Defect study on polyaniline by positron annihilation spectrometry.

Area of Science:

• Materials Science
• Nuclear Physics
• Analytical Chemistry

Background:

• Positron Annihilation Spectrometry (PAS) is a powerful technique for probing material defects.
• Optimizing time resolution in PAS is crucial for accurate lifetime measurements.
• Polyaniline's variable conductivity makes it an interesting material for PAS studies.

Purpose of the Study:

• To construct and evaluate a fast coincidence system for enhanced PAS.
• To investigate factors influencing time resolution in the developed system.
• To measure positron lifetime components in polyaniline with varying conductivity.

Main Methods:

• Development of a fast coincidence system utilizing scintillators and delay lines.
• Systematic study of time resolution influenced by scintillator properties and electronic settings.
• Application of a monoenergetic positron acceleration system for lifetime measurements in polyaniline.

Main Results:

• Achieved optimal time resolution by analyzing scintillator types, sizes, and electronic configurations.
• Measured bulk positron lifetimes in polyaniline samples ranging from 360-380 ps.
• Observed a correlation between increased electrical conductivity and longer bulk positron lifetimes.

Conclusions:

• The developed fast coincidence system enables precise PAS measurements.
• Higher electrical conductivity in polyaniline is associated with extended bulk positron lifetimes, potentially due to protonation (H+).
• Positron lifetime analysis provides insights into material defects and conductivity variations in polyaniline.