高温氮化反应烧成高强度氮化物结合氧化物-碳系材料的原理及性能研究

The novel preparation method of nitride reaction-bonded oxide-carbon system refractory composites would be studied in this proposal. The oxide-graphite/carbon refractory composites with high strength, excellent slag resistant, less pollution for molten steel, good thermal shock assistant and antioxidant ability are prepared by using nitriding reaction and sintering at high temperatures according to the design of combination phase, which could solve many problems existing in the carbon-containing refractory without chemical bond, such as low strength and more pollution for molten steel. So the research of the proposal has important theoretical and applied significances. The preparation mechanism, parameters and regularity of nitride combination phase of nitride reaction-bonded oxide-graphite/carbon system will be designed and analyzed. The dynamic model of reaction and sintering of silicon nitride phase in magnesia-carbon system and the combination phase between silicon nitride or sialon in alumina-carbon system will be established. The control mechanism of synthesis reaction will be clarified. The phase composition and microstructure of composite materials made by nitrided and sintered at high temperatures will be intensively studied. The chemical combination mechanism between oxide and graphite/carbon will be established. And the major relation between preparation process and microstructure will be demonstrated. The properties of nitride bonded oxide-carbon composite refractory will be characterized. All results will provide theoretical basis for the production and application of clean steel making.

项目拟研究氮化物结合氧化物-碳系复合耐火材料反应烧成制备的新途径，即通过对氧化物-石墨/碳素材料结合相的设计，利用高温反应氮化烧结技术，制备适合冶金工业需要的高强度、优异抗渣性能、对钢水污染小、热震稳定性好、抗氧化能力强的氧化物-碳复合材料,有效地解决现有含碳材料无化学结合导致的强度不高、易污染钢水等问题，项目具有重要的理论及应用意义。项目将设计和研究氮化烧成氧化物-石墨/碳素材料之间制备氮化物结合相的制备机理、参数及其规律性，构建高温氮化烧成镁碳系统中氮化硅相和铝碳系统氮化硅/Sialon结合相的反应生成及烧结的动力学模型，探明合成反应的控制机制，对高温氮化烧成复合材料的物相组成和显微结构进行深入研究，建立氮化物结合相在氧化物-石墨/碳素材料之间化学结合的机制，探明制备过程与显微结构之间的主要关系，表征项目制备的氮化物结合氧化物-碳复合耐火材料的性能，为其在洁净钢生产使用提供理论基础。

针对含碳耐火材料中碳和氧化物之间无化学结合、强度低等问题，项目采用高温原位氮化制备氮化物-氧化物-碳复合材料，研究了高温氮化原位反应技术和工艺参数、原料种类和粒度、成型结合方式对Sialon-Al2O3-C(SAC)、Si3N4-MgO-C(SMC)材料及Sialon/AlON -MgAl2O4-C (SMAC/AMAC)材料的结构及性能的作用机制，建立了原位反应动力学和渣侵蚀动力学模型；确定了材料内部化学结合的成键方式和位相关系，实现了通过原位氮化生成氮化物将氧化物和石墨结合的思想。.SMC的制备条件是1350°C/2h和1500°C/3h、氮气流量60ml/min及成型压力400MPa，β-Si3N4晶粒尺寸较大，性能好。制备SAC的适合条件是1450°C/4h、氮气流量90ml/min及成型压力300MPa，β-Sialon晶粒尺寸较大，性能好。SAC和SMC在制备过程中均受化学反应和扩散共同控速，表观活化能分别是370 kJ/mol和226kJ/mol。制备SMAC和AMAC的条件是1450°C/3h和1550°C/3h。刚玉粉与α-Al2O3超微粉复合添加，SAC形成致密网状结构，强度较高。添加200目石墨时，SAC内部生成锥状β-Sialon晶粒，材料强度较高。添加325目石墨时，SMC内部生成柱状β-Si3N4晶粒，材料性能较好。硅粉粒度的变化对SMC的性能影响不大。采用木质磺酸钙溶液作结合剂再氮化，SAC和SMC的综合性能较好。建立了SAC、SMAC、AMAC和SMC材料的抗渣侵蚀模型。材料内部生成的Sialon、AlON和Si3N4抑制渣的侵蚀和渗透，材料渣蚀表观活化能分别是：SAC为214kJ/mol，SMAC为202kJ/mol，AMAC是141kJ/mol，SMC为170kJ/mol。在SAC中，材料中含有β-Sialon相和Si2N2O相，结合键有Al-O、N-O、O-Si、C-C；在SMC中，材料中含有Si3N4相和SiC相，结合键有Mg-O、N-Si、O-O、Si-Si、Si-C。材料中位相关系分别是Sialon(1 0 1)//石墨(0 0 1)和Sialon(1 1 0)//Al2O3(0 1 2)，Si3N4(1 0 1)//石墨(0 0 1)、Si3N4(1 2 0)//MgO(1 0 0)。