Fabrication of Transparent AlON by Gel Casting and Pressureless Sintering

doi:10.15541/jim20220544

Abstract

Abstract:

Transparent AlON possesses good mechanical and optical properties, which shows great potential for application. However, high fabrication cost seriously restricts its wide usage. To solve this problem, gel-casting and pressureless sintering of transparent AlON was tentatively studied here, with emphasis on low temperature synthesis and anti-hydrolysis treatment of AlON powder. It was found that fine AlON powder could be readily synthesized at a low temperature of 1700 ℃ by a novel carbothermal nitridation technique, using polymer coated AlN/Al₂O₃ mixture as the starting materials. The powder obtained was submicron in size and its hydrolysis resistance could be significantly improved after surface coating with a polyurethane layer. On the basis of these findings, transparent AlON ceramics was successfully prepared through gel-casting and pressureless sintering. The material sintered at 1850 ℃ showed good optical and mechanical properties, with a high in-line transmittance of 83.1%-86.2% from ultraviolet to mid-infrared and three-point bending strength of 310 MPa.

Key words: transparent ceramics, AlON, powder synthesis, anti-hydrolysis treatment, gel casting, pressureless sintering

CLC Number:

TB333

JIN Xihai, DONG Manjiang, KAN Yanmei, LIANG Bo, DONG Shaoming. Fabrication of Transparent AlON by Gel Casting and Pressureless Sintering[J]. Journal of Inorganic Materials, 2023, 38(2): 193-198.

Figures/Tables 7

Fig. 1 XRD patterns and SEM images of AlON powder synthesized under different conditions (a) XRD patterns; (b) AlON powder synthesized at 1700 ℃, ball milled for 2 h; (c) AlON powder synthesized at 1700 ℃, ball milled for 15 h

Fig. 2 Influence of polyurethane surface coating on the hydrolysis behavior of AlON powder (a) Hydrolysis curves of pristine AlON powder and AlON powder surfaces coated with 1.0% polyurethane; (b) pH variance of AlON slurries after 72 h setting

Fig. 3 (a) Zeta potential curves of AlON powders after surface being coated with different mass amounts of polyurethane, and (b) rheological behavior of AlON slurry under different pH conditions Colorful figures are availuable on website

Fig. 4 Mercury porosimetry curves of the AlON green bodies formed by dry pressing-cold isostatic pressing (DP/CIP), gel casting (GC) and gel-casting-cold isostatic pressing (GC/CIP) （a）Cumulative intrution;（b）Incremental intrution

Fig. 5 Photographs and SEM images of transparent AlON sintered under different conditions （a, c）1820 °C×10 h; （b, d）1850 °C×10 h

Fig. 6 In-line transmittance of 2 mm thick transparent AlON pressurelessly sintered at different temperatures

Table 1 Mechanical properties of transparent AlON ceramics sintered at different temperatures

Sintering temperature/℃	Strength/ MPa	Toughness/ (MPa•m^1/2)	Hardness/ GPa
1820	325	2.3	17.5
1850	310	2.1	16.7

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