Recently, Sun Rong, a researcher at the Institute for Advanced Materials, Institute of Advanced Technology, Chinese Academy of Sciences, has made a series of progress in the research of high-performance thermal conductive composite materials.
Modern electronic devices are gradually becoming more highly integrated and higher in power. If the heat generated inside the device is not efficiently dissipated, it will cause thermal failure. In order to ensure the performance and life of electrical devices, effective heat dissipation has become a major factor that restricts the development of electronic products. Addressing thermal issues depends on the development of thermal management materials. Thermally conductive materials are usually composed of thermally conductive fillers and a polymer matrix, and solution blending is a common method for preparing composite materials containing randomly distributed fillers. However, due to the lack of effective interconnections between the internal fillers, the thermal conductivity of the composites is usually low. The lack of filler-composite thermal conduction means that the phonons will dissipate more heat at the filler/matrix interface, leading to greater interfacial thermal resistance. On the other hand, adding a large amount of fillers (>60 wt%/vol%) will give better thermal conductivity, but it will seriously affect the mechanical properties and processability of composites, making them difficult to use. Therefore, for thermally conductive composites, how to achieve a high thermal conductivity at a lower filler content is still a challenge.
The team's thermal team Mo Yimin and Zeng Xiaoliang designed the macroscopically oriented silicon carbide wire network using the ice template method through the structural design of the filler orientation, combined with the high thermal conductivity and aspect ratio of the silicon carbide nanowires. Filler made of high thermal conductivity composite material. For phonons, the easiest way to cross a polymer is to establish a channel of filler composition inside the polymer. Therefore, polymer composites containing highly thermally conductive, linear fillers show a dramatic increase in thermal conductivity. The thermal conductivity of the composite material is 3 to 8 times higher than that of other reported thermal insulating composite materials. The high thermal conductivity composite material with a three-dimensional interconnected filler network has a great potential in thermal management. Related Papers Vertically Aligned and Interconnected SiC Nanowire Networks Leading to Significantly Enhanced Thermal Conductivity of Polymer Composites Online Published in ACS Applied Materials & Interfaces (DOI: 10.1021/acsami) .8b00328).
The team also made progress in the construction of three-dimensional boron nitride-graphene heat-conducting networks. In order to make the three-dimensional filler skeleton have a certain mechanical strength, the previous researchers usually added a binder in the preparation process of the three-dimensional skeleton. However, the mismatch of the phonon spectra between the binder and the filler will weaken the heat transfer of the filler skeleton itself, so the thermal conductivity of the polymer matrix composite containing the three-dimensional filler skeleton is often not ideal. The project team constructed an oriented phonon heat conduction network with the boron nitride and graphene similar in nature to the phonon transmission. The out-of-plane thermal conductivity of the composite reaches 5.05 Wm-1K-1, which is higher than that of other reported boron nitride-based composites. Related papers Construction of Three-dimensional Skeleton for Polymer Composites Achieving a High Thermal Conductivity is published online in the journal Small (DOI: 10.1002/smll.201704044).
The team also proposed a novel material forming method. Due to factors such as cost and production equipment, vacuum-assisted suction filtration technology and ice-stencil self-assembly technology are difficult to realize industrialization and cannot contribute to China's electronic materials industry. Therefore, Zeng Xiaoliang's research group explored and invented a simple, rapid, and macro-scale method for preparing thermally conductive fillers. The three-dimensional aerogel spherical filler can be successfully constructed by directly dropping the aqueous dispersion containing the filler into liquid nitrogen, combining freeze-drying, and a simple automatic propulsion device. This spherical filler has a large porosity and specific surface area and is directly involved in the construction of a heat conduction network, and can effectively improve the thermal conductivity of the composite material. With the help of an automatic propulsion device, small-scale production can be realized in a laboratory scale. In addition, this special microstructure also shows great potential in the field of adsorption and energy. A related paper, Liquid nitrogen driven assembly of nanomaterials into spongy millispheres for various applications, was published in the journal Journal of Materials Chemistry A (DOI:10.1039/C8TA00310F).
The above research was supported by key research and development projects of the Ministry of Science and Technology (2017YFB0406000), Guangdong Innovation Research Team (2011D052), Guangdong Provincial Key Laboratory (2014B030301014) and Shenzhen Science and Technology Plan Project.
Figure 1. Schematic diagram of the heat transfer principle of a three-dimensional silicon carbide wire network
Figure 2. Schematic of the heat transfer principle of a three-dimensional boron nitride-graphene network
Figure 3. Schematic diagram of the principle of the preparation of three-dimensional aerogel balls
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