Ferrotec (United States)

This work validates a method for increasing the radial restoring force on the voice coil inaudio speakers containing ferrofluid. In addition, a study is made of factors influencingsplash loss of the ferrofluid due to shock. Ferrohydrodynamic analysis is employedthroughout to model behavior, and predictions are compared to experimentaldata.

Ferrofluidic devices have found applications in laser systems, high-vacuum equipment, computers, loudspeakers, inertia dampers, and motors. With the technique of magnetic-fluid sealing, one is called upon to produce custom solutions for complex and diverse seal problems, many of which may be characterized by very hostile environments, wide temperature ranges, and intense radioactive conditions. In designing a magnetic circuit for a magnetic-liquid seal, a number of factors, such as the size of the available envelope, pressure differential across the seal, chemical compatibility with various environments, and proper selection of permanent and soft magnetic materials need to be considered for achieving the most cost-effective solution while meeting the entire range of requirements for any specific application. In order to evaluate flux leakage and fringing while accounting for nonlinear characteristics of magnetic materials, it becomes necessary to resort to numerical techniques to determine the effect caused by varying the significant parameters and to achieve an optimized design for the device. This paper presents modeling techniques for simulating ferrofluidic seals, and methods to deal with various geometries including inherent symmetry. By numerically analyzing the model, detailed flux distribution plots have been obtained by means of a computer.

The thermal conductivity of a number of ferrofluids consisting of colloidally dispersed Fe3O4 particles in diester, hydrocarbon, water and fluorcarbon carriers have been measured at 38°C. The variation in thermal conductivity with particle concentration is well described by Tareef's equation (1940). This has enabled the ratio of the physical to magnetic size to be determined and compared with estimates of the ratio obtained from electron micrographs and magnetic measurements.

Transition metal elements substituted into Fe3Si were found to preferentially select one of the two inequivalent Fe sites in the Fe3Si structure, according to their location in the periodic table; a similar pattern of site occupation is observed in the Heusler alloys. Examination of the electronegativity of the transition metal impurities shows that the Fe site with 8 Fe 1nn is preferred by the less electronegative substitutions.(AIP)