Reinforcement of CVD grown multi-walled carbon nanotubes by high temperature annealing

Abstract

We report on the increase of the Young's modulus (E) of chemical vapor deposition (CVD) grown multi-walled carbon nanotubes (MWNTs) upon high temperature heat treatment. The post heat-treatment at 2200–2800ºC in a controlled atmosphere results in a considerable improvement of the microstructure, chemical stability and electro-physical properties of the nanotubes. The Young's modulus of MWNTs of different diameters was measured by the deflection of a single tube suspended across the hole of silicon nitride membrane and loaded by an atomic force microscope tip. Contrary to previous reports, a strong increase of E was feasible due to the improved growth conditions of pristine carbon nanotubes and to the improved heat treatment conditions. However, the elastic modulus of CVD grown MWNTs still shows strong diameter dependence resulting from the remaining structural inhomogeneities in large diameter nanotubes.

Effect of ultrasonic treatment on the properties of multiwalled carbon nanotubes – polymethylmethacrylate composites: Effect of applied voltage and pressure on conductivity of the composites

“…In both case the resistivity of the composite (C20) varied within the same order of magnitude. Taking into account the elastic modulus values for PMMA (3-3.5 GPa) and MWCNTs (~1000 GPa) [46], the expected change of the material properties will be mostly determined by deformation of the polymer matrix. An increase of the applied voltage leads to the growth of pressure on measuring electrodes in the composite.…”

Introductory Chapter: Carbon Nanotubes and Their Applications

“…One method for measuring the Young's modulus of a CNT is to fabricate a nanotube beam that is clamped at each end to a ceramic membrane (or otherwise supported) and to measure its vertical deflection versus the force applied at a point midway along its length [25]. The atomic force microscope is a natural and convenient means for studying the Young's modulus of CNTs, because it allows measurement of the deflection of a sample as a function of applied force when used in contact mode [26]. Furthermore, CNTs, which have potential in chemical stability, thermal and electrical conductivity, mechanical strength, and flexibility, may be the best alternative materials for application in flexible transparent conductive electrodes.…”

Mechanical and Fracture Properties of Carbon Nanotubes

“…The Young's modulus and strength of CNTs are well known to depend critically on the structure (e.g., geometry, crystallinity, and defect type and density), which in turn depends on the manufacturing route and subsequent treatment [28][29][30][31]. Quantum mechanics calculations [32][33][34][35][36] predict that defect-free single-walled CNTs possess Young's modulus values of ~1 TPa, tensile strengths >100 GPa, and failure strains of ~15-30%, depending on the chirality.…”

“…One method for measuring the Young's modulus of a CNT is to fabricate a nanotube beam that is clamped at each end to a ceramic membrane (or otherwise supported) and to measure its vertical deflection versus the force applied at a point midway along its length [28]. The atomic force microscope (AFM) is a natural and convenient means for studying the Young's modulus of CNTs, because it allows measurement of the deflection of a sample as a function of applied force when used in contact mode [28,30,[42][43][44][45][46]. Salvetat et al [28] deposited a droplet of a MWCNT suspension on a wellpolished alumina ultrafiltration membrane and evaluated the Young's modulus using the abovementioned method.…”

“…These values are considerably lower than the moduli of arc discharge-grown MWCNTs (600-1100 GPa). Recently, Elumeeva et al [30] investigated the Young's modulus of four types of MWCNTs synthesized by the CVD method followed by a series of high-temperature annealing steps at 2200, 2600, and 2800°C using a method similar to that of Salvetat et al's study [28]. The experimental results showed that the Young's modulus increased for the annealed MWCNTs with respect to the as-grown ones.…”