Showing papers in "Materia-rio De Janeiro in 2016"

FTIR analysis and quantification of phenols and flavonoids of five commercially available plants extracts used in wound healing

Abstract: Natural products are used in wound healing in order to prevent infection. Propolis is a well known antimicrobial with phenolic compounds and flavonoid content which vary according to the propolis origin. Besides propolis (from both Brazilian and UK sources), pomegranate, dragon's blood and sage are possible antimicrobials to be used in biomaterials. The goal of this work was to analyze the amount of phenols and flavonoid compounds in these natural products, their antioxidant activities and the bonds present by FTIR. The FTIR analysis revealed the presence of active compounds in all drug samples. The phenols quantification showed that Brazilian propolis was rich in phenols compared to the other drugs, followed by pomegranate and UK propolis. UK propolis was the most rich in flavonoids, which is expected on account of its origin. Pomegranate, UK propolis and Dragon's blood presented the highest antioxidant activity. All samples presented antioxidant activity > 82%.

Investigating atmospheric corrosion behavior of carbon steel in coastal regions of Mauritius using Raman Spectroscopy

Abstract: Low carbon steel was exposed at two sites in Mauritius, namely Port Louis and Belle Mare. The site at Port Louis is basically an industrial marine one whereas the one at Belle Mare is a purely marine site. Though the corrosion loss trend at both sites follow the power law, the corrosion loss at Port Louis was found to be higher than that at Belle Mare. This study has been performed to investigate the surface characteristics of the rust layers of the samples exposed at the two sites, through Raman spectroscopy and SEM, so as to get a better insight into the mechanism of the atmospheric corrosion process. For Port Louis, it was observed that there was not much change in the corrosion products in the rust layer over the 3 years period. The structure was less compact than that at Belle Mare with the presence of lepidocrocite and akaganeite as commonly observed corrosion products. The corrosion rate at Port Louis is, therefore, expected to follow the same trend over the long term. For Belle Mare, the corrosion products changed significantly after 3 years of exposure. Though lepidocrocite and akaganeite were observed on the surface after 0.2 years of exposure, magnetite was the most probable corrosion product in the more compact rust layer after 3 years of exposure. This compactness of the rust layer is expected to have reduced the corrosion rate as compared to that of Port Louis. Significant changes in the corrosion rate at Belle Mare are, therefore, expected over the medium and the long term.

Investigation of Adhesion and Tribological Behavior of Borided AISI 310 Stainless Steel

Abstract: In the present study, the effects of the boriding process on adhesion and tribological properties of AISI 310 steel were investigated. Boriding was performed in a solid medium consisting of Ekabor-II powders at 1123 and 1323K for 2 and 6 h. The boride layer was characterized by optical microscopy, the X-ray diffraction technique and the micro-Vickers hardness tester. The X-ray diffraction analysis of the boride layers on the surface of the steels revealed the existence of FexBy, CrxBy and NixBy compounds. Depending on the chemical composition of substrates, the boride layer thickness on the surface of the AISI 310 steel was found to be 56.74 μm. The hardness of the boride compounds formed on the surface of the AISI 310 steel ranged from 1658 to 2284 HV0,1, whereas the Vickers hardness value of the untreated steel AISI 310 was 276 HV0,1. The wear tests were carried out in a ball-disc arrangement under a dry friction condition at room temperature with an applied load of 10N and with a sliding speed of 0.3 m/s, at a sliding distance of 1000m. The wear surfaces of the steel were analyzed using an SEM microscopy and X-ray energy dispersive spectroscopy EDS. It was observed that the wear rate of unborided and borided AISI 310 steel ranged from 4.57 to 71.42 mm3/Nm.

Resistência da madeira ao cisalhamento paralelo às fibras segundo as normas ABNT NBR 7190:1997 e ISO 13910:2005

Abstract: O conhecimento das propriedades fisicas e mecânicas da madeira e essencial para o seu correto destino e uso final. Para uso estrutural, as normas tecnicas estabelecem metodologias de ensaios para a determinacao das propriedades mecânicas. No Brasil a norma para estruturas de madeira [ 1 ] atualmente encontra-se em processo de revisao. Uma das propostas da versao de revisao e a alteracao de alguns procedimentos de ensaios usados na determinacao das propriedades mecânicas da madeira. Tem-se observado que varios modelos de corpos de prova tambem vem sendo testados pela comissao de estudos CE - 02:126.10 da Associacao Brasileira de Normas Tecnicas para determinacao de um modelo mais representativo para os ensaios. Dentro deste contexto, o objetivo deste estudo foi analisar a resistencia ao cisalhamento atraves da atual norma brasileira [ 1 ] e tambem a partir da norma europeia [ 2 ]. Foram tambem avaliadas as relacoes simplificadas entre as resistencias ao cisalhamento e a compressao paralela as fibras (f v0,k /f c0,k ) propostas pela norma brasileira [ 1 ] para coniferas e dicotiledoneas. Foram consideradas neste estudo madeiras de Pinus elliottii e Eucalyptus saligna . Os resultados obtidos mostraram que a norma brasileira apresentou valores maiores para a resistencia de cisalhamento com relacao a norma europeia. Para as madeiras de eucalipto e pinus estudadas, as diferencas entre as resistencias de cisalhamento foram, respectivamente, 35% e 65%, neste caso, e a relacao simplificada (f v0,k /f c0,k ) obtida para o eucalipto foi a que mais se aproximou dos valores normatizados pela norma brasileira [ 1 ]. Palavras-chave: cisalhamento, resistencia, normatizacao.

Synthesis, characterization and cytotoxicity of Chitosan/Polyvinyl Alcohol/Bioactive Glass hybrid scaffolds obtained by lyophilization

Abstract: One of the important research topics in tissue engineering is the development of optimum three-dimensional scaffolds for regeneration and growth of bone tissue. The scaffold developed should promote an initial biomechanical support, provide the formation, deposition and organization of the new organic matrix generated, and degrade proportionally to the growth of the new tissue. In this study hybrid scaffolds based on the blend Chitosan (CHI)/Poly (vinyl alcohol) (PVA), with two different CHI:PVA molar ratios (1:1, and 3:1), and Bioactive Glass as the inorganic phase, were developed by a sol-gel route, followed by lyophilization. The materials were cross-linked with Glutaraldehyde. The obtained porous scaffolds were characterized by SEM, FTIR, porosity measurements by Archimedes method, and compression test. The in vitro degradation was studied by immersion in simulated body fluid for several time periods and evaluation of mass loss. Citotoxicity analysis was carried out on samples as prepared and after immersion in PBS solution for 24hrs, using human fibroblast cells and MTT method to evaluate cell viability. The matrices obtained showed promising results, presenting about 96% porosity, pore size varying in the range 20-300 µm, and interconnected pores. The mass loss presented by the matrices with CHI/PVA ratios 3:1 and 1:1 during the degradation test in vitro, was around 10% after a week of testing, with macroscopic preservation of their physical structure. Cytotoxicity tests showed that the samples were toxic as produced and not toxic after treatment with PBS, showing this approach was suitable as a final preparation step of these samples. Keywords: Chitosan, PVA, bioactive glass, lyophilization, porosity, scaffolds

Utilization of banana stalk fiber as reinforcement in low density polyethylene composite

Abstract: Natural fibers could serve as viable and abundant alternatives to the expensive and non - renewable synthetic fibers as reinforcement in thermoplastic composites. The potentiality of banana stalk fiber at reinforcing a low density polyethylene matrix was examined in this study. Fibers were extracted from the stalk of banana plant and characterized for its chemical composition and fiber contents. The fibers were modified by pulping with caustic soda to increase it wettability. The fiber dimension was measured using a binocular light microscope. FTIR spectra was used to identify the functional groups of modified and unmodified fibers. The composites were produced using a single -- screw extruder, pelletized and then processed into test specimen samples by injection molding. The fiber volume in the polymer matrix was varied from 5.4 to 20 %. The effects of chemical treatment and increasing fiber content on the moisture absorption and mechanical properties of the composites were examined. The results showed that fiber of banana plant were characterized by medium to long fiber length (2.84 mm). The lignin content (7.99 %) was relatively low indicating a lower value of chemical consumption in the modification step. The SEM micrograph of the composite cross section showed good fiber/matrix interfacial bonding. The water absorption capacity of the composites increased with increase in fiber loading while the treated fibers showed a reduction in hydrophylicity of the composites. The treated fibers showed improved tensile strength and can thus be utilized in the production of composites with better properties Keywords: Banana fiber, composites, reinforcement, polyethylene, mechanical properties

Parâmetros da areia que influenciam a consistência e a densidade de massa das argamassas de revestimento

Abstract: O consumo de areias de britagem para producao de argamassas vem aumentando, uma vez que as jazidas de areia natural estao cada vez mais escassas e que a exploracao dessa areia gera grande impacto ambiental. Nesse sentido, o objetivo deste trabalho e verificar a influencia do emprego de areias de britagem de diferentes origens e mineralogias nas propriedades de argamassas de revestimento no estado fresco. Com base em uma ampla caracterizacao de agregados originarios de diferentes fontes litologicas, a pesquisa visou avaliar quais parâmetros da areia melhor explicam os comportamentos de consistencia e de densidade de massa da argamassa. O estudo foi realizado com cinco areias, sendo uma areia natural e quatro de britagem oriundas de rochas de diferentes litologias (granito, dolomito, micaxisto e quartzito). Alem da caracterizacao granulometrica e da determinacao dos indices fisicos das areias, foram realizadas analises morfoscopica e petrografica, bem como a determinacao do ângulo de atrito interno por meio do ensaio de cisalhamento direto. Para verificar o efeito das caracteristicas das areias nas propriedades da argamassa no estado fresco, empregou-se uma mistura 1:1:6 (cimento:cal:areia, em volume), tendo-se realizados os ensaios de determinacao do indice de consistencia na mesa ABNT, penetracao do cone e densidade de massa. As principais conclusoes obtidas ressaltam que a porosidade (vazios entre particulas e graos de areia) e a massa unitaria da areia sao os parâmetros que melhor se correlacionam com a consistencia e a densidade de massa das argamassas, o que e explicado pela alteracao imposta no volume de pasta das argamassas devido ao volume de vazios deixado pelos graos das areias.

Mechanical characteristics of groundnut shell particle reinforced polylactide nano fibre

Abstract: The PLA-groundnut shell solution is electrospun to produce nanocomposite fibre. The spinneret containing the composite solution was placed 24.7 cm away from the aluminium collector, tilted at an angle of 30 °, and the solution flow rate kept at 1 mL/min. Groundnut Shell particle (GSP) weight fraction used was varied from 3 - 8 wt. %. Particle reinforced nanofibres were formed on the collector from the composite solution at 26 kV. These nanofibres were subjected to tensile test and the result indicates that at 6 wt. % untreated GSP reinforced fibre possessed the best tensile stiffness of 24.62 MPa. This corresponds to 2.201 % increase in Modulus of Elasticity over the unreinforced PLA (1.07 MPa). The 7 wt. % treated GSP fibre showed the least stiffness (0.33 MPa), which is 69 % reduction over that of unreinforced fibre. PLA fibre reinforced with 5 wt. % untreated GSP displayed best blend of properties over the unreinforced with increase of 286 % (4.43 x 10-4 HB), 1,502 % (1.07 MPa), 286 % (0.22 MPa), 6.8 % (0.05 J) and 1,081 % (~ 0.15 MPa) in hardness, stiffness, UTS, energy at break and stress at break respectively. However, ductility decreased by ~33.3 % when compared to the unreinforced (18.27). The 5 wt. % untreated GSP PLA reinforced fibre showed the highest UTS (0.855 MPa). The micrographs showed beads on reinforced fibres, while the virgin PLA showed no beads.

Avaliação das propriedades do concreto devido à incorporação de lodo de estação de tratamento de água

Abstract: O objetivo deste artigo foi avaliar as propriedades do concreto com adicao de diferentes teores de lodo de Estacao de Tratamento de Agua (ETA), de modo a diminuir este passivo ambiental gerado pelas empresas de saneamento. No presente estudo, foram confeccionados corpos de prova de concreto com teores de 5% e 10% de lodo de ETA em substituicao a areia. O lodo utilizado na fabricacao do concreto foi proveniente de uma ETA, responsavel pelo tratamento de agua de parte de Curitiba, na qual e utilizado sulfato de aluminio como coagulante. Primeiramente foi feita caracterizacao fisico-quimica do lodo coletado com determinacao de pH, temperatura, turbidez, DQO, ST, teor de umidade e massa especifica. Em seguida, foram moldados corpos de prova com dimensoes de (10x20) cm e com os respectivos teores de lodo a serem incorporados e avaliadas as propriedades no estado endurecido do concreto: resistencia a compressao, resistencia a tracao por compressao axial e absorcao de agua. Considerando os resultados obtidos, apenas as amostras com 5% de lodo de ETA apresentaram condicoes satisfatorias de resistencia a compressao axial quando comparadas ao concreto referencia, com 15,5 MPa aos 28 dias e perda de resistencia proxima a 11%. Portanto, o concreto confeccionado com substituicao de 5% de agregado miudo por lodo de ETA pode ser utilizado com finalidade nao estrutural, se consideradas apenas as propriedades mecânicas do material. Estudos como este sao fundamentais para criar solucoes para os residuos gerados nas Estacoes de Tratamento de Agua. Palavras-chave: Residuos Solidos. Construcao Civil. Reaproveitamento. Resistencia. Absorcao.

Effect of Rockwool and Steel fiber on the Friction Performance of Brake Lining Materials

Abstract: Wear resistance and Frictional stability are key performance requirements for brake lining. Automotive brake linings are usually made of various ingredients such as binder, filler, friction modifiers and reinforcement. Rockwool is a mineral fiber and steel fiber is a metallic fiber. In this work reinforcement fibers used are both the mineral and metallic fibers with six different composition prepared and tested. The result shows that metallic fibers should be high compared to mineral fiber for best frictional performance and wear resistance. Friction-wear properties of the reinforced samples were investigated on the cast iron disc as a counterpart using a pin on disc wear tester. The investigation confirmed that the sample with increase in steel fiber (4%, 8% and 12%) improves the wear resistance. On the other hand specimen with high content of Rockwool fiber forms an improper ratio among the other ingredients. The SEM images of the sample indicated that an increase in steel fiber higher than 12% content resulted in adhesive wear.Analysis of the experimental result shows that the sample with 12% steel fiber and 8% Rockwool fiber exhibited the optimum friction-wear behavior. Finally the effect of environment on the composites was investigated in water, salt water and oil.

Effective low-energy mixing procedure to develop high-fluidity cementitious pastes

Abstract: Preparing a high fluidity paste is a major step in ultra-high performance concrete (UHPC) development with respect to its self-compacting ability as well as its ultra-high strength. In this regard, some experiments have been carried out in order to study various superplasticizer (SP) addition methods and times. Among these procedures, stepwise and delayed methods seem to be more efficient compared to direct addition of SP with or immediately after water addition. However, few studies regarding water addition time and method have been conducted since now. In this research work, the effects of water and SP addition methods on the fluidity of paste were investigated. The results demonstrated that stepwise and delayed water beside delayed SP addition remarkably reduce the flow time. This maximum fluidity was achieved after totally 15 minutes of mixing including 3 minutes after 70% of water addition to powder, as first-part water, 6 minutes after SP addition and finally an extra 6 minutes after second-part water which is 30% of the total water. Based on this procedure, the opportunity for developing self-compacting and durable UHPC could be accessible. Furthermore, using higher content of aggregates and supplementary cementitious materials would be possible due to higher fluidity of the paste which finally results in an eco-efficient UHPC.

Efeito dos agentes de compatibilização SBS e SEBS-MA no desempenho de misturas de poliestireno/resíduo de borracha de SBR

Abstract: O reaproveitamento de residuos de borracha e de extrema importância atualmente, tanto para minimizar os efeitos nocivos no meio ambiente, quanto para reduzir o custo no desenvolvimento de novos materiais. Considerando que a maioria dos trabalhos relatados na literatura se refere ao reaproveitamento dos residuos de pneus, o presente trabalho tem como objetivo avaliar a influencia dos compatibilizantes SBS e SEBS-MA no desempenho da mistura de PS/residuo de borracha da industria de calcado (SBR), utilizando 5% em peso destes compatibilizantes. As misturas inicialmente foram preparadas em uma extrusora de rosca dupla corrotacional e, posteriormente, os grânulos extrudados moldados por injecao. Estas foram analisadas por ensaios de impacto, flexao, temperatura de deflexao termica (HDT), termogravimetria (TG) e microscopia eletronica de varredura (MEV). Os resultados evidenciaram que a utilizacao de qualquer um dos compatibilizantes na mistura PS/SBR aumentou expressivamente a resistencia ao impacto, enquanto que as propriedades de flexao e HDT foram inferiores em relacao a matriz polimerica. Em geral, ficou comprovado que o SBS e mais eficaz no processo de compatibilizacao do sistema PS/SBR, aumentando em 320% a resistencia ao impacto em relacao ao PS, bem como tendo uma perda de apenas 10,9% da HDT. Os resultados de termogravimetria ilustraram que a mistura PS/residuo apresentou uma maior estabilidade termica, em relacao ao PS puro, para temperatura superior a 376oC. As morfologias apresentadas pelas misturas ternaria e binaria foram bastante diferentes e tipicas de misturas imisciveis. Estes resultados mostram uma boa perspectiva de uso destes rejeitos industriais (SBR), uma vez que se pode valorizar um material que seria descartado. Alem disso, tem a possibilidade de desenvolver um novo material com boas propriedades, bem como minimizar o efeito negativo desses rejeitos nos ecossistemas.

Effect of wood particle treatment on the properties of gypsum plaster pastes and composites

Abstract: In this work the performance of gypsum plaster and wood particle in pastes and composites was investigated. Wood particles of fineness 0.42 mm and 1.20 mm were employed. Natural wood particles and the treated ones in cold or hot water (80 °C) were performed. The effects of the extractives solutions from the treatments applied to the wood particles on wood-gypsum compatibility were studied. For pastes and composites, water-to-gypsum ratio was 0.65. Wood particles-to-gypsum plaster ratios were 5%, 10% and 15%, in mass. Kinetics of temperature, mechanical performance and dynamic elasticity modulus by ultrasound measurements were applied to evaluate the gypsum plaster pastes and its composites behaviors. Results show that the extractive solutions changed the time of gypsum plaster hydration, being more sensitive to hot water treatment. The composites compressive strength increase with the wood particles pretreatment. The best result was to room temperature treatment. The same performance was found to the modulus of elasticity. Treatments have improved significantly the flexural strength. The best wood particle content was 10%. These results show the possibility of using this wood waste with an easy and simple treatment to make eco-efficient building materials. Keywords: Gypsum plaster, wood particle, composite, ultrasound, kinetics of temperature.

Effect of different carboxylic acids as solvent on chitosan fibers production by wet spinning

Abstract: Over the past decades, chitosan has been extensively investigated and used as a biomaterial due to a set of properties, such as biocompatibility, biodegradability and bioactivity. In the present work to produce the chitosan fibers was used the wet spinning technique and Two parameters, solvent and polymers concentration, were chosen as variables. For polymer concentration two concentrations were applied: 2%, 2.5%; and for solvents, three different acids were used: acetic, malic and lactic. Characterizations were carried out, using FTIR, Swelling Degree measurements, SEM and mechanical tests in terms of Traction. From the dimensional analysis of the fiber, different diameters where detected possibly due to steric effects cause by the presence of the acid. Other properties were also affected, revealing that as denser fibers are tend they have higher mechanical properties, and lesser tendency to swell. The fibers showed good potential for application as sutures.

Síntese, caracterização e performance catalítica de nanoferritas mistas submetidas a reação de transesterificação e esterificação via rota metílica e etílica para biodiesel

Abstract: As nanoferritas mistas de Ni 0,5 Zn 0,5 Fe 2 O 4 e Ni 0,2 Cu 0,3 Zn 0,5 Fe 2 O 4 foram sintetizadas por reacao de combustao usando ureia como combustivel e um reator conico como fonte de aquecimento para producao em bateladas de 10 g, e entao, testadas como nanocatalisadores heterogeneos nas reacoes de transesterificacao e esterificacao metilica e etilica do oleo de soja para producao de biodiesel. Durante as sinteses foram registrados o tempo e a temperatura das reacoes, bem como observadas a liberacao de gases e a cor das chamas emitidas. As amostras foram caracterizadas por DRX, EDX, FTIR, MEV/EDS, BET e cromatografia gasosa. Os testes reacionais foram executados para 10 g do oleo em duracao de 1 h, razao molar 1:12 oleo:alcool, 2 % (m/m) de catalisador e conduzidas a 180 oC. Os difratogramas de DRX e os espectros de FTIR revelaram presenca da fase espinelio inverso tipo B(AB) 2 O 4 . A morfologia apresentou a formacao de aglomerados de aspecto fragil e elevada area de superficie. As analises cromatograficas produziram excelentes resultados nas reacoes de esterificacao para ambas amostras nas condicoes testadas, com destaque especial para Ni 0,5 Zn 0,5 Fe 2 O 4 , cujas conversoes foram de 91,4 % em esteres metilicos e de 77,8 % em esteres etilicos, enquanto que a amostra Ni 0,2 Cu 0,3 Zn 0,5 Fe 2 O 4 apresentou conversoes de 75,1 e 65,1 %, respectivamente. As conversoes na transesterificacao metilica e etilica foram de 14 e 2 % para Ni 0,5 Zn 0,5 Fe 2 O 4 e de 11 e 3 % para Ni 0,2 Cu 0,3 Zn 0,5 Fe 2 O 4 . Palavras-Chave: Ferritas mistas, reacao de combustao, nanocatalisadores, transesterificacao, esterificacao, biodiesel.

Structural and morphological analysis of zinc incorporated non-stoichiometric hydroxyapatite nano powders

Abstract: In this study, Zn incorporated non-stoichiometric hydroxyapatite (nHAp) was synthesized via precipitation method and effect of the incorporation of Zn (fraction: 2, 4, 6 and 8 mol-%) on the microstructure of nHAp was studied by XRD, FTIR analysis and SEM-EDS techniques. The formation of nHAp was confirmed by XRD and FTIR those showed that no secondary phase was formed through the Zn incorporation. The SEM studies also revealed that particles were formed in nano-metric size (30-60 nm). It was found that crystallite and particle size of Zn incorporated nHAp gradually decreased up to 6 mol-%, and started to increase while the Zn fraction reached up to the 8 mol-% and hence the morphology of the aggregated products was also changed. It can be concluded that the incorporation of Zn cations cause to form nHAp phase. Furthermore, the nHAp microstructure has deviated from stoichiometric condition by incorporation of more Zn cations.

Carbon steel corrosion induced by sulphate-reducing bacteria in artificial seawater: electrochemical and morphological characterizations

Abstract: In this work, the corrosion behavior of carbon steel AISI 1020 was evaluated in artificial seawater in the presence of mixed sulfate-reducing bacteria (SRB) culture isolated from the rust of a pipeline. The corrosion evaluation was performed by electrochemical techniques (open circuit potential (E ocp ), polarization curves and electrochemical impedance spectroscopy (EIS)), while the formation of a biofilm and corrosion products were observed by scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). The presence of SRB in the medium shifted the open circuit potential to more positive values and increased the corrosion rate of the steel. Electrochemical and morphological techniques confirmed the presence of a biofilm on the steel surface. EDS spectra data showed the presence of sulfur in the corrosion products. After removing the biofilm, localized corrosion was observed on the surface, confirming that localized corrosion had occurred. The biogenic sulfide may lead to the formation of galvanic cells and contributes to cathodic depolarization. Keywords : sulphate-reducing bacteria, biofilm formation; carbon steel, electrochemical impedance spectroscopy, morphological characterization.

Pd-Impregnated activated carbon and treatment acid to remove sulfur and nitrogen from diesel

Abstract: Removal of sulfur and nitrogen compounds from national commercial diesel through adsorption onto activated carbon was studied. Brazilian commercial activated carbon samples (AC) were modified by acid oxidation and, alternatively, were impregnated with palladium chloride. Modified carbon samples showed a significant increase in the quantity of acid sites, particularly those AC submitted to impregnation with palladium. Adsorption capacity of the carbon samples increased proportionally to the increase in the acid groups. Adsorption efficiency of the activated carbon impregnated with palladium chloride was over 85% for nitrogen compounds and over 60% for sulfur compounds. The treatment studied was found to be an efficient option for the removal of sulfur and nitrogen compounds present in commercial diesel, and thus it could be an alternative pretreatment in the conventional hydrotreatment process.

Desenvolvimento e avaliação de uma fonte DC de alta tensão para utilização em sistema de deposição de filmes finos por pulverização catódica

Abstract: O trabalho em questao esta relacionado ao projeto e construcao de uma fonte de alta tensao em corrente continua utilizando materiais e dispositivos adquiridos no comercio local visando sua aplicacao no processo de pulverizacao catodica. Essa tecnica permite a deposicao de filmes finos de metais, oxidos e nitretos sobre substratos solidos. Como teste de funcionamento e aplicacao da fonte DC, com a mesma instalada em canhao de pulverizacao em alto vacuo, filmes finos de diferentes espessuras de cobre, aco inoxidavel 304 e tungstenio foram depositados e estudados. Analise de espessura, morfologia, e resistencia eletrica e resistividade foram conduzidas. Filmes com resistividade eletrica dependente das espessuras foram obtidos. A fonte DC se mostrou confiavel em operacao e permite a deposicao de uma infinidade de materiais nas mais diferentes espessuras sobre varios tipos de substratos.

Cold metal transfer welding of AA1050 aluminum thin sheets

Abstract: This study was aimed to investigate the welding parameters on mechanical behavior of 2 mm thick AA1050 sheet materials joined by cold metal transfer (CMT) method Macro structural examination showed that decreasing heat input decreased the pore size in the weld metal Tensile test was applied and failure occurred in heat affected zone of aluminum sheet metal Maximum tensile strength was found in the sample with minimum heat input Heat affected zone was observed explicitly in the sample produced with the maximum heat input Decreasing joint gap affected the bending strength positively Bending strength was found superior with maximum bonding line length

Polystyrene cellulose fiber composites: effect of the processing conditions on mechanical and dynamic mechanical properties

Abstract: The usage of natural fibers on the composites development has grown rapidly in the recent years due to the fibers plentiful availability, renewable source, low density and biodegradability. However, there are some drawbacks, for instance, the fiber dispersion on a polyolefin matrix. In this work, the influence of processing speed on the mechanical and dynamic mechanical properties of polystyrene (PS) filled with cellulose fiber composites was investigated. The composites were processed on a twin-screw co-rotating extruder, using screw speeds of 200 rpm, 400 rpm and 600 rpm. The dynamic mechanical properties and the mechanical properties were investigated as a function of fiber content. The composites processed on a screw speed of 400 rpm had presented an increase on flexural and impact strength, compared to the composites processed at 200 rpm. The flexural and storage modulus had increased when increasing the fiber content, as well as increasing the processing speed. The greater fiber dispersion obtained at a screw speed of 400 rpm hinders the agglomeration arrangement and distributes the fibers more equally on the matrix. The increase on processing speed probably generates a fiber size reduction, increasing the fiber superficial area and generating a greater contact with the matrix as well. Therefore, the efforts transference of matrix to fibers is improved, originating an increase on the evaluated properties.

Asphalt binders modified with Moringa Oleifera Lam oil

Abstract: The concern with sustainable development has driven efforts to the study of green technologies to minimize the environmental impacts without compromising pavement quality. In this scenery, the paving industry has started to research and apply warm asphalt mixtures, which are produced in lower temperatures than conventional mixtures and reduce the expenses in fuels. The warm mixtures can result from the addition of an oil, usually organic, to the conventional binder, decreasing the binder's viscosity. Moringa oleifera Lam Seeds possess an oil content varying between 38 and 40% and have antioxidant and lubricant properties. This study aimed to evaluate the changes in properties related to consistency and the effective variation of mixing and compaction temperatures due to asphalt modification with the oil of Moringa oleifera Lam as green additive. The Moringa oleifera Lam oil was extracted by pressing of seeds. Then, 6 mixtures were made using 50/70 PAC and Moringa Oleifera Lam oil in different proportions (0.5%, 1%, 1.5%, 2%, 2.5% and 3%), as well as a reference sample (pure PAC). The binders were analysed using Brookfield Viscosity, Penetration, Softening Point and Rolling Thin Film Oven (RTFOT) Tests. The results showed that the addition of Moringa oleifera Lam oil must be made for contents in the range of 0.5% to 1%, once that to these contents there is a significant reduction in machining and compaction temperatures (≈ 5 °C) without compromising the asphalt binder performance.

Resíduo de cerâmica vermelha e fíler calcário em compósito de cimento Portland: efeito no ataque por sulfatos e na reação álcali-sílica

Abstract: The red-clay waste (RCW) derives from blocks and bricks in their production process and also in the construction industry, when these materials are used in vertical walls. When originated in the production process, the RCW presents a lower degree of impurities, while when originated from construction sites, it contains a greater degree of impurities due to being stored with other residues before its disposal. According to the Brazilian Environmental Council (CONAMA) in its Resolution 307, RCW requires a proper disposal to avoid environmental impacts. The reactive capability of RCW and lime qualifies it to be used as a mineral admixture in Portland cement composition thus avoiding its disposal in landfills for construction waste. The viability of RCW incorporation in Portland cement requires analyses, such as studies of its compressive strength, and moreover of its performance when the hydrated paste is under physical and chemical deleterious interactions. This paper aims to evaluate the influence of milled RCW in Portland cement's composition, emphasizing two properties related to concrete's durability: its resistance to alkali-silica reaction (ASR) and its resistance to sodium sulfate attack. Therefore, CP V - ARI cement mortars (to be used as reference) and compositions of 10% replacement in cement mass by limestone filler or RCW, in three different fineness, were evaluated for ASR, according to NBR 15.577-5/2008, and for their expansion due to the sodium sulfate attack, according to NBR 13.583/2014. Although, the exposure time was extended aiming a more careful assessment of their degradation. Results showed that RCW increased the expansion caused by ASR, and, in most cases, also increased the expansion due to sodium sulfate attack. On the other hand, a higher comminution of RCW tends to improve the performance of the cementitious matrix when submitted to deleterious action, that is, a greater fineness of RCW has a positive impact on the material behavior under degradation. The limestone filler did not influence the result of expansion by ASR, but caused a reduction of the expansion induced by sodium sulfate attack. The analysis of the extended exposure time (66 days for ASR tests and 210 days for sulfate attack tests) showed that RCW milled for 1.5 hours might potentially be used as a mineral admixture in the binder material's composition, tending to show a similar performance to Portland cement matrix under sodium sulfate attack. Regarding the RAS, and increase in the comminution of RCW milled for 1.5 hours is required to make its particle size distribution similar to the cement's, which tends to enhance the mitigation capacity of this mineral admixture

Caracterização de compósitos obtidos a partir de polímero biodegradável e casca de arroz utilizando duas técnicas de processamento

Abstract: A adicao de fibras naturais a uma matriz de polimero biodegradavel tem sido uma alternativa para obter compositos com melhores propriedades termicas e mecânicas. Tendo em vista que as propriedades dos compositos possam ser influenciadas pelas condicoes de processamento, tipo e concentracao da fase dispersa, este trabalho teve como objetivo obter compositos a partir de uma blenda comercial constituida de Poli (butileno adipato co-tereftalato) - PBAT/ Amido (EB), de carater biodegradavel, e casca de arroz (CA). Inicialmente foram preparados compositos com PBAT/Amido contendo 10,20 e 30% de (CA) utilizando extrusora de dupla rosca e misturador interno. Posteriormente, foram determinadas propriedades mecânicas e termicas dos sistemas obtidos. Os resultados das propriedades mecânicas mostraram que o modulo elastico dos compositos foi afetado pelo tipo de processamento empregado, os compositos obtidos em extrusora apresentam maior modulo que os compositos obtidos no misturador: 92% maior em compositos com 10% de carga, e 38% maior em compositos com 30% de carga. A resistencia ao impacto diminuiu significativamente e a resistencia a tracao aumentou moderadamente com o teor de casca de arroz, independente do tipo de processamento utilizado. A resistencia ao impacto de compositos com 30% de carga e aproximadamente 33% da resistencia ao impacto da blenda pura. Ja na resistencia a tracao, observou-se um aumento de 25% nos compositos com 30% de carga. Analises de MEV indicam que as particulas de carga foram adequadamente molhadas pela matriz e que a adesao carga/matriz e boa. A avaliacao dos resultados obtidos com as analises de DSC indicou que a adicao de CA nos compositos extrusados altera a temperatura de cristalizacao, variando de 75oC da amostra pura, para 101oC para as amostras com casca de arroz, resultado atribuivel ao efeito nucleante causado pela maior dispersao da carga neste tipo de processamento.

Avaliação das propriedades físicas e mecânicas de blocos de solo-cimento formulados com coprodutos siderúrgicos

Abstract: Este trabalho tem por objetivo caracterizar o desempenho de resistencia mecânica e absorcao de agua de blocos solo-cimento para alvenaria, apos 28 dias de cura, com a incorporacao limite dos seguintes coprodutos siderurgicos em substituicao parcial ao solo: adicoes de ate 20 % em massa do po de balao coletado em alto-forno, ate 10 % de poeiras de despoeiramento de aciaria eletrica, e ate 20 % de escoria granulada de forno eletrico a arco. As formulacoes propostas incluem adicoes simultâneas de pos obtidos do descarte da producao de blocos solo-cimento, onde a substituicao parcial ao solo foi de ate 20 % em massa. Os resultados obtidos sugerem a potencialidade de uso dos residuos siderurgicos em blocos intertravados de solo-cimento para alvenaria sustentavel, como alternativa de aplicacao para esses residuos. Verificou-se a possibilidade de bons resultados confrontando os valores exigidos por norma (absorcao de agua 2,0 MPa) com destaque quando se utilizou 20% po de balao juntamente com 10% de reuso do bloco solo-cimento; 10% de escoria de aciaria ou 20% de escoria de aciaria juntamente com 10% de reuso do bloco solo-cimento; e 2,5% de po de despoeiramento juntamente com 20% de reuso do bloco solo-cimento.

Propriedades geotécnicas de um solo expansivo tratado com cal

Abstract: Argilas expansivas sao consideradas como depositos problematicos para obras de infraestrutura porque podem causar danos socioeconomicos e ambientais, uma vez que sao susceptiveis a mudanca de volume devido a variacao sazonal da umidade e temperatura. A estabilizacao da argila expansiva e de interesse para qualquer edificacao. As tecnicas de estabilizacao podem ser mecânicas ou quimicas. A cal e um agente estabilizante. Ensaios de laboratorio foram realizados com o objetivo de analisar o efeito da interacao da cal com um solo expansivo de Ipojuca/PE, quando e adicionado cal nas proporcoes de 1% a 11% em peso seco. Foram investigadas as caracteristicas fisicas, quimicas, mineralogicas, a expansao livre e a tensao de expansao do solo natural e na mistura solo-cal. Os resultados indicam que o solo tem alta expansividade, podendo causar danos as edificacoes levando a demolicao, principalmente as de pequeno porte. A adicao de cal ao solo causou uma agregacao ou floculacao das particulas originais e a reducao no indice de plasticidade. O percentual de 11% de cal hidratada reduziu a expansao livre e tensao de expansao a valores nulos. Isto e atribuido a capacidade de cimentacao do solo tratado com a cal que reduz a tendencia de absorcao de agua das argilas saturadas com calcio.

Produção, caracterização e avaliação da capacidade adsortiva de carvões ativado em forma de briquete

Abstract: Carvoes ativados em forma de briquetes foram preparados a partir do residuo da madeira de candeia, gerado no processo de extracao do oleo α-bisabolol. O material foi briquetado, carbonizado e ativado com CO2,variando-se a temperatura (700-900°C) e o tempo de ativacao (1-3 horas). Para a caracterizacao dos carvoes ativados foram realizadas analise elementar (CHN-O), analise dos grupos funcionais (titulacao de Boehm), bur-off, area superficial BET estimada, indice de iodo, calculo de area superficial com azul de metileno SAM, testes de adsorcao com azul de metileno e fenol e indice de resistencia mecânica. Os resultados mostraram que, com o aumento da temperatura e do tempo de ativacao, ocorre aumento da area superficial, do volume de poros, da basicidade do carvao e da capacidade de adsorcao de azul de metileno e de fenol.

Painéis sanduíches de poliéster reforçado com fibras de rami para aplicação na Construção Civil

Abstract: In this work, composites of polyester resin reinforced with ramie fiber bidirectional woven cloth in different content by volume have been produced and characterized. These composites were tested experimentally and numerically as faces of sandwiches panels with cores of sponge gourd impregnated with polyester resin and expanded polystyrene-EPS. Mechanical characterization of these materials was conducted in the laboratory from tensile and bending tests, and numerical simulation using Finite Element Method (FEM). The composite was analyzed by Scanning Electron Microscopy (SEM). The mechanical properties obtained for the composites and cores showed viable making sandwich panels for application in construction. The composites with 50% volume fibers presented the best mechanical properties and have been used as faces in prototypes of the panels. The cores in study showed good results, with emphasis on the sponge gourd impregnated with polyester resin, which showed the highest stiffness and making options with larger and thinner panels. The present study showed the potential of natural fibers for use as reinforcing of polymeric composites and sandwich panels cores and so a new alternative use of these fibers for applications in the construction.

Durabilidade de argamassas com adição de metacaulim para reforço de alvenaria

Abstract: Esta pesquisa tem como objetivo apresentar a contribuicao da pozolana na durabilidade de argamassas armadas com adicao de metacaulim utilizadas para reforco de alvenaria resistente. Sabe-se que, a partir da decada de 1960, cerca de 6.000 edificios foram erguidos com alvenaria de vedacao tendo funcao estrutural na Regiao Metropolitana do Recife. Essas edificacoes populares sao conhecidas como “predio caixao” por ter formato de caixa devido ao posicionamento dos apartamentos nos quatro pavimentos, bem como mostram elevados indices de patologias e ate acidentes com vitimas fatais. Em que pese o colapso das alvenarias de embasamento ser a causa principal, as alvenarias de elevacao da superestrutura nao apresentam fundamentacao acerca da estabilidade, particularmente pelos blocos serem de vedacao, o que conduz a insuficiencia de suporte das cargas atuantes e ruptura brusca. Entao, buscou-se estabelecer criterios para reforco com argamassa armada dentro da matriz que atendesse tres condicoes imprescindiveis: (i) capacidade de suporte; (ii) ductilidade e (iii) durabilidade. Neste trabalho, sao apresentadas conclusoes sobre durabilidade, onde o arranjo experimental englobou a especificacao de dois tracos [(1:1:6:1,5 e 1:0,5:4,5:1,5) -- cimento, cal, areia e relacao agua/cimento], com dois teores de adicao (8% e 15%), sendo duas formas de adicao (por substituicao de parte de cimento e por adicao pura). Foram realizados ensaios de resistencia a compressao, modulo de elasticidade, velocidade de propagacao da onda ultrassonica, absorcao de agua por imersao e metodos acelerados de envelhecimento para avaliacao de desempenho frente a carbonatacao e cloretos, em corpos de prova de argamassas. Os resultados indicam que o metacaulim pode mitigar substancialmente a acao de agentes deleterios, especialmente nas amostras com adicao pura de 15% e traco forte (1:0,5,4,5,1,5). Palavras-chave: Alvenaria Resistente; Argamassa armada; Metacaulim .

Influence of basal plane domains in the tribological behavior of graphites

Abstract: Many dynamic engineering systems have interferences and interactions that causes wear under friction effect. Carbonaceous materials, such as polycrystalline graphites, are of great interest in engineering systems due to their inherent lubricant properties and their versatility as a material for applications in the areas of mechanics, transportation, energy systems and sensitive technologies. In this work the tribological behavior of three identical pairs, pin-on-disc, of commercial polycrystalline graphites were evaluated, in a controlled environment at 20 °C and 50 % RH. Results of tribological behavior were correlated considering the prevalence of basal plane, identified by polarized light optical microscopy, as a function of the tribological behavior, measured by tests with pin on disc tribometer. The results showed that the coefficient of friction behavior is directly related to the basal plane mosaic domain and the extension of the damage generated on this plane due to the contact between the tribological pair. The materials studied presented an increase in the friction coefficient values, 0,10; 0;13 and 0,23 with increasing area of the basal plane mosaic domain, respectively 55; 64 and 81% respectively.