Processing, mechanical properties, and microstructures of dicalcium silicate-calcium zirconate composites
Hou, Tien-I
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Permalink
https://hdl.handle.net/2142/21108
Description
Title
Processing, mechanical properties, and microstructures of dicalcium silicate-calcium zirconate composites
Author(s)
Hou, Tien-I
Issue Date
1991
Doctoral Committee Chair(s)
Kriven, Waltraud M.
Department of Study
Materials Science and Engineering
Discipline
Materials Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Language
eng
Abstract
The two major aims of this research were: (1) to develop a chemical process for making Ca$\sb2$SiO$\sb4$ powder for composite preparation, and (2) to process the Ca$\sb2$SiO$\sb4$-CaZrO$\sb3$ composite through microstructural engineering to improve mechanical properties and to correlate these properties to microstructures. Pure CaZrO$\sb3$ was also studied in parallel.
For the first time, a modified Pechini method was successfully applied to fabricate Ca$\sb2$SiO$\sb4$ powder with high surface area of about 15 m$\sp2$/g. The shape of Ca$\sb2$SiO$\sb4$ particles was irregular and each particulate consisted of many fine spherical particles.
The toughness of pure CaZrO$\sb3$ was found to depend on its grain size. This was related to microcracking at the grain boundaries. The microcracking phenomenon was confirmed by the measurement of Young's modulus and by TEM observation.
Three types of microstructures were created in Ca$\sb2$SiO$\sb4$-CaZrO$\sb3$ composites. The first type was Ca$\sb2$SiO$\sb4$ added as a second phase, the second consisted of a 50 vol.%-Ca$\sb2$SiO$\sb4$-50 vol.%-CaZrO$\sb3$ mixture, and the third was a reverse of the first one. Results showed that the composite with the second type of microstructure had the highest toughness of about 4.0 MPa$\cdot$m$\sp{1/2}$, which was about double that of the base material. Microstructural observations indicated weak grain boundaries in CaZrO$\sb3$ agglomerates and weak interfaces between the two phases. The toughening was considered to be mainly from crack deflection and microcracking.
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