Mitsuhiro Kataoka

Perpendicular Magnetic Field Orientation of Acicular Particles: Oblique Orientation with Field Gradient and Viscosity Gradient in Coating

The LIPS (longitudinally oriented inside layer, perpendicularly oriented surface layer) method of film orientation was improved in order to enable preparation of obliquely oriented tapes with a definite orientation angle. The permanent magnet pairs previously used in LIPS perpendicular orientation were replaced by an electromagnet with long iron plates for extension of the magnetic poles. Obliquely oriented tapes are easily prepared by appropriately choosing the coating speed and drying conditions. Coatings dried in a perpendicular magnetic field with an intensity gradient were found to be oriented not perpendicularly, but obliquely. It is thought that inner-layer particles are more easily displaced by the field gradient force than surface particles because of the effect of the viscosity gradient in the coating drying process.

Physical Properties of (TiC/Polypropylene) Conductive Composites in Relation to Their Particle-filled Structures

Titanium carbide (TiC) ⁄ acid-modified polypropylene (m-PP) composite is one of the candidate as the PTC resistor stable in relatively high temperatures, which is utilized for a self-recoverable element protecting from over currents in many kinds of electrical circuits. In the present study, the m-PP-based composites containing various volume fraction (φ2) of TiC have been prepared; then, their viscoelastic characteristics were investigated in comparison with their electric conductivity as a function of temperature. Melting behaviors of the samples were also examined and discussed in terms of their morphological features. Alternatively, the changes in the storage moduli at room temperature with various φ2 values of the samples could be expressed by a modified Kerner equation with the maximum φ2 value of 0.69. When the value of φ2 exceeded up to be 0.36, the resistivities of the sample decreased steeply with increasing φ2 values. The filling structure of TiC⁄m-PP Composites is expected to be in random packing systems.

Recording Characteristics of Obliquely Oriented Particulate Tapes

It has been reported that high-density and wide-bandwidth characteristics may be obtained by using a ring head with obliquely oriented metal evaporated magnetic recording tape. We therefore developed new equipment for the preparation of obliquely oriented tapes based on ¿-Fe2O3 particles, and examined the morphology, magnetic properties, and wavelength response of the tapes. The experimental results showed that tape with an oblique orientation of 30° has the highest output and widest bandwidth characteristics.