Oxidizing catalytic activity of a slider is a factor which could affect wear of magnetic disks with a carbon overcoat. Al2O3 composites containing 2–50 mol% TiO2 were produced, which had different oxidizing catalytic activities but nearly the same hardness and thermal conductivity. Activation energy (Ec) for carbon oxidation when it is mixed with the composite was measured to get the oxidizing catalytic activity, and it was found that Ec changed from about 70 kJ/mol for Al2O3 to about 110 kJ/mol for Al2O3 containing 9.1–16.7 mol% TiO2. TiO2 addition increased and decreased Ec. The former was due to segregation of the Ti-Al-O phase at the Al2O3 grain boundary, which could inhibit the catalysis at the Al2O3 grain boundary. The latter was due to the unreacted TiO2 phase, which by itself has high catalytic activity. TiO2-Al2O3 sliders having different Ec were examined in sliding wear against a magnetic disk with a carbon overcoat using a pin-on-disk test system. It was found that wear rate of the carbon overcoat was lower when the slider had a larger Ec, i.e., lower catalytic activity. It was also found that wear particles of the carbon overcoat were likely to be larger with lower catalytic activity.

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