Catalysis of Organic..

Yamauchi 161was -0.0009, -0.0032 and -0.0030 (MPa/s) for conventional Raney Ni, RWA andMA, respectively.Although the activity obtained by the MA route was not the highest in this case, theeffectiveness of MA was still much higher than that of conventional catalyst. Insome cases, MA is more effective than rapid solidification for making supersaturatedprecursors. An example is the Al-Co-Cu ternary system (11). The rankingof effectiveness of these methods may in general depend on the alloy system.Extension of Rapid Solidification to Ternary AlloyNi and Co are immiscible elements with Ag or Cu. Especially Ag is not misciblewith Ni or Co even in liquid state. Therefore, there were no previous attempts tomake Raney Ni or Co with dissolved Ag and no studies on their catalytic properties.Here, we will show an approach to make Raney Ni or Co with Cu or Ag. In the caseof Al-Co-Cu system precursor, MA was an effective process to prepare a supersaturatedsingle solid solution as shown in Fig.9 (11). The crystallographic structureafter leaching of this specimen showed a broad fcc phase and no other phases wereobserved. To examine the as-leached state, the variation of magnetization wasmeasured with the temperature (12). Figure 10 shows the result. The magnetizationIntensity, I/arbitrary unitMechanical alloyedRapidly solidifiedSlowly solidifiedRelative saturated magenization (Ms/Mso)1.00.90.80.70.6heatingheatingheatingheatingcoolingMA+leachingrapid solidification+leachingMA(Co 50Cu 50)rapid solidification(Co 50 Cu 50 )20304050 602θ →Figure 9. XRD patterns of precursors ofAl 75 Co 12.5 Cu 12.57080900.5300400500600 700Temperature, K800900Figure 10. Variation of saturatedmagnetization with temperature1000change by heating was a maximum for MA + leaching specimen. It suggests thatsome amount of Co dissolved in the Cu phase as-leached state. The precipitation ofthe ferro-magnetic Co phase by heating increased the magnetization. The as-leachedstate was a metastable state which can not be attained by conventional methods.However, another possible explanation for Fig.10 is that Co particles already exist inthe as-leached state, but they are very small and may show super-paramagneticbehavior that is often observed in ferro-magnetic materials with a few nano-sizeparticles. The Co particle size became coarser by heating. This is the subject of a