Synthesis of AlN Nanopowder from γ‐Al₂O₃by Reduction–Nitridation in a Mixture of NH₃–C₃H₈

Abstract

Aluminum nitride (AlN) powders were synthesized by gas reduction–nitridation of γ‐Al2O3 using NH3 and C3H8 as the reactant gases. AlN was identified in the products synthesized at 1100°–1400°C for 120 min in the NH3–C3H8 gas flow confirming that AlN can be formed by the gas reduction–nitridation of γ‐Al2O3. The products synthesized at 1100°C for 120 min contained unreacted γ‐Al2O3. The 27A1 MAS NMR spectra show that Al–N bonding in the product increases with increasing reaction temperature, the tetrahedral AlO4 resonance decreasing prior to the disappearance of the octahedral AlO6 resonance. This suggests that the tetrahedral AlO4 sites of the γ‐Al2O3 are preferentially nitrided than the AlO6 sites. AlN nanoparticles were directly formed from γ‐Al2O3 at low temperature because of this preferred nitridation of AlO4 sites in the reactant. AlN nanoparticles are formed by gas reduction–nitridation of γ‐Al2O3 not only because the reaction temperature is sufficiently low to restrict grain growth, but also because γ‐Al2O3 contains both AlO4 and AlO6 sites, by contrast with α‐Al2O3 which contains only AlO6.

Kinetics of microwave synthesis of AlN by carbothermal‐reduction‐nitridation at low temperature

“…Yamakawa et al also synthesized AlN at 1200°C, but they used NH 3 -C 3 H 8 as the reactant gas. 19 Our results suggest that microwaves enhanced the CRN reaction without using a reactive gas such as NH 3 -C 3 H 8 , and microwave irradiation enabled us to synthesize single-phase AlN at temperatures above 1200°C.…”

Low‐Temperature Synthesis of Aluminum Nitride from Transition Alumina by Microwave Processing

“…The main alumina phase of (c), (d), (e), and (f) was h-Al 2 O 3 (Fig. In addition, Yamakawa et al reported 15 According to these reports, c-Al 2 O 3 is more easily nitrided than d-, h-, or a-Al 2 O 3 . On the other hand, (a), (b), and (g) had only the c, d, and a-Al 2 O 3 phases, respectively.…”

“…Figure 3 shows that nitridation ratios for (c)', (d)', (e)', and (f)' were higher than those of (a)', (b)' and (g)'. 15 These earlier works have suggested that a-Al 2 O 3 , which has only octahedral AlO 6 sites, is less readily nitrided than transition alumina. The main alumina phase of (c), (d), (e), and (f) was h-Al 2 O 3 (Fig.…”

Aluminum Nitride Formation From Aluminum Oxide/Phenol Resin Solid-Gel Mixture By Carbothermal Reduction Nitridation Method

“…It is a promising advanced ceramic material with many excellent properties such as high band gap of around 6.2 eV, high electrical resistivity (10 13 ), small dielectric constant (8.8 at 1 MHz), and low thermal expansion coefficient (which closely matched that of silicon, 4.7×10 −6 K −1 ) [1,2]. Many methods have been reported on the production of AlN powders including direct nitridation of Al metal in N 2 or NH 3 atmosphere, carbothemal reduction of Al 2 O 3 in Al 2 O 3 -C-N 2 system or Al 2 O 3 -NH 3 -C 3 H 8 system [3][4][5], vapor phase synthesis [6,7], plasma synthesis [8,9], and self-propagating high temperature synthesis [10,11]. Among them, two primary processes to manufacture AlN powders commercially are direct nitridation and carbothermal reduction [12].…”