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The firing parameters in ceramic masses incorporated with 0, 5, and 10 wt% of scheelite tailings were investigated. The ceramic masses were characterized by X-ray fluorescence, granulometric, mineralogical analysis, and Atterberg limits determination. The samples were obtained by uniaxial pressing (20 MPa), sintered at different temperatures (800, 900, and 1000 °C), and heating rates (5, 10, 15, and 20 °C∙min−1). Physical and mechanical tests (water absorption, apparent porosity, and flexural strength) and mineralogical tests were accomplished from the sintered samples. Natural aging tests were also carried out to assess carbonation resistance. For this, some samples were kept in an internal environment (inside the laboratory) for 3 months. The results showed a high content of calcium oxide in the scheelite tailings and a reduction in the plasticity index of the ceramic masses with the tailings addition. The best results were observed for the ceramic mass with 5% tailings. The best results were observed regarding the firing parameters for the temperature equal to 1000 °C, increasing the heating rate to 10 °C∙min−1 without compromising the material properties. The samples kept in an internal environment for 3 months showed a loss of physical and mechanical properties. Such behavior probably occurred due to the onset of the carbonation phenomenon.

New eco-friendly mass formulations based on the scheelite and kaolin residues were developed to manufacture ceramic tiles. The start raw materials (scheelite residue, kaolin residue, feldspar and plastic clay) were characterized as to their chemical composition, main mineralogical phases, and particle size distribution. Three ceramic masses with 37 wt% of kaolin residues and different contents of the scheelite residues (2 wt%, 5 wt%, and 10 wt%) were formulated. The mass formulations were uniaxially pressed (19.6 MPa) to obtain samples with dimensions of 60 mm × 40 mm x 7 mm, which were dried at 110 °C/24 h, and sintered at different temperatures (1150 °C, 1200 °C, and 1250 °C). Dilatometric experiments measured thermal expansion coefficients. The results are in agreement with the literature, i.e., 6.0 μm/m°C−1, 6.1 μm/m°C−1 and 6.4 μm/m°C−1 to samples with 2 wt%, 5 wt%, and 10 wt% of scheelite residues, respectively. The potential of the mass formulations studied was evaluated by linear shrinkage, water absorption, apparent density, apparent porosity, flexural strength, and mineralogical phase identification. The results were compared with the literature experimental data and International Technical Standards. It was concluded that the samples investigated have suitable properties for use as ceramic and porcelain tiles. Also, the pseudowollastonite and mullite phases were identified in the sample with the lowest concentration of scheelite residue. These phases are responsible for increasing flexural strength.

Porous N-carbon/silica nanofibers (PN-CSN) were successfully made by solution blow spinning (SBS), polymer solutions containing polyvinylpyrrolidone (PVP), tetraethyl orthosilicate (TEOS), and ethanol. The fibers samples were carbonized at 550 °C in a static air atmosphere. PN-CSN fibers were characterized using scanning electron microscopy, N2 adsorption/desorption, X-ray diffraction, thermogravimetric analysis and zeta potential. The adsorption capacity was determined using a dye (methylene blue, MB). The PN-CSN fibers had a small average diameter (233 ± 178 nm), high specific surface area (364 m2 g−1) and pore volume (0.18 cm3 g−1). The pore size distribution ranged from 10 to 170 nm. Chemical analyses of the fibers revealed a residual amount of N (6.2%) and C (20,85%) as is characteristic in ceramic nanofibers made with polyacrylonitrile (PAN). The PN-CSN fibers had an adsorption capacity of approximately 400 mg g−1. The best fit for the adsorption data was found using a Langmuir model. The adsorption kinetics followed a pseudo-second order model. Thermodynamic analyses revealed the adsorption mechanism was endothermic and spontaneous for PN-CSN adsorbents.

The main objective of this work was to study the use of kaolin processing wastes in the production of steatite ceramics, emphasizing mechanical strength and dielectric properties. Steatite ceramics were prepared using mixtures of talc with fine and coarse particle kaolin wastes (7.5, 10 and 12.5 wt.%) sintered at different temperatures (1200, 1250 and 1300°C). After sintering, the specimens were submitted to mineralogical and microstructural characterization. Linear shrinkage, apparent porosity, flexural strength and dielectric properties were also evaluated. Results showed the formation of the crystalline phases protoenstatite and quartz for all produced ceramics. The results verified for porosity, mechanical strength and dielectric properties proved to be suitable for the application of this material in electrical insulation.

The physical properties of porous silica nanofibers are an important factor that impacts their performance in various applications. In this study, porous silica nanofibers were produced via solution blow spinning (SBS) from a silica precursor/polymer solution. Two polyvinylpyrrolidone (PVP, Mw = 360,000 and 1,300,000) were chosen as spinning aids in order to create different pore properties. The effect of their physical properties on the adsorption of methylene blue (MB) in an aqueous solution was explored. After forming, the nanofibers were calcined to remove the organic phase and create pores. The calcined nanofibers had a large amount of micro and mesopores without the use of additional surfactants. The molecular weight of the PVP impacted the growth of silica particles and consequently the pore size. High Mw PVP inhibited the growth of silica particles, resulting in a large volume of micropores. On the other hand, silica nanofibers with a high fraction of mesopores were obtained using the lower Mw PVP. These results demonstrate a simple method of producing blow spun silica nanofibers with defined variations of pore sizes by varying only the molecular weight of the PVP. In the adsorption process, the accessible mesopores improved the adsorption performance of large MB molecules.

In this work technical ceramics containing industrial inorganic wastes was carried out. Ceramic formulations prepared with clay, magnesium oxide and residues of kaolin and alumina as raw materials, were formed in a disk-shaped specimens using the uniaxial pressing process and sintering at temperatures from 950°C to 1400°C. The mineralogical, physical and dielectric characteristics of the fired samples were investigated. The dielectric properties, the relative dielectric constant (er) and the loss tangent (tan δ) were evaluated at frequencies of 0.1, 1, 10, and 100 kHz at room temperature. Mullite and cordierite were present as major phases at the highest temperatures. Relative dielectric constant values closest to that of mullite (er = ~ 5 to ~ 6) and cordierite (er = ~ 4 to ~ 6) at 1 kHz. On the other hand, the lowest dielectric losses (tan δ ~ 0.06 to ~ 0.04) were observed for the formulations containing the mullite major phase, and tan δ ~ 0.009 to ~ 0.003 for formulations that showed cordierite as main phase. It was verified that an increase in temperature promoted a reduction of porosity, a property that had a direct influence on the dielectric properties of the formulations. The materials obtained from the residues presented low dielectric constants and loss tangents, which make them suitable for use in electrical and electronic systems.

In this study, tubular ceramic membranes were prepared from a mixture of ball clay, talc and alumina. The mixture was characterized by the following techniques: particle size analysis, X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD) and thermal analysis. Tubular membranes were produced by extrusion process and thermal treated at temperatures between 1025 °C and 1175 °C. The membranes were characterized by XRD, linear shrinkage, apparent porosity, flexural strength, mercury porosimetry, scanning electron microscope (SEM) and contact angle. To evaluate the efficiency of the membranes, permeability tests with distilled water and oil-in-water emulsion were conducted in a tangential flow system. The results showed that the sintering of the specimens promoted the formation of α-cordierite phase and directly influenced the physical and mechanical properties such as linear shrinkage, porosity and flexural strength. Separation tests revealed that these membranes promoted high oil-water separation efficiency with values above 99.0%.

Refractory ceramics were produced from clays and alumina waste. Specimens were shaped by uniaxial pressing, subjected to thermal analysis by dilatometry and heat-treated in a conventional furnace at 1300 and 1400ºC, applying a heating rate of 5ºC/min and a dwell time of 2 and 3 hours at the maximum temperature. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and physicomechanical properties. The dilatometric analysis before heat treatment indicated that the formulation containing the largest amount of fluxing oxides presented the highest linear shrinkage. The XRD analysis revealed that mullite was the major phase and needle shaped crystals typical of mullite obtained from clay minerals were observed by SEM. The increase in firing temperature and dwell time at the maximum temperature improved the physicomechanical properties of the specimens. The thermal expansion coefficient (TEC) in the range of 25 to 1000ºC varied from 6.2 to 6.9 x 10-6°C-1.

Ceramic nanofibers have been shown to be a new horizon of research in the biomedical area, due to their differentiated morphology, nanoroughness, nanotopography, wettability, bioactivity, and chemical functionalization properties. Therefore, considering the impact caused by the use of these nanofibers, and the fact that there are still limited data available in the literature addressing the ceramic nanofiber application in regenerative medicine, this review article aims to gather the state-of-the-art research concerning these materials, for potential use as a biomaterial for wound healing and bone regeneration, and to analyze their characteristics when considering their application.

New ceramic formulations based on scheelite tailing were developed, and their potential in the ceramic industry was evaluated. Green bodies with different contents of scheelite tailing (0&ndash, 8 wt%) were sintered (1150 &deg, C, 1200 &deg, C, and 1250 &deg, C) and characterized in terms of the main mineralogical phases, microstructure, and physico-mechanical properties. The mullite was the main phase identified in all sintered temperatures. This result was also ratified with the aid of scanning electron microscope (SEM) images, in which small needles of the mullite were detected. The presence of mullite is required because it contributes to increasing the mechanical resistance of the material. The physico-mechanical properties measured (water absorption, linear shrinkage, apparent porosity, and flexural strength) were compared to the ISO 13006, and the samples sintered at 1150 &deg, C presented potential to be used as semi-stoneware, while those sintered at 1200 &deg, C and 1250 &deg, C can be employed stoneware and porcelain tiles, respectively.

In this study, we develop ceramic formulations based on quartzite and scheelite tailings collected from mining companies in the northeast of Brazil (Rio Grande do Norte State). New ceramic samples (27 wt% of kaolin, 29 wt% of plastic clay, 11 wt% of quartzite tailing, and 0&ndash, 8 wt% scheelite tailing) were uniaxially pressed in two steps (20 MPa and 50 Mpa for 20 s), dried at 110 &deg, C for 24 h, and sintered at 1150 &deg, C, 1200 &deg, C, and 1250 &deg, C. The main mineralogical phases (mullite, quartz, calcite, and anorthite) of the sintered samples were identified using X-ray diffraction (XRD). After evaluation of the physical-mechanical properties (water absorption, linear shrinkage, apparent porosity, and flexural strength), it was observed that the incorporation of scheelite tailing by up to 8 wt% did not significantly alter the properties of samples sintered at all temperatures. Our results indicate that the new ceramics formulations developed have strong potentials in manufacturing sustainable materials such as ceramic tiles and porcelain stoneware.

Chitosan, derived from chitin, is a biopolymer consisting of arbitrarily distributed β-(1-4)-linked D-glucosamine and N-acetyl-D-glucosamine that exhibits outstanding properties— biocompatibility, biodegradability, non-toxicity, antibacterial activity, the capacity to form films, and chelating of metal ions. Most of these peculiar properties are attributed to the presence of free protonable amino groups along the chitosan backbone, which also gives it solubility in acidic conditions. Moreover, this biopolymer can also be physically modified, thereby presenting a variety of forms to be developed. Consequently, this polysaccharide is used in various fields, such as tissue engineering, drug delivery systems, and cancer treatment. In this sense, this review aims to gather the state-of-the-art concerning this polysaccharide when used as a biomaterial, providing information about its characteristics, chemical modifications, and applications. We present the most relevant and new information about this polysaccharide-based biomaterial’s applications in distinct fields and also the ability of chitosan and its various derivatives to selectively permeate through the cancer cell membranes and exhibit anticancer activity, and the possibility of adding several therapeutic metal ions as a strategy to improve the therapeutic potential of this polymer.

The aim was to study formulations containing aluminosilicate and alumina in order to obtain compositions with suitable properties to fabricate dielectric ceramic devices. Initially, the precursors were subjected to chemical, mineralogical and granulometric characterization. The formulations were defined and specimens were pressed (19.6 MPa) in shapes of disc and rectangular bar. Specimens were dried, heat-treated at 1400, 1450 and 1500 °C and the mineralogical, morphological, physical, dielectric and mechanical properties were evaluated. The relative dielectric constant (εr) and loss tangent (tanδ) were evaluated at 0.1, 1, 10 and 100 kHz at room temperature. The mullite was the major phase for the studied temperature range. Compositions with a higher content of fluxes showed lower porosity and better dielectric properties and flexural strength. Values of εr at 1 kHz (~3.5 to 4.5) were close to that of the mullite for the samples fired at 1400 °C.

RESUMO Resíduos de MDF (MediumDensityFiberboard) gerados nas indústrias de móveis de madeiras, geralmente, são depositados em locais inadequados, causando impactos ambientais. Este trabalho teve como objetivo desenvolver materiais porosos com a incorporação de resíduo de MDF (5, 10 e 15% de resíduo) em massas cerâmicas estruturais. As características mineralógicas, químicas e térmicas das massas foram analisadas. Corpos de prova (50mm x15mm x 5mm) foram conformados por prensagem uniaxial (13,3 MPa), os quais foram secos à 110 ºC/24 h e sinterizados à 750, 850 e 950 °C. Posteriormente, estes foram submetidos às seguintes caracterizações: absorção de água, densidade aparente, porosidade aparente e módulo de ruptura à flexão. As características mineralógicas e microestruturais, após queima, também foram analisadas. Os resultados evidenciaram que, até 10% do resíduo de MDF em forma de pó, poderá ser incorporado em massas cerâmicas estruturais para produção de materiais cerâmicos, como blocos porosos isolantes acústicos e térmicos. A porosidade aparente foi de 31,7%, a densidade aparente foi de 1,6 g/cm3 e o módulo de ruptura a flexão foi de 11,5 MPa.

The purpose of this study is to analyze the influence of an aluminum oxide-rich precursor added to clays (smectite/kaolinite) during heat treatment on their mineralogical and microstructural changes, emphasizing the presence of mullite phase. Three clays were used. The samples were subjected to physical, chemical, thermal and mineralogical characterizations. Clay compositions containing alumina waste were then formulated and heat-treated at temperatures ranging from 900 to 1400 °C, applying a heating rate of 5 °C/min and 60 min dwell time, after which mineralogical and morphological analyses were performed. The results indicated that mullite can be obtained from clay formulations containing alumina waste, and that the amount of the mullite phase formed is determined by the composition, particle size and applied temperature.

Na contemporaneidade os efeitos da utilização irracional dos recursos da natureza se fazem sentir através do eminente risco de esgotamento de tais recursos, como por exemplo, a água potável, petróleo, espécies vegetais e animais. Pesquisas têm sido realizadas visando demonstrar a aplicabilidade do Sensoriamento Remoto na área geológica e ambiental auxiliado tanto na localização e determinação de depósitos minerais como também no estudo das consequências geradas a partir da exploração mineral. Deste modo o objetivo deste artigo é avaliar os impactos ambientais gerados pela atividade mineradora no município de Pedra Lavrada – PB através da utilização do Albedo da superfície, do Índice de Vegetação Ajustado ao Solo em imagens Landsat e da verificação da curva espectral indivíduos sadios e afetados por resíduos de atividade mineradora. Através dos mapas de Albedo da superfície e do Índice de Vegetação ajustado ao Solo foi observado que o entorno das Indústrias de Beneficiamento encontraram-se destacadas com valores mais elevados de albedo e mais baixos de vegetação, já ás áreas utilizadas para a extração apresentavam valores de albedo superiores a 0,301 e valores de vegetação variando entre 0 e 0,10. Também foi possível observar mudanças significativas do uso e cobertura do solo no entorno da sede municipal de Pedra Lavrada e diferenças nos valores de reflectância da curva espectral dos indivíduos afetados pelos resíduos de atividade mineradora apresentando. A B S T R A C T Nowadays the effects of irrational use of the natural resources are perceived through the imminent risk of depletion of riches, such as drinking water, hydrocarbons, plant and animal species. Extensive research has been conducted to demonstrate the applicability of remote sensing in geological and environmental studies, assisting both in location and determination of mineral deposits as well as in the study of the effects and consequences generated by mineral exploration. Therefore, the main goal of this work is to evaluate the environmental impacts created by mining activities in the municipality of Pedra Lavrada - PB by using the surface albedo and the Soil Adjusted Vegetation Index on Landsat data as well as to monitoring the spectral curve of vegetation to identify the healthy and the affected individuals by mining activity waste. Through the maps of surface albedo and adjusted vegetation index for soil, the results point to an increase in the albedo nearby beneficiation Industries facilities when compared to the lowest values of vegetation, yet, the areas used for feature mineral extraction, showed albedo values exceeding 0.301 and vegetation values ranging between 0 and 0.10. It was also possible to observe significant changes in the land cover surrounding the urban areas of Pedra Lavrada, as well as differences in reflectance values of the spectral curve of vegetation affected by mining activity waste. Keywords: mining, remote sensing, land cover changes, spectroradiometry.

Knowledge about the relationships between mineralogical and microstructural characteristics of clays and the transformations that occur during firing is of fundamental importance for various industries, enabling the manufacture of better quality products and widespread use of those raw materials. The aim of this study was to interpret phase development and morphological transformations in clays subjected to different heat treatments, with emphasis on the effect of impurities (iron and alkalis), temperature and heating rate. The experiments were carried out using conventional and microwave heating, with characterization by X–ray diffraction and scanning electron microscopy. The interpretation of the results based on the mullite–silica–leucite phase diagram showed that crystallization and grain growth are closely related to the amount and viscosity of the liquid phase present at the firing temperature, which vary with the composition and can be predicted by the phase diagram. Faster heating rates tend to slightly delay the establishment of equilibrium, which appears to have special bearing on the liquid phase viscosity, hence, on grain growth. As a consequence, the resulting microstructure contains mullite needles that are shorter and more uniform in size.

Plastic clays are one of the main raw materials used in ceramic technology. However, there is a shortage of good quality plastic clays in the world for use in porcelain technology. The aim of this study was to characterize plastic clays from Northeastern Brazil. Chemical and mineralogical composition, particle size distribution, plasticity and green strength of the clays were determined. The analyzed clays were predominantly composed of kaolinite and quartz, and some contained smectite. The amount of iron oxide in the clays was higher than 1.0% and for some of them the values were higher than 3%; the liquid and plastic limits ranged from 22% to 48% and 10% to 32%, respectively. According to characterization data, three plastic clays had potential to be used as alternative ball clay, due to their plasticity and mineralogical characteristics. Resumo Argilas plásticas são uma das principais matérias-primas usadas em tecnologia cerâmica. No entanto, há uma escassez dessas argilas no mundo para o uso em tecnologia de porcelanas. O objetivo deste trabalho foi caracterizar argilas plásticas do nordeste brasileiro. Composições química e mineralógica, distribuição do tamanho de partículas, plasticidade e resistência à verde dessas argilas foram determinadas. As argilas analisadas foram constituídas predominantemente por caulinita e quartzo e algumas contiveram esmectita. A quantidade de óxido de ferro nessas argilas foi maior que 1,0% e em algumas alcançou valores superiores a 3%; os limites de liquidez e plasticidade variaram de 22% a 48% e 10% a 32%, respectivamente. De acordo com os dados de caracterização, três argilas plásticas apresentaram potencial para serem usadas como ‘ball clay’ alternativa de acordo com a plasticidade e características mineralógicas.

The development of ceramic membranes with different geometries and compositions extends the possibilities of industrial applications, inducing advantages in terms of increased permeability, membrane area by volume module and chemical, thermal and mechanical resistance. The use of low-cost raw materials is a trend that has grown in scientific research. The aim of this work is to prepare membranes with hollow fiber geometry from alumina and residue of quartzite, by the technique of immersion precipitation in distilled water from a mixture of ceramic mass with a solution of polyethersulfone and, synthesized in temperatures of 1100 ºC to 1500 °C. The hollow fiber membranes were characterized by chemical analysis, X-ray diffraction, particle size distribution, scanning electron microscopy, apparent porosity, flexural strength and permeated water flow by the membranes. The results indicated that the sintering temperature has direct influence on the formation of the mullite phase, and the properties of apparent porosity and permeate flow. The higher the sintering temperature (1400-1500 ° C) increase the formation of the mullite phase, the lower the porosity, as well as the lower the permeate water flow in the membranes. However, there was increase in flexural strength in the hollow fiber membranes with high temperature.

The properties of ceramic materials and microstructural changes are dependent on the raw materials from which they are made and on the manner in which they are processed, from the composition to the established thermal treatment, heating rate, and firing temperature. In this study, the influence of some processing parameters (formulation, maturation time, and firing temperature) on the physical-mechanical properties and microstructural aspects of ceramic pieces produced from natural aluminosilicates was investigated. Because Brazil does not have many quality ball clays reserves, bentonite was included as a plasticizing agent in this study. The formulations were submitted to maturation for a period of one to four weeks and their characteristics were determined to evaluate plasticity. Following this, the specimens were extruded and subjected to heat at temperatures of 1200, 1300, and 1400ºC. The physical-mechanical properties determined were: water absorption, linear retraction, and flexural strength. Statistical analysis was applied. The results showed that, for the analyzed masses, neither the maturation time nor the physical and mechanical properties analyzed had influence on plasticity. The firing temperature was the factor that generated the greatest alteration in results, increasing the mechanical resistance and altering the size and interlocking of the mullite needles.

Resumo Atualmente, há uma severa escassez de jazimentos de feldspato de boa qualidade. Por outro lado, o diopsídio vem se mostrando um fundente alternativo para a indústria cerâmica, mas ainda pouco estudado. Assim, este trabalho avaliou o efeito da substituição parcial do feldspato pelo diopsídio em formulações para grés sanitário. Substituiu-se de 2 a 20% da massa total de feldspato por diopsídio. As matérias-primas foram caracterizadas e as reologias das suspensões analisadas. Os corpos de prova foram conformados por colagem e queimados a 1160, 1180 e 1200 ºC. As características reológicas não foram prejudicadas quando do uso de diopsídio, podendo-se substituir até 20% do feldspato por diopsídio. Com o emprego do diopsídio, houve formação de anortita e redução na temperatura de sinterização de 1200 para 1160 ºC. Nas massas com mais de 10% do feldspato substituído por diopsídio obtiveram-se maiores valores de resistência e menores de absorção de água e porosidade aparente. Abstract There is a current severe shortage of good quality feldspar deposits. Nonetheless, diopside has been proved to be an alternative flux for the ceramic industry but still little studied. This work evaluated the effect of partial replacement of feldspar with diopside in formulations for sanitary ware. Replacement ratios ranged from 2 to 20% of the total mass of feldspar. Raw materials were characterized and rheology of suspensions was analyzed. The specimens were formed by slip casting and fired at 1160, 1180 and 1200 0C. Rheological characteristics were not impaired by using diopside, and up to 20% of feldspar could be replaced with diopside. Using diopside, it was noted anorthite formation and reduction of sintering temperature from 1200 to 1160 0C. Masses with over 10% of diopside replacement resulted in higher values for strength and smaller ones for water absorption and apparent porosity.

The potential of using quartzite residues in the composition of an industrial ceramic mass for porcelain tile production was investigated through experimental design. Chemical, physical and microstructural analyses were accomplished to understand how the incorporation of quartzite residues affects the material, before and after sintering. Central composite design was used to analyze the effects of firing temperature (1143; 1160; 1200; 1240; 1257ºC) and residue content (1.76; 3; 6; 9; 10.24 wt.%) on the physical-mechanical properties of the material, and regression models correlating these factors to the response variables linear shrinkage, water absorption, apparent density and flexural strength were adjusted. Firing temperature had statistically significant effect on the response variables, so that the elevation of its levels contributed to the properties improvement. Residue content presented non-significant effect. In conclusion, specimens containing quartzite residues, up to 10.24 wt.%, sintered at 1240 and 1257ºC, fulfil the ISO 13006 requirements for porcelain tiles.

[EN] Quartzite is a mineral that contains oxides that are present in the principal raw materials utilized in traditional ceramic production. However, during its extraction and processing, large amounts of waste are generated. This study, therefore, sought to investigate the incorporation of quartzite waste into the ceramic mass, replacing up to 25% of the feldspar by weight. Both, the waste and the conventional raw materials (clay, feldspar, quartz, and kaolin) were characterized. The compositions were formulated based on common industrial products. Suspensions were prepared to evaluate pH and deflocculant content. The specimens were produced using the slip casting process, dried, and fired at 1200 °C. The ceramic masses containing up to 15% waste had yield strength values greater than 35 MPa, water absorption in the 0.5% range and shrinkage from firing within the range recommended for sanitary ware manufacture. It was concluded that the quartzite waste can partially replace, up to 15 wt%, the feldspar in ceramics for sanitary ware production., The authors would like to acknowledge the financial support received from the PDSE program of CAPES and CNPq. The authors would also like to thank the Institute of Ceramics andGlass (ICV) in Madrid, Spain, where this work was partially done.

Herein, TiO2-CeO2 nanofibers (with 0, 10, 30, and 50 vol% CeO2) were produced, and their antimicrobial activity against Candida albicans, Candida glabrata, and Candida krusei was evaluated. The results confirmed the production of mesoporous TiO2-CeO2 fibers with average diameter ranging between 100 and 282 nm. The antimicrobial assay evidenced that the TiO2-CeO2 nanofibers significantly inhibited the growth of C. albicans, C. glabrata, and C. krusei biofilms. The antifungal response against C. glabrata increased with CeO2 content, whereas for C. albicans and C. krusei no increasing trend was observed. The TiO2-CeO2 nanofibers show interesting antifungal properties and, thus, can potentially be used in biomedical applications.

Nano and submicrometric fibers of TiO2 and ZnO were produced for the first time by solution blow spinning (SBS). High surface area, homogenous, crack free TiO2 and ZnO fibers were successfully spun, as confirmed by BET surface area, X ray diffraction (XRD), transmission electron (TEM) and scanning electron (SEM) microscopy studies. TiO2 and ZnO fibers presented mean diameters ranging from 300 nm to 600 nm and from 200 nm to 550 nm, respectively. SBS proved to be an efficient method of producing metal-oxide semiconductor nano and submicrometric fibers at high output rates when compared other fiber spinning techniques.

In the production of alumina by the Bayer process, the calcination step generates a waste containing ~90% aluminum oxide (Al 2 O 3 ). Due to the high content of this oxide, this waste can be used as a source of alumina in porcelain formulations, especially those used in the synthesis of mullite. The purpose of this study was to produce porous mullite blocks using compositions containing kaolin and alumina waste. The compositions were formulated based on a mullite stoichiometry of 3:2. Heat treatments were carried out in a conventional furnace at temperatures of 1450 to 1500 °C, applying a heating rate of 5 °C/min and a 1-h hold time at the firing temperature threshold. The powders were characterized by means of X-ray fluorescence (XRF); X-ray diffraction (XRD); thermal analysis (TGA-DTA); scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The physic mechanical properties of the test specimens: water absorption, apparent porosity, linear shrinkage and flexural strength were also evaluated. The XRD results revealed the formation of mullite as the major phase. The morphological analysis by SEM revealed typical mullite needles originating from clay minerals. The size of the mullite needles was calculated based on the TEM analysis, which indicated diameters smaller than 400 nm, confirming the nanometric dimensions of the needles. The flexural strength test of the specimens indicated that this parameter ​​tends to increase as the temperature is raised.

Kaolin is a white clay, formed by hydrated aluminum silicates, which has several industrial applications. Since it is associated to impurities and presents considerable contents of contaminant elements that interfere in its performance and in its applications, kaolin must pass through a beneficiation process in order to meet the market's demands. The purpose of this work is to study the use of a hydrocyclone in the beneficiation of primary kaolins from Província Pegmatítica da Borborema. The samples were characterized by cation-exchange capacity (CEC), granulometric analysis by laser diffraction (GA), chemical composition by X-ray fluorescence (EDX), X-ray diffraction (DRX), differential thermal analysis (DTA) and thermogravimetric analysis (TG). The purification process did not show good results for kaolin in ABNT 200 mesh in the attempt to obtain colloidal kaolin. On the other hand, it presented very promising results for the beneficiation of raw kaolin, proving the feasibility of the application of this technology to the granulometric classification of this mineral, being an alternative route for the processes adopted in the regional kaolin beneficiation plants, which use washing and sieving.

Currently there is a great concern on the part of the industries with the disposal of waste generated in the production process. The quartzite processing industry generates significant amount of residue, consisting primarily of quartz. The aim of this work is to evaluate the incorporation of quartzite residue, replacing partially the quartz and feldspar, in ceramic mass used in the production of sanitary ware. The raw materials were characterized by chemical and particle size analysis. Compositions were formulated by varying the amount of residue and comparing with an industrial mass, consisted of clay, kaolin, feldspar and quartz. The slip casting process was used in the preparation of the specimens. The results showed that the residue can be considered as an alternative raw material for use in sanitary ware industry, since the ceramic slip presented appropriate rheological properties and after firing process the specimens presented physical and mechanical properties according to the specifications.

Despite the directional growing of ice crystals, fire clays structures with non-allied macroscopically porosity were prepared using a water-based freeze casting process. Pores were generated subsequently by sublimation of the columnar ice during freeze casting. By sintering this green body, a fire clay with the amount of porosity as high as 74% was obtained. Initially, the cell size and size distribution of the fire clay foams could be efficiently adjusted by the control of some parameters such as type of fire clay and gelatin content. The influence of each parameter on the properties of the obtained structures were investigated. The analysis suggests as useful this route as a new approach to produce spherical porous ceramics by freeze casting. The characteristics (morphology, strength, chemical and thermal resistance) of the foams suggest that they could be employed in applications as thermal insulation and soundproofing materials.

Resumo Nos últimos anos novos depósitos de argilas foram descobertos no Estado da Paraíba e a caracterização desses depósitos é de fundamental importância para estabelecer o seu melhor uso industrial. O presente trabalho teve como objetivo caracterizar argilas provenientes de jazidas do município de Cubati, PB, visando estabelecer seus usos adequados como matérias-primas cerâmicas. Para tanto, as matérias-primas foram submetidas às caracterizações física, química, mineralógica e térmica. Posteriormente, foram preparados corpos de prova por prensagem uniaxial a 19 MPa, secos em estufa a 110 ªC, e submetidos a queima a 750, 850, 950 e 1150ºC. Foram determinadas as propriedades físico-mecânicas: retração linear de queima, absorção de água, densidade aparente e módulo de ruptura à flexão. Os resultados comprovaram que SiO2, Al2O3 e Fe2O3 foram os principais óxidos presentes nas argilas e que estas são constituídas por esmectita, quartzo e caulinita. A argila contendo maior razão Al2O3/SiO2, distribuição granulométrica mais larga e menor diâmetro médio de partícula foi a que apresentou o melhor desempenho mecânico. Três das argilas são adequadas para uso em cerâmica branca e uma para cerâmica vermelha. Abstract In recent years, new clay deposits have been discovered in the state of Paraíba, Brazil, the characterization of these deposits having fundamental importance to establish the best industrial application. The aim of this study was to characterize clays from Cubati, PB, Brazil, to establish their appropriate uses as ceramic raw materials. Therefore, the raw materials were subjected to physical, chemical, mineralogical and thermal characterizations. The specimens were prepared by uniaxial pressing at 19 MPa, dryng at 110 ºC, and fired at 750, 850, 950 and 1150 ºC. The following physical and mechanical properties were studied: firing linear shrinkage, water absorption, apparent density and flexural modulus of rupture. The results showed that SiO2, Al2O3 and Fe2O3 were the main oxides present in the clays, whicht are constituted by smectite, kaolinite and quartz. The clay containing higher Al2O3/SiO2ratio, wider size distribution and the lower average particle diameter was the one that presented best mechanical performance. Three clays are suitable for use in white ceramic and one to red ceramic.

An investigation was made of hybrid microwave-assisted sintering of dental porcelains, using five commercial ceramic frits employed in the production of dental porcelains. The powders were characterized, transformed into prismatic test specimens, and subjected to conventional and microwave sintering. Microwave sintering was performed at a frequency of 2.45 GHz, using a susceptor material and in the absence of vacuum. The apparent density and apparent porosity of the sintered samples were characterized based on the Archimedes principle. They were also analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and their flexural strength and microhardness were determined by the Vickers method. The powders, which showed a broad particle size distribution with a high fraction of particles of dimensions larger than 30 μm, were composed of amorphous phase and leucite particles. Microwave sintering yielded ceramic bodies whose apparent porosity (t-test, p

Front of the large number of applications of the mullite mineral, many researchers seek to synthesize it from the mixture of Al2O3and SiO2powders, or from aluminossilicates, such as smectite. The synthesis of mullite from clays via rapid heating by microwaves emerges as an alternative process. This process accelerates the kinetics of nucleation and the development of mullite phase. Thus, the aim of this work is to study the effect of power and timeon synthesis of mullite from clay, via rapid heating in microwave. The synthesis times were 15 and 20 minutes, with powers of 1.26 and 1.44kW. The obtained powderswere characterized by X-ray diffraction and scanning electron microscopy. The best results were obtained with a power of 1.44kW for 20 minutes.

Aluminum and zirconia oxides are ceramic materials widely used in the manufacturing of dental products, however, the thermal treatment stages demand high temperatures. Aiming at the reduction of the energy consumption and of the time necessary for the thermal treatments, this work intends to evaluate the influence of the microwave energy over the thermal processes of alumina substrate and of the alumina/zirconia system. The samples were made by slip-casting and then submitted to different thermal treatments. For the microwave oven, we used powers of 1.44 and 1.66 kW and heating times of 10, 15 and 20 minutes. The samples were submitted to the determination of physico-mechanical properties: flexural strength at three points, porosity and Vickers microhardness. Based on the analysis, we conclude that the microwaves energy is promising for the processing of dental ceramic, causing a significant reduction in the firing time.

Among the ceramic raw materials, mullite is highlighted for presenting features which are of great interest for industry. However, the process through which this material is obtained requires pure reagents, raising the production costs. Therefore, this work is intended to obtain mullite from bentonite clays (source of silicon and aluminum oxides) and alumina residue, resulting from the Bayer process, thus becoming an interesting process from the economic and environmental standpoint. For this purpose, we made use of the thermal treatment in conventional furnace, temperature of 1500°C, heating rate of 5°C/min and dwell time of 60 min at maximum temperature. The synthesized samples were characterized by X-ray fluorescence (EDX), X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled to an EDS, besides the quantification of the phases present in the samples. The results revealed that mullite was the major phase produced, but corundum appeared as secondary phase.

Clays are very important raw materials in the manufacturing of traditional ceramic products. The present study was intended to study the phase transformations of smectites submitted to thermal treatment in conventional stove, applying slow and fast cycles. We used three clays, two national and one imported, which were beneficiated and characterized by mineralogical analysis. Later, they were submitted to a thermal treatment at 1100, 1200 and 1250°C, with heating rate of 5 and 30°C/min, remaining under the maximum temperature for 60 minutes. We observed the presence of mullite peaks starting at 1100°C for all samples. It was verified that the sample with the highest alumina/silica ratio presented more intense mullite peaks, and the sample with the high MgO content, besides the mullite phase, also formed cordierite.

Na contemporaneidade os efeitos da utilizacao irracional dos recursos da natureza se fazem sentir atraves do eminente risco de esgotamento de tais recursos, como por exemplo, a agua potavel, petroleo, especies vegetais e animais. Pesquisas tem sido realizadas visando demonstrar a aplicabilidade do Sensoriamento Remoto na area geologica e ambiental auxiliado tanto na localizacao e determinacao de depositos minerais como tambem no estudo das consequencias geradas a partir da exploracao mineral. Deste modo o objetivo deste artigo e avaliar os impactos ambientais gerados pela atividade mineradora no municipio de Pedra Lavrada – PB atraves da utilizacao do Albedo da superficie, do Indice de Vegetacao Ajustado ao Solo em imagens Landsat e da verificacao da curva espectral individuos sadios e afetados por residuos de atividade mineradora. Atraves dos mapas de Albedo da superficie e do Indice de Vegetacao ajustado ao Solo foi observado que o entorno das Industrias de Beneficiamento encontraram-se destacadas com valores mais elevados de albedo e mais baixos de vegetacao, ja as areas utilizadas para a extracao apresentavam valores de albedo superiores a 0,301 e valores de vegetacao variando entre 0 e 0,10. Tambem foi possivel observar mudancas significativas do uso e cobertura do solo no entorno da sede municipal de Pedra Lavrada e diferencas nos valores de reflectância da curva espectral dos individuos afetados pelos residuos de atividade mineradora apresentando. A B S T R A C T Nowadays the effects of irrational use of the natural resources are perceived through the imminent risk of depletion of riches, such as drinking water, hydrocarbons, plant and animal species. Extensive research has been conducted to demonstrate the applicability of remote sensing in geological and environmental studies, assisting both in location and determination of mineral deposits as well as in the study of the effects and consequences generated by mineral exploration. Therefore, the main goal of this work is to evaluate the environmental impacts created by mining activities in the municipality of Pedra Lavrada - PB by using the surface albedo and the Soil Adjusted Vegetation Index on Landsat data as well as to monitoring the spectral curve of vegetation to identify the healthy and the affected individuals by mining activity waste. Through the maps of surface albedo and adjusted vegetation index for soil, the results point to an increase in the albedo nearby beneficiation Industries facilities when compared to the lowest values of vegetation, yet, the areas used for feature mineral extraction, showed albedo values exceeding 0.301 and vegetation values ranging between 0 and 0.10. It was also possible to observe significant changes in the land cover surrounding the urban areas of Pedra Lavrada, as well as differences in reflectance values of the spectral curve of vegetation affected by mining activity waste. Keywords: mining, remote sensing, land cover changes, spectroradiometry.

Heating with microwave power is a process in which the materials take up electromagnetic energy volumetrically and turn it into heat inside a piece. This is the great difference from the conventional method, where the heat flows between objects by means of conduction, radiation and convection, in which the surface of the materials is heated first, and then the heat is transferred to the interior of the piece, thus forming a temperature gradient. On the other hand, microwave heating generates heat first inside the piece, heating the whole volume later. [1]

The use of organophilic bentonites as additives in organic-based drilling fluids has long been a subject of study, but few studies have focused on the modification of these clays with nonionic surfactants. The advantage of nonionic surfactants over ionic ones is that they improve the thermal and chemical properties of organoclays (OC), and are also more readily biodegradable. The work described here involves a study of bentonites modified by nonionic surfactants, aiming at their use as dispersants in the composition of organic-based drilling fluids. The organophilization process was analyzed by X-ray diffraction and thermogravimetry, and the interaction of organoclays with the solvent medium was assessed based on the swell index and the determination of the apparent viscosity of clay-containing dispersions. The results indicate an effective intercalation of the nonionic surfactants in organoclays, and the content of incorporated surfactants was also quantified. The swelling results demonstrate chemical compatibility between diesel and kerosene organic media and the organoclays produced. From the rheological standpoint, some of the organophilic clay samples present a potential for use as raw materials for additives in organic-based drilling fluids, despite being considered of poor quality when analyzed for water-based drilling fluids.

As principais reservas de argilas bentonitas no Brasil encontram-se nos estados de S. Paulo, Bahia, Piauí e Paraíba, sendo este ultimo como maior produtor nacional. Os grandes depósitos dessas argilas provem do município de Boa Vista, PB, que atualmente encontra-se em fase exaustão devido à exploração desordenada. Outros novos depósitos foram descobertos nos municípios de Cubati, PB e Pedra Lavrada, PB, sendo o mais recente o município de Sossego, PB, fato que pode representar uma interessante alternativa tecnológica à futura escassez das argilas bentoníticas na Paraíba, ampliação da produção mineral na região e consolidação do estado como o maior produtor do país. Este trabalho tem por objetivo estudar as argilas esmectíticas do município de Sossego, PB. Inicialmente as amostras foram submetidas a uma caracterização física, química e mineralógica através das seguintes técnicas: análise granulometrica por difração a laser, composição química por fluorescência de raios X, difração de raios X, análise térmica diferencial e termogravimetrica. Após os ensaios de caracterização foram determinadas as propriedades reológicas com base na norma da Petrobrás para fluidos base água. Os resultados evidenciaram que as argilas apresentaram em sua composição mineralógica esmectita, caulinita, feldspato e quartzo. Em relação às propriedades reológicas, os resultados foram promissores para algumas amostras para uso em fluidos de perfuração. The main reserves of bentonite clays in Brazil are located in the states of S. Paulo, Bahia, Piauí and Paraíba, the latter being as a major national producer. Large deposits of these clays are found in Boa Vista, PB, which is currently in depletion phase due to uncontrolled exploitation. Other deposits were discovered in Districts of Cubati, and Pedra Lavrada, PB, and recently in the Sossego district, PB, Brazil, was discovered a new deposit which may represent an interesting alternative technology to future shortages of Paraíba bentonite clays, expansion of mineral production in region and consolidation of the state as the largest producer in the country. This work aims to study the smectite clays from Sossego District, PB. Initially the samples were submitted to characterize physical, chemical and mineralogical through the following techniques: granulometric analysis by laser diffraction, chemical composition by X-ray fluorescence, X-ray diffraction, thermal differential and thermogravimetric analysis. After those tests, were determined the rheological properties, based on standard Petrobras, for drilling water based fluids. The results showed that mineralogical composition clays were smectite, kaolinite, feldspar and quartz. The rheological properties results indicated that some samples were promising for use in drilling fluids.

The study of moisture expansion (ME) in ceramic products has been object of research in the past few years, especially in UFCG. The ME is the increase of the dimensions of the ceramic materials by adsorption of water, it occurs slowly and is relatively small, being able to compromise the adherence of the ceramic plates to the subfloor, lead to the cracking of the glaze and conduct to the appearance of cracks in bricks, if the tensions generated by the deformation contained in the pieces exceed the limit resistance of the materials. Aiming to contribute with this research, this study aimed to characterize the alternative ceramic masses from ceramic blocks, seeking to determinate their influence in the development of the moisture expansion phenomenon. Compositions were formulated through the design of simplexes network mixtures technique. The specimens were conformed by uniaxial pressing at 20 MPa, dried in an oven at 110 °C and fired at temperatures of 800°, 900° and 1000 °C. After firing the MEs were determined by boiling and immersion. The results showed that the higher the percentage of granite waste in the formulation, lower the ME.