Transient Soldering Reaction Mechanisms of SnCu Solder on CuNi Nano Conducting Layer and Fracture Behavior of the Joint Interfaces

Soldering can be used in the connection of thin film solar cells, while the soldering quality is difficult to control as the conducting layer on the solar cells is nano-sized and can be consumed within a few seconds. In this study, the microstructure and fracture behavior of the Sn-0.7wt.%Cu/Cu-30wt.%Ni joint interfaces were investigated. The use of CuNi conducting layer deposited on the Al/Si film with about 150 nm thickness and a soldering time of a few seconds were investigated. The results reveal that dense rod-like (Cu,Ni)(6)Sn-5 grains with a diameter of 100-200 nm are formed at the edge of the joint interface, which gradually transform into coarsely and loosely distributed rod-like (Cu,Ni)(6)Sn-5 grains from the edge to the inner of the solder joint. The CuNi layer is completely consumed at the inner region, and the diameter of the (Cu,Ni)(6)Sn-5 grain were constant at about 1 mu m. With longer soldering time, the width of the transition region between the fine and coarse (Cu,Ni)(6)Sn-5 grains decrease sharply from a few hundred micrometers to about 10 mu m, and the coarse rod-like (Cu,Ni)(6)Sn-5 grains distribute throughout all the joint interface. Tensile fracture of the Cu/SnCu/CuNi solder joints occurs around the (Cu,Ni)(6)Sn-5/CuNi interface at the edge and along the solder/Al or Al/Si interfaces at the inner region. The longer reaction time results in exhaustion of the CuNi layer, weakening of the bonding between the Al/Si/SnO2 films, and decreased joint strength from over 40 MPa to lower than 35 MPa

An Investigation of the Wear Resistance of Knitting Machinery Needle

Comparison tests of needles made in abroad and domestic on chemical composition, microstruture, mechanical property and so on, the main influence factors of the wear resistance were analysed. Approaches of improving the wear resistance of needles are given,such as hot process,surface treatment,local strengthening. Combined with finite element analysis, the stress and the strain of the needle hook were analysed. Comparative results of both abroad and domestic show that the carbide in the microstructure and structural design of needles are regarded as the main influence factors of the wear resistance

Preparation of thin NiCrBSi laser cladding layers with no microcracking and low dilution

Preparation of thin NiCrBSi laser cladding layers with no microcracking and low dilutio

Combined Effects of Deformation and Undercooling on Isothermal Bainitic Transformation in an Fe-C-Mn-Si Alloy

Both ausforming and transformation temperature affect the successive bainitic transformation and microstructure. The individual influence of each case is clear, whereas the combined effects are still unknown. Thermomechanical simulation and metallography were used to investigate the combined effects of ausforming and transformation temperature on bainitic transformation and microstructure. The kinetics of isothermal bainitic transformation in non-deformed and deformed materials was analyzed. A lower transformation temperature can lead to more bainite formation without deformation. However, ausforming with small strains can partially compensate for the decrease of bainite amount caused by the decreased undercooling. The larger the applied strain is, the smaller the difference between the final amounts of bainite with different undercooling. Ausforming at a relatively higher temperature is more favorable to the acceleration of subsequent isothermal bainitic transformation. The results in the present work provide reference for optimizing the fabrication technology of medium-carbon nanobainite steels

Effect of titanium addition on structure, corrosion resistance and mechanical properties of aluminum coatings on NdFeB by ion-beam-assisted magnetron sputtering

Titanium has been added in the Al coatings on sintered NdFeB magnets by ion-beam-assisted magnetron sputtering to improve the mechanical properties of coatings without corrosion resistance deterioration. The effect of Ti addition on structure, mechanical and electrochemical properties of Al coatings has been investigated, complemented by x-ray diffraction and transmission electron microscopy. The results show that the ion-beam-assisted magnetron co-sputtering of Al and Ti obtains a single-phase polycrystalline structure of Al-Ti solid solution. With the increasing Ti content, the coating structure becomes denser and the grain size is reduced. Both the mechanical and wear properties of the coatings are improved with the addition of Ti where the hardness of the Al-Ti coating increases with the increasing amount of Ti. Polarization and EIS testing results show that the titanium-doped coatings have an enhanced corrosion resistance by comparison with pure Al coatings when Ti content is lower than 4.3 at.%

Effect of the grain boundary Tb/Dy diffused microstructure on the magnetic properties of sintered Nd-Fe-B magnets

The effect of heavy rare earth element (HREE, Tb and Dy) coating thickness on the grain boundary diffusion process (GBDP) of sintered Nd-Fe-B magnets is investigated. The distribution of HREE concentration fits well with the distribution depicted by the dual-trend diffusion model for the magnets with thin HREE coatings. However, when the HREE coating is thicker than a critical value, two new types of structures of HREE distribution, namely, the anti-shell/core structure and the transitional structure, besides the well-reported shell/core structure, appear sequentially around the Nd-Fe-B grains near the close surface of the diffused magnets. The evolution of the microstructures and the magnetic properties of the diffused magnets are further studied on the basis of the dual-trend diffusion model. The coercivity of the diffused magnets with thick HREE coatings slowly improves when anti-shell/core and transitional structures form on the outer layer of the diffused magnets. The ultimate coercivity of the HREE-diffused magnets is the result of the combined action of the above three structures

Highly efficient catalytic direct air capture of CO2 using amphoyeric amino acid sorbent with acid‐base bi‐functional 3D graphene catalyst

Direct air capture (DAC) of CO2 is vital for combating global climate change, but DAC technologies have a low absorption efficiency due to the low concentration (∼400 ppm) of atmospheric CO2. A novel DAC technology was developed to solve this issue using lysine (an amino acid) as a sorbent and N-doped 3D graphene as an absorption/desorption-enhanced bifunctional catalyst. Introducing only 500 ppm N-3DG catalyst increased the working time (≥90% CO2 absorption efficiency) by 233% and its absorption capacity by 197%. The catalyst also significantly accelerated the CO2 working desorption capacity and rate by ∼280% and ∼338% at 70 °C, enabling regeneration of the sorbent by utilizing low-temperature waste heats. Furthermore, the excellent stability of the system was confirmed by 50 cyclic tests. The chemical mechanism driving catalytic CO2 capture was postulated and confirmed by density functional theory computations. This study provides a new strategy for developing next-generation DAC technologies