高导热铁尾矿多孔陶瓷及其相变复合材料的设计、制备与性能研究

The steel production in China ranked first in the world for many years. A huge amount of iron tailings, which produced by iron ore processing, could only be accumulated because of the limitation of reuse technology. The iron tailings not only occupied valuable land resources, but also caused a great threat to the environment. So it is urgent that accelerating the pace of comprehensive utilization of the iron tailings. In this project, fine mud-like iron tailings, which is completely unable to use currently, is used as the main raw material to prepare porous iron tailings ceramics by adding the appropriate graphite powder. The reaction law and mechanism between the tailings components and carbon in the sintering process will be studied, and the graphite content, sintering environment, sintering temperature and soaking time etc. will be optimized to promote the thermal conductivity of iron tailings ceramics. On this basis, porous iron tailings ceramics with high thermal conductivity are formed by stirring foaming and gel-casting process. And then the porous ceramics are used as a carrier to prepare a new phase change energy storage composite through the spontaneous melt infiltration process of the phase change materials paraffin, which can absorb or release heat by melting or solidification at a certain temperature. The energy storage mechanism and characteristics of the phase change composite are investigate detailly as the foundation of its application in the solar hot water floor heating system, power generation and other fields. This project is the first to explore the preparation of phase change composite using iron tailings as the raw materials, which opening up a new direction for iron tailings resources utilization. At the same time, the thermal conductivity of iron tailings ceramics can be significantly improved through the transformation of oxides in the tailings into metals or carbides by carbon thermal reduction reaction. Therefore, a new type of phase change composites with high efficiency of heat transfer will be obtained.

我国钢铁产量多年来高居世界首位，铁矿石选矿后排放的巨量铁尾矿受利用技术所限而大量堆积，不仅占用宝贵的土地资源，而且已对环境造成巨大威胁。本项目以目前完全无法利用的泥状细颗粒铁尾矿为原料，添加适量石墨粉均匀混合，深入研究烧结过程中尾矿各组分与碳的反应规律与机理，以提高铁尾矿陶瓷热导率为目标优化石墨含量、烧结环境、烧结温度与时间等参数。在此基础上采用搅拌发泡-凝胶注模成形工艺制备高导热多孔陶瓷，再以其为载体，通过熔融浸渗工艺将其与相变材料石蜡复合，制备出可在略高于室温下通过石蜡的熔融/凝固来吸收/释放热量的新型高性能相变复合材料，在太阳能热水地板采暖系统等领域应用前景广阔，社会效益与生态环境效益显著。本项目首次探索利用铁尾矿制备相变复合材料，开辟了尾矿资源化利用新方向；同时通过碳热还原反应将尾矿中部分氧化物转变为碳化物或金属相，可显著提高陶瓷载体的热导率，从而提升相变复合材料的换热效率。

本项目以细颗粒高硅铁尾矿为主要原料，通过模压成形及泡沫注凝成形-反应烧结工艺制备了碳化硅多孔陶瓷，深入研究了铁尾矿的碳热还原反应过程与反应机理，优化了原料配比与制备工艺。以碳化硅多孔陶瓷为载体，采用熔融浸渗工艺制备出的新型石蜡/多孔陶瓷复合相变材料，探讨了材料的力学性能、储能特性、循环稳定性及其影响因素，为铁尾矿在相变储能材料领域的应用奠定了基础，并开辟了铁尾矿资源化利用的新途径。本项目取得以下主要研究成果：.1..利用铁尾矿与石墨之间的碳热还原反应可获得碳化硅多孔陶瓷，铁尾矿中SiO2与石墨的碳热还原反应起始于1300 ℃~1400 ℃，1500 ℃保温2 h后，样品中原主晶相石英的XRD衍射峰消失，反应产物SiC成为新的主晶相，1600 ℃烧结后，SiC含量最高。.2..随铁尾矿和石墨的混合原料中石墨含量增加，SiC产物增多，石墨含量为25~30 wt.%时SiC含量达到最大值。确定最佳石墨含量为25 wt.%，最优工艺参数为 1600 ℃下保温2 h，此时样品中SiC 含量可达89 wt.%。.3..在混合原料中加入一定量的SiC粉，可有效提高多孔陶瓷的强度和热导率，确定最优的SiC加入量为15 wt.%，获得了高孔隙率 (91.6%)，较高压缩强度 (1.19 MPa) 和热导率 (0.31 W/m·K) 的碳化硅多孔陶瓷，与相同孔隙率的普通铁尾矿多孔陶瓷相比，热导率提高1~2个数量级。.4..以碳化硅多孔陶瓷为载体，采用熔融自发浸渗工艺成功制备了石蜡/多孔陶瓷复合相变储能材料。石蜡充满多孔载体的孔隙，浸渗率达97.5%。.5..随着浸渗温度升高，石蜡的浸润效率显著提高。最优浸渗温度为140 °C。相同浸渗工艺下，较小的孔径尺寸和较高的孔隙率有助于提高液相石蜡的浸渗效率。.6..多孔陶瓷载体与石蜡界面结合良好，两者之间可产生协同强化作用，使得复合相变材料的抗压强度明显改善。与纯石蜡相比，复合相变材料的传热效率可提升一倍以上，熔化时间缩短约一半。.7..石蜡/多孔陶瓷复合相变材料具有优异的循环稳定性。100次熔化/凝固循环后，多孔陶瓷载体与石蜡之间具有良好的物理和化学相容性，相变材料的熔点基本恒定，熔化潜热略有下降，并在80次循环后趋于稳定。