Preparation of zirconia aerogel by heating of alcohol–aqueous salt solution

Wu, Zhi Gang; Zhao, Yongxiang; Xu, Lin; Liu, Dian Sheng

doi:10.1016/j.jnoncrysol.2003.08.049

Cited by 35 publications

(17 citation statements)

References 15 publications

(12 reference statements)

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“…This observation is also consistent with previous studies of the effect of thermal processing on the structure of nanoparticles. In the case of annealing a zirconia aerogel, even after heating at 1000 o C, the particle size was found to be no larger than 30 nm [37]. For zinc oxide annealed at different temperatures, Ba-Abbad reported that the particle size increased from 20 nm at 400 o C to 41 nm at 600 o C [38].…”

Section: Morphologymentioning

confidence: 99%

The effects of hydration on the DC breakdown strength of polyethylene composites employing oxide and nitride fillers

Hosier

Praeger

Vaughan

et al. 2017

IEEE Trans. Dielect. Electr. Insul.

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Particle dispersion, water absorption/desorption and electrical breakdown behavior were studied in a range of polyethylene composites having a common matrix morphology. Three different conditioning routes (dry, ambient and wet) were used to vary the absorbed water content. Systems employing oxide fillers (silica and alumina) were found to have poor or intermediate levels of particle dispersion and could absorb/desorb significant amounts of water. Consequently, they required drying to provide breakdown strengths comparable to that of the host matrix. Systems based on calcined silica exhibited reduced water absorption and provided improved breakdown strength after ambient conditioning, despite having an identical dispersion to those utilizing untreated silica. Composites employing nitride fillers (silicon nitride and aluminum nitride) were found to have good or intermediate levels of particle dispersion. These absorbed far less water and hence provided breakdown strength values comparable to that of the host matrix following ambient conditioning. Their breakdown strength was degraded after wet conditioning with both exhibiting similar breakdown strengths despite there being a large difference in the level of particle dispersion between the two fillers. In composites based upon a hydrophobic host matrix, water absorption is largely determined by particle surface chemistry and, although the above results are presented in terms of water absorption, we suggest that changes in this characteristic can be interpreted as a proxy for changed surface chemistry. The results suggest that surface chemistry is at least as important as particle dispersion in determining the electrical breakdown strength.

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Section: Morphologymentioning

confidence: 99%

The effects of hydration on the DC breakdown strength of polyethylene composites employing oxide and nitride fillers

Hosier

Praeger

Vaughan

et al. 2017

IEEE Trans. Dielect. Electr. Insul.

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“…When zirconia powders (YSZ) are prepared using the sol-gel route [9][10][11][12][13][14] drying is mainly governed by the capillary pressure. Conventional drying consists of drying the gel at ambient temperature in an oven to remove the liquid phase (alcohol and water from the sol-gel synthesis) from the porous structure [6].…”

Section: Introductionmentioning

confidence: 99%

Morphology and structure of YSZ powders: Comparison between xerogel and aerogel

Fenech¹,

Viazzi²,

Bonino³

et al. 2009

Ceramics International

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Yttria-stabilized zirconia (YSZ) fine powders were prepared via sol-gel route in order to shape thermal barrier coatings (TBCs) from these powders. The main objective is to develop new undirectional coatings to allow best thermo-mechanical accommodations compared to conventional processes. To reach this aim, powders have to be able first to be highly dispersed into a sol (non-agglomeration, high specific surface area, etc.) and second to crystallize in the required metastable phase t 0. Two routes have been used to dry gels: the conventional way which consists of simple evaporation of the solvent is compared to drying in supercritical conditions. Both YSZ powders after calcination at 950 8C of xerogel (Ex-xero-YSZ powder) and aerogel (Ex-aero-YSZ powder) crystallize in the tetragonal form. N 2 adsorption/desorption analysis of the Ex-xero-YSZ powder indicates an S w of 2.8 m 2 /g. For the Ex-aero-YSZ powder, the S w (26 m 2 /g) is much higher than of Ex-xero-YSZ, leading to a better sintering capability. This high S w is correlated to the small crystallite size (26 nm) and the alveolar morphology of Ex-aero-YSZ powders compared to Exxero-powder (49 nm). By reducing particles size and increasing the S w of the powders, supercritical drying appears as a promising way to prepare stable slurries or loaded sols from fine YSZ particles for TBC applications. Indeed, after preparing nanometric powders, they are dispersed into a sol before shaping on superalloys substrates. After thermal treatment at 950 8C for 2 h which corresponds to the working temperature of TBC, the final aim will be to prepare ceramic YSZ coatings.

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“…Preparing a fine and an agglomerate free zirconia powder is the first and perhaps the most important step in obtaining a sintered zirconia ceramic of desirable microstructure and therefore mechanical properties. Various chemistry-based novel approaches have been taken for the preparation of zirconia powders including co-precipitation, hydrothermal, sol gel, sonochemical method, microemulsion and thermal decomposition processing (Ma et al, 2004;Wu et al, 2003;Lee et al, 1999;Tai et al, 2001;Djuricic et al, 1995;Bourell and Kaysser, 1993;Ward and Ko, 1993;Huang and Guo, 1992;Fang et al, 1997;Li et al, 1989;Juarez et al, 2000;Yashima et al, 1996;Yashima et al, 1994;Caruso et al, 1997;Chatterjee et al, 1992;Dodd and McCormick, 2002;Roy and Ghose, 2000;Kolen'ko et al, 2003;Noh et al, 2003;Somiya and Akiba, 1999;Piticescu et al, 2001). The chemical precipitation (CP) method is a suitable low cost technique for the mass production compared with the other mentioned technique.…”

Section: Introductionmentioning

confidence: 99%