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首页> 外文学位 >Mechanical and water sorption properties of nafion and composite nafion/titanium dioxide membranes for polymer electrolyte membrane fuel cells.
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Mechanical and water sorption properties of nafion and composite nafion/titanium dioxide membranes for polymer electrolyte membrane fuel cells.

机译：用于聚合物电解质膜燃料电池的nafion和复合nafion /二氧化钛膜的机械和水吸附特性。

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The mechanical properties of the membranes used in polymer electrolyte membrane fuel cells are important to the performance and longevity of the cell. The speed and extent of membrane water uptake depend on the membrane's viscoelastic mechanical properties, which are themselves dependent on membrane hydration, and increased hydration improves membrane proton conductivity and fuel cell performance. Membrane mechanical properties also affect durability and cell longevity, preventing membrane failure from stresses induced by changing temperature and water content during operational cycling. Further, membrane creep and stress-relaxation can change the extent of membrane/electrode contact, also changing cell behavior. New composite membrane materials have exhibited superior performance in fuel cells, and it is suspected that improved mechanical properties are responsible.; Studies of polymer electrolyte membrane (PEM) fuel cell dynamics using Nafion membranes have demonstrated the importance of membrane mechanical properties, swelling and water-absorption behavior to cell performance. Nonlinear and delayed dynamic responses to changing operating parameters were unexpected, but reminiscent of polymer viscoelastic behavior and water sorption dynamics, illustrating the need to better understand membrane properties to design and operate fuel cells. Further, Nafion/TiO2 composite membranes developed by the Princeton Chemistry Department improve fuel cell performance, which may be due to changes in membrane microstructure and enhanced mechanical properties.; Mechanical properties, stress-relaxation behavior, water sorption and desorption rates and pressures exerted during hydration by a confined membrane have been measured for Nafion and for Nafion/TiO2 composite membranes. Mechanical properties, including the Young's modulus and limits of elastic deformation are dependent on temperature and membrane water content. The Young's modulus decreases with increasing water content and temperature, is less temperature-dependent in hydrated membranes than dry membranes and is slightly higher in the composite membranes. Stress-relaxation also follows two distinct behaviors depending on its temperature, humidity and degree of strain. The water sorption and desorption dynamics are not controlled by diffusion rates but by interfacial mass transport resistance and, during sorption, by the kinetics of swelling and stress-relaxation. Pressure exerted by a swelling membrane scales with membrane thickness, is slightly higher for the composite membranes and is relevant to fuel cell design.
机译：用于聚合物电解质膜燃料电池的膜的机械性能对于电池的性能和寿命很重要。膜吸水的速度和程度取决于膜的粘弹性机械性能，而膜粘弹性机械性能本身又取决于膜的水合作用，而增加的水合作用可改善膜的质子传导性和燃料电池的性能。膜的机械性能也会影响耐久性和电池寿命，从而防止膜在操作循环中因温度和水含量变化而产生的应力而导致膜失效。此外，膜蠕变和应力松弛可以改变膜/电极接触的程度，也改变细胞行为。新的复合膜材料在燃料电池中表现出优异的性能，并且怀疑改善的机械性能是负责任的。使用Nafion膜对聚合物电解质膜（PEM）燃料电池动力学进行的研究表明，膜机械性能，溶胀和吸水行为对电池性能至关重要。对变化的运行参数的非线性和延迟动态响应是出乎意料的，但是让人想起聚合物的粘弹性行为和吸水动力学，这说明需要更好地了解膜的特性以设计和运行燃料电池。此外，普林斯顿化学系开发的Nafion / TiO2复合膜改善了燃料电池的性能，这可能是由于膜微结构的变化和机械性能的提高。对于Nafion和Nafion / TiO2复合膜，已测量了密闭膜在水合过程中施加的机械性能，应力松弛行为，吸水和解吸速率以及施加的压力。包括杨氏模量和弹性变形极限在内的机械性能取决于温度和膜中的水分含量。杨氏模量随水含量和温度的升高而降低，在水合膜中的温度依赖性低于干燥膜，而在复合膜中则略高。应力松弛还根据其温度，湿度和应变程度遵循两种不同的行为。水的吸附和解吸动力学不受扩散速率的控制，而受界面传质阻力的控制，在吸附过程中受溶胀和应力松弛动力学的控制。膨胀膜所施加的压力随膜厚度成比例增加，对于复合膜而言稍高，并且与燃料电池设计有关。

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