Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Preparation and Characterization of Ce_1-xM_xO_2-(x/2) Based

Electrolytes for Solid Oxide Fuel Cells

The development of electrochemical converters has attracted research interest due to an increasing concern on the depletion of available fossil fuel reserves and environmental issues such as global warming and emission of pollutant gases. The generation of energy by clean, efficient and environmental-friendly means is now one of the major challenges for engineers and scientists. Fuel cells convert chemical energy of a fuel gas directly into electrical energy, and are efficient and environmentally clean, since no combustion is required. Moreover, fuel cells have the potential for development to a sufficient size for applications for commercial electricity generation. Fuel cell systems are available to meet the needs of applications ranging from portable electronic devices to utility power plants. Promising applications for fuel cells include portable power, transportation, building cogeneration, and distributed power for utilities.

Solid oxide fuel cells have received special attention because of their higher energy efficiency, rapid electrode kinetics without using expensive electrocatalysts such as Pt, relative resistance to impurities in the fuel and the possibility of processing CO, CH₄ and other carbon based fuels. Most of the research efforts have focused on the development of solid oxide fuel cell materials such as yttria stabilized zirconia (YSZ) electrolytes, lanthanum or calcium doped strontium manganite (LSM) cathodes and Ni-YSZ cermet anodes. YSZ electrolytes require high operation temperatures (~1000 °C) in order to achieve sufficient ionic conductivity, placing large restrictions to candidate electrode, interconnect and housing materials. As a result, the cost of solid oxide fuel cell systems has become an important factor preventing their commercialization. To overcome these problems, electrolytes which have high ionic conductivity at intermediate temperatures are needed. According to the recent researchs, it was shown that a variety of rare earth metal doped cerium oxides can be used as electrolyte materials in order to develop solid oxide fuel cells operating in intermediate temperatures.
The aim of this work is to prepare metal oxide doped cerium oxide based electrolytes with dense structure and high ionic conductivity for intermediate temperature-solid oxide fuel cells by using polyol method and characterize them with TG/DTA, XRD, SEM, EIS, EDS. As a consequence of ionic conductivity analysis with EIS, it was obtained that the material which indicated the highest ionic conductivity value was SDC20.

  

YILMAZ Kadir

Tez Adı :İran Ağır Petrol Kalıntısının Hidrokraking Reaksiyonlarının İncelenmesi

Danışman : Prof. Dr. Muzaffer YAŞAR

Anabilim Dalı : Kimya Mühendisliği

Programı : Proses ve Reaktör Tasarımı

Mezuniyet Yılı : 2013

Tez Savunma Jürisi : Prof. Dr. Muzaffer Yaşar

Prof. Dr. Mehmet Ali GÜRKAYNAK

Prof. Dr. İsmail KIRBAŞLAR

Prof. Dr. Serpil GÖKSEL

Yrd. Doç. Dr. Solmaz AKMAZ