ABSTRACT
We report a rheological study of suspensions of non-Brownian chain-like magnetic particles in the presence of magnetic fields. These particles have been synthesized using spherical iron particles by linking them with a polymer and are called polymerized chains. We have shown that, in oscillatory squeeze mode, the suspensions of such chain-like particles develop yield stress several times higher than that of conventional magnetorheological fluids based on spherical iron particles. This is explained in terms of solid friction between polymerized chains, which form entangled aggregates in the presence of a magnetic field. For the suspension of spherical particles, the squeezing force increases with the magnetic field intensity at low magnetic fields, but decreases dramatically at higher fields because of cavitation or air entrainment. Such a decrease in transmitted force does not take place in suspensions of polymerized chains, at least for fields smaller than 30 kA m(-1), which could make these suspensions preferable for application in squeeze-film dampers.
ABSTRACT
Silver nanoparticles stabilized by a well-known antibacterial surfactant benzyldimethyl[3-(myristoylamino)propyl]ammonium chloride (Myramistin(®)) were produced for the first time by borohydride reduction of silver chloride sol in water. Stable aqueous dispersions of silver nanoparticles without evident precipitation for several months could be obtained. In vitro bactericidal tests showed that Myramistin(®) capped silver NPs exhibited notable activity against six different microorganisms-gram-positive and gram-negative bacteria, yeasts and fungi. The activity was up to 20 times higher (against E. coli) compared to Myramistin(®) at the same concentrations and on average 2 times higher if compared with citrate-stabilized NPs.
