著者

Duck Y. Hwang Yong M. Kim Dong H. Shin

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.50, no.3, pp.671-678, 2009-03-01 (Released:2009-02-25)

参考文献数

23

被引用文献数

39 46

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Plasma Electrolyte Oxidation (PEO) behavior of AZ91 Mg alloy was investigated in the electrolytes with/without potassium fluoride. Growth rate of coating thickness in the electrolyte containing potassium fluoride (Bath B) was much higher than that in the electrolyte without potassium fluoride (Bath A). The oxide layer formed on AZ91 Mg alloy in electrolyte with potassium fluoride and sodium silicate consisted of MgO, MgF2 and Mg2SiO4. Corrosion current density of oxide layer coated from the electrolyte with potassium fluoride was much lower than that of oxide layer coated from the electrolyte without potassium fluoride. From the result of EIS analysis, it was known that inner barrier layer in the oxide layer coated from the electrolyte with potassium fluoride had a good influence of the corrosion resistance of Mg alloy. The corrosion resistance curves of Bath B were similar to the thickness curves, indicating that the thickness of the oxide layer played an important role in corrosion resistance of AZ91 Mg alloy. The oxide layer in the Bath B containing potassium fluoride was found to be a compact barrier-type passive film in presence of fluoride ions. The existence of the dense MgO and MgF2 in the barrier layer had a favorable effect on the corrosion resistance of the AZ91 Mg alloy formed from Bath B by PEO process.

著者

Ryota Kasugai Yoshifumi Kadowaki Yasunori Yokoyama Naoyuki Katayama Yoshihiko Okamoto Koshi Takenaka

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.64, no.3, pp.638-642, 2023-03-01 (Released:2023-02-25)

参考文献数

30

被引用文献数

5

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For Mg-doped Zn2P2O7, this systematic investigation of co-doping onto Zn sites has elucidated specific effects on negative thermal expansion (NTE). The low-cost and low-environmental-impact NTE material Zn2−xMgxP2O7 shows large NTE in a temperature range including room temperature for x = 0.4. Although Mg doping broadens the operating-temperature window, it remains several dozen degrees wide. Moreover, the total volume change related to NTE becomes less than that of the Zn2P2O7 parent material. Findings obtained from this study demonstrate that co-doping of Mg and of another element onto the Zn site is effective for achieving simultaneous expansion of the operating-temperature window and maintenance of the volume change related to NTE. One illustrative case is that Zn1.64Mg0.30Al0.06P2O7 has a large negative coefficient of linear thermal expansion of about −65 ppm/K at temperatures of 300–375 K. In fact, at temperatures high above room temperature, Zn1.64Mg0.30Al0.06P2O7 powder shows better thermal expansion compensation capability than the composition without Al. The Al-doped phosphates are expected to have broad practical application because of their performance, cost, and environmental load characteristics.

著者

Naoto Todoroki Toshimasa Wadayama

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

pp.MT-MH2022002, (Released:2023-01-20)

被引用文献数

2

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Alkaline water electrolysis (AWE) is a hydrogen manufacturing process that generates “green hydrogen” using electricity derived from renewable energies. Stainless steel (SS), specifically austenitic SS, has recently attracted attention as an anode material for the oxygen evolution reaction (OER) of the AWE. SS anode surfaces are generally activated by generating surface catalyst layers (SCL) for the OER through specific chemical pre-treatment, although the precise chemical compositions and microstructures of the SCL remain under debate. Furthermore, because fluctuations in the electrode potential derived from renewable energies cause remarkable elution of the constituent elements into the electrolyte, corrosion behaviors of the SS anodes should be clarified. This review introduces the recent progress of the SS anodes, particularly in the context of surface treatments to generate surface catalyst layers with high OER performances under simulated AWE conditions. In general, recent reports have clearly shown that surface-treated SS anodes are superior to the commonly employed Ni-based anodes for AWE applications.

著者

Ikuya Yamada Yuta Kato Hiroshi Nakajima Hidekazu Ikeno Shigeo Mori Shogo Kawaguchi

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

pp.MT-MG2022005, (Released:2023-01-10)

参考文献数

37

被引用文献数

1

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A novel oxide YCu3Rh4O12 has been obtained using high-pressure and high-temperature conditions of 12 GPa and 1573 K. Electron diffraction and synchrotron X-ray powder diffraction data demonstrates that YCu3Rh4O12 crystallizes in a cubic AA′3B4O12-type quadruple perovskite structure. The valence state is estimated to be Y3+Cu3+3Rh3+4O12 by X-ray absorption spectroscopy. The electric resistivity and magnetization data prove that YCu3Rh4O12 is a diamagnetic insulator, which is expected from the electron configurations of Cu3+ (3d8, low spin, S = 0) and Rh3+ (4d6, low spin, S = 0) ions. The first-principle calculation displays the insulating band structure for YCu3Rh4O12. The valence state transition from Ca2+Cu2.8+3Rh3.4+4O12 to Y3+Cu3+3Rh3+4O12 indicates that the doped electrons by the substitution of Y3+ for Ca2+ are not simply injected to Cu and/or Rh ions, realizing unusual charge redistributions consisting of the simultaneous Cu oxidation (Cu2.8+ → Cu3+) and Rh reduction (Rh3.4+ → Rh3+).

著者

Arijit Roy Pil-Ryung Cha

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.63, no.12, pp.1662-1669, 2022-12-01 (Released:2022-11-25)

参考文献数

33

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Formation of oxygen vacancy-rich conducting filament in the metal-oxide insulating layer due to applied electric field is studied using phase field modelling. We consider that the formation of the Frenkel defects plays a dominant role in the process of filament formation. The choice of any other type of defects have been neglected due to the consideration of charge neutrality. We find that during the initial stages of filament formation, intrinsic defect concentration plays a crucial role. However, during the late stages, when the filament formation approaches completion, because of the increased electric field, the generation of new Frenkel defects dominates the growth mechanism. Our observation confirms that the intrinsic defects are not sufficient for the completion of conducting filament in the insulating memresistive layer. Our numerical analysis helps us to better understand the formation mechanism of conducting filament and to determine the key material parameters that influence the operation of oxide based non-volatile random access memory (RAM) i.e. resistive RAM (ReRAM).

著者

Michihiro Ohta Shinji Hirai Hisanaga Kato Vladimir V. Sokolov Vladimir V. Bakovets

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.50, no.7, pp.1885-1889, 2009-07-01 (Released:2009-06-25)

参考文献数

30

被引用文献数

34 40

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The thermal decomposition of ammonium thiocyanate (NH4SCN) was studied by thermogravimetry, differential thermal analysis, and mass spectrometry. It occurred in the temperature range from 400 to 530 K. The decomposition products contained NH3, CS2, H2S, and HNCS gases. Rare-earth oxides were reacted with these gases at 1273 K for 8 h in order to prepare rare-earth sulfides. The single tetragonal β-La2S3 phase was formed after the sulfurization of La2O3. In contrast, the single orthorhombic α-Gd2S3 phase was formed after the sulfurization of Gd2O3. These powders were consolidated by pressure-assisted sintering to fabricate the thermoelectric elements.

著者

Yuji Okuyama Takuya Ymaguchi Naoki Matsunaga Go Sakai

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.59, no.1, pp.14-18, 2018-01-01 (Released:2017-12-25)

参考文献数

12

被引用文献数

1 6

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In order to clarify the effect of the dopant concentration and phase transition on the proton conduction and proton concentration, the electrical conductivity and proton concentration were determined for La1−xBaxYb0.5In0.5O3−δ (x = 0.1. 0.3. 0.5, 0.7). The phase transition from the orthorhombic system to the cubic system was over x = 0.3. The proton/deuteron isotope effect on the conductivity was observed for all samples at 673 K. The proton concentration was independent of the barium content above 673 K. The proton concentration increased with the barium content below 673 K, but the concentration ratio of the proton to dopant decreased following an increase in the barium concentration. It was determined that the dopant concentration and phase transition do not have an influence on the conduction and incorporation of protons into the La1−xBaxYb0.5In0.5O3−δ.

著者

Masaki Moriuchi Yoshiharu Kariya Mao Kondo Yoshihiko Kanda

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.63, no.6, pp.805-812, 2022-06-01 (Released:2022-05-25)

参考文献数

29

被引用文献数

6

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The creep deformation mechanism of Sn–Ag–Cu alloy doped with Bi and Sb (SACBiSb) alloys is theoretically and experimentally analyzed in order to clarify the effect of solid solution additives in Sn–Ag–Cu alloys. The theoretical prediction results and test results are found to mostly agree with each other. The breakaway stress which is the stress at the transition from Class II to Class I in particular is finely reproduced in the theoretical prediction, with a stress of 25 MPa found both by the prediction and test results. In the stress range where the stress is higher than the breakaway stress, the creep strength of SACBiSb is higher than that of Sn–Ag–Cu, while it was predicted that the creep strength of Sn–Ag–Cu would be superior to that of SACBiSb in the range of stress lower than the breakaway stress. The thermal fatigue life of SACBiSb was predicted to be longer than that of Sn–Ag–Cu in the temperature profile mainly used above the breakaway stress. However, in the temperature profile mainly used in the low-stress range, a reversal of the creep strength between SACBiSb and Sn–Ag–Cu was predicted to occur and the loss of the superiority of SACBiSb in the thermal fatigue life was also predicted.

著者

Hidechika Karasawa Hiroki Shibasaki Go Itohiya Shinichiro Yamashita Kazuyoshi Arai

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

pp.MT-Z2022002, (Released:2022-05-20)

参考文献数

15

---

Sand erosion is a phenomenon in which the collision of solid particles erodes a material surface. The rate of sand erosion is higher in carbon fiber reinforced plastics (CFRP) than in metallic materials. Therefore, CFRP requires a light and protective coating material. Herein, to improve the erosion resistance of CFRP, five polyurethane coated CFRPs with different glass transition temperatures were investigated at elevated temperatures, and a prediction formula of the erosion rate at the elevated temperatures was established. Furthermore, computational fluid dynamics was used to predict the surface temperature and erosion rate of fan exit guide vane (FEGV) when polyurethane coating was applied, and the coating thickness for FEGV in the erosion environment was estimated based on these predictions. This Paper was Originally Published in Japanese in J. Soc. Mater. Sci., Jpn. 70 (2021) 896–903. The caption of Fig. 10 is slightly modified.

著者

Akihiko Miyauchi Toru H. Okabe

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.51, no.6, pp.1102-1108, 2010-06-01 (Released:2010-05-25)

参考文献数

27

被引用文献数

19 20

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A fundamental study was conducted on a new process for producing vanadium (V) metal by the preform reduction process (PRP) based on metallothermic reduction of vanadium pentoxide (V2O5). Feed preforms with good mechanical strength even at elevated temperatures were prepared by adding either CaO or MgO to V2O5 feed powder because V2O5 has a low melting point of 963 K; thus complex oxides (CaxVyOz, MgxVyOz) with high melting point at more than 1273 K were obtained. Reduction experiments were conducted by using either Ca or Mg vapor at 1273 K for 6 h. V metal with a purity of more than 99% was successfully obtained when using Mg as a reductant. The feasibility of producing V metal by the PRP will be discussed on the basis of fundamental experiments.

著者

John J. Jonas Chiradeep Ghosh Suresh Shrivastava

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.52, no.9, pp.1748-1751, 2011-09-01 (Released:2011-08-25)

参考文献数

8

被引用文献数

12 13

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Onaka has recently (2010) discussed the application of the Hencky equivalent strain to the description of large strains in simple shear in the Journal of the Japan Institute of Metals. We find this analysis in error and introduce below what we consider as the appropriate approach to this problem. We also explain why the Hencky strain is unsuitable for converting the experimental results obtained in large strain shear and torsion to loading along other strain paths.

著者

Masato Ueda Yuumi Sasaki Masahiko Ikeda Michiharu Ogawa Wataru Fujitani Takayoshi Nakano

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.50, no.9, pp.2147-2153, 2009-09-01 (Released:2009-08-25)

参考文献数

31

被引用文献数

8 6

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The synthesis of bioinert oxide films on pure Ti surfaces by chemical-hydrothermal treatment was investigated. Some pure Ti substrates were chemically treated with H2O2/HNO3 to form a TiO2 gel layer prior to hydrothermal treatment. Two types of solutions in the hydrothermal treatment were prepared: Zr(OH)4 gel dispersed NH3/CH3CH(OH)COOH solution and Zr dissolved NH3/CH3CH(OH)COOH solution. A uniform layer of very fine crystals were formed on the surfaces of the specimens subjected to the hydrothermal treatment. Sharp peaks attributed to TiO2 and/or ZrO2 appeared after the hydrothermal treatment. ZrO2-TiO2 composite films were successfully produced on the Ti surface by hydrothermal treatment with the Zr(OH)4 gel dispersed NH3/CH3CH(OH)COOH solution at 453 K for 12 h, following the chemical treatment. The proliferation of osteoblast-like MC3T3-E1 cells was also investigated. The cells were observed to have spread their pseudopodiums. The cell density increased monotonically with incubation period for all specimens. The proliferation of cells was strongly influenced by the surface roughness; the cell densities increased with decreasing roughness in the range of Ra=20–80 nm. Furthermore, the surface products with TiO2 showed a relatively low rate of proliferation. The strong attachment of cells to the surface may hinder cell migration.

著者

V. L. Cruz-Hernández M. A. García-Rentería R. García-Hernández V. H. López-Morelos

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.58, no.2, pp.225-230, 2017-02-01 (Released:2017-01-25)

参考文献数

20

被引用文献数

2

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This study evaluated the suitability of the depassivator in revealing low degrees of sensitization (DOS) in samples of wrought AISI 347H austenitic stainless steel in the as-received condition and solution heat treated (SHT) at 1050℃. Assessment of the electrolyte composition was performed by the double loop electrochemical potentiokinetic reactivation (DL-EPR) test at room temperature. The electrolyte 1.0M H2SO4 + 0.50M HCl was found to be adequate for detecting low DOS. Microstructural characterization of the as-received material revealed the presence of Cr-rich carbides. These carbides were responsible of the susceptibility to IGC.

著者

Koji Kimura Kouichi Hayashi Koji Hagihara Hitoshi Izuno Naohisa Happo Shinya Hosokawa Motohiro Suzuki Hiroo Tajiri

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.58, no.4, pp.539-542, 2017-04-01 (Released:2017-03-25)

参考文献数

24

被引用文献数

10 16

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We performed X-ray fluorescence holography measurements on a single crystal Mg85Zn6Y9 alloy, having a synchronized 18R long period stacking ordered structure, and successfully obtained Zn Kα holograms. The reconstruction shows “U”-shaped atomic images in remarkable contrast to the prediction of an existing model with Zn6Y8 L12 clusters. To explain this feature we calculated holograms using a model with positional fluctuations, and fit the reconstruction to the experimental results. It was found that large rotational fluctuations of the clusters can explain the “U”-shaped images.

著者

Yuji Ichikawa Kentaro Shinoda

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.62, no.6, pp.691-702, 2021-06-01 (Released:2021-05-25)

参考文献数

153

被引用文献数

16

---

Cold spray (CS) technology is a “solid-phase particle deposition process without melting”; however, it has been established as an additive manufacturing technology that can be applied beyond the framework of one field of thermal spraying. The scope of application of this technology has expanded to include ceramics and polymers. There are other solid particle deposition processes besides CS, such as aerosol deposition (AD), which differ in the material type, size, impact speed, and temperature of the target particles. We can expect that there is a common intrinsic mechanism through which solid-phase particles are joined and deposited in the solid phase. This review summarizes previous studies on the mechanism of cold-spray deposition and bonding, which can be understood as a mechanochemical phenomenon in part, and it is driven by the deformation of the particles and the resulting change in the chemical state of the particle surface, and stabilization by contact in a short time. When we understand these issues correctly, the optimal mechanical conditions (material size and collision conditions) for joining particles of various materials will be systematically understood, and it will be possible to perform different fabrication processes from thin films to additive manufacturing without melting various materials. This Paper was Originally Published in Japanese in J. Japan Thermal Spray Soc. 57 (2020) 58–71.

著者

Kohmei Halada Masanori Shimada Kiyoshi Ijima

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.49, no.3, pp.402-410, 2008-03-01 (Released:2008-02-25)

参考文献数

9

被引用文献数

38 57

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Forecasts up to 2050 are made of consumption of the following metals: Fe, Al, Cu, Mn, Zn, Cr, Pb, Ni, Si, Sn, rare earths, Mo, Li, Sb, W, Ag, Co, In, Au, Ga, Pt and Pd. The forecasts are based on the linear decoupling model of the relation between per capita metal consumption and per capita GDP. The models of each metal are applied to the economic development model of BRICs and G6 countries. According to these forecasts, the overall consumption of metals in 2050 will be five times greater than the current levels, and demand for metals, such as Au, Ag, Cu, Ni, Sn, Zn, Pb and Sb, is expected to be several times greater than the amount of their respective reserves. Demand for Fe and Pt, which is considered to be optimistic about the resource exhaustion, will also exceed the current reserves. Urgent measures are needed to find alternatives from common resources and to shift into sound materials circulation society.

著者

Kohta Koenuma Akinori Yamanaka Ikumu Watanabe Toshihiko Kuwabara

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.61, no.12, pp.2276-2283, 2020-12-01 (Released:2020-11-25)

参考文献数

31

被引用文献数

13

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The deformation of an aluminum alloy sheet is affected by its underlying crystallographic texture and has been extensively studied using the crystal plasticity finite element method (CPFEM). Numerical material test based on the CPFEM enables the quantitative estimation of the stress-strain curve and Lankford value (r-value), which depend upon the texture of aluminum alloy sheets. However, the application of CPFEM-based numerical material test to the optimization of aluminum alloy texture is computationally expensive. In this paper, we propose a method for rapidly estimating the stress-strain curves and r-values of aluminum alloy sheets using deep learning with a neural network. We train the neural network with the synthetic crystallographic texture and stress-strain curves calculated through the numerical material tests. To capture the features of synthetic texture from a {111} pole-figure image, the neural network incorporates a convolution neural network. Using the trained neural network, we estimate the uniaxial stress-strain curve and in-plane anisotropy of the r-value for various textures that contain Cube and S components. The results indicate that the application of a neural network trained with the results of numerical material test is a promising method for rapidly estimating the deformation of aluminum alloy sheets. This Paper was Originally Published in Japanese in J. JSTP 61 (2020) 48–55.

著者

Shinsuke Kunitsugu Norihide Nishida Takao Tomiya Masahiro Nagae Makoto Nakanishi Tatsuo Fujii Jun Takada

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.46, no.2, pp.215-218, 2005 (Released:2005-09-06)

参考文献数

12

被引用文献数

3 4

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A homogeneous layer of molybdenum alumininosilicide Mo(Si,Al)2 with C(40) structure was made on the sample surface of molybdenum by dip-coating technique using Al-25 mass%Si liquid at 1123 K. Adherent Al-Si was removed by soaking the dipped samples in the NaOH saturated hydraulic solution. The Mo samples coated with the Mo(Si,Al)2 layer were found to have excellent oxidation resistance in air even at 1473 K due to formation of a dense alumina film on the sample surface during oxidation. The formation of Mo5(Si,Al)3 layer was also observed at the interface between the Mo substrate and the Mo(Si,Al)2 layer.

著者

Mahiro Sawada Daiki Ichikawa Matej Borovinšek Matej Vesenjak Shinsuke Suzuki

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.61, no.9, pp.1782-1789, 2020-09-01 (Released:2020-08-25)

参考文献数

22

被引用文献数

5

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A drop in compressive stress in the plateau region is one of the issues in compressive behavior of porous metals since it has a negative effect on energy absorption efficiency. The compressive deformation behavior of porous aluminum with irregular unidirectional pores was investigated to clarify the mechanism of the drop. Compression tests of cubic specimens with various irregular circular pore geometries were performed. Digital image correlation and finite element analysis were also conducted to obtain strain and stress distribution of the surface perpendicular to the pores. Fracture of the cell walls was observed when the drop occurred. The results show that pore geometry has an effect on the number and the amount of drop in compressive stress. Measurement of an area of two nearest pores of the fractured cell walls suggests that the amount of drop in compressive stress increases as the area increases. Also, a calculation of normalized critical stress for the plastic collapse of the cell walls shows that the fractured cell walls tend to be geometrically weak. Furthermore, stress concentration occurred around the fractured cell walls, which resulted in a secondary fracture of the cell walls.

著者

Son Thanh Nguyen Tadachika Nakayama Masatoshi Takeda Nguyen Ngoc Hieu Tsuyoshi Takahashi

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.61, no.8, pp.1510-1516, 2020-07-01 (Released:2020-07-25)

参考文献数

32

被引用文献数

4

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Thermal barrier coatings (TBCs) are necessary to protect nickel-based alloy blades of gas turbine against oxidation and thermal fatigue in high-temperature operating conditions. Ceramic materials, which are very good natural thermal insulator, attract the most interests from engineers and scientists. However, the brittleness of ceramics is a major obstacle for utilizing them as the TBCs, which are also required very good damage tolerance against physical impacts. The cracks appear on the blade surfaces during its operation can lead to the severe failure. In this research, a composite of Y2Ti2O7 and Ni was developed as a self-crack healing material to overcome this problem. The crack-healing behavior is investigated by using Vickers indenter to create cracks on the composite surface intentionally, followed by annealing in an oxidizing environment. It is found that the main crack-healing mechanism is the filling of NiO, which was formed from the oxidation of the Ni fillers, into the cracks. Complete heal of cracks is achieved with 10 vol% Ni filler, which is confirmed by X-ray diffraction and scanning electron microscopy. Thermal conductivity and Weibull distribution for the strength of the composite were also investigated to find the appropriate volume fraction of Ni nanoparticles in this self-healing material.