Fast one‐step carbothermal reduction and nitridation method using nano‐sized Al₂O₃ and carbon black to prepare aluminium oxynitride powder for highly transparent ceramics

Abstract

By fast heating the nano-sized Al 2 O 3 and carbon black mixtures at 50 • C/min to 1750 • C for 30-120 min, single-phase AlON powders were successfully obtained by a fast one-step carbothermal reduction and nitridation (CRN) method. The AlON ceramics pressureless sintered at 1880 • C for 150 min by these powders show high transmittances up to 83%-84%, which indicates that the proposed fast one-step CRN method is an effective and efficient way with strong robustness to synthesize single-phase AlON powder for highly transparent AlON ceramics. It was found that α-Al 2 O 3 particles do not have enough time to aggregate and coalesce during heating due to the tremendously shortened heating span, which significantly inhibited particle coarsening until the formation of AlON starts. The fast-formed AlON further inhibits the coarsening of α-Al 2 O 3 during dwelling. Consequently, single-phase AlON powder of small primary particles can be obtained after 30 min dwelling at 1750 • C.

A novel strategy for the fabrication of AlN–AlON refractories: Nitrogen gas pressure sintering of Al4O4C

“…Al 2 O 3 and AlN diffraction peaks appeared after thermal treatment at 1600°C. The nitridation process is strongly dependent on atmosphere, pressures, temperature, and time 5,15,16,28 . Compare to the pressureless nitridation of Al 4 O 4 C, 28 the results indicate that GPS authentically promote the nitridation process.…”

“…Al 2 O 3 and AlN diffraction peaks appeared after thermal treatment at 1600 • C. The nitridation process is strongly dependent on atmosphere, pressures, temperature, and time. 5,15,16,28 Compare to the pressureless nitridation of Al 4 O 4 C, 28 the results indicate that GPS authentically promote the nitridation process. When the temperature rose to 1700 XPS was carried out to certify the combination of valence bonds of the specimen heated at 1700 • C. Figure 2A shows the specimen contained Al, O, C, and N elements after nitridation.…”

“…[11][12][13][14] To fabricate AlN-AlON composites, complex raw materials of Al, AlN, Al 2 O 3, and C were commonly prepared respectively prior to the mechanical mixing. [15][16][17] Although it is simple and readily regulates the constituent of the raw-material powders, the chemical compositions tend to exhibit inhomogeneous locally in the final composites due to the challenge in thorough mixing, and the mixing degree of various raw-material powders is also restricted by the grain size. In addition, the interfacial reaction between AlN and AlON on the mechanical properties is another main aspect that has to be considered.…”

Study on robust additive of CaCO3 for fast fabrication of highly transparent AlON ceramics by pressureless sintering

“…[1][2][3][4][5] AlON ceramics can be fabricated by consolidation of AlON powder or solid reaction of Al 2 O 3 /AlN. [6][7][8][9][10] Currently, most of AlON ceramics were prepared by consolidation of AlON powder by different sintering techniques, such as pressureless sintering (PS), [11][12][13][14] PS combined with hot isostatic pressing (HIP), [15][16][17][18][19] hot pressing, 20 and spark plasma sintering. 21,22 Among them, PS is the most favorite way for its low cost and feasibility in practice.…”

“…Aluminum oxynitride (AlON), as one of the transparent polycrystalline ceramics, exhibits excellent optical and mechanical properties, enabling its potential applications in infrared windows/domes and transparent armors 1–5 . AlON ceramics can be fabricated by consolidation of AlON powder or solid reaction of Al 2 O 3 /AlN 6–10 . Currently, most of AlON ceramics were prepared by consolidation of AlON powder by different sintering techniques, such as pressureless sintering (PS), 11–14 PS combined with hot isostatic pressing (HIP), 15–19 hot pressing, 20 and spark plasma sintering 21,22 .…”