Synthesis of AlN Powder by Carbothermal Reduction-nitridation of Alumina/Carbon Black Foam

doi:10.15541/jim20170067

Abstract

Abstract:

Alumina/carbon black foam was prepared by mechanical foaming and aqueous gelcasting and used as precursor for the production of AlN powder. The foam with large open pores ensures homogeneous solid-gas reaction during carbothermal reduction-nitridation (CRN) process. Further, the solid-gas contact is enlarged by oppositely feeding the foam and nitrogen in a vertical furnace. Solid-gas reaction efficiency of the CRN process was greatly enhanced when total porosity of the foam was ≥80%. XRD results revealed that γ-Al₂O₃ transformed to α-Al₂O₃ and then was carbothermal reduction-nitridationed to be AlN phase. AlN powder with an average particle size of less than 1 µm was synthesized at 1650℃ and contained 32.9wt% nitrogen.

Key words: chemical preparation, porosity, carbothermal reduction, aluminum nitride

CLC Number:

TQ174

MAO Xi-Xi, LI Jun, ZHANG Hai-Long, XU Yong-Gang, WANG Shi-Wei. Synthesis of AlN Powder by Carbothermal Reduction-nitridation of Alumina/Carbon Black Foam[J]. Journal of Inorganic Materials, 2017, 32(10): 1115-1120.

Figures/Tables 10

Fig. 1 Effect of dispersant on the Zeta potential of alumina and carbon black slurry

Fig. 2 Rheological behavior of Al2O3/C slurries with different solids loading and dispersant content

Fig. 3 Evolution of the foaming capacity versus surfactant content

Fig. 4 SEM micrographs of porous Al2O3/C foams with different surfactant additions(a) 0vol%; (b) 2.0vol%; (c) 2.4vol%; (d) 4.0vol%

Fig. 5 Effects of surfactant content on total porosity and open-pore ratio of foams

Fig. 6 Effect of porosity on nitridation rate under 1600℃

Fig. 7 XRD patterns of the products by heating Al2O3/C foams at different temperatures

Fig. 8 SEM micrographs of foam with addition of 2.4vol% surfactant before (a) and after (b) being calcined at 1300℃ for 2 h

Fig. 9 SEM photographs of AlN powders synthesized at different temperatures for 2 h(a) 1550℃; (b) 1600℃; (c) 1650℃

Table 1 Nitrogen and oxygen content of AlN powder synthesized at different temperatures

Element content/wt%	Reaction temperature/℃
Element content/wt%	1550	1600	1650
Nitrogen	31.9	32.4	32.9
Oxygen	1.6	1.2	1.1

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