Detection of free volumes in polymers and nano-composites by positron lifetime spectroscopy

In the paper is demonstrated the use of positron lifetime spectroscopy (PLS) in a comparative study of the free volume in polymers and nano-composite materials. The first part is devoted to the application of positronium as a probe for measurements of free volumes in polymers. The free volumes have been estimated by PLS in polyaniline (PANI) complexes with various inorganic and organic acids for the first time. It was found a correlation between the o-Ps lifetime, its intensity and ionic radius of the counter-ions in PANI complexes. In the second part the PLS analysis has been applied for examination the electronic and defect structure in selected hybrid nano-composite coatings on super fine, sub-nano level. The positron spectroscopy method is effective for measurements of extremely small defects and voids, which is important for the next exploitation period of the coatings. PLS measurements of nano-composite coatings show that about 80% of the positrons are directed to the porous nano-particles of aluminum oxide and only about 1% to CeCl3.