Vertical Alignment of Anisotropic Fillers Assisted by Expansion Flow in Polymer Composites

Abstract

Orientation control of anisotropic one-dimensional (1D) and two-dimensional (2D) materials in solutions is of great importance in many fields ranging from structural materials design, the thermal management, to energy storage. Achieving fine control of vertical alignment of anisotropic fillers (such as graphene, boron nitride (BN), and carbon fiber) remains challenging. This work presents a universal and scalable method for constructing vertically aligned structures of anisotropic fillers in composites assisted by the expansion flow (using 2D BN platelets as a proof-of-concept). BN platelets in the silicone gel strip are oriented in a curved shape that includes vertical alignment in the central area and horizontal alignment close to strip surfaces. Due to the vertical orientation of BN in the central area of strips, a through-plane thermal conductivity as high as 5.65 W m−1 K−1 was obtained, which can be further improved to 6.54 W m−1 K−1 by combining BN and pitch-based carbon fibers. The expansion-flow-assisted alignment can be extended to the manufacture of a variety of polymer composites filled with 1D and 2D materials, which can find wide applications in batteries, electronics, and energy storage devices.

Ultrahigh thermal conductive polymer composites by the 3D printing induced vertical alignment of carbon fiber

“…However, the low thermal conductivity of polymer materials (in the range of 0.1–0.5 W m −1 K −1 ), 3 significantly restricted their applications in electronics thermal management. Compositing with various thermal conductive fillers, including metal particles (Al, 4 Cu, 5 and Ag 6 ), ceramic particles (Al 2 O 3 , 7 BN, 8 AlN, 9 and SiC 10 ), and carbon-based materials (carbon fiber, 11–13 diamond, 14 graphene, 15,16 CNT, 17 and graphite flake 18 ), have been used to enhance the thermal conductivity of polymers.…”

Engineering HOF-Based Mixed-Matrix Membranes for Efficient CO2 Separation

“…With the advent of carbon neutrality, membrane-based technology has received a burgeoning interest in carbon capture, featured with the energy efficiency, module compactness and operational simplicity [ 1 – 5 ]. Mixed-matrix membrane (MMM) has deemed as an advanced membrane platform, with the merit of deploying distinct separation properties of fillers into processable matrix [ 6 – 10 ]. Along with the emergence of reticular chemistry, porous framework materials have been widely developed into advanced fillers to achieve membrane structure optimization and performance enhancement [ 11 – 13 ].…”

Vertically Aligned Boron Nitride Nanosheets Films for Superior Electronic Cooling

“…Comparing to the TIMs with randomly mixed BN nanosheets, the thermal conductivity of TIMs with aligned BN nanosheets has been improved significantly along the sheets basal plane direction. For instance, composite with aligned BN nanosheets (60 wt % filling content) presents a thermal conductivity of 3.8 Wm –1 K –1 along sheets’ plane direction, exceeding that of the composite with randomly mixed BN (1.01 Wm –1 K –1 ) . Nevertheless, the incorporation of BN nanosheets in the above-mentioned processes has not been able to construct continuous thermal pathways, resulting in high filling content with low enhancement efficiency.…”

“…Owing to the anisotropic 2D geometry with superior in-plane thermal conductivity, BN nanosheets have been sorted into a highly ordered alignment inside polymer matrix in order to achieve higher thermal conductivity. Several strategies have been proposed to obtain aligned BN nanosheets, including magnetic fields, electrical fields, freeze-casting, , and flow-assisted alignment . Comparing to the TIMs with randomly mixed BN nanosheets, the thermal conductivity of TIMs with aligned BN nanosheets has been improved significantly along the sheets basal plane direction.…”