Surface Stress Relaxation: Science and Effects on Glass Properties

非技术描述：大气中微量的水蒸气会对氧化物玻璃的机械强度产生很大影响。这种效果的一个重要步骤是快速消除表面应力。这种表面应力的去除会导致强化玻璃的弱化。同时，这种现象可以用来使玻璃机械强度更高。目前的研究可以阐明微量的水是如何导致这些看似矛盾的现象的。研究结果在学年期间的正式玻璃科学课程中进行讨论，以及在夏季课程期间的“弹出式”短期课程中，包括科学和工程以外的更广泛的受众。在这项研究中接受培训的男女学生、本科生和研究生都成为美国高科技公司的重要员工。 技术详情：与块状玻璃相比，氧化物玻璃表面（具有相同的组成）表现出更快的应力松弛，其通过空气中的水分实现。这种现象用于通过建立由快速表面应力松弛引起的表面压缩应力来制造机械强度更高的玻璃纤维。这些现象也可以解释长期以来与玻璃机械强度有关的谜团，如离子交换强化玻璃的强度退化和静态疲劳极限。快速表面应力弛豫的现象预计是重要的，在所有的非晶氧化物与大的表面积，如薄膜，纳米颗粒和曲面，很容易与微量的水蒸气相互作用。本研究的一个主要目的是澄清快速表面应力松弛的科学起源。第二个目标是优化纤维强化过程，并澄清各种异常的功能，如异常氧化动力学的小曲率半径的硅。在这项拟议的研究中，每年有两名研究生和四名本科生在玻璃科学领域接受培训。

Non-Technical Description: A trace amount of water vapor in the atmosphere can have large effects on mechanical strength of oxide glasses. One important step of this effect is the fast elimination of the surface stress. This surface stress removal can cause weakening of strengthened glasses. At the same time, the phenomenon can be used to make glass mechanically stronger. The present research can clarify how a trace amount of water can cause these seemingly contradictory phenomena. Research results are discussed in the formal Glass Science course during the academic year, as well as in a "pop-up' short course that includes a broader audience beyond science and engineering during summer sessions. Students - both women and men, and both undergraduates and graduates -trained in this research become valued employees for US high technology companies. Technical Details: In comparison to bulk glass, oxide glass surfaces (of the same composition) exhibit faster stress relaxation realized by moisture in air. This phenomenon is used to make mechanically stronger glass fibers by building the surface compressive stress caused by the fast surface stress relaxation. The phenomena can also explain long-standing mysteries related to mechanical strength of glasses such as the strength degradation of ion-exchange strengthened glasses, and static fatigue limit. The phenomenon of the fast surface stress relaxation is expected to be important in all amorphous oxides with large surface areas such as thin films, nano-particles and curved surfaces, which readily interact with a trace amount of water vapor. One main objective of the present research is to clarify the scientific origin of the fast surface stress relaxation. The second objective is to optimize the fiber strengthening process and clarify various anomalous features such as anomalous oxidation kinetics of Si with small radius of curvature. During this proposed research, two graduate students and four undergraduate students per year are trained in the glass science field.