热传导规律的研究在激光诱导薄膜材料改性等应用中有着重要的作用, 本文针对二氧化碳激光器辐照下的二氧化钛(TiO2)薄膜表面的热效应进行了理论仿真和实验研究。首先, 对具有粗糙上表面的TiO2薄膜, 利用有限元法构建了连续激光作用下的TiO2薄膜的立体模型并得到了其三维温度场分布。然后使用CO2激光器进行辐照实验, 分析了辐照时间和功率等参数对TiO2薄膜形貌、晶相以及颜色的影响。仿真表明, 连续激光辐照下TiO2薄膜的瞬态温度场呈高斯分布, 且与激光功率、光斑半径、辐照时间等因素有关。当表面温度小于分解温度时, 薄膜上表面最大平均温度与激光功率满足线性关系, 与光斑半径满足ExpAssoc非线性关系。实验结果表明, 激光辐照引起TiO2薄膜材料表面粗糙度降低且颜色变化。激光功率过小或辐照时间过短会导致有效作用面积小且不均匀, 反之会产生热形变 。结合仿真和实验可知使用功率为6 W, 半径为3 mm的连续激光辐照TiO2薄膜10 s时取得的处理效果最优。

The laws of heat conduction play an important role in the application of laser-induced film material modification. In this paper, the thermal effects of titanium dioxide(TiO2) film surfaces irradiated by a carbon dioxide laser was studied theoretically and experimentally. Firstly, a three-dimensional model of titanium dioxide thin film with a rough surface was constructed using a finite element method and their three-dimensional temperature distribution were calculated. Then, the TiO2 thin films were irradiated by a CO2 laser and the effects of irradiation time, power on the morphology, crystal phases and color were analyzed. Simulation results show that the transient temperature field of titanium dioxide irradiated by a CW laser is a Gaussian distribution, which is related to laser power, spot radius, irradiation time and other factors. When the surface temperature is less than the decomposition temperature, the maximum average surface temperature of the film meets the linear relationship with the laser power, and the ExpAssoc nonlinear relationship is satisfied with laser spot radius. Experimental results show that because of laser irradiation, the roughness of TiO2 thin film decreased and the color of the film changed. Small laser power or short irradiation time leads to small and uneven effective area, on the contrary thermal deformation will occur. Combined with the simulation and experiment results, it is found that the best treatment effect can be obtained when irradiating TiO2 thin film 10 seconds with a laser with a power of 6 W and a radius of 3 mm.