【作者】 陆德荣；

【导师】 何春霞；

【作者基本信息】 南京农业大学 ， 农业机械化工程， 2012， 博士

【摘要】 材料微观结构研究对宏观性能分析具有重要意义,目前聚合物基纳米复合材料微观结构以定性分析为主,定量分析较少。本文以PTFE基纳米复合材料微观结构定量分析及探讨其与宏观性能之间相关性为目标,以冷压烧结法制备了3种纳米材料在不同质量分数(3%、5%、7%、9%)及不同处理方式(纳米颗粒未处理与偶联剂表面处理)情况下的纳米AlN/PTFE、纳米SiC/PTFE、纳米Si3N4/PTFE复合材料,用JSM-6000扫描电子显微镜对PTFE基纳米复合材料微观结构进行图像采集,利用Visual C++及Matlab软件设计了纳米复合材料微观结构图像处理程序,包含图像预处理、图像分割、图像形态学处理、区域标记、微观结构特征参数提取(颗粒平均面积分数、颗粒面积相对标准差、颗粒分布均匀度、颗粒分布相对标准差、颗粒分布分形维数、微裂纹区域特征及微裂纹分布分形维数)等功能,定量表征了PTFE基纳米复合材料微观结构特征,并对复合材料宏观性能(拉伸强度、断裂伸长率、冲击强度、硬度、磨损量、摩擦系数)进行测试和分析,研究了PTFE基纳米复合材料宏观性能与微观结构之间关系。得出主要结论如下：(1) PTFE基纳米复合材料微观结构SEM图像经预处理后,图像质量提高,对比度明显加强,灰度级变宽,纳米颗粒及微裂纹显示清晰,易于图像分割。形态学处理有利于提取纳米颗粒及微裂纹在复合材料中的有用信息,区域标记能赋予各目标物不同灰度值,以便于区分纳米复合材料微观结构中目标物和定量分析微观结构特征参数。颗粒平均面积分数及颗粒面积相对标准差用于表征复合材料中纳米颗粒的团聚程度,颗粒平均面积分数及颗粒面积相对标准差越小,则纳米颗粒团聚程度越小,分散度高,分散质量越好。颗粒分布均匀度及颗粒分布相对标准差用于表征纳米颗粒在基体中的分布状况,颗粒分布均匀度越大,颗粒分布相对标准差越小,则颗粒在基体中分布越均匀。颗粒分布分形维数用于综合评价复合材料中纳米颗粒的分散质量及分布状况。微裂纹区域特征参数及分布分形维数用于表征复合材料中纳米颗粒与基体的界面结合质量,微裂纹面积分布、长度分布、取向角分布可用于分析微裂纹尺寸分布及数量分布,取向角分布相对标准差及分布分形维数可用于分析微裂纹在复合材料中的分布状况。(2)随着纳米颗粒质量分数增加,三种PTFE基纳米复合材料颗粒分散度均有下降趋势,纳米颗粒团聚程度增加,但在质量分数7%时颗粒分散度较大,纳米颗粒在PTFE中分散质量较好。随着纳米颗粒质量分数增加,三种PTFE基纳米复合材料颗粒分布均匀度先增大后减小,纳米A1N质量分数为5%,纳米SiC、Si3N4颗粒质量分数为7%时,颗粒分布均匀度较大,纳米颗粒在PTFE中分布均匀较好。颗粒分布分形维数随纳米颗粒质量分数增加而增大。(3)微裂纹面积分布、长度分布直方图表明,随着纳米颗粒质量分数增加,三种PTFE基纳米复合材料微观表面微裂纹数量先增多后减少；纳米A1N质量分数为5%,纳米SiC、Si3N4颗粒质量分数为7%时,微裂纹数量较多,同时微裂纹取向角分布相对标准差较小,微裂纹分布分形维数较大,表明微裂纹分布范围大且混乱,定向性低,更加趋于各向同性。(4)偶联剂处理使纳米SiC/PTFE.纳米Si3N4/PTFE复合材料颗粒分散度、颗粒分布均匀度、颗粒分布分形维数增大,纳米AlN.PTFE复合材料颗粒分散度及颗粒分布分形维数增大、颗粒分布均匀度减小；偶联剂处理使纳米SiC/PTFE、纳米Si3N4/PTFE复合材料微裂纹取向角分布相对标准差减小、分布分形维数减小,而纳米AlN/PTFE复合材料微裂纹取向角分布相对标准差及分布分形维数均增大。(5)纳米AlN/PTFE复合材料宏观机械性能与微观结构特征参数关系研究表明,纳米AlN/PTFE复合材料拉伸性能、冲击性能、硬度、耐磨性能、减摩性能与颗粒分布分形维数之间均存在较好的线性相关性,它们的相关系数R2值较大。(6)本文所设计的图像处理方法可以很好地完成PTFE基纳米复合材料微观结构SEM图像处理工作,可对微观结构特征参数进行提取并定量分析其与宏观性能之间相关性,简单、方便、实用、可靠。更多还原

【Abstract】 Research on material microstructure was vitally significant to the analysis of macroscopical performance. At present, most qualitative analysis and less quantitative analysis have been carried on microstructure of polymer matrix nano-composites. In this paper, in order to quantitatively analyze the microstructure and discuss the relativity between it and the macroscopical performance of PTFE matrix nano-composites, nano-AlN/PTFE, nano SiC/PTFE, nano-Si3N4/PTFE composites were prepared by cold-pressing and sintering method in the situation of different mass fraction of three nano-materials (mass fraction was3%,5%,7%and9%) and different treatment methods (untreated and coupling treated of nano-granules). The microstructure images of PTFE matrix nano-composites were gathered by JSM-6000scanning electron microscope. The program, used to process the microstructure images of nano-composites, was designed by the software Visual C++and Matlab, including functions of image preprocessing, image segmentation, image morphological processing, region marking, and character parameters of microstructure (granule average area fraction, relative standard deviation of granule area, uniformity of granule distribution, relative standard deviation of granule distribution, fractal dimension of granule distribution, microcrack district character and fractal dimension of microcrack distribution) obtaining. The microstructure characters of PTFE matrix nano-composites were taken attribute, and the macroscopical performance (tensile strength, break elongation ratio, impact strength, hardness degree, wear amount, friction coefficient) were tested and analyzed. The analysis was carried on the relationship between the macroscopical performance and the microstructure character parameters of PTFE matrix nano-composites. The main conclusions were as followed:(1) After the microstructure SEM images of PTFE matrix nano-composites were preprocessed, the image quality enhanced, the contrast enhanced obviously, the gray level became broader, and the nano-granules and the microcracks became clearer, which was helpful to image segmentation. Morphological processing was propitious to obtain the useful information of nano-granules and microcracks in composites. Various objects could be given different grey level by region marking, which was convenient to divide objects in the microstructure of nano-composites and quantitatively analyze microstructure character parameters. The agglomeration degree of nano-granules in composites was taken attribute by the granule average area fraction and the relative standard deviation of granule area. The smaller the granule average area fraction and the relative standard deviation of granule area were, then the lower the agglomeration degree of nano-granules was, the higher the dispersion degree was, and the better the dispersion quality was. The distribution status of nano-granules in PTFE matrix was taken attribute by the uniformity of granule distribution and the relative standard deviation of granule distribution. The bigger the uniformity of granule distribution was and the smaller the relative standard deviation of granule distribution was, then the more well-proportioned the granule distributed in PTFE matrix. The dispersion quality and distribution status of nano-granules in composites were taken general attribute by the fractal dimension of granule distribution. The surface connection quality between nano-granules and PTFE matrix was taken attribute by microcrack region character parameters and the fractal dimension of microcrack distribution. The size distribution and amount distribution of microcracks was analyzed by the area distribution, length distribution and oriented angle distribution of microcracks. The distribution status of microcracks in composites could be analyzed by the relative standard deviation of oriented angle distribution and the fractal dimension of distribution.(2) Along with the mass fraction of nano-granules increasing, the granule dispersion degree of three kinds of PTFE matrix nano-composites had the drop tendency, and the agglomeration degree of nano-granules enhanced. However, the granule dispersion degree was higher at the mass fraction of7%, and the dispersion quality of nano-granules in PTFE was better. Along with the mass fraction of nano-granules increasing, the uniformity of granule distribution of three kinds of PTFE matrix nano-composites increased first and then reduced. When the mass fraction of nano-AIN was5%and the mass fraction of nano-SiC and nano-Si3N4was7%, the uniformity of granule distribution was bigger and the distribution quality of nano-granules in PTFE was better. The fractal dimension of granule distribution increased along with the mass fraction of nano-granule increasing.(3) It was indicated by the area distribution histogram and the length distribution histogram of microcracks that the microcracks amount of three kinds of PTFE matrix nano-composites increased first and then reduced along with the mass fraction of nano-granules increasing. When the mass fraction of nano-AIN was5%and the mass fraction of nano-SiC and nano-Si3N4was7%, the microcracks amount was much more, the relative standard deviation of microcrack oriented angle distribution is smaller, and the fractal dimension of microcrack distribution is bigger, which indicated that the microcrack distribution range was big and disordered, the orientation property of microcracks was low and tended to isotropism.(4) By coupling treated, the granule dispersion degree, the uniformity and the fractal dimension of granule distribution of nano-SiC/PTFE, nano-Si3N4/PTFE composites increased. By coupling treated, the granule dispersion degree and the fractal dimension of granule distribution of nano-AlN/PTFE composites increased, while the uniformity of granule distribution reduced. By coupling treated, the relative standard deviation of microcrack oriented angle distribution and the fractal dimension of microcrack distribution of nano-SiC/PTFE, nano-Si3N4/PTFE composites reduced, while the relative standard deviation of microcrack oriented angle distribution and the fractal dimension of microcrack distribution of nano-AlN/PTFE composites increased.(5) It was indicated by the research of relation between the macroscopical mechanizm performance and the microstructure character parameters of nano-AlN/PTFE composites that:there was better linear relativity between tensile performance, impact performance, hardness degree, wear resistance, friction reducing of nano-AlN/PTFE composites and fractal dimension of granule distribution, while the correlation coefficient R2was bigger.(6) The processing work of microstructure images of PTFE matrix nano-composites could be well done by the image processing methods designed in this article. The microstructure character parameters could be obtained and the relativity between it and macroscopical performance could be quantitatively analyzed. The image processing methods were simple, convenient, practical and reliable.更多还原