Beryllium Intermetallic Compounds Research Articles

Reactivity with water vapor and hydrogen storage capacity of Be2Ti compound

Beryllium intermetallic compounds show a variety of excellent properties such as neutron multiplication, refractory function, hydrogen storage, and superconductivity. Be12M compounds (M = Ti, V, and Zr) have been investigated as neutron multipliers for fusion reactors, while Be17M2 compounds have been explored as refractory materials. Furthermore, Be2Ms are known to have Laves phases, which are characterized by an A2B type compound having high H2 gas storage potential. Because of its low density, the hydrogen properties of Be2Ms have attracted great interest from viewpoints of reactivity with H2O, trap site of hydrogen, and amount of H2 gas in this compound. However, few studies have dealt with Be2M, and its database remains unsatisfactory.Preliminary synthesis of a beryllium intermetallic compound (=Be2Ti) as a hydrogen storage material was conducted to clarify its reactivity with water vapor at high temperatures and high hydrogen storage capacity. X-ray diffraction profiles and electron-probe microanalysis results confirmed that the preliminary synthesis of single-phase Be2Ti by homogenization treatment and plasma sintering was successful. The hydrogen generation rate of Be2Ti by reaction with 1% H2O increased as the test temperature increased. High temperature exposure to H2O led to the formation of TiO2 on the surface. Furthermore, the hydrogen gas storage concentration of Be2Ti, evaluated using the pressure–concentration–temperature curve, was 0.56 wt.% (=0.125 H/M) at 298 K, which is relatively low considering that H2 pressure was increased up to 13 MPa. Based on additional pressure–composition–temperature measurements, it does not appear to have particle size dependence with regard to hydrogen capacity.A simulation based on first-principles calculation indicated the presence of two hydrogen trap sites, tetrahedral and center of triangle with solution energies of −0.52 and −0.05 eV, respectively, implying that the maximum trap site of hydrogen with 5.4 wt.%. This dissimilarity might be attributed to the fact that the Be2Ti sample contained a large fraction of surface oxide layer, which disturbed the surface penetration of hydrogen.

Hydrogen retention behavior of beryllides as advanced neutron multipliers

Beryllium intermetallic compounds (beryllides) are the most promising candidate materials for use as advanced neutron multipliers in future fusion reactors because of their low swelling and high stability at high temperatures. Recently, beryllium–titanium beryllide pebbles such as Be12Ti have been successfully fabricated using a novel granulation process. In this study, the fundamental aspects of the behavior of hydrogen isotopes in Be12Ti pebbles were investigated via thermal desorption spectroscopy and transmission electron microscopy. In addition, atomistic calculations using first principles electronic-structure methods were applied to determine the solution energy of hydrogen in Be12Ti. The results showed simpler and weaker hydrogen-trapping efficiency for Be12Ti than for pure Be.

Beryllide pebble fabrication of Be–Zr compositions as advanced neutron multipliers

Fusion reactors require advanced neutron multipliers with high stability at high temperatures. Beryllium intermetallic compounds (beryllides) have a universally robust potential for high temperature use. Fabrication of beryllide pebbles of Be–Zr compositions was conducted from the viewpoint of pebble mass production. Prototypic pebbles were successfully fabricated using the plasma-sintered electrodes with high Be and Zr contents for enhanced of the thermal shock resistivity of the electrodes during granulation by a rotating electrode method. From the results of granulation examinations, it was revealed that granulation yields varied greatly depending on compositions of the plasma-sintered electrodes themselves. By utilizing plasma-sintered electrodes with high Be and Zr contents, Be13Zr pebbles had a high granulation yield of 84%. Moreover, the Be13Zr pebbles displayed better oxidation properties as compared to pure Be pebbles.

Synthesis of Be–Ti–V ternary beryllium intermetallic compounds

Beryllium intermetallic compounds (beryllides) such as Be12Ti and Be12V are the most promising advanced neutron multipliers in demonstration power reactors. Advanced neutron multipliers are being developed by Japan and the EU as part of their Broader Approach activities. It has been previously shown, however, that beryllides are too brittle to fabricate into pebble- or rod-like shapes using conventional methods such as arc melting and hot isostatic pressing. To overcome this issue, we developed a new combined plasma sintering and rotating electrode method for the fabrication of beryllide rods and pebbles.Previously, we prepared a beryllide pebble with a Be–7.7at.% Ti composition as the stoichiometric value of the Be12Ti phase; however, Be17Ti2 and Be phases were present along with the Be12Ti phase that formed as the result of a peritectic reaction due to re-melting during granulation using the rotating electrode method. This Be phase was found to be highly reactive with oxygen and water vapor. Accordingly, to investigate the Be phase reduction and applicability for fabrication of electrodes prior to granulation using the rotating electrode method, Be–Ti–V ternary beryllides were synthesized using the plasma sintering method.Surface observation results indicated that increasing plasma sintering time and V addition led to an increase in the intermetallic compound phases compared with plasma-sintered beryllide with a Be–7.7at.% Ti composition. Additionally, evaluation of the reactivity of samples with water vapor at high temperature revealed that specimens with larger fractions of Be phases experienced larger weight gains and H2 generation rates because of oxidation, as Be12Ti and Be12V phases have a similar oxidation tendency.

Comparative study of sinterability and thermal stability in plasma-sintered niobium and vanadium beryllides

Niobium and vanadium–beryllium intermetallic compounds (beryllides) were synthesized by plasma sintering under different sintering times at 1273K. The beryllide with 7.7at.% Nb mainly consisted of various phases of Be, Be12Nb, Be17Nb2, and Be2Nb, whereas that with 7.7at.% V consisted of Be12V, Be2V, and V. As the sintering time increased, area fractions of the target compositions Be12Nb and Be12V increased while that of Be decreased. A comparative analysis demonstrated that the beryllide with 7.7at.% Nb a showed higher density as well as a greater hardness than that with 7.7at.% V, due to there being less difference between the sintering temperature and the melting point. In terms of thermal phase stability, the beryllide with 7.7at.% Nb showed good thermal phase stability with fewer pores and a smaller unhomogenized area, because the beryllide contained a smaller area fraction of the Be phase, which may cause evaporation resulting in pore formation.

Development of Advanced Neutron Multipliers for DEMO Blankets

Advanced neutron multipliers with low swelling and high stability at high temperatures are desired for the pebble bed blankets of demonstration fusion power (DEMO) reactors. Beryllium intermetallic compounds (beryllides) such as Be12Ti are the most promising material for this purpose. To fabricate the beryllide pebbles, a new granulation process has been established that combines a plasma sintering method for beryllide synthesis and a rotating electrode method using a plasma-sintered electrode for granulation. In trial granulation examinations, prototypic beryllide pebbles 1 mm in diameter were successfully fabricated. This study describes the results of a crush test and the characterization of the oxidation properties of the prototypic beryllide pebbles compared with those of Be pebbles. The crush test revealed that the prototypic beryllide pebble was more brittle than a Be pebble, and its crush load is one-third that of a Be pebble. The oxidation experiment showed that the weight gain ratios of the prototypic beryllide pebbles were significantly smaller than those of pure Be pebbles. The results confirmed that the prototypic beryllide pebbles have better oxidation resistance than pure Be pebbles.

Fabrication of beryllide pebble as advanced neutron multiplier

Fusion reactors require advanced neutron multipliers with great stability at high temperatures. Beryllium intermetallic compounds, called beryllides such as Be12Ti, are the most promising materials for use as advanced neutron multipliers. However, few studies have been conducted on the development of mass production methods for beryllide pebbles. A granulation process for beryllide needs to have both low cost and high efficiency. To fabricate beryllide pebbles, a new granulation process is established in this research by combining a plasma sintering method for beryllide synthesis and a rotating electrode method using a plasma-sintered electrode for granulation. The fabrication process of the beryllide electrode is investigated and optimized for mass production. The optimized beryllide electrode exhibits higher ductility and can be sintered at a lower temperature for a shorter time, indicating that it is more suitable not only for withstanding the thermal shock from arc-discharge during granulation but also for producing the beryllide pebbles on a large scale. Accordingly, because these optimization results can reduce the time required for electrode fabrication by 40%, they suggest the possibility of great reductions in time and cost for mass production of beryllide pebbles.

Oxidation resistance of Be12Ti fabricated by plasma-sintering method

Titanium beryllium intermetallic compounds (beryllides), such as Be12Ti, are alternatives to metallic beryllium as the neutron multiplier for the fusion reactor blanket. Be12Ti is known to have advantages over metallic beryllium, which includes a high melting point, lower swelling and higher chemical stability. This work examined the oxidation resistance of Be12Ti samples fabricated by a plasma-sintering. Metallic beryllium and Be12Ti samples were placed under a flow of an argon gas containing 10,000ppm of water vapor at the temperature of 1273K for 24h. The Be12Ti sample fabricated was shown to have higher oxidation resistance than metallic beryllium.

Novel granulation process of beryllide as advanced neutron multipliers

Advanced neutron multipliers with low swelling and high stability at high temperatures are desired for pebble bed blankets of demonstration fusion power (DEMO) reactors. Beryllium intermetallic compounds (beryllides) are the most promising advanced neutron multipliers. In order to fabricate the beryllide pebbles, beryllide with shapes of block and/or rod is necessary when a melting granulation process is applied such as a rotating electrode method. A plasma sintering method has been proposed as new technique which uses a non conventional consolidation process. It was clarified that the beryllide could be simultaneously synthesized and jointed by the plasma sintering method in the insert material region between two beryllide blocks. Beryllide rod of Be12Ti with 10mm in diameter and 60mm in length has been successfully fabricated by the plasma sintering method. Using this plasma-sintered beryllide rod, fabrication of prototype beryllide pebble was performed by a rotating electrode method as one of the melting methods. The prototype pebbles of Be12Ti with 1mm in average diameter were successfully fabricated.

Oxidation behavior of plasma sintered beryllium–titanium intermetallic compounds as an advanced neutron multiplier

Beryllium intermetallic compounds (beryllides) such as Be12Ti are very promising candidates for advanced neutron multiplier materials in a demonstration fusion power reactor (DEMO). However, beryllides are too brittle to be fabricated either into pebble-type or rod-type shapes via conventional methods (i.e. arc melting and hot isostatic pressing). We have proposed a plasma sintering technique as a new method for beryllide fabrication, and our studies on the properties of plasma sintered beryllides are ongoing.In the present work, the oxidation properties of plasma sintered beryllides were investigated at 1273K for 24h in a dry air atmosphere to evaluate the high temperature properties of this material. Thermal gravimetry measurements indicate that specimens with larger fractions of Be12Ti phase corresponding to samples that have been sintered for longer time periods, exhibit superior oxidation properties.Our evaluation of the oxidation behavior of each phase in our beryllide samples is as follows: Be12Ti and Be17Ti2 both have good oxidation resistance, owing to the formation of dense and protective scales, while the Be and Be2Ti phases are mainly responsible for thermal-gravimetry (TG) weight gains, which is indicative of severe oxidation. We attribute the degradation in oxidation resistance specifically to Be2Ti that transforms into TiO2, and also find this phase to be the cause of deterioration in the mechanical properties of samples, owing to cracks near Be2Ti phase conglomerates.

Homogenization treatment to stabilize the compositional structure of beryllide pebbles

Abstract Fusion reactors require advanced neutron multipliers with higher stability at high temperatures. Beryllium intermetallic compounds (beryllides) such as Be12Ti are the most promising advanced neutron multipliers. In order to fabricate the beryllide pebbles, a new granulation process has been established that combines a plasma sintering method for beryllide synthesis and a rotating electrode method for granulation. The results of synthesis show that beryllide rod has been successfully fabricated by the plasma sintering method. From this plasma-sintered beryllide rod, prototypic beryllide pebbles of 1 mm average diameter were also successfully fabricated, by the rotating electrode method. Unfortunately, remelting changed the compositional structure of the beryllide pebbles. To homogenize the Be12Ti phase, annealing treatments were examined. The pebble phase was successfully homogenized to a single phase of Be12Ti by annealing either at 1473 K for more than 8 h or at 1673 K for 1 h.

Preliminary characterization of plasma-sintered beryllides as advanced neutron multipliers

Advanced neutron multipliers with low swelling and high stability at high temperatures are desired for pebble bed blankets of demonstration fusion power (DEMO) reactors. Beryllium intermetallic compounds (beryllides) are the most promising advanced neutron multipliers. The plasma sintering method has been selected as a new synthesis method for beryllides because this method is very simple and easy to control. Plasma sintering is a non-conventional consolidation process. The plasma sintering results in starting-powder particle surface activation that enhances sinterability and reduces high temperature exposure. The sintering properties of beryllides were evaluated. Results show that intermetallic beryllide compounds such as Be12Ti, Be17Ti2 and Be2Ti can be directly synthesized by the plasma sintering method from mixed elemental powders of Be and Ti at a temperature below the melting point. The preliminary characterization of plasma-sintered Be–Ti beryllide was carried out including examination of oxidation with water vapor, microstructure analysis, irradiation effects, and deuterium retention compared with beryllium (Be) metal. The preliminary characterization revealed that the plasma-sintered Be–Ti beryllide sample performs well as a neutron multiplier. This beryllide sample has better oxidation resistance, higher radiation resistance and lower deuterium retention than Be metal.

Comparative study on arc-melted and plasma-sintered beryllides

This study compares arc-melted and plasma-sintered beryllides, beryllium intermetallic compounds, investigating the effects of density, hardness, microstructure, and annealing on stability. From the electron probe micro-analyzer and X-ray diffraction analysis results, it was obvious that the plasma-sintered samples, including those with 3 and 5at.% Ti, were composed of α-Be and Be12Ti phases, while Be17Ti2 and Be2Ti phases were additionally observed for the Be–7at.% Ti sample. In case of the arc-melted beryllides, it consisted of α-Be and Be12Ti in the 3at.% Ti and 5at.% Ti samples, whereas the Be12Ti phase surrounded Be10Ti as a peritectic phase for Be–7at.% Ti. Density and hardness measurements confirmed that the plasma-sintered beryllides were sintered with higher density and hardness than the arc-melted beryllides. It is suggested that the higher sinterability and greater amount of Be12Ti phase resulted in increased density and hardness, respectively. In addition, the annealing treatment at 1473K for 5h was carried out to investigate the homogenization of the compositional structure. From the results of observation analysis for the specimens denoted as Be–3at.% Ti and Be–5at.% fabricated by both methods, there was no change on compositional structure. However, for arc-melted Be–7at.% Ti, the Be phase was almost diminished, whereas there was a slight increase in the Be12Ti phase and a slight decrease in the Be10Ti phase. In the case of the plasma-sintered Be–7at.% Ti specimen, it was clarified that the Be17Ti2 and Be2Ti phases were homogenized into the Be12Ti phase.

Development of a synthesis method of beryllides as advanced neutron multiplier for DEMO reactors

Advanced neutron multipliers with low swelling and high stability at high temperature are desired for pebble bed blankets, which will impact on the DEMO design features, especially blanket operating temperature. Among candidates for multiplier, beryllium intermetallic compounds (beryllides) are one of the most promising advanced neutron multipliers. In order to fabricate the beryllide pebble, beryllide with the shape of rod are necessary if a melting granulation method is applied. A plasma sintering method and a high-frequency heating method have been proposed as a new technique, because these methods are simple process and easy to control. A plasma sintering method for beryllide synthesis has been proposed as a new technique which uses a non-conventional consolidation process. The present paper describes beryllide synthesis results using this method for development of fabrication technique for a beryllide rod. It was clarified that the beryllide could be both synthesized and jointed with no variation of phase and hardness by the plasma sintering method. Additionally, trial synthesis of beryllide by a melting process using high-frequency heating was carried out. Although there were some pores in a melted ingot, beryllides could be also synthesized by this method.

Development of fabrication technologies for advanced breeding functional materials For DEMO reactors

Demonstration power reactors (DEMOs) require advanced tritium breeders and neutron multipliers that have high stability at high temperatures. Lithium titanate (Li2TiO3) is one of the most promising candidates among tritium breeders because of its tritium release characteristics. Li2TiO3 with additional Li (Li2+xTiO3+y) has increased stability in a reducing atmosphere at high temperatures. In this work, Li2+xTiO3+y pebbles were fabricated using the emulsion method, which is a sol–gel method. The raw material for the fabrication of Li2+xTiO3+y pebbles was synthesized from a mixture of LiOH·H2O and H2TiO3 at specific ratios. The average diameter and the sphericity of the pebbles fabricated by the emulsion method were 1.40mm and 1.02, respectively. In addition, beryllium (Be) intermetallic compounds (beryllides) are promising materials for advanced neutron multipliers. The results of the trial fabrications in this work showed that beryllides of Be–Ti and Be–V intermetallics could be synthesized using the plasma sintering method.

Trial fabrication of beryllides as advanced neutron multiplier

Beryllium metal is considered as the neutron multiplier in the pebble bed blanket. On the other hand, advanced neutron multipliers with lower swelling and higher stability at high temperature are desired in pebble bed blankets for DEMO. Beryllium intermetallic compounds (beryllides) are the most promising advanced neutron multipliers. However, beryllides are too brittle to allow production of pebbles. Establishing fabrication techniques for beryllides is a key issue of advanced neutron multiplier development. In the previous study, it was clear that the intermetallic compound beryllides of Be–Ti can be directly synthesized by the plasma sintering method. In this study, it reports on the trial fabrication results of beryllides synthetic such as Be–V and Be–Nb using plasma sintering method for applicability evaluation of beryllide synthesis. The formation of Be–V and Be–Nb intermetallics was identified using a mixture of Be and V or Be and Nb particles for the plasma sintering method.

Sintering properties of beryllides for advanced neutron multipliers

Advanced neutron multipliers with low swelling and high stability at high temperature are desired for pebble bed blankets, which will impact the DEMO design features, especially the blanket operating temperature. Beryllium intermetallic compounds (beryllides) are the most promising advanced neutron multipliers. However, beryllides are too brittle to allow production of pebbles. Establishing fabrication techniques for beryllides is a key issue of advanced neutron multiplier development.Plasma sintering is a non-conventional consolidation process for beryllides synthesis. The sintering properties of beryllides were then evaluated. The formation of Be12Ti and Be17Ti2 intermetallics was identified using a mixture of Be and Ti particles for the plasma sintering method.

Application of beryllium intermetallic compounds to neutron multiplier of fusion blanket

Beryllium metal is commonest as a neutron multiplier of fusion blanket. However, the application of beryllium metal to DEMO reactor that requires higher temperature (600–900 °C) is very severe, because the melting point is low (1285 °C) and the starting temperature of swelling by neutron irradiation is low (∼500 °C). Therefore beryllium intermetallic compounds that have high melting point have been expected as the advanced material for fusion DEMO blanket. Several R&D concerning the characterization and the fabrication technology for beryllium intermetallic compounds have been performed in Japan that takes a leading part in these R&D. From the results of these R&D, it made clear that beryllium intermetallic compounds had excellent property and the feasibility as the neutron multiplier for fusion DEMO blanket. In addition, fabrication technology for the pebbles was studied.

Mechanical properties of high- temperature beryllium intermetallic compounds

Mechanical properties of high- temperature beryllium intermetallic compounds

Magnetic properties, hyperfine interactions, and spin dynamics of rare earth–beryllium intermetallic compounds

Measurements of lattice parameter, magnetic susceptibility, and 9Be nuclear magnetic resonance and relaxation were performed in a series of rare-earth–beryllium intermetallic compounds REBe13 (RE = La, Cc, Nd, Gd). The anomalous results in CeBe13 can be inter-preted in terms of the presence of variable concentrations of Ce3+ and Ce4+ ions in the sample with a lifetime of the order of 10−13 s. In NdBe13 it is found that crystal field effects are important in the temperature range investigated and they preclude magnetic order down to 1.5°K. GdBe13 becomes ferromagnetic at about 22°K but the magnetic susceptibility is anomalous below about 100°K. Both in NdBe13 and GdBe13 the 9Be asymmetric NMR spectrum at high temperature can be explained by considering only the magnetic dipolar interaction of the nuclei with the paramagnetic moments while the isotropic part of the shift is small and negative. From the 9Be spin–lattice relaxation at high temperature reasonable values for the electronic exchange coupling parameter are obtained. Messungen der Gitterparameter, der magnetischen Suszeptibilität und der 9Be-Kernresonanz und -Relaxation wurden an einer Reihe von intermetallischen Seltenen Erden–Beryllium-Verbindungen SEBe13 (SE = La, Ce, Nd, Gd) durchgeführt. Die anomalen Ergebnisse in CeBe13 lassen sich mit der Anwesenheit von verschiedenen Konzentrationen von Ce3+- und Ce4+-Ionen in der Probe mit einer Lebensdauer der Größenordnung 10−13 s erklären. Es wird gefunden, daß in NdBe13 Kristallfeldeffekte im untersuchten Temperaturbereich wesentlich sind, die bis herab zu 1,5°K magnetische Ordnung verhindern. GdBe13 wird bei ungefähr 22°K ferromagnetisch, jedoch ist die magnetische Suszeptibilität anomal unterhalb ungefähr 100°K. Sowohl in NdBe13 als auch in GdBe13 kann das asymmetrische 9Be-NMR-Spektrum bei hohen Temperaturen allein durch magnetische Dipolwechselwirkung der Kerne mit den paramagnetischen Momenten erklärt werden, während der isotrope Anteil der Verschiebung klein und negativ ist. Aus der 9Be-Spin–Gitter-Relaxation bei hohen Temperaturen werden vernünftige Werte für die elektronischen Austauschkopplungsparameter erhalten.