ZrC coatings were deposited on graphite substrates by low pressure chemical vapor deposition（LPCVD） with the Br2-Zr-C3H6-H2-Ar system. The effects of deposition time on the microstructures and growth behavior of ZrC...ZrC coatings were deposited on graphite substrates by low pressure chemical vapor deposition（LPCVD） with the Br2-Zr-C3H6-H2-Ar system. The effects of deposition time on the microstructures and growth behavior of ZrC coatings were investigated. ZrC coating grew in an island-layer mode. The formation of coating was dominated by the nucleation of ZrC in the initial 20 minutes, and the rapid nucleation generated a fine-grained structure of ZrC coating. When the deposition time was over 30 min, the growth of coating was dominated by that of crystals, giving a column-arranged structure. Energy dispersive X-ray spectroscopy showed that the molar ratio of carbon to zirconium was near 1：1 in ZrC coating, and X-ray photoelectron spectroscopy showed that ZrC was the main phase in coatings, accompanied by about 2.5mol% ZrO2 minor phase.展开更多
Phospho-olivine LiFePO4 has been prepared using a facile hydrothermal method by optimizing the reaction temperatures. Structural and morphological properties of the as-prepared LiFePO4 powders are systematically chara...Phospho-olivine LiFePO4 has been prepared using a facile hydrothermal method by optimizing the reaction temperatures. Structural and morphological properties of the as-prepared LiFePO4 powders are systematically characterized using X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, infrared spectra, UV-vis spectra, and Mossbauer spectroscopy. It is demonstrated that the samples prepared in the temperature range from 160 to 200℃ crystallize in a single phase of phospho-olivine structure. All particles are rod-like, showing dimensions of approximately 150-200 nm in width and 500-600 nm in length with a preferential growth direction of [001]. Within the lattice of LiFePO4 rods, Fe2＋ ions partially disorderly occupy the Li＋ sites, which increases the cell volume. The electrochemical performance of LiFePO4 is investigated by charge/discharge experiments. It is found that LiFePO4 rods prepared at 200℃ deliver a specific discharge capacity of 147 mAh g-1, which is apparently superior to those prepared at lower reaction temperatures like 160 and 180 ℃This observation is explained in terms of the thinner surface noncrystalline layer and lower level of Fe2＋ disorderly occupying the Li＋ sites.展开更多
We investigated microstructure morphologies of three asphalts（SK, Karamay, and Esso） used in China using atomic force microscopy（AFM）. The topography and phase contrast images were obtained. Topographic profile an...We investigated microstructure morphologies of three asphalts（SK, Karamay, and Esso） used in China using atomic force microscopy（AFM）. The topography and phase contrast images were obtained. Topographic profile and three dimensional images were described. Roughnesses of microstructure were calculated. And the chemical compositions of asphalt were tested to explain the microstructural mechanism of the asphalt. The results show that the topography and phase image in atomic force microscopy are appropriate to evaluate the microstructure of the asphalt binder. There are significant differences in microstructural morphologies including bee-like structure, topographic profile, 3D image, and roughness for three asphalts in this study. There are three different phases in microstructure of asphalt binder. The oil source and chemical composition of asphalt, especially asphaltenes content have a great influence on the microstructure.展开更多
基金Founded by the National Natural Science Foundation of China(No.91216302)the National Program on Key Basic Research Project of the People's Republic of China(No.2015CB655200)
文摘ZrC coatings were deposited on graphite substrates by low pressure chemical vapor deposition（LPCVD） with the Br2-Zr-C3H6-H2-Ar system. The effects of deposition time on the microstructures and growth behavior of ZrC coatings were investigated. ZrC coating grew in an island-layer mode. The formation of coating was dominated by the nucleation of ZrC in the initial 20 minutes, and the rapid nucleation generated a fine-grained structure of ZrC coating. When the deposition time was over 30 min, the growth of coating was dominated by that of crystals, giving a column-arranged structure. Energy dispersive X-ray spectroscopy showed that the molar ratio of carbon to zirconium was near 1：1 in ZrC coating, and X-ray photoelectron spectroscopy showed that ZrC was the main phase in coatings, accompanied by about 2.5mol% ZrO2 minor phase.
基金supported by NSFC (No.20831004)National Basic Research Program of China (2011CB935904)+1 种基金FIPYT (No.2009HZ0004-1,2008F3116)FJIRSM fund (Nos.SZD-09002-3,2010KL002)
文摘Phospho-olivine LiFePO4 has been prepared using a facile hydrothermal method by optimizing the reaction temperatures. Structural and morphological properties of the as-prepared LiFePO4 powders are systematically characterized using X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, infrared spectra, UV-vis spectra, and Mossbauer spectroscopy. It is demonstrated that the samples prepared in the temperature range from 160 to 200℃ crystallize in a single phase of phospho-olivine structure. All particles are rod-like, showing dimensions of approximately 150-200 nm in width and 500-600 nm in length with a preferential growth direction of [001]. Within the lattice of LiFePO4 rods, Fe2＋ ions partially disorderly occupy the Li＋ sites, which increases the cell volume. The electrochemical performance of LiFePO4 is investigated by charge/discharge experiments. It is found that LiFePO4 rods prepared at 200℃ deliver a specific discharge capacity of 147 mAh g-1, which is apparently superior to those prepared at lower reaction temperatures like 160 and 180 ℃This observation is explained in terms of the thinner surface noncrystalline layer and lower level of Fe2＋ disorderly occupying the Li＋ sites.
基金Funded by the National Natural Science Foundation of China(Nos.51408287,and 51668038)the Rolls Supported by Program for Changjiang Scholars and Innovative Research Team in University(IRT_15R29)+2 种基金the Distinguished Young Scholars Fund of Gansu Province(1606RJDA318)the Natural Science Foundation of Gansu Province(1506RJZA064)the Excellent Program of Lanzhou Jiaotong University(201606)
文摘We investigated microstructure morphologies of three asphalts（SK, Karamay, and Esso） used in China using atomic force microscopy（AFM）. The topography and phase contrast images were obtained. Topographic profile and three dimensional images were described. Roughnesses of microstructure were calculated. And the chemical compositions of asphalt were tested to explain the microstructural mechanism of the asphalt. The results show that the topography and phase image in atomic force microscopy are appropriate to evaluate the microstructure of the asphalt binder. There are significant differences in microstructural morphologies including bee-like structure, topographic profile, 3D image, and roughness for three asphalts in this study. There are three different phases in microstructure of asphalt binder. The oil source and chemical composition of asphalt, especially asphaltenes content have a great influence on the microstructure.
