Papers by Author: Jing Sun

Abstract: Two kinds of chemical functional single-wall carbon nanotubes (SWNTs) are covalently coupled into special V-type superstructure by the esterification in pyridine medium. Both SWNTs bundles and individual SWNTs can be bound effectively through the deacidification path. The esterification between different kinds of modified SWNTs takes place on their ends and the crystallinity of SWNTs are well remained during the course. Interestingly, the inclinations between coupled SWNTs are very closely to the ester bond angle (109^o18’). Furthermore, the formation mechanism about the peculiar structure has been proposed in the paper. The results suggest that selected connection bonds will determine the different angles of coupled SWNTs.

Abstract: Titania(B) nanobelt and anatase titania nanobelt could be prepared by calcining hydrogen titanate nanobelt at 450 °C and 550 °C respectively. When the hydrogen titanate was previously treated with HNO₃ for some time before calcination at 450 °C, titania(B) and anatase mixed phase titania could be obtained. The ratio of anatase phase in the product could be changed by control the time of HNO₃ treating. TEM images show that the mixed phase product was anatase nanocrystals doted on titania(B) nanobelts. The mixed phase product shows higher photocatalytic activity on the decomposition of Methylene Blue (MB) than the pure titania(B) nanobelt and anatase nanobelt.

Abstract: A novel surfactant, hydroxypropyl cellulose (HPC), was firstly used to debundle Meijo single walled carbon nanotubes (SWNTs) in distilled water and 1-propanol. As comparison, common surfactants (SDBS and Triton) were used to disperse Meijo SWNTs in 1-propanol and distilled water. And the dispersibility of mixed surfactants, HPC/SDBS and HPC/Triton, were also tested. After short ultrasonication and centrifugation, stable supernatant of HPC-SWNTs has been obtained, and HPC show the best dispersibility to Meijo SWNTs. The HPC-SWNTs solution was used to prepare transparent conductive films on PET substrate by spray coating method. After being soaked in 1-propanol and HNO₃, the sheet resistance decreased from 8,440 Ω/□ to 4,175Ω/□ at 90% transmittance. TEM, UV-Vis-NIR spectra, and Raman spectra were performed to characterize the SWNT solutions and films.

Abstract: TiO2/Multi-walled carbon nanotubes (MWNTs) were prepared via a wet chemical route with hydrolysis of titanium salts. The purification and oxidation treatment of MWNTs in concentrated HNO3 solution were conducted to modify the nanotubes. Then the pre-treated carbon nanotubes were added into the titanium salt and in the end the composites were formed. The microstructure of as-prepared TiO2/MWNTs composite was studied by TEM. The samples were calcined at different temperature. By X-ray diffraction (XRD), the phase transformation of nano-structured TiO2 in composites was determined. The photocatalytic activity of samples being calcined at different temperature was studied by using the conversion of methyl orange in aqueous solutions as probe reaction. The influence of the structure on photocatalysis efficiency was discussed. By contrast with that of pure TiO2 nanoparticles, the special structure of TiO2/MWNT composite could remarkably improve the efficiency of the photocatalytic reaction. The results indicated that the excited e- in conduction band of TiO2 might transfer into MWNTs and the possibility of the recombination of e-/h+ pairs decreased.

Abstract: The SWNT/Pt composite with high electrocatalytic property was successfully fabricated through pretreating SWNTs by acid and NH3 treatment. According to the hydrodynamic voltammograms and the current response for H2O2, the SWNT/Pt composite was demonstrated to have faster and more sensitive response than SWNTs, indicating the enhanced electrocatalytic property of SWNT/Pt composite.

Abstract: We report the synthesis and characterization of FePt nanoparticles (NPs)/single walled carbon nanotube (SWNTs) nanocomposites, which might have important potential applications to orient CNTs and the development of new catalysts. The crystallite size of FePt NPs is about 2.5-4 nm and the Fe atom content ranges from 50% to 65%. HiPCO SWNTs have been decorated with FePt nanoparticles under mild conditions without any pretreatment. When the bundle size of HiPCO SWNTs is about 20 nm, FePt NPs mostly attach on the sidewalls of SWNTs. The loading of FePt nanoparticles on the SWNTs bundles can be conveniently controlled by adjusting the initial amount of FePt NPs. The nanocomposite showed magnetic properties in a magnetic field. TEM, HRTEM, and EDS spectra were performed to observe the nanostructure of these nanocomposites.

Abstract: Single-walled carbon nanotubes (SWCNTs) were dispersed in water with the assistance of polyphenols (resorcinol and pyrogallol). SWCNTs have intrinsic tendency to adsorb aromatic compounds due to π-π dispersion interactions, which leads to SWCNTs noncovalently dispersed in water by adsorption of resorcinol or pyrogallol. The concentration of SWCNT suspension was determined by the absorbance value at 500 nm using UV-Vis spectrometer. The effects of polyphenol concentration and ultrasonication time on the dispersion state have been investigated. Resorcinol of 0.5 mg/mL was found to be most effective for solubilizing SWCNTs in water. Over 60 % of SWCNTs were well dispersed with ultrasonication time for 4 hours. However, SWCNTs were cut shorter and damages could be introduced with prolonged ultrasonication time. TEM images showed that SWCNT bundles became thinner with the presence of polyphenols. These aromatic compounds provide an effective way to disperse SWCNTs in water and might have potential application in nanocomposite preparation.

Abstract: Different opening and modifying methods of MWNTs are studied and compared in this paper. MWNTs are dipped in a refluxed HNO3 solution. The influence of temperature, concentration and holding time on the opening and modifying of MWNTs is studied. The compared process is that MWNTs are treated by O3. The solvent that can highly dissolve O3 and disperse MWNTs is crucial. In order to prompt the reaction, 1M CF3COOH is elected as reactant medium and catalysis. The opening of MWNTs is tested by BET and confirmed by TEM. The surface structure of MWNTs treated by different processes is analyzed by FT-IR. The optimum conditions of opening and modifying of MWNTs are discussed.

Abstract: SiC/ZTM nanocomposites were prepared, and the influence of nanosized SiC addition on the microstructure and mechanical properties were investigated. It was found that the addition of nanosized SiC significantly retarded the matrix grain growth, making the microstructure much finer and more uniform. This led to a significant improvement in the mechanical properties. And further enhancement in the mechanical property can be achieved through the addition of mullite seeds in the starting powder and improving the distribution homogeneity of SiC nanoparticles in the matrix.

Abstract: Co/ZnO and Ni/Al2O3 composites were prepared by in-situ decomposition of CoNx and NiNx during sintering, using CoNx/ZnO and NiNx/Al2O3 mixtures synthesized through an in-situ nitridation method as the starting powders. It was found that these composites showed a very uniform microstructure with metal particles homogeneously distributed among matrix grains. The microstructure and properties were tentatively studied.