Evaluation of crystalline perfection degree of multi‐walled carbon nanotubes: correlations between thermal kinetic analysis and micro‐Raman spectroscopy

Abstract

Commercially available and laboratory-prepared multi-walled carbon nanotubes (MWCNTs) are systematically investigated by the use of micro-Raman spectroscopy (MRS), thermogravimetric analysis (TGA) and complementary techniques (scanning electron microscopy (SEM) and transmission electron microscopy (TEM)) with the aim of establishing a standardised postgrowth diagnostic protocol for the assessment of their overall crystalline quality. By studying a set of 'reference' samples, clear correlations are evidenced between the Raman graphitisation indexes (D/G, G /G and G /D intensity ratios) commonly adopted to describe the crystalline arrangement of nanotubes, and their reactivity towards oxygen, as measured by the apparent activation energy needed for their oxidation, inferred from the kinetic analysis in quasi-isothermal conditions. The higher the crystalline perfection degree, the higher the energy needed for oxidising them. The efficacy of the found correlations in indirectly assessing the reactivity of nanotubes prepared under different conditions is successfully demonstrated by the use of a second set of samples. The physical meaning and range of validity of the shown correlations are further discussed. Copyright

Synthesis of Carbon Nanotubes from Ethanol Using RF-CCVD and Fe–Mo Catalyst

“…tion of MWCNT with good crystallinity and purity. [15,16] The obtained I G /I D and I 2D /I G values for the MWCNTs in this study are 0.9 and 0.47, respectively, which are very close to other reports. [7,17] This indicates the formation of highly crystalline and pure MWCNT.…”

On the Amorphisation Trajectory of Carbon Nanotubes

“…This finding supports the property of our previous choice [5] of a three-stage model, inspired to that proposed by Ferrari and Robertson for other nanocarbons [12], to explain the nonmonotonic dependence of strength of C bonds, as described by the Raman G-band position, on sp 3 C bonding fraction, as monitored by resistance to oxidation of NTs assessed by KTA.…”

“…2a, and ref. [5]); the presence of interconnects reflects on a broadening of the profile (compare curves 1 and 2 in Fig. 2c).…”

“…The rate constant for carbon (and NT) oxidation reaction is typically expressed as k(T) = -(1/m)·dm/dt [11], where m is the instantaneous mass of carbon and T is the temperature linearly increasing with t. Operating under quasi-isothermal conditions [5], the sample temperature can be assumed as constant, so that k(T) can be regarded as the instantaneous reaction rate constant at the given T. Figures 2a and 2b show experimental profiles typically obtained in absence and presence of amorphous phases, respectively. As previously reported [6], the presence of amorphous phases results in a very weak contribution on the lower-T side of the curve, as well as in a lower T M for given NT diameters.…”

Estudio de Nanocompuestos de Espumas de Poliuretano Reforzadas con Nanocargas en Base Carbono

“…Recently, Santangelo et al [154] have described a correlation between the Raman ID/IG ratio and the thermal oxidative stability of carbon nanotubes. The higher the degree of crystallinity of MWCNTs, the higher the energy needed to oxidise them.…”