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Efficiency improvement of power LED modules using a hybrid aluminum nitride substrate
摘要： This study combined experimental and theoretical analysis to investigate the hybrid aluminum nitride (AlN) substrate that can effectively improve efficiency and heat dissipation of multi-chip LED modules. The experimental results showed that hybrid AlN substrate can effectively reduce the thermal resistance from junction to substrate ΔRjs by 46% compared with metal core printed circuit board (MCPCB) as driving current increased from 0.6 A to 1.6 A. Under the rated current of 1.2 A, the Rjs and chip temperature of the AlN module was approximately 0.73 K/W and 10 °C lower than that in the MCPCB module. Compared to MCPCB, the hybrid AlN substrate also had 25% higher luminous flux at 1.2 A. Simulating results provided insight understanding of temperature distribution inside the LED modules and showed good consistency with experiments. Additionally, the decreasing rate of substrate temperature (Ts) outside the chips in AlN LED module is higher than in MCPCB LED module. This study demonstrated that the hybrid AlN substrate is a reliable and a cost effective design that can effectively improve both efficiency and heat dissipation of high power LED modules.
关键词： Thermal,Efficiency,Light emitting diode,Aluminum nitride
更新于2025-09-16 10:30:52
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Investigation on Industrial Screen-Printed Aluminum Point Contact and Its Application in n-PERT Rear Junction Solar Cells
摘要： As compared with the traditional back surface field (BSF) solar cells, the n-type passivated emitter rear and totally diffused rear-junction (n-PERT-RJ) solar cells have much lower carrier recombination losses on their rear sides. In order to obtain more benefits (higher open-circuit voltages) from the currently passivated rear sides, the implementation of the point contact concept is an intuitive solution. In this article, we present industrial screen-printed point contacts that are metallized with aluminum (Al) pastes containing silicon additives (Si-add). To understand the impacts of the Si-add on the performance our n-PERT-RJ solar cells, the detailed loss analysis on the open-circuit voltage (VOC), short-circuit current density (JSC), and fill factor are performed separately. The effect of Si-add and pitch of laser contact openings (LCO) on the point contact characteristics are also investigated. In the last part, we introduce an innovative “point-line” contact concept on the rear side, which is composed of dot-shaped LCO and Al metal finger design, resulting in an n-PERT-RJ solar cell to reach VOC of 692 mV and peak efficiency of 22%. The 60% bifaciality of the device opens the way for an additional power output on module level, which further reduces the levelized cost of electricity. These features make the rear-side point contact design more flexible to be applied in industrial mass production.
关键词： laser contact opening (LCO),levelized cost of electricity,Aluminum (Al) paste,n-type passivated emitter rear and totally diffused (n-PERT),bifaciality,silicon solar cell,industrial,point contacts,screen printed,n-type,rear junction
更新于2025-09-16 10:30:52
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Effects of laser peening on the fatigue strength and defect tolerance of aluminum alloy
摘要： The effects of laser peening (LP) on the bending fatigue strength of the 7075-T651 aluminum alloy were investigated. Accordingly, the defect tolerance of the aluminum alloy subjected to LP is discussed on the basis of fracture mechanics. The results indicate that a deeper compressive residual stress was induced by LP compared with the case of shot peening (SP). The fatigue strengths increased when both peening types were used. Semicircular slits with depths less than 0.4 and 0.1 mm were rendered harmless on the basis of the applications of LP and SP, respectively. The apparent threshold stress intensity factor range ΔKth,ap increased by approximately five and two times owing to LP and SP, respectively. The increase of the ΔKth,ap was caused by the compressive residual stress induced by the peening. The Kitagawa-Takahashi diagram of the laser-peened specimens shows that the defect tolerance of the aluminum alloy was improved by LP.
关键词： fatigue strength,laser peening,residual stress,shot peening,defect tolerance,aluminum alloy
更新于2025-09-16 10:30:52
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Fabrication and remote laser ignition of Al/CuO energetic nanocomposites incorporated with functional dyes for enhanced light absorption
摘要： In this study, we investigated the effects of dyes on the laser ignition characteristics of Al nanoparticles (NPs) and CuO NPs-based energetic nanocomposites. Various functional dyes (e.g., N-719, rose bengal (RB), methylene blue (MB)) were employed as a light absorbing medium for Al/CuO energetic nanocomposites. According to UV–vis spectrometer analysis results, N-719, RB, and MB dyes had relatively strong light absorption in the blue, green, and red wavelength ranges, respectively. The results of red, green, and blue (RGB) laser ignition tests for various dye-coated Al/CuO composites demonstrated that the laser ignition threshold power density for the composites gradually decreased with increasing dye concentration. To test the possibility of selective optical ignition, the various dye-coated Al/CuO composites were irradiated using RGB laser beams operating with a fixed and relatively low power density. The results showed that the N-719-, RB-, and MB-coated Al/CuO composites were only successfully ignited under the condition of blue, green, and red laser beam irradiation, respectively. This suggests that energetic nanocomposites coated with special dyes could be employed as potential igniters and heat energy sources, the reactions of which are initiated by selective and remote light-energy irradiation, in various thermal engineering applications.
关键词： Coating,Aluminum composites,Laser-induced reaction,Thermite reaction,CuO nanoparticles
更新于2025-09-16 10:30:52
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Immediate effect of pulsed high-intensity neodymium-doped yttrium aluminum garnet (Nd: YAG) laser on staphylococcus aureus and pseudomonas aeruginosa growth: an experimental study
摘要： The aim of this study was to evaluate the effect of pulsed high intensity neodymium-doped yttrium aluminum garnet (Nd: YAG) laser on staphylococcus aureus (S. aureus) and pseudomonas aeruginosa (P. aeruginosa) bacterial growth, which cause many health problems and establish which doses are effective in bacterial inhibition. Five samples of S. aureus and five samples of P. aeruginosa were prepared in the microbiology lab, one used as control sample and the other 4 samples acted as experimental samples. The experimental samples received pulsed high intensity Nd: YAG laser with a total dose of 500, 600, 700 and 800 joules. The primary measures are colony count and the percentage decrease in colony count, the colony count was assessed at baseline and after 24 h of laser application. There was significant decrease in colony count and the percentage decrease in colony count after pulsed high intensity Nd: YAG laser application in all experimental samples of S. aureus and P. aeruginosa after 24 h of application for all doses (500, 600, 700 and 800 j) as compared with the control sample, with the most effect in higher doses of pulsed high intensity Nd: YAG laser than lower doses in both types of bacteria. pulsed high intensity Nd: YAG laser was found to be an effective modality for inhibition of S. aureus and P. aeruginosa growth after a single application.
关键词： Bacterial growth,Pulsed high intensity neodymium-doped yttrium aluminum garnet (Nd: YAG) laser,Colony count
更新于2025-09-16 10:30:52
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Manufacture of the Transceiver Housing for an Active Phased Array Antenna with Built-In Cooling Channels by Selective Laser Melting
摘要： A cooled transceiver housing of an active phased array antenna is produced by 3D printing from aluminum, on the basis of selective laser melting (SLM). The housing walls contain cooling channels, whose geometry ensures effective heat transfer from the active electronic components of the transceiver and also permits the manufacture of high-quality samples on existing 3D printing systems and facilitates cleaning of the channels after printing. The housing is made of AlSi10Mg aluminum, with an acceptable content of closed pores (no more than 1%). Its physicomechanical properties correspond to those of regular aluminum alloys used in the traditional manufacturing technology for such components. This housing may be used in advanced radar systems. The research permits recommendations for further development of the technology.
关键词： cooling channels,3D printing,transceiver housing,active phased array antenna,AlSi10Mg aluminum
更新于2025-09-16 10:30:52
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Using erbium-doped yttrium aluminum garnet laser irradiation in different energy output levels versus ultrasonic in removal of root canal filling materials in endodontic retreatment
摘要： Objectives: The objective of this study was to evaluate the efficacy of erbium?doped yttrium aluminum garnet (Er:YAG) laser irradiation in different energy outputs versus ultrasonic in gutta-percha removal during the endodontic retreatment. Materials and Methods: A total of 21 extracted human lower premolars were divided into three groups (n = 7). Following the standardized preparation of the root canals with Wave One Rotary system and obturation with gutta-percha: Group I was treated with ultrasonic, Group II by Er:YAG laser with 40 mJ/Pulse, and Group III by Er:YAG laser with 50 mJ/Pulse for the removal of gutta?percha from the canals. Two extra teeth were treated by Er:YAG laser with 135 mJ/Pulse as control group. For all groups, time for gutta-percha removal was recorded. Samples were then splited into two halves and tested by scanning electron microscope and stereomicroscopic evaluation under different magnification power to observe the efficacy of each method used in the removal of gutta-percha. Results: Statistical analysis of Kruskal–Wallis suggested that there are significant difference between the groups in relation to removal time (P < 0.05) and 2 × 2 Mann–Whitney U-test among the groups revealed that there is no significant difference between 40 and 50 mJ laser outputs (P > 0.05), but ultrasonic versus 40 and/or 50 mJ laser outputs were significantly different (P < 0.05). Conclusions: Er:YAG laser beam was not so efficient when compared to ultrasonic to reach the deeper parts of the canals as it was asserted, thermal side effects and burning damages were observed on the root canal dentinal walls. Moreover, the delivery system was not flexible enough to compensate the curvature of the canal system even though we used more straight canals as the sample ones as well as more time-consuming than the ultrasonic and more clinical time, rendering it to be less efficient in the removal of the obturation material during endodontic retreatment procedures.
关键词： gutta-percha removal,erbium-doped yttrium aluminum garnet lasers,Endodontics,retreatment,lasers
更新于2025-09-16 10:30:52
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Selective rear-side ablation of aluminum thin layers with ultrashort-pulsed laser radiation
摘要： In recent years, several applications for laser ablation of thin metal layers from the fused silica substrate side have been studied. The rear-side ablation is a highly effective ablation method for thin layer structuring and reveals a high structuring quality. Therefore, the present work dealt with the selective rear-side ablation of thin aluminum layers (10–50 nm) on fused silica with ultrashort-pulsed laser radiation (λ = 1028 nm, ??H = 0.2–10 ps and w0,86 = 15.2 μm). The influences of pulse duration and layer thickness on the ablation thresholds as well as the incubation coefficients were determined. For layer thicknesses of 30 and 50 nm, a decrease of the ablation threshold with increasing pulse duration was determined. Whereas, the ablation threshold remained constant for layer thicknesses of 10 and 20 nm. Different morphologies were observed depending on the process parameters. The rear-side ablation of aluminum proceeded over the melting phase and no lift-off process had taken place. In addition to experimental investigations, calculations were carried out to determine the theoretical threshold fluences. The theoretical values were compared to experimental data. With the help of these investigations, the quality of the structuring of aluminum layers can be improved.
关键词： ultrashort-pulsed laser radiation,incubation coefficients,aluminum thin layers,laser ablation,rear-side ablation
更新于2025-09-16 10:30:52
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Laser-Induced Ignition and Combustion of Individual Aluminum Particles Below 10 ??m by Microscopic High-Speed Cinematography
摘要： Metal aluminum has been widely used as an ingredient in propellant, gunpowder and thermite, but there is less understanding of the combustion mechanism of aluminum particles from submicron to several microns in diameter. This paper proposes to experimentally investigate the ignition and combustion characteristics of individual aluminum particles below 10 μm. A specific in situ diagnostic experimental apparatus was first designed for directly observing the ignition and combustion behaviors of individual aluminum particles, with a submicrometer spatial resolution and a temporal resolution of tens of microseconds. Direct observation through microscopic high-speed cinematography demonstrated that, when heated by a continuous laser, individual aluminum particles thermally expanded, followed by shell rupture; the molten aluminum core overflowed and evaporated, leading to ignition and combustion. Further results showed that, when the laser power densities were gradually increased (5.88, 7.56 and 8.81 × 105 W/cm2), the durations of thermal expansion, melting and evaporation were shortened. The required time for the aluminum particles to expand to 150% of their initial diameter was shortened (34 s, 0.34 s and 0.0125 s, respectively). This study will be beneficial to further extend the investigation of other individual metal particles and reveal their combustion mechanism by direct observation.
关键词： combustion mechanism,microscopic high-speed cinematography,individual aluminum,laser ignition,submicron particle
更新于2025-09-16 10:30:52
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Investigation on the Surface Properties of 5A12 Aluminum Alloy after Nd: YAG Laser Cleaning
摘要： The surface of the aluminum alloy is prone to oxidation, which in turn a?ects the quality of the weld. The 5A12 aluminum alloy was cleaned by acousto-optic Q-switched diode-pumped Nd:YAG laser and the e?ects of di?erent laser powers and di?erent cleaning speeds on the surface roughness, microstructure, element content, microhardness, residual stress and corrosion resistance of aluminum alloy were investigated. The results show that when the power is 98W and the cleaning speed is 4.1 mm/s, the e?ect of Nd: YAG laser on the removal of oxide ?lm on 5A12 aluminum alloy surface is the most e?ective. After laser cleaning, the smoothness and strength of aluminum alloy surface can be e?ectively improved. However, as a major element in 5A12 aluminum alloy, the content of magnesium decreased. At the same time, the residual tensile stress was generated on the surface of the aluminum alloy after cleaning, and the corrosion resistance slightly decreased.
关键词： surface properties,5A12 aluminum alloy,laser cleaning
更新于2025-09-16 10:30:52