bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvement of Tribological Properties by Titanium Nitride Deposition in Titanium Alloys Produced by Powder Metallurgy
Authors: Galvani Eduardo T. , Henriques V.A.R. , Lemos T.G.
Published: August 2012

Titanium nitride (TiN) is a hard material, often used as coating to improve the wear properties of titanium alloys in machining, implant and aerospace applications. Electron Beam Physical Vapor Deposition (EB-PVD) is a technique which a target anode is bombarded with an electron beam given off by a charged tungsten filament under high vacuum, producing a thin film in a substrate. In this work, results of TiN films depositions on Ti-13Nb-13Zr substrates by EB-PVD are studied. Titanium targets were obtained by a purified ingot and the substrates produced by powder metallurgy. Sintered samples of Ti-13Nb-13Zr and TiN layers were characterized by X-ray diffraction, scanning electron microscopy, Vickers microhardness and wear tests. The TiN films presented high hardness values, continuity and large thickness. The coatings improved the tribological properties of the substrate due to high adhesion and low wear rate.
Metal Recovery of Discarded Stacks and Batteries, Liquid-Liquid Extraction and Stripping Parameters Effect
Authors: Provazi Kellie , Espinosa Denise Crocce Romano , Tenório Jorge Alberto Soares
Published: August 2012

The purpose of this paper is to study metal separation from a sample composed of a mixture of the main types of spent household batteries, using a hydrometallurgical route, evaluating the parameters effect of the liquidliquid extraction, with Cyanex 272, and stripping. The preparation of solution consisted of: grinding the waste of mixed batteries, reduction and volatile metals elimination using electric furnace and acid leaching. With the best results obtained after liquidliquid extraction and stripping it was possible to get 4 solutions of metal sulfates that they could be used in posterior metals recovery by electroplating, they are: 1) to copper recovery: Cu 203.7 g L-1+ Co 20.8 g L-1+ Mn 2,626.6 g L-1; 2) to cobalt recovery: Co 364.0 g L-1; to manganese recovery: Mn 49,929.0 g L-1and 4) to nickel recovery: Ni 1,241.9 g L-1.
Microstructural Analysis of Ti-6Al-4V Alloy after Plasma Immersion Ion Implantation (PIII)
Authors: Castagnet M. , Yogi L.M. , Silva M.M. , Ueda Mario , Couto A.A. , Reis D.A.P. , Moura Neto C.
Published: August 2012

The search for alloys with improved high-temperature specific strength and creep-resistance properties for aerospace applications has led in the last decades to sustained research activities to develop new alloys and/or improve existing ones. Titanium and its alloys are excellent for applications in structural components submitted to high temperatures owing to their high strength to weight ratio, good corrosion resistance and metallurgical stability. Its high creep resistance is of great importance in enhancing engine performance. However, the affinity by oxygen is one of main factors that limit its application as structural material at high temperatures. Materials with adequate behavior at high temperatures and aggressive environmental became a scientific requirement, technological and economically nowadays. The objective of this work is the mechanical and microstructural characterization of the Ti-6Al-4V alloy after treatment by nitrogen Plasma Immersion Ion Implantation (PIII) process. The aim of this process is the improvement of superficial mechanical properties of the Ti-6Al-4V alloy. The selected alloy after ionic implantation process by plasma immersion was submitted to creep tests at 600 °C, in constant load mode at 250 and 319 MPa. The techniques used in this work were optical microscopy and scanning electronic microscopy. The fractograph analysis of the samples tested in creep shows narrowing phenomena and microcavities. The creep results show the significant increase of material resistance, it can be used as protection of oxidation in high temperatures applications.
Ceramic Coating Based on La, Sr and Co on Ferritic Stainless Steel for ITSOFC Interconnects
Authors: Korb Matias de Angelis , Linhares Junior Raimundo Nonato Ferreira , Feistauer Eduardo Etzberger , Barreto Ledjane Silva , de Sousa Vânia Caldas , Müller Iduvirges Lourdes , Malfatti Célia de Fraga
Published: August 2012

Ferritic stainless steels have been used to produce interconnects for intermediate temperature solid oxide fuel cells (ITSOFC) due to their appropriate properties. Ferritic stainless steel presents mechanical stability, much higher thermal and electronic conductivities; significantly lower cost, and mechanical resistance than austenitic steels. Besides, it presents a thermal expansion coefficient compatible with the other materials of the cell components. However, in the range of this device operating temperature (600 °C 800 °C) it can occur the formation of poorly conducting oxide (Cr2O3) reducing the fuel cell performance. The aim of this work was to obtain oxide coatings starting with La, Sr and Co nitrates applied by spray-pyrolysis technique on a stainless steel AISI 430 substrate. The coatings obtained were characterized by X-ray diffraction and scanning electron microscopy/energy dispersive spectroscopy. The oxidation resistance of the ferritic stainless steel, coated with a perovskite (La0,6Sr0,4CoO3) film, was investigated by isothermal oxidation. The results showed that the coating obtained promoted the increase of the ferritic stainless steel oxidation resistance. However, after the oxidation test, it was observed a Cr enrichment and a very pronounced Sr enrichment, near to the alloy/coating interface, which can be associate to the decomposition of La0,6Sr0,4CoO3 film.
Electrical and Microstructural Properties of Varistors Based on Nanostructured Tetra-Needle Like Zinc Oxide Powders
Authors: Lucca Sánchez Felipe Antonio , Tarragó Diego Pereira , Takimi A.S. , Sousa V.C. , Pérez Bergmann Carlos
Published: August 2012

t is well known that nanostructured materials have relevant influences in properties behavior that can be achieved when compared with conventional materials. In this study is proposed an investigation of the electrical and microstructural properties of zinc oxide based varistors prepared with nanostructured zinc oxide powder obtained by a thermal evaporation process. Zinc oxide powder morphology was investigated by scanning and transmission electron microscopy (SEM and TEM, respectively) and the specific surface area evaluated by adsorption of N2. The varistors were prepared by the mixture of typical dopants with zinc oxide powders in a ball mill. The surface area of zinc oxide powder used was 17.4 m2/g with tetra-needle like morphology. After powder mixture process it was observed by TEM micrographs that most of the tetrapod shaped zinc oxide broke into needles well mixed with dopant particles. The compressed powders were sintering at 1050, 1150 and 1250°C for 1.5 h and densification over 94% were achieved in all tested temperatures. Preliminary electrical characterization reveals that nanostructured zinc oxide compositions have interesting varistor properties.
Quantification of Phase Compositions Present in the System [(NiO)x].[(CoO)1-x].[(Al2O3)], 0.05 ≤ X ≤ 0.95, and the Effect in the Electrical Properties of Semiconductor as a Consequence of the CO+2 Variation
Authors: Gomes Keydson Quarema , Bacelos Marcelo , Filho Pedro Iris Paulin
Published: August 2012

In this work were investigated the systems-NiOx-CoO1-x-Al2O3 using X-ray diffraction of the powder, which identified and quantified to phase in the sample was performed through the Rietveld method. The insertion of nickel oxide in the system obeyed the proportions of molar fraction of 0,05, 0,30, 0,50, 0,70 and 0,95 (x). Analyses were realized on samples which were treated at the temperature 1773K. From the results of refinement of spinel phase structure, was analyzed the relationship between lattice parameter refinement and the substitution of Co+2 ion by Ni+2ion in the structure. The electrical resistivity dc was observed as a respect to temperature and the results appears a decrease of resistivity when were simultaneously increased the temperature. It was observed that the conduction mechanism was the same in all samples and the results for activation energy, characterized like electron hopping, it due exchange setting the ion Co+2 D Co+3.
The Influence of Zinc Doping on the Grain Size and Productivity of Diamond Synthesis in the Ni-Mn-C System at High Pressure and High Temperature
Authors: Skury Ana Lúcia Diegues , Monteiro Sérgio Neves , Oliveira Simone S.S.
Published: August 2012

The development of technological processes for obtaining small size diamond powder is of industrial interest as basic products for roughing and finishing surfaces, like in the polishing of ornamental rocks. Therefore, this work investigates the influence of zinc, as a doping agent, in association with the graphite to diamond transformation, which occurs during high pressure and high temperature synthesis in the presence of Ni-Mn as a catalyst-solvent metallic alloy. Diamond synthesis was carried out at 4.7 GPa of pressure and 1300°C using a reactive mixture with 1:1 ratio of graphite and Ni-Mn alloy powders doped with up to 6% of Zn. The results indicated that the highest diamond yield was obtained for 0.5% while the lowest yield for 6% of Zn. Regardless the Zn content , the diamond crystal were produced with 212/150 μm of granulometry.
La2O3 Reinforced Al2O3-TiO2 Ceramic Composites for Inert Coating of Metallic Parts for Petroleum Industry
Authors: Yadava Yogendra Prasad , Mendes Catarina E. , Rêgo Sheila A.B.C. , Ferreira Ricardo A. Sanguinetti
Published: August 2012

Recent findings of Brazilian pre-salt petroleum reservoir has created an intense demand for new materials capable of withstanding direct contact with the crude petroleum as it is a highly corrosive and chemically reactive fluid. Ceramics materials are highly stable in hostile environment and therefore can serve as inert coating to solve some of these problems. In this context, in the present work we have developed La2O3reinforced Al2O3-TiO2ceramic composites in proportions of 5-20 wt% titanium oxide and 1-2 wt% with high mechanical strength, through thermo-mechanical processing and sintering techniques To assess the quality of these materials as the protective coatings of crude petroleum storage and transportation systems we have studied the physic-chemical and mechanical stability of these materials in crude petroleum, originated from earthen and offshore petroleum wells of Brazil. These studies present satisfactory results for use of 2 wt% La2O3reinforced Al2O3-TiO2 .ceramic composites for such applications. Keywords: La2O3reinforced Al2O3-TiO2 .ceramic composites, protective coatings, metallic parts, crude petroleum
Processing and Characterization of β-Ti Alloys by Means of Powder Metallurgy Processing and Blender Elemental
Authors: Devesa F. , Rial S. , Amigó Vicente
Published: August 2012

Titanium is an increasingly used material on industry. Based on Ti and titanium alloys characteristics, one of the most favorable processing methods is the powder metallurgy. Attending to microstructure, alloys showing β phase have singular characteristics of low elastic modulus, good specific properties and high corrosion resistance, which make β-Ti alloys very appropriated for specific uses covering a width list of fields including aeronautics or biomaterials. At this work, it has been obtained and characterized different β-Ti alloys. The processing technique has been optimized by means of an initial blender elemental followed by basic powder metallurgy. Microstructural and mechanical characterization of the studied alloys has been achieved. Results show that these kinds of alloys can be produced by this technique and the obtained properties are really interesting for a wide variety of applications.
Rheological Study of Iron Oxide Reinforced by Ceramic Nanoparticles
Authors: Vieira L.E. , Neto João B. Rodrigues , Hotza Dachamir
Published: August 2012

The aim of this work is to produce a stable suspension of iron oxide reinforced by different ceramic nanoparticles like SiO2, TiO2. Measurements of mean particle size, zeta potential and flow curves have been done. Additionally deflocculation curves and sedimentation were drawn to complement the study. The results showed that nanoparticles helped suspensions to maintain a deflocculated stable condition for longer periods of time.
Effect of Sense and Spacing in Parallel Scratches during Brittle Machining of Stoneware Tiles
Authors: de Souza Rafael Gonçalves , Pinho Guilherme D´Aquino , Sousa F.J.P. , Fredel Márcio Celso , Alarcon Orestes Estevam
Published: August 2012

Assuming that during the machining of stoneware tiles by flat grinding each grain on the abrasive wheel performs a single scratch, it is possible to simulate and analysis the effect generated by those employing esclerometry. This paper studied the effect between parallel scratches during brittle machining of stoneware tiles. Scratching tests were performed employing a CNC esclerometer; a Vickers indenter as abrasive tool; load of 10N by dead weight; three different configurations of sense in the same direction; three different configurations of spacing between the scratches incremented with a factor of 0.8, 1.0 and 1.2 times the average scratch width. The test samples were analyzed by optical microscopy and subsequent digital image analysis to quantify the worked area. The results showed variation of material removal as a function of the sense and spacing configuration. The sense configuration 1stR-3rdR-2ndR had the highest improve in material remotion. The spacing arrangement 1.2 remain with many not worked areas between the scratches, needing rework to remove this material. The configuration with 0.8 was found a redundancy of work specially when used with the sense configuration of 1stR-3rdL-2ndR.
Characterization of LSCF-Based Composite and LSCF as Cathodes for Intermediate Temperature SOFCs
Authors: Vargas Reinaldo Azevedo , Bonturim Everton , Andreoli Marco , Chiba Rubens , Seo Emília Satoshi Miyamaru
Published: August 2012

The (La0.60Sr0.40)(Co0.20Fe0.80)O3-δ - LSCF, (Ce0.90Gd0.10)O1.95 - CGO composites and LSCF were deposited by wet powder spraying deposition method for the purpose of investigating their potential use in Intermediate Temperature Solid Oxide Fuel Cells. The interlayers are necessary between CGO electrolytes and LSCF cathodes in order to improve the performance of these materials. LSCF particles synthesized by citrate technique were calcined at 900 °C for 4 h and, their LSCF-CGO composites and LSCF suspensions deposited on CGO substrate and, sintered in 1100 °C for 1 h, were formed pseudo-perovskite. The ceramics materials were analyzed by X-ray diffraction (XRD) and chemical composition of different half-cells layers by scanning electron microscope with energy dispersive (SEM-EDS). The results are in agreement with the literature and indicate that route studied is adequate for crystal structures formation compatible with films the 35 µm thick total for study of conductivity between the cathode and the electrolyte.
Influence of Firing Temperature on the Pozzolanic Activity of Kaolin Wastes
Authors: Dias Suellen Lisboa , Guimarães I.O. , Figueiredo S.S. , Bezerra I.M.T. , Ferreira H.C. , Neves G.A.
Published: August 2012

The volume of waste generated by mining and mineral processing industries has escalated each day because of increased demand caused by global economic growth. The kaolin processing industries are important economic segments in the state of Paraiba, but generate huge amounts of waste. An alternative for the recycling of this waste is its use in mortars. The kaolin contained in wastes after thermal treatment can reduce the consumption of cement in the production of mortars. It was evaluated the influence of firing temperatures of the residue on its pozzolanic activity. The residue was fired at temperatures of 600°C, 700°C and 800°C for 2h and subjected to mineralogical analysis. The evaluation produced the mortar with a mixture of kaolin waste burned at temperatures of 600°C, 700°C and 800°C with lime delivering true a good mechanical performance, reaching values of compressive strength greater than the legislated.
Porous Media of LZSA Glass-Ceramic for Burner Applications
Authors: do Rosário Jefferson Jean , Guimarães Rafael Paiotti Marcondes , Leite Mirella Alves , de Oliveira Antonio Pedro Novaes , Fredel Márcio Celso
Published: August 2012

A LZSA (Li2O-ZrO2-SiO2-Al2O3) glass-ceramic porous media produced by the replication method has been studied for relatively low temperature applications. Different suspensions have been tested, and appropriated parameters to obtain good impregnation and green strength were determined. The structures after the sintering process (975 °C for 120 min) were evaluated by scanning electron microscopy and showed a good reproducibility for the best tested suspensions (70.0 wt.% LZSA, 3.5 wt.% bentonite as binder and 1.5 wt.% Darvan 821A as dispersant) Strut and geometric densities were determined so that glass-ceramic foams with porosity of about 91% were obtained.
Characterization and Technological Applications for Kaolin Processing Wastes
Authors: Cruz Martelli Marlice , de Freitas Neves Roberto
Published: August 2012

The use of kaolin in any industrial segment requires previous physical and chemical treatment to minimize the amounts of impurities to or below standard levels established according to the desired application. Wastes from kaolin processing from the Amazon region were characterized by DTA-TGA and XRD. This paper shows the thermal transformations of the rejects studied at temperatures of 600°C, 700°C, 800°C, 900 °C, 1000°C, 1300°C, 1400°C and 1500°C, tests with pyrometric cones and ceramic properties of the sintered materials aiming their use in refractory materials.
Characterization of Blast Furnace Sludge for Clayey Ceramic Fabrication
Authors: Dias Claudio André Chagas M. , Monteiro Sérgio Neves , Faria Jr. Roberto da Trindade , Vieira Carlos Maurício Fontes
Published: August 2012

Operation in an integrated steel making plant, such as the processing of iron ore by blast furnace result in several wastes that need to be conveniently disposed to avoid environmental pollution. In the case of sludge wastes, a feasible solution is their addition to clayey ceramics. The objective of this work was then to characterize a steel making plant waste was subjected to mineralogical, chemical and physical tests. The combustion gases: CO, CO2, NO and SO2from thermal emission were analyzed. It was found that the blast furnace sludge has a high content of both iron and carbon. Its combustion generates enough heat to sensibly contribute to the firing of the ceramic, which is an energetical advantage associated with the sludge waste addition. The gas emission was monitored and, for relatively small addition of waste, no harm is apparently caused to the environment.
Influence of Firing Conditions on Properties of Red Ceramic
Authors: de Lima Santana Lisiane Navarro , da Silva Bartolomeu Jorge , Gonçalves Wherllyson Patrício , Cartaxo Juliana Melo , Lira Bruna Silveira , dos Santos Renato Correia , Menezes Romualdo Rodrigues
Published: August 2012

In the ceramic industry, the firing is one of the main stages of the production process. There are two heating rates prevailing at this stage: low heating rate (long residence time) and high heating rate (fast residence time), the low rate is more used in traditional ceramics. This study aims to evaluate the influence of firing conditions on technological properties of three compositions of clay, used in the manufacture of red ceramic products. Initially, the mixtures were characterized subsequently were extruded, dried and submitted to firing at temperatures at 900 and 1000 °C with heating rates of 1, 2, 5, 15, 20 and 30 °C/min. The crystalline evolution of the different samples was analyzed using X-ray diffraction and the technological properties were determined. For the mechanical resistance, it was not observed significant change with the increase of the temperature and heat rate
Bovine Bone Processing for Biofilter Application
Authors: Ferreiro Omayra , Yubero Fatima , Balestra Roseli Marins , Varella Marize , Monteiro Magna
Published: August 2012

This work involves the processing of bovine bone for use as biofilter collector of heavy metals in water. Before processing, it was necessary to clean the bone selected for removing the organic material adhered thereto. Drying was done in weathered during 18 days. Then the bones were calcined at a constant temperature of 750°C for 6 hour. The bone grinding was performed by means of an analytical mill in order to obtain a finer grain size. Once processed, the bovine bone powder was characterized by X-ray diffraction and fluorescence analyses. The results showed that the powder phase is less crystalline hydroxyapatite, when compared to highly crystalline synthetic hydroxyapatite, which favors the sorption capacity of lead by bovine bone.
Boron Nitride Ceramic Composite Obtained by High Pressure and High Temperature Sintering
Authors: Skury Ana Lucia D. , Monteiro Carlos A. Oliveira , Bobrovinitchii Guerold Sergueevitch , Monteiro Sérgio Neves
Published: August 2012

In the present work, by selecting Si3N4, TiB2 and Al2O3 as binding agents as well as La3O2 as an additive, sintered wBN composites were studied. By modifying the number of sintering cycles, the composites processed at 4.5GPa and 1800°C showed improved mechanical properties. The degree of transformation of the wBN, as well as the chemical reactions during the sintering process were discussed. This new composite material was found to present polycrystalline structure that provides superior cutting properties. Moreover, owing to superior properties, the wBN composite sharpens itself during cutting.
Manufacture of YSZ-LSM Semi-Cell by Colloidal Processing
Authors: Gómez Laura , Escobar J. , Colomer Maria Teresa , Moreno Rodrigo
Published: August 2012

Yttria stabilized zirconia (YSZ) is the most common electrolyte in solid oxide fuel cells (SOFC). The planar configuration is widely used for designing single cells, in which a thick cathode layer can be used as the supporting electrolyte film. The manufacture of the semi-cell formed by anode and electrolyte has been widely studied and there are many works dealing with its colloidal processing. However, the semi-cell formed by cathode and electrolyte has received much lower attention. This work deals with the manufacture of a semi-cell consisting of YSZ as electrolyte and strontium-doped lanthanum manganite (LSM) as a cathode through a colloidal processing route. The colloidal behavior of diluted suspensions of YSZ and the rheology of their concentrated suspensions were studied as a function of deflocculant content, mixing time by using ultrasounds probe and ageing time. The colloidal stability of aqueous suspensions of LSM was studied by measuring the zeta potential as a function of pH and deflocculant content. These concentrated suspensions were used to obtain thick self-sustained substrates by casting methods. The YSZ electrolyte and LSM cathode were prepared by tape casting in water medium.
8YSZ Tapes Produced by Aqueous Tape Casting
Authors: Moreno Verônica , Aguilar J.L. , Hotza Dachamir
Published: August 2012

In the last years many efforts have been spent to develop colloidal processes that use water instead of organic solvents. The aim of this study was to develop aqueous tape casting systems to produce zirconia tapes. Different types of binder were tested. Rheological properties of the slurries were measured at room temperature. The slurries were cast on a PET carrier with/without a silicone-based coating. Interactions between the slurry and the polymeric substrate were evaluated. It was found that an acrylic binder is more appropriate for colloidal processing. The acrylic-based suspensions showed a pseudoplastic behavior and remained stable after hours. Tapes with thicknesses between 90 and 200 µm were produced. Optimized tapes showed smooth and homogeneous surfaces and adequate plasticity.
Characterization of New Occurrences of Clays in the City of Pedra Lavrada-PB, for Use as Ceramics Raw Materials
Authors: Silva F.A. , Pereira I.D.S. , Dias Suellen Lisboa , Neves Gelmires Araújo , Lira Hélio Lucena
Published: August 2012

Paraiba State is a major instance of non-metallic mineral mainly of bentonite clay, balls clays, kaolin, feldspar, quartz, limestone, mica, etc. Recently it was discovered new deposits of clay in the region of Cubatí and Pedra Lavrada, PB, thereby providing an expansion of mineral inputs in the region. The aim of thi study is to characterize the clays from the city of Pedra Lavrada - PB, to be used as ceramic raw materials. The mineralogy of the clays was performed using the following techniques: laser diffraction (AG), thermogravimetric and differential thermal analysis (TG and DTA), chemical analysis (EDX), X-ray diffraction (XRD), cations exchange capacity (CEC) and surface area (AE). The specimens were molded by compression of 2 MPa, with dimensions of 60mm x 20 mm x 4 mm. The followed physical and mechanical properties were determined: firing shrinkage, water absorption, bending stress rupture and modulus after calcined at 800, 900, 1000, 1100 and 1200 °C. The results showed that the clays present smectite and kaolinite in their mineralogical composition and through the physical and mechanical properties this clays could probably be used as ceramic raw materials.
Zirconia Blocks Properties Used for CAD/CAM Dentistry Restorations
Authors: Santos C. , Elias Carlos Nelson , Melo Andréa Matos , Monteiro Sérgio Neves
Published: August 2012

Several CAD/CAM systems are available to dental prosthesis laboratories that can be used to make all-ceramic copings and frameworks. In Brazil, the use of these systems presents low demand, due principally the high blocks ceramics cost used for theses systems. The ceramic blocks are imported. To increase the dental ceramic CAD/CAM applications is necessary develop and produce the ceramics blocks in Brazil. The purpose of the present work is to compare the mechanical properties of blocks of zirconium developed in the Brazil (ProtMat® Co) and imported (VITA). It was determined the mechanical and physics properties of the two types of blocks of zirconium stabilized with ytria. The blocks have been sinterized at 1530 °C and their mechanical and physics properties were measured. The x-ray diffraction analysis showed only tetragonal phase, which improve the blocks toughness. The Vickers hardness and fracture toughness were 1300HV and 9 MPam1/2, respectively. High bending fracture resistance was obtained for both materials with average values of 910MPa. The Weibull modulus was m=10 for Brazilian and imported blocks. It was not observed an important difference among the microstructures and mechanical properties of the analyzed zirconium blocks.
Production of Porous Silicon Carbide Ceramics by Starch Consolidation Technique
Authors: Mesquita Rodrigo Mende , Bressiani Ana Helena de Almeida
Published: August 2012

Silicon carbide is used to produce abrasive and high-temperature structural ceramic materials due to its mechanical and chemical properties. The possible applications of porous silicon carbide ceramics are diesel engines catalysers and molten metal filters. In the last years the starch gained importance as a pore-forming and consolidation agent, due to it is environmental friendly and easily processing. The current work uses starch (corn, rice and potato) as pore forming and consolidation agent. The samples sintered at different sintering times were characterized by density and microstructure (XRD, SEM). The results show that the samples presented porosity between 20 and 40% and the microstructures obtained is homogeneous with a pore size similar to the starch particle added.
Effect of Surface Treatment of Yttria Stabilized Zirconia for Dental Prostheses
Authors: Carvalho Cristiane Fonseca , Melo-Silva Cláudio Luis , Santos Claudinei , Lins Jefferson Fabricio Cardoso
Published: August 2012

When it comes to providing reliable adhesion of low silica content alumina ceramic, hydrofluoric acid etching along with silanization has not shown sufficient efficacy because the microstructure of high-alumina content ceramics is unable to degrade them. The objective of this study was to analyze the effect of surface sandblasting of zirconia-based ceramic stabilized by yttria as used in dental prostheses, using a SEM and roughness average. The samples were divided in control, no surface treatment; Al2O3sandblasting; Al2O3sandblasting and Al2O3+ SIC particles 110 µm average sized; Al2O3sandblasting and Al2O3+ SIC particles 110 µm average sized milled for 2 hours; Al2O3sandblasting and Al2O3+ SIC particles 110 µm average sized milled for 6 hours. The Al2O3sandblasting and the 2-hour milled Al2O3+ SIC particles showed better results and better characterization of roughness in SEM with the silica deposition on the samples surface.
Sintering of B4C-SiC Composites with ALN-Y2O3 Addition
Authors: da Rocha Rosa Maria , de Melo Francisco Cristóvão Lourenço
Published: August 2012

One suitable material candidate to improve B4C mechanical properties is SiC. B4C-SiC ceramic composites are very promising armor materials because B4C and SiC are intrinsically very hard. In this work a pressureless sintering study of B4C-SiC ceramics was made. B4C-SiC mixtures were prepared with SiC concentration from 10 to 50 wt%. Without the external applied pressure during sintering it was necessary to add sintering aid. The additive system AlN-Y2O3was investigated as sintering aid. Samples were densified by pressureless sintering at 2000 °C/30 min in an argon atmosphere. B4C-SiC composites were analyzed by XRD and SEM. Bulk density and total weight loss were also measured. Density higher than 93 % of the theoretical value was determined and microhardness of 30.3 GPa was achieved for composite with 10 wt% of SiC sintered with AlN-Y2O3additive.
Nanostructured YSZ Thin Film for Application as Electrolyte in an Electrode Supported SOFC
Authors: Halmenschlager Cibele Melo , Korb Matias de Angelis , Neagu Roberto , Bergmann Carlos Pérez , Malfatti Célia de Fraga
Published: August 2012

The development of solid oxide fuel cell with thin film concepts for an electrode supported design based on the yttria-stabilized zirconia has demonstrated favourable results due to its high chemistry stability in oxidization and environment reduction. The spray pyrolysis process was investigated in order to obtain dense thin films of YSZ on different substrates. The precursor solution was obtained by zirconium and yttrium salt dissolutions in a mixture of water and glycerine in several ratios to study the solvent influence. The substrate was initially heated at 600 °C and during the deposition it ranged from 260-350°C, finishing at a fast increase in temperature of 600°C. The heat treatment was carried out in four different temperatures: 700 °C, 750 °C, 800 °C, and 900 °. The precursors were characterized by thermal analysis. The microstructures of the films were studied using scanning electron microscopy and X-ray diffraction. The results obtained showed that the films obtained were crystalline before the heat treatment process and have shown ionic conductivity above 800°C.
Applications of Fourier Transform Infrared and X-Ray Techniques to Analyze Nickel Ferrite Nanoparticles Produced
Authors: Porto Paulo Sergio da Silva , Proveti José Rafael C. , Muniz E.P. , Pereira R.D. , Araujo D.R.
Published: August 2012

Various methods have been reported to obtain nanosized ferrite particles such as chemical coprecipitation, sol-gel, spray-drying, microwave plasma, sonochemical, hydrothermal synthesis, reverse micelle technique and mechano synthesis. In this work Nickel Ferrite nanoparticles are produced using coconut water or pectin extracted from apple peel (using sulfuric or chloridric acid) as precursor for the proteic sol-gel (PSG) method. The samples are prepared by drying and subsequent isothermal treatment of the sol gel at 873 or 1173 K during 2 hours. The resultant materials were analyzed by Fourier Transform Infrared Spectroscopy (FTIRS) and discussed with emphasis in the purity of the samples produced.
ZnO-TiO2 Composite Formed by Mixed Oxides via Polyol
Authors: Filho Aureo Murador , dos Santos Dayse Iara , Kussuda Marcos Yukio , dos Santos Zanatta Camilla , Kim Jae Geon , Shi Don Qui , Dou Shi Xie
Published: August 2012

Among the researches on preparation and test of nanostructured materials, titanium dioxide and zinc oxide have been the most frequent studied oxides. In order to extend their properties, composites have been prepared using three different methods: Polyol Method, Sol-gel Process and a combination of the two processes (hybrid process). Recent research showed best properties in composite materials than in pure oxides. In this work is presented the preparation and the structural characterization of ZnO-TiO2 composite nanostructures to be tested for their performance in electrocatalysis and in further trial on photovoltaic cells.
Preparation of Organoclay for Polymeric Nanocomposites Membranes
Authors: Medeiros Keila Machado , de Gouveia Silva Taciana Regina , Kojuch Luana Rodrigues , Araújo Edcleide Maria , Lira Hélio Lucena
Published: August 2012

Bentonites are the most used fillers in the development of nanocomposites, due to their characteristics that provide nanosized particles, contributing to a large contact area between the clay and the polymer. In general, the additions of small amounts of organoclay improve the mechanical and thermal properties of nanocomposites. Bentonite clays and organoclays were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TG). The results of XRF, XRD and FTIR confirmed the presence of quaternary ammonium salt in the organoclay structure. From TG, it was observed that the organoclay showed better thermal stability when compared with bentonite clay.
Synthesis of Powders Nanometer Al2O3 Method by Sol-Gel
Authors: Santos Suzana Arleno S. , Lima Eduardo Sousa , Louro Luis Henrique Leme , da Costa Célio Albano
Published: August 2012

This study aimed to produce nanometric powders of alumina by sol-gel route. Six samples were produced by varying the amount of water for dilution of aluminum nitrate and the calcination temperature. The final products were evaluated by thermogravimetric analysis, scanning electron microscopy, X-ray diffraction and particle size. It could be noticed that, beyond the time of gelation and calcination temperature, the addition of water also influenced the average size of the clusters.
Ceramic Compacts Based on Sintered ZrO2 Nanopowder
Authors: Bobrovinitchii Guerold Sergueevitch , Skury Ana Lúcia Diegues , Monteiro Sérgio Neves , de Azevedo Marcia G.
Published: August 2012

Ceramic based compacts used in tool bits are of fundamental importance for high speed machining operations. Pure ceramic, however, is too brittle. Therefore, conventional hardmetal cermets such as WC-Co are commonly used, in spite of thermal limitations due to the metallic matrix. The present work investigates the properties of sintered ZrO2 nanopowder, stabilized with Yb2O3, as a tough enough pure ceramic with high thermal resistance for tooling compacts. Sintering of ZrO2 nanopowder with particle size below 0.1µm in presence of 2-3% of Yb2O3 was conducted under pressure of 180 to 300 MPa and temperatures from 1500 to 1600°C, during 40 to 60 minutes. Both the density and strength pass through maximum values with temperature and processing time. Strength of 9.500 MPa and hardness of 17.5GPa as well as fracture toughness of 12.5MPa.m1/2 were obtained
Firing Behaviour of a Clayey Ceramic Body for Rustic Floor Tiles
Authors: Vieira Carlos Maurício Fontes , Monteiro Sérgio Neves
Published: August 2012

This work had as its objective to evaluate the firing behavior and microstructure of a typical clayey ceramic body from Campos dos Goytacazes, Brazil, used to fabricate extruded rustic floor tiles. The firing behavior of samples fired at 650, 850 and 1050°C was studied by thermal analysis (DTA/TG) and their microstructural characteristics were evaluated by mercury porosimetry and X-ray diffraction. Technological properties such as water absorption, linear shrinkage and flexural strength were also evaluated. The results showed that the clayey body presents a relatively high weight loss during firing due to a significant amount of clay mineral associated with aluminum hydroxide decomposition. After firing the clayey body developed an elevated amount of porosity and low mechanical strength. Quartz was detected as the only crystalline phase originated from the unfired body. By contrast, mullite, plagioclase feldspar and hematite appeared during the firing.
Effect of the Dwell Temperature on Spark Plasma Sintered CaCu3Ti4O12
Authors: de Carvalho E. , Bertolete Marcelo , Machado Izabel Fernanda , Muccillo E.N.S.
Published: August 2012

Polycrystalline CaCu3Ti4O12 ceramics were prepared by solid state reactions by spark plasma sintering (SPS) technique. In this study, the effects of the dwell temperature on structural, microstructural and dielectric properties of CaCu3Ti4O12 ceramics have been investigated. Powder mixtures were calcined at 900°C for 18 h before SPS consolidation. The dwell temperatures were 850, 900, 915 and 930°C. Sintered pellets were characterized by X-ray diffraction, scanning electron microscopy and impedance spectroscopy. X-ray diffraction patterns show evidences of a single-phase perovskite-type structure. The calculated lattice parameter is 7.40 Å. The hydrostatic density increases slightly with increasing dwell temperature. Scanning electron microscopy observations revealed a heterogeneous microstructure for all samples. The dielectric loss remains constant over a wide temperature range. The obtained permittivity is approximately 103 at 1 kHz. The increase of the dwell temperature is found to produce a brittle ceramic.
Characterization and Thermal Behavior of Red Ceramic Incorporated with Flat Glass Waste
Authors: da Costa Caldas Thaís Cristina , Morais Alline Sardinha Cordeiro , Monteiro S.N. , Vieira C.M.F.
Published: August 2012

The amount of discarded glass wastes is increasing in Brazil and becoming of environmental concern. A possible solution is to incorporate into construction products such as clayey ceramics. Thus, the main objective of this work was to evaluate the firing behavior of a kaolinitic clayey body from Campos dos Goytacazes-RJ incorporated with flat glass waste (FGW) from civil construction. The characterization of the FGW was done by X-ray Fluorescence and optical dilatometry. Compositions were prepared with 0, 2.5, 5 and 10 wt.% of FGW incorporated into the clayey body. Specimens were prepared by uniaxial press-molding and then fired at 850 and 1050°C.The microstructural changes due to the firing process were evaluated by X-ray diffraction (DRX) and scanning electron microscopy (SEM). The results showed that the glass waste has a potential to be successfully employed in a clayey ceramic formulation for civil construction products.
Influence of Mould Cooling Rate on the Microstructure of AZ91 Magnesium Alloy Castings
Authors: Roskosz Stanisław , Dybowski Bartłomiej , Jarosz Robert
Published: August 2012

Magnesium alloys are the lightest, widely used structural material. They are often used in aeronautical and automotive industries, where the weight savings are essential. Due to high responsibility of the elements made from magnesium alloys it is important to achieve high quality castings without any defects. The paper presents results of investigations on impact of sand mould cooling rate on microstructure and quality of the castings. Six identical castings, fed and cooled in different ways were investigated. Studies consisted of: RTG investigations and SEM and LM observations. Microstructure was evaluated qualitatively and quantitatively. RTG investigations showed that casting without feeder and cooler, casting only with feeder and castings cooled with 20mm and 40mm thick cooler contains voids inside. Castings with feeder and coolers 20mm and 400mm thick were flawless. Microstructure evaluation showed that castings with and without defects have different structure. Castings with defects were characterized by higher volume fraction of Mg17Al12 intermetallic phase. Flawless castings were characterized by fully divorced eutectic.
Precipitate Processes in Mg-5Al Magnesium Alloy
Authors: Kiełbus Andrzej
Published: August 2012

In this article, the impact of long-term annealing on transformation of microstructure, in sand casting and die-casting Mg-5Al magnesium alloy was discussed. The Mg17Al12 phase of the diverse morphology is the basic strengthening phase in Mg-5Al alloys. After sand casting microstructure of Mg-5Al alloy consists of α-Mg solid solution with continuous and discontinuous precipitates of Mg17Al12 phase. After die-casting, the structure is characterized by significant grain refining of α-Mg solid solution, however Mg17Al12 phase, together with α-Mg solid solution, forms fully divorced eutectic. The Mg17Al12 phase undergo decomposition and coagulation at the temperature above 180°C and higher.
The Influence of Tin on the Microstructure and Creep Properties of Mg-5Al-3Ca-0.7Sr-0.2Mn Magnesium Alloy
Authors: Rzychoń Tomasz , Chmiela Bartosz
Published: August 2012

The paper presents results of microstructural investigations and creep properties of Mg-5Al-3Ca-0.7Sr-0.2Mn (ACJM53) and Mg-5Al-3Ca-0.8Sn-0.7Sr-0.2Mn (ACTJM531) magnesium alloys in as cast condition. The microstructure of the ACJM53 consists of α-Mg, (Mg,Al)2Ca - C36, Al3Mg13(Sr,Ca), Al2Ca - C15 and AlxMny. Additionally, the CaMgSn phase is observed in the ACTJM531 magnesium alloy. The addition of 0.8 wt% tin reduces the tensile strength at ambient temperature and creep resistance at 180°C.
On the Oxidation Behaviour of WE43 and MSR-B Magnesium Alloys in CO2 Atmosphere
Authors: Przeliorz Roman , Piątkowski Jaroslaw
Published: August 2012

The aim of the studies was to determine the oxidation kinetics of two magnesium alloys, i.e. WE43 and MSR-B, in CO2 atmosphere with and without the addition of 2 vol.% H2O. The rate of oxidation was measured by thermogravimetry in the temperature range of 530-580°C, i.e. below and above the eutectic melting point. The melting point of the eutectic mixture was determined by differential scanning calorimetry (DSC). The corrosion products were analysed by scanning electron microscopy (SEM) and X-ray microanalysis combined with EDS. Studies showed that on the WE43 alloy, a two-layer scale was formed, in which the outer part was composed of yttrium and magnesium oxides, while the inner part contained only yttrium oxide. The scale was found to preserve its good protective properties even above the eutectic temperature. Analysis of the results showed that on the MSR-B alloy, under a thin, uneven layer of scale, the process of internal oxidation occurred, and at a temperature of 580°C, the alloy underwent partial melting
Galvanic Corrosion Test of Magnesium Alloys after Plastic Forming
Authors: Przondziono Joanna , Walke Witold , Hadasik Eugeniusz
Published: August 2012

The purpose of this study was to evaluate resistance to galvanic and crevice corrosion of magnesium alloys AZ61 and AZ80. Resistance to galvanic corrosion was evaluated with additional application of aluminium alloy 2017A and 8Mn2Si steel as reference materials. The tests were carried out by means of potentiostat VoltaLab PGP 201 by Radiometer with application of Evans method. The tests were carried out in the solution with concentration of 0.01 M NaCl in ambient temperature. For comparison, the relations of the surface of magnesium alloys to aluminium alloys and steel (1:1, 5:1 i 10:1) was differentiated in the experiment. It was proved that AZ80 alloy features slightly higher corrosion resistance in contact with aluminium alloy and steel.
Creep Resistance of WE43 Magnesium Alloy Joints
Authors: Kierzek Agata , Adamiec Janusz
Published: August 2012

Magnesium alloys of Mg-Y-RE-Zr series are characterized by creep resistance up to a temperature of 250 ° C, and can work up to a temperature of 300oC. These properties allow for the application of alloys of Mg-Y-RE-Zr series for the elements of racing car engines operating in the conditions of high loads and temperatures. The requirement of high reliability components of aircraft propulsion system, with high strength and corrosion resistance, also led to the use of these alloys in the aerospace industry. Welding technologies in cast magnesium alloys are applied in order to repair defects in castings, occurring in the casting process, as well as to regenerate worn out castings. Joints made of magnesium alloys should have at least the same properties as a finished casting. The literature lacks information on the properties of joints welded of cast magnesium alloys.This work includes examination of influence of heat treatment on creep resistance of alloy WE43. Material for the study comprised joints made by the TIG method, welded in the cast state. Creep tests were carried out on joints without heat treatment and joints after heat treatment. The tests were performed at the temperatures of 200 ° C and 250 ° C during 100h. It was found that there is an increase in creep resistance of the joints after heat treatment.
Impact of Heat Treatment on the Structure and Properties of the QE22 Alloy Welded Joints
Authors: Kierzek Agata , Adamiec Janusz
Published: August 2012

The QE22 cast magnesium alloy containing silver, rare earth elements and zirconium is characterized by high mechanical properties and creep resistance of up to 200 ° C. It is cast gravitationally into sand moulds and permanent moulds. After the casting process any possible defects appearing in the cast are repaired with the application of welding techniques. The repaired cast should possess at least the same properties as the one which does not require any repairs. The aim of this thesis was to determine the impact of the heat treatment on the microstructure of the QE22 alloy welded joint. The creep resistance of the welded joints was also analyzed.
Grain Refinement of Ti-48Al-2Cr-2Nb Alloy by Heat Treatment Method
Authors: Szkliniarz Agnieszka
Published: August 2012

In this paper, the possibility of refining grain of Ti-48Al-2Cr-2Nb alloy in the processes of multi-stage heat treatment consisted of initial heat treatment, cyclic heat treatment and under-annealing was evaluated. Microstructural changes that take place during the particular heat treatment procedures were also described. It was demonstrated that due to the application of combined cyclic heat treatment and under-annealing almost 24-fold grain refinement in relation to the state after homogenising could be obtained. Probable mechanisms of grain refinement in the proposed heat treatment processes were also presented and influence of individual procedures of the proposed treatment on selected properties of the investigated alloy was described
Influence of Overheating Degree on Material Reliability of A390.0 Alloy
Authors: Piątkowski Jaroslaw
Published: August 2012

The object of the studies was A390.0 alloy (AlSi17Cu5Mg), similar to A3XX.X series, gravity cast into sand and metal moulds. This alloy is mainly used for cast pistons operating in I.C. engines, for cylinder blocks and housings of compressors, and for pumps and brakes. The A390.0 alloy was poured at temperatures 880 and 980°C, holding the melt for 30 minutes and casting from the temperature of 780°C. The assessment of the impact of the degree of overheating was to analysis the tensile strength. Studies were carried out on a normal-running fatigue testing machine, which was the mechanically driven resonant pulsator. For the needs of quantitative reliability evaluation and the time-to-failure evaluation, the procedures used in survival analysis, adapted to the analysis of failure-free operation with two-parametric Weibull distributions, were applied. Having determined the boundary value σ0 for Weibull distribution, the value of „m” modulus was computed along with other coefficients of material reliability, proposed formerly by the authors. Basing on the obtained results, a model of Weibull distribution function was developed for the tensile strength with respective graphic interpretation.