使用硫酸 (H 2 SO 4 )、硝酸 (HNO 3 ) 和盐酸( HCl ) 等酸的混合物对多壁碳纳米管 (MWCNT) 和单壁碳纳米管 (SWCNT) 进行酸功能化. 据观察，适度的酸浓度与适度的反应时间相结合，有效地对碳纳米管 (CNT) 进行表面改性，充分引入缺陷并附着必要的官能团。评估了酸处理的 CNT 的成分、形态和热性能，证明单独使用 H 2 SO 4不会损坏 CNT，而 H 2 SO 4 /HNO的组合3 /HCl 对 CNT 产生轻微损伤。能量色散 X 射线光谱 (EDX) 表明，功能化 CNT 中的氧百分比增加到 7.36-8.19%，而原始 CNT 中的氧百分比为零。在用所有酸处理处理的 CNT 的傅里叶变换红外 (FTIR) 光谱中证明了羟基、羧基和羰基的存在。热重研究 (TGA) 表明，与涉及 H 2 SO 4和 HNO 3的传统酸混合法相比，H 2 SO 4功能化的 CNT 显示出更高的 CNT 结构稳定性，尽管其具有更高的官能团连接. 从 TGA 还观察到，原始 MWCNT 的重量残留百分比为 89%，原始 SWCNT 为 94%，并且功能化残留百分比显着降低，表明 CNT 在功能化后更容易发生热降解。使用功能化碳纳米管作为填料和聚甲基丙烯酸甲酯 (PMMA) 作为基质制备纳米复合薄膜。评估了纳米复合膜的电性能。在比较纳米复合材料的电性能时，含有 H 2 SO 4的复合材料- 功能化的 CNT 显示出更高的电性能，因为它由稳定的 CNT 结构以及含氧官能团的连接支持。 据观察，PMMA-MWCNT 和 PMMA-SWCNT 纳米复合材料的电导率最大值分别从 纯 PMMA 的10-6 S/cm 提高到 10-3 S /cm 和 10-2 S /cm 的数量级1 兆赫。对于 PMMA-MWCNT 和PMMA-SWCNT 纳米复合材料，这种增强是电导率增加大约 10 3倍和 10 4倍。
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Characterization of MWCNT and SWCNT functionalized by acid treatments and the effect of functionalized carbon nanotubes on electrical properties of PMMA-MWCNT and PMMA-SWCNT nanocomposites
Acid functionalization of multi-walled carbon nanotubes (MWCNT) and single-walled carbon nanotubes (SWCNT) were conducted with combination of mixtures of acids including sulfuric acid (H2SO4), nitric acid (HNO3) and hydrochloric acid (HCl). It was observed that moderate acid concentration combined with moderate reaction time, efficiently surface modified the carbon nanotubes (CNT) with adequate introduction of defects and attachment of necessary functional groups. Acid-treated CNT was evaluated for its compositional, morphological, and thermal properties evidencing that individual usage of H2SO4 did not damage the CNT, whereas combination of H2SO4/HNO3/HCl produced mild damages to the CNT. Energy dispersive X-ray spectroscopy (EDX) showed that oxygen percentage in functionalized CNT increased to 7.36–8.19% as against zero percentage in pristine CNT. Presence of hydroxyl, carboxyl, and carbonyl groups was evidenced in Fourier transform infrared (FTIR) spectroscopy for CNT treated with all acid treatments. Thermogravimetric studies (TGA) displayed that H2SO4-functionalized CNT displayed a greater structural stability of CNT despite higher attachment of functional groups as compared with conventional acid mixture method involving H2SO4 and HNO3. It was also observed from TGA that weight residue percentage of pristine MWCNT was 89% and pristine SWCNT was 94% and with functionalization residue percentage significantly decreased, indicating that CNT were more prone to thermal degradation after functionalization. Nanocomposite films were fabricated using functionalized CNT as filler and polymethyl methacrylate (PMMA) as matrix. Electrical properties of the nanocomposite films were evaluated. On comparing the electrical properties of the nanocomposites, composites containing H2SO4-functionalized CNT displayed higher electrical properties as it was supported by stable CNT structure along with attachment of oxygen containing functional groups. It was observed that maximum value of electrical conductivity of PMMA-MWCNT and PMMA-SWCNT nanocomposites was enhanced to the order of 10–3 S/cm and 10–2 S/cm respectively, from 10–6 S/cm for pure PMMA at 1 MHz. This enhancement is an increase in conductivity of the order of 103 times for PMMA-MWCNT and 104 times for PMMA-SWCNT nanocomposites.
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