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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. [ABSTRACT FROM AUTHOR]

A large increase in the piezo-optical tensor components (3)xxxx (was)observed in composite films of fullerene derivatives added to a polyvinylalcohol (PVA) matrix at a concentration of 4.6 wt% . The piezo-optical coeDcient (3)xxxx was dependent on the applied mechanical stress. Simultaneously performed measurements on pure fullerene derivative films and PVA matrices do not show such a large increase in II[SUBxxxx] values. Semi-empirical quantum chemical calculations of piezo-optical susceptibilities show that trapping levels between the chromophore fullerene-like molecule and the surrounding polymer play a key role in the observed dependencies. [ABSTRACT FROM AUTHOR]

Abstract: We have established a principal role of the polarity of polymer matrices on the piezooptical dispersion of the γ-glycine nanocrystallites embedded into the polymethymethacrylate (PMMA) and polycarbonate (PC) matrices. We found that the optical treatment by bicolor two laser beams at 1064nm and 532nm which are originating from the same 10ns Nd:YAG laser, causes occurrence of the piezooptical effects. The optimal content of the γ-glycine nanocrystallites with respect to the magnitude of piezooptical coefficients was within the range of size 50–80nm, corresponding to the 6.5wt.%. We studied relaxation and spectral dependence of the corresponding coefficients of the piezooptic tensor. [Copyright &y& Elsevier]