bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of the Polymer Content in the Preparation of Polymeric Membranes
Authors: Nóbrega Karine Castro , Leite Amanda Melissa Damião , Araújo Edcleide Maria , Lira Hélio de Lucena , da Paz Renê Anísio
Published: August 2012

This work aims to evaluate the effect of polymer content in the preparation of membranes obtained from polyamide 6/national clay nanocomposites. The polymeric membranes were produced varying the polymer content at 20 and 22% and using the technique of precipitation by immersion, which consists of three main steps: preparation a homogeneous polymer solution, scattering the solution on a surface forming a film of determined thickness and finally formation of polymeric structure of membrane by separation phases the system. The obtained results by scanning electron microscopy (SEM) indicated that the content of polymer changes the pore formation, the distribution and density, thereby obtaining membranes with different pore sizes, and it was possible to observe that the higher the polymer content, the lower will the pore diameter and more thicker will be the selective membrane layer.
Influence of Molecular Weight of Polyamide 6 in Obtaining of Nanocomposites with National Organoclay
Authors: da Paz Renê Anísio , Araújo Edcleide Maria , Pessan Luiz Antonio , de Mélo Tomás Jefférson Alves , Leite Amanda Melissa Damião , Medeiros Vanessa Nóbrega
Published: August 2012

Much attention is being given to developing nanocomposites with layered silicates, owing to the great need for advanced materials engineering and the fact that the pure polymers do not present the behavior or properties needed for certain applications within that context, the objective of this study was to influence of the molecular weight of polyamide 6 in obtaining nanocomposites with national organoclay. For this, the mixture of polyamide 6/ organoclay was processed in a twin screw extruder, and then was characterized by thermogravimetry (TG), X-ray diffraction (XRD) and heat deflection temperature (HDT). It was then possible to observe by XRD to obtain a structure exfoliated or partially exfoliated in the studied systems. For TG, it was found that the nanocomposites were stabilities higher than the pure polymer. And the values of HDT of systems were significantly higher than those of pure polyamide 6.
Factorial Design for Experimental Planning of Sludge Waste Incorporated Cement Pavements
Authors: Bahiense A.V. , Monteiro Sérgio Neves , Vieira Carlos Maurício Fontes , Alexandre Jonas
Published: August 2012

Cement pavement block are worldwide used to cover streets as an alternative to petroleum-base asphalt. These blocks are required to be not only strong but also dense and impact resistant. Packing of the precursor materials is an important factor in the final properties. In principal, this could be improved by the incorporation of another stable powder material like a local cost mineral residue or waste. The objective of this work is to investigate the effect of addition of a powder waste on the composition of a cement pavement block by means of an experimental planning. This planning was associated with a factorial design modeling based on composition variables including sand, gravel and the waste as well as the water/cement ratio. The response surfaces were evaluated and optimum proportion variables defined for best combination of properties.
Effect of Alumina Ceramic Powder Dispersion on Mechanical Properties of PolyPropylene Polymers
Authors: Silva Germannya D.A. , Alves Kleber G.B. , Almeida Yeda B. , Sanguinetti Ricardo A. , Yadava Yogendra Prasad
Published: August 2012

The objectives of this paper are study effect of dispersion of hard alumina (Al2O3) microparticles-filled polypropylene (PP) composites. Al2O3/PP composites containing 1.0 – 5.0 wt% of the Al2O3 were prepared through melt blending and specimens were produced through injection moulding technique. This study sets out to evaluate the influence of adding hard particles to the mechanical properties of the composite obtained while keeping the processing characteristics of the material. The material was characterized as thermo gravimetric analysis (TGA) and scanning electron microscopy (SEM). The tensile tests performed showed an increase in the mechanical properties of the composite (modulus and elongation (%)) by increasing the Al2O3 content. The SEM images show a change in the fracture behavior between pure PP (brittle fracture) and Al2O3/PP composites containing 3.0 and 5.0 wt % (ductile fracture). The research aims to establish a new parameter for the development of products and advances in the application of this material.
Nanomaterial as Microbial Agent to Paints
Authors: da Silva Wagner Claudio , Valenzuela-Díaz F.R.
Published: August 2012

Quaternary ammonium compounds are widely used as antiseptic agents, disinfectants, detergents and preservatives. In addition, quaternary ammonium compounds are often used as algaecides, and chloride dodecyl dimethyl benzyl ammonium chloride (benzalkonium chloride) is the most effective against these microorganisms. However benzalkonium chloride is not used as surface algaecide compound due its high hydrophobicity, bring on high leaching of this compound when the surface is exposed to high humidity. Currently, compounds such as diuron and s-triazine are used as algaecides, but had been detected in coastal regions in high levels concentration showing the leaching of these biocides. Then raise the necessity to develop a new algaecide to overcome the failings of leaching of the compounds used nowadays. Nanomaterial as organoclay is an excellent alternative because they have highly hydrophobic. Therefore in this work was synthesized a new nanomaterial using benzalkonium chloride, which was applied in a house paint formulation. The nanomaterial was characterized by the techniques of X-ray diffraction and thermo gravimetric analysis. The biocide capability as well as resistance to weathering of the nanomaterial was checked thought microbiological and leaching test. The new nanomaterial synthesized in this study had a high potential to be used as a microbial agent in paints.
Discrete Simulation of the Infrastructure for Diamond Embedded Metallic Saw Production
Authors: Sá A.C.A. , Rangel J.J.A. , Skury Ana Lúcia Diegues , Bobrovinichii Guerold S. , Monteiro Sérgio Neves
Published: August 2012

Diamond embedded cutting saws (DCSs) are basic tools commonly used in every ornamental stone processing operation from the extraction of the quarry block to the finishing of tiles. Diamond particles are the hard and abrasive essential component that has to be well adhered to the saw matrix, whether metallic, ceramic or polymeric. This work presents a computer simulation analysis and experimental design for an optimized manufacturing process of DCSs. This discrete simulation assesses the basic parameters involved in a possible industrial production in order to maximize the dynamics of the system and operational rules needed for best final products.
Hybrids Films Obtained on ZnNi Substrates: Effect of Withdrawal Speed
Authors: Kunst Sandra Raquel , Oliveira Cláudia Trindade , dos Santos Rogério Freitas , Bonino Jean Pierre , Ansart Florence , Malfatti Célia de Fraga
Published: August 2012

Due to the environment and economical questions, the use of cadmium coatings, in the aeronautical and automotive industries, has been prohibited. In this context, ZnNi coating alloys have been propose to replace cadmium coatings due to its properties. However, in order to postpone the corrosion of ZnNi alloy, hybrids films obtained by sol-gel process have been studied. In this work, hybrids films were obtained on ZnNi coating by dip-coating process from a sol constituted of alkoxide precursors: γ-methacryloxypropyl-trimethoxysilane and tetraethoxysilane with cerium nitrate addition (0.01 M). Two withdrawal speeds of substrates from the sol were applied: 5 cm.min-1 and 10 cm.min-1 .The films obtained were evaluated by morphological (SEM and AFM) and electrochemical characterization. The superior corrosion protection performance was observed for the ZnNi/hybrid film system obtained with withdrawal speed of 10 cm.min-1, thought, the presence of discontinuities were observed in this film.
Physicochemical and Environmental Characterization of Industrial Wastes in Powder
Authors: Quaranta Nancy E. , Caligaris Marta G. , Lalla Nicolás , Pelozo Gisela , Cristobal Adrián
Published: August 2012

In the present work residual powders of diverse industries are characterized from the environmental and physicochemical point of view, in order to determine the properties of them and establish the feasibility of reutilization or recycling. Cinders of additives, waste of scrap shredding process, LD converter steel slag and other powders of industrial processes were characterized by using optical and electronic microscopic techniques, semiquantitative chemical analysis, particle size distribution, X-ray diffraction analysis, thermal and thermogravimetric analysis, leaching test, among others. As a function of the obtained results some possible ways for recycling or reuse of these residual powders were proposed.
The Influence of Ageing in Pseudoboehmites Synthesis
Authors: Munhoz Jr. Antônio Hortêncio , Martins Marcos V. Surmani , Ussui Valter , Cruz Karina , Zandonadi Alexandre R. , de Miranda Leila Figueiredo
Published: August 2012

The developing of nanosystems has been intensely studied because of their efficiency when applied to pharmaceutical excipients, frequently called as drugs delivery systems. Sol-gel obtained pseudoboehmite, a fine synthetic ceramic precursor of alumina, shows itself as very promising due to its adsorption/desorption properties with pharmaceutical molecules. The use of factorial planning of two levels is very effective in preliminary studies about the possible influence of specific factors in the reagent conversion to a product. A method of pseudoboehmite obtainment was adopted, that has been already reported. The factorial planning 2³ used for the pseudoboehmite synthesis involved three variables of synthesis: temperature (A), the aluminum nitrate (Al (NO3)3·9H2O) concentration (B) and the ageing time (C). The X-ray diffraction data shows that the aging time has influence in the crystalinity of the synthesis product.
Study of Polyamide66/Bentonite Clay Hybrid Membranes Obtained by Solution
Authors: Medeiros Keila Machado , de Oliveira Sara Verusca , Araújo Elaine Patrícia , Araújo Edcleide Maria , Lira Hélio Lucena
Published: August 2012

The development of nanocomposites polymer matrix with clay from Brazil has been naturally abundant and low cost alternative. In this study, we obtained nanocomposites polyamide66 (PA66) with 1% and 5% of bentonite clay from Brazil, to be used as microporous organic/inorganic hybrid membranes. The clay was treated with a quaternary ammonium salt in order to make it organophilic. The membranes in the form of thin films were prepared using the technique of immersion-precipitation of solution from the nanocomposites. Treated clay and untreated clay were characterized by X-ray diffraction (XRD) and Thermogravimetry (TG). The membranes were characterized by TG and XRD. The result of XRD showed the presence of quaternary ammonium salt in the structure of clay, after organophilization. For TG, we observed that the treated clay showed higher thermal stability when compared to untreated clay. For TG, we observed that in general the membranes of PA66 with treated clay, present decomposition temperature higher when compared with untreated clay, thus revealing a greater thermal stability of membranes PA66 with treated clay. Through the X-rays patterns, it was found that membranes with 1% of nanoclay present exfoliated structure and can therefore be applied as microporous membranes.
Polyamide66/National Bentonite Clay Nanocomposites Membranes for Water-Oil Separation
Authors: Medeiros Keila Machado , Souza Dayanne Diniz , de Gouveia Silva Taciana Regina , Araújo Edcleide Maria , Lira Hélio Lucena
Published: August 2012

Membranes can be defined as polymer film that acts as a semipermeable barrier to filtration in a molecular scale, separating two phases. In this work, microporous membranes were obtained from hybrid organic/inorganic polyamide66 (PA66) and clay mineral from Paraíba State, treated with a quaternary ammonium salt in order to make it organophilic. The membranes in the form of thin films were prepared by immersion-precipitation technique from the nanocomposites obtained by solution, with a pre-determined reaction time of 2 h, with characteristics suitable to be used in microfiltration process for separation of the oil present in water. Samples of natural and organophilic clay were characterized by X-ray fluorescence (XRF) and Fourier transform infrared spectroscopy (FTIR). Meanwhile, the membranes were characterized by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results of FRX and FTIR confirmed the presence of quaternary ammonium salt in the clay structure after treatment with organic salt. Through DSC analysis it was observed almost no change in the melting temperature of the pure polyamide66 membranes. By SEM, it was revealed an asymmetric morphology consisting of a skin layer and a porous sublayer, showing the pore size distribution appropriated to water-oil separation.
Experimental Determination of the Permeability of Non-Porous Planar Structures during Operation of Equipment in Own Industrial Unit
Authors: Rocha Sandra Mara Santana , Vieira Luiz Gustavo Martins
Published: August 2012

The permeability is a physical property related to porous structures. It is a physical quantity that quantifies the resistance that a permeable matrix has to the flow of a particular fluid. Knowledge of the permeability of a filter media is important for the design, optimization and operation of various equipment, such as fabric filters, sedimentary, filtering hydrocyclones and others. There is the routine that the experimental determination of permeability of a filter medium is not made during the operation of industrial equipment, because they require a specific instrumentation or because it not presents a flat filtration. Therefore the experimental determination of permeability occurs out the industrial, in testing of laboratory by flat filtration. The two different times (industrial and laboratory) increase operation costs for the user by requiring uninstalling or fragmentation of the equipment to take it the laboratory. This work aimed to present a methodology (experiments combined with CFD techniques) in which it is possible to determine the permeability of a filter media (non-flat geometry) in their own manufacturing plant. According to the main results achieved, the proposed methodology was satisfactory, eliminating the need for characterization of filter media in the laboratory.
Differential Evolution Algorithm and Response Surface Methodology Applied to Turning Process Optimization
Authors: Sousa Marcelo N. , Lobato Fran S. , Malagoni Ricardo A.
Published: August 2012

Modern engineering problems are often composed by a large number of variables that must be chosen simultaneously for better design performance. The optimization of phenomenological model is an impossible task in terms of computational time. To improve this disadvantage, the Response Surface Methodology (RSM), defined as a collection of mathematical and statistical methods that are used to develop, to improve, or to optimize a product or process, is configured as important alternative to model real process. In the literature, different approaches based on optimization methods have been proposed to design system engineering. In this context, the Differential Evolution algorithm (DE) is a stochastic optimization method that is based on vector operations to improve a candidate solution with regard to a given measure of quality. For illustration purposes, in the present contribution the DE is applied to optimize multiple correlated responses in a turning process. As a case study, the turning process of the AISI 52100 hardened steel is examined considering three input factors: cutting speed, feed rate and depth of cut. The outputs considered were: the mixed ceramic tool life, processing cost per piece, cutting time, the total turning cycle time, surface roughness and the material removing rate. The optimization of cutting speed, feed rate and depth of cut indicate the better configuration of process to minimize the cost.
Rheological Behavior of Xanthan Gum Solutions to Estimate the Settling Velocity of Particles during Stops Drilling Operation
Authors: Moreira Bruno Arantes , Netto Letícia Goulart , de Faria Rafael Eduardo A. , Arouca Fábio de Oliveira , Damasceno João Jorge Ribeiro
Published: August 2012

The time-dependent viscosity is a desirable feature in drilling fluids. The gel formation process during circulation stops avoid the settling of particles generated by the drill bit, keeping the solids in suspension in the annular space. However, when larger particles breakdown the gel strength, interfere in the recovery of circulation, causing operational problems such as stuck pipe and other drilling complications. Within this context, this study evaluated the main factors that affect fluid-gel properties or the gelling process. Understanding the factors that influence the rheological behavior of drilling fluids was possible to estimate the settling velocity of particles during oil well drilling. Non-newtonian solutions were prepared with water and xanthan gum with mass concentration of 0.2%. The results showed that the gelation of xanthan gum solutions showed a rapid and non-progressive gelling as desired for drilling fluids.
Influence of Filtration Velocity on Cake Formation in Fibrous Filters
Authors: Nunes Deivid Marques , Alvarez Felipe Ferreira Gonçalves , Arouca Fábio de Oliveira , Rocha Sandra Mara Santana , Damasceno João Jorge Ribeiro
Published: August 2012

The filtration operation is one of the most widely used procedures in gas-solid separation due to its high removal efficiency, low cost and low sensitivity to variations in operating conditions. Therefore, the objective of this work is to study the effects of operating variables (pressure drop, filtration velocities and cleaning velocity) on the formation of filter cakes using gas-solid polypropylene filter media and particulate matter as for instance phosphate rock. The filtration velocities evaluated were 5, 7.5 and 10 cm/s with maximum pressure drops of 100, 200, 300 and 400mm H2O and filter cleaning velocities of 15 cm/s by the reverse air flow method. The cake filtration porosity was estimated using the classical Ergun equation (1952) in the literature. The results led to important correlations for the use of fibrous filters in the removal of particles suspended in in micrometer aerosols.
Rheological Study of Polyamide 6/Waste Styrene-Butadiene Rubber (SBR) Blends
Authors: da Silva D.F. , Bezerra Daniella Cibele , Reul Lizzia Tanira Albuquerque , Araújo Edcleide Maria , de Mélo Tomás Jefférson Alves , Medeiros V.N.
Published: August 2012

The application of polyamides is limited by low impact performance when notched in room temperature conditions. This situation is worsening, especially for use in temperatures below zero degrees Celsius. One way to outline this limitation is to prepare polymer blends where the dispersed phase is an elastomer, and then classified as an immiscible blend. Therefore, this study aims to develop polyamide 6/waste styrene-butadiene rubber (SBR) blends, with addition of compatibilizer PP-g-MA and PE-g-MA in order to achieve a balance between stiffness and tenacity. The results obtained with the rheological study showed that mixtures of PA6/PE-g-MA presented the best results in comparison with mixtures of PA6/PP-g-MA, indicating that there was probably a reaction between the components, which may allow a better dispersion and thus can achieve better properties.
Effect of Mechanical Activation on Microstructure and Mechanical Properties of Aqueous Colloidal Processed Nickel Metal Matrix Nanocomposites
Authors: Vieira L.E. , Neto João B. Rodrigues , Klein Aloísio Nelmo , Hotza Dachamir , Moreno Rodrigo
Published: August 2012

Previous works studied the colloidal processing of nickel-silica and nickel-titania nanocomposites fabricated via slip casting. A rheological approach was used to characterize and optimize a 30 vol.% nickel aqueous suspension with up to 10 vol.% SiO2and 5 vol.% TiO2nanoparticles. In this work, the effect of mechanical activation of Ni-SiO2and Ni-TiO2nanocomposites on microstructural and mechanical properties was studied. For this aim Ni-SiO2and Ni TiO2slip-cast compacts were attrition milled for up to 12 hours. Green bodies of the mechanical-alloyed powders were obtained by cold pressing (300 MPa). Next, those green bodies were annealed at 700°C for 1 h, repressed at 700 MPa and sintered at 900°C for 1 h in flowing Ar/5%H2atmosphere. Porous and dense materials were characterized by SEM/FESEM, Archimedes densities and Vickers microhardness measurements. Mechanical alloying produces a remarkable improvement on microstructure homogenization, sintering densification and hardness comparing with slip-cast composites.
Variation of Tungsten Oxide Reduction Mode Using Different High Energy Milling Conditions
Authors: Cintho Osvaldo Mitsuyuki , Tsai H.I. , Bär M. , de Castro M. , Monlevade E.F. , Capochi José Deodoro Trani
Published: August 2012

High energy ball milling has been used like alternative route for processing of materials. In the present paper, the reduction of tungsten oxide by aluminum in order to obtain metallic tungsten was studied using a SPEX type high energy mill. A powdered mixture of WO3and metallic aluminum, weighed according to the stoichiometric proportion with an excess 10% Al, was processed with hardened steel utensils using a 1:6 powder-to-ball ratio. The processing was carried out with milling jar temperature measurement in order to detect the reaction type. The temperature evaluation indicated the self-propagating reaction occurrence by fast increase of the jar temperature after a short milling time. The tungsten oxide reduction was verified by X-Ray Diffraction (XRD) analysis and the milling products were characterized by Scanning Electron Microscopy (SEM). The results were slightly different from the literature due to the mill type and milling parameters used in the work.
Structural Evaluation of Mechanically Alloyed (67-x)Ti-xZr-22Si-11B Powders
Authors: Ramos Alfeu Saraiva , de Miranda Marzullo Ana Carolina , Ramos Erika Coaglia Trindade , dos Santos Dalcy Roberto , Henriques Vinicius André Rodrigues
Published: August 2012

The present work reports on the structural evaluation of mechanically alloyed Ti-xZr-22Si-11B (x = 5, 7, 10, 15 and 20 at-%) powders. Milled powders and hot-pressed alloys were characterized by X-ray diffraction, electron scanning microscopy, and electron dispersive spectrometry. The Si and B atoms were preferentially dissolved into the Ti and Zr lattices during ball milling of Ti-xZr-22Si-11B (x = 7, 10, 15 and 20 at-%) powders, and extended solid solutions were achieved. The displacement of Ti peaks was more pronounced to the direction of lower diffraction angles with increasing Zr amounts in mechanically alloyed Ti-Zr-Si-B powders, indicating that the Zr atoms were also dissolved into the Ti lattice.
On the Phase Transformation in Mechanically Alloyed Ni-Nb and Ni-Ta and Ni-Nb-Ta Powders
Authors: Ferraretto Ana Clara , Ramos Erika Coaglia Trindade , Ramos Alfeu Saraiva
Published: August 2012

This paper reports on the phase transformation during the preparation of Ni-25Nb, Ni-25Ta, Ni-20Nb-5Ta and Ni-15Nb-10Ta (at-%) powders by high-energy ball milling from elemental powders. The milling process was performed in a planetary ball milling using stainless steel balls and vials, rotary speed of 300rpm, and a ball-to-powder of 10:1. To minimize contamination and spontaneous ignition the powders were handled under argon atmosphere in a glove box. The milled powders were characterized by means of X-ray diffraction techniques. Results indicated that the Ni atoms were preferentially dissolved into the Nb (and/or Ta) lattice at the initial milling times, which contributed to change the relative intensity on the diffraction peaks. After the dissolution of Nb (and/or Ta) into the Ni lattice, the Ni peaks were moved to the direction of lower diffraction angles in Ni-25Nb, Ni-25Ta, Ni-20Nb-5Ta, Ni-15Nb-10Ta powders, indicating that the mechanical alloying was achieved. .
Structural Evaluation of Mechanically Alloyed and Heat-Treated Ti-25at-%Si Powders
Authors: de Souza Marisa Aparecida , Ramos Erika Coaglia Trindade , Ramos Alfeu Saraiva
Published: August 2012

This work discusses on the structural evaluation of mechanically alloyed and heat-treated Ti-25at%Si powders. The milling process was conducted in a planetary ball mill using stainless steel balls/vials, 200 rpm and ball-to-powder weight ratio of 5:1, whereas the heat treatment was conducted under Ar atmosphere at 1100°C for 4 h. Samples were characterized by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy and energy dispersive spectrometry. The Si peaks disappeared after milling for 30h, indicating that the Si atoms were dissolved into the Ti lattice in order to form an extended solid solution. The Ti peaks were broadened and their intensities reduced for longer milling times whereas a halo was formed in Ti-25Si powders milled for 200h suggesting that an amorphous structure was achieved. The crystallite size was decreased with increasing milling times. A large Ti3Si amount was found in mechanically alloyed Ti-25at%Si powders after heating at 1100°C for 4h.
Preparation of Ni-Ti-Mo and Ni-Ti-Mo-Zr Alloys by High-Energy Ball Milling and Subsequent Hot Pressing
Authors: Pereira Gilda Maria Cortez , de Souza Marisa Aparecida , Hashimoto Tomaz Manabu , Henriques Vinicius André Rodrigues , Ramos Alfeu Saraiva
Published: August 2012

This work discusses on the preparation of Ni-45Ti-5Mo, Ni-40Ti-10Mo and Ni-46Ti-2Mo-2Zr (at-%) alloys by high-energy ball milling and hot pressing, which are potentially attractive for dental and medical applications. The milling process was performed in stainless steel balls (19mm diameter) and vials (225 mL) using a rotary speed of 300rpm and a ball-to-powder weight ratio of 10:1. Hot pressing under vacuum was performed in a BN-coated graphite crucible at 900°C for 1 h using a load of 20 MPa. The milled and hot-pressed materials were characterized by X-ray diffraction, electron scanning microscopy, and electron dispersive spectrometry. Peaks of B2-NiTi and Ni4Ti3were identified in XRD patterns of Ni-45Ti-5Mo, Ni-40Ti-10Mo and Ni-46Ti-2Mo-2Zr powders milled for 1h. The NiTi compound dissolved small Mo amounts lower than 4 at%, which were measured by EDS analysis. Moreover, it was identified the existence of an unknown Mo-rich phase in microstructures of the hot-pressed Ni-Ti-Mo alloys.
Rheological Behavior of Blends Gas-Water Atomized Stainless Steel Powder
Authors: Pascoali Suzy , Dominguini Lucas , Borges Joel Brasil , Wendhausen Paulo A.P.
Published: August 2012

This work evaluates the influence of particle morphology in mixture rheology. Range of particle morphology was used, changing in the mixtures the proportion of spherical powders and irregular powders, respectively gas and water atomized powders, in fraction of 0, 25, 50, 75 and 100% in mass. Components were obtained by mixtures with solid loading very close to critical values. Rheological analysis of the mixtures was elaborated in a capillary rheometry. The solids loading maximum was larger in 10% for the mixtures with only gas atomized powder, when compared to the mixture with just water atomized powder. The mixtures between gas and water atomized powders with maximum solid loading present difficulties in obtaining homogeneity and presents high viscosity.
Three-Dimensional Reconstruction of the Porosity of Pellets of Iron Oxide and Coal Powders by Serial Sectioning
Authors: Rocha E.P. , de Castro José Adilson , Fonseca Gláucio Soares
Published: August 2012

The self-reducing agglomerates produced from powders generated within the electric arc furnace and LD converters is of special interest in process of recycling due to the amount of iron and other metals of high economical value. However, the reducibility and inner pore structures play important role on the processing technology of these materials. Aiming at investigating the influence of the agglomerate structure, some two-dimensional metallographic techniques have been used to evaluate the porosity in clusters with inaccurate results, essentially due its three-dimensional features. From the processing technological point of view, the shape and distribution of inner porosity of the powders agglomerates are of fundamental importance due to their effects on the reaction rates involving the present phases taking place into the reduction stage. In this study a 3D serial sectioning imaging reconstruction is proposed to determine local inner porosities and detailed measurements of parameters of pores connections and tortuosities. The averaged porosities results are discussed and compared with traditional measurements based on pycnometry method.
Influence of a TiС Coating on the Wear Resistance of Fe-Diamonds Composites
Authors: Cabral Stenio Cavalier , de Oliveira Luciano José , Filgueira Marcello
Published: August 2012

Some diamond tools use iron in their composition, and it is known that iron is a strong catalyst for the graphitization of diamonds. This graphitization occurs mainly during the processing of composite materials - conventional sintering or hot pressing, and during cutting operations. This work studies the influence of the behavior of the wear and adhesion, of iron-diamond composites, by considering the use of TiC coated diamonds. Samples were prepared by mixing powders of Fe (40 μm) and diamond (425 μm), and subsequent hot pressing at 35MPa/900°C, for a time of 3 minutes. It was evaluated the mechanism of wear, and the behavior of the samples during diametral compression test. It was used the cumulative times of 2, 6, 12 and 20 minutes during the testing of abrasion.
Hard Metal Matrix Composites Reinforced with Cubic Boron Nitride
Authors: Bobrovinitchii Guerold Sergueevitch , Skury Ana Lúcia Diegues , Monteiro Sérgio Neves , de Azevedo Marcia G.
Published: August 2012

Cubic boron nitride (cBN) composites with hardmetal such as metal turning and rocks drilling, WC-Co, matrix are alternative substitutes for similar diamond composites in high speed machining operations and rocks and drilling. Although it possesses related technical properties close to diamond, cBN has the inconvenience of reacting with hardmetals. This deteriorates the composite properties. A possible solution to this negative effect is to apply high pressures during the sintering operation. In this work, powder mixtures of cBN with a hardmetal (WC15%Co) were subjected to pressures up to 7.0GPa and temperatures up to 1400°C for 40 seconds. The results showed significantly higher values of hardness and compressive strength as well as an improved wear resistance.
Preparation and Characterization: The Effect of Incorporation by Ion Exchange of Pt, Ni and Ru on a H-ZSM5 Zeolite
Authors: dos S. Barbosa Antusia , Barbosa A. Santos , Freire Rodrigues Meiry Glaúcia , Grau J. M.
Published: August 2012

The objective of this work was based on catalysts Pt, Ni and Ru supported on zeolite NH4ZSM-5 and characterize them. In this work monometallic bifunctional catalysts were prepared (Pt/NH4ZSM-5; Ni/NH4ZSM-5; Ru/NH4ZSM-5), all containing the same concentration of each metal supported by competitive ion exchange, using solutions of platinum complexes [Pt (NH3)4] Cl2, Nickel [Ni (NH3)6] Cl2and chloride Ruthenium III (RuCl3). The samples were characterized by chemical analysis by X-ray Spectroscopy Energy dispersive (EDS), X-Ray Diffraction (XRD), nitrogen adsorption (BET method). Through the analysis of X-ray diffraction, its possible to identify the preservation of the structure of zeolite ZSM-5 after the competitive ion Exchange with metals (Ni, Pt, Ru) and calcination. The dispersion of platinum and ruthenium in zeolite ZSM-5, didnt modify the textural characteristics of the zeolite, but the dispersion of nickel caused a change in values of surface area of catalysts.
Metal Matrix Composites from Powder Mixtures of Copper, Tungsten, Aluminum and Nanodiamonds
Authors: Skury Ana Lúcia Diegues , Bobrovinichii G.S. , Monteiro S.N.
Published: August 2012

Composites are versatile materials owing to their extensive possibilities of improving mechanical properties by distinct matrix reinforcements. In particular, it has been shown that diamonds are very effective reinforcement for metal matrix composites (MMC). In this work, the properties and microstructure of plain Al matrix composites reinforced with up to 50 wt.% of nanodiamonds as well as Cu, W, Al MMCs reinforced with 1% nanodiamonds were investigated. Composites were fabricated by processing metallic powders of Cu, W and Al as well as nanodiamond particles at sintering conditions of 2 GPa of pressure and 700°C for times up to 5 minutes. As compared to the other nanodiamond reinforced MMCs, the investigated composite presented improved microhardness and reduced wear in abrasive tests.
Effect of the Milling Time and Addition of a Grinding Agent of Quasicrystalline Powder Based on AlCuFeB Alloys
Authors: de Lima Cavalcante Danielle Guedes , Barros T.P.S. , Lima B.A.S.G. , dos Passos Tibério Andrade , de Lima S.J.G. , Gomes Rodinei Medeiros
Published: August 2012

Quasicrystalline (QC) materials represent a new class of alloys differing from amorphous and crystalline materials due to quasicrystalline periodicity and therefore unusual properties. Applications of quasicrystals range from surface coatings, thin films to reinforcements of ductile matrix composites such aluminum and, more recently, polymers. Quasicrystalline alloys show fundamentally different behavior compared to crystalline alloys even when their compositions are very similar, including low friction coefficient, high hardness and high brittleness. Due to this brittle behavior there are some limitations with respect to what methods can be used to process QC materials restricting their applications to powder form. One of the techniques for particle size reduction is mechanical milling which, however may lead to destabilization of the icosahedral phase. Therefore, there is a need to study the stability of quasicrystalline alloys during this comminution process. In the present study, AlCuFeB alloys were milled with the aid of a grinding agent that helps reduce overheating and thus controlling the QC powder stability. It was found that QC phase was destabilized after 10 h while the addition of a grinding agent led to milling times of 20 h without destabilizing the QC phase.
Coated Steel Surfaces with WC by Lasers Action
Authors: de Vasconcelos G. , Campos D.C. , Lima M.S.F. , Oliveira A.C. , Simões J.G.A.B. , Riva R.
Published: August 2012

In this work low carbon steel samples were coated by tungsten carbide (WC), and then the properties of the obtained coatings were evaluated, such as morphology, hardness, phase composition and dimension of the layer. The results indicate the formation of a new phase, composed of iron carbide in the base metal, a more dense coating has been obtained when the WC powder was sprayed directly on to the steel and then irradiated with the laser beam.
Study of Sol-Gel/Powder Metallurgy Technique for Processing Titanium Parts
Authors: Ribeiro Alexandre Antunes , Morani L.M. , Balestra Roseli Marins , Dantas F.M.L. , Rocha-Leão Maria Helena M. , Varella Marize
Published: August 2012

The powder metallurgy processing of titanium devices for biomedical applications has complex steps. In order to introduce a new processing route, this work studied a sol-gel technique combined with powder metallurgy for producing porous titanium samples. The process involves the mixture of titanium powders with sodium alginate suspension, which undergoes reticulation by calcium salt solution contact, forming a titanium/calcium alginate hydrogel in granule shape. Later, the hydrogel granules were dried and sintered in a high vacuum furnace for titanium particles consolidation and calcium alginate removal. The samples characterization was performed by scanning electron microscopy, optical microscopy, metallographic analysis, semi-quantitative X-ray fluorescence spectroscopy and X-ray diffraction. The results showed that the methodology used is adequate for producing porous titanium parts, since the samples presented no contamination, a uniform shape, particle consolidation and interconnected porosity. The research continues aiming to obtain samples with different bulk morphology, like, discs or bars for surgical implant applications.
The Possibility of Production of Cemented Carbide under High Pressure and High Temperature
Authors: Marques C.M.F.G. , Bobrovnitchii G.S. , Holanda J.N.F.
Published: August 2012

In this work the possibility of production of cemented carbide doped with rare-earth element (Y2O3) under condition of high pressure and high temperature (HPHT) was investigated. Initially, the cemented carbide powder (WC10wt.%Co) was submitted to conventional pressing at 800 MPa. The compacts were then sintered at 1400 °C for 40 s under a pressure of 5.5 GPa. The cemented carbide pieces were characterized in terms of relative density, coercive force, mechanical strength, microhardness, and wear resistance. The phase analysis was done by X-ray diffraction. It was established promising results on the production of cemented carbide under high pressure. Moreover, the addition of up to 1.5 wt.% of yttrium oxide in relation the cobalt phase enhanced the technical properties of the cemented carbide.
Processing of Ti Scaffolds by Sintering with Different Spacers
Authors: Tojal Concepción , Candel J.J. , Amigó Vicente , Devesa F.
Published: August 2012

Titanium is a material used in biomedicine for osseous implants due to their low density and biocompatibility. Its use in this field is limited by the lack of similarity of their stiffness with the stiffness of bones. In order to reduce this difference, powder metallurgy offers ways to develop porous materials with a reduced stiffness. The main objective of this work is to develop titanium scaffolds by space-holder technique, concretely with using two different spacers: Ammonium bicarbonate and sodium chloride. It has been studied the best way for remove spacer of green compacts, which have been sintered in high vacuum. Materials obtained by using of two spacers, have been analyzed in order to value different results in porosity, microstructural and mechanical properties. The stiffness of new materials was obtained by testing of three points in bending. This research shows that the manufacturing method of porous materials for bone replacement using space holder technique with ammonium bicarbonate or sodium chloride, allows obtained samples with slightly difference in physical, microstructural and mechanical properties.
Techniques and Tips to Optimize, Control and Stabilize the Atmosphere inside a Continuous Sintering Furnace
Authors: Silva Gian R.C. , Philips Thomas , Dwyer John J. , Zurecki Zbigniew
Published: August 2012

The quality of the atmosphere inside a sintering furnace plays a key role in the final properties of the sintered part. Properties such as the hardness, ductility, dimensions, carbon content, microstructure and magnetic properties among others are influenced not only by time and temperature, but also by the composition, flow rate and stability of the atmosphere within the furnace. The different physical zones within the furnace require different degrees of oxidizing or reducing power to develop the optimum properties in the final sintered part. Presented in this paper are practical techniques and technologies developed over the last 30 years of experiences with production sintering furnaces. The concept of distributed atmosphere introduction, combined with the use of directional atmosphere injectors, flame curtains, and gas curtains are used to stabilize and maintain the atmosphere profile within the furnace. Optimum and proven designs for atmosphere injectors, flame curtains, gas curtains and exhaust systems are presented.
Study of the Elasticity Module through Indentation Instrumented Technical of AlCuFeB Quasicrystalline Alloy
Authors: de Lima Bruno Alessandro S. Guedes , dos Passos Tibério Andrade , de Lima Cavalcante Danielle Guedes , de Lima Severino Jackson Guedes , Gomes Rodinei Medeiros
Published: August 2012

Quasicrystalline materials have unique properties such as high hardness, excellent surface properties, good resistance to oxidation and corrosion and low electrical and thermal conductivities. These materials can be obtained by conventional methods of metallurgy. However, quasicrystals are quite weak and this characteristic complicates their use in the form of billets for the manufacture of mechanical components. For this reason, the evaluation of mechanical properties of quasicrystalline materials using conventional methods, such as tension, compression, fatigue, among others, is not feasible. One method to evaluate the mechanical properties of quasicrystals is through instrumented indentation, once it is a very efficient tool for the calculation of properties such as hardness, fracture toughness and modulus of elasticity. The latter was the property studied in this work and that it is an important design criterion for the manufacturing of quasicrystalline alloys for their use in industry.
Microstructure and Wear of a Cu-Si-B Alloy and Diamond Composites Obtained in High Pressure and High Temperature Conditions
Authors: Skury Ana Lúcia Diegues , de Azevedo Marcia G. , Monteiro Sérgio Neves , Sideris Apostolos J.
Published: August 2012

Cu-Si-B alloys are a new generation of metal matrix for producing composites incorporated with diamonds for cutting tools. These alloys have been developed as a special matrix in order to improve the thermal properties of the diamond composites used in machining tool bits. Despite the industrial interest, not much has been reported on this type of composite matrix. In this work, samples of Cu-Si-B alloys were processed at high pressure and high temperature (HPHT) sintering conditions. The microstructure changes that occurred were evaluated. Microstructural aspects were observed by SEM. Compounds formed during sintering were studied by EDS. Wear tests were performed in sintered diamond particle incorporated composites. The results revealed significant advantages of Cu-Si-B alloy as matrix for these composites.
Production of Aerospace Tial Intermetallics for High Temperature Applications by Powder Metallurgy
Authors: Henriques V.A.R. , Dutra A.C.S.M. , Cairo C.A.A.
Published: August 2012

During the recent years, alloys based on the intermetallic compound TiAl have attracted a considerable interest as potential competitors to steels and superalloys. Gamma-TiAl alloys are potential replacements for nickel and conventional titanium alloys in hot sections of turbine engines, as well as in orbital platform vehicles. The alloy design and efficient routes of TiAl processing are important technological challenges. Powder metallurgy is a near net shape process that allows the parts production with complex geometry at low costs. In this work, samples of Ti-48Al-2Cr-2Nb (at.%) were prepared from elemental and pre-alloyed powders mixed for 2 h, followed by cold uniaxial and isostatic pressing and sintered between 800 up to 1400°C, for 1 h, under vacuum. After metallographic preparation, sintered samples were characterized by SEM (Scanning Electron Microscopy), density analyses and Vickers microhardness measurements. The results indicated the viability of the pre-alloyed route and the tendency of a full lamellar microstructure of alternating gamma and α2 phases in high sintering temperatures.
Plasma Sintering of the Steel Reinforced with Nanostructured Carbides
Authors: Silva Ariadne de Souza , de Almeida Edalmy Oliveira , Gomes Uilame Umbelino , Silva José F. , de Medeiros Indira Aritana Fernandes
Published: August 2012

Particle reinforced metal matrix composites have received considerable interest over many years and continue still under constant development to gain wider industrial applications. New technique of production of carbetos of refractory metals (WC, NbC, TaC, TaxNby) has been developed, synthesizing nanostructured carbides that show improvement of diverse properties of the materials to the gotten ones for the conventional processes. The properties of sintered composites are determined not only by the nature and quality of the raw materials employed but also by microstructure and porosity resulting from the processing techniques e sintering method. In this study, additions of 20 wt% NbC nanoparticles or micro-particles in the ferrite matrix were performed with the aim of improving the mechanical and use properties. Ancorsteel Fe 1000B powder from Hoengans Corp. was used together with the graphite, and a small amount of Fe3P, to induce liquid phase sintering. NbC nanoparticles or micro-particles were inserted into the Fe 1000B matrix by wet grinding (acetone) in a mill of planetary type of high energy. The angular velocity of the mill was kept constant at 300 rpm with milling time of 10 hours. The composites powders milled were annealed at 900 ° C for 1 hour under flowing hydrogen e argon, and a priori were pressed into cylindrical pellets under 600 MPa and sintered the plasma. Finally, the sintered pellets were evaluated through the testing: SEM, microhardness and density. It was noticeable the behavior of the composites Fe 1000B - NbC was affected by the content of nanoparticles of NbC added as well as by processing parameters, particularly plasma sintering.
Overspray Powder Characterization of Fe-Based Glassy Alloy
Authors: Afonso Conrado Ramos Moreira , Bolfarini Claudemiro , Botta Filho Walter José , Kiminami Claudio Shyinti
Published: August 2012

Powder of Fe72Nb4Si10B14 (%at) glassy alloy was obtained by gas atomization in order to investigate the possibilities of amorphous phase formation due to the high cooling rates (103 105 K/s) involved in this process. The ratio between the gas volumetric and the metal mass flow rates used was 1.0, and nitrogen (N2) was used as the atomization gas. The powder, sieved in different granulometric size ranges, was characterized through: X-ray diffratometry (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Fe72Nb4Si10B14 (%at) bulk metallic glass (BMG) showed completely or partially glassy structure depending on the size range. The obtaining of powders with glassy structure that could be applied as shot penning powder particles and thermal spray feeding powder for metallic coatings or would make possible the production of bulk glassy materials by warm consolidation of such powders or even a millimeters thick deposit obtained by spray forming with glassy or metastable microstructure that would be very interesting considering applications as soft ferromagnetic parts.
Evaluation of Changes in Microstructural Coatings Deposited by Thermal Spray
Authors: Arnt A.B.C. , da Rocha Márcio Roberto , Angioletto Elidio , Meller J.
Published: August 2012

In this work, microstructural changes in coatings deposited by hypersonic thermal spraying technique (HVOF) were subjected to adhesive wear tests. Materials subjected to wear lose efficiency, increase costs and direct or indirect way can stop large production systems. The mechanisms involved in this type of wear can be minimized by the microstructural changes that in many cases reduces or stops the loss of material. To perform this assessment coatings compounds of Cr3C225 (80 Ni-20 Cr) e Al2O3.TiO2 (87-13) investigated had similar hardness values (1000 HV) and chemical characteristics. Were subjected to the ASTM G99 using commercial hard metal pin 2 mm, load 50N force and tangential velocity of 0.5 m/s. Worn surfaces and debris were analyzed by optical microscopy, scanning electron microscope and mass loss. The results show high resistance sprayed coatings worn surfaces and debris were fragile nature with little loss of material during the tests.