Amorphous Crystalline Research Articles

Steering surface reconstruction of hybrid metal oxides for efficient oxygen evolution reaction in water splitting and zinc-air batteries

Surface reconstruction yields real active species in electrochemical oxygen evolution reaction (OER) conditions; however, rationally regulating reconstruction in a targeted manner for constructing highly active OER electrocatalysts remains a formidable challenge. Here, an electrochemical activation strategy with selective etching was utilized to guide the reconstruction process of a hybrid cobalt-molybdenum oxide (CoMoO4/Co3O4@CC) in a favorable direction to improve the OER performance. Both in-situ Raman and multiple ex-situ characterization tools demonstrate that controlled surface reconstruction can be easily achieved through Mo etching, with the formation of a dynamically stable amorphous-crystalline heterostructure. Theoretical calculations together with experimental results reveal that the synergistic effects between amorphous CoOOH and crystalline Co3O4 are crucial in enhancing the catalytic performance. Consequently, the reconstructed CoMoO4/Co3O4@CC exhibits a low overpotential of 250 mV to achieve a current density of 10 mA cm−2 in 1 M KOH, and more importantly it can be practiced in electrolytic water splitting and rechargeable zinc-air batteries devices, achieving ultra-long stability for over 500 and 1200 h, respectively. This work provides a promising route for the construction of high-performance electrocatalysts.

NIR‐emitting Electrochromic Windows for Cold Climate Region Buildings

AbstractElectrochromic devices (ECDs) comprising visible/near‐infrared (NIR) transparent amorphous indium zinc oxide (a‐IZO) outermost layers and novel NIR‐emitting electrolytes are proposed for smart windows of buildings in cold climate regions. The electrolytes are composed of a di‐urethane cross‐linked poly(oxyethylene)(POE)/siloxane hybrid matrix (d‐Ut(600), 600 is the average molecular weight of the POE chains in gmol−1), 1‐butyl‐3‐methylimidazolium chloride ionic liquid, and the Er(tta)3(H2O)2 complex (tta− is 2‐thenoyltrifluoracetonate). The electrolytes, synthesized by sol‐gel route, were obtained as transparent, flexible, and hydrophilic monoliths with nanoscale surface roughness, exhibiting emission in the NIR wavelength region. The first electro‐optical tests, performed in 2019, with an archetypal ECD including amorphous tungsten oxide and crystalline nickel oxide as EC layers, a‐IZO as outermost layers, and d‐Ut(600)400Er(tta)3(H2O)2[Bmim]Cl (400 is the molar ratio of oxyethylene units/Er3+ ion) as the electrolyte, demonstrated rather low coloration efficiency (CEin/CEout) values of −4/+6 cm2 C−1 at 555 nm. After 3 years of storage at rest in the dark and at room temperature, the same device demonstrates a huge performance enhancement, leading to CEin/CEout values about two orders of magnitude higher, apart from higher optical density, and improved cycling stability. In addition, this device offers a bright hot, and semi‐bright warm dual modulation operation suitable for smart windows of skylights, roof lights, upper windows, inclined glazing, and privacy glazing of buildings located in cold climate regions.

Comparative study on gas-sensing properties of amorphous MoS2 nanoparticles and crystalline MoS2 nanoflowers

High-performance gas sensors for the field of gas sensing have drawn a lot of attention to molybdenum sulfide materials, but there is little research on the influence of crystallization state of MoS2 on gas sensitivity performance. In this study, amorphous MoS2 and crystalline MoS2 were prepared by the hydrothermal method. Then, the gas-sensing characteristics of the as-synthesized amorphous MoS2 and crystalline MoS2 toward NO2 gas were thoroughly investigated and compared. According to the results, with an excellent response value of 1.99 toward 5 ppm NO2 at room temperature, the crystalline MoS2 gas sensor outperformed the amorphous one, while that of the amorphous MoS2 under the same condition was 1.25. However, Four times faster recovery periods were observed in the amorphous MoS2 sample compared to the crystalline MoS2 sample. At the same time, the recovery level of amorphous MoS2 is high and can be fully restored. We discovered that the primary cause of the strong recovery performance of amorphous MoS2 is the presence of localized states that facilitate the easy transition of electrons from the conduction band to the valence band, allowing for effective recombination with the holes. Additionally, the surface of the material absorbs a significant amount of oxygen, which will occupy more of the NO2 adsorption site and hasten the desorption of NO2. This work may aid in the development of gas sensors based on amorphous molybdenum sulfide.

Recombinant microgels utilized to formulate green Pickering emulsions

The fabrication of a stable food-grade Pickering emulsion (PEs) system has been challenging because of difficulties in ensuring the safety of auxiliary reagents and the compatibility of the materials. In this study, inspired by our previous experiments, we devised recombinant microgels (RMs) with a compact structure by freeze–thaw cycles (FTCs) method, which was used to fabricate a green food-grade PE system. The application of FTCs demonstrated an enhancement of RMs in the crystallinity, surface wettability, and textural properties. Specifically, RMs subjected to 3 FTCs had a compact cube structure (0.6–1.1 μm), near neutral surface wettability (89.95°), and an amorphous crystallinity (55.93%), which may be attributed to the decrease of free water content and the formation of hydrogen bonds. A concentration of 0.5% RMs was used to stabilize PEs, which showed a uniform microscopic distribution and a particle size of 13.87 μm. It was found that when the concentration of the external phase exceeded 0.5% stable oil-in-water emulsions formed. Otherwise, multiple emulsions formed. This study underscores the viability of using RMs to construct green food-grade PE systems.

Amorphous Thickness-Dependent Strengthening–Softening Transition in Crystalline–Amorphous Nanocomposites

Amorphous Thickness-Dependent Strengthening–Softening Transition in Crystalline–Amorphous Nanocomposites

Amorphous and crystalline interface engineering of FeSeOx/Mo-NiSe2 nanoarrays for synergistically boosting electrocatalytic water oxidation

Exploring integrated regulation strategies to boosting electrocatalytic performance is essential to design more efficient and inexpensive OER catalysts. Herein, amorphous and crystalline (a-c) interface engineering and heteroatom doping are integrated to construct a novel electrocatalyst containing amorphous FeSeOx and crystalline Mo-doped NiSe2 (denoted as FeSeOx/Mo-NiSe2) via pseudocrystalline replication method and selenization treatment. The resultant FeSeOx/Mo-NiSe2 electrocatalyst with 3D hierarchical nanoarchitectures of nanorod arrays covered by interlocking nanoblocks exposes more active sites and accelerated reaction kinetics. Furthermore, a-c interface engineering and heteroatom doping can synergistically enhance the intrinsic activity and charge transfer capability of NiSe2 by decreasing the electron diffusion distance and flexibly modulating the electronic structure, which contributes to boost the oxygen evolution reaction (OER) performance. Consequently, the obtained FeSeOx/Mo-NiSe2 achieves a low overpotential of 205 mV at 10 mA cm−2, which outperforms many other transitions metal selenides electrocatalysts. Density functional theory (DFT) calculations demonstrate that the formation of an internal electric field between FeSeOx and Mo-NiSe2 accelerates charge transport and optimizes the adsorption/desorption of oxygen-containing intermediates, thereby accelerating the reaction kinetics and improving the OER performance. This work serves as a point of reference for designing innovative metal selenides based electrocatalysts combining a-c interface engineering and heteroatom doping.

Characterization of quinoa starch nanoparticles as a stabilizer for oil in water Pickering emulsion.

Quinoa starch nanoparticles (QSNPs) prepared by nanoprecipitation had a uniform particle size of 191.20nm. QSNPs with amorphous crystalline structure had greater contact angle than QS with orthorhombic crystalline structure, which can therefore be utilized to stabilize Pickering emulsions. QSNPs-based Pickering emulsions prepared by suitable formulations (QSNPs concentration of 2.0-2.5%, oil volume fraction of 0.33-0.67) exhibited good stability against pH of 3-9 and ionic strength of 0-200mM. The oxidative stability of the emulsions increased with increasing starch concentration and ionic strength. Microstructural and rheological results indicated that the structure of the starch interfacial film and the thickening effect of the water phase affected the emulsion stability. The emulsion had excellent freeze-thaw stability and can be produced as a re-dispersible dry emulsion using the freeze-drying technique. These results implied that the QSNPs had great potential for application in the preparation of Pickering emulsions.

Prediction by a hybrid machine learning model for high-mobility amorphous In2O3: Sn films fabricated by RF plasma sputtering deposition using a nitrogen-mediated amorphization method

In this study, we developed a hybrid machine learning technique by combining appropriate classification and regression models to address challenges in producing high-mobility amorphous In2O3:Sn (a-ITO) films, which were fabricated by radio-frequency magnetron sputtering with a nitrogen-mediated amorphization method. To overcome this challenge, this hybrid model that was consisted of a support vector machine as a classification model and a gradient boosting regression tree as a regression model predicted the boundary conditions of crystallinity and experimental conditions with high mobility for a-ITO films. Based on this model, we were able to identify the boundary conditions between amorphous and crystalline crystallinity and thin film deposition conditions that resulted in a-ITO films with 27% higher mobility near the boundary than previous research results. Thus, this prediction model identified key parameters and optimal sputtering conditions necessary for producing high-mobility a-ITO films. The identification of such boundary conditions through machine learning is crucial in the exploration of thin film properties and enables the development of high-throughput experimental designs.

High Isolation, Double-Clamped, Magnetoelectric Microelectromechanical Resonator Magnetometer.

Magnetoelectric (ME)-based magnetometers have garnered much attention as they boast ultra-low-power systems with a small form factor and limit of detection in the tens of picotesla. The highly sensitive and low-power electric readout from the ME sensor makes them attractive for near DC and low-frequency AC magnetic fields as platforms for continuous magnetic signature monitoring. Among multiple configurations of the current ME magnetic sensors, most rely on exploiting the mechanically resonant characteristics of a released ME microelectromechanical system (MEMS) in a heterostructure device. Through optimizing the resonant device configuration, we design and fabricate a fixed-fixed resonant beam structure with high isolation compared to previous designs operating at ~800 nW of power comprised of piezoelectric aluminum nitride (AlN) and magnetostrictive (Co1-xFex)-based thin films that are less susceptible to vibration while providing similar characteristics to ME-MEMS cantilever devices. In this new design of double-clamped magnetoelectric MEMS resonators, we have also utilized thin films of a new iron-cobalt-hafnium alloy (Fe0.5Co0.5)0.92Hf0.08 that provides a low-stress, high magnetostrictive material with an amorphous crystalline structure and ultra-low magnetocrystalline anisotropy. Together, the improvements of this sensor design yield a magnetic field sensitivity of 125 Hz/mT when released in a compressive state. The overall detection limit of these sensors using an electric field drive and readout are presented, and noise sources are discussed. Based on these results, design parameters for future ME MEMS field sensors are discussed.

Electrochemically induced crystalline-to-amorphization transformation in sodium samarium silicate solid electrolyte for long-lasting sodium metal batteries

Exploiting solid electrolyte (SE) materials with high ionic conductivity, good interfacial compatibility, and conformal contact with electrodes is essential for solid-state sodium metal batteries (SSBs). Here we report a crystalline Na5SmSi4O12 SE which features high room-temperature ionic conductivity of 2.9 × 10−3 S cm−1 and a low activation energy of 0.15 eV. All-solid-state symmetric cell with Na5SmSi4O12 delivers excellent cycling life over 800 h at 0.15 mA h cm−2 and a high critical current density of 1.4 mA cm−2. Such excellent electrochemical performance is attributed to an electrochemically induced in-situ crystalline-to-amorphous (CTA) transformation propagating from the interface to the bulk during repeated deposition and stripping of sodium, which leads to faster ionic transport and superior interfacial properties. Impressively, the Na|Na5SmSi4O12|Na3V2(PO4)3 sodium metal batteries achieve a remarkable cycling performance over 4000 cycles (6 months) with no capacity loss. These results not only identify Na5SmSi4O12 as a promising SE but also emphasize the potential of the CTA transition as a promising mechanism towards long-lasting SSBs.

Effect of structural disorder on the oxidation of Zr-based amorphous alloys: A focused review

Structural disordering leads to outstanding mechanical properties of amorphous alloys. Many properties are strongly related to formation of surface oxide layers. An in-depth understanding of effect of structural disordering of amorphous alloys on oxide evolution is essential for applications. This paper presents a review of recent comparative oxidation studies of Zr-based amorphous and single-phase crystalline counterpart alloys. Three representative model alloy systems are selected: Zr–Cu and Zr–Al representing alloys with components of different and similar oxygen affinities, respectively, and Zr–Cu–Al representing multi-component alloys. In combination with molecular dynamic simulations, the fundamental role of the structural disordering of parent alloys in the oxidation processes is revealed. The oxidation of Zr–Cu–Al–Ni amorphous alloys at the supercooled liquid temperature region is further reviewed to clarify the relationship between oxidation and substrate crystallization.

Electroless plating synthesis of bifunctional crystalline/amorphous Pd-NiFeB heterostructure catalysts for boosted electrocatalytic water splitting

The rational design of low-cost and high-efficient electrocatalysts to overcome the energy barrier of water splitting has aroused great attentions. The amorphous-crystalline interface heterostructure has been verified to be a promising design for modulating the charge redistribution at interface active sites for promoting water splitting, which, however, remains a challenge. Herein, a bifunctional electrocatalyst with amorphous-crystalline heterostructures is fabricated by hybridizing amorphous NiFeB alloy and crystalline Pd nanoclusters on the nickel foam (NF) via a simple electroless plating strategy. The as-synthesized Pd-NiFeB/NF catalyst exhibits excellent HER and OER performance. Moreover, the assembled Pd-NiFeB/NF//Pd-NiFeB/NF electrolytic system requires a rather low cell voltage of 1.81 V to drive the durable current density of 500 mA cm−2 for at least 100 h. Theoretical calculations reveal that the addition of Pd nanoclusters reduces the energy barriers for both HER and OER, which is due to the enhanced charge transfer and optimal adsorption of intermediates.

Manganese oxides as positive electrode materials for rechargeable aluminum batteries

Three composites of carbon and amorphous MnO2, crystalline α-MnO2, or Mn2O3 were synthesized and investigated as the positive electrode materials for rechargeable Al batteries. For amorphous MnO2 and crystalline Mn2O3, the maximum discharge capacity was about 300 mAh g−1, which is the highest capacity among nonaqueous rechargeable Al batteries using manganese oxide positive electrodes. The amorphous MnO2 electrode showed a discharge capacity of more than 150 mAh g−1 even after 10 charge-discharge cycles. Crystal structure analysis and electronic state analysis suggested that crystalline Mn2O3 changed to amorphous MnO2 during the first charge process. These results suggest that the amorphous MnO2/carbon composite can be an excellent positive electrode material for rechargeable Al batteries.

Crystalline–Amorphous Heterojunction for a Metal Halides Single Crystals X‐Ray Detector with Substantially Increased Sensitivity

AbstractIon migration‐induced noise is the main limiting factor for metal halides (MHs) single crystals (SCs) X‐ray detectors, and heterostructure design is the most efficient method to overcome this puzzle. However, the conventional stepwise solution method or heteroepitaxial method is greatly limited by the SCs secondary dissolution and the lattice parameters matching. Here, simple and universal crystalline–amorphous heterojunction is developed that proves to be extremely effective in suppressing noise. MAPbBr3 SCs are first chosen as representatives to form heterojunctions with amorphous MTP2MnBr4 by the melting method, and the related device shows an enhanced X‐ray response with significant noise suppression. Computational and experimental results demonstrate that the gradient energy levels formation and improved ion migration energy are responsible for this. Finally, the optimized device shows a low dark current (reduced from ≈1000 to ≈0.12 nA), ultra‐high sensitivity (10 569 µC Gyair−1 cm−2), lower detection limit (82.64 nGyair s−1), and negligible performance deterioration at a total radiation dose of ≈17 000 mGyair. Moreover, six other SCs are selected to verify the universal effect of the heterojunctions, all of which show excellent improved sensitivity, proving its versatility. Hence, it is believed that this work will give a strong impetus to develop sensitive MHs SCs X‐ray detectors.

Exploration of the physical states of riboflavin (free base) by mechanical milling

Amorphous riboflavin (free base) could be produced for the first time via high energy ball milling of a commercial crystalline form (Form I). Importantly, this solid state amorphization process allowed to circumvent chemical degradation occurring during melting as well as the lack of suitable solvents, which are required for amorphization via spray- or freeze-drying. The amorphous state of riboflavin was thoroughly characterized, revealing a complex recrystallization pattern upon heating, involving two enantiotropic polymorphic forms (II and III) and a dihydrate. The glass transition temperature (Tg) and heat capacity (Cp) jump of the amorphous form were determined as 144 °C and 0.68 J/g/°C. Moreover, the relative physical stability of the different physical states has been elucidated, e.g., at room temperature: I > II > III. The following rank order was observed for the dissolution rates in water at 37 °C during the first 4 h: amorphous > III ≈ II > I. Afterwards, a dihydrate crystallized from the solutions of amorphous and metastable crystalline riboflavin forms, the solubility of which was well above the solubility of the stable FormI.

Synthesis of Coconut Methyl Ester Using Organic Catalytic Agents

Biodiesel is one of the biomass materials or renewable energy, which is needed today to replace fuel from fossil energy, which can reduce global warming and has a high renewability cycle. Biodiesel is derived from plants, therefore it is also called biofuel. One type of biodiesel group is coconut methyl ester (CME), which is biodiesel obtained from coconut oil as a raw material. In this study, a synthesis of used coconut oil and methanol has been carried out with an organic catalyst based on coconut coir called the ASK catalyst. The results of transesterification have provided some important information, including: the yield is 15-19.5% after usage of the ASK catalyst consisting of amorphous phase and crystalline phase ClK0.8Na0.2, with the density and viscosity of products are 0.788-0.802 g/ml and 0.6-1 mm2/s. These results allow it to provide a distinctive advantage in its application.

Efficient activation of peroxymonosulfate by amorphous MnO2/α-Fe2O3 for the degradation of organic pollutants

Constructing bimetallic nanostructures with specific crystalline phases provides an attractive strategy to develop highly efficient catalysts and explore structure-dependent catalytic properties. Herein, a new iron-based bimetallic catalyst consisting of amorphous MnO2 and crystalline α-Fe2O3 was synthesized for peroxymonosulfate (PMS) activation, named as a-MnO2/α-Fe2O3. The results show that the removal efficiency of sulfamethoxazole is over 90% within 120 min by the a-MnO2/α-Fe2O3 in the presence of PMS at broad pH conditions ranging from 3 to 9. Furthermore, a complete degradation of bisphenol A (BPA) is achieved within 2 min in the a-MnO2/α-Fe2O3/PMS system under optimum conditions, and the BPA degradation rate constant of 1.67 min−1 outperforms most reported Fe- and Mn- based catalysts. The results of electron paramagnetic resonance analysis, quenching tests and Raman spectroscopy analysis show that the mechanism for the a-MnO2/α-Fe2O3-based PMS activation is dominated by the formation of activated surface-PMS complexes. ≡Mn(Ⅳ)–OH and ≡Fe(III)–OH of a-MnO2/α-Fe2O3 are active sites for PMS adsorption to form inner-sphere complexes (≡Mn(Ⅳ)-OOSO3-) through the replacement of surface hydroxyl groups. Finally, the a-MnO2/α-Fe2O3 exhibits a remarkable removal efficiency of over 99% for BPA in column-bed tests conducted over 600 cycles, demonstrating its immense potential for practical applications.

Fixed-dose dry powder for inhalation of nintedanib, pirfenidone and mycophenolic acid by thin-film freezing (TFF) technology

Nintedanib and pirfenidone have been approved to treat idiopathic pulmonary fibrosis (IPF) by delaying progression of the disease. Recently, mycophenolic acid has also been used as an additive treatment for IPF. This study aims to produce and evaluate fixed-dose combinations (i.e., two-drug and three-drug combinations) of nintedanib, pirfenidone, and mycophenolic acid dry powders for inhalation produced by thin-film freezing (TFF). The TFF process, which is a bottom-up particle engineering technology using a rapid freezing process, allows the formation of a homogeneous powder matrix of the fixed-dose combinations of the two or three drugs. X-ray powder diffraction (XRPD) and modulated differential scanning calorimetry (mDSC) confirmed the presence of amorphous nintedanib and crystalline pirfenidone (NIN-PIR), and amorphous nintedanib and amorphous mycophenolic acid (NIN-MPA) in the two-drug combinations. Two-drug formulations of nintedanib and mycophenolic acid prepared by the TFF process exhibited homogenous porous matrix powders with a high surface area and brittle fracture behavior. The in vitro aerodynamic testing of the two-drug combinations demonstrated that nintedanib and mycophenolic acid have similar particle size distributions and high aerodynamic performance of up to 78–82% fine particle fraction (FPF) of the recovered dose. However, pirfenidone was crystalline in the nintedanib/pirfenidone combinations, resulting in poor aerodynamic performance with FPF (of recovered dose) of 6%–28%. In the three-drug formulations, the TFF process produced a coformer of pirfenidone and mycophenolic acid that prevented pirfenidone crystallization and consequently enhanced aerosolization. Therefore, nintedanib, pirfenidone, and mycophenolic acid exhibited as homogenous brittle matrix powders, resulting in a similar aerodynamic performance with FPF (of recovered dose) of 56%–60%. In conclusion, the fixed-dose combinations produced by the TFF process exhibited drug-excipient miscibility and homogenous brittle matrix powders to enhance aerodynamic performance for inhalation.

Optimizing dry-wear performance of a Ti-based high entropy bulk metallic glass via isothermal annealing

The evolution of microstructure, thermal stability, mechanical response behavior and tribological properties of the Ti20Zr20Cu20Hf20Be20 high entropy bulk metallic glass (HE-BMG) before and after isothermal annealing were systematically studied. The results demonstrate that isothermal annealing affects the mechanical and tribological properties by modifying the microstructure and the consumption of free volume in the structure. Although the strength/hardness of HE-BMG can be improved after the isothermal annealing before crystallization, the deterioration of shear plastic deformation leads to serious brittle fracture, thus cancelling out the contribution of strength to wear resistance and resulting in negligible variation of wear rates. When the crystallization isothermal annealing is performed, the wear resistance can be dramatically enhanced and the wear mechanism changes to slight abrasive and oxidation wear, which can be mainly attributed to the good co-deformation between the amorphous matrix and precipitated crystalline phases.

Crafting amorphous VO2–crystalline NiS2 heterostructures as bifunctional electrocatalysts for efficient water splitting: The different cocatalytic function of VO2

The rational design of bifunctional electrocatalysts is essential to achieve efficient hydrogen production from water splitting. Here, inspired by cocatalysts widely utilized in photocatalysis, we designed a heterostructure comprising amorphous VO2 and crystalline NiS2, aiming at using VO2 cocatalyst to boost activity of NiS2 for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Intriguingly, we found that VO2 displayed different co-catalytic function in boosting the OER and HER. Specifically, the VO2 optimized the binding energy of hydrogen intermediate on NiS2 and thus improved the HER activity. As for the OER, the amorphous VO2 was easily dissolved in the KOH electrolyte, resulting in the generation of abundant oxygen vacancies in the in-situ generated active phase of NiOOH from NiS2, thereby drastically enhancing the OER activity. Consequently, the obtained VO2–NiS2@CC displayed excellent performance for overall water splitting, with a low voltage of 1.53 V at 10 mA cm−2.