Amorphous Research Articles

Strong Lewis Electron-Pair Bonding in Vanadium Oxide for Ultra-fast and Long-term Stable Zn-ion Storage

Vanadium-based oxides typically show low electrical conductivity, high repulsion for Zn2+, and severe structure collapse problems, resulting in unsatisfied cathode performance for aqueous Zn-ion batteries (AZIBs). Herein, we propose an advanced structural optimization strategy to address the above issues by constructing strong Lewis electron-pair bonding in vanadium oxide through initial doping Ca and a subsequent in-situ electrochemical activation process. We prepared the precursor of Ca-doped and amorphous carbon-encapsulated V2O3 material (Ca0.17V2O3-x@C) and verified a phase transition into a layered V2O5-typed cathode during the activation process. Importantly, we find the initial-doped Ca and generated abundant oxygen vacancy defects are well restored in the phase-transformed crystal lattice. We reveal that band and bond structures of the phase-transformed cathode are optimized, exhibiting an improved electrical conductivity, optimal Zn2+ binding energy, ultra-low Zn-ion transport barrier, and considerably strong bonds of Ca-O and V-O, thereby realizing enhanced reaction kinetics and stability. The Ca0.17V2O3-x@C exhibits surprisingly high-rate performance (233 mAh g–1 at 40 A g–1) and excellent cycling stability (10,000 cycles with 82% retention at 20 A g–1). This work offers a novel and simple band and bond structure engineering strategy for preparing high-performance phase transformation typed vanadium oxide cathodes for AZIBs.

Corrosion and wear mechanisms of rare earth (Gd, Sc, Y)-doped Zr-based amorphous alloys

Rare-earth elements have been utilized in the design and development of new amorphous alloys to improve the corrosion and wear resistance of Zr-based amorphous alloys. In this study, a rare-earth doped Zr-based amorphous alloy (Zr-BMG(RE)) was prepared by the copper mold casting method, which was investigated by corrosion and wear experiments. The results show that Zr-BMG(RE) has a completely amorphous structure, and the doping of rare earths Gd and Y raises the crystallization transition temperature of the amorphous. The addition of rare earth elements Gd and Sc increases the microhardness of Zr-based amorphous alloys, while rare earth element Y causes a slight decrease in microhardness. Gd and Sc will make Zr-based amorphous materials corrosion current density increases, the material pitting and localized corrosion, acid corrosion resistance is reduced. Y doping improves the self-corrosion potential of Zr-based amorphous alloys, reduces the corrosion current density, the surface passivation film is the densest, and the degree of charge transfer on the metal surface is the most difficult, Zr-BMG(Y) has a better corrosion resistance compared with other alloy materials. Zr-BMG(Gd) has the smallest friction rate (1.72×10-7mm3N-1mm-1), and the wear rates of the rare earth doped Zr-based amorphous alloys are all smaller than that of Zr-BMG, and the main loss mechanism of Zr-based amorphous alloys is the interaction of adhesive wear, abrasive wear, oxidative wear and fatigue wear. The mechanism of corrosion and wear resistance of rare earth to Zr-based amorphous alloys is discussed, which provides a new idea for the design of amorphous alloys.

Extended Tauc-Lorentz Model for Amorphous Materials With Non-Exponential Band Tails

Extended Tauc-Lorentz Model for Amorphous Materials With Non-Exponential Band Tails

Modeling of fluence-dependent hole-burned spectra and hole-growth kinetics using multiple two-level system model.

Numerical formalism is presented that perfectly describes resonant low-temperature hole-burned spectra (including zero-phonon holes, ZPHs) and spectral hole-growth dynamics of Al-phthalocyanine tetrasulphonate embedded in hyperquenched glassy water films over more than seven orders of fluence magnitude (0.4 µJ/cm2-5.9 J/cm2). Frequency changes during spectral hole-burning (HB) are traditionally explained with the help of a single extrinsic two-level-system (TLSext) associated with impurity molecules. The new multiple two-level system (n-TLSext) models and data analysis presented in this work show that each chromophore in an amorphous medium can couple with multiple independent TLSext, which maintain perfect photo-memory, allowing a full return of the photoproduct to the initial ("preburn") state. Modeling reveals that the experimentally observed narrow photoproduct peak at higher energies, in close vicinity of the zero-phonon hole (ZPH), reflects a dynamical feature of the HB process populating so-called "terminal" states (states that do not interact with laser excitation). Within the n-TLSext model, each chromophore possesses multiple possibilities to create a photoproduct when in interaction with the burning laser, i.e., chromophores can interact with burning laser-light multiple times until reaching the terminal states. Due to phonon-assisted absorption, terminal states are typically at higher energies than the ZPH, in agreement with the hole burned spectra reported for many molecules embedded in various amorphous solids. However, many HB systems reveal both blue- (high-energy) and red-shifted (low-energy) antiholes (i.e., photoproducts). We suggest that future modeling of resonant holes in various proteins using our n-TLSext model will provide more insight on the complexity of the protein energy landscape.

Elastic properties of Fe95-yNb2Mo2Cu1Siy-xBx (x=5-8, y=20-26) at % amorphous alloys

Amorphous materials exhibit complex atomic structures characterized by the absence of long-range order, in contrast to the well-defined periodicity of crystalline materials. This structural complexity is further pronounced in compositions such as FeMCuSiB (M = Nb, Mo, W and Ta), which incorporate elements with varying atomic radii and valencies. The Young's modulus of structures generated using traditional methods, such as melt-quenching and random packing, shows poor agreement with experimental data. In this study, we employ hybrid methods for generating the structures, which involve randomly packing elements without overlap, followed by thermalization at room temperature using Ab-initio Molecular Dynamics simulations. The Young's modulus evaluated from these structures aligns well with values measured using Dynamic Mechanical Analysis. Additionally, we utilize these structures to determine other elastic moduli including the bulk modulus and tetragonal shear modulus and find that the obtained values are consistent with the expected range for these compounds. We attribute the improved accuracy to a more representative approximation of the amorphous structure and the direct application of energy-strain relationships, rather than stress-strain relationships, for elastic moduli determination. Our methodology facilitates reliable predictions of the physical properties of amorphous materials and contributes to the design of FeMCuSiB (M = Nb, Mo, W and Ta) alloys with enhanced mechanical properties.

Amorphous Exsolution of Fe3O4 Nanoparticles in SrTiO3: A Path to High Activity and Stability in Photoelectrochemical Water‐Splitting

Exsolution creates metal nanoparticles embedded within perovskite oxide matrices, promoting optimal exposure, even distribution, and robust interactions with the perovskite structure. Fe3O4, an oxidized form of Fe, is an attractive catalyst for photoelectrochemical (PEC) water‐splitting due to its strong light absorption, excellent electrical conductivity, and chemical stability. However, exsolving Fe is challenging, often requiring harsh reduction conditions that can decompose the perovskite. Herein, hybrid composites are fabricated for PEC water‐splitting by reductively annealing a solution of SrTiO3 photoanode and Fe cocatalyst precursors. In situ transmission electron microscopy reveals uniform, high‐density Fe particles exsolving from amorphous SrTiO3 films, followed by film‐crystallization at elevated temperatures. This innovative process extracts entire Fe dopants while maintaining structural stability, even at doping levels exceeding 50%. Upon air exposure, the embedded Fe particles oxidize to Fe3O4, forming a Schottky junction and enhancing light absorption. These conditions yield a high activity of 5.10 mA cm−2 at 1.23 V versus reversible hydrogen electrode (an 11.86‐fold improvement over SrTiO3) from the 30% Fe‐doped SrTiO3, with excellent stability (97% retention) over 24 h. Theoretical calculations indicate that in the amorphous state, FeO bonds weaken while TiO bonds remain strong, promoting selective exsolution. The mechanisms driving amorphous exsolution versus crystal exsolution are elucidated.

Magnetic Order in Nanogranular Iron Germanium (Fe0.53Ge0.47) Films.

We study the effect of strain on the magnetic properties and magnetization configurations in nanogranular FexGe1-x films (x = 0.53 ±0.05) with and without B20 FeGe nanocrystals surrounded by an amorphous structure. Relaxed films on amorphous silicon nitride membranes reveal a disordered skyrmion phase while films near and on top of a rigid substrate favor ferromagnetism and an anisotropic hybridization of Fe d levels and spin-polarized Ge sp band states. The weakly coupled topological states emerge at room temperature and become more abundant at cryogenic temperatures without showing indications of pinning at defects or confinement to individual grains. These results demonstrate the possibility to control magnetic exchange and topological magnetism by strain and inform magnetoelasticity-mediated voltage control of topological phases in amorphous quantum materials.

High‐precision numerical simulation method for thermal–mechanical coupling in rubbers

AbstractImproving the precision of numerical simulations in thermal–mechanical coupling for amorphous polymer materials is crucial for their effective utilization. To enhance the precision of rubber numerical simulations, this study proposed a method considering the temperature and strain rate to establish tensile testing conditions based on the principle of time–temperature equivalence. Additionally, to obtain more precise parameters for hyperelastic constitutive equations, stress relaxation experiments were conducted to determine a set of stress values under complete rubber stress relaxation, which were used to fit the hyperelastic components of the hyper‐viscoelastic algorithm. A finite element model of rubber rebound was established, and a hyperelastic model based on loss factor and a hyperelastic model based on Prony series (hyper‐viscoelastic) were used to calculate the temperature changes caused by rubber rebound coefficient and energy dissipation during the rebound process at 110, 120, and 130°C. We compared the calculation results of these two algorithms with experimental data to verify their accuracy. The research results show that the average error of the rebound coefficient of the hyperelastic algorithm at three temperatures is 3.63%, and the average error of the rebound coefficient of the hyper‐viscoelastic algorithm at these three temperatures is 0.93%. The comparison with the rebound test results shows that the hyper‐viscoelastic method is more accurate and better captures the viscoelastic hysteresis of rubber, but the model calculation time is longer. In addition, at the moment of rebound sample impact, the maximum temperature rise amplitude of the hyperelastic algorithm sample impact position is 2.60, 1.75, and 0.91°C, which are 110, 120, and 130°C, respectively; The maximum heating amplitudes of the hyper‐viscoelastic algorithm are 2.05, 1.35, and 0.61°C. The hyper‐viscoelastic algorithm is closer to the actual test results.Highlights Applied the principle of time–temperature equivalence. Determination of material parameters using the hyper‐viscoelastic algorithm. Calculated the temperature change during the rubber rebound process.

Investigating Charge-Induced Transformations of Metal Nanoparticles in a Radically-Inert Liquid: A Liquid-Cell TEM Study

We present a novel in situ liquid-cell transmission electron microscopy (TEM) approach to study the behavior of metal nanoparticles under high-energy electron irradiation. By utilizing a radically-inert liquid environment, we aim to minimize radiolysis effects and explore the influence of charge-induced transformations. We observed complex dynamics in nanoparticle behavior, including morphological changes and transitions between amorphous and crystalline states. These transformations are attributed to the delicate interplay between charge accumulation on the nanoparticles and enhanced radiolysis, suggesting a significant role for charge-assisted processes in nanoparticle evolution. Our findings provide valuable insights into the fundamental mechanisms driving nanoparticle behavior at the nanoscale and demonstrate the potential of liquid-cell TEM for studying complex physicochemical processes in controlled environments.

Pyrolytic Carbon: An Inexpensive, Robust, and Versatile Electrode for Synthetic Organic Electrochemistry.

Synthetic organic electrochemistry is recognized as one of the most sustainable forms of redox chemistry that can enable a wide variety of useful transformations. In this study, readily prepared pyrolytic carbon electrodes are explored in several powerful rAP transformations as well as C-C and C-N bond forming reactions. Pyrolytic carbon provides an alternative to classic amorphous carbon-based materials that are either expensive or ill-suited to large-scale flow reactions.

Characterisation and Hydrochloric Acid Leaching of Rare Earth Elements in Discard Coal and Coal Fly Ash

Rare earth elements (REEs) have been identified as valuable and critical raw materials, vital for numerous technologies and applications. With the increasing demand for and supply gap in REEs, many research studies have focused on alternative sources of REEs. This study involved an elemental and mineralogical characterisation of discarded coal from a coal plant and coal fly ash (CFA) from a power station in South Africa for REE presence. XRD results revealed that the discard coal sample consisted mainly of kaolinite, pyrite, siderite, quartz, calcite, gypsum, and muscovite, whereas CFA contained abundant glassy amorphous phases, alumina silicates, quartz, gypsum, calcite, and minute levels of muscovite and hematite. SEM-EDAX showed REE-carrying grains containing phosphorus in both discard coal and CFA samples. This was followed by investigating the leaching potential of REEs using hydrochloric acid from discard coal and CFA. This research’s potential impact is possibly providing a new and sustainable source of REEs. For that purpose, multiple batch leaching tests were performed to investigate the effects of temperature and acid concentration on the leaching efficiencies of REEs from discard coal and CFA. The experimental results indicated that temperature strongly influences REE leaching efficiency, while acid concentration has a lesser impact. This study identifies the best leaching conditions for the total REE recovery as 1 M HCl and 80 °C for discard coal and CFA.

π-Conjugation-Induced In Situ Nanoscale Ordering of Spiro-OMeTAD Boosts the Efficiency and Stability of Perovskite Solar Cells.

Spiro-OMeTAD hole transport materials typically exhibit an amorphous state in perovskite solar cells. However, the lack of structural ordering leads to weak intermolecular interaction, inferior carrier transfer, and poor stability in devices. Herein, we developed a π-conjugation-induced short-range ordering strategy to modulate the stacking order of spiro-OMeTAD during film formation. A clear molecular ordering at the nanoscale is observed, which enhances intermolecular π-π stacking in spiro-OMeTAD and enables effective carrier extraction and favorable energy level alignment. The nanoscale-ordered spiro-OMeTAD allows the achievement of perovskite solar cells with a champion efficiency of 25.37%, surpassing devices utilizing amorphous spiro-OMeTAD (23.52%). The unencapsulated device demonstrates enhanced operational stability by retaining 98% of its initial efficiency under continuous 1 sun equivalent illumination at 60 °C for 840 h. This work establishes a significant and valid modulation concept for the stacking order of organic transport materials, paving the way for the development of efficient and stable perovskite solar cells.

Nanowires made of ternary alloys – synthesis features and magnetic properties

Nanowires of FexCoyCu(100–x–y) and FexNiyCu(100–x–y) alloys have been studied. The features of obtaining such structures by the matrix synthesis method have been investigated. Elemental analysis of nanowires grown at sequentially increasing voltages revealed a significant decrease in the amount of copper, as well as a change in the ratio of the main magnetic elements. X-ray phase analysis showed that FeCoCu is a three-component solid solution, while FeNiCu contains three phases of solid solutions: FeCu with copper content up to 80%, FeNi with high iron content, and NiCu in an amorphous or fine-crystalline state with nickel content up to 80%. Mössbauer spectroscopy revealed that the addition of copper can lead to a change in the angle of magnetic moment misalignment in nanowires, which correlates with magnetometry data.

Strain‐Induced Structural Rearrangement Towards a White‐Light‐Emitting Adamantane‐Type Cluster Dimer

AbstractGroup 14/16 adamantane‐type hybrid clusters of the type [(RT)4E6] (T=group 14 element, E=group 16 element, R=organic group) have been reported to emit white‐light when irradiated in an amorphous state with a continuous‐wave (CW) infrared laser diode. This effect is enhanced if the cluster core is varied from a binary to a more complex composition. To further explore this phenomenon, we synthesized clusters with a multinary R/R’‐T/T’‐E/E’ composition, including isolobal replacement of E with CH2, in [(2‐NpSi){CH2Sn(S)Ph}3] (1, Np=naphthyl). When expanding one of the CH2 moieties to a C2H4 group, thus generating a R/R’‐T/T’‐E/E’/E’’ cluster composition, we unexpectedly observed a dimerization of the initially formed, yet non‐isolable adamantane‐like cluster [(2‐NpSi){CH2Sn(S)Ph}2{C2H4Sn(S)Ph}] (2) to [(2‐NpSi){CH2Sn(S)Ph}2{C2H4Sn(S)Ph}]2 (3), exhibiting a heretofore unprecedented cluster architecture. Both monomeric 1 and dimeric 3, show white‐light emission as thin films. The nonlinear optical response of the compounds was also modelled with DFT methods.

Triggering Reversible Intercalation-Conversion Combined Chemistry for High-Energy-Density Lithium Battery Cathodes.

Combining intercalation and conversion reactions maximizes the utilization of redox-active elements in electrodes, providing a means for overcoming the current capacity ceiling. However, integrating both mechanisms within a single electrode material presents significant challenges owing to their contrasting structural requirements. Intercalation requires a well-defined host structure for efficient lithium-ion diffusion, whereas conversion reactions entail structural reorganization, which can undermine intercalation capabilities. Based on the previous study that successfully demonstrated reversible intercalation-conversion chemistry in amorphous LiFeSO4F, this study aims to provide an in-depth understanding on how this can be enabled. Experimental and theoretical investigations of a model system based on tavorite-structured LiFeSO4F revealed that amorphization governs the activation and reversibility of the combined reactions. Enhanced reversibility is achieved through the facile migration of transition metals within the amorphous matrix. Unexpectedly, it is found that amorphization also narrowed the voltage gap between the intercalation and conversion reactions. This voltage-gap reduction is explained by the thermodynamic metastability of the amorphous phase. The applicability of the approach to other intercalation hosts is further demonstrated, showing that amorphization enables reversible intercalation and conversion. These findings suggest a new strategy that leverages the full potential of intercalation and conversion reactions, introducing new avenues for cathode design.

Variations in the root mycobiome and mycorrhizal fungi between different types of Vanilla forest farms on Réunion Island.

The mycorrhizal fungi of cultivated Vanilla spp. have mainly been studied in America, while a recent study has investigated them on Réunion Island (Indian Ocean). However, there are many different types of cultivation on Réunion, from shade-house crops to forest farms of endemic or exotic trees. Here we fill a gap in the study of the root mycobiome of Vanilla by sampling vines in forest plantations on recent lava flows in the southeast of Réunion. Specifically, we aimed to characterize the fungal communities between terrestrial and epiphytic roots, between forest farms that differ mainly in the species of trees, and between Vanilla roots and ECM-like roots of nearby trees. By sequencing fungal ITS2, we showed that the Vanilla root mycobiome is diverse and differed between the root types and forest farms. Epiphytic and terrestrial roots host endophytic fungi, while a putative rust with visible urediniospores was abundant in terrestrial roots mainly. Other pathogens were detected in epiphytic roots (Colletotrichum) with no sign of disease. Following sequencing and electron microscopy, Tulasnellaceae, characterized by imperforate parenthesomes and cell wall expansion with an amorphous matrix, were shown to be the main mycorrhizal fungi in both vanilla root types. Interestingly, the dominant Tulasnellaceae OTU was found in ECM-type roots of trees belonging to the ectomycorrhizal family Sapotaceae. Further observations are needed to confirm the ectomycorrhizal association of endemic trees with Tulasnella. Moreover, labeling experiments will be instrumental in investigating the transfer of nutrients between the trees and the Vanilla through the network of mycorrhizal associations in the soil.

Rapid-annealed FeSiBPCu nanocrystalline alloy with high Bs approaching 1.9 T and good bendability

To promote energy savings, high efficiency and miniaturization of power electronic devices, Fe–Si–B–P–Cu nanocrystalline soft magnetic materials with high saturation magnetization (Bs) parallel to that of the 6.5 wt% Si steel and low coercivity (Hc) are desired. In this work, 30 μm-thick Fe84Si3B10P2Cu1 and Fe84.5Si3B9.5P2Cu1 (at.%) amorphous/nanocrystalline precursor ribbons were melt-spun, which has high Fe contents comparable to that of the 6.5 wt% Si steel. These ribbons consist of an amorphous matrix and pre-existing α-Fe of approximately 28–30 nm in size possessed relatively low and similar-value activation energy of nucleation and growth in the range of 224–249 kJ/mol. Which could induce strong crystallization competition and effectively suppress coarsening of the pre-existing α-Fe. The Fe84Si3B10P2Cu1 nanocrystalline alloy obtained by rapid-annealing (∼100 °C/s) the amorphous/nanocrystalline precursor at 480 °C for 30 s (Fe84-480) exhibited a fine and uniform nanostructure containing α-Fe with small average grain size of approximately 23.1 nm and high volume fraction. The Fe84-480 alloy possessed a high Bs of approximately 1.88 T, a low Hc of 8.6 A/m, and good bendability revealed by relatively large bending fracture strain of ∼1.65%, making it a promising soft magnetic material for power electronic devices.

Near-Infrared Room-Temperature Phosphorescence from Monocyclic Luminophores.

Compact luminophores with long emission wavelengths have aroused considerable theoretical and practical interest. Organics with room-temperature phosphorescence (RTP) are also desirable for their longer lifetimes and larger Stokes shifts than fluorescence. Utilizing the low electronic transition energy intrinsic to thiocarbonyl compounds, electron-withdrawing groups were attached to the 4H-pyran-4-thione core to further lower the excited state energies. The resulting mini-phosphors were doped into suitable polymer matrices. These purely organic, amorphous materials emitted near-infrared (NIR) RTP. Having a molar mass of only 162 g·mol-1, one of the phosphors emitted RTP that peaked at 750 nm, with a very large Stokes shift of 15485 cm-1 (403 nm). Thanks to the good processability of the polymer film, light-emitting diodes (LEDs) with NIR emission were easily fabricated by coating doped polymer on ultraviolet LEDs. This work provides an intriguing strategy to achieve NIR RTP using compact luminophores.

Near‐Infrared Room‐Temperature Phosphorescence from Monocyclic Luminophores

Compact luminophores with long emission wavelengths have aroused considerable theoretical and practical interest. Organics with room‐temperature phosphorescence (RTP) are also desirable for their longer lifetimes and larger Stokes shifts than fluorescence. Utilizing the low electronic transition energy intrinsic to thiocarbonyl compounds, electron‐withdrawing groups were attached to the 4H‐pyran‐4‐thione core to further lower the excited state energies. The resulting mini‐phosphors were doped into suitable polymer matrices. These purely organic, amorphous materials emitted near‐infrared (NIR) RTP. Having a molar mass of only 162 g·mol‐1, one of the phosphors emitted RTP that peaked at 750 nm, with a very large Stokes shift of 15485 cm‐1 (403 nm). Thanks to the good processability of the polymer film, light‐emitting diodes (LEDs) with NIR emission were easily fabricated by coating doped polymer on ultraviolet LEDs. This work provides an intriguing strategy to achieve NIR RTP using compact luminophores.

Colossal Dielectric Constant of Nanocrystalline/Amorphous Homo-Composite BaTiO3 Films Deposited via Pulsed Laser Deposition Technique.

We report the pulsed laser deposition (PLD) of nanocrystalline/amorphous homo-composite BaTiO3 (BTO) films exhibiting an unprecedented combination of a colossal dielectric constant (εr) and extremely low dielectric loss (tan δ). By varying the substrate deposition temperature (Td) over a wide range (300-800 °C), we identified Td = 550 °C as the optimal temperature for growing BTO films with an εr as high as ~3060 and a tan δ as low as 0.04 (at 20 kHz). High-resolution transmission electron microscopy revealed that the PLD-BTO films consist of BTO nanocrystals (~20-30 nm size) embedded within an otherwise amorphous BTO matrix. The impressive dielectric behavior is attributed to the combination of highly crystallized small BTO nanograins, which amplify interfacial polarization, and the surrounding amorphous matrix, which effectively isolates the nanograins from charge carrier transport. Our findings could facilitate the development of next-generation integrated dielectric devices.