Department of Mechanical Engineering, Universiti Teknologi PETRONAS, 32610 Bandar Seri Iskandar, Perak Darul Ridzuan, Malaysia.
Department of Mechanical Engineering, Universiti Teknologi PETRONAS, 32610 Bandar Seri Iskandar, Perak Darul Ridzuan, Malaysia.
Ultrason Sonochem. 2018 Jul;45:133-149. doi: 10.1016/j.ultsonch.2018.03.007. Epub 2018 Mar 19.
The exceptional properties of graphene and its structural uniqueness can improve the performance of nanocomposites if it can attain the uniform dispersion. Tip sonication assisted graphene solvent dispersion has been emerged as an efficient approach but it can cause significant degradation of graphene structure. This study aimed to evaluate the parametric influence of tip sonication on the characteristics of sp carbon structure in graphene nanoplatelets by varying the sonication time and respective energy at three different amplitudes (60%, 80% and 100%). The study is essential to identify appropriate parameters so as to achieve high-quality and defect-free graphene with a highly desirable aspect ratio after solvent dispersion for composite reinforcement. Quantitative approach via Raman spectroscopy is used to find the defect ratio and lateral size of graphene evolved under the effect of tip sonication parameters. Results imply that the defect ratio is steady and increases continually with GNPs, along with the transformation to the nano-crystalline stage I up to 60 min sonication at all amplitudes. Exfoliation was clearly observed at all amplitudes together with sheet re-stacking due to considerable size reduction of sheets with large quantity. Finally, considerable GNPs fragmentation occurred during sonication with increased amplitude and time as confirmed by the reduction of sp domain (La) and flake size. This also validates the formation of edge-type defect in graphene. Convincingly, lower amplitude and time (up to 60 min) produce better results for a low defect content and larger particle size as quantified by Raman analysis.
石墨烯的特殊性质及其结构独特性，如果能达到均匀分散，就能提高纳米复合材料的性能。在这种情况下，采用尖端超声辅助石墨烯溶剂分散法已成为一种有效的方法，但会导致石墨烯结构的严重降解。本研究旨在通过改变超声时间和三个不同振幅（60%、80%和 100%）的相应能量，评估尖端超声对石墨烯纳米片中 sp 碳结构特性的参数影响。该研究对于确定合适的参数非常重要，以便在溶剂分散后获得高质量、无缺陷且具有理想纵横比的石墨烯，从而用于复合材料增强。通过 Raman 光谱定量方法，研究了在尖端超声参数作用下，石墨烯的缺陷比和横向尺寸的演变。结果表明，在所有振幅下，缺陷比保持稳定并持续增加，同时随着超声时间的延长，石墨烯逐渐向纳米晶 I 转变。在所有振幅下都观察到了剥离现象，同时由于大量薄片的尺寸减小，薄片发生了重新堆积。最后，随着振幅和时间的增加，大量的 GNPs 发生了断裂，这也证实了 sp 域（La）和薄片尺寸的减少，这也验证了石墨烯中边缘型缺陷的形成。令人信服的是，较低的振幅和时间（长达 60 分钟）在 Raman 分析中产生了更好的结果，表现为低缺陷含量和更大的颗粒尺寸。
