高温下Cr_(2)AlB_(2)粉末在铝碳耐火材料中的结构演变及其对性能的影响

Structural Evolution of Cr_(2)AlB_(2)Powder and Its Effect on Properties in Al2O3–C Refractories at High Temperature

铝碳耐火材料是连铸滑动水口用关键材料,提高其强度和抗氧化性等服役性能,对于保障炼钢过程安全高效生产具有重要的意义。近年来,一种新型的MAB型层状化合物Cr_(2)AlB_(2)受到广泛关注,其具有高断裂韧性、高损伤容限和优异的抗氧化性。本工作在铝碳耐火材料中引入合成的Cr_(2)AlB_(2),借助X射线衍射仪、场发射扫描电子显微镜、透射电子显微镜等测试手段,研究了高温下Cr_(2)AlB_(2)在铝碳材料中的结构演变及其对材料性能影响。结果表明:Cr_(2)AlB_(2)在800~1200℃热处理后逐步分解生成Al2O3包覆CrB的核壳结构,并在核壳结构表面催化生成碳纳米管、碳纤维;在1200~1600℃热处理后,核壳结构内部进一步演变,生成了Cr3C2和BN。因此,Cr_(2)AlB_(2)在铝碳耐火材料中发生的上述结构演变,促进了材料的致密化程度,提高了材料常温抗折强度以及抗氧化性。当Cr_(2)AlB_(2)引入量为1%时,材料性能最佳,经1400、1600℃热处理后的铝碳材料常温抗折强度提升约9%,经1400℃空气中处理后氧化指数从44%降低至31%。

Al2O3–C refractories are important for the continuous casting process.It is essential for safe and effective steel making processes to enhance the strength and oxidation resistance of Al2O3–C refractories.A compound MAB phase Cr_(2)AlB_(2)has attracted recent attention due to its high fracture toughness,high damage tolerance and excellent oxidation resistance.In this work,a ternary layered compound Cr_(2)AlB_(2)was introduced into the Al2O3–C refractories.The structural evolution of Cr_(2)AlB_(2)in Al2O3–C refractories after treated at different temperatures and its effect on the comprehensive properties of Al2O3–C refractories were analyzed by X-ray diffraction,scanning electron microscopy and transmission electron microscopy.The results show that a gradual decomposition of Cr_(2)AlB_(2)in Al2O3–C refractories generates a core–shell structure of CrB and Al2O3covered with Al2O3,and catalyses the formation of carbon nanotubes and carbon fibers on the surface of the core–shell structure after thermal treatment at 800–1200℃.Cr3C2covered by BN structure is formed inside the core-shell structure after thermal treatment at 1200–1600℃.As a result,the densification of Al2O3–C refractories is facilitated,and the cold modulus of rupture and oxidation resistance is enhanced.The cold modulus of rupture after coking at 1400–1600℃is increased by approximately 9%,and the oxide index after treated in air at 1400℃is reduced from44%to 31%.