OPTIMISATION OF THE COMPOSITION AND PROCESS PARAMETER OF CsH2PO4/NaH2PO4/SiO2 SOLID ACID COMPOSITE VIA THE TAGUCHI METHOD

Abstract

Solid acid composites of CsH 2 PO 4 /NaH 2 PO 4 /SiO 2 (CDP/SDP/SiO 2) were synthesised with varied SDP to CDP and SiO 2 to CDP mole fractions. The composites were arranged for optimisation via the Taguchi method with L9 orthogonal array, which manipulates four factors: the amount of SDP, amount of SiO 2 , amount of pressure used for pellet production and operating temperature. Responses were recorded as the averaged conductivity value for each experimental set. The composite powders were uniaxially pressed to form pellets of 1 mm thickness for conductivity measurements. Conductivity value was averaged from three readings and used in the signal-to-noise (S/N) ratio formula. The S/N ratio was set such that larger is better and calculated to maximise the response required for the analysis. Operating temperature has the largest effect on the conductivity value of solid acid composites, whereas the amount of SiO 2 has the smallest effect. The amount of SDP in the composite has a larger effect than the pressure applied during pellet production prior to the conductivity measurements. The optimised composite consists of 0.2 mole fraction of SDP to CDP and 0.3 mole fraction of SiO 2 to CDP pressed at 3 tonnes cm-2 to produce pellets and tested at the temperature of 250 °C. The optimisation was validated by using analysis of variance from the Design-Expert ® software.

A synergistic approach to achieving high conduction and stability of CsH2PO4/NaH2PO4/ZrO2 composites for fuel cells

“…22 The conductivity of CDP increases up to 1 to 3 orders of magnitude by SDP at low temperatures. 23 For an SA-doped material, a higher proton conductivity of 5.28 Â 10 2 s cm was observed at 90 1C and 98% relative humidity. The conductivity of CDP/ZrO 2 was observed to be 1.8 Â 10 À2 S cm À1 for 2000 min in confined nature.…”