Thermal Stability of Nonequilibrium Alloys Produced by Vapor quenching

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In sputter-deposition process a high energy vapor solution is condenced onto a cold substate and a wide range and a wide variety of nonequilibrium alloys have been obtained. Although these nonequilibrium alloys reveal excellent magnetic and catalytic properties, they are thermally unstable. In order to improve their thermal stability we have studied effects of heat treatments on the structure and physical properties of nonequilibrium alloys: differential scanning calorimetry and measurements of X-ray diffraction patterns, magnetization and Mossbauer spectra before and after annealing in an infra-red image furnace. We have obtained the following results.(1) Nonequilibrium binary crystalline Fe-Cu and Fe-Ag alloys and ternary amorphous Fe-Cu-Ag alloys show a soft magnetic characteristic, i.e., the coercive force less than 1 oe and high magnetic flux density. However, the nonequilibrium bcc and fcc Fe-Cu and Fe-Ag alloys undergo a phase separation above 300 C, while the amorphous Fe-Cu-Ag alloys transform to bcc and fcc phases above 130 C.(2) Amorphous Fe-Ti alloys are good hydrogen storage and good hidrogen filters. Since they are thermally stable up to about 700 C, they will be used as industrial materials.(3) In nonequilibrium Fe-Pd alloys, the magnetic moment of Fe atoms are enlarged and a soft magnetic characteristic is observed, i.e., the coercive force is less than 10 Oe in the as-prepared state and it becomes about 5 Oe by annealing below 300 C. These alloys undergo a phase separation above 300 C, however, they show very interesting magnetic characteristics aFter annealing at 500 C, i.e., the coercive force is about 500 Oe and the magnetic flux density is about 18 kOe, being comparable to or getter than those of Co-Ni magnetic recording media.Now, we are studying EXAFS spectra and XPS spectra of the nonequilibrium alloys and their variation by annealing.