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/c2jm34741
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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.
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，合成了不同烷基链长(C-n=8，12，18)的烷基化石墨烯。FTIR、UV-Vis和TGA结果表明，在烷基化过程中，GRO的氧官能团显著减少，sp(2)碳结构域的平均尺寸增大，这一点得到了拉曼光谱的进一步支持。结果表明，烷基化石墨烯在碳氢溶剂中的分散性随(A)用于分散的碳氢溶剂和(B)连接在石墨烯上的烷基链长的增加而增加。烷基化石墨烯亚甲基单元与烃类溶剂之间的van der Waals相互作用对决定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元的增加而增加。十八胺官能化石墨烯(oda-Gr)在十六烷中的分散性由于其高度的内聚性而被发现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，当ODAGr的最佳掺杂量为0.06 mg mL(-1)时，与十六烷相比，其摩擦磨损分别降低了26%和9%。润滑性的提高可以归因于在摩擦表面下不间断地供应石墨烯纳米片，这些纳米片防止了摩擦表面之间的直接接触，提供了低剪切阻力。
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.