作者：张胜强1, 孙凌玉2
作者单位：1. 北京航空航天大学交通科学与工程学院, 北京 100191;
2. 北京航空航天大学 新能源汽车高效动力传动与系统控制北京重点实验室, 北京 100191
关键词：磁敏弹性体;扫描电镜;液氮脆断;高分子结晶;磁场
摘要：
对试样液氮脆断后进行扫描电镜观察是研究材料微观结构的常用方法，但应用于磁性羟基铁粉填充的磁敏弹性体试样时，却很难获得理想效果。通过对橡胶高分子结晶现象和低温脆断理论的分析，揭示脆断截面无法形成裸露的羟基铁粉链的机理；提出机械切割和抛光相结合的截面处理方法，得到的样品截面可满足扫描电镜对磁敏弹性体表面微结构的表征要求。通过对扫描电镜工作原理和成像理论的分析，阐述磁性材料产生的杂散磁场与扫描电镜磁透镜的磁场、入射电子束、收集器电压产生的耦合作用。这种耦合作用使在样品表面按一定时间和空间顺序做光栅式逐点扫描的入射电子束发生畸变，改变磁敏弹性体发射的二次电子的运行轨迹，使二次电子收集器收集效果变弱，降低图像质量。根据绝缘电阻测试得到不同体积分数羟基铁粉的磁敏弹性体的电导率，确定金属离子真空溅射和粘贴导电胶的试样处理方法。提出磁敏弹性体样品的退磁方案，并得到理想的微观形貌图像。
Analysis on scanning electron microscope representation theory of magnetic-sensing elastomer microstructure
ZHANG Shengqiang1, SUN Lingyu2
1. School of Transportation Science and Engineering, Beihang University, Beijing 100191, China;
2. Beijing Key Laboratory for High-efficient Power Transmission and System Control of Mwe Energy Resource Vehicle, Beijing University, Beijing 100191, China
Abstract: scanning electron microscope observation is a common method to study microstructure of materials after brittle failure of sampled liquid nitrogen. However, it is difficult to obtain an ideal effect when the method is applied for the magnetic-sensing elastomer filled with magnetic hydroxy iron powders. The analysis on polymer crystallization phenomenon of rubber and low temperature brittle fracture theory revealed the mechanism that brittle fracture cross section can not form an exposed hydroxy iron powder chain and proposed a method of combination of mechanical cutting and polishing for cross section processing and the cross section obtained in this way can meet the representation requirements of scanning electron microscope on surface microstructure of magnetic-sensing elastomer. Based on the analysis of working principle and imaging theory of scanning electron microscope, it explained the stray magnetic field of magnetic materials and the coupling effect generated by magnetic field and incident beam of magnetic lens of scanning electron microscope and collector voltage. This coupling effect will make incident beam that is in point-by-point raster scanning state as per a proper time and space sequence on sample surface distorted, which can change the moving path of secondary electron launched by magnetic-sensing elastomer, making the collection effect of secondary electron collector weaker and reducing image quality. According to insulation resistance test, the conductivity of magnetic-sensing elastomer filled with magnetic hydroxy iron powders with different volume fractions was obtained and procesing method for metal ion vacuum sputtering and pasting conducting resin sample were proven effective. Besides, demagnetization plan for magnetic-sensing elastomer sample was proposed and ideal microstructure image was also obtained.
Keywords: magnetic-sensing elastomer;scanning electron microscope;liquid nitrogen brittle fracture;polymer crystallization;magnetic field
2016, 42(9): 1-5 收稿日期: 2016-3-26;收到修改稿日期: 2016-5-23
基金项目: 国家自然科学基金项目（51175016）
作者简介: 张胜强(1990-),男,山东烟台市人,硕士研究生,专业方向为车辆工程。
参考文献
[1] SHUIB R K, PICKERING K L. Investigation and modelling of damping mechanisms of magnetorheological elastomers[J]. Journal of Applied Polymer Science,2016, 133(13):43247.
[2] CHEN W W, SUN L G, LI X H, et al. Numerical investigation on magnetostrictive effect of magneto-sensitive elastomers based on magneto-structural coupling algorithm[J]. Smart Materials and Structures,2013,22(10):105012.
[3] 韦春,桑晓明. 有机高分子材料实验教程[M]. 长沙:中南大学出版社,2009:43-45.
[4] 陈泉水,罗太安,刘晓东. 高分子材料实验技术[M]. 北京:化学工业出版社,2006:85-93.
[5] 张志广,车永兴,杨晨燕,等. 反式-1,4-聚异戊二烯的结晶性[J]. 合成橡胶工业,2012,35(1):36-39.
[6] 王延鹏. 聚偏氟乙烯/氟橡胶/硅橡胶共混材料的制备、结构与性能研究[D]. 广州:华南理工大学,2015.
[7] 钟群鹏,初飞,徐光宪. 冷脆断裂控制图的建立及其应用[J]. 北京航空航天大学学报,1990(4):11-16.
[8] 刘瑞良.2.25Cr1Mo钢中磷的平衡晶界偏聚及其对钢的韧脆转变温度的影响[D]. 哈尔滨:哈尔滨工业大学,2006.
[9] 王子瑜. 结构钢的低温冷脆及断裂机理概述[J]. 科技信息,2010(18):562.
[10] 李昂. 橡胶阻燃及其阻燃剂[J]. 特种橡胶制品,2002,23(3):25-30.
[11] CHEN L, GONG X, LI W. Microstructures and viscoelastics properties of anisotropic magnetorheological e-lastomers[J]. Smart Materials and Structures,2007,16(6):2645-2650.
[12] 王芹,汪怡,王露,等. 磁性固相萃取-火焰原子吸收光谱法测定工业废水中的Cu[J]. 理化检验(化学分册),2016,52(1):15-18.
[13] 谭和平,侯晓妮,孙登峰,等. 纳米材料的表征与测试方法[J]. 中国测试,2013,39(1):8-12.
[14] KARA E. The world of Electron microscopy[M]. Japan:Iwanami Shoten,1977:12-13.
[15] 张大同. 扫描电镜与能谱仪分析技术[M]. 广州:华南理工大学出版社,2009:7-8.
[16] UCHIYAMA I. Electron probe X ray micro analyzer[M]. Japan:Nikkan Kogyo Shimbun,1972:98-100.
