Towards In Situ Methods for Characterization of Porous Materials

Abstract

Automation is becoming ever more important in production processes. But its progress is being hampered because a large part of process control is currently based on tacit knowledge, which is lost when plant operators retire. To offset this fading of knowledge, process variables must be quantified, because another change underway is the evident shift from conventional mass production to lean and green production, which promotes ordered production flow and rational process optimization by minimizing non-valueadded work. Both of these changes have affected the analysis of materials and necessitated in situ study of processes through their material properties.<br/><br/>All the developed in situ methods in this thesis embody analysis of porous ceramics of different composition and pore structure, or the extent of added value in unfinished ceramic structures during powder compression [VII] and colloidal processing [V], in finished ceramic components in unsintered, high porosity fiber structures [I, III, VI], in ceramics composed of sintered, low porosity solids [II], and in oriented, lamellar structures [IV]. From the materials science perspective, the study of these porous ceramics provides information on their mechanical behavior in relation to pore structure: the effect of porosity changes in powder structure [VII], the effect of sintering in fibrous structure [III], and the effect of pore orientation in lamellar structure [IV]. The second investigated regime is the behavior of electrical signals in a porous material in sintered structure [II], and in suspensions [V]. Third regime is the investigation of local permeability of a fibrous structure [I, VI].<br/><br/>Whereas this thesis work focused mostly on the concrete development of 6 different characterization methods—thermal flow permeametry, grit blast-analysis, electrical pore analysis, adaptive image analysis, and granule bed compression—the results in the introduction demonstrate a systematic approach to developing process integrable in situ methods and discuss the relative importance of the methods’ robustness, integrability, reliability, and comprehensiveness. In the regime of materials science, this work contributes to the analysis of pore characteristics and the effects of pores by showing results of granule bed strength measurement, the effect of the pore parameter on compressive strength, the concept of fiber free length, and a strong hypothesis about the reactions of material interfaces with electrical signals.