Thermal stability of gas phase magnesium nanoparticles
Thermal stability of gas phase magnesium nanoparticles
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DOI：
10.1063/1.3305453
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发表时间：
2010-03-01
影响因子：
3.2
通讯作者：
Dam, Bernard
中科院分区：
文献类型：
--
作者：
Krishnan, Gopi;Kooi, Bart J.;Dam, Bernard
在这项工作中，我们提出了一个独特的透射电子显微镜研究的热稳定性的气相合成镁纳米粒子，这引起了强烈的兴趣，作为高容量的储氢材料。事实上，在真空和高压气体环境下，在300 ° C下退火的具有MgO壳（类似于3 nm厚）的Mg纳米颗粒在Mg核中显示出蒸发、空隙形成和空隙生长。这主要是由于Mg的向外扩散和蒸发，同时空位向内扩散，导致空穴生长（Kirkendall效应）。Mg蒸发和空隙形成的速率取决于退火条件。在真空中，并且在T=300摄氏度下，对于类似于15-20 nm的尺寸，Mg芯的完全蒸发发生（在几个小时内）。对于尺寸类似于20-50 nm的颗粒观察到空隙形成和生长，而对于尺寸>50 nm观察到稳定的Mg纳米颗粒。此外，即使在相对低温退火（低至60 ℃）下，在15-20 nm尺寸的Mg纳米颗粒中也发生空隙形成和生长，这表明空隙化对于小于10 nm的纳米颗粒将甚至更占主导地位。我们的研究结果证实，Mg蒸发和空隙形成的纳米粒子的尺寸小于50 nm的适用性在储氢提出了强大的障碍，但也可以启发未来的研究方向，以克服这些障碍。(C)2010年美国物理学会。[doi：10.1063/1.3305453]
In this work we present a unique transmission electron microscopy study of the thermal stability of gas phase synthesized Mg nanoparticles, which have attracted strong interest as high capacity hydrogen storage materials. Indeed, Mg nanoparticles with a MgO shell (similar to 3 nm thick) annealed at 300 C show evaporation, void formation, and void growth in the Mg core both in vacuum and under a high pressure gas environment. This is mainly due to the outward diffusion and evaporation of Mg with the simultaneously inward diffusion of vacancies leading to void growth (Kirkendall effect). The rate of Mg evaporation and void formation depends on the annealing conditions. In vacuum, and at T=300 degrees C, the complete evaporation of the Mg core takes place (within a few hours) for sizes similar to 15-20 nm. Void formation and growth has been observed for particles with sizes similar to 20-50 nm, while stable Mg nanoparticles were observed for sizes >50 nm. Furthermore, even at relative low temperature annealing (as low as 60 degrees C), void formation and growth occurs in 15-20 nm sized Mg nanoparticles, indicating that voiding will be even more dominant for nanoparticles smaller than 10 nm. Our findings confirm that Mg evaporation and void formation in nanoparticles with sizes less than 50 nm present formidable barriers for their applicability in hydrogen storage, but also could inspire future research directions to overcome these obstacles. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3305453]