Table 1: Selected characteristics for CNF A, B, C, and D, swCNT, mwCNT, and ufCBP. The CNF have been thoroughly characterized, reported in Jensen et al. [7]. Data for the swCNT, mwCNT, and ufCBP were previously reported in Nygaard et al. [2].


Description of morphology (SEM, TEM)a
Aggregated particles.
Medium fraction of fibres, mainly open channel fibres
Aggregated particles.
High fraction of fibres, mainly periodically closed channel fibres
Aggregated particles.
Low fraction of fibres, mainly open channel fibres
Aggregated particles.
Medium fraction of fibres, mainly periodically-closed channel fibres
Aggregated particles.
~50% graphitic material of arbitrary shape
~25% swCNT
~25% mwCNT
Open channels
Aggregated particles.
High fraction of tubes (>90%), but most are fibres with CNT aspect (the graphite layers make low angles with the channel direction). The fibres contain many defects.
Open channels
Aggregated particles. Near spherical particles whose structures are low-graphitized

Percent fibers/tubes versus other carbonous materiala
>50%>80%<50% >50%~50%>90%Not relevant

Fibre/tube widths ± standard error [range] (nm)
[11.25–108.69]a [18.90–302.21]a [14.46–185.75]a [18.52–286.85]a  nm
1.41–10.91 nm a
7.62–29.01 nm a
1.1 nmb20–30 nmb14.3 nmc

Fibre lengths
Up to 10 µmaUp to 10 µmaUp to 5 µmaUp to 5 µma0.5–100 µmb0.5–200 µmbNot relevant

Surface area (BET, m2/g)

>95% carbona>95% carbona>95% carbona>95% carbona>95% carbonb>95% carbonb>95% carbona
ADF-STEMaHigh number of Ni [5–500 nm] particles, some large Ti-Fe [>1 µm] particlesTraces of Ni [3–50 nm] and Ni-Fe [50–1000 nm] particlesHigh number of Ni [10–1000 nm] particles, traces of Cr, Fe and TiTraces of Ni [10–50 nm] particlesHigh number of impurities, mainly Co [1–20 nm], but some Fe [50–500 nm]Lower number of impurities, mainly Ni-(Fe) [5–40 nm]Traces
Nid (AAS, %)1.290.0704.970.036n.a.n.a.<0.0003
Fed (AAS, %)0.0080.0230.1480.002n.a.n.a.0.003

Structural defects ( as determined by Raman spectroscopy)d

Endotoxin (ng/mg)f
<0.0066 <0.0066<0.0066<0.00660.0079 <0.0066<0.0066

Acidity (pH)f
7.34 7.367.387.357.287.317.32

Abbreviations: ADF-STEM: annular dark field scanning transmission electron microscopy. AAS: atomic absorption spectrometer. BET: Braunauer, Emmet, and Teller method. Fe: iron. Ni: nickel. n.a.: not analyzed. SEM: scanning electron microscopy. TEM: transmission electron microscopy. : intensity ratio of the first order bands G and D.
aAuthors observation by electron microscopy. bSupplied by the manufacturer. cAccording to Renwick et al. [15]. dJensen et al. [7]. eNygaard et al. [2]. fLevels in supernatants after ultracentrifugation of particle suspensions. Endotoxin detection limit = 0.0066 ng/mg (0,25 EU/mL).