Nano-solder pastes have been proven to be used as a bonding material for power electronics packaging. Especially, the Ag-coated Cu nanoparticles (Cu@Ag NPs) solder paste is gradually becoming a potential candidate. Herein, the innovative structure of Cu@Ag micro-nano mixed particles (Cu@Ag MNPs) is fabricated in the same reaction system. It is found that the nanoparticle and microparticle sizes are dominated by the interaction of multiple parameters. The PVP molecular weight (MW) can mainly control the nanoparticle size by the steric hindrance effect. The reaction time (t) can mainly regulate the microparticle size by the particle growth time. The reaction temperature (T) can mainly control the microparticle size by the nucleation rate. Besides, based on the observation of in-situ TEM, the sintering behaviour of the Cu@Ag MNPs mainly includes particle connection, void evolution, coarsening, and smoothness in this work. The sintering mechanism includes the atom flow on the surface of the particle, grain boundary diffusion, and Ostwald ripening. Consequently, Cu@Ag MNPs solder paste obtained the lowest porosity and the highest shear strength of Cu-Cu joints compared to the Ag NPs and Cu MPs solder paste at 250 °C and 300 °C without pressure in the air condition. Accordingly, this work clarifies the fabrication mechanism and sintering behaviour of the Cu@Ag particles, which provides a facile strategy and theoretical basis for the development of power electronics packaging.

In recent years, the demand for glass beads for road marking is increasing, but the problem of low detection accuracy of heavy metal content in glass bead is prominent. Based on this background, this paper proposes an accurate and sensitive two-factor analysis of variance (Two-factor ANOVA) method to determine the content of Sb in glass beads by high-resolution continuous light source atomic absorption spectrometry (HG-HRCS-AAS).Firstly, the sample pretreatment conditions are optimized through orthogonal test design to determine the best digestion ratio of glass bead samples, and the combination of the best digestion temperature, holding time and heating time is obtained by combining range analysis and variance analysis methods. The best acid removal temperature and holding time are determined by the test results. Secondly, we use the two-factor ANOVA to optimize the instrument conditions and reaction conditions. The former includes sensitivity conditions, atomization conditions, and injection conditions. Another includes pre-reduction conditions and hydride generation conditions. Finally,using this method to analyze Sb standard material and get the following results: the relative standard deviation (RSD) of Sb in the glass bead sample was 1.33% and the Limit of detection(LOD) was 0.147μg/L, limit of quantit-ation(LOQ) is 0.490μg/L, the recovery rate of blank spiking is 96%-104%.

With the rapid development of the third-generation semiconductors SiC and GaN,traditional packaging materials,such as Si-based lead-free solder,cannot satisfy the requirements of high-power density and high-temperature loading in power electronic devices any more.Nowadays,the joints packaged by Cu nanoparticle sintering technique can not only be bonded at low-temperature and then serve at high-temperature,but also exhibit excellent thermal conductivity,electrical conductivity and relatively lower cost comparing with Ag nanoparticles.Thus,more and more attention has been attracted in the field of Cu nanoparticle sintering technique for power electronic packaging,which makes Cu nanoparticles become one of the most potential high-temperature-resistant packaging and interconnection materials.In this work,the current research progress of Cu nanoparticle sintering technique was summarized,including the fabrication of Cu nanoparticle pastes,the factors affecting the performance of sintered joints and the reliability of joints.Meanwhile,the oxidation behavior as well as the anti-oxidation methods of Cu nanoparticle were introduced.Besides,the high-temperature working reliability and failure mechanism of Cu nanoparticle sintered joints were discussed.This review aims to promote the application of low-cost Cu nanoparticle sintering technique for high-performance and high-reliability power electronic packaging.

In this research, camphorquinone (CQ)-mediated one-pot polyol methods to synthesize silver right bipyramids and nanorods with high yields are developed. The key strategy of these methods is the use of CQ which is first applied to selectively stabilize Ag(100) facets through capping. As CQ stabilizes small-sized nanocrystals, including single-twinned and nanorod structures, we successfully synthesized silver right bipyramids and nanorods as the two dominant products in a CQ-mediated polyol system. Further morphology control between silver nanorods and silver right bipyramids is conducted through adjusting the poly(vinylpyrrolidone) (PVP) concentration and reaction temperature, which can improve the formation of single-twinned and fivefold twinned particles through affecting the reduction kinetics. Silver nanorods with a yield of 87% are obtained under 150 degrees C with a PVP/CQ/AgNO3 molar ratio of 1.2:2:1, while silver right bipyramids with a yield of 88% are obtained under 120 degrees C with a molar ratio of 1.6:2:1.

The emission of chlorinated pollutants is one of the main problems when recovering copper (Cu) via pyrolysis from waste enameled wires. This is mainly attributed to other wastes which possess high poly(vinyl chloride) content, such as electrical wires and cables, which are often recycled together with enameled copper wires. In this research, to control the chlorinated pollutants, copper(II) oxide (CuO) was chosen and demonstrated to be an efficient dechlorinating agent, and CuO did not introduce any impurities that influence the quality of the recovered Cu. The pyrolysis and co-pyrolysis of polyester enameled wires, PVC, and CuO were investigated, and special attention was paid to chlorinated compounds in released pyrolytic products. In particular, the co-pyrolysis of this ternary mixture was studied for the first time, and some new pyrolysis behaviors were discovered. For example, the results of Py-GC/MS analyses showed that the addition of CuO removed about 75% of the chloro-organic products, the main types of which were chloroaromatic compounds rather than the more toxic chloroesters. Moreover, pyrolysis gases were collected and characterized via ion chromatography, and the results showed that the chlorine content in the pyrolysis gases decreased by about 71%. TG analysis indicated that CuO only minimally affected the pyrolysis of polyester paint. However, through the chlorine fixation effect, CuO influenced the dechlorination and dehydrochlorination of PVC, as well as secondary reactions between HCl and pyrolysis products of polyester paint, therefore changing the products and behaviors of co-pyrolysis. Mechanism of reducing chlorine-containing pollutants and reaction mechanism of forming typical pyrolysis products closely correlated to the effects of CuO were also proposed, providing theoretical guidance for the recycling of waste enameled wires.

Due to a lower intrinsic thermal conductivity, Cu2S-based thermoelectric materials are attracting extensive attention. However, they still confront the problems, such as higher electrical resistivity, which distinctly restricts their thermoelectric application. Herein, we synthesized Ag-incorporated Cu2-xS micro/nano composites using a hydrothermal method. It was found that the doping of Ag nanoparticle could effectively enhance the electrical transport, while the generated nanopores, caused by the Ag aggregation during the SPS process, reduced the thermal conductivity. As a result, a maximum ZT value of ~ 1.5 was obtained at 773 K in the Cu2-xAg0.5S micro/nano composites, much higher than that of the pristine Cu2-xS micro/nano composites. This work provides a new pathway to boosting thermoelectric performance through microstructural engineering.

Among the state-of-the-art thermoelectric materials, copper sulfides (Cu2S) have been predicted as promising thermoelectric materials due to their low intrinsic thermal conductivity. However, they still confront the problems with lower electrical properties, which distinctly restrict their thermoelectric application. Significant enhancement of thermoelectric properties is a great challenge owing to the common interdependence of electrical and thermal conductivity. Herein, a micro/nano Cu2-xS composite, with significantly enhanced thermoelectric properties, is prepared via a simple hydrothermal method. Due to the synergistic effect of the introduced nanostructure and the increased Cu1.96S contents, the micro/nano Cu2-xS bulk samples present a power factor of 10.1 mu W cm-1 K-2 at 773 K. Meanwhile, a decrease of the thermal conductivity to 0.69 W m-1 K-1 is obtained, originating from the strong phonon scattering of micro/nano structure. Remarkably, a ZTmax value of 1.1 at 773 K is obtained, which is higher than the reported Cu2-xS thermoelectric material using chemical methods. This study proposes a facile microstructure engineering strategy for the development of high-performance thermoelectric materials.

The structure stability, mechanical properties and thermodynamic behaviors of Al4Si6La3 compound in a wide pressure range 0-100 GPa have been explored by performing first-principles calculations based on density functional theory. The calculated formation enthalpy demonstrates that the Al4Si6La3 compound at 0 GPa is thermodynamically stable and exhibits unstable with the increasing of pressure. The single crystal and poly-crystalline elastic constants as a function of pressure are also calculated and discussed. Al4Si6La3 compound exhibits ductile nature at pressure up to 100 GPa by calculating Cauchy pressure, B/G ratio and Poisson's ratio. It is found that the Debye temperature and minimum thermal conductivity of Al4Si6La3 compound can be improved to some extent when the pressure is increasing. The analysis of electronic structures including charge density difference, Mulliken overlap population and density of state reveal that Al-Si and La-Si can form covalent bonds in Al4Si6La3 compound whereas Al-La form antibonding states at various pressures.

The applicability of wide bandage semiconductors at high temperatures promotes the development of high-temperature die-attach materials, such as silver nanoparticles (Ag NPs) paste. To enhance the bonding between Ag NPs and Cu substrate through an interdiffusion process, the Cu substrate was modified by electroplating a novel upright shell-like nanostructure. The optimized Cu substrate was then sintered with Ag NPs paste, in which the diffusion distance could achieve about 1.5 μm at 300 °C for 20 min. This sufficient interfacial diffusion is attributed to the numerous reactive positions and compatible sintering driving force between Ag NPs and modified Cu substrate caused by the upright shell-like Cu nanostructure.

The ductile-to-brittle-transition (DBT) of Sn occurring when the temperature decreases to a critical temperature poses a restriction on the Sn-based solders in the cryogenic electronics interconnection. Previous investigations about the DBT mainly adopt the Charpy impact test, however, the transient property of Charpy impact test makes it difficult to capture the deformation features accompanying DBT and clearly elucidate the DBT mechanism. In this paper, we studied the plastic deformation of Sn before cryogenic brittle fracture through in-situ cryogenic uniaxial tensile experiments under optical microscopy. It is found that {301} deformation twins were activated and thickened before the brittle fracture. Due to the occurrence of deformation twins, multiple twin-grain boundary intersections and twin-twin intersections formed within Sn grains, which could strongly prevent dislocation slip and thus lead to stress concentration. As a result, the brittle cracks initiate and propagate along these intersections. According to the suggested specific mechanism, we designed a green pre-treatment method of pre-twining-RT tempering to increase the cryogenic ductility of Sn-based solder alloys without any energy consumption. Eventually, the fracture elongation of Sn at LNT was significantly improved from ~6% to ~14%.

Among the state-of-the-art thermoelectric materials, copper sulfides (Cu2S) have been predicted as promising thermoelectric materials due to their low intrinsic thermal conductivity. However, they still confront the problems with lower electrical properties, which distinctly restrict their thermoelectric application. Significant enhancement of thermoelectric properties is a great challenge owing to the common interdependence of electrical and thermal conductivity. Herein, a micro/nano Cu2-xS composite, with significantly enhanced thermoelectric properties, is prepared via a simple hydrothermal method. Due to the synergistic effect of the introduced nanostructure and the increased Cu1.96S contents, the micro/nano Cu2-xS bulk samples present a power factor of 10.1 μW cm -1 K -2 at 773 K. Meanwhile, a decrease of the thermal conductivity to 0.69 W m -1 K -1 is obtained, originating from the strong phonon scattering of micro/nano structure. Remarkably, a ZT max value of 1.1 at 773 K is observed, higher than the reported Cu2-xS thermoelectric material using chemical methods. This study paves a facile microstructure engineering strategy for the development of high performance thermoelectric materials.

The accelerated application research of winde bandgap (WBG) power electronic devices intensively stimulates the interconnect materials to catch the capability of serving at high temperatures aligned with low-temperature sintering characteristics. Especially, it is urgently needed the interconnect materials to make the goal of anti-oxidation, anti-migration, and low porosity after sintering. Herein, a novel micro/nano-hybrid structure particles are fabricated by a mild one-step method, which structure is Ag nanoparticles coated Cu microparticle (Cu MP@Ag NPs) with the average size of Ag NPs and Cu MPs being 150 nm and 1.28 μm. Not only do the Cu MP@Ag NPs accomplish anti-oxidation properties at 200 °C for 30 min, but also achieve low-temperature bonding on bare Cu in the air atmosphere, and apart from that, Ag-Cu alloy is formed between Cu MPs and Ag NPs with the increase of sintering temperature. In comparison with Ag NPs paste and Cu MPs paste, Cu MP@Ag NPs paste swallows up the lowest porosity and highest shear strength results at 300 °C sintering, which ascribe to the exquisite micro/nano-hybrid structure particles and the formation of Ag-Cu alloy. The existence of Ag NPs makes the Cu MP@Ag NPs paste possess low-temperature sintering properties and decreases the porosity of the sintering layer by improving the staking density. Besides, the formation of Ag-Cu alloy for one reason is attributed to the formed metallic bonds between Ag NPs and Cu MPs in the synthesis process, and for another reason, it is caused by the greatly increased coarsening driving force by the size difference of the micro/nano-hybrid particles. Furthermore, the fracture mode of the joint using Cu MP@Ag NPs changes to ductile fracture from brittle fracture with the increase of sintering temperatures. This work demonstrates the facilely synthesized stunning micro/nano-hybrid structure particles (Cu MP@Ag NPs) achieve excellent sintering results and possess the potential application in WBG power electronic devices.