Carbon nanotube-polymer nanocomposites: The role of interfaces

Research aimed at producing new nanocomposites with improved properties has dramatically increased in the last decade, especially on materials tailored at a nanometric level, such as fullerenes and carbon nanotubes. The use of nanoforms as reinforcement of organic polymers has opened the possibility of developing novel ultra-strong and conductive nanocomposites. Nevertheless, the challenge of manufacturing multifunctional composite materials based on nanostructures is still open, in particular in the details of the corresponding interfacial properties, which are particularly relevant in these systems. This paper reviews the main technical activities in this field, focusing on the most important parameters that influence the behavior of their interface, discussing recent advances, as well as current and future trends in research.     

ESR Investigations on Polyethylene–Fluorine Functionalized Single Wall Carbon Nanotubes Composites

Electron spin resonance investigations on nanocomposites obtained by dispersing fluorinated single walled carbon nanotubes within polyethylene are reported. Three resonance lines assigned to uncoupled electronic spins confined within magnetic impurities, amorphous carbon, and single wall carbon nanotubes have been observed. The temperature dependence of these lines is analyzed in detail and used to assign each component of the as-recorded ESR spectrum to a precise component of the nanocomposite. Magnetic impurities are originating from catalysts residues (in our case, Fe impurities). Surprisingly, the narrowest line is due to paramagnetic defects (amorphous carbon) while the broad line originates from electrons delocalized over conducting nanotubes. The broadening of this line reflects a bottleneck in the relaxation mechanism, triggered by the interaction of the uncoupled electrons localized on carbon nanotubes with the magnetic impurities.     

The effect of surface treatment of carbon fiber on the flexural property of thermoplastic polyimide composite

Rare earth solution (RES) surface modification and air-oxidation methods were used to improve the interfacial adhesion of the carbon fiber reinforced polyimide (CF/PI) composite. The flexural property of the PI composites reinforced by the carbon fibers treated with different surface modification methods was comparatively investigated. Results showed that the flexural strength of CF/PI composite was improved after RES treatment. The improvement of impact and flexural property of the CF/PI composite was mainly due to the improvement in interfacial adhesion after RES treatment. X-ray photoelectron spectroscopy (XPS) study of carbon fiber surface showed that the oxygen concentration was obviously increased after RES treatment. The increase in the amount of organic functional groups increased the interfacial adhesion between CF and PI matrix.     

Covalent attachment of polystyrene on multi-walled carbon nanotubes via nitroxide mediated polymerization

A new method to attach polymers on carbon nanotubes has been studied. We used nitroxide mediated polymerization (NMP) to graft polystyrene from multi-walled carbon nanotubes (MWNTs). Carboxyl groups on MWNTs were activated with thionyl chloride (SOCl₂) to give acyl chloride derivative (MWNT-COCl). NMP initiator was introduced to MWNT by esterification of 1-hydroxy-2-phenyl-2-(2′,2′, 6′, 6′-tetramethyl-1′-piperidinyloxy)ethane (HO-PE-TEMPO) with acyl chloride groups of MWNTs. The obtained MWNT-PE-TEMPO was used for initiation of bulk polymerization of styrene, yielding polystyrene-grafted MWNTs (MWNT-g-pSt). The resulting composites of MWNT-g-pSt were analyzed by TEM, SEM, FT-IR and TGA.     

Relationship between the flexural properties and specimen aspect ratio in unidirectional composites

It is well known that the bending test provides a simple and convenient way of measuring the strength of unidirectional composite materials and gives very repeatable results. The aim of this research work was to study and analyze the flexural properties of unidirectional reinforced carbon fiber/epoxy (UD) specimens subjected to three-point loading. The effect of span-to-thickness ratio (L/h) and width-to-thickness ratio (b/h) on the three-point bending of UD composites has been investigated. Results have shown that unidirectional composites exhibit a transition in the failure mode from shear delamination to fiber yield with the span-tothickness ratio (L/h) is increased. The observed experimental data are confirmed by theoretical considerations presented here. Using the classical beam theory the conclusions of the tests could be extended by applying some reasonable requirements and simple rational fractional functions identified. This made it possible to express the asymptotic values of the flexural strength, the flexural modulus and apparent shear stress in a form that is independent from the values of the span-to-thickness ratio applied, and characterize the bending behavior of the composite materials at a more exact level.     

Nanocomposites based on multiblock polyester elastomers (PEE) and carbon nanotubes (CNT)

Polymer nanocomposites including those containing carbon nanotubes appear to be of particular significance. Polymer nanocomposites based on thermoplastic poly(ether-ester) elastomer and carbon nanotubes have been prepared and investigated. The nanocomposites are obtained (in situ) by introducing the fillers into the reaction mixture and the synthesis of copolymer by polycondensation in the molten state. The nanotubes are dispersed in 1,4-butanediol by ultrasonication. Physical properties of the resulting nanocomposites are studied using the DSC, DMTA, SEM and mechanical tensile tests.     

Tuning Surface Morphology of Inorganic Supports for Adsorptive Immobilization of Enzymatic Active Substances

A comprehensive study of composite carbon–mineral supports was performed to determine specific features of the adsorptive immobilization for such enzymes as glucoamylase and invertase. The catalytic properties (activity and stability) of immobilized enzymes were found to depend significantly on the morphology of the carbon layer synthesized on the support surface. After tuning the surface morphology towards immobilizing enzymes, a layer of catalytic filamentous carbon (CFC) was found to ensure the highest stability and activity of the prepared biocatalysts due to its mesoporous structure and optimal hydrophilic–hydrophobic balance. The supports used for immobilization of enzymes can be arranged in the following order of observed enzymatic activity and stability: supports coated by graphite-like carbon layer ≈ non-carbonized supports << CFC-coated supports.     

Measurement of fiber/matrix interface properties of C/C composites by single fiber and fiber bundle push-out methods

Interfacial fracture stresses of carbon/carbon composites were measured by indentation methods. Two types of test methods, namely, single fiber push-out, and bundle fiber push-out tests were conducted. Both methods successfully gave fiber/matrix interface mechanical properties, especially debonding behavior. However, when the interface was strong, the single fiber push-out test encountered technical difficulty in processing the extremely thin specimen required to realize the fiber push out. On the other hand, the bundle fiber push-out test gave a good estimation of interfacial fracture stresses.     

CO2电催化还原的研究 IV: 光透薄层电极(OTTLE)研究反应机理

本文用薄层电极的光谱电化学技术, 确定了催化剂碘化四[4-(三甲铵基)苯基]卟啉合钴(Co TMAPI)当恒电位控制在0.6-0.3, -1.0V时分别得以一价, 二价, 三价中心离子的可见紫外光谱, 检测到在咪唑存在下, CO2与一价钴卟啉生成的配合物, 并用易于与一价钴卟啉配位的碘甲烷来进一步证实, 从而肯定了CO2的电催化还原是通过形成CO2配合物中间体的反应途径。     

碳钢钝化膜在碳酸盐溶液中的阴极还原机理

本文采用动电位和恒电流技术研究了pH8.31-11.37的酸盐缓冲溶液中, 低碳钢钝化膜的阴极还原机理。认为钝化膜的还原与溶液pH值密切相关, 当8.31≤pH≤9.80时, Fe~2O~3还原为Fe用FeOH^+;当9.80相似文献