The power electronics tend to become miniaturized and multifunctionalized, such as thermal rotators, circuit breakers, and microchips, which have necessitated creating instruments for investigating thermal mechanisms and enhancing thermal conductivity. In this paper, we construct the heat flow network of spherical boron nitride (BN) and used multiscale spherical BN to improve the thermal conductivity of the composite synergistically. The multiscale spherical filler ratio optimization model based on the Dinger–Funk particle stacking theory is established, which obtained the optimal volume ratio of 0.224:0.374:0.402 with D 50 of 20, 70, and 160 μm. Meanwhile, the effects of multiscale filler ratio, morphology, filler content, and temperature are investigated. The thermal conductivity of composites can reach up to 1.84 W/(m·K) at 20 vol %. Significantly, the thermal conductivity of composites is 4.82 W/(m·K) at 30 vol %, which is achieved by optimizing the multiscale filler and particle size distribution.
Heat dissipation is necessary for the safer operation of high-power electronic devices and high-capacity batteries. Thermal meta-materials can efficiently manipulate heat flow by molding natural materials into specific structures. In this study, we construct a three-dimensional-printed meta-material structure with efficient and deterministic heat conduction through combining the 2D boron nitride (BN) with nano-diamond (DM) bridging. A research of thermal conductivity and dielectric properties exhibits that the nanosized diamond-bridged and oriented 2D boron nitride endows efficient heat transfer and maintains low dielectric loss with low filler loading. The composites loaded with 19 wt% BN platelets and 1 wt% DM have the highest thermal conductivity of 3.687 W/(m·K) in the heat flow orientation, while the thermal conductivity is only 0.632 W/(m·K) in the vertical heading of heat flow. The thermal conductive networks with thermal meta-materials based on the structural characteristics have been designed to secure critical device components from the heat source and dissipate heat flow in a definite way. The infrared images show that the temperature difference of monitoring points in different directions on the BN-oriented composite substrate is 9 °C, which realizes the protection of the heat source and key components. This study shows the latent capacity of 3D-printed structured materials for critical device component protection and heat administration applications in electronic devices and electric equipment.
Carbonization of epoxy resin under high voltage discharge or exposure to high temperatures results in insulation failure. Herein, multiscale spherical boron nitride (SBN) epoxy resin is developed with improved anticarbonization properties. The thermal conductivity, thermostability, dielectric performances, volume resistivity, breakdown strength, and flame retardancy of the epoxy-SBN composites were studied. The thermal conductivity, thermostability, volume resistivity, and breakdown strength of epoxy-SBN composites are higher than that of pure resin, with a ratio of high thermal conductivity of 24 and a volume resistivity of ∼10. The AC breakdown voltage of the epoxy-30SBN composites was as high as 29.96 kV/mm. In addition, epoxy-30SBN composites possess minimal carbonization surface area under high-voltage discharge. Increased thermal conductivity, lower mass loss rate, high flame resistance, and inhibited charge carrier migration contribute to the improved carbonization resistance of the arc. Densified SBN networks in epoxy resin act as a dense barrier to achieve anticarbonization under high voltage stress or high-temperature exposure. Therefore, epoxy-SBN composites are promising candidates for application in next-generation high-voltage devices to ensure electrical safety.
In this Letter, we report a simple approach for the preparation of bioinspired nacre-like structured materials with achievable high in-plane or through-plane thermal conductivity via digital light processing 3D printing under optimized printing parameters. Based on the 3D layer-by-layer formation, a vertical force exerted on each printing layer during the 3D printing process makes 2D platelets well-ordered in ultraviolet curable resin (hereafter UV resin), which is proved by the images of the scanning electron microscope and spectra of x-ray diffraction. It is found that a lower printing layer thickness leads to a higher orientation of Al2O3 platelets in the UV resin and greater thermal conductivity of the composites. The thermal conductivity of the structured composites reaches up to 2.622 W m−1 K−1 along the oriented direction at the loading of 30 wt. % of 2D Al2O3 platelets under the designed 3D printing layer thickness of 15 μm, which is about 14 times greater than that of pure UV resin. The surface temperature variations of the composites with time during heating and cooling, observed from the infrared thermograph, indicate the great potential of the 3D-printed structured materials for thermal management applications in electronic devices and electric equipment. It is predicted that fillers with greater intrinsic thermal conductivity and a larger diameter than the 3D printing layer thickness will lead to composites with greater thermal dissipation capability.
Digital light processing three-dimensional (DLP 3D) printing, as a promising manufacturing technology with the capability of fabricating 3D objects with complex shapes, typically develops inconsistent material properties due to the stair-stepping effect caused by weak layer-interface compatibility. Here, we report the regulation of the interface compatibility of the 3D-printing resin with versatile photocuring characteristics and the subsequent mechanical, thermal, and dielectric performances by introducing the interpenetration network (IPN). The preparation procedures, interface structure, flexural and tensile strength, modulus, and dielectric performances of the IPN are presented. The greater penetration depth in 3D printing and the subsequently thermocured epoxy network passing through the printing interface synergistically enhance the interface compatibility of 3D-printing samples, with an unobvious printing texture on the surface of the 3D-printing objects. The mechanical performances of the IPN demonstrate little anisotropy, with a bending strength twice as much as the photosensitive resin. Dynamic mechanical analysis of the IPN indicates that the storage modulus increases by 70% at room temperature and the glass transition temperature (T g) increases by 57%. The dielectric performance of the IPN demonstrates a 36% decrease in dielectric constant and a 28.4% increase in breakdown strength. Molecular dynamics studies have shown that the IPN takes on higher nonbonded energies and hydrogen bonds than the photosensitive resin, indicating a stronger bonding force between molecular chains, thus leading to better physical properties. These results illustrate the effectiveness of the IPN toward enhanced 3D-printing interlayer compatibility for excellent mechanical, thermal, and electrical performances.
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