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Reducing Water and Chloride Penetration Through Silicate Treatments for Concrete as a Mean to Control Corrosion Kinetics

Medeiros, M. H. F.; Castro-Borges, P.; Aleixo, D. M.; Quarcioni, V. A.; Marcondes, C. G. N.; Helene, P.
Fonte: ELECTROCHEMICAL SCIENCE GROUP; BELGRADE Publicador: ELECTROCHEMICAL SCIENCE GROUP; BELGRADE
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
588.40074%
There are currently many types of protective materials for reinforced concrete structures and the influence of these materials in the chloride diffusion coefficient and water penetration still needs more research. The aim of this work is to analyze the contributions regarding the typical three surface concrete protection systems (coatings, linings and pore blockers) and discusses the results of three pore blockers (sodium silicate) tested in this work. To this end, certain tests were used: one involving permeability mechanism (low pressure-immersion absorption), one involving capillary water absorption, and the last, a migration test used to estimate the effective chloride diffusion coefficient in saturated condition. Results indicated reduction in chloride diffusion coefficients and capillary water absorption, therefore, restrictions to water penetration from external environmental. As a consequence, a reduction of the corrosion kinetics and a control of the chloride ingress are expected.; Polytechnic School of University of Sao Paulo (POLIUSP); Polytechnic School of University of Sao Paulo (POLI-USP); Federal University of Parana (UFPR); Federal University of Parana (UFPR); IPT (Institute of Technological Research); IPT (Institute of Technological Research); Research Support Foundation of the State of Sao Paulo (FAPESP); FAPESP (Research Support Foundation of the State of Sao Paulo)

Uso da técnica de eletrocinética para estabilização de um solo arenoso

Fonini, Anderson
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
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495.82844%
A tentativa de modificar algumas propriedades dos solos é antiga. Alguns autores fazem considerações a tentativas ocorridas a três mil anos atrás. Com o crescimento populacional e o desenvolvimento de novos sistemas de produção ocorridos após a Revolução Industrial no século XVIII, houve uma intensa ocupação territorial exigindo obras de infra-estrutura e obras complementares, tornando cada vez mais comum o melhoramento de solos. Uma técnica in situ passível de aplicação para melhorar as propriedades mecânicas dos solos é a técnica de eletrocinética associada à injeção de soluções químicas. Esta é caracterizada pela aplicação de um baixo gradiente elétrico através de eletrodos num meio poroso inundado com soluções químicas. Nesta pesquisa, foram realizados ensaios associando as soluções de cloreto de cálcio com água carbonatada, cloreto de cálcio com bicarbonato de sódio além de cloreto de cálcio com silicato de sódio. Para verificação da ocorrência da cimentação entre as partículas de areia, após a saturação do corpo de prova com as devidas soluções, mas anterior à aplicação da diferença de potencial elétrico ao solo, foram realizados três ensaios de prospecção com um Miniature Cone...

Different particle size silicas from water glass.

Martines, MAU; Davolos, M. R.; Junior, M. J.
Fonte: Soc Brasileira Quimica Publicador: Soc Brasileira Quimica
Tipo: Artigo de Revista Científica Formato: 469-472
POR
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485.9721%
Non-crystalline silica was obtained with different particle sizes. Samples were prepared from soluble sodium silicate (water glass) and sulfuric acid solutions. Dialysis was performed for sodium sulfate elimination. Products were dried in a microwave oven, milled and characterized by X-ray powder diffraction, infrared spectrum and sedigraphic analysis. Products milled for more than 120 minutes showed uniform particle size distribution with average silica particle size of 4.5 mu m.

Effects of different treatments on purity of silica from soluble sodium silicate

Martines, MAU; Pecoraro, E.; Simoneti, J. A.; Davolos, M. R.; Jafelicci, M.
Fonte: Taylor & Francis Inc Publicador: Taylor & Francis Inc
Tipo: Artigo de Revista Científica Formato: 287-298
ENG
Relevância na Pesquisa
488.8017%
Noncrystalline silica was obtained with low iron, sodium, and nitrate ions concentrations from soluble sodium silicate (water glass) and nitric acid solution. Extractions with nitric acid solution and/or deionized water and/or dialysis were carried out to eliminate soluble metal ions. Products were dried in a microwave oven and characterized by chemical analysis, XRD, and IR. Dialysis seems to be the best treatment for the elimination of sodium and nitrate ions. Silica purified by nitric acid and water extractions followed by dialysis yields the purest silica sample.

Comparative in vivo study of commercially pure Ti implants with surfaces modified by laser with and without silicate deposition: Biomechanical and scanning electron microscopy analysis

Souza, Francisley A.; Queiroz, Thallita P.; Guastaldi, Antônio C.; Garcia-Júnior, Idelmo R.; Magro-Filho, Osvaldo; Nishioka, Renato S.; Sisti, Karin E.; Sonoda, Celso K.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 76-84
ENG
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602.06945%
The purpose of this study was to evaluate commercially pure titanium implant surfaces modified by laser beam (LS) and LS associated with sodium silicate (SS) deposition, and compare them with machined surface (MS) and dual acid-etching surfaces (AS) modified. Topographic characterization was performed by scanning electron microscopy-X-ray energy dispersive spectroscopy (SEM-EDX), and by mean roughness measurement before surgery. Thirty rabbits received 60 implants in their right and left tibias. One implant of each surface in each tibia. The implants were removed by reverse torque for vivo biomechanical analysis at 30, 60, and 90 days postoperative. In addition, the surface of the implants removed at 30 days postoperative was analyzed by SEM-EDX. The topographic characterization showed differences between the analyzed surfaces, and the mean roughness values of LS and SS were statistically higher than AS and MS. At 30 days, values removal torque LS and SS groups showed a statistically significant difference (p < 0.05) when compared with MS and AS. At 60 days, groups LS and SS showed statistically significant difference (p < 0.05) when compared with MS. At 90 days, only group SS presented statistically higher (p < 0.05) in comparison with MS. The authors can conclude that physical chemistry properties and topographical of LS and SS implants increases bone-implant interaction and provides higher degree of osseointegration when compared with MS and AS. © 2012 Wiley Periodicals...

Sodium silicate gel as a precursor for the in vitro nucleation and grow of a bone-like apatite coating in compact and porous polymeric structures

Oliveira, A. L.; Malafaya, P. B.; Reis, R. L.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2003 ENG
Relevância na Pesquisa
692.9988%
In the present work, a new methodology to produce bioactive coatings on the surface of starch-based biodegradable polymers or other polymeric biomaterials is proposed. A sodium silicate gel is employed as an alternative nucleating agent to the more typical bioactive glasses for inducing the formation of a calcium-phosphate (Ca-P) layer. The method has the advantage of being able to coat efficiently both compact materials and porous 3D architectures aimed at being used on tissue replacement applications and as tissue engineering scaffolds. By means of this treatment, it is possible to observe the formation of an apatite-like layer, only after 6 hours of simulated body fluid immersion. For the porous materials, this layer could also be observed inside the pores, clearly covering the cell walls. Furthermore, an increase of the surface hydrophilicity (higher amount of polar groups in the surface) might contribute to the formation of silanol groups that also act as apatite inductors. After 30 days of SBF immersion, the apatite-like films exhibit a partially amorphous nature and the Ca/P ratios became much closer to the value attributed to hydroxyapatite (1.67). The obtained results are very promising for the development of cancellous bone replacement materials and for pre-calcifying bone tissue engineering scaffolds.

Biomimetic Ca-P coatings Incorporating bisphosphonates produced on starch-based degradable biomaterials

Oliveira, A. L.; Pedro, A. J.; Saiz-Arroyo, C.; Mano, J. F.; Rodriguez, G.; Roman, J. San; Reis, R. L.
Fonte: Wiley InterScience Publicador: Wiley InterScience
Tipo: Artigo de Revista Científica
Publicado em /01/2010 ENG
Relevância na Pesquisa
499.12965%
In this study, sodium clodronate, a well-known therapeutic agent from the family of bisphosphonates (BPs), is incorporated in a biomimetic calcium phosphate (CaP) coating, previously formed on the surface of a starch-based biomaterial by a sodium silicate methodology, as a strategy to develop a site-specific drug delivery system for bone tissue regeneration applications. The effects on the resulting CaP coatings were evaluated in terms of morphology, chemistry, and structure. The dissolution of Ca and P from the coating and the release profiles of sodium clodronate was also assessed. As a preliminary approach, this first study also aimed at evaluating the effects of this BP on the viability of a human osteoblastic cell line since there is still little information available on the interaction between BPs and this type of cells. Sodium clodronate was successfully incorporated, at different doses, in the structure of a biomimetic CaP layer previously formed by a sodium silicate process. This type of BPs had a stimulatory effect on osteoblastic activity, particularly at the specific concentration of 0.32 mg/mL. It is foreseen that these coatings can, for instances, be produced on the surface of degradable polymers and then used for regulating the equilibrium on osteoblastic/osteoclastic activity...

Sodium silicate gel as a precursor for the in vitro nucleation and growth of a bone-like apatite coating in compact and porous polymeric structures

Oliveira, A. L.; Malafaya, P. B.; Reis, R. L.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2003 ENG
Relevância na Pesquisa
692.9988%
In the present work, a new methodology to produce bioactive coatings on the surface of starch-based biodegradable polymers or other polymeric biomaterials is proposed. A sodium silicate gel is employed as an alternative nucleating agent to the more typical bioactive glasses for inducing the formation of a calcium-phosphate (Ca-P) layer. The method has the advantage of being able to coat efficiently both compact materials and porous 3D architectures aimed at being used on tissue replacement applications and as tissue engineering scaffolds. By means of this treatment, it is possible to observe the formation of an apatite-like layer, only after 6 hours of simulated body fluid immersion. For the porous materials, this layer could also be observed inside the pores, clearly covering the cell walls. Furthermore, an increase of the surface hydrophilicity (higher amount of polar groups in the surface) might contribute to the formation of silanol groups that also act as apatite inductors. After 30 days of SBF immersion, the apatite-like films exhibit a partially amorphous nature and the Ca/P ratios became much closer to the value attributed to hydroxyapatite (1.67). The obtained results are very promising for the development of cancellous bone replacement materials and for pre-calcifying bone tissue engineering scaffolds.

Conversion of rice hull ash into soluble sodium silicate

Foletto,Edson Luiz; Gratieri,Ederson; Oliveira,Leonardo Hadlich de; Jahn,Sérgio Luiz
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2006 EN
Relevância na Pesquisa
711.145%
Sodium silicate is used as raw material for several purposes: silica gel production, preparation of catalysts, inks, load for medicines, concrete hardening accelerator, component of detergents and soaps, refractory constituent and deflocculant in clay slurries. In this work sodium silicate was produced by reacting rice hull ash (RHA) and aqueous sodium hydroxide, in open and closed reaction systems. The studied process variables were time, temperature of reaction and composition of the reaction mixture (expressed in terms of molar ratios NaOH/SiO2 and H2O/SiO2). About 90% silica conversion contained in the RHA into sodium silicate was achieved in closed system at 200 °C. The results showed that sodium silicate production from RHA can generate aggregate value to this residue.

Effect of sodium silicate application on the resistance of wheat plants to the green-aphids Schizaphis graminum (Rond.) (Hemiptera: Aphididae)

Basagli,Marco A.B.; Moraes,Jair C.; Carvalho,Geraldo A.; Ecole,Carvalho C.; Gonçalves-Gervásio,Rita de C.R.
Fonte: Sociedade Entomológica do Brasil Publicador: Sociedade Entomológica do Brasil
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2003 EN
Relevância na Pesquisa
492.99883%
The green-aphid Schizaphis graminum (Rond.) is considered the major important pest of wheat plant, for causing severe injuries to the plants in all phenological crop stages, being able even to cause plant death. The objective of this study was to evaluate the effects of the application of silicon on the resistance of wheat plants to this pest. The experiments were carried out under greenhouse and laboratory conditions. The greenhouse experiment was conducted in a completely randomized experimental design with two treatments, consisting on silicon application and a control (without silicon application) with 10 replications and without environmental control. The laboratory bioassays were conducted under controlled environmental conditions (25 ± 1°C temperature; 70 ± 10% RH; and 12h photophase), in a randomized block experimental design, with a sub-divided plot scheme. The silicon, in the form of sodium silicate solution at 0.4% SiO2 was applied in six doses of 50 ml/pot each, at five-day intervals, being the first application performed five days after emergence of the wheat plats. Thirty-five days after plants emergence the following evaluations were performed: a) feeding preference in the laboratory; b) feeding preference in the greenhouse; and c) reproduction and development of the green-aphid. Application of sodium silicate reduced preference...

Experimental Evaluation of Sodium Silicate-Based Nanosilica against Chloride Effects in Offshore Concrete

Kim, Kyoung-Min; Kim, Hak-Young; Heo, Young-Sun; Jung, Sang-Jin
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
488.40074%
This study investigates the effect of a new pore filling material, named sodium silicate-based nanosilica (SS), on resisting the diffusion of the chloride ions. The proposed SS is chosen, mainly due to its smaller particle size, compared to the conventional ethyl silicate-based nanosilica. Each particle of SS is chemically treated to have the negative (−) charge on its surface. Four types of mixes with different amounts of partial replacement with fly ash and slag are prepared. Effect of water to binder ratios (0.35, 0.40, and 0.45) is also examined. Test results showed that the inclusion of SS was significantly beneficial for protecting the concrete from chloride attack. At a given strength, the SS inclusion in concrete was up to three times more effective than the control concrete without SS. It is believed that these excellent results are attributed to the small particle size and the chemical surface treatment of SS. In this study, experiments of compressive strength, hydration heat, accelerated neutralization, and sulfate erosion tests were also conducted to find the general effect of SS inclusion on the fundamental properties and durability of concrete.

Manejo pós-colheita de Alpinia purpurata (Vieill) K. Schum (Zingiberaceae)

Silva, Antonio Tarciso Ciríaco da
Fonte: Universidade Federal de Alagoas; BR; Agronomia; Produção vegetal; Proteção de plantas; Programa de Pós-Graduação em Agronomia; UFAL Publicador: Universidade Federal de Alagoas; BR; Agronomia; Produção vegetal; Proteção de plantas; Programa de Pós-Graduação em Agronomia; UFAL
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
502.06945%
The growth of ornamental plant market in Brazil is remarkable nowadays with strong participation of Northeast region, particularly in Alagoas State on the commercialization of tropical flowers. Taking into account this economic aspect, it is of great importance for the productive chain of ornamental species the study of aspects of post harvest activities. Alpinia purpurata (Viell) K. Schum (Zingiberaceae) which occupies the second place in economic importance amongst tropical flowers. It is the main flower for growing and harvesting. The main objective of this research programme is to study the different aspects of Alpinia post-harvesting: (1) time of harvesting and cut of the basis of the stems, and (2) the use of solutions of pulsing ; and/or maintenance of the floral stem by using: (2.1.) biocide compounds and pH of the solution; (2.2) carbohydrates and carbohydrates plus biocides; (2.3) anti-ethylene compounds and antiethylene compounds plus carbohydrates; (2.4) elements as calcium and silicon; and (2.5) senescence retarding growth regulators. It was evaluated the influence of these factors in the water relations, quality and longevity of the stems. Six experiments were carried out in the laboratory (CECA) of the Federal University of Alagoas. In the first experiment...

Avaliação da adição de Nanosílica e silicato de sódio em pastas de cimento para poços de petróleo com baixo gradiente de fratura

Queiroz Júnior, Manoel Ivany de
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Ciência e Engenharia de Materiais; Processamento de Materiais a partir do Pó; Polímeros e Compósitos; Processamento de Materiais a part Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Ciência e Engenharia de Materiais; Processamento de Materiais a partir do Pó; Polímeros e Compósitos; Processamento de Materiais a part
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
492.99883%
The oil wells cementing is a critical step during the phase of well drilling, because problems during the operation of slurry pumping and an incomplete filling of the annular space between the metal casing and the formation can cause the slurry loss. Therefore, the slurry adopted in primary cementing an oil well must be properly dosed so that these problems are avoided during its pumping. When you drill a well in a weak rock formation requires even more careful, because should be a limit of hydrostatic pressure exerted during cementation, that does not occur rock collapse. With the objective of performing the cementing of a well whose formation is weak or unconsolidated are employed lighter slurries. Thus, this study used slurries with sodium silicate and nano silica in concentrations of 0,1; 0,4; 0,7 e 1,0 gpc, in which the slurries with nano silica showed the rheological parameters higher concentrations of up to 0.7 gpc and for concentration of 1.0 the slurry with sodium silicate obtained the highest values, remaining above the limits for application in fields, mainly wells with low fracture gradient, because a significant increase in viscosity may result in an increase in pressure pumping in operations of secondary cementations. Furthermore...

Acute Tubular Necrosis after Ingestion of a Fertilizer Containing Sodium Silicate

Lee, Hyeon Woo; Choi, Yong Jun; Oh, Se Won; Park, Hye Kyeong; Han, Kum Hyun; Kim, Han Seong; Han, Sang Youb
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
492.99883%
Silica nephropathy occurs after chronic heavy exposure to silica, resulting in the development of chronic kidney disease and progression to end-stage renal disease. However, acute kidney injury due to silica exposure is rare and its renal pathology remains unclear. Here, we report a case of acute sodium silica poisoning presenting as acute kidney injury. A 42-year-old man ingested a fertilizer containing sodium silicate. His serum creatinine increased by 5.06 mg/dL from 1.1 mg/dL 2 days after silicate ingestion. Owing to the decline in kidney function despite fluid therapy, a kidney biopsy was performed. The kidney showed acute tubular necrosis without infiltration of inflammatory cells. On day 5 of admission, hemodialysis was initiated to treat the hyperkalemia and oliguria, and treatment with methylprednisolone was initiated for the acute lung injury. The patient was administered 1 mg/kg of methylprednisolone intravenously daily for 2 weeks, followed by a 2-week taper. Hemodialysis was discontinued on day 10 and the patient's renal function recovered completely. However, he died on day 40 of hospitalization owing to complicated lung fibrosis and persistent pneumothorax/pneumomediastinum.

Structural and dynamical properties of sodium silicate melts: An investigation by molecular dynamics computer simulation

Horbach, Jurgen; Kob, Walter; Binder, Kurt
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 01/11/1999
Relevância na Pesquisa
495.6206%
We present the results of large scale computer simulations in which we investigate the static and dynamic properties of sodium disilicate and sodium trisilicate melts. We study in detail the static properties of these systems, namely the coordination numbers, the temperature dependence of the Q^(n) species and the static structure factor, and compare them with experiments. We show that the structure is described by a partially destroyed tetrahedral SiO_4 network and the homogeneously distributed sodium atoms which are surrounded on average by 16 silicon and other sodium atoms as nearest neighbors. We compare the diffusion of the ions in the sodium silicate systems with that in pure silica and show that it is much slower in the latter. The sodium diffusion is characterized by an activated hopping through the Si-O matrix which is frozen with respect to the movement of the sodium atoms. We identify the elementary diffusion steps for the sodium and the oxygen diffusion and find that in the case of sodium they are related to the breaking of a Na-Na bond and in the case of oxygen to that of a Si-O bond. From the self part of the van Hove correlation function we recognize that at least two successive diffusion steps of a sodium atom are spatially highly correlated with each other. With the same quantity we show that at low temperatures also the oxygen diffusion is characterized by activated hopping events.; Comment: 16 pages of Latex...

Nature and distribution of iron sites in a sodium silicate glass investigated by neutron diffraction and EPSR simulation

Weigel, Coralie; Cormier, L.; Calas, Georges; Galoisy, Laurence; Bowron, Daniel
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 13/05/2008
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492.7249%
The short and medium range structure of a NaFeSi2O6 (NFS) glass has been investigated by high-resolution neutron diffraction with Fe isotopic substitution, combined with Empirical Potential Structure Refinement (EPSR) simulations. The majority (~60%) of Fe is 4-coordinated ([4]Fe) and corresponds only to ferric iron, Fe3+, with a distance d[4]Fe3+-O=1.87$\pm$0.01{\AA} . This is at variance with the 3D-structure predicted by glass stoichiometry. The existence of a majority of [4]Fe3+ sites illustrates a glass structure that differs from the structure of crystalline NaFeSi2O6, which contains only octahedral Fe3+. The EPSR modeling of glass structure shows that [4]Fe3+ is randomly distributed in the silicate network and shares corner with silicate tetrahedra. The existence of a majority of [4]Fe3+ sites differs from the structure of the corresponding crystalline phase, which contains only octahedral Fe3+. The network-forming behavior of [4]Fe3+, coupled with the presence of Na+ ions acting as charge-compensators, is at the origin of peculiar physical properties of Fe-bearing glasses, such as the increase of the elastic modulus of sodium silicate glasses with increasing Fe-concentration. Our data provide also direct evidence for 5-coordinated Fe...

Slow Dynamics in Ion-Conducting Sodium Silicate Melts: Simulation and Mode-Coupling Theory

Voigtmann, Thomas; Horbach, Juergen
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 16/08/2005
Relevância na Pesquisa
492.1029%
A combination of molecular-dynamics (MD) computer simulation and mode-coupling theory (MCT) is used to elucidate the structure-dynamics relation in sodium-silicate melts (NSx) of varying sodium concentration. Using only the partial static structure factors from the MD as an input, MCT reproduces the large separation in relaxation time scales of the sodium and the silicon/oxygen components. This confirms the idea of sodium diffusion channels which are reflected by a prepeak in the static structure factors around 0.95 A^-1, and shows that it is possible to explain the fast sodium-ion dynamics peculiar to these mixtures using a microscopic theory.; Comment: 4 pages, 4 figures

Espumado de mezclas de silicato de sodio-wollastonita por microondas; Foaming of sodium silicate-wollastonite mixtures by microwaves

Peña, P.; Vargas Gutiérrez, G.; López-Cuevas, J.; Méndez Nonell, J.; Vázquez, F.; Méndez, M.
Fonte: Sociedad Española de Cerámica y Vidrio Publicador: Sociedad Española de Cerámica y Vidrio
Tipo: Artículo Formato: 447921 bytes; application/pdf
SPA
Relevância na Pesquisa
516.24855%
[ES] Se analiza el efecto de la aplicación de las microondas durante 1,5 minutos sobre el cambio de volumen, porosidad y conductividad térmica de probetas de silicato de sodio/wollastonita. Se han estudiado mezclas con 20 a 100 % de silicato de sodio1. Se obtuvo una pérdida en masa del 19 % y un incremento de volumen del 50 % en mezclas con 20 % de silicato de sodio. A medida que el contenido de éste aumentó, la pérdida en masa se incrementó hasta 27 % y el cambio de volumen hasta en 500 % para probetas con 100 % de silicato de sodio. Se obtuvieron espumas cerámicas con porosidades totales de 65 % en probetas con 20 % de silicato de sodio (densidades aparente de 1,0 y real de 2,75 g/cc) y de 91 % en muestras con 100 % de silicato de sodio (densidades aparente de 0,182 y real de 2,0 g/cc). El tamaño de poro más uniforme se obtuvo para contenidos del 80 % de silicato de sodio (10 a 30 μm). Las conductividades térmicas de las espumas cerámicas fueron de 0,2, 0,125 y 0,065 W/m·K para contenidos de 40, 70 y 100 % de silicato de sodio, respectivamente.; [EN] The effect of the application of microwaves on the volume, porosity and thermal conductivity of sodium silicate-wollastonite mixtures was studied. The compositional range studied was 20-100 wt% sodium silicate. A weight loss of 19% and a volume increase of 50% were obtained for mixtures with 20 wt% sodium silicate. The weight loss increased up to 27% with increasing sodium silicate content. Volume increased in 500% for samples with 100 wt% sodium silicate. Ceramic foams with total porosities of 65 vol % were obtained for specimens containing 20 wt% sodium silicate (with apparent and real densities of 1.0 and 2.75 g/cc...

Espumado por microondas de mezclas de silicato de sodio-ortofosfato cálcico dibásico; Microwave foaming of sodium silicate-ortodibasic calcium phosphate mixtures

Vargas Gutiérrez, G.; Méndez Nonell, J.; Peña, P.; Pérez, J. C.; Méndez, M.
Fonte: Sociedad Española de Cerámica y Vidrio Publicador: Sociedad Española de Cerámica y Vidrio
Tipo: Artículo Formato: 448828 bytes; application/pdf
SPA
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692.9988%
[ES] La acción de la energía de las microondas, genera porosidad interna en un material cerámico húmedo. En el presente trabajo, se analiza el efecto del tiempo de aplicación de las microondas sobre el comportamiento térmico, cambio de volumen, tamaño y distribución de poros, reacciones químicas y disolución de probetas cerámicas de silicato de sodio / ortofosfato cálcico dibásico (FCD). Para caracterizar las espumas cerámicas, se utilizó, análisis de imágenes, microscopía electrónica de barrido, difracción de rayos X y picnometría de helio. Se obtuvieron espumas cerámicas con una porosidad de 71 a 79 % y un rango de tamaño de poro de 10 a 200 μm. Después de 90 segundos, las probetas alcanzaron una temperatura de aproximadamente 130°C y una pérdida de peso de 23% con respecto al peso total de la muestra. Se observaron cambios de volumen y de los compuestos químicos en las muestras espumadas cuando se varió la proporción del FCD en la mezcla. Para contenidos de 10, 20 y 30% en peso de FCD, el incremento de volumen se redujo a 350, 300 y 250% respectivamente. En muestras con 30% de FCD calentadas por microondas durante 90 segundos la cantidad de un nuevo compuesto en la espuma, constituido por β-NaCaPO4...

Hydrothermal Synthesis of Mesoporous Silica MCM-41 Using Commercial Sodium Silicate

Meléndez-Ortiz,Héctor Iván; Mercado-Silva,Alfonso; García-Cerda,Luis Alfonso; Castruita,Griselda; Perera-Mercado,Yibran Argenis
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2013 EN
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692.9988%
In this work, ordered mesoporous silica MCM-41 was prepared by hydrothermal synthesis using industrial-grade sodium silicate (Na2SiO3) as silica source, hexadecyltrimethyl-ammonium bromide (CTAB) as template agent and ethyl acetate as pH regulator. The influence of CTAB/SiO2 molar ratio, reaction time, aging temperature, and co-surfactant type on the structural and morphological properties of the obtained silica was studied. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption-desorption isotherms. Ordered mesoporous MCM-41 silica was obtained at 80 °C by using a range of CTAB/SiO2 molar ratio from 0.35 to 0.71 and reaction times up to 72 h and isopropanol (i-PrOH) as co-surfactant.