Modeling and Effects of Non-Homogeneous Infiltration on Material Properties of Carbon-Infiltrated Carbon Nanotube Forests

• Main Author: Snow, Daniel Owens
• Format: Others
• Published: BYU ScholarsArchive 2020
• Subjects: Carbon Nanotubes; CNT; MEMS; CICNT; Carbon; Engineering
• Online Access: https://scholarsarchive.byu.edu/etd/9216; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=10225&context=etd

This work investigates the material properties and production parameters of carbon infiltrated carbon nanotube structures (CI-CNT's). The impact of non homogeneous infiltration and the porosity of cross section regions, coupled with changes in designed geometry, in this case beam width, on the density and modulus of elasticity are compared. Three potential geometric models of beam cross section are proposed and evaluated. 3-point bending, SEM images, and numerical optimization are used to assess the validity of each model and the implications they have for future CI-CNT material applications. Carbon capping near exterior beam surfaces is observed and determined to be a contributing factor to variations in material properties correlated with changes in designed geometry and infiltration parameters (temperature, time, and hydrogen flow rate). Unexpected relationships between beam width and elastic modulus are partially explained by modeling the carbon-capped beams as C-shaped structural members consisting of a graphitic carbon shell of varying porosity and thickness and uninfiltrated carbon nanotube internal regions with a near negligible stiffness. Findings of previous works on the effects of infiltration parameters and carbon capping on materials properties are confirmed and expanded. Flange and web thickness and porosity of the graphitic carbon shell are identified as potential design parameters for pursuing tunable material properties in high precision geometry MEMS and compliant mechanism applications.