Flow properties and electrical conductivity of carbon black–linseed oil suspension

Amari, Takeshi; Watanabe, Kenji

doi:10.1122/1.550124

Cited by 23 publications

(15 citation statements)

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“…The elastic modulus and yield stress depend on the flow history which can be used to tune the solid-like properties of the gel at rest [16,66]. Finally, shear-induced changes in microstructure are known to strongly affect the electrical properties of carbon black gels as the percolated network ruptures under shear [26,31,48]. Depending on the choice of the carbon black, the conductivity of the gel either decreases by several orders of magnitude as the material is sheared and undergoes a conductor to insulator transition [31], or, in the case of more conductive samples, the conductivity only decreases by a small factor under shear [26].…”

Section: Rheo-electric Study Of Carbon Black Gelsmentioning

confidence: 99%

“…Description of the test fixture Rheo-electric platforms typically involve coupling an electrical measuring system to a conventional torsional rheometer that is used to measure the rheological properties of the materials under investigation. In previous work, a number of different two-electrode geometries have been used including cylindrical Couette [26,27,31], plate-plate [28,39,43,45], ring geometries [29,30,37,38] and pipe flow [32]. The difficulty inherent in performing simultaneous rheo-electric measurements lies in the additional friction caused by the electrical connection to the rotating electrode (typically through a slip ring), which can induce large errors in the measurement of the torque, when measured at the same electrode.…”

Section: Rheo-electric Test Fixturementioning

confidence: 99%

“…Another microstructural probe, less frequently employed, is measurement of the electrical properties of * ahelal@mit.edu the fluid (e.g. conductivity σ, permittivity ), which coupled with standard rheological measurements also provides additional information on the evolution of the fluid microstructure under flow [26][27][28][29][30][31][32]. Previous rheoelectric studies have focused mostly on dielectric complex fluids such as polymeric materials [33][34][35], liquid crystals [28], colloidal suspensions [32] and electrorheological fluids [36], as well as weakly conductive materials (σ 1 mS/cm) such as CNT nanocomposites [29,30,[37][38][39][40][41] and weakly conductive carbon black gels [26,27,[42][43][44][45].…”

Section: Introductionmentioning

confidence: 99%

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Simultaneous Rheoelectric Measurements of Strongly Conductive Complex Fluids

Helal¹,

Divoux²,

McKinley³

2016

Phys. Rev. Applied

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We introduce an modular fixture designed for stress-controlled rheometers to perform simultaneous rheological and electrical measurements on strongly conductive complex fluids under shear. By means of a nontoxic liquid metal at room temperature, the electrical connection to the rotating shaft is completed with minimal additional mechanical friction, allowing for simultaneous stress measurements at values as low as 1 Pa. Motivated by applications such as flow batteries, we use the capabilities of this design to perform an extensive set of rheoelectric experiments on gels formulated from attractive carbon-black particles, at concentrations ranging from 4 to 15 wt %. First, experiments on gels at rest prepared with different shear histories show a robust power-law scaling between the elastic modulus G 0 0 and the conductivity σ 0 of the gels-i.e., G 0 0 ∼ σ α 0 , with α ¼ 1.65 AE 0.04, regardless of the gel concentration. Second, we report conductivity measurements performed simultaneously with creep experiments. Changes in conductivity in the early stage of the experiments, also known as the Andrade-creep regime, reveal for the first time that plastic events take place in the bulk, while the shear rate _ γ decreases as a weak power law of time. The subsequent evolution of the conductivity and the shear rate allows us to propose a local yielding scenario that is in agreement with previous velocimetry measurements. Finally, to establish a set of benchmark data, we determine the constitutive rheological and electrical behavior of carbon-black gels. Corrections first introduced for mechanical measurements regarding shear inhomogeneity and wall slip are carefully extended to electrical measurements to accurately distinguish between bulk and surface contributions to the conductivity. As an illustrative example, we examine the constitutive rheoelectric properties of five different grades of carbon-black gels and we demonstrate the relevance of this rheoelectric apparatus as a versatile characterization tool for strongly conductive complex fluids and their applications.

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Section: Rheo-electric Study Of Carbon Black Gelsmentioning

confidence: 99%

Section: Rheo-electric Test Fixturementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Simultaneous Rheoelectric Measurements of Strongly Conductive Complex Fluids

Helal¹,

Divoux²,

McKinley³

2016

Phys. Rev. Applied

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“…Rheological properties of CB/polymer compounds and CB suspensions are very important from both academic and industrial points of view. In attempting to elucidate these rheological responses, extensive studies have been carried out for the CB/polymer compounds1–11 and CB suspensions 12–30. The occurrence of both yield stress and thixotropy for these systems has been found.…”

Section: Introductionmentioning

confidence: 99%

Rheological characterization of carbon black/polystyrene solution systems

Aoki

2008

J of Applied Polymer Sci

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Steady-shear measurements of suspensions of carbon blacks (CB) in polystyrene (PS)/di-(butyl phthalate) (DBP) solution were investigated as a function of volume fraction (/) of CB to clarify the effect of the primary particle size and the structure of CB aggregates on the rheological properties. The suspensions show a typical shear-thinning behavior in the range of a shear rate studied. The Casson model was applied to evaluate the viscosity at infinite of shear rate h ' and the yield stress r y for the suspensions. Relative viscosity h ' /h m , (h m : medium viscosity) thus obtained was compared to the high-frequency viscosity for the ideal hard-sphere silica suspensions to evaluate the effective volume fraction / eff of CB aggregates. The / eff value was larger for the higher-structure CB with higher DBP absorption value, irrespective of the primary particle size. The yield stress r y had almost the same / eff dependence for neutral furnace CB/(PS/ DBP) suspensions, although it was larger for acetylene black (AcB)/(PS/DBP) suspensions. These results demonstrated that the effective volume fraction is the most important quantity to characterize the CB aggregates on the rheological properties. It was also found that the correction of the medium viscosity changes due to polymer adsorption on the CB surface is important since neutral furnace CB adsorbs PS polymers but AcB hardly adsorbs PS polymers in the solution.

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“…At concentrations above the percolation threshold, the carbon black creates an electrically conductive network inside the flowing electrolytes of the battery, allowing for higher reaction rates and overall system efficiency. However, it has been experimentally demonstrated that the networks in these carbon suspensions are highly sensitive to shearing [25][26][27][28]. In these studies, the conductivity of the carbon network drops precipitously with shear and recovers dynamically when brought to rest.…”

mentioning

confidence: 99%

Coupled dynamics of flow, microstructure, and conductivity in sheared suspensions

et al. 2016

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We propose a model for the evolution of the conductivity tensor for a flowing suspension of electrically conductive particles. We use discrete particle numerical simulations together with a continuum physical framework to construct an evolution law for the suspension microstructure during flow. This model is then coupled with a relationship between the microstructure and the electrical conductivity tensor. Certain parameters of the joint model are fit experimentally using rheo-electrical conductivity measurements of carbon black suspensions under flow over a range of shear rates. The model is applied to the case of steady shearing as well as time-varying conductivity of unsteady flow experiments. We find that the model prediction agrees closely with the measured experimental data in all cases.

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Flow properties and electrical conductivity of carbon black–linseed oil suspension

Cited by 23 publications

References 0 publications

Simultaneous Rheoelectric Measurements of Strongly Conductive Complex Fluids

Simultaneous Rheoelectric Measurements of Strongly Conductive Complex Fluids

Rheological characterization of carbon black/polystyrene solution systems

Coupled dynamics of flow, microstructure, and conductivity in sheared suspensions

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