Zeta Potential of Nanobubbles Generated by Ultrasonication in Aqueous Alkyl Polyglycoside Solutions.
A simple and convenient method to measure microelectrophoretic mobilities was proposed to determine the zeta potential of nanobubbles generated by ultrasonication. Bubbles in pure water solutions and in aqueous solutions of alkyl polyglycoside (AG) with different alkyl chain lengths and degrees of polymerization in the head group were sonicated with a palladium-coated electrode designed specially by the manufacturer. The zeta potentials of bubbles with ordinary cationic and ionic surfactants are consistent with others' previous results. The average size of the bubbles generated by sonication is in the range of 300 to 500 nm. The zeta potentials of bubbles in both pure water and AG solutions at all pH values are negative. As the chain length of AG increases, zeta potentials significantly decrease at high pH. For nonionic AG, a possible charging mechanism based on known mechanisms is suggested to explain the negative charge, known to be unusual. Even with a very high concentration of H(+) ions in solution the bubbles are charged negatively because the interface is covered with slightly acidic alcohol groups of AGs. At high pH, the less polar the surfactant, the more negative the charge, since nonpolar surfactant molecules induce the adsorption of OH(-) ions, rather than H(+) ions that prefer hydration by water molecules. Copyright 2000 Academic Press.
The ζ-Potential of Gas Bubbles
Abstract A technique for measuring the ζ-potential of a gas-liquid interface that overcomes the valid criticisms of previous attempts is proposed and demonstrated for the case of an air bubble in deionized water. The ζ-potential is found to be -65 mV with a reliability exceeding any previously reported results. The apparatus used is a horizontal tube that is rapidly rotating about its axis. The tube contains the liquid and small gas bubbles. An electric field imposed along the tube axis causes the bubble to move and the ζ-potential is related to the electrophoretic mobility.
Effect of various kinematic parameters of mine hoist on fretting parameters of hoisting rope and a new fretting fatigue test apparatus of steel wires
The effect of various kinematic parameters of mine hoist on fretting parameters of the hoisting rope was investigated and a new fretting fatigue test apparatus was designed. A simulation model of the rope tension was presented to examine the role of various kinematic parameters on the rope tension and tension amplitude during lifting. Ranges of fretting parameters of the rope during lifting with different kinematic parameters were determined. The results show that different kinematic parameters induce different modal shapes of the vibrating systems during lifting, which results in distinct ranges of fretting parameters of the rope.