Zheng Nianben, Wang Long, Sun Zhiqiang
School of Energy Science and Engineering, Central South University, Changsha 410083, China.
School of Energy Science and Engineering, Central South University, Changsha 410083, China.
Ultrason Sonochem. 2021 Dec;80:105816. doi: 10.1016/j.ultsonch.2021.105816. Epub 2021 Nov 2.
Few-layer graphene (FLG) nanofluids have received widespread interest in recent years due to their excellent thermal and optical properties. However, the low dispersion stability is one of the main bottlenecks for their commercialization. Ultrasonication is an effective method and almost an essential step to improve the stability of nanofluids. This work aimed to determine the optimal ultrasonication process for preparing stable FLG nanofluids, particularly under the constant ultrasonic energy consumption condition. For this purpose, FLG nanofluids were prepared under various amplitudes (20%-80%) and times (33.75-135 min) and evaluated by both sedimentation and optical spectrum analysis techniques. It was found that ultrasonication treatment at 30% amplitude for 90 min was sufficient for proper dispersion of FLG, and a further increase in the ultrasonication power would not benefit the stability enhancement much. However, for FLG nanofluids prepared at amplitudes higher than 30% under the constant ultrasonic energy consumption condition, their stability deteriorated seriously due to the reduced ultrasonication time, while for FLG nanofluids prepared at 20% amplitude for 135 min, they showed the higher stability, which indicates that the stability of FLG nanofluids is more sensitive to ultrasonication time than power. Therefore, a relatively longer ultrasonication time rather than a higher amplitude is recommended to prepare stable FLG nanofluids for practical applications at given ultrasonic energy consumption.
近年来，少层石墨烯（FLG）纳米流体因其优异的热学和光学性能而受到广泛关注。然而，低分散稳定性是其商业化的主要瓶颈之一。超声处理是提高纳米流体稳定性的有效方法，几乎是必不可少的一步。这项工作旨在确定制备稳定的FLG纳米流体的最佳超声处理工艺，特别是在恒定超声能量消耗条件下。为此，在不同振幅（20%-80%）和时间（33.75-135分钟）下制备了FLG纳米流体，并通过沉降和光谱分析技术进行了评估。结果发现，在30%振幅下超声处理90分钟足以使FLG充分分散，进一步提高超声功率对稳定性的提升作用不大。然而，在恒定超声能量消耗条件下，对于振幅高于30%制备的FLG纳米流体，由于超声处理时间缩短，其稳定性严重恶化，而对于在20%振幅下超声处理135分钟制备的FLG纳米流体，它们表现出更高的稳定性，这表明FLG纳米流体的稳定性对超声处理时间比对功率更敏感。因此，在给定的超声能量消耗下，为了实际应用制备稳定的FLG纳米流体，建议采用相对较长的超声处理时间而不是较高的振幅。
