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Intermetallics could be the key to faster jets and more efficient car engines. But these heat-resistant, lightweight compounds have stumped scientists for decades. Why do so many break so easily? A team from Brown University, Oak Ridge National Laboratory, and UES Inc. used the world’s most powerful electron microscope to see, for the first time, atomic details that may provide the answer for the most common class of intermetallics. Their results – which could open the door for new materials for commercial use – are published in the current issue of Science. Intermetallics can withstand searing heat and are often lightweight. These properties intrigue the aerospace, defense, energy and automotive industries, which are experimenting with this class of materials in hopes of building high-performance jet engines, improved rocket motors and missile components, more efficient steam turbines and better car engine valves. 然而，许多金属间学很容易破裂。这些化合物在高温下通常比简单金属强。然而，它们在室温下几乎和陶瓷一样脆弱。这种脆弱性限制了他们的商业用途。 但是，为什么大多数金属间的金属层都会破碎呢？如何预防？ 在一份新的科学报告中，布朗大学，橡树岭欧洲杯线上买球国家实验室和UES Inc.的研究人员首次描述了LAVES阶段中详细的原子安排，这是最常见的金属间代理类。他们的发现可能是解释其中一些化合物中这种脆性的起源的第一步。 “早就知道，当将力施加到材料上时，脱位或晶体缺陷会移动。移动这种缺陷的越容易，材料的脆弱就越脆弱。“在具有欧洲杯足球竞彩复杂晶体结构的材料中，例如Laves相，这些缺陷周围的原子排列以及这些缺陷的移动方式尚不清楚。”
在1950年代，提出了一个名为“同步”的概念，以解释该缺陷如何在许多复杂结构中移动。根据该理论，通过在两个相邻原子层中的原子的协调转移来实现这一运动。这种同步运动对于防止一层的原子与相邻层中的原子碰撞是必要的。 但是，由于原子在具有复杂结构的化合物中非常紧密地包装，因为它们处于Laves阶段，因此永远无法证明该理论。没有足够强大的显微镜，可以清楚地显示原子的表现。 进入橡树岭国家实验室的工作人员研究员Matthew Chisholm。Chisholm使用独特的Z对比度扫描透射电子显微镜（STEM）来研究材料中的缺陷。欧洲杯足球竞彩显微镜最近配备了一个像差校正系统，该系统纠正了电子镜头中缺陷所产生的误差。该系统使显微镜的分辨能力翻了一番，使其成为地球上最强大的电子显微镜。 Even though atoms in the test material – the Laves phase Cr2Hf – were spaced less than one ten-billionth of a meter away, the microscope produced crisp images of atoms arranged in tidy columns. Scientists put sheared material in the microscope, saw the defects and analyzed them. “Aberration-correction combined with direct Z-contrast imaging produces an ideal technique to study unknown defect structures,” Chisholm said. “The resulting images have clearly shown for the first time that the accepted dislocation models built up over years of research on simple metals do not work in this more complex material.” Kumar, who coordinated the project, said careful examination confirmed that synchroshear did indeed occur. “This is a first in science,” he said. In the case of Laves phases, it is important to understand defect structures. With this knowledge, materials scientists may be able to identify methods that enhance their motion – and create intermetallic compounds that resist shattering. 该研究说明了橡树岭茎在研究各种晶体结构和缺陷方面的效用。这些发现可以应用于具有其他复杂结构的材料，例如其他类别的金属间和陶欧洲杯足球竞彩瓷，无机盐等。 位于俄亥俄州代顿的材料科学研发公司UES Inc.的已故Peter Hazzled欧洲杯足球竞彩ine欧洲杯线上买球帮助分析和解释了实验结果。Hazzledine是位错理论的领先权威。 美国能源部基础能源科学办公室，布朗大学的国家科学基金会赞助的材料研究科学与工程中心以及美国空军研究实验室资助了欧洲杯线上买球这项工作。欧洲杯足球竞彩 |