Materials Science Forum Vol. 805

Abstract: The main objective was to synthesize in the laboratory and characterize the molecular sieve MCM-41. This study has a strong experimental character. The hydrothermal synthesis was performed at 100 ° C for a period of 7 days. The resulting materials were characterized by XRD, EDX, Adsorption Capacity and the Foster Swelling test. Through XRD verified the formation of mesoporous structure. Different organic solvents, namely gasoline, diesel and kerosene were used. The Foster Swelling Test results indicated that the affinity of molecular sieve MCM-41 occurred in the treated clay tested in all organic solvents (gasoline, diesel, kerosene), without and with agitation.

Abstract: The clay types, kaolinite and smectite, are the most used industrially, mainly due to its sorption characteristics. There have been several attempts to improve the quality and characteristics of the clays, modifying them with different techniques. Two of the common techniques are thermal activation and acid activation. For acid activation, hydrochloric acid was used with a reaction time of 1 hour while the thermal activation the samples calcined at 300oC for 24 hours. This work aims to characterize the gray clay (supplied by Süd-Chemie LTDA) and Brasgel (provided by Bentonit), both in its natural form, as well as in the acid and thermal activation form (300°C). Natural and treated clays were characterized by X-ray Spectroscopy Energy Dispersive (EDX), X-ray diffraction (XRD) and nitrogen adsorption (BET). The results showed a reduction of impurities in the samples and did not comprise changes in the structure of the constituent minerals.

Abstract: Clays modified with quaternary ammonium salts, organoclays, have an affinity for organic compounds undergoing expansion. In this study, the smectite clay Chocolate" A" was subjected to the process of organophilization with quaternary ammoniumchloride, stearyl dimethyl ammonium chloride (Praepagen WB) to improve its hydrophobic properties and thus increase the affinity for organic compounds. The samples were characterized by X ray diffraction (XRD), infrared spectroscopy and tests of expansion by swelling of Foster. The results showed appropriate conditions organophilization process. Through XRD confirmed the increase in basal spacing for the clay modified with respect to the clay in natural, 15.46Å to 19.99Å after treatment with the quaternary ammonium salt. Bands of the CH₃ and CH₂ were detected by infrared spectroscopy analysis of the sample and the organoclay according to the tests of expansion was possible to observe the affinity of the organoclay with organic compounds: gasoline, kerosene and diesel.

Abstract: The organoclays contain intercalated organic molecules in their structural layers. The more clay used to prepare organoclays are those derived from the smectite group bentonites mainly due to the small size of crystals and high cation exchange capacity, which facilitate the intercalation of organic compounds. This work aims to obtain organoclays from a mixture of two different quaternary ammonium salts in a 1:1 ratio through the direct method of organophilization. This procedure will be performed using the clay Chocolate from the municipality of Boa Vista, Paraíba state, which has in its composition of smectite clay minerals group. The samples were characterized by X-ray diffraction (XRD) and infrared spectroscopy (IR). The testing Foster swelling in a later step, using different organic solvents: gasoline, diesel and kerosene were used to investigate the compatibility clays after modification with the salts.

Abstract: In this study catalysts Fe/SBA-15 were prepared for Fischer-Tropsch Synthesis. SBA-15 samples were synthesized under acidic conditions using triblock copolymer Pluronic as a template and tetraethyl orthosilicate as a silica source.The molar composition was: 1.0 TEOS: 0017 P123: 8.14 HCl: 168 H₂O. Fe/SBA-15 catalysts with different iron loading (15 wt. % and 20 wt. %) were prepared by wetness impregnation of relative SBA-15 with the desired amount of aqueous iron nitrate. The obtained catalyst were characterized by X ray diffraction (XDR), nitrogen adsorption-desorption and energy dispersive X-ray spectrometry (EDX). After impregnation of Fe the XRD profiles were almost unchanged and exhibited the high diffraction peaks of SBA-15 at low angles. The analysis of nitrogen adsorption-desorption was observed that the values of specific surface area decreased as the concentration of metal impregnated increased. And by the EDX analysis verified that the iron contents obtained are close to nominal levels of iron.

Abstract: Mesoporous molecular sieves SBA-15 were prepared by using two different procedures taken from the scientific literature. In the first procedure, a hydrogel was prepared with the molar composition: 1.0 TEOS: 0017 P123: 5.7 HCl: 193 H₂O with stirring at 35 °C. In the second procedure a hydrogel was prepared with the molar composition: 1.0 TEOS: 0017 P123: 8.14 HCl: 168 H₂O with stirring at room temperature. In both procedures the samples were synthesized in a microwave. The samples were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), nitrogen adsorption-desorption analysis, and scanning electron microscopy (SEM). The analysis of XRD and nitrogen adsorption-desorption showed that the samples prepared with stirring at 35°C presented a higher ordering degree, an increase of crystallinity and larger volume of adsorbed nitrogen. The differential thermal analysis reveals that the SBA-15 presented high thermal stability, and the SEM revealed fiber type morphology consistent with this type of material.

Abstract: The elastic properties of a Ti₃Al intermetallic compound were studied using full potential (FP LAPW ) with the APW+lo method. The FP-LAPW is among the most accurate band structure calculations currently available and is based on the density functional theory with general gradient approximation for the exchange and correlation potential. This method provides the structural properties of the ground state as bulk modulus, equilibrium lattice parameter, and equilibrium minimum energy, and the elastic properties as shear modulus, young modulus, Zener coefficient (anisotropy), and Poisson coefficient. The calculated elastic properties are coherent with the elastic properties of the material.

Abstract: The major effort of sintered metallic alloys (compression, homogenization and sintering of metallic powder) is the observation of the evolution of electrical conductivity, mechanical properties (microhardness tests) and microstructures changes after appropriate thermomechanical treatments with the use of copper-nickel-aluminum alloys as electric material. In this case, the purpose was to verify the possible changes in these materials when subjected at low temperatures. Samples of Cu_x%Ni_y%Al_z% initially compressed, sintered and homogenized were characterized by optical metallography (microstructure) and mechanical strength (hardness Vickers) at room temperature. Data of x-ray diffraction of polycrystalline samples were collected with a conventional Difractometer. After this was made measurements of electrical properties (electrical conductivity) at low temperatures of samples obtained from precursors of high purity in powder form, for the study of the influence of powder metallurgy processes in physical properties of metallic alloys in this condition.

Abstract: When used commercially, the zirconium alloys are utilized in the shape of tubes to encapsulate the UO2 pellets in the PWR and BWR Power reactors. The metallic zirconium is an essential metallic element for the types of alloys in which the obtainment route rests in the ore opening for the production of zirconium oxide followed by the processes of pelletizing, chlorination, purification, reduction and distillation. Through the technique of X-Ray Diffraction the present phases were identified. Using the Fluorescence of an X ray it was possible to determined the chemical composition of the zirconium sponge. The mechanical properties of Vickers microhardness were obtained using a microdurometer. As a result, it was established that it is possible to define a methodology for the preparation of a sample of metallic zirconium for the microstructure analysis, as well as that its chemical purity is 97,265% linked to the microhardness of approximately 51 HV.

Abstract: β-tricalcium phosphate based ceramics (β-TCP) are resorbable biomaterials used as bone substitutive materials. Several ions can substitute specific Ca positions in the crystalline structure of TCP, so that general Me-TCP can be obtained. Particularly, magnesium can increase the temperature of β-α-TCP transformation while zinc stimulates the bone formation. In this work, the influence of magnesium or zinc ions on the sintering behavior of Me-TCP was investigated. The powders were produced through wet chemical synthesis with a freeze drying process. The powders were calcined and subsequently uniaxially pressed into pellets. The pellets were sintered up to 1300°C/1h. The influence of Mg or Zn doping was investigated by dilatometric studies, thermal analysis and XRD. The microstructure was evaluated through SEM. The results suggest that Mg increased temperature of β-α-TCP phase transformation. The Me-doped TCP samples can be considered as promising biomaterials, having stimulatory effect of Zn or suitable densification due to Mg addition.