Papers by Author: Xu Ping Lin

Abstract: The double-perovskite La_0.4Sr_1.6CoNbO_6-δ (LSCN) powders were synthesized by the solid-state reaction method. The electrical conductivities of LSCN samples were tested in air and 5 vol%H₂/Ar. The results show that the conductivity of LSCN in 5 vol%H₂/Ar (8.12 Scm^-1) at 850 °C was higher than that in air (7.03 Scm^-1). The activation energy obtained from the Arrhenius function was 0.821 eV in air and 0.707 eV in 5 vol%H₂/Ar. The analysis of XPS shows that there exit three valence states of Co (Co⁺², Co⁺³, Co⁺⁴) and two of Nb (Nb⁺⁴, Nb⁺⁵). The loss of lattice oxygen in LSCN not only produces oxygen vacancies, but also generates excess electrons, which contributes to the electrical conductivity of the LSCN samples.

Abstract: Double-perovskite Sr₂Fe_1-xMn_xNbO_6-δ (x = 0, 0.1, 0.2, 0.3, 0.5, 0.8) (SFMN) powders which will be applied to the electrode of solid oxide electrolysis cells (SOEC) were synthesized by Solid State Reaction Method. The mixed oxide powders SrCO₃, Fe₂O₃, MnO₂ and Nb₂O₅, were homogeneously calcined at different temperatures and in different atmospheres. The influence of the preparation process on the structure and the morphology of the powder were investigated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). It is found that the formation of perovskite structure is directly related to the content of Mn and calcining temperature. Controllable synthesis of pure phase of double perovskite powders was realized after calcining for12h at 1150 °C in air. Moreover, the experimental results show that the perovskite structure of SFMN is stable in whether oxidizing or reducing atmosphere, which indicates that this material has a potential to be used as electrode of solid oxide electrolysis cell.

Abstract: Two different types of morphology are observed in synthesis of SiC nanowires by catalyst-assisted pyrolysis of polymeric precursor while Au acts as the catalyst. Both two types of SiC nanowires are well oriented and uniform in diameter. The results indicate that longer (~20 μm) and slimmer (~100 nm) nanowires are tends to be produced in high temperature (1450°C), while shorter (~10 μm) and thicker (200~300 nm) ones are tends to be produced in low temperature (1420°C). Then we make a discussion on the mechanism of the growth of SiC nanowires based on the VLS (Vapor-Liquid-Solid) process.

Abstract: This work investigated the wear behavior of cemented carbide cermet YG8B under different concentrations of abrasive slurries using a modified ASTM B611 wet sand rubber rimmed wheel test system with a load of 225 N. The angular sand abrasives involved in carborundum, corundum and silica with particle size of about 350 μm, and were dispersed into water with different mass fractions. It was found that, with increasing sand concentration in slurry, the wear loss of the cermet samples increased, and with the increase of duration time, the wear loss of the cermet samples also increased. Under the same conditions, the cermet samples presented the biggest wear loss with carborundum as abrasive. On the basis of the observations on the worn surfaces by scanning electron microscope and 3D white-light interfering surface profiler, the wear mechanism of the cermet samples was proposed, which includes in extensive plastic deformation, groove, fracture and pullout.

Abstract: Double-perovskite Sr2Fe1-xScxMoO6- (x = 0, 0.05, 0.1, 0.2, 0.3, 0.4) powders have been synthesized by sol-gel citrate method. Initial powders were calcined in different temperature and atmosphere (air, H2(4vol%)/Ar), then analyzed by using the methods of X-ray, scanning electron microscopy (SEM), as well as thermal analysis. It is found that the formation of perovskite structure is related to the content of Sc, pH value, calcination temperature and sintering atmosphere. Especially, a pure perovskite structure almost completely formed after three hours sintering in atmosphere of H2(4vol%)/Ar. Although the formation of perovskite structure also happened in the air atmosphere, at the same time the SrMoO4 structure formed undesirably as a result of oxidization of Mo.

Abstract: The solid oxide electrolysis cell (SOEC) has been receiving increasing research and attention worldwide due to its potential usage for large-scale production of hydrogen. Tape casting and lamination technique were successfully used to fabricate the NiO-YSZ hydrogen electrode substrate cermets of planar solid oxide electrolysis cell. In this paper the green tape with thickness of 350μm was prepared by tape casting and then the lamination was used to obtain the required thickness for the NiO-YSZ hydrogen electrode-supported electrolyte cermets. The rheological properties of the suspensions with NiO-YSZ and YSZ were studied, respectively. The optimal temperature and pressure of the lamination were determined, and four direction of lamination mode was used according to tape casting direction to obtain symmetrical and even hydrogen electrode-supported electrolyte after co-sintering. Pore-formers were used to increase the porosity of the hydrogen electrode. The green tape was analyzed by TG-DSC analysis, the microstructure was observed by scanning electron microscope. The electrochemical performance of unit cell was measured at 850°C.

Abstract: The influence of CuO-V2O5-Bi2O3 addition on the sintering behavior, phase composition, microstructure and microwave dielectric properties of Zn3Nb2O8 ceramics were investigated. The co- doping of CuO, V2O5 and Bi2O3 can significantly lower the sintering temperature of Zn3Nb2O8 ceramics from 1150°C to 900°C. The Zn3Nb2O8-0.5wt% CuO-0.5wt% V2O5-2.0wt% Bi2O3 ceramic sintered at 900°C showed a relative density of 97.1%, a dielectric constant (εr) of 18.2, and a quality factor (Q×f) of 36781 GHz. The dielectric properties in this system exhibited a significant dependence on the relative density, content of additives and sintering temperature. The relative density and dielectric constant (εr) of Zn3Nb2O8 ceramics increased with increasing CuO-V2O5-Bi2O3 additions. And also the relative density and dielectric constant of Zn3Nb2O8 ceramics increased by the augment of the sintering temperature.

Abstract: The dielectric ceramics of CaTiSiO5-CaTiO3 with ZnO and B2O3 as additives were sintered at 950°C. Of the ceramics with a small quantity of 2ZnO-B2O3 as the additive, the density is nearly the same as the one reported, εr= 83 ~ 99, tgδ < 7×10-4, αε= (-100~+100) ppm/°C. The crystal phases and microstructures are analyzed by X-ray diffraction and scanning electron microscope. It is found that the sintered ceramics is of biphase, comprising monoclinic CaTiSiO5 and orthorhombic CaTiO3, and the grains are mostly the small circular ones, having diameters of 1~29m. By adjusting the composing of the ceramic, a high frequency dielectric ceramic CaTiSiO5-CaTiO3, of which αε= (-50~+50) ppm/°C was attained.

Abstract: Gelcasting and dry pressing are used to produce anode composites for SOFC. In this paper a composite material Ni/Ce-YSZ containing Ni and Ce-doped Y2O3-stabilized ZrO2 (Ce-YSZ) based on Ce-YSZ electrolyte was fabricated via sintering infiltration of NiO at the temperature of 1400°C, followed Ni/Ce-YSZ materials are successfully produced by reduction- sintering process. Hydrogen reduction of NiO in the NiO/Ce-YSZ anode material was accomplished successfully through pore channels of debinded carbon volume. XRD results suggest that a solid solution of Ce-YSZ was produced. The microstructure of NiO/Ce-YSZ, and Ni/Ce-YSZ material was observed by SEM. This study confirms that sintering infiltration of NiO is a viable process for fabricating anode materials based on zirconia electrolyte and there are a good interface between electrolyte and anode.

Abstract: Microstructure and mechanical properties of CeO2/Y2O3/ZrO2 ceramics were investigated using ultrafine CeO2/Y2O3/ZrO2 powder as the starting material. The structures of CeO2/Y2O3/ZrO2 containing 8~12mol% CeO2 were composed of tetragonal phases. They exhibited an extremely high bending strength (950 MPa) and fracture toughness (12MPa·m1/2). The structural details of CeO2/Y2O3/ ZrO2 were studied by TEM, SEM and XRD. The effects of the structure on mechanical properties were discussed. Plungers and ball valves by the CeO2/Y2O3/ZrO2 ceramics have higher wear resistance and corrosion resistance than metal. Their service life is about 6 ~ 10 fold more than that of metal.