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The fast exploration of low energy configuration by surface atoms is believed to favor the formation of ultrastable metallic glasses, prepared by physical vapor deposition. Here, we find that the rearrangement of surface atoms is collective, rather than being dominated by individual atoms. Specifically, we experimentally observe the growth process of ultrastable metallic glasses at monolayer resolution, which follows a periodic island-layer-island pattern with morphology variation between islands and flat surfaces. The estimated surface diffusion coefficient is orders of magnitude higher than that for bulk diffusion. The fast surface dynamics allow the newly deposited clusters on the flat surface to form local islands with spherical shape, which substantially reduces the surface free energy in each island-layer-island growth cycle. Our findings are helpful for understanding the growth mechanisms of ultrastable metallic glasses and potentially for tailoring their properties. Ultrastable metallic glasses form by surface diffusion on a substrate during deposition. Here, this process is shown to involve the collective diffusion of atoms in a cyclic process, involving the formation of islands, their coalescence into a layer, followed by further island formation.

The atomic-scale structural rearrangement of glasses on applied stress is central to the understanding of their macroscopic mechanical properties and behaviour. However, experimentally resolving the atomic-scale structural changes of a deformed glass remains challenging due to the disordered nature of the glass structure. Conventional structural analyses such as X-ray diffraction are based on the assumption of structural isotropy and hence cannot discern the subtle atomic-scale structural rearrangement induced by deformation. Here we show that structural anisotropy correlates with non-affine atomic displacements—meaning those that do not preserve parallel lines in the atomic structure—in various types of glass. This serves as an approach for identifying the atomic-scale non-affine deformation in glasses. We also uncover the atomic-level mechanism responsible for plastic flow, which differs between metallic glasses and covalent glasses. The non-affine structural rearrangements in metallic glasses are mediated through the stretching or contraction of atomic bonds. The non-affinity of covalent glasses that occurs in a less localized manner is mediated through the rotation of atomic bonds or chains without changing the bond length. These findings provide key ingredients for exploring the atomic-scale process governing the macroscopic deformation of amorphous solids.Resolving the structural changes of a deformed glass on the atomic scale is challenging due to its disordered nature. Now, high-energy diffraction measurements show that non-line-preserving atomic displacements in glasses correlate with structural anisotropy.

Electrical resistance strain gauges （SGs） are useful tools for experimental stress analysis and the strain sensing elements in many electromechanical transducers including load cells, pressure transducers, torque meters, accelerometers, force cells, dis- placement transducers and so forth. The commonly used commercial crystalline strain sensing materials of SGs are in the form of wire or foil of which performance and reliability is not good enough due to their low electrical resistivity and incapacity to get thin thickness. Smaller SGs with single straight strand strain sensing materials, which are called ideal SG, are highly desir- able for more than seven decades since the first SG was invented. Here, we show the development of a type of minuscule length scale strain gauge by using a bare and single straight strand metallic glassy fiber （MGF） with high resistivity, much smaller lengthscale, high elastic limits （2.16%） and especially the super piezoresistance effect. We anticipate that our metallic glassy fiber strain gauge （MGFSG）, which moves toward the ideal SGs, would have wide applications for electromechanical transducers and stress analysis and catalyze development of more micro-and nanoscale metallic glass applications.

The ultra-slow relaxation dynamics of glasses at ambient temperature provide a promising alternative for dating glasses with extremely low isotopic content that cannot be dated using traditional radiometric methods. However, these ultra-slow, nonlinear aging dynamics remain poorly understood due to the lack of accurate theoretical models and long-term experimental validation. Existing equilibrium-based dynamics models substantially overestimate relaxation times at temperatures far below the glass transition temperature, making it difficult to model and quantify non-equilibrium aging over geological timescales. We address this challenge by formulating an empirical equation that quantifies the non-equilibrium effective relaxation time (τ ) for various glasses, including metallic glasses, organic amber, and lunar glasses. Our findings demonstrate a universal nonlinear aging dynamics governed by a single τ , which follows a robust empirical relation parameterized by aging temperature and material-specific fragility. Employing this equation, we propose a universal glass kinetics dating method, conceptually analogous to radioactive decay, where τ serves as a material-specific decay constant. This approach enables dating of glassy materials over timescales spanning decades to billions of years. This work bridges a fundamental gap in glass aging theory and establishes a practical framework for dating geological and planetary glasses.

Nanophase iron particles (npFe 0 ) are generated on the surface of airless bodies by space weathering and can alter surficial optical properties substantially. However, the details of their formation pathways are still unclear. Here we use impact glasses returned from the Moon by Chang’e-5 to distinguish the relative contributions of solar wind irradiation and (micro)meteorites impacts to the production of different-sized npFe 0 . We show that solar wind irradiation can solely produce small npFe 0 , via implantation of solar wind ions into the topmost grain surfaces. On the other hand, (micro)meteorite impacts produce directly large npFe 0 in melts, through impact-triggered disproportionation reaction or thermal decomposition. These nanoparticles are also capable to further coalesce into micrometre-sized Fe 0 particles during impacts. These findings can help in predicting the space-weathering behaviour of regions exposed to different space environments. A lunar glass bead can preserve nanophase iron (npFe 0 ) of varying sizes via multiple mechanisms. The formation of small and large npFe 0 with distinct weathering effects is independently governed by solar wind irradiation and micrometeorite impacts.

We investigate the effects of high pressure and physical aging on the boson peak and thermal expansion of a typical metallic glass. Specifically, the thermal expansion coefficient and boson peak intensity monotonically decrease during physical aging. With the increase of high pressure, the boson peak intensity and the thermal expansion coefficient coincidently experience an incipient decrease and then a subsequent increase. The boson peak intensity shows an approximately linear relationship with the thermal expansion coefficient. The thermal expansion can be affected by structural relaxation or rejuvenation, which can reflect the flow units variation and atomic packing of a metallic glass. Our results indicate a direct link between structural relaxation or rejuvenation and fast boson peak dynamics, providing insights into the boson peak behavior and structural heterogeneity of metallic glasses.

AbstractsThe magnetocaloric effect (MCE) has made great success in very low temperature refrigeration, which is highly desirable for application to the extended higher temperature range. Here we report the giant enhancement of MCE in the metallic glass composite. The large magnetic refrigerant capacity (RC) up to 103 J·kg−1 is more than double the RC of the well-known crystalline magnetic refrigerant compound Gd5Si2Ge1.9Fe0.1 (357 J·kg−1) and MnFeP0.45As0.55 (390 J·kg−1)(containing either exorbitant-cost Ge or poisonous As). The full width at half maximum of the magnetic entropy change (ΔSm) peak almost spreads over the whole low-temperature range (from 303 to 30 K), which is five times wider than that of the Gd5Si2Ge1.9Fe0.1 and pure Gd. The maximum ΔSm approaches a nearly constant value in a wide temperature span over 100 K, and however, such a broad table-like region near room temperature has seldom been found in alloys and compounds. In combination with the intrinsic amorphous nature, the metallic glass composite may be potential for the ideal Ericsson-cycle magnetic refrigeration over a broad temperature range near room temperature.

This paper reports a class of bulk metallic glass including Ce-, LaCe-, CaLi-, Yb-, and Sr-based metallic glasses, which are regarded as glassy metallic plastics because they combine some unique properties of both plastics and metallic alloys. These glassy metallic plastics have very low glass transition temperature ( T g ∼25°C to 150°C) and low Young’s modulus (∼20 GPa to 35 GPa). Similar to glassy plastics, these metallic plastics show excellent plastic-like deformability on macro-, micro- and even nano-scale in their supercooled liquid range and can be processed, such as elongated, compressed, bent, and imprinted at low temperatures, in hot water for instance. Under ambient conditions, they display such metallic properties as high thermal and electric conductivities and excellent mechanical properties and other unique properties. The metallic plastics have potential applications and are also a model system for studying issues in glass physics.

We investigate the effects of high pressure and physical aging on the boson peak and thermal expansion of a typical metallic glass. Specifically, the thermal expansion coefficient and boson peak intensity monotonically decrease during physical aging. With the increase of high pressure, the boson peak intensity and the thermal expansion coefficient coincidently experience an incipient decrease and then a subsequent increase. The boson peak intensity shows an approximately linear relationship with the thermal expansion coefficient. The thermal expansion can be affected by structural relaxation or rejuvenation, which can reflect the flow units variation and atomic packing of a metallic glass. Our results indicate a direct link between structural relaxation or rejuvenation and fast boson peak dynamics, providing insights into the boson peak behavior and structural heterogeneity of metallic glasses. metallic glass, thermal expansion, boson peak, high pressure, aging PACS number(s): 61.43.Dq, 61.20.Lc, 62.50.+p, 61.72.Cc, 65.60.+a

Energetic materials are solids that release a large amount of energy in combustion. The evaluation depends on both combustion heat and ignition temperature. Conventional non-metallic materials have low ignition temperature but small combustion heat, whereas metals have large combustion heat but high ignition temperatures. We show that many metallic glasses, combining the merits of both metals and non-metals, have large combustion heat, approximately twice that of the non-metals, and low ignition temperature that is several hundreds of Kelvin lower than that of the metals. The ease in igniting metallic glass results from the low thermal conductivity of the materials and the storage of energy in their liquid-like atomic structure. Metallic glass ribbons outweigh metallic nanoparticles due to their high production efficiency, low cost and nontoxicity. The findings suggest that metallic glasses are alternative energetic materials.