Materials Science Forum Vols. 498-499

Abstract: The high pure synthetic zeolite have a large application in industry and agriculture, being nowadays in majority imported in Brazil. The biomass like rice hull ash (RHA), a rice industry waste, can be real advantageous in manufacture of different materials, since that is produced in large scale in the country. The silica extraction from RHA by alkaline leaching is a low energetic coast process and high efficiency, obtaining high pure silica with high reactive amorphous structure, very interesting for zeolite production. In this work was developed a economically feasible route for the production of high purity and crystallinity ZSM-5 zeolite, free of expensive template, starting from a low value intake, a industrial waste, producing a high value materials. The extracted silica from RHA in sodium silicate form is precipitated in the proper zeolite formation reactional mixture. The ZSM-5 have a lot of industrial applications due your high selectivity in catalytic reactions and high thermal and acid stability.

Abstract: Benzene, toluene, ethylbenzene, and the xylenes (BTEX) are the major water-soluble constituents of gasoline that may contaminate soils and natural waters, which can be sorbed by organoclays. This study investigates the sorption of toluene and xylene by organoclays produced from Brazilian bentonite (SVC) and from Wyoming bentonite (SSA) with hexadecyltrimethylammonium (HDTMA), as well as by a commercial organoclay (SCo). The organoclays were characterized by X-Ray Diffraction, Differential Thermal Analysis, Thermogravimetry. Isothermal sorption were performed. The efficiencies of the organoclays on removing toluene increased in the order: SVC-HDTMA < SSA-HDTMA < SCo. The xylene sorption by SVC-HDTMA and SSA-HDTMA organoclays was about two times higher than by the SCo. These organoclays may be used as permeable reactive barriers or in ceramic filters for petroleum waste-water treatment systems.

Abstract: Disposal or reuse of hazardous waste is a major consideration in chemical manufacturing and processing. Waste residuals from the tannery industry can contain high levels of chromium. Considered as a hazardous waste by the Brazilian environmental laws, the chromium-containing waste requires treatment before final disposal. This paper proposes a solution for the disposal of tannery wastes, which are rich in chromium by solidification in a Portland cement matrix using combinations of sodium bentonite and organoclay admixtures. This research is part of a series of experimental studies where Brazilian sodium bentonite, and organoclay materials are used to adsorb both inorganic and organic chromium. The solidified matrix is formed by Type II Portland cement, in which the hydration process stabilizes the tannery waste. Wyoming sodium bentonite and a commercial organoclay are analyzed and compared with the Brazilian clays. X-ray Diffraction is used to characterize the samples and leaching tests are performed to analyze the chromium concentration in the extract solution. In terms of leachate tests, the stabilization by solidification with cement is a process that can be used in the treatment of tannery waste.

Abstract: Zinc oxide is widely used in semiconductors fabrication, pigments and mainly in varistors. The electrical properties of ZnO based varistors are related to the grain boundary characteristics, and it can be modified using additives. In this work, zinc oxide based powders were prepared by chemical route derived from the Pechini’s method, and small amounts of tin ions were added to the system. The XRD measurements showed that the tin oxide not forming solid solution in the bulk, and it was observed that the increasing of tin concentration causes an increasing of the surface area at isothermal conditions of calcination. Once the isoelectric point was dislocated to more acid values, the hypothesis of segregation onto surface was considered.

Abstract: TiN thin film has been produced on the surface of AISI D6 tool steel by using a titanium interlayer. In this work, the morphology, the microstructure and interface depth profile of TiN films deposited at two substrate temperatures (220 oC and 450 oC) in the coating process are presented and discussed. The AISI D6 tool steel substrates were coated with titanium thin film as the underlayer and with TiN thin film as the top layer. They were deposited by conventional cathodic arc process. The surfaces of TiN films were observed by scanning electron microscopy (SEM). The microstructure of these samples was analysed by X-ray diffractometry (XRD). The influence of the substrate temperature on the TiN film-Ti film-AISI D6 interface region were investigated by energy dispersive spectrometry (EDS) and its cross section were observed using backscattered electron image (BEI). The results showed that TiN films deposited at 220 oC formed a film of strongly (111) preferred orientation, while in 450 oC formed a film of (111) and (220) preferred orientation. The thickness of the TiN films increased with increasing substrate temperature. The results show that the interface region of the TiN film-Ti film-AISI D6 substrate system was significantly improved when higher substrate temperature during deposition is used.

Abstract: Conventional methods to obtain ceramic powders are inadequate for many technological applications because these powders react but slightly to sinterization, displaying weak reproducibility, nonhomogeneity and imprecise stoichiometric control of cations. Better results can be obtained by chemical synthesis because the powder retains its homogeneity on the atomic scale and may be calcined at low temperatures, yielding fine particulate oxides whose chemistry can be precisely controlled. Therefore, the objective of this work was to obtain the NiAl2O4 phase by the Pechini and combustion reaction methods, and comparatively analyze how these two synthesization methods affect the characteristics of the resulting powder, which was characterized by DRX, MEV and BET. The results revealed that both methods yield nanometric and crystalline NiAl2O4 powder having homogenous particle sizes and shapes. The powder obtained by the Pechini method exhibited agglomerate sizes 60% smaller than those obtained by combustion reaction.

Abstract: This work had as its objective the characterization of a granite powder waste from sawing operations with a view to its incorporation in red ceramic. The granite waste came from the municipal area of Santo Antônio de Pádua, State of Rio de Janeiro, Brazil. The characterization was performed in terms of chemical composition, particles size distribution, X-ray diffraction and thermal analysis (DTA/TG). The results indicate that the granite waste presents favorable characteristics for incorporation in red ceramic compositions due to its fine granulometry as well as a considerable fluxing potential related to its high amount of alkaline oxides.

Abstract: Carbon/mineral complexes are materials with surfaces covered partially or totally by carbon materials contains. They have high industrial potential uses as material adsorbents and ceramic filters. The objective of this work is to evaluate the corrosion strength in acid and alkaline solutions, and the adsorption capacity of methylene blue of some materials prepared in the LMPSol. The compositions were prepared with an industrial common clay named “taguá” and organic and inorganic additives from industrial residues up to 50%. The corrosion test was performed in water at 60°C and in aqueous solutions of HCl and NaOH at room temperature, with mass losses measured after 15 days. The samples were pressed manually and heated at different temperatures: 110°C, 350°C and 500°C. The performed tests were transverse flexural strength, porosity and water absorption.