Dispersion of graphene in silane coupling agent aqueous solutions

石墨烯在硅烷偶联剂水溶液中的分散性能

In order to reduce the agglomeration of nanographene and improve its dispersibility,six silane coupling agents were used to modify the surface of the nanographene particles.Visual inspection,Fourier-transform infrared spectroscopy,transmission electron microscopy,Raman spectroscopy,and X-ray diffraction were employed to evaluate the dispersion properties of the resulting graphene in an aqueous solution of silane coupling agents.Results show that all six types of silane coupling agents are efficient in promoting the dispersion of graphene in aqueous solutions,and no obvious sedimentation of the graphene dispersion solution is observed after a stationary storage period of 30 d.Taking 3-aminopropyltriethoxysilane(KH-550)as an example,after the graphene is dispersed in the KH-550 aqueous solution,the carboxyl group on the surface of the graphene reacts with the KH-550 amino group to form an amide bond,and KH-550 is successfully grafted onto the graphene surface.Polar functional groups ionize in water,creating an electrostatic repulsion effect,or hydrophilic functional groups form hydrogen bonds with water molecules,which is believed to improve the dispersion stability of graphene.The dispersed graphene is curled and contains many folds.Each fold has about three or four layers,with an interlayer spacing of about 0.65 nm.The dispersed graphene also has a complete lattice and a reduced number of defects.Nanographene disperses well in silane coupling agent aqueous solutions and can,therefore,be used to prepare cement-based composites.

为了降低纳米石墨烯的团聚现象、提高其分散性能,采用6种硅烷偶联剂对纳米石墨烯颗粒进行了表面改性,并采用目测法、傅里叶红外光谱、透射电镜、拉曼光谱和X射线衍射等方法,对石墨烯在硅烷偶联剂水溶液中的分散性能进行了评价.结果表明:6种硅烷偶联剂对促进石墨烯在水溶液中分散有较好的效果,石墨烯分散液静置30 d未见明显沉降;以3-氨丙基三乙氧基硅烷(KH-550)为例,石墨烯在KH-550水溶液种分散后,石墨烯表面的羧基和KH-550的氨基反应生成酰胺键,KH-550成功接枝在石墨烯表面,极性官能团在水中电离形成静电排斥效应,或亲水官能团与水分子形成氢键,提高了石墨烯的分散稳定性;分散后的石墨烯呈卷曲状态,含大量褶皱,厚度大致3~4层厚,层间距约为0.65 nm,晶格完整,缺陷减少.纳米石墨烯在在硅烷偶联剂水溶液中的分散性较好,可用于制备水泥基复合材料.