Mechanism for Hydrothermal-carbothermal Synthesis of AlN Nanopowders

doi:10.15541/jim20240279

Abstract

Abstract:

Currently, the carbothermal reduction-nitridation (CRN) process is the predominant method for preparing aluminum nitride (AlN) powder. Although AlN powder prepared by CRN process exhibits high purity and excellent sintering activity, it also presents challenges such as the necessity for high reaction temperatures and difficulties in achieving uniform mixing of its raw materials. This study presents a comprehensive investigation into preparation process of AlN nanopowders using a combination of hydrothermal synthesis and CRN. In the hydrothermal reaction, a homogeneous composite precursor consisting of carbon and boehmite (γ-AlOOH) is synthesized at 200 ℃ using aluminum nitrate as the aluminum source, sucrose as the carbon source, and urea as the precipitant. During the hydrothermal process, the precursor develops a core-shell structure, with boehmite tightly coated with carbon (γ-AlOOH@C) due to electrostatic attraction. Compared with conventional precursor, the hydrothermal hybrid offers many advantages, such as ultrafine particles, uniform particle size distribution, good dispersion, high reactivity, and environmental friendliness. The carbon shell enhances thermodynamic stability of γ-Al₂O₃ compared to the corundum phase (α-Al₂O₃) by preventing the loss of the surface area in alumina. This stability enables γ-Al₂O₃ to maintain high reactivity during CRN process, which initiates at 1300 ℃, and concludes at 1400 ℃. The underlying mechanisms are substantiated through experiments and thermodynamic calculations. This research provides a robust theoretical and experimental foundation for the hydrothermal combined carbothermal preparation of non-oxide ceramic nanopowders.

Key words: aluminum nitride, carbothermal reduction-nitridation, mechanism, hydrothermal synthesis, precursor

CLC Number:

TM282

FENG Guanzheng, YANG Jian, ZHOU Du, CHEN Qiming, XU Wentao, ZHOU Youfu. Mechanism for Hydrothermal-carbothermal Synthesis of AlN Nanopowders[J]. Journal of Inorganic Materials, 2025, 40(1): 104-110.

Figures/Tables 17

Fig. 1 TEM image, HAADF image and elemental mappings of the precursor (a) TEM; (b) HAADF; (c-f) Elemental mappings of (c) Al, (d) O, (e) C, and (f) N

Fig. 2 (a) γ-AlOOH and (b) carbon electrically charged in an aqueous solution

Fig. 3 (a) Zeta potential of γ-AlOOH and carbon dispersions at different pH and (b) mechanism of precursor formation

Fig. 4 XRD patterns of the nitridation products synthesized at (a) different temperatures and (b) different C/Al molar ratios at 1500 ℃

Table 1 Compilation of measured and calculated surface energies in literature

Phase	Surface energy/ (J·m^-2)	Ref.	Method
α-Al₂O₃	2.04	[34]	MD simulation
	2.64	[33]	High-temperature calorimetry
	2.57	[35]	Static lattice calculation
	2.03	[36]	MD simulation
	4.89	[37]	Ab initio calculation
γ-Al₂O₃	0.79	[34]	MD simulation
	1.66	[33]	High-temperature calorimetry
	1.53	[38]	High-temperature calorimetry

Fig. 5 (a) Gibbs free energy of the transformation from γ-Al2O3 to α-Al2O3 at different temperatures calculated as a function of specific surface area, and (b) N2 adsorption-desorption isotherm of γ-Al2O3 with inset showing pore size distribution determined by application of BJH method to the isotherm

Fig. S1 (a) XRD pattern and (b) FESEM image of the precursor obtained at 200 ℃

Fig. S2 TEM images of the precursor (a) Precursor; (b) γ-AlOOH; (c) Carbon

Fig. S3 (a, b) Survey spectra of the precursors at (a) Al : U : C=1 : 2 : 0 and (b) Al : U : C=1 : 2 : 4; (c-f) XPS spectra of (c) Al2s, (d) C1s, (e) O1s, and (f) N1s for the precursors at Al : U : C=1 : 2 : 4

Fig. S4 FTIR spectra of the precursors (a) Al : U : C=1: 2: 0; (b) Al : U : C=1 : 2 : 4

Fig. S5 Experimental procedure for validating the mechanism of precursor formation through electrostatic adsorption

Fig. S6 XRD patterns of the products in Fig. S5 (a) Boehmite; (b) Precursor; (c) AlN

Fig. S7 FESEM images of the products in Fig. S5 (a) Boehmite; (b) Precursor; (c) AlN

Fig. S8 TGA curve of the product calcined at 1400 ℃ in air

Fig. S9 FESEM image of AlN nanopowder produced at 1400 ℃

Fig. S10 FESEM image of the product after calcination at 1200 ℃ and carbon removal at 700 ℃

Fig. S11 Structure diagram of α-Al2O3, γ-Al2O3 and AlN

References 39

[1]	YIM W M, PAFF R J. Thermal expansion of AlN, sapphire, and silicon. Journal of Applied Physics, 1974, 45(3): 1456.
[2]	SLACK G A, TANZILLI R A, POHL R O, et al. The intrinsic thermal conductivity of AIN. Journal of Physics and Chemistry of Solids, 1987, 48(7): 641.
[3]	SELVADURAY G, SHEET L. Aluminium nitride: review of synthesis methods. Materials Science & Technology, 1993, 9(6): 463.
[4]	RUTKOWSKI P J, KATA D. Thermal properties of AlN polycrystals obtained by pulse plasma sintering method. Journal of Advanced Ceramics, 2013, 2(2): 180.
[5]	SHEPPARD L M. Aluminum nitride: a versatile but challenging material. American Ceramic Society Bulletin, 1990, 69(11): 1801.
[6]	BAIK Y, DREW R A L. Aluminum nitride: processing and applications. Key Engineering Materials, 1996, 122: 553.
[7]	LEE H M, BHARATHI K, KIM D K. Processing and characterization of aluminum nitride ceramics for high thermal conductivity. Advanced Engineering Materials, 2014, 16(6): 655.
[8]	CHIKAMI H, FUKUSHIMA J, HAYASHI Y, et al. Kinetics of microwave synthesis of AlN by carbothermal-reduction-nitridation at low temperature. Journal of the American Ceramic Society, 2018, 101(11): 4905.
[9]	WANG Y M, QIAO L, ZHENG J W, et al. Preparation of AlN with low agglomeration using polyethylene glycol and emulsifier to disperse the ultrafine raw powders. Ceramics International, 2023, 49(1): 1390.
[10]	KOMEYA K, MATSUKAZE N, MEGURO T. Synthesis of AlN by direct nitridation of Al alloys. Journal of the Ceramic Society of Japan, 1993, 101(1180): 1319.
[11]	KIMURA I, ICHIYA K, ISHII M, et al. Synthesis of fine AlN powder by a floating nitridation technique using an N₂/NH₃ gas mixture. Journal of Materials Science Letters, 1989, 8(3): 303.
[12]	WEI Z L, LI K, GE B Z, et al. Synthesis of nearly spherical AlN particles by an in-situ nitriding combustion route. Journal of Advanced Ceramics, 2021, 10(2): 291.
[13]	YAMAKAWA T, TATAMI J, WAKIHARA T, et al. Synthesis of AlN nanopowder from γ-Al₂O₃ by reduction-nitridation in a mixture of NH₃-C₃H₈. Journal of the American Ceramic Society, 2006, 89(1): 171.
[14]	ZHANG Q H, GAO L. Synthesis of nanocrystalline aluminum nitride by nitridation of δ-Al₂O₃ nanoparticles in flowing ammonia. Journal of the American Ceramic Society, 2006, 89(2): 415.
[15]	KIM J K, JUNG W S. Nitridation of δ-alumina to aluminum nitride under a flow of ammonia and its mechanism. Journal of the Ceramic Society of Japan, 2011, 119(1389): 351.
[16]	JUNG W S. Synthesis of aluminum nitride powder from δ-alumina nanopowders under a mixed gas flow of nitrogen and hydrogen. Ceramics International, 2012, 38(1): 871.
[17]	YOSHIMURA M, BYRAPPA K. Hydrothermal processing of materials: past, present and future. Journal of Materials Science, 2008, 43(7): 2085.
[18]	WANG Q, LI H, CHEN L Q, et al. Monodispersed hard carbon spherules with uniform nanopores. Carbon, 2001, 39(14): 2211.
[19]	GONG Y T, XIE L, LI H R, et al. Sustainable and scalable production of monodisperse and highly uniform colloidal carbonaceous spheres using sodium polyacrylate as the dispersant. Chemical Communications, 2014, 50(84): 12633. DOI PMID
[20]	CHEN W, LI D, TIAN L, et al. Synthesis of graphene quantum dots from natural polymer starch for cell imaging. Green Chemistry, 2018, 20(19): 4438.
[21]	XIANG M, ZHOU Y, XU W, et al. Hydrothermal-carbothermal synthesis of highly sinterable AlN nanopowders. Journal of the American Ceramic Society, 2017, 100(6): 2482.
[22]	XIANG M, ZHOU Y F, XU W T, et al. Transparent AlN ceramics sintered from nanopowders produced by the wet chemical method. Journal of the Ceramic Society of Japan, 2018, 126(4): 241.
[23]	YANG J, CONG Y, LING J R, et al. Preparation of transparent AlON from powders synthesized by novel CRN method. Journal of the European Ceramic Society, 2022, 42(3): 935.
[24]	FANKHÄNEL J, SILBERNAGL D, GHASEM Z K M, et al. Mechanical properties of boehmite evaluated by atomic force microscopy experiments and molecular dynamic finite element simulations. Journal of Nanomaterials, 2016, 2016(1): 5017213.
[25]	WU J, XU W, DONG T, et al. Self-assembly of graphene reinforced ZrO₂ composites with deformation-sensing performance. Ceramics International, 2022, 48(21): 32131.
[26]	ANSI V A, SREELAKSHMI P, RAVEENDRAN P, et al. Table sugar derived carbon dot—a promising green reducing agent. Materials Research Bulletin, 2021, 139: 111284.
[27]	YANG J, WANG L H, JIANG X X, et al. AlN nanoparticles prepared through a gelation-polymerization process. Ceramics International, 2020, 46(11): 17486.
[28]	HE Q, QIN M L, HUANG M, et al. Mechanism and kinetics of combustion-carbothermal synthesis of AlN nanopowders. Ceramics International, 2017, 43(12): 8755.
[29]	MAO X X, XU Y G, MAO X J, et al. Synthesis of fine AlN powders by foamed precursor-assisted carbothermal reduction- nitridation method. Journal of Inorganic Materials, 2019, 34(10): 1123.
[30]	CARSTENS S, MEYER R, ENKE D. Towards macroporous α-Al₂O₃—routes, possibilities and limitations. Materials, 2020, 13(7): 1787.
[31]	CESTEROS Y, SALAGRE P, MEDINA F, et al. Several factors affecting faster rates of gibbsite formation. Chemistry of Materials, 1999, 11(1): 123.
[32]	MCHALE J M, NAVROTSKY A, PERROTTA A J. Effects of increased surface area and chemisorbed H₂O on the relative stability of nanocrystalline γ-Al₂O₃ and α-Al₂O₃. The Journal of Physical Chemistry B, 1997, 101(4): 603.
[33]	MCHALE J M, AUROUX A, PERROTTA A J, et al. Surface energies and thermodynamic phase stability in nanocrystalline aluminas. Science, 1997, 277(5327): 788.
[34]	BLONSKI S, GAROFALINI S H. Molecular dynamics simulations of α-alumina and γ-alumina surfaces. Surface Science, 1993, 295(1/2): 263.
[35]	TASKER P W. Surfaces of magnesia and alumina. Advances in Ceramics, 1984, 10: 176.
[36]	MACKRODT W C, DAVEY R J, BLACK S N, et al. The morphology of α-Al₂O₃ and α-Fe₂O₃: the importance of surface relaxation. Journal of Crystal Growth, 1987, 80(2): 441.
[37]	CAUSÀ M, DOVESI R, PISANI C, et al.Ab initio characterization of the (0001) and (101̄0) crystal faces of α-alumina. Surface Science, 1989, 215(1/2): 259.
[38]	CASTRO R H R, USHAKOV S V, GENGEMBRE L, et al. Surface energy and thermodynamic stability of γ-alumina: effect of dopants and water. Chemistry of Materials, 2006, 18(7): 1867.
[39]	TSUGE A, INOUE H, KASORI M, et al. Raw material effect on AIN powder synthesis from Al₂O₃ carbothermal reduction. Journal of Materials Science, 1990, 25(5): 2359.