碳纳米管增强火山灰基地聚合物的制备与性能表征

Preparation and characterization of carbon nanotubes reinforced volcanic ash-based geopolymer

为研究多壁碳纳米管对火山灰基地聚合物的增强效果与机理,通过显微观察和图像识别对比了不同超声时间多壁碳纳米管分散液中团聚体的数量和面积,确定了适宜的超声分散时长;以不同顺序混合分散液、碱激发剂溶液和火山灰制备地聚合物,通过所得浆体的稠度试验、硬化试件的三点弯曲试验、单轴压缩试验研究了不同掺量、不同种类的多壁碳纳米管对地聚合物工作性能与力学性能的影响,并利用扫描电子显微镜-能谱仪、压汞试验对地聚合产物的微观形貌和孔隙结构进行表征。分析结果表明:随着超声时间的增加,多壁碳纳米管的分散效果改善明显,45 min超声后超过85%的团聚体面积减小至0~100μm~2,总团聚体面积占比小于1%,且平均面积小于50μm~2;先添加多壁碳纳米管分散液再添加碱激发剂溶液的材料混合顺序更有利于纤维的均匀分散和地聚合物工作性能的保持;多壁碳纳米管在0.10%质量掺量时,对火山灰基地聚合物流动度影响不大,且能够有效提升其力学性能;功能化的多壁碳纳米管由于具有更强的亲水性和润湿性,对浆体工作性能的影响更轻微,对硬化试件力学性能的提升更显著,28 d时抗折、抗压强度较参照组最高可分别提升31.0%、15.9%;微观检测结果显示,多壁碳纳米管在地聚合物中发挥了桥接、填充、成核作用,因而实现性能的改善。

To investigate the reinforcing effect and mechanism of multi-walled carbon nanotubes on volcanic ash-based geopolymer,the numbers and areas of aggregates of multi-walled carbon nanotubes dispersions at different ultrasonic times were compared by using microscopy and image recognition,and an appropriate ultrasonic dispersion time was determined.Geopolymers were prepared by mixing the dispersion,alkaline activator solution,and volcanic ash in different orders.The effects of different types and concentrations of multi-walled carbon nanotubes on the workability and mechanical properties of the geopolymer were investigated by the consistency test of the slurry and the three-point bending test and the uniaxial compression test of hardened specimens.The micro-morphologies and pore structures of the geopolymer products were characterized by scanning electron microscope-energy dispersive spectrometer and mercury intrusion porosimetry.Analysis results show that the dispersion effect of multi-walled carbon nanotubes improves with the increase of ultrasonic time.After 45 min ultrasonication,the areas of more than 85% aggregates decrease to 0-100 μm~2,the total ratio of the aggregate areas is less than 1%,and the average area is less than 50 μm~2.The order of adding multi-walled carbon nanotube dispersion before adding NaOH solution is more favorable for the uniform dispersion of fibers and the preservation of the geopolymer workability.At a mass content of 0.10%,the multi-walled carbon nanotubes have little effect on the flowability of volcanic ash-based geopolymer and can effectively enhance the mechanical properties.The functionalized multi-walled carbon nanotubes have stronger hydrophilicity and wettability,leading to a slighter impact on the workability of the slurry and a more significant improvement in the mechanical properties of the hardened specimens.The 28 d flexural and compressive strengths can increase by up to 31.0% and 15.9%,respectively,compared with the reference group.The microscopic test results show that multi-walled carbon nanotubes play bridging,filling,and nucleation roles in the geopolymer,thus achieving the improvement of the performance.5 tabs,11 figs,44 refs.