| Budget Amount *help |
¥11,900,000 (Direct Cost: ¥11,900,000)
Fiscal Year 2001: ¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 2000: ¥9,500,000 (Direct Cost: ¥9,500,000)
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| Research Abstract |
Ceramics superlattice, which has a laminated structure of heterogeneous ceramics combination in nanometer scale, is one of the promising approaches for highly functional coating films. As a superlattice film shows remarkable enhancement in indentation hardness and wear-resistance with a specified laminating period, it is expected to be a material of coating films subjected to heavy friction. However, the mechanism of strength enhancement has not been understood well.
In this research, to clarify the correlation between the microstructure and mechanical properties of ceramics superlattice and to establish the guidelines for design of highly functional ceramics coating films, molecular dynamics (MD) computer simulations of uniaxial and biaxial strength testing are carried out on TiN/AIN superlattice films with various laminating periods.
Experimental results of microindentation on arc ion-plated TiN/AIN ceramics superlattice films show that the hardness increases as the laminating period d
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ecreases and that the highest hardness enhancement is observed on the film with 2.5 nm laminating period.
Interatomic potential functions are proposed for ceramics with rock salt structure, such as TiN, AiN are and ZrN, by the fitting with the results of first- principle calculations. Using the interatomic potential functions, MD simulations of uni- axial and biaxial strength testing of the ceramics and superlattice films composed of the ceramics are carried out successfully.
The MD simulations show that residual tensile and compressive stresses are observed in the layers of AIN and TiN, respectively, in the films with superlattice structure. The strength for fracture initiation decreases as the laminating period decreases. Under the biaxial loading, crack extension and plastic deformation occur in the layers of AIN and TiN, respectively. However, the fracture and deformation are stopped on the TiN/AIN interface. The longer the laminating period of superlattice film, the longer the crack extension. This results in the lower indentation hardness on the superlattice film with longer laminating period. The results of the MD simulations suggest that there is an optimum laminating period for highest enhancement of indentation hardness.
MD simulation can be an useful tool for clear understanding in principle the correlation between miorostructure and mechanical properties and for structure design of ceramics superlattice. Less
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