Preparation of short carbon nanotubes by mechanical ball milling and their hydrogen adsorption behavior

Liu, Fu; Zhang, Xiaobin; Cheng, J.P.; Tu, J. P.; Kong, Fanchao; Huang, Wei‐Pin; Chen, Changpin

doi:10.1016/s0008-6223(03)00302-6

Cited by 148 publications

(82 citation statements)

References 28 publications

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“…The applied mild milling resulted in compacting of samples and increase of aggregate bulk density. The mechanical milling is an accepted method for shortening MWCNTs, though strong mechanical milling may result in opening of the tips, destroying of the original structure and appearance of amorphous carbon [41]. The microstructure characteristics of MWCNTs before and after grinding were checked by SEM.…”

Section: Methodsmentioning

confidence: 99%

Microstructure and incubation processes in composite liquid crystalline material (5CB) filled with multi walled carbon nanotubes

Lisetski

Minenko

Ponevchinsky

et al. 2011

Materialwissenschaft Werkst

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This work reports a study on microstructure, electrical conductivity and phase transitions of 5CB(4-pentyl-49-cyanobiphenyl) + multi-walled carbon nanotubes (MWCNTs) composite materials. The concentration of MWCNTs was varied within 0.025 and 1 wt.%. The unmodified (o) and modified (m) MWCNTs were used. The mild milling was applied for shortening length of MWCNTs. Direct microscopic observation of composites at different concentrations C of MWCNTs evidenced the presence of aggregation and percolation processes. Formation of percolation networks was observed at C p L 0.025 -0.05% wt and C=C p L 0.1 -0.25% wt for o-MWCNTs and m-MWCNTs composites, respectively. Increase of the percolation threshold for m-MWCNTs, possibly, reflected their smaller aspect ratio r. The conductivity exponents were approximately the same (t L 3.3 l 0.1) for both o-MWCNTs and m-MWCNTs. The microstructure of MWCNT aggregates was not stable in time. The initially formed loose aggregates (L-aggregates) transformed into the more compact C-aggregates during the incubation time of one week. The incubation resulted in decrease of anisotropy, change in phase behaviour near the nematic-isotropic transition, and influenced external electric field response of the studied composite material. Inkubation führt zu einer Abnahme der Anisotropie, einem Wechsel der Phase in der Nähe der nematischen-isotropen Umwandlung und beeinflusst die Antwort auf ein externes elektrisches Feld der studierten Kompositmaterialien.

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Section: Methodsmentioning

confidence: 99%

Microstructure and incubation processes in composite liquid crystalline material (5CB) filled with multi walled carbon nanotubes

Lisetski

Minenko

Ponevchinsky

et al. 2011

Materialwissenschaft Werkst

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“…(%) of TTNT, revealed an enhancement of the hydrogen absorption/desorption kinetics when the catalyst was added. This can be attributed to the fact that the hydrogen diffusion on nanotubes occurs preferably along the nanotube length than in the radial direction 1,11 . This is based on the fact that the hydrogen molecules penetration is more likely to occur on the channels along the tube than on the walls that are formed by a dense layer of TiO6 octhaedrons 1 .…”

Section: Resultsmentioning

confidence: 99%

The effect of TTNT nanotubes on hydrogen sorption using MgH2

et al. 2013

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Nanotubes are promising materials to be used with magnesium hydride, as catalysts, in order to enhance hydrogen sorption. A study was performed on the hydrogen absorption/desorption properties of MgH 2 with the addition of TTNT (TiTanate NanoTubes). The MgH 2 -TTNT composite was prepared by ball milling and the influence of the TTNT amount (1.0 and 5.0 wt. (%)) on the hydrogen capacity was evaluated. The milling of pure MgH 2 was performed for 24 hours and afterwards the MgH 2 -TTNT composite was milled for 20 minutes. Transmission Electronic Microscopy (TEM) and Scanning Electron Microscopy (SEM) were used to evaluate the nanotube synthesis and show the particle morphology of the MgH 2 -TTNT composite, respectively. The Differential Scanning Calorimetry (DSC) examination provided some evidence with the shifting of the peaks obtained when the amount of TTNT is increased. The hydrogen absorption/desorption kinetics tests showed that the TTNT nanotubes can enhance hydrogen sorption effectively and the total hydrogen capacity obtained was 6.5 wt. (%).

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“…During milling, NH 4 HCO 4 is decomposed into NH 3 gas, water and CO 2 . The ball milling process also introduces defects and breaks the -C-C-bonds of the CNT surface [20][21][22][23], which is further promoted by the presence of NH 4 HCO 4 (see below). These in turn allow the amine and amide groups to form covalent bonds with the broken -C-Cbonds of the CNT surface.…”

Section: Resultsmentioning

confidence: 99%

“…These contrasting behaviors strongly suggested that NH 4 HCO 3 played an important role for the improvement of electrical conductivity of CNTs during milling. Ball milling conducted in the absence of any chemicals created defects and amorphous materials [20][21][22][23], resulting in a negative effect on electrical properties of CNTs due to the destruction of the graphite layer and perturbation of the π electron system on the CNT walls. However, the current study revealed a positive effect of ball milling on electrical conductivity.…”

Section: Resultsmentioning

confidence: 99%

Conversion of semiconducting behavior of carbon nanotubes using ball milling

Cheng¹,

Tang²,

Kim³

2008

Chemical Physics Letters

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This paper proposes a novel chemo-mechanical method to in-situ functionalize carbon nanotubes (CNTs). Ball milling in the presence of ammonium bicarbonate allowed the introduction of amine and amide groups onto the surface of CNTs, resulting in the conversion of the semiconducting behavior of CNTs from p-type to n-type. The corresponding electrical conductivity of CNT increased gradually with ball milling time, presenting a remarkable 250% increase after 9 hrs of milling. These interesting observations are attributed to the nitrogen compounds introduced on CNTs, which function as the electron donor in the material.

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Preparation of short carbon nanotubes by mechanical ball milling and their hydrogen adsorption behavior

Cited by 148 publications

References 28 publications

Microstructure and incubation processes in composite liquid crystalline material (5CB) filled with multi walled carbon nanotubes

Microstructure and incubation processes in composite liquid crystalline material (5CB) filled with multi walled carbon nanotubes

The effect of TTNT nanotubes on hydrogen sorption using MgH2

Conversion of semiconducting behavior of carbon nanotubes using ball milling

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