Fabrication and Properties of AlN-SiC Multiphase Ceramics via Low Temperature Reactive Melt Infiltration

doi:10.15541/jim20230091

Abstract

Abstract:

AlN-SiC multiphase ceramics possess robust mechanical strength, high thermal conductivity and good oxidization resistance, and show great potential as the matrix material of fiber reinforced ceramic matrix composites. In this work, AlN-SiC multiphase ceramics were fabricated via low temperature reactive melt infiltration of Si-Al alloy into porous C-Si₃N₄ preforms. Influence of Si-Al source on the melt infiltration process was studied, and impact of residual silicon on the mechanical and thermal properties of the AlN-SiC ceramics was investigated. It was found that an Al-O layer was in-situ formed at the interface between Si-Al melt and C-Si₃N₄ preform, when Si-Al powder was used as the infiltration medium. This seriously retarded the melt infiltration process and made the penetration of Si-Al melt into the C-Si₃N₄ preform hardly possible. However, when Si-Al ingot was used as the infiltration medium, a well infiltration of Si-Al melt into the C-Si₃N₄ preform occurred, which led to the formation of dense AlN-SiC ceramics. Mechanical and thermal property measurements indicated that the strength of the AlN-SiC ceramics was significantly improved as the residual silicon content in it was reduced, while a reverse trend was observed for the thermal conductivity. AlN-SiC ceramics with 4%(in mass) residual silicon showed a high strength of 320.1 MPa, nearly comparable to that of conventional reaction bonded SiC, although its thermal conductivity was modest (26.3 W·m^-1·K^-1). The fundamental reasons for the above phenomena were discussed. This study is of great significance for the preparation of SiC_f/AlN-SiC composites by low temperature reactive melt infiltration.

Key words: reactive melt infiltration (RMI), AlN-SiC, mechanical property, thermal conductivity

CLC Number:

TB484

SUN Xiaofan, CHEN Xiaowu, JIN Xihai, KAN Yanmei, HU Jianbao, DONG Shaoming. Fabrication and Properties of AlN-SiC Multiphase Ceramics via Low Temperature Reactive Melt Infiltration[J]. Journal of Inorganic Materials, 2023, 38(10): 1223-1229.

Figures/Tables 8

Table 1 Chemical composition of the slurries used for different types of C-Si3N4 infiltration preform preparation

Material	Mass percent of LCP/%	Mass percent of HCP/%
α-Si₃N₄	20.17	15.66
Carbon black	8.65	6.71
Phenolic resin	17.29	26.85
Dibutyl phthalate (DBP)	5.76	4.47
Polyvinyl butyral (PVB)	7.20	5.59
Castor oil	0.58	0.45
Ethanol absolute	40.35	40.27

Fig. 1 SEM images of porous C-Si3N4 infiltration preforms with different carbon contents (a, b) Low carbon content preform (LCP); (c, d) High carbon content preform (HCP)

Fig. 2 Mercury porosimetry curves of the C-Si3N4 infiltration preforms with different carbon contents (a) Cumulative volume percentage vs pore diameter; (b) Incremental intrusion vs pore diameter

Fig. 3 SEM image and EDS line scanning of the melt/preform interface region in the post melt infiltrated Si-Al/C-Si3N4 system, using (a, b) Si-Al ingot and (c, d) Si-Al powder as infiltration medium Colorful figures are available on the website

Fig. 4 (a) XRD patterns of AlN-SiC multiphase ceramics prepared from different types of C-Si3N4 preform, and (b) changes of standard Gibbs free energy of reaction (3-6) as a function of temperatures calculated with HSC 6.0 software

Fig. 5 SEM images of AlN-SiC multiphase ceramics prepared from different C-Si3N4 preforms and their corresponding EDS mapping (a-e) Low carbon content preform; (f-j) High carbon content preform

Table 2 Density and mechanical properties of AlN-SiC multiphase ceramics prepared from different types of C-Si3N4 preform

Preform type	Bulk density/ (g·cm^-3)	Hardness/GPa	Bending strength/MPa
LCP	2.83	12.8±0.2	198.3±4.6
HCP	2.95	16.9±0.4	320.1±25.1

Fig. 6 Thermal diffusivity (a), specific heat (b) and thermal conductivity (c) of AlN-SiC ceramics prepared from the LCP and HCP preforms

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