A Tracer Study of Porous Anodic Alumina

摘要: The present study employs a tungsten tracer incorporated into the aluminum substrate to investigate development of porosity in anodic alumina formed phosphoric acid electrolyte. An unusual inversion distribution is revealed as layer traverses barrier region. Although initially at locations beneath pore bases, associated with scalloped metal/oxide interface, these subsequently lags behind that found cell walls. behavior contrary expectations field-assisted dissolution model development, usual migration behaviors film species layer. However, findings are consistent formation due mainly flow from toward walls, driven by growth stresses. Flow material can also account for presence phosphorus and increased thickness relative oxidized metal. Anodic films used extensively protection functionalization alloys, electronics through aerospace architecture. usually aqueous electrolytes, two morphological types recognized depend upon composition electrolyte, pH, current density, voltage, temperature, etc. Fig. 1. 1-4 Barrier consist compact, amorphous uniform thickness, up few hundred nanometers. Porous comprise thin next metal an outer porous alumina, tens m thick. 2,3 pores approximately cylindrical section extend surface diameter related forming ratios 1n V 1 , while depends primarily anodizing charge particular density. has often been explained massively base under high electric field 5 early suggestion was made role oxide process, occurring electrostriction stresses, estimated be order 100 MPa sufficient deform oxides. 6