片状β-Sialon阵列在Al2O3-C耐火材料中原位定向生长及增强增韧机制

The in-situ orientated growth of flaky β-Sialon arrays in Al2O3-C refractories would form laminated structure with reinforcing and toughening effects in the matrix, which could significantly improve the comprehensive properties of these functional mechanical components in continuous casting process of steel production. At the same time, the safety of this process could also be improved greatly. Through controlling chemical composition, preferential attachment of catalyst and atmosphere, this project will realize the in-situ orientated growth of flaky β-Sialon arrays, which helps to establish new type bonding structure in Al2O3-C refractories. The in-situ orientated growing mechanism of flaky β-Sialon arrays will be revealed from aspects of crystal lattice energy, interfacial reaction/diffusion, surface tension and vapor concentration difference. The controlling mechanism of flaky β-Sialon with shapes of random and array will also be illustrated. The influence mechanism of morphology, composition, preferential orientation and concentration of flaky β-Sialon arrays on high temperature properties, such as strength, toughness, oxidation resistance and thermal shock resistance, of Al2O3-C refractories will be investigated. Furthermore, the relative model between flaky β-Sialon arrays and high temperature properties will be established. The obvious improvement mechanism of resistance to both oxidation and thermal shock for Al2O3-C refractories with flaky β-Sialon arrays would be revealed. The result of this project research will enrich the theory of the bonding system and performance design for carbon containing refractories. It is believed that this project research will significantly facilitate the service life lengthening of Al2O3-C functional refractories and the reliability of continuous casting process.

片状赛隆(β-Sialon)阵列在Al2O3-C耐火材料中原位定向生成，可在基质中形成层状增强增韧结构，显著改善Al2O3-C质连铸功能部件综合性能，有效保障连铸工艺安全性。本项目将通过组分、催化剂优先附着和气氛调控，实现片状β-Sialon阵列式结合相的原位定向生长，从晶核晶面能差异、界面反应与扩散、表面张力及气相浓度梯度等方面，来揭示Al2O3-C耐火材料中片状β-Sialon阵列的原位定向生长机理，并探明片状β-Sialon从随机向阵列生长的控制机制。研究片状β-Sialon形貌分布、组成、择优取向和含量等对材料强度、韧性、抗氧化和抗热震等性能的影响规律，构建片状阵列结构与高温性能间的相关性模型，阐明片状阵列结构对材料高温下抗氧化性和热震稳定性的显著改善机制。研究成果可丰富含碳耐火材料结合体系及性能设计理论，亦有利于Al2O3-C功能耐火材料的长寿化和连铸工艺的可靠性。

洁净钢冶炼和高温工业节能降耗，要求铝碳质耐火材料向着低碳、超低碳化方向发展，然而Al2O3-C质耐火材料低碳化后往往存在着抗热震性降低和抗侵蚀恶化的普遍问题。为解决以上问题，本项目将具有高强和低热膨胀系数的β-Sialon引入到Al2O3-C质耐火材料之中，研究了片状β-Sialon在Al2O3-C质耐火材料中的形成热力学条件。借助第一性原理，考察了不同催化原子作用下的β-Sialon的形貌调控与仿真，揭示了β-Sialon的生长机理。同时，开展了片状β-Sialon结合Al2O3-C质耐火材料抗氧化性和抗热震性的研究。通过上述的研究工作，得到以下结论：.（1）基于拟抛物线规则，得到了β-Sialon生成的标准吉布斯自由能和Z值之间的拟抛物线方程。通过Al-Si-O-N-C系统的反应方程及热力学优势区域相图确定了β-Sialon形成的热力学条件。.（2）探究了一维β-Sialon在铝碳质耐火材料中的合成工艺（煅烧温度、氮气分压、保温时间和硅铝比），及其对铝碳质耐火材料力学性能的影响。研究发现，当煅烧温度提升至1400℃时，开始形成片状β-Sialon相。氮气分压过高或过低都会抑制β-Sialon的生。.（3）在无催化剂的试样中，β-Sialon晶体为圆柱状；Fe2O3催化试样中的β-Sialon晶体呈现二维片状结构，Ni催化试样中的β-Sialon晶体呈现六棱柱状结构。基于密度泛函理论，构建了不同催化剂时的气体吸附模型，发现催化剂的添加增加了晶面对Al2O的吸附，进而增加了Al-O在Si3N4的固溶，从而促进了片状β-Sialon的形成。.（4）在铝碳质耐火材料中引入稀土La2O3可促进片状β-Sialon的生成，这些陶瓷相的形成可增强颗粒之间的结合能力，提升材料的高温力学强度。添加0.6 wt%La2O3试样的高温抗折强度提升了21%；三次热震后试样的残余强度保持率达93.4%。二维片状β-Sialon凭借着穿晶断裂和裂纹偏转而阻碍了裂纹的扩展。