氧化石墨烯基对水泥基材料微观形貌的影响

发布时间：2018-01-24 15:17

本文关键词： 氧化石墨烯丙烯酸分散性水化晶体微观形貌　出处：《陕西科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：氧化石墨烯(GO)是石墨烯的氧化物,其结构特点是石墨烯的二维片层上连有羧基、羰基、羟基和环氧基等基团。这些含氧基团使GO具有亲水性,从而可以应用到水溶液中。在课题组前期研究中发现在水泥基材料中掺入GO,不仅能够调控水泥的水化产物和微观结构,还可以提高水泥基材料的力学性能,但GO纳米片层在水溶液中易团聚,不能均匀分散到水泥基材料中。此外,由于GO各种含氧官能团含量不能定量控制,因此GO也无法定性调控水泥的微观形貌。针对此问题,本论文通过丙烯酸与GO进行复合制备了改性氧化石墨烯(MGO),增强在水泥浆中的分散性,并研究了GO和MGO对水泥基材料的微观形貌的影响,为研究水泥基材料微观结构提供了理论依据。(1)采用Hummer法和超声剥离制备得到GO纳米片层分散液,并对GO纳米片层的化学结构、纳米尺寸及层间距进行了表征分析。结果表明GO结构中含有羧基(-COOH)、羟基(-OH)以及环氧基(-O-)等基团;GO纳米片层厚度为1.23 nm,片层大小为200 nm至500 nm。冷冻干燥后的GO片层间距由0.34 nm扩大至0.86 nm。同时研究了GO在不同溶剂和不同pH值环境中的分散性,结果显示GO在常见的有机溶剂(乙醇、丙酮)和强酸强碱性的环境中分散性差,在水和表面活性剂溶液中的分散效果较好。(2)通过Hummer法制备了氧化石墨,再采用N,N-亚甲基双丙烯酰胺为交联剂,与丙烯酸聚合形成MGO,并对MGO纳米片层的结构和分散性进行了表征与测试。研究结果表明:改性后的MGO纳米片层上的含氧官能团种类与GO相同,但-COOH和C=C含量分别增加了2.56%、5.26%;MGO纳米片层大小为100 nm至500 nm,片层厚度为0.67 nm,比GO纳米片层的薄。此外,MGO在中性和碱性条件下纳米片层不会出现团聚现象。(3)研究了分别掺入GO和MGO后的发泡轻质水泥复合材料的表观密度与吸水率之间的关系、微观形貌的变化、孔结构以及其力学性能的变化。研究结果表明:掺入质量分数为0.03%GO或0.05%MGO可以提高发泡轻质水泥复合材料的吸水率,但掺入MGO提高幅度较大。相比较于掺入0.03%GO时形成的花瓣状、螺纹片状、鸟巢状和多面体状等多种水泥基材料微观形貌,掺入0.05%MGO的发泡轻质水泥复合材料形成的微观形貌以花片螺纹状为主。掺入GO和MGO降低了水泥石的孔隙率,减少了裂缝的产生,提高了水泥基材料的抗压强度和抗折强度。(4)通过对GO和MGO影响水泥基材料的微观形貌的作用机理的讨论,可以发现GO有利于水化晶体的生长,而且羧基增多的MGO更有利于水化晶体的形成。GO纳米片层上的含氧官能团对水泥水化产物的作用具有竞争和选择的作用。
[Abstract]:Graphene oxide (GOO) is an oxide of graphene. Its structure is characterized by the existence of carboxyl, carbonyl, hydroxyl and epoxy groups on the two-dimensional lamellar of graphene, which make go hydrophilic. So it can be applied to aqueous solution. In the previous study of our group, it was found that the incorporation of goo in cement based materials can not only regulate the hydration products and microstructure of cement, but also improve the mechanical properties of cement based materials. However, go nanoparticles are easy to agglomerate in aqueous solution and can not be uniformly dispersed into cement based materials. In addition, the content of various oxygen functional groups in go cannot be quantitatively controlled. Therefore, go can not qualitatively control the microstructure of cement. In order to solve this problem, the modified graphene oxide (MGOA) was prepared by the combination of acrylic acid and go to enhance the dispersion in cement slurry. The effects of go and MGO on the microstructure of cement-based materials were studied. It provides a theoretical basis for studying the microstructure of cement-based materials. (1) the go nano-lamellar dispersion was prepared by Hummer method and ultrasonic peeling, and the chemical structure of go nano-lamellar was also studied. The nano size and interlayer spacing were characterized and analyzed. The results showed that the go structure contained carboxyl group, hydroxyl group, hydroxyl group and epoxy group group. The thickness of go nanochip is 1.23 nm. The lamellar size ranged from 200 nm to 500 nm. The gap between the freeze-dried go layers increased from 0.34 nm to 0.86 nm. At the same time, the dispersion of go in different solvents and pH was studied. The results showed that the dispersion of go was poor in common organic solvents (ethanol, acetone) and strong acid and strong alkalinity. Graphite oxide was prepared by Hummer method and then the crosslinking agent was N- N- methylene bisacrylamide. The structure and dispersity of MGO nanocrystalline were characterized and tested. The results showed that the types of oxygen-containing functional groups on the modified MGO nanoparticles were the same as go. However, the contents of -COOH and CnC increased 2.56% and 5.26%, respectively. The size of MGO nanocrystals ranged from 100nm to 500nm, and the thickness of the layers was 0.67nm, which was thinner than that of go nanoliths. The relationship between apparent density and water absorption of foamed lightweight cement composites doped with go and MGO respectively was studied. The change of micromorphology. The change of pore structure and mechanical properties. The results show that the water absorption of foamed lightweight cement composites can be improved by adding 0.03GO or 0.05 MGO. Compared with 0.03GO, the microstructures of cement-based materials, such as petal, threaded, bird's nest and polyhedron, were increased by adding MGO. The micro-morphology of foamed lightweight cement composites with 0.05% MGO was mainly floral thread. Incorporation of go and MGO reduced the porosity of cement stone and the formation of cracks. The compressive strength and flexural strength of cement-based materials were improved. (4) by discussing the action mechanism of go and MGO on the micromorphology of cement-based materials, it was found that go was beneficial to the growth of hydrated crystals. Moreover, MGO with more carboxyl groups is more conducive to the formation of hydrated crystals. The oxygen-containing functional groups on the nanocrystalline go have a competitive and selective effect on the hydration products of cement.
【学位授予单位】：陕西科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ172.1

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