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摘要: 采用动态渗透法研究了不同结构的纳米炭纤维(Carbon nanofibers, CNF)表面润湿性以及在不同溶剂中润湿性的变化和表面改性对其润湿性的影响。结果表明,生长条件如催化剂组成、碳源等对CNF的表面性质有显著影响,并最终决定其在溶剂中的润湿能力。以Fe/γ-Al2O3为催化剂,以C2H4为碳源得到的CNF在水中的润湿性能最差;而以Ni/γ-Al2O3为催化剂,CO为碳源得到的CNF在环己烷中的润湿性能最好。CNF在不同溶剂中的相对接触角测定表明CNF是一种表面非极性较强的材料。设CNF在润湿性能最好的环己烷中的接触角为0°,则CNF在水,丙酮,乙醇中的相对接触角分别为81.6°,45.2°,24.8°。不同的表面改性手段可对CNF的表面性质进行调变以控制其在不同溶剂中的润湿行为。在浓硝酸中液相氧化可提高其对水溶液和环己烷的润湿性能;在氩气中的高温热处理可提高其对水溶液的润湿性能,但降低了对环己烷的润湿能力;而在过氧化氢溶液中的处理则同时降低了对水溶液以及环己烷的润湿能力。
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关键词:
- 纳米炭纤维,润湿,动态法,相对接触角
Abstract: The surface chemical properties and wettability of carbon nanofibers(CNFs)synthesized by CVD were studied by wicking kinetic measurements. The influence of the microstructure, preparation conditions and the surface modification of the CNFs on their wettability in different solvents were investigated. Results indicated that the preparation conditions such as catalyst composition, and especially the carbon source, have an obvious effect on the surface properties and wettability of CNFs. CNFs from Fe/γ- Al2O3 and C2H4 has the worst wettability in water, while CNFs from Ni/γ- Al2O3 and CO has the best wettability in cyclohexane. Measurement of contact angle in cyclohexane, acetone, ethanol and water showed that interaction between the CNF surface and the solvent changed significantly with the solvent used. The contact angles of CNFs from Fe/γ- Al2O3 and CO in water, acetone and ethanol relative to that in cyclohexane (in which the contact angle is arbitrarily set to 0°), are 81.6°,45.2°,24.8° respectively. It is believed that a small polarity of the CNF surface leads to its higher wettability in a non-polar solvent such as cyclohexane than in polar solvent such as water. The nature of the CNF surface groups and the wettability of CNFs in different solvents could be tailored by different surface modifications. Treatment in concentrated nitric acid increased the CNF wettability both in water and in cyclohexane, while treatment in hydrogen peroxide decreased the CNF wettability in both solvents. Interestingly, thermal treatment in argon increased the CNF wettability in water, but decreased it in cyclohexane.
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