Papers by Author: Lian Gao

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: Carbon fiber reinforced silicon carbide (C/SiC) composites are considered as one of the most potential thermal structure materials. However, the non-machinability of the three dimension woven fabric restrict the wide application of the c/sic composites. In this paper, we discuss the effect of machinability on the properties of 3D-c/sic composites, such as the modulus, mechanical properties, and so on. The results show that c/sic composites exhibit excellent mechanical properties after machinability, an extensive microstructure study is also carried out to understand the properties of the composites.

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: 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: In this paper, we reported the preparation of nanocrystalline Ta3N5 particles by nitridation of Ta2O5 nanoparticles using NH3 as reactant gas. It was found that nanocrystalline Ta2O5 was converted into Ta3N5 completely at 700°C within 5.0 h, which was much lower than the temperature 850°C for the complete nitridation of micron-sized Ta2O5 powder. The resulting nitride was characterized by X-ray diffraction analysis (XRD) and field emission scanning electron microscopy (FE-SEM). The nitrogen contents in the prepared Ta3N5 powders were quantitatively determined with CHN elemental analyzer and thermogravimetry and differential scanning calorimetry (TG-DSC). The color of nanocrystalline Ta3N5 is in fresh red while the one of micrometer-sized Ta3N5 is in dark red.

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.