| 0389 Effect of Zirconia Additions to Novel Machinable Mica based Glass-Ceramics | ||
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S.M. JAMBI, University of Leeds, Leeds Dental Institute, United Kingdom, N.L. BUBB, Dr, University of Leeds, England, Uk, and D.J. WOOD, Leeds Dental Institute, University of Leeds, England, Uk Objectives: This study examined how the addition of zirconia to glass compositions affected (1) the subsequent transformation of glasses to glass-ceramics upon heat treatment and (2) their mechanical properties with a view to the materials' potential use as machinable glass-ceramics for use in CAD/CAM dentistry. Methods: Three novel glasses were produced based upon a parent ternary composition 90 % mol barium fluormica, 6 % mol cordierite and 4 % mol calcium phosphate. To this original composition zirconia was added incrementally (5, 10 and 15 % mol ZrO2). Glasses were heat treated to produce glass-ceramics. SEM, TEM and X-ray Diffraction were performed to look at the microstructure and the nature of crystallisation in the glass-ceramics produced. Biaxial flexural strengths and micro-hardness were determined. Results: SEM indicated that all samples had a random distribution of interlocking discs or plate like mica crystals embedded within a glassy matrix. X-ray Diffraction showed a dominant barium fluormica phase and a small amount of monoclinic zirconia. TEM micrographs indicated that zirconia was only partially dissolved in the glass melt („T1 atomic % of the total zirconia). The surface dissolution of zirconia caused the particles to have a rounded appearance. The remaining zirconia crystals acted as nucleating agent for mica crystallisation. Addition of 5, 10 and 15 % mol zirconia increased the biaxial flexural strength to 137°"4, 168°"11 and 170°"22 MPa respectively in comparison with that of the parent glass ceramic (100°"15 MPa). Hardness values of the glass ceramics with 5, 10 and 15 % mol zirconia were 171.97, 145.7 and 134.3kg/m2 HV respectively. Conclusion: Biaxial flexural strength of the glass ceramics increased significantly with addition of zirconia. Zirconia acted as a nucleating agent for the subsequent crystallisation of mica. This work is supported by The Ministry of Health, Saudi Arabia | ||
| Seq #72 - Ceramics: Mechanical Properties and Fracture Behavior 2:00 PM-3:15 PM, Thursday, March 22, 2007 Ernest N. Morial Convention Center Exhibit Hall I2-J | ||
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