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.

中文翻译：

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具有准各向同性导热系数的块状六方氮化硼

六方氮化硼（BN）具有电绝缘性，并且具有很高的面内热导率。但是，它的跨平面导热系数非常低，这限制了其在有效散热方面的应用。在这里，使用火花等离子体烧结（SPS）技术由BN纳米片生产出具有准各向同性导热系数的大型BN球团。BN粒料从垂直方向和平行方向到粒料表面都具有相同的热导率。整体BN的高准各向同性热导率归因于SPS过程中形成的准各向同性结构，其中带电的BN纳米片在SPS压缩和电场的两个相反力的作用下，在各个方向上形成大片。在2300°C下烧结的球团的截面导热率很高，为280 W m^-1 K ^-1（平行于SPS压紧方向），并由于在垂直方向上更有效的热传递而具有出色的散热性能。