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Formation of (Al 2 OC) 1− x (AlN) x solid solution starting from Al–Si–Al 2 O 3 powder matrix at 1300°C in flowing nitrogen
Author(s) -
Ma Chenhong,
Li Yong,
Zhang Lixin,
Xue Wendong,
Sun Jialin
Publication year - 2019
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.16486
Subject(s) - composite number , materials science , oxide , cladding (metalworking) , solid solution , nitride , metal , pyrolysis , metastability , nitrogen , composite material , chemical engineering , metallurgy , chemistry , layer (electronics) , organic chemistry , engineering
(Al 2 OC) 1− x (AlN) x solid solution‐reinforced Si–Al 2 O 3 composite was successfully synthesized by designed heating of the Al–Si–Al 2 O 3 composite to 580°C and held for 8 hours, followed by heating to 1300°C at a rate of 12°C/h in flowing nitrogen. The reaction mechanism is as follows: after the Al–Si–Al 2 O 3 composite is heated to 580°C and held for 8 hours, an AlN cladding is formed on the surface of the Al powder, thus the composite is preconverted into (Al–AlN cladding structure)–Si–Al 2 O 3 system. With increasing temperature, the AlN cladding ruptures and the reactive Al(l) flows out. The Al(l) preferentially undergoes active oxidation to form metastable Al 2 O(g), which lowers P O2 inside the composite and inhibits the active oxidation of Si. Moreover, ultrafine carbon is produced by the pyrolysis of the phenolic resin binder. Both metastable Al 2 O(g) and ultrafine carbon are highly reactive. Therefore, under the induction of AlN and N 2 , (Al 2 OC) 1− x (AlN) x solid solution is formed by the reactionAl 2 O ( g ) + AlN ( s ) + C ( s ) → ( Al 2 OC ) 1 - x( AlN ) x ( s ) , which easily occurs at a relatively low temperature. In the presence of a large amount of Al 2 O(g), the P O2 in the composite does not satisfy the condition required for both Si nitridation and active oxidation, so the free Si remains stable in the composite, forming a metal‐non‐oxide‐oxide composite. The cold crushing strength of the composites is up to 305 MPa, and the composites do not show hydration after 20 months of storage in the environment.