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Title: Directional solidification of the alumina-zirconia ceramic eutectic system

Abstract

It is possible to produce alumina-zirconia ceramic samples through existing solidification techniques. The resulting microstructures typically consist of rods of zirconia in an alumina matrix, although a lamellar structure has been noted in some cases. In nearly all cases, colony growth was present which may possibly result from grain size, repeated nucleation events, and lamellar oscillations. In the same vein, it appears that the amount of impurities within the system might be the underlying cause for the colony growth. Colony growth was diminished through impurity control as the higher purity samples exhibited colony free behavior. In addition to colony formations, faceted alumina dendrites or nonfaceted zirconia dendrites may result in the ceramic if the sample is solidified out of the coupled zone. In all cases, for larger-sized Bridgman samples, a lower limit in the eutectic spacing was noted. The solidification model which includes the kinetic effect has been developed, although the effect appears to be negligible under present experimental conditions. A spacing limit might also occur due to the result of heat flow problems. Heat flow out of the ceramic is difficult to control, often causing radial and not axial growth. This behavior is exaggerated in the presence of impurities.more » Thus, higher purity powders should always be used. Higher purity samples, in addition to yielding a more microstructurally uniform ceramic, also showed increased directionality. In the future, the kinetic model needs to be examined in more detail, and further research needs to be accomplished in the area of molten ceramics. Once better system constants are in place, the kinetic model will give a better indication of the behavior in the alumina-zirconia system.« less

Authors:
 [1]
  1. Iowa State Univ., Ames, IA (United States)
Publication Date:
Research Org.:
Iowa State Univ. of Science and Technology, Ames, IA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
10190639
Report Number(s):
IS-T-1621
ON: DE95001677; TRN: 94:021239
DOE Contract Number:  
W-7405-ENG-82
Resource Type:
Thesis/Dissertation
Resource Relation:
Other Information: TH: Thesis (Ph.D.); PBD: 27 Jul 1994
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM OXIDES; SOLIDIFICATION; MICROSTRUCTURE; ZIRCONIUM OXIDES; FABRICATION; MATHEMATICAL MODELS; EUTECTICS; EXPERIMENTAL DATA; YTTRIUM OXIDES; SCANDIUM OXIDES; CASTING; CRUCIBLES; 360202; STRUCTURE AND PHASE STUDIES

Citation Formats

Boldt, Christopher. Directional solidification of the alumina-zirconia ceramic eutectic system. United States: N. p., 1994. Web. doi:10.2172/10190639.
Boldt, Christopher. Directional solidification of the alumina-zirconia ceramic eutectic system. United States. https://doi.org/10.2172/10190639
Boldt, Christopher. 1994. "Directional solidification of the alumina-zirconia ceramic eutectic system". United States. https://doi.org/10.2172/10190639. https://www.osti.gov/servlets/purl/10190639.
@article{osti_10190639,
title = {Directional solidification of the alumina-zirconia ceramic eutectic system},
author = {Boldt, Christopher},
abstractNote = {It is possible to produce alumina-zirconia ceramic samples through existing solidification techniques. The resulting microstructures typically consist of rods of zirconia in an alumina matrix, although a lamellar structure has been noted in some cases. In nearly all cases, colony growth was present which may possibly result from grain size, repeated nucleation events, and lamellar oscillations. In the same vein, it appears that the amount of impurities within the system might be the underlying cause for the colony growth. Colony growth was diminished through impurity control as the higher purity samples exhibited colony free behavior. In addition to colony formations, faceted alumina dendrites or nonfaceted zirconia dendrites may result in the ceramic if the sample is solidified out of the coupled zone. In all cases, for larger-sized Bridgman samples, a lower limit in the eutectic spacing was noted. The solidification model which includes the kinetic effect has been developed, although the effect appears to be negligible under present experimental conditions. A spacing limit might also occur due to the result of heat flow problems. Heat flow out of the ceramic is difficult to control, often causing radial and not axial growth. This behavior is exaggerated in the presence of impurities. Thus, higher purity powders should always be used. Higher purity samples, in addition to yielding a more microstructurally uniform ceramic, also showed increased directionality. In the future, the kinetic model needs to be examined in more detail, and further research needs to be accomplished in the area of molten ceramics. Once better system constants are in place, the kinetic model will give a better indication of the behavior in the alumina-zirconia system.},
doi = {10.2172/10190639},
url = {https://www.osti.gov/biblio/10190639}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jul 27 00:00:00 EDT 1994},
month = {Wed Jul 27 00:00:00 EDT 1994}
}

Thesis/Dissertation:
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