2019, 8(1):3-14. DOI: 10.12146/j.issn.2095-3135.20180913001
Abstract:Filled high thermally conductive polymer composites will be vital materials to resolve heat dissipation problem in electronics. Herein, boron nitride nanosheet/silver nanoparticles (BNNSs/AgNPs) hybrids were prepared through liquid exfoliation and chemical reduction method, and then were added into epoxy resin (EP) to prepare BNNSs/AgNPs/EP composites. Previous study has proved that the thermal conductivities of the composites were enhanced with the addition of the BNNSs/AgNPs hybrids. Further, the over-all properties are also important to evaluate the performance of the polymer composites. In this paper, electrical and mechanical properties of the BNNSs/AgNPs/EP composites were investigated by thermogravimetric analysis, dynamic thermomechanical analysis and dielectric strength measurement. The result shows that the decomposed temperature is increased with the addition of BNNSs/AgNPs hybrids, the dielectric constant is increased with the increase of the filler content, and the dielectric constant of BNNSs/ AgNPs/EP is higher than that of BNNSs/EP. Energy storage modulus and glass transition temperature are both increased with increasing the filler content. Compared with BNNSs, impregnation of BNNSs/AgNPs hybrids to the EP makes the composite with higher glass transition temperature. The results indicate that the obtained BNNSs/AgNPs/EP composites, possessing good thermal, electrical and mechanical properties, will meet the requirement in modern electronics packaging field.
2019, 8(1):15-23. DOI: 10.12146/j.issn.2095-3135.20180909001
Abstract:Heat dissipation problems have limited the further development of the chip technique, therefore, searching for thermal interfacial materials with high thermal conductivity becomes one of the most important methods to break through the bottlenecks. Among these thermal interfacial materials, organic-inorganic composites are believed to be a promising alternative of the traditional silicon grease, due to their flexibility and controllable thermal conductivity. The fabrication methods of organic-inorganic composites, such as physical blending, phase precipitation, in-situ oxidation have been widely adopted on experiment. In this paper, we fabricated the polyvinylidene fluoride/graphene composites by using physical blending method, and their thermal conductivities could achieve as high as 83 W/(m·K) by using non-steady measurements with temperature T＝360 K and volume ratio f＝76 vol%. Furthermore, the thermal conductivity of the organicinorganic shapes, and the interactions between the organic and inorganic materials. We adopted the improved Bruggeman model and Agarimodel based on the effective medium theory to explain the thermal transport mechanism. Investigation results showed that, improved Bruggeman model cannot interpret the reason of high thermal conductivity of composites. The larger the fraction of the fillers, according to Agari model, the easier could the thermal conductive channels form among the fillers, thus the higher the thermal conductivities of these composites. composites is highly depends on factors including the volume ratio of the fillers, grain sizes and
2019, 8(1):24-37. DOI: 10.12146/j.issn.2095-3135.20180910001
Abstract:Rapid development of electronic devices, power systems and communication equipments present an increasing requirement for the heat dissipation. Hexagonal boron nitride (h-BN) is very useful as an insulating and thermal conductive filler, and more and more attentions have been paid to its thermal conductive composites. In this article, we focus on the detail progress of h-BN-based thermal conductive composites, including thermal transfer mechanism and present situation. Furthermore, some current technical defects and difficulties are summarized, and the future developing trend of h-BN-based thermal conductive composites is also prospected.
2019, 8(1):38-44. DOI: 10.12146/j.issn.2095-3135.20180912001
Abstract:With the rapid development of modern electronic products, efficient thermal management is becoming a global challenge. The interface thermal resistance is the most important factor limiting the high thermal conductivity of thermally conductive nanocomposites. Here, we designed and hydrothermally synthesized a hexagonal boron nitride (BN)/molybdenum disulfide (MoS2) heterostructure with low interfacial thermal resistance, and integrated them into the final BN/MoS2-epoxy nanocomposite. During the hydrothermal reaction, MoS2 grows and wraps on the BN nanosheet, which ensures better interfacial contact. BN nanosheet acts as a structural skeleton and heat transfer channel. MoS2 nanosheets can effectively collect heat due to its large specific surface area. With the infiltration of MoS2, the interfacial thermal resistance between the filler and the polymer matrix can be effectively reduced. The experimental results show that the thermal conductivity of the synthesized BN/MoS2-epoxy nanocomposites was increased from 0.254 W/(m·K) to 0.526 W/(m·K), which is an increasement of 107% as compared to pure epoxy resin. The findings may contribute to the development of new types of high-performance thermal conductivity materials.
2019, 8(1):45-53. DOI: 10.12146/j.issn.2095-3135.20180913002
Abstract:In recent years, as components in electronic products have developed towards higher integration degree, the large amount of heat generated by components has affected various performances of electronic devices. In order to efficiently diffuse the heat, it is necessary to prepare composite materials with high thermal conductivity. In this study, liquid crystal epoxy resin with excellent performance was used as the matrix, and hexagonal flake boron nitride and glass fiber were used as fillers to prepare composite materials with high thermal conductivity and excellent comprehensive performance. Experiment results show that the prepared liquid crystal epoxy resin/boron nitride nanosheet/glass fiber composite has a thermal conductivity of up to 1.6 W/(m·K) in the thickness direction and up to 5.85 W/(m·K) in the plane direction. In addition, the composite also possesses a high glass transition temperature (above 180 ℃) and excellent thermal stability with a thermal decomposition temperature higher than 365 ℃.
2019, 8(1):54-67. DOI: 10.12146/j.issn.2095-3135.20181008001
Abstract:The researches on interfacial thermal contact resistance between inorganic solids and polymers have been paid more and more attention in recent years. In this paper, the mechanism of interfacial heat transfer and the measurement approaches on interfacial thermal contact resistance of polymer-based materials are reviewed. Currently, many scholars have established different thermal contact resistance models from macroscopic and microscopic perspective to study the heat transfer mechanism of solid-polymer contact thermal resistance. However, the heat transfer mechanism is complex due to many factors affecting thermal contact resistance. Presently, there are still many difficulties and challenges in the research of solid-polymer thermal contact resistance. For the measurement of interfacial thermal contact resistance of polymer-based materials, novel characterization methods and techniques of micro/nano-scale materials, such as polymer films, have become one of the international research frontiers. This paper mainly introduces the technical methods such as 3ω method and time-domain thermoreflectance method which can be used to characterize the thermal contact resistance between solids and polymers. In addition, the research progresses of polymer-based interface materials in recent years have been also introduced. The polymer based interfacial materials are reviewed and compared based on the types of molecular forces (van der Waals force, covalent bond and non-covalent strong force). Finally, the future research directions of interfacial thermal management are overviewed.
2019, 8(1):68-77. DOI: 10.12146/j.issn.2095-3135.20181121001
Abstract:In this paper, a novel method based on the liquid nitrogen-driven rotation and ice-templated assembly was proposed to fabricate a new kind of boron nitride nanosheet (BNNS) and BNNS-Ag spongy miscrosphere used as thermally conductive fillers. The liquid nitrogen driven assembly ultimately led to hierarchical 3D BNNS frameworks with radial alignments, forming a sea urchin-like microstructure. BN sphere/epoxy resin composites were finally obtained by infiltrating the as-prepared spongy microsphere with epoxy resin followed by thermal curing. At the sphere content of 2.7 vol%, the through-plane thermal conductivity of BNNS sphere/epoxy resin composite reaches 0.57 W/(m·K), while the value for BNNSAg sphere/epoxy resin composite reaches 0.64 W/(m·K), indicating the corresponding enhancement of 276.5% towards pure epoxy resin. The obtained composites exhibit strong potential for thermal management applications for a variety of technological needs, particularly electronic packaging. The combination of liquid nitrogen-driven rotation and ice-templated assembly was demonstrated to a useful tool to fabricate efficient fillers for thermal management applications.
2019, 8(1):78-87. DOI: 10.12146/j.issn.2095-3135.20180831001
Abstract:In recent years, with the rapid development of high integration and high power electronic devices, the demand for high thermal conductivity materials for electronic devices is more urgent. Carbon nanotubes (CNTs), due to their unique one-dimensional nanostructures and excellent thermal, electrical and mechanical properties, have attracted much attention. In this paper, the status of research in preparation methods of CNTs, including graphite arc method, chemical vapor deposition method, laser evaporation method are reviewed. The thermal-conductive mechanism and heat-conductivity performance of CNTs and their composites are reported. At last, based on the existing development of carbon nanotubes, the future for thermal-conductive of CNTs composites is looked forward.