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Direct metal laser sintered Ti–6Al–4V samples, with intentionally induced defects generated by varying the process parameters, were analyzed using microtensile testing techniques. Samples with defects exhibited statistically-significant larger microtensile than macrotensile ultimate strengths. Weibull microtensile moduli are smaller than macrotensile moduli indicating greater variability. Comparing the microtensile results to macrotensile properties reveals how changing these process parameters affects the range of mechanical behaviors potentially present in additively-manufactured parts due to the varying microstructures in the material.

The discovery of piezoelectricity inspired several sensing applications. For these applications, the thinness and flexibility of the device increase the range of implementations. A thin lead zirconate titanate (PZT) ceramic piezoelectric sensor is advantageous compared with bulk PZT or a polymer when it comes to having minimal impacts on dynamics and high-frequency bandwidth provided by low mass or high stiffness, while satisfying constraints regarding tight spaces. PZT devices have traditionally been thermally sintered inside a furnace and this process consumes large amounts of time and energy. To overcome such challenges, we employed laser sintering of PZT that focused the power onto selected areas of interest. Furthermore, non-equilibrium heating offers the opportunity to use low-melting-point substrates. Additionally, carbon nanotubes (CNTs) were mixed with PZT particles and laser sintered to utilize the high mechanical and thermal properties of CNTs. Laser processing was optimized for the control parameters, raw materials and deposition height. A multi-physics model of laser sintering was created to simulate the processing environment. Sintered films were obtained and electrically poled to enhance the piezoelectric property. The piezoelectric coefficient of laser-sintered PZT increased by approximately 10-fold compared with unsintered PZT. Moreover, CNT/PZT film displayed higher strength compared with PZT film without CNTs after the laser sintering while using less sintering energy. Thus, laser sintering can be effectively used to enhance the piezoelectric and mechanical properties of CNT/PZT films, which can be used in various sensing applications. [ABSTRACT FROM AUTHOR]

The one-step AM process is considered the goal many researchers seek in the field of Additive Manufacturing (AM) of high-technology ceramics. Among the several AM techniques, only Powder Bed Fusion (PBF) can directly print high-technology ceramics using one step. However, the PBF technique faces numerous challenges to efficiently be employed in the PBF of ceramics. These challenges include the formation of cracks, generated thermal stress, effective laser–powder interaction, and low acquired relative density. This study developed a new preheating mechanism for ceramic materials using two laser systems to surpass beyond these challenges and successfully print ceramics with a single-step AM method. One laser is used to preheat the powder particles before the second laser is utilised to complete the melting/sintering process. Both lasers travel along the same scanning path. There is a slight delay (0.0001 s) between the preheating laser and the melting/sintering laser to guarantee that the melting/sintering laser scans a properly preheated powder. To further facilitate testing of the preheating system, a numerical model has been developed to simulate the preheating and melting process and to acquire proper process parameters. The developed numerical model was shown to determine the correct process parameters without needing costly and time-consuming experiments. Alumina samples (10 × 10 × 6 mm3) were successfully printed using alumina powder as feedstock. The surface of the samples was nearly defect-free. The samples' relative densities exceeded 80%, the highest reported relative density for alumina produced by a single-step AM method. This discovery can significantly accelerate the transition to a one-step AM process of ceramics. [ABSTRACT FROM AUTHOR]

The paper presents the dynamic impact properties of laser-sintered polyamide PA2200 in accordance with the building orientation. The idea of deTermining the impact properties in relation to building orientation lays on orientation-property dependence founded in our previous studies of tensile, bending and fracture mechanics testing. The specimens were manufactured under the same energy density and temperature conditions, at four orientations, as described in the paper content. The experimental investigation was carried out on a pendulum impact testing machine to deTermine the impact energy and strength according to the building orientation. Brittle fracture was observed for all specimens, independent of building orientation, and a similar behavior was also observed in the elastic zone of deflection. However, impact strength and impact energy are influenced by orientation. [ABSTRACT FROM AUTHOR]

This editorial highlights the results presented in the second Special Issue dedicated to obtaining and characterizing new materials, wherein one review paper and 13 research articles have been published. The most important field covered is that of materials involved in civil engineering, focusing on geopolymers and insulating materials alongside developing new methods for enhancing the characteristics of different systems. Another important field is that of the materials used for environmental issues, and finally, those involved in human health. [ABSTRACT FROM AUTHOR]

The laser induced forward transfer and sintering of metal nanoparticle inks has been proven a key enabling technology for flexible electronics. Nevertheless, many challenges concerning the conformal processing of non-planar substrates incorporating thermally sensitive layers are yet to be addressed. In this work, we study the behaviour of conformal laser printing of silver nanoparticle inks on patterned samples comprising sensitive underlying structures, by correlating the laser sintering powers employed to the undesired effects on the adjacent interfaces. The latter include demanding surface topographies with periodic patterns and microcomponents exhibiting aspect ratio in the nano to 100-micron scale. We investigate the contribution of crucial processing parameters, such as the per pulse energy, repetition rate and the pulse to pulse spatial and temporal overlap to the overall result. The demonstrated results validate the versatility of laser processing which can offer application specific solutions on different use cases involving multilayered and multimaterial electronics. [ABSTRACT FROM AUTHOR]

Over the past couple of decades, additive manufacturing and the use of root-analogue-printed titanium dental implants have been developed. Not all powder particles are sintered into the final product during the additive manufacturing process. Reuse of the remaining powder could reduce the overall implant manufacturing cost. However, Ti-6Al-4V powder particles are affected by heat, mechanical factors, and oxidization during the powder bed fusion manufacturing process. Degradation of the powder may harm the final surface composition and decrease the biocompatibility and survival of the implant. The uncertainty of the recycled powder properties prevents implant fabrication facilities from reusing the powder. This study investigates the chemical composition of controlled, clean, and recycled titanium alloy powder and root-analogue implants (RAI) manufactured from these powders at three different depths. The change in titanium's quantity, oxidization state, and chemical composition in powder and RAI implants have been demonstrated and analyzed. While not identical, the surface chemical composition of the recycled powder implant and the implant manufactured from unused powder are similar. The results also indicate the presence of TiO2 on all surfaces. Many studies confirmed that titanium dioxide on the implant's surface correlates with better osteointegration, reduced bacterial infection, and increased corrosion resistance. Considering economic and environmental aspects, surface chemical composition comparison of clean and reused powder is crucial for the future manufacturing of cost-effective and biocompatible implants. [ABSTRACT FROM AUTHOR]

Nanoelectrospray laser deposition (NELD) of nanoparticles (NPs) on various substrates has attracted considerable attention as a fast, cost-effective, and scalable technique for precise control of heating time and zone. In this work, NELD-assisted sintering of titanium dioxide (TiO2) NPs on borosilicate glass and quartz substrates is addressed. A 10.6 μ m CO2 laser was used for patterning and sintering titania nanoparticles in ambient air. The effects of laser dose and deposition process parameters on the morphological, structural, and optical characteristics of the sintered TiO2 patterns were characterized using optical microscopy, scanning electron microscopy, and x-ray diffraction. The results point out that the anatase phase was preserved after laser sintering, without the appearance of any TiO2 rutile traces. We show that the improvement in the morphological properties of TiO2 patterns is due to the laser sintering of a dense layer of ceramic with enhanced interconnectivity and connection between single nanoparticles. A theoretical model was developed to select the temperature required to sinter TiO2 nanoparticles and to correlate it with the laser power and scanning speed to prevent cracking on the substrate and sintered nanoparticles and also to get transparent TiO2 films. An optical transmittance of ∼ 91 % was achieved. The experimental data were in accordance with the theoretical model, predicting the success of the model. [ABSTRACT FROM AUTHOR]

Non-isothermal laser-based powder bed fusion (LPBF) of polymers suggests the potential for significantly extending the range of materials applicable for powder-based additive manufacturing of polymers, relying on the absence of a material-specific processing window. To allow for the support-free manufacturing of polymers at a build chamber temperature of 25 °C, applied processing strategies comprise the combination of fractal exposure strategies and locally quasi-simultaneous exposure of distinct segments of a particular cross section for minimizing crystallization-induced part deflection. Based on the parameter-dependent control of emerging cooling rates, formed part morphologies and resulting mechanical properties can be modified. Thermographic in situ measurements allow for correlating thermal processing conditions and crystallization kinetics with component-specific mechanical, morphological, and microstructural properties, assessed ex situ. Part morphologies formed at crystallization temperatures below 70 °C, induced by reduced laser exposure times, are characterized by a nano-spherulitic structure, exhibiting an enhanced elongation at break. An ambient temperature of 25 °C is associated with the predominant formation of a combined (α + γ)-phase, induced by the rapid cooling and subsequent laser-induced tempering of distinct layers, yielding a periodic microstructural evolution. The presented results demonstrate a novel approach for obtaining nano-spherulitic morphologies, enabling the exposure-based targeted adaption of morphological properties. Furthermore, the thermographic inline assessment of crystallization kinetics allows for the enhanced understanding of process-morphology interdependencies in laser-based manufacturing processes of semi-crystalline polymers. [ABSTRACT FROM AUTHOR]

Digital dentistry and new techniques for the dental protheses' suprastructure fabrication have undergone a great evolution in recent years, revolutionizing the quality of dental prostheses. The aim of this work is to determine whether the best horizontal marginal fit is provided by the CAD-CAM technique or by laser sintering. These values have been compared with the traditional casting technique. A total of 30 CAD-CAM models, 30 laser sintering models, and 10 casting models (as control) were fabricated. The structures realized with chromium–cobalt (CrCo) have been made by six different companies, always with the same model. Scanning electron microscopy with a high-precision image analysis system was used, and 10,000 measurements were taken for each model on the gingival (external) and palatal (internal) side. Thus, a total of 1,400,000 images were measured. It was determined that the CAD-CAM technique is the one that allows the best adjustments in the manufacturing methods studied. The laser sintering technique presents less adjustment, showing the presence of porosities and volume contraction defects due to solidification processes and heterogeneities in the chemical composition (coring). The technique with the worst adjustments is the casting technique, containing numerous defects in the suprastructure. The statistical analysis of results reflected the presence of statistically significant gap differences between the three manufacturing methods analyzed (p < 0.05), with the samples manufactured by CAD-CAM and by traditional casting processes being the ones that showed lower and higher values, respectively. No statistically significant differences in fit were observed between the palatal and gingival fit values, regardless of the manufacturing method used. No statistically significant differences in adjustment between the different manufacturing centers were found, regardless of the process used. [ABSTRACT FROM AUTHOR]

Background: Even though mandibular condyle fractures have a high clinical relevance, their treatment remains somewhat challenging. Open reduction and internal fixation are difficult due to narrow surgical approaches, poor overview during reduction, and a possible risk of facial nerve damage. In times of technical endeavors in surgery, there is a trend towards the usage of stable CAD-CAM-implants from additive manufacturing or titanium laser sintering. Up until now, there have not been any reports of fracture treatment of the mandibular condyle using this technique. Results and conclusion: We present a workflow for virtual repositioning of the fractured mandibular condyle, to manufacture patient-specific implants for osteosynthesis with the intention of use of resorbable metal alloys in the future. [ABSTRACT FROM AUTHOR]

Featured Application: 3D-printed metal surgical guides offer several advantages (open-frame, stability) over traditional resin guides. This proof-of-concept study demonstrates the feasibility and the potential use of such guides during endodontic microsurgery procedures. Thanks to recent advances, printed surgical guides are now fully integrated into digital workflows and are beneficial in terms of accuracy in endodontic microsurgery (EMS). The aim of this study was to evaluate the accuracy of new 3D-printed surgical metal guides (SMGs) with open-frame structures in an endodontic surgical simulation model ex vivo based on a pig jaw. Twenty-nine roots were included. SMGs were produced using 3D implant planning software and printed using cobalt-chrome and a laser sintering printer. The SMGs were designed to allow for surgical access at 3 mm from the apex of each root. Virtual planning and postoperative CBCT scans were compared by analysing the apical and angular deviations. To test for deviations equal to zero, a one-sample test was used. The differences between the virtually planned implant and the actual position of the drill path were statistically significant for five SMGs on the eight produced guides, whereas there were no differences for the three others. The mean apical deviation was 3.2 mm ± 1.7 using SMGs, and the angular deviation was measured at 3.10 degrees ± 2.37. Although deviations were observed, the results demonstrate the feasibility and the potential for such guides during EMS procedures. [ABSTRACT FROM AUTHOR]

Additive manufactured (AM) metals are attractive materials for medical implants, as their geometries are directly produced from computer-aided design (CAD)/computer-aided manufacturing (CAM) data. However, the fatigue properties of AM metals are weak compared with bulk metals, which is an obstacle to the practical applications of AM metals. To improve the fatigue properties of AM metals, we developed a mechanical surface treatment using laser cavitation. When we irradiate a pulsed laser to a metallic surface in water, laser ablation is generated, and a bubble that behaves like a cavitation is produced. The bubble is referred to as a "laser cavitation". In the surface treatment using laser cavitation, we use the plastic deformation caused by the impact force at the bubble collapse and pulsed laser energy that produces local melting at the same time. Thus, the mechanical surface treatment using laser cavitation is a type of surface mechanical alloying. In this study, to demonstrate the improvement in the fatigue properties of AM metals, we treated titanium alloy Ti6Al4V, which was manufactured by direct metal laser sintering (DMLS), with laser cavitation, and we evaluated the surface morphology, roughness, residual stress, hardness, and finally tested it using a torsion fatigue test. Unmelted particles on the DMLS surface, which cause fatigue cracks, were melted and resolidified using laser cavitation, resulting in a reduction of the maximum heights of roughness (Rz) of about 75% and the arithmetical mean roughness (Ra) of about 84% of the non-peened one. Although tensile residual stresses of about 80–180 MPa were generated on the as-built surface, compressive residual stresses of about −80 MPa were introduced by laser cavitation. Furthermore, laser cavitation formed Ti4O5 oxide film, which increased the surface hardness by about 106%. Finally, we performed torsional fatigue tests and revealed that laser cavitation extended the fatigue life from 19,791 cycles to 36,288 cycles at an applied shear stress (τa) at 460 MPa, which is effective in suppressing crack initiation. [ABSTRACT FROM AUTHOR]

Lattice structure topology is a rapidly growing area of research facilitated by developments in additive manufacturing. These low-density structures are particularly promising for their medical applications. However, predicting their performance becomes a challenging factor in their use. In this article, four lattice topologies are explored for their suitability as implants for the replacement of segmental bone defects. The study introduces a unit-cell concept for designing and manufacturing four lattice structures, BCC, FCC, AUX, and ORG, using direct melt laser sintering (DMLS). The elastic modulus was assessed using an axial compression strength test and validated using linear static FEA simulation. The outcomes of the simulation revealed the disparity between the unit cell and the entire lattice in the cases of BCC, FCC, and AUX, while the unit-cell concept of the full lattice structure was successful in ORG. Measurements of energy absorption obtained from the compression testing revealed that the ORG lattice had the highest absorbed energy (350 J) compared with the others. The observed failure modes indicated a sudden collapsing pattern during the compression test in the cases of BCC and FCC designs, while our inspired ORG and AUX lattices outperformed the others in terms of their structural integrity under identical loading conditions. [ABSTRACT FROM AUTHOR]

This work presents the multi-objective optimization results of three experimental cases involving the laser sintering/melting operation and obtained by a virus evolutionary genetic algorithm. From these three experimental cases, the first one is formulated as a single-objective optimization problem aimed at maximizing the density of Ti6Al4V specimens, with layer thickness, linear energy density, hatching space and scanning strategy as the independent process parameters. The second one refers to the formulation of a two-objective optimization problem aimed at maximizing both the hardness and tensile strength of Ti6Al4V samples, with laser power, scanning speed, hatch spacing, scan pattern angle and heat treatment temperature as the independent process parameters. Finally, the third case deals with the formulation of a three-objective optimization problem aimed at minimizing mean surface roughness, while maximizing the density and hardness of laser-melted L316 stainless steel powder. The results obtained by the proposed algorithm are statistically compared to those obtained by the Greywolf (GWO), Multi-verse (MVO), Antlion (ALO), and dragonfly (DA) algorithms. Algorithm-specific parameters for all the algorithms including those of the virus-evolutionary genetic algorithm were examined by performing systematic response surface experiments to find the beneficial settings and perform comparisons under equal terms. The results have shown that the virus-evolutionary genetic algorithm is superior to the heuristics that were tested, at least on the basis of evaluating regression models as fitness functions. [ABSTRACT FROM AUTHOR]

The possibility of producing spherical titanium powders by application of the technology of plasma-arc atomization of compact current-conducting Ti wire of Grade 2 of 1.6 mm diameter was experimentally confirmed. Analysis of granulometric composition of the powder showed that the main fraction of the powder is 25…250 μm, making up 95 % of the total powder volume, quantity of particles of <25 μm and 250…315 μm fractions not exceeding 5 %. Parameters of the titanium powder shape were studied. It was shown that the majority of the particles are of a regular spherical shape with sphericity coefficient close to 0.8. The quantity of defective particles is not more than 3 % of the total weight of the powder. It was found that atomization by the wire-anode scheme leads to a considerable increase of wire heating efficiency (by approximately 4 times), compared to the scheme of atomization of neutral wire, which promotes an increase of process efficiency from 2…5 to 12 kg/h. It is shown that application of the technology of plasma-arc spheroidizing of the titanium wire allows producing spherical powders for 3D printing of high-quality products for the aerospace industry by the technologies of selective and direct laser melting and sintering and by the methods of powder (granulated) metallurgy (hot isostatic pressing with subsequent thermomechanical treatment). Ref. 21, Tabl. 2, Fig. 6. [ABSTRACT FROM AUTHOR]

In this work, we propose a capillarity-promoted laser re-sintering method of printed semisolid Cu nanoparticles for facile fabrication of conductive patterns with voidless structure and improved conductivity. Conductive circuits with a thickness of 5 μm are fabricated. By using a semisolid Cu particle paste instead of a dry paste, a more compact sintered structure is obtained, and the resistivity is reduced from 18 to 9.2 μΩ cm. Thermal diffusion tests reveal that the semisolid paste exhibits a much higher thermal diffusion coefficient (∼7 × 10−6 m2/s) than the dry paste (∼3 × 10−6 m2/s). Through four repeated laser scannings, the fully sintered layer on the upper surface of the circuits thickens and transits into a solid structure without internal voids. The resistivity is further reduced to 3.8 μΩ cm, which is only two times that of bulk copper. The capillary phenomena of the semisolid paste also promotes the closure of large-scale voids. These effects drive the improvement of the properties and formable thickness of the sintered circuits. These findings could provide new experimental basis for structure and property modifications of printed circuits by similar techniques.

[Display omitted] • Transforming large/long steel sections into small/short damage-controlled elements (DCE) through metal additive manufacturing (AM). • Optimization is performed to obtain the same tensile and compressive strength between AM DCE and steel sections. • DCE is additively manufactured using the powder bed fusion-direct metal laser sintering using 17-4PH stainless steel. • Additively manufactured DCE is experimentally tested and numerically modeled with good result agreement. • A parametric study is conducted to transform different structural steel sections into damage-controlled elements. This paper develops hybrid steel members by integrating additively manufactured, ultra-lightweight, damage-controlled elements (DCEs) into hot-rolled structural steel members. This approach relies on segmenting a structural member into distinct sections; one or two segments are enlarged to be capacity protected; however, another end or middle DCE segment is optimized to emulate the conventional member's strength and stiffness. A small-scale DCE was topologically optimized and then additively manufactured using a powder bed fusion technique through a direct metal laser sintering process of 17-4PH stainless steel and then was experimentally tested to study the buckling behavior under compression. The experimental testing of the optimized DCE shows a compressive strength of 81,000 times the specimen's weight with stable post-peak buckling behavior. Numerical simulation confirms experimental results, showing a good correlation in fracture energy. A parametric study on four DCE specimens, scaled up by three, four, five, and six times, was performed and compared to hollow structural sections (HSS) of A500 Gr. C in tensile and compression strengths. The numerical simulation shows a linear relation between the weight ratio and HSS length. Additionally, numerical simulation of conventional member, DCE (scaled by three), and three hybrid members revealed that failure occurred in DCE as intended. [ABSTRACT FROM AUTHOR]

The article is a message from the Editor-in-Chief of the SAMPE Journal, Norman M. Wereley. He discusses his recent attendance at the SAMPE Europe Conference in Belfast, where technical presentations and exhibitions were held at the Titanic Museum. The conference included over 120 oral and poster presentations on various topics in materials and process engineering. The Editor-in-Chief also highlights the SAMPE Europe University Research Symposium, where he served as a judge for the student paper competition. The rest of the article mentions the six articles in the current issue of the SAMPE Journal, which focus on automotive and aerospace composites. The articles cover topics such as polypropylene-paper composites, high-rate thermoplastic composites, laser sintering of thermoplastic polymer composites, forming of thermoplastic sandwich structures, high throughput over-molding manufacturing process, and innovative liquid crystal composites. The Editor-in-Chief encourages readers to cite these papers in their future research and mentions that the SAMPE Journal has transitioned to a web-based editorial process. [Extracted from the article]

Selective laser sintering (SLS) of copper components manufactured via powder metallurgy is widely studied due to minimal material wastage. However, copper has poor optical absorption when exposed to infrared (IR) lasers, such as in laser-based additive manufacturing or laser surface processing. To address this issue, an innovative approach to enhance the optical absorption of copper powders during infrared laser sintering is presented in this study. Carbon nanotubes (CNTs) have several unique properties, including their high surface area, plasmonic response, excellent conductivity, and optical absorption properties. CNTs were mixed with copper powders at different weight percentages using an acoustic method. The resulting Cu-CNT compositions were fabricated into pellets. The Box-Behnken Design of Experiments methodology was used to optimize the IR laser processing conditions for sintering. Spectroscopic analysis was conducted to evaluate the reflection and thermal absorption of the IR wavelengths by the Cu-CNT composites. Density and hardness measurements were taken for the laser-sintered Cu-CNT pellets. The coating of copper powders with CNTs demonstrated enhanced optical absorption and correspondingly reduced reflection. Due to the enhanced optical absorption, increased control and sensitivity of the laser sintering process was achieved, which enabled improvement in the mechanical properties of strength, hardness, and density, while also enabling control over the composite thermal expansion coefficient. A maximum average hardness of 66.5 HV was observed. Indentation test results of the samples revealed maximum tangential and radial stresses of 0.148 MPa and 0.058 Mpa, respectively.

Air compressors are widely used in factories to power automation systems and store energy. Several studies have been conducted on the performance of reciprocating and screw compressors. Advancements in design and manufacturing techniques, such as generative design and topology optimization, are leading to improved performance and turbomachinery growth. This work presents a methodology to design and manufacture air compressor pistons using topology optimization and metal additive manufacturing. The existing piston is converted to 3D CAD data and topology optimization is conducted to reduce material in stress concentration regions. Thermal and mechanical loads are considered in boundary conditions. The results show reduced material and improved efficiency, which is validated using ANSYS fluent. The optimized 3D model of the piston is too complex for conventional subtractive manufacturing, so laser sintering 3D printing is proposed. Honeycomb pattern infill patterns are used in 3D printing. This investigation is a step toward researching similar methods in other reciprocating compressor components such as cylinder, cylinder head, piston pins, crankshaft, and connecting rods, which will ultimately lead to improved compressor efficiency.

Prosthetic rehabilitation takes place in the final stage of complete care of a patient born with a cleft lip and palate. Due to the prosthetic rehabilitation, in addition to the restored chewing function, the patient’s voice formation, speech, as well as his social integration and social relations, could improve further. A new denture can also reduce the patient’s mental problems mainly caused by his/her appearance. As a result, at the end of a long, complex care, a child born with a developmental disorder can live a nearly full adult life. In prosthetic rehabilitation, there are several problems, such as difficult occlusion (crossbite, open bite, Angle III class, pillar teeth with different axial positions etc.), narrowed vestibulum caused by the scarring of the area due to the restorative surgeries, or lack of continuity of the alveolar process. In such cases, for the more precise design and construction, the use of CAD/CAM procedure is a great help: dentures can be planned and seen, and thus, fit well from biomechanical, hygienic, and aesthetic perspectives, despite the individual soft tissue conditions.

Lattice-type periodic metamaterials with beam-like struts have been extensively investigated in recent years thanks to the progress in additive manufacturing technologies. However, when lattice structures are subject to large deformations, computational simulation for design and optimization remains a major challenge due to complex nonlinear and inelastic effects, such as instabilities, contacts, rate-dependence, plasticity, or damage. In this contribution, we demonstrate for the first time the efficient and accurate computational simulation of beam lattices using a finite deformation 3D beam formulation with inelastic material behavior, instability analysis, and contacts. In particular, the constitutive model captures elasto-visco-plasticity with damage/softening from the Mullins effect. Thus, the formulation can be applied to the modeling of both stiffer metallic and more flexible polymeric materials. The approach is demonstrated and experimentally validated in application to additively manufactured lattice structures made from Polyamide 12 by laser sintering and from a highly viscous polymer by vat photopolymerization. For compression tests executed until densification or with unloading and at different rates, the beam simulations are in very good agreement with experiments. These results strongly indicate that the consideration of all nonlinear and inelastic effects is crucial to accurately model the finite deformation behavior of lattice structures. It can be concluded that this can be effectively attained using inelastic beam models, which opens the perspective for simulation-based design and optimization of lattices for practical applications.

Nature's systems have evolved over a long period to operate efficiently, and this provides hints for metal nanoparticle synthesis, including the enhancement, efficient generation, and transport of electrons toward metal ions for nanoparticle synthesis. The organic material-based ink composed of the natural materials used in this study requires low laser power for sintering compared to conventional nanoparticle ink sintering. This suggests applicability in various and sophisticated pattern fabrication applications without incurring substrate damage. An efficient electron transfer mechanism between amino acids (e.g., tryptophan) enables silver patterning on flexible polymer substrates (e.g., PET) by laser-direct writing. The reduction of silver ions to nanoparticles was induced and sintered by simultaneous photo/thermalchemical reactions on substrates. Furthermore, it was possible to fabricate a stable, transparent, and flexible heater that operates under mechanical deformation. [ABSTRACT FROM AUTHOR]

This research study combines surface modification techniques with back‐end‐of‐line (BEOL) methods for cost‐effective, scalable front contact electrode deposition on III–V solar cells. Copper nanoparticle grids are deposited by inkjet printing on surface‐modified III–V solar cells. The deposition of a self‐assembled monolayer (such as 1,8‐octanedithiol) as an intermediate layer is a proven method for surface modification to improve the wettability of the substrate surface and the adhesion of the printed copper nanoparticle structures on the substrate to perform inkjet printing of coherent and narrow electrode structures. Then, the printed copper ink is converted to a conductive copper grid by a picosecond pulsed laser with optimized settings and an additional galvanic plating step is required for the thickening of inkjet‐printed and laser‐sintered seeding layer for solar cell applications. As a result, an ohmic copper contact on III–V layer with low contact resistivity (5 mΩ cm2) is realized successfully. The processed solar cell shows a functioning behavior with 20% conversion efficiency. [ABSTRACT FROM AUTHOR]

Direct application of TiO 2 nanopowder in water remediation is hindered due to sophisticated separation of the photocatalyst. Therefore, alternative partially crystallized porous glass based photocatalysts were prepared on the basis of combined phase separation and partial crystallization of 55.4SiO 2 –23B 2 O 3 –7Na 2 O-14.6TiO 2 (mol.-%) initial glass composition followed by selective leaching. The advantage of this glass composition is that, 3-D shaping is possible via selective laser sintering technique. Therefore, various macroscopic shapes were fabricated via selective laser sintering and conventional techniques and their resulting properties and photocatalytic activities were compared. Selective laser sintered glasses contain slightly less content of anatase phase due to formation of rutile during sintering process as opposed to conventional glasses. Textural properties are similar in both selective laser sintered and conventional shaped glasses which indicate similar phase separation mechanism and microstructure. In terms of macroscopic shapes, photocatalytic activity increases in the order: monolith < granulate < "macropowder" due to increase in the surface area to volume ratio. The photocatalytic activity is mainly determined by the amount of the anatase phase, thus conventional glasses exhibit slightly higher activity than selective laser sintered glasses. [Display omitted] [ABSTRACT FROM AUTHOR]

The material constriction is one of the important factors that influence the forming accuracy of selective laser sintering (SLS). Currently, in order to reduce the shrinkage and improve the quality of products, the optimal combination of machining process parameters is mainly determined by numerous experiments. This often takes valuable time and costs a lot, but the results are mediocre. With the development of intelligent optimization algorithms, they are applied in various disciplines for solving complex problems. Hence, for reducing the shrinkage of parts and overcoming the limitation in the optimization of the process parameters, this paper proposes a novel hybrid improved Hunger Games Search algorithm (HGS) with extreme learning machine (ELM) model for predicting the shrinkage of parts. Firstly, the orthogonal experiments were conducted based on the five key process parameters, the obtained parts datasets were divided into the training set and test set. Secondly, the Cube mapping and refracted opposition-based learning strategies are adopted to increase the convergence speed and solution accuracy of HGS. In addition, the regression prediction model was constructed with the improved HGS(IHGS) and ELM, and this model is trained using the training set. Finally, the test set is used to evaluate the trained model and find the optimal combination of process parameters with the lowest shrinkage of parts. The experimental results suggest that the IHGS-ELM model proposed in this study has high forecasting precision, with the R2 and RMSE are only 0.9124 and 0.2433, respectively. This model can guide the laser sintering process of polyether sulfone (PES) powder. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D)-printed electronic technology is considered to have great potential as it can be utilized to make electronic products with complex 3D shapes. In this study, based on a 3D printer with single UV laser equipment, we continuously performed photo-polymerization (PP) and selective metal powder sintering to fabricate a conductive pattern. For this, 3D structures were printed at a low energy using a 355 nm DPSS laser with a galvanometer scanner, which are widely used in PP-type 3D printing, and then the selective sintering of metal powders was performed with a high energy. In order to obtain a high-conductivity pattern by laser sintering, a circuit pattern that could actually be operated was fabricated by experimenting with various condition changes from mixing the metal composite resin to the laser process. As a result, it was found that the optimal result was to irradiate a 0.8 W UV laser with a beam spot size of 50 µm to 50 vol% aluminum composite resin. At this time, an optimal conductive pattern with a resistance of 0.33 Ω∙cm−1 was obtained by setting the pulse repetition rate, scan path interval, and scanning speed to 90 kHz, 10 μm, and 50 mm/s, respectively. This suggested process may be of great help in the manufacturing of practical 3D sensors or functional products in the future. [ABSTRACT FROM AUTHOR]

Owing to its high melting point, limestone powder cannot be directly used to fabricate parts through laser sintering. To address this issue, a polyethersulfone (PES)-based polymer matrix composite material, in which PES serves as a binder between particles of limestone powder, is introduced to prepare composite artificial stone parts using the selective laser sintering technology. Preliminary single-factor experiments were conducted for sintered limestone/PES (LPES) composite parts with different component ratios (R), laser sintering power (P), and powder bed preheating temperature (T) to determine the range of test parameters. Subsequently, using the laser power (x1), scanning speed (x2), scan spacing (x3), and layer thickness (x4) as experimental factors and the impact strength (y1) and dimensional accuracy along X, Y, and Z directions, respectively (y2, y3, and y4), of impact sintered parts as experimental indices, a four-factor three-level orthogonal experiment was conducted for optimization. The optimal combination of parameters affecting the multiobjective function within the tested range was obtained: laser power (15 W), scanning speed (1800 mm/s), scan spacing (0.1 mm), and layer thickness (0.1 mm). For this optimal combination, the sintered LPES model possesses an impact strength of 170.69 MPa and dimensional accuracies of 98.29% along the X direction, 97.36% along the Y direction, and 92.81% along the Z direction. Compared with a pure PES specimen, the impact strength was improved by 42.89%, and the dimensional accuracy was improved by 0.91% along the X direction, 1.23% along the Y direction, and 3.43% along the Z direction. [ABSTRACT FROM AUTHOR]

Despite extensive research, new plastic powders must still be qualified for laser-based powder bed fusion using trial and error. Furthermore, part properties such as mechanical properties, surface roughness, or density exhibit a comparatively low reproducibility. Recent progress in the field of process monitoring, however, indicates that infrared thermography can be used to correlate melt pool temperatures with the resulting part properties. The analysis of the influence of process parameters on the resulting melt pool temperatures has up until now been limited to the evaluation of the maximum temperature during exposure and the mean temperature at arbitrary moments after exposure. However, the cooling rate of the polymer melt is also essential. To prove this hypothesis, a continuous data stream, which enables an automated calculation of characteristic processing times and temperatures, is introduced within the scope of this work. Single-layer specimens are manufactured with various energy inputs, while the resulting temperature of the melt is recorded using thermal imaging. The peak temperatures are combined with the characteristics that describe the temperature decay after exposure, such as a decay time determined at a specific cooling rate. These metrics quantify the cooling behavior of melt pools in a systematic and reproducible way. Furthermore, the sequence of decay values at different cooling rates can potentially be combined with existing process knowledge to differentiate process regimes. The presented approach can be used to create a more in-depth process understanding in later works, thereby enabling applications such as in-situ quality assurance. [ABSTRACT FROM AUTHOR]

Starting from Quartz-Enhanced Photo-Acoustic Spectroscopy (QEPAS), we have explored the potential of a tightly linked method of gas/vapor sensing, from now on referred to as Tuning-Fork-Enhanced Photo-Acoustic Spectroscopy (TFEPAS). TFEPAS utilizes a non-piezoelectric metal or dielectric tuning fork to transduce the photoacoustic excitation and an optical interferometric readout to measure the amplitude of the tuning fork vibration. In particular, we have devised a solution based on Additive Manufacturing (AM) for the Absorption Detection Module (ADM). The novelty of our solution is that the ADM is entirely built monolithically by Micro-Metal Laser Sintering (MMLS) or other AM techniques to achieve easier and more cost-effective customization, extreme miniaturization of internal volumes, automatic alignment of the tuning fork with the acoustic micro-resonators, and operation at high temperature. This paper reports on preliminary experimental results achieved with ammonia at parts-per-million concentration in nitrogen to demonstrate the feasibility of the proposed solution. Prospectively, the proposed TFEPAS solution appears particularly suited for hyphenation to micro-Gas Chromatography and for the analysis of complex solid and liquid traces samples, including compounds with low volatility such as illicit drugs, explosives, and persistent chemical warfare agents. [ABSTRACT FROM AUTHOR]

Printed magnetic field sensors enable a new generation of human‐machine interfaces and contactless switches for resource‐efficient printed interactive electronics. As printed magnetoresistors rely on scarce or hard to manufacture magnetosensitive powders, their scalability and demonstration of printing with industry‐grade technologies are the key material science challenges. Here, the authors report dispenser printing of a commodity scale nonmagnetic bismuth‐based paste processed by large area laser sintering to obtain printed magnetoresistive sensors. The sensors are printed on different substrates including ceramics, paper, and polymer foils. It is validated experimentally that the peculiar quantum large orbital magnetoresistive effect remains effective in printed bismuth sensors, allowing their operation in high magnetic fields. The sensors reveal up to 146% resistance change at 5 T at room temperature with a maximum resolution of 2.8 μT. If printed on flexible foils, these sensors show resilience to bending deformation for more than 2000 bending cycles and withstand even thermal forming, as relevant for smart wearables and in‐mold electronics. The freedom in the substrate choice and sensor design enabled by dispenser printing allows to implement the proposed sensor technology for different applications focused on touchless interactive platforms, such as advertisement materials, interactive wallpapers, and printed security panels. [ABSTRACT FROM AUTHOR]

Inorganic solid electrolytes are the most important component for realizing all-solid-state batteries with lithium metal anodes and enable safe battery cells with high energy densities. Their synthesis and processing are the subject of current research, especially the NASICON-type Li1+xAlxTi2-x(PO4)3 (LATP). Herein, the ability of sintering with electro-magnetic irradiation is investigated and correlated with different properties of prepared LATP pellets. First of all, an infrared camera records the temperature of the surface during the treatment. Second, the effect of the pulse fluence is investigated in terms of the topology and morphology of the pellets. Here, the arithmetic surface roughness Ra is the main parameter. Then, the depth of the radiation interaction in the pellet is measured. The focus of this paper is on the different pulse widths of the laser sources, and therefore, similar pulse and hatch overlap ensure equivalent areal energy input in both cases. As a summarized result, treatment with a shorter pulse width generates high peak pulse powers, resulting in higher temperatures, rougher surfaces and affecting deeper layers of the pellets compared to treatment with longer pulse width. On the contrary, excessive power leads to the ablation of the material up to destruction. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is a niche process that has seen extensive growth and adoption in the past decade in the industrial sector. Among the AM techniques present on the market today there are identified only a few methods allowing the 3D printing of metallic materials to be of special interest for their applications in various domains like the automotive, aeronautical, and healthcare industries. The most important questions needing answers are how to produce components from metallic materials that have superior qualities like versatility, wear resistance, ease of customization, and ease of integration with existing components. Compared to traditional metalworking methods where it has been studied how the metal behaves and morphs during the process and where it is known exactly what to do in order to modify the properties of the resulting component into a favor metal, AM changes everything, forcing a researcher to start from the beginning. While the technology is starting to be used more and more, the need to find production methods leads to consistent quality products and with outstanding material properties. New methods need to be developed to help attune the properties of the 3D printed parts to the requirements of their respective uses. The present study refers to 3D metal additive manufacturing (MAM), providing an overview on the process itself and its possible results as well as hurdles with added methods to overcome them. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM), also known as 3D printing, is associated with significant promise in the manufacturing sector. However, it has been shown that the risk of build failure has a substantial impact on the costs of AM and that this results from a relatively high level of process instability. Importantly, for such a promising technology, the effects of the risk of build failure on energy consumption have not yet been studied, which creates a significant gap in the knowledge of the real environmental performance of AM. This research addresses this gap by investigating the energy consumption of AM subject to the possibility of build failure. This is done by constructing a novel expected energy consumption model, integrating process energy consumption, the energy embedded in the raw material, and the probability of build failure as a function of the number of layers deposited. Model parameters are obtained from a series of build experiments conducted on the AM technology variant polymeric laser sintering, also known as laser powder bed fusion of polymers. The energy consumption model shows that the risk of build failure accounts for a substantial share of overall expected energy consumption, amounting to up to approximately 31% at full capacity utilization. Additionally, this paper uncovers a complex relationship between the risk of build failure and efficiency gains in per unit energy consumption resulting from increasing levels of capacity utilization (Supporting Information S1). [ABSTRACT FROM AUTHOR]

With the development of additive manufacturing technology, the quantity of devices that can be used in small office with the commercial or educational purposes increases. In this research, the goal is to build a desktop 3D printer with selective laser sintering technology, which can be used for research purposes. The main concentration is focused on fabrication with parts that can be manufactured in the country or can be procured from the domestic market. It is also tried to make the 3D printer compatible with the common open-source additive manufacturing softwares. The fabricated 3D printer has the ability to work with all kinds of common polymer powders. In addition, it is easy to update the device's firmware according to the researcher's needs. The capabilities of the device was tested with Glucose powder, paraffin wax powder, and thermoplastic-ceramic material combinations. It is currently used for research on fabricating ceramic parts with indirect laser sintering. [ABSTRACT FROM AUTHOR]

This study demonstrates the use of nanoparticles prepared by a gas aggregation source for fabricating structures by combining laser sintering and ablation. At first, the morphology and optical properties of prepared nanoparticle coatings were characterized. Then, the response of coatings to laser irradiation at different powers or exposure times was studied by in situ time-of-flight mass spectrometry, followed by scanning electron microscopy measurements of the resulting structures. By comparing the numbers of detected Ag ions, that were ablated and desorbed, with changes in morphology after irradiation, the optimum conditions for laser sintering and ablation of Ag nanoparticle coatings were found. As a proof of concept we fabricated micromirrors from sintered metal, microwires from both sintered metal and interconnected nanoparticles, and arbitrary metallic bulky or nanoparticle patterns. Vacuum compatibility and the possibility of fabrication of both metallic and nanoparticle structures in one step predetermines applications of developed method in electronics or sensing.

Selective laser sintering (SLS) process is the most perfect seven three-dimensional printing processes that produces three-dimensional parts from a polyamide or metal powders in stratified, the need of this process is in all different fields, the medical field, art, aerospace and other industries. The thermal phenomena generated by SLS is essential to analysis the microstructure, mechanical properties, residual stress, and all deformation of produced parts. This study applied three-dimensional element finite (EF) method by COMSOL Multiphysics software to investigate the temperature evolution in SLS. The surface heat source and the dependence of material properties on temperature are considered. It is found that the developed element finite (EF) method is able to capture the high gradients of temperature in the center of the spot laser of polyamide powder 12 (heat affected zoon). The effects of physical proprieties and laser parameters are also investigated, it was observed in the polyamide 12 powder bed, the temperature increase with the increase of pre-heating temperature and also with increasing the power laser which sintered the polyamide powder bed, the temperature increases. Also, this simulation helps us to control all the parameters and optimize the SLS process of polyamide 12, to make a perfect polyamide part manufactured by this machine with excellent quality.

Laser sintering of polymers (LS) is one of the most promising additive manufacturing technologies as it allows for the fabrication of complexly structured parts with high mechanical properties without requiring additional supporting structures. Semi-crystalline thermoplastics, which are preferably used in LS, need to be processed within a certain surface temperature range enabling the simultaneous presence of the material in both, the molten and solid state. In accordance with the most common processing models, these high temperatures are held throughout the entire building phase. In the state of the art, this leads to high cooling times and delayed component availability.In this paper, process-adapted methods, in-situ experiments and numerical simulations were carried out in order to prove that this drawback can be overcome by material-adapted processing strategies based on a deepened model understanding. These strategies base on the fact, that the crystallization and solidification of polyamide 12 is initiated a few layers below the powder bed surface at high temperature and quasi-isothermic processing conditions. Therefore, isothermal crystallization and consolidation behaviour is analyzed by process-adapted material characterization. The influence of temperature fields during laser processing was analyzed in dependence of part cross-section, layer number and fabrication parameters and correlated to the resulting part properties. Furthermore, the possibility to homogenize the parts thermal history by controlling the part cooling is highlighted by a simulational approach. The authors show that the material-dependent solidification behavior must be taken into account as a function of the geometry- and layer-dependent temperature fields and demonstrate a major influence on the material and component properties. From these findings, new processing strategies for the laser exposure process as well as for the temperature control of the build chamber in z-direction arise, which allow for the acceleration of the LS process and earlier availability of components with more uniform part properties.