Materials Science Forum Vol. 805

Abstract: The production of materials from crystallization of glass, called glassceramic, have proved interesting by the possibility of development of different microstructures, with reduced grain size and the presence of residual amorphous phase in different quantities. The method that uses the differential thermal analysis (DTA) provides research on the material properties over a wide temperature range, it ́s widely applied to crystallization processes of glassceramic materials. Within this context, this paper aims to study the kinetics of nucleation and crystal growth in glassceramic materials in the system SiO₂-Al₂O₃-Li₂O, obtained with the addition of mineral coal bottom ash as source of aluminosilicates, through the technique of differential thermal analysis.

Abstract: The paper aims to conduct a study of glass design in the decoration, emphasizing the work done by Dale Chihuly. The methodology applied in this article has the means to research the work of that artist as well as based on the knowledge acquired in lectures and reading books that address the subject hereof. One of the expected outcomes of this study is to traverse the course of the glass until it becomes a piece of art created by Chihuly.

Abstract: Two-step sintering has been able to produce fully dense bodies and with controlled grain size, without pressure during sintering. In this study, it was studied the sintering behavior of alumina-5% vol zirconia powders submitted to high energy milling. For this, the mixture of 5% vol of Y₂O₃ partially stabilized zirconia and 95% vol alumina powder was performed by high-energy ball milling (Spex 8000) with a ball ratio: mass of material at 7:1, in a steel vial with balls of steel, in milling times from 0 to 7 hours. The milled powders were characterized by X-ray fluorescence (XRF) and X-ray diffraction (XRD). After milling, the powders were uniaxially pressed and two-step sintered with heating at a temperature of 1500 oC for 5 minutes, cooling until 1450°C and then sintering at this temperature for 2 hours. The sintered composites were analyzed by X-ray diffraction, apparent density and scanning electron microscopy. The results were compared with the conventional sintering and showed that the microstructure of the nanocomposites appears more refined and homogeneous when they are sintered in steps.

Abstract: This papers studies the use of robots in the green machining of ceramics, specifically, the machining of high alumina porcelain insulators. The green state has very low strength and high brittleness where the forces applied during machining can generate and/or develop defects in the part that will reduce their properties after sintering. This work aims to study the machining by robot models of electrical insulators in 1:10 scale. Blanks were compacted in high alumina porcelain by isostatic pressing and green machined with a manual grinder attached to a Kuka KR16 robot. Models of insulators in gypsum were successfully machined and used for setup and configuration of the process. They were machined with cutting depth 0.87 mm and feed of 20 mm/s, this is the minimum programmable velocity for this robot model, and these parameters for the machining of the green porcelain generated excessive cracks at the tips of the fins. Changing the cutting depth to values of 0.25 mm, an established value in CNC machining, allowed to conclude that insufficient stiffness of the robot together with its high forward speed and excessive vibration of the grinding limits its use for thin thicknesses, although with potential for improvement.

Abstract: Ceramic materials have limited use due to their brittleness. The inclusion of nanosized particles in a ceramic matrix, which are called nanocomposites, and ceramic processing control by controlling the grain size and densification can aid in obtaining ceramic products of greater strength and toughness. Studies showed that the zirconia nanoinclusions in the matrix of alumina favor an increase in mechanical properties by inhibiting the grain growth of the matrix and not by the mechanism of the transformation toughening phase of zirconia. In this work, the microstructural evolution of alumina nanocomposites containing 15% by volume of nanometric zirconia was studied. From the results it was possible to understand the sintering process of these nanocomposites.

Abstract: This work presents the preparation of silver nanoparticles (AgNPs) with montmorillonite to produce a nanomaterial with bactericidal properties. The modified montmorillonite was characterized through the techniques of Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray diffraction (XRD). The FTIR and Raman spectrum’s showed specific bands of involving stretching silver. In the XRD analyses was observed the occurrence of the following crystallographic planes (111), (200) e (220) silver related. The nanocomposites of polyethylene with AgNPs did not show loss in mechanical properties, this fact was important and indicate that the nanomaterial can be inserted in this polymer matrix with considerable technological interest.

Abstract: The gas separation is a very expensive step in the chemical industry and unquestionable relevance. In this work, was verified the efficiency of the use of type A-zeolites in the separation of CO₂ in a gas mixture containing 25% CO₂, 4% O₂ and 71% N₂. These concentrations are similar to the effluent gases from combustion processes. To this end, was synthesized type A-zeolites using commercial kaolin and mounted to an adsorption column to test the effectiveness of zeolites in the adsorption of CO₂. The synthesized zeolites had surface area equal to 66.22 m²/g. The CO₂ concentration was determined by gas chromatography with TCD detector. After adjusting the data to the Langmuir model, it was obtained the kinetic parameters of adsorption. Based on these parameters was found the ability of the zeolite to adsorb CO₂, using a column of 0.461285 mg/g. The adsorption results have proved promising and showed maximum adsorption of 78.4% after a time of 10 seconds.

Abstract: The zeolites differ from traditional adsorbents for selective adsorption of small molecules, the high adsorption capacity at low concentrations and affinity for organic compounds and unsaturated polar molecules. In this work a Y-type zeolite was synthesized, characterized by x-ray diffraction, scanning electron microscopy and adsorption of nitrogen and subjected to test adsorption capacity where it was found that the Y zeolite has the potential adsorption capacity compared to other materials being studied and marketed.

Abstract: Brazil is a great producer of rice generating large amounts of husks after rice processing. These hulls contain high percentage of SiO₂, and a great potential as raw material for the development of silica based materials, as zeolites. Thus, this work aims to use the silica of rice hulls as an alternative raw material for the production of zeolite MCM-22. This material was characterized through X-ray diffraction, X-ray spectrophotometry and physical adsorption of N₂ (BET). The diffraction pattern of precursor MCM-22 presented typical peaks of topology MWW. Calcined sample did not presented peaks related with the organic material used in of the zeolite MCM-22, indicating that the thermal treatment was efficient for organic removal. It was confirmed, through the EDX, that the synthesized materials present high amount of SiO₂ and low quantity of Al₂O₃. The BET isotherms indicated that the materials presented structures with microporous, concluding that the alternative silica was promisingly for the development of zeolites.

Abstract: The objective of this work is to obtain synthesis of ZSM-5 zeolite using kaolin as Si and Al alternative source. Kaolin powder was dispersed under constant stirring into the sílica sol where the mass ratio of kaolin to silica was 1:2. After stirring for 2 hours, the dispersion was dried at 160 °C and calcined at 700 °C/2 hours. The synthesis of ZSM-5 zeolite was by hydrothermal treatment at 170 °C/48 hours under autogenous pressure. The materials were characterized by XRD, SEM, EDX, BET. According to the XRD, was possible to observe the formation of ZSM-5 zeolite with intense and well defined peaks set located between 2θ = 7-9° and 23-25°, typical of a crystalline material. The SEM showed the formation of particles clusters with orthorhombic shape characteristic of MFI structure. The results show that the hydrothermal treatment was efficient to produce ZSM-5 using calcined kaolin as alternative source.