Liquid Tin Research Articles

Dissolution of solid copper in liquid tin enhanced by the liquid structural transition

Physicochemical properties of liquid metals have great impact on many technological processes. Anomalies in liquid structure of metals are affected by temperature at constant pressure. This study investigated the dissolution kinetics of solid Cu in liquid Sn under the influence of structural transition of liquid Sn at temperatures varying from 673 K to 823 K. Structural transition significantly affected the dissolution rate constant of solid Cu. Correspondingly, application of liquid structural transition significantly decreased the activation energy of dissolution and the apparent activation energy of diffusion.

Direct glass-to-metal joining by simultaneous anodic bonding and soldering with activated liquid tin solder

Anodically bonded glass/titanium and glass/steel were investigated for applications in a variety of industrial sectors. Residual stresses that build up during the bonding or cooling down of a joint to room temperature represent the main challenge to the joining process since they drastically weaken the mechanical strength of the joint. A layer of liquid tin-based solder in between the glass and metal part of the joint is used to reduce the internal stresses and improve the contact between the surfaces. The microstructural characterization of glass/solder/titanium and glass/solder/steel joints formed from Ni coated metal substrates indicated that Ni3Sn4 was formed for both types of joint but with a different morphology and location depending on the type of metal substrate. The average shear strength of the joints was 24MPa for glass–titanium and 21MPa for glass–steel joints. For both types of joint, the fracture crack propagated along the glass–solder interface.

The Processing Behavior of Liquid Sn/Molten Polyethylene during Internal Mixing

Abstract In our study, liquid tin (Sn) was mixed with molten polyethylene using an internal mixer; the interfacial tension between the liquid Sn and molten polyethylene was measured using the deformed drop retraction method. The results showed that liquid Sn separated when the Sn content was higher than approximately 2 % by volume because of the interfacial tension of up to 167 mN/m and the 106-fold viscosity difference between the liquid Sn and the molten polyethylene. When Sn separation did not occur, the effects of the mixing time and rotary speed on the degree of mixing and the Sn particle size were analyzed using thermogravimetric analysis and scanning electron microscopy. The results showed that the effects of mixing time and rotary speed on the degree of mixing and Sn particle size can be combined as the impact of specific energy input. With increasing specific energy input, the degree of mixing initially increased and subsequently remained constant, while the Sn particle size initially decreased and subsequently remained constant. The refinement of the dispersed phase was completed with a low specific energy input, but the homogenization of the dispersed phase required a higher specific energy input to achieve completion, revealing the relationship between distributive mixing and dispersive mixing.

First-principles calculation of entropy for liquid metals

We demonstrate the accurate calculation of entropies and free energies for a variety of liquid metals using an extension of the two-phase thermodynamic (2PT) model based on a decomposition of the velocity autocorrelation function into gas-like (hard sphere) and solid-like (harmonic) subsystems. The hard sphere model for the gas-like component is shown to give systematically high entropies for liquid metals as a direct result of the unphysical Lorentzian high-frequency tail. Using a memory function framework we derive a generally applicable velocity autocorrelation and frequency spectrum for the diffusive component which recovers the low-frequency (long-time) behavior of the hard sphere model while providing for realistic short-time coherence and high-frequency tails to the spectrum. This approach provides a significant increase in the accuracy of the calculated entropies for liquid metals and is compared to ambient pressure data for liquid sodium, aluminum, gallium, tin, and iron. The use of this method for the determination of melt boundaries is demonstrated with a calculation of the high-pressure bcc melt boundary for sodium. With the significantly improved accuracy available with the memory function treatment for softer interatomic potentials, the 2PT model for entropy calculations should find broader application in high energy density science, warm dense matter, planetary science, geophysics, and material science.

Growth behavior and properties of atomic layer deposited tin oxide on silicon from novel tin(II)acetylacetonate precursor and ozone

In this work, a novel liquid tin(II) precursor, tin(II)acetylacetonate [Sn(acac)2], was used to deposit tin oxide films on Si(100) substrate, using a custom-built hot wall atomic layer deposition (ALD) reactor. Three different oxidizers, water, oxygen, and ozone, were tried. Resulting growth rates were studied as a function of precursor dosage, oxidizer dosage, reactor temperature, and number of ALD cycles. The film growth rate was found to be 0.1 ± 0.01 nm/cycle within the wide ALD temperature window of 175–300 °C using ozone; no film growth was observed with water or oxygen. Characterization methods were used to study the composition, interface quality, crystallinity, microstructure, refractive index, surface morphology, and resistivity of the resulting films. X-ray photoelectron spectra showed the formation of a clean SnOx–Si interface. The resistivity of the SnOx films was calculated to be 0.3 Ω cm. Results of this work demonstrate the possibility of introducing Sn(acac)2 as tin precursor to deposit conducting ALD SnOx thin films on a silicon surface, with clean interface and no formation of undesired SiO2 or other interfacial reaction products, for transparent conducting oxide applications.

The role of plasma evolution and photon transport in optimizing future advanced lithography sources

Laser produced plasma (LPP) sources for extreme ultraviolet (EUV) photons are currently based on using small liquid tin droplets as target that has many advantages including generation of stable continuous targets at high repetition rate, larger photons collection angle, and reduced contamination and damage to the optical mirror collection system from plasma debris and energetic particles. The ideal target is to generate a source of maximum EUV radiation output and collection in the 13.5 nm range with minimum atomic debris. Based on recent experimental results and our modeling predictions, the smallest efficient droplets are of diameters in the range of 20–30 μm in LPP devices with dual-beam technique. Such devices can produce EUV sources with conversion efficiency around 3% and with collected EUV power of 190 W or more that can satisfy current requirements for high volume manufacturing. One of the most important characteristics of these devices is in the low amount of atomic debris produced due to the small initial mass of droplets and the significant vaporization rate during the pre-pulse stage. In this study, we analyzed in detail plasma evolution processes in LPP systems using small spherical tin targets to predict the optimum droplet size yielding maximum EUV output. We identified several important processes during laser-plasma interaction that can affect conditions for optimum EUV photons generation and collection. The importance and accurate description of modeling these physical processes increase with the decrease in target size and its simulation domain.

Computational study of twisted-tape-induced swirl flow heat transfer and pressure drop in a vertical circular tube under velocities controlled

The twisted-tape-induced swirl flow heat transfer due to exponentially increasing heat inputs with various exponential periods and twisted-tape-induced pressure drop were systematically measured with mass velocity G=4120 to 13570kg/m2/s, inlet liquid temperature Tin=300.13 to 305.78K and inlet pressure Pin=866.52 to 945.86kPa by an experimental water loop flow. Measurements were made on a 59.2mm effective length and its three sections (upper, mid and lower positions), which were spot-welded four potential taps on the outer surface of a 6mm inner diameter, a 69.6mm heated length and a 0.4mm thickness of Platinum circular test tube with the twisted-tape insert. The SUS304 twisted-tape of width w=5.6mm, thickness δT=0.6mm, total length l=372mm, pitch of 180° rotation H=20.34mm and twist ratio y=H/d=3.39 was employed in this work. On the other hand, theoretical equations for k–ɛ turbulence model in a circular tube of a 6mm in diameter and a 636mm long with the twisted-tape insert were numerically solved for heating of water with heated section of a 6mm in diameter and a 70mm long by using PHOENICS code under the same conditions as the experimental ones considering the temperature dependence of thermo-physical properties concerned. The twisted-tape of w=5.6mm, δT=0.6mm, l=370mm, H=20mm and y=3.33 was installed under the same experimental position. The surface heat flux q and the average surface temperature Ts,av on the circular tube with the twisted-tape of y=3.33 obtained theoretically were compared with the corresponding experimental values on q versus the temperature difference between average heater inner surface temperature and liquid bulk mean temperature ΔTL [=Ts,av−TL, TL=(Tin+Tout)/2] graph. The numerical solutions of q and ΔTL are almost in good agreement with the corresponding experimental values of q and ΔTL with the deviations less than 0% to +20% for the range of ΔTL tested here. The numerical solutions of the local surface temperature (Ts)z, local average liquid temperature (Tf,av)z and local liquid pressure drop ΔPz were also compared with the corresponding experimental data of (Ts)z, (Tf,av)z and ΔPz versus heated length L or distance from inlet of the test section Z graph, respectively. The numerical solutions of (Ts)z, (Tf,av)z and ΔPz are within ±5% difference of the corresponding experimental data on (Ts)z, (Tf,av)z and ΔPz. The thickness of the conductive sub-layer δCSL [=(Δr)out/2] and the non-dimensional thickness of the conductive sub-layer y+CSL [=(fF/2)0.5ρluδCSL/μl] for the turbulent heat transfer on the circular tube with the twisted-tape insert are clarified based on the numerical solutions at the swirl velocity usw ranging from 5.39 to 18.03m/s. The correlations of δCSL and y+CSL for twisted-tape-induced swirl flow heat transfer in a vertical circular tube are derived.

Effect of native oxide film on interaction between stainless steels and liquid Sn

The effect of native oxide films on the reaction of liquid Sn with stainless steels has been investigated by analysing the growth of intermetallic layers. The diversity of the oxide layers has been employed by exposure of various stainless steels [martensite stainless steel (MSS), austenite stainless steel (ASS) and duplex stainless steel (DSS)] in air for different times. Liquid tin was prone to metallurgically interact with MSS by formation of interfacial (Fe, Cr)Sn2 intermetallics. The native oxide film on MSS decreased (Fe, Cr)Sn2 layer thickness growth but cannot prevent the intermetallic formation. The reaction of Sn with ASS was hindered by the native oxide layer, and the thickness and coverage ratio of the (Fe, Cr)Sn2 intermetallics decreased with the increasing exposure time in air. The oxide film grown on DSS was stable enough to prevent the formation of (Fe, Cr)Sn2 and changed the tin from metallurgical interaction to physical attachment.

Essential aspects of controlling the oxygen content of molten tin in engineering applications

This work investigated issues regarding the control of the dissolved oxygen content of molten tin in engineering applications. It has been shown that the oxygen content of liquid tin can be adequately monitored with commercial, off-the-shelf, ultra-high-impedance electrometers and ceramic oxygen sensors, requiring only minor modifications for use in a liquid metal environment. Hydrogen and argon gases were used to modify and maintain the oxygen content. It was found that the oxygen can be removed from the tin successfully only above about 600°C in reasonable time, as would be expected from thermodynamics and kinetics. Several scenarios of various ways to handle the tin were investigated, to determine the extent to which one must go in order to maintain a desired oxygen content in molten tin. The electromotive-force and diffusion-coefficient measurements agree reasonably well with the values published in the scientific literature and indicate the range of error to be expected in engineering applications.

Laser produced plasma sources for nanolithography—Recent integrated simulation and benchmarking

Photon sources for extreme ultraviolet lithography (EUVL) are still facing challenging problems to achieve high volume manufacturing in the semiconductor industry. The requirements for high EUV power, longer optical system and components lifetime, and efficient mechanisms for target delivery have narrowed investigators towards the development and optimization of dual-pulse laser sources with high repetition rate of small liquid tin droplets and the use of multi-layer mirror optical system for collecting EUV photons. We comprehensively simulated laser-produced plasma sources in full 3D configuration using 10–50 μm tin droplet targets as single droplets as well as, for the first time, distributed fragmented microdroplets with equivalent mass. The latter is to examine the effects of droplet fragmentation resulting from the first pulse and prior to the incident second main laser pulse. We studied the dependence of target mass and size, laser parameters, and dual pulse system configuration on EUV radiation output and on atomic and ionic debris generation. Our modeling and simulation included all phases of laser target evolution: from laser/droplet interaction, energy deposition, target vaporization, ionization, plasma hydrodynamic expansion, thermal and radiation energy redistribution, and EUV photons collection as well as detail mapping of photons source size and location. We also simulated and predicted the potential damage to the optical mirror collection system from plasma thermal and energetic debris and the requirements for mitigating systems to reduce debris fluence. The debris effect on mirror collection system is analyzed using our three-dimensional ITMC-DYN Monte Carlo package. Modeling results were benchmarked against our CMUXE laboratory experimental studies for the EUV photons production and for debris and ions generation.

Interaction of liquid tin and zinc with AISI 304 stainless steel after passivation in air and nitric acid

The reaction of liquid Sn and Zn with passivated AISI 304 stainless steel has been investigated by analyzing the growth of interfacial intermetallic layers. Both Sn and Zn are prone to metallurgically react with ground stainless steel by the formation of interfacial (Fe, Cr)Sn2 and ζ-(Fe, Cr)Zn13, δ-(Fe, Cr)Zn10 intermetallics, respectively. The native oxide film grown in air has retarded the growth of (Fe, Cr)Sn2 layer. The chemical oxide film grown in nitric acid has prevented the formation of (Fe, Cr)Sn2 layer and changed the metallurgical combination to physical attachment. In the liquid Zn, both native and chemical oxide films become unstable and slightly decrease the growth of intermetallic layer. It is supposed that the composition and structure differences in those two oxide films and the fast diffusion of zinc at relatively high temperature are responsible for the instability of oxide film and the growth of the intermetallic Fe–Zn compound.

Prospective Engineering Applications of Dynamic Transfer Processes Possessing the Self-Organized Fractal Interfaces

General formulation of practically applicable fundamental approach for development of engineering applications in systems with dynamically appearing and disappearing fractal structures is proposed. The approach is illustrated on the low-temperature pyrolysis of butane/propane mixture being pumped via the liquid tin and bismuth alloy preserved at the temperature 200 ± 20°C in the U-shaped test glass. Other prospective engineering applications of the approach are proposed on the base of analysis of selected experiments described in literature.

Glass-to-Glass Anodic Bonding with Liquid Tin Based Fillers: A Mechanistic Study

A new variant of solid state anodic bonding termed activated liquid tin solder anodic bonding (ALTSAB) was recently developed. Here, we report the systematic investigation of bonding parameters temperature, bonding voltage and the alloy composition in a sandwich type configuration with soda-lime glass. Of the five different alloys tested (Sn, SnAl0.6, SnMg0.6, SnLi0.02 and SnLi0.06), SnAl shows the best mechanical integrity of the glass-metal-glass bonds and the lowest current density values during bonding. SnLi alloys entail very high bonding current densities up to 4 mA cm−2 at 270°C and 800 V but poor mechanical performance due to alkali corrosion of the glass at the bonding interface. Supported by the large drift currents in the case of Li containing alloys, it is believed that the overall ALTSAB process is anode limited. With SnAl0.6 alloys, bonds with a shear strength >35 MPa can be produced in less than 7 minutes at a mere 270°C. From temperature dependent data, apparent activation energies in the 70–100 kJ mol−1 range were extracted for all alloys, as it is expected for ion transport processes in soda lime glass. Compared to conventional anodic bonding, ALTSAB offers improved mechanical strength at far lower process temperature and voltage.

Room temperature ionic liquid assisted well-dispersed core-shell tin nanoparticles through cathodic corrosion

Cathodic corrosion has been successfully applied to obtain well-dispersed core–shell tin/tin oxide nanoparticles in room temperature ionic liquids (RTILs) for the first time. RTILs served as a reactant, and to some extent, solvents and electrolytes as well, avoiding the use of nocuous organic solvents.

Production of Silicon by Solid Oxide Membrane-Based Electrolysis Process

ABSTRACTThe solid oxide membrane (SOM) electrolysis process has been successfully tested on a laboratory scale to produce silicon directly from silica in a cost-effective and eco-friendly way. A one-end-closed yttria-stabilized zirconia (YSZ) tube was employed to separate a molten salt containing dissolved silica from a liquid metal anode placed inside the YSZ tube. When an applied electric potential between a liquid tin cathode in the molten salt and the anode exceeds the dissociation potential of silica, oxygen ions are transported out of the molten salt through the YSZ membrane and oxidized at the anode while the silicon cations in the flux are reduced to silicon on the surface of the liquid tin cathode. A potentiodynamic scan (PDS) was performed to determine the dissociation potential of silica in the molten salt system. Electrolysis was performed at 1.05 V for 8 hours. The presence of high-purity silicon crystals on the surface of liquid tin cathode was confirmed by scanning electron microscopy (SEM) and electron dispersive X-ray spectroscopy (EDS).

Analysis of Direct Carbon Fuel Cell Based Coal Fired Power Cycles With CO2 Capture

This work presents an analysis of the application of direct carbon fuel cells (DCFC) to large scale, coal fueled power cycles. DCFCs are a type of high temperature fuel cell featuring the possibility of being fed directly with coal or other heavy fuels, with high tolerance to impurities and contaminants (e.g., sulfur) contained in the fuel. Different DCFC technologies of this type are developed in laboratories, research centers or new startup companies, although at kW-scale, showing promising results for their possible future application to stationary power generation. This work investigates the potential application of two DCFC categories, both using a “molten anode medium” which can be (i) a mixture of molten carbonates or (ii) a molten metal (liquid tin) flowing at the anode of a fuel cell belonging to the solid oxide electrolyte family. Both technologies can be considered particularly interesting for the possible future application to large scale, coal fueled power cycles with CO2 capture, since they both have the advantage of oxidizing coal without mixing the oxidized products with nitrogen; thus releasing a high CO2 concentration exhaust gas. After a description of the operating principles of the two DCFCs, it is presented a lumped-volume thermodynamic model which reproduces the DCFC behavior in terms of energy and material balances, calibrated over available literature data. We consider then two plant layouts, using a hundred-MW scale coal feeding, where the DCFC generates electricity and heat recovered by a bottoming steam cycle, while the exhaust gases are sent to a CO2 compression train, after purification in appropriate cleaning processes. Detailed results are presented in terms of energy and material balances of the proposed cycles, showing how the complete system may surpass 65% lower heating value electrical efficiency with nearly complete (95%+) CO2 capture, making the system very attractive, although evidencing a number of technologically critical issues.

Static and dynamic structures of liquid tin at high pressure fromab initiomolecular dynamics

Static and dynamic structures of liquid Sn were studied by ab initio molecular-dynamics simulations from a state near the melting point (573 K, 0 GPa) to one at higher temperature and pressure (1273 K, 14 GPa). The calculated static structures are in good agreement with the experimental data for a wide range of temperatures and pressures. The dynamic structure factors also agree reasonably well with the available experimental data. Though a cage effect and a transverse mode exist near the melting point, they tend to fade out with increasing temperature. On the other hand, at high pressure, we found that the cage effect and the transverse mode recover even at high temperature. We have also confirmed that a mixing effect exists; that is, when a transverse collective mode occurs in liquid Sn, it also produces a longitudinal mode with a frequency similar to itself. This mixing effect is crucially important for experimental observations of transverse modes.

High temperature fast response pressure probe for use in liquid metal droplet dispensers

A miniature fast response high temperature pressure probe, with demonstrated use in liquid metals up to 255 °C (528 K), has been developed. Innovative packaging technologies have been applied to integrate a conventional piezoresistive silicon pressure sensor into the probe, without the need of an auxiliary water-cooling system. In situ static calibrations are used to verify the linearity of the pressure signal and the stability of the pressure sensitivity (0.5% standard deviation over 70 min at 255 °C). Dynamic calibration, completed in an air shock tube facility, yields the probe's natural frequency. This frequency, when corrected for probe operation in liquid tin, is found to be 100 kHz. The reliability and accuracy of the probe is assessed by mounting it in a tin droplet dispenser for use in an extreme ultraviolet light source. Droplet dispensers typically include an excitation mechanism, which can be based on the generation of acoustic pressure waves to impose a desired droplet frequency. The probe accuracy is verified by the comparison of pressure measurements with laser Doppler vibrometry measurements of the pressure generating structure. A reference pressure measurement, conducted at representative conditions, shows a complex frequency response, with peaks distributed over three orders of magnitude and maximum amplitude of 440 mbar. Time variance of the excitation mechanism due to thermal transients is studied by monitoring the pressure response during operation. Finally, the linearity of the excitation system, with respect to the excitation amplitude, is verified by response measurements. In conclusion, the developed probe is capable of characterizing the excitation mechanism of a liquid metal droplet dispenser. Additionally, real-time monitoring of the performance of the excitation system during long-term operation is possible.

Laser-produced plasma versus laser-assisted discharge plasma: physics and technology of extreme ultraviolet lithography light sources

Powerful extreme ultraviolet (EUV) sources at 13.5 nm are a prerequisite for the economical operation of lithography scanners for semi-conductor manufacturing. These sources have been under development for more than 10 years. At the beginning, many source concepts were considered. Compact technologies like dense plasma focus or capillary Z-pinch discharges reached very rapidly fundamental limits as far as power scalability and lifetime were concerned. Other complex technologies-like synchrotrons-eventually dropped out of the race as well, exceeding by far the footprint and cost targets. Over time, the technology solidified toward the two source concepts: on one hand, the discharge produced plasmas (DPP), which eventually led to the development of the current laser-assisted discharge plasma (LDP); on the other hand, the laser-produced plasmas (LPP). All these technologies generate hot and dense plasmas of similar properties, which emit EUV radiations efficiently as a black body radiator or Planck emitter, in a pulsed manner. The plasma generation method, however, is quite different. DPP uses a pulsed high-voltage current discharge to generate plasma heating a gaseous or vaporized material up to temperatures close to 200,000°C. As for LPP, microscopic droplets of molten tin are fired through a vacuum chamber, individually tracked, vaporized by a pre-pulse laser, and eventually irradiated by a pulsed high-power infrared CO2 laser at 50 to 100 kHz, creating a high-temperature tin plasma, which radiates EUV light. In the case of LDP the plasma is generated between two rotating discs. Partially immersed in baths filled with liquid tin, the discs are wetted and covered with a thin layer of liquid tin. A pulsed laser beam focused on one of the discs evaporates a small amount of tin and generates a tin cloud between the two discs. Next a capacitor bank, which is connected to the discs via the liquid tin, discharges and converts the tin cloud into a plasma heated up to 200,000°C as well.

New type of discharge-produced plasma source for extreme ultraviolet based on liquid tin jet electrodes

A new approach for discharge-produced plasma (DPP) extreme ultraviolet (EUV) sources based on the usage of two liquid metallic alloy jets as discharge electrodes has been proposed and tested. Discharge was ignited using laser ablation of one of the cathode jets. A system with two jet electrodes was tested at a repetition rate of 1 to 5 kHz with dissipated electrical power up to 20 kW. Radiating spectra, time characteristics, and conversion efficiency are similar to conventional DPP schemes with rotating wheels. In the first experiments, the Ga:Sn eutectic alloy, which is liquid at room temperature, was circulating in a closed loop. The high velocity of the jets (30 m/s) ensures a renewed electrode surface for every shot, for a repetition rate frequency of up to 30 to 50 kHz, and provides effective heat transportation from the discharge zone. Modeling and experiments demonstrate that the proposed scheme is able to dissipate up to 200 kW of electrical power without overheating the nozzles and tin surface. It was found that the flexible electrode configuration allows the channeling of essential parts of debris plasma in directions opposite to the EUV collector.