锆英石微波碳热原位合成ZrB2-SiC复合粉体及其应用基础研究

Low-carbon refractories are very important for clean steel production and energy-saving of iron-steel industry, the investigations of new nonoxides to replace graphite are crucial for the development of low-carbon refractories. Zirconium diboride (ZrB2) possesses many unique properties, such as high melting point (>3000 C), high hardness, high oxidation resistance at elevated temperatures, good thermal shock resistance, and excellent corrosion resistance against molten iron and slags. Thus, ZrB2-based composites are suitable candidates for high temperature applications of structural ceramics and refractories. It was reported that the life-span of ZrB2-C is two times longer than that of ZrO2-C. However, the high production cost and the low oxidation resistance limits the application of ZrB2 in large scales in refractories. The present research project aims to in-stiu synthesize ZrB2-SiC composite powders by microwave carbothermal reaction using zircon as main raw materials. The following investigations will be carried out in the project, (1) the synthesis mechanism of the ZrB2-SiC composite powders and the optimum of the crystalline phases in final product; (2) The role of the impurities arising from raw zircon in the microwave carbothermal reaction; (3) The controlling formation of SiC whisker in the final ZrB2-SiC composite powders; (4) The preparation of ZrB2-SiC/MgO-C low-carbon refractories and its high temperature properties. The basic theory on the formation of ZrB2-SiC composites powders will be elucidated on the basis of the experimental results and new kinds of refractories with good thermal shock resistance, slag erosion resistance and long life-span for clean steel production will be prepared.

研究开发一种能全部或者部分替代石墨的新型非氧化物材料对低碳耐火材料的发展至关重要。ZrB2是很有发展前景的高性能结构陶瓷和耐火材料，ZrB2-C质耐火材料的使用寿命是ZrO2-C质材料的2倍。但是目前ZrB2价格高、抗氧化性能差等缺点限制了其在耐火材料中的大规模应用。为解决该问题，本课题拟采用锆英石、硼酸/氧化硼/B4C、碳等为原料，采用微波碳热还原工艺原位合成成本低廉、抗氧化性能良好的ZrB2-SiC复合粉体。重点研究，(1) ZrB2-SiC复合粉体的生成机理及产物相成分优化和控制；(3)锆英石中主要杂质的去向及作用；(2)SiC晶须在ZrB2-SiC复合粉体中的可控原位生成。(4) ZrB2-SiC/MgO-C低碳耐火材料的制备及其高温使用性能等内容。通过研究为微波碳热高效、低成本制备ZrB2-SiC复合粉体奠定理论基础，为我国纯净钢生产提供新型高效、长寿命的低碳或者无碳耐火制品

ZrB2-SiC具有良好的抗热震稳定性能、抗渣侵蚀性能及抗氧化性能，是很有前途的新型耐火材料。针对低碳、无碳耐火材料的发展趋势，为寻求可替代天然石墨的新材料，项目以天然锆英石等为主要原料，通过微波碳热还原法、微波溶胶凝胶碳热还原法以及熔盐镁热还原法合成了ZrB2-SiC、ZrC-SiC、ZrB2及ZrC等耐高温粉体，研究ZrB2-SiC/MgO-C复合低碳耐火材料的常温物理性能、高温力学性能、热震稳定性、抗氧化性及抗渣性。.采用微波碳热还原硼化法在n(ZrSiO4):n(B2O3):n(C)=1:1.5:10、1300℃/3h的条件下可以合成纯相的ZrB2-SiC复合粉体。适当延长保温时间和埋SiC粉有利于微波碳热还原硼化反应的进行，ZrB2-SiC复合粉体中ZrB2呈粒状或柱状，SiC呈纤维状。微波碳热还原硼化法合成ZrB2-SiC复合粉体的合成温度比传统加热工艺低200℃左右。采用溶胶凝胶、微波硼热/碳热还原工艺合成ZrB2粉体的反应温度为1573 K，该温度也比常规加热工艺的反应温度低200 K；采用微波硼热/碳热还原工艺可在1573 K/3 h的条件下合成纯相的ZrB2-SiC超细复合粉体，该温度比常规加热合成复合粉体的温度低约200K，复合粉体中ZrB2和SiC的晶粒尺寸分别为58 nm和27 nm；采用熔盐法制备了CaZrO3、La2Zr2O7、La2Ce2O7及La2Ti2O7等耐高温粉体。随着ZrB2-SiC复合粉体对石墨替代量的增加，ZrB2-SiC/MgO-C复合低碳耐火材料在埋碳气氛下的抗热震性有所降低，但在氧化气氛下的抗热震性则逐渐增强；用ZrB2-SiC替代石墨可以显著提高低碳耐火材料的抗氧化性能；相同渣蚀条件下，ZrB2-SiC复合粉体替代石墨对低碳耐火材料的抗渣性能影响不大。.项目研究结果为微波碳热高效、低成本制备ZrB2-SiC复合粉体奠定了理论基础，为我国纯净钢生产提供新型高效、长寿命的低碳或者无碳耐火制品。