Zirconium phosphates (ZrP) were incorporated into Nafion® 117 membrane by impregnating method to obtain a reduced methanol permeation and improved proton conductivity for fuel cell application. The mechanical properties and water uptake of Nafion® membrane incorporated with zirconium phosphates nanoparticles was more improvement when compared to the commercial Nafion® 117, due to the presence of phosphoric acid within the nanoparticles. The effect of ZrP nano filler on the membrane structural morphology and thermal properties were investigated by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Thermal gravimetric analysis (TGA) and Scanning Electron Microscopy (SEM). The improved ion conductivity and decreased methanol permeability on the nanocomposite membranes showed a great potential for fuel cell applications. The nanocomposite membrane with high tensile strength was obtained due to the well dispersed zirconium phosphates within the Nafion® matrix.

Stable and high surface area zirconium oxide nanoparticles have been synthesised by means of the hydrothermal method. The Brunauer-Emmett-Teller results show that a high surface area of 543 m 2 /g was obtained in the hydrothermal process, having a high porosity in nanometre range. The hydrothermal method was applied at 120°C by using an autoclave with a Teflon liner at an ambient pressure for 48 h. High-resolution scanning electron microscopy shows the different morphologies of zirconia nanoparticles, which could be categorised as one-dimensional and zerodimensional, as they had a high crystallite orientation, which was also confirmed by the X-ray diffraction (XRD). The mixture of two types of cubic phases in one sample was obtained from XRD and confirmed by the zirconia nanostructure, showing the stable phase of fluorite, which has full cubic symmetry (Im-3m), and also an Arkelite zirconia nanostructure, showing the stable phase of fluorite, which has full cubic symmetry (Fm-3m). The XRD results also show the different structure orientations of face-centred cubic and body-centred cubic in one sample.

Membranes are widely used daily, such as for filtration in reverse osmosis, or in the form of electrolyte membrane fuel cells. Modified Nafion ® membranes were synthesised by impregnation and their mechanical properties were observed. The effect of the incorporation of a ZrO 2 -CNT nano-filler within Nafion ® membrane on the thermal stability and crystallinity was investigated by TGA and XRD. Tensile test results show the increases in the mechanical properties of Nafion ® 117 membranes impregnated with ZrO 2 -CNT when compared with that of commercial Nafion ® 117 membranes. The results also show that adding ZrO 2 -CNT in Nafion ® 117 membranes improves the water contact angle and water uptake, as it enhances water retention within the membrane. The SEM results indicated that ZrO 2 -CNT was well distributed in the Nafion ® 117 membrane pores through the impregnation method.

Zirconia nanoparticles were prepared by the precipitation and ageing methods. The precipitation method was performed by adding ammonium solution to the aqueous solution of zirconium chloride at room temperature. The ageing method was performed by leaving the precipitate formed in the mother liquor in the glass beaker for 48 hours at ambient temperatures. The nanoparticles from both methods were further sulphated and phosphated to increase their acid sites. The materials prepared were characterised by X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), Brunauer-EmmettTeller (BET), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) methods. The XRD results showed that the nanoparticles prepared by the precipitation method contained mixed phases of tetragonal and monoclinic phases, whereas the nanoparticles prepared by ageing method had only tetragonal phase. The TEM results showed that phosphated and sulphated zirconia nanoparticles obtained from the ageing method had a smaller particle size (10-12 nm) than the nanoparticles of approximately 25-30 nm prepared by precipitation only. The BET results showed that the ZrO 2 nanoparticles surface area increased from 32 to 72 m 2 /g when aged.

Nafion ® membrane blended with polyacrylonitrile nanofibers decorated with ZrO 2 was successfully fabricated. The composite membrane showed improved proton conductivity, swelling ratio, thermal and mechanical stability, reduced methanol crossover, and enhanced fuel cell efficiency. The nanocomposite membranes achieved a reduced methanol crossover of 5.465 × 10 −8 cm 2 S −1 compared to 9.118 × 10 −7 cm 2 S −1 of recast Nafion ® membrane using a 5 M methanol solution at 80 C. The composite membrane also showed an ion conductivity of 1.84 compared to 0.25 S cm −1 recast Nafion ® at 25 C. The composite membranes showed a peak power density of 68.7 mWÁcm −2 at 25 C, these results show a promising composite membrane for fuel cell application.

The mechanical stability of modified membranes has become a priority for fuel cell applications as the membranes must endure all the fuel cell operations (to prevent crossover of the fuel while still conducting). Their mechanical stress and yielding stress in the recast and impregnation methods compared with the commercial Nafion® membrane were observed under tensile tests. The modulus of elasticity of wet commercial Nafion117 membrane, Nafion®/ Zr-0, Nafion®/Zr-50 and Nafion®/ Zr-80 membranes and Nafion®/ Zr-100 nano-composite membrane using impregnation methods in the region between 0 and 0.23 strain were determined to be 4817.5 kPa, 2434.7 kPa, 1872.4 kPa, 2092.1 kPa and 2661.4 kPa respectively. The tensile strength of the dry nano-composite membrane prepared using the recast method is higher than the wet nano-composite membrane prepared using the recast methods. It was found that the impregnation method plays an important role in strengthening the nan-composite membranes.

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This paper presents constitutive laws suitable for the prediction of mechanical behaviour of nano-composite membrane compared with the commercial membrane Nafion®117. The uniaxial tensile data of commercial Nafion®117 and Nafion®/ Zr-150 nano-composite membrane utilised for fitting hyperelastic models was determined experimentally. Several material models on mechanical behaviour of nano-composite and commercial Nafion® 117 membrane material was fitted to determined accuracy. In order to observe yield and fracture behaviour, the com-mercial Nafion®117 and Nafion®/ Zr-150 nano-composite membranes were loaded in uniaxial direction at a constant strain rate. To obtain the optimal material constants form six different material models considered in this study, the OriginLab® version 9 was used and the Leven-berg-Marquardt (M) optimization logarithm. Hyperplastic material models including Mooney-Rivlin, Yeoh, Ogden, Humphrey, Martins and Veronda-Westmann were selected to use in an inverse method to fit the experimental uniaxial data of nano-composite material. The hyper-plastic material parameters could then be used to simulate material behaviour of nano mem-brane using finite element analysis (FEA) technique. The procedure discussed in this paper could be used to accurately determine the constitutive parameters of various constitutive models of Polymer Nafion presented.