was verified that the theoretical conclusions accorded with the experimental results. It was shown that the EOF can be easily adjusted by changing the ratio of stationary phases or the number of permanent magnets.

Tuning domain size and crystallinity in isoindigo/PCBM organic solar cells via solution shearing

DOE PAGES

Gu, Kevin L.; Zhou, Yan; Gu, Xiaodan; ...

2016-11-01

Despite having achieved the long sought-after performance of 10% power conversion efficiency, high performance organic photovoltaics (OPVs) are still mostly constrained to lab scale devices fabricated by spin coating. Efforts to produce printed OPVs lag considerably behind, and the sensitivity to different fabrication methods highlights the need to develop a comprehensive understanding of the processing-morphology relationship in printing methods. Here we present a systematic experimental investigation of a model low bandgap polymer/fullerene system, poly-isoindigo thienothiophene/PC 61BM, using a lab-scale analogue to roll-to-roll coating as the fabrication tool in order to understand the impact of processing parameters on morphological evolution. Wemore » report that domain size and polymer crystallinity can be tuned by a factor of two by controlling the temperature and coating speed. Lower fabrication temperature simultaneously decreased the phase separation domain size and increased the relative degree of crystallinity in those domains, leading to improved photocurrent. We conclude that domain size in isoindigo/PCBM is dictated by spontaneous phase separation rather than crystal nucleation and growth. Moreover we present a model to describe the temperature dependence of domain size formation in our system, which demonstrates that morphology is not necessarily strictly dependent on the evaporation rate, but rather on the interplay between evaporation and diffusion during the printing process.« less

Effective Parameters in Axial Injection Suspension Plasma Spray Process of Alumina-Zirconia Ceramics

NASA Astrophysics Data System (ADS)

Tarasi, F.; Medraj, M.; Dolatabadi, A.; Oberste-Berghaus, J.; Moreau, C.

2008-12-01

Suspension plasma spray (SPS) is a novel process for producing nano-structured coatings with metastable phases using significantly smaller particles as compared to conventional thermal spraying. Considering the complexity of the system there is an extensive need to better understand the relationship between plasma spray conditions and resulting coating microstructure and defects. In this study, an alumina/8 wt.% yttria-stabilized zirconia was deposited by axial injection SPS process. The effects of principal deposition parameters on the microstructural features are evaluated using the Taguchi design of experiment. The microstructural features include microcracks, porosities, and deposition rate. To better understand the role of the spray parameters, in-flight particle characteristics, i.e., temperature and velocity were also measured. The role of the porosity in this multicomponent structure is studied as well. The results indicate that thermal diffusivity of the coatings, an important property for potential thermal barrier applications, is barely affected by the changes in porosity content.

Aggregation in complex triacylglycerol oils: coarse-grained models, nanophase separation, and predicted x-ray intensities

NASA Astrophysics Data System (ADS)

Quinn, Bonnie; Peyronel, Fernanda; Gordon, Tyler; Marangoni, Alejandro; Hanna, Charles B.; Pink, David A.

2014-11-01

Triacylglycerols (TAGs) are biologically important molecules which form crystalline nanoplatelets (CNPs) and, ultimately, fat crystal networks in edible oils. Characterizing the self-assembled hierarchies of these networks is important to understanding their functionality and oil binding capacity. We have modelled CNPs in multicomponent oils and studied their aggregation. The oil comprises (a) a liquid componentt, and (b) components which phase separately on a nano-scale (nano-phase separation) to coat the surfaces of the CNPs impenetrably, either isotropically or anisotropically, with either liquid-like coatings or crystallites, forming a coating of thickness Δ. We modelled three cases: (i) liquid-liquid nano-phase separation, (ii) solid-liquid nano-phase separation, with CNPs coated isotropically, and (iii) CNPs coated anisotropically. The models were applied to mixes of tristearin and triolein with fully hydrogenated canola oil, shea butter with high oleic sunflower oil, and cotton seed oil. We performed Monte Carlo simulations, computed structure functions and concluded: (1) three regimes arose: (a) thin coating regime, Δ \\lt 0.0701 u (b) transition regime, 0.0701 u≤slant Δ ≤slant 0.0916 u and (c) thick coating regime, Δ \\gt 0.0916 u . (arbitrary units, u) (2) The thin coating regime exhibits 1D TAGwoods, which aggregate, via DLCA/RLCA, into fractal structures which are uniformly distributed in space. (3) In the thick coating regime, for an isotropic coating, TAGwoods are not formed and coated CNPs will not aggregate but will be uniformly distributed in space. For anisotropic coating, TAGwoods can be formed and might form 1D strings but will not form DLCA/RLCA clusters. (4) The regimes are, approximately: thin coating, 0\\lt Δ \\lt 7.0 \\text{nm} transition regime, 7.0\\ltΔ \\lt 9.2 \\text{nm} and thick coating, Δ \\gt 9.2 \\text{nm} (5) The minimum minority TAG concentration required to undergo nano-phase separation is, approximately, 0.29% (thin coatings) and 0.94% (thick coatings). Minority components can have substantial effects upon aggregation for concentrations less than 1%.

Phase evolution and thermal properties of yttria-stabilized hafnia nano-coatings deposited on alumina

NASA Astrophysics Data System (ADS)

Rubio, Ernesto Javier

High-temperature coatings are critical to the future power-generation systems and industries. Thermal barrier coatings (TBCs), which are usually the ceramic materials applied as thin coatings, protect engine components and allow further increase in engine temperatures for higher efficiency. Thus, the durability and reliability of the coating systems have to be more robust compared to current natural gas based engines. While a near and mid-term target is to develop TBC architecture with a 1300 °C surface temperature tolerance, a deeper understanding of the structure evolution and thermal behavior of the TBC-bond coat interface, specifically the thermally grown oxide (TGO), is of primary importance. In the present work, attention is directed towards yttria-stabilized hafnia (YSH) coatings on alumina (α-Al2O 3) to simulate the TBC-TGO interface and understand the phase evolution, microstructure and thermal oxidation of the coatings. YSH coatings were grown on α-Al2O3 substrates by sputter deposition by varying coating thickness in a wide range ˜30-1000 nm. The effect of coating thickness on the structure, morphology and the residual stress has been investigated using X-ray diffraction (XRD) and high resolution scanning electron microscopy (SEM). Thermal oxidation behavior of the coatings has been evaluated using the isothermal oxidation measurements under static conditions. X-ray diffraction analyses revealed the existence of monoclinic hafnia phase for relatively thin coatings indicating that the interfacial phenomena are dominant in phase stabilization. The evolution towards pure stabilized cubic phase of hafnia with the increasing coating thickness is observed. The SEM results indicate the changes in morphology of the coatings; the average grain size increases from 15 to 500 nm with increasing thickness. Residual stress was calculated employing XRD using the variable ψ-angle. Relation between residual stress and structural change is also studied. The results obtained on the thermal oxidation behavior indicate that the YSH coatings exhibit initial mass gain in the first 6 hours and sustained structure for extended hours of thermal treatment.

Fundamental study of an industrial reactive HPPMS (Cr,Al)N process

NASA Astrophysics Data System (ADS)

Bobzin, K.; Brögelmann, T.; Kruppe, N. C.; Engels, M.; von Keudell, A.; Hecimovic, A.; Ludwig, A.; Grochla, D.; Banko, L.

2017-07-01

In this work, a fundamental investigation of an industrial (Cr,Al)N reactive high power pulsed magnetron sputtering (HPPMS) process is presented. The results will be used to improve the coating development for the addressed application, which is the tool coating for plastics processing industry. Substrate-oriented plasma diagnostics and deposition of the (Cr,Al)N coatings were performed for a variation of the HPPMS pulse frequency with values from f = 300 Hz to f = 2000 Hz at constant average power P = 2.5 kW and pulse length ton = 40 μs. The plasma was investigated using an oscilloscope, an intensified charge coupled device camera, phase-resolved optical emission spectroscopy, and an energy-dispersive mass spectrometer. The coating properties were determined by means of scanning electron microscopy, glow discharge optical emission spectroscopy, cantilever stress sensors, nanoindentation, and synchrotron X-ray diffraction. Regarding the plasma properties, it was found that the average energy within the plasma is nearly constant for the frequency variation. In contrast, the metal to gas ion flux ratio is changed from JM/JG = 0.51 to JM/JG = 0.10 for increasing frequency. Regarding the coating properties, a structure refinement as well as lower residual stresses, higher universal hardness, and a changing crystal orientation from (111) to (200) were observed at higher frequencies. By correlating the plasma and coating properties, it can be concluded that the change in the gas ion to metal ion flux ratio results in a competitive crystal growth of the film, which results in changing coating properties.

Preparation and evaluation of enteric coated tablets of hot melt extruded lansoprazole

PubMed Central

Alsulays, Bader B.; Kulkarni, Vijay; Alshehri, Sultan M.; Almutairy, Bjad K.; Ashour, Eman A.; Morott, Joseph T.; Alshetaili, Abdullah S.; Park, Jun-Bom; Tiwari, Roshan V.; Repka, Michael A.

2017-01-01

The objective of this work was to use hot-melt extrusion (HME) technology to improve the physiochemical properties of lansoprazole (LNS) to prepare stable enteric coated LNS tablets. For the extrusion process, we chose Kollidon® 12 PF (K12) polymeric matrix. Lutrol® F 68 was selected as the plasticizer and magnesium oxide (MgO) as the alkalizer. With or without the alkalizer, LNS at 10% drug load was extruded with K12 and F68. LNS changed to the amorphous phase and showed better release compared to that of the pure crystalline drug. Inclusion of MgO improved LNS extrudability and release and resulted in over 80% drug release in the buffer stage. Hot-melt extruded LNS was physically and chemically stable after 12 months of storage. Both formulations were studied for compatibility with Eudragit® L 100-55. The optimized formulation was compressed into a tablet followed by coating process utilizing a pan coater using L 100-55 as an enteric coating polymer. In a two-step dissolution study, the release profile of the enteric coated LNS tablets in the acidic stage was less than 10% of the LNS, while that in the buffer stage was more than 80%. Drug content analysis revealed the LNS content to be 97%, indicating the chemical stability of the enteric coated tablet after storage for 6 months. HME, which has not been previously used for LNS, is a valuable technique to reduce processing time in the manufacture of enteric coated formulations of an acid-sensitive active pharmaceutical ingredient as compared to the existing methods. PMID:27486807

Cycling Performance of a Columnar-Structured Complex Perovskite in a Temperature Gradient Test

NASA Astrophysics Data System (ADS)

Schlegel, N.; Sebold, D.; Sohn, Y. J.; Mauer, G.; Vaßen, R.

2015-10-01

To increase the efficiency of turbines for the power generation and the aircraft industry, advanced thermal barrier coatings (TBCs) are required. They need to be long-term stable at temperatures higher than 1200 °C. Nowadays, yttria partially stabilized zirconia (YSZ) is applied as standard TBC material. But its long-term application at temperatures higher than 1200 °C leads to detrimental phase changes and sintering effects. Therefore, new materials have to be investigated, for example, complex perovskites. They provide high melting points, high thermal expansion coefficients and thermal conductivities of approx. 2.0 W/(m K). In this work, the complex perovskite La(Al1/4Mg1/2Ta1/4)O3 (LAMT) was investigated. It was deposited by the suspension plasma spraying (SPS) process, resulting in a columnar microstructure of the coating. The coatings were tested in thermal cycling gradient tests and they show excellent results, even though some phase decomposition was found.

Optically transparent, mechanically durable, nanostructured superhydrophobic surfaces enabled by spinodally phase-separated glass thin films

NASA Astrophysics Data System (ADS)

Aytug, Tolga; Simpson, John T.; Lupini, Andrew R.; Trejo, Rosa M.; Jellison, Gerald E.; Ivanov, Ilia N.; Pennycook, Stephen J.; Hillesheim, Daniel A.; Winter, Kyle O.; Christen, David K.; Hunter, Scott R.; Haynes, J. Allen

2013-08-01

We describe the formation and properties of atomically bonded, optical quality, nanostructured thin glass film coatings on glass plates, utilizing phase separation by spinodal decomposition in a sodium borosilicate glass system. Following deposition via magnetron sputtering, thermal processing and differential etching, these coatings are structurally superhydrophilic (i.e., display anti-fogging functionality) and demonstrate robust mechanical properties and superior abrasion resistance. After appropriate chemical surface modification, the surfaces display a stable, non-wetting Cassie-Baxter state and exhibit exceptional superhydrophobic performance, with water droplet contact angles as large as 172°. As an added benefit, in both superhydrophobic and superhydrophilic states these nanostructured surfaces can block ultraviolet radiation and can be engineered to be anti-reflective with broadband and omnidirectional transparency. Thus, the present approach could be tailored toward distinct coatings for numerous markets, such as residential windows, windshields, specialty optics, goggles, electronic and photovoltaic cover glasses, and optical components used throughout the US military.

Optically transparent, mechanically durable, nanostructured superhydrophobic surfaces enabled by spinodally phase-separated glass thin films.

PubMed

Aytug, Tolga; Simpson, John T; Lupini, Andrew R; Trejo, Rosa M; Jellison, Gerald E; Ivanov, Ilia N; Pennycook, Stephen J; Hillesheim, Daniel A; Winter, Kyle O; Christen, David K; Hunter, Scott R; Haynes, J Allen

2013-08-09

We describe the formation and properties of atomically bonded, optical quality, nanostructured thin glass film coatings on glass plates, utilizing phase separation by spinodal decomposition in a sodium borosilicate glass system. Following deposition via magnetron sputtering, thermal processing and differential etching, these coatings are structurally superhydrophilic (i.e., display anti-fogging functionality) and demonstrate robust mechanical properties and superior abrasion resistance. After appropriate chemical surface modification, the surfaces display a stable, non-wetting Cassie-Baxter state and exhibit exceptional superhydrophobic performance, with water droplet contact angles as large as 172°. As an added benefit, in both superhydrophobic and superhydrophilic states these nanostructured surfaces can block ultraviolet radiation and can be engineered to be anti-reflective with broadband and omnidirectional transparency. Thus, the present approach could be tailored toward distinct coatings for numerous markets, such as residential windows, windshields, specialty optics, goggles, electronic and photovoltaic cover glasses, and optical components used throughout the US military.

The structure, bond strength and apatite-inducing ability of micro-arc oxidized tantalum and their response to annealing

NASA Astrophysics Data System (ADS)

Wang, Cuicui; Wang, Feng; Han, Yong

2016-01-01

In this study, the tantalum oxide coatings were formed on pure tantalum (Ta) by micro-arc oxidation (MAO) in electrolytic solutions of calcium acetate and β-glycerophosphate disodium, and the effect of the applied voltage on the microstructure and bond strength of the MAO coatings was systematically investigated. The effect of annealing treatment on the microstructure, bond strength and apatite-inducing ability of the MAO coatings formed at 350 and 450 V was also studied. The study revealed that during the preparation of tantalum oxide coatings on Ta substrate by MAO, the applied voltage considerably affected the phase components, morphologies and bond strength of the coatings, but had little effect on surface chemical species. After annealing treatment, newly formed CaTa4O11 phase mainly contributed to the much more stronger apatite-inducing ability of the annealed tantalum oxide coatings than those that were not annealed. The better apatite-inducing ability of the MAO coatings formed at 450 V compared to those formed at 350 V was attributed to the less amorphous phase and more crystalline phase as well as more Ca and P contained in the MAO coatings with increasing the applied voltage.

Results of thermal modeling of Smart Energy Coating with phase-transition material for independent electricity generation

NASA Astrophysics Data System (ADS)

Pospelova, I. Y.; Pospelova, M. Y.; Bondarenko, A. S.; Kornilov, D. A.

2018-05-01

The modeling for Smart Energy Coating is presented. The coating is able to produce electricity on the surface of pipelines and structural elements. Along with electric output, Smart Energy Coating ensures the stable temperature conditions of work for structures, pipelines and regulating elements. The energy production scheme is based on the Peltier principle and the insulating layer with a phase transition. Thermally conductive inclusions of the inside layer with a phase transition material ensure the stable operation of the Peltier element.

Time-resolved quantitative-phase microscopy of laser-material interactions using a wavefront sensor.

PubMed

Gallais, Laurent; Monneret, Serge

2016-07-15

We report on a simple and efficient technique based on a wavefront sensor to obtain time-resolved amplitude and phase images of laser-material interactions. The main interest of the technique is to obtain quantitative self-calibrated phase measurements in one shot at the femtosecond time-scale, with high spatial resolution. The technique is used for direct observation and quantitative measurement of the Kerr effect in a fused silica substrate and free electron generation by photo-ionization processes in an optical coating.

Role of precursors and coating polymers in sol-gel chemistry toward enhanced selectivity and efficiency in solid phase microextraction.

PubMed

Bagheri, Habib; Piri-Moghadam, Hamed; Ahdi, Tayebeh

2012-09-12

To evaluate the selectivity and efficiency of solid phase microextraction (SPME) fiber coatings, synthesized by sol-gel technology, roles of precursors and coating polymers were extensively investigated. An on-line combination of capillary microextraction (CME) technique and high performance liquid chromatography (HPLC) was set up to perform the investigation. Ten different fiber coatings were synthesized in which five of them contained only the precursor and the rests were prepared using both the precursor and coating polymer. All the coatings were chemically bonded to the inner surface of copper tubes, intended to be used as the CME device and already functionalized by self-assembly monolayers of 3-(mercaptopropyl)trimethoxysilane (3MPTMOS). The selected precursors included tetramethoxysilane (TMOS), 3-(trimethoxysilyl)propylmethacrylate (TMSPMA), 3-(triethoxysilyl)-propylamine (TMSPA), 3MPTMOS, [3-(2,3-epoxypropoxy)-propyl]-trimethoxysilane (EPPTMOS) while poly(ethyleneglycol) (PEG) was chosen as the coating polymer. The effects of different precursors on the extraction efficiency and selectivity, was studied by selecting a list of compounds ranging from non-polar to polar ones, i.e. polycyclic aromatic hydrocarbon, herbicides, estrogens and triazines. The results from CME-HPLC analysis revealed that there is no significant difference between precursors, except TMOS, in which has the lowest extraction efficiency. Most of the selected precursors have rather similar interactions toward the selected analytes which include Van der Walls, dipole-dipole and hydrogen bond while TMOS has only dipole-dipole interaction and therefore the least efficiency. TMOS is silica but the other sorbents are organically modified silica (ORMOSIL). Our investigation revealed that it is rather impossible to prepare a selective coating using conventional sol-gel methodologies. The comparison study performed among the fiber coatings contained only a precursor and those synthesized by a precursor along with coating polymer proved that the extraction efficiency obtained for all coatings are the same. This is an indication that by selecting the appropriate precursor there is no need to use any coating polymer. In overall, a fiber coating in sol-gel process could be synthesize with no coating polymer which leads to faster, easier, cheaper and more controllable synthesis. Copyright © 2012 Elsevier B.V. All rights reserved.

X-ray powder diffractometry of intact film coated tablets--an approach to monitor the physical form of the active pharmaceutical ingredient during processing and storage.

PubMed

Yamada, Hiroyuki; Suryanarayanan, Raj

2007-08-01

The antiviral compound, 2-amino-6-(4-methoxyphenylthio)-9-[2-(phosphonomethoxy)ethyl]purine bis(2,2,2-trifluoroethyl)ester (MCC-478), can exist in several anhydrous polymorphic forms and also as a hemihydrate. The XRD patterns of the tablets, containing each form of the active pharmaceutical ingredient (API), revealed at least one peak unique to each form. A semiquantitative microdiffractometric method was developed to nondestructively characterize the physical form of the API in intact film-coated tablets. This was accomplished even though the weight fraction of the API was <0.2 and that of mannitol, a highly crystalline excipient, was approximately 0.6. The method was used to determine the effect of aqueous film-coating process on the physical form of the API. The final dosage form was also monitored following storage at 40 degrees C/75% RH for 6 months. There was no phase transformation of the API either due to the film-coating process or following accelerated storage. This technique has potential utility not only for process control during manufacture, but also for the quality control of the final product. (c) 2007 Wiley-Liss, Inc. and the American Pharmacists Association.

About structural phase state of coating based on zirconium oxide formed by microplasma oxidation method

NASA Astrophysics Data System (ADS)

Gubaidulina, Tatiana A.; Sergeev, Viktor P.; Kuzmin, Oleg S.; Fedorischeva, Marina V.; Kalashnikov, Mark P.

2017-12-01

The oxide-ceramic coating based of zirconium oxide is formed by the method of microplasma oxidation. The producing modes of the oxide layers on E110 zirconium alloy are under testing. It was found that using microplasma treatment of E110 zirconium in aluminosilicate electrolyte makes possible the formation of porous oxide-ceramic coatings based on zirconium alloyed by aluminum and niobium. The study is focused on the modes how to form heat-shielding coatings with controlled porosity and minimal amount of microcracks. The structural-phase state of the coating is studied by X-ray diffraction analysis and scanning electron microscopy (SEM). It was found that the ratio of the monoclinic and tetragonal phases changes with the change occurring in the coating formation modes.

Statistical Optimization of Reactive Plasma Cladding to Synthesize a WC-Reinforced Fe-Based Alloy Coating

NASA Astrophysics Data System (ADS)

Wang, Miqi; Zhou, Zehua; Wu, Lintao; Ding, Ying; Xu, Feilong; Wang, Zehua

2018-04-01

A new compound Fe-W-C powder for reactive plasma cladding was fabricated by precursor carbonization process using sucrose as a precursor. The application of quadratic general rotary unitized design was highlighted to develop a mathematical model to predict and accomplish the desired surface hardness of plasma-cladded coating. The microstructure and microhardness of the coating with optimal parameters were also investigated. According to the developed empirical model, the optimal process parameters were determined as follows: 1.4 for C/W atomic ratio, 20 wt.% for W content, 130 A for scanning current and 100 mm/min (1.67 mm/s) for scanning rate. The confidence level of the model was 99% according to the results of the F-test and lack-of-fit test. Microstructural study showed that the dendritic structure was comprised of a mechanical mixture of α-Fe and carbides, while the interdendritic structure was a eutectic of α-Fe and carbides in the composite coating with optimal parameters. WC phase generation can be confirmed from the XRD pattern. Due to good preparation parameters, the average microhardness of cladded coating can reach 1120 HV0.1, which was four times the substrate microhardness.

Influence of the cooling method on the structure of 55AlZn coatings

NASA Astrophysics Data System (ADS)

Mendala, J.

2011-05-01

In metallization processes, metals or metal alloys are used which have a low melting point and good anticorrosion properties. Moreover, they must form durable intermetallic compounds with iron or its alloys. The most common hot-dip metallization technology involves galvanizing, however, molten multi-component metal alloys are used as well. An addition of aluminium to the zinc bath causes an increase in corrosion resistance of the obtained coatings. The article presents results of tests of obtaining coatings by the batch hot-dip method in an 55AlZn bath. Kinetics of the coating growth in the tested alloys were determined in the changeable conditions of bath temperature, dip time and type of cooling. The structure of coatings and their phase composition were revealed. As a result of the tests performed, it has been found that an increase in total thickness of the coatings as a function of the dipping time at a constant temperature is almost of a parabolic nature, whereas an increase in the transient layer is of a linear nature. The structure was identified by the XRD analysis and the morphology of the coatings was tested by means of SEM. It has been found that the cooling process with the use of higher rates of cooling causes a size reduction of the structure in the outer layer and a reduction of thickness of both the intermediate diffusion layer and the whole coating by ca. 25 %.

Novel biodegradable calcium phosphate/polymer composite coating with adjustable mechanical properties formed by hydrothermal process for corrosion protection of magnesium substrate.

PubMed

Kaabi Falahieh Asl, Sara; Nemeth, Sandor; Tan, Ming Jen

2016-11-01

Ceramic type coatings on metallic implants, such as calcium phosphate (Ca-P), are generally stiff and brittle, potentially leading to the early failure of the bone-implant interface. To reduce material brittleness, polyacrylic acid and carboxymethyl cellulose were used in this study to deposit two types of novel Ca-P/polymer composite coatings on AZ31 magnesium alloy using a one-step hydrothermal process. X-ray diffraction and scanning electron microscopy showed that the deposited Ca-P crystal phase and morphology could be controlled by the type and concentration of polymer used. Incorporation of polymer in the Ca-P coatings reduced the coating elastic modulus bringing it close to that of magnesium and that of human bone. Nanoindentation test results revealed significantly decreased cracking tendency with the incorporation of polymer in the Ca-P coating. Apart from mechanical improvements, the protective composite layers had also enhanced the corrosion resistance of the substrate by a factor of 1000 which is sufficient for implant application. Cell proliferation studies indicated that the composite coatings induced better cell attachment compared with the purely inorganic Ca-P coating, confirming that the obtained composite materials could be promising candidates for surface protection of magnesium for implant application with the multiple functions of corrosion protection, interfacial stress reduction, and cell attachment/cell growth promotion. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1643-1657, 2016. © 2015 Wiley Periodicals, Inc.

Link between mechanical strength and laser damage threshold for antireflective coating made by sol-gel

NASA Astrophysics Data System (ADS)

Avice, J.; Piombini, H.; Boscher, C.; Belleville, P.; Vaudel, G.; Brotons, G.; Ruello, P.; Gusev, V.

2017-11-01

The MegaJoule Laser (LMJ) for inertial confinement fusion experiments is currently in operation at CEA-CESTA in France. All the lenses are coated by an antireflective (AR) layer to optimize the light power transmission. This AR layer is manufactured by sol-gel process, a soft chemical process, associated with a liquid phase coating technique to realize thin film of metal oxide. These optical components are hardened into ammoniac vapors in order to mechanically reinforce the AR coating and to make them more handling. This hardening induces a thickness reduction of the layer so an increase of the stiffness and sometimes a crazing of the layer. As these optical components undergo a high-power laser beam, so, it is important to verify if the AR properties (optical and mechanical) influence the value of the threshold laser damage. A series of coated samples have been manufactured having variable elastic moduli to discuss this point. In that purpose, a homemade Laser Induced Damage Threshold (LIDT) setup has been developed to test the layers under laser flux. We describe the used methods and different results are given. Preliminary results obtained on several coated samples with variable elastic moduli are presented. We show that whatever are the elastic stiffness of the AR coating, an overall decrease of the threshold appears with no noticeable effect of the mechanical properties of the AR coatings. Some possible explanations are given.

Preparation and application of carbon nanotubes/poly(o-toluidine) composite fibers for the headspace solid-phase microextraction of benzene, toluene, ethylbenzene, and xylenes.

PubMed

Behzadi, Mansoureh; Noroozian, Ebrahim; Mirzaei, Mohammad

2013-11-01

A novel nanocomposite coating of poly(o-toluidine) and oxidized multiwalled CNTs (MWCNTs, where CNTs is carbon nanotubes) was electrochemically prepared on a stainless-steel wire. The applicability of the fiber was assessed for the headspace solid-phase microextraction of benzene, toluene, ethylbenzene, and xylenes in aqueous samples followed by GC with flame ionization detection. In order to obtain an adherent and stable composite coating, several experimental parameters related to the coating process, such as polymerization potential and time, and the concentration of o-toluidine and oxidized MWCNTs were optimized. The combination of MWCNTs and polymer in a nanocomposite form presents desirable opportunities to produce materials for new applications. The effects of various parameters on the efficiency of the headspace solid-phase microextraction process, such as desorption temperature and time, extraction temperature and time, and ionic strength were also investigated. At the optimum conditions, LODs were 0.03-0.06 μg/L. The method showed linearity in the range of 0.5-300 μg/L with coefficients of determination >0.99. The intraday and interday RSDs obtained at a 5 μg/L concentration level (n = 5) using a single fiber were 1.2-5.2 and 3.2-7.5%, respectively. The fiber-to-fiber RSD (%; n = 3) at 5 μg/L was 6.1-9.2%. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Assessment of antibacterial and cytotoxic effects of orthodontic stainless steel brackets coated with different phases of titanium oxide: An in-vitro study.

PubMed

Baby, Roshen Daniel; Subramaniam, Siva; Arumugam, Ilakkiya; Padmanabhan, Sridevi

2017-04-01

Our objective was to assess the antibacterial and cytotoxic effects of orthodontic stainless steel brackets coated with different phases of photocatalytic titanium oxide. From a total sample of 115 brackets, 68 orthodontic stainless steel brackets were coated with titanium oxide using a radiofrequency magnetron sputtering machine. The coated brackets were then converted into 34 each of the anatase and rutile phases of titanium oxide. These brackets were subdivided into 4 groups for antibacterial study and 3 groups for cytotoxicity study. Brackets for the antibacterial study were assessed against the Streptococcus mutans species using microbiologic tests. Three groups for the cytotoxicity study were assessed using the thiazolyl tetrazolium bromide assay. The antibacterial study showed that both phases were effective, but the rutile phase of photocatalytic titanium oxide had a greater bactericidal effect than did the anatase phase. The cytotoxicity study showed that the rutile phase had a greater decrease in viability of cells compared with the anatase phase. It is recommended that orthodontic brackets be coated with the anatase phase of titanium oxide since they exhibited a significant antibacterial property and were only slightly cytotoxic. Copyright © 2016 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

Development of a fiber coating based on molecular sol-gel imprinting technology for selective solid-phase micro extraction of caffeine from human serum and determination by gas chromatography/mass spectrometry.

PubMed

Rajabi Khorrami, Afshin; Rashidpur, Amene

2012-05-21

In this work, a molecular sol-gel imprinting approach has been introduced to produce a fiber coating for selective direct immersion solid-phase microextraction (SPME) of caffeine. The polymerization mixture was composed of vinyl trimethoxysilane and methacrylic acid as vinyl sol-gel precursor and functional monomer, respectively. Caffeine was used as template molecule during polymerization process. The prepared fibers could be coupled directly to gas chromatography/mass spectrometry (GC/MS) and used for trace analysis of caffeine in a complex sample such as human serum. The parameters influencing SPME such as time, temperature and stirring speed were optimized. The prepared coating showed good selectivity towards caffeine in the presence of some structurally related compounds. Also, it offered high imprinting capability in comparison to bare fiber and non-imprinted coating. Linear range for caffeine detection was 1-80 μg mL(-1) and the limit of detection was 0.1 μg mL(-1). The intra-day and inter-day precisions of the peak areas for five replicates were 10 and 16%, respectively. Copyright © 2012 Elsevier B.V. All rights reserved.

Influence of laser irradiation on deposition characteristics of cold sprayed Stellite-6 coatings

NASA Astrophysics Data System (ADS)

Li, Bo; Jin, Yan; Yao, Jianhua; Li, Zhihong; Zhang, Qunli; Zhang, Xin

2018-03-01

Depositing hard materials such as Stellite-6 solely by cold spray (CS) is challengeable due to limited ability of plastic deformation. In this study, the deposition of Stellite-6 powder was achieved by supersonic laser deposition (SLD) which combines CS with synchronous laser irradiation. The surface morphology, deposition efficiency, track shape of Stellite-6 coatings produced over a range of laser irradiation temperatures were examined so as to reveal the effects of varying laser energy inputting on the deposition process of high strength material. The microstructure, phase composition and wear/corrosion resistant properties of the as-deposited Stellite-6 coatings were also investigated. The experimental results demonstrate that the surface flatness and deposition efficiency increase with laser irradiation temperature due to the softening effect induced by laser heating. The as-deposited Stellite-6 tracks show asymmetric shapes which are influenced by the relative configuration of powder stream and laser beam. The SLD coatings can preserve the original microstructure and phase of the feedstock material due to relatively low laser energy inputting, which result in the superior wear/corrosion resistant properties as compared to the counterpart prepared by laser cladding.

Sequential Infiltration Synthesis for the Design of Low Refractive Index Surface Coatings with Controllable Thickness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berman, Diana; Guha, Supratik; Lee, Byeongdu

Control over refractive index and thickness of surface coatings is central to the design of low refraction films used in applications ranging from optical computing to antireflective coatings. Here, we introduce gas-phase sequential infiltration synthesis (SIS) as a robust, powerful and efficient approach to deposit conformal coatings with very low refractive indices. We demonstrate that the refractive indices of inorganic coatings can be efficiently tuned by the number of cycles used in the SIS process, composition and selective swelling of the of the polymer template. We show that the refractive index of Al 2O 3 can be lowered from 1.76more » down to 1.1 using this method. The thickness of the Al 2O 3 coating can be efficiently controlled by the swelling of the block copolymer template in ethanol at elevated temperature, thereby enabling deposition of both single-layer and graded-index broadband anti-reflective coatings. Using this technique, Fresnel reflections of glass can be reduced to as low as 0.1% under normal illumination over a broad spectral range.« less

Sequential Infiltration Synthesis for the Design of Low Refractive Index Surface Coatings with Controllable Thickness

DOE PAGES

Berman, Diana; Guha, Supratik; Lee, Byeongdu; ...

2017-01-31

Control over refractive index and thickness of surface coatings is central to the design of low refraction films used in applications ranging from optical computing to antireflective coatings. Here, we introduce gas-phase sequential infiltration synthesis (SIS) as a robust, powerful and efficient approach to deposit conformal coatings with very low refractive indices. We demonstrate that the refractive indices of inorganic coatings can be efficiently tuned by the number of cycles used in the SIS process, composition and selective swelling of the of the polymer template. We show that the refractive index of Al 2O 3 can be lowered from 1.76more » down to 1.1 using this method. The thickness of the Al 2O 3 coating can be efficiently controlled by the swelling of the block copolymer template in ethanol at elevated temperature, thereby enabling deposition of both single-layer and graded-index broadband anti-reflective coatings. Using this technique, Fresnel reflections of glass can be reduced to as low as 0.1% under normal illumination over a broad spectral range.« less

Sequential Infiltration Synthesis for the Design of Low Refractive Index Surface Coatings with Controllable Thickness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berman, Diana; Guha, Supratik; Lee, Byeongdu

Control over refractive index and thickness of surface coatings is central to the design of low refraction films used in applications ranging from optical computing to antireflective coatings. Here, we introduce gas-phase sequential infiltration synthesis (SIS) as a robust, powerful, and efficient approach to deposit conformal coatings with very low refractive indices. We demonstrate that the refractive indices of inorganic coatings can be efficiently tuned by the number of cycles used in the SIS process, composition, and selective swelling of the of the polymer template. We show that the refractive index of Al2O3 can be lowered from 1.76 down tomore » 1.1 using this method. The thickness of the Al2O3 coating can be efficiently controlled by the swelling of the block copolymer template in ethanol at elevated temperature, thereby enabling deposition of both single-layer and graded-index broadband antireflective coatings. Using this technique, Fresnel reflections of glass can be reduced to as low as 0.1% under normal illumination over a broad spectral range.« less

Oxidation Behavior of Titanium Carbonitride Coating Deposited by Atmospheric Plasma Spray Synthesis

NASA Astrophysics Data System (ADS)

Zhu, Lin; He, Jining; Yan, Dianran; Liao, Hanlin; Zhang, Nannan

2017-10-01

As a high-hardness and anti-frictional material, titanium carbonitride (TiCN) thick coatings or thin films are increasingly being used in many industrial fields. In the present study, TiCN coatings were obtained by atmospheric plasma spray synthesis or reactive plasma spray. In order to promote the reaction between the Ti particles and reactive gases, a home-made gas tunnel was mounted on a conventional plasma gun to perform the spray process. The oxidation behavior of the TiCN coatings under different temperatures in static air was carefully investigated. As a result, when the temperature was over 700 °C, the coatings suffered from serious oxidation, and finally they were entirely oxidized to the TiO2 phase at 1100 °C. The principal oxidation mechanism was clarified, indicating that the oxygen can permeate into the defects and react with TiCN at high temperatures. In addition, concerning the use of a TiCN coating in high-temperature conditions, the microhardness of the oxidized coatings at different treatment temperatures was also evaluated.

Sequential Infiltration Synthesis for the Design of Low Refractive Index Surface Coatings with Controllable Thickness.

PubMed

Berman, Diana; Guha, Supratik; Lee, Byeongdu; Elam, Jeffrey W; Darling, Seth B; Shevchenko, Elena V

2017-03-28

Control over refractive index and thickness of surface coatings is central to the design of low refraction films used in applications ranging from optical computing to antireflective coatings. Here, we introduce gas-phase sequential infiltration synthesis (SIS) as a robust, powerful, and efficient approach to deposit conformal coatings with very low refractive indices. We demonstrate that the refractive indices of inorganic coatings can be efficiently tuned by the number of cycles used in the SIS process, composition, and selective swelling of the of the polymer template. We show that the refractive index of Al 2 O 3 can be lowered from 1.76 down to 1.1 using this method. The thickness of the Al 2 O 3 coating can be efficiently controlled by the swelling of the block copolymer template in ethanol at elevated temperature, thereby enabling deposition of both single-layer and graded-index broadband antireflective coatings. Using this technique, Fresnel reflections of glass can be reduced to as low as 0.1% under normal illumination over a broad spectral range.

Reactive processing and mechanical properties of polymer derived silicon nitride matrix composites and their use in coating and joining ceramics and ceramic matrix composites

NASA Astrophysics Data System (ADS)

Stackpoole, Margaret Mary

Use of preceramic polymers offers many advantages over conventional ceramic processing routes. Advantages include being able to plastically form the part, form a pyrolized ceramic material at lower temperatures and form high purity microstructures which are tailorable depending on property requirements. To date preceramic polymers are mostly utilized in the production of low dimensional products such as fibers since loss of volatiles during pyrolysis leads to porosity and large shrinkage (in excess of 30%). These problems have been partially solved by use of active fillers (e.g. Ti, Cr, B). The reactive filler converts to a ceramic material with a volume expansion and this increases the density and reduces shrinkage and porosity. The expansion of the reactive filler thus compensates for the polymer shrinkage if the appropriate volume fraction of filler is present in a reactive atmosphere (e.g. N2 or NH3). This approach has resulted in structural composites with limited success. The present research investigates the possibility of using filled preceramic polymers to form net shaped ceramic composite materials and to investigate the use of these unique composite materials to join and coat ceramics and ceramic composites. The initial research focused on phase and microstructural development of bulk composites from the filled polymer/ceramic systems. A processing technique was developed to insure consistency between different samples and the most promising filler/polymer choices for this application have been determined. The processing temperatures and atmospheres have also been optimized. The work covers processing and characterization of bulk composites, joints and coatings. With careful control of processing near net shape bulk composites were fabricated. Both ambient and high temperature strength and fracture toughness was obtained for these composite systems. The potential of using reactively filled preceramic polymers to process joints and coatings was also investigated. A critical thickness below which crack free joints/coatings could be processed was determined. Finally, mechanical properties of the joints and coatings at ambient and elevated temperatures (including oxidation studies) have been evaluated. The interfacial fracture behavior of the joints and coatings was also evaluated.

Evaluating electrically insulating films deposited on V-4% Cr-4% Ti by reactive CVD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, J.H.; Cho, W.D.

1997-04-01

Previous CaO coatings on V-4%Cr-4%Ti exhibited high-ohmic insulator behavior even though a small amount of vanadium from the alloy was incorporated in the coating. However, when the vanadium concentration in the coatings is > 15 wt%, the coating becomes conductive. When the vanadium concentration is high in localized areas, a calcium vanadate phase that exhibits semiconductor behavior can form. To explore this situation, CaO and Ca-V-O coatings were produced on vanadium alloys by chemical vapor deposition (CVD) and by a metallic-vapor process to investigate the electrical resistance of the coatings. Initially, the vanadium alloy specimens were either charged with oxygenmore » in argon that contained trace levels of oxygen, or oxidized for 1.5-3 h in a 1% CO-CO{sub 2} gas mixture or in air to form vanadium oxide at 625-650{degrees}C. Most of the specimens were exposed to calcium vapor at 800-850{degrees}C. Initial and final weights were obtained to monitor each step, and surveillance samples were removed for examination by optical and scanning electron microscopy and electron-energy-dispersive and X-ray diffraction analysis; the electrical resistivity was also measured. The authors found that Ca-V-O films exhibited insulator behavior when the ratio of calcium concentration to vanadium concentration R in the film was > 0.9, and semiconductor or conductor behavior for R < 0.8. However, in some cases, semiconductor behavior was observed when CaO-coated samples with R > 0.98 were exposed in liquid lithium. Based on these studies, the authors conclude that semiconductor behavior occurs if a conductive calcium vanadate phase is present in localized regions in the CaO coating.« less

Optical coating design for the annular mirrors of the Alpha I HF laser

NASA Astrophysics Data System (ADS)

Shellan, Jeffrey B.

The dielectric-coating design for the annular mirrors of the Alpha I HF laser is described along with the numerous other designs that were considered. The coatings were required to produce a 0-deg phase shift after one round trip, which involved reflections from six surfaces. Although novel high-reflectivity multilayer dielectric coatings satisfied this requirement, single-layer phase control coatings were preferred because the use of these greatly reduced coating layer-thickness control and thus resulted in significant program savings. Among the single-layer designs investigated, a coating consisting of a 0.06-micron-thick SiO layer was found to be sufficient for all surfaces except those of the rear cone, for which a 0.515-micron thick SiO layer was recommended. The metallic substrate selected was Au. These coatings were found to have a high damage threshold, provide the necessary polarization phase control, and to be quite forgiving to thickness deposition errors that were anticipated using existing chambers.

The effect of graphene oxide on surface features, biological performance and bio-stability of calcium phosphate coating applied by pulse electrochemical deposition

NASA Astrophysics Data System (ADS)

Fathyunes, Leila; Khalil-Allafi, Jafar

2018-04-01

In the current study, the effect of second phase of graphene oxide (GO) on the surface features and biological behavior of calcium phosphate (CaP) coating was evaluated. To do so, the GO-CaP composite coating was applied on TiO2 nanotubular arrays using pulse electrochemical deposition. The SEM and AFM images showed that, the CaP-based coating with uniform and refined microstructure could be formed through its compositing with GO sheets. The biological assessment of the coatings was also conducted by cell culture test and MTT assay. Based on findings, the GO-CaP coating showed the better biocompatibility compared to the CaP coating. This could be owing to the fact that the composite coating provided the lower roughness, moderately wettable surface with a contact angle of 23.5° ± 2.6° and the higher stability in the biological environments because of being involved with only the stable phase of CHA. However, in the CaP coating, spreading of cells could be limited by the plate-like crystals with larger size. The higher solubility of the CaP coating in the cell culture medium possibly owing to the existence of some metastable CaP phases like OCP in addition to the dominant phase of CHA in this coating could be another reason for its less biocompatibility. At last, the CaP coating showed the higher apatite-forming ability in SBF solution after its compositing with GO.

Microstructural characteristics of plasma sprayed nanostructured partially stabilized zirconia

NASA Astrophysics Data System (ADS)

Lima, Rogerio Soares

Thermal barrier coatings have been extensively applied in the aerospace industry in turbines and rocket engines as an insulation system. Partially stabilized zirconia, due to its high thermal stability and low thermal conductivity at high temperatures has been traditionally employed as the ceramic element of the thermal barrier coating system. Different approaches have been taken in order to improve the performance of these coatings. Nanostructured materials are promising an interesting future in the beginning of the 21st century. Due to its enhanced strain to failure and superplasticity new applications may be accomplished or the limits of materials utilization may be placed at higher levels. Single nanostructured particles can not be thermal sprayed by conventional thermal spray equipment. Due to its low mass, they would be deviated to the periphery of the thermal spray jet. To overcome this characteristic, single nanostructured particles were successively agglomerated into large microscopic particles, with particle size distribution similar to the conventional feedstocks for thermal spray equipment. Agglomerated nanostructured particles of partially stabilized zirconia were plasma sprayed in air with different spray parameters. According to traditional thermal spray procedure, the feedstock has to be melted in the thermal spray jet in order to achieve the necessary conditions for adhesion and cohesion on the substrate. Due to the nature of the nanostructured particles, a new step has to be taken in the thermal spray processing; particle melting has to be avoided in order to preserve the feedstock nanostructure in the coating overall microstructure. In this work, the adhesion/cohesion system of nanostructured coatings is investigated and clarified. A percentage of molten particles will retain and hold the non-molten agglomerated nanostructured particles in the coating overall microstructure. Controlling the spray parameters it was possible to produce coatings with different levels of non-molten particles in the coating microstructure; from 25 to 50%. The presence of non-molten and molten phases in the coating microstructure, results in an unique mechanical behavior. The nanostructured coatings present a bimodal distribution with respect to the mechanical properties; each mode has origin from one of the phases. The phases were carefully mapped via scanning electron microscopy and microhardness measurements. These results enabled us to create a model for mechanical properties prediction. This finding is considered one of the most important achievements of this work.

Investigation of phase-change coatings for variable thermal control of spacecraft

NASA Technical Reports Server (NTRS)

Kelliher, W. C.; Young, P. R.

1972-01-01

An investigation was conducted to determine the feasibility of producing a spacecraft coating system that could vary the ratio of its solar absorptance to thermal emittance to adjust automatically for changes in the thermal balance of a spacecraft. This study resulted in a new concept called the phase-change effect which uses the change that occurs in the optical properties of many materials during the phase transition from a crystalline solid to an amorphous material. A series of two-component model coatings was developed which, when placed on a highly reflecting substrate, exhibited a sharp decrease in solar absorptance within a narrow temperature range. A variable thermal control coating can have a significant amount of temperature regulation with the phase-change effect. Data are presented on several crystallite-polymer formulations, their physical and optical properties, and associated phase-change temperatures. Aspects pertaining to their use in a space environment and an example of the degree of thermal regulation attainable with these coatings is also given.

Bacteria and fungi inactivation by photocatalysis under UVA irradiation: liquid and gas phase.

PubMed

Rodrigues-Silva, Caio; Miranda, Sandra M; Lopes, Filipe V S; Silva, Mário; Dezotti, Márcia; Silva, Adrián M T; Faria, Joaquim L; Boaventura, Rui A R; Vilar, Vítor J P; Pinto, Eugénia

2017-03-01

In the last decade, environmental risks associated with wastewater treatment plants (WWTPs) have become a concern in the scientific community due to the absence of specific legislation governing the occupational exposure limits (OEL) for microorganisms present in indoor air. Thus, it is necessary to develop techniques to effectively inactivate microorganisms present in the air of WWTPs facilities. In the present work, ultraviolet light A radiation was used as inactivation tool. The microbial population was not visibly reduced in the bioaerosol by ultraviolet light A (UVA) photolysis. The UVA photocatalytic process for the inactivation of microorganisms (bacteria and fungi, ATCC strains and isolates from indoor air samples of a WWTP) using titanium dioxide (TiO 2 P25) and zinc oxide (ZnO) was tested in both liquid-phase and airborne conditions. In the slurry conditions at liquid phase, P25 showed a better performance in inactivation. For this reason, gas-phase assays were performed in a tubular photoreactor packed with cellulose acetate monolithic structures coated with P25. The survival rate of microorganisms under study decreased with the catalyst load and the UVA exposure time. Inactivation of fungi was slower than resistant bacteria, followed by Gram-positive bacteria and Gram-negative bacteria. Graphical abstract Inactivation of fungi and bacteria in gas phase by photocatalitic process performed in a tubular photoreactor packed with cellulose acetate monolith structures coated with TiO 2 .

Phase and electrical properties of PZT thin films embedded with CuO nano-particles by a hybrid sol-gel route

NASA Astrophysics Data System (ADS)

Sreesattabud, Tharathip; Gibbons, Brady J.; Watcharapasorn, Anucha; Jiansirisomboon, Sukanda

2013-07-01

Pb(Zr0.52Ti0.48)O3 or PZT thin films embedded with CuO nano-particles were successfully prepared by a hybrid sol-gel process. In this process, CuO (0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1 wt. %) nanopowder was suspended in an organometallic solution of PZT, and then coated on platinised silicon substrate using a spin-coating technique. The influence of CuO nano-particles' dispersion on the phase of PZT thin films was investigated. XRD results showed a perovskite phase in all films. At the CuO concentration of 0.4-1 wt. %, a second phase was observed. The addition of CuO nano-particles affected the orientation of PZT thin films. The addition was also found to reduce the ferroelectric properties of PZT thin films. However, at 0.2 wt. % CuO concentration, the film exhibited good ferroelectric properties similar to those of PZT films. In addition, the fatigue retention properties of the PZT/CuO system was observed, and it showed 14% fatigue at 108 switching bipolar pulse cycles while the fatigue in PZT thin films was found to be 17% at the same switching bipolar pulse cycles.

PERMANENT PRIMER/REPLACEABLE TOPCOAT AIRCRAFT COATING SYSTEM WITH MINIMUM VOC AND CHROMIUM EXPOSURE - PHASE I

EPA Science Inventory

In Phase I, Foster-Miller, Inc., will develop the permanent primer replacement topcoat (PPRT), produce coated test panels, and analyze test panels for key performance properties. Topcoat stripping also will be demonstrated. The team includes coating experts and an aircraft ...

Ultralow protein adsorbing coatings from clickable PEG nanogel solutions: Benefits of attachment under salt-induced phase separation conditions and comparison with PEG/albumin nanogel coatings

PubMed Central

Donahoe, Casey D.; Cohen, Thomas L.; Li, Wenlu; Nguyen, Peter K.; Fortner, John D.; Mitra, Robi D.; Elbert, Donald L.

2013-01-01

Clickable nanogel solutions were synthesized by using the copper catalyzed azide/alkyne cycloaddition (CuAAC) to partially polymerize solutions of azide and alkyne functionalized poly(ethylene glycol) (PEG) monomers. Coatings were fabricated using a second click reaction: a UV thiol-yne attachment of the nanogel solutions to mercaptosilanated glass. Because the CuAAC reaction was effectively halted by the addition of a copper-chelator, we were able to prevent bulk gelation and limit the coating thickness to a single monolayer of nanogels in the absence of the solution reaction. This enabled the inclusion of kosmotropic salts, which caused the PEG to phase-separate and nearly double the nanogel packing density, as confirmed by Quartz Crystal Microbalance with Dissipation (QCM-D). Protein adsorption was analyzed by single molecule counting with total internal reflection fluorescence (TIRF) microscopy and cell adhesion assays. Coatings formed from the phase-separated clickable nanogel solutions attached with salt adsorbed significantly less fibrinogen than other 100% PEG coatings tested, as well as poly-L-lysine-g-PEG (PLL-g-PEG) coatings. However, PEG/albumin nanogel coatings still outperformed the best 100% PEG clickable nanogel coatings. Additional surface crosslinking of the clickable nanogel coating in the presence of copper further reduced levels of fibrinogen adsorption closer to those of PEG/albumin nanogel coatings. However, this step negatively impacted long-term resistance to cell adhesion and dramatically altered the morphology of the coating by atomic force microscopy (AFM). The main benefit of the click strategy is that the partially polymerized solutions are stable almost indefinitely, allowing attachment in the phase-separated state without danger of bulk gelation, and thus, producing the best performing 100% PEG coating that we have studied to date. PMID:23441808

Dense and high-stability Ti2AlN MAX phase coatings prepared by the combined cathodic arc/sputter technique

NASA Astrophysics Data System (ADS)

Wang, Zhenyu; Liu, Jingzhou; Wang, Li; Li, Xiaowei; Ke, Peiling; Wang, Aiying

2017-02-01

Ti2AlN belongs to a family of ternary nano-laminate alloys known as the MAX phases, which exhibit a unique combination of metallic and ceramic properties. In the present work, the dense and high-stability Ti2AlN coating has been successfully prepared through the combined cathodic arc/sputter deposition, followed by heat post-treatment. It was found that the as-deposited Ti-Al-N coating behaved a multilayer structure, where (Ti, N)-rich layer and Al-rich layer grew alternately, with a mixed phase constitution of TiN and TiAlx. After annealing at 800 °C under vacuum condition for 1.5 h, although the multilayer structure still was found, part of multilayer interfaces became indistinct and disappeared. In particular, the thickness of the Al-rich layer decreased in contrast to that of as-deposited coating due to the inner diffusion of the Al element. Moreover, the Ti2AlN MAX phase emerged as the major phase in the annealed coatings and its formation mechanism was also discussed in this study. The vacuum thermal analysis indicated that the formed Ti2AlN MAX phase exhibited a high-stability, which was mainly benefited from the large thickness and the dense structure. This advanced technique based on the combined cathodic arc/sputter method could be extended to deposit other MAX phase coatings with tailored high performance like good thermal stability, high corrosion and oxidation resistance etc. for the next protective coating materials.

Development of Surfaces Optically Suitable for Flat Solar Panels. [using a reflectometer which separately evaluates spectral and diffuse reflectivities of surfaces

NASA Technical Reports Server (NTRS)

1979-01-01

A reflectometer which can separately evaluate the spectral and diffuse reflectivities of surfaces is described. A phase locked detection system for the reflectometer is also described. A selective coating on aluminum potentially useful for flat plate solar collector applications is presented. The coating is composed of strongly bound copper oxide (divalent) and is formed by an etching process performed on an aluminum alloy with high copper content. Fabrication costs are expected to be small due to the one stop fabrication process. A number of conclusions gathered from the literature as to the required optical properties of flat plate solar collectors are discussed.

Optimization of sol-gel technique for coating of metallic substrates by hydroxyapatite using the Taguchi method

NASA Astrophysics Data System (ADS)

Pourbaghi-Masouleh, M.; Asgharzadeh, H.

2013-08-01

In this study, the Taguchi method of design of experiment (DOE) was used to optimize the hydroxyapatite (HA) coatings on various metallic substrates deposited by sol-gel dip-coating technique. The experimental design consisted of five factors including substrate material (A), surface preparation of substrate (B), dipping/withdrawal speed (C), number of layers (D), and calcination temperature (E) with three levels of each factor. An orthogonal array of L18 type with mixed levels of the control factors was utilized. The image processing of the micrographs of the coatings was conducted to determine the percentage of coated area ( PCA). Chemical and phase composition of HA coatings were studied by XRD, FT-IR, SEM, and EDS techniques. The analysis of variance (ANOVA) indicated that the PCA of HA coatings was significantly affected by the calcination temperature. The optimum conditions from signal-to-noise ( S/N) ratio analysis were A: pure Ti, B: polishing and etching for 24 h, C: 50 cm min-1, D: 1, and E: 300 °C. In the confirmation experiment using the optimum conditions, the HA coating with high PCA of 98.5 % was obtained.

Thermal stability and chemical resistance of (Ti,Al)N-Cu and (Ti,Al)N-Ni metal-ceramic nanostructured coatings

NASA Astrophysics Data System (ADS)

Belov, D. S.; Blinkov, I. V.; Volkhonskii, A. O.; Kuznetsov, D. V.; Kiryukhantsev-Korneev, F. V.; Pustov, Yu. A.; Sergevnin, V. S.

2016-12-01

This work represents the results of research on thermal stability, oxidation resistance at temperatures of up to 800 °C and electrochemical behaviour of (Ti,Al)N-(∼3 at.%)Cu and (Ti,Al)N-(∼8 at.%)Ni nanocrystalline coatings in acidic and alkaline media. The coatings were deposited by the arc-PVD method with a thickness of approximately 4 μm and crystallite size of less than 20 nm. It has been demonstrated that the composition and properties of the coating structures do not change when the coatings are heated in 10-4 Pa vacuum at temperatures of 600, 700 °C for 1.5 h. Heating up to 800 °C caused an increase of crystallite size and reduction microstrain in the crystal lattice of the ceramic phase. The process is accompanied by deterioration of the coating hardness from 48 to 52 to 33-36 GPa. The (Ti,Al)N-Cu and (Ti,Al)N-Ni metal-ceramic nanostructured coatings are characterized by heat resistance up to the temperatures of 700 and 800 °C respectively. The coatings under study have tendency for self-passivation and resistance to pitting corrosion.

Supersonic Plasma Spray Deposition of CoNiCrAlY Coatings on Ti-6Al-4V Alloy

NASA Astrophysics Data System (ADS)

Caliari, F. R.; Miranda, F. S.; Reis, D. A. P.; Essiptchouk, A. M.; Filho, G. P.

2017-06-01

Plasma spray is a versatile technology used for production of environmental and thermal barrier coatings, mainly in the aerospace, gas turbine, and automotive industries, with potential application in the renewable energy industry. New plasma spray technologies have been developed recently to produce high-quality coatings as an alternative to the costly low-pressure plasma-spray process. In this work, we studied the properties of as-sprayed CoNiCrAlY coatings deposited on Ti-6Al-4V substrate with smooth surface ( R a = 0.8 μm) by means of a plasma torch operating in supersonic regime at atmospheric pressure. The CoNiCrAlY coatings were evaluated in terms of their surface roughness, microstructure, instrumented indentation, and phase content. Static and dynamic depositions were investigated to examine their effect on coating characteristics. Results show that the substrate surface velocity has a major influence on the coating properties. The sprayed CoNiCrAlY coatings exhibit low roughness ( R a of 5.7 μm), low porosity (0.8%), excellent mechanical properties ( H it = 6.1 GPa, E it = 155 GPa), and elevated interface toughness (2.4 MPa m1/2).

In situ synthesis of hydroxyapatite coating by laser cladding.

PubMed

Wang, D G; Chen, C Z; Ma, J; Zhang, G

2008-10-15

HA bioceramic coatings were synthesized on titanium substrate by laser cladding using cheap calcium carbonate and calcium hydrogen phosphate. The thermodynamic condition for synthesizing HA was calculated by software Matlab 5.0, the microstructure and phase analysis of laser clad HA bioceramic coatings were studied by electron probe microanalyser (EPMA), X-ray diffractometer (XRD) and transmission electron microscopy (TEM). The theoretical results show that the Gibbs free enthalpy for the synthesis of HA phase is satisfied, and the presence of HA phase in the clad coatings was then further verified by XRD and the selected area diffraction patterns. When the laser power is 600W and the scanning speed is 3.5mm/s, the compact HA bioceramic coatings were obtained, which have cellular dendritic structure and consist of the phases of HA, alpha-Ca(2)P(2)O(7), CaO and CaTiO(3).

Phase Constituents and Microstructure of Ti3Al/Fe3Al + TiN/TiB2 Composite Coating on Titanium Alloy

NASA Astrophysics Data System (ADS)

Li, Jianing; Chen, Chuanzhong; Zhang, Cuifang

Laser cladding of the Fe3Al + B4C/TiN + Al2O3 pre-placed powders on the Ti-6Al-4V alloy can form the Ti3Al/Fe3Al + TiN/TiB2 composite coating, which improved the wear resistance of the Ti-6Al-4V alloy surface. In this study, the Ti3Al/Fe3Al + TiN/TiB2 composite coating has been researched by means of X-ray diffraction and scanning electron microscope. It was found that during the laser cladding process, Al2O3 can react with TiB2, leading to the formations of Ti3Al and B. This principle can be used to improve the Fe3Al + B4C/TiN laser-cladded coating on the Ti-6Al-4V alloy. Furthermore, during the cladding process, C consumed the oxygen in Fe3Al + B4C /TiN + Al2O3 molten pool, which retarded the productions of the redundant metal oxides.

Joint Test Report For Validation of Alternatives to Aliphatic Isocyanate Polyurethanes

NASA Technical Reports Server (NTRS)

Lewis, Pattie

2007-01-01

National Aeronautics and Space Administration (NASA) and Air Force Space Command (AFSPC) have similar missions and therefore similar facilities and structures in similar environments. The standard practice for protecting metallic substrates in atmospheric environments is the application of an applied coating system. The most common topcoats used in coating systems are polyurethanes that contain isocyanates. Isocyanates are classified as potential human carcinogens and are known to cause cancer in animals. The primary objective of this effort was to demonstrate and validate alternatives to aliphatic isocyanate polyurethanes resulting in one or more isocyanate-free coatings qualified for use at AFSPC and NASA installations participating in this project. This joint Test Report (JTR) documents the results of the laboratory and field testing as well as any test modifications made during the execution of the testing. The technical stakeholders agreed upon test procedure modifications documented in this document. This JTR is made available as a reference for future pollution prevention endeavors by other NASA centers, the Department of Defense and commercial users to minimize duplication of effort. All coating system candidates were tested using approved NASA and AFSPC standard coating systems as experimental controls. This study looked at eight alternative coating systems and two control coating systems and was divided into Phase I Screening Tests, Phase II Tests, and Field Testing. The Phase I Screening Tests were preliminary tests performed on all the selected candidate coating systems. Candidate coating systems that did not meet the acceptance criteria of the screening tests were eliminated from further testing. Phase I Screening Tests included: Ease of Application, Surface Appearance, Dry-To-Touch (Sanding), Accelerated Storage Stability, Pot Life (Viscosity), Cure Time (Solvent Rubs), Cleanability, Knife Test, Tensile (pull-off) Adhesion, and X-Cut Adhesion by Wet Tape After a review of the Phase I test results, four of the alternative coating systems showed substandard performance in relation to the Control Systems and were eliminated from the Phase II testing. Due to the interest of stakeholders and time constraints, however, all eight alternatives were subjected to the following Phase II tests, along with field testing at Stennis Space Center (SSC), Mississippi: Hypergol Compatibility, Liquid Oxygen Compatibility, 18-Month Marine Exposure (Gloss Retention, Color Retention, Blistering, Visual Corrosion, Creepage from Scribe, Heat Adhesion), and Field Exposure (6- and 12-month Evaluation for Coating Condition, Color Retention, Gloss Retention). The remaining four alternative coating systems determined to be the best viable alternatives were carried on to Phase II testing that included: Removability, Repairability, Abrasion Resistance, Gravelometer, Fungus Resistance, Accelerated Weathering, Mandrel Bend Flexibility, and Cyclic Corrosion Resistance. Of the systems that continued to Phase II, three (3) alternative coating systems meet the performance requirements as identified by stakeholders. Two (2) other systems, that were not included in Phase II testing, performed well enough on the 18-Month Marine Exposure, the primary requirement for NASA technical standard NASA-STD-5008, Protective Coating of Carbon Steel, Stainless Steel, and Aluminum on Launch Structures, Facilities, and Ground Support Equipment, that they were also considered to be successful candidates. In total, five (5) alternative coating systems were approved for inclusion in the NASA-STD- 5008 Qualified Products List (QPL). The standard is intended to provide a common framework for consistent practices across NASA and is often used by other entities. The standard's QPL does not connote endorsement of the products by NASA, but lists those products that have been tested and meet the requirements as specified.

Effect of spark plasma sintering on the microstructure and in vitro behavior of plasma sprayed HA coatings.

PubMed

Yu, L-G; Khor, K A; Li, H; Cheang, P

2003-07-01

The crystalline phases and degree of crystallinity in plasma sprayed calcium phosphate coatings on Ti substrates are crucial factors that influence the biological interactions of the materials in vivo. In this study, plasma sprayed hydroxyapatite (HA) coatings underwent post-spray treatment by the spark plasma sintering (SPS) technique at 500 degrees C, 600 degrees C, and 700 degrees C for duration of 5 and 30 min. The activity of the HA coatings before and after SPS are evaluated in vitro in a simulated body fluid. The surface microstructure, crystallinity, and phase composition of each coating is characterized by scanning electron microscopy and X-ray diffractometry before, and after in vitro incubation. Results show that the plasma sprayed coatings treated for 5 min in SPS demonstrated increased proportion of beta-TCP phase with a preferred-orientation in the (214) plane, and the content of beta-TCP phase corresponded to SPS temperature, up to 700 degrees C. SPS treatment at 700 degrees C for 30 min enhanced the HA content in the plasma spray coating as well. The HA coatings treated in SPS for 5 min revealed rapid surface morphological changes during in vitro incubation (up to 12 days), indicating that the surface activity is enhanced by the SPS treatment. The thickest apatite layer was found in the coating treated by SPS at 700 degrees C for 5 min.

Lead zirconate titanate (PZT)-based thin film capacitors for embedded passive applications

NASA Astrophysics Data System (ADS)

Kim, Taeyun

Investigations on the key processing parameters and properties relationship for lead zirconate titanate (PZT, 52/48) based thin film capacitors for embedded passive capacitor application were performed using electroless Ni coated Cu foils as substrates. Undoped and Ca-doped PZT (52/48) thin film capacitors were prepared on electroless Ni coated Cu foil by chemical solution deposition. For PZT (52/48) thin film capacitors on electroless Ni coated Cu foil, voltage independent (zero tunability) capacitance behavior was observed. Dielectric constant reduced to more than half of the identical capacitor processed on Pt/SiO2/Si. Dielectric properties of the capacitors were mostly dependent on the crystallization temperature. Capacitance densities of almost 350 nF/cm2 and 0.02˜0.03 of loss tangent were routinely measured for capacitors crystallized at 575˜600°C. Leakage current showed dependence on film thickness and crystallization temperature. From a two-capacitor model, the existence of a low permittivity interface layer (permittivity ˜30) was suggested. For Ca-doped PZT (52/48) thin film capacitors prepared on Pt, typical ferroelectric and dielectric properties were measured up to 5 mol% Ca doping. When Ca-doped PZT (52/48) thin film capacitors were prepared on electroless Ni coated Cu foil, phase stability was influenced by Ca doping and phosphorous content. Dielectric properties showed dependence on the crystallization temperature and phosphorous content. Capacitance density of ˜400 nF/cm2 was achieved, which is an improvement by more than 30% compared to undoped composition. Ca doping also reduced the temperature coefficient of capacitance (TCC) less than 10%, all of them were consistent in satisfying the requirements of embedded passive capacitor. Leakage current density was not affected significantly by doping. To tailor the dielectric and reliability properties, ZrO2 was selected as buffer layer between PZT and electroless Ni. Only RF magnetron sputtering process could yield stable ZrO2 layers on electroless Ni coated Cu foil. Other processes resulted in secondary phase formation, which supports the reaction between PZT capacitor and electroless Ni might be dominated by phosphorous component. (Abstract shortened by UMI.)

Corrosion behavior and cytocompatibility of fluoride-incorporated plasma electrolytic oxidation coating on biodegradable AZ31 alloy

PubMed Central

Tian, Peng; Peng, Feng; Wang, Donghui; Liu, Xuanyong

2017-01-01

Fluoride-incorporated plasma electrolytic oxidation (PEO) coating was fabricated on biodegradable AZ31 alloy. The surface morphologies and phases were investigated by scanning electron microscopy and X-ray diffraction. The effect of fluoride incorporation in coatings on corrosion behaviour was investigated in simulated body fluid and in vitro cytocompatibility of the coatings was also studied by evaluating cytotoxicity, adhesion, proliferation and live–dead stain of osteoblast cells (MC3T3-E1). Furthermore, the corrosion morphologies in vivo were examined. The results showed that the fluoride could be incorporated into the coating to form MgF2 phase. In vitro and in vivo degradation tests revealed that the corrosion resistance of the coating could be improved by the incorporation of fluoride, which may attribute to the chemical stability of MgF2 phase. Moreover, good cytocompatibility of fluoride-incorporated coating was confirmed with no obvious cytotoxicity, enhanced cell adhesion and proliferation. However, when the fluoride content was high, a slight inhibition of cell growth was observed. The results indicate that although fluoride incorporation can enhance the corrosion resistance of the coatings, thus resulting a more suitable environment for cells, the high content of fluoride in the coating also kill cells ascribed to the high released of fluorine. If the content of fluoride is well controlled, the PEO coating with MgF2 phase is a promising surface modification of Mg alloys. PMID:28149524

Corrosion behavior and cytocompatibility of fluoride-incorporated plasma electrolytic oxidation coating on biodegradable AZ31 alloy.

PubMed

Tian, Peng; Peng, Feng; Wang, Donghui; Liu, Xuanyong

2017-02-01

Fluoride-incorporated plasma electrolytic oxidation (PEO) coating was fabricated on biodegradable AZ31 alloy. The surface morphologies and phases were investigated by scanning electron microscopy and X-ray diffraction. The effect of fluoride incorporation in coatings on corrosion behaviour was investigated in simulated body fluid and in vitro cytocompatibility of the coatings was also studied by evaluating cytotoxicity, adhesion, proliferation and live-dead stain of osteoblast cells (MC3T3-E1). Furthermore, the corrosion morphologies in vivo were examined. The results showed that the fluoride could be incorporated into the coating to form MgF 2 phase. In vitro and in vivo degradation tests revealed that the corrosion resistance of the coating could be improved by the incorporation of fluoride, which may attribute to the chemical stability of MgF 2 phase. Moreover, good cytocompatibility of fluoride-incorporated coating was confirmed with no obvious cytotoxicity, enhanced cell adhesion and proliferation. However, when the fluoride content was high, a slight inhibition of cell growth was observed. The results indicate that although fluoride incorporation can enhance the corrosion resistance of the coatings, thus resulting a more suitable environment for cells, the high content of fluoride in the coating also kill cells ascribed to the high released of fluorine. If the content of fluoride is well controlled, the PEO coating with MgF 2 phase is a promising surface modification of Mg alloys.

Effect of Feedstock Size and its Distribution on the Properties of Detonation Sprayed Coatings

NASA Astrophysics Data System (ADS)

Suresh Babu, P.; Rao, D. S.; Rao, G. V. N.; Sundararajan, G.

2007-06-01

The detonation spraying is one of the most promising thermal spray variants for depositing wear and corrosion resistant coatings. The ceramic (Al2O3), metallic (Ni-20 wt%Cr) , and cermets (WC-12 wt%Co) powders that are commercially available were separated into coarser and finer size ranges with relatively narrow size distribution by employing centrifugal air classifier. The coatings were deposited using detonation spray technique. The effect of particle size and its distribution on the coating properties were examined. The surface roughness and porosity increased with increasing powder particle size for all the coatings consistently. The feedstock size was also found to influence the phase composition of Al2O3 and WC-Co coatings; however does not influence the phase composition of Ni-Cr coatings. The associated phase change and %porosity of the coatings imparted considerable variation in the coating hardness, fracture toughness, and wear properties. The fine and narrow size range WC-Co coating exhibited superior wear resistance. The coarse and narrow size distribution Al2O3 coating exhibited better performance under abrasion and sliding wear modes however under erosion wear mode the as-received Al2O3 coating exhibited better performance. In the case of metallic (Ni-Cr) coatings, the coatings deposited using coarser powder exhibited marginally lower-wear rate under abrasion and sliding wear modes. However, under erosion wear mode, the coating deposited using finer particle size exhibited considerably lower-wear rate.

Thermal barrier coating life prediction model

NASA Technical Reports Server (NTRS)

Pilsner, B. H.; Hillery, R. V.; Mcknight, R. L.; Cook, T. S.; Kim, K. S.; Duderstadt, E. C.

1986-01-01

The objectives of this program are to determine the predominant modes of degradation of a plasma sprayed thermal barrier coating system, and then to develop and verify life prediction models accounting for these degradation modes. The program is divided into two phases, each consisting of several tasks. The work in Phase 1 is aimed at identifying the relative importance of the various failure modes, and developing and verifying life prediction model(s) for the predominant model for a thermal barrier coating system. Two possible predominant failure mechanisms being evaluated are bond coat oxidation and bond coat creep. The work in Phase 2 will develop design-capable, causal, life prediction models for thermomechanical and thermochemical failure modes, and for the exceptional conditions of foreign object damage and erosion.

Microfluidic Controlled Conformal Coating of Particles

NASA Astrophysics Data System (ADS)

Tsai, Scott; Wexler, Jason; Wan, Jiandi; Stone, Howard

2011-11-01

Coating flows are an important class of fluid mechanics problems. Typically a substrate is coated with a moving continuous film, but it is also possible to consider coating of discrete objects. In particular, in applications involving coating of particles that are useful in drug delivery, the coatings act as drug-carrying vehicles, while in cell therapy a thin polymeric coating is required to protect the cells from the host's immune system. Although many functional capabilities have been developed for lab-on-a-chip devices, a technique for coating has not been demonstrated. We present a microfluidic platform developed to coat micron-size spheres with a thin aqueous layer by magnetically pulling the particles from the aqueous phase to the non-aqueous phase in a co-flow. Coating thickness can be adjusted by the average fluid speed and the number of beads encapsulated inside a single coat is tuned by the ratio of magnetic to interfacial forces acting on the beads.

Effects of Laser Power Level on Microstructural Properties and Phase Composition of Laser-Clad Fluorapatite/Zirconia Composite Coatings on Ti6Al4V Substrates

PubMed Central

Chien, Chi-Sheng; Liu, Cheng-Wei; Kuo, Tsung-Yuan

2016-01-01

Hydroxyapatite (HA) is one of the most commonly used materials for the coating of bioceramic titanium (Ti) alloys. However, HA has poor mechanical properties and a low bonding strength. Accordingly, the present study replaces HA with a composite coating material consisting of fluorapatite (FA) and 20 wt % yttria (3 mol %) stabilized zirconia (ZrO2, 3Y-TZP). The FA/ZrO2 coatings are deposited on Ti6Al4V substrates using a Nd:YAG laser cladding system with laser powers and travel speeds of 400 W/200 mm/min, 800 W/400 mm/min, and 1200 W/600 mm/min, respectively. The experimental results show that a significant inter-diffusion of the alloying elements occurs between the coating layer (CL) and the transition layer (TL). Consequently, a strong metallurgical bond is formed between them. During the cladding process, the ZrO2 is completely decomposed, while the FA is partially decomposed. As a result, the CLs of all the specimens consist mainly of FA, Ca4(PO4)2O (TTCP), CaF2, CaZrO3, CaTiO3 and monoclinic phase ZrO2 (m-ZrO2), together with a small amount of θ-Al2O3. As the laser power is increased, CaO, CaCO3 and trace amounts of tetragonal phase ZrO2 (t-ZrO2) also appear. As the laser power increases from 400 to 800 W, the CL hardness also increases as a result of microstructural refinement and densification. However, at the highest laser power of 1200 W, the CL hardness reduces significantly due to the formation of large amounts of relatively soft CaO and CaCO3 phase. PMID:28773503

High temperature oxidation behavior of gamma-nickel+gamma'-nickel aluminum alloys and coatings modified with platinum and reactive elements

NASA Astrophysics Data System (ADS)

Mu, Nan

Materials for high-pressure turbine blades must be able to operate in the high-temperature gases (above 1000°C) emerging from the combustion chamber. Accordingly, the development of nickel-based superalloys has been constantly motivated by the need to have improved engine efficiency, reliability and service lifetime under the harsh conditions imposed by the turbine environment. However, the melting point of nickel (1455°C) provides a natural ceiling for the temperature capability of nickel-based superalloys. Thus, surface-engineered turbine components with modified diffusion coatings and overlay coatings are used. Theses coatings are capable of forming a compact and adherent oxide scale, which greatly impedes the further transport of reactants between the high-temperature gases and the underlying metal and thus reducing attack by the atmosphere. Typically, these coatings contain beta-NiAl as a principal constituent phase in order to have sufficient aluminum content to form an Al2O3 scale at elevated temperatures. The drawbacks to the currently-used beta-based coatings, such as phase instabilities, associated stresses induced by such phase instabilities, and extensive coating/substrate interdiffusion, are major motivations in this study to seek next-generation coatings. The high-temperature oxidation resistance of novel Pt+Hf-modified gamma-Ni+gamma'-Ni 3Al-based alloys and coatings were investigated in this study. Both early-stage and 4-days isothermal oxidation behavior of single-phase gamma-Ni and gamma'-Ni3Al alloys were assessed by examining the weight changes, oxide-scale structures, and elemental concentration profiles through the scales and subsurface alloy regions. It was found that Pt promotes Al 2O3 formation by suppressing the NiO growth on both gamma-Ni and gamma'-Ni3Al single-phase alloys. This effect increases with increasing Pt content. Moreover, Pt exhibits this effect even at lower temperatures (˜970°C) in the very early stage of oxidation. It was also inferred that Pt enhances the diffusive flux of aluminum from the substrate to the scale/alloy interface. Relatively low levels of hafnium addition to Pt-free gamma'-Ni 3Al increased the extent of external NiO formation due to non-protective HfO2 formation. Accordingly, this effect intensified with increasing Hf content from 0.2 to 0.5at.%. The synergistic effect of Pt and Hf co-addition was realized by examining Pt+Hf-modified gamma'-Ni3Al alloys. It was inferred that Pt decreases the chemical activity of Hf so that HfO2 formation could be suppressed with increasing Pt content. Thus, the early-stage Al2O3 formation facilitated by Pt additions and NiO development assisted by Hf additions are the competing scale growth processes that are influenced by the relative contents of Pt and Hf. Large interfacial voids were observed on the gamma'-Ni 3Al alloy after 4-days isothermal oxidation at 1150°C, which could be attributed to the Kirkendall effect. Platinum addition was also found to improve Al2O3-scale adhesion. Pt and Hf effects on two-phase gamma-Ni+gamma'-Ni3Al alloys of compositions Ni-20Al-20Pt-xHf (x ranges from 0 to 0.91) were examined by both thermal gravimetric analyses and cyclic oxidation tests. Scale microstructures were characterized by confocal photo-stimulated microspectroscopy (CPSM), in-lens SEM, and FIB-TEM. Hafnium additions up to about 0.48at.% markedly decreased the weight change of isothermally oxidized Pt-modified gamma+gamma' alloys by forming thinner oxide scales than that on the Hf-free Ni-20Al-20Pt base alloy. This could be attributed to an Al2O3 grain boundary blocking effect imparted by the segregated Hf. However, an over-doped alloy with 0.91at.% Hf exhibited detrimental effect by forming internal HfO 2. It was observed that Hf additions altered the Al2O3 scale microstructure. The most remarkable difference was that the columnar width of the Al2O3 scale grains formed on Ni-20Al-20Pt was much larger than it was on Ni-20Al-20Pt-0.48Hf. Even so, the Hf-doped alloys exhibited much slower scaling kinetics with a correspondingly thinner scale. This behavior could be ascribed to the Hf blocking diffusing paths as it segregated into Al2O3 grain boundaries. Therefore, the Hf-doped scale grew at a lower rate even though it contained more grain boundaries. Accompanied with this scale microstructure modification, Hf additions led to the following two additional effects: (1) Hf delayed the theta→alpha structural transformation of Al2O3; and (2) compressive residual stress in the scale formed on Hf-doped alloys was lower than that on the Hf-free Ni-20Al-20Pt alloy. Guided by the results from the bulk-alloy studies, a feasible method to deposit Pt+Hf-modified gamma+gamma' coatings having overall compositions closely approaching Ni-Al15-20-Pt15-20-Hf was subsequently developed. A key improvement of the application of Pt+Hf-modified gamma-Ni+gamma'-Ni 3Al coatings is the relief of TCP phases generated from coating/substrate interdiffusion. This could be simply attributed to the inherited phase compatibility between gamma+gamma' coatings with Ni-based superalloys. Another important advantage of gamma+gamma' coatings is the exclusion of phase transformations during thermal cycling. The Pt+Hf-modified gamma-Ni+gamma'-Ni3Al coating compositions had a strong dependence on the temperature and time in both pack cementation and post-heat-treatment processes. Meanwhile, coating performance was apparently more sensitive to the Hf content than what was observed with the alloys. Coating performance was also considerable affected by the surface finish and the composition of the superalloy substrate.

Sol–gel method as a way of carbonyl iron powder surface modification for interaction improvement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Małecki, P., E-mail: pawel.malecki@pwr.edu.pl; Kolman, K.; Pigłowski, J.

2015-03-15

This article presents a method for modification of carbonyl iron particles’ surface (CIP), (d{sub 50}=4–9 µm) by silica coatings obtained using the sol–gel method. Reaction parameters were determined to obtain dry magnetic powder with homogeneous silica coatings without further processing and without any by-product in the solid or liquid phase. This approach is new among the commonly used methods of silica coating of iron particles. No attempt has been made to cover a carbonyl iron surface by silica in a waste-free method, up to date. In the current work two different silica core/shell structures were made by the sol–gel process,more » based on different silica precursors: tetraethoxy-silane (TEOS) and tetramethoxy-silane (TMOS). The dependence between the synthesis procedure and thickness of silica shell covering carbonyl iron particles has been described. Surface morphology of the modified magnetic particles and the coating thickness were characterized with the use of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Determination of the physicochemical structure of the obtained materials was performed by the energy-dispersive X-ray spectroscope (EDS), and the infrared technique (IR). The surface composition was analyzed using X-ray photoelectron spectroscopy (XPS). Additionally, distribution of particle size was measured using light microscopy. The new, efficient process of covering micro-size CIP with a nanometric silica layer was shown. Results of a performed analysis confirm the effectiveness of the presented method. - Highlights: • Proper covering CIP by sol–gel silica layer avoids agglomeration. • A new solid waste-free method of CIP coating is proposed. • Examination of the properties of modified CIP in depends on washing process. • Coatings on CIP particles doesn’t change the magnetic properties of particles.« less

Bioactivity of fluorapatite/alumina composite coatings deposited on Ti6Al4V substrates by laser cladding

NASA Astrophysics Data System (ADS)

Chien, C. S.; Liu, C. W.; Kuo, T. Y.; Wu, C. C.; Hong, T. F.

2016-04-01

Hydroxyapatite (HA) is one of the most commonly used coating materials for metal implants. However, following high-temperature deposition, HA easily decomposes into an unstable phase or forms an amorphous phase, and hence, the long-term stability of the implant is reduced. Accordingly, the present study investigates the use of fluorapatite (FA) fortified with 20 wt% alumina (α-Al2O3) as an alternative biomedical coating material. The coatings are deposited on Ti6Al4V substrates using a Nd:YAG laser cladding process performed with laser powers and travel speeds of 400 W/200 mm/min, 800 W/400 mm/min and 1200 W/600 mm/min, respectively. The results show that for all of the specimens, a strong metallurgical bond is formed at the interface between the coating layer and the transition layer due to melting and diffusion. The XRD analysis results reveal that the cladding layers in all of the specimens consist mainly of FA, β-TCP, CaF2, Ti and θ-Al2O3 phases. In addition, the cladding layers of the specimens prepared using laser powers of 400 and 800 W also contain CaTiO3 and CaAl2O4, while that of the specimen clad using a power of 1200 W contains TTCP and CaO. Following immersion in simulated body fluid for 14 days, all of the specimens precipitate dense bone-like apatite and exhibit excellent bioactivity. However, among all of the specimens, the specimen that is prepared with a laser power of 800 W shows the best biological activity due to the presence of residual FA, apatite-generating CaTiO3 and a rough cladding layer surface.

Phase transitions of doped carbon in CrCN coatings with modified mechanical and tribological properties via filtered cathodic vacuum arc deposition

NASA Astrophysics Data System (ADS)

Guan, J. J.; Wang, H. Q.; Qin, L. Z.; Liao, B.; Liang, H.; Li, B.

2017-04-01

The CrCN coatings were fabricated onto Si (1 1 1) wafers and SUS304 stainless steel plates using filtered cathodic vacuum arc deposition (FCVAD) technique under different flow ratios of N2/C2H2 gas mixture. The morphology, crystalline structure and chemical composition of the coatings were characterized. It was found that the grain size reduce with increasing carbon content, which makes the CrCN coatings refined and smooth. The quasi-one-dimensional carbolite phase was also found in CrN host lattice with C2H2 content ranging from 5% to 20%, and it will be evolved into amorphous carbon and amorphous CNx phases as C2H2 content exceeds 20%. Moreover, we examined the mechanical and tribological properties of the CrCN coatings, and the experimental results confirmed that the friction coefficient of the coatings descend to the lowest value as 0.39 with 30% C2H2 content, due to the graphite (sp2 Csbnd C) phase embed in CrN host lattice; while the chromium carbon (Cr3C2) and diamond (sp3 Csbnd C) phases may give rise to the increase of the coating hardness with the highest value at 23.97 GPa under 20% C2H2 content.

Sectioning studies of biomimetic collagen-hydroxyapatite coatings on Ti-6Al-4V substrates using focused ion beam

NASA Astrophysics Data System (ADS)

Hu, Changmin; Yu, Le; Wei, Mei

2018-06-01

A biomimetic bone-like collagen-hydroxyapatite (Col-HA) composite coating was formed on a surface-treated Ti-6Al-4V alloy substrate via simultaneous collagen self-assembly and hydroxyapatite nucleation. The coating process has been carried out by immersing sand-blasted, acid-etched and UV irradiated Ti-6Al-4V alloy in type I collagen-containing modified simulated body fluid (m-SBF). The surface morphology and phase composition of the coating were characterized using various techniques. More importantly, dual-beam FIB/SEMs with either gallium ion source (GFIB) or xenon plasma ion source (PFIB) were used to investigate the cross-sectional features of the biomimetic Col-HA composite coating in great details. As a result, the cross-sectional images and thin transmission electron microscopy (TEM) specimens were successfully obtained from the composite coating with no obvious damages or milling ion implantations. Both the cross-sectional SEM and TEM results have confirmed that the Col-HA coating demonstrates a similar microstructure to that of pure HA coating with homogeneously distributed elements across the whole cross section. Both coatings consist of a uniform, crack-free gradient structure with a dense layer adjacent to the interface between the Ti-6Al-4V substrate and the coating facilitating a strong bonding, while a porous structure at the coating surface aiding cell attachment.

Effect of different thickness h-BN coatings on interface shear strength of quartz fiber reinforced Sisbnd Osbnd Csbnd N composite

NASA Astrophysics Data System (ADS)

Wang, Shubin; Zheng, Yu

2014-02-01

Hexagonal boron nitride (h-BN) coatings with different thickness were prepared on quartz fibers to improve mechanical properties of quartz fiber reinforced Sisbnd Osbnd Csbnd N composite. Scanning electron microscopy (SEM), push-out test and single edge notched beam (SENB) in three point bending test were employed to study morphology, interface shear strength and fracture toughness of the composite. The results showed that h-BN coatings changed the crack growth direction and weaken the interface shear strength efficiently. When the h-BN coating was 308.2 nm, the interface shear strength was about 5.2 MPa, which was about one-quarter of that of the sample without h-BN coatings. After the heating process for obtaining composite, the h-BN nanometer-sized grains would grow up to micron-sized hexagonal grains. Different thickness h-BN coatings had different structure. When the coatings were relatively thin, the hexagonal grains were single layer structure, and when the coatings were thicker, the hexagonal grains were multiple layer structure. This multiple layer interface phase would consume more power of cracks, thus interface shear strength of the composite decreased steadily with the increasing of h-BN coatings thickness. When the coating thickness was 238.8 nm, KIC reaches the peak value 3.8 MPa m1/2, which was more than two times of that of composites without h-BN coatings.

Post-Plasma SiOx Coatings of Metal and Metal Oxide Nanoparticles for Enhanced Thermal Stability and Tunable Photoactivity Applications

PubMed Central

Post, Patrick; Jidenko, Nicolas; Weber, Alfred P.; Borra, Jean-Pascal

2016-01-01

The plasma-based aerosol process developed for the direct coating of particles in gases with silicon oxide in a continuous chemical vapor deposition (CVD) process is presented. It is shown that non-thermal plasma filaments induced in a dielectric barrier discharge (DBD) at atmospheric pressure trigger post-DBD gas phase reactions. DBD operating conditions are first scanned to produce ozone and dinitrogen pentoxide. In the selected conditions, these plasma species react with gaseous tetraethyl orthosilicate (TEOS) precursor downstream of the DBD. The gaseous intermediates then condense on the surface of nanoparticles and self-reactions lead to homogeneous solid SiOx coatings, with thickness from nanometer to micrometer. This confirms the interest of post-DBD injection of the organo-silicon precursor to achieve stable production of actives species with subsequent controlled thickness of SiOx coatings. SiOx coatings of spherical and agglomerated metal and metal oxide nanoparticles (Pt, CuO, TiO2) are achieved. In the selected DBD operating conditions, the thickness of homogeneous nanometer sized coatings of spherical nanoparticles depends on the reaction duration and on the precursor concentration. For agglomerates, operating conditions can be tuned to cover preferentially the interparticle contact zones between primary particles, shifting the sintering of platinum agglomerates to much higher temperatures than the usual sintering temperature. Potential applications for enhanced thermal stability and tunable photoactivity of coated agglomerates are presented. PMID:28335219

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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 investigated, 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 ± 0.5 μm 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 substrate 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.

Development of electrically insulating coatings for service in a lithium environment

NASA Astrophysics Data System (ADS)

Natesan, K.; Uz, M.; Wieder, S.

2000-12-01

Several experiments were conducted to develop electrically insulating CaO coatings on a V-4Cr-4Ti alloy for application in a Li environment. The coatings were developed by vapor-phase transport external to Li, and also in situ in a Li-Ca environment at elevated temperature. In the vapor-phase study, several geometrical arrangements were examined to obtain a uniform coating of Ca on the specimens, which were typically coupons measuring 5 to 10 × 5 × 1 mm 3. After Ca deposition from the vapor phase, the specimens were oxidized in a high-purity argon environment at 600°C to convert the deposited metal into oxide. The specimens exhibited insulating characteristics after this oxidation step. Several promising coated specimens were then exposed to high-purity Li at 500°C for 48-68 h to determine coating integrity. Microstructural characteristics of the coatings were evaluated by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis. Electrical resistances of the coatings were measured by a two-probe method between room temperature and 700°C before and after exposure to Li.

Investigation of Various Surface Acoustic Wave Design Configurations for Improved Sensitivity

NASA Astrophysics Data System (ADS)

Manohar, Greeshma

Surface acoustic wave sensors have been a focus of active research for many years. Its ability to respond for surface perturbation is a basic principle for its sensing capability. Sensitivity to surface perturbation changes with every inter-digital transducer (IDT) design parameters, substrate selection, metallization choice and technique, delay line length and working environment. In this thesis, surface acoustic wave (SAW) sensors are designed and characterized to improve sensitivity and reduce loss. To quantify the improvements with a specific design configuration, the sensors are employed to measure temperature. Four SAW sensors design configurations, namely bi-directional, split electrode, single phase unidirectional transducer (SPUDT) and metal grating on delay line (shear transvers wave sensors) are designed and then fabricated in Nanotechnology Research and Education Center (NREC) facility using traditional MEMS fabrication processes Additionally, sensors are then coated with guiding layer SU8-2035 of 40µm using spin coating and SiO 2 of 6µm using plasma enhanced chemical vapor deposition (PECVD) process. Sensors are later diced and tested for every 5°C increment using network analyzer for temperature ranging from 30°C±0.5°C to 80°C±0.5°C. Data acquired from network analyzer is analyzed using plot of logarithmic magnitude, phase and frequency shift. Furthermore, to investigate the effect of metallization technique on the sensor performance, sensors are also fabricated on substrates that were metallized at a commercial MEMS foundry. All in-house and outside sputtered sensor configurations are compared to investigate quality of sputtered metal on wafer. One with better quality sputtered metal is chosen for further study. Later sensors coated with SU8 and SiO2 as guiding layer are compared to investigate effect of each waveguide on sensors and determine which waveguide offers better performance. The results showed that company sputtered sensors have higher sensitivity compared to in-house sputtered wafers. Furthermore after comparing SU8 and SiO2 coated sensors in the same instrumental and environmental condition, it was observed that SU8 coated di-directional and single phase unidirectional transducer (SPUDT) sensors showed best response.

In situ synthesis of Fe-based alloy clad coatings containing TiB2-TiN-(h-BN)

NASA Astrophysics Data System (ADS)

Jiang, Shao-qun; Wang, Gang; Ren, Qing-wen; Yang, Chuan-duo; Wang, Ze-hua; Zhou, Ze-hua

2015-06-01

Fe-based alloy coatings containing TiB2-TiN-(h-BN) were synthesized in situ on Q235 steel substrates by a plasma cladding process using the powders of Fe901 alloy, Ti, and h-BN as raw materials. The effects of Ti/h-BN mass ratio on interfacial bonds between the coating and substrate along with the microstructures and microhardnesses of the coatings were investigated. The results show that the Ti/h-BN mass ratio is a vital factor in the formation of the coatings. Free h-BN can be introduced into the coatings by adding an excess amount of h-BN into the precursor. Decreases in the Ti/h-BN mass ratio improve the microstructural uniformity and compactness and enhance the interfacial bonds of the coatings. At a Ti/h-BN mass ratio of 10/20, the coating is free of cracks and micropores, and mainly consists of Fe-Cr, Fe3B, TiB2, TiN, Ti2N, TiB, FeN, FeB, Fe2B, and h-BN phases. Its average microhardness in the zone between 0.1-2.8 mm from the coating surface is about Hv0.2 551.5.

Deposition behavior of mixed binary metallic powders in cold spraying process

NASA Astrophysics Data System (ADS)

Zhou, X. L.; Mou, S. J.; Wu, X. K.; Zhang, J. S.

2011-10-01

In the present study, Zn/Al composite coating was selected for the typical case to study the deposition behavior and the deformation of binary mixing particles in cold spraying process by means of an experiment and numerical simulation. The experimental results demonstrated that the coating had a dense microstructure, and that Zn and Al were uniformly distributed in the coating. Al particles deformed more severely than Zn particles, and extensively deformed Al particles had a local jet-metallic mixing area. The steel substrate underwent a small amount of deformation when impacted by Zn particles, whereas the substrate did not deform when impacted by Al particles. XRD results show that the Zn/Al composite coating did not form a new phase, and only resulted in the mechanical mixing of Zn and Al, producing a pseudo-alloy coating. In addition, a binary Zn/Al multiparticle impact was first simulated using the finite element analysis software ANSYS/LS-DYNA. The effective plastic strain contour, which enabled the description of the particle deposit procedure, was demonstrated. The plastic deformation evolution of Zn and Al particles in the composite coating was analyzed individually, and the curves of effective plastic strain versus time of typical monitored elements at the edge of the Zn and Al particles were plotted. The simulations showed good concordance with the experimental results.

Revisiting the Birth of 7YSZ Thermal Barrier Coatings: Steve Stecura

NASA Technical Reports Server (NTRS)

Smialek, James L.; Miller, Robert A.

2017-01-01

Thermal barrier coatings are widely used in all turbine engines, typically using a 7 wt% Y2O3-ZrO2 formulation. Extensive research and development over many decades have refined the processing and structure of these coatings for increased durability and reliability. New compositions demonstrate some unique advantages and are gaining in application. However, the "7YSZ" formulation predominates and is still in widespread use. This special composition has been universally found to produce nanoscale precipitates of metastable t' tetragonal phase, giving rise to a unique toughening mechanism via ferro-elastic switching under stress. This note recalls the original study that identified superior properties of 6 to 8 wt% YSZ plasma sprayed thermal barrier coatings, published in 1978. The impact of this discovery, arguably, continues in some form to this day. At one point, 7YSZ thermal barrier coatings were used in every new aircraft and ground power turbine engine produced worldwide. It is a tribute to its inventor, Dr. Stephan J. Stecura, NASA retiree.

Development and Characterization of High Performance Shape Memory Alloy Coatings for Structural Aerospace Applications.

PubMed

Exarchos, Dimitrios A; Dalla, Panagiota T; Tragazikis, Ilias K; Dassios, Konstantinos G; Zafeiropoulos, Nikolaos E; Karabela, Maria M; De Crescenzo, Carmen; Karatza, Despina; Musmarra, Dino; Chianese, Simeone; Matikas, Theodore E

2018-05-18

This paper presents an innovative approach, which enables control of the mechanical properties of metallic components by external stimuli to improve the mechanical behavior of aluminum structures in aeronautical applications. The approach is based on the exploitation of the shape memory effect of novel Shape Memory Alloy (SMA) coatings deposited on metallic structural components, for the purpose of relaxing the stress of underlying structures by simple heating at field-feasible temperatures, therefore enhancing their structural integrity and increasing their stiffness and rigidity while allowing them to withstand expected loading conditions safely. Numerical analysis provided an insight in the expected response of the SMA coating and of the SMA-coated element, while the dependence of alloy composition and heat treatment on the experienced shape memory effect were investigated experimentally. A two-phase process is proposed for deposition of the SMA coating in an order that induces beneficial stress relaxation to the underlying structure through the shape memory effect.

Development and Characterization of High Performance Shape Memory Alloy Coatings for Structural Aerospace Applications

PubMed Central

Exarchos, Dimitrios A.; Dalla, Panagiota T.; Tragazikis, Ilias K.; Zafeiropoulos, Nikolaos E.; Karabela, Maria M.; De Crescenzo, Carmen; Karatza, Despina; Matikas, Theodore E.

2018-01-01

This paper presents an innovative approach, which enables control of the mechanical properties of metallic components by external stimuli to improve the mechanical behavior of aluminum structures in aeronautical applications. The approach is based on the exploitation of the shape memory effect of novel Shape Memory Alloy (SMA) coatings deposited on metallic structural components, for the purpose of relaxing the stress of underlying structures by simple heating at field-feasible temperatures, therefore enhancing their structural integrity and increasing their stiffness and rigidity while allowing them to withstand expected loading conditions safely. Numerical analysis provided an insight in the expected response of the SMA coating and of the SMA-coated element, while the dependence of alloy composition and heat treatment on the experienced shape memory effect were investigated experimentally. A two-phase process is proposed for deposition of the SMA coating in an order that induces beneficial stress relaxation to the underlying structure through the shape memory effect. PMID:29783626

Design Optimization of Liquid Fueled High Velocity Oxy- Fuel Thermal Spraying Technique for Durable Coating for Fossil Power Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choudhuri, Ahsan; Love, Norman

High-velocity oxy–fuel (HVOF) thermal spraying was developed in 1930 and has been commercially available for twenty-five years. HVOF thermal spraying has several benefits over the more conventional plasma spray technique including a faster deposition rate which leads to quicker turn-around, with more durable coatings and higher bond strength, hardness and wear resistance due to a homogeneous distribution of the sprayed particles. HVOF thermal spraying is frequently used in engineering to deposit cermets, metallic alloys, composites and polymers, to enhance product life and performance. HVOF thermal spraying system is a highly promising technique for applying durable coatings on structural materials formore » corrosive and high temperature environments in advanced ultra-supercritical coal- fired (AUSC) boilers, steam turbines and gas turbines. HVOF thermal spraying is the preferred method for producing coatings with low porosity and high adhesion. HVOF thermal spray process has been shown to be one of the most efficient techniques to deposit high performance coatings at moderate cost. Variables affecting the deposit formation and coating properties include hardware characteristics such as nozzle geometry and spraying distance and process parameters such as equivalence ratio, gas flow density, and powder feedstock. In the spray process, the powder particles experience very high speeds combined with fast heating to the powder material melting point or above. This high temperature causes evaporation of the powder, dissolution, and phase transformations. Due to the complex nature of the HVOF technique, the control and optimization of the process is difficult. In general, good coating quality with suitable properties and required performance for specific applications is the goal in producing thermal spray coatings. In order to reach this goal, a deeper understanding of the spray process as a whole is needed. Although many researchers studied commercial HVOF thermal spray systems, there exists a lack of fundamental understanding of the effect of hardware characteristics and operating parameters on HVOF thermally sprayed coatings. Motivated by these issues, this study is devoted to investigate the effect of hardware characteristics (e.g. spraying distance) and operating parameters (e.g. combustion chamber pressure, equivalence ratio, and total gas flow rate) on HVOF sprayed coatings using Inconel 718 alloy. The current study provides extensive understanding of several key operating and process parameters to optimize the next generation of HVOF thermally sprayed coatings for high temperature and harsh environment applications. A facility was developed to support this endeavor in a safe and efficient way, including a HVOF thermal spray system with a Data Acquisition and Remote Controls system (DARCS). The coatings microstructure and morphology were examined using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Nanoindentation.« less

NASA Astrophysics Data System (ADS)

Sampath, S.; Wayne, S. F.

1994-09-01

Thermally sprayed molybdenum coatings are used in a variety of industrial applications, such as auto-motive piston rings, aeroturbine engines, and paper and plastics processing machinery. Molybdenum ex-hibits excellent scuffing resistance under sliding contact conditions. However, plasma-sprayed molybde-num coatings are relatively soft and require dispersion strengthening (e.g., Mo2C) or addition of a second phase (e.g., NiCrBSi) to improve hardness, wear resistance, and thus coating performance. In this study, Mo-Mo2C composite powders were plasma sprayed onto mild steel substrates. Considerable decarburi-zation was observed during air plasma spraying—a beneficial condition because carbon acts as a sacrifi-cial getter for the oxygen, thereby reducing the oxide content in the coating. Finer powders showed a greater degree of decarburization due to the increased surface area; however, the starting carbide con-tent in the powder exerted very little influence on the extent of decarburization. The friction properties of Mo-Mo2C coatings were significantly improved compared to those of pure molybdenum under con-tinuous sliding contact conditions. It also was found that the abrasion resistance of the coatings improved with increasing carbide addition.

A new thermally immobilized fluorinated stationary phase for RP-HPLC.

PubMed

Maldaner, Liane; Jardim, Isabel C S F

2010-02-01

A new fluorinated stationary phase was prepared through thermal immobilization of poly(methyl-3,3,3-trifluoropropylsiloxane) onto 5 microm Kromasil silica particles. The best conditions of immobilization time and temperature were determined through a central composite design and response surface methodologies. Physical-chemical characterization using solid-state (29)Si NMR measurements, infrared spectroscopy and elemental analysis showed that the immobilization process was effective to promote a coating of the support that corresponds to a monolayer of polymer. The stationary phase presents selectivity for positional isomers and good peak shape for basic compounds.

Effect of Coatings and Processing on Failure Mechanisms of Polycarbonate Material. Phase 1

DTIC Science & Technology

1991-11-01

PHASE I By R.D. Eisler A.K. Chatterjee G. Burghart A.H. Koivu C.D. Newlander S.F. Stone Mission Research Corporation Costa Mesa, CA 92626 and...PHASE I ’ 6. AUTHOR(S) DAAK60-89- C-0011 R.D. EISLER , A.K. CHATTERJEE, G. BURGHART, A.H. KOIVU, C.D. NEWLANDER, S.F. STONE, E. HEALY* : 7...response to Department of Defense solicitation 88.1 dated 8 January 1987 , SBIR Topic ABB-140. The published description of SBIR topic A88-140 is included

Preparation and application of the sol-gel-derived acrylate/silicone co-polymer coatings for headspace solid-phase microextraction of 2-chloroethyl ethyl sulfide in soil.

PubMed

Liu, Mingming; Zeng, Zhaorui; Fang, Huaifang

2005-05-27

Three types of novel acrylate/silicone co-polymer coatings, including co-poly(methyl acrylate/hydroxy-terminated silicone oil) (MA/OH-TSO), co-poly(methyl methacrylate/OH-TSO) (MMA/OH-TSO) and co-poly(butyl methacrylate/OH-TSO) (BMA/OH-TSO), were prepared for the first time by sol-gel method and cross-linking technology and subsequently applied to headspace solid-phase microextraction (HS-SPME) of 2-chloroethyl ethyl sulfide (CEES), a surrogate of mustard, in soil. The underlying mechanisms of the coating process were discussed and confirmed by IR spectra. The selectivity of the three types of sol-gel-derived acrylate/silicone coated fibers was studied, and the BMA/OH-TSO coated fibers exhibited the highest extraction ability to CEES. The concentration of BMA and OH-TSO in sol solution was optimized, and the BMA/OH-TSO (3:1)-coated fibers possessed the highest extraction efficiency. Compared with commercially available polyacrylate (PA) fiber, the sol-gel-derived BMA/OH-TSO (3:1) fibers showed much higher extraction efficiency to CEES. Therefore, the BMA/OH-TSO (3:1)-coated fibers were chosen for the analysis of CEES in soil matrix. The reproducibility of coating preparation was satisfactory, with the RSD 2.39% within batch and 3.52% between batches, respectively. The coatings proved to be quite stable at high temperature (to 350 degrees C) and in different solvents (organic or inorganic), thus their lifetimes (to 150 times) are longer than conventional fibers. Extraction parameters, such as the volume of water added to the soil, extraction temperature and time, and the ionic strength were optimized. The linearity was from 0.1 to 10 microg/g, the limit of detection (LOD) was 2.7 ng/g, and the RSD was 2.19%. The recovery of CEES was 88.06% in agriculture soil, 92.61% in red clay, and 101.95% in sandy soil, respectively.

Anodized porous titanium coated with Ni-CeO2 deposits for enhancing surface toughness and wear resistance

NASA Astrophysics Data System (ADS)

Zhou, Xiaowei; Ouyang, Chun

2017-05-01

In order to make large improvements of surface toughness and wear resistance for pure titanium (Ti) substrate, anodic titanium oxide (ATO) surface with nanoporous structure was coated with the Ni-CeO2 nanocomposite coatings. Regarding TiO2 barrier layer on Ti surface to inhibit its electrochemical activity, pre-treatments were successively processed with anodizing, sensitizing, activating, and then followed by electroless Ni-P film to be acted as an activated layer for electroplating Ni-CeO2 deposits. The existing Pd atoms around ATO nanopores were expected as the heterogeneous nucleation sites for supporting the growing locations of electroless Ni-P film. The innovative of interface design using porous structure was introduced for bonding pinholes to achieve a metallurgical adhesion interface between Ti substrate and surface coatings. Besides the objectives of this work were to elucidate how effects by the adding CeO2 nanoparticles on modifying microstructures and wear mechanisms of Ni-CeO2 nanocomposite coatings. Many efforts of XRD, FE-SEM, TEM and Nanoindentation tests were devoted to comparing different wear behaviors of Ni-CeO2 coatings relative to pure nickel. Results indicated that uniform-distributed Ti nanopores with an average diameter size of ∼200 nm was achieved using the Phosphate-type anodizing solution at DC 150 V. A worn surface without fatigue cracks was observed for TAO surface coated with Ni-CeO2 deposits, showing the existing Ce-rich worn products to be acted as a solid lubricant phase for making a self-healing effect on de-lamination failures. More important, this finding will be the guidelines for Ce-rich precipitations to be expected as the strengthening phase in anodized porous of Ti, Al and Mg alloys for intensifying their surface properties.

Determination of Young's modulus of epoxy coated polyethylene micro-cantilever using phase-shift shadow moiré method

NASA Astrophysics Data System (ADS)

Lim, J. H.; Ratnam, M. M.; Azid, I. A.; Mutharasu, D.

2011-11-01

Young's moduli of various epoxy coated polyethylene terephthalate (PET) micro-cantilevers were determined from the deflection results obtained using the phase-shift shadow moiré (PSSM) method. The filler materials for epoxy coatings were aluminum and graphite powders that were mixed with epoxy at various percentages. Young's moduli were calculated from theory based on the deflection results. The PET micro-cantilever coated with aluminum-epoxy coating showed increasing value of Young's modulus when the ratios of the aluminum-epoxy were increased. The graphite-epoxy coating on the PET micro-cantilever also showed the same trend. The experimental results also show that Young's modulus of the graphite-epoxy coating is higher than aluminum-epoxy coating in comparison at the same mixing ratio.

Development of heat transfer enhancement techniques for external cooling of an advanced reactor vessel

NASA Astrophysics Data System (ADS)

Yang, Jun

Nucleate boiling is a well-recognized means for passively removing high heat loads (up to ˜106 W/m2) generated by a molten reactor core under severe accident conditions while maintaining relatively low reactor vessel temperature (<800 °C). With the upgrade and development of advanced power reactors, however, enhancing the nucleate boiling rate and its upper limit, Critical Heat Flux (CHF), becomes the key to the success of external passive cooling of reactor vessel undergoing core disrupture accidents. In the present study, two boiling heat transfer enhancement methods have been proposed, experimentally investigated and theoretically modelled. The first method involves the use of a suitable surface coating to enhance downward-facing boiling rate and CHF limit so as to substantially increase the possibility of reactor vessel surviving high thermal load attack. The second method involves the use of an enhanced vessel/insulation design to facilitate the process of steam venting through the annular channel formed between the reactor vessel and the insulation structure, which in turn would further enhance both the boiling rate and CHF limit. Among the various available surface coating techniques, metallic micro-porous layer surface coating has been identified as an appropriate coating material for use in External Reactor Vessel Cooling (ERVC) based on the overall consideration of enhanced performance, durability, the ease of manufacturing and application. Since no previous research work had explored the feasibility of applying such a metallic micro-porous layer surface coating on a large, downward facing and curved surface such as the bottom head of a reactor vessel, a series of characterization tests and experiments were performed in the present study to determine a suitable coating material composition and application method. Using the optimized metallic micro-porous surface coatings, quenching and steady-state boiling experiments were conducted in the Sub-scale Boundary Layer Boiling (SBLB) test facility at Penn State to investigate the nucleate boiling and CHF enhancement effects of the surface coatings by comparing the measurements with those for a plain vessel without coatings. An overall enhancement in nucleate boiling rates and CHF limits up to 100% were observed. Moreover, combination of data from quenching experiments and steady-state experiments produced new sets of boiling curves, which covered both the nucleate and transient boiling regimes with much greater accuracy. Beside the experimental work, a theoretical CHF model has also been developed by considering the vapor dynamics and the boiling-induced two-phase motions in three separate regions adjacent to the heating surface. The CHF model is capable of predicting the performance of micro-porous coatings with given particle diameter, porosity, media permeability and thickness. It is found that the present CHF model agrees favorably with the experimental data. Effects of an enhanced vessel/insulation structure on the local nucleate boiling rate and CHF limit have also been investigated experimentally. It is observed that the local two-phase flow quantities such as the local void fraction, quality, mean vapor velocity, mean liquid velocity, and mean vapor and liquid mass flow rates could have great impact on the local surface heat flux as boiling of water takes place on the vessel surface. An upward co-current two-phase flow model has been developed to predict the local two-phase flow behavior for different flow channel geometries, which are set by the design of insulation structures. It is found from the two-phase flow visualization experiments and the two-phase flow model calculations that the enhanced vessel/insulation structure greatly improved the steam venting process at the minimum gap location compared to the performance of thermal insulation structures without enhancement. Moveover, depending on the angular location, steady-state boiling experiments with the enhanced insulation design showed an enhancement of 1.8 to 3.0 times in the local critical heat flux. Finally, nucleate boiling and CHF correlations were developed based on the data obtained from various quenching and steady-state boiling experiments. Additionally, CHF enhancement factors were determined and examined to show the separate and integral effects of the two ERVC enhancement methods. When both vessel coating and insulation structure were used simultaneously, the integral effect on CHF enhancement was found much less than the product of the two separate effects, indicating possible competing mechanisms (i.e., interference) between the two enhancement methods.

Factors influencing phase compositions and structure of plasma sprayed hydroxyapatite coatings during heat treatment

NASA Astrophysics Data System (ADS)

Lu, Yu-Peng; Song, Yi-Zhong; Zhu, Rui-Fu; Li, Mu-Sen; Lei, Ting-Quan

2003-02-01

Heat treatment was expected to enhance the long-term reliability of hydroxyapatite (HA) coatings on metal substrates. In this study, factors influencing phase compositions and structure of plasma sprayed hydroxyapatite coatings during heat treatment were carefully analyzed. The phases were characterized by using X-ray diffraction (XRD), the OH - ion contents were determined by Fourier transform infrared (FTIR) spectroscopy. Of the involved factors, heating temperature is of more importance. The appropriate heat treatments is (600- 700 ° C)×2 h for coatings made from fine particles (10-20 μm) and 600 ° C×2 h for coatings made from coarse particles (50-80 μm). The excessive high temperatures and long holding times were unfavorable for the structural integrity of HA.

Data Compilation for AGR-3/4 Designed-to-Fail (DTF) Fuel Particle Batch LEU04-02DTF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hunn, John D; Miller, James Henry

2008-10-01

This document is a compilation of coating and characterization data for the AGR-3/4 designed-to-fail (DTF) particles. The DTF coating is a high density, high anisotropy pyrocarbon coating of nominal 20 {micro}m thickness that is deposited directly on the kernel. The purpose of this coating is to fail early in the irradiation, resulting in a controlled release of fission products which can be analyzed to provide data on fission product transport. A small number of DTF particles will be included with standard TRISO driver fuel particles in the AGR-3 and AGR-4 compacts. The ORNL Coated Particle Fuel Development Laboratory 50-mm diametermore » fluidized bed coater was used to coat the DTF particles. The coatings were produced using procedures and process parameters that were developed in an earlier phase of the project as documented in 'Summary Report on the Development of Procedures for the Fabrication of AGR-3/4 Design-to-Fail Particles', ORNL/TM-2008/161. Two coating runs were conducted using the approved coating parameters. NUCO425-06DTF was a final process qualification batch using natural enrichment uranium carbide/uranium oxide (UCO) kernels. After the qualification run, LEU04-02DTF was produced using low enriched UCO kernels. Both runs were inspected and determined to meet the specifications for DTF particles in section 5 of the AGR-3 & 4 Fuel Product Specification (EDF-6638, Rev.1). Table 1 provides a summary of key properties of the DTF layer. For comparison purposes, an archive sample of DTF particles produced by General Atomics was characterized using identical methods. This data is also summarized in Table 1.« less

In vitro degradation, hemolysis, and cytocompatibility of PEO/PLLA composite coating on biodegradable AZ31 alloy.

PubMed

Wei, Zhongling; Tian, Peng; Liu, Xuanyong; Zhou, Bangxin

2015-02-01

Magnesium and its alloys have large potential as degradable and absorbable biomaterials because of their mechanical properties and biocompatibility. However, their corrosion resistance is usually inadequate especially in physiological environment, which limits their broad applications in biomedical areas. In this work, plasma electrolytic oxidized/poly(l-lactide) (PEO/PLLA) composite coating was successfully fabricated on biodegradable AZ31 alloy by combing PEO process and sealing with PLLA. The microstructure, elemental composition, and phase composition of the PEO/PLLA composite coating were investigated. The in vitro degradation of the PEO/PLLA composite coating in simulated body fluid (SBF) was also systematically evaluated. The results revealed that the PEO/PLLA composite coating improved the corrosion resistance of AZ31 alloy significantly. The corrosion potential shifted from -1.663V to more positive position -1.317 V and the corrosion current density was reduced with six-order of magnitude. The Mg(2+) ions, hydrogen release, and pH value change of solution caused by degradation were all decreased significantly. Moreover, the PEO process played a critical role in sustaining the integrity of the implant in long-term service. The result of hemolysis test showed that the PEO/PLLA composite coating vested AZ31 alloy a low hemolysis ratio (0.806 ± 0.771)%, which is much lower than the safe value of 5% according to ISO 10993-4. For the cytocompatibility test, compared with bare AZ31 alloy and PEO coating, MC3T3-E1 cells showed much better adhesion and proliferation on the PEO/PLLA composite coating with nearly 4-fold increase of cells after 7-day cultivation, indicating that the PEO/PLLA composite coating has good biocompatibility for biomedical applications. © 2014 Wiley Periodicals, Inc.

Thermal insulating coating for spacecrafts

NASA Technical Reports Server (NTRS)

Kaul, Raj K. (Inventor)

2005-01-01

To protect spacecraft and their contents from excessive heat thermal protection systems are essential. For such thermal protection, metal coatings, ceramic materials, ablative materials, and various matrix materials have all been tried, but none have been found entirely satisfactory. The basis for this thermal protection system is the fact that the heat required to melt a substance is 80 to 100 times larger than the heat required to raise its temperature one degree. This led to the use herein of solid-liquid phase change materials. Unlike conventional heat storage materials, when phase change materials reach the temperature at which they change phase they absorb large amounts of heat without getting hotter. By this invention, then, a coating composition is provided for application to substrates subjected to temperatures above 100? F. The coating composition includes a phase change material.

Thermal Insulating Coating for Spacecrafts

NASA Technical Reports Server (NTRS)

Kaul, Raj K. (Inventor)

2005-01-01

To protect spacecraft and their contents from excessive heat thermal protection system are essential. For such thermal protection, metal coatings, ceramic materials, ablative materials, and various matrix materials have all been tried, but none have been found entirely satisfactory. The basis for this thermal protection system is the fact that the heat required to melt a substance is 80 to 100 times larger than the heat required to raise its temperature one degree. This led to the use herein of solid-liquid phase change materials. Unlike conventional heat storage materials, when phase change materials reach the temperature at which they change phase they absorb large amounts of heat without getting hotter. By this invention, then, a coating composition is provided for application to substrates subjected to temperatures above 100 F. The coating composition includes a phase change material.

Structure and properties of Hardox 450 steel with arc welded coatings

NASA Astrophysics Data System (ADS)

Ivanov, Yu. F.; Konovalov, S. V.; Kormyshev, V. E.; Gromov, V. E.; Teresov, A. D.; Semina, O. A.

2017-12-01

The paper reports on a study of the surface structure, phase composition, and microhardness of Hardox 450 steel with coatings deposited by arc welding of powder wires differing in chemical composition. The study shows that to a depth of 6-8 mm, the microhardness of the thus formed coatings is more than two times the microhardness of the base metal and that their higher mechanical properties are provided by martensite structure containing Nb2C and NbC carbides and Fe2B borides as eutectic lamellae with a transverse size of 30-70 nm; their volume reveals a net-like dislocation substructure with a scalar dislocation density of 1011 cm-2. The highest surface hardness is found for the steel coated with boron-containing wire material. Some ideas are suggested on possible mechanisms and temperature for the formation of Nb and B carbides during the process.

Improvement of transmission properties of visible pilot beam for polymer-coated silver hollow fibers with acrylic silicone resin as buffer layer for sturdy structure

NASA Astrophysics Data System (ADS)

Iwai, Katsumasa; Takaku, Hiroyuki; Miyagi, Mitsunobu; Shi, Yi-Wei; Zhu, Xiao-Song; Matsuura, Yuji

2017-02-01

Flexible hollow fibers with 530-μm-bore size were developed for infrared laser delivery. Sturdy hollow fibers were fabricated by liquid-phase coating techniques. A silica glass capillary is used as the substrate. Acrylic silicone resin is used as a buffer layer and the buffer layer is firstly coated on the inner surface of the capillary to protect the glass tube from chemical damages due to the following silver plating process. A silver layer was inner-plated by using the conventional silver mirror-plating technique. To improve adhesion of catalyst to the buffer layer, a surface conditioner has been introduced in the method of silver mirror-plating technique. We discuss improvement of transmission properties of sturdy polymer-coated silver hollow fibers for the Er:YAG laser and red pilot beam delivery.

CVD aluminiding process for producing a modified platinum aluminide bond coat for improved high temperature performance

NASA Technical Reports Server (NTRS)

Nagaraj, Bangalore A. (Inventor); Williams, Jeffrey L. (Inventor)

2003-01-01

A method of depositing by chemical vapor deposition a modified platinum aluminide diffusion coating onto a superalloy substrate comprising the steps of applying a layer of a platinum group metal to the superalloy substrate; passing an externally generated aluminum halide gas through an internal gas generator which is integral with a retort, the internal gas generator generating a modified halide gas; and co-depositing aluminum and modifier onto the superalloy substrate. In one form, the modified halide gas is hafnium chloride and the modifier is hafnium with the modified platinum aluminum bond coat comprising a single phase additive layer of platinum aluminide with at least about 0.5 percent hafnium by weight percent and about 1 to about 15 weight percent of hafnium in the boundary between a diffusion layer and the additive layer. The bond coat produced by this method is also claimed.

In situ ceramic layer growth on coated fuel particles dispersed in a zirconium metal matrix

DOE Office of Scientific and Technical Information (OSTI.GOV)

Terrani, Kurt A; Silva, G W Chinthaka M; Kiggans, Jim

2013-01-01

The extent and nature of the chemical interaction between the outermost coating layer of coated fuel particles embedded in zirconium metal during fabrication of metal matrix microencapsulated fuels was examined. Various particles with outermost coating layers of pyrocarbon, SiC, and ZrC have been investigated in this study. ZrC-Zr interaction was least substantial while PyC-Zr reaction can be exploited to produce a ZrC layer at the interface in an in situ manner. The thickness of the ZrC layer in the latter case can be controlled by adjusting the time and temperature during processing. The kinetics of ZrC layer growth is significantlymore » faster from what is predicted using literature carbon diffusivity data in ZrC. SiC-Zr interaction is more complex and results in formation of various chemical phases in a layered aggregate morphology at the interface.« less

Modification of the structure and composition of Ca10(PO4)6(OH)2 ceramic coatings by changing the deposition conditions in O2 and Ar

NASA Astrophysics Data System (ADS)

Donkov, N.; Zykova, A.; Safonov, V.; Kolesnikov, D.; Goncharov, I.; Yakovin, S.; Georgieva, V.

2014-05-01

Hydroxyapatite Ca10(PO4)6(OH)2 (HAp) is a material considered to be used to form structural matrices in the mineral phase of bone, dentin and enamel. HAp ceramic materials and coatings are widely applied in medicine and dentistry because of their ability to increase the tissue response to the implant surface and promote bone ingrowth and osseoconduction processes. The deposition conditions affect considerably the structure and bio-functionality of the HAp coatings. We focused our research on developing deposition methods allowing a precise control of the structure and stoichiometric composition of HAp thin films. We found that the use of O2 as a reactive gas improves the quality of the sputtered hydroxyapatite coatings by resulting in the formation of films of better stoichiometry with a fine crystalline structure.

Effect of Mg on the Microstructure and Corrosion Resistance of the Continuously Hot-Dip Galvanizing Zn-Mg Coating

PubMed Central

Dong, Anping; Li, Baoping; Lu, Yanling; Zhu, Guoliang; Xing, Hui; Shu, Da; Sun, Baode; Wang, Jun

2017-01-01

The microstructure of continuously hot-dip galvanizing Zn-Mg coating was investigated in order to obtain the mechanism of the effects of Mg on the corrosion resistance. In this paper, the vertical section of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner was calculated. The results indicates that the phase composition of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner is the same as Zn-Mg binary phase diagram, suggesting Al in the Zn-Mg (ZM) coatings mainly concentrates on the interfacial layer between the coating and steel substrate. The microstructure of continuously hot-dip galvanizing ZM coatings with 0.20 wt % Al containing 1.0–3.0 wt % Mg was investigated using tunneling electron microscopy (TEM). The morphology of Zn in the coating changes from bulk to strip and finally to mesh-like, and the MgZn2 changes from rod-like to mesh-like with the Mg content increasing. Al in the ZM coatings mainly segregates at the Fe2Al5 inhibition layer and the Mg added to the Zn bath makes this inhibition layer thinner and uneven. Compared to GI coating, the time of the first red rust appears increases by more than two-fold and expansion rate of red rust reduces by more than four-fold in terms of salt spray experiment. The ZM coating containing 2.0 wt % Mg has the best corrosion resistance. The enhanced corrosion resistance of ZM coatings mainly depends on different corrosion products. PMID:28829393

Effect of Mg on the Microstructure and Corrosion Resistance of the Continuously Hot-Dip Galvanizing Zn-Mg Coating.

PubMed

Dong, Anping; Li, Baoping; Lu, Yanling; Zhu, Guoliang; Xing, Hui; Shu, Da; Sun, Baode; Wang, Jun

2017-08-22

The microstructure of continuously hot-dip galvanizing Zn-Mg coating was investigated in order to obtain the mechanism of the effects of Mg on the corrosion resistance. In this paper, the vertical section of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner was calculated. The results indicates that the phase composition of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner is the same as Zn-Mg binary phase diagram, suggesting Al in the Zn-Mg (ZM) coatings mainly concentrates on the interfacial layer between the coating and steel substrate. The microstructure of continuously hot-dip galvanizing ZM coatings with 0.20 wt % Al containing 1.0-3.0 wt % Mg was investigated using tunneling electron microscopy (TEM). The morphology of Zn in the coating changes from bulk to strip and finally to mesh-like, and the MgZn₂ changes from rod-like to mesh-like with the Mg content increasing. Al in the ZM coatings mainly segregates at the Fe₂Al₅ inhibition layer and the Mg added to the Zn bath makes this inhibition layer thinner and uneven. Compared to GI coating, the time of the first red rust appears increases by more than two-fold and expansion rate of red rust reduces by more than four-fold in terms of salt spray experiment. The ZM coating containing 2.0 wt % Mg has the best corrosion resistance. The enhanced corrosion resistance of ZM coatings mainly depends on different corrosion products.

CuMn1.8O4 protective coatings on metallic interconnects for prevention of Cr-poisoning in solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Sun, Zhihao; Wang, Ruofan; Nikiforov, Alexey Y.; Gopalan, Srikanth; Pal, Uday B.; Basu, Soumendra N.

2018-02-01

Cr-poisoning of the cathodes due to the presence of metallic interconnects is detrimental to the performance of intermediate temperature solid oxide fuel cell stacks. Applying a protective coating on the interconnect is an effective solution to preventing Cr-poisoning. In this study, the application of a protective CuMn1.8O4 spinel coating is explored. Dense coatings are deposited on both metallic flat plates and meshes by electrophoretic deposition followed by thermal densification steps. The coating is found to be a mixture of Mn3O4 and cubic spinel phases at room temperature but is a pure cubic spinel phase between 750 °C and 850 °C. A reaction layer between the Cr2O3 scale at the coating/interconnect interface and CuMn1.8O4 coating is found to be a mixture of (Cu,Mn,Cr)3-xO4 cubic spinel phases with Cr-rich precipitates believed to be Cr2O3, indicating that the coating layer acts as a Cr getter. Solubility experiments show that 1 mol of the CuMn1.8O4 phase can getter at least 1.83 mol of Cr2O3 at 800 °C. Electrochemical testing of cells in the presence of coated interconnects show that the CuMn1.8O4 coating getters Cr effectively for 12 days at 800 °C, leading to no performance loss of the cell due to Cr-poisoning.

Influence of heat-treated Al-Si coating on the weldability and microstructural inhomogeneity for hot stamped steel resistance nut projection welds

NASA Astrophysics Data System (ADS)

Chun, Eun-Joon; Lim, Sung-Sang; Kim, Young-Tae; Nam, Ki-Sung; Kim, Young-Min; Park, Young-Whan; Murugan, Siva Prasad; Park, Yeong-Do

2018-03-01

Resistance nut projection weldability of Al-Si coated hot stamped steel (HSS) was investigated under the viewpoint of weldable current range and joint strength (pull-out load). The microstructural inhomogeneities in the welds were also studied in order to elucidate the factors affecting the joint strength of the welds. The weldability of the given Al-Si coated HSS was compared with the weldability of an identical HSS without the Al-Si coating (Al-Si coating was polished out) and Zn coated dual phase steel. The weldable current range of Al-Si coated HSS was found to be narrower than that of the other materials. Furthermore, the average pull-out load within the weldable current range of the Al-Si coated HSS was the lowest among the three materials. The reason for poor weld mechanical property of the Al-Si coated hot-stamped steel was attributed to the microstructural inhomogeneities such as unmixed Al-Si coating layer at the edge of the nugget and the second phase Fe3(Al, Si) intermetallic compound. The formation of Fe3(Al, Si) phase was attributed to the solidification segregation of Al and Si during the weld solidification and was confirmed with the numerical analysis of solidification segregation.

Ferromagnetism in spin-coated cobalt-doped TiO2 thin films and the role of crystalline phases

NASA Astrophysics Data System (ADS)

Salazar Cuaila, J. L.; Alayo, W.; Avellaneda, César O.

2017-11-01

Two sets of Cobalt-doped (1-10% at) TiO2 thin films, for different molar concentrations of the Ti precursor (0.3 and 0.5 mol/L), have been deposited onto Si substrates by combining the Sol Gel process and the Spin Coating technique. The structure of the samples was studied by X-ray reflectivity (XRR) and X-ray diffraction (XRD) and their magnetic properties were analyzed by magnetization measurements as a function of the applied magnetic field. The XRR results provided the thickness and interfacial roughness of the films, while XRD patterns revealed the crystalline phases and lattice parameters. Room temperature ferromagnetic behaviour was observed for some of the atomic Co concentrations by the magnetization measurements. This behaviour has been correlated to the crystalline phases, which were found to be modified by both the molar ratio of Ti precursor and the concentration of the Co dopant. A suppression of ferromagnetism is observed for some atomic Co fractions and it was attributed to the presence of secondary crystalline phases.

Influence of process parameters on plasma electrolytic surface treatment of tantalum for biomedical applications

NASA Astrophysics Data System (ADS)

Sowa, Maciej; Woszczak, Maja; Kazek-Kęsik, Alicja; Dercz, Grzegorz; Korotin, Danila M.; Zhidkov, Ivan S.; Kurmaev, Ernst Z.; Cholakh, Seif O.; Basiaga, Marcin; Simka, Wojciech

2017-06-01

This work aims to quantify the effect of anodization voltage and electrolyte composition used during DC plasma electrolytic oxidation (PEO), operated as a 2-step process, on the surface properties of the resulting oxide coatings on tantalum. The first step consisted of galvanostatic anodization (150 mA cm-2) of the tantalum workpiece up to several limiting voltages (200, 300, 400 and 500 V). After attaining the limiting voltage, the process was switched to voltage control, which resulted in a gradual decrease of the anodic current density. The anodic treatment was realized in a 0.5 M Ca(H2PO2)2 solution, which was then modified by the addition of 1.15 M Ca(HCOO)2 as well as 1.15 M and 1.5 M Mg(CH3COO)2. The increasing voltage of anodization led to the formation of thicker coatings, with larger pores and enriched with electrolytes species to a higher extent. The solutions containing HCOO- and CH3COO- ions caused the formation of coatings which were slightly hydrophobic (high contact angle). In the case of the samples anodized up to 500 V, scattered crystalline deposits were observed. Bioactive phases, such as hydroxyapatite, were detected in the treated oxide coatings by XRD and XPS.

Laser cladding assisted by friction stir processing for preparation of deformed crack-free Ni-Cr-Fe coating with nanostructure

NASA Astrophysics Data System (ADS)

Xie, Siyao; Li, Ruidi; Yuan, Tiechui; Chen, Chao; Zhou, Kechao; Song, Bo; Shi, Yusheng

2018-02-01

Although laser cladding has find its widespread application in surface hardening, this technology has been significantly limited by the solidification crack, which usually initiates along grain boundary due to the brittle precipitation in grain boundary and networks formation during the laser rapid melting/solidification process. This paper proposed a novel laser cladding technology assisted by friction stir processing (FSP) to eliminate the usual metallurgical defects by the thermomechanical coupling effect of FSP with the Ni-Cr-Fe as representative coating material. By the FSP assisted laser cladding, the crack in laser cladding Ni-Cr-Fe coating was eliminated and the coarse networks of laser cladding coating was transformed into dispersed nanoparticles. Moreover, the plastic layers with thicknesses 47-140 μm can be observed, with gradient grain refinement from substrate to the top surface in which grain size reached 300 nm and laser photocoagulation net second phase crushed in the layer. In addition, cracks closed in the plastic zone. The refinement of grain resulted the hardness increased to over 400 HV, much higher than the 300 HV of the laser cladding structure. After FSP, the friction coefficient decreased from 0.6167 to 0.5645 which promoted the wear resistance.

Solution-processed copper-nickel nanowire anodes for organic solar cells

NASA Astrophysics Data System (ADS)

Stewart, Ian E.; Rathmell, Aaron R.; Yan, Liang; Ye, Shengrong; Flowers, Patrick F.; You, Wei; Wiley, Benjamin J.

2014-05-01

This work describes a process to make anodes for organic solar cells from copper-nickel nanowires with solution-phase processing. Copper nanowire films were coated from solution onto glass and made conductive by dipping them in acetic acid. Acetic acid removes the passivating oxide from the surface of copper nanowires, thereby reducing the contact resistance between nanowires to nearly the same extent as hydrogen annealing. Films of copper nanowires were made as oxidation resistant as silver nanowires under dry and humid conditions by dipping them in an electroless nickel plating solution. Organic solar cells utilizing these completely solution-processed copper-nickel nanowire films exhibited efficiencies of 4.9%.This work describes a process to make anodes for organic solar cells from copper-nickel nanowires with solution-phase processing. Copper nanowire films were coated from solution onto glass and made conductive by dipping them in acetic acid. Acetic acid removes the passivating oxide from the surface of copper nanowires, thereby reducing the contact resistance between nanowires to nearly the same extent as hydrogen annealing. Films of copper nanowires were made as oxidation resistant as silver nanowires under dry and humid conditions by dipping them in an electroless nickel plating solution. Organic solar cells utilizing these completely solution-processed copper-nickel nanowire films exhibited efficiencies of 4.9%. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr01024h

Formation of ZrO{sub 2} in coating on Mg–3 wt.%Al–1 wt.%Zn alloy via plasma electrolytic oxidation: Phase and structure of zirconia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Kang Min; Kim, Yeon Sung; Yang, Hae Woong

2015-01-15

An investigation of the coating structure formed on Mg–3 wt.%Al–1 wt.%Zn alloy sample subjected to plasma electrolytic oxidation was examined by field-emission transmission electron microscopy. The plasma electrolytic oxidation process was conducted in a phosphoric acid electrolyte containing K{sub 2}ZrF{sub 6} for 600 s. Microstructural observations showed that the coating consisting of MgO, MgF{sub 2}, and ZrO{sub 2} phases was divided into three distinctive parts, the barrier, intermediate, and outer layers. Nanocrystalline MgO and MgF{sub 2} compounds were observed mainly in the barrier layer of ~ 1 μm thick near to the substrate. From the intermediate to outer layers, variousmore » ZrO{sub 2} polymorphs appeared due to the effects of the plasma arcing temperature on the phase transition of ZrO{sub 2} compounds during the plasma electrolytic oxidation process. In the outer layer, MgO compound grew in the form of a dendrite-like structure surrounded by cubic ZrO{sub 2}. - Highlights: • The barrier layer containing MgO and MgF{sub 2} was observed near to the Mg substrate. • In the intermediate layer, m-, t-, and o-ZrO{sub 2} compounds were additionally detected. • The outer layer contained MgO with the dendrite-like structure surrounded by c-ZrO{sub 2}. • The grain sizes of compounds in oxide layer increased from barrier to outer layer.« less

Inherent and Apparent Scattering Properties of Coated or Uncoated Spheres Embedded in an Absorbing Host Medium

NASA Technical Reports Server (NTRS)

Yang, P.; Gao, B.-C.; Wiscombe, W. J.; Mishchenko, M. I.; Platnick, S.; Huang, H.-L.; Baum, B. A.; Hu, Y. X.; Winkler, D,; Tsay, S.-C.;

Photo-acoustic excitation and detection of guided ultrasonic waves in bone samples covered by a soft coating layer

NASA Astrophysics Data System (ADS)

Zhao, Zuomin; Moilanen, Petro; Karppinen, Pasi; Määttä, Mikko; Karppinen, Timo; Hæggström, Edward; Timonen, Jussi; Myllylä, Risto

2012-12-01

Photo-acoustic (PA) excitation was combined with skeletal quantitative ultrasound (QUS) for multi-mode ultrasonic assessment of human long bones. This approach permits tailoring of the ultrasonic excitation and detection so as to efficiently detect the fundamental flexural guided wave (FFGW) through a coating of soft tissue. FFGW is a clinically relevant indicator of cortical thickness. An OPO laser with tunable optical wavelength, was used to excite a photo-acoustic source in the shaft of a porcine femur. Ultrasonic signals were detected by a piezoelectric transducer, scanning along the long axis of the bone, 20-50 mm away from the source. Five femurs were measured without and with a soft coating. The coating was made of an aqueous gelatin-intralipid suspension that optically and acoustically mimicked real soft tissue. An even coating thickness was ensured by using a specific mold. The optical wave length of the source (1250 nm) was tuned to maximize the amplitude of FFGW excitation at 50 kHz frequency. The experimentally determined FFGW phase velocity in the uncoated samples was consistent with that of the fundamental antisymmetric Lamb mode (A0). Using appropriate signal processing, FFGW was also identified in the coated bone samples, this time with a phase velocity consistent with that theoretically predicted for the first mode of a fluid-solid bilayer waveguide (BL1). Our results suggest that photo-acoustic quantitative ultrasound enables assessment of the thickness-sensitive FFGW in bone through a layer of soft tissue. Photo-acoustic characterization of the cortical bone thickness may thus become possible.

Coating stainless steel plates with Ag/TiO2 for chlorpyrifos decontamination

NASA Astrophysics Data System (ADS)

Abdel Fattah, Wafa I.; Gobara, Mohammed M.; El-Hotaby, Walid; Mostafa, Sherif F. M.; Ali, Ghareib W.

2016-05-01

Spray coatings of either nanosilver (Ag), titanium (TiO2) or nanosilver titanium (Ag/TiO2) on stainless steel substrates prepared by sol-gel process were successfully achieved. The efficiency of the Ag/TiO2 coat onto 316 stainless steel surface towards cloropyrifos degradation as a chemical warfare agent (CWA) was proved. The crystalline structure and morphological characterization, as well as surface roughness measurements, were assessed. X-ray diffraction results proved the crystalline TiO2 anatase phase. The uniform distribution of Ag along with TiO2 nanoparticles was evidenced through transmission electron microscopy and scanning electron microscopy mapping. The hydrophilic nature of individual Ag, TiO2 and Ag/TiO2 coats was proved by contact angle measurements. The loading of Ag nanoparticles influenced positively the Ag/TiO2 coats surface roughness. The photocatalytic cloropyrifos degradation achieved about 50% within one-hour post UV treatment proving, therefore, the promising Ag/TiO2 continued decontamination efficiency. In conclusion, tuning the physical and morphological properties of TiO2 coated on stainless steel surface could be significantly enhanced by Ag nanoparticles incorporation. The developed Ag/TiO2 coat could be conveniently applied as CWA decontaminant.

Microstructure and Mechanical Properties of Cr-SiC Particles-Reinforced Fe-Based Alloy Coating

NASA Astrophysics Data System (ADS)

Wang, Fu-cheng; Du, Xiao-dong; Zhan, Ma-ji; Lang, Jing-wei; Zhou, Dan; Liu, Guang-fu; Shen, Jian

2015-12-01

In this study, SiC particles were first coated with Cr to form a layer that can protect the SiC particles from dissolution in the molten pool. Then, the Cr-SiC powder was injected into the tail of molten pool during plasma-transferred arc welding process (PTAW), where the temperature was relatively low, to prepare Cr-SiC particles reinforced Fe-based alloy coating. The microstructure and phase composition of the powder and surface coatings were analyzed, and the element distribution and hardness at the interfacial region were also evaluated. The protective layer consists of Cr3Si, Cr7C3, and Cr23C6, which play an important role in the microstructure and mechanical properties. The protective layer is dissolved in the molten pool forming a flocculent region and a transition region between the SiC particles and the matrix. The tribological performance of the coating was also assessed using a ring-block sliding wear tester with GGr15 grinding ring under 490 and 980 N load. Cr-SiC particles-reinforced coating has a lower wear rate than the unreinforced coating.

BIOGEOCHEMICAL PROCESSES CONTROLLING ARSENIC SPECIATION AND BIOTRANSFORMATION IN GRANULAR FERRIC HYDROXIDE COATED SAND

EPA Science Inventory

Arsenic mobilization from solid phase Fe (III) hydroxides is an issue of concern, as water-borne arsenic can migrate into pristine environments, endangering aquatic and human life. In general, metal oxide (hydroxides) exerts a dominating effect on the fate and transport of arseni...

An Application of X-Ray Fluorescence as Process Analytical Technology (PAT) to Monitor Particle Coating Processes.

PubMed

Nakano, Yoshio; Katakuse, Yoshimitsu; Azechi, Yasutaka

2018-06-01

An attempt to apply X-Ray Fluorescence (XRF) analysis to evaluate small particle coating process as a Process Analytical Technologies (PAT) was made. The XRF analysis was used to monitor coating level in small particle coating process with at-line manner. The small particle coating process usually consists of multiple coating processes. This study was conducted by a simple coating particles prepared by first coating of a model compound (DL-methionine) and second coating by talc on spherical microcrystalline cellulose cores. The particles with two layered coating are enough to demonstrate the small particle coating process. From the result by the small particle coating process, it was found that the XRF signal played different roles, resulting that XRF signals by first coating (layering) and second coating (mask coating) could demonstrate the extent with different mechanisms for the coating process. Furthermore, the particle coating of the different particle size has also been investigated to evaluate size effect of these coating processes. From these results, it was concluded that the XRF could be used as a PAT in monitoring particle coating processes and become powerful tool in pharmaceutical manufacturing.

Core-shell microstructured nanocomposites for synergistic adjustment of environmental temperature and humidity

NASA Astrophysics Data System (ADS)

Zhang, Haiquan; Yuan, Yanping; Zhang, Nan; Sun, Qingrong; Cao, Xiaoling

2016-11-01

The adjustment of temperature and humidity is of great importance in a variety of fields. Composites that can perform both functions are prepared by mixing phase change materials (PCMs) with hygroscopic materials. However, the contact area between the adsorbent and humid air is inevitably decreased in such structures, which reduces the number of mass transfer channels for water vapor. An approach entailing the increase in the mass ratio of the adsorbent is presented here to improve the adsorption capacity. A core-shell CuSO4/polyethylene glycol (PEG) nanomaterial was developed to satisfy the conflicting requirements of temperature control and dehumidification. The results show that the equilibrium adsorption capacity of the PEG coating layer was enhanced by a factor of 188 compared with that of the pure PEG powder. The coating layer easily concentrates vapor, providing better adsorption properties for the composite. Furthermore, the volume modification of the CuSO4 matrix was reduced by 80% by the PEG coated layer, a factor that increases the stability of the composite. For the phase change process, the crystallization temperature of the coating layer was adjusted between 37.2 and 46.3 °C by interfacial tension. The core-shell CuSO4/PEG composite reported here provides a new general approach for the simultaneous control of temperature and humidity.

Processing of AlCoCrFeNiTi high entropy alloy by atmospheric plasma spraying

NASA Astrophysics Data System (ADS)

Löbel, M.; Lindner, T.; Kohrt, C.; Lampke, T.

2017-03-01

High Entropy Alloys (HEA) are gaining increasing interest due to their unique combination of properties. Especially the combination of high mechanical strength and hardness with distinct ductility makes them attractive for numerous applications. One interesting alloy system that exhibits excellent properties in bulk state is AlCoCrFeNiTi. A high strength, wear resistance and high-temperature resistance are the necessary requirements for the application in surface engineering. The suitability of blended, mechanically ball milled and inert gas atomized feedstock powders for the development of atmospheric plasma sprayed (APS) coatings is investigated in this study. The ball milled and inert gas atomized powders were characterized regarding their particle morphology, phase composition, chemical composition and powder size distribution. The microstructure and phase composition of the thermal spray coatings produced with different feedstock materials was investigated and compared with the feedstock material. Furthermore, the Vickers hardness (HV) was measured and the wear behavior under different tribological conditions was tested in ball-on-disk, oscillating wear and scratch tests. The results show that all produced feedstock materials and coatings exhibit a multiphase composition. The coatings produced with inert gas atomized feedstock material provide the best wear resistance and the highest degree of homogeneity.

Silica-based ionogels: nanoconfined ionic liquid-rich fibers for headspace solid-phase microextraction coupled with gas chromatography-barrier discharge ionization detection.

PubMed

Pena-Pereira, Francisco; Marcinkowski, Lukasz; Kloskowski, Adam; Namieśnik, Jacek

2014-12-02

In this work, hybrid silica-based materials with immobilized ionic liquids (ILs) were prepared by sol-gel technology and evaluated as solid-phase microextraction (SPME) fiber coatings. High loadings of the IL 1-methyl-3-butylimidazolium bis(trifluoromethylsulfonyl)imide ([C4MIM][TFSI]) were confined within the hybrid network. Coatings composition and morphology were evaluated using scanning electron microscopy and energy dispersive X-ray spectrometry. The obtained ionogel SPME fibers exhibited high extractability for aromatic volatile compounds, yielding good sensitivity and precision when combined with a gas chromatograph with barrier ionization discharge (GC-BID) detection. A central composite design was used for assessing the effect of experimental parameters on the extraction process. Under optimized conditions, the proposed ionogel SPME fiber coatings enabled the achievement of excellent enrichment factors (up to 7400). The limits of detection (LODs) were found in the range 0.03-1.27 μg L(-1), whereas the repeatability and fiber-to-fiber reproducibility were 5.6% and 12.0% on average, respectively. Water samples were analyzed by the proposed methodology, showing recovery values in the range of 88.7-113.9%. The results obtained in this work suggest that ionogels can be promising coating materials for future applications of SPME and related sample preparation techniques.

Structural evolution of plasma-sprayed nanoscale 3 mol% and 5 mol% yttria-stabilized zirconia coatings during sintering

NASA Astrophysics Data System (ADS)

Zhao, Yan; Gao, Yang

2017-12-01

The microstructure of plasma-sprayed nanostructured yttria-stabilized zirconia (YSZ) coatings may change during high-temperature exposure, which would influence the coating performance and service lifetime. In this study, the phase structure and the microstructural evolution of 3YSZ (zirconia-3 mol% yttria) and 5YSZ (zirconia-5 mol% yttria) nanostructured coatings were investigated by means of sintering at 1400 °C for 50-100 h. The microhardness, elastic moduli, and thermal shock cycles of the 3YSZ and 5YSZ nanostructured coatings were also investigated. The results showed that the redistribution of yttrium ions at 1400 °C caused the continuous increase of monoclinic-phase zirconia, but no obvious inter-splat cracking formed at the cross-sections, even after 100 h. Large voids appeared around the nanoporous zone because of the sintering of nanoscale granules upon high-temperature exposure. The microhardness and elastic moduli of the nanostructured coatings first increased and then decreased with increasing sintering times. The growth rate of the nanograins in the 3YSZ coating was lower than that in 5YSZ, which slowed the changes in 3YSZ coating porosity during sintering. Although the 3YSZ coating was prone to monoclinic phase transition, the experimental results showed that the thermal shock resistance of the 3YSZ coating was better than that of the 5YSZ coating.

Neutron and X-ray diffraction of plasma-sprayed zirconia-yttria thermal barrier coatings

NASA Technical Reports Server (NTRS)

Shankar, N. R.; Herman, H.; Singhal, S. P.; Berndt, C. C.

1984-01-01

ZrO2-7.8mol. pct. YO1.5, a fused powder, and ZrO2-8.7mol. pct. YO1.5, a prereacted powder, were plasma-sprayed onto steel substrates. Neutron diffraction and X-ray diffraction of the as-received powder, the powder plasma sprayed into water, as-sprayed coatings, and coatings heat-treated for 10 and 100 h were carried out to study phase transformations and ordering of the oxygen ions on the oxygen sublattice. The as-received fused powder has a much lower monoclinic percentage than does the pre-reacted powder, this resulting in a much lower monoclinic percentage in the coating. Heat treatment increases the percentages of the cubic and monoclinic phases, while decreasing the tetragonal content. An ordered tetragonal phase is detected by the presence of extra neutron diffraction peaks. These phase transformations and ordering will result in volume changes. The implications of these transformations on the performance of partially stabilized zirconia thermal barrier coatings is discussed.

Investigation of absorptance and emissivity of thermal control coatings on Mg–Li alloys and OES analysis during PEO process

PubMed Central

Yao, Zhongping; Xia, Qixing; Ju, Pengfei; Wang, Jiankang; Su, Peibo; Li, Dongqi; Jiang, Zhaohua

2016-01-01

Thermal control ceramic coatings on Mg–Li alloys have been successfully prepared in silicate electrolyte system by plasma electrolytic oxidation (PEO) method. The PEO coatings are mainly composed of crystallized Mg2SiO4 and MgO, which have typical porous structure with some bulges on the surface; OES analysis shows that the plasma temperature, which is influenced by the technique parameters, determines the formation of the coatings with different crystalline phases and morphologies, combined with “quick cooling effect” by the electrolyte; and the electron concentration is constant, which is related to the electric spark breakdown, determined by the nature of the coating and the interface of coating/electrolyte. Technique parameters influence the coating thickness, roughness and surface morphology, but do not change the coating composition in the specific PEO regime, and therefore the absorptance (αS) and emissivity (ε) of the coatings can be adjusted by the technique parameters through changing thickness and roughness in a certain degree. The coating prepared at 10 A/dm2, 50 Hz, 30 min and 14 g/L Na2SiO3 has the minimum value of αS (0.35) and the maximum value of ε (0.82), with the balance temperature of 320 K. PMID:27383569

Reflectance Infrared Spectroscopy on Operating Surface Acoustic Wave Chemical Sensors During Exposure to Gas-Phase Analytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hierlemann, A.; Hill, M.; Ricco, A.J.

We have developed instrumentation to enable the combination of surface acoustic wave (SAW) sensor measurements with direct, in-situ molecular spectroscopic measurements to understand the response of the SAW sensors with respect to the interfacial chemistry of surface-confined sensing films interacting with gas-phase analytes. Specifically, the instrumentation and software was developed to perform in-situ Fourier-transform infrared external-reflectance spectroscopy (FTIR-ERS) on operating SAW devices during dosing of their chemically modified surfaces with analytes. By probing the surface with IR spectroscopy during gas exposure, it is possible to understand in unprecedented detail the interaction processes between the sorptive SAW coatings and the gaseousmore » analyte molecules. In this report, we provide details of this measurement system, and also demonstrate the utility of these combined measurements by characterizing the SAW and FTIR-ERS responses of organic thin-film sensor coatings interacting with gas-phase analytes.« less

Microstructure, thermal shock resistance and thermal emissivity of plasma sprayed LaMAl11O19 (M = Mg, Fe) coatings for metallic thermal protection systems

NASA Astrophysics Data System (ADS)

Liu, Hong-Zhi; Ouyang, Jia-Hu; Liu, Zhan-Guo; Wang, Ya-Ming

2013-04-01

LaMAl11O19 (M = Mg, Fe) ceramic coatings were plasma-sprayed on nickel-based superalloy with NiCoCrAlYTa as the bond coat. The microstructure, thermal shock resistance and thermal emissivity of these two ceramic coatings were investigated. LaMAl11O19 coatings exhibit a characteristic of stacked lamellae, and consist mainly of a magnetoplumbite-type hexaaluminate phase and an amorphous phase. During thermal cycling, the amorphous phase disappears and a LaAlO3 phase is formed at temperatures of both 1000 and 1200 °C. The thermal cycling numbers of LaMgAl11O19 coating are 102 at 1000 °C and 42 at 1200 °C; LaFeAl11O19 has a thermal cycling lifetime of 87 at 1000 °C and 30 at 1200 °C, respectively. Normal spectral emissivity of nickel-based superalloy is about 0.2 over the whole wavelength range of 3-14 μm. However, the emissivity of LaFeAl11O19 coating is about 0.7 at short wavelengths and above 0.9 in the wavelength range of 7-14 μm.

Impact of organic coating on optical growth of ammonium sulfate particles.

PubMed

Robinson, Carly B; Schill, Gregory P; Zarzana, Kyle J; Tolbert, Margaret A

2013-01-01

Light extinction by particles in Earth's atmosphere is strongly dependent on particle size, chemical composition, hygroscopic growth properties, and particle mixing state. Here, the influence of an organic coating on particle optical growth was studied. The particle optical growth factor, fRHext, was measured using cavity ring-down aerosol extinction spectroscopy at 532 nm. The particles were composed of ammonium sulfate (AS), 1,2,6-hexanetriol, and mixed particles containing a wet or dry ammonium sulfate core and a 1,2,6-hexanetriol coating. Dry, coated particles were generated by atomization followed by drying. Wet, coated particles were formed via liquid-liquid phase separation (LLPS). LLPS was achieved by deliquescing and then drying the particles to a relative humidity (RH) between the phase separation RH and the efflorescence RH. For the LLPS particles, the fRHext at each RH was between the fRHext of ammonium sulfate and that of 1,2,6-hexanetriol. In contrast, for the mixed dry, coated particles, the fRHext was the same as 1,2,6-hexanetriol particles. At room temperature, the water uptake properties of AS coated with 1,2,6-hexanetriol are largely dictated by the phase of the AS. Thus, the total water uptake depends on the RH history of the particle and the resulting phase of AS.

Investigation of proposed process sequence for the array automated assembly task, phases 1 and 2

NASA Technical Reports Server (NTRS)

Mardesich, N.; Garcia, A.; Eskenas, K.

1980-01-01

Progress was made on the process sequence for module fabrication. A shift from bonding with a conformal coating to laminating with ethylene vinyl acetate and a glass superstrate is recommended for further module fabrication. The processes that were retained for the selected process sequence, spin-on diffusion, print and fire aluminum p+ back, clean, print and fire silver front contact and apply tin pad to aluminum back, were evaluated for their cost contribution.

Preparation and in vitro evaluation of plasma-sprayed Mg(2)SiO(4) coating on titanium alloy.

PubMed

Xie, Youtao; Zhai, Wanyin; Chen, Lei; Chang, Jiang; Zheng, Xuebin; Ding, Chuanxian

2009-07-01

In this paper, chemically synthesized Mg(2)SiO(4) (MS) powder was plasma-sprayed onto a titanium alloy substrate to evaluate its application potentials in biomedicine. The phase composition and surface morphology of the MS coating were analyzed. Results showed that the MS coating was composed mainly of Mg(2)SiO(4) phase, with a small amount of MgO and glass phases. Mechanical testing showed that the coating exhibited good adhesion strength to the substrate due to the close thermal expansion coefficient between the MS ceramic and the titanium alloy substrate. The measured bonding strength was as high as 41.5+/-5.3MPa, which is much higher than the traditional HA coating. In vitro cytocompatibility evaluation of the MS coating was performed using canine bone marrow stem cells (MSCs). The MSCs exhibited good adhesion, proliferation and differentiation behavior on the MS coating surface, which can be explained by the high protein adsorption capability of the MS coating, as well as the stimulatory effects of Mg and Si ions released from the coating. The proliferation rate of the MSCs on MS coating was very close to that on the hydroxylapatite (HA) coating. Alkaline phosphatase (ALP) activity analysis demonstrated that the ALP level of the MSCs on the MS coating remained high even after 21days, implying that the surface characteristics of the coating are beneficial for the differentiation of MSCs. In summary, our results suggest that MS coating might be a new approach to prepare bone implants.

Phase Evolution of YBa2Cu3O7-x films by all-chemical solution deposition route for coated conductors

NASA Astrophysics Data System (ADS)

Zhao, Yue; Tang, Xiao; Wu, Wei; Grivel, Jean-Claude

2014-05-01

In order to understand the all-chemical-solution-deposition (CSD) processes for manufacturing coated conductors, we investigated the phase evolution of YBa2Cu3O7 (YBCO) films deposited by a low-fluorine metal-organic solution deposition (LF-MOD) method on CSD derived Ce0.9La0.1O2/Gd2Zr2O7/NiW. It is shown that the phase transition from the pyrolyzed film to fully converted YBCO film in the LF-MOD process is similar to that in typical trifluoroacetates-metal organic deposition (TFA-MOD) processes even though the amount of TFA in the solution is reduced by almost one half compared with typical TFA-MOD cases. Moreover, we found that the formation of impurities (mainly BaCeO3, NiWO4 and NiO) is strongly related to the annealing temperature, i.e., the diffusion controlled reactions become intensive from 760 oC, which might be connected with the poor structural and superconducting properties of the films deposited at high sintering temperatures. Based on these results, the optimized growth conditions of YBCO films were established, and a high critical current density (Jc) of about 2 MA/cm2 (77 K, self field) is achieved in a 200 nm thick YBCO film in the architecture made by our all CSD route.

Wear Characteristic of Stellite 6 Alloy Hardfacing Layer by Plasma Arc Surfacing Processes

PubMed Central

Zhou, Xiaowei

2017-01-01

The microstructure and wear resistance of Stellite 6 alloy hardfacing layer at two different temperatures (room temperature and 300°C) were investigated by plasma arc surfacing processes on Q235 Steel. Tribological test was conducted to characterize the wear property. The microstructure of Stellite 6 alloy coating mainly consists of α-Co and (Cr, Fe)7C3 phases. The friction coefficient of Stellite 6 alloys fluctuates slightly under different loads at 300°C. The oxide layer is formed on the coating surface and serves as a special lubricant during the wear test. Abrasive wear is the dominant mechanism at room temperature, and microploughing and plasticity are the key wear mechanisms at 300°C. PMID:29359005

Microstructure control of Al-Cu films for improved electromigration resistance

DOEpatents

Frear, D.R.; Michael, J.R.; Romig, A.D. Jr.

1994-04-05

A process for the forming of Al-Cu conductive thin films with reduced electromigration failures is useful, for example, in the metallization of integrated circuits. An improved formation process includes the heat treatment or annealing of the thin film conductor at a temperature within the range of from 200 C to 300 C for a time period between 10 minutes and 24 hours under a reducing atmosphere such as 15% H[sub 2] in N[sub 2] by volume. Al-Cu thin films annealed in the single phase region of a phase diagram, to temperatures between 200 C and 300 C have [theta]-phase Al[sub 2] Cu precipitates at the grain boundaries continuously become enriched in copper, due, it is theorized, to the formation of a thin coating of [theta]-phase precipitate at the grain boundary. Electromigration behavior of the aluminum is, thus, improved because the [theta]-phase precipitates with copper hinder aluminum diffusion along the grain boundaries. Electromigration, then, occurs mainly within the aluminum grains, a much slower process. 5 figures.

Improving the corrosion properties of magnesium AZ31 alloy GTA weld metal using microarc oxidation process

NASA Astrophysics Data System (ADS)

Siva Prasad, M.; Ashfaq, M.; Kishore Babu, N.; Sreekanth, A.; Sivaprasad, K.; Muthupandi, V.

2017-05-01

In this work, the morphology, phase composition, and corrosion properties of microarc oxidized (MAO) gas tungsten arc (GTA) weldments of AZ31 alloy were investigated. Autogenous gas tungsten arc welds were made as full penetration bead-on-plate welding under the alternating-current mode. A uniform oxide layer was developed on the surface of the specimens with MAO treatment in silicate-based alkaline electrolytes for different oxidation times. The corrosion behavior of the samples was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy. The oxide film improved the corrosion resistance substantially compared to the uncoated specimens. The sample coated for 10 min exhibited better corrosion properties. The corrosion resistance of the coatings was concluded to strongly depend on the morphology, whereas the phase composition and thickness were concluded to only slightly affect the corrosion resistance.

Surface phase separation, dewetting feature size, and crystal morphology in thin films of polystyrene/poly(ε-caprolactone) blend.

PubMed

Ma, Meng; He, Zhoukun; Li, Yuhan; Chen, Feng; Wang, Ke; Zhang, Qing; Deng, Hua; Fu, Qiang

2012-12-01

Thin films of polystyrene (PS)/poly(ε-caprolactone) (PCL) blends were prepared by spin-coating and characterized by tapping mode force microscopy (AFM). Effects of the relative concentration of PS in polymer solution on the surface phase separation and dewetting feature size of the blend films were systematically studied. Due to the coupling of phase separation, dewetting, and crystallization of the blend films with the evaporation of solvent during spin-coating, different size of PS islands decorated with various PCL crystal structures including spherulite-like, flat-on individual lamellae, and flat-on dendritic crystal were obtained in the blend films by changing the film composition. The average distance of PS islands was shown to increase with the relative concentration of PS in casting solution. For a given ratio of PS/PCL, the feature size of PS appeared to increase linearly with the square of PS concentration while the PCL concentration only determined the crystal morphology of the blend films with no influence on the upper PS domain features. This is explained in terms of vertical phase separation and spinodal dewetting of the PS rich layer from the underlying PCL rich layer, leading to the upper PS dewetting process and the underlying PCL crystalline process to be mutually independent. Copyright © 2012 Elsevier Inc. All rights reserved.

Biocompatibility of hydroxyapatite coatings deposited by pulse electrodeposition technique on the Nitinol superelastic alloy.

PubMed

Marashi-Najafi, F; Khalil-Allafi, J; Etminanfar, M R

2017-07-01

The present study deals with pulse electrochemical deposition of HA on NiTi alloy and in vitro evaluation of coatings. At first step, a thermo-chemical surface modification process was applied to control the Ni release of the alloy. The electrochemical deposition of CaP coatings was examined at both dilute and concentrated solutions. The morphology and the composition of coatings were studied using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Plate like and needle like morphologies were formed for dilute and concentrated solution respectively and HA phase was formed by increasing the pulse current density for both electrolyte. The thickness of the samples was measured using cross sectioning technique. Fibroblast cell culture test on the coated samples revealed that the HA coating obtained by dilute solution shows the best biocompatibility. Also, MTT assay showed the highest cell density and cell proliferation after 5days for the HA coating of dilute solution. The contact angle of samples was measured and the coated samples showed a hydrophilic surface. Soaking the sample in SBF revealed that the crystallization rate of calcium-phosphate compounds is higher on the plate like HA coating as compared to the needle like morphology. The P release of the HA coated samples was measured in a physiological saline solution and the results show that the ions releasing in the plate like coating are less than the needle like coating. It seems that the stability of the plate like coating in biological environments is responsible for the better biocompatibility of the coating. Copyright © 2017 Elsevier B.V. All rights reserved.

Electrically atomised formulations of timolol maleate for direct and on-demand ocular lens coatings.

PubMed

Mehta, Prina; Al-Kinani, Ali A; Haj-Ahmad, Rita; Arshad, Muhammad Sohail; Chang, Ming-Wei; Alany, Raid G; Ahmad, Zeeshan

2017-10-01

Advances in nanotechnology have enabled solutions for challenging drug delivery targets. While the eye presents numerous emerging opportunities for delivery, analysis and sensing; issues persist for conventional applications. This includes liquid phase formulation localisation on the ocular surface once administered as formulated eye-drops; with the vast majority of dosage (>90%) escaping from the administered site due to tear production and various drainage mechanisms. The work presented here demonstrates a single needle electrohydrodynamic (EHD) engineering process to nano-coat (as an on demand and controllable fiber depositing method) the surface of multiple contact lenses rendering formulations to be stationary on the lens and at the bio-interface. The coating process was operational based on ejected droplet charge and glaucoma drug timolol maleate (TM) was used to demonstrate surface coating optimisation, bio-surface permeation properties (flux, using a bovine model) and various kinetic models thereafter. Polymers PVP, PNIPAM and PVP:PNIPAM (50:50%w/w) were used to encapsulate the active. Nano-fibrous and particulate samples were characterised using SEM, FTIR, DSC and TGA to confirm structural and thermal stability of surface coated formulations. More than 52% of nano-structured coatings (for all formulations) were <200nm in diameter. In vitro studies show coatings to exhibit biphasic release profiles; an initial burst release followed by sustained release; with TM-loaded PNIPAM coating releasing most drug after 24h (89.8%). Kinetic modelling (Higuchi, Korsmeyer-Peppas) was indicative of quasi-Fickian diffusion whilst biological evaluation demonstrates adequate ocular tolerability. Results from permeation studies indicate coated lenses are ideal to reduce dosing regimen, which in turn will reduce systemic drug absorption. Florescent microscopy demonstrated probe and probe embedded coating behaviour from lens surface in vitro. The multiple lens surface coating method demonstrates sustained drug release yielding promising results; suggesting both novel device and method to enhance drug activity at the eyes surface which will reduce formulation drainage. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.

Biological influence of Ca/P ratio on calcium phosphate coatings by sol-gel processing.

PubMed

Catauro, M; Papale, F; Sapio, L; Naviglio, S

2016-08-01

The objective of this work has been to develop low temperature sol-gel glass coatings to modify the substrate surface and to evaluate their bioactivity and biocompatibility. Glasses, based on SiO2·CaO·P2O5, were synthesized by the sol-gel technique using tetraethyl orthosilicate, calcium nitrate tetrahydrate and triethyl phosphate as precursors of SiO2, CaO and P2O5, respectively. Those materials, still in the sol phase, have been used to coat substrates by means of the dip-coating technique. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) has been used for characterize coatings and a microstructural analysis has been obtained using scanning electron microscopy (SEM). The potential applications of the coatings in the biomedical field were evaluated by bioactivity and biocompatibility tests. The coated substrate was immersed in simulated body fluid (SBF) for 21days and the hydroxyapatite deposition on its surface was subsequently evaluated via SEM-EDXS analysis, as an index of bone-bonding capability. In order to study the cell behavior and response to our silica based materials, prepared via the sol-gel method, with various Ca/P ratio and coating substrate, we have used the human osteoblast-like U2OS cell line. Copyright © 2016 Elsevier B.V. All rights reserved.

Decreasing Bio-Degradation Rate of the Hydrothermal-Synthesizing Coated Mg Alloy via Pre-Solid-Solution Treatment

PubMed Central

Song, Dan; Li, Cheng; Zhang, Liwen; Ma, Xiaolong; Guo, Guanghui; Zhang, Fan; Jiang, Jinghua; Ma, Aibin

2017-01-01

In this study, we report an effective approach, pre-solid solution (SS) treatment, to reduce the in-vitro bio-degradation rate of the hydrothermal-synthesizing coated Mg–2Zn–Mn–Ca–Ce alloy in Hanks’ solution. Pre-SS treatment alters the microstructure of alloys, which benefits the corrosion resistances of the substrate itself and the formed coating as well. The micro-galvanic corrosion between the secondary phase (cathode) and the α-Mg phase (anode) is relieved due to the reduction of the secondary phase. Meanwhile, coating formed on the SS-treated alloy was compacter than that on as-cast alloy, which provides better protection against initial corrosion. PMID:28773223

New NbCd2 Phase in Niobium-Cadmium Coating Films

NASA Astrophysics Data System (ADS)

Volodin, V. N.; Tuleushev, Yu. Zh.; Zhakanbaev, E. A.; Tsai, K. V.; Rofman, O. V.

2018-02-01

Solid solutions in the form of alloy coatings have been obtained for the first time in the Cd concentration range of 64.5% using ion-plasma sputtering and the codeposition of Nb and Cd ultrafine particles. This supports thermal fluctuation melting and the coalescence of fine particles. A coating of niobium and cadmium layers less than 2 nm thick at 68 at % Cd results in the formation of a new phase identified as NbCd2. The tetragonal fcc phase with lattice parameters a = 0.84357 nm and c = 0.54514 nm forms directly during film coating. XRD data for the identification of the intermetallic compound have been determined. The thermal stability of the NbCd 2 intermetallic compound is limited by 200°C. The properties of the synthesized NbCd 2 phase are typical of semiconductors.

Thermal barrier coating life prediction model

NASA Technical Reports Server (NTRS)

Hillery, R. V.; Pilsner, B. H.; Cook, T. S.; Kim, K. S.

1986-01-01

This is the second annual report of the first 3-year phase of a 2-phase, 5-year program. The objectives of the first phase are to determine the predominant modes of degradation of a plasma sprayed thermal barrier coating system and to develop and verify life prediction models accounting for these degradation modes. The primary TBC system consists of an air plasma sprayed ZrO-Y2O3 top coat, a low pressure plasma sprayed NiCrAlY bond coat, and a Rene' 80 substrate. Task I was to evaluate TBC failure mechanisms. Both bond coat oxidation and bond coat creep have been identified as contributors to TBC failure. Key property determinations have also been made for the bond coat and the top coat, including tensile strength, Poisson's ratio, dynamic modulus, and coefficient of thermal expansion. Task II is to develop TBC life prediction models for the predominant failure modes. These models will be developed based on the results of thermmechanical experiments and finite element analysis. The thermomechanical experiments have been defined and testing initiated. Finite element models have also been developed to handle TBCs and are being utilized to evaluate different TBC failure regimes.

Research on residual stress inside Fe-Mn-Si shape memory alloy coating by laser cladding processing

NASA Astrophysics Data System (ADS)

Ju, Heng; Lin, Cheng-xin; Zhang, Jia-qi; Liu, Zhi-jie

2016-09-01

The stainless Fe-Mn-Si shape memory alloy (SMA) coating was prepared on the surface of AISI 304 stainless steel. The principal residual stress measured by the mechanical hole-drilling method indicates that the Fe-Mn-Si SMA cladding specimen possesses a lower residual stress compared with the 304 stainless steel cladding specimen. The mean stress values of the former and the latter on 10-mm-thick substrate are 4.751 MPa and 7.399 MPa, respectively. What's more, their deformation values on 2-mm-thick substrate are about 0° and 15°, respectively. Meanwhile, the variation trend and the value of the residual stress simulated by the ANSYS finite element software consist with experimental results. The X-ray diffraction (XRD) pattern shows ɛ-martensite exists in Fe-Mn-Si SMA coating, which verifies the mechanism of low residual stress. That's the γ→ɛ martensite phase transformation, which relaxes the residual stress of the specimen and reduces its deformation in the laser cladding processing.

Synthesis of carbon-coated Na2MnPO4F hollow spheres as a potential cathode material for Na-ion batteries

NASA Astrophysics Data System (ADS)

Wu, Ling; Hu, Yong; Zhang, Xiaoping; Liu, Jiequn; Zhu, Xing; Zhong, Shengkui

2018-01-01

Hollow sphere structure Na2MnPO4F/C composite is synthesized through spray drying, following in-situ pyrolytic carbon coating process. XRD results indicate that the well crystallized composite can be successfully synthesized, and no other impurity phases are detected. SEM and TEM results reveal that the Na2MnPO4F/C samples show intact hollow spherical architecture, and the hollow spherical shells with an average thickness of 150 nm-250 nm are composed of nanosized primary particles. Furthermore, the amorphous carbon layer is uniformly coated on the surface of the hollow sphere, and the nanosized Na2MnPO4F particles are well embedded in the carbon networks. Consequently, the hollow sphere structure Na2MnPO4F/C shows enhanced electrochemical performance. Especially, it is the first time that the obvious potential platforms (∼3.6 V) are observed during the charge and discharge process at room temperature.

Characteristics of ZrC/Ni-UDD coatings for a tungsten carbide cutting tool

NASA Astrophysics Data System (ADS)

Chayeuski, V. V.; Zhylinski, V. V.; Rudak, P. V.; Rusalsky, D. P.; Višniakov, N.; Černašėjus, O.

2018-07-01

This work deals with the features of the structure of combined ZrC/Ni-ultradisperse diamonds (UDD) coating synthesized by electroplating and cathode arc evaporation physical vapor deposition (CAE-PVD) techniques on the tungsten carbide WC - 2 wt% Co on cutting inserts to improve tool life. The microstructure, phase composition, and micro-scratch test analysis of the ZrC/Ni-UDD coating were studied. The ZrC/Ni-UDD coating consists of separate phases of zirconium carbide ZrC, α-Ni, and Ni-UDD phase. The surface morphology of the coating shows a pattern with pits, pores, and particles. Separated nanodiamond particles are present in the pores of the combined coating. Therefore, the structure of the bottom layer of Ni-UDD affects the morphology of the surface of the ZrC/Ni-UDD coating. The obtained value of the critical loads on the scratch track of the coating in 26 N proves a sufficiently high value of the adhesion strength of the intermediate Ni-UDD-layer with hard alloy of WC-Co substrate. Due to their unique structure ZrC/Ni-UDD-coatings can be used to increase the durability period of a wood-cutting milling tool for cutting chipboard by CNC machines.

ZnO nanorod array polydimethylsiloxane composite solid phase micro-extraction fiber coating: fabrication and extraction capability.

PubMed

Wang, Dan; Wang, Qingtang; Zhang, Zhuomin; Chen, Guonan

2012-01-21

ZnO nanorod array coating is a novel kind of solid-phase microextraction (SPME) fiber coating which shows good extraction capability due to the nanostructure. To prepare the composite coating is a good way to improve the extraction capability. In this paper, the ZnO nanorod array polydimethylsiloxane (PDMS) composite SPME fiber coating has been prepared and its extraction capability for volatile organic compounds (VOCs) has been studied by headspace sampling the typical volatile mixed standard solution of benzene, toluene, ethylbenzene and xylene (BTEX). Improved detection limit and good linear ranges have been achieved for this composite SPME fiber coating. Also, it is found that the composite SPME fiber coating shows good extraction selectivity to the VOCs with alkane radicals.

TEM Observation of the Ti Interlayer Between SiC Substrates During Diffusion Bonding

NASA Technical Reports Server (NTRS)

Tsuda, Hiroshi; Mori, Shigeo; Halbig, Michael C.; Singh, Mori

2012-01-01

Diffusion bonding was carried out to join SiC to SiC substrates using titanium interlayers. In this study, 10 m and 20 m thick physical vapor deposited (PVD) Ti surface coatings, and 10 and 20 m thick Ti foils were used. Diffusion bonding was performed at 1250 C for PVD Ti coatings and 1200 C for Ti foil. This study investigates the microstructures of the phases formed during diffusion bonding through TEM and selected-area diffraction analysis of a sample prepared with an FIB, which allows samples to be taken from the reacted area. In all samples, Ti3SiC2, Ti5Si3Cx and TiSi2 phases were identified. In addition, TiC and unknown phases also appeared in the samples in which Ti foils were used as interlayers. Furthermore, Ti3SiC2 phases show high concentration and Ti5Si3Cx formed less when samples were processed at a higher temperature and thinner interlayer samples were used. It appears that the formation of microcracks is caused by the presence of intermediate phase Ti5Si3Cx, which has anisotropic thermal expansion, and by the presence of an unidentified Ti-Si-C ternary phase with relatively low Si content.

Characteristics of laser clad α-Ti/TiC+(Ti,W)C1-x/Ti2SC+TiS composite coatings on TA2 titanium alloy

NASA Astrophysics Data System (ADS)

Zhai, Yong-Jie; Liu, Xiu-Bo; Qiao, Shi-Jie; Wang, Ming-Di; Lu, Xiao-Long; Wang, Yong-Guang; Chen, Yao; Ying, Li-Xia

2017-03-01

TiC reinforced Ti matrix composite coating with Ti2SC/TiS lubricant phases in-situ synthesized were prepared on TA2 titanium alloy by laser cladding with different powder mixtures: 40%Ti-19.5%TiC-40.5%WS2, 40%Ti-25.2%TiC-34.8%WS2, 40%Ti-29.4%TiC-30.6%WS2 (wt%). The phase compositions, microstructure, microhardness and tribological behaviors and wear mechanisms of coatings were investigated systematically. Results indicate that the main phase compositions of three coatings are all continuous matrix α-Ti, reinforced phases of (Ti,W)C1-x and TiC, lubricant phases of Ti2SC and TiS. The microhardness of the three different coatings are 927.1 HV0.5, 1007.5 HV0.5 and 1052.3 HV0.5, respectively. Compared with the TA2 titanium alloy (approximately 180 HV0.5), the microhardness of coatings have been improved dramatically. The coefficients of friction and the wear rates of those coatings are 0.41 and 30.98×10-5 mm3 N-1 m-1, 0.30 and 18.92×10-5 mm3 N-1 m-1, 0.34 and 15.98×10-5 mm3 N-1 m-1, respectively. Comparatively speaking, the coating fabricated with the powder mixtures of 40%Ti-25.2%TiC-34.8%WS2 presents superior friction reduction and anti-wear properties and the main wear mechanisms of that are slight plastic deformation and adhesive wear.

National Dam Safety Program. Tivoli Lake Dam (Inventory Number N.Y. 52), Hudson River Basin, Rockland County, New York. Phase I Inspection Report,

DTIC Science & Technology

1980-09-30

3/8" pea gravel., Apply I coat of Uniweld or Sika Dur Hi-Mod over old concrete to insure the proper bonding. V 2. Repeat process one for section over...Bay 1. 3. Chip out cracked concrete along Bays 7 and 8, apply one coat Colma Joint Primer and fill with Colma Joint Sealer (As manufactured by Sika ) 4...deck. Cracked concrete should be repaired with Sika Dur. Hi-Mod and application of low slump nonshrink grout’ made with antihydro cement

Synthesis and Characterization of Zr-BASED Amorphous and Crystalline Composite Coating on Ti Substrate by Laser Cladding

NASA Astrophysics Data System (ADS)

Tang, D. M.; Zhang, D. C.; Peng, W.; Luo, Z. C.; Wu, X. Q.; Wang, Y. M.; Lin, J. G.

2014-02-01

A thin strip of a Zr-based alloy with a composition of Zr60Cu25Fe5Al10 (in atom percent) was used as a raw material, and the composite coatings containing Zr-based amorphous phase and crystallites on Ti substrate were fabricated by a one-step laser cladding method without protection. The microstructure, phase constitution, microhardness and wear properties of the coatings were investigated. The results indicate that the microstructure of the coatings is strongly dependent on the laser scanning speed under the conditions of the laser power of 1300 W and laser beam diameter of 6 mm, and the composite coating mainly containing amorphous phase with a small amount of the crystallites can be obtained at the laser scanning speed of 10 mm/s. The composite coating exhibits much higher microhardness than the pure Ti substrate, and thus it behaves superior wear resistance in comparison with the substrate.

Effect of Hydrogen Exposure on Mechanical and Tribological Behavior of CrxN Coatings Deposited at Different Pressures on IN718

PubMed Central

Obrosov, Aleksei; Sutygina, Alina N.; Volinsky, Alex A.; Manakhov, Anton; Weiß, Sabine; Kashkarov, Egor B.

2017-01-01

In the current study, the properties of the CrxN coatings deposited on the Inconel 718 superalloy using direct current reactive magnetron sputtering are investigated. The influence of working pressure on the microstructure, mechanical, and tribological properties of the CrxN coatings before and after high-temperature hydrogen exposure is studied. The cross-sectional scanning electron micrographs indicate the columnar structure of the coatings, which changes from dense and compact columns to large columns with increasing working pressure. The Cr/N ratio increases from 1.4 to 1.9 with increasing working pressure from 300 to 900 mPa, respectively. X-ray diffraction analysis reveals a change from mixed hcp-Cr2N and fcc-CrN structure to approximately stoichiometric Cr2N phase. After gas-phase hydrogenation, the coating deposited at 300 mPa exhibits the lowest hydrogen absorption at 600 °C of all investigated coatings. The results indicate that the dense mixed cubic and hexagonal structure is preferential for hydrogen permeation resistance due to the presence of cubic phase with higher packing density in comparison to the hexagonal structure. After hydrogenation, no changes in phase composition were observed; however, a small amount of hydrogen is accumulated in the coatings. An increase of coating hardness and elastic modulus was observed after hydrogen exposure. Tribological tests reveal that hydrogenation leads to a decrease of the friction coefficient up to 20%–30%. The best value of 0.25 was reached for hydrogen exposed CrxN coating deposited at 300 mPa. PMID:28772923

Mixed ionic and electronic conducting ceramic membranes for hydrocarbon processing

DOEpatents

Van Calcar, Pamela; Mackay, Richard; Sammells, Anthony F.

2002-01-01

The invention relates to mixed phase materials for the preparation of catalytic membranes which exhibit ionic and electronic conduction and which exhibit improved mechanical strength compared to single phase ionic and electronic conducting materials. The mixed phase materials are useful for forming gas impermeable membranes either as dense ceramic membranes or as dense thin films coated onto porous substrates. The membranes and materials of this invention are useful in catalytic membrane reactors in a variety of applications including synthesis gas production. One or more crystalline second phases are present in the mixed phase material at a level sufficient to enhance the mechanical strength of the mixture to provide membranes for practical application in CMRs.

Separation and Detection of Toxic Gases with a Silicon Micromachined Gas Chromatography System

NASA Technical Reports Server (NTRS)

Kolesar, Edward S.; Reston, Rocky R.

1995-01-01

A miniature gas chromatography (GC) system was designed and fabricated using silicon micromachining and integrated circuit (IC) processing techniques. The silicon micromachined gas chromatography system (SMGCS) is composed of a miniature sample injector that incorporates a 10 microliter sample loop; a 0.9 meter long, rectangular shaped (300 micrometer width and 10 micrometer height) capillary column coated with a 0.2 micrometer thick copper phthalocyanine (CuPc) stationary phase; and a dual detector scheme based upon a CuPc-coated chemiresistor and a commercially available 125 micrometer diameter thermal conductivity detector (TCD) bead. Silicon micromachining was employed to fabricate the interface between the sample injector and the GC column, the column itself, and the dual detector cavity. A novel IC thin-film processing technique was developed to sublime the CuPc stationary phase coating on the column walls that were micromachined in the host silicon wafer substrate and Pyrex (r) cover plate, which were then electrostatically bonded together. The SMGCS can separate binary gas mixtures composed of parts-per-million (ppm) concentrations of ammonia (NH3) and nitrogen dioxide (NO2) when isothermally operated (55-80 degrees C). With a helium carrier gas and nitrogen diluent, a 10 microliter sample volume containing ammonia and nitrogen dioxide injected at 40 psi ((2.8 x 10(exp 5)Pa)) can be separated in less than 30 minutes.

Thermal conductivity of ZrO2-4mol%Y2O3 thin coatings by pulsed thermal imaging method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jang, Byung-Koog; Sun, Jiangang; Kim, Seongwon

Thin ZrO2-4mol% Y2O3 coatings were deposited onto ZrO2 substrates by electron beam-physical vapor deposition. The coated samples revealed a feather-like columnar microstructure. The main phase of the ZrO2-4mol% Y2O3 coatings was the tetragonal phase. To evaluate the influence of the coating’s thickness on the thermal conductivity of thin ZrO2-4mol% Y2O3 coatings, the pulsed thermal imaging method was employed to obtain the thermal conductivity of the coating layer in the two-layer (coating and substrate) samples with thickness between 56 and 337 micrometers. The thermal conductivity of the coating layer was successfully evaluated and compared well with those obtained by the lasermore » flash method for similar coatings. The thermal conductivity of coatings shows an increasing tendency with an increase in the coating’s thickness.« less

Refinement of Promising Coating Compositions for Directionally Cast Eutectics

NASA Technical Reports Server (NTRS)

Strangman, T. E.; Felten, E. J.; Benden, R. S.

1976-01-01

The successful application of high creep strength, directionally solidified gamma/gamma prime-delta (Ni-19.7Cb-6Cr-2.5Al) eutectic superalloy turbine blades requires the development of suitable coatings for airfoil, root and internal blade surfaces. In order to improve coatings for the gamma/gamma prime-delta alloy, the current investigation had the goals of (1) refining promising coating compositions for directionally solidified eutectics, (2) evaluating the effects of coating/ substrate interactions on the mechanical properties of the alloy, and (3) evaluating diffusion aluminide coatings for internal surfaces. Burner rig cyclic oxidation, furnace cyclic hot corrosion, ductility, and thermal fatigue tests indicated that NiCrAlY+Pt(63 to 127 micron Ni-18Cr-12Al-0.3Y + 6 micron Pt) and NiCrAlY(63 to 127 micron Ni-18Cr-12Al-0.3Y) coatings are capable of protecting high temperature gas path surfaces of eutectic alloy airfoils. Burner rig (Mach 0.37) testing indicated that the useful coating life of the 127 micron thick coatings exceeded 1000 hours at 1366 K (2000 deg F). Isothermal fatigue and furnance hot corrosion tests indicated that 63 micron NiCrAlY, NiCrAlY + Pt and platinum modified diffusion aluminide (Pt + Al) coating systems are capable of protecting the relatively cooler surfaces of the blade root. Finally, a gas phase coating process was evaluated for diffusion aluminizing internal surfaces and cooling holes of air-cooled gamma/gamma prime-delta turbine blades.

GSFC specification electronic data processing magnetic recording tape

NASA Technical Reports Server (NTRS)

Tinari, D. F.; Perry, J. L.

1980-01-01

The design requirements are given for magnetic oxide coated, electronic data processing tape, wound on reels. Magnetic recording tape types covered by this specification are intended for use on digital tape transports using the Non-Return-to-Zero-change-on-ones (NRZI) recording method for recording densities up to and including 800 characters per inch (cpi) and the Phase-Encoding (PE) recording method for a recording density of 1600 cpi.

Mechanistic Insights on the Photosensitized Chemistry of a Fatty Acid at the Air/Water Interface

PubMed Central

2016-01-01

Interfaces are ubiquitous in the environment and many atmospheric key processes, such as gas deposition, aerosol, and cloud formation are, at one stage or another, strongly impacted by physical and chemical processes occurring at interfaces. Here, the photoinduced chemistry of an air/water interface coated with nonanoic acid—a fatty acid surfactant we use as a proxy for chemically complex natural aqueous surface microlayers—was investigated as a source of volatile and semivolatile reactive organic species. The carboxylic acid coating significantly increased the propensity of photosensitizers, chosen to mimic those observed in real environmental waters, to partition to the interface and enhance reactivity there. Photochemical formation of functionalized and unsaturated compounds was systematically observed upon irradiation of these coated surfaces. The role of a coated interface appears to be critical in providing a concentrated medium allowing radical–radical reactions to occur in parallel with molecular oxygen additions. Mechanistic insights are provided from extensive analysis of products observed in both gas and aqueous phases by online switchable reagent ion-time of flight-mass spectrometry and by off-line ultraperformance liquid chromatography coupled to a Q Exactive high resolution mass spectrometer through heated electrospray ionization, respectively. PMID:27611489

Plasma spray processing of TiC-based coatings for sliding wear resistance

NASA Astrophysics Data System (ADS)

Mohanty, Mahesh

Titanium carbide-reinforced metallic coatings, produced by plasma spraying, can be used for sliding wear resistant applications. The sliding wear properties of such coatings are governed to a large extent by the strength, structure and stability of the bond interface between the carbide and the metallic phases. In the present investigation, the microstructure and sliding wear properties of plasma sprayed metal-bonded TiC coatings containing up to 90 v/o carbide have been studied. It was shown that alloying of the metallic phase improved carbide retention in TiC cermets due to better interface bonding, and increased wear resistance and lowered sliding coefficient of friction. TiC-based coatings were produced from both physically blended and synthesized feed powders. It was observed that the precursor TiC-based powder morphology and structure greatly affected the plasma sprayed coating microstructures and the resultant physical and mechanical characteristics. Physical blending of powders induced segregation during spraying, leading to somewhat lower deposit efficiencies and coating uniformity, while synthesized and alloyed titanium carbide/metal composite powders reduced problems of segregation and reactions associated with plasma spraying of physically blended powders where the TiC was in direct contact with the plasma jet. To understand oxidation effects of the environment, Ti and TiC-based coatings were produced under low pressure (VPS), air plasma (APS) and shrouded plasma sprayed conditions. APS Ti and TiC-based powders with reactive matrices suffered severe oxidation decomposition during flight, leading to poor deposition efficiencies and oxidized microstructures. High particle temperatures and cold air plasma spraying. Coating oxidation due to reactions of the particles with the surrounding air during spraying reduced coating hardness and wear resistance. TiC-with Ti or Ti-alloy matrix coatings with the highest hardness, density and wear resistance was achieved by spraying under vacuum plasma spray conditions. VPS coating microstructures of synthesized 40, 60 and 80 v/o TiC in Ti10Ni10Cr5Al and 80 v/o TiC in Fe30Cr alloy matrices exhibited fine and uniform distributions of spheroidal carbides. High volume fraction carbides were also obtained with no segregation effects. It was also shown that coatings produced from mechanically blended powders of 50, 70 and 90 vol. % TiC and commercially pure (C.P.) Ti, using low pressure plasma spray process (VPS), had densities >98% and were well bonded to steel, aluminum alloy or titanium alloy substrates. Reductions in jet oxygen contents by the use of an inert gas shroud enabled Ti and TiC-based coatings to be produced which were cleaner and denser than air plasma sprayed and comparable to vacuum plasma sprayed coatings. Direct oxygen concentration measurements in shrouded plasma jets made using an enthalpy probe and a gas analyzer also showed significant reductions in the entrainment of atmospheric oxygen. VPS and shrouded plasma spraying minimized carbide-matrix interface oxidation and improved coating wear resistance. The sliding wear resistance of synthesized coatings was very high and comparable with standard HVOF sprayed WC/Co and Crsb3Csb2/NiCr coatings. Shrouded plasma spray deposits of Crsb3Csb2/NiCr also performed much better than similar air plasma sprayed coatings, as result of reduced oxidation.

Sorption and redox reactions of As(III) and As(V) within secondary mineral coatings on aquifer sediment grains.

PubMed

Singer, David M; Fox, Patricia M; Guo, Hua; Marcus, Matthew A; Davis, James A

2013-10-15

Important reactive phenomena that affect the transport and fate of many elements occur at the mineral-water interface (MWI), including sorption and redox reactions. Fundamental knowledge of these phenomena are often based on observations of ideal mineral-water systems, for example, studies of molecular scale reactions on single crystal faces or the surfaces of pure mineral powders. Much less is understood about MWI in natural environments, which typically have nanometer to micrometer scale secondary mineral coatings on the surfaces of primary mineral grains. We examined sediment grain coatings from a well-characterized field site to determine the causes of rate limitations for arsenic (As) sorption and redox processes within the coatings. Sediments were obtained from the USGS field research site on Cape Cod, MA, and exposed to synthetic contaminated groundwater solutions. Uptake of As(III) and As(V) into the coatings was studied with a combination of electron microscopy and synchrotron techniques to assess concentration gradients and reactive processes, including electron transfer reactions. Transmission electron microscopy (TEM) and X-ray microprobe (XMP) analyses indicated that As was primarily associated with micrometer- to submicrometer aggregates of Mn-bearing nanoparticulate goethite. As(III) oxidation by this phase was observed but limited by the extent of exposed surface area of the goethite grains to the exterior of the mineral coatings. Secondary mineral coatings are potentially both sinks and sources of contaminants depending on the history of a contaminated site, and may need to be included explicitly in reactive transport models.

RF models for plasma-surface interactions

NASA Astrophysics Data System (ADS)

Jenkins, Thomas; Smithe, David; Lin, Ming-Chieh; Kruger, Scott; Stoltz, Peter

2013-09-01

Computational models for DC and oscillatory (RF-driven) sheath potentials, arising at metal or dielectric-coated surfaces in contact with plasma, are developed within the VSim code and applied in parameter regimes characteristic of fusion plasma experiments and plasma processing scenarios. Results from initial studies quantifying the effects of various dielectric wall coating materials and thicknesses on these sheath potentials, as well as on the ensuing flux of plasma particles to the wall, are presented. As well, the developed models are used to model plasma-facing ICRF antenna structures in the ITER device; we present initial assessments of the efficacy of dielectric-coated antenna surfaces in reducing sputtering-induced high-Z impurity contamination of the fusion reaction. Funded by U.S. DoE via a Phase I SBIR grant, award DE-SC0009501.

One-step triple-phase interfacial synthesis of polyaniline-coated polypyrrole composite and its application as electrode materials for supercapacitors

NASA Astrophysics Data System (ADS)

Lei, Wen; He, Ping; Zhang, Susu; Dong, Faqin; Ma, Yongjun

2014-11-01

We first present an alternative one-step route for constructing a novel polyaniline (PANI)-coated polypyrrole (PPy) composite in an ingenious triple-phase interface system, where PPy and PANI are prepared in individual non-interference interfaces and, in the middle aqueous phase, smaller PANI particles are uniformly coated on the surface of PPy particles, forming a core-shell structure. The prepared PPy/PANI composite electrode shows a superior capacitance behavior that is more suitable for supercapacitor application.

An update on pharmaceutical film coating for drug delivery.

PubMed

Felton, Linda A; Porter, Stuart C

2013-04-01

Pharmaceutical coating processes have generally been transformed from what was essentially an art form in the mid-twentieth century to a much more technology-driven process. This review article provides a basic overview of current film coating processes, including a discussion on polymer selection, coating formulation additives and processing equipment. Substrate considerations for pharmaceutical coating processes are also presented. While polymeric coating operations are commonplace in the pharmaceutical industry, film coating processes are still not fully understood, which presents serious challenges with current regulatory requirements. Novel analytical technologies and various modeling techniques that are being used to better understand film coating processes are discussed. This review article also examines the challenges of implementing process analytical technologies in coating operations, active pharmaceutical ingredients in polymer film coatings, the use of high-solids coating systems and continuous coating and other novel coating application methods.

Investigation on wear resistance and corrosion resistance of electron beam cladding co-alloy coating on Inconel617

NASA Astrophysics Data System (ADS)

Liu, Hailang; Zhang, Guopei; Huang, Yiping; Qi, Zhengwei; Wang, Bo; Yu, Zhibiao; Wang, Dezhi

2018-04-01

To improve surface properties of Inconel 617 alloy (referred to as 617 alloy), co-alloy coating metallurgically bonded to substrate was prepared on the surface of 617 alloy by electron beam cladding. The microstructure, phase composition, microhardness, tribological properties and corrosion resistance of the coatings were investigated. The XRD results of the coatings reinforced by co-alloy (Co800) revealed the presence of γ-Co, CoCx and Cr23C6 phase as matrix and new metastable phases of Cr2Ni3 and Co3Mo2Si. These hypoeutectic structures contain primary dendrites and interdendritic eutectics. The metallurgical bonding forms well between the cladding layer and the matrix of 617 alloy. In most studied conditions, the co-alloy coating displays a better hardness, tribological performance, i.e., lower coefficient of frictions and wear rates, corrosion resistance in 1 mol L‑1 HCl solution, than the 617 alloy.

Ultrathin TiO2 layer coated-CdS spheres core-shell nanocomposite with enhanced visible-light photoactivity.

PubMed

Chen, Zhang; Xu, Yi-Jun

2013-12-26

Development of various strategies for controllable fabrication of core-shell nanocomposites (CSNs) with highly active photocatalytic performance has been attracting ever-increasing research attention. In particular, control of the ultrathin layer TiO2 shell in constructing CSNs in an aqueous phase is a significant but technologically challenging issue. Here, this paper demonstrates the interface assembly synthesis of CdS nanospheres@TiO2 core-shell photocatalyst via the electrostatic interaction of negatively charged water-stable titania precursor with positively charged CdS nanospheres (CdS NSPs), followed by the formation of the ultrathin-layer TiO2 shell through a facile refluxing process in aqueous phase. The as-formed CdS NSPs@TiO2 core-shell nanohybrid exhibits a high visible-light-driven photoactivity for selective transformation and reduction of heavy metal ions. The ultrathin TiO2 layer coated on CdS NSPs results in excellent light transmission property, enhanced adsorption capacity, and improved transfer of charge carriers and lifespan of photoinduced electron-hole pairs, which would prominently contribute to the significant photoactivity enhancement. It is anticipated that this facile aqueous-phase synthesis strategy could be extended to design a variety of more efficient CSN photocatalysts with controllable morphology toward target applications in diverse photoredox processes.

The influence of the ion plasma flow on the phase composition and microhardness of carbon coatings doped with metals

NASA Astrophysics Data System (ADS)

Rudenkov, A. S.; Piliptsou, D. G.; Luchnikov, P. A.; Rogachev, A. V.; Jiang, Xiaohong; Fedosenko, N. N.

2018-01-01

The Raman spectroscopy method established that subsequent treatment with ion ions leads to a change in the microstructure of coatings based on carbon and metals. It is established that the structure change is determined by the changes occurring at the interface and depends on the sp3 → sp2 phase transition due to the appearance of local thermal peaks at the end of tracks of nitrogen ions implanted in the coating volume. It is shown that the microhardness of metal-carbon coatings (α-C: Cu, α-C: Ti, α-C:Al) increases after ion-plasma treatment, which is determined by the formation of solid interstitial phases based on CNx and metal carbonitrides.

Development of a Catalytic Coating for a Shuttle Flight Experiment

NASA Technical Reports Server (NTRS)

Stewart, David A.; Goekcen, Tahir; Sepka, Steven E.; Leiser, Daniel B.; Rezin, Marc D.

2010-01-01

A spray-on coating was developed for use on the shuttle wing tiles to obtain data that could be correlated with computational fluid dynamics (CFD) solutions to better understand the effect of chemical heating on a fore-body heat shield having a turbulent boundary layer during planetary entry at hypersonic speed. The selection of a spray-on coating was conducted in two Phases 1) screening tests to select the catalytic coating formulation and 2) surface property determination using both arc-jet and side-arm facilities at NASA Ames Research Center. Comparison of the predicted surface temperature profile over a flat-plate with measured values obtained during arc-jet exposure (Phase I study) was used to validate the surface properties obtained during Phase II.

Article Including Environmental Barrier Coating System

NASA Technical Reports Server (NTRS)

Lee, Kang N. (Inventor)

2015-01-01

An enhanced environmental barrier coating for a silicon containing substrate. The enhanced barrier coating may include a bond coat doped with at least one of an alkali metal oxide and an alkali earth metal oxide. The enhanced barrier coating may include a composite mullite bond coat including BSAS and another distinct second phase oxide applied over said surface.

A major advance in powder metallurgy

NASA Technical Reports Server (NTRS)

Williams, Brian E.; Stiglich, Jacob J., Jr.; Kaplan, Richard B.; Tuffias, Robert H.

1991-01-01

Ultramet has developed a process which promises to significantly increase the mechanical properties of powder metallurgy (PM) parts. Current PM technology uses mixed powders of various constituents prior to compaction. The homogeneity and flaw distribution in PM parts depends on the uniformity of mixing and the maintenance of uniformity during compaction. Conventional PM fabrication processes typically result in non-uniform distribution of the matrix, flaw generation due to particle-particle contact when one of the constituents is a brittle material, and grain growth caused by high temperature, long duration compaction processes. Additionally, a significant amount of matrix material is usually necessary to fill voids and create 100 percent dense parts. In Ultramet's process, each individual particle is coated with the matrix material, and compaction is performed by solid state processing. In this program, Ultramet coated 12-micron tungsten particles with approximately 5 wt percent nickel/iron. After compaction, flexure strengths were measured 50 percent higher than those achieved in conventional liquid phase sintered parts (10 wt percent Ni/Fe). Further results and other material combinations are discussed.

Electroless nickel – phosphorus coating on crab shell particles and its characterization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arulvel, S., E-mail: gs.arulvel.research@gmail.com; Elayaperumal, A.; Jagatheeshwaran, M.S.

Being hydrophilic material, crab shell particles have only a limited number of applications. It is, therefore, necessary to modify the surface of the crab shell particles. To make them useful ever for the applications, the main theme we proposed in this article is to utilize crab shell particles (CSP) with the core coated with nickel phosphorus (NiP) as a shell using the electroless coating process. For dealing with serious environmental problems, utilization of waste bio-shells is always an important factor to be considered. Chelating ability of crab shell particles eliminates the surface activation in this work proceeding to the coatingmore » process. The functional group, phase structure, microstructure, chemical composition and thermal analysis of CSP and NiP/CSP were characterized using Fourier transform infra-red spectroscopy (FTIR), x-ray diffraction analyzer (XRD), scanning electron microscope (SEM), energy-dispersive x-ray spectroscopy (EDS), and thermogravimetric analysis (TGA). The combination of an amorphous and crystalline structure was exhibited by CSP and NiP/CSP. NiP/CSP has shown a better thermal stability when compared to uncoated CSP. Stability test, adsorption test, and conductivity test were conducted for the study of adsorption behavior and conductivity of the particles. CSP presented a hydrophilic property in contrast to hydrophobic NiP/CSP. NiP/CSP presented a conductivity of about 44% greater compared to the CSP without any fluctuations. - Highlights: • Utilization of crab shell waste is focused on. • NiP coating on crab shell particle is fabricated using electroless process. • Thermal analysis, stability test, adsorption test and conductivity test were done. • Organic matrix of crab shell particle favors the coating process. • Results demonstrate the characterization of CSP core – NiP shell structure.« less

Plasma sprayed hydroxyapatite coatings on titanium substrates. Part 1: Mechanical properties and residual stress levels.

PubMed

Tsui, Y C; Doyle, C; Clyne, T W

1998-11-01

Hydroxyapatite (HA) coatings have been sprayed on to substrates of Ti-6Al-4V, using a range of input power levels and plasma gas mixtures. Coatings have also been produced on substrates of mild steel and tungsten, in order to explore certain aspects of the mechanical behaviour of HA without the complication of yielding or creep in the substrate. Studies have been made of the phase constitution, porosity, degree of crystallinity, OH ion content, microstructure and surface roughness of the HA coatings. The Young's moduli in tension and in compression were evaluated by the cantilever beam bend test using a tungsten/HA composite beam. The flexural Young's modulus was determined using a free-standing deposit under the same test. Adhesion was characterised using the single-edge notch-bend test; this is considered superior to the tensile bond strength test in common use. Measured interfacial fracture energies were of the order 1-10 J m(-2). Stress levels were investigated using specimen curvature measurements in conjunction with a numerical process model. The quenching stress for HA was measured to be about 10-25 MPa and the residual stress level in HA coatings at room temperature are predicted to lie in the approximate range of 20-40 MPa (tensile). These residual stresses could be reduced in magnitude by maintaining the substrate at a low temperature (possibly below room temperature) during spraying and it may be worthwhile to explore this. Ideally, the HA coating should have low porosity, high cohesive strength, good adhesion to the substrate, a high degree of crystallinity and high chemical purity and phase stability. In practice, such combinations are rather difficult to achieve by just varying the spraying parameters.

Improvement of flow and bulk density of pharmaceutical powders using surface modification.

PubMed

Jallo, Laila J; Ghoroi, Chinmay; Gurumurthy, Lakxmi; Patel, Utsav; Davé, Rajesh N

2012-02-28

Improvement in flow and bulk density, the two most important properties that determine the ease with which pharmaceutical powders can be handled, stored and processed, is done through surface modification. A limited design of experiment was conducted to establish a standardized dry coating procedure that limits the extent of powder attrition, while providing the most consistent improvement in angle of repose (AOR). The magnetically assisted impaction coating (MAIC) was considered as a model dry-coater for pharmaceutical powders; ibuprofen, acetaminophen, and ascorbic acid. Dry coated drug powders were characterized by AOR, particle size as a function of dispersion pressure, particle size distribution, conditioned bulk density (CBD), Carr index (CI), flow function coefficient (FFC), cohesion coefficient using different instruments, including a shear cell in the Freeman FT4 powder rheometer, and Hansen flowability index. Substantial improvement was observed in all the measured properties after dry coating relative to the uncoated powders, such that each powder moved from a poorer to a better flow classification and showed improved dispersion. The material intrinsic property such as cohesion, plotted as a function of particle size, gave a trend similar to those of bulk flow properties, AOR and CI. Property improvement is also illustrated in a phase map of inverse cohesion (or FFC) as a function of bulk density, which also indicated a significant positive shift due to dry coating. It is hoped that such phase maps are useful in manufacturing decisions regarding the need for dry coating, which will allow moving from wet granulation to roller compaction or to direct compression based formulations. Copyright © 2011 Elsevier B.V. All rights reserved.

Dip coating of sol-gels

NASA Astrophysics Data System (ADS)

Schunk, P. R.; Hurd, A. J.; Brinker, C. J.

Dip coating is the primary means of depositing sol-gel films for precision optical coatings. Sols are typically multicomponent systems consisting of an inorganic phase dispersed in a solvent mixture, with each component differing in volatility and surface tension. This, together with slow coating speeds (less than 1cm/s), makes analysis of the coating process complicated; unlike most high-speed coating methods, solvent evaporation, evolving rheology, and surface tension gradients alter significantly the fluid mechanics of the deposition stage. These phenomena were studied with computer-aided predictions of the flow and species transport fields. The underlying theory involves mass, momentum, and species transport on a domain of unknown shape, with models and constitutive equations for vapor-liquid equilibria and surface tension. Due accounting is made for the unknown position of the free surface, which locates according to the capillary hydrodynamic forces and solvent loss by evaporation. Predictions of the effects of mass transfer, hydrodynamics, and surface tension gradients on final film thickness are compared with ellipsometry measurements of film thickness on a laboratory pilot coater. Although quantitative agreement is still lacking, both experiment and theory reveal that the film profile near the drying line takes on a parabolic shape.

Robust infrared-shielding coating films prepared using perhydropolysilazane and hydrophobized indium tin oxide nanoparticles with tuned surface plasmon resonance.

PubMed

Katagiri, Kiyofumi; Takabatake, Ryuichi; Inumaru, Kei

2013-10-23

Robust infrared (IR)-shielding coating films were prepared by dispersing indium tin oxide (ITO) nanoparticles (NPs) in a silica matrix. Hydrophobized ITO NPs were synthesized via a liquid phase process. The surface plasmon resonance (SPR) absorption of the ITO NPs could be tuned by varying the concentration of Sn doping from 3 to 30 mol %. The shortest SPR wavelength and strongest SPR absorption were obtained for the ITO NPs doped with 10% Sn because they possessed the highest electron carrier density. Coating films composed of a continuous silica matrix homogeneously dispersed with ITO NPs were obtained using perhydropolysilazane (PHPS) as a precursor. PHPS was completely converted to silica by exposure to the vapor from aqueous ammonia at 50 °C. The prepared coating films can efficiently shield IR radiation even though they are more than 80% transparent in the visible range. The coating film with the greatest IR-shielding ability completely blocked IR light at wavelengths longer than 1400 nm. The pencil hardness of this coating film was 9H at a load of 750 g, which is sufficiently robust for applications such as automotive glass.

Microstructure and wear resistance of Ti-Cu-N composite coating prepared via laser cladding/laser nitriding technology on Ti-6Al-4V alloy

NASA Astrophysics Data System (ADS)

Yang, Yuling; Cao, Shiyin; Zhang, Shuai; Xu, Chuan; Qin, Gaowu

2017-07-01

Ti-Cu-N coatings with three different Cu contents on Ti-6Al-4V alloy (TC4) were obtained via laser cladding together with laser nitriding (LC/LN) technology. Phase constituents, microstructure, microhardness, and wear resistance of the coatings were investigated. The evolution of the coefficients of friction for the three coatings was measured under dry sliding conditions as a function of the revolutions until the coating failure. The results show that the coatings are mainly composed of TiN, CuTi3 and some TiO6 phases dispersed in the matrix. A good metallurgical bonding between the coating and substrate has been successfully obtained. The prepared Ti-Cu-N composite coatings almost doubly enhance the microhardness of the TC4 alloy and reduce the friction down to 1/4-1/2 of the TC4 alloy, and thus significantly improve the wear resistance. The coefficient of friction depends on the Cu content in the coating.

Characterisation, corrosion resistance and in vitro bioactivity of manganese-doped hydroxyapatite films electrodeposited on titanium.

PubMed

Huang, Yong; Ding, Qiongqiong; Han, Shuguang; Yan, Yajing; Pang, Xiaofeng

2013-08-01

This work elucidated the corrosion resistance and in vitro bioactivity of electroplated manganese-doped hydroxyapatite (MnHAp) film on NaOH-treated titanium (Ti). The NaOH treatment process was performed on Ti surface to enhance the adhesion of the MnHAp coating on Ti. Scanning electron microscopy images showed that the MnHAp coating had needle-like apatite crystals, and the approximately 10 μm thick layer was denser than HAp. Energy-dispersive X-ray spectroscopy analysis revealed that the MnHAp crystals were Ca-deficient and the Mn/P molar ratio was 0.048. X-ray diffraction confirmed the presence of single-phase MnHAp, which was aligned vertically to the substrate. Fourier transform infrared spectroscopy indicated the presence of phosphate bands ranging from 500 to 650 and 900 to 1,100 cm(-1), and a hydroxyl band at 3,571 cm(-1), which was characteristic of HAp. Bond strength test revealed that adhesion for the MnHAp coating was more enhanced than that of the HAp coating. Potentiodynamic polarisation test showed that the MnHAp-coated surface exhibited superior corrosion resistance over the HAp single-coated surface. Bioactivity test conducted by immersing the coatings in simulated body fluid showed that MnHAp coating can rapidly induce bone-like apatite nucleation and growth. Osteoblast cellular tests revealed that the MnHAp coating was better at improving the in vitro biocompatibility of Ti than the HAp coating.

Co-blasting of titanium surfaces with an abrasive and hydroxyapatite to produce bioactive coatings: substrate and coating characterisation.

PubMed

Dunne, Conor F; Twomey, Barry; O'Neill, Liam; Stanton, Kenneth T

2014-01-01

The aim of this work is to assess the influence of two blast media on the deposition of hydroxyapatite onto a titanium substrate using a novel ambient temperature coating technique named CoBlast. CoBlast was developed to address the problems with high temperature coating techniques. The blasting media used in this study were Al2O3 and a sintered apatite powder. The prepared and coated surfaces were compared to plasma sprayed hydroxyapatite on the same substrates using the same hydroxyapatite feedstock powder. X-ray diffraction analysis revealed the coating crystallinity was the same as the original hydroxyapatite feedstock powder for the CoBlast samples while evidence of amorphous hydroxyapatite phases and β-TCP was observed in the plasma sprayed samples. The blast media type significantly influences the adhesive strength of the coating, surface roughness of both the substrate and coating and the microstructure of the substrate. The coating adhesion increased for the CoBlasted samples from 50 MPa to 60 MPa for sintered apatite powder and alumina, respectively, while plasma spray samples were significantly lower (5 MPa) when tested using a modified pull-test. In conclusion, the choice of blast medium is shown to be a key parameter in the CoBlast process. This study indicates that sintered apatite powder is the most suitable candidate for use as a blast medium in the coating of medical devices.

On the Electrodeposition of Ca-P Coatings on Nitinol Alloy: A Comparison Between Different Surface Modification Methods

NASA Astrophysics Data System (ADS)

Etminanfar, M. R.; Khalil-Allafi, J.

2016-02-01

In this study, a combination of surface modification process and the electrochemical deposition of Ca-P coatings was used for the modification of the Nitinol shape memory alloy. DSC, SEM, GIB-XRD, FT-Raman, XPS, and FTIR measurements were performed for the characterization of the samples. Results indicated that chemical etching and boiling of the samples in distilled water formed TiO film on the surface. After the chemical modification, subsequent aging of the sample, at 470 °C for 30 min, converted the oxide film to a stable structure of titanium dioxide. In that case, the treated substrate indicated a superelastic behavior. At the same electrochemical condition, the treated substrate revealed more stable and uniform Ca-P coatings in comparison with the abraded Nitinol substrate. This difference was attributed to the presence of hydroxyl groups on the titanium dioxide surface. Also, after soaking the sample in SBF, the needle-like coating on the treated substrate was completely covered with the hydroxyapatite phase which shows a good bioactivity of the coating.

Effectiveness of edible coatings combined with mild heat shocks on microbial spoilage and sensory quality of fresh cut broccoli (Brassica oleracea L.).

PubMed

Moreira, María del R; Ponce, Alejandra; Ansorena, R; Roura, Sara I

2011-08-01

The use of edible coatings and mild heat shocks is proposed as postharvest treatments to prevent microbial deterioration of refrigerated broccoli. Minimally processed broccoli was coated with either chitosan or carboxymethyl-cellulose (CMC) combined or not with a previous application of a mild heat shock. The evolution of microbial populations (mesophilic, psycrotrophic, Enterobacteriaceae, molds and yeast, and lactic acid bacteria) was studied during 20 d of storage and fitted to Gompertz and logistic models. Results revealed that, at the end of the storage, chitosan coating significantly reduced all microbiological population counts, except lactic acid bacteria; while higher reduction was observed with chitosan coating combined with a heat shock treatment. A significant delay at the beginning of the exponential phase was observed for all the bacterial populations analyzed. On the other hand, CMC coating, with and without a previous thermal treatment, did not exert any antibacterial effect. Excellent agreement was found between experimental microbial counts and predicted values obtained from Gompertz and logistic models. Kinetic modeling was found to be valuable for prediction of microbiological shelf life of broccoli during storage. Results showed that the application of chitosan coating effectively maintained microbiological quality and extended shelf life of minimally processed broccoli. According to these results, the use of the edible chitosan coating alone or in combination with a heat mild shock appear to be a viable alternative for controlling microbiological growth and sensory attributes in minimally processed broccoli. The continuous consumer interest in high quality and food safety, combined with environmental concern has induced to the development and study of edible coatings that avoid the use of synthetic materials. The edible coatings, formed from generally recognized as safe materials, have the potential to reduce weight loss, respiration rate, and improve food appearance and integrity. It is one of the most effective methods to maintain food quality. On the other hand, heat treatments have been demonstrated to be effective as a nonchemical means of improving postharvest quality for a variety of horticultural products. The applications of mild heat shocks combined with edible coatings constitute an alternative for the natural preservation of crops for which the use of synthetic chemicals is objectionable. © 2011 Institute of Food Technologists®

Tribological Behavior of Plasma-Sprayed Al2O3-20 wt.%TiO2 Coating

NASA Astrophysics Data System (ADS)

Cui, Shiyu; Miao, Qiang; Liang, Wenping; Zhang, Zhigang; Xu, Yi; Ren, Beilei

2017-05-01

Al2O3-20 wt.% TiO2 ceramic coatings were deposited on the surface of Grade D steel by plasma spraying of commercially available powders. The phases and the microstructures of the coatings were investigated by x-ray diffraction and scanning electron microscopy, respectively. The Al2O3-20 wt.% TiO2 composite coating exhibited a typical inter-lamellar structure consisting of the γ-Al2O3 and the Al2TiO5 phases. The dry sliding wear behavior of the coating was examined at 20 °C using a ball-on-disk wear tester. The plasma-sprayed coating showed a low wear rate ( 4.5 × 10-6 mm3 N-1 m-1), which was <2% of that of the matrix ( 283.3 × 10-6 mm3 N-1 m-1), under a load of 15 N. In addition, the tribological behavior of the plasma-sprayed coating was analyzed by examining the microstructure after the wear tests. It was found that delamination of the Al2TiO5 phase was the main cause of the wear during the sliding wear tests. A suitable model was used to simulate the wear mechanism of the coating.

Preparation and bioactive properties of nanocrystalline hydroxyapatite thin films obtained by conversion of atomic layer deposited calcium carbonate.

PubMed

Holopainen, Jani; Kauppinen, Kyösti; Mizohata, Kenichiro; Santala, Eero; Mikkola, Esa; Heikkilä, Mikko; Kokkonen, Hanna; Leskelä, Markku; Lehenkari, Petri; Tuukkanen, Juha; Ritala, Mikko

2014-09-01

Nanocrystalline hydroxyapatite thin films were fabricated on silicon and titanium by atomic layer deposition (ALD) of CaCO3 and its subsequent conversion to hydroxyapatite by diammonium hydrogen phosphate (DAP) solution. The effects of conversion process parameters to crystallinity and morphology of the films were examined. DAP concentration was found to be critical in controlling the crystal size and homogeneity of the films. The hydroxyapatite phase was identified by XRD. ToF-elastic recoil detection analysis studies revealed that the films are calcium deficient in relation to hydroxyapatite with a Ca/P ratio of 1.39 for films converted with 0.2 M DAP at 95 °C. The coatings prepared on titanium conformally follow the rough surface topography of the substrate, verifying that the good step coverage of the ALD method was maintained in the conversion process. The dissolution tests revealed that the coating was nondissolvable in the cell culture medium. Annealing the coated sample at 700 °C for 1 h seemed to enhance its bonding properties to the substrate. Also, the biocompatibility of the coatings was confirmed by human bone marrow derived cells in vitro. The developed method provides a new possibility to produce thin film coatings on titanium implants with bone-type hydroxyapatite that is biocompatible with human osteoblasts and osteoclasts.