Water-based magnetic fluid

Dry dense medium (pneumatic fluidized-bed) separation has been used, but has not received wide attention by the industry. An area of promise for future development is the use of magnetically stabilized dense medium beds by using ferro or magnetic fluids (2,10). Laboratory and pilot-scale units such as Magstream are available. In this unit, material is fed into a rotating column of water-based magnetic fluid. Particles experience centtifugal forces and... 

Stripped magnetite particles. Applications of the double surfactant layer. Principle in the preparation of water based magnetic fluids. J. Colloid Interface Sci. 149 98-104 Wuehn, M, JosephJ., Bagus, P.S. Niklewski.A., Puettner, R., Reis,S., Weiss,W., Martins, M.,... 

Fig. 13.1.4 Schematic picture of dispersion states of particles in magnetic flu ids (a) core particle (b) oil-based magnetic fluid (c) water-based magnetic fluid.

The results obtained will be useful in practical application of nanocomposites and magnetic fluids in oncotherapy. Besides the magnetic fluids in Table 10.16, water-based magnetic fluids (physiologic solution) and nanocomposites containing B and Gd were synthesized and investigated. 

In a next step, the hydrophobic magnetite particles in octane as dispersion medium are reformulated to stable water-based magnetic fluids for the encapsulation... 

Concerning the enhanced steric and electrostatic stabilisation mechanism, for example, the secondary DBS layer has the -SO3- groups oriented towards the dispersion medium forming a local electric field with hydrated NH4+ ions around the particles. Consequently, the degree of stability of water-based magnetic fluids depends on the pH of the medium and the stabilization mechanism outlined earlier is specific only to water as the dispersion medium. 

Fig. 3 Mean intensity as a function of time r after demagnetization for a water-based magnetic fluid samples 6 ( bland 7 (ST) and b pentanol-based magnetic fluid sample 10 (SIO). Horizontal lines in the graphs correspond to the mean intensity value of the initial ferrofluids before they are set in the magnetic field applied field (B= 1.2 T) (squares) zero field (B = 0 T) (continuous line and broken line)...

The surfactant double-layer steric stabilization procedure was used with good results for a large number of polar carrier liquids, in particular to obtain high-magnetization (up to approximately 950 G) samples on a pentanol carrier, as well as medium-magnetization (up to approximately 300 G) water-based magnetic fluids. 

Using the above-mentioned nm magnetite particles the following water based magnetic fluids were prepared ... 

Since the magnetic fluid appeared, techniques for l he production of variety of magnetic fluids including water-based and oil-based magnetic fluids were developed. Recently a number of magnetic fluids prepared by a variety of methods are on markets (19). 

As shown later, in the case of water and various organic polar carriers, the preparation process [6, 9, 10, 11, 12, 13, 14] is quite different from that developed for nonpolar organic carriers. Owing to specific difficulties encountered in stable dispersion of magnetic nanoparticles in the strongly polar water carrier, most of the preparation procedures were used for low-magnetization (100-200 G) samples. The preparation of alcohol-based magnetic fluids was first reported in Ref [7] and implies a stabilization mechanism, different from that applied in the case of water carrier. 

For a deeper insight into microstructural processes, SANS investigations were extended to detect microstructural changes in water- and pentanol-based magnetic fluids induced by the application of a strong magnetic field. The particle agglomerates were also followed after the field was turned off. 

The delivery of nanoparticles in the human body usually requires suspending the nanoparticles in a water-based fluid. In-vitro applications also usually require an aqueous environment. Magnetic nanoparticles must remain... 

Morais PC, da Silva SW, Soler MAG, Sousa MH, Tourinho FA (1999) Raman study of ionic water-based copper and zinc ferrite magnetic fluids. J Magn Magn Mater 201 105-109... 

Magnetic fluids can be used as a high-density solution for the sink-and-float separation of solids in suspension. This separation technique for non-ferrous metals is based on the anomalous viscosity increase of a magnetic suspension as a function of applied field. The magnetic fluid consists typically of magnetite particles with an average diameter of 100 A in water, with 15-25 wt% of ferrite. To prevent particle aggregation, a surfactant such as kerosene and oleic acid, or a polymer is usually... 

The qualitative differences just outlined determined the choice of water-based samples, one the one hand, and the pentanol magnetic fluids, on the other hand, for further comparative investigations by small-angle neutron scattering (SANS). 

The complex magnetic analyses of the magnetic fluids on polar and strongly polar carrier liquids evidence clear differences existing at the microstructural level between samples on organic polar carriers (e.g., alcohols) and water-based samples. It is expected that these differences... 

Particle interactions and the formation of agglomerates produce important changes in the flow properties [4, 17,18] compared to the flow behaviour of a highly stable magnetic fluid. Such quahtative differences between flow properties are easy to evidence in the case of water-based samples when compared to pentanol magnetic fluids. 

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