Papers by Keyword: Suspension Plasma Spraying

Abstract: On the help of the atmosphere plasma spraying (APS) and suspension plasma spraying (SPS) conditions optimized previously, APS and SPS were both introduced to prepare the PEN (Positive- Electrolyte-Negative) of planar solid oxide fuel cells (SOFCs). Then the microstructure and material components of the PEN cells were analyzed. Experimental results show that the electrolyte layer fabricated by SPS represents higher densification, thinner thickness and more homogeneous component distribution than that manufactured by APS, and meets the microstructure and density requirements of SOFC. The porosities of cathode and anode layers by APS and SPS reached 25%-35%. Therefore, the SPS could be a better and suitable approach to fabricate PENs of SOFC stacks, and effectively improve the conductivity of electrodes.

Abstract: Plasma spraying is employed to prepare porous La0.8Sr0.2MnO3 (LSM) cathode for solid oxide fuel cells (SOFCs) using both liquid suspension and solid feedstocks. The surface morphology and microstructure of the LSM deposits are characterized by SEM. The electrochemical behavior is investigated through the impedance spectroscopy. The specific surface resistance of 0.36 Ω•cm2 and 0.74 was obtained at 1000oC for SPS and APS LSM cathodes, respectively. The polarization of SPS LSM cathode is lower than APS LSM cathode by a factor of 2 to 2.4 in the temperature range from 850 to 1000 oC.

Abstract: In recent years, suspension plasma spraying (SPS) was investigated regarding the spraying of functional coatings with deterministic abilities. In this contribution the possibilities are discussed to achieve oxide ceramic coatings based on titania by SPS, which show a reduction of their coefficient of friction under dry sliding conditions. Besides the possibility to mix different feedstock suspensions in the process, the achievable low thickness and homogenous microstructure of suspension-sprayed coatings shall allow an operation in fields, where high demands towards the adhesion, cohesion and near net shape are made.

Abstract: Thermal spraying consists in a technology aiming at producing coatings whose thicknesses range from 10 μm to a few millimeters onto mechanical components to confer them specific and unique functional properties, such as wear and corrosion resistances, friction coefficient adaptation, thermal and electrical insulation, biocompatibility, repair, etc., among the principals. Thermal spraying consists in injecting in a viscous enthalpic jet (animated by a momentum) powder with particles which average size ranges from 0.01 to 100 μm. These particles are melted and simultaneously accelerated towards the surface of the part to be covered. They form, after impact, spreading and solidification, near-circular lamellae the stacking of which form the coating. Due to the versatility of the available processes exhibiting a wide range of enthalpic and momentum contents, virtually any kind of material exhibiting congruent melting behavior can be processed, from alloys and ceramics to polymers, ever since its melting temperature differs from its vaporization or decomposition temperature by at least 300 K and that it can be processed previously under the form of powder particles or wires. Thermal spray techniques offer the unique capability to manufacture a large variety of coatings on components of a large variety and geometry. However, thermal spraying constitutes a special process for which the coating service properties derive mostly from the structure and indirectly from the selection of the operating parameters. Very significant improvements over the past years permitted to diagnose the in-flight particle characteristics, mostly in terms of velocity and temperature. Recently, these new capabilities have made possible the development of on-line process controls. This should participate to a drastic increase in coating reliability. In convetntional thermal spraying processes, a pulverulent feedstock (i.e., powder particles) is injected within the plasma jet via a carrier gas. This approach does not permit to process small diameter particles; i.e., nano-sized particles, which could permit to form finely grained coatings. Replacing gas by liquid to carry particles offer the unique possibility to process nano-sized particles. Cold gas spraying may appear as an alternative process to reach the same goal. Indeed, thermal spray processes experienced very significant developments over the past years, opening new doors to manufacture coatings with a high reliability and superior properties. This papepr indend at presenting some of those developments.

Abstract: Intermediate temperature SOFC components, such as dense, nanostructured SDC electrolytes (samarium doped ceria) and porous anode sublayers were fabricated by suspension plasma spraying using an axial feed dc plasma torch. The liquid carrier employed in this approach allowed for controlled injection of much finer particles than in conventional thermal spraying, leading to thin coatings with a refined microstructure. Dense, thin (<10(m) and non-fractured electrolytes were created. Various processing routes for SOFC half-cells, using tape-cased, plasmasprayed and suspension-sprayed anodes, were explored. Loss of integrity and non-continuous coverage of the anode constituted the principal difficulties in the subsequent electrolyte deposition. The role of suspension feedstock particle size is discussed. Amongst various schemes investigated, a processing route that employs sequential suspension plasma spraying steps for both the electrolyte and the anode, using relatively large primary particles in the feedstock, constituted the most promising approach.