Department of Mechanical Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia.
Nanoscale Res Lett. 2014 Jan 13;9(1):15. doi: 10.1186/1556-276X-9-15.
In the present study, stable homogeneous graphene nanoplatelet (GNP) nanofluids were prepared without any surfactant by high-power ultrasonic (probe) dispersion of GNPs in distilled water. The concentrations of nanofluids were maintained at 0.025, 0.05, 0.075, and 0.1 wt.% for three different specific surface areas of 300, 500, and 750 m2/g. Transmission electron microscopy image shows that the suspensions are homogeneous and most of the materials have been well dispersed. The stability of nanofluid was investigated using a UV-visible spectrophotometer in a time span of 600 h, and zeta potential after dispersion had been investigated to elucidate its role on dispersion characteristics. The rheological properties of GNP nanofluids approach Newtonian and non-Newtonian behaviors where viscosity decreases linearly with the rise of temperature. The thermal conductivity results show that the dispersed nanoparticles can always enhance the thermal conductivity of the base fluid, and the highest enhancement was obtained to be 27.64% in the concentration of 0.1 wt.% of GNPs with a specific surface area of 750 m2/g. Electrical conductivity of the GNP nanofluids shows a significant enhancement by dispersion of GNPs in distilled water. This novel type of nanofluids shows outstanding potential for replacements as advanced heat transfer fluids in medium temperature applications including solar collectors and heat exchanger systems.
在本研究中，通过高功率超声波（探针）将 GNPs 在去离子水中分散，制备了没有任何表面活性剂的稳定均一的石墨烯纳米片（GNP）纳米流体。纳米流体的浓度保持在 0.025、0.05、0.075 和 0.1wt.%，对应三种不同的比表面积 300、500 和 750m2/g。透射电子显微镜图像表明，悬浮液是均匀的，并且大部分材料已经得到了很好的分散。通过在 600h 的时间跨度内使用紫外可见分光光度计研究纳米流体的稳定性，并研究分散后的动电位以阐明其对分散特性的作用。GNP 纳米流体的流变性能接近牛顿和非牛顿行为，即粘度随温度升高呈线性下降。导热系数结果表明，分散的纳米颗粒总是可以增强基液的导热系数，在浓度为 0.1wt.%、比表面积为 750m2/g 的 GNPs 中，最高增强率达到 27.64%。GNP 纳米流体的电导率通过在去离子水中分散 GNPs 得到显著提高。这种新型纳米流体在中温应用中作为先进的传热流体具有很大的应用潜力，包括太阳能集热器和换热器系统。
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