Rheological properties and orientational distributions of dilute ferromagnetic spherocylinder particle dispersions. Part II. Analysis for the two typical magnetic field directions.

Journal of colloid and interface science · 2002 · Mixed · Insufficient evidence

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MixedInsufficient evidencePaper 3796

Study snapshot

PublicationJournal of colloid and interface science · 2002

Study typeother

Reported directionMixed

Evidence ratingInsufficient

Abstract

We have investigated the orientational distributions and rheological properties of dilute colloidal dispersions, which consist of ferromagnetic spherocylinder particles. First, the governing equation of the orientational distribution function has been derived for the typical two cases of magnetic field directions: the direction parallel to the shear flow and the direction parallel to the angular velocity vector of the shear flow. The equation has been solved approximately by Galerkin's method. With these numerical solutions we have obtained the results of the orientational distribution and viscosity. The results obtained for the magnetic field in the shear flow direction are summarized as follows. In the case of a weak magnetic field, the particle tends to orient nearly toward the shear flow direction and its opposite direction. As the magnetic field increases, the orientation of the particle is restricted and the viscosity increases significantly. As the influence of the magnetic field becomes dominant, an overshoot in the viscosity curve appears. This is due to the fact that there is a maximum deviation of the averaged particle direction from the magnetic field direction. When the strength of the magnetic field increases significantly, the particle inclines close to the magnetic field direction and the viscosity converges to a constant value. Particles with a larger aspect ratio give rise to a larger increment in the viscosity since such elongated particles induce larger resistance in a flow field. We also have obtained results for the case of the magnetic field in the direction parallel to the angular velocity vector of the shear flow. When the flow field is dominant over both the rotational Brownian motion and the magnetic interaction, the particle rotates in the plane nearly perpendicular to the magnetic field direction. As the magnetic field increases, the particle inclines toward the magnetic direction. For this direction of field, the viscosity is independent of the magnetic field and is always zero.

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AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeother

Effect directionmixed

PopulationNot supplied

Sample sizeNot supplied

ExposureNot supplied

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

A governing equation for the orientational distribution of dilute ferromagnetic spherocylinder dispersions was derived for two magnetic-field directions relative to shear flow and solved approximately (Galerkin method). For magnetic field parallel to the shear-flow direction, increasing field strength restricted particle orientation and increased viscosity, with an overshoot at intermediate dominance and convergence to a constant viscosity at high field; larger aspect ratio increased viscosity increment. For magnetic field parallel to the angular-velocity vector of the shear flow, particles inclined toward the magnetic direction as field increased, and the viscosity was reported to be independent of magnetic field and always zero for this field direction.

Outcomes measured

orientational distribution
viscosity
rheological properties

Limitations

No biological/health outcomes assessed (engineering/physics rheology study).
Magnetic field characteristics (e.g., strength, frequency/time variation) not specified in the abstract.
Solutions described as approximate (Galerkin method), suggesting model-based rather than direct experimental measurement.

View raw extracted JSON

{
  "study_type": "other",
  "exposure": {
    "band": null,
    "source": "magnetic field",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "orientational distribution",
    "viscosity",
    "rheological properties"
  ],
  "main_findings": "A governing equation for the orientational distribution of dilute ferromagnetic spherocylinder dispersions was derived for two magnetic-field directions relative to shear flow and solved approximately (Galerkin method). For magnetic field parallel to the shear-flow direction, increasing field strength restricted particle orientation and increased viscosity, with an overshoot at intermediate dominance and convergence to a constant viscosity at high field; larger aspect ratio increased viscosity increment. For magnetic field parallel to the angular-velocity vector of the shear flow, particles inclined toward the magnetic direction as field increased, and the viscosity was reported to be independent of magnetic field and always zero for this field direction.",
  "effect_direction": "mixed",
  "limitations": [
    "No biological/health outcomes assessed (engineering/physics rheology study).",
    "Magnetic field characteristics (e.g., strength, frequency/time variation) not specified in the abstract.",
    "Solutions described as approximate (Galerkin method), suggesting model-based rather than direct experimental measurement."
  ],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "ferromagnetic",
    "spherocylinder",
    "colloidal dispersion",
    "magnetic field direction",
    "shear flow",
    "orientational distribution",
    "viscosity",
    "Galerkin method",
    "rheology"
  ],
  "suggested_hubs": []
}

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Identifiers and source

DOI: 10.1006/jcis.2002.8451
PubMed: 16290877

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