研究了线圈状和麻花状两种典型螺旋形手征碳纤维以及直线形碳纳米管在8.2-12.4GHz的微波介电特性.螺旋形手征碳纤维通过催化化学气相沉积法制备,直线形碳纳米管用催化裂解浮游法以苯为碳源制备.螺旋形手征碳纤维与石蜡复合体的介电常数的实部(ε′)和虚部(ε″)比直线形碳纳米管与石蜡复合体的小,但线圈状螺旋形碳纤维的介电损耗角正切(tgδ=ε″/ε′)却明显偏大,线圈状和麻花状螺旋形碳纤维的tgδ分别为0.77—0.80和0.47—0.53,直线形碳纳米管的tgδ为0.45-0.77.螺旋形碳纤维与微波作用时的手征特性是导致其tgδ增大的主要原因,螺旋形手征碳纤维对微波的吸收与其自身的形状和尺寸密切相关,所以线圈状螺旋形碳纤维的tgδ比麻花状的大得多,探讨了螺旋形手征碳纤维与微波的作用机理,螺旋形手征碳纤维是一种非常有发展前景的微波吸收材料.
The microwave permittivity of micro-coiled chiral carbon fibers and straight carbon nanotubes suspended in paraffin wax was studied at the frequency range of 8.2～12.4GHz.
The micro-coiled chiral carbon fibers were synthesized by the chemical vapor deposition. The straight carbon nanotubes were prepared by catalytic
decompose of benzene using the floating transition method. The dissipation factors of the micro-coiled chiral carbon fibers are high at the microwave
frequencies. The ε’ and ε’’ of the micro-coiled chiral carbon fibers decrease with frequency at the frequency range of 8.2～12.4GHz. The promising features of micro-coiled chiral carbon fibers
would be due to their micro-coiling morphology. The ε’’ and tgδ of the large-coiled carbon fibers are higher than those of the
small-coiled carbon fibers. Although the ε’ and ε’’ of the straight carbon nanotubes are much higher than those of the micro-coiled
chiral carbon fibers, their dissipation factor tgδ is much less than that of the large-coiled chiral carbon fibers. The tgδ of the large-coiled carbon fibers and small-coiled carbon fibers is 0.77\sim0.80
and 0.47～0.53 respectively, the straight carbon nanotubes, 0.45～0.77. The micro-coiled chiral carbon fiber would be a promising candidate as a novel
microwave absorbent, especially in the GHz region, because of its micro-coiling morphology (microwave chirality). And microwave chirality is related to the
size and microstructure of the micro-coiled chiral carbon fibers.
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