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在氢气气氛下用反应球磨法制备了镁碳复合储氢材料70Mg30C,用透射电子显微镜(TEM)和选区电子衍射(SAED)观测了材料的微观形貌和晶态特征,用X射线衍射仪(XRD)分析了其物相组成,并通过材料放氢的p-c-T曲线得到的放氢平台压强以及Van’t Hoff方程计算了材料放氢的焓变和熵变。结果表明:材料的主相是MgH2,并混有少量的Fe和MgO;在一定范围内,延长球磨时间可使材料的粒径进一步减小,并可增加非晶纳米晶在材料中的含量,而且可降低材料的放氢平台压强和材料放氢时的焓变,从而降低材料的相结构稳定性,增强体系的解氢能力,最终改善材料的放氢性能;在300~380℃范围内,lnpH2与1/T基本呈线性关系,同时材料具有较长的放氢平台和较高的放氢量。
The Mg-C composite hydrogen storage material 70Mg30C was prepared by reactive ball milling under hydrogen atmosphere. The microstructure and crystalline characteristics of the material were observed by transmission electron microscopy (TEM) and selected area electron diffraction (SAED) XRD, and the enthalpy and entropy change of the material were calculated by the pressure of the hydrogen release platform obtained from the pcT curve of material discharge and Van’t Hoff equation. The results show that: the main phase of the material is MgH2, and a small amount of Fe and MgO mixed; within a certain range, extending the milling time can further reduce the particle size of the material, and can increase the amorphous nanocrystalline content in the material, But also can reduce the pressure of the hydrogen releasing platform of the material and the enthalpy change of the material when the hydrogen is discharged, so as to reduce the phase structure stability of the material, enhance the hydrogen desorption capability of the system and finally improve the hydrogen releasing performance of the material; lnpH2 and 1 / T basically linear relationship, while the material has a longer release of hydrogen platform and a higher amount of hydrogen release.