We investigate the rheograms of concentrated suspensions of magnetic particles obtained under imposed shear rate in parallel plate geometry. We show that under magnetic field application the usual trend of the rheogram, i.e., increasing shear stress for the whole range of shear rates, is altered by the appearance of a region in which the shear stress decreases as the shear rate is increased. The existence of this region gives to the rheograms an N-like shape. The two initial regions (preyield regime) of these N-like rheograms present unstable flow, characterized by the oscillation of the shear stress with time for each imposed value of shear rate. We also show that rheograms obtained at different sample thicknesses approximately overlap in the developed flow regime, whereas there is a tendency of the shear stress to increase as the thickness is decreased in the preyield regime. This tendency is likely due to the strengthening of pre-existing particle structures by compression as the gap thickness is decreased. Finally, we analyze the effect of the applied magnetic field strength, H, and demonstrate that the rheograms scale with H1.5 to a single master curve, for the range of applied magnetic fields under study.

1.
Bossis
,
G.
,
O.
Volkova
,
S.
Lacis
, and
A.
Meunier
, “
Magnetorheology: Fluids, Structures and Rheology
,”
Lect. Notes Phys.
594
,
202
230
(
2002
).
2.
Park
,
B. J.
,
F. F.
Fang
, and
H. J.
Choi
, “
Magnetorheology: Materials and application
,”
Soft Matter
6
,
5246
5253
(
2010
).
3.
Bell
,
R. C.
,
J. O.
Karli
,
A. N.
Vavreck
,
D. T.
Zimmerman
,
G. T.
Ngatu
, and
N. M.
Wereley
, “
Magnetorheology of submicron diameter iron microwires dispersed in silicon oil
,”
Smart Mater. Struct.
17
,
015028
(
2008
).
4.
López-López
,
M. T.
,
G.
Vertelov
,
P.
Kuzhir
,
G.
Bossis
, and
J. D. G.
Durán
, “
New magnetorheological fluids based on magnetic fibers
,”
J. Mater. Chem.
17
,
3839
3844
(
2007
).
5.
López-López
,
M. T.
,
P.
Kuzhir
, and
G.
Bossis
, “
Magnetorheology of fiber suspensions. I. Experimental
,”
J. Rheol.
53
,
115
126
(
2009
).
6.
de Vicente
,
J.
,
J. P.
Segovia-Guitérrez
,
E.
Anablo-Reyes
,
F.
Vereda
, and
R.
Hidalgo-Alvarez
, “
Dynamic rheology of sphere- and rod-based magnetorheological fluids
,”
J. Chem. Phys.
131
,
194902
(
2009
).
7.
Bell
,
R. C.
,
D.
Zimmerman
, and
N. M.
Wereley
, “
Impact of nanowires on the properties of magnetorheological fluids and elastomer composites
,” in
Electrodeposited Nanowires and Their Applications
, edited by
N.
Lupu
(
Intech
,
Vienna, Austria
,
2010
), Chap. 8, pp.
189
212
.
8.
Zubarev
,
A.
,
M. T.
López-López
,
L.
Iskakova
, and
F.
González-Caballero
, “
N-Like rheograms of suspensions of magnetic nanofibers
,”
Soft Matter
9
,
1902
1907
(
2013
).
9.
López-López
,
M. T.
,
P.
Kuzhir
,
L.
Rodríguez-Arco
,
J.
Caballero-Hernández
,
J. D. G.
Durán
, and
G.
Bossis
, “
Stick–slip instabilities in the shear flow of magnetorheological suspensions
,”
J. Rheol.
57
,
1101
1119
(
2013
).
10.
Quemada
,
D.
, “
Unstable flows of concentrated suspensions
,”
Lect. Notes Phys.
164
,
210
247
(
1982
).
11.
López-López
,
M. T.
,
P.
Kuzhir
,
J.
Caballero-Hernández
,
L.
Rodríguez-Arco
,
J. D. G.
Durán
, and
G.
Bossis
, “
Yield stress in magnetorheological suspensions near the limit of maximum-packing fraction
,”
J. Rheol.
56
,
1209
1224
(
2012
).
12.
Laun
,
H. M.
,
C.
Gabriel
, and
C.
Kieburg
, “
Wall material and roughness effects on transmittable shear stresses of magnetorheological fluids in plate–plate magnetorheometry
,”
Rheol. Acta
50
,
141
157
(
2011
).
13.
Buscall
,
R.
,
J. I.
McGowan
, and
A. J.
Morton-Jones
, “
The rheology of concentrated dispersions of weakly attracting colloidal particles with and without wall slip
,”
J. Rheol.
37
,
621
642
(
1993
).
14.
Gómez-Ramírez
,
A.
,
M. T.
López-López
,
F.
González-Caballero
, and
J. D. G.
Durán
, “
Wall slip phenomena in concentrated ionic liquid-based magnetorheological fluids
,”
Rheol. Acta
51
,
793
803
(
2012
).
15.
Kuzhir
,
P.
,
M. T.
López-López
,
G.
Vertelov
,
C.
Pradille
, and
G.
Bossis
, “
Shear and squeeze rheometry of suspensions of magnetic polymerized chains
,”
Rheol. Acta
47
,
179−187
(
2008
).
16.
Jiang
,
J.
,
G.
Hu
,
Z.
Zhang
,
Y.
Meng
, and
Y.
Tian
, “
Stick-slip behavior of magnetorheological fluids in simple linear shearing mode
,”
Rheol. Acta
54
,
859
867
(
2015
).
17.
Jonkkari
,
I.
,
E.
Kostamo
,
J.
Kostamo
,
S.
Syrjala
, and
M.
Pietola
, “
Effect of the plate surface characteristics and gap height on yield stresses of a magnetorheological fluid
,”
Smart Mater. Struct.
21
,
075030
(
2012
).
18.
Pignon
,
F.
,
A.
Magnin
, and
J. M.
Piau
, “
Thixotropic colloidal suspensions and flow curves with minimum: Identification of flow regimes and rheometric consequences
,”
J. Rheol.
40
,
573
587
(
1996
).
19.
Tang
,
X.
,
X.
Zhang
,
R.
Tao
, and
Y.
Rong
, “
Structure-enhanced yield stress of magnetorheological fluids
,”
J. Appl. Phys.
87
,
2634
2638
(
2000
).
20.
Tao
,
R.
, “
Super-strong magnetorheological fluids
,”
J. Phys.: Condens. Matter
13
,
R979
R999
(
2001
).
You do not currently have access to this content.