固体材料中气泡在电子束辐照下的微观结构变化

In the experiment known as sonoluminescence, bubbles in liquid would emit light under ultrasonic wave. This phenomenon has attracted lots of people to research, but its mechanism is not yet clear. It is reasonable to think that similar phenomenon involving bubbles may happen in solid materials, but its opacity prevented researchers to detect such kind of phenomenon. This project would investigate the change of gas bubbles by transmission electron microscope (TEM), being able to overcome the difficulty of opacity of materials. Thin film samples of pure metals, such aluminum, copper, would be implanted at first by gas ions, such deuterium, hydrogen, helium, argon, using ion accelerator, followed by electron beam irradiation under TEM. The electron diffraction tool of TEM would be used to analysis the change of crystal, and the energy dispersive spectrometer in TEM would be used to detect possible unique X-ray signal during electron irradiation. As a part of this project, we have found that electron diffraction rings of polycrystalline appeared together when irradiating deuterium bubbles or hydrogen bubbles in aluminum. It is considered that a kind of heat emission occurred when the gas bubbles were irradiated by electron beam. This project will investigate in detail the relation between the heat emission and the accelerating voltage of TEM, implanted gas, or solid metal type. From the results the possible mechanism of the heat emission would be detected.

声致发光实验一直是物理学界的热门课题之一。 声致发光实验由于涉及的是透明液体中的气泡的发光现象，因而容易观察，再现性好，实验难度不大。但是产生声致发光现象的机理仍未明了。受此实验现象的启发，人们有理由认为，固体材料中可能也存在类似的“气泡发光”现象。之所以未有此类实验现象的报道，可能是由于固体材料的不透明性而使得这些现象不为我们所知。本课题利用离子加速器在室温下对铝、铜等固体金属材料注入氘、氢、氦、氩等离子，在金属材料中形成气泡，然后在透射电镜中对这些中气泡进行电子束辐照，观察在电子束辐照下气泡的形貌变化，同时可以利用透射电镜的电子衍射功能分析材料晶体结构变化，利用透射电镜的EDS能谱分析实验过程中可能释放的射线信号。本课题的前期实验已发现，铝中氘气泡或氢气泡在电子束辐照后，在选区电子衍射花样中出现了表示多晶存在的衍射环。这表明电子束辐照气泡时，发生某种放热现象，从而使附近的铝先熔化后再凝

本课题利用离子加速器在室温下对金属材料进行离子注入，在金属材料中形成气泡和晶体缺陷，然后在透射电镜中对这些气泡和晶体缺陷进行电子束辐照，观察其变化，尤其是间隙型位错环在电子辐照下的一维迁移现象进行了观察和分析。发现在200keV电子辐照下,注氢纯铝中的位错环可多个、同时发生一维迁移运动,也可单个、独立进行一维迁移运动。位错环沿柏氏矢1/3<111>的方向可进行微米尺度的一维长程迁移,沿柏氏矢量1/2<110>的方向一维迁移也可达数百纳米。电子束辐照时产生的间隙原子浓度梯度是引起位错环一维迁移并决定其迁移方向的原因。位错环发生快速一维迁移时,其后会留下一条运动轨迹；位错环一维迁移的速率越快,运动的轨迹则越长,在完成迁移过后的几十秒内这些运动轨迹会逐渐消失。 这种一维迁移轨迹是本课题组首次观察到的现象，另外也许是一种可以获得有关氢存在信息的新方法。点缺陷团簇的一维迁移实验，难度比较高，属于辐照损伤基础研究的前沿课题。本研究成果的获得，将为此领域的深入工作，提供了很好的经验基础。

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