Magnetic field-induced convection in solutions containing electroactive species that can undergo reduction-oxidation (redox) chemistry has been demonstrated using a 125-m-diameter platinum disk electrode embedded in Nd-Fe-B bonded magnets. Stirring near the electrode surface occurs through several convective forces: the Lorentz force (magnetohydrodynamics), the magnetic field gradient force, and the paramagnetic gradient force. Stirring was determined by comparing the mass transport-limited current before and after magnetization of the bonded material. Magnetic field effects were studied by performing cyclic voltammetry (CV) in a solution of nitrobenzene at different concentrations. The CV responses showed that with concentrations from 0.25 to 2.0 mol/L, the limiting current increased as large as 54% because of magnetic forces being parallel to and in the same direction as natural convection. Above 2.0 mol/L, the solution viscosity in the diffusion layer dominates, resulting in a decrease in current and, hence, less convection. Embedding microelectrodes in magnetic materials yields measurable enhancements of stirring of a small volume ( 1 L), defined by the diffusion layer adjacent to the electrode, even at weak magnetic fields of 0 13 T.

Increasing fuel costs and regulation of emissions are encouraging operators, shipbuilders and researchers to seek improvements in marine vessel efficiency. In the area of vessel electrical systems, there are increasing choices as a result of research and development over the past decade giving rise to a number of promising new technologies. Promising new battery chemistries are being developed and existing chemistries are being enhanced with nano-technology. Supercapacitors and fuel cells are now powering ferries. Permanent magnets are enabling novel motor topologies and solar panel prices are decreasing. In addition to new technologies recently commercialised for vessels, new developments in electric vehicles and grid electrical systems will be applicable to the marine environment. This article reviews emerging electrical technologies and it focusses on those with potential for improving vessel efficiency within the next decade.

No abstract

No abstract