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1.
The graphite was modified using pitch through dynamical melt-carbonization, and the effects of modification temperature and the amount of pitch on the characteristics of graphite were investigated. The structure and characteristics of the graphite were determined by X-ray diffractometry(XRD), scanning electron microscopy(SEM), particle size analysis and electrochemical measurements. The results show that the modified graphite has a disordered carbon/graphite composite structure, larger average particle diameter, greater tap density, and better electrochemical characteristics than the untreated graphite. The sample coated with 10% pitch dynamical melt-carbonized at 400 ℃ for 3 h and heat-treated at 850 ℃ for 2 h has better electrochemical performances with a reversible capacity of 360.5 mA·h/g, a irreversible capacity of 41.0 mA·h/g, and an initial coulombic efficiency of 89.8% compared with natural graphite and disordered carbon. The cycling stability of the Li/C cell with modified graphite as anodes is improved, and its capacity retention ratio at the 30th cycle is up to 94.37%. 相似文献
2.
The adsorption capability of D318 resin for Cr(VI) was investigated by chemistry analysis. Experimental results show that
D318 resin has the best adsorption ability for Cr(VI) at pH=3.16 in HAc-NaAc medium. The statically saturated adsorption capacity
of the resin is 265.4 mg/g. The thermodynamic adsorption parameters, enthalpy change ΔH and free energy change ΔG
298 of the adsorption reaction are 4.81 and −5.16 kJ/mol, respectively. The apparent activation energy E
a is 22.4 kJ/mol. The adsorption behavior obeys the Freundlich isotherm. The molar coordination ratio of the functional group
of resin to Cr(VI) is 3:2. Cr(VI) adsorbed on D318 resin can be eluted by 5%NaOH-5%NaCl quantitatively.
Foundation item: Project (Y304121) supported by the Natural Science Foundation of Zhejiang Province, China 相似文献
3.
To improve the adsorption properties of chemically modified chitosan, the chelating resin of salicylal chitosan Schiff bases was prepared by the template cross-linking method using Cu(Ⅱ) as template ion and ethylene glycol bisglycidyl ether as cross-linking agent in microwave, and was characterized by IR. The adsorption capacity and selectivity coefficient of the chemically modified chitosan for Cu(Ⅱ), Fe(Ⅲ) and Zn(Ⅱ) were investigated, respectively. The results show that the adsorption capacity of the resin 2.73 mmol/g for Cu(Ⅱ) is bigger than that for other two metal ions, 0.22 mmol/g for Fe(Ⅲ), and 0.42 mmol/g for Zn(Ⅱ), and the selectivity coefficients are as follows: KCu(Ⅱ)/Fe(Ⅲ)=12.4, KCu(Ⅱ)/Zn(Ⅱ)=6.5. 相似文献
4.
Using novolac phenolic resin, aniline and formaldehyde as raw materials, benzoxazine-phenolic copolymers with different percentages
of benzoxazine rings were prepared. FT-IR was adopted to characterize the molecular structure of the novolac-type phenolic
resin and the benzoxazine-phenolic copolymer BP31. In order to understand the curing process of the copolymers, the curing
behavior and curing kinetic characteristics were studied by differential scanning calorimetry (DSC), and the catalytical effect
of phenolic hydroxyl on the curing behavior of copolymers was investigated. To investigate the thermal properties of this
resin, the thermal degradation behaviors of the cured samples were studied by thermal gravimetric (TG) method, and glass-transition
temperatures (T
g) of the cured copolymers were also evaluated by DSC. The dynamic Ozawa method was adopted to determine the kinetic parameters
of the curing process as well. The activation energy is 78.8 kJ/mol and the reaction rate constant is in the range from 40.0
to 5.2 (K/min)
n
according to reaction temperatures. The Ozawa exponent decreases from 2.4 to 0.7 with the increase of reaction temperature,
and curing mechanism is expounded briefly according to the results. TG result shows that the highest char yield of copolymers
is 50.3%. The highest T
g of copolymers is 489 K, which is much higher than that of pure benzoxazine resin.
Foundation item: Project (20050106) supported by the Key Science and Technology Item of Guangdong Province, China 相似文献
5.
A robust decentralized H∞ control problem was considered for uncertain multi-channel discrete-time systems with time-delay. The uncertainties were assumed to be time-invariant, norm-bounded, and exist in the system, the time-delay and the output matrices. Dynamic output feedback was focused on. A sufficient condition for the multi-channel uncertain discrete time-delay system to be robustly stabilizable with a specified disturbance attenuation level was derived based on the theorem of Lyapunov stability theory. By setting the Lyapunov matrix as block diagonal appropriately according to the desired order of the controller, the problem was reduced to a linear matrix inequality (LMI) which is sufficient to existence condition but much more tractable. An example was given to show the efficiency of this method. 相似文献
6.
A water-in-oil (W/O) microemulsion composed of Triton X-100, n-hexanol, n-hexane and water solution with hydrochloric acid was prepared. K3Fe(CN)6 was added in as a water-soluble electroactive probe, and its electrochemical behavior was investigated by cyclic voltammetry
(CV) and electrochemical impedance spectroscopy (EIS). It is found that the H+ concentration of the water phase has a great effect on the conductivity of the W/O microemulsion, and hence influences the
electrochemical behavior of K3Fe(CN)6. When the pH value of water phase is about 7, the electrical conductivity of the W/O microemulsion is only 1.2×10−6 S/cm, and K3Fe(CN)6 almost cannot react at the glassy carbon electrode. But when the H+ concentration is more than 3 mol/L, the W/O microemulsion has a good electrical conductivity and K3Fe(CN)6 shows good electrochemical performance in it. The results of CV and EIS studies indicate that the electrochemical behavior
of Fe(CN)6
3−/Fe(CN)6
4− in the W/O microemulsion is different from that in the aqueous solution. This may be due to the unique liquid structure of
the W/O microemulsion and the unique mass transfer in the W/O microemulsion.
Foundation item: Projects(20673036, J0830415) supported by the National Natural Science Foundation of China; Projects(05JT1026, 2007JT2013)
supported by the Science Technology Project of Hunan Province, China 相似文献
7.
The problem of designing a non-fragile delay-dependent H∞ state-feedback controller was investigated for a linear time-delay system with uncertainties in state and control input. First, a recently derived integral inequality method and Lyapunov-Krasovskii stability theory were used to derive new delay-dependent bounded real lemmas for a non-fragile state-feedback controller containing additive or multiplicative uncertainties. They ensure that the closed-loop system is internally stable and has a given H∞ disturbance attenuation level. Then, methods of designing a non-fragile H∞ state feedback controller were presented. No parameters need to be tuned and can be easily determined by solving linear matrix inequalities. Finally, the validity of the proposed methods was demonstrated by a numerical example with the asymptotically stable curves of system state and controller output under the initial condition of x(0)=[1 0 -1]^T and h=0.8 time-delay boundary. 相似文献
8.
Synthesis and characterization of triclinic structural LiVPO4F as possible 4.2 V cathode materials for lithium ion batteries 总被引:2,自引:1,他引:1
A potential 4.2 V cathode material LiVPO4F for lithium batteries was prepared by two-step reaction method based on a carbon-thermal reduction (CTR) process. Firstly, V2O5, NH4H2PO4 and acetylene black are reacted under an Ar atmosphere to yield VPO4. The transition-metal reduction is facilitated by the CTR based on C→CO transition. These CTR conditions favor stabilization of the vanadium as V^3+ as well as leaving residual carbon, which is useful in the subsequent electrode processing. Secondly, VPO4 reacts with ElF to yield LiVPO4F product. The property of the LiVPO4F was investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and electrochemical measurement. XRD studies show that LiVPO4F synthesized has triclinic structure(space group p I ), isostructural with the naturally occurring mineral tavorite, EiFePO4-OH. SEM image exhibits that the particle size is about 2μm together with homogenous distribution. Electrochemical test shows that the initial discharge capacity of LiVPO4F powder is 119 mA·h/g at the rate of 0.2C with an average discharge voltage of 4.2V (vs Ei/Li^+), and the capacity retains 89 mA·h/g after 30 cycles. 相似文献
9.
Split Hopkinson pressure bar(SHPB) apparatus, usually used for testing behavior of material in median and high strain-rate, is now widely used in the study of rock dynamic constitutive relation, damage evolvement mechanism and energy consumption. However, the possible reasons of sampling disturbance, machining error and so on often lead to the scattering of test results, and bring ultimate difficulty for forming general test conclusion. Based on the stochastic finite element method, the uncertain parameters of specimen density ps, specimen radius Rs, specimen elastic modulus Es and specimen length Ls in the data processing of SHPB test were considered, and the correlation between the parameters and the test results was analyzed. The results show that the specimen radius Rs has direct correlation with the test result, improving the accuracy in preparing and measuring of specimen is an effective way to improve the accuracy of test and minish the scattering of results for SHPB test. 相似文献
10.
A new cyclometalated platinum complex containing 2, 5-bis(naphthalene-1-yl)-1,3,4-oxadiazole ligand was synthesized and characterized. The UV-Vis absorptions and photoluminescent properties of the ligand and its platinum complex were investigated A characteristic metal-ligand charge transfer absorption peak at 439 nm in the UV spectrum and a strong emission peak at 625 nm in the photoluminescence spectrum were observed for this complex in dichloromethane. Cyclic voltammtry (CV) analysis shows that the EHOMO (energy level of the highest occupied molecular orbital) and ELUMO (energy level of the lowest unoccupied molecular orbital) of the platinum complex are about -5.69 and -3.25 eV, respectively, indicating that the oxadiazole-based platinum complex has a potential application in electrophosphorescent devices used as a red-emitting material. 相似文献
11.
Wang Zhi-xing Fang Hai-sheng Yin Zhou-lan Li Xin-hai Guo Hua-jun Peng Wen-jie 《中南工业大学学报(英文版)》2005,12(1):54-58
LiNi0.5Mn1.5O4 was prepared under various conditions by one-step solid-state reaction in air and its properties were investigated by X-ray
diffractormetry (XRD), scanning electron microscopy (SEM) and electrochemical measurement. XRD patterns show that LiNi0.5Mn1.5O4 synthesized under various conditions has cubic spinel structure. SEM images exhibit that the particle size increases with
increasing calcination temperature and time. Electrochemical test shows that the LiNi0.5Mn1.5O4 calcined at 700 °C for 24 h delivers up to 143 mA · h/g, and the capacity retains 132 mA · h/g after 30 cycles.
Foundation item: Project (76600) supported by Postdoctoral Science Foundation of Central South University 相似文献
12.
Dong Li-hong Xu Bin-shi Dong Shi-yun Chen Qun-zhi Wang Yu-ya Zhang Lei Wang Dan Yin Da-wei 《中南工业大学学报(英文版)》2005,12(2):102-106
In order to investigate the physical mechanism of metal magnetic memory testing, both the influences of earth magnetic field
and applied stress on magnetic domain structure were discussed. Static tension and fatigue tests for low carbon steel plate
specimens were carried out on hydraulic servo testing machine of MTS810 type and magnetic signals were measured during the
processes by the type of EMS-2003 instrument. The results indicate that the initial magnetic signals of specimens are different
before loading. The magnetic signals curves are transformed from initial random to regular pattern due to the effect of two
types of loads. However, the shape and distribution of magnetic signal curves in the elastic region are different from that
of plastic region in tension test. While in fatigue test those magnetic signals curves corresponding to different cycles are
similar. The H
p(y) value of magnetic signals on the fracture zone increases dramatically at the breaking transient time and positive-negative
magnetic poles occur on the two parts of fracture zone.
Foundation item: Project(50235030) supported by the National Natural Science Foundation of China 相似文献
13.
Phase composition, transition and structure stability of functionally graded cemented carbide with dual phase structure 总被引:1,自引:0,他引:1
The phase composition, phase transition and phase structure transformation of the wire-cut section of functionally graded WC-Co cemented carbide with dual phase structure were investigated by XRD phase analysis. It is shown that the composition of η phase in the core zone is Co3W3C (M6C type). The structure of cobalt based solid solution binder phase is fcc type. At the cooling stage of the sintering process, the phase transition of η phase, i.e. M6C→M12C and the martensitic phase transition of the cobalt based solid solution binder phase, i.e. fcc→hcp are suppressed, which facilitates the strengthening of the alloy. Because the instantaneous temperature of the discharge channel is as high as 10 000 ℃ during the wire cutting process, the processed surface is oxidized. Nevertheless, the oxide layer thickness is in micro grade. In the oxide film, η phase is decomposed into W2C and CoO, and cobalt based solid solution binder is selectively oxidized, while WC remains stable due to the existence of carbon containing liquid organic cutting medium. 相似文献
14.
Preparation and electrochemical characterization of C/PANI composite electrode materials 总被引:2,自引:3,他引:2
1 INTRODUCTIONRecently , surpercapacitor has attracted greatattention for its unique power performance[1 ,2],while electrode materials ,as one key factor to de-termine the performance of supercapacitor , nowbecome the focus of many researches . The super-capacitor materials can be categorized into threetypes :carbon electrode materials[3], metal oxide e-lectrode materials[4]and conductive polymer elec-trode materials[5].Conductive polymer electrode materials havehigher capacitance than tha… 相似文献
15.
Hybrid supercapacitor based on polyaniline doped with lithium salt and activated carbon electrodes 总被引:1,自引:1,他引:0
Polyaniline(PANI) nanofiber was synthesized by interfacial polymerization utilizing the interface between HCl and CCl4. The hybrid type supercapacitors (PLi/C) based on Li-doping polyaniline and activated carbon electrode were fabricated and
compared with the redox type capacitors (PLi/PLi) based on two uniformly Li-doping polyaniline electrodes. The electrochemical
performances of the two types of supercapacitors were characterized in non-aqueous electrolyte. PLi/C supercapacitors have
a wider effective energy storage potential range and a higher upper potential. At the same time, the PLi/C supercapacitor
exhibits a specific capacity of 120.93 F/g at initial discharge and retains 80% after 500 cycles. The ohmic internal resistance
(R
ES) of PLi/C supercapacitor is 5.0 Ω, which is smaller than that of PLi/PLi capacitor (5.5 Ω). Moreover, it can be seen that
Et4NBF4 organic solution is more suitable for using as organic electrolyte of PLi/C capacitor compared with organic solution containing
LiPF6.
Foundation item: Project(2008AA03Z207) supported by the National High-Tech Research and Development Program of China 相似文献
16.
Based on the microscopic phase-field dynamic model and the microelasticity theory, the coarsening behavior of L12 and DO22 phases in Ni75Cr
x
Al25−x
alloy was simulated. The results show that the initial irregular shaped, randomly distributed L12 and DO22 phases are gradually transformed into cuboidal shape with round corner, regularly aligned along directions [100] and [001],
and highly preferential selected microstructure is formed during the later stage of precipitation. The elastic field produced
by the lattice mismatch between the coherent precipitates and the matrix has a strong influence on the coarsening kinetics,
and there is no linear relationship between the cube of the average size of precipitates and the aging time, which does not
agree with the results predicted by the classical Lifshitz-Slyozov-Wagner. The coarsening processes of L12 and DO22 phases are retarded in elastically constrained system. In the concurrent system of L12 and DO22 phases, there are two types of coarsening modes: the migration of antiphase domain boundaries and the interphase Ostwald
ripening.
Foundation item: Project(50671084) supported by the National Natural Science Foundation of China; Project(20070420218) supported by China
Postdoctoral Science Foundation 相似文献
17.
Separation of baicalin from Scutellaria Baicalensis Georgi with polyamide was studied. The adsorption isotherm, kinetic equation and desorption law were investigated by static and dynamic adsorption methods. The results show that the kinetic behavior is mainly controlled by the liquid film diffusion process and obeys the Boyd film diffusion equation. Equilibrium data for the adsorption of baicalin are correlated with Freundlich isotherm equation, i.e. q=3.8Ce2.057, suggesting that the relative capacity of polyamide to baicalin is somewhat small. The desorption results indicate that the baicalin with mass fraction of 33.86% and the least impurities can be obtained by chromatography using 60% ethanol as the eluant at room temperature. 相似文献
18.
Electrochemical behavior of wound supercapacitors with propylene carbonate and acetonitrile based nonaqueous electrolytes 总被引:1,自引:0,他引:1
The activated carbon wound supercapacitors with TEABF4/propylene carbonate (PC) and TEABF4/acetonitrile (AN) electrolytes were prepared. The effects of the electrolyte and temperature on the capacitance behavior
were investigated by cyclic voltammetry (CV) and constant current charge-discharge. Compared with the PC-based supercapacitor,
the AN-based supercapacitor has higher capacitance and lower equivalent serial resistance (R
ES) at discharge currents ranging from 5 to 1 000 mA and 25 °C. Moreover, temperature effects are more prominent for PC-based
supercapacitor than for AN-based supercapacitor. When the measurement temperature ranges from 60 °C to −40 °C the capacitance
changes from 5.1 to 2.5 F and R
ES changes from 135 to 876 mΩ for the PC-based supercapacior, while the AN-based supercapacitor shows less change in capacitance
and R
ES. Thus AN-based supercapacitor exhibits excellent power characteristics and temperature property.
Foundation item: Project(20803095) supported by the National Natural Science Foundation of China; Project(2008AA03Z207) supported by the National
High Technology Research and Development Program of China 相似文献
19.
Thiobacillus ferrooxidans might be the most important bacteria used in biometallurgy. The foundation way of its growth process is oxidizing ferrous
in order to obtain energy needed for metabolism, but the variation of ferrous concentration and mixed potential of the culture
media would have crucial effect on the bacteria growth. Based on the characteristics of Thiobacillus ferroxidans growth and redox potential of ferric and ferrous, an electrochemical cell was designed conventionally to study growth rule
and the relationship between redox potential and bacteria growth was built up, and some growth kinetics of Thiobacillus ferrooxidans were elucidated. It demonstrates that the variation of open potential of electrochemical cell ΔE shows the growth tendency of Thiobacillus ferrooxidans, at the initial growth stage, the value of δE increases slowly, when at logistic growth stage, it increases drastically, and the growth rate of bacteria is linear with
the oxidation rate of ferrous. The bacteria growth kinetics model is proposed using Monod and Michealis-Menten equation, and
the kinetics parameters are got. The consistence of the measured and the calculated results proves that it is proper to use
the proposed kinetics model and the electrochemical cell method to describe the growth rule of Thiobacillus ferrooxidans.
Foundation item: Project (50204001) supported by the National Science Foundation of China 相似文献
20.
Urea-isobutyraldehyde-formaldehyde (UIF) resin was synthesized from urea, isobutyraldehyde, and formaldehyde using sulfuric
acid as a catalyst by one pot method. The effects of molar ratios of isobutyraldehyde to formaldehyde (n(I)/n(F)) and aldehyde to urea (n(A)/n(U)) on the yield, hydroxyl value (vs KOH) and softening point of the resin were investigated. The structure of the resin
was characterized by FT-IR, 1H-NMR and 13C-NMR. The results show that when the molar ratio of urea to isobutyraldehyde to formaldehyde (n(U)/n(I)/n(F)) is 1.0/3.0/3.0, the yield UIF resin is 67.1%, and the softening point and hydroxyl value are 88 °C and 37 mg/g, respectively.
The FT-IR, 1H-NMR and 13C-NMR results show that the lactam is formed by aminomethylation from urea, isobutyraldehyde, and formaldehyde.
Foundation item: Project(2006A10902001) supported by the Science and Technology Plan of Guangdong Province, China; Project(2007Z3-D0351) supported
by the Science and Technology Plan of Guangzhou City, China 相似文献