Bioinspired MWCNT-reinforced alumina composite materials

<p>Nacre, a ceramic composite found in seashells, has baffled scientists due to its extraordinary mechanical properties. Consequently, nacre has been a main source of inspiration to create strong and tough ceramic composites that mimic nacre’s microstructure. The precise microstructural featur...

Disgrifiad llawn

Manylion Llyfryddiaeth
Prif Awdur: Evers, K
Awduron Eraill: Todd, R
Fformat: Traethawd Ymchwil
Iaith:English
Cyhoeddwyd: 2019
Pynciau:
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author Evers, K
author2 Todd, R
author_facet Todd, R
Evers, K
author_sort Evers, K
collection OXFORD
description <p>Nacre, a ceramic composite found in seashells, has baffled scientists due to its extraordinary mechanical properties. Consequently, nacre has been a main source of inspiration to create strong and tough ceramic composites that mimic nacre’s microstructure. The precise microstructural features responsible for its unique combination of high strength and toughness are however debated, and efforts to mimic and improve upon nature’s design have not led to commercial applications of ceramic nacre-like composites.</p> <p>This dissertation details the replication of nacre’s microstructural architecture with technical ceramics and nanomaterials. Instead of nacre’s calcium carbonate building blocks, alumina was used, and instead of its organic phase, multi-walled carbon nanotubes (MWCNTs) were incorporated. To design a nacreous microstructure, freeze casting of alumina nanoparticles was used to template a microstructure of aligned lamellae over macroscopic length scales. Although successful, the fabricated lamellar microstructures’ macroscopic orientation was hard to consistently reproduce using this technique and the resulting composites, unlike nacre, fail in a completely brittle fashion. Therefore, alumina platelets that closely resemble the platelets in nacre were investigated. A recipe to homogeneously coat these platelets in situ with MWCNT was developed, and MWCNT growth and catalyst modification was studied in-depth. The resulting combined building blocks were sintered into a composite that displays a graceful failure mechanism like nacre does, with several toughening mechanisms observed to be active. In addition, nacre-like alumina/MWCNT composite materials have been synthesised using a variety of MWCNT dispersion techniques. All studied nacre-like composites showed characteristic macroscopic interlocking behaviour and remain interlocked after crack initiation which prevented complete failure and gave these composites a residual strength. Pure nacre-like alumina specimens have also been tested in high strain rate and impact tests, where these materials showed a significant improvement over nontextured alumina. </p>
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spelling oxford-uuid:a84de7db-a161-4ec0-9f6f-4aac0b1fbbd52022-03-27T03:00:42ZBioinspired MWCNT-reinforced alumina composite materialsThesishttp://purl.org/coar/resource_type/c_db06uuid:a84de7db-a161-4ec0-9f6f-4aac0b1fbbd5NanotechnologyNanoscienceChemistryMaterials ScienceEnglishHyrax Deposit2019Evers, KTodd, RGrobert, N<p>Nacre, a ceramic composite found in seashells, has baffled scientists due to its extraordinary mechanical properties. Consequently, nacre has been a main source of inspiration to create strong and tough ceramic composites that mimic nacre’s microstructure. The precise microstructural features responsible for its unique combination of high strength and toughness are however debated, and efforts to mimic and improve upon nature’s design have not led to commercial applications of ceramic nacre-like composites.</p> <p>This dissertation details the replication of nacre’s microstructural architecture with technical ceramics and nanomaterials. Instead of nacre’s calcium carbonate building blocks, alumina was used, and instead of its organic phase, multi-walled carbon nanotubes (MWCNTs) were incorporated. To design a nacreous microstructure, freeze casting of alumina nanoparticles was used to template a microstructure of aligned lamellae over macroscopic length scales. Although successful, the fabricated lamellar microstructures’ macroscopic orientation was hard to consistently reproduce using this technique and the resulting composites, unlike nacre, fail in a completely brittle fashion. Therefore, alumina platelets that closely resemble the platelets in nacre were investigated. A recipe to homogeneously coat these platelets in situ with MWCNT was developed, and MWCNT growth and catalyst modification was studied in-depth. The resulting combined building blocks were sintered into a composite that displays a graceful failure mechanism like nacre does, with several toughening mechanisms observed to be active. In addition, nacre-like alumina/MWCNT composite materials have been synthesised using a variety of MWCNT dispersion techniques. All studied nacre-like composites showed characteristic macroscopic interlocking behaviour and remain interlocked after crack initiation which prevented complete failure and gave these composites a residual strength. Pure nacre-like alumina specimens have also been tested in high strain rate and impact tests, where these materials showed a significant improvement over nontextured alumina. </p>
spellingShingle Nanotechnology
Nanoscience
Chemistry
Materials Science
Evers, K
Bioinspired MWCNT-reinforced alumina composite materials
title Bioinspired MWCNT-reinforced alumina composite materials
title_full Bioinspired MWCNT-reinforced alumina composite materials
title_fullStr Bioinspired MWCNT-reinforced alumina composite materials
title_full_unstemmed Bioinspired MWCNT-reinforced alumina composite materials
title_short Bioinspired MWCNT-reinforced alumina composite materials
title_sort bioinspired mwcnt reinforced alumina composite materials
topic Nanotechnology
Nanoscience
Chemistry
Materials Science
work_keys_str_mv AT eversk bioinspiredmwcntreinforcedaluminacompositematerials