Nucleation Density on the Synthesis of AlON Powder and Preparation of Transparent Ceramics

doi:10.15541/jim20170206

Abstract

Abstract:

Aluminum oxynitride (AlON) powders were synthesized by carbothermal reduction and nitridation process using α-Al₂O₃ powder as starting material. Activated charcoal powder and submicron carbon powder were mixed with α-Al₂O₃ respectively to vary nucleation density of AlON. Influence of nucleation density on phase assemblages, morphology of AlON powders and transparence of AlON ceramics were studied. Single phase AlON powders were synthesized after holding at 1750℃ for 60 min with for both mixture powders of different nucleation density. The results show that the synthesized powders exhibit different morphology and milling property. The AlON powder synthesized by α-Al₂O₃ and activated charcoal mixture show irregular shape, loose structure and small particle size, due to its high nucleation density. Moreover, it is easier to mill the obtained AlON powder into small particle (0.93 μm). However, for the AlON powder synthesized by mixture of α-Al₂O₃ and submicron carbon powder, their grain grow obviously during the synthesis of the AlON powder, due to its low nucleation density with large near sphere particles close to 2.13 μm in diameter. Therefore, nucleation density plays a key role in controlling morphology, structure characteristics and milling performance of the AlON powders. Using the AlON powder synthesized by high nucleation density powders, high transparent AlON ceramics was fabricated by pressureless sintering at 1880℃ for 150 min, the maximum transmittance was ~76.5% (3 mm in thickness). It is 48.3% higher than that using AlON powder synthesized by low nucleation density powders. Therefore, for using α-Al₂O₃ as starting material to prepare AlON powder, high nucleation density is beneficial to AlON powder with small particle size and high sintering ability, which contributes to the high transmittance of AlON ceramics.

Key words: AlON, α-Al₂O₃;, nucleation density, activated charcoal powder, submicron carbon

CLC Number:

TB321
TB332

XU Jian-Xin, SHAN Ying-Chun, WANG Guang, XU Jiu-Jun, WANG Liang, LI Jiang-Tao. Nucleation Density on the Synthesis of AlON Powder and Preparation of Transparent Ceramics[J]. Journal of Inorganic Materials, 2018, 33(4): 373-379.

Figures/Tables 13

Fig. 1 SEM image of α-Al2O3 powder

Fig. 2 SEM images of activated charcoal powder (a, b) and submicron carbon (c)

Fig. 3 Particle size distribution curve of submicron carbon powder

Fig. 4 Particle size distribution curves of milled powders (α-Al2O3 and carbon)

Fig. 5 SEM images of the mixtures of α-Al2O3 and C(a) AA powder; (b) SA powder

Fig. 6 XRD patterns of powders synthesized by activated charcoal powder (a) and submicron carbon (b)

Fig. 7 SEM images of AlON powders synthesized by activated charcoal powder (a)-(b) and submicron carbon (c)-(d)

Fig. 8 SEM images of milled AlON powders synthesized by activated charcoal powder (a) and submicron carbon (b)

Fig. 9 Particle size distribution of milled AlON powders synthesized by activated charcoal powder (a) and submicron carbon (b)

Fig. 10 Formation process of AlON powder synthesized by carbothermal reduction and nitridation(a) Mixture of Al2O3 and C; (b) Heated to 1550℃; (c) Held at 1550℃ for 60 min; (d) ≥1700℃; (e) After holding at 1750℃ for a period of time (<60 min); (f) Held at 1750℃ for 60 min

Fig. 11 XRD patterns of AlON ceramics

Fig. 12 Fracture surfaces of AlON ceramics(a) Activated charcoal powder; (b) Submicron carbon

Fig. 13 Transmittance curves of the transparent ceramics (a) Visible light; (b) Infrared band

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