Hot-pressing and the ?-? phase transformation in silicon nitride

Bowen, L.J.; Weston, Rachel; Carruthers, T. G.; Brook, R. J.

doi:10.1007/bf00647779

Cited by 165 publications

(48 citation statements)

References 15 publications

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“…However, the α-phase is chemically unstable compared with the β-phase. At high temperatures (HTs) when a liquid phase is present, the α-phase always transforms into the β-phase via the solution-precipitation process, during which α-grains dissolve into the liquid phase and precipitate as β-grains, known as the α-β phase transformation [4][5][6]. Therefore, β-Si 3 N 4 is the major form used in Si 3 N 4 ceramics.…”

Section: Introductionmentioning

confidence: 99%

“…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%

“…Using seeding and extrusion, Teshima et al [50] obtained highly textured Si 3 N 4 with a bending strength of ≈1. 4 GPa and a fracture toughness of ≈14 MPa m 1/2 along the direction perpendicular to the grain alignment. Using the sinter-forging (SF) method, Kondo et al [51] produced textured Si 3 N 4 with a superhigh bending strength of 2.1 GPa and a high fracture toughness of 8.3 MPa m 1/2 in the direction perpendicular to the grain alignment.…”

Section: Introductionmentioning

confidence: 99%

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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%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Textured silicon nitride: processing and anisotropic properties

Zhu

Sakka

2008

Science and Technology of Advanced Materials

158

104

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“…The phase transformation from ¡-to ¢-Si 3 N 4 is mainly dependent on the densification. 51) Consequently, because the densification of the nanosized amorphous Si 3 N 4 powder was achieved at a temperature lower than that for the submicron-sized ¡-Si 3 N 4 powder, the transformation to the ¢-phase would be completed at a low temperature.…”

Section: )mentioning

confidence: 99%

Microstructural control for ultrafine-grained non-oxide structural ceramics

Hotta

2012

J. Ceram. Soc. Japan

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Ultrafine-grained non-oxide ceramics were prepared by combining the synthesis technology for fine-grained starting powders and the rapid sintering technology for spark plasma sintering (SPS); the two technologies were combined for obtaining ceramics with improved heat and corrosion resistance and improved mechanical properties. Hollow spherical Ca-¡ SiAlON powders composed of nanosized particles were synthesized by carbothermal reductionnitridation of a SiO 2 Al 2 O 3 CaCO 3 powder mixture. Using the Ca-¡ SiAlON powder, dense Ca-¡ SiAlON nanoceramics and porous Ca-¡ SiAlON ceramics with excellent mechanical properties and high heat and corrosion resistance were fabricated by the SPS technique. Ultrafine-grained Si 3 N 4 and SiC ceramics were prepared from fine-grained Si 3 N 4 and SiC powders by SPS. The densification of cubic-BN-dispersed ceramics composites was achieved without the phase transformation of cubic BN to low-hardness hexagonal BN, at a moderate pressure by the SPS technique.

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“…A reaction in this sense may be the formation of the intended product [40][41][42][43]. However, the term is also used when oxidation-reduction reactions [42], phase transitions [44], or the formation of a solid solution [45] or a liquid phase [46,47] are involved.…”

Section: Chemical Reactions In High-temperature Sintering Processesmentioning

confidence: 99%

Chemical research needed to improve high-temperature processing of advanced ceramic materials (Technical report)

Kolář

2000

Pure and Applied Chemistry

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Republication or reproduction of this report or its storage and/or dissemination by electronic means is permitted without the Chemical research needed to improve high-temperature processing of advanced ceramic materialsAbstract: Of the principal classes of engineering materials, ceramics are in many ways the most interesting and challenging. Many properties, or combination, of properties, not achievable with other classes of materials give ceramics enormous technical potential. The main obstacles that prevent the wider use of ceramics include insufficient reliability, reproducibility, and high cost. The physical basis of the processing steps is well established, however, the chemical reactions which occur during the high-temperature processing frequently influence the densification process and microstructure development of ceramics in an unpredictable way. Therefore, an ability to understand and control the chemical processes that occur during ceramic processing are necessary to advance and open up new uses for technical ceramics. The aim of this present report, resulting from discussions of an ad hoc group of ceramists and chemists, is to expose the areas of chemical research that can most benefit the processing, and further the use, of ceramic materials.

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Hot-pressing and the ?-? phase transformation in silicon nitride

Cited by 165 publications

References 15 publications

Textured silicon nitride: processing and anisotropic properties

Textured silicon nitride: processing and anisotropic properties

Microstructural control for ultrafine-grained non-oxide structural ceramics

Chemical research needed to improve high-temperature processing of advanced ceramic materials (Technical report)

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