Liquid Metal Phase Research Articles

Qualification of tritium permeation barriers in liquid Pb–17Li

The reduction of tritium permeation from the Pb–17Li, or plasma, into the coolant is of crucial importance in order to reduce the radiological hazard in the steam generator vault as well as in the turbine/condenser area and to optimise the tritium balance in the reactor. The use of aluminium rich coatings has been selected as reference solution for the water cooled lithium lead (WCLL) blanket in order to produce reliable tritium permeation barriers (TPB). TPB qualification activities performed in the past allowed the selection of two reference deposition techniques, the chemical vapour deposition (CVD) process developed on laboratory scale by CEA, and the hot dipping (HD) process developed by FZK. On the basis of the results obtained in the past with the Corelli I–II devices, a new apparatus named Vivaldi was designed to perform comparative tests on two hollow cylindrical specimens in the same operating conditions. The performance of alumina coating on EUROFER 97 steel has been tested in gas and liquid metal phase. The obtained results in terms of permeated fluxes and permeation reduction factors (PRF) are herein presented and discussed. A post experiment examination of coatings was performed by use of optical and SEM microscopy.

Polarizability, correlation energy, and dielectric liquid phase of Bose-Einstein condensate of two-dimensional excitons in a strong perpendicular magnetic field

The coherent pairing of electrons and holes occupying only the lowest Landau level in a two-dimensional (2D) system with a strong perpendicular magnetic field is studied using the Keldysh-Kozlov-Kopaev method and generalized random phase approximation. Bose-Einstein condensation of the correlated pairs takes place in a single particle state with an arbitrary wave vector $\mathbf{k}$ in a symmetric 2D model. We show that the ground state energy per exciton and the chemical potential are nonmonotonic functions of the filling factor, so that metastable dielectric liquid states with positive compressibility exist, consisting of Bose-Einstein condensate of magnetoexcitons. It is shown that this dielectric liquid phase of the Bose condensed excitons is more stable than the metallic electron-hole liquid phase. The polarizability of the Bose-condensed magnetoexcitons is calculated using Anderson-type wave functions of the coherent excited states, which correspond to the appearance of one out-of-condensate electron-hole $(e\ensuremath{-}h)$ pair in the presence of the BCS-type ground state. The polarizability is characterized by a coherent factor which depends on $\mathbf{k}$ and vanishes when $\mathbf{k}$ tends to zero, as well as by a resonance frequency equal to the ionization potential of a magnetoexciton, and differs considerably from the polarizability of a noncondensed exciton gas. The condensate polarizability is used to determine the correlation energy of the system and the correction to the chemical potential beyond the Hartree-Fock-Bogoliubov approximation.

Structural transitions in silicon induced by a femtosecond laser pulse: The role of an electron-hole plasma and phonon-phonon anharmonicity

It is shown by the methods of time-resolved self-reflection and linear reflection that irradiation of a silicon target by a 100-fs laser pulse induces successive structural transitions of the target material to new crystal and liquid metal phases, which can occur during the laser pulse or 0.1–103 ps after the pulse termination, depending on the excitation conditions. The thresholds of these structural transitions are determined, and “’soft” phonon modes involved in them are identified, which represent “hot” short-wavelength LA modes. The dynamics of the structural transitions in silicon in the time interval from 0.1 to 103 ps is described using the model of instability of phonon modes caused by an electron-hole plasma and intra-and intermode phonon-phonon anharmonic interactions

Hydrogen permeation through tritium permeation barrier in Pb–17Li

One of the main problems in the development of water cooled lithium lead (WCLL) DEMO fusion reactor is the reduction of the tritium permeation from the Pb–17Li, or the plasma, into the cooling water. The control of tritium losses is an important issue in fusion technology because of its safety and operational implications. This goal can be achieved using a tritium permeation barrier (TPB). The use of aluminium rich coatings, which forms Al 2O 3 at their surface, has been selected as reference solution for WCLL blanket in order to produce reliable TPB. The hot dipping process is one of the two candidates for the production of coatings on large blanket segments. The effectiveness of hot dipped aluminium coating on MANET II steel has been verified in gas phase and in liquid Pb–17Li, using a test apparatus named Corelli II. The permeation rate measured in gas phase is one order of magnitude lower than the one in liquid metal phase. Performing SEM-EDS analysis on the specimen, it was observed that micro cracks on the coating surface were present. The permeation curves in gas and Pb–17Li are reported and discussed. The characteristics of the new experimental device Vivaldi will be briefly described.

The thermal state of a small spherical body in an air plasma

Heat exchange between an air plasma and a low-heat-capacity spherical body made from a refractory (tungsten) or fusible (aluminum) material is studied under conditions when the body exhibits the properties typical of either a thermally thin or thermally thick body. The problem is solved for an unperturbed plasma temperature of 5000–20000 K, a pressure of up to 1 atm, and a body (particle) size of 10 µm to 1 cm. The model developed accounts for the possible phase transitions at melting and boiling. It is shown that, under proper physical conditions, a refractory particle can relax to a steady thermal state (in various aggregate states). This property can be used in plasma sputtering of refractory coatings, which requires the preparation of a spatially homogeneous thermal state of the sputtered macroparticles that underwent a metal-liquid phase transition.

Vortex states at low temperature in disordered thin and thick films of a-MoxSi1–x

We have measured the ac complex resistivity in thelinear regime, as well as dc resistivity, for thick (100, 300 nm)amorphous (a-)MoxSi1–x films at low temperatures(T > 0.04 K) in constant fields B. The critical behaviorassociated with the second-order transition has been observedfor both dc and ac resistivities, which is similar to that observedfor granular indium films. This is the first convincing evidencefor the vortex glass transition (VGT) in the homogeneouslydisordered low-TC superconductors containing microscopicpinning centers. We have found that the VGT persists down to T ∼ 0.1TC0 up to B ∼ 0.9BC2(0), where TC0 and BC2(0) are themean-field transition temperature and upper critical field at T = 0, respectively. At T → 0 the VGT line Bg(T) extrapolatesto a field below BC2(0), indicative of the presence of a T = 0quantum-vortex-liquid phase in the region Bg(0) < B < BC2(0).For thin (4 nm) films the (T = 0) field-driven superconductor–insulator transition takes place at BC. We have notobtained evidence of the metallic quantum liquid phase below BC, while in B > BC an anomalous negative magnetoresistance(MR) suggesting the presence of the localized Cooper pairs hasbeen observed. The negative MRis commonly observed for thinfilms; however, for thick films the MR is always positive. Thismeans that the two-dimensionality plays an important role inthe appearance of the negative MR (or localized Cooper pairs).The negative MR is no longer visible as the field is appliedparallel to the film surface, consistent with the view that mobilevortices, as well as localized Cooper pairs, are present in B > BC.

Morphological instability of liquid metallic nuclei condensing on charged inhomogeneities.

We analyze the heterogeneous nucleation of liquid metallic phase from vapor on an electrically charged inhomogeneity. It is demonstrated theoretically that, regardless of magnitudes of surface tension of the phase interface and electric charge carried by the inhomogeneity, all spherical nuclei are necessarily unstable at all external pressures for which the system is undersaturated. In other words, small perturbations to the shape of the interface will cause it to move away from the equilibrium configuration. Our treatment of the problem is based on the continuum thermodynamic approach pioneered by Gibbs and Thomson.

Evaluation of the mechanical properties of T91 steel exposed to Pb and Pb–Bi at high temperature in controlled environment

It is known that liquid metal embrittlement (LME) is strongly dependent on a so-called `intimate contact' between the solid and liquid metal (LM) phases. This point is emphasised in this paper aimed at determining suitable contact conditions to favour LME of T91 steel after short exposure to stagnant molten Pb or Pb–55%Bi. The temperature range ( T∼540°C) is high with respect to the expected operating conditions of spallation targets. We determine three temperature cycles, in pure lead or lead–bismuth under flowing He–4%H 2 for LME testing. Good contact is obtained between T91 and Pb–Bi, but poor contact between T91 and Pb. Accordingly, the T91 steel tensile properties are not degraded by Pb, but modified after exposure to Pb–Bi. In such case, rupture of the test bar occurs in regions where Pb–Bi is `adherent' onto the steel. The rupture facies is not fully ductile as for T91 in Pb.

Band gap collapse and ultrafast “cold” melting of silicon during femtosecond laser pulse

It is established experimentally that a high concentration of electron-hole plasma produced in silicon by femtosecond laser pulse induces a sequential “collapse” of the band gap in the [111] and [100] directions and leads to the formation of a “cold” metallic liquid phase during the pulse.

溶融鉛‐アンチモン‐酸素系の相平衡と成分の活量

Phase equilibria and activities of the components in the liquid lead-antimony-oxygen ternary system have been investigated at 1,173 and 1,223 K to discuss the recovery of lead and antimony from an used lead-battery thermodynamically.The two liquid phases of metal and oxide were observed at the temperatures studied, and the tie lines indicating isoactivities were determined. The activities of PbO, SbO1.5 and Sb2O3 in the PbO-SbO1.5 and PbO-Sb2O3 pseudo-binary systems were then calculated by applying the Gibbs-Duhem equation to the phase relation of metal-oxide equilibrium. Both in the pseudo-binary systems the activities exhibit negative deviations from Raoult's law. The vapor pressures of lead, antimony and lead oxide, antimony oxide were calculated by using the activities of the components in the lead-antimony-oxygen ternary system. As a result, an oxidation of antimony in the anode slime concentrated from an used lead-battery followed by evaporation as antimony oxide (Sb4O6) was found to be considerably effective for the recovery of lead and antimony.

Phase Explosion of Conductor with Current

The paper deals with the effect of a magnetic field developed by the current flowing in a liquid-metal conductor on the parameters of its phase equilibrium with own vapors. A phase explosion occurs as a result of loss of thermodynamic stability of a two-phase system, when, as the conductor is heated with current, the vapor in equilibrium with the liquid metal phase compressed by ponderomotive forces reaches the state of limiting supersaturation (spinodal). This instability initiates the dispersion and scattering of the conductor upon its electric explosion. The parameters of electric explosion of a copper conductor are calculated. It is demonstrated that the conductor temperature at the moment of explosion depends considerably on the parameters of the electric circuit and may vary in a wide range almost from the boiling point to a close-to-critical temperature without, however, reaching the critical temperature.

Positron diffusion in the liquid phase

We introduce effective Lagrangian with spontaneously broken density and the massive internal gauge fields based on the Sethna–Sachdev–Nelson formula, and propose an explanation for the increase of the positron diffusion length in the liquid metal phase with temperature. It is shown that the effective mass of the positron in the liquid phase decreases with temperature due to restoration of the spontaneously broken density and the massive gauge fields around the positron.

Probing ion-ion and electron-ion correlations in liquid metals within the quantum hypernetted chain approximation

We use the Quantum Hypernetted Chain Approximation (QHNC) to calculate the ion-ion and electron-ion correlations for liquid metallic Li, Be, Na, Mg, Al, K, Ca, and Ga. We discuss trends in electron-ion structure factors and radial distribution functions, and also calculate the free-atom and metallic-atom form-factors, focusing on how bonding effects affect the interpretation of X-ray scattering experiments, especially experimental measurements of the ion-ion structure factor in the liquid metallic phase.

Analytical applicability of transition metals and boron anionic complexes formed with iodide, chloride, cyanide, and fluoride in electrospray mass spectrometry

A negative-mode electrospray ionization mass spectrometry study of some transition metal ions and boron was carried out. Several experiments combining these elements with iodide, fluoride, chloride, and cyanide are presented. Methanol/water was used mainly as the solvent in order to reduce the surface tension and, thus, the voltage at the capillary tip. Some common behaviors could be observed. Metals give more abundant peaks with iodide and chloride, while boron gives an abundant cluster for BF 4 −. In general, the complexes are singly charged, formed by association of the metal ions with the anions present in the solution, or by loss of one or more ligands from species previously present in solution. In some cases, this tendency surpasses the maintenance of the oxidation state of the metal in liquid phase. The interconversion of low and high oxidation states of copper and iron ions depends on the solvent and other species from the solution, but in the gas phase the high oxidation state species can be reduced by collision induced dissociation at low sampling cone voltages. Surprisingly, ferricyanide and ferrocyanide anions render almost the same spectrum. The results suggest that [Fe(CN) 6] 4− loses one electron to a leaving solvent molecule to form [Fe(CN) 6] 3− in the final steps of desolvation. These and other results suggest that, for the ligands studied in this work, quantitation and speciation are not easy tasks, but there is the possibility of performing isotope ratio measurements with the complexes formed with monoisotopic anions. The main advantages in this case would be the shift of the m/z to high mass region, which diminishes the chance of isobaric interference, and the inexistence of hydrides, commonly observed in the positive mode electrospray mass spectrometry spectra of metal ions and that cause isobaric interference.

Liquid metal embrittlement in the absence of liquid metal phase: in studies of surface damageability and in hard materials machining

The liquid metal embrittlement (LME) effect has been studied by a new approach, in the absence of the liquid metal phase. A melt was replaced by the ions of selected surface-active metals induced by electrochemical reduction on treated surface. New methods were elaborated based on this idea. The electrochemical microscratching method has been developed to study the stability and damageability of solid metal surfaces. Electro–chemo–mechanical treatment (ECMT) tests were performed to search for new ways in practical applications of the LME effect in optimizing processes of mechanical machining, friction

Melting boundary of Fe‐17%Si up to 5.5 GPa and the timing of core formation

Melting of Fe‐17wt%Si has been investigated at temperatures up to 1600°C and pressures up to 5.5 GPa in a cubic anvil press. The melting temperature, TM, was identified with the discontinuity in temperature and pressure dependence of electrical resistance. Two types of electrode materials, Pt and Fe, were used and gave consistent melting results. TM increases with pressure from 1200°C at 1 atm to 1430°C at 5.5 GPa. dTM/dP decreases with pressure and reaches a value of zero at P∼5 GPa. Combined with the thermal profiles of the proto‐Earth, the pressure independence of the melting boundary of Fe‐17%Si at the highest pressures of this study suggests core formation began early in Earth accretion with a substantial liquid metal phase fraction between 30 Ma and 42 Ma.

Kinetics and mechanisms of the reverse Boudouard reaction over metal carbonates in connection with the reactions of solid carbon with the metal carbonates

The decomposition processes of alkali or alkaline earth carbonates with a large excess of carbon, and the reverse Boudouard reaction given by CO2/C→2CO over metal carbonates, were compared. The carbonates of Li+, Na+, K+, Cs+, Sr2+ and Ba2+ generated CO exclusively by an intermolecular redox reaction given by CO32-+C→2CO+O2-. The reverse Boudouard reaction over these metal carbonates at 700°C proceeded at a steady rate until just before the carbon was completely consumed, and in the cases of Li+, Sr2+ and Ba2+, the rates agreed with the initial rates of the intermolecular redox reaction. On the other hand, the rates over the carbonates of Na+, K+ and Cs+, the oxides of which undergo a disproportionation reaction to produce gas-phase metal and liquid-phase metal peroxide, were much higher than the initial rates of the intermolecular redox reaction. This discrepancy can be explained by the presence of a catalytic process on the metal-covered surface of the silica wool that was used for preventing the highly basic gas-phase metals from escaping.

Microscratching in electrochemical cells: the effect of gallium on surface deformation in aluminum

The microscratching method has been combined with the electrochemical reduction of an active component at the tested surface for studying initial surface damages in metals and effects caused by active media. This allows the modeling of the active liquid metal influence in the absence of the liquid metal phase, at room temperature. Surface plasticizing of aluminum caused by gallium ions reduction has been observed and discussed in terms of microscopic (dislocation) and macroscopic (finite elements) approaches.

The overdoped regime in La2−xSrxCuO4

Recent experimental data for the overdoped LSCO have firmly established the properties which characterize the transition between the superconducting and the Fermi liquid metallic phases. The thermodynamic response functions show a pronounced feature at this point, while the Fermi surface undergoes a dramatic change. By use of the Composite Operator Method for the two-dimensional Hubbard model, it is found that the presence of a van Hove singularity in the lower Hubbard band can explain these behaviors.

Electrical charge of metal oxides in liquid metals

An attempt was made to determine the electrical charging characteristics of metal oxide particles suspended in a liquid metal. A liquid metal and metal oxide particles in the liquid were respectively chosen as a cathode and anode for the potential measurements. By taking a close symmetry of electrical circuit, the potential difference between electrodes could be measured successfully. Experimental results show that alumina carries a positive charge by providing electrons to the liquid metal phase such as molten lead and molten aluminum. The potential difference was in the range of 0.01 and 0.08 mV, and was increased with increasing temperature and the amount of oxide added to the liquid metal. Most metal oxides in liquid metal carry a positive charge owing to the formation of the space-diffused charge layer.