Beryllium Intermetallic Compounds Research Articles

Effect of temperature on mechanical properties of beryllium intermetallic compounds fabricated by plasma sintering

This purpose of study is to establish the material database of neutron multiplier for the JA DEMO design. In the previous study, we reported the effects of sintering conditions as temperature and pressure on hardness and sintered density mainly in the sintering temperature from 1050 °C to 1200 °C. In this study, the microstructure observation and compressive tests were carried out. As results of microstructure observations, the pores were almost disappeared, and the grain size increased with increase in sintering temperature. Compression tests were carried out from room temperature (R.T.) to 1000 °C with the samples sintered at 1200 °C. The compressive strength at R.T. was approximately 1.69 GPa. With the increase in testing temperature, there was a tendency for the strength to decrease from 800 °C to 1000 °C. In addition, the load-compressibility indicated that the yield point appears at 850 °C.

Development of advanced ternary beryllium intermetallic compounds

A ternary beryllide was prepared by mixing Be12V with Be12Ti and using plasma sintering. After preparation at a pressure of 54 MPa for 20 min at 1200 °C, the changes in mechanical and thermal properties due to the addition of 1 wt.% Be12V and 10 wt.% Be12V were investigated. The Vickers hardness of both Be12Ti+1 wt.%Be12V and Be12Ti+10 wt.%Be12V were lower than Be12Ti. In addition, the fracture toughness was calculated using the IF method, and the calculation formula was calculated using various equations. According to the Anstis equation, it was 3.23 ± 0.13 MPa·m0.5 for Be12Ti, and it increased to 4.47 ± 0.13 MPa·m0.5 for Be12Ti+1 wt.%Be12V. As Be12V was added, it increased compared to Be12Ti. In the case of thermal properties, the thermal diffusivity of Be12Ti and Be12Ti+1 wt.%Be12V showed almost the same value, while that of Be12Ti+10 wt.%Be12V was lower than others. In the case of specific heat, moreover, it tended to decrease as the temperature increased in comparison to Be12Ti. This trend was particularly evident when 10 wt.% Be12V was added. Thus, the results of the thermal conductivity calculation indicated a decrease in tendency as the amount of addition increased in comparison to Be12Ti. Therefore, the addition of 1 wt.% Be12V seems to be more effective than the addition of 10 wt.% Be12V.

Study of Vacancy Clusters and Antisite Defects in Titanium Beryllide Be12Ti Using Positron Annihilation Spectroscopy

Beryllium (Be) intermetallic compounds (beryllides) are promising materials for neutron multiplication in fusion reactors. In particular, titanium beryllide (Be12Ti) exhibits low swelling and good corrosion resistance compared to other beryllides. Herein, the defects in neutron‐irradiated Be12Ti are investigated using positron annihilation spectroscopy, and the results are analyzed based on positron annihilation calculations. Calculation results indicate that the positron lifetime in a perfect Be12Ti crystal is 134.2 ps, while that of a Be monovacancy is found to be within the 177.3–195.0 ps range, depending on the configuration of the monovacancy. On the other hand, the positron lifetime of the Ti monovacancy is 222.7 ps. In addition, the lifetimes of the Be and Ti vacancy clusters increase with an increase in the number of vacancies. Finally, the positron lifetimes of the antisite defects in different configurations are found to be within the 137.9–141.7 ps range. In contrast to the calculated results, the positron lifetime of unirradiated Be12Ti is 141.1 ps. Furthermore, in the neutron‐irradiated Be12Ti, no vacancies are detected and only Be dislocation loop formation occur based on the calculation results. Although the irradiation dose of Be12Ti is low, its irradiation resistance is satisfactory.

Helium swelling behavior for neutron multipliers after irradiation with He ions at high temperatures

Beryllides as beryllium intermetallic compounds are the advanced multiplier materials as candidate materials for fusion demonstration power plant (DEMO) due to having good properties such as low swelling rate and stable chemical properties.Under DEMO operation environment, the generated He amounts in beryllium are estimated around 20,000 appm He. This study was evaluated the effect of He fluence and irradiation temperature on the bubble behaviors in Be12Ti and beryllium. The irradiation of He ion was carried out using an In-situ transmission electron microscope equipped with an ion gun by implantation up to 25,000 appm He. For comparison, beryllium was carried out in similar experiments.Bubbles were observed in Be12Ti at 873 K after the implantation of 15,000 appm He, while in Be at the same temperature, their appearance occurred post-implantation of 4,500 appm He. In addition, growth of bubbles in beryllium was observed with increase of He ion fluence. Sizes and densities of bubbles in Be12Ti and beryllium were evaluated irradiated in 25,000 appm He at 673 and 873 K.In the case of Be12Ti, fine bubbles were observed in a high density state, and it was found that the swelling rate was a few percent. By contrast, bubbles in beryllium had a diameter in the range from tens to several tens nanometers, and growth of these bubbles were observed. The swelling rate of beryllium was approximately 18 %.

Compression properties of beryllide pebbles at high temperatures

DEMO (demonstration) fusion reactors require advanced neutron multipliers with low swelling and high stability at high temperatures. Research on beryllium intermetallic compounds (beryllides (Be12V)) has been conducted, and the authors have successfully fabricated Be12V and Be12Ti0.3V0.7 ternary pebbles, which are considerably stable at high temperatures. In this study, to evaluate the mechanical properties of these pebbles, compression tests for a single pebble were performed at room temperature and high temperatures of 600 and 800 K. Be12Ti0.3V0.7 pebbles exhibited a higher crush load than Be12V pebbles; Be12Ti0.3V0.7 pebbles comprised remarkably fine grains due to dual phases. Scanning electron microscopy images of the fractured area demonstrated that the Be12V pebbles had a relatively large fracture with sharp edges, whereas the Be12Ti0.3V0.7 pebbles included considerably small grains. There was no noticeable temperature dependence of the crush load. The fracture and tensile strengths of Be12V and Be12Ti0.3 V0.7 pebbles were evaluated.

Comparative study of surface modification and D retention between beryllium and beryllides under high flux plasma exposure

• The microstructure and D retention of Be and beryllides, Be 12 Ti and Be 12 V were investigated. • Cone structures form on the Be surface exposed to the plasmas by sputtering. • The amorphous layer is induced on the surface of beryllides, which might effectively trap D. • The surface enrichment of Ti or V on beryllides occurs due to preferential sputtering of Be. • Beryllides exposed to the D + 10%He plasma show lower total retentions of D than in Be. The microstructures and deuterium (D) retention properties were investigated for beryllium intermetallic compounds (beryllides), such as Be 12 Ti and Be 12 V, compared to pure beryllium (Be), exposed to high density pure D and helium (He) mixed plasmas. TEM cross-sectional observations revealed the formation of cone structures on the Be surface exposed to the plasmas at a moderate temperature of 573 K. The crystal structure of the cones and the mass loss caused by the plasma exposure implied that the cone structures were generated by sputtering. The Ti or V surface enrichment was observed on both beryllides with no cone structures developed. TDS measurements indicated that He seeding to D plasma caused a ~ 4 times reduction of the D retention for both beryllides, while no reduction was observed for Be. As a result, the beryllide samples exposed to D + He mixture plasmas showed a lower total D retention than in Be.

Deuterium desorption and retention of Beryllium intermetallic compounds for fusion applications

Beryllium intermetallic compounds (beryllides) such as Be12Ti and Be12V are the most promising advanced neutron multipliers in demonstration (DEMO) power reactors because of their low swelling and high stability at high temperatures. In this work, beryllides pebbles with binary and ternary compositions were successfully fabricated by combining plasma sintering and rotating electrode methods. After 3 keV D2+ ions were implanted to the beryllides pebbles, the deuterium desorption and retention properties were investigated by thermal desorption spectroscopy to investigate hydrogen desorption and retention of these materials for fusion application.The desorption properties and retention of hydrogen isotopes (deuterium) using the newly developed beryllide pebbles indicated that the beryllide pebbles exhibited better deuterium desorption properties, such as lower starting-up temperature, total retention, and activation energy for deuterium desorption than beryllium.

A recycling process on vanadium beryllium intermetallic compounds as advanced neutron multipliers for DEMO fusion applications

Abstract Beryllium intermetallic compounds (beryllides) are known as promising materials for advanced neutron multipliers for fusion applications owing to their high stability and low swelling. Because a large amount of beryllium is used for each solid breeding blanket in fusion reactors, the development of effective and efficient recycling processes is essential. In this study, a proper recycling process of Be12V pebbles was proposed, which combines a plasma sintering and a rotating electrode method for the fabrication of beryllide pebbles. As a result of experiments, it is determined that the rotating electrode method is available to reduce oxygen impurities, whereas the plasma sintering process can eliminate Li impurities and hydrogen isotope depending on sintering temperature. Regarding the recycling process, the beryllide pebbles used can be recycled into rods by plasma sintering, in which Li impurity and tritium can be eliminated. Then, recycled rods can be granulated by the rotating electrode method. During this process, it is anticipated that oxygen impurities and irradiation defects can be eliminated because the rotating electrode method includes the melting process. Thus, the current process was determined to be appropriate as a recycling process for beryllide pebbles.

The role of beryllium in alloys, Zintl phases and intermetallic compounds

AbstractAlthough beryllium is widely used as alloying component in diverse light-weight alloys, the crystal chemistry of beryllium containing Zintl phases and intermetallic compounds is only scarcely developed and only few phase diagrams, mostly the industrially relevant ones, have been studied in detail. The present review summarizes the crystal chemical data of binary and ternary beryllium intermetallic compounds along with the results of the few documented physical property studies.

Effect of grain size on the sinterability and reactivity of vanadium-beryllium intermetallic compounds

Vanadium beryllium intermetallic compounds (Be12V beryllides) are attractive materials for refractory and fusion applications at high temperatures. In this study, to investigate the effect of grain size on sinterability and reactivity of beryllides at high temperatures (expecting operation temperatures), single-phase vanadium beryllides with different grain sizes were fabricated via pulverization of homogenized powders and plasma sintering.While evaluating sintered Be12V, as the ball-milling time increased, the powder size decreased. As this grain size deceased, density and hardness increased. With respect to thermal expansion, the coefficient of thermal expansion slightly increased with decreasing grain size. As results of reactivity and the scanning electron microscopic observations, it indicated that grain boundary oxidation is predominant at 1273 K, whereas intergranular oxidation prevails at 1473 K. Accordingly, as the grain size increased up to 10 μm, the weight gain and the H2 generation amount decreased at 1273 K and 1473 K, respectively.

Anomalous oxidation behavior in a zirconium beryllium intermetallic compound

Beryllium intermetallic compounds (beryllides) are well-known refractory and functional materials for fission and fusion applications, specifically as reflectors and multipliers. For advanced neutron multipliers, our research group has investigated many kinds of beryllides. Due to its nuclear properties, single phase Be13Zr beryllide was selected and successfully fabricated via plasma sintering of the homogenized Be13Zr powder. Its reactivity against 15% H2O was evaluated, and unexpected catastrophic oxidation (pest reaction) occurred at a low temperature range, from 973 to 1123 K, leading to the disintegration into a powder. This is caused by the intergranular degradation on the boundaries between the oxide layer and the matrix, as well as the continuous oxidation through cracks that arise from stress generation on the oxides. However, this pest reaction was suppressed by Si doping. Si likely relieves the stress near the grain boundary and in the oxide layer. The Si-doped Be13Zr had the lowest hydrogen generation rate among the evaluated samples at 1273 and 1473 K, which is also much lower by approximately two or three orders of magnitude than that of Be at 1273 K.

Reactivity and thermal stability of ternary Be-Zr-V beryllides

A water-cooled solid breeder blanket of a fusion reactor has been adopted in Japan, which focuses on safety concerns; safety is one of the most critical issues. In particular, as a multiplier, Be pebbles are well known to possibly generate hydrogen and react in an exothermic manner due to reaction with H2O during the loss of coolant accident. In contrast to these Be pebbles, beryllium intermetallic compounds (beryllides) demonstrate promise due to their more stable chemical reactivity at high temperatures. Currently, several studies have reported the development of advanced neutron multipliers in Japan, and the EU is part of the demonstration R&D activities at the International Fusion Energy Research Center project, which forms a part of the Broader Approach program. Fabrication methods for beryllide pebbles have been successfully developed by the combination of plasma sintering synthesis and a rotating electrode granulation method.By employing these methods, ternary beryllide pebbles with mixtures of Be13Zr and Be12V were first synthesized with ratios of 1.0:1.0, 1.0:0.8, 1.0:0.6, 1.0:0.4, 1.0:0.2, and 1.0:0.1. The small-sized Be13Zr phase as the precipitate and the Be12V phase were formed without the formation of the Be phase as these compositions did not exhibit the peritectic reaction. In addition, ternary beryllide pebbles exhibited a lower reactivity to water vapor as well as a higher thermal stability than Be pebble. In this study, not only the synthesis but also characterizations at high temperatures were discussed.

Granulation of Be12V pebbles using the rotating electrode method

Hydrogen generation via the oxidation of beryllium (Be) in the presence of water vapor at high temperatures needs to be minimized in fusion reactors because of safety concerns. Advanced neutron multipliers with increased stability at high temperatures are desirable in pebble bed blanket design with water coolant. Beryllium intermetallic compounds (e.g., vanadium beryllide Be12V) are a promising material that can be used as advance neutron multipliers. Granulation aims to produce beryllide pebbles that are a critical element in the development of advanced neutron multipliers.Based on previous trial granulations of beryllides, a rotating electrode method (REM) was selected [1–3]. Furthermore, its experimental dataset is broad, covering beryllium and metallic pebbles. Rod-shaped beryllide blocks are necessary to fabricate beryllide pebbles via the REM. Hot isostatic pressing and casting have been proposed to synthesize beryllides. However, pure beryllium-based intermetallic compounds have very limited plasticity at high rotational speeds. The use of Be–V rods containing pure beryllium phase was considered a reasonable solution to this problem. The microstructure of Be–V rods and pebbles confirmed that the REM produced single-phase Be12V pebbles from multiphase Be–V rods. Special emphasis has been placed on the yield properties, size distribution, and sphericity of vanadium beryllide pebbles fabricated under different granulation conditions. The effect of rotational speed and electric current on pebble fabrication with the REM is discussed in this study. Taking into account the high costs and restricted availability of beryllium products, the perspective of material re-use was also considered by the process development and appropriate granulation trials were performed.

Fabrication and characterization of Be-Zr-Ti ternary beryllide pebbles

Beryllium intermetallic compounds (beryllides) such as Be12Ti, Be13Zr and Be12V are the most promising advanced neutron multipliers for DEMO reactors (DEMOnstration fusion power plant). Plasma sintering and the rotating electrode methods for the fabrication of beryllide rods and pebbles have been established and a new chemical composition has been suggested as development of more advanced neutron multipliers. By using these methods, preliminary synthesis of the ternary Be-Zr-Ti pebbles has been conducted. In the Be13Zr1-xTix composition (x = 0.1, 0.3, 0.5, 0.7 and 0.9), some of the pebbles showed the existence of a Be phase on the surface, which results in mass gain and hydrogen generation. Ternary beryllide pebbles were successfully fabricated from mixtures of Be12Ti and Be13Zr with ratios of 1:1, 1:0.6, 1:0.4, 1:0.2 and 1:0.1. As a result of the SEM observations, it was clear that no Be phase was found on the surface of the pebbles despite of the fact that some fractions were identified inside the pebbles. For stability with 1% water vapor of as-received ternary pebbles at high temperatures, it was clear that those indicated much lower hydrogen generation, which corresponds to much higher stability than Be pebbles at high temperatures.

Characterization of vanadium beryllide pebble bed for the Japan DEMO blanket application

Beryllium intermetallic compounds (beryllides) are promising materials as advanced neutron multipliers for high-temperature applications. Methods of fabricating beryllides pebbles have been successfully developed by combining plasma sintering and rotating electrode granulation. To prevent an increase in the surface area and reactivity, as in the homogenized Be12Ti, we fabricated and characterized prototype pebbles of Be12 V, which do not undergo peritectic reactions during cooling. The Be12V pebbles were successfully fabricated without homogenization. The Be12V pebbles have good oxidation resistance with low hydrogen generation. The granulation yield of Be12 V pebbles was 70%. Packing fraction exhibited 60.5%. by vibration compaction with constrain. The effective thermal conductivity of a Be12V pebble bed with no-constraint was successfully measured.

Fabrication and characterization of crushed titanium–beryllium intermetallic compounds

To develop a technique for the mass production of beryllide pebbles, a crushing method for the granulation of beryllides was used in this study. Two types of crushed Be12Ti pebbles were prepared using mortar-ground (MG) and planetary-ball-milled (PM) powders. A granulation yield of approximately 50 wt.% with sizes in the range of 0.85–1.18 mm was achieved. Scanning electron microscopy (SEM) images revealed that the MG pebbles exhibited larger porosity because the larger size of the powder resulted in lower density with higher porosity. However, the considerably larger fraction of fine pores in the PM pebbles resulted in an increased Brunauer–Emmett–Teller (BET) specific surface area, as clearly demonstrated by high-magnification SEM images. To evaluate the reactivity with water vapor, the weight gain and H2 generation rate were also investigated. The results suggested that the PM pebbles exhibited notably lower reactivity, weight gain, and H2 generation rate, which may be due to the dramatically decreased BET specific surface. The fine pores were filled with stable oxides followed by a significant decrease of the surface area during oxidation. Optimization was performed to improve the circularity of the crushed pebbles. Grinding tests using planetary milling without balls for different times clearly demonstrated that the circularity improved (with an estimated value of 0.8) by cutting and polishing the sharp edges; however, long-duration milling for 99 h resulted in attachment of the polished powders to the pebble surface, leading to surface color variation of the crushed pebbles.

Development of beryllide pebbles with low-hydrogen generation as advanced neutron multipliers

Hydrogen generation via an oxidation reaction of Be with water vapor at high temperatures should reduce the safety associated with fusion reactors. Advanced neutron multipliers with higher stability at high temperatures are desired as replacements for the existing Be neutron multipliers for the pebble bed blanket design using a water coolant. Beryllium intermetallic compounds (beryllides) are the most promising material for advanced neutron multipliers. In this study, prototypic beryllide pebbles, Be12Ti and Be12V, were successfully fabricated using the rotating electrode granulation method with a plasma-sintered beryllide electrode. The beryllides pebbles were much more resistant to water vapor than pure Be pebbles. The surface BeO layer on the beryllide pebbles was shown to act as a protective barrier against hydrogen generation reaction.

Deuterium retention and desorption properties of ternary beryllide pebbles as advanced neutron multipliers

Beryllium intermetallic compounds (beryllides) such as Be12Ti and Be12V are the most promising advanced neutron multipliers in demonstration (DEMO) power reactors because of their low swelling and high stability at high temperature. In this work, single-phase Be12Ti and Be12V pebbles produced by a novel process combining plasma sintering and rotating electrode methods were successfully fabricated. In parallel to the successful fabrication of binary beryllide pebbles, new research and development on ternary beryllides was begun to determine preferable pebble compositions in terms of mass production and improved properties. The desorption properties and retention of hydrogen isotopes (deuterium) using the newly developed ternary beryllide pebbles indicated that the ternary pebbles exhibited better deuterium desorption properties, such as lower starting-up temperature, total retention, and activation energy for deuterium desorption, than these for beryllium.

Thermal analyses of beryllide pebbles in water vapor atmosphere as advanced neutron multipliers

The safety of the water coolant solid breeder blanket of a fusion reactor has become one of the most critical issues. In particular, Be pebbles as a multiplier material have been well-known to generate hydrogen and exothermally react while reacting with water vapor at high temperature. Unlike these Be pebbles, beryllium intermetallic compounds (i.e., beryllides) are one of the most promising materials because of their significantly higher chemical stability.Beryllides pebbles have been successfully fabricated by a number of approaches developcombining plasma sintering synthesis and rotating electrode granulation methods Thus, as-received Be12Ti pebbles (consisting of Be, Be12Ti, and Be17Ti2 phases), homogenized Be12Ti pebbles, and as-received Be17Ti2 pebbles have been successfully fabricated. The oxidation, hydrogen generation, and thermal expansion properties of these pebbles were investigated and compared with those of the reference Be pebbles.Beryllides pebbles were significantly more resistant to oxidation by H2O while generating lower amounts of hydrogen as compared to Be pebbles. Among these beryllides pebbles, homogenized Be12Ti pebbles and as-received Be17Ti2 pebbles showed lower weight gain and hydrogen generation than as-received Be12Ti because the latter contained some fractions of Be phase inside the pebbles. With regard to thermal expansion, it was obvious that the beryllides exhibited lower coefficients of thermal expansion (CTE) than Be.

Reactivity and deuterium retention properties of titanium-beryllium intermetallic compounds

Beryllium intermetallic compounds (beryllides), such as Be12Ti and Be12V, are the most promising advanced neutron multipliers in demonstration (DEMO) fusion power reactors because of higher stability, lower retention, and swelling. The advanced neutron multipliers are being developed by Japan and the EU as a framework of Broader Approach (BA) activities, targeted at broadening the research fields to not only establish fabrication methods but also for their characterization. Our group has proposed a plasma sintering method for the synthesis of beryllides. When the mixed powder was plasma-sintered at the beginning of the experiment, consolidation of the target composition was so insufficient that single-phase beryllides could not be synthesized. In order to obtain single-phase beryllides, an additional homogenization treatment of the sintered beryllides at 1473 K was necessary, resulting in increased porosity. Using the homogenized powder as the starting material, single-phase Be12Ti and Be17Ti2 intermetallic compounds were successfully synthesized. As experimental results, the hardness of the compounds was relatively low owing to low sintering density. In addition, the oxidation behavior of the beryllides, when exposed to 15% H2O/Ar at high temperatures, were investigated and the results indicate the presence, gray colored Be oxide formed on the surface in Be12Ti tested at above 1073 K and Be oxide with a small fraction of white colored Ti oxide even tested at 873 K in Be17Ti2 phase resulting in the bigger increase of the weight gain than Be12Ti. In addition, this oxidation occurring at lower temperature can be reasoned by the assumption that the existence of BeO (=oxygen content) in Be12Ti (1.95%) and Be17Ti2 (2.95%) may facilitate increased reactivity. Furthermore, thermal expansion of Be17Ti2 was found out to be bigger than that of Be12Ti because Be17Ti2 has more complex crystal structure and higher melting temperature. In terms of deuterium desorption and retention properties, the maximum peaks are detected around 600 K in beryllides, while those in beryllium occur at 800 and 980 K. From the comparison of deuterium retention, it was obvious that Be17Ti2 has a lower retention than Be12Ti, while Be has the highest value.