بهينه سازي كاتد پيل سوختي اكسيد جامد دماي مياني بر پايه باريوم

چكيده انگليسي :

Optimization of Barium Based Cathode for Intermediate Temperature Solid Oxide Fuel Cells Samira daneshmandi s daneshmandi@ph iut ac ir Date of Submission 2012 02 9 Department of physics Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Dr Hadi Salamati Salamati @cc iut ac irAbstract Fuel cells are considered to be a promise device to convert chemical to electrical energy that exhibits mainadvantages such as high efficiency and low environmental impact Among different kinds of fuel cells solid oxidefuel cells SOFCs have received tremendous attention due to their high efficiency low pollution and highflexibility of fuels in high operation temperature The traditional SOFCs that operated at high temperature 800 1000 C has some problems related to the cost of the materials and fabrication However high operationtemperature is useful in increasing the rate of electrode reactions and decreasing the cell ohmic resistance possibility of additional reaction between cell components increase the need to use costly metal interconnects Therefore an important research is to get lower cost components for operation temperatures under 800 C Accordingly intermediate temperature solid oxide fuel cells IT SOFC operating in range 600 800 Ctemperatures have attracted much attention in recent years Reduction of SOFC operating temperature under the 800 C range allows for a greater choice of materials To counteract the increased ohmic resistance across the electrolyteduring reduced temperature operation and improve cell performance micro SOFCs SOFCs utilizing thin filmcomponent are being actively developed One of the vital SOFC components is the cathode with importantcharacteristic of high electrical conductivity and sufficient ionic conductivity In particular perovskite materials arewell known for their more than adequate characteristics as SOFC cathode materials Studies on the mixed electronicand ionic conduction MIEC materials show that Ba0 5Sr0 5Co0 8Fe0 2O3 BSCF is a good candidate to be used inintermediate solid oxide fuel cells In this study powder of BSCF oxide was prepared by two solid state reaction and sol gel methods for solidoxide fuel cell cathode applications Furthermore to investigation of oxygen pressure impact thin films of BSCFhave been grown successfully on single crystal SrTiO3 STO and Si substrates in different oxygen pressures bypulsed laser deposition PLD Crystal structures of bulk and thin films were studied by X Ray Diffraction XRD X Ray patterns of Bulk show monoclinic cubic structure The XRD pattern obtained for thin films on STO substrateshowed a preferred 00l crystalline orientation in the direction of substrate The surface morphology of films wasanalyzed by atomic force microscope AFM The films surface consist of different separated BSCF islands Thediameter and height of this islands increase with oxygen pressure in such a way so that spherical island are formedin higher oxygen pressure The electrical resistivity of bulk and thin films were measured from room temperature upto operation temperature of IT SOFC 800 C by four point probe method in air atmosphere that showed a sharpdrop compared to initial value for bulks and thin films Furthermore it has shown that increasing of oxygen pressureobtain thin films with lower initial resistance The surface exchange coefficient Kchem of the BSCF thin film determined by electrical conductivity relaxation ECR technique The conductivity change was sharp upon thesudden switch in oxygen pressure and followed an exponential relaxation curve which well fit with electricalconductivity relaxation model Results show that BSCF is a good candidate to be used as cathode in intermediatesolid oxide fuel cells and SOFCs structure Keywords Solid Oxide Fuel Cell Cathode Perovskite Pulsed Laser Deposition Thin Film ElectricalResistance

دانشمندي، سميرا

بهينه سازي كاتد پيل سوختي اكسيد جامد دماي مياني بر پايه باريوم

پروسكايت , لايه نشاني تپش ليزري , لايه نازك , مقاومت الكتريكي