Search

We have investigated the surface structure and relative stability of ZnV2O6(001) using a thermodynamic technique based on density functional theory (DFT).

A molecular crystal structure model of the lead-free halide chalcogenide semiconductor Cs2LiInX6 (X = F, Cl, and Br) was established, and its energy band, density of states, optical properties, and...

ZnV2O6 nanomaterials have attracted great interest in the fields of photocatalysis, sensors, solar cells, supercapacitors, and so on. Some investigators already feel that access to morphology contr...

A new type of Cu3V2O7(OH)2·2H2O nanosheet was synthesized by precipitation from. The powder X-ray diffraction (XRD) of Cu3V2O7(OH)2·2H2O sample shows that the sample has high purity, good crystalli...

In this paper, a CSVO3 phosphor for white LED has been successfully prepared by solid-state synthesis and has been characterized. The CsVO3 was simulated by Materials Studio software based on densi...

Nowadays, low-dimensional graphene nanomaterials, such as two dimensional (2D) graphene nanosheets (2D GNs), have been widely reported and suggested for, e.g., catalysts, solar cells, and photovoltaic devices, but previous works still do not pay much attention to the flexible electronics sensor that base on the 2D graphene nanomaterials. Here we report on using a highly conductive polyoxometalate (POM) and 2D GNs foam to fabricate the 2D GNs-based supercapacitors capable of detecting the pulse beat rate. Characterization techniques, such as the X-ray diffraction, energy dispersive X-ray spectra, transmission electron microscopy, galvanostatic charge–discharge and cyclic voltammetry, are used to illustrate the structural and electrochemical properties. Our results reveal that the POM can disperse into 2D GNs to form the POM/2D GNs nanocomposites. In the meanwhile, we find the specific cycling stability of POM/2D GNs can be significantly enhanced as compared to bulk 2D GNs foam. Moreover, we design a flexible pulse sensor device, which is based on depositing the POM/2D GNs foam on a conductive adhesive substrate. Our results reveal that the POM/2D GNs-based sensor is sensitive to the external pulse beat, which can linearly detect a bending area within the range of 0.483 mm2. This work indicates that the POM/2D GNs can act as a type of sensor material to monitor the human body health.

Polyanion-type LiVPO4F has been regarded as a potential candidate of cathode material for lithium-ion batteries due to its high working voltage, excellent thermal stability and good safety. However, the pure LiVPO4F has a low electronic conductivity of 10−11 S cm−1, which greatly limits its application in high-power density batteries. In this research, the core-shell carbon-coated LiVPO4F composite is prepared using a facile sol-gel method followed by a solid-state reaction. Owing to the synergistic effects rendered by the LiVPO4F nanoparticles and conductive carbon coating, the as-prepared composite exhibits high reversible capacity (147.9 mAh g−1 at 0.1 C), excellent rate capability (121.2 mAh g−1 at 5 C) and stable cyclic performance (94% capacity retention after 200 cycles at 2 C). These results reveal that the carbon-coated LiVPO4F material is a promising cathode material for high-power lithium-ion batteries.

Zn3V2O8 phosphors were synthesized by combustion with (NH4VO3), C6H8O7 • H2O and Zn (NO3) 2 as raw materials. The crystal structure, morphology and optical properties of the films were characterize...

ZnV2O6 materials have been successfully prepared by solid-state synthesis. The phase of ZnV2O6 by X-ray Diffraction (XRD) characterization was carried out. The band structure, density of states (DOS) and optical properties of ZnV2O6 have been simulated by Materials Studio software based on density functional theory (DFT). The calculation results show that the bandgap of ZnV2O6 crystal is 2.104eV and it is a direct band gap semiconductor. The calculation results of optical properties show that ZnV2O6 exhibits better properties than TiO2 in visible light range, the absorption and reflection spectrum of ZnV2O6 are in the ultraviolet region, which has potential applications in the fabrication of ultraviolet semiconductor detectors, ultraviolet shielding devices and so on. Compared with the application of TiO2 with good performance in the ultraviolet region, there may be a complementary and substitutional role.

RbVO3 luminescent materials have been successfully prepared by solid-state synthesis. The phase, surface morphology and photoluminescence properties of RbVO3 have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and luminescence spectrophotometer, respectively. The band structure, Density of States and optical properties of RbVO3 have been simulated by Materials Studio software based on density functional theory (DFT). According to the experimental results and the First-principles, the electronic structure and optical properties of RbVO3 were studied. The results show that RbVO3 crystal has a direct band gap with a band gap of 2.973 eV. Under ultraviolet excitation in the range of 210–390 nm, and the excitation spectrum peak appears at 340 nm. The emission spectrum of RbVO3 phosphors ranges from 400 to 700 nm, and its peak emission spectrum is near 507 nm, showing white luminescence emission.

Zn3V2O8 phosphors were synthesized by combustion with (NH4VO3), C6H8O7 • H2O and Zn(NO3)2 as raw materials. The crystal structure and optical properties of the films were characterized by X-ray diffraction (XRD) and emission spectra. And based on the first-principles of density functional theory (DFT) The α-Zn3V2O8 crystal model was established under zero pressure, and the dielectric and optical properties of the model were calculated. The experimental results show that the crystal structure of Zn3V2O8 has no effect on the crystal structure of Zn3V2O8. The emission intensity of the sample at 600℃ is the weakest, the light intensity of the sample is the strongest at 700℃, and the optical properties is changed with calcination temperature changed of Zn3V2O8. The excitation spectrum of the phosphor is between 300nm and 420nm and the peak at 360nm, The emission spectrum of the range between 420-690nm, the peak at 550nm. The absorption coefficient of α-Zn3V2O8 appears at 5.44 eV, the reflection peak is at 6.28 eV.

Used CaCO3 and Co (NO3)2·6H2O as raw materials of the Experiments, that successfully synthesized Ca3Co4O9 thermoelectric material by sol-gel method. Observation of morphology and microstructure of materials by X-ray diffraction pattern (XRD) and scanning electron microscopy (SEM), explore different sintering temperature on the structure Ca3Co4O9 thermoelectric material. By Ca3Co4O9 honeycomb structure it found Ca3Co4O9 can get a good performance thermoelectric material has broad application prospects.

By choosing zinc acetate dehydrate (Zn(CH3COO)2·2H2O) and ammonium metavanadate (NH4VO3) as starting materials, we succeeded in fabricating Zn3V2O8 phase suitable for broad light emission by sol–gel process. X-ray diffraction (XRD), scanning electron microscope, photoluminescence (PL) and PL quantum yield (PL-QY) measurements have been performed for analyzing the relation between crystallographic and light emission characteristics. The PL-QY is determined by both the crystalline phase purity of the Zn3V2O8 phase defined by XRD patterns and the crystalline size. With optimizing the sintering condition at a slightly Zn-rich side, a pure Zn3V2O8 phase with enough large crystalline size was obtained with the PL-QY value of 52 %, which was higher than our previously obtained value by solid state reaction.

China. Abstract. The sample of Zn3V2O8 has been preparation by high temperature solid phase method with fluxing, and studied the effect of preparation condition and the luminescence property with fluxing. The results of phase studied show that the crystal morphology was improved, the reunite of grain crystal was decreased, and the effect of crystal structure was none by fluxed. The results of luminescence property shows that the emission peak was appeared at the wave-length of 400—700 nm, and the highest peak appeared at the wave-length of 550nm under the near ultraviolet excitation light of 360nm, the results shows that the luminescence property was improved by flux of NH4Cl, NH4F and H3BO3.

One of promising phosphors in vanadium oxide family, Zn3V2O8, was successfully synthesized by a solid state reaction of ZnO and V2O5. Characterization by XRD, photoluminescence (PL) and SEM was done for samples with different temperature and time in the sintering process. Residual percentage of secondary Zn2V2O7 phase, subsidiary ZnO and Zn4V2O9 phases was dependent on the sintering condition. The crystalline purity (CP) was defined by the integral intensity ratio of Zn3V2O8 phase and that of residual phases in XRD spectra, which showed a reasonable correspondence to the PL quantum yield (QY) of each sample. The highest QY exceeding 50% was obtained by the sintering condition of 750?C for 48 h. It turned out that the CP value is a good measure of high QY, which can be utilized for developing phosphor materials and controlling their processes.

The Zn3V2O8 and (Zn1-xEux)3V2O8 have been production by Solid phase method. The crystal structure, the crystal morphology and the luminescence property of Zn3V2O8 and (Zn1-xEux)3V2O8 have been studied. Based on the first-principles planar wave super-soft pseudopotential method of density functional theory (DFT), the α-Zn3V2O8 crystal model was used to calculate the electronic structure and optical properties of the model. The results show that the crystal structure of Zn3V2O8 and (Zn1-xEux)3V2O8 were the same, and the particle uniformity of (Zn1-xEux)3V2O8 was better than Zn3V2O8. The emission band Zn3V2O8 and (Zn1-xEux)3V2O8 were present at the wave length of 420-690 nm and 300-400nm, the luminescence property of (Zn1-xEux)3V2O8 was enhance by Eu-doped. α-Zn3V2O8 is an indirect band gap, α-Zn3V2O has a band gap of 2.715eV, pure α-Zn3V2O8 has a peak, appeared at 3.91eV that is caused by the optical transition between V 3d and O 2p states.

In this paper, Zn3V2O8 phosphors were synthesized by high temperature solid method. The effect of flux on the luminescent properties was studied. And based on the first-principles planar wave super-soft pseudo potential method of density functional theory (DFT), the α- Zn3V2O8 crystal model was used to calculate the electronic structure and optical properties of the model. The results show that the crystal morphology of the sample is improved, the grain agglomeration is reduced and the crystal structure isn't changed. The excitation spectrum ranges from 300-400nm, the excitation peak is at 360nm, and the emission spectrum is in the range of 420-690 nm, the peak at 550 nm. α- Zn3V2O8 is an indirect band gap, α- Zn3V2O8 has a band gap of 2.715eV, α- Zn3V2O8 has a strong UV-near ultraviolet light absorption capacity.

In this paper, CaCO3, CoO, CuO as raw materials, using solid phase preparation of Ca3Co4O9-based thermoelectric materials doping Cu. The Ca3Co4O9-based thermoelectric material intermediates were prepared according to the stoichiometric ratio x=0.01, and the sintered crystals were prepared by using muffle furnace under different temperature setting conditions. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) were used to analyze the crystallinity and morphology of the samples after sintering. The results show that the crystallinity of Ca3Co4O9-based thermoelectric materials is best when sintered at 800-850°C, and the crystallinity of samples sintered at 850°C is better than that at 800°C, The diffraction intensity ratio is stronger than 800°C. Continue to raise the temperature, Ca3Co4O9-based thermoelectric materials phase transition to Ca3Co2O6-based thermoelectric materials, When the sintering temperature is 1000°C, the product is Cu-doped Ca3Co2O6-based thermoelectric materials.

Based on investigation dada on petroleum hydrocarbon (PHC) in April, June, Juny and October 1982 in Jiaozhou Bay, this paper analyzed the content, distribution and seasonal variations of PHC. Results showed that PHC contents in April, June, July and October in surface waters ranged from 0.03-0.07 mg.L-1, 0.05-0.10 mg.L-1,0.04-0.07 mg.L-1 and 0.03-0.04 mg.L-1, respectively, and were meeting Grade II and III in National Sea Water Quality Standard (GB 3097-1997), and were generally decreasing with time within the year. For spatial distribution, the ranges of PHC contents in April, July and October were 0.02 mg.L-1, 0.03 mg.L-1 and 0.01 mg.L-1, respectively, indicated that the distributions of PHC in the southwest were tended to be homogenous. The results confirm that tide and current are stirring and transporting all of the materials in the ocean, resulting in the homogous distributions of the contents of various materials in waters.

Cr is one of the critical industrial heavy metal pollutants. Understanding the pollution level and source of Cr in the early stage of the reform is helpful to provide background information to environmental remediation. This paper analyzed the content and distribution of Cr in Jiaozhou Bay waters in 1983. Results showed that Cr contents ranged from 0.13-4.17 μg L -1 , and were confirmed with Grade I(50 μg L -1 ) in according to Chinese Sea Water Quality Standard (GB 3097-1997), indicated that the pollution level of Cr was very low in 1983. In according to the distributions of Cr in surface waters in Jiaozhou Bay, we found that the major inflow rivers such as Loushan River and Licun River were the major input channels of Cr, and industrial point source was the major source of Cr in the early stage of the reform. The source strength was stable all around the year, ranged from 3.78-4.17μg L -1 .

In this paper, the (Zn1-xYx)3V2O8 and (Zn1-xEux)3V2O8 phosphors were successfully prepared by high temperature solid state method. The effect of the doping amount of Y3+ and Eu3+ on the luminescent properties of phosphors was discussed. The phase, surface morphology and luminescent properties of the phosphors were characterized by X ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL). The results show that the phosphor is the target product, the sample of the composite particles is bulky, the excitation spectral range of (Zn1-xYx)3V2O8 phosphors is 300-400nm, the excitation peak is at 361nm, and (Zn1-xYx)3V2O8 phosphor emission spectra in the range of 420-690nm, the emission peak in 559nm. The results show that the crystal structure of Zn3V2O8 and (Zn1-xEux)3V2O8 were the same, and the particle uniformity of (Zn1-xEux)3V2O8 was better than Zn3V2O8. The emission band Zn3V2O8 and (Zn1-xEux)3V2O8 were present at the wave length of 420-690 nm, the luminescence property of (Zn1-xEux)3V2O8 was enhance by Eu-doped.

Magnetic and magnetoresistance effect of needle shaped crystal and slightly Co rich Ca3Co2O6 was investigated in a temperature range between 2 and 100 K and in a dc magnetic field range less than 7 T and in pulsed fields less than 20 T. We found 1/3m(s) and 2/3m(s) plateaus of the magnetization for the full magnetization m, and large negative magnetoresistance effect of 10% at the same magnetic fields, respectively. (c) 2006 Elsevier B.V. All rights reserved.

Pulsed high magnetic field generator up to 33T with a long pulsed half-width of 70ms was constructed. Effective fields of coercivity in Nd-Fe-B sintered samples were measured in the pulsed high fields. The measurement errors were estimated experimentally and also by numerical simulations using EMAG. We found errors of coercivity fields of more than 30 % in these samples and discussed on the relationship among the sample insertion gaps in the probe and the systematic errors.

The Co spin states on trigonal prisms and octahedral were clarified, and the large magnetoresistance during phase transitions induced by externally applied fields was obtained. The magnetic susceptibility of Ca/sub 3/Co/sub 2/O/sub 6/ single crystals were measured for varying temperatures. A second magnetic transition was observed to occur at T/sub c2/=12 K. Results reveal an intra-chain ferromagnetic ordering at T/sub c1/=23 K and a weak antiferromagnetic inter-chain coupling at T/sub c2/=12 K. The field induced phase transition from a ferrimagnetic to ferromagnetic state and the prominent magnetic hysteresis suggests that the sample behaves as an Ising-like antiferromagnetic triangular lattice.

The effects of annealing temperature and duration on the formation of iron silicides prepared by magnetron sputtering (MS) are investigated. The Fe/Si structures were annealed at 1073 K–1223 K for 6–18 hours. The results show that 1143 K is a critical temperature to the formation of β - FeSi 2 from Fe/Si structures deposited at room temperature. The single phase semiconducting β - FeSi 2 can be obtained after annealing at 1173 K for 12–18 hours. The SEM images indicate that both annealing temperature and duration have obvious effects on microstructures of the film. When annealing time is more than 15 hours, the crystallinity of β - FeSi 2 improves and the distribution of grains becomes homogeneous. Most of the grains of β - FeSi 2 grow toward substrate and embed themselves into Si matrix.