Effect of Crystallizing the Grain‐Boundary Glass Phase on the High‐Temperature Strength of Hot‐Pressed Si3N4 Containing Y2O3

Tsuge, Akihiko; Nishida, Katsutoshi; Komatsu, Michiyasu

doi:10.1111/j.1151-2916.1975.tb11488.x

Cited by 224 publications

(55 citation statements)

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“…The softening of the glassy phase is the major factor detrimental to their HT properties. There are two major strategies for improving the HT properties of Si 3 N 4 ceramics: (i) the crystallization of the secondary amorphous phase by a postheating treatment [18][19][20][21]30] and (ii) the use of more refractory RE oxide additives that can provide crystalline secondary phases with high melting points [24,25,[30][31][32][33][34][35][36][37]. Previous studies have suggested that out of the RE oxides, Yb 2 O 3 and Lu 2 O 3 are the best additives for improving HT resistance up to 1400 and 1500 • C due to the formation of crystalline Yb 4 Si 2 O 7 N 2 [24,25,32,33,36] and Lu 4 Si 2 O 7 N 2 [31,34,37] grain boundary phases, respectively.…”

Section: Introductionmentioning

confidence: 99%

Textured silicon nitride: processing and anisotropic properties

Zhu

Sakka

2008

Science and Technology of Advanced Materials

158

104

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Textured silicon nitride (Si 3 N 4 ) has been intensively studied over the past 15 years because of its use for achieving its superthermal and mechanical properties. In this review we present the fundamental aspects of the processing and anisotropic properties of textured Si 3 N 4 , with emphasis on the anisotropic and abnormal grain growth of β-Si 3 N 4 , texture structure and texture analysis, processing methods and anisotropic properties. On the basis of the texturing mechanisms, the processing methods described in this article have been classified into two types: hot-working (HW) and templated grain growth (TGG). The HW method includes the hot-pressing, hot-forging and sinter-forging techniques, and the TGG method includes the cold-pressing, extrusion, tape-casting and strong magnetic field alignment techniques for β-Si 3 N 4 seed crystals. Each processing technique is thoroughly discussed in terms of theoretical models and experimental data, including the texturing mechanisms and the factors affecting texture development. Also, methods of synthesizing the rodlike β-Si 3 N 4 single crystals are presented. Various anisotropic properties of textured Si 3 N 4 and their origins are thoroughly described and discussed, such as hardness, elastic modulus, bending strength, fracture toughness, fracture energy, creep behavior, tribological and wear behavior, erosion behavior, contact damage behavior and thermal conductivity. Models are analyzed to determine the thermal anisotropy by considering the intrinsic thermal anisotropy, degree of orientation and various microstructure factors. Textured porous Si 3 N 4 with a unique microstructure composed of oriented elongated β-Si 3 N 4 and anisotropic pores is also described for the first time, with emphasis on its unique mechanical and thermal-mechanical properties. Moreover, as an important related material, textured α-Sialon is also reviewed, because the presence of elongated α-Sialon grains allows the production of textured α-Sialon using the same methods as those used for textured β-Si 3 N 4 and β-Sialon.

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Section: Introductionmentioning

confidence: 99%

Textured silicon nitride: processing and anisotropic properties

Zhu

Sakka

2008

Science and Technology of Advanced Materials

158

104

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“…Three groups of additives have been used [1, [5][6][7]: (a) oxides (MgO, ^2 Q 3> ^2°3 * Al2°3) > which do not form solid solutions with 813114; (b) oxide and non-oxide additives (BeO, BeSiN2, Al2C>3 + A1N, A1N + Y2°3) which do form solid solutions with Si3N4; and (c) non-oxide additives (863^, ZrN, ZrC, Zr + A1N, Mg3N2) which give higher viscosity grain boundary phases. Additives such as MgO result in a continuous, amorphous, magnesium silicate intergranular phase [8][9][10][11], whilst those containing Y203~Al203 additions may possess both crystalline and amorphous grain boundary phases [12][13][14][15]. The presence of a glassy grain boundary phase is deleterious to both the room temperature and elevated temperature mechanical properties of silicon nitride.…”

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The high temperature creep deformation of Si3N4-6Y2O3-2Al2O3

Todd

1989

J Mater Sci

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The creep properties of silicon nitride containing 6 wt% yttria and 2 wt% alumina have been determined in the temperature range 1573 to 1673 K. The stress exponent, n, in the equation e « a , was determined to be 2.00 +_0.15 and the true activation energy was found to be 692 +_ 25 kJ mol~. Transmission electron microscopy studies showed that deformation occurred in the grain boundary glassy phase accompanied by microcrack formation and cavitation. The steady state creep results are consistent with a diffusion controlled creep mechanism involving nitrogen diffusion through the grain boundary glassy phase.

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“…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 . En un sistema de micromorfología análoga a la mullita, como es el Si 3 N 4 , está bien documentado que la adición de Y 2 O 3 mejora la sinterización mediante la formación de líqui-dos [10][11][12] . A posteriori, la cristalización de la fase secundaria (fundamentalmente Y 2 Si 2 O 7 ) mediante tratamiento térmico da lugar a unas propiedades mecánicas mejores que las del material con fase secundaria en estado amorfo 6,11,13,14 .…”

Section: -Introducciónunclassified

“…En un sistema de micromorfología análoga a la mullita, como es el Si 3 N 4 , está bien documentado que la adición de Y 2 O 3 mejora la sinterización mediante la formación de líqui-dos [10][11][12] . A posteriori, la cristalización de la fase secundaria (fundamentalmente Y 2 Si 2 O 7 ) mediante tratamiento térmico da lugar a unas propiedades mecánicas mejores que las del material con fase secundaria en estado amorfo 6,11,13,14 . El objetivo fundamental de este trabajo es conocer el efecto que la presencia de fases vítreas tiene sobre la deformación plástica de la mullita policristalina en un rango típico de alta temperatura, y en particular como evoluciona la ductilidad.…”

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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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Effect of Crystallizing the Grain‐Boundary Glass Phase on the High‐Temperature Strength of Hot‐Pressed Si₃N₄ Containing Y₂O₃

Cited by 224 publications

References 4 publications

Textured silicon nitride: processing and anisotropic properties

Textured silicon nitride: processing and anisotropic properties

The high temperature creep deformation of Si3N4-6Y2O3-2Al2O3

Deformación plástica de compuestos mullita/óxido de itrio

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