Liquid Metal Phase Research Articles

Dripping Liquid Metal Flow in the Lower Part of a Blast Furnace

Numerical simulation of blast furnace phenomena has significantly contributed to the better understanding of iron making process. Recent interest on minimizing fuel consumption and reducing environmental problems have also benefitted from the development of comprehensive simulation models based on physical principles. One of the under-developing fields, however, is related with the internal phenomena in the lower part of the blast furnace under the cohesive zone, where the liquid phase of metal and slag flows downward over the bed of solid coke particles. Hot flow of sluggish liquid phase is further complicated by the chemical reactions including the transfer of silica into the silicon in the hot metal. Silica enters the furnace as a constituent of coke ash and ferrous gangue, and exits as either molten silica in slag or dissolved Si in the hot metal. Silica reduction is an endothermic reaction, which would alter the heat transfer in the lower furnace, thus affecting the hot metal temperature. Effective flow in the dripping zone is important for stable operation of the blast furnace with high productivity of iron. Study of the liquid flow behavior and secondary reactions in a packed bed allows to investigate the effect of various operational changes in the dripping zone. In this research, a systematic numerical approach for the liquid flow is presented where the flow behavior is solved along with heat transfer associated with physic-chemical reactions among representative components.

Minor element partitioning between fcc Fe metal and Fe–S liquid at high pressure: The role of crystal lattice strain

We present a new approach to model element distribution between solid and liquid metal phases, based on experimentally determined data for the partitioning of P, S, selected transition metals, and chalcophile elements between face-centred cubic (fcc) Fe and Fe–S liquid at pressures of 9, 15 and 23 GPa and temperatures between 1523 and 1773 K. Solid/liquid partition coefficients ( D) for the transition metals V, Cr, Mn, Fe, Co, and Ni range from a minimum D of 0.16–0.64 for V to a maximum D of 1.1–1.2 for Co, indicating modest but significant fractionation. D for the chalcophile elements Cu, Zn, Ga, Sn, and Pb varies from 0.029–0.051 for D Pb up to 1.6–2.4 for D Ga and for non-metals from 0.02–0.04 for S to 0.23–0.66 for P. A modified lattice strain model (as in common use for silicate mineral-melt partitioning) describes the variations in D values for the first row transition metals through the deviance in metal radius from the ideal site radius of Fe in solid metal, indicating that these metals all substitute into the iron site of the solid phase. Variations in D values for the chalcophile elements can also be rationalized using a lattice strain model, but chalcophiles occupy a different site in the solid metal, probably related to the presence of sulphur defects. We show that the lattice strain model can be applied to previously published low pressure experimental data, as well as to third-row transition metals as to first-row transition metals and chalcophiles. The fact that solid–liquid metal D values are amenable to interpretation using lattice strain models paves the way for the development of a new class of element partitioning models applicable to metallic core crystallization processes.

Design of Liquid Metal Phase Change Heat Exchanger for Next-Generation Nuclear Plant Process Heat Application

The Next Generation Nuclear Plant will most likely produce electricity and its reactor heat will be further utilized for the production of hydrogen, oil recovery from tar sands and oil shales, and other process heat applications, that will further the nation's pursuit of energy independence. An intermediate heat exchanger is required to transfer heat from the Next-Generation Nuclear Plant to the hydrogen plant (or other processes) in the most efficient way possible. Phase change heat exchangers are quite attractive in this regard, as they can transfer process heat more efficiently than for the single phase due to the advantage of high-enthalpy transport that includes the sensible heat of liquid, the latent heat of vaporization, and possible vapor superheat. This paper explores the overall heat transfer characteristics and pressure drop of the phase change heat exchanger with helium as the primary and sodium as the secondary heat exchanger coolant. For a two-phase boiling regime, the convective heat transfer coefficient is based on the concept of an additive, interacting mechanism of micro- and macroconvective heat transfer. In this analysis an improved design is proposed for given conditions, so as to obtain a lower overall pressure drop and a moderate/high overall heat transfer coefficient. The analysis presented in this paper will be useful as a guide for future experimental work for Next Generation Nuclear Plant process heat transfer.

Pulsed laser deposition of ZnO honeycomb structures on metal catalyst prepatterned Si substrates

Honeycomb structures with controllable size are of great interest for many potential applications such as containers for microencapsulating and controlled delivery, gas sensors, catalysis and photonic crystals and devices. A ZnO honeycomb structure was successfully fabricated on metal prepatterned Si substrates by the nanosphere lithography method combined with the pulsed laser deposition (PLD) technique. SEM images show that a Pt template gives rise to the regular ZnO honeycomb structure which has the same cell size as the diameter of polystyrene (PS) spheres; a Au template also leads to honeycomb structure but the average cell size is smaller than the diameter of PS spheres; while Ag fails to generate a ZnO honeycomb structure. The different ZnO patterns are related to the morphology and distribution of the metal nanoparticles when processed at 600 °C in a PLD vacuum chamber. The growth mechanism of a ZnO honeycomb structure is attributed to the catalysis of liquid-phase metal nanoparticles. X-ray diffraction measurements indicate that ZnO on all metal templates have the (0 0 2) preferential orientation. The photoluminescence properties of the ZnO patterns were also examined and compared. Such a method can be extended to produce honeycomb structures of other materials with controlled cell size and periodicity.

Thermodynamic Properties of Lanthanides and Actinides for Reductive Extraction of Minor Actinides

The excess thermodynamic quantities of lanthanides and actinides in molten salts and liquid metals were studied for reductive extraction of minor actinides. The excess enthalpies and entropies of those elements in the molten chloride phase were found to be correlated with the ionic radii of metal ions possibly due to complex formation. In the liquid metal phase, on the other hand, the excess enthalpies were explained with Miedema's atomistic model and the excess entropies were explained with the vibrational entropy due to alloy formation. Using these correlations and models, some missing values of the excess thermodynamic quantities were evaluated and the separation factors of minor actinides from lanthanides were calculated in different reductive extraction systems. The higher separation factors were obtained in the system using aluminum or gallium than in the system using bismuth or cadmium as the liquid metal phase.

Design of Liquid Metal Phase Change Heat Exchanger for Next-Generation Nuclear Plant Process Heat Application

The Next Generation Nuclear Plant will most likely produce electricity and its reactor heat will be further utilized for the production of hydrogen, oil recovery from tar sands and oil shales, and other process heat applications, that will further the nation's pursuit of energy independence. An intermediate heat exchanger is required to transfer heat from the Next-Generation Nuclear Plant to the hydrogen plant (or other processes) in the most efficient way possible. Phase change heat exchangers are quite attractive in this regard, as they can transfer process heat more efficiently than for the single phase due to the advantage of high-enthalpy transport that includes the sensible heat of liquid, the latent heat of vaporization, and possible vapor superheat. This paper explores the overall heat transfer characteristics and pressure drop of the phase change heat exchanger with helium as the primary and sodium as the secondary heat exchanger coolant. For a two-phase boiling regime, the convective heat transf...

The Transformation of Core/Shell Aluminium/Alumina Nanoparticles into Nanowires

AbstractCore/shell nanowires of Al/Al2O3 are obtained by decomposition of tert‐butoxyalane on metal, silicon or glass substrates heated up to 650 °C without use of a noble metal seed. These biphasic nanowires are characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), scanning energy dispersive X‐ray spectroscopy (EDX), transmission electron microscopy (TEM) and high‐resolution TEM. They have uniform diameters of about 20–30 nm, are composed of an inner aluminium wire, wrapped up by aluminium oxide at a constant molar ratio, and have lengths of several micrometers. As the temperatures approach the melting point of Al (660.4 °C), we propose a growth mechanism for the nanowires which resembles to vapour‐liquid‐solid (VLS) growth of ceramic nanowires with a liquid metal phase catalyst seed which in this case is aluminium. The biphasic nature of the wires is due to the disproportionation of aluminium in the transient “AlO” and to Ostwald ripening.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Thermodynamics of liquid d- and f-shell metals: a variational approach

The Gibbs–Bogoliubov variational method is applied to investigate the thermodynamic properties of some d- and f-shell metals in liquid phase namely; Rh, Ir, Cu, Ag, Ni, Pd, Pt, Au, La, Yb, Ce, and Th using pseudopotential theory. For description of the structure, Percus-Yevick hard sphere model is used as a reference system. Ashcroft's well-known empty core model potential is used to describe the electron-ion interaction. The local field correction function proposed by Hartree, Taylor, Ichimaru–Utsumi, Farid et al., and Sarkar et al. are applied to introduce the exchange and correlation effects in the study of thermodynamics of these metals. The comparison with available experimental or theoretical findings is found in qualitative agreement and establishes the use of the local field correction functions in such study.

Elastic softening of peridotite due to the presence of melt phases at high pressure

Here we report an observation of softening of Young's modulus of a sample of KLB-1 peridotite as a metallic Ni melt intruded into it at 2.5 GPa and about 1500 °C. A uniaxial oscillation of stress was applied to the sample with frequency of 0.01–0.02 Hz and an amplitude up to 500 MPa. The Young's modulus is measured as the amplitude ratio between the sample and a reference material, while the attenuation is determined by the phase angle delays. The Ni intrusion was captured by in situ X-ray radiography. A planar intrusion occurred gradually, but advanced only during the extension; eventually, the Ni melt dissected the sample on a plane normal to the extension axis. Accompanied softening of Young's modulus was observed after the Ni intrusion was completed. This study suggests that percolation of a liquid metallic phase is possible within a partially melted mantle rock in the presence of a differential stress field.

Positron diffusion and restoration of local symmetry breaking induced by positrons in liquid metals

We present the effective Lagrangian with spontaneously broken density (the hedgehog-like fluctuation) and the massive internal gauge fields, and propose one explanation for the increase of the positron diffusion length in the liquid metal phase with temperature. From the view point of the restoration of the spontaneously broken density around the positron, the positron diffusion length data in the liquid phase of Bi metal are analyzed.

The Second Born Corrections to the Electrical and Thermal Conductivities of Dense Matter in the Liquid Metal Phase

The second Born corrections to the electrical and thermal conductivities are calculated for the dense matter in the liquid metal phase for various elemental compositions of astrophysical importance. Inclusion up to the second Born corrections is sufficiently accurate for the Coulomb scattering of the electrons by the atomic nuclei with Z < 26. Our approach is semi-analytical, and is in contrast to that of the previous authors who have used fully numerical values of the cross section for the Coulomb scattering of the electron by the atomic nucleus. The merit of the present semi-analytical approach is that this approach affords us to obtain the results with reliable Z-dependence and \rho-dependence. The previous fully numerical approach has made use of the numerical values of the cross section for the scattering of the electron off the atomic nucleus for a limited number of Z-values, Z=6, 13, 29, 50, 82, and 92, and for a limited number of electron energies, 0.05MeV, 0.1MeV, 0.2MeV, 0.4MeV, 0.7MeV, 1MeV, 2MeV, 4MeV, and 10MeV. Our study, however, has confirmed that the previous results are sufficiently accurate. They are recovered, if the terms higher than the second Born terms are taken into account. We make a detailed comparison of the present results with those of the previous authors. The numerical results are parameterized in a form of analytic formulae that would facilitate practical uses of the results. We also extend our calculations to the case of mixtures of nuclear species. The corresponding subroutine can be retrieved from http://www.ph.sophia.ac.jp/~itoh-ken/subroutine/subroutine.htm

Carbon Tubular Morphologies in Blast Furnace Coke

The paper reports on the first occurrence of microscale carbon tubular morphologies (CMTs) in a blast furnace (BF) coke. The CMTs were probably formed as a result of the conversion of solid disordered carbon via liquid phase metal particles involving a gas phase containing a substantial amount of and . The presence of CMTs may lie behind the generation of the smallest fraction of fines in BF exhaust dust. If the amount of CMTs present in the BF exhausts gases at any particular metallurgical site proves to be substantial, it could become a subject of environmental concern.

Structure of eutectic Fe–FeS melts to pressures up to 17 GPa: Implications for planetary cores

In situ X-ray diffraction experiments have been conducted using the Paris–Edinburgh press to study the Fe–FeS eutectic liquid structure from 3 to 17 GPa near the melting temperature. The eutectic temperature is steadily decreasing over the studied pressure range. The liquid structure evolves discontinuously towards a compact structure, with a non-uniform contraction at pressures between 13 and 17 GPa. We show that this evolution may be correlated to the Fe–S–Si miscibility gap closure (Sanloup, C., Fei, Y., Closure of the Fe–S–Si liquid miscibility gap at high pressure, Phys. Earth Planet. Inter. 147 (2004) 57.) and the magnetic transition observed in Fe 3S compound (Lin, J.F., Fei, Y., Sturhahn, W., Zhao, J., Mao, H.K., Hemley, R.J., Magnetic transition and sound velocities of Fe 3S at high pressure: implications for Earth and planetary cores, Earth Planet. Sci. Lett. 226 (2004) 33–40.). The occurrence of such structural change in liquids Fe-alloys show that the extrapolation of their physical properties up to Earth's core pressure might not be relevant. As Fe–S liquid alloy acquires a compact structure close to that of pure liquid iron at high pressure, sulfur could be considered as one of the possible light element for the Earth's core from a pure elastic point of view. In addition, this structural modification could affect the partitioning coefficients of elements between liquid silicates and S-bearing liquid metallic phase.

Abnormal Grain Growth and New Core–Shell Structure in (K,Na)NbO3‐Based Lead‐Free Piezoelectric Ceramics

A unique core–shell structure was observed in coarse grains in (K,Na)NbO3 (KNN)‐based lead‐free piezoelectric ceramics. It is morphologically different from the chemical inhomogeneity‐induced core–shell grain structure reported previously in BaTiO3‐based ceramics. The core region is composed of highly parallel nanosized subgrains, whereas the shell region consists of larger‐sized but similar self‐assembled subgrains. The electron‐backscattered diffraction analysis and selected area electron diffraction pattern confirmed that coarse grains with a core–shell structure were single‐crystalline‐like grains. The formation process of such coarse grains was then discussed based on mesocrystal growth along with the classical theory of grain growth. The two studied KNN‐based systems showed a similar grain growth transformation: from self‐assembled aggregation clusters with nanosized subgrains to a typical core–shell grain structure when the sintering temperature was increased only by a range of 10°–20°C. The volatilized alkali metal oxides and liquid phase were supposed to accelerate such grain growth transformation. When abnormal grown grains with a core–shell structure occurred, both systems showed the highest densities and dielectric constants along with the lowest dielectric losses, while their piezoelectric properties tended to decline.

TRIEX facility: An experimental loop to test tritium extraction systems from lead lithium

The first and main step of the HCLL (helium cooled lithium lead) blanket fuel cycle consists of tritium extraction from the liquid breeder. In DEMO reactor a dedicated system, called TES (tritium extraction system), will be devoted to accomplish this task. Different technologies, belonging to the families of gas–liquid contactors, getters and tritium permeators have been studied in the last years, some of them mainly theoretically, others with much more experimental effort. Gas–liquid contactors, which have been more experimentally studied, showed contradictory results. Plate, spray and bubble columns resulted in a very low-extraction efficiency. On the contrary, packed columns gave better results, although some doubts arise about the accuracy of the experiments performed in the past. However, packed columns seem to be the most attractive technology and for this reason was decided for a further optimisation and testing of their performances. In order to accomplish this task, a dedicated facility called TRIEX (tritium extraction) was designed and built and is now available in ENEA-Brasimone. In TRIEX the extraction efficiency of different packed columns will be tested in a systematic way paying particular attention to the hydrogen monitoring system in gas and liquid metal phase. The design and the main instrumentation of TRIEX facility, as well as the operating modes and the planned experimental campaign are presented in this paper.

Prereduction of self-reducing pellets of manganese ore

A brief review of alternative processes for production of high C Fe–Mn is presented. Experimental results of the reduction behaviour of charcoal bearing pellets with manganese concentrate at temperatures up to 1400°C are discussed. At temperatures up to 1000°C iron and manganese oxides are reduced to MnO, Fe and some Fe–Mn. At temperatures between 1000 and 1250°C, there is the formation of a liquid phase (Fe–Mn) by dissolution of reduced Mn into Fe. At temperatures between 1250 and 1350°C, manganese continues to be reduced and incorporated into Fe–Mn, and the composition of the metallic phase is similar to that of commercial Fe–Mn. The results have also shown that it is possible to obtain a Fe–Mn alloy with good recovery yield of Mn at temperatures within 1300 and 1400°C, without disintegration of the charcoal bearing pellet, but obtaining a liquid metallic phase inside it, favouring the coalescence of Fe–Mn. This result allows the prospect of new processes for Fe–Mn production with low energy consumption.

An extended criterion for estimation of glass-forming ability of metals

If a metal contracts upon solidification, the specific volume of a metallic liquid phase must not be smaller than that of the corresponding crystal. As molten metals have higher thermal expansion coefficients compared with those of the corresponding crystals, the intersection point of two specific-volume–temperature plots of the liquid and the corresponding solid crystalline phase by analogy with Kauzmann’s paradox for entropy could be treated as an ideal glass-transition temperature. This paper describes this phenomenon observed for a number of pure metals and gives a semiempirical criterion for the achievement of a good glass-forming ability.

Application of electrochemical techniques in pyrochemical processes – Electrochemical behaviour of rare earths at W, Cd, Bi and Al electrodes

The electrochemical behaviour of some rare earths ions (REs) – from the light to heavy lanthanides (i.e. Ce, La, Pr, Gd, Er, Ho) and Y – were investigated in the eutectic LiCl–KCl at different substrates: (i) liquid metals Cd and Bi, (ii) aluminium, and (iii) tungsten. The electrode reaction of the RE(III)/RE couples at the Cd and Bi pool electrodes was elucidated by cyclic voltammetry. The differences between the equilibrium potential adopted by a RE electrode and the E1/2r observed with the same RE(III) solution at the liquid electrodes were consistent with the activity coefficients of RE in the liquid metal phase. The relative partial molar Gibbs energies and activities of RE in the RE–Cd and RE–Bi intermetallic compounds could be estimated by the analysis of the open circuit chronopotentiograms using Cd and Bi coated tungsten electrodes. The Gibbs energies of formation of different intermetallic compounds, as well as their molar entropies and enthalpies of formation were also calculated from the temperature dependence of the emf. The redox potential of the RE(III)/RE couples at the Al electrode was observed at more positive potentials than that at the inert electrode (W). This potential shift was explained by a lowering of the activity of the REs in the Al phases due to the formation of intermetallic compounds. Electromotive force measurements for various intermetallic compounds in two-phase coexisting states were carried out. The activities and relative partial molar Gibbs energies of REs were also obtained. Moreover, the molar entropies and enthalpies of the aluminium-rich alloys were also calculated from the temperature dependence of the emf measurements.

Chemical states of fission products in irradiated (U 0.3Pu 0.7)C 1+ x fuel at high burn-ups

The chemical states of fission products have been theoretically determined for the irradiated carbide fuel of Fast Breeder Test Reactor (FBTR) at Kalpakkam, India, at different burn-ups. The SOLGASMIX-PV computer code was used to determine the equilibrium chemical composition of the fuel. The system was assumed to be composed of a gaseous phase at one atmosphere pressure, and various solid phases. The distribution of elements in these phases and their chemical states at different temperatures were calculated as a function of burn-up. The FBTR fuel, (U 0.3Pu 0.7)C 1+ x , was loaded with C/M values in the range, 1.03–1.06. The present calculations indicated that even for the lowest starting C/M of 1.03 in the FBTR fuel, the liquid metal phase of (U, Pu), should not appear at a burn-up as high as 150 GWd/t.

Maximum Copper and Tin Contents in LC‐steel Thin Strip ‐ Hot Shortness Model Calculations

For conventional casting processes low copper and tin contents have to be ensured in LC‐steel to avoid hot shortness. It is expected that higher cooling rates, e.g. in thin strip casting, permit higher copper and tin limits. Hot shortness occurs because of selective oxidation of the iron whereby the more noble copper is enriched at the steel‐oxide interface. A liquid metallic copper phase which wets the grain boundaries supports cracking during hot deformation. The enrichment of the liquid copper phase depends on the oxidation temperature: At low temperatures copper is solid, cannot wet the steel surface and is incorporated into the growing oxide layer. At mid temperatures (1083‐1177 °C) the copper phase is liquid, wets the grain boundaries of the steel surface and causes hot shortness. At high temperatures a liquid fayalitic slag is formed in the oxide layer if the steel contains silicon. The fayalitic phase occludes parts of the steel surface and removes copper from the steel surface; then hot shortness is reduced or even avoided. Other mechanisms to remove copper from the steel surface need the presence of Fe3O4 and Fe2O3 in the oxide layer. These iron oxides are not formed for short oxidation times where linear oxidation takes place. Diffusion of copper into the steel is too slow to reduce hot shortness if copper has an elevated concentration in the steel, e.g. 0.5 wt.‐%. Therefore, only the occlusion mechanism is of importance during linear oxidation. A model is established on the basis of these observations in order to predict an upper copper limit in dependence of the steel strip thickness (cooling behaviour) and the oxygen content in the cooling atmosphere (nitrogen‐oxygen mixture). The model is compared to experimental results from KIMAB which are presented in this issue. It is demonstrated that a copper layer thickness of 0.098 μm at the steel‐oxide interface is sufficient to cause cracks of a depth of more than 0.2 mm. For strip thicknesses below 5 mm a simple approximation can be used to predict the maximum copper content in LC‐steel to avoid hot shortness. For example, thin strip of a thickness of 2 mm will have no cracks (above 0.2 mm) even if 0.7 wt.‐% of copper is contained in the LC‐steel. For atmospheres with a reduced oxygen partial pressure even higher copper contents are possible.Tin is with short oxidation times not a problem concerning hot shortness, as shown by the KIMAB results. This may be explained by the much higher diffusivity of tin in iron compared to copper.