Ricardo Peixoto Suassuna Dutra

Preparação de compósitos alumina-mulita de baixo custo via sinterização reativa entre uma argila caulinítica da Paraíba e hidróxido de alumínio

This work aimed to evaluate the effects of processing on microstructure and properties of alumina-mullite composites via reactive sintering of a mixture of kaolinite clay and aluminum hydroxide. Cylindrical pellets were pressed at 40 MPa and sintered between 1300 and 1600 °C. The technological properties were determined as a function of sintering temperature. The evaluation of crystalline phases and microstructure was performed by X-ray diffraction and electron microscopy. Structural results indicate the attainment of mullite and alumina at 1300 °C. Apparent porosity below 0.8% and flexural strength higher than 40 MPa were obtained for sintering temperatures above 1450 °C. A flexural strength as high as 70 MPa was obtained after sintering at 1600 °C. This study demonstrates the possibility of preparing low cost alumina-mullite composites with technological properties compatible with those of ceramics produced by companies with large operations in the international market of refractory products.

Study of the Effect of Feldspar Replacement from a Mixture of Glass / Syenite in Technological Properties of Ceramic Coatings

Obtaining new raw materials for the production of ceramic coating is increasingly highlighted, however, it is desirable to maintain or improve the technological properties of the formed product. Thinking about it, and aiming at the environmental context, the aim of this work is to study the mixing recycled glass effect with syenite, an alternative melting often used in the production of ceramic tiles, in replacing to feldspar. The raw materials were characterized and subsequently the technological properties were determined for the standard formulation and the formulations with 5, 10, 15 and 20% mixing glass / syenite, in replacing to feldspar. The test bodies were prepared by wet, and sintered at different temperatures, with a rate of 30 °C /min and a level of 20 minutes. The results indicate that the mixing glass / syenite has the potential to be used as melting material in the composition of the ceramic mass.

The Incorporation of the Ceramic Industry Firewood Ash into Clayey Ceramic

Much industrial waste has mineralogical, chemical and physical characteristics similar to clays used in ceramic materials, enabling the reuse of these as raw materials in the ceramic industry. The ashes are a type of waste containing metals, which can cause air pollution, responsible for serious respiratory problems in the affected population. This study investigate the use of waste derived from the carbonization of a solid fuel (wood) in ceramic paste used for the manufacture of rustic floors, aiming its incorporation into the mix, partially replacing (lessening the environmental problem) the usage of raw material (saving clay), enabling the analysis of certain variables of sample preparation (characterization and formulation) and their influence on the final properties of the material. Results indicate that the partial replacement of clay by ash is feasible in the chemical and mineralogical aspects in the formulation of ceramic paste in the manufacturing of rustic floors.

Use of Sewage Sludge in the Production of Light-Weight Ceramic Bricks

Sewage sludge consists of a solid mixture of biological and mineral origin. It is the main byproduct of Effluent Treatment Stations. Its final draining has been a relevant environmental problem in several countries. In Brazil, due to the growth of the urban population and the requirements of environmental agencies, efficient ways for sludge disposal or effluent treatment have been investigated. Possible discarding solutions include incineration, pelletization, energy production and addition to fertilizers. This work focuses on the use of sludge in the ceramic industry for the production of light ceramic blocks, since this residue is basically composed of organic substances which volatilize during high temperature sintering. Mixtures containing different contents residue and clayed materials were prepared. For each mixture, after processing, the physical and mechanical properties of the burned pieces were measured, with emphasis on water absorption and linear shrinkage tests carried out as a function of the sintering temperature. Gresification diagrams were plotted for the temperature range of 850 °C to 1150 °C. The addition of the residue provided an increase in the porosity of the material. Light blocks were sintered and presented adequate mechanical resistance for application as building material.

Residue Characterization from Polishing Granite Submitted to the Hydrocycloning Process

The waste generated in granite processing has caused great social and environmental concern due to the release of its solid effluents into landfills and other places. The recycling and reuse of waste from different industrial processes as new raw materials has been the object of various researches. The use of hydrocyclone in the treatment of residues can represent a very efficient tool for separation and purification of the granite residue. This work aims to characterize and analyse the technological properties of the granite sawdust residues submitted to the hydrocyclone process in comparison with the same residue without going through the hydrocyclone process. The results indicate that the material resulting from this process presented different characteristics from the material without the process, mainly in terms of granulometric distribution and technological properties.

Estudo da incorporação de pó de concha de marisco em massa de porcelanato

The fishing of shellfish is one of the most important commercial activities of the fishing community of the municipality of Cabedelo (Paraíba, Brazil). The step of processing, after the extraction of the mollusk, generates a large amount of shells, whose discharge, in considerable volume, causes silting of large areas and consequent environmental imbalance. In the search for the use of these residues (mollusk shells) and aiming at reducing the environmental problems caused, this work had the aim of studying the incorporation of mollusk shell powder in the mass of porcelain tile. Ceramic compositions were formulated from an industrial standard mass and mollusk shell powder or commercial CaCO3 ranging from 0 to 7% by weight. Samples prepared by uniaxial pressing had their technological properties evaluated as a function of the sintering temperature. The results indicated that the use of up to 7 wt% of the mollusk shell powder maintains the technological properties within the standards required by the ABNT (Brazil) for classification as BIa type porcelain tiles.

One-step synthesis and microstructure of CuO-SDC composites

An in situ one step synthesis route based on the polymeric precursor method was used to produce dual phase CuO-samaria doped ceria (SDC) nanocomposite powders. This chemical route allowed to obtain composite powders with reduced particle size and uniform distribution of Cu, Ce and Sm elements. The particulate material was characterized by powder X-ray diffraction (XRD) combined with Rietveld refinement. CuO-SDC sintered in air between 950 to 1050 °C and subsequently reduced to Cu-SDC cermets were further characterized by XRD and scanning electron microscopy. The open porosity was measured using the Archimedes’ principle. Suitable microstructures for both charge transfer and mass transport processes (30 to 45% porosity) were attained in Cu-SDC cermets previously fired at 1000 to 1050 °C. Overall results indicated that CuO-SDC composites and Cu-SDC cermets with potential application as anodes for solid oxide fuel cells (SOFCs) can be obtained by microstructural design. An anode supported half-cell was prepared by co-pressing and co-firing gadolinia doped ceria (CGO) and the herein synthesized CuO-SDC nanocomposite powder.

Improvement of Rheological Properties of Little Noble Varieties from Boa Vista Bentonites - Part I: Experimental Design

The noble variety of the Boa Vista bentonites became scarce, originating fluids which do not answer the Petrobras specifications. The utilization of a blending with available samples have been used in industry successfully. Thus, the present work aims to use the mixture modeling methodology with design in simplex-centroid network and further purification by hydrocycloning, trying to optimize rheological properties of dispersions prepared with little noble clays, obtaining drilling fluids that attend the normative requirements. Initially, the rheological behavior of dispersions on each of the five clays, activating them in proportions of 50, 75, 100, 125 e 150 meq of Na2CO3/100 g of dry clay. After result analyzing, the mixtures were formulated, using experimental planning with the five clays, but with activation in proportions of 100 and 125 meq of Na2CO3/100 g of dry clay.

Influence of Clay Content and Surfactant on the Rheology of Non Aqueous Drilling Fluids

Organophilic clays are widely used in non-aqueousdrilling fluids, mixtures of different components being used in a well bore. As bentonite claysare not naturally organophilic, they can be modified by specific treatments with surfactants (ionic or nonionic). Recent studies demonstrate the influence of clay, surfactant,and the presence of a dispersant in the rheology of fluids. In this study we verified the influence of clay, and surfactant in the production of organophilic clays using an alcoholic route for the rheology of non-aqueous fluids.As such, we performed the characterization of organophilic clays by X-ray diffraction (XRD),these non-aqueous fluids were produced according to Petrobras norms for rheological testing. The results evidenced influences of the clay / surfactant ratio on the rheology of non-aqueous drilling fluids.

Analysis of Color of the Ceramic Coatings Submitted to Different Processing Conditions

Color is a very important characteristic in ceramic products. In ceramic coatings, the basis of ceramic is normally classified as red or white basis. Another relevant factor for color variation is the processing to which the material is submitted. In this sense, this work aims to analyze and quantify the color of ceramic pieces used as coatings, which were developed from a formulation of masses, using raw materials such as clay, feldspar, kaolin and quartz. Each raw material was analyzed separately and then a standard formulation was made, involving all of them, and these ones were submitted to different processing temperatures. All the samples were quantified regarding the color, by using the tridimensional colorimetric space by CIELAB method. Results point out that each raw material has an own value regarding color and the temperature has contributed directly to the color variation of the ceramic pieces.