Dataset Information

Investigation on the Microscopic/Macroscopic Mechanical Properties of a Thermally Annealed Nafion® Membrane.

ABSTRACT: The Nafion® electrolyte membrane, which provides a proton pathway, is an essential element in fuel cell systems. Thermal treatment without additional additives is widely used to modify the mechanical properties of the membrane, to construct reliable and durable electrolyte membranes in the fuel cell. We measured the microscopic mechanical properties of thermally annealed membranes using atomic force microscopy with the two-point method. Furthermore, the macroscopic property was investigated through tensile tests. The microscopic modulus exceeded the macroscopic modulus over all annealing temperature ranges. Additionally, the measured microscopic modulus increased rapidly near 150 °C and was saturated over that temperature, whereas the macroscopic modulus continuously increased until 250 °C. This mismatched micro/macroscopic reinforcement trend indicates that the internal reinforcement of the clusters is induced first until 150 °C. In contrast, the reinforcement among the clusters, which requires more thermal energy, probably progresses even at a temperature of 250 °C. The results showed that the annealing process is effective for the surface smoothing and leveling of the Nafion® membrane until 200 °C.

SUBMITTER: Pham TA

PROVIDER: S-EPMC8620802 | biostudies-literature | 2021 Nov

REPOSITORIES: biostudies-literature

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Investigation on the Microscopic/Macroscopic Mechanical Properties of a Thermally Annealed Nafion<sup>®</sup> Membrane.

Pham Tuyet Anh TA Koo Seunghoe S Park Hyunseok H Luong Quang Thien QT Kwon Oh Joong OJ Jang Segeun S Kim Sang Moon SM Kim Kyeongtae K

Polymers 20211120 22

The Nafion<sup>®</sup> electrolyte membrane, which provides a proton pathway, is an essential element in fuel cell systems. Thermal treatment without additional additives is widely used to modify the mechanical properties of the membrane, to construct reliable and durable electrolyte membranes in the fuel cell. We measured the microscopic mechanical properties of thermally annealed membranes using atomic force microscopy with the two-point method. Furthermore, the macroscopic property was invest ...[more]

PMID: 34833318

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Project description:Four multicomponent charge gradients containing acidic and basic functionalities were prepared via sol-gel processes and the controlled-rate infusion (CRI) method to more clearly understand how preparation conditions influence macroscopic properties. CRI is used to form gradients by infusing reactive alkoxysilanes into a glass vial housing a vertically oriented modified silicon wafer. The concentration and time of infusion of the silane solutions were kept constant. Only the sequence of infusion of the silane solutions was changed. The first set of samples was prepared by initially infusing a solution containing 3-aminopropyltriethoxysilane (APTES) followed by a mercaptopropyltrimethoxysilane (MPTMS) solution. The individual gradients were formed either in an aligned or opposed fashion with respect to the initial gradient. The second set of samples was prepared by infusing the MPTMS solution first followed by the APTES solution, again in either an aligned or opposed fashion. To create charge gradients (NH3 +, SO3 -), the samples were immersed into H2O2. The extent of modification, the degree of protonation of the amine, and the thicknesses of the individual layers were examined by X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry. The wettability of the individual gradients was assessed via static contact angle measurements. The results demonstrate the importance of infusion order and how it influences the macroscopic and microscopic properties of gradient surfaces including the surface concentration, packing density, degree of protonation, and ultimately wettability. When the gradient materials are prepared via infusion of the APTES sol first, it results in increased deposition of both the amine and thiol groups as evidenced by XPS. Interestingly, the total thickness evaluated from ellipsometry was independent of the infusion order for the aligned gradients, indicative of significant differences in the film density. For the opposed gradients, however, the infusion of APTES first leads to a significantly thicker composite film. Furthermore, it also leads to a more pronounced gradient in the protonation of the amine, which introduces a very different surface wettability. The use of aminosilanes provides a viable approach to create gradient surfaces with different functional group distributions. These studies demonstrate that the controlled placement of functional groups on a surface can provide a new route to prepare gradient materials with improved performance.

Dataset Information

Investigation on the Microscopic/Macroscopic Mechanical Properties of a Thermally Annealed Nafion® Membrane.

Publications

Investigation on the Microscopic/Macroscopic Mechanical Properties of a Thermally Annealed Nafion<sup>®</sup> Membrane.

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