预膨胀制备氮化硼纳米片及其导热复合材料性能

Properties of Thermal Conductive Composites Filled with Boron Nitride Nanosheets Prepared Via Pre-Expansion Method

由六方氮化硼(h-BN)剥离制备氮化硼纳米片(BNNS)需破坏相邻层中B与N原子交替堆积产生的Lip-lip作用,因此,单层或少层BNNS制备效率低是限制其广泛应用的重要原因。文中采用预先膨胀辅助液相超声的方法,利用碳酸氢铵受热分解产生CO_(2)和NH3气体插层到h-BN层间,得到预先膨胀的h-BN,后经超声处理成功制备了横向尺寸约1μm、厚度2.5nm的高质量BNNS。所得BNNS与纤维素纳米纤维(CNF)经溶液共混、抽滤,制得了CNF/BNNS复合材料。当CNF/BNNS复合材料中BNNS质量分数为50%时,复合材料的面内热导率高达18.85W/(m·K),相比较基体提高了3.5倍,高度取向的超薄BNNS在基体内形成了有效的导热通路,使得复合材料的导热性能得到显著提高。

The preparation of hexagonal boron nitride nanosheets(BNNS)from hexagonal boron nitride(h-BN)needs to overcome the lip-lip interactions caused by the alternating stacking of B and N atoms in adjacent layers.Therefore,the efficient preparation of mono-layer or few-layer BNNS is essential which limits its wide application.In this work,high quality BNNS with the lateral size of about 1μm and thickness of 2.5 nm were successfully prepared by pre-expansion assisted liquid phase ultrasonic exfoliation.In the pre-expansion stage,CO_(2) and NH3 gases generated by the thermal decomposition of ammonium bicarbonate were intercalated into the h-BN layers to obtain the pre-expanded h-BN.After the ultrasonic treatment of the pre-expanded h-BN,BNNS were obtained.Then BNNS and cellulose nanofibers(CNF)were blended and filtered to obtain CNF/BNNS composites with a high orientation of BNNS in the matrix.With 50%BNNS added,the in-plane thermal conductivity of the composite is as high as 18.85 W/(m·K),which is 3.5 times higher than that of the matrix.The highly oriented ultra-thin BNNS significantly improves the thermal conductivity of the composites.