Boron Phosphide with High Thermal Conductivity: Synthesis by Molten Salt Method and Thermal Management Performance

doi:10.15541/jim20210721

Abstract

Abstract:

With the increase of packaging density of power electronic devices, the development of thermal interface materials with excellent thermal conductivity has received widely spread attention. Due to most traditional heat conductors showing relatively low thermal conductivity, synthesis of new high thermal conductive fillers is an important way to improve the thermal conductivity of thermal interface materials. In this study, boron phosphide (BP) particles were synthesized by a facile molten salt method, then mixed with boron nitride (h-BN) and filled into epoxy resin (EP) to prepare epoxy resin matrix composites (BP-BN/EP) by stirring and casting. With the three salts (NaCl : KCl : LiCl) method, the experimental data showed that the highest yield of BP reached 74%, 33% and 35% higher than that of the single salt method (41%) and the double salt method (39%), respectively. In the BP-BN/EP composites, BP and BN particles were uniformly dispersed in the EP matrix. When the hybrid filler loading at 30% (in volume), the thermal conductivity reached 1.81 W·m^-1·K^-1, 8.6 times of that of pure epoxy (0.21 W·m^-1·K^-1). The thermal conductivity improvement was related to the construction of thermal conductive network by BP particles linking adjacent BN sheets. In addition, to excellent thermal conductivity, the BP-BN/EP composites also showed good thermal stability and good thermodynamic properties. Therefore, the synthesized BP by molten salt method has great application prospects in the field of heat management.

Key words: molten salt method, boron phosphide, epoxy composite, thermal conductivity

CLC Number:

TQ174

HU Jiajun, WANG Kai, HOU Xinguang, YANG Ting, XIA Hongyan. Boron Phosphide with High Thermal Conductivity: Synthesis by Molten Salt Method and Thermal Management Performance[J]. Journal of Inorganic Materials, 2022, 37(9): 933-940.

Figures/Tables 8

Fig. 1 Optical photo of BP powders

Table 1 Yields of BP under different synthetic conditions

Sample	Salt types	Holding time/h	Yield/%
1	NaCl	1	41
2	NaCl-KCl	1	39
3	NaCl-KCl-LiCl	1	67
4	NaCl-KCl-LiCl	5	74
5	NaCl-KCl-LiCl	10	64

Fig. 2 Morphological and structural characterizations of BP (a) XRD pattern; (b) Raman spectrum; (c) Size distribution; (d) SEM image; (e) TEM image

Fig. 3 Cross-sectional SEM images of composites (a) Pure epoxy; (b) SBN-BN/EP composite; (c) BP-BN/EP composite

Fig. 4 Thermal conductivity of the composites (a) Thermal conductivity of the composites; (b) Comparison of BP-BN/EP composites with relevant literatures[16,28⇓⇓⇓⇓⇓⇓ -35]

Fig. 5 Thermal transport properties of pure EP, BP-BN/EP and SBN-BN/EP composites (a) IR thermal images at different time; (b) Temperature changes of sample surface at different time Colorful figures are available on website

Fig. 6 Thermal stability of composites (a) TG curves of BP-BN/EP composites; (b) TG curves of SBN-BN/EP composites

Fig. 7 Thermodynamic property of BP-BN/EP and SBN-BN/EP composites (a,d) Curves of storage modulus with temperature change; (b,e) Curves of loss modulus with temperature change; (c,f) Curves of loss factor (tanδ) with temperature change

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