Materia-rio De Janeiro最新文献

{"title":"Tribological Properties of Fly Ash Blended Polymer Composites","authors":"I. Gunes, T. Uygunoğlu, A. Çelik","doi":"10.1590/S1517-707620210001.1229","DOIUrl":"https://doi.org/10.1590/S1517-707620210001.1229","url":null,"abstract":"In this study, it was studied that the abrasion resistance and characteristics of polymer composites with fly ash (FA). The epoxy based polymer composites are produced with resin and FA as mineral additive. Mixtures of different ratio by replacing the FA were added to the resin from 0 to 30% by weight. Polymeric samples were cured in air conditioning and they were taken from the molds after 24 hours. Polymeric samples gain ultimate strength after 7 days. Therefore, abrasion tests were performed on 7 aged specimens. Abrasion characteristics of polymer composites were defined by pin-on-disc test for 500 m under a dry friction condition and room temperature. Three types of loading conditions were carried out as 5, 10, 15 and 30 N. The hardness and wear resistance values increased with the increase in the content of fly ash. Showing the relationship between wear rate and hardness, an equation with parameters dependent on load was provided. There was an increase in the friction coefficient with an increase in the surface roughness values. In addition, dynamic friction was as a function of the wear rate. The wear surfaces of the polymer composites were analyzed using scanning electron microscopy. It was observed that the wear rate of the polymer composites and pure epoxy samples ranged from 17.82 to 172.96 mm3/Nm. Keywords: Fly ash; polymer composite; characterization; wear; friction.","PeriodicalId":18260,"journal":{"name":"Materia-rio De Janeiro","volume":null,"pages":null},"PeriodicalIF":0.4,"publicationDate":"2021-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90827740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of magnetic stirring, grain modification and refinement on the solidification structure of an A356 aluminum alloy","authors":"Ó. Bustos, R. Allende, R. Leiva, C. Sánchez","doi":"10.1590/S1517-707620210001.1227","DOIUrl":"https://doi.org/10.1590/S1517-707620210001.1227","url":null,"abstract":"The effect of the application of forced convection during the continuous solidification of Al-Si alloys has been presented in this work. The investigation has been made on the hypothesis that as an alloy solidifies under the action of a rotating magnetic field, a nondendritic casting structure would be obtained. The Al-Si alloy has been studied in its three different states (original, modified, and modified with a grain refiner), using a magnetic stirring equipment with permanent magnets, a device that has allowed the study of the effect of the rotational speed (degree of stirring) on the micro- and macro- solidification structure, as well as on the material’s mechanical properties. With the purpose of validating the hypothesis, different analyses and tests have been carried out, such as thermal analysis of the solidification process, micro- and macrostructural analysis, and hardness measurements for the different process conditions studied. The results have shown that magnetic stirring affects the cooling curves, expanding the solidification range. A microstructural evolution of the alloys has also been observed, from a 100% dendritic structure to a mature rosette type structure, in addition to a notable decreasing of grain size, which results in the improvement of the material’s mechanical behavior. Keywords: Grain Refinement, forced convection, solidification, Al-Si.","PeriodicalId":18260,"journal":{"name":"Materia-rio De Janeiro","volume":null,"pages":null},"PeriodicalIF":0.4,"publicationDate":"2021-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81121345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A nanofibrous membrane fluorescent sensor for fluoride ions prepared by electrospinning and host-guest interaction","authors":"Huan Zhang, Chen Zhou, Jing Sun, Xiao Li, Juan Tang","doi":"10.1590/S1517-707620210002.1258","DOIUrl":"https://doi.org/10.1590/S1517-707620210002.1258","url":null,"abstract":"A novel inclusion complexes nanofibrous membrane fluorescent sensor was prepared for recognizing F- via electrospinning and host–guest interaction. The host α-cyclodextrin on the surface of the electrospun nanofiber membrane is assembled into the guest azobenzene molecule which modified with F- fluorescent probe，and the formation of the inclusion complex is fixed on the surface of the nanofibrous membrane without external force，to prepare a novel surface controllable composite nanofiber membrane for F- detection. The inclusion complexes nanofibrous membrane exhibited favourable sensitivity and selectivity for F-. The introduction of F- would result in notable fluorescent decreasing of the membrane, but the other most common anions would not disturb the detection of F-. Moreover, this nanofibrous membrane was not only a fluorescent sensor for detecting F-, but also a good adsorbent for F- in solution. Keywords: Host–guest interaction，Nanofibrous membrane，Fluorescent sensor，Fluoride ions， Adsorbent","PeriodicalId":18260,"journal":{"name":"Materia-rio De Janeiro","volume":null,"pages":null},"PeriodicalIF":0.4,"publicationDate":"2021-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86159563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A chemical patterning approach of dense and porous titanium surfaces by using a combination of concentrated acid and oxidant","authors":"A. Ribeiro, R. C. D. Silva, D. Way, Lais de Souza Alves, E. B. Silveira, F. Mendes, M. V. Oliveira","doi":"10.1590/S1517-707620210002.1284","DOIUrl":"https://doi.org/10.1590/S1517-707620210002.1284","url":null,"abstract":"Commercially dense pure titanium sheets and porous titanium samples processed by powder metallurgy were treated with a mixture consisting of equal volumes of H2SO4 and H2O2 for 2 or 4 hours. Characterization was performed by scanning electron microscopy, energy dispersive X-ray spectroscopy, confocal scanning optical microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The analyses showed that the chemical patterning approach using a combination of concentrated acid and oxidant was able to generate a nanotexture on dense and porous titanium surfaces. In addition, the treated samples presented an oxide layer consisting predominantly of titanium dioxide with negative charge conferred by the presence of hydroxyl groups, which is an important factor that favors apatite nucleation and protein adsorption. It was also observed that oxide formation was more effective on porous samples than on dense samples, which can be explained by the higher surface area intrinsic to porous media. Finally, the findings indicated that both treatment times promoted similar modifications in surface properties, such as nanotexture and chemical composition, suggesting that the time of 2 hours were enough to induce the surface alterations at the nanoscale. Keywords: titanium; surface modification; chemical oxidation, powder metallurgy.","PeriodicalId":18260,"journal":{"name":"Materia-rio De Janeiro","volume":null,"pages":null},"PeriodicalIF":0.4,"publicationDate":"2021-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75693838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Análise microestrutural de ligas semissólidas da série 7XXX submetidas a ensaios de compressão a quente entre placas paralelas","authors":"Luis Vanderlei Torres, E. Zoqui","doi":"10.1590/S1517-707620210001.1234","DOIUrl":"https://doi.org/10.1590/S1517-707620210001.1234","url":null,"abstract":"O presente trabalho visa a analise microestrutural de ligas de aluminio da serie 7XXX, a saber: AA7004 e AA7075, em vista de sua aplicacao nos processos de tixoconformacao. As ligas foram reaquecidas as temperaturas semissolidas, ou seja, as temperaturas correspondentes as fracoes solidas de 60% e 45% e mantidas nos tempos de tratamento termico de reaquecimento de 0, 30, 90 e 210 s e na sequencia submetidas a ensaios de compressao a quente entre placas paralelas. Como resultado, a condicao de 60% de fracao solida de ambas as ligas apresentaram diferencas significativas na aparencia das amostras tixoconformadas, com bordas mal preenchidas e quebradicas, quando comparadas com a condicao de 45% de fracao solida, isto devido as ligacoes existentes na microestrutura que possivelmente ainda estavam fortemente ligadas entre si, exigindo maior tensao para sua deformacao; a fracao solida de 45% adotada durante os ensaios foi satisfatoria, pois as bordas das amostras nao apresentaram trincas e/ou quebras intensas como tambem apresentou um bom acabamento superficial. Quanto ao seu comportamento microestrutural, as ligas semissolidas AA7004 e AA7075, apresentaram morfologia globular na regiao da borda das amostras com graos/globulos primarios bastante esferoidizados, devido aos fenomenos de ostwald ripening e coalescencia e na regiao central das amostras graos/globulos primarios totalmente deformados, com pouca presenca de liquido e grande presenca de fase solida, devido a deformacao imposta. Palavras-chave: Tixoconformacao, comportamento microestrutural, AA7004, AA7075.","PeriodicalId":18260,"journal":{"name":"Materia-rio De Janeiro","volume":null,"pages":null},"PeriodicalIF":0.4,"publicationDate":"2021-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84630728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Torcímetro digital para teste de torção em materiais e avaliação dos parâmetros elasto-plásticos de cisalhamento","authors":"Maurício Ireno Betemps, R. Barbieri, G. Verran","doi":"10.1590/S1517-707620210001.1216","DOIUrl":"https://doi.org/10.1590/S1517-707620210001.1216","url":null,"abstract":"Neste trabalho estao mostrados o projeto, os principais componentes e os resultados obtidos com o prototipo de um torcimetro digital que foi construido para medir a variacao do ângulo de torcao em ensaios mecânicos de materiais. Este dispositivo foi construido utilizando um encoder magnetico, modelo AS5048A, com 14 bits de resolucao e para o processamento dos dados foi utilizada uma placa microcontroladora Arduino Mega 2560. Alem do baixo custo dos componentes eletronicos e mecânicos, outra vantagem do sistema de medicao desenvolvido e a grande quantidade de aplicativos gratuitos disponiveis para o processamento e aquisicao dos dados com a placa microcontroladora utilizada. Foram realizados testes para verificar a exatidao nas leituras da variacao angular e ensaios de torcao com corpos de prova tubulares de aluminio (liga AA6351T6) para avaliar o desempenho do sistema de medicao em ensaios monotonicos. A relacao de Ramberg-Osgood foi utilizada para descrever o comportamento do material e as tensoes de cisalhamento foram avaliadas empregando relacoes nao lineares propostas por diferentes autores. Os dados obtidos indicam que o torcimetro digital apresentou resultados satisfatorios para a obtencao do ângulo de torcao e as principais vantagens deste dispositivo incluem a medicao do ângulo de torcao sem contato, linearidade, boa acuracia, faixa de medicao ilimitada, tamanho reduzido e baixo custo para confeccao.  Palavras-chave: torcimetro, ensaio de torcao, ângulo de torcao.","PeriodicalId":18260,"journal":{"name":"Materia-rio De Janeiro","volume":null,"pages":null},"PeriodicalIF":0.4,"publicationDate":"2021-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79647905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Aplicación de drenaje electroosmótico a pasivos ambientales mineros","authors":"J. Valenzuela, M. Cánovas, P. González, C. Cuevas","doi":"10.1590/S1517-707620210001.1242","DOIUrl":"https://doi.org/10.1590/S1517-707620210001.1242","url":null,"abstract":"Chile es el mayor exportador de cobre del mundo. Sin embargo, este liderazgo tiene importantes costos medioambientales como la generacion de enormes cantidades de residuos solidos procedentes del tratamiento de las menas de cobre. Con objeto de abordar esta problematica, se propone la aplicacion de la tecnica de drenaje electroosmotico a ripios y relaves. La parte experimental del trabajo consiste en un diseno experimental con matrices solidas sinteticas. El porcentaje de finos y la humedad inicial se definen como factores de tres niveles. El volumen de liquido drenado se define como la variable respuesta. Los resultados muestran que el drenaje electroosmotico es mas eficiente que el drenaje gravitacional cuando el contenido de humedad y el porcentaje de finos se encuentran en su nivel mas alto. Mediante un analisis de varianza del diseno experimental, se corrobora el efecto de los factores y su interaccion en la variable de respuesta. Finalmente, se genera una ecuacion que describe la relacion entre las variables de respuesta y los factores del modelo.   Palabras claves: pasivos medioambientales mineros, drenaje electroosmotico, ANOVA, porcentaje de finos y reduccion de humedad.","PeriodicalId":18260,"journal":{"name":"Materia-rio De Janeiro","volume":null,"pages":null},"PeriodicalIF":0.4,"publicationDate":"2021-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86063749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study of the interaction of the bioactive compound saponin from Glycyrrhiza glabra with a carbon nanotube matrix","authors":"C. Santos, Nélida Simona Marín Huachaca, A. D. S. Santos, Rodrigo Sá de Jesus, É. Almeida, L. C. Salay","doi":"10.1590/S1517-707620210001.1246","DOIUrl":"https://doi.org/10.1590/S1517-707620210001.1246","url":null,"abstract":"Saponins are bioactive compounds belonging to the secondary metabolism of plants widely used for their beneficial actions to human health. In this work the association of the saponin from Glycyrrhiza glabra with a matrix of multi-walled carbon nanotubes was promoted to obtain a composite material with improved functional characteristics. For this investigation, chemically modified electrodes (CME) based on carbon paste were developed. Firstly, a carbon paste electrode (CPE) modified with the addition of saponin (SAP) was developed. For the electrochemical optimization of this system, CPE/SAP, studies were carried out using cyclic voltammetry. The determination of parameters such as formal potential (Eo) and potential separation (ΔE) indicated that the saponin used as a carbon paste modifying agent generated a matrix that favors the transfer of electrons even at low applied potentials. The second step was performed by preparing the modified carbon paste electrode with the carbon nanotube matrix (CPE/CNT). This material, surprisingly, showed a redox pair probably due to the presence of iron atoms from the preparation method, something very beneficial for the purposes of this work. Next the saponin was associated to the carbon nanotube matrix in order to investigate the behavior of the hybrid material formed (CPE/SAP-CNT), which evidenced a significant improvement in the electron transfer process when the saponin interacts with the carbon nanotube matrix, increasing the anodic peak current by more than 3.6 times in relation to the CPE/SAP and 2.1 times when compared to the CPE/CNT. Another important issue concerns the stability of the systems, with the saponin associated with the carbon nanotube matrix presenting significantly improved stability, being able to be used for more than 8 hours or 200 voltammetric cycles with loss of signal of the order of only 2%, while the CPE/SAP showed a 60% loss of signal under the same conditions of use. Keywords: Saponin, muti-walled carbon nanotubes, modified electrodes, carbon paste.","PeriodicalId":18260,"journal":{"name":"Materia-rio De Janeiro","volume":null,"pages":null},"PeriodicalIF":0.4,"publicationDate":"2021-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83815314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Process of converting human hair into hollow carbon filament for electrochemical capacitor","authors":"Guilherme Charles Blanco, Manuella Gobbo de Castro Munhoz, A. Rodrigues, A. Cuña, Ana Claudia Pina, J. Marcuzzo, M. Baldan","doi":"10.1590/S1517-707620210002.1264","DOIUrl":"https://doi.org/10.1590/S1517-707620210002.1264","url":null,"abstract":"Carbon material is the largest material used as electrode on advanced energy storage devices. The modern lifestyle requires more energy, consequently, more smart energy use and efficient devices are needed. The constant evolution of materials technologies looking for green material and renewable raw material, that have minimal impact on the environment, is one of the most important subjects studied in recent years.  The scientific and industry community are paying more attention to new forms of carbon such as nanotubes, graphene, and activated carbon fiber. The purpose of this work is to convert human hair into a hollow carbon filament to be used as a supercapacitor electrode. The human hair needs 3 stages to be converted into carbon filament: textile manufacture, oxidation, and carbonization. The electrochemical behavior was analyzed in a threeelectrode electrochemical cell system with 2 M of H2SO4 electrolyte medium. The behavior of the electrode was characterized electrochemically by galvanostatic charge/discharge curves, cyclic voltammetry, and electrochemical impedance spectroscopy, showing 163 F g-1 of a maximum value of specific capacitance. Keywords: Residue. Human hair. Felt. Carbon filament. Supercapacitor.","PeriodicalId":18260,"journal":{"name":"Materia-rio De Janeiro","volume":null,"pages":null},"PeriodicalIF":0.4,"publicationDate":"2021-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78394254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Análise do conforto termo fisiológico e da resistência à tração em tecido tramado com algodão reciclado e filamentos obtidos da reciclagem de resíduos pós-consumo de garrafas pet","authors":"Juliana Lunkes Schmitt, L. Folle","doi":"10.1590/S1517-707620210001.1221","DOIUrl":"https://doi.org/10.1590/S1517-707620210001.1221","url":null,"abstract":"O Brasil e um importante produtor de texteis e confeccao. Possui o quarto maior parque fabril e e o quinto maior produtor de texteis do mundo. Em contrapartida, tambem e responsavel pela producao de toneladas de residuos solidos que, na sua maioria, e descartada em aterros sanitarios, aterros controlados e lixoes. Parte dos residuos texteis descartados e encaminhado para reciclagem, gerando diferentes tipos de produtos finais, inclusive novos tecidos. Os tecidos reciclados sao produzidos no Brasil ha mais de duas decadas, porem, somente nos ultimos anos que esta materia prima esta sendo empregada na producao de vestuario, calcados e acessorios. Este trabalho tem por objetivo analisar a estrutura de um tecido produzido a partir de fios obtidos da reciclagem de algodao e garrafas PET (polietileno tereftalato) e avaliar seu desempenho em relacao ao conforto termo fisiologico e a resistencia a tracao, quando comparado a um tecido produzido a partir de fibras virgens. A metodologia utilizada partiu da selecao de um tipo de tecido que apresentasse caracteristicas similares relacionadas a composicao, ligamento e a gramatura, sendo ele constituido de filamentos reciclados e 100% virgens. O tecido selecionado para a pesquisa foi do tipo sarja 3x1com composicao mista de algodao e poliester. Foram realizados ensaios de tracao, permeabilidade ao vapor de agua, condutividade termica, titulacao e micrografias. Os resultados obtidos indicam que o tecido reciclado utilizado nesta pesquisa e viavel para a producao de roupas para as estacoes outono/inverno, e para desenvolvimento de roupas cujas modelagens apresentem folga de vestibilidade. Palavras-chave: Tecidos reciclados. Algodao. PET. Resistencia a tracao. Conforto termo fisiologico.","PeriodicalId":18260,"journal":{"name":"Materia-rio De Janeiro","volume":null,"pages":null},"PeriodicalIF":0.4,"publicationDate":"2021-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75043410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}