In order to increase the electrode surface area and enhance the charge storage capacity, we study the micro electro mechanical system technology to fabricate three-dimensional high aspect ratio micro-electrode structure based on glass. The anodic constant potential method is employed to deposit manganese oxide as electroactive substances on the micro-electrode surface. Cyclic voltammetry and constant current charge-discharge method are both used to prepare electrode electrochemical performance testing, with a two-dimensional electrode without structure for comparison. Experimental results show that three-dimensional electrode structure can effectively enhance the charge storage capacity. At 1.0 mA/cm2 charge-discharge density, the three-dimensional electrode shows a capacitance of 17.88 mF/cm2, seven times higher than the two-dimensional electrode.
The electronic state and potential data of U2 molecules are performed by first principle calculations with B3LYP hybrid exchange-correlation functional, the valence electrons of U atom are treated with the (5s4p3d4f)/[3s3p2d2f] contraction basis sets, and the cores are approximated with the relativistic effective core potential. The results show that the ground electronic state is X 9Σ+ g. The pair potential data are fitted with a Murrell-Sorbie analytical potential function. The U-U embedded atom method (EAM) interatomic potential is determined based on the generalized gradient approximation calculation within the framework of the density functional theory using Perdew-Burke-Ernzerhof exchange-correlation functional at the spin-polarized level. The physical properties, such as the cohesive energy, the lattice constant, the bulk modulus, the shear modulus, the sc/fcc relative energy, the hcp/fcc relative energy, the shear modulus and the monovacancy formation energy are used to evaluate the EAM potential parameters. The U-U pair potential determined by the first principle calculations is in agreement with that defined by the EAM potential parameters. The EAM calculated formation energy of the monovacancy in the fcc structure is also found to be in close agreement with DFT calculation.
The hydrogen adsorption properties and uptake capacities of the A, X and ZSM-5 types of zeolites were investigated at temperatures of 77, 195 and 293 K and pressures up to 7 MPa, using a conventional volumetric adsorption apparatus. All hydrogen adsorption isotherms were basically type 1, but the maximum in isotherm, a unique feature of supercritical adsorption, was observed at high pressures of 2-5 MPa at 77 K. The isosteric heats of adsorption were determined from the isotherms and the factors that influence their variations were discussed. Different types of zeolites exhibited remarkably different hydrogen uptake, based on both the framework structure and the nature of the cations present. The highest gravimetric storage capacity of 2.55wt% was obtained for NaX-type zeolite at 4 MPa and 77 K. In CaA, NaX and ZSM-5 types of zeolites, hydrogen uptakes were proportional to the specific surface areas, which were associated with the available void volumes of the zeolites. A threshold in hydrogen adsorption observed in NaA and KA was attributed to a pore blocking effect by large cations in KA. A ratio of the kinetic diameter of adsorbate to the effective opening diameter of zeolite was used to judge the blocking effect for physisorption.
The electronic and magnetic properties of Ce doped SrMnO3 have been investigated using the pseudo-potential plane wave method within the generalized gradient approximation method by first principles. The different Mn—O bond lengths indicate that there is a strong Jahn-Teller distortion of the MnO6 octahedron, which associates with a structural phase transition from cubic symmetry (Pm3̄m) to tetragonal symmetry (I4/mcm), and the Jahn-Teller ordering stabilizes a chain like (C-type) antiferromagnetic ground state. The electronic structures indicate that SrMnO3 and Sr1−x Ce x MnO3 (x = 0.125 and 0.25) are semiconductor and metallic, respectively. The doping of SrMnO3 with cerium induces simultaneously a decrease in the electrical resistivity, which can be attributed to the formation of Mn3+ as a result of charge compensation. The density of states and charge density map present that hybridization exists between some of O bands with those of Mn and Ce bands, the bonding between Sr and O is mainly ionic. Density of states and magnetic moment calculations show that the formal valence state of the Ce ion is trivalence.
Quasi-classical trajectory calculations have been employed to investigate the influence of collision energy on the stereodynamics of the title reaction C+CD→C2+D on the potential energy surface of the 12A′ state developed by Boggio-Pasqua et al. [Mol. Phys. 98, 1925 (2000)]. The product angular distributions which reflect the vector correlation have been calculated. In addition, two polarization-dependent different cross-sections are also presented in the center-of-mass frame respectively. The results indicate that the product C2 is sensitively affected by collision energy.
The F+HCl and F+DCl reactions are studied by the time-dependent quantum wave packet method, using the most recent potential energy surface reported by Deskevich et al.. Total reaction probabilities for a number of initial ro-vibrational states of HCl and DCl diatomic moiety are presented in the case of total angular momentum J=0. It is found that for both reactions the initial rotational excitation of the diatomic moiety enhances greatly the reaction probabilities but this effect is more significant for F+HCl system. This is mainly due to larger rotational constant of the HCl reagent. The initial vibrational excitation of the diatomic moiety has little effect on the reactivity for both systems except shifting down the collision energy threshold. The results indicate that the reaction coordinates for these two systems are effectively along rotational freedom degree. More quantum phenomena, such as tunneling and resonance, are observed in F+HCl reaction than F+DCl reaction, and for the initial states studied, the reactivity of the later is lower. Different skewing angles of these two systems account for these isotopic differences.
Photon-induced dissociation pathways of thymine are investigated with vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. The photoionization mass spectra of thymine at different photon energy are measured and presented. By selecting suitable photon energy exclusively molecular ion m/z = 126 is obtained. At photon energy of 12.0 eV, the major ionic fragments at m/z = 98, 97, 84, 83, 70, and 55 are obtained, which are assigned to C4H6N2O+, C4H5N2O+, C3H4N2O+ (or C4H6NO+), C4H5NO+, C2NO2 +, and C3H5N+, respectively. With help of theoretical calculations, the detailed dissociation pathways of thymine at low energy are well established.
A global three dimensional potential energy surface for the F+H-2 -> HF+H reaction has been developed by spline interpolation of about 15,000 syminetry-unique ab initio points, obtained from the multi-reference configuration interaction level with Davidson correction using the aug-cc-pV5Z basis set. In the entrance channel the spin-orbit coupling energy is also included.
A flow system was set up to measure the quenching probability γ of O2(1Δg) on various O2-adsorbed metal surfaces including Cu, Cr, Ni, and Ag. γ increased with both the duration of the experiment and the O2(1Δg) concentration. After several hours evacuation to a few Pa, γ can return to its original value. A deactivation mechanism of O2(1Δg) is suggested by considering first the weak chemisorption of O2(1Δg) on the surface adsorption sites, followed by the near resonant energy transfer between the gas phase O2(1Δg) and surface O2(3Σ− g). A phenomenological model in accord with the experimental fact has been proposed together with relevant kinetic equations.
Superexcited states of NO molecule and their neutral dissociation processes have been studied both experimentally and theoretically. Neutral excited N* and O* atoms are detected by fluorescence spectroscopy for the NO molecule upon interaction with 800 nm intense laser radiation of duration 60 fs and intensity 0.2 PW/cm2. Intense laser pulse causes neutral dissociation of superexcited NO molecule by way of multiphoton excitation, which is equivalent to single photon excitation in the extreme-ultraviolet region by synchrotron radiation. Potential energy curves (PECs) are also built using the calculated superexcited state of NO+. In light of the PECs, direct dissociation and pre-dissociation mechanisms are proposed respectively for the neutral dissociation leading to excited fragments N* and O*.
Thickness effects of thin La0.7Sr0.3MnO3 (LSMO) films on (LaAlO3)0.3(Sr2AlTaO6)0.7 substrates were examined by a slow positron beam technique. Doppler-broadening line shape parameter S was measured as a function of thickness and differnt annealing conditions. Results reveal there could be more than one mechanism to induce vacancy-like defects. It was found that strain-induced defects mainly influence the S value of the in situ oxygen-ambience annealing LSMO thin films and the strain could vanish still faster along with the increase of thickness, and the oxygen-deficient induced defects mainly affect the S value of post-annealing LSMO films.
MnxNi0.5-xZn0.5Fe2O4 nanorods were successfully synthesized by the thermal treatment of rod-like precursors that were fabricated by the co-precipitation of Mn2+, Ni2+, and Fe2+ in the lye. The phase, morphology, and particle diameter were examined by the X-ray diffraction and transmission electron microscopy. The magnetic properties of the samples were studied using a vibrating sample magnetometer. The results indicated that pure Ni0.5Zn0.5Fe2O4 nanorods with a diameter of 35 nm and an aspect ratio of 15 were prepared. It was found that the diameter of the MnxNi0.5-xZn0.5Fe2O4 (0 <= x <= 0.5) samples increased, the length and the aspect ratio decreased, with an increase in x value. When x=0.5, the diameter and the aspect ratio of the sample reached up to 50 nm and 7-8, respectively. The coercivity of the samples first increased and then decreased with the increase in the x value. The coercivity of the samples again increased when the x value was higher than 0.4. When x=0.5, the coercivity of the MnxNi0.5-xZn0.5Fe2O4 sample reached the maximal value (134.3 Oe) at the calcinatiou temperature of 600 degrees C. The saturation magnetization of the samples first increased and then decreased with the increase in the x value.. When x=0.2, the saturation magnetization of the sample reached the maximal value (68.5 emu/g) at the calcination temperature of 800 degrees C.
Based on the magnetic interaction energy, using derivative of the magnetic energy density, a model is proposed to compute the magnetic-induced shear modulus of magnetorheological elastomers. Taking into account the influences of particles in the same chain and the particles in all adjacent chains, the traditional magnetic dipole model of the magnetorheological elastomers is modified. The influence of the ratio of the distance between adjacent chains to the distance between adjacent particles in a chain on the magnetic induced shear rhodulus is quantitatively studied. When the ratio is large, the multi-chain model is compatible with the single chain model, but when the ratio is small, the difference of the two models is significant and can not be neglected. Making certain the size of the columns and the distance between adjacent columns, after constructing the computational model of BCT structures, the mechanical property of the magnetorheological elastomers composed of columnar structures is analyzed. Results show that, conventional point dipole model has overrated the magnetic-induced shear modulus of the magnetorheological elastomers. From the point of increasing the magnetic-induced shear modulus, when the particle volume fraction is small, the chain-like structure exhibits better result than the columnar structure, but when the particle volume fraction is large, the columnar structure will be better.