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Recently, it was shown that the nanocrystallization of B i 2 O 3 glasses with the addition of S i O 2 and A l 2 O 3 leads to the stabilization of the δ -like B i 2 O 3 phase at least down to room temperature, which is significantly below its stability range in bulk form. In this research, we investigated the properties of bismuthate glasses synthesized with various glass-forming agents such as S i O 2 , G e O 2 , B 2 O 3 , and A l 2 O 3 . It was demonstrated that vitrification of all these systems is possible using a standard melt quenching route. Furthermore, we investigated the crystallization processes in pristine glasses upon increasing the temperature and the thermal stability of arising phases using thermal analysis and high-temperature XRD in situ experiments. It was shown that it is possible to stabilize crystallites' isostructures with δ - B i 2 O 3 embedded in a residual glassy matrix down to room temperature. The temperature range of the appearance of the δ -like phase strongly depended on the nominal composition of the glasses. We postulate that the confinement effect depends on the local properties of the residual glassy matrix and its ability to introduce sufficient force to stretch the structure of the δ -like B i 2 O 3 phase in the nanocrystallites. [ABSTRACT FROM AUTHOR]

This study aims to examine the effects of milling time on the morphological, structural, and magnetic properties of nanostructured Ni50Ti50 powders prepared by high-energy mechanical alloying using a Fritsch Pulverisette 7 planetary ball mill. Scanning electron microscopy and electron dispersive X-ray spectroscopy, results revealed a novel particle folding phenomenon during high-energy milling, significantly diverging from conventional welding and fracture processes. With increasing milling time, it was observed reduced particle size, and enhanced spherical equiaxial morphology, alongside a mixture of the amorphous phase, NiTi-martensite (Ms), NiTi-austenite (As), and solid solution phases (SS). Rietveld refinements of X-ray diffraction patterns and magnetic measurements highlighted the critical role of the amorphous phase in determining the Ms and Mr values of synthesized Ni50Ti50 powders. After 72 h of milling, the coercive field increased to 285.8 Oe, and the martensitic phase proportion reached 21.58%. [ABSTRACT FROM AUTHOR]

In response to the growing demand for high-performance magnesium alloys in the aerospace and transportation industries, researchers conducted a study on the AZ80 magnesium alloy. The primary objective was to achieve a nanocrystalline structure in the alloy through severe plastic deformation using low-strain multi-directional compression at room temperature. Subsequently, an aging treatment was performed to induce the transformation of the structure into a stable state. The study aimed to investigate the morphology and mode of the second phase precipitation in the magnesium alloy after undergoing severe plastic deformation. The research findings revealed that the application of multi-directional and multi-pass compression during room temperature deformation of the magnesium alloy effectively prevented instability and fracture. Moreover, this process facilitated the accumulation of larger true strain. As the number of compression passes increased, deformation twins became increasingly denser, particularly in the intersecting areas. Consequently, ultrafine high-angle grain structures were preferentially formed in these regions. Furthermore, the number of fine-grained areas gradually increased with each deformation pass. After ΣΔε 5.12, the grain size was refined to a range of 100–200 nm. Additionally, the aging treatment following severe plastic deformation brought about a significant change in the traditional lamellar precipitation mode of the second phase Mg17Al12 in the magnesium alloy. Instead, spherical precipitation occurred.

The purpose of the research is to analyze the possibility of obtaining an amorphous nanostructured state from the original amorphous state by ion irradiation. The processes of phase formation in the Fe75Mo5Si6B14 amorphous alloy under the influence of argon ion irradiation were investigated using the methods of highly sensitive dilatometry, microhardness measurements, and electron microscopy. The surface treatment of the amorphous alloy with argon ions was carried out at a voltage on the anode of 1 kV and a current through the sample of 1 mA. The surface morphology of the amorphous alloy treated with argon ions was studied under a LensSEI scanning electron microscope. The structure of amorphous alloys is characterized by the presence of frozen-in crystallization centers. It was found that the phenomenon of nanocrystallization is not observed during exposure to ion irradiation for up to 30 minutes. This is explained by the fact that, as a result of ion irradiation, the local temperature on the surface of the sample rises and reaches such values, at which, according to the thermodynamic theory of thermal stability, the frozen centers of crystallization can dissolve in the amorphous matrix. When the ion irradiation time of the source alloy is increased to 45 minutes, a decrease in thermal stability of 25 °C and an increase in microhardness of 8.2% are observed, therefore, the alloy is strengthened. This indirectly indicates the formation of an amorphous-nanocrystalline state in the alloy. Structural changes are also confirmed by the results of studies of the amorphous alloy surface morphology by scanning electron microscopy. After irradiation, both the number of crystal nuclei and their average size increase significantly (from 20 nm in the source alloy to 65 nm in the irradiated one). The changes in the number and size of crystal nuclei are explained by the fact that at an irradiation time of 45 minutes, the temperature in the regions of the ion tracks reaches threshold values and thermodynamic conditions are created for the growth of frozen crystallization centers. [ABSTRACT FROM AUTHOR]

The phase transition temperatures for amorphous metals based on aluminum Al87(Ni,Fe)8(REM)5 system were determined by differential scanning calorimetry (DSC). The mechanisms of formation and growth of nanocrystals in an amorphous matrix were predicted using kinetic models (Matusita model). It was found that after annealing at the temperature of stable nanocrystalline growth, an X-ray amorphous structure with a volume fraction of disordered nanocrystalline phases of solid state of Al(X), GdFe2, AlFe2Ni, GdFe2 for the amorphous metal alloy (AMA) Al87Y4Gd1Ni4Fe4 alloy and microcrystalline phases of solid state of Al(X), GdFe2 AlFe2Ni for the Al87Gd5Ni4Fe4 alloy are formed, which significantly affects the mechanical properties of the Al87(Ni,Fe)8(REM)5 system. The effect of annealing on the mechanical properties of amorphous aluminum-based alloys was investigated using Oliver-Pharr and Young's modulus methods it was found that thermal modification of AMAs: Al87Gd5Ni4Fe4 as a result of heat treatment of AMAs from 5 to 15 min., the microhardness increases from 0.20 GPa to 2.75 GPa, and when heat treated for 60 min at a temperatures of T3 = 645±5 K, 647±5 K, it decreases to 0.35 GPa and 0.45 GPa, respectively.

Griseofulvin (GRFV1) is used in the treatment of many fungal infections, including ringworm and athlete’s foot, as well as fungal infections of the scalp, fingernails, and toenails. However, its bioavailability is limited by poor water solubility. This work was aimed at improving the aqueous solubility of the drug via Polysorbate 80 - modulated nanocrystallization. Two types of nanocrystals (GRFV3 and GRFV2) were generated, respectively, with and without the inclusion of Polysorbate 80 in the nanocrystallization process. The three forms of the drug were subjected to a flowability test, differential scanning calorimetry, Fourier transform infrared spectroscopy, particle size analysis, and aqueous solubility determination. The flowability of the particles was in the order GRFV3 > GRFV2 > GRFV1. The thermogram of the drug powder showed a sharp endothermic transition with a peak at 75 ºC; that of the nanocrystals GRFV2 showed a single sharp endothermic transition with a peak at 170 ºC, while that of GRFV3 showed two endotherms with peaks at 75 ºC and 164 ºC. The nanocrystallization with or without a surfactant did not result in any observable change in the chemical integrity of the drug. The mean particle size was in the order GRFV3 < GRFV2 < GRFV1. There was a significant difference (P < 0.0001) in the aqueous solubility of the three forms of the drug, with GRFV3 having the highest value. Polysorbate 80 - modulated nanocrystallization can increase the aqueous solubility of griseofulvin by 4.14 folds; it is a potential way of improving the bioavailability of the drug.

Nucleation behaviors in glasses/supercooled liquids (SCLs) such as lithium disilicate Li2O–2SiO2, cordierite Mg2Al4Si5O18, fresnoite Ba2TiSi2O8, and K2O–Nb2O5–GeO2/TeO2 glasses were analyzed and discussed from the interfacial energy γ at SCL–nucleus interfaces and nanoscale composition fluctuations. Based on the fragility concept for SCLs and the intrinsic origin of γ, the magnitude order of γ(fragile SCL) < γ(strong SCL) was proposed to be a crucial guide for an understanding of high homogeneous nucleation rates and prominent nanocrystallization. The role of nucleating agent TiO2/ZrO2 in accelerating the nucleation rate in cordierite‐based and β‐spodumene‐type Li2O–Al2O3–SiO2‐based glasses was discussed from the new perspective of γ(homoepitaxial‐like nucleation) < γ(heteroepitaxial‐like nucleation). Ferroelectric nanocrystals such as SrxBa1–xNb2O6 in borate glasses and fluoride nanocrystals such as CaF2 are also well understood from the proposed guidelines. The present article provides a new perspective for nucleation in glasses/SCLs, contributing to the comprehensive composition design of new innovative glass‐ceramics. [ABSTRACT FROM AUTHOR]

Recently, it was shown that the nanocrystallization of Bi2O3 glasses with the addition of SiO2 and Al2O3 leads to the stabilization of the δ-like Bi2O3 phase at least down to room temperature, which is significantly below its stability range in bulk form. In this research, we investigated the properties of bismuthate glasses synthesized with various glass-forming agents such as SiO2, GeO2, B2O3, and Al2O3. It was demonstrated that vitrification of all these systems is possible using a standard melt quenching route. Furthermore, we investigated the crystallization processes in pristine glasses upon increasing the temperature and the thermal stability of arising phases using thermal analysis and high-temperature XRD in situ experiments. It was shown that it is possible to stabilize crystallites’ isostructures with δ-Bi2O3 embedded in a residual glassy matrix down to room temperature. The temperature range of the appearance of the δ-like phase strongly depended on the nominal composition of the glasses. We postulate that the confinement effect depends on the local properties of the residual glassy matrix and its ability to introduce sufficient force to stretch the structure of the δ-like Bi2O3 phase in the nanocrystallites.

The magnetization process is based on bringing about a unified arrangement of the magnetic domains. During this process, there are shifts and then the rotations of the domain walls. At a later stage, domains with a direction of magnetization that do not correlate with the applied magnetic field disappear. The turnover depends on the size of the domains. For an amorphous structure, the key factors determining the size of the magnetic domains are the distance between the magnetic atoms and the possible presence of crystalline grains. The paper presents the results of research on the influence of Cu addition on the distances between magnetic atoms and the magnetization process in high magnetic fields. The structure of the alloys was studied using X-ray diffraction. The mean grain size was estimated using the Scherrer method. The magnetic properties were determined on the basis of measurements with a vibrating magnetometer. A numerical analysis of the primary magnetization curves was performed. Despite the significant reorganization of the structure, no changes in the distance between the magnetic atoms were observed, as indicated by slight changes in the Dspf parameter. It was found that a small addition of Cu positively influences the improvement of the magnetic properties, in particular the reduction of the value of the coercive field. [ABSTRACT FROM AUTHOR]

In this work, the formation of nanoscale phases in Al30Cu40Si30, Al33.3Cu33.3Si33.3 and Al60Cu20Si20 alloys as a result of rapid crystallization was investigated. For this purpose, the microstructure of alloys in the crystalline state after equilibrium and rapid crystallization was investigated by electron microscopy. The phase analysis of the alloys was carried out by the X-ray diffraction method, as a result of which it was established that aluminum, silicon and binary compounds based on aluminum and copper are present in the studied alloys. To explain the mechanism of formation of nanoscale phases during crystallization, the cluster structure and atomic composition of clusters in the liquid state before crystallization were investigated. The study of the atomic structure of alloys in the liquid state was carried out by the method of molecular dynamics. To check the accuracy of the models, the simulation results were compared with experimental data. From the analysis of the atomic configurations of the melts, the presence of clusters with a structure that corresponds to the structure of the crystalline phases was revealed. It was concluded that the presence of such atomic clusters causes the formation of nanoscale phases during rapid cooling. [ABSTRACT FROM AUTHOR]

Electrical current annealing based on the Joule-heating technique, known also as the thermal electrical resistivity method, was applied for nanocrystallyzation of the Fe73.5Nb3Cu1Si15.5B7 amorphous ribbon. The feature of the Joule-heating technique is high heating rates of the material internal volume that in the case of amorphous alloys causes the evolution of the metastable amorphous state. Structure transformation was investigated by the X-ray diffraction method, which allows obtaining the phase composition of the material as well as nanograin size. The nanocrystalline phases that precipitate during current annealing are Fe3Si and hexagonal phase with a nanoscale grain size, the average value of which tends to depend on annealing duration as well as applied voltage and varies in the range of 10–200 nm. Field-emission scanning electron microscopy was used to investigate the surface topology and nanograins, and at some samples, petal-like structures were observed on the ribbon's surface after the Joule-heating technique application. Saturation magnetization and microhardness were studied in relation to electrical current parameters, and optimal values were observed for its improvement. Obtained results could be helpful for controlling the conditions of the formation of fully or partially nanocrystalline structured materials from amorphous ribbons based on Fe-Si-B-Nb-Cu. [ABSTRACT FROM AUTHOR]

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The bulk-inhomogeneous crystallization of amorphous microwires of the composition Fe73.8Cu1Nb3.1B9.1Si13 is studied. An assumption is put forward concerning the influence of the inhomogeneous distribution of tensile and compressive stresses in the bulk of microwires on their crystallization. It is established that, at the initial stages of crystallization, crystallization occurs in the surface region of the microwire with a thickness of about 2.5 μm. It is established that the sizes of the nanocrystals in the surface region of the microwire are about 10 nm. It is found that the formation of an amorphous nanocrystalline layer on the microwire surface leads to an increase in the Mr/Ms ratio (ratio of remanent magnetization to saturation magnetization), which is associated with a decrease in the magnetic anisotropy due to a decrease in the stress level during heat treatment and nanocrystallization. The chemical etching of annealed microwires leads to a significant increase in the Mr/Ms ratio, which is due to an increase in the relative volume of the central domain layer. The results obtained indicate the potential for creating composite amorphous-nanocrystalline structures based on microwires. In the case of microwires of Fe73.8Cu1Nb3.1B9.1Si13 composition, the predominant crystallization of the surface layer can increase the effect of the giant magnetic impedance. Such objects may have potential applications in sensorics, in particular, in magnetic field and strain sensors. [ABSTRACT FROM AUTHOR]

Hydrogenation and nanocrystallization of Ti6Al4V alloy were achieved by electrolytic hydrogenation and SMAT processing. The hydride δ phase appeared when the hydrogenation time reached 4 h. The grain size of Ti6Al4V alloy after surface nanocrystallization reached below 35 nm when the SMAT processing time was 2 h. Surface morphology and roughness were characterized by AFM. The diffusion bonding between Ti6Al4V alloys at low temperature was achieved under different parameters. It is demonstrated that the porosity at the interface decreased correspondingly when the hydrogenation time or nanocrystallization time was extended. The porosity of the joint reached 0 when the hydrogenation time was 24 h or the nanocrystallization time was 4 h. Then hydrogenation and nanocrystallization treatments were combined. It is found that there are more bonding defects in both hydrogenation-nanocrystallization and nanocrystallization-hydrogenation joints than in joints with single hydrogenation or nanocrystallization treatment. It can be concluded that the porosity of the joints with nanocrystallization first is lower than that with hydrogenation first.

The local deformation behavior and dynamic recrystallization of a shock compressed Mg-1Zn alloy was investigated through EBSD and TEM. Since dislocation slipping and twinning were locally suppressed during high strain-rate deformation, a more flexible kinking deformation was activated to adjusted local orientation and facilitate slipping and twinning within the kinks. Meanwhile, due to the slow heat dissipation that resulted in a local temperature elevating, the kink bands were evolved into deformation bands with recrystallized nano-grains. Such a finding provides a new perspective for kinking-facilitated nanocrystallization in Mg alloys and other anisotropic metallic materials.

The magnetic properties of the amorphous Co57Fe5Ni10Si11B17 alloy have been studied by a vibrating sample magnetometer. The temperature dependence of saturation magnetization was measured and the Curie point and crystallization onset temperature were determined as 560 K and 760 K respectively. The coercive force was obtained as 200 A/m and saturation magnetization - 65 Am2 /kg. The alloy was produced in the form of a ribbon thickness of 30 µm using the melt spinning method, and its internal amorphous structure was examined by the X-ray diffraction method. The crystallization behavior of the alloy was studied using series of isothermal annealing of the samples of the alloy at temperatures in the range of 723-1023 K for different exposures (up to 240 minutes) and nanocrystalline phases were detected by the X-ray diffraction analysis.

Co-Zr amorphous alloys exhibit soft magnetic properties, whereas the Co-rich crystalline magnetic phases in this alloy system displayed a hard magnetic behavior. In this study, an initial two-phase Co-Zr composite with an overall composition of 75 at.% Co and 25 at.% Zr was processed by high-pressure torsion (HPT), and the effects of severe plastic deformation and subsequent thermal treatment on the composite's structural evolution and its magnetic properties were investigated. HPT processing allowed us to achieve an amorphous microstructure with low coercivity in its as-deformed state. To further tune the alloy's magnetic properties and study its crystallization behavior, various annealed states were investigated. The microstructural properties were correlated with the magnetic properties, and a decreasing coercivity with increasing annealing temperatures was observed despite the onset of crystallization in the amorphous alloy. At higher annealing temperatures, coercivity increased again. The results appear promising for obtaining tuneable rare-earth free magnetic materials by severe plastic deformation. [ABSTRACT FROM AUTHOR]

Through surface nanocrystallization and low-temperature ion sulfurization, the nanocrystalline/FeS thin film with excellent friction-reduction and antiwear properties was fabricated on the surface of AISI321 stainless steel. The nanocrystallization treatment formed the high hardness and active nanocrystalline structure on the surface of AISI321, with the harness increased from 4.6 GPa to 7.56 GPa. Furthermore, the significantly refined nanostructure strongly increased the concentration of S element in comparison with the single-sulfurized layer on the substrate. Tribological tests reveal that both the original AISI321 substrate and the single-sulfurizing-treated samples are subject to severe abrasion. Single nanocrystallization treatment can improve the wear resistance of AISI321, while the compound treatment can obviously improve the comprehensive tribological properties. The compound-modified layer presents excellent tribological properties with the lowest coefficient of friction (COF) of 0.33, which is related to the increased hardness of the substrate and increased thickness, density, and homogeneity of the sulfurized layer. Furthermore, a physical model is developed for the vacuum tribological behavior of the samples after different treatments. This model provides a reference for revealing the tribological mechanism of the compound-modified layer treated using surface nanocrystallization-assisted chemical heat treatment. [ABSTRACT FROM AUTHOR]

Magnetic properties of amorphous Co70Fe3Mn3.5Mo1.5Si11B11 and Co73Fe1Mn3Mo1Si13B9 alloys, manufactured in the form of ribbons by rapid cooling from the melt, were studied using vibrating sample magnetometer and thermo-magnetic methods. The Curie point (648 K and 683 K), coercive force (180 A/m and 40 A/m), and saturation magnetization (83 Am2/kg and 85 Am2/kg) were defined. The nanocrystallization process of the amorphous Co70Fe3Mo1.5Mn3.5Si11B11 and Co73Fe1Mo1Mn3Si13B9 alloys were studied by DTA, X-ray diffraction, and using the thermo-magnetic method in the high magnetic field 800 kA/m. The crystallization onset temperatures of the alloys were defined as about 787 K and 729 K, respectively. The effect of a magnetic field on the crystallization behavior, revealed in a notable crystallization onset temperature decrease, was observed. The structure evolution induced by the isothermal annealing at temperature 753 K was studied and the X-ray diffraction structure analyses revealed nanocrystallization with hcp-Co, fcc-Co, and Co3B phases. FESEM studies revealed a nanoscale and flower-like structure on the ribbon surface after annealing at 753 K. [ABSTRACT FROM AUTHOR]

At present, the vascular grafts used in clinic are mainly autologous blood vessels, but they often face the dilemma of no blood vessels available due to limited sources. However, synthetic blood vessels made of polytetrafluoroethylene (ePTFE), which is commonly used in clinic, are prone to thrombosis and intimal hyperplasia, and the long-term patency rate is poor, so its effectiveness is severely limited, which is far from meeting the clinical needs. With the development of nano-materials, stem cells and 3D bio-printing technology, people began to explore the preparation of new endothelialized vascular grafts through this technology. Nano-peptide materials have excellent biocompatibility, can be compounded with different bioactive molecules, and have unique advantages in cultivating stem cells. It has been reported that self-assembled nano-polypeptide hydrogel was successfully constructed, mesenchymal stem cells were correctly isolated and cultured, and their transformation into blood vessels was studied. It was confirmed that the 3D bio-printed nano-polypeptide hydrogel tissue ADMSCs still had strong vascular endothelial differentiation ability. The application of mesenchymal stem cells and nano-polypeptide hydrogel in tissue engineering blood vessels has gradually become a research hotspot, and it is expected to develop a new type of transplanted blood vessel that meets the physiological functions of human body in terms of vascular endothelialization, cell compatibility and histocompatibility, so as to realize the customized and personalized printing of the endothelialized transplanted blood vessel according to the shape of the target blood vessel, which has attractive prospects and far-reaching social and economic benefits.

Recent investigations have demonstrated that the plasticity of bulk metallic glasses (BMGs) at room temperature can be improved by artificially introducing both macroscopic and microscopic defects. In this work, both surface grooves and multiple shear bands (MLSBs) are concurrently introduced into the surface of a Zr65Cu15Ni10Al10 BMG employing an ultrasonic bonding machine, whose sizes are also tailored by tuning gas pressures and times. After surface treatment, MLSBs appear around grooves due to the pre-plastic deformation, while numerous nano-scale crystals resulting from thermal-induced nanocrystallization appear within the grooves, leading to the emergence of hierarchical structural heterogeneities. As a result, the strength and plasticity are effectively enhanced compared to as-cast samples when suitable experimental parameters are adopted. The plastic deformation mechanisms change from single main shear banding to multiple shear banding. Therefore, the serrated plastic behaviors exhibit a transition from chaotic to self-organized critical dynamics after surface treatment, confirming the modification of the shear banding instability. The present study provides a viable method to tailor the mechanical properties of BMGs and sheds light on their dynamic plastic deformation behaviors.

Melanin is an insoluble, amorphous polymer that forms planar sheets that aggregate naturally to create colloidal particles with several biological functions. Based on this, here, a preformed recombinant melanin (PRM) was utilized as the polymeric raw material to generate recombinant melanin nanoparticles (RMNPs). These nanoparticles were prepared using bottom-up (nanocrystallization—NC, and double emulsion–solvent evaporation—DE) and top-down (high-pressure homogenization—HP) manufacturing approaches. The particle size, Z-potential, identity, stability, morphology, and solid-state properties were evaluated. RMNP biocompatibility was determined in human embryogenic kidney (HEK293) and human epidermal keratinocyte (HEKn) cell lines. RMNPs prepared by NC reached a particle size of 245.9 ± 31.5 nm and a Z-potential of −20.2 ± 1.56 mV; 253.1 ± 30.6 nm and −39.2 ± 0.56 mV compared to that obtained by DE, as well as RMNPs of 302.2 ± 69.9 nm and −38.6 ± 2.25 mV using HP. Spherical and solid nanostructures in the bottom-up approaches were observed; however, they were an irregular shape with a wide size distribution when the HP method was applied. Infrared (IR) spectra showed no changes in the chemical structure of the melanin after the manufacturing process but did exhibit an amorphous crystal rearrangement according to calorimetric and PXRD analysis. All RMNPs presented long stability in an aqueous suspension and resistance to being sterilized by wet steam and ultraviolet (UV) radiation. Finally, cytotoxicity assays showed that RMNPs are safe up to 100 μg/mL. These findings open new possibilities for obtaining melanin nanoparticles with potential applications in drug delivery, tissue engineering, diagnosis, and sun protection, among others. [ABSTRACT FROM AUTHOR]

A crucial step in creating cutting-edge soft magnetic alloys is the nanocrystallization of Fe-based amorphous alloys. However, it is unclear how the thermal history affects the nanocrystallization. In this work, high-precision nanocalorimetry and in-situ high-temperature transmission electron microscopy are used to systematically examine how the pre-annealing relaxation process affects the nanocrystallization of Fe-based amorphous alloys. We discover that the glass with more thermal energy storage will crystallize into superb nanocrystalline structures with exceptionally advanced soft magnetism. The soft magnetic properties of Fe-B nanocrystalline alloys can be improved by increasing the relaxation temperature. This finding provides solid and clear evidence for the influences of thermal history on crystallization behavior for Fe-based amorphous alloys, which is helpful for designing advanced soft magnetic nanocrystalline alloys. [ABSTRACT FROM AUTHOR]

The local deformation behavior and dynamic recrystallization of a shock compressed Mg-1Zn alloy was investigated through EBSD and TEM. Since dislocation slipping and twinning were locally suppressed during high strain-rate deformation, a more flexible kinking deformation was activated to adjusted local orientation and facilitate slipping and twinning within the kinks. Meanwhile, due to the slow heat dissipation that resulted in a local temperature elevating, the kink bands were evolved into deformation bands with recrystallized nano-grains. Such a finding provides a new perspective for kinking-facilitated nanocrystallization in Mg alloys and other anisotropic metallic materials. [ABSTRACT FROM AUTHOR]

Nanostructured materials exhibit superior properties with respect to their bulk counterpart. Recently, a new processing method for surface nanostructuring of metallic materials called surface mechanical impact treatment (SMIT) was developed. In this study, the surface microstructural features due to the refinement process of AISI 316L stainless steel by means of SMIT and subsequent mechanical performance were investigated. The effects of SMIT processing parameters, i.e. ball size and treatment duration, were studied in terms of microstructural evolutions using X-ray diffraction, transmission electron microscopy, optical microscopy, and field emission scanning electron microscopy analyses, and mechanical properties through hardness and tensile tests. A gradient nanostructured surface layer was successfully formed on the surface of the treated samples. The mean grain size was measured to be ~ 20 nm in the topmost surface layer and increased with increasing depth. Microstructural examinations showed that the twins and their intersections (rhombic blocks) formed in the surface layers. It was found that the mechanical performance of the treated samples is effectively enhanced. The surface hardness of the treated samples increased about 3 times while the yield strength of the samples increased with increasing SMIT time and size of the ball up to 2.5 times. The grain refinement mechanisms, mechanical properties, and fracture behavior were subsequently analyzed and discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] Annealing and cyclic voltammetry (CV) are essential for the activation of amorphous alloy ribbons. Various amorphous alloy ribbons have been activated in the fields of environmental catalysts using either annealing or CV. However, the combination of the two methods for improving the oxygen evolution reaction (OER) performance has rarely been reported. This combination is expected to significantly improve the OER performance of amorphous ribbons. Here, we developed an "annealing +CV-activation" integrated strategy to treat a free-standing NiFeBSiP ribbon, which as an efficient and stable oxygen-evolving electrode. The "annealing +CV-activation" strategy induces the nanocrystallization and oxidation effects on the surface of the NiFeBSiP ribbon. The effects significantly increase the electron transfer ability, the Ni/Fe/P oxidation state and the surface area of the NiFeBSiP ribbon, which consequently leads to enhancing the OER performance. As a result, the treated ribbon exhibits a low overpotential of 269 mV at 10 mA cm−2 and a small Tafel slope of 40.5 mV dec−1, which are much better than the OER performance of the as-spun ribbon. The enhanced OER performance of the NiFeBSiP ribbon demonstrates the significant and promising effect of the "annealing +CV-activation" integrated strategy for designing high-efficiency amorphous alloy ribbons electrocatalysts. [ABSTRACT FROM AUTHOR]

Recently, an interest in NASICON-type materials revived, as they are considered potential cathode materials in sodium–ion batteries used in large-scale energy storage. We applied a facile technique of thermal nanocrystallization of glassy analogs of these compounds to enhance their electrical parameters. Six nanomaterials of the Na3M2(PO4)2F3 (M = V, Ti, Fe) system were studied. Samples with nominal compositions of Na3V2(PO4)2F3, Na3Ti2(PO4)2F3, Na3Fe2(PO4)2F3, Na3TiV(PO4)2F3, Na3FeV(PO4)2F3 and Na3FeTi(PO4)2F3 have been synthesized as glasses using the melt-quenching method. X-ray diffraction measurements were conducted for as-synthesized samples and after heating at elevated temperatures to investigate the structure. Extensive impedance measurements allowed us to optimize the nanocrystallization process to enhance the electrical conductivity of cathode nanomaterials. Such a procedure resulted in samples with the conductivity at room temperature ranging from 1 × 10 − 9 up to 8 × 10 − 5 S/cm. We carried out in situ impedance spectroscopy measurements (in an ultra-high-frequency range up to 10 GHz) and compared them with thermal events observed in differential thermal analysis studies. [ABSTRACT FROM AUTHOR]

This work grounds the relevance of the new ways for modifying the structure and properties of amorphous metallic alloys using severe plastic deformation (SPD) resulting the formation of nanocrystalline materials with new physical and mechanical properties. In this work, for the first time, the peculiarities of deformation nanocrystallization of one of the representatives of this class of material, such as NANOMET doped with phosphorus, namely, alloy Fe81B7Si1P10Cu1 are studied. To perform SPD, the method of high-frequency mechanical-impact (HFMI) treatment is used in modes, which will ensure the maximum hardening effect as compared to the original rapidly solidified amorphous ribbon. The special features of the structure and kinetics of the deformation-induced crystallization of the alloy underwent the SPD by the HFMI method are studied. Two crystallization effects are established during heating of the amorphous ribbon of maximum hardness induced by the applied HFMI. First one, this is the shift of critical temperatures towards low exothermal temperatures, and second one, this is the lowering of the activation energy for crystallization as compared to the undeformed amorphous sample. The reasons of the observed SPD-induced changes in thermodynamic characteristics are established. [ABSTRACT FROM AUTHOR]

The effects of severe plastic deformation (SPD) by means of high-pressure torsion (HPT) on the structural properties of the two iron-based metallic glasses Fe73.9Cu1Nb3Si15.5B6.6 and Fe81.2Co4Si0.5B9.5P4Cu0.8 have been investigated and compared. While for Fe73.9Cu1Nb3Si15.5B6.6, HPT processing allows us to extend the known consolidation and deformation ranges, HPT processing of Fe81.2Co4Si0.5B9.5P4Cu0.8 for the first time ever achieves consolidation and deformation with a minimum number of cracks. Using numerous analyses such as X-ray diffraction, dynamic mechanical analyses, and differential scanning calorimetry, as well as optical and transmission electron microscopy, clearly reveals that Fe81.2Co4Si0.5B9.5P4Cu0.8 exhibits HPT-induced crystallization phenomena, while Fe73.9Cu1Nb3Si15.5B6.6 does not crystallize even at the highest HPT-deformation degrees applied. The reasons for these findings are discussed in terms of differences in the deformation energies expended, and the number and composition of the individual crystalline phases formed. The results appear promising for obtaining improved magnetic properties of glassy alloys without additional thermal treatment. [ABSTRACT FROM AUTHOR]

For amorphous alloy Fe77,5Ni3,5Mo1Si2B16 the possibility of obtaining the amorphous-nanocrystalline state by controlled annealing of source alloy is evaluated. Based on theory of high-temperature stability of amorphous alloys the temperature interval in which the condition of growth of frozen-in crystallization centers is fulfilled, but the process of intensive crystallization has not yet begun, is calculated. With proposed method alloy in the amorphous-nanocrystalline state is obtained, that is confirmed by the results of X-ray diffraction and electron microscopic studies. Using the highly sensitive dilatometric technique, the onset temperatures of intense crystallization for the source amorphous alloy and for alloy in the amorphous-nanocrystalline state have been determined. It has been shown that the proposed heat treatment reduces the onset temperature of intense crystallization by 15°С. Calculated according to the dilatometric experiment, the part of the nanocrystalline phase in the obtained amorphous-nanocrystalline specimen does not exceed 24%. In the paper the micromechanical and electrical properties of obtained alloy in the amorphous-nanocrystalline state are investigated. [ABSTRACT FROM AUTHOR]

Fe-based amorphous alloys with good glass-forming ability (GFA), superior soft magnetic properties, low cost, and a wide heat treatment window have long been pursued in the field of soft magnetic materials due to their importance for mass production and broad applications. In the present study, by strategically adjusting the composition of a low-cost Fe-Si-B-P-Cu-C alloy, we achieved a saturation magnetization (M s) of approximately 186 emu/g and a coercivity (H c) of about 6 A/m for the Fe82.5 alloy with a good GFA. Specifically, the limited Cu content and suitable contents of metalloid elements played pivotal roles in enhancing the nuclei barrier and stabilizing the amorphous matrix. This, in turn, facilitated the formation of a finely uniform nanocrystalline structure dispersed within the amorphous matrix, enhancing soft magnetic properties during annealing. Notably, this magnetic softening behavior occurred at a lower heating rate. Structural characterizations revealed that a transient metalloid-rich shell and a stable amorphous matrix contributed to the slow growth of the α-Fe (Si) during prolonged isothermal annealing. This is in contrast to the agglomeration of small nanograins into larger clusters at high heating rates, which enhances the versatility and potential applicability of the alloy. The successful development of this novel nanocrystalline alloy offers promising guidance for addressing the challenges associated with the mass production of soft magnetic materials. [Display omitted] • Fe82.5-Si-B-P-Cu-C amorphous alloy exhibits excellent soft magnetic properties and good glass-forming ability was developed. • Magnetic softness can be finely tuned within a wide heat treatment window to solve challenges in industrial production. • Formation of a transient metalloid-rich shell and a stable amorphous matrix is instrumental in slowing the growth of bcc-Fe. • The advantages are a result of composition adjustments by reducing nuclei precursor and augmenting metalloid elements. [ABSTRACT FROM AUTHOR]

The review is devoted to the state-of-the-art views on the microstructure evolution in structural and tool carbon steels during the surface severe plastic deformation (SPD). The main focus is on the effects of the nanocrystallization in the near-surface area of the low-carbon steel (C 0.05–0.2%), medium-carbon steel (C 0.35–0.65%), and high-carbon steel (C 1.0–1.5%). It is reviewed the following advanced surface SPD methods for the metal surfaces in recent years: an ultrasonic impact peening (UIP), high-frequency impact peening (HFIP), air blast shot peening (ABSP), surface mechanical attrition treatment (SMAT), and laser shock peening (LSP). Microstructure evolution before and after SPD is studied by optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The effects of the SPD parameters on the nanocrystalline modification of such main phase components of the carbon steels as ferrite, pearlite and cementite are analysed. The atomic mechanism of the nanocrystallization is presented. The strain-hardening effect induced by SPD is demonstrated by the data of the near-surface microhardness profiles.

Nanograins were obtained in the AZ31 Mg alloy bars with different initial grain sizes via cold rotary swaging. Microstructure evolution during deformation was investigated through electron backscatter diffraction analysis and transmission electron microscopy studies. The results indicate that initial grain size had little effect on the mechanism of grain refinement during swaging. The nanocrystallization process of the alloys with different initial grain sizes included extensive twinning followed by the further refinement of the twin lamellae through the formation of massive dislocation arrays. However, as the initial grain size decreased, the formation rate of nanograins increased, resulting in a higher degree of nanocrystallization after the same swaging pass. The mean grain size and yield strength of the sample with the smallest initial grain size were about 91 nm and 489 MPa, respectively. The slower rate and lower degree of nanocrystallization in the alloy with a larger initial grain size were mainly attributed to the less grain boundary areas and higher activity of twinning. [ABSTRACT FROM AUTHOR]

Thermal processing of soft magnetic amorphous and nanocrystalline alloys is explored under the influence of radio‐frequency induction‐heating techniques. Direct induction‐heating concepts based on longitudinal and transverse flux heating are examined and the details of electromagnetic fields interaction with metallic strips are discussed by analytical calculations as well as finite element analysis. Initial experimental results confirming spatial control of phase transformations and nanocrystallization within a single strip of Finemet Fe‐based amorphous ribbons are reported. The degree to which primary and secondary crystallization temperature are achieved depends on the spacing between the ribbon relative to the induction coil as well as the coil design and configuration. For transverse coil configurations, the local temperature and therefore microstructural evolution is different across the lateral dimension of processed ribbons, with reduced gap sizes producing enhanced peak temperatures and larger temperature distributions with greater spatial variation in microstructure. In addition, indirect susceptor‐based induction heating under tension is performed and the impact of microstructure is demonstrated. Herein, potential for exploiting spatially optimized phase transformations is illustrated through electromagnetic field–assisted processing in a scalable manufacturing process with amorphous and nanocrystalline soft magnetic alloys. [ABSTRACT FROM AUTHOR]

The early stages of nanocrystallization in amorphous Fe73.8Si13B9.1Cu1Nb3.1 ribbons and microwires were compared in terms of their internal stress effects. The microstructure was investigated by the X-ray diffraction method. Classical expressions of crystal nucleation and growth were modified for microwires while accounting for the internal stress distribution, in order to justify the XRD data. It was assumed that, due to the strong compressive stresses on the surface part and tensile stresses on the central part, crystallization on the surface part of the microwire proceeded faster than in the central part. The results revealed more rapid nanocrystallization in microwires compared to that in ribbons. During the initial period of annealing, the compressive surface stress of a microwire caused the formation of a predominantly crystallized surface layer. The results obtained open up new possibilities for varying the high-frequency properties of microwires and their application in modern sensorics. [ABSTRACT FROM AUTHOR]

Co-Zr amorphous alloys exhibit soft magnetic properties, whereas the Co-rich crystalline magnetic phases in this alloy system displayed a hard magnetic behavior. In this study, an initial two-phase Co-Zr composite with an overall composition of 75 at.% Co and 25 at.% Zr was processed by high-pressure torsion (HPT), and the effects of severe plastic deformation and subsequent thermal treatment on the composite’s structural evolution and its magnetic properties were investigated. HPT processing allowed us to achieve an amorphous microstructure with low coercivity in its as-deformed state. To further tune the alloy’s magnetic properties and study its crystallization behavior, various annealed states were investigated. The microstructural properties were correlated with the magnetic properties, and a decreasing coercivity with increasing annealing temperatures was observed despite the onset of crystallization in the amorphous alloy. At higher annealing temperatures, coercivity increased again. The results appear promising for obtaining tuneable rare-earth free magnetic materials by severe plastic deformation.

Through surface nanocrystallization and low-temperature ion sulfurization, the nanocrystalline/FeS thin film with excellent friction-reduction and antiwear properties was fabricated on the surface of AISI321 stainless steel. The nanocrystallization treatment formed the high hardness and active nanocrystalline structure on the surface of AISI321, with the harness increased from 4.6 GPa to 7.56 GPa. Furthermore, the significantly refined nanostructure strongly increased the concentration of S element in comparison with the single-sulfurized layer on the substrate. Tribological tests reveal that both the original AISI321 substrate and the single-sulfurizing-treated samples are subject to severe abrasion. Single nanocrystallization treatment can improve the wear resistance of AISI321, while the compound treatment can obviously improve the comprehensive tribological properties. The compound-modified layer presents excellent tribological properties with the lowest coefficient of friction (COF) of 0.33, which is related to the increased hardness of the substrate and increased thickness, density, and homogeneity of the sulfurized layer. Furthermore, a physical model is developed for the vacuum tribological behavior of the samples after different treatments. This model provides a reference for revealing the tribological mechanism of the compound-modified layer treated using surface nanocrystallization-assisted chemical heat treatment.

This study demonstrated for the first time that it is possible to prepare nanocrystalline δ-Bi2O3 that is stable at room temperature by twin-rollers and free cooling methods, using a ceramic crucible. The phase composition of prepared samples and upper limit of the thermal stability of nanograins confined in an amorphous matrix were determined by the X-ray diffraction (XRD) method. The average size of crystallites and the microstructure of studied samples was determined by SEM and XRD methods. The average grain size varied from 38 to 85 nm, depending on the preparation technique; however, it was also observed that agglomerations consisted of smaller crystallites ca. 10–30 nm. Using the EDX method, it was found that a crucial role in the preparation of nanocrystalline δ-Bi2O3 glass-ceramics was played by Si and Al impurities and their glass forming oxides from ceramic crucible. By impedance spectroscopy (IS), the temperature dependencies of electric conductivity (via oxygen ions) were studied and the activation energies of conductivity were determined. [ABSTRACT FROM AUTHOR]

With the wide application of titanium alloys in the aerospace industry, the burn resistance properties and surface strengthening processes of titanium alloys have been received increasing attention. In this study, Ti40 burn-resistant titanium alloy was cladded on the surface of TC4 by electron beam cladding, and the surface layer of the nanostructure was prepared by ultrasonic impact treatment (UIT). The nanostructure layer was examined by pulse laser ablation. The results showed that when the moving speed was 16 mm/s, the maximum thickness of the plastic deformation zone of the UIT Ti40 cladding layer reached 150 μm. The highest hardness value was 531 HV, which was approximately 43.5% higher than the original microstructure of the Ti40 cladding layer without UIT. Moreover, the surface microstructure of the Ti40 burn resistant titanium alloy cladding layer was nanocrystalline with uniform distribution and random orientation, and the average grain size was 50 nm. The UIT process can effectively increase the relative content of burn-resistant alloy elements on the surface of the Ti40 cladding layer and increase the content of dense oxidation protective films after laser ablation, which hinders the diffusion and migration of oxygen elements to the matrix alloy in the process of ablation and then improves the burn resistance of the Ti40 cladding layer.

Melanin is an insoluble, amorphous polymer that forms planar sheets that aggregate naturally to create colloidal particles with several biological functions. Based on this, here, a preformed recombinant melanin (PRM) was utilized as the polymeric raw material to generate recombinant melanin nanoparticles (RMNPs). These nanoparticles were prepared using bottom-up (nanocrystallization—NC, and double emulsion–solvent evaporation—DE) and top-down (high-pressure homogenization—HP) manufacturing approaches. The particle size, Z-potential, identity, stability, morphology, and solid-state properties were evaluated. RMNP biocompatibility was determined in human embryogenic kidney (HEK293) and human epidermal keratinocyte (HEKn) cell lines. RMNPs prepared by NC reached a particle size of 245.9 ± 31.5 nm and a Z-potential of −20.2 ± 1.56 mV; 253.1 ± 30.6 nm and −39.2 ± 0.56 mV compared to that obtained by DE, as well as RMNPs of 302.2 ± 69.9 nm and −38.6 ± 2.25 mV using HP. Spherical and solid nanostructures in the bottom-up approaches were observed; however, they were an irregular shape with a wide size distribution when the HP method was applied. Infrared (IR) spectra showed no changes in the chemical structure of the melanin after the manufacturing process but did exhibit an amorphous crystal rearrangement according to calorimetric and PXRD analysis. All RMNPs presented long stability in an aqueous suspension and resistance to being sterilized by wet steam and ultraviolet (UV) radiation. Finally, cytotoxicity assays showed that RMNPs are safe up to 100 μg/mL. These findings open new possibilities for obtaining melanin nanoparticles with potential applications in drug delivery, tissue engineering, diagnosis, and sun protection, among others.

In this paper, ultrasonic surface rolling (USRP) and laser heating-assisted USRP (Laser-USRP) techniques are employed to enhance the fretting fatigue strength of TC11 titanium alloy. Furthermore, the surface deformation mechanism and fretting fatigue behavior are investigated. The properties of the reinforced surfaces were observed using transmission electron microscope (TEM), microhardness test, residual stress test and fretting fatigue experiments. The results showed that laser-USRP led to a remarkable enhancement in the fretting fatigue life of TC11 titanium alloy compared to traditional USRP. This was mainly due to the fact that laser heating improved the plasticity of TC11 titanium alloy, contributed to the formation of a smoother surface and increased the degree of surface oxidation, which could improve surface lubrication. Under high temperature, more slip systems were activated and more stable dislocations were formed, which resulted in larger compressive residual stress (CRS) with higher stability. The superposition of the elevated temperature field and the kinetic energy of the ultrasonic vibration produced an annealing effect in localized regions, resulting in the formation of more stable gradient nanograins. This study demonstrated the immense potential of laser-assisted plastic deformation in improving the surface properties of titanium alloys. [ABSTRACT FROM AUTHOR]