Two-stage plasma nitridation approach for rapidly synthesizing aluminum nitride powders
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Yi-Ming Kuo Department of Environmental and Safety Engineering, Chung Hwa College of Medical Technology, Tainan 717, Taiwan
Lien-Te Hsieh Department of Environmental Engineering and Science, National Pingtung University of Science and Technology, Pingtung 912, Taiwan
Cheng-Hsien Tsaia) Department of Chemical and Materials Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung 807, Taiwan (Received 28 August 2016; accepted 7 December 2016)
The synthesis of aluminum nitride (AlN) powders from aluminum (Al) particles via a thermal nitridation process was carried out at high temperature (.900 °C) with a long reaction time (;several hours). This study proposes a two-stage plasma-chemical synthesis process to efficiently minimize the agglomeration of Al particles, reduce the reaction time and temperature, and promote the formation of AlN powders. In the first stage, partially nitrided Al powders were produced at temperatures lower than 600 °C in atmospheric-pressure microwave N2 plasma. The particle size of the as-prepared powders was similar to that of the original Al powders. In the second stage, the reaction temperature was increased to 700–800 °C and the reaction time was less than 5 min in N2 plasma. Well-dispersed AlN powders with almost no agglomeration were produced. Moreover, the particle size was lower than that of the original Al.
I. INTRODUCTION
Aluminum nitride (AlN) is an attractive ceramic material for packaging and microelectrical substrates due to its high thermal conductivity [200–320 W/(m K)], low dielectric constant (9), high volume resistivity (1011 X m), low thermal expansion coefficient (2.6–5.5 106 K1), good mechanical strength, non-toxicity, and wide band gap (6.2 eV).1,2 AlN powders have been produced using techniques such as a solid–solid reaction via a carbothermal reduction method that reduces Al2O3 or Al2SiO5 with carbon in a N2 environment at 1650–1800 °C,3,4 liquid–liquid reaction via organometallic precursors (such as [(CH3)2AlNH2]3) reacting with liquid NH3 at 1000 °C,3 chemical vapor deposition reaction of gaseous AlCl3 and gaseous N2/NH3 at 1200–1400 °C,3,5 liquid–gas reaction of metal Al powder via direct thermal nitridation with N2 gas at 1000–1400 °C,3,6 and self-propagating high-temperature synthesis (or combustion synthesis) via ignition of Al and
Contributing Editor: Yanchun Zhou a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.505
NH4X (X 5 F, Cl, Br) compact in N2 at 1000–1200 °C and at high pressure.7,8 The aluminum metal thermal nitridation method is most often used for producing AlN powders. The Al powders are melted at temperatures above the melting point of Al metal (660 °C), causing the aggregation of Al powders, which hinders nitridation. Although adding an additive such as NH4Cl powders to Al powders can reduce agglomeration,7,9 traditional thermal synthesis methods for producing AlN powders usually require a long reaction time (3–6 h) and a high temperature (1000–1500 °C) or post-calcination treat
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