Oxidation Mechanism of Cu2O to CuO at 600?1050�C

Abstract

To clarify the oxidation mechanism of Cu 2 O to CuO, Cu 2 O oxidation was studied at 600-1050 • C under 1 atm O 2 . The Cu 2 O specimens were prepared through completely oxidizing 99.99999 and 99.5% pure copper at 1000 • C in an Ar + 1% O 2 atmosphere. The oxidation kinetics of Cu 2 O specimens prepared from both purity levels followed the logarithmic law, not the parabolic law or the cubic law as reported in the literature. The activation energy for Cu 2 O oxidation is relatively high in the lower-temperature range, but becomes very small or even negative at higher temperatures. The logarithmic oxidation rate law can be explained by Davies et al.'s model related to grain-boundary diffusion in the oxide layers. The very small or negative activation energies in the higher-temperature range can be attributed to the very small thermodynamic driving force and the fast lateral growth of CuO grains related to a sintering effect. The influence of small amount of impurities is also discussed.

Chemical Looping with Copper Oxide as Carrier and Coal as Fuel

“…Above 800°C, oxidation of Cu 2 O shows a progressive decrease in rate with increasing temperature. This unusual behaviour has been observed previously for the oxidation of copper [29] and cuprous oxide [30]. These references underline the complexity of the mechanism of Chemical Looping with Oxygen Uncoupling results with copper oxide at 950°C for a single cycle.…”

“…Since bulk diffusion through the CuO is slow, the rate is controlled by the diffusion through grain boundaries in the CuO. As temperature increases, the grains grow rapidly, reducing the rate of increase in oxidation [29] and even leading to a decrease in rate [30]. A further complication is provided by the changes in surface areas resulting from the changes in porosity governed in part by the difference in molar volumes of CuO and Cu 2 O.…”

The oxidation behavior of Cu–Zr–Ti–base bulk metallic glasses in air at 350–500 °C

“…For the oxidation of the quaternary BMG, the formation of CuO was faster than that of Cu 2 O despite the low defective nature of the former. In addition, as reported in the literature [20][21], the oxidation of Cu 2 O to CuO takes place at 600-1050°C at 1 atm O 2 , according to kinetics that follow the logarithmic rate law. Although the temperature range in the current study is much lower, the reaction from Cu 2 O to CuO may be still favorable.…”

“…The cubic ZrO 2 is stable only at temperatures higher than 1500°C, while monoclinic and tetragonal ZrO 2 are stable at lower (a) 20 30 formation of c-ZrO 2 at T £ 500°C was unexpected in the current study, and it was deemed necessary to further clarify the exact phase structure of zirconia through TEM analyses. A TEM sample of the cross-sectional scales formed after 48 h exposure at 450°C was prepared, and the results together with the corresponding SAD patterns are shown in Fig.…”

Oxidation Behavior of Copper at a Temperature below 300 °C and the Methodology for Passivation

“…The oxidation behavior of copper has therefore received considerable interest for a very long time [1][2][3] . At temperatures above 600 °C, it is believed that the oxidation is controlled by the lattice diffusion of copper ions through a Cu 2 O layer [4][5][6] . In contrast, the reported kinetic data on the oxidation below 500 °C varied significantly 7 .…”