Nucleation Research Articles

Oriented and Continuous Phase Epitaxy Enabled by A Highly Dendrite‐Resistant Plane Toward Super‐High Areal Capacity Zinc Metal Batteries

AbstractUnstable Zn metal anodes with dendrites/side reactions are becoming the main obstacle to the practical application of zinc‐based aqueous batteries. Epitaxial growth has been considered to be an effective strategy for solving these issues, especially for inducing the (002) plane growth. Nonetheless, the (002)‐textured Zn is difficult to achieve highly stable Zn anode under high capacity resulting from its large lattice distortion. Herein, the Cu single atom anchored polymeric carbon nitride (Cu@PCN) is synthesized by a facile thermal polymerization method. Serving as multifunctional protective layer on Zn surface, the Cu@PCN can provide massive nucleation sites at a nano‐level and uniformize the electron distribution through coordination engineering. Optimizing the coordination structures of single Cu and N atoms within the carbon matrix enables a redistribution for electric field and regulates ion flux. More importantly, this coordination strategy with single atoms is first reported to customize oriented and continuous phase epitaxy along highly dendrite‐resistant Zn(101) plane by reducing (101) surface energy. This pattern of oriented dense deposition leads to stable and reversible Zn plating/stripping is achieved, which delivers an extended cycling life of 550 h at 10 A cm−2, 20 mAh cm−2. The practical full cell also displays stable performance for 1200 cycles.

In Situ Fluorescent Visualization of the Interfacial Layer of Induced Crystallization in Polyvinyl Chloride

Despite the remarkable progress in the modification and application of polyvinyl chloride (PVC), developing processing aids for the induced crystallization of PVC and characterizing its interfacial layer remain challenges. Herein, we propose a new polymeric nucleating agent, polyamidea12-graft-styrene–maleic anhydride copolymer (PA12-g-SMA), which possesses high compatibility and crystallinity, effectively improving the crystallinity to 15.1%, the impact strength to 61.03 kJ/m2, and the degradation temperature of PVC to 267 °C through a single and straightforward processing step. Additionally, after the introduction of two different fluorescent sensors in PA12-g-SMA and PVC, the interfacial layer of the induced crystallization can be monitored in situ via a confocal laser scanning microscope (CLSM). This study highlights a rare strategy for significantly enhancing the physical properties of rigid PVC through simply adding a polymeric nucleating agent during processing, while also emphasizing the importance of visualizing the interfacial layer to understand various polymer crystallization processes.

Fatigue Behavior of Al/Steel Dissimilar Friction Stir Welds and the Effect of Die‐Press Forming

ABSTRACT6016‐T4 aluminum (Al) alloy plate was butt welded to the cold‐rolled steel plate by a friction stir welding (FSW) technique, and the fatigue properties of Al/steel dissimilar welds were investigated. Some dissimilar welds were die‐press formed to the hat shape, and specimens were sampled from the corners of the hat shape, where severe plastic deformation occurred by the die‐press forming. The die‐press‐formed samples had better tensile strengths and hardness than the as‐welded ones because of the work hardening. It indicates that the die‐press forming is applicable for the Al/steel dissimilar welds. However, large voids were formed around the steel fragments dispersed into Al matrix by die‐press forming. Those voids acted as the fatigue crack nucleation sites, thus reducing the fatigue lives of the die‐press‐formed specimens. When the bottom side of the welds experienced tension plastic deformation, the fatigue strength was the lowest.

Experimental investigation of pool boiling on Ti-Cu composite coated surfaces prepared using Electric Discharge Coating

Boiling heat transfer has become a very potent two-phase heat transfer mechanism for cooling high heat-producing devices such as microelectronic devices, fusion reactors or turbine blades. Increasing research has shown that micro/nano-structures on surfaces increase the number of nucleation sites for bubble formation, which ultimately results in a major improvement in boiling performance. This led to studies on developing various coated surfaces in order to generate micro/nano-structures on surfaces. In the current study, microstructured boiling surfaces were prepared using the Electric Discharge Coating (EDC) process. Titanium-copper (Ti-Cu) composite microparticles were coated on copper surface under reverse polarity in the Electric Discharge Machine. Four surfaces were prepared by using current settings of 3 A, 4 A, 5 A and 6 A. It was followed by characterisation of the surfaces which included, wettability analysis, porosity, pore size estimation, mean roughness measurement and elemental analysis, in order to better understand the boiling results on the surfaces. The surfaces formed were hydrophilic in nature, with contact angles varying from 47° to 65°. Pool boiling were performed with the developed surfaces and critical heat flux (CHF) and nucleate boiling heat transfer coefficient (NBHTC) improvement of 37.17 % and 172 % respectively were observed with the best performing surface compared to the bare surface. The best performing surface was also compared with relevant published literature to determine its standing against the present state of the art.

Rational design of MoS2/CNT heterostructure with rich S-vacancy for enhanced HER performance

Molybdenum disulfide (MoS2) is a promising electrocatalyst for the hydrogen evolution reaction (HER) due to excellent stability and low cost. However, the utilization in electrocatalytic hydrogen evolution is constrained by inherent shortcomings, including fewer edge active sites, poor dispersion, and electrical conductivity. In this work, MoS2 was compounded with carbon nanotubes (CNTs), which are known for their high specific surface area and excellent electrical conductivity. These CNTs, laden with oxygen-containing functional groups, provided nucleation sites that facilitated the rapid assembly of MoS2 nanoflowers under hydrothermal conditions within 3 h. Due to their diminutive size (∼300 nm), these nanoflowers possess a large specific surface area and numerous active sites at their edges. Furthermore, MoS2 nanoflowers exhibited a high concentration of intrinsic S-vacancies. This heterojunction material exhibited superior HER properties. In addition, density functional theory simulation further confirmed that the MoS2 with S vacancy and CNT heterojunction electrocatalysts (VS-M/C) provided a fast charge transfer pathway for water electrolysis, and analysis showed that the conduction band minimum and valence band maximum were mainly contributed by the d orbits of Mo and the p orbits of C. This study proffered a novel approach for the engineering of high-performance MoS2-based HER electrocatalysts.

Dendrite‐Free Zinc Anode for Zinc‐Based Batteries by Pre‐Deposition of a Cu–Zn Alloy Layer on Copper Surface via an In Situ Electrochemical Oxidation–Reduction Reaction

ABSTRACTThe prevention of uncontrollable growth of zinc dendrites on the zinc electrodes is one of the key challenges, hindering the widespread commercialization of zinc‐based energy storage technologies. Herein, we report a facile method to mitigate dendrite growth on a copper surface by an initial in situ coating of a Cu–Zn alloy layer, before zinc deposition. During further zinc deposition, the initially formed Cu–Zn alloy layer provides uniform nucleating sites and promotes homogeneous zinc deposition. A symmetrical cell, assembled using a Cu–Zn/Cu electrode could be stably cycled for over 1000 cycles in ZnSO4 solution, at a current density of 30 mA/cm2 and a coulombic efficiency of 99.9%. A zinc–air cell, assembled using Zn@Cu–Zn/Cu as the anode and rGO/Co3O4 composite as the cathode, exhibited a very stable performance at a high current density of 50 mA/cm2 and coulombic efficiency of ~93%, for over 400 cycles. After cycling experiments, the X‐ray photoelectron spectroscopy and the X‐ray diffraction analysis confirmed the formation of the Cu–Zn alloy layer. Hence, the present method provides an easy route for fabricating a dendrite‐free zinc electrode, for a wide range of zinc anode‐based batteries.

Surface modified cellulose nanospheres with simultaneous nucleation and degradation-accelerating effects on poly(lactic acid)

As a novel type of nanocellulose material, cellulose nanospheres (CNSs) have gained significant attention and rapid development in recent years. In this work, the surface hydrophobic modification of CNSs was achieved by employing maleic anhydride as an esterifying agent. The effects of modified cellulose nanospheres (CNS-MA) on the crystallization and hydrolysis behaviors of polylactic acid (PLA)-based composites were systematically investigated. The results demonstrate that surface modification improves the dispersion of CNSs in the PLA matrix. Well-dispersed particles act as nucleation sites, which increases the crystallization rate and crystallinity of PLA and endows the composites with remarkable heat distortion resistance. The storage modulus of the PLA/CNS-MA composites exceeds 300 MPa, even at an elevated temperature of 90 °C. Furthermore, the hydrolytic degradation of PLA is dramatically accelerated with the addition of CNS-MA. Combining the morphology observations and theoretical calculations, it is speculated that the fast hydrolytic degradation is related to a transition in the main hydrolytic degradation mechanism from surface erosion to bulk erosion, because the presence of CNS-MA provides particular pathways for water molecules to diffuse into the interior of the composites. This research highlights the potential of CNSs as a multifunctional filler with both reinforcing and degradation-promoting effects, offering valuable insights for the study of other biomass nanomaterials.

Crystallization behavior and thermal properties of octa-phenyl-substituted silsesquioxane-modified polylactide (PLA)

AbstractThis study aims to understand the effects of adding octa-phenyl-substituted silsesquioxane (phSQ) on the crystallization process and thermal stability of polylactide (PLA). Nowadays, PLA is the most industrially used compostable polymer, but its uses are limited by its low crystallization and thermal degradation during processing. The possibility of introducing functionalized silsesquioxanes (SQs) to improve thermal stability and increase its crystallinity and ductility in a controlled way is desirable. The nanometric size of the Si-O-Si cage, coupled with the influence of the functional groups attached to its structure, enables it to function as a heterogeneous nucleating agent. In this work, a specially synthesized octa-phenyl-substituted SQ (phSQ) was added to the PLA in 0.5–5 wt%. Crystallization in non-isothermal and isothermal conditions was conducted and monitored using differential scanning calorimetry (DSC); the course of the spherulite formation under identical conditions to DSC was also assessed using optical microscopy in polarized light. The results showed that phSQ increases the degree of crystallinity of PLA by introducing additional sites of heterogeneous nucleation but does not increase the spherulite growth coefficient. Additionally, the analysis of thermal properties indicates that the presence of phSQ could not have a positive impact on thermal stability. The agglomeration of the nanometric particles and changes in the main structural features of the polymeric matrix could be present in the samples, affecting the obtained results. Graphical abstract

Highly Reversible Sodium Metal Batteries Enabled by Extraordinary Alloying Reaction of Single‐Atom Antimony

AbstractThe unique coordination configuration of single‐atom materials (SAMs) allows precise reaction control at atomic‐level and a potential of unusual electrochemical reaction. Nevertheless, it is a big challenge to prepare main group element with high loading content. Here, multifield‐regulated synthesis (MRS) technology is utilized to rapidly produce single‐atom antimony (Sb) metal with a high loading of 15 wt.%. Ab initio molecular dynamics simulations reveal the significantly enhanced reaction kinetics of Sb and nitrogen‐doped graphene by multi‐physics field coupling. Compared with common metallic Sb nanoparticles, atomically dispersed Sb displays remarkably improved electrochemical reaction kinetics and stable structure due to the negligible variation of stresses and volume expansion during the pseudocapacitive alloying‐dealloying process. Such extraordinary alloying reaction in well‐dispersed Sb atoms enabling homogeneous ion flow can serve as active nucleation sites for regulating even Na metal nucleation and growth. As a result, copper foil coated with only ≈3 µm thickness of such material exhibits a high Coulombic efficiency of up to 99.99%, an ultra‐low overpotential of 3 mV, and a long lifetime exceeding 2500 h in symmetrical cells. Furthermore, an anode‐free MRS‐SbSA||Na3V2(PO4)3 battery is constructed, which demonstrates exceptionally high energy density (≈362 Wh Kg−1), outstanding rate capability and good cycling stability.

Investigation of bubble interaction in a temporal and spatial heat flux partitioning model for subcooled flow boiling

CFD methodology for subcooled flow boiling is significantly affected by the heat flux partitioning model, which plays a crucial role in predicting the mass source term generated by wall boiling of the liquid phase. Although numerous models have been proposed, most research efforts have focused on the spatial dimensions of boiling heat transfer mechanisms, neglecting the temporal aspect. This study presents a heat flux partitioning model for subcooled flow boiling that considers both temporal and spatial dimensions. The model accounts for the contribution of heat flux from the superheated liquid layer during the bubble growth stage, liquid convection during the bubble wait stage within the bubble influence area in the temporal dimension, and heat flux from the overlapping area of bubble influence in the spatial dimension. An approach was developed to determine the bubble influence area by considering the bubble interaction based on the stochastic nature of nucleation sites on the heated wall, verified by the Monte Carlo method. The bubble dynamics parameters were experimentally derived to reduce the uncertainty associated with the boiling sub-models on the calculation. A comparative analysis of boiling curves and wall heat flux partitioning was conducted between the present model and the RPI model under various flow conditions. The results indicate that both models could reasonably predict the boiling curve. However, the RPI model tends to over-predict the proportion of evaporative heat flux, which is considered a weakness. Based on physical principles, the present model accurately captures the fundamental trend of wall heat flux partitioning. This research enhances the understanding of subcooled flow boiling and increases confidence in multiphase CFD methodology predictions.

Crystallization Control of Anionic Thiacalixarenes on Silicon Surface Coated with Cationic Poly(ethyleneimine).

Surface modification of solid substrates with organic molecules and polyelectrolytes is a promising strategy toward advanced soft materials due to the control of molecular arrangement and supramolecular organization; however, understanding the nature of interactions within the assembly is challenging. Here a facile approach to the control of the architecture of calixarene macrocycles on soft surfaces is presented through the interplay of weak interactions involving a solid silicon substrate, a cationic polyelectrolyte layer, and anionic sulfonatothiacalix[4]arene (STCA). Topological analysis of atomic force microscopy (AFM) images of STCA on silicon, as well as silicon wafers modified with neutral polyethylenimine (PEI) and cationic PEI-H+, indicates different surface morphology and assembly behavior of STCA on such substrates. Drop-casting a calixarene solution onto silicon induces the formation of chaotically oriented needle crystals. When there is globular PEI, a nucleation point for the STCA crystals is formed on the polyelectrolyte surface, which grows into rosette structures. In contrast, protonated PEI with a chain-like structure alters the self-organization of STCA on silicon surfaces, leading to a dense uniform fiber-like network. Density functional theory modeling of the system components' self-assembly reveals thermodynamically favorable face-to-face antiparallel aggregation of STCA monomers and contribution of H-bonding into PEI(PEI-H+)-STCA and Si-STCA association.

Suppressing the thermal conduction in glass–ceramic foams by controlling crystallization

AbstractGlass‐based insulating materials have attracted considerable attention owing to their tailorable properties. It is known that the thermal conductivity of glass ceramics can be greatly influenced by varying their crystallinity. However, the mechanism of such influence in glass–ceramic foams remains poorly understood. In this study, we demonstrate our new findings regarding the correlation between thermal conductivity and crystallinity in silicate glass–ceramic foams. The foams were produced by mixing ZrO2‐containing soda‐lime glass powder with CaCO3 as foaming agent and foam them using a thermochemical approach. ZrO2 was introduced as a nucleation agent. The crystallinity of the foams was varied by adjusting the heating protocol, i.e., by varying temperature, time, and number of heating cycles. The glass–ceramic foams exhibited relative crystallinities of <30%. The identity of the crystalline phases in the glass–ceramic foams varies with crystallinity. Specifically, cristobalite diminished, but devitrite grew with increasing crystallinity. It was observed that the crystallinity had a nonmonotonic impact on the thermal conductivity of the glass–ceramic foams. The optimum crystallinity for achieving the lowest thermal conductivity was 8–10%, resulting in an approximately 20% lower thermal conductivity compared to noncrystalline. Our findings have implications for the future design of glass–ceramic foams.

Insights into surrogate respiratory droplet behaviour on inclined surfaces: Implications for disease transmission

Disease transmission via fluid ejections from infected individuals presents a significant public health challenge. The ejected droplet frequently lands on substrates with varying orientations, including horizontal, vertical, and inclined. However, the behaviour of disease-causing droplets on inclined substrates remains unexplored. Recent research has demonstrated that droplet evaporation, flow, and colloidal deposition are significantly altered when surfaces are inclined. Changes in contact angle impact evaporative flux and induce flow between the top and bottom edges of the droplet. This study examines the behaviour of simulated respiratory droplets containing NaCl, mucin, and micrometer-sized particles as pathogen surrogates, focusing on substrate inclinations of 0°, 45°, and 90° on glass surfaces. As respiratory droplets evaporate, their solute concentration rises, altering both surface tension and viscosity. The study explores the coupled effects of solute concentration variations and asymmetric evaporative flux at varying relative humidity conditions and droplet volumes. The presence of salt and mucin induces Marangoni flow, potentially altering evaporation, flow patterns, and deposition dynamics. Additionally, sedimentation flow influences crystal nucleation sites and precipitation patterns. Results reveal unprecedented crystallization dynamics on inclined substrates, with notable differences in nucleation and growth based on the angle of inclination. Optical profilometry and confocal microscopy further show that surrogate bacterial particles accumulate excessively at the bottom edge of inclined droplets, suggesting an elevated risk of pathogen survival on inclined fomites. These findings highlight the critical importance of considering substrate orientation in understanding the transmission of disease through surface-bound droplets, offering insights that could inform public health strategies.

Crystal Chemistry at Interfaces Between Liquid Al and Polar SiC{0001} Substrates

Silicon carbide (SiC) has been widely added into light metals, e.g., Al, to enhance their mechanical performance and corrosion resistance. SiC particle-reinforced metal matrix composites (SiC-MMCs) exhibit low weight/volume ratios, high strength/hardness, high corrosion resistance, and thermal stability. They have potential applications in aerospace, automobiles, and other specialized equipment. The macro-mechanical properties of Al/SiC composites depend on the local structures and chemical interactions at the Al/SiC interfaces at the atomic level. Moreover, the added SiC particles may act as potential nucleation sites during solidification. We investigate local atomic ordering and chemical interactions at the interfaces between liquid Al (Al(l) in short) and polar SiC substrates using ab initio molecular dynamics (AIMD) methods. The simulations reveal a rich variety of interfacial interactions. Charge transfer occurs from Al(l) to C-terminating atoms (Δq = 0.3e/Al on average), while chemical bonding between interfacial Si and Al(l) atoms is more covalent with a minor charge transfer of Δq = 0.04e/Al. The prenucleation at both interfaces is moderate with three to four recognizable layers. The information obtained here helps increase understanding of the interfacial interactions at Al/SiC at the atomic level and the related macro-mechanical properties, which is helpful in designing novel SiC-MMC materials with desirable properties and optimizing related manufacturing and machining processes.

Improvement of superconducting, morphological, and flux pinning ability of YBa2Cu3O7−y matrix with oxygen and Mn2O3 impurity

Abstract In the current work, the influence of oxygen and Mn2O3 impurity levels intervals 0.00 ≤ x ≤ 0.30 on various key properties such as electrical resistivity, superconducting, flux pinning ability, stabilization of ceramic system, and morphological properties of YBa2Cu3O7-y (Y-123) superconductor were examined by electrical resistivity, critical current density, and scanning electron microscopy (SEM), electron dispersive x-ray (EDX) measurements. The EDX test results indicated that all the Y-123 ceramics produced possessed different composition distributions on the sample surface. SEM photomicrographs also confirmed the improvement in the appearance of surface morphology and crystallinity quality of the YBa2Cu3O7-y system. Moreover, the development in the interaction quality between grains, pinning ability and strength quality of 2D coupled vortices was obtained with the oxygen ambient and optimum manganese impurity addition highly dispersing throughout the intra grain and inter-grain boundary couplings due to the increase in the artificial flux pinning nucleation sites in the Y-123 system. Thus, the best sample with the highest Jc value of 98 A/cm2 showed the most resistance to the applied magnetic field and current. Similarly, the same sample exhibited the greatest superconductive offset (98.320 K) and onset (100.504 K) temperatures values based on the development of the Cu-O coordination and stability of the crystal structure. In conclusion, this comprehensive study based on the analysis of oxygen and Mn2O3 impurity addition mechanism through the YBa2Cu3O7-y ceramic matrix may open a new and applicable field for advanced engineering, heavy industry technology and large-scale applications.

Impact of Substrate upon Morphology, Luminescence, and Wettability of ZnMgO Layers Deposited by Spray Pyrolysis

In this work, we report on a comparative study of the topology, luminescence, and wettability properties of ZnMgO films prepared by a cost-effective spray pyrolysis technology on GaAs substrates with (100), (001), and (111) crystallographic orientations, as well as on Si(100) substrates. Deposition on nanostructured GaAs substrates was also considered. It was found that film growth is not epitaxial or conformal, but rather, it is granular, depending on the nucleating sites for the crystallite growth. The distribution of nucleation sites ensured the preparation of nanostructured films with good uniformity of their topology. The observed difference in columnar growth on Si substrates and pyramidal growth on GaAs ones was explained in terms of the impact of chemical bonding in substrates. The films grown on GaAs substrates with a (001) orientation were found to be made of larger crystallites compared to those deposited on substrates with a (111) orientation. These effects resulted in a difference in roughness of a factor of 1.5, which correlates with the wetting properties of films, with the most hydrophobic surface being found on films deposited on GaAs substrates with a (111) orientation. The prospects for photocatalytic and gas sensor applications of films produced on flat substrates, as well as for plasmonic and other applications of films deposited on nanostructured substrates, are discussed, taking into account the results of the analysis of their photoluminescence properties.

Effects of amino alcohols-intercalated MgAl-LDH nanocomposites on the properties of sulfoaluminate cement-based materials

Sulfoaluminate cement-based materials (SCBMs) have low mechanical properties in the early stages when they are used in grouting reinforcement engineering. The mechanical properties of cement-based materials can be improved by nanotechnology. Hydrotalcite is a layered anionic clay with adjustable interlayer anions and nanometer spacing. To date, the effect of amino alcohols (ethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA))-intercalated MgAl-layered double hydroxides (LDH) nanocomposites (denoted as MgAl-LDH-TEA, MgAl-LDH-DEA, and MgAl-LDH-MEA) on the properties of SCBMs have not been studied. Herein, we demonstrate that intercalated MgAl-LDH exhibit a decrease in crystallinity, an increase in particle size, and improved early mechanical properties compared to unmodified LDHs. MgAl-LDH modified by TEA, DEA, and MEA all have a nucleation effect and provide nucleation sites for ettringite. Simultaneously, the intercalated hydrotalcite can release higher concentrations of magnesium ions into the slurry, forming a magnesium-containing ettringite phase and accelerating the hydration of SCBMs. Modified MgAl-LDH can also release amino alcohols, affecting the hydration process of the paste. The modified LDHs affect the hydration and compressive strength of SCBMs owing to the combined action of the nucleation of LDHs and the release of magnesium ions and amino alcohols compounds.

Improving the removal of fine particles in cyclone using heterogeneous vapor condensation enhanced by atomization

Using a heat exchanger to cool high humidity flue gas can create a supersaturated water vapor environment, allowing fine particles to grow into large droplets by heterogeneous vapor condensation, which is conductive to the removal of fine particles by traditional equipment. However, due to the limited condensable vapor obtained by cooling, this technology can only be used in the flue gas with low particle concentration. In this study, atomization droplets were added before the heat exchanger to improve the effect of heterogeneous vapor condensation at high particle concentration, and then coupled with a cyclone separator, which was used for the deep treatment of the flue gas after the wet dedusting system. The particle removal characteristics were investigated through laboratory experiments and bypass experiments in a metallurgical company. The experimental results show that the application of atomization-heterogeneous condensation reduced the particles concentration after cyclone by 74.2 % compared with that of single heterogeneous condensation. Temperature-drop and atomized volume affected the removal of particles with size < 2 μm and > 2 μm, respectively. The industrial flue gas bypass experiment indicated that the system had strong adaptability to fluctuating conditions. When the inlet particle concentration did not exceed 2000 mg/Nm3, the outlet particle concentration can be maintained within 20 mg/Nm3.

Electrophoretic Deposition of Bioactive Glass 58S- xSi3N4 (0

This paper aims to investigate the biocompatibility, bioactivity and properties of bioactive glass 58S-xSi3N4 (0<x<20 wt.%) nanocomposite coating on AISI 316L stainless steel substrate, applied by electrophoretic deposition method. The implications of adding Si3N4 nanoparticles up to 20 wt.% to the bioactive glass coating for the structural and biomedical properties of deposited coatings were investigated. The deposited coating samples were characterized by X-ray diffraction (XRD) analysis, field emission scanning electron microscope (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), and energy dispersive X-ray spectroscopy (EDS). For the evaluation of cellular toxicity, the MTT cytotoxicity test with MG63 bone cell was performed. Bioactivity test was also conducted in simulated body fluid (SBF) up to 28 days. Results showed that increase in the Si3N4 content of composite samples is associated with a significant decrease in the average size of composite powder, inferring that Si3N4 additive has become nucleation sites during synthesis. Stereomicroscope images showed that with an increase in deposition time up to 70 min, a uniform coating can be attained. An increase in the Si3N4 content is associated with a significant reduction in surface roughness and non-uniformities of the deposited layer. The addition of Si3N4 in the composite layer slightly increases the wetting angle. The highest cellular toxicity was observed for the AISI 316L sample at the concentration of 10 micromolar, while the lowest cellular toxicity is attributed to the BG-20%Si3N4 sample at the concentration of 75 micromolar, exhibiting viability values similar to the control sample. Bioactivity assessment of deposited coatings indicated a remarkable improvement in the bone-forming ability of Si3N4-containing bioactive glass composite.

Laser powder bed fusion of high-strength crack-free Al7075 alloy with the in-situ formation of TiB2/Al3Ti-reinforced phases and nucleation agents

The existence of solidification cracks caused by columnar grains in precipitation-hardened aluminium alloys limit the applicability of Al7075 components manufactured via laser powder bed fusion (LPBF) additive manufacturing. A novel approach was developed to co-incorporate submicron-sized B and micron-grade Ti6Al4V to eliminate hot cracks and to effectively transform coarse columnar grains into fine equiaxed grains, thus improving the mechanical performance of LPBF-fabricated modified Al7075 material. The grain refinement was mainly attributable to the heterogeneous nucleation promoted by the combination of in-situ-formed L12-Al3Ti and TiB2 nano-sized phases. After an optimised T6 heat treatment, excellent comprehensive mechanical properties were achieved, with a tensile strength of 460 MPa and an elongation of 13 %. This research provides an efficient and cost-effective path for addressing crack-sensitive metallic materials used for LPBF additive manufacturing processes.