Improving thermal conductivity through welding boron nitride nanosheets onto silver nanowires via silver nanoparticles (original) (raw)
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Scientific reports, 2016
Polymer composites with high thermal conductivity have recently attracted much attention, along with the rapid development of the electronic devices toward higher speed and performance. However, a common method to enhance polymer thermal conductivity through an addition of high thermally conductive fillers usually cannot provide an expected value, especially for composites requiring electrical insulation. Here, we show that polymeric composites with silver nanoparticle-deposited boron nitride nanosheets as fillers could effectively enhance the thermal conductivity of polymer, thanks to the bridging connections of silver nanoparticles among boron nitride nanosheets. The thermal conductivity of the composite is significantly increased from 1.63 W/m-K for the composite filled with the silver nanoparticle-deposited boron nitride nanosheets to 3.06 W/m-K at the boron nitride nanosheets loading of 25.1 vol %. In addition, the electrically insulating properties of the composite are well pr...
Bulk Hexagonal Boron Nitride with a Quasi‐Isotropic Thermal Conductivity
Advanced Functional Materials, 2018
Hexagonal boron nitride (BN) is electrically insulating and has a high in-plane thermal conductivity. However, it has a very low cross-plane thermal conductivity which limits its application for efficient heat dissipation. Here, large BN pellets with a quasi-isotropic thermal conductivity are produced from BN nanosheets using a spark plasma sintering (SPS) technique. The BN pellets have the same thermal conductivity from both perpendicular and parallel directions to the pellet surface. The high quasi-isotropic thermal conductivity of the bulk BN is attributed to a quasi-isotropic structure formed during the SPS process in which the charged BN nanosheets form large sheets in all directions under two opposite forces of SPS compression and electric field. The pellet sintered at 2300 °C has a very high cross-section thermal conductivity of 280 W m −1 K −1 (parallel to the SPS pressing direction) and exhibits superior heat dissipation performance due to more efficient heat transfer in the vertical direction.
Highly Thermally Conductive Papers with Percolative Layered Boron Nitride Nanosheets
ACS Nano, 2014
In this work, we report a dielectric nanocomposite paper with layered boron nitride (BN) nanosheets wired by onedimensional (1D) nanofibrillated cellulose (NFC) that has superior thermal and mechanical properties. These nanocomposite papers are fabricated from a filtration of BN and NFC suspensions, in which NFC is used as a stabilizer to stabilize BN nanosheets. In these nanocomposite papers, two-dimensional (2D) nanosheets form a thermally conductive network, while 1D NFC provides mechanical strength. A high thermal conductivity has been achieved along the BN paper surface (up to 145.7 W/m K for 50 wt % of BN), which is an order of magnitude higher than that in randomly distributed BN nanosheet composites and is even comparable to the thermal conductivity of aluminum alloys. Such a high thermal conductivity is mainly attributed to the structural alignment within the BN nanosheet papers; the effects of the interfacial thermal contact resistance are minimized by the fact that the heat transfer is in the direction parallel to the interface between BN nanosheets and that a large contact area occurs between BN nanosheets.
Isotope effect on the thermal conductivity of boron nitride nanotubes
Physical review letters, 2006
We have measured the temperature-dependent thermal conductivity κ(T) of individual multiwall boron nitride nanotubes using a microfabricated test fixture that allows direct transmission electron microscopy characterization of the tube being measured. κ(T) is exceptionally sensitive to ...
Journal of Materials Science: Materials in Electronics, 2014
With increased power density and continued miniaturization, effective thermal dissipation is of significant importance for operational lifetime and reliability of electronic system. Advanced thermal interface materials (TIMs) with excellent thermal performance need to be designed and developed. Here we report novel TIMs consisted of boron nitride (BN) nanofibers and pure indium (In) solder for heat dissipation applications. The BN nanofibers are fabricated by electrospinning process and nitridation treatment. After surface metallization by sputtering, the porous BN film is infiltrated with liquid indium by squeeze casting to form the final solid composites. The new composites show the in-plane and through-plane thermal conductivity respectively of 60 and 20 W/m K. The direction dependence thermal properties of the TIM are due to the anisotropic thermal performance of BN nanofibers in the composite. A low thermal contact resistance of 0.2 K mm 2 /W is also achieved at the interface between this new composite and copper substrate. These competent thermal properties demonstrate the great potential of the BN-In TIMs in thermal management for electronic system.
Characterization of thermal transport in low-dimensional boron nitride nanostructures
Physical Review B, 2011
Recent advances in the synthesis of hexagonal boron nitride (BN) based nanostructures, similar to graphene, graphene nanoribbons, and nanotubes, have attracted significant interest into characterization of these materials. While electronic and optical properties of BN-based materials have been widely studied, the thermal transport has not been thoroughly investigated. In this paper, the thermal transport properties of these BN nanostructures are systematically studied using equilibrium molecular dynamics with a Tersoff-type empirical interatomic potential which is re-parametrized to represent experimental structure and phonon dispersion of two-dimensional hexagonal BN. Our simulations show that BN nanostructures have considerably high thermal conductivities but are still quite lower than carbon-based counterparts. Qualitatively, however, the thermal conductivity of carbon and BN nanoribbons display similar behavior with respect to the variation of width and edge structure (zigzag and armchair). Additionally, thermal conductivities of (10,10) and (10,0) nanotubes, both carbon and BN, are found to have very weak dependence on their chirality.
Structural and thermal properties of boron nitride nanoparticles
Journal of the European Ceramic Society, 2012
In the present study, our main motivation was to investigate the structural and thermal stability of BN nanoparticles (B 1.0 N 0.9 -NPs) produced by spray-pyrolysis (SP) of borazine at 1400 • C by thermogravimetric experiments and X-ray diffraction. We observed that B 1.0 N 0.9 -NPs are relatively stable in air below 850 • C in which only oxidation of the NP surface proceeded. Above 850 • C, the powders started to strongly react with air due to bulk oxidation. Under nitrogen, they appeared to be less stable than plate-like BN synthesized from borazine at 1400 • C through conventional pyrolysis. This is related to the low degree of crystallization of B 1.0 N 0.9 -NPs that clearly affects their stability. Using a post-pyrolysis treatment at 1400 • C, B 1.0 N 0.9 -NPs remained stable up to 1600 • C similarly to plate-like BN. However, above 1600 • C, a relatively fast weight loss occurred for B 1.0 N 0.9 -NPs, whereas plate-like BN remained stable up to 1800 • C. This indicated that their lower size also affects their high temperature thermal behavior.
Journal of the American Ceramic Society, 2016
Hexagonal BN is an unusual material in that it is both highly thermally conductive as well as an electrical insulator. Additionally, hBN is also thermally stable in air. This unusual combination of properties makes hBN of significant interest for thermal management. Unfortunately, hBN is not easily consolidated into substrates without the addition of second phases which generally result in poorer thermal performance. This research investigates the potential to utilize this material to dissipate heat from high-voltage, high-power electrical devices. Specifically, a process to coat individual platelets of commercial hexagonal BN powder with a layer of amorphous aluminum oxide was developed. The coated hexagonal BN was then hot-pressed to form a highly thermally conductive substrate. The process to coat hexagonal BN platelets with aluminum oxide was accomplished by mixing hexagonal BN with AlCl 3 containing some water, then evaporation of excess AlCl 3 to form a Al, Cl, and O layer on hexagonal BN. This product was then heated in air to convert the surface layer into aluminum oxide. Following hot pressing to 1950°C and 10 ksi, the consolidated composite has through-plane and in-plane thermal conductivity of 14 and 157 WÁ(mÁK)-1 , respectively, at room temperature.
Thermal Conductance along Hexagonal Boron Nitride and Graphene Grain Boundaries
Energies, 2018
We carried out molecular dynamics simulations at various temperatures to predict the thermal conductivity and the thermal conductance of graphene and hexagonal boron-nitride (h-BN) thin films. Therefore, several models with six different grain boundary configurations ranging from 33-140 nm in length were generated. We compared our predicted thermal conductivity of pristine graphene and h-BN with previously conducted experimental data and obtained good agreement. Finally, we computed the thermal conductance of graphene and h-BN sheets for six different grain boundary configurations, five sheet lengths ranging from 33 to 140 nm and three temperatures (i.e., 300 K, 500 K and 700 K). The results show that the thermal conductance remains nearly constant with varying length and temperature for each grain boundary.