bluuebunny/crossref_metadata_2025 huggingface dataset:
Wear of Diamond Composites Applied as Inserts in Drilling Tools
Authors: Bobrovinitchii Guerold Sergueevitch , Filgueira Marcello , Monteiro Sérgio Neves , Tardim Rômulo Crespo
Published: October 2010

In the rock-drilling industry, double layer polycrystalline diamond-hardmetal (Dia-HM) inserts for cutting tools are subjected to elevated levels of wear due to the high power involved in the process. A research performed by focusing on the wear mechanism has shown that the complexity of the actual industrial operation can be reproduced in laboratories. The present work developed a methodology to calculate the theoretical values of wear of drilling tools. The main parameter selected for this methodology was the amount of disaggregated rock. The information acquired through this methodology gives one a complete perspective about the application of Dia-HM inserts to be used in drilling tools.
A Novel Method for Obtaining Polycrystalline Diamond Cutters
Authors: Tardim Rômulo Crespo , Bobrovinitchii Guerold Sergueevitch , Monteiro Sérgio Neves , Skury Ana Lúcia Diegues , Filgueira Marcello
Published: October 2010

The present work comprises a study about the possibility of obtaining polycrystalline diamond cutters through a novel method of sintering both layers at the same time. This possibility was tested through the sintering of a diamond layer over a hard metal (WC+15wt%Co) support under conditions of 5.0 and 6.5 GPa of pressure and 1400 to 1600º C of temperature. The sintering conditions were imposed in two ways: directly, or with pre-sintering. The samples were tested by measuring microhardness, wear resistance, densification, and SEM. The results of the tests have shown the possibility of obtaining good quality inserts by sintering both layers of compacted powder.
Automatic Computer Controlled Process for Superhard Materials Production
Authors: Bobrovinitchii Guerold Sergueevitch , Vianna William Silva , Skury Ana Lúcia Diegues , Monteiro Sérgio Neves , Tardim Rômulo Crespo
Published: October 2010

The technologies of superhard materials production, including those for industrial synthesis of diamond and cubic boron nitride at high pressure and high temperature conditions, depend on the operator experience. Moreover, these manually operated processes usually vary in terms of yield and quality of the final product. Owing to the design and construction methods of conventional high pressure devices (HPD), it has not yet been possible to adapt computerized systems for both research and industrial production. In this work, the synthesis of superhard materials was treated as a guided problem under uncertain pressure, temperature, time, and electrical power conditions using the theory of automatic commanded systems. This concept was applied to develop an automatic control for the hydraulic presses that generate the necessary force for the high pressure, based on variable sensors associated with computer programs that command the conditions inside the HPD.
Study on WC-Co-Diamond-Based Composites Used in Cutters of Drill Bits
Authors: Bobrovinitchii Guerold Sergueevitch , Skury Ana Lúcia Diegues , Filgueira Marcello , Monteiro Sérgio Neves , Tardim Rômulo Crespo
Published: October 2010

Inserts of drill bits used in perforation of wells are employed to cut many different kinds of stone. The material that shows the best performance on this application is the WC+Co+Diamond composite, obtained via powder metallurgy. However, heterogeneous microstructural aspects in these composites may impair their efficiency. On this work, WC+6%Co-based composites were obtained via high pressure sintering at 5.0 GPa, with diamonds, WC and Co powders. The particle size of the diamond was 400/315 μm, and for the WC and Co, 100/63 μm. Part of the samples also received 2wt%CrB2 as a doping agent. Wear tests were carried out in an abrasimeter with a maximum axial load of 50 kg. Linear and volumetric wear indices achieved values of 821∙10-6 g/m and 10.7 g/m3, that are superior to inserts produced via conventional powder metallurgy.
Sintering of a SiC-Diamond Composite with a New Setup for the Reactive Cell
Authors: Bobrovinitchii Guerold Sergueevitch , Skury Ana Lúcia Diegues , Monteiro Sérgio Neves , Tardim Rômulo Crespo
Published: October 2010

Polycrystalline SiC-diamond composites have been fabricated by high pressure and high temperature, HPHT, sintering conditions using a Si infiltration method. However, infiltration of liquid Si around the diamond particles results not only in SiC but also in free Si, which causes deterioration of the composite properties. In this work, a novel sintering procedure was developed to avoid the formation of free Si in the composite structure. A disk composed of a mixture of graphite and Si was first press-molded at room temperature. The disk was then placed above the diamond powder inside a high pressure chamber used for the HPHT sintering process. This arrangement permitted to preferentially form liquid SiC, which infiltrates in between the diamond particles. Using this procedure, free Si formation is inhibited and the SiC-diamond composite forms a rigid structure with improved properties.
Mechanical Properties Evaluation of a Spray Formed AA-6082 Aluminum Alloy
Authors: Siqueira G. , Safra L.C.P.G. , Mucsi C.S. , Fernandes M.G. , Rossi J.L.
Published: October 2010

The spray forming technology combines in a single step the advantages of the rapid solidification techniques and high the productivity of the conventional casting processes, allowing obtention of preforms with a refined microstructure, almost without porosity and macrosegregation free. The development and research efforts are leading to interesting alloys and materials production. The rapid solidification processes inherent to the spray forming allow the production of alloys with different compositions from those obtained by conventional ingot processes. The aim of this work was to carry out mechanical properties characterization of a spray formed AA-6082 alloy. The hardness results are presented in different sections related to the height of the spray formed preform (in a three-dimensional arrangement). The material was evaluated in the as sprayed formed condition and after heat treatments of solution at 525 °C for 1 h and aging for 1 h, 10 h, 100 h and 500 h periods at 125 °C. It is showed that the spray formed AA 6082 aluminum alloy is very stable regarding hardness variation during aging.
Application of CFD in the Study of Performance the Cyclone with Different Shapes
Authors: Lacerda A.F. , Lourenço R.O. , Macêdo E.N.
Published: October 2010

Gas cyclone separators are widely used in industrial processes for separation of dust from gas streams or for product recovery. Their design normally has tangential entrance inlets and the cyclones are defined as funnel-shaped industrial inertial devices. Cyclones are particularly well suited for high temperature and pressure conditions because of their rugged design and ﬂexible components materials. Cyclone collection efﬁciencies can reach 99% for particles bigger than 5 μm, and can be operated at very high dust loading. One of the aims of this research was simulate, through computational fluid dynamics (CFD), the operation of the cyclones with different geometrics and to analyze the influence its different geometrics in the performance of the cyclones. The numerical solutions were carried out using commercial CFD. A two-dimensional computational fluid dynamics (CFD) Reynolds stress model (RSM) was used to describe the gas–solid flow in cyclones.
Influence of Fuel in the Synthesis of ZnAl2O4 Catalytic Supports by Combustion Reaction
Authors: de Souto Viana Kaline Melo , Dantas Bruno Brito , Nogueira N.A.S. , Sasaki J.M. , de Freitas Normanda Lino , Kiminami Ruth Herta Goldsmith Aliaga , de Melo Costa Ana Cristina Figueiredo
Published: October 2010

The aim of this work is to evaluate the influence of fuel in the synthesis of ZnAl2O4 catalytic supports by combustion reaction. For this, it was used the fuels: urea, carbohidrazide, glycine and aniline. The total amount of reagents was calculated according to the theory of propellants and explosive using urea in the stoichiometric proportion (Φe = 1). The structural and morphological characteristics of the powders were evaluated by XRD, FTIR, TEM, SEM and particle size distribution. The results from XRD showed the formation of the normal cubic spinel structure. The powders presented nanosized particles with narrow agglomerates size distribution. The powders prepared with urea showed better value of surface area and smaller crystallite size.
Fluid Dynamics Study of the Influence of Direction of the Gas Flow in Fabric Filter
Authors: Rocha Sandra Mara Santana , Vieira Luiz Gustavo Martins , Aguiar M.L. , Damasceno João Jorge Ribeiro
Published: October 2010

The new environmental laws, as well as the search for technologies of accuracy production, have leaded companies to search for more and more efficient equipment. Regarding the emission of particulate material, the fabric filter is the most used equipment in the industry, for presenting a high efficiency and low operational costs, essential in any project of this type. In the search for a more efficient and economic filtering operation, this work studied, by techniques of CFD, the modification of the traditional way of feeding a filtering box (usually accomplished by the side of the system) by another in which the feeding was accomplished through the bottom of the equipment, in order to review the distribution of volumetric outflows in the bags and pressure drop. The fluid dynamic simulations had shown that the feeding fluid - through the bottom of the filtering box - provides an inferior operational pressure drop and a better distribution of fluids between the bags.
Prediction of Performance of a Hydrocyclone with Filtering Cylinder
Authors: Oliveira D.C. , Pires L.N. , Vieira Luiz Gustavo Martins , Damasceno João Jorge Ribeiro , Barrozo Marcos A.S.
Published: October 2010

Hydrocyclones are centrifugal devices widely used in chemical industries and they are used to the solid or liquid particles separation of a fluid according to the density and size distribution of the dispersed phase. In order to maximize the separation in these devices, this work had as objective to study the influence of the filtration during the process of separation in hydrocyclones. Thus, experimental data were used to predict the behavior of a hydrocyclone having a porous cylinder in the same operating conditions of a conventional hydrocyclone (impermeable cylinder). The experimental studies showed that the filtration interferes directly in the performance of the separator, so the filtering hydrocyclone required a higher pumping power. Moreover, the experimental data also indicated that the presence of the porous cylinder in the hydrocyclone was able to increase the number of dragged particles in the underflow, increasing therefore the efficiency of separation.
Numerical Methodology for Orifice Meter Calibration
Authors: Oliveira Natalia M.B. , Vieira Luiz Gustavo Martins , Damasceno João Jorge Ribeiro
Published: October 2010

Orifice Meters are mechanical devices used to measure gases and liquids flows. Due to manufacturing, installation and operation simplicity, the orifice meters are widely used in the industrial processes in which there is flow of gases or liquids. Moreover, their acquisition and operation costs are smaller than the ones verified for other flow meters (Venturi, flowmeter). However, before the utilization of any calibration orifice meters, they demand an experimental calibration procedure. Thus, in order to suppress this laborious experimental procedure, this work objectified to apply computational fluid dynamics techniques (CFD) to numerically predict the Calibration Coefficient of the orifice meter. The adopted numerical methodology was able to satisfactorily predict the discharge coefficients, presenting an economic alternative when compared to traditional experimental approaches.
Use of a Short Duration Electronic Flash in the Study of the Trajectory of Liquid Jet in a Pease-Anthony Venturi Scrubber
Authors: Puentes Néstor Alejandro Gómez , Zoccal João Victor Marques , Guerra Vádila Giovana , Coury José Renato , Gonçalves José Antônio Silveira
Published: October 2010

A Pease-Anthony Venturi scrubber is a relatively simple and very efficient device used for gas cleaning. This paper presents photographic images of the atomization of a liquid jet in the throat of a Pease-Anthony Venturi scrubber, obtained through the development and use of an electronic flash of short duration. This new evidence was used to improve the parameters of the model of Gonçalves et al. (2000) [1]. The experimental conditions used were: throat gas velocities between 59 and 74m/s, jet velocities between 3.18 and 19.10m/s and liquid injected into the throat through different orifices.
Structural and Morphology Characterization ZSM-5 Zeolite by Hydrothermal Synthesis
Authors: da Silva Valmir José , Crispim Alana Carolyne , Queiroz M.B. , Menezes Romualdo Rodrigues , Laborde Herve M. , Freire Rodrigues Meiry Glaúcia
Published: October 2010

Zeolite ZSM-5 have been synthesized by hydrothermal method, using tetrapropylammonium bromide as template. This work aims to evaluate the preparation and characterization structural and morphology of zeolite ZSM-5 resulting in a pure and crystalline material. The ZSM-5 zeolite was prepared by hydrothermal synthesis at 170 °C, using silica, deionized water and structure-directing salt (tetrapropylammonium bromide-TPABr). Several techniques like X ray diffraction (XRD), scanning electron microscopy (SEM) and X ray energy dispersion spectrophotometer (EDX) have been utilized to characterize the framework structure and morphology of the sample. Obtaining ZSM-5 zeolite could be confirmed by X ray diffratograms. The result X ray diffraction showed that the synthesized sample presented typical peaks of the ZSM-5 zeolite. According to the XRD, it is possible to observe intense and well defined peaks. The acquired X ray patterns identified the product as highly-crystalline materials, without the presence of impurities. From the images obtained by SEM, it was possible are composed of showed that the crystal accumulations of ZSM-5 zeolite, without the presence secondary phases on the crystals.
Film Fraction and Droplet Size inside of a Rectangular Venturi Scrubber
Authors: Guerra Vádila Giovana , Daher M.A.F. , Gonçalves José Antônio Silveira , Coury José Renato
Published: October 2010

The Venturi scrubber, equipment frequently used in the removal of particles from gases, is constituted basically by a duct with a convergent section followed by a constriction, or throat, and a divergent section. A liquid, usually injected in the throat, is atomized by the flowing air at high speed. The formed droplets act as collectors of particles from the gas. The process of droplet formation from an injected liquid can be described as follows: the liquid enters the gas stream in the form of a jet, perpendicular to the gas flow. As the jet penetrates the gas stream, it is bent by the gas drag. After a given penetration distance, a burst occurs, and the remaining jet is disintegrated as a droplet cloud. Depending on the liquid and gas flow rates, the penetration on the jet into the gas stream may reach the walls of the equipment, and a fraction of liquid deposits in the form of a film. This film contributes little for the removal of particles from the dust laden gas. Few studies have analyzed the formation of film at the scrubber walls and its influence in the droplet size inside the Venturi scrubber. For this reason, the present study is focused on the experimental measurement of the deposition of the liquid film on the walls of a rectangular Venturi scrubber and, simultaneously, the estimation of the droplet size measured in the Venturi throat. The experiments were carried out varying the liquid flow rate, the gas velocity and the number of orifices of liquid injection. A correlation, using a dimensionless number, was proposed to quantify the influence of each experimental condition. The results indicate that film fraction has a significant influence in the droplet size measured inside of Venturi scrubber.
Evaluation of the Influence of Process Variables on Flotation of Phosphate
Authors: Santana R.C. , Santos M.A. , Ataíde Carlos Henrique , Barrozo Marcos A.S.
Published: October 2010

Froth flotation is an adsorptive-bubble separation method based on the selective attachment of particles on the surfaces of gas bubbles passing through a suspension. Reagents as collectors, frothers and pH modifiers are added to perform specific roles to facilitate and to improve the separation. In the present work the process of apatite flotation in column has been investigated experimentally. The influence of the reagents (collector and frother dosages and interactions), percentage of solids and pH value on the column flotation of coarse particles of apatitic ore was analyzed. Percentage of solids was the variable that more influenced on the apatite recovery and the P2O5 grade was more affected by varying pH. The best results were achieved by using lower pH values and lower pulp density. Frother addition only had significant effect for lower collector dosage.
Synthesis and Characterization of the Catalysts 5 wt.% and 10 wt.% Co/SBA-15
Authors: Lima L.A. , Sousa B.V. , Freire Rodrigues Meiry Glaúcia
Published: October 2010

Catalysts supported on SBA-15 were obtained by wet impregnation using aqueous solution of cobalt nitrate, where different contents of cobalt (5 wt% and 10 wt%) were prepared. The molecular sieve SBA-15 was synthesized using tetra ethyl ortho silicate (TEOS) as silicate source, and triblock copolymer, poly-(ethylene oxide)-poly (propylene oxide)-poly-(ethylene oxide) PEO-PPO-PEO as the organic structure directing agent. These materials were characterized by X-ray diffraction (XRD), X-ray energy dispersion spectrophotometer (EDX) and Nitrogen adsorption–desorption isotherms (BET). The results from the XRD showed that the molecular sieve mesoporous (SBA-15) was identified by X-ray diffraction, especially from the (210) and (300) peaks, which represent a typical spectrum for the SBA-15. Characterization of catalysts by Nitrogen adsorption–desorption isotherms (BET) made it possible to verify the the samples had been of type IV with hysteresis of corresponding the H2 type the porous materials.
Influence of Crystallization Time on Structural and Morphological Characteristics the Precursor of Zeolite MCM-22
Authors: Barbosa A. Santos , Lima L.A. , Sousa B.V. , dos Santos Everton R.F. , Freire Rodrigues Meiry Glaúcia
Published: October 2010

In this work the layered precursor of zeolite MCM-22 was synthesized as per the hydrothermal synthesis method, the length of crystallization varying from 8 to 9 days. The preparation of the lamellar precursor of MCM-22 zeolite broke the hydrogels with the following molar composition: 0.511 SiO2: 0.039 NaOH: 0.024 Al2O3: 23.06 H2O. The hydrothermal crystallization occurred in a preheated oven at 150 °C for different periods of 8-9 days. The originality of the work consists in the synthesis of lamellar precursor of MCM-22 zeolite with a variation in the crystallization time from 8 to 9 days, since the literature is used longer times. The materials were characterized by X-ray diffraction (XRD), chemical analysis by atomic energy dispersive X-ray (EDX) and scanning electron microscopy (SEM). The achievement conversion the precursor of MCM-22 zeolite was confirmed by diffracting X-ray, indicating that these materials are crystalline, with typical properties of the samples free of amorphous materials and also that the material became more crystalline as the crystallization increased. From the micrographs, it was observed that the lamellar precursor of MCM-22 zeolite consist of clusters of particles of spherical shape.
Coating of Particles in Spouted Bed: Flow Regime and Stability
Authors: Neto J.L. Vieira , Borges J.E. , Duarte Claudio Roberto , Barrozo Marcos A.S.
Published: October 2010

The coating and encapsulating of particles presents many applications in the chemical, pharmaceutical, food and agricultural products industries. Among the many applications of seeds coating, the enlargement of small seeds is included in order to facilitate the planting, the addition of herbicides, fungicides, fertilizers, micronutrients and inoculation. The spouted bed has often been used in studies related to the coating of particles, due to the cyclical motion of the material, which promotes a fast axial mixture of particles and an excellent gas-particle contact. In this work, the coating of soybean seeds with inoculum and micronutrients in spouted bed has been studied. The different flow regimes were investigated using the pressure fluctuations and power spectrum. The results of the present work showed that it was possible to identify the main flow regimes and to analyze the influence of the coating in the stability of those regimes.
Influence of the External Heating Type in the Morphological and Structural Characteristics of Alumina Powder Prepared by Combustion Reaction
Authors: Cordeiro V.V. , de Freitas Normanda Lino , de Souto Viana Kaline Melo , Dias G. , de Melo Costa Ana Cristina Figueiredo , Lira Hélio Lucena
Published: October 2010

The aim of this work is to evaluate the influence of the external heating in the morphological and structural characteristics of the alumina powder prepared by combustion reaction. It was evaluated different types of external heating: muffle oven, microwave oven and ceramic plate with electrical spiral resistance. The powders were prepared according to the propellants and explosives theory, using urea in the stoichiometric proportion (Φe = 1). During the synthesis parameters such as flame combustion time and temperature were measured. The structural and morphological characteristics of the powders were evaluate by XRD, particle size distribution, SEM and nitrogen adsorption (BET). The results showed the production of -alumina as unique phase and formed by agglomerates with irregular plate shape of thin particles for all studied conditions. The powders prepared by electrical oven presented small particle size, with narrow agglomerates size distribution.
Effect of the Salt Solution Concentration in the Number and Size Distribution of Atomized Nanometric Aerosol Particles
Authors: Amaral C.D. , Guerra Vádila Giovana , Arouca Fábio de Oliveira , Coury José Renato
Published: October 2010

The objective of this work is to study the dynamics of nanoparticle formation by atomization of saline solutions at different concentrations. The nanoparticles were generated by a two fluid particle atomizer. Saline solutions were atomized and, with the immediate evaporation of the dispersion liquid in the droplets, resulted in an aerosol of solid nanoparticles. Test replicates were performed with aqueous solutions of sodium chloride (NaCl) at concentrations ranging from 0.01 to 50.0 g/L. The solutions were characterized as for density, viscosity and surface tension. The size and concentration distributions of the particles were measured utilizing a TSI Scanning Mobility Particulate Sizer, SMPS, and the sampling was directly performed in the aerosol cloud. The results showed that, as expected, the increase of the saline solution concentration caused an increase in particle mean diameter. Also, and less obvious, it resulted in an increase in the number of particles. The results, when compared to theoretical prediction, indicate that particle formation and deposition after atomization is responsible for this phenomenon.
Solidification of Eutectic Bi32.5In51Sn16.5 Alloy under Microgravity Using a Drop Tube
Authors: Toledo Rafael Cardoso , Mattos M.B. , An Chen Y. , Bandeira I.N.
Published: October 2010

Containerless solidification of Bi32.5In51Sn16.5 eutectic alloy under microgravity conditions was investigated by using a 3 m length drop tube. The Bi-In-Sn system is an important material for lead-free solder and fuse element for electrical protection. It has a low eutectic melting temperature of 60°C, which is suitable for experiments in restricted environments like the International Space Station (ISS), where the security requirements are very strict. Droplets, with diameters in the range of 200 to 400 m, solidified under microgravity, were obtained consistently with irregular ternary eutectic structure, whereas, previous results under normal gravity presented both regular lamellar and irregular structures.
Pyrolysis of Sugarcane Bagasse: A Consecutive Reactions Kinetic Model from TGA Experiments
Authors: dos Santos Kássia Graciele , Lira Taisa S. , Murata Valéria V. , Gianesella Marco , Barrozo Marcos A.S.
Published: October 2010

The pyrolysis kinetics of sugarcane bagasse in nitrogen flow was studied by thermogravimetric analysis from room temperature to 1173 K at different heating rates (1.5, 3, 5, 10, 15, 20, 30 and 50 K/min). As there are three distinct devolatilization peaks in the DTG curve, each peak was associated to thermal decomposition of an individual biomass subcomponent (hemicellulose, cellulose and lignin). The kinetic model adopted was a consecutive reactions model. The kinetic parameters of the pyrolysis process, such as activation energy and pre-exponential factor, were calculated by least squares non-linear method and Scilab are used as the simulation tool. The simulated results showed a good agreement with the experimental data and the parameters found are similar to reported by the literature.
Plasma Etching of Stearic Acid in Ar and Ar-O2 DC Discharges
Authors: Bernardelli E.A. , Souza T. , Maliska A.M. , Belmonte Thierry , Mafra M.
Published: October 2010

Stearic acid is treated in a DC Ar-O2 plasma created by a cathode-anode confined system. The influence of the most important process parameters (gas flow rate, sample temperature, output power and exposure time) on the acid modification is studied. The evaluation of the influence of these parameters on grafting and etching of stearic acid was done by measuring the mass variation rate (MVR). The results show that when charged and chemically active species increase in density, what is directly connected with plasma parameters, the MVR increases too. In all experimental conditions, a negative MVR was obtained, due to the etching of the sample. The etching rate decreases with processing time, probably because of the formation of a product which is more resistant to plasma etching.
Cost Reductions - Materials
Authors: Eugênio Marcelo Luiz , Colosio Marco Antonio , Santos José Carlos
Published: October 2010

Currently, new and uncommon materials are being more used in automotive components, such as the manufactured by Powder Metallurgy due to new cost reduction strategies adopted by carmakers. The companies are searching more and with stronger aggressiveness the ways of finding cost reduction opportunities of a product and/or process. With this intention and for being it tracked by technical and commercial interests, new departments are being created with different names and structures. The ways to find out a reduction of viable cost are discussed in different ways of approaching of this question, which may be originated from the standardization of an item utilized in similar products, in the removal of components with questionable importance, in the change of manufacture processes, in the localization of items and finally, in the change of material and/or project. Starting from known approaches, the present work relates the most different ways of proposals and characterizes and quantifies them in graphical forms, adopted procedures, and by descriptions of ways pursued to reach a financial goal of reduction, mentioning typical examples of proposals with potential of implementation after a technical and critical analysis. Finally, the focus of this study is the approach of materials and specifications, said currently as the most complex and difficult field; however, with inexhaustible ways in the last instance in the field of Cost Reductions, and then the acquired knowledge should be used in sintered material.
A Comparative Study of the Corrosion Resistance of Stainless Steels Obtained by Powder Metallurgy Techniques for Application in Dental Prosthesis
Authors: Marques Rogério Albuquerque , Saliba-Silva Adonis M. , Rogero Sizue Ota , Montemor Maria de Fátima , Costa Isolda
Published: October 2010

- Ferromagnetic stainless steels (SS) produced by powder metallurgy (PM) techniques have been investigated as potential candidates for dental prosthesis applications in replacement of magnetic attachments made of noble and expensive alloys. Two SS were investigated: SS 17-4 PH produced by powder injection (PIM) and SS PM2000 obtained by mechanical alloying. In vitro cytotoxicity analysis of the two SS showed no cytotoxic effects. The magnetic retention force of both tested SS was also evaluated and they were comparable to noble commercially available material that is in use at the moment. The corrosion resistance of both SS was evaluated by electrochemical techniques in sodium phosphate buffer solution (PBS) at 37°C. The AISI 316L SS was also tested under the same conditions for comparison reasons. SS samples tested showed passive behaviour in the electrolyte, but they also presented susceptibility to pitting. The best pitting resistance was associated to the PM2000 whereas the 17-4PH PIM showed the highest pitting susceptibility among the tested steels. The results pointed out that the PM2000 SS might be considered a potential candidate for substitution of high cost magnetic alloys used in dental prosthesis.
Effect of Compacting Pressure on Liquid Phase Sintering of ASTM 2124 Alloy
Authors: Barbosa Luzinete Pereira , Lima E.P.R. , Rodrigues Daniel , Ambrozio Filho F.
Published: October 2010

The use of pressed and sintered aluminum, obtained by the powder metallurgy route, to produce large quantities of near-net-shaped components is increasing rapidly in the automobile industry. The production of lightweight pieces of Al by powder metallurgy has attracted increasing attention due to its unique properties. Sintering helps develop mechanical strength and other properties in commercial alloys obtained by powder metallurgy. Sintering of Al can be achieved only upon formation of a liquid phase capable of destroying the extremely stable oxide layer on the surface of the Al particles. The aim of this investigation was to analyze the effect of compaction pressure on sintering of atomized ASTM 2124 type alloy. Powder characterization was carried out using scanning electron microscopy (SEM). The specimens were axially compacted at pressures of 500, 600 and 700 MPa. Differential scanning calorimetry (DSC) was carried out to determine the sintering temperature of the alloy powder. The specimens were sintered at 570° C. Characterization of the sintered material consisted of density measurements and optical as well as SEM examinations. Nevertheless, even the low recycling cost of Al , what increases its useful time and stabilizes its value, the large amount of energy required to obtain it reduce its application.
Electrical Conductivity and Microstructure by Rietveld Refinement of Doped Cu-Ni Powder Alloys
Authors: Fambrini A.S. , Monteiro Waldemar Alfredo , Orrego R.M.M. , Marques I.M. , Carrió Juan Alfredo Guevara
Published: October 2010

This work presents a comparative study of microstructural and electrical properties of polycrystalline material from two different Cu-Ni alloys: Cu-Ni-Pt and Cu-Ni-Al. The first one of them was produced in electric furnace with voltaic arc and the other was produced by powder metallurgy. The microstructure of the samples was studied by optical microscopy, Vickers micro hardness and x rays powder diffraction. Their electrical conductivity was measured with a milliohmeter Agilent (HP) 4338B. Refinements of the crystalline structure of the samples were performed by the Rietveld method, using the refinement program GSAS. The refinement results and Fourier differences calculations indicate that the copper matrix structure presents not significant distortions by the used amounts of the other metal atoms. In both cases a sequence of thermo mechanical treatments was developed with the intention of increasing the hardness maintaining the electrical conductivity of the alloys. The refinements also allowed a study of the dependence of the micro-structure and the thermo mechanical treatments of the samples. Acknowledgments: Mackpesquisa, CAPES.
Preparation and Characterization of YSZ Closed-End Tubes for Oxygen Sensors
Authors: Caproni E. , Muccillo R.
Published: October 2010

Closed-end tubes of yttria-stabilized zirconia (YSZ) are required in oxygen sensors for automotive applications to control fuel consumption and pollutant emission. High temperature oxygen sensors were prepared by electrophoretic deposition (EPD) of submicron YSZ particles after suitably adjusting the rheological characteristics of the suspension of the ceramic particles in alcoholic medium. The ceramic tubes were analyzed by X-ray diffraction and impedance spectroscopy. The morphology of sintered specimens was studied by scanning electron microscopy. The processing by EPD of tubular ceramic solid electrolytes with electrical conductivity similar to the ones found in commercial lambda sensors has been successfully achieved.
Strontium Dopant Concentrations Influence on Nd1-xSrxMnO3±δ Structural and Electrical Conductivity
Authors: Vargas Reinaldo Azevedo , Chiba Rubens , Andreoli Marco , Seo Emília Satoshi Miyamaru
Published: October 2010

Many different types of ceramic materials are currently being studied as possible cathodes in Solid Oxide Fuel Cells (SOFC), in an attempt to reduce operating temperatures. Strontium-doped neodymium manganite (Nd1-xSrxMnO3±δ) was used as an intermediate temperature solid oxide fuel cell cathode. X-ray diffraction and electrical conductivity of the Nd1-xSrxMnO3±δ system with a perovskite structure were studied in function of x equal to 0.10, 0.30 and 0.50. An orthorhombic pseudo-perovskite structure was assigned to all powder compositions prepared by standard ceramic technique. Electrical conductivity was described by the small polaron hopping conductivity model, as well as, increases due to regular increments of Sr content for all compositions. Electrical conductivity was measured at 25.2, 26.4 and 37.1Scm-1 for x = 0.10, 0.30 and 0.50, respectively at 800°C.
Microstructure, Crystalline Phase, and Dielectric Property Analyses of TiO2 Composition with ZrO2 Addition
Authors: Souza José Vitor C. , Castro Pedro José , Nono Maria do Carmo de Andrade , Mineiro Sergio Luiz
Published: October 2010

For microwave applications, including mobile and satellite communications, ceramic resonators should have a high dielectric constant, low dielectric losses, and high frequency stability. In this sense, TiO2-ZrO2 ceramics have been investigated as a function of sintering behavior, phase composition, and microstructure. The ceramics were densified reaching a value of about 86% of theoretical density at 1400°C sintering temperature. The ceramics are prepared by mixing raw materials with the following TiO2-ZrO2 weight % ratio: 100 to 0, 90 to 10, and 80 to 20, respectively. The measured dielectric constants are between 79 and 88 values, while the quality factor due to dielectric losses are between 2820 and 5170. These results point out the influence of Ti/Zr ratio on controlling the dielectric properties.
Sintering Temperature Influence on Microwave Dielectric Properties of TiO2-ZrO2 Ceramics
Authors: Souza José Vitor C. , Castro Pedro José , Nono Maria do Carmo de Andrade , Mineiro Sergio Luiz
Published: October 2010

Dielectric ceramics have been widely investigated and used for microwave applications such as resonators and filters. The present study deals with the influence of sintering temperature on microwave dielectric properties of TiO2 ceramics with 10, 20, and 30 wt% ZrO2. Three compositions have been developed through mixing procedures and then tested for each sintering temperature: 1500 and 1400 °C. X-ray diffraction and scanning electron microscopy are carried out aiming to explain the ceramic behavior of each sample. The dielectric constants of different ceramics for both temperatures varied from 85.4 to 62.6, while their quality factor due to dielectric losses varied from 3110 to 1630. The Q decrease is attributed to the non uniform grain growth and to the obtained crystalline phases. The best microwave parameters were obtained for the ceramics sintered at 1400 °C, which can be applied in microwave circuits as dielectric resonators.
Effect of Rare Earth Addition on Electrical Properties of Zirconia Based Ceramics
Authors: Muñoz R.A. , Rodrigues A.C. , Santos C. , Silva Cosme Roberto Moreira
Published: October 2010

Applications of stabilized zirconia include uses related to its low thermal conductivity, strength and electrical properties. Rare earth oxides (REO) were used as additives to stabilize appropriate crystalline phases at zirconia compacts. In this work zirconia based solid electrolytes were sintered with 10, 15 and 20 wt % of REO as sintering aids. Samples were prepared by uniaxial cold press and sintered at 1400 °C, followed by electric properties determination via impedance spectroscopy. Complimentary characterization was made by X-Ray diffractometry and quantitative phase analysis by Rietveld refinement. The ionic conductivity is affected by the amount of REO additive and this effect is correlated to the existing tetragonal and cubic phases for each composition
Intermediate Oxide Layers for Direct Bonding of Copper (DBC) to Aluminum Nitride Ceramic Substrates
Authors: Molisani André Luiz , Yoshimura Humberto Naoyuki
Published: October 2010

DBC is a process where copper foils are bonded to ceramic substrates for manufacturing hybrid electronic circuits and packages with high power-handling capabilities. For aluminum nitride (AlN) ceramics, a heat-treatment is required to grow an oxide layer to promote the bonding with copper. The oxidation treatment, however, must be conducted in special conditions to avoid the occurrence of severe cracking. In this work, an alternative method is proposed to form an intermediate oxide layers for DBC to AlN substrates. By this method, eutectic powder mixtures (CuO-CaO and CuO-Al2O3 systems) were applied to dense AlN substrates and then heat-treated at 1200 °C for 1 h in air. Different types of AlN ceramics sintered between 1650 and 1700 °C for 4 h in nitrogen atmosphere with additives of the system Y2O3-CaO-SrO-Li2O were investigated. The prepared oxide layers (thickness of ~25 m) presented good microstructural joining with the AlN substrates (characterized by SEM and EDS analysis), and did not affect significantly the thermal conductivity in the working temperature range of electronic devices (~100 to 50 W/m.K determined by laser flash method between 100 and 200 °C) compared to the AlN substrates.
Ceramics Composites Derived From Polysiloxane / Al2O3 / Ti
Authors: Godoy Ana Lúcia Exner , Bressiani José Carlos , Bressiani Ana Helena Almeida
Published: October 2010

In this work alumina based composites ceramics with a polymeric precursor (polysiloxane) and metallic Ti with two different size particle distribution, Ti without milling (ATM) and 5h milling (ATM5), were characterized. PMS thermogravimetric curve indicates that the weight loss percentage was about 20%. The densities achieved were 3,50g/cm3 and 3,70g/cm3 for samples prepared with Ti as received and 5h milling, respectively. During decomposition of the polymer during pyrolysis and sintering, the particles of the matrix may react with carbon and Si from the polymer precursor, metallic Ti and gas atmosphere, nitrogen, to form different phases. The ATM samples presented Al2O3 and TiCN. The specimens prepared with 5h milling Ti (ATM5) is constituted by mullite besides Al2O3 and TiCN. The ATM5 samples have smaller densities than ATM but there is no significant difference in the hardness values.
Use of Nepheline-Syenite, Talc and Kaolinitic Clay to Obtain Ceramic Tiles
Authors: Teixeira Kênia Oliveira , Monteiro Sérgio Neves , Vieira Carlos Maurício Fontes
Published: October 2010

This work has for objective to obtain vitrified ceramic tiles by adding nepheline-syenite flux and talc to a kaolinitic clay from Campos dos Goytacazes. Specimens were prepared by uniaxial pressure at 30 MPa followed by firing at 1100, 1150 and 1200oC. The fired specimens were submitted to the following tests: bulk density, linear shrinkage, three point bending mechanical strength and water absorption. The microstructure of the ceramic was evaluated by SEM. The results showed that the incorporation of nepheline-syenite and talc significantly enhanced the properties of the clay making it possible to attain the standard specification corresponding to vitrified ceramic tile.
Incorporation of Petroleum Coke into Red Ceramic
Authors: Vieira Carlos Maurício Fontes , Freitas Lussandra Arêdes , Rodríguez Rubén Jesus Sánchez , Monteiro Sérgio Neves
Published: October 2010

This work has as its objective to evaluate the effect in the physical and mechanical properties of a red ceramic by the incorporation of petroleum coke from a refining plant. The characterization of the coke was done by optical microscopy and DTA/TG. Compositions were prepared with 0, 1, 2 and 4 wt.% of petroleum coke incorporated into a kaolinitic clayey body. Rectangular specimens were formed by extrusion before firing at 950°C. The determined physical and mechanical properties were: flexural rupture strength and water absorption. The microstructure of the fired ceramics was evaluated by SEM. The results showed that the incorporation of up to 4 wt.% of petroleum coke is not deleterious to the water absorption and mechanical strength of the clayey ceramic fired at 950oC.
Use of Steel Slag into Clayey Ceramics
Authors: Vieira Carlos Maurício Fontes , Monteiro Sérgio Neves
Published: October 2010

This work has for objective to evaluate the microstructural aspects and technological properties of a clayey ceramic incorporated with up to 30 wt.% of a waste generate during the steel-making process, denoted as steel slag. To determine the physical and mechanical properties such as linear shrinkage, water absorption and flexural strength, specimens were prepared by 18 MPa uniaxial pressure-molding and then fired in a laboratory furnace at 700, 900 and 1100oC. The microstructure of the compositions was evaluated by scanning electron microscopy and X-ray diffraction. The results showed that it is possible to recycle the finer particles of steel slag by incorporating into red ceramic as long as they are used in amounts not higher than 10 wt.% to avoid the increase in porosity and decrease of the mechanical strength.
Thermal Interdiffusion Products of U-10Mo in Al Matrix
Authors: Martins Ilson C. , Soriano Guilherme Z. , Durazzo Michelangelo , de Carvalho Elita F. Urano , Montagna Léa Sarita , Saliba-Silva Adonis M.
Published: October 2010

New nuclear fuel material with high density in uranium is envisaged for intense irradiation research reactors. The alloy U-Mo has been researched as a feasible candidate to be used in such reactors. This nuclear fuel is conceived to be used encapsulated in aluminum matrix. Nevertheless, there are interaction products of U-Mo/Al which form porosity during irradiation, leading to routine operation harms in research reactors. This interaction is due to solid solution interdiffusion of species, mainly of Al towards U-Mo region forming reaction products. This interaction could be studied by on-pile method, observing the occurrence of formed products during irradiation, but this method is costly and used only for long term experiments in very few reactors in the world. For this, several out-of-pile studies using heat treatments of diffusion pairs are carried out at adequate temperatures and times, just below the -phase eutectoid temperature to simulating the interdiffusion and formation U-Mo-Al phases. In the present study, it was employed a new developed assembling method to prepare interdiffusion pairs by immersing sliced U-10Mo sticks inside molten Al. These samples are made by induction furnace, in temperature range ~660-670 °C, under controlled argon atmosphere, in order to entrap molten Al around U-Mo sticks and so keeping this entangled structure after solidification. The interdiffusion pairs are then cut and prepared for treatments. This novel sample preparation guarantees full contact between the U-Mo and Al without oxidation contact, creating so, the ideal conditions for interdiffusion investigation of the interfaces of Al/U-Mo. Preliminary results to study interaction products where achieved by heat treatments during 5h at 550°C. Observations and calculations from SEM/EDS microstructures and XRD diffractograms revealed few microns interaction layer between the matrix and the fuel material, resembling phases reported in the literature for the interaction products between U-Mo-Al. This layer is mainly composed by Al and U, Mo phases, probably (U, Mo)Al3 and phases containing Si, as U3Si5 and a proposed one Al2Si3U3 that fits better to XRD spectrum of experimented diffusion pairs.
Electrical Porcelain Containing Ornamental Rock Waste: Microstructural Development
Authors: Silva M.A. , Holanda J.N.F.
Published: October 2010

Aluminous electrical porcelains are used in the production of materials of high voltage insulators. The microstructure plays an important role in the performance of electrical porcelain. On the other hand, the porcelain materials undergo a series of physical and chemical transformations during firing. This makes the understanding of their microstructures rather complex. In this work was studied the microstructural development of electrical porcelain containing up to 35 wt.% of ornamental rock waste. The pieces ceramics were pressed at 50 MPa and sintered at 1300 °C. The porcelain pieces were characterized via X-ray diffraction and scanning electron microscopy. The results indicate that the presence of the ornamental rock waste influenced the microstructural development of the pieces of electrical aluminous porcelain.
Development and Characterization of Si3N4 Coated AlCrN Ceramic Cutting Tool
Authors: Souza José Vitor C. , Nono Maria do Carmo de Andrade , Silva Olivério Moreira Macedo , Martins G.V. , Machado João Paulo Barros , Pimenta M.
Published: October 2010

Nowadays, silicon nitride based cutting tools are used to machine cast iron from the automotive industry and nickel superalloys from the aero industries. Advances in manufacturing technologies (increased cutting speeds, dry machining, etc.) induced the fast commercial growth of physical vapor deposition (PVD) coatings for cutting tools, in order to increase their life time. In this work, a new composition of the Si3N4 ceramic cutting tool was developed, characterized and subsequently coated, using a PVD process, with aluminum chromium nitride (AlCrN). The Si3N4 substrate properties were analyzed by XRD, AFM, hardness and fracture toughness. The AlCrN coating was analyzed by AFM, grazing incidence X-ray diffraction (GIXRD) and hardness. The results showed that this PVD coating could be formed homogeneously, without cracks and promoted a higher surface hardness to the insert and consequently it can produce a better wear resistance during its application on high speed machining.
102213 Use of High Energy Ball Milling on the Sintering Optimization of Alumina Ceramics
Authors: Simoni Helio R. , Saito Eduardo , dos Santos Claudinei , Santos Felipe Antunes , Ramos Alfeu Saraiva , Silva Olivério Moreira Macedo
Published: October 2010

In this work, the effect of the milling time on the densification of the alumina ceramics with or without 5wt.%Y2O3, is evaluated, using high-energy ball milling. The milling was performed with different times of 0, 2, 5 or 10 hours. All powders, milled at different times, were characterized by X-Ray Diffraction presenting a reduction of the crystalline degree and crystallite size as function of the milling time increasing. The powders were compacted by cold uniaxial pressing and sintered at 1550°C-60min. Green density of the compacts presented an increasing as function of the milling time and sintered samples presented evolution on the densification as function of the reduction of the crystallite size of the milled powders.