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論文

Stress evaluation method by neutron diffraction for HCP-structured magnesium alloy

Harjo, S.; Gong, W.; 川崎 卓郎

Quantum Beam Science (Internet), 7(4), p.32_1 - 32_13, 2023/12

https://doi.org/10.3390/qubs7040032

Tensile deformation in situ neutron diffraction of an extruded AZ31 alloy was performed to validate conventional procedures and to develop new procedures for stress evaluation from lattice strains by diffraction measurements of HCP-structured magnesium alloys. Increases in the lattice strains with respect to the applied true stress after yielding largely vary among [${it hk.l}$] grains. The newly proposed procedure of stress evaluation from the lattice strains shows very high accuracy and reliability by weighting the volume fraction of [${it hk.l}$] grains and evaluating them in many [${it hk.l}$] orientations in addition to multiplication by the diffraction elastic constant. When multiple ${it hk.l}$ peaks cannot be obtained simultaneously, we recommend to use the 12.1 peak for stress evaluation.

論文

Effect of extrusion ratio in hot-extrusion on kink deformation during compressive deformation in an $$alpha$$Mg/LPSO dual-phase magnesium alloy monitored by ${it in situ}$ neutron diffraction

Harjo, S.; Gong, W.; 相澤 一也; 川崎 卓郎; 山崎 倫昭*; 眞山 剛*; 河村 能人*

Materials Transactions, 64(4), p.766 - 773, 2023/02

https://doi.org/10.2320/matertrans.MT-MD2022004
 被引用回数：4 パーセンタイル：90.35(Materials Science, Multidisciplinary)

To elucidate the effect of extrusion ratio in hot-extrusion on the deformation behavior during compression of Mg$$_{97}$$Zn$$_{1}$$Y$$_{2}$$ alloy containing about 25-vol% long-period stacking ordered phase (LPSO) in the HCP structured $$alpha$$ matrix ($$alpha$$Mg), ${it in situ}$ neutron diffraction measurements were performed under compressive loading using four types of samples: as-cast and after hot extrusion at 623 K with extrusion ratios of 5.0, 7.5 and 12.5. The macroscopic yielding was observed to appear by the occurrence of basal slip of $$alpha$$Mg in the as-cast sample and at the onset of twinning in the hot extruded samples. The applied stress to initiate slip, twinning, and kinking increased by hot extrusion and then decreased with increasing extrusion ratio. LPSO shared higher stress than $$alpha$$Mg and the ratio to the strength increased as the extrusion ratio increased.

論文

Effect of magnesium silicate hydrate (M-S-H) formation on the local atomic arrangements and mechanical properties of calcium silicate hydrate (C-S-H); In situ X-ray scattering study

Kim, G.*; Im, S.*; Jee, H.*; Suh, H.*; Cho, S.*; 兼松 学*; 諸岡 聡; 小山 拓*; 西尾 悠平*; 町田 晃彦*; et al.

Cement and Concrete Research, 159, p.106869_1 - 106869_17, 2022/09

https://doi.org/10.1016/j.cemconres.2022.106869
 被引用回数：18 パーセンタイル：87.96(Construction & Building Technology)

This study explored the effect of M-S-H formation on the local atomic arrangements and mechanical properties of C-S-H. The elastic moduli of the samples were calculated using shifted atomic distances (r) and d-spacings (d) acquired by applying an external load on the pastes during X-ray scattering experiments. The experimental results indicated that the crystal structure of C-S-H remained intact with MgCl$$_{2}$$ addition. At the highest Mg/Si ratio (Ca/Si = 0.6, Mg/Si = 0.2), change in the dominant phase occurred from C-S-H to M-S-H because the low pH environment hindered the formation of C-S-H and facilitated the formation of M-S-H. The elastic modulus decreased with increasing Mg/Si ratio up to 0.1 owing to both C-S-H destabilization and low M-S-H content in the samples. Conversely, the elastic modulus increased in the paste synthesized with the highest Mg/Si ratio because considerable M-S-H had formed, which exhibited a higher elastic modulus than C-S-H.

論文

A Novel method to improve methane generation from waste sludge using iron nanoparticles coated with magnesium hydroxide

Eljamal, R.*; Maamoun, I.; Bensaida, K.*; Yilmaz, G.*; 杉原 裕司*; Eljamal, O.*

Renewable and Sustainable Energy Reviews, 158, p.112192_1 - 112192_13, 2022/04

https://doi.org/10.1016/j.rser.2022.112192
 被引用回数：25 パーセンタイル：95.67(Green & Sustainable Science & Technology)

In response to the low efficiency of the anaerobic digestion (AD) process in generating methane gas, we apply for the first time the use of coated/ Fe$$^{0}$$ with Mg(OH)$$_{2}$$ to enhance the production rate of methane gas from the degradation of waste sludge. A series of batch tests investigated several operations factors followed by a semi-continuous operation system examined the long-term production of methane gas in the presence of the coated/ Fe$$^{0}$$ were performed. The coating ratio of Mg(OH)$$_{2}$$/Fe$$^{0}$$ and the dosage of coated/Fe$$^{0}$$ were optimized to acquire the highest production rate of methane as 0.5% and 25 mg/gVS, respectively. Under these optimum conditions, the methane production increased by 46.6% in the batch tests and 120% in the semi-continuous operation system compared to the control reactor. The results revealed that both Fe$$^{0}$$ and Mg(OH)$$_{2}$$ did not significantly improve the production of methane when each one was used alone at different dosages, and the improved methane production originated from the synergetic effect of combining these two materials. The crucial role of Mg(OH)$$_{2}$$ coating layer was associated with the controlled reactivity release of Fe$$^{0}$$, which was indicated by the slow release of ferrous and ferric ions in the bioreactors. Furthermore, the addition of coated/Fe$$^{0}$$ stimulated bacterial growth, increased methane content, and maintained the pH within the optimum range in the bioreactors. The dosing time of coated/Fe$$^{0}$$ was investigated during the four stages of AD process, and the best dosing time was found in the methanogenic stage (on Day 4). Overall, based on the experimental and predicted methane production, the coated/Fe$$^{0}$$ has a great potential for the practical applications of AD.

論文

中性子イメージングによる純パラジウムおよびアルミニウム合金中の水素濃度解析

清水 一行*; 林田 洋寿*; 戸田 裕之*; 甲斐 哲也; 松本 吉弘*; 松本 佳久*

日本金属学会誌, 83(11), p.434 - 440, 2019/11

https://doi.org/10.2320/jinstmet.J2019016
 被引用回数：1 パーセンタイル：6.23(Metallurgy & Metallurgical Engineering)

Neutron imaging experiment was performed to visualize the distribution of solute hydrogen in an Al-10.1%Zn-1.2%Mg alloy and a pure palladium after hydrogen charging. Changes in the contrast of neutron transmission images caused by hydrogen were clearly observed in a palladium. In the wavelength range of 2-3 AA and 5-13.5 AA, the mean neutron transmission around the center of a hydrogen-charged palladium were 0.692 and 0.511, respectively. The hydrogen content in a palladium was estimated to be 10.8 mol% from the measured neutron transmission. This study has demonstrated that hydrogen content can be analyzed by considering the wavelength dependence of neutron intensity. On the other hand, hydrogen could not be observed from the neutron transmission image in Al-Zn-Mg alloys. This was due to the low hydrogen content, which was mass ppm level even after hydrogen charging, and statistical precision was not sufficient to discuss the amount of hydrogen of the mass ppm order.

論文

Oxidation and reduction behaviors of a prototypic MgO-PuO$$_{2-x}$$ inert matrix fuel

三輪 周平; 逢坂 正彦

Journal of Nuclear Materials, 487, p.1 - 4, 2017/04

https://doi.org/10.1016/j.jnucmat.2017.01.048
 被引用回数：4 パーセンタイル：37.06(Materials Science, Multidisciplinary)

MgOを母材としたPuO$$_{2-x}$$含有イナートマトリックス原型燃料の酸化還元挙動を熱分析により調べ、MgO-PuO$$_{2-x}$$試料の酸化還元速度を実験的に決定した。MgO-PuO$$_{2-x}$$試料の酸化還元速度はPuO$$_{2-x}$$試料に比べ低くなった。また、高い酸素分圧条件において、MgO-PuO$$_{2-x}$$試料の定比からのO/Pu比の変化はPuO$$_{2-x}$$試料に比べ小さくなることがわかった。これより、MgOを母材にすることによりイナートマトリックス燃料からの酸素供給及び放出が抑制されることがわかり、被覆管酸化等の観点で懸念となる高い酸素ポテンシャルを有するマイナーアクチニド酸化物の母材としてMgOが有効であることがわかった。

論文

Effect of solute atoms on dislocation motion in Mg; An electronic structure perspective

都留 智仁; Chrzan, D. C.*

Scientific Reports (Internet), 5, p.8793_1 - 8793_8, 2015/03

https://doi.org/10.1038/srep08793
 被引用回数：68 パーセンタイル：86.71(Multidisciplinary Sciences)

性能を犠牲にすることなく機械製品の効率を向上する技術において、軽量で高強度の構造材合金の開発が重要となる。マグネシウム合金は構造材料への応用に大きく期待されているが、強度において重要な欠点がある。転位の運動は合金中の電子の結合によって決定され、この結合は量子力学に基づくアプローチによってモデル化される。ここで、我々はMgの柱面上でのらせん転位の電子構造の計算を行った。そして、いくつかの添加元素がらせん転位の運動に必要な転位の収縮を安定化させることによりMgの延性を向上することを示した。

論文

Radiation-induced swelling and softening in magnesium aluminate spinel irradiated with high-flux Cu$$^{-}$$ ions

Lee, C. G.; 大村 孝仁*; 武田 良彦*; 松岡 三郎*; 岸本 直樹*

Journal of Nuclear Materials, 326(2-3), p.211 - 216, 2004/03

https://doi.org/10.1016/j.jnucmat.2004.01.010
 被引用回数：4 パーセンタイル：29.26(Materials Science, Multidisciplinary)

耐照射損傷材として注目されているMg-Alスピネルにおいて、大電流イオン照射による体積及び硬度の変化を調べた。イオン照射は、60keV銅負イオンを線量3$$times$$10$$^{16}$$ions/cm$$^{2}$$に固定し、最大線量率100$$mu$$A/cm$$^{2}$$まで行った。ナノインデンテーションで測定した硬度は全体に照射に伴い大きな減少を示した。硬度のイオン線量率依存性は体積変化の線量率依存性と強い相関を示し、硬度が減少すると体積が増加することがわかった。照射後のRBS測定結果、非晶質化は起きていないことから、本研究での照射誘起軟化の原因は一般に知られている照射誘起非晶質化ではないことを意味する。一方、光吸収の測定結果から、スピネル結晶の陰イオン副格子での照射誘起点欠陥及びその集合体が、照射誘起スエリングに大きく関与していることがわかった。

論文

Post-irradiation examination of high burnup Mg doped UO$$_{2}$$ in comparison with undoped UO$$_{2}$$, Mg-Nb doped UO$$_{2}$$ and Ti doped UO$$_{2}$$

藤野 威男*; 白鳥 徹雄; 佐藤 修彰*; 福田 幸朔; 山田 耕太*; 鈴木 康文; 芹澤 弘幸

Journal of Nuclear Materials, 297(2), p.176 - 205, 2001/08

https://doi.org/10.1016/S0022-3115(01)00609-2
 被引用回数：20 パーセンタイル：79.16(Materials Science, Multidisciplinary)

高燃焼度用LWR酸化物燃料の開発を目的として、Mgを添加したUO$$_{2}$$燃料の照射挙動を調べた。2.5~15mol% MgO添加UO$$_{2}$$と比較用無添加UO$$_{2}$$の焼結体小ディスク試料をJRR-3Mで最高94GWd/t($$<$$1000$$^{circ}C$$) まで照射した。照射後試験で、試料の外観と健全性、組織観察、スエリング率測定、FP放出挙動、熱伝導率測定等の高燃焼度における挙動のデータを得た。65GWd/t($$<$$700$$^{circ}C$$) 以上では試料全体にリム組織の生成がみられた。Mg添加UO$$_{2}$$でMgの固溶度が小さく、おもにMgOとしてUO$$_{2}$$マトリックス中に分散している燃料の高燃焼度照射挙動は、全般的に無添加UO$$_{2}$$と顕著な相違はみられない結果となった。(U,Mg)O$$_{2}$$の固溶体の照射挙動が今後の課題である。

論文

Oxygen potential and defect structure of the solid solution, Mg-Gd-UO$$_{2}$$

藤野 威男*; 佐藤 修彰*; 山田 耕太*; 岡崎 学*; 福田 幸朔; 芹澤 弘幸; 白鳥 徹雄*

Journal of Nuclear Materials, 289(3), p.270 - 280, 2001/03

https://doi.org/10.1016/S0022-3115(01)00427-5
 被引用回数：2 パーセンタイル：19.66(Materials Science, Multidisciplinary)

(Mg, Gd, U)O$$_{2+x}$$固溶体の酸素ポテンシャルを1000~1250$$^{circ}C$$の温度領域において、O/M比の関数として求めた。酸素ポテンシャルが急変するO/Mの値は、固溶体中のMg量の増加とともに低下した。一方、平衡する酸素分圧が低下すると、固溶体中のMg原子の一部が、格子間位置にシフトすることが、密度測定から明らかになった。Mgの固溶限は、平衡する酸素分圧に対して複雑な挙動を示した。

論文

Interstitial fluorine centers in the neutron-irradiated MgF$$_{2}$$

数又 幸生; 植田 義文*; 西 正任*

Solid State Communications, 19(3), p.181 - 183, 1976/03

https://doi.org/10.1016/0038-1098(76)90845-0
 被引用回数：4

格子間弗素が、中性子照射したMgF$$_{2}$$単結晶中で観測された。この格子間弗素は、asymmetric F$$_{2}$$$$^{-}$$分子イオンである。ESRスペクトルの角度依存性から、spin Hamiltonianのparametersが決定された。この格子間弗素分子イオンは、550Kで熱的に不安定となる。

論文

Neutron Irradiation Hardening in Aluminum-Magnesium Alloys

白石 健介

Trans.JIM, 11(6), p.440 - 441, 1970/00

抄録なし

口頭

Use of NaH$$_{2}$$PO$$_{4}$$ and (NaPO$$_{3}$$)$$_{n}$$ as a phosphate source for development of magnesium phosphate cements

Garc$'i$a-Lodeiro, I.*; Kai Wuen, O.*; 入澤 啓太; 中澤 修; 木下 肇*

no journal, , 

Magnesium phosphate cements (MPCs) is an important engineering material that have been extensively used as fast setting repair cements in civil engineering. MPCs are formed through an exothermic acid-base reaction between MgO and a soluble phosphate source (commonly NH$$_{4}$$H$$_{2}$$PO$$_{4}$$ or KH$$_{2}$$PO$$_{4}$$) forming a crystalline magnesium phosphate salt (struvite or K-struvite respectively). The present study investigates the effect of using different sodium phosphate sources (NaH$$_{2}$$PO$$_{4}$$ and/or (NaPO$$_{3}$$)$$_{n}$$) and reduction of water content can be highly beneficial for encapsulation of radioactive wastes, since it would minimise the risk of hydrogen gas generation from the radiolysis of water by the radioactive waste components. Our preliminary investigation revealed that the use of these phosphates all resulted in the generation of amorphous products, and curing at 80$$^{circ}$$C also led to a scueessful reduction of the water contents by $$>$$50% in all systems investigated. However, the type of phosphates used appears to have a significant impact on the stability of the products in water, and the mixed use of NaH$$_{2}$$PO$$_{4}$$ and (NaPO$$_{3}$$)$$_{n}$$ indicated the best outcome.

口頭

Improvement of both elongation and strength of magnesium alloy consisting long period stacking ordered phase by hot-extrusion

Harjo, S.; 相澤 一也; Gong, W.; 山崎 倫昭*; 川崎 卓郎

no journal, , 

The elongation of an LPSO type Mg alloy consisting 25 vol% of LPSO phase was found to increase without sacrificing the tensile strength, when the extrusion ratio or the equivalent strain of the hot-extrusion became higher. This phenomenon is very interesting, considering that the improvements of elongation and of tensile strength due thermo-mechanical processes are usually contradictory properties. In this study, monitoring deformation behavior of the $$alpha$$Mg and LPSO phases in hot-extruded LPSO type Mg alloys consisting 25 vol% of LPSO phase by in situ neutron diffraction was carried out to elucidate the reason of the improvement of both elongation and strength by hot-extrusion with high extrusion ratio.

口頭

Cyclic tension-compression in situ neutron diffraction of extruded LPSO typed magnesium alloys

Harjo, S.; Gong, W.; 川崎 卓郎; 相澤 一也; 山崎 倫昭*

no journal, , 

An in situ neutron diffraction experiment during cyclic tension-compression with an applied strain of $$pm$$0.01 and was conducted at room temperature using a Mg$$_{97}$$Zn$$_{1}$$Y$$_{2}$$ alloy, after hot-extrusion at 723 K with the extrusion ratio of 10, to understand the deformation behavior of both $$alpha$$Mg and LPSO phases and to elucidate kinking in the LPSO phase including its effect to the strength during the cyclic tension-compression deformation. The evolutions of textures, lattice strains of individual constituent phases measured from neutron diffraction will be plotted with the applied stress, strain and the cyclic number, and details will be presented in this presentation.

口頭

Neutron diffraction analysis method to elucidate deformation mechanisms of metals with multimodal-structures and -deformation modes

Harjo, S.; Gong, W.; 川崎 卓郎; Mao, W.; 山崎 倫昭*

no journal, , 

Many advanced metallic materials composed of not only multiphases but also multi-morphological structures within one of the constituent phases, so-called multimodal structure metallic material. In this presentation, we will introduce and discuss our methods to understand the deformation behavior in metallic materials with multimodal structure, using a case of strengthening of $$alpha$$Mg and long-period stacking ordered phases in a Mg-Zn-Y alloy by hot-extrusion with low extrusion ratio.

口頭

Characterization of internal stresses in Mg-Zn-Y alloy with multimodal microstructure by deformation operando neutron diffraction

Harjo, S.; Gong, W.; 山崎 倫昭*; 川崎 卓郎; 相澤 一也

no journal, , 

An as-cast sample and two hot-extruded samples with different R values of Mg$$_{97}$$Zn$$_{1}$$Y$$_{2}$$ alloy, the $$alpha$$Mg-LPSO alloy containing LPSO of about 25-vol%, were used in tensile deformation operando neutron diffraction experiments. $$alpha$$Mg behaved as the soft phase and LPSO as the hard phase, and hot-extrusion improved the strength of both. At the R value of 5.0, dynamic recrystallization partly occurred in $$alpha$$Mgg creating a bimodal microstructure, consisting of the deformed $$alpha$$Mg microstructure and the recrystallized $$alpha$$Mg microstructure. The yield strength of $$alpha$$Mg was significantly improved due to the optimal effects of dislocation density accumulation and texture development in the deformed $$alpha$$Mg microstructure, and grain refinement in the recrystallized $$alpha$$Mg microstructure.

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