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2009

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Articles 91 - 120 of 145

Full-Text Articles in Physical Chemistry

Mesoporous Carbon For High Power Supercapacitors, Bin Xu, Lu Peng, Guo-Qing Wang, Gao-Ping Cao, Feng Wu, Yu-Sheng Yang Feb 2009

Mesoporous Carbon For High Power Supercapacitors, Bin Xu, Lu Peng, Guo-Qing Wang, Gao-Ping Cao, Feng Wu, Yu-Sheng Yang

Journal of Electrochemistry

Mesoporous carbon for supercapacitors was prepared from sucrose using nano-CaCO3 as template.The microstructure of the carbon was characterized with N2 adsorption and transmission electron microscopy(TEM) observation.The electrochemical performances were evaluated in 6mol·L-1 KOH aqueous electrolyte with galvanostatic charge/discharge,cyclic voltammetry,and ac impedance spectroscopy.The sucrose-based mesoporous carbon had a surface area of 606 m2/g and enriched mesopores in the range of 10～30 nm.The mesoporous carbon presented a specific capacitance of 125 F/g at a current density of 50 mA/g and outstanding excellent rate performance.As the current density increased to 20 000 mA/g,its capacitance remained at 88 F/g,much …

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Power Characteristics Of The Energy Storage System Based On All-Vanadium Solution, Jun-Ping Hu, Qi Zhang, Xi Yang, Yi-Ning Shi, Ming-Sen Zheng, Quan-Feng Dong, Zhao-Wu Tian Feb 2009

Power Characteristics Of The Energy Storage System Based On All-Vanadium Solution, Jun-Ping Hu, Qi Zhang, Xi Yang, Yi-Ning Shi, Ming-Sen Zheng, Quan-Feng Dong, Zhao-Wu Tian

Journal of Electrochemistry

The energy storage system based on all-vanadium solution was studied for high power applications.The influences of the electrode thickness, the electrolyte concentration and velocity in performance of the storage system were investigated in detail. The power density could achieve 3121 W/L at the current density 750 mA/cm2 under the optimal conditions.

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Preparation And Performance Of The Thin-Film Libpon Electrolyte, Feng Wu, Ya-Dong Liu, Ren-Jie Chen, Shi Chen Feb 2009

Preparation And Performance Of The Thin-Film Libpon Electrolyte, Feng Wu, Ya-Dong Liu, Ren-Jie Chen, Shi Chen

Journal of Electrochemistry

The LiBPON thin-film electrolyte was prepared by magnetron sputtering,and the relationship between the performance and the deposition condition was investigated.As seen in the SEM images,the thin films are dense and uniform without cracks,and according to the XRD patterns they have an amorphous structure.The electrochemical performance of the electrolyte was characterized by electrochemical impedance spectroscopy(EIS).The ionic conductivities of the thin film decreased with the RF power,but increased with the N2 pressure.The an ionic conductivity of 3.5×10-6 S/cm at room temperature was found from the electrochemical measurement.While the deposition rate increased with the RF power,but decreased with the N2 …

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Hydrothermal Preparation And Electrochemical Characterizations Of Vanadate Compound Nav2O5 Crystals, Fang Hu, Xing Ming, Fei Du, Ying-Jin Wei, Gang Chen, Chun-Zhong Wang Feb 2009

Hydrothermal Preparation And Electrochemical Characterizations Of Vanadate Compound Nav2O5 Crystals, Fang Hu, Xing Ming, Fei Du, Ying-Jin Wei, Gang Chen, Chun-Zhong Wang

Journal of Electrochemistry

The NaV2O5 was prepared by a low temperature hydrothermal process. The material crystallized in the layered orthorhombic structure with space group Pmmn. X-ray diffraction confirmed that the material was pure and the scanning electron microscopy showed that the material was composed of needle crystals with 20 μm in length and 200 nm in width. X-ray photoelectron spectroscopy indicated the co-existence of V4+ and V5+ in the material,which results in an average V4.5+ oxidation state of the material. The observed Raman bands were ascribed to different V-O vibrations. The first specific capacity about 120 mAh/g …

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Photoelectrochemical Properties Of Tio2 Nanoparticles, Jie Qu, Ying Li, Qi-Wei Jiang, Xue-Ping Gao Feb 2009

Photoelectrochemical Properties Of Tio2 Nanoparticles, Jie Qu, Ying Li, Qi-Wei Jiang, Xue-Ping Gao

Journal of Electrochemistry

The protonated titanate nanoparticles were obtained at room temperature and subsequently calcined at different temperatures(300 ℃,400 ℃,500 ℃,600 ℃ and 700 ℃) in air.The obtained products were characterized by XRD,TEM and UV-Vis.It is found that the grain sizes of TiO2 nanoparticles calcined at 300 ℃ were about 20 nm,and increased gradually with the temperature rise.Photoelectric performance was measured with I～V curve and electrochemical impedance spectroscopy(EIS).The TiO2 nanoparticles obtained at 500 ℃ showed the best photoelectrochemical properties with a photovoltaic conversion efficiency of 6.39%,which is much higher than those at other temperatures.In addition,it is also demonstrated that the charge …

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Electrooxidation Behaviors Of Tib2 As High Capacity Anodic Material In Neutral Aqueous Electrolytes, Ya-Dong Wang, Xian-Yong Guang, Zhi-Xin Wang, Xin-Ping Ai, Han-Xi Yang Feb 2009

Electrooxidation Behaviors Of Tib2 As High Capacity Anodic Material In Neutral Aqueous Electrolytes, Ya-Dong Wang, Xian-Yong Guang, Zhi-Xin Wang, Xin-Ping Ai, Han-Xi Yang

Journal of Electrochemistry

Titanium diborides were investigated as an anodic material for neutral aqueous batteries. It is revealed that this material shows superiorly high electrochemical activities in the neutral electrolytes. The discharge capacities observed for TiB2 reached 1300 mAh/g at the constant current density of 50 mA/g, exceeding all the metal electrodes reported so far. The electrooxidation of this compound was found to proceed via the electrochemical dissolution of boron to form borofluoride, while titanium remained unchanged at the electrode. These results suggest a possible use of the boride compounds as a new material for constructing neutral aqueous batteries with high electrochemical …

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The Electrochemical Performance Of Ncf-Sulfur Cathode, Chun-Rong Zhao, Zhong-Bao Yu, Wei-Kun Wang, Yu-Sheng Yang Feb 2009

The Electrochemical Performance Of Ncf-Sulfur Cathode, Chun-Rong Zhao, Zhong-Bao Yu, Wei-Kun Wang, Yu-Sheng Yang

Journal of Electrochemistry

The electrochemical performance of NCF-sulfur cathode, with different NCF contents, was investigated by constant current discharge, cyclic voltammetry and AC impedance methods. The morphologies of the cathodes were observed using scanning electron microscopy. The results indicate that the cycle life and rate capability of NCF-sulfur cathode increased. Better performance of sulfur cathode was obtained by 3% and 5% NCF conductive addition. When the current density was 0.4 mA/cm2, the 3% NCF-sulfur cathode had an initial capacity of 880 mAh/g and a reversible capacity of 630 mAh/g after 20 cycles.

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Preparation And Characterization Of Tin-Nickel Alloy Electromagnetic Shielding Fabric, Ke-Jing Chu, Wei Wang, Bin Sun, Mei-Fang Zhu Feb 2009

Preparation And Characterization Of Tin-Nickel Alloy Electromagnetic Shielding Fabric, Ke-Jing Chu, Wei Wang, Bin Sun, Mei-Fang Zhu

Journal of Electrochemistry

A soft electromagnetic shielding fabric was successfully prepared by electroplating tin-nickel alloy on the Cu-plated PET fabric in potassium pyrophosphate system. Results show that the different tin content and different colour can be obtained by changing the ratio of metals in bath. Better corrosion resistance and anti-tarnishing were achieved with the fabric consisting of 68.96% Sn. The tin-nickel alloy surface for the electromagnetic shielding fabric had excellent conductivity, softness, permeability and soft luster, non-sensitized to the human body. Thereby it has broad prospect in EMI field and shielding clothing.

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Electrosynthesis Of 2,2-Dimethylolpropionic Acid, Hong-Yan Sun, Zhen-Hai Liang Feb 2009

Electrosynthesis Of 2,2-Dimethylolpropionic Acid, Hong-Yan Sun, Zhen-Hai Liang

Journal of Electrochemistry

The Ti/SnO2+Sb2O4/PbO2 electrode was prepared.The structure phase and valent state were characterized by means of XRD and XPS.The 2,2-dimethylolpropionic acid was synthesized on the Ti/SnO2+Sb2O4/PbO2 anode by direct electro-oxidation of 2,2-dimethylolpropionaldehyde.The product and crude material were analyzed by HPLC,the effects of the concentration of 2,2-dimethylolpropionaldehyde,pH,potential and reaction temperature were studied.The results showed that the optimum conditions were anode potential 1.8 V,pH=1,reaction temperature 15 ℃ and 2,2-dimethylolpropionaldehyde concentration 0.10mol/L.Under the optimum conditions,the selectivity of 36%,the current efficiency of 28% and the conversion of 58% were reached.The reported …

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The Electrochemical Behavior And Determination Of Carbendazim On Iron Montmorillonite Modified Electrode, Xiao-Li Jiang, Rong Li, Xiao-Ying He, Jiang Li, Ying Li Feb 2009

The Electrochemical Behavior And Determination Of Carbendazim On Iron Montmorillonite Modified Electrode, Xiao-Li Jiang, Rong Li, Xiao-Ying He, Jiang Li, Ying Li

Journal of Electrochemistry

The FeCl3 modified clay electrode was made.The electrochemical behavior of carbendazim(BCM) on the modified electrode was studied by cyclic voltammetry.The impacts of pH,scan rate and dosages of modifier were discussed and the important kinetic parameters of the electrochemical process were determined.The results indicated that the process was controlled by diffusion.The effective area of FeMM-CMC/GCE(A)=0.027 cm2,the transfer electron numbers(n)=2 and the diffusion coefficient(D)=5.115×10-6cm2/s.Under the optimized conditions,a good linearity was found between the first order derivative of peak current and concentration of BCM in the range of 2.00×10-5～8.00×10-4mol/L,with i′p=-8.045×10-7-0.0237c,correlation …

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Voltage Delay On Li/Socl2 And Bcx Cells During Discharge, Shu-Tao Liu, Yi-Ping Wu, Hong-Hua Ge, Guo-Ding Zhou Feb 2009

Voltage Delay On Li/Socl2 And Bcx Cells During Discharge, Shu-Tao Liu, Yi-Ping Wu, Hong-Hua Ge, Guo-Ding Zhou

Journal of Electrochemistry

The impedance change of both lithium and carbon electrodes during the process of discharge was studied by AC impedance spectroscopy.It shows that the impedance of lithium electrode at initial stage was reduced by 80%～90% and kept nearly unchanged after wards;the carbon electrode impedance initially did not change much but quickly increased just before the end of discharge.The improvement of voltage delay might be related with the higher open-circuit voltage of BCX cell.It is suggested that the voltage delay problem may be solved by the application of supercapacitor.

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Effect Of Irco Intermediate Layer On Electrochemical Property Of Rutisn Anode, Yan Zhao, Gui-Chang Liu, Yong-Lan Liao, Wei-Guang Ji, Shu-Jun Song Feb 2009

Effect Of Irco Intermediate Layer On Electrochemical Property Of Rutisn Anode, Yan Zhao, Gui-Chang Liu, Yong-Lan Liao, Wei-Guang Ji, Shu-Jun Song

Journal of Electrochemistry

The Ti based-RuTiSn anodes with IrCo intermediate layer were prepared by thermal decomposition method. The electrochemical properties of Ti/RuTiSn anodes with different Ir-Co intermediate layers were studied. The surface and elements compositions of the anodes were charactered by scanning electron microscopy(SEM) and electronic probe microanalysis (EPMA). The effects of intermediate layer on the electro-catalytic activity and stability were assessed by chlorine evolution potentials, accelerated lifetime test and cyclic voltammetric curves(CV). It was concluded that the anode, which contained several Ir-Co intermediate layers, could hold not only high electro-catalytic activity but also the increased stability. The enhanced life was up to …

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Synthesis,Characteristics And Electrochemical Performance Of Nano-Sized Snco/Graphite Composites As Anode For Lithium Ion Batteries, Jin-Shu Cai, Ling Huang, Fu-Sheng Ke, Shi-Gang Sun Feb 2009

Synthesis,Characteristics And Electrochemical Performance Of Nano-Sized Snco/Graphite Composites As Anode For Lithium Ion Batteries, Jin-Shu Cai, Ling Huang, Fu-Sheng Ke, Shi-Gang Sun

Journal of Electrochemistry

The nano-structural Sn-Co/graphite composites were prepared by chemical reduction of the alloy electroless deposition solution in graphite suspensions, and the composites were annealed at 500 ℃. The phase structure and surface morphology of the composites were measured by XRD, SEM and Raman. The results indicate that there were high dispersions and high loadings of Sn-Co nanoparticles on graphite by thermal treatment. Electrochemical lithium storage performance was studied preliminarily on the obtained samples. The graphite modified with the Sn-Co nanoparticles possessed a higher electrochemical reversible capacity than that of graphite during the charge and discharge process. The appetency between the Sn-Co …

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Electrochemical Characteristics Of Silicon-Based Composites, Xin-Xin Xu, Jun Yang Feb 2009

Electrochemical Characteristics Of Silicon-Based Composites, Xin-Xin Xu, Jun Yang

Journal of Electrochemistry

The nano-porous Si/G/C composite was obtained by two-step ball milling with SiO, Al and graphite, along with HCl acid etching followed by carbon incorparation. This composite demonstrated the reversible capacity of 600 mAh/g with excellent cycling stability, but low initial cycle efficiency is low.A high-temperature treatment after ball-milling of SiO and A1 could promote the complete reduction of SiO. However, the crystalline structure of Al2O3 product changed from γ-phase to α-phase, which it can no longer be etched by HCl. The Si/Al2O3/G/C composite exhibited higher efficiency at the first cycle but relatively poorer …

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Paramagnetic Resonance Studies Of Bistrispyrazolylborate Cobalt(Ii) And Related Derivatives, William K. Myers Jan 2009

Paramagnetic Resonance Studies Of Bistrispyrazolylborate Cobalt(Ii) And Related Derivatives, William K. Myers

Chemistry and Chemical Biology ETDs

Herein, a systematic frozen solution electron-nuclear double resonance (ENDOR) study of high-spin Co(II) complexes is reported to demonstrate the efficacy of methyl substitutions as a means of separating dipolar and contact coupling, and further, to increase the utility of high-spin Co(II) as a spectroscopic probe for the ubiquitous, but spectroscopically-silent Zn(II) metalloenzymes. High-spin (hs) Co(II) has been subject of paramagnetic resonance studies for over 50 years and has been used as a spectroscopic probe for Zn metalloenzymes for over 35 years. However, as will be seen, the inherent complexity of the electronic properties of the cobaltous ion remains to be …

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Guessing Harmonic Oscillator Wavefunctions Using Maple, Carl W. David Jan 2009

Guessing Harmonic Oscillator Wavefunctions Using Maple, Carl W. David

Chemistry Education Materials

The guessing of eigenfunctions is not trivial at higher quantum numbers, no matter what the system being considered. Instead of guessing, one can employ a symbolic calculus progam (Maple in this case) to aid in the reasoning process.

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The Driven Harmonic Oscillator In Chemistry, Carl W. David Jan 2009

The Driven Harmonic Oscillator In Chemistry, Carl W. David

Chemistry Education Materials

The molecular dynamical simulation of the normal vibrational mode of water which involves H-O-H angle deformation, when driven by an external force, can be used to see how a driven harmonic oscillator, classically, is associated with the infra-red spectrum of water (and the absorption for this particular normal mode).

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Using The Morse Potential To Understand Reaction Coördinates Using Maple, Carl W. David Jan 2009

Using The Morse Potential To Understand Reaction Coördinates Using Maple, Carl W. David

Chemistry Education Materials

The interactions employed in the “linear” reaction A(g)+BC(g) -> AB(g) + C(g) in a “one dimensional world” can be used to illustrate the “reaction coördinate”, using Maple, in a manner which allows students to inspect potential energy surfaces, make contour maps of those surfaces, and conceptually construct the “reaction coördinate” by tracing the local minimum path on the surface created.“one dimensional world” can be used to illustrate the “reaction coördinate”, using Maple, in a manner which allows students to inspect potential energy surfaces, make contour maps of those surfaces, and conceptually construct the “reaction coördinate” by tracing the local minimum …

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Frobenius Solution For Legendre's Equation, Rodrigue's Formula And Normalization, Carl W. David Jan 2009

Frobenius Solution For Legendre's Equation, Rodrigue's Formula And Normalization, Carl W. David

Chemistry Education Materials

The Frobenius solution to Legendre/s equation is developed in detail as is Rodrigue's formula, which is employed to normalize Legendre polynomials.

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1s_A 1s_B Overlap Integrals, Analytic And Maple Approches, Carl W. David Jan 2009

1s_A 1s_B Overlap Integrals, Analytic And Maple Approches, Carl W. David

Chemistry Education Materials

The calculation of overlap between adjacent orbitals (not on the same center) requires a slight facility with calculus which is quite instructive. That calculation is presented here.

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Rationale For Studying Physical Chemistry, Carl W. David Jan 2009

Rationale For Studying Physical Chemistry, Carl W. David

Chemistry Education Materials

The various rationales for studying physical chemistry, and specifically the theoretical component thereof are presented in what is hoped in a coherent package.

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The Harmonic Oscillator's Frobenius Solution, Carl W. David Jan 2009

The Harmonic Oscillator's Frobenius Solution, Carl W. David

Chemistry Education Materials

The Frobenius solution to the differential equations associated with the harmonic oscillator (QM) is carried out in detail.

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The Hartree-Fock Method Applied To Helium's Electrons, Carl W. David Jan 2009

The Hartree-Fock Method Applied To Helium's Electrons, Carl W. David

Chemistry Education Materials

The difficulties of applying the Hartree-Fock method to many body problems is illustrated by treating Helium's electrons up to the point where tractability vanishes. Second, the problem of applying Hartree-Fock methods to the helium atom's electrons, when they are constrained to remain on a sphere, is revisited. The 6-dimensional total energy operator is reduced to a 2-dimensional one, and the application of that 2-dimensional operator in the Hartree-Fock mode is discussed.

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Multiple-Choice Testing In Science And Technology Courses, Carl W. David Jan 2009

Multiple-Choice Testing In Science And Technology Courses, Carl W. David

Chemistry Education Materials

Wide spread and continuing use of multiple-choice testing in technical subjects is leading to a mindset amongst students which is antithetical with actual use of intellect.

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L'Hopital's Rule In Chemistry: Irreversible Morphing Into Reversible Isothermal Expansions, Carl W. David Jan 2009

L'Hopital's Rule In Chemistry: Irreversible Morphing Into Reversible Isothermal Expansions, Carl W. David

Chemistry Education Materials

L'Hopital's Rule is discussed in the cvase of an irreversible isothermal expansion.

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Mo Visualization Of Pi Orbitals, Carl W. David Jan 2009

Mo Visualization Of Pi Orbitals, Carl W. David

Chemistry Education Materials

In the spirit of trying to convert people to understanding atomic orbitals centered elsewhere than the origin, we continue the discussion of visualizing molecular orbitals, so called LCAO-MO, using various plotting tricks in Maple.

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A Review Of Helium Hamiltonians, Carl W. David Jan 2009

A Review Of Helium Hamiltonians, Carl W. David

Chemistry Education Materials

Helium Hamiltonian transformations are discussed in extreme detail.

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Lee O Case's "Elements Of The Phase Rule", Introduction And Explanation, Carl W. David Jan 2009

Lee O Case's "Elements Of The Phase Rule", Introduction And Explanation, Carl W. David

Chemistry Education Materials

This out of print 1939 manuscript, updated, is added to the literature with slight additions

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The Runge0lenz Vector (Continued), Carl W. David Jan 2009

The Runge0lenz Vector (Continued), Carl W. David

Chemistry Education Materials

We continue our discussion of the Runge-Lenz vector in a quantum mechanical context. The traditional form of the Runge-Lenz vector is obtained, and the commutation relations between the Runge-Lenz vector, the Hamiltonian, and the Angular Momentum are obtained using Maple.

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Lee O Case's "Elements Of The Phase Rule", Chapter 2, Carl W. David Jan 2009

Lee O Case's "Elements Of The Phase Rule", Chapter 2, Carl W. David

Chemistry Education Materials

The second chapter of the Case text on the phase rule, this time dealing with two component systems, added to by the author, is presented here.

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