title: Effect of processing variables on texture development in a mica-based glass-ceramic.
abstract: The purpose of this study was primarily to determine the feasibility of heat-pressing a mica-based glass-ceramic with the use of commercially available dental equipment, and secondly to evaluate the effect of various processing variables on the degree of crystal alignment in the pressed glass-ceramic. The hypotheses were that the mica-based glass-ceramic could be successfully heat-pressed and that some degree of crystal orientation would be obtained, depending on the processing variables. The glass composition was melted at 1400 degrees C for 2 h and cast into 12 x 60-mm rods. Ingots (10 x 12 mm) were cut from the glass rods, heat treated, and heat-pressed under various conditions. The microstructure of the pressed specimens was investigated by SEM and compared to that of heat-treated controls. The length of Vickers-induced cracks was measured on heat-pressed specimens and heat-treated controls. The results showed that mica-based glass-ceramics could be successfully pressed with the use of commercially available dental equipment. The resulting degree of crystal alignment (texture) along the direction of pressing varied between 35 +/- 6 and 79 +/- 6. There was a linear relationship between the degree of texture and the apparent aspect ratio of the mica platelets. A significant decrease in the length of the Vickers-induced cracks in the direction perpendicular to pressing was observed, associated with an increase in length in the direction of pressing.
authors.affiliation: College of Dentistry, Section of Restorative Dentistry, Prosthodontics, and Endodontics, The Ohio State University, 305 West 12th Avenue, Box 191, P.O. Box 182357, Columbus, Ohio 43218, USA. denry.1@osu.edu
authors.forename: I L
authors.initials: IL
authors.lastname: Denry
authors.forename: G
authors.initials: G
authors.lastname: Baranta
authors.forename: J A
authors.initials: JA
authors.lastname: Holloway
authors.forename: P K
authors.initials: PK
authors.lastname: Gupta
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D001672:Biocompatible Materials / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry; D003460:Crystallization; D006358:Hot Temperature; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D013499:Surface Properties; D014961:X-Ray Diffraction
chemical_list: D000538:Aluminum Silicates; D001672:Biocompatible Materials; C023506:Glass ceramics; C011934:mica