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12 pages, 7808 KiB

Open AccessArticle

Decreasing Electrical Resistivity of Ag Film by Low-Temperature Evaporation and Sintering through Azeotrope Application

by Sang Hoon Jung, Jae Eun Park and Jong-Hyun Lee

Metals 2024, 14(10), 1123; https://doi.org/10.3390/met14101123 - 2 Oct 2024

Viewed by 465

In the temperature-sensitive components, such as perovskite solar cells, large-area electrical connections with high electrical conductivity are also required. To fulfill the requirements, low-temperature evaporation was realized by preparing binder-free pastes with Ag flakes and a solvent mixture, followed by sintering at 140 [...] Read more.

In the temperature-sensitive components, such as perovskite solar cells, large-area electrical connections with high electrical conductivity are also required. To fulfill the requirements, low-temperature evaporation was realized by preparing binder-free pastes with Ag flakes and a solvent mixture, followed by sintering at 140 °C. The mixed solvent was based on viscous α-terpineol with the addition of an appropriate amount of dipropylene glycol methyl ether acetate or diethylene glycol diethyl ether to achieve an azeotrope composition, followed by the addition of a low-molecular-weight hydroxypropyl cellulose to increase the viscosity and thixotropy. During sintering at 140 °C in air for up to 30 min, the paste with 49.5 wt% α-terpineol, 49.5 wt% dipropylene glycol monomethyl ether acetate, and 1 wt% hydroxypropyl cellulose mixture exhibited an excellent electrical conductivity of 7.72 × 10⁻⁶ Ω·cm despite the implementation of low-temperature sintering. The excellent processability of the prepared Ag-based pastes at 140 °C demonstrated their potential for novel application areas. Full article

(This article belongs to the Special Issue Metallic Functional Materials: Development and Applications)

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15 pages, 2833 KiB

Open AccessArticle

Improvement in the Hydrogen Storage Properties of MgH₂ by Adding NaAlH₄

by Young-Jun Kwak, Myoung-Youp Song and Ki-Tae Lee

Metals 2024, 14(2), 227; https://doi.org/10.3390/met14020227 - 13 Feb 2024

Cited by 2 | Viewed by 1385

Abstract

Milled MgH₂, MgH₂-10NaAlH₄, MgH₂-30NaAlH₄, MgH₂-50NaAlH₄, and MgH₂-2Ni-10NaAlH₄ samples were prepared by milling in a planetary ball mill in hydrogen atmosphere (reactive mechanical milling, RMM). Decomposition temperatures [...] Read more.

Milled MgH₂, MgH₂-10NaAlH₄, MgH₂-30NaAlH₄, MgH₂-50NaAlH₄, and MgH₂-2Ni-10NaAlH₄ samples were prepared by milling in a planetary ball mill in hydrogen atmosphere (reactive mechanical milling, RMM). Decomposition temperatures of milled MgH₂, NaAlH₄, MgH₂-10NaAlH₄, and MgH₂-30NaAlH₄ were examined in a Sieverts-type hydrogen absorption and release apparatus, in which the hydrogen pressures were kept nearly constant during hydrogen absorption or release. As the content of NaAlH₄ in the sample increased, the temperature at the highest peak in the ratio of increase in released hydrogen quantity to increase in temperature versus temperature curve decreased. Hydriding in 12 bar hydrogen and dehydriding in 1.0 bar hydrogen at 593 K of MgH₂-30NaAlH₄ are performed by the reversible reactions MgH₂ ⇔ Mg + H₂ and 17MgH₂ + 12Al ⇔ Mg₁₇Al₁₂ + 17H₂. MgH₂-30NaAlH₄ was the best Mg-based composite among Mg-based alloys in which an oxide, a halide, a fluoride, or a complex hydride was added, with a high hydrogen absorption rate for 2.5 min (2.20 wt% H/min) and a large effective hydrogen storage capacity (7.42 wt% H). Full article

(This article belongs to the Special Issue Metallic Functional Materials: Development and Applications)

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14 pages, 15928 KiB

Open AccessArticle

Inverse Magnetocaloric Effect in Heusler Ni_44.4Mn_36.2Sn_14.9Cu_4.5 Alloy at Low Temperatures

by Alexander P. Kamantsev, Yuriy S. Koshkid’ko, Ruslan Yu. Gaifullin, Irek I. Musabirov, Anatoliy V. Koshelev, Alexey V. Mashirov, Vladimir V. Sokolovskiy, Vasiliy D. Buchelnikov, Jacek Ćwik and Vladimir G. Shavrov

Metals 2023, 13(12), 1985; https://doi.org/10.3390/met13121985 - 7 Dec 2023

Cited by 1 | Viewed by 1277

Abstract

Direct measurements of the magnetocaloric effect were performed in a Heusler Ni_44.4Mn_36.2Sn_14.9Cu_4.5 alloy at cryogenic temperatures in magnetic fields up to 10 T. The maximum value of the inverse magnetocaloric effect in a 10 T field [...] Read more.

Direct measurements of the magnetocaloric effect were performed in a Heusler Ni_44.4Mn_36.2Sn_14.9Cu_4.5 alloy at cryogenic temperatures in magnetic fields up to 10 T. The maximum value of the inverse magnetocaloric effect in a 10 T field was ∆T_ad = –2.7 K in the vicinity of the first-order magnetostructural phase transition at T₀ = 117 K. Ab initio and Monte Carlo calculations were performed to discuss the effect of Cu doping into a Ni-Mn-Sn compound on the ground-state structural and magnetic properties. It is shown that with increasing Cu content the martensitic transition temperature decreases and the Curie temperature of austenite slightly increases. In general, the calculated transition temperatures and magnetization values correlated well with the experimental ones. Full article

(This article belongs to the Special Issue Metallic Functional Materials: Development and Applications)

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12 pages, 2580 KiB

Open AccessArticle

The Cyclic Stability of the Superelasticity in Quenched and Aged Ni₄₄Fe₁₉Ga₂₇Co₁₀ Single Crystals

by Ekaterina Timofeeva, Elena Panchenko, Maria Zherdeva, Aida Tokhmetova and Yuriy I. Chumlyakov

Metals 2023, 13(9), 1538; https://doi.org/10.3390/met13091538 - 30 Aug 2023

Cited by 3 | Viewed by 995

Abstract

The effect of aging (at 773 K for 1 h) on the cyclic stability of superelasticity was studied in preliminarily quenched (after annealing at 1448 K for 1 h) Ni₄₄Fe₁₉Ga₂₇Co₁₀ [001]-oriented single crystals. It was shown [...] Read more.

The effect of aging (at 773 K for 1 h) on the cyclic stability of superelasticity was studied in preliminarily quenched (after annealing at 1448 K for 1 h) Ni₄₄Fe₁₉Ga₂₇Co₁₀ [001]-oriented single crystals. It was shown that NiFeGaCo single crystals (both quenched and aged) exhibited highly stable superelasticity during more than 10⁵ loading/unloading cycles in compression without destruction. The degradation of the superelasticity curves was divided into stages, and each stage of degradation was carefully considered. The precipitation of ω-phase particles led to a change in the degradation mechanism of superelasticity in the aged crystals. The main degradation mechanism for quenched crystals is a formation of uniform distribution of dislocations; for aged crystals, the microstructural degradation mechanisms consist of a non-uniform distribution of dislocations around the particles and the appearance of residual martensite. Full article

(This article belongs to the Special Issue Metallic Functional Materials: Development and Applications)

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13 pages, 1491 KiB

Open AccessArticle

Magnetostriction of Heusler Ferromagnetic Alloy, Ni₂MnGa_0.88Cu_0.12, around Martensitic Transition Temperature

by Takuo Sakon, Koki Morikawa, Yasuo Narumi, Masayuki Hagiwara, Takeshi Kanomata, Hiroyuki Nojiri and Yoshiya Adachi

Metals 2023, 13(7), 1185; https://doi.org/10.3390/met13071185 - 26 Jun 2023

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Abstract

In this study, magnetostriction measurements were performed on the ferromagnetic Heusler alloy, Ni₂MnGa_0.88Cu_0.12, which is characterized by the occurrence of the martensitic phase and ferromagnetic transitions at the same temperature. In the austenite and martensite phases, the [...] Read more.

In this study, magnetostriction measurements were performed on the ferromagnetic Heusler alloy, Ni₂MnGa_0.88Cu_0.12, which is characterized by the occurrence of the martensitic phase and ferromagnetic transitions at the same temperature. In the austenite and martensite phases, the alloy crystallizes in the L2₁ and D0₂₂-like crystal structure, respectively. As the crystal structure changes at the martensitic transition temperature (T_M), a large magnetostriction due to the martensitic and ferromagnetic transitions induced by magnetic fields is expected to occur. First, magnetization (M-H) measurements are performed, and metamagnetic transitions are observed in the magnetic field of μ₀H = 4 T at 344 K. This result shows that the phase transition was induced by the magnetic field under a constant temperature. Forced magnetostriction measurements (ΔL/L) are then performed under a constant temperature and atmospheric pressure (P = 0.1 MPa). Magnetostriction up to 1300 ppm is observed around T_M. The magnetization results and magnetostriction measurements showed the occurrence of the magnetic-field-induced strain from the paramagnetic austenite phase to the ferromagnetic martensite phase. As a reference sample, we measure the magnetostriction of the Ni₂MnGa-type (Ni₅₀Mn₃₀Ga₂₀) alloy, which causes the martensite phase transition at T_M = 315 K. The measurement of magnetostriction at room temperature (298 K) showed a magnetostriction of 3300 ppm. The magnetostriction of Ni₂MnGa_0.88Cu_0.12 is observed to be one-third that of Ni₅₀Mn₃₀Ga₂₀ but larger than that of Terfenol-D (800 ppm), which is renowned as the giant magnetostriction alloy. Full article

(This article belongs to the Special Issue Metallic Functional Materials: Development and Applications)

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14 pages, 3768 KiB

Open AccessArticle

Terahertz Metamaterial Absorber Based on Ni–Mn–Sn Ferromagnetic Shape Memory Alloy Films

by Rui Liu, Xiaochuan Wang, Jiachen Zhu, Xiaohua Tian, Wenbin Zhao, Changlong Tan and Kun Zhang

Metals 2023, 13(7), 1162; https://doi.org/10.3390/met13071162 - 22 Jun 2023

Cited by 1 | Viewed by 2087

Abstract

Terahertz absorbers have been extensively investigated by researchers due to their applications in thermophotovoltaic energy conversion and sensors, but a key factor limiting their development is the lack of vital and versatile materials. Ferromagnetic shape memory alloys (FSMAs) offer a novel remedy for [...] Read more.

Terahertz absorbers have been extensively investigated by researchers due to their applications in thermophotovoltaic energy conversion and sensors, but a key factor limiting their development is the lack of vital and versatile materials. Ferromagnetic shape memory alloys (FSMAs) offer a novel remedy for tunable metamaterials due to their brilliant recovery of deformation, remote control, and transient response. In this study, we propose a tunable absorber based on magnetic field tuning, consisting of Ni–Mn–Sn ferro-magnetic shape memory alloy films in fractal geometry and optically excited Si plates. Numerical analysis shows that the proposed absorber has an absorbance bandwidth of 1.129 THz above 90% between 1.950 THz and 3.079 THz. The absorber geometry can be regulated by an external magnetic field, allowing dynamic switching between broadband and narrowband absorption modes, the latter showing an ultra-narrow bandwidth and a high-quality factor Q of ~25.8. The proposed terahertz absorber has several advantages over current state-of-the-art bifunctional absorbers, including its ultra-thin structure of 10.39 μm and an additional switching function. The absorption can be continuously tuned from 90% to 5% when the light-excited silicon plate is transferred from the insulator state to the metal state. This study presents a promising alternative strategy for developing actively regulated and versatile terahertz-integrated devices. Full article

(This article belongs to the Special Issue Metallic Functional Materials: Development and Applications)

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17 pages, 6238 KiB

Open AccessArticle

Enhanced Fatigue Resistance of Nanocrystalline Ni_50.8Ti_49.2 Wires by Mechanical Training

by Peng Chen, Xiaorong Cai, Na Min, Yunfan Liu, Zhengxiong Wang, Mingjiang Jin and Xuejun Jin

Metals 2023, 13(2), 361; https://doi.org/10.3390/met13020361 - 10 Feb 2023

Viewed by 1413

Abstract

In this paper, the fatigue resistance of superelastic NiTi shape memory alloy (SMA) wires was improved by combining mechanical training and nanocrystallization. Fatigue tests were performed after mechanical training with a peak stress of 600 MPa for 60 cycles of nanocrystalline (NC) NiTi [...] Read more.

In this paper, the fatigue resistance of superelastic NiTi shape memory alloy (SMA) wires was improved by combining mechanical training and nanocrystallization. Fatigue tests were performed after mechanical training with a peak stress of 600 MPa for 60 cycles of nanocrystalline (NC) NiTi wires, and the associated microscopic mechanism was investigated by using transmission electron microscopy (TEM) and transmission Kikuchi diffraction (TKD). The results showed that stress-controlled training effectively improved the functional stability (the accumulated residual strain decreased by 83.8% in the first 5000 cycles) of NC NiTi SMA wires, as well as increased the average structural fatigue life by 187.4% (from 4538 cycles to 13,040 cycles). TEM observations and TKD results revealed that training-induced dislocations resulted in lattice rotation and preferential grain orientation. The finite element method (FEM) simulation results indicated that the training-induced preferential grain orientation tended to decrease the local stress concentration and strain energy density. Combined with fractography analysis, the uniform deformation caused by mechanical training changed the crack growth mode from multi-regional propagation to single-regional propagation, improving the structural fatigue life. Full article

(This article belongs to the Special Issue Metallic Functional Materials: Development and Applications)

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9 pages, 1969 KiB

Open AccessArticle

Large Magnetic Entropy Change in GdRuSi Optimal for Magnetocaloric Liquefaction of Nitrogen

by Anatoly G. Kuchin, Sergey P. Platonov, Roman D. Mukhachev, Alexey V. Lukoyanov, Aleksey S. Volegov, Vasilii S. Gaviko and Mari Yu. Yakovleva

Metals 2023, 13(2), 290; https://doi.org/10.3390/met13020290 - 31 Jan 2023

Cited by 11 | Viewed by 1425

Abstract

The search for new magnetocaloric materials for application in magnetic refrigerants is highly motivated by high efficiency, reliability, and environmental safety. The values of the magnetocaloric effect MCE and the refrigerant capacity RC for the equiatomic GdRuSi compound were determined to be MCE [...] Read more.

The search for new magnetocaloric materials for application in magnetic refrigerants is highly motivated by high efficiency, reliability, and environmental safety. The values of the magnetocaloric effect MCE and the refrigerant capacity RC for the equiatomic GdRuSi compound were determined to be MCE = 10.7 and 4.94 J/kgK and RC = 336 and 92 J/kg with a change in the field of 0–50 and 0–17 kOe, respectively. These high values of MCE and RC for GdRuSi appear in the region of nitrogen liquefaction temperature of 77.4 K, due to which the compound can be useful in practice. The densities of states and magnetic moments of GdRuSi were calculated theoretically, taking into account strong electron correlations in the 4f Gd shell. The total magnetic moment of GdRuSi was found to be composed of the Gd moment only with the value calculated in very good agreement with the experimental one. Full article

(This article belongs to the Special Issue Metallic Functional Materials: Development and Applications)

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