Shigeo Aoyama

Recording characteristics of tapes prepared using iron oxide particles treated with organic titanate

The adsorption behavior of organic titanate on an iron foil having an ideal iron oxide surface is examined to improve read‐write characteristics of particulate magnetic recording media by the surface treatment of iron oxide magnetic particles with organic titanate. Organic titanate significantly reduces the surface hydrophilicity of iron oxide surface of the iron foil. Heat treatment is required to form the chemical bonding between the organic titanate and the iron oxide surface. The method of surface treatment is applied to Co‐modified iron oxide particles. As a result, the magnetic properties and surface roughness of the tape are remarkably improved by the increase of dispersibility of particles due to the reduction of hydrophilicity with the organic titanate treatment. The carrier‐to‐noise ratio (C/N) at the frequency of 6.0 MHz in the tape is increased about 2 dB compared with the tape prepared using untreated particles.

Adsorption of silane coupling agent on Co-γ-Fe2O3 a nd its effect on dispersibility

The adsorption of a new type of silane coupling agent containing polyethylene oxide (EOS) on cobalt-modified iron oxide (Co-γ-Fe2O3) particles and its effect on dispersibility are examined by measuring the surface chemical properties. The EOS is adsorbed on Co-γ-Fe2O3 in the form of a monolayer and reduces the hydrophilicity of the surface of the particles with the adsorption. The surface hydrophilicity of EOS-treated iron foil (the iron foil has an ideal iron oxide surface) becomes lower with the increasing heat-treatment temperature. Heat treatment at 80°C or higher is required to achieve chemical bonding between EOS and the iron foil. By the same heat treatment, EOS polymerizes on the iron foil resulting in the formation of a polysiloxane network. The dispersibility of the particles in vinyl chloride-vinyl acetate-vinyl alcohol copolymer solution is improved dramatically by the surface treatment with EOS. The improvement in dispersibility is explained by considering the increase of the wettability of Co-γ-Fe2O3 for the solvent due to EOS treatment.[/p]

Interaction between polymers and magnetic particles: effect on the properties of particulate magnetic recording media

The interaction between vinyl chloride–vinyl acetate-vinyl alcohol copolymers and cobalt-modified γ-Fe2O3(Co–γ-Fe2O3) magnetic particles has been studied. Adsorption isotherms and heats of adsorption were measured for polymers with various kinds and concentrations of functional groups. The interaction of the polymer with Co–γ-Fe2O3, and the amount of polymer adsorbed, increased in proportion to the hydroxy-group concentration of the polymer. Introducing a few carboxy groups into the polymer also produced stronger interaction. This interaction affected the properties of particulate magnetic recording media considerably. The interaction strength of the polymer with Co–γ-Fe2O3 has been shown to determine the Youngs modulus of a magnetic coating layer. Stronger interaction led to higher dispersibility of Co–γ-Fe2O3 in the magnetic coating layer.

Effects of lead on annealing properties of cold-drawn copper wire

Cold-drawn copper wires were made by cold-drawing after hot-rolling tough pitch copper rods which had been pre-heated at 673–973 K. The wires were annealed at 293–673 K to study their annealing properties. The effects of pre-heating the hot-rolled tough pitch copper rods, including lead, on the recrystallization behaviour of the cold-drawn copper wires were investigated by tensile tests, electrical resistivity measurements and structural observations. The half-softening temperature of annealed cold-drawn copper wires decreased when the hot-rolled copper rods were pre-heated at 873 K before cold-drawing. This behaviour was attributed to separation of lead dissolved in the copper matrix which is known to lower the half-softening temperature.

The behavior of lauric acid lubricant in a magnetic coating layer and its effect on mechanical properties of magnetic media

The fundamental behavior of a lubricant, lauric acid, in a magnetic coating layer is studied by means of solvent extractions. In the magnetic layer, lauric acid is shown to be present in three different states: adsorption on the surface of the magnetic particles, dissolution in the binder, and the free state at the interface. The amount of free lauric acid depends on the amounts of lauric acid adsorbed on the magnetic particles and dissolved in the binder. The runnability of the magnetic tape is found to be governed by the free lauric acid.

The surface chemical properties of cobalt-modified γ-Fe2-O3 magnetic particles

The surface chemical properties of cobalt-modified γ-Fe2O3 (Co-γ-Fe2O3) magnetic particles were studied by adsorption isotherms, FT-i.r. spectroscopy and microcalorimetry. The monolayer-adsorption amount of water on Co-γ-Fe2O3 surfaces is 4.8 molecules per square nanometre, and the surface is considered to be covered with a thin water film in its normal environment. The surface hydrophilicity of Co-γ-Fe2O3 is comparable to that of TiO2. The acidic carboxyl group shows the strongest interaction with Co-γ-Fe2O3, and a portion of this group chemically interacts. The basic amino group indicates stronger interaction with Co-γ-Fe2O3 than the neutral hydroxyl group. It is concluded that the Co-γ-Fe2O3 surface possesses a basic rather than an acidic character. This is interpreted in terms of the inherent nature of the adsorption site of Co-γ-Fe2O3. Furthermore, the Co-γ-Fe2O3 adsorption site appears to be energetically heterogeneous.

Effects of small additions of lead, sulphur and oxygen on annealing characteristics of cold-drawn pure copper

Softening of cold-drawn wires of a tough pitch copper containing a small amount of lead as well as oxygen and sulphur is enhanced when hot-rolled rods of the copper are heated at 600 °C before cold-drawing. Enhancement causes were examined using wires of pure Cu, Cu-O, Cu-S, Cu-Pb, Cu-Pb-O, Cu-Pb-S, Cu-Pb-S-O. The softening enhancement appearing in the Cu-Pb-S-O specimen was attributed to the decrease in the amount of dissolved Pb and S in the copper matrix due to precipitation during heating at 600 °C. The addition of lead in the presence of oxygen was shown to decrease the solid solubilities of S in the copper matrix.