The critical potential of hydrogen absorption and the hydrogen absorption rate into titanium under catholic polarization have been measured in artificial sea water with flow velocity of 2.0m/ sec and then the effect of flow velocity, dispersed sand, dissolved zinc ion and dissolved chlorine or oxygen gas on the hydrogen absorption rate of titanium have been examined. The results obtained are summarized as follows: (1) The critical potential of hydrogen absorption of titanium in artificial sea water lies in between -0.6 and -0.7 V (vs SCE). (2) The hydrogen absorption rate increases as the potential becomes less noble and increases sharply at potentials less noble than -1.1 V. (3) The hydrogen absorption rate decreases with increasing the flow velocity. (4) The dispersed sand, dissolved chlorine gas, or deaeration in sea water promote the hydrogen absorption. (5) The passive oxide film on the titanium surface obstructs the hydrogen absorption.

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Ni–Co ultrafine particles (UFPs) were prepared by hydrogen plasma metal reaction. Particle characteristics, oxidation, and magnetic properties were investigated and compared. fcc structured Ni–Co UFPs with a sphere shape were prepared over the whole composition range. The particles distribute from 5 to 100 nm in size with an average particle size of about 35 nm. They are thermally stable in air below 433 K, but oxidize quickly at the higher temperatures. The saturation magnetization of the UFPs is lower than that of the corresponding bulk alloy, especially in the Co rich side. Formation of oxide layer on the particle’s surface is an important reason for this reduction. Ni–Co UFPs possess large residual magnetization and coercive force above 60% Co. The composition dependence of the saturation magnetization and the coercive force changes remarkably around 60% Co, which implies a large variation in magnetic status around this composition.

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