Key Engineering Materials Vol. 1053

Abstract: The importance of the solar energy arose from the low cost and clean source. Collection and utilization of solar energy are two of the most important steps in dealing with this valuable energy source. It is promoted extensively and this need for energy also prevents the environment from further destruction. The work is divided into two parts; preparing a suitable cooling system for the substrate of PVT and designing the CPC. The reason for designing a new CPC is that the current CPCs in use are still not performing to a satisfactory level. The work towards a better design has progressed satisfactorily and is being tested. Besides that, it was found that the method of cooling the photovoltaic (PV) cell could be seen as an important role in the design of a better collector. The work performed in this article has outlined several factors to test the superiority and the success of the objectives of this work. These factors are the electrical and thermal efficiency of the PV cell when it is cooled with and without CPC. Regarding the cooling process, a new method of cooling PVT-CPC was employed by using water impingement through designing a nozzle system which was tested at a different spacing of 10 mm from the PV-plate. The experimental results have pointed out an improvement in the thermal efficiency from 41.51% to the highest value of 67.53% showing very promising improvement by 38.53%. The experimental setting and the subsequent parameters for the highest thermal efficiency value occurred with a PVT-CPC-40-mm spacing at an irradiance of 400 W/m² and water mass flow of 0.334 kg/s. The highest value was obtained at 16.40% showing an improvement of 38.48%. This is in comparison to 32.64% obtained by energy balanced-thermodynamics approach.

Abstract: For solar collectors to be more durable and effective in renewable energy applications, surface enhancement is essential. The limited hardness and wear resistance of conventional aluminum alloys, including Al-6063, impair their long-term performance. By employing the pulsed laser deposition (PLD) technology to produce AlO₃ nano-coatings, this study seeks to overcome these constraints. The goal of this research is to use nanostructuring to improve the mechanical characteristics, resistance to corrosion, and optical performance of solar collectors. The surface of the solar collector alloy was coated with a nano- material (Al2O3) that had a particle size of 30 ± 5 nm. An Al2O3 nano material coating's micro-structure, phase composition, and effects were examined. PLD was applied to reduce erosion and corrosion and improve the mechanical performance of the aluminum alloy (AL-6063) used on the solar collector's surface. Using PLD, a 10 μm layer of aluminum dioxide was applied to the aluminum alloy's surface to ensure high hardness and a long fatigue life. Hardness testing on the samples showed an improvement in the alloy mechanical characteristics. Before and after deposition, an energy-dispersive X-ray spectroscopy test was carried out. The mechanical characteristics improved after an Al2O3 Nano layer was deposited. The samples' hardness increased from 626 HLD to 672 HLD, and erosion and corrosion decreased. Because of the Nano layer applied via PLD, the atomic percentage of oxygen deposited on the surface of the solar collectors changed between 8.3% and 9.4%, the roughness (x) decreased from 738 µm to 309 µm and the reflection ratio decreases. These outcomes confirm that PLD-deposited Al₂O₃ coatings improve the durability and efficiency of solar collectors, offering a promising solution for future renewable energy systems.

Abstract: Excessive heat generation during bone drilling is a leading cause of thermal osteonecrosis—a serious risk in medical departments. Despite extensive drill design research, the influence of margin geometry remains underexplored. This study presents finite element modeling and statistical optimization to evaluate and optimize drill margin geometry—specifically margin width (Mw) and height (Mh)—to reduce bone temperature rise during surgery. A thermo-mechanical finite element model was developed in DEFORM-3D to simulate cortical bone drilling using drill bits with varied margin dimensions. The models were validated experimentally using bovine cortical bone, with an average temperature prediction errors of 2.4–8.0%. The maximum bone temperature (T_max) was selected as the objective function. A central composite design (CCD) was applied to generate experimental runs, followed by response surface methodology (RSM) and desirability-based optimization. The second-order effect of Mw contributed 47.2% to T_max. The optimal Mh (0.05 mm) and Mw (0.22 mm)—with a desirability value of 0.985—could reduce T_max below the osteonecrosis level with only a 44.8 °C temperature rise. This study demonstrates a novel computational approach for optimizing surgical drill margins—a previously underutilized parameter. The findings may support future developments in drill bit customization and robotic surgery systems to minimize thermal injury to bone cells.

Abstract: Manufacturing defects in drill bits, especially those with helical oil holes, pose significant challenges in quality control because traditional inspection methods, like optical microscopy and fluid-based testing, often fail to detect internal defects as they are typically focused on surface characteristics. To improve defect detection in drill bit manufacturing, a vibration-based non-destructive testing (NDT) method is proposed. This approach combines finite element analysis (FEA) for simulations with experimental vibration analysis to identify frequency changes that indicate the presence of defects. The methodology now systematically includes the fundamental Bending-1 mode and employs statistical analysis (t-tests) to validate the statistical significance of detected frequency shifts and numerically express uncertainty. The results unequivocally confirm that vibration analysis can effectively distinguish defective drill bits by identifying characteristic frequency changes.

Abstract: This study investigates the micro-drilling parameters to minimize perforation error in biodegradable and composite materials: Oil Palm Fiberboard (OPF), Polylactic Acid (PLA), and Printed Circuit Board (PCB). Two biodegradable materials (OPF and PLA) were compared to a standard industrial PCB for benchmarking. Micro perforated hole is important in sound absorber to provide better absorption performance. A Taguchi L27 design of experiments was used to assess the effects of support presence, post-penetration spin time, and spindle speed on dimensional accuracy. For OPF, the lowest average error (0.031 mm) was achieved using no support, a 1 second spin time, and a spindle speed of 6,000 RPM, minimizing tool deflection in the fibrous structure. PLA showed the best result (0.344 mm error) with no support, no spin time, and a moderate spindle speed of 8000 RPM, reducing thermal distortion. For PCB, a layered and brittle material, a sandwiched support setup, no spin time, and a high spindle speed of 10,000 RPM achieved the lowest error (0.040 mm), reducing delamination and chipping. Although the exact optimal settings were not found in the experimental runs, very similar combinations yielded the best accuracy in each material. These findings validate the inferred trends and emphasize the importance of spin time and spindle speed over support. The results provide actionable guidelines for high-precision fabrication of eco-friendly acoustic absorbers, contributing to environmentally sustainable material processing and enhanced indoor acoustic control.

Abstract: This study aimed to demonstrate the susceptibility of 5% Ni steel to stress corrosion cracking, SCC, in anhydrous liquid ammonia. SCC tests using four-point bend specimens cut from welds in SPV315, HT780 and 5% Ni steel were carried out in anhydrous liquid ammonia with 5wt% NH₄CO₂NH₂ and 0.1MPa O₂ at +2.0V, which is an accelerated SCC test condition. No SCC was observed in SPV315, whose strength is within the allowable strength of IGC code 17.12, but SCC was observed in the HAZ of HT780, whose strength is higher than the upper limit of IGC code 17.12. Furthermore, SCC was recognized in the HAZ and base metal of 5% Ni steel, whose nickel content is higher than the upper limit of IGC code 17.12, and this suggests that 5% Ni steel is susceptible to SCC in anhydrous liquid ammonia.

Abstract: The demand for refractory materials continues to increase, particularly in the copper smelting industry. Flash Smelting Funaces (FSF) require refractories that can withstand high temperatures and aggressive chemical interactions. This study evaluates the performance of Magnesia – Chromite as refractory materials in FSF through tests such as Thermal Expansion, Porosity, Cold Crushing Strength, Bulk Density and Thermal Conductivity. Initial test results show that the brick has high resistance to thermal shock, with a thermal expansion value of -0.3% cold crushing strength of 63.4 Mpa, bulk density of 3.22 g/cm3, porosity of 12.76% and thermal conductivity ranging from 2.8 to 2.9 W/m.K.

Abstract: For the single-particle erosion of an iron target under low impact angles, normal impact mechanism and tangential cutting mechanism operate through a synergistic interaction yet also compete with each other, each demonstrating distinct emphases. Their relative roles under varying low-incidence angles are worth studying. In this paper, physical experiments of single-particle erosion are conducted on an iron target by impingement of an Al₂O₃ particle at an impact velocity of 120 m/s and impact angles of 30, 20 and 10 degrees. Results show that tangential cutting dominates the penetration stage for three degree cases. However, normal impact also plays a relatively important role during the penetration stage at 30º. Normal impact dominates the critical stage between penetration and rebound for all three low incident angles, but its influence is weaker at 20º and 10º compared to 30º. Normal impact dominates the rebound stage at 30º, while tangential cutting dominates the rebound stage at both 20º and 10º. Additionally, the influence of normal impact is more pronounced at 20º than at 10º during the rebound stage.

Abstract: Phase change materials (PCMs) are increasingly regarded as promising candidates for thermal energy storage (TES) in buildings. However, their low intrinsic thermal conductivity significantly limits their effectiveness. In this study, a novel thermal energy storage aggregate (TSA) was developed by integrating butyl stearate (BS) as a cost-effective organic PCM with high-conductivity graphene nanoplatelets (GN) embedded into expanded clay (EC) aggregates. The composite demonstrated improved thermal conductivity, with 2% GN by weight of PCM yielding the best results in terms of heat transfer and phase change performance. The TSA coated in a dual-layer system exhibited long-term stability and no leakage during thermal cycling. When incorporated into a concrete matrix, the thermal energy storage concrete (TSC) containing EC aggregates with 3.5 wt% 2GN-PCM effectively reduced peak ambient temperature fluctuations by up to 5.2 °C compared to concrete with EC at ≤5% and 50 % humidity. Thermal conductivity increased by 244% compared to normal concrete. Moreover, ultrasonic wave speed rose by ~20%, confirming improved homogeneity. These findings demonstrated that the proposed TSA is a robust and efficient solution for energy storage concrete that improves indoor comfort and energy savings in next-generation buildings.