BIOMIMETIC METHODS BASED ON SOLUBLE AMMONIUM PHOSPHATE PRECURSORS FOR THE CONSOLIDATION OF WALL PAINTINGS

技术摘要：在材料研究部固体与材料化学（SSMC）项目的支持下，本项目将开发以羟基磷灰石（HAP）为基础的无机矿物体系，以保护和巩固由碳酸钙（CaCO3）丰富的石膏层组成的粉状壁画，具有考古、历史和艺术价值。通过触发碳酸盐底物与肽和磷酸铵前体之间的反应，利用仿生原理诱导脱胶石膏中HAP的形成。空间，结构和成分敏感分析，包括扫描电子显微镜，3D-CT成像，动态蒸汽吸附方法和机械和流体输运分析，应用于量化HAP处理。本研究从科学的角度描述了：(1)磷酸盐反应物与CaCO3石膏之间的化学相互作用和反应；(2)HAP的形成对强化微观结构和改善涂层的影响。耐用性，同时保持原有的光学/美学特性。本研究的跨学科性质，在保护科学、生物技术和材料科学的界面上，开发了量身定制的保护处理方法，考虑了衬底化学和结构的基本特征，以规定和计量处理方案。该研究提高了我们设计、操作和评估多孔多色表面固结处理的能力，并允许改进方法来保护全球文化遗产。重要的是，该项目以物理科学和材料工程为基础，为从绘画和岩石艺术到石头结构、古生物化石和考古骨骼等历史文物制定保护策略。壁画是艺术、文化和智力发展的见证，因此具有深刻的考古、历史和文化意义。不幸的是，随着时间的推移，由于人类活动和环境力量的影响，壁画经历了相当大的退化。虽然已经提出了几种方法来限制或停止这种退化，但这些方法往往会损害绘画的内在质量和属性。通过加州大学洛杉矶分校（UCLA）的多学科合作，本研究开发了基于羟基磷灰石的固结处理，以保护多层、多色、异质壁画免受时间和环境影响引起的风化和变质，而不会对其物理和化学性质造成重大变化。通过使用对材料成分和结构敏感的分析工具，处理方法以上下文敏感的方式应用和计量；也就是说，关注一幅特定画作的特征和它的执行技术（即壁画或塞科）。为一名博士后研究员、一名研究生和几名本科生提供的研究和学术培训，将知识传授给新一代的保护科学家，他们可以为保护我们的集体文化遗产做出贡献。通过与国内和国际合作者的互动，该研究为学术卓越/交流提供了一个平台，同时创造了适用于不同地理领域的保护实践的新知识。最后，该研究还开发了应用于牙齿/骨骼重建和土木工程基础设施修复的生物工程知识。本研究由材料研究部（DMR）固态与材料化学（SSMC）项目支持。

TECHNICAL ABSTRACTWith support from the Solid State and Materials Chemistry (SSMC) program in the Division of Materials Research (DMR), this project will develop hydroxyapatite (HAP) based, inorganic mineral systems to preserve and consolidate powdery wall paintings composed on calcium carbonate (CaCO3) rich plaster layers of archaeological, historic and artistic value. Biomimetic principles are used to induce HAP formation in the decohesive plaster by triggering reactions between the carbonate substrate and the peptidic and ammonium phosphate precursors. Spatially, structurally and compositionally sensitive analytics including scanning electron microscopy, 3D-CT imaging, dynamic vapor sorption methods and mechanical and fluid-transport analyses are applied to quantify HAP treatments. From a scientific perspective, the research describes: (1) chemical interactions and reactions between the phosphate reactant and the CaCO3 plaster and (2) the impact of HAP formation on strengthening the microstructure, and improving the painting?s durability while maintaining the original optical/aesthetic properties. The interdisciplinary nature of this research, at the interface of conservation science, biotechnology and materials science develops tailored conservation treatments that consider fundamental characteristics of the substrate chemistry and structure to prescribe and metricate treatment protocols. The research advances our ability to design, manipulate and evaluate consolidation treatments for porous polychrome surfaces and allows for improved methodologies to preserve global cultural heritage. Significantly, the effort develops conservation strategies for historic objects ranging from paintings and rock-art to stone structures, paleontological fossils and archaeological bone with a basis rooted in the physical sciences and materials engineering. NON-TECHNICAL ABSTRACTWall paintings provide a testimony of artistic, cultural, and intellectual developments and are consequently of profound archaeological, historical and cultural significance. Unfortunately, with the passage of time, wall paintings experience considerable degradation due to their exposure to human activity and environmental forces. While several methods have been proposed to limit or halt such degradation, these methods often compromise the intrinsic quality and attributes of the painting. Through a multi-disciplinary collaboration at the University of California, Los Angeles (UCLA), this research develops hydroxyapatite-based consolidation treatments to enable the protection of multi-layered, polychrome, heterogeneous wall paintings from weathering and deterioration induced by passage-of-time and environmental effects without causing significant change to their physical and chemical properties. By using analytical tools sensitive to the composition and structure of the material, treatment methods are applied and metricated in a context sensitive fashion; i.e., with attention to the characteristics of a specific painting and its execution technique (i.e., fresco or secco). The research and academic training provided to a post-doctoral researcher, a graduate student and several undergraduate students imparts knowledge to a new generation of conservation scientists who can contribute to preserving our collective cultural heritage. Through interactions with national and international collaborators the research offers a platform for academic excellence/exchange and at the same time creates new knowledge of conservation practices applicable across diverse geographical domains. Finally, the research also develops knowledge with applications in bioengineering for tooth/bone reconstruction and for infrastructure rehabilitation in civil engineering. This research is supported by the Solid State and Materials Chemistry (SSMC) program in the Division of Materials Research (DMR).