Hydrogen embrittlement in single- and poly-crystal niobium

Farahani, Mostafa; Attia, Farouk; Saláma, K.

doi:10.1007/bf02649738

Cited by 16 publications

(4 citation statements)

References 17 publications

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“…A niobium cavity body is a possible choice because of the relatively mature technology of niobium cavity fabrication and its superconducting properties. But the brittleness of hydrogen at a high temperature [9] and the high fabrication cost counteract its application at large scale. Taking the material cost into account, copper and stainless steel may be the suitable options.…”

Section: Introductionmentioning

confidence: 99%

MgB₂films fabricated on molybdenum substrate by hybrid physical–chemical vapor deposition for superconducting RF cavity applications

Xie

Feng

et al. 2012

Supercond. Sci. Technol.

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Magnesium diboride (MgB2) is a good candidate material for superconducting RF cavities because of its higher transition temperature of ∼39 K and because of the absence of weak links between grains which prevents other high-Tc superconducting materials, such as YBCO, from being used for SRF cavities. Differently from MgB2 films fabricated on Cu or stainless steel(SS), we have fabricated MgB2 films on Mo substrate by hybrid physical–chemical vapor deposition. The films are about 0.7 µm thick and the Tc (onset) is as high as 38 K, with a corresponding transition width of 0.9 K. The upper critical field at T = 0 K, HC2(0), is extrapolated as 13.5 T and the critical current density at 5 K, JC (5 K, 0 T), is 6.5 × 105 A cm−2. Analysis results indicate that MgB2 film on molybdenum substrate has suitable superconducting properties and does not show the problems which often occur for MgB2 films fabricated on other metal substrates, such as the large cracks on SS substrate and the reaction between the substrate and the Mg on Cu substrate.

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Section: Introductionmentioning

confidence: 99%

MgB₂films fabricated on molybdenum substrate by hybrid physical–chemical vapor deposition for superconducting RF cavity applications

Xie

Feng

et al. 2012

Supercond. Sci. Technol.

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“…[19] However, the mechanism of hydrogen-induced pulverization is not well understood, and the available literature concerning the hydrogenation of pure Nb is limited to articles about fundamental features of hydride formation, as exemplified in the Nb-H phase diagram (Figure 1), [20][21][22][23] and hydrogen embrittlement. [24,25,26] To apply a powder fabrication process by hydrogenation to pure Nb, it is necessary to better understand the mechanism of hydrogen-induced pulverization from metallographic points of view.…”

Section: Introductionmentioning

confidence: 99%

Fracture behavior of niobium by hydrogenation and its application for fine powder fabrication

Semboshi

Masahashi

Konno

et al. 2006

Metall Mater Trans A

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Fracture behavior of pure niobium (Nb) by several hydrogenation procedures has been investigated to elucidate the fundamental mechanisms of hydrogen pulverization, which can then be used to produce fine Nb powders with high purity. Concentric cracks and microcracks were introduced in recrystallized Nb specimens, leading to pulverization, when they absorb hydrogen enough to form a large volume of the face-centered orthorhombic ␤-NbH phase. This hydride phase exhibits anisotropic expansion of Nb lattice and embrittlement. Thus, the fracture of Nb plates occurs in the following sequence: hydrogen absorption, the formation of the ordered hydride phase, strain generation arising from the phase transformation, and crack nucleation and propagation. The authors also show that Nb powders less than 1 m were prepared by hydrogenation and ball-milling at a temperature below 203 K, in which hydrogen was removed by dehydrogenation at above 724 K. Thus, fine and contamination-free Nb powders can be effectively fabricated by using hydrogenation, ball-milling, and dehydrogenation procedures.

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“…As background gas, H 2 or Ar would suppress the reaction between magnesium and oxygen. In the deposition process, the substrate is kept at 760°C, and Ar is introduced into the reactor to suppress Nb's brittleness of hydrogen [10].…”

Section: Methodsmentioning

confidence: 99%

High Quality MgB<sub>2</sub>/Nb Deposited by HPCVD Method

Chen

Zhang

et al. 2013

MSF

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Niobium with the transition temperature of 9 K is the usual material for TESLA superconducting accelerate cavity. The cavity must work at the temperature range of of 2~1.8 K, which would consume large energy. In addition, the low upper critical field is one of reasons causing the problem of accelerate cavities' Q-slop. Comparing with Nb material, MgB 2 has several advantages in this application, such as higher Tc of ~39 K, higher upper critical field and the possible lower microwave loss, which would help increasing accelerating gradient and saving operation cost. Because of these benefit, more and more focus is put on this style of accelerating cavity, MgB 2 -thick-film/metal-cavity-body. Using Hybrid Physical-Chemical Vapor Deposition method, the micronmeter-thick MgB 2 film on Nb substrate was prepared in the present investigation. The experimental results showed that Tc(0) reached 38.5 K and the Hc 2 was about 20 T. In order to test the film's fracture toughness the film as the inner surface was bended. It was found that at small bending angle the influence on the superconducting properties was little. When the bend radius increased to 5 mm, some cracks smaller than 1 micron occured on the film surface. However, the film still attached to the Nb substrate and the Tc was as high as ~33.5 K, showing that the MgB 2 film fabricated by HPCVD had a good compact state with the Nb substrate and good mechanical toughness. These results indicate that the clean MgB 2 thick film has a better feature in the application of superconducting accelerate cavity.

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Hydrogen embrittlement in single- and poly-crystal niobium

Cited by 16 publications

References 17 publications

MgB₂films fabricated on molybdenum substrate by hybrid physical–chemical vapor deposition for superconducting RF cavity applications

MgB₂films fabricated on molybdenum substrate by hybrid physical–chemical vapor deposition for superconducting RF cavity applications

Fracture behavior of niobium by hydrogenation and its application for fine powder fabrication

High Quality MgB<sub>2</sub>/Nb Deposited by HPCVD Method

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Hydrogen embrittlement in single- and poly-crystal niobium

Cited by 16 publications

References 17 publications

MgB2films fabricated on molybdenum substrate by hybrid physical–chemical vapor deposition for superconducting RF cavity applications

MgB2films fabricated on molybdenum substrate by hybrid physical–chemical vapor deposition for superconducting RF cavity applications

Fracture behavior of niobium by hydrogenation and its application for fine powder fabrication

High Quality MgB<sub>2</sub>/Nb Deposited by HPCVD Method

Contact Info

Product

Resources

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MgB₂films fabricated on molybdenum substrate by hybrid physical–chemical vapor deposition for superconducting RF cavity applications

MgB₂films fabricated on molybdenum substrate by hybrid physical–chemical vapor deposition for superconducting RF cavity applications