bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the Use of a Filtering Medium in Different Parts of a Centrifugal Separator
Authors: Façanha J.M.F. , Silva D.O. , Barrozo M.A.S. , Vieira Luiz Gustavo Martins
Published: August 2012

Hydrocyclones are devices used in solid-liquid, liquid-liquid, and solid-liquid gas separation process applied in several industry fields such as mining, food and petrochemical. With the rising need of diminishing energy consumption and enhancing process efficiency, modifications on these equipments have been proposed in order to elevate their performance. It can be found in literature optimized geometric relations for a hydrocyclone (designated CH11), aiming to conjugate low energy consumption and small cut size diameters. Hence, the purpose of this paper is to study the influence of filtration on CH depending on where the filtering wall is settled (cylindrical or conical part). The main experimental results suggest that the placement of the permeable region (conical or cylindrical parts) influenced the performance of the equipment regarding the main variables. In conclusion, setting a filtering wall brought expressive changes for the separation process.
Processing of Cu-Al-Ni and Cu-Zn-Al Alloys by Mechanical Alloying
Authors: Traleski André Victor , Vurobi Jr. Selauco , Cintho Osvaldo Mitsuyuki
Published: August 2012

The mechanical alloying process provides alloys with extremely refined microstructure, reducing the need for alloying elements to grain growth restriction, as in casting techniques. The Cu-Al-Ni and Cu-Zn-Al alloys produced by casting may have the shape memory effect when plastically deformed at relatively low temperatures, returning to its original shape upon heating at a given temperature. This work aimed at the production of Cu-Al-Ni and Cu-Zn-Al alloys by mechanical alloying, followed by microstructural characterization and investigation of the shape memory effect by means of differential scanning calorimetry (DSC). Metal powders of Cu, Al, Ni and Cu, Zn, Al were processed in a SPEX high energy vibratory mill during 8 hours, with ball-to-powder weight ratio of 5:1. The milled products were characterized by X-ray diffraction. For each alloy, specimens with 8 mm diameter and 2 mm thickness were shapes by uniaxial pressing, sintered in a tube furnace with argon atmosphere, solubilized and then quenched in water. Samples were characterized by optical and scanning electron microscopy (SEM), Vickers hardness testing and DSC. An ultrafine microstructure was obtained in the Cu-Al-Ni alloy but the shape memory effect was not detected by DSC analysis because of second phase precipitation. The shape memory effect was not present in the Cu-Zn-Al alloy also, because of zinc oxidation during the sintering.
Effect of Molybdenum on the Formation of Ti6Si2B in Mechanically Alloyed Ti-Mo-Si-B Powders
Authors: Nunes Perseu Amaral , Ramos Alfeu Saraiva , Ramos Erika Coaglia Trindade
Published: August 2012

This paper discusses on effect of molybdenum on the Ti6Si2B formation in mechanically alloyed and hot-pressed Ti-xMo-22Si-11B (x= 2, 5, 7 and 10 at%) alloys. High-energy ball milling and hot pressing were utilized to produce homogeneous and dense materials, which were characterized by scanning electron microscopy, X-ray diffraction, electron dispersive spectrometry, and Vickers hardness. The excessive agglomeration during milling was more pronounced in Mo-richer powders, which was minimized with the formation of brittle phases. Hot pressing of mechanically alloyed Ti-xMo-22Si-11B powders produced dense samples containing lower pore amounts than 1%. Ti6Si2B was formed in microstructure of the hot-pressed Ti-2Mo-22Si-11B alloy only. In Mo-richer quaternary alloys, the Ti3Si and Ti5Si3phases were preferentially formed during hot pressing. Oppositely to the ternary phase, the Ti3Si phase dissolved a significant Mo amount. Vickers hardness values were reduced in hot-pressed Ti-xMo-22Si-11B alloys containing larger Mo amounts, which were dissolved preferentially in Ti solid solution.
Processing and Manufacturing of Metal Matrix Aluminum Alloys Composites Reinforced by Silicon Carbide and Alumina through Powder Metallurgy Techniques
Authors: de Araujo Everthon Rodrigues , Alves Sérvulo José Ferreira , Filho Francisco Ambrozio , Filho Severino Leopoldino Urtiga , de Araújo Filho Oscar Olimpio
Published: August 2012

Composites are combinations of two materials in which one of the materials, called the reinforcing phase, is in the form of fibers, sheets, or particles and is embedded in the other materials called the matrix phase. If the composite is designed and fabricated correctly, it combines the strength of the reinforcement with the toughness of the matrix to achieve a combination of desirable properties not available in any single conventional material. In this work of research aluminium alloy AA6061 was reinforced by 5, 10 and 15% (in mass %) of SiC and Al2O3 by mechanical alloying in a vibratory type SPEX mill, cold uniaxial compaction and vacuum sintering in order to investigate the influence of the particulate phase in the microstructure and mechanical properties of the composites obtained. The microstructure of the powders and the sintered materials were evaluated by SEM and the hardness was evaluated by hardness tests.
Obtention of Aluminium-Quasicrystal Composites by Mechanical Alloying
Authors: de Sousa Fernando Luís Vieira , Romio Pedro Cordeiro , Passos Tibério Andrade , de Lima Severino Jackson Guedes
Published: August 2012

The quasicrystals materials possess a combination of unusual properties, since they present a long range ordered atomic structure, which is not periodic. Because of this, these materials have been object of study of many researchers in the last few years. Currently, the research is focused on determining new techniques able to produce these materials in a large scale, as well as finding new utilities. One of the ways to do so, is to use quasicrystals as coating; another way is the fabrication of composites. In this paper, aluminum composites with the strengthening of quasicrystalline particles from the alloy Al59,2Cu25,5Fe12,3B3in volumetric fractions of 6% to 20% were developed by high energy ball milling. The powders obtained by mechanical alloying was compacted at 300MPa, sintered and submitted to micro hardness tests. The characterization was made by X-ray diffraction and SEM. In the grinding we used a 2² factorial design with factors time and speed, and the hardness of composite as response. The specimens had an average hardness of 25.75GPa for reinforcement with 6% QC and 34.75GPa for reinforcement of 20% QC.
Titanium Metal Matrix Composite Laser Coatings Based on Carbides
Authors: Amigó Vicente , Candel J.J. , Franconetti P.
Published: August 2012

Laser cladding is an adequate technique to fabricate Metal Matrix Composite (MMC) layers because of its focused high energy which allows the partial melting of hard ceramic reinforces particles like carbides. Thus, the wettability and gradual transition between metal and particle can be improved. However, metastable or new intermetallic phases can be formed during laser processing due to severe thermal cycle imposed to the clad with unknown properties in some cases. In this work our experience on microstructural analysis of Ti-MMC coatings acquired during the last five years is summarized. Special attention is paid on carbide dilution and secondary carbides formation mechanisms when TiC, SiC, Cr3C2, WC and B4C are mixed with titanium alloys.
Structural Comparison of Amorphous, Nanocrystalline and Microcrystalline Al90Fe7Nb3 Alloys
Authors: Rodrigues C.A.D. , Botta Filho Walter José , Tremiliosi-Filho G.
Published: August 2012

This work presents the structural comparison of Al90Fe7Nb3alloys obtained by different techniques: (i) partly amorphous powder alloy produced by mechanical milling and their consolidation by hot extrusion (cylindrical bar), (ii) from millimeter portion by casting centrifuged system (square shape), and (iii) from millimeter portion by melt-spinning (ribbon shape). The cylindrical consolidated alloy presented an Al matrix with Al3Nb and Al13Fe4nanophases (intermetallic compounds), the square consolidated alloy resulted in the same structure composed of Al matrix with Al3Nb and Al13Fe4in micro-phase scale. On the other hand, the ribbon alloy exhibits an amorphous matrix with primary Al nanocrystals (fcc-Al phase).
Covering with Carbon Black and Thermal Treatment by a CO2 Laser Surfaces of Aisi 4340 Steel
Authors: de Vasconcelos G. , Chagas D.C. , Campos D.C. , Dias A.N.
Published: August 2012

This work presents the evaluation of the use covering with carbon black to replace the graphite covering used in previous work, aiming to eliminate the grinding step to the process. The results of this treatment were characterized by optical microscopy, scanning electron and hardness. The micro hardness achieved was near to 760 HV 0.05, coefficient of friction of 0.2. Scanning electron microscopy showed that the extent of the treated area by laser reaches near to 90μm, and the thickness coating of carbon black is about to 2μm. The graphite can be substituted by carbon black, acting as coupling of the laser beam radiation, and as a solid lubricant, according to REIS (2009).
Fabrication of Powder from Ductile U-Mo Alloys for Use as Nuclear Dispersion
Authors: Durazzo Michelangelo , da Rocha Cláudio José , Mestnik-Filho José , Neto Ricardo Mendes Leal
Published: August 2012

For the last 30 years high uranium density dispersion fuels have been developed in order to accomplish the low enrichment goals of the Reduced Enrichment for Research and Test Reactors (RERTR) Program. Gamma U-Mo alloys, particularly with 7 to 10 wt% Mo, as a fuel phase dispersed in aluminum matrix, have shown good results concerning its performance under irradiation tests. Thats why this fissile phase is considered to be used in the nuclear fuel of the Brazilian Multipurpose Research Reactor (RMB), currently being designed. Powder production from these ductile alloys has been attained by atomization, mechanical (machining, grinding, cryogenic milling) and chemical (hydriding-dehydriding) methods. This work is a part of the efforts presently under way at IPEN to investigate the feasibility of these methods. Results on alloy fabrication by induction melting and γ-stabilization of U-10Mo alloys are presented. Some results on powder production and characterization are also discussed.
Quantitative Evaluation of Interstitial Elements in the Processing of Ti-6Al-4V Alloy by Powder Metallurgy
Authors: Petroni S.L.G. , Henriques V.A.R. , Paula M.S.M. , Cairo C.A.A.
Published: August 2012

The use of hydride powders in titanium powder metallurgy (P/M) is a low cost alternative for the manufacture of titanium alloys. However, due to the high reactivity of these powders, parts produced using this technique may contain interstitial impurities such as oxygen, nitrogen and carbon. In this work a factorial design approach was used to evaluate the influence of some stages of P/M upon the levels of these elements in sintered samples of Ti-6Al-4V. Milling time of titanium hydride powders, sintering temperature and holding time were evaluated. The effect of milling time was detected as the most significant for the increase in oxygen levels. The contents of all elements were affected by the increase of sintering temperature from 1200 °C to 1400 °C. Holding time was shown to be significant only for the carbon absorption in the samples sintered at 1400 °C.
TiN/ZrN Multilayer PVD Coatings on Titanium Alloys Produced by Powder Metallurgy
Authors: Schichi O.C. , Henriques V.A.R. , Galvani Eduardo T. , Cairo C.A.A.
Published: August 2012

Multilayer coatings are synthetic structures constituted by alternate layers of different materials. The technological applications of the multilayer coatings can involve optical, electromagnetism and wear areas. The target of this work is the production of multilayer TiN/ZrN coatings by Electron Beam Physical Vapor Deposition (EB-PVD) over titanium alloys produced by powder metallurgy. P/M-Ti-35Nb-7Zr-5Ta cylindrical samples used as substrates were produced by mixing of the elemental powders with subsequent cold pressing steps and sintering at 1400°C, in high vacuum. TiN/ZrN coatings were obtained by evaporation of alternating Ti and Zr cylindrical targets. The multilayers were characterized by optical and scanning electron microscopy (SEM), chemical analysis via energy dispersive spectrometry (EDS) and Vickers indentation. Besides the possibility of obtaining several layers, the results show coatings with coherent columnar structure, low discontinuity, large and homogenous thickness and high adhesion to substrate.
Modeling the Densification of 316L Stainless Steels
Authors: de Castro José Adilson , Filho Nelson Karsokas , Rodrigues Daniel , de Campos Marcos Flavio
Published: August 2012

Stainless steels are employed as filters, and in this application the amount of pores and their size distribution are very important. Here it is discussed a densification model, which takes into account both, grain size and density. After this model is applied to experimental data, the obtained parameters can be used for extrapolation in other sintering conditions, for example other temperatures and heating rates. The studied material is the austenitic alloy 316L.
Sintering of Cubic Boron Nitride Using Titanium Based Binders
Authors: Bobrovinitchii Guerold Sergueevitch , Skury Ana Lúcia Diegues , Monteiro Sérgio Neves , de Azevedo Marcia G.
Published: August 2012

As a superhard material, next to diamond, the cubic boron nitride (cBN) is of great interest owing to its efficiency in machining ferrous alloys. In nature, only the hexagonal, hBN, exists. In practice, high pressure and high temperature (HPHT) synthesis has to be used to produce small cBN crystals. For larger size machining inserts, the powder-like cBN crystals need to be sintered at specific HPHT conditions using a metallic binder. The present work investigates the sintering of cBN inserts using a Ti-based binder at 7 GPa of pressure and 1800°C. The results disclosed relatively high hardness for the inserts and revealed their effectiveness in machining high strength steels.
Liquid Phase Migration during Diamond Powder Sintering by Infiltration Method
Authors: Skury Ana Lúcia Diegues , Bobrovinichii Guerold S. , Monteiro Sérgio Neves , de Azevedo Marcia G. , Silva Apostolos
Published: August 2012

Compacts made of sintered diamond powder (DP) are not only extensively used but also essential cutting inserts for operations such as machining metal components or drilling rocks for petroleum extraction. The high pressure and high temperature (HPHT) sintering can be achieved either by an initial mixture of DP with a metallic binder or by first processing the DP at HPHT, which creates a sintered skeleton, followed by the molten metallic binder infiltration. This work investigates the infiltration of Cu, Co and Ni, as binders, into sintered diamond powders with different particles size. It was found that migration of the liquid phase through the sintered diamond skeleton complies with the Darci Law. The penetration coefficient varied from 0.89 x 10-7to 6.41 x 10-7μm2indicating that the migration is affected by several factors.
High-Pressure Assisted Sintering of Ti-20Si-10B and Ti-10Si-5B Powders
Authors: Pereira Wladimir Leite , Ramos Erika Coaglia Trindade , Ramos Alfeu Saraiva , Silva Alexandro Nakano , Lima Filipe Tavares Caetano , Filgueira Marcello
Published: August 2012

This work presents the structural characterization of Ti-10Si-5B and Ti-20Si-10B (at-%) alloys produced by high-pressure assisted sintering. Sintering was performed in air at 1100 and 1200 °C for 60 s using pressure levels of 5 GPa. Structural evaluation of sintered samples was conducted by means of scanning electron microscopy and energy dispersive spectrometry. Samples were successfully consolidated after sintering, which presented theoretical density values higher than 99%. The microstructures of the sintered Ti-10Si-5B and Ti-20Si-10B alloys revealed the presence of the TiSS, TiB, TiB2, Ti5Si3, Ti5Si4, TiSi, and TiSi2.phases. A small amount of Ti6Si2B was formed after high-pressure assisted sintering of the Ti-20Si-10B alloy (5GPa, 1100°C for 60 s) indicating that equilibrium structures were not achieved during short sintering times. No oxygen and carbon contamination was detected in structures of Ti-Si-B alloys after high-pressure sintering at 1100 and 1200 °C without controlled atmosphere.
Applications of PZT Dielectric Ceramics in High-Energy Storage Systems
Authors: Silva Neto L.P. , Rossi J.O. , Silva A.R.
Published: August 2012

The barium and strontium titanate (BST) ceramics have been used with great success as excellent dielectrics in the construction of high voltage (HV) commercial ceramic capacitors with reduced dimensions because of their high dielectric constant. However, the main point of this paper is to investigate other type of ceramic known as PZT (Lead Zirconate Titanate) normally used as piezoelectric sensors in industrial applications. The idea herein is to use the PZT ceramics as HV dielectrics for applications in high-energy storage systems by de-poling their piezoelectric properties in order to avoid dielectric damage and losses at high frequencies. For this, de-poled PZT-4 ceramic samples (30 mm × 2 mm) were submitted to HV tests, in which their dielectric breakdown strength and dielectric constant variation with the applied voltage were assessed. These results obtained confirmed the use of PZT in applications that require reasonable dielectric constant stability (< 15 %) with voltage and HV dielectric breakdown (40 kV/cm) for compact high-energy storage devices.
Structural Characterization, and Magnetic Morphological Study of Ni+2 Doped ZnO Synthesized by Combustion Reaction Application for DMS
Authors: Torquato R. , Sagar E. Shirsath , Kiminami Ruth Herta Goldsmith Aliaga , de Melo Costa Ana Cristina Figueiredo
Published: August 2012

ZnO is a semiconductor that can be doped with transition metal ions, and thus becomes feasible to use in the diluted magnetic semiconductor (DMS), or semiconductor with magnetic properties. In this work we have studied the influence of doping of Ni+2on the structural, morphological and magnetic properties of Zn1-xNixO system, to x = 0.07, 0.1 and 0.2 mol of Ni+2synthesized by combustion reaction. The systems were characterized by XRD, SEM and VSM. The maximum temperatures ranged from 639 K and 683 K. All systems showed a majority phase formation of ZnO, with the presence of the second phase NiO. The crystallite size for the majority phase varied between 49 and 56nm. All systems have resulted in samples with a morphology consisting of dense clusters, formed by particles pre-sintered and shaped roughly hexagonal plates. The magnetic measurements showed that the values of saturation magnetization lies between 4.6 to 28.5emu/g, remanent magnetization of 0.01 to 0.3 emu/g, coercive force values varies between 12.7 and 62.4 Oe and Curie temperature ranging from 308 to 311K.
Effect of Attrition Milling and Calcination Temperature on Phase Composition of Strontium-and Magnesium-Doped Lanthanum Gallate
Authors: Reis S.L. , Muccillo E.N.S.
Published: August 2012

Oxygen-ion conductors based on strontium-and magnesium-doped lanthanum gallate have been proposed to be used as solid electrolyte in solid oxide fuel cells operating at intermediate temperatures (500-700 °C), due to their high ionic conductivity and stability over a wide range of oxygen partial pressures. In this work, the effect of attrition milling on phase composition of powder and consolidated specimens prepared by solid state synthesis has been investigated. The results show that both the attrition milling and the calcination temperature play a major role in the phase composition. Powders with negligible amount of secondary phases were obtained after two steps of calcination at high temperature followed by attrition milling.
Magnetic Evaluation of Ni-Zn Ferrites Doped with Aluminium
Authors: Santos P.T.A. , Cornejo Daniel , Santos P.T.A. , Lira Hélio Lucena , de Melo Costa Ana Cristina Figueiredo
Published: August 2012

Ni0.5Zn0.5Fe1.97Al0.3O4ferrites were synthesized by combustion reaction method and after calcined at 700°C/1 h, with the aim to investigate how the Al3+ions substitution byNi2+ions can influence the magnetic properties. The results from X-ray diffraction showed the formation of a unique Ni-Zn ferrite phase with average crystallite size of 8 and 22nm, before and after calcination, respectively. The synthesize samples presented a superparamagnetic behavior, with saturation magnetization of 0.9 emu/g, and coercive field of 0.05 kOe, and after calcination the samples presented soft magnetic behavior with saturation magnetization of 40.0 emu/g and coercive field of 0.04 kOe.
Variation of Resonant Frequency with Temperature in Ceramic Resonators Based on Ba2Ti9O20 Compositions
Authors: Castro Pedro José , Nono Maria do Carmo de Andrade , Souza José Vitor C. , Mineiro Sergio Luiz
Published: August 2012

Ceramic samples based on barium nanotitanate (Ba2Ti9O20) have been produced for application as dielectric resonators aiming at good microwave properties as high dielectric permittivity, low dielectric loss, and high frequency stability. Two different samples were prepared: first a Ba2Ti9O20specimen and second a 1wt% Nb2O5-added Ba2Ti9O20composition, using BaO and TiO2as precursor materials. Variation of resonant frequency with temperature is commonly represented by temperature coefficient. Experimental tests were carried out to determine the dielectric permittivity (ε) and the temperature coefficient (τ) using a metal box where the specimen was placed between parallel metal surfaces. The resonant frequencies were measured as function of temperature from-20°C to +50°C in a programmable climatic chamber. As a result, the ceramics presented relatively good microwave properties: ε1=34.6, τ1=20.5 ppm/°C from initial frequency f1=7.23 GHz for the former composition, and ε2=27.5, τ2=10.1ppm/°C from initial frequency f2=7.80 GHz for the latter.
Porous Ceramic as Air Humidity Sensors
Authors: Oliveira Rodrigo de Matos , de Andrade Maria do Carmo
Published: August 2012

The development of sensors for relative humidity monitoring, with national technology, is one of the greatest needs identified by National Institute for Space Research (INPE) to allow concerned future projects and minimize dependence on imported components and materials. Therefore, in this work, porous ceramic was manufactured from ZrO2 and TiO2 powders, compacted and sintered at different temperatures, for application as air humidity sensing elements. The characterization of the sintered ceramics were carried out through x-ray diffraction (crystalline phases), scanning electron microscopy, SEM (microstructure), density determination and capacitance measurements using a RLC bridge in a climatic chamber. The results evidenced that the air humidity ceramic sensing elements are very promising ones.
Modeling of Ceramic Oxide Fiber Bundles Mechanical Properties
Authors: da Silva João Gustavo Pereira , Hotza Dachamir , Janssen Rolf , Al-Qureshi Hazim Ali
Published: August 2012

s common knowledge that for bundles of fibers, that the bundle strength is always less than the sum of the fiber strengths. This behavior can be explained by load-sharing models. So even when the weakest fiber fails, the remaining fibers share the load, and thus increase the effective stress in these fibers. At this work, different load sharing models were implemented on a simulated tensile test of ceramic oxide fibers using Matlab. The results are in agreement with the theoretical predictions and are a powerful tool for design of composites.
Nickel-Polyaniline Composite Electrodes for Electrocatalytic Reduction of Hydrogen in Alkaline Media
Authors: Torres Camila dos Santos , Falcade Tiago , Malfatti Célia de Fraga
Published: August 2012

The use of hydrogen fuel cell for generating electricity is one of the potential solutions to solve the energy crisis problem. Electrolysis of water is a promising technique to produce hydrogen, however, the large-scale application is, at present, restricted by its high HER (hydrogen evolution reaction) overpotential. Nickel-conductive polymers composites have been proposed as potential electrodes for the electrocatalytic reduction of hydrogen, due to the combination of good mechanical and electrical properties. In this work, it was investigated the electrochemical behavior of Ni and Nickel-Polyaniline (Ni/PAni) composite electrodes. The electrodes were obtained by electrodeposition from a suspension containing PAni particles. The electrocatalytic activity was monitored from polarization curves and the morphology was evaluated by scanning electron microscopy. The results showed that the incorporation of PAni in nickel metal matrix promotes an increase in electrocatalytic activity of HER, compared to nickel electrode.
Sintering Study of Al2O3/NbC/Wc Micro-Nanocomposite
Authors: Trombini Vania , Tonello Karolina Pereira Santos , Santos Thais , Bressiani José Carlos , Bressiani Ana Helena de Almeida
Published: August 2012

Ceramic materials based on alumina are considered excellent for produce cutting tools used to machining hard metals. However, low mechanical strength and toughness presented by these materials limit their application. Traditionally particles, such as TiC, TiN and ZrO2, are added to the alumina matrix to improve their mechanical properties, increasing the range of applications. Recent studies have shown that the addition of particles of different sizes in alumina matrix can promote simultaneous increase in mechanical strength and tenacity. In this work sintering behavior of Al2O3micro-nanocomposite containing nanometric particles of NbC and micrometric particles of WC, was studied by dilatometry using heating rate of 20°C/min up to 1800°C. The addition of carbides in alumina matrix is prejudicial to sintering causing an increase in temperature of shrinkage.
Effects of Femtosecond Laser Irradiation on the Surfaces of Alumina and Alumina-Zirconia Composites
Authors: Aguiar Amanda Abati , de Lima Nelson Batista , de Rossi W. , Samad R.E. , Vieira N.D. , Braga F.J.C.
Published: August 2012

Alumina and zirconia-alumina composite has been micro-structured in air using femtosecond laser. The threshold fluence of 6.2 J.cm-2 found in this work is close to that found published in literature [1]. In the case of Al-Zr, the threshold fluence is 2.2 J.cm-2.Surface femtosecond laser treatment increase the apatite deposition by biomimetic method on alumina and alumina-zirconia composite and depends on the condition of laser treatments.
Simplex Network Modeling for Press-Molded Ceramic Bodies Incorporated with Granite Waste
Authors: Pedroti Leonardo Gonçalves , Monteiro Sérgio Neves , Vieira Carlos Maurício Fontes , Alexandre Jonas , Destafani A.Z. , Xavier G.C.
Published: August 2012

Ceramics for structural blocks are usually composed of a mixture of clays and sand with addition of water before a final temperature sintering. In the molding stage, the mixtures should attend a packing condition between the different particles sizes, to allow required properties of the ceramic after firing. The introduction of another compatible powder material, with a convenient particle size, may improve the ceramic properties such as the strength and water absorption. The number of variables in this system demands a modeling procedure to optimize conditions for the best results. In this work, a Simplex network modeling was used as an experimental planning to determine the optimum combination of clays, sand and water as well as incorporated granite waste, for ceramic blocks fabrication. The pressing load and firing temperature were also used as variables to determine the best response surfaces for final strength and water absorption of the ceramic blocks.
Three-Dimensional Stochastic Modeling and X-Ray Microtomography Applied to Titanium Scaffolds: A Comparative Approach
Authors: Moreira Anderson Camargo , Rouxinol Ricardo Leo Marques , de Azevedo Santos Pedro Alvim , Fernandes Celso Peres , Ribeiro Alexandre Antunes , Balestra Roseli Marins , Varella Marize
Published: August 2012

The performance of biomaterial scaffolds for bone tissue engineering, as porous titanium implants, is strongly dependent of its structural features. A reliable structural characterization of this kind of implant is very important. The most of image analysis techniques just supplies 2D information about the structure of specimens. X-ray microtomography is imaging technique that can produce 3D images of samples, however, stochastic models can also estimate properties of porous materials in 3D. This work presents the evaluation of a 3D model (using a truncated Gaussian method) in comparison to 3D microtomography volume, both from a titanium scaffold sample. In order to compare, geometrical parameters were measured for both 3D volumes. By the results, the truncated Gaussian 3D method reproduced a model with similar values to the microtomography volume, showing a good agreement among data, which suggests the use of this technique to estimate physical parameters of titanium scaffolds
Characterization of Geological Materials of São Fidélis/BR for Slip Use
Authors: Chrispim Zélia Maria Peixoto , Almeida Luciana Lezira Pereira , Ramos Izabel de Souza , Alves Maria da Gloria , Alexandre Jonas
Published: August 2012

The present work was performed in São Fidélis/BR, technologically characterizing four types of soil. Aiming to use them in artistic ceramic, some of their properties were determined, such as the analysis of color after burn. In order to do so, essays regarding their granulometry (sifting and sedimentation), specific gravity, chemical analysis of xray fluorescence, mineralogical identification through x-ray diffraction (DRX), differential thermal analysis (ATD), thermal gravimetric analysis (TG) and scanning electron microscopy (MEV) were carried out in the Laboratories of Universidade Estadual do Norte Fluminense (UENF).The soils were analyzed before drying at 110°C and after burn under temperatures of 750°C and 1,050°C. The analyses of results returned their physical, chemical and mineralogical compositions. Many variations of color could be observed after burn.
Fatigue Strength of Ti-35Nb-7Zr-5Ta
Authors: Franco H. Alexander , Silva Cosme Roberto Moreira , Ferreira J.L.A. , Araújo José A.
Published: August 2012

Mean stress on fatigue strength of Ti-35Nb-7Zr-5Ta, used in the manufacture of orthopedic prostheses, was evaluates. Samples of Ti-35Nb-7Zr-5Ta were pressureless, sintered and tested using microhardness (Vickers) and four point bending fatigue conditions. Characterization was carried out using optical microscopy, scanning electron microscopy, EDS analysis, oxygen analysis and density. The microstructural analysis shows low densification after sintering (almost 86% of theoretical) and some precipitates of α phase and presumably ω phase at the grain and grain boundaries. The bending fatigue resistance limit reached (Se (106) = 90 MPa), due to, presumably, the influence of the medium-high porosity, α phase precipitates at grain boundaries as well as the high oxygen content in the material after sintering (0.96 %). In this case, Kwofie model best explains the influence of mean stress on fatigue strength of this alloy.
Production, Sintering and Mechanical Properties of Ca2MgWO6, a New Complex Cubic Perovskite Ceramic
Authors: da Silva Oliveira José Carlos , Ferreira Ricardo Arthur Sanguinetti , Yadava Yogendra Prasad
Published: August 2012

In the present work we have carried out production and characterization of a new complex cubic perovskite ceramic Ca2MgWO6 to evaluate its application viability as inert material for petroleum industry. Ca2MgWO6 was produced by thermo-mechanical processing and calcinations at 1.200°C, using stoichiometric amounts of constituent chemicals CaCO3, MgO and WO3. The calcined material was examined by x-ray diffraction, which identified the phase formation Ca2MgWO6. Calcined material was powdered in a ball mill, compacted as circular discs and subjected to sintering at temperatures of 1.250, 1.300 and 1.350°C. The powders, both those employed in the calcined pellets as those produced by the mill, were characterized by size distribution. The sintered discs were characterized by SEM. The results showed that the ceramics sintered at 1.250°C presented better results in terms of microstructural features and mechanical properties for their possible application as inert material for petroleum industry.
The Effect of the Dust Cake Resistance on Fluid Flow Passing through the Filter Media
Authors: Rocha Sandra Mara Santana , Bacelos M.S. , Damasceno João Jorge Ribeiro , Vieira L.G.M. , Aguiar M.L.
Published: August 2012

A filter box was used to obtain the experimental data of filtration operation with different air velocities as 5, 10 and 15 cm/s. The experimental data were compared to the simulated ones using CFD technique. For all range of air velocity and dust cake porosity and permeability employed, data of pressure drop in filter box could be satisfactorily predicted by simulations in CFD. Furthermore, the CFD simulations showed that undesirable patchy cleaning might be overcome using air velocities lower than 15cm/s.
Effect pH Variation of Powder Materials of the Composite Oxide Ba(x)Sr(1-x)Co(y)Fe(1-y)O3-d Obtained by Citrate-EDTA Method
Authors: Bonturim Everton , Vargas Reinaldo Azevedo , Andreoli Marco , Seo Emília Satoshi Miyamaru
Published: August 2012

The Ba(x)Sr(1-x)Co(y)Fe(1-y)O3-d (BSCF) powder, used with cathode in intermediated temperature solid oxide fuel cells (ITSOFCs), has been prepared by Citrate-EDTA method and calcined at 900°C for 5h. Among the parameters to be checked in a liquid phase reaction, the pH of precursor solution is very important to control the disposal of organic, crystal structure and powders morphology. In this work, precursor solution pH has been variegated 2, 4, 6 and 8. The thermal decomposition has been observed in infrared, two absorption peaks are observed at 1436 and 860 cm-1, after calcination, corresponding to the presence of CO32-, in the samples with pH 2, 6 and 8. The single phase of Perovskite crystalline structure is seen only in the synthesis at pH 4 and 6, verified by X-ray diffraction (XRD). Morphological analysis, by scanning electron microscope (SEM), shows the powder is agglomerated and has similar trend independent of precursor solution pH.
Rheological Studies of Brazilian Clays in Water-Alcohol Suspensions
Authors: Miyahara Ricardo Y. , Lins Pedro G. , Valera Ticiane S. , Toffoli Samuel Marcio
Published: August 2012

In this paper, the rheological behaviors of dispersions of two types of clays a kaolin and a smectitic clay from Paraíba State, Northeastern Brazil, were investigated. Both clays are mainly employed by ceramics industries in the Southern States of São Paulo and Santa Catarina. Viscosity measurements of dispersions in water and three types of alcohols (methanol, ethanol, and propanol) were carried out in a concentric cylinder geometry viscometer. The concentration of the dispersions was 20 wt.% of clay in water-alcohol suspensions containing up to 75 wt.% of each one of the three alcohols. The results are compared and discussed.
Properties and Microstructure of Clay Ceramics with Granite Waste for Press-Molded Structural Block
Authors: Pedroti Leonardo Gonçalves , Monteiro S.N. , Vieira C.M. , Alexandre J.
Published: August 2012

Extrusion of a clay body is the most applied process in the ceramic industries for manufacturing structural blocks. Nowadays, the assembly of such blocks through a fitting system is gaining attention owing to the saving in material and reducing in the cost of the building construction. However, this fitting system requires a press-molding, rather than extrusion, to allow blocks to be fabricated with different shapes. In this work, the ideal composition of clay bodies incorporated with granite powder waste was investigated for the production of press-molded ceramic blocks. An experimental design was applied to determine the optimum properties and microstructures. Press load of 15 ton and temperatures from 850 to 1050°C were considered. The results indicated that mechanical strength of 30 MPa and water absorption of 15% could be attained with the incorporation of up to 17% of granite powder waste.
Evaluation of the Influence of the Silane Drying Temperature on the Feldspar and Zirconia-Based Ceramics Surfaces
Authors: Melo-Silva Cláudio Luis , Carvalho Cristiane Fonseca , Santos Claudinei , Lins Jefferson Fabrício Cardoso
Published: August 2012

Ceramics are widespread used in restorative dentistry, mainly due to their aesthetics features. However, adequante bond strenght of this type on restoration to tooth structure spawned several investigations which aim to develop a clinical protocol for ceramic surface treatment. The objective of this study was to evaluate the influence of air temperature on the drying process of silane agent and the adhesion of feldspar and yttrium stabilized zirconia. They were divided into three groups (n=10): control; room temperature dried silane; and silane drying at 70º C. Then, composite resin cylinders were bonded to the samples and taken to a shear test. The results showed that air temperature rise, in silane drying, improved bonding resistance in Y-TZP ceramics, nevertheless in feldspatic ceramics, the bonding resistance was not altered.
Analysis of the Incorporation of Scheelite Residue in Kaolinitic Clay of Boa Saúde-RN
Authors: Machado Tércio G. , Umbelino Gomes Uilame , Monteiro Flanelson M. , Valcacer Samara M. , da Silva Gilson G.
Published: August 2012

The scheelite occurs mainly in northeastern Brazil, with highest abundance in the states of Rio Grande do Norte and Paraíba - Scheelite Seridó Province. Mining is considered an activity that provides a high environmental degradation due to the large amount of minerals and waste involved. Most mining companies have no technologies or processes that allow the recycling of mineral waste generated. The aim of this study is to evaluate the influence of different percentages of reject on the mechanical properties of scheelite and aesthetic (staining of the final product after firing) of the clay of the city of Boa Saúde - RN. The raw materials used were characterized by XRD, XRF and particle size analysis. Assay was performed by water absorption, linear retraction and bending tests on three points for the characterization of the final product. The raw materials used were from the city of Currais Novos-RN.
Size Distribution of TiO2 Nanoparticles Generated by a Commercial Aerosol Generator for Different Solution Concentrations and Air Flow Rates
Authors: Zoccal João Victor Marques , Arouca Fábio de Oliveira , Coury José Renato , Gonçalves José Antônio Silveira
Published: August 2012

Advances in scientific research in the field of nanotechnology sparked an increase in technological and industrial applications involving nanoparticles, Moreover, there was increasing concern about the control of nanoscale particles released to the atmosphere, driven by concerns over air quality and human health. In this context, this study aims to determine the size distribution of TiO2nanoparticles generated by the commercial TSI Atomizer Aerosol Generator model 3079 for different solution concentrations and air flow rates. The concentrations of the TiO2solutions used in the generator were 0.0125, 0.025 and 0.05 g.L-1, while the aerosol flow rates were 1.27, 2.55 and 3.82 L.min-1. The size distribution was measured with the TSI Scanning Mobility Particle Sizer (SMPS) equipment, which provides the number of particles per size range. The results showed that even changing the concentration of TiO2in solution, peak concentrations of nanoparticles remained in the same range between 15 to 45 nm. Moreover, it was observed that particle concentration in the gas stream decreased with increasing flow rate.
Modification of Brazilian Bentonite Clay for Use Nano-Biocomposites
Authors: Morais Dayanne Diniz Souza , Barbosa Renata , Medeiros Keila Machado , Araújo Edcleide Maria , de Mélo Tomás Jefférson Alves
Published: August 2012

Biopolymers are a growing research issue since they appear as a solution to the emerging environmental concerns that have risen in recent years. They represent an interesting alternative to synthetic polymers for a short-life range of applications. Recently, great attention has been paid to the association between biopolymers with nanosized llers, in particular, to those in which layered silicates are dispersed at a nanometric level in a biopolymer matrix. Surch materials called nanobiocomposites. In this work, Brazilian bentonite clay was organophilized with three organic intercalants by ion-exchange reactions for use in nanobiocomposites. The clay was characterized by X-ray Fluorescence (XRF), X-ray Diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR) and Thermogravimetry (TG). The XRD results confirmed the increased spacing basal because the presence of intercalant molecules in the clay, too confirmed by FTIR. The organoclay showed greater weight loss than the clay without modification. The structure had produced nanobiocomposites exfoliated and/or partially exfoliated.
Study of Nanocomposites of Polyamide 6.6/National Bentonite Clay
Authors: Kojuch Luana Rodrigues , Medeiros Keila Machado , Morais Dayanne Diniz de Souza , Araújo Edcleide Maria , Lira Hélio de Lucena
Published: August 2012

Polymers nanocomposites are a class of materials where inorganic substances with nanometrics dimensions are modified and used as dispersed loads in polymers matrices. In this work, polyamide 6.6 was chosen because of its excellent chemical, mechanical and thermal properties. The bentonite clay was treated with quaternary ammonium salt (Cetremide®) to make it organophilic and to improve the interaction with the polymer matrix. It was verified by the Torque Rheometry that the system with salt presented a bigger torque in relation to the torque of the system with untreated clay and pure polyamide 6.6. The nanocomposites presented an exfoliated and partially exfoliated structure, as evidenced by XRD. By DSC, it was observed that the treated clay increases the decomposition temperature of the nanocomposite.
Sintering of AISI M2 High Speed Steel with the Addition of NbC
Authors: Wentzcovitch Alexandre , Ambrozio Filho Francisco , da Silva Luís Carlos Elias , das Neves Maurício David Martins
Published: August 2012

The influence of adding 6 wt% (NbC) niobium carbide on the sintering temperature and microstructure of high speed steel - AISI M2(0.87% C, 5.00% Mo, 6.00% W, 4,00% Cr, 2.00% V and Fe bal.) powder was studied. The starting material was obtained by vacuum melting followed by atomization in water. The samples were axially cold compacted in a cylindrical matrix and then vacuum sintered at 1250 and 1350 °C. Dilatometry and differential scanning calorimetry measurements indicated an increase in sintering temperature with addition of niobium to the AISI M2steel. Optical and scanning electron microscope observations revealed a microstructure with uniformly distributed niobium carbides.
Synthesis and Characterization of Strontium and Calcium Titanate Polycrystalline Powders by a Modified Polymeric Precursor Technique
Authors: Muccillo R. , Carmo J.R.
Published: August 2012

SrTi0,65Fe0,35O3-δ, Ca0,5Sr0,5Ti0,65Fe0,35O3-δ, CaTi0,65Fe0,35O3-δceramic powders were synthesized by the polymeric precursor technique using CaCO3, SrCO3, C12H28O4Ti and Fe (NO3)3.9H2O. After calcination, each powder was heat treated at temperatures chosen according to data collected on thermogravimetric-differential thermal analysis experiments. The compositions were analyzed by X-ray diffraction for structural phase evaluation (either perovskite cubic or orthorhombic), laser scattering for determination of particle size distribution and average particle size, transmission electron microscopy (TEM) for observation of particle shape and average true size. Pressed powders sintered at 1250°C were analyzed by X-ray diffraction and X-ray fluorescence; their surfaces were observed by scanning probe microscopy (SPM) for topographical analysis of grains and grain boundaries. TEM results show that the powders consist of agglomerated nanoparticles. Sr-based compounds have cubic perovskite phases whereas Ca-based compounds are orthorhombic. SPM images show intergranular features which might be responsible for reported blocking of charge carriers observed in impedance spectroscopy diagrams.
Ceramic Processing of NBC Nanometric Powders Obtained by High Energy Milling and by Reactive Milling
Authors: dos Santos Tonello Karolina Pereira , Trombini Vânia , Bressiani Ana Helena de Almeida , Bressiani José Carlos
Published: August 2012

Production of nanometric ceramic powders is one of the most recent advances in materials science. However the large scale production of some materials is still a challenge. There are two approaches to the fabrication of nanomaterials that results in powders with distinct characteristics. In high energy milling the particle size is reduced by mechanical forces to achieve nanosized particles. Another technique is reactive milling in which nanometric particles are synthesized by mechanically activated reactions. In this work NbC nanoparticles were produced by high energy milling of commercial NbC and by self-sustained high energy reactive milling of Nb2O5-Al-C powder mixture. The NbC particles were desagglomerated for 1h in a planetary mill. The obtained powders were characterized by X-ray diffraction, scanning electron microscopy and laser diffraction. The objective of this study was to compare the efficiency of two employed techniques to determine the most of producing nanoscale NbC.
Purification of a Brazilian Smectite Clay
Authors: Lins Pedro Garcia , Valera Ticiane Sanches , Demarquette Nicole Raymonde
Published: August 2012

In this work, a commercial Brazilian clay (BUN Bentonit União Nordeste), was purified by three different processes. Impurities and iron oxides limit the use of the Brazilian clays in applications such as filler for nanocomposites. The first purification method refers to the separation of the colloidal fraction of the clay, to remove the remaining larger than clay-size impurities. The second step involves the removal of iron oxide or hydroxide (dithionite-citrate-bicarbonate method). Finally, hydrogen peroxide was used to remove from the clay the organic residues. The clays were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), and had their particle size distribution measured (laser scattering). The clays were treated with a quaternary ammonium salt, to investigate the modification in its cationic exchange capacity. XRD results showed that the structure of the clay was not significantly modified with the removal of iron, and that there was incorporation of the organic salt into the interlayer space. Approximately 30wt.% of the iron ion content was removed (XRF).
Effect of Glassy Phase Additions to Zirconia on its Sintering Behavior and Microstructure
Authors: de Oliveira Vera Lúcia Praxedes , Prado da Silva Marcelo Henrique , de Sousa Lima Eduardo , dos Santos Claudinei , Louro Luis Henrique Leme
Published: August 2012

TZP yttria-stabilized zirconia powder was mixed with two types of glasses as sintering additives: CAS glass and a bioactive glass. These additions were designed toward the material applications as bioceramics. The glassy phase was chosen to promote liquid phase sintering at lower temperature, when compared to pure material. This procedure contributed to reduce the fabrication costs while keeping the material biocompatibility. Each type of glass was added in concentrations of 1, 3, and 5 wt%. The prepared powders were uniaxially pressed at 50 MPa, and then sintered at 1300°C for two hours. The sintering behavior was evaluated by measuring the final sintered densities. It was found that the samples with bioactive glass additions were denser than those with CAS glass. Zirconia TZP powders without glassy additions would not sinter in this temperature. The microstructure of the sintered samples was characterized by SEM and XRD. The sintered ceramics exhibited both submicrometric and uniform grains. The analyzed grain sizes were slightly lower for the samples with CAS additions than for those with bioactive glass additions.