Final Material Research Articles

Facile and ecofriendly green synthesis of Co3O4/MgO-SiO2 composites towards efficient asymmetric supercapacitor and oxygen evolution reaction applications.

The development of low-cost, eco-friendly, and earth-friendly electrode materials for energy storage and conversion applications is a highly desirable but challenging task for strengthening the existing renewable energy systems. As part of this study, orange peel extract was utilized to synthesize a magnesium oxide-silicon dioxide hybrid substrate system (MgO-SiO2) for coating cobalt oxide nanostructures (Co3O4) via hydrothermal methods. A variety of MgO-SiO2 compositions were used to produce Co3O4 nanostructures. The purpose of using MgO-SiO2 substrates was to increase the porosity of the final hybrid material and enhance its compatibility with the electrode material. This study investigated the morphology, chemical composition, optical properties, and functional group properties. In hybrid materials, the shape structure is inherited from nanoparticles with uniform size distributions that are well compacted. A relative decrease in the optical band was observed for Co3O4 when deposited onto an MgO-SiO2 substrate. An improvement in the electrochemical properties of Co3O4/MgO-SiO2 composites was observed during the measurements of supercapacitors and oxygen evolution reaction (OER) in alkaline solutions. The Co3O4/MgO-SiO2 composite prepared on 0.4 g of the MgO-SiO2 substrate (sample 2) demonstrated excellent specific capacitance, high energy density, and recycling stability for 40 000 galvanic charge-discharge cycles. The assembled asymmetric supercapacitor (ASC) device demonstrated a specific capacitance of 243.94 F g-1 at a current density of 2 A g-1. Co3O4/MgO-SiO2 composites were found to be highly active towards the OER in 1 M KOH aqueous solution with an overpotential of 340 mV at 10 mA cm-2 and a Tafel slope of 88 mV dc-1. It was found that the stability and durability were highly satisfactory. Based on the use of orange peel extract, a roadmap was developed for the synthesis of porous hybrid substrates for the development of efficient electrode materials for energy storage and conversion.

Improved Graphitization of Lignin by Templating Using Graphene Oxide Additives.

Techniques to improve the graphitization of lignin, the second most abundant natural polymer, are in great demand as a viable means to obtain cost-effective and less energy-intensive graphite for various applications. In this work, we report the effects of two-dimensional nanomaterials, graphene oxide (GO) and its derivative, reduced graphene oxide (RGO), used as templating agents for the graphitization of alkali-derived lignin. The hypothesis is that during heat temperature treatment, the GO additives act as a template that allows the lignin matrix to align on its basal planes through π-π interactions. In addition, possible chemical bonding between the GO additives and lignin may extend the two planar frameworks. Results from X-ray diffraction and Raman spectroscopy showed improved graphitic quality in the lignin-GO and lignin-RGO samples compared to pure lignin at 2500 °C. Transmission electron microscopy images and selected area electron diffraction patterns also revealed ordered nanostructures and defined polycrystalline patterns in the lignin-GO and lignin-RGO samples. This work presents a method to synthesize graphitic-like materials using carbon-based templates with the advantage that there is no need for further purification of the final material as in the case of transition metal catalysts.

Maximizing surface reactivity: The impact of electrochemical oxidation as a polydopamine modification step

Melanin-based materials are highly versatile and widely utilized across various industries, thanks to their customizable surface properties and excellent biocompatibility. Dopamine, a well-studied precursor, has the remarkable ability to self-oxidize and form melanin-like compounds. This molecule can be tailored using cations during the oxidation process or via the chelation of hydroxyl groups in the final material. In order to explore the adaptability of dopamine-based melanin materials, our research focuses on producing particles using an innovative double-step process. The first oxidation is catalyzed by Y3+ in an electrochemical process, followed by further cyclization in a basic medium. We examined the resulting products to gauge the impact of the process on the final molecular arrangement and chelation capacity by utilizing Fe2+ as a cation probe. Surface reactivity was assessed using voltammetry techniques and electrochemical impedance spectroscopy. The results clearly indicate significant improvements in the molecular arrangement, demonstrating that the double-step process delivers higher material stability and superior surface reactivity compared to the conventional alkali self-oxidation method.

РАЗРАБОТКА ТЕХНОЛОГИЧЕСКОЙ СХЕМЫ И ОБОСНОВАНИЕ ПАРАМЕТРОВ ОЧИСТКИ СЕМЯН ЛЮЦЕРНЫ

Despite the high effectiveness of chemical preparations against weeds, this fight begins with the preparation of seed material on seed cleaning lines. An urgent problem in cleaning crop seeds is the isolation of dodder seeds in the preparation of alfalfa seeds. Alfalfa cleaning is a time-consuming process in itself, due to the complex structure of the combine heap. In this regard, it is important to develop a technological scheme for cleaning the alfalfa heap, which will allow you to effectively separate dodder seeds on a par with other impurities. When developing the technological scheme for alfalfa purification, the parameters of the initial heap and its components were determined. When determining the composition of the alfalfa heap, it was found that the alfalfa heap consists of 40-60% of organic impurities, 10% of puny seeds, and up to 10% of the heap consists of unthreshed beans, and the alfalfa seeds themselves in the initial heap are usually no more than 30% of the total weight, it was also determined that weed seeds make up less than 1% of the original weight, nevertheless, the heap contained 0.02% of dodder seeds. On laboratory screens with slotted notches and round holes, the dimensional characteristics of the components are determined. On the sail classifier, the distributions of the components according to the critical speed of vinow were established. The data obtained made it possible to develop a technological scheme for cleaning alfalfa seeds, which allows you to effectively remove dodder seeds with minimal losses. Using the same equipment in laboratory conditions, the proposed alfalfa cleaning scheme was tested, which showed that by combining aspiration and sieve cleaning, it is possible to achieve 99.45% purity of seeds, with losses of no more than 1%, dodder was not found in the final material.

Validation of quantitative aortic valve calcification assessment by photon-counting computed tomography from contrast-enhanced data sets using virtual non-contrast reconstructions

Abstract Background The spectral information of photon-counting computed tomography (PCCT) permits the reconstruction of energy-selective images. Purpose We evaluated two methods for the reconstruction of virtual non-contrast-enhanced images from contrast-enhanced CT angiographic data sets regarding their ability to quantify aortic valve calcification. Results were validated by comparison to non-enhanced computed tomography. Methods A total of 100 subjects with severe aortic valve stenosis who underwent ECG-synchronized cardiac photon-counting CT for diagnostic workup prior to transcatheter aortic valve implantation (TAVI) were included in the current analysis. A standard true non-contrast acquisition was performed for aortic valve calcium quantification in each subject. In addition, two virtual non-enhanced data sets were reconstructed from contrast-enhanced CT angiographic data: a calcium-specific image ("pure calcium scan", PCS) and a virtual non-contrast (VNC) scan by subtraction of iodine. The PCS algorithm separates calcium and iodine in spectral PCCT images, creating a non-calcium mask for denoised spectral input and preserving calcium contrast in final material decomposition. Iodine extraction is achieved by measurement of the iodine content and its differentiation from native soft tissue attenuation. The Agatston Score was assessed in each of the three image data sets using semi-automated software. Results The mean age of the subjects was 78 ± 7 years, 66% were male. Mean EUROSCORE II was 4 ± 4%, mean STS Score for morbidity and mortality was 16 ± 11%. In the true non-contrast scan used for validation, the mean Agatston Score was 3028 ± 1820. The mean Agatston Score obtained from the PCS data set was 3004 ± 2042 and did not differ significantly from true non—contrast image sets (p=0.716). In the VNC data sets, the mean Agatston score was 1726 ± 1288, significantly lower than in the true non-contrast and the PCS data sets (both <0.001). Both, PCS and VNC data showed a significant correlation with true non-contrast scans (correlation coefficient PCS: 0.978, VNC scan: 0.975, both p<0.001). Conclusion In conclusion, the current results show the possibility to reliably quantify the Agatston Score of larger cardiac calcifications in virtual non-contrast data sets – however, there is substantial influence of the algorithm that is used so that validation of new techniques is of key importance.

Morphology Control of Polymer-Inorganic Hybrid Nanomaterials Prepared in Miniemulsion: From Solid Particles to Capsules.

The preparation of so-called hybrid nanomaterials has been widely developed in terms of functional and morphological complexity. However, the specific control of the arrangement of organic and inorganic species, which determines the properties of the final material, still remains a challenge. This article offers a review of the strategies that have been used for the preparation of polymer-inorganic hybrid nanoparticles and nanocapsules via processes involving miniemulsions. Different polymer-inorganic nanostructures are classified into four main groups according to the sequential order followed between the synthesis of the polymer and the inorganic species, and the presence or not of their counterpart precursors. The minimization of the energy of the system governs the self-assembly of the different material components and can be addressed by the miniemulsion formulation to reduce the interfacial tensions between the phases involved. The state of the art in the preparation of hybrid nanoparticles is reviewed, offering insight into the structural possibilities allowed by miniemulsion as a versatile synthetic technique.

Colloidal Ag2SbBiSe4 nanocrystals as n‑type thermoelectric materials

Materials with low intrinsic thermal conductivity are essential for the development of high-performance thermoelectric devices. At the same time, the solution processing of these materials may enable the cost-effective production of the devices. Herein, we detail a high-yield and scalable colloidal synthesis route to produce Ag2SbBiSe4 nanocrystals (NCs) using amine-thiol-Se chemistry. The quaternary chalcogenide material is consolidated by a rapid hot-press maintaining the cubic crystalline structure. Transport measurements confirm that n-type Ag2SbBiSe4 exhibits an inherently ultralow lattice thermal conductivity of ca. 0.34 W m−1K−1 at 760 K. Moreover, a modulation doping strategy based on the blending of semiconductor Ag2SbBiSe4 and metallic Sn NCs is demonstrated to control the charge carrier concentration in the final composite material. The introduction of Sn nanodomains additionally blocks phonon propagation thus contributing to reducing the thermal conductivity of the final material. Ultimately, a peak thermoelectric figure of merit value of 0.64 at 760 K is achieved for n-type Ag2SbBiSe4-Sn nanocomposites that also demonstrate a notable Vickers hardness of 185 HV.

Covalently Linked 2D-Co3O4/GO Heterostructures: Catalytic and Electrochemical Properties.

Covalently cross-linked 2D heterostructures may represent a ground-breaking approach to creating materials with multifunctionalities. To date, however, this field still remains relatively unexplored. In the present work, Co3O4/GO covalently linked heterostructures (Co3O4/GO-CL) were produced using 2D-Co3O4 functionalized with (3-aminopropyl)triethoxysilane (APTES) to react with the carboxyl groups of graphene oxide (GO). The surface and interface properties of the final material were assessed through electrochemical and catalytic studies. We found that the covalent bonds lead to a self-standing and ordered final structure, not observed for the noncovalent material (Co3O4/GO-nCL), also produced for comparison. The catalytic activity of Co3O4/GO-CL over the degradation of Rhodamine 6G showed great performance and the possibility of recycling the catalyst. Electrochemical evaluation stated higher specific capacitance for the covalently bonded material (468 F g-1 against 110 F g-1). Overall, results showed that the covalent bonds may be improving charge-transfer and interfacial area features, thus leading to enhanced catalytic and electrochemical performances.

Effect of welding gas mixtures on weld material and bead geometry

Abstract Shielding gas is an essential parameter in welding processes, serves to shield the molten material from the atmosphere and external contaminations while providing a stable electric-arc pathway during the process, thus influencing the quality of the weld bead and several other aspects of the process. Therefore, any welding-based process, such as wire-arc additive manufacturing, could benefit from shielding gas mixture optimisation to selectively improve the processing and possibly the final mechanical properties of the welded material. In this study welding of EN AW 5183 aluminium (single weld bead and wire-arc additive manufacturing build-up) was conducted using several gas mixtures and their influence on final geometry defects, and microstructure measured. The gas mixtures used were a combination of varying amounts of carbon dioxide, nitrogen, and oxygen. These were added to commercially available argon gas. It was observed that: CO2 additions led to an unfavourable bonding defect and increased mean grain size; nitrogen additions caused a decrease in mean grain size, decreased pore count while maintaining a similar pore volume fraction to the reference argon mixture samples; oxygen additions showed slight reduction of mean grain size, decreased pore count and decreased pore volume fraction. These results further showcase that varying shielding gas mixtures influence the final material properties and should be considered as an additional improvement route for conventional welding and additive manufacturing.

Assessing melt pool temperature independence from hardness via photodiode-based plank thermometry (PDPT)

Directed Energy Deposition (DED) has emerged as a promising metal additive manufacturing technique due to its ability to create components comparable or superior to traditional fabrication. Although industrial adoption of this technology is underway, there exists a considerable need to improve the predictability of the components it manufactures to promote wider adoption of this technology. Currently, melt pool temperature is the primary metric for build monitoring and control. However, stronger correlations must be established between the process parameters, including melt pool temperature, and resulting material outcomes to determine if melt pool control is a sufficient metric to control part quality. The goal of this research is to establish correlations between laser power (W), scanning speed (mm/s), powder flow rate (g/min), average melt pool temperature (C), and hardness. The average melt pool temperature was measured through Photodiode-based Planck thermometry (PDPT) with dual on-axis photodiodes. To obtain the correlation between these factors, 54 samples of Inconel 718 were printed, cross-sectioned, and tested using a Vickers diamond indenter. The resulting correlations exhibited extremely low R2 values and validated the findings of previous studies in that process parameters are exceedingly poor predictors of component properties. Average melt pool temperature lacked a significant correlation with hardness, instead process scanning speed demonstrated a more significant impact on the final material hardness. Since hardness is largely dictated by average grain size which in turn is controlled primarily by solidification rate, solidification rate should be the focus of future work to control material properties. The results of this study indicate that melt pool thermal control is not a sufficient metric to control part quality, and a solution is needed that can oversee the build process in such a way that solidification rate can be monitored and controlled in addition or instead of melt pool temperature. Future work must be done to apply the PDPT methodology to real time calibrated indirect measurement of melt pool solidification rates to improve prediction and control of final part mechanical properties.

Electrically Conductive Lignin Reinforced Polyacrylic Acid/Hyaluronic Acid Scaffolds With PEDOT:HA Nanoparticles

ABSTRACTHydrogel materials are continually developing in biomedical engineering and recently a lot of effort has gone into their engineered performance in physiological applications. Porosity is an important characteristic for tissue engineering scaffolds to allow enhanced biocompatibility and the pore size needed is dependent on the application and type of tissue for which the hydrogel is being used to regenerate. Regarding biomedical applications, the use of conducting polymers is gaining in popularity due to their promising biocompatibility and potential to stimulate cell growth and proliferation through electrical stimulation. Building on previous hydrogel development by the authors, this study focuses on developing a biocompatible hydrogel scaffold with adjustable porosity and swelling capabilities, robust mechanical properties, electrical conductivity, and high thermal stability. The objective of this work is to examine the effect of freezing temperature, cross‐linker and porosity on the final characteristics of the scaffold and to then determine possible applications. The porosity, swelling degree, compression strength, biocompatibility, electrical conductivity, and thermal characteristics of the final material were analyzed and were found to be affected by the varied synthesis methods used. Overall, the synthesized scaffolds exhibit good biocompatibility with increased fluorescence over 3 days and over 70% cell viability, thermal stability up to 200°C and a range of swelling of 1725% to 8472%. They also portray robust mechanical properties with a Young's Moduli range of 11 kPa to 4.54 MPa and a porosity range of 0.78–71.98 μm depending on the synthesis methods used. Through variations in synthesis methods, highly porous, absorbent, and stable scaffolds have been synthesized. Notably, this single recipe is highly tailorable for use in a range of biomedical applications from tissue engineering to drug delivery and wound repair.

Enhancing epoxy resin curing: Investigating the catalytic role of water as a trace impurity in dense crosslinked network formation using an advanced cat-GRRM/MC/MD Method1

The catalytic effect of water, a trace impurity in resins, facilitates efficient curing, affording a dense crosslinked network structure. Crosslinked networks are crucial for polymer properties. Water considerably influences the reaction pathways and kinetics and the final network structure and material properties. This study advances the cat-GRRM/MC/MD method to explore the specific role of water molecules as catalysts, though an impurity, in the curing of epoxy resins. Global reaction route mapping was used to compute the chemical reaction pathways and the corresponding energies. The resin properties were predicted via molecular dynamics simulations, complemented by the Monte Carlo method to simulate reaction kinetics and bond formation processes. Water molecules act as unique catalysts in the curing of epoxy resins, altering the reaction pathways and reducing the activation energies. The study revealed significant improvements in the physical properties of the resulting epoxy resins, aligning them more closely with the experimental material characteristics.

Impact of environmental conditions on organic matter in astrophysical ice analogues

ABSTRACT The existence of organic matter presenting a high molecular diversity in extraterrestrial environments is well documented. To understand the origin of this organic diversity, laboratory experiments were developed and showed that irradiation and thermal alteration of simple molecules such as methanol, water, and ammonia in conditions mimicking astrophysical ice environments. Ices containing water, methanol, and ammonia (H2O: MeOH: NH3) photolyzed and monitored by infrared spectroscopy, while the organic matter formed at room temperature was analyzed in situ with infrared spectroscopy and ex situ with high-resolution mass spectrometry. Those ices irradiated at 77 K and 10−8 mbar shows a significant organic molecular diversity: residual organic compounds contain up to 78 C, 188 H, 123 N, and 37 O. Most of them contains all four CHNO atoms (76–86 per cent), followed by CHO (11–17 per cent), and CHN compounds (5–6 per cent). CHNO and CHO compounds are more aliphatic (34–53 per cent), while CHN compounds are mostly condensed aromatics (83–90 per cent). In this work, our objective is to investigate impacts of environment on this organic molecular diversity by focusing on three parameters: photon dose, pressure, and heating rate during the warming process. Analyses of the residue formed showed that the heating rate and pressure weakly alter the abundance of the final organic material, while the irradiation rate reduced its abundance at high photon doses by a factor of 8. These results give insights on the impact of icy environment conditions in the evolution of astrophysical organic matter.

Effect of Different Porous Size of Porous Inorganic Fillers on the Encapsulation of Rosemary Essential Oil for PLA-Based Active Packaging.

Essential oils are interesting active additives for packaging manufacturing as they can provide the final material with active functionalities. However, they are frequently volatile compounds and can be degraded during plastic processing. In this work Rosmarinus officinalis (RO) essential oil was encapsulated into Diatomaceous earth (DE) microparticles and into Halloysite nanotubes (HNTs) and further used to produce eco-friendly active packaging based on polylactic acid (PLA). PLA-based composites and nanocoposites films based on PLA reinforced with DE + RO and HNTs + RO, respectively, were developed by melt extrusion followed by cast-film, simulating the industrial processing conditions. As these materials are intended as active food packaging films, the obtained materials were fully characterized in terms of their mechanical, thermal and structural properties, while migration of antioxidant RO was also assessed as well as the compostability at laboratory scale level. Both DE and HNTs were able to protect the Rosmarinus officinalis (RO) from thermal degradation during processing, allowing to obtain films with antioxidant properties as demonstrated by the antioxidant assays after the materials were exposed for 10 days to a fatty food simulant. The results showed that incorporating Rosmarinus officinalis encapsulated in either DE or HNTs and the good dispersion of such particles into the PLA matrix strengthened its mechanical performance and sped up the disintegration under composting conditions of PLA, while allowing to obtain films with antioxidant properties of interest as antioxidant active food packaging materials.

Effects of crosslinker concentration on curing process and performances of needled fiber preform reinforced phenolic aerogel composite using process simulation and comprehensive experiments

A kind of needled quartz/carbon fiber preform reinforced phenolic aerogel composite (NQCF/PR) was fabricated through impregnating needled fiber preform with phenolic resin precursor solution, followed by sol–gel polymerization and solvent drying. The needled fiber preform serves as lightweight quasi-three-dimensional reinforcement, while phenolic aerogel matrix provides high porosity and low thermal conductivity. During fabrication of aerogel composite part using vacuum-assisted resin infusion process, distribution of crosslinker hexamethylenetetramine (HMTA) in precursor solution can be problematic, as precipitated crosslinker particles may be filtered by fibrous preform. In this study, the impact of HMTA filtration induced heterogeneous structure on subsequent curing process was investigated using process simulation. Temperature effects of sol–gel polymerization and solvent evaporation were considered through establishment of corresponding kinetic models. Impacts of heterogenous structure on distribution of temperature, resin curing degree and solvent conversion degree in large hemispherical aerogel composite structure were investigated. This leads to variations in gel network and pore structure of aerogel, thereby affecting final material performance. Based on experimental results, as HMTA concentration increases, compressive performance of NQCF/PR obviously increases. Among these, NQCF/PR with 4.7 wt% HMTA provides a balance of lightweight nature (0.25 g/cm3), excellent thermal insulation property (0.052 W·m−1·K−1) and compressive performance (strength of 0.35 MPa).

A Self-Skin Permeable Doxorubicin Loaded Nanogel Composite as a Transdermal Device for Breast Cancer Therapy.

Modern drug delivery research focuses on developing biodegradable nanopolymer systems. The present study proposed a polymer-based composite nanogel as a transdermal drug delivery system for the pH-responsive targeted and controlled delivery of anticancer drug doxorubicin (DOX). Nanogels have properties of both hydrogels and nanomaterials. The β-cyclodextrin-based nanogels can enhance the loading capacity of poorly soluble drugs and promote a sustained drug release. The β-cyclodextrin-grafted methacrylic acid conjugated hyaluronic acid composite nanogel was successfully synthesized. β-Cyclodextrin was first grafted onto methacrylic acid. The composite nanogel-based drug carrier was prepared by controlled radical polymerization (CRP) of β-cyclodextrin-grafted methacrylic acid with hyaluronic acid. The doxorubicin-loaded carrier was characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, zeta potential analysis, dynamic light scattering (DLS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The drug loading and release efficiencies were carried out at different pH levels. The maximum drug loading and encapsulation efficiencies of the synthesized final nanogel composite material at pH 8.0 were 86.44 ± 2.12 and 96.07 ± 2.01%, respectively. The DOX-loaded final material showed a 90.0 ± 2.6% release percentage of DOX at pH 5.5, whereas at pH 7.4, the release percentage of DOX was observed to be only 35.0 ± 0.3%. In vitro swelling, degradation, hemocompatibility, drug release kinetics, cytotoxicity, apoptosis, cell colocalization, skin irritation, and skin permeation studies, along with in vivo pharmacokinetic studies, were performed to prove the efficacy of the synthesized nanogel composite as a transdermal carrier for doxorubicin.

Sensitive detection of NH3 at room temperature at ppb level via facile ZIF calcination

This study introduces an innovative approach for preparing gas sensors involving the formation of metal oxides from metal–organic framework materials via a two-step calcination process. A gas-sensitive material capable of detecting NH3 at a concentration of 11 ppb at room temperature was developed using a simple and facile experimental method. Compared with materials produced in previous studies by one-step calcination, the C-doped ZnO developed in this study had a dispersed cubic porous morphology with a higher specific surface area and smaller pore size. During two-step calcination, urea acts as a structure-directing agent and increases the gas adsorption capacity of the final material. Additionally, the incorporation of urea slightly reduced the material's band gap. Further examinations confirmed the material's exceptional selectivity and long-term stability in detecting NH3, and response tests at 59 %, 75 %, and 85 % relative humidity indicated its tolerance to high-humidity environments. These outstanding characteristics suggest that the proposed fabrication method can produce metal-oxide materials with substantially enhanced gas-sensing performance.

Gelatin-Sodium Alginate Hydrogels Cross-Linked by Squaric Acid and Dialdehyde Starch as a Potential Bio-Ink.

Hydrogels as biomaterials possess appropriate physicochemical and mechanical properties that enable the formation of a three-dimensional, stable structure used in tissue engineering and 3D printing. The integrity of the hydrogel composition is due to the presence of covalent or noncovalent cross-linking bonds. Using various cross-linking methods and agents is crucial for adjusting the properties of the hydrogel to specific biomedical applications, e.g., for direct bioprinting. The research subject was mixtures of gel-forming polymers: sodium alginate and gelatin. The polymers were cross-linked ionically with the addition of CaCl2 solutions of various concentrations (10%, 5%, 2.5%, and 1%) and covalently using squaric acid (SQ) and dialdehyde starch (DAS). Initially, the polymer mixture's composition and the hydrogel cross-linking procedure were determined. The obtained materials were characterized by mechanical property tests, swelling degree, FTIR, SEM, thermal analysis, and biological research. It was found that the tensile strength of hydrogels cross-linked with 1% and 2.5% CaCl2 solutions was higher than after using a 10% solution (130 kPa and 80 kPa, respectively), and at the same time, the elongation at break increased (to 75%), and the stiffness decreased (Young Modulus is 169 kPa and 104 kPa, respectively). Moreover, lowering the concentration of the CaCl2 solution from 10% to 1% reduced the final material's toxicity. The hydrogels cross-linked with 1% CaCl2 showed lower degradation temperatures and higher weight losses than those cross-linked with 2.5% CaCl2 and therefore were less thermally stable. Additional cross-linking using SQ and DAS had only a minor effect on the strength of the hydrogels, but especially the use of 1% DAS increased the material's elasticity. All tested hydrogels possess a 3D porous structure, with pores of irregular shape and heterogenic size, and their swelling degree initially increased sharply to the value of approx. 1000% during the first 6 h, and finally, it stabilized at a level of 1200-1600% after 24 h. The viscosity of 6% gelatin and 2% alginate solutions with and without cross-linking agents was similar, and they were only slightly shear-thinning. It was concluded that a mixture containing 2% sodium alginate and 6% gelatin presented optimal properties after gel formation and lowering the concentration of the CaCl2 solution to 1% improved the hydrogel's biocompatibility and positively influenced the cross-linking efficiency. Moreover, chemical cross-linking by DAS or SQ additionally improved the final hydrogel's properties and the mixture's printability. In conclusion, among the tested systems, the cross-linking of 6% gelatin-2% alginate mixtures by 1% DAS addition and 1% CaCl2 solution is optimal for tissue engineering applications and potentially suitable for 3D printing.

Influence of Process Parameters on Selected Properties of Ti6Al4V Manufacturing via L-PBF Process.

This study investigates the microstructural effects of process parameters on Ti6Al4V alloy produced via powder bed fusion (PBF) using laser beam melting (LB/M) technology. The research focuses on how variations in laser power, exposure velocity, and hatching distance influence the final material's porosity, microhardness, and microstructure. To better understand the relationships between process parameters, energy density, and porosity, a simple mathematical model was developed. The microstructure of the alloy was analyzed in the YZ plane using a confocal microscope. The study identified optimal parameters-302.5 W laser power, 990 mm/s exposure velocity, and 0.14 mm hatching distance-yielding the lowest porosity index of 0.005%. The material's average hardness was measured at 434 ± 18 HV0.5. These findings offer valuable insights for optimizing printing parameters to produce high-quality Ti6Al4V components using PBF-LB/M technology, shedding light on the critical relationship between process parameters and the resulting microstructure.

Research Progress on Laser Powder Bed Fusion Additive Manufacturing of Zinc Alloys.

Zinc, along with magnesium and iron, is considered one of the most promising biodegradable metals. Compared with magnesium and iron, pure Zn exhibits poor mechanical properties, despite its mild biological corrosion behavior and beneficial biocompatibility. Laser powder bed fusion (LPBF), unlike traditional manufacturing techniques, has the capability to rapidly manufacture near-net-shape components. At present, although the combination of LPBF and Zn has made great progress, it is still in its infancy. Element loss and porosity are common processing problems for LPBF Zn, mainly due to evaporation during melting under a high-energy beam. The formation quality and properties of the final material are closely related to the alloy composition, design and processing. This work reviews the state of research and future perspective on LPBF zinc from comprehensive assessments such as powder characteristics, alloy composition, processing, formation quality, microstructure, and properties. The effects of powder characteristics, process parameters and evaporation on formation quality are introduced. The mechanical, corrosion, and biocompatibility properties of LPBF Zn and their test methodologies are introduced. The effects of microstructure on mechanical properties and corrosion properties are analyzed in detail. The practical medical application of Zn is introduced. Finally, current research status is summarized together with suggested directions for advancing knowledge about LPBF Zn.