Hollow carbon nanospheres: a structural integrity investigation.

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dc.contributor.advisorBlaine, Deborahen_ZA
dc.contributor.authorDu Toit, Jessicaen_ZA
dc.contributor.otherStellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.en_ZA
dc.date.accessioned2018-02-28T11:03:05Z
dc.date.accessioned2018-04-09T07:07:39Z
dc.date.available2018-02-28T11:03:05Z
dc.date.available2018-04-09T07:07:39Z
dc.date.issued2018-03
dc.descriptionThesis (MEng)--Stellenbosch University, 2018.en_ZA
dc.description.abstractENGLISH ABSTRACT: Hollow carbon nanospheres (HCNSs) have high strength, thermal and electrical conductivities which allow for applications in electrochemical capacitors, lithium ion battery anodes and catalyst supports. When used as a catalyst support, a HCNS encapsulates a nanoparticle, preventing sintering and increasing the catalyst lifespan. The structural integrity of the HCNS is of importance since failure of the HCNS shell will result in the sphere no longer fulfilling its purpose. The aim of this investigation was to evaluate the structural integrity and to link synthesis conditions to the structural integrity of HCNSs. HCNSs were synthesised using two different coating methods: chemical vapour deposition (CVD) and resorcinol formaldehyde (RF) treatment. The synthesis variables significantly affected the spherical shell. At best, the CVD synthesis method produced only partial spheres. Unlike the CVD method, the RF method successfully produced HCNSs with whole, unbroken shells. A bulk powder compaction testing method was developed for the nanospheres where the Heckel yield pressure, a qualitative powder parameter, was extracted from fitting the Heckel equation to the experimental data. The Heckel yield pressures for the silica nanospheres showed a clear decrease with increasing sphere diameter. An inverse relationship between Young’s modulus and nanosphere diameter is reported in literature for both polystyrene nanospheres and amorphous HCNSs. Additionally, a proportional correlation between Young’s modulus and Heckel yield pressure is reported in literature. This relationship extended to include a similar relationship between nanosphere diameter and failure stress. Therefore, the size dependency of Heckel yield pressure for the silica nanospheres studied here is supported. In this investigation, the Heckel yield pressure was used as a qualitative parameter to determine the structural integrity of the nanospheres.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Koolstof holnanosfere (HCNS) besit eienskappe van hoë strukturele sterkte, hitte- en elektriese geleidingsvermoë, wat maak dat hulle geskik is vir toepassing in elektrochemiese kapasitors, litium ioon sel-anodes en ondersteuning vir katalisators. Indien dit gebruik word as ondersteuning vir ʼn katalisator, word die nanopartikel deur die HCNS inkapsel; daardeur word die sinterproses verhoed en die katalisator-lewensduur bevorder. Die strukturele betroubaarheid van die HCNS is belangrik aangesien dat die faling van die HCNS-dop die gevolgtrek sal hê dat die sfeer nie meer aan sy doel sal voldoen nie. Die uitkoms van hierdie navorsing is om 'n beter begrip van die HCNS strukturele eienskappe te vorm en om die sinteseparameters aan die HCNS strukturele betroubaarheid te koppel. HCNS’e word deur twee verskillende bedekkingsmetodes gesintetiseer: chemiese-dampneerslag (CVD) en resorsinol formaldehied (RF) metodes. Die sintesisveranderlikes het ʼn waarnemende effek op die sferiesedop. Op sy beste, word slegs gedeeltelikesfere met die CVD proses vervaardig. In teenstelling met die CVD proses, het die RF metpde heel HCNS’e gelewer wat nie stukkend is nie. 'n Massa poeiersamedrukkingtoetsmetode is vir die HCNS ontwikkel, waar die Heckel-swigdruk, ‘n kwalitatiewe poeierparameter, bepaal word deur die data by die Heckel-vergelyking te pas. Die Heckel-swigdruk vir die silika-nanosfere toon 'n duidelike afname met toenemende sfeerdiameter. ʼn Omgekeerde verwantskap tussen Young se modulus en nanosfeerdiameter word vie beide polistreen nanosfere en amorfiese HCNS’e in die literatuur gevind. Verder, word daar ʼn proposioneleverwantskap tussen Young se modulus en Heckel-swigdruk in die literatuur gevind. Hierdie verwantskap word uitgebrei om ʼn soortgelyke verwantskap tussen nanosfeerdiameter en falingsspanning in te sluit. Daarom word die afhanklikheid van Heckel-swigdruk op grootte vir die silikananosfere wat hier bestudeer word, ondersteun. In hierdie ondersoek, word die Heckel-swigdruk as ʼn kwalitatiewe parameter gebruik om die strukturele betroubaarheid van die nanosfere te bepaal. Die massa poeiersamedrukkingtoets, gevolg deur die Heckel-swigdruk berekening, verskaf ‘n goeie kwalitatiewe parameter wat gebruik kan word om die verskillende nanosfeer monsters te vergelyk. Die Heckel-swigdruk resultate toon 'n duidelike afname met laer sfeerdop strukturele betroubaarheid.af_ZA
dc.format.extent116 pages : illustrationsen_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/103728
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subjectHollow carbon nanospheresen_ZA
dc.subjectHeckel yield pressureen_ZA
dc.subjectStructural analysis (Engineering)en_ZA
dc.subjectTensegrity (Engineering)en_ZA
dc.subjectUCTDen_ZA
dc.titleHollow carbon nanospheres: a structural integrity investigation.en_ZA
dc.typeThesisen_ZA
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