Detrapping of interstitial helium in metal tritides—NMR studies

Weaver, H. T.; Camp, William J.

doi:10.1103/physrevb.12.3054

Cited by 36 publications

(15 citation statements)

References 12 publications

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“…However, it should be realized that the films are strained during charging by tritium which could lead to bubble formation in the surface region inves-tigated in the TEM experiments. NMR line shape data has been interpreted as evidence of bubble formation [10], whereas similar data have been discussed by other authors [31] in terms of trapped He at interstitial sites. Furthermore, in desorption experiments, Kass [32] found a single trap with an activation energy of 17 kcal in the aged tritide, whereas two traps with activation energies of 15 and 62 kcal are found in He + -implanted tritides.…”

Section: Effect Of He On the Electronic Structure Of Pdtmentioning

confidence: 87%

Electronic structure of hydrogen storage materials

Gupta

2000

Int. J. Quantum Chem.

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ABSTRACT:The electronic structure of two types of hydrogen storage materials has been investigated by ab initio band structure methods. We show that the helium produced by the radioactive decay of tritium in a palladium matrix remains stable at the octahedral site of the fcc lattice for He/Pd ratio of at least 0.25. Such He production results in a lattice expansion of 2%. The experimentally observed increased stability of aged tritium in a palladium matrix is not entirely due to lattice expansion, which amounts to only 28% of the effect, but also to modifications of the electronic structure in the presence of helium. In addition, we show that He leads to lattice decohesion. The effect of Ni substitution in LaNi 5 by 3d and s-p elements on the electronic structure of the intermetallic and its hydrides has been also investigated. These substitutions are found to affect drastically the properties at the Fermi level and the filling of the Ni-d states. The Fermi level, E F , of LaNi 4 M (M = Fe, Co, Mn) is found to lie in the narrow additional M-3d subband above the Ni-d states, leading to an increase in the density of states (DOS) at E F . In contrast, the substitution of Ni by an s element of the 3d series, Cu, or by an s-p element, Al or Sn, results in a progressive filling of the Ni-d bands and in a decrease of the DOS at E F . In all the substituted intermetallic compounds, we find that the lattice expansion accounts for less than 50% of the observed decreased stability. This shows the importance of chemical effects. We also discuss the factors that affect the electronic structure and the stability of the hydrides, and compare our results with available experimental data.

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Section: Effect Of He On the Electronic Structure Of Pdtmentioning

confidence: 87%

Electronic structure of hydrogen storage materials

Gupta

2000

Int. J. Quantum Chem.

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“…It is surprising that 3 He atoms produced from tritium decay do not immediately diffuse out of the lattice until some critical atomic ratio of 3 He/metal is reached [2,3] almost all tritides for its inert reactivity with other elements. To understand this phenomenon, there have been many experimental and theoretical studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14] of 3 He in tritides, however, the states of 3 He atoms in metals and metal tritides are still in debate. Camp [2] and Weaver [4] believed the 3 He atoms are trapped at the octahedral interstitial sites in tritides with the fluorite crystal structure while Bowman and Attalla [10] suggested the 3 He atoms primarily reside in microscopic gas bubbles with dimensions <100 Å .…”

Section: Introductionmentioning

confidence: 99%

“…To understand this phenomenon, there have been many experimental and theoretical studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14] of 3 He in tritides, however, the states of 3 He atoms in metals and metal tritides are still in debate. Camp [2] and Weaver [4] believed the 3 He atoms are trapped at the octahedral interstitial sites in tritides with the fluorite crystal structure while Bowman and Attalla [10] suggested the 3 He atoms primarily reside in microscopic gas bubbles with dimensions <100 Å . To refrain from the damage caused by 3 He bubbles, Shaw et al [8], Mansur et al [12] and Goodhew et al [13] proposed that by trapping 3 He in specific solutes, either the clustering of 3 He could be inhibited or a large quantity of very small 3 He clusters would be created to prevent the occurrence and consequently the outburst of large bubbles.…”

Section: Introductionmentioning

confidence: 99%

First-principles study of alloying effect of transition metals on He in titanium ditritide

Yang

He³

et al. 2006

Journal of Nuclear Materials

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“…There are three traditional methods to artificially introduce helium into materials: tritium ageing [4], neutron irradiation [5] and helium ion implantation [6]. In recent years, a magnetron sputtering technique [7][8][9] which works in a mixture of helium (He) and argon (Ar) gas ambient has been developed.…”

Section: Introductionmentioning

confidence: 99%

Study of helium evolution in nanocrystalline titanium films by slow positron beam analysis

Deng¹,

Zhou²,

Zhang³

et al. 2011

J. Phys.: Conf. Ser.

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IntroductionHelium can be produced in tritium storage materials and structural materials of fission reactors, accelerators and future controlled fusion reactors. Its insolubility and high mobility of the helium in the materials are crucial to study its formation and evolution in materials. Helium atoms can not be naturally dissolved in the materials, but are easily trapped by dislocation, vacancies and voids. With the increment of helium concentration, helium bubbles in the materials will be formed by migrating, diffusing and coalescence of helium atoms. Helium may change microstructure of the materials，and even cause serious degradation of some macroscopic mechanical properties of the materials, such as swelling and helium-induced brittleness [1][2][3]. Therefore, studies of the behavior of helium in materials are critically important in material applications. However, helium behavior studies in materials are quite complicated, many problems, such as the evolution of helium-related defects and mechanism of helium brittleness, are still under investigation.There are three traditional methods to artificially introduce helium into materials: tritium ageing [4], neutron irradiation [5] and helium ion implantation [6]. In recent years, a magnetron sputtering technique [7][8][9] which works in a mixture of helium (He) and argon (Ar) gas ambient has been developed. This method can introduce helium into the growing metal films. It has many advantages, such as controllable helium concentration and a uniform He distribution in depth.Many experiments have been used to study the behavior of helium in titanium film. As a sensitive method for studying vacancy-like defects, positron annihilation technique has been effectively

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Detrapping of interstitial helium in metal tritides—NMR studies

Cited by 36 publications

References 12 publications

Electronic structure of hydrogen storage materials

Electronic structure of hydrogen storage materials

First-principles study of alloying effect of transition metals on He in titanium ditritide

Study of helium evolution in nanocrystalline titanium films by slow positron beam analysis

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