Low Melting Point Research Articles

Influence of alloying elements on microstructure, mechanical properties and corrosion behaviour of hypoeutectic Sn-6.5wt%Zn-0.5 wt%X (X = Ag, Al, Cu) lead-free solders

Lead-free solders are promising candidates for the replacement of Sn–Pb solders due to their environmental friendly, good thermal properties and wettability which render them suitable for this application. In this study, a set of lead-free solders Sn-6.5 wt. and Sn-6.5 wt% Zn-0.5 wt% X (X = Ag, Al, Cu) were studied by metallography, mechanical and electrochemical techniques. The results show that the addition of the alloying elements Ag, Al and Cu modifies the amount of the eutectic phase and promotes the formation of intermetallic compounds (IMCs). The corrosion resistance of the samples also modified, showing that the formation of IMCs can have detrimental effects with higher current densities in saline media, as determined for the Ag and Al alloyed solders. The corrosion resistance is higher for the unalloyed and the Sn-6.5 wt%Zn-0.5 wt% Cu alloy. However, the addition of Cu not only stabilizes the corrosion products thus increasing the protective properties of the alloy, but also modifies the mechanical behaviour of the lead-free solders and so enhancing the UTS values and ductility. Furthermore, the surface morphology is influenced by the alloying elements showing a smooth surface (Sn-Zn, Cu) or a highly corroded appearance with round aggregates (Ag and Al). These new lead-free solders have a lower melting point with higher ductility than the commercial SAC 305. Therefore, these alternatives have high potential in applications in mechanical engineering.

A low-cost and convenient route of fabricating GaN films with P-type mixed microcrystalline and amorphous structure deposited via Ga target of magnetron sputtering

GaN, a third-generation semiconductor, has gained widespread attention owing to its high temperature resistance, wide bandgap, and high critical breakdown electric fields. Magnetron sputtering has a broad potential in the field of low-cost growth of GaN on account of high efficiency, superior quality, and convenient operation. However, challenges caused from the pure Ga targets with a huge refrigeration system need to be resolved for wide practices. Here, a new and cost-effective Ga target for magnetron sputtering was fabricated by utilizing the wetting properties of CuGa2 and Ga. Mixed microcrystalline and amorphous GaN films were obtained via reactive magnetron sputtering employing the Ga target. The average deposition rate is about 1.68 nm/min, and the average roughness is ∼7.45 ± 0.26 nm under 100 W of sputtering power. In addition, the sputtered GaN films were found to be wide-bandgap and p-type semiconductors with high transmittance, as revealed by x-ray photoelectron spectroscopy and absorption spectra. The GaN films display a bandgap of ∼3.60 eV and a transmittance exceeding 88.5% in the visible range. Furthermore, field-effect transistors and metal–semiconductor–metal photodetectors have been fabricated using the obtained GaN films, demonstrating favorable response characteristics. The prospects of microcrystalline/amorphous GaN films in sensing, power devices, and flexible electronics were forecasted. Overall, a low-cost and pervasive route of target fabrication process expands the possibilities of using low melting point metals in magnetron sputtering.

Assessing Structures and Solution Behaviors of Molecular and Ionic Cocrystals with a Common Bioactive Molecule: 2,4-Pyridinedicarboxylic Acid with Tranexamic Acid and Nicotinamide.

Cocrystals of 2,4-pyridinedicarboxylic acid (PDA) with either nicotinamide (NTD) or tranexamic acid (TXA) as (PDA)·(NTD) and 2(PDA)·(TXA), respectively, are reported, with the former being a molecular cocrystal and the latter being an ionic cocrystal. Single-crystal structure analyses showed that PDA and its coformers are sustained by neutral and ionic hydrogen bonds. Suspensions of (PDA)·(NTD) resulted in complete conversion to PDA monohydrate after 48 h, while 2(PDA)·(TXA) was thermodynamically stable at a lower pH and showed a 2-fold increase in the PDA concentration, relative to pure PDA monohydrate under similar conditions. Thermal characterization of 2(PDA)·(TXA) displayed a lower melting point and a lower heat of fusion, relative to the pure components. Powder dissolution studies were evaluated for PDA, (PDA)·(NTD), and 2(PDA)·(TXA) and the corresponding physical mixtures. The percent of PDA dissolved rapidly reached near 100% for most cases; however, for 2(PDA)·(TXA), complete dissolution was not achieved, and the amount of PDA dissolved decreased to 85% after 3 h. Instability of 2(PDA)·(TXA) was likely a result of a high solution pH during dissolution, and our results confirm that the solution pH plays a key role in determining the solution behavior and phase stability of the cocrystals.

Comparative characterization and dyeing properties of poly(ethylene terephthalate-co-polyethylene glycol) fibers and poly(ethylene terephthalate) fibers

A comparative characterization of poly(ethylene terephthalate-co-polyethylene glycol) (PCP) fibers was performed using various parameters, including chemical and supramolecular structures, thermal properties, and physical properties. Dynamic scanning calorimetry and X-ray diffraction analyses revealed that PCP exhibits a lower melting point, glass transition temperature, and crystallinity than PET. In terms of tensile properties, PCP exhibited reduced tensile strength but increased elongation at break, indicating enhanced toughness. Dyeing test results demonstrated that PCP fibers are disperse dyeable at lower temperatures and exhibited optimal dyeability at 100 °C, surpassing PET, without compromising leveling properties or color fastness. These findings underscore the potential for energy savings and process streamlining through atmospheric-pressure dyeing.

No-Insulation BSCCO Coils Impregnated With Low-Melting Point Metal

No-Insulation BSCCO Coils Impregnated With Low-Melting Point Metal

A novel plasma-facing NdB6 particulate reinforced W1Ni matrix composite: Powder metallurgical fabrication, microstructural and mechanical characterization

Tungsten (W) is one of best candidate metal for plasma-facing materials (PFM), especially due to its high melting temperature and neutron absorption capability. However, converting W into bulk PFM is hard because of its high melting point. This problem can be solved by adding metallic sintering aids with low melting points. In this study, W matrix with 1 wt% Ni aid was reinforced by adding NdB6 particles (1, 5, and 10 wt%). It can be introduced as a novel potential PFM, thanks to its low volatility and high neutron absorbability. The ceramic and composite powders produced via mechanochemical synthesis and mechanical alloying were examined in terms of composition, particle size, crystallite size, and lattice strain. Samples sintered via pressureless sintering (PS) and spark plasma sintering (SPS) were microstructurally analyzed by using an X-ray diffractometer (XRD), a scanning electron microscope (SEM) attached with an energy dispersive spectroscope (EDS), and mechanically analyzed in terms of microhardness and wear behavior. Based on the results, W2B and WB phases emerged in the SPS'ed W1Ni-5NdB6 and PS'ed./SPS'ed W1Ni-10NdB6 composites. SPS'ed W1Ni-10NdB6 composite had the highest hardness value and the lowest specific wear rate. The SPS'ed W1Ni-5NdB6 composite showed fewer surface damages and higher irradiation resistance as compared with other samples after exposure of He+ irradiation.

A Congruent-Melt Infrared Nonlinear Optical Crystal Na4SrAs2S8.

A quaternary metal thioarsenate infrared (IR) nonlinear optical (NLO) compound Na4SrAs2S8 was successfully prepared by a high-temperature reaction method from stoichiometric agents. It crystallizes in the tetragonal P4n2 with the unit cell parameters a = 10.0393(3) Å, c = 6.9638(3) Å, and Z = 2, with the basic structural groups of isolated AsS4 tetrahedra. Compared with benchmark IR NLO crystal AgGaS2 (AGS), the title compound exhibits balanced optical properties of large band gap (3.05 eV vs. 2.60 eV) and considerable second harmonic generation response (0.95 × AGS). Moreover, the combined powder X-ray diffraction and differential scanning calorimetry analyses demonstrate that Na4SrAs2S8 is a congruent-melting compound with a low melting point of 668 °C, which is benefical for bulk single crystal growth. Experimental and theoretical calculation results indicate that Na4SrAs2S8 is a practically usable IR NLO crystal, also motivating the exploration of thioarsenates as high-performance IR NLO candidates.

Environmental Analysis of the Impact of Changing Shrink Film in the Mass Bottle Packaging Process

The aim of this study was to assess the environmental impact of using recycled polyethylene film for shrink-wrapping bottles. For this aim, film properties were tested and the harmfulness of the packaging process was simulated for film made from virgin and recycled material. For the recycled film, the results showed an increase of 14.7% in impact resistance, a change from −21.6 to +94.3% in tear resistance, and a decrease of up to 45.4% in tensile strength in dependence on the test direction. Using differential scanning calorimetry (DSC), the changes in the properties of the two types of film with temperature changes were evaluated. DSC analysis showed that recycled film has a 1.94 °C lower glass transition temperature and a 1.85 °C lower melting point in comparison to polyethylene film. This can reduce the temperature of the packaging process and lead to energy savings. A study conducted with SimaPro 9.3 software showed that a change in films made of virgin raw material to recycled films reduces the negative impact on the environment from 68.5 to 11.5%. The change also reduces resource consumption by about 80 percent. The results of conducted tests and simulations showed that using recycled film for bottle packaging allows reducing the negative environmental impact of examined process, especially in terms of resource consumption and energy savings.

Effect of Alkyl Side Chains in BDT and 2D‐BDT Small‐Molecules as Donor Materials for Vacuum‐Processed Organic Photovoltaic Devices

Nine molecules based on benzo[1,2‐b:4,5‐b′]dithiophene (BDT) and 2D‐BDT derivatives are studied as donor materials in organic photovoltaic (OPV) devices fabricated by thermal evaporation, aiming to understand how different alkyl lateral substituents affect the molecular packing, the charge transport, and, subsequently, the device performance. Synthesis of the molecules is followed by a comprehensive characterization using thermal and differential scanning calorimetry analyses, which confirm their thermal stability and suitability for vacuum‐processed OPV devices. Thermal analysis also demonstrates a strong correlation between the melting point reduction of the molecules and the disorder caused by the alkyl chains. As the synthesized molecules present similar optical properties, the differences in the device performance are caused by the different substituents. BDT derivatives with low melting point temperatures produce reduced current density, hole mobility, and overall device performance, which are attributed to poor molecular packing. Additionally, energy‐dispersive X‐ray spectroscopy analysis suggests phase separation with fullerene, further impacting the efficiency of the devices. The findings indicate that the photovoltaic performance of BDT‐based molecules can be modulated by avoiding aliphatic substituents, providing a strategy for the design of more efficient materials, with thermal evaporation as an ideal method to evaluate and decouple molecular packing from solubility.

Study on the properties of anorthite-based porous sound-absorbing materials prepared by steel slag and fly ash

The efficient utilization of solid wastes, such as fly ash and steel slag, has attracted significant attention across the globe. In this paper, these two kinds of waste materials are used to prepare porous sound-absorbing materials, so as to achieve efficient resource utilization and environmental protection, and promote green manufacturing and circular economy. In this study, steel slag and high-alumina fly ash were used as the primary raw materials to prepare green bodies via organic foam impregnation. Subsequently, a high-temperature sintering process was implemented to get the porous sound absorption material product from the green bodies. The effects of several factors, including the ratio of steel slag and fly ash, sintering temperature, and pore structure, on the sound absorption and mechanical properties of the product were investigated. Based on the anorthite region in the CaO–Al2O3–SiO2 ternary phase diagram region, the composition ratio of the material was designed. The composition and microstructure of the material were characterized by X-ray diffraction and scanning electron microscopy. From the results, with the increase of the ratio of fly ash and steel slag, the composition of low melting point substances in the system decreases, and the amount of liquid phase decreases, which weakens the pore blocking phenomenon inside the material, resulting in the increase of pore size and noise reduction coefficient of the material. Besides, higher sintering temperature tends to correlate to greater density and higher compressive and flexural strengths but lower porosity, and the sound absorption coefficient demonstrated a peak with respect to sintering temperature. Furthermore, when the reduction of polyurethane sponge body pore size was taken into account, the product's sound absorption coefficient also showed a peak. The optimal parameters for our porous materials are as follows: fly ash:steel slag = 48 : 25, polyurethane sponge pore size = 40 ppi, sintering temperature = 1160 °C at 1-h duration (bulk density = 573.98 kg/m3), compressive strength = 1 MPa, porosity = 79.35 %, and noise reduction coefficient = 0.47.

Brazing of TC4 Alloy Using Ti-Zr-Ni-Cu-Sn Amorphous Braze Fillers.

In order to address the issues of excessive brittle intermetallic compounds (IMC) formation in the TC4 brazed joints, two types of novel Ti-Zr-Cu-Ni-Sn amorphous braze fillers were designed. The microstructure and shear strength of the TC4/Ti-Zr-Ni-Cu-Sn/TC4 brazed joints were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometer (XRD) and electronic universal materials testing machine. The results show that the optimized Ti35Zr25Ni15Cu20Sn5 braze filler whose chemical composition is closer to the eutectic point possesses a lower melting point compared with the equiatomic Ti23.75Zr23.75Ni23.75Cu23.75Sn5. This was beneficial to the sufficient diffusion of Cu and Ni elements with the base metal during brazing and reduces the residual (Ti,Zr)2(Ni,Cu) content in the joint, which helps to improve the joint performance. The room-temperature and high-temperature shear strength of the TC4 brazed joints using the near eutectic component Ti35Zr25Ni15Cu20Sn5 filler reached a maximum of 472 MPa and 389 MPa at 970 °C/10 min, which was 66% and 48% higher than that of the TC4 joints brazed with the equiatomic Ti23.75Zr23.75Ni23.75Cu23.75Sn5 braze filler. Microstructural evolution and the corresponding mechanical response were in-depth discussed.

A room-temperature liquid eutectic GaSn anode with regulated wettability for lithium ion batteries

The alloy-type anodes in lithium ion batteries (LIBs) often suffer from the pulverization/failure of active materials caused by the drastic volume variations during cycling. Liquid Ga-based materials with low melting points and intrinsic self-healing feature are one of the best candidates for enhancing the Li storage property. Herein, a liquid eutectic GaSn (EGaSn) electrode was fabricated based upon a simple painting method and directly used as the anode for LIBs at room temperature. Furthermore, the wettability of liquid EGaSn alloy on the current collector in the Ar atmosphere was greatly improved through the construction of Ag3Ga modified layer on the stainless steel mesh (ssm) surface. And the Ag3Ga-EGaSn anode displays the much better Li storage performance (specific capacity, rate performance and cycling stability) than the untreated EGaSn anode. More importantly, operando XRD measurement clearly clarified the electrochemical reaction mechanism of Ag3Ga-EGaSn in LIBs. This work indicates a potential strategy to directly use liquid Ga-based electrode with regulated wettability for LIBs.

Cryo STEM of Low Melting Point Metals Enabled by Cryo FIB and EXLO

Cryo STEM of Low Melting Point Metals Enabled by Cryo FIB and EXLO

Interlaminar toughening of carbon fiber/epoxy composites via interleaving co‐polyamide (Co‐PA) veils

AbstractThermoplastic veil interlayers offer a promising approach to improve interlaminar reinforcement in composite materials. This study investigates co‐polyamide (Co‐PA) interleaved veils, fabricated through the hot melt adhesive (HMA) technique. These veils are then applied with varying areal weight densities as interleaves to simultaneously toughen and strengthen carbon fiber/epoxy (CF/EP) composites, utilizing the vacuum‐assisted resin infusion (VARI) method. Integrating Co‐PA veils with a low melting point in the interlaminar of CF/EP composites improves compatibility and promotes strong adhesion between thermoplastics and epoxy resins. As result, The Co‐PA laminates exhibited significant improvements compared with the untoughened composites, with a maximum enhancement of 148.1% and 67.8% for Mode‐I (GIC) and Mode‐II (GIIC), respectively. Moreover, ILSS, tensile strength, and flexural strength improvements were also 20.9%, 34.9%, and 14.5%, respectively. The fracture surface analysis via scanning electron microscopy directly revealed the crack propagation on the fracture surfaces of Mode‐I and Mode‐II specimens. This analysis revealed that Co‐PA demonstrated excellent compatibility with epoxy resin, melts during the stage of epoxy curing, and undergoes phase separation in the later stage, resulting in the formation of “bead‐like” structures within the fibrous network. Remarkably, this structure significantly enhanced the toughness of the CF/EP composites. The Co‐PA veils can improve the interlaminar toughness of CF/EP composites due to their compatibility with the epoxy matrix and high inherent toughness and strength. This method is straightforward to manage and can be utilized for manufacturing large‐scale composite materials incorporating CF fabrics, demonstrating promise for industrial applications.Highlights With its low melting point, co‐polyamide helps prevent structural failure or excessive damage and is proposed to be utilized in composites to enhance the interlaminar fracture toughness properties. The effects of Co‐PA veils of different areal densities on the mechanical characteristics of interlaminar composites were examined. Co‐polyamide particles with fiber‐carbon laminates offer superior fatigue properties and an optimum carbon fiber‐bridging mechanism. Co‐polyamide veils with CF/EP laminates are feasible for structural use in high‐tech automotive applications.

Li2O addition as a means of achieving low-temperature densification of SiC ceramic

In order to achieve low-temperature densification of SiC ceramic, β-SiC nanopowder was doped with Li2O together with Y2O3–Al2O3–MgO as sintering aids, and then spark plasma sintered at temperatures ranging from 1450 °C to 1600 °C for 30 min under 30 MPa pressure in argon. The densities, microstructures and mechanical properties of SiC ceramics were systematically investigated, in comparison to the counterparts sintered with Y2O3–Al2O3–MgO additives. Since Li2O has a low melting point, Li2O addition effectively decreased the formation temperature of liquid secondary phase, enabling SiC ceramics to obtain higher density and lower porosity after low-temperature sintering (T ≤ 1550 °C). Besides, Li2O addition was found to decrease the viscosity of liquid phase and enhance grain growth of SiC through dissolution-reprecipitation process. When sintered at 1550 °C, Li2O addition led to a remarkable increase of density from 3.03 g/cm3 to 3.21 g/cm3 for SiC ceramic. Meanwhile, the SiC ceramic with Li2O addition exhibited a high Vickers hardness of 22.75 ± 0.35 GPa and a good fracture toughness of 3.83 ± 0.27 MPa m1/2. The research results are expected to benefit the low-cost fabrication of SiC ceramics based on pressure-assisted sintering and alleviate the thermal damage of SiC fiber in hot-pressed SiCf/SiC composites.

Fabrication of three-dimensional bicontinuous porous aluminum by vapor phase dealloying

The development of lightweight, high-specific-surface-area, and exceptionally tough porous aluminum (Al) through dealloying has been consistently captured the attention of the porous metal field. However, widely employed dealloying approaches such as electrochemical dealloying (ECD) and liquid metal dealloying (LMD) face limitations in constructing porous metals with high chemical reactivities. In this study, we employed an emerging vapor phase dealloying (VPD) method, utilizing the differences in saturated vapor pressures among alloy constituents to selectively remove elements with high vapor pressures under optimized temperature and vacuum conditions. The VPD process, characterized by its chemical-free nature and the application of high temperatures, rapidly produces porous Al with varying ligament sizes from the MgZnAl system. The resulting porous Al, distinguished by its crack-free structure and substantial ligament size, exhibits remarkable toughness. The successful fabrication of porous Al using the VPD method effectively bridges the existing gap in generating porous metals with low melting points and high chemical reactivity through ECD and LMD methods. This advancement holds significance for broadening the range of systems and application fields for porous metals.

Low-temperature sintering of SiC ceramics using a mixture of preceramic precursor and metal nanoparticles

Polymer infiltration and pyrolysis (PIP) has a limitation in increasing the relative density of SiC ceramics above 90 %. This is due to the blockage of open pore channels. In this study, a new process that incorporates Ni and graphite nanoparticles into SiC preceramic precursor is examined. Ni nanoparticles react with the SiC precursor to form low melting point nickel silicide phases which infiltrate into pores of the bulk without a blockage problem. In later infiltration cycles, graphite nanoparticles are added to convert the nickel silicide to nickel carbide and silicon carbide, which may prevent the deterioration of mechanical strength at high temperature. The relative density of SiC ceramics in this study increases to 92 % and above, which is higher than that of SiC ceramics prepared by the traditional PIP. The results of this study show a pathway to process high density SiC ceramics at relatively low sintering temperatures.

Parametric study to investigate mechanical properties of welded dissimilar Al6063 and Al 7073 alloys through FSW process

Aluminium alloys have been the most prominent materials that have applications in every industry due to their high strength-to-weight ratio. The low melting point and easy recyclability also attract the scientific community to apply such material in modern manufacturing. The revolution in aluminium alloys came after the invention of friction stir welding, which provided high-end welding results and catastrophically increased its application in aerospace industries. Still, many inconclusive studies need to be explored for its high-end application, especially for newly invented aluminium alloy composites. Hence, this study investigates the application of friction stir welding process for welding dissimilar Aluminium alloy compositions. The investigation starts by analysing the effect of rotational speed, feed rate, and force on temperature generation, hardness, and welding strength. Three levels of process parameters, i.e. rotational speed in the range of 1000–1200 rpm, force of 12–18 N and feed rate of 40–60 mm min−1, are selected to analyse the effect on hardness and strength of the weld. After analysis, the optimum conditions obtained were a rotational speed of 1200 rpm, a feed rate of 50 mm min−1, and an average load of 15 N for a maximum hardness of 93.16 BHN and welding strength of 228 MPa. The investigation’s findings indicated that several phenomena, including the effects of high blending activity, plastic disfigurement, the repercussions of grain structure, and frictional intensity, may influence the hardness and strength of the weld. The growth of uniform structure at the stirred area is caused by pin movement during welding, specifically from the retreating side to the advancing side.

Mechanical properties and thermal shock resistance of BaAl2Si2O8/BN ceramic composites

BaAl2Si2O8/BN (BAS/BN) ceramic composites were prepared using hot press sintering. The amorphous state of BAS ceramics exhibits a low melting point, high liquid-phase mobility, and good infiltration with BN grains, facilitating the sintering process. Conversely, the crystalline state of BAS has a high melting point and strength, contributing to the strengthening and toughening of the composite. The mechanical properties, thermal properties and thermal shock resistance of BAS/BN ceramic composite was investigated. Ceramic composites containing 40 vol% BAS have the best overall mechanical properties with bending strength, elastic modulus, fracture toughness, and hardness of 175 ± 3 MPa, 114.0 ± 1.2 GPa, 2.02 ± 0.10 MPa·m1/2, and 1.08 ± 0.01 GPa, respectively. The BAS/BN ceramic composite has excellent thermal shock resistance, and the residual bending strength shows a pattern of increasing and then decreasing with increasing thermal shock temperature difference. Finite element calculation results show that the cooling process is basically completed after 20 s of water quenching, the maximum thermal stress generated is about 22 MPa.

Enabling the Strengthened Structural and Interfacial Stability of High‐Nickel LiNi0.9Co0.05Mn0.05O2 Cathode by a Coating‐Doping‐Microstructure Regulation Three‐In‐One Strategy

AbstractHigh‐nickel layered cathodes exhibit great promise in advancing high‐energy‐density batteries owing to their significant advantages in high energy capacity and low cost, but they suffer severe structural and interfacial deterioration during cycling, resulting in safety risk and reduced cycle life. Herein, drawing inspiration from the low melting point infusion capability of Sb2Se3, a three‐pronged strategy aimed at simultaneously achieving coating on primary and secondary particles surface, Sb doping and elongated and slimed primary particle morphology is proposed and developed to fortify the structural and interfacial stability of high‐nickel LiNi0.9Co0.05Mn0.05O2 (NCM90) cathode. The “melted and infused” Sb2Se3 plays a beneficial role in the defensive effect on primary and secondary particle's surfaces, mitigating the interfacial deterioration. In addition, the enhanced structural stability is achieved by both Sb5+ doping and regulated primary particle morphology, contributing to the alleviated particle breakage and ultimately reinforced cycling stability. Consequently, the Sb2Se3‐NCM90 electrodes significantly improve cycling performance, which maintain higher capacity retentions of 96.6% at 4.3 V after 100 cycles and 80.2% at 1C/5C after 500 cycles. The proposed coating‐doping‐microstructure regulation three‐in‐one strategy for improving the cycling stability of high‐nickel NCM cathodes offers innovative ideas for the design and advancement of high‐energy‐density lithium‐ion batteries.