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Thermal Properties of Nitrogen-Rich Ca-α-Sialons
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
Vise andre og tillknytning
2009 (engelsk)Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 29, nr 16, s. 3409-3417Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Nitrogen-rich Ca-α-Sialon (CaxSi12−2xAl2xN16 with x = 0.2, 0.4, and 0.8, 1.2 and 1.6) ceramics were prepared from the mixtures of Si3N4, AlN and CaH2 powders in a hot press at 1800 °C using a pressure of 35 MPa and a holding time of 4 h, and then were investigated with respect to reaction mechanism, phase stability and oxidation resistance. In addition the sample with x = 1.6 was prepared in the temperature range 600–1800 °C using a pressure of 35 MPa and a holding time of 2 h. The α-Sialon phase was first observed at 1400 °C but the α-Si3N4 and AlN phases were still present at 1700 °C. Phase pure Ca-α-Sialon ceramics could not be obtained until the sintering temperature reached 1800 °C. The phase pure nitrogen-rich Ca-α-Sialon exhibited no phase transformation in the temperature range 1400–1600 °C. In general, mixed α/β-Sialon showed better oxidation resistance than pure α-Sialon in the low temperature range (1250–1325 °C), while α-Sialons with compositions located at α/β-Sialon border-line showed significant weight gains over the entire temperature range tested (1250–1400 °C). The phases formed upon oxidation were characterized by X-ray, SEM and TEM studies.

sted, utgiver, år, opplag, sider
2009. Vol. 29, nr 16, s. 3409-3417
Identifikatorer
URN: urn:nbn:se:su:diva-25769DOI: 2122/10.1016/j.jeurceramsoc.2009.07.015ISI: 000270694400014OAI: oai:DiVA.org:su-25769DiVA, id: diva2:200493
Merknad
Part of urn:nbn:se:su:diva-8568Tilgjengelig fra: 2009-02-26 Laget: 2009-02-17 Sist oppdatert: 2017-12-13bibliografisk kontrollert
Inngår i avhandling
1. Synthesis and Characterization of Nitrogen-rich Calcium α-Sialon Ceramics
Åpne denne publikasjonen i ny fane eller vindu >>Synthesis and Characterization of Nitrogen-rich Calcium α-Sialon Ceramics
2009 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

In this thesis, a synthesis concept has been developed, which uses nitrogen-rich liquid phases for sintering of Ca-α-sialon ceramics. First, keeping the Si/Al ratios constant, the effects of N/O ratio on the properties and microstructure were investigated through a liquid phase sintering process. Second, nitrogen-rich Ca-α-sialon ceramics, with nominal compositions: CaxSi12-2xAl2xN16, x < 2.0, was synthesized and characterized. Third, mechanical and thermal properties of nitrogen-rich Ca-α-sialons were investigated in terms of high temperature deformation resistance,reaction mechanism, phase stability and oxidation resistance, and further correlated to their phase assemblage and microstructure observation.

It has been found that increasing the N/O and Ca/Al ratio simultaneously in the materials could result in development of a microstructure with well shaped, high-aspect-ratio Ca-α-sialon grains, and an improvement in both toughness and hardness.

For the nitrogen-rich Ca-α-sialon, mono-phasic α-sialon ceramics were obtained for 0.51 ≤ x ≤ 1.32. The obtained Ca-α-sialon ceramics with elongated-grain microstructures show a combination of high hardness and high fracture toughness. Compared with the oxygen-rich Ca-α-sialons, the nitrogen-rich Ca-α-sialons exhibited approximately 150 oC higher deformation onset temperatures and decent properties even after the deformation.

The α-sialon phase was first observed at 1400 oC, however the phase pure Ca-α-sialon ceramics couldn’t be obtained until 1800 oC. The nitrogen-rich Ca-α-sialons were thermal stable, no phase transformation observed in the temperatures range1400-1600 oC. In general, mixed α/β-sialon showed better oxidation resistance than pure α-sialon in the low temperature range (1250-1325 oC), while α-sialons with compositions located at α/β-sialon border-line showed significant weight gains over the entire temperature range (1250-1400 oC).

sted, utgiver, år, opplag, sider
Stockholm: Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, 2009. s. 57
Emneord
Nitrogen-rich, SiAlON, Sintering, Microstructure, Properties
HSV kategori
Forskningsprogram
oorganisk kemi
Identifikatorer
urn:nbn:se:su:diva-8568 (URN)978-91-7155-823-7 (ISBN)
Disputas
2009-03-20, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 13:00
Opponent
Veileder
Tilgjengelig fra: 2009-02-26 Laget: 2009-02-17bibliografisk kontrollert

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