Papers by Author: Lan Zhang

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Authors: Gang Chen, Hui Zhong Ma, Lan Zhang, Hong Ye Chen, Qiue Xia, Ning Yao, Bing Lin Zhang
Abstract: Three kinds of different diameter carbon nanotubes (CNTS) films deposited on aluminum sheets by electrophoretic deposition method. Scanning electron microscopy was used to observe the surface morphology of the films. The field emission properties of the films were tested by using a diode structure. The turn-on field for 8nm diameter CNTs film was 0.8V/μm and the current density of 5200μA/cm2 was obtained at 2.3V/μm. While corresponding data for 15nm and 30nm CNTs films were 1.6V/μm, 1.4V/μm, and 2200μA/cm2, 850μA/cm2 at 3.0V/μm respectively. The deposited film with 8nm diameter CNTs appeared excellent emission properties.
Authors: Lan Zhang, Hui Zhong Ma, Ning Yao, Bing Lin Zhang
Abstract: White carbon films with sp1-hybridization of carbon were synthesized by microwave plasma chemical vapor deposition. The surface morphology of the deposited film, which consisted of nanograins and nanofibers, was observed by scanning electron microscope. The x-ray diffraction peak at 2θ=21.69o corresponds to the (110) facet of β modifications of white carbon material. The peak position at 283.2 eV in x-ray photoelectron spectrum represents binding energy of C1s core level of sp1-hybridization of carbon. Field electron emission properties of the film were tested by using a diode structure in a vacuum chamber. The turn-on field of 2.3V/μm and the emission current density of 360μA/cm2 at electric field of 7V/μm were obtained.
Authors: Hui Zhong Ma, Lan Zhang, Jun Jie Zhang, Yun Hai Du, Ning Yao, Bing Lin Zhang
Abstract: A flexible carbon thin film was prepared by laser induced when phase changing of polyimide thin film. There is no substrate for this thin film. It could be curved at any angle. The electron emission properties of the prepared thin film were measured by a diode mechanism; the thin film was used as a cathode and indium-tin-oxide (ITO) glass as an anode. The turn-on field of the thin film was about 2.1 V/µm. The current density of the thin film was about 150 µA/cm2 at the electric field of 4.5 V/µm. The electron emission measurements indicate that the thin film could be a good candidate electron emission material in flat panel display or be used as other electron source. The morphology and structure of the thin film were investigated by optical microscope and Raman spectroscopy.
Authors: Lan Zhang, Hui Zhong Ma, Xue Xiang Li, Ning Yao, Bing Lin Zhang
Abstract: Carbon nitride nanotubes (CN-NT) thin films were prepared on Ni-Cr coated glass substrate by microwave plasma enhanced chemical vapor deposition at a relatively low temperature of 600~650 °C. The morphology of the films were observed by scanning electron microscopy. The microstructure of the film were analyzed by x-ray photoelectron spectroscopy, x-ray diffraction, and Raman spectroscopy. The characteristics of field emission of CN-NT thin films were measured. Experimental results indicate that the film structure and properties of the field electron emission are related to flow ratio of N2 to CH4. When the flow ratio of N2 to CH4 was 3.3, the obtained film had a better field electron emission characteristics. The turn-on field of the film was 3.7 V/µm . The current density was 413.3 µA/cm2 at an electric field of 8 V/µm.
Authors: Yan Rong, Lei Shi, Hui Ping He, Lan Zhang
Abstract: A model for the isothermal flow-induced crystallization (FIC) of polypropylene melt in a simple shear flow is developed. The model is based on the molecular kinetic theory. The first normal stress difference of the stress tensor, calculated according to a molecular model, is assumed as the driving force of the flow-induced nucleation. Crystallization is described as a spherulitical nucleation and growth process. The theoretical predictions of the evolution of the viscosity in steady shear flow of iPP are in agreement with the experimental findings. The relative influence of the mechanical and thermal phenomena on the crystallization development is then analyzed as a function of the shearing intensity in terms of nucleation density. The results show the enhancement of the crystallization kinetics due to the shearing.
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