49 Int. Jnl. of Multiphysics Volume 11 · Number 1 · 2017 Multi-parameter Improvement Method for (Micro-) Structural Properties of High Performance Ceramics G Boiger 1 *, T Ott 1 , L Holzer 1 , D Penner 2 , M Gorbar 2 ,Y Hasan 2 1. ICP Institute of Computational Physics, School of Engineering, Zurich University of Applied Sciences, Winterthur, Switzerland 2. IMPE Institute of Materials and Process Engineering, School of Engineering, Zurich University of Applied Sciences, Winterthur, Switzerland ABSTRACT Many pH-measurement electrodes rely on porous diaphragms to create a liquid electrolyte junction between reference-electrolyte and the fluid to be measured. In field applications, the diaphragm is required to meet partly contradictory improvement criteria. To minimize measurement errors and to ensure durability of the measurement device, the diaphragm is supposed to maximize electrolyte conductivity and reference-electrolyte outflow velocity, while simultaneously minimizing reference electrolyte flow rate. The task of optimizing the overall performance of this small piece of ceramics has lead to the development of a novel multi-parameter improvement scheme for its (micro-) structural design. The method encompasses the consideration of microscopic material design parameters, such as porosity, pore- tortuosity and constrictivity, macroscopic material parameters such as diaphragm diameter and length, as well as process parameters like internal electrode pressure or the electrolyte viscosity and specific resistivity. Comprising sets of design parameters to dimensionless groups, concrete design guidelines as well as the introduction of a three-dimensional improvement space concept are proposed. The novel design space concept allows the improvement of each possible diaphragm-based measurement set-up, by considering the simultaneous, dimensionless interaction of all relevant design parameters. 1. INTRODUCTION Many pH-probes require a liquid junction between a reference electrolyte and the substrate solution. Its main task is to provide a conductive bridge between the two liquids, while simultaneously preventing the reference electrolyte to be polluted by substrate ions [4]. In the case of this study, the device in charge of maintaining such a junction is a small, cylindrical, porous piece of ceramics, Ddia= 1 mm in width, Ldia= 2 mm in length, referred to as diaphragm [5]-[7]. A schematic illustration of the type of pH-probes in question is shown in Figure 1 [1]. ___________________________________ *Corresponding Author: gernot.boiger@zhaw.ch