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Abstract In the realm of materials science and engineering, the pursuit of advanced materials with tailored properties has been a driving goal behind technological progress. Scientific interest in laser powder bed fusion (L-PBF) fabricated NiTi alloy has in recent times seen an upsurge of activity. In this study, we investigate the impact of varying volume energy density (VED) during L-PBF on the microstructure and corrosion behaviour of NiTi alloys in both scan (XY) and built (XZ) planes. The microstructural evolution in both planes was characterized by electron backscatter diffraction and phase change temperatures were characterized using differential scanning calorimeter measurements. Electrochemical experiments were carried out to compare the specimens produced at high laser energy density and low laser energy density. The results indicate that employing high laser energy density in the production of NiTi alloy induces discontinuous dynamic recrystallization, contributing to grain refinement. This in turn enhances the corrosion resistance of the specimen. X-ray photoelectron spectroscopy was employed to examine the type of oxide layer that developed on the samples. The increased resistance to corrosion in a high laser energy density sample can be associated with the formation of a stable and homogeneous passive layer with enriched TiO2 as opposed to Ti2O3. This exploration has unravelled the intricate relationship between VED, the microstructure, and the corrosion properties of L-PBF fabricated NiTi alloys, offering valuable insights into their performance for diverse applications.

This study aimed to provide a comprehensive understanding of how aging treatments (namely, HT1 and HT2) affect the microstructure, cracking behavior, and crystallographic texture of IN939 fabricated by powder bed fusion-laser beam (PBF-LB) method. Although both aged samples demonstrated similar grain structure and recrystallization behavior according to the electron backscatter diffraction (EBSD) analysis, as well as the precipitation of bimodal γ′ phase and MC- and M23C6-type carbides, notable differences were observed in the size and morphology, particularly the γ′ phase. The HT1 sample displayed coarsened primary γ′ phase, with sizes reaching up to 2 μm and exhibiting varied morphologies, including irregular and cuboidal shapes. Additionally, this treatment led to the formation of some γ′-γ eutectic regions and plate-like η phase, along with the decomposition of MC-type carbides into M23C6-type carbides. In contrast, the HT2 sample displayed uniformly distributed spherical primary γ′ phase with sizes ranging from 70 to 120 nm, accompanied by very fine secondary γ′ phase. Furthermore, it was found that changes in both aged sample microstructures could result in the formation of strain-age cracks due to the γ′ phase formation and liquation cracks due to the partial remelting of lower melting point phases. The findings also revealed that with the application of aging treatments, the hardness of the as-fabricated sample (339.8 ± 3.4 HV) increased to 440.2 ± 5.6 HV and 508.1 ± 4.8 HV for the heat treatment of HT1 and HT2, respectively.

This study provides a comprehensive investigation into the effects of different scanning strategies on the material properties of IN939 fabricated using the PBF-LB process. The scanning strategies examined included alternating bi-directional scanning with rotation angles of 0°, 45°, 67°, and 90° between adjacent layers (named as shown), as well as alternating chessboard scanning with rotation angles of 67° and 90° (named as Q67° and Q90°). The results revealed that the 45° and 67° samples had the highest relative density, while the 0° and Q67° samples showed the highest average porosity. Moreover, various types of cracks, including solidification, solid-state, and oxide-induced cracks, were observed. Among the bi-directional scan samples, the 0° sample displayed the most extensive cracking and the highest σmax residual stress values in both XZ and XY planes. Conversely, the 45° and 67° samples exhibited fewer cracks. Notably, the lowest σmax residual stress in the XZ planes among the bi-directional scan samples was observed in the 67° sample. Additionally, microstructural analyses indicated differences in grain size and morphology, among the samples. Texture analysis indicated that the 0° and 90° samples exhibited strong cube textures, whereas the texture intensity weakened for the 45° and 67° samples. Moreover, the alternating chessboard scanning strategy led to rougher surfaces (higher Sa and Sz values) compared to the alternating bi-directional scanning strategy, regardless of the rotation angles. Furthermore, the microhardness values among the samples showed minimal variance, ranging between 321 ± 14 HV and 356± 7 HV.

One potentially useful technique for producing NiTi intermetallic components is the laser powder bed fusion (LPBF). However, due to the deterioration of the mechanical qualities, other defects including the poor surface quality and the near surface porosity that are inherent to the process are restricting the technology's standardisation and broad use. This study employed a thorough investigation to use laser polishing of additively manufactured samples made from pre-alloyed NiTi powder by LPBF to enhance the surface quality and remove the near surface porosity. The use of laser polishing technique on the LPBF parts is preferred because it eliminates or reduces the amount of material removal through remelting and relocation of material from the high peaks to the lower valleys. Two types of laser systems carbon-dioxide (CO2) and femtosecond were used to process the surface and near-surface area. The optimum results for porosity healing have been found when using the CO2 laser power of 75 W, scanning speed of 11 mm/s and an input energy density of 34 J/mm2 and laser spot size of 200 μm. An improvement in the average surface roughness of 91 % was achieved when the CO2 laser beam was used. The X-ray test results showed slight intensity change for the samples polished by the CO2 laser. In contrast, a phase change was observed on the surface of the samples polished by the femtosecond laser due to the formation of oxide layer. Also, limited improvement in the surface quality was obtained when the femtosecond laser irradiation was used.

Elastocaloric Ni-Ti alloys offer solid-state heat pump and cooling applications. The environmental impact of elastocaloric Ni-Ti parts manufactured via powder bed fusion was assessed using life cycle assessment with the ReCiPe method. These solid-state heat pumps can mitigate the environmental impacts of current air conditioning/refrigeration methods that use harmful chemicals like CFCs, HCFCs, and HFCs. Measurements of electricity, Ar gas, and compressed air consumption were considered within the gate-to-gate boundary, covering powder transportation, printing, and use-phase. Nickel was identified as the most damaging input, reducible through geometry optimization. Optimized geometries (given the same number of printing layers) require more energy during powder bed fusion however, the environmental benefit from material saving outweighs the damage from increased electrical usage by far. The powder bed fusion machine's standby mode consumes more energy and Ar gas than the printing process, presenting an opportunity for mitigation. Additively manufactured Ni-Ti elastocaloric structures were used as heat generators/sinks in flowing water during compression cycles, achieving 11 °C and 10 °C water temperature change per cycle for the solid geometry and the optimized geometry respectively. A 10 x 10 × 55 mm Ni-Ti structure, providing >2 °C temperature span under compressive cycles, served as the functional unit.

This paper examines the effect of ageing temperatures (400, 500, & 600 °C) and times (30, 60, & 90 min) on Ni-rich NiTi samples produced via the Laser Powder Bed Fusion (L-PBF) technique. Variations in the process parameters of the L-PBF which were examined included laser power at 150W and 180W, and the scanning strategy at 500 mm/s and 1000 mm/s. Ageing heat treatment enabled setting the functional properties of phase change temperatures, stress-strain response, and phase change enthalpies. Samples aged at 400 °C were found to have much higher austenitic finish temperature (40–60 °C) whereas those aged at 600 °C had near-zero or sub-zero Af temperatures. This was due to the lower nickel concentration resulting from the higher heat treatment temperature. Samples heat-treated at 500 °C exhibited Af temperature which was near to the room temperature and showed co-existence of both austenitic and martensitic phases. It was also found that the crystallite size increased from 6 to 22 nm for an ageing temperature of 400 °C, to between 38 and 48 nm for an ageing temperature of 600 °C. The highest microhardness value of 380HV was recorded from the lower heat treatment temperature and the lowest microhardness of 270HV was recorded for samples heat-treated at 600 °C. This decrease in the microhardness values is attributed to the increased crystallite size of the aged samples at higher temperatures. This work identifies for the first time the novel ability to control NiTi phase change temperature and mechanical properties using ageing heat treatments which is critical for the materials application for personalised stents. Higher heat treatment temperatures were found to lead to larger crystallite sizes.

This study investigates the greater coefficient of Performance (COP) exhibited by the Ni–Ti lattice geometry (LS) over the solid geometry (SS) for solid-state heating and cooling. The LS's advantageous COP can be attributed to factors including variations in phase transformation behavior, a larger surface area facilitating enhanced heat transfer, and a greater volume of water heated per cycle owing to the cavities. Moreover, the LS demands lower compression forces due to its lower mass and geometry, which contribute to its heightened energy efficiency. Remarkably, the LS achieved a maximum temperature span of 11.2 °C at 40 kN compression force, whereas the SS required 80 kN to attain a similar 12.9 °C span. Both the SS and LS showcased a non-linear correlation with compression force which was attributed to Lauder's transformation and pseudo-elastic behaviors. Additionally, the temperature span of the SS exhibited symmetrical behavior during heating-cooling cycles. Conversely, the LS displayed asymmetry, with a more substantial temperature change during the cooling phase than the heating phase.

Powder characteristics such as flow energy, bulk density, compressibility, morphology, particle size distribution (PSD) and laser energy absorbtivity have a significant impact on the Laser Bed Powder Fusion (L-PBF) process. The impact of powder characteristics on in-situ nickel-titanium alloy formation within the L-PBF process is not well understood. In this work, the characteristics of nickel, titanium and two elemental blends of nickel-titanium powder were compared with those of a pre-alloyed nitinol powder. L-PBF solidification tracks were generated using selected powders and characterised for resulting track dimensions and chemical homogeneity. This study demonstrates that the melt homogenisation time and the size of titanium particles relative to nickel particles are critical factors for successful in-situ alloying of nitinol within the L-PBF process. The variation in elemental composition within solidification track cross sections, as measured by EDX point spectra, was found to increase significantly for laser scanning speeds of 400 mm/s and above. Furthermore, the elemental composition inhomogeneity with increasing laser scan speed was found to be significantly more pronounced for a nickel-titanium powder blend of spherical particles with average titanium particle size of 48 μm compared to an otherwise similar blend with an average titanium particle size of 32 μm. There was no significant difference recorded between solidification track widths of in-situ alloyed blends compared to pre-alloyed blends, indicating that optimal hatch spacing for in-situ alloying is likely to be similar to that required for pre-alloyed powders.

The equiatomic face-centred cubic (FCC) CoNiCrFeMn alloy, known as the Cantor alloy, is renowned for its high ductility under extreme conditions, such as cryogenic temperatures. Despite this, it suffers from low hardness and yield strength (YS) and includes elements with significant supply concerns. This study introduces novel non-equiatomic CoNiCrFeMn alloys, designed using machine learning (ML)-assisted-high-throughput atomistic simulations to enhance sustainability and mechanical properties such as hardness and YS while maintaining the alloy's single-phase FCC structure. We incorporated two critical sustainability indicators, end-of-life recycling rate (EOL−RR) and lifetime (τ), to guide the alloy design process. Mean-flow stress (MFS), measured from the yield point to 15% strain during tensile tests, was used to assess and predict the mechanical properties. Two alloys, with cobalt contents of 12.5% and 21.5%, were developed and analysed. The Co12.5 alloy showed better sustainability (44% improvement in τ with almost the same mechanical properties), while the Co21.5 alloy exhibited better mechanical properties (20% improvement in MFS with almost the same sustainability) as the equiatomic system. Their stable FCC microstructures were confirmed through CALPHAD modelling and X-ray diffraction (XRD) analysis of vacuum arc melted, as-cast samples. The results highlight the potential of integrating sustainability metrics into high-performance alloy design.

This study delves into the corrosion resistance enhancement of stainless steel through laser processing, focusing on the interplay between surface chemistry, morphology, and electrochemical properties. Two sets of 3 × 3 full factorial design of experiment (DoE) designs were employed to explore the influence of laser process parameters, including power, scan speed, frequency, and hatching distance. The findings underscore the superiority of reduced areal energy in producing optimal corrosion resistance 10 times better then unprocessed stainless steel, demonstrating the best results under optimized conditions of a 15 µm hatching distance, 250 mm/s scan speed, 100 kHz frequency, and 80 % power. X-ray Photoelectron Spectroscopy (XPS) analysis reveals the predominant surface composition of iron and chromium oxides, with variations in the oxide combinations correlating closely with areal energy. Depth profiling revealed the transformation of oxide layers and highlights the importance of chromium-to-iron ratio in surface corrosion behaviour. Cyclic polarisation results demonstrate the formation of passive, transpassive, and pitting domains, with metastable pitting observed in some samples. The direct positive correlation recorded between corrosion current and Cr/Fe ratio underscores the significance of oxide composition in corrosion resistance. Electrochemical impedance spectroscopy (EIS) further confirmed the superior corrosion resistance of laser-processed samples to non-laser processed samples, with lower areal energy exhibiting higher resistance compared to higher areal energy. SEM morphology analysis revealed the removal of surface defects and the formation of a protective oxide layer in laser-processed samples, with lower areal energy samples exhibiting the lowest level of surface defects. The 3D optical profilometer measurements of corrosion pits corroborate these findings, with lower areal energy samples demonstrating the lowest pit depth and area, indicating superior corrosion resistance. Overall, this study provides comprehensive insights into optimizing laser processing parameters to enhance the corrosion resistance of stainless steel, offering valuable understanding and strategy for improving the metal surface corrosion resistance.

Abstract Calcia-Magnesia-Alumino Silicate (CMAS) is a form of molten siliceous residue generated at elevated temperatures within aeroengines. CMAS adheres to the surface of thermal barrier coatings (TBCs) and has the potential to cause significant damage to engine components, resulting in TBC failures. The aviation industry has long recognized CMAS as a substantial threat to aircraft engines, and this threat persists today. A substantial amount of research has been carried out, primarily focusing on gaining a fundamental understanding of the degradation mechanism of traditional TBCs manufactured using air plasma spraying (APS) and electron beam physical vapor deposition (EB-PVD) technologies after CMAS attack. A thorough understanding of why CMAS forms, its role in causing severe spallation, and how to prevent it is of significant concern both academically and industrially. This review article provides a detailed examination of the chemistry of CMAS and the resulting degradation mechanisms that the TBC may encounter throughout the aeroengine service life. This article also explores recent research, incorporating case studies, on the impact of CMAS attack on the resulting chemical and structural modifications of the ceramic topcoats. Current strategies designed to mitigate CMAS infiltration and perspectives for enhanced mitigation are discussed.

Screen-printed copper electrodes have the potential to replace silver and lithium electrodes in printed batteries and sensors owing to the abundance of copper, its competitive electrical properties, and the low cost of raw materials. Herein, copper microparticle-glycerol-based inks were screen-printed onto paper to develop highly conductive electrodes. The conductivity and particle connectivity enhancement of screen-printed electrodes are the main research topics. These parameters translate to usability including increased sensitivity for sensor applications and reduced resistivity for battery electrode applications. CuO nanoparticles of 50 nm were deposited onto the electrodes at a concentration of 1 μl/cm2, which led to a 4-fold decrease in sheet resistivity from 200 to 50 Ω/m2. The increased connectivity and formation of new channels due to the addition of nanoparticles were visualised via field emission scanning electron microscopy. The CuO nanoparticles were developed via a hybrid approach incorporating wet chemistry for high yield and laser ablation for colloidal conductivity and Zeta potential enhancement which reached up to −45 mV. An optimal screen-printing viscosity of 62 mPa s was achieved through a precise 1.95:1 mass ratio of Cu microparticles to glycerol. Heat treatment at 100 °C after screen-printing enhanced particle connectivity by reducing glycerol content in the ink.

Abstract This paper presents the development of a model for Nd:YAG laser surface oxidation of 316L stainless steel. A full factorial design of experiments (DOE) are implemented to produce a model for the prediction of elemental composition and color. The elemental composition of the films produced where measured using an X‐ray photoelectron spectroscopic (XPS) and the color is measured using optical reflectance spectroscopy. Oxide layers produced have a Cr/Fe ratio in the range of 0.13–2.09, and highly controllable color variation via single‐pass laser process. The effect of the process parameters used such as power, frequency, and scan speed on laser‐induced oxides is examined with an aim to produce a model suitable for predictive control of the elemental composition and color of the oxide film. Surface morphology control via alteration of the laser power is an important factor for defining the resulting coloration. A new finding from this work is the discovery that within the range of laser surface processing parameters investigated, the molybdenum concentration is inversely proportional to the chromium concentration. This paper provides data required for control of 316L‐SS surface chemistry, and for the expansion of the current thermokinetic model to incorporate the mechanistic effect of molybdenum.

This study examined the effect of variations in the laser power and scan speed for 52.39 at.%Ni-47.61 at.%Ti samples produced via laser powder bed fusion (L-PBF). The laser power was varied between 150W and 180 W, the scanning speeds were varied between 500 mm/s and 1000 mm/s, and other process parameters were kept constant. The resulting microstructures and physical properties of the produced samples were evaluated. In particular, the phase type and phase transformation characteristics, composition, Vickers microhardness, and microstructures were examined. It was observed that variation in the mean microhardness and relative density were not significant at a constant scan speed of 1000 mm/s, regardless of the laser power value. Samples processed at a laser power of 180W (with all other parameters kept constant) exhibited a bimodal micro- and nano structures. It was found that the samples with bimodal microstructure had a higher lattice strain, extent of B2 phase, and higher phase transformation temperatures.

Abstract The advancement of biosensor research has been a primary driving force in the continuing progress of modern medical science. While traditional nanofabrication methods have long been the foundation of biosensor research, recent years have seen a shift in the field of nanofabrication towards laser-based techniques. Here we report a gold-based biosensor, with a limit of detection (LoD) 3.18 µM, developed using environmentally friendly Laser Ablation Synthesis in Liquid (LASiS) and Confined Atmospheric Pulsed-laser (CAP) deposition techniques for the first time. The sensors were able detect a DNA fragment corresponding to the longest unpaired sequence of the c-Myc gene, indicating their potential for detecting such fragments in the ctDNA signature of various cancers. The LoD of the developed novel biosensor highlights its reliability and sensitivity as an analytical platform. The reproducibility of the sensor was examined via the production and testing of 200 sensors with the same fabrication methodology. This work offers a scalable, and green approach to fabricating viable biosensors capable of detecting clinically relevant oncogenic targets.

NiTi is one the metal alloys exhibiting shape memory and superelasticity which makes it suitable for a wide range of engineering and biomedical applications. Nickel-rich NiTi requires heat treatment and cold work as post-processing steps to enable appropriate phase production for final applications. In the current work, NiTi tubes (50.8%Ni-49.2%Ti) produced using Laser Powder Bed Fusion (PBF-LB) and conventional drawing were heat treated at a constant temperature of 500 °C for 10, 30, and 60 min. Differential scanning calorimetry results indicate that the austenite finish temperatures for the tubes were set at 25.4 °C and 26.62 °C after 60 min of heat treatment for the PBF-LB and conventionally drawn tubes respectively. The enthalpy of phase transformation for PBF-LB tubes increased from 2.89 J/g to 17.14 J/g while for conventionally drawn tubes it increased from 5.41 J/g to 16.08 J/g. The EDX measurements on as-built and heat-treated tubes indicated no loss of nickel during the heat-treatment process. The thermal expansion results show an unstable evolution of CTEs in as-built NiTi tubes which were stabilized via heat-treated with resulting CTE ≈11.4 × 10−6/ºC. The hardness decreased in the heat-treated tubes as compared to the as-built tubes. The hardness decreased by 12.6% for PBF-LB and 12.4% for the conventionally drawn tubes respectively.

Utilizing Pulsed Laser Ablation in Liquid (PLAL), we demonstrate a novel route for producing metallic and metalloid nanoinks. 11 nanoinks, incorporating Mg, C, and C–Mg in diverse liquids of isopropyl alcohol (IPA), ethanol, hydrochloric acid, and glycerine were fabricated. Remarkably, metalloid C–Mg nanoinks with 70 nm NP diameter exhibit resistivity below 1 Ohm/square, surpassing constituent Mg or C nanoinks and a commercial graphene nanoink (>390 Ohm/square). Comprehensive characterization via XPS, TEM, SEM, EDX, DLS, and UV–Vis spectroscopy elucidates nanoink attributes. These nanoinks hold promising prospects for nanoink and surface coating applications. Intriguing morphologies including quasi-spherical and rod-shaped carbon NPs, tree-branch-like Mg NPs, and NP colonies with interstitial gaps emerge from SEM images. TEM reveals ultra-small particles (

This study comprehensively examines the effects of ageing temperatures (400, 500, and 600 ᵒC); age-dwelling times (30, 60, and 90 min) and the role of volumetric energy densities (VEDH) of initial processing, on the physical properties of additively manufactured (AM) NiTi samples. Response Surface Modelling (RSM) and curve fitting analysis were employed to establish correlations between the parameters. The samples were processed at different VEDH of 40, 80, and 120 J/mm3 using NiTi (50 at. %) powders via the AM technique of powder bed fusion with a laser beam source (PBF-LB). The melt pool thermal radiation was in-situ monitored using infrared (IR) pyrometers and the collated data post-analysed. Physical properties investigated include microstructure, relative density, composition and phase characteristics, thermal gradient, melt layer temperatures, transformation temperatures, nanohardness and Young's modulus. Mean melt layer temperatures (normalised) increased with VEDH resulting; in all as-built samples being Ti-rich NiTi (>50 at. % Ti), the co-existence of NiTi2, martensite and residual austenite phases, while density was highest in samples processed at VEDH of 80 J/mm3. Ageing at higher temperatures >400 ᵒC for longer dwell times led to recrystallisation and crystallographic re-orientation, but at different degrees depending on the initial thermal history. This recrystallisation effect and initial densities had compounding effects on the observed trends of other examined properties in the aged samples. These findings reveal for the first time, the significant importance of the VEDH of initial processing compared to the ageing temperatures and dwell times.

Metalloid nanoparticles (MNPs) possess unique physicochemical properties but are challenging to create through biological or chemical routes. Using Pulsed Laser Ablation in Liquid (PLAL), Mg–C MNPs are fabricated from powders. The produced nanocolloids were ablated after the target was removed to tailor the particle size. MNPs with a mean size 300 nm could be reduced to 60 nm. Alternatively, MNPs with a mean size of 60 nm could be increased to 90 nm. The increase/decrease in size is controlled by the laser processing parameters and showcases the ability of PLAL for real-world applications that require meticulous control of size. The as-fabricated nanocolloids were successfully inkjet printed on paper, achieving a low resistivity of 75 Ω/square after 60 prints, highlighting their potential in printed electronics. To address a historical research gap, this article explored the impact of PLAL processing parameters, including fluence (1–2 J/cm2), pulse width (0.2–0.9 ns), repetition rate (10–20 kHz), and pH, factors often overlooked which is partly limiting applications. The influence of powder vs rod target on the PLAL process was addressed revealing that powders produce better size control and are easier to handle but they produce lower colloid concentrations.

The usefulness of additively manufactured (AM) nitinol and Ti6Al4V parts for the aerospace, automotive, machine and tooling, and biomedical industries depends on how well they withstand corrosion. AM is a manufacturing process that makes it possible to create intricate geometries at a reasonable price. Although significant progress has been made in decreasing metal corrosion, not much research has been done on optimizing input processing parameters to lower corrosion rates. Unique phase structures and preferential evaporation of alloying components might arise because of the melting and quick re-solidification that take place during additive manufacturing. This study looks at how processing parameter changes impact the metal parts made by laser-powder bed fusion (L-PBF) in terms of their ability to resist corrosion in a bodily environment. Electrochemical testing was used to conduct the research at a body temperature of 37 °C in both Hanks and Ringers solutions. The findings suggest that an increase in laser power during AM improves the passivation layer of the metal. Furthermore, compared to nitinol, Ti6AL4V exhibits a greater corrosion resistance. When a smaller hatch distance and lower laser beam strength were used, the nitinol sample's susceptibility to corrosion was reduced. This study demonstrates how the corrosion resistance of metal parts made by additive manufacturing can be increased by adjusting the laser powder bed fusion processing parameters in a bodily environment.

This study explores the compression and antibacterial properties of 10x10 × 10 mm polylactic acid (PLA) cubes manufactured through FDM additive printing for biomedical parts. A 3x3 full factorial DOE with 3 replicates examines the impact of printing parameters (infill %, print speed, and layer height). The highest compression strength and stiffness recorded were 91 MPa and 0.76 GPa, respectively. Despite minor mass variations (1.05 ± 0.09 g) under all the investigated parameters, the mean strength of all printed parts was 67.6 ± 10.6 MPa, highlighting the significant influence of processing parameters on mechanical properties. Heat treatment at 60 °C for 30 min improved stiffness. Investigation of various parameters, including layer height and orientation, revealed that larger layer heights resulted in reduced compression strength. Anisotropic compression properties persisted post-heat treatment due to thermal stresses and interlayer bonding. The flat direction (top view) exhibited higher compression properties due to a homogeneous microstructure, minimized interlayer bonding impact, and increased crystallinity. Antibacterial properties against E.coli were induced via coating with peanut-shaped copper nanoparticles (68–267 nm). Nanoparticles were fabricated via a combination of wet chemistry and laser ablation.

Abstract Surface biofouling, corrosion, and wettability are important parameters to understand and characterize aluminum alloys to prevent the failure in marine environments. Antifouling technologies predominantly encompass chemical and biocidal approaches with negative environmental consequences. Therefore, this study focuses on a new method of producing non‐toxic and effective antifouling and corrosion‐resistant surfaces. In this study, ultrafast laser texturing is used to modify the surface of an aluminum alloy using a femtosecond laser system. Five different unique texture patterns are designed and fabricated using 3 W laser power, 100 kHz pulse repetition rate, and 4 mm s−1 scanning speed in order to make the aluminum surface antifouling and corrosion resistant. The non‐textured sample has a contact angle of 85° while the textured samples have contact angles of up to 157°. The contact angle increased with time up to 90 days of aging. Biofouling assessment is conducted using marine algae Nitzschia ovalis as a marine fouling test organism. A reduction of biofilm coverage of 79% is recorded from the laser‐produced star pattern texture. This study demonstrates that laser‐textured surfaces have the potential to mitigate the formation of biofilms on the surfaces while also providing a mechanism to control the relative level of corrosion.

The additive manufacturing (AM) of nitinol (NiTi) has gained considerable attention due to the capability of this material and processing combination to produce complex structures with desired shape memory or superelastic properties. Finite element analysis models were developed in this work to simulate the load-bearing capability of Laser Powder Bed Fusion (PBF-LB) produced NiTi lattice structures. The Auricchio numerical method, with exponential hardening law, was implemented within the FEA model to take account of the martensite-austenite reorientation upon change of stress state. The strut diameter and the unit cell side length were varied which in turn varied the lattice relative density. The lattice structures were subjected to 7 % compressive strain under isothermal conditions. The highest energy absorption efficiency of 40 % was achieved from the lattice structure with a strut diameter of 2 mm, a 6 mm unit cell side length, and a relative density of 42 %; however, the highest specific peak stress was recorded within the lattice structure having a strut diameter of 2.5 mm, a 4 mm unit cell side length, and a relative density of 62 %. Transient analysis was performed by varying the compression rate from 0.25 mm/s to 1 mm/s. For all loading conditions, the energy absorption increased linearly until a stable stress plateau was reached. Moreover, for these examined compression rates, the maximum stress absorption efficiencies varied within the range of 25 %–33 %.

The current work encompasses a study of as-fabricated martensitic NiTi samples printed via Laser Powder Bed Fusion (L-PBF) in the horizontal and vertical build orientations, with systematic variations in the L-PBF process parameters. The sample densities, compositions, thermal characteristics, and mechanical responses were analysed and correlated with L-PBF parameters. Mechanical responses measured and analysed included microhardness, impact energies, and elastic modulus. The process parameters were found to have a significant effect on the resulting properties. The variation in physical properties and mechanical responses between each sample of the vertical build were less compared to those measured for the horizontal built samples. The L-PBF samples were compressed to 6% engineering strain (within elastic limit), and their shape memory strains were thermally recovered. Digital Image Correlation (DIC) based full-field strain analysis was performed during compression to measure local strain fields which revealed in detail the macroscopic effects during detwinning. The shape memory capability of the L-PBF samples was quantised based on strain recoveries attained after thermal recovery. Microstructural variations in submicron scale were also analysed in as-fabricated, post-compression and post-recovery stages, showing the sample response during different deformation mechanisms.

The effect of various solution heat treatment temperatures (i.e., 1120, 1160, 1200 and 1240 °C) on the microstructure, grain morphology and crystallographic texture of IN939 fabricated by powder bed fusion-laser beam (PBF-LB) was investigated. Microstructural analyses showed that the high-temperature gradient and rapid solidification of the PBF-LB processing caused different resulting microstructures compared to conventionally produced counterparts. The melt pool morphologies and laser scanning paths were examined in the as-fabricated samples in the XZ- and XY-planes, respectively. After the application of solution heat treatment at 1120 °C, the as-fabricated PBF-LB initial microstructure was still apparent. For solution heat treatments of 1200 °C and above, the melt pool and scanning path morphologies disappeared and converted into a mixture of columnar grains in the XZ-plane and equiaxed grains in the XY-plane. On the other hand, large equiaxed grains were observed when the samples were solutionized at 1240 °C. Additionally, γ′ phase precipitated within the matrix after all solution heat treatment conditions, which led to increase in the microhardness values. According to electron backscatter diffraction (EBSD) analyses, both as-fabricated and solution heat-treated samples had intense texture with {001} plane normal parallel to the building direction. The first recrystallized grains began to appear when the samples were subjected to the solution heat treatment at 1160 °C and the fraction of the recrystallized grains increased with increasing temperature, as supported by kernel average misorientation (KAM) and grain spread orientation (GOS) analyses.

Is additive manufacturing (AM) a sustainable process? Can the process be optimised to produce sustainable AM parts and production techniques? Additive manufacturing offers the production of parts made of different types of materials in addition to the complex geometry that is difficult or impossible to produce by using the traditional subtractive methods. This study is focused on the optimisation of laser powder bed fusion (L-PBF), one of the most common technologies used in additive manufacturing and 3D printing. This research was carried out by modulating the build layer thickness of the deposited metal powder and the input volumetric energy density. The aim of the proposed strategy is to save the build time by maximizing the applied layer thickness of nitinol powder while retrieving the different AM part properties. The saving in the process time has a direct effect on the total cost of the produced part as a result of several components like electric energy, inert gas consumption, and labour. Nickel-rich nitinol (52.39 Ni at.%) was selected for investigation in this study due to its extremely high superplastic and shape memory properties in addition to the wide application in various industries like aerospace, biomedical, and automotive. The results obtained show that significant energy and material consumption can be found by producing near full dens AM parts with limited or no alteration in chemical and mechanical properties.

Surface fouling is a major challenge faced within various engineering applications, especially in marine, aerospace, water treatment, food and beverage, and the energy generation sectors. This can be prevented or reduced in various ways by creating artificial surface textures which have fouling resistance properties. Ultrafast laser texturing provides an efficient method for the texturing of surfaces of different materials with high accuracy, precision, and repeatability. Laser texturing methods can enhance the production of well-defined surface nano- and microscale patterns. These surfaces with nano- and micro-scale patterning can be tailored to have inherent properties such as hydrophobicity, hydrophilicity, and resistance to fouling. This review gives an overview of the various types of fouling that can occur, the properties affecting a surface's fouling resistance, as well as the latest physical and chemical strategies for the generation of antifouling surfaces. Surfaces architectures which have inherent antifouling capabilities are presented. This review focuses on the utilization of the higher precision laser-based texturing offered from femtosecond laser systems for enhance fouling resistance. The process parameters to fabricate these textures and the current state of art femtosecond laser sources are presented and discussed. The challenges and future research requirements in the field of laser-based methods to fabricate antifouling surfaces are presented.

This study is focused on a comprehensive characterization of virgin and spatter IN939 powders and the effects of a certain amount of spatter powder on the part quality of IN939 fabricated by the L-PBF process. A brown tint coloration formed Al2O3 oxide, pores, a 124.4% increase in the average particle size, a 10.2% decrease in the powder circularity, and a 7.5% decrease in the powder aspect ratio were observed in the spatter powder. Additionally, higher average grain size and lower nanohardness were obtained for the spatter powder. In order to understand the effect of a certain amount of spatter powder on the part quality, 10 wt% spatter powder was mixed with the virgin powder. This addition was found to decrease the flowability of the powder. Moreover, this addition decreased relative density by around 0.3% and increased surface roughness by around 80.8% in the fabricated samples (termed as V and SV). On the other hand, there was no considerable microstructural, texture, microhardness, and nanohardness difference between V and SV samples, although the spatter powder addition caused a 30.2% increase in the average grain size of SV. The overall texture for both V and SV samples exhibit (001)//BD.

In this study, direct comparisons between the properties of three groups of as-built nitinol (NiTi) samples fabricated using three pre-determined volumetric energy densities (VED) as calculated based on hatch spacings (VEDH = 40, 80, and 120 J/mm3), were examined. The additive manufacturing technique adopted is the powder bed fusion using a laser beam (PBF-LB), and the powder feedstock is Ni50Ti50. Although the three VEDH's increased by 100% for each sample group, each VEDH value was within the range of those recommended in the literature, as well as equivalent to 100 J/mm3 (VEDf), VED as calculated based on laser spot size. Significant differences were found between the thermal profiles and normalised thermal gradients, resulting in compositional differences, defects, phase, and phase transformation behaviour, Young's modulus, hardness, and microstructure. Thermal gradients and full-wave amplitude of the in-situ melt pool thermal radiation waveforms increased as VEDH increased. Higher VEDH's resulted in more martensitic NiTi samples with larger melt pool volume and >98% sample relative density. Austenite transformation temperatures increased with an increase in at.% Ti for each increase in VEDH, consequent on the higher normalised average melt pool temperatures. The calculated thermal gradient (normalised) was correlated to higher thermal stresses as VEDH increased, resulting in residual stress-induced weld-metal liquation microcracks. This work has demonstrated the potential of post-processed in-situ melt pool thermal radiation data, in providing insights into the physical property variations of as-built nitinol samples fabricated via PBF-LB.

In the last few decades, Nitinol (NiTi) actuators have created a massive impact at the commercial level due to their application in various engineering and medical fields. In this paper, an experimental analysis study is presented on commercially manufactured nitinol tubes for performance enhancement. As received tubes were super-elastic at room temperature with Af temperature of 1.7°C. The nitinol tubes were heat treated at 500°C for different time ranging from 30 min to 60 min to raise the Af temperature. Metallography was performed on pristine and heat-treated samples to analyse the changes in the physical properties. XRD analysis revealed the crystalline structure present in the tubes (as received and heat treated) was nitinol cubic (110) while nitinol cubic (211) at room temperature. Moreover, dilatometry was performed which showed thermal expansion coefficients very close as noted in the literature as 11.4x10-6/°C. In the last section of this paper, the actuation force of the tubes was experimentally measured and analysed using different springs attached to the tubes connected to a conductive heating stage. A full factorial Design of Experiments (DoE) was used based on factors of time, temperature, and spring constant. For a surface temperature of 125°C and a spring constant of 2.39 kN/m, 131 N force was attained from the tube. The maximum actuation force of 145 N was obeserved for surface temperature of 145°C at an exposure time of 60 s with k = 2.39 kN/m.

Enzyme and amino acid immobilisation increase the efficiency of biochemical reactions while facilitating a mechanism for their delivery to tissues. Herein, clean MgNPs were fabricated via laser ablation and were mixed and ultrasonicated together with trypsin and glutamine for immobilisation. The as-synthesised MgNPs of various concentrations exhibited human dermal fibroblast cell growth-promoting effects and an improved dynamic reciprocity environment as demonstrated via cell adhesion. Adsorption was the mechanism used for immobilising amino acids and enzymes onto MgNPs. The resulting composites, visualised via FESEM, appeared as highly connected needle structures. Immersion in DI water was employed for chemical elution while centrifugation at 12,000 rpm and filtration through 200 nm pore sizes were applied to induce physical elution. The microstructure of the MgNPs-trypsin composites did not change significantly after elution while the MgNPs-trypsin composites showed morphological changes from a monolithic structure to a disaggregated structure.

The recrystallization and grain growth behaviour of IN718 alloy additively manufactured by laser powder bed fusion (L-PBF) is presented herein. The effects of three different temperatures (1050, 1150 and 1250 °C) and holding times (15, 45 and 90 min) were investigated. The texture evolution of the samples was recorded via electron backscatter diffraction (EBSD). The as-built sample is composed of bowl-shaped melt pools, a chessboard-like grain pattern and has a cube texture {100}. Recrystallized grains were observed in the samples treated at 1150 °C for 15 min, as well as the samples treated for longer periods and at higher temperatures. Recrystallization was observed to start from high dislocation density regions, including the overlapping melt pools and the borders of the chessboard-like pattern. The initial cube texture transforms into a first-generation cube-twin texture {122} via a twinning-assisted recrystallization mechanism. Then, those recrystallization nuclei sweep through the high defect density matrix; during which almost no new twins are formed. The samples treated at 1250 °C are almost completely recrystallized, which forms a weaker cube texture and a stronger P-orientation {011}. However, the growth of recrystallized grains is very limited due to the presence of non-coherent precipitates.

This paper presents an examination of the production of copper air filters via the Hydraulic Pressing (HP) method. Processing conditions examined included powder particle type (spherical and dendritic), varying compaction pressures (635, 714, and 793 MPa) and different pore forming (polyvinyl alcohol (PVA)) concentrations (1, 2, and 3 wt.%). Following compaction, the samples were thermally sintered in a two stage sintering regime at 200 °C and 750 °C. The morphology, porosity, and mechanical properties of the sintered samples were characterised. Morphological analysis demonstrated better consolidation and overlapping of the copper powder particles in samples with a higher weight percentage of the PVA. Highest porosity was achieved in the sample produced using the dendritic copper powder mixed with highest weight percentage of PVA. As the samples were very porous, the hardness of the samples varied greatly. Samples prepared with spherical powders at high pressure demonstrated the highest hardness. The results in this study show that copper filters with 14%–26% porosity can effectively be produced using spherical and dendritic copper powders by controlling the compaction pressure and PVA concentration.

Laser-powder bed fusion was identified as a promising technique for manufacturing metal matrix composites. However, over a decade later, little progress has been made in addressing the persisting issues hindering the wider exploitation and industrial usage of metal matrix composites. Therefore, the present study proposes the implementation of a feasible solution to accomplish research advancements in metal matrix composites. Where, the issues concerning their performance and cost have driven this study towards the development of a novel scanning strategy. A hatching system based on a sine wave was successfully developed and employed in the printing of metal matrix composites. Composites printed using the sinusoidal hatching exhibited an enhanced yield strength and ductility owing to the resultant grain refinement and texture. The dabber mode formation of material tracks promoted the growth of highly oriented intragranular cellular structures. Apart for playing an important role at the obtained hardness, this control over the cellular growth could also be used towards improving composite toughness. Additionally, besides improving composite performance, the sinusoidal hatching was also effective in reducing manufacturing lead time and process energy consumption.

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.

Three-dimensional printing or additive manufacturing (AM) has enabled innovative advancements in tissue engineering through scaffold development. The use of scaffolds, developed by using AM technology for tissue repair (like cartilage and bone), could enable the growth of several cell types on the same implant. Scaffolds are 3D-printed using polymer-based composites. polyether ether ketone (PEEK)-based composites are ideal for scaffold 3D printing due to their excellent biocompatibility and mechanical properties resembling human bone. It is therefore considered to be the next-generation bioactive material for tissue engineering. Despite several reviews on the application of PEEK in biomedical fields, a detailed review of the recent progress made in the development of PEEK composites and the 3D printing of scaffolds has not been published. Therefore, this review focuses on the current status of technological developments in the 3D printing of bone scaffolds using PEEK-based composites. Furthermore, this review summarizes the challenges associated with the 3D printing of high-performance scaffolds based on PEEK composites.

Laser processing has become a viable method of synthesising bimetallic and biomolecule-free nanoparticles. Laser processing enable for different materials to be processed via the same laser system with ease, unlike chemical and biological methods that require special equipment/organisms for each material. The objective of this paper is to study the laser processing of powders for the fabrication of nanoparticles of various types, shapes, sizes and concentration. A Nd:YAG 1064 nm laser system was used to perform ablation processes of Cu and BaTiO3 powders under isopropyl alcohol, hydrochloric acid and ammonium buffer solution. This produced nanoparticles of various shapes including rods, spheres and pyramids and various sizes (14–280 nm). The effect of the laser processing parameters such as hatch spacing (10 or 30 μm) and scan speed (2 or 3 m/s) were examined. These processing parameters are seldom studied in the literature. Furthermore, this paper describes a way to produce nanoparticles from powder targets instead of the conventional rod, plate or thin film targets that are difficult to reuse. However, powders are compatible with a limited number of liquids than rods, plates and thin films and this issue is addressed herein.

The present study reports the glass-forming ability, density change on crystallization and corrosion behavior of newly developed rare-earth free Cu-based metallic glasses (CBMGs). The critical casting thickness of these new CBMGs increased from 15 mm at 8 at.% Hf to 22 mm at 12 at.% Hf, reaching a maximum value of 28.5 mm at 13.5 at.% Hf. It dropped to 24 mm and 15 mm thereafter, for 15 and 20 at.% Hf, respectively. The alloys showed a monotonic increase in density going from 8 at.% Hf to 20 at.% Hf, with the density of amorphous samples increasing from 7.83 g/cm3 to 8.84 g/cm3 and crystallized samples increasing from 7.92 g/cm3 to 8.91 g/cm3. Potentiodynamic polarization tests carried out in 0.1, 0.2 and 0.5 M NaCl solution at 25 °C showed a direct correlation between corrosion resistance and Hf content in the order: 8 at.% < 13.5 at.% < 20 at.% Hf. Increase in NaCl concentration also had a significant impact on the corrosion intensity due to the chaotropic effect. Scanning electron microscopy of corroded sample surfaces showed formation and eventual merging of individual micro cracks resulting in a mud-cracking pattern. Energy-dispersive X-ray spectroscopy maps of pitted regions revealed reduction in Zr and Al concentration with increase in Hf and Cu percentage for all compositions. An increase in the O concentration along with the appearance of new peaks in the X-ray photoelectron spectroscopy results, measured post corrosion, confirmed the formation of metal oxides and oxyhydroxides in the passive layer.

Lactobacillus rhamnosus (L. rhamnosus) is a commensal bacterium with health-promoting properties and with a wide range of applications within the food industry. To improve and optimize the control of L. rhamnosus biomass production in batch and fed-batch bioprocesses, this study proposes the application of artificial neural network (ANN) modelling to improve process control and monitoring, with potential future implementation as a basis for a digital twin.Three ANNs were developed using historical data from ten bioprocesses. These ANNs were designed to predict the biomass in batch bioprocesses with different media compositions, predict biomass in fed-batch bioprocesses, and predict the growth rate in fed-batch bioprocesses.The immunomodulatory effect of the L. rhamnosus samples was examined and found to elicit an anti-inflammatory response as evidenced by the inhibition of IL-6 and TNF-α secretion.Overall, the findings of this study reinforce the potential of ANN modelling for bioprocess optimization aimed at improved control for maximising the volumetric productivity of L. rhamnosus as an immunomodulatory agent with applications in the functional food industry.

The growth and development in the biomedical field are very essential for the sustainable and holistic well-being of our entire society. The shortage of patient-specific products is the main limitation in the biomedical field. This cutting-edge technology can contribute to the advancement of several sectors including aviation, automotive, biomedical etc. It has revolutionized the production of medical instruments, organs, tissue regeneration, drug delivery platform, scaffolds, and implants. Many operative and post-operative processes in the medical field are now quite easy due to the new inventions in 3D printing. In this review, different additive manufacturing techniques and various applications of 3D printing in the biomedical field are compiled. Using examples to analyze the technology in depth, existing challenges and future outlooks are presented.

This paper discusses the novel features of DNA-templated one dimensional photonic crystals (1D PC) for additive manufacturing (AM) or 3D printing applications. AM applications utilize a variety of materials with tailored thermal, physical, chemical, and mechanical properties. However, the integration of optical properties into AM materials is less explored. AM parts produced from the materials having specific optical properties opens up many opportunities to develop novel integrated optoelectronic and photonic systems and provide sustainable structural color to the produced parts. This work proposes micro level periodic structures which can be used to replace existing color dyes for durable, non-toxic, cost-effective 3D printing applications. Based on ink jet printing technology, we designed DNA templated one dimensional (1D) photonic crystal (PC) of three-layer unit cell. The light transfer properties of the proposed 1D PC were examined theoretically in the range of 400 nm–800 nm of visible region of light using transfer matrix method (TMM). The photonic bandgap for DNA templated 1D PC is obtained around 450 nm and 650 nm of visible spectra region. The theoretical simulation shows that the presence of DNA template decreases the band gap width in the visible region and the three-layered periodic system helped to control the formation of multiple color bands in the visible region. The dispersion relation also confirmed that the electromagnetic fields in the stratified structure have been undergone multiple scattering and that results the formation of bandgap within the visible region. We also presented the standard deviation of the transmission coefficients in the range of 450 nm–650nm of visible spectra. Based on these observation and analysis, DNA templated PCs can be effective for tuning desired color spectra. Besides, this system can be used to replace the existing health hazardous synthetic dyes by incorporating with inkjet printing processes to create durable and colored 3D objects for aesthetic as well as technical purposes.

With the evolution of additive manufacturing and flexible printed electronic (PE) technologies, conductive inks have received a lot of interest. Nanomaterials are an important component of conductive ink composition. LASIS (Laser Ablation Synthesis in Solution) is a physical method for creating nanoparticles in a liquid environment. This top-down technique employs well-known laser-based technologies to generate additive-free nanocolloids that are less harmful and more ecologically friendly. This study discusses recent advancements in the manufacturing of LASiS nanomaterials and their printed electronic applications. The parameters that determine the yield and attributes of LASiS nanoparticles are examined, with emphasis on specific use of such nanoparticles as conductive inks in the field of printed electronics. The advantages of LASiS-synthesised nanoparticles in printing applications, as well as the challenges that must be resolved to reach optimum performance, are also explored.

Additively manufactured synthetic bone scaffolds have emerged as promising candidates for the replacement and regeneration of damaged and diseased bones. By employing optimal pore architecture, including pore morphology, sizes, and porosities, 3D-printed scaffolds can closely mimic the mechanical properties of natural bone and withstand external loads. This study aims to investigate the deformation pattern exhibited by polymeric bone scaffolds fabricated using the PolyJet (PJ) 3D printing technique. Cubic and hexagonal closed-packed uniform scaffolds with porosities of 30%, 50%, and 70% are utilized in finite element (FE) models. The crushable foam plasticity model is employed to analyze the scaffolds’ mechanical response under quasi-static compression. Experimental validation of the FE results demonstrates a favorable agreement, with an average percentage error of 12.27% ± 7.1%. Moreover, the yield strength and elastic modulus of the scaffolds are evaluated and compared, revealing notable differences between cubic and hexagonal closed-packed designs. The 30%, 50%, and 70% porous cubic pore-shaped bone scaffolds exhibit significantly higher yield strengths of 46.89%, 58.29%, and 66.09%, respectively, compared to the hexagonal closed-packed bone scaffolds at percentage strains of 5%, 6%, and 7%. Similarly, the elastic modulus of the 30%, 50%, and 70% porous cubic pore-shaped bone scaffolds is 42.68%, 59.70%, and 58.18% higher, respectively, than the hexagonal closed-packed bone scaffolds at the same percentage strain levels. Furthermore, it is observed in comparison with our previous study the μSLA-printed bone scaffolds demonstrate 1.5 times higher elastic moduli and yield strengths compared to the PJ-printed bone scaffolds.

This study is focused on the 3D printing of NiTi shape memory alloy (SMA) in cuboidal shaped samples via the Laser Powder Bed Fusion (L-PBF) process using a dissimilar material build plate of 316L stainless steel. Four processing parameters were investigated at three levels for the optimization of the process. Those parameters were the laser beam power, scanning speed, laser beam spot size and hatch spacing. The produced samples exhibited varying levels of bonding with the substrate. Compression testing, Archimedes density measurement and EDX chemical composition were carried out. A design of experiment model was developed relating the input process parameters to the output properties. The effect of the calculated volumetric energy density and the sample melt-pool temperatures on the output measures were also investigated for the strong bonding and weldability with the substrate metal.

This study evaluates the phase and microstructural evolution of additively manufactured (AM) Nickel Titanium (NiTi) alloy, across the interface with 316L stainless steel build plate, in order to understand the processing parameter (input power, layer thickness and scan speed), composition, and microstructure interrelationships necessary to achieve excellent multi-material bonding between NiTi and 316L. The effect of the process parameters utilised was characterised using the Scanning Electron Microscope (SEM), Electron Backscatter Diffraction (EBSD), X-ray diffraction (XRD), and Energy-dispersive X-ray spectroscopy (EDX). SEM/EBSD results demonstrated, for the first time, that the microstructure and phase close to the interface was complex and comprised martensite, austenite and Fe phases, sequentially arranged in a layered sandwich pattern across the build direction. This complexity was necessary for excellent bonding. The L-PBF process parameters influenced the diffusion behaviour and the concentration of elements found at the interface. The diffusion rate of Fe and Ti across the NiTi-316L interface was 3.05×10-6m2/s and 3.27×10-8m2/s, respectively, representing a 93.27-fold increase. The observed microstructural and phase evolution is related to the generated interface chemistry and the thermomechanical history related strain resulting from the L-PBF process.

Despite the recent progress in additive manufacturing (AM) process and technology, challenges in the repeatability and reproducibility of AM parts still hinders the adoption of this technique in many industries. This is particularly difficult when a part is qualified on a particular part on a certain machine using optimised parameters. If a manufacturer wishes to expand production to multiple machines, the ability to translate these optimised parameters to different machines much be understood. In this study, four different metal L-PBF printers were used to produce 316L tensile testing samples using the same processing parameters and metal powder supplied from a single batch from the same supplier. In addition to the analysis of the correlation between the input parameters and the output measures, this study reports that despite the same set process parameters, there is significant variations were found in the mechanical performance and properties of the AM samples produced on the different L-PBF metal additive manufacturing machines. For the range of the input processing parameters and the resulting input volumetric energy density applied of 21–37 J/mm3, values of (4–42)%, (200–716) MPa, and (52–214) GPa were obtained for the elongation, ultimate tensile strength and elastic modulus on additively manufactured 316L samples respectively.

In this work, nitinol samples were produced via Laser Powder Bed Fusion (L-PBF) in the horizontal and vertical orientations with systematic variations in laser power, scan speed and hatch spacing parameters. Increased density was positively correlated with increased laser power, scan speed and hatch spacing for the horizontally built samples but not for the vertically built samples. A smaller difference in the average temperature within a printed layer, associated with the vertically built samples, was linked with reduced porosity and reduced porosity variability between samples. Control of the L-PBF parameters was found to allow control of the resulting part chemical composition which also directly affected phase transformation temperatures, and related phase structures. The laser process parameters were found to have a significant effect (p

Abstract Over 80% of wastewater worldwide is released into the environment without proper treatment. Whilst environmental pollution continues to intensify due to the increase in the number of polluting industries, conventional techniques employed to clean the environment are poorly effective and are expensive. MXenes are a new class of 2D materials that have received a lot of attention for an extensive range of applications due to their tuneable interlayer spacing and tailorable surface chemistry. Several MXene‐based nanomaterials with remarkable properties have been proposed, synthesized, and used in environmental remediation applications. In this work, a comprehensive review of the state‐of‐the‐art research progress on the promising potential of surface functionalized MXenes as photocatalysts, adsorbents, and membranes for wastewater treatment is presented. The sources, composition, and effects of wastewater on human health and the environment are displayed. Furthermore, the synthesis, surface functionalization, and characterization techniques of merit used in the study of MXenes are discussed, detailing the effects of a range of factors (e.g., PH, temperature, precursor, etc.) on the synthesis, surface functionalization, and performance of the resulting MXenes. Finally, the limits of MXenes and MXene‐based materials as well as their potential future research directions, especially for wastewater treatment applications are highlighted.

Achieving good surface profile and low levels of porosity are prime challenges in the Laser-Powder Bed Fusion (L-PBF) additive manufacturing technique. In order to optimise these properties, post-processing is often required. However, the compression of powder spread on the build plate and re-melting of each build layer during the L-PBF process could address these challenges. In this study, the effect of different powder compression ratios and laser re-melting regimes on the density, microstructure morphology, surface profile and mechanical properties of L-PBF produced parts were investigated. Two different metal printers with same laser processing parameters were used to fabricate 10 × 10 × 10 mm3 stainless steel 316L samples. To examine the impact of compression ratio and layer re-melting, one set of samples was prepared with three different compression levels for each layer and a second set of samples either a single or double set of laser passes for each layer. The Volumetric Energy Density (VED) range examines was from 26.7 J/mm3 to 80 J/mm3. Density, hardness, elastic modulus, microstructure and surface profiles of the printed samples were characterised. A 3% increment in density and a 50% reduction in the surface roughness were achieved using a laser double pass over each layer. The results demonstrate, by applying different powder compression ratios onto the powder bed and by re-melting each layer, that the density, surface roughness and the elastic modulus of the produced samples can be improved.

Pulsed laser ablation in liquid (PLAL) is a physical and top-down approach used to fabricate nanoparticles (NPs). Herein, the research methods and current trends in PLAL literature are reviewed, including the recent uses of PLAL for fabricating bimetallic nanoparticles (BNPs) and composites. BNPs have gained attention owing to their advanced physicochemical properties over monometallic NPs. PLAL involves the irradiation of a solid target (usually a rod, plate, or thin film) under a liquid medium. The liquid collects the ejected NPs resulting from the laser processing, which produces a colloid that can be in various applications, including plasmon sensing, energy harvesting, and drug delivery. The most used fabrication techniques, including the use of microorganisms, do not have precise NP size control and require the separation of the microorganisms from the produced NPs. PLAL is quicker at producing NPs than bottom-up methods. The drawbacks of PLAL include the need to find the required laser processing parameters, which requires extensive experimentation, and the complex and non-linear relationships between the inputs and the outputs (e.g., NP size).