J. Plasma Fusion Res. SERIES, Vol. 10 (2013)

Hydrogen generation property on the surface of plasma sintered Be12Ti
Kohei WADA1), Kenzo MUNAKATA1), Yusuke AKIMOTO1), Haruki TAKEDA1),
Jae-Hwan KIM2), Daisuke WAKAI2),Kazuo YONEHARA2) and Masaru Nakamichi2)
1)

Faculty of engineering and resource science, Akita university, 1-1, Tegatagakuen-cho, Akita, 010-8502, Japan

2)

Fusion Research and Development Directorate, Japan Atomic Energy Agency, 2-166, Omotedate, Obuchi, Rokkasho,Kamikita, Aomori, 039-3212, Japan(Received: 9 May 2012 / Accepted: 5 December 2012)

Central and peripheral parts of a plasma sintered titanium beryllide disc were exposed to water vapor attemperature rising up to 1273 K. Hydrogen generation on and oxidation properties of the titanium beryllide surfaces
were investigated. According to electron probe microanalysis, the titanium beryllide parts were characterized bydifferent surface area fractions of Be, Be12Ti, Be17Ti2, and Be2Ti phases, and the central part contained lower
fraction of Be phase than the peripheral part. H2 gas generation rate in the central part was found to be lower thanthat in the peripheral part, and this difference can be attributed to larger fraction of the Be phase. Secondary
electron microscopy and X-ray diffraction revealed that the parts of the plasma sintered Be12Ti disc had higher
oxidation resistance than metallic beryllium.
Keywords: beryllide, plasma sintering, hydrogen generation, oxidation, gas chromatograhphy

1. Introduction

caused by interaction of water vapor with titanium
beryllides. Besides, oxidation resistance of the titanium
beryllides with slightly different phase compositions
was studied.

Metallic beryllium has been considered as a leading
candidate for a neutron multiplier in water- or
helium-cooled solid breeder blankets in future fusion
reactors. In these blankets, beryllium will be subjected
to a high neutron flux and located in high temperatureenvironment. However, beryllium is highly reactivewith water vapor at temperatures above 873 K,producing hydrogen that may lead to accidents due toH2 gas explosion.
Be + H2O = BeO + H2
(1)
Titanium beryllides such as Be12Ti have many
advantages over beryllium from the perspectives ofhigher melting point, lower chemical reactivity, lowerswelling, etc. Therefore, Be12Ti material has attracted
attention as an alternative of beryllium, and could beused as an advanced neutron multiplier in the fusion
reactor blankets [1].
Titanium beryllides have been fabricated by various
methods. Nakamichi et al. [2, 3] have developed newsynthesis process of Be12Ti material called“plasma-sintering method”. This process consists ofloading raw material powder in the punch and the dieunit, direct current pulse plasma generation to activate
the surface of powder particles, and uniaxial pressing toenhance the sinterability [2,3].
In this study, we report results on H2 generation

2. Experimental
Be and Ti powders, characterized by average grain sizesof 27 ȝm and 28 ȝm, respectively, were mixed for 60 min
by using a mortar grinder RM200 (Retsch, Germany). The
mixed ratio was adjusted to the stoichiometric compositionof Be12Ti (69.3:30.7 wt.%). The mixed powder was placedin a plasma electrical discharge sintering device KE-PAS III(manufactured by KAKEN Co. Ltd), and Be12Ti disc, 20MS3A

CuO
bed

H2O
Ar

H2O

MS3A

Ar

M.F.

H2G.C.

M.F.

Electric
Electricfurnace
furnaceAr

H2/Ar

M.F.͏͏͏͏Mass
M.F.͏͏͏͏Massflow
flowcontroller
controller
MS3A䈇䈇䈇Molecular
MS3A䈇䈇䈇Molecularsieve
sieve3A
3A
CuO
CuObed䈇䈇Oxidized
bed䈇䈇Oxidizedcopper
copper
G.C.䈇䈇䈇䈇Gas
G.C.䈇䈇䈇䈇GaschromatographchromatographFig. 1 Schematic flow diagram of test apparatus.

authors e-mail : kohei.wada1986@gmail.com

98©2013 by The Japan Society of Plasma
Science and Nuclear Fusion ResearchK. Wada et al., Hydrogen Generation Property on the Surface of Plasma Sintered Be12Ti

Be12Ti, Be17Ti2, and Be2Ti with different fractions.
Percentages of the surface areas of the phases for each partof the disc, evaluated with the use of an image analyzer, areshown in Table 1. It is evident that the central part iscomposed mainly of Be12Ti phase with relatively large
fraction of Be17Ti2 phase. Additionally, smaller fractions ofBe and Be12Ti phases were observed. Note that phasecompositions for the central and peripheral parts wereslightly different. This observation is in good agreementwith results obtained by Kim et al. [4] proposing that thephase difference for the central and peripheral parts can beexplained by a temperature gradient maintained during thesintering process.
Experiments on generation of H2 gas on the surfaces ofthe plasma sintered titanium beryllides were carried out toinvestigate the effect of the phase composition. Fig. 3 showschanges in hydrogen concentrations in the outlet stream ofreactor with central and peripheral part of the plasma
sintered titanium beryllide disc exposed to a 10,000 ppm
H2O/Ar gas. In case of the central part, generation ofhydrogen started at a temperature of 673 K and continued
for about 27 h. The total amount of hydrogen generated for
24 h is 1.210-4 mol/cm2. For the peripheral part, however,
the hydrogen generation started at a temperature above 423
K and continued for 40 hr. The total amount of hydrogengenerated on the peripheral part for 24 h is 3.010-4mol/cm2. As mentioned above, the samples used in thiswork included the phase of Be2Ti (Table 1) that is known tomm in diameter and 5 mm in thickness, was synthesized bysintering for 40 min at a temperature of 1273 K and apressure of 50 MPa. Then the disc was cut into two small
samples to separate central and peripheral parts of the discfor comparative analyses. The surface area of the central
parts was 83 mm2 while that of the peripheral part was 128
mm2. The samples were mechanically polished with a#2400 SiC abrasive paper.
The surface morphology of the Be12Ti samples wasexamined by secondary electron microscopy (SEM)
combined with the electron probe microanalysis (EPMA) ina SEM/EPMA instrument JXA-8230 (JEOL Co.)
Schematic flow diagram of apparatus for ameasurement of the hydrogen generation rate is shown inFig. 1. The Be12Ti sample was wrapped by platinum meshto avoid direct contact with the test tube, and then placed
between silica wools. 10,000 ppm H2O/Ar gas wasgenerated by passing 10,000 ppm H2 /Ar gas throughcopper oxide bed heated at 623 K, and then introduced tothe test tube with a flow rate of 300 cm3/min. An electric
furnace was used to heat the test tube at a heating rate of 5
K/min, and a temperature inside the tube was raised up to1273 K. This temperature was kept constant until hydrogengeneration terminated.
The concentrations of hydrogen in the outlet streamsof the reactor were measured with a gas chromatograph
GC-8A manufactured by SHIMADZU Co. The state ofoxidized sample surface was characterized by X-ray
diffraction (XRD) analysis with the Ultima IV instrument(RIGAKU Co.) and electron probe micro analysis (EPMA)
with the SEM/EPMA JXA-8230 instrument (JEPL Co.).

Table 1 Surface area fractions (in %) of phases constituent
central and peripheral parts of titanium beryllide disc.

3. Result and discussion
Figure 2 shows the SEM images using back-scatteredelectron for central and peripheral parts of the plasma
sintered titanium beryllide disc prepared in this study. The
results of EPMA analysis demonstrated that the titanium
beryllide is composed of four different phases such as Be,

Fig. 2 SEM images of central part (a) and peripheral part (b) of plasma sintered titanium beryllide disc.

99

K. Wada et al., Hydrogen Generation Property on the Surface of Plasma Sintered Be12Ti

have capability of hydrogen storage [5]. The existence ofthis phase might affect the hydrogen generation of thesamples, while the fractions of the phase in the bothsamples were almost the same. The Be17Ti2 phase could
also affect the hydrogen generation, but this phase isprobably stable and tolerant to oxidation as much as theBe12Ti phase [Kim paper Numat]. Thus, it is thought thatthe sample with larger fraction of Be phase generates moreamounts of H2, since Be is known as highly reactive withoxygen [6] and water vapor [7]. As shown in the EPMA
analysis (Table 1), the edge sample was composed of largerfraction of Be, which affect the amount of generated H2 gas.
This agrees with the report by Anderl et al. [8],demonstrating that the rate of the reaction between
beryllium surface and water vapor is associated withdifferences in the specific surface areas for the tested
materials.
The weight gain for the Be12Ti and beryllium samples
indicate that the center sample part increased by 3.6 % of
the initial weight for the central part of the titanium
beryllide and 4.7 % for the peripheral part. However, asreported in our previous study [9], for metallic beryllium
used as a reference material, the weight gain was 50 % of
the initial weight. Data on the weight gain and amount ofgenerated hydrogen for the titanium beryllide parts indicatethat the peripheral part is more oxidized.
SEM observation and XRD analysis were performed toinvestigate the surface state of the two samples after
exposure to 10,000 ppm H2O/Ar gas. Fig. 4 shows the SEM
images of central (a) and peripheral (b) parts of the plasma
sintered titanium beryllide disc and metallic beryllium (c)after exposure to water vapor. The Be sample (shown in Fig.
4 (c)) was used in our previous work and the surface of thesample was observed using the SEM/EPMA apparatus [9].
The result of the SEM analysis clarified that after oxidation
the surfaces of the titanium beryllide parts are covered with
dense and protective oxide scales (see Fig. 4 (a) and (b)).
Gray and white areas in the SEM pictures correspond to
1400

1000
800

Hydrogenconcentration

50600
40025(b)

(a)
01200

Temperature

7505101520

Temperature (K)Hydrogen concentration (ppm)

100

BeO and TiO2, respectively. Comparison of the oxidation
behavior of Be12Ti and beryllium metal indicate that more
protective BeO scales are present on the surface of theBe12Ti sample parts. In contrast, it could be stated thatmetallic Be possesses poor oxidation resistance due tocracked and fractured BeO scales present of the surface.
Sato et al. [10] had demonstrated that BeO formed on thesurface of metallic Be is affected by compressive stresscaused by coherency of the lattice structures between thescale and the bulk metal, since the atomic distances in theBeO scale are smaller than those in the metallic Besubstrate.
The results of the XRD analysis (Fig. 5) demonstrated
that the intensity of peaks corresponding to BeO formed on
the peripheral part are higher than those for the central part.
This is in good agreement with the result of the weight gain

200
2530

35

040

Time (h)Fig. 3 Change in concentration of hydrogen in the outlet streamof reactor with central part (a) and peripheral part (b) of theFig. 4 SEM images of central (a) and peripheral (b) parts of theplasma sintered titanium beryllide disc exposed to a 10 000 ppm

plasma sintered titanium beryllide disc and metallic beryllium

H2O/Ar gas.

[8] (c) after exposure to water vapor.

100

K. Wada et al., Hydrogen Generation Property on the Surface of Plasma Sintered Be12Ti

Border Approach activities.

6. References[1] H. Kawamura, H. Takahashi, N. Yoshida, V. Shestakov, Y. Ito,
M. Uchida, H. Yamada, M. Nakamichi and E. Ishitsuka,Fusion Eng. Des. 61-62, 391-397 (2002).
[2] M. Nakamichi, K. Yonehara and D. Wakai, Fusion Eng. Des.
86, 2262-2264 (2011).
[3] M. Nakamichi and K. Yonehara, J. Nucl. Mater. 417, 765-768(2011).
[4] J.-H. Kim, K. Yonehara and M. Nakamichi, Thermal
Stability of Plasma Sintered Beryllides, Proc. 15th Int. Conf.
on Fusion Reactor Materials, Charleston, USA, October
2011 (submitted to J. Nucl. Mater.).
[5] A. J. Maeland and G. G. Libowits, J. Less Common Met. 89,
197-200 (1983).
[6] D. W. Aylmore, S. J. Gregg and W. B. Jepson, J. Nucl. Mater.
2, No.2, 169-175 (1960).
[7] D. W. Aylmore, S. J. Gregg and W. B. Jepson, J. Nucl. Mater.
3, No.2, 190-200 (1961).
[8] R. A. Anderl, K. A. McCarty, M. A. Oates, D. A. Petti, R. J.
Pawelko and G. R. Smolik, J. Nucl. Mater. 258-263, 750-756(1998).
[9] K K. Wada, K. Munakata, M. Nakamichi, J. H. Kim,K. Yonehara and D. Wakai, Oxidation Resistance of Be12Ti
Fabricated by Plasma-Sintering, Proc. 15th Int. Conf. on
Fusion Reactor Materials, Charleston, USA, October 2011
(submitted to J. Nucl. Mater.).
[10] Y. Sato, M. Uchida, H. Kawamura, High Temperature
Oxidation Behavior of Titanium Beryllide in Air, Proc. 6thIEA Int. Workshop on Beryllium Technology for Fusion,
Miyazaki, Japan, December 2003, JAERI-Conf 2004-006,p. 203.

Fig. 5 XRD spectra of central (a) and peripheral (b) parts ofthe plasma sintered titanium beryllide disc after exposure towater vapor.

and H2 gas generation. These results obviously suggest thatthe oxidation resistance for the central sample part of theplasma sintered beryllide disc is higher than that for theperipheral part. Therefore, as mentioned above, larger
fraction of highly reactive Be in the titanium beryllide leads(i) to increase in the amount of H2 gas generated underexposure to water vapor and (ii) to poor oxidation resistanceof the surface.

4. Conclusion

Center and peripheral parts (with different surface area
fractions of Be, Be12Ti, Be17Ti2, and Be2Ti phases) were cut
and extracted from a plasma sintered Be12Ti disk in order toinvestigate the effect of the surface area fraction difference
on not only the H2 gas generation under exposure to watervapor but also oxidation property. It has been shown that theamount of hydrogen generated for the surface of the central
part of the titanium beryllide disc was smaller than that forthe peripheral part. This difference can be explained bylower fraction of the Be phase surface area on the surface ofthe central part in comparison with that for the peripheral
part. The oxidation property for both parts did not exhibit
big difference, while both titanium beryllides parts
demonstrated higher oxidation resistance compared tometallic beryllium.

5. Acknowledgments

This work was supported by Japan Atomic Energy
Agency under the Joint Work contract 23K131, as a part of101