Glasses and Glass Ceramics for Medical Applications

Abstract

), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identifi ed as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights.Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) v Glass-ceramics are a special group of materials whereby a base glass can crystallize under carefully controlled conditions. Glass-ceramics consist of at least one crystalline phase dispersed in at least one glassy phase created through the controlled crystallization of a base glass. Examples of glass-ceramics include the machinable glass-ceramics resulting from mica crystallization, the low thermal expansion glass-ceramics resulting from β-eucryptite and β-spodumene crystallization, high toughness glass-ceramics resulting from enstatite crystallization, high mechanical strength resulting from canasite crystallization or the high chemical resistance glass-ceramic resulting from mullite crystallization.These materials can provide a wide range of surprising combinations of physical and mechanical properties as they are able to embrace a combination of the unique properties of sintered ceramics and the distinctive characteristics of glasses. The properties of glass-ceramics principally depend on the characteristics of the fi nely dispersed crystalline phases and the residual glassy phases, which can be controlled by the composition of the base glass, the content and type of mineralizers and heat treatment schedules. By precipitating crystal phases within the base glasses, exceptional novel characteristics can be achieved and/or other properties can be improved.In this way, a limitless variety of glass-ceramics can be prepared with various combinations of different crystalline and residual glassy phases. With the appropriate knowledge on the right way to modify the chemical compositions and the heat treatment schedules, one can effectively control the phase contents, scale the developed properties and control the fi nal product qualities. Consequently, a skilled glass-ceramist is able to play with the constituting chemical elements and their contents in the composition to regulate the different ceramic properties.Admittedly, the success in controlling functional properties is much more diffi cult if opposing properties such as high hardness and good machineability are desired. Similarly, achieving good chemical resistance in the presence of high content of alkalis and alkaline earths or rendering inactive glass ceramics into bioactive glass ceramics through composition modifi cation are diffi cult to reconcile. Thus there are some real challenges and some serious limitations to what can be achieved. Preface vi P...

Improving shear bond strength between feldspathic porcelain and zirconia substructure with lithium disilicate glass-ceramic liner

“…It has been reported that the probable cause of porcelain chipping leading to delamination is due to the stress generated by CTE mismatch between the zirconia substructure and veneering porcelain 16,17) . In the case of lithium disilicate, CTE mismatch would be less of a consequence since it has a low CTE 12) , which is also compatible with both feldspathic porcelain and zirconia. Therefore, the CTE of lithium disilicate glass-ceramic liner tends to be stable after multiple firings.…”

“…is another type of glass ceramic which offers thermal shock resistance, thus leading to a more stable CTE after multiple firing 12) . Moreover, lithium disilicate has CTE close to that of the veneering feldspathic porcelain and zirconia substructure.…”

Survey about Safe and Reliable Use of EAF Slag

“…Probably, rankinite could form amorphous or glass-ceramic structures able to blind barium and prevent its releasing. 23,24,25) This behaviour seems to be related to its low melting point, of about 1 450°C (Fig. 7), and to the presence of other oxide which can alter the tetrahedral chains order.…”

MgF2 katkısının Vermikülit esaslı cam-seramiklerin işlenebilirlik özellikleri üzerine etkisi

“…Mika fazının oluşumu ile ilgili en önemli reaksiyon potasyum feldspat ile MgF2 arasındaki etkileşim olarak rapor belirtilmiştir. Bu fazın kristallenmesi ile ilgili bir diğer yaklaşımda; uygun bileşenlerin olduğu bir ortamda 1000 o C sıcaklıklarda forsterite ve MgF2 'nin etkileşimi ile meydana gelen reaksiyondur [13]. Bu çalışmada meydana gelen Mika fazının ikinci yaklaşıma uygun şekilde oluştuğu düşünülmektedir.…”

“…Genel olarak mika kristalleri iki tetrahedral tabaka arasındaki bir oktahedral tabaka olarak yapılanır. Oktahedral tabaka oksijen, hidroksil ve katyonların bulunduğu florin gruplarını içerirken, tetrahedral tabakalar ise hegzagonal ağda birbirine bağlı Si-O tetrahedronlarından oluşur [13]. Mika kristalleri bu şekilde tekrarlı olarak üç boyutlu bünyede tabakalı yapıda uzanırlar.…”