[Composites Part B]Nest-like hetero-structured BNNS@SiCnws fillers and significant improvement on thermal conductivities of epoxy composites
writer：Yixin Han, Xuetao Shi*, Shuangshuang Wang, Kunpeng Ruan, Chuyao Lu, Yongqiang Guo and Junwei Gu*
keywords：Thermally conductive composites
source：期刊
specific source：Composites Part B-Engineering
Issue time：2021年
AbstractSilicon carbide nanowires (SiCnws) were in-situ grown on boron nitride nanosheets (BNNS) to construct a novel kind of nest-like hetero-structured BNNS@SiCnws thermally conductive fillers from natural bamboo leaves and tetraethyl orthosilicate (TEOS) by means of ultrasonic impregnation, sol-gel followed by carbothermic reduction. Then, the thermally conductive & electrically insulating BNNS@SiCnws/epoxy composites were prepared via blending-casting method. When the amount of BNNS@SiCnws-II (65/35, wt/wt) was 20 wt%, BNNS@SiCnws/epoxy composites presented the optimal overall performances. Thermal conductivity coefficient (λ) of BNNS@SiCnws-II (20 wt%) /epoxy composites increased from 0.22 W/mK of pure epoxy matrix to 1.17 W/mK, higher than that of SiCnws/epoxy (0.72 W/mK), BNNS/epoxy (0.82 W/mK) and (BNNS/SiCnws)/epoxy composites (direct mixing BNNS/SiCnws, 65/35, wt/wt 0.76 W/mK) with the same filler concentration of 20 wt%. Meanwhile, BNNS@SiCnws/epoxy composites presented excellent heat transfer/heat dissipation efficiency, due to synergistic effect of the “line-to-surface” hetero-structure of SiCnws and BNNS, which could significantly improve the formation probability of the thermally conductive paths. Furthermore, the BNNS@SiCnws/epoxy composites possessed favorable electrical insulation, thermostability and ideal mechanical properties. Furthermore, the related surface & volume resistivities, the electric breakdown strength, the glass-transition temperature, the heat resistant index, the flexural strength as well as the impact strength of BNNS@SiCnws-II (20 wt%)/epoxy composites reached to be 3.7×1015 Ω, 5.17×1015 Ω·cm, 22.1 kV/mm, 126.7 oC, 185.5 oC, 75.7 MPa and 8.2 kJ/m2, respectively.
本文以天然竹葉為生物質碳源結合正硅酸乙酯（TEOS，硅源），通過超聲浸漬-溶膠凝膠-碳熱還原法在氮化硼納米片（BNNS）上原位生長碳化硅納米線（SiCnws）構筑制備“鳥巢狀”異質結構BNNS@SiCnws導熱絕緣填料，進而與環氧樹脂基體共混復合-澆注成型制備BNNS@SiCnws/環氧樹脂導熱絕緣復合材料。結果表明，當BNNS@SiCnws-II質量分數為20 wt%時，BNNS@SiCnws-II/環氧樹脂導熱絕緣復合材料具有最佳的綜合性能。其熱導率（λ）從純環氧樹脂的0.22 W/mK提升到1.17 W/mK，均高于相同質量分數（20 wt%）的SiCnws/epoxy（單一SiCnws，0.72 W/mK）、BNNS/epoxy（單一BNNS，0.82 W/mK）和（SiCnws/BNNS）/epoxy（直接共混復合SiCnws和BNNS，0.76 W/mK）導熱絕緣復合材料的熱導率，且具有優越的傳熱/散熱效能，主要歸因于BNNS@SiCnws-II能充分發揮SiCnws和BNNS“線-面”異質結構的協同作用，顯著提升導熱通路的形成概率。此時BNNS@SiCnws-II/環氧樹脂導熱絕緣復合材料具有優異的電絕緣性能、熱穩定性以及理想的力學性能，其表面電阻率（ρs）、體積電阻率（ρv）、電擊穿強度（Eb）、玻璃化轉變溫度（Tg）、耐熱指數（THRI）、彎曲強度和沖擊強度分別為3.7×1015 Ω、5.17×1015 Ω·cm、22.1 kV/mm、126.7oC、185.5oC、75.7 MPa和8.2 kJ/m2。