多壁碳纳米管水泥基复合材料的耐久性能及机理研究

Carbon nanotubes (CNTs) are fibrous materials with best comprehensive properties yet discovered, whose nanoscale effect, lightweight, high tensile strength, high elastic modulus and excellent flexibility, toughness and electrical properties, make carbon nanotubes cement based composites exhibit excellent strength, toughness and conductivity performance, etc., nonetheless, the durability and micromechanism are not clear and perfect, therefore, it has great significance to extend carbon nanotubes cement based composites' engineering application scope by researching its durability and the relationship of characters between microscopical and macroscopical sides. The durability contains permeability resistance, frost resistance, early age shrinkage, sulphate resistance performance and so on. The research studies the physical and chemical dispersion technology and mechanism, to improve the homogeneity of multi-walled carbon nanotubes in suspension and cement matrix. The research studies representative durability factors, such as permeability resistance, frost resistance, early age shrinkage, sulphate resistance performance et al, to put forward durability evaluation methods and comprehensive evaluation index system suitable for multi-walled carbon nanotubes cement based composites, identifying their application range and offering scientific proof for application. The research investigates the microeffect and action mechanism of durability improvement, and micromechanism of durability degradation process by means of microscopic test and analysis, to provide basic theoretical support for practical engineering application and intensive studies, and offer guides for optimizing preparation techniques of multi-walled carbon nanotubes cement based composites as well.

碳纳米管具有小尺度、轻质、高强、高弹模以及良好的弹性、韧性和电学性质，是综合性能最好的纤维材料；碳纳米管水泥基复合材料同样也具备优异的强度、韧性和导电等性能。通过研究其抗渗透性、抗冻性、早龄期收缩和抗硫酸盐侵蚀等耐久性指标及微观架构与宏观性能的关系，对于拓展碳纳米管水泥基复合材料的工程应用范围具有重要意义。本课题利用多壁碳纳米管的物理、化学分散技术，提高其在悬浮液及水泥基复合材料中的分散均匀性；通过研究多壁碳纳米管水泥基复合材料的耐久性指标，掌握其工程应用特性和耐久规律，提出适合于多壁碳纳米管水泥基复合材料的耐久性评价方法和综合评价指标体系，并确定其工程适用范围；通过微观测试分析，研究多壁碳纳米管提高水泥基复合材料耐久性能的微观效应和作用机理，研究其耐久性能劣化过程的微观机制，为其工程应用及深入研究提供基础理论支撑，亦为进一步优化多壁碳纳米管水泥基复合材料的制备技术提供指导。

碳纳米管（MWNTs）是综合性能最好的纳米级纤维材料，具有优异的力学、电学等性质。碳纳米管水泥基复合材料（MWCNTs/CC）也同样具备优异的力学性质和电学等性能。深入系统的研究了MWCNTs的分散性能，MWCNTs/CC的力学性能、电磁屏蔽性能以及耐久性能，纳米碳纤维(CNFs)的分散性能及其水泥基复合材料的力学性能，研究了MWCNTs提高水泥基复合材料性能的微观作用机理。. MWCNTs的分散性研究成果表明：单掺分散剂时阿拉伯胶（GA）对MWNTs分散效果最好，其最佳掺量为0.45g/L；通过对GA的分散机理进行研究发现GA在MWCNTs表面为典型的“SL”型两阶段吸附，GA浓度为0.45g/L时在MWCNTs表面达到吸附饱和；GA能够通过其分子长链的包覆作用改善MWCNTs的亲水性和分散性。. MWCNTs/CC的力学性能、电磁屏蔽性能和耐久性能研究成果表明：MWCNTs的掺入能够显著提高水泥基材料的力学性能和弯曲韧性，其抗折强度最多提高了43.6%，抗压强度最多提高了21.6%，其断裂能提高165.1%，韧度指数提高52.8%；MWCNTs可以极大提高水泥基复合材料的吸波性能，MWCNTs 掺量为0.6wt.%、厚度为25mm 的试样在2.9 GHz 处获得最强吸收峰值- 28dB，并能够在2~8GHz 范围内对出现在吸收峰值附近的电磁波进行充分吸收；MWCNTs的掺入降低了水泥基复合材料的氯离子扩散系数，最小值为1.43×10-12m2/s，相比空白试件下降了39.7%；MWCNTs提高了水泥基复合材料的抗硫酸盐侵蚀性能，减小了水泥基复合材料的早龄期自收缩值。. CNFs的分散性及其水泥基复合材料的力学性能研究成果表明：甲基纤维素(MC)对CNFs分散效果最佳，低掺量掺入CNFs时，复合材料的7d抗弯强度有所降低，而14d、28d强度有提高，最高提升21%。. 微观作用机理研究表明，MWCNTs在悬浮液及水泥浆基体中具有较好的分散性，MWCNTs能够促进水泥基复合材料的水化，水泥基复合材料具有较强的界面粘结强度并且MWCNTs能够改善水泥基复合材料的微观结构。. 研究成果对碳纳米管水泥基复合材料的深入研究及工程应用提供理论支撑，亦为进一步优化碳纳米管水泥基复合材料的制备技术提供指导。