Synthesis and electrochemical characterization of La0.75Sr0.25Mn0.5Cr0.5‐xAlxO3, for IT- and HT- SOFCs

The authors, A M Abdalla and S Hossain, are grateful to Suez Canal University and Universiti Brunei Darussalam and their collaborative for supporting this research work.The main emphasis of this work is to create a new perovskite material with three different compositions (La0.75Sr0.25Mn0.5Cr0.5‐xAlxO3, x = 0.1, 0.2, 0.3) applied in both Intermediate and high Temperature ‐ Solid Oxide Fuel Cells (IT & HT‐SOFCs). Perovskite‐type polycrystalline La0.75Sr0.25Mn0.5Cr0.5‐xAlxO3‐δ (x = 0.1, 0.2, 0.3) powders were synthesized and formed in a single phase structure by a dry chemistry route (standard solid‐state reaction method). The effect of Al‐doping on physicochemical and surface properties has been discovered. The compounds were crystallized in single phase rhombohedral symmetry (R‐3C Space. Group). Total conductivity of Al‐doping in wet 5% H2 was higher than both dry 5% H2 and air. The obtained results enhance the electro‐catalytic performance and the material conductivity as well, which will be good for anode materials in IT‐ HT‐SOFCs and the optimum doping is 10%.PostprintPeer reviewe

Vibrational Signatures in the THz Spectrum of 1,3-DNB: A First-Principles and Experimental Study

Understanding the fundamental processes of light-matter interaction is important for detection of explosives and other energetic materials, which are active in the infrared and terahertz (THz) region. We report a comprehensive study on electronic and vibrational lattice properties of structurally similar 1,3-dinitrobenzene (1,3- DNB) crystals through first-principles electronic structure calculations and THz spectroscopy measurements on polycrystalline samples. Starting from reported x-ray crystal structures, we use density-functional theory (DFT) with periodic boundary conditions to optimize the structures and perform linear response calculations of the vibrational properties at zero phonon momentum. The theoretically identified normal modes agree qualitatively with those obtained experimentally in a frequency range up to 2.5 THz and quantitatively at much higher frequencies. The latter frequencies are set by intra-molecular forces. Our results suggest that van der Waals dispersion forces need to be included to improve the agreement between theory and experiment in the THz region, which is dominated by intermolecular modes and sensitive to details in the DFT calculation. An improved comparison is needed to assess and distinguish between intra- and intermolecular vibrational modes characteristic of energetic materials.Comment: 5 pages, 5 figure

Effect of Penalty Function Parameter in Objective Function of System Identification

The evaluation of an objective function for a particular model allows one to determine the optimality of a model structure with the aim of selecting an adequate model in system identification. Recently, an objective function was introduced that, besides evaluating predictive accuracy, includes a logarithmic penalty function to achieve a suitable balance between the former model’s characteristics and model parsimony. However, the parameter value in the penalty function was made arbitrarily. This paper presents a study on the effect of the penalty function parameter in model structure selection in system identification on a number of simulated models. The search was done using genetic algorithms. A representation of the sensitivity of the penalty function parameter value in model structure selection is given, along with a proposed mathematical function that defines it. A recommendation is made regarding how a suitable penalty function parameter value can be determined

Planar Metamaterials for Antireflection Coating

We present a novel antireflection approach utilizing planar metamaterials on dielectric surfaces. It consists of a split-ring resonator array and a metal mesh separated by a thin dielectric spacer. The coating dramatically reduces the reflectance and greatly enhances the transmittance over a wide range of incidence angles and a narrow bandwidth. Antireflection is achieved by tailoring the magnitude and phase shifts of waves reflected and transmitted at metamaterial boundaries, resulting in a destructive interference in reflection and constructive interference in transmission. The coating can be very thin and there is no requirement for the spacer dielectric constant

Novel layered perovskite SmBaMn2O5+δ for SOFCs anode material

The authors Abdalla M. Abdalla and Shahzad Hossain are thankful to the Graduate Research Office of Universiti Brunei Darussalam for Graduate Research Scholarship (GRS) for funding this research work done.SmBaMn2O5+δ (SBMO), a novel layered perovskite compound with samarium based material (Sm+3) as rare earth doped in A-site was synthesized and processed by using dry chemistry method (solid state solution). Structural characterization of SBMO has been investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). While, thermal and electrochemical testing were done by using thermogravimetric analysis (TGA) and current voltage measurements. The Rietveld analysis of XRD data shows that SBMO was crystallized in the orthorhombic structure with the Pmmm space group. The surface morphology images showed a porous structure which indicates that this material can be used as a potential electrode in solid oxide fuel cells (SOFCs). TGA result showed the mass loss of 0.022% for SmBaMn2O5+δ which is very small and indicates that the material is very stable. DC conductivity and performance test were done at RT in air atmosphere. The performance tests have done at 800 °C and 750 °C and the maximum power density was found to be 0.4 W/cm2 at 800 °C.PostprintPeer reviewe

A new high-performance proton-conducting electrolyte for next-generation solid oxide fuel cells

N. Radenahmad and A. Afif are thankful to Universiti Brunei Darussalam for sponsoring the UBD graduate scholarship to perform Ph.D. work at Brunei Darussalam. The authors are also grateful to the late Professor Sten Eriksson for supporting a summer scholarship for NR to accomplish a part of this work at Chalmers University of Technology, Sweden. This work was also partially funded by research grant UBD/OVAORI/CRGWG(006)/161201.Conventional solid oxide fuel cells (SOFCs) are operable at high temperatures (700 – 1,000 °C) with the most commonly used electrolyte, yttria‐stabilized zirconia (YSZ). SOFC R&D activities have thus been carried out to reduce the SOFC operating temperature. At intermediate temperatures (400 – 700 °C), barium cerate (BaCeO3) and barium zirconate (BaZrO3) are good candidates for use as proton‐conducting electrolytes due to their promising electrochemical characteristics. Here, we combined two widely studied proton‐conducting materials with two dopants and discovered an attractive composition for the investigation of electrochemical behaviors. Ba0.9Sr0.1Ce0.5Zr0.35Y0.1Sm0.05O3‐δδ(BSCZYSm), a perovskite‐type polycrystalline material, has shown very promising properties to be used as proton‐conducting electrolytes at intermediate temperature range. BSCZYSm shows a high proton conductivity of 4.167×10−3 S cm−1 in a wet argon atmosphere and peak power density of 581.7 mW cm−2 in Ni‐BSCZYSm | BSCZYSm | BSCF cell arrangement at 700 °C, which is one of the highest in comparison to proton‐conducting electrolyte‐based fuel cells reported till now.PostprintPeer reviewe