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

本文研究了熔融生长复合材料（MGC），该材料可在空气中1500℃左右的高温区域用作结构材料。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。我们研究了几种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研制一种可在1700℃下使用的热稳定增强材料，研究了高质量、均匀、显微结构可控的共晶晶体的稳定生长条件。通过坩埚、热区等对微拉下法进行改进，建立了一种新的共晶生长工艺。通过TEM电子衍射分析，明确了钇铝石榴石和蓝宝石共晶组分的相对取向和控制微观结构的方法。半月板的生长受坩埚端部形状的控制，并且发现半月板与生长晶体的形状有很强的关系。基于这一观察，我们实现了直径达5mmφ的大块共晶晶体、宽度达10mm的板晶、直径约150μm的纤维晶体的生长。这种晶形控制技术可应用于相关行业的各个领域。为了寻找比蓝宝石/钇铝石榴石双晶体系具有更高强度的材料，我们研究了几种共晶体系。其中蓝宝石/YAG/氧化锆三元体系强度最高。在室温和1500℃氩气条件下进行了拉伸强度测试，并测量了生长晶体的基本物理性质，如热膨胀系数等。室温抗拉强度达1730MPa， 1200℃氩气抗拉强度达970MPa，为世界最高。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