Thermal conductivity and electrical properties of Al2O3-Sn57Bi43/epoxy composites
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摘要: 在聚合物基体中构建由高导热填料相互连接而成的导热通路是提高复合材料导热性能的有效策略。本文采用共还原法,在Al2O3微球表面沉积低熔点纳米锡铋合金颗粒(Sn57Bi43),制备杂化材料(Al2O3-Sn57Bi43),用于环氧树脂的导热绝缘填料。当环氧树脂受热固化时,Al2O3-Sn57Bi43表面Sn57Bi43纳米颗粒熔融,将填料相互连接而形成有效的导热通路,提高复合体系导热性能。当填料体积含量为60vol%时,Al2O3-Sn57Bi43/环氧树脂复合材料的导热系数为2.95 W·(m·K)−1,比Al2O3/环氧树脂复合材料的导热系数(1.82 W·(m·K)−1)提高了62.1%。Fogyel及Agari模型分析表明,Al2O3表面沉积Sn57Bi43有利于降低填料间接触热阻,形成导热通路。与Al2O3/环氧树脂复合材料相比,Al2O3-Sn57Bi43/环氧树脂复合材料的介质损耗增加,介电强度及体积电阻率降低,但仍具有电绝缘性能。由于填料-基体间界面性能改善及Al2O3-Sn57Bi43形成的网链结构能起到传递应力,阻止裂纹扩张的作用,Al2O3-Sn57Bi43/环氧树脂复合材料的拉伸断裂强度提高。Abstract: Constructing thermal conductive pathways in polymer matrix with interconnected high conductive thermal fillers is an effective strategy to enhance the thermal conductivity of the composites. In this paper, eutectic Sn-Bi alloy (Sn57Bi43) nanoparticles are deposited on the surface of Al2O3 microspheres by coreduction method to prepare Al2O3-Sn57Bi43 hybrids as thermal conductive and electrical insulating fillers for epoxy resin. During the heat curing of epoxy resin, Sn57Bi43 nanoparticles on the Al2O3 surface melt and bridge the separate fillers together to form effective thermal conductive pathway, and thus enhance the thermal conductivity of the composites. When filler volume fraction is 60vol%, the thermal conductivity of Al2O3-Sn57Bi43/epoxy composites is 2.95 W·(m·K)−1, 62.1% higher than that of Al2O3/epoxy composites (1.82 W·(m·K)−1). The results of Fogyel and Agari simulation demonstrate that the deposition of Sn57Bi43 on Al2O3 surface reduces the thermal contact resistance between fillers and forms thermally conductive networks more easily. The Al2O3-Sn57Bi43/epoxy composites exhibit higher dielectric loss, lower dielectric strength and volume resistivity than Al2O3/epoxy composites, still with electrical insulating properties. What is more, the tensile strength of the Al2O3-Sn57Bi43/epoxy composites is improved, because the improved interfacial properties of filler-matrix and the formed networks could transfer stress and prevent crack expansion.
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Key words:
- epoxy resin /
- Al2O3 /
- eutectic Sn-Bi alloy /
- hybrid materials /
- thermal conductivity /
- electrical insulation
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图 7 Al2O3/环氧树脂和Al2O3-Sn57Bi43/环氧树脂复合材料的lg(λ-λ1)-lg[(Vf-Vc)/(1-Vc)]曲线
λ1 and λ2—Thermal conductivity of polymer and fillers respectively; Vf—Volume fraction of fillers; Vc—Critical volume fraction of fillers
Figure 7. lg(λ-λ1)-lg[(Vf-Vc)/(1-Vc)] curves of Al2O3/epoxy and Al2O3-Sn57Bi43/epoxy composites
表 1 Al2O3和Al2O3-Sn57Bi43的元素组成
Table 1. Element compositions of Al2O3 and Al2O3-Sn57Bi43
wt% Sample Al O Sn Bi Al2O3 50.72 47.36 0.00 0.00 Al2O3-Sn57Bi43 40.25 37.98 8.51 11.38 表 2 Al2O3/环氧树脂和Al2O3-Sn57Bi43/环氧树脂复合材料的密度、比热容及热扩散系数
Table 2. Density, specific heat capacity and thermal diffusion coefficient of Al2O3/epoxy and Al2O3-Sn57Bi43/epoxy composites
Vf/% Al2O3/epoxy Al2O3-Sn57Bi43/epoxy Density/
(kg·m−3)Specific heat
capacity/[J·(kg·K)−1]Thermal diffusion
coefficients/(m2·s−1)Density/
(kg·m−3)Specific heat
capacity/[J·(kg·K)−1]Thermal diffusion
coefficients/(m2·s−1)0 1.19×103 1106.43 1.52×10−7 1.19×103 1106.43 1.52×10−7 6 1.35×103 1045.03 1.42×10−7 1.38×103 1016.70 1.50×10−7 11 1.49×103 1004.05 1.41×10−7 1.54×103 958.87 1.49×10−7 14 1.57×103 982.84 1.43×10−7 1.63×103 929.55 1.51×10−7 17 1.65×103 963.71 1.76×10−7 1.73×103 903.46 2.05×10−7 22 1.78×103 935.68 2.46×10−7 1.89×103 865.83 3.12×10−7 29 1.97×103 902.86 3.04×10−7 2.11×103 822.64 4.09×10−7 38 2.21×103 868.87 4.94×10−7 2.39×103 778.87 7.77×10−7 48 2.48×103 838.89 5.81×10−7 2.71×103 741.04 10.05×10−7 55 2.67×103 821.50 7.48×10−7 2.93×103 719.42 12.90×10−7 60 2.80×103 810.51 8.03×10−7 3.09×103 705.88 13.51×10−7 表 3 Al2O3/环氧树脂和Al2O3-Sn57Bi43/环氧树脂复合材料导热系数的非线性Foygel模拟结果
Table 3. Simulation results of nonlinear Foygel model for the thermal conductivity of Al2O3/epoxy and Al2O3-Sn57Bi43/epoxy composites
Sample Vc/% λ0/(W·(m·K)−1) β Rc/(K·W−1) Al2O3 19.23 3.42 1.088 1.17×105 Al2O3-Sn57Bi43 18.25 6.73 1.253 8.35×104 Notes: Vc—Critical volume fraction of filler; λ0—Pre-exponential factor; β—Conductivity exponent that depends on the aspect of filler; Rc—Interface thermal resistance. 表 4 Al2O3/环氧树脂和Al2O3-Sn57Bi43/环氧树脂复合材料导热系数的Agari模拟结果
Table 4. Agari simulation results for the thermal conductivity of Al2O3/epoxy and Al2O3-Sn57Bi43/epoxy composites
Sample C1 C2 Al2O3 0.7661 0.8991 Al2O3-Sn57Bi43 0.7495 1.1465 Notes: C1 is a factor affecting crystallinity and crystal size of polymer; C2 is a factor of ease in forming conductive chains of fillers. 表 5 填料体积含量对Al2O3/环氧树脂和Al2O3-Sn57Bi43/环氧树脂复合材料拉伸断裂强度的影响
Table 5. Effects of filler volume fraction on tensile properties of Al2O3/epoxy and Al2O3-Sn57Bi43/epoxy composites
Vf/% Al2O3/epoxy Al2O3-Sn57Bi43/epoxy Tensile strength/MPa Elongation at break/% Tensile strength/MPa Elongation at break/% 0 44.56±1.83 4.47±0.17 44.56±1.83 4.47±0.17 20 40.31±1.20 4.06±0.14 46.84±2.04 4.75±0.21 40 37.41±1.15 3.54±0.15 49.65±2.16 5.09±0.19 60 32.28±1.09 3.21±0.11 51.62±2.62 5.36±0.24 表 6 填料体积含量对Al2O3/环氧树脂和Al2O3-Sn57Bi43/环氧树脂复合材料电性能的影响
Table 6. Effects of filler volume fraction on electric properties of Al2O3/epoxy and Al2O3-Sn57Bi43/epoxy composites
Vf/% Al2O3/epoxy Al2O3-Sn57Bi43/epoxy Volume resistivity/
(1013 Ω·m)Dielectric strength/
(MV·m−1)Dielectric loss tanδ/
10−3Volume resistivity/
(1013 Ω·m)Dielectric strength/
(MV·m−1)Dielectric loss tanδ/
10−30 2.67±0.68 25.8±1.6 4.75±0.08 2.670±0.680 25.8±1.6 4.75±0.08 20 2.79±0.51 25.2±2.1 3.98±0.06 0.921±0.106 22.1±1.4 11.02±0.22 40 2.81±0.62 24.5±1.9 5.22±0.07 0.264±0.096 19.6±1.2 15.46±0.97 60 2.87±0.75 24.3±1.3 4.75±0.07 0.086±0.034 18.5±1.3 19.43±1.46 -
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