Sn Powders Research Articles

Solid solubility extension of copper‐tin immiscible system during mechanical alloying

AbstractIn this paper, copper‐5 wt.%‐tin (Cu‐5wt%Sn) powder mixture was mechanically alloyed in order to study the solid solubility extension during the alloying process. Nanocrystalline supersaturated solid solution has been prepared in this system by high energy ball milling. Based on the thermodynamic model, the Gibbs free energy change in this alloy system during the formation of solid solution is calculated to be positive, which means that there is no driving force to form solid solution in copper‐tin (Cu−Sn) immiscible system. It has been found that a large fraction of grain boundaries and a high density of dislocations play a significant role in the solid solubility extension of immiscible copper and tin.

Optimization of cellular structure of aluminum foams produced by powder metallurgy method

This paper describes a new method for optimizing the cellular structure of AlMg4Si8 alloy foams manufactured via powder metallurgy. The cellular structure was improved by pretreating TiH2 with a layer of Sn powder, which was then remixed with an AlMg4Si8 alloy used as the raw material for the preparation of the precursor. TiH2 was completely encapsulated in the molten Sn at an early stage of foaming when the matrix alloy was still solid, so that liberated H2 was fully captured when TiH2 began to decompose. The interpore flow of H2 along the cracks in the solid matrix was avoided, improving the utilization ratio of TiH2 as a blowing agent. After determining that 4.0 wt% Sn cladding was capable of almost completely encapsulating 0.5 wt% TiH2, the final cellular structure was optimized and regular circular pores were obtained.

Table-like magnetocaloric effect and large refrigerant capacity in Gd65Mn25Si10-Gd composite materials for near room temperature refrigeration

Amorphous Gd65Mn25Si10 as well as crystalline Gd have technologically significant Curie temperature and large magnetic entropy change. Two types of composite materials Gd65Mn25Si10-Gd were fabricated: laminating Gd sheets and amorphous Gd65Mn25Si10 ribbons (multilayer composite) and hot pressing a mixture of amorphous Gd65Mn25Si10 thin ribbons, Gd particles and a small amount of Sn powders (bulk composite). A table-like magnetocaloric effect (MCE) in a wide, commercially useful, temperature span of 73 K (220 K-293 K) were observed in these composites. The values of full-width at half maximum of (−ΔSM) − T plots (ΔTFWHM) and enhanced refrigerant capacity (RC) for the multilayer and bulk composites are 212 K, 724 J/kg, and 248 K, 617 J/kg, respectively, for a field of 5 T. Large ΔTFWHM and RC values and the table-like (−ΔSM)max feature suggest that both multilayer and bulk Gd65Mn25Si10-Gd composites can meet the requirements of different magnetic refrigeration based on Ericsson-cycle.

Understanding the combustion process for the synthesis of mechanically robust SnSe thermoelectrics

Recently, very good thermoelectric performance in both n-type and p-type SnSe has been achieved but was accompanied by poor mechanical properties. Moreover, the synthesis routes used, either the Bridgeman method for single crystal growth or conventional melting methods for polycrystalline samples, are highly energy and time intensive. In the present study, single phase SnSe was synthesized by the Self-Propagating High Temperature Synthesis (SHS) combined with Spark Plasma Sintering (SPS) in a very short time of less than 1h, and with minimum consumed energy. The thermodynamic and kinetic parameters, as well as the role of a pre-synthesized powder of SnSe added to the elemental Se and Sn powders prior to the SHS process, were systematically investigated for the first time. The presence of the pre-synthesized SnSe powder in the mixture of elemental Se and Sn powders promotes multipoint nucleation and inhibits the grain growth, resulting in a weak preferential orientation after SHS that is maintained in the bulk samples after SPS. Thermoelectric and mechanical properties of such samples are superior in comparison to the samples that do not contain the pre-synthesized powder of SnSe in the starting material. The compressive strength, bending strength and fracture toughness of the sample containing 30% of the pre-synthesized SnSe were 74.7MPa, 40.6MPa and 0.32MPam1/2, respectively. A maximum ZT value of 0.5 was achieved for this sample at 773K, which is comparable with polycrystalline samples synthesized by the conventional melting method. This work shows that the SHS reaction combined with SPS densification is an exceptionally rapid and cost effective synthesis process that yields mechanically robust bulk SnSe, a crucial step for large scale commercial applications of this thermoelectric material.

Structural studies of the layered SnSe produced by mechanical alloying and melting technique

The Sn-Se based materials were synthetized by mechanical alloying and simple melting techniques. By mechanical alloying technique we observed a very fast nucleation of the SnSe orthorrombic layered compound with a remarkable structural stability. On the other hand, the milling atmosphere showed a strong influence on the final result. By simple melting of the elemental Se and Sn powders we obtained a very oriented SnSe layered structures. The microstructural details were evaluated by Stephens's microstrain model, differential scanning calorimetry and thermic treatment.

Synthesis and characteristics of p-type CdS nanobelts

We report, for the first time, the synthesis of single crystalline p-type CdS nanobelts using a simple thermal evaporation of mixture of CdS and trace tin (Sn) powder. Single-crystal Sn doped CdS nanobelts are grown along the direction. The Raman spectrum of Sn-doped CdS nanobelts has a ~2 cm−1 red-shift in comparison with that of undoped CdS nanobelts. The neutral-acceptor bound exciton (AOX) and donor–acceptor pair (DAP) emissions in the low temperature photoluminescence spectroscopy of Sn doped CdS nanobelts studies support the p-type conduction in Sn doped CdS. Electrical transport measurements reveal that the tin-doped CdS nanobelts show p-type conductivity. The synthesis of p-type CdS nanobelts is expected to shed light on p-type doping difficulty of II–VI wide semiconductor.

The thermoelectric properties of CoSb3 compound doped with Te and Sn synthesized at different pressure

The skutterudite CoSb[Formula: see text]Te[Formula: see text]Sn[Formula: see text] compound was synthesized successfully by high pressure and high temperature (HPHT) method using Co, Sb, Te and Sn powder as raw materials. The effects of pressure on its structure and the thermoelectric properties are investigated systematically from 300 K to 800 K. The electrical resistivity and the absolute value of the Seebeck coefficient for the sample increases with rising synthetic pressure. The thermal conductivity of the sample decreases with synthetic pressure and temperature rising in the range of 300–800 K. In this study, the maximum dimensionless figure of merit (ZT) value of 1.17 has been achieved at 793 K, 3 GPa for this thermoelectric material.

Highly visible-light active with Co/Sn co-doping of TiO2 nanoparticles for degradation of methylene blue

We report the changes in the structural and optical property of TiO2 nanoparticles on co-doping Sn and Co ions. Different amounts of Co and Sn co-doped TiO2 (with 1–2–4 mol% Co and 1–5–10 mol% Sn) powders were prepared at temperatures in the range of 475 and 875 °C by simple sol–gel synthesis technique and were thoroughly characterized by means of X-ray diffraction (XRD), field emission scanning electron microscope, fourier-transform infrared, Brunauer, Emmett and Teller (BET) surface area, zeta potential and flat band potential measurements. Photo-catalytic ability of co-doped TiO2 powders was evaluated by means of methylene blue degradation experiments conducted under the irradiation of simulated solar light. The XRD showed the presence of only anatase TiO2 for the un-doped and Co-doped titania samples. Titania rutile phase formation in nanoparticles was promoted by Sn4+ addition. XRD analysis also pointed out the decrease in the crystal size with the increase in Sn concentration in the samples. The BET analysis reported an increase in the surface area with the increase in the Sn concentration. It was found that the photo-catalytic activity of TiO2 was obviously enhanced by the co-doping. The excellent photo-catalytic activities due to the contribution from the increased visible light absorption, promoted separation of photo-generated electrons and holes as well as enhanced photo-catalytic oxidizing species with the doping of Co and Sn in TiO2.

Electrochemical Reduction of Carbon Dioxide to Formic Acid in Ionic Liquid [Emim][N(CN)2]/Water System

The electrochemical reduction of CO2 to formic acid or formate is a promising process for addressing technological challenges of transporting and storing energy produced by intermittent renewable energy sources. However, this electrochemical CO2 conversion process requires high overpotentials to activate CO2 into “an energetically unfavorable” radical anion intermediate on metal electrodes under the aqueous electrolyte systems. For our present study, we introduce a novel solvent additive such as 1-ethyl-3-methylimidazolium dicyanamide ([Emim][N(CN)2]) ionic liquid into the aqueous solution to increase the electrochemical reduction activity of CO2 for the formic acid formation, to increase the CO2 solubility, and to suppress the competitive hydrogen evolution reaction. Cyclic voltammetry is performed in an [Emim][N(CN)2] aqueous solution on a Sn powder electrode to determine the onset potential of CO2 electrolysis and its electrochemical stability. In addition, CO2 electrolysis is carried out by chronoamperometry measurements at various fixed potentials and electrolyte concentrations to understand their effects on the faradaic efficiency for the conversion of CO2 into the formic acid. The maximum faradaic efficiency obtained during electrolysis with a 0.5M concentration of [Emim][N(CN)2] is 81.9% towards the formation of formic acid at −1.2V vs. RHE and at the overpotential of 1.08V.

Elemental Precursor Solution Processed (Cu1–xAgx)2ZnSn(S,Se)4 Photovoltaic Devices with over 10% Efficiency

The partial substitution of Cu+ with Ag+ into the host lattice of Cu2ZnSn(S,Se)4 thin films can reduce the open-circuit voltage deficit (Voc,deficit) of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. In this paper, elemental Cu, Ag, Zn, Sn, S, and Se powders were dissolved in solvent mixture of 1,2-ethanedithiol (edtH2) and 1,2-ethylenediamine (en) and used for the formation of (Cu1-xAgx)2ZnSn(S,Se)4 (CAZTSSe) thin films with different Ag/(Ag + Cu) ratios. The key feature of this approach is that the impurity atoms can be absolutely excluded. Further results indicate that the variations of grain size, band gap, and depletion width of the CAZTSSe layer are generally determined by Ag substitution content. Benefiting from the Voc enhancement (∼50 mV), the power conversion efficiency is successfully increased from 7.39% (x = 0) to 10.36% (x = 3%), which is the highest efficiency of Ag substituted devices so far.

Structure and Magnetic Properties of Ternary Nanosized FeAlSn and CuFeCo Powders Synthesized by Mechanical Milling

Ternary Fe72Al26Sn2 and Cu70Fe18Co12 alloys were obtained by mechanical alloying of pure Fe, Al, Sn, Cu and Co powders using a high energy ball mill. X-ray diffraction and electron microscopy supported by magnetic measurements have been applied to follow changes in the microstructure, phase composition and magnetic properties in dependence on milling time. With the increase of milling time all Al and Sn atoms dissolved in the bcc Fe and the final product of the MA process was the nanocrystalline Fe (Al, Sn) solid solution in a metastable state with a large amount of defects and mean crystallite size of 5 nm. However, the obtained crystallite size value is about 10 nm for the ball milled Cu70Fe18Co12 powders. The electron microscope observations show the morphology of powder particles. Magnetic properties of the nanocrystalline mechanically alloyed FeAlSn and CuFeCo were also investigated and were related to the microstructural changes.

Ethanol sensing properties and dominant sensing mechanism of NiO-decorated SnO2 nanorod sensors

NiO-decorated SnO2 nanorods were synthesized by the thermal evaporation of Sn powders followed by the solvothermal deposition of NiO. A multi-networked p-n heterostructured nanorod sensor was fabricated by dropping the p-NiO-decorated n-SnO2 nanorods onto the interdigited electrode pattern and then annealing. The multi-networked p-n heterostructured nanorod sensor exhibited enhanced response to ethanol compared with the pristine SnO2 nanorod and NiO nanoparticle sensors. The former also exhibited a shorter sensing time for ethanol. Both sensors exhibited selectivity for ethanol over other volatile organic compounds (VOCs) such as HCHO, methanol, benzene and toluene and the decorated sensor exhibited superior selectivity to the other two sensors. In addition, the dominant sensing mechanism is discussed in detail by comparing the sensing properties and current-voltage characteristics of a p-NiO/n-SnO2 heterostructured nanorod sensor with those of a pristine SnO2 nanorod sensor and a pristine NiO nanoparticle sensor. Of the two competing electronic mechanisms: a potential barrier-controlled carrier transport mechanism at a NiO-SnO2 p-n junction and a surface-depletion-controlled carrier transport mechanism, the former has some contribution to the enhanced gas sensing performance of the p-n heterostructured nanorod sensor, however, its contribution is not as significant as that of the latter.

On-chip growth of single phase Zn2SnO4 nanowires by thermal evaporation method for gas sensor application

Ternary oxide nanowires have attracted significant research attention in recent years due to their advanced physicochemical properties. The synthesis of single phase ternary oxide nanowires is, however, a challenge because of the differences in vapour conditions of the evaporative sources. Herein, we report the on-chip synthesis of single phase Zn2SnO4 nanowires for highly sensitive NO2 gas sensor applications by a thermal evaporation method. The Zn2SnO4 nanowires were obtained using a precursor mixture of ZnO, C and Sn powders. To obtain single phase Zn2SnO4 nanowires, we varied the amount of Sn in the precursor mixture, while the ZnO and C contents were fixed. The morphology, crystal structure and phase composition of the products were characterised by scanning electron microscopy and X-ray diffraction. The gas-sensing characteristics of the synthesised nanowires were tested at different temperatures, and we found that the single phase Zn2SnO4 nanowires showed superior sensitivity to NO2 gas.

Ethanol gas sensing using a networked PbO-decorated SnO2 nanowires

PbO-decorated SnO2 nanowires (NWs) were synthesized using a two-step process consisting of thermal evaporation of Sn powders in an oxygen atmosphere and solvothermal decoration of the SnO2 NWs with PbO nanoparticles. Chemiresistive gas sensors were fabricated by deposition of the synthesized PbO-decorated SnO2 NWs onto interdigitated electrodes. The pristine and PbO-decorated SnO2 NW sensors exhibited responses of 24.0 and 60.0 to 200-ppm ethanol at 300°C, respectively, suggesting that the response of the SnO2 NWs is significantly improved by decorating them with PbO nanoparticles. This result also suggests that the ability of enhancing the gas sensing performance of the original sensor material further is more important than the gas sensing ability of the decorating material itself. The response of the PbO-decorated SnO2 NWs was compatible or higher than those of the SnO2 NWs decorated with other well-known semiconducting metal oxide or noble metal nanoparticles. The response/recovery times of the decorated NWs were shorter than the pristine one, respectively. Both the pristine and PbO-decorated SnO2 NW sensors exhibited selectivity toward ethanol against other volatile organic compounds such as acetone, methanol, benzene, and toluene. The underlying mechanisms for the enhanced sensing performance of the PbO-decorated SnO2 NW sensors toward ethanol was discussed.

Decomposition of equilibrium interphase boundary in substitutional alloys upon mechanical alloying

The vacancy-flux-induced decomposition of an interphase boundary in substitutional alloys has been considered. The interphase boundary decomposition has been described using the nonequilibrium thermodynamics approach, which considers a heterogeneous system to be continuous medium, including the interphase boundary. A hypothesis of local equilibrium in the thermodynamics of a continuous medium has been substituted for a more general hypothesis that takes into account the nonlocal dependence of thermodynamic forces and fluxes on order parameters. The interpretation of the formation of spatial composition modulations during the mechanical alloying of pure metallic Cu–Co, Cu–Fe, and Fe–Cr–Sn powder mixtures has been given.

Comparative Analysis of SnOx Thin Films Deposited by RF Reactive Sputtering with Different SnO/Sn Target Compositions

A p-type oxide is a key element for transparent thin-film transistor applications. Among the various p-type oxides currently available, SnOx deposited by sputtering is the subject of interest in this study for high-performance and reliable thin films. A tin target or a tin oxide target is typically used to fabricate p-type SnOx during sputtering. A metallic target provides easy control of various film properties and chemical compositions, while a ceramic target offers structural stability and better control of stoichiometry. To use the advantages of both metallic and ceramic targets, a composite target of Sn and SnO was devised, which may provide reliable p-type SnOx and better control of structural defects. We evaluated four different composition ratios of Sn+SnO targets: a 100 mol% metallic Sn target, a composite target with 50 mol% Sn powder + 50 mol% SnO powder, a composite target with 20% Sn powder + 80 mol% SnO powder, and a 100 mol% ceramic SnO target. SnOx films were deposited under various sputtering conditions and analyzed structurally, electrically and optically. The composite target with 20 mol% Sn was found to be a promising candidate for p-type SnOx films, showing >75% transmittance and high mobility up to 9.07 cm2V−1s−1.

Growth, structural and optical properties of orderly SnO2 microhemispheres on patterned sapphire substrates

One-dimensional nanoscaled materials, such as nanotubes, nanowires and nanobelts, have attracted a great deal of attention in recent years because of their unique electronic, optical, and mechanical properties. Their potential applications are found in next generation devices, functional materials, and sensors. A material of particular interest is stannic oxide (SnO2), which is a novel oxide semiconductor material for ultraviolet and blue luminescence devices due to its wide band gap of 3.6 eV at room temperature. SnO2 can also be widely used in many fields, such as gas sensors, optoelectronic devices, and transparent conductive glass, because of its high optical transparency in the visible range, low resistivity, and higher chemical and physical stability. In recent years, one-dimensional nanostructures of SnO2 materials, such as nanobelts, nanotubes, and nanowires, have been reported. However, the preparations of orderly SnO2 micro/nanostructures have been rarely reported. In this paper, orderly SnO2 microhemispheres with different sizes are grown on patterned sapphire substrates by a traditional chemical vapor deposition method without using any catalyst. The patterned sapphire substrates are cleaned by using a standard sapphire wafer cleaning procedure. High-purity metallic Sn powders (99.99%) and oxygen gas are used as Sn and oxygen sources, respectively. The flow rate of high-purity Ar carrier gas is controlled at 200 sccm, and the oxygen reactant gas with a flow rate of 100 sccm is introduced into the system. In the growth process, the whole system is kept at 1000℃ for 30 min. The surface morphologies, structural and optical properties of the SnO2 microhemispheres are investigated by the field emission scanning electron microscope (HITACHI S4800), the X-ray diffraction with a Cu Kup radiation (0.15418 nm), the optical absorption spectroscope (UV-3600 UV-VIS-NIR, Shimadzu), and the photoluminescence spectroscope with an excitation source of He-Cd laser (=325 nm) to identify the As related acceptor emission, respectively. These results show that the diameters of SnO2 microhemispheres become larger, and the crystal quality is degraded with the increase of Sn powder mass. The special selective growth of SnO2 microhemisphere on a patterned sapphire substrate is found. In addition, we also find that the optical band gaps of the samples A-D are all redshifted with the increase of Sn powder mass. The shrinkage of Eg in the absorption spectrum should be partly attributed to the degradation of crystal quality because of excess Sn sources. This growth method of SnO2 microhemisphere provides a feasible and effective way of preparing the high density, orderly arrangement of SnO2 micro/nanostructures.

Optical Properties of Nano–Structured ZnO : Sn Powders Prepared in a Micro Drop Fluidized Reactor

Optical Properties of Nano–Structured ZnO : Sn Powders Prepared in a Micro Drop Fluidized Reactor

Gd–Sn alloys and Gd–Sn–graphene composites as anode materials for lithium-ion batteries

Gd–Sn alloys and Gd–Sn–graphene composites are prepared by a simple route. GdSn6/G composites have higher reversible discharge capacities than Gd–Sn powders.

Nanoporous Tin with a Granular Hierarchical Ligament Morphology as a Highly Stable Li-Ion Battery Anode.

Next generation Li-ion batteries will require negative electrode materials with energy densities many-fold higher than that found in the graphitic carbon currently used in commercial Li-ion batteries. While various nanostructured alloying-type anode materials may satisfy that requirement, such materials do not always exhibit long cycle lifetimes and/or their processing routes are not always suitable for large-scale synthesis. Here, we report on a high-performance anode material for next generation Li-ion batteries made of nanoporous Sn powders with hierarchical ligament morphology. This material system combines both long cycle lifetimes (more than 72% capacity retention after 350 cycles), high capacity (693 mAh/g, nearly twice that of commercial graphitic carbon), good charging/discharging capabilities (545 mAh/g at 1 A/g, 1.5C), and a scalable processing route that involves selective alloy corrosion. The good cycling performance of this system is attributed to its nanoporous architecture and its unique hierarchical ligament morphology, which accommodates the large volume changes taking place during lithiation, as confirmed by synchrotron-based ex-situ X-ray 3D tomography analysis. Our findings are an important step for the development of high-performance Li-ion batteries.