Novel solution processing and characterization of aligned carbon nanotube materials for rapid composition-property relationship determination and additive manufacturing

At the microscopic scale, carbon nanotubes (CNTs) combine impressive tensile strength and electrical conductivity; however, their macroscopic counterparts have yet to meet expectations. The reasons have been variously attributed to inherent CNT sample properties (diameter and helicity polydispersity, high defect density, insufficient length) and manufacturing shortcomings (inadequate ordering and packing) which can lead to poor transmission of stress and current. To efficiently investigate the disparity between molecular and macroscopic properties, we have simplified CNT purification and developed a method for solution processing sub-milligram quantities of CNTs dissolved in chlorosulfonic acid (CSA) into films and fibers with high structural order. The aligned films have a high degree of order and exhibit anisotropic optical, electrical, and mechanical properties homogeneously over 10 cm2. We utilize this process to reduce the experimental time required for high performance CNT fiber production from two days to one hour, enabling efficient analysis of the structure-property relations that govern CNT fiber properties. A new vibroscopic linear density measurement technique capable of accurately characterizing the specific properties of the small-scale short (~7 cm) CNT fibers is also introduced. These novel processing methods can be performed at a scale low enough to be accessible to exotic SWCNT materials such as those enriched in metallicity, which are currently only available in the few milligram quantities. A selective reaction to remove metallic SWCNTs and the aqueous two phase extraction (ATPE) method are explored as possible sources for type and helicity enriched SWCNT samples for further solution processing. We successfully scale the ATPE method and obtain relatively large quantities of a semiconducting sample enriched in two chiralities and another sample enriched in (6,6) armchair SWCNTs. Importantly, the materials can be cleaned of impurities introduced during the separation process and behave as expected after dissolution in CSA. However, the separated CNTs are found to be too short for aligned film and fiber fabrication. Finally, this thesis introduces versatile solvents composed of phosphoric acid, methanesulfonic acid, and p-toluenesulfonic acid (pToS) mixed with oleum for assembling high quality, large diameter CNTs into 2 and 3D structures. The new acid solvents spontaneously dissolve CNTs to high concentrations and allow Mayer rod coating, silkscreen printing, and injection of CNTs onto substrates such as polyethylene terephthalate, polyester fabric, and polycarbonate. We prepare flexible transparent electrodes with properties matching the performance obtained when using superacid solvents. Additionally, pToS gently solidifies upon exposure to ambient moisture, enabling 3D-printing neat structures with commercially available equipment.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Natural Sciences

Grantor

Rice University

Year dc:date.issued

2018

Author dc:creator

• Headrick, Robert J

Advisor dc:contributor.advisor

• Pasquali, Matteo

• carbon nanotube
• 3D printing
• CNT fiber

Statement dc:rights

• Copyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1911/105701

OAI identifier oai:identifier

oai:repository.rice.edu:1911/105701