Elvia Leal

Evaluation of the Cu Doping Effects in CeO2 Catalytic Supports Obtained by Combustion Reaction

This work has for aim to synthesize CeO2 catalytic supports doped with Cu2+ by combustion reaction method. Thus were obtained catalytic supports with the composition Ce1-xCuxO2 and the effect caused by doped element in the structure of the CeO2 was evaluated. The concentration value (x) of the Cu doped took over the values of 0.0; 0.3 and 0.5 mol. The catalytic supports developed were submitted to the structural characterization by X-ray diffraction, morphologic analysis by SEM and textural analysis by means of adsorption-dessorption of N2 by BET method. The results showed that the doped element (Cu) was not completely incorporated in the CeO2 structure and was evidenced that how much larger the quantity of Cu larger maid the disorder of the atomic structure of the obtained material. The analyzed supports present mesoporous nature structure.

Combustion Synthesis of ZnAl2O4 Catalyst Using Glycine as Fuel for the Esterification and Transesterification of Soybean Oil: Influence the Form of Heating

The aim of this work is to evaluate the esterification and transesterification activity of ZnAl2O4 catalysts obtained by different ways of heating during the combustion synthesis using glycine as fuel. Samples were prepared according to the propellants and explosives theory using a vitreous silica crucible as container, and as heating source, plate, muffle furnace and microwave oven. After synthesis, the samples were structural and morphologically characterized by: XRD, nitrogen adsorption and carbon content analysis, and employed in the esterification and transesterification reactions, the percentage of biodiesel formed (FAME) was determined by gas chromatography. The samples obtained on the plate, muffle furnace and microwave showed that even using different heating ways, led to the formation of ZnAl2O4 as majority phase, with crystallite sizes of 11, 15 and 10 nm, respectively. The samples present values of surface area ranging from 16 to 77 m2/g, particle size from 17 to 81 nm, and carbon content lower than 11%. The forms used for heating influenced the esterification and transesterification reactions, showing that there was a gap in the production of biodiesel, which is a promising indication that this material has potential to be used as catalysts on the biodiesel production.

Microstructural and Mechanical Properties of Al2O3/HAp Composites for Use as Bone Substitute Material

This work involved the development of alumina/hydroxyapatite (Al2O3/HAp) composites for use as bone graft material in maxillofacial reconstruction. The effect of introducing 20 and 30 wt% of hydroxyapatite into the alumina matrix was also investigated. The composites were produced from hydroxyapatite synthesized by the precipitation method, using commercial alumina as a matrix. Samples of the composite material were compacted under 260 MPa of isostatic pressure, followed by sintering at 1200°C/2h and characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), and diametral compression. The XRD results confirmed the presence of Al2O3 and Ca10(PO4)6(OH)2 – HAp crystalline phases in all composites. The addition of HAp to the alumina matrix inhibited alumina grain growth, reducing intergranular porosity and thus promoting greater densification and mechanical strength of the composites.

Biodiesel from Fatty Acids Found in Brazilian Native Cultures as Soybean and Cotton Using the Nanocatalyst Ni0.5Zn0.5Fe2O4

Biodiesel is a biodegradable fuel derived from renewable biomass, such as soybean and cottonseed oil, which may be obtained by different processes and requires a material to catalyze the obtaining reactions. The irons spinel comes overlapping as excellent materials to catalyze the biodiesel production reactions. Thus, the purpose of this work was the use of Ni0.5Zn0.5Fe2O4 nanoferrite as a catalyst in esterification reactions. The nanoferrite was synthesized by combustion in large scale, 200g/batch, where time and the temperature of the reactions were measured, and characterized by XRD and measuring its surface area. The biodiesel was obtained from methyl and ethyl esterification of acidified soybean oil and cottonseed, at a temperature of 160°C for 1 hour, molar ratio 1:15, 3% of catalyst and analyzed by chromatography. The nanoferrite has shown peaks of greater intensity corresponding to a majority crystal phase of the spinel and a surface area of 64.17m2/g. The conversion results for the soybean oil were 99.08% in methyl route and 98.38% in ethyl route. For cottonseed oil were 88.79% in methyl route and 78.65% in ethyl route.

Immobilized Enzyme Gox with Ferrite CoFe2O4 and Hybrid CoFe2O4/APTS

This work aims to evaluate the immobilization of glucose oxidase (GOx) with CoFe2O4 nanoparticles and hybrids CoFe2O4/APTS. The nanoparticles were synthesized by combustion reaction and silanized using 3-aminopropyltrimethoxysilane (APTS). The samples were characterized by XRD, FTIR, magnetic measurements and immobilization of GOx. The results indicated single phase of spinel CoFe2O4 and the addition of APTS did not alter the structure of the ferrite. The characteristic bands of spinel and characteristic bands were observed in the silane silanized sample proving the silanization of nanoparticles of CoFe2O4. The CoFe2O4 nanoparticles and the hybrid had saturation magnetization of 58.0 and 53.0 emu/g and coercivity of 1.14 kOe and 1.15, indicating that the silanization does not interfere with the magnetism of the particles. The immobilized GOx was obtained with values of 0.047 and 0.050 mg/g efficiency of 84.86 and 80.30% for CoFe2O4/APTS and CoFe2O4.

Evaluation of the Cytotoxicity of NiFe2O4/SiO2 Hybrid Nanoparticles Aiming its Application as Drug Carriers

Magnetic nanoparticles have potential application in biomedicine since their features allow a wide variety of applications, such as drug carriers, destruction of tumor cells and magnetic separation of cells and proteins. Overlooking that, the proposal is to obtain the hybrid NiFe2O4/SiO2 from the surface modifying with the 3-aminopropyltriethoxysilane, and evaluate the structure, morphology and cytotoxicity, to obtain a biocompatible hybrid for biological applications, such as, e.g., drug carrier. The samples were analyzed by XRD, FTIR, SEM, magnetic measurements and cytotoxicity. The results showed the formation of single phase of the NiFe2O4 spinel with crystallite size of 35 and 32 nm referring to the samples before and after the surface modification, and presence of characteristic absorption bands of the spinel and of the silanol group from the silane agent, confirming the hybrid formation. The presence of the silane agent kept the ferrimagnetic characteristic and increased the cell viability, making it a non-cytotoxic material.

Synthesis of ZnAl2O4 Catalytic Support by Combustion Reaction Using Different Fuels

This work shows the influence of the fuels aniline, carbohydrazide and glycine on structural and morphological characteristics of ZnAl2O4 synthesized by combustion reaction. Samples were prepared according to the propellants and explosives theory using a vitreous silica crucible and a muffle furnace as heating source. During the synthesis was measured the time and temperature of the reaction. After The samples were structurally and morphologically characterized by the following techniques: XRD, nitrogen adsorption / desorption (BET / BJH), and SEM. The higher temperature was achieved by the synthesis using aniline, whose value was of 876°C. XRD results showed that all the samples presented the ZnAl2O4 spinel as majority phase and, ZnO and Al2O3 as segregated phases. The samples also showed low surface area, varying of 23.6 to 28.7 m2/g, and particle size of 45 to 55 nm, besides mesoporous characteristic and irregular agglomerates formation.

Influence of the Ratio between the Amounts of Reagent Total/H2O to Obtain Ferrites Mn0.65Zn0.35Fe2O4 by Combustion Reaction

This work proposes to study the influence of dilution on the synthesis of ferrites Mn0.65Zn0.35Fe2O4 using glycine. It was used the reactants/H2O proportions of 1:0; 1:3.5; 1:7; 1:10, and 1:14 (100 mL of H2O). During the synthesis were measured the time and temperature of combustion. The samples were characterized by X-ray diffraction and X-ray fluorescence. The dilution in the samples increased with the increasing of the reaction time and flame temperature. For samples synthesized with 1:0, 1:3.5; and 1:7 ratio were observed traces of hematite, and to the remaining samples only the single phase of the Mn0.65Zn0.35Fe2O4 spinel. The crystallite sizes ranged from 32 to 42 nm.

Characterization and Efficiency of ZnAl2O4 Spinel Synthesized by Combustion Reaction on the Esterification and Transesterification of Soybean Oil

This paper proposes to assess the efficiency of ZnAl2O4 obtained by combustion reaction on the process of esterification and transesterification of soybean oil to biodiesel production. In the synthesis it was used three heating conditions: spiral resistance, muffle furnace, and microwave oven. In order to investigate the influence of the heating source on the structure, morphology, and on the catalytic activity, the samples were characterized by XRD, FTIR, granulometric analysis, TGA, carbon content, TEM, and gas chromatography. The results showed that it was possible to obtain the ZnAl2O4 cubic phase with traces of ZnO. The ZnAl2O4 monophasic was just obtained by the synthesis carried out in the microwave oven and in the electrical resistance. All the samples showed a typical morphology of dense agglomerates and low carbon content. The samples also presented low catalytic activity in the esterification and transesterification process under the adopted conditions.

Influence of Preparation Method of the CeO2 over their Structural Characteristics

The aim this work is to synthesize the CeO2 in the ceramic powder form through three different methods of synthesis, they are: method of combustion, Pechini method and hydrothermal method. Will be evaluated the influence exerted by these methods of preparing of the metallic oxide on the structural features presented in the same. Three samples of CeO2 were synthesized in this work, they were analysed by x-ray diffraction, SEM and adsorption and desorption of N2 by BET method. According to the results has been observed that the synthesis method has great influence on the structural characteristics of CeO2 obtained. The sample of CeO2 synthesized by Pechini method showed a structure with a higher percentage of crystallinity and average pore diameter smaller when compared to samples of CeO2 synthesized by means of the combustion method and of the hydrothermal method. The sample synthesized by the combustion reaction method presented larger agglomerated of unitary particles.