On the Selective Oxidation of Novel Electrodeposited Nanocomposites Distributing Cr or/and Al Nanoparticles

摘要

Using an electrochemical deposition method,nanoparticles of Cr or/and Al were assembled into a nanocrystalline metal template to fabricate novel metal-matrix nanocomposites.The nanocomposites would be easier to develop protective scales of chromia or alumina during high temperature exposure, based on a selective oxidation model proposed for these types of nanocomposites.That is,the nanoparticles in the near-surface zone of the nanocomposites would convert into chromia or alumina islands at the onset of oxidation.Then,the nano length scale distribution of the nanoparticles,together with the nanograined metal-matrix structure,would favor a rapid linkage of the oxide islands to form a continuous layer of chromia or alumina.Using the oxidation model,we can explain the oxidation behavior of various nanocomposite systems such as Ni-Cr,Ni-Al,Ni-Cr-Al,Cu-Ni-Cr,etc.,by comparing to those of conventionally coarse-grained alloys of similar composition and the electrodeposited composites dispersing conventional micron-sized particles instead of equivalent weight of nanoparticles.