Fragmentation of diffusion zone in high-temperature oxidation of copper

doi:10.1016/j.jssc.2004.07.058

Journal of Solid State Chemistry

Volume 177, Issue 11, November 2004, Pages 4258-4268

https://doi.org/10.1016/j.jssc.2004.07.058 Get rights and content

Abstract

Using thermogravimetry, microscopy and X-ray diffraction, high-temperature (600–900 °C) oxidation of copper wires and plates has been studied. An abrupt decrease in reaction rate after complete consumption of metal phase but long before reaching equilibrium has been observed. This phenomenon is connected to an irregular character of the development of the reaction diffusion zone. In contrast to the usually applied layer model, initially formed oxide layers separate into numerous aggregates of Cu₂O crystals chaotically scattered throughout the zone between thinner layers of CuO grains. Such fragmentation of the diffusion zone is induced by macro- and microcracks formed in copper scale under influence of mechanical stresses at metal-oxide phase boundary due to the difference in molar volume between copper and its oxides. The pattern of cracks provides channels of fast diffusion and maintains the reaction rate at high level but only until the source of crack formation remains in action.

Graphical abstract

Pattern of diffusion fluxes in fragmented copper scale symbolizes the central conception of the paper.

Introduction

A very special place occupied by copper in the history of human civilization seems to remind of itself again in the unique role of cuprates among high-temperature superconductors and other advanced materials intensively studied during the last decades. This supports the interest to many aspects of copper physical and chemical behavior and, in particular, to the properties of copper oxides and their formation.

The phase equilibria and nonstoichiometry of oxides in the system Cu–O have been studied, starting with classical works of the first half of the 20th century, quite completely and reviewed in many literature sources, e.g., [1], [2], [3], [4]. The data of different authors on the kinetics of high-temperature oxidation of metallic copper to oxide Cu₂O agree with each other as well as with the measurements of electrical conductivity and isotope diffusion [1], [2], [4], [5], [6], [7]. At the same time, the details of deeper copper oxidation to CuO are much less lucid. In fact, there are no reports on kinetic studies in the course of complete copper oxidation to single-phased CuO as an equilibrium product. Valenci (as cited in [4], [6]) noticed that the copper scale formed on metallic surface in air up to 1000 °C contains both CuO and Cu₂O layers in ratio that depends on the temperature of oxidation. It has been reported also that copper scale contains both CuO and Cu₂O not only in the course of reaction but also after complete oxidation of metallic phase [5], [6]. This observation shows that equilibrium state was not reached in these studies otherwise it contradicts to both phase rule and p(O₂)–T phase diagram [1] according to which the equilibrium phase under stated conditions is CuO. In spite of these facts, the reported data on the parabolic rate constants of copper scale formation in air are in fair agreement between each other [1], [2], [5], [6].

The aim of this work is the study of oxidation kinetics and also composition, structure and development of reaction diffusion zone in the course of copper oxidation in air in temperature interval 600–900 °C.

Section snippets

Experimental

The specimens of electro-technical copper 99.99% pure in the form of wires 0.30 and 1.7 mm in diameter and also plates 0.10 and 0.50 mm thick have been used in the study.

The equilibria and kinetics of copper oxidation were studied gravimetrically in the experimental setup shown schematically in Fig. 1. Continuous measurement of the specimen mass (±0.1 mg) was conducted by an electronic balance (VLA-200, Novosibirsk) connected to a recording potentiometer. The specimen was suspended with a Pt wire

Retardation of oxidation kinetics

The results of gravimetric study of copper oxidation under isothermal conditions at 600, 700, 800 and 900 °C in air are presented in Fig. 2 as dependences of the overall oxygen content in the specimen, expressed as x in CuO_x, on time. In all experimental runs, an abrupt decrease in reaction rate is observed at values of x somewhat higher than 0.5. For example, the average oxygen content in the specimen of copper wire 1.7 mm in diameter reaches $x = 0.50$ after 38 h of oxidation at 900 °C (Fig. 2d).

Conclusions

The structure of the diffusion zone undergoes a series of basic rearrangements in the process of deep copper oxidation. They take place against the background of increasing packing density of recrystallizing tenorite CuO grains in oxide layer. Initially, highly permeable fine-grained tenorite layer is formed on the specimen's surface. Then, after the outer dense layer of recrystallized CuO grains develops, the two-layered oxide zone with dominating Cu₂O layer arises. Under mechanical stress due

References (13)

Yu.D. Tretyakov
The Chemistry of Nonstoichiometric Crystals
(1974)
P. Kofstad
Nonstoichiometry, Diffusion and Electrical Conductivity in Binary Metal Oxides
(1972)
N.P. Lyakishev (Ed.), Diagrams of State of Binary Metallic Systems. V.2, Mashinostroyeniye, Moscow, 1997 (in...
O. Kubaschewski et al.
Oxidation of Metals and Alloys
(1953)
J. Benard (Dir.), Oxydation des metaux. T.2, Gauthier-Villars, Paris,...
K. Hauffe
Reaktionen in und an Festen Stoffen. Bd. 2
(1955)

There are more references available in the full text version of this article.

Cited by (28)

Enhancing electrochemical carbon dioxide reduction efficiency through heat-induced metamorphosis of copper nanowires into copper oxide/copper nanotubes with tunable surface
2024, Journal of Colloid and Interface Science
Electrochemical CO₂ reduction reaction (CO₂RR) presents a unique opportunity to convert carbon dioxide (CO₂) to value-added products while simultaneously storing renewable energy in the form of chemical energy. However, particle applications of this technology are limited due to the poor efficiency and product selectivity of the existing catalyst. In this study, we demonstrate a facile method for the heat-induced transformation of copper nanowires into CuO_x/Cu nanotubes with defect-enriched surfaces. During this transformation, the outward migration of copper results in the formation of tubular structures encased within nanosized oxide grains. Notably, the hydrogen faradaic efficiency (FE) decreases with extended heat treatment, while carbon monoxide (CO) FE increases. As compared to Cu NWs, Cu NTs exhibit lower selectivity towards H₂ and single-carbon (C₁) products and favor the formation of multi-carbon (C₂₊) products. Consequently, a 2-fold increase in the single pass CO₂ conversion (SPCC) and C₂₊ half-cell energy efficiency (EE_{half cell}) was noted after heat treatment. The Cu NT-4 variant, synthesized under optimized conditions, exhibits the highest FE of 72.1 % for C₂₊ products at an operating current density (I_D) of 500 mA cm⁻².
A chemo-mechanical coupling model of oxidation and interlayer cracking of copper nanowires
2023, Journal of the Mechanics and Physics of Solids
Copper nanowires have received extensive attention for their potential applications in optics, electricity and catalysis, while oxidation erosion has become the biggest obstacle to their widespread application. Here, we present a chemo-mechanical coupling model to investigate the interlayer cracking behaviors of nanowires during oxidation. In contrast to existing chemo-mechanical models, the present model emphasizes that the process of oxygen entry into copper nanowires is chemical reaction-mediated layer-by-layer replacement rather than vacancy-mediated diffusion, which means the oxygen ions in the outer layer would not cross over the oxygen atoms in the inner layer during their entry. These conclusions are validated by molecular dynamics simulations. We then discuss the effect of the chemical reaction-induced free energy on the stress state of the nanowire during the reaction. Finally, a self-developed finite difference procedure is used to solve the control equations and the fracture location is determined according to the energy release rate analysis. We find the fracture of nanowires is closely dependent on the size of nanowire, the reaction rate and the oxygen concentration. This work deepens our understanding of the mechanism of chemo-mechanical coupling and fracture behavior of metals due to oxidation, thus has implications in other areas involving chemo-mechanical coupling.
Comparing the mechanical and thermal-electrical properties of sintered copper (Cu) and sintered silver (Ag) joints
2021, Journal of Alloys and Compounds
This review compares the mechanical and thermal-electrical properties of sintered copper (Cu) with sintered silver (Ag) as bonding materials in the microelectronics joint applications. Sintered Cu is explored as a possible replacement for sintered Ag, which suffered from electrochemical migration and high cost. However, sintered Cu faces severe oxidation throughout its product lifecycle, from Cu particle synthesis to joint formation, and finally, post-sinter reliability testing. This review discusses the various sintering conditions and related metallization/treatments to control this Cu oxidation and microstructural evolutions to form a reliable joint (in mechanical-thermal-electrical properties) for as-sintered, thermal aged, and thermal-mechanical cycled conditions. Separately, the patent information showed that the sintered Cu’s development and materials paste formulation followed those of sintered Ag closely and often claimed along as one of the sintered elements included in the patents. This review intends to guide new and experienced researchers to this sintered bonding to understand the sintering science, technologies, and related patents on sintered Cu and Ag.
The effect of surface preparation on high temperature oxidation of Ni, Cu and Ni-Cu alloy
2019, Applied Surface Science
In the present paper, the analysis of polishing, grinding and sand-blasting processes on oxidation behavior of nickel, copper and Ni30Cu70 alloy has been performed for three different temperatures. Surface roughness has been analyzed using two methods: contact profilometer and fractal analysis. It has been proved that R_a parameter for sand-blasted samples is greater about one order of magnitude from ground and two order of magnitude from polished samples. Obtained mass gain plots after isothermal oxidation tests, SEM microphotographs and SEM/EDS analysis of the samples prove that morphology of the polished and ground samples does not vary significantly after oxidation at investigated temperatures, but differences in oxide layer thicknesses and mass gains were observed. Oxidized sand-blasted samples revealed that increased surface roughness and alumina intrusions remained in the surface after sand-blasting process change the oxidation process–mixed Al/(Ni, Cu or Ni-Cu) oxide is formed and separate Al₂O₃ particles are visible. Moreover, differences in thickness ratio of copper oxides: Cu₂O to CuO on copper samples oxidized at 750 °C (26, 20; 29, 64; 43, 45 for polished, ground and sand-blasted samples, respectively) prove that surface preparation influence high-temperature oxidation of the samples by promoting new diffusion mechanism.
Low scale reheating of semi-finished metal products in furnaces with recuperative burners
2018, Applied Thermal Engineering
Industrial furnaces for reheating semi-finished metal products are often direct fired with natural gas and air. Oxidation of the metals exposed to the furnace atmosphere causes significant material losses and additional work during furnace operation and in further processing. A reheating concept, which reduces scale formation, was developed for direct fired reheating furnaces. It involves fuel rich combustion, post-combustion of the unburned off-gas and efficient preheating of the combustion air. This paper focuses on the reheating of copper and steel in direct fired furnaces with recuperative burners. Therefore, the post-combustion in an annular gap, according to a recuperative burner was examined, concerning temperature profile in the gap and off-gas emissions, to determine technical limits of the concept. Based on energy balances and scale formation the costs for fuel and metal loss were calculated to determine economic impact on the reheating process. The results show economic potential of the concept in terms of cost savings for the reheating of copper with a fuel rich combustion but no significant cost savings for the reheating of steel.
Intermetallics in CP-Ti/X65 bimetallic sheets filled with Cu-based flux-cored wires
2016, Materials and Design
Citation Excerpt :
It is mainly because of the inevitable oxidation of the copper. During the solidification of the weld metal, the oxygen combines with copper to form Cu2O, and at 1065 °C the eutectics of Cu and Cu2O form at the grain boundaries of the α-Cu [20]. As discussed by Li et al. [18], Ti had the ability to suppress the oxidation of the Cu welding pool.
This work is aimed to join the explosion-bonded CP-Ti/X65 bimetallic sheets with Cu-based flux-cored wires. Tungsten-inert gas (TIG) welding method was applied. The effect of V ratio on microstructure and mechanical properties was investigated. Ti–Fe, Ti–Cu and Ti–Cu–Fe intermetallics were identified in the reaction zones. The results showed that enhancing V ratio in the flux-cored wires led to the extension of the reaction zones, which eventually decreased the crack susceptibility of the joints. With V ratio rising to 25 wt.%, a sound joint was obtained. The ultimate strength of the joints fit the requirements. However, the bend tests showed extremely low bend ductility. Enhancing V ratio in the filler metals allowed diluting but not suppressing the formation of brittle intermetallics.

View all citing articles on Scopus

View full text

Fragmentation of diffusion zone in high-temperature oxidation of copper

Abstract

Graphical abstract

Introduction

Section snippets

Experimental

Retardation of oxidation kinetics

Conclusions

The Chemistry of Nonstoichiometric Crystals

Nonstoichiometry, Diffusion and Electrical Conductivity in Binary Metal Oxides

Oxidation of Metals and Alloys

Reaktionen in und an Festen Stoffen. Bd. 2