Abstract
The aim of this study was to investigate the oxidation kinetics of copper at low temperatures (60 °C to 100 °C) in air by isothermal thermogravimetric analysis (TGA) and quartz crystal microbalance (QCM). The weight change in thermogravimetric tests showed periodic weight increase and decrease. In thermogravimetric tests the mass of the copper sample increased until the oxidation gradually slowed down and finally started to decrease due to cracking and spalling of the oxide formed on the surface. In QCM tests using electrodeposited copper film, the weight change was rapid at the beginning but slowed to a linear relationship after few minutes. Temperature and exposure time appeared to have a large effect on oxide film thickness and composition. With QCM, oxidation at 60–80 °C produced less than 40 nm films in 10 days. Oxidation at 90–100 °C produced 40 nm thick films in a day and over 100 nm films in a week. Although SEM-EDS analyses in TGA tests indicated that oxygen was adsorbed on the copper surface, neither XRD patterns nor Raman spectroscopy measurements showed any trace of Cu2O or CuO formation on the copper surface. Electrochemical reduction analysis of oxidized massive copper samples indicated that the oxide film is mostly Cu2O, and CuO develops only after several days at 90–100 °C.
Highlights
Copper and copper alloys have always been of interest due to their unique properties such as thermal and electrical conductivity, ease of fabrication, and corrosion resistance [1]
In thermogravimetric tests the mass of the copper sample increased until the oxidation gradually slowed down and started to decrease due to cracking and spalling of the oxide formed on the surface
The current study focuses on studying copper oxidation before the final underground deposition
Summary
Copper and copper alloys have always been of interest due to their unique properties such as thermal and electrical conductivity, ease of fabrication, and corrosion resistance [1]. These properties are needed in a wide range of applications, including automotive and transportation, electrical power, electronics, energy, and nuclear waste management [2,3,4]. Many researchers have studied the oxidation behavior of bulk copper metal [5,6,7,8] and copper thin films [9,10,11,12,13,14] at elevated temperatures in air. The main outcome of these studies indicated that copper oxidation products, Cu2O (cuprous oxide) and CuO (cupric oxide), are formed on the surface of copper at various temperatures and exposure times, and the growth of these oxide layers follows most frequently the parabolic law, indicating that the growth rate decreases with time and some maximum thickness range is expected
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