Influence of Annealing Time of Aluminum AA1050 on the Quality of Cu and Co Nanocones
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Influence of Annealing Time of Aluminum AA1050 on the Quality of Cu and Co Nanocones Katarzyna Skibinska
, Grzegorz Smola, Lukasz Bialo, Dawid Kutyla, Karolina Kolczyk-Siedlecka, Anna Kwiecinska, Marek Wojnicki, and Piotr Zabinski
Submitted: 13 April 2020 / Revised: 21 July 2020 / Accepted: 7 October 2020 / Published online: 16 November 2020 Anodization is a widespread surface treatment method for aluminum and its alloys; it also allows the formation of 1D nanostructures by a two-step process. Microstructure of the Al substrate and crystallographic texture after rolling and annealing have influence on the properties of AAO templates with conical nanopores. Synthesized free-standing 1D nanostructures ensure better electrocatalytic properties than bulk materials due to larger active surface area. In this work, the influence of annealing time at 500 °C on Vickers hardness and microstructure of aluminum AA1050 used in a two-step anodization process was investigated. The geometrical features of the templates such as interpore distance and number of pores per 1 lm2 were determined and compared. There is dependence between the time of the annealing process and surface quality of synthesized 1D Cu nanocone layers. The template, after 1 h of annealing, due to the largest active area and satisfactory quality of the nanocone surface, was chosen for synthesis of Co nanocones. The electrocatalytic properties of samples were measured in 1 M NaOH solution and compared with bulk material electrodeposited in the same conditions. The open circuit potential, connected with starting of hydrogen evolution reaction, was determined from the LSV curves. Active surface areas were determined for all samples using SEM photographs and taken into consideration during electrocatalytic tests. Possible behavior of hydrogen bubbles for the formation of nanostructures was considered. Keywords
1D nanocones, annealing, electrodeposition, hydrogen evolution reaction
1. Introduction Anodization is one of the commonly used surface treatment methods for aluminum and its alloys. The simplest process is carried out galvanostatically or potentiostatically. Porous anodic alumina oxide (AAO) consists of a close-packed hexagonal array of parallel nanopores perpendicular to the surface of aluminum called honeycomb structure (Ref 1). Anodic oxidizing can be also applied for other metals like Ti (Ref 2, 3), Sn (Ref 4), Fe (Ref 5), W (Ref 6), etc. Two-step anodization used for fabrication of high-quality and well-ordered 1D nanostructures is characterized by the simplicity and low cost of the process. In the case of nanocones, the first step usually consists long-period anodization in oxalic acid. Before the second step of anodization, an oxide layer has to be removed in a mixed solution of phosphoric and chromic acids. Repeated anodizing in oxalic acid and a pore-widening process in phosphoric acid are called usually the second step of anodization. Geometrical features of AAO can be influenced by changing the electrolyte and its con
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