酸氧化处理对多壁碳纳米管表面基团的影响

120℃下用浓硝酸对多壁碳纳米管(MWCNTs)进行不同时间的酸氧化处理,考察处理前后碳纳米管的形貌和元素变化,分析酸氧化处理MWCNTs表面功能基团的种类和含量.结果表明:浓硝酸处理,可在MWCNTs表面产生不同数量的羧基、羟基和羰基含氧基团;在最初2h内,羧基含量增加,羟基和羰基含量先增后减,含氧基团总量迅速增加;处理时间继续增加,羧基含量逐渐减少,羟基和羰基含量发生不规则变化,含氧基团总量趋于稳定;MWC-NTs表面首先形成羟基和羰基,这些基团继续被氧化生成羧基,并且它们被氧化生成羧基的能力不同,生成的羧基可进一步氧化最终以CO2释放出来;可通过控制浓硝酸处理的时间来控制MWCNTs表面含氧基团的种类和数量.     

聚乙烯/马来酸酐接枝聚合物修饰多壁碳纳米管

多壁碳纳米管(MWCNTs)与混酸(浓硫酸∶浓硝酸体积比为3∶1)和无水乙二胺进行酸化、胺化反应使MWCNTs表面产生羧基和氨基基团,进而与聚乙烯/马来酸酐接枝聚合物(PE-g-MA)发生开环反应制备PE-g-MWCNTs,以提高MWCNTs在聚乙烯基体中的分散性。采用红外光谱、X-射线光电子能谱(XPS)和拉曼光谱对MWCNTs的化学修饰进行定性表征。结果表明:当MWCNTs的体积分数为0.67%时,MWCNT/PE复合材料的体积电阻率发生渗流突变。MWCNTs的体积分数在0.1%～1.2%时,MWCNT/PE复合材料体积电阻率由1016Ω.m下降至105Ω.m。     

功能化碳纳米管负载钯纳米催化剂提高苯甲醇选择性氧化

对多壁碳纳米管进行纯化和功能化处理,比较了未氧化处理与经浓硝酸和浓硫酸混酸(浓硫酸与浓硝酸体积比为3∶1)处理后的不同多壁碳纳米管(MWCNTs)为载体的Pd催化剂(Pd/MWCNTs)的分散性和粒径。利用X线粉末衍射仪(XRD)、透射电镜(TEM)、X射线能谱(EDS)和傅里叶变换红外光谱仪(FT-IR)等测试手段对所得的样品进行了表征。结果表明,MWCNTs表面不修饰不利于金属Pd纳米粒子的沉积,混酸处理使MWCNTs表面有大量的含氧活性基团,能够促进负载的Pd纳米粒子均一分布,明显提高了苯甲醇氧化为苯甲醛的选择性和转化率。     

碳纳米管/壳聚糖载体的静电自组装及其表征

采用混酸氧化法制备表面带负电的羧基化碳纳米管分散体系,以叶酸靶向受体改性壳聚糖,通过羧基化碳纳米管与叶酸改性壳聚糖进行静电自组装,制备了生物相容性好、肿瘤靶向性高的碳纳米管/壳聚糖药物复合载体材料(FA/CS-SWCNTs).利用FTIR、XPS、SEM和TG等分析方法对相应产物的形貌和结构进行了研究.实验结果表明叶酸改性壳聚糖成功组装到羧基化碳纳米管上,热重分析显示该复合材料中壳聚糖的质量分数达到35％,其中叶酸在壳聚糖上的偶联率为8.1％,该载体材料具有良好的亲水性、安全性和靶向性等优点,有望成为新型的肿瘤靶向功能载体材料.     

碳纳米管的表面修饰及其对碳纳米管/氟橡胶复合材料导电性能的影响

分别采用混酸和四氟化碳(CF4 ) 等离子体处理技术对碳纳米管(MWCNTs) 进行了表面修饰, 将处理前后的碳纳米管进行了XPS 和SEM 测试, 获得了处理后前的表面形貌和结构, 并采用溶液浇注的方式制备了MWCNTs/氟橡胶(FE) 复合材料, 探讨了不同碳纳米管状态(未处理、混酸处理、CF4等离子体处理) 的导电性能, 结果表明两种表面处理方式可以使MWCNTs 表面接上极性官能团。而且在相同的碳纳米管添加量下(质量分数分别为0. 1 %、0. 5 %、1. 0 %、2. 0 %) , 酸处理MWCNTs/ FE 的渗流阈值最小, 达0. 5 %。      

多壁碳纳米管的对氨基苯磺酸钠修饰及对Cu2+的吸附性能

通过在多壁碳纳米管(MWCNTs)表面氧化出羧基,将羧基转化为酰氯,然后将对氨基苯磺酸钠与MWCNTs表面的酰氯发生酰胺化反应,制备了对氨基苯磺酸钠接枝的水溶性多壁碳纳米管(MWCNT-C6H5SO3Na)。红外光谱研究表明,对氨基苯磺酸钠以共价键方式接枝到MWCNTs表面;热重分析表明对氨基苯磺酸钠在MWCNTs表面的质量分数达到29.9%。MWCNT-C6H5SO3Na具有良好的水溶性及分散性。吸附性能测试结果表明,MWCNT-C6H5SO3Na对Cu2+的吸附性能较MWCNTs原粉有了显著的提高,吸附等温线符合Freundlich等温吸附方程。     

CNTs的表面改性及其在环氧树脂复合材料中的应用

首先采用浓硫酸/浓硝酸对多壁碳纳米管(MWCNTs)进行混酸氧化处理,再将氧化后的CNTs与DOPO改性后的硅烷偶联剂(DOPO-KH560)进行改性,制备了DOPO-KH560表面化学修饰的MWC-NTs。在此基础上,将改性前后的CNTs分散在环氧树脂体系中,制成样条,研究了处理前后样条力学性能的变化。材料表面结构的红外光谱(FT-IR)分析表明,CNTs混酸氧化成功,表面成功引入了羟基和羧基,而且DOPO-KH560成功接枝到酸化CNTs上。材料微结构的透射电子显微镜(TEM)观察表明,酸化后MWCNTs被截短,分散性变好,接枝DOPO-KH560后CNTs表面包覆了一层低聚物。对处理后的样条进行力学性能测试并用扫描电镜(SEM)分析观察断面形态的变化。结果表明,环氧树脂中加入CNTs,能有效地增加环氧树脂的韧性和强度,且加入原CNTs、氧化CNTs、改性后的CNTs时增强增韧效果逐渐增加,加入最终CNTs后环氧树脂的增强增韧效果最明显。     

多壁碳纳米管的氧化剪断处理及其分散性

利用混合强酸对多壁碳纳米管(MWCNTs)进行氧化浸泡处理。采用透射电镜、原子力显微镜、Raman光谱、红外光谱等分析手段对处理前后的MWCNTs进行表征,探索氧化浸泡时间对MWCNTs微观形貌及剪断过程的影响,并对氧化剪断后短碳管在水溶液中的分散性进行研究。结果表明,MWCNTs在混酸中浸泡72 h左右可以使其从缺陷处剪断,形成管长为200~1 500 nm的短直管,且碳管表面及端口处嫁接上羟基和羧基活性基团。由于极性官能团的存在,使得MWCNTs的等电点从4.5下降到3.5,沉降实验和分光光度测试显示短碳管在有适量阴离子型表面活性剂存在的pH≈2的水溶液中超声振荡40min后具有良好的分散效果。     

多壁碳纳米管负载纳米二氧化钛的制备及其分散性研究

在超声波震荡作用下,采用浓硝酸浸泡,对多壁碳纳米管( MWCNTs)进行纯化;以钛酸四丁酯为前驱体,利用溶胶-凝胶法制备负载纳米二氧化钛的MWCNTs,并研究了不同处理工艺对MWCNTs分散性能的影响.利用TEM,XRD分析分别对MWCNTs的形貌和物相组成进行表征.结果表明:采用浓硝酸浸泡可以有效地纯化MWCNTs;利用溶胶-凝胶法可以在MWCNTs表面负载纳米TiO2;纯化、负载纳米TiO2和超声波震荡可以提高MWCNTs在乙醇中的分散性.     

单壁碳纳米管的氧化修饰及表面官能团研究

为了丰富单壁碳纳米管（SWNTs）表面的官能团,增加碳管的化学反应活性,采用混酸氧化和紫外光辐照催化条件下氨-氧化等表面修饰手段对SWNTs进行表面修饰,傅立叶变换红外光谱（FTIR）、透射电子显微镜（TEM）和X射线光电子能谱（XPS）测试表明,混酸氧化使SWNTs端口打开,表面变得粗糙,管壁引入了羧基等活性官能团,进一步的氨-氧化使得SWNTs表面引入氨基,同时部分羧基转变为酰胺基。     

Effective chemical oxidation on the structure of multiwalled carbon nanotubes

A two-step chemical oxidation of multiwalled carbon nanotubes (MWCNTs) with different oxidation reagents was particularly studied. The reagents used in first step were the acidic mixture of sulfuric acid and nitric acid, and the reagents used in the second step were a mixture of sulfuric acid and hydrogen peroxide for different time. After each treatment, the functionalization yield of the oxygen-containing groups such as carboxylic group, hydroxyl functional groups and other functional groups on the surface of the carbon nanotubes (CNTs), was quantified by the analysis of XPS measurements. Two-step for a short period of time treated MWCNTs exhibited a larger fraction of carboxyl (COOH) groups compared to one step and two step for longer-time oxidative treatments, and the defect formation on the CNTs was verified mild by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy and transmission electron microscopy (TEM) graphs, which is necessary for derived reaction and better manipulation of the material and use in the application of the carbon nanotubes.     

Adsorption of Dinitrogen Tetroxide (N2O4) on Multi-walled Carbon Nanotubes (MWCNTs)

The adsorption of dinitrogen tetroxide (N₂O₄) on multi-walled carbon nanotubes (MWCNTs) has been studied by FT-IR, Raman and X-ray photoelectron spectroscopy (XPS). The N₂O₄ adsorption is fully reversible, and after the desorption there is no evidences of MWCNTs nitration. Instead, the MWCNTs have been found oxidized by the action of N₂O₄. By thermogravimetric analysis (TGA) about 5% by weight of oxygenated groups have been found. Thermal analysis has revealed that MWCNTs having a surface area of 275 m²/g are able to reversibly adsorb about 25% by weight of N₂O₄, a value comparable to that observed for certain active carbons.     

Functionalization of textiles with multi-walled carbon nanotubes by a novel dyeing-like process

Multi-walled carbon nanotubes (MWCNTs) were functionalized with oxygen-containing surface groups and subsequently incorporated in cotton and polyester fabrics by a process that mimics the traditional industrial dyeing process. The washing fastness, hydrophobicity and flame retardancy of the functional textiles were evaluated. The MWCNTs surface chemistry was modified by three different routes: (i) liquid phase oxidation with nitric acid, in order to introduce acidic oxygen-containing groups, (ii) thermal treatment of the sample oxidized in (i), in order to remove the carboxylic acid functionalities and (iii) gas phase oxidation with 5% oxygen in nitrogen to incorporate basic and neutral groups. All samples were characterized by temperature programmed desorption, pH at the point of zero charge and N₂ adsorption–desorption isotherms at −196 °C. The effect of the MWCNTs acidity/basicity and of the type of substrate in the nanomaterials incorporation efficiencies and in the performance of the final textile materials was assessed. The scanning electron microscopy images and the whiteness degree values of the functional textiles before and after washing indicated that the incorporation efficiency was higher for the textiles containing the most acidic MWCNTs, especially for the polyester textiles. The immobilization of the less acidic MWCNTs in polyester imparted hydrophobic properties to the fabrics surface; in particular, the polyester samples functionalized with unmodified and O₂-oxidized MWCNTs presented an almost superhydrophobic behaviour. In the case of the cotton-based samples, a hydrophobic behaviour was not achieved. Finally, the flame-retardant properties of both substrates improved upon the MWCNTs immobilization.     

Catalytic performance of acid-treated multi-walled carbon nanotube-supported platinum catalyst for PEM fuel cells

Effects of the surface functional groups of multi-walled carbon nanotubes (MWCNTs) as catalyst support for the durability of polymer electrolyte membrane fuel cells (PEMFCs) were examined at high Pt loading conditions. The amount of oxygen functional groups on the MWCNTs surface was increased as the acid treatment time and temperature increased. We found that more functional groups in MWCNTs improved initial Pt dispersion but deteriorated durability due to the reduced carbon corrosion resistance. The experimental results also showed that despite the surface oxidation, Pt/MWCNT catalysts showed highly improved durability than Pt/C catalysts due to the graphitic nature of MWCNTs. Membrane electrode assembly (MEA) fabricated by 4 h acid treated MWCNTs at 25 °C showed 4 times better durability than commercial Pt/C based MEA at the reverse potential operation generated by fuel starvation conditions. We believe that MWCNTs can be effectively used for PEMFCs even at high loading due to their excellent anti-corrosion properties.     

On the Role of Stearic Acid on the Surface Properties of Carbon Nanotubes

In this article, modification of multiwalled carbon nanotubes (MWCNTs) with stearic acid (SA) was done using the wet chemical method. For this aim, MWCNTs were treated with high-concentrated nitric acid to create a functional group as a linkage between MWCNTs and SA. The modified MWCNTs with SA were examined by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), differential scanning calorimeter (DSC), and thermogravimetery analysis (TGA) instruments. The results of TGA and DSC indicate the deposition of about 4.3 wt% of SA on the surface of MWCNTs. This proves that the deposition of stearate with a medium diameter size of 20 nm on the surface of MWCNTs can be divided into physical and chemical adsorption. As well, the esterification occurs on the surface of functionalized MWCNTs and there is no SA unreacted on the surface of MWCNTs.     

碳纳米管的表面改性对环氧树脂低温(77 K)冲击性能及热膨胀系数的影响

采用混酸氧化及表面接枝改性的方法制备了表面含不同官能团的多壁碳纳米管(MWCNTs), 并研究了不同MWCNTs对环氧树脂的低温(77 K)抗冲击性能及热膨胀系数(CTE)的影响。结果表明: 通过接枝反应将—NCO基团封端的PEO齐聚物引入MWCNTs表面, 可提高MWCNTs在环氧树脂基体中的分散性, 加强MWCNTs与环氧树脂的界面作用; 相对于纯环氧树脂, 添加质量分数为0.5%的纯MWCNTs、 氧化MWCNTs和表面接枝MWCNTs改性后的环氧树脂的低温冲击强度分别升高了10.27%、 26.13%和32.95%, 而CTE则分别降低了14.79%、 29.59%和40.29%。这表明表面接枝改性MWCNTs可明显提高环氧树脂基体的低温抗冲击性能并降低环氧树脂在玻璃化转变温度下的CTE。     

羰基、羧基和羟基表面官能团对碳纳米管电容量的影响

分别采用混酸、空气、硝酸和高锰酸钾对碳纳米管进行氧化处理,以在其表面引入官能团,进而研究了表面官能团对碳纳米管电化学性能的影响.X-射线光电子谱分析表明:混酸氧化处理引入的官能团主要为羰基和羧基;空气氧化使碳纳米管表面链接较多的羟基,但羰基和羧基的含量最少;而硝酸处理和高锰酸钾处理引入了中等数量的羰基和羧基.经四种处理方法所得碳纳米管具有相近的比表面积和孔结构.通过比较它们的比电容发现:羰基和羧基贡献了最多的准电容,尤其羰基含量与碳纳米管的电容量呈正比关系;而羟基主要增强了双层电容,并未引入明显的准法拉第容量.由于羰基和羧基比羟基具有更低的电荷传递电阻,有利于快速的法拉第反应,从而引入准电容.     

Microstructure and mechanical properties of Al2O3 composites with surface-treated carbon nanotubes (CNTs): dispersibility of modified carbon nanotubes (CNTs) on Al2O3 matrix

Aluminum oxide (Al2O3) matrix have been reinforced by the multi-walled carbon nanotubes (MWCNTs) to overcome the inherent brittleness of Al2O3 matrix. In order to increase mechanical properties of MWCNTs-Al2O3 composites, MWCNTs need to be well dispersed and individually incorporated in Al2O3 matrix. In this work, aluminum hydroxide (Al(OH)3) used as a Al2O3 precursor and MWCNTs were mixed in an aqueous solution for the homogeneous mixing of hetero-particles, as functions of the content of MWCNTs and the potential hydrogen (pH) of Al(OH)3 suspension. Firstly, MWCNTs were purified and modified by an acid reagent, inducing that the dispersibility of MWCNTs is increased in an aqueous solution by carboxylic group given on the surface of MWCNTs. The modified MWCNTs were added in the Al(OH)3 suspension, and then the mixture was filtered at room temperature. The filtered powders were formed using an uniaxial pressing and then densified by a pressureless heat treatment. As the pH is decreased the Al(OH)3 particles are well dispersed in an aqueous solution, due to the increment of repulsive force between particles with a same surface charge. MWCNTs are individually incorporated into Al2O3 matrix up to 1 vol.% MWCNTs, whereas MWCNTs are aggregated at the composite with 3 vol.% MWCNTs. Therefore, control of the pH and the MWCNTs content are key factors to be considered for the fabrication of MWCNTs-Al2O3 composites with high functional properties.