Relationship between laser ablation threshold of graphite-SiO2 and scattering light signal
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摘要: 石墨-二氧化硅作为无机添加材料,广泛应用于各类航空航天器烧蚀涂层领域,其在高温下具有较高的反应吸热焓,在高能激光烧蚀领域具有良好的应用前景。目前,关于石墨-二氧化硅的高能激光烧蚀研究较少,尤其在高能激光烧蚀中的反应时间和烧蚀阈值难以确定。针对此问题,利用近红外探测器对激光辐照样品表面的散射光进行实时探测,并对其散射光曲线进行微分拟合处理。基于此散射光信号,结合样品烧蚀后的形态结构分析,研究了石墨-二氧化硅在不同激光功率密度下的反应时间阈值。研究结果表明:在激光输出功率密度为500 W/cm2持续辐照10 s时,散射光拟合曲线持续升高无突变,表明未发生明显的烧蚀;当激光功率密度升高至1 000~1 500 W/cm2时,散射光微分拟合曲线出现明显转折点,对应的反应时间阈值分别为1.5 s和0.8 s。Abstract: As inorganic additional compositions, graphite and SiO2 have been widely used in ablation coating in the flied of aerospace. Since graphite and SiO2 have high endothermic enthalpy of reaction under high temperature, graphite-SiO2 composite has potential applications in the field of high power laser ablation resistance. At present, there are rare reports about laser ablation behavior of graphite-SiO2, especially the reaction time and ablation threshold. In this paper, the near infrared(NIR) detector was used to detect the scattering light from the irradiated sample surface, and the scattering spectra were processed by differential and fitting method. Based on the scattering signal, the reaction time thresholds of graphite-SiO2 under different power density were studied combining shape structure analysis of samples after ablation. The result shows that when the sample is irradiated by laser 500 W/cm2 for 10 s, there is no mutation abserred in the scattering fitting curve, which indicates that no obvious ablation happened. But when the laser power density increases to 1 000-1 500 W/cm2, the apparent turning point in the scattering fitting curve can be observed. The reaction thresholds are 1.5 s and 0.8 s, respectively. By using the laser scattering light signal from the sample surface, the time threshold value of graphite-SiO2 composite can be effectively characterized.
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Key words:
- graphite-SiO2 /
- laser ablation /
- scattering light /
- ablation time threshold /
- differential fitting
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