Sn Particle Size Research Articles

Pressure Tuning and Sn Particle Size Optimization for Enhanced Performance in PbSnF4-Based All-Solid-State Fluoride Ion Batteries.

All-solid-state fluoride ion batteries (ASSFIBs) show remarkable potential as energy storage devices due to their low cost, superior safety, and high energy density. However, the poor ionic conductivity of F- conductor, large volume expansion, and the lack of a suitable anode inhibit their development. In this work, PbSnF4 solid electrolytes in different phases (β- and γ-PbSnF4) are successfully synthesized and characterized. The ASSFIBs composed of β-PbSnF4 electrolytes, a BiF3 cathode, and micrometer/nanometer size (µ-/n-) Sn anodes, exhibit substantial capacities. Compared to the μ-Sn anode, the n-Sn anode with nanostructure exhibits superior battery performance in the BiF3/β-PbSnF4/Sn battery. The optimized battery delivers a high initial discharge capacity of 181.3 mAh g-1 at 8mA g-1 and can be reversibly cycled at 40mA g-1 with a high discharge capacity of over 100.0 mAh g-1 after 120 cycles at room temperature. Additionally, it displays high discharge capacities over 90.0 mAh g-1 with excellent cyclability over 100 cycles under -20°C. Detailed characterization has confirmed that reducing Sn particle size and boosting external pressure are crucial for achieving good defluorination/fluorination behaviors in the Sn anode. These findings pave the way to designing ASSFIBs with high capacities and superior cyclability under different operating temperatures.

Influence of the 1% Ti content on microstructure, friction coefficient and contribution to the strengthening mechanisms in the Al20Sn1Cu alloy

Al–Sn alloys are widely used as plain bearings in several engineering applications, particularly in internal combustion engines, where the surface properties are the main properties determining the bearing performance and lifetime. Advanced combustion engines and hybrid systems demand the reduction of wear as well as an increase in loading capacity for plain bearings. Thus, new bearing alloys with improved strength and friction properties have to be developed. For this purpose, Al20Sn1Cu and Al20Sn1Cu1Ti (wt.%) ribbons were produced by single roller melt spinning at low speeds. The ribbons were subsequently bonded by co-rolling with Al with 99.9% purity. Microstructure characterization, hardness and wear tests were used to characterize the ribbons and the co-rolled ribbons. The melt-spun samples show that the microstructures of these alloys are composed of an α-Al matrix and homogeneously distributed β-Sn and γ−Al3Ti. The addition of Ti affects the microstructure by reducing the size of α-Al grains and by changing the distribution and size of Sn particles, resulting in increased hardness and a reduction of the friction coefficient.

Preparation of a novel multi-layered AlSnCu coating for journal bearings

ABSTRACT This paper described preparation process and tribological performance of a novel overlay material used in journal bearings. A new kind of multi-layered AlSnCu coating with good wear resistance and high load capacity was fabricated by arc assisted magnetron sputtering method. The multi-layered structure was implemented by the intermittent sputtering of Al target during the continuous sputtering of AlSnCu target. As a result, the normal growth of Sn crystals was interrupted by introducing periodic sputtering of Al target, which reduced the size of Sn particles in AlSnCu coating. These small size Sn particles played better anti-friction function under both dry and lubricated conditions. Especially, the self-formed Sn-oil synergic lubricating film played a vital role to enhance its tribological performance in oil environment even under a high applied load of 30 N. Therefore, this novel multi-layered AlSnCu coating with small Sn phase displayed considerable application prospects in journal bearings of diesel engine.

Experimental study on eutectic reaction between fuel debris and reactor structure using simulant materials

It is important to ascertain the mechanisms underlying the eutectic reaction between different reactor materials that might be encountered during a Core Disruptive Accident (CDA) of Sodium-cooled Fast Reactors (SFR) since such reactions will affect the accurate progression of a severe accident. In this study, motivated to understand the characteristics of the probable eutectic reaction between fuel debris and the lower head of reactor vessel, a series of simulated experiments has been conducted at the Sun Yat-sen University using a couple of rather lower-eutectic-point (456 K) materials (namely Sn particles and Pb pellet). The experiments were carried out in a self-designed experimental system, which mainly consists of a sample holder and a visible resistance furnace. To acquire a relatively comprehensive understanding, a variety of experimental parameters such as the reaction temperature (463–483 K), contact pressure (0.4–1.2 MPa), Pb pellet diameter (10–25 mm) along with the diameter (0.3–3 mm) and geometry (spherical, cylindrical and droplet-shaped) of the Sn particles have been taken. Through detailed analyses, it is found that the reaction temperature and contact pressure can have noticeable positive impact on the reaction rate. As for the size of Pb pellet and Sn particles, with increasing the diameter ratio of Sn particles to Pb pellet, a non-monotonous effect is observed due to the competing role between the contact area and contact pressure. An evident influence of Sn particle geometry on reaction rate has been verified in accordance with the variation of particle-bed porosity. The analyses in this work also suggest that the reaction rate in previous experiments using block-block samples is generally larger than present experiments using particle-pellet ones, especially at a higher temperature. Knowledge and evidence obtained from this work will be utilized for the design of future high-temperature experiments using actual reactor materials as well as for the improved validations of eutectic-reaction-related models incorporated in fast reactor severe accident codes.

Structural, optical, thermal and electrochemical analysis of annealed SnO2–C nanocomposite

In this present work, Tin Oxide-Carbon (SnO2–C) nanocomposite (NCs) was synthesized via annealing method using glucose and SnCl2 as precursors. As-prepared SnO2–C NCs were investigated by X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), Energy dispersive X-ray (EDX) diffraction, Thermo-gravimetric analysis (TGA) and UV–visible spectral analyses. The electrochemical galvanostatic charge/discharge test shows that SnO2–C NCs possesses excellent electrochemical performance and enhanced cycling life. It exhibits a capacity of 180 mAh/g at the current density of 100 mAh/g and maintains the same capacity up to150 cycles. The observed efficient electrochemical property should have originated from the nanostructured carbon present in SnO2–C NCs, which in turn could have conferred the ability to accommodate the volume changes and prevented changes in Sn particle size during the charge/discharge process. It provides effective channels for lithium ion transport.

Conductivity tuning of the ITO sol-gel materials by adjusting the tin oxide concentration, morphology and the crystalline size

A facile epoxide-driven method has been used to synthesize a series of highly electrically conductive mesoporous indium tin oxide (ITO) sol-gel nanomaterials with different morphologies and particle sizes. By altering the Sn content, the morphology and particle size of these materials undergo a drastic change. The effect of altering the morphology ultimately results in significant changes in the observed conductance of these materials. It became apparent that increasing the dopant concentration in the In2O3 matrix resulted in an increase in the average crystallite size present in the material. Additionally, altering Sn concentration modifies the morphology of the materials which at low concentration exhibit a sponge-like microstructure that gradually changes to a to spherical-type architecture as the concentration of Sn increases. The coupling of the changing effect of particle size and morphology resulted in an observable difference in the materials conductivity. There was a general increase in conductivity observed which correlated with increasing Sn concentration with the maximum conductivity being observed for the sample with 17 wt% Sn. Increasing the Sn concentration above this point resulted in a decrease in the observed conductivity. This work provides a simple method to tune to the conductivity of ITO aerogels by simply altering the Sn concentration to modify the morphology and crystallite size of present within the materials.

Development of Novel Tin Nanostructures Using Pulse Plating Methods for the Electroreduction of Carbon Dioxide to Formic Acid

The development of energy efficient carbon dioxide (CO2) electroreduction processes would simultaneously curb anthropogenic CO2 emissions and provide sustainable pathways for generation of fuels and chemicals. While significant efforts have focused on heterogeneous CO2 electroreduction to various products, to date, no process has demonstrated both high energetic efficiencies and high current densities. A key challenge in the development of active, selective, and stable electrocatalysts in scaling performance nanomaterials to appropriate electrode structures which augment catalytic activity by maximizing utilization, facilitating species transfer, and minimizing undesirable side reactions. The electroreduction of CO2 to formic acid (FA) is attractive due to the low charge requirement (e.g., 2 e- per FA), liquid state product, and high selectivity on a number of low cost catalytic materials. Furthermore, FA has a range of contemporary commercial uses including leather tanning, latex processing, and animal feeds. FA may also find use as a fuel in direct liquid fuel cells. Tin (Sn) is of particular interest due to its high current efficiency for electroreduction of CO2 to FA as well as low cost and toxicity. Prior reports have demonstrated electroreduction of CO2 to FA on Sn catalysts at high faradaic efficiencies (10-95%) on disk electrodes, metal meshes, and gas diffusion electrodes (GDEs) which operate at a range of currents (10-200 mA/cm2) depending on modes of CO2transport.[1-4] Recent work has also indicated that product selectivity decreases with increasing catalyst loading likely due to mass transport losses within a thick catalyst layer.[4] Prior GDE studies have used Sn catalyst particles (150 nm to 150 µm) incorporated into an ionomer which is then applied to a microporous carbon layer (MPL). The MPL is “supported” by a gas diffusion layer (GDL) consisting of hydrophobic (i.e., TEFLON) carbon paper or carbon cloth (Figure 1a). As depicted in Figure 1b this approach limits the electroreduction of CO2 due to 1) low tin catalyst specific surface area due to the relatively large Sn particle size (>150 nm), and 2) unutilized Sn catalyst particles within the ionomer but not in electrical contact with the carbon in the MPL. Previous work directed towards platinum (Pt) catalyst utilization in PEM fuel cell GDEs demonstrated a novel “electrocatalyzation” approach to obtain highly dispersed (~5 nm) Pt catalyst particles using pulse and pulse reverse electrodeposition.[5-7] Additionally, since the Pt catalyst was electrodeposited through an ionomer applied to an uncatalyzed carbon MPL, the catalyst was inherently in electronic and ion contact within the GDE and consequently catalyst utilization was enhanced. Specifically, for oxygen reduction, the electrodeposited catalyst exhibited equivalent performance at 0.05 mg/cm2 loading compared to a conventionally prepared GDE with a catalyst loading of 0.5 mg/cm2.[5] Herein we investigate the electrocatalytic performance of novel Sn nanostructures electrodeposited directly onto the MPL after the application of ionomer devoid of Sn catalyst particles. Using pulse and reverse pulse waveforms to electrodeposit the Sn catalyst particles, as shown in Figure 1c, our goal is to improve the electrochemical reduction of CO2 by 1) increasing the Sn catalyst specific surface area by decreasing the Sn catalyst particle size (<<150 nm), and 2) improve the Sn catalyst utilization by eliminating Sn catalyst particles not in electronic contact with the carbon in the MPL. This approach enables the deposition of robust and uniform catalytic Sn layers on the surface of highly structured GDL/MPL substrates. State of the art Sn catalysts (150 nm) mixed within the ionomer and applied to the MPL are used as a benchmark for comparison with the electrodeposited Sn catalysts. Electrolysis experiments are conducted in a continuous mode lab-scale reactor with flowing gaseous CO2 delivered across a GDE using advanced flow fields. FA production is measured as at cell outlets and used to determine the activity, efficiency, and stability of these novel catalytic structures for CO2to FA conversions.

Pulsed current electrodeposition parameters to control the Sn particle size to enhance electrochemical performance as anode material in lithium ion batteries

Abstract The Sn nanoparticles were synthesized through pulsed current electrodeposition in an acidic electrochemical bath containing polyvinylpyrrolidone (PVP) in order to control the electrodeposition rate of Sn reduction on copper collector electrode. The anode prepared at electrochemical bath containing PVP concentration of about 10 g·L−1 showed highest discharge capacity and cycleability as two main criteria in lithium ion batteries. Also, the pulsed current characteristics such as frequency and current density were investigated and 10 Hz and 20 mA·cm− 2, respectively, are obtained as the optimum parameters. The synthesis of Sn nanoparticles in such media was successfully developed. The sizes and morphologies of NPs were characterized by X-ray diffraction and scanning electron microscopy. Our findings indicated that the nanosized spherical particles with a diameter ranging from 80 to 100 nm could be formed at optimum concentration. The discharge capacity of synthesized Sn nanoparticles was obtained about 1350 mAh g− 1, indicating a 32% increase compared to the synthesized Sn particles with constant current electrodeposition method. Additionally, the discharge capacity of around 550 mAh g–1 is obtained in the 50th cycle, which shows an appropriate cycleability compared to the Sn film electrode prepared by a constant current electrodeposition. The discharge capacities obtained indicated a considerable improvement compared to similar works. The particles size of coated Sn on collector electrode is resulted from interplay between the rate of nucleation and growing rate of particles. PVP affects the kinetic of electrodeposition through surface capping and complexing of Sn2 + species.

Melting behavior of Sn x (SiO 2 ) 100− x granular metal films

We have prepared a series of Sn x SiO 2 ) 100− x granular metal films by RF magnetron sputtering with nominal Sn compositions from x = 30 to x = 90 at. %. X-ray diffraction and transmission electron microscopy measurements confirm that these films consist of small Sn particles, ranging from about 10 nm to 200 nm in mean diameter, embedded in an amorphous SiO 2 matrix. These measurements also indicate that the mean Sn particle size decreases and the particle size distribution becomes more narrow as the Sn concentration is reduced. A differential scanning calorimeter has been used to study the size dependence of the melting temperature of the Sn particles. The melting temperature has been found to be increasingly depressed from the bulk value as the Sn particle size decreases. No evidence of an enhancement in the melting temperature at any particle size has been found. The evolution of the melting behavior of each sample with repeated melting and solidification cycles has also been studied.

Electrochemical Performance of Micro-Sized Sn for Na-Ion Battery

Electrode materials for Na-ion battery (NIB) have been extensively studied to realize a low-cost and high-energy battery. Hard carbon, which delivers 300 mAh g-1, is one of the promising candidates as negative electrode materials for NIB.[1] However, its reversible capacity and energy density are still lower compared to those of graphite in Li-ion battery. Therefore, material developments for higher capacity are required for the practical application. We recently reported that nano-sized Sn delivers ca. 600 mAh g-1 reversible capacity with a good capacity retention in a voltage range of 0.00 − 0.65 V, in spite of ca. 420% volume change of the Sn during charge and discharge.[1, 2] In this research, the impact of the Sn particle size of NIB electrochemical properties was examined. The differences of the electrode surface depending on the Sn particle size are discussed based on the results of surface analyses; secondary ion mass spectroscopy and soft and hard photoelectron spectroscopy to elucidate mechanism of the capacity deterioration. Furthermore we have reported that the FEC additive function as the formation of stable solid electrolyte interphase (SEI) on the surface of the active materials.[3] We also examined the impact of FEC concentrations. To prepare the working electrode, 80 wt% Sn powder (<150 nm or 10 μm, Sigma-Aldrich Co., Ltd), 10 or 20 wt% sodium polyacrylate (PANa) and 10 wt% graphite were mixed with 10 vol% methanol aqueous solution, and the resultant slurry was pasted onto an Al foil. Na metal was used as the counter electrode and 1 mol dm-3 NaPF6/EC:DEC:FEC (49:49:2 vol%) was used as the electrolyte. The charge/discharge measurements were carried out using coin-type cells with a sodiation/desodiation current density of 25/25 or 10/25 mA g-1 only for the 1st cycle. After that, the test was continued with the current density of 50/50 mA g-1. Nano-sized Sn composite electrode with 10 wt% PANa delivers a reversible capacity of ca. 600 mAh g-1 over 100 cycles at 50 mA g-1 (Figure 1(a)). On the other hand, Figure 1(b) confirms that micro-sized Sn electrode with 10 wt% PANa delivers ca. 700 mAh g-1 for only 10 cycles and the capacity rapidly decays after 20 cycles. In this case, the desodiation capacity corresponding to a plateau region at ca. 0.18 V decreases as a function of the cycle number. However, by increasing amount of PANa binder to 20 wt% and changing the 1st sodiation rate from 25 mA g-1 to 10 mA g-1, micro-sized Sn delivers ca. 600 mAh g-1 over 50 cycles at 50 mA g-1 (Figure 1(c)). Even if micro-sized Sn electrode was prepared with 20 wt% of PANa, higher capacity is not delivered at a current density of 25 mA g-1for the initial sodiation. These results suggest that the low initial sodiation rate influences the electrode performance and could be related to SEI formation. Results of surface analysis will be also discussed.

Forcespinning: A new method for the mass production of Sn/C composite nanofiber anodes for lithium ion batteries

The development of nanostructured anode materials for rechargeable Lithium-ion Batteries has seen a growing interest. We herein report the use of a new scalable technique, Forcespinning (FS) to produce binder-free porous Sn/C composite nanofibers with different Sn particle size loading. The preparation process involves the FS of Sn/PAN precursor nanofibers and subsequently stabilizing in air at 280°C followed by carbonization at 800°C under an inert atmosphere. The Sn/C composite nanofibers are highly flexible and were directly used as binder-free anodes for lithium-ion batteries. The produced Sn/C composite nanofibers showed an improved discharge capacity of about 724mAhg−1 at a current density of 100mAg−1 for over 50cycles compared to most nanofiber electrodes prepared by electrospinning and centrifugal spinning. The FS method clearly produces Sn/C nanofiber composite electrodes that have a high specific capacity and excellent cyclic performance, owing to the unique structure and properties of the nanofibers. The FS technology is thus a viable method for the large scale production of nano/micro fibers for battery electrodes, separators, and other applications. To the best of our knowledge, this is the first time to report results on the use of Forcespinning technology to produce composite nanofiber anodes for lithium-ion batteries.

Plasma Assisted Synthesis of Sn Based Nanocomposites As High Performance Li-Ion Anodes

Sn-based alloys /oxides /composite, which have been regarded as potential alternative anode materials, not only have a high theoretical capacity, but also have moderate operation potential to avert the safety concern of Li deposition and co-insertion of solvents to the active materials as is the case with graphite anodes. However, the capacity and cycle performance of the Sn-based anodes should be further improved to meet widely application in Li-ion batteries. For the Sn-based anode materials, further attention should not only be focussed on the exploration of new material system and the modification of currently available materials, but emphasis should also be placed on the microstructure design of the active materials of electrodes, in terms of tuning the volume stress/strain of electrodes and maintaining their integrity during cycling. We proposed that manipulating the multi-phase and multi-scale structures represents an important strategy for further improving the capacity and cycleability of Sn-based and other high-capacity alloy anodes, together with the development of new materials, new technology, and new mechanism. Mechanical milling has long been a versatile method for synthesis of nanostructured materials for lithium ion electrodes. However, difficult control of subtle nanostructure, too long time of milling and the related contamination of materials have been barriers for its application. By combining discharge plasma with mechanical milling, referred as Plasma-milling, a synergetic effect between mechanical impact and plasma is generated, which shows unusual significant effect in the synthesis of nanostructured materials. With this method, we have synthesized a series of nanostructured materials, such as WC-based hardmetals, hydrogen storage materials and especially anode materials for Li ion batteries. And very significantly, this method shows great advantage in massive synthesis (kg scale in lab) of a series of Li storage anodes, such as Si-C, Ge-C, Fe2O3-C. All these materials show excellent electrode performances due to the unique multiscale structure created by the P-milling. In this presentation, P-milling was used to prepare different kinds of Sn–C anode materials. By short-time Ar plasma-milling, a unique Sn–C nanocomposite is obtained with a microstructure of multi-scale Sn particles homogeneously dispersed in a graphite matrix (Figure1). Furthermore, an advanced Sn@SnOx/C nanocomposite was synthesized by using oxygen plasma-milling, in which Sn nanoparticles coated by an ultrathin amorphous/nanocrystalline SnOxlayer are homogeneously embedded within a graphite matrix (Figure 2a, b). As lithium ion anodes, both the plasma Sn-C and Sn@SnOx/C nanocomposites displayed superior electrochemical performance (Figure 2c) to Sn-C composites prepared by conventional ball milling methods. Our results demonstrate that plasma assisted milling is a simple and efficient method to prepare Sn–C composite anodes on a large scale with good performance for lithium ion battery applications. References (1) Liu, H., Hu, R. Z.; Zhu, M. J. Mater Chem. 2012, 22,8022. (2) Liu, H., Hu, R. Z.; Zhu, M. J. Power Sources. 2013, 242,114. (3) Hu, R.Z.; Sun, W.; Zhu, M. J. Mater Chem.A. 2014, 2,9118. (4) Sun, W.; Hu, R. Z.; Zhu, M. J. Power Sources. 2014, I 268, 610. Acknowledgements : This work was supported by the National Science Foundation of China under projects No.51201065 and 51231003, by Doctorate Foundation of Ministry of Education under projects No. 20120172120007, by the Fundamental Research Funds for the Central Universities under project No.2014ZM0002. Figure 1 . Back-scattering electron SEM images of Sn-C composites. (a) Plasma milling-10h; (b) Conventional milling-10h; (c) HRTEM images of P-10h Sn-C composites, (d) Histograms of Sn particle size distributions of P-10h. Figure 2 (a) SEM , (b) TEM image of Sn@SnOx/C nanocomposite via plasma-milling 10h; (c) cycle performance of Sn-C and Sn@SnOx/C nanocomposite Figure 1

Synthesis of tin and tin oxide nanoparticles using liquid phase plasma in an aqueous solution

Liquid phase plasma method was applied to the synthesis of Sn nanoparticles. Tin chloride was used as the tin precursor. Dendrite-shaped particles were formed at the initial stage of the reaction, while spherical nanoparticles were generated at longer discharge time. When the discharge time was too long (longer than 50min in this study), anisotropic SnO2 nanoparticles were produced. With increasing dosage of Cetyltrimethylammonium bromide, used as the surfactant, the Sn particle size decreased, while the degree of dispersion of the particles increased. Higher electrical conductivity of the reactant solution resulted in the production of larger Sn nanoparticles. The solution pH decreased with increasing plasma discharge time until 50min, after which pH slightly increased, co-occurring with the formation of SnO2 nanoparticles.

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.

Microstructure and melting behavior of tin nanoparticles embedded in alumina matrix processed by ball milling

Tin dioxide and aluminum powders were ball milled for different time periods. Sn particles embedded in Al2O3 matrix formed through a displacement reaction after ball milling. However, SnO2 cores remain within some larger particles, while in smaller particles pure Sn cores exist. The embedded Sn particle size was found to increase with the milling time, which is attributed to the thermal effect provided by the exothermic displacement reaction during prolonged milling. Melting point depressions were observed. The melting temperatures of the Sn particles scale linearly with the inverse particle sizes. The extent of melting point depressions is observed to be slightly larger than those in the literature. This is ascribed to the simultaneous presence of Sn–Al2O3 and Sn–SnO2 interfaces.

Improved Electrocatalytic Ethanol Oxidation Activity in Acidic and Alkaline Electrolytes Using Size-Controlled Pt–Sn Nanoparticles

The promotion of the electrocatalytic ethanol oxidation reaction (EOR) on extended single-crystal Pt surfaces and dispersed Pt nanoparticles by Sn under acidic conditions is well known. However, the correlation of Sn coverage on Pt nanoparticle electrocatalysts to their size has proven difficult. The reason is that previous investigations have typically relied on commercially difficult to reproduce electrochemical treatments of prepared macroscopic electrodes to adsorb Sn onto exposed Pt surfaces. We demonstrate here how independent control over both Sn coverage and particle size can yield a significant enhancement in EOR activity in an acidic electrolyte relative to previously reported electrocatalysts. Our novel approach uses electroless nanoparticle synthesis where surface-adsorbed Sn is intrinsic to Pt particle formation. Sn serves as both a reducing agent and stabilizing ligand, producing particles with a narrow particle size distribution in a size range where the mass-specific electrocatalytic activity can be maximized (ca. 1-4 nm) as a result of the formation of a fully developed Sn shell. The extent of fractional Sn surface coverage on carbon-supported Pt nanoparticles can be systematically varied through wet-chemical treatment subsequent to nanoparticle formation but prior to incorporation into macroscopic electrodes. EOR activity for Pt nanoparticles is found to be optimum at a fractional Sn surface coverage of ca. 0.6. Furthermore, the EOR activity is shown to increase with Pt particle size and correlate with the active area of available Pt (110) surface sites for the corresponding Sn-free nanoparticles. The maximum area- and mass-specific EOR activities for the most active catalyst investigated were 17.9 μA/cm(2)Pt and 12.5 A/gPt, respectively, after 1 h of use at 0.42 V versus RHE in an acidic electrolyte. Such activity is a substantial improvement over that of commercially available Pt, Pt-Sn, and Pt-Ru alloy catalysts under either acidic or alkaline conditions.

Morphological Stability of Sn Electrode for Electrochemical Conversion of CO2

The morphological stability of 100 nm Sn particles as the electrode for electrochemical reduction of CO2 was studied in a full electrochemical cell at room temperature and pressure. A degradation of selectivity towards CO2 reduction, accompanied by the pulverization of Sn particles was observed during long-term measurements. During the pulverization process, the size of Sn particles decreased from ~ 100 nm to ~ 3 nm in approximately 60-hour operation. The Faradaic efficiency towards the formation of formate decreased from ~90% to ~56%. On the contrary, the Faradaic efficiency for H2 evolution increased during the measurement. The degradation of the selectivity towards CO2 reduction is primarily attributed to the decrease of the potential atthe cathode.

Tandem plasma reactions for Sn/C composites with tunable structure and high reversible lithium storage capacity

The Sn/C nanocomposites are of great interest as high capacity anode materials for lithium ion batteries (LIBs). In this paper, we employ a tandem plasma reaction method for controlled preparation of Sn/C binary composites. The Sn and C components are generated by magnetron sputtering and plasma decomposition of CH4 in two tandem plasma zones, respectively. The obtained Sn/C composites are composed of ultrafine Sn particles homogeneously embedded in carbon matrix, which exhibit very high reversible lithium storage capacity. The tandem plasma reaction method offers great versatility in controlling the Sn/C ratio and the Sn particle size, allowing a systematic study on the relationship between the structural parameters and the electrode performance. The reversible anode capacity is found to be strongly affected by the Sn particle size while it shows a much weaker correlation with the carbon coating layer.

Fracture of nanostructured Sn/C anodes during Li-insertion

Abstract Sn/C nanocomposites, in the form of Sn or SnO 2 islands attached on carbon surfaces, provide a high initial capacity when used as anodes in rechargeable Li-ion batteries. Upon Li-insertion, however, the Sn undergoes significant volume changes which result in fracture and, hence, a fade in capacity. In the present study a detailed electron microscopy analysis was used for the first time to document the fracture that occurred throughout the Li-insertion and de-insertion process. Particularly, scanning and transmission (SEM&TEM) electron microscopy was performed on four different Sn/C nanocomposites, before and after, electrochemical cycling. Analysis of the Sn particle size distribution showed that the greatest amount of fracture occurred during the first cycle. It was concluded that both the particle volume average and the area fraction of the as prepared Sn or SnO 2 islands must be kept at low values in order to minimize fracture and, therefore, retain a stable capacity. A simple empirical expression was, hence, presented to relate the capacity with the initial microstructure.

Effect of Sn particle size on the intermetallic compound formations of cold sprayed Sn–Ni coatings

Comparative studies on the intermetallic compound (IMC) formations of small (aggregated) and large Sn (irregular) with Ni and Cu in cold gas dynamic sprayed coatings were carried out. The Sn with high purity were selected and prepared as raw materials mixture in order to be sprayed onto Ni and Cu plate-shape substrates. The small particles of Sn (<1μm) were successfully coated under conventional coating parameters when they are mixed with larger powder materials. And microstructural observation regards to compound formation similarly worked out for both small and large Sn mixture. However, the intermetallic formation behavior was turned out to be different. After post-annealing, the larger Sn particles in the composite coating formed larger amount of IMC with Ni than small Sn although, owing to larger interfacial area, more intensive reactivities were expected. Also, there were significant differences in the size and distribution of eutectic pores as well.