Mengjing Liu,Sun-Wai Chiang,Xiaodong Chu,Jia Li,Lin Gan,Yanbing He,Baohua Li,Feiyu Kang,Hongda Du
Herein, oriented boron nitride (BN)/alumina (Al 2 O 3 )/polydimethylsiloxane (PDMS) composites were obtained by filler orientation due to the shear-inducing effect via 3-D printing. The oriented BN platelets acted as a rapid highway for heat transfer in the matrix and resulted in a significant increase in the thermal conductivity along the orientation direction. Extra addition of spherical Al 2 O 3 enhanced the fillers networks and resulted in the dramatic growth of slurry viscosity. This, together with filler orientation induced the synergism and provided large increases in the thermal conductivity . A high orientation degree of 90.65% and in-plane thermal conductivity of 3.64 W/(m∙K) were realized in the composites with oriented 35 wt% BN and 30 wt% Al 2 O 3 hybrid fillers. We attributed the influence of filler orientation and hybrid fillers on the thermal conductivity to the decrease of thermal interface resistance of composites and proposed possible theoretical models for the thermal conductivity enhancement mechanisms.
Xiao-yu Zhang,Min Xu,Sheng-zhu Cao,Wen-bo Chen,Wen-yao Yang,Qin-yu Yang
Diamond/copper composite has been considered as one of the next generation thermal management materials. Interfacial modification is an essential means of ameliorating interface wettability and bonding of diamond/copper composite for improving its thermal conductivity . In the present work, Diamond/copper composite was manufactured by using spark plasma sintering (SPS) technology with 60% volume fraction of diamond mixed with 40% volume fraction of copper power, chromium powder (0.7 wt%) and scandium oxide powder (0.21 wt%). A series of material analysis methods were used to characterize the microstructure, interfacial layer , phase compositions and distributions of Diamond/copper composite. The total and partial electron density of states (DOS) for Diamond-Cr-Sc 2 O 3 interfacial model was investigated by means of first-principles calculations from CASTEP modules. The results showed Sc 2 O 3 made a 5–20 nm well-arranged and uniformly distributed interfacial chromium carbide layer in the interface region, which played a critical role in increasing the amount of reactive interfacial bonding and decreasing defect. The addition of Sc 2 O 3 brought the increasing number of heat transfer carriers at the interface and made the interface energy system more stable. The obtained diamond/copper composite exhibited that the wettability between diamond particles and copper was effectively improved. The thermal conductivity of diamond/copper is 872 W/(m·K) and the possible reasons for doping rare-earths Sc 2 O 3 to improve the thermal conductivity were discussed.
The partial reduced graphene oxide (P-rGO) sheets-wrapped nickel foams (NF@P-rGO) were prepared by hydrothermal method, and then their epoxy composites were fabricated via a simple drop-wetting process. The P-rGO sheets on the metal networks could effectively improve the compatibility between nickel foam and epoxy resin, thus greatly accelerate the wetting of epoxy resin on the foams and avoid cracks in the network–polymer interface. Owing to the existence of high-efficiency conductive metal networks, the NF@P-rGO/epoxy composite has a high thermal conductivity of 0.584 W m −1 K −1 , which is 2.6 times higher than that of neat epoxy resin. Additionally, owing to the improved wetting ability, NF@P-rGO-10 wt% boron nitride (BN) microsheets/epoxy composites could be fabricated and have a further higher thermal conductivity of 0.71 W m −1 K −1 . We believe the use of P-rGO as a novel surface modifier and the following liquid polymer drop-wetting could be an effective method to obtain novel and outstanding metal foam/polymer composites.
Dielectric polymers with high thermal conductivity are very promising in the fields of aerospace and electronic device packaging. However, composites with excellent dielectric properties usually have low thermal conductivity. It is usually to fill the polymer with thermal conductivity particles to improve the thermal conductivity, but the high content of filler often reduces the mechanical properties of the polymer. In this paper, the traditional insulating polymer epoxy resin was used as the matrix, by covering the surface of silicon carbide with graphene to form a core-shell structure and co-filled with nano diamonds to achieve the preparation of high-performance epoxy resin at low content. The results showed that at the filling content of 30 wt%, the thermal conductivity of epoxy nanocomposites showed a dramatic thermal conductivity enhancement of 1263%, the energy storage modulus increased by 1.1 GPa, and the dielectric loss remained unchanged at 50 Hz. The advantages of the composite are the structural design and surface modification of the filler, which not only take advantage of its inherent advantages, but also improve the interface area with the epoxy matrix. The composite materials with excellent properties are expected to provide theoretical guidance for the application of high thermal conductivity dielectric materials.
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