Pub Date : 2021-06-04DOI: 10.1590/S1517-707620210002.1292
Bárbara Bulhões Cazula, R. Fonseca, F. B. Noronha, H. J. Alves
O hidrogenio e um produto de grande apelo industrial, ainda mais quando proveniente de uma cadeia renovavel de baixo impacto ambiental. Visando a reducao de custos relacionados ao preparo dos catalisadores utilizados para a obtencao de H2, o presente trabalho teve como objetivo avaliar a influencia de dois diferentes suportes de Si-MCM-41, sintetizados a partir de duas diferentes fontes de silica (uma comercial, ortossilicato de tetraetila – TEOS e outra residual, silica de cinzas de casca de arroz – CCA), no desempenho de catalisadores de niquel quando aplicados na reacao de reforma a seco do metano (RS). Os catalisadores foram sintetizados com 20% (m/m) de niquel por meio de impregnacao umida e foram caracterizados pelas tecnicas de MEV/EDS, fisissorcao de N2, DRX, FTIR, TPD–NH3 e TPR. Os ensaios reacionais foram conduzidos em reator de leito fixo, a 800 oC por 24 h. Os resultados de caracterizacao do material evidenciaram que a sintese catalisadores foi eficiente. Os catalisadores apresentaram significativas diferencas estruturais se tratando das diferentes fontes de silica utilizadas na sintese do suporte catalitico, diferencas essas que foram mais evidentes na area especifica e no diâmetro de poros dos materiais. Essa diferenca pode estar relacionada com a diferenca morfologica do suporte catalitico que influencia diretamente na maneira com a qual a fase ativa ficara disposta na superficie do catalisador. A avaliacao dos produtos gasosos, realizada por cromatografia gasosa, evidenciou resultados de conversao e seletividade muito semelhantes para os dois catalisadores, levando a conversoes de 45% de H2. A formacao de coque no catalisador no qual o suporte precursor foi sintetizado a partir de CCA foi significativamente menor. Nesse sentido, a CCA se destaca como um promissor substituinte para o TEOS na sintese de suportes cataliticos para catalisadores de niquel de alta performance quando aplicados na RS. Palavras-chave: Si-MCM-41, reforma a seco do metano, hidrogenio, silica de cinzas de casca de arroz.
氢是一种具有巨大工业吸引力的产品，特别是当它来自一个对环境影响小的可再生链时。旨在降低成本的催化剂用于申请H2的准备,这个任务的目的是评估影响的两种不同的媒体政策办公室-41,当两种不同来源的四乙基硅(一个商业tetraetila—有另一个残余石英稻壳灰—CCA)时对镍催化剂的性能,应用于甲烷干(RS)改革的反应。采用湿法浸渍法制备了20% (w / w)镍催化剂，并用sem /EDS、N2物理吸附、xrd、FTIR、TPD - NH3和TPR等技术对催化剂进行了表征。在800℃的固定床反应器中进行了24 h的反应试验，材料表征结果表明，催化剂的合成是有效的。在合成催化剂载体时，催化剂表现出显著的结构差异，这些差异在材料的比表面积和孔径上最为明显。这种差异可能与催化剂载体的形态差异有关，后者直接影响活性相在催化剂表面的排列方式。气相色谱法对产物进行了评价，结果表明两种催化剂的转化率和选择性非常相似，转化率为45%的H2。以CCA为基础合成前驱体载体的催化剂的焦炭生成量明显较低。关键词:Si-MCM-41、干重整甲烷、氢气、稻壳灰硅等，在合成高性能镍催化剂催化剂载体方面，CCA是TEOS的一个很有前景的取代基。
{"title":"Desempenho de catalisadores Ni/Si-MCM-41 na reforma a seco do metano para geração de H2: avaliação de TEOS e cinzas de casca de arroz como fontes de sílica no preparo do suporte catalítico","authors":"Bárbara Bulhões Cazula, R. Fonseca, F. B. Noronha, H. J. Alves","doi":"10.1590/S1517-707620210002.1292","DOIUrl":"https://doi.org/10.1590/S1517-707620210002.1292","url":null,"abstract":"O hidrogenio e um produto de grande apelo industrial, ainda mais quando proveniente de uma cadeia renovavel de baixo impacto ambiental. Visando a reducao de custos relacionados ao preparo dos catalisadores utilizados para a obtencao de H2, o presente trabalho teve como objetivo avaliar a influencia de dois diferentes suportes de Si-MCM-41, sintetizados a partir de duas diferentes fontes de silica (uma comercial, ortossilicato de tetraetila – TEOS e outra residual, silica de cinzas de casca de arroz – CCA), no desempenho de catalisadores de niquel quando aplicados na reacao de reforma a seco do metano (RS). Os catalisadores foram sintetizados com 20% (m/m) de niquel por meio de impregnacao umida e foram caracterizados pelas tecnicas de MEV/EDS, fisissorcao de N2, DRX, FTIR, TPD–NH3 e TPR. Os ensaios reacionais foram conduzidos em reator de leito fixo, a 800 oC por 24 h. Os resultados de caracterizacao do material evidenciaram que a sintese catalisadores foi eficiente. Os catalisadores apresentaram significativas diferencas estruturais se tratando das diferentes fontes de silica utilizadas na sintese do suporte catalitico, diferencas essas que foram mais evidentes na area especifica e no diâmetro de poros dos materiais. Essa diferenca pode estar relacionada com a diferenca morfologica do suporte catalitico que influencia diretamente na maneira com a qual a fase ativa ficara disposta na superficie do catalisador. A avaliacao dos produtos gasosos, realizada por cromatografia gasosa, evidenciou resultados de conversao e seletividade muito semelhantes para os dois catalisadores, levando a conversoes de 45% de H2. A formacao de coque no catalisador no qual o suporte precursor foi sintetizado a partir de CCA foi significativamente menor. Nesse sentido, a CCA se destaca como um promissor substituinte para o TEOS na sintese de suportes cataliticos para catalisadores de niquel de alta performance quando aplicados na RS. Palavras-chave: Si-MCM-41, reforma a seco do metano, hidrogenio, silica de cinzas de casca de arroz.","PeriodicalId":18260,"journal":{"name":"Materia-rio De Janeiro","volume":null,"pages":null},"PeriodicalIF":0.4,"publicationDate":"2021-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77270249","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}
Pub Date : 2021-06-04DOI: 10.1590/S1517-707620210002.1260
A. P. Melo, Anne Raquel Sotiles, E. A. V. Ferri, Mariana de Souza Sikora, Cristiane Regina Budziak Parabocz
No presente trabalho, utilizou-se a caulinita como material base para a obtencao de materiais nanocompositos. A caulinita foi utilizada na forma in natura, tratada termicamente a 700 oC e quimicamente com acidos fosforico e sulfurico na concentracao de 6 mol L-1. O objetivo dos tratamentos foi modificar e preparar a estrutura da caulinita para ser usada como um suporte para o TiO2. Por meio do metodo dos precursores polimericos foi sintetizado o TiO2 e nanocompositos a base de caulinita e TiO2. Os nanomateriais foram caracterizados por Difratometria de Raios X (DRX), UV-Vis, para determinar o Bandgap, Espectroscopia na Regiao do Infravermelho com Transformada de Fourier (FTIR), Microscopia Eletronica de Varredura (MEV) e Espectroscopia de Energia Dispersiva (EDS). Por meio dos espectros de FTIR foi possivel verificar as bandas caracteristicas da caulinita in natura e o aparecimento de vibracoes caracteristicas da metacaulinita. A analise de DRX revelou que foi possivel promover o aumento da cristalinidade das amostras de caulinita apos tratamento com o citrato de titânio, isto pode ser decorrente da adesao do oxido de titânio na superficie da caulinita. Pela analise de EDS foi possivel determinar a porcentagem de Ti (m/m) nas amostras sintetizadas, sendo que seu valor ficou entre 2,03 e 4,16 %. As analises por ICP-OES indicam que as amostras apresentam de 2,65 a 4,07% de Ti e os dados do Bandgap variam de 1,69 a 3,44 eV para as amostras com e sem Ti em sua composicao. Palavras-chave: Caulinita, metacaulinita, ativacao acida, Metodo dos Precursores Polimericos, Dioxido de Titânio.
{"title":"Síntese e caracterização de nanocompósitos de caulinita e TiO2 utilizando o método dos precursores poliméricos","authors":"A. P. Melo, Anne Raquel Sotiles, E. A. V. Ferri, Mariana de Souza Sikora, Cristiane Regina Budziak Parabocz","doi":"10.1590/S1517-707620210002.1260","DOIUrl":"https://doi.org/10.1590/S1517-707620210002.1260","url":null,"abstract":"No presente trabalho, utilizou-se a caulinita como material base para a obtencao de materiais nanocompositos. A caulinita foi utilizada na forma in natura, tratada termicamente a 700 oC e quimicamente com acidos fosforico e sulfurico na concentracao de 6 mol L-1. O objetivo dos tratamentos foi modificar e preparar a estrutura da caulinita para ser usada como um suporte para o TiO2. Por meio do metodo dos precursores polimericos foi sintetizado o TiO2 e nanocompositos a base de caulinita e TiO2. Os nanomateriais foram caracterizados por Difratometria de Raios X (DRX), UV-Vis, para determinar o Bandgap, Espectroscopia na Regiao do Infravermelho com Transformada de Fourier (FTIR), Microscopia Eletronica de Varredura (MEV) e Espectroscopia de Energia Dispersiva (EDS). Por meio dos espectros de FTIR foi possivel verificar as bandas caracteristicas da caulinita in natura e o aparecimento de vibracoes caracteristicas da metacaulinita. A analise de DRX revelou que foi possivel promover o aumento da cristalinidade das amostras de caulinita apos tratamento com o citrato de titânio, isto pode ser decorrente da adesao do oxido de titânio na superficie da caulinita. Pela analise de EDS foi possivel determinar a porcentagem de Ti (m/m) nas amostras sintetizadas, sendo que seu valor ficou entre 2,03 e 4,16 %. As analises por ICP-OES indicam que as amostras apresentam de 2,65 a 4,07% de Ti e os dados do Bandgap variam de 1,69 a 3,44 eV para as amostras com e sem Ti em sua composicao. Palavras-chave: Caulinita, metacaulinita, ativacao acida, Metodo dos Precursores Polimericos, Dioxido de Titânio.","PeriodicalId":18260,"journal":{"name":"Materia-rio De Janeiro","volume":null,"pages":null},"PeriodicalIF":0.4,"publicationDate":"2021-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78340346","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}
Pub Date : 2021-05-24DOI: 10.1590/S1517-707620210002.1297
Mariany Ludgero Maia Gomes, G. Amaral-Labat, A. Oliveira, M. Baldan, A. M. Silva
This contribution reports the use of an organic gel, xerogel, as catalyst support for Cu. The xerogel was synthesized from the system tannin-formaldehyde at pH 3, using F-127 Pluronic as surfactant. The surface area values were higher than 900 m2/g even after the Cu (10%, wt) impregnation. The morphological analysis by SEM-FEG revealed the presence of spheres arranged in a tridimensional structure. XRD diffractograms showed the presence of CuO and Cu2O crystalline phases combined with the amorphous structure of the porous carbon. From XRD analysis it is possible to infer the Cu species are heterogeneously dispersed on the support with the co-existence of small and larger clusters, which is in agreement with Raman spectroscopy. Raman study also indicated a highly defect/disorder structure of the xerogel derivatives, ensuing the short-range structural order of the carbonic structure and oxygen groups decorating the carbon surface. XPS results corroborate with XRD and Raman results, detecting the presence of CuO and Cu2O. In addition to the mentioned Cu species, XPS also detected Cu0 which may be originated from the chemical interaction between the electron oxygen groups with the Cu precursor. The high surface area and the thermal stability (~ 300 oC) of Cu/XCTF envisages its feasibly for relevant catalytic applications. Keywords: Carbon xerogels, tannin, renewable process, catalyst support.
{"title":"Study and characterization of carbon xerogels from tannin-formaldehyde system as catalyst support applications","authors":"Mariany Ludgero Maia Gomes, G. Amaral-Labat, A. Oliveira, M. Baldan, A. M. Silva","doi":"10.1590/S1517-707620210002.1297","DOIUrl":"https://doi.org/10.1590/S1517-707620210002.1297","url":null,"abstract":"This contribution reports the use of an organic gel, xerogel, as catalyst support for Cu. The xerogel was synthesized from the system tannin-formaldehyde at pH 3, using F-127 Pluronic as surfactant. The surface area values were higher than 900 m2/g even after the Cu (10%, wt) impregnation. The morphological analysis by SEM-FEG revealed the presence of spheres arranged in a tridimensional structure. XRD diffractograms showed the presence of CuO and Cu2O crystalline phases combined with the amorphous structure of the porous carbon. From XRD analysis it is possible to infer the Cu species are heterogeneously dispersed on the support with the co-existence of small and larger clusters, which is in agreement with Raman spectroscopy. Raman study also indicated a highly defect/disorder structure of the xerogel derivatives, ensuing the short-range structural order of the carbonic structure and oxygen groups decorating the carbon surface. XPS results corroborate with XRD and Raman results, detecting the presence of CuO and Cu2O. In addition to the mentioned Cu species, XPS also detected Cu0 which may be originated from the chemical interaction between the electron oxygen groups with the Cu precursor. The high surface area and the thermal stability (~ 300 oC) of Cu/XCTF envisages its feasibly for relevant catalytic applications. Keywords: Carbon xerogels, tannin, renewable process, catalyst support.","PeriodicalId":18260,"journal":{"name":"Materia-rio De Janeiro","volume":null,"pages":null},"PeriodicalIF":0.4,"publicationDate":"2021-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78257362","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}
Pub Date : 2021-05-24DOI: 10.1590/S1517-707620210002.1291
S. Amico, Honória de Fátima Gorgulho
{"title":"A Revista Matéria e o 8º Congresso Brasileiro de Carbono","authors":"S. Amico, Honória de Fátima Gorgulho","doi":"10.1590/S1517-707620210002.1291","DOIUrl":"https://doi.org/10.1590/S1517-707620210002.1291","url":null,"abstract":"","PeriodicalId":18260,"journal":{"name":"Materia-rio De Janeiro","volume":null,"pages":null},"PeriodicalIF":0.4,"publicationDate":"2021-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78177105","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}
Pub Date : 2021-03-25DOI: 10.1590/S1517-707620210002.1267
Matheus Carvalho Bispo, B. H. K. Lopes, B. C. S. Fonseca, R. C. Portes, J. Matsushima, Miriam K.H. Yassuda, G. Amaral-Labat, M. Baldan, Antonio C. C. Migliano
The electromagnetic properties of Carbon-Graphene Xerogel (CGX), Flaky graphite (GR) and Nickel-Zinc ferrite (FeNiZn) composites in polystyrene (PS) matrix were studied in the X-Band range (8.2 – 12.4 GHz). In this work the Expanded Polystyrene (EPS) waste material was processed into polystyrene through the recycling of EPS. The polystyrene obtained was utilized as dielectric matrix, mainly because PS is a wellknown organic polymer that presents low dielectric loss and light weight, which contribute to applications in composites for the aerospace field. In order to produce the final composite specimens, the CGX additive was previously synthesized through a sustainable method that employed the use of waste from the paper and pulp industry (black liquor). Afterwards, the morphological and structural analysis were made through Scanning Electron Microscope (SEM) and Raman Spectrometer, respectively. On the other hand, the magnetic ferrite material, FeNiZn, was obtained for the composite production through calcination, whereas the GR utilized was commercially obtained. It was observed that the increase of CGX and GR influenced on the increase of the Complex Permittivity, and that 10 wt% CGX + 50wt% FeNiZn composite sample demonstrated an absorption peak at 10.5 GHz. The results are relevant concerning the recycling of EPS waste through its use as dielectric matrix, thus developing greener and low-weight composite materials to be used in microwave applications. Keywords: Carbon-Graphene. Composite. Recycling. Polystyrene. Microwave.
{"title":"Electromagnetic properties of Carbon-Graphene Xerogel, Graphite and Ni-Zn Ferrite composites in polystyrene matrix in the X-Band (8.2 – 12.4 GHz)","authors":"Matheus Carvalho Bispo, B. H. K. Lopes, B. C. S. Fonseca, R. C. Portes, J. Matsushima, Miriam K.H. Yassuda, G. Amaral-Labat, M. Baldan, Antonio C. C. Migliano","doi":"10.1590/S1517-707620210002.1267","DOIUrl":"https://doi.org/10.1590/S1517-707620210002.1267","url":null,"abstract":"The electromagnetic properties of Carbon-Graphene Xerogel (CGX), Flaky graphite (GR) and Nickel-Zinc ferrite (FeNiZn) composites in polystyrene (PS) matrix were studied in the X-Band range (8.2 – 12.4 GHz). In this work the Expanded Polystyrene (EPS) waste material was processed into polystyrene through the recycling of EPS. The polystyrene obtained was utilized as dielectric matrix, mainly because PS is a wellknown organic polymer that presents low dielectric loss and light weight, which contribute to applications in composites for the aerospace field. In order to produce the final composite specimens, the CGX additive was previously synthesized through a sustainable method that employed the use of waste from the paper and pulp industry (black liquor). Afterwards, the morphological and structural analysis were made through Scanning Electron Microscope (SEM) and Raman Spectrometer, respectively. On the other hand, the magnetic ferrite material, FeNiZn, was obtained for the composite production through calcination, whereas the GR utilized was commercially obtained. It was observed that the increase of CGX and GR influenced on the increase of the Complex Permittivity, and that 10 wt% CGX + 50wt% FeNiZn composite sample demonstrated an absorption peak at 10.5 GHz. The results are relevant concerning the recycling of EPS waste through its use as dielectric matrix, thus developing greener and low-weight composite materials to be used in microwave applications. Keywords: Carbon-Graphene. Composite. Recycling. Polystyrene. Microwave.","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":"77749082","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}
Pub Date : 2021-03-25DOI: 10.1590/S1517-707620210002.1290
Xuewen Wang, Xin Zhang, Jiacheng Xie
The objective of this work is to test the strength reserve, the working stability, the vibration performance and the dynamic response under stochastic load on the optimized main body frame structure of a type of electrical dust precipitator. The test program is established which is a test process, as well as a feedback process. The strength prototype test is carried out to study the strength reserve of the structure. Based on the mechanical model, the modal analysis, the buckling analysis, and the seismic analysis is carried out using ANSYS to study the working stability and the vibration performance of the structure. The test results show that the strength reserve of the structure is sufficient, the main body structure will not be instability in working, the structure’s landscape orientation rigidity is feasible, the two-dimensional rigidity is even, and its torsional rigidity is better. The Maximum lateral displacement and stress meet the standard requirements. Obviously, the main body structure is optimized perfectly and the method is feasible that to do the performance tests after structure optimization design. Key words: Electrical dust precipitator, Steel braced frame structures, Strength, Stability, Seismic analysis
{"title":"Mechanical property test and analysis on the main body frame structure of electrical dust precipitator","authors":"Xuewen Wang, Xin Zhang, Jiacheng Xie","doi":"10.1590/S1517-707620210002.1290","DOIUrl":"https://doi.org/10.1590/S1517-707620210002.1290","url":null,"abstract":"The objective of this work is to test the strength reserve, the working stability, the vibration performance and the dynamic response under stochastic load on the optimized main body frame structure of a type of electrical dust precipitator. The test program is established which is a test process, as well as a feedback process. The strength prototype test is carried out to study the strength reserve of the structure. Based on the mechanical model, the modal analysis, the buckling analysis, and the seismic analysis is carried out using ANSYS to study the working stability and the vibration performance of the structure. The test results show that the strength reserve of the structure is sufficient, the main body structure will not be instability in working, the structure’s landscape orientation rigidity is feasible, the two-dimensional rigidity is even, and its torsional rigidity is better. The Maximum lateral displacement and stress meet the standard requirements. Obviously, the main body structure is optimized perfectly and the method is feasible that to do the performance tests after structure optimization design. Key words: Electrical dust precipitator, Steel braced frame structures, Strength, Stability, Seismic analysis","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":"80485929","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}
Pub Date : 2021-03-25DOI: 10.1590/S1517-707620210002.1254
G. Paganotto, G. Barros, V. G. Marques, A. Takimi
Centrifugal spinning is a new technique for producing of nano and microfibers that has a great differential: a higher production rate than those presented by traditional methods. Due to a great interest in using nano and microfibers in technological applications along with the environmental interest in polymer recycling, this research had the purpose of production fibers by centrifugal spinning from the expanded poly-styrene recycling and the evaluation of the influence of operational parameters such as the concentration of polymer solution and the speed of rotation in the average diameter and in the distribution of the diameters of fibers formed. The fibers obtained were characterized using the Scanning Electronic Microscopy (SEM) and they had their diameters measured using ImageJ software. The fibers obtained in this research were entangled, woven, fused, with a rough and porous surface, with bead formation and without directional ordering. The results obtained show that the polymer solution concentration was the most influential parameter in the fibers analyzed characteristics and, in general, its increase generates an increase in the average diameter. With the increase in rotation speed, there has been often a reduction in the presence of beads and microparticles due to the better stretching of the fibers. In less concentrated solutions, continuous fibers with more regular surfaces were obtained, however, promoting the higher production of beads. In the most concentrated solutions, we noticed the formation of porous fibers and very rough surfaces, as well as fused and woven fibers. Through the measurement of its diameters, it was possible to observe the obtaining of fibers with average diameters of 407,02 nm to 38113,20 nm, and the smallest value was obtained with the parameters of 5% w/w of polymer concentration and rotation speed of 15000 rpm and the highest value had 15% w/w concentration polymer and 10000 rpm. Keywords: centrifugal spinning, nanofibers, microfibers, recycled expanded polystyrene. 1
{"title":"Production of recycled EPS fibers by centrifugal spinning","authors":"G. Paganotto, G. Barros, V. G. Marques, A. Takimi","doi":"10.1590/S1517-707620210002.1254","DOIUrl":"https://doi.org/10.1590/S1517-707620210002.1254","url":null,"abstract":"Centrifugal spinning is a new technique for producing of nano and microfibers that has a great differential: a higher production rate than those presented by traditional methods. Due to a great interest in using nano and microfibers in technological applications along with the environmental interest in polymer recycling, this research had the purpose of production fibers by centrifugal spinning from the expanded poly-styrene recycling and the evaluation of the influence of operational parameters such as the concentration of polymer solution and the speed of rotation in the average diameter and in the distribution of the diameters of fibers formed. The fibers obtained were characterized using the Scanning Electronic Microscopy (SEM) and they had their diameters measured using ImageJ software. The fibers obtained in this research were entangled, woven, fused, with a rough and porous surface, with bead formation and without directional ordering. The results obtained show that the polymer solution concentration was the most influential parameter in the fibers analyzed characteristics and, in general, its increase generates an increase in the average diameter. With the increase in rotation speed, there has been often a reduction in the presence of beads and microparticles due to the better stretching of the fibers. In less concentrated solutions, continuous fibers with more regular surfaces were obtained, however, promoting the higher production of beads. In the most concentrated solutions, we noticed the formation of porous fibers and very rough surfaces, as well as fused and woven fibers. Through the measurement of its diameters, it was possible to observe the obtaining of fibers with average diameters of 407,02 nm to 38113,20 nm, and the smallest value was obtained with the parameters of 5% w/w of polymer concentration and rotation speed of 15000 rpm and the highest value had 15% w/w concentration polymer and 10000 rpm. Keywords: centrifugal spinning, nanofibers, microfibers, recycled expanded polystyrene. 1","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":"85564479","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}
Pub Date : 2021-03-25DOI: 10.1590/S1517-707620210001.1244
Leonardo Martins e Silva, A. Christoforo, R. Carvalho
Reinforced concrete structures are relatively complex to analyze, with nonlinear effects like cracking, crushing, steel yielding, aggregate interlock, dowel effect, concrete-rebar interaction and so on. The concrete damaged plasticity CDP model is a consolidated smeared-crack model which accounts for multiaxial behavior with good agreement to experimental results. One particular relevant application which benefits greatly from such feature is the shear wall, as shear stress significantly influences its overall behavior, therefore multiaxial constitutive models and three-dimensional finite elements usage consist in a fitting modeling approach. Reinforced concrete shear walls are structures especially useful for lateral force-resisting systems, as they provide ductility, stiffness and strength. Albeit CDP is widely applied, its parameters are not consensus in the literature, which represents a relevant research gap. The present work considers and compares CDP parameters from relevant literature, in order to calibrate those parameters for the case of reinforced concrete shear walls. To this purpose, four wall experiments related in the bibliography are modeled using solid finite elements for concrete and trusses for rebars using commercial package ABAQUS. All walls are flexure-controlled with aspect ratio greater than 2.0. By varying those parameters and comparing obtained force vs. displacement curves and interesting values attained, like yield lateral force and displacement, stiffness and maximum lateral force, it is settled a set of parameters with acceptable response focusing in the post-peak response based on the lower estimated error of displacement capacity. Those parameters agree reasonably with literature, although it is possible that obtained calibration is restricted to flexure controlled shear walls scope. It is possible that usage of trusses to represent reinforcement does not consider dowel effect, so a suggestion for future studies is to change trusses for elements with transverse stiffness, like beams or solids. Keywords: calibration, concrete damaged plasticity, concrete constitutive model, shear walls.
{"title":"Calibration of Concrete Damaged Plasticity Model parameters for shear walls","authors":"Leonardo Martins e Silva, A. Christoforo, R. Carvalho","doi":"10.1590/S1517-707620210001.1244","DOIUrl":"https://doi.org/10.1590/S1517-707620210001.1244","url":null,"abstract":"Reinforced concrete structures are relatively complex to analyze, with nonlinear effects like cracking, crushing, steel yielding, aggregate interlock, dowel effect, concrete-rebar interaction and so on. The concrete damaged plasticity CDP model is a consolidated smeared-crack model which accounts for multiaxial behavior with good agreement to experimental results. One particular relevant application which benefits greatly from such feature is the shear wall, as shear stress significantly influences its overall behavior, therefore multiaxial constitutive models and three-dimensional finite elements usage consist in a fitting modeling approach. Reinforced concrete shear walls are structures especially useful for lateral force-resisting systems, as they provide ductility, stiffness and strength. Albeit CDP is widely applied, its parameters are not consensus in the literature, which represents a relevant research gap. The present work considers and compares CDP parameters from relevant literature, in order to calibrate those parameters for the case of reinforced concrete shear walls. To this purpose, four wall experiments related in the bibliography are modeled using solid finite elements for concrete and trusses for rebars using commercial package ABAQUS. All walls are flexure-controlled with aspect ratio greater than 2.0. By varying those parameters and comparing obtained force vs. displacement curves and interesting values attained, like yield lateral force and displacement, stiffness and maximum lateral force, it is settled a set of parameters with acceptable response focusing in the post-peak response based on the lower estimated error of displacement capacity. Those parameters agree reasonably with literature, although it is possible that obtained calibration is restricted to flexure controlled shear walls scope. It is possible that usage of trusses to represent reinforcement does not consider dowel effect, so a suggestion for future studies is to change trusses for elements with transverse stiffness, like beams or solids. Keywords: calibration, concrete damaged plasticity, concrete constitutive model, shear walls.","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":"80796913","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}
Pub Date : 2021-03-25DOI: 10.1590/S1517-707620210002.1278
Mayara Cristina Fernandes de Carvalho, Iago Magella Fernandes Costa Rossi e Silva, Pâmara Larissa Alves Macedo, M. Tokumoto, R. S. D. Cruz, V. R. Capelossi
Carbon steel is used in various applications because of its excellent weldability, good mechanical resistance and low cost. However, its application becomes restricted due to its low corrosion resistance in neutral and acidic media, and it is necessary to use processes to retard the corrosive mechanism, such as the use of inhibitors. Many of the effective synthetic inhibitors used are associated with high cost and some have a high toxicity. In recent years, studies of corrosion inhibitors obtained from natural products have been increasing because they are environmentally sustainable and presents low-cost. Therefore, in the present study, different concentrations of the cocoa shell powder (Theobroma cacao) and hydroalcoholic extract were evaluated as a corrosion inhibitors of SAE 1008 carbon steel in 0.5 mol.L-1 sodium chloride solution. The inhibitory action of the cocoa residue was studied through gravimetric technique and electrochemical impedance spectroscopy (EIS). For the chemical characterization of the inhibitor, the Fourier Transform Infrared Spectroscopy (FTIR) was used. The EIS results showed that the corrosion inhibition efficiency of the steel decreased with the inhibitor concentration, reaching maximum values of 55.97% and 72.93%, for cocoa shell powder and hydroalcoholic extract, respectively. The gravimetric data confirmed the electrochemical results and through the study of the adsorption mechanism it was verified that the adsorbed inhibitor molecules follow the FloryHuggins isotherm model, for both forms of the inhibitor. For all the concentrations evaluated, the cocoa shell powder did not represent an efficient corrosion inhibitor. In contrast, for the hydroalcoholic extract, at the concentration of 0.44 g.L-1, a good performance was verified as a corrosion inhibitor of SAE 1008 carbon steel in 0.5 mol.L-1 sodium chloride solution. Keywords: Carbon steel, Theobroma cacao, Natural Corrosion Inhibitor, EIS, Gravimetric Technique.
{"title":"Assessment of the hydroalcoholic extract and powder cocoa bean shell as corrosion inhibitors for carbon steel in sodium chloride solution","authors":"Mayara Cristina Fernandes de Carvalho, Iago Magella Fernandes Costa Rossi e Silva, Pâmara Larissa Alves Macedo, M. Tokumoto, R. S. D. Cruz, V. R. Capelossi","doi":"10.1590/S1517-707620210002.1278","DOIUrl":"https://doi.org/10.1590/S1517-707620210002.1278","url":null,"abstract":"Carbon steel is used in various applications because of its excellent weldability, good mechanical resistance and low cost. However, its application becomes restricted due to its low corrosion resistance in neutral and acidic media, and it is necessary to use processes to retard the corrosive mechanism, such as the use of inhibitors. Many of the effective synthetic inhibitors used are associated with high cost and some have a high toxicity. In recent years, studies of corrosion inhibitors obtained from natural products have been increasing because they are environmentally sustainable and presents low-cost. Therefore, in the present study, different concentrations of the cocoa shell powder (Theobroma cacao) and hydroalcoholic extract were evaluated as a corrosion inhibitors of SAE 1008 carbon steel in 0.5 mol.L-1 sodium chloride solution. The inhibitory action of the cocoa residue was studied through gravimetric technique and electrochemical impedance spectroscopy (EIS). For the chemical characterization of the inhibitor, the Fourier Transform Infrared Spectroscopy (FTIR) was used. The EIS results showed that the corrosion inhibition efficiency of the steel decreased with the inhibitor concentration, reaching maximum values of 55.97% and 72.93%, for cocoa shell powder and hydroalcoholic extract, respectively. The gravimetric data confirmed the electrochemical results and through the study of the adsorption mechanism it was verified that the adsorbed inhibitor molecules follow the FloryHuggins isotherm model, for both forms of the inhibitor. For all the concentrations evaluated, the cocoa shell powder did not represent an efficient corrosion inhibitor. In contrast, for the hydroalcoholic extract, at the concentration of 0.44 g.L-1, a good performance was verified as a corrosion inhibitor of SAE 1008 carbon steel in 0.5 mol.L-1 sodium chloride solution. Keywords: Carbon steel, Theobroma cacao, Natural Corrosion Inhibitor, EIS, Gravimetric Technique.","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":"84026360","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}
Pub Date : 2021-03-25DOI: 10.1590/S1517-707620210002.1273
Marielle Jordane da Silva, Bruno Rocha Santos Lemos, Marcelo Machado Viana
O oxido de grafeno (GO) e um nanomaterial de carbono que apresenta propriedades unicas e dentre elas, a excelente condutividade termica que pode ser explorada em nanocompositos, como tambem em nanofluidos. O etilenoglicol (ETG) e um fluido de troca termica que pode ter suas propriedades termicas potencializadas pela adicao de GO. Porem, tanto o nivel de dispersao de GO quanto a reologia da suspensao, podem influenciar as caracteristicas dos nanofluidos, como o fluxo, a estabilidade e a transferencia termica. Assim, o estudo reologico de nanofluidos ETG/GO e importante para o entendimento da estabilidade coloidal dessas suspensoes e do potencial de aplicacao como fluido de transferencia termica. Neste trabalho, GO sintetizado pelo metodo de Hummers modificado foi utilizado para preparar nanofluidos ETG/GO para estudos reologicos. Tecnicas instrumentais como microscopia eletronica de varredura (MEV), difracao de raios X (DRX), espectroscopia na regiao do infravermelho por transformada de Fourier (FTIR), microscopia eletronica de transmissao (MET) e termogravimetria (TGA), confirmaram a obtencao de GO com cerca de 4 folhas de grafeno e funcionalizacao de 38% com grupos oxigenados. A superficie hidrofilica do GO permitiu que as nanofolhas tivessem boa compatibilidade com o ETG. Foram investigados os perfis de curvas de fluxo das suspensoes de nanofluidos ETG/GO, e estes foram classificados como: nao Newtonianos e pseudoplasticos pelo modelo de Ostwald-de Waele. A insercao de GO ao ETG, aumentou a viscosidade e o modulo de armazenamento (G’) em 21% e 8%, respectivamente. As propriedades aprimoradas evidenciam o potencial de uso de nanofluidos de GO para aplicacoes em sistemas termicos. Palavras-chave: Reologia; Oxido de grafeno; Etilenoglicol; Nanofluidos.
{"title":"Estudo das propriedades reológicas de nanofluidos à base de etilenoglicol e óxido de grafeno","authors":"Marielle Jordane da Silva, Bruno Rocha Santos Lemos, Marcelo Machado Viana","doi":"10.1590/S1517-707620210002.1273","DOIUrl":"https://doi.org/10.1590/S1517-707620210002.1273","url":null,"abstract":"O oxido de grafeno (GO) e um nanomaterial de carbono que apresenta propriedades unicas e dentre elas, a excelente condutividade termica que pode ser explorada em nanocompositos, como tambem em nanofluidos. O etilenoglicol (ETG) e um fluido de troca termica que pode ter suas propriedades termicas potencializadas pela adicao de GO. Porem, tanto o nivel de dispersao de GO quanto a reologia da suspensao, podem influenciar as caracteristicas dos nanofluidos, como o fluxo, a estabilidade e a transferencia termica. Assim, o estudo reologico de nanofluidos ETG/GO e importante para o entendimento da estabilidade coloidal dessas suspensoes e do potencial de aplicacao como fluido de transferencia termica. Neste trabalho, GO sintetizado pelo metodo de Hummers modificado foi utilizado para preparar nanofluidos ETG/GO para estudos reologicos. Tecnicas instrumentais como microscopia eletronica de varredura (MEV), difracao de raios X (DRX), espectroscopia na regiao do infravermelho por transformada de Fourier (FTIR), microscopia eletronica de transmissao (MET) e termogravimetria (TGA), confirmaram a obtencao de GO com cerca de 4 folhas de grafeno e funcionalizacao de 38% com grupos oxigenados. A superficie hidrofilica do GO permitiu que as nanofolhas tivessem boa compatibilidade com o ETG. Foram investigados os perfis de curvas de fluxo das suspensoes de nanofluidos ETG/GO, e estes foram classificados como: nao Newtonianos e pseudoplasticos pelo modelo de Ostwald-de Waele. A insercao de GO ao ETG, aumentou a viscosidade e o modulo de armazenamento (G’) em 21% e 8%, respectivamente. As propriedades aprimoradas evidenciam o potencial de uso de nanofluidos de GO para aplicacoes em sistemas termicos. Palavras-chave: Reologia; Oxido de grafeno; Etilenoglicol; Nanofluidos.","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":"82294187","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}
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