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The findings of the experimental study into optimizing the heat transfer rate of a PCM-based heat sink for high-power LEDs are presented in this work. The study investigated five heat sink types, with and without PCM. The LED case and junction temperatures, LED module temperatures, heat storage and release rate analyses, analyses of three types of cyclic operation modes, luminous flux, and heat sink thermal resistance were all examined independently. The results indicated that the PCM-based LED heat sink had improved thermal performance. The LED junction temperature of the PCM-equipped E-20 heat sink is nine degrees Celsius lower at 10 W than that of the heat sink without PCM. Furthermore, the E-20 heat sink with PCM extends the LED module’s critical lifespan. As a bonus, the E-20 with PCM had a 38.19 percent lower thermal resistance at 10 W than the E-20 without PCM. According to these results, the heat sink E-20 emits 715 lm at 10 W when operated without a phase-change material (PCM). With the same input power, the luminous flux of an E-20 equipped with a heat sink and a phase-change material (PCM) is 750 lm, a gain of 4.7%. Finally, clearly recommend the heat E-20 sink with PCM suitable for high-power LED thermal management system.

Material deterioration due to erosion and oxidation in high-temperature environments is a major cause of wear in power plants, aircraft engines and petrochemical industries. NiCrSiB based surface coatings using thermal spray techniques such as High-Velocity Oxy-Fuel (HVOF) offer a cost-effective route to improve the tribological properties for a range of substrate materials. The study investigates the high-temperature oxidation and erosion resistance of HVOF coated NiCrSiB reinforced with Al2O3 and WCCo on SS304 stainless steel substrate. The oxidation kinetics and erosion responses of the coatings at 750 °C were evaluated for a period of 160 hrs and the coating microstructure, morphology and chemical compositions characterised. A total of three coating compositions were studied namely: NiCrSiB/Al2O3, NiCrSiB/n-Al2O3 and NiCrSiB/WCCo where the results indicate a superior oxidation and erosion resistance in all cases in comparison to uncoated SS304. However, it was found that the NiCrSiB reinforced with micro-structured Al2O3 outperformed all the other coatings in terms of oxidation resistance. When it comes to erosion resistance, NiCrSiB/WCCo was found to demonstrate the highest performance.

Development of nanostructured high velocity oxy-fuel (HVOF) coatings with low porosity, high strength and increased wear resistance is still in its infancy. Combining nanoparticles with conventional microscale powders are increasingly being investigated to use with feedstock materials for thermal spray processes. Accordingly, this work investigates the addition of nano-Al _2 O _3 particles on the microstructure and erosion wear of NiCrSiB HVOF coating in a stainless steel (AISI 304) substrate. Particle analysis of the NiCrSiB feedstock was conducted and the maximum allowable addition of Al _2 O _3 nanoparticles have been identified using the ‘mass mixture ratio’ model considering both the particle size and density. Consequently, two cases are considered and their performance analysed: a maximum allowable case of 1.4 wt%, followed by a 0.17 wt% addition of nano-Al _2 O _3 with NiCrSiB. Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and x-ray Diffraction (XRD) analysis were employed to inform the microstructure, material composition and phase spectrum of the resulting coatings. Subsequently, the nanostructured coating was exposed to both a pull-off adhesion strength test and hot air jet (450 °C) hard particle erosion to characterise its performance. It was found that the microhardness of the HVOF NiCrSiB coating improved from 576 HV _0.3 to 748 HV _0.3 with the addition of 1.4 wt% nano-Al _2 O _3 . Furthermore, the nanostructured coating also exhibited high erosion resistance at a 90° erodent impact angle. The increase in erosion wear resistance was due to the increase in the hardness as a result of the nano-Al _2 O _3 addition.

Direct Ink writing, one of the types of 3D-printing technologies is a novel method for fabricating electronic circuits. This method of printing electronic circuits is a one-step process and overcomes the limitations of fused deposition modelling where the fabrication of circuits is possible if the material is in filament form and the usage of material is limited to thermoplastic. This work proposes the fabrication of strain gage circuit using functionalised Multi-walled carbon nanotubes (MWCNTs) and Polyvinyl alcohol (PVA) conductive ink by direct writing method. In this work, Fourier-transform infrared analysis is performed to study the existence of functional groups on acid treated MWCNT. According to micro-structural studies, it is observed that MWCNTs were homogeneously distributed. Rheology tests carried out using cone and plate method concluded that the prepared inks exhibited shear thinning behaviour, which is a very important parameter to state the ink made is appropriate for printing electronic circuits. The effects of functionalised MWCNT (a-MWCNT) concentration on the printed strain gage circuitry are analysed using two-point probe method and electrical properties like resistance, resistivity and electrical conductivity are studied. The electrical conductivity of the 3D-printed strain gage circuit is found to be 2.53 × 102 S/m for PVA/a-MWCNT(0.5) ink. Varying the concentration of a-MWCNT, electrical conductivity is observed to be increased to 4.08 × 102 S/m for PVA/a-MWCNT(1.0) and 7.87 × 102 S/m for PVA/a-MWCNT(1.5). Flexibility of PVA and conductivity of a–MWCNT contributed to superior performance of the printed circuit. [ABSTRACT FROM AUTHOR]