Materials Science Forum Vol. 805

Abstract: This work aims to study the effects of reducing the level of template HMI (100, 75, 50, 25 and 0% HMI) and time (10, 9 and 8 days) of static synthesis in the structure of MCM-22 zeolite. The synthesis of the MCM-22 (P) precursors was carried out by using hexamethyleneimine (HMI) as organic template under static conditions. The MCM-22 zeolites (100, 75 e 50% HMI) was obtained by the calcination of precursors MCM-22 (P) in a muffle to remove the occluded organic of precursors. These materials were characterized by X-ray diffraction (XRD), spectroscopy of X-ray for energy dispersive (EDX), adsorption isotherms of N₂ (BET method), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The XRD's and EDX's of all samples have confirmed the static synthesis of MCM-22, whose precursor and zeolite materials showed all the characteristic peaks of the topology MWW. The Adsorption isotherms of N₂ are of type I, represented by microporous materials, whose hysteresis (type H3) are representative of solids with pores of different geometries. The FTIR's shown that the precursors showed the characteristic bands of a laminated material. From the SEM's, it was found the samples calcined MCM-22 are constituted by strip-shaped crystals agglomerated with a depression in the central region. In the sample MCM-22 (P) 75% HMI (8 days), showed no crystals uniform due to the presence of unreacted material in relation to crystalline phases.

Abstract: Lead zirconate titanate, with Zr/Ti ratio of 53/47 was prepared by the polymeric precursor method. The powders were doped with 0, 0.2, 0.4 end 0.6 mol% of Ca²⁺ and characterized by XRD. The percentages of tetragonal and rhombohedral phases were calculated through Rietveld refinement. A systematic study of the effect of dopant on the ferroelectric and piezoelectric properties of PZT was carried out. The remanent polarization, planar coupling factor and piezoelectric charge constant, increase with dopant concentration.

Abstract: Superduplex stainless steel is an important class of stainless steels because it combines the benefits of ferrite and austenite phases, resulting in steels with better mechanical properties and corrosion resistance. However, a significant problem of this steel is the precipitation of deleterious phases during heat treatment. Among these precipitated phases, the most relevant is the sigma phase, because it causes higher loss of properties. The objective of this work therefore is to study the sigma phase precipitation in the superduplex stainless steel UNS S32520 when submitted to heat treatment of solubilization in three different temperatures (1050 C, 1150o C and 1250° C) and subsequently aged in the temperature of 850oC during 10 minutes, 30 minutes, 60 minutes, 3 hours and 10 hours, followed by water quenching. The results showed that as the solubilization temperature increases, there is a significant grain growth and an increase of the ferrite volumetric fraction, which delays the sigma phase precipitation in this superduplex stainless steel. Moreover, it can be verified that the hardness of the material is directly related to volumetric fraction of sigma present in the steel.

Abstract: This work proposes a methodology to obtain the carbon fiber/epoxy composite limit strain for structures surviving 120000 cycles. The damage progression was also evaluated using stiffness reduction and hysteresis loop analysis in order to obtain dynamic and secant modulus. The results provide information about composite fatigue behavior. This approach determined a limit strain range from 0.83 to 0.87%, a fatigue stress limit of 0.8% of the static strength, stiffness degradation (damage index) of about 5% (within the limit strain). The methodology presented herein may be used for determining of material design allowable when fatigue is key consideration.

Abstract: The Solid oxide fuel cell is a very efficient and clean source of energy. The planar design of SOFC requires sealant at the edges of the cell to prevent fuel leakage (H₂, CH₄, etc) and air mixing at its working temperature (700 to 900°C). The extreme operation conditions of current cell designs involve both high temperatures and highly corrosive environments. As a consequence is necessary a material to seal the chambers of the anode and cathode along each cell unit (the anode-cathode-electrolyte and interconnects). The present work is an attempt to engineering glass compositions based on the BaO-Al₂O₃-SiO₂-B₂O₃ system chosen due its thermal properties and good glass forming tendency. The glass formation or stability against crystallization and the coefficient of thermal expansion were determined by Differential Scanning Calorimeter and Dilatometric analysis, including sinterization curves. The main subject of this work is the development and selection of sealing glasses composition for SOFCs applications and also the development of new methodologies for preparation and evaluation of glass ceramics suitable for SOFC seals applications.

Abstract: The AISI 52100 steel is a material widely used in the industry due to its high fatigue resistance, dimensional stability, high hardness and wear resistance. This steel is used for production of ball bearings, stamping tools, etc. In case of production of ball bearings and its track this material is spherodized because, due to its high content of carbon, about 1%, it has high mechanical strength making it impossible to cold forming. To obtain a wear resistant surface, after forming, this material is hardened and tempered. Normally to obtain the AISI 52100 steel, arc electric melting furnace is used. This work aims the reuse of AISI 52100 steel by powder metallurgy route, starting from the machined chips using high energy mill (planetary) to obtain the powder. Then, the powder was uniaxially pressed into a press with a load of 4 tons, to form the specimen, later on pressed in an isostatic press at a pressure of 300MPa to obtain a better densification. To analyze the powder morphology and the phases obtained after sintering, was used a scanning electron microscope and X-ray diffraction to calculate the crystallite size. It was verified that with more than 10 hours of grinding, the crystallite size does not change significantly, the particles gained rounded shapes with a size distribution between 30 and 5μm. The microstructure obtained by the two routes was nearly identical after sintering.

Abstract: Titanium is a metal that has high melting point 1668 ° C, the boiling point of 3287° C, low density (4.54 g/cm3) and modulus of elasticity around 12.7 MPa x104. However, one of the most important properties is the biocompatibility, which makes this metal to be the most widely used in biomedical. Several alloys were developed using titanium such as the alloy Ti-6Al-4V, however Al and V show toxic characteristics to the organism. The alloy TiNb has been studied to replace the alloy Ti-6Al-4V, because it presents high biocompatibility, low modulus of elasticity, high corrosion resistance and low toxicity. The alloy TiNb can be obtained by conventional melting route or powder metallurgy, where the powders can be obtained by spray drying, chemical reactions and the process of hydrogenation and dehydrogenation (HDH).The hydrogenation is carried out by inserting hydrogen in the structure of Ti and Nb in vacuum at high temperatures, forming a phase extremely fragile called hydride of Ti and Nb, thus enabling the reduction of particle size by milling. Upon heating under vacuum, the hydrogen is extracted to yield the metals Ti and Nb since the hydrogen forms a reversible phase with metals. This work aims the production and characterization of the alloy TiNb where the powders are obtained through the HDH process, varying the concentration of Nb by weight from 10 to 50%.To analyze the morphology and pore size, formation and composition of phases, we used the techniques of microstructural characterization and mechanical by scanning electron microscopy, BET, X-ray diffraction and compression test. The results showed a heterogeneous distribution of Nb in the matrix Ti as well as a decrease in the modulus of elasticity with increase in percentage of Nb.

Abstract: The incorporation of waste from various industrial activities in ceramic products comes as a technological alternative to reduce the environmental impacts caused by the indiscriminate disposal of wastes in the environment. The kaolin and granite processing industries have been mentioned as sources of contamination and pollution, due to the enormous amounts of wastes they produce. The use of these wastes as raw material and its transformation into products that can be commercialized and/or show economic viability, presents as an alternative to the industries. The aim of this work was to use ceramic masses incorporated with kaolin waste (35%), granite (35%) and bentonite (30%) for the confection of tubular ceramic membranes using extrusion as production process. The ceramic mass was characterized through analysis techniques of thermogravimetric, chemical, particle size and X-ray. The membranes produced, after sintering in temperatures of 850, 900, 950 and 1000 ^oC, were submitted to characterizations of scanning electron microscopy, mercury porosimetry and permeability test by tangential flow. The preliminary result of the particle size analyses identified that the ceramic mass presents an average particle diameter of 37.00μm. The membranes presented porosity of approximately 32%, and average pore diameter within the ultrafiltration range.

Abstract: This work evaluated the influence of additions of the ceramic shell residue (CSR), from the industries of Lost Wax Casting, in the modulus of elasticity and porosity of concrete. The CSR was ground and underwent a physical, chemical, and microstructural characterization. It was also analyzed, the environmental risk of the residue. In the physical characterization of the residue were analyzed, the surface area, and particle size distribution. In chemical characterization, the material powder was subjected to testing of X-ray fluorescence (XRF). Microstructural characterization was performed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The residue was utilized like addition by substitution of cement in concrete in the percentages of 10% and 15% by weight of Portland cement. It was evaluated properties of concrete in the fresh and hardened state, such as compressive strength, modulus of elasticity, absorption of water by total immersion and by capillarity. The results showed that the residue can be used in cement matrix and improve some properties of concrete. Thus, the CSR may contribute to improved sustainability and benefit the construction industry.

Abstract: The use of the Rietveld refinement method has been highlightened as essential in the characterization of polycrystalline materials. With the aid of this method, combined with the application of the X-ray diffraction, it was possible to develop a type of cement that can temporarily substitute the Portland cement for Oil well. This cement was developed from the mixture of Portland cements commonly found in the market. The cements were passed through various sieves, then characterized by X-ray diffraction, being identified the main phases (C₃A, C₄AF, C₃S and C₂S) and quantified by the Rietveld refinement method. With the values obtained in the quantification of the phases, a new cement was made through the method of linear programming. From the results, it was possible to conclude that the developed cement presented a composition (levels of the main phases) that satisfies the requirements of NBR 9831, mainly in relation to the low levels of C₃A.