纳秒激光清洗技术在紫禁城大理石上的应用

Application of nanosecond laser cleaning technology on marble in the Forbidden City

故宫博物院现存较多的石质文物,这些石质文物放置在自然环境中,长期受到环境的侵蚀,会在表面形成较硬的难以去除的黑色结壳污染物,严重影响石质文物的美观和体现雕刻的细节。文章选取两件故宫博物院内不同区域撤下的石质构件作为研究对象,利用扫描电镜、拉曼和X射线荧光三种方法取样测试黑色结壳污染物的成分。为避免变黄效应,对于黑色结壳污染物采用红外与紫外相结合的双波长进行激光清洗,同时改变两束激光的能量,但不改变两者的能量比。实验结果显示,当红外和紫外的能量分别为16.8mJ和1.2mJ时,对较厚的黑色结壳污染物有良好的清洗效果。将清洗部分和未清洗部分进行对比,证明激光清洗技术能有效清除石质文物表面的黑色结壳污染物,并利用显微的方法对清洗效果进行评价。

The Palace Museum currently has many stone heritage.These stone artifacts are placed in the natural environment and have been eroded by the environment for a long time,which can form hard black crust pollutants to remove difficultly on the surface of these stones.It could affect the beauty of stone artifacts and the details of carving seriously.This paper selects two stone components that removed from different areas of the Palace Museum as the research objects.By utilizing these method including scanning electron microscopy,Raman spectroscopy,and X-ray fluorescence technique,the composition of black crust pollutants could be obtained.To avoid the yellowing effect,a dual wavelength laser cleaning technology is used for black crust pollutants by combining infrared with ultraviolet.The energy of the two laser beams should be changed,but the ratio of the energy is constant.The experimental results show that the energy of the infrared and ultraviolet is 16.8mJ and 1.2mJ,respectively.The black crust pollutants have good cleaning effect.Comparing the cleaned and uncleaned parts of the stone components,it proves the advantages of laser cleaning technology in removing black crust pollutants from the surface of stone cultural relics.The cleaning effect is evaluated by microscopic methods.