Zirconia sintering

As for n, which is the parameter that provides the gap between the actual capacitace and a pure capacitance, it is independent of temperature. The values are close to 0.5 (Warburg diffusion mechanism), sUghtly higher for sintered beta-alumina and sintered zirconia (0.62 and 0.59), slightly lower for glass and the... 

Agglomeration of macroemulsion-generated nanoparticles was also avoided by Gao et al [182] through a heterogeneous distillation method. These authors converted Y-doped Zr02 particles of 14 nm size obtained by this process to sintered zirconia ceramics of 97% theoretical density. 

Figure 5.12. Grain boundaries of a sintered zirconia alloy (from S. Meriani. Thirteenth International Conference on Science of Ceramics, p. 485. Orleans (1985). With permission from les editions de physique.

Fig. 2.30 Morphologies of fracture surfaces of sintered zirconia ceramic moulds with different PSDs a CSZl b CSZ2 c CSZ3 [15]. With kind permission of Elsevier...

Figure 11.35 Delamination of a sintered zirconia thin film produced by a sol-gel method on a nanoporous alumina substrate. (Courtesy of L. C. De Jonghe.)...

In order to understand the influence of sol-gel processing and consequently the particle characteristics on compaction behavior and sintering, zirconia powders prepared from inorganic sols were compared (Jorand, 1995 Taha, 1995) with a commercially available zirconia powder. The characteristics of as-prepared powders P2 and P3 calcined at 600° C are given in Table 6-5 along with the data on commercially available zirconia powder PI prepared by sol-gel decomposition. 

Infiltration (67) provides a unique means of fabricating ceramic composites. A ceramic compact is partially sintered to produce a porous body that is subsequently infiltrated with a low viscosity ceramic precursor solution. Advanced ceramic matrix composites such as alumina dispersed in zirconia [1314-23-4] Zr02, can be fabricated using this technique. Complete infiltration produces a homogeneous composite partial infiltration produces a surface modified ceramic composite. 

The measures of solid state reactivity to be described include experiments on solid-gas, solid-liquid, and solid-solid chemical reaction, solid-solid structural transitions, and hot pressing-sintering in the solid state. These conditions are achieved in catalytic activity measurements of rutile and zinc oxide, in studies of the dissolution of silicon nitride and rutile, the reaction of lead oxide and zirconia to form lead zirconate, the monoclinic to tetragonal transformation in zirconia, the theta-to-alpha transformation in alumina, and the hot pressing of aluminum nitride and aluminum oxide. 

The co-precipitation technique starts with an aqueous solution of nitrates, carbonates, chlorides, oxychlorides, etc., which is added to a pH-controlled solution of NH4OH, allowing the hydroxides to precipitate immediately. This method requires water-soluble precursors and insoluble hydroxides as a final product. The hydroxides are filtered and rinsed with water when chlorides are employed as starting materials and chlorine is not desired in the final product. After drying the filtrate, it is calcined and sintered. This method is being applied very successfully for oxygen-ion conducting zirconia ceramics [30],... 

Other potential applications are ceramic powders coated with their sintering aids, zirconia coated withyttria stabilizer, tungsten carbide coated with cobalt, or nickel, alumina abrasive powders coated with a relatively brittle second phase such as MgAl204 and plasma spray powders without the segregation of alloying elements. 

X-ray diffraction and surface area measurements suggest that these W-atom surface densities correspond to saturation coverages, which markedly inhibit zirconia sintering and tetragonal to monoclinic transformations at high temperatures. Zr02 surface areas after 1073 K calcination are 4 m g" and increase to an asymptotic value of 51 m g for W surface densities above 5-6 W-atoms nm (Figure 4). Similarly,... 

Lei and Zhu [63] found that adding 2.0 mol% Mn203 to llScSZ can inhibit the cubic-rhombohedral phase transformation in both oxidation and reduction atmospheres, and the codoped zirconia can reach nearly full density when sintered at temperatures as low as 850°C. The conductivity of 2Mn203-l IScSZ sintered at 900°C is 0.1 Scm-1 at 800°C. Figure 1.11 illustrates the conductivity of some zirconia-based ternary systems [32,42,57,63-67],... 

Primdahl S, Sprensen BF, and Mogensen M. Effect of nickel oxide/yttria-stabilized zirconia anode precursos sintering temperature on the properties of solid oxide fuel cells. J Am Ceram Soc 2000 83 489 -94. 

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