羧化多壁碳纳米管/维生素B_(12)修饰电极测定多巴胺

制备了羧化多壁碳纳米管/维生素B12修饰玻碳电极,利用循环伏安法研究了多巴胺(DA)在此修饰电极上的电化学行为。结果表明,在pH为6.48的PBS缓冲溶液中,此修饰电极对DA有很强的电催化作用,明显增强了峰电流,峰电位差ΔEp由196 mV减小至69 mV,提高了电极反应的可逆性。在优化实验条件下,此修饰电极所测DA氧化峰电流与DA浓度在1.0×10-5~5.0×10-5mol/L及1.0×10-3~1.0×10-2mol/L范围内均呈线性,线性方程分别为y=373.78x+71.726(R2=0.995 8)和y=57.2x+365.22(R2=0.986 6),其中低浓度区的相关系数较高,应用于实际样品测定时结果较为满意。检测限可达8.0×10-8mol/L。     

Improvements in interfacial and heat-resistant properties of carbon fiber/methylphenylsilicone resins composites by incorporating silica-coated multi-walled carbon nanotubes

The multi-scale reinforcement and interfacial strengthening on carbon fiber (CF)-reinforced methylphenylsilicone resin (MPSR) composites by adding silica-coated multi-walled carbon nanotubes (SiO₂-CNTs) were investigated. SiO₂-CNT has been successfully prepared via the hydrolysis of tetraethoxysilane in the presence of acid-oxidized multi-walled carbon nanotubes. Transmission electron microscopy, X-ray diffraction, and Fourier Transform infrared spectroscopy were carried out to examine the functional groups and structures of CNTs. Then, SiO₂-CNT was incorporated into MPSR matrix to prepare CF/MPSR-based composites by the compression molding method. The effects of the introduced SiO₂-CNT on the interfacial, impact, and heat-resistant properties of CF/MPSR composites were evaluated by short-beam bend method, impact test, and thermal oxygen aging experiments, respectively. Experimental results revealed that the CF/MPSR composites reinforced with 0.5 wt% SiO₂-CNT showed a significant increase 34.53% in the interlaminar shear strength (ILSS) and 20.10% in impact properties. Moreover, the heat-resistant properties of composites were enhanced significantly by adding SiO₂-CNT hybrid nanoparticles. These enhancements are mainly attributed to the improved matrix performance resulted from the molecular-level dispersion of SiO₂-CNT in MPSR matrix and the strong interfacial adhesion between SiO₂-CNT and matrix resin, which are beneficial to improve the mechanical stress transfer from MPSR matrix to CFs reinforcement and alleviate stress concentrations.     

多壁碳纳米管吸附处理柴油废水的动力学特性

通过静态吸附实验研究了多壁碳纳米管(MWCNTs)对柴油废水中油的吸附特性,并与活性炭进行了比较。表明MWCNTs和活性炭对柴油的吸附量均在前10 min上升迅速60 min左右可达到吸附平衡,但MWCNTs的吸附能力远大于活性炭。在动力学分析中发现准二级动力学模型能较好地符合研究体系,且随温度的升高,吸附速率增加。根据Arrhenius公式,算得MWCNTs吸附柴油2^#的活化能(E_a)的值为14.21 kJ·mol^-1,可推断吸附应是物理吸附。利用颗粒内扩散模型发现MWCNTs吸附分外表面吸附、碳管间大空隙的内扩散和管间小空隙内扩散3阶段,而活性炭对柴油2^#的吸附分为外表面吸附和颗粒内扩散两个阶段,且受边界层的影响较大。MWCNTs对柴油的吸附存在初始吸附行为。在298 K下MWCNTs对3种柴油的吸附及在288、298和308 K下对柴油2^#的吸附,都是中等起始吸附,柴油2^#的吸附,随温度的升高,起始吸附行为增强,在318 K时吸附过程具有较强烈的起始吸附行为。     

Parameters regulating interfacial and mechanical properties of short glass fiber reinforced polypropylene

The performance of thermoplastic composites is known to depend on the intrinsic properties of the two composite components, the quality of the fiber–matrix interface, and the crystalline properties of their matrix. The objective of this work is to characterize the effect of the addition of modified polypropylene (PP) and silane coupling agent on the mechanical and interfacial properties of short fiber reinforced PP composites. Differential scanning calorimetry (DSC), single fiber composite fragmentation tests (SFC), and mechanical testing are used to understand the different parameters regulating the interfacial properties of composites. No influence of the modified PP on the level of crystallinity is observed. Some differences in the size of the spherulites are observed for acrylic acid grafted PP (PP‐g‐AA). Those samples also show lower mechanical properties in spite of good interfacial interactions. Maleic anhydride grafted PP (PP‐g‐MAh) leads to better mechanical performances than PP‐g‐AA. A high MAh content PP‐g‐MAh grade with low viscosity is the best polymeric additive used in the present work. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2047–2060, 2000     

TPU/PLA nanocomposites with improved mechanical and shape memory properties fabricated via phase morphology control and incorporation of multi-walled carbon nanotubes nanofillers

Shape memory polymer nanocomposites based on thermoplastic polyurethane (TPU)/polylactic acid (PLA) blends filled with pristine multi-walled carbon nanotubes (MWCNTs) and modified MWCNTs─COOH were fabricated by direct melt blending technique and investigated for its morphology, mechanical, thermal, electrical, and shape memory properties. Morphological characterizations by using transmission electron microscope (TEM) and field emission scanning electron microscope (FESEM) revealed better dispersion of MWCNTs─COOH in the polymer blend, which is attributed to the improved interfacial interactions between the polymer blends and MWCNTs-COOH. Loading of the MWCNTs-COOH in the TPU/PLA blends resulted in the significant improvements in the mechanical properties such as tensile strength and elastic modulus and these effects are more pronounced on increasing the MWCNTs─COOH loading amount, when compared to the pristine MWCNTs filled system. Thermal analysis showed that the glass transition temperature of the blends increases slightly with increasing loading of both pristine and modified MWCNTs in the system. The resistance of nanocomposites decreased from 2 × 10¹² Ω to 3.2 × 10¹⁰ Ω after adding 3% MWCNTs─COOH. The shape memory performance tests showed that the enhancement of shape recovery by 252% could be achieved at 3% MWCNTs loading, when compared to that of TPU/PLA blends.     

Capacitance properties of multi-walled carbon nanotubes modified by activation and ammoxidation

Catalytic multi-walled carbon nanotubes were modified by KOH activation at 800 °C and/or ammoxidation at 350 °C, and the effect of these treatments on the physicochemical and electrochemical properties was investigated. Whereas texture is moderately changed by ammoxidation, the chemical composition is significantly modified due to the formation of various nitrogen containing groups. The influence of nitrogenated functionality (pyridine, pyridone, NH) on charge accumulation is considered in full electrochemical capacitors, as well as in positive and negative electrodes separately, using acidic (4 mol L⁻¹ H₂SO₄) and alkaline (7 mol L⁻¹ KOH) electrolytes. The presence of nitrogen in the carbon network, especially in the form of pyridone/pyrrolic (N5) and/or pyridine (N6) groups, affects the electron density and enhances the charge affinity of the carbon material. It seems that the nitrogen groups improve particularly the capacitance performance of the negative electrode operating in alkaline medium. Besides the nitrogenated groups, the oxygenated functionality plays also an important role for the ammoxidized nanotubes. Generally, a few-fold increase of capacitance was observed in the N-enriched carbon nanotubular samples. Apart of this capacitance improvement, the presence of nitrogen in the carbon network limits significantly the leakage current and diminishes the self-discharge of supercapacitors.     

多壁碳纳米管的有机修饰与表征

为了增加多壁碳纳米管(MWCNTs)表面活性,通过浓H2SO4和浓HNO3处理过的MWCNTs与SOCl2回流进而与合成的N-乙基-3,6-二氨基咔唑反应,得到了有机修饰的MWCNTs.用傅立叶变换红外(FTIR)光谱对有机修饰的MWCNTs结构进行研究.研究结果结构表明:有机修饰的MWCNTs红外光谱在1617和16...     

Formation of Ziegler-type catalytic systems on the surface of multi-walled carbon nanotubes for the production of composite materials by in situ polymerization

The peculiarity of formation of Ziegler-type catalytic systems prepared using organoaluminum (AlR₃) and organomagnesium (MgR₂) on the surface of multi-walled carbon nanotubes (MWCNTs) was revealed. We have found first AlR₃ and MgR₂ interact with different sites on MWCNT surface. It was demonstrated by IR spectroscopy that organoaluminum compounds were immobilized on the hydroxyl-containing groups on MWCNT surface. Organomagnesium compounds were immobilized on the topological structural defects of MWCNTs; hydroxyl-containing groups were not required for their immobilization. Further interaction between TiCl₄ and organomagnesium compound immobilized on the MWCNT surface yielded a catalyst containing titanium and magnesium chlorides (an analogue of the known titanium–magnesium catalysts), which exhibits an enhanced activity in ethylene polymerization. The effect of polymerization conditions on molecular weight characteristics of polyethylene in the MWCNT/PE composite material produced by in situ polymerization over the catalyst immobilized on the MWCNT surface was studied. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48212.     

Processing of yttria stabilized zirconia reinforced with multi-walled carbon nanotubes with attractive mechanical properties

The improvement of the mechanical properties of carbon nanotube reinforced polycrystalline yttria-stabilized zirconia (CNT-YSZ) was questionable in earlier investigations due to several difficulties for processing of these composites. In the present article, the authors are proposing a successful technique for mixing pre-dispersed CNTs within YSZ particles followed by a fast spark plasma sintering at relatively low temperature, resulting in near full-dense structure with well-distributed CNTs. Composites with CNT quantities ranging within 0.5-5 wt% have been analyzed and a significant improvement in mechanical properties, i.e. Young's modulus, indentation hardness and fracture toughness with respect to monolithic YSZ could be observed. To support these interesting mechanical properties, high-resolution electron microscopy and Raman spectroscopy measurements have been carried out. The analysis of densification shows that the lower densification rate of CNT reinforced composites with respect to the pure YSZ could be attributed to a slower grain boundary sliding or migration during sintering.     

Effects of fiber surface grafting by functionalized carbon nanotubes on the interfacial durability during cryogenic testing and conditioning of CFRP composites

Carbon fiber reinforced epoxy (CE) composite is ideal for a cryogenic fuel storage tank in space applications due to its unmatched specific strength and modulus. In this article, inter-laminar shear strength (ILSS) of carbon fiber/epoxy (CE) composite is shown to be considerably improved by engineering the interface with carboxyl functionalized multi-walled carbon nanotube (FCNT) using electrophoretic deposition technique. FCNT deposited fibers from different bath concentrations (0.3, 0.5, and 1.0 g/L) were used to fabricate the laminates, which were then tested at room (30°C) and in-situ liquid nitrogen (LN) (−196°C) temperature as well as conditioning for different time durations (0.25, 0.5, 1, 6, and 12 h) followed by immediate RT testing to study the applicability of these engineered materials at the cryogenic environment. A maximum increment in ILSS was noticed at bath concentration of 0.5 g/L, which was ~21% and ~ 17% higher than neat composite at 30°C and − 196°C, respectively. Short-term LN conditioning was found to be detrimental due to developed cryogenic shock, which was further found to be compensated by cryogenic interfacial clamping upon long-term exposure.     

Enhancement of physical and mechanical properties of polyamide 66 fibers using polysiloxane-functionalized multi-walled carbon nanotubes

A polyamide 66/3-aminopropyl-terminated poly(dimethylsiloxane) (PA66/APDMS)-carboxylate multiwalled carbon nanotubes (CMWNTs) nanocomposite (PA66/APDMS-CMWNTs) was synthesized using a one-pot method, and the product was melt-spun into fibers. The glass transition temperature (T_g) of the PA66/APDMS-CMWNTs nanocomposite fiber is 68.0°C, which is 22% higher than that of the pure PA66 fiber. This result indicates that there is a strong interfacial interaction between APDMS-CMWNTs and the PA66. Furthermore, the crystallinity of PA66/APDMS-CMWNTs nanocomposite fiber reaches a maximum due to the addition of APDMS-CMWNTs. Additionally, the tensile strength and Young's modulus of PA66/APDMS-CMWNTs nanocomposite fiber are 167% and 631% higher, respectively, than that of the pure PA66 fiber. The strengthening mechanism was discussed using force balance-based expression, which demonstrates that the stress on the PA66 is more efficiently transferred to the APDMS-CMWNTs. These results argue that using APDMS-CMWNTs as a filler can enhance the physical-mechanical properties of PA66 with an elevated degree never being reported.     

Preparation and mechanical properties of natural rubber powder modified by carbon nanotubes

A suspension of carbon nanotubes in natural latex was obtained by liquid mixing and then was used to prepare powder natural rubber composites modified with carbon nanotubes by means of spray drying process. The composite powders were round‐like and fine, with an average diameter of less than about 5 μm. The dispersion of carbon nanotubes in the rubber matrix was improved remarkably compared with that obtained by the mechanical mixing method. By means of vulcanization tests, it was found that the addition of vulcanizing agent necessary for the powder rubber containing carbon nanotubes should be evidently greater than that in rubber prepared by mechanical mixing, there evidently existed vulcanization reversions for the natural rubber prepared by mechanical mixing, which disappeared in the powder rubber containing carbon nanotubes prepared by the spray drying process. The mechanical properties of the powder natural rubber containing carbon nanotubes were much improved because of the modification effect of carbon nanotubes in rubber. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4697–4702, 2006     

Morphology and tensile properties of polypropylene‐multiwalled carbon nanotubes composite fibers

In this work, we analyzed tensile properties of polypropylene‐multiwalled carbon nonotubes composite fibers. The multiwalled carbon nanotubes (MWCNTS) were used in different contents of 0, 1, 2, 3, 4, and 5 wt %. Dispersing agents were used to disperse MWCNTs in polypropylene matrix. After the dispersing agent was removed, the mixture was melt mixed. The fibers were spun by a home‐made melt spinning equipment and stretching was done at a draw ratio of 7.5. By using 1–5 wt % of MWCNTs, the modulus of composite fibers increased by 69–84% and tensile strength increased about 39% when compared with the virgin polypropylene fibers. In addition, the MWCNTs dispersion in the matrix was monitored by scanning electron microscopy and transmission electron microscopy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

多壁碳纳米管的氨表面改性及其臭氧催化降解草酸

采用水热方法制备了一系列用浓氨水改性的多壁碳纳米管催化剂,该催化剂的活性通过非均相催化臭氧化降解水溶液中的草酸来进行评价。降解过程符合零级反应动力学模型,且催化剂的表观动力学常数与其表面碱性基团数量以及零电位pH值（pHPZC）呈正相关。为此,可断定用浓氨在水热条件下处理多壁碳纳米管能明显提高催化臭氧降解草酸能力是因为提高了催化剂的表面碱性基团数量和pHPZC。     

Preparation and electrochemical properties of polyaniline doped with benzenesulfonic functionalized multi-walled carbon nanotubes

Nanocomposite of benzenesulfonic functionalized multi-walled carbon nanotubes doped polyaniline (PANi/f-MWCNTs) was synthesized via a low-temperature in situ polymerization method. The PANi/f-MWCNTs composite has a thin film of PANi coating uniformly on the surface of the f-MWCNTs. The electrochemical results show that PANi/f-MWCNTs nanocomposite possesses good rate response, which could ascribe to the uniform structure and the better conductivity of composite as well as the in situ doping/de-doping process between the benzenesulfonic acid groups of f-MWCNTs and PANi chain. In addition, the composite also has better capacity and cyclability than PANi/p-MWCNTs composite. It could attribute to the presence of f-MWCNTs, which makes more electrolyte contact with PANi to participate in faradaic redox reactions and dopes with the PANi polymer chain through the benzenesulfonic acid groups to form stable polyemeraldine salts.     

短碳纤维增强碳化硅基复合材料的制备

短纤维的分散均匀性一直是短纤维复合材料应用受限的主要原因．采用固相球磨分散和熔融渗硅工艺,可得到均匀分散的短碳纤维增强碳化硅基复合材料．并利用金相显微镜见察复合材料微观形貌,测试复合材料的抗弯强度和断后韧性．     

Thermo-physical and impact properties of epoxy nanocomposites reinforced by single-wall carbon nanotubes

The thermo-physical properties and the impact strength of diglycidyl ether of bisphenol F (DGEBF) epoxy nanocomposites reinforced with fluorinated single-wall carbon nanotubes (FSWCNT) are reported. A sonication technique was used to disperse FSWCNT in the glassy epoxy network resulting in nanocomposites having large improvement in modulus with extremely small amount of FSWCNT. The glass transition temperature decreased approximately 30 °C with an addition of 0.2 wt% (0.14 vol%) FSWCNT, without adjusting the amount of the anhydride curing agent. This was because of non-stoichiometry of the epoxy matrix that was caused by the fluorine on the single-wall carbon nanotubes. The correct amount of the anhydride curing agent needed to achieve stoichiometry was experimentally examined by dynamic mechanical analysis (DMA). The storage modulus of the epoxy at room temperature (which is below the glass transition temperature of the nanocomposites) increased up to 0.63 GPa with the addition of only 0.30 wt% (0.21 vol%) of FSWCNT, representing an up to 20% improvement compared with the neat epoxy. The Izod impact strength slightly decreased when the amount of FSWCNT was increased to 0.3 wt%. The excellent improvement in the storage modulus was achieved without sacrificing impact strength.     

Polymer adsorption in the grafting reactions of hydroxyl terminal polymers with multi-walled carbon nanotubes

Melt stirring of non-functional polymers such as poly(ethylene oxide) dimethylether (PEO-Me) and polystyrene (PS-H) with multiwalled carbon nanotubes (MWNTs) in the absence of solvent for 48 h induced a substantial amount of polymer adsorption on the MWNTs. The chloroform extraction of the reaction products using centrifugation yielded black colored solutions exhibiting UV absorbance corresponding to the presence of MWNTs. The adsorption of polymer was confirmed on the surfaces of solvent washed residual and recovered MWNTs from the reactions using thermogravimetric analysis (TGA) and FT-IR spectroscopy. Covalent grafting reactions carried out using hydroxyl-terminated PEO-OH and PS-OH with acid chloride containing MWNTs under identical melt stirring condition produced similar results. The presence of polymer on the residual and recovered MWNTs irrespective of the nature of the terminal groups indicates that the adsorption of polymers poses a problem in accurately determining the grafting efficiency. FT IR spectra of the PEO-g-MWNTs shows a substantial shift in CH stretching vibrations indicating a plausible weak intermolecular interaction with π electrons of the MWNTs.     

Mechanical properties of carbon fiber reinforced bisphenol A dicyanate ester composites modified with multiwalled carbon nanotubes

A novel electrophoretic deposition (EPD) method was employed for grafting multiwalled carbon nanotubes (MWCNTs) on carbon fibers, which, after impregnation with bisphenol A dicyanate ester (BADCy), synergistically reinforced BADCy matrix composites (CNT‐C/BADCy). The effect of MWCNT presence on the mechanical properties of the composites was investigated. Composite tensile strength increased by 45.2% for an EPD duration of 2 min, while flexural strength exhibited a decreasing trend with EPD duration. Optical microscopy revealed that the existence of MWCNTs enhanced the fiber‐matrix interface while a large number of CNTs were observed to have pulled‐out from the matrix, a finding which explained the observed tensile strength increase in terms of energy dissipation by the specific toughening mechanism. The flexural strength decrease of the composites with CNTs as compared to specimens without nanotubes was found linked to the increased stress concentration in the BADCy matrix due to tube presence which weakens the adhesion between carbon fabrics. In a word, carbon nanotubes will enhance the micro interface and weaken the macro interface of the composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45100.     

碳纳米管/丙烯酸酯橡胶复合材料的制备及性能研究

采用自制的大分子表面改性剂对多壁碳纳米管(MWNTs)进行表面改性,制备改性MWNTs/丙烯酸酯橡胶(ACM)复合材料,研究改性MWNTs用量对复合材料性能的影响,并与炭黑补强的ACM性能进行对比.结果表明:用MWNTs填充ACM制备的材料,其性能远优于炭黑补强的ACM橡胶的性能;随着改性MWNTs用量的增大,复合材料...