基于激光诱导击穿光谱的青铜文物清洗评价试验研究

Experimental Study on Laser Cleaning of Bronze Cultural Relics with Evaluation of Laser-induced Breakdown Spectroscopy

山西是青铜文物的出土大省,也是早期青铜器铸造重要区域,但出土的青铜文物大多受到严重的腐蚀。较传统化学清洗和机械清洗法相比,激光清洗法因具有高能量、短时间、不损害基底、绿色环保等优势,已成为传统清洗方法的补充和延伸。首先,利用脉冲激光清洗技术针对铜币表面的锈迹污染物进行了清洗试验研究,通过优化激光脉冲能量、光斑大小、重复次数等参数对待清洗样品进行激光清洗对比试验,得到最佳的清洗能量阈值为105 mJ。其次,基于激光诱导击穿光谱技术,使用Nd:YAG脉冲激光器产生的高能量脉冲激光束作用于铜币样品表面产生等离子体,分析了激光清洗过程中等离子体的特定谱线强度与激光清洗效果的一般变化规律,通过分析对比等离子体的谱线变化特征对激光清洗效果进行了评价。最后,选用最佳激光清洗参数对铜币样品进行整体清洗,最终得到了清晰的纹理。试验表明,脉冲激光清洗具有时间短、不损伤基底、效果好等优点,在青铜器文物的保护工作中的具有一定的应用价值。

Shanxi is a large province for the excavation of bronze cultural relics, and also an important area for early bronze casting, but most of the unearthed bronze cultural relics have been severely corroded. Compared with traditional chemical cleaning and mechanical cleaning method, the laser cleaning method has become a supplement and extension due to its advantages such as high energy, short time, no damage to the substrate and environmental protection. Firstly, the laser cleaning technology was used to conduct an experimental study on the surface of copper coin for the contamination of rust, by optimizing the parameters of laser pulse energy, spot size, repetition times and other parameters. The cleaning comparison test was performed on the samples to be cleaned, and the optimal cleaning energy threshold value was set by 105 mJ. Secondly, the high-energy pulsed laser beam generated by a Nd: YAG laser was used to simulate on the surface of the copper coin sample to generate plasma based on Laser-induced breakdown spectroscopy(LIBS). Then the interaction correlation between the specific spectral line intensity of the plasma during the laser cleaning process and the laser cleaning intensity was analyzed and concluded. Therefore, the laser cleaning effect was evaluated by comparing the spectral line characteristics of the plasma. Finally, a clear and auroral texture was obtained while the optimal laser cleaning parameters were selected to clean the copper coin samples. The experimental results show that the laser cleaning method has the advantages of short time, no damage to the base, good effect and so on, and has certain application value in the conservation of bronze relics.