Journal ArticleDOI
Origin and development of residual stresses in the NiNiO system: in-situ studies at high temperature by X-ray diffraction
Chun Liu,A.M. Huntz,J.L. Lebrun +2 more
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TLDR
In this article, two high temperature chambers for X-ray diffraction were designed, allowing us to determine the stresses in both the oxide and the substrate with the sin2 ϕ technique, at high temperatures or room temperature and during heating-cooling sequences.Abstract:
In order to characterize the respective importance of the growth stresses, thermal stresses and stress relaxation developed in oxide scales, two high temperature chambers for X-ray diffraction were designed, allowing us to determine the stresses in both the oxide and the substrate with the sin2 ϕ technique, at high temperatures or room temperature and during heating-cooling sequences. It was applied to NiNiO. At room temperature after oxidation, NiO is subjected to compressive stresses whose level depends on the substrate thickness and on the oxidation time and temperature. In the substrate, compressive stresses are mainly due to internal oxidation. During oxidation at 900 °C, the oxide scale is subjected to slight tensile stresses which can be due partially to anionic diffusion, internal oxidation or the heating process. During heating-cooling sequences, the stresses in the scale decrease with increasing temperature and become negligible when the oxidation temperature is reached. The reversibility of the stress-temperature curve indicates that no stress relaxation occurs. The stresses found at room temperature are due only to thermal stresses and fit well the theoretical calculation of thermal stresses in NiO scale based on the newly determined thermal expansion coefficients of Ni and NiO. All these results show that the stresses found at room temperature are mainly generated during cooling and that the effect of the Pilling-Bedworth ratio or of factors playing a role during isothermal growth is negligible.read more
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Journal ArticleDOI
Mechanical properties of NiO/Ni–YSZ composites depending on temperature, porosity and redox cycling
TL;DR: In this article, the Impulse Excitation Technique (IET) was used to determine the elastic modulus and specific damping of different Ni/NiO-YSZ composites suitable for use in solid oxide fuel cells (SOFC).
Journal ArticleDOI
Stresses in NiO, Cr2O3 and Al2O3 oxide scales
TL;DR: In this article, it is suggested that growth stresses are particularly related to the scale growth mechanism, and that they are of minor importance compared with thermal stresses so that, for the systems considered, the adherence loss mainly results from the thermal stresses and/or from the poor quality of the scale-metallic substrate interface due to the defect concentration at this interface.
Journal ArticleDOI
Redox stability of SOFC: Thermal analysis of Ni-YSZ composites
TL;DR: In this paper, the authors used a high precision dilatometer to show the dimensional behavior of the Ni-YSZ composites simultaneously with the Degree of Oxidation (DoO) as a function of time during redox cycling and the activation energy for reduction was 84.4 kJ/mol and the kinetics was largely linear.
Journal ArticleDOI
Microstructure and Residual Stress of Alumina Scale Formed on Ti2AlC at High Temperature in Air
Jai Won Byeon,Jai Won Byeon,J. Liu,M. Hopkins,W. Fischer,Narayana Garimella,K. B. Park,Michael P. Brady,Miladin Radovic,Tamer El-Raghy,Yongho Sohn +10 more
TL;DR: In this paper, isothermal and cyclic oxidation were performed in air to examine the oxidation behavior of Ti2AlC ternary carbide and α-Al2O3.
Journal Article
Microstructure and Residual Stress of Alumina Scale Formed on Ti2AlC at High Temperature in Air
Jai Won Byeon,Jia Liu,M. Hopkins,W. Fischer,K. B. Park,Michael P. Brady,Miladin Radovic,Yongho Sohn +7 more
TL;DR: In this paper, isothermal oxidation at 1000 XC, 1200 XC and 1400 XC for up to 25 hours, as well as 1,000 1-hour cyclic oxidation at 1200 xC were performed in air to examine the oxidation behavior of Ti2AlC.
References
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Journal ArticleDOI
Transport processes during the growth of oxide films at elevated temperature
TL;DR: In this article, the authors reviewed the current understanding of the growth of thermal oxide films in terms of the transport properties of the oxides and examined quantitative relationships between the film growth rate and other measurable parameters of oxides.
Journal ArticleDOI
High-temperature thermal expansion of six metallic elements measured by dilatation method and X-ray diffraction
I.-K. Suh,H. Ohta,Yoshio Waseda +2 more
TL;DR: In this paper, the thermal expansion of six metals, namely, silver, gold, copper, nickel, molybdenum and tungsten, was measured by the dilatation method.
Journal ArticleDOI
Stress generation and relief in growingoxide films
TL;DR: In this article, the experimental techniques for determining the growth stresses in oxide scales are described, and the results briefly summarized, and theories proposed by various workers to account for the existence of growth stresses are critically reviewed.
Journal ArticleDOI
Cracking and spalling of protective oxide layers
TL;DR: In this paper, the role of thermal stresses on the mechanical integrity of oxide layers is discussed, and it is shown that the processes of cracking and spalling of oxides differ depending on the stress state (tensile or compressive) and on the relative strengths of oxide and oxide-metal interface.
Journal ArticleDOI
Transport processes in the oxidation of Ni studied using tracers in growing NiO scales
TL;DR: In this article, experimental techniques have been developed for determining Ni63 and O18 tracer distributions in NiO scales ranging in thickness from ∼0.1 to 100 µm and were used to investigate Ni and O transport in scales on {100} Ni crystals and polycrystalline Ni in the temperature range 500-1300° C.
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