A novel anions and cations co-doped strategy for developing high-performance cobalt-free cathode for intermediate-temperature proton-conducting solid oxide fuel cells

The sluggish activity of cathode at intermediate-temperature limits commercialization of proton-conducting solid oxide fuel cells (H-SOFCs). In this investigation, a novel cathode of Ba_0.95Ca_0.05Fe_0.85Sn_0.05Y_0.1O_2.9−δF_0.1 was successfully developed by co-doping of anion F and cations Ca, Sn, Y. We studied the effect of F⁻-doping on phase structure, electrical conductivity and electrochemical properties of the cell. Compared with Ba_0.95Ca_0.05Fe_0.85Sn_0.05Y_0.1O_3−δ, F⁻-doped Ba_0.95Ca_0.05Fe_0.85Sn_0.05Y_0.1O_3−δ exhibited higher conductivity. Composite cathode consisting of Ba_0.95Ca_0.05Fe_0.85Sn_0.05Y_0.1O_2.9−δF_0.1 and Sm_0.2Ce_0.8O_2−δ was applied in H-SOFCs with BaZr_0.1Ce_0.7Y_0.2O_3−δ electrolyte which achieves an encouraging performance with the maximum power density of 1050 mW cm⁻² and polarization resistance of 0.04 Ω cm² at 700 °C. The result of First-principles calculations based on spin-polarized Density Functional Theory shows that doping of F⁻ reduces the activation energy required for migration of oxygen ions. These results demonstrate that the anions and cations co-doped strategy can provide a new horizon for the cathode in H-SOFCs.     

Photoluminescence of (ZnO)X-Z(SiO2)Y:(MnO)Z green phosphors prepared by direct thermal synthesis: The effect of ZnO/SiO2 ratio and Mn2+ concentration on luminescence

Green light emitting Zn₂SiO₄:Mn²⁺ phosphors have been synthetised by the solid-state reaction in ambient atmosphere at 1300 °C for 2 h, with ZnO, SiO₂ and MnO₂ as the reagents. The ZnO/SiO₂ molar ratio varied from 2 to 0.5. The doping level was in a lower concentration range (0.01≤x≤0.05). The effect of both the Mn²⁺ concentration and ZnO/SiO₂ molar ratio on luminescence intensity and decay was investigated in detail. The microstructure and phase composition of prepared phosphors were characterised by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). XRD results indicate that the pure α-Zn₂SiO₄ phase with rhombohedral structure was obtained after heat treatment. The prepared phosphors exhibit a strong green emission centred at 525 nm from the ⁴T₁→⁶A₁ forbidden transition. The highest emission intensity was observed for phosphors with ZnO/SiO₂ molar ratio equal to 1.0, and the Mn²⁺ concentration x=0.03 (ZSMn3). The emission intensity of the ZSMn3 phosphor is comparable with the commercial Zn₂SiO₄:Mn²⁺ phosphor. The decay curves can be characterised by double exponential function. After fitting a fast component τ₁∼2 ms and a slow component τ₂∼10 ms were obtained. The decay times decrease significantly with increasing Mn²⁺ concentration. The decay time and luminescence mechanism depend on the excitation light wavelength. Temperature dependent luminescence of the ZSMn3 phosphor in the temperature range of 25–200 °C was studied.     

Conductive nonwetting flexible substrate

In this paper an easy method to prepare flexible conductive substrates has been demonstrated. The substrates are mainly PET (PolyEthyleneTerephthalate), on which AgNW (silver nanowire) were deposited by spin casting method. For adhesion purpose a common cosmetic material has been utilized. The material provides versatile features to these coated substrates, including robustness, hydrophobicity with transparent bracing of nanowires (NW) with the flexible substrate. Four probe conductivity measurement shows the resistivity is 12 Ω/cm and is comparable to that of commercially available indium tin oxide (ITO) coated substrates. This method is cheap, easy and can be used for different objectives like flexible thin film photovoltaic, light emitting diodes, photosensors etc.     

Crystal structure,luminescent properties and white light emitting diode application of Ba3GdNa(PO4)3F:Eu2+ single-phase white light-emitting phosphor

A series of single-phase white-light-emitting phosphors, Eu²⁺-activated Ba₃GdNa(PO₄)₃F phosphors were synthesized by solid-state reactions. The crystal structure of Ba₃GdNa(PO₄)₃F was been identified by Rietveld refinement of X-ray diffraction pattern. The Eu²⁺-activated Ba₃GdNa(PO₄)₃F phosphors exhibit broad excitation spectra from 250 to 420 nm, which matched well with the n-UV LED chips. Under the excitation of 365 nm, the emission spectrum almost covered the entire visible region including two emission bands peaked at 472 nm and 640 nm. Three different Eu²⁺ emission centers in Ba₃GdNa(PO₄)₃F:Eu²⁺ phosphor were confirmed by their fluorescence decay lifetimes. The optimal concentration of Eu²⁺ in Ba₃GdNa(PO₄)₃F:xEu²⁺ was 3 mol% and the corresponding concentration quenching mechanism was verified to be exchange coupling interaction. Furthermore, the white light-emitting diode fabricated with Ba₃GdNa(PO₄)₃F:0.05Eu²⁺ phosphor and a 370 nm UV chip has a CIE of (0.3267, 0.2976) with a color-rendering index of 78.4 at the CCT of 5287 K.     

Atomic layer deposition of platinum thin films on anodic aluminium oxide templates as surface-enhanced Raman scattering substrates

Platinum thin films are deposited on anodic aluminium oxide (AAO) templates by atomic layer deposition (ALD). The highly ordered island-like platinum nanostructures formed on the AAO template produce a high Raman scattering signal because of the periodical hexagonal arrangement. As an illustration, dramatic enhancement is achieved using Rhodamine 6G (R6G) as a molecular probe.Field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) show that the gap between the island-like structures is below 10 nm. Owing to activation by the incident laser beam, the localized electromagnetic field on the platinum island surface can be dramatically enhanced by the sub-10 nm regime subsequently amplifying the Raman signal. Finite-difference time-domain (FDTD) calculation matches the experimental phenomena suggesting that the excellent surface-enhanced Raman scattering (SERS) characteristics of the platinum structure arise from the high density and abundance of hot spots. Because the platinum film is inert in air, the SERS enhancing substrate can be used reliably in many trace chemical and biological detection applications.     

Preparation of c-axis textured SiC ceramics by a strong magnetic field of 6 T assisted gel-casting process

C-axis textured SiC ceramics were prepared by a strong magnetic field of 6 T assisted gel-casting and subsequent pressureless sintering. The optimal suspension parameters for gel-casting were determined by analyzing the influences of pH value and dispersant content on the stability and dispersibility of suspensions. The effect of sintering conditions on the texture development and properties of SiC ceramics was discussed. It was found that the increasing sintering temperature or holding time promoted the densification process of SiC ceramics. The c-axis of SiC grain was aligned parallel to the magnetic field by applying a strong magnetic field of 6 T. The degree of texture of SiC ceramics showed a slightly increasing trend with the increase of sintering temperature or holding time. When the samples were sintered at 1950 °C for 4 h or 6 h, the large elongated grains were formed in the samples, leading to the extremely evident anisotropic microstructure on different planes. Textured SiC ceramics exhibited the anisotropic bending strength.     

Color-tunable up-conversion emission from Yb3+/Er3+/Tm3+/Ho3+ codoped KY(MoO4)2 microcrystals based on energy transfer

Tunable up-conversion luminescent material KY(MoO₄)₂: Yb³⁺, Ln³⁺ (Ln=Er, Tm, Ho) has been synthesized by a typical hydrothermal process. Under 980 nm laser diode (LD) excitation, the emission intensity and the corresponding luminescence colors of KY(MoO₄)₂: Yb³⁺, Ln³⁺ (Ln=Er, Tm, Ho) have been investigated in detail. The energy transfer from the Yb³⁺ sensitizer to Ho³⁺, Er³⁺ and Tm³⁺ activators plays an important role in the development of color-tunable single- phased phosphors. The emission intensity keep balance through control of the Ho³⁺ co-doping concentrations, white light was experimentally shown at KY(MoO₄)₂: 20 mol% Yb³⁺, 0.8 mol% Er³⁺, 0.5 mol% Tm³⁺, 1.0 mol% Ho³⁺ phosphor with further calcination at 800 °C for 4 h under 980 nm laser excitation. The color tunability, high quality of white light and high intensity of the emitted signal make these up-conversion (UC) phosphors excellent candidates for applications in solid-state lighting.     

Low temperature synthesis of plate-like Na0.5Bi0.5TiO3 via molten salt method

In this study, plate-like Na_0.5Bi_0.5TiO₃ (BNT) templates with perovskite structure were obtained by two-step molten salt synthesis (MSS) method at a low temperature. Firstly, Bi₄Ti₃O₁₂ precursors were synthesized at 1030 °C in NaCl–KCl molten salt. Secondly, plate-like Na_0.5Bi_0.5TiO₃ particles with perovskite structure were obtained from plate-like layer-structured ferroelectric ceramic of Bi₄Ti₃O₁₂ by topochemical microcrystal conversion method. Result showed that excessive Na₂CO₃ was beneficial to facilitate the low temperature synthesis. In the case of an excess of 30 mol% Na₂CO₃, plate-like BNT particles could be obtained by synthesis at temperatures ranging from 760 °C to 800 °C, which indicated a flexible processing route. Also, it has been observed that plate-like BNT particles show a high aspect ratio with 1 μm in thickness and 10–20 μm in length. These Na_0.5Bi_0.5TiO₃ plate-like particles can be good candidates for the preparation of lead-free BNT-based piezoelectric ceramics with oriented grain microstructure.     

Novel organic inverters with dual-gate pentacene thin-film transistor

We report on the fabrication and characterization of dual-gate pentacene organic thin-film transistors (OTFTs) with plasma-enhanced atomic-layer-deposited (PEALD) 150 nm thick Al₂O₃ as a bottom-gate dielectric and PEALD 200 nm thick Al₂O₃ as a top-gate dielectric. The V_th of dual-gate OTFT has changed systematically with the application of voltage bias to top-gate electrode. When voltage bias from −10 V to 10 V is applied to top gate, V_th changes from 1.95 V to −9.8 V. Two novel types of the zero drive load logic inverter with dual-gate structure have been proposed and fabricated using PEALD Al₂O₃ gate dielectrics. Because the variation of V_th due to chemical degradation and the spatial variation of V_th are inherent in OTFTs, the compensation technology by dual-gate structure can be essential to OTFT applications.     

Extrusion of AlSBA-15 molecular sieves: An industrial point of view

AlSBA-15 in the powder form with different n_Si/n_Al ratios (45, 136 and 215) were synthesized by hydrothermal technique. The powdered materials were made into cylindrical extrudates with the addition of bentonite as a binder. The AlSBA-15 materials were characterized by XRD, N₂ adsorption, AAS and thermogravimetric analysis. The orderly growth of AlSBA-15 is evidenced by its XRD. The surface area of the powder catalyst is around 950 m²/g and that of extrudate is close to 600 m²/g. Vapor phase alkylation of phenol with tert-butanol was carried out over the extrudates of AlSBA-15 as a model reaction. The activity of AlSBA-15 extrudates follows the order: AlSBA-15 Si/Al = 45 > AlSBA-15 Si/Al = 136 > AlSBA-15 Si/Al = 215. The reaction products were found to be 2-TBP, 4-TBP and 2,4-DTBP. The selectivity to para tertiary butylation is higher than other reactions.