Analysis of Tetragonal to Monoclinic Phase Transformation Caused by Accelerated Artificial Aging and the Effects of Microstructure in Stabilized Zirconia PDF Download
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Author: Thomas J. Lucas
Publisher:
ISBN:
Category : Body temperature
Languages : en
Pages : 92
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Book Description
This investigation addresses the issue that yttria stabilized zirconia is being used as a dental biomaterial without substantial evidence of its long-term viability. Furthermore, stabilized zirconia (SZ) undergoes low temperature degradation (LTD), which can lead to roughening of the surface. A rougher exterior can lead to increased wear of the antagonist in the oral environment. Despite the LTD concerns, SZ is now widely used in restorative dentistry, including full contour crowns. A comparison of aging methods to determine the role of artificial aging on inducing the transformation has not been extensively studied. Therefore, simulations of the transformation process were investigated by comparing different methods of accelerated aging. The rejected null hypothesis is that the temperature of aging treatment will not affect the time required to cause measurable monoclinic transformation of yttria stabilized zirconia.The transformation of SZ starts at the surface and progresses inward; however, it is unclear whether the progression is constant for different aging conditions. This investigation analyzed the depth of transformation as a function of aging conditions for stabilized zirconia in the top 5-6 micrometers from the surface. The rejected null hypothesis is that the transformation amount is constant throughout the first six micrometers from the surface. The effects of grain size on the amount of monoclinic transformation were also investigated. This study aimed to determine if the grain size of partially stabilized zirconia affects the amount of monoclinic transformation, surface roughness, and property degradation due to aging. The rejected null hypothesis is that the grain size will not affect the amount of monoclinic transformation, thus have no effect on surface roughening or property degradation. The final part of this study addresses the wear of enamel when opposing zirconia by observing how grain size and aging affected the wear rate of an enamel antagonist. The rejected null hypothesis is that neither zirconia grain size, nor aging condition affects the wear of an enamel antagonist.
Author: Thomas J. Lucas
Publisher:
ISBN:
Category : Body temperature
Languages : en
Pages : 92
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Book Description
This investigation addresses the issue that yttria stabilized zirconia is being used as a dental biomaterial without substantial evidence of its long-term viability. Furthermore, stabilized zirconia (SZ) undergoes low temperature degradation (LTD), which can lead to roughening of the surface. A rougher exterior can lead to increased wear of the antagonist in the oral environment. Despite the LTD concerns, SZ is now widely used in restorative dentistry, including full contour crowns. A comparison of aging methods to determine the role of artificial aging on inducing the transformation has not been extensively studied. Therefore, simulations of the transformation process were investigated by comparing different methods of accelerated aging. The rejected null hypothesis is that the temperature of aging treatment will not affect the time required to cause measurable monoclinic transformation of yttria stabilized zirconia.The transformation of SZ starts at the surface and progresses inward; however, it is unclear whether the progression is constant for different aging conditions. This investigation analyzed the depth of transformation as a function of aging conditions for stabilized zirconia in the top 5-6 micrometers from the surface. The rejected null hypothesis is that the transformation amount is constant throughout the first six micrometers from the surface. The effects of grain size on the amount of monoclinic transformation were also investigated. This study aimed to determine if the grain size of partially stabilized zirconia affects the amount of monoclinic transformation, surface roughness, and property degradation due to aging. The rejected null hypothesis is that the grain size will not affect the amount of monoclinic transformation, thus have no effect on surface roughening or property degradation. The final part of this study addresses the wear of enamel when opposing zirconia by observing how grain size and aging affected the wear rate of an enamel antagonist. The rejected null hypothesis is that neither zirconia grain size, nor aging condition affects the wear of an enamel antagonist.
Author: M., Bannister
Publisher: CRC Press
ISBN: 1000940322
Category : Technology & Engineering
Languages : en
Pages : 881
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Book Description
This book is based on the Fifth International Conference that was held on 16-21 August, 1992 in Melbourne, Australia, in conjunction with AUSTCERAM 92. It demonstrates that the field of Zirconia ceramics remains one of scientific challenge and technical attraction.
Author: Mahmood Mamivand
Publisher:
ISBN:
Category :
Languages : en
Pages : 176
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Book Description
Zirconia based ceramics are strong, hard, inert, and smooth, with low thermal conductivity and good biocompatibility. Such properties made zirconia ceramics an ideal material for different applications form thermal barrier coatings (TBCs) to biomedicine applications like femoral implants and dental bridges. However, this unusual versatility of excellent properties would be mediated by the metastable tetragonal (or cubic) transformation to the stable monoclinic phase after a certain exposure at service temperatures. This transformation from tetragonal to monoclinic, known as LTD (low temperature degradation) in biomedical application, proceeds by propagation of martensite, which corresponds to transformation twinning. As such, tetragonal to monoclinic transformation is highly sensitive to mechanical and chemomechanical stresses. It is known in fact that this transformation is the source of the fracture toughening in stabilized zirconia as it occurs at the stress concentration regions ahead of the crack tip. This dissertation is an attempt to provide a kinetic-based model for tetragonal to monoclinic transformation in zirconia. We used the phase field technique to capture the temporal and spatial evolution of monoclinic phase. In addition to morphological patterns, we were able to calculate the developed internal stresses during tetragonal to monoclinic transformation. The model was started form the two dimensional single crystal then was expanded to the two dimensional polycrystalline and finally to the three dimensional single crystal. The model is able to predict the most physical properties associated with tetragonal to monoclinic transformation in zirconia including: morphological patterns, transformation toughening, shape memory effect, pseudoelasticity, surface uplift, and variants impingement. The model was benched marked with several experimental works. The good agreements between simulations results and experimental data, make the model a reliable tool for predicting tetragonal to monoclinic transformation in the cases we lack experimental observations.
Author: Peter Glenn Valentine
Publisher:
ISBN:
Category :
Languages : en
Pages : 86
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Book Description
Author: Clark F. Grain
Publisher:
ISBN:
Category : Zirconium oxide
Languages : en
Pages : 28
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Book Description
Author: S. Meriani
Publisher: Springer Science & Business Media
ISBN: 9400911394
Category : Science
Languages : en
Pages : 371
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Book Description
This meeting, ZIRCONIA 'SS - Advances in Zirconia Science and Technology, was held within the framework of the 7tb SIMCER - International Symposium on Ceramics (Bologna, December 14-17, 1988) organized by the Italian Ceramic Center of Bologna, with the sponsorship of ENEA and Agip and the endorsement of the American Ceramic Society, and under the auspices of the European Ceramic Society. In the year 1988, the University of Bologna celebrated its 900th Anniversary. ZIRCONIA '88 was one of the celebration events which brought together academics and researchers from allover the world. Under the chairmanship of Prof. C. Palmonari, Director of the Italian Ceramic Center of the University of Bologna, the Organizing Committee consisting of J. Castaing (C.N.R.S. Meudon, France), S. Meriani (University of Trieste, Italy), V. Prodi (Un-iversity of Bologna, Italy) and J. Routbort (U.S. Dept. of Energy, Washington, USA) conducted a conference program of 47 contributions presented to the 220 enrolled Zirconia participants, out of the 775 enlisted within the main SIMCER framework. The aim of ZIRCONIA '88 was to follow the stream of the well known International Conferences on the Science and Technology of zj rconia held in Cleveland, Ohio (1980), Stuttgart, Federal Republic of Germany (1983) and Tokyo, Japan (1986). SIMCER's goal was to bring together not only scientists and engineers directly involved with "advanced" ceramics but also a larger audience connected to the nearby Italian Ceramic District of Sassuolo.
Author: B. C. Weber
Publisher:
ISBN:
Category : Ceramics
Languages : en
Pages : 18
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Author:
Publisher:
ISBN:
Category : Physics
Languages : en
Pages : 1384
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Author: Alistair Garner
Publisher:
ISBN:
Category : Microstructure
Languages : en
Pages : 33
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Book Description
Scanning precession electron diffraction in the transmission electron microscope has been used to simultaneously map the phase, orientation, and grain morphology of oxides formed on Zircaloy-2 after three and six cycles in a boiling water reactor in unprecedented detail. For comparison, a region of a preoxidized autoclave-formed oxide was also proton-irradiated at the Dalton Cumbrian Facility. The proton irradiation was observed to cause additional stabilization of the tetragonal phase that was attributed to the stabilizing effect of irradiation-induced defects in the oxide. In the reactor-formed oxides, no extra stabilization of the tetragonal grains was observed under neutron irradiation, as indicated by the similar tetragonal phase fraction and transformation twin-boundary distributions between the nonirradiated and reactor-formed oxides. It is suggested that the damage rate is too low in the newly formed oxide to cause significant stabilization of the tetragonal phase. This technique also reveals that the oxide formed under reactor conditions has a more heterogeneous microstructure, and the growth of well-oriented columnar monoclinic grains is significantly reduced compared with a nonirradiated oxide. High-angle annular dark-field scanning transmission electron microscopy also revealed the development of extensive networks of intergranular porosity and eventually grain decohesion in the reactor-formed oxides. These results suggest that the tetragonal-monoclinic transformation is not responsible for the accelerated corrosion exhibited under reactor conditions. It is proposed that the usual out-of-reactor oxide growth and nucleation processes are significantly modified under reactor conditions, resulting in a more heterogeneous and randomly oriented oxide microstructure with reduced columnar grain growth. It is suggested that this disordered oxide microstructure allows for the formation of extensive intergranular porosity that could lead to accelerated in-reactor corrosion.
Author: Shigeyuki Somiya
Publisher:
ISBN: 9780916094874
Category : Ceramics
Languages : en
Pages : 600
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