This study investigates the effect of deposition temperature and particle size on lanthanum strontium chromite (LSC) deposits produced by atmospheric plasma spraying. The results show that dense deposits with lamellar interface bonding can be achieved at temperatures above the critical bonding temperature and that particle size has a significant effect on chromium vaporization losses. The loss of chromium may be responsible for the low electrical conductivity of LSC deposits produced from small powders, which suggests that conductivity can be controlled with appropriate process adjustments.

This study assesses the potential of scandia-stabilized zirconia (ScSZ) produced by very low-pressure plasma spraying (VLPPS) for metal-supported solid oxide fuel cell (MS-SOFC) applications. To investigate the microstructure of ScSZ, coating samples were deposited at spraying distances of 150, 250, 350 mm. The fragile nature of coating cross-sections suggests that the typical lamellar structure of zirconia is replaced by a transgranular structure. Nonetheless, apparent porosity, ionic conductivity, open circuit voltage, and ohmic resistance measurements indicate that VLPPS is a viable method for producing MS-SOFCs.

In this work, silicon carbide coatings were fabricated by plasma spray-vapor deposition in order to study the effect of plasma gas mixtures on coating microstructure and phase composition. Coatings deposited by Ar-H 2 plasma gas were found to contain a composite phase of SiC and Si. Moreover, the content of Si increased with increasing H 2 content in the gas. The deposition of Si is possibly due to the reaction of C and hydrogen species in the plasma jet, which would explain why pure SiC coatings were obtained when Ar-N 2 gas was used.

This study demonstrates a method of plasma spraying in which the plasma is maintained in a laminar (rather than turbulent) state, achieving a much greater jet length with less ambient air engulfment. In the experiments, NiCr coatings were produced at spraying distances between 250 mm and 500 mm, showing that specific structures can be realized by changing stand-off distance. Structures with high porosity, for example, are generated at relatively short distances; dense structures, on the other hand, are obtained at longer stand-off distances that allow feedstock powder to reach a fully melted state. XRD analysis shows that the spraying process does not change the chemical composition of the material, and EDS results indicate that chemical and metallurgical bonding are achieved.

In this study, NiCrBSi powders with a size range of 30-50 μm were deposited on mild steel substrates by self-fusing atmospheric plasma spraying. Particle temperatures exceeded 2400 °C and the deposits were remarkably dense with low oxygen content. Based on the results, a novel strategy is proposed to directly deposit dense, oxide-free coatings by plasma spraying without the need of post-spray fusing processes.

Rare-earth complex oxide ceramics are promising candidate materials for next-generation thermal barrier coatings due to their low thermal conductivity and phase stability. During plasma spraying, the component with a higher vapor pressure may experience severe preferential vaporization, resulting in significant composition change from the starting powder. In this study, Gd 2 Zr 2 O 7 (GZO) powder with a hollow spherical structure is used as the feedstock material to assess the vaporization behavior of G d2 O 3 during atmospheric plasma spraying (APS). Isolated Gd 2 Zr 2 O 7 splats with regular disc shapes in different sizes were deposited on stainless steel substrates at a deposition temperature of 300 °C to study the effects of particle size on vaporization loss. The elemental composition of each splat was analyzed by EDS, and the ratio of Gd to Zr in different splats with different diameters was obtained. The results show that the vaporization loss of Gd increases markedly with decreasing particle size due to the preferential vaporization of G d2 O 3 . Using Gd 2 Zr 2 O 7 powders of a certain size can reduce Gd loss, although the effect is determined by molten droplet size rather than apparent powder particle size.

High manufacturing costs and long-term degradation are the main problems that have become a “bottleneck” and impeded SOFC’s further development. It is well known that a high operating temperature is the major cause that leads to these problems. As such, reducing the operating temperature becomes a hotspot of research. It has been reported that a uniform and dense coating can be prepared by using very low pressure plasma spraying (VLPPS) technology. The current study focuses on VLPPS for application in large-area (~100 × 100 mm) porous metal supported solid oxide fuel cell (MSSOFC), especially for the preparation of the electrolyte. It was found that the densification of the electrolyte was very good, as confirmed by the open-circuit voltage (OCV) of the cell. In the temperature range of 550~750°C, the OCV of the cell stabilized between 1.05 V and 1.1 V. The power density of the cell was also measured.

Atmospheric plasma sprayed (APS) thermal barrier coatings (TBCs) with lamellar structure exhibit low thermal conductivity and low stiffness. However, high temperature exposure for certain long duration causes the sintering which heals two-dimensional (2D) inter-lamellar pores and intrasplat pores. Such sintering effect increases the stiffness and thermal conductivity of the coatings and consequently reduces the stability and durability of TBCs. It can be expected that large 2D pores with a wide opening is difficult to be eliminated. In this study, inter-lamellar 2D pores with large opening width were fabricated in the La 2 Zr 2 O 7 (LZO) coatings through spraying LZO+SrO coatings and removing the SrO splats in the water. Then, the conventional LZO coating and the porous LZO coating were subjected to high temperature exposure in the air at 1300 °C for different durations. The microstructure evolution especially in terms of the shape and density of inter-lamellar 2D pores was examined. In addition, the change of thermo-physic properties and the mechanical properties of the coatings with increasing exposure duration were studied. Results show that the 2D pores in LZO coating created by those SrO splats inherit primarily large opening width from 200nm to about 1 µm which endows the LZO coating with high sustainability at high temperature environment. Under thermal exposure at 1300°C, it was found that 2D pores resulting from SrO splats are free from healing while conventional 2D inter-lamellar pores with small opening width formed during splat cooling became healed rapidly. Thus, thermal conductivity and Young's modulus of the conventional LZO coating increased rapidly, while unhealed 2D pores in the highly porous LZO coatings contributed to the low Young's modulus and low thermal conductivity of LZO coating with remarkably high stability. With addition of 30% SrO in spray powder, a LZO coating with a thermal conductivity of about 0.39 W.m -1 .K -1 in the as-prepared state was obtained. The coating maintained a thermal conductivity of 0.57 W.m -1 .K -1 even after 100 hours exposure at 1300°C. The present results indicated that high sintering-resistant thermal barrier coating can be fabricated though designing inter-lamellar 2D pores with large opening width in the coating by the present novel approach.

LSCF(La 0.6 Sr 0.4 Co 0.2 Fe0 .8 O 3 ) with a perovskite structure has been widely studied as cathode materials for intermediate solid oxide fuel cell(SOFC). It has well-known excellent electrode performance due to its high ionic and electronic conductivity. However, application of LSCF cathode is likely to be limited by the surface catalytic properties and long term stability. Sr and Co may segregate from LSCF under cathode polarization, leading to increased resistance of the cathode. Oxygen hyper-stoichiometric La 2 NiO 4+δ with a K 2 NiF 4 structure possesses a higher catalytic properties, ionic conductivity and stability compared to LSCF cathode. However, the electrical conductivity of the La 2 NiO 4+δ (76 S cm –1 at 800 °C ) in the IT range are lower than 100 S/cm, which is regarded as the minimum requirement in electrical conductivity for an SOFC cathode. Taking account of both the advantages and disadvantages of the two different cathode materials, and good chemical compatibility of those two cathode materials, it is possible to prepare a composite cathode by infiltrating a thin film of La 2 NiO 4+ä on the porous LSCF to enhance the LSCF cathode performance. Therefore, in this study, the LSCF cathode was deposited by atmospheric plasma spray. The porous LSCF cathode was infiltrated by La 2 NiO 4+δ . The microstructure was characterized by SEM and TEM. The effect of infiltration on the polarization of LSCF cathode was investigated.

Based on the specific structure of tubular solid oxide fuel cell stacks, a good chemical, microstructural and phase stability for the protective coating are required in both the oxidizing and reducing environments. In this work, MnCO 2 O 4 coatings of approximately 150 µm were deposited onto porous Ni50Cr50-Al 2 O 3 substrate by atmospheric plasma spray (APS) process. The coated samples were tested at 800°C with the coating exposed in air environment and the substrate in H 2 environment. Reducing and pre-oxidizing treatments were performed prior to the stability test. Then the tested coatings were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results elucidated that the tested coating had a high structural stability on the upper layer, while presented a reducing microstructure on the substrate side. The surface morphology of 100 hours tested coating indicated that the spinel granules still arranged closely with small particle size of ~ 250 nm and no obvious grain enlargement was observed. According to the cross-section, the upper layer kept stable and dense. While at the underneath region, the microstructure presented to be rather porous. However, the resistance presented a decreasing trend with the extension of exposure duration. After exposure for 95 h, the ASR decreased to 18.5 mΩ·cm 2 although a substantial Cr diffusion from the substrate was detected.

Microstructure of cermet support influences significantly the performance and stability of solid oxide fuel cells (SOFCs). The properties required for the support include high electrical conductivity, necessary permeability, good match of thermal expansion with other layers and high temperature strength. In this study, a porous Ni50Cr50-Al 2 O 3 cermet was designed as the support of SOFC. The porous cermet was deposited by flame spraying with a powder mixture of 30%vol Al 2 O 3 and 35%vol Ni50Cr50 and 35%vol polyester. The effect of cermet microstructure on its gas permeability was investigated. The electrical conductivity, thermal expansion coefficient and bending strength of cermet support were also studied. The results showed that the gas leakage rate of the cermet support increased with the increase of polyester content in the starting powder. The thermal expansion coefficient of the composite cermet decreased with the increase of the volume fraction of Al 2 O 3 . Moreover, the electric conductivity of the cermet increased significantly after high temperature sintering, and reached 1015 S/cm after sintering at 1000°C for 15 hours. The three point bending strength of the Ni50Cr50-based cermet support reached 171 MPa. The cermet stability at high temperatures and SOFCs performance were discussed.