基于原子力显微镜PeakForce QNM模式下的水泥基材料微区力学性能研究

Research on Local Mechanical Properties of Cement-based Materials Based on PeakForce QNM Mode

基于原子力显微镜中峰值力纳米尺度力学性能定量表征模式,对水泥净浆和砂浆等材料在微区的力学性能进行了分析测试研究,研究结果显示:PF-QNM对于表征水泥基材料微纳结构下的力学性能具有良好的效果。它对测试的环境要求不高,在测试的时候对材料的表面没有损伤,可以很容易的获取高分辨率图像并进行统计分析,测试的结果来源于面扫描而获得的大量数据,结果的可靠性大大增强。上述这些情况都优于纳米压痕的测试方法。唯一比较困难的方面是该测试对于试样表面的平整度要求较高,但是纳米压痕技术也有同样的问题。PFQNM模式也优于AFM一般的成像模式。在AFM普通的接触模式或轻敲模式下,只能获得材料表面的形貌信息,但是PF-QNM不仅能够获得形貌信息,还可以同时获取杨氏模量、粘附力、变形、能量耗散等信息,研究效率显然优于前者。验结果显示,PF-QNM不仅可以测试水泥浆体的力学性能,也能够对材料的界面区域进行研究,包括界面区域力学性能的变化、界面区域的范围等。在测试的过程中,需注意的是测试范围大小的设定。测试范围如太小,则不具有代表性,测试范围太大,则测试结果缺乏稳定性。建议的测试范围是10～30μm。

In this paper, the cement paste and the mortar were tested using the PF-QNM technique and the following conclusions are: The PF-QNM technique is very powerful to characterize the mechanical properties of micro- and nanostructures in the cement-based materials. It doesn't have strict requirements for test environment and it does not damage the surface of the material. High-resolution images can be obtained very easily, and they can be analyzed statistically. The only difficult aspect is that the PF-QNM technique has a high requirement for the surface flatness of the specimen, but nanoindentation also has the same problem. PF-QNM methodology is also better than the conventional AFM imaging method. The conventional contacting or tapping mode of AFM can only give information about the surface morphology of the material, while with PF?QNM, Young's modulus, adhesion force, deformation and energy diffusion can be obtained, in addition to topography information. The test results show that PF-QNM analysis can test not only the mechanical properties of the cement paste, but also investigate the interfacial regions in the cement-based material, including the variation in the mechanical properties of interface regions and the extension of the interfacial regions. During the test, care must be taken to choose the size of test area;indeed, a test area too small is not representative but too large leads to lack of stability. The recommended side is a square with a length of in the range 10-30μm.