Papers by Author: Lian Gao

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Authors: R. Zhang, Lian Gao, Hai Long Wang, Hong Liang Xu, Jing Kun Guo
Authors: Yan Wang, Yang Qiao Liu, Jing Sun, Lian Gao
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.
Authors: Yang Qiao Liu, Lian Gao
Abstract: In this paper, the dispersing abilities of three polyelectrolytes, poly (acrylic acid), poly (acrylic acid-co-acrylate), and a four-member copolymer containing various anionic functional groups were tested for aqueous Al2O3 suspensions. The influence of the dispersants on the surface charge of the powder was evaluated by measuring the zeta potential in dilute Al2O3 suspensions. It was found that all the three dispersants shifted the isoelectric point to a lower pH value. Rheological measurements showed that the four-member dispersant decreased the viscosity in the widest pH range, which should be ascribed to the synergistic effect of different functional groups. The 58vol% concentrated Al2O3 slurry using the four-member dispersant was further consolidated using gel casting and was fully sintered at 1600oC.
Authors: Qiu Liao, Jing Sun, Lian Gao
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.
Authors: Jian Qiang Luo, Lian Gao, Jing Sun
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.
Authors: Xiao Feng Xie, Lian Gao, 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 (109o18’). 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.
Authors: Shan Zheng, Lian Gao, Hiroshi Watanabe, Junichi Tatami, Toru Wakihara, Katsutoshi Komeya, Takeshi Meguro
Abstract: Dense and homogenous Si3N4-TiN composites (5 vol% TiN) were prepared by using in situ synthesis method from Si3N4, AlN and TiO2 mixtures, containing Y2O3 and Al2O3 as sintering aids. In the prepared Si3N4-TiN composites, TiN grains were formed from TiO2 and AlN powders during the sintering process, in which ammonium citrate was used as a dispersant for raw TiO2 powders. The microstructures of the Si3N4-TiN composites with the increase of ammonium citrate were investigated by scanning electron microscopy (SEM). Citrate ions modified on the surface of TiO2 particles and protected the TiO2 particles in the mixed slurry to reduce the aggregations of TiO2 powders, and homogenous Si3N4-TiO2-AlN composite powder was prepared for sintering. The microstuctures of Si3N4-TiN were developed after sintering with the uniform distribution of TiN grains in the Si3N4 ceramics. It was found that the microstructure of Si3N4-TiN composite was improved significantly with 0.20 g ammonium citrate in the system, TiN grains with 0.2-0.3 μm in diameter distributed throughout Si3N4 matrix. It was a practical and useful way to improve the microstructure of Si3N4-TiN composite without the alteration of the preparation procedure.
Authors: Jing Sun, Lian Gao
Abstract: In this paper, a colloidal processing route was adopted to disperse multi-walled carbon nanotubes (MWNTs) into alumina powders homogenously. Alumina matrix composites containing 0.1 to 2 weight percent of MWNTs were successfully fabricated by pressureless sintering. Also, 1wt% MWNTs-alumina composites were prepared by hot pressing for comparison. It was found that when the sample was sintered at 1450oC, the addition of 1wt% carbon nanotubes led to 10% increase in bending strength compared with monolithic alumina. The reinforcement mechanism was discussed based on the microstructure investigation. The broken nanotubes and pullout of MWNTs at interfaces are efficient in transferring the load from the alumina matrix to the nanotubes, leading to the improvement of the mechanical properties.
Authors: Xi Hai Jin, Lian Gao, Jing Sun
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.
Authors: Xi Hai Jin, Lian Gao, Jing Sun
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.
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