Linghui Meng

Omnidirectionally Stretchable High-Performance Supercapacitor Based on Isotropic Buckled Carbon Nanotube Films.

The emergence of stretchable electronic devices has attracted intensive attention. However, most of the existing stretchable electronic devices can generally be stretched only in one specific direction and show limited specific capacitance and energy density. Here, we report a stretchable isotropic buckled carbon nanotube (CNT) film, which is used as electrodes for supercapacitors with low sheet resistance, high omnidirectional stretchability, and electro-mechanical stability under repeated stretching. After acid treatment of the CNT film followed by electrochemical deposition of polyaniline (PANI), the resulting isotropic buckled acid treated CNT@PANI electrode exhibits high specific capacitance of 1147.12 mF cm(-2) at 10 mV s(-1). The supercapacitor possesses high energy density from 31.56 to 50.98 μWh cm(-2) and corresponding power density changing from 2.294 to 28.404 mW cm(-2) at the scan rate from 10 to 200 mV s(-1). Also, the supercapacitor can sustain an omnidirectional strain of 200%, which is twice the maximum strain of biaxially stretchable supercapacitors based on CNT assemblies reported in the literature. Moreover, the capacitive performance is even enhanced to 1160.43-1230.61 mF cm(-2) during uniaxial, biaxial, and omnidirectional elongations.

Interfacial properties and impact toughness of dendritic hexamethylenetetramine functionalized carbon fiber with varying chain lengths

In order to understand the effects of chain length on the interfacial adhesion of PAN-based carbon fiber (CF)/epoxy composites, dendritic hexamethylenetetramine (HMTA) was functionalized on carbon fibers through quaternary ammonium salt reaction using alkyl dihalide of varying chain length [Cl(CH2)nCl, n = 2, 6 and 12]. Fourier transform infrared spectroscopy (FTIR), Raman spectra and X-ray photoelectron spectroscopy (XPS) confirmed the successful grafting of dendritic HMTA and alkyl dihalide. AFM images showed that dendritic HMTA modified CF surfaces enhanced roughness, and this effect was more pronounced with increasing alkyl dihalide chain length. The results of dynamic contact angle (DCA) and interfacial shear strength (IFSS) demonstrated that the surface energy and interfacial adhesion increased and then decreased with the chain length of alkyl dihalide. The tensile strength and impact roughness of the composites enhanced as the alkyl dihalide chain length grew. Moreover, the reinforcing and toughening mechanisms were also discussed.

Interfacially reinforced carbon fiber/epoxy composites by grafting melamine onto carbon fibers in supercritical methanol

Melamine used as a coupling agent was functionalized onto a carbon fiber (CF) surface in supercritical methanol to improve the interfacial properties of CF reinforced epoxy composites. Fourier transform infrared spectroscopy (FTIR), Raman spectra and X-ray photo electron spectroscopy (XPS) confirmed the successful grafting of melamine molecules onto the fiber surface. Scanning electron microscopy (SEM) images showed that melamine was grafted onto the CF surface uniformly and the surface roughness was enhanced obviously. Dynamic contact angle analysis (DCA) revealed the significant improvement in the surface energy and wettability. Compared with the untreated CF composites, the interfacial shear strength (IFSS) and inter-laminar shear strength (ILSS) of composites after melamine modification increased by 41.3% and 36.4%, respectively. The impact properties were also improved significantly. In addition, the reinforcing and toughening mechanisms were also discussed. Meanwhile, supercritical treatment did not decrease the single filament tensile strength obviously.

Chemically grafting carbon nanotubes onto carbon fibers by poly(acryloyl chloride) for enhancing interfacial strength in carbon fiber/unsaturated polyester composites

We propose a novel method to uniformly graft high density carbon nanotubes (CNTs) onto carbon fiber (CF) using poly (acryloyl chloride) (PACl) as coupling agents. Compared to micromolecule couping agent previously reported in literature [2,3], PACl can supply much more active groups, which is beneficial for grafting high density CNTs onto CF surface. Moreover, in order to further increase the grafting density of CNTs, the solvothermal strategy was used for improving the reactive activity between CF and CNTs. After CNTs grafting treatment, there are still substantial amounts of reactive groups which can further react with various types of molecules to meet different requirements. In order to create chemical bonding between CF and unsaturated polyester (UP), CF-CNT was further grafted with undecylenic alcohol (UA) to get CF-CNT-UA hierarchical reinforcement. The interfacial adhesion of the resulting composites showed a dramatic improvement.

Preparation and properties of carbon nanotube/carbon fiber hybrid reinforcement by a two-step aryl diazonium reaction

Raw carbon nanotube (CNT)/carbon fiber (CF) hybrids were achieved through a two-step aryl diazonium reaction in mild, eco-friendly conditions. Raman spectra, Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) confirmed the grafting of CNT onto the CF surface. The surface topography and surface free energy of the modified CFs were examined by scanning electron microscopy (SEM), transmission electron microscope (TEM) and dynamic contact angle (DCA) tests, respectively. The resulting CNT/CF hybrid formed a strong chemical bond between the fiber and matrix and enhanced the surface wettability of the modified CFs. The interfacial shear strength (IFSS) of the CNT/CF hybrid reinforced composites increased by 104% compared with that of the untreated CFs. Moreover, the mechanical properties of the CNT/CF hybrid showed a slight improvement after modification.

Catalyzed Hydrolysis of Waste MC nylon Using Zeolites in Subcritical Water

In contrast with the conventional physical methods, the suband supercritical hydrolysis is not only a more environmentally friendly method to recycle the monomer casting nylon (MC nylon) wastes, but also a more feasible way to produce the corresponding monomer. In subcritical water, MC nylon was decomposed completely into water-soluble oligomers. The catalyzed hydrolysis of waste MC nylon using a series of H-form zeolites in subcritical water is presented in this work. Among them, H-Beta especially showed an excellent catalytic property and remarkably high yield of the monomer e-caprolactam.