Materials Science Forum Vol. 820

Abstract: The State of Paraíba has gained prominence in the production of raw bentonite in Brazil, where a new deposit has been found in the town of Sossego-PB, besides the deposit in the town of Boa Vista-PB. With the raise in the demand, the traditional reserves are depleting after several years of exploration, and this fact may result in a higher dependence on imported clays, thus existing a great interest in the discovery and characterization of new deposits, also guaranteeing technological improvements for the region. So, the objective of this work is to characterize the new deposits of the State of Paraíba, aiming at analyzing the characteristics the prove their classification as smectitic clays. The characterization was made through the analysis of chemical composition by X-ray fluorescence (EDX), X-ray diffraction (XRD), thermogravimetric analysis and thermal differential analyses (TG and DTA), cation-exchange capacity (CEC) and specific area (SA). The results prove that the studied samples presented, in their mineralogical composition, smectite, kaolinite and quartz, besides thermal and chemical behavior typical smectitic clays.

Abstract: Used in various branches of the industry, bentonitic clays are considered a valuable mineral, used specially in the petroleum industry for manufacturing of fluids used the drilling of petroleum wells in long depth. Recently, a deposit of this valuable mineral was discovered in the town of Olivedos-PB. There are data that prove that this is a very poor and underdeveloped town. So, this work aims at the physico-mineralogical characterization of clays recently discovered and, this way, verify if they present similar characteristics which allow them to replace the clays from Boa Vista-PB, and if they can be used by the industry, thus bringing social development for that town. The characterization was made by means of the analysis of chemical composition by X-ray fluorescence (EDX), thermogravimetric and thermal differential analyses (TG and DTA), X-ray diffraction (XRD), cation-exchange capacity (CEC) and specific area (SA). The results show that the clays recently discovered in Olivedos-PB are polycationic clays, presenting MgO, CaO and K₂O content, and that they are constituted by smectitic clay mineral, by quartz and kaolinite.

Abstract: Smectite clays or bentonites are used in several industrial applications. The aim of this study was to describe the characterization and organophilization of a green clay sample coming from the State of Paraíba, Brazil. The clay was characterized by XRD, XRF, CEC, SEM, stereoscopic microscopy, Fann viscosity (before and after the organophilization process), swelling capacity in water and some organic solvents. Prismatic specimens were conformed by pressing, for which were conformed the mechanical sthegth after drying at 110°C and after burning at 950°C. The burned specimens were analyzed to evaluate dimensional variations, water absorption, apparent porosity and apparent density. XRD showed that the sample was constituted mainly for montmorillonite claymineral. Analysis of rheological properties of the modified clay indicates its potential to meet the specifications of the standard N-2604 of Petrobras, concerning clays used to oil drilling.

Abstract: Bentonite exhibt a range of industrial applications moving millions of dollars on the market per year. Among several applications if highlights it is use for petroleum drilling fluids. Thus, this work aims to characterize physical, mineralogical and technologically, the bentonitics clays of Sossego County, Paraíba, Brazil. Mineralogical characterization of clays was done through the following techniques: particle size analysis by laser diffraction, thermogravimetric and differential thermal analysis, chemical analysis and x-ray diffraction. The clays were turned in by treatment with sodium in Na₂CO₃ and then determined whether the apparent viscosity, plastic and volume of filtrate of clay-water dispersions. The results showed that the samples are of polycationic, showing levels of MgO, CaO and K₂O, similar to those from Boa Vista County, Paraíba, Brazil, and consist of clay mineral kaolinite, quartz and esmec. The clays showed rheological properties that indicate potential for use in drilling fluids.

Abstract: Improvements of the catalytic efficiency of nickel–aluminum oxides in reforming reactions for hydrogen production have been achieved by the development of synthesis processes that provide powders with high surface area. The reduction of the crystallization temperature is one of the procedures in this direction. In this work, the effect of solvothermal treatment on coprecipitated gels with 15 wt% nickel content in alumina matrix was evaluated. Powders were obtained by coprecipitation with and without treatment of gels under n-butanol vapor pressure at 150oC. Products were characterized by TG/DTA, X-ray diffraction, specific surface area measurements, scanning electron microscopy and laser beam scattering for granulometric distribution determination. The results showed that calcined powders have high specific surface area (ranging from 170 to 260 m².g^-1) and are composed by gamma alumina and nickel aluminate phases. Aging treatment did not promote hydroxides decomposition under solvothermal conditions, indicating the need of calcination step.

Abstract: Given the diversity of areas in which applications of ceramic membranes are included, the literature has shown great interest of researchers to obtain these materials with powders synthesized by different chemical methods. Thus, this work aims at the synthesis of alumina by Pechini method, the 2:1 ratio of citric acid: metal cations, calcined to 1100°C, to obtain membranes. The synthesized powders were characterized by thermal analysis, XRD and particle size distribution, since the membranes were characterized by SEM and mercury porosimetry. The results for the obtained powders showed total mass loss of 61.60%, an alpha-alumina phase with crystallite size of 45.2 nm. As for the membranes, these showed heterogeneously distributed particles with different sizes and irregular geometry, reaching average pore diameter of 0.6 μm me 47% porosity, and thus are characterized for application in microfiltration processes.

Abstract: Among the ceramic raw materials, mullite is highlighted for presenting features which are of great interest for industry. However, the process through which this material is obtained requires pure reagents, raising the production costs. Therefore, this work is intended to obtain mullite from bentonite clays (source of silicon and aluminum oxides) and alumina residue, resulting from the Bayer process, thus becoming an interesting process from the economic and environmental standpoint. For this purpose, we made use of the thermal treatment in conventional furnace, temperature of 1500°C, heating rate of 5°C/min and dwell time of 60 min at maximum temperature. The synthesized samples were characterized by X-ray fluorescence (EDX), X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled to an EDS, besides the quantification of the phases present in the samples. The results revealed that mullite was the major phase produced, but corundum appeared as secondary phase.

Abstract: Front of the large number of applications of the mullite mineral, many researchers seek to synthesize it from the mixture of Al₂O₃ and SiO₂ powders, or from aluminossilicates, such as smectite. The synthesis of mullite from clays via rapid heating by microwaves emerges as an alternative process. This process accelerates the kinetics of nucleation and the development of mullite phase. Thus, the aim of this work is to study the effect of power and timeon synthesis of mullite from clay, via rapid heating in microwave. The synthesis times were 15 and 20 minutes, with powers of 1.26 and 1.44kW. The obtained powderswere characterized by X-ray diffraction and scanning electron microscopy. The best results were obtained with a power of 1.44kW for 20 minutes.

Abstract: Magnesium aluminate (MgAl₂O₄) was synthesized via combustion reaction, using as fuel glycerine from biodiesel, for the production of cellular ceramics. A rheologically stable suspension was prepared in a ball mill and polyurethane sponges were impregnated. In order to define a firing cycle which would result in ceramic foams with high density ceramic walls (struts), synthesized and calcined powders were uniaxially pressed at 5.4 MPa and, after drying (110°C/120 min), fired at different temperatures (1450-1650°C) for 120 min. Thus, ceramic foams (fired at 1600°C/120 min) containing MgAl₂O₄ as the only formed crystalline phase with a porosity of 88 ± 0.5% and compression strength of 1.0 ± 0.3 MPa were obtained.

Abstract: This work aims to synthesize ZrO₂ by the combustion reaction method and its sulfating for future use as a catalyst in esterification of the cottonseed oil. The synthesized sample was produced in batches of 15g, using as precursor the zirconium IV n-propoxide and urea as fuel. The sulfating occurred with an ion content of SO₄^-2 with 30% in relation to the mass of ZrO₂. The samples were characterized by XRD, SEM and particle size distribution. The results revealed the formation of the monoclinic majority phase with traces of the orthorhombic phase referring to the synthesized sample, and a transformation of the orthorhombic phase to the tetragonal phase when sulfated. The morphology have shown the formation of homogeneous and spherical agglomerates, with a mean particle size of 24.34nm. The presence of traces of the tetragonal phase in the XRD of the SO₄^2-/ZrO₂ was a great indicator for future use in the esterification reaction to obtain biodiesel, because this type of phase after sulfating becomes very promising for the ester obtaining.