The influence of temperature and of a longitudinal magnetic field upon the electrical conductivity of magnetorheological suspensions

doi:10.1016/j.physb.2005.09.046

Physica B: Condensed Matter

Volume 371, Issue 1, 15 January 2006, Pages 145-148

https://doi.org/10.1016/j.physb.2005.09.046 Get rights and content

Abstract

The magnetorheological suspension (MRS) is based on mineral oil, stearic acid and iron micro-particles. The mean diameter of the iron micro-particles is 2.10 μm. MRS becomes conductive only in magnetic field, starting from intensities of 72 kA/m. By means of an experimental installation, described in this paper, the MRS function of temperature is measured (300 K⩽T⩽400 K) for intensities of the longitudinal magnetic field of 72, 112, 148 and 175 kA/m. From measurements of electrical resistance the electrical conductivity of MRS is determined, and the results obtained are discussed.

Introduction

The magnetorheological suspension (MRS) resembles electrorheological fluids (ERF). Both modify their rheological properties dramatically—the former, in magnetic field, the lather, in electric field.

In both cases, chains of micro-particles are formed [1], [2], [3] along the field lines. There results the growth, by some magnitude orders, of the value of the apparent viscosity. This phenomenon is used in various applications [4], [5], [6], [7].

Of great interest is the study of the electrical conductivity of the metal micro-particles systems dispersed in non-conductive matrices. Thus, Ref. [8] details a method of prediction of the actual electrical conductivity of such systems. On the other hand, Refs. [9], [10] detail methods for determining the electrical conductivity of MRS, while Ref. [11] describes a method for the simultaneous measuring of viscosity and electrical conductivity of ERF.

The phenomenon of electrical conductivity of MRS, in the presence of magnetic field of well-chosen intensities and directions, is used for the devising of sensors for detection of fringe fields in magnetic fields [12], as well as of warfare agents [13], etc.

In considering these applications, we set ourselves to show how the temperature and longitudinal magnetic field influence the electrical conductivity of MRS.

Section snippets

MRS

MRS is obtained by the thermal decomposition of Fe₂(CO)₉ in mineral oil mixed up with stearic acid. The experimental installation and the procedure are described in Ref. [14]. At temperatures of 423 K±10% for 150 s, the thermal decomposition of Fe₂(CO)₉ in the liquid matrix (mineral oil with stearic acid) occurs. On this occasion, a mixture of iron micro-particles and liquid matrix (Fig. 1a), called MRS, is formed. The mean diameter of the micro-particles is $d_{m} = 2.1 0 μ m$ (Fig. 1b), at a standard

Experimental installation

The block scheme of the experimental installation, used for the study of the influence of magnetic field and temperature upon the electrical resistance is described in Fig. 3.

The installation comprises the electromagnet A, the measuring cell B, measurement apparatus and power sources. The core of the electromagnet is made of carbon steel. Its cross-section is a square with the side of 0.020 m. The poles of the electromagnet have their section equal to that of the core. Between the poles, the

Experimental results and discussion

The study of the influence of longitudinal magnetic field and temperature upon the electrical resistance of MRS is achieved by means of the experimental installation in Fig. 3. In the measuring cell, MRS has a volume concentration of the solid phase of $Φ = 0.3 0$ .

The temperature T of MRS is a mean value. It is obtained from the values of the temperatures measured by means of the thermometers 8 and 9 in Fig. 3. Regulation of the temperature of MRS is achieved by means of the power source S₁.

The

Conclusions

•
The MRS formed of mineral oil with stearic acid and iron micro-particles ( $d_{m} = 2.1 μ m$ , $φ = 0.3 0$ ) is electroconductive in a longitudinal magnetic field, starting with intensities of 72 kA/m.
•
In the interval of temperatures ranging between 300 and 400 K, the electrical conductivity of MRS increases by up to 96.8%, and it depends on the intensity of the magnetic field applied (Fig. 5).
•
The electrical conductivity of MRS at fixed T (Fig. 5) increases considerably with the intensity H of the longitudinal

Acknowledgements

I am thankful to Professors E. Papp and. C.T. Cheveresan of the West University of Timisoara for interesting discussions.

References (17)

M. Parthasarathy et al.
Mater. Sci. Eng. Rep.
(1996)
I. Bica
J. Magn. Magn. Mater.
(2002)
I. Bica
J. Magn. Magn. Mater.
(2004)
S. Bednarek
J. Magn. Magn. Mater.
(1999)
I. Bica
J. Magn. Magn. Mater.
(2004)
P. Gould
Mater. Today
(2004)
R.D. Edelstein et al.
Biosens. Bioelectron.
(2000)
I. Bica
Mater. Sci. Eng.
(2003)

There are more references available in the full text version of this article.

Cited by (24)

State of the art of medical devices featuring smart electro-rheological and magneto-rheological fluids
2017, Journal of King Saud University - Science
Citation Excerpt :
Therefore, numerous engineering applications have been proposed by many scholars. Especially, damping force performance of MR damper which can control the damping force according to magnetic field has been intensively worked in Bica (2002, 2004, 2006a,b, 2009), Bica and Choi (2008), Bica et al. (2013, 2015a,b). The basic principle of the prosed medical applications are same that used for MR dampers. Kim and Oh (2001) introduced an above knee prosthesis using a rotary MR damper and tested its effectiveness by adopting leg simulator.
Recently, smart fluids have drawn significant attention and growing a great interest in a broad range of engineering applications such as automotive and medical areas. In this article, two smart fluids called electro-rheological (ER) fluid and magneto-rheological (MR) fluid are reviewed in terms of medical applications. Especially, this article describes the attributes and inherent properties of individual medical and rehabilitation devices. The devices surveyed in this article include multi-degree-of-freedom haptic masters for robot surgery, thin membrane touch panels for braille readers, sponge-like tactile sensors to feel human tissues such as liver, rehabilitation systems such as prosthetic leg, and haptic interfaces for dental implant surgery. The operating principle, inherent characteristics and practical feasibility of each medical device or system are fully discussed in details.
Influence of magnetic field on dispersion and dissipation of electric field of low and medium frequencies in hybrid magnetorheological suspensions
2015, Journal of Industrial and Engineering Chemistry
We have obtained hybrid magnetorheological suspensions (MRS-hybrid) consisting of magnetorheological suspension (MRS), magnetorheological elastomer (MRE) and polyurethane sponge foam (PSF). We measure the capacitance and resistance of a plane capacitor based on MRS-hybrid, as a function of frequency f of an electric field superimposed with a magnetic field of intensity H. The relative dielectric permittivity ϵ′, dielectric loss factor $ϵ^{''}$ and electrical conductivity σ are significantly changed when 0.02 ≤ f(kHz) ≤ 200 at H = 0, 100, 200 and 400 kA/m. The static and optical dielectric constants are greatly influenced by the magnetic field intensity. We present and discuss the results using the model of dipolar approximation.
Magnetodielectric effects in hybrid magnetorheological suspensions
2015, Journal of Industrial and Engineering Chemistry
Citation Excerpt :
The latter property of MRSs is used for development of vibration dampers and mechanical shock attenuators or for production of clutches with a coefficient of mechanical coupling (coefficient which depends on the volume of magnetizable phase) controlled by the intensity of an applied magnetic field [8]. Recently, it has been shown that under the influence of a magnetic field, MRSs have electroconductive properties [9–14]. Microparticles having a diameter between 1 and 10 μ m settle in the liquid matrix, and solving this issue (partially or totally) is achieved by introducing additives such as carbon nanotubes [15] or of graphene nanoparticles [16].
The magnetodielectric material obtained is a hybrid magnetorheological suspension (MRS-hybrid) which contains polyurethane sponge foam, magnetorheological suspensions (MRS) and polymerized silicone rubber. We create a plane capacitor based on MRS-hybrid. Using a programmable bridge we measure the capacitance C and the dissipation factor D of the capacitor as a function of intensity H of a constant magnetic field, and as a function of frequency f of an electric field. We determine the components ϵ′ (relative dielectric permittivity) and $ϵ^{''}$ (dielectric loss factor) of the complex dielectric permittivity ϵ^* of MRS-hybrid. We present and discuss the obtained results.
An inductance-based technique for the measurement of magnetic moment of the magnetorheological fluids
2014, Measurement: Journal of the International Measurement Confederation
Citation Excerpt :
The ferromagnetic particles in MRF will become polarized and be thereby arranged into chains and clusters when a magnetic field is applied, and the material will transform from the liquid phase to the solid phase. This dynamic process will directly change the conductive and mechanical properties of MRF as reported [13,14]. However, according to Eq. (4), the inductance property of our system is just related with the magnetization property of the Fe3O4 particles in the MRF, noting that the variation of the distribution and reconfiguration of the ferromagnetic particles in MRF have no influence on its inductance measurement.
We presented a detailed study of the inductance properties of a MRF-based system with different MRF volume fractions under a magnetic field. The inductance of the system raised firstly and then decreased while the magnetic field kept increasing. We theoretically analyzed the mechanism of the field-induced variation of the inductance and deduced that the magnetic field dependence of the inductance could be represented by the derivative of the magnetic moment of MRF, thus the M–H curves of the MRF could be derived from the inductance measurement proceeded in our work. This method for the magnetization calibration was very convenient and economic for manipulation compared with the traditional magnetization meter techniques and has been proved to be feasible according to the experimental results which showed a satisfactory measurement precision.
The research of the conductive mechanism and properties of magnetorheological fluids
2013, Physica B: Condensed Matter
Citation Excerpt :
The controllable rheological properties of MRF have been used in various fields such as automobile suspensions system, bridge-stay cables, and medical apparatus and instruments [6–8], making MRF a kind of new generation popular intelligent material. However, despite the significant success in the research of its rheological properties and the related application, a systematic study on the electrical conductive properties of MRF is still lacking [9] and the corresponding application is rarely reported. In this paper, we have studied the electrical conductive characters of MRF according to the experimental results, and referenced the theory advanced by Zhu et al. [10,11], which qualitatively described the chaining process of the ferromagnetic particles of MRF under the magnetic field with different intensities, and theoretically analysed the intrinsic mechanism of the resistance-change process.
We investigated the resistance response induced by the magnetic field in magnetorheological fluids, the resulting magnetization process alters the distribution of the ferromagnetic particles from unordered distribution to catenulate distribution. Consequently the electrical conductive property of the whole sample changes. A four-stage model has been built to describe the distinct characteristics of the variation of the magnetorheological fluids resistance with a sectional formalism, which is found in excellent agreement with the experimental results. Also, the application of the electrical properties of the magnetorheological fluids in the engineering field is discussed.
Improved thermooxidation and sedimentation stability of covalently-coated carbonyl iron particles with cholesteryl groups and their influence on magnetorheology
2013, Journal of Colloid and Interface Science
Citation Excerpt :
Thus, such MR fluids find perspective application, for example, as dumping systems or torque transducers [14,15]. Furthermore, such suspensions can be successfully applied as a magnetoresistors in various devices, due to their electro-conducting character [16–25]. Unfortunately, MR fluids exhibit some shortcomings such as particle sedimentation and poorer oxidation stability.
Sedimentation of particles in magnetorheological suspensions represents a crucial problem that concerns their efficient long-term application in practice. Prepared carbonyl iron (CI) microparticles coated with a low density substance, cholesteryl chloroformate, via a two-step reaction and immersed in silicone oil, exhibit three positive aspects: (1) the CI particle modification increased the compatibility between the particles and the silicone oil resulting in improved long-term stability (reduction in sedimentation); (2) the coating provided the particles with enhanced thermal stability in the oxygen atmosphere; and (3) rheological measurements proved a promising magnetorheological performance at different particle weight fractions.

View all citing articles on Scopus

View full text

The influence of temperature and of a longitudinal magnetic field upon the electrical conductivity of magnetorheological suspensions

Abstract

Introduction

Section snippets

MRS

Experimental installation

Experimental results and discussion

Conclusions

Acknowledgements

Mater. Sci. Eng. Rep.

J. Magn. Magn. Mater.

J. Magn. Magn. Mater.

J. Magn. Magn. Mater.

J. Magn. Magn. Mater.

Mater. Today

Biosens. Bioelectron.

Mater. Sci. Eng.