New lead-free solder alloy

As the electronics industry is moving towards lead-free manufacturing processes, a new lead-free solder alloy based on Sn–9Zn–1Bi–2Cu–In is described. The quaternary alloy with indium additions exhibits melting, wetting, and mechanical properties superior to those in binary, ternary, and quaternary alloys. Indium as a penternary addition decreases the melting point of this alloy to 181 ^°C which it is a lower value when compared with the eutectic Sn–Pb solder (183 ^°C), it decreases the contact angle to 23^° which is very close to that for Sn–Pb solder alloy, it increases the Young’s modulus to higher values, and it increases its hardness to 19 kgf/mm² when compared with 12.9 kgf/mm² for the Sn–Pb solder alloy.     

Electrochemical and structural properties of a polymer electrolyte system based on the effect of CeO<Subscript>2</Subscript> nanofiller with PVDF-co-HFP for energy storage devices

In the present work, a series of five different nanocomposite polymer electrolytes (NCPEs) have been reported with varying contents of ceria, CeO₂ nanofiller suitably incorporated within an optimized composition having 75:25 wt% ratio of poly(vinylidenefluoride-co-hexafluoropropylene) [(PVDF-co-HFP)] and zinc trifluoromethanesulfonate (ZnTf) in the form of films obtained by mean of solution casting technique with a general formula [75 wt% PVDF-co-HFP:25 wt% ZnTf]-x wt% CeO₂ where x = 1, 3, 5, 7, and 10, respectively. The chosen NCPE system is found to exhibit the maximum electrical conductivity of 3 × 10^?4 S cm^?1 for 5 wt% loading of CeO₂ nanofiller at ambient temperature. The observed conductivity enhancement has been attributed to the occurrence of an increase in the amorphous content as confirmed by X-ray diffraction (XRD) analysis. Detailed Fourier transform infrared (FTIR) spectral analysis has indicated the feasibility of complexation of the host polymer matrix with ZnTf salt and CeO₂ nanofiller. The incorporation of CeO₂ nanofiller has further increased the decomposition voltage of the polymer electrolyte from 2.4 to 2.7 V as revealed from the voltammetric studies performed on such NCPEs, thereby suggesting the suitability of these NCPE films with an enhanced electrical conductivity as new electrolytes in order to design and fabricate eco-friendly zinc rechargeable batteries and other electrochemical devices.     

Effect of copper addition on some properties of rapidly solidified lead-free Sn–-10 wt% Zn alloys

This study aimed at investigating the effect of adding copper (Cu) on some properties of the lead-free alloys which rapidly solidified from melt. X-ray analysis, hardness, elastic modulus, electrical conductivity and resistivity were studied. The results indicated that the alloy hardness and elastic modulus improved by increasing the copper (Cu) content and decreasing the zinc (Zn) content. The electrical conductivity ranged from 0.250 to 0.847?×?10⁷ ohm^?1 m^?1 for the alloy under study. The electrical resistivity increases linearly with temperature until the melting point is reached. The residual resistivity results from disturbances in the lattice rather than caused by thermal vibration and the most drastic increases in the residual resistivity are caused by foreign atoms in solid solution with matrix metal. The electrical resistivity values ranged from 11.8 to 40?×?10^?8 ohm m, when the copper content changed from 0.0 to 2.0 wt% and zinc changed from 8.0 to 10.0 wt%.     

Fabrication and electrochemical performance of La<Subscript>0.5</Subscript>Sr<Subscript>0.5</Subscript>CoO<Subscript>3</Subscript> impregnated porous YSZ cathode

La_0.5Sr_0.5CoO₃-yttria-stabilized zirconia (LSCO-YSZ) composite cathode for solid oxide fuel cell (SOFC) has been fabricated by wet impregnation method. Nitrate precursors of La, Sr, and Co have been impregnated into the pre-sintered porous YSZ matrix, which is converted into LSCO phase after calcination at 850 °C in the presence of glycine as confirmed from X-ray diffraction. LSCO of 5, 7, and 10 wt% impregnated porous YSZ have been electrochemically characterized using 2-probe AC conductivity method. Maximum ionic conductivity of 0.27 S/cm at 800 °C and activation energy of 0.15 eV between 600 and 800 °C have been observed for 10 wt% LSCO-YSZ cathode. Area-specific resistance of 1.01 Ω cm² at 800 °C is estimated for the electrolyte-supported half-cell (10 wt% LSCO-YSZ/YSZ). After testing the LSCO-YSZ cathode matrix, the electrolyte-supported full cell (10 wt% LSCO-YSZ/YSZ/NiO-YSZ) has been tested and produced maximum power density 51.12 mW/cm² (109.38 mA/cm²) at 800 °C. The electrolyte-supported full cell exhibited 6 Ω cm² electrode polarization at 800 °C in H₂, which is in higher side leading to low performance. LSCO-YSZ/YSZ/NiO-YSZ SOFC found to give stable performance up to 2 h and scanning electron microscopy analysis has been carried out before and after cell testing to assess the morphological changes.     

Decomposition behavior and properties for tin–antimony alloy with bismuth content

The peritectic alloy Sn–10Sb, was chosen as one of the lead-free solder alloys to be subjected to many studies. Bi atoms were added to this alloy in the range of 1–3 wt%. The experimental results obtained from this study show a complete solubility of Bi atoms when added by 2 wt%. More additions of Bi tend to increase the formation of the intermetallic compound SnSb by reducing the precipitations of Sb as a single phase. This intermetallic compound with the precipitation of Bi as a third phase tends to improve the mechanical properties of this alloy.     

Investigations of redistribution of iron in a zirconium alloy due to neutron irradiation

Data were obtained with the help of ⁵⁷Fe Mössbauer spectroscopy about the redistribution of iron atoms between intermetallic precipitates and between precipitates and the solid solution phase in E635-type alloy (Zr-1.2 wt% Sn-0.34 wt% Fe-1.0 wt %Nb-0.03–0.05 wt% O) due to neutron irradiation.     

Interfacial reactions between Al7075 alloy and BaAl2Si2O8 + CaAl2Si2O8 mixture

The present work reports the SEM, EPMA and TEM examination of reactions at the interface of Al7075 alloy and a 50/50 wt% mixture of BaAl₂Si₂O₈ + CaAl₂Si₂O₈ feldspars at 850 °C, 1150 °C and 1250 °C. Sintering of the feldspar mixture at 1450 °C caused dissolution of ~1.0 wt% Ca in BaAl₂Si₂O₈ and 0.5 wt% Ba in CaAl₂Si₂O₈. The interaction of the Al alloy with the sintered feldspars shifted the alloy composition to the Al–Si–αBaAl₂Si₂ and Al–Si–βaAl₂Si₂ compatibility triangles. The feldspars underwent a series of phase transformations, leading ultimately to the formation of Al₂O₃.     

Enhanced electrical properties of polyethylene oxide (PEO) + polyvinylpyrrolidone (PVP):Li<Superscript>+</Superscript> blended polymer electrolyte films with addition of Ag nanofiller

Polymer blended films of polyethylene oxide (PEO)?+?polyvinyl pyrrolidone (PVP):lithium perchlorate (LiClO₄) embedded with silver (Ag) nanofiller in different concentrations have been synthesized by a solution casting method. The semi-crystalline nature of these polymer films has been confirmed from their X-ray diffraction (XRD) profiles. Fourier transform infrared spectroscopy (FTIR) and Raman analysis confirmed the complex formation of the polymer with dopant ions. Dispersed Ag nanofiller size evaluation study has been done using transmission electron microscopy (TEM) analysis. It was observed that the conductivity increases when increasing the Ag nanofiller concentration. On the addition of Ag nanofiller to the polyethylene oxide (PEO)?+?polyvinyl pyrrolidone (PVP):Li⁺ electrolyte system, it was found to result in the enhancement of ionic conductivity. The maximum ionic conductivity has been set up to be 1.14?×?10^?5 S cm^?1 at the optimized concentration of 4 wt% Ag nanofiller-embedded (45 wt%) polyethylene oxide (PEO)?+?(45 wt%) polyvinyl pyrrolidone (PVP):(10 wt%) Li⁺ polymer electrolyte nanocomposite at room temperature. Polyethylene oxide (PEO)?+?polyvinyl pyrrolidone (PVP):Li⁺ +Ag nanofiller (4 wt%) cell exhibited better performance in terms of cell parameters. This is ascribed to the presence of flexible matrix and high ionic conductivity. The applicability of the present 4 wt% Ag nanofiller-dispersed polyethylene oxide (PEO)?+?polyvinyl pyrrolidone (PVP):Li⁺ polymer electrolyte system could be suggested as a potential candidate for solid-state battery applications. Dielectric constants and dielectric loss behaviours have been studied.     

Conductivity studies of poly(ethylene oxide)(PEO)/poly(vinyl alcohol) (PVA) blend gel polymer electrolytes for dye-sensitized solar cells

Poly(ethylene oxide)(PEO)–poly(vinyl alcohol) (PVA) blend-based gel polymer electrolytes (GPEs) have been prepared by blending equal weights of PEO and PVA in ethylene carbonate (EC), dimethyl sulfoxide (DMSO), tetrabutylammonium iodide (TBAI), and iodine crystals (I₂). The conductivity, diffusion coefficient, number density, and ion mobility of the electrolytes have been calculated from the impedance data obtained from electrochemical impedance spectroscopy (EIS) measurements. The GPE with the composition of 7.02 wt%, PVA, 7.02 wt% PEO, 30.11 wt% ethylene carbonate (EC), 30.11 wt% DMSO, 24.08 wt% TBAI and 1.66 wt% I₂ exhibits the highest conductivity of 5.5 mS cm^?1 at room temperature. Dye-sensitized solar cells (DSSCs) with configuration fluorine tin oxide (FTO)/titanium dioxide/N3-dye/GPE/platinum/FTO have been fabricated and tested under the white light of intensity 100 mW cm^?2. The DSSC containing the highest conducting GPE exhibits the highest power conversion efficiency, η of 5.36 %.     

Effects of Bi2O3 Addition in Micro- and Nanoscale on the Structural and Electrical Properties of Zn1-xBixO varistors

Two similar sets of Zn_1-xBi_xO ceramic varistors with various x values (0.00?≤x≤?0.20) have been prepared by using Bi₂O₃ additions with two different sizes. In the first set, Bi₂O₃ nanoparticles (≈200 nm) were used, while Bi₂O₃ microparticles (≈5 μm) were used in the second set. It was found that addition of Bi up to 5 % for both sets did not affect the wurtzite-type hexagonal structure of ZnO, but with increasing Bi above 5 %, some unknown lines were clearly observed in XRD spectra. The grain sizes are increased in both sets with increasing Bi content up to 2.5 %, followed by a decrease with further increase of Bi up to 20 %, and their values for microparticle additions were larger than that of the sets containing nanoparticle additions. Two nonlinear regions were formed in the I–V curves of ZnO due to Bi₂O₃ nanoparticle additions above 5 %. However, this behavior was completely absent in the samples containing Bi₂O₃ microparticles. Moreover, the breakdown field and nonlinear coefficient decreased with Bi₂O₃ addition up to 5 % for both sets, followed by an increase with further increase of Bi up to 20 %, and their values were higher for nanoparticle additions than that of microparticles. A reverse behavior was recorded for the electrical conductivity. The results have been discussed in terms of Bi₂O₃ nanosize grains which may be localized at the grain boundaries of ZnO ceramics.     

Rheological Property and Thermal Conductivity of Multi-walled Carbon Nano-tubes-dispersed Non-Newtonian Nano-fluids Based on an Aqueous Solution of Carboxymethyl Cellulose

The non-Newtonian nano-fluids with 0.1, 0.5, 1, and 2 wt% of multi-walled carbon nano-tubes have been prepared by dispersing different amounts of multi-walled carbon nano-tubes into an aqueous solution of carboxymethyl cellulose at a weight fraction of 3 wt%, respectively. The nano-fluids exhibit the shear-thinning rheological behavior. The viscosity of the nano-fluid increases with the weight fraction of multi-walled carbon nano-tubes and decreases with the increase in temperature. The thermal conductivity of all the nano-fluids is higher than that of the base liquid. The thermal conductivity enhancement is as high as 14.6% for the nano-fluid containing 2 wt% of multi-walled carbon nano-tubes.     

Effects of B and P content on structural and magnetic properties of cast iron based amorphous alloys

Mössbauer spectroscopy, DSC and magnetic measurements have been used to study the influence of B and P on structural; magnetic properties and thermal stability of cast iron based alloys. Results reveal that addition of B and P affects appreciably: (1) the crystallization temperature and supercooled liquid region ranging between 690–781 and 53–81 K respectively; (2) the spin texture, disorder and (3) the obtained magnetization parameters. Coercive field values range between 10.09 and 16.37 A/m, with lowest value of 10.09 A/m obtained for Ci_87.82B_12.17. Saturation induction (B _s) values vary between 1.32 and 1.85 T. Highest B _s value of 1.85 T is obtained for the Ci_95.65B_4.32 alloy which is at the edge of glass forming ability, with only 4.32 at.% of boron was added to the cast iron composition. Losses (at 50 Hz and 0.32 kA/m) for the studied samples range between 0.43 and 0.82 W/kg. Lowest losses of 0.43 W/kg was obtained for the Ci_91.3P_4.35B_4.35 alloy. Phosphorous and boron additions, helps in the bulk glass forming ability, suggesting perspective applications of these cheap cast iron based soft magnetic alloys as a substitute of the conventional materials.     

Effect of nano-size fumed silica on ionic conductivity of PVdF-HFP-based plasticized nano-composite polymer electrolytes

Nano-composite polymer electrolytes containing poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), ammonium tetrafluoroborate (NH₄BF₄), and nano-size fumed silica (SiO₂) have been prepared and characterized by complex impedance spectroscopy. Ionic conductivity of polymer has been found to increase with the addition of NH₄BF₄, and a maximum conductivity of 3.62 × 10^?6 S/cm has been obtained at 30 wt% NH₄BF₄. The formation of ion aggregates at high concentration of salt has been explained by Bjerrum’s law and mass action considerations. The conductivity of polymer electrolytes has been increased by three orders of magnitude (10^?6 to 10^?3 S/cm) with the addition of plasticizer, and a maximum conductivity of 1.10 × 10^?3 S/cm has been observed at 80 wt% DMA. An increase in conductivity with the addition of nano-size fumed silica is attributed due to the formation of space-charge layers. A maximum conductivity of 7.20 × 10^?3 S/cm has been observed for plasticized nano-composite polymer electrolytes at 3 wt% SiO₂. X-ray diffraction analysis of polymer electrolyte system was also carried out. A small change in conductivity of nano-composite polymer electrolytes observed over the 30–130 °C temperature range and for a period of 30 days is also desirable for their use in various applications.     

The development of Li<Superscript>+</Superscript> conducting polymer electrolyte based on potato starch/graphene oxide blend

Solid polymer electrolytes based on potato starch (PS) and graphene oxide (GO) have been developed in this study. Blending GO with PS has improved the ionic conductivity and mechanical properties of the electrolytes. In this work, series of polymer blend consisting of PS and GO as co-host polymer were prepared using solution cast method. The most amorphous PS-GO blend was obtained using 80 wt% of PS and 20 wt% of GO as recorded by X-ray diffraction (XRD). Incorporation of 40 wt% lithium trifluoromethanesulfonate (LiCF₃SO₃) into the PS-GO blend increases the conductivity to (1.48 ± 0.35) × 10^?5 S cm^?1. Further enhancement of conductivity was made using 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]). The highest conductivity at room temperature is obtained for the electrolyte containing 30 wt% of [Bmim][Cl] with conductivity value of (4.8?0 ± 0.69) × 10^?4 S cm^?1. Analysis of the Fourier transform infrared spectroscopy (FTIR) spectra confirmed the interaction between LiCF₃SO₃, [Bmim][Cl], and PS-GO blend. The variation of the dielectric constant and modulus studies versus frequency indicates that system of PS-GO-LiCF₃SO₃-[Bmim][Cl] obeys non-Debye behavior.     

Automatic dispersion,long-term stability of multi-walled carbon nanotubes in high concentration electrolytes

Nanoparticles have been known as the useful materials in working fluids for petroleum industry. But the stabilization of nano-scaled materials in water-based working fluids at high salinities is still a big challenge. In this study, we successfully prepared the anionic polymer/multi-walled carbon nanotubes (MWNTs) composites by covalently wrapping of MWNTs with poly (sodium 4-styrenesulfonate) (PSS) to improve the stability of MWNTs in high concentration electrolytes. The PSS/MWNTs composites can automatically disperse in salinity up to 15 wt% NaCl and API brines (8 wt% NaCl?+?2 wt% CaCl₂). Hydrodynamic diameters of composites were measured as a function of ionic strength and API brines by dynamic light scattering (DLS). By varying the concentration of brines, hydrodynamic diameter of PSS/MWNTs composites in brines fluctuated between 545?±?110 nm for 14 days and 673?±?171 nm for 30 days. Above results showed that PSS/MWNTs could be well stable in high salts solutions for a long period of time. After wrapped with PSS, the diameters of nanotubes changed from 30?~?40 to ~?430 nm, the thickness of wrapped polymer is about ~?400 nm by analysis of morphologies. The zeta potentials of PSS/MWNTs composites in various salinity of brines kept at approximately ??41?~???52 mV. Therefore, the well dispersion of PSS/MWNTs in high salinity is due to large negative charges of poly (sodium 4-styrenesulfonate), which provide enough electrostatic repulsion and steric repulsion to hinder compression of electric double layer caused by high concentration electrolytes.     

Synthesis,Characterization and Luminescent Properties of Anthracen- or Pyrene-Based Coumarin Derivatives

Three anthracen- or pyrene-based coumarin derivatives have been successfully synthesized and characterized by EA, IR and ¹H NMR. The photophysical properties of all derivatives were investigated by UV-Vis and photoluminescence spectroscopic analysis. Their thermal stabilities were demonstrated by TGA. These compounds exhibit strong blue mission under ultraviolet light excitation and have potential possible to explore organic electroluminescent materials. The vacuum-processed doped devices with a configuration of ITO/TAPC (20 nm)/TBADN: b1 (x wt%, 30 nm)/TPBi (50 nm)/Liq (2 nm)/Al (150 nm) was fabricated, in which the devices based on b1 exhibited the best electroluminescence performance with a maximum brightness of 8165 cd/m² and a maximum luminous efficiencies of 6.13 cd/A and a maximum external quantum efficiency (EQE) of 2.75%.     

Enhanced electrochemical properties of ZnO-coated LiMnPO<Subscript>4</Subscript> cathode materials for lithium ion batteries

We demonstrated the effect of ZnO (different wt%)-coated LiMnPO₄-based cathode materials for electrochemical lithium ion batteries. ZnO-coated LiMnPO₄ cathode materials were prepared by the sol-gel method. X-ray diffraction (XRD) analysis indicates that there is no change in structure caused by ZnO coating, and field emission scanning electron microscopy (FESEM) images depict the closely packed particles. Galvanostatic charge-discharge tests show the ZnO-coated LiMnPO₄ sample has an enhanced electrochemical performance as compared to pristine LiMnPO₄. The 2 wt% of ZnO-based LiMnPO₄ exhibited maximum discharge capacity of 102.2 mAh g^?1 than pristine LiMnPO₄ (86.2 mAh g^?1) and 1 wt% of ZnO-based LiMnPO₄ (96.3 mAh g^?1). The maximum cyclic stability of 96.3 % was observed in 2 wt% of ZnO-based LiMnPO₄ up to 100 cycles. This work exhibited a promising way to develop a surface-modified LiMnPO₄ using ZnO for enhanced electrochemical performance in device application.     

Effect of different compositions of ethylene carbonate and propylene carbonate containing iodide/triiodide redox electrolyte on the photovoltaic performance of DSSC

The effect of different compositions (in weight percent) of ethylene carbonate (EC) and propylene carbonate (PC) containing iodide/triiodide redox electrolyte on the photoelectrochemical performance of N719-sensitized nanocrystalline TiO₂ solar cell was studied. The cells consisted of 0.6 M 1-hexyl-2,3-dimethylimidazolium iodide, 0.1 M LiI, 0.05 M I₂ and 0.5 M 4-tert-butylpyridine in different compositions such as 1:1, 1:2, and 2:1 wt% of EC and PC. In 1:1 wt% of EC and PC containing redox electrolyte, short circuit photocurrent density (J _sc) increased and open circuit voltage (V _oc) decreased. But in 1:2 and 2:1 wt% of EC and PC containing redox electrolytes, V _oc increased and J _sc decreased but fill factor remained relatively constant. Dye-sensitized solar cells (DSSCs) prepared using these electrolytes give a short circuit photocurrent densities of 16.86, 12.71, and 12.09 mA/cm²; an open circuit voltages of 0.73, 0.78, and 0.79 V; fill factors of 0.63, 0.64, and 0.64; and an overall conversion efficiencies of 7.76, 6.34, and 6.13 % at an incident light of 100 mWcm^?2 for 1:1, 2:1, and 1:2 wt% of EC/PC containing redox electrolytes, respectively. The incident photon-to-current conversion efficiency was higher in the case of 1:1 wt% of EC and PC containing redox electrolyte than 1:2 and 2:1 wt% of EC and PC containing redox electrolyte. It revealed that 1:1 wt% of EC and PC containing iodide/triiodide redox electrolyte is an effective electrolyte system for the fabrication of long-term stable DSSC.     

Quantum cutting effect and photoluminescence emission at about 1,000 nm from Er–Yb co-doped ZnO nanoplates prepared by wet chemical precipitation method

ZnO nanoplates with Er-doping concentrations varying in the range from 3 to 7 wt% and co-doped with (Er–Yb) (7 + 7 wt%) were successfully prepared by wet chemical precipitation method. The effects of doping on the structural and optical properties of ZnO nanostructures have been systematically investigated. The structural morphology of the prepared nanostructures was found to change with increasing Er-doping concentrations. The visible photoluminescence and infrared photoluminescence of the prepared nanostructures were measured at room temperature. The intensity of visible emission spectra was found to increase with increasing Er-doping concentrations and was further enhanced for (Er–Yb) co-doped ZnO nanoplate samples. Additionally, Er-doped (7 wt%) and Yb-doped (7 wt%) ZnO nanoplates showed an enhanced emission peak at 950 nm, whereas two enhanced emission peaks at 950 and 980 nm have been found for (Er–Yb)-co-doped (7 + 7 wt%) ZnO nanoplates samples when excited at 310, 365 and 371 nm excitation wavelengths.     

Effects of annealing and additions on dynamic mechanical properties of SnSb quenched alloy

The elastic modulus, internal friction and stiffness values of quenched SnSb bearing alloy have been evaluated using the dynamic resonance technique. Annealing for 2 and 4 h at 120, 140 and 160 °C caused variations in the elastic modulus, internal friction and stiffness values. This is due to structural changes in the SnSb matrix during isothermal annealing such as coarsening in the phases (Sn, Sb or intermetallic compounds), recrystallization and stress relief. In addition, adding a small amount (1 wt.%) of Cu or Ag improved the bearing mechanical properties of the SnSb bearing alloy. The SnSbCu₁ alloy has the best bearing mechanical properties with thermo-mechanical stability for long time at high temperature.