Recently, Sun Rong, a researcher at the Institute of Advanced Materials, Institute of Advanced Technology, Chinese Academy of Sciences, has made a series of progresses in the research of high performance and thermal conductive composite materials.
Modern electronic devices are gradually becoming more highly integrated and have higher power. If the heat generated inside the device is not effectively dissipated, it will cause thermal failure. In order to ensure the performance and life of electrical devices, effective heat dissipation becomes a constraint on electronic devices. The main factors for product development. Resolving thermal issues depends on the development of thermal management materials. Thermal conductive materials are usually composed of thermally conductive fillers and a polymer matrix. Solution blending is a common method for preparing composites containing randomly distributed fillers. However, due to internal fillers In the absence of effective interconnections, the thermal conductivity of the composites is usually low. The lack of fillers in the thermal path means that the phonons will dissipate more heat at the filler/matrix interface, leading to a larger interface. 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 the composite materials. It is difficult to use. Therefore, for the thermal conductivity Composites, how to achieve a high thermal conductivity at a lower filler content is still a big challenge.
Based on the structural design of the orientation of the fillers and the high thermal conductivity and aspect ratio of the silicon carbide nanowires, the team's thermal conducting team Mo Yimin and Zeng Xiaoliang used the ice template method to prepare a macroscopically oriented silicon carbide wire network. Fillers produce highly thermally conductive composites. For phonons, the easiest way to penetrate a polymer is to establish a channel of filler composition inside the polymer. Therefore, polymer composites containing highly thermally conductive, linear fillers will exhibit thermal conductivity. Significant improvement in performance. The thermal conductivity of the composite material is 3 to 8 times that of other reported thermal insulation composite materials. The high thermal conductivity composite material with a three-dimensional interconnected filler network has great potential for thermal management. Related Papers Vertically Aligned and Interconnected SiC Nanowire Networks Leading to Significantly Enhanced Thermal Conductivity of Polymer Composites Published in the journal ACS Applied Materials & Interfaces (DOI: 10.1021/acsami) .8b00328) .
The team also made progress in the construction of a three-dimensional boron nitride-graphene heat-conducting network. In the past, researchers had to add a binder in the preparation process of the three-dimensional framework in order to make the three-dimensional filler skeleton have a certain mechanical strength. However, the mismatch of phonon spectra between the binder and the filler will weaken the heat transfer of the filler matrix itself, so the thermal conductivity of the polymer matrix composite containing the three-dimensional filler skeleton is often not ideal. The project team communicates with the phonon. The boron nitride and graphene with similar properties are assembled units, and an oriented phonon heat conduction network is constructed. The out-of-plane thermal conductivity of the composite material reaches 5.05 Wm-1K-1, higher than that of other reported boron nitride-based composite materials. Thermal conductivity values. Related papers Construction of Three-dimensional Skeleton for Polymer Composites Achieving a High Thermal Conductivity (Published in the journal Small (DOI: 10.1002/smll.201704044).
The team also proposed a novel material forming method. Constrained by 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 has explored and invented a simple, rapid and macro method for preparing thermally conductive fillers. By directly dropping the aqueous dispersion containing the filler into liquid nitrogen, combined with freeze drying and a simple automatic propulsion device, it can be successfully constructed. Three-dimensional aerogel spherical filler. This spherical filler has a large porosity and specific surface area. It is directly involved in the construction of a heat conduction network and can effectively improve the thermal conductivity of composite materials. Experiments can be performed with the aid of an automatic propulsion device. Room-scale, small-batch production. In addition, this special microstructure also shows great potential for application in the fields of adsorption and energy. Related papers Liquid nitrogen driven assembly of nanomaterials into spongy millispheres for various applications Three-dimensional aerogel ball) Published online in the journal Jo Urnal of Materials Chemistry A (DOI:10.1039/C8TA00310F) .
The above research was supported by the Ministry of Science and Technology's key R&D projects (2017YFB0406000), the Guangdong Provincial Innovation Research Team (2011D052), the Guangdong Provincial Key Laboratory (2014B030301014) and the 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
