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Enhanced Electrical Conductivity in Carbon Nanotube Composites Through Segregated Networks by the Addition of Silica
KTH, School of Chemical Science and Engineering (CHE).
2016 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Förbättrad konduktivitet i kolnanorörbaserade kompositer genom segregerade ledande nätverk via tillsats av kiseldioxid (Swedish)
Abstract [en]

This thesis reports the effect of silica-particles on conductive polymer nanocomposites based on polymethylmethacrylate (PMMA) and carbon nanotubes (CNTs). The goal was to lower the percolation threshold by adding silica and therefore achieving a higher conductivity in finished composites at the same CNT concentration. Different sizes of silica were investigated, from nano - to micromet er-sized, where only the nano-silica was found to disperse and not sediment within the matrix. Addition of neat silica-particles of any size, without the use of a surfactant, to the conductive composite did not improve the conductive properties. However with the addition of an anionic surfactant in combination with the nano -sil ica a shift of the percolation threshold to lower concentrations of CNT was seen, which improved the conductivity with ca 1 order of magnitude in the finished composites compared to that of composites containing only CNTs. The characterization by microscopy revealed a segregation of the nano-sized silica into clusters where no CNTs were observed. The detailed analysis revealed that the nano -sized silica therefore occupied a larger volume fraction in the matrix than expected, thus concentrating the CNTs into the remaining volume which resulted in a much greater conductivity than explained by theory.

Abstract [sv]

Denna avhandling rapporterar effekten av kiseldioxidpartiklar på elektriskt ledande nanokompositer tillverkade från polymetylmetakrylat (PMMA) och kolnanorör (CNT). Denna eftersökta effekt från tillsatsen av kiseldioxid var att flytta perkolationströskeln till lägre koncentrationer av CNT och där med även öka ledningsformågan utan att öka halten CNT. Kiseldioxidpartiklar av olika storlekar undersöktes, från nanostorlek till mikrostorlek, där enbart nanopartiklarna visade sig kunna skapa en stabil dispersion med kompositen. Tillsatsen av enbart kiseldioxidpartiklar oavsett storlek utan dispergeringsmedel gav ingen märkbar effekt på ledningsformågan. Men när kiseldioxiden kombinerades med en anjonisk tensid under de rätta proportionerna så kunde både perkolationströskeln sänkas och ledningsformågan ökas med en storleksordning jämfört med den ursprungliga kompositen med enbart CNT. Den morfologiska karakteriseringen avslöjade en segregation av kiseldioxid och CNT i matrisen och att kiseldioxiden ockuperade en större volym än förväntat genom att den skapade gel-liknande kluster, vilket resulterande i en bättre konduktivitet än forväntat fran teorin eftersom.

Place, publisher, year, edition, pages
2016.
Keyword [en]
Carbon Nanotubes, Hybrid Nanocomposite, Percolation Threshold, silica, Segregated
Keyword [sv]
Kolnanoröror, hybrid nanokomposit, perkolation tröskelvärden, kiseldioxid, segregerad ledande polymer
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-207053OAI: oai:DiVA.org:kth-207053DiVA: diva2:1095499
Available from: 2017-06-29 Created: 2017-05-15 Last updated: 2017-06-29Bibliographically approved

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