It is an effective method to protect components from high power laser damage using high reflective materials. The rare earth tantalates RETaO4 with high dielectric constant suggests that they may have very high reflectivity, according to the relationship between dielectric constant and reflectivity. The crystal structures, electronic structures, and optical properties of RETaO4 (RE=Y, La, Sm, Eu, Dy, Er) have been studied by first-principle calculations. With the increasing atomic number of RE (i.e., the number of 4f electrons), a 4f electron shell moves from the bottom of conduction band to the forbidden gap and then to the valence band. The relationship between the electronic structures and optical properties is explored. The electron transitions among O 2p states, RE 4f states, and Ta 5d states have a key effect on optical properties such as dielectric function, absorption coefficient, and reflectivity. For the series of RETaO4, the appearance of the 4f electronic states will obviously promote the improvement of reflectivity. When the 4f states appear at the middle of the forbidden gap, the reflectivity reaches the maximum. The reflectivity of EuTaO4 at 1064 nm is up to 93.47%, indicating that it has potential applications in the antilaser radiation area.
With the increasing in laser power, it is necessary to prepare protective coatings for components and devices under high power laser irradiation environment. Yttria-stabilized zirconia has high melting point, good stability and low thermal conductivity, and is often used as thermal barrier coating material. However, the study on its anti high power CW laser performance is rare. In this paper, the yttria-stabilized zirconia coating was deposited using atmospheric plasma spraying. The spectrophotometer, X-ray diffraction, scanning electron microscope and energy dispersive spectrometer were used to characterize the coating before and after high power CW laser irradiation. The temperature of substrate in back side was measured during irradiation. The results show that under the 2000 W/cm2 laser power density continuously irradiated for 20 s, the back temperature is only 250 °C. Even continuously irradiated for 60 s under this power, no obvious damage appears on the coating. Only the phenomenon of micro melting in the irradiation center was observed under scanning electron microscope. The coating shows excellent anti-laser irradiation ability.
It is an effective method to protect components from high power laser damage by using high reflective materials. The rare earth tantalates RETaO4 with high dielectric constant suggests that they may have very high reflectivity, according to the relationship between dielectric constant and reflectivity. In this paper, the crystal structure, electronic structure and optical properties of RETaO4 (RE=Y, La, Sm, Eu, Dy, Er) have been studied by first-principles calculation. The calculated lattice parameters are in good agreement with the previously reported values. With increasing the atomic number of RE (i.e., the number of 4f electrons), 4f electron shell moves from high energy region to low energy region, showing the tendency of moving from conduction band bottom to forbidden gap and then to valence band. The relationship between the electronic structures and optical properties is explored. The electron transitions between O 2p states, RE 4f states and Ta 5d states have a key effect on optical properties such as dielectric function, refractive index, absorption coefficient and reflectivity. For the series of RETaO4, the appearance of the 4f electronic states will obviously promote the improvement of reflectivity. When the 4f states appear at the middle of forbidden gap, the reflectivity reaches the maximum. The reflectivity of EuTaO4 at 1064nm is up to 93.47%, indicating that it has potential applications in the anti-laser radiation area.
Benzoxazine resin with good heat resistance, low combustion heat release and high char yield is a promising thermosetting resin. Meanwhile, research shows that the inorganic filler can effectively improve the thermodynamic property of the resin. It makes that the inorganic filler modified benzoxazine may have a potential application in laser ablation. The benzoxazine coating with and without inorganic filler ammonium polyphosphate, melamine and pentaerythritol (P-BOZ and BOZ) were prepared by brush and thermal curing method. The ablation properties of these coatings irradiated by high-intensity laser were investigated. The scanning electron microscope, Raman spectroscopy and thermal gravimetric analysis were used to characterize the micrographs, carbon layer structure and thermodynamic property of the sample. Results show that the composite coating has excellent thermal protective properties. The back temperature of 20 wt% P-BOZ coating under different parameter laser power (1000W/cm2, 5s; 1000W/cm2, 10s) are 40% lower than these of the BOZ coating and the 20 wt% P-BOZ has higher mass ablation rate. In the surface layer of the irradiated area, dense carbon layer is produced which reduces the absorb of the laser energy of the interior. In the interior of the sample, a large number of closed bell shaped holes are generated which are beneficial to obstruct the heat conduction.
It's well known that Al has a very high reflectivity in the visible/near-infrared range, which makes it become a promising anti-laser material. But for a plasma sprayed coating, there are usually many defects, such as pores, cracks and interfaces among particles, which lead to properties difference with its bulk material. In this paper, the reflectivity of plasma sprayed Al coating and its laser irradiation effect were investigated. Its reflectivity, surface roughness, porosity, microstructure, and cross-section microstructure were characterized. The results show that a high reflectivity (98.1% at CO2 laser 10.6μm wavelength) of plasma sprayed Al coating, which is comparable with bulk material, could be obtained. Its optical laser damage threshold is 2×104W/cm2 that makes its reflectivity obviously decrease. Its damage mechanism is oxidation.
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