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Fluid property evaluation by using transversal effects of piezoelectric transducer
Journal of Magnetism and Magnetic Materials 252 (2002) 98–100
Fluid property evaluation by using transversal effects of piezoelectric transducer B. Jeyadevana,*, S. Momozawab, K. Imanob, K. Tohjia a
Department of Geoscience and Technology, Tohoku University, Aramaki Aoba 01, Aoba-ku, Sendai 980-8597, Japan b Akita University, 1-1 Tegatagakuencho, Akita 010-8502, Japan
Abstract In this paper, we describe a highly sensitive device that utilizes the transversal effect of rectangular piezoelectric transducer to measure the viscosity of water-based and ionic MFs. This device could monitor the differences in MF types and also have overcome the design limitations of the conventional viscometer for measurements in external magnetic fields. r 2002 Elsevier Science B.V. All rights reserved. Keywords: Fluid property; Transversal effects; Piezoelectric transducer
1. Introduction
2. Experiment
Recent studies on ionic, oil- and water-based magnetic fluids (MFs) dispersing magnetite suggest that the particle dispersion characteristics are different among them [1]. Furthermore, the dimensional characteristics of field-induced clusters among different type of MFs also have been found to be different. These basic differences in cluster characteristic are believed to influence the viscoelastic properties of MF. However, the conventional measuring devices are less sensitive to monitor these differences and also have design limitations for measurements in external magnetic fields [2]. Authors have been working on the development of a device that utilizes the transversal effects of piezoelectric transducer to determine the fluid properties [3,4]. In this paper, we describe a highly sensitive device that utilizes the transversal effect of a rectangular piezoelectric transducer to measure the viscosity of fluids. We also report the results of magnetic fluid property measured using this device in applied magnetic field.
(i) Measuring device: A rectangular type PZT transducer of 70 10 0.5 mm that acts as both actuator and sensor was suspended by thin lead wire and partially immersed in the MF as shown in Fig. 1. One side of the surface of the transducer was electrically isolated from the MF, while the other was contacted to the MF. The electrical impedance was measured by an impedance meter (HP 4800A) and a frequency counter (Sabtronics Model 8000). The resonance of the transversal effect for the vibration in the longitudinal direction around 22.850 kHz was used to sense the viscosity of the fluid. The variation of electrical admittance and resonant frequency due to the change in viscosity of the liquid were measured using the impedance meter. (ii) Sample: MFs used in this study are (a) W40 (water-based—Taiho Co. Ltd.) and (b) ionic MF (IFF20) prepared by one of the authors. A DC magnet was used to apply a uniform magnetic field (max. 0.06 T) perpendicular to the transducer.
3. Results
*Corresponding author.
The resonant frequency change and the elastic film mass change on the piezoelectric disk [5] can be
0304-8853/02/$ - see front matter r 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 8 8 5 3 ( 0 2 ) 0 0 6 4 8 - 0
B. Jeyadevan et al. / Journal of Magnetism and Magnetic Materials 252 (2002) 98–100
FREQUENCY COUNTER
99
30
IMPEDANCE METER HP4800A R r [ohm]
20
10
Holder Rectangular plate type transducer
Container
0 0
Magnetic Fluid
( ×
ð1Þ
where, fr ; Dfr ; Dm; m; rQ ; A and rL are the resonant frequency, resonant frequency shift, surface mass change, shear modulus, density, and the surface area of the transducer, and density of the liquid, respectively. The Rr of the transducer in contact with magnetic fluid is given by Rr ¼ ð2pfr rL ZÞ
2
A=k ;
ð2Þ
Resonance Resistance (ohm)
given by
1=2
20 ) 1/2
[g 1/2
30 cm -3/2
40
cP 1/2 ]
Fig. 2. Experimental results of Rr vs. ðr ZÞ1=2 for water– glycerin mixtures.
Fig. 1. Experimental setup for viscosity measurements.
Dfr ¼ Dmfr2 =ðmrQ Þ1=2 A;
10
16 Water-based (W40) Ionic (IFF20)
14 12 10 8 6 0
10 20 30 40 Solid Concentration, wt. %
50
where, k is the electro-mechanical coupling factor. The Rr reflects the mechanical resistance of the transducer. The fr change reflects the mass effect of the liquid that moves with the disk of the transducer. This liquid mass effect is defined as
Fig. 3. Relation between magnetic solid concentrations and Rr for IFF20 and W40.
Dm ¼ AðZrL =pfr Þ1=2 :
Fig. 3 shows the relation between magnetic solid concentrations in IFF20 and W40 against Rr : For the measurements of zero solid concentrations of W40 and IFF20, water samples containing surfactant (SDBS) and tetra methyl ammonium were used, respectively. The change in Rr at very low solid concentration was marginal. However, the resonant resistance increased for any increase in the solid concentration in both cases. The change in Rr for W40 became larger at higher solid concentrations. This is in agreement with the conventional measurements. Furthermore, the plot between Rr and ðrZÞ1=2 ; based on the viscosity values determined using the conventional cone plate viscometer showed a linear relationship. This confirmed the viability of this method for fluid property evaluation. And also, it should be noted that the present setup could sense any change in viscosity as small as 0.1 cP or lower. For any specific solid concentration, the Rr increased with the strength of applied magnetic field suggesting the
ð3Þ
Eq. (3) could be substituted into Eq. (1) to obtain the change in frequency. Therefore, both Dfr and Rr have a linear relation such that for any decrease in fr ; Rr increases. 3.1. Water–glycerin suspension Fig. 2 shows the experimental results for water– glycerin mixtures with various viscosities. The abscissa is ðrZÞ1=2 ; where r and Z are the density and viscosity of the liquid, respectively. The ordinate of Fig. 1 shows the Rr derived from Cole–Cole plots of admittance. On the other hand, the ðrZÞ1=2 and Dfr also showed good linearity. Though the change in Rr against ðrZÞ1=2 was large, the magnitude of frequency shift was only 2%. Therefore, Rr was used to evaluate the difference in the flow property of magnetic fluid.
3.2. Ionic and water-based magnetic fluid
B. Jeyadevan et al. / Journal of Magnetism and Magnetic Materials 252 (2002) 98–100
Resonance Resistance, (ohm)
100
the external magnetic field modifies the contact surface area leading to erroneous measurements, here, the change in fluid level caused by external magnetic field was adjusted by introducing additional fluid to maintain the length of the transducer dipped in the fluid constant (Fig. 1). In summary, a new method to measure the viscosity of fluid using piezoceramic transducer has been developed. This device was found highly sensitive in detecting the change caused to the magnetic fluid properties by solid concentrations and applied magnetic field strengths.
12 20 wt. % Water-based (W40) 11 10 9 8 7 6 0
200
400
600
Magnetic Field Strength, G Fig. 4. Relation between magnetic field strength and Rr ; for 20 wt% of W40.
increase in viscosity caused by the formation of secondary clusters. The results of the measurements for 20 wt% water-based MF for varying magnetic field strength is shown in Fig. 4. Though the changes in Rr at any specific concentration for low magnetic field strengths were small, considerable increase in Rr was observed for higher magnetic field strengths. Unlike in the case of conventional cone plate viscometer, where
References [1] B. Jeyadevan, I. Nakatani, J. Magn. Magn. Mater. 201 (1999) 62. [2] S.J. Odenbach, T. Rylewicz, M. Heyen, J. Magn. Magn. Mater. 201 (1999) 155. [3] K. Imano, R. Shimazaki, S. Momozawa, IEICE Trans. Fundam. E83-A (1) (2000) 162. [4] B. Jeyadevan, D. Asano, S. Momozawa, K. Imano, K. Tohji, Seventh Japanese–French Meeting on MFs, 2000, pp. 23–25. [5] G.Z. Sauerbrey, Phyzik 155 (1959) 206.
Fluid property evaluation by using transversal effects of piezoelectric transducer B. Jeyadevana,*, S. Momozawab, K. Imanob, K. Tohjia a
Department of Geoscience and Technology, Tohoku University, Aramaki Aoba 01, Aoba-ku, Sendai 980-8597, Japan b Akita University, 1-1 Tegatagakuencho, Akita 010-8502, Japan
Abstract In this paper, we describe a highly sensitive device that utilizes the transversal effect of rectangular piezoelectric transducer to measure the viscosity of water-based and ionic MFs. This device could monitor the differences in MF types and also have overcome the design limitations of the conventional viscometer for measurements in external magnetic fields. r 2002 Elsevier Science B.V. All rights reserved. Keywords: Fluid property; Transversal effects; Piezoelectric transducer
1. Introduction
2. Experiment
Recent studies on ionic, oil- and water-based magnetic fluids (MFs) dispersing magnetite suggest that the particle dispersion characteristics are different among them [1]. Furthermore, the dimensional characteristics of field-induced clusters among different type of MFs also have been found to be different. These basic differences in cluster characteristic are believed to influence the viscoelastic properties of MF. However, the conventional measuring devices are less sensitive to monitor these differences and also have design limitations for measurements in external magnetic fields [2]. Authors have been working on the development of a device that utilizes the transversal effects of piezoelectric transducer to determine the fluid properties [3,4]. In this paper, we describe a highly sensitive device that utilizes the transversal effect of a rectangular piezoelectric transducer to measure the viscosity of fluids. We also report the results of magnetic fluid property measured using this device in applied magnetic field.
(i) Measuring device: A rectangular type PZT transducer of 70 10 0.5 mm that acts as both actuator and sensor was suspended by thin lead wire and partially immersed in the MF as shown in Fig. 1. One side of the surface of the transducer was electrically isolated from the MF, while the other was contacted to the MF. The electrical impedance was measured by an impedance meter (HP 4800A) and a frequency counter (Sabtronics Model 8000). The resonance of the transversal effect for the vibration in the longitudinal direction around 22.850 kHz was used to sense the viscosity of the fluid. The variation of electrical admittance and resonant frequency due to the change in viscosity of the liquid were measured using the impedance meter. (ii) Sample: MFs used in this study are (a) W40 (water-based—Taiho Co. Ltd.) and (b) ionic MF (IFF20) prepared by one of the authors. A DC magnet was used to apply a uniform magnetic field (max. 0.06 T) perpendicular to the transducer.
3. Results
*Corresponding author.
The resonant frequency change and the elastic film mass change on the piezoelectric disk [5] can be
0304-8853/02/$ - see front matter r 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 8 8 5 3 ( 0 2 ) 0 0 6 4 8 - 0
B. Jeyadevan et al. / Journal of Magnetism and Magnetic Materials 252 (2002) 98–100
FREQUENCY COUNTER
99
30
IMPEDANCE METER HP4800A R r [ohm]
20
10
Holder Rectangular plate type transducer
Container
0 0
Magnetic Fluid
( ×
ð1Þ
where, fr ; Dfr ; Dm; m; rQ ; A and rL are the resonant frequency, resonant frequency shift, surface mass change, shear modulus, density, and the surface area of the transducer, and density of the liquid, respectively. The Rr of the transducer in contact with magnetic fluid is given by Rr ¼ ð2pfr rL ZÞ
2
A=k ;
ð2Þ
Resonance Resistance (ohm)
given by
1=2
20 ) 1/2
[g 1/2
30 cm -3/2
40
cP 1/2 ]
Fig. 2. Experimental results of Rr vs. ðr ZÞ1=2 for water– glycerin mixtures.
Fig. 1. Experimental setup for viscosity measurements.
Dfr ¼ Dmfr2 =ðmrQ Þ1=2 A;
10
16 Water-based (W40) Ionic (IFF20)
14 12 10 8 6 0
10 20 30 40 Solid Concentration, wt. %
50
where, k is the electro-mechanical coupling factor. The Rr reflects the mechanical resistance of the transducer. The fr change reflects the mass effect of the liquid that moves with the disk of the transducer. This liquid mass effect is defined as
Fig. 3. Relation between magnetic solid concentrations and Rr for IFF20 and W40.
Dm ¼ AðZrL =pfr Þ1=2 :
Fig. 3 shows the relation between magnetic solid concentrations in IFF20 and W40 against Rr : For the measurements of zero solid concentrations of W40 and IFF20, water samples containing surfactant (SDBS) and tetra methyl ammonium were used, respectively. The change in Rr at very low solid concentration was marginal. However, the resonant resistance increased for any increase in the solid concentration in both cases. The change in Rr for W40 became larger at higher solid concentrations. This is in agreement with the conventional measurements. Furthermore, the plot between Rr and ðrZÞ1=2 ; based on the viscosity values determined using the conventional cone plate viscometer showed a linear relationship. This confirmed the viability of this method for fluid property evaluation. And also, it should be noted that the present setup could sense any change in viscosity as small as 0.1 cP or lower. For any specific solid concentration, the Rr increased with the strength of applied magnetic field suggesting the
ð3Þ
Eq. (3) could be substituted into Eq. (1) to obtain the change in frequency. Therefore, both Dfr and Rr have a linear relation such that for any decrease in fr ; Rr increases. 3.1. Water–glycerin suspension Fig. 2 shows the experimental results for water– glycerin mixtures with various viscosities. The abscissa is ðrZÞ1=2 ; where r and Z are the density and viscosity of the liquid, respectively. The ordinate of Fig. 1 shows the Rr derived from Cole–Cole plots of admittance. On the other hand, the ðrZÞ1=2 and Dfr also showed good linearity. Though the change in Rr against ðrZÞ1=2 was large, the magnitude of frequency shift was only 2%. Therefore, Rr was used to evaluate the difference in the flow property of magnetic fluid.
3.2. Ionic and water-based magnetic fluid
B. Jeyadevan et al. / Journal of Magnetism and Magnetic Materials 252 (2002) 98–100
Resonance Resistance, (ohm)
100
the external magnetic field modifies the contact surface area leading to erroneous measurements, here, the change in fluid level caused by external magnetic field was adjusted by introducing additional fluid to maintain the length of the transducer dipped in the fluid constant (Fig. 1). In summary, a new method to measure the viscosity of fluid using piezoceramic transducer has been developed. This device was found highly sensitive in detecting the change caused to the magnetic fluid properties by solid concentrations and applied magnetic field strengths.
12 20 wt. % Water-based (W40) 11 10 9 8 7 6 0
200
400
600
Magnetic Field Strength, G Fig. 4. Relation between magnetic field strength and Rr ; for 20 wt% of W40.
increase in viscosity caused by the formation of secondary clusters. The results of the measurements for 20 wt% water-based MF for varying magnetic field strength is shown in Fig. 4. Though the changes in Rr at any specific concentration for low magnetic field strengths were small, considerable increase in Rr was observed for higher magnetic field strengths. Unlike in the case of conventional cone plate viscometer, where
References [1] B. Jeyadevan, I. Nakatani, J. Magn. Magn. Mater. 201 (1999) 62. [2] S.J. Odenbach, T. Rylewicz, M. Heyen, J. Magn. Magn. Mater. 201 (1999) 155. [3] K. Imano, R. Shimazaki, S. Momozawa, IEICE Trans. Fundam. E83-A (1) (2000) 162. [4] B. Jeyadevan, D. Asano, S. Momozawa, K. Imano, K. Tohji, Seventh Japanese–French Meeting on MFs, 2000, pp. 23–25. [5] G.Z. Sauerbrey, Phyzik 155 (1959) 206.