Processing, microstructure and properties of polymer-based nano-composite dielectrics for capacitor applications
<p>The processing and properties of novel polymer-based nano-composite (PNC) dielectrics for capacitor applications has been studied. PNCs were fabricated via a vacuum based deposition technique and their micro/nano-structure, chemical and dielectric properties investigated. After process deve...
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| Format: | Thesis |
| Language: | English |
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2014
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| _version_ | 1797105486328233984 |
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| author | Mahadevegowda, A |
| author2 | Grant, P |
| author_facet | Grant, P Mahadevegowda, A |
| author_sort | Mahadevegowda, A |
| collection | OXFORD |
| description | <p>The processing and properties of novel polymer-based nano-composite (PNC) dielectrics for capacitor applications has been studied. PNCs were fabricated via a vacuum based deposition technique and their micro/nano-structure, chemical and dielectric properties investigated. After process development and optimisation, co-deposited Al and nylon-6 PNCs had a dielectric constant <em>k∼7</em> at an approximate Al volume fraction of 0.3 that agreed with analytical predictions if it was assumed that the Al transformed to an oxide <em>in-situ</em> and/or after deposition. The significant effect of absorbed water vapour and temperature on PNC dielectric properties was revealed using different types of post-deposition heat treatment.</p> <p>Alternately-deposited PNCs consisting of Al or Ag 2-20 nm layers sandwiched between nylon-6 layers were fabricated in which the overall PNC Al or Ag volume fraction was controlled by varying the nominal Al or Ag layer thickness. Ag layers comprised of discrete nano-islands that produced a nano-capacitor network effect that increased <em>k</em> to ∼11. In the case of Al layers, when the layer thickness was ≥ 5 nm, corresponding to a nominal volume fraction of 0.1, Al (core)-oxide (shell) nanoparticles were formed and the PNC dielectric constant increased to ∼19. The detailed nano-structure of the core-shell particles was studied using various types of transmission electron microscopy (TEM), and the elevations in dielectric constant ascribed to multiple-interface polarisation effects dependent on the formation of the core-shell structure.</p> <p>PNCs based on alternate deposition of Ti sandwiched in nylon-6, and then both Ti and Ag in nylon-6 were also fabricated, with <em>k</em> reaching ∼73 for Ag+Ti/nylon-6 PNCs. As well as Ti-based core (metal)-shell (oxide) particles, the Ag volume fraction was sufficiently high in the 10 nm nylon-6 layers to again form a nano-capacitor network that contributed to the overall device capacitance and effective dielectric constant. Again, various types of high magnification TEM were critical in resolving the Ti-based core-shell structure and its role in high-<em>k</em> behaviour.</p> <p>The vacuum-based alternate deposition technique has been developed to offer ease of operation, reliability, flexibility and applicability to chemically different filler and matrix systems in the fabrication of high-<em>k</em> PNC based capacitors, in which high-<em>k</em> performance relies critically on the formation of core (metal)-shell (oxide) particles in both Al and Ti based systems.</p> |
| first_indexed | 2024-03-07T06:48:16Z |
| format | Thesis |
| id | oxford-uuid:fb974b13-2ec5-4104-9f80-45d1cb97eb48 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T06:48:16Z |
| publishDate | 2014 |
| record_format | dspace |
| spelling | oxford-uuid:fb974b13-2ec5-4104-9f80-45d1cb97eb482022-03-27T13:15:02ZProcessing, microstructure and properties of polymer-based nano-composite dielectrics for capacitor applicationsThesishttp://purl.org/coar/resource_type/c_db06uuid:fb974b13-2ec5-4104-9f80-45d1cb97eb48Materials SciencesEnglishOxford University Research Archive - Valet2014Mahadevegowda, AGrant, PYoung, N<p>The processing and properties of novel polymer-based nano-composite (PNC) dielectrics for capacitor applications has been studied. PNCs were fabricated via a vacuum based deposition technique and their micro/nano-structure, chemical and dielectric properties investigated. After process development and optimisation, co-deposited Al and nylon-6 PNCs had a dielectric constant <em>k∼7</em> at an approximate Al volume fraction of 0.3 that agreed with analytical predictions if it was assumed that the Al transformed to an oxide <em>in-situ</em> and/or after deposition. The significant effect of absorbed water vapour and temperature on PNC dielectric properties was revealed using different types of post-deposition heat treatment.</p> <p>Alternately-deposited PNCs consisting of Al or Ag 2-20 nm layers sandwiched between nylon-6 layers were fabricated in which the overall PNC Al or Ag volume fraction was controlled by varying the nominal Al or Ag layer thickness. Ag layers comprised of discrete nano-islands that produced a nano-capacitor network effect that increased <em>k</em> to ∼11. In the case of Al layers, when the layer thickness was ≥ 5 nm, corresponding to a nominal volume fraction of 0.1, Al (core)-oxide (shell) nanoparticles were formed and the PNC dielectric constant increased to ∼19. The detailed nano-structure of the core-shell particles was studied using various types of transmission electron microscopy (TEM), and the elevations in dielectric constant ascribed to multiple-interface polarisation effects dependent on the formation of the core-shell structure.</p> <p>PNCs based on alternate deposition of Ti sandwiched in nylon-6, and then both Ti and Ag in nylon-6 were also fabricated, with <em>k</em> reaching ∼73 for Ag+Ti/nylon-6 PNCs. As well as Ti-based core (metal)-shell (oxide) particles, the Ag volume fraction was sufficiently high in the 10 nm nylon-6 layers to again form a nano-capacitor network that contributed to the overall device capacitance and effective dielectric constant. Again, various types of high magnification TEM were critical in resolving the Ti-based core-shell structure and its role in high-<em>k</em> behaviour.</p> <p>The vacuum-based alternate deposition technique has been developed to offer ease of operation, reliability, flexibility and applicability to chemically different filler and matrix systems in the fabrication of high-<em>k</em> PNC based capacitors, in which high-<em>k</em> performance relies critically on the formation of core (metal)-shell (oxide) particles in both Al and Ti based systems.</p> |
| spellingShingle | Materials Sciences Mahadevegowda, A Processing, microstructure and properties of polymer-based nano-composite dielectrics for capacitor applications |
| title | Processing, microstructure and properties of polymer-based nano-composite dielectrics for capacitor applications |
| title_full | Processing, microstructure and properties of polymer-based nano-composite dielectrics for capacitor applications |
| title_fullStr | Processing, microstructure and properties of polymer-based nano-composite dielectrics for capacitor applications |
| title_full_unstemmed | Processing, microstructure and properties of polymer-based nano-composite dielectrics for capacitor applications |
| title_short | Processing, microstructure and properties of polymer-based nano-composite dielectrics for capacitor applications |
| title_sort | processing microstructure and properties of polymer based nano composite dielectrics for capacitor applications |
| topic | Materials Sciences |
| work_keys_str_mv | AT mahadevegowdaa processingmicrostructureandpropertiesofpolymerbasednanocompositedielectricsforcapacitorapplications |