X-ray study of surface layers of air-annealed Be12Ti and Be12V samples using synchrotron radiation

doi:10.1016/j.fusengdes.2012.02.047

Fusion Engineering and Design

Volume 87, Issues 5–6, August 2012, Pages 872-875

https://doi.org/10.1016/j.fusengdes.2012.02.047 Get rights and content

Abstract

Titanium beryllide Be₁₂Ti and vanadium beryllide Be₁₂V are considered to be promising materials for advanced neutron multipliers in the helium-cooled breeding blanket of DEMO reactor. A study of the surface layers of oxidized beryllide specimens by means of powder X-ray diffraction technique is presented in this work. The phase composition of the near-to-surface layers of Be₁₂Ti and Be₁₂V specimens was investigated at the Single Crystal Diffraction (SCD) beamline at ANKA synchrotron facility after air-annealing at 800 °C. A high surface sensitivity of measurements was achieved at grazing incidence conditions by varying the incidence angle. Since beryllium has low values of X-ray absorption, the near-surface regions having depths from 2 up to 20 μm were investigated. The main objective of the work is the evaluation of composition of the reactant products which can influence the parameters of retention and release of radiogenic gases.

Highlights

► Surface layers of air-annealed Be₁₂Ti and Be₁₂V samples were investigated. ► X-ray diffraction analysis using synchrotron radiation allowed the study of near-surface regions with the depths of a few microns. ► Presence of beryllium oxide BeO was found in all investigated surface layers of Be₁₂Ti and Be₁₂V samples. ► Volatilization of vanadium oxide V₂O₅ was observed from the surface of Be₁₂V sample after annealing at 800 °C.

Introduction

Titanium beryllide Be₁₂Ti and vanadium beryllide Be₁₂V are considered to be advanced materials for the use as neutron multipliers in the solid breeding blanket [1], [2], [3]. However as the gas release kinetics and the compatibility with structural materials strongly depend on the oxidation behavior, the proper investigation of their resistance to oxidation at elevated temperatures is needed.

Gas release characteristics of neutron multiplier are in a strong dependency on the presence of oxide layer on the surface of beryllium-based materials. It is known that the diffusivity and solubility of hydrogen isotopes (e.g., tritium) can be influenced by the presence of different oxides in near-to-surface layers of beryllium-containing materials [4], [5], [6].

In this article we report on phase composition of six layers deposited at the depths up to 20 μm from the surfaces of Be₁₂Ti and Be₁₂V samples investigated by means of synchrotron radiation using X-ray diffraction technique.

Section snippets

Materials

This work was performed using Be₁₂Ti and Be₁₂V intermetallic compounds delivered by Company Brush Wellman, Inc., USA. Both types of beryllide specimens were produced using powder metallurgical methods and have nearly equal densities of about 2.40 g/cm³.

Investigations of initial and air-annealed Be₁₂Ti and Be₁₂V samples by scanning electron microscope (SEM)

SEM observations of the surfaces of beryllide specimens in as-received state show the separate grains on the surfaces of Be₁₂Ti and Be₁₂V samples, accordingly (Fig. 1 and Fig. 2).

After investigations of the surfaces of beryllide samples in the

Results and discussion

Fig. 7, Fig. 8 show X-ray diffraction patterns corresponding to annealed Be₁₂Ti and Be₁₂V samples. One should emphasize that 10.2 keV X-ray wavelength in vacuum is 1.215534 A. Therefore, peak positions of beryllides and appropriate oxides were recalculated using Diffrac Plus evaluation software taking into account the wavelength corresponding to incident synchrotron radiation. The X-ray penetration depth decreased from the lowermost down to the uppermost curves (attenuation lengths decrease,

Conclusions

The study of the surface layers of air-annealed Be₁₂Ti and Be₁₂V samples showed that beryllium oxide is present in the whole volume of materials’ near-to-surface region. In the case of oxidation of Be₁₂Ti specimen, only one peak identified as TiO₂ (3 1 0) was found in deeper layers located closer to material bulk. Oxidation of Be₁₂V specimen led to additional formation of highly volatile V₂O₅ which may cause the appearance of undesirable gas species in the breeding blanket. For both, Be₁₂Ti and Be

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Cited by (1)

Synthesis and characteristics of ternary Be–Ti–V beryllide pebbles as advanced neutron multipliers
2016, Fusion Engineering and Design
Citation Excerpt :
In contrast, the Zr in Be13Zr is so highly reactive that it is difficult to handle without a globe box controlled by an inert gas. Furthermore, vanadium beryllide has some disadvantages such as high cost and an insufficiency of data on granulated pebbles, although a study on the fabrication of Be12V blocks with the powder metallurgical method has been reported [6]. Therefore, to solve issues pertaining to binary beryllides, granulation of Be12Ti1−xVx ternary beryllides with different amounts of V was conducted in the present study.
A new combined plasma sintering and rotating electrode method for fabricating beryllide rods and pebbles has been suggested. Using these methods, preliminary synthesis of ternary beryllide pebbles with different chemical compositions, Be₁₂Ti_1−xV_x (x = 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0), was successful. Scanning electron microscopy observations revealed that grain size on the surface decreased, whereas the area fraction of the Be phase in the cross-section decreased as the amount of V increased. These decreases may be attributed to the fact that the chemical composition of the pebble was closely varied to single-phase Be₁₂V, with no peritectic reaction as the amount of V increased, while the Be, Be₁₂Ti, and Be₁₇Ti₂ phases were formed with large grains caused by a peritecic reaction in Be₁₂Ti. This feature influenced the variation of reactivity with 1% water vapor at high temperatures. It was concluded that weight gain and H₂ generation decreased with decreases in grain size as well as Be phase on the surface, as the amount of V increased in Be₁₂Ti_1−xV_x. Based on cross-sectional observations after oxidation measurement for 24 h, we found that Be₁₂Ti_0.3V_0.7 and Be₁₂Ti_0.1V_0.9 pebbles showed high phase stability.

¹: Present address: Insitut für Angewandte Physik und Zentrum für Mikrostrukturforschung, Jungiusstrasse 11, D-20355 Hamburg, Germany.

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X-ray study of surface layers of air-annealed Be12Ti and Be12V samples using synchrotron radiation

Abstract

Highlights

Introduction

Section snippets

Materials

Investigations of initial and air-annealed Be12Ti and Be12V samples by scanning electron microscope (SEM)

Results and discussion

Conclusions

J. Nucl. Mater.

J. Nucl. Mater.

Fusion Eng. Des.

J. Nucl. Mater.

J. Nucl. Mater.

X-ray study of surface layers of air-annealed Be₁₂Ti and Be₁₂V samples using synchrotron radiation

Investigations of initial and air-annealed Be₁₂Ti and Be₁₂V samples by scanning electron microscope (SEM)