Zirconia dispersion

Wernet, J. and Feke, D.L., Effects of solids loading and dispersion schedule on the state of aqueous alumina/zirconia dispersions, J. Am. Ceram. Soc., 77, 2693, 1994. Nob. J.S. and Schwarz, J.A., Estimation of the point of zero charge of simple oxides by mass titration, J. Colloid Interf. Sci., 130, 157, 1989. 

In this context, the aims of this study are to clarify the effect of different fast sintering techniques such as microwaves field at 2.45 GHz and external pulsed electrical field (Spark Plasma Sintering-SPS) on densification behavior of zirconia dispersed alumina nanopowders, on the microstructure and mechanic properties and to enhance the mechanical properties of the sintered composites. 

Renger, C, Kuschel, P., Kristoffersson, A., Clauss, B., Oppermann, W. and Sigmund, W. (2004) Colloid probe investigation of the stabilization mechanism in aqueous 1,2-propanediol nano-zirconia dispersions. Physical Chemistry Chemical Physics, 6,1467-74. 

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 addition of MgO leads to the formation of a naiTow range of solid solutions at high temperamre, which decompose to precipitate inclusions of tetragonal Zr02 dispersed in cubic zirconia. The material, which functions as a solid electrolyte, has the added advantage that the inclusions stop the propagation of any cracks which may arise from rapid temperature change. 

S. Wodiunig, F. Bokeloh, J. Nicole, and C. Comninellis, Electrochemical Promotion of R11O2 Catalyst Dispersed on an Yttria-Stabilized Zirconia Monolith, Electrochemical and Solid State Letters 2(6), 281-283 (1999). 

Electron micrographs (scanning and transmission) showed that tungsten carbide is well dispersed on the surface of each support as nanosized particles (20 - 50 nm) as typified by the images in Figs. 3 (a b). However, BET surface area decreased in the order alumina > silica > titania > zirconia. With highest surface area obtained for each support being 240,133,18 and 9 m g respectively. 

X-ray dififtaction (XRD) analysis of the freshly calcined catalysts as well as samples used for several hours in the isomerization reaction, only presented the peaks corresponding to the tetragonal form of zirconia. At the same time, for the silica series, XRD confirmed the presence of NiO on the unsulfated catalysts and NiS04 on the sul ted ones. However, XRD did not show any evidence of any of these species for the zirconia series, probably due to their high state of dispersion. Similarly, the XPS data clearly showed the presence of NiO and NiS04 on the unsulfated and sulfated silica-supported catalysts, respectively, but they were not conclusive in the case of zirconia series since both sulfate and oxide species were observed. 

The comparison of the results of TPR with those of NO TPD on Cu on silica and alumina suggests that a better dispersion of the Cu species induces a higher reducibility of Cu, as reported elsewhere [16]. On the other hand, a strong support effect appears in the case of Cu supported on zirconia or titania, which shows the easiest reducibility in spite of a low dispersion as judged from XRD. 

The same behaviour has been found with Cu/ZrOa. A highly dispersed Cu phase was obtained at the surface of zirconla by reacting the support with Cu acetylacetonate [19]. This procedure yields an active catalyst. This catalyst was selective for Na formation at low temperature (< 550 K), but produced only NO2 when the temperature becomes higher than 650 K. However, the same type of catalyst prepared from sulfated zirconia did not produce NO2 but selectively reduces NO to N2 whatever the temperature, with a yield of about 40% at 670 K, and a GHSV of 70000 h l, using only 300 ppm of decane. 

Moafi et al. [143] studied the ability of titania versus zirconia to photocatalyze methylene blue and eosin yellow on polyacrylonitrile fibers. Ti02 particles ranging from 10-20 nm in size and Zr02 particles ranging from 20-40 nm in size were dispersed on the fiber surface. Photocatalytic activity of Ti02 was greater. 

It has been observed that solid oxide fuel cell voltage losses are dominated by ohmic polarization and that the most significant contribution to the ohmic polarization is the interfacial resistance between the anode and the electrolyte (23). This interfacial resistance is dependent on nickel distribution in the anode. A process has been developed, PMSS (pyrolysis of metallic soap slurry), where NiO particles are surrounded by thin films or fine precipitates of yttria stabilized zirconia (YSZ) to improve nickel dispersion to strengthen adhesion of the anode to the YSZ electrolyte. This may help relieve the mismatch in thermal expansion between the anode and the electrolyte. 

Inorganic particles such as the dispersion of carbon black, chromatographic silica, glass beads, silica beads, silica sol, silver sol, titania, and polydispersed zirconia colloidal suspensions have been... 

Another solution proposed for the low-temperature deposit process for fluorhy-droxyapatite onto porous zirconia bone scaffold was reported by Kim et al. [161], It is based on the immersion of the scaffold in a slurry of dispersed HA-FA powders in polyvinylbutyl for several hours, followed by drying and subsequent heat treatments at 800°C and 1200°C for binder (polyvinylbutyl) burnout. The process can be repeated fora multilayer film deposit. 

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