Wu Yanze, Li Jinli, Wang Min, Wang Huaiyou, Zhong Yuan, Zhao Youjing, Wei Ming, Li Yan
Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences Xining 810000 China
Key Laboratory of Salt Lake Resources Chemistry of Qinghai Province Xining 810000 China.
RSC Adv. 2018 May 24;8(34):19251-19260. doi: 10.1039/c8ra03019g. eCollection 2018 May 22.
Solar salt has great advantages in solar thermal power generation compared to other molten salts, but its thermal conductivity needs to be further improved. Multi-walled carbon nanotubes (MWCNTs) have excellent thermal properties that can improve the thermal conductivity of materials as additives. In this study, five kinds of solar salt/MWCNTs composites with different doping amounts were prepared by a high-temperature melting method. The results showed that doping with MWCNTs can indeed improve the thermal properties of solar salt. We studied their quantitative structure-activity relationship (QSAR) in order to explain these phenomena. According to the TG-DSC analysis, there was almost no change in the melting point and decomposition temperature; the XRD analysis revealed that the bulk of the material was still NaNO and KNO, which did not change; and according to Archimedes' method, the density of the materials also changes little. The thermal conductivity of the material was measured by the laser flash method; the results showed that the thermal conductivity of the sample with 0.3% doping increased by 293%, reaching 1.65 W (m K). XPS analysis showed that the MWCNTs were purified and the impurity groups were largely removed after high-temperature melting. From the laser Raman analysis, the V frequency peak of the sample with 0.3% doping was red-shifted, and for the other samples was blue-shifted. The SEM images showed that the sample with 0.3% doping was the most uniformly dispersed. When the doping amounts are appropriate, the improvement in thermal conductivity may be attributed to two reasons: (1) the MWCNTs can be uniformly dispersed, as the SEM shows; (2) tiny thermally conductive channels may be formed on the interface between the molten salt and the MWCNTs, thereby generating a boundary effect. This kind of composite material may help improve solar heat storage and heat transfer capacity, and thereby increase the efficiency of solar thermal power generation.
与其他熔盐相比，太阳能盐在太阳能热发电方面具有很大优势，但其热导率有待进一步提高。多壁碳纳米管（MWCNTs）具有优异的热性能，可作为添加剂提高材料的热导率。本研究采用高温熔融法制备了五种不同掺杂量的太阳能盐/MWCNTs复合材料。结果表明，掺杂MWCNTs确实可以提高太阳能盐的热性能。我们研究了它们的定量构效关系（QSAR）以解释这些现象。根据TG-DSC分析，熔点和分解温度几乎没有变化；XRD分析表明，材料的主体仍然是NaNO和KNO，没有变化；根据阿基米德法，材料的密度变化也很小。通过激光闪光法测量材料的热导率；结果表明，掺杂量为0.3%的样品热导率提高了293%，达到1.65W/(m·K)。XPS分析表明，MWCNTs经过高温熔融后得到了纯化，杂质基团大量去除。从激光拉曼分析来看，掺杂量为0.3%的样品的V频率峰发生了红移，其他样品发生了蓝移。SEM图像显示，掺杂量为0.3%的样品分散最均匀。当掺杂量适当时，热导率的提高可能归因于两个原因：（1）如SEM所示，MWCNTs可以均匀分散；（2）在熔盐和MWCNTs之间的界面上可能形成微小的导热通道，从而产生边界效应。这种复合材料可能有助于提高太阳能的蓄热和传热能力，从而提高太阳能热发电的效率。
