中文摘要：

在Na2O-B2O3-SiO2系统的凝胶过程中，溶胶在凝胶过程当中会产生较大的体积收缩，凝胶容易产生裂纹或开裂。在凝胶体内部和干燥表面收缩率的差别是干燥应力产生的主要原因。而引起碎裂的应力并不是作用在凝胶网络上的宏观应力，而是集中在长度为C的裂纹顶端的应力。引起裂纹开裂的另一个因素是由于凝胶孔径尺寸分布不均，由于大小孔毛细管压力差的存在，极易使孔壁变形引起开裂。从导致凝胶开裂的干燥应力和毛细管应力入手，避免了不利因素的影响，可以制备干燥透明而又无裂纹的Na2O-B2O3-SiO2系统干胶。

英文摘要：

Cracks tend to be present during the gelation of Na2O-B2O3-SiO2 system due to stress accumulation. The volume shrinkage difference between the interior gel and the exterior gel is the main reason of drying stress. While the crack stress of gel is not the macro stress on the gel net, but the stress accumulated at the flaw top with length of C. Another reason is from the different pore size distribution Through analysis on the drying stress and the capillary stress to produce flaw, transparent bulk gel without flaw can be obtained at optimized conditions.