Experimental Studies On Zirconia Toughened Fluorosilicic Mica Glass-ceramic Composites

Fluorosilicic mica glass ceramics has excellent machinability, and become all-ceramic restoration material suiting for dentistry CAD/CAM. However, the glass ceramics exhibits low strength and toughness which limit the application of the clinic. The studies of fluorosilicic mica glass-ceramics mainly aim at keeping its excellent properties, and simultaneously enhancing its fracture strength and toughness in order to hold the dependability in clinical use. Recently, ceramic composite toughed by zirconia has become a study hotspot. The key idea of this work is to enhance fracture strength and toughness of Fluorosilicic Mica Glass-ceramics by adding zirconia. The aim is to provide important laboratory reference for future study.Content and methods:1. The first part of this study (experimentⅠ) is to compare the melt cast method with the sintering method in order to choose the better method to prepare zirconia toughened fluorosilicic mica glass-ceramic composites. Mechanical properties of zirconia toughened fluorosilicic mica glass ceramic composites were tested by three point bending strength and fracture toughness, and the microstructure and crystalline phase composition were analyzed by SEM and XRD apparatus.2. The purpose of experimentⅡis to determine which size of particle can more effectively improve the strength and toughness of the glass ceramics. This experiment is adopting the sintering method and adding different particle size (50nanometer and 10micron) of zirconia with the same content (25wt%) to fluorosilicic mica glass-ceramics, which is to investigate the influence of different particle size of zirconia on mechanical properties and microstructure of the glass-ceramics composites.3. ExperimentⅢis adding zirconia with the same particle size (50nanometer) but with different contents (5wt%, 10wt%, 20wt%, 30wt%) to fluorosilicic mica glass-ceramics and adopting the sintering method to prepare some samples. This experiment is to discuss the effect of different contents of nanometer zirconia toughened fluorosilicic mica glass-ceramics on the mechanical properties of the composites.Results:1. Zirconia toughened fluorosilicic mica glass-ceramics composite which prepared by the melt cast method and the sintering method have higher flexural strength and fracture toughness than that without zirconia. Composites which prepared by the sintering method showed much higher flexural strength and fracture toughness, which were134.4±10.2Mpa and 1.88±0.16MPa·m1/2 respectively. Composites which prepared by the melt cast were 128.5±12.1MPa and 1.62±0.06MPa·m1/2.2. Fluorosilicic mica glass-ceramics composites with nana-size powder of zirconia showed much higher flexural strength and fracture toughness, which were 220.8±9.30Mpa and 2.54±0.10 MPa·m1/2 respectively. There have significant difference between nana-size zirconia and micro-size zirconia toughened fluorosilicic mica glass-ceramics composite which prepared by sintering method in the flexural strength and fracture toughness(P<0.05).3. The flexural strength and fracture toughness of glass-ceramics with 30wt% ZrO2 which did not influence the crystallization process were 224.3±10.3MPa and 2.80±0.13MPa·m1/2 respectively. The flexural strength and fracture toughness with 5wt% and 10wt% nana-size zirconia toughened fluorosilicic mica glass-ceramics had no significant(P>0.05).Conclusions:1. The flexural strength and fracture toughness of zirconia toughened fluorosilicic mica glass-ceramics composite prepared by sintering method were much higher than those prepared by the melt cast method.2. Fluorosilicic mica glass-ceramics composites prepared by sintering method with the same content but different particle size of zirconia shows that the composite with nano-size powder of zirconia has higher flexural strength and fracture toughness than that with micro-size powder of zirconia.3. The mechanical property of fluorosilicic mica glass-ceramics composites is higher and higher with the increase of the zirconia content. The flexural strength and fracture toughness of glass-ceramics with 30 wt% nano-size of zirconia was reinforced significantly.