The residues of ornamental rocks, especially quartzite, cause great environmental impact. More impulse has been given to research on the recycling of these residues over the last years, particularly for use as aggregates in concrete and mortar. Nevertheless, the studies conducted so far do not mention the behavior of the mortar blended with aggregates coming from residues of ornamental rocks when under chemical attacks in sulfate-rich environment. Thus, in the present study it was sought to add quartzite residues to the mortar, verifying its mechanical behavior and its durability when attacked by sodium sulfate (Na₂SO₄). The durability of the mortar blended with quartzite residues under sulfate attack was evaluated by the dimensional variation of the test specimens when immersed in sodium sulfate solution, according to the methodology of the NBR 13583 standard. Were used the following complementary techniques: simple compressive strength, X-ray diffraction and thermogravimetric and differential analysis. From the tests, it was verified that the mortars, after attack of sodium sulfate, presented dimensional expansions superior to 0.06%, as well as increased mechanical strength. Therefore, although it was found that the specimens incorporated with quartzite residues were attacked by sulfate, it was observed that it was not able to form sufficient secondary ettringite to mechanically damage the specimens submitted to the sodium sulfate attack.

O Estado do Rio Grande do Norte, mais especificamente no município de Parelhas, Brasil, a indústria cerâmica já é bastante consolidada, crescendo ano após ano. Entretanto, o estímulo do setor tem provocado acelerada exaustão das jazidas de argilas locais utilizadas pela indústria e, por conseguinte, ameaçando a manutenção da indústria cerâmica no município e na região Seridó. Por esta razão, tem-se aprofundado o interesse de buscar novos jazimentos de argilas, a fim de suprir as suas demandas atuais e futuras. Recentemente, foram descobertos novos jazimentos no município, todavia, estas argilas não têm sido devidamente caracterizadas, causando prejuízos tanto a qualidade final do produto, como ao seu pleno aproveitamento industrial. Assim, este trabalho tem como objetivo caracterizar física, química e mineralogicamente argilas extraídas de três novos jazimentos do município de Parelhas/RN, com a finalidade de classificá-las visando sua aplicação na indústria de cerâmica vermelha da região. As amostras foram beneficiadas por secagem a 60 °C, seguida de moagem e peneiramento em malha de 200 mesh. Então, foram caracterizadas por fluorescência de raios-x, difração de raios-x, análise termogravimétrica e diferencial, análise granulométrica, perda ao fogo e plasticidade. Os constituintes das amostras identificados por fluorescência de raios X foram SiO₂, Al₂O₃, Fe₂O₃, MgO, K₂O, CaO e TiO₂. Os difratogramas de raios-X revelaram a presença predominante dos argilominerais esmectita, feldspato, caulinita e quartzo nas amostras. A perda de massa total para as amostras variou entre 14% a 22,65%. A distribuição de partículas variou entre 0,2 a 40 µm, com diâmetro médio entre 6 e 16 µm. As amostras são classificadas como altamente plásticas e apresentam viabilidade para serem utilizadas na indústria de cerâmica vermelha.

In the petroleum industry, one of the most important functions fluids must perform is to carry cuttings efficiently. In this context, the contamination of drilling fluids represents a challenge to the industry because it alters the properties of these fluids. This work compares two drilling fluids (one palygorskite-based and the other polymer-based), evaluating the effects of contaminants on these drilling fluids and their ability to carry cuttings. A contaminant is considered to be any material that causes undesirable changes in the properties of the drilling fluid. Contamination of an aqueous drilling fluid by calcium hydroxide (Ca(OH)2) and brine can increase the filtrate volume, decrease the perforation rate and alter the rheological properties of the fluid. This work analyses the effects of contamination by Ca(OH)2 and brine on the properties of salted water-based drilling fluids viscosified with palygorskite. For comparison, tests were performed with a polymeric drilling fluid. The cutting-carrying capacity of these fluids was verified using the empirical correlations of Moore (1974), Chien (1994) and Walker & Mayes (1975). The results show that the drilling fluid with palygorskite is resistant to contamination with Ca(OH)2 and brine, presenting low filtrate volume values. The drilling fluid with palygorskite presented greater slip velocities than the polymeric drilling fluid. Regarding the cutting-carrying capacity, the drilling fluid with palygorskite presented positive transport ratio values (>0), making it suitable for carrying rock cuttings. However, the polymeric drilling fluid showed better performance in terms of cutting-carrying capacity.

The study of the strontium-doped lanthanum manganites in the form of films covers a large area of technological applications, such as ceramics semiconductors and solid oxide fuel cell cathode. Strontium-doped lanthanum manganite and samarium-doped ceria has been used as composite cathode of solid oxide fuel cells (SOFCs) because of its excellent performance in electronic and ionic conductivity. In this work, we produced films of the cathode LSM / SDC on yttria stabilized zirconia (YSZ) electrolytes. La0.8Sr0.2MnO3 (LSM) and Ce0.8Sm0.2O1.9 (SDC) powders were synthesized by a synthesis route similar to the Pechini method, in which the gelatin replaced the ethylene glycol as polymerizing agent. Precursor powders of LSM and SDC phases were calcined at 900 ºC. In the step of films production were prepared suspensions of the LSM and SDC powders with addition of ethyl cellulose as a pore-forming agent. The ceramic suspensions were deposited on YSZ electrolyte using the spin coating method. After sintering to 1150 °C for 4 h the films were characterized by XRD and SEM. The film with 10 wt.% ethyl cellulose presented porous and strongly adhered to the YSZ substrate.

The mixture of mortars with quartzite residues is a recycling technique that has been widely used to promote the adequate management of solid waste generated in the municipality of Várzea-PB, Brazil. However, there are no reports in the literature that prove the durability of the mortar mixed with these residues when subjected to environmental conditions over time. Thus, the present work has as objective to study the durability of mortars incorporated with quartzite residues when submitted to natural aging. The reference mortar and incorporated with quartzite were prepared according to NBR 13281 and submitted to natural aging for 28, 60, 120, 180 and 360 days. Then, they were characterized by x-ray diffraction, thermogravimetric analysis and simple compression strength and carbonation and pozzolanic measurements. The results showed that, despite the decrease in compressive strength of quartzite containing mortars, the durability was not compromised, since the values were maintained in the range suggested by NBR 13281. Finally, it was concluded that mortars produced with quartzite residues presented good mechanical behavior when submitted to natural aging.

Este trabalho tem como objetivo obter óxidos com estrutura tipo espinélio de composição CaFe_1,8Cr_0,2O₄ pelo método gelatina, visando aplicação em esmaltes transparentes brilhantes e mate. Os pós precursores, resultantes do processo de síntese, foram calcinados a 600 °C e a 800 °C para a obtenção da fase espinélio. Os pós foram caracterizados por espectroscopia na região do infravermelho, difração de raios-x, seguido por refinamento Rietveld, espectroscopia de reflectância difusa UV-visível e colorimetria CIE-L*a*b*. Em seguida, os pós foram misturados aos esmaltes transparentes brilhante e mate na proporção de 2% em peso, revestido substratos cerâmicos e, posteriormente, sinterizados a 1100 °C. De acordo com os difratogramas de raios-x, os pós possuíram estrutura espinélio ortorrômbica. As ferritas de cálcio dopadas com cromo apresentaram coloração alaranjada, sendo mais escura nos pós calcinados a temperaturas mais altas. Os resultados da esmaltação revelaram que houve compatibilidade entre o pigmento e o esmalte brilhante. Já nos esmaltes mate, houve variação abrupta da cor. O ataque por ácido clorídrico mostrou que os esmaltes preparados são altamente resistentes ao ataque químico. Por fim, este trabalho conclui que a rota gelatina foi eficiente em sintetizar óxidos com estrutura espinélio monofásicos em baixas temperaturas de síntese e que os pigmentos obtidos são viáveis para aplicação industrial.