Liquid Tin Research Articles

Advancement in Liquid Tin Anode - Solid Oxide Fuel Cell Technology

The first Liquid Tin Anode Solid Oxide Fuel Cell (LTA-SOFC) was tested in 1998. Since 1998 the LTA-SOFC has been operated on a range of carbonaceous fuels in the form of gases, liquids and solids. Over this time, several design revisions at the cell, stack and system levels have resulted in multiple technical, performance and commercial milestones, increasing the volumetric and gravimetric power densities. The Gen 3.0 cell and stack (2005-2006) achieved a power density of 40 mW/cm2 by direct JP-8 conversion to electricity. However for mobile/portable applications, compact LTA-SOFC systems are preferred which requires a higher power density. This paper discusses key development areas and performance of the current Gen 3.1 cells/stack which have lead to a 4 times reduction in weight and volume over Gen 3.0. Performance of the Gen 3.1 cell on direct JP-8 conversion with a sulfur content of 1400 ppm shows a power density of 120 mW/cm2 and fuel efficiency over 40%.

Effect of solidification velocity on weld solidification process of alloy tool steel

In order to clarify the effect of solidification velocity on the weld solidification process of alloy tool steel during the welding, the information about microstructure evolution was obtained by the concurrent experiments of liquid tin quenching and time resolved X-ray diffraction technique using intense synchrotron radiation. It was found from the experiments that the solidification mode was transferred from an FA to an A mode at the high solidification velocity. The effect of solidification velocity on the phase selection during solidification between the primary δ-ferrite and γ-austenite was theoretically proved by the Kurz, Giovanola and Trivedi (KGT) model. It is thus explained that the solidification cracking susceptibility of the weld metal of alloy tool steel was enhanced due to the δ to γ transition of the primary phase.

Wetting and capillarity in the Sn/graphite system

Aiming to investigate the role of wettability in the infiltration of tin into graphite particle compacts, sessile drop and infiltration experiments have been carried out at temperatures in the range of 300–700 °C. The surface tension of liquid tin and the contact angle at the tin/graphite interface have been measured in an argon atmosphere by means of the sessile drop technique, while pressure infiltration of Sn into compacts of graphite particles (27.2 μm of average diameter) has been carried out in air. The results indicate that the threshold pressure for infiltration is proportional to the work of immersion, as predicted by the capillary law. The particle geometric factor derived from the slope of the straight line is similar to that obtained previously from infiltration of aluminum. Although these results may indicate that the oxide layer that covers the tin surface plays a minor role in the infiltration process, a definitive conclusion may require a more detailed analysis of this interesting system.

Structure of liquid tin under high pressure by ab initio molecular-dynamics simulation

Pressure-induced structural change of liquid tin was studied by constant-pressure ab initio molecular-dynamics simulations from 0 to 4 GPa. We have found that with increasing pressure the liquid tin is not compressed uniformly but very gradually changes from complex anisotropic structures to more simple isotropic close-packed structure.

Physical properties of some Sn-Cu melts at high temperatures

Several physical properties (density, viscosity, ultrasound velocity, electroresistivity and magnetic susceptibility) of pure tin, copper, silver and their alloys with near eutectic compositions are investigated in the wide temperature range up to 1600° C. In cases of copper and silver the temperature dependences of properties are found to be smooth. As for liquid tin, three temperature ranges with abnormal behaviour of properties were discovered: t1 near 400° C (anomalies in density and electroresistivity); t2 = 1000–10500 °C (anomalies in viscosity and electroresistivity); t3 approx. 1400° C (anomalies in density, electroresistivity and magnetic susceptibility). The decrease in heating rate from 4 to 1 °C/min shifts t2 down to 800° C, and the purification of samples from 99.9 to 99.999% provides the incoincidence of viscosity heating and cooling curves for all the temperatures below 800° C. The introduction of copper into liquid tin (99.9 % purity) shifts the temperature of anomaly t2 from 1000–1050° C to 790° C. We connect this abnormal behaviour of physical properties at tan with β-γ structural transformation. Hence, by warring regimes of melts heat treatment before solidification it becomes possible to obtain samples with different properties in solid state.

Dynamic fragmentation of melted metals upon intense shock wave loading. Some modelling issues applied to a tin target

We are interested in the dynamic fragmentation event produced in shock-melted metals called micro-spalling. Global energetic approach is briefly reviewed. It provides a general modelling framework that leads to realistic fragment-size predictions. But the actual physical mechanisms involved remain poorly understood. We attempt to explore the conditions under which cavitation, i.e. nucleation and growth of microvoids, may be responsible for fragmentation. This cavitation process is described by means of a hollow sphere model whose matrix is made of liquid tin.

初晶選択を考慮した熱間工具鋼の凝固割れ感受性評価

The solidification cracking susceptibility with the dependence of the selection of the primary phase was clarified with the Trans-Varestraint test, since the solidification mode of alloy tool steel (SKD61) was transited from FA mode (L → L+δ → L+δ+γ → L+γ→γ) to A mode (L → L+γ → γ) at high solidification velocity. It was obtained that the Brittle Temperature Range was enhanced to 587K for A mode while it was 105K for FA mode in the augmented strain of 2%.In order to clarify the change of dendrite morphology during the solidification process, the liquid tin quenching was curried out. Though the interdendritic microsegregation can be reduced due to the dendrite arm development, the solidification cracking susceptibility was sensitized in A mode solidification. Therefore, the selection of the primary phase is extremely important.The effect of primary phase selection on the interdendritic microsegregation was theoretically proven using the solidification velocity dependence of microsegregation model taking into the diffusion of the solute in the solid phase. It was found that the solidification cracking susceptibility obtained by the Trans-Varestraint test can be simply evaluated as the influence of the mode transition below the solidification velocity of 10 mm s−1 and the reduction of Si, P and S content can be effective on decreasing the risk of solidification crack.

Liquid Tin Irrigated Packed Bed for Hot Fuel Gas Desulfurization

Hot fuel gas cleaning for gasification of coal can increase the energy efficiency by minimizing the loss of thermal energy. The current hot gas desulfurization studies focus on the development of various metal oxide sorbents. This paper presents a novel approach using liquid tin as a nonwetting scrubbing medium in a countercurrent packed bed. The H2S removal efficiency of liquid tin was investigated in a 200 mm high reactor for various tin and gas flow rates, bed heights, and H2S concentration at operating temperatures of 300−400 °C. For tested conditions, gas transfer unit heights of 0.084−0.181 m were obtained at H2S concentration of 1000 ppm, which corresponded to an H2S removal efficiency of up to 91% in the small test reactor. These results are promising since higher efficiencies can be achieved at larger scales. The effects of thermal equilibrium and interaction with other gases are also discussed. Further studies are required on various aspects including higher operating temperatures, larger flow rates, and the regeneration of tin using zinc.

Anode Polarization in Liquid Tin Anode Solid Oxide Fuel Cell

The Liquid Tin Anode Solid Oxide Fuel Cell (LTA-SOFC) is a modified version of SOFC that allows the direct conversion of carbonaceous fuels. The LTA-SOFC uses conventional SOFC electrolytes and cathodes but its anode is liquid tin allowing direct oxidization of fuel without reforming or other fuel processing. A porous ceramic separator was introduced in CellTech Power's Gen 2 and Gen 3 LTA-SOFC designs. The separator holds the liquid tin anode in place while allowing free exchange of fuel molecules and products. This paper describes anode polarization of LTA-SOFC and a capillary model for porous tin anode separator

Liquid Tin Anode Solid Oxide Fuel Cell for Direct Carbonaceous Fuel Conversion

The Liquid Tin Anode Solid Oxide Fuel Cell (LTA-SOFC) is a modified version of SOFC that allows the direct oxidation of carbonaceous fuels. The LTA-SOFC uses many conventional SOFC components but differs from conventional SOFC because its anode is liquid tin allowing directly oxidization of fuel without fuel reforming or other fuel processing. In addition, the anode stores energy, allowing the cell to deliver power in case fuel flow has been interrupted. As a result, the LTA-SOFC requires less components resulting in simpler and more efficient system. This paper describes the basic LTA-SOFC cell architecture and cell/stack test results using carbonaceous fuels such as JP-8, natural gas, coal, bio-mass and plastic feedstock.

Penetration of liquid tin along grain boundaries and triple grain-boundary junctions of aluminum

A new procedure for investigation of liquid-metal etching grooves that form owing to wetting and penetration of the liquid phase along the triple grain-boundary junctions (triple junction) and grain boundaries in the Al-Sn system is described. The investigations were carried out by the method of layer-by-layer polishing of the end surface of the wetted sample. The obtained slices were investigated by methods of optical and electron scanning microscopy. It was shown that the groove depth is virtually invariable along a single grain boundary and increases as the groove approaches the triple junction. The penetration depth of Sn along the triple junctions is much larger than along the grain boundaries. It is shown that, owing to wetting processes in the triple junction, as in the grain boundaries, the Sn-based alloy is formed.

Influence of pore size on the Knight shift in liquid tin and mercury in a confinedgeometry

119Sn and 199Hg NMR studies were carried out for metallic tin and mercury embedded in synthetic opalsand porous glasses. The Knight shift for confined liquid tin and mercury was found todecrease monotonically with decreasing pore size, evidence for the reduction of electronsusceptibility. Size-induced alterations in the Knight shift were more pronouncedfor confined mercury than for tin. The influence of pore filling on the NMR lineshape and Knight shift was observed for tin within opal. The reasons for thedecreasing Knight shift for liquid metals in a confined geometry are discussed.Correlations between the alteration in the Knight shift and atomic number are shown,the changes in fractional values of the Knight shift remaining almost identical.

放射光を利用したオーステナイト系ステンレス鋼溶接凝固過程の解析

In order to verify the validity of the developed numerical model to predict the solidification microstructure of austenitic stainless steel weld metal proposed in the previous report, spatially resolved X-ray diffraction measurements using synchrotron radiation have been carried out for Fe-20Cr-11.5Ni and Fe-20Cr-12.7Ni weld metals, quenched in liquid tin. X-ray diffraction analysis of Fe-20Cr-11.5Ni quenched weld metal, solidifying in FA mode (L→L +δ→L +δ+γ→δ+γ), showed that the leading γ phase crystallized in a eutectic growth mode down to a temperature drop of 6 K from the initiation of solidification. Also, from X-ray diffraction analysis of Fe-20Cr-12.7Ni quenched weld metal, which solidified in AF mode (L→L +γ→L +γ+δ→γ+δ), it was found that the leading δ phase crystallized in a eutectic growth mode within the temperature drop range between 18 and 24 K from the initiation of solidification. The crystallization temperatures predicted by the developed numerical model for leading γ and δ phases in Fe-20Cr-11.5Ni and Fe-20Cr-12.7Ni weld metals agreed with experimental data. These agreements support the validity of the developed numerical model. Furthermore, time-resolved in-situ observation of welding solidification process using synchrotron radiation have been carried out for Fe-20Cr-12.5Ni and Fe-20Cr-11.4Ni weld metals, it was found that γ and δ phase crystallized down to a temperature drop within about 47 K and 55 K from the initiation of solidification respectively. These results also coincided with the calculated results for Fe-20Cr-12.5Ni and Fe-20Cr-11.4Ni weld metal using the developed numerical model.

Development of an Efficient EUV Source by Use of a Liquid Tin Oxide Micro-Target

We report on a low-debris, efficient extreme ultraviolet (EUV) source by use of a liquid micro-target containing low-concentration tin oxide nano-particles. Conversion efficiency from a laser pulse energy to an in-band EUV energy (2% bandwidth (BW) and 2πIsr solid angle) depended on various experimental parameters, such as tin oxide concentration, laser intensity, and pulse separation time between dual laser pulses. By using a low concentration (6%) colloidal target together with dual laser pulses under the optimum separation time, we observed the EUV conversion efficiency of 1.2% with undetectable debris.

Polymorphism and metastable phenomena in liquid tin under pressure

Polymorphism of substances under high pressures is observed and used to obtain materials with new physical properties. Here the authors present experimental results revealing phase transitions and structure of liquid tin at high pressure under metastable conditions using x-ray absorption spectroscopy and x-ray diffraction. They show that there is an abrupt change in the undercooling limit of liquid Sn above 2GPa, where nucleation takes place into the Sn-III metastable solid phase. The liquid local structure is found to be composed of tetrahedral and close-packed configurations. The latter are found to dominate at high pressure favoring crystallization to the Sn-III metastable solid phase.

Composition transients and saturation phenomena at a liquid metal–vapour interface—The oxidation of tin and aluminium

This paper presents a detailed interpretation of the interface saturation data of liquid tin and aluminium drops, on the basis of a mathematical description of the interface evolution described in a previous paper. We also discuss the relevance of evolution times towards the stationary condition for both metal drops, which have given us a better understanding of the interface behaviour and also allowed us to attempt a quantitative estimation of the excess interface concentration.

Target fabrication of low-density and nanoporous materials to generate extreme ultraviolet (EUV)

Our institute has been investigating laser-produced tin, lithium and xenon plasma for extreme ultraviolet (EUV) light source of EUV lithography system, and found the highest conversion efficiency of 3% at 13.5 nm in 2% bandwidth. In the present paper, we introduce fabrication methods of density-controlled tin targets to generate relatively monochromatic EUV, and higher conversion efficiency than bulk tin. The first method is the nano-template method, where liquid tin solution was immersed into a polymer film with monodispersed size nanoparticle. The density can be controlled by tin concentration of the solution. The target can be classified into mass-limited target. We have shown a tendency of monochromatic EUV emission around 13.5 nm with decreasing of tin density. The intensity was higher than tin foil with bulk density. The tendency has a merit to mitigate heat effect of the first EUV mirror. The fabrication method has another merit to control not only density but also the poresize of tin oxide to be 100 nm ∼ 10 μm. The second is liquid crystalline template method to obtain porous tin oxide. The precursor with tin oxide and cellulose provides mechanically stable and transparent film. The film has wavy sub-microstructure derived from microscopic liquid crystal domain structure. The method is simple and short duration for the hydrolysis reaction to solidify tin compound. This material has a merit of feasibility of fabrication, and has been applied for rotation target for 10 Hz and 5 kHz laser repetition.

A numerical study of flow and thermal fields in tilted Rayleigh–Bénard convection

Convection in enclosures heated from below can affect crystals grown from melts. Experiments designed to study such convection can be influenced by small tilts of the experimental system with respect to gravity. Because of the additional body force, tilting can mask flow transition points, making comparisons with stability studies difficult. In this study, the classic Rayleigh–Bénard problem is re-examined numerically with the addition of various tilt angles in cubical enclosures of liquid tin ( Pr = 0.008). The results presented are applied to experiments which measure both molecular diffusivities as well as convection in the melt.

Composition transients and saturation phenomena at a liquid metal–vapour interface: An advanced theoretical approach and an application to the oxidation of tin in a vacuum

This work is aimed to advance the understanding of interfacial saturation phenomena for liquid metal surfaces. The interactions between a liquid metal drop and an oxidising atmosphere can be described by a physical–mathematical description of the liquid metal interface/surrounding environment interface evolution. The closed system and equilibrium assumption were rejected and reference was made to a liquid metal drop as an open system and its related time variation conditions (stationary drop assumption). A better demonstration of the experimental relevance of evolution times towards the stationary condition, in particular for liquid tin is done.

Anomalous change of electrical resistivity with temperature in liquid Pb–Sn alloys

The patterns of electrical resistivity of lead–tin (Pb–Sn) alloys with different compositions, along with pure liquid lead and tin, have been investigated as a function of temperature, using the DC four-probe technique. Evident turning points are observed on resistivity–temperature curves of the four liquid Pb–Sn alloys, and the resistivities increase linearly with rising temperature before the turning points. Moreover, the turning points are all at the temperature scope far above the liquidus. In case of both liquids pure lead and tin, however, the resistivity–temperature curves are linear within the measured temperature. Since resistivity is one of the physical properties sensitive to structures, it is suggested that there are temperature-induced structure changes in the liquid Pb–Sn alloys.