Optimization of Boron Nitride Sphere Loading in Epoxy: Enhanced Thermal Conductivity and Excellent Electrical Insulation
Optimization of Boron Nitride Sphere Loading in Epoxy: Enhanced Thermal Conductivity and Excellent Electrical Insulation
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DOI：
10.3390/polym11081335
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发表时间：
2019-08
期刊：
影响因子：
5
通讯作者：
Hua Zhang;Rongjin Huang;Yong Li;Hongbo Li;Zhixiong Wu;Jian-Jun Huang;Bin Yu;Xiang Gao;Jian-gang Li;Laifeng Li
中科院分区：
文献类型：
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作者：
Hua Zhang;Rongjin Huang;Yong Li;Hongbo Li;Zhixiong Wu;Jian-Jun Huang;Bin Yu;Xiang Gao;Jian-gang Li;Laifeng Li
导热但电绝缘的材料对于电气封装和未来能源领域的热管理应用非常理想，例如核聚变系统中的超导磁体绝缘。然而，传统的方法通常存在导热系数低效且各向异性增强或电绝缘性能恶化的问题。在这项研究中，我们以氮化硼（BN）片团聚的氮化硼球（BNS）为填料，通过重力混合的新方法制备了一系列环氧树脂/BNS复合材料，并实现了BNS负载分数在5-40 wt%范围内的可控。该复合材料表现出约 765% 的导热率，并且 BNS 负载量为 40 wt% 时导热率有所提高。正如预期的那样，在 77 K 时热导率高达 0.84 W·m−1·K−1，在 298 K 时热导率高达 1.66 W·m−1·K−1，同时保持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介电材料。值得注意的是，由于环氧树脂中 BNS 的球形结构，热性能几乎是各向同性的。同时，热膨胀系数（CTE）的降低幅度也大大降低，在77-298 K的温度范围内降低了高达42.5%。
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−1·K−1 at 77 K and 1.66 W·m−1·K−1 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.