Synthesis of yttria-stabilized zirconia nanoparticles by decomposition of metal nitrates coated on carbon powder
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Synthesis of yttria-stabilized zirconia nanoparticles by decomposition of metal nitrates coated on carbon powder Shusheng Jiang, Gregory C. Stangle, Vasantha R. W. Amarakoon, and Walter A. Schulze School of Ceramic Engineering and Sciences, New York State College of Ceramics at Alfred University, Alfred, New York 14802 (Received 11 September 1995; accepted 4 March 1996)
Weakly agglomerated nanoparticles of yttria-stabilized zirconia (YSZ) were synthesized by a novel process which involved the decomposition of metal nitrates that had been coated on ultrafine carbon black powder, after which the carbon black was gasified. The use of ultrafine, high-surface-area carbon black powder apparently allowed the nanocrystalline oxide particles to form and remain separate from each other, after which the carbon black was gasified at a somewhat higher temperature. As a result, the degree of agglomeration was shown to be relatively low. The average crystallite size and the specific surface area of the as-synthesized YSZ nanoparticles were 5–6 nm and 130 m2yg, respectively, for powder synthesized at 650 ±C. The as-synthesized YSZ nanoparticles had a light brown color and were translucent, which differs distinctly from conventional YSZ particles which are typically white and opaque. The mechanism of the synthesis process was investigated, and indicated that the gasification temperature had a direct effect on the crystallite size of the as-synthesized YSZ nanoparticles. High-density and ultrafine-grained YSZ ceramic articles were prepared by fast-firing, using a dwell temperature of 1250 ±C and a dwell time of two minutes or less.
I. INTRODUCTION
The production of nanoparticles is currently the focus of great interest for densifying ceramics at lower sintering temperatures, and for achieving ultrafinegrained ceramics, since these materials are expected to exhibit some special features that are distinct from either single-crystal or microcrystalline ceramics. In this regard, many material systems have been studied in the effort to produce nanoparticles. Furthermore, yttriastabilized zirconia (YSZ) ceramics are considered to be one of the most important ceramic materials for use in structural applications, due to the high strength and toughness of yttria-stabilized tetragonal zirconia polycrystals (Y-TZP), as well as for use in electrical applications, due to the high oxygen-ion conductivity of YSZ at elevated temperatures.1 Moreover, finegrained Y-TZP ceramics are superplastic at elevated temperatures if the grain size is below 1 mm. In addition, it has been shown that higher strain rates and larger elongations-to-failure can be obtained by decreasing the grain size.2–4 As a result, YSZ is one of the material systems on which a great deal of attention has been focused, in order to produce ultrafine-grained ceramics for which nanocrystalline powder is typically used as the starting material.5–11 A number of processing methods used to synthesize ceramic nanoparticles have been reported,
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