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

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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.