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[en] We report that the arrangement of the electrode materials is a significant contributor for constructing high performance supercapacitor. Here, vertically-aligned Mn(OH)2 nanosheet thin films were synthesized by cathodic electrodeposition technique on flexible Au coated polyethylene terephthalate substrates. Morphologies, microstructures, chemical compositions and valence state of the nanosheet films were characterized systematically. It shows that the nanosheets arranged vertically to the substrate, forming a porous nanowall structures and creating large open framework, which greatly facilitate the adsorption or diffusion of electrolyte ions for faradaic redox reaction. Electrochemical tests of the films show the specific capacitance as high as 240.2 F g-1 at 1.0 A g-1. The films were employed to assemble symmetric all-solid-state supercapacitors with LiCl/PVA gel severed as solid electrolyte. Finally, the solid devices exhibit high volumetric capacitance of 39.3 mF cm-3 at the current density 0.3 mA cm-3 with robust cycling stability. The superior performance is attributed to the vertically-aligned configuration.
[en] Cantilever testing is an underutilized test method from which results and interpretations promote greater understanding of the tensile and shear failure responses of interconnects, metallizations, or bonded joints. The use and analysis of this method were pursued through the mechanical testing of sintered-silver interconnects that joined Ni/Au-plated copper pillars or Ti/Ni/Ag-plated silicon pillars to Ag-plated direct bonded copper substrates. Sintered-silver was chosen as the interconnect test medium because of its high electrical and thermal conductivities and high-temperature capability—attractive characteristics for a candidate interconnect in power electronic components and other devices. Deep beam theory was used to improve upon the estimations of the tensile and shear stresses calculated from classical beam theory. The failure stresses of the sintered-silver interconnects were observed to be dependent on test-condition and test-material-system. In conclusion, the experimental simplicity of cantilever testing, and the ability to analytically calculate tensile and shear stresses at failure, result in it being an attractive mechanical test method to evaluate the failure response of interconnects.
[en] A novel self-supporting carbon thin film flexible supercapacitor electrode with high volumetric and areal capacitance was developed. The increase in capacitance performance is achieved by introducing channels across the carbon thin film using ion-track technology. In the first step of the electrode synthesis, latent tracks are inscribed in the starting polyimide (Kapton) foil by irradiation with 253 MeV Kr ions. Next, macropores in the form of cylindrical channels are formed by selective chemical etching with NaOCl along the ion tracks, creating ion-track polymer. With subsequent carbonization and activation of the ion-track polymer, activated ion-track carbon is produced. A range of samples are obtained by varying the chemical etching time of the irradiated polymer. In addition to channel formation the chemical etching time influences the composition of surface functional groups. The best results are obtained by chemical etching for 40 min, the thickness of the sample is 21 A mu m with channel density 2.4 x 10(6) cm(-2) and average channel diameter 430 nm. Beside cylindrical macro channels this material is mainly microporous with 0.62 nm pore diameter and shows the highest areal (494 mF/cm(2)), volumetric (224 F/cm(3)) and gravimetric (178 F/g) capacitance. As a consequence of channel formation, the rate capability of the supercapacitor was also increased.
[en] MgZnO is emerging as a vital semiconductor-alloy system with desirable optical properties that can span a large range of the UV spectrum. Due to its benign chemical character, MgZnO is considered to be an environmentally friendly material. This paper presents studies on annealing as a useful and straightforward approach for the enhancement of the optical and crystal quality of Mg 0.17Zn 0.83O nanocrystalline films grown via DC sputtering. The alloys were studied via several imaging and optical techniques. It was found that high-temperature annealing, ~900 °C, in Argon atmosphere, significantly improves the solubility of the alloy. This temperature range is consistent with the thermal diffusion temperature of Mg needed for the creation of a soluble alloy. Moreover, the annealing process was found to minimize the undesirable visible luminescence, attributed to Mg and Zn interstitials, while significantly enhancing the bandgap sharpness and the efficiency of the UV-luminescence at ~3.5 eV. The analysis indicated that these optical attributes were achieved due to the combined effects of good solubility, an improved morphology, and a reduction of native defects. The annealing was also proven to be beneficial for the reduction of the compressive stress in the alloy: a relaxation ~1.8 GPa was calculated viamore » Raman scattering. The inherent stress was inferred to originate mainly from the granular morphology of the alloys.
[en] The article titled “Strontium-substituted La0.75Ba0.25−xSrxFeO3 (x = 0.05, 0.10 and 0.15) perovskite: dielectric and electrical studies”, written by F. B. Abdallah, A. Benali, S. Azizi, M. Triki, E. Dhahri, M. P. F. Graça, M. A. Valente, was originally published electronically on the publisher's internet portal (currently SpringerLink) on March 2019 with open access.
[en] The original version of this article unfortunately contains errors in Abstract, Section 4.4 Vickers microhardness test and Section 5 Conclusion. In Abstract (7th line) the word “hard” should be changed to “soft”, in Section 4.4 Vickers microhardness test, 15th line the value 1.04 should be changed to 3.27 and in the same sentence the word “hard” should be changed to “soft”. In Section 5 Conclusion (18th line) the word “hard” should be changed to “soft”.
[en] Solution combustion synthesis, a simple and efficient route was adopted to synthesize color tunable Ba3Y4O9: Eu3+ nanophosphor with varying composition of trivalent europium ions. Structural analysis using powder X-ray diffraction technique reveals trigonal crystal system belonging to hexagonal crystal family with R3 (143) space group and nanocrystalline nature of the synthesized phosphor. The average size of the synthesized phosphor in nano-scale range was confirmed by using Scherrer’s equation and transmission electron microscope (TEM) analysis. A structure refinement technique i.e. Rietveld refinement was employed over powder X-ray diffraction data that fits the entire powder pattern together with peak shapes and background. Photoluminescent features were analyzed via recording excitation (200–500 nm), emission profile (415–750 nm) and luminescence decay curves for optoelectronic applications. The emission spectrum shows characteristic intense peak at 615 nm by means of 5D0 → 7F2 electric dipole transition. Judd–Ofelt parameters for all concentration of Eu3+ doped system were determined by employing Judd–Ofelt theory. The optimum doping concentration of Eu3+ ions in Ba3Y4(1−x)O9: 4x Eu3+ was found to be x = 0.10. Moreover, the critical distance was computed to be 10.91 Å suggesting d–d interactions as a major reason for concentration quenching phenomenon. The energy band gap values for pure host lattice and optimized system were calculated as 5.41 eV and 5.91 eV respectively via Kubelka–Munk theory. CIE (Commission Internationale De I’eclairage) color coordinates lie in blue–white–red region depending upon the composition of dopant ion. The potential use of synthesized nanophosphor as a warm light source was evident from the correlated color temperature (CCT) result.
[en] A new semiorganic single crystal, catena-Poly[bis(4-methylbenzylammonium) [[dibromidocadmate(II)]-di-l-bromido]],[4MLBDCB], has been developed by evaporating the solvent at a 37 °C. It crystallizes in centrosymmetric space group Pnma. In the crystal structure, 4-methylbenzylammonium cation and tetrabromido cadmate anion are connected by N–H⋯Br and C-H⋯Br hydrogen bonds. Functional groups vibrations of 4MLBDCB were analysed by FT-Raman and FTIR spectroscopy. The stretching vibration of NH and CH shifted towards lower frequency side and their bending vibrations (–NH, –CH) to higher frequency when compared with pure 4 methylbenzylamine (4MLBA) vibrations. The observed variations in CH bond length are discussed. Presence of Raman active CdBr42− vibrations ensures the formation of the molecule. Transmittance bandwidth of the crystal extends from 260 and 1100 nm. In 1H and 13C NMR spectra, the observed variations in the chemical shifts are interpreted through intermolecular interactions. The presence of hydrogen bonds enhances the third order nonlinear susceptibility (χ3) value of the grown crystal and found to be 5.04 × 10−6 esu. The third order nonlinear optical parameters such as absorption coefficient (β) and refractive index (n2) are also determined using Z-scan technique.