A New, Low‐Temperature Polymorph of Ó‐SiAlON

Bowden, Mark E.; Barris, G.C.; Brown, I. W. M.; Jefferson, D. A.

doi:10.1111/j.1151-2916.1998.tb02605.x

Cited by 11 publications

(8 citation statements)

References 10 publications

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“…Similar pair substitutions in Si 2 N 2 O result in the so-called OЈ-SiAlON series, which also has gained recent attention. 8,29 Epitaxial growth of SiAlON on ␤-Si 3 N 4 particles has been observed. Sun et al 15 found that an increase of (Al,O) content appears to strengthen the interfacial toughness of the SiAlON epitaxial layer at the interface.…”

Section: Introductionmentioning

confidence: 94%

Electronic Structure and Bonding of β‐SiAlON

Ching

Huang

2000

Journal of the American Ceramic Society

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The ␣-and ␤-SiAlONs are ceramic solid solutions with charge-neutral substitutions in ␣-and ␤-Si 3 N 4 . They have high potential for applications as structural materials. We have calculated the electronic structure and bonding of ␤-Si 6 -z Al z O z N 8 -z for z ‫؍‬ 0, 1, 2, 3, 4 using a first-principles method. Total energy calculations show that the bulk modulus of ␤-Si 6 -zAl z O z N 8 -z decreases as z increases, in general agreement with experimental trends. Simultaneous substitution of the (Si,N) pair by (Al,O) results in impurity-like states in the upper portion of the bandgap of ␤-Si 3 N 4 . As z increases, more and more states are introduced into the gap, forming a new conduction band (CB) edge for SiAlON. At z ‫؍‬ 4, the calculated bandgap is ϳ1.3 eV. Density of states (DOS) calculations show the top of the valence band remains steep for all z, and the bottom of the CB is formed predominately by Si-O antibonding states. Orbitally resolved partial DOS calculations in the CB region are used to predict the trends of the electron-energy-loss near-edge spectra (ELNES) of Si-L 2,3 , Al-L 2,3 , Si-K, Al-K, O-K, and N-K edges in ␤-SiAlON. The impurity-like states near the CB edge result in pre-edge structures in all ELNES spectra. Effective charge and bond order calculations show that the overall bond strength in ␤-SiAlON decreases only slightly as z increases. Although the stronger Si-N bonds are replaced by weaker Al-O bonds, the remaining Si-N and Al-O bonds actually strengthen as z increases because of the effective charge redistribution after substitution. This is a very interesting finding that may partly explain the superior mechanical properties of the SiAlON system that render them suitable for structural applications.

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Section: Introductionmentioning

confidence: 94%

Electronic Structure and Bonding of β‐SiAlON

Ching

Huang

2000

Journal of the American Ceramic Society

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“…The unknown phase was identified on the ground of a phase belonging to the Si-Al-O-N chemical system. The characterized structure corresponds to a compound initially reported by Bowden et al [70] was simulated and compared with the XRD spectrum of a green body sample prepared in our reactor. Using this sample, the XRD analysis could be performed over a wide angular range (10-70 2θ • ), since the silicon carbide from the fiber preform was absent.…”

Section: Characterization Of the Processed Compositesmentioning

confidence: 96%

Densification of Ceramic Matrix Composite Preforms by Si2N2O Formed by Reaction of Si with SiO2 under High Nitrogen Pressure. Part 1: Materials Synthesis

2021

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Ceramic matrix composites (CMCs) have been designed and developed for extreme operating environments. The aim of the present study is to look for a rapid densification process providing a high level of material performance. The fibrous preform was made of Hi-Nicalon S fibers woven in a 3D interlock weave. The matrix was composed of Si2N2O prepared inside the CMCs by reacting a mixture of Si and SiO2 under high nitrogen pressure (1 to 3 MPa). Silica was either impregnated by slurry or obtained by oxidation of silicon grains inside the preform. The synthesis reaction was initiated by heating the impregnated preform by means of a carbon resistor submitted to Joule effect. Composition, homogeneity and porosity of the formed matrix were studied and interpreted as a function of the experimental parameters (nitrogen pressure, heating rate of the preform) as well as the recorded thermal history of the process. The present results show that the matrix formation is almost completed in less than one minute. Melting of silicon has a major influence on the process. Competition was observed between the formation of Si3N4 and Si2N2O, which could be mainly controlled by the heating rate of the preform and the nitrogen partial pressure.

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“…Sialon ceramics have attracted more attention since they were discovered 28 years ago, and are now established materials -used in cutting tools, wire drawing, dies, tappets and shot blast nozzles, for example [1][2]. As with Si 3 N 4 , there are two forms, and , with atomic arrangements related to the equivalent and forms of silicon nitride, ABCD and ABAB respectively [3][4].…”

Section: Introductionmentioning

confidence: 99%

A Novel Processing Route for Fabricating One-Dimension Elongated Ca α-Sialon Crystalline Powders

Chen

Oliveira

Ferreira

2002

KEM

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A novel process route was developed for fabricating Ca -sialon crystalline powders in the present work. Loose powders with an average diameter of about 0.5 µm and an average length of about 5 µm were obtained by combustion synthesis process, followed by ultrasonic dispersion in acid to dissolve the liquid phase and obtain loose powders. The phase formation was detected by XRD. The particle morphology was observed by SEM.

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A New, Low‐Temperature Polymorph of Ó‐SiAlON

Cited by 11 publications

References 10 publications

Electronic Structure and Bonding of β‐SiAlON

Electronic Structure and Bonding of β‐SiAlON

Densification of Ceramic Matrix Composite Preforms by Si2N2O Formed by Reaction of Si with SiO2 under High Nitrogen Pressure. Part 1: Materials Synthesis

A Novel Processing Route for Fabricating One-Dimension Elongated Ca α-Sialon Crystalline Powders

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