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  • 1
    Electronic Resource
    Electronic Resource
    Dissolution of Yttrium Ions and Phase Transformation of 3Y-TZP Powder in Aqueous Solution (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In order to understand the reactions of yttria-containing zirconia powder in aqueous solution, the dissolution behavior of yttrium and the formation of the monoclinic (m) phase of the Y-TZP powder were investigated. The tests were conducted in aqueous solution at temperatures up to 95°C. The results showed that the reaction order of yttrium dissolution from the surface of TZP powder is 5-9, and the activation energy is about 8.4 kJ/mol. However, the value of the reaction order is different from that (0.96-1.20) of the formation of m-phase. However, the yttrium dissolution of the slurries with the addition of 2 mol% dispersant (D-134) was reduced greatly to an extremely low (〈2 ppm) level up to 24 h at the testing temperatures. The results also showed that the amounts of m-phase formation were nearly the same for the powders in the slurries with or without D-134 addition. The decrease of yttrium content in the presence of D-134 and the formation of the m-phase of the TZP powder were not closely related. The degradation mechanism, or the formation of m-phase, should not be directly related to the dissolution of yttrium ions from a zirconia surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01971.x
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  • 2
    Electronic Resource
    Electronic Resource
    Electrokinetic Properties of Colloidal Zirconia Powders in Aqueous Suspension (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Pure zirconia, yttria, and three yttria-doped zirconia powders of submicrometer size have been dispersed in various aqueous solutions. The zeta potential (zeta) of the zirconia powders is determined primarily via streaming-current (SC) detection and is confirmed using electrophoretic spectroscopy techniques. The results reveal that the isoelectric point (IEP) of these zirconia powders is in the pH range of 5.6-7.2 and zeta is controlled primarily by the yttrium content of the zirconia powders and the type of electrolyte. In addition, the yttria content strongly affects the potential and SC in zirconia suspensions only at high solids contents (〉1 vol%). The electrokinetic data reveal that the surface of the yttria-doped tetragonal zirconia powder (TZP) can be modified via the adsorption of ionic molecules or polymeric species in the suspension. The adsorption of an anionic polymer can stabilize zirconia particles in a solution that is almost neutral or weakly basic (in the IEP range of pure ZrO2). The interaction of the zirconia and yttria particles with the electrolytes in an aqueous suspension will be discussed to reveal the roles of hydrated oxide formation and zirconia surface interaction with polymeric dispersants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb02255.x
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of (Cr,Mo) Oxycarbide Films Grown on Stainless Steel via Metalloorganic Chemical Vapor Deposition (1997)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A mixture of hexacarbonyl of chromium and molybdenum ((Cr,Mo)(CO)6) was used to deposit oxycarbide films on stainless steel at temperatures of 175°–450°C. Through the analysis of deposition kinetics in various temperature regions, the controlling mechanism was determined to be exothermic surface reactions. Activation energies of the low- and medium-temperature regions were determined to be 71.2 and −60.1 kJ/mol, respectively. Some properties including densities, composition, and crystalline phases of the films were investigated. Results revealed that the chromium content of coating products increased as the temperature increased. The dominating surface reactions switched as temperature increased, because of the increase of chromium content in the precursor gas. Hence, the coating rate and density increased to a maximum, then decreased as the coating temperature was increased to 275°C. Deposited phases were determined by X-ray diffractometry, and the relationship with film density phases has been discussed, using their microstructural textures from scanning electron microscopy micrographs. Corrosion resistance was measured by an electrochemical method. The films obtained in the low- and medium-temperature regions improved the corrosion resistance of stainless-steel substrates by a factor of 24. In addition, the latter case showed the effect of passive protection and was an optimized selection for corrosive protection. The relationship of the improvement of corrosion resistance, physical properties, and the contribution of composed phases was discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb02918.x
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  • 4
    Electronic Resource
    Electronic Resource
    Electrokinetic Properties of Nanosized SiC Particles in Highly Concentrated Electrolyte Solutions (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In this research, the electrokinetic behavior and stability of nanosized SiC particles suspended in various electroplating solutions were studied. Analyses were performed using electrophoretic mobility photometry and streaming current (SC) techniques. The electrolytes included NiCl2, Ni(SO3NH2)2, and Na3Co(NO2)6, which are currently used in composite plating solutions with concentrations as high as 0.5M. The results showed that the adsorption of dissolved Ni2+ ions onto the surface of the SiC in the pH range 4–8 changed the sign and magnitude of the surface potential. Moreover, trivalent complex species Co(NO2)63− replaced nickel species on the SiC surface and decreased the surface charge of SiC to between pH 3 and pH 5. Even in a highly concentrated electrolyte solution, the SiC particles still maintained a positive charge in a Ni(SO3NH2)2 suspension with nickel coplating on the cathode. The difference between the SC reading and the zeta potential, as well as the surface adsorption of various species onto the SiC, are discussed here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00852.x
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  • 5
    Electronic Resource
    Electronic Resource
    Reaction Kinetics and Mechanisms between La0.65Sr0.3MnO3 and 8 mol% Yttria-Stabilized Zirconia (2004)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 87 (2004), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The reaction kinetics and mechanisms between 8 mol% yttria-stabilized zirconia (YSZ) and 30 mol% Sr-doped lanthanum manganite (La0.65Sr0.30MnO3, LSM) with A-site deficiency for the application of planar solid oxide fuel cells (SOFCs) were investigated. The LSM/YSZ green tapes were cofired from 1200° to 1400°C for 1 to 48 h and then annealed at 1000°C for up to 1000 h. The results showed that the diffusion of manganese cations first caused the amorphization of YSZ, and then the formation of small La2Zr2O7 (LZ) or SrZrO3 (SZ) crystals if treated for a longer time at 1400°C. The ambipolar diffusion of the Mn–O pair, transported through the migration of oxygen vacancy, plays an important role in the formation of secondary phases. The diffusion of LSM to YSZ and substitution of Mn for Zr both result in the enhanced concentration of oxygen vacancy, leading to the formation of a void-free zone (VFZ). No additional reaction products in annealed LSM/YSZ specimens, treated at 1000°C for 1000 h, were detected. The interfacial reactions, detailed reaction kinetics, and mechanisms are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2004.01110.x
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