Influence of solution heat treatment on microstructure and tensile properties of Gd-Treated Al-15% Mg-2 Si in-situ composites

Microstructural alteration and tensile properties of Al-15% Mg2Si composite specimens was examined after addition of gadolinium (Gd) and conducting solution heat treatment. Various percentages of gadolinium (0.5, 1.0, 2.0 and 5.0 wt. % Gd) were added to the composite Al-15% Mg2Si composite. The specimens then solutionized at 500 °C for 4h followed by quenching. The results showed that regular morphology and small size of primary Mg2Si particles is achieved after addition of 1.0 wt.% Gd compared to untreated composite. Due to solutionizing effect, Mg2Si dissolution occurred which led to alter the morphology of primary Mg2Si particles to round shape. Tensile testing results revealed that enhancement in UTS and El% values owns to influence of both Gd addition and solution heat treatment on the Al-15% Mg2Si composite. The fracture surface of untreated composite depicted a cellular fracture, while the fracture surface of Gd treated and heat treated composite showed a ductile surface containing fine dimples, in which alteration of fracture mode is due to the role of Gd and heat treatment on microstructural modification, which results in reduction of potential sites for stress concentration and crack initiation areas

Effect of tin coating thickness on tin whiskers formation and growth

The effect of various thicknesses of tin coating towards tin whiskers formation and growth in 30°C/60%RH environmental condition had been studied. Electroless plating method was used to coat a layer of tin onto copper, Cu substrates. Three different thicknesses were obtained by controlling the plating times of immersion tin. 8 minutes, 12 minutes, and 20 minutes of plating times produced 1.2μm, 1.5μm, and 2.3μm thickness of tin coating respectively. After storage time up to twelve weeks under 30°C/60%RH environmental condition, it was found that the length of tin whiskers in thinnest tin coating (1.2μm) is 48.96pm, followed by 54.24μm in thicker tin coating (1.5μm), and the longest tin whiskers was recorded as 58.58μm in thickest tin coating (2.3μm). Based oil the results, it was clearly shows that the thickness of tin coating affects the growth of whiskers as the thickest tin coating promotes longest whiskers compare to the thinnest tin coating

A review of transition metal sulfides as counter electrodes for dye-sensitized and quantum dot-sensitized solar cells

Third-generation solar cells, including dye-sensitized solar cells (DSSCs) and quantum dot-sensitized solar cells (QDSSCs), have been associated with low-cost material requirements, simple fabrication processes, and mechanical robustness. Hence, counter electrodes (CEs) are a critical component for the functionality of these solar cells. Although platinum (Pt)-based CEs have been dominant in CE fabrication, they are costly and have limited market availability. Therefore, it is important to find alternative materials to overcome these issues. Transition metal chalcogenides (TMCs) and transition metal dichalcogenides (TMDs) have demonstrated capabilities as a more cost-effective alternative to Pt materials. This advantage has been attributed to their strong electrocatalytic activity, excellent thermal stability, tunability of bandgap energies, and variable crystalline morphologies. In this study, a comprehensive review of the major components and working principles of the DSSC and QDSSC are presented. In developing CEs for DSSCs and QDSSCs, various TMS materials synthesized through several techniques are thoroughly reviewed. The performance efficiencies of DSSCs and QDSSCs resulting from TMS-based CEs are subjected to in-depth comparative analysis with Pt-based CEs. Thus, the power conversion efficiency (PCE), fill factor (FF), short circuit current density (Jsc) and open circuit voltage (Voc) are investigated. Based on this review, the PCEs for DSSCs and QDSSCs are found to range from 5.37 to 9.80% (I−/I3− redox couple electrolyte) and 1.62 to 6.70% (S−2/Sx− electrolyte). This review seeks to navigate the future direction of TMS-based CEs towards the performance efficiency improvement of DSSCs and QDSSCs in the most cost-effective and environmentally friendly manner

Synthesis and characterization of nickel boride nanoparticles for energy conversion catalyst materials – the effect of annealing temperature

In the recent technology development, fuel cell has been widely used in many applications, including transportation and industry. Platinum catalysts are used to catalyst the reaction at the oxygen electrode, but they are expensive and has limited supply. A nickel-boron nanoparticle catalyst is proposed as a substitute for fuel cell catalyst material. The objectives are to evaluate the effect of the annealing process and to determine the characteristics of the annealed nanoparticles using scanning electron microscopy - energy dispersive X-ray (SEM-EDS), inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis, total organic carbon (TOC) analysis and X-ray diffraction (XRD). A wet chemical method was used to synthesize nickel-boron nanoparticles by chemical reduction (co-reduction) of nickel chloride and sodium borohydride. As-synthesized nickel-boron nanoparticles were annealed at temperatures of 200, 300, 400, 500, and 700 °C in an argon atmosphere for 2 h. From the experimental results, nickel-boron nanoparticles annealed at 300 °C with equal dispersion of crystalline Ni and crystalline Ni3B showed the highest catalyst performance. The yield of nickel-boron nanoparticles sized 1.1364 nm was smaller than in the literature (37 nm). The size of Ni-B nanoparticles was calculated by using the Scherrer equation with the values of full width half maximum (FWHM) obtained by peak fitting following the Gaussian model. Smaller Ni-B nanoparticles have a higher surface-area-to-volume ratio, which increases the exposure of the active sites (crystalline Ni and crystalline Ni3B phase) to the reactants (methanol) and improves catalytic activity

Tribological Investigation of Nickel Titanium Shape Memory Alloy (NiTi SMA) Coatings

Nickel titanium shape memory alloy (NiTi SMA) coatings demonstrate shape memory effects, superelasticity and excellent biocompatibility. It has been widely used in various applications such as in dentistry, orthopaedics and micro electro mechanical system. However, the application of NiTi SMA coating in the tribological field is still limited due to its low hardness and low wear resistance properties. In this study, the aim is to design a NiTi SMA coating structure with excellent mechanical properties and high wear resistance for tribological applications. The approach was undertaken by considering the potential of the Ni rich NiTi SMA precipitations and creating the TiO2 rutile layer onto the NiTi SMA structure so as to improve their mechanical and wear properties. The physical vapour deposition (PVD) sputtering technique is the most commonly used method for the production of amorphous NiTi SMA coating with various composition. This material is very sensitive to its process parameters and to the process-structure-properties relationship. Thus, the post-sputtering annealing process was successful in producing a crystalline Ni rich NiTi SMA coating with excellent mechanical and wear properties for tribological applications. The existence of a TiO2 rutile layer with a combination of the Ni rich NiTi SMA (Ni3Ti) and NiTi B2 parent phase within the annealed NiTi SMA coatings produced a significant improvement in the adhesion, hardness and wear resistance performance compared to the as-deposited NiTi SMA coating. The post-sputtered annealing process succeeded in increasing the adhesion and wear resistance of the NiTi SMA coating. The adhesion properties of the NiTi SMA coating increased with a critical load to failure of twelve times higher than the as-deposited NiTi SMA coating. The major enhancement of the adhesion properties significantly influenced the wear of NiTi SMA with a decrease in wear track morphology (wear width/wear depth) four times lower than the as-deposited NiTi coating. The post-sputtering annealing parameters and the coating thickness were shown to be the main parameters that affected the NiTi SMA coating properties. In this study, an annealing temperature of 600°C for a period of 30 minutes provided the optimum adhesion at a coating thickness of 2 µm. However, the optimum wear resistance for the same coating was achieved at a temperature of 550°C for a period of 60 minutes. The findings show the potential the post-sputtering annealing process has, in creating an excellent structure for NiTi SMA coating which demonstrate significant adhesion and wear resistance properties for tribological applications

Mechanical performance of the annealed NiTi Shape Memory Alloy coating onto 316L stainless bio-steel

This paper presents the mechanical performance of the annealed NiTi Shape Memory Alloy (SMA) coating deposited onto 316L stainless steel substrate The as-deposited SMA coating, Ni559 Ti441, showed an amorphous behaviour The crystalline NiTi (SMA) coating was produced byannealing the as-deposited NiTi with a thickness about 20 µm, at above its crystallisation temperature in a vacuum ambient The annealed NiTi coatings were characterised to determine the effect of the annealing parameters on their mechanical behaviour The NiTi phases and structures were determined by x-ray diffraction (XRD) and scanning electron microscopy (SEM) whereas the mechanical properties were measured using the Rockwell C adhesion test Three main phases; NiTi B2 parent phase, Ni3Ti and TiO2 were found in the annealed samples and the intensities of each phase were dependent on the annealing temperature and annealing time Each phase significantly affected the mechanical behaviour of the coatings Higher intensities of Ni3Ti and TiO2 phases were believed to contribute to the low adhesion of the annealed NiTi coatings due to their brittle properties The annealing parameters; 600 ºC for durations of 30 min was considered as the optimum parameter, yielding no fine cracks at the Rockwell C indentation interface compared to other samples at high magnification under the SEM Adding a hard top layer of TiN would potentially provide a hard coating with an interlayer capable of absorbing impact which would be very suitable for ball joints used in hip replacement therap

A novel method to enhance the performance of an ex-situ Al/Si-YSZ metal matrix composite

A novel technique was used to synthesise an Al–Si/YSZ composite with improved bonding strength between the matrix and YSZ particles. Based on thermal analysis results, Bi was added in slurry state at 605 ± 5 °C, and two-step stirring was applied. It was found that the duration of mushy zone decreased and solidification rate increased with the addition of YSZ particles. Elemental mapping analysis on etched and deep-etched conditions revealed that these YSZ particles were surrounded by Bi. Mechanical characterisation showed that YS, UTS, El% and the hardness of the A356 + Bi/YSZ composite increased by 25.5%, 2%, 43% and 24% respectively. Fractography analysis confirmed that the interfacial bonding strength at Al/YSZ improved significantly with the addition of Bi. The wear rate and friction coefficient of A356 + Bi/YSZ decreased to 0.464 and 0.55 mm3/Km respectively, which are 34.6% and 6.7% lower than the values obtained for the A356/YSZ composite. The worn surface revealed mild abrasion wear mechanisms in the A356 + Bi/YSZ composite

Influence of solution heat treatment on microstructure and tensile properties of gd-treated al-15% mg2si in-situ composites

Microstructural alteration and tensile properties of Al-15% Mg2Si composite specimens was examined after addition of gadolinium (Gd) and conducting solution heat treatment. Various percentages of gadolinium (0.5, 1.0, 2.0 and 5.0 wt. % Gd) were added to the composite Al-15% Mg2Si composite. The specimens then solutionized at 500 degrees C for 4h followed by quenching. The results showed that regular morphology and small size of primary Mg2Si particles is achieved after addition of 1.0 wt.% Gd compared to untreated composite. Due to solutionizing effect, Mg2Si dissolution occurred which led to alter the morphology of primary Mg2Si particles to round shape. Tensile testing results revealed that enhancement in UTS and El% values owns to influence of both Gd addition and solution heat treatment on the Al-15% Mg2Si composite. The fracture surface of untreated composite depicted a cellular fracture, while the fracture surface of Gd treated and heat treated composite showed a ductile surface containing fine dimples, in which alteration of fracture mode is due to the role of Gd and heat treatment on microstructural modification, which results in reduction of potential sites for stress concentration and crack initiation areas