Ceramic functional coating is frequently applied to the structure material of turbine blades, and it is very important to investigate its properties during thermal shock, thermal cycle and thermo-mechanical fatigue. In this study, we measured acoustic emission (AE) caused by microfracture of the coatings to investigate the fracture mechanism during thermo-mechanical test of coatings. We have developed the method to detect AE signal using laser interferometer, and it was demonstrated that it was very powerful tool for non-contact measurement of AE. This technique was applied to the thermal cycle test of coatings, and microfracture mode was analyzed by simulation of wave propagation using finite element method (FEM). The change in energy release rate of interfacial cracks in the specimen due to heating and cooling was also calculated by FEM and correlation between propagation of interfacial crack and AE behavior was evaluated.
We have fabricated GaP two-dimensional photonic crystals (PCs) for terahertz (THz) wave generation by a reactive ion etching in Ar/Cl 2 gas chemistries. We performed 75-mm-deep etching of GaP, in which Al 2 O 3 layer is applied as a hard mask with its selectivity as high as 125. We demonstrated the THz-wave generation from the fabricated GaP slab waveguide with the PC structure as a cladding layer under a collinear phase-matched difference frequency generation. In the frequency dependence of THz output power for the PC slab waveguide is seen at around 1.1 THz. From the in-plane transmission spectrum of THz-wave, we confirmed that the THz output characteristics had relation with the photonic structure for THz wave.
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