Materials Science Forum Vols. 775-776

Abstract: The aim of this study is to evaluate the effect of temperature during the synthesis of alumina by combustion in a muffle furnace. The alumina was characterized by X-ray diffraction, particles size distribution and scanning electron microscopy. The results showed that the synthesis temperature of the alumina can affect the structure of the produced samples. The size distribution of the median particle diameter reached higher value for the alumina synthesized at 500°C with 16.07 μm, the range of the total distribution of particles is introduced to the large alumina synthesized 500 and 600°C and close synthesized when 700 and 800°C. The phase of the alumina was identified only after the synthesized sample at 800°C with crystallite size of 22.16 and 6.75 μm synthesized samples 800 and 900°C, respectively. With respect to morphology, increased synthesis temperature was not enough to significantly change.

Abstract: The present work intends to prepare ZnAl₂O₄/chitosan films with a mass proportion of 3:1and evaluate the influence of the ZnAl₂O₄ filler on the chitosan films morphology, structure and thermogravimetric properties. The films were characterized by XRD, SEM, TG and FTIR. With the XRD, it has been verified that both the chitosan and the ZnAl₂O₄/chitosan films presented the chitosan peaks. However, the ZnAl₂O₄/chitosan film also presented the ZnAl₂O₄ peaks. Through the SEM, it has been observed that the chitosan film presented a flat surface. On the other hand, the ZnAl₂O₄/chitosan presented a protruding surface. The TGA/DTA curves of the ZnAl₂O₄/chitosan film showed an increase in the thermal stability at temperatures greater than 720oC, comparing with the chitosan film.

Abstract: Wastes generated by processing ornamental stones are an increasing environmental problem in Brazil. Recycling alternatives are being investigated for the different types of wastes. The addition into clay ceramic is a possibility as long as the stone waste presents compatible characteristics. Therefore the objective of this work was to characterize a waste obtained from the sawing operation of granite by a steel multi-wire equipment as well as to evaluate its effect on the plasticity of clayey formulations. This characterization was performed in terms of chemical composition, X-ray diffraction and particle size distribution. The results indicated not only similar chemical and physical aspects but also a potential for addition into clay bodies of Campos dos Goytacazes in the state of Rio de Janeiro, Brazil, by the adjustment of the excessive plasticity of the clay.

Abstract: Research with emphasis on substitution of energy sources used in worldwide for renewable energy undoubtedly indicates that the use of biodiesel would be an option to increase the income in rural areas, reduction in oil derivatives spending and also new opportunities for job creation. Soon, in purpose to contribute with the research growth, this research proposes to evaluate the new catalysts performance as nanoferrites Ni_0,5Zn_0,5Fe₂O₄ (pure) and Ni_0,1Cu_0,4Zn_0,5Fe₂O₄ (doped with 0.4 mol of Cu²⁺) in transesterification reactions of soybean oil methyl. For both samples were synthesized by chemical method in the stoichiometry of the combustion reaction, using urea as a fuel source and a resistance heating coil. During synthesis were measured time and combustion temperature. Later they were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), textural analysis (BET) and subjected to catalytic tests bench. The reaction conditions used in the transesterification were: 10 g of oil, 2 h reaction time, molar ratio of 1:20 oil and alcohol, 4% (w/w) of catalyst and reaction temperature of 160°C. Finally, the reaction product was characterized for conversion into methyl esters by gas chromatography. Results has shown only the presence of the inverse spinel phase, characteristic of Ni-Zn ferrite for both samples, with crystallite size of 26 and 29 nm, respectively. The thermogravimetric analysis has shown that samples are thermally stable, with a weight loss of 4.9 and 3.7%, respectively. The surface area and particle size were 48.89 m²g^-1 and 23 nm, and 18.06 m²g^-1 and 62 nm, respectively. The conversion results obtained by the transesterification reaction were 13 and 50% Ni_0,5Zn_0,5Fe₂O₄ and Ni_0,1Cu_0,4Zn_0,5Fe₂O₄, respectively, indicating that sample with presence of copper was 26% more effectively, thus being one promising catalyst for the transesterification reaction, which aims to obtain biodiesel.

Abstract: This work has as its objective to evaluate effect of the incorporation of an ash, obtained from burning wood from coffee plant, in the physical and mechanical properties of incorporated clayey ceramic. The ash has undergone characterization tests by the techniques of XRF, DTA / TG and XRD. Formulations were prepared with 5, 10, 20 and 30 wt% of ash incorporated into clay bodies that were then homogenized, dried and finally moistened. Rectangular test specimens were prepared by uniaxial pressing in a steel mold at 20 MPa, followed by firing at 700 °C. The fired ceramics were subjected to physical and mechanical tests for determining the bulk density, linear shrinkage, water absorption and tensile strength. The results indicate that the ash is composed predominantly of calcium, magnesium and potassium oxides. The incorporation of ash up to 20 wt% decreased the water absorption and notably increased the ceramic mechanical strength in the temperature investigated.

Abstract: The microstructure of a clay ceramic added with blast furnace sludge, a residue generated at integrate steel making plants, has been analyzed. This analysis was performed by means of optical microscopy and scanning electron microscopy coupled with energy dispersive spectroscopy. The green clay body was added with 5 and 10 wt% of blast furnace sludge. A pure clay body was also considered as reference. These clay bodies were fired at 750°C and 950°C. The results indicated that the ceramic microstructure is non-uniform with both residue particles and pores dispersed throughout the clay matrix. Microcracks are also observed as a consequence of weak adhesion of the residue to the clay. At the higher firing temperature of 950°C the microstructure displayed a smoother surface due to the formation of low melting phases.

Abstract: Foster swelling is one of the methods used to determine the compatibility between organoclays and organic dispersant media, improving the quality of organoclays. The need for replacing imported clays by national ones for the oil industry has recently resulted in the discovery of new deposits of smectites in the cites of Cubati and Pedra Lavrada, PB, reflecting great social and economic effects for that region. So, the objective of this work is to obtain organoclays from smectites from Pedra Lavrada, PB, aiming at the study of how to make these clays suitable with some organic dispersant media through Foster swelling. After organofilization, the clays were characterized by X-ray diffraction and Foster swelling. The results pointed that some media are compatible with organoclays, being diesel, kerosene and varsol the descendant order of compatibility between the clays and the organic media.

Abstract: Squeeze casting process of Zamac 5 for obtain faucets enables higher productivity associated with better dimensional characteristics. In this process, the die cooling system can influence the solidification of the alloy and its properties. This study evaluates the influence of die temperature on solidification under pressure from Zamac 5. Pieces were removed from the die at several temperatures. Samples were evaluated by neutral salt spray corrosion, optical microscopy and microhardness. The results show that the corrosion is related to the porosity defects, which was most intense in part regions which solidified lastly. These regions also showed different results of microhardness. However, the behavior of the samples was similar in the range of die temperatures studied.

Abstract: Changes in the structure and properties of a TiNi alloy, which possesses shape memory effect by means of reversible martensitic transformation (RMT), after annealing at different temperatures in the interval of 300 to 550oC, were investigated. These changes were characterized by chemical analysis, X-ray diffraction, electrical resistivity, microhardness and differential scanning calorimetry. The results showed that the as-fabricated TiNi alloy presented a multiphase structure. An additional high temperature phase was revealed upon 550oC annealing. The alloy displayed sensible changes in its electrical resistivity that were attributed to the influence of the several existing phases. A tendency for the increase in the RMT critical temperatures was also observed with increasing annealing temperature.

Abstract: Magnetic microparticles were formulated by encapsulating magnetite nanoparticles with cellulose acrylamidemetyl propionate acetate (CAPA) chemically modified with acrylamide (AM) in order to immobilize, through covalent bonds, enzymes. The microparticles were characterized by means of scanning electron microscopy and thermogravimetry. The magnetic CAPA + AM microparticles display a quite regular spherical geometry with smooth surface and a magnetite load corresponding to 11.2% of the total mass. These particles were considered as convenient supports for enzyme immobilization in biodiesel transesterification process.