Effects of Preparation Conditions on the CuInS 2

CuInS2 thin films were prepared onto indium tin oxide (ITO) substrates by sulfurization of electrodeposited CuxInySz precursor films under S atmosphere. The influences of deposition potential, Cu2+/In3+ ratio, sulfurization temperature, and sulfur content on the CuInS2 thin films were investigated. Phases and structures were characterized by powder X-ray diffraction and Raman spectroscopy; surface morphology was characterized by Scanning Electron Microscopy; optical and electrical properties were characterized by UV-Vis absorption and Mott-Schottky curves, respectively. As a result, the optimal well-crystallized CuInS2 films preparation parameters were determined to be deposition potential of −0.8 V, Cu2+/In3+ ratio of 1.4, sulfur content of 1 g, and the sulfurization temperature of 550°C for 1 h; CuInS2 thin films prepared by one-step electrodeposition present the p-type semiconductor, with thickness about 4-5 μm and their optical band gaps in the range of 1.53~1.55 eV

Fabrication of Porous TiO2 Hollow Spheres and Their Application in Gas Sensing

In this work, porous TiO2 hollow spheres with an average diameter of 100 nm and shell thickness of 20 nm were synthesized by a facile hydrothermal method with NH4HCO3 as the structure-directing agent, and the formation mechanism for this porous hollow structure was proved to be the Ostwald ripening process by tracking the morphology of the products at different reaction stages. The product was characterized by SEM, TEM, XRD and BET analyses, and the results show that the as-synthesized products are anatase phase with a high surface area up to 132.5 m2/g. Gas-sensing investigation reveals that the product possesses sensitive response to methanal gas at 200°C due to its high surface area

The Luminescence Properties and Energy Transfer from Ce3+ to Pr3+ for YAG:Ce3+Pr3+ Phosphors

Y2.94−xAl5O12(YAG):Ce0.06Prx phosphors with various Pr3+ concentrations (x=0, 0.006, 0.01, 0.03, 0.06, and 0.09) were synthesized by using a coprecipitation method. The phases, luminescent properties, and energy transfer phenomenon from Ce3+ to Pr3+ were investigated. The results indicated that the doping of Pr3+  (x≤0.09) did not produce any new phases but caused a slight lattice parameters increase. After Pr3+ doping, the YAG:CePr phosphor emits red light at 610 nm, which was regarded helpful for improving the colour rendering index of the phosphor. With Pr3+ concentration increase from 0.006 to 0.01 mol, the intensity of red light emission increased slightly; further increasing Pr3+ concentration from 0.01 to 0.09, the red light emission intensity decreased gradually. Excitation at 340, and 460 nm could not lead to the direct electronic excitation of Pr3+ ions; however, when YAG:CePr was excited at 340 nm a red light emission at 610 nm appeared, which implied the energy transfer phenomenon from Ce3+ to Pr3+

Shape-control and characterization of iron nanocrystals prepared via a one-step solvothermal method

In the present work, iron nanocubes, nanorods and nanovvires are successfully synthesized by one-step I eduction approach in a solvothermal environment. It is analyzed that the iron nanocubes, nanorods and nanowires belong to the pure body-centered cubic structure of alpha-Fe. Effects of additive sort and the amount of Anionic Gemini surfactant 12-4-12 on the morphology evolution of Fe are discussed based On SEM and TEM images. The possible formation mechanisms of iron nanocubes, nanorods and nanowires are proposed. The Anionic Gemini surfactant 12-4-12 regarded as template plays an important role in the formation of iron nanocrystals. The microwave electromagnetic (EM) (SO wt% Fe) and calculated microwave-absorbing (0.5 mm thickness) properties in 2-18 GHz of the iron nanocubes, nanorods and nanowires are studied systematically. Results show that iron nanovvires are superior to nanorods and nanocubes, which indicates the potential to be a super-thin microwave absorber. (C) 2015 Elsevier B.V. All rights reserve

A Virtual Network Embedding Algorithm Based on Graph Theory

Part 1: Session 1: Parallel Programming and AlgorithmsInternational audienceNetwork virtualization is becoming a promising way of removing the inherent ossification of the Internet, and has been steadily attracting more and more researchers’ attention during the decades. The major challenges in this field are improving the efficiency of virtual network embedding procedure and raising the rate of virtual network requests being successfully accepted by the substrate network. This paper introduces a new virtual network embedding algorithm based on node similarity, which means the similarity between the virtual nodes and the substrate nodes. For more details, by calculating the degree of nodes both in virtual network and substrate network, which is actually the number of links associated with them, the algorithm achieves better mapping results between virtual network and the substrate network on the topology aspect

Fabrication of Porous TiO₂ Hollow Spheres and Their Application in Gas Sensing

Abstract In this work, porous TiO2 hollow spheres with an average diameter of 100 nm and shell thickness of 20 nm were synthesized by a facile hydrothermal method with NH4HCO3 as the structure-directing agent, and the formation mechanism for this porous hollow structure was proved to be the Ostwald ripening process by tracking the morphology of the products at different reaction stages. The product was characterized by SEM, TEM, XRD and BET analyses, and the results show that the as-synthesized products are anatase phase with a high surface area up to 132.5 m2/g. Gas-sensing investigation reveals that the product possesses sensitive response to methanal gas at 200&#176;C due to its high surface area.</p

Synthesis of hollow carbonyl iron microspheres via pitting corrosion method and their microwave absorption properties

In this paper, we report a new method to prepare hollow carbonyl iron microspheres, which is called pitting corrosion method. The comparison of the morphology, specific surface area and apparent density of the initial and pitting corroded carbonyl iron microspheres demonstrate that the pitting corroded carbonyl iron has a hollow structure. The pitting corrosion process is uncovered through the concentration change of ferrous ion in the reaction solution and the TEM images with different pitting corrosion time. The formation mechanism of hollow microspheres via pitting corrosion is analyzed. Furthermore, this pitting corrosion method can also be used to prepare other hollow metal particles, such as Ni, Co, and Cu particles. The electromagnetic parameters of the samples before and after pitting corrosion are measured. The calculated reflection loss of the pitting corroded sample for single layer of 0.5 mm or 1.0 mm thickness at 2-18 GHz is much better than that of the initial one. The mechanism of the improvement of the microwave absorption properties is discussed. (c) 2013 Elsevier B.V. All rights reserved

Simplified Regional Prediction Model of Long-Term Trend for Critical Frequency of Ionospheric F2 Region over East Asia

To improve the accuracy of predictions and simplify the difficulty with the algorithm, a simplified empirical model is proposed in developing a long-term predictive approach in determining the ionosphere&rsquo;s F2-layer critical frequency (foF2). The main distinctive features introduced in this model are: (1) Its vertical incidence sounding data, which were obtained from 18 ionosonde stations in east Asia between 1949 and 2017, used in reconstructing the model and verification; (2) the use of second-order polynomial and triangle harmonic functions, instead of linear ones, to obtain the relationship between the seasonal vs. solar-cycle variations of foF2 and solar activity parameters; (3) the flux of solar radio waves at 10.7 cm and sunspot number are together introduced in reconstructing the temporal characteristics of foF2; and (4) the use of the geomagnetic dip coordinates rather than geographic coordinates in reconstructing the spatial characteristics of foF2. The statistical results reveal that foF2 values calculated from the proposed model agree well with the trend in the monthly median statistical characteristics obtained from measurements. The results are better than those obtained from the International Reference Ionosphere model using both the CCIR and URSI coefficients. Furthermore, the proposed model has enabled some useful guidelines to be established for a more complete and accurate Asia regional or global model in the future