Wear analysis of glassy carbon in the fused silica molding process depending on the surface quality of the glassy carbon

熔融石英的精密玻璃成型是一种替代和有前途的方法，用于生产由熔融石英制成的中大批量光学元件。玻璃碳是目前最有前途的熔融石英成型模具材料。但是，即使玻璃碳符合模具的机械、热和化学要求，这种材料也会随着成型时间的增加而表现出玻璃粘附形式的磨损行为。这使得模具的再加工成为必要，并导致整个过程的效率低下。在以前的项目中的调查表明，即使在抛光的玻璃碳模具的表面上的微和纳米缺陷的存在，在磨损的发展中起着重要的作用。在这些看起来像凹口的缺陷中，随着模制时间的增加，在模制过程中出现高的压应力和特别是高的拉应力。 这导致材料的逐渐剥落，这再次导致缺陷的增加，并因此导致光学功能表面的损坏。此外，玻璃沉积在这些缺陷中，也会损害或破坏光学表面的功能。玻璃存款现象是由玻璃和模具之间的粘附过程所促成的。由于相对较长的接触时间，特别是在下模具上，在熔融石英的SiO2分子和玻璃碳网络之间产生结合。这些结合可以足够强，使得在模制过程期间，玻璃材料从玻璃化合物中溶解并保留在模具表面上。因此，后续项目的总体目标是详细描述熔融石英成型时玻璃碳的磨损机制，以了解其根本原因，并在此基础上制定预防策略。研究的重点是材料的制造和加工方法以及可能的耐磨保护层。

Precision glass molding of fused silica is an alternative and promising method for the production of optical components made of fused silica in medium and large quantities. At present glassy carbon is the most promising mold material for fused silica molding. But even glassy carbon fits the mechanical, thermal and chemical requirements for the molds this material also shows wear behavior in the form of glass adhesions with increasing molding time. This makes a remachining of the molds necessary and leads to an inefficiency of the whole process. Investigations in the previous project have shown that even on the surface of the polished glassy carbon molds micro- and nano-defects exist which play an important role in the development of wear. In these defects, which appear like notches, high compressive stresses and especially high tensile stresses occur during the molding process with increasing molding time. This leads to a gradual spalling of material, which again lead to an increase of defects and therefore to damaging of the optical functional surface. In addition, glass is deposited in these defects, which also impair or destroy the function of the optical surface. The phenomenon of the glass deposit is favored by adhesion processes between the glass and the mold. Due to the relatively long contact times, especially on the lower mold, bindings between the SiO2 molecules of the fused silica and the glassy carbon network are generated. These bindings can be strong enough that during the molding process glass material is dissolved from the glass compound and remains on the mold surface. The overall goal of the follow-up project is therefore to describe the wear mechanisms of glassy carbon while molding fused silica in detail to understand their root causes and based on this to develop prevention strategies. The focus of the research is the manufacturing and processing methods of the material and possible wear protective layers.