Materials Science Forum Vols. 798-799

Abstract: The bentonite clays are rich in accessory minerals, the presence of these minerals, depending on the application can impact the value of an industrial warehouse, reducing its value and compromising its quality and industrial applications. Thus, the need to go through clay beneficiation processes to meet market specifications in order to use more than one hundred industrial applications. The objective of this work is to study the influence of pressure in the process of purification of hydrocycloning betonites clays: Superior Grey, Green Superior and Inferior Green District Cubati-PB performed to optimize the process of organophilization . The characterization of natural clays betonites was taken and purified at pressures of 1.5-2bar and 3-3.5bar through techniques: AG, XRD, EDX, TG and DTA. The results showed that the purification process is more efficient pressure 3-3.5bar.

Abstract: Heating with microwave power is a process in which the materials take up electromagnetic energy volumetrically and turn it into heat inside a piece. This is the great difference from the conventional method, where the heat flows between objects by means of conduction, radiation and convection, in which the surface of the materials is heated first, and then the heat is transferred to the interior of the piece, thus forming a temperature gradient. On the other hand, microwave heating generates heat first inside the piece, heating the whole volume later. [1]

Abstract: The objectives of this study were to produce ZrO₂-based nanoparticles doped with silver, using the polymeric precursor method (Pechini), and to verify their bactericidal activity against Escherichia coli and Staphylococcus aureus. Zirconium and silver oxides were chosen due to their bactericidal activity. The oxides were characterized by X-ray diffraction and field emission gun-scanning electron microscopy. The support for the oxides was a porous surface used in gravity filters. The method was not effective against the bacterium Escherichia coli in the sample subjected to UV light for 45 min, since it did not eliminate the bacterium, and did not inhibit colony growth and formation. However, the bactericidal activity test proved effective against Staphylococcus aureus, eliminating the bacterium when the sample was subjected to UV light for 45 min, thus preventing colony growth and formation.

Abstract: This paper presents the synthesis, characterization and influence of oxidizing atmosphere in the calcinations and sintering processes on microstructural properties of mixed oxides of Cerium and Zinc, obtained by the polymeric precursor method, aiming at a subsequent catalytic application. The material was submitted to calcinations and sintering at 900 and 1050 °C. The samples were characterized by XRD analysis techniques, surface area by BET method and refined by the Rietveld method. The results of X-ray diffraction showed that interest phase was formed, indicating that the method for obtaining the phase is effective. The results of surface area for the system calcined in air were 85 m²/g and 65 m²/g for the system subjected to oxidizing atmosphere both at 900°C, in the same temperature. It was observed that the temperature increase leads to an increase in crystallite size. This fact is in line with other studies in the literature.

Abstract: This work had the aim to optimize the synthesis process of a geopolymer using experimental planning of mixtures. The geopolymer was prepared with different proportions of bauxite mud (R), rice husk ash (C) and metakaolin (M). The aluminosilicatealkaline activation was made with sodium hydroxide (NaOH) solution of 12 mol/L. Afterwards, the obtained material was submitted through a thermal treatment for 6 hours in an oven followed by a cure time of 28 days at room temperature. The final material was characterized through combinations of different techniques such as Scanning Electron Microscopy (SEM) and X-Ray Diffraction. Through carefully analysis of the flexural strength results, it was possible to conclude that the geopolymeric material (R6C2M) had a greater resistance in the seventh cure day at 0.6 MPa, however, it also can be said that the other samples presented an increase in the resistance over the 28 days of cure time.

Abstract: Al₂(WO₄)₃ was synthesized by co-precipitation using Na₂WO₄ and Al (NO₃)₃ as precursors. After drying the precipitate, it was calcined at different temperatures between 500°C and 800°C. The crystallization and degradation temperatures of the samples were evaluated by means of Differential Scanning Calorimetry (DSC), Thermogravimetry (TG) and X-Ray Diffraction (XRD). It was observed that the crystallization starts at around 600°C, however Transmission Electron Microscopy (TEM) analysis showed that at this temperature the sample is partially amorphous. The degradation of the material starts at around 1200°C and at 1400°C the tungsten oxide has almost completely evaporated and the material is transformed mainly in alpha-alumina.

Abstract: The mechanical properties and creep resistance of the Al₂O₃ have been improved with the use of other oxide ceramics, among these the Y₃Al₅O₁₂ (YAG - "yttrium aluminum garnet"), to obtain the Al₂O₃-YAG composite. The aim of this work is to study the effect of addition of Nb₂O₅ at low sintering temperatures of the composite, starting from the eutectic composition Al₂O₃-Y₂O₃. In this work, the compositions were produced by powder mixtures of Al₂O₃-Y₂O₃ and Al₂O₃-Y₂O₃-Nb₂O₅ using high energy ball milling. The green bodies were pressed at 70 MPa and sintered at 1000, 1100, 1200 and 1300°C for 2 h. The materials were characterized by shrinkage and X-Ray Diffraction (XRD) using the Rietveld method. The presence of Nb₂O₅ does not show any improve neither for the YAG phase formation nor for the shrinkage of the sintered samples in the temperature range studied.

Abstract: A mesoporous molecular sieve MCM-41 dimensional hexagonal arrangement has a diameter of 2-10 nm, thermal stability, high pore volume and high surface area. In the synthesis of MCM-41 is used as the CTMABr directing agent and tetraethyl orthosilicate (TEOS) as silica source. Several studies have been developed using the residue of bagasse sugar cane, due to the high percentage of silica in its composition, making it a promising source for materials synthesis, favoring the use of this product impactful to the environment. This paper aims at the synthesis and characterization of MCM-41 with molar composition: 1.0 CTMABr: 4.0 SiO₂: 1 Na₂O: 200 H₂O using waste. The materials were characterized by the techniques of X-ray Diffraction (XRD), chemical analysis by X-ray spectrometry, energy dispersive (EDX) spectroscopy and in the infrared (IR). ). By XRD and IR verified the formation of mesoporous molecular sieve MCM-41. The XRD of the as-synthesized samples MCM-41 displayed the characteristic (1 0 0) reflection of typical MCM-41, with EDX was observed high silica content in the residue of bagasse sugar cane.

Abstract: A series of mesoporous materials have been synthesized in an acid medium, with various structures, such as SBA-15. These materials have many properties which make them potential catalysts. Among these we highlight their high surface areas and pore walls relatively thick, resulting in a greater hydrothermal stability. This work aims at the synthesis and characterization of molecular sieve SBA-15 with molar composition: 1.0 TEOS: 0.017 P123: 5.7 HCl: 193 H₂O and Co/SBA-15 and catalysts for the reaction of Ru/Co/SBA-15 Fischer Tropsch process. The materials were characterized by the techniques of X-ray diffraction (XRD), chemical analysis by X-ray spectrometry, energy dispersive (EDX) and Nitrogen adsorption (BET method). X-ray diffraction showed that the calcined cobalt catalyst did not modify the structure of SBA-15 and that Co was present under the form of Co3O4 in the catalyst. The addition of cobalt in the SBA-15 decreased the specific superficial area of the molecular sieve.

Abstract: Organophilic clays are widely used in non-aqueousdrilling fluids, mixtures of different components being used in a well bore. As bentonite claysare not naturally organophilic, they can be modified by specific treatments with surfactants (ionic or nonionic). Recent studies demonstrate the influence of clay, surfactant,and the presence of a dispersant in the rheology of fluids. In this study we verified the influence of clay, and surfactant in the production of organophilic clays using an alcoholic route for the rheology of non-aqueous fluids.As such, we performed the characterization of organophilic clays by X-ray diffraction (XRD),these non-aqueous fluids were produced according to Petrobras norms for rheological testing. The results evidenced influences of the clay / surfactant ratio on the rheology of non-aqueous drilling fluids.