Search Results (256)

The emulsification of a molten fusible metal alloy in a liquid epoxy matrix with its subsequent curing is a novel way to create a highly concentrated phase-change material. However, numerous challenges have arisen. The high interfacial tension between the molten metal and epoxy resin and the difference in their viscosities hinder the stretching and breaking of metal droplets during stirring. Further, the high density of metal droplets and lack of suitable surfactants lead to their rapid coalescence and sedimentation in the non-cross-linked resin. Finally, the high differences in the thermal expansion coefficients of the metal alloy and cross-linked epoxy polymer may cause cracking of the resulting phase-change material. This work overcomes the above problems by using nanosilica-induced physical gelation to thicken the epoxy medium containing Wood’s metal, stabilize their interfacial boundary, and immobilize the molten metal droplets through the creation of a gel-like network with a yield stress. In turn, the yield stress and the subsequent low-temperature curing with diethylenetriamine prevent delamination and cracking, while the transformation of the epoxy resin as a physical gel into a cross-linked polymer gel ensures form stability. The stabilization mechanism is shown to combine Pickering-like interfacial anchoring of hydrophilic silica at the metal/epoxy boundary with bulk gelation of the epoxy phase, enabling high metal loadings. As a result, epoxy shape-stable phase-change materials containing up to 80 wt% of Wood’s metal were produced. Wood’s metal forms fine dispersed droplets in epoxy medium with an average size of 2–5 µm, which can store thermal energy with an efficiency of up to 120.8 J/cm³. Wood’s metal plasticizes the epoxy matrix and decreases its glass transition temperature because of interactions with the epoxy resin and its hardener. However, the reinforcing effect of the metal particles compensates for this adverse effect, increasing Young’s modulus of the cured phase-change system up to 825 MPa. These form-stable, high-energy-density composites are promising for thermal energy storage in building envelopes, radiation-protective shielding, or industrial heat management systems where leakage-free operation and mechanical integrity are critical. Full article

In this study, bulk metallic glasses (BMGs) of Zr₅₆Cu₂₃Al₁₀Ni_11-xTa_x (x = 0, 0.5, 1, 1.5, 2, and 2.5 at.%) were prepared by copper mold suction-casting. The glass-forming ability, mechanical properties, crystallization kinetics, and corrosion resistance of the as-obtained amorphous alloys were all investigated. Experimental results showed enhanced forming ability of amorphous alloys in the presence of small amounts of Ta element. By adding appropriate amounts of Ta, the supercooled liquid region of bulk metallic glass increased from 64 K to 73 K. The critical diameter of the alloy rod at x = 1, 1.5 rose from 5 mm to 6 mm. The addition of Ta also reduced the sensitivity coefficients of the amorphous alloys to the heating rate during crystallization, while other quantities, like Eg, Ex, and Ep, all incremented. Thus, the addition of Ta declined the temperature sensitivity of amorphous alloy systems. This also increased the energy barrier required for atom rearrangement, nucleation and growth, as well as greatly enhancing the stability of the systems. At 2% Ta content, the plastic strain of the amorphous alloy exceeded 2.6%, and yield strength reached 1900 MPa. In sum, the mechanical properties of the amorphous alloys after the addition of Ta element obviously improved when compared to the original alloy. As Ta content raised, the corrosion current densities of BMGs in different corrosion solutions gradually decreased, while the corrosion potential gradually increased. Full article

Pt-Fe alloys with abundant inclusions are from the Camumbi River placer deposit, Ecuador. They are derived from unknown Alaskan–Uralian-type intrusion(s) within the Late Cretaceous Naranjal accreted terrane. Compositions of our previously documented chilled silicate glass inclusions are increasingly fractioned from hydrous ferrobasalt to rhyolite in terms of TAS (total alkalis vs. silica). Their liquid lines of descent change from tholeiitic to the calc-alkaline magma series. Here, we document seven rare composite inclusion parageneses of Cu–PGM (platinum-group mineral) sulfides, each coexisting with and exsolved from related fractionated silicate glass (melt). Differentiation is dominated by fractional crystallization in PGM bulk compositions from tholeiitic silicate melts at the highest T (temperature): ~1018 °C. Silicate glass inclusions following the lower T calc-alkaline trend coexist with sulfide PGM parageneses that were likely differentiated, in terms of Pt-Rh-Pd and BMs (base metals), by incongruent melting due to decompression and S-degassing at ~983–830 °C. S-saturated sulfide melts become S-undersaturated below 845 °C. The calculated temperatures are for silicate glass. Pt-rich braggite shows increasing fractionation towards Pd-rich vysotskite within one inclusion paragenesis. A late braggite–vysotskite fractionation trend shows decreasing minor base metals (BMs). Thiospinels are dominated by cuprorhodsite. Minor thiospinels indicate Fe and then strong Ni enrichment at the lowest T. Decompression exsolutions, deflation, and the partial melting of some sulfide inclusion parageneses support rapid ascent to higher crustal levels within a deep-sourced cumulate intrusion. Full article

Titanium-based bulk metallic glasses (BMGs) offer high strength, lower stiffness than Ti-6Al-4V, and superior corrosion resistance, but conventional Ti glass-forming systems often contain toxic Ni, Be, or Cu. This work investigates five novel Ti-based alloys free of these elements—Ti₄₂Zr₃₅Si₅Co_12.5Sn_2.5Ta₃, Ti₄₂Zr₄₀Ta₃Si₁₅, Ti₆₀Nb₁₅Zr₁₀Si₁₅, Ti₃₉Zr₃₂Si₂₉, and Ti_65.5Fe_22.5Si₁₂—synthesized by arc melting and suction casting. Single-track laser remelting using a selective laser melting (SLM) system was performed to simulate additive manufacturing and examine microstructural evolution, cracking behavior, mechanical properties, and cytocompatibility. All alloys solidified into fully crystalline α/β-Ti matrices with Ti/Zr silicides; no amorphous structures were obtained. Laser remelting refined the microstructure but did not induce glass formation, consistent with the known limited glass-forming ability of Cu/Ni/Be-free Ti systems. Cracking was observed at low laser energies but crack density decreased as laser energy increased. Cracks were eliminated above ~0.4 J/mm for most alloys. Ti₄₂Zr₃₅Si₅Co_12.5Sn_2.5Ta₃ exhibited the lowest stiffness (~125 GPa), while Ti₆₀Nb₁₅Zr₁₀Si₁₅ showed the highest due to silicide precipitation. Cytotoxicity tests (ISO 10993-5) confirmed all alloys to be non-toxic, with some extracts even enhancing fibroblast proliferation. This rapid laser-remelting approach enables cost-effective screening of Ti-based glass-forming alloys for additive manufacturing. Ti–Zr–Ta–Si systems demonstrated the most promising properties for further testing using the powder bed method. Full article

Bulk metallic glasses (BMGs), classified as metastable materials, necessitate melt quenching at critical cooling rates higher than 10² K/s to kinetically bypass crystalline phase formation during solidification. Owing to this rapid quenching, the microstructure of BMGs can be regarded as melt quenched. This study examines how their melt state governs the thermal stability, structural characteristics, and plasticity behavior of Zr₅₀Cu₄₀Al₁₀ BMG. Rod samples were prepared via injection casting at controlled melt temperatures and suction casting. Experimental observations demonstrated a positive correlation between elevated melt temperatures and enhanced glass forming ability (GFA) along with improved thermal stability (T-A) in BMGs during processing. Structural analyses confirmed the glassy nature of the prepared BMGs with different melt states and revealed their temperature-dependent atomic-scale heterogeneity: the samples quenched at low melt temperatures exhibited significant Cu-rich clustering as determined via energy-dispersive X-ray spectroscopy (EDS) mapping, and those at high melt temperatures formed homogeneous structures. This structure heterogeneity was directly correlated with good plastic deformation behavior, i.e., the rod sample prepared at the lowest melt temperature achieved 9.7% plastic strain. The transition is attributed to liquid-liquid phase transition (LLPT): below the LLPT threshold, metastable Cu-rich clusters persist in the melt and are retained upon quenching, creating structural defects that facilitate shear band multiplication. These findings highlight melt temperature as a crucial factor in tailoring the structure characteristic and mechanical behavior of Zr₅₀Cu₄₀Al₁₀ BMGs. Full article

This study systematically investigates the effect of substituting Copper (Cu) with Nickel (Ni) on the glass-forming ability (GFA) and corrosion resistance of a Pt-based bulk metallic glass (BMG). We demonstrate that a minor substitution of 5 at.% Ni for Cu in the Pt₄₀Pd₂₀Cu₂₀P₂₀ base alloy significantly enhances both properties. The GFA is markedly improved, as evidenced by the supercooled liquid region (ΔTx) widening from 68 K to 91 K. The optimized Pt₄₀Pd₂₀Cu₁₅Ni₅P₂₀ alloy exhibits a compressive fracture strength of 1.38 GPa. Electrochemical tests in a 3.5 wt.% NaCl solution reveal a substantial improvement in corrosion resistance. Compared to the Ni-free baseline alloy, the passive film resistance (R_f) and charge-transfer resistance (R_ct) of the Ni-containing alloy are enhanced by factors of 2.75 and 2.60, respectively. This superior performance is attributed to a synergistic effect wherein Ni alloying both stabilizes the amorphous structure and promotes the formation of a more robust passive film. This work presents a viable strategy for designing cost-effective, high-performance multi-component BMGs for applications in aggressive chloride environments. Full article

Metallic glass alloys exhibit excellent properties, yet suffer from poor room-temperature plasticity, a limitation that restricts their engineering applications. Bulk metallic glass matrix composites (BMGMCs) have proven effective in enhancing the plasticity of metallic glasses, and the addition of alloying elements serves as a key strategy to regulate their microstructure and optimize the properties of these composites. This study aims to investigate the effects of a vanadium (V) addition on the mechanical properties and microstructure of Ti-based BMGMCs, while exploring the underlying mechanism of V’s influence. Using (Ti₅₁Zr₂₅Cu₆Be₁₈)_100−xV_x (x = 0, 4, 8, 12, 16, 20) BMGMCs as test specimens, microstructural characterization was performed via X-ray diffraction (XRD) and scanning electron microscopy (SEM), and compressive mechanical properties were tested. The results indicate that a V addition refines dendrites without altering the phase composition, which remains composed of β-Ti crystals and an amorphous matrix. With the increase in V content, the compressive plastic strain shows a trend of first increasing and then decreasing; when x = 12, the specimen exhibits the maximum compressive plastic strain, reaching 7.9%. Additionally, the volume fraction of the crystalline phase gradually increases with increasing V content. This study clarifies the mechanism by which V regulates the microstructure and properties of Ti-based BMGMCs, thereby providing theoretical and experimental insights for optimizing alloy compositions to enhance the mechanical performance. Full article

Dealloying technique has been used for centuries as an attractive method for producing porous surfaces by removing one or more undesirable elements from the surface. Since early 2000s, the technique has been further developed for understanding the dealloying mechanism and tailoring it to produce chemically homogeneous materials with nanoporous (np) morphology. Dealloying has found numerous applications such as sensors, catalysts, as well as in the biomedical field, which is fairly recent and has attracted great attention on this topic. This review investigates the dealloying technique for preparing nanoporous materials and nanoporous surfaces by using different modification routes on various types of Ti-based alloys for biomedical implant application. There has been significant growth in studying dealloying of crystalline, amorphous, shape memory, and composites-based Ti alloys. This review aims to summarise the findings from literature and discuss the scope of this technique and challenges involved for future aspects. Full article

Cobalt-based bulk metallic glasses (Co-based BMGs) offer a combination of high strength, corrosion resistance, and soft magnetic properties, yet their limited glass-forming ability (GFA) and poor room-temperature ductility restrict broader application. In this study, a microalloying strategy was applied to the Co₆₁Nb₈B₃₁ base composition to develop Co-Nb-B-Si and Co-Fe-Nb-B-Si systems. The effects of Si addition and Fe substitution on GFA, thermal stability, and mechanical properties were systematically investigated. Si doping combined with Co/B ratio tuning broadened the supercooled liquid region and increased the critical glass-forming diameter from 1 mm to 3 mm. Further addition of 5 at.% Fe expanded the supercooled liquid region and enabled the fabrication of a fully amorphous plate with 1 mm thickness. The optimized Co₆₃Nb₈B₂₇Si₂ alloy exhibited a compressive strength of 5.18 GPa and a plastic strain of 3.81%. Fracture surface analysis revealed ductile fracture features in the Si-containing alloy and brittle characteristics in Fe-rich compositions. These results demonstrate that microalloying is effective in optimizing the balance between GFA and mechanical performance of Co-based BMGs, offering guidance for composition and processing design. Full article

During the operation of structures, the components and materials from which they are made are exposed to various environmental, technological, and operational impacts. In this context, the use of a modified water-dispersion composition containing finely dispersed fillers with enhanced protective and performance characteristics proves to be effective. This article examines the development of a paint-and-coating composition using hollow glass microspheres and modified diatomite as finely dispersed fillers. The influence of technological factors on the properties of coating materials based on a synthesized acrylic dispersion and fillers—such as modified diatomite and hollow glass microspheres ranging from 20 to 100 μm in size with a bulk density of 0.107–0.252 g/cm³—is analyzed. The optimal formulation of the coating materials was determined to ensure the required coating quality. Experimental results demonstrate the improved strength and hardness of the coating due to the use of acrylic dispersion obtained through an emulsifier-free method and modifiers in the form of finely dispersed fillers. It has been established that the resulting samples also exhibit high adhesion to mineral and metallic substrates, along with excellent corrosion resistance. Moreover, the incorporation of acrylic dispersion contributes to increased elasticity of the coating, resulting in improved resistance to washing and abrasion. The developed protective material can be applied to a variety of surfaces, including walls, ceilings, and roofs of buildings and structures, pipelines, and many other applications. Thus, modified water-dispersion compositions based on synthesized acrylic dispersion showed the following results: resistance to sticking—5, which is the best; chemical resistance and gloss level with standard single-phase acrylic dispersion—no destruction or change in gloss. The adhesion of coatings cured under natural conditions and under the influence of UV radiation was 1 point. The developed formulations for obtaining water-dispersion paint and varnish compositions based on synthesized polymer dispersions, activated diatomite, and hollow glass microspheres, meet all the regulatory requirements for paint and varnish materials in terms of performance, and in terms of economic indicators, the cost of 1 kg of paint is 30% lower than the standard. Full article

The identification of suitable alloy compositions for the formation of bulk metallic glasses (BMGs) is a key challenge in materials science. In this study, we developed machine learning (ML) models to predict the critical casting diameter ($D_{max}$) of Fe-based BMGs, enabling rapid assessment of glass-forming ability (GFA) using composition-based and calculated thermophysical features. Three datasets were constructed: one based on alloy molar fractions, one using thermophysical quantities calculated via the CALPHAD method, and another utilizing Magpie-derived features. The performance of various ML models was evaluated, including support vector machines (SVM), XGBoost, and ensemble methods. Models trained on thermophysical features outperformed those using only molar fractions, with XGBoost and SVM models achieving test $R^2$ scores of up to 0.63 and 0.60, respectively. Magpie features yielded similar results but required a larger feature set. To enhance predictive accuracy, we explored data augmentation using the PADRE method and a modified version (PADRE-2). While PADRE-2 demonstrated slight improvements and reduced data redundancy, the overall performance gains were limited. The best-performing model was an ensemble combining SVM and XGBoost models trained on thermophysical and Magpie features, achieving an $R^2$ score of 0.69 and MAE of 0.69, comparable to published results obtained from larger datasets. However, predictions for high $D_{max}$ values remain challenging, highlighting the need for further refinement. This study underscores the potential of leveraging thermophysical features and advanced ML techniques for GFA prediction and the design of new Fe-based BMGs. Full article

The inherent brittleness and limited toughness of bulk metallic glasses (BMGs) remain critical challenges for their application as structural engineering materials. In this study, ultrasonic excitation was applied to Zr_58.75Cu_21.15Fe_4.7Al_9.4Nb₆ BMG with the aim of enhancing its mechanical performance. The results reveal that ultrasonic treatment significantly increases the fracture toughness by approximately 28% and induces a pronounced plastic deformation plateau following yielding. This improvement in both strength and ductility is attributed to the formation of nanoscale crystalline phases and ultrasound-induced phase separation within the amorphous matrix, which collectively promote shear band multiplication and inhibit crack propagation. Full article

Titanium thin films with thicknesses of up to 105 nm were deposited on borosilicate glass implementing low-power continuous (25 W) and pulsed (85 W, with an ultra-low duty cycle) DC magnetron sputtering. The characteristics of the resulting films were studied via atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), VIS spectroscopy, and four-point-probe measurements. Both deposition modes yield films with low surface roughness, and AFM analysis showed no topographical features indicative of columnar-and-void structures. The films exhibited high optical reflectivity and stable transmittance and reflectance across the visible spectrum. The electric resistivity could be measured even at single nanometer thickness, emphasizing the metallic character of the films and approaching the bulk titanium value at higher film thicknesses. The low power regime of magnetron sputter deposition not only offers the possibility of studying the development of physical characteristics during the growth of ultra-thin films but also provides the advantage of extremely low heat development and no evident mechanical stress on the substrate during the coating process. These results outline a path for low-power DC sputtering as a reliable approach for studying the evolution of functional properties in ultra-thin films and for the gentle fabrication of coatings where thermal stress must be avoided, making the method compatible with temperature-sensitive applications. Full article

This study explores the enhancement of antimicrobial and biomedical properties in Fe-based bulk metallic glasses (BMGs) through the addition of Ag. Fe_55-xCr₂₀Mo₅P₁₃C₇Ag_x (x = 0, 1, 2, 3 at.%) master alloy ingots were synthesized by the induction melting technique and industrial-grade raw materials, the master alloy ingots were prepared as bulk metallic glasses (referred to as Ag0, Ag1, Ag2, and Ag3) by the water-cooled copper-mold suction casting technique, and their glass-forming ability, corrosion resistance, biocompatibility, and antimicrobial properties were systematically investigated. The results indicate that the glass forming ability (GFA) decreased with increasing Ag content, reducing the critical diameter for fully amorphous formation from 2.0 mm for Ag0 to 1.0 mm for Ag3. Electrochemical tests in Hank’s solution revealed the superior corrosion resistance of the Fe-based BMGs as compared with conventional 316 L stainless steel (316L SS) and Ti6Al4V alloy (TC4), with Ag3 demonstrating the lowest corrosion current density and the most stable passivation. Biocompatibility assessments, including fibroblast cell viability and adhesion tests, showed enhanced cellular activity and morphology on Fe-based BMG surfaces as compared with 316L SS and TC4, with minimal harmful ion release. Antimicrobial tests against E. coli and S. aureus revealed significantly improved performance with the Ag addition, achieving bacterial inhibition rates of up to 87.5% and 86.7%, respectively, attributed to Ag⁺-induced reactive oxygen species (ROS) production. With their excellent corrosion resistance, biocompatibility, and antimicrobial activity, the present Ag-containing Fe-based BMGs, particularly Ag3, are promising candidates for next-generation biomedical implants. Full article

In the present investigation, high stability Vitreloy Zr₄₄Ti₁₁Cu₁₀Ni₁₀Be₂₅ bulk metallic glass has been subjected to severe shear deformation by high-pressure torsion for 0.1 revolutions under an applied pressure of 4 and 8 GPa. The fully glassy nature of the as-cast glass has been confirmed by X-ray powder diffraction and differential scanning calorimetry. Deformation-induced surface features on an internal plane of the deformed disk-shaped specimens were studied in detail at the macroscopic level by optical reconstruction method and at microscopic scales by white-light optical profilometry. Shear and compressive strain components were measured based on surface changes and it was determined that compressive strain gradient with 0.2–0.4 strain change builds up toward the disk edge, while only part of the nominal shear deformation occurs in the disk interior. The effect of strain localization in the Vitreloy bulk metallic glasses has been quantified by a surface distortion model based on simple shear. The model was then validated experimentally by the reconstructed z-profiles. Full article