Chen Yunxia, Gao Zhiming, Hoo Simon A, Tipnis Varun, Wang Renjing, Mitevski Ivan, Hitchcock Dale, Simmons Kevin L, Sun Ya-Ping, Sarntinoranont Malisa, Huang Yong
Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL, 32611, USA.
Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN, 37830, USA.
Adv Mater. 2024 Jun;36(25):e2314097. doi: 10.1002/adma.202314097. Epub 2024 Mar 19.
Planarly aligning 2D platelets is challenging due to their additional orientational freedom compared to 1D materials. This study reports a sequential dual-alignment approach, employing an extrusion-printing-induced shear force and rotating-magnetic-field-induced force couple for platelet planarly alignment in a yield-stress support bath. It is hypothesized that the partial alignment induced by a directional shear force facilitates subsequent axial rotation of the platelets for planar alignment under an external force couple, resulting in a synergistic alignment effect. This sequential dual-alignment approach achieves better planar alignment of 2D modified hexagonal boron nitride (mhBN). Specifically, the thermal conductivity of the 40 wt% mhBN/epoxy composite is significantly higher (692%) than that of unaligned composites, surpassing the cumulative effect of individual methods (only 133%) with a 5 times more synergistic effect. For 30, 40, and 50 wt% mhBN composites, the thermal conductivity values (5.9, 9.5, and 13.8 W m K) show considerable improvement compared to the previously reported highest values (5.3, 6.6, and 8.6 W m K). Additionally, a 3D mhBN/epoxy heat sink is printed and evaluated to demonstrate the feasibility of device fabrication. The approach enables the planar alignment of electrically or thermally conducting 2D fillers during 3D fabrication.
由于二维血小板与一维材料相比具有额外的取向自由度，因此实现其平面排列具有挑战性。本研究报告了一种顺序双排列方法，该方法利用挤出印刷诱导的剪切力和旋转磁场诱导的力偶，在屈服应力支撑浴中实现血小板的平面排列。据推测，定向剪切力引起的部分排列有助于血小板在外力偶作用下随后的轴向旋转以实现平面排列，从而产生协同排列效果。这种顺序双排列方法实现了二维改性六方氮化硼（mhBN）更好的平面排列。具体而言，40 wt% mhBN/环氧树脂复合材料的热导率显著高于未排列复合材料（692%），超过了单独方法的累积效果（仅133%），协同效果提高了5倍。对于30 wt%、40 wt%和50 wt%的mhBN复合材料，其热导率值（5.9、9.5和13.8 W m K）与之前报道的最高值（5.3、6.6和8.6 W m K）相比有显著提高。此外，还打印并评估了一种3D mhBN/环氧树脂散热器，以证明器件制造的可行性。该方法能够在3D制造过程中实现导电或导热二维填料的平面排列。
