Effects of Rare Earth Oxide Addition on the Sintering of Mullite

Mitamura, Takashi; Kobayashi, Haruo; Ishibashi, Noboru; Akiba, T.

doi:10.2109/jcersj.99.351

Cited by 12 publications

(10 citation statements)

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“…[21][22][23][24][25] Especially, Si 3 N 4 /SiC/Y 2 O 3 also exhibits very interesting in situ crack-healing ability at 1073-1473 K. [26][27][28] Al 2 O 3 /SiC/Y 2 O 3 exhibits very high bending strength (≈1300 MPa) at room temperature. 29 It has been reported that the optimal Y 2 O 3 content of mullite is 0.5 mass%.…”

Section: Introductionmentioning

confidence: 99%

Crack-healing behaviour of mullite/SiC/Y2O3 composites and its application to the structural integrity of machined components

Lee

Ono

Nakao

et al. 2005

Journal of the European Ceramic Society

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Section: Introductionmentioning

confidence: 99%

Crack-healing behaviour of mullite/SiC/Y2O3 composites and its application to the structural integrity of machined components

Lee

Ono

Nakao

et al. 2005

Journal of the European Ceramic Society

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“…Earlier observations of anisotropic grain growth or needlelike mullite shapes were reported by Perera and Allott, 6 who fired kaolin minerals at 1400°-1600°C. However, the length (0.5-5.0 m) and aspect ratio [3][4][5][6][7][8] of the whiskers obtained were small. Hong et al 7 studied the anisotropic grain growth of B 2 O 3 -doped mullite that was seeded using mullite whiskers.…”

Section: Introductionmentioning

confidence: 99%

“…The effect of rare-earth additions on the sintering of high-purity mullite grains, including erbia in the 0 -10 wt% range, was studied by Mitamura et al 8 For 2 wt% doping, the bulk density increased as sintering increased in the 1400°-1600°C range, and the microstructures showed no evidence of pronounced anisotropic grain growth. Chan and Ko, 9 who studied the effect of the concentration of rare-earth oxide on mullite densification, found no significant morphologic changes in mullite grains, with or without the addition of bastanasite, other than an increase in grain growth as the concentration of added rare earths increased.…”

Section: Introductionmentioning

confidence: 99%

Mullite Whiskers Grown from Erbia‐Doped Aluminum Hydroxide–Silica Gel

Souza

Yamamoto

Regiani

et al. 2000

Journal of the American Ceramic Society

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Mullite whiskers and anisotropic grains that were derived from erbia-doped aluminum hydroxide-silica gel were studied. Firing 3.0-mol%-erbia-doped isostatically pressed pellets at 1600°C for 1.0 -8.0 h resulted in a high surface concentration of mullite whiskers. Their c-axes were aligned preferentially along the pellet surface; the maximum length was 50 m, and the maximum aspect ratio was 23. The pellet surface was fully covered by mullite whiskers, and small anisotropic grains with a low aspect ratio were observed in the bulk. The voids that were observed in the fracture surfaces were covered fully by mullite whiskers. The large number of voids resulted in an apparent density of 1.60 g/cm 3 in the sintered pellets. The molar ratio of alumina to silica in the whiskers was in the range of 1.30 -1.45 (an average value of 1.31), regardless of whether the alumina/silica powder compositions were mixed in a 3:2 or 2:1 ratio.

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“…La literatura sobre el procesado de la mullita es extensa [1][2][3][4][5][6][7] . Precisamente, las buenas propiedades mecánicas de la mullita a alta temperatura dificultan su sinterizado.…”

Section: -Introducciónunclassified

“…Adicionalmente, la presencia de vidrios remanentes en las cerámicas estructurales puede incrementar su ductilidad de cara a dar a los materiales formas complejas 8 . En el caso de la mullita, a partir de una exhaustiva revisión bibliográfica [1][2][3][4][5][6][7] y algunas pruebas preliminares, el aditivo elegido en este estudio fue óxido de itrio (Y 2 O 3 ). Con este aditivo la mullita sinteriza por fase líquida, como cabe esperar a partir del diagrama de fases del sistema ternario SiO 2 -Al 2 O 3 -Y 2 O 3 , que ha sido publicado en un trabajo reciente 9 .…”

Section: -Introducciónunclassified

Deformación plástica de compuestos mullita/óxido de itrio

Lopez¹,

Martínez²,

Routbort³

et al. 2001

Bol. Soc. Esp. Ceram. Vidr.

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Los compuestos a partir de mullita (3Al 2 O 3 .2SiO 2 ) presentan unas magníficas propiedades mecánicas y térmicas. Las mismas características que hacen de la mullita resistente a la deformación plástica, dificultan su densificación. El óxido de itrio es uno de los aditivos más utilizados para reducir la temperatura de sinterización de la mullita. Adicionalmente la presencia de silicatos vítreos (en este caso Y 2 Si 2 O 7 ) incrementan la ductilidad. En esta investigación se han usado muestras de mullita con diversas cantidades de Y 2 O 3 (0%, 5% y 9% en peso). Los detalles sobre el procesado y caracterización de los compuestos han sido objeto de una publicación previa. Se ha estudiado comparativamente la ductilidad de estos materiales mediante experimentos de deformación en compresión a alta temperatura. Los ensayos se han desarrollado entre 1300 y 1400ºC, en atmósfera de aire, cubriendo un rango de tensiones de compresión entre 0.69 y 34.4 MPa. Palabras clave: mullita, óxido de itrio, deformación plástica, microestructura Plastic Deformation of Mullite/Yttria CompositesMullite (3Al 2 O 3 .2SiO 2 ) based composites have excellent mechanical and thermal properties. The same characteristics that give mullite good resistance to plastic deformation also make its sintering difficult. Yttria is one of the most commonly used additives to reduce sintering temperatures in mullite. Additionally vitreous silicates (Y 2 Si 2 O 7 ) could improve ductility. In this work we have used mullite samples with various amounts of Y 2 O 3 (0, 5 and 9 wt.%). Details of processing and characterization of these composites have been the subject of a previous publication. We have compared the ductility of these composites by means of compressive deformation tests at elevated temperatures. Creep tests were performed at temperatures between 1300 and 1400ºC, in air, in a stress range of 0.69 to 34.5 MPa.Key words: mullite, yttria, plastic deformation, microstructurea 1.-INTRODUCCIÓNLa mullita (3Al 2 O 3 .2SiO 2 ) es una cerámica estructural que ha encontrado importantes aplicaciones como refractario. La mullita presenta excelentes propiedades a alta temperatura 1 : estabilidad química, baja conductividad térmica, resistencia choques térmicos, resistencia a la deformación plástica, etc.La literatura sobre el procesado de la mullita es extensa [1][2][3][4][5][6][7] . Precisamente, las buenas propiedades mecánicas de la mullita a alta temperatura dificultan su sinterizado. Normalmente la mullita se sinteriza a temperaturas próximas a 1650ºC durante varias horas, obteniéndose altas densidades finales. El uso de aditivos puede reducir la temperatura de sinterizado mediante la formación de líquidos a partir de la reacción de los aditivos con la mullita a alta temperatura. Adicionalmente, la presencia de vidrios remanentes en las cerámicas estructurales puede incrementar su ductilidad de cara a dar a los materiales formas complejas 8 . En el caso de la mullita, a partir de una exhaustiva revisión bibliográfica 1-7 y algunas pruebas preliminares, el...

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Effects of Rare Earth Oxide Addition on the Sintering of Mullite

Cited by 12 publications

References 0 publications

Crack-healing behaviour of mullite/SiC/Y2O3 composites and its application to the structural integrity of machined components

Crack-healing behaviour of mullite/SiC/Y2O3 composites and its application to the structural integrity of machined components

Mullite Whiskers Grown from Erbia‐Doped Aluminum Hydroxide–Silica Gel

Deformación plástica de compuestos mullita/óxido de itrio

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