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This paper aims to investigate the structural, corrosion and the study of tribocorrosion features of the AA7075 aluminum alloy with and without the application of electroless Ni-P/Ni-B duplex coating with a thickness of approximately 40 microns.

Surface characterization of the samples was made by structural surveys (light optic microscope, scanning electron microscopic examinations and X-ray diffraction analyses), hardness measurements, corrosion and tribocorrosion tests.

Results of the experiments showed that upper Ni-B coating deposited on the surface of first Ni-P layer by duplex treatment caused remarkable increment in the hardness, corrosion resistance and tribocorrosion performance as compared to the AA7075 aluminum alloy.

This study can be a practical reference and offers insight into the effects of duplex treating on the increase of hardness, corrosion and tribocorrosion performance.

This paper aims to coat ternary composite NiBP-graphite films by Dynamic Chemical Plating “DCP” technique with a growth rate of at least 5 μm/h, which makes this technique a worthy candidate for production of composite films. Electroless nickel plating method can be used to deposit nickel–phosphorous and nickel–boron coatings on metals or plastic surface. However, restrictions such as toxicity, short lifetime of the plating-bath and limited plating rate have limited applications of conventional electroless processes.

DCP is an alternative for producing metallic deposits on non-conductive materials and can be considered as a modified electroless coating process. Using a double-nozzle gun, two different solutions containing the precursors are sprayed simultaneously and separately onto the surface. With this technique, NiBP-graphite films are fabricated and their corrosion and tribological properties are investigated.

With a film thickness of 2 μm, tribological analysis confirms that these coatings have favorable anti-friction and anti-wear properties. Corrosion resistance of NiBP-graphite composite films was investigated, and it was found that graphite incorporation significantly enhances corrosion resistance of NiBP films.

DCP is faster and simpler to perform compared to other electroless deposition techniques. Using a double-nozzle gun, metal salt solution and reducing agents are sprayed to the surface, forming a deposit. Previously, coatings such as Cu, Cu-graphite, Cu-PTFE, Ni-B-TiO2, Ni-P, Ni-B-P and Ni-B-Zn with favorable compactness and adherence by DCP were reported. In this paper, the authors report the application of the DCP technique for depositing NiBP-PTFE nanocomposite films.

This paper presents an experimental study to assess the reliability of solder ball attachment to the bond pads of PBGA substrate for various plating schemes. The basic structure of the under bump metallisation is Cu/Ni/Au. Three different kinds of electroless plating solutions are used to deposit the Ni layer, namely, Ni‐B, Ni‐P (5 per cent), and Ni‐P (10 per cent). Also, conventional electrolytic Ni/Au plating is performed to provide a benchmark. After solder ball attachment, mechanical tests are conducted to characterize the ball shear strength for comparison. Furthermore, some specimens are subjected to multiple reflows to investigate the thermal aging effect.

Plasma transferred arc (PTA) coating is a novel method for surface-coating applications. In this method, the substrate is melted using a plasma arc, and surfacing agents such as carbides are introduced to the melt pool. The purpose of this study is to investigate the effect of boron carbide (B₄C) in nickel-based coating on AISI 4140 steel.

Samples were tested on a ball-on-disc wear device, and the microstructure, as well as wear properties, were investigated using SEM and XRD.

The effect of B₄C addition was shown to be linear, with a p-value of 0.0248, indicating strong evidence. The reason for this increase was found to be the increase in third-body generation resulting from hard phases that form couples with the soft base material, nickel. It was concluded that using 6 per cent B₄C was the optimal solution.

In the literature, the effect of neither low temperature on a nickel coating with B₄C nor B₄C as a single surfacing agent in a nickel base has been investigated.

This paper aims to systematically study the effect of reinforcement type, processing methods and reflow cycle on actual retained ratio of foreign reinforcement added in solder joints.

Two kinds of composite solders based on SAC305 (wt.%) alloys with reinforcements of 1 wt.% Ni and 1 wt.% TiC nano-particles were produced using powder metallurgy and mechanical blending method. The morphology of prepared composite solder powder and solder pastes was examined; retained ratios of reinforcement (RRoR) added in solder joints after different reflow cycles were analysed quantitatively using an Inductively Coupled Plasma optical system (ICP-OES Varian-720). The existence forms of reinforcement added in solder alloys during different processing stages were studied using scanning electron microscope, X-ray diffractometry and energy dispersive spectrometry.

The obtained experimental results indicated that the RRoR in composite solder joints decreased with the increase in the number of reflow cycles, but a loss ratio diminished gradually. It was also found that the RRoR which could react with the solder alloy were higher than that of the one that are unable to react with the solder. In addition, compared with mechanical blending, the RRoRs in the composite solders prepared using power metallurgy were relatively pronounced.

Present study offer a preliminary understanding on actual content and existence form of reinforcement added in a reflowed solder joint, which would also provide practical implications for choosing reinforcement and adjusting processing parameters in the manufacture of composite solders.

Molecular dynamics is an emerging simulation technique in the field of machining in recent years. Many researchers have tried to simulate different processing methods of various materials with the theory of molecular dynamics (MD), and some preliminary conclusions have been obtained. However, the application of MD simulation is more limited compared with traditional finite element model (FEM) simulation technique due to the complex modeling approach and long computation time. Therefore, more studies on the MD simulations are required to provide a reliable theoretical basis for the nanoscale interpretation of grinding process. This study investigates the crystal structures, dislocations, force, temperature and subsurface damage (SSD) in the grinding of iron-nickel alloy using MD analysis.

In this study the simulation model is established on the basis of the workpiece and single cubic boron nitride (CBN) grit with embedded atom method and Morse potentials describing the forces and energies between different atoms. The effects of grinding parameters on the material microstructure are studied based on the simulation results.

When CBN grit goes through one of the grains, the arrangement of atoms within the grain will be disordered, but other grains will not be easily deformed due to the protection of the grain boundaries. Higher grinding speed and larger cutting depth can cause greater impact of grit on the atoms, and more body-centered cubic (BCC) structures will be destroyed. The dislocations will appear in grain boundaries due to the rearrangement of atoms in grinding. The increase of grinding speed results in the more transformation from BCC to amorphous structures.

This study is aimed to study the grinding of Fe-Ni alloy (maraging steel) with single grit through MD simulation method, and to reveal the microstructure evolution within the affected range of SSD layer in the workpiece. The simulation model of polycrystalline structure of Fe-Ni maraging steel and grinding process of single CBN grit is constructed based on the Voronoi algorithm. The atomic accumulation, transformation of crystal structures, evolution of dislocations as well as the generation of SSD are discussed according to the simulation results.

The purpose of this paper is to investigate the impact of efficient working capital management (WCM) on a firm’s bond quality ratings (BQR) and debt refinancing risk (RFR).

To fulfill its purpose, this study adopted a co-relational research design. Additionally, the COMPUSTAT of Wharton Research Data Services was used to collect data from American production firms for a period of five years (from 2013 to 2017).

The results of this study suggest that efficient WCM does, in fact, play a role in improving BQR of American production firms. Furthermore, the findings go on to suggest that efficient WCM plays a very little role in reducing RFR for American production firms.

This is a correlational study that investigated the presence of an association between efficient WCM and firms’ BQR and between efficient WCM and RFR. However, the two do not necessarily share a causal relationship. Moreover, the findings of this study may only be generalized to firms that are similar to those that were included in this research.

This study contributes to the literature on financial factors that improve a firm’s BQR. Firms should consider maintaining an optimal net working capital as it improves BQR. Moreover, the findings of this study may prove useful for financial managers, investors, financial management consultants and other stakeholders.

This paper aims to comprehensively review the preparation methods of superhydrophobic surfaces (SHPS) for corrosion protection of Mg alloy in recent years.

The preparation methods, wettability and corrosion resistance of SHPS on Mg alloy in the past three years are systematically described in this paper.

Two types of SHPS, including single-layer and multilayer coatings for corrosion protection of Mg alloy are summarized. Preparing multilayered coatings with multifunction is the current trend in developing SHPS on Mg alloy.

This paper reviewed the preparation methods and corrosion resistance of SHPS on Mg alloys. It provides a valuable reference for researchers to develop highly durable SHPS with excellent corrosion resistance for Mg alloys.

The paper aims to investigate the interfacial reactions between two Sn‐Cu based multicomponent Pb‐free solders, Sn‐2Cu‐0.5Ni and Sn‐2Cu‐0.5Ni‐0.5Au (wt per cent), and Ni substrates during soldering and aging.

Differential scanning calorimetry (DSC) was performed to measure the melting behaviors of the solders and determine the temperature of soldering. DSC tests showed that the onset temperature were 227.47 and 224.787°C for Sn‐2Cu‐0.5Ni and Sn‐2Cu‐0.5Ni‐0.5Au, respectively. Two intermetallic compounds (IMCs), Cu₆Sn₅ and (Cu,Ni)₆Sn₅, were formed in Sn‐2Cu‐0.5Ni solder. While the IMCs detected in Sn‐2Cu‐0.5Ni‐0.5Au matrix were (Cu,Ni)₆Sn₅, (Cu,Au)₆Sn₅ and (Cu,Ni)₆Sn₅. The IMC layer formed at the both solder/Ni interfaces was (Cu,Ni)₆Sn₅ with stick‐lick morphology after soldering at 260°C.

The interfacial IMC layers became planar when aged at 170°C for 500 h. However, cracks were found in the IMC layers at both joints when the aging time reached 1,000 h, that implies reliability problem may exist in the joints. Moreover, Au‐containing IMCs were found on the top of the IMC layer in Sn‐2Cu‐0.5Ni‐0.5Au/Ni joint after for 1,000 h.

This study focuses on the interfacial reactions of Sn‐2Cu‐0.5Ni/Ni and Sn‐2Cu‐0.5Au/Ni during soldering and isothermal aging.

Load balancing is an effective enhancement to the proposed routing protocol, and the basic idea is to share traffic load among cluster members to reduce the dropping probability due to queue overflow at some nodes. This paper aims to propose a novel hierarchical approach called distributed energy efficient adaptive clustering protocol (DEACP) with data gathering, load-balancing and self-adaptation for wireless sensor network (WSN). The authors have proposed DEACP approach to reach the following objectives: reduce the overall network energy consumption, balance the energy consumption among the sensors and extend the lifetime of the network, the clustering must be completely distributed, the clustering should be efficient in complexity of message and time, the cluster-heads should be well-distributed across the network, the load balancing should be done well and the clustered WSN should be fully connected. Simulations show that DEACP clusters have good performance characteristics.

A WSN consists of large number of wireless capable sensor devices working collaboratively to achieve a common objective. One or more sinks [or base stations (BS)] which collect data from all sensor devices. These sinks are the interface through which the WSN interacts with the outside world. Challenges in WSN arise in implementation of several services, and there are so many controllable and uncontrollable parameters (Chirihane, 2015) by which the implementation of WSN is affected, e.g. energy conservation. Clustering is an efficient way to reduce energy consumption and extend the life time of the network, by performing data aggregation and fusion to reduce the number of transmitted messages to the BS (Chirihane, 2015). Nodes of the network are organized into the clusters to process and forwarding the information, while lower energy nodes can be used to sense the target, and DEACP makes no assumptions on the size and the density of the network. The number of levels depends on the cluster range and the minimum energy path to the head. The proposed protocol reduces the number of dead nodes and the energy consumption, to extend the network lifetime. The rest of the paper is organized as follows: An overview of related work is given in Section 2. In Section 3, the authors propose an energy efficient level-based clustering routing protocol (DEACP). Simulations and results of experiments are discussed in Section 4. In Section 5, the authors conclude the work presented in this paper and the scope of further extension of this work.

The authors have proposed the DEACP approach to reach the following objectives: reduce the overall network energy consumption, balance the energy consumption among the sensors and extend the lifetime of the network, the clustering must be completely distributed, the clustering should be efficient in complexity of message and time, the cluster-heads should be well-distributed across the network, the load balancing should be done well, the clustered WSN should be fully connected. Simulations show that DEACP clusters have good performance characteristics.