Correlations Between Structures of Expanded Graphite – Polymer Composites and Acoustic Emission Phenomena / Korelacje Pomiędzy Strukturą Kompozytów Grafit Ekspandowany-Polimer A Zjawiskami Emisji Akustycznej

Abstract

IntroductionDetermination of physical, mechanical and chemical properties of the compressed expanded graphite (CEG) composites prepared from poly-furfuryl alcohol is important to resolve whether the materials can be used as good quality catalysts [1][2] or composite membranes for gas separation [3][4] and also as proton exchange membranes in fuel cells [5][6][7][8].The purpose of this paper was to search the relations between the structure of the CEG composites on successive stages of technological treatment and parameters describing the acoustic emission (AE) phenomena in these materials.These investigations are a continuation of our earlier studies [9] concerning physical and chemical properties of porous composites created on the basis of a CEG matrix, obtained after successive technological procedures of Compressed expanded graphite was applied as a base matrix to the preparation of microporous composites as products of impregnation, polymerization and carbonization of poly-furfuryl alcohol. During carbonization, the original polymeric structure is transformed into an amorphous turbostratic carbon structure with ultramicropores. The structure, porosity and many chemical and physical properties change after each stage of their technological treatment.The acoustic emission method was used for accurate determination of these changes. It is possible to determine a large number of acoustic emission parameters and therefore to increase the amount of information provided by the studied materials. Acoustic emission pulses, counts rate, events rate, signal peak value and their sums were measured. Also frequency spectrum was received as a result of acoustic emission signal analysis with use of Fourier transformation procedure. The conclusions resulting from the Fourier analysis of the registered spectrum are very interesting and provide information about composite structures as well as bonds between the graphite matrix and the polymer that fills it. Analysis of acoustic emission parameters provides data on physical and chemical processes that would be very difficult to study by means of other techniques. Wide applications of these porous composites make them very interesting subject of the study.

Archives of Metallurgy and Materials

“…These investigations are a continuation of our earlier studies concerning physical and chemical properties of porous composites created on the basis of a CEG matrix, obtained after successive technological procedures of impregnation, polymerization and carbonization of poly-furfuryl alcohol [15,16]. Exact description of the technological process can be found in our earlier paper [15].…”

“…2. Some results of AE measurements in CEG composites for strain applied in the direction parallel to the bedding plane are described in our previously published paper [16]. The all presented in this paper results were obtained for the uniaxial strain applied in the direction perpendicular to the bedding plane of the composite structure.…”