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Electronic products are evolving towards miniaturization, high integration, and multi-function, which undoubtedly puts forward higher requirements for the reliability of solder joints in electronic packaging. Approximately 70% of failure in electronic devices originates during the packaging process, mostly due to the failure of solder joints. With the improvement of environmental protection awareness, lead-free solder joints have become a hot issue in recent years. This paper reviews the research progress on the reliability of lead-free solder joints and discusses the influence of temperature, vibration, tin whisker and electromigration on the reliability of solder joints. In addition, the measures to improve the reliability of solder joints are analyzed according to the problems of solder joints themselves, which provides a further theoretical basis for the study of the reliability of solder joints of electronic products in service.

With the development of lead-free solders in electronic packaging, Sn-Cu lead-free solder has attracted wide attention due to its excellent comprehensive performance and low cost. In this article, we present recent developments in Sn-Cu lead-free solder alloys. From the microstructure and interfacial structure, the evolution law of the internal structure of solder alloy/solder joint was analysed, and the model and theory describing the formation/growth mechanism of interfacial IMC were introduced. In addition, the effects of alloying, particle strengthening and process methods on the properties of Sn-Cu lead-free solders, including wettability, melting and mechanical properties, were described. Finally, we outline the issues that need to be resolved in the future research. This figure presents the interface morphology of Sn-Cu-Ni-xPr joint. (a) x = 0, (b) x = 0.05wt%. It was clear that with the addition of 0.05% Pr, the thickness of IMC layer decreases significantly and the formation of voids at the interface is inhibited.

A nearly fully dense grade 300 maraging steel was fabricated by selective laser melting (SLM) additive manufacturing with optimum laser parameters. Different heat treatments were elaborately applied based on the detected phase transformation temperatures. Microstructures, precipitation characteristics, residual stress and properties of the as-fabricated and heat-treated SLM parts were systematically characterized and analyzed. The observed submicron grain size (0.31 μm on average) suggests an extremely high cooling rate up to 10 7  K/s. Massive needle-shaped nanoprecipitates Ni 3 X (X = Ti, Al, Mo) are clearly present in the martensitic matrix, which accounts for the age hardening. The interfacial relations between the precipitate and matrix are revealed by electron microscopy and illustrated in detail. Strengthening mechanism is explained by Orowan bowing mechanism and coherency strain hardening. Building orientation-based mechanical anisotropy, caused by 'layer-wise effect', is also investigated in as-fabricated and heat-treated specimens. The findings reveal that heat treatments not only induce strengthening, but also significantly relieve the residual stress and slightly eliminate the mechanical anisotropy. In addition, comprehensive performance in terms of Charpy impact test, tribological performance, as well as corrosion resistance of the as-fabricated and heat-treated parts are characterized and systematically investigated in comparison with traditionally produced maraging steels as guidance for industry applications.

The reactive metal-support interaction in the Cu-In 2 O 3 system and its implications on the CO 2 selectivity in methanol steam reforming (MSR) have been assessed using nanosized Cu particles on a powdered cubic In 2 O 3 support. Reduction in hydrogen at 300 °C resulted in the formation of metallic Cu particles on In 2 O 3 . This system already represents a highly CO 2 -selective MSR catalyst with ~93% selectivity, but only 56% methanol conversion and a maximum H 2 formation rate of 1.3 µmol g Cu −1  s −1 . After reduction at 400 °C, the system enters an In 2 O 3 -supported intermetallic compound state with Cu 2 In as the majority phase. Cu 2 In exhibits markedly different self-activating properties at equally pronounced CO 2 selectivities between 92% and 94%. A methanol conversion improvement from roughly 64% to 84% accompanied by an increase in the maximum hydrogen formation rate from 1.8 to 3.8 µmol g Cu −1  s −1 has been observed from the first to the fourth consecutive runs. The presented results directly show the prospective properties of a new class of Cu-based intermetallic materials, beneficially combining the MSR properties of the catalyst's constituents Cu and In 2 O 3 . In essence, the results also open up the pathway to in-depth development of potentially CO 2 -selective bulk intermetallic Cu-In compounds with well-defined stoichiometry in MSR.

We developed ceramic core-shell materials based on abundant halloysite clay nanotubes with enhanced heavy metal ions loading through Schiff base binding. These clay tubes are formed by rolling alumosilicate sheets and have diameter of c.50 nm, a lumen of 15 nm and length ~1 μm. This allowed for synthesis of metal nanoparticles at the selected position: (1) on the outer surface seeding 3-5 nm metal particles on the tubes; (2) inside the tube's central lumen resulting in 10-12 nm diameter metal cores shelled with ceramic wall; and (3) smaller metal nanoparticles intercalated in the tube's wall allowing up to 9 wt% of Ru, and Ag loading. These composite materials have high surface area providing a good support for catalytic nanoparticles, and can also be used for sorption of metal ions from aqueous solutions.

The young history of sputtering onto a liquid features great achievements in the green production of various metal and metal oxide nanoparticles (NPs) and nanoclusters (NCs). Studies on how the sputtering parameters affect the properties of NPs and NCs have elucidated their formation mechanism and marked a crucial role of liquid matrix in the nucleation and growth of particles, controlling their various properties. Current research has been devoted to making alloy bi- and trimetallic NPs with a high level of control over the NP structure, composition, and size via well-designed target systems, sputtering steps, and liquid matrix materials. In this minireview, we discuss the recent advances in the use of various types of targets to prepare different bi- and trimetallic NPs. In single target sputtering, systems with alternative configurations of metals, alloy targets, monometallic targets in sequence, and a combination of sputtering and chemical reactions have been developed. On the other hand, a double head system was introduced to widen the range of controllable sputtering parameters yielding more versatility in particle composition and fine structure. The synergistic and tuneable properties exhibited by the multi-metallic components in small NPs and NCs for their use in catalysis and optical applications are discussed.

This is a preliminary study of a material comprising gelatin (Gel), silver nanoparticles (AgNPs) and curcumin (Cur) aimed for wound-healing treatment. Gelatin was used to stabilize AgNPs and encapsulate curcumin to form a therapeutic composite (GelCurAg) for their strong bactericidal and antioxidant properties. GelCurAg formulations with different gelatin concentrations were characterized to attain information about their physiochemical properties and the loading efficiency of therapeutic agents. In vitro assessment of GelCurAg focused on antibacterial, antioxidant and cytotoxic aspects. The results suggested that Gel 1 CurAg (synthesized from 1% gelatin solution) could be utilized as potential therapeutic agents in treating infectious wound owing to its bactericidal and antioxidant effects and low toxicity for clinical uses.

Tribological coatings made of MoS 2 and WSe 2 phases and their corresponding combinations with tungsten carbide (WC) were prepared by non-reactive magnetron sputtering of individual targets of similar composition. A comparative tribological analysis of these multiphase coatings was done in both ambient air (30-40% relative humidity, RH) and dry nitrogen (RH<7%) environments using the same tribometer and testing conditions. A nanostructural study using advanced transmission electron microscopy of the initial coatings and examination of the counterfaces after the friction test using different analytical tools helped to elucidate what governs the tribological behavior for each type of environment. This allowed conclusions to be made about the influence of the coating microstructure and composition on the tribological response. The best performance obtained with a WSe x film (specific wear rate of 2 × 10 −8  mm 3  N -1 m -1 and a friction coefficient of 0.03-0.05) was compared with that of the well-established MoS 2 lubricant material.

Metal oxide nanoparticles of different nature have been used in different fields such as therapeutics, biomarkers, tribology or environmental remediation, among others. Besides, the surface modification of such nanoparticles is of particular interest to bring designed functions. In this paper we describe the synthesis of CuO nanoparticles with two different geometries (spherical and prolate) and decorated with long alkyl chains in order to use as dye removers by adsorption and/or photo-degradation of a persistent model dye (Congo Red) and as lubricant additives to improve the tribological performance of base lubricant oils. Alkyl-functionalized CuO nanoparticles demonstrated a high stability in oily suspensions and an improvement in the friction reducing the CoF ca. 26%; the alkyl-decorated nanoparticles showed also higher adsorption kinetics for Congo Red than the neat ones following a pseudo-second-order trend, although with lower adsorption efficiency. The synthesis, surface modification and physic-chemical characterization of spherical and prolate CuO nanoparticles are described as well as their applications as lubricant additives and Congo Red photocatalytic removal.

In an aging society, bone disorders such as osteopenia, osteoporosis, and degenerative arthritis cause serious public health problems. In order to solve these problems, researchers continue to develop therapeutic agents, increase the efficacy of developed therapeutic agents, and reduce side effects. Gold nanoparticles (GNPs) are widely used in tissue engineering applications as biosensors, drug delivery carriers, and bioactive materials. Their special surface property enables easy conjugation with ligands including functional groups such as thiols, phosphines, and amines. This creates an attractive advantage to GNPs for use in the bone tissue engineering field. However, GNPs alone are limited in their biological effects. In this study, we used thiol-PEG-vitamin D (SPVD) to conjugate vitamin D, an essential nutrient critical for maintaining normal skeletal homeostasis, to GNPs. To characterize vitamin D-conjugated GNPs (VGNPs), field emission transmission electron microscopy, energy dispersive X-ray spectroscopy, dynamic light scattering, and ultraviolet/visible absorption analysis were carried out. The developed VGNPs were well bound through the thiol groups between GNPs and vitamin D, and were fabricated in size of 60 nm. Moreover, to demonstrate VGNPs osteogenic differentiation effect, various assays were carried out through cell viability test, alkaline phosphatase assay, calcium deposition assay, real-time polymerase chain reaction, and immunofluorescence staining. As a result, the fabricated VGNPs were found to effectively enhance osteogenic differentiation of human adipose-derived stem cells (hADSCs) in vitro. Based on these results, VGNPs can be utilized as functional nanomaterials for bone regeneration in the tissue engineering field.