The synergistic effects of Nb/Mn and Sb/Mn on the microstructure and electrical characteristics of BaTiO3 based ceramics

The microstructure and dielectric properties of Nb-Mn or Sb-Mn codoped BaTiO3 compositions were investigated. Starting ceramics powders were prepared by Pechini method. The composites were sintered at 1310°C and 1330°C in an air atmosphere for two hours. The microstructure and compositional investigations were done with SEM equipped with EDS. Two distinguish microstructure regions are observed in Nb/0.05Mn doped BaTiO 3 ceramics sintered at low temperature. The first, large one, with grain sizes from 5-40 μm and the second region with small grain sizes from 1 to 5 μm. Sintering at higher temperature, independent of Mn content, enables to achieve a uniform microstructure with grains less than 6 μm. In Sb/Mn doped ceramics, for both sintering temperatures, bimodal microstructures with fine grained matrix and grains up to 10 μm is formed. The highest value of permittivity at room temperature and the greatest change of permittivity in function of temperature are observed in Nb/0.01Mn doped ceramics compared to the same ones in Sb/Mn doped ceramics. The greatest shift of Curie temperature towards lower temperature has been noticed in Sb/Mn BaTiO3 ceramics compared to others samples. In all investigated samples the dielectric loss after initially large values at low frequency maintains a constant value for f>3 kHz.

Geologic e geoquímica do batólito Rapakivi Rio Branco, SW do Craton Amazônico - MT

The Rio Branco Rapakivi Batholith belongs to the Cachoeirinha Tectonic Domain, part of the Rio Negro-Juruena Geochronological Province located on the southwestern portion of the Amazonian Craton in Mato Grosso, Central Brasil. A systematic geological mapping on a 1:100.000 scale, coupled with petrographic and geochemical studies allowed to redefine this batholithic unit, to recognize faciological variations and to characterize the geochemical features of this rapakivi magmatism. The batholith is constituted by two major plutonic suites, the first forming a basic suite of fine-grained, equigranular, mesoto melanocratic gray to black lithotypes, with usually discontinuous porphyritic varieties located near the margins of the intrusion. The second one is characterized by acid to intermediate rocks constituted by porphyritic granites, in part granophyric, with rapakivi textures. They have K-feldspar phenocrysts of up to 4cm. Three distinct petrographic facies are recognized in this suite: 1. equigranular to pegmatitic monzogranites; 2. red rapakivi leuco-monzogranites; 3. dark red rapakivi monzogranites to quartz-monzonites. Rocks present SiO2 contents from 67% to 73%, show peraluminous to metaluminous compositions and define a high-K calc-alkaline to shoshonitic magmatism in an I- and A-type, post-orogenic to anorogenic intraplate environment. The magmatic processes are associated with the end of the collisional event that consolidated and stabilized the SW part of the Amazonian Craton.

Diffuse Effect of the Tungsten Doped Ba(Zr0.10Ti0.90)O3 Ferroelectric Ceramics

Barium zirconate titanate Ba(Ti0.90Zr0.10)O3 ceramics doped with WO3 (BZT:2W) have been prepared by a traditional solid phase reaction. The effect of temperature on the structural and electrical properties was investigated. X ray diffraction data evidenced formation of secondary phases for the samples sintered at 1300oC end 1350oC while the pure phase was attained at 1200oC. A modified Curie-Weiss law was used to describe the diffuseness of a phase transition. As temperature increases, the maximum dielectric permittivity decreased. The fine-grained sample showed a 'diffuse-like' ferroelectric behavior. The dielectric permittivity reaches a maximum value (εm ~6420 at 10 kHz) for the ceramics sintered at 1200oC for 4 hours.

Suíte vulcânica serra da bocaina, grupo amoguijá, maciço rio apa-MS

The Rio Apa Massif corresponds to the southeastern portion of the Amazonian Craton and crops out in the Mato Grosso do Sul State, Brazil. It is constituted by rocks of paleoproterozoic age of Rio Apa Complex, Alto Tererê Group and the plutonic-volcanic suites of the Amoguijá Group, subdivided in Alumiador Intrusive suits and Serra da Bocaina Volcanic. The Volcanic Suite is represented by São Francisco and Bocaina mountains and is constituted by terms of the composition of alkali - rhyolitic to rhyolitic, including in minor amounts riodacite, andesite and dacite. It consists of a variety of textual subvolcanic rocks, volcanic and varied volcanoclastics. The pyroclastic deposits are very expressive and consist of pyroclastic particle immerse in aphanitic matrix, fine grained or amorphous, where quartz, feldspar, chlorite, sericite, microlithes of carbonate, sparse spherulites and reliquiar volcanic glass can be distinguished. The pyroclastic rocks are represented by breccias, ignimbrites, agglomerate, tuffs, lapillistones and pumices and contain commonly vitroclasts, lithoclasts and crystalloclasts, pumices, fiammes, glass shards, spherulites, vesicles and amygdales. They are calc-alkaline rocks with dominant peraluminous character high to middle potassium series and define a sin-colisional dominant tectonic and are genetically associated to the evolution of the Amoguijá Magmatic Arc.

Development of ceramic cutting tools for future application on dry machining

Advanced ceramic materials constitute a mature technology with a very broad base of current and potential applications and a growing list of material compositions. Within the advanced ceramics category, silicon nitride based ceramics are wear-resistant, corrosion-resistant and lightweight materials, and are superior to many materials with regard to stability in high-temperature environments. Because of this combination the silicon nitride ceramics have an especially high potential to resolve a wide number of machining problems in the industries. Presently the Si3N4 ceramic cutting tool inserts are developed using additives powders that are pressed and sintered in the form of a cutting tool insert at a temperature of 1850 °C using pressureless sintering. The microstructure of the material was observed and analyzed using XRD, SEM, and the mechanical response of this array microstructure was characterized for hardness Vickers and fracture toughness. The results show that Si3N4/20 wt.% (AlN and Y 2O3) gives the best balance between hardness Vickers and fracture toughness. The Si3N4/15 wt.% (AlN and Y 2O3) composition allows the production of a very fine-grained microstructure with low decreasing of the fracture toughness and increased hardness Vickers. These ceramic cutting tools present adequate characteristics for future application on dry machining. © (2010) Trans Tech Publications.

Magmatismo do batólito rapakivi Rio Branco, sw do Cráton Amazônico (MT)

Rio Branco Rapakivi Batholith is located on the southwestern portion of the Amazonian Craton in Mato Grosso and belongs to the Cachoeirinha Tectonic Domain, part of the Rio Negro-Juruena Geochronological Province, Central Brasil. The batholith is constituted by microgabbros to quartz microgabbros and microdiorites to quartz microdiorites, middle to fine-grained equigranular to porphyritic varieties form the Rio Branco Intrusive Basic Suite, showing a discontinuous distribution and located near the margins of the intrusion.Majorly constituted by porphyritic, granophyric and isotropic facies of Rio Branco Intrusive Acid Suit which is composed by older dark red rapakivi monzogranites to quartz monzonites and quartz sienites (1403±0.6 Ma) and the younger red rapakivi leuco-monzogranites (1382±49 Ma) and late equigranular to pegmatitic monzogranites. The magmatism is constituted by two distinct magmas related to the end of the collisional event of Cachoeirinha Orogeny, one with alkaline basalts generated in an intraplate environment and the other postorogenic to anorogenic with peraluminous to metaluminous compositions and define a high-K calc-alkaline to shoshonitic magmatism in transition among the I- and A-types. The contacts are marked by extensive mafic sills and dikes of alkaline basalts derived from intraplate environment of the Salto do Céu Intrusive Basic Suite (±808 Ma) associate to the Sunsás-Aguapei Orogenic Belt and metasedimentary rocks of the Aguapeí Grup.

Suíte plutônica Alumiador, grupo Amonguijá, maciço rio apa - MS

The Rio Apa Massif corresponds the southern portion of the Amazon Craton and is located in the southwest of Mato Grosso do Sul State. It consists on Paleoproterozoic rocks of Rio Apa Complex, Alto Tererê Group and Amonguijá Group, is subdivided into Alumiador Plutonic Suite and Serra da Bocaina Volcanic Suite. The volcanic suite is comprises sub volcanic, volcanic and varied volcanoclastics rocks with composition ranging from alkali-rhyolitic to rhyolite types. The plutonic suite corresponds to an N-S elongated batholith and is characterized by four main segments delimited by NW-SE faults. The southern and central main segments, discussed in this paper, are characterized by the following petrographic facies: medium to fine grained hornblende-biotite monzogranites, coarse grained biotite monzogranites, graphic biotite sienogranites and muscovite sienogranites and the northern segment is contemporaneous and is composed of two different sequences of rocks, one acid and another of basic to ultrabasic composition. The southern and central segment consists of to chemically compatible rocks with the types I and A Granites. These are calc-alkaline rocks of high potassium to the shoshonitic and subalkaline. Constitute sin-collisional granites of metaluminous the peraluminous characters of the Amonguijá Magmatic Arc, but they exhibit late litotypes with chemical characteristics of post tectonic granites from intraplate environment.

Avaliação do desempenho de argamassas com adição de cinza do bagaço de cana-de-açúcar

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Processos, fácies e geometria do sistema turbidítico da formação Taciba/Membro Rio Segredo, faixa aflorante norte catarinense

Pós-graduação em Geociências e Meio Ambiente - IGCE

Diagênese da Formação Corumbataí na Mina Partezani, Rio Claro - SP

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Caracterização litogeoquímica dos basaltos do município de Monções -SP

The paper deals with the petrographic and geochemical investigation of basalt flows present in a gravel quarry in the town of Monções in northwestern São Paulo State, members of the Serra Geral Formation of the Paraná Basin. Were collected 11 samples from different horizons within a topographic vertical profile with an average of 18 meters in height. The samples were subjected to macroscopic and microscopic petrographic and chemical major, minor and trace. The results indicated that it is tholeiitic basalts with dense fine grained average. Petrographic analyzes show that basalts studied are basically constituted by plagioclase (between 33 and 49%), labradorite and clinopyroxenes (between 29 and 46%) represented by the subordinate pigeonite and augite, having as accessories opaque (between 3 and 15% ), olivine (<2%), apatite and zircon as dashes. The secondary minerals correspond to cloropheite, chlorite, serpentine, epidote, albite and iron oxides and hydroxy as well as bowlingit of clay, nontronite, and celadonite. The basalts are kind of high-titanium (Hti)> 1.8% TiO2, and apparently belong to the Pitanga magma-type. The geochemical analyzes proved unsatisfactory for the determination of a probable lithogeochemistry differentiation within the vertical stroke for generating multiple data correlation or no immediately discernible trends

Análise da curva de resfriamento e refino de grão da liga de alumínio AA 356

The macrostructure of an alloy solidification in the raw state is of utmost importance due to its influence on mechanical properties. A structure showing columnar grains is generally undesirable in most applications of cast products and grain refining aims to suppress the formation of these grains and get a fine-grained equiaxed structure that improves the supply of liquid metal and the mechanical properties, as yield strength and tensile strength limit, as well as the tendency of formation of hot cracks. The type and size of grains formed are determined by chemical composition, cooling rate and the use of inoculum for grain refining. Titanium and boron are the major refiners in the aluminum industry and can be added to the molten metal in the form of alloys such as Al-Ti, Al-Ti-B or Al-B. In this paper we will discuss the information obtained from cooling curves and first derivative of the cooling curve to obtain the thermal parameters that influence the process of grain refining alloy AA 356.0

Estudo sobre o potencial de alguns latossolos da região do Vale do Paraíba, estado de São Paulo, para uso em camadas estruturais de pavimentos de baixo volume de tráfego

The main purpose of this research is to raise, through lab rehearsals, the geometric properties of some oxisols from the region of Vale do Paraíba as well as comparing them to demands prescribed by Technical Specifications ESP08/05 of the Road Department of the State of Paraná, for sub-base or fine grained lateritic soil base (SAFL) and in the Technical Specification ET-DEP00/006 of the Road Department of the State of São Paulo (DER/SP) for subbase or crushed stone base. According to the results that were obtained it will be feasible to appraise the usage of these sorts of soils in structure layers of low-weight traffic pavements

Comportamento fractal de superfícies de fadiga em ligas aeronaúticas

Fracture surfaces express sequences of events of energy release with crack propagation in metal alloys, the evolution of topographic features can indicate the lines of load action, failures during the use or processing. The quantitative fractography is an important tool in the study of fracture surfaces, because it allows their interpretation and characterization. In order to evaluate the effectiveness of the characterization of fracture surfaces grounded on concepts such as selfsimilarity and self-affinity, it used the 15-5PH steel that was characterized by metallographic and tensile tests. The metallography allows the microstructural characterization of this steel and proved the presence of the martensite phase in the slats form and a fine-grained, both in the radial and in the axial direction of the dowel. The tensile test (ASTM E8) of this material allowed the determination of the mechanical properties, so based on the obtained results it was possible to affirm that the 15-5PH steel has high mechanical properties and a good stretch. Besides, the specimens also underwent testing of crack propagation, standardized by ASTM E647-00, thus it was obtained the fracture surfaces for characterization under monofractal and multifractal approaches. In front of all the exposed it was possible to conclude that in all measurements the correlation between the crack tip position and the fractal dimension was established in accordance with changes in the thickness and in the fracture micromechanisms presents. Furthermore, the multifractal approach was more sensitive to these variations allowing a more detailed characterization of the morphology

Mapeamento geológico, caracterização litoquímica e potencial econômico do corpo de cromitito de Cedrolina, Santa Terezinha de Goiás - GO

Studies of mafic-ultramafic bodies have been carried out through the years due to their great use on the interpretation of geochemical and geotectonic processes that took place in Earth's history. Amongst them, chromitites are notably recognized for being excellent indicators of their parental magma chemistry and of different geotectonic environments, as well for frequently containing associated noble metals mineralization. Thus the investigation of one of this ultramafic bodies that occurs inside the Pilar de Goiás Greenstone Belt was proposed, resulting in a detailed map of the chromitites and country rocks, as well as innumerous new data on the chemistry of chromite and associated matrix and accessory minerals. These studies were based upon geological field observations, optic and Scanning Electron Microscope (SEM), besides electron microprobe and cathodoluminescence analysis performed at the “Eugen F. Stumpfl Laboratory” of the Montanuniversität Institute of Resource Mineralogy, University of Leoben - Leoben, Austria. The chromitites are composed of 40-70% in volume of chromite (~50% on average), 14-55% of talc (~30% on average), 3-60% of chromium rich chlorite (~20% on average), traces to 4% of iron hydroxides and traces to 3% of rutile (1,5% on average). The chromite occurs as large spherical aggregates or as fine grained subhedral crystals disseminated in the matrix. This aggregates have diameters of 0.3-1.5 cm (1 cm on average) and are extremely well rounded, massive to intensively fractured, and commonly deformed to ellipsoids. When observed under the microscope, these aggregates show well rounded to slightly irregular borders, but on their interiors, these structures are represented by fine to medium grained euhedral to subhedral chromite crystals that have sharp contacts between themselves. The rock's matrix is basically made of chlorite and talc that define a metamorphic foliation (Sn), being the talc an alteration product ...