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This paper aimed to investigate the effects of nano-copper particles on the melting behaviors, wettability and defect formation mechanism of the Sn58Bi composite solder pastes.

In this paper, the mechanical stirring method was used to get the nano-composite solder pastes.

Experimental results indicated that the addition of 3 wt.% (weight percentage) 50 nm copper particles showed limited effects on the melting behaviors of the Sn58Bi composite solder paste. The spreading rate of the Sn58Bi composite solder paste showed a decreasing trend with the increase of the weight percentage of 50 nm copper particles from 0 to 3 wt.%. With the addition of copper particles of diameters 50 nm, 500 nm or 6.5 μm into the Sn58Bi solder paste, the porosities of the three types of solder pastes showed a similar trend. The porosity increased with the increase of the weight percentage of copper particles. Based on the experimental results, a model of the void formation mechanism was proposed. During reflow, the copper particles reacted with Sn in the matrix and formed intermetallic compounds, which gathered around the voids produced by the volatilization of flux. The exclusion of the voids was suppressed and eventually led to the formation of defects.

This study provides an optimized material for the second and third level packaging. A model of the void formation mechanism was proposed.

This study aims to investigate the synergistic friction reduction and antiwear effects of lyophilized graphene loading nano-copper (RGO/Cu) as lubricating oil additives, compared with graphene.

The friction performance of freeze-drying graphene (RGO) and RGO/Cu particles was investigated at different addition concentrations and under different conditions.

Graphene plays a synergistic friction reduction and antiwear effect because of its large specific surface area, surface folds and loading capacity on the nanoparticles. The results showed that the average friction coefficients of RGO and RGO/Cu particles were 22.9% and 6.1% lower than that of base oil and RGO oil, respectively. In addition, the widths of wear scars were 62.3% and 55.3% lower than those of RGO/Cu particles, respectively.

The RGO single agent is suitable for medium-load and high-speed conditions, while the RGO/Cu particles can perform better in the conditions of heavy load and high speed.

The purpose of this paper is to improve the antifriction and antiabrasive behavior of the used oil through the addition of a lubricant.

The author selected 85W-90 used oil with three kinds of 4,758, 10,507 and 16,223 km mileages, which may represent run-in wear period, steady-state wear period and rapid wear for used oil, respectively. Nano copper, molybdenum dithiocarbamate (MoDTC) and copper dioctyl dithiocarbamate (CuDTC) of lubricant additive are added to the used oil to improve its antifriction performances and service life. The influence of lubricant additive on the tribological properties of used oil is investigated by the friction tests.

An abnormal phenomenon has been observed by the friction test under high mileage used oil with CuDTC in presence of MoDTC lubrication, and superlow friction coefficient of 0.04 has been achieved after a running-in period for the first time. It is found that CuDTC additive is beneficial to improve greatly the antifriction behavior of used oil, especially when MoDTC is present. The results indicate that the dissoluble of CuDTC and the tribochemical reaction of MoDTC play an important role in superlow friction of high mileage used oil. Moreover, the superlow friction is also closely related to the viscosity of used oil.

The possible mechanism of superlow friction is attributed to the additive thinning effect and the synergistic effect of the dissoluble of CuDTC and the tribochemical reaction of MoDTC binary lubricant additives in high mileage used oil. This work will extend the application of CuDTC additive widely and explore a new method to the reutilization and the life extension of used lubricating oil.

This paper aims to investigate the effects of different ultrasonic-assisted loading degrees on the microstructure, mechanical properties and the fracture morphology of Cu/Zn+15%SAC0307+15%Cu/Al solder joints.

A new method in which 45 μm Zn particles were mixed with 15% 500 nm Cu particles and 15% 500 nm SAC0307 particles as solders (SACZ) and five different ultrasonic loading degrees were applied for realizing the soldering between Cu and Al at 240 °C and 8 MPa. Then, SEM was used to observe and analyze the soldering seam, interface microstructure and fracture morphology; the structural composition was determined by EDS; the phase of the soldering seam was characterized by XRD; and a PTR-1102 bonding tester was adopted to test the average shear strength.

The results manifest that Al–Zn solid solution is formed on the Al side of the Cu/SACZ/Al joints, while the interface IMC (Cu₅Zn₈) is formed on the Cu side of the Cu/SACZ/Al joints. When single ultrasonic was used in soldering, the interface IMC (Cu₅Zn₈) gradually thickens with the increase of ultrasonic degree. It is observed that the proportion of Zn or ZnO areas in solders decreases, and the proportion of Cu–Zn compound areas increases with the variation of ultrasonic degree. The maximum shear strength of joint reaches 46.01 MPa when the dual ultrasonic degree is 60°. The fracture position of the joint gradually shifts from the Al side interface to the solders and then to the Cu side interface.

The mechanism of ultrasonic action on micro-nanoparticles is further studied. By using different ultrasonic loading degrees to realize Cu/Al soldering, it is believed that the understandings gained in this study may offer some new insights for the development of low-temperature soldering methodology for heterogeneous materials.

3D printing is gaining attention in the medical sector for the development of customized solutions for a wide range of applications such as temporary external implants. The materials used for the manufacturing process are critical, as they must provide biocompatibility and adequate mechanical properties. This study aims to evaluate and model the influence of the printing parameters on the mechanical properties of two biocompatible materials.

In this study, the mechanical properties of 3D-printed specimens of two biocompatible materials (ABS medical and PLActive) were evaluated. The influence of several printing parameters (infill density, raster angle and layer height) was studied and modelled on three response variables: ultimate tensile strength, deformation at the ultimate tensile strength and Young’s modulus. Therefore, statistical models were developed to predict the mechanical responses based on the selected printing parameters.

The used methodology allowed obtaining compact models that show good fit, particularly, for both the ultimate tensile strength and Young’s modulus. Regarding the deformation at ultimate tensile strength, this output was found to be influenced by more factors and interactions, resulting in a slightly less precise model. In addition, the influence of the printing parameters was discussed in the work.

The presented paper proposed the use of statistical models to select the printing parameters (infill density, raster angle and layer height) to optimize the mechanical response of external medical aids. The models will help users, researchers and firms to develop optimized solutions that can reduce material costs and printing time but guaranteeing the mechanical response of the parts.

This paper aims to explore the leaf-surface wax as green lubricant additive and compare the tribological properties between coastal and inland leaf-surface waxes of the same species plant.

The leaf-surface waxes were extracted from the leaves of Robinia pseudoacacia cv. Idaho and Populus nigra in coastal and inland areas, and then the compositions of the four kinds of leaf-surface waxes were characterized using a gas chromatography–mass spectrometry. The tribological properties of these leaf-surface waxes as lubricant additives in the base oil of synthetic ester (SE) were investigated by an MFT-R4000 reciprocating friction and wear tester. As well as the surface morphologies and chemical compositions of the wear scars were characterized by a scanning electron microscope and time-of-flight secondary ion mass spectrometry, respectively.

The results indicate that all the leaf-surface waxes as additives can effectively improve the friction reduction and anti-wear performances of SE for steel–aluminum friction pairs. Therein, coastal leaf-surface waxes have better tribological performances than inland leaf-surface waxes, which are attributed to that the leaf-surface waxes extracted from coastal plants can form a better protective film on the worn surface throughout the friction process.

This paper investigated a new kind of environmentally friendly lubricant additive and compared the tribological properties of the leaf-surface wax extracted from coastal and inland plants. The associated conclusions can provide a reference to explore the tribological performances of leaf-surface wax as green lubricant additive.

This paper aims to investigate the friction and wear performance of Hazelnut oil with copper (Cu) nano additives.

The experiments were performed on a pin-on-disc tribometer in boundary and mixed lubrication regimes. Copper nanoparticles were added in 0.5 and 1 Wt.% concentrations and corresponding Stribeck curves were generated with a base oil and with oil containing Cu nanoparticles. Surface analysis of aluminium 6061 pins was conducted using an optical microscope, scanning electron microscope and energy dispersive spectroscopy.

The lubricant with 0.5 Wt.% Cu nanoparticles exhibited better results. An improvement of around 80 per cent in coefficient of friction and around 99 per cent in specific wear rate was observed. The film formation capability of the Cu nanoparticles led to an overall improvement in tribological properties of the base oil.

Experiments were performed to evaluate the tribological performance of a new lubricant (Hazelnut oil) using Cu nanoparticles. The results obtained herein suggest that Hazelnut oil has a great potential to replace the conventional mineral oils in the field of industrial lubrication.

This paper aims to review recent reports on mechanical properties of Sn-Bi and Sn-Bi-X solders (where X is an additional alloying element), in terms of the tensile properties, hardness and shear strength. Then, the effects of alloying in Sn-Bi solder are compared in terms of the discussed mechanical properties. The fracture morphologies of tensile shear tested solders are also reviewed to correlate the microstructural changes with mechanical properties of Sn-Bi-X solder alloys.

A brief introduction on Sn-Bi solder and reasons to enhance the mechanical properties of Sn-Bi solder. The latest reports on Sn-Bi and Sn-Bi-X solders are combined in the form of tables and figures for each section. The presented data are discussed by comparing the testing method, technical setup, specimen dimension and alloying element weight percentage, which affect the mechanical properties of Sn-Bi solder.

The addition of alloying elements could enhance the tensile properties, hardness and/or shear strength of Sn-Bi solder for low-temperature solder application. Different weight percentage alloying elements affect differently on Sn-Bi solder mechanical properties.

This paper provides a compilation of latest report on tensile properties, hardness, shear strength and deformation of Sn-Bi and Sn-Bi-X solders and the latest trends and in-depth understanding of the effect of alloying elements in Sn-Bi solder mechanical properties.

This work describes a metal-metal bonding process by the use of Cu nanoparticles as a filler material. The Cu particles used were prepared by reduction of Cu²⁺ with hydrazine in the presence of cetyltrimethylammonium bromide as a dispersing agent (uncoated Cu particles). Polypyrrole (PPy)-coated Cu nanoparticles were also used as the filler. Strong bonding for Cu discs was not obtained by using the PPy-coated particles. For the uncoated Cu particles, a shear strength required for separating the discs bonded by annealing at 400°C in H₂ gas was as large as 18.1 MPa.