铵盐电解质溶液中高模碳纤维的电化学氧化机制

宫浩婷; 钱鑫; 郭梅; 李春洁; 张永刚

doi:10.13801/j.cnki.fhclxb.20230616.004

铵盐电解质溶液中高模碳纤维的电化学氧化机制

doi: 10.13801/j.cnki.fhclxb.20230616.004

宫浩婷^{1, 2},
钱鑫^2, ,,
郭梅^{1, 2},
李春洁^{1, 2},
张永刚²

1.
宁波大学　材料科学与化学工程学院，宁波 315211
2.
中国科学院宁波材料技术与工程研究所　碳纤维制备技术国家工程实验室，宁波 315201

基金项目: 宁波市自然科学基金重点项目(202003 N4027)；浙江省‘尖兵’‘领雁’研发攻关计划(2021 C01004)

详细信息

通讯作者:
钱鑫，博士，高级工程师，硕士生导师，研究方向为国产高性能碳纤维及其复合材料　E-mail: qx3023@nimte.ac.cn

中图分类号: TQ342；TB332
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出版历程
- 收稿日期: 2023-04-14
- 修回日期: 2023-05-23
- 录用日期: 2023-06-11
- 网络出版日期: 2023-06-19
- 刊出日期: 2024-02-01

Electrochemical oxidation mechanism of high modulus carbon fibers in ammonium electrolyte solution

GONG Haoting^{1, 2},
QIAN Xin^{2
, ,},
GUO Mei^{1, 2},
LI Chunjie^{1, 2},
ZHANG Yonggang²

1.
School of Material Science and Chemical Engineering, Ningbo University, Ningbo 315211, China
2.
National Engineering Laboratory of Carbon Fiber Preparation Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China

Funds: Key Project of Natural Science Foundation of Ningbo (202003 N4027); "Pioneer" and "Leading Goose" R&D Program of Zhejiang (2021 C01004)

摘要

摘要: 聚丙烯腈基高模碳纤维(HMCFs)具有高比强度、高比模量、低热膨胀系数等优异性能，在航空航天、高端运动器材等领域应用广泛，但因其表面呈现极高惰性而难以与树脂基体有效结合，直接影响了复合材料性能。目前，电化学氧化是唯一实现在线配套的碳纤维表面改性工艺，而有关高模碳纤维表面的电化学氧化研究尤其是电解质溶液对HMCF表面的氧化机制尚缺乏系统研究。通过采用具有4种不同酸碱性特征的铵盐溶液对HMCF进行电化学氧化处理，表征并分析了处理前后纤维表面结构、力学性能及复合材料界面性能变化。结果表明：碳纤维经铵类电解质溶液处理后，表面发生氧化的同时引入N元素、产生含氮官能团，纤维表面无序化程度及含氧量随电解质溶液酸碱性的增强而增加；电化学处理后纤维模量都有不同程度地提高，而只有弱碱性的NH₄HCO₃和酸性的NH₄H₂PO₄电解质溶液处理后的纤维拉伸强度出现增加，分别从处理前的4.21 GPa提升到4.82 GPa和4.75 GPa，并且其复合材料界面剪切强度相对于从未处理碳纤维的复合材料分别提高了49.86%和49.02%，证明电化学氧化过程中适度的氧化刻蚀能够在纤维表面改性的同时提高纤维拉伸强度。
- 高模碳纤维 /
- 电化学氧化 /
- 铵盐电解质溶液 /
- 碳纤维复合材料 /
- 界面结合
Abstract: Polyacrylonitrile-based high-modulus carbon fibers (HMCFs) have excellent properties such as high specific strength, high specific modulus, and low coefficient of thermal expansion. So far, HMCFs have been widely used in aerospace and high-end sports equipment, etc. However, it is really difficult for HMCFs to effectively bond with the matrix owing to their extremely high surface inertness, which directly affects the performance of the corresponding composites. At present, electrochemical oxidation is one feasible surface modification process of carbon fiber which has been equipped online, whereas there is a lack of systematic research on the surface electrochemical oxidation of HMCFs, especially the oxidation mechanism of HMCF surface oxidized by different electrolyte solutions. In this paper, the electrochemical oxidation of HMCFs in four ammonium solutions with different acid-base characteristics was conducted. Changes in fiber surface structure, mechanical properties and composite interfacial properties before and after treatment were characterized and analyzed in detail. The results showed that after the treatment with ammonium electrolyte solutions, the fiber surface was oxidized together with the introduction of N elements and the generation of nitrogen-containing functional groups. Meantime, the degree of fiber surface disordering and the oxygen content also increased with the enhancement of the acidity and alkalinity of the electrolyte solutions. The fiber modulus increased to varying degrees after electrochemical treatment, while the fiber samples oxidized in NH₄HCO₃ and NH₄H₂PO₄ electrolyte solutions showed an increase in fiber tensile strength after treatment, from 4.21 GPa to 4.82 GPa and 4.75 GPa, respectively, and the interfacial shear strength of their compo-sites also increased by 49.86% and 49.02%, respectively, compared with composites reinforced by untreated fibers. It is demonstrated that moderate oxidative etching during electrochemical oxidation can improve the tensile strength of fibers while modifying the fiber surface.
- high-modulus carbon fibers /
- electrochemical oxidation /
- ammonium electrolyte solution /
- carbon fiber composites /
- interface bonding

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图 1 电化学氧化处理前后高模量碳纤维(HMCF)的SEM图像

Figure 1. SEM images of high-modulus carbon fiber (HMCF) before and after electrochemical oxidation

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图 2 电化学氧化前后HMCF的XRD图谱

Figure 2. XRD patterns of HMCF before and after electrochemical oxidation

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图 3 电解质溶液pH值与石墨微晶堆砌厚度(L_C)及半峰宽(β_1/2)的关系

Figure 3. Relationship between pH of electrolyte solution and crystallite thickness (L_C) and full width at half maxima of (002) peak (β_1/2)

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图 4 电化学氧化处理前后HMCF的Raman图谱及其拟合曲线

Figure 4. Raman spectra of HMCF before and after electrochemical oxidation treatment and their fitted curves

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图 5 电化学氧化处理前后HMCF的XPS图谱

Figure 5. XPS patterns of HMCF before and after electrochemical oxidation

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图 6 处理前后HMCF的XPS C1s峰拟合曲线

Figure 6. Curve fitting of XPS C1s peak of untreated and modified HMCF

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图 7 处理前后HMCF的XPS O1s峰拟合曲线

Figure 7. Curve fitting of XPS O1s peak of untreated and modified HMCF

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图 8 处理前后HMCF的XPS N1s峰拟合曲线

Figure 8. Curve fitting of XPS N1s peak of untreated and modified HMCF

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图 9 电化学氧化前后HMCF的力学性能

Figure 9. Mechanical properties of HMCF before and after electrochemical oxidation

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图 10 电化学氧化机制

Figure 10. Electrochemical oxidation mechanism

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图 11 复合材料层间剪切强度(ILSS) (a)及其与纤维表面氧含量的关系(b)

Figure 11. Interfacial shear strength (ILSS) of composites (a) and its relationship with oxygen content on the fiber surface (b)

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图 12 碳纤维增强环氧树脂复合材料的形貌结构

Figure 12. Morphological structure of carbon fiber reinforced epoxy resin composites

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图 13 碳纤维增强环氧树脂复合材料中拔出纤维的表面形貌

Figure 13. Surface morphology of fibers pulled out in carbon fiber reinforced epoxy resin composites

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表 1 化合物缩写及涵义

Table 1. Appendix main abbreviations and meanings of samples

Fiber sample	Composite sample	Electrolyte type in oxidation
UCF	UCFC	Untreated
NPCF	NPCFC	(NH₄)₃PO₄
NHCCF	NHCCFC	NH₄HCO₃
NSCF	NSCFC	(NH₄)₂SO₄
NHPCF	NHPCFC	NH₄H₂PO₄
Notes: CF—Carbon fiber; C—Composite.

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表 2 电解质溶液pH值

Table 2. pH of electrolyte solutions

Electrolyte solutions (2.5wt%)	pH
(NH₄)₃PO₄	8.5
NH₄HCO₃	8.0
(NH₄)₂SO₄	5.7
NH₄H₂PO₄	4.6

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表 3 电化学氧化处理前后HMCF的XRD结构参数

Table 3. XRD structural parameters of HMCF before and after electrochemical oxidation

Sample	2θ/(º)	d₍₀₀₂₎/nm	β_1/2/(º)	L_C/nm
UCF	26.084	0.34134	1.727	4.68
NPCF	26.328	0.33823	1.810	4.46
NHCCF	26.152	0.34046	1.702	4.74
NSCF	26.250	0.33922	1.769	4.57
NHPCF	26.285	0.33877	1.789	4.52
Notes: θ—Diffraction angle; d₍₀₀₂₎—Average interlayer spacing; L_C—Crystallite thickness; β_1/2—Full width at half maxima of (002) peak.

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表 4 电化学氧化处理前后HMCF的Raman图谱参数

Table 4. Raman spectrum parameters of HMCF before and after electrochemical oxidation

Sample	D-line		G-line		D'-line		I_D/I_G	I_D'/I_G
Sample	Peak position/cm⁻¹	Area	Peak position/cm⁻¹	Area	Peak position/cm⁻¹	Area	I_D/I_G	I_D'/I_G
UCF	1346.45	326039.05	1576.82	780519.02	1613.95	33604.87	0.418	0.043
NPCF	1346.33	1945521.02	1583.71	1066397.18	1614.47	155600.84	1.824	0.146
NHCCF	1348.04	180253.59	1578.84	359296.04	1615.35	17618.14	0.502	0.049
NSCF	1346.91	1054326.44	1579.69	879123.16	1615.73	72909.15	1.199	0.083
NHPCF	1343.08	2520042.64	1576.66	1672045.13	1610.80	217845.53	1.507	0.130
Notes: I_D/I_G—Integral area ratio of D-band and G-band; I_D'/I_G—Integral area ratio of D'-band and G-band.

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表 5 电化学氧化处理前后HMCF的表面元素含量

Table 5. Surface element content of HMCF before and after electrochemical oxidation

Sample	C1s/%	O1s/%	N1s/%	O/C/%	N/C/%
UCF	98.72	0.93	0.00	0.01	0.00
NPCF	73.35	20.70	3.71	0.28	0.05
NHCCF	93.00	4.83	0.36	0.05	0.00
NSCF	86.64	12.24	0.07	0.14	0.00
NHPCF	77.04	19.55	1.32	0.25	0.02

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表 6 电化学氧化处理前后HMCF的表面官能团相对含量

Table 6. Relative contents of surface functional groups on HMCF before and after electrochemical oxidation

Sample	C=C/%	C—C/%	C—O/C—N/%	C=O/%
UCF	53.26	25.15	21.59	—
NPCF	43.38	23.39	20.18	13.15
NHCCF	53.78	26.55	19.68	—
NSCF	33.88	39.05	22.42	4.65
NHPCF	55.10	12.17	24.44	8.28

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表 7 电化学氧化处理前后HMCF的直径

Table 7. Diameter of HMCF before and after electrochemical oxidation treatment

Sample	Diameter/nm
UCF	4.89
NPCF	4.73
NHCCF	4.87
NSCF	4.87
NHPCF	4.86

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