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Formation Process of AlN Through Precursors and Its Application to Joining AlN Ceramics
Author(s) -
Kai Ayako,
Kamita Yasunobu,
Miki Toshikatsu
Publication year - 2012
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.12010
Subject(s) - amorphous solid , crystallization , materials science , chemical engineering , phase (matter) , crystallography , chemistry , organic chemistry , engineering
Formation process of AlN from urea and aluminum chloride hexa‐hydrate ( N/Al = 60) under nitrogen is investigated. An aluminum hexa‐urea complex crystallizes on mixing the two raw materials at room temperature. The complexes react with excess urea and/or its decomposed products, such as biuret above 160°C, and form an amorphous phase containing Al , N , C , and O around 400°C after releasing volatile products. The resultant amorphous phase undergoes changes as the temperature increases, and then crystalline carbon with a fullerene‐like XRD pattern forms at 850°C. AlN crystallization follows the decomposition of the fullerene‐like crystals. At the AlN precursor stage, a large number of radicals ( g = 2.0029 and S = 1/2) are detected by ESR. The radicals are assumed to be due to dangling bonds with an unpaired electron in amorphous carbon. Joining AlN ceramics is conducted using the 850°C product at the AlN precursor stage as the filler material, and is successfully achieved at temperatures above 1000°C. The shear strengths of the joints formed at 1500°C are 88 ± 29 MPa.