Development of new heat-resistant structural composite materials by MGC bulk and fiber crystals

本文研究了可在空气气氛中1500℃左右高温区用作结构材料的熔融生长复合材料（MGC）。建立了MGC材料的晶体生长方法。我们应用形状控制技术，实现了纤维状、板状和棒状MGC材料的制备。研究了几种MGC晶体体系，发现Y_3Al_5O_<12>（YAG）/Al_2O_3（蓝宝石）/ZrO_2（氧化锆）三元体系强度最高. MGC材料晶体生长方法的建立为了开发一种可在1700℃下使用的热稳定增强材料，我们研究了高质量、均匀、微观结构可控的共晶晶体的稳定生长条件。通过对坩埚、热区等微下拉法的改进，我们建立了一种新的共晶晶体生长技术。阐明了共晶化合物的相对取向和控制其显微组织的方法 ...更多信息 通过TEM电子衍射分析了YAG和蓝宝石的成分.弯月面受坩埚端面形状的控制，我们发现弯月面与生长晶体的形状有很强的关系。在此基础上，生长出直径达5 mm φ的块状共晶、宽度达10 mm的片状共晶和直径约150μm的纤维状共晶。该晶型控制技术可应用于相关行业的各个领域.高温强度我们研究了几种共晶系统，以寻找比蓝宝石/YAG二元系统具有更高强度的材料。其中，蓝宝石/YAG/氧化锆三元体系显示出最高的强度。测试了晶体在空气气氛中的室温抗拉强度和在Ar气氛中的1500℃抗拉强度，并测量了晶体的热膨胀系数等基本物理性能，室温抗拉强度达到1730 MPa，Ar气氛中的1200℃抗拉强度达到970 MPa，是目前世界上最高的抗拉强度。少

In this study, we investigated Melt Growth Composite (MGC) materials which can be used as structural materials at high temperature region around 1500℃ in air atmosphere. We established crystal growth method of MGC materials. We applied shape-control technique and achieved to fabricate fiber, plate and rod-shaped MGC materials. We studied several systems of MGC crystals and discovered highest strength in Y_3Al_5O_<12>(YAG)/AL_2O_3(sapphire)/ZrO_2(zirconia) ternary system.1. Establishment of crystal growth method of MGC materialsTo develop a thermally stable reinforcement materials which can be used at 1700℃, we investigated the conditions for stable growth of high quality, homogeneous eutectics crystals with controlled microstructure. By modifying the micro-pulling-down method with crucible, hot zone etc., we have established a new crystal growth technique for the eutectic crystals. We have clarified the relative orientations and method to control the microstructure of the eutectic comp … More onents of YAG and sapphire, by TEM electron diffraction analysis.2. Shaped crystal growthThe meniscus was well controlled by the end shape of the crucible, and we found a strong relation between meniscus and shape of grown crystals. Based on this observation, we achieved growing bulk eutectic crystals up to 5mmφ in diameter, plate crystals up to 10mm width, fiber crystals around 150μm in diameter. This crystal shape control technique can be applied for various field of related industry.3. Strength in high temperatureWe investigated several eutectic systems to search for the material which has higher strength than sapphire/YAG binary system. Among these, sapphire/YAG/zirconia ternary system showed highest strength. We tested tensile strength at room temperature in air atmosphere and at 1500℃ in Ar, and measured fundamental physical properties of the grown crystals such as thermal expansion coefficient etc. Tensile strengths reached 1730MPa at room temperature and 970MPa at 1200℃ in Ar atmosphere which is highest value in the world. Less