Hélio Lucena Lira

Utilization of kaolin processing waste for the production of porous ceramic bodies

The kaolin processing industry generates large amounts of waste in producing countries such as Brazil. The aim of this study was to characterize kaolin processing waste and evaluate its suitability as an alternative ceramic raw material for the production of porous technical ceramic bodies. The waste material was physically and chemically characterized and its thermal behaviour is described. Several formulations were prepared and sintered at different temperatures. The sintered samples were characterized to determine their porosity, water absorption, firing shrinkage and mechanical strength. Fired samples were microstructurally analysed by X-ray diffraction and scanning electron microscopy. The results indicated that the waste consisted of quartz, kaolinite, and mica, and that ceramic formulations containing up to 66% of waste can be used for the production of ceramics with porosities higher than 40% and strength of about 70 MPa.

Bentonites from Boa Vista, Brazil: physical, mineralogical and rheological properties

The aim of this work is to characterize physically and mineralogically six samples of natural and industrialized bentonites from Paraiba, Brazil, and to study its rheological properties to be used as a components of water based drilling fluids. Also it is intended to compare the evolution of the mineralogical composition and rheology of these clays after 40 years of exploitation. The natural bentonite clays were transformed into sodium bentonite by addition of concentrated Na2CO3 solution. The suspensions were prepared with 4.86% w/w to measure their rheological properties (apparent and plastic viscosities and water loss). The results showed that: i) the samples present typical mineralogical compositions of bentonites, but after four decades of exploitation, presents inferior quality and ii) among the clays samples, only one presented satisfactory rheological properties be used as a components of water based drilling fluids.

Fluidos de perfuração à base de água. Parte I: efeitos de aditivações poliméricas nas propriedades reológicas

Foram estudados os efeitos da incorporacao de quatro diferentes aditivos polimericos nas propriedades reologicas e de filtracao de fluidos de perfuracao a base de agua e argilas bentoniticas de Boa Vista, PB. Os resultados mostraram que estas propriedades sao fortemente influenciadas pela presenca dos polimeros e que o tamanho da cadeia polimerica e um fator determinante.

Kaolin processing waste applied in the manufacturing of ceramic tiles and mullite bodies

In the last few years, mineral extraction and processing industries have been identified as sources of environmental contamination and pollution. The kaolin processing industry around the world generates large amounts of waste materials. The present study evaluated the suitability of kaolin processing waste as an alternative source of ceramic raw material for the production of ceramic tiles and dense mullite bodies. Several formulations were prepared and sintered at different temperatures. The sintered samples were characterized to determine their porosity, water absorption, firing shrinkage and mechanical strength. The fired samples were microstructurally analysed by X-ray diffraction. The results indicated that ceramic tile formulations containing up to 60% of waste could be used for the production of tiles with low water absorption (~ 0.5%) and low sintering temperature (1150 °C). Mullite formulations with more than 40% of kaolin waste could be used in the production of bodies with high strength, of about 75 MPa, which can be used as refractory materials.

Síntese e caracterização de nanopartículas de TiO2

Several methods of chemical synthesis have been developed and used to obtain powder for production of ceramic membranes. Amongst the alternative methods used in laboratory scale, the Pechini method has been used successfully for the preparation of several types of materials. The objective of this work is to synthesize and characterize TiO2 powders obtained by this method, aiming the preparation of ultra-filtration ceramic membranes. The powder has been characterized by gravimetric and differential thermal analysis, X-ray diffraction, infrared spectroscopy, nitrogen adsorption by BET, and scanning electron microscopy. The X-ray diffraction of the powders showed the presence of the anatase crystalline phase, with crystallite size 15 nm. The particle size calculated from the surface area was 19 nm and the powder morphology shows the presence of soft agglomerates. These results evidence that the Pechini method is interesting for the production of nanometric TiO2 appropriate for ceramic membranes preparation.

Structure and mechanical properties of polyamide 6/Brazilian clay nanocomposites

Recent interest in polymer/organoclays nanocomposites systems is motivated by the possibility of achieving enhanced properties and added functionality at lower clay loading as compared to conventional micron size fillers. By adding montmorillonite clay to polyamide 6 increases the Young modulus, yield strength and also improves barrier properties. In this work, nanocomposites of polyamide 6 with montmorillonite clay were obtained. The clay was chemically modified with three different quaternary ammonium salts such as: Dodigen, Genamin and Cetremide. In this case, a dispersion of Na-MMT was stirred and a salt equivalent to 1:1 of cation exchange capacity (CEC) of Na-MMT was added to the dispersion. The montmorillonite clay (untreated and treated by ammonium salts) and nanocomposites were characterized by X ray diffractions. Also the nanocomposites were characterized by transmission electron microscopy and mechanical properties. The results indicated that all the quaternary ammonium salts were intercalated between the layers of clay, leading to an expansion of the interlayer spacing. The obtained nanocomposites showed better mechanical properties when compared to polyamide 6. The clay acted as reinforcing filler, increasing the rigidity of nanocomposites and decreasing its ductility.

Preparação e caracterização de membranas cerâmicas de cordierita

Membrane separation processes find large applications. Ceramic membranes are applied in several processes, mainly in application above 250 oC, as well as in separation of solutions with pH extremely acid and even in systems with organic solvents. On the other hand, ceramic membranes show high cost of fabrication, mainly in relation to the raw synthetic materials (zirconia, alumina, titania and silica). Therefore, the main concern in the development of these membranes is to optimize the cost using natural non-expensive raw materials and more efficient ceramic processing, such as extrusion. The fabrication of ceramic membranes by extrusion gives the possibility to use cross flow system, which is very useful in microfiltration and ultrafiltration separation processes. The aim of this work is to prepare tubular cordierite membranes from raw materials such as clays and talc and by extrusion processing. Four sintering temperatures (1150, 1200, 1250 and 1280 oC) were used to show the effect on the morphological characteristics of the membranes. The membranes were characterized by X-ray diffraction, scanning electron microscopy and mercury intrusion porosimetry. The results showed the formation of cordierite phase at all sintering temperatures. The membranes presented pore size of 1.4, 2.2, 3.3 and 4.1 µm and porosity content of 28.7, 29.1, 27.7 and 24.3% for sintering temperaturesf 1150, 1200, 1250 and 1280 oC, respectively. These values show that these membranes are suitable to be applied in microfiltration separation processes. The results of water flux, at steady state, show that the membrane sintered at 1280 oC presented the highest value, 587.3 kg/m2.h, followed by 377.7 kg/m2.h (1250 oC), 143.4 kg/m2.h (1200 oC) and 67.8 kg/m2.h (1150 oC).

Polyamide 6 Nanocomposites with Inorganic Particles Modified with Three Quaternary Ammonium Salts

The purpose of this study was to obtain polyamide 6 nanocomposites with national organically modified clay with three quaternary ammonium salts. The obtained results confirm the intercalation of molecules of salt in the clay layers, and a good interaction with the polymer, showing the formation of intercalated and/or partially exfoliated structures. The nanocomposites showed similar thermal stability compared to pure polymer, and the mechanical properties presented interesting and promising results.

Mullite Preparation from Kaolin Residue

In the process of kaolin improvement to types of residue are generated and dispose in the environment. The first residue, about 70%wt, generated from the washing of the kaolin and the second generated residue from the improvement in sieve 200 mesh (0.074mm), of the remaining of the washed kaolin 30%. These residues can present excellent qualities to be used as raw materials rich in kaolinite. Kaolinite when is submitted to heat give two stable phases: mullite and crystobalite. The properties of mullite, such as, low thermal expansion, low dielectric constant and high mechanical resistance, make this material as a good candidate to be applied in electronic products and in structural high temperature uses. In this work, compositions with residue from kaolin, alumina and ball-clay were studied to obtain mullite. The compositions were established starting from proportion between silica and alumina to obtain mullite (2SiO 2 .3Al 2 O 3 ). The samples were made by pressing processing with 27 MPa and sintering at temperatures of 1350 and 1500°C, with heating rate of 10°C/min. Through the results from chemical analysis of the formulated masses, it can be verified that the proportions of the oxides were close to the stoichiometric of the mullite and that the sintering, at studied temperatures, give the formation of mullite, and confirmed by the DRX analysis. The preliminary results showed that the compositions with low alumina content and submitted to a high temperatures, presented the best results.

Study of Morphology Membrane of Polymeric Nanocomposites Obtained by Phases Inversion

In this work, were obtained nanocomposite membranes polyamide66/Paraíba bentonite clay, treated with a quaternary ammonium salt in order to make it organophilic. The membranes were prepared as thin films using the technique of phase inversion from the nanocomposites obtained by solution. The membranes were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TG) and scanning electron microscopy (SEM). By means of X-ray diffractogram, it was revealed that the membranes remained organically treated clay presented exfoliated and/or partially exfoliated structure. From curves of DSC and TG, it was observed that membrane of PA66 with 3% w/w of with treatment clay showed higher thermal stability compared with the same content of clay without treatment. From the SEM photomicrographs, there was a selective layer (skin filter) on top and one porous layer at the bottom of all membranes studied. Moreover, it was verified that the presence of clay provided a significant structural modification in the membranes of polymer nanocomposites.