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:
Monolithic t-ZrO2 (tetragonal structure) nanopowder is synthesized with an amorphous ZrO(OH)2·xH2O polymer precursor. The H2O molecules impart the structure and promote reconstructive thermal decomposition of the structure to t-ZrO2 nanoparticles on heating at temperatures as low as 200°C. A prevalent endothermic heat output in the dissociation process controls the local temperature in exothermic nucleation and growth of various groups of the reaction species so that it is self-controlled in high-energy nanoparticles. Crystallites are, on average, d= 8 nm diameter, and they have a high value of Gibbs free energy or lattice volume Vo= 0.06770 nm3. The excess volume decreases to Vo= 0.06705 nm3 if the reaction temperature is increased to 〉200°C, i.e., approximately the bulk value of 0.06681 nm3; there is a minor increase to d= 12 nm at 600°C. Many oxygen vacancies in the thin surface space-charge layers seem to support the stability of small particles in this particular polymorph. A pure m-ZrO2 (monoclinic structure) appears with d= 22 nm at temperature as low as 800°C. The results are analyzed using X-ray diffractometry, microstructure, infrared spectroscopy, and thermal studies of the polymer precursor and derivative t-ZrO2 nanoparticles.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1151-2916.2004.tb07489.x
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