| 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. |
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