bluuebunny/crossref_metadata_2025_split huggingface dataset:
Processing Strategies for Tailoring Ceramic-Based Nanostructured Thermal Spray Coatings
Authors: Marple B.R. , Lima R.S. 
Published: September 2022

Abstract
New and more demanding applications and higher performance requirements are creating the need for a greater degree of sophistication in engineering coating structures. The use of nanostructured feedstocks provides the possibility of tailoring the structure of thermal spray ceramic-based coatings at the nanoscale. In the present study, it has been found that such an approach can produce coatings with enhanced mechanical, thermal and bioperformance characteristics. It has been shown that the internal structure and external size of agglomerates as well as the spray conditions employed for deposition play a key role in determining the nature and extent of zones of nanostructured material produced in coatings. The characteristics (such as porosity and bonding) of these zones can have an important effect on the coating performance. This approach has been used to tailor Al2O3-TiO2, ZrO2-Y2O3, WC-Co, TiO2, and hydroxyapatite coatings targeted for use as abradables, for TBCs, against wear and on orthopedic implants.
Liquid Plasma Sprayed Coatings of Yttria Stabilized Zirconia for SOFC Electrolytes
Authors: Rampon R. , Bertrand G. , Toma F.-L. , Coddet C. 
Published: September 2022

Abstract
In order to achieve SOFC with reduced costs, the atmospheric plasma spray process (APS) could be an attractive technique. To obtain dense layer as electrolyte, the route has been adapted by providing a suspension as feedstock material. Suspensions of yttria stabilized zirconia powders in methanol have been prepared with various solid loadings and states of dispersion. An external injection system was used to ensure the atomisation and radial injection of the suspension into the Ar-H2 plasma under atmospheric conditions. The coatings were characterized by SEM, Archimedes porosity and differences in the microstructure of the deposits were observed. The aim of this work has thus been to study the influence of various parameters (of the suspensions, plasma, torch, injection) on the layer morphology. For this purpose, the atomization has been investigated and efforts have been made to understand relationships between suspension properties, atomization and microstructure.
Proven and Promising Applications of Thermal Sprayed Nanostructured Coatings
Authors: Kim G.E. 
Published: September 2022

Abstract
Since its inception, the Office of Naval Research (ONR) program entitled, “Thermal Spray Processing of Nanostructured Coatings”, has produced numerous successes relating to military and industrial applications. Commercially available thermal spray processes have been used to apply ceramic coatings from nanostructured powders, producing dramatically improved wear performance over coatings from conventional non-nanostructured powder. The nanostructured alumina-titania coating has been instrumental in extending the life of a critical Navy need, the protection of the main propulsion shaft of mine countermeasures ships. The advancement in nanostructured oxide coatings has led to the development of the first industrial application of a thermal sprayed nanostructured coating. A nanostructured titanium oxide coating has been developed and successfully incorporated into severe-service ball valves used in hydrometallurgical extraction of gold, nickel, and cobalt. This paper will also present promising results from current development work relating to nanostructured coatings for thermal barrier, biomaterial, and reconditioning applications.
Fabrication of Nanostructured TiO2 Fibers on TiO2 Coatings Produced from a Nanostructured Feedstock
Authors: Lima R.S. , Marple B.R. , Lee H. , Akbar S.A. 
Published: September 2022

Abstract
Titania (TiO2) coatings were produced using the high velocity oxy-fuel (HVOF) technique on Ti-6Al-4V substrates. The titania feedstock powder exhibited nanostructured morphology, formed by the agglomeration of individual nanostructured titania particles (spray-drying) smaller than 100 nm. The resulting coatings were dense (porosity &lt;1%) and exhibited rutile and anatase as phases with percentages of ~75% and ~25%, respectively. These coatings were heat-treated in a H2/N2 environment at 700oC for 8 h. During the heat-treatment, nanostructured titania fibers were formed on specific surface regions of the coatings. The nanofibers formed by this “chemical or reaction-based texturing” exhibited diameters of 50-400 nm and lengths in the order to 1-5 µm. It is thought that engineering these surfaces at nano and microscales may lead to interesting applications of titania coatings related to cell attachment/growth (for biomedical applications).
Effects of Powder Injection on Deposit Efficiency in Plasma Spraying
Authors: Abukawa S. , Takabatake T. , Tani K. 
Published: September 2022

Abstract
In plasma spraying, generally, powders are radially injected into plasma jet. However, percentage of particles which have enough enthalpy to melt is not high in radial injection, possibly leading to low deposit efficiency especially for high melting point powders. In this research, powder port for radial injection was attached to an axial injection plasma torch in order to compare the plasma flame in both cases of axial and radial powder injections. The powder trajectory and the shape of the plasma plume were observed, and particle flux density, temperature, velocity, and deposit efficiency of alumina powders were measured and the results were compared between the two powder injection methods.
Instabilities in Plasma Spray Jets
Authors: Outcalt D. , Hallberg M. , Yang G. , Heberlein J. , Pfender E. , Strykowski P. 
Published: September 2022

Abstract
Instabilities in plasma spray jets can result in coatings with inconsistent properties. The arc root fluctuation and shear layer instability due to strong gradients are of foremost concern. The shear layer instabilities result from shear between the high velocity, low density hot core gas, the intermediate density and velocity boundary layer, and the high density quiescent environment. A cold-flow facility with density gradients similar to a plasma torch has been used for implementation of traditional fluid dynamics measurements such as hot-wire anemometry. Methods to control these instabilities are developed and tested using both the plasma torch and the cold flow facility. Through nozzle design modifications the instabilities resulting from arc root fluctuations and high density gradients have been reduced. The effectiveness of the control on the plasma jet is determined using in-flight particle characterization along with high speed imaging and photodiode measurements of the jet.
Effect of Powder Gas on Low Pressure Plasma Sprayed Yttria Coatings
Authors: Young S. , Hall A.C. , Huskisson D. , Hirschfeld D.A. , Muehlberger E. , Barbash D. 
Published: September 2022

Abstract
The morphology and chemistry of low pressure plasma sprayed (LPPS) yttria coatings was investigated. White yttria powder used as the coating source material was 99.99% pure and contained particles from 1 to 5 microns in size. This yttria powder was plasma sprayed onto 8.9 cm diameter, 0.635 cm thick aluminum substrates using Ar-He as the arc gas. The powder gas was varied from Ar, to air to O2 between samples. The sample sprayed using Ar as the powder gas used a chamber pressure of 2.5 kPa and resulted in a very dark colored coating. Subsequent samples were sprayed using air and then oxygen as the powder gas, both using a chamber pressure of 4.0 kPa. The resulting coating colors were medium gray and very light gray, respectively. A duplicate spraying using oxygen as the powder gas was performed to demonstrate repeatability. Porosity, splat shape, and the presence of amorphous phases were determined using secondary and backscattered electron microscopy imaging and related to processing conditions. Energy dispersive spectrometry was used to examine the chemistry of the coating and substrate. X-ray photoelectron spectroscopy (XPS) was used to determine the oxide stoichiometry of each of the coatings and this was correlated to coating color.
Vacuum Plasma Spraying of Thick W Coatings onto Surface Sculptures for Fusion Armour Applications
Authors: Thomas G. , Grant P.S. , Coad P. , Matthews G. , Castro R. 
Published: September 2022

Abstract
Vacuum plasma sprayed (VPS) tungsten (W) coatings hold great promise for plasma facing components in future fusion devices. However, the large coefficient of thermal expansion (CTE) mismatch between W and underlying structural steels poses a significant problem for manufacturing and service life because of the evolution of large thermally induced stresses leading to failure. In this paper both the concept of functionally graded material (FGM) W/steel interlayers and the use of steel substrate surfaces with regular surface sculptures of millimetre scale created by e-beam surface manipulation, termed surfi-sculpt and developed by TWI of the UK are investigated. The objective of these approaches is to enhance coating adhesion and to engineer macroscopic variations in the effective CTE through the thickness of the subsequently VPS deposited W coating. The effects of surface geometry on coating adhesion and microstructure have been investigated, and preliminary conclusions on the key surface sculpture geometrical features required for high adhesion dense W coatings have been identified.
Mechanical Properties of Plasma Sprayed Titania Coatings
Authors: Ctibor P. , Neufuss K. , Chraska P. 
Published: September 2022

Abstract
Agglomerated titania nanopowder and a “classical” titania were sprayed by the high throughput WSP and thoroughly compared. Optical microscopy with image analysis as well as mercury intrusion porosimetry were utilized for quantification of porosity. Results indicate that the “nano” coatings in general exhibit finer pores than coatings of the “conventional” micron-sized powders. Mechanical properties like Vickers microhardness and slurry abrasion response were measured and linked to the structural investigation. Impact of the variation in the slurry composition on wear resistance of tested coatings and on character of the wear damage is discussed. The over-all results however suggest that the “nano” coatings properties are better only for carefully selected sets of spraying parameters, which seem to have a very important impact.
Improving Plasma Sprayed YSZ Coatings for SOFC Electrolytes
Authors: Syed A.A. , Ilhan Z. , Arnold J. , Schiller G. , Weckmann H. 
Published: September 2022

Abstract
Using a D-optimal design of experiments (DOE), influence of feedstock powder and plasma gases were examined on deposition efficiency, gas tightness and electrochemical behavior of vacuum plasma sprayed YSZ for SOFC electrolytes. In-flight particle temperature and velocity, measured by on-line particle diagnostics, were correlated with plasma and deposit properties. Electrochemical testing of cells was performed to determine the influence of gas tightness and microstructure of electrolyte deposit on cell behavior.
Improvement of Plasma Spraying Conditions for SOFC Applications: Effect of Nozzle Geometry and Gas Shrouds
Authors: Kavka T. , Henne R. , Arnold J. 
Published: September 2022

Abstract
Thermal plasma jets interact intensively with the surrounding atmosphere. This interaction leads to strong changes of the plasma jet properties affecting the resulting products. Modification of the nozzle parameters and conditions at the exit of the torch helps to vary and better control the process of plasma jet and ambient air interaction. In the present study, the DC arc plasma torch was equipped with a modified anode nozzle (M2.5) and a surrounding shroud at the jet exit. The process of air entrainment was investigated when shroud gas was supplied producing a protecting envelope to reduce the air entrainment. Schlieren photography and the enthalpy probe with the mass spectrometer were applied to study the influence on plasma jet behavior. The effect of shroud nozzle geometry as well as the effect of the shroud gas flow rate was investigated. Likewise, influence of gas shrouding on the resulting coatings was studied.
High Velocity DC-VPS for Diffusion and Protecting Barrier Layers in SOFCs
Authors: Henne R.H. , Franco T. , Ruckdäschel R. 
Published: September 2022

Abstract
High temperature fuel cells of SOFC type as direct converter of chemical into electrical energy show a high potential for reducing considerably the specific energy consumption in different application fields. Of particular interest are advanced light-weight planar cells for electricity supply systems in cars and other mobile systems. Such cells, in one current design, consist mainly of metallic parts, e.g. of ferrite steels. These cells shall operate in the temperature range of 700 to 800 °C where oxidation and diffusion processes can be of detrimental effect on cell performance for long-term operation. Problems arise in particular by diffusion of Cr-species from the inter-connect or the casing into the electrolyte/cathode interface forming insulating phases and the mutual diffusion of substrate and anode material, e.g. iron and chromium from the ferrite into the anode and nickel from the anode into the ferrite which in both cases reduces performance and system lifetime. Protecting intermediate layers, can reduce such effects considerably if they are dense, stable and of high electronic conductivity. Perovskite-type layers (e.g. doped LaCrO3) applied with high-velocity Direct Current-Vacuum Plasma Spraying (DCVPS) promise to solve reliably such problems.
Effect of Copper Ion Doping on Photocatalytic Performance of Liquid Flame Sprayed TiO2 Coatings
Authors: Yang G.-J. , Li C.-J. , Li C.-X. , Wang Y.-Y. , Huang X.-C. 
Published: September 2022

Abstract
Copper ion was added in liquid feedstock to deposit ion doping TiO2 photocatalytic coatings through liquid flame spraying. The coating microstructure was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The photocatalytic performance of coatings was examined by photodegradation of acetaldehyde. XRD analysis shows that the crystalline structure of coatings is not significantly influenced by the metal ion doping. The photocatalytic activity of the TiO2 coatings is enhanced by the copper ion doping. It is found that a high concentration of ion doping decreases the activity. XPS analysis shows that the adsorbed oxygen concentration is increased with the increase of Cu2+ dopant concentration and decreases with the further increase of dopant concentration. The enhancement of photocatalytic activity can be attributed to the adsorption ability of oxygen and other reactants on the surface of doping TiO2 coatings.
Spraying of Agglomerated TiO2 Nanopowder by Water-Stabilized Plasma
Authors: Ctibor P. , Neufuss K. , Dubsky J. , Kolman B. , Rohan P. , Chraska P. 
Published: September 2022

Abstract
TiO2 nanopowder was used as a feedstock for spraying with the water stabilized plasma (WSP®) in search for superior mechanical properties and wear resistance of titania coatings. It has been proved that good quality coatings can be made even with the high throughput WSP®. Single splats evaluation and the free flight particles were used for the spray optimization. Phase compositions, stoichiometry and selected properties, such as density and elastic modulus, were then studied at the as-sprayed coatings. As for the phase composition of coatings, mainly rutile with possible traces of Magneli phases have been found. A comparison between tension and compression loading shows that values of the Elastic modulus for compression are slightly higher than these for tension, as it is usual in plasma sprayed coatings.
Influence of Feedstock Powder in Reactive Plasma Spraying for Fabrication of Aluminum Nitride Coatings
Authors: Yamada M. , Lee C.C. , Kouzaki Y. , Yasui T. , Fukumoto M. , Takahashi K. 
Published: September 2022

Abstract
Aluminum nitride (AlN) is one of the attractive ceramics with respect to its excellent mechanical and electrical properties. In this study, AlN coatings were fabricated and the influence of feedstock powders was investigated by reactive RF (Radio Frequency) plasma spraying. Two different particle sizes of commercial aluminum (Al) powders and Al/AlN mixed powders were used as the feedstock powder. The feedstock powder was injected into a RF plasma, and sprayed particles were deposited onto carbon steel or quartz substrates. As a result, it was possible to fabricate thick and dense AlN coating using smaller particle size of Al powders and quartz substrate. However, many agglomerates were formed in the coatings. On the other hand, 50 wt% or above of AlN addition in the feedstock powders was effective to prevent the formation of the agglomerates. Therefore, Al/AlN mixed powder with smaller particle size was useful for fabrication of AlN coatings by reactive RF plasma spraying.
Plasma Spray Synthesis from Precursors: Progress, Issues and Considerations
Authors: Ravi B.G. , Sampath S. , Gambino R. , Devi P.S. , Parise J.B. 
Published: September 2022

Abstract
Precursor plasma spray synthesis is an innovative and rapid method to make functional oxide ceramic coatings by starting from solution precursors and directly producing inorganic films. This emerging method, utilizes molecularly mixed precursor liquids, which essentially avoids the handling and selection of powders, opening up new avenues for developing compositionally complex functional oxide coatings. Precursor plasma spray also offers excellent opportunities in exploring the non-equilibrium phase evolution during plasma spraying of multi-component oxides from inorganic precursors. Although there have been efforts in this area since the 1980s and early 1990s with the goal of synthesizing nanoparticles, only recently has the work progressed in the area of functional systems. At the Center for Thermal Spray Research an integrated investigative strategy has been conducted to explore the benefits and limits of this synthesis strategy. Water and alcohol based sol/solution precursors derived from various chemical synthesis methods were used as feedstocks to deposit thin/thick films of spherical and nanostructured coatings of yttrium aluminum garnet (YAG), yttrium iron garnet (YIG), lanthanum strontium manganite (LSM) and Zr-substituted yttrium titanates, compositions of Y2O3-Al2O3 and their microstructural space centered around stochiometric YAG. A detailed discussion of the salient features of RF induction plasma spraying (RFPPS) approach, results obtained in the investigations to develop various functional oxide coatings and process issues and challenges are presented.
Examination of Substrate Surface Melting-Induced Splashing During Splat Formation in Plasma Spraying
Authors: Li C.-J. , Li C.-X. , Yang G.-J. , Wang Y.-Y. 
Published: September 2022

Abstract
Impacting of a molten droplet with melting point much higher than substrate results in melting of substrate around the impact area. The melting of the substrate surface to certain depth alters the flow direction of droplet fluid. The significant change of fluid flow direction leads to detaching of fluid from contact with the substrate. Consequently, splashing occurs during droplet spreading process. In the present study, Mo splats were formed on stainless steel substrate under different plasma spraying conditions. For comparison, Mo splats were also deposited on Mo surface. The substrate surface was polished prior to deposition. The powders used have a narrow particle size distribution. The results show that the morphology of splats depends significantly on the thermal interaction between the molten particle and the substrate. The splat observed was only a central part of an ideal disk-like complete splat. The typical pattern of Mo splats was the split type presenting a small split structure on stainless steel substrate surface. With Mo particles, the preheating of steel substrate has no effect on splat morphology. On the other hand, disk-like type Mo splat with a reduced diameter of a dimple-like structure at the central area of the splat was formed on Mo substrate and splashing can be suppressed through substrate preheating. Based on the experimental results, a surface-melting- induced splashing model was proposed to explain the formation mechanism of Mo splat on steel surface.
Photographing Impact of Plasma-Sprayed Particles on Metal Substrates
Authors: McDonald A. , Chandra S. , Lamontagne M. , Moreau C. 
Published: September 2022

Abstract
Plasma-sprayed, molten molybdenum particles (~40 µm diameter) were photographed during impact (with velocity ~110 m/s) on Inconel surfaces that were preheated or maintained at room temperature or 400oC. A droplet approaching the surface was sensed using a photodetector and after a known delay, a fast CCD camera was triggered to capture images of the spreading splat from the substrate front surface. A rapid two-color pyrometer was used to collect the thermal radiation from the impacting particles to follow the evolution of their temperature and size after impact. Molten molybdenum particles impacting on surfaces at room temperature disintegrated and splashed, after achieving a maximum diameter larger than 400 µm. Impact on preheated and heated Inconel produced splats with maximum diameters between 200 µm and 300 µm and with less splashing. The cooling rate of splats on the preheated Inconel was larger than that of splats on non-heated Inconel, suggesting that the splat-substrate contact was improved.
Fragmentation of Plasma-Sprayed Molybdenum Particles on Glass Surfaces
Authors: McDonald A. , Raessi M. , Chandra S. , Mostaghimi J. , Moreau C. 
Published: September 2022

Abstract
The impact of plasma-sprayed molybdenum particles on glass surfaces held at 25 and 400°C was photographed. A two-color pyrometer was used to collect thermal radiation from the particles to follow their temperature evolution and to calculate the splat cooling rate. Significant fragmentation of the splat on the surface at 25°C was observed. A 3D model of droplet impact and solidification was used to estimate the thermal contact resistances between the splat and glass. It was found that the thermal contact resistance was approximately two orders of magnitude smaller on the surface at 400°C, indicating faster solidification, which reduced splashing. The larger thermal contact resistance between the non-heated glass and splat was attributed to the presence of a gas barrier at the surface.
Phase Transformation of Al-Cu-Cr Quasicrystalline Coatings in the Plasma Spray Processes
Authors: Fu Y.Q. , Gao Y. , Hei Z.K. 
Published: September 2022

Abstract
The effects of substrate temperature during the low-power plasma spraying (2.5~8.0kW) and subsequent annealing on the phase transformation of Al-Cu-Cr quasicrystalline coatings were investigated. Compared with the original powder mainly composed of icosahedral I-Al65Cu24Cr11 quasicrystalline phase and monoclinic θ-Al13Cr4, the coatings show an icosahedral quasicrystal I-Al65Cu24Cr11 and its body-centered cubic approximate phase α-Al69Cu18Cr13. XRD patterns indicated that, for identical spraying condition, a rise in substrate temperature resulted in an increase of the I/α peak intensity ratio in the coatings, and the crystalline phases of AlCu4 and Al86Cr14 were observed in the coatings after annealing at 1113K for half an hour.