Sharif Digital Repository

Dry reforming methane is a process during which two greenhouse gases, CH4 and CO2, using Ni-based catalysts, are altered into valuable H2 and CO gases, which are very useful from an economic and environmental point of view. The main problem with Ni-based catalysts is the formation of carbon in the dry methane reforming, which leads to rapid deactivation of the catalyst. In this research, a 10Ni-5Co/Al2O3 bimetallic catalyst was prepared by one-pot microwave-assisted combustion synthesis with a stoichiometric amount of fuel (urea) and without the use of additives. The catalyst was then calcined for 12 h at 550oC. The structure, chemical composition, particle distribution, and morphology of... 

Methane steam reforming (MSR) is an assuring reaction using steam to produce H2 as clean energy over a nickel-based catalyst. We synthesized monometallic NiMgAl2O4 and bimetallic NiCoMgAl2O4 catalysts in a two-step combustion method using urea, glycine, and sucrose, as fuel. BET-BJH, XRD, TGA, TPR, FESEM, and EDX-mapping characterized surface area, porosity, morphology, crystalline structure, and metal-support interaction behavior. The products exhibited well-structured, simple MgAl2O4 spinel and NiO without NiAl2O4, in both specimens. The MSR evaluation tests at 750℃ under atmospheric pressure, CH4: H2O feed ratio of 1:1.6 showed the bimetallic catalyst has the highest conversion (99.30%)... 

Interconnects in SOFC’s has oxidation problems which is Because of high temperature operation. Also Cr migration to cathode make chroumiom poisoning problems and all of this affects SOFC’s efficiency. To solve this problem researchers decided to use some protective coating on interconnect. The best group of coatings is Mn-Co Spinels. In this thesis (Mn,Co)3O4 spinels was synthesized via solid state reaction. MC reffered to Mn1.5Co1.5O4 was calcined at 850°C and then sintered at 1200°C. It’s electrical conductivity measured by 4-point probe DC method. It had the lowest ASR (17mΩ.cm2) among other stochiometries. To reduce the sintering temperature, Cu and Y was added as dopants. Among the... 

Solid oxide fuel cell (SOFC) is one of the promising candidates for clean energy production. Due to the high operating temperature of SOFC, a protective coating is commonly applied on the surface of interconnects to prevent oxidation. In this study, electrophoretic deposition was employed to prepare a manganese-cobalt spinel coating on the surface of ferritic stainless steel (AISISAE430) substrates. MnCo2O4 powder with an average particle size of 60 nm was utilized and the sintering behavior of the coatings at different temperatures was studied. Non-isothermal and isothermal sintering behavior of the powder compacts were examined by employing a sensitive dilatometer. Master sintering curve... 

Due to recent progresses in lowering the temperature of SOFC, using metallic interconnects instead of ceramic interconnects was possible. Among the alloys used for interconnects, ferritic stainless steels (FSS) due to thermal expansion coefficient compatible with other cell components and cheap fabrication, have become the most widely used material for interconnects. Because of improvement of oxidation resistance of these FSSs, many studies have been made on coating of oxides on FSSs and results show that the spinel oxides have the best performance. In this study, the CuCo2O4 performance as coating in SOFC's interconnects was investigated. Coating process used was sol-gel dip coating and raw... 

In this study, nano-powders of copper-cobalt spinel (CuCo2O4) were fabricated by solution combustion synthesis (SCS) of Cu and Co nitrates with urea, glycine,acid citric and alanine. The method involved exothermic decomposition of viscous liquid nitrates and the fuel. Products which were synthesized by using this fuels contained less impurity constituents. Duo to low purity, other factors which have influence on synthesis process investigated and observed that pH have key role on process. X-ray diffraction (XRD) patterns gave crystal structure and the existing phases. Particle size distribution and morphology changes were studied by dynamic light scattering (DLS) and field emission scanning... 

Because of the high operating temperature, interconnect surface tends to be oxidized and Cr2O3 oxide layer will be created on the surface. This phenomenon is undesirable due to decreasing electrical conductivity, so a preservative coating is needed to improve the interconnect properties. In this paper, a dense spinel thin film was successfully synthesized on a ferritic stainless steel (type 430) substrate by a sol-gel dip coating method. This coating improved chemical stability, oxidation behavior of the substrate and decreased cathode poisoning. The Nickel-Cobalt spinel was coated on the substrate by sol-gel coating process. First, during a hydrolyze process, a stable sol was made up from... 

Zirconia Toughened Alumina (ZTA) is a well-known ceramic matrix composite due to its high fracture toughness and good mechanical properties. Addition of spinel (MgAl2O4) to ZTA inhibits alumina grain growth and produces phase boundaries with low strength. This phenomenon leads to formation of a ceramic matrix composite with special mechanical properties such as high temperature super plastic deformation. However, the room temperature mechanical properties of alumina-spinel-zirconia (AMZ) composite such as fracture toughness were rarely investigated by researchers. In this research the AMZ nanocomposite powders were synthesized via solution combustion method. The dense AMZ composite samples... 

In this research, a powder containing magnesium-aluminate spinel particles is prepared based on co-precipitation method and 5% , 10%, 15% and 20% zirconia-contained composites are produced as second phase from the synthesized powder. The raw materials used in the synthesis comprise hexa-hydrated magnesium nitrate, nona-hydrated aluminum nitrate, ammonium bicarbonate, 28% ammonium solution and distilled water. The properties of the powder is then investigated using STA, XRD and SEM tests. Also, XRD and SEM analyses as well as triple point flexural strength and Vickers hardness tests are carried out in order to investigate the effect of adding zirconia to the powders. The variations of the... 

Ferrite spinels are very valuable as heterogeneous catalysts and have the ability to separate. In this dissertation, ferrite nanoparticles were synthesized by co-precipitation method and used in carbon-phosphorus and phosphorus-sulfur bond formation reactions. The structure of these compounds was investigated by different techniques. The ferromagnetic CuFe2O4 ferrite catalyst was expanded in the C-P bond formation reaction, resulting in a convenient and efficient method. Phosphorylation of alkenes was performed using a model reactant, dialkyl phosphite as a source of phosphorous compounds, and beta-ketophosphosphonates were synthesized. Beta-ketophosphonates are important intermediates for... 

Due to many vast application of C-C bond formation in the areas including bioactive compounds and natural products, over the past few years, the C-C coupling reactions have become a versatile tool in organic synthesis.First, a two-metal catalyst (CoFe2O4) was synthesized and its catalytic activity was evaluated in unsymmetrical thioether synthesis which offered an odorless, ligand-free and aryl halide-free rout for the formation of desired products. The catalyst was recovarable and was able to catalyze the reaction for 10 runs with retention of catalytic activity.In the next step, three-metal catalyst (CoCuFe2O4) was synthesized using the co-precipitation method and characterized.Then, these... 

The ability of Ferro spinels to catalyze the reactions, along with their ability to become easily separated, has attracted many attentions. These Ferro spinels are synthesized in an efficient way and are used as a catalyst for carbon-carbon bond formation. Nanoparticles of Spinel ferrites, for instance three-metal ferrites, have unique characteristics and have very interesting and important applications in synthetic organic chemistry. In the first section of this thesis, synthesis and analysis of copper cobalt ferrite is considered. In the second section, several organic chemical reactions are investigated to evaluate the catalytic activity of these nanoparticles. Finally, the catalytic role...