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Search Results: 1 - 10 of 56387 matches for " Carlos Renato;Hotza "
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Síntese do pigmento ceramico verde vitória (Ca3Cr2Si3O12) a partir de CaCO3, Cr2O3 e SiO2
Della, Viviana Possamai;Junkes, Janaina Accordi;Rambo, Carlos Renato;Hotza, Dachamir;
Química Nova , 2008, DOI: 10.1590/S0100-40422008000500011
Abstract: the synthesis of the ceramic pigment victoria green (ca3cr2si3o12 ) is described. as raw materials caco3, cr2o3, and sio2 obtained from rice husk were used. borax was used as mineralizer. raw materials were formulated stoichiometrically and calcined from 1000 to 1200 oc for 180 min. the main phase detected was uvarovite with particle size below 45 mm. the pigments were applied on ceramic tiles and sintered at 1150 oc for 40 min. the synthesis process showed to be adequate to produce the green pigment, whose characteristics resemble those of a commercial pigment.
Biomorphous ceramics as porous supports for zeolite coating
Carlos Renato Rambo,Janaína Accordi Junkes,Heino Sieber,Dachamir Hotza
Exacta , 2006,
Abstract: Biotemplating is the processing of microcellular ceramics by reproduction of natural morphologies, where the microstructural features of the biotemplate are maintained in the biomorphic ceramic. Different biotemplates with distinct pore anatomies were used to produce biomorphic supports for the zeolite coating: wood, cardboard, sea-sponge and sisal. The biomorphic ceramics were produced by distinguished processing routes: Al-gas infiltration-reaction, liquid-metal infiltration, dip-coating and sol-gel synthesis, in order to produce nitrides, carbides and oxides, depending on the processing conditions. The zeolite coating was performed by hydrothermal growth of MFI-type (Silicalite-1 and ZSM-5) zeolite crystals onto the internal pore walls of the biomorphic templates. The final biomorphic ceramic-zeolite composites were physically characterized, evaluated in terms of their gas adsorption capabilities and correlated to their microstructure and specific pore anatomy. The combination of the properties of the biomorphic ceramics with the adsorption properties of zeolites results in materials with distinct properties as potential candidates for adsorption and catalytic applications due to their characteristic porosity, molecular sieving capabilities and high thermo-mechanical strength.
Vitroceramicas porosas do sistema LZSA utilizando resíduos organicos como agentes formadores de poros
Eliandra de Sousa,Carlos Renato Rambo,Oscar Rubem Klegues Montedo,Dachamir Hotza
Exacta , 2006,
Abstract: Nas últimas décadas, tem crescido o uso de ceramicas porosas em aplica es tecnológicas, tais como filtros, suportes catalíticos, materiais para implantes ósseos e estruturais. Entre os métodos de obten o de ceramicas porosas, o de adi o do agente formador de poros ao pó ceramico é amplamente utilizado, devido à sua simplicidade. Visando a um reaproveitamento de resíduos organicos e subprodutos vegetais, este trabalho trata sobre a produ o de vitroceramicas porosas do sistema Li2OZrO 2-SiO2-Al2O3 (LZSA) por meio da adi o de baga o da cana-de-a úcar e de pó de madeira ao pó vítreo, como agentes formadores de poros. A degrada o térmica desses agentes, após calcina o/sinteriza o a 750 graus Celsius (°C), foi estudada por termogravimetria e espectroscopia de infravermelho. na. Avaliou-se a microestrutura dos materiais porosos por microscopia eletr nica de varredura (MEV) e foram obtidas porosidades na faixa de 49 a 73%.
Processamento e caracteriza o de espumas ceramicas de microfibras naturais de sílica amorfa obtidas pelo método de réplica
Karina Donadel,Jer?nimo Moraes Gomes,Carlos Renato Rambo,Dachamir Hotza
Exacta , 2008,
Abstract: Cellular ceramics are brittle materials containing high porosity and constituted by a regular and tridimensional arrangement of hollow cells. The great interest on this group of materials is related to their specific properties such as low density, low thermal conductivity and high permeability. In this work, ceramic foams were processed by the replication method. Commercial polyurethane foams with different cell sizes were used to produce foams constituted by microfibers of natural amorphous silica. The polymeric foams were immersed in the ceramic suspension (natural amorphous silica fibers- NASF, bentonite, sodium silicate and water) and then dried and heat-treated for consolidation. The polymeric foam was burned out at 400°C and sintering was carried out at 1150° C for 15-120 min. The obtained sintered samples were subjected to mechanical strength tests, so that compression strength values between 6 and 260 kPa were obtained.
Decomposi??o térmica de espumas de poliuretano para fabrica??o de vitroceramica celular de Li2O-ZrO2-SiO2-Al2O3 (LZSA)
Silveira, Cristian Berto da;Escobar, Jairo A.;Quintero, Miguel W.;Sousa, Eliandra de;Moraes, Elisangela Guzzi de;Oliveira, Ant?nio Pedro Novaes de;Rambo, Carlos Renato;Hotza, Dachamir;
Química Nova , 2007, DOI: 10.1590/S0100-40422007000500010
Abstract: characterization of the thermal decomposition of polyurethane (pur) foams was performed by fourier-transformed infrared (ft-ir) spectroscopy and thermogravimetric analysis (tga). three main weight loss paths were observed by tga, the residue being lower than 3 wt.% for 3 different pur foams analyzed. ft-ir spectra indicated co2, co, nh3 and isocyanides as main decomposition products. pur foams of different cell sizes were immersed in a slurry of the parent glass ceramic of composition li2o-zro2-sio2-al 2o3 (lzsa) and submitted to heat treatment. the lzsa cellular glass ceramics obtained after sintering and crystallization resembled the original morphology of the pur foams.
Prototipagem rápida de pilhas a combustível de óxido sólido
Hotza, D.;
Matéria (Rio de Janeiro) , 2009, DOI: 10.1590/S1517-70762009000400003
Abstract: rapid prototyping (rp) technologies can automatically manufacture near-net shape parts with complicated geometry from computer-aided design (cad) data. the three dimensional part is built up by powder consolidation in layers ("additive" or "generative" process). for this reason, these techniques are often referred to as solid freeform fabrication or layered manufacturing. in general, a five-step approach of the product development is commonly applied: creating a cad model, converting the cad model into stl format, slicing the stl file into cross-sectional layers, fabrication of the product, and finally surface finishing of the product. rp techniques have many benefits over traditional methods for model generation, tools and even construction of production-quality parts. for instance, in contrast to "subtractive" processes (e.g., drilling, milling, grinding) the "additive"-rp methods allow fabrication of products with complex geometries like undercuts, internal cavities or overhangs that cannot be manufactured by other approaches. additive rp methods also offer the possibility to generate parts with an orientated internal pore structure. rp techniques can significantly shorten fabrication times of solid oxide fuel cells (sofc) with small operational expenditure and reduced product costs when applied properly. technologies such as selective laser sintering (sls), laminated object manufacturing (lom) and 3d printing (3dp) may be used for the fabrication of fuel cell prototypes particularly for planar configuration.
Artigo revis?o: colagem de folhas ceramicas
Hotza, Dachamir;
Ceramica , 1997, DOI: 10.1590/S0366-69131997000400002
Abstract: tape casting is a fabrication technique of thin ceramic sheets with large surface areas which are used mainly in the electronic industry as substrates and multilayered capacitors. the process consists essentially in forming a slurry and in casting it through a doctor blade on a generally moving surface. after drying, a flexible, resistant tape is produced which can be then sintered. in this review some theoretical concepts involved in the slurry formulation, as well as technical points of the tape casting process are discussed.
Uso de pronomes no texto "Sendbrief von Dolmetschen" de Martinho Lutero
Hotza, Dachamir;
Revista Brasileira de Linguística Aplicada , 2010, DOI: 10.1590/S1984-63982010000300007
Abstract: this article presents an analysis about the use of pronouns in the text "sendbrief von dolmetschen" ("open letter on translating") originally written by martin luther in germany in 1530. the objective is to try to identify the addressee(s) referred by luther from frequency and location of pronouns use in this text. regarding the question about justification by belief, there is clearly a debate of ideas between luther and his opponents ("i" against "them"). when the question about the intercession of saints is concerned, the text is directed to his followers (noticeable use of "we"). it is concluded that there is not a single addressee, but many of them, which are highlighted along the text.
Artigo revis o: colagem de folhas ceramicas
Hotza Dachamir
Ceramica , 1997,
Abstract: A colagem de folhas ceramicas (tape casting) é uma técnica de fabrica o de pe as ceramicas de espessura fina e grande área superficial, usadas principalmente na indústria eletr nica como substratos de circuitos e capacitores de multicamadas. O processo consiste essencialmente na forma o de uma barbotina e na colagem desta por meio de uma lamina niveladora sobre uma superfície, geralmente móvel. Depois da secagem, é produzida uma folha flexível e resistente que pode ent o ser sinterizada. Neste artigo de revis o, s o discutidos alguns conceitos teóricos envolvidos na formula o da barbotina, bem como aspectos tecnológicos do processo de colagem de folhas ceramicas.
Em busca do gênero lenda urbana
Lopes, Carlos Renato;
Linguagem em (Dis)curso , 2008, DOI: 10.1590/S1518-76322008000200009
Abstract: the present essay aims at locating, from a theoretical point of view, a narrative genre in widespread circulation in contemporary societies, particularly in the virtual media: the so-called urban legends. firstly, we discuss different definitions of urban legends - proposed within distinct research areas, such as folklore studies and sociology -, with a focus on the discursive aspects involved in the constitution of the genre. secondly, we explore the boundaries and intersections between this and two similar, and frequently confused genres: the rumor and the fait divers. we conclude our discussion by reviewing and questioning the very issue of the delimitation of a genre.
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