Investigations On Fabrication And Related Mechanisms Of Porous Anodic Aluminum Oxide Templates In Wide Range Of Temperature

With the development of the information era,nanomaterials have come into people's life.Reducing production cost,improving performance and production efficiency have become the key points in the research of nanomaterials.Porous anodic aluminum oxide(AAO)has been commonly used as a template for the fabrication of various functional nanomaterials due to their simple fabricating process,adjustable parameters,low cost and good stability.Now,they are widely used in magnetics,energy storage,photocatalysis and sensors.In this paper,based on 0.3M oxalic acid or 0.3M oxalic acid and ethanol mixed solution as electrolyte,the fabrication of porous AAO templates and related intrinsic mechanisms have been studied in detail with wide temperature range(20?50 ?)by using constant voltage anodization(40?260V).1.A more accurate method for calculating the ordered degree of densely packed patterns has been presented based on the theory of roundness by analysing the structural cells of porous AAO templates.Based on the calculation method,the influence of electrolyte temperature and anodization voltage on the regional order of structural cells of porous AAO templates has been studied in detail.2.The influence of the temperature of electrolyte(5?50?)on the growth process and microstructure of porous AAO templates,especially the degree of order,has been studied in detail by using two-step anodization method(40?50V)in 0.3M oxalic acid electrolyte.It was found that the degree of order of the porous AAO showed a tendency of rising first and then decreasing with the increase of the electrolyte temperature in the present experimental temperature range,and there is a critical temperature(Tc)which corresponds to the order/disorder critical point of porous AAO.When the temperature was increased above the temperature which corresponds to the optimal degree of order,Tc will decrease with the increase of anodization voltage holding other anodization conditions unchanged.This phenomenon has been investigated in detail on the perspective of the internal stress.3.The porous AAO was obtained in oxalic acid electrolyte(-20 ?)modified by adding ethanol which has extremely low freezing point.The effects of the anodization voltage(120?260V),electrolyte temperature(-20?10?)and electrolyte composition(0.3M oxalic acid:ethanol = 1:1,2:1,3:1,v/v)on the anodization process of aluminum and the degree of order of porous AAO have been studied carefully.It was found that the change of the anodization voltage,electrolyte temperature,or the volume ratio of mixed solution of oxalic acid and ethanol will lead to the transformation from mild anodization to hard anodization holding other anodization conditions unchanged.4.The anodization process of aluminum at ultra-low temperature(-20?0?)in modified electrolyte(0.3M oxalic acid:ethanol = 1:1,v/v)under anodization voltage of 40?50V has been investigated in detail.In this condition,highly order porous AAO with ultra-low growth rate have been fabricated successfully.The proposed preparation method makes it possible to precisely adjust the thickness and other structural features of porous AAO templates,which is significant for the research and applications of porous AAO templates.