Papers by Author: Gai Rong Chen

Abstract: The carbon materials prepared by PVDF carbonization at different temperatures have similar BET surface area and pores volume. The content of fluorine in the carbons decreased with the carbonization temperature from 1.46% (atm %) at 600°C to 0.18 %( atm %) at 1000°C. The first cycle specific capacity and the initial coulombic efficiency decreases with the decrease of fluorine content in the samples. The first cycle discharge capacity decreased from 982 mAh/ g at 600°C to 752 mAh/ g at 1000°C and the initial coulombic efficiency decreased from 31.8% at 600°C to 24% at 1000°C. It is believed that fluorine contained in the carbon materials has a positive effect to improve the electrochemical properties as anode materials for Li-ion batteries.

Abstract: The precursor of LiNi_0.5 Mn_{Subscript text}1.5O₄ cathode material with high density was synthesized by two-dryness co-precipitation method. The optimized parameters were found out by studying the relationship between the density of precursor and the concentration of reactants, the manner of adding agglomerating agent, the remaining water in filter cake and the manner of dryness. The highest density (1.74 g/cm3) of precursor can be achieved under optimized condition: NiSO₄ 0.375 mol/L, coagulation agent added with little amount but many times, 28% of water in filter cake and two-step dryness, which is much better than that made by other methods. Our experiment provides a significant reference for the synthesis of excellent-performance cathode materials of lithium-ion battery. LiNi_0.5 Mn_{Subscript text}1.5O₄has a good cycle performance, a higher discharge capacity and a discharge platform of 4.7v, so it has become a research focus of 5-voltage cathode materials in the field of lithium ion battery recently.[1-4] However, LiNi0.5Mn1.5O4 prepared by common methods usually has a lower tap volume capacity.[5-9] HiroyuKi Ito[6] reported a continuous fabricated high-density cobalt-manganese-doped nickel hydroxide method with which the density of product was between 1.5-1.91g/cm3, however the used ammonia as a complexation agent in the preparation process not only increased the cost of the preparation, but also led to environmental pollution. Research results show that the cathode material synthesized using high-density precursor has a higher tap density, a larger volume capacity and a good electrochemical performance.[10] In this paper, we find out the optimized parameters of preparation of precursor of LiNi_0.5 Mn_{Subscript text}1.5O₄ by studying the relationship between the density of precursor and concentration of reactants, the manner of adding agglomerating agent, the remaining water in filter cake and the manner of dryness.

Abstract: The reactions were carried out by decomposing acetylene at 1000 °C in a two-stage furnace system for 10 min. In the first furnace no catalyst was placed and an AAO template with average diameter about 50 nm was placed in the second furnace whose temperature was designed to be 700 °C. The samples were characterized by scanning electron microscopy and high resolution transmission electron microscopy. The results show that carbon spheres with average diameter about 50 nm on the AAO template surface were obtained and these carbon spheres are composed of unclosed graphene layers with an interlayer distance of 0.33–0.35 nm between the layers.

Abstract: Catalytic decomposition of acetylene was carried out at 400 °C using iron supported on sodium chloride as catalyst and the product was heat-treated at 650 °C under an argon atmosphere for 2 h directly. The sample was examined by scanning electron microscopy, high resolution transmission electron microscopy and X-ray diffraction. The results show that nano onion-like fullerenes encapsulating Fe cores with diameters in the range 20-50 nm were obtained.

Abstract: By studying the definition of DHT (distinguished hyperbolic trajectory) and existing measure function in phase space, a measure function in the extended phase space is presented in this paper. Effect of system frequency on computation of DHT is explored. Two-dimensional and three-dimensional Duffing systems are taken as examples. The comparison between measure function in extended phase space and that in phase space and the comparison between natural frequency and twice frequency are both given by figures.

Abstract: According to pseudo-periodicity and ergodicity of chaotic systems, we put forward a fast algorithm to determine delay time in phase state reconstruction. The traditional method to calculate mutual information is time-consuming and complicated to realize, which greatly restricts its application. In our algorithm we gradually reduce the feasible computing interval and adjust the calculating step until satisfactory result is gotten. This method overcomes the tedious calculation of mutual information and meanwhile guarantees high precision. Finally the simulation results of Rössler and Lorenz systems verify the feasibility of our algorithm.