孔径尺寸可控超塑性Al2O3基闭孔耐火骨料及闭孔形成机理的研究

It’s proposed to substitute closed-pore porous refractory aggregate for traditional dense aggregate as refractory raw materials to fabricate refractory taking aim at the lightweight refractory and energy-saving of metallurgical vessel. After controlling the speed of densification of Al2O3-based ceramic and oxidation of SiC, closed-pore porous Al2O3-based refractory aggregate will be fabricated by employing its superplasticity and using SiC as high-temperature pore-forming agent. Taking the controlling of closed-pore size distribution as study point, SiC with Al2O3 coating, which prepared by sol-gel method, will be used as pore-forming agent to improve the structure of pore walls in refractory aggregate. Taking the tailoring of closed-pore size as study point, the sintering behavior, superplastic deformation ability and reaction behavior of SiC in Al2O3-based refractory aggregate will be studied. The mathematical model among superplastic deformation ability, partial pressure in the closed-pore and closed-pore size will be established. In addition, the effects of closed-pore porous refractory aggregate on properties of refractories will be investigated. This proposal is not only an academic subject on fabrication of closed-pore porous ceramics by employing their superplasticity, but also a basic issue to study on a new-type refractory. The implementation of this proposal is of great significance for improving efficient use ability of mineral resources and energy resources.

以耐火材料的轻量化和冶金容器的节能减排为目的，本申请项目提出以闭孔多孔耐火骨料替代传统致密骨料为耐火原料并开展相关研究。通过控制Al2O3基陶瓷的致密化烧结速率和SiC氧化速率，利用Al2O3基陶瓷的高温超塑性，将SiC高温反应生成的气体封闭于陶瓷基体中制备闭孔多孔Al2O3基耐火骨料。通过采用溶胶-凝胶法在SiC颗粒表面包覆Al2O3涂层，并将其引入Al2O3基耐火骨料中，用以改善闭孔孔壁结构，以实现孔径尺寸分布的可控化。通过研究Al2O3基体材料的烧结行为、超塑性变形能力及SiC的高温反应过程，构建超塑性变形能力、闭孔内分压与闭孔孔径大小的数学模型，以实现孔径大小的可控化。最后考察闭孔多孔耐火骨料对耐火制品性能的影响。本研究既是利用超塑性特征制备闭孔多孔陶瓷所涉及的学术问题，又是一种新型耐火材料研究方面的基础问题，对促进“资源+能源”的高效利用具有积极的意义。

本项目利用Al2O3基材料在高温下具有超塑性的特点，通过控制其超塑性变形能力和SiC发泡剂的高温反应过程，成功地制备了闭孔多孔Al2O3基耐火骨料。利用溶胶-凝胶法在SiC颗粒表面包覆了Al2O3涂层，改善了闭口气孔的孔壁结构，实现了孔径尺寸分布的均匀性。通过研究原料粒度、烧结制度和添加剂对Al2O3基材料高温超塑性变形能力及其烧结行为的影响，明确了闭口气孔孔径大小的控制因素，实现了孔径尺寸大小可控化。利用热力学计算和动力学实验研究，揭示了多孔Al2O3基耐火骨料中闭口气孔的形成机制。研究结果表明：随着MgO含量、SiC含量和保温时间的增加，闭口气孔率和孔径大小均增大。涂层后的SiC可有效改善闭口气孔孔径分布的均匀性。闭口气孔的形成主要为SiC高温反应生成了SiO、CO和Mg气体，在Al2O3基材料高温超塑性变形能力的作用下，被封闭于材料中。制备闭孔多孔Al2O3基耐火骨料的最佳工艺为：以亚微米Al2O3粉末为原料，MgO添加量为10wt%，包覆Al2O3涂层的SiC添加量为1wt%，在1600℃保温6h。所制备的闭孔耐火骨料孔径大小约2μm，且孔径分布均匀，同时表现出优良的使用性能。该项目的成功实施，对于新型闭孔多孔耐火骨料的研究和开发具有重要的理论价值和实际意义。