【作者】 梁艳；

【导师】 王来； 赵杰；

【作者基本信息】 大连理工大学 ， 材料学， 2008， 博士

【摘要】 自然界中一些天然生物材料的分级结构和优异性能为复合材料和陶瓷材料的仿生设计提供新的思路,研究其结构和性能是研制仿生材料的一个最基本的前提。贝壳作为天然生物材料的一种,由于其优异的力学性能而受到材料设计和研究者的关注。本文以大连地区特有的腹足纲的香螺贝壳及几种热带海螺贝壳(唐冠螺、黄米螺和蜘蛛螺)为研究对象,通过光学显微镜、扫描电镜、x射线仪和透射电镜等仪器观察了其无机相组成和微观组织结构;并对这几种贝壳中的有机蛋白质进行了提取分析;用差示扫描热分析仪(DSC)和傅立叶变换红外光谱(FTIR)对香螺贝壳粉末的热行为进行了细致的研究;用三点弯曲、压缩和纳米压痕等方法对香螺和唐冠螺贝壳的力学性能进行了分析,并用有限元分析的方法对其力学性能进行了初步的模拟计算。最后对交错纹片结构的贝壳的结构和性能之间的关系进行了探讨。1.产自温带海域的香螺壳由方解石和文石两相构成,产自热带海域的黄米螺和唐冠螺及蜘蛛螺均由单一的文石相组成。香螺壳除胚壳由单一的文石相构成外,螺塔和体螺环部位都是由最外层方解石和两层或多层文石内层构成,壳口边缘只有一层方解石。方解石为柱状结构,文石层为交错纹片结构。黄米螺、唐冠螺的体壳都是由三层文石结构构成,蜘蛛螺由四层文石结构构成,其文石相的显微结构也为交错纹片结构。贝壳中的方解石和文石层均呈多级超微结构,微量的有机质在晶界和晶内呈不连续分布。2.在对不同处理状态贝壳的三点弯曲、压缩和纳米压痕等力学性能实验的对比中,发现在空气中加热后的贝壳力学性能较低,应用加热前后贝壳文石层中有机蛋白质分子和文石晶体界面处模型的变化,较好的说明了贝壳作为一种典型的天然生物材料,其性能不仅仅与贝壳独特的微观结构相关,与其中的有机质以及有机质和无机相之间的健合等因素也是相关的。3.对香螺贝壳纳米压痕的结果表明文石的弹性模量和硬度要高于方解石层,贝壳的性能和微观裂纹扩展与晶体类型以及晶体结构的排列方式是密切相关的。方解石层压痕四周均存在裂纹,其裂纹形状曲折、不规则且沿着方解石层的边界扩展,不抗裂纹扩展。文石压痕周围平直清晰,裂纹沿着其二级结构扩展。新鲜的贝壳其纳米压痕的变形功、硬度和模量要高于烘干以后的贝壳的变形功、硬度和模量,这与其三点弯曲的实验结果是一致的。4.采用三点弯曲、压缩、显微硬度、纳米压痕等几种实验方法表征贝壳的力学性能,对实验结果的综合分析后发现纳米压痕功与贝壳的纳米硬度以及弹性模量等力学性能指标有较好的对应关系,表明纳米压痕实验对于表征贝壳类天然生物材料的微/纳米尺度的力学性能比较合理。5.通过对不同生长期香螺贝壳文石板条特征尺寸和力学性能的比较,发现随着香螺贝壳生长期的增加,文石板条特征尺寸也在增大,香螺贝壳的强度、硬度和弹性模量等力学性能指标也在增大,其三点弯曲曲线的斜率呈现出增大的趋势,而且承载能力也表现出明显的增强。揭示了贝壳类天然生物材料的性能不同于传统工程材料尺寸越小,强度越高的准则,而是综合考虑结构、有机质等多因素作用的结果。更多还原

【Abstract】 In nature, many natural biomaterials with hierarchical structure and mechanical properties provide new ideas for designing the composite material and ceramic material. And studying the hierarchical structure and mechanical properties is the most basic premise for producing biomaterial. The mollusk shell, as a typical natural biomaterial, has attracted the attention of the researchers due to its special microstructure and excellent mechanical properties. This paper takes Hemifusus tuba conch shell from the region of Yellow Sea and Bohai Sea and several tropical conch shell of gastropoda (Horned Helme conch shell, Conus betulina linnaeus shell, Common Spider Conch shell) as the object, and studies the composition, structure and characteristics of morphology by optical microscopy (OM), scanning electron microscopy (SEM), x-ray diffraction (XRD) and transmitted electron microscopy (TEM). The structure and characteristics of morphology of Hemifusus tuba conch shell in different growth period are observed by optical microscopy (OM). The organic protein of above several mollusc shells is extracted and analyzed and the thermal behaviour is researched in detail by differential scanning caloricity (DSC) and Fourier transform infrared spectra (FTIR). The mechanical properties of Hemifusus tuba and Horned Helme conch shell are studied by 3-point bending test, compressive test and nanoindentation, and then it simulates the mechanical properties using finite element analysis. At last two biomaterials are fabricated simulating the mollusk shell’s structure and the mechanical properties of them are analyzed.1. The Hemifusus tuba conch shell of temperate sea is composed of calcite and aragonite phase, and other three tropical conch shells are all composed of single phase of aragonite of crossed-lamellar. The Hemifusus tuba conch shell has different component, and the prodissoconch is composed of single aragonite, and the spire and body loop-coil are composed of outer layer of calcite and two or more layer of aragonite, yet the shell aperture fringe consists of single layer of calcite. The calcite is irregular cylindrical grains and aragonite is crossed-lamellar structure. The calcite and aragonite layer are all multiarchitecture, and a small quality of organic matrix presents discontinuous distribution at grain boundary and in grain.2. The comparative results of 3-point bending tests, compressive tests and nanoindentation tests of conch shell in different states including fresh shell ands heated shells indicate that the micromechanical properties of the heated shells at 250℃are lower than that of fresh shells..Applying the interface models of organic protein and inorganic crystal in the shell’s aragonite between former and after heating states preferably explain that the mechanical properties are not only correlative to unique microstructure, but also relate with the organic matrix and the bond between the organic matrix and inorganic mineral.3. The nanoindentation results of Hemifusus tuba conch shell indicate that the modulus and hardness of aragonite are higher than that of calcite. The mechanical properties and the microcracks propagation are related to the crystal type and crystal structure. The cracks around the indentation of calcite crystals are irregular and propagate along the interface of calcite. However the cracks around the indentation of aragonite are regular and obvious, and propagate along the second-order structure. The deformation work, hardness and modulus of fresh shells are higher than that of heated shells, and which is accorded with the 3-point bending tests results.4. The 3-point bending tests, compression, microhardness and nanoindentation tests etc several experiments are applied to test the the mechanical properties of mollusc shells. The synthetical test results indicate that there exists the better corresponding relation between nanoindentation work and bending strength, nanohardness, moduls etc. And which shows that the nanoindentation test is more reasonable to test the micro/nano mechanical properties mollusk shells of biomaterial.6. The comparison between size of aragonite fiber and mechanical properties shows that the thickness of aragonite fibre increase with the accretion of growth period of Hemifusus tuba conch shell. And the slope of 3-point bending curves increases, and the bearing capacity, hardness, modulus and nanoindentation work present obvious enhancement. And which shows that the mechanical properties of mollusk shells of biomaterial are different from the higher strength and little dimension of the traditional engineering material, but it synthetically considers the microstructure and organic matrix etc factors.更多还原