PMID- 19508094
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20090813
LR  - 20090610
IS  - 1089-7690 (Electronic)
IS  - 0021-9606 (Linking)
VI  - 130
IP  - 21
DP  - 2009 Jun 7
TI  - Orientation dynamics in multiwalled carbon nanotube dispersions under shear flow.
PG  - 214903
LID - 10.1063/1.3139446 [doi]
AB  - We report studies of the orientation state of multiwalled carbon nanotubes 
      (MWNTs) dispersions in steady and transient shear flows. Uncured epoxy was used 
      as a viscous Newtonian suspending medium and samples were prepared from "aligned" 
      MWNTs using methods previously reported [S. S. Rahatekar et al., J. Rheol. 50, 
      599 (2006)]. Orientation measurements were performed in both the flow-gradient 
      (1-2) and flow-vorticity (1-3) plane of simple shear flow using in situ x-ray 
      scattering techniques. Steady state measurements in the 1-2 plane indicate that 
      the MWNT orientation is shear rate dependent, with the MWNTs orienting closer to 
      the flow direction at higher shear rates. During steady shear, anisotropy was 
      measured to be higher in the 1-2 plane than in the 1-3 plane, demonstrating that 
      the nanotube orientation state is not unaxially symmetric in shear. It is 
      hypothesized that the steady state MWNT orientation is governed primarily by a 
      rate-dependent state of nanotube aggregation/disaggregation, which was separately 
      characterized by optical microscopy of the same samples under shear. High flux 
      synchrotron radiation allowed for time-resolved structural studies in transient 
      flows. A partial relaxation of flow-induced anisotropy was observed following 
      flow cessation, despite the very small rotational diffusivity estimated for these 
      nanotubes. Long transients are observed in step-down experiments, as the 
      orientation state changes in response to the slow tube aggregation process.
FAU - Pujari, Saswati
AU  - Pujari S
AD  - Department of Chemical and Biological Engineering, Northwestern University, 
      Evanston, Illinois 60208, USA.
FAU - Rahatekar, Sameer S
AU  - Rahatekar SS
FAU - Gilman, Jeffrey W
AU  - Gilman JW
FAU - Koziol, Krzysztof K
AU  - Koziol KK
FAU - Windle, Alan H
AU  - Windle AH
FAU - Burghardt, Wesley R
AU  - Burghardt WR
LA  - eng
PT  - Journal Article
PL  - United States
TA  - J Chem Phys
JT  - The Journal of chemical physics
JID - 0375360
EDAT- 2009/06/11 09:00
MHDA- 2009/06/11 09:01
CRDT- 2009/06/11 09:00
PHST- 2009/06/11 09:00 [entrez]
PHST- 2009/06/11 09:00 [pubmed]
PHST- 2009/06/11 09:01 [medline]
AID - 10.1063/1.3139446 [doi]
PST - ppublish
SO  - J Chem Phys. 2009 Jun 7;130(21):214903. doi: 10.1063/1.3139446.