• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Mechanical characterization of perfluorosulfonic acid (PFSA) ionomer membranes.
【24h】

Mechanical characterization of perfluorosulfonic acid (PFSA) ionomer membranes.

机译：全氟磺酸（PFSA）离聚物膜的机械表征。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Perfluorosulfonic Acid (PFSA) ionomer membranes are commonly used as electrolytes in electrochemical devices. The membranes must be able to remain intact and function under a wide range of operating temperatures and humidities for the durability and efficiency of the electrochemical devices, such as fuel cells. Thus, characterization of the structural and physical properties of the ionomer membranes is important for the optimization of the mechanical and sorption behavior of the electrolytes in fuel cells. The goal of this work is this characterization through multiscale mechanistic models and to develop effective strategies to optimize durability.;A geometry-dependent, mechanics model is developed to predict the swelling pressure in, and sorption behavior of, PFSA ionomers during water uptake. The membrane is represented as a two-phase system, where the water-filled hydrophilic domains, in spherical or cylindrical form, are dispersed throughout the hydrophobic backbone, which maintains the structural integrity. The model starts with the non-affine swelling behavior of the membrane to characterize the relationship between macroscopic and microscopic deformation. The results suggest that with increasing temperature or decreasing backbone stiffness, the constraining pressure due to the deformation of the polymer region decreases and therefore, water uptake in the membrane increases. The model can also account for the effect of residual water in the membrane -- which is associated with the membrane's thermal history -- on the sorption behavior. The proposed mechanics-model can serve as a tool for deeper understanding of the sorption behavior of PFSA by bridging the gap between the molecular level descriptions and the experimental observations of macroscopic swelling.;The large-deformation stress-strain behavior of the PFSA membranes is found to follow that of semicrystalline polymers at low water contents, whereas at high water contents, the membrane exhibits characteristic features of elastomers. Pursuing these similarities, measured stress-strain data are reproduced by extending the constitutive models for semicrystalline polymers and elastomers. Then, the structure-property relationship of PFSA membranes is investigated using a mechanics approach for several proposed representative geometries to predict Young's modulus at a wide range of temperatures (from --20 to +85°C) and water fractions (0-0.45). The agreement between the calculated and measured moduli enables us to suggest a possible nanostructural transition for the water domains during sorption, from spherical to cylindrical. The modulus-polymer fraction relationship of the membrane is further discussed and compared with those seen in other porous structures and gels.;Lastly, the mechanical and swelling properties are incorporated into a finite element model to determine the evolution and distribution of the water and swelling-induced stresses in an operating fuel cell. Swelling of the constrained membrane induces compressive stresses, which can lead to plastic deformation and subsequent residual tension upon dehydration. The results suggest that it may be possible to optimize a membrane with respect to its swelling behavior and mechanical properties to achieve better fatigue resistance, potentially enhancing the durability of fuel cell membranes.
机译：全氟磺酸（PFSA）离聚物膜通常用作电化学装置中的电解质。膜必须能够在很宽的工作温度和湿度范围内保持完好无损并发挥作用，以确保电化学装置（例如燃料电池）的耐用性和效率。因此，离聚物膜的结构和物理性质的表征对于优化燃料电池中电解质的机械和吸附行为很重要。这项工作的目的是通过多尺度力学模型进行表征，并开发出有效的策略来优化耐久性。开发了几何相关的力学模型，以预测PFSA离聚物在吸水过程中的溶胀压力和吸附行为。该膜被表示为两相系统，其中球形或圆柱形的充水亲水域分散在整个疏水主链中，从而保持了结构完整性。该模型从膜的非仿射溶胀行为开始，以表征宏观和微观形变之间的关系。结果表明，随着温度升高或骨架刚度降低，由于聚合物区域变形而引起的约束压力降低，因此膜中的吸水率增加。该模型还可以说明膜中残留水与膜的热历史有关对吸附行为的影响。通过弥合分子水平描述与宏观溶胀的实验观察之间的差距，所提出的力学模型可作为更深入了解PFSA吸附行为的工具。PFSA膜的大变形应力-应变行为是发明人发现，在低水含量下，该膜遵循半结晶聚合物，而在高水含量下，该膜表现出弹性体的特征。遵循这些相似性，通过扩展半结晶聚合物和弹性体的本构模型，可以复制测得的应力-应变数据。然后，使用力学方法研究了几种提议的代表性几何结构的PFSA膜的结构-特性关系，以预测在宽温度范围（-20至+ 85°C）和水含量（0-0.45）下的杨氏模量。计算模量与测量模量之间的一致性使我们能够提出在吸附过程中水域从球形到圆柱形的可能的纳米结构转变。进一步讨论膜的模量-聚合物分数关系，并将其与其他多孔结构和凝胶中观察到的关系进行比较。最后，将机械和溶胀特性纳入有限元模型中，以确定水和溶胀的演变和分布在运行的燃料电池中引起的应力。受约束的膜的膨胀会引起压应力，这会导致塑性变形和脱水时的残余张力。结果表明，就其溶胀行为和机械性能而言，有可能优化膜以获得更好的抗疲劳性，从而有可能增强燃料电池膜的耐久性。

著录项

  • 作者

    Kusoglu, Ahmet.;

  • 作者单位

    University of Delaware.;

  • 授予单位 University of Delaware.;
  • 学科 Alternative Energy.;Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 202 p.
  • 总页数 202
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号