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首页> 美国卫生研究院文献>Materials >Contamination Effects on Improving the Hydrogenation/Dehydrogenation Kinetics of Binary Magnesium Hydride/Titanium Carbide Systems Prepared by Reactive Ball Milling
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Contamination Effects on Improving the Hydrogenation/Dehydrogenation Kinetics of Binary Magnesium Hydride/Titanium Carbide Systems Prepared by Reactive Ball Milling

机译：反应球磨制备的二元氢化镁/碳化钛体系的污染对改善加氢/脱氢动力学的影响

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Ultrafine MgH2 nanocrystalline powders were prepared by reactive ball milling of elemental Mg powders after 200 h of high-energy ball milling under a hydrogen gas pressure of 50 bar. The as-prepared metal hydride powders were contaminated with 2.2 wt. % of FeCr-stainless steel that was introduced to the powders upon using stainless steel milling tools made of the same alloy. The as-synthesized MgH2 was doped with previously prepared TiC nanopowders, which were contaminated with 2.4 wt. % FeCr (materials of the milling media), and then ball milled under hydrogen gas atmosphere for 50 h. The results related to the morphological examinations of the fabricated nanocomposite powders beyond the micro-and nano-levels showed excellent distributions of 5.2 wt. % TiC/4.6 wt. % FeCr dispersoids embedded into the fine host matrix of MgH2 powders. The as-fabricated nanocomposite MgH2/5.2 wt. % TiC/4.6 wt. % FeCr powders possessed superior hydrogenation/dehydrogenation characteristics, suggested by the low value of the activation energy (97.74 kJ/mol), and the short time required for achieving a complete absorption (6.6 min) and desorption (8.4 min) of 5.51 wt. % H2 at a moderate temperature of 275 °C under a hydrogen gas pressure ranging from 100 mbar to 8 bar. van’t Hoff approach was used to calculate the enthalpy (∆H) and entropy (∆S) of hydrogenation for MgH2, which was found to be −72.74 kJ/mol and 112.79 J/mol H2/K, respectively. Moreover, van’t Hoff method was employed to calculate the ΔH and ΔS of dehydrogenation, which was found to be 76.76 kJ/mol and 119.15 J/mol H2/K, respectively. This new nanocomposite system possessed excellent absorption/desorption cyclability of 696 complete cycles, achieved in a cyclic-life-time of 682 h.
机译：超细MgH2纳米晶体粉末是通过在50 bar氢气压力下进行200 h高能球磨后，对元素Mg粉进行反应性球磨而制得的。所制备的金属氢化物粉末被2.2重量％的污染物污染。使用由相同合金制成的不锈钢铣削工具引入粉末中的FeCr不锈钢的％。合成后的MgH2掺杂有先前制备的TiC纳米粉，该粉被2.4 wt。 ％FeCr（研磨介质的材料），然后在氢气气氛下球磨50小时。与所制备的纳米复合材料粉末的微观和纳米水平以外的形态学检查相关的结果表明，其良好的分布为5.2 wt。％。 TiC / 4.6重量％ ％FeCr弥散体嵌入MgH2粉末的精细主体基质中。制成的纳米复合材料MgH2 / 5.2 wt。 TiC / 4.6重量％ ％FeCr粉末具有优异的加氢/脱氢特性，这是由于活化能值低（97.74 kJ / mol），以及达到5.51 wt。％的完全吸收（6.6分钟）和脱附（8.4分钟）所需的时间短。在275°C的中等温度和100 mbar至8 bar的氢气压力下的H2％。使用van’t Hoff方法计算MgH2的氢化焓（ΔH）和熵（ΔS），分别为-72.74 kJ / mol和112.79 J / mol H2 / K。此外，采用van’t Hoff方法计算脱氢的ΔH和ΔS，分别为76.76 kJ / mol和119.15 J / mol H2 / K。这种新的纳米复合材料系统具有出色的696个完整循环的吸收/解吸循环能力，循环寿命为682 h。

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