Quinn J B, Sundar V, Lloyd I K
ADAHF Paffenbarger Research Center, National Institute of Standards and Technology STOP8546, Gaithersburg, MD 20899-8546, USA.
Dent Mater. 2003 Nov;19(7):603-11. doi: 10.1016/s0109-5641(03)00002-2.
the primary aim of this research was to measure fracture toughness for several groups of dental ceramics, and determine how this property is affected by chemistry and microstructure.
Fracture toughness (KIc) values were obtained using Single Edge Precracked Beam (SEPB) and Single Edge V-Notch Beam (SEVNB) methods. Dynamic Young's modulus, which often scales with strength and has been used in explaining the microstructure/toughness relationship on a theoretical basis, was also obtained for the three groups of materials comprising this study. The first group, consisting of micaceous glass ceramics, included model materials that varied systematically in microstructure but not in chemistry. The second group, the feldspathic porcelains, varied significantly in microstructure, but little in chemistry. The ceramics comprising the third group were significantly different in both chemistry and microstructure.
Upper toughness limits for the micaceous glass-ceramics and feldspathic porcelains were significantly raised compared to the base glasses, but remained under 2 MPa m(1/2). The highest toughnesses were associated with high percent crystallinity, large grains and high aspect ratios. The third group KIc values were 2.8 MPa m(1/2) for a lithium disilicate glass-ceramic, 3.1 MPa m(1/2) for a glass-infused alumina, and 4.9 MPa m(1/2) for zirconia.
the correlations between microstructural characteristics and measured properties supports theoretical predictions in the literature. From a practical standpoint, microstructural effects were found to be important, but only within a limited range; the chemistry apparently defined a band of achievable property values. This suggests very large increases in fracture toughness are unlikely to be attained by changes in microstructure alone. A functional relationship determined for the micaceous glass-ceramics enables quantitative predictions of fracture toughness based on the microstructure.
本研究的主要目的是测量几组牙科陶瓷的断裂韧性，并确定该性能如何受到化学组成和微观结构的影响。
采用单边预裂纹梁（SEPB）和单边V型缺口梁（SEVNB）方法获得断裂韧性（KIc）值。还对构成本研究的三组材料测定了动态杨氏模量，其通常与强度相关，并已用于从理论基础上解释微观结构/韧性关系。第一组由云母微晶玻璃组成，包括微观结构系统变化但化学组成不变的模型材料。第二组是长石质瓷，微观结构变化显著，但化学组成变化不大。构成第三组的陶瓷在化学组成和微观结构上均有显著差异。
云母微晶玻璃和长石质瓷的韧性上限与基础玻璃相比显著提高，但仍低于2MPa·m(1/2)。最高韧性与高结晶度、大晶粒和高纵横比相关。第三组中，二硅酸锂微晶玻璃的KIc值为2.8MPa·m(1/2)，玻璃增强氧化铝为3.1MPa·m(1/2)，氧化锆为4.9MPa·m(1/2)。
微观结构特征与测量性能之间的相关性支持了文献中的理论预测。从实际角度来看，发现微观结构效应很重要，但仅在有限范围内；化学组成显然定义了一组可实现的性能值范围。这表明仅通过微观结构变化不太可能大幅提高断裂韧性。为云母微晶玻璃确定的函数关系能够基于微观结构对断裂韧性进行定量预测。
