辅助性胶凝材料负载纳米碳纤维的优化设计及其与水泥基材料相互作用机理研究

Nano-carbon fiber is a new reinforced cement-based materials, presenting a high specific strength and specific modulus, less defect, compact structure, large length-diameter ratio and etc. The application and reinforcing effect of nano-carbon fiber in cement-based materials are limited due to its poor dispersion property in cement-based materials and lack of investigation on the interaction mechanism of nano-carbon fiber and cement-based materials. In this project, a new approach by which nano-carbon fiber grows directly on the matrix surface and matrix precursor particles is proposed. Supplementary cementitious materials are selected as the precursor matrix. A novel supplementary cementitious materials supported nano-carbon fiber is synthesized in which nano-carbon fibers are attached to the supplementary cementitious materials. The in-situ synthesis method, synthesis conditions, structural parameters, micro-morphology, and structure control methods for supplementary cementitious materials supported nano-carbon fiber will be systematically investigated. The influence of supplementary cementitious materials supported nano-carbon fiber on the formation and growth behavior of hydration products (e.g. Ca(OH)2, C-S-H gel, Ettringite) will be explored to reveal the interaction mechanism between cement-based materials and supplementary cementitious materials supported nano-carbon fiber, the correlation between alterations of the composition and structure of the hydration products and enhancement effect of cement-based materials. This project will provide a theoretical basis for the adjustment and control of nano-carbon fiber structure and promote the application of nano-carbon fiber in cement-based materials.

纳米碳纤维具有高比强度、高比模量、缺陷数量少、结构致密、长径比大等优异特性，是一种新型的水泥基增强材料，但纳米碳纤维的分散问题，以及缺乏对纳米碳纤维与水泥基材料相互作用机理研究，限制了其在水泥基材料中应用和增强效果发挥。本项目从纳米碳纤维生产工艺出发，以辅助性胶凝材料为基质，采用原位合成方式制备纳米碳纤维，使纳米碳纤维分散在辅助性胶凝材料中，形成辅助性胶凝材料负载纳米碳纤维复合材料；系统研究辅助性胶凝材料负载纳米碳纤维原位合成方式、合成条件、结构参数、微观形态以及结构调控方法。探明辅助性胶凝材料负载纳米碳纤维对Ca(OH)2、 C-S-H凝胶、钙矾石等水泥水化产物形成和生长行为的影响，揭示辅助性胶凝材料负载纳米碳纤维与水泥基材料相互作用的机制，明确水化产物组成和结构的变化对水泥基材料增强增韧的关联性。本项目的开展将为纳米碳纤维结构调控、推广纳米碳纤维在水泥基材料中的应用起到理论指导作用。

碳纳米纤维（CNFs）突出的性能使之成为改善水泥基材料性能的优选纤维。然而，由于碳纳米纤维之间范德华力的存在使其难以均匀分散。本研究通过化学气相沉积法在、粉煤灰、钢渣和水泥颗粒上原位合成碳纳米纤维来解决碳纳米纤维的分散性问题，研究了原位合成条件对合成的碳纳米纤维的结构和性能的影响，探讨了合成的碳纳米纤维对水泥性能的影响。取得的主要研究成果如下：探讨了不同反应时间和合成温度对钢渣、水泥和粉煤灰表面原位合成碳纳米纤维结构与性能的影响，研究结果表明：以钢渣为基体，可以在钢渣表面原位合成碳纳米纤维，合成时间为45min条件下在钢渣颗粒表面原位合成碳纳米纤维，合成温度为600℃较佳，此温度条件下合成碳纳米纤维的产率高、抗氧化性较好、石墨化程度低、管径较细长；合成时间为45min条件下在水泥颗粒表面原位合成碳纳米纤维，合成温度为600℃较佳，此温度条件下合成碳纳米管的产率较高、抗氧化性好、石墨化程度低、管径较细长；在600℃时粉煤灰颗粒上合成碳纳米纤维产率较高，700℃时合成碳纳米纤维的缺陷较多。碳纳米纤维/粉煤灰复合材料会表现出一定的疏水性，经氧化处理后，疏水性会消失。阐明了水泥-CNF、钢渣-CNF、粉煤灰-CNF复合材料对水泥性能影响的规律，研究结果表明：掺入水泥-CNF、钢渣-CNF、粉煤灰-CNF复合材料降低了浆体的流动度，对水化放热影响不大；其力学性能具有较大的提升，对水泥基材料的韧性有显著提升；能够降低水泥基材料的电阻率，水泥基材料具有一定压电性能；均匀分散的碳纳米纤维横跨孔隙和裂缝之间，起着连接孔隙裂缝的桥梁的作用，增强了水泥基的韧性。