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Modeling and predicting total hydrogen adsorption in nanoporous carbon materials for advanced nuclear systems
Journal of Nuclear Materials ( IF 2.8 ) Pub Date : 2018-09-07 , DOI: 10.1016/j.jnucmat.2018.09.009
Stephen T. Lam , Ronald Ballinger , Charles Forsberg

The retention of hydrogen in a variety of disordered carbon materials including graphene nanoplatelets and amorphous carbon was measured by volumetric adsorption and modeled using thermodynamic methods. To date, high temperature hydrogen adsorption research in carbon has predominately focused on graphite used as plasma-facing materials in fusion systems, moderators in high temperature gas reactors, and fuel components in molten-salt cooled reactors. Tritium, a hydrogen isotope that is produced in these systems, adsorbs on carbon surfaces that could be used effectively as sinks to remove tritium. Since hydrogen has chemical similarity to tritium, it can be used as a surrogate to simplify experimental studies, greatly expediting materials exploration. Thus, an understanding and prediction of hydrogen behavior on carbon materials is essential for evaluation of performance and safety of present and future reactor designs. Chemisorption experiments were conducted on 9 different materials with a range of surface areas, pore volumes, and pore size distributions. The results showed that carbons with higher surface area and pore volume exhibit higher hydrogen adsorption, which is attributed to larger quantities of active sites. Further, hydrogen adsorption was found to increase in materials with greater micropore (<10 Å) surface area, which was interpreted as being a result of in-pore trapping. In contrast to previous studies that assumed a single isotherm, four isotherms were examined including two- and three-parameter methods and homo- and heterogeneous surface methods—the Langmuir, Temkin, Freundlich and Sips isotherms. Analyses of non-linear models by ordinary least squares and Marquardt's percent standard deviation minimization were performed. It was found that constant order homogeneous models that have been used in the past lack the ability to describe pathways and reactions steps that occur. Further, it was found that Sips isotherm consistently provided the best minimization of error and most accurate prediction.



中文翻译:

建模和预测用于先进核系统的纳米多孔碳材料中的总氢吸附

通过体积吸附测量氢在各种无序碳材料(包括石墨烯纳米片和无定形碳)中的保留量,并使用热力学方法进行建模。迄今为止,碳中高温氢吸附的研究主要集中在用作聚变系统中面向等离子体的材料,高温气体反应堆中的调节剂以及熔融盐冷却反应堆中的燃料成分的石墨上。systems是这些系统中产生的氢同位素,它吸附在碳表面上,可以有效地用作去除sink的吸收剂。由于氢与tri具有化学相似性,因此可以用作替代品以简化实验研究,从而大大加快了材料探索的速度。因此,了解和预测碳材料上氢的行为对于评估当前和将来的反应堆设计的性能和安全性至关重要。化学吸附实验是在9种不同的材料上进行的,这些材料具有一定的表面积,孔体积和孔径分布。结果表明,具有较高表面积和孔体积的碳表现出较高的氢吸附性,这归因于大量的活性位点。此外,发现具有更大的微孔(<10Å)表面积的材料中的氢吸附会增加,这被认为是孔内捕集的结果。与以前的假设单一等温线的研究相反,我们检查了四个等温线,包括两参数和三参数方法以及同质和异质表面方法(Langmuir,Temkin,Freundlich和Sips等温线。通过普通最小二乘法和Marquardt标准偏差百分比最小化对非线性模型进行了分析。发现过去使用的恒定阶均质模型缺乏描述发生的途径和反应步骤的能力。此外,还发现Sips等温线始终能够最大程度地减少误差并提供最准确的预测。

更新日期:2018-09-07
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