Search

A new red phosphor Ca3SiO4Cl2:Sm3+ has been synthesized and its luminescent properties have been investigated. The X-ray powder diffraction (XRD) was measured for studying the host structure. The excitation and emission spectra were measured at room temperature. The effect of Sm3+ ion content on the luminescent intensity and concentration quenching mechanism were studied. The results suggest that this phosphor maybe a good candidate of red phosphor for near UV-based white LED.

Using ab-initio ultrasoft pseudopotential plane wave approximation method based on density functional theory (DFT), a systematic investigation on electronic and optical properties of ZnS with and without Al-doping has been performed. Calculation results show that Al-doping narrows the band gap of ZnS systems and Al-doped ZnS system changes from semiconductor into metal through the Mott transition. Moreover, with Al-doping increasing, the increase of absorption coefficient and redshift of absorption spectra are obtained. Absorption spectra of pure ZnS and Al-doped ZnS are in good agreement with the experimental results.

The electronic structure and optical properties of pristine and Pd-doped or Ag-doped zinc blende ZnS were calculated with the ab-initio ultrasoft pseudopotential plane wave approximation method based on density functional theory (DFT). The results show that doping significantly alters the system band structure and the electronic density of states (DOS), effectivly enhancing the ZnS optical response and the photocatalytic activity in the visible light range. The microscopic mechanism shows that ZnS photocatalysis efficiency is observably improved through doping.

Dodecylbenzenesulfonic acid (DBSA) doped polypanilines (PANIs) were chemically synthesized in different molar ratios of aniline (An) to ammonium persulfate (APS) and An to DBSA. The microstructures of these PANIs were investigated by means of scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier Transform Infrared (FTIR). UV-Vis spectrometer, semiconductor parameter analyzer, ubbelohde viscometer and electrospinning technique were used to characterize the optical, electrical properties, viscosity and solubility of these PANIs. The results show that the molar rations of An to APS and An to DBSA had strong effect on the microstructure, molecular weight, degree of crystallinity, optical property, solubility and conductivity of obtained DBSA doped PANI. With the increase of the molar ratios of An to APS and An to DBSA, the conductivities and molecular weight of DBSA doped PANIs decreased, while the degree of crystallinity and solubility of DBSA doped PANIs increased. The DBSA doped PANI could dissolve in dichloromethane or HFIP and could be fabricated short fibers by electrospinning. Moreover, the solution of DBSA doped PANIs in concentrated sulphuric acid showed liquid crystal property.

Single ion conducting polymer electrolytes synthesized through a copolymer poly(lithium 2-acrylamido-2-methylpropanesulfonic acid-co-vinyl triethoxysilane) and a crosslinker poly(etheylene glycol) dimethacrylate (PEGDMA) were prepared. Scanning electron microscope (SEM) was used to observe the morphology of the surface and cross-section of the polymer electrolyte membrane. AC impedance and linear sweep voltammetry were used to investigate the electrochemical properties of the polymer electrolytes. It was found that the obtained membrane had a typical amorphous structure and possessed a smooth surface. The bulk resistance of the polymer electrolyte increased with the increase in the plasticizer uptake. The electrochemical stability increased with the increase in the content of VTES.

After the implement of ERP system in electric power enterprise, the enterprise's management had a great change. Financial management work, as an important part of enterprise management, the improving of the performance of it will have an important impact on the management of the whole enterprise competitiveness. This paper mainly analyzes the implementation effect of electric power enterprise ERP financial management. By constructing evaluation index system, using the AHP method to analyze it, and then have a conclusion that the quantitative evaluation results, what will have a strong boost role to the electric power enterprise ERP financial management work.

Electrolysis and plasma polishing(EPP) is a new “green” technique that can efficiently polish metal workpieces and provide high-quality surface of the workpieces. In this paper, mechanism of EPP and why metal parts can be polished by EPP are expounded on by Streamer theory. EPP is a dynamic process consisting of oxidation and discharge. A precondition of EPP is that the removal rate of discharge is faster than oxidation. It is deduced from the mechanism and demonstrated experimentally that the material removal rate is direct proportion to the electric current density.

First-principles calculations were performed to study the relative stabilities of YNi2 and YMgNi4.The calculated results show that YMgNi4 has the higher stability than YNi2, duing to stress relaxation and ionic contribution. The preferential stability of YMgNi4 has been confirmed by calculating elastic constants and melting points.The calculated results show that YMgNi4 has the larger bulk modulus and melting point than YNi2.

First-principles calculations were performed to study the electronic and optical properties of Cu3N and Cu4N. The calculated density of states show that Cu3N is a semiconductor with a 0.5ev gap while Cu4N is metallic. The dielectric functions, absorption coefficients, refractive coefficients and extinction coefficients of Cu3N and Cu4N were obtained and compared with some experiment results. It shows the calculated results agree well with the experimental values.

We performed first-principles calculations to the electronic structure and bonding characteristic of NdMgNi4H4. The calculation results show that the H—Ni units are formed by the covalent H—Ni bonds, the surrounding Mg and Nd atoms provide electrons to the H—Ni units, and the Ni-Ni bonds between the different H—Ni units are covalent, making the H—Ni units not isolated. These bonding characteristics show that NdMgNi4H4 is similar with interstitial metal hydride in some aspects, and similar with complex metal hydrides in other aspects, indicating NdMgNi4H4 is the intermediate between interstitial metal hydrides and complex metal hydrides.

In the present paper, the lattice structure, band structure and density of state of LaAlO3 and LaAlO3:Mg are calculated by first-principle method based on density functional theory. Firstly, we select the different cutoff energy and k-point grid in the calculations, and obtain the most stable geometry structure of single crystal LaAlO3. The calculated lattice parameters are a=b=5.441 Å, c=13.266 Å, which matches with experimental values. To deeply understand the electronic structure of LaAlO3, a 2×1×1 super-cell structure is established and the doping concentration of Mg at Al sites is 25%. From the band structure and density of states, it can be seen that LaAlO3 has a direct band gap Eg=3.6 eV. However, LaAlO3:Mg has a larger band gap Eg=3.89 eV and the Fermi level enters into the valence band, which indicates the holes are introduced. The calculated results show that the conductivity of LaAlO3:Mg is better than pure LaAlO3, which is in good agreement with experimental results.

In the present paper, the lattice structure, band structure and density of state of pure and P-doped ZnO are calculated by first-principle method based on density functional theory. By analyzing the Mulliken charge overlap population and bond length, it is found that the bond of P-Zn is longer and stronger than O-Zn bond for PO-ZnO. But for PZn-ZnO, the O-P bond becomes shorter and more powerful than O-Zn bond. Also, weak O-O bonds are formed in this case. Our results show that the final total energy of PO-ZnO is lower than PZn-ZnO. The lattice structure of PO-ZnO is more stability than PZn-ZnO. For PO-ZnO, The Fermi level moves into the valence band, which expresses that the holes appear on the top of valence band and thus the PO-ZnO exhibits p-type conductivity. For PZn-ZnO, the Fermi level moves up to the conductor band and the total density of states shifts to the lower energy region, thus PZn-ZnO shows the n-type conductivity.

Density functional theory plane-wave pseudopotential with the general gradient approximation (GGA) was used to investigate electronic structural properties and the bulk spontaneous polarization (Ps) of PbZr0.4Ti0.6O3. It is found that there are strong hybridizations between Ti 3d states or Zr 4d states and O 2p states, which can reduce short-range repulsion in atoms and enhance the stability of the ferroelectric phase of PbZr0.4Ti0.6O3. Compared with cubic ideal structure, the calculated internal electronic structural data indicate that the slightly distorted O6 octahedrons around the central Ti and Zr atoms change to the Ti-O5 and Zr-O5 pyramid in the optimized structure, respectively. The major contribution to the spontaneous polarization along [001] comes from the stronger interaction along the c axis between the Ti and O rather than the Zr and O ions. The Pb atom’s relative displacement of oxygen octahedral implies that the Pb-O bonding interaction is also a key factor impacting the ferroelectricity of PbZr0.4Ti0.6O3. A theoretical spontaneous polarization of 0.78 C/m2 was computed in the tetragonal PbZr0.4Ti0.6O3 along [001] direction, consistent with the single crystal experimental data.

In this study, a novel green phosphor Ca2SrAl2O6:Ce3+,Tb3+ were prepared by solid state method. The crystal structure and particle morphology of phosphors were measured by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The result indicated that the phosphor belonged to a single Ca2SrAl2O6 phase and crystalline grain sizes were about 2.0~5.0 μm. The excitation and emission spectra were studied in this paper. Monitored at 545 nm, the excitation spectrum consisted of a broad band at UV region (320-400 nm), which was attributed to the abstract of Ce3+ and Tb3+ ions. Excited by 360 nm UV light, the emission spectrum was composed of four groups narrow band and the emission peaks located at 497, 545, 595 and 623nm, respectively. Luminescent intensity increased with Tb3+ and Ce3+ ions concentration and it would reach the maximum when the activator molar fraction was 0.04 for the highest emission intensity at 545 nm. Concentration quenching would occur if the activator concentration exceeded 0.04 mol-1. Li2CO3 could be used for flux and Li+ ion was used for charge compensation in this experiment. Thus, Ca2SrAl2O6:Ce3+, Tb3+ phosphor was a good candidate of green phosphor for UV based white LED.

Using the density functional theory method, we have characterized the geometrical structures and adsorption energy of water clusters adsorption on graphite surface. When one water molecule inter- acts with graphite surface, one of the H-O bonds formed hydrogen-bond with carbon atom in graphite sheet; in the two water molecules structure, the linear dimmer nearly parallel to the graphite surface, and also formed the hydrogen-bond; when the number of water molecules increased to six, all the H-O bond that point to the graphite surface has formed Hydrogen-bond with it. The binding energy of the water clusters with a graphite surface depends only on the number of water molecules that form hydrogen bond.