Structural, mechanical, and electrochemical properties of Ceria doped Scandia stabilized Zirconia

The properties of Ceria doped Scandia Stabilized Zirconia (1Ce10ScSZ) nano-powder produced in Ukraine (Ukr, VMMP) are compared to the properties of commercial ones produced by Daiichi Kigenso Kagaku Kogyo (DKKK, Japan) and Praxair (USA). In comparison to DKKK and Praxair, the Ukr nano-powder demonstrated the smallest size of the particles ranging from 20 to 50 nm. The bending strength of the isostatically pressed samples made of Ukr powder was 100–120 MPa similar to that of Praxair. The bending strength of DKKK was lower (50–100 MPa) depending on the isostatic pressure. The biaxial strength of uniaxially pressed samples was the highest for DKKK (375 MPa) decreasing to 250 MPa for Ukr and 220 MPa for Praxair. Among three tested samples, the highest electric conductivity measured at 700 °C was found for Ukr electrolyte.Вивчено й порівняно властивості нанопорошків двоокису цирконію, стабілізованого двоокисами церію та скандію 1Ce10ScSZ, які виготовлено в Україні на Вільногірському державному гірничо-металургійному комбінаті (ВДГМК), в Японії компанією «Daiichi Kigenso Kagaku Kogyo» (DKKK) та в США компанією «Praxair». Порівняно з порошками виробництва DKKK та «Praxair» порошок виробництва ВДГМК (позначено як «Ukr») має найменший розмір частинок в інтервалі 20-50 нм. Міцність зразків, виготовлених із порошку «Ukr» із використанням ізостатичного пресування, становить 100-120 МПа при згині та є подібною до міцності порошку виробництва «Praxair». Міцність зразків виробництва DKKK менша (50-100 МПа) й залежить від ізостатичного тиску. Міцність одновісно пресованих зразків найвища в порошку DKKK (375 МПа), у зразках «Ukr» і «Praxair» вона становить відповідно 250 МПа та 220 МПа. Із-поміж трьох досліджених серій зразків найвищу електричну провідність при 700 °С мали електроліти, виготовлені з порошку «Ukr».Были изучены и сравнены свойства нанопорошков двуокиси циркония, стабилизированного окислами церия и скандия 1Ce10ScSZ, которые произведены в Украине на Вольногорском государственном горно-металлургическом комбинате (ВГГМК), в Японии компанией «Daiichi Kigenso Kagaku Kogyo» (DKKK) и в США компанией «Praxair». В сравнении с порошками производства DKKK и «Praxair» у порошка производства ВГГМК (обозначен как «Ukr») наименьший размер частиц в интервале 20–50 нм. Прочность образцов, изготовленных из порошка «Ukr» с использованием изостатического прессования, составляет 100–120 МПа при изгибе и подобна прочности образцов из порошка производства «Praxair». Прочность образцов из порошка DKKK меньше (50–100 МПа) и зависит от давления изостатического прессования. Прочность одноосно прессованных образцов наиболее высока (375 МПа) у порошка DKKK, в образцах «Ukr» и «Praxair» она составляет соответственно 250 МПа и 220 МПа. Из трех испытанных серий образцов самая высокая электропроводность при 700 °С была у электролитов, изготовленных из порошка «Ukr»

Roadmap on exsolution for energy applications

Over the last decade, exsolution has emerged as a powerful new method for decorating oxide supports with uniformly dispersed nanoparticles for energy and catalytic applications. Due to their exceptional anchorage, resilience to various degradation mechanisms, as well as numerous ways in which they can be produced, transformed and applied, exsolved nanoparticles have set new standards for nanoparticles in terms of activity, durability and functionality. In conjunction with multifunctional supports such as perovskite oxides, exsolution becomes a powerful platform for the design of advanced energy materials. In the following sections, we review the current status of the exsolution approach, seeking to facilitate transfer of ideas between different fields of application. We also explore future directions of research, particularly noting the multi-scale development required to take the concept forward, from fundamentals through operando studies to pilot scale demonstrations

Simulated biogas for nickel-based solid oxide fuel cells

Biogas is composed of variable gases including hydrogen, nitrogen and sulphur, with methane and carbon dioxide as the main components. The common ratio of methane to carbon dioxide is 60/40 in volume and this high amount of methane causes carbon deposition when biogas is used in solid oxide fuel cells. To prevent carbon deposition, dry reforming, steam reforming or partial oxidation is the common method. In this paper, a nickel cermet solid oxide fuel cell was investigated with a simulated biogas based on 63% CH4 and 37% CO2, which was obtained by presuming 80% fuel utilisation and 25% recirculation of anode gas. Supplied with a 30 ml/min of simulated biogas, the cell generated a maximum power density of 856 mW cm-2 at 850 °C. The cell ran stably at loads of 100 mA cm-2, 300 mA cm-2and 500 mA cm-2 over a period of 16 hours at each level.Publisher PD

Fabrication and characterisation of a large-area solid oxide fuel cell based on dual tape cast YSZ electrode skeleton supported YSZ electrolytes with vanadate and ferrite perovskite-impregnated anodes and cathodes

The authors thank the U.S. Office of Naval Research for support for this collaboration. CSN and JTSI also thank EPSRC (UK) for support. JTSI thanks the Royal Society for support.Infiltration of ceramic materials into a pre-formed ceramic scaffold is an effective way of fabricating a solid oxide fuel cell with nano-structured ceramic electrodes by avoiding detrimental interfacial reactions through low-temperature processing for achieving high performance using hydrogen as well as a carbonaceous fuel. However, there are significant concerns about the applicability of this method because of the difficulty in fabricating a large-area gas-tight but thin electrolyte between two highly porous ceramic and the multiple repetitions of infiltration process. Here, a large-area (5 cm by 5 cm) scaffold with a thin yttria-stabilized zirconia (YSZ) electrolyte sandwiched between two identical porous structures is prepared by tape casting and co-firing, and then solution precursors are impregnated into the porous scaffolds to prepare nano-structured La0.8Sr0.2FeO3 (LSF) and La0.7Sr0.3VO3−δ (LSVred). The thus prepared solid oxide fuel cell with 10 wt% ceria + 1 wt% Pd as a catalyst in anodes shows a peak power of 489 mW cm−2 (~6 W per cell) at 800 °C using H2 as a fuel and air as an oxidant. This large-area fuel cell retained the integrity of the thin electrolyte and high performance after the reducing-oxidation cycle at 900 °C, showing superiority over the conventional Ni(O)-YSZ based support.PostprintPeer reviewe

Electrolysis of CO2 in a proton conducting membrane

The electrolysis of CO2 is examined in a proton conducting solid electrolyser using BaCe0.5Zr0.3Y0.16Zn0.04O3 − δ as the electrolyte, nickel as the anode to oxidize H2O/H2 and copper, nickel or iron as the cathode to reduce CO2. The electrolyte and porous scaffolds were prepared by tape casting and the electrodes by impregnation. During electrolysis at 600ºC, currents as high as 35 mA/cm² (iron), 20 mA/cm² (copper) or 15 mA/cm2 (nickel) at 1.5 V pass through the 200 μm thick electrolytes. Small additions of Pt improve considerably the performance of the electrodes. For iron based cathodes Faradaic efficiencies up to 100% are achieved with production rates of H ≈ 0.14 μmol/cm2s, HO ≈ 0.25 μmol/cm2s and CO ≈ 0.05 μmol/cm2s. The possibilities of increasing these yields are discussed.</p

La-doped SrTiO3 as anode material for IT-SOFC

A-site deficient La-doped SrTiO3 (La0.2Sr0.7TiO3) was evaluated as a potential anode component material for intermediate temperatures SOFCs. Button fuel cells were produced by tape casting and impregnation, comprising YSZ electrolyte, a porous, conductive backbone of La0.2Sr0.7TiO3 anode impregnated via solutions with Gd-doped CeO2 and a metal (i.e. Cu). Thin films of La0.6Sr0.4CoO3 cathode produced in-situ in the fuel cell test experiment. Fuel cells tests using pure, humidified H2 as fuel demonstrated that remarkable power densities in excess of 0.5 W/cm2 at 750 °C can be achieved with suitable pre-reduction of the titanate material

La-doped SrTiO3 as anode material for IT-SOFC

A-site deficient La-doped SrTiO3 (La0.2Sr0.7TiO3) was evaluated as a potential anode component material for intermediate temperatures SOFCs. Button fuel cells were produced by tape casting and impregnation, comprising YSZ electrolyte, a porous, conductive backbone of La0.2Sr0.7TiO3 anode impregnated via solutions with Gd-doped CeO2 and a metal (i.e. Cu). Thin films of La0.6Sr0.4CoO3 cathode produced in-situ in the fuel cell test experiment. Fuel cells tests using pure, humidified H2 as fuel demonstrated that remarkable power densities in excess of 0.5 W/cm2 at 750 °C can be achieved with suitable pre-reduction of the titanate material

Phase transition, thermal expansion and electrical properties of BiCu2VO6

Phase transition in BiCU2VO6 has been studied by variable temperature powder and single crystal X-ray diffraction. A reversible siiigle-crystal-to-single-crystaI phase transition has been identified and the high-temperature beta-BiCu2VO6 polymorph structurally characterized. beta-BiCu2VO6 is monoclinic 1-centered and related to the alpha-form by a subgroup-supergroup relationship. Bi atoms are coordinated to oxygen so as to give rise to (BiO2)(-) chains parallel to the c-axis. The magnetic Cu-O sublattice forms a complex system of quasi one-diniensional ladders, built up by five- and six-coordinate Cu atoms. Dynamic disorder in the high temperature structure can be described in terms of librational motion of VO4 tetrahedral group. AC impedance measurements suggest predominantly electronic conduction in this material. (c) 2005 Elsevier Inc. All rights reserved.</p

Crystal structure, thermochemical stability, electrical and magnetic properties of the two-phase composites in the La0.8Sr0.2MnO3-CeO2 system

Crystal structure, thermochemical stability, transport and magnetic properties of compositions in the (100-x) La(0.8)Sr(0.2)MnO(3 +/- delta)xCeO(2) (LSMC) system were studied. All compositions in the LSMC series containing more than 2 mol% CeO2 were two phase and consisted of the modified perovskite constituent with rhombohedral structure (R3c) and ceria as a secondary phase with cubic structure (Fm3m). The presence of both Ce4+ and Ce3+ cations in LSMC compositions was revealed by X-ray Photoelectron Spectroscopy (XPS). CeO2 and compositions in the LSMC series showed good thermochemical stability in air and argon. However. in H-2-Ar atmosphere all LSMC compositions underwent reduction followed by decomposition. Transport and magnetic properties change in a non-linear way with the increase in the CeO2 content. The LSMC2 composition showed enhanced electronic conductivity and magnetic characteristics. Metallic type conductivity was observed for LSMC compositions with x <= 36 mol% CeO2 in a narrow temperature range of 770-900 degrees C. A small degree of substitution of Ce into LSM was found to change structural, magnetic and electrical properties. (C) 2009 Elsevier B.V. All rights reserved