Efeito da tecnologia de microondas nas propriedades tecnológicas dos componentes de cerâmica estrutural

O processamento térmico de materiais cerâmicos via energia de microondas, no estágio atual, vem ganhando cada dia mais importância, tendo em vista suas inúmeras aplicações, como por exemplo: aplicação de microondas na área de processamento mineral (aquecimento de minérios antes da moagem, secagem, redução carbotérmica de óxidos minerais, lixiviação, fusão, pré-tratamento de minérios e concentrados de ouro refratário, regeneração de carvão, etc. de acordo com Kigman & Rowson, 1998). Em virtude de uma série de vantagens em potencial, frente aos métodos convencionais de aquecimento, como redução no tempo de processamento; economia de energia; diminuição do diâmetro médio das partículas e melhoramento nas propriedades tecnológicas em geral, esta tecnologia vem se destacando. Neste contexto, o objetivo geral deste trabalho, é desenvolver uma pesquisa visando identificar e caracterizar novas opções de matérias-primas cerâmicas como argilas, feldspatos e caulins que sejam eficazes para definir a formulação de uma ou mais massas para produção de componentes de cerâmica estrutural com propriedades físicas, mecânicas e estéticas adequadas após passarem por sinterização convencional e por energia de microondas destacando as vantagens desta última. Além dos requisitos técnicos e de processo, as formulações apresentadas deverão atender às expectativas de preço e de logística de fornecimento. No estudo foram conformados corpos-de-prova por extrusão e prensagem, sinterizados em fornos microondas e convencional, sob ciclos de queima mais rápidos que os atualmente praticados. As matérias-primas foram caracterizadas e analisadas, utilizando as técnicas de fluorescência por raios X (FRX), difração por raios X (DRX), análise térmica diferencial (DTA), análise térmica gravimétrica (DTG), análise granulométrica (AG), microscopia eletrônica de varredura (MEV), absorção d agua (AA), massa especifica aparente (MEA), porosidade aparente (PA), retração linear (RL) e tensão de ruptura e flexão (TRF). Os resultados obtidos indicaram que as propriedades tecnológicas de Absorção de água (AA) e Tensão de Ruptura e flexão (TRF), proposto no trabalho foram adquiridos com sucesso e estão bem além do limite exigido pelas especificações das normas da ABNT NBR 15.270/05 e 15.310/09

Sinterização de matrizes cerâmicas à base de alumina reforçadas por carbetos a partir de precursores poliméricos

Ceramic composites produced with polymerics precursors have been studied for many years, due to the facility of obtaining a complex shape, at low temperature and reduces cost. The main objective of this work is to study the process of sintering of composites of ceramic base consisting of Al2O3 and silicates, reinforced for NbC, through the technique of processing AFCOP, as well as the influence of the addition of LZSA, ICZ and Al as materials infiltration in the physical and mechanical properties of the ceramic composite. Were produced ceramic matrix composites based SiCxOy e Al2O3 reinforced with NbC, by hidrosilylation reaction between D4Vi and D1107 mixtured with Al2O3 as inert filler, Nb and Al as reactive filler. The specimens produced were pyrolised at 1200, 1250 and 1400°C and infiltred with Al, ICZ and LZSA, respectively. Density, porosity, flexural mechanical strength and fracture surface by scanning electron microscopy were evaluated. The microstructure of the composites was investigated by X-ray diffraction to identify the presence of crystalline phases. The composites presented apparent porosity varying of 31 up to 49% and mechanical flexural strength of 14 up to 34 MPa. The infiltration process improviment of the densification and reduction of the porosity, as well as increased the values of mechanical flexural strength. The obtained phases had been identified as being Al3Nb, NbSi2, Nb5S3, Nb3Si and NbC. The samples that were submitted the infiltration process presented a layer next surface with reduced pores number in relation to the total volume

Aplicação de termogravimetria acoplada à espectrometria de massas para caracterização de petróleo e determinação da curva de evolução de gás sulfídrico

With the new discoveries of oil and gas, the exploration of fields in various geological basins, imports of other oils and the development of alternative fuels, more and more research labs have evaluated and characterized new types of petroleum and derivatives. Therefore the investment in new techniques and equipment in the samples analysis to determine their physical and chemical properties, their composition, possible contaminants, especification of products, among others, have multiplied in last years, so development of techniques for rapid and efficient characterization is extremely important for a better economic recovery of oil. Based on this context, this work has two main objectives. The first one is to characterize the oil by thermogravimetry coupled with mass spectrometry (TG-MS), and correlate these results with from other types of characterizations data previously informed. The second is to use the technique to develop a methodology to obtain the curve of evaluation of hydrogen sulfide gas in oil. Thus, four samples were analyzed by TG-MS, and X-ray fluorescence spectrometry (XRF). TG results can be used to indicate the nature of oil, its tendency in coke formation, temperatures of distillation and cracking, and other features. It was observed in MS evaluations the behavior of oil main compounds with temperature, the points where the volatilized certain fractions and the evaluation gas analysis of sulfide hydrogen that is compared with the evaluation curve obtained by Petrobras with another methodology

Desenvolvimento (in) sustentável das indústrias cerâmicas da microrregião do Vale-do-Açu/RN

A great discussion of this work refers to development that is related to the common census of economic growth, in addition, another component of this discussion is related to socio-cultural and environmental impacts of this conception of progress. Giving economic progress is not necessary, since the development in its fullness, that progress depends, but what is sought is a harmony between capital accumulation and environmental limits and social interactions between men and between them and nature. The presence or absence of this harmonious relationship can be observed in various industrial activities, more punctual can cite the example of the developed ceramic activity in the meso-Valley-Acu in Rio Grande do Norte where such activity has great economic representativeness for the region, but that does not have good relations with social and environmental issues and is more focused on the accumulation of capital by increasing its level of industrial activity. Given this debate, the present paper aims to present the profile of a ceramic tile Valley-of-Acu and impacts, ecosocioambientais generated as a result of this activity as well. Methodologically the research will be conducted through literature research papers in books and other work carried out on the same theme, the second time will be held the empirical part of the research through interviews with managers of industries (selected through sample with the criteria set later ) as well as with employees working on the factory floor and city managers in the region under analysis and other agencies responsible for regulation and control of activity potter in the state

Anodização para obtenção de membranas cerâmicas

This a study on the achievement of alumina membranes by the method of anodizing. From this method got up a layer of aluminum oxide on the anodic metal, who presented the basic properties necessary for the application as a support for the production and acquisition of nanomaterials, such as porosity nano and resistance to high temperature, and other properties, as resistance to corrosion, and chemical, high ranking of the structure and pore size of the pores. The latter, ranging from 10 to 100nm depended on the electrolyte used, which in this study was the H2SO4. To remove all remaining aluminum, it is a bath of dissolution with HCl and CuCl where the residual aluminum has been withdrawn, and the deep pores were opened after chemical treatment with NaOH. After the dissolution, the membranes were calcined at temperatures of 300, 600 and 900° C, and sintered at temperatures of 1200 and 1300º C to win mechanical strength, porosity and observe the desired crystallization. Then went through analyses of composition through X-ray diffraction and morphology of the microstructure through a scanning electron microscope. The method was effective for obtaining alumine membranes applied in the processes of production of materials in nano

Obtenção de cerâmicas à base de tricálcio fosfatos utilizando óxido de magnésio como aditivo

The tricalcium phosphate ceramics has been widely investigated in the last years due its bioresorbable behavior. The limiting factor of the application of these materials as temporary implants is its low strength resistance. The tricalcium phosphate presents an allotropic transformation β→α around 1250 ºC that degrades its resistance. Some studies have been developed in order to densify this material at this temperature range. The objective of this work is to study the influence of the addition of magnesium oxide (MgO) in the sintering of β-TCP. The processing route was uniaxial hot pressing and its objective was to obtain dense samples. The samples were physically characterized through density and porosity measurements. The thermal behavior was studied through dilatometric, thermal differential and thermogravimetric analysis. The mechanical properties were characterized by three point flexure test and Vickers microhardness measurements, analyzed of the microstructure. The addition of magnesium oxide doesn t cause an improvement of the mechanical strength in relation to material without additive.

Obtenção de cerâmicas à base de tricálcio fosfatos utilizando óxido de manganês como aditivo

The calcium phosphate ceramics have been very investigated as material for bone implants. The tricalcium phosphate (β-TCP) had a great potential for application in temporary implants like a resorbable bioceramic. This material presents a limitation in its sintering temperature due to occurrence of the allotropic transformation β → α at temperatures around 1200°C, not allowing the attainment of dense ceramic bodies. This transformation also causes cracks, what diminishes the mechanical strength, limiting its use to applications of low mechanical requests. This work studies the influence of the addition of manganese oxide in the sintering of β-TCP. Two processing routes were investigated. The first was the powder metallurgy conventional process. The test bodies (samples) were pressed and sintering at temperatures of 1200 and 1250°C. The second route was uniaxial hot pressing and its objective was to obtain samples with high relative density. The samples were physically characterized through density and porosity measurements. The thermal behavior was studied through dilatometric, thermal differential and thermogravimetric analysis. The mechanical properties were characterized by three point flexure test and Vickers microhardness measurements. The microstructure was analyzed by scanning electron microscopy. The addition of manganese oxide caused an improvement of the mechanical strength in relation to the material without additive and promoting the stabilization of β-TCP to greater temperatures

Estudo do efeito da substituição de caulim por resíduo de caulim na fabricação de cerâmica de revestimento

Companies involved in kaolin mining and treatment represent an important area of industrial development in Brazil, significantly contribution to the worldwide production of such mineral. As a result, large volumes of kaolin residue are constantly generated and abandoned in the environment, negatively contributing to its preservation. In this scenario, the objective of the present study was to characterize the residue generated from kaolin mining as well as to assess its potential use as raw material for the production of ceramic tiles. Ceramic mixtures were prepared from raw materials characterized by X-ray fluorescence, X-ray diffraction, particle size analysis and thermal analysis. Three compositions were prepared using kaolin residue contents of 10%, 20% and 30%. Samples were uniaxially pressed, fired at 1200ºC and characterized aiming at establishing their mineralogical composition, water absorption, apparent porosity, specific mass, linear retraction and modulus of rupture. The results showed that the residue basically consisted of kaolinite and successfully replaced raw kaolin in the preparation of ceramic title formulations without significantly affecting the properties of the fired material

Caracterização de cerâmicas porosas de alumina reforçada com zircônia produzidas pelo método da réplica

Porous ceramics have many applications: thermal insulation, catalytic support, materials to fire protection, filters, and others. There are many techniques to production of ceramic filters. One technique to obtain ceramic filters is the replication method. This method consists in the impregnation of polymeric foam with ceramic slurry followed by a heating treatment that will burn out the organic elements and sintering of the material, resulting of a replication of the original foam. To perform their functions ceramic filters must satisfy mechanical requirements and permeability parameters (darcian k1 and no-darcian k2). The permeability and the strength of the ceramic material are dependent of the pore size and pore distribution. To the use at high temperatures the evaluation of mechanical properties in these temperatures is necessary. In this work the mechanical behavior of two commercial porous ceramics (10 and 40 poros per inch) was studied these materials were submitted to compression and four-point flexure test (room temperature, at 1000 °C, after thermal shock). Density and porosity measurements, permeability tests and microstructural analysis by scanning electronic microscopy (SEM) were realized. The Results showed that the decrease of mechanical strength of these materials, when submitted to thermal shock, occur for propagation of new cracks from cracks pre-existing and the permeability depends of the pore size

Estudo do efeito do óxido de bário no comportamento de massas para porcelanato

In this work, it is proposed the study of the effect of barium oxide acting as synthetic flow in the behavior of masses for stoneware from the use of raw materials found in the deposits of minerals of the Rio Grande do Norte that it makes use of a great natural potential for the industrialization of the product. The porcelanato is a sophisticated product with excellent final properties being applied as ceramic coating in buildings of high standard of engineering. The raw materials selected for the development of the study had been two types of argilas, two types of feldspatos, dolomita, talco, barium carbonate and silica, being characterized by X-ray fluorescence, X-ray diffraction, granulometric analysis, dilatometric analysis and thermal analysis. Thus, it is intended to define four formulations using the cited raw materials that will be processed, conformed and sintered in the temperatures of 1150 °C, 1175 °C, 1200 °C, 1225 °C e 1250 °C. From the physical characterizations, chemical and morphologic of the formed formulations, the effect of barium oxide is determined in the physical and mechanical properties of the studied system carrying water absorption tests, linear retraction, apparent porosity, apparent specific mass, compacting curve, flexural strength and microstructural analysis by XRD and SEM. After analyzing the results, indicated that barium oxide acts as a flux of high temperature and as the ordering of structure, where the embedded glass phase has the nucleating effect phase potassium silico-aluminum reacting with free silica which together with the high content of potassium concentrated form a new crystalline phase called microcline. The masses studied with the addition of barium oxide present physical-mechanical properties highly satisfactory in reduced firing temperatures, which implies a saving in energy given off in the production and increased productivity

Análise do comportamento mecânico de espumas cerâmicas a base de alumina obtidas pelo método da réplica

Ceramics with porous cellular structure, called ceramic foams, have a potential use in several applications, such as: thermal insulation, catalyst supports, filters, and others. Among these techniques to obtain porous ceramics the replication method is an important process. This method consists of impregnation of a sponge (usually polymer) with ceramic slurry, followed by a heat treatment, which will happen the decomposition of organic material and sintering the ceramic material, resulting in a ceramic structure which is a replica of impregnated sponge. Knowledge of the mechanical properties of these ceramics is important for these materials can be used commercially. Gibson and Ashby developed a mathematical model to describe the mechanical behavior of cellular solids. This model wasn´t for describing the ceramics behavior produced by the replica method, because it doesn´t consider the defects from this type of processing. In this study were researched mechanical behavior of porous alumina ceramics obtained by the replica method and proposed modifications to the model of Gibson and Ashby to accommodate this material. The polymer sponge used in processing was characterized by thermogravimetric analysis and scanning electron microscopy. The materials obtained after sintering were characterized by mechanical strength tests on 4-point bending and compression, density and porosity and by scanning electron microscopy. From these results it was evaluated the mechanical strength behavior compared to Gibson and Ashby model for solid cellular structure and was proposed a correction of this model through a factor related to struts integrity degree, which consider fissures present in the structure of these materials besides defects geometry within the struts

Incorporação de cinzas da casca de café na produção de placas cerâmicas para revestimento

Brazil is the world s leading coffee producer. In 2008, 45.99 million of 60 kg bags of benefited coffee were produced. In the process of improvement 50% is grain and 50% is husk, thus, 1.38 million tons of coffee husk are produced annually. The husk is used as combustible in the drying and improvement ovens in the coffee farms, generating ash as residue. These ashes contain a high concentration of alkaline metals and earth metals, mainly K2O and CaO. This work studies the use of this residue in the ceramic tiles industry, as fluxing agents in substitution to the feldspar. Ten mixtures with equal ratios of clay and kaolin, proceeding from Bahia and the residue (varying from 30 to 5%) were defined and produced in uniaxial tool die of 60x20mm with approximately 5 mm of thickness and 45MPa compacting pressure. The samples were fired in four different temperatures: 1100 °C, 1150 °C, 1185 °C and 1200 °C during 60 minutes and characterized by means of X-ray fluorescence, X-ray diffraction, gravimetric thermal analysis and differential thermal analysis. The results of water absorption, apparent porosity, linear shrinkage, XRD, dilatometry, flexural strength and SEM were also analysed. The test specimen with addition of 10% of ash fired in 1200 °C resulted in 0.18% water absorption and 40.77 MPa flexural strength, being classified as porcelain stoneware tiles according to ABNT, UNI and ISO norms

Adição de chamote de velas de ignição inservíveis na obtenção de cerâmica branca a base de alumina

This work presents research into the addition of chamotte obtained from the ceramic isolator of unusable spark plugs in formulations of material mixes for standard white ceramic material with aluminum oxide bases. After the physical chemical characterization of the primary materials, standard clay and the chamotte, three mixtures were prepared with concentrations of 10, 20 and 30% chamotte by weight in relation to the standard clay. The test samples underwent heating at a rate of 30 0C/min to levels that included 100o , 200o , 300o, 400o, 500o e 600 0C and also we submitted to three distinct burn temperatures: 1450o, 1500o e 1550 0C, remaining at these temperatures for 2 hour periods. After sintering, the physical and microstructural properties of the different test samples were measured and analyzed. The results show that the materials obtained present good technical properties and that the chamotte can be reutilized as an additive in the production of white ceramic material with an aluminum oxide base

Análise das propriedades termofísicas, mecânicas e geométricas de telhas cerâmicas queimadas em forno caieira e forno abóbada

In the industry of ceramic in Rio G. do Norte, tile stands out as the most manufactured product by this industry, being the intermittent kiln abóbada and caieira the principal type of kiln used in burning. There was a need to make a study of the influence exerted by the type of kiln in which tiles are burnt in their thermo physical properties. The analysis started with 24 raw samples of tile, which was split in two groups of 12 samples and burnt in Abóbada and Caieira kiln. Besides that, it was made study of the tax of heat transfer to the environment (for each kiln). After having been burnt the samples were taken for laboratory analysis. The properties verified were impermeability, determination of dry mass, absorption of water, the load of bending rupture and its geometric characteristics, the tests were conducted following the currents standards. The tests were carried out according to the ABNT - NBR 15310. The calculation of the rate of heat transfer showed that the abóbada kiln is more efficient than the Caieira, however the results of tests on the samples revealed no superiority of one over another sample. So the furnace had no influence on the performance of the ceramic tiles

Estudo de formulação de massa para aplicação em placas cerâmicas

The sector of civil construction is strongly related to the red ceramic industry. This sector uses clay as raw material for manufacturing of various products such as ceramic plates. In this study, two types of clay called clay 1 and clay 2 were collected on deposit in Ielmo Marinho city (RN) and then characterized by thermogravimetric analysis (TG/DTG), differential thermal analysis (DTA), X-ray diffraction (XRD), X-ray fluorescence (XRF), rational analysis and particle size distribution and dilatometric analyses. Ceramic plates were manufactured by uniaxial pressing and by extrusion. The plates obtained by pressing were produced from the four formulations called 1, 2, 3 and 4, which presented, respectively, the following proportions by mass: 66.5% clay 1 and 33.5% clay 2, 50% clay 1 and 50% clay 2, 33.5% clay 1 and 66.5% clay 2, 25% clay 1 and 75% clay 2. After firing at 850, 950 and 1050 °C with heating rate of 10 °C/min and soaking time of 30 minutes, the following technological properties were determined: linear firing shrinkage, water absorption, apparent porosity, apparent specific mass and tensile strength (3 points). The formulation containing 25% clay 1 produced plates with most satisfactory results of water absorption and mechanical resistance, because of that it was chosen for manufacturing plates by extrusion. A single firing cycle was established for these plates, which took place as follow: heating rate of 2 °C/min up to 600 ºC with soaking time of 60 minutes, followed by heating using the same rate up to 1050 ºC with soaking time of 30 minutes. After this cycle, the same technological properties investigated in the plates obtained by pressing were determined. The results indicate (according to NRB 13818/1997) that the plates obtained by pressing from the mixture containing 25 wt% clay 1, after firing at 1050 °C, reach the specifications for semi-porous coating (BIIb). On the other hand, the plates obtained by extrusion were classified as semi-stoneware (group AIIa)