Preparation and Properties of Si2N2O Ceramics for Microwave Sintering Furnaces

doi:10.19691/j.cnki.1004-4493.2020.02.008

China's Refractories ›› 2020, Vol. 29 ›› Issue (2): 42-46.DOI: 10.19691/j.cnki.1004-4493.2020.02.008

• Original article • Previous Articles

Preparation and Properties of Si₂N₂O Ceramics for Microwave Sintering Furnaces

ZHENG Han¹, LI Wei², DU Jiaolong², LI Hongxia¹, LIU Guoqi¹, CHEN Zihao¹, CHEN Yongqiang¹^,²

1 Sinosteel Luoyang Institute of Refractories Research Co., Ltd., Luoyang 471039, China
2 School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China

Revised:2021-05-13 Online:2020-06-15 Published:2020-06-15
About author:Zheng Han, born in 1995, obtained his bachelor's degree from Shenyang University of Chemical Technology and is now pursuing his master's degree in Sinosteel Luoyang Institute of Refractories Research Co., Ltd. His main research interests are refractories and ceramic materials.

Abstract

Abstract:

Si₂N₂O ceramics were prepared using amorphous Si₃N₄ as the raw material and Li₂CO₃ as the sintering additive through vacuum multi-stage sintering. The influence of the Li₂CO₃ addition (0%, 1%, 2%, 3%, and 5%, by mass) on the phase composition, the microstructure, the porosity, the mechanical properties, the dielectric constant and the tangent of the dielectric loss angle of the porous Si₂N₂O ceramics was investigated. The results reveal that a suitable addition of Li₂CO₃ can promote the generation of Si₂N₂O but excessive or inadequate Li₂CO₃ causes decomposition of Si₂N₂O ceramics. The prepared porous Si₂N₂O ceramics have good mechanical properties, good thermal shock resistance, and low dielectric properties, which have excellent potential for application in microwave sintering furnaces.

Key words: Si₂N₂O porous ceramics, lithium carbonate, vacuum sintering, dielectric properties, microwave sintering

ZHENG Han, LI Wei, DU Jiaolong, LI Hongxia, LIU Guoqi, CHEN Zihao, CHEN Yongqiang. Preparation and Properties of Si₂N₂O Ceramics for Microwave Sintering Furnaces[J]. China's Refractories, 2020, 29(2): 42-46.

Figures/Tables 9

Fig. 1 XRD patterns of specimens with different Li2CO3 additions

Table 1 Chemical composition of specimens /mass%

Specimen number	Si₂N₂O	β-Si₃N₄	α-Si₃N₄	SiO₂
0^#	37. 90	9. 7	52. 4	-
1^#	85. 56	1. 3	13. 1	-
2^#	99. 63	-	-	-
3^#	83. 84	2. 6	-	13. 1
5^#	71. 07	4. 6	-	23. 6

Fig. 2 SEM photographs of specimens sintered at 1 650 ℃ for 2 h

Table 2 Physical properties and mass loss of specimens

Items	1^#	2^#	3^#	5^#
Apparent porosity /%	52.16	49.19	47.43	45.82
Bulk density /(g · cm^-3)	1.23	1.34	1.41	1.51
Modulus of rupture /MPa	18±5.1	30±4.7	44±6.6	72±6.2
Modulus of elasticity /GPa	8.16±1.5	13.7±2.6	19.4±2.2	31.7±3.1
Mass loss /%	5.89	8.71	10.66	15.47

Fig. 3 Residual MOR and MOR retention ratio of specimens after one thermal shock from different temperatures

Fig. 4 Effects of Li2CO3 addition on εr and tanδ of specimens

Fig. 5 Effects of oxidation time on εr and tanδ of specimen 2# oxidized at 1 300 ℃

Fig. 6 SEM photographs of surface of specimens oxidized at 1 300 ℃ for 30 h

Fig. 7 XRD patterns of surface of specimens oxidized at 1 300 ℃ for 30 h

References 7

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