Effect of the pressureless post-sintering on the hot isostatic pressed Al2O3 prepared from the oxidized AlN powder

K. Balázsi; D. Varanasi; Zs E. Horváth; M. Furkó; F. S. Cinar; C. Balázsi

doi:10.1038/s41598-022-12456-2

Effect of the pressureless post-sintering on the hot isostatic pressed Al₂O₃ prepared from the oxidized AlN powder

K. Balázsi^*, D. Varanasi, Zs E. Horváth, M. Furkó, F. S. Cinar, C. Balázsi

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

1 Citation (Scopus)

Abstract

The effect of the pressureless post-sintering in hydrogen on the structural and mechanical properties of the hot isostatic pressed Al₂O₃ prepared by oxidized AlN powder has been studied. The micrometer size AlN powder has been oxidized in air at 900° C and sintered by hot isostatic pressing (HIP) at 1700 °C, 20 MPa nitrogen atmosphere for 5 h. Pressureless sintering (PS) has been applied for all HIP sintered samples in H₂ gas at 1800° C for 10 h. It has been shown that the oxidation caused a core–shell AlN/Al₂O₃ structure and the amount of Al₂O₃ increased with increasing of the oxidation time of the AlN powder. For the first time, the green samples obtained from oxidized AlN powder have been successfully sintered first by HIP followed by post-sintering by PS under hydrogen without adding any sintering additives. All post-sintered samples exhibited the main α-Al₂O₃ phase. Sintering in H₂ caused the full transformation of AlN to α-Al₂O₃ phase and their better densification. Therefore, the hardness values of post-sintered samples have been increased to 17–18 GPa having apparent densities between 3.11 and 3.39 g/cm³.

Original language	English
Article number	8250
Journal	Scientific Reports
Volume	12
Issue number	1
DOIs	https://doi.org/10.1038/s41598-022-12456-2
Publication status	Published - Dec 2022
Externally published	Yes

Bibliographical note

Publisher Copyright:
© 2022, The Author(s).

Funding

The authors sincerely thank to colleagues from Centre for Energy Research, namely Viktor Varga for helping us in carrying out the sample preparation, Noémi Szász and Levente Illés for helping us in the SEM analysis of the samples, András Hiripi (Tungsram Operations Ltd.) for pressureless sintering of samples. This research was funded by the Hungarian National Research Development and Innovation Office (project NKFIH-NNE 129976). The authors sincerely thank to colleagues from Centre for Energy Research, namely Viktor Varga for helping us in carrying out the sample preparation, Noémi Szász and Levente Illés for helping us in the SEM analysis of the samples, András Hiripi (Tungsram Operations Ltd.) for pressureless sintering of samples. This research was funded by the Hungarian National Research Development and Innovation Office (project NKFIH-NNE 129976).

Funders	Funder number
Tungsram Operations Ltd.
National Research, Development and Innovation Office	NKFIH-NNE 129976

Access to Document

10.1038/s41598-022-12456-2

Cite this

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title = "Effect of the pressureless post-sintering on the hot isostatic pressed Al2O3 prepared from the oxidized AlN powder",

abstract = "The effect of the pressureless post-sintering in hydrogen on the structural and mechanical properties of the hot isostatic pressed Al2O3 prepared by oxidized AlN powder has been studied. The micrometer size AlN powder has been oxidized in air at 900° C and sintered by hot isostatic pressing (HIP) at 1700 °C, 20 MPa nitrogen atmosphere for 5 h. Pressureless sintering (PS) has been applied for all HIP sintered samples in H2 gas at 1800° C for 10 h. It has been shown that the oxidation caused a core–shell AlN/Al2O3 structure and the amount of Al2O3 increased with increasing of the oxidation time of the AlN powder. For the first time, the green samples obtained from oxidized AlN powder have been successfully sintered first by HIP followed by post-sintering by PS under hydrogen without adding any sintering additives. All post-sintered samples exhibited the main α-Al2O3 phase. Sintering in H2 caused the full transformation of AlN to α-Al2O3 phase and their better densification. Therefore, the hardness values of post-sintered samples have been increased to 17–18 GPa having apparent densities between 3.11 and 3.39 g/cm3.",

author = "K. Bal{\'a}zsi and D. Varanasi and Horv{\'a}th, {Zs E.} and M. Furk{\'o} and Cinar, {F. S.} and C. Bal{\'a}zsi",

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AU - Furkó, M.

AU - Cinar, F. S.

AU - Balázsi, C.

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N2 - The effect of the pressureless post-sintering in hydrogen on the structural and mechanical properties of the hot isostatic pressed Al2O3 prepared by oxidized AlN powder has been studied. The micrometer size AlN powder has been oxidized in air at 900° C and sintered by hot isostatic pressing (HIP) at 1700 °C, 20 MPa nitrogen atmosphere for 5 h. Pressureless sintering (PS) has been applied for all HIP sintered samples in H2 gas at 1800° C for 10 h. It has been shown that the oxidation caused a core–shell AlN/Al2O3 structure and the amount of Al2O3 increased with increasing of the oxidation time of the AlN powder. For the first time, the green samples obtained from oxidized AlN powder have been successfully sintered first by HIP followed by post-sintering by PS under hydrogen without adding any sintering additives. All post-sintered samples exhibited the main α-Al2O3 phase. Sintering in H2 caused the full transformation of AlN to α-Al2O3 phase and their better densification. Therefore, the hardness values of post-sintered samples have been increased to 17–18 GPa having apparent densities between 3.11 and 3.39 g/cm3.

AB - The effect of the pressureless post-sintering in hydrogen on the structural and mechanical properties of the hot isostatic pressed Al2O3 prepared by oxidized AlN powder has been studied. The micrometer size AlN powder has been oxidized in air at 900° C and sintered by hot isostatic pressing (HIP) at 1700 °C, 20 MPa nitrogen atmosphere for 5 h. Pressureless sintering (PS) has been applied for all HIP sintered samples in H2 gas at 1800° C for 10 h. It has been shown that the oxidation caused a core–shell AlN/Al2O3 structure and the amount of Al2O3 increased with increasing of the oxidation time of the AlN powder. For the first time, the green samples obtained from oxidized AlN powder have been successfully sintered first by HIP followed by post-sintering by PS under hydrogen without adding any sintering additives. All post-sintered samples exhibited the main α-Al2O3 phase. Sintering in H2 caused the full transformation of AlN to α-Al2O3 phase and their better densification. Therefore, the hardness values of post-sintered samples have been increased to 17–18 GPa having apparent densities between 3.11 and 3.39 g/cm3.

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