Bystrzycki J, Polanski M, Plocinski T
Faculty of Advanced Technology and Chemistry, Military University of Technology, 00-908 Warsaw, Poland.
J Nanosci Nanotechnol. 2009 Jun;9(6):3441-8. doi: 10.1166/jnn.2009.ns14.
We studied a possibility of destabilization of MgH2 by chemical reaction with Si by using a nano-engineering method for reducing diffusion distances and increasing surface area. The structure, morphology, chemical composition and dehydriding properties were investigated by XRD, SEM, EDS, DTA-TG and the volumetric Sievert method. The commercial MgH2 and Si powder mixture corresponded to the stoichiometry of the ideal Mg2Si intermetallic compound was ball-milled under argon atmosphere to reach a nanocrystalline composite structure (< 50 nm). The ball-milling of the MgH2-Si mixture leads to the formation only a small amount of the Mg2Si compound. Microstructural studies showed that Si after ball-milling is heterogeneously distributed on the surface of MgH2 particles and incorporated in the nanocrystalline MgH2 matrix, forming a nanocomposite structure. The sluggish destabilization of MgH2 by solid-state reaction with Si forming the Mg2Si intermetallic compound was observed at 250 degrees C. The XRD and EDS analysis confirmed that the Mg2Si compound is formed after the dehydrogenation of the synthesized MgH2-Si composite. The activation energy of the destabilization reaction for the investigated composite significantly decreased (162 kJ/mol) as compared with unmilled MgH2-Si powder mixture (213 kJ/mol).
我们通过一种纳米工程方法研究了利用与硅发生化学反应使氢化镁失稳的可能性，该方法可缩短扩散距离并增加表面积。采用X射线衍射（XRD）、扫描电子显微镜（SEM）、能谱仪（EDS）、差示热分析-热重联用（DTA-TG）以及容量法西韦特法对其结构、形态、化学成分和脱氢性能进行了研究。将对应于理想金属间化合物Mg2Si化学计量比的商用氢化镁和硅粉混合物在氩气气氛下进行球磨，以形成纳米晶复合结构（<50纳米）。氢化镁-硅混合物的球磨仅导致少量Mg2Si化合物的形成。微观结构研究表明，球磨后的硅在氢化镁颗粒表面呈不均匀分布，并掺入纳米晶氢化镁基体中，形成纳米复合结构。在250℃下观察到氢化镁通过与硅发生固态反应形成金属间化合物Mg2Si而出现缓慢失稳现象。XRD和EDS分析证实，合成的氢化镁-硅复合材料脱氢后形成了Mg2Si化合物。与未球磨的氢化镁-硅粉末混合物（213千焦/摩尔）相比，所研究复合材料失稳反应的活化能显著降低（162千焦/摩尔）。
