Controlled Crystal Habit of Metal Particles and their Properties and Catalysis.

迄今为止，人们认为晶体习惯是一种动力学现象，可以用晶体平面的相对生长速度来解释。在真空条件下，将Au原子沉积在NaCl晶体表面，形成大量的二十面体和/或十面体颗粒，即多孪晶颗粒。二十面体和/或十面体粒子的最外层具有像（111）平面一样的闭包六边形Au原子阵列。虽然多孪粒子的表面能可能较低，但是。应变随晶粒尺寸的增大而增大，使多孪晶颗粒不能大尺寸生长。如果这是正确的，那么多孪生粒子的形成就不是动力学现象，而是热力学或能量现象。另一方面，Au（111）、Au（110）和Au（100）表面通过真空加热进行表面重构，形成最上层的六边形阵列。我们知道，在一定的负电位下，金表面在电解质溶液中经历非常相似的重构。我们发现，当电极在溶液中保持负电位时，电极上的多孪金粒子生长。这些现象表明，表面能可以由电极电位控制，我们可以说，晶体习惯可以通过改变表面能来控制。这种新现象成功地扩展到其他fcc金属，如Cu、Ag、Ni、Pd、Pt、Rh、Ir和au合金。这些结果发表在北海道大学出版社出版的一本书中。

So far, crystal habit has been recognized as a kinetic phenomenon which can be explained by relative growth rate of the crystal planes. When Au atoms are deposited on NaCl crystal surface in vacuum, a lot of icosahedral and/or decahedral particles, so called multi-twin particles, are formed. The outer most layer of the icosahedral and/or decahedral particles has a closed pack hexagonal array of Au atoms like the (111) plane. Although the surface energy of multi-twin particles may be low but. the strain is increased as the growth of particle size so that the multi-twin particles can not grow in large size. If this is correct, the formation of multi-twin particles is not the kinetic phenomenon but the thermodynamic or energetic phenomenon. On the other hand, Au (111), Au (110) and Au (100) surfaces undergo surface reconstruction forming hexagonal array of the topmost layer by heating in vacuum. It is known that Au surfaces undergo very similar reconstruction in electrolyte solution at a certain negative potential. We found the growth of multi-twin Au particles on electrode in solution when the electrode holds negative than this potential. These phenomena suggest that the surface energy can be controlled by electrode potential, and we could say that the crystal habit can be controlled by changing the surface energy. This new phenomenon is successfully extended to other fcc metals such as Cu, Ag, Ni, Pd, Pt, Rh, Ir, and Au-alloys. These results are reviewed in a book published from the Hokkaido University Press.