Chemical treatments are used to introduce active functional groups and/or to increase the surface roughness of carbon fibres (CF) aiming to improve their interaction with polar polymeric matrices in composites. Considering the new challenges in the field of composite materials, such as the processing of hybrid composites and the growing use of thermoplastic structural composites, the modification of the CF surface has been increasingly studied. In this paper, the effect of various chemical treatments (with HCl, HNO₃, H₂SO₄, CH₃COOH, NH₄OH, or H₂O₂) on the thermal stability, chemical composition, and microstructural parameters of a polyacrylonitrile-based carbon fibre was investigated. Raman results indicated greater degree of crystallinity at the surface for the fibres treated (at 80°C for 1 h) with HCl, HNO₃, H₂SO₄, and H₂O₂. The treatment with HCl at 80°C for 1 h was effective in reducing disturbance of the carbon structure, as indicated by the higher FWHM_G value compared with those of the as-received, acetone pretreated, and the other chemically treated carbon fibres. Fourier transform infrared (FTIR) showed that some treatments promoted an increase in CF polarity (H₂SO₄ at 80°C/1 h and NH₄OH at 20°C/1 h), with the incorporation of organic polar groups (i.e., –OH). The apparent roughness of pretreated carbon fibre increased when treated with HNO₃ at 80°C/1 h and H₂SO₄ at 80°C/1 h, as observed in the AFM analyses. AFM, FTIR, and Raman results suggest that the fibres treated with HNO₃, H₂SO₄, and NH₄OH were the most promising as reinforcement in high-performance polymer composites.

中文翻译：

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化学改性碳纤维的光谱分析

化学处理用于引入活性官能团和/或增加碳纤维 (CF) 的表面粗糙度，旨在改善它们与复合材料中极性聚合物基质的相互作用。考虑到复合材料领域的新挑战，如混合复合材料的加工和热塑性结构复合材料的日益普及，CF 表面的改性得到越来越多的研究。在本文中，各种化学处理（用 HCl、HNO ₃、H ₂ SO ₄、CH ₃ COOH、NH ₄ OH 或 H ₂ O ₂) 对聚丙烯腈基碳纤维的热稳定性、化学成分和微观结构参数进行了研究。拉曼结果表明，用 HCl、HNO ₃、H ₂ SO ₄和 H ₂ O ₂处理（在 80°C 下 1 小时）的纤维的表面结晶度更高。用 HCl 在 80°C 下处理 1 小时可有效减少碳结构的干扰，如与原样、丙酮预处理和其他化学处理的碳纤维相比，FWHM _G值更高。傅里叶变换红外 (FTIR) 表明，一些处理促进了 CF 极性（H ₂ SO ₄80°C/1 小时和 NH ₄ OH 20°C/1 小时），并加入有机极性基团（即 -OH）。正如在 AFM 分析中观察到的那样，当用 HNO ₃在 80°C/1 h 和 H ₂ SO ₄在 80°C/1 h处理时，预处理碳纤维的表观粗糙度增加。AFM、FTIR 和拉曼结果表明，用 HNO ₃、H ₂ SO ₄和 NH ₄ OH处理的纤维最有希望作为高性能聚合物复合材料的增强材料。