title: Effect of sodium content on the crystallization behavior of fluoramphibole glass-ceramics.
abstract: The purpose of this study was to evaluate the effect of sodium content on the crystallization behavior of glass-ceramics in the system SiO(2)-MgO-CaO-Na(2)O-K(2)O-F. Five glass compositions were prepared with increasing sodium content. The compositions were melted at 1400 degrees C for 2 h and cast into 60 x 12-mm ingots. Differential thermal analyses were performed on the glasses up to 1400 degrees C. Discs (1.5 x 12 mm) were cut from the ingots, nucleated in the temperature range 600-650 degrees C for 1-2 h, and crystallized in the temperature range 900-1000 degrees C for 0.5-4 h. The crystalline phases were analyzed by x-ray diffraction. The microstructure was investigated by scanning electron microscopy. Differential thermal analyses showed that the crystallization exotherm occurred in the temperature range 600-750 degrees C. There was a linear relationship between the amount of sodium and the transformation temperatures. X-ray diffraction revealed the presence of mica and diopside as major crystalline phases in the sodium-free composition. Mica, diopside, and fluorrichterite were present in all other glass-ceramics. The microstructure of the sodium-free glass-ceramic was characterized by the presence of hexagonal mica crystals and prismatic diopside crystals. All other compositions exhibited needle-shaped fluorrichterite crystals (2-5 microm in length) in addition to mica and diopside crystals.
authors.affiliation: The Ohio State University, College of Dentistry, Section of Restorative Dentistry, Prosthodontics, and Endodontics, 305 W. 12(th) Avenue, Box #191, Columbus, Ohio 43218-2357, USA. denry.1@osu.edu
authors.forename: I L
authors.initials: IL
authors.lastname: Denry
authors.forename: J A
authors.initials: JA
authors.lastname: Holloway
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D017609:Barium Compounds / Q000737:chemistry; D002124:Calcium Fluoride / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D003460:Crystallization; D004055:Differential Thermal Analysis; D004305:Dose-Response Relationship, Drug; D008277:Magnesium Oxide / Q000737:chemistry; D017633:Magnesium Silicates / Q000737:chemistry; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010087:Oxides / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry; D012824:Silicic Acid / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D012964:Sodium / Q000737:chemistry*; D017670:Sodium Compounds / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D000538:Aluminum Silicates; D017609:Barium Compounds; D017633:Magnesium Silicates; D010087:Oxides; D017680:Potassium Compounds; D017670:Sodium Compounds; C454689:fluorrichterite; C454690:taeniolite; D012824:Silicic Acid; C074224:diopside; C096707:sodium oxide; D008277:Magnesium Oxide; C068440:potassium oxide; D012822:Silicon Dioxide; C077606:barium oxide; C023506:Glass ceramics; D012964:Sodium; D002124:Calcium Fluoride; C011934:mica