摘要
受限于商业氮化硼(BN)晶体尺寸及BN独特的层间相互作用,传统的剥离法难以实现高宽厚比(>5000)氮化硼纳米片(BNNSs)的制备.以氨硼烷为前驱体,经烧结和分离得到了高宽厚比的BNNSs.通过FTIR,TG,TEM,XRD等手段对BNNSs的组成结构及形成机理进行表征.结果表明:当温度超过80℃时,氨硼烷之间开始交联脱氢,氢气释放使得在交联过程中形成泡沫结构,并最终在1000℃完成无机化,得到含有BNNSs的BN泡沫,其中的膜结构即为BNNSs.所制备的BNNSs为六方晶型结构,厚度约为1.5 nm,宽度约30 μm,宽厚比达到20000.将高宽厚比的BNNSs与聚乙烯醇(PVA)复合制备成复合膜,其导热及力学性能相较于小宽厚比BNNSs所制备的复合膜有显著提升,充分说明了高宽厚比BNNSs在BN基复合材料领域的应用优势.
Abstract
Due to the small size of commercial BN crystal and the unique interlayer interaction of BN,the traditional exfoliate method makes it difficult to fabricate BN nanosheets(BNNSs)with high aspect ratio(>5000).High aspect ratio BNNSs were obtained by sintering ammonium borane and centrifugal separation of the sintering products.The synthesis mechanism and structure of BN nanosheets were characterized by FTIR,TG,TEM and XRD.The results show that the cross-linking and dehydrogenation of ammonium borane begin when the temperature is over 80℃.Hydrogen releasing results in the formation of foam structure during the cross link process of ammonium borune,and finally the inorganic process was completed at 1000℃to obtain the BN foam containing BNNSs.The as-prepared BNNSs are hexagonal crystal structure,with a thickness of about 1.5 nm and an average width of 30 μm.The width-thickness ratio reaches 20000.The high aspect ratio BNNSs were introduced to polyvinyl alcohol(PVA)to prepare the BNNS/PVA composite film.The composite film shows significant improvement in thermal conductivity and mechanical properties,fully explains the application advantages of high aspect ratio BNNSs in the field of BN based composites.
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