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Physics of Electrostatic Projection Revealed by High-Speed Video Imaging
摘要： Processes based on electrostatic projection are used extensively in industry, e.g., for mineral separations, electrophotography, or manufacturing of coated abrasives, such as sandpaper. Despite decades of engineering practice, there are still unanswered questions. In this paper, we present a comprehensive experimental study of the projection process of more than 1500 individual spherical alumina particles with a nominal size of 500 μm, captured by high-speed video imaging and digital image analysis. Based on flight trajectories of approximately 1100 projected particles, we determine the acquired charge and dynamics as a function of the relative humidity (RH) and the electric field intensity and compare the results with classical theories. For RH levels of 50% and above, more than 85% of distributed particles are projected, even when the electric field intensity is at its minimum level. This suggests that, beyond a critical value of the electric field intensity, the RH plays a more critical role in the projection process. We also observe that the charging time is reduced dramatically for RH levels of 50% and above, possibly due to the buildup of thin water films around the distributed particles, which can facilitate charge transfer. In contrast, projected particles at the 30% RH level exhibit excessive amounts of electric charge, between 2 and 4 times than that of the saturation value, which might be attributed to triboelectric charging effects. Finally, the physics of electrostatic projection is compared and contrasted with those of induced-charge electrokinetic phenomena, which share similar field-square scaling, as the applied electric field acts on its own induced charge to cause particle motion.
关键词： electric field intensity,high-speed video imaging,alumina particles,charge transfer,electrostatic projection,triboelectric charging,relative humidity
更新于2025-09-19 17:13:59
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - A Compact Butler Matrix Design Based on Metallic Nanowire Filled Membrane Technology and Tunable Phase Shifter at 160 GHz
摘要： This paper presents the design of a planar miniaturized 4x4 Butler matrix, with implementation of 4 tunable 135° delay line phase shifters for a 160 GHz application. The Butler matrix and phase shifters are both realized with a metallic nanowire filled slow-wave alumina membrane microstrip line to miniaturize the size. Tunability is achieved by filling in a microwave liquid crystal. Comparing with commonly used corporate feed network, the simulation results show such a Butler matrix with 135°-phase shifters has less insertion loss and reduced size.
关键词： 160 GHz,slow-wave alumina membrane,Butler matrix,metallic nanowire,phase shifters,liquid crystal
更新于2025-09-16 10:30:52
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A SIMPLIFIED IMPLEMENTATION OF SUBSTRATE INTEGRATED NON-RADIATIVE DIELECTRIC WAVEGUIDE AT MILLIMETER-WAVE FREQUENCIES
摘要： The substrate integrated non-radiative dielectric (SINRD) guide presents a rather complicated process of design and implementation because of multiple interrelated design parameters involved in the de?nition of structures. In this work, the size of SINRD guide is halved by using a perfect electrical conductor (PEC) image plane. Consequently, the number of modes in the resulting image SINRD (iSINRD) guide is equally reduced since all even modes including the LSE 10 mode are suppressed. Furthermore, a simple yet accurate design method is proposed that takes into account many parameters involved in the design of an SINRD guide, especially dimensions of perforation and dispersion e?ects.Three iSINRD prototypes are fabricated to test the proposed method over the W-band frequency range. Two of the prototypes are based on Alumina substrate with di?erent perforation pro?les, and both exhibit insertion loss around 1 dB while the return loss is around 16 dB. The third is based on RO6002 substrate and exhibits an insertion loss of around 3 dB and a return loss of around 14 dB. To test the leakage loss caused by periodic gaps in the PEC wall, two iSINRD lines with one and three gaps were fabricated. The insertion and return losses of the former case are respectively 1.2 dB and 17 dB compared to 2.5 dB and 18 dB of the latter case.
关键词： return loss,insertion loss,W-band,image SINRD (iSINRD) guide,Alumina substrate,millimeter-wave frequencies,RO6002 substrate,Substrate Integrated Non-Radiative Dielectric (SINRD) guide
更新于2025-09-16 10:30:52
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Study on laser-stricken damage to alumina ceramic layer of different surface roughness
摘要： This study examines the laser-stricken damage to different alumina ceramic surfaces of different roughness through multi-physical field coupling simulations and laser-striking experiments. The surfaces of different morphologies can be described by waves of different frequencies and amplitudes, and the waves which are discretized can be described by rectangular microstructures of different heights. In this paper, we found that the reaction of roughness surfaces to gauss lasers stricken on them could be simulated by the reaction of rectangular microstructures of different heights to laser strike. The simulation was carried out through the multi-physical field coupling method. The distribution of temperature and stress on rectangular microstructure were examined after being treated by high energy laser. It was found that overhigh temperature and stress were the main causes of laser-stricken damage, but there existed a critical rectangular column height value. The microstructure became increasingly prone to damage and fall-off with the increase of the rectangular column’s height, but it became decreasingly prone to damage after the rectangular column reached the critical value. In the experiments, seven roughness zones of alumina ceramic layer were chosen as sample surfaces for laser-striking experiment. The results showed that there was a critical roughness value at a fixed laser energy density. As a result, the amount of particles falling off the surfaces caused by laser strike was rising when the roughness was increasing. However, the amount of particles falling off the surfaces was decreasing after roughness reached the critical value. The critical rectangular column height value in the simulation corresponded to the critical roughness value in the experiment. Therefore, an appropriate selection of roughness is an important factor for obtaining high laser-stricken damage threshold.
关键词： simulation and experiment,surface roughness,rectangular microstructure,laser-stricken damage,alumina ceramic layer
更新于2025-09-16 10:30:52
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[IEEE 2019 8th International Conference on Modeling Simulation and Applied Optimization (ICMSAO) - Manama, Bahrain (2019.4.15-2019.4.17)] 2019 8th International Conference on Modeling Simulation and Applied Optimization (ICMSAO) - Numerical Study of Laser Hole Cutting in Zirconia Toughened Alumina Plate
摘要： The main cause of cracks formation in laser cut holes is due to thermal stress. These formed cracks alter the mechanical properties of work material and degrade the cut hole quality. Therefore thermal analysis of laser cut holes become essential. Laser cutting of structural ceramic possess extra constraints due to their brittle nature. In present paper, laser cutting of hole in Zirconia Toughened Alumina ceramic plate is simulated to investigate the temperature and stress profile. The numerically predicted results show that maximum temperature of 3300 °C is developed near the cut hole region whereas maximum stress of 5 GPa is observed.
关键词： Laser cutting,Zirconia Toughened Alumina,Temperature,Stress
更新于2025-09-12 10:27:22
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Doping of Alumina Substrates for Laser Induced Selective Metallization
摘要： Laser induced selective activation and metallization of ceramics is a novel additive metal plating process enabling the application fine metallic paths or metallic surfaces on complex three-dimensionally shaped ceramic substrates. Metal deposition by electroless plating occurs selectively where the substrate has been locally activated by a preceding selective laser activation. The main influences on the process are the ceramic substrate material, its microstructural and optical properties as well as the laser type, laser process parameters and metallization parameters. Recent positive results with activation by a green picosecond laser were obtained only with oxygen vacancy containing alumina substrates sintered in hydrogen atmosphere. In order to be able to apply inexpensive conventional state-of-the-art sintering in air it was tried to modify the composition by doping with different oxides. 2 mass-% of fine particles of neodymium-, manganese-, samarium-, chromium-, nickel- iron-, ceria- and antimony doped tin-oxide were introduced into an alumina matrix by mixing and milling. Slip cast samples were sintered at 1500°C in air and machined. Laser activation was performed on polished sample surfaces using a Nd:YVO4 laser with a wavelength of 532 nm and a pulse length of 10 ps. Electroless plating was performed with commercially available copper electrolytes. Microstructural properties, laser-matter interaction and metallization effectivity were investigated. Doping of alumina substrates with antimony doped tin-oxide, chromium-, iron- and nickel-oxide results in very good metallization of laser activated areas. Dopants enable plating larger areas and writing fine circuit paths to integrate microelectronic devices. Other additives were ineffective. The activation mechanisms triggered by the dopants is not fully understood yet. Separation and identification of single mechanisms of the dopants is required. The influence of dopants and laser activation on the mechanical properties is to be studied.
关键词： laser activation,alumina,3D interconnect device,slip casting,Ceramics,electroless plating
更新于2025-09-12 10:27:22
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Reflection Spectra of Composite Photonic Crystals Based on Anodic Alumina Filled with Ferroelectric Sodium Nitrite
摘要： Re?ection spectra of a composite one-dimensional photonic crystal (PC) based on porous anodic alumina ?lled with ferroelectric sodium nitrite have been recorded in the wavelength range of 400 to 1200 nm. Signi?cant spectral shifts of the ?rst and second stopbands are revealed for the composite PC. The stopband spectral half-width is found to decrease by a factor of four to ?ve. The possibility of applying composite alumina-based photonic crystals as selective narrowband mirrors is discussed.
关键词： reflection spectra,ferroelectric sodium nitrite,photonic crystals,anodic alumina,stopbands
更新于2025-09-12 10:27:22
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Femtosecond laser microstructuring of alumina toughened zirconia for surface functionalization of dental implants
摘要： The continuous need for high-performance implants that can withstand mechanical loads while promoting implant integration into bone has focused recent research on the surface modification of hard ceramics. Their properties of biocompatibility, high mechanical and fatigue resistance and aesthetic color have contributed to its successful applications in dentistry. Alumina toughened Zirconia (ATZ) has been gaining attention as a material for dental implants applications due to its advanced mechanical properties and minimal degradation at body temperature. Still, in order to improve tissue response to this bioinert material, additional modifications are desirable. Improving the surface functionality of this ceramic could lead to enhanced implant-tissue interaction and subsequently, a successful implant integration. In this work, microtopographies were developed on the surface of Alumina toughened Zirconia using an ultrafast laser methodology, aiming at improving the cellular response to this ceramic. Microscale grooves and grid-like geometries were produced on ATZ ceramics by femtosecond laser ablation, with a pulse width of 150 fs, wavelength of 800 nm and repetition rate of 1 kHz. The variation of surface topography, roughness, chemistry and wettability with different laser processing parameters was examined. Cell-surface interactions were evaluated for 7 days on both microstructured surfaces and a non-treated control with pre-osteoblasts, MC3T3-E1 cells. Both surface topographies showed to improve cell response, with increased metabolic activity when compared to the untreated control and modulating cell morphology up to 7 days. The obtained results suggest that femtosecond laser texturing may be a suitable non-contact methodology for creating tunable micro-scale surface topography on ATZ ceramics to enhance the biological response.
关键词： Femtosecond laser microtexturing,Dental implants,Hard ceramics,Alumina toughened zirconia,Surface topography,Biological response
更新于2025-09-11 14:15:04
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Effects of Laser Fluence and Pulse Overlap on Machining of Microchannels in Alumina Ceramics Using an Nd:YAG Laser
摘要： The quality of micro-features in various technologies is mostly affected by the choice of the micro-fabrication technique, which in turn results in several limitations with regard to materials, productivity, and cost. Laser beam micro-machining has a distinct edge over other non-traditional methods in terms of material choices, precision, shape complexity, and surface integrity. This study investigates the effect of laser fluence and pulse overlap while developing microchannels in alumina ceramic using an neodymium-doped yttrium aluminum garnet (Nd:YAG) laser. Microchannels 200 μm wide with different depths were machined using different laser peak fluence and pulse overlap (percentage of overlap between successive laser pulses) values. It was found that high pulse overlaps and fluences should be avoided as they give rise to V-shaped microchannels i.e., 100% bottom width errors. The optimal peak fluence range was found to be around 125–130 J/cm2 corresponding to 3–5 μm depth per scan. In addition, channels fabricated with moderate pulse overlap were found to be of good quality compared to low pulse overlaps.
关键词： microchannels,laser,fluence,alumina,micromachining
更新于2025-09-11 14:15:04
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Low-Damage Reactive Ion Etching of Nanoplasmonic Waveguides with Ultrathin Noble Metal Films
摘要： Nanoplasmonic waveguides utilizing surface plasmon polaritons (SPPs) propagation have been investigated for more than 15 years and are now well understood. Many researchers make their efforts to find the best ways of using light and overcoming the speed limit of integrated circuits by means of SPPs. Here, we introduce the simulation results and fabrication technology of dielectric-metal-dielectric long-range nanoplasmonic waveguides, which consists of a multilayer stack based on ultrathin noble metals in between alumina thin films. Various waveguide topologies are simulated to optimize all the geometric and multilayer stack parameters. We demonstrate the calculated propagation length of Lprop = 0.27 mm at the 785 nm wavelength for the Al2O3/Ag/Al2O3 waveguides. In addition, we numerically show the possibility to eliminate signal cross-talks (less than 0.01%) between two crossed waveguides. One of the key technology issues of such waveguides’ nanofabrication is a dry, low-damage-etching of a multilayer stack with extremely sensitive ultrathin metals. In this paper, we propose the fabrication process flow, which provides both dry etching of Al2O3/Au(Ag)/Al2O3 waveguides nanostructures with high aspect ratios and non-damage ultrathin metal films patterning. We believe that the proposed design and fabrication process flow provides new opportunities in next-generation photonic interconnects, plasmonic nanocircuitry, quantum optics and biosensors.
关键词： plasmonic nanocircuitry,multilayer waveguide,nanoplasmonic waveguide,low-damage alumina etch,noble metals etching,multilayer stack etching
更新于2025-09-11 14:15:04