Preparation Of Biomimetic Silica Film In Historic Stone Conservation

China is home to many precious historic stones, mostly exposed the wild, which have been subjected to varying degrees of weathering erosion in a lengthy historical changes, and especially been aggravated damage by the pollution caused with the development of modern industrial. At present, the application of many materials in historic stone conservation has a certain effect. But there are also some problems, so the research of new materials appears to be particularly important in order to provide more effective protection historic stone.Recently, the researchers have found a layer of natural protective coating formed on the surface of carved stone in the field investigation at home and abroad, whose main component is the calcium oxalate. The historic stones with this protective film are intact after Millennium, showing the film's good performance. After the preliminary biomimetic synthesis and evaluation of oxalate calcium film, the heritage conservation workers note the biomimetic inorganic material is a new potential protecting material in stone conservation for its advantages of excellent weatherability. suitable compatibility with the basement of stone, moderate reaction condition and environment pollution-free.Enlightened by the natural oxalate calcium protective films, for the first time the SiO₂ film was prepared on the surface of stone substrates, respectively Ethyl silicate (TEOS) and Sodium fluosilicate (Na₂SiF₆) as silicon source, at room temperature conditions in the way of biomimetic synthesis. One method is that the SiO₂ film was prepared on the surface of stone, by ammonia catalytic hydrolysis of TEOS in alcohol solvent, under the control of Cetyltrimethyl ammonium bromide(CTAB) templates. The other is that the CTAB templated silica film was prepared by hyfrolysis of Sodium fluosilicate under the condition of adding boric acid. The pretreatment of stone, the resource ratio, the amount of catalyst, the additive, the time of reaction, and the condition of drying etc. on the preparation and capability of film were investigated in the experiments of resisting acid, soil and water, the contact angle, water permeability, XRD. SEM, and FTIR. The optimized preparation process was determined. Furthermore, the reaction mechanism was simply discussed. Experimental results show: the protected stone in previous ways, compared with the original stone, has an excellent performance of resisting acid and soil; a slight decline breathe, the improved contact angle, but still maintains the good breath and hydrophilicity, and no significant changes in appearance. Especially, the resisting acid and soil performance of prepared film is better when Na₂SiF₆ as the silica source. Adding Glycerin and increasing humidity can prevent film cracking in the drying process. After pretreatment by using CTAB. the film on the stone surface has a better performance. The prepared biomimetic SiO₂ film is a new potential protecting material in stone conservation for its feasibility and superiority.