The obtaining of magneto-rheological suspensions based on silicon oil and iron particles Ioan Bica Department of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 1900 Timisoara, Romania Received 4 October 2001; accepted 24 March 2002 Abstract The paper reports the experimental installation and the obtaining of magneto-rheological suspensions (MRS) by thermal decomposition of Fe 2 (CO) 9 in liquid matrices (silicon oil and stearic acid), under argon protection. The volume ratio of the particles is 35%. The magneto-rheological material is made homogeneous by a high-speed dispersion process. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Magneto-rheological suspensions; Silicon oil; Thermal decomposition; Iron micro-particles; Nanocarboxyldiiron 1. Introduction The fluids characterized by a viscosity that changes in the presence of a magnetic field are also known [1  /3] as magneto-rheological suspensions (MRS). The MRS consists of fero- and paramagnetic particles, with dimensions exceeding 0.1 mm [1 /3], dispersed in a carrier fluid. In the presence of the magnetic fluid, the particles become polarized and gather in chains in all the fluid’s mass. The particle chains formed in this way increase the fluid viscosity. When the magnetic field is canceled, the particles chains break and the fluid viscosity returns instantaneously to its initial value [2  / 4]. The control of the fluid viscosity through the means of a magnetic field created by a coil makes the MRS very useful in applications much discussed in various publications [3,5  /9]. Hence, the obtaining of MRS having superior physi- cal characteristics, at low costs, is a very actual issue. For this reason, in the following paper we present a method of obtaining MRS in situ, which hopefully will meet all these conditions. 2. Installation The block scheme of the experimental installation designed to produce MRS is presented in Fig. 1. The installation consists of: the chemical reactor A, the vacuum pump B, the gas deposit C, the electric motor D, the temperature indicator E and the supplier F. The installation presented in Fig. 1 functions as follows: first, the installation shown in Fig. 1 has to be assembled, and then it has to be connected to the water and sewer plumbing. The mixture of silicon oil, stearic acid and Fe 2 (CO) 9 , in well determined quantities, are being introduced in the chamber 1 of the chemical reactor (see Table 1). A relative pressure up to  /550 mm col. H 2 O( /5391 N m 2 ) is created in the chamber 1 with the water ejector vacuum pump. Using the pressure reducers equipped with flowmeters on the argon tubes (the gas container) the gas flows are being fixed. The gas flows can be adjusted continuously from 0.6 l min 1 9 /10% (1 /10 5 m 3 s 1 9 /10%) to 24 l min 1 9 /5% (0.4 /10 3 m 3 s 1 9 /5%). The argon is dispersed in the liquid matrix through the pipe 2 from the chamber 1. The electric motor D rotates the palette 3. At rotations that can be adjusted continuously from 0.6 rpm9 /10% (1 /10 2 rotations per s9 /10%) to 6 rpm9 / 5% (1 /10 1 rotations per s9 /5%) the mixture in chamber 1 is homogenized. Next, the autotransformer 6 has to be connected to the electrical power supply of the installation. The voltage of the heater 7 can be adjusted now. Using the thermocouple 4 the temperature of the mixture can be Materials Science and Engineering B98 (2003) 89  /93 www.elsevier.com/locate/mseb 0921-5107/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0921-5107(02)00202-7