Zhang Hua, Huang Rongjin, Li Yong, Li Hongbo, Wu Zhixiong, Huang Jianjun, Yu Bin, Gao Xiang, Li Jiangang, Li Laifeng
Advanced Energy Research Center, Shenzhen University, Shenzhen 518060, China.
Key Laboratory of Optoelectronic Devices and System of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
Polymers (Basel). 2019 Aug 12;11(8):1335. doi: 10.3390/polym11081335.
Thermally conductive but electrically insulating materials are highly desirable for thermal management applications in electrical encapsulation and future energy fields, for instance, superconducting magnet insulation in nuclear fusion systems. However, the traditional approaches usually suffer from inefficient and anisotropic enhancement of thermal conductivity or deterioration of electrical insulating property. In this study, using boron nitride sphere (BNS) agglomerated by boron nitride (BN) sheets as fillers, we fabricate a series of epoxy/BNS composites by a new approach, namely gravity-mix, and realize the controllable BNS loading fractions in the wide range of 5-40 wt%. The composites exhibited thermal conductivity of about 765% and enhancement at BNS loading of 40 wt%. The thermal conductivity up to 0.84 W·m·K at 77 K and 1.66 W·m·K at 298 K was observed in preservation of a higher dielectric constant and a lower dielectric loss, as expected, because boron nitride is a naturally dielectric material. It is worth noting that the thermal property was almost isotropous on account of the spherical structure of BNS in epoxy. Meanwhile, the reduction of the coefficient of thermal expansion (CTE) was largely reduced, by up to 42.5% at a temperature range of 77-298 K.
对于电气封装和未来能源领域的热管理应用，例如核聚变系统中的超导磁体绝缘，具有高导热性但电绝缘的材料是非常理想的。然而，传统方法通常存在导热率增强效率低下且各向异性，或者电绝缘性能恶化的问题。在本研究中，我们以由氮化硼（BN）片团聚而成的氮化硼球（BNS）作为填料，通过一种新的方法即重力混合制备了一系列环氧/BNS复合材料，并在5-40 wt%的宽范围内实现了BNS负载分数的可控性。这些复合材料在BNS负载量为40 wt%时表现出约765%的热导率增强。在77 K时热导率高达0.84 W·m·K，在298 K时为1.66 W·m·K，同时如预期的那样保持了较高的介电常数和较低的介电损耗，因为氮化硼是一种天然的介电材料。值得注意的是，由于环氧中BNS的球形结构，热性能几乎是各向同性的。与此同时，热膨胀系数（CTE）在77-298 K的温度范围内大幅降低，降幅高达42.5%。
