【作者】 刘强；

【导师】 张秉坚；

【作者基本信息】 浙江大学 ， 物理化学， 2007， 博士

【摘要】 暴露在野外的众多大型石质古迹，由于自然因素的风化作用和人为因素的破坏，许多表面劣化现象严重。如不采取有效措施，许多珍贵的实物记录将不复存在。但是，目前所使用的保护材料几乎都不能完全满足保护者的要求。所以，研制性能良好的石质文物保护功能材料已成为文物保护研究领域的迫切任务之一。本论文综述了石质文物风化的特征和条件，以及国内外相关保护材料的性能、保护效果和存在的问题。在天然生成的草酸钙生物矿化保护膜的启示下，根据“生物矿化”原理，提出了采用“仿生”方法对石质文物进行保护的新思路，仿生合成了一系列无机生物矿化保护材料。通过研究实验，获得了如下的结果：(1)选用目前应用广泛的有机硅类保护剂作为表面防护材料，以常见的文物石材：砂岩、凝灰岩、白云岩、大理岩和花岗岩为保护对象，试验研究了文物的主要破坏因素，包括干湿循环、盐结晶、冻融和加热等作用，以及它们的联合作用，证实石质文物表面憎水性化学保护有可能起不到保护作用，甚至会产生严重的破坏。破坏的主要原因是被保护表层的憎水性和岩石基底的亲水性引起的化学物理性质的差异和界面应力的加剧。并提出解决这一矛盾的有效途径之一是开发非严格憎水且具有耐酸、耐污等效果的与石材相容良好的保护材料，如生物矿化材料。(2)试验研究了石材的表面预处理方法，包括有机溶剂的清洗，以及生物性大分子的表面功能化。通过表面能的表征，确定了最佳的石材表面预处理条件，即使石材的表面最佳功能化。选用一种生物粘多糖——硫酸软骨素作为有机模板，以亚稳态的草酸钙过饱和溶液为前驱液，在大理岩石表面仿生合成了草酸钙表面防护材料。通过设计正交试验，考察了仿生合成的各个因素的影响程度，以及较佳的合成条件。仿生合成的影响因素的影响程度为：有机模板的影响＞成矿离子前驱液的影响＞石材表面预清洁方式的影响＞保护膜层数的影响，较佳的制备条件是：石材表面用乙醇预清洁，较浓浓度的有机模板溶液使之表面功能化，过滤的草酸钙过饱和溶液作前驱液，多层制膜。分别采用XRD、SEM和AFM分析表征了材料的物相组成及微观形貌，证明石材表面的防护材料为一层约100 nm厚的薄片状的一水草酸钙晶体，并解释了材料的合成机理。通过憎水性、耐酸性、耐污性、耐老化性和透气性的测试，表明该材料亲水、防酸、防污、透气，且耐老化性能良好。在仿生合成草酸钙表面防护材料的基础上，进一步拓宽了仿生合成生物矿化保护材料的研究范围，包括草酸钙系列、磷灰石系列和碳酸钙系列。采用SEM表征了材料的微观形貌。以耐酸性、耐污性和耐老化性表征了各系列材料的表面防护效果，结果表明几种考察的材料均有不同程度的防护效果，尤以草酸钙为佳，其耐酸性达到pH≈0.8，耐污性≈2级，耐老化性及透气性能良好。对石质文物表面进行仿生防护，将生物矿化作用引入石质文物保护研究领域，提出采用“仿生”的方法保护石质文物的新思路，试验证明方法可行。(3)考虑到濒危石质文物表面结构疏松，本工作进一步探讨了仿生矿化保护材料的加固性能。借鉴岩土工程学的理论，用颗粒碳酸钙和粉末碳酸钙仿制了劣化的岩石。将仿生合成的一系列表面保护材料应用到仿制的样品上，考察了它们的抗压强度和抗水浸泡分解能力。结果表明，仿生矿化保护材料的加固效果良好，抗压强度和抗水浸泡能力都得到了较大的提高。加固效果最佳的是磷灰石材料，加固后，仿制样品的抗压强度可提高3～4倍，并可抗水浸泡6个月以上。(4)在实验研究结果的基础上，选择草酸钙和其它常用的有机保护材料，在洛阳龙门石窟做了现场保护对比实验，初期效果显示，仿生矿化材料的保护效果良好，显示了仿生矿化保护材料在石质文物保护领域具有良好的应用前景。总之，本工作证实了有机憎水性保护材料的副作用，研制出系列仿生矿化保护材料，检测表明它们具有较好的表面防护效果和表层加固性能，并且制作工艺简便。文献检索表明，目前尚未发现有类似的研究报道。这些成果对于发展新型石质文物保护材料具有重要的现实意义，同时也拓宽了生物矿化材料研究的领域。更多还原

【Abstract】 A good many of historic stones exposed out-of-doors are badly damaged due to natural and human factors. Their weathering state is badly serious. If people should not take effective measures to minimize damage from circumstances and slow down the ageing process of stones, a lot of historical value of historic stones will be fading away. However, hardly any protective materials do meet with all requirements now. Consequently, it is a very urgent task to explore new protective materials with a good performance which are fit for historic stones.In this paper, a review of the historic stone weathering and protective materials is summarized. Inspired by a crude biomimetic protective film of calcium oxalate, a novel idea on the application of biomimetic method to stone conservation is brought forward on the principle of biomineralization. Moreover, a series of inorganic biomimetic protective materials has been synthesized by biomimetic methods.The following results have been obtained by investigating:（1） Organic silicon, which was widely used in stone conservation now, was selected as surface protectant. Some common relic-used stone were used as protected objects, such as sandstone, tuff, dolomite, marble and granite. A series of artificial weathering experiments, which included single or cooperative effect of major ruinous factors—dry-wet cycle, salt crystallization, freezing and heating were simulated and researched. It is advanced that the surface hydrophobic protection can damage historic stones rather than protect in opposition to expectation. The reasons that decaying of stone is aggravated are a great contrast between hydrophilic stone and hydrophobic organic materials and aggravation of stress damage. An effective method to resolve this problem is to develop a new harmonious protective material which is non-absolutely hydrophobic, acid-resistant and soil- resistant, such as biomimetic materials.（2） In this work, the stone surface treatment, including surface cleaning and functionalization, was studied. The optimal processing parameters, by which stone surface was functionalized well, were made certain by tests of specimens’ surface energy.Selecting chondroitin sulfate, a category of principal acidic mucopolysaccharide, as an organic macromolecule template, the supersaturated solution of calcium oxalate as precursor, a protective material was synthesized on the marble surface by a biomimetic method. The effect degree of various factors and optimal processing parameters of biomimetic synthesis were investigated by an orthogonal experiment. The effect degree order is: first, organic template; second, mineralization ion precursor; third, surface treatment; fourth, lay amount of thin film. In the process of biomimetic synthesis, first of all, the stone surface was pretreated with ethanol and functionalized with organic template solution, and then filmed repetitiously by using filtered CaC₂O₄ supersaturation solution as precursor.The composition and microstructure of the material were characterized by using XRD, SEM and AFM. The analysis results show that the stone was covered by a lay of calcium oxalate monohydrate thin film which is approximately 100 nm thick. The synthesis mechanism of the protective material is explained. The tests of hydrophobicity, acid resistance, soil resistance, UV-lighting aging and breathing proved that the protective film functions well.On the basis of biomimetic synthesis exploration of calcium oxalate protection material on the stone surface, a series of protective materials, including calcium oxalate, apatite and calcium carbonate, were further investigated in biomimetic synthesis and surface protection performance. The microtopography of materials was characterized by SEM images. The protective performance was characterized by testing acid resistance, soil resistance and UV-lighting aging. The results show that all of them have various degrees of capabilities in surface protection. Calcium oxalate is the best of them. For example, the stone sample coated calcium oxalate can resist a pH 0.8 acid solution and achieve 2nd level of soil resistance. Moreover, they can breathe and serve for long.（3） With a view to the loose structure of historic stones, the further investigation of biomimetic protection is developed in consolidation. Referring to the architectonics theory, the replicas of rotten stones were prepared by using the powders and particles of calcium carbonate. Biomimetic surface protection materials were applied to the replicas of historic stones. It was investigated how about the capabilities in consolidating of biomimetic surface protection materials. The results from testing compressive strength and water soaking resistance show that these materials have great capabilities of consolidation. The compressive strength and water soaking resistance of treated replicas have been greatly improved. Apatite is the best of them. The stone replica consolidated by apatite has an increase of about four times in compressive strength, and can resist soaking for more than six months.（4） On the basis of summarization of experiments, some protective materials, including calcium oxalate and other common organic protective materials, were selected to do a fieldwork experiment at the Longmen Grottoes in Luoyang. The initial results show that the biomimetic method function well, which open up a good prospect for the conservation of historic stones by biomimetic methods.In conclusion, the side effects of organic hydrophobic protective materials are proved. A series of biomimetic protective materials is investigated. The test results show that they can function well in surface protection and consolidation. The process is simple. Currently, the literature on it has not been found yet. The production is of great significance to the development of new materials for historic stones conservation. Meanwhile, this work can develop the research field of biomimetic materials.更多还原