Otimização do processo de síntese do aluminato de cobalto via método de polimerização de complexos (MPC) através do planejamento fatorial fracionado

In the ceramics industry are becoming more predominantly inorganic nature pigments. Studies in this area allow you to develop pigments with more advanced properties and qualities to be used in the industrial context. Studies on synthesis and characterization of cobalt aluminate has been widely researched, cobalt aluminate behavior at different temperatures of calcinations, highlighting especially the temperatures of 700, 800 and 900° C that served as a basis in the development of this study, using the method of polymerization of complex (CPM), economic, and this method applied in ceramic pigment synthesis. The procedure was developed from a fractional factorial design 2 (5-2) in order to optimize the process of realization of the cobalt aluminate (CoAl2O4), having as response surfaces the batch analysis data of Uv-vis spectroscopy conducted from the statistic software 7.0, for this were chosen five factors as input variables: citric acid (stoichiometric manner), puff or pyrolysis time (h), temperature (° C), and calcinations (° C/min), at levels determined for this study. By applying statistics in the process of obtaining the CoAl2O4 is possible the study of these factors and which may have greater influence in getting the synthesis. The pigments characterized TG/DSC analyses, and x-ray diffraction (XRD) and scanning electron microscope (SEM/EDS) in order to establish the structural and morphological aspects of pigment CoAl2O4, among the factors studied it were found to statically with increasing calcinations temperature 700°< 800 <900 °C, the bands of Uv-vis decrease with increasing intensity of absorbance and that with increasing time of puff or pyrolysis (h) there is an increase in bands of Uv-vis proportionally, the generated model set for the conditions proposed in this study because the coefficient of determination can explain about 99.9% of the variance (R²), response surfaces generated were satisfactory, so it s possible applicability in the ceramics industry of pigments

Síntese de catalisadores do tipo LaNixFe1-xO3 como precursores catalíticos para reação oxidação parcial do metano

Nickel-bases catalysts have been used in several reform reactions, such as in the partial oxidation of methane to obtain H2 or syngas (H2 + CO). High levels of conversion are usually obtained using this family of catalysts, however, their deactivation resulting from carbon deposition still remains a challenge. Different approaches have been tested aiming at minimizing this difficulty, including the production of perovskites and related structures using modern synthesis methods capable of producing low cost materials with controlled microstructural characteristics at industrial scale. To establish grounds for comparison, in the present study LaNixFe1-xO3 (x=0, 0.3 or 0.7) perovskites were prepared following the Pechini method and by microwave assisted self-combustion. All samples were sub sequently calcined at 900 °C to obtain the target phase. The resulting ceramic powders were characterized by thermogravimetric analysis, infrared spectroscopy, X ray diffraction, specific area and temperature programmed reduction tests. Calcined samples were also used in the partial oxidation reaction of methane to evaluate the level of conversion, selectivity and carbon deposition. The results showed that the calcined samples were crystalline and the target phase was formed regardless of the synthesis method. According to results obtained by Rietveld refinement, we observed the formation of 70.0% of LaNi0.3Fe0.7O3 and 30.0% of La2O3 for samples LN3F7-900- P, LN3F7-900-M and 41,6% of LaNi0.7Fe0.3O3, 30.7% of La2NiO4 and 27.7% of La2O3 for samples LN7F3-900-P and LN7F3-900-M.Temperature-programmed profiles of the LaNiO3 sample revealed the presence of a peak around 510 °C, whereas the LaFeO3 sample depicted a peak above 1000°C. The highest l evel of methane conversion was obtained for LaNiO3 synthesized by the Pechini method. Overall, catalysts prepared by the Pechini method depicted better conversion levels compared to those produced by microwave assisted self-combustion

Estudo da viabilidade técnica para obtenção de superfície duplex em aço inoxidável martensítico AISI 410 através do processo de deposição a plasma por gaiola catódica

The technique of plasma nitriding by the cathode cage mainly stands out for its ability to produce uniform layers, even on parts with complex geometries. In this study, it was investigated the efficiency of this technique for obtaining duplex surface, when used, simultaneously, to nitriding treatment and thin film deposition at temperatures below 500°C. For this, were used samples of AISI 41 0 Martensitic Stainless Steel and performed plasma treatment, combining nitriding and deposition of thin films of Ti and/or TiN in a plasma atmosphere containing N2-H2. It was used a cathodic cage of titanium pure grade II, cylindrical with 70 mm diameter and 34 mm height. Samples were treated at temperature 420ºC for 2 and 12 hours in different working pressures. Optical Microscopy (OM), Scanning Electron Microscopy (SEM) with micro-analysis by Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM) and analysis of Vickers Microhardness were used to investigate coating properties such as homogeneity and surface topography, chemical composition, layer thickness, crystalline phase, roughness and surface microhardness. The results showed there is a direct proportionality between the presence of H2 in plasma atmosphere and the quantity of titanium in surface chemical composition. It was also observed that the plasma treatment at lowpressure is more effective in formation of TiN thin film

Diagnóstico das espécies ativas do plasma usado em tratamentos termoquímicos do titânio

Plasma diagnostics by Optical Emission Spectroscopy were performed for electrical discharge in three gas mixture respecting the combinations z N2 y Ar x H2, z N2 y Ar x O2 e z N2 y Ar x CH4, in which the indexes z and y systematically vary from 1 to 4 and x varies from 0 to 4, every one has dimension SCCM, resulting in 80 combinations. From the all obtained spectrums, the species CH (387,1 nm), N2+ (391,4 nm), Hβ (486,1 nm), Hα (656,3 nm), Ar (750,4 nm), O (777,4 nm) e O (842,6 nm) were analyzed because of their abundance and importance on the kinetic of reaction from the plasma to surface, besides their high dependences on the gases flows. Particularly interesting z, y and x combinations were chosen in order to study the influence of active species on the surface modification during the thermochemical treatment. From the mixtures N2 Ar O2 e N2 Ar CH4 were chosen three peculiar proportions which presented luminous intensity profile with unexpected maximum or minimum values, denominated as plasma anomaly. Those plasma concentrations were utilized as atmosphere of titanium treatment maintaining constant the control parameters pressure and temperature. It has been verified a relation among luminous intensity associated to N2+ and roughness, nanohardness and O atoms diffusion into the crystalline lattice of treated titanium and it has been seen which those properties becomes more intense precisely in the higher points found in the optical profile associated to the N2+ specie. Those parameters were verified for the mixture which involved O2 gas. For the mixture which involves CH4 gas, the relation was determinate by roughness, number of nitrogen and carbon atoms diffused into the titanium structure which presented direct proportionality with the luminous intensity referent to the N2+ and CH. It has been yet studied the formation of TiCN phases on the surface which presented to be essentially directly proportional to the increasing of the CH specie and inversely proportional to the increasing of the specie N2+

Tratamentos de fibras de carnaúba [copernicia prunífera (miller) h. e. moore] para o desenvolvimento de compósito biodegradável com matriz de polihidroxibutirato

The use of raw materials from renewable sources for production of materials has been the subject of several studies and researches, because of its potential to substitute petrochemical-based materials. The addition of natural fibers to polymers represents an alternative in the partial or total replacement of glass fibers in composites. In this work, carnauba leaf fibers were used in the production of biodegradable composites with polyhydroxybutyrate (PHB) matrix. To improve the interfacial properties fiber / matrix were studied four chemical treatments to the fibers..The effect of the different chemical treatments on the morphological, physical, chemical and mechanical properties of the fibers and composites were investigated by scanning electron microscopy (SEM), infrared spectroscopy, X-ray diffraction, tensile and flexural tests, dynamic mechanical analysis (DMA), thermogravimetry (TGA) and diferential scanning calorimetry (DSC). The results of tensile tests indicated an increase in tensile strength of the composites after the chemical treatment of the fibers, with best results for the hydrogen peroxide treated fibers, even though the tensile strength of fibers was slightly reduced. This suggests a better interaction fiber/matrix which was also observed by SEM fractographs. The glass transition temperature (Tg) was reduced for all composites compared to the pure polymer which can be attributed to the absorption of solvents, moisture and other low molecular weight molecules by the fibers

Uso de resíduo e de minerais de pegmatito da região do seridó RN e de argilas portuguesas em formulações de grês porcelanato

In the State Rio Grande do Norte, Brazil, the most significant deposits of minerals in the production of granite and pegmatite are Seridó region. Municipalities of Parelhas and Equador are the main responsible for the production of feldspar, quartz, kaolin and granite. The ceramic industries are always in search of competitiveness by investing in new products or improving existing techniques. The stoneware is a type of pottery that stands in the market because it presents technical and aesthetic characteristics superior to other existing products. Characteristics of the raw materials initially obtained with chemical analysis and mineralogical analysis are crucial in getting a product that satisfies the conditions in a manufacturing process and is, in principle, directly related to the firing cycle. This research aimed at developing new formulations for the mass production of ceramic stoneware. The raw materials initially characterized were feldspar, quartz, kaolin and granite. As part of the research was developed at the University of Aveiro, in Portugal, we used two clays used in the production of Portuguese ceramics. The raw material Brazilian and Portuguese and the final product, both in Portugal and Brazil, were analyzed for X-ray fluorescence, X-ray diffraction, granulometric analysis, dilatometric analysis, thermal analysis and analysis of scanning electron microscopy (MEV). The specimens prepared at the University of Aveiro (DECV) were sintered at 10000C and 12000C and the specimens prepared in UFRN were sintered at 10000C, 10500C, 11000C, 11500C, 12000C, 12500C and 13000C, but the best results and demonstrating the presence of the mineral mullite were at temperatures of 12000C, 12500C and 13000C. The results showed that the granite waste used may be considered raw material of excellent quality for use in the ceramic industry and coating floors and more accurately by the industry of stoneware. Physical and mechanical tests conducted on samples of the formulations F01 and F02 developed in UFRN showed a water absorption and mechanical strength suitable for the stoneware

Caracterização microestrutural e elétrica de La(FexNi1-x)O3 sintetizado pelo método da gelatina

The present work deals with the synthesis of materials with perovskite structure with the intention of using them as cathodes in fuel cells SOFC type. The perovskite type materials were obtained by chemical synthesis method, using gelatin as the substituent of citric acid and ethylene glycol, and polymerizing acting as chelating agent. The materials were characterized by X-ray diffraction, thermal analysis, spectroscopy Fourier transform infrared, scanning electron microscopy with EDS, surface area determination by the BET method and Term Reduction Program, TPR. The compounds were also characterized by electrical conductivity for the purpose of observing the possible application of this material as a cathode for fuel cells, solid oxide SOFC. The method using gelatin and polymerizing chelating agent for the preparation of materials with the perovskite structure allows the synthesis of crystalline materials and homogeneous. The results demonstrate that the route adopted to obtain materials were effective. The distorted perovskite structure have obtained the type orthorhombic and rhombohedral; important for fuel cell cathodes. The presentation material properties required of a candidate cathode materials for fuel cells. XRD analysis contacted by the distortion of the structures of the synthesized materials. The analyzes show that the electrical conductivity obtained materials have the potential to act as a cell to the cathode of solid oxide fuel, allowing to infer an order of values for the electrical conductivities of perovskites where LaFeO3 < LaNiO3 < LaNi0,5Fe0,5O3. It can be concluded that the activity of these perovskites is due to the presence of structural defects generated that depend on the method of synthesis and the subsequent heat treatment

Estudo de massa cerâmica triaxial visando à otimização do ciclo de queima da indústria de cerâmica estrutural

Over recent years the structural ceramics industry in Brazil has found a very favorable market for growth. However, difficulties related to productivity and product quality are partially inhibiting this possible growth. An alternative for trying to solve these problems and, thus, provide the pottery industry the feasibility of full development, is the substitution of firewood used in the burning process by natural gas. In order to contribute to this process of technological innovation, this paper studies the effect of co-use of ceramic phyllite and kaolin waste on the properties of a clay matrix, verifying the possible benefits that these raw materials can give to the final product, as well as the possibility of such materials to reduce the heat load necessary to obtain products with equal or superior quality. The study was divided into two steps: characterization of materials and study of formulations. Two clays, a phyllite and a residue of kaolin were characterized by the following techniques: laser granulometry, plasticity index by Atterberg limits, X-ray fluorescence, X-ray diffraction, mineralogical composition by Rietveld, thermogravimetric and differential thermal analysis. To study the formulations, specifically for evaluation of technological properties of the parts, was performed an experimental model that combined planning involving a mixture of three components (standard mass x phyllite x kaolin waste) and a 23 factorial design with central point associated with thermal processing parameters. The experiment was performed with restricted strip-plot randomization. In total, 13 compositional points were investigated within the following constraints: phyllite ≤ 20% by weight, kaolin waste ≤ 40% by weight, and standard mass ≥ 60% by weight. The thermal parameters were used at the following levels: 750 and 950 °C to the firing temperature, 5 and 15 °C/min at the heating rate, 15 and 45min to the baseline. The results showed that the introduction of phyllite and/or kaolin waste in ceramic body produced a number of benefits in properties of the final product, such as: decreased absorption of water, apparent porosity and linear retraction at burn; besides the increase in apparent specific mass and mechanical properties of parts. The best results were obtained in the compositional points where the sum of the levels of kaolin waste and phyllite was maximal (40% by weight), as well as conditions which were used in firing temperatures of 950 °C. Regarding the prospect of savings in heat energy required to form the desired microstructure, the phyllite and the residue of kaolin, for having small particle sizes and constitutions mineralogical phases with the presence of fluxes, contributed to the optimization of the firing cycle.

Preparação e caracterização de filmes cerâmicos para cátodos de células a combustível de óxido sólido

Alternative and clean energy generation research has been intensified in last decades. Among the alternatives, fuel cells are one of the most important. There are different types of fuel cells, among which stands out intermediate temperature solid oxide fuel cell (IT-SOFC) matter of the present work. For application as cathode on this type of devices, the ceramic Ba0.5Sr0.5C0.8Fe0.2O3-δ doped with rare earth ions (Nd, Sm) have been quite promising because they show good ionic conductivity and operate at relatively low temperatures (500 - 800°C). In this work, Ba0.5Sr0.5Co0.8Fe0.2O3-δ, (BaSr)0.5Sm0.5Co0.8Fe0.2O3-δ and (BaSr)0.5Nd0.5C0.8Fe0.2O3-δ were obtained by modified Pechini method, making use of gelatin as polymerizing agent. The powders were characterized by X-Ray Diffraction (XRD), Temperature Programmed Reduction (TPR) and Scanning Electron Microscopy (SEM). The perovskite phase was observed in all X-ray patterns for the materials Ba0.5Sr0.5C0.8Fe0.2O3-δ doped with rare earth ions (Nd, Sm). The SEM images showed that the materials have a characteristics porous, with very uniform pore distribution, which are favorable for application as cathodes. Subsequently, screen-printed assymmetrical cells were studied by impedance spectroscopy, to assess the kinetics of the cathode for the reduction reaction of oxygen. The best resistance to the specific area was found for the cathode BSSCF sintered at 1050 °C for 4 hours with around 0.15 Ω.cm2 at 750 °C as well as cathodes BSNCF and BSCF obtained resistances specific area of 0.2 and 0.73 Ω.cm2, respectively, for the same conditions. The polarization curves showed similar behavior to the best cathodes BSSCF and BSNCF, such combination of properties indicates that the film potentially depict good performance as IT-SOFC cathodes

Construção de um aparato experimental para monitoramento in situ da deposição de filmes finos de titânio por magnetron sputtering

The technique of surface coating using magnetron sputtering is one of the most widely used in the surface engineering, for its versatility in obtaining different films as well as in the micro / nanometric thickness control. Among the various process parameters, those related to the active species of the plasma are of the most fundamental importance in the mechanism and kinetics of deposition. In order to identify the active species of the plasma, parameters such as gas flow, pressure and density of electric power were varied during titanium coating on glass substrate. By flowing argon gas of 10, 20, 30, 40 and 50 sccm (cubic centimeters per minute) for each gas flow a sequential scan of the electric current of 0.10, 0.20, 0.30, 0.40 , 0.50 A. The maximum value of 0.50 A was chosen based both on literature data and on limitations of the equipment. The monitoring of plasma species present during the deposition was carried out in situ by the technique of optical emission spectroscopy (OES) through the spectrometer Ocean Optics USB2000 Series. For this purpose, an apparatus was developed to adapt the OES inside the plasma reactor to stay positioned closest to the target. The radiations emitted by the species were detected by an optical fiber placed behind the glass substrate and their intensities as a function of wavelength were, displayed on a monitor screen. The acquisition time for each condition of the plain parameters was related to the minima of spectral lines intensities due to the film formed on the substrate. The intensities of different emission lines of argon and titanium were then analyzed as a function of time, to determine the active species and estimate the thickness of the deposited films. After the deposition, the coated glasses thin films were characterized by optical transmittance through an infrared laser. It was found that the thickness and deposition rate determined by in situ analysis were consistent with the results obtained by laser transmittance

Impregnação de metais em xisto retortado para uso como adsorventes

Concern with the environment has lead to an increase in the research for new adsorption techniques, low cost adsorvent materials and with high availability. Many works search the development of higher selectivity modified adsorvents. The Brazil has the second world reserve of oiled shale, because of it, the use of that reject is of great interest. This study has the goal of characterize and analyze the retorted shale, reject of the pirobetuminous shale pyrolysis, and the retorted shale modified through the humid impregnation method, wich the precursors were the metals nitrates ( Cobalt, Nickel and Copper), to the usage has adsorvent materials. The samples were characterized chemically, textually and structurally by the X ray fluorescence (XRF), BET, X ray diffraction (XRD) and scanning electronic microscopy (SEM) techniques. The impregnated samples showed a reduction in the superficial area and in the pore volume when compared with the retorted shale. Besides that, diffractions referred to the impregnated metals where observed in the XRD analysis, wich were the same metals detected in the XRF and SEM analysis. The materials showed homogeneity in it s composition. The results shows that the materials presents adequate adsorption characteristics

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

Síntese de pigmento cerâmico ferrita de cobalto utilizando planejamento experimental

Synthetic inorganic pigments are the most widely used in ceramic applications because they have excellent chemical and thermal stability and also, in general, a lower toxicity to man and to the environment. In the present work, the ceramic black pigment CoFe2O4 was synthesized by the polymerization Complex method (MPC) in order to form a material with good chemical homogeneity. Aiming to optimize the process of getting the pigment through the MPC was used a fractional factorial design 2(5-2), with resolution III. The factors studied in mathematical models were: citric acid concentration, the pyrolysis time, temperature, time and rate of calcination. The response surfaces using the software statistica 7.0. The powders were characterized by thermal analysis (TG/DSC), x-ray diffraction (XRD), scanning electron microscopy (SEM) and spectroscopy in the UV-visible. Based on the results, there was the formation of phase cobalt ferrite (CoFe2O4) with spinel structure. The color of the pigments obtained showed dark shades, from black to gray. The model chosen was appropriate since proved to be adjusted and predictive. Planning also showed that all factors were significant, with a confidence level of 95%

Estudos comparativos do ciclo de regeneração de diferentes tipos de silicoaluminofosfatos

Different types of heterogeneous catalysts of the silicoaluminophosphate type, (SAPO-5, SAPO-11, SAPO-31, SAPO-34 and SAPO-41), molecular sieves with a: AFI, AEL, ATO, CHA and AFO structure, respectively, were synthesized through the hydrothermal method. Using sources such as hydrated alumina (pseudobohemita), phosphoric acid, silica gel, water, as well as, different types of organic structural templates, such as: cetyltrimethylammonium bromide (CTMABr), di-isopropylamine (DIPA), di-n- propylamine (DNPA) and tetraethylammonium hydroxide (TEOS), for the respective samples. During the preparation of the silicoaluminophosphates, the crystallization process of the samples occurred at a temperature of approximately 200 ° C, ranging through periods of 18-72 h, when it was possible to obtain pure phases for the SAPOs. The materials were furthermore washed with deionized water, dried and calcined to remove the molecules of the templates. Subsequently the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), absorption spectroscopy in the infrared region (FT-IR), specific surface area and thermal analysis via TG/DTG. The acidic properties were determined using adsorption of n-butylamine followed by programmed termodessorption. These methods revealed that the SAPO samples showed a typically weak to moderate acidity. However, a small amount of strong acid sites was also detected. The deactivation of the catalysts was conducted by artificially coking the samples, followed by n-hexane cracking reactions in a fixed bed with a continuous flow micro-reactor coupled on line to a gas chromatograph. The main products obtained were: ethane, propane, isobutene, n-butane, n-pentane and isopentane. The Vyazovkin (model-free) kinetics method was used to determine the catalysts regeneration and removal of the coke

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