Abstract It is described for the first time the synthesis and characterization of NiMn2O4 employing the Mn ores from the Amazon Region as starting material, instead of using commercial reagents as normally occurs in its synthesis process. Initially, an Mn ore was transformed into a single product, the octahedral layer (OL) manganese oxide with Ni2+ ions interlayer (Ni-OL-2), which was used as a matrix to obtain NiMn2O4 by thermal decomposition. The following techniques were used for characterization: X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), infrared spectroscopy (FTIR), thermal analysis (TG-DTA), scanning (SEM) and transmission (TEM) electron microscopies. The results revealed that Mn oxide ore composed of nsutite mineral transformed into a well-ordered crystalline Ni-OL-2 phase, after the hydrothermal and cation exchange process. The thermal decomposition of Ni-OL-2 produced the nickel manganite phase at 850 °C with spherical ball morphology and crystal sizes in the range of 200-300 nm.

Abstract Strong acids used in industrial applications as cleaning, descaling, among others, can severely damage metallic structures, requiring corrosion inhibitors to diminish or avoid these issues. Since many conventional compounds used for this purpose may result in environmental and human health issues, eco-friendly compounds such as Schiff bases have been recently investigated. The synthesis of three novel Schiff bases (SBs) was confirmed by infrared spectroscopy (FTIR) and hydrogen nuclear magnetic resonance (1H-NMR). Weight loss measurements were carried out in 1 M HCl over 303K-333K. Furthermore, the combination of these compounds with a surfactant improved the efficiencies, reaching an efficiency of 93%. Optical and scanning electron microscopies confirmed the reduced roughness and pit depths of carbon steel samples. Density-functional theory calculations for neutral forms of SBs revealed that the geometrical and the energetical parameters are similar for the three studied SBs. The geometrical results exhibited more planar structures of protonated species, improving the chemical and physical interactions between aromatic rings and metallic atoms.

The use of thin films as solid lubricating makes it an excellent option for controlling wear and friction under certain operating conditions, in addition to not harming the environment. Thus, this work aims to study plasma deposition with a cathodic cage of MoS2 thin films on AISI 1020 steel substrates. From the adaptation of the cathode Cage named cathode cylinders, the samples were treated in cathodic and floating potential with temperatures of 300 °C, 350 °C, and 400 °C in an argon atmosphere. After the treatments, they were subjected to chemical analysis by X-ray diffraction (XRD) and Raman spectroscopy, in addition to a calotest tribological test. Also, it was possible to quantify the coating thickness using scanning electron microscopy (SEM). In general, the results indicated success in the deposition of molybdenum disulfide in all samples treated at fluctuating potential, as it is possible to visualize in the XRD since it indicated the presence of peaks referring to MoS2 and its compounds, in addition to an expressive reduction in wear through the calotest test.

Abstract Low density sugarcane plantation (LDSP) has been implemented by some sugarcane producers in Brazil, aiming to save seeds and operational costs. The study was carried out in the municipality of Areia, Paraíba, Brazil. Five planting densities were used, varying from 5 to 25 m-2 of buds arranged in randomized blocks, with four replications. Data were measured annually over three cultivation cycles (2017 to 2020), during which the field was fertilized with NPK and the harvests were carried out manually without prior burning. The lower planting density presents higher productivity only in the cane plant (101.03 t ha-1) due to the higher plant height (2.37 m) and the higher number of stalks (11 stalks m-2), suggesting that these variables are due to the greater availability of light, water and photosynthate. However, there is a drastic reduction in sugarcane yield for this lower population in the 2nd ratoon by up to 65.62%, which is correlated with number of stalks per meter. We demonstrate the agronomic viability of LDSP in the population of 10 buds m-2 in relation to conventional planting of sugarcane until the 2nd ratoon. Data are important for future studies to present additional considerations for other production factors, such as the effects of mechanized harvesting and the management of nutrients and water, assessing the sustainability of this large-scale planting system.

Resumo O método de plantio de cana-de-açúcar de baixa densidade (LDSP) vem sendo implementado por alguns produtores de cana-de-açúcar no Brasil, visando economia de sementes e custos operacionais. O estudo foi realizado no município de Areia, Paraíba, Brasil. Utilizou-se cinco densidades de plantio, variando de 5 a 25 m-2 de gemas dispostas em blocos casualizados, com quatro repetições. Os dados foram medidos anualmente ao longo de três ciclos de cultivo (2017 a 2020). Menor densidade de plantio mostrou maior produtividade (101,03 t ha-1) devido à maior altura de planta (2,37 m) e ao maior número de hastes (NS) (11 hastes m-2), sugerindo que essas variáveis são devido à maior disponibilidade de luz, água e fotoassimilados. No entanto, houve redução drástica na produtividade da cana-de-açúcar para esta população menor na 2ª soca em 65,62%, estando correlacionado com o número de colmos por metro. Demonstramos a viabilidade agronômica do LDSP em uma população de 10 gemas m-2 em relação ao plantio convencional de cana-de-açúcar até a 2ª soca. Os dados são importantes para que estudos futuros apresentem considerações adicionais sobre outros fatores de produção, como os efeitos da colheita mecanizada e do manejo de nutrientes e água, avaliando a sustentabilidade desse sistema de plantio em larga escala.

Abstract Morphological studies provide knowledge that allow us to understand how animals interact with the natural environment or the captivity. The goal of this study was to describe the origin and antimeric distribution of lumbosacral plexus nerves in Didelphis aurita and D. albiventris. Fourteen adult cadavers of D. aurita, seven males and seven females, and 13 adult cadavers of D. albiventris, nine males and four females were used. The specimens were sexed, identified, fixed and dissected until the origins of the lumbosacral plexus nerves were exposed. Data were represented as absolute frequency and simple percentage. The lumbosacral plexuses derived a trunk for the femoral and obturator nerves from the ventral branches of L3-L4 (75%) in D. aurita, and in D. albiventris the femoral nerve of L3-L4 (73.1%) and the obturator nerve of L3-L4 (61.5%). In both species, formation of a lumbosacral trunk derived from L5-L6-S1 occurred in 78.6% of D. aurita and 61.5% of D. albiventris. The origin and distribution of lumbosacral plexus nerves of the studied species present similarities with domestic and wild eutherian mammals.

Resumo Estudos morfológicos fornecem conhecimentos que permitem entender o modo como os animais interagem com o ambiente natural ou em cativeiro. O objetivo desse estudo foi descrever a origem e distribuição antimérica dos nervos do plexo lombossacral de Didelphis aurita e D. albiventris. Foram utilizados 14 cadáveres adultos de D. aurita, sete machos e sete fêmeas, e 13 cadáveres adultos de D. albiventris, nove machos e quatro fêmeas. Os espécimes foram sexados, identificados, fixados e dissecados até a exposição das origens dos nervos do plexo lombossacral. Os dados foram representados em frequência absoluta e percentual simples. Os plexos lombossacrais derivaram um tronco para os nervos femoral e obturatório dos ramos ventrais de L3-L4 (75%) em D. aurita, e em D. albiventris o nervo femoral de L3-L4 (73,1%) e nervo obturatório de L3-L4 (61,5%). Nas duas espécies, ocorreu formação de um tronco lombossacral derivado de L5-L6-S1 em 78,6% no D. aurita e em 61,5% no D. albiventris. A origem e distribuição dos nervos do plexo lombossacral das espécies estudadas apresentam similaridades com os mamíferos eutérios domésticos e silvestres.

Abstract West Indian cherry cultivation has proved to be an important economic activity in northeastern Brazil. However, irrigation with brackish waters limits cultivation, requiring new strategies to minimize the effect of salt stress. In this context, the present study aimed to evaluate the effect of nitrogen (N), phosphorus (P), and potassium (K) combinations on the photosynthetic pigments and quantum yield of West Indian cherry cultivated under salt stress, in the second year of production. The assay was conducted in a protected environment by adopting an experimental design in randomized blocks, with treatments distributed in a 2×10 factorial arrangement referring to two electrical conductivity levels of irrigation water - ECw (0.6 and 4.0 dS m-1) and 10 NPK fertilization combinations - FC (80-100-100; 100-100-100; 120-100-100; 140-100-100; 100-80-100; 100-120-100; 100-140-100; 100-100-80; 100-100-120, and 100-100-140% of the recommendation, in the second year of production), with three replications, each consisting of one plant. Irrigation with the electrical conductivity of 4.0 dS m-1 negatively affected the synthesis of photosynthetic pigments and the photochemical efficiency of the West Indian cherry cv. Flor Branca. The NPK combinations did not attenuate the effects of salt stress on the analyzed variables. However, the combinations referring to 120-100-100%, 140-100-100%, and 100-120-100% of NPK recommendation improved the quantum yield of photosystem II by reducing the initial fluorescence and increasing the maximum fluorescence of the West Indian cherry cv. Flor Branca.

Resumo Na região Nordeste do Brasil, o cultivo da acerola tem se mostrado uma importante atividade econômica; entretanto, a irrigação com águas salobras limita o cultivo, sendo necessário a busca por estratégias que minimizem o efeito do estresse salino. Neste contexto, objetivou-se avaliar combinações de adubação com nitrogênio (N), fósforo (P) e potássio (K) sobre os teores de pigmentos fotossintéticos e o rendimento quântico do fotossistema II da aceroleira cv. Flor Branca cultivada sob estresse salino, no segundo ano de produção. O ensaio foi conduzido em ambiente protegido sob delineamento experimental em blocos casualizados, com os tratamentos distribuídos em esquema fatorial 2×10, referentes a dois níveis de condutividade elétrica da água de irrigação - CEa (0,6 e 4,0 dS m-1) e 10 combinações de adubação com NPK - CA (80-100-100; 100-100-100; 120-100-100; 140-100-100; 100-80-100; 100-120-100; 100-140-100; 100-100-80; 100-100-120 e 100-100-140% da recomendação referente ao segundo ano de produção), com três repetições cada uma constituída por uma planta. A irrigação com água de 4,0 dS m-1 de condutividade elétrica reduziu os teores de pigmentos fotossintéticos e o rendimento quântico do fotossistema II da aceroleira. As combinações de NPK não atenuaram os efeitos do estresse salino sobre as variáveis analisadas. Entretanto, as combinações de 120-100-100, 140-100-100 e 100-120-100% da recomendação de NPK melhoraram o rendimento quântico do fotossistema II, uma vez que reduziram a fluorescência inicial e aumentaram a fluorescência máxima da aceroleira cv. Flor Branca.

Abstract This paper presents an equipment for monitoring synchronous generators condition through characteristics of the time derivative of the external magnetic field. The developed monitoring methodology allows the identification of established or incipient faults, by detecting changes in the magnetic signature of the synchronous generator. In this methodology, the measurement of signals outside the machine gives this equipment a non-invasive characteristic, allowing its monitoring without interfering or disturbing its operation. The developed system includes the specification of magnetic field sensors, signal measurement and processing equipment, as well as software for analysis and monitoring. The validation of the methodology used in this system was carried out through the analysis of experimental data, presenting efficient results in the detection of electrical and mechanical faults in synchronous generators of an experimental test bench and a hydroelectric power plant. As a result, the commercial specification of this equipment was obtained and two units were implemented in a hydroelectric power plant to monitor 305 MVA synchronous generators.

Abstract Vermiculite clays are adsorbent materials that have good chemical adsorption capacity, which makes them applicable in the removal of drugs from aqueous solutions. Their lamellar structure can be easily expanded and organophilized. To assess the efficacy and environmentally-tolerant capacity of the adsorption method, the organophilized vermiculite clay was compared to both natural and expanded vermiculite clays. To prepare the organophilized clays, a natural clay sample was expanded at 900 °C. The expanded clay was thus treated by immersion in a 1.0 M NaCl solution and organophilized using a cetyltrimethylammonium bromide (CTMA-Br) surfactant, for 24 h at 50 °C. Natural, expanded, and organophilized samples were characterized using the techniques of XRD, FTIR, TG/DSC, and SEM to observe structural changes after expansion and organophilization. These characterizations indicated that there was an increase in the interlamellar space of the expanded and organophilized sample. In addition, a study of the point of zero charge was performed to determine the surface changes of the samples and the amount of doxazosin adsorption in the samples was determined by the time adsorption test. Further, the organophilized sample showed potential adsorption of the drug doxazosin and high performance in relation to the expanded and natural samples.

Resumo A incorporação de estanho na zeólita ZSM-12 de alta sílica foi avaliada utilizando diferentes concentrações de estanho e diferentes agentes direcionadores de estrutura (ADS), a fim de ser utilizada na reação de isomerização da glicose para frutose. A síntese com hidróxido de tetraetilamônio como ADS formou a estrutura da zeólita ZSM-12 de alta sílica, entretanto, neste sistema, a adição de Sn impediu a formação da zeólita ZSM-12. Portanto, o brometo de tetraetilamônio foi utilizado como ADS, mas as sínteses com e sem a incorporação de Sn não produziram a zeólita ZSM-12. Em seguida, o cloreto de metiltrietilamônio foi utilizado como ADS e a estrutura ZSM-12 de alta sílica foi formada apenas com a incorporação de estanho. As amostras com estrutura ZSM-12 e diferentes concentrações de estanho foram avaliadas na reação de conversão de glicose em frutose. Verificou-se que a amostra com menor teor de estanho ( Sn / Si = 0 , 005 ) obteve a maior conversão de glicose e o maior rendimento de frutose.

Abstract Tin incorporation in high-silica ZSM-12 zeolite was evaluated using different concentrations of tin and different structure-directing agents (SDA), in order to be used in the glucose isomerization reaction in fructose. The tetraethylammonium hydroxide SDA successfully formed the structure of the high silica zeolite ZSM-12; however, in this system, the addition of Sn prevented the formation of the ZSM-12 zeolite. Therefore, tetraethylammonium bromide was used as SDA, but the syntheses of high-silica ZSM-12 zeolite without and with tin incorporation were not effective. Then methyltriethylammonium chloride was used as SDA, and the high-silica ZSM-12 structure was formed only with the incorporation of tin. The samples with ZSM-12 structure and different concentrations of tin were evaluated in reaction of glucose conversion to fructose. It was found that the sample with the lowest tin content ( Sn / Si = 0 . 005 ) achieved the highest glucose conversion and the highest fructose yield.

Resumo Filmes finos multicamadas de TiO2-CeO2 foram depositados pelo método de spin coating e calcinados a 500 e 700 °C. Os filmes finos foram caracterizados por difração de raios-X (DRX), microscopia eletrônica de varredura por emissão de campo (MEV-FEG), microscopia de força atômica (MFA) e espectroscopia de reflectância difusa. As propriedades fotocatalíticas foram estimadas variando a concentração do corante azul de metileno (AM) quando iluminado por radiação UV. Os padrões de DRX mostraram que as temperaturas de 500 e 700 °C foram efetivas para obter as fases de TiO2 e CeO2. A diferença na homogeneidade dos filmes de TiO2 e CeO2 foi evidente nas imagens de MFA, onde os filmes apresentaram rugosidade média de 2,0 e 5,3 nm, respectivamente. Filme fino de TiO2-CeO2 obtido a 700 °C apresentou a melhor atividade fotocatalítica, reduzindo a concentração de AM em aproximadamente 80%, enquanto os filmes de CeO2 e TiO2 obtidos a 700 °C reduziram apenas 20% e 29%, respectivamente. O teste de reutilização mostrou que os filmes finos mantiveram sua atividade após 4 ciclos, não havendo necessidade de tratamento térmico, indicando ser um fotocatalisador imobilizado com alta eficiência na degradação do corante orgânico.

Abstract TiO2-CeO2 multilayer thin films were deposited by the spin coating method and calcined at 500 and 700 °C. Thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and diffuse reflectance spectroscopy. Photocatalytic properties were estimated by varying the concentration of the methylene blue dye (MB) when illuminated by UV radiation. The XRD patterns showed that the temperatures of 500 and 700 °C were effective to obtain TiO2 and CeO2 phases. The difference in the homogeneity of TiO2 and CeO2 films was evident in the AFM images, where the films showed an average roughness of 2.0 and 5.3 nm, respectively. The CeO2-TiO2 thin film obtained at 700 °C showed the best photocatalytic activity, reducing the concentration of MB by approximately 80%, while the CeO2 and TiO2 films obtained at 700 °C reduced only 20% and 29%, respectively. The reuse test showed that the thin films maintained their photocatalytic activity after 4 cycles, and there was no need for thermal treatment, indicating that it is an immobilized photocatalyst with high efficiency in the degradation of organic dyes.

Resumo Estudos de morfologia fornecem conhecimentos que permitem entender o modo como os animais interagem com o ambiente natural ou em cativeiro. O objetivo desse estudo foi descrever a origem e a distribuição antimérica dos nervos do plexo braquial e os músculos inervados em Bradypus variegatus. Foram utilizadas 12 preguiças adultas com mortes de diferentes causas naturais no Estado do Rio de Janeiro. Os espécimes foram fixados com perfusão de solução de formaldeído a 10%. Os dados foram representados em frequência absoluta e percentual simples. Os plexos braquiais originaram os nervos supraescapular, subescapular, radial, mediano, ulnar e musculocutâneo para a musculatura intrínseca e os nervos peitoral cranial, peitoral caudal, torácico lateral, torácico longo, toracodorsal para a musculatura extrínseca. Os ramos espinhais envolvidos na formação do plexo foram C8, C9, C10, T1 e T2. Os ramos que mais contribuíram em suas formações foram C8 e C9.

Abstract Morphology studies provide knowledge that allow us to understand how animals interact with the natural environment or in captivity. The aim of this study was to describe the origin and antimeric distribution of brachial plexus nerves and the innervated muscles in Bradypus variegatus. Twelve adults three-toed sloths were used, arising from the Serra dos Órgãos National Park and Wild Animals Rehabilitation Center of Estácio de Sá University and donated to Animal and Human Anatomy Department of the Rural Federal University of Rio de Janeiro. The specimens were fixed in formaldehyde solution for infusion to 10%. Data were presented in absolute and percentage frequency simple. The brachial plexus originated the suprascapular, subscapular, radial, median, ulnar and musculocutaneous nerves for the intrinsic musculature and the cranial pectoral nerves, caudal pectoral, lateral thoracic, long thoracic, thoracodorsal nerves for the extrinsic musculature. The spinal branches involved in the formation of the plexus were C8, C9, C10, T1 andT2. The branches that contributed most were ventral spines C8 and C9.

Resumo Neste trabalho, pós do espinélio aluminato de zinco foram preparados por um método Pechini modificado, rápido, simples, ambientamento seguro e de baixo custo, utilizando gelatina comercial como precursor orgânico. Os materiais foram calcinados a 600, 700 e 800 °C e caracterizados por análise termogravimétrica, difratometria de raios X (DRX) in situ e ex situ, isotermas de adsorção/dessorção de N2 e microscopia eletrônica de varredura. Os resultados mostraram que as partículas de ZnAl2O4 monofásicas com estrutura espinélio foram obtidas com sucesso resultando em materiais de alta pureza, nanométricos, homogêneos e mesoporosos. Os resultados de DRX in situ mostraram que a estrutura cristalina do espinélio ZnAl2O4 começou a se formar em temperaturas inferiores a 600 °C, revelando pós com tamanho de cristalito menor que 40 nm, que cresceram com o aumento da temperatura (91% de aumento entre 600 e 800 °C). O efeito do tempo de calcinação mostrou que os materiais calcinados a 600 °C por 3 h apresentaram maior porcentagem do crescimento do cristalito devido ao aumento da cristalinidade. As amostras de ZnAl2O4 mantiveram o tamanho dos poros até 700 °C.

Abstract In this work, zinc aluminate spinel powders were prepared by a fast, simple, eco-friendly and low-cost modified Pechini method using commercial gelatin as the organic precursor. The materials were calcinated at 600, 700 and 800 °C and characterized by thermogravimetric analysis, in situ and ex situ X-ray diffraction (XRD), N2-adsorption/desorption isotherms and scanning electron microscopy. The results showed that single phase ZnAl2O4 particles with spinel structure were successfully obtained resulting in a high purity, nanometric, homogeneous and mesoporous materials. The in situ XRD results showed that the crystalline spinel structure of ZnAl2O4 started forming at a temperature lower than 600 °C, revealing powders with crystallite size smaller than 40 nm, which increased with increasing the temperature (91% of increase between 600 and 800 °C). The effect of calcination time showed that the materials calcinated at 600 °C for 3 h presented the higher percentage of crystallite growth due to the increase of crystallinity. The ZnAl2O4 samples retained their pore size up to 700 °C.

Resumo As argamassas de revestimento aplicadas ao restauro de obras e edifícios históricos devem ser compatíveis com os materiais pré-existentes, contribuindo com a preservação e reabilitação do patrimônio edificado sem comprometimento de seu valor arquitetônico. As argamassas mais empregadas no restauro de edifícios antigos são os traços de cal e agregado miúdo na razão de 1:3 por não serem tão duras quanto as de cimento. O desempenho e a durabilidade dessas argamassas podem ser melhorados, reduzindo o número de intervenções. A adição de resíduos finos pode contribuir com estes objetivos por meio do preenchimento de poros da argamassa no estado endurecido. O resíduo do polimento do porcelanato (RPP) possui granulometria fina e pode ser aplicado substituindo parcialmente o agregado miúdo. Assim, o objetivo desse trabalho foi avaliar o efeito da adição de RPP em argamassas de restauro à base de cal, substituindo o agregado fino. Concentrações entre 5 e 30% foram estudadas e o comportamento comparado ao da argamassa padrão. Foram realizados ensaios de consistência, densidade de massa aparente, retenção de água e teor de ar incorporado no estado fresco. Para a avaliação do estado endurecido, foram moldados corpos de prova prismáticos ensaiados aos 90 dias de idade para avaliação da resistência mecânica à tração, flexão e compressão e aderência. Todos os ensaios realizados são normatizados pela ABNT. Os resultados mostraram que a substituição de areia por RPP resultou em maior densidade e compacidade em consequência da diminuição no teor de ar incorporado. As argamassas com concentrações de RPP entre 10 e 20% apresentaram melhor conjunto de propriedades no estado endurecido, com ganho em retração livre, maior resistência mecânica e aderência. A adição de RPP em substituição parcial da areia resultou em argamassas com melhor desempenho que sugere maior durabilidade, contribuindo para o restauro arquitetônico e preservação do patrimônio histórico com menor número de intervenções.

Abstract Mortar coatings applied to historic buildings and artwork must be compatible with the pre-existing materials, thus contributing with both the restoration and preservation of heritage without affecting its architectonic value. Lime mortars consisting of fine aggregate ratio of 1:3 are softer than cement mortars and therefore more adequate for restoration. The performance and durability of the conventional lime mortar can be further improved in order to reduce the number of interventions. The addition of fine residues can contribute to this goal as they fill the pores of the hardened mortar. The residue of porcelain tile polishing (RPP) is a fine material and can be added to the mortar partially replacing the fine aggregate. Therefore, the present study aimed at evaluating the effect of the addition of RPP on the fresh and hardened states of the lime mortar. Contents from 5 to 30 wt% of RPP were investigated and the properties of the corresponding mortars were compared to those of the conventional mortar. In the fresh state, consistency, density, water retention and air content were measured. Rectangular samples of each mortar composition were then dried and aged during 90 days to analyze the mechanical strength and adherence. All tests are standardized by ABNT. The results revealed that mortars containing RPP depicted higher density and compactness as a consequence of the reduction in the air content. Mortars with RPP contents between 10 and 20% showed enhanced properties in the hardened state compared to the RPP-free mortar, including better retraction behavior, higher mechanical and adherence strength. The addition of RPP, partially replacing the fine aggregate in lime mortar, resulted in mortar compositions with improved overall behavior for restoration, and possibly longer durability, thus contributing to the architectural restoration and preservation of historical heritage with fewer interventions.

Resumo Uma rota de síntese em uma etapa baseada no método dos precursores poliméricos foi usada para produzir pós do nanocompósito contendo as fases CuO e céria dopada com samária (SDC). Esta rota química permitiu obter pós compósitos com reduzido tamanho de partícula e uniforme distribuição dos elementos Cu, Ce e Sm. O material particulado foi caracterizado por difração de raios X (DRX) combinado com refinamento Rietveld dos dados de difração. Compósitos CuO-SDC sinterizados em ar entre 950 e 1050 °C e em seguida reduzidos a Cu-SDC foram caracterizados por DRX e microscopia eletrônica de varredura. A porosidade aberta foi medida usando o princípio de Arquimedes. Microestruturas adequadas para os processos de transferência de carga e transporte de massa (30 a 45% de porosidade) foram obtidas em cermets Cu-SDC previamente sinterizados a 1000 a 1050 °C. Os resultados indicaram que compósitos CuO-SDC e cermets Cu-SDC com potencial aplicação como anodos de células a combustível de óxido sólido (CCOS) podem ser obtidos por projeto microestrutural. Meia célula suportada no anodo foi preparada por coprensagem e cossinterização de céria dopada com gadolínia (CGO) e o nanocompósito obtido neste trabalho.

Abstract 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.

Resumo Este trabalho teve como objetivo caracterizar o sedimento proveniente de dragagem de canais pluviais (SCP), do município de Salvador-BA, visando sua máxima substituição pela argila em cerâmica estrutural, uma vez que essa mistura binária faz parte do projeto piloto da massa padrão, na pesquisa da formulação de blocos intertravados cerâmicos. Inicialmente o sedimento foi submetido aos ensaios de índice de plasticidade, analise química por fluorescência de raios X, análise mineralógica por difração de raios X, analise térmica e granulométrica. A morfologia do material foi analisada utilizando-se microscopia eletrônica de varredura, acompanhada de espectroscopia de energia dispersiva. Em seguida foram feitas adições de sedimento (SCP) a uma argila do município de Candeias-BA, nas proporções de 10, 20, 30 e 40% em massa. Foram preparados corpos de prova por prensagem uniaxial nas dimensões 60 mm x 20 mm, com pressão de compactação de 25 MPa, sendo que o material foi umidificado com 8% de água. A queima foi realizada em forno resistivo a 850, 950 e 1050 °C, com taxa de aquecimento de 5 °C/min. As propriedades avaliadas foram retração linear, absorção de água e módulo de ruptura à flexão. Os resultados indicaram que é possível a utilização do SCP em cerâmica estrutural, mediante os pré-requisitos exigidos em normas, na fabricação de telhas, blocos de vedação e tijolos.

Abstract The aim of this study was to characterize sediment from the dredging of stormwater channels (SCP) in the city of Salvador, Bahia, aiming its maximum replacement by clay in structural ceramics, since this binary mixture is part of the pilot project of the standard mass, in the research of interlocked block ceramic formulation. Initially, the sediment was submitted to the following tests: plasticity index; chemical analysis by X-ray fluorescence; mineralogical analysis by X-ray diffraction; thermal and particle size analyses. The morphology of the material was analyzed by scanning electron microscopy, coupled with energy dispersive spectroscopy. Then, sediment (SCP) was added to clay from the municipality of Candeias, Bahia, in the proportions of 10, 20, 30 and 40 wt%. Specimens were prepared by uniaxial pressing in dimensions of 60 mm x 20 mm, with compacting pressure of 25 MPa, and the material was humidified with 8% of water. Firing was conducted in resistive furnace at temperatures of 850, 950 and 1050 ºC, with 5 ºC/min heating rate. The properties evaluated were: linear shrinkage; water absorption and modulus of rupture. The results indicated the possibility of using SCP in structural ceramics by the prerequisites required in standards, in the manufacture of tiles, sealing blocks and bricks.