Interface enhancement with carbon nanotubes (CNTs) provides a promising approach for improving shock strength and toughness of glass fiber reinforced plastic (GFRP) composites. The effects of incorporating flame-synthesized CNTs (F-CNTs) into GFRP were studied, including on hand lay-up preparation, microstructural characterization, mechanical properties, fracture morphologies, and theoretical calculation. The experimental results showed that: (1) the impact strength of the GFRP modified by F-CNTs increased by more than 15% over that of the GFRP modified by CNTs from chemical vapor deposition; and (2) with the F-CNT enhancement, no interfacial debonding was observed at the interface between the fiber and resin matrix on the GFRP fracture surface, which indicated strong adhesive strength between them. The theoretical calculation revealed that the intrinsic characteristics of the F-CNTs, including lower crystallinity with a large number of defects and chemical functional groups on the surface, promoted their surface activity and dispersibility at the interface, which improved the interfacial bond strength of GFRP.
This paper presents a new process for synthesizing a kind of nitrogen- doped carbon nanotubes (N-CNTs) with primarily a ‘graphite-like’ structure at N substitutions from flames using n-propylamine and n-butylamine as fuels. When the N-CNTs are used as the supercapacitor electrode materials, they exhibit a much larger capacitance than the regular carbon nanotubes (CNTs). It is proposed that the high proportional ‘graphite-like’ N dopant in the as-grown N-CNTs improves their surface chemical activity and conductivity and then results in a desirable performance for electro-chemical capacitors
Different electric field intensities were added along the growth direction of CuO nanoneedles when using a thermal oxidation process. The results show that: (1) the length of CuO nanoneedles increased with the electric field, but when the voltage was greater than a certain value, the growth stopped and (2) the diameter of CuO nanoneedles from top to root became more uniform. Therefore, it is further demonstrated the “solid state based-up diffusion growth mechanism” for CuO nanoneedles prepared by thermal oxidation. The recent study also provides a possibility for controlling the growth of metal oxide nanowires which will promote their potential applications in nanodevices.
A novel approach has been developed for synthesizing nitrogen-doped carbon nanotubes (N-CNTs) from flames using liquid amines as fuels, such as isopropylamine, n-propylamine and n-butylamine, which not only created a high reaction temperature but also provided a source of C and N. The microstructure and morphologies of the N-CNTs were characterized by scanning and transmission electron microscopy, laser Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. These N-CNTs were different from the conventional N-CNTs from a chemical vapor deposition process with primarily a 'pyridine-like' structure at N substitutions (one N atom only bonded to two C atoms). They were dominantly 'graphite-like' (one N atom substituted for C in graphite layers and bonded to three C atoms) with few C congruent N bonds due to the special formation conditions of high temperature and oxidative environment. It was found that: (1) amine fuel with a side chain structure was less suitable for preparation of orderly grown N-CNTs; (2) amine fuels with a higher N content generally introduced a larger quantity of N dopant; (3) the proportion of the 'graphite-like' N dopant decreased with increasing flame temperature, which provided a possibility for controllable N doping in N-CNTs from amine flames. The growth mechanism of the N-CNTs was also simulated and discussed.
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