Estudo da adição de resíduo de scheelita em matriz cerâmica: formulação, propriedades físicas e microestrutura

Extractivism mineral is considered an activity highly degrading, due to the large volume of material that he moves in the form of ore and residues. The vast majority of mining companies do not show any technology or economically viable application that will allow the recycling of mineral residue, these being launched in areas receiving located the "open skies" degrade the environment. In Rio Grande do Norte to the production of ceramic red restricts their activities to the production of products such as: solid bricks, ceramic blocks, tiles, among others. Seeking to unite experiences and technical information that favor sustainable development, with important benefits to the construction sector and civil society in general, the present work studies the incorporation of the residue of scheelite in ceramic matrix kaolinitic, coming from the municipality of Boa Saúde - RN, in percentage of 5 %, 10 %, 20 %, 30% 40% and 50 %, by evaluating its microstructure, physical properties and formulation. The raw materials were characterized through the trials of X ray fluorescence, Diffraction of X rays, Differential Thermal Analysis and Termogravimetric Analysis. The samples were formed and fired at temperatures of 850o, 900o, 1000o, 1050o, 1100o, 1150o and 1200 oC, with isotherm of 1 hour and heating rate of 10 oC/min. Assays were performed technological of loss to fire, Water Absorption, Apparent Porosity, Apparent Density, Mass Loss in Fire and Bending Resistance; in addition to the Scanning Electron Microscopy, analyzing their physical and mechanical properties. The use of residue of scheelite in ceramic mass kaolinitic provided a final product with technological properties that meet the technical standards for the production of bricks and roofing tiles, with the percentage of 20% of waste that showed the best results

Síntese e caracterização de ferrita ni-zn pelo método dos precursores poliméricos calcinada por energia de microondas

Magnetic ceramics have been widely investigated, especially with respect to intrinsic and extrinsic characteristics of these materials. Among the magnetic ceramic materials of technological interest, there are the ferrites. On the other hand, the thermal treatment of ceramic materials by microwave energy has offered various advantages such as: optimization of production processes, high heat control, low consumption of time and energy among others. In this work were synthesized powders of Ni-Zn ferrite with compositions Ni1- xZnxFe2O4 (0.25 ≤ x ≤ 0.75 mols) by the polymeric precursor route in two heat treatment conditions, conventional oven and microwave energy at 500, 650, 800 and 950°C and its structural, and morphological imaging. The materials were characterized by thermal analysis (TG/ DSC), X-ray diffraction (XRD), absorption spectroscopy in the infrared (FTIR), scanning electron microscopy (SEM), X-ray spectroscopy and energy dispersive (EDS) and vibrating sample magnetometry (VSM). The results of X-ray diffraction confirmed the formation of ferrite with spinel-type cubic structure. The extrinsic characteristics of the powders obtained by microwave calcination and influence significantly the magnetic behavior of ferrites, showing particles ferrimagnéticas characterized as soft magnetic materials (soft), is of great technological interest. The results obtained led the potential application of microwave energy for calcining powders of Ni-Zn ferrite

Estudo da molhabilidade de ligas de adição à base de prata sobre insertos cerâmicos para aplicação em brocas perfuração de poços de petróleo

Metal-ceramic interfaces are present in tricone drill bits with hard ceramic inserts for oil well drilling operations. The combination of actions of cutting, crushing and breaking up of rocks results in the degradation of tricone drill bits by wear, total or partial rupture of the drill bit body or the ceramic inserts, thermal shock and corrosion. Also the improper pressfitting of the ceramic inserts on the bit body may cause its total detachment, and promote serious damages to the drill bit. The improvement on the production process of metal-ceramic interfaces can eliminate or minimize some of above-mentioned failures presented in tricone drill bits, optimizing their lifetime and so reducing drilling metric cost. Brazing is a widely established technique to join metal-ceramic materials, and may be an excellent alternative to the common mechanical press fitting process of hard ceramic inserts on the steel bit body for tricone drill bit. Wetting phenomena plays an essential role in the production of metal/ceramic interfaces when a liquid phase is present in the process. In this work, 72Silver-28Copper eutectic based brazing alloys were melted onto zirconia, silicon nitride and tungsten carbide/Co substrates under high vacuum. Contact angle evolution was measured and graphically plotted, and the interfaces produced were analysed by SEM-EDX. The AgCu eutectic alloy did not wet any ceramic substrates, showing high contact angles, and so without chemical interaction between the materials. Better results were found for the systemns containing 3%wt of titanium in the AgCu alloy. The presence os titanium as a solute in the alloy produces wettable cand termodinamically stable compounds, increasing the ceramics wetting beahviour

Desenvolvimento de membranas porosas de alumina para fins de tratamento de efluente industrial têxtil

Textile production has been considered as an activity of high environmental impact due to the generation of large volumes of waste water with high load of organic compounds and strongly colored effluents, toxic and difficult biodegradability. This thesis deals with obtaining porous alumina ceramic membranes for filtration of textile effluent in the removal of contaminants, mainly color and turbidity. Two types of alumina with different particle sizes as a basis for the preparation of formulation for mass production of ceramic samples and membranes. The technological properties of the samples were evaluated after using sintering conditions: 1,350ºC-2H, 1,450ºC-30M, 1,450ºC-2H, 1,475ºC-30M and 1,475ºC-2H. The sintered samples were characterized by XRD, XRF, AG, TG, DSC, DL, AA, MEA, RL, MRF-3P, SEM and Intrusion Porosimetry by Mercury. After the characterization, a standard membrane was selected with their respective sintering condition for the filterability tests. The effluent was provided by a local Textile Industry and characterized at the entry and exit of the treatment plant. A statistical analysis was used to study the effluent using the following parameters: pH, temperature, EC, SS, SD, oil and grease, turbidity, COD, DO, total phosphorus, chlorides, phenols, metals and fecal coliform. The filtered effluent was evaluated by using the same parameters. These results demonstrate that the feasibility of the use of porous alumina ceramic membranes for removing contaminants from textile effluent with improved average pore size of 0.4 micrometre (distribution range varying from 0,025 to 2.0 micrometre), with total porosity of 29.66%, and average percentages of color removal efficiency of 89.02%, 92.49% of SS, turbidity of 94.55%, metals 2.70% (manganese) to 71.52% (iron) according to each metal and COD removal of 72.80%

Efeito da Gália como aditivo de sinterização em eletrólitos cerâmicos à base de céria sintetizados pelo método de complexação de cátions

Fuel cells are considered one of the most promising ways of converting electrical energy due to its high yield and by using hydrogen (as fuel) which is considered one of the most important source of clean energy for the future. Rare earths doped ceria has been widely investigated as an alternative material for the electrolyte of solid oxide fuel cells (SOFCs) due to its high ionic conductivity at low operating temperatures compared with the traditional electrolytes based on stabilized zirconia. This work investigates the effect of gallium oxide (Gallia) as a sintering aid in Eu doped ceria ceramic electrolytes since this effect has already been investigated for Gd, Sm and Y doped ceria electrolytes. The desired goal with the use of a sintering aid is to reduce the sintering temperature aiming to produce dense ceramics. In this study we investigated the effects on densification, microstructure and ionic conduction caused by different molar fraction of the dopants europium (10, 15 and 20%) and gallium oxide (0.3, 0.6 and 0.9%) in samples sintered at 1300, 1350 and 1450 0 C. Samaria (10 and 20%) doped ceria samples sintered between 1350 and 1450 °C were used as reference. Samples were synthesized using the cation complexation method. The ceramics powders were characterized by XRF, XRD and SEM, while the sintered samples were investigated by its relative density, SEM and impedance spectroscopy. It was showed that gallia contents up to 0.6% act as excellent sintering aids in Eu doped ceria. Above this aid content, gallia addition does not promote significant increase in density of the ceramics. In Ga free samples the larger densification were accomplished with Eu 15% molar, effect expressed in the microstructure with higher grain growth although reduced and surrounded by many open pores. Relative densities greater than 95 % were obtained by sintering between 1300 and 1350 °C against the usual range 1500 - 1600 0 C. Samples containing 10% of Sm and 0.9% of Ga reached 96% of theoretical density by sintering at 1350 0 C for 3h, a gain compared to 97% achieved with 20% of Sm and 1% of Ga co-doped cerias sintered at 1450 0 C for 24 h as described in the literature. It is found that the addition of gallia in the Eu doped ceria has a positive effect on the grain conductivity and a negative one in the grain boundary conductivity resulting in a small decrease in the total conductivity which will not compromise its application as sintering aids in ceria based electrolytes. Typical total conductivity values at 600 and 700 °C, around 10 and 30 mS.cm -1 respectively were reached in this study. Samples with 15% of Eu and 0.9 % of Ga sintered at 1300 and 1350 °C showed relative densities greater than 96% and total conductivity (measured at 700 °C) between 20 and 33 mS.cm -1 . The simultaneous sintering of the electrolyte with the anode is one of the goals of research in materials for SOFCs. The results obtained in this study suggest that dense Eu and Ga co-doped ceria electrolytes with good ionic conductivity can be sintered simultaneously with the anode at temperatures below 1350 °C, the usual temperature for firing porous anode materials

Estudo da viabilidade do processo de reciclagem do material descartado do sistema Zirkonzanh® de produção de próteses dentárias

At present, the material of choice for performing aesthetic dental prosthetic work is in the ceramic. Among them, the ceramic base of stabilized zirconia with 3% yttria (3Y - TZP) stand out for having excellent physical and mechanical properties. During the machining of blocks of zirconia in the laboratory to prepare the various types of prostheses, much of the material is given off in the form of powder, which is subsequently discarded. The waste of this material results in financial loss, reflecting higher final cost treatment for patients, as well as damage to the environment, thanks to the processes involved in the manufacture and disposal of the ceramic. This research, pioneered the recycling of zirconium oxide powder obtained during milling of dental crowns and bridges, we highlight the social and environmental aspects and aims to establish a protocol for the reuse of waste (powder of zirconia Zirkonzahn® system) discarded to obtain a new block of compacted zirconia to maintain the same mechanical and microstructural properties of commercial high-cost imported material. To compare with the commercial material, samples were uniaxially (20 MPa) and isostatically (100 MPa), and its mechanical and microstructural characterization was performed through tests of density, porosity, dilatometry, X-ray diffraction (XRD), hardness, fracture toughness, resistance to fracture electron microscopy (SEM) and analysis of grain size. The results observed in the samples were isostatically pressed similiares those obtained with samples from the commercial material demonstrating the viability of the process

Estudo de Matérias-Primas do Rio Grande do Norte para Uso em Revestimento Poroso: Influência do teor de dolomita e temperatura de calcinação nas propriedades físico-mecânicas

The state of Rio Grande do Norte presents a great potentiality for the production of ceramic tiles because of having natural raw material in quantity and quality making its economical exploration possible, beyond the great energetic differential of the state, the natural gás. This works aims to study the influence of the dolomite and granulometry concentration and calcinations temperature in the obtaining of formulations for porous coverings which have to be coherent to the project,s specifications. The experiments have involved the physical-chemical and mineralogical characterizations of raw materials and mechanical tests in the dry and burnt proof bodies preceding a mixture experiment planning with the use of the response surface methodology, in order to get the best raw materials combinations to produce a ceramic mass with specific properties. The twelve ceramic masses studied in this work were prepared by the via dry process, characterized, shaped by uniaxial pressing and sinterized in the temperatures of 940ºC, 1000ºC, 1060ºC, 1120ºC and 1180ºC, using a fast burning cycle. The crystalline phases formed during the sintering in the temperatures in study have revealed the presence of anorthite and diopside beyond quartz with a remaining phase. These phases were the main responsible ones by the physical- mechanical properties of the sinterized proof bodies. The proof bodies after the sintering stage have presented water absorption higher than 10% and a good dimensional stability in all studied temperatures. However, the flexural breaking strength results in the temperatures of 940ºC, 1000ºC and 1060ºC, under the temperature zone of the vitrification of ceramic whiteware do not reach the flexural breaking strength specific for the porous wall tile (15 MPa), but in the temperature of 1120ºC next to the vitrification temperature zone, some whiteware ceramic (formulations) has reached the specified value for the porous wall tile. The results of this work have showed that the studied raw materials have great importance for used in the production of porous wall tiles (BIII)

Aproveitamento de resíduo de beneficiamento do caulim na produção de porcelanato cerâmico

Nowadays, industries from all sectors have great concerns over the disposition of the residues generated along the productive process. This is not different in the mineral sector, as this generates great volumes of residues. It was verified that the kaolin improvement industry generates great volumes of residue basically constituted of kaolinite, muscovite mica and quartz, which are basic constitution elements to formularisations of ceramics masses to the production of covering of stoneware tiles type. This happens because the methodology applied to the improvement process is still very rudimentary, what causes a very low yield, only ¼ from all the material volume that enters the improvement process, in the end, is marketable. The disposal of this residue, in a general way, causes a very big negative environmental impact, what has justified the researches efforts aiming to find a rational solution to this problem. In this way, the intention of this present work is the utilization of this residue in the manufacture of products to high quality ceramics covering, stoneware tiles in an industrial scale. For this purpose, the influence of the addition of the residue to a standard ceramics mass used by a ceramics sector company, already established in the market, with the intention of verifying the possibility of use of this residue as the mass complementary raw material and even the possible partial or total substitution of one of the components of the mass for the raw material in evidence will be studied. To the accomplishment of this work, the kaolin improvement residue generated by an industry of exploitation and improvement of kaolin, located in the region of Equador-RN, in the levels 1,2,4,8, 16 and 32% will be added to the standard mass already used for the production of stoneware tiles. The raw materials used, kaolin residue and the standard mass, were characterized through DRX, FRX, DTA, TGA and dilatometry. After the sintering of the bodies of test, tests of water absorption, apparent porosity, post burning linear retraction, apparent specific mass and flexural strength (3 point bending) were realized to determinate the technological properties of these materials. The results show the studied residue can be considered raw material of great potential to the industry of floor and ceramics covering of the stoneware tiles type

Estudio comparativo de la fiabilidad y reproducibilidad en la medición de los tamaños dentarios y las medidas de las arcadas dentarias entre registros manuales y digitales 3d obtenidos por escaneado intraoral y extraoral

Tradicionalmente, los ortodoncistas han realizado las mediciones dentales en los modelos de yeso, pero los avances tecnológicos permiten ahora a los ortodoncistas realizar esas mediciones en los modelos digitales. El propósito de este estudio fue comparar la fiabilidad y reproducibilidad de las medidas de los tamaños dentarios y las arcadas dentarias entre el método manual y los métodos digitales 3D obtenidos por un escáner intraoral CEREC Omnicam (Sirona Dental Systems) y dos escáneres extraorales: inEos X5 (Sirona Dental Systems) y Dental Scanner SMART (Open Technologies). Un modelo de yeso, un escaneado intraoral y dos modelos digitales con un escáner extraoral fueron realizadas para cada uno de los 20 sujetos. Las medidas de los tamaños dentarios, la distancia intercanina y la distancia intermolar de los modelos digitales se compararon con los correspondientes modelos de yeso (estándar de oro) Se utilizó el test de ANOVA para establecer la fiabilidad entre los cuatro métodos y el coeficiente de correlación intraclase fue calculado para determinar la reproducibilidad intra- e inter-examinador. Los resultados encontrados fueron que no existieron diferencias estadísticamente significativas entre las medidas hechas directamente en los modelos de yeso y los modelos digitales. Los coeficientes de correlación intraclase tanto intra- e inter-examinador fue alto y considerado bueno para los cuatro métodos de medición. CCI> 0.90. Se concluyó que las mediciones en los modelos digitales obtenidos con un escáner extraoral e intraoral son fiables y reproducibles

[Texto del convenio de colaboración suscrito entre Artesanías de Colombia S. A. y la asociación de productores de mimbre de Ibagué – ASPROMI].

32 documentos : ilustraciones, fotografías.

Defeitos de desenvolvimento do esmalte e respetivo tratamento

As estruturas dentárias são revestidas pelo esmalte dentário. O esmalte é um tecido de alta dureza, avascular e predominantemente branco. No entanto, distingue-se dos outros tecidos mineralizados do corpo pela sua incapacidade de remodelação. Devido a esse facto qualquer alteração que ocorra, quer ao longo da vida, quer no seu desenvolvimento fica, permanentemente, registada (Seow, 1997). Procurou-se nesta monografia aprofundar os conhecimentos sobre os mais comuns defeitos de desenvolvimento do esmalte existentes, assim como o respetivo tratamento. Para a realização desta monografia foram utilizados os seguintes motores de busca B-on, PubMed, Science Direct e Sci-elo, para a realização da pesquisa de informação, aplicando-se um critério de seleção temporal dos últimos 10 anos. As palavras-chaves e combinações de palavras utilizadas nos motores de busca referidos para a realização da pesquisa foram “Enamel”, “Enamel Development”, “Enamel Defects”, “Amelogenisis Imperfecta”, “Hypoplasia”. Dos 300 artigos encontrados nesta pesquisa, foram selecionados 68. O desenvolvimento dos tecidos dentários é um processo complexo conhecido por odontogénese, podendo ser simplisticamente dividido em três fases Fase de Botão, Fase de Capuz e por último a Fase de Campânula (Thesleff et al.,2009) Existem inúmeros defeitos de desenvolvimento do esmalte registados na literatura, não sendo mesmo possível em muitos casos enquadrar indubitavelmente o referido defeito numa categoria, ou até atribuir-lhe uma designação (Seow, 1997). Optou-se pela sua relevância e epidemiologia abordar nesta monografia os seguintes defeitos: Defeitos de desenvolvimento do esmalte; Opacidades; Opacidade difusa; Hipoplasia; Amelogenese imperfeita e todas as suas categorias; Fluorose e manchas por tetraciclinas assim como os seus respectivos tratamentos. Os defeitos de desenvolvimento de esmalte apresentam diversas características próprias e outras semelhantes entre si, verificando-se assim diversas possibilidades de tratamentos a realizar, uns mais invasivos e outros menos, que vão desde microabrasões na superfície do esmalte, à colocação de cerâmicas, dependendo sempre da preferência do paciente e do seu poder socioeconómico (Azevedo DT et al., 2011). Conclui-se que apesar de todos os problemas que acarretam quer a nível estético quer a nível funcional para os indivíduos nos quais não existe uma grande gravidade das lesões esses casos podem ser resolvidos por um Médico Dentista generalista desde que este tenha o conhecimento adequado dos protocolos de atuação.

Estudio comparativo de la resistencia a la fractura de pilares de zirconia totalmente cerámicos y con base de titanio, en conexión externa e interna

Tesis inédita presentada en la Universidad Europea de Madrid. Facultad de Ciencias Biomédicas. Programa de Doctorado en Odontología Avanzada

Ensayo aleatorizado "in vitro" sobre la capacidad de obturación de tres sistemas con vástago en conductos curvos

Tesis inédita presentada en la Universidad Europea de Madrid. Facultad de Ciencias Biomédicas. Programa de Doctorado en Odontología Avanzada

Ceramic-veneered zirconia frameworks in full-arch implant rehabilitations: A 6-month to 5-year retrospective cohort study

Purpose: This was a retrospective cohort study designed to evaluate the clinical performance of ceramicveneered zirconia frameworks. Materials and Methods: Patients were recruited according to defined inclusion criteria. All patients were checked every 4 months from the time of definitive rehabilitation. At the end of 2013, all patients were rescheduled and rechecked for study purposes. The restorative procedures assessment was performed by previously established methods. The primary outcomes were the survival and success rates of the prosthesis. Descriptive statistics were used for the patient's demographics, implant distribution, and occurrence of complications. To study the survival and success of the prostheses, a Cox Regression analysis was used with a model constructed in a forward conditional stepwise mode. Predictive variables were included in the model, and adjusted survival curves were obtained for each outcome. Results: From 2008 to 2013, 75 patients were rehabilitated with 92 implant-supported, screw-retained, full-arch ceramic-veneered zirconia framework rehabilitations. The range of follow-up was between 6 months and 5 years. From the 92 full implant-supported screw-retained full-arch rehabilitations, Cox regression analysis indicated that within a 5-year time frame, the probability of framework fracture, major chipping, minor chipping, or any of the former combined to occur was 17.6%, 46.5%, 69.2%, and 90.5%, respectively. Conclusion: Results suggest zirconia as a suitable material for framework structure in implant-supported, full-arch rehabilitations. However, it experiences a high incidence of technical complications, mainly due to ceramic chipping. Further clinical studies should aim to ascertain the effects of clinical features and manufacturing procedures on the survival rates of these prostheses. © 2016 by Quintessence Publishing Co Inc.

As representações da nas primeiras sociedades camponesas do Alentejo Central (Portugal)

O Alentejo Central é detentor de um dos mais importantes conjuntos megalíticos a nível europeu. Esta importância decorre não só do elevado número de monumentos megalíticos conservados, mas também do numeroso e variado espólio progressivamente recolhido que nos permite compreender, em parte, a forma como viviam estas sociedades. Os projetos de investigação realizados nas últimas décadas em torno de alguns núcleos megalíticos alentejanos permitiu, por um lado, proceder a uma revisão e medição da orientação das antas e, por outro, compreender melhor as suas diversas e originais manifestações artísticas que se encontram profundamente marcadas por um simbolismo associado aos astros. De fato, em termos gerais, existe algum consenso sobre o simbolismo existente em torno da escolha das orientações dos monumentos megalíticos (funerários e não funerários) marcadamente associados ao Sol e/ou à Lua, ou hipoteticamente, a outras constelações. Nesta comunicação apontam-se e caracterizam-se sucintamente algumas destas orientações e as representações gráficas em espólios (cerâmicas, placas de xisto…) mais significativas e exemplificativas da importância da LUZ, na vida e nas crenças religiosas destas primeiras sociedades camponesas.