Mechanical Properties and Structure of Abalone: Self-Assembled Ceramic Nanostructures

非技术描述：在过去的一个世纪里，研究实验室开发的合成材料(金属、聚合物、陶瓷和复合材料)给生活带来了革命性的变化。然而，目前设计和生产性能更好的合成材料的可能性正在耗尽。因此，研究人员正将他们的注意力转向自然，试图更好地理解它，目标是模仿它的设计。这个新兴的仿生学领域寻求将特性设计成模仿生物系统的材料。这项拟议的研究涉及鲍鱼壳，它被认为是珍珠层或珍珠母的高度珍贵的来源。然而，它是由95%的白垩岩组成的，这是脆弱和易碎的。贝壳的复杂纳米结构和微结构是这样的：加入5%的有机胶水就能产生比白垩粉高出数量级的韧性。这项拟议研究的目标是从根本上了解壳体如此坚固的原因，并利用这一知识开发具有优异性能的新一代陶瓷复合材料。技术细节：将开展一个具有强大表征和分析成分的四年计划：开发新的微观和纳米机械测试方法，以确定作为瓷砖之间粘合剂的蛋白质层的粘弹性机械响应(S)。这种方法需要使用原子力显微镜、纳米压痕和纳米裂缝测试、微型剪切测试(类似于PI使用的介观测试)，通过结合有机层的粘弹性响应的新机制来模拟机械响应；使用显微拉曼光谱和FTIR来识别和量化变形后有机层的变化，以及确定瓷砖以“圣诞树”模式生长并将其取向从一层传递到另一层的机制。在这些观察的基础上，将建立文石(CaCO3的正交相)的详细生长模型。最终目标是使用生物启发的技术来合成新材料。研究将在加州大学圣地亚哥分校、墨西哥国立自治大学和劳伦斯·利弗莫尔国家实验室进行。来自圣地亚哥和墨西哥的研究生和本科生以及高中生将参与学习过程。普赖斯学校是一所特许高中，旨在为6-12年级的低收入学生提供密集的大学预科教育计划，将参与其中。这些学生来自父母没有接受过大学培训的家庭。两名高中生将在学年期间工作(普赖斯学校允许的每周4-6小时)和暑假期间的全职工作(6周)。需要强调的是，这些实验不会伤害或杀死鲍鱼。该项目由国际科学与工程办公室和材料研究部共同资助。

NON-TECHNICAL DESCRIPTION: The synthetic materials (metals, polymers, ceramics, and composites) developed in research laboratories during the past century have revolutionized life. However, at present, the possibilities of designing and producing synthetic materials with improved performance are being exhausted. Therefore researchers are turning their attention to nature, trying to understand it better, with the goal of mimicking its designs. This emerging field of Biomimetics seeks to design properties into materials modeled after biological systems. The proposed study addresses the abalone shell that is highly prized as a source of nacre, or mother-of-pearl. Yet, is comprised of 95% chalk, which is weak and brittle. The complex nanostructure and microstructure of the shell are such that adding 5% of an organic glue leads to a toughness that is orders of magnitude higher than that of chalk. The goal of the proposed research is to understand, at the fundamental level, why the shell is so strong and to use this knowledge to develop a new generation of ceramic composites with superior properties. TECHNICAL DETAILS: A four-year program with strong characterization and analysis components will be carried out: development of new micro- and nano-mechanical testing methods to establish viscoelastic mechanical response of the protein layer(s) that act as an adhesive between tiles. This approach requires the use of atomic force microscopy, nanoindentation and nanoscratch tests, a miniaturized shear test (analogous to the meso scale test used by the PI), modeling mechanical responses through novel mechanisms incorporating viscoelastic response of organic layer; identification and quantification of the changes in the organic layers that occur after deformation using micro-Raman spectroscopy and FTIR, and identification of mechanisms by which tiles grow in "Christmas tree" pattern and transmit their orientation from level to level. Based on these observations, a detailed growth model for aragonite (the orthorhombic phase of CaCO3) will be developed. The ultimate goal is the use of biologically-inspired techniques to synthesize new materials. Research will be carried out at University of California San Diego, Universidad Nacional Autonoma de Mexico, and the Lawrence Livermore National Laboratory. Graduate and undergraduate students from San Diego and Mexico will be involved in the learning process, as well as high school students. The Preuss School, a charter high school that is designed as in intensive college preparatory educational program for low-income students in the grades 6-12, will be involved. These students come from families whose parents have not received college training. Two senior high school students will work during the school year (4-6 hrs/week, as allowed by The Preuss School) and full time during their summer breaks (6 weeks). It is emphasized that no abalone are harmed or killed for these experiments. This project is co-funded by the Office of International Science and Engineering and the Division of Materials Research.