Papers by Keyword: Nafion

Abstract: This chapter is devoted to organic-inorganic composite ion exchange resins and membranes. We ascertain interrelation between composition, morphology and porous structure of the materials on the one hand and ion transport through them on the other hand. The composites for different practical application (fuel cells, ion exchange columns, electrodialysis) are in a focus of attention. Porosity of a polymer constituent of the composite was determined with a method of standard contact porosimetry, which gives information about pores in a very wide diapason (from 2 nm to 200 μm). In this context, pore formation in ion exchange polymers during swelling is considered. A number of parameters, which are obtained from porosimetric measurements, can be used for interpretation of ion transport regularities, particularly evolution of electrical conductivity. Embedded non-aggregated nanoparticles, their aggregates and agglomerates affect differently porosity of the polymer constituent: they are able to block, stretch and squeeze pores, As a result, the composites demonstrates different rate of ion transport depending on amount and size of the inorganic particles. The approach to purposeful formation of one or other types of particles has been proposed.

Abstract: Phosphate buffer saline (PBS) is commonly applied as an electrolyte for glucose sensor application because ion concentration and osmolality of PBS are similar to the human body. Therefore, it is important to study the effect of concentration and pH of PBS to the electrocatalytic performance of the modified electrode in glucose detection. In this study, the modification of indium tin oxide (ITO) glass electrode by utilizing iron oxide nanoparticles (IONP) coated with citric acid (CA), glucose oxidase (GOx) enzyme and Nafion layer (Nafion/Gox/IONP-CA/ITO) were performed. IONP was prepared by using the precipitation technique through formation of colloidal stable IONP in water at physiological pH. The size of IONP-CA precipitates was ~19 nm with maghemite (γ-Fe₂O₃) phase characterized using transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. Increasing the PBS concentration increased the electrocatalytic performance of the bioelectrode whereas pH of PBS buffer solution affected the GOx bioactivity. The modified electrode Nafion/Gox/IONP-CA/ITO displayed good electrochemical and electrocatalytic performance in glucose detection.

Abstract: In this work, a novel electrochemical sensor was proposed for the simultaneous determination of fat-soluble vitamins (A, D, E, K) using a screen-printed graphene/Nafion electrode (SPGNE). The scanning electron microscopy was used for morphological characterization of the electrode surface. The electrochemical behaviors of fat-soluble vitamins have been studied in a mixture of ethanol and sodium perchlorate monohydrate using square-wave voltammetry (SWV). The results obtained indicated that the oxidation peak of each fat-soluble vitamin appeared at different potentials leading to the possibility for the simultaneous detection. The influences of experimental parameters such as the effects of proportions of ethanol, potential increment, amplitude, frequency and quiet time were examined. Under the optimized conditions, the linearity between oxidative currents and concentrations of fat-soluble vitamins ranged from 0.1 μg mL^-1 to 5 μg mL^-1 for vitamin A, 0.08 μg mL^-1 to 5 μg mL^-1 for vitamin D and E, and 0.2 μg mL^-1 to 1.6 μg mL^-1 for total vitamin K, with the limits of detection of 0.018, 0.013, 0.012 and 0.004 μg mL^-1, respectively. These developed sensors provide high sensitivity in detection and offer high potential to apply them for the simultaneous determination of fat-soluble vitamins in dietary supplements.

Abstract: Zinc antimonate (ZnSb₂O₆) nanoparticles were prepared by an inexpensive chemical precipitation method and its structural properties were studied using X-ray diffraction (XRD). Further in electrochemical analysis, Nafion, a per-fluorinated sulfonic acid polymer solution that serves as a binder, wherein the hydrophilic sulfonic acid group provides proton-exchange between electrolyte and active electrode material thereby, it is beneficial in the improvement of the capacitance, chemical and mechanical stability of a material. Considering this key point, the significance of the nafion on the electrochemical characteristics of zinc antimonate nanoparticles were studied through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analysis in 1 M H₂SO₄ electrolyte. The significant changes in the capacitance, electrochemical behavior and electrochemical stability of the nanostructure with and without the binder were investigated.

Abstract: IPMC (Ionic Polymer Metal Composite) is promising candidate actuator for bio-related applications mainly due to its biocompatibility, soft properties and operation in wet condition. In this paper, a new actuator will be presented. The tubular actuator, based on the concept of tip-displacement of IPMC actuator and capable of generating bending of tube with surface outside electrodes, was proposed and studied experimentally. The actuator is a Nafion tube consisting of an even number of Pt segments along the length, which are plated outside of tube surface, and the Pt segments act as electrodes to apply the driving voltage. The experimental data measured on prototype actuators prove the proposed concept of bending depend on the shape of Nafion. Show that the actuator functions well both displacement and force.

Abstract: The aim of this paper is to present the results of laboratory research on Ionic Polymer-Metal Composite (IPMC), with measurements of electrical values (voltage and current) measured simultaneously with the displacement. The obtained values were used to investigate the possibility of parametric model building. The research is focused mainly on constant frequency sine wave voltage signals. Phase offsets between voltage, current and displacement for different frequencies are calculated. Envelope and mean values of the electrical values are also described.

Abstract: The amino functionalized magnesium phyllosilicate clay (AC) intercalated over PVA-Nafion hybrid nanocomposite membranes were prepared by sol-gel method. The free standing membranes were obtained by solution recasting. The composition of clay materials such as AC and montmorillonite (MMT) was varied between 2-10 wt.% with respect to PVA-Nafion content. The molecular interactions and surface morphology of nanocomposite membranes were investigated by FT-IR and SEM analyses respectively. The thermal and mechanical stabilities of nanocomposite membranes were studied using TGA and Nanoindentation techniques. For 6 wt. % AC/PVA-Nafion, TGA results showed no appreciable mass change up to 380 °C and hardness calculated from nanoindentation studies was nearly 30 % higher than the other compositions. An improved conductivity was obtained for 6 wt. % AC/PVA-Nafion (1.4×10^-2 S/cm) compared to pure Nafion (1.2×10^-2 S/cm) and PVA-Nafion and MMT/PVA-Nafion composite membranes. From these studies, we observed that 6 wt. % AC/PVA-Nafion membrane possessed a good conductivity with higher thermal and mechanical stabilities.

Abstract: Nafion-azole (benzimidazole, 1,2,4-triazole, 1,2,3-triazole) composite membranes were prepared by room temperature and autoclave solution processing for high temperature (above 100 °C) PEMFC. Among the various Nafion – azole composite membranes, Nafion – 1,2,3-triazole membrane showed excellent flexibility, thermal stability, and homogeneous structure. Nafion – 1,2,4-triazole composite membrane had high thermal and mechanical properties, and also showed high proton conductivity of 0.02 S/cm at the temperature of 160 °C under dry (N₂) condition.

Abstract: To deal with the durability analysis of PEM fuel cell, it is necessary to carry out a further understanding of each component response, especially each layer of the MEA. So the main purpose of this paper is to understand the mechanical properties of electrode layer and find out the effect of temperature and the content of catalyst particles on the electrode yield stress. To overcome the experimental limitations, numerical method is used here. A 3-phase model of the electrode is built, which includes a user-defined material with catalyst particles. Due to the porosity of the electrode, the user-defined material is defined as a nafion ionomer glassy constitutive model by bringing in the effect of foam structure. Catalyst agglomerate particles are assumed as isotropic elastic spheres with relatively high Young’s modulus. The yield stress is extracted from the simulation, and the influences of temperature and agglomerate fraction on it are discussed.

Abstract: Nafion/Silica hybrid membranes were prepared via in situ solgel method for redox flow battery (RFB) system. In this work, a novel Nafion/organically modified silicate hybrids nanocomposite membrane was prepared via in situ solgel reactions for mixtures of tetraethoxysilane (TEOS) and trimethoxyprohanthiol (TMSP). The primary properties of Nafion/Silica hybrids membrane were measured and compared with Nafion and Nafion/SiO₂ hybrid membranes. Fourier transform infrared spectra (FT-IR) analysis of the hybrids membranes reveal that the silica and organic modified silica phase is well formed within hybrids membrane. The XRD results indicate thatthe Nafionhybrid membranes are not influenced by SiO₂ nanoparticles.Nafion/Silica hybrid membrane shows nearly the same ion exchange capacity (IEC) and slightly greater of proton conductivity as pristine Nafion-117 membrane. The water uptake for Nafion/Organosilica hybrids membrane shows greatly reduced than a pristine Nafion 117, suggesting of low water cross over that is mostly faced in the RFB applications.