| With the development of the information age,nanomaterials have come into people's life.Reducing production cost,improving performance and production efficiency become the key points in the research of nanomaterials.Anodic alumina oxide(AAO)is often used as a template for the fabrication of different types of nanomaterials due to its high controllability and simplicity.High purity Al is usually used as base material for AAO template,but its high prices lead to high production costs.Furthermore,the template needs an complicated pretreatment because of the insulation characteristics of the barrier layer.In present thesis,commercial purity Al(1090Al)was used as raw material for fabrication of AAO template and the semiconductor characteristics of the barrier layer were analyzed.Electroless plating,direct current(DC)electrodeposition and pulse electrodeposition were carried out to get metal nanowires based on the semiconductor characteristics of the barrier layer.Furthermore,the deposition model was established together with the discussion of the influencing factors of filling ratio.Based on commercial purity Al(1090Al),hole-defects and branching channels were generated due to the oxidation or dissolution of impurities during the anodic oxidation process,and it also resulted in the disorder of AAO template.The volt-current characteristic test results showed that the barrier layer of AAO template on 1090 Al had a unidirectional conduction in a certain range of negative potential,while the barrier layer of AAO on high purity Al showed the insulating property.Mott-Schottky analysis pointed out that the barrier layer of the AAO template on 1090 Al had a characteristic of n-type semiconductor and its flat band potential was-1.7 V.The rectifying characteristics also confirmed the semiconductor characteristics of barrier layer.Based on the electronic conduction characteristics of the barrier layer,electroless plating can be carried out in the pore channel of AAO template with the aluminum substrate,and the copper nanowires can be obtained.In the process of electroless plating,no pore opening was found on the barrier layer and the adjustment of pore diameter by chemical etching was beneficial to the transfer of the solution and the migration of ions.DC electrodeposition can be carried out on the AAO template on commercial purity Al based on the semiconductor characteristics of the barrier layer.The self-supported Ni nanowires arrays can be fabricated by adjusting the pore size of the template.The deposition model pointed out that the nucleation and growth of Ni can occur simultaneously at the top edge and bottom of the pore channel for AAO template on 1090 Al.The Ni on the top surface of pore channel can merge with the Ni overgrowths from nanowires to form smooth covering layer.The thickness and pore size of the template on 1090 Al had a significant influence on the filling ratio of Ni electrodeposition.The self-supported Ni nanowires with high filling ratio can be obtained by DC electrodeposition on 24 h-anodized AAO template grown on 1090 Al after chemical etching in 5% H3PO4 at 30? for 10 min.DC constant voltage electrodeposition suggested that the nucleation of Ni was related to the distribution of current.The uniform distribution of current was favorable to the nucleation,and the non-uniform distribution of current contributed to the local overgrowth.DC electrodeposition was easy to cause the non-uniform current distribution because of the difficulty for timely supplement of ions.It was difficult to control current density for DC electrodeposition and it was not suitable to fabricate Ni nanowires arrays with high filling ratio.Pulse electrodeposition of current source was beneficial to the timely supplement of ions,which can ensure the uniform distribution of current and improve the filling ratio of the template.By using the step-wise increasing current density method,the nucleation driving force can be improved,and the homogeneous nucleation in the template was promoted.DC electrodeposition was also used to enhance the growth of the Ni nanowires arrays.In this way,Ni nanowires arrays with high filling ratio can be obtained by combination of pulse and DC electrodeposition. |
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