Tin dioxide sol-gel derived thin films deposited on porous silicon

Undoped and Sb-doped SnO2 sol¿gel derived thin films have been prepared for the first time from tin (IV) ethoxide precursor and SbCl3 in order to be utilised for gas sensing applications where porous silicon is used as a substrate. Transparent, crack-free and adherent layers were obtained on different types of substrates (Si, SiO2/Si). The evolution of the Sn¿O chemical bonds in the SnO2 during film consolidation treatments was monitored by infrared spectroscopy. By energy dispersive X-ray spectroscopy performed on the cross section of the porosified silicon coupled with transmission electron microscopy, the penetration of the SnO2 sol¿gel derived films in the nanometric pores of the porous silicon has been experimentally proved

Wet chemical synthesis and characterisation of Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3 − δ proton conductor

M. N. Khan would like to thank University of Brunei Darussalam for a Graduate Research Scholarship. L.C. Lim and P. Hing thank UBD, and Government of Brunei Darussalam (S&T 17) for a generous research grant under the UBD Energy programme.Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3 − δ (BSCZGY) proton conducting electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs) has been synthesized by a sol-gel modified Pechini process and its sinterability, thermal expansion, microstructure, ionic conductivity and chemical stability have been investigated. Ionic conductivity at 700 °C was measured to be ~ 8 × 10− 3 S cm− 1 in wet 5 vol.% H2/Ar atmospheres. Chemical stability test in pure CO2 up to 1200 °C shows that the material is highly stable; better than the stability of BaZr0.3Ce0.5Y0.1Yb0.1O3 − δ.PostprintPeer reviewe

´Waste-to-energy' fuel cell systems

Funding: Defence Science and Technology Lab.In this paper, a review of the different possible gas and solid fuels for solid oxide fuel cells (SOFCs) is presented. Much research has been performed with gaseous fuels in SOFCs. On the contrary, much work remains on the direct use of solid fuels in SOFCs to overcome all the technical challenges that these systems present. The challenges are even greater when the use of complex solid waste is considered. However, the development of efficient and sustainable energy systems that can operate with waste is of general interest to the energy sector and the environment, as waste management is of major concern. In particular, the re-utilisation or disposal of plastics is of great importance due to their worldwide usage and their slow degradation. The use of an untreated wood and polystyrene mixture in an electrolyte-supported fuel cell with a NiO-YSZ anode and LSM-based cathode was also investigated in this work.Postprin

Rapid Plasma Exsolution from an A-site Deficient Perovskite Oxide at Room Temperature

The research was supported by EPSRC (Award Nos. EP/R023522/1, EP/R023603/1, EP/R023921/1, EP/R023638/1, EP/R008841/1, and EP/V055232/1) and financial support from the UK Catalysis Hub funded by EPSRC Grant reference EP/R027129/1. J.W. and S.C.P. gratefully acknowledge support from the EPSRC (EP/P007821/1) and also thank the U.K. ARCHER HPC facility and the THOMAS HPC (the UK Materials and Molecular Modelling Hub, partially funded by EPSRC EP/P020194) for providing computation resources, via the membership of the UK's HEC Materials Chemistry Consortium (funded by the EPSRC Grant Nos. EP/L000202, EP/709 P007821/1, EP/R029431, and EP/T022213).High‐performance nanoparticle platforms can drive catalysis progress to new horizons, delivering environmental and energy targets. Nanoparticle exsolution offers unprecedented opportunities that are limited by current demanding process conditions. Unraveling new exsolution pathways, particularly at low‐temperatures, represents an important milestone that will enable improved sustainable synthetic route, more control of catalysis microstructure as well as new application opportunities. Herein it is demonstrated that plasma direct exsolution at room temperature represents just such a step change in the synthesis. Moreover, the factors that most affect the exsolution process are identified. It is shown that the surface defects produced initiate exsolution under a brief ion bombardment of an argon low‐pressure and low‐temperature plasma. This results in controlled nanoparticles with diameters ≈19–22 nm with very high number densities thus creating a highly active catalytic material for CO oxidation which rivals traditionally created exsolved samples.Publisher PDFPeer reviewe

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»

Intermediate temperature SOFC anode component based on A-site deficient La-doped SrTiO3

Surface modified A-site deficient lanthanum-doped SrTiO3 (La0.2Sr0.7TiO3) was evaluated as a potential anode component material for intermediate temperatures SOFCs. The reduction of the material has been investigated and results of thermal expansion and conductivity dependence of the oxygen partial pressures are presented revealing a strong dependence of the material's thermal and electrical properties on temperature and atmosphere and the fact that reduction may become more facile as the extent of reduction increases. 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 ceria and copper and thin films of La 0.6Sr0.4CoO3 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/cm 2 at 750°C can be achieved using these cells with suitable pre-reduction of the titanate material.</p

Anodes

Anodes form the surface upon which fuel oxidation takes place with the cell, as such, correct design and materials selection are vital for high performance and long term durability. This becomes even more critical where hydrocarbon or other more complex fuels are considered, as tolerance to carbon and other potential impurities are vital in the realisation of a robust electrode for these environments. This chapter starts by defining the performance criteria for an SOFC anode followed by discussion of the lifetime requirements and catalysis demands for different fuels. The advantages and disadvantages of the state of the art engineering designs and materials (i.e Ni/YSZ cermets) are then covered.Newer alternative electrode materials are then introduced, initially cermets based on other metals, such as Cu. Thereafter, the chapter continues with the newer all ceramic oxide anode, typically perovskite materials based on transition metals such as: La0.75Sr0.25Cr0.5Mn0.5O3 (LSCM) or doped SrTiO3. These can be used either by themselves or as composites with electrolyte materials. The chapter concludes with sections on modifying the anodes via impregnation and ex solution to improve performance and lower cost.</p

Investigation of proton conducting BaZr0.9Y0.1O2.95 : BaCe0.9Y0.1O2.95 core-shell structures

Barium zirconate shows better chemical and mechanical stability than the corresponding cerate, but lower protonic conductivity largely due to resistive grain boundary contributions. In this work we attempted to reduce the grain boundary resistance of BaZr0.9Y0.1O2.95 starting from a core shell modification of its grain with a thin film of BaCe0.9Y0.1O2.95. The resultant core - shell material was characterised by X-ray powder diffraction (XRD), thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM). Impedance spectroscopy performed on the material in wet 5% H-2/Ar atmosphere showed a significant reduction in terms of both bulk and grain boundary resistances of the initial barium zirconate when modified with a thin film of barium cerate. As by thin films modification the total conductivity of the sample increases by about one order of magnitude, this surface modification concept appears to be a promising way to control the grain boundary properties for a given material.</p