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Dissertation
Experimental study and numerical simulation on synthesis, properties, and applications of oxide-coated ceramic particles
Doctor of Philosophy (Ph.D.), Drexel University
2000
DOI:
https://doi.org/10.17918/00007988
Abstract
This thesis combines experimental studies and numerical simulations to gain qualitative and/or quantitative understanding on the synthesis and properties of oxide-coated ceramic particles. Experimentally, boehmite had been successfully coated on the surface of SiC by a sol-gel coating approach. We found that as the amount of added boehmite precursor increases, the thickness of coating layer increases, and reaches a saturated value. Also, the maximum sedimentation density of boehmite-coated SiC suspensions, [special characters omitted] increased with increasing coating thickness from under 25vol% with 10wt% boehmite to above 65vol% with 10wt% boehmite. The coated-particle suspensions exhibited viscoelastic behaviors and the maximum storage modulus, [special characters omitted] decreased with an increasing coating thickness, t, as [special characters omitted] The boehmite sol-gel coating technique was applied to various ceramic particles, and the results showed that the presence of carbon on the surface of core particles is important for the boehmite coating. There were two possible morphologies, continuous shell-like coating and patchy island-like coating, depending on the Hamaker constant of core particles. Monte Carlo simulations was used to investigate the controlling factors of coating morphology. Our model was based on a reversible cluster-cluster aggregation model. It allows particles to aggregate and unbind, and performs precipitation and coating at the same time. The model includes two levels of interactions: one is the attraction energy, -E, between monomers that aggregate to form particles; the other is the interparticle interaction energy that affects the aggregation of particles. We found that a system with a weaker (stronger) monomer-monomer attraction energy has a higher (lower) solubility. The monomer-wall attraction energy, - Ew was used to determine the stickiness of the walls, which represented the surface of core particles. The result showed that the system with a higher solubility grew a thicker coating layer with a faster growth rate. Also, the morphology of coating layer was controlled by a combination effect of E and Ew. When a system has a E/Ew ratio larger than unity, it tends to form patchy and island-like coating; on the other hand, a system with E/Ew ratio smaller than unity favors the formation of continuous shell-like coating layer. The sol-gel coating technique was employed to coat boehmite onto zirconia. It showed an improvement in the thermal stability, which is important in catalytic applications.
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Details
- Title
- Experimental study and numerical simulation on synthesis, properties, and applications of oxide-coated ceramic particles
- Creators
- Chia-Yi Yang
- Contributors
- Wan Y. Shih (Advisor) - Drexel University, Drexel University (1970-)Wei-Heng Shih (Advisor) - Drexel University, Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xviii, 238 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Drexel University
- Other Identifier
- 991021888991704721