测度关系法评价水泥基材料孔隙SEM分形特征

目的以测度关系法对混凝土孔隙的SEM图像分形维数进行精细测量和计算,分析其孔隙分形特征.方法以砂浆中集料界面区域孔隙SEM照片为例,用测度关系法、分别以250 nm和200 nm,125 nm和100 nm不同尺度的网格测试评价界面孔隙的分形维数,与改变粗视化方法进行比较.结果传统的改变粗视化程度的方法与网格边长的关系太大,网格边长受测试条件的限制,导致误差过大,而采用测度关系法计算SEM图像孔隙显微结构分形维数比较可靠.采用测度关系法用边长差异为50 nm网格测试其孔隙分形维数为1.293 5,用边长差异为25 nm的网格测试的孔隙分形维数为1.280 9,误差只有0.012 6;当考虑中间水化产物时,用边长差异为50 nm网格测试其孔隙分形维数为1.577 3,用边长差异为25 nm网格测试的孔隙分形维数为1.570 1,误差只有0.0072;此外,考虑中间水化产物后,孔隙的分形维数增大,表明孔隙复杂程度明显增大.结论采用测度关系法计算分形维数比改变粗视化程度方法更为精细.分形理论分析评价多孔材料SEM图像孔结构分形特征是有效的,对于深入了解水泥基复合材料的内部微结构、提升性能、扩大应用具有重要意义.

Evaluation on the Fractal Characteristics of Pore in SEM Photo of Cement Matrix Materials with the Measure Relation

The fractal dimension of pores in a SEM photo of cement matrix materials is tested and counted accurately with the measure relation.In this paper,as an example,the fractal dimension of the SEM photo of interfacial area of the aggregate in the mortar is tested in different sizes,at 250 nm,200 nm,25 nm and 200 nm.Furthermore,the testing result is compared with the traditional result.The result shows that,in the traditional method of'changing scale',the testing result of the fractal dimension is affected by the grid size and the error is large.But,with the measure relation,the tested result of the fractal dimension of the SEM photo is very credible.When the differences of the grid sizes are 50nm and 25nm,the pore fractal dimensions are 1.2935 and 1.2809,and the error is only 0.0126.If hydration products are considered and the grid size difference is 50nm and 25nm,the pore fractal dimension are 1.5773 and 1.5701 respectively.The error is only 0.0072.With the increase of the pore fractal dimension,the complexity of the pore also increases.Besides,the measure relation is more accurate than the traditional method.Evaluating fractal characteristics of the pore structure by SEM photos are effectual.It is useful for further investigating the inner microstructures of cementing composite materials,increasing its high performance and enlarging its application.