Amorphous Crystalline Research Articles

Hyperuniform point sets on the sphere: probabilistic aspects

The concept of hyperuniformity has been introduced by Torquato and Stillinger in 2003 as a notion to detect structural behaviour intermediate between amorphous disorder and crystalline order. The present paper studies a generalisation of this concept to the unit sphere. It is shown that several well studied determinantal point processes are hyperuniform, one recently introduced process, the projective ensemble, is shown not to be hyperuniform.

Different Fe(Al) transition coatings on the performance of Al2O3 coating

Three kinds of Al2O3-based tritium permeation barriers with different Fe(Al) transition layers, namely, FeAl/Al2O3, FeAl2/Al2O3 and Fe3Al/Al2O3 coatings were prepared on Si substrates using radio frequency magnetron sputtering technology. The microstructure, mechanical properties, and electron-irradiation resistance of the coatings were investigated systematically to explore the effect of Fe(Al) transition layers on the growth and performance of the Al2O3 coatings. These different coatings were fabricated successfully on Si substrates, while FeAl, FeAl2 and Fe3Al transition layers exhibited a columnar grain structure and the Al2O3 coatings were composed of amorphous and γ-Al2O3 crystalline phases. FeAl and Fe3Al transition layers enhance the formation of γ-Al2O3 crystalline phase, whereas the surface of FeAl2 transition layer is mainly amorphous Al2O3. The FeAl2/Al2O3 coating exhibits the highest adhesive force of 49.75 N among the three samples, and the adhesive forces of the FeAl/Al2O3 and Fe3Al/Al2O3 coatings are 37.75 N and 47.4 N respectively. The surface roughness values of the FeAl/Al2O3, FeAl2/Al2O3 and Fe3Al/Al2O3 coatings are 3.483 nm, 1.042 nm, 4.565 nm, while the hardness values of three samples are 4199 MPa, 6812 MPa, 4796 MPa, respectively. The surface roughness of the FeAl/Al2O3 and Fe3Al/Al2O3 coatings decreased, but the surface roughness of FeAl2/Al2O3 increased after electron irradiation tests. Moreover, the hardness of all three samples was reduced after electron irradiation. These results provide a reference for further studies of the Fe(Al)/Al2O3 coating.

Reduced sintering temperature in ex situ processed MgB2 tapes using filling powders with Sn addition

Ex situ processed tapes using ball milled MgB2 powders with Sn addition were sintered at various temperatures. Sn addition causes the formation of some amorphous or poor crystalline phase in the as-milled powders and reduces the optimal sintering temperature (Tsin), at which best performance in transport critical current density (Jc) at 4.2 K in 10 T is obtained for the tapes, to about 600 °C. This temperature is lower than that by about 100 °C for the tapes using the milled powders without Sn addition. However, Tsin reduction brings about the decrease of critical temperature (Tc) as well. Nevertheless the addition of small amount of Sn does not cause Jc deterioration at all and the Jc value at 4.2 K and 10 T is around 200 A/mm2. Although the Jc property degrades with further decreasing the Tsin, the corresponding value is still 100 A/mm2 when sintered at 500 °C. The Jc curves as a function of Tsin just shift to lower temperatures by about 100 °C by Sn addition. The anisotropy of the transport Jc property with respect to the applied magnetic field direction is negligible, which is independent of Sn addition.

Electrochromic Device Composed of a Di-Urethanesil Electrolyte Incorporating Lithium Triflate and 1-Butyl-3-Methylimidazolium Chloride

A di-urethane cross-linked poly(oxyethylene)/silica hybrid matrix (di-urethanesil, d-Ut(600)), sinthesized by the sol-gel process, was doped with lithium triflate (LiCF3SO3) and the 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) ionic liquid. The as-produced xerogel film is amorphous, transparent, flexible, homogeneous, hydrophilic, and has low nanoscale surface roughness. It exhibits an ionic conductivity of 3.64×10−6 and 5.00×10−4 S cm-1 at 21 and 100 oC, respectively. This material was successfully tested as electrolyte in an electrochromic device (ECD) with the glass/ITO/a-WO3/d-Ut(600)10LiCF3SO3[Bmim]Cl/c-NiO/ITO/glass configuration, where a-WO3 and c-NiO stand for amorphous tungsten oxide and crystalline nickel oxide, respectively. The device demonstrated attractive electro-optical performance: fast response times (1-2 s for coloring and 50 s for bleaching), good optical memory (loss of transmittance (T) of only 41% after three months, at 555 nm), four mode modulation (bright mode (+3.0 V, T = 77% at 555 nm), semi-bright mode (−1.0 V, T = 60% at 555 nm), dark mode (−1.5 V, T = 38 % at 555 nm), and very dark mode (−2.0 V, T = 11% and −2.5 V, T = 7% at 555 nm )), excellent cycling stability denoting improvement with time, and high coloration efficiency (CEin = −6727 cm2 C−1 (32th cycle) and CEout = +2794 cm2 C−1 (480th cycle), at 555 nm).

Optimization of Cu and Mn Dissolution from Black Coppers by Means of an Agglomerate and Curing Pretreatment

Black coppers are mineraloids with a high content of Cu and Mn. These have an amorphous crystalline structure that makes them refractory to conventional leaching processes. For this reason, these mineral resources are not incorporated in industrial leaching heap processes and are taken to dumps. In the present study, an agglomerate pretreatment process incorporating NaCl is evaluated, and a curing stage, followed by acid-reducing leaching for Cu and Mn dissolution from a high-grade black copper mineral. For this, an experimental design was developed both to evaluate the impact of the dependent variables on the response, to generate analytical models that represent the copper and manganese recoveries under the set of sampled conditions. The models indicate that the curing time and the NaCl concentration have a primary effect on the recovery of both elements. In contrast, the optimization model suggests that the optimal operating levels are reached at relatively high levels of time (>130 h) and of NaCl concentration (>22 kg/t).

Fabrication of a Novel Ta(Zn)O Thin Film on Titanium by Magnetron Sputtering and Plasma Electrolytic Oxidation for Cell Biocompatibilities and Antibacterial Applications

Pure titanium (Ti) and titanium alloys are widely used as artificial implant materials for biomedical applications. The excellent biocompatibility of Ti has been attributed to the presence of a natural or artificial surface layer of titanium dioxide. Zinc oxide and tantalum oxide thin films are recognized due to their outstanding antibacterial properties. In this study, high power impulse magnetron sputtering (HiPIMS) was used for the deposition of tantalum oxide and zinc-doped Ta(Zn)O thin films on Ti with rough and porous surface, which was pretreated by plasma electrolytic oxidation (PEO). Surface morphology, antibacterial property as well as cell biocompatibility were analyzed. The antibacterial effect was studied individually for the Gram-positive and Gram-negative bacteria Staphylococcus aureus (S. aureus) and Actinobacillus actinomycetemcomitans (A. actinomycetemcomitans). The deposited Ta (Zn)O coating was composed of amorphous tantalum oxide and crystalline ZnO. The antibacterial results on the tantalum oxide and Ta(Zn)O coated Ti indicated a significant inhibition of both S. aureus and A. actinomycetemcomitans bacteria when compared with the uncoated Ti samples. The deposited Ta(Zn)O showed the best antibacterial performance. The Ta(Zn)O coated Ti showed lower level of the cell viability in MG-63 cells compared to other groups, indicating that Zn-doped Ta(Zn)O coatings may restrict the cell viability of hard tissue-derived MG-63 cells. However, the biocompatibility tests demonstrated that the tantalum oxide and Ta(Zn)O coatings improved cell attachment and cell growth in human skin fibroblasts. The cytotoxicity was found similar between the Ta2O5 and Ta(Zn)O coated Ti. By adopting a first PEO surface modification and a subsequent HiPIMS coating deposition, we synthetized amorphous tantalum oxide and Ta(Zn)O coatings that improved titanium surface properties and morphologies, making them a good surface treatment for titanium-based implants.

Block copolymer electrolyte with adjustable functional units for solid polymer lithium metal battery

Abstract Solid polymer electrolytes have been considered as the promising candidates to improve the safety and stability of high-energy lithium metal batteries. However, the practical applications of solid polymer electrolytes are still limited by the low ionic conductivity, poor interfacial contact with electrodes, narrow electrochemical window and weak mechanical strength. Here, a series of novel block copolymer electrolytes with three-dimensional networks are designed by cross-linked copolymerization of the polyethylene glycol soft segments and hexamethylene diisocyanate trimer hard segments. Their ionic migration performances and interface compatibilities with Li metal anode have been optimized delicately by tailoring the ratio of these functional units. The optimized block copolymer electrolyte has shown an amorphous crystalline structure, a high ionic conductivity of ~5.7 × 10−4 S cm−1, high lithium ion transference number (~0.49), wide electrochemical window up to ~4.65 V (vs. Li+/Li) and favorable mechanical strength at 55 °C. Furthermore, the enhanced interface compatibility can well support the normal operations of lithium metal batteries using both LiFePO4 and LiNi0.8Co0.15Al0.05O2 cathodes. This study not only paves a new way to develop solid polymer electrolyte with optimizing functional units, but also provides a polymer electrolyte design strategy for the application demand of lithium metal battery.

"Lewis Base-Hungry" Amorphous-Crystalline Nickel Borate-Nickel Sulfide Heterostructures by In Situ Structural Engineering as Effective Bifunctional Electrocatalysts toward Overall Water Splitting.

The development of high-performance, low-cost, and long-lasting electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is urgently needed for effective electrochemical water splitting. In the present study, an engineering process was employed to prepare "Lewis base-hungry" amorphous-crystalline nickel borate-nickel sulfide (Ni3(BO3)2-Ni3S2) heterostructures, which exhibited unprecedentedly high electrocatalytic activity toward both OER and HER in alkaline media. The optimal Ni3(BO3)2-Ni3S2/nickel foam (Ni3(BO3)2-Ni3S2/NF) electrode displayed an ultralow overpotential of only -92 and +217 mV to reach the current density of 10 mA cm-2 for HER and OER, respectively. When the Ni3(BO3)2-Ni3S2/NF electrode was used as both the anode and cathode for overall water splitting, a low cell voltage of 1.49 V was needed to achieve the current density of 10 mA cm-2, which was superior to the performance of most noble metal-free electrocatalysts. Results from density functional theory calculations showed that the Lewis base-hungry sites in the heterostructures effectively enhanced the chemisorption of hydrogen and oxygen intermediates, a critical step in HER and OER electrocatalysis. Results from this study highlight the significance of rational design and engineering of heterostructured materials for the development of high-efficiency electrocatalysts.

Effect of Precursor Concentration and Annealed Substrate Temperature on the Crystal Structure, Electronic and Optical Properties of ZnO thin film

This study carried out on the effect of precursor concentration and annealed substrate temperature on the crystal structure, electronic and optical properties of ZnO thin film. An aqueous solution of Acid Nitrite was used as precursors and its concentration was varied from 0.1 M to 0.4 M. The ZnO thin film was deposited on the glass substrate by Spray Pyrolysis Deposition and annealed with different temperature from 300 oC to 600 oC. The crystal structure, electronic and optical properties were investigated by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and UV-Spectrometer. XRD result showed that all thin films have amorphous hexagonal wurtzite crystalline. Particle sizes ranging from 21.83 to 43.67 nm were calculated through Debye-Scherer Method. It showed that the concentration of the precursor had slightly impact on the particle size. Meanwhile, the increase in particle size with increasing annealed temperature is found to be gradual. The average transparent of all thin film was more than 80%. The bandgap of the ZnO thin films was estimated by Tauc Plot Relation. It showed that the bandgap values were increased with the increasing of precursor concentration due to Burstein-Moss Effect. In addition, the decrease in band gap values was found with increasing annealed temperature. Our results demonstrated that the varying precursor concentration and annealed substrate temperature can enhance the structure, electronic and the optical properties of ZnO thin films.

Atomic simulation of interaction mechanism between dislocation and amorphous phase in dual-phase crystalline/amorphous Mg/MgAl alloys

The introduction of the amorphous phase and crystalline–amorphous interface (CAI) is an efficient approach for enhancing the mechanical performance of the Mg-based composites. Here, the interaction behavior between dislocations and amorphous phase in the dual-phase crystalline/amorphous Mg/MgAl alloys is investigated under tensile loading by molecular dynamics simulation. The results indicate that when the amorphous phase orientation (i.e., the angle between the tensile direction and the normal direction of CAI) is 0°, the amorphous phase with a larger thickness (≥ the critical value of 2.0 nm) can effectively prevent dislocation slips, and the plastic deformation of the alloys is dominated by the nucleation and growth of a new grain in the crystalline phase. The research also shows that, with the increase in the amorphous phase orientation from 0° to 90°, the deformation mechanism changes from dislocation activities to CAI slips and then again to the nucleation and movement of dislocations. The change in the deformation mode is attributed to the variation of the quasi-Schmid factor of the amorphous layer in different orientations of the amorphous phase. Moreover, some qualitative and quantitative analyses about the plastic deformation behavior of the dual-phase nanostructure Mg alloy are also presented.

Phase engineering of nanomaterials.

Phase has emerged as an important structural parameter - in addition to composition, morphology, architecture, facet, size and dimensionality - that determines the properties and functionalities of nanomaterials. In particular, unconventional phases in nanomaterials that are unattainable in the bulk state can potentially endow nanomaterials with intriguing properties and innovative applications. Great progress has been made in the phase engineering of nanomaterials (PEN), including synthesis of nanomaterials with unconventional phases and phase transformation of nanomaterials. This Review provides an overview on the recent progress in PEN. We discuss various strategies used to synthesize nanomaterials with unconventional phases and induce phase transformation of nanomaterials, by taking noble metals and layered transition metal dichalcogenides as typical examples. Moreover, we also highlight recent advances in the preparation of amorphous nanomaterials, amorphous-crystalline and crystal phase-based hetero-nanostructures. We also provide personal perspectives on challenges and opportunities in this emerging field, including exploration of phase-dependent properties and applications, rational design of phase-based heterostructures and extension of the concept of phase engineering to a wider range of materials.

The potential use of volcanic deposits for geopolymer materials

Volcanic deposits are abundant in the vicinity of an active and inactive volcano. They are produced from the cooling of magma during explosive volcanic eruptions. They have varying physical properties and can range in size from sub-millimetric ash up to boulder size. As Indonesia is considered as an active volcanic region, volcanic materials are abundant but they are still unexploited to full capacity such as geopolymer raw material. Geopolymers are generally understood as alkali-activated aluminosilicates. They may be considered as an inorganic two-component system which consists of: [1] a reactive solid source of SiO2 and Al2O3, and [2] an alkaline activation solution. The aim of the research is to identify the chemical and mineralogical properties of Merapi and Mt. Sinabung volcanic ashes as the raw material of geopolymers. Results showed that Mt. Merapi contained amorphous volcanic glass and crystalline [feldspar] minerals with 61.13% SiO2; 17.78% Al2O3; 3.47% Fe2O3; 6.22% CaO. Mount Sinabung deposit contains amorphous volcanic glass also and crystalline [feldspar] minerals with an oxide content of 49.33% SiO2; 15.93% Al2O3; 6.48% Fe2O3; 5.87% CaO. The high content of silica and alumina in this material showed that it was pozzolan material which can be synthesized to geopolymers. The molar ratio of SiO2/Al2O3 was high, Merapi is 5.84 and Sinabung is 5.26.

Fabrication and characterization of the Ni–Al energetic structural material with high energy density and mechanical properties

Abstract The fully dense Ni–Al energetic structural material (ESM) was successfully fabricated by using shock consolidation, with no reaction between the constituents. The microstructure, quasi-static and dynamic compressive behavior and energetic characteristics were investigated. The results revealed a uniform microstructure along the cross-section and both phases were continuously distributed. No intermetallic was detected by the XRD and a 5 nm thick interlayer composed of amorphous phase and crystalline phase was observed at the Ni–Al interface by TEM. The interfacial strength was shown to have a strong effect on the ductility and the strength of Ni–Al ESM, and could be significantly improved by solid-state diffusion during the shock loading and the following heat-treatment. After heat-treatment the samples showed a high quasi-static compressive strength of 300 MPa and a ductility of 14.5%. At impact velocity above 671 m/s, the Ni–Al ESM was initiated and released a large amount of rising the shock temperature or energy. Its reaction efficiency strongly depends on the impact velocity. The good mechanical properties and energetic characteristics of the Ni–Al ESM shows a great potential for the shock consolidation in fabrication of metallic energetic structural materials.

High hardness and fatigue resistance of CoCrFeMnNi high entropy alloy films with ultrahigh-density nanotwins

Development of film materials has been limited by the hardness-fatigue resistance trade-off. The purpose of the present study was to obtain films with a combination of both high hardness and strong fatigue resistance. To achieve this, CoCrFeMnNi high entropy alloy films (HEAFs) were fabricated with three different structures: amorphous, high-density nanotwinned crystal structure with twin spacings of 2.2–5.6 nm, and ultrahigh-density nanotwinned columnar grains with twin spacings of 1.2–2.5 nm. Nanoindentation with dynamic mechanical analysis was used to measure the hardness and perform the fatigue tests. While higher twin densities could dissipate more energy by detwinning during fatigue loading to enhance the fatigue resistance, twin spacings larger than and small than 2 nm could, respectively, result in hardening and softening. Our results showed a high hardness of ~9 GPa and fair fatigue resistance (~104 cycles) for both amorphous and high-density nanotwinned crystalline layers. For the ultrahigh-density nanotwinned columnar grain structure, a high hardness of ~8.5 GPa and an excellent fatigue resistance (~106 cycles) were obtained. The outstanding fatigue resistance and high hardness were attributed to the synergistic effect of strain hardening and detwinning of ultrahigh-density nanotwins. The results not only enable CoCrFeMnNi HEAFs with a predominant combination of hardness and fatigue resistance, but also shed light on a new perspective for overcoming the conflict between hardness and fatigue resistance in film materials for microelectromechanical applications.

Transport and magnetic phenomena in ZnO-С thin-film heterostructures

Abstract ZnO- and C-based heterostructures were fabricated by the layer-by-layer deposition technique using the ion-beam sputtering process. Structure, electrical and magnetic properties of fabricated heterostructures are discussed. The two-phase (ZnO and C) films are evolved into a multilayer structure, consisting of amorphous carbon and crystalline ZnO layers when the bilayer thickness increases. When carbon is added to ZnO, its electrical resistivity reduces. The conduction mechanism changes from the variable-range hopping in a narrow energy band to the nearest neighbors hopping in ZnO–C films with a thickness of h

Amorphous Bimetallic Oxides Fe-V-O with Tunable Compositions toward Rechargeable Zn-Ion Batteries with Excellent Low-Temperature Performance.

Vanadium oxides have been considered as promising cathode candidates for zinc-ion batteries (ZIBs) because of their high theoretical specific capacity. However, the poor rate performance and the unsatisfactory cycle life resulting from the sluggish electrode kinetics seriously impede their practical implementation. Herein, we report the rational design of amorphous Fe-V-O bimetallic oxides with tunable compositions as cathodes for aqueous ZIBs. The bimetallic Fe-V-O oxides show improved composition-dependent Zn2+ storage performance and superior structural integrity during cycling. The enhanced electrode kinetics is attributed to the superior electronic conductivity of Fe-V-O oxides than pristine V2O5 owing to the introduction of the Fe element and an amorphous crystalline structure, which can provide reduced diffusion paths and more free volume for Zn2+ insertion. As a result, the as-prepared Fe-V-O exhibits outstanding rate capability and impressive cycling stability. Particularly, a stable reversible capacity of 70 mA h g-1 can be still maintained after 2500 cycles at 5 A g-1, corresponding to the high capacity retention of 95%.

Surface-Dependent Osteoblasts Response to TiO2 Nanotubes of Different Crystallinity.

One of the major challenges of implantology is to design nanoscale modifications of titanium implant surfaces inducing osseointegration. The aim of this study was to investigate the behavior of rat osteoblasts cultured on anodized TiO2 nanotubes of different crystallinity (amorphous and anatase phase) up to 24 days. TiO2 nanotubes were fabricated on VT1–0 titanium foil via a two-step anodization at 20 V using NH4F as an electrolyte. Anatase-phase samples were prepared by heat treatment at 500 °C for 1 h. VT1–0 samples with flat surfaces were used as controls. Primary rat osteoblasts were seeded over experimental surfaces for several incubation times. Scanning electron microscopy (SEM) was used to analyze tested surfaces and cell morphology. Cell adhesion and proliferation were investigated by cell counting. Osteogenic differentiation of cells was evaluated by qPCR of runt-related transcription factor 2 (RUNX2), osteopontin (OPN), integrin binding sialoprotein (IBSP), alkaline phosphatase (ALP) and osteocalcin (OCN). Cell adhesion and proliferation, cell morphology and the expression of osteogenic markers were affected by TiO2 nanotube layered substrates of amorphous and anatase crystallinity. In comparison with flat titanium, along with increased cell adhesion and cell growth a large portion of osteoblasts grown on the both nanostructured surfaces exhibited an osteocyte-like morphology as early as 48 h of culture. Moreover, the expression of all tested osteogenic markers in cells cultured on amorphous and anatase TiO2 nanotubes was upregulated at least at one of the analyzed time points. To summarize, we demonstrated that amorphous and anodized TiO2 layered substrates are highly biocompatible with rat osteoblasts and that the surface modification with about 1500 nm length nanotubes of 35 ± 4 (amorphous phase) and 41 ± 8 nm (anatase phase) in diameter is sufficient to induce their osteogenic differentiation. Such results are significant to the engineering of coating strategies for orthopedic implants aimed to establish a more efficient bone to implant contact and enhance bone repair.

Progress in the measurement and reduction of thermal noise in optical coatings for gravitational-wave detectors.

Coating thermal noise is a fundamental limit for precision experiments based on optical and quantum transducers. In this review, after a brief overview of the techniques for coating thermal noise measurements, we present the latest worldwide research activity on low-noise coatings, with a focus on the results obtained at the Laboratoire des Matériaux Avancés. We report new updated values for the Ta2O5, Ta2O5-TiO2, and SiO2 coatings of the Advanced LIGO, Advanced Virgo, and KAGRA detectors, and new results from sputtered Nb2O5, TiO2-Nb2O5, Ta2O5-ZrO2, MgF2, AlF3, and silicon nitride coatings. Amorphous silicon, crystalline coatings, high-temperature deposition, multi-material coatings, and composite layers are also briefly discussed, together with the latest developments in structural analyses and models.

Design of microgrippers based on amorphous-crystalline TiNiCu alloy with two-way shape memory

Functional layered composites of the shape memory alloys are recently recognized as promising basic active element for microsystem technology and microrobotics. Amorphous-crystalline TiNiCu alloy ribbons at around 40 μm of thickness with an interface separating the amorphous and crystalline phases into layers were produced by melt spinning technique. It is shown that a decrease in the cooling rate of the melt from 8.9·105 to 4.2·105 K/s leads to an increase in the thickness of the crystalline layer from 2 to 10 μm. The ratio of the thicknesses of the amorphous dam and crystalline dcr layers was also varied by an electrochemical polishing method. The composite ribbons have exhibited the two-way shape memory effect (TWSME) of thermal induced bending deformation without additional thermomechanical training. It was established that when the ratio dcr/dam is changed from 0.06 to 0.35, the minimum bending radius of the ribbon decreases from 37.1 to 6.3 mm, and the maximum reversible strain increases by 0.05% to 0.27%. The minimum time of the shape recovery of the composite ribbons when heated by an electric current pulse was 14 ms, and the force generated by the ribbon with a length of 3 mm in bending reached 1.2 mN. A series of the microgrippers (microtweezers) were fabricated on the basis of the composite ribbons with TWSME. Complete technological process of manipulating graphite filaments with a diameter of 5 to 25 μm using developed microgrippers was demonstrated.

Metal Organic Framework Derivative Improving Lithium Metal Anode Cycling

AbstractThis work demonstrates a new approach in using metal organic framework (MOF) materials to improve Li metal batteries, a burgeoning rechargeable battery technology. Instead of using the MIL‐125‐Ti MOF structure directly, the material is decomposed into intimately‐mixed amorphous titanium dioxide and crystalline terephthalic acid. The resulting composite material outperforms the oxide alone, the organic component alone, and the parent MOF in suppressing Li dendrite growth and extending cycle life of Li metal electrodes. Coated on a commercial polypropylene separator, this material induces the formation of a desirable solid electrolyte interphase layer comprising mechanically flexible organic species and ionically conductive lithium nitride species, which in turn leads to Li||Cu and Li||Li cells that can stably operate for hundreds of charging–discharging cycles. In addition, this material strongly adsorbs lithium polysulfides and can also benefit the cathode of lithium–sulfur batteries.