Microstructural Characterization Research Articles

Effect of microstructural anisotropy and heat treatment on the corrosion behaviour of additively manufactured Ti-6Al-2Sn-4Zr-6Mo alloy

The electrochemical behaviour of Ti-6Al-2Sn-4Zr-6Mo alloy produced by Powder Bed Fusion – Laser Based/Metals has been investigated to identify the corrosion mechanism characteristic of the material processed by additive manufacturing technology. A microstructural characterisation of the material in as-built and heat-treated conditions was carried out to identify the different phases and assess the degree of anisotropy of the additive manufactured material. After that, the corrosion behaviour was studied by potentiodynamic polarisation and electrochemical impedance spectroscopy. Results showed that a homogeneous and compact oxide layer characterises the as-built material due to the presence of a finely dispersed α’’ phase in the β grains. Conversely, in the heat-treated alloy, the corrosion attack proceeds preferentially on the large α phase domains, where the oxide layer is less protective. Despite the anisotropy in the microstructure of the as-built material, the electrochemical behaviour was revealed to be the same for the section parallel and perpendicular to the building direction, noting the less influential factor of grain orientation on corrosion mechanisms.

Fabrication, microstructure and hemostatic activity of Cu-Zn manganite nanoparticles

Copper subbed zinc manganite Zn(1-x)CuxMn2O4 (x = 0.05,0.15,0.25,0.35,0.45,0.55) (BCZMO) NPs were prepared by sol–gel co-precipitation technique at surrounding temperature. BCZMO NPs were analyzed by XRD, SEMfor microstructure characterizations. XRD study confirms the tetragon structure of BCZMO NPs and effect of copper on ZMO NPs. SEM micrographs supports our findings. The BCZMO NPs interfered in blood coagulation and exhibited pro-coagulant property. BCZMO NPs decreased the coagulation time of citrated plasma from control 4.31 min to 1.35 min. In addition, the BCZMO NPs aggregated platelets up to 80 % at a concentration of 600 µg while the agonist epinephrine prompted platelet collection of around 90 % at 10 mM concentration.No kind of hemolytic activity in RBC cells shown by these BCZMO-NPs insisting their non-toxic nature. These BCZMO-NPs exhibited pro-coagulant effect with their interference in blood coagulation cascade and initiation in platelet aggregation. Thus, BCZMO NPs can be a potential candidate in biomedical field as hemostatic agents.

Recent Advances in Additive Manufacturing of Refractory High Entropy Alloys: A Critical Review

Refractory High Entropy alloys (RHEAs) have evolved as a superior multicomponent material having a unique combination of microstructures and mechanical properties. RHEAs are a particular grade of high entropy alloys (HEAs) known for their outstanding high-temperature properties achieved thorough their constituent refractory elements. To date, majority of the RHEAs have been manufactured through several conventional methods, but are limited by certain limitations. Additive manufacturing (AM) has the potential to revolutionize the manufacturing industry by providing excellent opportunities to fabricate RHEAs while providing opportunities for enhancing the design freedom and complex geometrical shapes. As the field is rapidly evolving, a systematic examination of our comprehension is beneficial, and this article attempts to address this issue. To find the right place in industrial markets, additively manufactured RHEAs require further advancements. The present review provides a comprehensive overview of the additively manufactured RHEAs in terms of microstructural characterization, mechanical behaviour and other environmental properties published so far. This review article is presented lucidly with an aim of better understanding for the readers in this domain. To this end, future works and current challenges are also included and discussed briefly.

The role of coherent nano precipitates on stacking fault and deformation twin formation during tensile deformation of wire arc additive manufactured nickel-aluminum-bronze

The strain hardening mechanisms and dislocation interactions of a wire arc additively manufactured (WAAM) nickel-aluminum-bronze (NAB) alloy was investigated using multi-scale characterization approach cross-correlating scanning electron microscopy (SEM), SEM-based electron back-scatter diffraction (EBSD), site- and crystallographic orientation-specific focused ion beam (FIB) nanofabrication, scanning transmission electron microscopy (STEM) and STEM-based energy dispersive X-ray spectroscopy (EDS). Flat, rectangular dog bone specimens were strained under uniaxial tension conditions. To understand the micro- and nanometer scale deformation mechanisms throughout the microstructure, tensile test specimens were interrupted near the yield strength and ultimate tensile strength. STEM microstructural characterization revealed that tensile deformation occurs by planar slip and multiple slip bands interacting on different {111} planes as well as the nucleation of dislocations from the interfaces associated with grains and secondary phase particles. To the authors knowledge for the first time the Center of symmetry (COS) analysis revealed that in both samples the shearing of nanoscale precipitates led to the formation of extended stacking faults including a combination of intrinsic stacking faults and 2-layer extrinsic stacking faults. At high strain levels more dislocations and stacking faults were nucleated, as well as intersecting slip bands further facilitating the activation of the stair-rod cross-slip mechanism and thickening of an ESF to create a 3-layer nano-twin. Activated mechanisms of plastic deformation and associated role of the precipitates are discussed with respect to the microscopic strength-plasticity characteristics as well as macroscopic mechanical properties of WAAM NAB alloy.

Experimental and modeling investigation of the thermal shock behavior of TiC-based self-healing coatings on AISI 321 stainless steel

The AISI 321 steels of structural components serviced at high temperature are usually subjected to oxidation and thermal shock damage during service. Therefore, to improve their high-temperature oxidation and thermal shock resistance, the self-healing coating consisting of Al2O3-13 %TiO2 layer, TiC layer and NiCrAlY layer was prepared for 321 steels in this work. The experimental and microstructural characterization results showed that the thermal shock resistance of such self-healing coating was remarkably improved as compared to the counterpart double-AT13 coating. This is because the volume increment resulting from the oxidation reaction between the TiC and oxygen decreased the porosity of the self-healing coating and retarded crack growth, which also led to the improved high-temperature oxidation resistance. Further, a thermal shock life model based on the crack growth model of Paris formula were developed. The modeling results not only agreed well with the experimental results but also indicated that thickening of thermal grown oxide (TGO) is the main cause of crack initiation and growth.

Microstructure and compressive behaviour of PLA/PHA-wood lattice structures processed using additive manufacturing

This study investigates the microstructure and compressive behaviour of PLA/PHA-wood lattice structures manufactured using fused filament fabrication (FFF). The primary objective is to evaluate the effects of defects, such as porosity and surface roughness, on the mechanical properties of these lattice structures. X-ray micro-tomography (XRT) and finite element analysis are employed to compare CAD models with real lattice structures, offering insights into defect-induced performance deviations. The novel approach integrates experimental and numerical methods to better understand damage accumulation in porous structures. The methodology includes uniaxial compression testing and image processing for microstructural characterization. Results reveal significant differences in relative density and stress concentration due to manufacturing defects. In particular, 3D printed lattice structures display typical cellular material behaviour with a primary bending deformation mechanism. X-ray tomography reveals that process-induced porosity generate stress heterogeneity, which is not captured from CAD-based model resulting in an overestimation of the stiffness. The study concludes that accounting for these defects can be quantified by shifting the target relative density to compensate lack of performance in 3D-printed lattice materials.

Study on tensile behavior at various temperatures of the Mg-7Gd-5Y-1Nd-2Zn-0.5Zr alloy

Mg-rare earth (RE)-Zn alloys with long-period stacking ordered (LPSO) structure show excellent room temperature, elevated temperature mechanical properties. In this work, microstructure and mechanical properties of Mg-7Gd-5Y-1Nd-2Zn-0.5Zr (wt%) alloy after tensile deformation at various temperatures (room temperature (RT), 250 °C and 300 °C) were investigated. The pre-precipitated alloy exhibited tensile yield strength (TYS) of 149 MPa at room temperature, while it maintained relatively high TYS at 250 °C (154 MPa) and 300 ℃ (123 MPa). The microstructural characterizations revealed that such outstanding heat resistance is mainly attributed to the blocky LPSO structure near the grain boundary; basal plate-like precipitates, twins and kink bands inside the grain. The blocky LPSO structure exhibits a coherent boundary with one α-Mg grain, while being incoherent with other α-Mg grains or the LPSO structure. Cracks primarily occured along the incoherent interface. Basal plate-like precipitates formed during elevated temperature tensile deformation included GP zones, γ', metastable LPSO building blocks, and fine 14H-LPSO structure. A probable γ-precipitation sequence is supersaturated solid solution → GP zones (ABAB-type) → single LPSO building block (γ')→ various metastable LPSO building block clusters→ 14H-LPSO (γ). The deformation modes (sliding, twinning, kinking, grain boundary sliding, etc) modified with the tensile temperature increase. <c+a> dislocations were observed at elevated temperatures. As the temperature of tensile test increases, twins become less. Grain boundary sliding occurs at elevated temperatures.

Effect of second-phase precipitates on deformation microstructure in AA2024 (Al–Cu–Mg): dislocation substructures and stored energy

The importance of comprehensive multiscale characterisation in advancing our understanding of engineering materials is undeniable but remains a challenging pursuit. Combining complimentary microstructure characterisation techniques, including transmission electron microscopy, electron backscatter diffraction and dark-field X-ray microscopy (DFXM), the formation of deformation microstructures is investigated in presence of shearable and non-shearable hardening precipitates in an industrial aluminium alloy (AA) 2024 (Al–Cu–Mg family). The alloy was used in naturally aged T3 (with shearable co-clusters and Guinier–Preston–Bagaryatsky (GPB) zones) and peak-hardened T8 (with non-shearable S-phase precipitates) states. After cold rolling with thickness reductions varying from 25 to 60% (or corresponding von Mises strain from 0.33 to 1.06), the T8 state revealed a higher sub-boundary density with slightly smaller mean disorientation angle, as compared to those in the T3 state. At a von Mises strain of 0.33, the T8 state exhibited higher long-range orientation gradients, as compared to the T3 state, for higher strain orientation gradients in T3 surpass those in T8 state. With DFXM, distinct 3D substructures are shown, revealing ellipsoidal sub-grains in the T8 state and pancake-like sub-grains in the T3 state. Moreover, the stored energy induced by cold rolling is higher for the T8 state. These results indicate different deformation microstructures, formed in the same AA2024 but hardened by shearable and non-shearable precipitates.Graphical abstract

Intergranular phase transformation in post-sinter annealed Nd–Dy–Fe–Cu–Ga–B magnet: from Ia[formula omitted]-cubic to I4/mcm-tetragonal structure

High-coercivity Nd–Fe–B permanent magnets crucially depend on the deliberate modulation of intergranular phases, an important embodiment being I4/mcm-tetragonal Nd6Fe13Ga intergranular phase in the Nd–Fe–Ga–B magnet. Particularly, for the Nd–Dy–Fe–Cu–Ga–B magnet containing multiple rare earths (RE) and alloying metals (M), understanding the evolution of RE6(Fe,M)14 intergranular phase becomes more critical in the quest for higher coercivity. Here we design the (Nd,Pr)29.0Dy3.0FebalCu0.5Ga0.5B0.9N1.15 (N=Co, Al, Zr, wt.%) as-sintered magnets, where the major RE/Cu/Ga-rich Ia3¯-cubic intergranular phase is agglomerated in triple junctions. These pristine as-sintered magnets are subjected to annealing over a wide temperature range (390∼900 °C for 3 h) and quenching over a wide time range (0.5∼12 h at 460 °C). Through systematic microstructural characterization and first-principle calculation, the intergranular phase transformation from RE/Cu/Ga-rich Ia3¯-cubic to Fe/Ga-rich I4/mcm-tetragonal structure, and accompanying elemental segregation is unveiled. During post-sinter annealing, metastable state I firstly occurs, consisting of nanostructured RE/Cu-rich Ia3¯-cubic and I4/mcm-tetragonal lamellas, with the emergence of multi-twins and coherent interface. Then it evolves into metastable state II, consisting of lath-shaped Fe/Cu/Ga-rich I4/mcm-tetragonal structure with fluctuating Fe/Cu concentrations. Simultaneously, metastable state III occurs, exhibiting P4-tetragonal platelets with lower Cu content and reduced crystallographic symmetry. Finally, heightened Fe/Ga diffusion into the lattice of tetragonal phase with synchronous Cu discharge generates the thermodynamically more stable Fe/Ga-rich RE6Fe13Ga phase. The implication of phase transformation pathways on the coercivity is discussed, offering valuable insights into the optimization of RE6(Fe,M)14 intergranular phase and allowing more space for enhanced coercivity.

Optimization of Geopolymers for Sustainable Management of Mine Tailings: Impact on Mechanical, Microstructural, and Toxicological Properties

This study investigates the use of geopolymer technology as an alternative for the management of mine tailings, which is a serious environmental problem in mining areas, including the Arequipa region of Peru. In this study, the mixture of stabilized mine tailings with different percentages of binders (i.e., metakaolin and pumice) and their impact on the mechanical, microstructural, and toxicological properties of the synthesized geopolymers were analyzed. The ratios of mine tailings to binder material varied between 100/0 and 0/100. The activation was carried out with an alkaline solution of sodium hydroxide (10 M) and sodium silicate (modulus 2.5). Specimens were fabricated as 50 mm cubes, and the seven mix designs were evaluated in triplicate. The evaluations included compressive strength at 7, 14, 28, and 56 days of curing, chemical analysis by Fourier Transform Infrared Spectroscopy (FT-IR), microstructural characterization by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM/EDS), thermal behavior by thermogravimetry and differential thermal analysis (TGA/DTA) between 40 °C and 1000 °C, and toxicological tests by the Toxicity Characteristic Leaching Procedure (TCLP, EPA 1311) to determine the efficiency of immobilization of toxic metals. The results demonstrate significant improvements in compressive strength for the F50 specimens compared to A0, with increases of approximately 300%, 270%, and 461% observed at 7, 28, and 56 days of curing, respectively, with microstructural stability with an average pore size of 7.21 μm, and efficiency in the immobilization of heavy metals in geopolymers with 30% or 40% binder (60%–70% mine tailings). The leachate concentrations of As, Cd, Pb, and Hg were below the established thresholds, indicating that the stabilized mine tailings can be classified as “non-hazardous materials”. Geopolymers with 30% to 50% binder showed strength development with microstructural stability and efficiency in the immobilization of heavy metals, complying with current regulations. Therefore, these geopolymers are suitable for various applications and in different environmental conditions.

Microstructural characterization and wear analysis of AlTiVZrMoCr HEA coating on SS410 steel by atmospheric plasma spraying

In recent research, noteworthy progress is made in developing Lightweight High Entropy Alloy (LWHEA) with superior performance and characteristics. A novel AlTiVZrMoCr LWHEA is synthesized through 50 h of ball milling with a 19 µm mean size of powders. The microstructural analysis of synthesized LWHEA powders revealed minor FCC and predominate BCC phases. The powders are coated on SS410 substrate by Atmospheric Plasma Spraying (APS) and the LWHEA coating significantly improves the structural characteristics of the substrate. Notably, the coated sample exhibits a uniform and homogeneous distribution across the substrate surface with an average grain of 1.71 µm. The microhardness of the coated sample is 1.67 times higher than the substrate, owing to the elemental bonding. Pin-on-disc tribometer is employed to measure the wear rate using different process parameters. Response Surface Methodology (RSM) is employed for the optimization of process parameters to obtain optimum wear rate. The technique of Analysis of Variance (ANOVA) is used to determine the most influential wear process parameter. Among various process parameters, the applied load is found to be the most influential factor in achieving an optimal wear rate. The worn morphology revealed the formation of grooves, micro-cracks, and oxides on the coated sample.

Supercapacitor and Photocatalytic Applications of Hydrothermally Synthesized of Polydymite Nanoparticles

The hydrothermal technique for producing polydymite nanoparticles (Ni3S4 NPs) for photocatalytic and supercapacitor utilization is the main emphasis in present work. The microstructural and electrochemical characterizations were conducted to determine the performance parameters of supercapacitor such as specific capacitance, efficiency, energy density and power density values using cyclic voltammetric (CV) and electrochemical impedance spectroscopic (EIS) techniques. The electrochemical characteristics of Ni3S4 NPs were studied using a TMS electrode in a 2 M KOH solution. This showed a specific capacitance value of 524 F g–1 at a current density of 1 A g–1. The Ni3S4 NPs showed good photocatalytic activities for the photodegradation of fast blue dye, the Ni3S4 NPs exhibits a 75.6% colour loss rate following the exposure for 120 min to UV radiation.

Formation of Bainite in a Low‐Carbon Steel at Slow Cooling Rate – Experimental Observations and Thermodynamic Validation

Bainitic microstructures in high‐strength steels are obtained either by continuous cooling or isothermal holding. Both scenarios necessitate faster cooling to keep the parent austenite phase untransformed till the bainite‐start temperature. The present study reports the development of bainitic microstructure in a low‐carbon steel with minimal alloying additions, under continuous cooling at very slow rates, similar to furnace cooling. For understanding the related transformation pathways, samples from the forged‐steel ingot are austenitized and cooled at different rates, viz. water quenching, air cooling, and furnace cooling. Microstructural characterization reveals development of acicular microstructures in all samples including the forged one, with gross absence of carbides. X‐ray diffraction confirms the ferritic nature of acicular plates and also indicated retained austenite present in some samples, the content of which could be correlated to the extent of bainitic transformation. Thermodynamic calculations together with microstructural observations (e.g., ferrite plate size) and hardness data established the development of fully martensitic microstructure on water quenching, while that of a mixed microstructure comprising predominantly of bainite in the forged, air cooled, and furnace‐cooled condition. The aforementioned findings could have wider implications in developing fully bainitic microstructures in large components, where uniform rapid cooling is not practically feasible.

Comprehensive characterization of the irradiation effects of glassy carbon

Carbon materials have become increasingly diverse, finding applications in high-temperature and high-radiation environments. Glassy carbon, an allotrope known for its exceptional chemical inertness and desirable mechanical properties. However, understanding neutron irradiation effects in glassy carbon has proven challenging, primarily because of its unique nanopore structure. This study presents a highly detailed microstructural characterization investigation of neutron-induced changes in glassy carbon, revealing how changes in nanopore structure and crystallinity impact the irradiation-induced shrinkage. Aberration-corrected scanning transmission electron microscopy (STEM) reveals pore closure that leads to material densification in the irradiated samples. Dimensional analysis combined with comparison to historical data suggest significant length shrinkage to occur. Neutron and in situ electron irradiation experiments suggest that glassy carbon transforms into so-called carbon onions, supporting the concept of shrinkage saturation. Investigating irradiation temperature effects using STEM, electron energy loss spectroscopy, x-ray diffraction, and Raman spectroscopy revealed partial amorphization at 210 °C–230 °C and preserved order in glassy carbon at 860 °C, coinciding with pore closure. Thermal property measurements were also conducted to assess the effects of densification and other changes in the atomic structure of glassy carbon. The results of this study have broad implications in the deployment of glassy carbon to nuclear environments, based around the observed changes in the thermal properties, and demonstrates the operational window for the onset of densification.

Microstructure and phase composition of Ti-coated cBN powders intended for active coating technology (ACT) processes

Development of an active coating technology (ACT) was aimed at fabricating high strength sinters using metallized powders like in case of titanium coated cubic boron nitride (cBN). It helps to avoid inhomogeneity in distribution of the binder phase during their mixing, being the main defects in such compacts. The information concerning phase composition of the coating formed over cBN during their metallization would be of much help as it concerns setting a proper sintering temperature securing both durable fusion of boride particles and elimination of porosity. Presently, two commercial Ti coated cBN powders are available, i.e. CBN-B-TA, 6–12 µm, from Van Moppes, Switzerland and CeraMicron CM-CBN 80 Ti, 20–30 µm, from Ceratonia, Germany (coded as cBN-VM and cBN-CM, respectively). The present investigation was aimed at characterization of the coatings microstructure and phase composition, being necessary for optimising sintering procedure. The scanning and transmission electron microscopy observations backed with energy dispersive X-ray microanalysis (SEM/TEM/EDS) showed that the cBN-VM particles carried a coating of thickness varying from 50 nm to 150 nm consisting of TiB and TiN phases, while the cBN-CM ones were covered by a much thicker (∼500 nm) coating built of mostly of TiB and TiN2-type crystallites. As the columnar nitride phases formed bulk of the coatings, though at the coating/cBN substrate boundary a nano-crystalline layer of TiB phase was documented in both powders. The crystallites of boride phase were accompanied by a strings of porosity. The XRD measurements indicated also presence of small amounts of the α-Ti(N) phase, which was probably intermixed with the other phases without forming a separate sub-layer. The thinner coating, i.e. one that formed over cBN-VM powder, was contaminated with Cl and K being a residue from the molten salts synthesis (MSS) deposition, as well as some surface oxides. The gathered information makes a basis for elaboration of new generation of cBN sinters of improved properties.

Assessment of underutilized Mangifera indica peels for nutritional, phytochemical and techno-functional attributes as well as its microstructural and thermal characterization

Assessment of underutilized Mangifera indica peels for nutritional, phytochemical and techno-functional attributes as well as its microstructural and thermal characterization

Mechano-thermochemical preparation of nanostructured (FeCoNiCr/Mn)3O4 high and medium entropy oxides: Structural, microstructural, magnetic and Li-ion storage characterization

Mechano-thermochemical synthesis of (FeCoNiCrMn)3O4 high-entropy oxide (HEO) and (FeCoNiCr)3O4 medium-entropy oxide (MEO), and their structural, microstructural, magnetic, surface and electrochemical characteristics are investigated. Ball milling substantially reduces crystalline sizes of oxide precursors, causing their partial solid-state dissolution, driving the rapid formation of HEO and MEO during the subsequent thermal treatment. Nanostructured HEO prepared at 900 °C (HEO-900) comprises single-phase octahedral crystals mostly within the range 60–80 nm, while MEO-900 crystals (80–120 nm) exhibit a greater degree of agglomeration. The contribution of oxygen vacancies to total surface oxygen in MEO-900 (20.6 %) is lower than that of HEO-900 (27.6 %). HEO-900 exhibits a superior reversible Li-ion storage capacity of 1050.6 mAh/g after 300 cycles at 100 mA/g, outperforming MEO-900. However, at the higher current density of 500 mA/g, MEO-900 shows superior performance, with a reversible capacity of 432.2 mAh/g (70.3 % retention) after 750 cycles. The charge transfer resistance of fresh HEO-900 (359.0 Ω) is greater than that of MEO-900 (241.4 Ω), and the average Li-ion diffusion coefficient in HEO-900 (10-13.3 cm2 s−1) is lower than that on MEO-900 at (10-13.1 cm2 s−1) due to the greater structural complexity of the former. Full cells incorporating HEO-900 and MEO-900 anodes with LiFePO4 cathode demonstrate an energy density of 296.4 and 274.6 Wh kg−1, respectively. The saturation magnetization of HEO-900 and MEO-900 is significantly high at 33.98 and 33.80 emu/g, respectively, enabling the easy magnetic recovery of electrodes made from these compounds in spent LIBs.

Microstructural Characterization of Friction Stir Welds of Aluminum 6082 Produced with Bobbin Tool.

This study utilized a bobbin tool to friction stir weld aluminum 6082 workpieces under two sets of process parameters: a tool rotation speed of 280 rev/min with a weld velocity of 280 mm/min (280/280) and a tool rotation speed of 450 rev/min with a weld velocity of 450 mm/min (450/450). The weld microstructures were characterized through optical microscopy utilizing polarized light and through transmission electron microscopy (TEM) and scanning electron microscopy (SEM) coupled with chemical analysis by energy dispersive spectroscopy and electron back scatter diffraction. The microstructural studies were supplemented by hardness measurements (Vickers) performed on the same sections as the metallographic examinations. The produced weldments were free from cracks and any discontinuities. Fine, equiaxed grains that were several microns in size characterized the stir zones (SZs), and the advancing (AS) and retreating (RS) sides revealed distinct microstructural features. On the AS, the transition from the thermo-mechanically affected zone to the SZ was well defined and sharp, but on the RS, the transition appeared as a continuous, gradual change in microstructure. The lower weld energy (280/280) produced lower hardness in the stir zone than the higher energy weld (450/450), ~95 HV1 versus ~115 HV1; however, the 280/280 welds showed higher tensile strengths than the 450/450 welds, ~238 MPa as opposed to ~172 MPa. These behaviors in mechanical performance correlated with the temperature histories produced by each set of weld parameters in relation to the precipitation behavior of the alloy. The fracture characteristics of the weldments were notably different with the 450/450 sample fracturing in a quasi-brittle manner with slight plastic deformation and the 280/280 sample fracturing ductilely. A numerical simulation supported the investigation by elucidating the temperature and material flow behavior during the joining process.

In Vitro Digestion and Fermentation of Cowpea Pod Extracts and Proteins Loaded in Ca(II)-Alginate Hydrogels.

Antioxidants derived from food by-products are known for their bioactive properties and impact on human health. However, the gastrointestinal behavior is often poor due to their degradation during digestion. The development of Ca(II)-alginate beads supplemented with biopolymers and enriched with cowpea (Vigna unguiculata) extract could represent a novel environmentally friendly technological solution to produce functional ingredients in the food industry. The present study evaluates the impact of in vitro digestion/fermentation by analyzing global antioxidant response (GAR), production of short-chain fatty acids (SCFAs) as a modulation of gut microbiota, and behavior of proton transverse relaxation times by low-field nuclear magnetic resonance (as an indicator of gelation state and characterization of microstructure). Results revealed that guar gum and cowpea protein preserved a high GAR of total phenolic compounds and antioxidant capacity by ABTS and FRAP methods after digestion/fermentation, promoting an adequate protection of the bioactives for their absorption. Alginate-based beads have great potential as prebiotics, with the guar gum-containing system contributing the most to SCFAs production. Finally, the overall higher mobility of protons observed in the intestinal phase agrees with structural changes that promote the release of phenolic compounds during this stage. Beads are excellent carriers of bioactive compounds (cowpea phenolic compounds and peptides) with potential capacities.

Investigation of the Effects of Gamma Radiation and Y2O3 on the Elastic Properties of Al2024 Composites by Ultrasonic Method

In this study, the effect of Y2O3 contribution and γ-irradiation on the elastic properties of pure Al2024 and Al2024/Y2O3 composites was precisely investigated with the help of determined density and ultrasonic wave velocities. Ultrasonic longitudinal and shear wave velocity measurements of the samples were performed at room temperature using the ultrasonic pulse-echo method at 20 and 5 MHz frequencies, respectively. X-ray diffraction analysis and scanning electron microscopy examined the microstructural properties and phase characterizations of metal matrix composite (MMC) samples. A gamma cell type 60Co source was used to irradiate MMC samples in the air at room temperature. The absorbed dose rate was measured to be approximately 1.5 kGy/h, and the total delivered dose was 50 kGy. According to the findings obtained from the research, the contribution of Y2O3 to pure Al 2024 at 0.5, 1, and 5 wt.% ratios and exposure to gamma rays of 50 kGy caused a decrease in VL, L, K, and μ values and a significant increase in ρ, VS, G, HV, H, and E values. The highest Young’s modulus values compared with pure Al2024 were obtained in both unirradiated and irradiated Al2024/0.5Y2O3 composites.