Rheology of concentrated carbon nanotube suspensions

Hobbie, Erik K.; Fry, D.

doi:10.1063/1.2711176

Cited by 128 publications

(98 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1C). The value of the exponent is comparable to that reported earlier for fibers and nanotube suspensions, which lies in the range of 2.5-3.5 (10,21). A shear-thickened region (region C) always occurs over the range of nanotube weight fractions (1-10%) studied though the critical stress for the onset of ST (σ st ) increases with Φ, and could be fitted to a functional form σ st ¼ σ 0 ðΦ − Φ c Þ α with σ 0 ¼ 780 Pa, Φ c ¼ 0.005, and α ∼ 2.…”

Section: Resultssupporting

confidence: 75%

“…This trend is further encouraged by recent experimental and theoretical studies which surmised that a strong ST will not be observed in flocculated suspensions because the attractive interactions that drive flocculation increase the yield stress and mask the ST behavior, leading to a monotonic shear-thinning viscosity curve (7)(8)(9). Consistent with this picture, a shear-thinning behavior is always seen, for example, in flocculated suspensions of carbon nanotubes (10,11).…”

supporting

confidence: 62%

“…In fact, ST behavior was not known for flocculated suspensions until recently, where a modest continuous ST (when the viscosity increases by a factor of 3) was reported in flocculated fumed colloidal suspensions at low weight fractions (>2 wt %) (13,14). Nevertheless, the consistent shear-thinning behavior of flocculated multiwalled carbon nanotubes (MWNT) suspensions in aqueous medium, organic solvents, as well as polymeric melts (10,15) indicate that predicting the conditions and the mechanism that drive shear-thickening behavior in non-Brownian flocculating suspensions has yet to be understood. The mechanism of ST in non-Brownian flocs will be distinct from that of Brownian particles where ST arises from the clustering of particles around the compression axis of shear flow when the hydrodynamic viscous force dominates over Brownian forces above a shear rate k B T η s a 3 where a is average particle size.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Discontinuous shear thickening in confined dilute carbon nanotube suspensions

Majumdar

Krishnaswamy

Sood

2011

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

A monotonic decrease in viscosity with increasing shear stress is a known rheological response to shear flow in complex fluids in general and for flocculated suspensions in particular. Here we demonstrate a discontinuous shear-thickening transition on varying shear stress where the viscosity jumps sharply by four to six orders of magnitude in flocculated suspensions of multiwalled carbon nanotubes (MWNT) at very low weight fractions (approximately 0.5%). Rheooptical observations reveal the shear-thickened state as a percolated structure of MWNT flocs spanning the system size. We present a dynamic phase diagram of the non-Brownian MWNT dispersions revealing a starting jammed state followed by shearthinning and shear-thickened states. The present study further suggests that the shear-thickened state obtained as a function of shear stress is likely to be a generic feature of fractal clusters under flow, albeit under confinement. An understanding of the shear-thickening phenomena in confined geometries is pertinent for flow-controlled fabrication techniques in enhancing the mechanical strength and transport properties of thin films and wires of nanostructured composites as well as in lubrication issues.A n increase in viscosity of fluids with increasing flow rate termed as "shear thickening" (ST) is of tremendous interest in basic sciences as well as for many applications which include the design of smart materials like soft body armors and shock absorbers (1). Traditionally, the candidates for shear-thickening fluids have been dense suspensions of Brownian/non-Brownian, nonaggregating, monodisperse spherical or rod-like particles (2-6). This trend is further encouraged by recent experimental and theoretical studies which surmised that a strong ST will not be observed in flocculated suspensions because the attractive interactions that drive flocculation increase the yield stress and mask the ST behavior, leading to a monotonic shear-thinning viscosity curve (7-9). Consistent with this picture, a shear-thinning behavior is always seen, for example, in flocculated suspensions of carbon nanotubes (10, 11).The rheophysics of flocculated suspensions formed by colloidal particles with attractive interactions also raises several interesting issues. A universal jamming phase diagram proposed for attractive particles (12) with particle volume fraction Φ, interparticle attraction U, and stress σ as the control parameters is consistent with the nonequilibrium shear diagram for multiwalled nanotubes mapped out using rheooptical studies (11). Here, the nanotubes, which are entangled at low shear stress to exhibit a solidlike behavior, transform to a liquid-like state by dispersing the nanotubes that align along flow to form a nematic phase above a critical shear stress. However, the feasibility of achieving a reentrant jamming phase behavior by tuning the attractive interactions in these systems has not been examined. In fact, ST behavior was not known for flocculated suspensions until recently, where a modest continuous ST (whe...

show abstract

Section: Resultssupporting

confidence: 75%

supporting

confidence: 62%

mentioning

confidence: 99%

See 1 more Smart Citation

Discontinuous shear thickening in confined dilute carbon nanotube suspensions

Majumdar

Krishnaswamy

Sood

2011

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…The behavior described here is completely analogous to the type of yield-stress behavior exhibited by concentrated carbon-nanotube suspensions. 40 Although the film modulus is extrapolated as a fitting parameter and is thus to some extent approximate, the reported trends with thickness and concentration are robust. The small yield strains are further supported by small-strain measurements that exploit a degree of PDMS swelling to introduce a controlled isotropic strain (Figure 7).…”

Section: ' Results and Discussionmentioning

confidence: 99%

Structural Stability of Transparent Conducting Films Assembled from Length Purified Single-Wall Carbon Nanotubes

et al. 2011

View full text Add to dashboard Cite

ABSTRACT:Single-wall carbon nanotube (SWCNT) films show significant promise for transparent electronics applications that demand mechanical flexibility, but durability remains an outstanding issue. In this work, thin membranes of length purified single-wall carbon nanotubes (SWCNTs) are uniaxially and isotropically compressed by depositing them on prestrained polymer substrates. Upon release of the strain, the topography, microstructure, and conductivity of the films are characterized using a combination of optical/fluorescence microscopy, light scattering, force microscopy, electron microscopy, and impedance spectroscopy. Above a critical surface mass density, films assembled from nanotubes of well-defined length exhibit a strongly nonlinear mechanical response. The measured strain dependence reveals a dramatic softening that occurs through an alignment of the SWCNTs normal to the direction of prestrain, which at small strains is also apparent as an anisotropic increase in sheet resistance along the same direction. At higher strains, the membrane conductivities increase due to a compression-induced restoration of conductive pathways. Our measurements reveal the fundamental mode of elasto-plastic deformation in these films and suggest how it might be suppressed. ' INTRODUCTIONIn the past two decades, single-wall carbon nanotubes (SWCNTs) have received considerable attention due to their outstanding mechanical, optical, and electronic properties, and a vast amount of research has been devoted to the characterization of these attributes 1 and the potential applications they suggest. 2 Promising applications are rapidly emerging in such areas as high performance composites, 3 thermoelectric materials, 4 and conducting polymer composites.5 Thin SWCNT films, in particular, show exceptional promise for applications that require transparent coatings with superior mechanical, electronic, and optical qualities. [6][7][8][9] The natural tendency for SWCNTs to form flexible, transparent networks with high electrical conductivity at remarkably low surface coverage is a direct consequence of the magnitude of the typical SWCNT aspect ratio, 10 suggesting that nanotube length is a critical factor in dictating the physical properties of such membranes.The electronic and optical properties of SWCNTs are determined by their electronic band structure, 1 which is specified by the chiral vector (n, m) characterizing the symmetry of rolling a two-dimensional graphene sheet into a hollow tube of diameter a. All existing synthetic techniques therefore produce raw material that contains a distribution of electronic types, ranging from semiconducting to metallic, as well as a broad range of lengths, from 10 nm up to hundreds of micrometers. Since scalable processes for purifying lab-grade quantities of SWCNTs have only recently been formulated, 11-13 thin films of exemplary purified materials have just now become readily available for fundamental research, pointing toward a number of promising applications. Thin SWCNT membranes have rece...

show abstract

“…nano-particles, CNT) in a base fluid (nanofluid) has evolved over the past decade. The experiments have unveiled improvements in the rheological (Aladag et al 2012;Chen et al 2011;Jyothirmayee Aravind et al 2011;Lei et al 2008;Murshed et al 2008;Hobbie and Fry 2007;Vakili-nezhaad and Dorany 2009;Phuoc et al 2011;Liu et al 2005) as well as in the thermal (Ding et al 2006;Hwang et al 2006;Kalinina et al 2011;Ö zerinç et al 2010;Venkata Sastry et al 2008;Xie and Chen 2009;Kleinstreuer and Feng 2011;Choi et al 2001;Karthikeyan et al 2008;Xie et al 2002) properties of the nanofluid system, compared to its base fluid.…”

Section: Introductionmentioning

confidence: 99%

Thermal and rheological properties improvement of drilling fluids using functionalized carbon nanotubes

Fazelabdolabadi¹,

Khodadadi

Sedaghatzadeh

2014

Appl Nanosci

View full text Add to dashboard Cite

The application of functionalized/unfunctionalized (multi-walled) carbon nanotubes (CNT) was investigated in the context of formulating nano-based drilling fluids from water/oil-based fluid templates. CNT functionalization was attempted by applying hydrophilic functional groups onto the surface of the nanotubes via acid treatment. Experimental data were collected for thermal conductivity, viscosity/yield point, and filtrate amount in all samples. The time evolution of thermal conductivity was studied, as well as the effects of temperature and CNTs volume fraction on the parameter. Scanning electron microscopy (SEM) was used to monitor CNTs dispersion quality. The thermal conductivity results unveil considerable enhancements, by as much as 23.2 % (1 % vol. functionalized CNT) in CNT-water-based case at ambient temperature, with extended improvement of 31.8 % at an elevated temperature of 50°C. Corresponding results for the CNT-oil-based case exhibit an improvement in thermal conductivity by 40.3 % (unfunctionalized) and 43.1 % (functionalized) and 1 % volume fraction of CNT. The rheological results follow an analogous improvement trend. For the CNT-oil-based case, the filtration tests conducted at 138°C and 500 (psi) show a 16.67 % reduction in filtrate amount (1 % vol. CNT). The time evolution of thermal conductivity was found to nearly equalize (at an amount of 9.7 %) after 100 h of sample preparation in both functionalized and unfunctionalized CNT-oil-based cases.

show abstract

Rheology of concentrated carbon nanotube suspensions

Cited by 128 publications

References 32 publications

Discontinuous shear thickening in confined dilute carbon nanotube suspensions

Discontinuous shear thickening in confined dilute carbon nanotube suspensions

Structural Stability of Transparent Conducting Films Assembled from Length Purified Single-Wall Carbon Nanotubes

Thermal and rheological properties improvement of drilling fluids using functionalized carbon nanotubes

Contact Info

Product

Resources

About