Improved conductivity of carbonized polyimide by CO2laser graphitization
| Autor: | Gerard M. O'Connor, Ratul Kumar Biswas, Nazar Farid, Patricia Scully |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Materials science
chemistry.chemical_element 02 engineering and technology Conductivity 010402 general chemistry 01 natural sciences Fluence law.invention symbols.namesake law Materials Chemistry business.industry Carbonization General Chemistry 021001 nanoscience & nanotechnology Laser 0104 chemical sciences Amorphous solid chemistry symbols Optoelectronics 0210 nano-technology business Raman spectroscopy Carbon Polyimide |
| Zdroj: | Journal of Materials Chemistry C. 8:4493-4501 |
| ISSN: | 2050-7534 2050-7526 |
| Popis: | Direct laser writing (DLW) is a fast and cost-effective technique for printing conductive structures on flexible substrates such as polyimide (PI) by the conversion of insulative PI to conductive carbon. However, the conductivity (∼103 S m−1) obtained by this method needs to be improved to compete with ink-jet printing of carbon-based materials. The reason behind the low conductivity achieved by the DLW process is due to the crystallinity and hybridization of bonding in carbonaceous structures. In this work, the DLW process has been implemented in two steps: the first step called carbonization was performed by writing pulsed CO2 laser on PI to form tracks which consist of amorphous tetrahedral carbon (a mixture of sp2 and sp3 hybridized carbon) having intrinsically low conductivity. The second step called graphitization is overwriting of the laser on the pre-carbonized tracks to convert sp3 hybridized bonds to sp2 hybridized bonds by the process called laser graphitization. The conductivity of tracks carbonized at (0.21 ± 0.02) W and fluence (3.31 ± 0.32) × 103 mJ cm−2 at a repetition rate of 0.1 kHz was 56.1 ± 3.1 S m−1 which increased to 146.7 ± 5.1 S m−1 upon overwriting with the laser at (0.50 ± 0.03) W and fluence (7.88 ± 0.47) × 103 mJ cm−2 at the same repetition rate. The photothermal process of carbonization and graphitization is modeled for the DLW process and the threshold power of both the processes is calculated and validated by Raman spectroscopy. Improved conductivity achieved by detailed understanding of the laser and material parameters involved in this transformation enables process optimization leading to future applications in scalable manufacturing of flexible bio-sensors and electrochemical energy storage devices. |
| Databáze: | OpenAIRE |
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