Sn Particles Research Articles

Self- Agglomeration of Tin Nanoparticle Array on Porous Anodic Alumina Membranes: Fabrication and Characterization

In this paper, a facile method to fabricate two-dimensional (2D) Sn nanoparticles is demonstrated. Sn nanoparticles are deposited on porous anodic alumina membrane (PAA) by using thermal vapor deposition (TVD) technique. A set of PAA membranes fabricated under the same conditions was coated with Sn for different periods of time. SEM images showed the formation of hexagonal nanoarrays of Sn around each nanopore following a selective agglomeration growth mechanism on the active dots of the PAA surface. As the deposition time increased from 1 to 3 min, the agglomerated particles height increased from 20 to 75 nm. Moreover, Sn was thermally deposited for 2 min onto PAA substrates of different pore diameters. As the pore diameter increases, the formed Sn particles diameter decreases and their density distribution around each pore is improved, which may be attributed to the dimensions of the active area of the PAA surface. According to reflection spectra, it was found that the oscillation strength of the samples increased as the deposition time increased to 2 min. For the time greater than 2 min, the oscillation strength decreased due to the scattering of light, particularly in the short wavelength region, that caused by the increase of sample roughness. Keywords: Growth mechanism, nanoparticles, porous anodic alumina membrane, reflection spectra, thermal evaporation technique.

The synthesis of ordered Sn–C composite microspheres and their mechanical properties

Abstract A method for the fabrication of carbon–tethered Sn micro/nano composite spheres, a facile one-pot hydrothermal route followed by heat treatment in N2, is described. Heating of an aqueous solution of SnCl4 and resorcinol–formaldehyde (RF) to 85 °C for about 3 h in a 50 mL Teflon-lined stainless steel autoclave obtained the SnO2 encapsulated RF composite polymer spheres. Subsequent heat-treatment at 800 °C for 2 h under N2 atmosphere, the RF polymer was carbonized to spherical carbon spheres, whereas SnO2 reduced into nanosized Sn metal that was melted, migrated, and then deposited outside the carbon surface. Variation of the concentration of the two jointly dissolved chemicals and heat treatment temperature enables a variation of the size of the Sn particles. The ordered carbon–tethered Sn composite spheres were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetrical analysis, and mechanical stable process measurements by ultrasonic oscillations. The mechanical stability of Sn–C is strong enough for ultrasonic oscillations for 30 and 60 min.

The Effect of Hydroxyapatite Composition on β Titanium Nanocomposites

The effect of hydroxyapatite (HA) particle composition on the microstructure, Vickers microhardness, relative density and phases of β titanium nanocomposite prepared by powder metallurgy method were investigated experimentally. Hydroxyapatite particle in the range of 5 wt% to 25 wt% were mixed with Ti-35Nb-2.5Sn particles. The samples were pressed at 111 MPa and sintered at 900°C for 2 hours in a vacuum furnace. Result shows that by increasing the hydroxyapatite composition from 5 wt% to 15 wt %, the relative density and Vickers mirohardness increased. Phase analysis of raw materials was studied by XRD analysis and microstructure of composite by SEM.

Positron accumulation effect in particles embedded in a low-density matrix

Systematic studies of the so-called positron accumulation effect for samples with particles embedded in a matrix are reported. This effect is related to energetic positrons which penetrate inhomogeneous medium. Due to differences in the linear absorption coefficient, different amounts of positrons are accumulated and annihilate in the identical volume of both materials. Positron lifetime spectroscopy and Doppler broadening of the annihilation line using Na-22 positrons were applied to the studies of the epoxy resin samples with embedded micro-sized particles of transition metals, i.e., Ni, Sn, Mo, W, and nonmetal particles, i.e., Si and NaF. The significant difference between the determined fraction of positrons annihilating in the particles and the particle volume fraction indicates the positron accumulation effect. The simple phenomenological model and Monte Carlo simulations are able to describe the main features of the obtained dependencies. The aluminum alloy with embedded Sn nanoparticles is also considered for demonstration differences between the accumulation and another related effect, i.e., the positron affinity.

Effect of porosity on electrochemical and mechanical properties of composite Li-ion anodes

The electrochemical and mechanical performance of composite anodes for Li+ batteries is greatly affected by the matrix porosity. The role of porosity in the retention of the electrochemical capacity and mechanical durability was investigated for composite anodes with polyvinylidene fluoride/acetylene black matrix and graphite or Sn microscale particles. Graphite anodes with porosities between 40% and 50% demonstrated reliable mechanical performance after electrochemical cycling and consistent electrochemical capacity above 45% porosity cycled at C/5 rate. However, graphite anodes with porosities larger than 50% had negligible mechanical strength. The results of the mechanical and electrochemical studies identified an optimum porosity of ∼45% at which the graphite anodes had the highest initial elastic modulus and good strength and extensibility, which also agreed with the properties of the polyvinylidene fluoride/acetylene black matrix for the same porosity. The mechanical performance of Sn anodes, however, was quite inferior to that of graphite, which was largely due to the large volumetric expansion of the Sn particles in the first lithiation cycle.

Improved stability of nano-Sn electrode with high-quality nano-SEI formation for lithium ion battery

Sn materials offer high theoretical capacities in lithium ion batteries, but they must have good cycling stability and high rate-capability in order to be commercialized. Complex and costly material treatments of Sn have been effective in reducing capacity fade, but conventionally produced bare Sn is desired for reducing cost. One simple method is to form a high-quality solid electrolyte interphase (SEI) on Sn particles with low resistance and high passivation. Fluoroethylene carbonate (FEC) added to the electrolyte forms a protective and less-resistant SEI on Sn particles during the in-situ electrochemical SEI formation cycle. FEC is a good oxidizing agent that removes highly oxidized carbon compounds and makes a SEI thinner during an oxidation process (delithiation) of SEI formation cycle. The high-quality SEI greatly improves the rate-capability and capacity of nano-sized bare Sn electrodes without any treatments: minimal capacity fade (0.014% cycle−1) at 320mAhg−1 (1.3C) for 150 cycles. The mitigating effect of FEC on capacity fade is not seen with electrodes fabricated from micro-scale (0.1~0.2μm) Sn. The long lithium-ion diffusion path makes these micro-sized materials susceptible to decrepitation during repeated volume changes.

Preparation and electrochemical properties of profiled carbon fiber-supported Sn anodes for lithium-ion batteries

Tin (Sn)-based lithium-ion battery (LIB) anodes are among the most promising alternatives for conventional graphite anodes due to their high specific capacity and safety. The applications of this anode material are restricted by its fast capacity fading during battery operation and its poor rate capacity. In this study, a novel architecture of profiled carbon fiber supported Sn anodes is developed. The profiled carbon fibers have numerous surface grooves where Sn particles are embedded to provide enough capillary channels for rapid lithium-ion transport and enough inter-fiber space for the accommodation of large Sn volume changes on lithium insertion and extraction. This anode architecture is demonstrated by enhanced electrochemical performance. The reversible capacity of 740mAhg−1 at 0.1C after 160cycles is two times higher than that of the state-of-the-art graphite anode. The simple and applicable synthesis process also provides a new path for designing and preparing carbon fiber-based anode materials with improved electrochemical properties.

Optimal design of hollow core–shell structural active materials for lithium ion batteries

To mitigate mechanical and chemical degradation of active materials, hollow core–shell structures have been applied in lithium ion batteries. Without embedding of lithium ions, the rigid coating shell can constrain the inward volume deformation. In this paper, optimal conditions for the full use of inner hollow space are identified in terms of the critical ratio of shell thickness and inner size and the state of charge. It is shown that the critical ratios are 0.10 and 0.15 for Si particle and tube (0.12 and 0.18 for Sn particle and tube), and above which there is lack of space for further lithiation.

Amorphous Cu-added/SnOx/CNFs composite webs as anode materials with superior lithium-ion storage capability

Cu-addition plays a significant role in restricting the aggregation of Sn particles during a continuous charge–discharge progress and improving the cycling stability of SnOx/CNFs electrode.

A hierarchical tin/carbon composite as an anode for lithium-ion batteries with a long cycle life.

Tin is a promising anode candidate for next-generation lithium-ion batteries with a high energy density, but suffers from the huge volume change (ca. 260 %) upon lithiation. To address this issue, here we report a new hierarchical tin/carbon composite in which some of the nanosized Sn particles are anchored on the tips of carbon nanotubes (CNTs) that are rooted on the exterior surfaces of micro-sized hollow carbon cubes while other Sn nanoparticles are encapsulated in hollow carbon cubes. Such a hierarchical structure possesses a robust framework with rich voids, which allows Sn to alleviate its mechanical strain without forming cracks and pulverization upon lithiation/de-lithiation. As a result, the Sn/C composite exhibits an excellent cyclic performance, namely, retaining a capacity of 537 mAh g(-1) for around 1000 cycles without obvious decay at a high current density of 3000 mA g(-1) .

Deflated Carbon Nanospheres Encapsulating Tin Cores Decorated on Layered 3-D Carbon Structures for Low-Cost Sodium Ion Batteries

Novel deflated carbon nanospheres encapsulating metallic tin cores were successfully synthesized and decorated on 3-D layered carbon with wall-like structures. The composite was synthesized by facile in situ carbonization of walnut shell membranes and chemical vapor deposition (CVD) and can be used as negative electrodes for sodium ion batteries. The in situ reduction of SnO2 particles to metallic Sn particles could induce volumetric shrinkage of the particles due to the density difference. The encapsulation of Sn particles by carbon nanospheres under CVD conditions can form unique deflated Sn@C nanoparticles firmly attached on the surface of the 3-D carbon derived from a typical agricultural waste. Particularly interesting, all the carbon nanospheres are in deflated spherical shape, which could provide extra space for volume expansion during charging in Na insertion into the enclosed Sn. The as-prepared composite in the form of pieces of materials are ready electrodes that can be directly assembled into ...

Microstructure, Tensile Properties and Creep Resistance of Sub-rapidly Solidified Mg-Zn-Sn-Al-Ca Alloys

Abstract Microstructures, tensile properties and creep resistances of seven kinds of sub-rapidly solidified Mg-Zn-Sn-Al-Ca alloys were studied. Results show that as for the Mg- x Zn- y Sn-2Al-0.2Ca ( x + y =9, x / y =2, 1 and 0.5, in mass%) alloys, the highest UTS and YTS at RT are obtained with the Zn/Sn mass ratio of 1. The YTS at 150 °C increases but that at 200 °C decreases with the increase of Zn/Sn mass ratio. It is possibly ascribed to the elevated-temperature strengthening of Mg 2 Sn particles since the alloy with the lower Zn/Sn mass ratio contains a higher amount of Mg 2 Sn and a lower fraction of Zn-containing phases. As for the Mg-4.5Zn-4.5Sn-2Al- z Ca ( z =0, 0.2, 0.4 and 0.6) alloys, UTS and YTS increase at first and then decrease with the increase of Ca content at both RT and 200 °C. The strength peaks occur at 0.2% Ca and 0.4% Ca, respectively. Both the initial strain and the steady creep rate decrease with the increase of Ca content below 0.4% Ca at 200 °C under the compression stress of 55 MPa. Minor Ca addition can improve the RT and elevated temperature strength and enhance the compressive creep resistance of the Mg-4.5Zn-4.5Sn-2Al alloy, but reduce the elevated-temperature plasticity. In addition, it also has an obvious influence on the tensile fracture mode, which changes from cleavage to quasi-cleavage at RT and from ductile to quasi-cleavage at 200 °C with the increasing of Ca addition.

Morphology and Formation Mechanism of Sn Nanoparticles Synthesized by Modified Polyol Process at Various pH Values

To synthesize Sn nanoparticles (NPs) less than 30 nm in diameter, a modified polyol process was conducted at room temperature using a reducing agent, and the effects of different pH values of the initial solutions on the morphology and size of the synthesized Sn NPs were analyzed. tin(II) 2-ethylhexanoate, diethylene glycol, sodium borohydride, polyvinyl pyrrolidone (PVP), and sodium hydroxide were used as a precursor, reaction medium, reducing agent, capping agent, and pH adjusting agent, respectively. It was found by transmission electron microscopy that the morphology of the synthesized Sn NPs varied according to the pH of the initial solution. Moreover, while the size decreased to 11.32 nm with an increase up to 11.66 of the pH value, the size increased rapidly to 39.25 nm with an increase to 12.69. The pH increase up to 11.66 dominantly promoted generation of electrons and increased the amount of initial nucleation in the solution, finally inducing the reduced-size of the Sn particles. However, the additional increase of pH dominantly induced a decrease of PVP by neutralization, which resulted in acceleration of the agglomeration by collisions between particles.

The Kinetic Theory of Growth of Zr-Sn Diffusion Layers on Zr55 Cu30 Al10 Ni5 Metallic Glass

The growth kinetics of the intermetallic compound layer between molten pure Sn and Zr55 Cu30 Al10 Ni5 bulk metallic glass (BMG) is mainly controlled by the diffusion mechanism at stage I at which the value of the time exponent is approximately 1/2, also there is unusual or unique stage II whose time exponent of the growth is suppressed to 1/3. It is deduced that phase transition such as nucleation, coalescence occurring in the vicinity of the interface of the diffusion layer within the BMG and the average size growing as one-third power of time, called the Lifshitz—Slezov law. A more elegant means of attack is based upon the Fokker—Planck approach, which permits us to calculate directly the probability of the distribution of steady-state thickness fluctuations. Physical implications of the analytical results also give the one-third power of time of distance scale. The transmission of Sn particles through a disorder system of the BMG, scattered by the local fluctuation levels, is the source of the time exponent from 1/2 to 1/3 as a macroscopic cumulative effect.

Characterization of the microstructure of GaP films grown on {111} Si by liquid phase epitaxy.

The development of a cost-effective Si based platform on which III-V's can be grown is of great interest. This work investigates the morphology of gallium phosphide (GaP) films grown on {111} silicon (Si) substrates by means of liquid phase epitaxy in a tin (Sn) - based solvent bath. Two types of single-crystal {111} Si substrates were used; the first type was oriented exactly along the ⟨111⟩ surface (no-miscut) and the second was miscut by 4°. The growth rate of the GaP films was found to be markedly different for the two types of substrates; the GaP films on the miscut Si substrate grew ∼4 times faster than those on the no-miscut substrate. The GaP films grew epitaxially on both types of substrates, but contained Si and Sn as inclusions. In the case of the no-miscut substrate, a number of large Sn particles were incorporated at the GaP/Si interface. As a result, these interfacial Sn particles affected the strain state of the GaP films dramatically, which, in turn, manifested itself in the form of a duplex microstructure that consists of strained and strain-free regions.

Tin clustering and precipitation in the oxide during autoclave corrosion of Zircaloy-2

Atom probe tomography has been used to study the evolution of tin distribution during the corrosion process in Zircaloy-2. From being completely soluble in the Zr metal matrix, some clustering is evident already in the newly formed oxide close to the metal–oxide interface. Analysis of thicker oxides a few hundred nanometers away from the interface reveals fully developed precipitates of metallic Sn particles of up to 20nm in size. Although the precipitates contain significant amounts of Zr, it is concluded that they are in the process of being depleted in Zr, which is limited only by the slow diffusion in the oxide scale. The findings are interpreted as being a result of the nobility of the Sn yielding a strong driving force to remain in a metallic state after incorporation in the barrier oxide layer. As Sn occupies substitutional sites in the ZrO2 lattice it is oxidized to a 4+ state when incorporated into the oxide, and in order to remain metallic it must nucleate into precipitates within the inner part of the oxide scale before being re-oxidized to 2+ and eventually to 4+ when the oxygen activity is sufficiently high in the outer parts of the oxide.

Transmission Electron Microscopy Study of Mg2Si0.5Sn0.5 Solid Solution for High-Performance Thermoelectrics

A Mg2Si0.5Sn0.5 solid solution was prepared by mixing Mg2Si and Mg2Sn powders and hot-pressing the mixture. The Mg2Si0.5Sn0.5 samples exhibited a much lower thermal conductivity (1.92 W m−1 K−1 at 300 K) than the parent Mg2Si (8.75 W m−1 K−1) and Mg2Sn compounds (6.28 W m−1 K−1). X-ray diffraction measurements confirmed the successful synthesis of the Mg2Si0.5Sn0.5 solid solution. Electron microscopy observations revealed that the grains were mainly 10–20 μm in size and had clean grain boundaries without obvious inclusions and precipitates. The major phase was cubic Mg2Si0.5Sn0.5. MgO nanoparticles 10–20 nm in diameter were evenly dispersed in the Mg2Si0.5Sn0.5 matrix, which probably reduced its thermal conductivity; moreover, uneven structures containing pure Si and Sn particles were found in the Mg2Si0.5Sn0.5 grains. The origin and the formation mechanisms of the MgO and other impurity particles, and their effect on thermoelectric properties of Mg2Si0.5Sn0.5, are discussed. The low thermal conductivity of Mg2Si0.5Sn0.5 resulted in a relatively high dimensionless figure of merit ZT = 0.0132 at 300 K, which may be further increased by optimizing the synthesis procedure, alloy composition, and doping level. This work provides information on the structure and chemistry and their relationship with the thermoelectric properties of the Mg2Si0.5Sn0.5 solid solution; it may help in developing other Mg2Si1−xSnx compounds with superior thermoelectric properties.

Profilometric Evaluation of the Worn Surfaces under Dry Reciprocating Wear Conditions of a Composite Material to Repair Brass Made Parts

This paper presents the results of the profilometric analysis of wear tracks from tribological tests of a composite material made by Diamond Metallplastic GmbH, Germany. This material has a polymer matrix reinforced with Cu, Zn, Sn particles, and various allotropic forms of SiO2. The material belongs to Multimetall Messing category and is recommended by the manufacturer for repairing brass made parts. This composite material was tribologically tested in dry friction reciprocating conditions, in ball-on-flat configuration, using the tribotester CETR-UMT-2 (Bruker Corporation). The counterpiece was a steel ball. The tests were conducted at normal loads of 20, 30, 40 and 50N, over a distance of 100 m, at an average sliding speed of 3,50 mm/s, at room temperature and relative humidity of 40-60%. The wear tracks were examined with the help of a laser profilometer and the profilometric module of the tribotester CETR-UMT-2 (Bruker Corporation). The profilometric analysis results for the composite are compared to those obtained for brass. Comparing the wear tracks of the two materials, it can be found that the composite material has a better tribological behavior than the brass.

Discontinuous finite element discretizations for the [formula omitted] neutron transport equation in problems with spatially varying cross sections

We examine the accuracy of arbitrary degree discontinuous finite element spatial discretizations of the SN particle transport equations with cross sections that are continuous functions of space. For cell-wise constant cross section problems in purely absorbing materials, it has previously been shown that using arbitrary degree DFEM with quadrature-based mass matrix lumping techniques can result in fully accurate schemes with strictly positive angular flux outflows in 1-D slab geometry. We adapt these quadrature-based, or “self-lumping”, schemes to problems with arbitrarily varying spatial cross sections and incorporate the cross-section spatial dependence into the definition of the mass matrices.We compare two approaches to deal with the cross-section spatial dependence. The first approach approximates the true cross section as a cell-wise constant that preserves the cell-average cross-section value. The second method uses self-lumping quadrature to evaluate the exact cross section at quadrature points. Regardless of DFEM trial space degree, approximating a spatially varying cross section with a cell-wise constant cross section results in schemes that are at most second-order accurate in space. Additionally, we demonstrate that assuming a cell-wise constant cross section generates interaction rate profiles that have highly non-physical, non-monotonic discontinuities. Using the self-lumping technique to account for cross-section spatial variation with Gauss or Lobatto quadrature yields fully accurate DFEM schemes for problems with spatially varying cross section. Self-lumping schemes that evaluate the cross section at quadrature points do not exhibit non-physical interaction rate profiles. Unfortunately, only a self-lumping linear DFEM with Lobatto quadrature is guaranteed to produce strictly positive angular flux outflow in a pure absorber when accounting for cross-section spatial variation.Robustness and convergence order comparisons are first carried out using a pure absorber test problem. The cross-section spatial variation is chosen such that an analytical solution can be obtained. Next, we study the spatial effects of isotopic concentration changes during fuel depletion. The depletion problem confirms the accuracy results of the pure-absorber problem.

Influence of Oxides on the Stress Evolution and Reversibility during SnOx Conversion and Li‐Sn Alloying Reactions

The effect of varying the oxygen content in Sn and SnOx films during potential dependent SnOx conversion reactions and LiySn alloying relevant to Li ion battery anodes is examined. For metallic Sn films, the stresses and stability of the films are controlled by Li alloying reactions. Small, non‐contacting separated Sn particles exhibit higher electrochemical stability relative to more continuous polycrystalline films with larger particles. Metallic Sn particles develop tensile stress during LiySn de‐alloying as porous structures are formed. The amount of stress associated with lithiation and delithiation of well‐separated metallic particles decreases as a porous, easy to lithiate, material forms with cycling. During the lithiation of oxides, conversion reactions (SnOx → Sn) and the lithiation of the metallic Sn control the stress responses of the films, leading to highly potential‐dependent stress development. In particular, evidence for a multistep electrochemical mechanism, in which partially reversible lithiation of the oxygen‐containing phases is conjoined with a fully reversible lithiation of the metallic phases of the Sn, is found. The electrochemical stress analysis provides new insight into these mechanisms and delineates the extent of the reversibility of lithiation and conversion reactions of oxides.