摘要
本研究以间位芳纶纤维、浆粕为基体,单壁碳纳米管(SWNT)和多壁碳纳米管(MWNT)为填料,采用造纸湿法成形技术,制备了间位芳纶/单壁碳纳米管纸基复合材料(SP)和间位芳纶/多壁碳纳米管纸基复合材料(MP)。探讨了碳纳米管含量和种类对碳纳米管纸基复合材料导电性能、介电性能、电磁屏蔽效能的影响,并分析了碳纳米管纸基复合材料与电磁波的相互作用。结果表明,SP的表面电导率和体积电导率的逾渗阈值均为0.16%,MP的表面和体积电导率的逾渗阈值分别为0.37%和0.93%。碳纳米管含量相同时,SP比MP具有更高的电导率、介电常数实部、介电损耗和电磁波吸收率,其中SP在8~12 GHz的频率下(厚度0.15 mm)具有27 dB的电磁屏蔽效能。
自21世纪以来,通信技术与智能电子设备发展迅猛,给人们带来便利的同时,产生的电磁辐射污染对电子设备和人体健康均产生一定程度的危
碳纳米管是一种由s
在造纸湿法成形过程中,研究填料的留着率对加填纸性能的影响有着非常重要的意义,但是传统的燃烧灰分法会破坏碳纳米管。碳纳米管种类繁多,导电性和长径比存在较大差异,在大多数文献中与聚合物复合制备材料,鲜有文献报道碳纳米管种类对纸张电磁性能的影响。本研究以单壁碳纳米管(SWNT)和多壁碳纳米管(MWNT)为填料,具有较低介电常数、且能够溶解在二甲基乙酰胺/LiCl溶液中的间位芳纶纤维和间位芳纶浆粕为基体,采用造纸湿法成形工艺,分别制备了2种具有微波吸收能力的间位芳纶/碳纳米管纸基复合材料——间位芳纶/单壁碳纳米管纸基复合材料(SP)和间位芳纶/多壁碳纳米管纸基复合材料(MP),系统研究了碳纳米管种类和含量对纸基复合材料的导电性、介电性和电磁波吸收性能的影响。
单壁碳纳米管水分散液(SWNT,直径1~2 nm,长度5~30 μm),多壁碳纳米管水分散液(MWNT,直径30~80 nm,长度1~10 μm),间位芳纶纤维(长度 5 mm,直径13 μm),间位芳纶浆粕(平均长度1.2 mm,平均宽度23 μm),二甲基乙酰胺(DMAc),均由天津市大茂化学试剂厂提供。
KRK2530纤维疏解器、KRK2542-A自动纸页成型器,日本熊谷理机工业株式会社;Z-400F超声波细胞粉碎仪,宁波新芝生物科技有限公司;SU8220扫描电子显微镜(SEM),德国蔡司公司;B2985A高阻表、34405A数字万用表、N5222B矢量网络分析仪,美国Keysight公司。
选用间位芳纶作为基体,间位芳纶纤维与间位芳纶浆粕按照质量比6∶4,碳纳米管按基体质量称量,参照GB/T 24324—2009制备定量40 g/
参考GB/T 41418—2022的检测方法对PBCs中的碳纳米管留着率进行测试,具体步骤为:①配制DMAc/LiCl溶液,将LiCl与DMAc按照1∶104(g∶mL)的比例混合,在80 ℃下搅拌,使LiCl完全溶解;②向DMAc/LiCl溶液中加入待测纸样,并按照待测纸样∶DMAc/LiCl溶液=1∶200(g∶mL)的比例,在80 ℃下充分搅拌并反应4 h,直至间位芳纶完全溶解;③将反应完的溶液进行离心处理,碳纳米管在离心作用下沉积,取沉淀物依次用DMAc和去离子水洗涤并干燥;④称量绝干沉淀物的质量,计算碳纳米管留着率。
PBCs导电性测试采用GB/T 31838.3—2019《固体绝缘材料 介电和电阻特性 第3部分:电阻特性(DC方法) 表面电阻和表面电阻率》和GB/T 31838.2—2019《固体绝缘材料 介电和电阻特性第2部分:电阻特性(DC方法) 体积电阻和体积电阻率》所示方法进行测试,该方法测试示意图如
(1) |
(2) |
式中,Rs为按

图1 PBCs电导率测试示意图
Fig. 1 Schematic diagram of PBCs conductivity testing
采用在GJB 1651A-2017-5012基础上对柔性薄层材料优化的Nicholson-Ross-Weir (NRW)法,测试 PBCs的电磁参

图2 纸张复电磁参数测试示意图
Fig. 2 Schematic diagram of paper complex electromagnetic parameter testing
目前,普遍采用矢量网络分析仪进行电磁干扰屏蔽能力测试,可直接测得材料反射系数S11和S12,PBCs对电磁波的反射系数(R)、透过系数(T)、吸收系数(A)和电磁屏蔽效能(EMI SE,dB)由Schelkunoff方程获得,其计算如式(3)~
(3) |
(4) |
(5) |
(6) |

图3 碳纳米管和PBCs的SEM图
Fig. 3 SEM images of carbon nanotubes and PBCs
碳纳米管作为纳米尺度的填料,在造纸湿法成形过程中存在一定的流失,准确测量碳纳米管在纸张中的实际含量对研究PSCs的电磁屏蔽效能具有重要意义。本研究利用DMAc/LiCl溶液可以溶解间位芳纶而碳纳米管不溶的特性,测定了碳纳米管在PBCs中的留着率,结果见
碳纳米管添加量 | SWNT 留着率 | SWNT实际含量 | MWNT 留着率 | MWNT实际含量 |
---|---|---|---|---|
0.25 | 65.1 | 0.16 | 42.4 | 0.11 |
0.5 | 62.1 | 0.31 | 39.8 | 0.20 |
1 | 58.6 | 0.59 | 36.5 | 0.37 |
3 | 46.5 | 1.40 | 31.1 | 0.93 |
5 | 42.2 | 2.11 | 26.3 | 1.32 |
10 | 40.1 | 4.01 | 22.8 | 2.28 |
20 | 20.4 | 4.08 |
PBCs的导电性直接影响其电磁屏蔽效

图4 碳纳米管含量和种类对PBCs电导率的影响
Fig. 4 Effect of carbon nanotube content and type on the conductivity of PBCs
在X波段对PBCs的电磁参数进行测试,结果如

图5 碳纳米管含量对PBCs电磁参数的影响
Fig. 5 Effect of carbon nanotube content on the electromagnetic parameters of PBCs

图6 10 GHz下碳纳米管种类对PBCs电磁参数的影响
Fig. 6 Effect of carbon nanotube types on the electromagnetic parameters of PBCs at 10 GHz

图7 PBCs的电磁屏蔽效能和功率系数
Fig. 7 Electromagnetic shielding efficiency and power coefficient of PBCs
由
综上所述,SP和MP具有相似的电磁波损耗机理,主要是通过导电损耗和多孔结构带来的多重散射,对电磁波进行耗
本研究以间位芳纶纤维、浆粕为基体,单壁碳纳米管(SWNT)和多壁碳纳米管(MWNT)为填料,通过造纸湿法成形制备了2种碳纳米管纸基复合材料(PBCs),研究了碳纳米管含量和种类对PBCs导电性能、介电性能、电磁屏蔽效能和对电磁波反射、吸收和透过性能的影响。
3.1 SWNT含量在0~4.01%时,SP的表面电导率和体积电导率的逾渗阈值均为0.16%,MP的表面电导率和体积电导率的逾渗阈值分别为0.37%和0.93%;相同水平碳纳米管含量情况下SP导电性优于MP。
3.2 碳纳米管含量在0~4.08%之间时,SP介电常数实部随碳纳米管含量增加而增大,介电损耗先增大后减小,在碳纳米管含量1.40%时有最大值;MP介电常数实部和介电损耗随碳纳米管含量增加而增大。
3.3 碳纳米管含量在0~4.08%之间时,PBCs的电磁屏蔽效能和反射率随碳纳米管含量的增加而增大,透过率随碳纳米管含量增大而减小,SP吸收率先增大后减小,在碳纳米管含量0.31%时SP吸收率有最大值50.7%,MP吸收率随碳纳米管含量增大而增大,相同水平碳纳米管含量下SP的电磁屏蔽效能优于MP。
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