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Otani, Kyohei; Kato, Chiaki; Igarashi, Takahiro
Corrosion, 79(11), p.1277 - 1286, 2023/11
Nagata, Sho*; Miyake, Shugo*; Igarashi, Takahiro; Ota, Hiromichi*; Nishi, Tsuyoshi*
Jikken Rikigaku, 22(2), p.105 - 111, 2022/06
Thermal easy axis and thermal diffusivity of uniaxial carbon fiber-reinforced plastic sheets were determined by a offset periodic laser heating method, and investigated relationship between the thermal easy axis and fiber orientation with different thickness of CFRP sheet specimen, experimentally. It was clarified that the orientation of the thermal easy axis spreads in the in-plane direction with the sheet thickness deceases. Then, thermal diffusivity of CFRP specimens in the out-of-plane and in-plane direction were measured by two method: a variable-frequency method and a variable-displacement method, respectively. In the results of the out-of-plane directions, thermal diffusivity almost consistent with the carbon fiber direction were obtained. In contrast, the in-plane directions of those were exhibited unexpected value. Moreover, thermal diffusivity determination by offset periodic heating method was carried out. Finally, it is found that the thermal diffusivity considering the thermal easy axis with fiber angle was different characteristics from the in-plane direction measurement.
Igarashi, Takahiro; Otani, Kyohei; Komatsu, Atsushi; Kato, Chiaki; Sakairi, Masatoshi*
Bosei Kanri, 66(4), p.141 - 145, 2022/04
Metal corrosion is a material deterioration phenomenon based on electrochemical reactions on an atomic scale. In this paper, various methods for acquiring physical properties on metal surfaces using first-principles calculations were described. As examples of applying first-principles calculation to metal corrosion, the effect of hydrogen adsorption on the metal surface on the potential change and the effect of cation atoms in the aqueous solution on the corrosion resistance of the metal were reported.
Igarashi, Takahiro; Komatsu, Atsushi; Kato, Chiaki; Sakairi, Masatoshi*
Tetsu To Hagane, 107(12), p.998 - 1003, 2021/12
Times Cited Count：0 Percentile：0(Metallurgy & Metallurgical Engineering)In order to clarify the effect of environmental factors on the amount of atmospheric corrosion of steel, novel model for predicting the reduction of atmospheric corrosion considering relative humidity and rain falls was developed. We conducted a one-year calculation simulation of atmospheric corrosion in Miyakojima City, Choshi City, and Tsukuba City using the developed model. Corrosion weight loss by the simulation could reproduce the measured value well. Corrosion weight loss at each point was greatly affected by the amount of flying sea salt, relative humidity, and rain falls.
Igarashi, Takahiro; Komatsu, Atsushi; Kato, Chiaki; Sakairi, Masatoshi*
Bosei Kanri, 65(10), p.365 - 370, 2021/10
We have developed a new atmospheric simulation model considering important environmental factors such as airborne sea salt, temperature, relative humidity, and rainfall. The developed model was verified by comparing predicted values by the simulation and measured data for the weight loss by atmospheric corrosion. In addition, atmospheric corrosion simulations under open and sheltered exposure condition were conducted, and it was confirmed that the air corrosion weight loss was strongly suppressed by the surface cleaning effect due to rainfall.
Nagata, Sho*; Nishi, Tsuyoshi*; Ota, Hiromichi*; Igarashi, Takahiro; Miyake, Shugo*
Proceedings of 34th International Microprocesses and Nanotechnology Conference (MNC 2021) (CD-ROM), 2 Pages, 2021/10
Due to the increasing heat generation density of electronic devices, unidirectional Carbon-fiber-reinforced Plastic (CFRP) has gained interest as a heat-dissipating material owing to its high thermal conductivity, high anisotropy, and high strength. If CFRPs can be used to conduct heat in the desired direction of dissipation, more efficient thermal designs are possible. To control heat propagation, it is necessary to understand the heat propagation behavior within CFRPs at each fiber angle by determining the direction of heat propagation, referred to as thermal orientation. We previously demonstrated an approach for determining the thermal orientation of CFRPs using a periodic heating method, wherein the heat propagation in CFRPs was classified into two directions: the direction of the carbon fiber direction and the direction of the fiber-matrix interface. It has been suggested that the fiber-matrix interface has a significant effect on the heat propagation of CFRPs, which increases with the increase in CFRP thickness. However, the effect of CFRP thickness on thermal orientation is yet unknown. In the current study, we investigated the effect of the fiber-matrix interface on thermal orientation using the periodic heating method for CFRPs with varying thicknesses.
Igarashi, Takahiro; Komatsu, Atsushi; Motooka, Takafumi*; Ueno, Fumiyoshi; Yamamoto, Masahiro
Corrosion Science and Technology, 20(3), p.105 - 111, 2021/06
We constructed three dimensional computational model using cellular automata method to simulate the intergranular corrosion propagation of stainless steel. In the model, the computational system was constructed by three types of cells: grain (bulk), grain boundary (GB), and solution cell. Our simulations revealed that the surface roughness calculated by the model adopted distributed dissolution rates of GBs was greater than that adopted constant dissolution rates of GBs. The cross-sectional images obtained by our simulation were comparable with that obtained by corrosion tests. These results indicate that the surface roughness during corrosion relates the distribution of corrosion rate.
Kano, Koichi*; Hagiwara, Satoshi*; Igarashi, Takahiro; Otani, Minoru*
Electrochimica Acta, 377, p.138121_1 - 138121_10, 2021/05
Times Cited Count：17 Percentile：71.29(Electrochemistry)We investigated the free corrosion potential at an interface between an Al electrode and an aqueous NaCl solution under acidic conditions via density functional theory combined with the effective screening medium and reference interaction site model (ESM-RISM). The electrode potentials for the anodic and cathodic corrosion reactions were obtained from the grand potential profile as a function of the electron chemical potential at the interface. Thereafter, we determined the free corrosion potential using the Tafel extrapolation method. The results of the free corrosion potential were consistent with previous experimental data. By controlling the pH, we determined the pH dependence of the free corrosion potential, and the results agreed well with the experimental results. Our results indicated that the ESM-RISM method duly described the environmental effect of an acidic solution and precisely determined the free corrosion potential.
Igarashi, Takahiro; Otani, Kyohei; Kato, Chiaki; Sakairi, Masatoshi*; Togashi, Yusuke*; Baba, Kazuhiko*; Takagi, Shusaku*
ISIJ International, 61(4), p.1085 - 1090, 2021/04
Times Cited Count：1 Percentile：8.06(Metallurgy & Metallurgical Engineering)In order to clarify the effect of metal cations (Zn
, Mg, Na
) in aqueous solution on hydrogen permeation into iron, the amount of hydrogen permeation from iron surface was measured by electrochemical tests with a laser ablation. Moreover, in order to obtain the basic mechanism of hydrogen permeation with metal cation, first-principles calculations were used to acquire the adsorption potential of the metal cation and the electronic state around iron surface. By Zn in solution, anodic reaction on ablated surface by laser irradiation was suppressed. Also, by quantum analysis Zn atoms were chemically bonded stronger than Na and Mg atoms to iron surface. It was suggested that the dissolution reaction of iron was suppressed by the formation of the Zn layer, and that lead suppression of hydrogen permeation into iron.
Yamamoto, Masahiro; Irisawa, Eriko; Igarashi, Takahiro; Komatsu, Atsushi; Kato, Chiaki; Ueno, Fumiyoshi
Proceedings of Annual Congress of the European Federation of Corrosion (EUROCORR 2019) (Internet), 5 Pages, 2019/09
Intergranular corrosion phenomena were analysed using modified reprocessing solution. The data indicated that corrosion rates increased with time at the initial stage, and these stayed at constant value. Intergranular corrosion propagated at grain boundary in the initial stage and then attacked whole grain boundary causing drop out of grains. Corrosion rates of steady state were sum of intergranular corrosion amounts and weight losses of dropped grains. Surface appearances and cross sections of corroded samples were analyzed. The results indicated that the initial stage of intergranular corrosion was characterized by the ratio of corrosion rates between grain boundary and matrix. These ratios differed from individual grain boundaries. Total corrosion rates were affected by the distribution of these ratios. These data were based on the numerical modelling of intergranular corrosion using cellular automata. And also, calculated results were compared with these analytical data.
Yamamoto, Masahiro; Soma, Yasutaka; Igarashi, Takahiro; Ueno, Fumiyoshi
Proceedings of Annual Congress of the European Federation of Corrosion (EUROCORR 2018) (USB Flash Drive), 7 Pages, 2018/09
In order to clarify the SCC behavior of SUS316L under BWR environment, mass transfer inside crevice of SUS316L in high temperature water using various crevice gap samples was investigated. The samples were prepared by put together two SUS316L sheets. Crevice gap differs from 0.005 mm to 0.1 mm. Corrosion tests were conducted in 8 ppm dissolved oxygen (DO) conditions. Surface oxide film was analysed by laser Raman spectroscopy (LRS) after immersion. Numerical simulations were also conducted by using COMSOL Maltiphysics. Diffusion process of DO and the other chemical species were calculated with connected to electrochemical process. Electrical conductivities inside the crevice were 100 times larger than these of outer water. The reason of high conductivity is existence of Fe ions at the DO depletion crevice.
Yamamoto, Masahiro; Sato, Tomonori; Igarashi, Takahiro; Ueno, Fumiyoshi; Soma, Yasutaka
Proceedings of European Corrosion Congress 2017 (EUROCORR 2017) and 20th ICC & Process Safety Congress 2017 (USB Flash Drive), 6 Pages, 2018/09
The authors have studied the differences between outer surface and the crevice-like portion of SUS316L in high pressurized and high temperature water containing dissolved oxygen. We have already introduced that changes in the characteristics of corrosion products along the crevice directions and gap width. It is suggested that the environmental conditions are different with the features of crevice from these results. In this report, we introduce the changes in oxide films with crevice gaps and comparison with the numerical simulation data utilizing of FEM calculation.
Satou, Yukihiko; Sueki, Keisuke*; Sasa, Kimikazu*; Yoshikawa, Hideki; Nakama, Shigeo; Minowa, Haruka*; Abe, Yoshinari*; Nakai, Izumi*; Ono, Takahiro*; Adachi, Koji*; et al.
Geochemical Journal, 52(2), p.137 - 143, 2018/00
Times Cited Count：68 Percentile：97.15(Geochemistry & Geophysics)Ono, Takahiro*; Iizawa, Yushin*; Abe, Yoshinari*; Nakai, Izumi*; Terada, Yasuko*; Satou, Yukihiko; Sueki, Keisuke*; Adachi, Koji*; Igarashi, Yasuhito*
Bunseki Kagaku, 66(4), p.251 - 261, 2017/04
Times Cited Count：32 Percentile：79.03(Chemistry, Analytical)no abstracts in English
Ueno, Fumiyoshi; Irisawa, Eriko; Kato, Chiaki; Igarashi, Takahiro; Yamamoto, Masahiro; Abe, Hitoshi
Proceedings of European Corrosion Congress 2016 (EUROCORR 2016) (USB Flash Drive), 7 Pages, 2016/09
In this study, we focused on the effect of the boiling of nitric acid solution on the corrosion of a stainless steel-made concentrator in reduced pressure in fuel reprocessing plant. In order to perform the simulation test in a non-radioactive condition, nitric acid solution with the addition of vanadium as an oxidizing metal ion were used. Corrosion tests were carried out under the conditions of boiling at reduced pressure, and of non-boiling at normal pressure and several temperatures. As a result, corrosion was accelerated by the solution boiling while it was not by non-boiling at the same temperature. It was found also that the temperature dependence of corrosion rate is the same in the both conditions of boiling and non-boiling. The corrosion accelerating effect will be discussed on the basis of the reaction among nitric acid, NOx and vanadium, etc.
Igarashi, Takahiro; Komatsu, Atsushi; Motooka, Takafumi; Ueno, Fumiyoshi; Yamamoto, Masahiro
Proceedings of 19th International Corrosion Congress (19th ICC) (CD-ROM), 7 Pages, 2014/11
We constructed three dimensional computational model using cellular automata method to simulate the intergranular corrosion propagation of stainless steel. By the simulation using the model, we verified the relationship between surface roughness during corrosion and dispersion of dissolution rate of grain boundaries (GB). The relationship was investigated by the simulation applying constant dissolution rate for GB cells and distributed dissolution rate of GB cells. Our simulations revealed that the surface roughness calculated by the model adopted distributed dissolution rates of GBs was greater than that adopted constant dissolution rates of GBs. The cross-sectional images obtained by our simulation were comparable with that obtained by corrosion tests. These results indicate that the surface roughness during corrosion relates the distribution of corrosion rate.
Ueno, Fumiyoshi; Komatsu, Atsushi; Igarashi, Takahiro; Yamamoto, Masahiro
Proceedings of European Corrosion Congress 2014 (EUROCORR 2014) (USB Flash Drive), 10 Pages, 2014/09
In this paper, the effect of phosphorous concentration in grain boundary (GB) on intergranular corrosion (IC) progress was studied to understand GB corrosion behavior of stainless steels in boiling nitric acid solution. Phosphorus (P) added extra high purity type 310 stainless alloy was corroded in boiling nitric acid solution, and P in GB was detected by three-dimensional atom probe. IC progress considering with P profile in GB was studied by numerical simulation using cellular automaton method. As the results, we concluded that P concentration change around 1.4at% in GB of the alloy caused IC rate change in boiling nitric acid solution. The developed numerical method could simulate GB corrosion change with P distribution in GB.
Igarashi, Takahiro; Komatsu, Atsushi; Motooka, Takafumi; Ueno, Fumiyoshi; Kaji, Yoshiyuki; Yamamoto, Masahiro
Zairyo To Kankyo, 63(7), p.431 - 437, 2014/07
In order to obtain the relation between an intergranular corrosion behavior and an impurities for stainless steel, cellular automata modeling and simulation of intergranular corrosion was carried out. From intergranular corrosion simulation considering non-uniform phosphorus component distribution on grain boundary, it suggested that complicated intergranular corrosion shape as in experimental data was caused by the large precipitation of phosphorus compounds in part of grain boundary.
Li, Y.; Kaji, Yoshiyuki; Igarashi, Takahiro
Nuclear Engineering and Design, 242, p.100 - 107, 2012/01
Times Cited Count：8 Percentile：52.49(Nuclear Science & Technology)Igarashi, Takahiro; Nakazawa, Tetsuya; Suzuki, Chikashi; Tsuru, Tomohito; Kaji, Yoshiyuki
Computational Materials Science, 50(12), p.3346 - 3349, 2011/12
Times Cited Count：1 Percentile：4.5(Materials Science, Multidisciplinary)The authors have developed a new approach for large-scale systems including over 100,000 atoms to obtain physical strength from the viewpoint of atom-atom bonding energy. In this study, the authors applied this method to SiH
molecule and crystalline silica system, and carried out bond order and bonding energy analyses. In this analysis, the developed method offered almost the same analytical accuracy as the first principle method, while its calculation speed was much faster than that of the latter.
