Dispersion of alkylated graphene in organic solvents and its potential for lubrication applications
Dispersion of alkylated graphene in organic solvents and its potential for lubrication applications
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DOI：
10.1039/c2jm34741e
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发表时间：
2012-01-01
影响因子：
--
通讯作者：
Khatri, Om P.
中科院分区：
文献类型：
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作者：
Choudhary, Shivani;Mungse, Harshal P.;Khatri, Om P.
我们报道了烷基化石墨烯的大规模制备及其在有机溶剂中的分散。通过烷基胺与氧化石墨烯（GrO）的羧基偶联制备了可变烷基链长的烷基化石墨烯（C-n = 8,12,18）。红外光谱（FTIR）、紫外可见光谱（UV-Visible）和热重分析（TGA）结果表明，在烷基化过程中，GrO的氧官能团明显减少，sp(2)碳畴的平均尺寸增大，拉曼特性进一步支持了这一结果。我们观察到，烷基化石墨烯在烃溶剂中的分散性随着(a)用于分散的烃溶剂和(b)附着在石墨烯上的烷基的链长的增加而增加。与烷基化石墨烯相关的亚甲基单位与烃溶剂之间的范德华相互作用对其分散特性起着至关重要的作用，并且这种相互作用随着亚甲基单位的增加而增加。十八胺功能化石墨烯（ODA-Gr）在十六烷中的分散由于其高度的内聚相互作用而具有长期的分散稳定性。通过对含ODA-Gr的十六烷的摩擦磨损性能的评价，探讨了其润滑特性。结果表明，与十六烷相比，掺0.06 mg mL(-1) ODA-Gr的十六烷可使摩擦和磨损分别降低26%和9%。润滑性的增强可能归因于摩擦表面下不间断的石墨烯纳米片供应，这些纳米片防止摩擦表面之间的直接接触，提供低剪切阻力。
We report on the preparation of alkylated graphenes on a large scale followed by their dispersion in organic solvents. The alkylated graphenes with variable alkyl chain lengths (C-n = 8, 12, 18) are prepared by coupling of alkylamine with carboxylic groups of graphene oxide (GrO). The FTIR, UV-Visible, and TGA results reveal that, during alkylation, the oxygen functionalities of GrO are reduced significantly and the average size of the sp(2) carbon domain increased, which is further supported by Raman characteristics. It is observed that the dispersibility of alkylated graphene in hydrocarbon solvents increases on increasing the chain length of (a) hydrocarbon solvents used for the dispersion and (b) alkyl groups attached to the graphene. The van der Waals interaction between methylene units associated with alkylated graphenes and hydrocarbon solvents plays a crucial role in determining their dispersion characteristics, and such an interaction increases with increasing methylene units. Octadecylamine functionalized graphene (ODA-Gr) dispersion in hexadecane is found to have long-term dispersion stability due to its high degree of cohesive interaction. The lubrication characteristics of hexadecane containing ODA-Gr were probed by evaluating its friction and wear properties. The results reveal that hexadecane doped with an optimized dose of 0.06 mg mL(-1) ODA-Gr reduced friction and wear by 26% and 9%, respectively, compared to hexadecane. The lubricity enhancement could be attributed to uninterrupted supplies of graphene nanosheets under the rubbing surfaces, where these nanosheets prevent direct contact between the rubbing surfaces, providing low resistance to shear.