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Reconfigurable H‐plane waveguide phase shifters prototyping with additive manufacturing at K‐band
摘要： This work presents the design and manufacturing of a K-band reconfigurable phase shifter completely implemented in waveguide technology for reduced insertion loss, good matching, and large phase shifting range. The device is based on the combination of a short slot coupler and two tunable reactive loads implemented as a section of short-circuited waveguide where an adjustable metallic post is inserted. Three prototypes of this design have been manufactured using different techniques (conventional computer numerical control machining, a low-cost fused filament fabrication technique and direct metal laser sintering) in order to assess its performance for different applications. The prototypes have been characterized experimentally and the achieved results are evaluated and compared. The proposed phase shifter, since it is fully developed in waveguide technology, eliminates the need of adding transitions to planar structures in order to integrate lumped components like pin diodes or varactors. Therefore, this device has a great potential in high-power beam steering phased arrays.
关键词： reconfigurable,selective laser sintering,additive manufacturing,waveguide,fused filament fabrication,phase shifter
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 58th Conference on Decision and Control (CDC) - Nice, France (2019.12.11-2019.12.13)] 2019 IEEE 58th Conference on Decision and Control (CDC) - Design and implementation of a backstepping controller for regulating temperature in 3D printers based on selective laser sintering
摘要： In this paper we investigate the preheating temperature control problem in 3D printers based on the selective laser sintering (SLS) technology. We formulate the process as a temporal sequence of diffusion partial differential equations (PDEs), where each of these PDEs represent the temperature distribution of the layers and the control variable appears at one of the boundary conditions. We propose a full-state feedback control law, an state observer and the associated output feedback control law for the boundary input. The associated output feedback controller ensures the exponential stability of the estimation error in the L2 norm. The theoretical results were tested through numerical simulations and experiments. These results are promising as a method for industrial implementation of the backstepping controller.
关键词： 3D printers,backstepping control,selective laser sintering,temperature control,partial differential equations
更新于2025-09-19 17:13:59
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Direct fabrication mechanism of pre-sintered Si3N4 ceramic with ultra-high porosity by laser additive manufacturing
摘要： Complex structural Si3N4 ceramics with ultra-high porosity were innovatively formed by selective laser sintering (SLS) technology without any binder. Due to rapid cooling rate, the high temperature phase constituent and microstructure of the SLSed Si3N4 poly hollow microspheres (PHMS) were preserved, thus revealing the bonding mechanism of Si3N4 under the nonequilibrium heat source. Si3N4 PHMS are bonded by microvilli composed of bamboo-structure SiO2 nano?ber clusters, stacked SiO2 nanospheres and smooth α-Si3.72N4 nanowires. Finally, the pre-sintered Si3N4 ceramics with a porosity of 80% are directly fabricated in the atmosphere by SLS, which have the enough strength to satisfy the post-treatment requirements.
关键词： Bonding mechanism,Selective laser sintering,Additive manufacturing,Nanostructure,Silicon nitride
更新于2025-09-16 10:30:52
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Fabrication of Carbon-decorated Al<sub>2</sub>O<sub>3</sub> Composite Powders using Cellulose Nanofiber for Selective Laser Sintering
摘要： In this study, systematic investigation using cellulose nanofiber (CellNF) as a carbon source for selective laser sintering (SLS) of Al2O3 was conducted. A composite powder that consisted of CellNF and Al2O3 was fabricated using electrostatic adsorption (EA) method in aqueous suspension. Heat-treatment temperature of 500 and 800°C was compared for the conversion of CellNF to carbon residue (CR) in the Al2O3 composite. After that, the parameters involving the volume fraction of CR and effect of Al2O3 particle size in the CR-Al2O3 composite particle were also investigated in order to obtain an optimized condition of the CR-Al2O3 composite particle for SLS. From the results obtained, 1.5 wt% CR-Al2O3 with alumina size of 0.8 μm that was heat-treated at 800°C exhibited optimum laser sinter ability owing to the good CR distribution over a higher surface area that promoted good laser adsorption for the alumina sintering.
关键词： additive manufacturing,nano-assembly technique,selective laser sintering,cellulose nanofiber,electrostatic adsorption
更新于2025-09-16 10:30:52
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Comparative study of selected indoor concentration from selective laser sintering process using virgin and recycled polyamide nylon (PA12)
摘要： Additive manufacturing (AM) stands out as one of the promising technologies that have huge potential towards manufacturing industry. The study on additive manufacturing impact on the environment and occupational exposure are attracting growing attention recently. However, most of the researcher focus on desktop and fused deposition modelling type and less attention given to the industrial type of AM. Usually, during the selective laser sintering process, recycle powder will be used again to reduce cost and waste. This article compares the PM 2.5, carbon dioxide (CO2) and total volatile organic compound (TVOC) concentration between virgin and recycles powder using polyamide-nylon (PA12) towards indoor concentration. Four phases of sampling involve during air sampling accordingly to the Industry Code of Practice on Indoor Air Quality 2010 by DOSH Malaysia. It was found that PM 2.5 and CO2 are mainly generated during the pre-printing process. The recycle powder tended to appear higher compared to virgin powder in terms of PM 2.5, and CO2. The peak value of PM 2.5 is 1452 μg/m3 and CO2 is 1218 ppm are obtained during the pre-printing process during 8 hours of sampling. TVOC concentration from recycling powder is slightly higher during the post- printing phase where confirm the influence of the powder cake and PA12 temperature from the printing process. In summary, this work proves that elective laser sintering (SLS) machine operators are exposed to a significant amount of exposure during the SLS printing process. Mitigation strategies and personal protective equipment are suggested to reduce occupational exposure.
关键词： selective laser sintering,occupational exposure,indoor air quality,polyamide-nylon,Additive manufacturing
更新于2025-09-16 10:30:52
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3D printing of mixed matrix films based on metal-organic frameworks and thermoplastic polyamide 12 by selective laser sintering for water applications
摘要： The fabrication of metal-organic framework (MOF)-based macro-materials is considered as a promising strategy towards the practical applications of powdered MOF crystals. In this study, selective laser sintering (SLS), an advanced three-dimensional (3D) powder printing technique, has been employed to fabricate MOF-polymer mixed matrix films (MMFs) using thermoplastic polyamide 12 (PA12) powder as the matrix material and five types of MOFs including ZIF-67, NH2-MIL-101(Al), MOF-801, HKUST-1 and ZIF-8 crystals as the fillers. A three-layer HKUST-1-PA12 complex with a grid pattern is fabricated to demonstrate the printability of 3D MOF-polymer structure. Single-layer MMFs with grid patterns are printed using the five types of MOF fillers with different mass loadings to study their free-standing characteristic, thickness, specific surface area, hydrophilia, water permeate flux and mechanical stability. The methylene blue (MB) adsorption tests are conducted using the NH2-MIL-101(Al)-PA12 MMFs with different grid patterns to exemplify the applications of the MMFs for water purification. It is confirmed that the MOF components retain their high maximum adsorption capacity and the printed MMFs can be conveniently regenerated for cyclic utilization. This work provides an insight into the utilization of advanced 3D printing technology to manufacture macro MOF-polymer materials for practical applications.
关键词： water purification,metal-organic framework,3D printing,selective laser sintering,mixed matrix film
更新于2025-09-16 10:30:52
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Application Of Artificial Neural Networks In Modeling Of Manufactured Front Metallization Contact Resistance For Silicon Solar Cells
摘要： This paper presents the application of artificial neural networks for prediction contact resistance of front metallization for silicon solar cells. The influence of the obtained front electrode features on electrical properties of solar cells was estimated. The front electrode of photovoltaic cells was deposited using screen printing (SP) method and next to manufactured by two methods: convectional (1. co-fired in an infrared belt furnace) and unconventional (2. Selective Laser Sintering). Resistance of front electrodes solar cells was investigated using Transmission Line Model (TLM). Artificial neural networks were obtained with the use of Statistica Neural Network by Statsoft. Created artificial neural networks makes possible the easy modelling of contact resistance of manufactured front metallization and allows the better selection of production parameters. The following technological recommendations for the screen printing connected with co-firing and selective laser sintering technology such as optimal paste composition, morphology of the silicon substrate, co-firing temperature and the power and scanning speed of the laser beam to manufacture the front electrode of silicon solar cells were experimentally selected in order to obtain uniformly melted structure well adhered to substrate, of a small front electrode substrate joint resistance value. The prediction possibility of contact resistance of manufactured front metallization is valuable for manufacturers and constructors. It allows preserving the customers’ quality requirements and bringing also measurable financial advantages.
关键词： Co-firing in the furnace,Screen printing,Computational material science,Artificial neural networks,Selective laser sintering,Silicon solar cell
更新于2025-09-16 10:30:52
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Powder Bed Based Laser Additive Manufacturing Process of Stainless Steel: A Review
摘要： This study presents a review on powder bed laser additive manufacturing of stainless steel. The powder bed laser additive manufacturing processes that are presented in this paper are the selective laser sintering and selective laser melting. The powder bed laser additive manufacturing process of stainless steel are reviewed in this paper. The process parameters was found to plat an important role in the evolving properties of the powder bed based laser additive manufacturing process. The paper ends with the perspective of future research directions.
关键词： Materials characterization,laser additive manufacturing,selective laser sintering,Additive manufacturing,selective laser melting
更新于2025-09-12 10:27:22
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A new approach to coat PA12 powders with laser-generated nanoparticles for selective laser sintering
摘要： The modification of selective laser sintering (SLS) powder materials by nanoadditives offers the possibility to adapt the powder properties to the laser sintering process or the resulting part properties. To avoid agglomeration of the nanofiller, a new approach in which surfactant-free laser-generated colloidal nanoparticles are adsorbed onto the polymer surface directly in an aqueous solution is demonstrated. Based on this novel approach, polyamide 12 (PA12) powders are decorated with metal and oxide nanoparticles and processed via SLS. Electron microscopy and confocal laser scanning imaging are utilized to analyze the dispersion of the filler.
关键词： selective laser sintering,laser additive manufacturing,polymer powders,pulsed laser ablation in liquids,nanoparticles
更新于2025-09-12 10:27:22
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Thermal and laser sintering of a highly stable inkjet ink consisting of silver nanoparticles stabilized by a combination of a short chain carboxylic acid and a polymeric dispersant
摘要： A mixture of silver nanoparicles and its organic salt has been used for the development of conductive inks for inkjet printing. Silver nanoparticles stabilized with butanoic acid (C4) with the average size of 11.1±2.4 nm have been synthesized via the reduction of solid silver carboxylate with hydrazine hydrate in benzyl alcohol. An inkjet ink formulation consisting of the silver nanoparticles capped with butanoic acid (up to 50 wt.%) with the addition of polymeric BYK dispersant in a mixture of nontoxic solvents with different boiling temperatures and different polarities has been developed and its physical properties and stability have been studied. Silver layers were spin coated and printed on a polyimide film using the developed ink. Experiments on the thermal annealing of the silver films showed that the curing temperature can be below 200 oC to obtain a layer having the electrical resistivity less than 10 μ?×cm. A study of the laser sintering of the printed and spin coated elements on a polyimide film using a diode laser operating at 453 nm in impulse mode showed that the best mode is a multi-pass sintering, which can be divided into two steps: the evaporation of the solvent and sintering of the silver nanoparticles.
关键词： silver nanoparticles,selective laser sintering,conductive ink,chemical synthesis,printed electronics
更新于2025-09-12 10:27:22