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Most current laser sintering (LS) machines for polymer powders operate with a maximum bed temperature of 200 °C, limiting the use of higher melting polymers like polyethylene terephthalate (PET), which melts at ~250 °C. Using bed temperatures of ≤200 °C leads to severe part-distortion due to curl and warpage during the sintering process. The paper presents a processing method for LS at low bed temperatures, using an in situ printed anchor film to conquer curl and warpage. With the use of the anchor film, PET parts were successfully printed without machine stoppage at bed temperatures as low as 150 °C, which is about 80 °C lower than the bed temperature for a regular process for PET without the anchor film. The anchor film acts as a frictional restraint, effectively preventing the curling and warping during printing that typically result from crystallization-induced shrinkage at low bed temperatures. Whereas previous studies have employed 13 mm thick anchoring sheets bolted to the machine to prevent curl and warpage at low bed temperatures, our method uses a flexible in situ printed ~70 μm thick film to which the built part naturally adheres. The in situ printed film is easily detachable from the part after the build. The standard LS material, polyamide 12 (PA12), was also printed with lowered bed temperaturewhere the benefit would be reduced thermal degradation of the powder and decreased energy consumption during the sintering process. [ABSTRACT FROM AUTHOR]

This study investigates the development of biomimetic sound-absorbing components through laser sintering technology, drawing inspiration from wood's natural porous structure. Using a pine wood powder/phenolic resin composite, various specimens were fabricated with different structural configurations (solid, fully porous, and varying straight-pore ratios) and cavity thicknesses. Sound absorption performance was evaluated using the impedance tube transfer function method. The effect of different composite structures, placement orientations, and cavity thicknesses on sound absorption performance was evaluated. The results demonstrate that solid laser-sintered samples exhibit inherent sound absorption properties due to microscopic pores, with absorption coefficients exceeding 0.234. The biomimetic wood-like structure, featuring multi-scale porosity at both microscopic and mesoscopic levels, shows enhanced broadband sound absorption, particularly in mid-high frequencies, with characteristic double-peak absorption curves. The study reveals that absorption performance can be optimized by adjusting structural parameters and thickness, enabling targeted frequency-specific sound absorption. This research establishes the feasibility of creating multi-frequency sound-absorbing materials using laser-sintered biomimetic wood structures, providing a foundation for future applications and development in acoustic engineering. [ABSTRACT FROM AUTHOR]

In conventional laser-based powder bed fusion of polymers (PBF-LB/P), aging of the powder due to preheating of the powder bed is a significant issue. This paper proposes a method for low-temperature PBF-LB/P using a semi-sintering process that minimizes powder aging caused by preheating. By partially semi-sintering the low-temperature powder bed, it was possible to execute the PBF-LB/P while avoiding the aging of most of the powder. Furthermore, the suppression of curling by the semi-sintered body eliminated the need to connect the base plate to the parts, which was necessary in previously reported low-temperature PBF-LB/P. Using the semi-sintering process, we successfully built cuboid and tensile test specimens in a polyamide 11 powder bed maintained below the crystallization temperature, where the powder hardly aged. The apparent densities of the built specimens were comparable to those produced using high-temperature PBF-LB/P. However, the elongation in the building direction of the built parts by the semi-sintering process should be improved. This study represents the first step toward the practical application of low-temperature PBF-LB/P using semi-sintering. [ABSTRACT FROM AUTHOR]

Copper-direct writing using laser reductive sintering of CuO nanoparticles has received significant interest for printing technology. We investigated the effect of the particle size distribution in CuO nanoparticle inks on patterns fabricated using femtosecond laser-pulse-induced thermochemical reduction. First, Gaussian- and bimodal-type inks were prepared using commercially available and chemically synthesized nanoparticles, respectively. Both types of inks on glass substrates with a thickness of approximately 10 µm were estimated to be absorbed 80% of the irradiated near-infrared femtosecond laser pulses, as indicated by both absorption coefficients. The bimodal-type ink increased the density of the patterns, as expected using the packing theory. However, the patterns comprised non-reduced CuO and Cu2O, as well as residual polyvinylpyrrolidone. In contrast, the patterns fabricated using the Gaussian-type ink were well-reduced to Cu and exhibited a low density and high surface area. In addition, the patterns were advantageous for electrochemical applications, which exhibited intense peaks corresponding to the reduction of CuO and Cu2O surface oxides back to metallic copper in comparison of the patterns fabricated using the bimodal-type ink, regardless of laser irradiation conditions. [ABSTRACT FROM AUTHOR]

Organic room temperature phosphorescence (RTP) from polymers holds significant promise for information encryption and anti‐counterfeiting applications. However, conventional patterning techniques limit the development of advanced RTP encryption, highlighting the need for an efficient method that achieves encryption processes quickly and conveniently. In this study, the UV laser marking machine is applied to create traceless phosphorescent patterns by leveraging the photothermal effect of the laser and the water‐absorbent quenching RTP property of polyacrylamide. A series of biaryl derivative phosphors with low π‐electron numbers are designed to limit UV absorption to below 355 nm, thereby preventing polymer sintering by the UV laser (355 nm). Additionally, two phosphorescent polymers, PB2COOH (phosphorescence lifetime τP = 2.34 s; phosphorescence quantum yield ΦP = 13.59%) and PBN (τP = 1.46 s; ΦP = 20.33%), possessing relatively excellent phosphorescent properties, are obtained. The controllable program and non‐contact processing of the marking machine enable the rapid realization of complex patterns, such as the Twelve Chinese Zodiac Signs, effectively overcoming the constraints of traditional techniques. Based on this laser technology, applications such as dual‐locking QR (quick response) codes, misleading double QR codes, labeling, and other advanced encryption methods are developed. [ABSTRACT FROM AUTHOR]

Herein, a novel metallization technique is reported for crystalline silicon heterojunction (SHJ) solar cells in which silver (Ag) fingers are printed on the SHJ substrates by dispensing Ag nanoparticle‐based inks through a needle and then sintered with a continuous‐wave carbon dioxide (CO2) laser. The impact of the Ag ink viscosity on the line quality and the line resistance is investigated on three Ag inks with different viscosities. Increasing ink viscosity yields higher Ag contact heights, larger aspect ratios, and lower line resistance values. The Ag line height increases from less than a micrometer to ≈18.62 ± 3.48 μm with the increasing viscosity. Photoluminescence imaging shows that the low‐resistance Ag metal contacts obtained do not result in any passivation damage of the SHJ substrate. This is because the wavelength of light emitted from the CO2 laser (i.e., 10.6 μm) leads to optical absorption in the Ag, but this light is effectively transparent to the transparent conductive oxide film, amorphous silicon films, and crystalline silicon substrate. Bulk resistivity values as low as 6.5 μΩ cm are obtained for the laser‐sintered Ag contact and printed using the Ag ink with the highest viscosity in this work. [ABSTRACT FROM AUTHOR]

Direct Metal Laser Sintered (DMLSed) titanium grade 5 alloy (Ti-6Al-4V alloy) is one of the widely used 3D Printed alloy in structural aerospace components. In the present work, the effect of laser sintering on the microstructure and the mechanical and corrosion behavior of DMLSed Ti-6Al-4V alloy has been studied. The samples were printed by varying the laser power and scan speed over a wide range, one parameter at a time. The fabricated Ti-6Al-4V alloy predominantly showed the martensitic structure, which governs the overall performance of the printed alloy. The mechanism of martensitic laths formation in the microstructures is presented to understand their evolution and effect on the mechanical behavior. As a result, the tensile strength and hardness of the fabricated Ti-6Al-4V alloy increased by nearly 33 and 5%, respectively, when the laser power was increased from 150 to 300 W at a fixed scan speed of 1250 mm/s. An 8% increase in tensile strength and 1-2% increase in hardness was observed when the scan speed was increased from 500 to 1250 mm/s, at a fixed laser power of 150 W. The corrosion resistance of fabricated Ti-6Al-4V alloy improved with an increase in laser power but deteriorated with an increase in scan speed. This study led to new insights into the microstructural evolution of direct laser-sintered Ti-6Al-4V alloy, which is likely to assist in producing superior quality DMLS parts. [ABSTRACT FROM AUTHOR]

Selective Laser Sintering (SLS) is an additive manufacturing technique that builds 3D models layer by layer using a laser to selectively melt cross sections in powdered polymeric materials, following sequential slices of the computer-aided design (CAD) model. SLS generally uses thermoplastic polymeric powders such as polyamides. The resultant 3D-printed objects are often weaker in their strength compared to traditionally processed materials, due to their higher porosity. This paper described the process development of using melt-processable imide oligomers terminated with reactive 4-phenylethynylphthalic anhydride (4-PEPA) to conduct laser sintering (LS). The first successful 3D-printing of high temperature RTM370 thermoset polyimide carbon fiber composite was further post-cured to promote additional crosslinking for achieving higher temperature (Tg = 370°C) capability. Another novel imide oligomer, RTM385-SLS, formulated with a complex melt viscosity [h*] of ~104-105 poise is also suitable for LS. RTM385-SLS resin powder was mixed with 20-25% of hexagonal boron nitride (h-BN) and subjected to LS to print out "Green" specimens which could be further post-cured to afford a thermally conductive but electrically insulating composites with high Tg of 385°C. The cured composite specimens were then subjected to mechanical testing, thermal conductivity and porosity evaluation as well as SEM characterization. [ABSTRACT FROM AUTHOR]

Electronic devices are being produced in substantial quantities and have become an essential component of our daily existence. Furthermore, interest in printed electronics has increased due to the straightforwardness of the manufacturing process, decreased expenses, and diminished ecological footprint. Despite these advantages, there are still some challenges in the field of printed electronics. In this study, a process for manufacturing electrical wiring on a three-dimensional (3D) plastic substrate was developed using a pneumatic dispenser that utilizes a continuous-wave laser for laser sintering, and enables rapid and selective sintering at ambient temperature and pressure. The metal paste consists of spherical Ag-coated Cu with a diameter of 5–10 µm, Sn-Bi powders, and epoxy binders and has a high viscosity. In addition, a thermo-mechanical characterization of the metal paste was performed to explain the metallurgical bonding behavior during sintering. Using a pneumatic-based dispenser equipped with a rotary valve, a high-viscosity metal paste was precisely patterned at a pressure of 1.0 bar and a dispensing speed of 5 mm/s. The patterned metal paste was then sintered with a continuous-wave laser to achieve electrical conductivity. When sintering with a power of 5 W and a scanning speed of 5 mm/s, at which the induced temperature is 280 ℃, a specific resistivity of 0.193 mΩ·cm was determined. Under these conditions, the metal paste was directly patterned and sintered onto a 3D plastic substrate as electrical wiring, and LEDs were then affixed to the substrate to validate the interconnections' functionality. In addition, the feasibility of industrial applications was demonstrated by fabricating a garnish model for automotive interiors. [ABSTRACT FROM AUTHOR]

The quest for sustainable energy solutions drives ongoing research into proton-conducting oxides, also known as protonic ceramics, which hold promise for revolutionizing electrochemical energy technologies. These materials exhibit unique proton conductivity at moderate temperatures, offering advantages over traditional electrolytes. Since Francis Forrat's mid-20th-century discovery of ceramic proton conduction, significant advancements have propelled the field forward, focusing on fuel cells, electrolysis cells, and other energy applications. Challenges persist, including poor electrode adhesion and the need for cost-effective fabrication methods. Recent studies explored cathode material design, innovative fabrication techniques like rapid laser reactive sintering, and theoretical simulations using density functional theory to understand proton migration mechanisms. This review discusses the properties, methodologies, innovations, applications, and future directions of proton-conducting oxide materials. By addressing existing challenges and exploring emerging opportunities, this review aims to contribute valuable insights to the evolving field of protonic ceramics as it continues to evolve. Scheme presentation. [Display omitted] • Overview of Proton-Conducting Oxide Materials: Defines, classifies, explains conduction, and explores applications. • Evaluates benefits and drawbacks of conventional synthesis methods. • Examines recent progress in creating high-performance materials using advanced methods and nanotech. • Investigates methods to enhance proton conductivity through interface engineering. • Assesses potential and obstacles in utilizing proton-conducting oxides for energy conversion and storage applications. [ABSTRACT FROM AUTHOR]

The implementation of the laser sintering for inkjet-printed nanoparticles and metal organic decomposition (MOD) inks on a flexible polymeric film has been analyzed in detail. A novel approach by implementing, next to a commonly 3.2 mm diameter spot laser optic, a line laser optic with a laser beam area of 2 mm × 80 mm, demonstrates the high potential of selective laser sintering to proceed towards a fast and efficient sintering methodology in printed electronics. In this work, a multiplicity of laser parameters, primary the laser speed and the laser power, have been altered systematically to identify an optimal process window for each ink and to convert the dried and non-conductive patterns into conductive and functional silver structures. For each ink, as well as for the two laser optics, a suitable laser parameter set has been found, where a conductivity without any damage to the substrate or silver layer could be achieved. In doing so, the margin of the laser speed for both optics is ranging in between 50 mm/s and 100 mm/s, which is compatible with common inkjet printing speeds and facilitates an in-line laser sintering approach. Considering the laser power, the typical parameter range for the spot laser lays in between 10 W and 50 W, whereas for the line optics the full laser power of 200 W had to be applied. One of the nanoparticle silver inks exhibits, especially for the line laser optic, a conductivity of up to 2.22 × 107 S‧m−1, corresponding to 36% of bulk silver within a few seconds of sintering duration. Both laser sintering approaches together present a remarkable facility to use the laser either as a digital tool for sintering of defined areas by means of a spot beam or to efficiently sinter larger areas by means of a line beam. With this, the utilization of a laser sintering methodology was successfully validated as a promising approach for converting a variety of inkjet-printed silver patterns on a flexible polymeric substrate into functionalized conductive silver layers for applications in the field of printed electronics. [ABSTRACT FROM AUTHOR]

In this study, a three-dimensional thermal analysis of the laser sintering additive manufacturing process was conducted. Analytical heat sink methods and numerical finite element analysis in Abaqus software were employed to assess the thermal behavior of the workpiece. Comparing the analytical method used in this study with those in the existing literature reveals the superiority of the results obtained in this research. Additionally, it has been demonstrated that the numerical and analytical results in this study are in good agreement with each other. Furthermore, the proposed method in this study has yielded significant findings, indicating its applicability in addressing the complexity of the problem. The findings demonstrated that optimizing the temperature distribution is attainable through adjustments to the initial workpiece temperature and scanning speed. [ABSTRACT FROM AUTHOR]

[Display omitted] • New powder reuse schema in powder bed fusion of polymers was demonstrated. • The characteristics of the recycled PA12 powder were investigated. • Recycled PA12 allowed to produce components with satisfactory properties. The laser-based powder bed fusion of polymers (PBF-LB/P) process often utilizes a blend of powders with varying degrees of degradation. Specifically, for polyamide 12, the traditional reuse schema involves mixing post-processed powder with virgin powder at a predetermined ratio before reintroducing it to the process. Given that only about 15% of the powder is utilized in part production, and powders are refreshed in equal proportions, there arises a challenge with the incremental accumulation of material across build cycles. To mitigate the consumption of fresh powder relative to the actual material usage, this study introduces the incorporation of recycled material into the PBF-LB/P process. This new powder reuse schema is presented for the first time, focusing on the laser sintering process. The characteristics of the recycled powder were evaluated through scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, particle size distribution, and dynamic powder flowability assessments. The findings reveal that waste powders can be effectively reused in PBF-LB/P to produce components with satisfactory mechanical properties, porosity levels, dimensional accuracy, and surface quality. [ABSTRACT FROM AUTHOR]

High-speed sintering (HSS) is an additive manufacturing (AM) technique with high potential for end-use products. Previous research has identified differential scanning calorimetry (DSC) as being a viable method for evaluating the mechanical performance of parts manufactured using the (similar) laser sintering (LS) process through the determination of the degree of particle melt (DPM). This research expands this to demonstrate the applicability of DPM measurement to the HSS process, demonstrating a clear linear correlation between tensile properties and DPM. The DPM increased from 64.9% to 75.8% as sinter speed was reduced from 180 mm/s to 140 mm/s (a slower speed providing a higher energy input), with the ultimate tensile strength approximately doubling over this range. High coefficients of determination (>0.9) indicate that the DPM is a strong indicator of tensile properties, demonstrating the potential for DPM measurements as quality assessment tools for the HSS process. [ABSTRACT FROM AUTHOR]

Porous alumina structures were developed by indirect Powder Bed Fusion with Laser Beam (PBF-LB), employing a novel feedstock (composite granules) based on alumina (Al 2 O 3), bio-renewable polyamide 612 (PA612), and micron-sized graphite (MG) using a commercial PBF-LB machine that operates with a low-power visible light diode laser. Regular and slightly rounded composite granules were prepared via the thermally induced phase separation (TIPS) process in dimethyl sulfoxide (DMSO) using 0.05 vol% of PA612, 40/60 vol% of Al 2 O 3 /PA612 and 6.25 wt% of MG, and then characterized via density measurements, Hausner's ratio, SEM-EDS, particle size distribution, Raman spectroscopy, DSC, and TGA. Experimental conditions to be used in the PBF-LB process were determined in order to obtain high-quality green porous structures with a controlled geometry. After the heating treatments, sintered components with good structural integrity, a high open porosity associated with interconnected pores in the struts, and a ceramic matrix with microsized-equiaxial grains were obtained. The evaluation of the mechanical properties was performed by diametral compression testing. In order to improve these properties, a vacuum infiltration process involving a low-concentration alumina-ethanol suspension was used on pre-sintered discs. As a consequence of the infiltration process, the discs showed improved mechanical properties after sintering without the porosity having been significantly affected. [ABSTRACT FROM AUTHOR]

With the rapid development of integrated circuits, glass substrates are frequently utilized for prototyping various functional electronic circuits due to their superior stability, transparency, and signal integrity. In this experiment, copper wire was printed on a glass substrate using inkjet printing, and the electronic circuit was sintered through laser irradiation with a 532 nm continuous green laser. The relationship between resistivity and microstructure was analyzed after laser sintering at different intensities, scanning speeds, and iterations. The experimental results indicate that the conductivity of the sintered lines initially increases and then decreases with an increase in laser power and scanning speed. At the same power level, multiple sintering runs at a lower scanning speed pose a risk of increased porosity leading to reduced conductivity. Conversely, when the scanning speed exceeds the optimal sintering speed, multiple sintering runs have minimal impact on porosity and conductivity without altering the power. [ABSTRACT FROM AUTHOR]

This research delves into an upscale, personalised packaging paradigm employing 3D printing and a bio-composite derived from esteemed rosewood. The study incorporates a design for additive manufacturing, enhancing designers' flexibility, and fostering innovation. To address global sustainability imperatives, including efficiency, energy conservation, a low carbon footprint and ecological compatibility, a premium and sustainable rosewood/polyethersulfone (PES) composite is developed. Laser sintering (LS), renowned for its processing flexibility, is applied for crafting intricate packages. A weight ratio of 1:4 of rosewood to PES is highly suitable for LS processing. The resultant custom carton, embodying natural rosewood aesthetics and fragrance, exhibits commendable mechanical robustness and precision. Tensile and bending strengths reach peaks of 4.880 MPa and 7.870 MPa, respectively, under a 9-W laser power. Scanning electron microscope (SEM) analysis confirms the favourable dispersion of rosewood fibres in LS specimens, providing insights into the microstructure of the composite powder. [ABSTRACT FROM AUTHOR]

Copyright of Foundry Technology (1000-8365) is the property of Foundry Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Exploring the integration of 3D‐printing technology in space maintainer (SM) manufacturing could offer innovative solutions and insights for enhancing SMs. Aim: To compare the clinical success, retention, and periodontal effect of traditional band–loop (TBL) SMs with 3D‐printed SMs. Design: Seventy children (mean age: 6.99 ± 1.18) were divided into two groups. Laser sintering (LS) group (n = 34): Patients were scanned with an intraoral scanner. SMs were produced with LS 3D‐printing method from a titanium‐based metal powder. T group (n = 36): Impressions were taken with alginate. SMs were produced by adjusting the bands and soldering the wires on the model. The retention and effects on oral hygiene of the SMs were evaluated at the sixth month. Preference for impression technique was assessed by a five‐question survey. Results: Thirty‐eight percent of T SMs and 66% of LS SMs failed (p =.007). The mean survival time was significantly higher in the T group (p =.035). No difference was found between the initial and control full‐mouth Gingival Index (GI) and Plaque Index (PI) values of the two groups. Both groups had increased GI/PI values in abutment teeth. Patients in the LS group interpreted their impression experience more positively. Conclusion: It is important to provide oral hygiene education before applying fixed SMs and utilize more digital workflow in paediatric dentistry. [ABSTRACT FROM AUTHOR]

The control of powder aging during Selective Laser Sintering (SLS) processing is one of the challenges to be overcome for the implementation of this technique in serial production. Aging phenomena, because of the elevated temperatures and long processing times, need to be considered when a fraction of the polymer powders present in the build chamber and not used to manufacture the parts are reused at various times. The aim of this study was to investigate the influence of successive reuse of blends of pure Polyamide 12 and its blends with two types of flame retardants (FR): ammonium polyphosphate (APP) and zinc borate (ZB). The composition of the blends was 70/30 (wt/wt) PA 12/FR. Four successive processing stages have been carried out by collecting the remaining powder blend each time. The powders were re-used using the same processing parameters after sieving. DSC measurements showed that the incorporation of FRs entailed a reduction in the processing window up to 4 °C; nevertheless, no further reduction was noted after aging. The TGA curves of aged blends of powders were also similar for pure PA 12 and PA 12 with FR. In addition, initial and reused powders presented a higher degree of crystallinity than the specimens processed from the powders. The heterogeneous character of the PA 12 after LS processing or reprocessing was shown through Pyrolysis Combustion Flow Calorimetry (PCFC) and cone calorimeter (CC) tests. FTIR analysis also showed that post-condensation reactions have occurred. The mode of action of the flame retardants was clearly seen on HRR curves at both tests. The first reuses of PA 12 powders entailed a significant reduction in time to ignition at the cone calorimeter (150 for the initial material to around 90 s for the reused material), indicating the formation of short polymer chains. Only in the case of zinc borate was it noticed that re-used powder was detrimental to the fire performance because of a strong increase in the value of pHRR (between 163 and 220 kW/m2 for reused material instead of 125 kW/m2 for the initial one). [ABSTRACT FROM AUTHOR]

Liquid metal is a compelling material for making soft and stretchable devices due to its high electrical conductivity and extreme stretchability. One way to pattern liquid metal is to nebulize it into small droplets, spray it onto a surface as a film, and then use a laser to "sinter" it into circuit patterns. Here, it is shown that including poly(amic acid) in the spray‐deposited film has multiple benefits: it (1) allows the unsintered regions to be removed easily, (2) lowers the power required for sintering, (3) converts to carbon upon exposure to create a carbon‐metal composite, and (4) increases the surface area of the film by 2632% compared to bulk EGaIn. The conductive liquid metal‐carbon circuits can also be transferred to a soft substrate to produce stretchable conductors. The circuits slightly increase in conductivity up to ≈30% strain and then decrease such that by 100% strain, the resistance is only ≈1.02 times its initial resistance. Lastly, the film is highly reactive with water molecules in the air, increasing in resistance over time in humid conditions. The high reactivity and surface area of the film indicate potential applications in batteries, catalysts, and capacitors. Meanwhile, the facile patterning indicates potential applications in soft circuits. [ABSTRACT FROM AUTHOR]

Copyright of Current Research in Dental Sciences is the property of Ataturk University Coordinatorship of Scientific Journals and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

ABSTRACTThe optimisation of selective laser sintering (SLS) of polymeric materials, based on analytical equations providing fast predictions, can broaden the SLS application area. However, the selection of SLS polymeric materials is currently rather limited, due to specific requirements regarding sufficient flowability and limited molecular degradation. The present work highlights that upgrading existing analytical equations, by incorporating a well-calculated overlay factor and correcting for pre-heating starting at ambient conditions, can accelerate SLS screening. Model validation is performed based on density, colorimetric, morphological and mechanical analysis of printed parts, focusing on the prediction of the laser power which corresponds to the onset of degradation, taking polyamide powder as a reference case. Furthermore, the optimised model is successfully applied for two other polymer powders, namely thermoplastic co-polyester and thermoplastic polyurethane powder, to highlight a better overall description of the SLS degradation mechanism.

In this paper, the feasibility of using additive manufacturing (AM) technologies for the fabrication of corrugated horn antennas for the E-band (60 to 90 GHz) is investigated. Stereolithography apparatus (SLA) and selective laser melting (SLM) are identified as the most suitable technologies for manufacturing horn antennas in this frequency range. To ensure good manufacturing, slanted corrugations are utilized. The antennas have a gain of 13 dBi at 72 GHz and are designed in CST Microwave Studio. For the fabrication of the plastic parts, SLA and the finer-scaled projection micro stereolithography (PµSL) technology are applied. The metal antennas are printed with direct metal laser sintering (DMLS) from the aluminum alloy AlSi10Mg and the finer scaled micro metal laser sintering (µMLS) from 316L stainless steel. Overall, four antennas are fabricated. The plastic antennas are plated with copper. Dimensional tolerances and surface roughness of the antennas are evaluated. The antennas are investigated considering H- and E-plane beam shapes, input reflection, and realized gain. The measurement is conducted in an anechoic chamber using the Single-Antenna method. The µMLS antenna supplies the best results. [ABSTRACT FROM AUTHOR]

In order to expand the application of 3D printing technology to the thick-film hybrid integrated circuits and to improve sintering efficiency of the thick films, four kinds of thick films including three conductor films and a dielectric film were prepared via 3D direct printing followed by laser sintering. Subsequently, microstructures and properties of the obtained films were compared with those of the thick films fabricated by commonly-used screen printing & high-temperature furnace sintering. The results show that the thick conductor and dielectric films produced by using the common method exhibit fine microstructures and good properties. In contrast, the thick conductor films prepared by the 3D direct printing & laser sintering are flat and continuous with a uniform thickness and good welding performance, but the density of the films is not large enough to ensure acceptable adhesion and square resistance. The relative density of the thick dielectric film is much lower than those of the thick conductor films. As a result, the insulation performance of the thick dielectric film does not meet the standard requirements. Overall, it is feasible to prepare the thick conductor/dielectric films via 3D direct writing, but the laser sintering parameters should be optimized to fulfill sintering densification of the thick films, and further to improve their bonding strengths with the ceramic substrates. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of the Ni element on the properties of AlCoCrFeMn HEAs, this experiment prepared AlCoCrFeMn and AlCoCrFeNiMn HEAs by using a laser-ignition self-propagation sintering technique with an equal molar ratio. And analyzed the effect of the Ni element on the microstructure of AlCoCrFeMn HEAs by using a metallurgical optical microscope (OM), scanning electron microscope (SEM), energy spectroscopic analysis (EDS), X-ray diffraction (XRD), and other experiments. Characterization equipment was used to analyze the effect of the Ni element on the microstructure, physical phase structure, wear resistance, compressive properties, and corrosion resistance of AlCoCrFeMn HEA materials. The results show that after the addition of the Ni element, the AlCoCrFeNiMn HEA changes from a single BCC phase to one consisting of BCC and a small amount of an FCC phase, with an equiaxial organization, and the yield strength reaches 780 MPa and the compressive strength is 3920 MPa. The corrosion rate is 2.08 × 10−3 mm/a, and the corrosion resistance and mechanical properties are greatly increased. [ABSTRACT FROM AUTHOR]

In this article, the particle concentration of finely dispersed copper(II) oxide nanosuspensions as precursors for reductive laser sintering (RLS) is optimized on the basis of rheological investigations. For this metallization process, a smooth, homogeneous and defect-free precursor layer is a prerequisite for adherent and reproducible copper structures. The knowledge of the rheological properties of an ink is crucial for the selection of a suitable coating technology as well as for the adjustment of the ink formulation. Different dilutions of the nanosuspension were examined for their rheological behavior by recording flow curves. A strong shear thinning behavior was found and the viscosity decreases exponentially with increasing dilution. The viscoelastic behavior was investigated by a simulated doctor blade coating process using three-interval thixotropy tests. An overshoot in viscosity is observed, which decreases with increasing thinning of the precursor. As a comparison to these results, doctor blade coating of planar glass and polymer substrates was performed to prepare precursor layers for reductive laser sintering. Surface morphology measurements of the resulting coatings using laser scanning microscopy and rheological tests show that homogeneous precursor layers with constant thickness can be produced at a particle–solvent ratio of 1.33. A too-high particle content results in an irregular coating layer with deep grooves and a peak-to-valley height S z of up to 7.8 μm. Precise dilution control allows the fabrication of smooth surfaces with a S z down to 1.5 μm. [ABSTRACT FROM AUTHOR]

The additive manufacturing (AM) of functional copper (Cu) parts is a major goal for many industries, from aerospace to automotive to electronics, because Cu has a high thermal and electrical conductivity as well as being ~10× cheaper than silver. Previous studies on AM of Cu have concentrated mainly on high-energy manufacturing processes such as Laser Powder Bed Fusion, Electron Beam Melting, and Binder Jetting. These processes all require high-temperature heat treatment in an oxygen-free environment. This paper shows an AM route to multi-layered microparts from novel nanoparticle (NP) Cu feedstocks, performed in an air environment, employing a low-power (<10 W) laser sintering process. Cu NP ink was deposited using two mechanisms, inkjet printing, and bar coating, followed by low-power laser exposure to induce particle consolidation. Initial parts were manufactured to a height of approximately 100 µm, which was achieved by multi-layer printing of 15 (bar-coated) to 300 (inkjetted) layers. There was no evidence of oxidised copper in the sintered material, but they were found to be low-density, porous structures. Nonetheless, electrical resistivity of ~28 × 10−8 Ω m was achieved. Overall, the aim of this study is to offer foundational knowledge for upscaling the process to additively manufacture Cu 3D parts of significant size via sequential nanometal ink deposition and low-power laser processing. [ABSTRACT FROM AUTHOR]

It is essential to treat high-level liquid waste (HLLW) in a secure and effective manner. As a result, we first propose rapid vitrification of simulated HLLW using an ultra-high power laser. First, a cured body with a mass of 24.4 kg was obtained by using ultra-high power laser sintering. Subsequently, four different locations of the curing body were tested and the measured performance indicators were all in accordance with the regulations. This demonstrates the potential of ultra-high power lasers in HLLW glass curing processes. [ABSTRACT FROM AUTHOR]

Laser sintering is a widely used process for producing complex shapes from particulate materials. However, understanding the complex interaction between the laser and particles is a challenge. This investigation provides new insights into the sintering process by simulating the laser source and the neck growth of particle pairs. First, a multi-physics discrete element method (DEM) framework is developed to incorporate temperature-dependent contact rheological and thermal properties, incorporating heat transfer and neck formation between the particles. Next, energy transport by ray tracing is added to allow for computing the amount of laser energy absorbed during sintering. The DEM model is calibrated and validated using experimental data on neck growth and temperature evolution of particle pairs made of polystyrene and Polyamide 12. The findings show that the proposed DEM model is capable of accurately simulate the neck growth during the laser sintering paving the way for better controlling and optimizing the process. [ABSTRACT FROM AUTHOR]

Incorporating continuous carbon fibre-reinforced polymer (CCFRP) parts within additive manufacturing processes presents a significant advancement in the fabrication of robust lightweight parts, particularly relevant to aerospace, engineering, and various industrial sectors. Nonetheless, prevailing additive manufacturing methodologies for CCFRP parts exhibit notable limitations. Techniques reliant on resin and extrusion entail extensive and costly post-processing procedures to eliminate support structures, constraining design versatility and complicating small-scale production endeavours. In contrast, laser sintering (LS) emerges as a promising avenue for industrial application. It facilitates the efficient and cost-effective manufacturing of resilient parts without needing support structures. However, the current state of research and technological capabilities has yet to yield an LS machine that integrates the benefits of continuous fibre reinforcement with the inherent advantages of the LS process. This paper describes the systematic development process according to VDI 2221 of a new type of LS machine with automated continuous fibre integration while keeping the advantages of the LS process. The resulting physical prototype of the machine is also presented. Furthermore, this study presents an approach to integrate the cost and Product Carbon Footprint of the process in the product design. For this purpose, a machine state model was developed, and the costs and Product Carbon footprint of a part were analysed based on the model. The promising potential for future lightweight products is demonstrated through the production of CCFRP parts. [ABSTRACT FROM AUTHOR]

Copyright of Structural Integrity & Life / Integritet i vek Konstrukcija is the property of University of Belgrade, Faculty of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As a material for conventional manufacturing, iron and its alloys had been an object of numerous studies in the past and, as a result, steel became one of the best-known metal alloys in industry. However, new manufacturing technologies, such as additive manufacturing (AM), open new possibilities for the same materials. In this paper, we investigate stainless steel powder for additive manufacturing technologies and parts fabricated from it. Powder chemical composition and morphology are presented in the study. The influence of laser power and laser scanning speed on the mechanical properties of materials and microstructure was studied, and the experimental results showed the optimal energy density values between 50 and 65 J/mm³. However, the value of energy density varies depending on which parameters are observed, i.e. the optimum energy density value is different for the ultimate tensile stress (UTS) and surface roughness or the Young’s modulus and hardness. [ABSTRACT FROM AUTHOR]

Synthetic biomaterials play a crucial role in developing tissue-engineered heart valves (TEHVs) due to their versatile mechanical properties. Achieving the right balance between mechanical strength and manufacturability is essential. Thermoplastic polyurethanes (TPUs) and elastomers (TPEs) garner significant attention for TEHV applications due to their notable stability, fatigue resistance, and customizable properties such as shear strength and elasticity. This study explores the additive manufacturing technique of selective laser sintering (SLS) for TPUs and TPEs to optimize process parameters to balance flexibility and strength, mimicking aortic valve tissue properties. Additionally, it aims to assess the feasibility of printing aortic valve models with submillimeter membranes. The results demonstrate that the SLS-TPU/TPE technique can produce micrometric valve structures with soft shape memory properties, resembling aortic tissue in strength, flexibility, and fineness. These models show promise for surgical training and manipulation, display intriguing echogenicity properties, and can potentially be personalized to shape biocompatible valve substitutes. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) offers many potential advantages to constructing gas turbine components such as allowing for more complex geometry in carefully optimized designs. AM processes, such as direct laser sintering, create roughness with distinct characteristics including periodicity from layers of fused material and varying roughness element size depending on surface print orientation. Understanding how this affects airflow through micro cooling channels is essential for component design. Individual roughness elements may block up to 15% of a cooling channel. The fluid responses to this level of roughness are difficult to characterize using traditional models. Three test surfaces were constructed using CT scans of a micro cooling channel printed in Inconel 718 and Hastelloy-X to act as the floor of the roughness internal flow tunnel (RIFT) wind tunnel. These surfaces included an Upskin and Downskin surface to contrast roughness variation caused by print orientation. A tomographic particle tracking system was constructed to examine a 40 × 40 × 6 mm section of the RIFT with the goal of providing a more detailed analysis of flow behavior over roughness elements than previous studies. This system uses a micro bubble generator to provide seed particles, a 15 Hz Evergreen laser, and four 8 MP cameras mounted horizontally to view the test volume. Detailed particle tracking velocimetry measurements of flow around individual roughness elements including velocities, Reynolds stress and dispersive stress above the rough surface are discussed within the limitations of the particle tracking system. [ABSTRACT FROM AUTHOR]

Purpose: Selective laser sintering (SLS) is an essential technology in the field of additive manufacturing. However, SLS technology is limited by the traditional point-laser sintering method and has reached the bottleneck of efficiency improvement. This study aims to develop an image-shaped laser sintering (ISLS) system based on a digital micromirror device (DMD) to address this problem. The ISLS system uses an image-shaped laser light source with a size of 16 mm × 25.6 mm instead of the traditional SLS point-laser light source. Design/methodology/approach: The ISLS system achieves large-area image-shaped sintering of polymer powder materials by moving the laser light source continuously in the x-direction and updating the sintering pattern synchronously, as well as by overlapping the splicing of adjacent sintering areas in the y-direction. A low-cost composite powder suitable for the ISLS system was prepared using polyether sulfone (PES), pinewood and carbon black (CB) powders as raw materials. Large-sized samples were fabricated using composite powder, and the microstructure, dimensional accuracy, geometric deviation, density, mechanical properties and feasible feature sizes were evaluated. Findings: The experimental results demonstrate that the ISLS system is feasible and can print large-sized parts with good dimensional accuracy, acceptable geometric deviations, specific small-scale features and certain density and mechanical properties. Originality/value: This study has achieved the transition from traditional point sintering mode to image-shaped surface sintering mode. It has provided a new approach to enhance the system performance of traditional SLS. [ABSTRACT FROM AUTHOR]

Additively manufactured fibre-reinforced polymers are gaining traction. After the development and optimisation of a novel fibre-deposition system in a laser sintering (LS) setup, polyamide 12 specimens were produced with and without glass fibres. In this study, the relation between the crystallinity, porosity, and mechanical properties of LS specimens with and without fibres is investigated. After testing as-built LS specimens, a detrimental effect of the fibres on the specimens' performance was observed with a decrease in UTS of 6%. The degree of crystallinity remained the same; however, a porosity content of 2.6% was observed in specimens with fibres. These pores can have a negative influence on the bonding between the fibres and the matrix. To investigate the influence of the pores, warm isostatic pressing (WIP) was performed on LS specimens with and without fibres. The WIP process shows a positive influence on the specimens without fibres, resulting in an increase in UTS of 8.5%. The influence of the WIP process on specimens with fibres, however, is much less pronounced, with an increase in UTS of only 2%. Neither the crystallinity nor the porosity are the cause of the less-than-expected increase in UTS in LS specimens with fibres. A number of hypotheses and mitigation strategies are provided. [ABSTRACT FROM AUTHOR]

Microanalysis of carbon and magnesium isotopes in dolomite is gaining increasing attention as a valuable tool in various fields of earth sciences. However, the matrix effect poses a major challenge for determining C and Mg isotopes using laser ablation multi-collector ICP-MS, particularly due to the wide range of chemical compositions found in natural dolomite. A preferred solution is to use a matrix-matched reference material with homogeneous isotope compositions at the micron scale. In this contribution, we established a new protocol for preparing a dolomite reference material for isotopic microanalysis through pressureless sintering. The effects of particle size and sintering temperature on the isotopic homogeneity of sintered dolomite powder pellets (SDPPs) were carefully evaluated. Our results indicate that a smaller d90 particle size improves isotope homogeneity, and SDPPs with a d90 of 3.17 μm show the best laser ablation repeatabilities of δ26Mg and δ25Mg (0.11‰ and 0.09‰) that are 2–4 times better compared to the repeatability of those with a d90 of 10.37 μm. Higher sintering temperature enhances particle cohesion and pellet hardness, which are crucial for laser ablation performance; Vickers hardness (HV) is improved to 41.58 kgf mm−2 when SDPPs are heated up to 400 °C below decomposition temperature. These SDPPs show the best δ13C, δ26Mg and δ25Mg homogeneity with a twice standard deviation value of 0.37‰, 0.11‰ and 0.06‰ (n = 15), respectively. Of note, in situ carbon and magnesium isotope characterization of SDPPs using LA-MC-ICP-MS shows negligible isotope fractionation against natural dolomites. This further confirms the reliability and robustness of the proposed protocol for dolomite isotopic reference preparation via pressureless sintering. [ABSTRACT FROM AUTHOR]

Copyright of Quintessenz der Zahntechnik is the property of Quintessenz Verlags GmbH and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The digital transformation has revolutionized various sectors, including dentistry. Dentistry has emerged as a pioneer in embracing digital technologies, leading to advancements in surgical and prosthetic oral healthcare. Immediate loading for full-arch edentulous dental implants, once debated, is now widely accepted. This case report describes a 74-year-old patient with dental mobility and significant bone loss who was rehabilitated using a Toronto Bridge protocol on four dental implants with immediate loading. Digital planning, surgical guides, 3D printing, and precision techniques were employed. The surgery involved implant placement and prosthetic procedures. The patient reported minimal post-operative discomfort, and after four months, the definitive prosthesis was successfully placed. This case demonstrates the efficacy of immediate loading in complex dental scenarios with digital innovation, resulting in improved patient outcomes. The full digital workflow, including 3D printing and the use of modern materials, enhances the efficiency and predictability of oral rehabilitation, marking a transformative era in dental care. The integration of digital technology in all phases of treatment, from diagnosis to finalization, makes this approach safer, reliable, and efficient, thereby benefiting both patients and clinicians. [ABSTRACT FROM AUTHOR]

This study investigates the experimental parameters of the laser sintering process of Y 3 Al 5 O 12 ceramics. Ceramic powders were produced using the polymeric precursor method and sintered using a CO 2 laser as the heating source. The samples were characterized using differential thermal analysis, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy techniques. The results showed that parameters such as powder calcination temperature, dwell time, and laser power density rate are crucial in obtaining dense ceramic bodies. Furthermore, developing and using a sample holder made of the same material composition to be sintered showed significant advances in the laser sintering process. [ABSTRACT FROM AUTHOR]

The optimisation of selective laser sintering (SLS) of polymeric materials, based on analytical equations providing fast predictions, can broaden the SLS application area. However, the selection of SLS polymeric materials is currently rather limited, due to specific requirements regarding sufficient flowability and limited molecular degradation. The present work highlights that upgrading existing analytical equations, by incorporating a well-calculated overlay factor and correcting for pre-heating starting at ambient conditions, can accelerate SLS screening. Model validation is performed based on density, colorimetric, morphological and mechanical analysis of printed parts, focusing on the prediction of the laser power which corresponds to the onset of degradation, taking polyamide powder as a reference case. Furthermore, the optimised model is successfully applied for two other polymer powders, namely thermoplastic co-polyester and thermoplastic polyurethane powder, to highlight a better overall description of the SLS degradation mechanism. [ABSTRACT FROM AUTHOR]

To overcome the most important concerns, such as harsh storage conditions and the removal of solvents and surfactants in aerosol jet printing (AJP) technology, a nano-powder aerosol pining device with sheath gas assisted aerodynamic lens focusing was proposed, and the aerosol jet pining system was established, and the effects of pining speed, volume flow ratio of sheath gas and carrier gas on printing efficiency and line morphology were explored. The effects of laser treatment on the resistivity, microscopic morphology and oxidation degree of aerosol printing lines were analyzed by laser sintering experiments and electrochemical performance test experiments. Experimental results show that when the printing speed is 19.20 mm/min and the volume low ratio of sheath gas to carrier gas is 2.65, the minimum width of the printing line is 56.52 µm, After laser sintering, the nano silver powder particles in the printing lines melt and agglomerate and form filaments to bond with each other, which significantly reduces the resistivity of the aerosol printing lines. [ABSTRACT FROM AUTHOR]

Copyright of Selcuk Dental Journal is the property of Selcuk Dental Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)