Amorphous Quantum Nanomaterials

In quantum materials, macroscopic behavior is governed in nontrivial ways by quantum phenomena. This is usually achieved by exquisite control over atomic positions in crystalline solids. Here, it is demonstrated that the use of disordered glassy materials provides unique opportunities to tailor quantum material properties. By borrowing ideas from single‐molecule spectroscopy, single delocalized π‐electron dye systems are isolated in relatively rigid ultrasmall (<10 nm diameter) amorphous silica nanoparticles. It is demonstrated that chemically tuning the local amorphous silica environment around the dye over a range of compositions enables exquisite control over dye quantum behavior, leading to efficient probes for photodynamic therapy (PDT) and stochastic optical reconstruction microscopy (STORM). The results suggest that efficient fine‐tuning of light‐induced quantum behavior mediated via effects like spin‐orbit coupling can be effectively achieved by systematically varying averaged local environments in glassy amorphous materials as opposed to tailoring well‐defined neighboring atomic lattice positions in crystalline solids. The resulting nanoprobes exhibit features proven to enable clinical translation.     

An Amorphous Nickel–Iron‐Based Electrocatalyst with Unusual Local Structures for Ultrafast Oxygen Evolution Reaction

Rationally designing active and durable catalysts for the oxygen evolution reaction (OER) is of primary importance in water splitting. Perovskite oxides (ABO₃) with versatile structures and multiple physicochemical properties have triggered considerable interest in the OER. The leaching of A site cations can create nanostructures and amorphous motifs on the perovskite matrix, thus facilitating the OER process. However, selectively dissolving A site cations and simultaneously obtaining more active amorphous motifs derived from the B site cations remains a great challenge. Herein, a top‐down strategy is proposed to transform bulk crystalline perovskite (LaNiO₃) into a nanostructured amorphous hydroxide by FeCl₃ post‐treatment, resulting in an extremely low overpotential of 189 mV at 10 mA cm^?2. The top‐down‐constructed amorphous catalyst with a large surface area has dual NiFe active sites, where high‐valence Ni³⁺‐based edge‐sharing octahedral frameworks are surrounded by interstitial distorted Fe octahedra and contribute to the superior OER performance. This top‐down strategy provides a valid way to design novel perovskite‐derived catalysts.     

Cluster‐Assembled Nanocomposites: Functional Properties by Design

The unique functional properties of nanocomposites meet many of the material requirements sought after in numerous applications of today's high‐tech industry. This, in turn, inspires material scientists to devise new methods that can further expand the palette of available nanocomposites. Precise control over the chemistry, morphology, and microstructure of nanocomposites' constituents promises the eventual ability to design any composite material for any specific requirement. However, today's synthesis methods still lack the ability to simultaneously control all chemical, morphological, and microstructural features of nanocomposites in a one‐step process. Here, an alternative approach to fabricate fully tailorable nanocomposites under well‐defined conditions is described. In particular, this progress report focuses on the combination of cluster ion beam and thin‐film deposition technologies to fabricate cluster‐assembled nanocomposites via codeposition of cluster ions and matrix materials. Emphasis is given to the state‐of‐the‐art cluster deposition system, designed and built by our research group, as well as to its unique abilities. Moreover, case studies on two cluster‐assembled nanocomposite material systems (Fe/Ag_m and Fe/Cr_m) prepared with this method are presented. Finally, an outlook on research directions for cluster‐assembled nanocomposites is discussed.     

Atomic Interface Engineering and Electric‐Field Effect in Ultrathin Bi2MoO6 Nanosheets for Superior Lithium Ion Storage

Ultrathin 2D materials can offer promising opportunities for exploring advanced energy storage systems, with satisfactory electrochemical performance. Engineering atomic interfaces by stacking 2D crystals holds huge potential for tuning material properties at the atomic level, owing to the strong layer–layer interactions, enabling unprecedented physical properties. In this work, atomically thin Bi₂MoO₆ sheets are acquired that exhibit remarkable high‐rate cycling performance in Li‐ion batteries, which can be ascribed to the interlayer coupling effect, as well as the 2D configuration and intrinsic structural stability. The unbalanced charge distribution occurs within the crystal and induces built‐in electric fields, significantly boosting lithium ion transfer dynamics, while the extra charge transport channels generated on the open surfaces further promote charge transport. The in situ synchrotron X‐ray powder diffraction results confirm the material's excellent structural stability. This work provides some insights for designing high‐performance electrode materials for energy storage by manipulating the interface interaction and electronic structure.     

Out‐of‐Plane Magnetic Patterning Based on Indentation‐Induced Nanocrystallization of a Metallic Glass

Periodic arrays of micrometer‐sized ferromagnetic structures with perpendicular magnetic anisotropy are prepared by nanoindentation at the surface of a Fe_67.7B₂₀Cr₁₂Nb_0.3 glassy ribbon initially showing in‐plane magnetic anisotropy. The indented regions exhibit enhanced coercivity and saturation magnetization with respect to the surrounding nondeformed matrix. These effects are due to a mechanically driven selective nanocrystallization of the metallic glass, induced by nanoindentation, even without the need for thermal annealing. In addition, while the amorphous matrix becomes paramagnetic above 325 K, the crystallized regions (consisting of α‐Fe) remain ferromagnetic upon heating to high temperatures. The local change in the magnetic anisotropy direction is ascribed to a certain degree of crystallographic texture, together with the inverse magnetostriction effect caused by the compressive indentation stresses.     

Ultrafast Sodium Full Batteries Derived from X?Fe (X = Co,Ni, Mn) Prussian Blue Analogs

Exploring high‐rate electrode materials with excellent kinetic properties is imperative for advanced sodium‐storage systems. Herein, novel cubic‐like X? Fe (X = Co, Ni, Mn) Prussian blue analogs (PBAs), as cathodes materials, are obtained through as‐tuned ionic bonding, delivering improved crystallinity and homogeneous particles size. As expected, Ni‐Fe PBAs show a capacity of 81 mAh g^?1 at 1.0 A g^?1, mainly resulting from their physical–chemical stability, fast kinetics, and “zero‐strain” insertion characteristics. Considering that the combination of elements incorporated with carbon may increase the rate of ion transfer and improve the lifetime of cycling stability, they are expected to derive binary metal‐selenide/nitrogen‐doped carbon as anodes. Among them, binary Ni_0.67Fe_0.33Se₂ coming from Ni‐Fe PBAs shows obvious core–shell structure in a dual‐carbon matrix, leading to enhanced electron interactions, electrochemical activity, and “metal‐like” conductivity, which could retain an ultralong‐term stability of 375 mAh g^?1 after 10 000 loops even at 10.0 A g^?1. The corresponding full‐cell Ni‐Fe PBAs versus Ni_0.67Fe_0.33Se₂ deliver a remarkable Na‐storage capacity of 302.2 mAh g^?1 at 1.0 A g^?1. The rational strategy is anticipated to offer more possibilities for designing advanced electrode materials used in high‐performance sodium‐ion batteries.     

Herstellung massiver metallischer Gläser aus kristallinen Gefügen durch lokales kleinvolumiges Umschmelzen

Metallic glasses, or the so‐called bulk metallic glasses (BMGs), have peculiar properties such as extreme strengths and hardness while their specific ferromagnetic properties can be controlled accurately by the alloy content which is due to their amorphous structure. This special properties combination makes them interesting for research and technology. In the current research work, the development of a novel method for the creation of amorphous structure via locally limited re‐melting of the crystalline Fe‐based pre‐alloys is presented. Two alloys, namely Fe₇₆Si₉B₁₀P₅ and Fe₄₃Co₇Cr₁₅Mo₁₄C₁₅B₆ (at.‐%), are produced by melting and slow solidification. The solidified dendritic, crystallographic bulk afterwards is locally heat treated by electron beam welding. Here, a high‐energy electron beam is focused onto the crystalline surface of the pre‐alloy, so that the material is melted rapidly at the surface for a short time and then re‐solidified very fast by self‐quenching. By this process technique both the surface and a relative big volume of the material is glazed. For the evaluation of the amorphous phase scanning electron microscopy coupled with energy dispersive X‐ray analysis (SEM/EDX) and high‐resolution electron diffraction based on transmission electron microscopy (HRTEM) were used. These methods are able to show the lack of structural order of the atoms and by that amorphous structures were evaluated [1].     

High‐Energy X‐Ray Diffraction Study of the Inhomogeneous Zr43Cu43Al7Ag7 Bulk‐Metallic Glasses

In the present work, the microscopic structure of an as‐cast Zr₄₃Cu₄₃Al₇Ag₇ bulkmetallic glass (BMG) had been investigated in detail. The structure analyses are performed using the laboratory X‐ray diffraction (XRD), high‐energy synchrotron X‐ray diffraction, and transmission‐electron microscopy (TEM). The results from different techniques are compared and discussed. The specimen shows a typical amorphous hallo using the conventional laboratory XRD. However, tiny crystalline particles, roughly ≈10 nm in size, are found in the sample by the high‐energy XRD as well as the TEM. The standard laboratory XRD measurement is not adequate to differentiate amorphous from a nano‐composite phase. The high‐energy XRD method is an essential technique to determine the glassy nature of a BMG.     

Chemische Zusammensetzung und Mikrostruktur polymerabgeleiteter Gläser und Keramiken im System Si–C–O. Teil 2: Charakterisierung der Gefügeausbildung mittels hochauflösender Durchstrahlungselektronenmikroskopie und Feinbereichsbeugung

Chemical Composition and Microstructure of Polymer‐Derived Glasses and Ceramics in the Si–C–O System. Part 2: Characterization of microstructure formation by means of high‐resolution transmission electron microscopy and selected area diffraction Liquid or solid silicone resins represent the economically most interesting class of organic precursors for the pyrolytic production of glass and ceramics materials on silicon basis. As dense, dimensionally stable components can be cost‐effectively achieved by admixing reactive filler powders, chemical composition and microstructure development of the polymer‐derived residues must be exactly known during thermal decomposition. Thus, in the present work, glasses and ceramics produced by pyrolysis of the model precursor polymethylsiloxane at temperatures from 525 to 1550 °C are investigated. In part 1, by means of analytical electron microscopy, the bonding state of silicon was determined on a nanometre scale and the phase separation of the metastable Si–C–O matrix into SiO₂, C and SiC was proved. The in‐situ crystallization could be considerably accelerated by adding fine‐grained powder of inert fillers, such as Al₂O₃ or SiC, which permits effective process control. In part 2, the microstructure is characterized by high‐resolution transmission electron microscopy and selected area diffraction. Turbostratic carbon and cubic β‐SiC precipitate as crystallization products. Theses phases are embedded in an amorphous matrix. Inert fillers reduce the crystallization temperature by several hundred °C. In this case, the polymer‐derived Si–C–O material acts as a binding agent between the powder particles. Reaction layer formation does not occur. On the investigated pyrolysis conditions, no crystallization of SiO₂ was observed.     

Amorphous Mn3O4 Nanocages with High‐Efficiency Charge Transfer for Enhancing Electro‐Optic Properties of Liquid Crystals

Improving electro‐optic properties is essential for fabricating high‐quality liquid crystal displays. Herein, by doping amorphous Mn₃O₄ octahedral nanocages (a‐Mn₃O₄ ONCs) into a nematic liquid crystal (NLC) matrix E7, outstanding electro‐optic properties of the blend are successfully obtained. At a doping concentration of 0.03 wt%, the maximum decreases of threshold voltage (V_th) and saturation voltage (V_sat) are 34% and 31%, respectively, and the increase of contrast (C_on) is 160%. This remarkable electro‐optic activity can be attributed to high‐efficiency charge transfer within the a‐Mn₃O₄ ONCs NLC system, caused by metastable electronic states of a‐Mn₃O₄ ONCs. To the best of our knowledge, such remarkable decreased electro‐optic activity is observed for the first time from doping amorphous semiconductors, which could provide a new pathway to develop excellent energy‐saving amorphous materials and improve their potential applications in electro‐optical devices.     

Mechanical behavior of Al-based matrix composites reinforced with Mg58Cu28.5Gd11Ag2.5 metallic glasses

Al-based composites reinforced with Mg₅₈Cu_28.5Gd₁₁Ag_2.5 glassy particles have been synthesized by powder metallurgy. Powder consolidation was carried out by uniaxial hot pressing at temperatures within the super-cooled liquid region of the reinforcement to take advantage of the viscous flow of the glassy particles. The composites have improved yield and compressive strength compared to the unreinforced Al matrix without deteriorating the plasticity of the material. The relationship between mechanical properties and structure of the composites was investigated and described through the modified shear lag and mixture models.     

The Relation between Chemical Bonding and Ultrafast Crystal Growth

Glasses are often described as supercooled liquids, whose structures are topologically disordered like a liquid, but nevertheless retain short‐range structural order. Structural complexity is often associated with complicated electron‐charge distributions in glassy systems, making a detailed investigation challenging even for short‐range structural order, let alone their atomic dynamics. This is particularly problematic for lone‐pair‐rich, semiconducting materials, such as phase‐change materials (PCMs). Here, this study shows that analytical methods for studying bonding, based on the electron‐charge density, rather than a conventional atomic pair‐correlation‐function approach, allows an in‐depth investigation into the chemical‐bonding network, as well as lone pairs, of the prototypical PCM, Ge₂Sb₂Te₅ (GST). It is demonstrated that the structurally flexible building units of the amorphous GST network, intimately linked to the presence of distinctly coexisting weak covalent and lone‐pair interactions, give rise to cooperative structural‐ordering processes, by which ultrafast crystal growth becomes possible. This finding may universally apply to other PCMs.     

Free‐Standing Crystalline@Amorphous Core–Shell Nanoarrays for Efficient Energy Storage

Structures comprising high capacity active material are highly desirable in the development of advanced electrodes for energy storage devices. However, the structure degradation of such material still remains a challenge. The construction of amorphous and crystalline heterostructure appears to be a novel and effectual strategy to figure out the problem, owing to the distinct properties of the amorphous protective layer. Herein, crystalline‐Co₃O₄@amorphous‐TiO₂ core–shell nanoarrays directly grown on the carbon cloth substrate are rationally designed to construct the free‐standing electrode. In the unique structure, the 3D porous nanoarrays provide increased availability of electrochemical active sites, and the array with a unique heterostructure of crystalline Co₃O₄ core and amorphous TiO₂ shell exhibits intriguing synergistic properties. Besides, the amorphous TiO₂ protective layer shows elastic behavior to mitigate the volume effect of Co₃O₄. Benefiting from these structural advantages, the as‐prepared free‐standing electrode exhibits superior lithium storage properties, including high coulombic efficiency, outstanding cyclic stability, and rate capability. Pouch cells with high flexibility are also fabricated and show remarkable electrochemical performances, holding great potential for flexible electronic devices in the future.     

High Detectivity and Transparent Few‐Layer MoS2/Glassy‐Graphene Heterostructure Photodetectors

Layered van der Waals heterostructures have attracted considerable attention recently, due to their unique properties both inherited from individual two‐dimensional (2D) components and imparted from their interactions. Here, a novel few‐layer MoS₂/glassy‐graphene heterostructure, synthesized by a layer‐by‐layer transfer technique, and its application as transparent photodetectors are reported for the first time. Instead of a traditional Schottky junction, coherent ohmic contact is formed at the interface between the MoS₂ and the glassy‐graphene nanosheets. The device exhibits pronounced wavelength selectivity as illuminated by monochromatic lights. A responsivity of 12.3 mA W^?1 and detectivity of 1.8 × 10¹⁰ Jones are obtained from the photodetector under 532 nm light illumination. Density functional theory calculations reveal the impact of specific carbon atomic arrangement in the glassy‐graphene on the electronic band structure. It is demonstrated that the band alignment of the layered heterostructures can be manipulated by lattice engineering of 2D nanosheets to enhance optoelectronic performance.     

热处理对(Fe_(0.52)Co_(0.30)Ni_(0.18))_(73)Cr_(17)Zr_(10)非晶合金的组织结构及磁性能的影响

采用单辊急冷法制备(Fe_(0.52)Co_(0.30)Ni_(0.18))_(73)Cr_(17)Zr_(10)非晶薄带,并对该合金进行等温退火。采用XRD,AFM,VSM研究退火温度对(Fe_(0.52)Co_(0.30)Ni_(0.18))_(73)Cr_(17)Zr_(10)非晶合金的组织结构和磁性能的影响。结果表明:非晶合金晶化过程为Am→α-Fe(Co)+Am′→α-Fe(Co)+Cr_2Ni_3+Fe_3Ni_2+Cr_2Zr+未知相。当退火温度Ti玻璃转变温度Tg时,由于结构弛豫、内应力的释放,合金的饱和磁化强度Ms有所提高;当晶化起始温度TxTi第一晶化峰值温度Tp1时,由于铁磁性α-Fe(Co)相的析出,Ms显著提升;当TiTp1时,由于晶粒长大和第二相的析出,Ms急剧恶化,565℃退火能够获得最好磁性能(Ms=106.8A·m~2·kg~(-1))。490℃和565℃退火后薄带表面的AFM观察表明,AFM图片所呈现的颗粒尺寸要比用Scherrer法测得的α-Fe(Co)纳米晶尺寸大得多,这是典型的包裹晶粒现象。     

Material Design of p‐Type Transparent Amorphous Semiconductor,Cu–Sn–I

Transparent amorphous semiconductors (TAS) that can be fabricated at low temperature are key materials in the practical application of transparent flexible electronics. Although various n‐type TAS materials with excellent performance, such as amorphous In‐Ga‐Zn‐O (a‐IGZO), are already known, no complementary p‐type TAS has been realized to date. Here, a material design concept for p‐type TAS materials is proposed utilizing the pseudo s‐orbital nature of spatially spreading iodine 5p orbitals and amorphous Sn‐containing CuI (a‐CuSnI) thin film is reported as an example. The resulting a‐CuSnI thin films fabricated by spin coating at low temperature (140 °C) have a smooth surface. The Hall mobility increases with the hole concentration and the largest mobility of ≈9 cm² V^?1 s^?1 is obtained, which is comparable with that of conventional n‐type TAS.     

Graphene Caging Silicon Particles for High‐Performance Lithium‐Ion Batteries

Silicon holds great promise as an anode material for lithium‐ion batteries with higher energy density; its implication, however, is limited by rapid capacity fading. A catalytic growth of graphene cages on composite particles of magnesium oxide and silicon, which are made by magnesiothermic reduction reaction of silica particles, is reported herein. Catalyzed by the magnesium oxide, graphene cages can be conformally grown onto the composite particles, leading to the formation of hollow graphene‐encapsulated Si particles. Such materials exhibit excellent lithium storage properties in terms of high specific capacity, remarkable rate capability (890 mAh g^?1 at 5 A g^?1), and good cycling retention over 200 cycles with consistently high coulombic efficiency at a current density of 1 A g^?1. A full battery test using LiCoO₂ as the cathode demonstrates a high energy density of 329 Wh kg^?1.     

SnO2‐Based Nanomaterials: Synthesis and Application in Lithium‐Ion Batteries

The development of new electrode materials for lithium‐ion batteries (LIBs) has always been a focal area of materials science, as the current technology may not be able to meet the high energy demands for electronic devices with better performance. Among all the metal oxides, tin dioxide (SnO₂) is regarded as a promising candidate to serve as the anode material for LIBs due to its high theoretical capacity. Here, a thorough survey is provided of the synthesis of SnO₂‐based nanomaterials with various structures and chemical compositions, and their application as negative electrodes for LIBs. It covers SnO₂ with different morphologies ranging from 1D nanorods/nanowires/nanotubes, to 2D nanosheets, to 3D hollow nanostructures. Nanocomposites consisting of SnO₂ and different carbonaceous supports, e.g., amorphous carbon, carbon nanotubes, graphene, are also investigated. The use of Sn‐based nanomaterials as the anode material for LIBs will be briefly discussed as well. The aim of this review is to provide an in‐depth and rational understanding such that the electrochemical properties of SnO₂‐based anodes can be effectively enhanced by making proper nanostructures with optimized chemical composition. By focusing on SnO₂, the hope is that such concepts and strategies can be extended to other potential metal oxides, such as titanium dioxide or iron oxides, thus shedding some light on the future development of high‐performance metal‐oxide based negative electrodes for LIBs.     

Single‐Atom Nanozyme Based on Nanoengineered Fe–N–C Catalyst with Superior Peroxidase‐Like Activity for Ultrasensitive Bioassays

Single‐atom catalysts are becoming a hot research topic owing to their unique characteristics of maximum specific activity and atomic utilization. Herein, a new single‐atom nanozyme (SAN) based on single Fe atoms anchored on N‐doped carbons supported on carbon nanotube (CNT/FeNC) is proposed. The CNT/FeNC with robust atomic Fe–N_x moieties is synthesised, showing superior peroxidase‐like activity. Furthermore, the CNT/FeNC is used as the signal element in a series of paper‐based bioassays for ultrasensitive detection of H₂O₂, glucose, and ascorbic acid. The SAN provides a new type of signal element for developing various biosensing techniques.     

Microstructure and elevated temperature mechanical properties of Al–8Fe–4RE alloy fabricated by spray forming

Al–8Fe–4Ce alloy is currently manufactured by consolidating the atomized powders. With the aim to reduce the cost, spray forming process was applied in manufacturing with misch metal as raw materials. Spray forming (SF) as well as casting were employed to prepare Al–8Fe–4RE alloy, followed by hot‐press to compact the samples. The mechanical properties of SFed and cast Al–8Fe–4RE alloys are characterized at a temperature of 350 °C. The results show that the Al₃Fe phases contained in SF alloy is comparatively refined, forming needle‐shaped phases embedded in the Al matrix, and the SF alloy also showed lower degree of preferred orientation in (111) plane. Although both factors might explain the superior performance of the SF sample, the fracture appearance after tensile test at 350 °C shows that the contribution from crystallographic feature might be predominant. Spray forming is proved to be a very promising technique for manufacture of Al–Fe–Ce alloys of high strength at an elevated temperature.