Sol-gel synthesis of SiO2P2O5 glasses

Fernández‐Lorenzo, Concha; Esquivias, L.; Barboux, P.; Maquet, Jocelyne; Taulèlle, Francis

doi:10.1016/0022-3093(94)90077-9

Cited by 85 publications

(62 citation statements)

References 17 publications

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“…In the present study, the geopolymer cement after soaking in water for 28 days remains a consolidated material but the compressive strength decreases from 87.71 (for the specimens cured at room temperature) to 40.71 MPa (for the specimens soaked in water) (Figure 8). This could be related to the easy hydrolysis of Si-O-P bonds in the presence of water [34]. This corroborates the result obtained on the IR spectrum of GPP ( Figure 6) which indicates the higher intensity of the bands at 1638 and 3407 cm −1 (following the reaction H 2 0 + Si-O-P Si-OH + H-O-P).…”

Section: Compressive Strengthsupporting

confidence: 80%

Water resistance and thermal behavior of metakaolin-phosphate-based geopolymer cements

Bewa

Tchakouté

Fotio

et al. 2018

Journal of Asian Ceramic Societies

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The main target of this work was to investigate the thermal behavior and water resistance of geopolymer cement made from metakaolin as an aluminosilicate source using phosphoric acid solution (10 M) as a hardener. The obtained geopolymer cements were cured at room temperature for 28 days, the one part was treated at 200°C, 400°C, 600°C, 800°C and 1000°C, and the others were soaked in water for 28 days. The geopolymer cements were characterized by microstructural properties using X-ray diffractometry, infrared spectroscopy, microstructure, physical property based on water resistance and thermo-mechanical properties (thermal analysis, compressive strength). The results show that the compressive strength of the unheated geopolymer cement was 87.96 MPa. The ones soaked in water revealed a strength of 40.71 MPa. This indicates that the specimens soaked in water lose about 54% of their strengths. The X-ray patterns of heated geopolymer cements showed the formation of crystalline phases even at relatively low temperatures. It was typically found that the compressive strength of metakaolin-phosphate-based geopolymer cements decreases due to the hydrolysis of Si-O-P bonds in the presence of water. ARTICLE HISTORY

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Section: Compressive Strengthsupporting

confidence: 80%

Water resistance and thermal behavior of metakaolin-phosphate-based geopolymer cements

Bewa

Tchakouté

Fotio

et al. 2018

Journal of Asian Ceramic Societies

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“…Ramírez-del-Solar et al have proposed a model of statistical balls or polymeric growing clusters [26,27] (Figure 20.9), R g . For t ¼ t G, R g~1 .5 nm and a~0.25 nm.…”

Section: From Sol To Gelmentioning

confidence: 99%

“…The Zarzycki and Esquivias groups conducted early extensive work to establish the practical consequences of this approach on the kinetic and textural characteristics of the sonogels [13,14]. These studies encompass numerous systems on pure SiO 2 [15][16][17][18][19][20][21][22][23][24], SiO 2 -P 2 O 5 [16,25,26], SiO 2 -TiO 2 [27][28][29][30][31][32][33], ZrO 2 [34,35], SiO 2 -Al 2 O 3 -MgO [36,37] (cordierite), and SiO 2 /SiO 2 composites [38,39].…”

Section: Sonogelsmentioning

confidence: 99%

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Aerogels Synthesis by Sonocatalysis: Sonogels

et al. 2011

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High power ultrasound applied to liquids produces cavities that attain very high temperatures and pressures ("hot spots"). When an alkoxide/water mixture is sonicated, the cavities act as nanoreactors, where the hydrolysis reaction starts. The products (alcohol, water, and silanol) help continue the dissolution of that immiscible mixture. The reactions depend on catalyst content, temperature bath, and alkyl group length. When the resultant sonosol gels, it produces a sonogel; it is denser, with finer and more homogeneous porosity than that of a classic counterpart. Thus, acoustic cavitation makes it possible to obtain nanostructured materials. Sono-aerogels have a high surface-to-volume ratio and are built by small particles (~1 nm radius) and a highly cross-linked network with low surface coverage of -OH radicals. The processing as well as their short-range order at an atomic scale and at a micrometric scale is presented in this chapter. Finally, these materials find application, among others as biomaterials for tissue engineering and for CO 2 sequestration. 20

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“…La presencia de vapor de agua en el medio incrementa considerablemente la velocidad de evaporaci-n del -xido de boro, reduciendo su capacidad de protecci-n antioxidante, ya sea en la disminuci-n de la temperatura m ‡xima de trabajo o en el tiempo que proporciona protecci-n (2,8,15,23,47,48). TambiŽn se aplican vidrios basados en P 2 O 5 mezclados con otros -xidos como SiO 2 , Al 2 O 3 , -xidos alcalinos, -xido de boro y -xidos met ‡licos, en proporciones variables en funci-n del intervalo de la temperatura de trabajo (24,49).…”

Section: 21-capa Internaunclassified

Materiales compuestos C/SiC para aplicaciones estructurales de alta temperatura. Parte II: Sistemas de protección contra la oxidación

Aparicio¹,

Durán²

2001

Bol. Soc. Esp. Ceram. Vidr.

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La utilizaci-n de los materiales compuestos C/SiC en aplicaciones estructurales a alta temperatura est ‡ limitada por la elevada velocidad de oxidaci-n de la fibra de carbono a temperaturas superiores de 450¼C. En esta segunda parte del trabajo se realiza una revisi-n de las posibilidades de protecci-n contra la oxidaci-n de estos materiales, incluyendo inhibidores, modificaci-n superficial del material compuesto, recubrimientos e infiltraci-n previa del sustrato. La eficacia de los inhibidores de la reacci-n de oxidaci-n est ‡ restringida a temperaturas de hasta 850¼C, mientras que la modificaci-n superficial del material compuesto da lugar a capas delgadas y poco resistentes a los ciclos tŽrmicos. En cambio, los recubrimientos son el mŽto-do m ‡s empleado porque permiten combinar composiciones y espesores de capa muy variados. La estructura multicapa es especialmente interesante en el caso de aplicaciones con intervalos de temperatura de trabajo amplios y cuando el material va a estar sometido a choques tŽrmicos. La infiltraci-n de la porosidad del sustrato s-lo mejora ligeramente la resistencia a la oxidaci-n del material compuesto C/SiC al reducir los caminos de acceso del ox'geno a las fibras de carbono. Sin embargo, la infiltraci-n complementa en gran medida las propiedades antioxidantes de los recubrimientos en el intervalo de bajas temperaturas, ya que Žstos suelen presentar fisuras abiertas por diferencias de dilataci-n tŽrmica con el sustrato. Palabras clave: C/SiC, materiales compuestos, protecci-n antioxidante C/SiC composites for high temperature structural applications. Part II: Oxidation protection systemsThe fact which currently excludes the use of C/SiC composites in high temperature structural applications is the high oxidation rate of carbon fibres at temperatures higher than 450¼C. In this second part of the paper, a review of the different oxidation protection systems, including inhibitors, surface modification of composites, coatings and previous infiltration of the substrates, has been carried out. The addition of inhibitors reduces the oxidation rate, but only up to 850¼C, while the surface modification of composites leads to thin coatings with poor thermal shock resistance. On the other hand, the external layers are the most usual method employed because allows combining different compositions and thicknesses. The multilayer coatings are especially interesting in applications with wide temperature range and thermal shocks requirements. The infiltration of substrate porosity improves slightly the oxidation resistance of C/SiC composites reducing the oxygen accessibility to carbon fibres. However, the infiltration complements very well the oxidation protection performance of a coating system at low temperature, since these normally present open cracks due to mismatch between coating and substrate thermal expansion coefficients. Keywords: C/SiC, composites, oxidation protection 1.-INTRODUCCIîNLas importantes propiedades de los materiales compuestos C/SiC, propiedades mec ‡nicas a alta tempe...

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Sol-gel synthesis of SiO2P2O5 glasses

Cited by 85 publications

References 17 publications

Water resistance and thermal behavior of metakaolin-phosphate-based geopolymer cements

Water resistance and thermal behavior of metakaolin-phosphate-based geopolymer cements

Aerogels Synthesis by Sonocatalysis: Sonogels

Materiales compuestos C/SiC para aplicaciones estructurales de alta temperatura. Parte II: Sistemas de protección contra la oxidación

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