Conclusions

In order to evaluate effect of carbon dissolution reaction on the wetting behaviour of carbonaceous materials substrate by liquid Fe-C sample, the wetting behaviour of liquid Fe-C samples on the substrates was investigated using the sessile drop method with a molten sample injection system. Besides, the wetting behaviour of the Fe-C sample on the substrate in the initial contact period was studied using the sessile drop method with a molten injection and quenching systems. The quenching system allows to terminate the carbon atoms transferred from the substrate to the Fe-C sample after the elapse of predetermined time in the initial contact period. The results of this study are revealed as follow.

(1) Wetting behaviour of the Fe-C sample on the simulant coke substrate.

 In the wetting of the liquid Fe-C sample on the simulant coke substrate, the apparent contact angle variation had two stages. The apparent contact angle experienced a significant decrease over the first 300 s of contact between the liquid Fe-C and the simulant coke substrate. The apparent contact angle stabilized at a constant value, apparently equilibrium contact angles.

 Mixed alumina powder in the substrate prevented wetting of the carbon saturated Fe-C sample on the substrate, and they increased their apparent equilibrium contact angles. The alumina powder had effects on not only the wetting behaviour but also the reaction between Fe-C sample and the simulant coke.

 Concave geometries formed when the carbon-unsaturated liquid Fe-C sample was wetted on the substrates containing 0, 5, and 10 vol% Al2O3. The effect of Al2O3 on the carbon dissolution reaction was a main factor affecting the wettability of the simulant coke substrates against the Fe-C

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samples.

(2) Wetting behaviour of the liquid Fe-C sample on the simulant coke substrate in the initial contact period.

 The initial contact angles increased with increasing carbon concentrations of the Fe-C samples. The initial apparent contact angle also correlated with the amount of Al2O3 in the substrates. The initial contact angles increased almost linearly with increasing amounts of Al2O3 in the substrates.

 The apparent contact angle in the initial contact period significantly decreased in the wetting of the liquid Fe-C sample on the substrate containing 10 vol% Al2O3 or less in the substrates. The apparent contact angle decreased with decreasing of Al2O3 content in the substrate. The apparent contact angle decreased with decreasing of carbon concentration of Fe-C sample in the initial contact period.

 In the initial contact period, the apparent contact angle depended on the interfacial energy of solid-liquid phases before the formation of concave.

After the concave formation, the apparent contact angles dominantly depended on the interfacial morphology change due to carbon dissolution process.

 In the case of the wetting of carbon saturated Fe-C samples on the graphite substrate in the initial contact period, the droplet spread on the flat surface of the substrate in the initial contact period. The carbon dissolution amount was enough to decrease the interfacial energy of solid-liquid phases which caused the apparent contact angle to decrease.

 The apparent contact angle significantly decreased in the wetting of liquid Fe-C sample on the substrate containing 0 and 10 vol% Al2O3 in substrates.

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Increasing of amount of Al2O3 in the substrate caused the apparent contact angle to increase. In the case of the substrate containing 20 vol% Al2O3, the apparent contact angle decreased during 180 s of contact period, and then dramatically increased by 30°.

 The formation of simulant Al2O3 layer was observed in the contact are between the carbon unsaturated Fe-C sample and the substrate containing 20 vol% Al2O3. The formation of this layer in the contact area between the Fe-C sample and the substrate caused the interfacial energy of solid-liquid phases to change. The change cause interfacial energy to be imbalanced at triple line, which change the apparent contact angle significantly.

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References

1) Y. Bando, S. Hayashi, A. Matsubara and M. Nakamura: ISIJ Int., 45(2005), 1461.

2) K. Ohno, T. Miyake, S. Yano, C.S. Nguyen, T. Maeda and K. Kunitomo: ISIJ Int., 55(2015), 1252.

3) A. Babich, D. Senk, H.W. Gudenau and K. Th. Mavrommatis: Ironmaking, Aachen, (2008), 174.

4) S.J. Chew, P. Zulli, D. Maldonado and A. Yu: ISIJ Int., 43(2003), 304.

5) A.K. Biswas: Principles of Blast furnace Ironmaking, Brisbane, Australia, (1981).

6) S. Natsui, T. Kikuchi, R.O. Suzuki, T. Kon, S.Ueda and H. Nogami: ISIJ Int., 55(2015), 1259.

7) H. Kawabata, Z. Liu, F. Fujita and T. Usui: ISIJ Int., 45(2005), 1466.

8) H. Kawabata, K. Shinmyou, T. Harada and T. Usui: ISIJ Int., 45(2005), 1474.

9) H. Ohgusu, Y. Sassa, Y. Tomita, K. Tanaka and M. Hasegawa: Tetsu-to-Hagané, 78(1992), 1164.

10) I.H. Jeong, H.-S. Kim and Y. Sasaki: ISIJ Int., 53(2013), 2090.

11) C. Wu and V. Sahajwalla: Metall. Mater. Trans. B, 29B(1998), 471.

12) M.W. Chapman, B.J. Monaghan, S.A. Nightingle, J.G. Mathieson and R.J.

Nightingle: Metall. Mater. Trans. B, 39B(2008), 418.

13) S.T. Cham, R. Sakurovs, H. Sun and V. Sahajwalla: ISIJ Int., 46(2006), 652.

14) F. Mc Carthy, V. Sahajwalla, J. Hart and N. Saha-Chaudhury: Metall. Mater.

Trans. B., 34B(2003), 573.

15) C. Wu, R. Wiblen and V. Sahajwalla: Metall. Mater. Trans. B., 31B(2000), 1099.

16) L. Zhao and V. Sahajwalla: ISIJ Int., 43(2003), 1.

91

17) S.T. Cham, V. Sahajwalla, R. Sakurovs, H. Sun and M. Dubikova: ISIJ Int., 44(2004) 1835.

18) H. Sun: ISIJ Int., 45(2005), 1482.

19) E. Saiz, A.P. Tomsia and R.M. Cannon: Acta Mater., 46(1998), 2349.

20) N. Eustathopoulos, R. Voytovych: J. Mater Sci., 51(2016), 425.

21) J. Kurikkala, O. Mattila, T. Fabritius and Jouko Harkki: ISIJ Int., 50(2010), 356.

22)M. Ikram-ul-haq, R. Khanna, P. Koshy and V. Sahajwalla: ISIJ Int., 50(2010), 804.

23) N. Eustathopoulos, M.G. Nicholas and B. Drevet: Wettability at High Temperature, (1999), 54.

24) C.S Nguyen, K. Ohno, T. Maeda and K. Kunitomo: ISIJ Int., 56(2016), 1325.

25) E. B. Hawbolt: Master thesis, the University of British Columbia, Canada, (1964), 29.

26) O. Dezellus and N. Eustathopoulos: J. Mater Sci., 45(2010), 4256.

27) P. G. Read: Gemmological Instrument: Their Use and Principles of Operation.

Butterworths, England, (1983),125.

28) M. Humenik, D.W. Hall and R. L. Alsten: Met. Prog., 81 (1982), 101.

29) B.V. Tsarevskii and S. I. Popel: Vuz. Chern. Metall., 8 (1960), 15.

30) S. Ueda, T. Kon, S. Kikuchi, S. Natsui, S. Sukenaga and H. Nogami: ISIJ Int., 55(2015), 1277.

31) J. Lee and K. Morita: ISIJ Int., 44(2004), 235.

32) N. Shinozaki, N. Satoh, H. Shinozaki, K. Wasai and H. Era: J. Jpn. Inst. Met., 70(2006), 950.

33) K. Morohoshi, M. Uchikoshi, M. Isshiki and H. Fukuyama: ISIJ Int., 53(2013),

92

1351.

34) T. Mori, K. Fujimura, H. Okajima and A. Yamauchi: Tetsu-to-Hagané, 54(1968), 321.

35) S. K. Rlee: J. Am. Ceram. Soc., 55(1972), 300.

36) S. Jung, T. Ishikawa, S. Sekizuka and N. Nakae: J. Mater. Sci., 40(2005), 2227.

37) P. Sharps, A. Tomsia and J. Pask: Acta Metall., 29 (1982), 855.

38) J. G. Li: Ceramics Int., 20(1994) 391

39) E. B. Hawbolt: Master thesis, the University of British Columbia, Canada, (1964), 36.

40) N. Eustathopoulos: JIMIS-8, Interface Science of Materials interconnection Conf. Proc, Toyama, Japan, (1996), 61.

41) I. Aksay, C. Hoye and J. Pask: J. Phys. Chem., 78(1974), 1178.

42) K. Monma and H. Suto: J. Jpn. Inst. Met., 24(1960), 167.

43) K. Morohoshi, M. Uchikoshi, M. Isshiki and H. Fukuyama: ISIJ Int., 51(2011), 1315.

44) D.R. Poirier, H. Yin, M. Suzuki and T. Emi: ISIJ Int., 38(1998), 229.

45) N. Sobczak, M. Singh and R. Asthana: Solid State & Materials Science., 9(2005), 241.

46) K. Morohoshi, M. Ushikoshi, M. Isshiki and H. Fukuyama: ISIJ Int., 53(2013), 1315.

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Acknowledgements

First of all, I would like to express my sincere gratitude to Professor Kazuya Kunitomo, my supervisor, for giving me the opportunity to pursue my PhD study in his group, for encouraging and guiding me, and for creating the best environment for my scientific and personal growth in the period of three years. I quite simple cannot image a better adviser.

Besides my supervisor, I am deeply indebted to Professor Ko-ichiro Ohno for very valuable discussions and suggestions on the experimental and technological background of this work. I gratefully acknowledge the advice and guidance given by Professor Takayuki Maeda throughout the investigation.

I am very thankful to Professor Kunihiko Nakashima and Professor Noritaka Saito of Kyushu University for their experimental help and the valuable comments on this investigation. I would like to thank Professor Setsuo Takaki of Kyushu University for giving me the valuable comments on this thesis.

Many thanks to my labmates for your positive attitude, for the enjoyable moment we have had in the last three years. I thank to Yano san for your help during the early period of my research. Thank you Doji san for help in various computer problems. Thanks to Hori san and Otsuka san for technical supports in laboratory work.

Koga san who is a secretary of laboratory, is appreciated for giving me many supports to do the paperwork.

I would like to thank AUN/SEED-Net and Japan International cooperation Agency (JICA) who give me financial support to do the doctoral course at Kyushu University. I am very thankful to JICA Kyushu international center, whose help