bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparation between Pulsed Nd:YAG Laser Superficial Treatment and Ceramic Coating in Creep Test of Ti-6-4V Alloy
Authors: Reis Adriano G. , Reis Danieli A.P. , de Moura Neto Carlos , Onõro Javier , Oliveira H.S. , Couto Antônio Augusto
Published: October 2010

The objective of this work was evaluating the creep resistance of the Ti-6Al-4V alloy with superficial treatment of pulsed Nd:YAG laser and ceramic coating in creep test of Ti-6Al-4V alloy. It was used Ti-6Al-4V alloy as cylindrical bars under forged and annealing of 190oC by 6 hours condition and cooled by air. The Ti-6Al-4V alloy after the superficial treatment of pulsed Nd:YAG laser and ceramic coating was submitted to creep tests at 600°C and 125 at 319 MPa, under constant load mode. In the Nd:YAG pulsed laser treatment was used an environment of 40 % N and 60 % Ar, with 2.1 W of power and 10 m/s of speed. Yttria (8 wt.%) stabilized zirconia (YSZ) with a CoNiCrAlY bond coat was atmospherically plasma sprayed on Ti-6Al-4V substrates by Sulzer Metco Type 9 MB. The obtained results suggest the laser treatment on Ti-6Al-4V alloy improved its creep resistance.
Effect of Different Concentrations and Sizes of Particles of Rice Husk Ash - RHS in the Mechanical Properties of Polypropylene
Authors: Nascimento G.C. , Cechinel D.M. , Piletti R. , Mendes Erlon , Paula M.M.S. , Riella Humberto Gracher , Fiori M.A.
Published: October 2010

The minerals powders are much applied on polymeric materials to better its properties and to promote new applications. The rice husk ash powder - RHS is a mineral compound has been applied on polymeric compounds to increase the stiffness. This work presents studies of different sizes of particles of RHS applied at different concentrations in polypropylene. To study the mechanical properties were applied techniques of Charpy Impact Resistance and Uniaxial Tensile Analysis. The morphology was observed using the optical microscope. The results showed that the CCA may be an alternative in the incorporation of mineral loads in polypropylene, since this is a waste product generated in the production of rice, thus the complete closure of the production cycle of the cereal.
Evaluation of Heat Treatment and Ceramic Coating in Creep of Ti-6Al-4V
Authors: Sugahara Tarcila , Briguente L.A.N.S. , Yogi L.M. , Reis Danieli A.P. , de Moura Neto Carlos , Barboza M.J.R. , Couto Antônio Augusto
Published: October 2010

This study aimed to evaluate the resistance of a Ti-6Al-4V alloy in creep after heat treatments. It was used a Ti-6Al-4V alloy in cylindrical bars forms, forged condition and annealing at 190oC for 6 hours and cooled in air. The microstructure of Ti-6Al-4V alloy was evaluated after heat treatment and was submitted to creep tests at 600oC and stress conditions from 125 to 319 MPa at constant load. The Widmanstätten structure was obtained by heat treatment. Yttria (8 wt.%) stabilized zirconia (YSZ) with a CoNiCrAlY bond coat was atmospherically plasma sprayed on Ti-6Al-4V substrates by Sulzer Metco Type 9 MB. The alloy with Widmanstätten structure and ceramic coating shows greater resistance to creep and oxidation with a longer life time in creep. At higher stress condition, 600°C and 319 MPa, the Ti-6Al-4V alloy with ceramic coating didn’t show higher creep resistance. This condition presented higher tp value and the value. It occurred because at high stress condition the coating is very fragile, decreasing your creep resistance.
Oxidation Kinetics of the Sintered Iron Parts Steam Treated in an Industrial Continuous Furnace
Authors: Nunes Eduardo , Falleiros Ivan Gilberto Sandoval
Published: October 2010

It has been studied a steam treatment process in an industrial continuous furnace for sintered iron parts in a temperature range varying from 490 to 570 °C and sample´s sintered densities of 6,52 and 6,77 g / cm3 . The tests have showed oxidation kinetics with two stages, each of them obeying a parabolic law. The first stage was faster than the second. The oxidation time when the oxidation kinetics of the first stage has changed for the second stage showed off very sensitive to the process temperature and sintered densities of the parts which are in agreement with the process rate controlling mechanism that was found to be the iron diffusion through the oxide layer.
Covering Steel Surface with Carbon Black by CO2 Laser
Authors: de Vasconcelos G. , da Costa Gabriela N.P. , Chagas Daniele C. , Mello Carina Barros , Antunes Erica F.
Published: October 2010

This study investigate the laser surface hardening in tool steel, avoiding the high reflectivity of the metal to the CO2 radiation by covering the surface sample with black carbon. Hardening process using graphite was effective in many works in the word, although, the particles size of graphite powder was in the range of some micrometers. In order to reduce the particle size, the carbon black was used in the laser thermal treatment of 4340 steel. The microhardness change to 850HV, compared to the substrate of 250HV and the friction coefficient ranged 0.2 and 0.3, because of the covered surface by carbon black. These thin coating of carbon black reduced the wear rate near to a hundred in comparison to the surface without carbon coating.
Sulfur Dioxide Production from Phosphogypsum: Thermodynamic Analysis and Experimental Results
Authors: Henrique Humberto Molinar , Parreira Priciane Martins
Published: October 2010

Phosphogypsum or chemical gypsum is a by-product generated in the manufacture of phosphoric acid, generated in the proportion of 4 to 6 tons for every ton of acid produced by the fertilizer industry. Its reuse is important from the economic, social and environmental point of view. The purpose of this paper is to investigate the thermodynamic condition of sulfur dioxide recovering from thermal decomposition of phosphogypsum. The main advantage of this process is to return the sulfur dioxide to sulfuric acid manufacturing. In this case, sulfur demand by fertilizer industry and phosphogypsum generation could be greatly reduced. Experimental results were obtained from a lab scale rotary kiln. Theoretical approach and experimental setup were validated by using the actual data from thermal decomposition of limestone. Theoretical and experimental results showed the thermal decomposition of phosphogypsum is thermodynamically feasible only at high temperatures.
Biomass Pyrolysis: Use of Some Agricultural Wastes for Alternative Fuel Production
Authors: Kimura Lygia Maestri , Santos Larissa Cardoso , Vieira Paula Fraga , Parreira Priciane Martins , Henrique Humberto Molinar
Published: October 2010

The use of biomass for energy generation has aroused great attention and interest because of the global climate changes, environmental pollution and reduction of availability of fossil energy. This study deals with pyrolysis of four agricultural wastes (sawdust, sugarcane straw, chicken litter and cashew nut shell) in a fixed bed pyrolytic reactor. The yields of char, liquid and gas were quantified at 300, 400, 500, 600 and 700oC and the temperature and pressure effects were investigated. Pyrolytic liquids produced were separated into aqueous and oil phases. XRF spectroscopy was used for qualitative and quantitative elemental analysis of the liquids and solids produced at whole temperature range. Calorific value analysis of liquids and solids were also performed for energy content evaluation. Experimental results showed sawdust, sugarcane straw and cashew nut waste have very good potential for using in pyrolysis process for alternative fuel production.
Curie Temperature, Microstructure and Magnetic Properties Analysis of Fe-6.5wtSi Alloy Spray Formed as Function of Process Parameters
Authors: Muniz J.C.R. , Silva M.C.A. , Bolfarini Claudemiro , Sobral M.D.C.
Published: October 2010

Fe-6.5%Si alloy spray formed has the Curie temperature variation measured as a function of the parameters process. In this work the magnetic transition temperature was obtained by Differential Scanning Calorimeter although it can be also gotten by Vibration Samples Magnetometer. The process parameters controlled were gas pressure (P), tube diameter (T) and fly height (H) and the properties analyzed were coercive force, maximum permeability, power loss and Curie temperature. The chemical composition was determined using the Curie temperature. The microstructure of deposits was observed in different conditions of light microscopy, bright field, polarized light and dark field, and the grain size was measured according to ASTM 112-95. The process parameters combination P5T6H360 has produced the minimum power loss of 2.26 W/kg and maximum permeability of 9,000. The Curie temperature measured was 683°C, which indicates a Si content of 6.5wt%.
The Effect of Cu, P, Ga and Gd on Microstructure and Magnetic Properties in the PrFeCoBNb HD Sintered Magnets
Authors: Mendes T. , Silva S.C. , Périgo E.A. , de Faria Jr. Rubens Nunes , Takiishi Hidetoshi
Published: October 2010

An evaluation of the effect of alloying elements on the microstructure and magnetic properties of Pr15FebalCo8B7Nb0.05Mx (M = Cu, P, Gd and Ga; 0 ≤ x ≤ 0.25) sintered magnets has been carried out. A mixture of alloys and the high-energy milling technique have been used to prepare the magnets. The alloying elements have influenced the remanence, intrinsic coercivity and particularly the squareness factor (SF). Phosphorus addition improved (BH)max (254 kJm-3 ) and SF around 10% (0.89). The same improvement addition on intrinsic coercivity was observed with Gallium (1100mT) compared to the standard composition Pr15FebalCo8B7Nb0.05 (1000mT) magnet. Comparisons between the squareness factors obtained using the J×μ0H curve profile (SF), the estimated (sf) using microstructural parameters and Sf using a (BH)max and Br correlation have also been carried out.
The Critical Volume for Nucleation
Authors: de Campos Marcos Flavio , de Castro José Adilson
Published: October 2010

In magnets based in phases with high magnetocrystalline anisotropy like Nd2Fe14B or SmCo5 there is a competition between magnetostatic energy and domain wall energies. If the grain size is large, the formation of domain walls is energetically favorable. When the formation of domain walls is an unfavorable process, coercivity is larger. A better comprehension of this phenomenon is possible if the energy necessary for the first domain wall formation is properly evaluated. To address this problem, the magnetostatic energy of a sphere magnetized in two opposite directions, separated by a domain wall, is calculated using Legendre Polynomials. The data allow the determination of the reversible volume for nucleation. It is predicted a “recoil effect”, the magnetization may be reversible until a given volume of reverse magnetization.
Effect of Grain Size on the Coercivity of Sintered NdFeB Magnets
Authors: de Campos Marcos Flavio
Published: October 2010

Sintered NdFeB magnets typically exhibit grain size above 2 micrometers, a value above the single domain particle size (~0.3 micrometers). It is discussed how to obtain relationships between grain size and coercivity with energy balance models, considering formation and annihilation of domain walls as a dissipative process. In the case of nanocrystaline magnets, the Stoner-Wohlfarth model is very suitable. For larger grain sizes, the contribution of the magnetostatic energy of each grain has to be considered. From the concept of meta-stability of domains and domain walls structure, a relation between coercive field and grain size can be estimated.
Microstructure and Microanalysis Studies of Copper-Nickel-Tin Alloys Obtained by Conventional Powder Metallurgy Processing
Authors: Monteiro Waldemar Alfredo , Carrió Juan Alfredo Guevara , Masson Terezinha Jocelen , Abreu C.D. , Marques I.M. , da Silva L.C.E.
Published: October 2010

The aim of this article was to analyze the microstructural development in samples of Cu-Ni-Sn alloys (weight %) obtained by powder metallurgy (P/M). The powders were mixed for 1/2 hour. After this, they were pressed, in a cold uniaxial pressing (1000 kPa). In the next step the specimens were sintered at temperatures varying from 650 up to 780°C under vacuum. Secondly, the samples were homogenized at 500oC for several special times. The alloys were characterized by optical microscopy, electrical conductivity and Vickers hardness. X rays powder diffraction data were collected for the sintered samples in order to a structural and microstructural analysis. The comparative analysis is based on the sintered density, densification parameter, hardness, macrostructures and microstructures of the samples.
Optimizing the Heat Treatment of Rare Earth-Transition Metal Sintered Magnets
Authors: de Campos Marcos Flavio , de Castro José Adilson
Published: October 2010

Rare earth transition metals magnets, as for example SmCo5, NdFeB and Sm(CoCuFeZr)z magnets are, very often, submitted to a post-sintering heat treatment where the coercivity increases. In many cases, a slow cooling between the sintering and the annealing temperatures is applied. To optimize the time and cooling rate of heat treatment, it was developed a model using the finite volume method. This model takes into account the diffusivities of the different atom species and also the boundaries of phase diagrams.
The Influence of Praseodymium Content on the Hydrogen Absorption Capability of PrFeCoBNb Magnetic Alloys
Authors: Périgo E.A. , Galdino Gabriel Souza , Matos Jivaldo R. , Takiishi Hidetoshi , de Faria Jr. Rubens Nunes
Published: October 2010

The hydrogen absorption capability of PrxFe77.9-xCo16.0B6.0Nb0.1 (12.0 ≤ x ≤ 14.0) magnetic alloys was evaluated. A practical methodology was developed so that the hydrogen pressure decrease inside a closed system was correlated to the mass gain (%W) of the sample. %W increases linearly with the Pr concentration in the magnetic alloy either in the as-cast state or annealed during 20 hours at 1070°C. Comparisons between %Wtheoretical and %Wexperimental showed a satisfactory agreement.
Interstitial Control in Titanium Alloys Produced by Powder Metallurgy
Authors: Henriques Vinicius André Rodrigues , Petroni S.L.G. , Paula M.S.M. , Cairo Carlos Alberto Alves , Galvani Eduardo T.
Published: October 2010

The titanium alloys are used for applications that demand high performance, including surgical implants and aerospace applications. Powder metallurgy is an advantageous alternative for titanium parts production with complex geometries at a relative low cost. Despite that, it is verified that the introduction of interstitial elements (oxygen, nitrogen and carbon) wile processing these alloys, though can increase hardness and mechanical resistance, which is frequently related to the reduction of ductility and fragility increase. The objective of this work is to investigate the influence of the interstitial elements in commercially pure Ti and Ti-13Nb-13Zr alloy produced by powder metallurgy (P/M). Samples were produced by the mixing of hydrided metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering at 1400 °C, in vacuum. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. The interstitial content was analyzed by Leco equipment. It was shown that the samples were sintered to high densities with a Widmanstatten microstructure. The oxygen and nitrogen contents are above the ELI (Extra Low Interstitial) and the critical issues were identified in the original blended elemental route.
Effect of Variables the HDDR Processing on Magnetic Properties and Microstructure in Permanent Magnets Based on Pr-Fe-B
Authors: Santos P.B. , Silva S.C. , de Faria Jr. Rubens Nunes , Takiishi Hidetoshi
Published: October 2010

The first goal of this work involved the study of the effect of variables the HDDR processing, such as: the added pressure of H2 in the system, the time of heat treatment and recombination of Pr12Fe65.9Co16B6Nb0.1 alloy with the aim of improving the magnetic properties like the magnetic properties of the Pr14Fe63.9Co16B6Nb0.1 alloy (Br= 865mT and iHc= 790mT). The second aim of the work involved the characterization of HDDR powders that were analyzed by X-ray diffraction for identification and quantification of crystalline phases. These materials were analyzed by scanning electron microscopy (SEM).
Crystallite Size and Magnetic Properties of HDDR Powders Obtained from PrFeCoBNb Alloys
Authors: Silva S.C. , Duvaizem José Hélio , de Faria Jr. Rubens Nunes , Takiishi Hidetoshi
Published: October 2010

The first goal of this work involved the study of HDDR powders obtained from annealed alloys with the general formula: PrxFe77.9-xCo16B6Nb0.1 (x = 12; 12.5; 13; 13.5 and 14). The alloys were processed at desorption / recombination temperature of 840°C. The highest magnetic properties were obtained with 13.5 at. % Pr (Br= 1000mT and µ0iHc= 890mT). The alloy with a minimum praseodymium content (12 at. %) exhibited the lowest magnetic properties (Br= 350mT e iHc= 120mT). The second aim of the work involved the characterization of HDDR powders using X-ray diffraction for phase quantification and mean crystallite sizes determination of the hard magnetic phase. The processed powders were characterized by scanning electron microscopy (SEM).
Effect of the Reinforcement Volume Fraction on Mechanical Alloying of AA2124 – SiC Composite
Authors: Candido Grazziani Maia , Guido Vanessa , Silva Gilbert , Cardoso Kátia Regina
Published: October 2010

Mixtures of AA2124 aluminum alloy powder and SiC particles at volume fractions of 10 vol.% and 20 vol.% were milled in a high energy planetary ball mill under an argon atmosphere, for times of 2.5h to 60 h, aiming to produce Al alloy-SiC nanocomposites. Optical microscopy (MO) and scanning electron microscopy (SEM) were used to evaluate the morphological and microstructural evolution of the powder composite, occurred during mechanical alloying. The crystallite size was determined using the Williamson-Hall method to analyze the X-ray peak broadening. It was observed that increasing the volume fraction of SiC, the mechanical alloying stages were accelerated: a finer composite powder was obtained at a shorter milling time as well as the morphology of the particles became more equiaxed. The XRD analysis showed the reduction of crystallite size of the aluminum alloy matrix with increasing milling time and that this effect is more pronounced with high volume fraction of SiC. The results show that the increase in the volume fraction of reinforcement particles increases the work hardening and fracture occurrence in the aluminum alloy powder during the milling, affecting the structural evolution of the composite.
High-Energy Mechanical Milling of Ultra-High Molecular Weight Polyethylene (UHMWPE)
Authors: Gabriel Melina C. , Mendes Luciana B. , de Melo Carvalho Benjamim , Pinheiro Luís A. , Capochi José Deodoro Trani , Kubaski Evaldo T. , Cintho Osvaldo Mitsuyuki
Published: October 2010

Ultra-high molecular weight polyethylene (UHMWPE) is a polyethylene with a very long chain, which provides excellent features, however it makes the processing difficult due to high melt viscosity. Many studies intend to found out means to make its processing easier. Recently, the high-energy mechanical milling has been used for polymeric materials and it was detected that physical and chemical changes occur during milling. In such case, powder of UHMWPE was milled in three types of mills: SPEX, attritor e planetary, in different times of milling. The polymer was characterized by SEM and XRD. Thus, it was observed that the material processed in attritor mill showed larger phase transformation from orthorhombic to monoclinic. This is most likely due to the smaller milling temperature of attritor mill when compared with the other two mills and the high shear force generated during milling.
An Investigation on the Mechanical Alloying of TiFe Compound by High-Energy Ball Milling
Authors: Falcão Railson Bolsoni , Dammann Edgar Djalma Campos Carneiro , da Rocha Cláudio José , Neto Ricardo Mendes Leal
Published: October 2010

This work reports the efforts to obtain TiFe intermetallic compound by high-energy ball milling of Ti and Fe powder mixtures. This process route has been used to provide a better hydrogen intake in this compound. Milling was carried out in a SPEX mill at different times. Strong adherence of material at the vial walls was seen to be the main problem at milling times higher than 1 hour. Attempts to solve this problem were accomplished by adding different process control agents, like ethanol, stearic acid, low density polyethylene, benzene and cyclohexane at variable quantities and keeping constant other milling parameters like ball to powder ration and balls size. Better results were attained with benzene and cyclohexane, but with partial formation of TiFe compound even after a heat treatment (annealing) of the milled samples.
The Effect of Mechanical Activation of Elemental Powders on Combustion Synthesis of NbAl3
Authors: da Rocha Cláudio José , Neto Ricardo Mendes Leal
Published: October 2010

The effect of mechanical activation procedures on the combustion synthesis of NbAl3 was investigated. The activation was carried out by a two-step high energy ball milling procedure. In the first milling, aluminum and niobium were milled separately (pre-activation). The mixture of pre-activated powders was then activated in the second milling. Reaction synthesis, by simultaneous combustion mode, was conducted on compacted pellets made of powder mixtures with and without pre-activation. The thermal behavior of the compacted pellets upon heating was recorded and the main thermal combustion reaction characteristics were evaluated. The two-step procedure produced aggregates with a globular dispersion of niobium due to increased particle hardness and decreasing mean particle size during pre-activation milling. Analysis of pellet thermal behavior showed the two-step milling procedure could enhance reaction performance by increasing maximum reaction heating rate and temperature gain during reaction.
Formation of Si0.80Ge0.20 Solid Solution by Mechanical Alloying
Authors: Chen Y.A. , Silva Cosme Roberto Moreira , Rowe D. Michael
Published: October 2010

In general, semiconductor materials for thermoelectric generation prepared by vacuum metallurgy shows a relatively high value of figure-of-merit. However, differences in some properties of alloys elemental constituents can cause processing problems. Recently, Mechanical Alloying (MA) has been used to produce polycrystalline thermoelectric materials, such as (Bi,Sb)2 and (Te,Se)3(1). The industry is using this process since early 70’s to produce oxide dispersion strengthened alloys and those with widely different melting temperatures (2) In the present work, Si0.80Ge0.20 alloys were prepared via Mechanical Alloying (MA), using 99.9 % pure silicon and germanium powders, with a sieve size of 100 mesh. The MA has been performed, for several balls - to - powder ratio, in a SPEX 8000 vibratory high energy milling with tungsten carbide balls. Time for alloy formation was in a range from 3 to 9 hours, corresponding to charge ratio of 12:1 and 4:1, respectively. After two hours of processing time, the grinding temperature reached 80 0 C, and remained at this level until the end of the process. It was possible to follow the SiGe alloy formation by x-ray diffractometry, as the peak lines positions of elemental Si and Ge were continuously shifted, and end up to merge into a single broad peak. There was a convergence of the individual lattice parameters of Si and Ge to a single value of 5.470 A, measured within the limit of  0.005 A. For the Si0.80Ge0.20 system evaluated in this work, the alloying progress occurred continuously, and changed inversely with charge ratio.
Synthesis of PbTe Intermetalic Compound by Mechanical Alloying
Authors: Chen Y.A. , Silva Cosme Roberto Moreira , Rowe D. Michael
Published: October 2010

The formation of PbTe intermetallic compound by mechanical alloying (MA) has been investigated. The elemental starting materials were 99.5% pure lead and tellurium, with a sieve size of 80 and 200 mesh, respectively. A SPEX 8000 shaker milling was used to perform the MA, using WC balls as milling media in a cylindrical hardened tool steel vial. X-ray diffraction analysis was performed with a profile-fitting program, to evaluate time evolution of the alloy formation. An exotermical reaction occurs on PbTe formation, with entalphy H= - 16.3 Kcal/mol. The *T value is confirmed by the heat exchange equation *Q = |*Hf | =* i (mici ) *T, where the summation comprises the mass and specific heat of vial, balls and powder material. For the standard milling conditions employed, the PbTe formation occurs at aproximately 90 seconds of milling, when using charge ratios between 3:1 and 7.5:1. However, for lower charge ratios (8:1 to 10:1), isolated reactions at the mixture occurs, but the amount of material is not enough to raise the temperature of adjacent regions, and the propagation of the reaction is avoided. There is therefore a minimum amount of powder (“critical mass”), and below this value the reaction will not be self-sustained.
Microstructural and Electrical Investigation of Cu-Ni-Cr Alloys Obtained by Powder Metallurgy Method
Authors: Carrió Juan Alfredo Guevara , Carvalhal M.A. , Ayabe L.M. , da Silva L.C.E. , Silva Junior R.V. , Monteiro Waldemar Alfredo
Published: October 2010

The aim of this work, using the powder metallurgy process, is to synthesize metallic alloys with high mechanical strength and high electric conductivity, after melting optimizing and thermal treatments. The Cu-Ni-Cr (wt%) alloys are characterized in their mechanical and electrical properties as well as the obtained microstructure. Through the process of powder metallurgy, contacts and structural parts can be obtained. The alloys elements are added to copper with the intention to improve their strength, ductility and thermal stability, without causing considerable damages in their form, electrical and thermal conductivity, and corrosion resistance. The metallic powders were mixed for a suitable time and then they were pressed in a cold uniaxial pressing (1000 kPa). Afterwards, the specimens were sintered in temperatures varying from 700 up to 800oC under vacuum. At last, the samples were homogenized at 550oC under vacuum, for special times. The comparative analysis is based on the sintered density, densification parameter, hardness, macrostructures and microstructures of the samples. The alloys were characterized by optical microscopy, x rays powder diffraction, electrical conductivity and Vickers hardness.
The Influence of the Milling Environment on the Structure of a W-Cu Composite
Authors: Costa Franciné Alves , Ambrozio Filho Francisco , Silva A.G.P. , Gomes Uilame Umbelino , de Lima Severino Jackson Guedes , Acchar Wilson
Published: October 2010

This work reports an investigation about the influence of the environment of milling on the characteristics of the powders and on the structure and density of sintered samples made of these powders. Mixtures of composition W-30wt%Cu were milled for 51 hours in a high energy planetary mill in dry and wet (cyclohexane) conditions. The milled powders have composite particles. The powders were pressed and sintered at 1050º, 1150º and 1200°C under flowing hydrogen. The isothermal times were 0 minutes for the first two temperatures and 60 minutes for the latter. The samples reached around 95% of relative density. The powders were characterized by means of XRD and SEM. The sintered samples were characterized by means of SEM, optical microscopy and density measurement.
Is Ni a Good Substitue for Co in PM Diamond Cutting Tools?
Authors: Oliveira H.C.P. , Cabral Stenio Cavalier , Guimarães R.S. , Filgueira Marcello
Published: October 2010

This work have like object to research the metallic matrix, Ni-Sn and Co-Sn, and subsequent to add up to diamond for analyses the possibility the to replace the Co with Ni in the metallic matrix for to act like binder for subsequent use in cutting tools. The metallic powders and the composites were mixed and then hot pressed and processed at 35MPa/800°C/3 min. In these sintered samples, it was made hardness HRB, wear resistance test and scanning electron microscopy for to identify which one matrix owns better mechanical resistance and diamond adherence required for diamond cutting tools.
New Integrated Cermet Powder Preparation and Consolidation Method–Ni-ZrO2 Case
Authors: Restivo Thomaz Augusto Guisard , de Mello-Castanho Sonia Regina Homem
Published: October 2010

A new integrated method for direct preparation of cermet materials is proposed consisting of a powder processing method allied to a special sintering step. The powder is obtained by mechanical alloying route where a specific morphologic design is searched to yield thin metal plated ceramic particles. These have the proper characteristics to engage the sintering by activated surface (SAS) consolidation method. The last is triggered by partial evaporation and reactive sintering of thin metal layers, therefore exposing high active surfaces with superior sinterability. Refractory sacrifice metal components are found to play an important role. The application of the integrated method to Ni-ZrO2 cermet with selected metal additives is investigated. Sintering temperatures can be reduced by more than 300°C for the same final density range. The resulted powders and pellets microstructures are analysed accordingly to the projected expected ones. The thermophysical and electrical properties measurements are performed for evaluate phases percolation.
Effect of Cr3C2-NiCr Powder Characteristics on Structure and Properties of Thermal Sprayed Nanostructured Coatings
Authors: Padial A.G.F. , Cunha C.A. , Correa Olandir Vercino , de Lima Nelson Batista , Ramanathan Lalgudi Venkataraman
Published: October 2010

In most engineering fields there is increasing demand for materials with enhanced physical properties. Components of complex systems exposed to severe environments often require coatings for adequate thermal insulation and to prevent wear, erosion and/or oxidation. Coatings prepared with nanostructured material have, in general, exhibited higher hardness and strength compared to conventional coatings. This paper presents the microstructure, mechanical properties, thermal stability and erosion-oxidation resistance of HVOF (High Velocity Oxygen Fuel) sprayed coatings of Cr3C2-X(Ni20Cr) prepared using nanocrystalline and as-received (AR) powder as feedstock. Details about nanocrystalline powder synthesis and characterization are also presented.
Synthesis and Characterization of TiO2 Nanoparticles by the Method Pechini
Authors: Zoccal João Victor Marques , Arouca Fábio Oliveira , Gonçalves José Antônio Silveira
Published: October 2010

In recent years, scientific research showed an increasing interest in the field of nanotechnology, resulting in several techniques for the production of nanoparticles, such as methods of chemical synthesis. Among the various existing methods, the Pechini method has been used to obtain nanoparticles of titanium dioxide (TiO2). Thus, this work aims to synthesize and characterize nanoparticles of TiO2 obtained by this method. The technique constitutes in the reaction between citric acid with titanium isopropoxide, resulting as the product the titanium citrate. With the addition of the ethylene glycol polymerization occurs, resulting in a polymeric resin. At the end of the process, the resin is calcined to remove organic matter, creating nanoparticles of TiO2. The resulting powders were characterized by thermogravimetric analysis (TGA) and thermal differential analysis (DTA), X-ray diffraction, absorption spectrophotometry in the infrared, method of adsorption nitrogen / helium (BET method) and scanning electron microscopy. The results obtained in the characterization techniques showed that the Pechini method is promising in obtaining nanosized TiO2.
Porous 3-D Titanium Substrates Obtained by Powder Metallurgy for Nanodiamond Film Growth
Authors: Braga N.A. , Cairo Carlos Alberto Alves , Ferreira N.G. , Baldan M.R. , Trava-Airoldi Vladimir J.
Published: October 2010

Power metallurgy has been used to produce compacts by two different routes. In this work, porous three-dimensional (3-D) substrates were prepared by the conventional pre-forms sintering method. Titanium powders were uniaxial pressed at 110 Mpa and vacuum (1 x 10-5 Pa) sintered at 1500 K. Another group of substrates were obtained by the space holder technique. Irregular shaped carbamide particles (210 – 250 m diameters) were mixed to Ti powders, pressed and sintered. Before the sintering the compacts were heated at 470 K for 3 h to eliminate the spacing holder agent. Nanodiamond films were grown by hot-filament chemical vapor deposition technique on such substrates at 870 K from a mixture of Ar/H2 (80%-18,5%) respectively and a solid carbon source. SEM images show the substrates totally covered by a nanodiamond film including deeper planes. Raman Spectra confirm the good quality of the nanodiamond film.
Preparation of Cutting Inserts with Binder of UHCS
Authors: Martinez M.A. , Calabrés R. , Abenojar J. , Velasco Francisco
Published: October 2010

From studies on the Damascus steel, the manufacturing of ultra-high carbon content steel (UHCS) by powder metallurgy has been carried out in previous works. UHCSs have been manufactured mixing iron and graphite powders, uniaxial compacting, and sintering in vacuum atmosphere. Finally, they have been hot-rolled at relatively low temperatures using their superplasticity to obtain optimum properties. High hardness particles of SiC (micro and nanometric size) and diamond (with and without coating) were added to UHCS to produce inserts for cutting discs. Their mechanical properties have been studied through bending tests and hardness measurements. SEM observations have shown how the structure of the steel and the particles has been modified depending on the performed thermo-mechanical treatment. This way, it is possible to justify the effect of the addition of high hardness particles in the reduction of plasticity and wear resistance of the material.
Beta Ti-45Nb and Ti-50Nb Alloys Produced by Powder Metallurgy for Aerospace Application
Authors: Martins G.V. , Silva Cosme Roberto Moreira , Nunes C.A. , Trava-Airoldi Vladimir J. , Borges L.A. , Machado João Paulo Barros
Published: October 2010

Beta titanium alloys parts are used on advanced aerospace systems because of their high strength to weight ratio and excellent corrosion resistance. Production of powder metallurgy titanium alloys components may lead to a substantial reduction in the cost, compared to those produced by conventional cast and wrought processes, because additional working operations and material waste can be avoided. In this work, beta Ti-45Nb and Ti-50Nb were produced by the blended elemental technique, followed by uniaxial and cold isostatic pressing with subsequent densification by sintering. Sintered samples were characterized for phase composition by XRD, microstructure by SEM, hardness by Vickers indentation, specific mass by the Archimedes method and elastic modulus by resonance ultrasound. The sintered samples presented only the beta phase, higher hardness and lower elastic modulus when compared to Ti6Al4V alloy and experimental specific mass value near theoretical specific mass. These characteristics are adequate for application on several aerospace parts.
Structural and Electrical Properties of Copper-Nickel-Aluminum Alloys Obtained by Conventional Powder Metallurgy Method
Authors: Monteiro Waldemar Alfredo , Carrió Juan Alfredo Guevara , Da Silveira C.R. , Vitor E. , Buso S.J.
Published: October 2010

This work looked for to search out systematically, in scale of laboratory, copper-nickel-aluminum alloys (Cu-Ni-Al) with conventional powder metallurgy processing, in view of the maintenance of the electric and mechanical properties with the intention of getting electric connectors of high performance or high mechanical damping. After cold uniaxial pressing (1000 kPa), sintering (780oC) and suitable homogenization treatments (500oC for different times) under vacuum (powder metallurgy), the obtained Cu-Ni-Al alloys were characterized by optical microscopy, electrical conductivity, Vickers hardness. X rays powder diffraction data were collected for the sintered samples in order to a structural and microstructural analysis. The comparative analysis is based on the sintered density, hardness, macrostructures and microstructures of the samples.
Fluid Dynamic Study of the Fluidized Bed Wit Jambu Seeds (Sphilantes oleracea L.)
Authors: Lourenço R.O. , Costa C.M.L. , Sandra Cristina dos Santos Rocha , Mesquita A.L.A. , Macêdo E.N.
Published: October 2010

This work has as objective the study experimental and computational of the hydrodynamics of gas-solid fluidized bed. The gas-solid fluidized beds present important applications in chemical industry; among typical examples of fluidized beds some applications could be outlined: the syntheses and catalytic reactions, the catalytic regeneration, the combustion and gasification of coal, coating, drying, etc. The simulated data were obtained through the commercial CFD (Computational fluid dynamics), and the results were compared to those obtained by experiments conducted in a fluidized bed, containing jambu seeds (Sphilantes oleracea L.) of 772.21  2.98 μm in diameter, sphericity de 0.45  0.0066, bulk density 1130.8 ± 0.22 Kg/m3 and with porosity 0.2303  0.0099. In this work the porosity profile and characteristic curve of fluidized bed were calculated by using an Eulerian multiphase model. The comparisons showed a very good agreement between experimental and simulation results.
Effect of Process Variables on Efficiency and Particle Growth of Spilanthes oleracea Seeds Coating
Authors: Costa C.M.L. , Faria L.J.G. , Sandra Cristina dos Santos Rocha
Published: October 2010

The coating of vegetable seeds is a very common technique, mainly for the species which have small seeds. One of its functions is to increase the seed size to direct sowing. In the present study the coating of Spilanthes oleracea L. seeds with a polymeric suspension in fluidized bed was analyzed. The effects of process variables on the coating efficiency of top-spray fluidized bed coating were evaluated. The independent variables studied were the flow rate of coating suspension and the air mass flow. The quantification for the entrance variables influence on the coating efficiency and granule growth, as well as the identification of optimal conditions were made by means of an experiment factorial design technique. Polynomial models for the responses: efficiency and relative growth of the particles were deduced. The highest coating efficiency was achieved at a high flow rate of coating suspension.
Study of the Viability to Obtain Quasicrystal in the Composition AlCuFe Using High-Energy Milling, Followed by Pressing and Sintering
Authors: Coelho Rodrigo Estevam , Cruz Ramon Mateus Santos , Esteves Paulo Jesus Costa , Viana Silvana Garcia , de Lima Severino Jackson Guedes
Published: October 2010

This work was observed the phase formations of the mixture Al-Cu-Fe processed vial mechanical alloying, powders pressing at room temperature and subsequent heat treatment. The mixture of powders was made on the nominal composition Al65Cu20Fe15. A mill of high energy of the horizontal atrittor type was used to process the powders mixtures, in fixed time of two hours of milling. After milling, the powders were pressing in a die closed, with a diameter of about 28mm. The samples were observed by optical microscopy and analyzed X-ray diffractometry. The results obtained in this study provide a basis for setting parameters may be used as a basis for future research and possible applications.
Coating of Granular Polymeric Spacers with Copper by Sputter-Deposition for Enhancing Cell Wall Structure of Sintered Highly Porous Aluminum Materials
Authors: Sonoda Tsutomu , Katou Kiyotaka
Published: October 2010

The deposition of copper onto acrylic resin powder in its self-convective motion by magnetron DC sputtering was examined in order to prepare granular polymeric spacers coated with the metal, aiming at enhancing the cell wall structure of sintered highly porous aluminum materials. The fabrication of sintered highly porous aluminum materials was carried out in an ordinary powder metallurgy processing combined with a space-holder method with the polymer-copper binary spacer granules prepared by powder-coating using the sputter-deposition technique. The effects of the sputter-deposition of copper onto the spherical polymeric spacers on cell structures of the sintered porous compacts were investigated. According to optical observations, it was found that the sputtered copper could be uniformly and adherently deposited onto the surface of the acrylic granules. According to EPMA analysis on the cross-section on a sintered porous compact, it was found that Cu atoms were distributed at the vicinity of its cell walls, concluding that cell wall structures could be enhanced by this processing. Therefore it was expected that the compressive properties of the sintered highly porous aluminum materials were also improved by this powder coating process.
Production of Milk of Lime for Sugar Cane Industry: Study of Factors Influencing Lime Slaking
Authors: Henrique Humberto Molinar , Santos Larissa Cardoso , Parreira Priciane Martins
Published: October 2010

Milk of lime is used in the sugar industry for pH correction and as auxiliary of flocculation in bleaching of the sugar solution. Despite its intense use in sugar cane industry, the milk of lime is rudimentarily produced. The milk of lime badly produced adds great quantities of incrustation in process pipelines and equipments and increases its specific consumption in the process. To mitigate these undesirable effects it is necessary to prepare a milk of lime with appropriated chemical, physical and morphological characteristics. In this paper, several different suspensions of milk of lime were tested in bleaching of the sugar solution. These suspensions were characterized chemical, physical and morphologically and the results were correlated with the performance of the bleaching of the sugar solution. Experimental results showed chemical composition, reactivity, particle size, surface area and slaking process of quicklime affect greatly the quality of the milk of lime.
Synthesis of Niobium Carbide (NbC) by Powder Metallurgy High Energy Milling Technique
Authors: Antonello Rodrigo Tecchio , de Araújo Filho Oscar Olimpio , Gonzalez Cezar Henrique , Filho U.S.L. , Ambrozio Filho Francisco
Published: October 2010

The aim of this work is to obtain and characterize the Niobium Carbide (NbC) by a suitable high energy milling technique using a SPEX Mill vibratory type and niobium and carbon (graphite) powders. Since this carbide is scarced in the national market and it’s necessary to apply this NbC as a reinforcement in two molybdenum high speed steels (AISI M2 and AISI M3:2) object of another work motivated this research. The powders were submitted to a high energy milling procedure for suitable times and conditions and then were characterized by means of Scanning Electronic Microscopy (SEM) and X-ray diffraction (DRX) techniques. The ball-to-powder weight ratio was 10:1. The analyzed samples showed that the high-energy milling is an alternative route of the NbC synthesis.
Mixture of Particles' Influence in Computer Simulations of a Spouted Bed
Authors: Santos D.A. , Petri Junior I. , Barrozo Marcos A.S. , Duarte Claudio Roberto
Published: October 2010

This article aims to assess the influence of the way of simulating monoparticles as just monoparticles or as a mixture of particles, the latter, unlike the first, considering the effect of particle-particle interaction. The Eulerian–Eulerian multiphase model is used in the computational simulation of fluid dynamics of spouted beds and compared with experimental data. A half column of cylindrical spouted bed with a full plane glass attached to the front open surface of the bed as the transparent window was used for observation and photographing. Images of solid flows were recorded using a high speed camera (2000 frames per second). Glass beads with a diameter of 0.00368, 0.005 and 0.00252 mm are used as bed material. The simulated characteristic fluid dynamic curves of spouted bed for 0.15 m static bed heights (Ho) were obtained with good agreement with experimental data when the monoparticles was simulated as a mixture of particles with mixture’s percentage of 50%. The same occurred for the simulation of vertical velocities of particles profile, that is, when the monoparticles was simulated as a mixture of particles with mixture’s percentage of 50% we observed a more approach to the experimental data. It was also observed that the air concentration distribution seem to be independent of the changing of the composition.
TIG Welding of Sintered AISI 316 L Stainless Steel
Authors: das Neves Maurício David Martins , Barbosa Luzinete Pereira , da Silva Luís Carlos Elias , Correa Olandir Vercino , Costa Isolda
Published: October 2010

Stainless steel (SS) powders are used in the preparation of sintered SS products. One of the applications of sintered SS products is as filters in the petrochemical and food processing industries. In these industries, the SS filters are subject to severe conditions associated with the removal of solid particles from the fluid. Hence, SS filters should have adequate mechanical strength and high corrosion resistance. Welding can be used to manufacture SS filters. In this study, sintered AISI 316L specimens were welded using the TIG (Tungsten Inert Gas) process. The weld joints were examined by optical microscopy and by scanning electron microscopy. Electrochemical polarization measurements were carried out to evaluate the influence of welding on the corrosion resistance of sintered filters.
The Influence of the Velocity of Filtration in the Formation and Removal the Dust Cake
Authors: Rocha Sandra Mara Santana , Vasconcelos C.B. , Vieira Luiz Gustavo Martins , Aguiar M.L. , Damasceno João Jorge Ribeiro
Published: October 2010

The effective filtration area determined in a design of fabric filter depends on the filtration velocity, also known as air-to-cloth ratio that will be used. Low filtration velocities may demand big effective filtration areas. But then high filtration velocities may wear the filters out early. By searching for more efficient and economic equipments, this paper investigated the influence of the filtration velocity by formatting and removing the dust cake. Concluding that filtering at higher velocities a higher penetration of particles in the filter media occurs. Decreasing the filtration time and increasing the number which regenerates the cloth, consequently decreasing the life cycle of the filters.
Performance of Thermally Sprayed Coatings under Reciprocal Sliding Test
Authors: Arnt A.B.C. , da Rocha Márcio Roberto , da Silva F. Costa
Published: October 2010

This study aims to evaluate the behavior of thermally sprayed coatings with the HVOF technique (High Velocity Oxygen Fuel), subject to tribological testing of reciprocal movement with the SAE 52100 flat steel pin, in accordance with ASTM G 133. The carbon with Cr2C3-25NiCr and WC-12Co were evaluated under conditions of intense surface fatigue. The microstructure and surface modifications were analyzed by optical microscopy and scanning electron microscopy. By using these techniques were possible to compare the modifications of the coatings under repeated loading conditions, and to expand the knowledge about wear mechanisms, mainly the adhesive one, present in several mechanical components, particularly in bearing and internal combustion engines. The coatings tested showed lower wear rate when compared to SAE52100 steel and equivalent behavior among the different loading conditions applied.