Abstract
The high temperature oxidation of Cu-32.02% Zn-2.30%Pb brass was carried in N2-5wt.% O2 and N2-12 wt.% O2 atmospheres. The amounts of oxygen in the oxidizing atmospheres and the time of the oxidation affected the oxide morphologies and kinetics of the oxide growth. In the first hour of the oxidation at 650 °C, oxide nanowires were noted. The average diameter, length and distance between the observed nanowires were 27 ± 0.01 nm, 0.20 ± 0.04 µm and 0.20 ± 0.04 µm respectively for the samples oxidized in N2-5wt.% O2 atmosphere and 102 ± 23 nm, 0.36 ± 0.24 μm and 0.24 ± 0.08 μm respectively for the samples oxidized in N2-12wt.% O2 atmosphere. The EDX and XRD analyses of the nanowires and the oxide granules confirmed ZnO nanowires and a continuous oxide layer of ZnO. The x-ray diffraction confirmed minor presence of PbO. The oxide growth kinetics followed the linear oxide growth model, for the alloy samples that were thermally oxidized in N2-5 wt.% O2 atmposphere and parabolic growth model for those thermally oxidized in N2-12 wt.% O2 atmospheres respectively. The values of 6.8 µm/hour and 23.03 µm/(hour)1/2were determined for growth constant (k), based on the two models respectively.
Highlights
Brass is an alloy that consist of mainly copper and zinc[1,2]
This work is aimed at investigating the effect of the amount of oxygen and thermal oxidation time on the chemistry of the oxide scale, the morphology and the growth kinetics of the oxides formed on the high temperature thermal oxidation of Cu-32.05% Zn- 2.30% Pb brass
The results of the thermal oxidation of the Cu-32.02% Zn-2.30% Pb brass in the N2-O2 gas mixtures at 650 ̊C are discussed in terms of the chemistry of the oxide layer, the effect of the amount of oxygen available for the thermal oxidation, the effect of time of the thermal oxidtion on the oxide morphology and the growth kinetics of the oxidae layer
Summary
Brass is an alloy that consist of mainly copper and zinc[1,2]. Depending on the amount of zinc, brass as an alloy can exist with a single alpha-phase[6]. Thermal oxidation has been used as a means of growing oxide nanostructures on the surfaces of metals and their alloys and several of such works are available in literature[7,8,9]. These oxide nanostructures are reported to exist in various forms such as nanowires, nanorods, nanoflakes, nanotubes, nanoneedle, nanorings, nanofibers and nanocombsetc[10,11]. The nature, form and type of these nanostructures have been found to be dependent on the oxidizing conditions such as time, temperature and pressure etc
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