TY - JOUR
T1 - Temperature dependence of thermal diffusivity and conductivity of FeO scale produced on iron by thermal oxidation
AU - Li, Mu
AU - Endo, Rie
AU - Akoshima, Megumi
AU - Susa, Masahiro
N1 - Funding Information:
This study was supported by the 25th ISIJ Research Promotion Grant, and has also been conducted as one of the projects in Research Group II for the “Investigation on Factors Controlling Heat Transfer Characteristics of Scales” in the Rolling Theory Committee, The Iron and Steel Institute of Japan. The authors are grateful for the financial support from the Institute and useful advice from the Committee members. The authors are also grateful to Professor Hiromichi Ohta for his valuable discussions and advice about the interphase heat resistance.
Publisher Copyright:
© 2017 ISIJ.
PY - 2017
Y1 - 2017
N2 - The thermal diffusivity/conductivity of FeO scales produced on iron substrates by thermal oxidation have been determined as functions of temperature. Iron plates (99.99%) were oxidised at 973 K in air to obtain oxide scales of FeO, Fe3O4, and Fe2O3, and then were reduced at 1 273 K in nitrogen to obtain FeO-only. The densities of these scales were 5.85–6.05 g cm−3. The laser flash method was used to measure the apparent thermal diffusivity of the whole sample from room temperature to 1 164 K during the heating/ cooling cycles. This was converted to the thermal diffusivity of the scale only, which in turn was converted to the thermal conductivity. However, these values depended on the scale thickness, which suggests an interfacial heat resistance occurs between the scale layer and iron substrate. In addition, scanning electron microscopy (SEM) observations revealed that the scales contained Fe and Fe3O4 phases after heating. The scale thermal diffusivity/conductivity were corrected considering the interfacial heat resistance and dispersed phases to derive the corresponding values for FeO only. The interfacial heat resistance derived from the thickness dependence of the scale thermal conductivity was 8.3 × 10−6 m2 K W−1. Using this value, the thermal diffusivity of FeO was derived as 3.7 × 10−7–5.8 × 10−7 m2 s−1 and the thermal conductivity as 1.8–2.5 W m−1 K−1 between room temperature and 1 164 K. The temperature coefficients of the thermal conductivity were mostly negative, which would be dominated by the phonon mean free path.
AB - The thermal diffusivity/conductivity of FeO scales produced on iron substrates by thermal oxidation have been determined as functions of temperature. Iron plates (99.99%) were oxidised at 973 K in air to obtain oxide scales of FeO, Fe3O4, and Fe2O3, and then were reduced at 1 273 K in nitrogen to obtain FeO-only. The densities of these scales were 5.85–6.05 g cm−3. The laser flash method was used to measure the apparent thermal diffusivity of the whole sample from room temperature to 1 164 K during the heating/ cooling cycles. This was converted to the thermal diffusivity of the scale only, which in turn was converted to the thermal conductivity. However, these values depended on the scale thickness, which suggests an interfacial heat resistance occurs between the scale layer and iron substrate. In addition, scanning electron microscopy (SEM) observations revealed that the scales contained Fe and Fe3O4 phases after heating. The scale thermal diffusivity/conductivity were corrected considering the interfacial heat resistance and dispersed phases to derive the corresponding values for FeO only. The interfacial heat resistance derived from the thickness dependence of the scale thermal conductivity was 8.3 × 10−6 m2 K W−1. Using this value, the thermal diffusivity of FeO was derived as 3.7 × 10−7–5.8 × 10−7 m2 s−1 and the thermal conductivity as 1.8–2.5 W m−1 K−1 between room temperature and 1 164 K. The temperature coefficients of the thermal conductivity were mostly negative, which would be dominated by the phonon mean free path.
KW - FeO
KW - Interfacial heat resistance
KW - Temperature dependence
KW - Thermal conductivity
KW - Thermal diffusivity
KW - Thermally grown iron oxide scale
UR - http://www.scopus.com/inward/record.url?scp=85039808087&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85039808087&partnerID=8YFLogxK
U2 - 10.2355/isijinternational.ISIJINT-2017-301
DO - 10.2355/isijinternational.ISIJINT-2017-301
M3 - Article
AN - SCOPUS:85039808087
SN - 0915-1559
VL - 57
SP - 2097
EP - 2106
JO - ISIJ International
JF - ISIJ International
IS - 12
ER -