Study on ultimate strength of bonding interface in dissimilar materials based on nano-scale interface design

本研究的目的是对下一代核系统和聚变动力系统中可能需要的异种材料之间的连接机理有一个基本的了解，并测量界面强度。采用第一性原理计算和传统划痕法及先进的激光冲击法直接测量界面强度，分别对金属与钒/钙氧化物、镍/钙氧化物等陶瓷材料的最大理想界面强度进行了第一性原理计算和评价。氧化锆表明，强度取决于界面中参与界面键合的原子之间的键合数密度。因此，发现晶体的取向和界面原子间的距离对界面强度有影响。使用氧化工艺和使用钇靶的溅射涂覆来制备涂层。通过划痕试验测量的粘附强度表明，结晶度和少量钇添加到基体金属中增加了强度。采用激光冲击法对界面施加拉应力。尚未观察到添加钇对界面强度影响的明显证据，但激光冲击法施加的拉应力在方向上与第一性原理计算相当，因此进一步的讨论将有助于从根本上了解不同材料之间的结合机制。

The objectives of this study were fundamental understanding for bonding mechanism between dissimilar materials which may needed in next generation nuclear system and fusion power system and measuring the interface strength. Evaluation of the interface strength was carried out using the first-principles calculation and direct measurements were adopted with conventional scratch test and advanced laser shock method.The results of the evaluation of the maximum ideal interface strength using the first-principles calculation for the bonding between metals and ceramics including vanadium/calcium oxide and nickel/zirconium oxide indicated that the strength depended on the number density of the bonding between the atoms in the interface which involved in the interface bonding. Therefore, it was found that orientation of the crystal and distance between the atoms in the interface affected the strength.Measurements of interface strength were carried out for vanadium/yttrium oxide and bonding. The coating layer was made using oxidation process and sputter coating using yttrium target. Adhesion strength measured by scratch test indicated that crystallinity and small addition of yttrium to the base metal increased the strength. The laser shock method was adopted to apply the tensile stress to the interface. It was not observed clear evidence of the effects of yttrium addition for the interface strength, but the tensile stress applied by the laser shock method is comparable to the first-principles calculation in terms of direction, so that further discussion will be useful for the fundamental understanding for the bonding mechanism between the dissimilar materials.