University of Wollongong Research Online Australian Institute for Innovative Materials - Papers Australian Institute for Innovative Materials 2017 BN Nanosheet/Polymer Films with Highly Anisotropic Thermal Conductivity for Thermal Management Applications Yuanpeng Wu Deakin University Ye Xue Rowan University Si Qin Deakin University Dan Liu Deakin University Xuebin Wang Nanjing University See next page for additional authors Publication Details Wu, Y., Xue, Y., Qin, S., Liu, D., Wang, X., Hu, X., Li, J., Wang, X., Bando, Y., Golberg, D., Chen, Y., Gogotsi, Y. & Lei, W. (2017). BN Nanosheet/Polymer Films with Highly Anisotropic Thermal Conductivity for Thermal Management Applications. ACS Applied Materials and Interfaces, 9 (49), 43163-43170. Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: [email protected] BN Nanosheet/Polymer Films with Highly Anisotropic Thermal Conductivity for Thermal Management Applications Abstract The development of advanced thermal transport materials is a global challenge. Two-dimensional nanomaterials have been demonstrated as promising candidates for thermal management applications. Here, we report a boron nitride (BN) nanosheet/polymer composite film with excellent flexibility and toughness prepared by vacuum-assisted filtration. The mechanical performance of the composite film is highly flexible and robust. It is noteworthy that the film exhibits highly anisotropic properties, with superior in-plane thermal conductivity of around 200 W m -1 K -1 and extremely low through-plane thermal conductivity of 1.0 W m -1 K -1 , making this material an excellent candidate for thermal management in electronics. Importantly, the composite film shows fire-resistant properties. The newly developed unconventional flexible, tough, and refractory BN films are also promising for heat dissipation in a variety of applications. Disciplines Engineering | Physical Sciences and Mathematics Publication Details Wu, Y., Xue, Y., Qin, S., Liu, D., Wang, X., Hu, X., Li, J., Wang, X., Bando, Y., Golberg, D., Chen, Y., Gogotsi, Y. & Lei, W. (2017). BN Nanosheet/Polymer Films with Highly Anisotropic Thermal Conductivity for Thermal Management Applications. ACS Applied Materials and Interfaces, 9 (49), 43163-43170. Authors Yuanpeng Wu, Ye Xue, Si Qin, Dan Liu, Xuebin Wang, Xiao Hu, Jingliang Li, Xungai Wang, Yoshio Bando, Dmitri Golberg, Ying I. Chen, Yury Gogotsi, and Weiwei Lei This journal article is available at Research Online: http://ro.uow.edu.au/aiimpapers/2895 Page 1 of 26 ACS Applied Materials & Interfaces 1 2 3 4 5 6 7 BN nanosheet/polymer films with highly 8 9 10 11 anisotropic thermal conductivity for thermal 12 13 14 15 16 management application 17 18 19 20 Yuanpeng Wu1,2, Ye Xue3, Si Qin1, Dan Liu1, Xuebin Wang4,6, Xiao Hu3, Jingliang Li1, Xungai 21 22 Wang1, Yoshio Bando4, Dmitri Golberg4,7, Ying Chen1, Yury Gogotsi5, Weiwei Lei1* 23 24 1 25 Institute for Frontier Materials, Deakin University, Waurn Ponds Campus, Locked Bag 20000, 26 27 Victoria 3220, Australia 28 2 School of Materials Science and Engineering, Southwest Petroleum University, Chengdu 29 30 610500, China 31 3 32 Department of Physics and Astronomy and Department of Biomedical Engineering, Rowan 33 University, 201 Mullica Hill Road, Glassboro, New Jersey 08028, United States 34 35 4 International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for 36 37 Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan 38 5 39 A. J. Drexel Nanomaterials Institute, and Materials Science and Engineering Department, 40 Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, United States 41 42 6 College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China 43 7 44 School of Chemistry, Physics and Mechanical Engineering Science and Engineering Faculty, 45 46 Queensland University of Technology, Brisbane, QLD 4001, Australia 47 48 49 50 51 KEYWORDS: BN nanosheet, poly (diallyl dimethyl ammonium chloride), composite film, 52 53 thermal conductivity 54 55 56 57 58 59 60 ACS Paragon Plus Environment 1 ACS Applied Materials & Interfaces Page 2 of 26 1 2 3 ABSTRACT: Development of advanced thermal transport materials is a global challenge. Two- 4 5 6 dimensional nanomaterials have been demonstrated as promising candidates for the thermal 7 8 management applications. Here, we report a boron nitride (BN) nanosheet/polymer composite 9 10 film with excellent flexibility and toughness prepared by vacuum-assisted filtration. The 11 12 mechanical performance of the composite film is highly flexible and robust. It is noteworthy that 13 14 15 the film exhibits highly anisotropic properties, with superior in-plane thermal conductivity 16 17 around 200 W m-1 K-1 and extremely low through-plane thermal conductivity (1.0 W m-1 K-1), 18 19 making this material an excellent candidate for thermal management in electronics. Importantly, 20 21 22 the composite film shows fire-resistance properties. The newly developed unconventional 23 24 flexible, tough, and refractory BN films are also promising for heat dissipation in a variety of 25 26 applications. 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 ACS Paragon Plus Environment 2 Page 3 of 26 ACS Applied Materials & Interfaces 1 2 3 4 5 6 INTRODUCTION 7 8 9 The development of nanomaterials with anisotropic thermal transport properties has attracted 10 11 increasing attention for thermal management applications, such as coatings in electronics and 12 13 heat sinks.1 An ideal candidate should be electrically insulating and have thermal conductivity 14 15 1 16 in-plane significantly greater than through-plane. Two-dimensional (2D) nanomaterials such as 17 18 graphene and black phosphorus, both of which possess highly anisotropic thermal conductivity, 19 20 have recently provided a new platform for addressing heat dissipation in devices.2,3 However, it 21 22 23 is difficult to employ either in thermal management or build components owing to their electrical 24 25 conductivity and fast oxidation of phosphorus. BN nanosheets offer a high thermal conductivity, 26 27 large and direct band gap, resistance to oxidation, high elastic modulus, and a low friction 28 29 4-10 30 coefficient. BN nanosheets have been widely explored for use in functional nanocomposite 31 11-15 32 materials, ultraviolet-light emitters, hydrogen storage, and sorbents. In contrast with other 33 34 conductive and semiconducting 2D materials, such as graphene, transition metal 35 36 dichalcogenides, and MXenes, BN nanosheets are electrically insulating, which suggests utility 37 38 39 in thermal management applications in electronics. 40 41 42 Much effort has recently been devoted to the preparation of highly flexible, strong, and tough 43 44 graphene, clay, and MXene films for applications in gas separation, molecular- and ion-selective 45 46 16-20 47 devices, and energy storage. However, pure BN nanosheet films do not offer strength and 48 49 flexibility required in real-life application. Creating nanocomposite with polymers is an effective 50 51 approach to improve the mechanical properties of nanomaterials.21,22 There have been many 52 53 5,23-25 54 studies on BNpolymer nanocomposites with high polymer contents. However, the total 55 56 strength, elongation and thermal conductivities of such composites are largely controlled by the 57 58 59 60 ACS Paragon Plus Environment 3 ACS Applied Materials & Interfaces Page 4 of 26 1 2 3 polymer, staying far from the inherent properties of BN. To date, some studies have 4 5 6 demonstrated that 2D materials such as MXene and graphene-based nanocomposites with low 7 16,26,27 8 contents of polymer exhibit enhanced mechanical strength and electrical conductivity. 9 10 Therefore, to fully take advantage of the extraordinary properties of these 2D materials, the 11 12 content of polymer in the composite should be limited. BN nanosheet-based composites with 10 13 14 15 wt% polyvinyl alcohol (PVA) have recently been fabricated, exhibiting an excellent tensile 16 17 strength (125.2 MPa).28 However, the reported composites show a low thermal conductivity of 18 19 less than 6.9 W m-1 K-1 owing to the surfactant involved and the thickness of the nanosheet. 20 21 22 Therefore, developing a BN/polymer composite film with the flexibility of a polymer, superior 23 24 thermal conductivity of BN and the high mechanical strength remains a challenge. Additionally, 25 26 the fire hazard of polymeric materials restricts their application in thermal management fields, 27 28 29 which necessitates the addition of fire resistance. Recent works have shown that graphene oxide 30 31 and clay can be considered fire resistance while simultaneously improving the mechanical and 32 33 thermal properties of the composite.29,30 This justifies the use BN nanosheets, which are 34 35 chemically inert and oxidation resistant,31 in the construction of multifunctional fire-resistance 36 37 38 nanocomposites. 39 40 41 Here, we report a free-standing BN nanosheet/polymer composite film with a unique 42 43 combination of properties including flexibility and toughness, anisotropic thermal conductivity, 44 45 46 and fire resistance, which is produced by the vacuum-assisted filtration (VAF) of colloidal 47 48 suspensions of BN nanosheets and polymers (Figure 1a). In this work, poly (diallyl dimethyl 49 50 ammonium chloride) (PDDA) was chosen, which is a cationic polymer that combines with 51 52 26 53 negatively charged the BN nanosheet through electrostatic interactions. Owing to the merits, 54 55 56 57 58 59 60 ACS Paragon Plus Environment 4 Page 5 of 26 ACS Applied Materials & Interfaces 1 2 3 the BN film exhibit highly potential applications in high-performance flexible electrically 4 5 6 insulating substrates, superior thermal conductivities and fire-resistance coatings. 7 8 9 EXPERIMENTAL 10 11 12 Preparation of boron nitride (BN) nanosheets.