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

Abstract

A novel strategy was exploited for the fabrication of AlN-AlON refractories via nitrogen gas pressure sintering of Al 4 O 4 C. The phase transformation and microstructure evolution during the reaction at 1600-1800 • C were thoroughly investigated. The results indicated that the high N 2 pressure was essential for the effective nitridation. The in situ generated AlN-AlON refractories had a homogeneous local chemical composition, and the (101) plane of AlN and the (222) lattice plane of Al 5 O 6 N were bonded at their grain boundary with no amorphous phase. The as-fabricated AlN-AlON refractories treated at 1700 • C by a 20 atmnitrogen pressure exhibited an optimum bending strength of 111.10 MPa, combining an apparent porosity of 20% with a low bulk density of 1.97 g/cm 3 . The diffusion of the generated oxygen led to an increase in the apparent porosity and decrease in the bulk density at 1800 • C. Furthermore, the fabrication mechanism of AlN-AlON refractories under the nitrogen gas-pressure was discussed.

Effect of In Situ Mg-Sialon on the Oxidation Behavior of Low-Carbon MgO-C Refractories

“…Mg-sialon(s) + O2(g) → MgO(s) + Al2O3(s) + SiO2(s) + N2(g) (5) Mg-sialon(s) + CO(g) → MgO(s) + Al2O3(s) + SiO2(s) + N2(g)+ C(s) (6) MgO(s) + Al2O3(s) = MgAl2O4(s), (7) The ΔrG θ for Equations ( 5) and ( 6) could not be calculated due to a lack of thermodynamic data from the Mg-sialon phase (Mg3.29Si1.89Al2.82O4.41N4.59), and this reaction was given based on the relevant references and the present experimental results [26]. Meanwhile, the thermodynamic calculations for Equations ( 4) and ( 7) are shown in Figure 4.…”

“…Magnesia-carbon refractories have been widely employed as the linings of BOF/LD converters, electric arc furnaces (EAF), and refining furnaces because of their excellent resistance to thermal shock and slag corrosion [1,2]. The application of low-carbon refractories became one of the prime tasks due to the demand for advanced steel-making technologies [3,4], energy saving, and carbon neutralization in recent years [5,6]. However, the decrease in graphite content would increase thermal stress and impair corrosion resistance; meanwhile, a loose decarbonization layer was easily caused by the oxidation of graphite, further damaging the overall performance of MgO-C refractories.…”

Enhanced oxidation resistance of low‐carbon MgO–C refractories with Al3BC3–Al antioxidants: A synergistic effect

“…7,8,9,[18][19][20][21][22][23] Ternary carbides have outstanding properties for high-temperature applications, such as low density, high strength, low thermal expansion coefficient, high resistance to thermal shock, good thermal conductivity, and hydration resistance. [24][25][26][27][28][29][30][31] Considerable research efforts have been performed to develop alternative antioxidants with optimized properties and less drawbacks, and the exploration and application of single ternary carbide, such as Al 4 O 4 C, "Al 8 B 4 C 7 ," Al 4 SiC 4 , Ti 3 AlC 2 , and Ti 3 SiC 2 , have been proved to have benefits. 25,27,[29][30][31] Besides the usage of single antioxidant, the combination of two antioxidants like B 4 C-Al additions has also been developed 32 ; the advantage of this type of antioxidants is that they protect carbon oxidation more effectively than the single one.…”

“…The most acceptable and effective approach is the usage of antioxidant in the form of metal powders, alloys, carbides, borides, and even oxides 7,8,9,18–23 . Ternary carbides have outstanding properties for high‐temperature applications, such as low density, high strength, low thermal expansion coefficient, high resistance to thermal shock, good thermal conductivity, and hydration resistance 24–31 . Considerable research efforts have been performed to develop alternative antioxidants with optimized properties and less drawbacks, and the exploration and application of single ternary carbide, such as Al 4 O 4 C, “Al 8 B 4 C 7 ,” Al 4 SiC 4 , Ti 3 AlC 2 , and Ti 3 SiC 2 , have been proved to have benefits 25,27,29–31 .…”