Plasma Processing Laboratory, Department of Chemical Engineering, McGill University, Montréal, QC, H3A 0C5, Canada. Biomimetic Surface Engineering, Department of Chemical Engineering, McGill University, Montréal, QC, H3A 0C5, Canada.
Nanotechnology. 2017 Mar 10;28(10):105706. doi: 10.1088/1361-6528/aa5a5f. Epub 2017 Jan 19.
Nanofluids-engineered colloidal suspensions in base liquids-have captivated the interest of researchers over the last two decades for various existing as well as emerging technological applications. The main impetus for the synthesis of such novel nanocomposite liquids is the potential to alter properties of the base liquid, such as its viscosity, thermal conductivity, and surface tension, and to introduce specific optical and magnetic properties. Numerous studies suggest trends and explanations for the effects associated with the addition of nanoparticles, and that deviation from the base liquid properties are dependent on nanoparticle concentration. However, there remains a certain ambiguity in the available literature. The wetting behavior and surface tension of nanofluids are particular examples where highly conflicting results exist. In this study, we used multi-walled carbon nanotubes (MWCNTs) functionalized by plasma treatment and dispersed in reverse osmosis water and 99% anhydrous ethanol. Our observations reveal that the surface tension and wetting behavior of the stable aqueous and ethanol-based nanofluids containing plasma functionalized MWCNTs are unaffected by the MWCNT loading up to 120 (0.012) and ∼210 (0.021) ppm (vol%), respectively. The ethanol-based MWCNT nanofluids allowed us to extend the study to higher loadings, and a linear increase of the surface tension past ∼200 ppm was observed. Conversely, nanofluids containing non-functionalized or surfactant-stabilized MWCNTs show drastically different contact angle values when compared to the base liquids even at very low concentrations (less than 100 ppm). We demonstrate that the stability of nanofluid and method of stabilization are crucial parameters in determining the wetting behavior of nanofluids.
在过去的二十年中，基于基液的纳米流体——即胶体悬浮液——因其在各种现有和新兴技术应用中的潜力而引起了研究人员的关注。合成这种新型纳米复合材料液体的主要动力是改变基液性质的潜力，例如其粘度、热导率和表面张力，并引入特定的光学和磁学性质。许多研究表明了与添加纳米颗粒相关的效应的趋势和解释，并且与基液性质的偏差取决于纳米颗粒的浓度。然而，在现有文献中仍然存在一定的模糊性。纳米流体的润湿性和表面张力就是特别明显的例子，在这些例子中存在着高度冲突的结果。在这项研究中，我们使用等离子体处理的多壁碳纳米管（MWCNTs）并将其分散在反渗透水和 99%无水乙醇中。我们的观察结果表明，含有等离子体功能化 MWCNTs 的稳定水基和乙醇基纳米流体的表面张力和润湿性行为不受 MWCNT 负载的影响，直到分别达到 120（0.012）和 210（0.021）ppm（体积%）。乙醇基 MWCNT 纳米流体允许我们将研究扩展到更高的负载，并且观察到表面张力在超过 200ppm 时呈线性增加。相比之下，与基液相比，即使在非常低的浓度（小于 100ppm）下，含有非功能化或表面活性剂稳定化 MWCNTs 的纳米流体的接触角值也会发生明显变化。我们证明了纳米流体的稳定性和稳定化方法是决定纳米流体润湿性的关键参数。
