热处理对二硅酸锂微晶玻璃结构和强度的影响

以SiO_2-Li_2O-K_2O-B_2O_3-P_2O_5为基础组成,P_2O_5为形核剂,采用传统熔体冷却法制备了该系统基础玻璃.利用DSC、XRD、SEM等检测手段研究了热处理制度对玻璃析晶行为、析出晶相种类、晶粒尺寸、晶粒分布及微晶玻璃力学性能的影响.结果表明,当引入P_2O_5为形核剂时,玻璃在核化温度范围内发生分相,并诱导Li_2SiO_3的异相成核.随温度的升高,亚稳态的Li_2SiO_3最终转变成Li_2Si_2O_5稳定相.基础玻璃经核化处理后,分两步晶化比一步晶化更有利于Li_2Si_2O_5的生长,并在一定程度上提高了微晶玻璃的抗弯强度.延长晶化时间能使Li_2Si_2O_5晶体进一步生长,联锁微观结构聚集体的尺寸增大,晶粒与晶粒间交联程度更高,晶粒间有更牢固的化学键合,抗弯强度有所提高.

Effects of Heat Treatments on Structure and Strength of Lithium Disilicate Glass-ceramics

The SiO_2-Li_2O-K_2O-B_2O_3-P_2O_5 glasses introducing P_2O_5 as the nucleating agent are prepared by traditional melting quenching method. The effects of heat treatment conditions on the crystallization behavior, crystalline phase, crystalline distribution, crystal dimensions and the mechanical properties of the glass-ceramics are investigated by DSC, XRD and SEM. The results show that P_2O_5 is an efficient nucleating agent and can induce phase separation to promote heterogeneous nucleation of Li_2SiO_3 in SiO_2-Li_2O-K_2O-B_2O_3-P_2O_5 glass system. With the increasing of the crystallization temperature, the unstable Li_2SiO_3 crystal phase disappears and is transformed into stable Li_2Si_2O_5.Compared with one-step crystallization treatment, after the precursor glasses Are treated at the nucleating temperature, two-step crystallization treatment is more favorable for growing up of Li_2Si_2O_5 and enhancing of bending strength of the glass-ceramics. And the crystal phase doesn't change by prolonging the crystallization time, however, it can make the Li_2Si_2O_5 crystal further grow, the interconneetion mierostructure aggregate size increase and the bending strength of the glass-ceramics enhance because of stronger bonding among the crystal grains.